Heavy ions light flashes and brain functions: recent observations at accelerators and in spaceflight

Interactions between ionizing radiation in space and brain functions, and the related risk assessments, are among the major concerns when programming long permanence in space, especially when outside the protective shield of the Earth's magnetosphere. The light flashes (LF) observed by astronauts in space, mostly when dark adapted, are an example of these interactions; investigations in space and on the ground showed that these effects can originate with the action of ionizing radiation in the eye. Recent findings from ALTEA, an interdisciplinary and multiapproach program devoted to the study of different aspects of the radiation?brain functions interaction, are presented in this paper. These include: (i) study of radiation passing through the astronauts' eyes in the International Space Station (?20?ions?min?1, excluding H and fast and very slow He), measured in conjunction with reporting of the perception of LF; (ii) preliminary electrophysiological evidence of these events in astronauts and in patients during heavy ion therapy; and (iii) in vitro results showing the radiation driven activation of rhodopsin at the start of the phototransduction cascade in the process of vision. These results are in agreement with our previous work on mice. A brief but complete summary of the earlier works is also reported to permit a discussion of the results

Beyond convergence rates: Exact recovery with Tikhonov regularization with sparsity constraints

The Tikhonov regularization of linear ill-posed problems with an $\ell^1$ penalty is considered. We recall results for linear convergence rates and results on exact recovery of the support. Moreover, we derive conditions for exact support recovery which are especially applicable in the case of ill-posed problems, where other conditions, e.g. based on the so-called coherence or the restricted isometry property are usually not applicable. The obtained results also show that the regularized solutions do not only converge in the $\ell^1$-norm but also in the vector space $\ell^0$ (when considered as the strict inductive limit of the spaces $\R^n$ as $n$ tends to infinity). Additionally, the relations between different conditions for exact support recovery and linear convergence rates are investigated. With an imaging example from digital holography the applicability of the obtained results is illustrated, i.e. that one may check a priori if the experimental setup guarantees exact recovery with Tikhonov regularization with sparsity constraints

Spin systems with dimerized ground states

In view of the numerous examples in the literature it is attempted to outline a theory of Heisenberg spin systems possessing dimerized ground states (``DGS systems") which comprises all known examples. Whereas classical DGS systems can be completely characterized, it was only possible to provide necessary or sufficient conditions for the quantum case. First, for all DGS systems the interaction between the dimers must be balanced in a certain sense. Moreover, one can identify four special classes of DGS systems: (i) Uniform pyramids, (ii) systems close to isolated dimer systems, (iii) classical DGS systems, and (iv), in the case of $s=1/2$, systems of two dimers satisfying four inequalities. Geometrically, the set of all DGS systems may be visualized as a convex cone in the linear space of all exchange constants. Hence one can generate new examples of DGS systems by positive linear combinations of examples from the above four classes.Comment: With corrections of proposition 4 and other minor change

Ion rates in the International Space Station during the December 2006 Solar Particle Event

International audienceSolar Particle Events (SPEs) are a major concern during prolonged space missions. During such events, a large amount of light ions, mostly protons and helium nuclei, are accelerated with enough energy to traverse the spacecraft hull and therefore represent a high hazard for the crew health. The ALTEA particle telescope was collecting continuous data inside the USLab module of the International Space Station (ISS) during most of the December 2006 SPEs. The telescope is able to measure protons and helium respectively in the 42-45 MeV and 42-250 MeV/nucleon energy ranges, heavier ions up to relativistic molybdenum, and to discriminate nuclei for Zr. First measurements of the charged radiation environment inside the USLab during a SPE are presented. The data averaged over the entire SPE week show an increase of the light ion rate (about a factor 1.5 in the energy range of the detector) when compared to quiet Sun conditions. The increase becomes much higher during the SPE climax (December 13 th) reaching a factor 10 (when averaged over three ISS orbits showing the highest activity). The extension of these results beyond the detector range is discussed. Conversely, the rates of ions with Z5 are shown not to change significantly during the SPE week

Human skeletal muscle fibre contractile properties and proteomic profile: Adaptations to 3 weeks of unilateral lower limb suspension and active recovery

Following disuse, muscle fibre function goes through adaptations such as a loss of specific force (PO/CSA) and an increase in unloaded shortening velocity, which could be a result of both quantitative changes (i.e. atrophy) and qualitative changes in protein pattern. The underlying mechanisms remain to be clarified. In addition, little is known about the recovery of muscle mass and strength following disuse. In the present study, we report an extensive dataset describing, in detail,the functional and protein content adaptations of skeletal muscle in response to both disuse and re-training. Eight young healthy subjects were subjected to 3 weeks of unilateral lower limb suspension (ULLS), a widely used human model of disuse skeletal muscle atrophy. Needle biopsies samples were taken from the vastus lateralis muscle Pre-ULLS, Post-ULLS and after 3 weeks of recovery during which heavy resistance training was performed. After disuse, cross-sectional area (CSA), PO/CSA and myosin concentration (MC) decreased in both type 1 and 2A skinned muscle fibres. After recovery, CSA and MC returned to levels comparable to those observed before disuse, whereas Po/CSA and unloaded shortening velocity reached a higher level. Myosin heavy chain isoform composition of muscle samples did not differ among the experimental groups. To study the mechanisms underlying such adaptations, a two-dimensional proteomic analysis was performed. ULLS induced a reduction of myofibrillar, metabolic (glycolytic and oxidative) and anti-oxidant defence system protein content. Resistance training was very effective in counteracting ULLS-induced alterations, indicating that long-term ULLS did not prevent the positive effect of exercise on human muscle. © 2015 The Physiological Society

Skeletal Muscle Mitochondrial and Perilipin Content in a Cohort of Obese Subjects Undergoing Moderate and High Intensity Training

Obesity is a complex condition characterized by abnormal and excessive fat accumulation, resulting in an increased risk for severe health problems. Skeletal muscles play a major role in movement and fat catabolism, but the insulin resistance that comes with obesity makes it difficult to fulfill these tasks. In this study, we analyse two types of training protocols, moderate intensity continuous training (MICT) versus high intensity interval training (HIIT), in a cohort of obese subjects to establish which muscle adaptations favour fat consumption in response to exercise. Mitochondria play a role in fat oxidation. We found protein upregulation of mitochondrial biomarkers, TOMM20 and Cox-4, in HIIT but not in MICT, without detecting any shifts in fibre composition phenotype of the vastus lateralis in both training groups. Interestingly, both MICT and HIIT protocols showed increased protein levels of perilipin PLIN2, which is involved in the delivery and consumption of fats. HIIT also augmented perilipin PLIN5. Perilipins are involved in fat storage in skeletal muscles and their upregulation, along with the analysis of circulatory lipid profiles reported in the present study, suggest important adaptations induced by the two types of training protocols that favour fat consumption and weight loss in obese subjects

Functions of several Cayley-Dickson variables and manifolds over them

Functions of several octonion variables are investigated and integral representation theorems for them are proved. With the help of them solutions of the ${\tilde {\partial}}$-equations are studied. More generally functions of several Cayley-Dickson variables are considered. Integral formulas of the Martinelli-Bochner, Leray, Koppelman type used in complex analysis here are proved in the new generalized form for functions of Cayley-Dickson variables instead of complex. Moreover, analogs of Stein manifolds over Cayley-Dickson graded algebras are defined and investigated

Positive energy balance is associated with accelerated muscle atrophy and increased erythrocyte glutathione turnover during 5 wk of bed rest

Background: Physical inactivity is often associated with positive energy balance and fat gain. Objective: We aimed to assess whether energy intake in excess of requirement activates systemic inflammation and antioxidant defenses and accelerates muscle atrophy induced by inactivity. Design: Nineteen healthy male volunteers were studied before and at the end of 5 wk of bed rest. Subjects were allowed to spontaneously adapt to decreased energy requirement (study A, n = 10) or were provided with an activity-matched diet (study B, n = 9). Groups with higher (HEB) or lower (LEB) energy balance were identified according to median values of inactivity-induced changes in fat mass (\u394FM, assessed by bioelectrical impedance analysis). Results: In pooled subjects (n = 19; median \u394FM: 1.4 kg), bed rest-mediated decreases in fat-free mass (bioelectrical impedance analysis) and vastus lateralis thickness (ultrasound imaging) were significantly greater (P < 0.03) in HEBAB (-3.8 \ub1 0.4kg and -0.32 \ub1 0.04 cm, respectively) than in LEBab (-2.3 \ub1 0.5 kg and -0.09 \ub1 0.04 cm, respectively) subjects. In study A (median \u394FM: 1.8 kg), bed rest-mediated increases in plasma leptin, C-reactive protein, and myeloperoxidase were greater (P < 0.04) in HEBA than in LEBA subjects. Bed rest-mediated changes of glutathione synthesis rate in eythrocytes (L-[3,3-2H2]cysteine incorporation) were greater (P = 0.03) in HEBA (from 70 \ub1 19 to 164 \ub1 29%/d) than in LEBA (from 103 \ub1 23 to 84 \ub1 27%/d) subjects. Conclusions: Positive energy balance during inactivity is associated with greater muscle atrophy and with activation of systemic inflammation and of antioxidant defenses. Optimizing caloric intake may be a useful strategy for mitigating muscle loss during period of chronic inactivity

A compact Time-Of-Flight detector for space applications: The LIDAL system

Abstract LIDAL (Light Ion Detector for ALTEA system) is a compact detector designed to upgrade ALTEA (Anomalous Long Term Effects on Astronauts) silicon detector apparatus, in order to study in detail the low-Z part of ions spectrum inside the International Space Station (ISS) and to enhance the Particle Identification (PID) capability of the system. The new detector is designed to trigger ALTEA and to perform Time-Of-Flight measurements. It is based on plastic scintillators for fast timing applications read by Photo-Multiplier-Tubes (PMTs). A custom Front End Electronics (FEE) has been designed to reach time resolutions less than 100 ps ( σ ) for protons. A LIDAL prototype has been developed at the University of Rome Tor Vergata to test the timing performance of the scintillators, the PMTs and of the custom FEE using the proton beam line at the TIFPA (Trento Institute for Fundamentals Physics Applications) center in Trento, Italy. The results of these tests are reported and discussed. They have also been used for a preliminary evaluation of the Particle Identification (PID) capability of the final LIDAL-ALTEA detector system in response to the ions spectra expected on-board the ISS