Improving sensitivity of XANES structural fit to the bridged metal-metal coordination.

Hard X-ray absorption spectroscopy is a valuable in situ probe for non-destructive diagnostics of metal sites. The low-energy interval of a spectrum (XANES) contains information about the metal oxidation state, ligand type, symmetry and distances in the first coordination shell but shows almost no dependency on the bridged metal-metal bond length. The higher-energy interval (EXAFS), on the contrary, is more sensitive to the coordination numbers and can decouple the contribution from distances in different coordination shells. Supervised machine-learning methods can combine information from different intervals of a spectrum; however, computational approaches for the near-edge region of the spectrum and higher energies are different. This work aims to keep all benefits of XANES and extend its sensitivity towards the interatomic distances in the first and second coordination shells. Using a binuclear bridged copper complex as a case study and cross-validation analysis as a quantitative tool it is shown that the first 170 eV above the edge are already sufficient to balance the contributions of Cu-O/N scattering and Cu-Cu scattering. As a more general outcome this work highlights the trivial but often overlooked importance of using `longer' energy intervals of XANES for structural refinement and machine-learning predictions. The first 200 eV above the absorption edge still do not require parametrization of Debye-Waller damping and can be calculated within full multiple scattering or finite difference approximations with only moderately increased computational costs.

Hemodynamic effects of microgravity and their ground-based simulations.

Hemodynamic effects of simulated microgravity were investigated, in various experiments, using radioactive isotopes, in which 40 healthy men, aged 35 to 42 years, took part. Blood shifts were evaluated qualitatively and quantitatively. Simulation studies included bedrest, head-down tilt (-5 degrees and -15 degrees), and vertical water immersion, it was found that none of the methods could entirely simulate hemodynamic effects of microgravity. Subjective sensations varied in a wide range. They cannot be used to identify reliably the effects of real and simulated microgravity. Renal fluid excretion in real and simulated microgravity was different in terms of volume and time. The experiments yielded data about the general pattern of circulation with blood displaced to the upper body.

[Body fluids during 120-day anti-orthostatic hypokinesia]. / Sostoianie zhidkostnykh faz tela v dinamike 120-sutochnoi antiortostaticheskoi gipokinezii.

Body fluid variations were examined during 120-day antiorthostatic (-5 degrees) hypokinesia in 21 test subjects, 9 of which comprised a control group (Group 1). The remaining 12 subjects formed three groups (four subjects each) who received drugs to normalize mineral and lipid metabolism (Group 2), or performed specially developed exercises (Group 3), or were on the combined treatment (Group 4). Total body water (TBW), intracellular fluid volume (IFV), extracellular fluid volume (EFV), and EFV composition were measured by nuclear physical methods. Measurements were taken prior to exposure, on head-down tilt days 1, 60 and 120, and on recovery day 15. Body composition and K40 content were investigated before and after head-down tilt. The controls showed body dehydration that began on tilt day 1 at the expense of vascular fluid and continued by day 60 at the expense of interstitial fluid and by day 120 at the expense of IFV. Group 2 subjects exhibited variations that were similar to those of controls. Group 3 subjects were in better shape due to the beneficial effect of exercise which diminished as head-down tilt continued. In the recovery period the above changes regressed.

[Effect of space flight factors on hydration homeostasis in monkeys]. / Vliianie faktorov kosmicheskogo poleta na gidratatsionnyi gomeostaz obez'ian.

Using nuclear physics methods, hydration homeostasis of three monkeys flown on Cosmos-1514 and Cosmos-1667 was investigated. Measurements were made before flight 1.5 hours after touchdown and during the recovery period. Total water content, extracellular and tissue fluid volumes were measured and intracellular and interstitial fluid volumes were calculated. Postflight, all the animals showed hydration status changes of similar sign: total water content, intracellular and extracellular fluid volumes decreased. Most significant changes occurred in tissue and interstitial fluid volumes. Hydration status responses to space flight factors were variable and the above changes disappeared in the course of the recovery period. The variations recorded were viewed as adaptive.

[Characteristics of the hydration status of patients with hypothyroidism]. / Osobennosti gidratatsionnogo statusa u bol'nykh gipotireozom.

The hydratation status of 15 patients of various age groups with hypothyrosis was studied using nuclear physical methods. Their body composition was calculated. All the examinees demonstrated considerable hyperhydratation of the extracellular water sector with prevailing liquid accumulation in the interstitial space. Some changes in the infrastructure of the hydratation status including those in the nature of interrelationships of liquid media, were noted. The dependence of the hydratation status and its infrastructure in patients with hypothyrosis on age and gravity of disease but not on its duration was revealed.

[Individual characteristics of water-mineral metabolism during 120-day head-down tilt hypokinesia and the effectiveness of prophylactic measures]. / Individual'nye osobennosti vodno-mineral'nogo obmena v usloviiakh 120-sutochnoi ANOG i éffektivnost' profilakticheskikh sredstv.

Sodium balance and circulating plasma, intracellular, extracellular and interstitial fluid volumes were measured in the test subjects exposed for 120 days to head-down tilt at -5 degrees. The large scatter of the above parameters was associated with individual variations and with the use of different countermeasures against demineralization (exercise and drugs-xydiphone and glucamak). The effect of the countermeasures was different both in qualitative and quantitative terms. It appears that the target of their action was different. The best prophylactic effect was seen when exercise and drugs were used in combination. These findings suggest that individual variations of fluid-electrolyte metabolism during prolonged hypokinesia are related to the different capacity of tissues for water and electrolytes.

[Effect of dihydroergotamine on blood circulation in man in conditions of orthostasis]. / Vliianie digidroérgotamina na gemotsirkuliatsiiu cheloveka v usloviiakh ortostaza.

The physiological effects of zero-g were simulated by 6-hour antiorthostatic hypokinesia at -15 degrees, using eight healthy volunteers. They took part in two experimental runs at a 2 week interval. During the first study the test subjects received a placebo and during the second study they got 6 mg dihydroergotamine methane sulfonate per os. Radiometric examinations of the whole body and its compartments (head, chest, abdomen, legs) showed that the drug increased blood pooling in the upper body and decreased it in the lower body at every position of the long axis of the body relative to the gravity vector.

[Effects of sidnocarb on hemodynamics and blood redistribution during functional tests after 6-hour antiorthostatic hypokinesis]. / Vliianie sidnokarba na gemodinamiku i pereraspredelenie krovi pri funktsional'nykh probakh posle 6-chasovoi antiortostaticheskoi gipokinezii.

Man's orthostatic tolerance and physical work capacity declined in response to 6-hour head-down tilt at -15 degrees. During tilt tests heart rate increased, blood pressure fell, and blood pooling in the upper body decreased. During exercise tests the circulating blood volume, total amount of the work performed, and consumed oxygen decreased. Sydnocarb given at a dose of 25 mg during head-down tilt did not influence the circulating blood volume and oxygen consumption. All other parameters varied approaching the pretest values.

[Effect of short-term antiorthostatic hypokinesia on the central and intracardiac hemodynamics and metabolism in a healthy human being]. / Vliianie kratkovremennoi antiortostaticheskoi gipokinezii na tsentral'nuiu i vnutriserdechnuiu gemodinamiku u metabolizm u zdorovogo cheloveka.

The right parts of the heart and the radial artery were catheterized in healthy male volunteers before and 5 days after strict bed rest in antiorthostatic position of the body (-4.5 degrees) After immobilization most values of central circulation showed no essential changes; the only exception were indices characterizing the inotropic myocardial condition. A shift in the direction of acidosis of a mixed character was noted in mixed venous blood, the beta-lipoprotein content increased. A decrease in the arteriovenous difference in oxygen was encountered in blood draining from the heart (from the coronary sinus).