Superionic states formation in group III oxides irradiated with ultrafast lasers.

After ultrafast laser irradiation, a target enters a poorly explored regime where physics of a solid state overlaps with plasma physics and chemistry, creating an unusual synergy-a warm dense matter state (WDM). We study theoretically the WDM kinetics and chemistry in a number of group III-metal oxides with highly excited electronic system. We employ density functional theory to investigate a possibility of nonthermal transition of the materials into a superionic state under these conditions. Atomic and electronic properties of the materials are analyzed during the transitions to acquire insights into physical mechanisms guiding such transformations.

Mechanism of the enhancing effect of glycyrrhizin on nifedipine penetration through a lipid membrane.

The saponin glycyrrhizin from liquorice root shows the ability to enhance the therapeutic activity of other drugs when used as a drug delivery system. Due to its amphiphilic properties, glycyrrhizin can form self-associates (dimers, micelles) and supramolecular complexes with a wide range of hydrophobic drugs, which leads to an increase in their solubility, stability and bioavailability. That is why the mechanism of the biological activity of glycyrrhizin is of considerable interest and has been the subject of intensive physical and chemical research in the last decade. Two mechanisms have been proposed to explain the effect of glycyrrhizin on drug bioavailability, namely, the increase in drug solubility in water and enhancement of the membrane permeability. Interest in the membrane-modifying ability of glycyrrhizic acid (GA) is also growing at present due to its recently discovered antiviral activity against SARS-CoV-2 Bailly and Vergoten (2020) [1]. In the present study, the passive permeability of the DOPC lipid membrane for the calcium channel blocker nifedipine was elucidated by parallel artificial membrane permeability assay (PAMPA) and full atomistic molecular dynamics (MD) simulation with free energy calculations. PAMPA experiments show a remarkable increase in the amount of nifedipine (NF) permeated with glycyrrhizin compared to free NF. In previous studies, we have shown using MD techniques that glycyrrhizin molecules can integrate into the lipid bilayer. In this study, MD simulation demonstrates a significant decrease in the energy barrier of NF penetration through the lipid bilayer in the presence of glycyrrhizin both in the pure DOPC membrane and in the membrane with cholesterol. This effect can be explained by the formation of hydrogen bonds between NF and GA in the middle of the bilayer.

Response of free-standing graphene monolayer exposed to ultrashort intense XUV pulse from free-electron laser.

The response of a free-standing graphene monolayer exposed to a few tens of femtoseconds long extreme ultraviolet (XUV) pulse was studied theoretically in order to analyze and compare contributions of various mechanisms to the graphene damage, understood here as a global atomic disintegration. Our simulation results indicate that nonthermal disintegration of the atomic structure is the predominant damage mechanism for a free-standing graphene layer. Only at high absorbed doses, charge-induced disintegration of the graphene structure prevails. We also demonstrate that the progressing damage can be probed by femtosecond optical pulses in the soft UV regime (4 eV photon energy). The achieved quantitative understanding of the damage mechanisms may enable a better control of graphene-based devices when they are exposed to x-ray radiation, as well as an efficient processing of graphene layers with ultrashort intense XUV pulses.

An interplay of various damage channels in polyethylene exposed to ultra-short XUV/X-ray pulses.

Polyethylene (PE) irradiated with femtosecond extreme ultraviolet or X-ray laser pulses in a single-shot damage regime is studied theoretically. The employed microscopic simulation tool XTANT-3 traces nonequilibrium electron kinetics, energy exchange between electrons and atoms, nonthermal modification of interatomic potential, and the induced atomic response. It is found that the nonthermal detachment of hydrogen atoms in bulk PE starts at the threshold deposited dose of ∼0.05 eV per atom. With an increase in the dose, more hydrogen atoms detach from the carbon backbone. At a dose of ∼0.3 eV per atom, hydrogen behaves like a liquid flowing around carbon chains. It is accompanied by the appearance of defect energy levels within the band gap. At a dose of ∼0.5 eV per atom, carbon chains actively bend and cross-link. In the range of doses from ∼0.5 eV per atom to ∼0.9 eV per atom, the electronic excitation induces formation of new carbon structures embedded in the hydrogen liquid, such as benzene-like rings. The band gap collapses at such doses, merging the valence and the conduction bands. Finally, at doses above ∼0.9 eV per atom, the carbon subsystem also melts into liquid. All of these damage mechanisms are mainly nonthermal, triggered by promotion of electrons from the valence into the conduction band of PE. At high doses, however, thermal electron-ion coupling is extremely fast causing equilibration of the electronic and the ionic temperatures within a hundred femtoseconds.

Dependence of nonthermal metallization kinetics on bond ionicity of compounds.

It is known that covalently bonded materials undergo nonthermal structure transformations upon ultrafast excitation of an electronic system, whereas metals exhibit phonon hardening in the bulk. Here we study how ionic bonds react to electronic excitation. Density-functional molecular dynamics predicts that ionic crystals may melt nonthermally, however, into an electronically insulating state, in contrast to covalent materials. We demonstrate that the band gap behavior during nonthermal transitions depends on a bonding type: it is harder to collapse the band gap in more ionic compounds, which is illustrated by transformations in Y2O3 vs. NaCl, LiF and KBr.

Ruthenium under ultrafast laser excitation: Model and dataset for equation of state, conductivity, and electron-ion coupling.

Interaction of ultrashort laser pulses with materials can bring the latter to highly non-equilibrium states, where the electronic temperature strongly differs from the ionic one. The properties of such excited material can be considerably different from those in a hot, but equilibrium state. The reliable modeling of laser-irradiated target requires careful analysis of its properties in both regimes. This paper reports a procedure which provides the equations of state of ruthenium using density functional theory calculations. The obtained data are fitted with analytical functions. The constructed equations of state are applicable in the one- and two-temperature regimes and in a wide range of densities, temperatures and pressures. The electron thermal conductivity and electron-phonon coupling factor are also calculated. The obtained analytical expressions can be used in two-temperature hydrodynamics modeling of Ru targets pumped by ultrashort laser pulses. The data is related to the research article "Similarity in ruthenium damage induced by photons with different energies: From visible light to hard X-rays" [1].

Recrystallization as the governing mechanism of ion track formation.

Response of dielectric crystals: MgO, Al2O3 and Y3Al5O12 (YAG) to irradiation with 167 MeV Xe ions decelerating in the electronic stopping regime is studied. Comprehensive simulations demonstrated that despite similar ion energy losses and the initial excitation kinetics of the electronic systems and lattices, significant differences occur among final structures of ion tracks in these materials, supported by experiments. No ion tracks appeared in MgO, whereas discontinuous distorted crystalline tracks of ~2 nm in diameter were observed in Al2O3 and continuous amorphous tracks were detected in YAG. These track structures in Al2O3 and YAG were confirmed by high resolution TEM data. The simulations enabled us to identify recrystallization as the dominant mechanism governing formation of detected tracks in these oxides. We analyzed effects of the viscosity in molten state, lattice structure and difference in the kinetics of metallic and oxygen sublattices at the crystallization surface on damage recovery in tracks.

Femtosecond phase-transition in hard x-ray excited bismuth.

The evolution of bismuth crystal structure upon excitation of its A1g phonon has been intensely studied with short pulse optical lasers. Here we present the first-time observation of a hard x-ray induced ultrafast phase transition in a bismuth single crystal at high intensities (~1014 W/cm2). The lattice evolution was followed using a recently demonstrated x-ray single-shot probing setup. The time evolution of the (111) Bragg peak intensity showed strong dependence on the excitation fluence. After exposure to a sufficiently intense x-ray pulse, the peak intensity dropped to zero within 300 fs, i.e. faster than one oscillation period of the A1g mode at room temperature. Our analysis indicates a nonthermal origin of a lattice disordering process, and excludes interpretations based on electron-ion equilibration process, or on thermodynamic heating process leading to plasma formation.

[Involutive and hypertensive fibrosive transformation of the heart in formation of myocardial dysfunction and chronic heart failure.]

To assess the conjugation of involutive and hypertensive fibrotic transformation of the heart formation with myocardial dysfunction and chronic heart failure (CHF), 30 normotensive individuals and 60 elderly patients with arterial hypertension (AH) (mean age - 66±0,7 years) were examined by echo and dopplercardiography, estimation of the volume fraction of interstitial collagen (VFIC) in the myocardium, serum concentrations of markers of systemic collagenogenesis, using a six-minute walk test. A higher intensity of LV myocardial fibrosis was revealed with a significant increase in the VFIC content in elderly patients with AH compared with normotensive patients, which indicates the predominance of interstitial collagenogenesis over collagenolysis. The increased content of fibrous tissue in myocardial interstitium caused the development of unfavorable types of cardiac remodeling and the progression of diastolic dysfunction, negatively affecting the functional reserve of the circulatory system, as evidenced by negative correlations between the level of the VFIC and the results of a 6-minute walk test: weak in patients with I FC CHF, moderate strength in patients with AH with II FC CHF.

[The state of geriatric care in the Kursk region: problems of formation and development prospects.]

The article presents the main promising directions for the development of geriatric care for the elderly population implemented in the Kursk region thanks to the efforts of the Polyclinic Therapy and General Practice Department of the Kursk State Medical University, the Kursk Branch of the Gerontological Society of the Russian Academy of Sciences, and the team of the Kursk Local Center of the Global Aging Network for the International Association Gerontology and geriatrics, consisting in the professional retraining of specialists for working with the elderly population, providing quality advisory services to specialists of outpatient medical institutions, organizing scientific and practical conferences devoted to the discussion of urgent problems of gerontology and geriatrics, effective cooperation with the service of social protection of the population. The important role of training qualified medical staff, conducting modern scientific research, introducing their results into healthcare practice, the need to organize additional education for the elderly, involving them in performing volunteer activities to maintain a functional socially-demanded activity, and quality of life are emphasized.

[Significance of insulin resistance in the pathogenesis of sarcopenia and chronic heart failure in elderly hypertensive patients].

To determine the pathogenic role of insulin resistance in the formation of involutive sarcopenia and chronic heart failure (CHF) were examined 88 elderly patients with arterial hypertension (AH) and 32 elderly patients without cardiovascular disease by methods of carbohydrate metabolism and the level of brain natriuretic peptide precursor evaluation, muscle mass and strength measuring, echocardiography, 6 minute walking test. It was found that in the group of hypertensive patients with low mass and muscle strength significantly increased indices of insulin resistance and more expressed signs of the left ventricle myocardial dysfunction and functional class of heart failure, probably as a result of disorders of energy homeostasis, resulting from the deterioration of glucose into the muscle cells of the heart and skeletal muscles.

Impact of industrial contamination on the populations of small forest rodents.

Investigations performed for monitoring the impact of industrial contamination from the Kostomuksha ore mining and processing enterprise (northern Karelia) on the populations of forest mouse-like rodents revealed increased embryonic mortality (three to four times higher compared to the control) in breeding females from the areas contaminated by nitrogen and sulfur oxides within the territory studied. The toxicants also influence other parameters of the population: abundance dynamics, ecological and spatial structure of the population, and reproduction rates. The results demonstrate that the population reactions of species may turn out to be more accurate and demonstrative when estimating the consequences of industrial contamination than the direct concentrations of a particular toxicant in the animal body.

[Significance age-related predictors of chronic heart failure in determining the risk of death in elderly patients with hypertension].

In order to establish the prognostic value of age-related pathogenesis and the development of heart failure related to lipid peroxidation, endogenous subclinical inflammation, apoptosis, sarcopenia, interstitial myocardial fibrosis in the risk of mortality and survival rates, for the first time the results of echocardiography, enzyme immunoassay, bioimpedansmetry with the scale of the Seattle model of heart failure performed in 84 elderly patients with arterial hypertension stage II (middle age 68,3 +/- 1,8 years) were compared. We found that the increased activity of markers of chronic heart failure progression was associated with an increased risk of death in patients. We identified the most important indicators in assessing the risk of death and prognosis of heart failure in elderly patients; their timely correction will imply an increase in life expectancy of older patients with chronic heart failure.

Multiple spine boutons are formed after long-lasting LTP in the awake rat.

The formation of multiple spine boutons (MSBs) has been associated with cognitive abilities including hippocampal-dependent associative learning and memory. Data obtained from cultured hippocampal slices suggest that the long-term maintenance of synaptic plasticity requires the formation of new synaptic contacts on pre-existing synapses. This postulate however, has never been tested in the awake, freely moving animals. In the current study, we induced long-term potentiation (LTP) in the dentate gyrus (DG) of awake adult rats and performed 3-D reconstructions of electron micrographs from thin sections of both axonal boutons and dendritic spines, 24 h post-induction. The specificity of the observed changes was demonstrated by comparison with animals in which long-term depression (LTD) had been induced, or with animals in which LTP was blocked by an N-methyl-D-aspartate (NMDA) antagonist. Our data demonstrate that whilst the number of boutons remains unchanged, there is a marked increase in the number of synapses per bouton 24 h after the induction of LTP. Further, we demonstrate that this increase is specific to mushroom spines and not attributable to their division. The present investigation thus fills the gap existing between behavioural and in vitro studies on the role of MSB formation in synaptic plasticity and cognitive abilities.

[Pathogenetic significance of interstitial fibrosis in development myocardial dysfunction and chronic heart failure in elderly patients with arterial hypertension].

To estimate the pathogenetic significance of interstitial fibrosis in development myocardial dysfunction in elderly patients with arterial hypertension the complex investigation of 84 patients (76 women and 8 men), suffering from arterial hypertension (AH) II stage and practically healthy 22 persons of advanced age was spent. It is established, that expressiveness of myocardial fibrosis in the elderly patients with AH, confirmed by an increase of volume fraction of interstitial collagen was accompanied by authentic change of serous level markers of its exchange: decrease in concentration of the matrix metalloproteinasum-1 predecessor and increase its inhibitor. Progressing of myocardial dysfunction from diastolic variant to sistolo-diastolic one is interfaced to maintenance increase of extracellular matrix and its negative changes of serous markers, decrease of index collagen degradation, tolerance to physical activity, development forecasting adverse variants of heart remodelling

[Pathology of the anterior cingulate cortex in obsessive compulsive disorder].

In the present article the features of the functional activity of the anterior cingulate cortex (ACC), a key element of neuroanatomical brain system of an error detection, in drug-resistant forms of obsessive-compulsive disorder (OCD) are discussed on a basis of both original and literature data. Available data indicate the presence of functional deficit in the ACC during OCD. This allows to suggest that functions of the ACC in OCD patient are partially redistributed between other brain areas. Thus in contrast to the previously accepted notion, the ACC as the target ofstereotactic surgery for OCD is pathologically altered brain region. Probably this is the reason why stereotactic destruction of ACC does not lead to significant changes in the patient's psyche. The essence of the pathological reorganisation of the functional activity of the brain in OCD remains unclear and requires further investigation.

Single-shot pulse duration monitor for extreme ultraviolet and X-ray free-electron lasers.

The resolution of ultrafast studies performed at extreme ultraviolet and X-ray free-electron lasers is still limited by shot-to-shot variations of the temporal pulse characteristics. Here we show a versatile single-shot temporal diagnostic tool that allows the determination of the extreme ultraviolet pulse duration and the relative arrival time with respect to an external pump-probe laser pulse. This method is based on time-resolved optical probing of the transient reflectivity change due to linear absorption of the extreme ultraviolet pulse within a solid material. In this work, we present measurements performed at the FLASH free-electron laser. We determine the pulse duration at two distinct wavelengths, yielding (184±14) fs at 41.5 nm and (21±19) fs at 5.5 nm. Furthermore, we demonstrate the feasibility to operate the tool as an online diagnostic by using a 20-nm-thin Si3N4 membrane as target. Our results are supported by detailed numerical and analytical investigations.

[Apoptosis and interstitial fibrosis in development of myocardial remodelling in elderly patients with arterial hypertension].

To determine the apoptosis and interstitial myocardial fibrosis pathogenetic role in development of myocardium dysfunction we surveyed 84 patients of elderly age suffering from an arterial hypertension (AH) II stage by methods of echo- and dopplercardiometry, enzyme multiplied immunoassay of Nt-proBNP level, serumal markers of collagen exchange, apoptosis activity. The patients with normal geometrical model of heart due to AH demonstrated a low level of apoptosis and fibrosis activity. Structural reorganization of a myocardium from concentric to eccentric hypertrophy and concentric remodelling of left ventricle was characterized by strengthening of cellular apoptosis and interstitial myocardial fibrosis in extracellular matrix expressiveness, prevalence of collagen synthesis over collagen degradation, progressing of myocardium dysfunction.

Tracks and voids in amorphous Ge induced by swift heavy-ion irradiation.

Ion tracks formed in amorphous Ge by swift heavy-ion irradiation have been identified with experiment and modeling to yield unambiguous evidence of tracks in an amorphous semiconductor. Their underdense core and overdense shell result from quenched-in radially outward material flow. Following a solid-to-liquid phase transformation, the volume contraction necessary to accommodate the high-density molten phase produces voids, potentially the precursors to porosity, along the ion direction. Their bow-tie shape, reproduced by simulation, results from radially inward resolidification.