Kazan Federal University

About: Kazan Federal University is a education organization based out in Kazan’, Russia. It is known for research contribution in the topics: Population & Chemistry. The organization has 9868 authors who have published 14390 publications receiving 135726 citations. The organization is also known as: Kazan (Volga region) Federal University & Kazan State University.

Calibrated entanglement entropy

Abstract: The Ryu-Takayanagi prescription reduces the problem of calculating entanglement entropy in CFTs to the determination of minimal surfaces in a dual anti-de Sitter geometry. For 3D gravity theories and BTZ black holes, we identify the minimal surfaces as special Lagrangian cycles calibrated by the real part of the holomorphic one-form of a spacelike hypersurface. We show that (generalised) calibrations provide a unified way to determine holographic entanglement entropy from minimal surfaces, which is applicable to warped AdS3 geometries. We briefly discuss generalisations to higher dimensions.

RNase1 as a potential mediator of remote ischaemic preconditioning for cardioprotection

Abstract: OBJECTIVES: Remote ischaemic preconditioning (RIPC) is a non-invasive and virtually cost-free strategy for protecting the heart against acute ischaemia–reperfusion injury (IRI). We have recently shown that the inhibition of extracellular RNA (eRNA) using non-toxic RNase1 protected the heart against acute IRI, reduced myocardial infarct (MI) size and preserved left ventricular systolic function in rodent animal MI models. Based on this previous work in animals, the role of the eRNA/RNase1 system in cardiac RIPC in humans should be defined. METHODS: Fourteen patients underwent cardiac surgery without RIPC; from each patient, six separate 5 ml blood specimens from radial artery and two blood specimens from coronary sinus at different time points during heart surgery were taken. Six healthy donors received RIPC (4 × 5 min upper limb ischaemia); blood parameters were quantified before and after RIPC. Twelve patients underwent cardiac surgery of which 6 received RIPC, whereas the remaining 6 were exposed to sham procedure. Circulating eRNA was quantified in plasma from arterial and coronary sinus blood obtained from patients undergoing cardiac by standard procedures. Tumour necrosis factor-α (TNF-α) production by heart tissue was assessed by enzyme-linked immuno-sorbent assay; RNase activity was quantified by an enzymatic assay. RESULTS: Before surgery, eRNA levels were similar in both groups (14 ± 6 vs 13 ± 5 ng/ml; P= 0.9967). In patients without RIPC, arterial eRNA levels rose during surgery (87 ± 12 ng/ml) and peaked after (127 ± 11 ng/ml) aortic declamping; accordingly, eRNA levels in coronary sinus blood were significantly higher (206 ± 32 ng/ml; P= 0.0129) than that in radial artery. Moreover, significant elevation of TNF-α (36 ± 6 ng/ml; P= 0.0059) particularly in coronary sinus blood after opening of the aortic clamping was observed. Interestingly, applying a RIPC protocol significantly increased levels of plasma endogenous vascular RNase1 by >7-fold, and the levels of arterial (31 ± 7 ng/ml; P= 0.0024) and coronary sinus (37 ± 9 ng/ml; P< 0.0001) circulating eRNA, as well as circulating TNF-α (20 ± 4 ng/ml; P= 0.0050) levels were significantly reduced. CONCLUSIONS: Upon RIPC, the level of cardioprotective RNase1 increased, while the concentration of damaging eRNA and TNF-α decreased. The present findings imply a significant contribution of the RIPC-dependent (endothelial) RNase1 for improving the outcome of cardiac surgery. However, the exact mechanism of RNase1-induced cardioprotection still remains to be explored.

New Derivatives of Pyridoxine Exhibit High Antibacterial Activity against Biofilm-Embedded Staphylococcus Cells.

Abstract: Opportunistic bacteria Staphylococcus aureus and Staphylococcus epidermidis often form rigid biofilms on tissues and inorganic surfaces. In the biofilm bacterial cells are embedded in a self-produced polysaccharide matrix and thereby are inaccessible to biocides, antibiotics, or host immune system. Here we show the antibacterial activity of newly synthesized cationic biocides, the quaternary ammonium, and bisphosphonium salts of pyridoxine (vitamin B6) against biofilm-embedded Staphylococci. The derivatives of 6-hydroxymethylpyridoxine were ineffective against biofilm-embedded S. aureus and S. epidermidis at concentrations up to 64 μg/mL, although all compounds tested exhibited low MICs (2 μg/mL) against planktonic cells. In contrast, the quaternary ammonium salt of pyridoxine (N,N-dimethyl-N-((2,2,8-trimethyl-4H-[1,3]dioxino[4,5-c]pyridin-5-yl)methyl)octadecan-1-aminium chloride (3)) demonstrated high biocidal activity against both planktonic and biofilm-embedded bacteria. Thus, the complete death of biofilm-embedded S. aureus and S. epidermidis cells was obtained at concentrations of 64 and 16 μg/mL, respectively. We suggest that the quaternary ammonium salts of pyridoxine are perspective to design new synthetic antibiotics and disinfectants for external application against biofilm-embedded cells.

The dynamic crossover in dielectric relaxation behavior of ice Ih

Abstract: The main mechanism of the dielectric relaxation process of ordinary hexagonal ice (ice Ih) and its temperature dependence remains unclear. The most interesting and as yet unexplained feature of ice is the presence of the dynamical crossover in relaxation time behavior around Tc = 230 ± 3 K. Since there are no phase transitions in the ice at this temperature (first or second order), we cannot correlate the origin of this crossover with any structural change. Here we present a model according to which the temperature of the crossover is defined by the polarization mechanism. The dielectric relaxation driven by the diffusion of L–D orientational Bjerrum defects (at high temperature, T > Tc) is transformed into a dielectric relaxation dominated by the diffusion of intrinsic ionic H3O+/OH− defects (at low temperature, T < Tc). In the framework of the model, we propose an analytical equation for the complex dielectric permittivity that takes into account the contribution of both types of defects.

Contact statement of mechanical problems of reinforced on a contour sandwich plates with transversally-soft core

Abstract: For the sandwich plates and shells with transversally-soft core and carrier layers having on the outer contour of the reinforcing rod, for small deformations, and middle displacements we construct refined geometrically nonlinear theory. This theory allows to describe the process of the subcritical deformation and identify all possible buckling of carrier layers and reinforcing rods. It is based on the introduction as unknown contact forces at the points of interaction mating surface of the outer layers with core and carrier layers and a core with reinforcing rods at all points of the surface of their conjugation to the shell contour. To derive the basic equations of equilibrium, static boundary conditions for the shell and reinforcing rods, as well as conditions of the kinematic coupling of the carrier layers with a core, the carrier layers and a core with reinforcing rods we use previously proposed generalized Lagrange variational principle.