Black Holes in Higher-Dimensional Gravity

These lectures review some of the recent progress in uncovering the phase structure of black hole solutions in higher-dimensional vacuum Einstein gravity. The two classes on which we focus are Kaluza-Klein black holes, i.e. static solutions with an event horizon in asymptotically flat spaces with compact directions, and stationary solutions with an event horizon in asymptotically flat space. Highlights include the recently constructed multi-black hole configurations on the cylinder and thin rotating black rings in dimensions higher than five. The phase diagram that is emerging for each of the two classes will be discussed, including an intriguing connection that relates the phase structure of Kaluza-Klein black holes with that of asymptotically flat rotating black holes.Comment: latex, 49 pages, 5 figures. Lectures to appear in the proceedings of the Fourth Aegean Summer School, Mytiline, Lesvos, Greece, September 17-22, 200

Quartz ceramics modified by nanodispersed silica additive

The article considers one of the ways to improve physical and technical characteristics of Quartz Ceramics. The method consists in adding the sintering activator into the quartz ceramic composition, i.e. Nanodispersed Silicon Dioxide obtained by means of sol-gel method based on Ethyl Silicate or Tetraethoxysilane. The amount of the additive amounts to 10 wt.%. Samples containing the activator absorb water 40-45 % less than the samples without activator, while the mechanical strength is increasing by 1.2-1.3 times. Moreover, this activator prevents the formation of Cristobalite phase being undesirable in the Quartz Ceramics

Radio-transparent ceramic materials of spodumene-cordierite composition

The paper deals with the processes of obtaining radio-transparent ceramic materials with a complex of high physical and chemical indices. Directional regulation of the ceramics' microstructure and phase composition was carried out by introducing Li₂O-Al₂O₃-B₂O₃-SiO² (LABS) glass into main matrix that consisted of cordierite phase. Optimal composition and temperature conditions for firing of the developed spodumene-cordierite ceramics were established. It is shown that the introduction of LABS glass into experimental compositions contributes to significant intensification of the process of formation of α-cordierite crystalline phase, as well as sintering of ceramic materials obtained. Besides, the product of crystallization of parent glass is β-spodumene which promotes the reduction of CLTE of the obtained ceramic material, on average, to (12.4-17.8)·10⁻⁷ deg⁻¹. The highest indices of mechanical compressive strength (165.8-202.6 MPa) and thermal stability (not lower than 1050 °C) are achieved at the most rational content of LABS glass is 10-20 wt. %. Under this composition the water absorption is within 0.28-0.34 %, apparent density 2.16-2.18 g/cm³, CLTE (16.6-17.8)·10⁻⁷ deg⁻¹. Studies of electrophysical properties of the developed material at the frequency of 10¹⁰ Hz showed that the level of the dielectric constant (ε = 3.8) and dielectric losses (tg δ = 0.0014) spodumene-cordierite ceramics synthesized at reduced temperature of 1300-1350 °C are fully complied with the requirements to the modern radio-transparent materials

Adaptation of the Er-Yb microchip laser for use in phase-sensitive optical time domain reflectometry

We report on the experiments related to the Er-Yb microchip laser setup with fiber diode pumping. The main goal is a new radiation source for the use in the phase-sensitive optical time domain reflectometry (-OTDR) development

Structure impact on photodynamic therapy and cellular contrasting functions of colloids constructed from dimeric Au(I) complex and hexamolybdenum clusters

Electrostatically driven self-assembly of [Au2L2]2+ (L is cyclic PNNP ligand) with [{Mo6I8}(L')6]2− (L' = I−, CH3COO−) in aqueous solutions is introduced as facile route for combination of therapeutic and cellular contrasting functions within heterometallic colloids (Mo6-Au2). The nature of L' affects the size and aggregation behavior of crystalline Mo6-Au2 aggregates, which in turn affect the luminescence of the cluster units incorporated into Mo6-Au2 colloids. The spin trap facilitated electron spin resonance spectroscopy technique indicates that the level of ROS generated by Mo6-Au2 colloids is also affected by their size. Both (L' = I−, CH3COO−) Mo6-Au2 colloids undergo cell internalization, which is enhanced by their assembly with poly-DL-lysine (PL) for L' = CH3COO−, but remains unchanged for L' = I−. The colloids PL-Mo6-Au2 (L' = CH3COO−) are visualized as huge crystalline aggregates both outside and inside the cell cytoplasm by confocal microscopy imaging of the incubated cells, while the smaller sized (30–50 nm) PL-Mo6-Au2 (L' = I−) efficiently stain the cell nuclei. Quantitative colocalization analysis of PL-Mo6-Au2 (L' = CH3COO−) in lysosomal compartments points to the fast endo-lysosomal escape of the colloids followed by their intracellular aggregation. The cytotoxicity of PL-Mo6-Au2 differs from that of Mo6 and Au2 blocks, predominantly acting through apoptotic pathway. The photodynamic therapeutic effect of the PL-Mo6-Au2 colloids on the cancer cells correlates with their intracellular trafficking and aggregation