Dynamics of Switching Waves in a Nanofluid in a Light Field

The dynamics of the concentration of nanofluids placed in a light field with a Gaussian intensity profile is studied theoretically. The investigation is based on the analytical and numerical solutions of the system of linearized heat conduction and convectiondiffusion equations. The convection-diffusion equation contains terms that correspond both to the Soret effect and to the transfer of nanoparticles, caused by the action of a light field on them (electrostriction). The dependence of the coefficient of thermal conductivity of the medium on the concentration is taken into account. It is shown that under these conditions single travelling waves appear in the medium, the velocity of which depends not only on the thermal physical parameters of the medium, but also on the polarization of the particles. Conditions under which the stratification of the medium is possible are found

Direct measurements of hydrophobic slippage using double-focus fluorescence cross-correlation

We report results of direct measurements of velocity profiles in a microchannel with hydrophobic and hydrophilic walls, using a new high precision method of double-focus spacial fluorescence cross-correlation under a confocal microscope. In the vicinity of both walls the measured velocity profiles do not turn to zero by giving a plateau of constant velocity. This apparent slip is proven to be due to a Taylor dispersion, an augmented by shear diffusion of nanotracers in the direction of flow. Comparing the velocity profiles near the hydrophobic and hydrophilic walls for various conditions shows that there is a true slip length due to hydrophobicity. This length, of the order of several tens of nanometers, is independent on electrolyte concentration and shear rate

Surface Roughness and Effective Stick-Slip Motion

The effect of random surface roughness on hydrodynamics of viscous incompressible liquid is discussed. Roughness-driven contributions to hydrodynamic flows, energy dissipation, and friction force are calculated in a wide range of parameters. When the hydrodynamic decay length (the viscous wave penetration depth) is larger than the size of random surface inhomogeneities, it is possible to replace a random rough surface by effective stick-slip boundary conditions on a flat surface with two constants: the stick-slip length and the renormalization of viscosity near the boundary. The stick-slip length and the renormalization coefficient are expressed explicitly via the correlation function of random surface inhomogeneities. The effective stick-slip length is always negative signifying the effective slow-down of the hydrodynamic flows by the rough surface (stick rather than slip motion). A simple hydrodynamic model is presented as an illustration of these general hydrodynamic results. The effective boundary parameters are analyzed numerically for Gaussian, power-law and exponentially decaying correlators with various indices. The maximum on the frequency dependence of the dissipation allows one to extract the correlation radius (characteristic size) of the surface inhomogeneities directly from, for example, experiments with torsional quartz oscillators.Comment: RevTeX4, 14 pages, 3 figure

Extremely broadband ultralight thermally emissive metasurfaces

We report the design, fabrication and characterization of ultralight highly emissive metaphotonic structures with record-low mass/area that emit thermal radiation efficiently over a broad spectral (2 to 35 microns) and angular (0-60 degrees) range. The structures comprise one to three pairs of alternating nanometer-scale metallic and dielectric layers, and have measured effective 300 K hemispherical emissivities of 0.7 to 0.9. To our knowledge, these structures, which are all subwavelength in thickness are the lightest reported metasurfaces with comparable infrared emissivity. The superior optical properties, together with their mechanical flexibility, low outgassing, and low areal mass, suggest that these metasurfaces are candidates for thermal management in applications demanding of ultralight flexible structures, including aerospace applications, ultralight photovoltaics, lightweight flexible electronics, and textiles for thermal insulation

Aspectos metodológicos de la evaluación de la eficiencia de la política social regional en la superación de la orfandad social

Among the methodological issues of studying the problem of social orphanhood, an important place is occupied by the search for effective markers for assessing dynamics on the one hand, and the effectiveness of social policy in overcoming social orphanhood on the other. That attempt to systematically evaluate the scale and severity of the phenomenon, as well as the key factors that determine its dynamics. However, these approaches do not allow us to identify the connection between social work and the dynamics of improving the situation with social orphanhood in the region. The presented study proposes a new model for assessing the dynamics of social orphanhood. Its difference from other methodological approaches is that the main emphasis is on assessing the orientation of the complex of shifts in the processes of identifying, placement of orphans and canceling decisions on their transfer to families. This model allows us to assess the role of social policy in overcoming social orphanhood. In this model, we developed authoring methods for ranking the regions of Russia by the dynamics of indicators integrated into the "auspiciousness" index of changes in the social orphanhood. Also, the author presents a model that assesses the situation in the region from the point of view of the "social support efficiency index" to overcome the social orphanhood. The models used to assess the dynamics of social orphanhood have been tested as a tool for identifying key markers of the efficiency of social policy.Entre las cuestiones metodológicas de estudiar el problema de la orfandad social, un lugar importante está ocupado por la búsqueda de marcadores efectivos para evaluar la dinámica, por un lado, y la efectividad de la política social para superar la orfandad social, por el otro. Ese intento de evaluar sistemáticamente la escala y la gravedad del fenómeno, así como los factores clave que determinan su dinámica. Sin embargo, estos enfoques no nos permiten identificar la conexión entre el trabajo social y la dinámica de mejorar la situación con la orfandad social en la región. El estudio presentado propone un nuevo modelo para evaluar la dinámica de la orfandad social. Su diferencia con otros enfoques metodológicos es que el énfasis principal está en evaluar la orientación del complejo de cambios en los procesos de identificación, colocación de huérfanos y cancelación de decisiones sobre su transferencia a las familias. Este modelo nos permite evaluar el papel de la política social en la superación de la orfandad social. En este modelo, desarrollamos métodos de autor para clasificar las regiones de Rusia por la dinámica de los indicadores integrados en el índice de "auspiciosidad" de los cambios en la orfandad social. Además, el autor presenta un modelo que evalúa la situación en la región desde el punto de vista del "índice de eficiencia del apoyo social" para superar la orfandad social. Los modelos utilizados para evaluar la dinámica de la orfandad social se han probado como una herramienta para identificar marcadores clave de la eficiencia de la política social

Optical echo in photonic crystals

The dynamics of photonic wavepacket in the effective oscillator potential is studied. The oscillator potential is constructed on a base of one dimensional photonic crystal with a period of unit cell adiabatically varied in space. The structure has a locally equidistant discrete spectrum. This leads to an echo effect, i.e. the periodical reconstruction of the packet shape. The effect can be observed in a nonlinear response of the system. Numerical estimations for porous-silicon based structures are presented for femtosecond Ti:Sapphire laser pump.Comment: 4 page

Lattice Boltzmann simulations in microfluidics: probing the no-slip boundary condition in hydrophobic, rough, and surface nanobubble laden microchannels

In this contribution we review recent efforts on investigations of the effect of (apparent) boundary slip by utilizing lattice Boltzmann simulations. We demonstrate the applicability of the method to treat fundamental questions in microfluidics by investigating fluid flow in hydrophobic and rough microchannels as well as over surfaces covered by nano- or microscale gas bubbles.Comment: 11 pages, 6 figure

Contents of heavy metals in fructicose epiphytic lichens of Karelia as indicator of atmospheric transport of pollutants

Results of studies of heavy metals contents in fruticose epiphytic lichens in Karelia are presented and the influence of different sources on the elemental composition of lichens has been estimated. It has been shown, that long-range atmospheric transport influences strongly the accumulation of Pb, Zn, Cd, Sb. For Al, Fe and Co lithogenic source is the main one. In the Northern Karelia atmospheric transport of Cu, Co and Ni from metallurgic enterprises of the Murmansk Region is important source of these elements

Comprehensive analysis of draft genomes of two closely related pseudomonas syringae phylogroup 2b strains infecting mono- and dicotyledon host plants

Comparison of the prophage region in Pseudomonas syringae strain SM (A) with the corresponding regions in strains 1845 (B) and 2507 (C) using MAUVE software (Darling et al. 2010). (PNG 2118 kb

Prednisolone Targets Claudins in Mouse Brain Blood Vessels

Endothelial cells in brain capillaries are crucial for the function of the blood–brain barrier (BBB), and members of the tight junction protein family of claudins are regarded to be primarily responsible for barrier properties. Thus, the analysis of bioactive substances that can affect the BBB’s permeability is of great importance and may be useful for the development of new therapeutic strategies for brain pathologies. In our study, we tested the hypothesis that the application of the glucocorticoid prednisolone affects the murine blood–brain barrier in vivo. Isolated brain tissue of control and prednisolone-injected mice was examined by employing immunoblotting and confocal laser scanning immunofluorescence microscopy, and the physiological and behavioral effects were analyzed. The control tissue samples revealed the expression of barrier-forming tight junction proteins claudin-1, -3, and -5 and of the paracellular cation and water-channel-forming protein claudin-2. Prednisolone administration for 7 days at doses of 70 mg/kg caused physiological and behavioral effects and downregulated claudin-1 and -3 and the channel-forming claudin-2 without altering their localization in cerebral blood vessels. Changes in the expression of these claudins might have effects on the ionic and acid–base balance in brain tissue, suggesting the relevance of our findings for therapeutic options in disorders such as cerebral edema and psychiatric failure