Year-to-year dynamics of trophic links of the main commercial fishes in the Barents Sea as indicating the state of ecosystem

Ecosystem dynamics and optimal long-term harvest in the Barents Sea fisheries. Proceedings of the 11th Russian-Norwegian Symposium. Murmansk, 15-17 August 2005

Numerical study of the effect of methemoglobin concentration in the blood on the absorption of light by human skin

Lasers are widely used in dermatology to remove telangiectasias. Increasing the efficiency of sclerosis of deep-lying and large telangiectasias with laser radiation is possible by changing the optical transmission of the skin when it is heated and converting the hemoglobin of the blood contained in it into methemoglobin. The influence of the concentration of methemoglobin in the blood on the absorption of light in human skin is poorly understood, which determines the relevance of this study in the context of finding ways to improve the efficiency of laser removal of telangiectasias. Seven-layer optical models of human skin without telangiectasia and with it for numerical simulation were developed. The extinction coefficients and the degree of change in the optical transmission of whole blood and skin layers were calculated in the range of wavelength from 400 to 1600 nm for skin model without and with arteriolar and venular telangiectasias at various concentrations of methemoglobin in the blood. Based on the analysis of these data, the wavelengths with the biggest change in the optical transmission of whole blood and skin layers occurred during the transformation of hemoglobin to methemoglobin were selected. At the selected wavelengths, the Monte Carlo method was used in optical modelling to get the distribution of the absorbed optical power in each layer of the skin model without and with telangiectasia at various concentrations of methemoglobin. It has been shown that the spectra of extinction coefficients for arteriolar and venular telangiectasias do not differ significantly. During the transformation of hemoglobin to methemoglobin, the largest decrease in the degree of change in the optical transmission of whole blood occurs at wavelengths of 629 nm and 1105 nm, and the largest increase occurs at wavelengths of 447 nm and 578 nm. The part of absorbed optical power in the layer of superficial vascular plexus without and with telangiectasia at wavelengths of 629 nm and 1105 nm increases, and at wavelengths of 441 nm and 574 nm it decreases with a growth of the methemoglobin concentration from 0 to 100 % in the skin model. At the same time, in the layer of deep vascular plexus the value of part of absorbed optical power increases at wavelengths of 441 nm, 574 nm and 1105 nm, but at a wavelength of 629 nm first increases with a growth of the methemoglobin concentration up to 25 %, and then decreases, but to values exceeding the value of part of absorbed optical power without methemoglobin. The change in optical transmission associated with the replacement of blood hemoglobin with methemoglobin is more pronounced for the superficial vascular plexus layer, which is associated with high blood content in it and a limited contribution of the overlying skin layers to the deformation of the spectrum of light incident on this layer. In skin with telangiectasia, a change in the concentration of methemoglobin changes the proportion of absorbed optical power by a greater amount than in skin without telangiectasia, which can be associated with an increase in the volume concentration of blood in skin layers with telangiectasia and an increase in their thickness. The obtained results can be applied in the development of laser systems and technologies for the treatment of skin diseases, including laser sclerosis of telangiectasias

Barriers to motion and rotation of graphene layers based on measurements of shear mode frequencies

Both van der Waals corrected density functional theory and classical calculations show that the potential relief of interaction energy between layers of graphite and few-layer graphene can be described by a simple expression containing only the first Fourier components. Thus a set of physical quantities and phenomena associated with in-plane relative vibration, translational motion and rotation of graphene layers are interrelated and are determined by a single parameter characterizing the roughness of the potential energy relief. This relationship is used to estimate the barriers to relative motion and rotation of graphene layers based on experimental measurements of shear mode frequencies.Comment: 16 pages, 1 figur

Effect of Peierls transition in armchair carbon nanotube on dynamical behaviour of encapsulated fullerene

The changes of dynamical behaviour of a single fullerene molecule inside an armchair carbon nanotube caused by the structural Peierls transition in the nanotube are considered. The structures of the smallest C20 and Fe@C20 fullerenes are computed using the spin-polarized density functional theory. Significant changes of the barriers for motion along the nanotube axis and rotation of these fullerenes inside the (8,8) nanotube are found at the Peierls transition. It is shown that the coefficients of translational and rotational diffusions of these fullerenes inside the nanotube change by several orders of magnitude. The possibility of inverse orientational melting, i.e. with a decrease of temperature, for the systems under consideration is predicted.Comment: 9 pages, 6 figures, 1 tabl

Centrality evolution of the charged-particle pseudorapidity density over a broad pseudorapidity range in Pb-Pb collisions at root s(NN)=2.76TeV

Peer reviewe

Year-to-year dynamics of trophic links of the main commercial fishes in the Barents Sea as indicating the state of ecosystem

Ecosystem dynamics and optimal long-term harvest in the Barents Sea fisheries. Proceedings of the 11th Russian-Norwegian Symposium. Murmansk, 15-17 August 2005

Year-to-year dynamics of trophic links of the main commercial fishes in the Barents Sea as indicating the state of ecosystem [presentation]

Ecosystem dynamics and optimal long-term harvest in the Barents Sea fisheries. Proceedings of the 11th Russian-Norwegian Symposium. Murmansk, 15-17 August 2005

Controlling the Temperature on the Vein Wall Based on the Analysis of the IR Signal during Endovasal Laser Treatment

Possibility of controlling the temperature of the vein wall during endovasal laser treatment (EVLT) is investigated. The desired medical effect is achieved by the coagulation of the vein wall at the temperature of 80 °C. Heating of the vein wall is mainly due to the efficient conversion of laser radiation into heat in an optothermal fiber converter (OTFC) located at the output end of the optical fiber placed inside the vein. Titanium-containing optothermal fiber converter (TOTFC) is very promising for EVLT application due to its high efficiency in converting laser energy into thermal energy and its smooth shape that excludes perforation of the vein wall when the fiber moves inside the vein. During the endovasal laser treatment heated by laser radiation TOTFC emits an IR signal which can be used for controlling the temperature on the vein wall during endovasal laser treatment. At present study, a computer thermophysical model of the EVLT with TOTFC has been developed in the COMSOL Multiphysics 5.4 program (COMSOL Inc., Burlington, MA, USA). In the EVLT model, a laser radiation wavelength of 980 nm with an average laser power of 8–14 W to the traction speed of the optical fiber in range of 1–7 mm/s is applied. The dependence of the TOTFC temperature and the temperature on the vein wall has been numerically investigated. In accordance with Planck’s formula, the dependence of the spectral luminosity density of a blackbody simulating IR signal from TOTFC on its temperature has been determined. The spectral luminosity density in a wide range the wavelength of 0.4–20 μm, as well as in spectral ranges limited by the transmission of the quartz fiber and the sensitivity of Ge and PbS photodetectors was defined. The possibility of controlling the average power of the laser radiation depending on the magnitude of the change in the spectral luminosity density of TOTFC during EVLT is demonstrated. The results obtained can be useful in developing laser medical equipment and materials for use in vascular surgery at endovasal laser treatment