Free space optical system performance for a Gaussian beam propagating through non Kolmogorov weak turbulence

Atmospheric turbulence has been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately several experiments have been reported recently that show Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular in portions of the troposphere and stratosphere. It is known that free space laser system performance is limited by atmospheric turbulence. In this paper we use a non-Kolmogorov power spectrum which uses a generalized exponent instead of constant standard exponent value 11/3 and a generalized amplitude factor instead of constant value 0.033. Using this spectrum in weak turbulence, we carry out, for a Gaussian beam propagating along a horizontal path, analysis of long term beam spread, scintillation, probability of fade, mean signal to noise ratio and mean bit error rate as variation of the spectrum exponent. Our theoretical results show that for alpha values lower than 11/3 , but not for alpha close to 3 , there is a remarkable increase of scintillation and consequently a major penalty on the system performance. However when alpha assumes values close to 3 or for alpha values higher than 11/3 scintillation decreases leading to an improvement on the system performanc

Angle of arrival Fluctuations for Laser Beam Propagation through non Kolmogorov turbulence

Atmospheric turbulence induces significant variation on the angle-of-arrival of laser beams used in free space laser communication. Angle-of-arrival fluctuations of an optical wave in the plane of the receiver aperture can be described in terms of the phase structure function that already has been calculated by Kolmogorov\u27s power spectral density model. Unfortunately several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly. In this paper, for horizontal path and weak turbulence, we carry out analysis of angle-of-arrival fluctuations using a non Kolmogorov power spectrum which uses a generalized exponent factor instead of constant standard exponent value 11/3 and a generalized amplitude factor instead of constant value 0.033. Also our non Kolmogorov spectrum includes both inner scale and outer scale effects

Scintillation index of optical plane wave propagating through non Kolmogorov moderate-strong turbulence

An optical plane wave propagating through atmospheric turbulence is affected by irradiance fluctuations known as scintillation. The scintillation index of an optical wave in strong turbulence can be analyzed by extended Rytov theory, which uses filter functions to eliminate the effect of cell turbulence sizes that do not contribute to scintillation, and it already has been calculated by Kolmogorov\u27s power spectral density model. However several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric turbulence properly. In this paper, for a horizontal path, we use extended Rytov theory to carry out plane wave scintillation index analysis in non Kolmogorov strong turbulence. We do it using a non Kolmogorov power spectrum which uses a generalized exponent factor and a generalized amplitude factor. Although our final expressions for the scintillation have been obtained by extended Rytov theory, which is necessary to adopt in strong turbulence conditions, they reduce to the proper results also in weak turbulence

Editorial: New Training Strategies and Evaluation Methods for Improving Health and Physical Performance

Physical activity is among the most effective methods for improving health, body composition, and physical function, and its practice is suitable for every population [...]

Free-space optical system performance for laser beam propagation through non-Kolmogorov turbulence

It is well know that free-space laser system performance is limited by atmospheric turbulence. Most theoretical treatments have been described for many years by Kolmogorov\u27s power spectral density model because of its simplicity. Unfortunately, several experiments have been reported recently that show that the Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular, in portions of the troposphere and stratosphere. We present a non-Kolmogorov power spectrum that uses a generalized exponent instead of constant standard exponent value 11/3, and a generalized amplitude factor instead of constant value 0.033. Using this new spectrum in weak turbulence, we carry out, for a horizontal path, an analysis of long-term beam spread, scintillation index, probability of fade, mean signal-to-noise ratio (SNR), and mean bit error rate (BER) as variation of the spectrum exponent. Our theoretical results show that for alpha values lower than alpha=11/3, but not for alpha close to alpha=3, there is a remarkable increase of scintillation and consequently a major penalty on the system performance. However, when alpha assumes a value close to alpha=3 or for alpha values higher than alpha=11/3, scintillation decreases, leading to an improvement on the system performance

Loss of AND-34/BCAR3 Expression in Mice Results in Rupture of the Adult Lens

PURPOSE. AND-34/BCAR3 (Breast Cancer Anti-Estrogen Resistance 3) associates with the focal adhesion adaptor protein, p130CAS/BCAR1. Expression of AND-34 regulates epithelial cell growth pattern, motility, and growth factor dependence. We sought to establish the effects of the loss of AND-34 expression in a mammalian organism. METHODS. AND-34−/− mice were generated by homologous recombination. Histopathology, in situ hybridization, and western blotting were performed on murine tissues. RESULTS. Western analyses confirmed total loss of expression in AND-34−/− splenic lymphocytes. Mice lacking AND-34 are fertile and have normal longevity. While AND-34 is widely expressed in wild type mice, histologic analysis of multiple organs in AND-34−/− mice is unremarkable and analyses of lymphocyte development show no overt changes. A small percentage of AND-34−/− mice show distinctive small white eye lesions resulting from the migration of ruptured cortical lens tissue into the anterior chamber. Following initial vacuolization and liquefaction of the lens cortex first observed at postnatal day three, posterior lens rupture occurs in all AND-34−/− mice, beginning as early as three weeks and seen in all mice at three months. Western blot analysis and in situ hybridization confirmed the presence of AND-34 RNA and protein in lens epithelial cells, particularly at the lens equator. Prior data link AND-34 expression to the activation of Akt signaling. While Akt Ser 473 phosphorylation was readily detectable in AND-34+/+ lens epithelial cells, it was markedly reduced in the AND-34−/− lens epithelium. Basal levels of p130Cas phosphorylation were higher in AND-34+/+ than in AND-34−/− lens epithelium. CONCLUSIONS. These results demonstrate the loss of AND-34 dysregulates focal adhesion complex signaling in lens epithelial cells and suggest that AND-34-mediated signaling is required for maintenance of the structural integrity of the adult ocular lens.National Institutes of Health (RO1 CA114094); Logica Foundatio

Hydrophobic and Oleophobic Coatings Based on Perfluoropolyether/Silica Hybrids by the Sol-Gel Method

Glass substrates were spin-coated with a perfluoropolyether oligomer based organic-inorganic hybrid material, and prepared by the sol-gel process. Contact angle analysis and atomic force microscopic analysis were carried out to characterize the surface of the prepared coatings. All systems exhibited strong hydrophobic and oleopophobic characteristics. The wettability behavior was found to be almost independent of both molecular weight and functionality of the fluorinated oligomer. The low values obtained for the contact angle and surface tension indicate that surface segregation of perfluoropolyether segments is likely to take place within the network. On the basis of these results and the high quality of the obtained coatings, these materials could be used as functional coatings to impart water and oleo-repellent characteristics to glasses and other similar substrates

Multispace and Multilevel BDDC

BDDC method is the most advanced method from the Balancing family of iterative substructuring methods for the solution of large systems of linear algebraic equations arising from discretization of elliptic boundary value problems. In the case of many substructures, solving the coarse problem exactly becomes a bottleneck. Since the coarse problem in BDDC has the same structure as the original problem, it is straightforward to apply the BDDC method recursively to solve the coarse problem only approximately. In this paper, we formulate a new family of abstract Multispace BDDC methods and give condition number bounds from the abstract additive Schwarz preconditioning theory. The Multilevel BDDC is then treated as a special case of the Multispace BDDC and abstract multilevel condition number bounds are given. The abstract bounds yield polylogarithmic condition number bounds for an arbitrary fixed number of levels and scalar elliptic problems discretized by finite elements in two and three spatial dimensions. Numerical experiments confirm the theory.Comment: 26 pages, 3 figures, 2 tables, 20 references. Formal changes onl

Prevalence of overweight and obesity in adults from North Africa.

The share of North African immigrants in Europe is growing continuously. In this review, we aimed to systematically analyse and describe the literature on weight status and physical activity in North African adults, both in their home country and after immigration to Europe. Existing data on North African residents and on North African immigrants in Europe were analysed by a systematic search on PUBMED. There is a wide variation among countries in the prevalence of overweight/obesity, with immigrants showing higher values. The overall results revealed a higher prevalence of overweight and obesity in females than in males in North African residents. Females also show higher levels of obesity among immigrants. In particular, literature reports indicate that 1.3-47.8% of North African residents and 3.6-49.4% of North African immigrants in adult age are overweight or obese. Physical inactivity is higher than 20% in males and 40% in females in North African residents. The highest frequency of physically inactive or lightly active people among immigrants was observed in first-generation Sudanese and Moroccans in Amsterdam (males: 57.1%; females: 74.2%), with increasing rates in second-generation females. The results underline a higher health risk in North African immigrants than in residents. Specific public health strategies should be adopted in various populations of North African origin to control the obesity epidemic