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

Anthropometric parameters in relation to glycaemic status and lipid profile in a multi-ethnic sample in Italy.

OBJECTIVE: To examine the health status of ethnic minorities in Italy. Furthermore, we aimed to assess the association between anthropometric and blood parameters connected with health status. DESIGN: A cross-sectional study. Anthropometric data were collected by direct measurements and blood glucose, total cholesterol and TAG were analysed. SETTING: Bologna, northern Italy. SUBJECTS: A multi-ethnic sample of adult immigrants and Roma. RESULTS: Significant correlations between anthropometric and blood parameters were found. Among the ethnic groups, Roma males had the highest values of glucose, total cholesterol and TAG. In the females the situation was more balanced among ethnic groups. CONCLUSIONS: The data from this survey indicate that poor health status is a very common problem among ethnic groups living in Italy, especially the Roma. The use of anthropometric parameters as rapid indicators of health status in screenings of a large number of subjects could be an effective and cheap method to provide preliminary indications on individuals or ethnic groups at greater risk of poor health

Time dependent thermal lensing measurements of V–T energy transfer from highly excited NO2

The time dependent thermal lensing technique has been used to measure the vibrational relaxation of NO2 (initially excited at 21 631 cm−1) by Ar, Kr, and Xe. The energy transfer analysis was carried out in terms of 〈〈ΔE〉〉, the bulk average energy transferred per collision. This quantity was found to have a very strong dependence on vibrational energy, with a marked increase at energies greater than about 10 000 cm−1, where several electronic excited states (2B2, 2B1, and 2A2) mix with the ground state (2A1). This effect may be due to large amplitude vibrational motions associated with the coupled electronic states. Even at low energies, deactivation is faster than in other triatomic systems, probably because NO2 is an open shell molecule and electronic curve crossings provide efficient pathways for vibrational deactivation. The V–T rate constant for deactivation of NO2(010) by argon is estimated to be (5.1±1.0)×10−14 cm3 s−1. Results obtained for NO@B|2–NO2 collisions gave 〈〈ΔE〉〉 values in good agreement with literature results from fluorescence quenching experiments, indicating that V–T may be more important than V–V energy transfer in the quenching process.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70683/2/JCPSA6-92-8-4793-1.pd

Maturity related differences in body composition assessed by classic and specific bioimpedance vector analysis among male elite youth soccer players

The aim of this study was to analyze the efficiency of classic and specific bioelectrical impedance vector analysis (BIVA) in the assessment of maturity related differences in body composition among male elite youth soccer players, and to provide bioelectrical impedance reference data for this category. A group of 178 players (aged 12.1 \ub1 1.6 years) were registered in a professional Italian soccer team participating in the first division (Serie A). They were divided into three groups according to their maturity status while bioelectrical resistance and reactance were obtained. The classic and specific BIVA procedures were applied, which correct bioelectrical values for body height and body geometry, respectively. Percentage of fat mass (FM%) and total body water (TBW (L)) were estimated from bioelectrical values. Age-specific z-scores of the predicted age at peak height velocity identified 29 players as earlier-, 126 as on time-, and 23 as later-maturing. TBW was higher (p < 0.01) in adolescents classified as \u201cearly\u201d maturity status compared to the other two groups and classic BIVA confirmed these results. Conversely, no differences in FM% were found among the groups. Specific vector length showed a higher correlation (r = 0.748) with FM% compared with the classic approach (r = 0.493). Classic vector length showed a stronger association (r = 120.955) with TBW compared with specific (r = 120.263). Specific BIVA turns out to be accurate for the analysis of FM% in athletes, while classic BIVA shows to be a valid approach to evaluate TBW. An original data set of bioelectric impedance reference values of male elite youth soccer players was provided

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

Comparison of the effect of different resistance training frequencies on phase angle and handgrip strength in obese women: A randomized controlled trial

Phase angle (PA) is a strong predictor of sarcopenia, fragility, and risk of mortality in obese people, while an optimal muscular function and handgrip strength (HS) are required to perform different daily activities. Although there is a general agreement that resistance training improves health status in obese people, the optimal weekly training frequency forPA and physical performance parameters is not clear.This study aimed to compare the effects of different weekly resistance training frequencies performed over a 24week exercise program on PA and HSin obese people. Forty-two women (56.2 \ub1 9.1 years, body mass index (BMI) 37.1 \ub1 4.9 kg/m2) were randomly allocatedto one of two groups: a group with a highweekly training frequency of three times a week (HIGH, n= 21) and a group that performed only one weekly session (LOW, n= 21). The groups trained with an identical exercise intensity and volume per session for 6 months. Before and after the intervention period, the participants were assessed for anthropometric measures, bioimpedance analysis, and HS. There was a significant group 7 time interaction (p<0.05) for waist circumference, bioimpedance reactance divided by body height (Xc/H), PA, and HS measures. In addition, only the HIGH group increased Xc/H, PA, and HS after the intervention period (p<0.05), even after adjusting for weight loss and menopausal status. Physical exercise performed three times a week promotes better adaptations in PA and HSwhen compared with the same program performed once a week in obese women