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We employ a Monte Carlo ray-tracing code along with the ANSYS package to predict the optical and structural behavior in end-pumped CW Yb:YAG disk lasers. The presence of inhomogeneous temperature, stress, and strain distributions is responsible for many deleterious effects for laser action through disk fracture, strain-induced birefringence, and thermal lensing. The thermal lensing, in turn, results in the optical phase distortion in solid-state lasers. Furthermore, the dependence of optical phase distortion on variables such as the heat transfer coefficient, the cooling fluid temperature, and crystal thickness is discussed. [c] 2010 Optical Society of America OCIS codes: 140.0140, 140.3480, 140.6810, 190.4870.

Generation of the terahertz (THz) radiation based on the beating of two cross‐focused high intensity Gaussian laser beams in a warm rippled density plasma is numerically investigated, taking into account the ponderomotive force, Ohmic heating, and collisional nonlinearities. The beat ponderomotive force as a result of cross‐focusing of beams induces a vertical velocity component that by coupling with the rippled density gives rise to a nonlinear current deriving THz radiation. The effect of laser beams spot size evolution and plasma parameters on the THz generation is studied. It was found that there exist special electron temperature and laser intensity ranges with "turning points" where the generation of THz radiation reaches its maximum value and outside of these ranges, it disappears. The results also indicated that increasing the background electron density as well as taking into account the collision frequency help THz generation. Moreover, the maximum yield of THz radiation occurs when the beat wave frequency approaches the plasma frequency. [ABSTRACT FROM AUTHOR]

Mother's and infant exposure to cigarette smoke is one of the most important public health problems. There is no study in Iran evaluating the impact of cigarette smoke on infant growth and development. The purpose of this study was to determine the effects of cigarette. This prospective cohort study was conducted on 51 cigarette smoke-exposed infants (exposed group) and 51 non-exposed infants (non-exposed group). They were evaluated for weight, height and head circumference three times; five to seven days, two months and four months after birth. Urine samples were also collected in each turn. Exposure to secondhand smoke was assessed through questionnaires and urinary cotinine levels. The analysis was performed using an independent t-test, Mann-Whitney U test, chi-square and Fisher's exact and Kappa tests. Mean urinary cotinine level in the exposed group was 38.57±2.85 ng/mg creatinine at baseline, 86.95±1.16 at two months and 63.32±2.08 at four months of age. These indicated a gradual reduction of exposure from two to four months. The weight and height of the exposed group were significantly lower than the non-exposed group (P<0.001) at two and four months after birth. The results of the present study showed that the exposure to secondhand smoke during infancy may lead to weight and height growth reduction in the first four months of life. [ABSTRACT FROM AUTHOR]

The interaction between a high-power electromagnetic wave with an inhomogeneous underdense plasma is studied by considering the ohmic heating caused by laser radiation. Considering the plasma inhomogeneity and ohmic heating, the nonlinear dielectric permittivity is obtained in the collisional regimes. The wave equation is numerically solved and the electromagnetic fields, electron density, electron temperature, and dielectric permittivity profiles are achieved. These profiles show that in the presence of three density profiles, by increasing the laser energy flux, the modified electron density deviates from background electron density and its structure near the critical density becomes highly peaked. Finally, it is found that the amplitude of electron density distribution decreases by increasing the laser wavelength. [ABSTRACT FROM PUBLISHER]

The propagation characters of an intense Gaussian laser beam in underdense plasma are investigated taking into account the combined effects of relativistic and ponderomotive nonlinearities. The nonlinear second-order differential equation of the dimensionless beamwidth parameter is obtained and numerically solved. The effect of initial electron temperature on self-focusing and defocusing of Gaussian laser beam propagation in plasma are studied. Moreover, the behavior and variation of modified electron density and laser beam intensity as a function of plasma length in both self-focusing and defocusing regimes are discussed. [ABSTRACT FROM AUTHOR]

Background: American pediatric Association proposes to screen all neonates with Oto-Acoustic Emission (OAE). In developing countries, because of several limitations, health policy makers recommend to screen only in high risk patients. This study is performed with the aim to screen hearing loss in 950 high risk newborns hospitalized in hospitals affiliated to Tehran University using the OAE test. Methods: A total of 950 neonates hospitalized in the Neonatal and NICU wards of Valie- Asr, Shariati, Medical Center and Bahrami Hospitals during the years 2004-2006 who showed at least one risk factor using TEOAE hearing test were enrolled into this crosssectional descriptive analytical study and were diagnosed with mild deafness and total deafness. Blood exchange due to hyperbillirubinemia, septicemia, congenital heart disease, the fifth minute apgar scores below six, PROM more than six hours, epilepsia, need to NICU more than five hours, pneumonia and Oto-Toxic drugs were considered as risk factors. Data was past medical history, current disease, admission cause, sign & symptoms and complications of disease. Results: Multivariate logistic regression and paired t-test showed that blood exchange, low birth weight and low first minute Apgar scores had the highest independent risk for hearing loss among newborn. Conclusion: Despite of the low prevalence of neonatal hearing loss, screening of hearing loss at early stages is important. [ABSTRACT FROM AUTHOR]

Ophthalmia neonatorum is a form of bacterial conjunctivitis contracted by newborns during delivery and occurs during the first month of life. Etiologic factors include Neisseria gonorrhoeae, Chlamydia trachomatis, viruses and chemicals. Its prevalence differs in different parts of the world and is dependent mainly upon socioeconomic conditions, level of knowledge about general health, standard of maternal healthcare as well as the type of prophylactic program used. This randomized clinical trial was performed during the years 2004–05 in the Delivery Section of Vali-e-Asr Hospital on 330 neonates who were divided into three equal groups of 110; Group A received betadine eye drops, Group B received Erythromycin eye drops and Group C (control group) received no treatment. Results showed that clinical conjunctivitis occurred in 52 subjects (17%), 58% of whom constituted males. On the whole, 9% of the infected newborns were from group A, 18.4% from group B and 22.4% from group C. It was concluded that 2.5% sterile betadine eye drops had a pronounced effect on ophthalmia neonatorum (p = 0.030). [ABSTRACT FROM AUTHOR]

This study focuses on multiple linear regression models relating six climate indices (temperature humidity THI, environmental stress ESI, equivalent temperature index ETI, heat load HLI, modified HLI (HLI new ), and respiratory rate predictor RRP) with three main components of cow's milk (yield, fat, and protein) for cows in Iran. The least absolute shrinkage selection operator (LASSO) and the Akaike information criterion (AIC) techniques are applied to select the best model for milk predictands with the smallest number of climate predictors. Uncertainty estimation is employed by applying bootstrapping through resampling. Cross validation is used to avoid over-fitting. Climatic parameters are calculated from the NASA-MERRA global atmospheric reanalysis. Milk data for the months from April to September, 2002 to 2010 are used. The best linear regression models are found in spring between milk yield as the predictand and THI, ESI, ETI, HLI, and RRP as predictors with p -value < 0.001 and R ² (0.50, 0.49) respectively. In summer, milk yield with independent variables of THI, ETI, and ESI show the highest relation ( p -value < 0.001) with R ² (0.69). For fat and protein the results are only marginal. This method is suggested for the impact studies of climate variability/change on agriculture and food science fields when short-time series or data with large uncertainty are available.

This study analyzes the linear relationship between climate variables and milk components in Iran by applying bootstrapping to include and assess the uncertainty. The climate parameters, Temperature Humidity Index (THI) and Equivalent Temperature Index (ETI) are computed from the NASA-Modern Era Retrospective-Analysis for Research and Applications (NASA-MERRA) reanalysis (2002-2010). Milk data for fat, protein (measured on fresh matter bases), and milk yield are taken from 936,227 milk records for the same period, using cows fed by natural pasture from April to September. Confidence intervals for the regression model are calculated using the bootstrap technique. This method is applied to the original times series, generating statistically equivalent surrogate samples. As a result, despite the short time data and the related uncertainties, an interesting behavior of the relationships between milk compound and the climate parameters is visible. During spring only, a weak dependency of milk yield and climate variations is obvious, while fat and protein concentrations show reasonable correlations. In summer, milk yield shows a similar level of relationship with ETI, but not with temperature and THI. We suggest this methodology for studies in the field of the impacts of climate change and agriculture, also environment and food with short-term data.