Simulation of optical interstellar scintillation

Stars twinkle because their light propagates through the atmosphere. The same phenomenon is expected on a longer time scale when the light of remote stars crosses an interstellar turbulent molecular cloud, but it has never been observed at optical wavelengths. The aim of the study described in this paper is to fully simulate the scintillation process, starting from the molecular cloud description as a fractal object, ending with the simulations of fluctuating stellar light curves. Fast Fourier transforms are first used to simulate fractal clouds. Then, the illumination pattern resulting from the crossing of background star light through these refractive clouds is calculated from a Fresnel integral that also uses fast Fourier transform techniques. Regularisation procedure and computing limitations are discussed, along with the effect of spatial and temporal coherency (source size and wavelength passband). We quantify the expected modulation index of stellar light curves as a function of the turbulence strength --characterised by the diffraction radius $R_{diff}$-- and the projected source size, introduce the timing aspects, and establish connections between the light curve observables and the refractive cloud. We extend our discussion to clouds with different structure functions from Kolmogorov-type turbulence. Our study confirms that current telescopes of ~4m with fast-readout, wide-field detectors have the capability of discovering the first interstellar optical scintillation effects. We also show that this effect should be unambiguously distinguished from any other type of variability through the observation of desynchronised light curves, simultaneously measured by two distant telescopes.Comment: 11 pages, 11 figures, accepted for publication in Astronomy and Astrophysic

Sky reconstruction from transit visibilities: PAON-4 and Tianlai Dish Array

The spherical harmonics $m$-mode decomposition is a powerful sky map reconstruction method suitable for radio interferometers operating in transit mode. It can be applied to various configurations, including dish arrays and cylinders. We describe the computation of the instrument response function, the point spread function (PSF), transfer function, the noise covariance matrix and noise power spectrum. The analysis in this paper is focused on dish arrays operating in transit mode. We show that arrays with regular spacing have more pronounced side lobes as well as structures in their noise power spectrum, compared to arrays with irregular spacing, specially in the north-south direction. A good knowledge of the noise power spectrum $C^{\mathrm{noise}}(\ell)$ is essential for intensity mapping experiments as non uniform $C^{\mathrm{noise}}(\ell)$ is a potential problem for the measurement of the HI power spectrum. Different configurations have been studied to optimise the PAON-4 and Tianlai dish array layouts. We present their expected performance and their sensitivities to the 21-cm emission of the Milky Way and local extragalactic HI clumpsComment: 20 pages, 18 figures - Submitted to MNRAS ( the appendix A,B are not included in the accepted version

The characteristics of a sustainable bridge: a case study of Second Penang Bridge

The aging and deterioration of bridges and the new requirements for sustainable infrastructures and communities require innovative approaches for their management that can achieve an adequate balance between social, economic, and environmental sustainability. This study presents the common criteria which can make a sustainable bridge in the construction industry by considering three objectives, which are, to identify the common criteria for a sustainable structure, then to observe the criteria to the bridges, and to investigate the applications of the criteria in bridge design and construction. The study was carried out through a literature survey and case studies. Result from the study found that there were 29 critical criteria have been identified and significantly influenced on sustainable bridges in the design and construction. The whole criteria, then, were categorized into three aspects such as economic, environmental, and social. A case study was carried out on the underconstruction of the Second Penang Bridge. The results of the case study revealed that it has achieved most of the criteria of the sustainability bridge. It rendered useful references in designing sustainable bridges and could be classified as the top ranking of bridges in the case of sustainability. Additionally, the model of ranking for bridge sustainability is suggested

Cytogenetic Evaluation of Couples With Spontaneous Abortion, Still Birth and Recurrent Miscarriage in Qazvin: Report and Review

Background: Chromosomal abnormality plays an important role in different types of miscarriages. Objectives: The present study was designed to investigation chromosomal anomalies in three groups of couples with recurrent abortion (RA), spontaneous abortion (SA) and still birth (SB). PatientsandMethods: In this retrospective study, the frequency of chromosomal aberrations was investigatedamong 260 couples with miscarriage, which had referred to the cytogenetic section of a reference laboratory in Buali hospilal, Qazvin, Iran from 2009 to 2014. Metaphase spreads were analyzed using G-banding. Results: In this study, 7.6% of couples had chromosomal aberrations including, balanced reciprocal translocations, robertsonian translocations, inversions and sex chromosome aneuploidy. Frequency of balanced translocations was higher, specifically in couples with SA. Conclusions: In this investigation we showed that chromosomal abnormalities could be one of the important causes of miscarriages. Cytogenetic evaluation of couples, which experienced different types of miscarriage, may prevent unnecessary treatments. Keywords: Recurrent Abortion, Spontaneous Abortion, Still Birth, Chromosome Abnormalit

Sky reconstruction for the Tianlai cylinder array

In this paper, we apply our sky map reconstruction method for transit type interferometers to the Tianlai cylinder array. The method is based on the spherical harmonic decomposition, and can be applied to cylindrical array as well as dish arrays and we can compute the instrument response, synthesised beam, transfer function and the noise power spectrum. We consider cylinder arrays with feed spacing larger than half wavelength, and as expected, we find that the arrays with regular spacing have grating lobes which produce spurious images in the reconstructed maps. We show that this problem can be overcome, using arrays with different feed spacing on each cylinder. We present the reconstructed maps, and study the performance in terms of noise power spectrum, transfer function and beams for both regular and irregular feed spacing configurations.Comment: 15 pages, 12 figures, accepted by RA

A comparative study on dust exposure, respiratory symptoms and lung function among farmers and non-farmers

Considering the importance and essence of farmers’ health, this study has been conducted with the aim of evaluating the amount of the dust confronting farmers and the farmers’ respiratory symptoms and function during the course of wheat collection in 2014 in Zabul villages (Sistan & Balouchestan province, Iran). For this cross sectional study, the dust of the respiratory scope of two groups (farmers and non-farmers) was sampled by PVC filter for 90 minutes with the flow rate of 1.5 lit/min on the basis of NIOSH 0500 method during daily 8 work hours of 5 successive days of manual wheat reaping. Data regarding respiratory symptoms (n=50 rural men over the age of 40) was gathered through interviews and questionnaires, and pulmonary function was measured by Spiro lobe (made in MIR of the US); besides, data analysis was done by SPSS 18, T-Test, Chi-Square, and Logistic regression. The mean dust intensity confronting the farmers was 36.7 mg/m3, and the rate of some breathing complaints namely coughing (P≤0.001), sputum (P≤0.009) and shortness of breath (P≤0.026) became meaningful in the two groups. The average amounts of spirometer parameters of the farmers were less than that of the non-farmers, and the statistical difference of all the parameters except for FEV1/FVC (P=0.06) was meaningful (P≤0.05). The results of the present study indicated that confronting with dust could cause respiratory complaints and decrease spirometer parameters in the farmers

Role of reinforcement methods in retention of composite restorations of primary anterior teeth

Objectives This study aimed to evaluate the retention of composite restorations of primary anterior teeth reinforced with composite posts, glass fiber posts, para-pulpal pins with composite posts, and para-pulpal pins alone.Methods Forty freshly extracted sound primary canine teeth with at least two-third of the root length remaining were selected. After disinfection, the tooth crown was cut perpendicular to the longitudinal axis. Root canals were prepared and filled using zinc oxide eugenol paste. The teeth were randomly allocated into four groups and restored using one of the following: Composite posts, glass fiber posts, para- pulpal pins with composite posts, and para-pulpal pins alone. Composite cores were constructed while a preformed U-shaped orthodontic wire was placed in the composite tip, samples were then placed in a universal testing machine for measurement of retention. The minimum force required to dislodge the restoration or cause fracture was considered as the retentive strength. The collected data were analyzed using one-way ANOVA and Tukey’s test (P < 0.05).Results There were statistically significant differences between groups (P = 0.011). The mean retention in the para-pulpal pins with composite post group (131.72 ± 32.35N) was greater than that in composite posts (93.65 ± 24.45N), glass fiber post (95.92 ± 25.35N), and the para-pulpal pin group (95.34 ± 29.56N) (P < 0.05). Other differences were not significant (P > 0.05).Conclusion para-Pulpal pin alone may not help in improving the retention of full crown restoration of primary anterior teeth. However, when used along with a composite post, it appears to improve the retention of restoration