Evaluation of occupational noise pollution and attitudes of exposed workers in two metal industries

The purpose of the present study was to determined noise levels and to show the annoyance reaction, hearing loss, hearing impairment by the workers due to the occupational noise exposure according to Iran development of Environment （IDE） and also awareness about effects of noise and use of hearing protective devices （HPD） in the two manufacturing electronic equipment （metal） industries. The present study was carried out among industrial workers and included a sample of lao workers, site 1 （n = 52） and site 2 （n = 78） from two metal industries located in south eastern Iran province of Kerman. In order to attend the objectives of the current study, noise levels evaluation was determined throughout all different work stations in both industries. The results of the study revealed that noise levels in 75% of the stations are higher than limits used for assessment of noise for community response. The result of the study indicated that noise levels in the workplace are （66%） very high, （28%） high and only 6% low. Workers having higher education are much aware of the health impact due to occupational noise. Chi-square analysis indicated that the difference in educational background and not wearing HPD was significant and also a significant relationship was also observed between the impact of occupational noise on the health and education status. This research has clearly demonstrated that the workers in both the metal industries included in this study are at high risk of developing noise induced hearing loss and other associated ailments due to excessive occupational exposure to noise. There is a need to develop and apply a well-defined, comprehensive and enforceable training programs and noise regulation. The study revealed that the workers having higher education （9-12 grades） are much aware of the health impact due to occupational noise exposure. There is a need to establish a hearing conservation programs in both industries, the components of such program include noise assessment, use of hearing protection devices, audiometric and increasing awareness among the workers about the adverse effects of noise.     

FeNH4(SO4)2·12H2O (alum)-catalyzed preparation of 1,4-dihydropyridines: improved conditions for the Hantzsch reaction

Abstract  

FeNH₄(SO₄)₂·12H₂O (alum) efficiently catalyzes the one-pot three-component reaction of dimedone, aldehydes, and 3-aminocrotonate to afford 1,4-dihydropyridines. The work-up is easy, and the products are obtained in good to excellent yields and high purity.     

Monitoring the effects of homogeneity methanol/water/monomer on the mode of polymerization of styrene: dispersion polymerization versus emulsion polymerization

The polymerization of styrene (St) was carried out with varying amounts of methanol in aqueous medium. As methanol content decreased (to 50 %), the phase of polymerization mixture (methanol/water/monomer) changed to a heterogeneous state; the homogeneous state was obtained in samples that contain 75 and 100 % methanol. In order to verify the mechanism of polymerization in heterogeneous and homogeneous mixtures, the nucleus formation rate during polymerization, the stability equilibrium of the media and seeded particles, and the size of particles and their growth in polymerization were experimentally being monitored. With the homogeneous mixture in 75 wt% methanol, dumbbell, triangle, and peanut-like particles have been formed. On the other hand, the characteristics of the polymerization products were different from those typically obtained in the emulsion polymerization and in the sample with 100 wt% methanol dispersion polymerization. In the sample with 100 % methanol and in one with 50 % methanol, monodispersed spherical particles are formed in the final conversion. Thus, homogeneity in the aqueous methanol mixture can be a critical factor in determining the polymerization modes between dispersion and emulsion polymerization.     

Improved photonic crystal directional coupler with short length

We investigate a photonic crystal (PC) waveguide coupler which is formed by two closely spaced linear waveguides in a two-dimensional triangular lattice of air holes. Our study shows that shifting one row of the air holes between the waveguides affects the dispersion curves of the guided modes and if the triangular lattice of air holes between the waveguides is replaced by a rectangular lattice, this modification results in an ultra-short coupling structure with coupling length less than 3a, where a is the lattice constant. Also, we investigate the effect of changing the radii of air holes that are adjacent to or between the waveguides on the coupling length and show that increasing the radius of air holes between the waveguides decreases the coupling length. We analyze the output spectrum of an ultra-short channel drop filter designed based on this structure.     

Controlling morphology and structure of nanocrystalline cadmium sulfide (CdS) by tailoring solvothermal processing parameters

Cadmium sulfide (CdS) with different morphologies was successfully prepared by solvothermal process by controlling the processing parameters, including nature of precursor and solvent, reaction temperature and process time. X-ray diffraction patterns revealed that, in all cases highly pure and crystallized CdS with hexagonal structure were obtained. In addition, it was found that the processing parameters influence on preferable growth direction of CdS nanostructures. Field emission scanning electron microscope analysis showed that CdS nanowires with different aspect ratios were obtained (depending upon the reaction temperature and process time) in presence of sulfur powder and ethylenediamine, whereas CdS nanoparticles were produced by sulfur powder and ethanolamine. Moreover, CdS nanorods were prepared using thiourea and ethylenediamine. Transmission electron microscope image confirmed that CdS nanowire with one of the highest aspect ratio reported in the literature (i.e., 255) was achieved using sulfur powder and ethylenediamine at 200 °C reaction temperature for 72 h process time. UV–Vis absorption spectra of CdS nanostructures prepared under different conditions displayed a blue shift relative to that of bulk CdS due to the quantum size effect.     

Effect of three vitrification methods on development of two-cell mouse embryos

The purpose of this study was to investigate the effect of three vitrification procedures [conventional straw (CS), open pulled straw (OPS) and closed pulled straw (CPS)] on the development of two-cell mouse embryos. Two-cell mouse embryos were randomly divided into vitrified and non-vitrified control groups. Embryos in the vitrified group were cryopreserved within a combination of 5.5 M ethylene glycol and 1M sucrose as cryoprotectants, loaded within three different straws (CS, OPS and CPS) and warmed in stepwise sucrose solutions. The survived embryos from each procedure were cultured in human tubal fluid (HTF). The non-vitrified control embryos were also cultured in the same manner. The rates of the development in all the groups were daily determined and statistically compared. On day 4 of the cultivation period, several expanded blastocysts from each group were randomly selected and stained either with propidium iodide (PI) and bisbenzimide or with terminal transferase- mediate DNA end labeling (TUNEL) Technique. The mean number of the inner cell mass (ICM), trophoectoderm (TE), necrotic and apoptotic cells were counted and statistically compared. The survival rate of embryos in CPS was significantly higher than that in OPS and CS. The rate of hatched blastocysts did not differ in the three vitrification procedures, but in comparison with that of the control, CS and OPS showed a significant reduction. The mean number of ICM and TE decreased in CS and OPS, whereas in CPS it was almost identical to that of the control. The incidence of apoptosis and necrosis appeared to be almost similar in all the groups. In conclusion, CPS seems to be an effective, easy and rapid method for the cryopreservation of two-cell mouse embryos.     

Synthesis of Some Novel γ-Spirolactones

Summary. We report on the addition of dialkyl acetylenedicarboxylate to 1-alkylisatins or tryptanthrine in the presence of triphenylphosphine which leads to highly functionalised novel unsaturated -spirolactones.     

Shape invariance for the bent brane with two scalar fields

In this paper, we study the braneworld scenarios in the presence of two real scalar fields coupled by gravity. The first-order formalism for the bent brane (for both de Sitter and anti-de Sitter geometry), leads us to discuss the shape invariance method in the bent brane systems. So, by using the fluctuations of metric and fields we obtain the Schrödinger equation. Then we factorize the corresponding Hamiltonian in terms of multiplication of the first-order differential operators. These first-order operators lead us to obtain the energy spectrum with the help of shape invariance method.