179 research outputs found

    The first record of bobtail squid, Euprymna hyllebergi Nateewathana, 1997 (Cephalopoda:Sepiolidae) from the Persian Gulf, Iran

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    The family Sepiolidae comprises over 50 species in 14 genera. They are commonly known as bobtail squids with a worldwide distribution from tropical to temperate and sub-polar latitudes of all oceans (Nateewathana, 1997; Aungtonya et al., 2011). Euprymna hyllebergi belongs to the Sepiolidae family and Sepiolinae subfamily. This species has a wide distribution in the Eastern Indian Ocean, and has been recorded up to the depth of 47 meters in Andaman Sea, Thailand (Jereb and Roper, 2005). The family Sepiolidae, includes all bobtail squids with kidney-shape fins. Little is known about their biology, but they are common in tropical, temperate and sub polar waters of all oceans (Jereb and Roper, 2010). This is the first record of the bobtail squid, E. hyllebergi from the Persian Gulf. On 27th of March 2013 during a scuba diving session in Persian Gulf (Figure 1, coordinates: 54° 49’39.5”E, 26° 26’ 55.3”N) about 200 eggs of E. hyllebergi were collected at the depth of 40 meters in northern Persian Gulf. The eggs (Fig. 2a) were transferred to the Persian Gulf Shellfishes Research Center laboratory for further incubation and hatching

    A numerical method for solving nonlinear integral equations

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    Abstract Integral equations occur naturally in many field of mechanics and mathematical physics. In this paper, an iterative scheme based on the homotopy analysis method (HAM) has been used for solving one of the most important cases in nonlinear integral equations which is called urysohn form. For this scope, we applied some examples with known exact solutions and the numerical solutions obtained confirm that the method is very effective and simple. Also, show the advantage of this method, the results obtained by (HAM) are compared with NewtonKantorovich-quadrature method. Convergence is also observed

    IMECE2008-66292 EXPERIMENTAL ANALYSIS OF VIBRATION OF MICROMACHINED RESONATORS

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    ABSTRACT Among many different mechanisms that are used for excitation and detection of vibration of micro-beam resonators, electrostatic comb-drives have the benefit of simplicity and large range of linear operation. The disadvantage of using comb-drives is the effect of added mass to the beam; however, the analytical model of the beam-mass system predicts that this shortcoming can be overcome by proper adjustment of the mass, rotary inertia, and location of the comb-drive. In addition, the analytical model can predict the effect of the axial force of the beam on the resonance frequencies. In this paper, the results of the experiments on two resonators are presented. These results are used to verify the validity of the analytical model and finding its parameters. Very close agreement between the theory and experiment is observed. The residual stress of the MEMS structural layer is measured using the calibrated analytical model parameters

    Oesophageal cancer among the Turkomans of northeast Iran

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    A Caspian Littoral Cancer Registry survey in the early 1970s established northern Iran as one of the highest oesophageal cancer incidence regions of the world. To verify this, an oesophageal cancer survey was carried out between 1995 and 1997 in the Turkoman Plain at the southeastern corner of the Caspian Sea. Oesophageal balloon cytology screening was carried out on 4192 asymptomatic adults above age 30 years in one town and three adjoining villages with a total population of 20 392 people at risk. Oesophagoscopy was performed on 183 patients with abnormal cytological findings. The discovery of two asymptomatic small squamous cell cancers and one ‘carcinoma- suspect’ implied a prevalence ranging from 47.7 per 100 000 to 71.5 per 100 000. During a 1-year active surveillance, 14 patients were found with clinically advanced oesophageal squamous cell cancer, yielding age-standardized incidence rates of 144.09 per 100 000 for men and 48.82 per 100 000 for women. The very high frequency of oesophageal cancer reported for northern Iran 25 years ago stands confirmed. Differences in incidence rates, then and now, can be attributed to survey methods used and diagnostic criteria applied, but not to socioeconomic factors, which have remained relatively stable. Oesophageal balloon cytology is a practical method of mass screening for oesophageal cancer in Iran. © 2000 Cancer Research Campaig

    Big Bang Nucleosynthesis Constraints on Primordial Magnetic Fields

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    We reanalyze the effect of magnetic fields in BBN, incorporating several features which were omitted in previous analyses. We find that the effects of coherent magnetic fields on the weak interaction rates and the electron thermodynamic functions (\rhoe, \Pe, and \drhoedt ) are unimportant in comparison to the contribution of the magnetic field energy density in BBN. In consequence the effect of including magnetic fields in BBN is well approximated numerically by treating the additional energy density as effective neutrino number. A conservative upper bound on the primordial magnetic field, parameterized as ζ=2eBrms/(TÎœ2)\zeta=2eB_{rms}/(T_\nu^2), is ζ≀2\zeta \le 2 (ρB<0.27ρΜ\rho_B < 0.27 \rho_\nu). This bound can be stronger than the conventional bound coming from the Faraday rotation measures of distant quasars if the cosmological magnetic field is generated by a causal mechanism.Comment: Latex, 20 pages, 3 uuencoded figures appende

    Testing The Friedmann Equation: The Expansion of the Universe During Big-Bang Nucleosynthesis

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    In conventional general relativity, the expansion rate H of a Robertson-Walker universe is related to the energy density by the Friedmann equation. Aside from the present day, the only epoch at which we can constrain the expansion history in a model-independent way is during Big-Bang Nucleosynthesis (BBN). We consider a simple two-parameter characterization of the behavior of H during BBN and derive constraints on this parameter space, finding that the allowed region of parameter space is essentially one-dimensional. We also study the effects of a large neutrino asymmetry within this framework. Our results provide a simple way to compare an alternative cosmology to the observational requirement of matching the primordial abundances of the light elements.Comment: 18 pages, Final version to be published in Phys. Rev.

    Multiple solutions and corresponding power output of a nonlinear bistable piezoelectric energy harvester

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    We examine multiple responses of a vibrational energy harvester composed of a vertical beam and a tip mass. The beam is excited horizontally by a harmonic inertial force while mechanical vibrational energy is converted to electrical power through a piezoelectric patch. The mechanical resonator can be described by single or double well potentials depending on the gravity force from the tip mass. By changing the tip mass we examine the appearance of various solutions and their basins of attraction. Identification of particular solutions of the energy harvester is important as each solution may provide a different level of power output

    Solar Neutrino Constraints on the BBN Production of Li

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    Using the recent WMAP determination of the baryon-to-photon ratio, 10^{10} \eta = 6.14 to within a few percent, big bang nucleosynthesis (BBN) calculations can make relatively accurate predictions of the abundances of the light element isotopes which can be tested against observational abundance determinations. At this value of \eta, the Li7 abundance is predicted to be significantly higher than that observed in low metallicity halo dwarf stars. Among the possible resolutions to this discrepancy are 1) Li7 depletion in the atmosphere of stars; 2) systematic errors originating from the choice of stellar parameters - most notably the surface temperature; and 3) systematic errors in the nuclear cross sections used in the nucleosynthesis calculations. Here, we explore the last possibility, and focus on possible systematic errors in the He3(\alpha,\gamma)Be7 reaction, which is the only important Li7 production channel in BBN. The absolute value of the cross section for this key reaction is known relatively poorly both experimentally and theoretically. The agreement between the standard solar model and solar neutrino data thus provides additional constraints on variations in the cross section (S_{34}). Using the standard solar model of Bahcall, and recent solar neutrino data, we can exclude systematic S_{34} variations of the magnitude needed to resolve the BBN Li7 problem at > 95% CL. Additional laboratory data on He3(\alpha,\gamma)Be7 will sharpen our understanding of both BBN and solar neutrinos, particularly if care is taken in determining the absolute cross section and its uncertainties. Nevertheless, it already seems that this ``nuclear fix'' to the Li7 BBN problem is unlikely; other possible solutions are briefly discussed.Comment: 21 pages, 3 ps figure
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