6,908 research outputs found

    Predictions of Vertically Vibrating Foundation Response With Modified Radiation Damping

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    A simple solution technique for evaluating the response of a surface or embedded foundation under vertical vibrations in a homogeneous soil has been developed. The effects of soil nonlinearity on shear modulus and material damping, frequency on stiffness and radiation damping, and embedment of foundation on stiffness and radiation damping have been considered. A computer program has been developed based on the Elastic Half Space (EHS) analog technique (Lysmer and Richart, 1966), to compute the response amplitude of both surface and embedded footings. The computed response has been verified by comparing it with measured data from Novak (1970). The predicted response is underestimated in all cases because the (EHS) analog computed radiation damping is overestimated. A modification factor, λ, has been proposed and applied to correct the estimated radiation damping. A unique relationship between λ, (correction factor for radiation damping), and shear strain (γ) has been established for field use. A rational correction factor to radiation damping for computing vibration footing response has been proposed for the first time and this has been shown to provide computed results which compare quite well to measured results

    Laparoscopic Cholecystectomy in Chronic Calculus Cholecystitis

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    Introduction: Laparoscopic cholecystectomy has clearly become the choice over open cholecystectomy in the treatment of hepatobiliary disease since its introduction by Mouret in 1987. This study evaluates a series of patients with chronic calculus cholecystitis who were treated with laparoscopic and open cholecystectomy and assesses the outcomes of both techniques. Objective: To evaluate the efficacy of laparoscopic vs open cholecystectomy in chronic calculus cholecystitis and establish the out-comes of this treatment modality at Lumbini Medical College and Teaching Hospital. Methods: This was a retrospective analysis over a one-year period (January 1, 2012 to December 31, 2012), per-formed by single surgeon at Lumbini Medical College and Teaching Hospital located midwest of Nepal. 166 patients underwent surgical treatment for chronic calculus cholecystitis. Patients included were only chronic calculus cholecystitis proven histopathologocally and the rest were excluded. Data was collected which included patients demographics, medical history, presentation, complications, conversion rates from laparoscopic. cholecystectomy to open cholecystectomy, operative and postoperative time. Results: Patients treated with laparoscopic cholecystectomy for chronic calculus cholecystitis had shorter operating times and length of stay compared to patients treated with open cholecystectomy for chronic calculus cholecystitis. Conversion rates were 3.54% in chronic calculus cholecystitis during the study period. Complications were also lower in patients who underwent laparoscopic cholecystectomy versus open cholecystectomy for cholelithiasis. Conclusions: Laparoscopic cholecystectomy appears to be a reliable, safe, and cost-effective treatment modality for chronic calculus cholecystitis

    Dynamic crossover scaling in polymer solutions

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    The crossover region in the phase diagram of polymer solutions, in the regime above the overlap concentration, is explored by Brownian Dynamics simulations, to map out the universal crossover scaling functions for the gyration radius and the single-chain diffusion constant. Scaling considerations, our simulation results, and recently reported data on the polymer contribution to the viscosity obtained from rheological measurements on DNA systems, support the assumption that there are simple relations between these functions, such that they can be inferred from one another.Comment: 4 pages, 6 figures, 1 Table. Revised version to appear in Physical Review Letters. Includes supplemental material

    Nonlinear optical properties of stilbene and azobenzene derivatives containing azaphosphane groups

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    We have studied the nonlinear optical (NLO) properties of some donor-acceptor molecules with stilbene and azobenzene molecules as backbone. We have used the nitro group as the acceptor and azaphosphane (R3P=N-) as the donor group. To study the effect of variation of NLO properties, we have replaced the substituents (Rs) connected to the phosphorus atom by methyl, amine and phenyl groups. We find that both first-order polarizability and hyperpolarizabilities are larger for stilbene derivatives and is maximum for the phenyl substitution. Second-order polarizability is higher for methyl substitution. We have also obtained the two-photon absorption cross-section for these molecules. We find that both one-photon and two-photon absorption cross-sections are maximum for the same excited state (first excited state in the case of stilbene and second excited state in the case of azobenzene derivatives)

    Market reaction to dividend announcements during pandemic: An event study

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    This study analyses the difference in stock market reactions to dividend announcement during the pandemic. The thirty constituent stocks of Sensex, the index of Bombay Stock Exchange (BSE), is used for analysis. This allows cross-industry comparison of the market reaction. The study examines stock market reactions covering 44 days around the dividend announcement dates. The primary objective of this study is to understand whether the price adjustment linked to the dividend announcement news during the pandemic was different from the earlier years. This empirical study employs the conventional event study methodology using abnormal returns (ARs) to examine the stock market reaction to dividend announcement. The market reaction to dividend announcement was increasingly positive during the pandemic, compared to previous years. The statistical pooled t-tests showed there was a significant relationship between the pandemic and ARs. The findings also indicate that the difference in the market reaction to dividend announcement was more prominent in services stocks than that in manufacturing. Further, the results also verify the weak-form of efficiency of Indian stock exchange

    Rapid Cooling of the Neutron Star in Cassiopeia A Triggered by Neutron Superfluidity in Dense Matter

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    We propose that the observed cooling of the neutron star in Cassiopeia A is due to enhanced neutrino emission from the recent onset of the breaking and formation of neutron Cooper pairs in the 3P2 channel. We find that the critical temperature for this superfluid transition is ~0.5x10^9 K. The observed rapidity of the cooling implies that protons were already in a superconducting state with a larger critical temperature. Our prediction that this cooling will continue for several decades at the present rate can be tested by continuous monitoring of this neutron star.Comment: Revised version, to be published in Phys. Rev. Let

    Effect of Agrobacterium Infection Time, Co-Cultivation and Cell Density on in vitro Response in Hypocotyl of Eggplant (Solanum melongena L.)

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    The present study purports to assess the effect of Agrobacterium infection time, co-cultivation and cell density on in vitro response in hypocotyl explants of eggplant (brinjal) cv. Manjarigota. Agrobacterium(OD600 0.3-0.5) infection for 10-15 minutes (24.44±2.34%) was found to be optimum, while, higher or lower infection-time resulted in reduced callus initiation, shoot regeneration and explant survival. Explants with no (only Agrobacterium infection) or short (1 day) co-cultivation, showed reduced callus-initiation response and turned yellow, with no regeneration. Callus-initiation response increased from Day 1 (96.66±03.33%), and reached a maximum on Day 2 and Day 3 (100±00.00%). It decreased on further increase in co-cultivation time. Explants co-cultivated for three days showed highest regeneration response (30.00±02.96%) which thereafter reduced with further increase in co-cultivation time. Explants infected with Agrobacterium culture at 0.05 OD600 showed hardly any regeneration, and turned yellow and necrotic on the selection medium. Highest regeneration response (28.33±02.33%) was obtained in explants infected with 0.1 OD600 culture, and this gradually reduced as celldensity increased (upto 1.0 OD600), becoming zero in explants treated with cultures at 1.5 OD600 or above. Agrobacterium overgrowth was noticed on explants infected with cultures of 0.5 OD600 and above. Exposure of hypocotyl explants to higher cell-density, longer infection-time and prolonged co-cultivation regime resulted in severe necrosis of explants; time taken for development of Agrobacterium overgrowth was less with increase in the level of these factors. Regenerated shoots were healthy, green, elongated and showed root induction on culture medium containing Kanamycin
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