1,973 research outputs found

    Pion radiative weak decay from the instanton vacuum

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    We investigate the vector and axial-vector form factors for the pion radiative weak decays π+e+νeγ\pi^+\to e^+\nu_e \gamma and π+e+νee+e\pi^+\to e^+\nu_e e^+ e^-, based on the gauged effective chiral action from the instanton vacuum in the large NcN_c limit. The nonlocal contributions, which arise from the gauging of the action, enhance the vector form factor by about 20%20\,\%, whereas the axial-vector form factor is reduced by almost 30%30\,\%. Both the results for the vector and axial-vector form factors at the zero momentum transfer are in good agreement with the experimental data. The dependence of the form factors on the momentum transfer is also studied. The slope parameters are computed and compared with other works.Comment: 13 pages, 7 figures. Final version accepted for publication in Phys.Lett.

    A study on ship’s routeing and port zoning audit scheme for eradicating or reducing circumstantial factors of marine casualties and incidents

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    This dissertation is a study on Ship’s routeing and Port zoning Audit Scheme (SPAS) for eradicating or reducing risky circumstantial factors of marine casualties and incidents in coastal waters. It aims to show methods of preventing marine accident from the human element, and to discuss the further development for the maritime safety system of the Republic of Korea as the world’s first compulsory scientific audit scheme on ship’s routeing and port zoning. At the outset, this study intended to review the statistics of marine accidents to analyse which causes and places should be focused on to secure maritime safety. It also attempted to analyse serious marine accidents which occurred in ports and approaches. This was to demonstrate which tools were applied successfully to reduce marine accidents caused by the human element. A controversy over a harbour bridge was introduced to prove the importance of objective ship handling simulation. The STCW, Navigational Aids, the ISM Code and the User-Centred Design were studied as methods of reducing human errors in error enforcing circumstances. To verify that the IMO’s safety measures on the human element are corresponding to all categories of human errors, the Marine Casualty Investigation Code of the IMO was referred to. It was found that the IMO could contribute further to preparing any appropriate measures to deal with the loose interface between liveware and the environment, in other words, navigators and the navigational circumstances. Accordingly, it reviewed the schemes of several maritime States that were relevant to safety of navigation in ports and approaches. As a successful example, the SPAS of the Republic of Korea was analysed. The SPAS is evaluated in Korea as an effective risk finding system in port design and its operation, and a tool for providing the navigators in coastal waters with a better navigational environment. In addition, from the shore-based perspectives, the SPAS has reduced social disputes over maritime safety and accelerated economic construction of infrastructures. Despite of the successful implementation of the SPAS project, some issues are still open. Chapter 5.5 provides the future direction of the SPAS system as the world’s first compulsory scientific audit scheme on ship’s routeing and port zoning. Also it contains some recommendations to policy planners for achieving efficient port construction and management taking into account safe navigation. Ultimately, this dissertation aimed to study how human error as a principal causation factor would not turn in marine accidents in heavy traffic zones such as coastal waters. At the end, it is reiterated that the human element and navigator-friendly circumstances should be considered together in order to reduce marine accidents in coastal waters, to protect the marine environment and to save human lives at sea

    Cyclo­hexane-1,2-diammonium bis­(pyridine-2-carboxyl­ate)

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    In the dication of the title salt, C6H16N2 2+·2C6H4NO2 −, the two ammonium groups are in the equatorial positions of the chair-shaped cyclo­hexyl ring. In the crystal, the cations and anions are linked by N—H⋯O and N—H⋯N hydrogen bonds, forming a layer network parallel to the ac plane. Weak π–π inter­actions between adjacent pyridine rings with a centroid–centroid distance of 3.589 (2) Å are also present

    Bis(2,2′-bipyridine-κ2 N,N′)dichlorido­platinum(IV) dichloride monohydrate

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    In the title complex, [PtCl2(C10H8N2)2]Cl2·H2O, the Pt4+ ion is six-coordinated in a distorted octa­hedral environment by four N atoms from the two 2,2′-bipyridine ligands and two Cl atoms. As a result of the different trans influences of the N and Cl atoms, the Pt—N bonds trans to the Cl atom are slightly longer than those trans to the N atom. The compound displays inter­molecular hydrogen bonding between the water mol­ecule and the Cl anions. There are inter­molecular π–π inter­actions between adjacent pyridine rings, with a centroid–centroid distance of 3.962 Å

    Prenatal Diagnosis of Down Syndrome

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    Optical Spectroscopy of Supernova Remnants in M81 and M82

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    We present spectroscopy of 28 SNR candidates as well as one H II region in M81, and two SNR candidates in M82. Twenty six out of the M81 candidates turn out to be genuine SNRs, and two in M82 may be shocked condensations in the galactic outflow or SNRs. The distribution of [N II]/H{\alpha} ratios of M81 SNRs is bimodal. M81 SNRs are divided into two groups in the spectral line ratio diagrams: an [O III]-strong group and an [O III]-weak group. The latter have larger sizes, and may have faster shock velocity. [N II]/H{\alpha} ratios of the SNRs show a strong correlation with [S II]/H{\alpha} ratios. They show a clear radial gradient in [N II]/H{\alpha} and [S II]/H{\alpha} ratios: dLog ([N II]/H{\alpha})/dLog R = -0.018 {\pm} 0.008 dex/kpc and dLog ([S II]/H{\alpha})/dLog R = -0.016 {\pm} 0.008 dex/kpc where R is a deprojected galactocentric distance. We estimate the nitrogen and oxygen abundance of the SNRs from the comparison with shock-ionization models. We obtain a value for the nitrogen radial gradient, dLog(N/H)/dLogR = -0.023 {\pm} 0.009 dex/kpc, and little evidence for the gradient in oxygen. This nitrogen abundance shows a few times flatter gradient than those of the planetary nebulae and H II regions. We find that five SNRs are matched with X-ray sources. Their X-ray hardness colors are consistent with thermal SNRs.Comment: 19 pages, 24 figures, 5 tables, ApJ accepte

    Why Is It Difficult to Adopt Innovative Technologies? The Role of Coordination and Collateral Borrowing in Technology Adoption

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    Adopting highly innovative technologies is difficult due to many socioeconomic factors. We analyze the economic mechanisms associated with the large fixed costs jointly faced by various subsectors of an economy and the financing difficulty. We construct a Romer (1990) type growth model of technology adoption with fixed cost and then analyze macro dynamics showing why adopting innovative technology is difficult. We show that exercising coordination power in centralized economies can boost aggregate demand, facilitating the adoption of new technologies. Similarly, collateral lending in decentralized economies can play the role of helping technology adoption. Only when a threshold level of investment (i.e., the tipping point) is funded will the increasing returns to scale property arising from fixed costs generate a dynamic path toward a stable equilibrium with high output. We draw some implications
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