Nuclear-resonant electron scattering

We investigate nuclear-resonant electron scattering as occurring in the two-step process of nuclear excitation by electron capture (NEEC) followed by internal conversion. The nuclear excitation and decay are treated by a phenomenological collective model in which nuclear states and transition probabilities are described by experimental parameters. We present capture rates and resonant strengths for a number of heavy ion collision systems considering various scenarios for the resonant electron scattering process. The results show that for certain cases resonant electron scattering can have significantly larger resonance strengths than NEEC followed by the radiative decay of the nucleus. We discuss the impact of our findings on the possible experimental observation of NEEC.Comment: 24 pages, 2 plots, 5 table

Baryon Loading of Gamma Ray Bursts by Pick-up Neutrons

It is proposed that the baryons in gamma ray burst (GRB) fireballs originate as "pick-up" neutrons that leak in sideways from surrounding baryonic matter and convert to protons in a collision avalanche. The asymptotic Lorentz factor is estimated, and, in the absence of collimation, is shown to be angle dependent. Reasonable agreement is obtained with existing limits on the GRB baryonic component. The charged decay and collision products of the neutrons become ultrarelativistic immediately, and a UHE neutrino burst is produced with an efficiency that can exceed 0.5. Other signatures may include lithium, beryllium and/or boron lines in the supernova remnants associated with GRB's and high polarization of the gamma rays.Comment: 12 pages, substantial changes from previous versio

Tuning the Josephson current in carbon nanotubes with the Kondo effect

We investigate the Josephson current in a single wall carbon nanotube connected to superconducting electrodes. We focus on the parameter regime in which transport is dominated by Kondo physics. A sizeable supercurrent is observed for odd number of electrons on the nanotube when the Kondo temperature Tk is sufficiently large compared to the superconducting gap. On the other hand when, in the center of the Kondo ridge, Tk is slightly smaller than the superconducting gap, the supercurrent is found to be extremely sensitive to the gate voltage Vbg. Whereas it is largely suppressed at the center of the ridge, it shows a sharp increase at a finite value of Vbg. This increase can be attributed to a doublet-singlet transition of the spin state of the nanotube island leading to a pi shift in the current phase relation. This transition is very sensitive to the asymmetry of the contacts and is in good agreement with theoretical predictions.Comment: 5 pages, 4 figure

The Kodaira dimension of the moduli of K3 surfaces

The moduli space of polarised K3 surfaces of degree 2d is a quasi-projective variety of dimension 19. For general d very little has been known about the Kodaira dimension of these varieties. In this paper we present an almost complete solution to this problem. Our main result says that this moduli space is of general type for d>61 and for d=46,50,54,58,60.Comment: 47 page

Photon angular distribution and nuclear-state alignment in nuclear excitation by electron capture

The alignment of nuclear states resonantly formed in nuclear excitation by electron capture (NEEC) is studied by means of a density matrix technique. The vibrational excitations of the nucleus are described by a collective model and the electrons are treated in a relativistic framework. Formulas for the angular distribution of photons emitted in the nuclear relaxation are derived. We present numerical results for alignment parameters and photon angular distributions for a number of heavy elements in the case of E2 nuclear transitions. Our results are intended to help future experimental attempts to discern NEEC from radiative recombination, which is the dominant competing process

Theory of nuclear excitation by electron capture for heavy ions

We investigate the resonant process of nuclear excitation by electron capture, in which a continuum electron is captured into a bound state of an ion with the simultaneous excitation of the nucleus. In order to derive the cross section a Feshbach projection operator formalism is introduced. Nuclear states and transitions are described by a nuclear collective model and making use of experimental data. Transition rates and total cross sections for NEEC followed by the radiative decay of the excited nucleus are calculated for various heavy ion collision systems

Optical tomography of Fock state superpositions

We consider optical tomography of photon Fock state superpositions in connection with recent experimental achievements. The emphasis is put on the fact that it suffices to represent the measured tomogram as a main result of the experiment. We suggest a test for checking the correctness of experimental data. Explicit expressions for optical tomograms of Fock state superpositions are given in terms of Hermite polynomials. Particular cases of vacuum and low photon-number state superposition are considered as well as influence of thermal noise on state purity is studied.Comment: 5 pages, 2 figure

Avaliação do impacto do gerenciamento de riscos de TI no desempenho financeiro das empresas : uma análise empírica entre empresas abertas brasileiras

Considerando a importância da TI no ambiente de negócios e os riscos inerentes ao emprego dessa tecnologia, este estudo visa buscar evidências de melhoria de desempenho de empresas com a realização de gerenciamento de riscos de TI (GRTI). A pesquisa em curso seguiu a metodologia da Hipótese de Eficiência de Mercado, na sua forma semiforte, isto é, utilizando o método de janela de eventos. Com essa metodologia estimaram-se os retornos anormais na valorização das ações de empresas, oriundos da publicação de eventos de GRTI pelas empresas de capital aberto brasileiras, obtidos a partir do site da BMF&BOVESPA. Foram analisadas todas as empresas listadas em todo o período disponível no site, isto é, de 2003 até 2016, perfazendo um total aproximado de 400 empresas em cada ano. Essa análise utilizou ferramentas de busca do próprio site para encontrar anualmente todos os documentos que contivessem menção à palavra risco. Todos os documentos públicos obtidos com essa filtragem foram examinados detalhadamente para identificar evidências de que a empresa realizou, pela primeira vez, ações de GRTI, isto é, de que a empresa anunciou ao mercado que o GRTI passou a fazer parte de suas rotinas operacionais e administrativas. Depois dessa análise pormenorizada de todos os documentos publicados por essas empresas no site da BMF&BOVESPA, chegou-se a 22 empresas que evidenciaram ao mercado que fazem GRTI. Essas 22 empresas foram examinadas à luz da metodologia de janela de eventos. Os resultados obtidos indicam que, no cenário brasileiro, não é possível afirmar que o GRTI traz uma melhora no desempenho financeiro das empresas, uma vez que a hipótese nula de alteração do valor do retorno das ações não foi invalidada. Infere-se que o mercado não percebe uma diferença de valor nas ações dessas empresas, em função dos eventos de GRTI. Com intuito de suportar teoricamente esta pesquisa, foram reunidas as principais pesquisas em governança de TI e GRTI e relacionando-as a um desempenho financeiro empresarial.Considering the importance of IT in the business environment and the risks inherent in the use of this technology, this study aims to seek evidence of improved performance of companies with IT Risk Management (ITRM). The research followed the methodology of the Market Efficiency Hypothesis, in its semi-strong-form, that is, using the event window method. This methodology was used to estimate the abnormal returns on the valuation of companies' shares, resulting from the publication of ITRM events by Brazilian publicly traded companies, obtained from the BMF&BOVESPA website. All listed companies were analyzed throughout the period available on the site, that is, from 2003 to 2016, approximately 400 companies in each year. This analysis used search tools from the site itself to find annually all documents that contained mention to the word risk. All public documents obtained by this filtering were examined in detail to identify evidence that the company held, for the first time, ITRM actions. That is, the company announced that ITRM became part of their administrative and operational routines. After this detailed analysis of all documents published by these companies from Brazilian stock exchange, 22 companies evidenced to the market that do ITRM. These 22 companies were examined under the event window methodology. The results indicate that, in the Brazilian scenario, it is not possible to affirm that the ITRM brings an improvement in companies’ financial performance, since the null hypothesis of change shares’ return values was not negated. It is inferred that the market does not notice a difference in these companies’ share values due to ITRM events. In order to theoretically support this research, the main studies in IT governance and ITRM were gathered and related to a business financial performance

Rentabilidade fisica e econômica de inseticidas para pulgões safra de trigo de 1977.

bitstream/item/84146/1/CNPT-COM.-TEC.-1-77.pd

Probing the Planck Scale with Neutrino Oscillations

Quantum gravity "foam", among its various generic Lorentz non-invariant effects, would cause neutrino mixing. It is shown here that, if the foam is manifested as a nonrenormalizable effect at scale M, the oscillation length generically decreases with energy $E$ as (E/M)^(-2). Neutrino observatories and long-baseline experiments should have therefore already observed foam-induced oscillations, even if M is as high as the Planck energy scale. The null results, which can be further strengthened by better analysis of current data and future experiments, can be taken as experimental evidence that Lorentz invariance is fully preserved at the Planck scale, as is the case in critical string theory.Comment: 11 pages, 2 figures. Final version published in PRD. 1 figure, references, clarifications and explanations added. Results unchange