How much time does a measurement take?

We consider the problem of measurement using the Lindblad equation, which allows the introduction of time in the interaction between the measured system and the measurement apparatus. We use analytic results, valid for weak system-environment coupling, obtained for a two-level system in contact with a measurer (Markovian interaction) and a thermal bath (non-Markovian interaction), where the measured observable may or may not commute with the system-environment interaction. Analysing the behavior of the coherence, which tends to a value asymptotically close to zero, we obtain an expression for the time of measurement which depends only on the system-measurer coupling, and which does not depend on whether the observable commutes with the system-bath interaction. The behavior of the coherences in the case of strong system-environment coupling, found numerically, indicates that an increase in this coupling decreases the measurement time, thus allowing our expression to be considered the upper limit for the duration of the process.Comment: REVISED VERSION: 17 pages, 2 figure

Neutron Stars with Hyperons subject to Strong Magnetic Field

Neutron stars are one of the most exotic objects in the universe and a unique laboratory to study the nuclear matter above the nuclear saturation density. In this work, we study the equation of state of the nuclear matter within a relativistic model subjected to a strong magnetic field. We then apply this EoS to study and describe some of the physical characteristics of neutron star, especially the mass-radius relation and chemical compositions. To study the influence of a the magnetic field and the hyperons in the stellar interior, we consider altogether four solutions: two different values of magnetic field to obtain a weak and a strong influence, and two configurations: a family of neutron stars formed only by protons, electrons and neutrons and a family formed by protons, electrons, neutrons, muons and hyperons. The limit and the validity of the results found are discussed with some care. In all cases the particles that constitute the neutron star are in $\beta$ equilibrium and zero total net charge. Our work indicates that the effect of a strong magnetic field has to be taken into account in the description of magnetars, mainly if we believe that there are hyperons in their interior, in which case, the influence of the magnetic field can increase the mass by more than 10%. We have also seen that although a magnetar can reach 2.48$M_{\odot}$, a natural explanation of why we do not know pulsars with masses above 2.0$M_{\odot}$ arises. We also discuss how the magnetic field affects the strangeness fraction in some standard neutron star masses and, to conclude our paper, we revisit the direct URCA process related to the cooling of the neutron stars and show how it is affected by the hyperons and the magnetic field.Comment: 16 pages, 8 figure

Epitaxial-tau(Mn,Ni)Al/(Al,Ga)As heterostructures: Magnetic and magneto-optic properties

Ferromagnetic Perpendicularly magnetized epitaxial thin films of tau (Mn,Ni)AI have been successfully grown on AlAs/GaAs heterostructures by molecular beam epitaxy. We have investigated the polar Kerr rotation and magnetization of tau MnAl and (Mn,Ni) Al as a function of Mn and Ni concentration. The largest polar Kerr rotation and remnant magnetization were obtained for Mn0.5Al0.5 thin films with values of 0.16-degrees and 224 emu/cm3, respectively. We observed that the Kerr rotation and magnetization remained constant with Ni additions up to about 12 at. % and subsequently decreased with further Ni additions. We discuss these results and one possible method of enhancing the Kerr rotation

Avaliação e manejo do solo com a tecnologia de corte e trituração visando a sustentabilidade do sistema de produção da agricultura familiar, com ênfase em alternativas ao uso do fogo na Amazônia.

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Business ethics: international analysis of codes of ethics and conduct

Codes of ethics and code of conduct formalize an ideal of expected behavior patterns to managers and employees of organizations, providing standards and orientation that states companies interactions with the community, through products /services, sales force, marketing communications, investments, and relationships with other stakeholders, influencing company reputation and overall Marketing performance. The objective of this study is to analyze the differences in codes of ethics of the largest companies based in Brazil and in Portugal, given their cultural and linguistic similarities. Findings show that the use of codes of ethics are more common in Brazil than in Portugal and that codes of ethics are substantially more extensive and cover a larger number of categories in Brazilian companies, reflecting the organizations’ mission and perception of stakeholders concerns and priorities. We conclude that ethical issues severely impact company reputation and, in a comprehensive sense, overall Marketing performance. Marketing professionals should be systematically aware of how company core values are transmitted to different audiences, including the use of code of ethics to communicate both with internal and external publics.info:eu-repo/semantics/publishedVersio

Efeito da adubação mineral na produção de matéria seca de pimenta longa (Piper hispidinervium).

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A characterization of quadric constant mean curvature hypersurfaces of spheres

Let $\phi:M\to\mathbb{S}^{n+1}\subset\mathbb{R}^{n+2}$ be an immersion of a complete $n$-dimensional oriented manifold. For any $v\in\mathbb{R}^{n+2}$, let us denote by $\ell_v:M\to\mathbb{R}$ the function given by $\ell_v(x)=\phi(x),v$ and by $f_v:M\to\mathbb{R}$, the function given by $f_v(x)=\nu(x),v$, where $\nu:M\to\mathbb{S}^{n}$ is a Gauss map. We will prove that if $M$ has constant mean curvature, and, for some $v\ne{\bf 0}$ and some real number $\lambda$, we have that $\ell_v=\lambda f_v$, then, $\phi(M)$ is either a totally umbilical sphere or a Clifford hypersurface. As an application, we will use this result to prove that the weak stability index of any compact constant mean curvature hypersurface $M^n$ in $\mathbb{S}^{n+1}$ which is neither totally umbilical nor a Clifford hypersurface and has constant scalar curvature is greater than or equal to $2n+4$.Comment: Final version (February 2008). To appear in the Journal of Geometric Analysi