Suppression of quantum chaos in a quantum computer hardware

We present numerical and analytical studies of a quantum computer proposed by the Yamamoto group in Phys. Rev. Lett. 89, 017901 (2002). The stable and quantum chaos regimes in the quantum computer hardware are identified as a function of magnetic field gradient and dipole-dipole couplings between qubits on a square lattice. It is shown that a strong magnetic field gradient leads to suppression of quantum chaos.Comment: 8 pages, 8 figures, research done at http://www.quantware.ups-tlse.fr

Composition law for polarizers

The polarization process when polarizers act on an optical field is studied. We give examples for two kinds of polarizers. The first kind presents an anisotropic absorption - as in a polaroid film - and the second one is based on total reflection at the interface with a birefringent medium. Using the Stokes vector representation, we determine explicitly the trajectories of the wave light polarization during the polarization process. We find that such trajectories are not always geodesics of the Poincar\'e sphere as it is usually thought. Using the analogy between light polarization and special relativity, we find that the action of successive polarizers on the light wave polarization is equivalent to the action of a single resulting polarizer followed by a rotation achieved for example by a device with optical activity. We find a composition law for polarizers similar to the composition law for noncollinear velocities in special relativity. We define an angle equivalent to the relativistic Wigner angle which can be used to quantify the quality of two composed polarizers.Comment: 23 pages, 9 figures, accepted for publication in Physical Review

Decoherence by a chaotic many-spin bath

We numerically investigate decoherence of a two-spin system (central system) by a bath of many spins 1/2. By carefully adjusting parameters, the dynamical regime of the bath has been varied from quantum chaos to regular, while all other dynamical characteristics have been kept practically intact. We explicitly demonstrate that for a many-body quantum bath, the onset of quantum chaos leads to significantly faster and stronger decoherence compared to an equivalent non-chaotic bath. Moreover, the non-diagonal elements of the system's density matrix decay differently for chaotic and non-chaotic baths. Therefore, knowledge of the basic parameters of the bath (strength of the system-bath interaction, bath's spectral density of states) is not always sufficient, and much finer details of the bath's dynamics can strongly affect the decoherence process.Comment: 4 pages, RevTeX, 5 eps figure

Phase of bi-particle localized states for the Cooper problem in two-dimensional disordered systems

The Cooper problem is studied numerically for the Anderson model with disorder in two-dimensions. It is shown that the attractive Hubbard interaction creates a phase of bi-particle localized states in the regime where non-interacting states are delocalized. This phase cannot be obtained in the mean-field approximation and the pair coupling energy is strongly enhanced in this regime. The effects of magnetic field are studied and it is shown that under certain conditions they lead to delocalization.Comment: revtex, 7 pages, 8 figure

Cooper problem in the vicinity of Anderson transition

We study numerically the ground state properties of the Cooper problem in the three-dimensional Anderson model. It is shown that attractive interaction creates localized pairs in the metallic noninteracting phase. This localization is destroyed at sufficiently weak disorder. The phase diagram for the delocalization transition in the presence of disorder and interaction is determined.Comment: revtex, 4 pages, 4 figure

Insulin glycation by methylglyoxal results in native-like aggregation and inhibition of fibril formation

<p>Abstract</p> <p>Background</p> <p>Insulin is a hormone that regulates blood glucose homeostasis and is a central protein in a medical condition termed insulin injection amyloidosis. It is intimately associated with glycaemia and is vulnerable to glycation by glucose and other highly reactive carbonyls like methylglyoxal, especially in diabetic conditions. Protein glycation is involved in structure and stability changes that impair protein functionality, and is associated with several human diseases, such as diabetes and neurodegenerative diseases like Alzheimer's disease, Parkinson's disease and Familiar Amyloidotic Polyneuropathy. In the present work, methylglyoxal was investigated for their effects on the structure, stability and fibril formation of insulin.</p> <p>Results</p> <p>Methylglyoxal was found to induce the formation of insulin native-like aggregates and reduce protein fibrillation by blocking the formation of the seeding <it>nuclei</it>. Equilibrium-unfolding experiments using chaotropic agents showed that glycated insulin has a small conformational stability and a weaker dependence on denaturant concentration (smaller m-value). Our observations suggest that methylglyoxal modification of insulin leads to a less compact and less stable structure that may be associated to an increased protein dynamics.</p> <p>Conclusions</p> <p>We propose that higher dynamics in glycated insulin could prevent the formation of the rigid cross-β core structure found in amyloid fibrils, thereby contributing to the reduction in the ability to form fibrils and to the population of different aggregation pathways like the formation of native-like aggregates.</p

2-Chloro-6,6-dimethyl-5,6-dihydro­indazolo[2,3-c]quinazoline

Two independent but virtually identical mol­ecules comprise the asymmetric unit of the title compound, C16H14ClN3. The mol­ecules have a slightly curved shape owing to puckering in the six-membered C4N2 ring; the respective dihedral angles formed between the benzene rings are 12.64 (7) and 11.72 (7)°. In the crystal, layers sustained by a combination of N—H⋯N hydrogen bonding as well as C—H⋯N and C—H⋯π contacts are formed; these stack along [011] and are connected by further C—H⋯π contacts

Spontaneous B-cell lymphoma in hamster

Durante estudo anatomopatológico, incluindo imunoistoquímica, sobre pancreatite chagásica, experimentalmente induzida em hamsters machos, não-isogênicos, com quatro meses de idade, pesando 107,8 ± 10,9g, infiltração por linfoma foi observada em um animalcontrole normal, com 15 meses de idade. A neoplasia foi notada na ocasião da necropsia, 330 dias após o início do experimento. Lirifoma similar não foi achado nos demais controles normais (n=73), nem nos hamsters do grupo infectado, pareados para peso e idade (n=94). As alterações histopatológicas e imunoistoquímicas foram consistentes com linfoma difuso, não-Hodgkin, de grandes céiulas-B; porém, a hipótese de eventual origem leucêmica não foi inteiramente excluída. Linfomas experimentalmente induzidos têm sido relatados em animais de laboratório; entretanto, relatos de caso de linfoma, ocorrendo espontaneamente em hamsters, não têm sido freqüentes. No presente caso, o desenvolvimento da doença poderia ter alguma relação com o processo de envelhecimento.During anatomopathologic study, including immunohistochemistry, about chagasic pancreatitis experimentally induced in four month aged male non-isogenic hamsters, weighing 107.8 ± 10.9g, lymphoma&nbsp;infiltration was observed in a 15 month-aged normal control animal. The neoplasia was disclosed on the occasion of necropsy studies, 330 days after the beginning of experiment. Similar lymphoma was not found in the remainder normal controls (n=73), nor in the group of infected hamsters age and weight matched (n=94). The neoplasia histopathologic and immunohistochemical changes were consistent with non-Hodgkin diffuse large B-ceIl lymphoma; nevertheless, the hypothesis of eventual leukemic origin was not entirely excluded. Experimentally induced lymphomas have been related in laboratory animais; however, cases of spontaneously occurring lymphoma have been infrequently described in hamsters. In the present case, the development of the disease could have some relation with the animal aging process

Governança de implementação do ODS 16.4: possibilidades e limites para a administração pública federal a partir das experiências da Unasul e OEA

O presente trabalho tem como foco o exame de um desafio de governança regional importante para o Brasil, ligado à implementação dos Objetivos do Desenvolvimento Sustentável (ODS), e que demanda estreita cooperação com organismos internacionais: a promoção da paz e justiça diante de um contexto social permeado pela criminalidade organizada. Configurado como o 16o ODS, a temática “Paz, Justiça e Instituições Fortes” (ODS 16) aparece como uma das novidades entre as metas para o desenvolvimento divulgada em 2015 pela Organização das Nações Unidas (ONU). Em seu parágrafo 4º, o ODS 16 (ou ODS 16.4) coloca a meta de reduzir até 2030 “significativamente os fluxos financeiros e de armas ilegais, reforçar a recuperação e devolução de recursos roubados e combater todas as formas de crime organizado” (ONU, 2015). No presente relatório, apresentamos como a temática pertinente ao 16.4 vem sendo debatida nos últimos anos em dois organismos regionais latino-americanos: União das Nações Sul-Americanas (Unasul) e Organização dos Estados Americanos (OEA). Ao final, após comparar ambas organizações, examinamos as possibilidades que tal cooperação abre para a administração pública federal.Caderno Enap, 103Coleção: Cátedras 2019Desenvolvimento SustentávelGovernanç