Absence of Chaos in Bohmian Dynamics

The Bohm motion for a particle moving on the line in a quantum state that is a superposition of n+1 energy eigenstates is quasiperiodic with n frequencies.Comment: 1 pag

Quantum fidelity approach to the ground state properties of the 1D ANNNI model in a transverse field

In this work we analyze the ground-state properties of the $s=1/2$ one-dimensional ANNNI model in a transverse field using the quantum fidelity approach. We numerically determined the fidelity susceptibility as a function of the transverse field $B_x$ and the strength of the next-nearest-neighbor interaction $J_2$, for systems of up to 24 spins. We also examine the ground-state vector with respect to the spatial ordering of the spins. The ground-state phase diagram shows ferromagnetic, paramagnetic, floating, $\Braket{2,2}$ phases, and we predict an infinite number of modulated phases in the thermodynamic limit ($L \rightarrow \infty$). The transition lines separating the modulated phases seem to be of second-order, whereas the line between the floating and the $\Braket{2,2}$ phases is possibly of first-order.Comment: 10 pages, 20 figure

Multicritical Points And Reentrant Phenomenon In The BEG Model

The Blume - Emery - Griffiths model is investigated by use of the cluster variation method in the pair approximation. We determine the regions of the phase space where reentrant phenomenon takes place. Two regions are found, depending on the sign of the reduced quadrupole - quadrupole coupling strength $\xi$. For negative $\xi$ we find Para-Ferro-Para and Ferro-Para-Ferro-Para transition sequences; for positive $\xi$, a Para$_-$-Ferro-Para$_+$ sequence. Order parameters, correlation functions and specific heat are given in some typical cases. By-products of this work are the equations for the critical and tricritical lines.Comment: 14 pages, figures available upon reques

Comparação entre tomografia computadorizada e ressonância magnética nos esclarecimento etiológico de epilepsias parciais.

Trabalho de Conclusão de Curso - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Departamento de Clínica Médica, Curso de Medicina, Florianópolis, 200

Phase transitions in the two-dimensional super-antiferromagnetic Ising model with next-nearest-neighbor interactions

We use Monte Carlo and Transfer Matrix methods in combination with extrapolation schemes to determine the phase diagram of the 2D super-antiferromagnetic (SAF) Ising model with next-nearest-neighbor (nnn) interactions in a magnetic field. The interactions between nearest-neighbor (nn) spins are ferromagnetic along x, and antiferromagnetic along y. We find that for sufficiently low temperatures and fields, there exists a region limited by a critical line of 2nd-order transitions separating a SAF phase from a magnetically induced paramagnetic phase. We did not find any region with either first-order transition or with re-entrant behavior. The nnn couplings produce either an expansion or a contraction of the SAF phase. Expansion occurs when the interactions are antiferromagnetic, and contraction when they are ferromagnetic. There is a critical ratio R_c = 1/2 between nnn- and nn-couplings, beyond which the SAF phase no longer exists.Comment: 12 pages, 10 figure

Regulation of mTOR signaling by nutrients and post-translational modifications

The mTOR (mechanistic target of Rapamycin) signaling pathways are at the center of cellular physiology. As such, their dysregulation is a common characteristic of many conditions, such as cancer, neurodegeneration and aging. mTORC1 (mTOR complex 1) regulates cellular growth by controlling protein synthesis, autophagy and lysosomal biogenesis. On the other hand, mTORC2 (mTOR complex 2) is involved in the regulation of cell survival and proliferation. mTOR responds to upstream cues that control its function via the activity of key GTPases that regulate its localization, and via alterations in PTMs (post-translational modifications) on several signaling components. In particular, AAs (amino acids) regulate mTORC1 via changes in its subcellular localization, promoting mTORC1 recruitment to lysosomes. However, the reasoning for the lysosomal localization of mTORC1 and whether mTORC1 is active in different subcellular locations is an open question. Here, using multiple approaches to disrupt lysosomal function, I show that mTORC1 localization to lysosomes is linked to lysosomal activity. This observation indicates that mTORC1 is found at lysosomes likely due to basal protein degradation in the lysosomal lumen and subsequent nutrient release. Unexpectedly, under AA sufficiency, delocalization of mTORC1 from lysosomes led to a complete loss of TFEB phosphorylation, with very mild effects on the canonical substrates S6K1 and 4E-BP1. PTMs primarily include phosphorylation and ubiquitination events. Although the former is well-described in the control of mTOR complexes, the latter is less well-understood. Nonetheless, work over the recent years established that ubiquitination of several components of the mTORC1 and mTORC2 pathways is also an important part of their regulation. mTOR, the catalytic component of both mTORC1 and mTORC2, is itself heavily ubiquitinated. Hence, the identification of proteins able to modulate mTOR ubiquitination is of great importance to understand mTOR regulation. In this thesis, I identified the DUB (deubiquitinase) CYLD as an interacting partner of mTOR. Strikingly, CYLD is able to modulate mTOR ubiquitination and activity. Overall, my work expanded the knowledge on mTOR signaling regulation by uncovering the spatial separation of mTORC1 functions and a novel DUB for mTOR

The Beauty of Impertinence in World Literature from 1740 to 1977

Samuel Richardson, Jane Austen, Leo Tolstoy, and Jorge Amado have often been accused of making their heroines too beautiful. But these heroines are also accomplished in ways that demonstrate that their personalities are important. The ambiguous character of the novels by these authors has divided critics who find it difficult to categorize them as supporters of patriarchal oppression, or supporters of female autonomy. In face of this critical impasse, my research looks deeply into character description and character behavior to determine if these authors’ female characters should be viewed as pretty objects or not. As I demonstrate, in Samuel Richardson’s Pamela or Virtue Rewarded (1740), Jane Austen’s Pride and Prejudice (1813) and Mansfield Park (1814), Leo Tolstoy’s War and Peace (1869), and Jorge Amado’s Gabriela Clove and Cinnamon (1958) and Tieta, the Goat Girl (1977), authors emphasize their heroine’s beauty in order to distract readers from their characters’ inappropriate acts. These acts are imprudent because they are considered improper for females in their society. Thus, by creating female characters who challenge social roles, these authors suggest successful ways for women to defy patriarchy without losing their power of agency

Breakdown of the perturbative renormalization group for S >= 1 random antiferromagnetic spin chains

We investigate the application of a perturbative renormalization group (RG) method to random antiferromagnetic Heisenberg chains with arbitrary spin size. At zero temperature we observe that initial arbitrary probability distributions develop a singularity at J=0, for all values of spin S. When the RG method is extended to finite temperatures, without any additional assumptions, we find anomalous results for S >= 1. These results lead us to conclude that the perturbative scheme is not adequate to study random chains with S >= 1. Therefore a random singlet phase in its more restrictive definition is only assured for spin-1/2 chains.Comment: 5 pages, 3 figures. To appear in Physical Review