Classical magnetoresistance of a ballistic electron gas constrained to non-planar topographies in a lattice of antidots under tilted magnetic field

The classical magnetoresistance of a two-dimensional electron gas constrained to non-planar topographies, in antidot lattices, and under the influence of tilted magnetic field in arbitrary direction is numerically studied. (C) 2012 Elsevier B.V. All rights reserved.

Cannabidiol injected into the bed nucleus of the stria terminalis reduces the expression of contextual fear conditioning via 5-HT1A receptors

Systemic administration of cannabidiol (CBD) attenuates cardiovascular and behavioral changes induced by re-exposure to a context that had been previously paired with footshocks. Previous results from our group using cFos immunohistochemistry suggested that the bed nucleus of the stria terminalis (BNST) is involved in this effect. The mechanisms of CBD effects are still poorly understood, but could involve 5-HT1A receptor activation. Thus, the present work investigated if CBD administration into the BNST would attenuate the expression of contextual fear conditioning and if this effect would involve the activation of 5-HT1A receptors. Male Wistar rats with cannulae bilaterally implanted into the BNST were submitted to a 10 min conditioning session (six footshocks, 1.5 mA/3 s). Twenty-four hours later freezing and cardiovascular responses (mean arterial pressure and heart rate) to the conditioning box were measured for 10 min. CBD (15, 30 or 60 nmol) or vehicle was administered 10 min before the re-exposure to the aversive context. The second experiment was similar to the first one except that animals received microinjections of the 5-HT1A receptor antagonist WAY100635 (0.37 nmol) 5 min before CBD (30 nmol) treatment. The results showed that CBD (30 and 60 nmol) treatment significantly reduced the freezing and attenuated the cardiovascular responses induced by re-exposure to the aversive context. Moreover, WAY100635 by itself did not change the cardiovascular and behavioral response to context, but blocked the CBD effects. These results suggest that CBD can act in the BNST to attenuate aversive conditioning responses and this effect seems to involve 5-HT1A receptor-mediated neurotransmission.

Effect of acute and chronic GVHD on relapse and survival after reduced-intensity conditioning allogeneic transplantation for myeloma

We evaluated the effect of acute and chronic GVHD on relapse and survival after allogeneic hematopoietic SCT (HSCT) for multiple myeloma using non-myeloablative conditioning (NMA) and reduced-intensity conditioning (RIC). The outcomes of 177 HLA-identical sibling HSCT recipients between 1997 and 2005, following NMA (n = 98) or RIC (n = 79) were analyzed. In 105 patients, autografting was followed by planned NMA/RIC allogeneic transplantation. The impact of GVHD was assessed as a time-dependent covariate using Cox models. The incidence of acute GVHD (aGVHD; grades I-IV) was 42% (95% confidence interval (CI), 35-49%) and of chronic GVHD (cGVHD) at 5 years was 59% (95% CI, 49-69%), with 70% developing extensive cGVHD. In multivariate analysis, aGVHD (>= grade I) was associated with an increased risk of TRM (relative risk (RR) = 2.42, P = 0.016), whereas limited cGVHD significantly decreased the risk of myeloma relapse (RR = 0.35, P = 0.035) and was associated with superior EFS (RR = 0.40, P = 0.027). aGVHD had a detrimental effect on survival, especially in those receiving autologous followed by allogeneic HSCT (RR = 3.52, P = 0.001). The reduction in relapse risk associated with cGVHD is consistent with a beneficial graft-vs-myeloma effect, but this did not translate into a survival advantage. Bone Marrow Transplantation (2012) 47, 831-837; doi:10.1038/bmt.2011.192; published online 26 September 2011

What ethologically based models have taught us about the neural systems underlying fear and anxiety

Classical Pavlovian fear conditioning to painful stimuli has provided the generally accepted view of a core system centered in the central amygdala to organize fear responses. Ethologically based models using other sources of threat likely to be expected in a natural environment, such as predators or aggressive dominant conspecifics, have challenged this concept of a unitary core circuit for fear processing. We discuss here what the ethologically based models have told us about the neural systems organizing fear responses. We explored the concept that parallel paths process different classes of threats, and that these different paths influence distinct regions in the periaqueductal gray - a critical element for the organization of all kinds of fear responses. Despite this parallel processing of different kinds of threats, we have discussed an interesting emerging view that common cortical-hippocampal-amygdalar paths seem to be engaged in fear conditioning to painful stimuli, to predators and, perhaps, to aggressive dominant conspecifics as well. Overall, the aim of this review is to bring into focus a more global and comprehensive view of the systems organizing fear responses.

Spectral characteristics of the hippocampal LFP during contextual fear conditioning

OBJECTIVE: The hippocampus has an important role in the acquisition and recall of aversive memories. The objective of this study was to investigate the relationship among hippocampal rhythms. METHODS: Microeletrodes arrays were implanted in the hippocampus of Wistar rats. The animals were trained and tested in a contextual fear conditioning task. The training consisted in applying shocks in the legs. The memory test was performed 1 day (recent memory) or 18 days (remote memory) after training. We proposed a measure based on the FFT power spectrum, denominated "delta-theta ratio", to characterize the different behaviors (active exploration and freezing) and the memories types. RESULTS: The delta-theta ratio was able to distinguish recent and remote memories. In this study, the ratio for the 18-day group was smaller than for the 1-day group. Moreover, this measure was useful to distinguish the different behavior states active exploration and freezing. CONCLUSIONS: The results suggest delta-theta oscillations could reflect the demands on information processing during recent and remote memory recalls.

The 3C cooperation model applied to the classical requirement analysis

Aspects related to the users' cooperative work are not considered in the traditional approach of software engineering, since the user is viewed independently of his/her workplace environment or group, with the individual model generalized to the study of collective behavior of all users. This work proposes a process for software requirements to address issues involving cooperative work in information systems that provide distributed coordination in the users' actions and the communication among them occurs indirectly through the data entered while using the software. To achieve this goal, this research uses ergonomics, the 3C cooperation model, awareness and software engineering concepts. Action-research is used as a research methodology applied in three cycles during the development of a corporate workflow system in a technological research company. This article discusses the third cycle, which corresponds to the process that deals with the refinement of the cooperative work requirements with the software in actual use in the workplace, where the inclusion of a computer system changes the users' workplace, from the face to face interaction to the interaction mediated by the software. The results showed that the highest degree of users' awareness about their activities and other system users contribute to a decrease in their errors and in the inappropriate use of the system.

Classical bifurcation in a quadrupolar NMR system

The Josephson junction model is applied to the experimental implementation of classical bifurcation in a quadrupolar nuclear magnetic resonance system. There are two regimes, one linear and one nonlinear, which are implemented by the radio-frequency and the quadrupolar terms of the Hamiltonian of a spin system, respectively. These terms provide an explanation of the symmetry breaking due to bifurcation. Bifurcation depends on the coexistence of both regimes at the same time in different proportions. The experiment is performed on a lyotropic liquid crystal sample of an ordered ensemble of 133Cs nuclei with spin I = 7/2 at room temperature. Our experimental results confirm that bifurcation happens independently of the spin value and of the physical system. With this experimental spin scenario, we confirm that a quadrupolar nuclei system could be described analogously to a symmetric two-mode Bose-Einstein condensate.

Vascular wall stem cells. Selection and conditioning of progenitors useful for cell therapy. A pathological case study

The arterial wall contains MSCs with mesengenic and angiogenic abilities. These multipotent precursors have been isolated from variously-sized human adult segments, belying the notion that vessel wall is a relatively quiescent tissue. Recently, our group identified in normal human arteries a vasculogenic niche and subsequently isolated and characterized resident MSCs (VW-MSCs) with angiogenic ability and multilineage potential. To prove that VW-MSCs are involved in normal and pathological vascular remodeling, we used a long-term organ culture system; this method was of critical importance to follow spontaneous 3-D vascular remodeling without any influence of blood cells. Next we tried to identify and localize in situ the VW-MSCs and to understand their role in the vascular remodeling in failed arterial homografts. Subsequently, we isolated this cell population and tested in vitro their multilineage differentiation potential through immunohistochemical, immunofluorescence, RT-PCR and ultrastructural analysis. From 25-30cm2 of each vascular wall homograft sample, we isolated a cell population with MSCs properties; these cells expressed MSC lineage molecules (CD90, CD44, CD105, CD29, CD73), stemness (Notch-1, Oct-4, Sca-1, Stro-1) and pericyte markers (NG2) whilst were negative for hematopoietic and endothelial markers (CD34, CD133, CD45, KDR, CD146, CD31 and vWF). MSCs derived from failed homografts (H-MSCs) exhibited adipogenic, osteogenic and chondrogenic potential but scarce propensity to angiogenic and leiomyogenic differentiation. The present study demonstrates that failed homografts contain MSCs with morphological, phenotypic and functional MSCs properties; H-MSCs are long-lived in culture, highly proliferating and endowed with prompt ability to differentiate into adipocytes, osteocytes and chondrocytes; compared with VW-MSCs from normal arteries, H-MSCs show a failure in angiogenic and leiomyogenic differentiation. A switch in MSCs plasticity could be the basis of pathological remodeling and contribute to aneurysmal failure of arterial homografts. The study of VW-MSCs in a pathological setting indicate that additional mechanisms are involved in vascular diseases; their knowledge will be useful for opening new therapeutic options in cardiovascular diseases.

The relation between geometry and matter in classical and quantum gravity and cosmology

The present thesis is divided into two main research areas: Classical Cosmology and (Loop) Quantum Gravity. The first part concerns cosmological models with one phantom and one scalar field, that provide the `super-accelerated' scenario not excluded by observations, thus exploring alternatives to the standard LambdaCDM scenario. The second part concerns the spinfoam approach to (Loop) Quantum Gravity, which is an attempt to provide a `sum-over-histories' formulation of gravitational quantum transition amplitudes. The research here presented focuses on the face amplitude of a generic spinfoam model for Quantum Gravity.

Inverse problems in classical and quantum physics

The subject of this thesis is in the area of Applied Mathematics known as Inverse Problems. Inverse problems are those where a set of measured data is analysed in order to get as much information as possible on a model which is assumed to represent a system in the real world. We study two inverse problems in the fields of classical and quantum physics: QCD condensates from tau-decay data and the inverse conductivity problem. Despite a concentrated effort by physicists extending over many years, an understanding of QCD from first principles continues to be elusive. Fortunately, data continues to appear which provide a rather direct probe of the inner workings of the strong interactions. We use a functional method which allows us to extract within rather general assumptions phenomenological parameters of QCD (the condensates) from a comparison of the time-like experimental data with asymptotic space-like results from theory. The price to be paid for the generality of assumptions is relatively large errors in the values of the extracted parameters. Although we do not claim that our method is superior to other approaches, we hope that our results lend additional confidence to the numerical results obtained with the help of methods based on QCD sum rules. EIT is a technology developed to image the electrical conductivity distribution of a conductive medium. The technique works by performing simultaneous measurements of direct or alternating electric currents and voltages on the boundary of an object. These are the data used by an image reconstruction algorithm to determine the electrical conductivity distribution within the object. In this thesis, two approaches of EIT image reconstruction are proposed. The first is based on reformulating the inverse problem in terms of integral equations. This method uses only a single set of measurements for the reconstruction. The second approach is an algorithm based on linearisation which uses more then one set of measurements. A promising result is that one can qualitatively reconstruct the conductivity inside the cross-section of a human chest. Even though the human volunteer is neither two-dimensional nor circular, such reconstructions can be useful in medical applications: monitoring for lung problems such as accumulating fluid or a collapsed lung and noninvasive monitoring of heart function and blood flow.

Analog Signal Acquisition and Conditioning for Near-Field Capacitive Communication and Active Combined EEG-EIT Monitoring

The work of the present thesis is focused on the implementation of microelectronic voltage sensing devices, with the purpose of transmitting and extracting analog information between devices of different nature at short distances or upon contact. Initally, chip-to-chip communication has been studied, and circuitry for 3D capacitive coupling has been implemented. Such circuits allow the communication between dies fabricated in different technologies. Due to their novelty, they are not standardized and currently not supported by standard CAD tools. In order to overcome such burden, a novel approach for the characterization of such communicating links has been proposed. This results in shorter design times and increased accuracy. Communication between an integrated circuit (IC) and a probe card has been extensively studied as well. Today wafer probing is a costly test procedure with many drawbacks, which could be overcome by a different communication approach such as capacitive coupling. For this reason wireless wafer probing has been investigated as an alternative approach to standard on-contact wafer probing. Interfaces between integrated circuits and biological systems have also been investigated. Active electrodes for simultaneous electroencephalography (EEG) and electrical impedance tomography (EIT) have been implemented for the first time in a 0.35 um process. Number of wires has been minimized by sharing the analog outputs and supply on a single wire, thus implementing electrodes that require only 4 wires for their operation. Minimization of wires reduces the cable weight and thus limits the patient's discomfort. The physical channel for communication between an IC and a biological medium is represented by the electrode itself. As this is a very crucial point for biopotential acquisitions, large efforts have been carried in order to investigate the different electrode technologies and geometries and an electromagnetic model is presented in order to characterize the properties of the electrode to skin interface.

Classical limit of the Nelson model

Since the development of quantum mechanics it has been natural to analyze the connection between classical and quantum mechanical descriptions of physical systems. In particular one should expect that in some sense when quantum mechanical effects becomes negligible the system will behave like it is dictated by classical mechanics. One famous relation between classical and quantum theory is due to Ehrenfest. This result was later developed and put on firm mathematical foundations by Hepp. He proved that matrix elements of bounded functions of quantum observables between suitable coherents states (that depend on Planck's constant h) converge to classical values evolving according to the expected classical equations when h goes to zero. His results were later generalized by Ginibre and Velo to bosonic systems with infinite degrees of freedom and scattering theory. In this thesis we study the classical limit of Nelson model, that describes non relativistic particles, whose evolution is dictated by Schrödinger equation, interacting with a scalar relativistic field, whose evolution is dictated by Klein-Gordon equation, by means of a Yukawa-type potential. The classical limit is a mean field and weak coupling limit. We proved that the transition amplitude of a creation or annihilation operator, between suitable coherent states, converges in the classical limit to the solution of the system of differential equations that describes the classical evolution of the theory. The quantum evolution operator converges to the evolution operator of fluctuations around the classical solution. Transition amplitudes of normal ordered products of creation and annihilation operators between coherent states converge to suitable products of the classical solutions. Transition amplitudes of normal ordered products of creation and annihilation operators between fixed particle states converge to an average of products of classical solutions, corresponding to different initial conditions.