Near-infrared spectroscopy study of tourniquet-induced forearm ischaemia in patients with coronary artery disease

Near-Infrared Spectroscopy (NIR) can be employed to monitor local changes in haemodynamics and oxygenation of human tissues. A preliminary study has been performed in order to evaluate the NIRS transmittance response to induced forearm ischaemia in patients with coronary artery disease (CAD). The population consists in 40 patients with cardiovascular risk factors and angiographically documented CAD, compared to a group of 13 normal subjects. By inflating and subsequently deflating a cuff placed around the patient arm, an ischaemia has been induced and released, and the patients have been observed until recovery of the basal conditions. A custom LAIRS spectrometer (IRIS) has been used to collect the backscattered light intensities from the patient forearm throughout the ischaemic and the recovery phase. The time dependence of the near-infrared transmittance on the control group is consistent with the available literature. On the contrary, the magnitude and dynamics of the NIRS signal on the CAD patients show deviations from the documented normal behavior, which can be tentatively attributed to abnormal vessel stiffness. These preliminary results, while validating the performance of the IRIS spectrometer, are strongly conducive towards the applicability of the NIRS technique to ischaemia analysis and to endothelial dysfunction characterization in CAD patients with cardiovascular risk factors.Publisher PD

19F nuclear spin relaxation and spin diffusion effects in the single ion magnet LiYF4:Ho3+

Temperature and magnetic field dependences of the 19F nuclear spin-lattice relaxation in a single crystal of LiYF4 doped with holmium are described by an approach based on a detailed consideration of the magnetic dipole-dipole interactions between nuclei and impurity paramagnetic ions and nuclear spin diffusion processes. The observed non-exponential long time recovery of the nuclear magnetization after saturation at intermediate temperatures is in agreement with predictions of the spin-diffusion theory in a case of the diffusion limited relaxation. At avoided level crossings in the spectrum of electron-nuclear states of the Ho3+ ion, rates of nuclear spin-lattice relaxation increase due to quasi-resonant energy exchange between nuclei and paramagnetic ions, in contrast to the predominant role played by electronic cross-relaxation processes in the low-frequency ac-susceptibility.Comment: 27 pages total, 5 figures, accepted for publication, Eur. Phys. J.

Óleos de macaúba: uma alternativa para a oleoquímica.

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Transesterificação de óleo de soja com diversos catalisadores alcalinos.

Amostras de óleo de soja neutralizado e seco foram transesterificadas com etanol comercial a 99,5% na presença de quantidades equivalentes de hidróxido, metóxido, etóxido e gliceróxido de sódio como catalisadores. Com o uso dos três alcóxidos obteve-se a separação do glicerol formado durante a reação, o que não ocorreu com o uso de hidróxido de sódio. O rendimento de sódio, como catalisador na transesterificação, apresenta vantagens econômicas e tecnológicas quando comparado com o hidróxido de sódio.bitstream/item/65433/1/CTAA-DOCUMENTOS-12-TRANSESTERIFICACAO-DE-OLEO-DE-SOJA-COM-DIVERSOS-CATALISADORES-ALCALINOS-FL-021.pd

Fast response and temporal coherent oscillations in small-world networks

We have investigated the role that different connectivity regimes play in the dynamics of a network of Hodgkin-Huxley neurons by computer simulations. The different connectivity topologies exhibit the following features: random topologies give rise to fast system response yet are unable to produce coherent oscillations in the average activity of the network; on the other hand, regular topologies give rise to coherent oscillations, but in a temporal scale that is not in accordance with fast signal processing. Finally, small-world topologies, which fall between random and regular ones, take advantage of the best features of both, giving rise to fast system response with coherent oscillations.We acknowledge G. Laurent, A. Bäcker, M. Bazhenov, M. Rabinovich, and H. Abarbanel for insightful discussions. We thank the Dirección General de Enseñanza Superior e Investigación Científica for financial support (PB97-1448), the CAM for financial support to L. F. L., and the CCCFC (UAM) for the use of computation resources

Anharmonic transitions in nearly dry L-cysteine I

Two special dynamical transitions of universal character have been recently observed in macromolecules at $T_{D}\sim 180 - 220$ K and $T^{*}\sim 100$ K. Despite their relevance, a complete understanding of the nature of these transitions and their consequences for the bio-activity of the macromolecule is still lacking. Our results and analysis concerning the temperature dependence of structural, vibrational and thermodynamical properties of the orthorhombic polymorph of the amino acid L-cysteine (at a hydration level of 3.5%) indicated that the two referred temperatures define the triggering of very simple and specific events that govern all the biochemical interactions of the biomolecule: activation of rigid rotors ($T<T^{*}$), phonon-phonon interactions with phonons of water dimer ($T^{*}<T<T_{D}$), and water rotational barriers surpassing ($T>T_{D}$).Comment: 4 pages, 4 figures, submitted to Physical Review Letter

ANÁLISE DO PROCESSAMENTO DE DADOS GPS EM FUNÇÃO DAS DIFERENTES CONDIÇÕES DE RASTREIO

As observações GPS estão suscetíveis, principalmente, ao efeito do multicaminho e das perdas de ciclo devido a existência de obstruções nas estações de rastreio. Neste trabalho procurou-se determinar qual o tipo de observável fornece melhor resultado na determinação das coordenadas bidimensionais e tridimensionais em função das diferentes situações de rastreio. Associou-se os resultados deste experimento com as precisões requeridas nas diversas áreas da cartografia. A GPS observation analysis as a consequence of different tracking conditions Abstract GPS observations are susceptible, mainly, to the effect of multipath and cycle slips due to obstructions in the surveying stations. In this work, we tried to determine which the observable type supplies produced better results in the determination of the coordinates 2D and 3D in function of the different surveying situations. The results of this experiment were associated with the precisions required in the several areas of cartography

Network analysis identifies weak and strong links in a metapopulation system

The identification of key populations shaping the structure and connectivity of metapopulation systems is a major challenge in population ecology. The use of molecular markers in the theoretical framework of population genetics has allowed great advances in this field, but the prime question of quantifying the role of each population in the system remains unresolved. Furthermore, the use and interpretation of classical methods are still bounded by the need for a priori information and underlying assumptions that are seldom respected in natural systems. Network theory was applied to map the genetic structure in a metapopulation system by using microsatellite data from populations of a threatened seagrass, Posidonia oceanica, across its whole geographical range. The network approach, free from a priori assumptions and from the usual underlying hypotheses required for the interpretation of classical analyses, allows both the straightforward characterization of hierarchical population structure and the detection of populations acting as hubs critical for relaying gene flow or sustaining the metapopulation system. This development opens perspectives in ecology and evolution in general, particularly in areas such as conservation biology and epidemiology, where targeting specific populations is crucial