Histological assessment of a chronically implanted cylindrically-shaped, polymer-based neural probe in the monkey.

Objective.Previous studies demonstrated the possibility to fabricate stereo-electroencephalography probes with high channel count and great design freedom, which incorporate macro-electrodes as well as micro-electrodes offering potential benefits for the pre-surgical evaluation of drug resistant epileptic patients. These new polyimide probes allowed to record local field potentials, multi- and single-unit activity (SUA) in the macaque monkey as early as 1 h after implantation, and yielded stable SUA for up to 26 d after implantation. The findings opened new perspectives for investigating mechanisms underlying focal epilepsy and its treatment, but before moving to possible human application, safety data are needed. In the present study we evaluate the tissue response of this new neural interface by assessing post-mortem the reaction of brain tissue along and around the probe implantation site.Approach.Three probes were implanted, independently, in the brain of one monkey (Macaca mulatta) at different times. We used specific immunostaining methods for visualizing neuronal cells and astrocytes, for measuring the extent of damage caused by the probe and for relating it with the implantation time.Main results.The size of the region where neurons cannot be detected did not exceed the size of the probe, indicating that a complete loss of neuronal cells is only present where the probe was physically positioned in the brain. Furthermore, around the probe shank, we observed a slightly reduced number of neurons within a radius of 50µm and a modest increase in the number of astrocytes within 100µm.Significance.In the light of previous electrophysiological findings, the present data suggest the potential usefulness and safety of this probe for human applications.

Ferrofluidic adaptive mirrors.

A magnetic liquid mirror based on ferrofluids was demonstrated. Magnetic liquid mirrors represent a major departure from solid mirror technology. They present both advantages and disadvantages with respect to established technologies. Stroke (from a fraction of a wave to several hundreds of micrometers), cost (a few dollars per actuator), and scalability (hundreds of thousands of actuators) are the main advantages. Very large mirrors having diameters of the order of a meter should be feasible. There are a few disadvantages. The most important disadvantage is the time response, which is of the order of a few milliseconds. Although this time response could be further decreased with additional technical developments, it is unlikely to match the speed of solid mirrors. The technology is still in its infancy, and considerable work must still be done. However, the advantages are such that the technology is worth pursuing.

Cell size reduction induced by inhibition of the mTOR/S6K-signaling pathway protects Jurkat cells from apoptosis.

In Jurkat cells, the decreased cell growth rate associated with a long-lasting deactivation of the mammalian target of rapamycin (mTOR)/p70 ribosomal S6 kinase (S6K)-signaling pathway generates a cell population of progressively reduced cellular mass and size. When promoted by rapamycin as prototype inhibitor, the mTOR deactivation-dependent cell size reduction was associated with slowed, but not suppressed, proliferation. Small-size cells were significantly protected from apoptosis induced by Fas/Apo-1 death-receptor activation (as shown by reduced procaspase cleavage and decreased catalytic activity of relevant caspases) or by stress signals-dependent mitochondrial perturbation (as shown by reduced cleavage of caspase-2, lower dissipation of mitochondrial membrane potential and decreased release of cytochorome c and apoptosis-inducing factor from mitochondria). Protection faded when reactivation of the mTOR/S6K pathway promoted the cell recovery to normal size. These results suggest that cells induced to reduce their mass by the mTOR deactivation-dependent inhibition of cell growth become more resilient to lethal assaults by curbing the cell's suicidal response.

Optical tests of a 3.7-m-diameter liquid mirror: behavior under external perturbations.

We built and tested a 3.7-m-diameter liquid mirror that rotates on a ball bearing. Although the ball bearing is of a poor quality, the mirror is surprisingly good for one that comprises 1-mm-thick mercury layers. We found no evidence of the strong astigmatism that might have been expected from Coriolis forces. We did not detect effects of turbulence might or vibrations for thin mercury layers, illustrating the necessity of using thin layers: Large liquid mirrors would have had unacceptable optical qualities for layers much thicker than 2 mm.

La representación social de las condiciones y medio ambiente de trabajo en La Biblioteca Central UCV / The social representation of the conditions and environment of work in The Libraries Central UCV

La presente investigación se fundamenta en la Teoría de las Representaciones sociales; como modelo teórico plantea la génesis y la estructura del conocimiento del sentido común, afirmando que éste, en nuestra cambiante sociedad moderna, constituye el tipo de conocimiento práctico del cual se valen los grupos para captar e interpretar activamente la realidad que nos rodea. Hemos aplicado una metodología cualitativa en el análisis de los datos, utilizamos la técnica del análisis del contenido. Encontramos que para los trabajadores de la Biblioteca Central, el trabajo lo representa como graficador y como una función, aparece expresado el desempeño del cargo, el cual se vincula directamente al Manual de Cargo de la UCV. Se detectó una representación positiva del trabajo, éste se concibe como una actividad fundamental e inherente al ser humano, donde prevalece un alto grado de efectividad. Para este grupo el contexto de trabajo no presenta riesgo laborales tales como problemas alérgicos, asmáticos y respiratorios, que pueden estar presentes en estos espacios

Telecentric three-dimensional sensor with a liquid mirror for large-object inspection.

We describe a device that applies the advantages of the space invariance of telecentric triangulation with the measurement of large objects (1 m(3)). Because the scan motion of the laser beam is decoupled from the physical transport of the sensor head, the fast scanning of large volumes becomes feasible. The device consists of a triangulation laser telemeter head that uses a large liquid primary mirror and an aspheric secondary mirror to realize the telecentric f-theta objective. We propose using liquid-mirror technology to make low-cost large objectives that have low f numbers, a diffraction-limited performance, and low scattering in the visible. This new optical system is useful for 3-D measurement. We discuss the optical configuration of the system and the performance of a laboratory prototype. The prototype has a standoff distance of 1.5 m, a telecentric scan as long as 1 m, a depth of view of 1 m, and a relative depth resolution of 0.5-1 mm.

Corrector design with active vase mirrors that allows a fixed telescope to access a large region of the sky.

We investigate a family of two-mirror correctors to compensate for the aberrations of a parabolic mirror observing at a large angle from the zenith. We constrain our designs to optical elements that can be built with currently available technology. The secondary and the tertiary mirrors are warped by Zernike polynomials, which we know can be generated with active vase mirrors. The performances of these corrector designs are usable for imagery.

Optical tests of a 2.5-m-diameter liquid mirror: behavior under external perturbations and scattered-light measurements.

Interferometric tests of an f/1.2, 2.5-m-diameter liquid mirror show rms surface deviations of ~lambda/20 and Strehl ratios of the order of 0.6, which show that it is diffraction limited. The mirror is certainly better than what is implied by the data because of aberrations introduced by the auxiliary testing optics. We made detailed studies of the scattered light of the mirror. We studied the behavior of the mirror under external perturbations. We reached an important milestone because we now have a good understanding of liquid mirrors.

Cardiopulmonary adaptation to exercise after acute weight loss in severely obese subjects.

The aim of our study was to investigate the effects on baseline and exercise cardiopulmonary function and metabolic parameters of an acute (3-4 weeks) loss of at least 10% of initial weight in severely obese patients. Eight obese patients, 3 males and 5 females, mean age +/- SEM 42 +/- 6 yrs, body mass index (BMI) > 35 kg.m-2, underwent two cardiopulmonary function tests separated by 3 weeks of very low calorie protein-sparing diet (589 kcal.day-1) and a weight loss of 10% of initial weight (mean 8.43 +/- 0.72 kg). Eight normal subjects, matched for sex and age with the obese patients, served as controls. In the obese subjects, maximal workload (+15 +/- 3.6 W) and maximal oxygen consumption (V' O2) (+188 +/- 40.5 mL.min-1) were significantly increased after weight loss. Interestingly, exercise capacity at anaerobic threshold was not significantly different in obese subjects after weight loss with respect to normal subjects. Our results show that an acute but significant weight loss obtained with a very low calorie diet in obese patients is able to significantly improve maximal V' O2 and V' CO2 at anaerobic threshold. Moreover, this acute weight loss is able to partially reverse all of the cardiopulmonary alterations seen in obese patients both at baseline and during exercise.

Lidar measurements taken with a large-aperture liquid mirror. 1. Rayleigh-scatter system.

A lidar system has been built to measure atmospheric-density fluctuations and the temperature in the upper stratosphere, the mesosphere, and the lower thermosphere, measurements that are important for an understanding of climate and weather phenomena. This lidar system, the Purple Crow Lidar, uses two transmitter beams to obtain atmospheric returns resulting from Rayleigh scattering and sodium-resonance fluorescence. The Rayleigh-scatter transmitter is a Nd:YAG laser that generates 600 mJ/pulse at the second-harmonic frequency, with a 20-Hz pulse-repetition rate. The sodium-resonance-fluorescence transmitter is a Nd:YAG-pumped ring dye laser with a sufficiently narrow bandwidth to measure the line shape of the sodium D(2) line. The receiver is a 2.65-m-diameter liquid-mercury mirror. A container holding the mercury is spun at 10 rpm to produce a parabolic surface of high quality and reflectivity. Test results are presented which demonstrate that the mirror behaves like a conventional glass mirror of the same size. With this mirror, the lidar system's performance is within 10% of theoretical expectations. Furthermore, the liquid mirror has proved itself reliable over a wide range of environmental conditions. The use of such a large mirror presented several engineering challenges involving the passage of light through the system and detector linearity, both of which are critical for accurate retrieval of atmospheric temperatures. These issues and their associated uncertainties are documented in detail. It is shown that the Rayleigh-scatter lidar system can reliably and routinely measure atmospheric-density fluctuations and temperatures at high temporal and spatial resolutions.