17,067 research outputs found
Acute Effects of Exercise on Cognitive Performances of Older Adults
Accelerating rates of structural decline become evident during the third and fourth decades of human life, with disproportionate degeneration occurring in the frontal, parietal, and temporal brain lobes. As the structure of the brain declines, a broad array of cognitive processes involving memory, decision making, and selective attention are reduced as well (Raz 2000, Park et al. 2001). Cardiovascular exercise has been associated with improved cognitive functioning in aging humans, suggesting that increased vascular supply enhances availability of oxygen, nutrients, and other physical entities to nourish the brain. Previous experimentation on older adults revealed significant positive effects of exercise on a variety of memory types following participation in a program six or more months in duration (Colcombe 2003, Kramer et al.1999). The primary focus of this study was to test the effects of acute aerobic exercise on cognitive functioning of adults over the age of 60. A second purpose was to determine that the positive neurological effects of exercise can start taking place immediately. The hypothesis is that memory retention, mental processing speed, and selective attention would acutely improve in the participants after they had exercised, in comparison to their cognitive state prior to exercise. Cognitive performances both before and after exercise were tested using the Stroop test. All participants completed the post-exercise test with improved scores (p=0.000) indicating an increase in cognitive ability, relating exercise and improved cognitive function
Method and apparatus for precision control of radiometer
A radiometer controller of a radiation detector is provided with a calibration method and apparatus comprised of mounting all temperature sensitive elements of the controller in thermostatically controlled ovens during calibration and measurements, using a selected temperature that is above any which might be reached in the field. The instrument is calibrated in situ by adjusting heater power (EI) to the receptor cavity in the radiometer detector to a predetermined full scale level and is displayed by a meter
Efficient superfluorescent light sources with broad bandwidth
We demonstrate various efficient broad-band light sources at ~1µm wavelength with a 3dB bandwidth of up to 65nm at 108mW output power, based on rare-earth doped silica fibers and a simple adjustable spectral filter
Evolution of the bilayer nu = 1 quantum Hall state under charge imbalance
We use high-mobility bilayer hole systems with negligible tunneling to
examine how the bilayer nu = 1 quantum Hall state evolves as charge is
transferred from one layer to the other at constant total density. We map
bilayer nu = 1 state stability versus imbalance for five total densities
spanning the range from strongly interlayer coherent to incoherent. We observe
competition between single-layer correlations and interlayer coherence. Most
significantly, we find that bilayer systems that are incoherent at balance can
develop spontaneous interlayer coherence with imbalance, in agreement with
recent theoretical predictions.Comment: 4 pages, 4 figure
Dispersal of \u3ci\u3eFenusa Dohrnii\u3c/i\u3e (Hymenoptera: Tenthredinidae) From an \u3ci\u3eAlnus\u3c/i\u3e Short-Rotation Forest Plantation
The European alder leafminer, Fenusa dohrnii, is a defoliating insect pest of Alnus in short-rotation forest plantations. A 2-year study was performed to quantify movement from infested stands to uninfested areas. Sticky traps and potted monitor trees were installed at different locations within and at various distances from (0,5, 10, and 20 m) an infested stand to measure adult flight and oviposition activity, respectively. Trap catch and oviposition activity fell off sharply with distance, few insects being trapped or eggs laid at distances of 5 m or greater from the infestation
Fear and the human amygdala
We have previously reported that bilateral amygdala damage in humans compromises the recognition of fear in facial expressions while leaving intact recognition of face identity (Adolphs et al., 1994). The present study aims at examining questions motivated by this finding. We addressed the possibility that unilateral amygdala damage might be sufficient to impair recognition of emotional expressions. We also obtained further data on our subject with bilateral amygdala damage, in order to elucidate possible mechanisms that could account for the impaired recognition of expressions of fear. The results show that bilateral, but not unilateral, damage to the human amygdala impairs the processing of fearful facial expressions. This impairment appears to result from an insensitivity to the intensity of fear expressed by faces. We also confirmed a double dissociation between the recognition of facial expressions of fear, and the recognition of identity of a face: these two processes can be impaired independently, lending support to the idea that they are subserved in part by anatomically separate neural systems. Based on our data, and on what is known about the amygdala's connectivity, we propose that the amygdala is required to link visual representations of facial expressions, on the one hand, with representations that constitute the concept of fear, on the other. Preliminary data suggest the amygdala's role extends to both recognition and recall of fearful facial expressions
Impact-induced acceleration by obstacles
We explore a surprising phenomenon in which an obstruction accelerates,
rather than decelerates, a moving flexible object. It has been claimed that the
right kind of discrete chain falling onto a table falls \emph{faster} than a
free-falling body. We confirm and quantify this effect, reveal its complicated
dependence on angle of incidence, and identify multiple operative mechanisms.
Prior theories for direct impact onto flat surfaces, which involve a single
constitutive parameter, match our data well if we account for a characteristic
delay length that must impinge before the onset of excess acceleration. Our
measurements provide a robust determination of this parameter. This supports
the possibility of modeling such discrete structures as continuous bodies with
a complicated constitutive law of impact that includes angle of incidence as an
input.Comment: small changes and corrections, added reference
Out-of-plane focusing grating couplers for silicon photonics integration with optical MRAM technology
We present the design methodology and experimental characterization of compact out-of-plane focusing grating couplers for integration with magnetoresistive random access memory technology. Focusing grating couplers have recently found attention as layer-couplers for photonic-electronic integration. The components we demonstrate are designed for a wavelength of 1550 nm, fabricated in a standard 220 nm SOI photonic platform and optimized given the fabrication restrictions for standard 193-nm UV lithography. For the first time, we extend the design based on the phase matching condition to a two-dimensional (2-D) grating design with two optical input ports. We further present the experimental characterization of the focusing behaviour by spatially probing the emitted beam with a tapered-and-lensed fiber and demonstrate the polarization controlling capabilities of the 2-D FGCs
X-Ray Tomography To Measure Size Of Fragments From Penetration Of High-Velocity Tungsten Rods
Behind-armor debris that results from tungsten rods penetrating armor steel at 2 km/s was studied by analysis of recovered fragments. Fragment recovery was by means of particle board. Individual fragments were analyzed by x-ray tomography, which provides information for fragment identification, mass, shape, and penetration down to masses of a few milligrams. The experiments were complemented by AUTODYN and EPIC calculations. Fragments were steel or tungsten generated from the channel or from the breakout through the target rear surface. Channel fragment motions were well described by Tate theory. Breakout fragments had velocities from the projectile remnant to the channel velocity, apparently depending on where in the projectile a fragment originated. The fragment size distribution was extremely broad and did not correlate well with simple uniform-fragment-size models.Mechanical Engineerin
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