Human Space Exploration: The Next Fifty Years

Preparation for the fftieth anniversary of human spacefight in the spring of 2011 provides the space faring nations with an opportunity to refect on past achievements as well as consider the next fifty years of human spacefight. The International Space Station is a unique platform for long duration life science research that will play a critical role in preparing for future human space exploration beyond low earth orbit. Some feel the future path back to the Moon and on to Mars may be delayed with the current commitment of the united States to support the development of human-rated commercial spacecraft. others see this as a unique opportunity to leverage the capability of the private sector in expanding access to space exploration. This article provides an overview of the past achievements in hu- man spacefight and discusses future missions over the next ffty years and the role space medicine will play in extending the time-distance constant of human space exploration.

Effect of EBW Parameters on Weldment Quality of Ti6Al4V Alloy

The penetration characteristics of EBW are primarily dependent on the main beam current (Iw), potential difference between the cathode and anode (voltage, V) and the welding speed (S). There are other influencing parameters like weld focus current (If), welding gun to work distance (GW) and beam oscillation.In the present study, the effect of work distance on focus current and on penetration of Ti6Al4V weld is studied using a 60kV, 30kW EB welding machine. Weld focus current is measured over a range of work distance and variation in its pattern is studied. Similarly, the variation of depth of penetration by varying the work distance and varying the focus current at a particular work distance constant are also analyzed.It is observed that, focus current is inversely proportional to the work distance and the variation in focus current per unit change of work distance is high in the shorter work distance region. The change in focus current and work distance affects the weld penetration and fusion zone geometry. For optimum penetration at a given work distance, the beam focus should be below the surface in keyhole welding. As the work distance increases, the penetration capacity of the beam decreases and maximum penetration is obtained in lesser work distance region.

The effect of perceptual grouping on haptic numerosity perception

In order to investigate the effect of perceptual grouping on haptic numerosity perception, we asked participants to explore tangible dot patterns and report the number of dots present in the display. We hypothesized that when there are subsets of dots that can be grouped together, exploration time will be shorter as compared to a display where no grouping takes place. The base display consists of dots that are equally spaced on a straight line. We manipulated subset grouping by using both proximity and configurational cues. By placing subsets of dots closer together or placing them in a spatial configuration (e.g., in a triangular shape with three dots, or a rectangular shape with four dots), while keeping the total exploration distance constant, we expected to find shorter exploration times as compared to the base display. The results indeed show that both these cues yield faster exploration. We therefore conclude that both proximity and configurational information can influence haptic grouping for numerosity judgments.

Observation of Scattered Evanescent Waves

Spatial resolution in the conventional optical microscopy depends on diffraction limit. Photon scanning tunneling microscopy is one of the microscopic methods that surpass the diffraction limit. It scans an object with detecting evanescent wave on object surface. Evanescent wave is scattered by the tip of a fiber probe and guided to a detector by the fiber probe. Not all of the scattered ray can be detected. Only the scattered ray from the aperture of a fiber probe can be detected. We propose to improve an image by detecting the state of scattered ray and a new method to maintain the probe sample distance constant by keeping the quantity of scattered ray constant.

Magnitude Estimation of Velocity in the X, Y, and Z Axes

The present study examined the perception of velocity along different axes. Participants viewed the movement of two small circles on a computer display and gave verbal responses for the perceived velocity of one of the circles relative to the other using the psychophysical method of magnitude estimation. Stimuli were presented along the x, y, and z axes. Other variables included direction traveled, time and distance constant, and velocity. Movement in the z axis was represented through angular expansion. As expected, results indicated that velocity judgments increased with increases in stimulus velocity. Perceived velocity was expected to be higher for vertical as compared to horizontal stimuli. The results provided partial support for this hypothesis. Estimates for velocity along the z axis were qualitatively different than for the other two axes. Further, velocity estimates depended upon whether the time or distance was held constant and suggest that the perception of velocity is tied to both spatial and temporal properties of the stimuli.

Visual Latency Difference Determined by Two ‘‘Rotating’’ Pulfrich Techniques

We tested the validity of Nickalls’ formula for determining visual latency difference by using two rotating Pulfrich techniques: (A) varying viewing distance while keeping target angular velocity constant (33 rev/min) and (B) varying the target angular velocity while keeping the viewing distance constant (180 cm). The formula predicts that the latency differences estimated by the two techniques are equal with a given neutral density filter. Observers were asked to judge whether or not the rotating target (clockwise) appeared to move back-and-forth from side-to-side with a neutral density filter (OD = 0.7, 1.0, 1.3) in front of the right eye. The results with ten observers showed that the mean visual latency differences associated with each technique for a given filter were not significantly different. These results further validate the Nickalls’ formula and, therefore, support the visual-latency hypothesis to account for the Pulfrich phenomenon.

Terabit Density Cobalt Nanowire Arrays With Tunable Magnetic Properties

Nanoporous templates made from diblock copolymer films are used for electrochemical fabrication of hexagonal arrays of vertical cobalt magnetic nanowires at terabit/in2 density. The nanowire diameter and areal density are determined by the copolymer molecular weight, whereas the nanowire length and internal crystal morphology are controlled through the dc electrodeposition growth process. The array magnetic properties can be modified substantially by electrodeposition pH conditions while keeping wire size and interwire distance constant. Optimum pH control results in preferential growth of c-axis oriented crystallites with large perpendicular coercivity. The appearance of exchange bias behavior, exhibited at low temperatures, is also investigated.

Magnetic Properties of 100 NM-Period Nickel Nanowire Arrays Obtained from Ordered Porous-Alumina Templates

Ni nanowires were grown in highly-ordered anodic alumina templates using pulsed electrodeposition. This technique yields completely metal-filled alumina membranes. The magnetic behavior of 100 nm period arrays of Ni nanowires with a length of 1 μ and different diameters has been characterized using SQUID magnetometry and magnetic force microscopy. Reducing the diameter from initially 50 to 25 nm while keeping the interwire distance constant leads to increasing coercive fields from 600 Oe to 1200 Oe and to increasing remanence from 30% to 100% of the hysteresis. The deposition of Ni65Fe35 gave a further improvement of the coercive fields up to 1350 Oe.

Average distance constants for polygons in spaces with non-positive curvature

In this paper we show that the average distance constant of a general polygon which is a subset of an M-space with non-positive curvature can be expressed as the extreme value of either of two nonlinear programs and discuss the practical application of one of these nonlinear programs for the determination of the average distance constant for a polygon in general, and in particular for a planar triangle.