SCANNER DESIGN SPECIFICITY FOR HELMET-MOUNTED TARGETING SYSTEM

Following design principles are important for helmet-mounted targeting systems. Two scanners on base of the polygonal reflector-type prisms forming the fanned field of view are fastened to head-up display. Three LEDs installed on pilot helmet form a plane, the normal of which is collinear to helmet indi-cator viewing line. Angles of LED bearings are measured with triangulation method and angular position of viewing line is calculat-ed. Two options for organization of scanning process are analyzed in the paper. In the first variant, one prism rotates in clockwise and the other in counterclockwise direction. In the second variant both prisms rotate in the same direction, clockwise for example. It is shown that if the prisms rotate in the same direction the targeting accuracy is greater. The algorithm developed for determination of targeting accuracy may be used to matching the rate of scanning and geometric parameters of helmet-mounted targeting system at prescribed accuracy of targeting.

The Effect of Aberrant Rotation on Radiographic Patellar Height Measurement Using Canton-Deschamps Index: A Cadaveric Analysis

The Caton-Deschamps Index (CDI) is a measurement used to evaluate patella alta based on true lateral radiographs; however, no prior study has investigated how altering the degree of radiograph aberrancy affects CDI measurement. The primary and secondary purpose of this study was to evaluate effects of rotational radiographic changes on patella height measurements and compare these findings to MRI measurements, respectively. Five cadaver knees (n = 5) were utilized in this study. True lateral radiographs were obtained for each specimen by using a fluoroscopic C-arm machine. The C-arm was then altered in two planes (axial and coronal) in both the clockwise and counterclockwise direction and radiographs were taken at 5, 10, and 15 degrees of error from the true lateral position. A CDI measurement of each specimen was performed based on sagittal magnetic resonance imaging (MRI) slices and compared with radiographic CDI measurements. Three orthopedic surgeons measured the CDI for each radiograph and MRI performed. Interrater reliability and changes in CDI were analyzed. Clinically significant difference in CDI was set to 0.1. Mean intraclass correlation coefficient was high (≥0.7) at true lateral and at all varying degrees of error. When performing a pairwise comparison of mean CDI from the true lateral position to increasing degrees of error, statistically significant differences were observed in the axial plane. The largest change in CDI measurements was seen with rotational malposition in the axial plane and counterclockwise direction. No statistically significant differences in mean CDI were observed in the coronal plane. The change in CDI from the true lateral position reached an absolute maximum of at least 0.1 in all four scenarios at each tested degree of error. This study found that aberrant radiographic rotation in the axial plane resulted in a significantly different mean CDI measurement when compared with true lateral radiographs. All degrees of error in both directions and in both planes could have a clinically significant effect on CDI (≥0.1). Our findings confirm the importance of a perfect true lateral radiograph when measuring patella height.

Fast degradation of the circular flare ribbon on 2014 August 24

Context. The separation and elongation motions of solar flare ribbons have extensively been investigated. The degradation and disappearance of ribbons have rarely been explored. Aims. We report our multiwavelength observations of a C5.5 circular-ribbon flare associated with two jets (jet1 and jet2) on 2014 August 24, focusing on the fast degradation of the outer circular ribbon (CR). Methods. The flare was observed in ultraviolet (UV) and extreme-ultraviolet (EUV) wavelengths by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory spacecraft. Soft X-ray fluxes of the flare in 0.5−4 and 1−8 Å were recorded by the GOES spacecraft. Results. The flare, consisting of a short inner ribbon (IR) and outer CR, was triggered by the eruption of a minifilament. The brightness of IR and outer CR reached their maxima simultaneously at ∼04:58 UT in all AIA wavelengths. Subsequently, the short eastern part of the CR faded out quickly in 1600 Å but only gradually in EUV wavelengths. The long western part of the CR degraded in the counterclockwise direction and decelerated. The degradation was distinctly divided into two phases: phase I with faster apparent speeds (58−69 km s−1), and phase II with slower apparent speeds (29−35 km s−1). The second phase stopped at ∼05:10 UT when the western CR disappeared entirely. In addition to the outward propagation of jet1, the jet spire experienced untwisting motion in the counterclockwise direction during 04:55−05:00 UT. Conclusions. We conclude that the event can be explained by the breakout jet model. The coherent brightenings of the IR and CR at ∼04:58 UT may result from the impulsive interchange reconnection near the null point, whereas sub-Alfvénic slipping motion of the western CR in the counterclockwise direction indicates the occurrence of slipping magnetic reconnection. Another possible explanation of the quick disappearance of the hot loops that are connected to the western CR is that they are simply reconnected sequentially without the need for significant slippage after the null-point reconnection.

MOUNTAINS AND CAVES IN THE ANDIS’ RITES OF THE SUN AND RAIN MAKING

Mod and Bakhargan were the most revered mountains for the Andis. According to the authors, the Andis used mountains and caves, as parts of the sacred landscape, on calendar holidays and in the rites of meteorological and healing magic. Thus, rites of the sun and rain making were held here. On the mountain of Bakhargan, there was a spring with healing water. The mountain of Bakhargan was used in the ceremonies of folk medicine: praying for healing, sick people described three circles round the rocks of the sacred mountain in the counterclockwise direction. In the mythology of the Andis, the tops of the mountains were the habitat of the supreme god and mountain angels. The Andis associated mountains with legends, containing the motifs of the biblical legend of the Flood. After converting to Islam, the most revered mountains were turned into places of worship, where the rite of dhikr was conducted and alms were dealt out during the prayers. Many of the rites for changing weather were led by local religious authorities or elders. Besides the use of mountains and caves in the rites of the sun and rain making, the Andis also had other rites of meteorological magic. The most common of them was the rite with a mummer. There were also rites with the use of the skull of a stallion and a snake, probably related to zoolatry. Analysis of orolatry, meteorological and healing magic of the Andis testifies to the syncretism of their spiritual culture. This confusion of traditional beliefs and Muslim religious prescriptions is peculiar to the so-called “everyday Islam”. This syncretism was common to other peoples of Dagestan and the North Caucasus.

The Rotating Tilted Lines Illusion

This chapter describes the Rotating-Tilted-Lines illusion , which is a new motion illusion that arises in a circular pattern composed by black, radial lines tilted to the right and presented on a white background. When one approaches the stimulus pattern, the radial lines appear to rotate in the counterclockwise direction, whereas when one recedes from it, they appear to rotate clockwise. It is the simplest pattern able to elicit illusory rotatory motion in presence of physical radial expansion. This surprising misperception of motion seems to be a result of the competition between two motion processing units in the primary visual cortex (V1, V5)

Survivability of bouncing robots

Bouncing robots are mobile agents with limited sensing capabilities adjusting their movements upon collisions either with other robots or obstacles in the environment. They behave like elastic particles sliding on a cycle or a segment. When two of them collide, they instantaneously update their velocities according to the laws of classical mechanics for elastic collisions. They have no control on their movements which are determined only by their masses, velocities, and upcoming sequence of collisions. We suppose that a robot arriving for the second time to its initial position dies instantaneously. We study the survivability of collections of swarms of bouncing robots. More exactly, we are looking for subsets of swarms such that after some initial bounces which may result in some robots dying, the surviving subset of the swarm continues its bouncing movement, with no robot reaching its initial position. For the case of robots of equal masses and speeds we prove that all robots bouncing in the segment must always die while there are configurations of robots on the cycle with surviving subsets. We show the smallest such configuration containing four robots with two survivors. We show that any collection of less than four robots must always die. On the other hand, we show that [Formula: see text] robots always die where [Formula: see text] (and [Formula: see text]) is the number of robots starting their movements in clockwise (respectively, counterclockwise) direction in swarm [Formula: see text]. When robots bouncing on a cycle or a segment have arbitrary masses we show that at least one robot must always die. Further, we show that in either environment it is possible to construct swarms with [Formula: see text] survivors. We prove, however, that the survivors in the segment must remain static indefinitely while in the case of the cycle it is possible to have surviving collections with strictly positive kinetic energy.

Dynamic helical cyclophanes with two quadruply-bridged planes arranged in an “obverse and/or reverse” relation

We describe the design of two types of cyclophanes that generate dynamic helicity through the twisting of two planes in a clockwise or counterclockwise direction to give (M)- or (P)-helicity.

Documenting a Rare Tornado Merger Observed in the 24 May 2011 El Reno–Piedmont, Oklahoma, Supercell*

Unique observations of the interaction and likely merger of two cyclonic tornadoes are documented. One of the tornadoes involved in the interaction was the enhanced Fujita scale (EF5) El Reno–Piedmont, Oklahoma, tornado from 24 May 2011 and the other was a previously undocumented tornado. Data from three S-band radars: Twin Lakes, Oklahoma (KTLX); Norman, Oklahoma (KOUN); and the multifunction phased-array radar (MPAR), are used to detail the formation of the second tornado, which occurred to the northwest of the original tornado in an area of strong radial convergence. Radar data and isosurfaces of azimuthal shear provide evidence that both tornadoes formed within an elongated area of mesocyclone-scale cyclonic rotation. The path taken by the primary tornado and the formation location of the second tornado are different from previous observations of simultaneous cyclonic tornadoes, which have been most often observed in the cyclic tornadogenesis process. The merger of the two tornadoes occurred during the sampling period of a mobile phased-array radar—the Mobile Weather Radar, 2005 X-Band, Phased Array (MWR-05XP). MWR-05XP electronic scanning in elevation allowed for the merger process to be examined up to 4 km above radar level every 11 s. The tornadic vortex signatures (TVSs) associated with the tornadoes traveled around each other in a counterclockwise direction then merged in a helical manner up through storm midlevels. Upon merging, both the estimated intensity and size of the TVS associated with the resulting tornado increased dramatically. Similarities between the merger observed in this case and in previous cases also are discussed.

Rotational movement of a spermatozoon around its long axis

The rotational movement of a spermatozoon around its longitudinal axis was investigated by two methods: by observing a spermatozoon attached vertically to a coverslip by the tip of its head, and by observing a spermatozoon freely swimming in a medium by means of ‘double-focal microscopy’, which yielded simultaneous images at two different focal planes. Similar results were obtained by these two methods. Sea urchin, starfish, medaka, human, golden hamster and bull spermatozoa rolled in both clockwise and counterclockwise directions, although there was a large difference in the proportion of spermatozoa rolling in each direction in the different species. The majority of sea urchin and starfish spermatozoa rolled in a clockwise direction when an observer viewed the cell from its anterior end, whereas the majority of medaka, golden hamster, human and bull spermatozoa rolled in a counterclockwise direction relative to the same observer. Moreover, some spermatozoa occasionally changed their rotational direction. These results suggest that the mechanism regulating the direction of rotation of the spermatozoa is lax. As rotational movement of a spermatozoon around its longitudinal axis is due to the three-dimensional component of the beat of the flagellum, the direction of the three-dimensional movement presumably changes as the spermatozoa swim.