Speckle interferometry of asteroids. IV - Reconstructed images of 4 Vesta

NASA Technical Reports Server (NTRS)

Drummond, J.; Eckart, A.; Hege, E. K.

1988-01-01

The images of 4 Vesta obtained by means of speckle interferometric observations on November 16 and 17, 1983, support a 5-hr 20.5-min rotational period. The 4 Vesta visible light curve was approximately matched by the placing of circular 'spots' with 135-km diameter over the three dark and three bright features, followed by the assigning of albedos of 0 to the dark spots and 2 to the bright. The light curve is found to be primarily defined by albedo structure, rather than shape; this results in one maximum and one minimum/rotation, rather than the two of each that would be associated with 4 Vesta's triaxial ellipsoid morphology.

Universal Dark Halo Scaling Relation for the Dwarf Spheroidal Satellites

NASA Astrophysics Data System (ADS)

Hayashi, Kohei; Ishiyama, Tomoaki; Ogiya, Go; Chiba, Masashi; Inoue, Shigeki; Mori, Masao

2017-07-01

Motivated by a recently found interesting property of the dark halo surface density within a radius, {r}\\max , giving the maximum circular velocity, {V}\\max , we investigate it for dark halos of the Milky Way’s and Andromeda’s dwarf satellites based on cosmological simulations. We select and analyze the simulated subhalos associated with Milky-Way-sized dark halos and find that the values of their surface densities, {{{Σ }}}{V\\max }, are in good agreement with those for the observed dwarf spheroidal satellites even without employing any fitting procedures. Moreover, all subhalos on the small scales of dwarf satellites are expected to obey the universal relation, irrespective of differences in their orbital evolutions, host halo properties, and observed redshifts. Therefore, we find that the universal scaling relation for dark halos on dwarf galaxy mass scales surely exists and provides us with important clues for understanding fundamental properties of dark halos. We also investigate orbital and dynamical evolutions of subhalos to understand the origin of this universal dark halo relation and find that most subhalos evolve generally along the {r}\\max \\propto {V}\\max sequence, even though these subhalos have undergone different histories of mass assembly and tidal stripping. This sequence, therefore, should be the key feature for understanding the nature of the universality of {{{Σ }}}{V\\max }.

Asymmetric mass models of disk galaxies. I. Messier 99

NASA Astrophysics Data System (ADS)

Chemin, Laurent; Huré, Jean-Marc; Soubiran, Caroline; Zibetti, Stefano; Charlot, Stéphane; Kawata, Daisuke

2016-04-01

Mass models of galactic disks traditionally rely on axisymmetric density and rotation curves, paradoxically acting as if their most remarkable asymmetric features, such as lopsidedness or spiral arms, were not important. In this article, we relax the axisymmetry approximation and introduce a methodology that derives 3D gravitational potentials of disk-like objects and robustly estimates the impacts of asymmetries on circular velocities in the disk midplane. Mass distribution models can then be directly fitted to asymmetric line-of-sight velocity fields. Applied to the grand-design spiral M 99, the new strategy shows that circular velocities are highly nonuniform, particularly in the inner disk of the galaxy, as a natural response to the perturbed gravitational potential of luminous matter. A cuspy inner density profile of dark matter is found in M 99, in the usual case where luminous and dark matter share the same center. The impact of the velocity nonuniformity is to make the inner profile less steep, although the density remains cuspy. On another hand, a model where the halo is core dominated and shifted by 2.2-2.5 kpc from the luminous mass center is more appropriate to explain most of the kinematical lopsidedness evidenced in the velocity field of M 99. However, the gravitational potential of luminous baryons is not asymmetric enough to explain the kinematical lopsidedness of the innermost regions, irrespective of the density shape of dark matter. This discrepancy points out the necessity of an additional dynamical process in these regions: possibly a lopsided distribution of dark matter.

Moon - North Polar Mosaic, Color

NASA Technical Reports Server (NTRS)

1996-01-01

During its flight, the Galileo spacecraft returned images of the Moon. The Galileo spacecraft surveyed the Moon on December 7, 1992, on its way to explore the Jupiter system in 1995-1997. The left part of this north pole view is visible from Earth. This color picture is a mosaic assembled from 18 images taken by Galileo's imaging system through a green filter. The left part of this picture shows the dark, lava-filled Mare Imbrium (upper left); Mare Serenitatis (middle left), Mare Tranquillitatis (lower left), and Mare Crisium, the dark circular feature toward the bottom of the mosaic. Also visible in this view are the dark lava plains of the Marginis and Smythii Basins at the lower right. The Humboldtianum Basin, a 650-kilometer (400-mile) impact structure partly filled with dark volcanic deposits, is seen at the center of the image. The Moon's north pole is located just inside the shadow zone, about a third of the way from the top left of the illuminated region. The Galileo project is managed for NASA's Office of Space Science by the Jet Propulsion Laboratory.

Do Galactic Potential Wells Depend on Their Largescale Environment

NASA Astrophysics Data System (ADS)

Mo, H. J.; Lahav, O.

1993-04-01

We study the dependence of the intrinsic velocities of galaxies on their large-scale environment, using a cross-correlation technique that provides an objective way of defining the local overdensity of `trace' galaxies around `target' galaxies. We use galaxies in optical (CfA and SSRS) and IRAS redshift surveys as tracers of the density field, and about 1000 spiral galaxies with measured circular velocities and elliptical galaxies with measured velocity dispersion as `targets'. We find that the correlation function tends to increase with circular velocity, the trend being weak except in the case of cD-like elliptical galaxies with the highest velocity dispersions (σ >~ 300 km s^-1^), where the effect is strong, possibly due to morphological segregations in clusters of galaxies. A fit to the mean overdensity δ(r < r_p_) of the trace galaxies (in spheres of radius r_p_) around target galaxies as a function of the circular velocities V_c_ shows a weak increase of δ with v_c_, with slope {DELTA}δ(r<~3.6 h^-1^ Mpc)/{DELTA}V_c_ <~ 0.02. The observed weak correlation is contrasted with the strong dependence of the correlation functions of dark haloes on their circular velocities predicted in some (e.g. high-biasing cold dark matter) models for galaxy formation. In particular, our results are inconsistent with the prediction of the `natural' (high) biasing model at a high significance level. Comparison of our results with those of a simple biasing model suggests that either the observed circular velocities of galaxies are not simply related to the circular velocities of dark haloes, or most dark haloes were formed at high redshifts, or the galaxy distribution does not trace the matter distribution in a simple way.

Exploring triplet-quadruplet fermionic dark matter at the LHC and future colliders

NASA Astrophysics Data System (ADS)

Wang, Jin-Wei; Bi, Xiao-Jun; Xiang, Qian-Fei; Yin, Peng-Fei; Yu, Zhao-Huan

2018-02-01

We study the signatures of the triplet-quadruplet dark matter model at the LHC and future colliders, including the 100 TeV Super Proton-Proton Collider and the 240 GeV Circular Electron Positron Collider. The dark sector in this model contains one fermionic electroweak triplet and two fermionic quadruplets, which have two kinds of Yukawa couplings to the Higgs doublet. Electroweak production signals of the dark sector fermions in the monojet+ ET, disappearing track, and multilepton+ET channels at the LHC and the Super Proton-Proton Collider are investigated. Moreover, we study the loop effects of this model on the Circular Electron Positron Collider precision measurements of e+e-→Z h and h →γ γ . We find that most of the parameter regions allowed by the observed dark matter relic density will be well explored by such direct and indirect searches at future colliders.

THE VELOCITY FUNCTION OF DARK MATTER HALOS AT R = 20 kpc: REMARKABLY LITTLE EVOLUTION SINCE z Almost-Equal-To 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weinmann, Simone M.; Franx, Marijn; Van Dokkum, Pieter

We investigate the evolution in the dark matter halo circular velocity function, measured at a fixed physical radius of 20 kpc (v{sub 20}), which is likely to be a good proxy for galaxy circular velocity, in the Millennium-II simulation. We find that the v{sub 20} function evolves remarkably little since z Almost-Equal-To 4. We analyze the histories of the main progenitors of halos, and we find that the dark matter distribution within the central 20 kpc of massive halos has been in place since early times. This provides evidence for the inside-out growth of halos. The constancy of the centralmore » circular velocity of halos may offer a natural explanation for the observational finding that the galaxy circular velocity is an excellent predictor of various galaxy properties. Our results also indicate that we can expect a significant number of galaxies with high circular velocities already at z = 4 (more than one per 10{sup 6} h {sup -3} Mpc{sup 3} with circular velocities in excess of 450 km s{sup -1}, and more than one per 10{sup 4.5} h {sup -3} Mpc{sup 3} with circular velocities in excess of 350 km s{sup -1}). Finally, adding baryonic mass and using a simple model for halo adiabatic contraction, we find remarkable agreement with the velocity-dispersion functions inferred observationally by Bezanson et al. up to z Almost-Equal-To 1 and down to about 220 km s{sup -1}.« less

Disappearance of the Propontis Regional Dark Albedo Feature on Mars

NASA Astrophysics Data System (ADS)

Lee, Steven W.; Thomas, P. C.; Cantor, B. A.

2013-10-01

The appearance of Propontis, one of many distinct classical dark albedo features on Mars, has been documented by ground-based observers for well over a century; Propontis was once thought to be the location of a “typical Martian canal”. The roughly circular feature (centered at 38°N, 179°W) covers about 500km in north-south extent. Modern spacecraft observations have shown the northern plains in which Propontis is located to include many subdued craters, knobs, and troughs. Observations by the Mars Color Imager (MARCI) onboard the Mars Reconnaissance Orbiter (MRO) have documented dramatic changes in the Propontis feature during August 2009. Daily MARCI mosaics (spatial resolution of 1 km/pixel) revealed extensive dust storm activity in this region over a ten day period (August 16-25, Ls ~ 322°-327°). At this time, the north polar seasonal ice cap was at maximum extent (reaching southward to about 55°N), and dust storm activity was frequently observed southward of the seasonal cap. These storms apparently led to sufficient deposition of bright dust to effectively “erase” the dark Propontis feature - yielding one of the most significant changes in regional albedo since Mars Global Surveyor began routine global mapping in 1997. Only minor changes have been detected over the course of repeated MARCI observations of this region since late-2009 - Propontis has not yet “recovered” to its previous extent and appearance. MRO is expected to provide ongoing MARCI mapping, enhanced with regular Context Imager (CTX, spatial resolution of 6 m/pixel) monitoring. An overview of the accumulated observations to date will be presented, along with interpretation of the magnitude of sediment transport required to account for the observed changes in Propontis.

Exploring fermionic dark matter via Higgs boson precision measurements at the Circular Electron Positron Collider

NASA Astrophysics Data System (ADS)

Xiang, Qian-Fei; Bi, Xiao-Jun; Yin, Peng-Fei; Yu, Zhao-Huan

2018-03-01

We study the impact of fermionic dark matter (DM) on projected Higgs precision measurements at the Circular Electron Positron Collider (CEPC), including the one-loop effects on the e+e-→Z h cross section and the Higgs boson diphoton decay, as well as the tree-level effects on the Higgs boson invisible decay. As illuminating examples, we discuss two UV-complete DM models, whose dark sector contains electroweak multiplets that interact with the Higgs boson via Yukawa couplings. The CEPC sensitivity to these models and current constraints from DM detection and collider experiments are investigated. We find that there exist some parameter regions where the Higgs measurements at the CEPC will be complementary to current DM searches.

Comparative morphology analysis of live blood platelets using scanning ion conductance and robotic dark-field microscopy.

PubMed

Kraus, Max-Joseph; Seifert, Jan; Strasser, Erwin F; Gawaz, Meinrad; Schäffer, Tilman E; Rheinlaender, Johannes

2016-09-01

Many conventional microscopy techniques for investigating platelet morphology such as electron or fluorescence microscopy require highly invasive treatment of the platelets such as fixation, drying and metal coating or staining. Here, we present two unique but entirely different microscopy techniques for direct morphology analysis of live, unstained platelets: scanning ion conductance microscopy (SICM) and robotic dark-field microscopy (RDM). We demonstrate that both techniques allow for a quantitative evaluation of the morphological features of live adherent platelets. We show that their morphology can be quantified by both techniques using the same geometric parameters and therefore can be directly compared. By imaging the same identical platelets subsequently with SICM and RDM, we found that area, perimeter and circularity of the platelets are directly correlated between SICM and dark-field microscopy (DM), while the fractal dimension (FD) differed between the two microscopy techniques. We show that SICM and RDM are both valuable tools for the ex vivo investigation of the morphology of live platelets, which might contribute to new insights into the physiological and pathophysiological role of platelet spreading.

1. Dyea Dock looking south. Note faint evenly spaced circular ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

1. Dyea Dock looking south. Note faint evenly spaced circular dark pieces of grass up through the middle of the picture indicating posts making up the pier. Photograph made from park service cherry picker. - Dyea Dock & Association (Ruins), Skagway, Skagway, AK

Closer Look at Schiaparelli Impact Site on Mars

NASA Image and Video Library

2016-10-27

This Oct. 25, 2016, image shows the area where the European Space Agency's Schiaparelli test lander reached the surface of Mars, with magnified insets of three sites where components of the spacecraft hit the ground. It is the first view of the site from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter taken after the Oct. 19, 2016, landing event. The Schiaparelli test lander was one component of ESA's ExoMars 2016 project, which placed the Trace Gas Orbiter into orbit around Mars on the same arrival date. This HiRISE observation adds information to what was learned from observation of the same area on Oct. 20 by the Mars Reconnaissance Orbiter's Context Camera (CTX). Of these two cameras, CTX covers more area and HiRISE shows more detail. A portion of the HiRISE field of view also provides color information. The impact scene was not within that portion for the Oct. 25 observation, but an observation with different pointing to add color and stereo information is planned. This Oct. 25 observation shows three locations where hardware reached the ground, all within about 0.9 mile (1.5 kilometer) of each other, as expected. The annotated version includes insets with six-fold enlargement of each of those three areas. Brightness is adjusted separately for each inset to best show the details of that part of the scene. North is about 7 degrees counterclockwise from straight up. The scale bars are in meters. At lower left is the parachute, adjacent to the back shell, which was its attachment point on the spacecraft. The parachute is much brighter than the Martian surface in this region. The smaller circular feature just south of the bright parachute is about the same size and shape as the back shell, (diameter of 7.9 feet or 2.4 meters). At upper right are several bright features surrounded by dark radial impact patterns, located about where the heat shield was expected to impact. The bright spots may be part of the heat shield, such as insulation material, or gleaming reflections of the afternoon sunlight. According to the ExoMars project, which received data from the spacecraft during its descent through the atmosphere, the heat shield separated as planned, the parachute deployed as planned but was released (with back shell) prematurely, and the lander hit the ground at a velocity of more than 180 miles per hour (more than 300 kilometers per hour). At mid-upper left are markings left by the lander's impact. The dark, approximately circular feature is about 7.9 feet (2.4 meters) in diameter, about the size of a shallow crater expected from impact into dry soil of an object with the lander's mass -- about 660 pounds (300 kilograms) -- and calculated velocity. The resulting crater is estimated to be about a foot and a half (half a meter) deep. This first HiRISE observation does not show topography indicating the presence of a crater. Stereo information from combining this observation with a future one may provide a way to check. Surrounding the dark spot are dark radial patterns expected from an impact event. The dark curving line to the northeast of the dark spot is unusual for a typical impact event and not yet explained. Surrounding the dark spot are several relatively bright pixels or clusters of pixels. They could be image noise or real features, perhaps fragments of the lander. A later image is expected to confirm whether these spots are image noise or actual surface features. http://photojournal.jpl.nasa.gov/catalog/PIA21131

The Sahara's Diverse Landscape

NASA Technical Reports Server (NTRS)

2002-01-01

Vast stretches of uninterrupted sand are only one kind of Saharan landscape. This true-color MODIS image from November 9, 2001, reveals a diversity of land surface features, including ancient lava flows and volcanoes. Beginning at upper left and moving clockwise are the countries of Algeria, Tunisia, Libya, Chad, and Niger. Evidence of previous volcanic activity in the Sahara can be found in northeastern Chad, in particular, in a region known as Tibesti. Reaching up out of the surrounding desert, the dark rock of the Tibesti Plateau stands out in dark brown against the sand. Scattered throughout the region are the circular cones and calderas of several volcanoes. The dark remains of a lava flow mark the location of the Tousside volcano. North of Tibesti, in Libya, more dark-colored lava beds leave their mark on the landscape. Variety exists in Algeria, where the Grand Erg Oriental desert (far upper left) is hemmed in to the south by the Tinrhert Plateau. South of the Plateau, desert resumes briefly, only to give way to a mountainous region traced with impermanent rivers. In northern Niger, a sinuous gray-green line marks the edge of an escarpment that separates the Mangueni Plateau to the north from the rock deserts to the south. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

Circular electrode geometry metal-semiconductor-metal photodetectors

NASA Technical Reports Server (NTRS)

Mcaddo, James A. (Inventor); Towe, Elias (Inventor); Bishop, William L. (Inventor); Wang, Liang-Guo (Inventor)

1994-01-01

The invention comprises a high speed, metal-semiconductor-metal photodetector which comprises a pair of generally circular, electrically conductive electrodes formed on an optically active semiconductor layer. Various embodiments of the invention include a spiral, intercoiled electrode geometry and an electrode geometry comprised of substantially circular, concentric electrodes which are interposed. These electrode geometries result in photodetectors with lower capacitances, dark currents and lower inductance which reduces the ringing seen in the optical pulse response.

Galileo's First Images of Jupiter and the Galilean Satellites

PubMed

Belton, M J S; Head, J W; Ingersoll, A P; Greeley, R; McEwen, A S; Klaasen, K P; Senske, D; Pappalardo, R; Collins, G; Vasavada, A R; Sullivan, R; Simonelli, D; Geissler, P; Carr, M H; Davies, M E; Veverka, J; Gierasch, P J; Banfield, D; Bell, M; Chapman, C R; Anger, C; Greenberg, R; Neukum, G; Pilcher, C B; Beebe, R F; Burns, J A; Fanale, F; Ip, W; Johnson, T V; Morrison, D; Moore, J; Orton, G S; Thomas, P; West, R A

1996-10-18

The first images of Jupiter, Io, Europa, and Ganymede from the Galileo spacecraft reveal new information about Jupiter's Great Red Spot (GRS) and the surfaces of the Galilean satellites. Features similar to clusters of thunderstorms were found in the GRS. Nearby wave structures suggest that the GRS may be a shallow atmospheric feature. Changes in surface color and plume distribution indicate differences in resurfacing processes near hot spots on Io. Patchy emissions were seen while Io was in eclipse by Jupiter. The outer margins of prominent linear markings (triple bands) on Europa are diffuse, suggesting that material has been vented from fractures. Numerous small circular craters indicate localized areas of relatively old surface. Pervasive brittle deformation of an ice layer appears to have formed grooves on Ganymede. Dark terrain unexpectedly shows distinctive albedo variations to the limit of resolution.

Galileo's first images of Jupiter and the Galilean satellites

USGS Publications Warehouse

Belton, M.J.S.; Head, J. W.; Ingersoll, A.P.; Greeley, R.; McEwen, A.S.; Klaasen, K.P.; Senske, D.; Pappalardo, R.; Collins, G.; Vasavada, A.R.; Sullivan, R.; Simonelli, D.; Geissler, P.; Carr, M.H.; Davies, M.E.; Veverka, J.; Gierasch, P.J.; Banfield, D.; Bell, M.; Chapman, C.R.; Anger, C.; Greenberg, R.; Neukum, G.; Pilcher, C.B.; Beebe, R.F.; Burns, J.A.; Fanale, F.; Ip, W.; Johnson, T.V.; Morrison, D.; Moore, J.; Orton, G.S.; Thomas, P.; West, R.A.

1996-01-01

The first images of Jupiter, Io, Europa, and Ganymede from the Galileo spacecraft reveal new information about Jupiter's Great Red Spot (GRS) and the surfaces of the Galilean satellites. Features similar to clusters of thunderstorms were found in the GRS. Nearby wave structures suggest that the GRS may be a shallow atmospheric feature. Changes in surface color and plume distribution indicate differences in resurfacing processes near hot spots on lo. Patchy emissions were seen while Io was in eclipse by Jupiter. The outer margins of prominent linear markings (triple bands) on Europa are diffuse, suggesting that material has been vented from fractures. Numerous small circular craters indicate localized areas of relatively old surface. Pervasive brittle deformation of an ice layer appears to have formed grooves on Ganymede. Dark terrain unexpectedly shows distinctive albedo variations to the limit of resolution.

Moon - Western Hemisphere

NASA Technical Reports Server (NTRS)

1990-01-01

This image of the western hemisphere of the Moon was taken through a green filter by the Galileo spacecraft at 9:35 a.m. PST Dec. 9 at a range of about 350,000 miles. In the center is the Orientale Basin, 600 miles in diameter, formed about 3.8 billion years ago by the impact of an asteroid-size body. Orientale's dark center is a small mare. To the right is the lunar nearside with the great, dark Oceanus Procellarum above and the small, circular, dark Mare Humorum below. Maria are broad plains formed mostly over 3 billion years ago as vast basaltic lava flows. To the left is the lunar far side with fewer maria but, at lower left, the South-Pole-Aitken basin, about 1200 miles in diameter, which resembles Orientale but is much older and more weathered and battered by cratering. The intervening cratered highlands of both sides, as well as the maria, are dotted with bright, young craters. This image was 'reprojected' so as to center the Orientale Basin, and was filtered to enhance the visibility of small features. The digital image processing was done by DLR, the German Aerospace Research Establishment near Munich, an international collaborator in the Galileo mission.

Modified circular velocity law

NASA Astrophysics Data System (ADS)

Djeghloul, Nazim

2018-05-01

A modified circular velocity law is presented for a test body orbiting around a spherically symmetric mass. This law exhibits a distance scale parameter and allows to recover both usual Newtonian behaviour for lower distances and a constant velocity limit at large scale. Application to the Galaxy predicts the known behaviour and also leads to a galactic mass in accordance with the measured visible stellar mass so that additional dark matter inside the Galaxy can be avoided. It is also shown that this circular velocity law can be embedded in a geometrical description of spacetime within the standard general relativity framework upon relaxing the usual asymptotic flatness condition. This formulation allows to redefine the introduced Newtonian scale limit in term of the central mass exclusively. Moreover, a satisfactory answer to the galactic escape speed problem can be provided indicating the possibility that one can also get rid of dark matter halo outside the Galaxy.

A radar image of Venus.

NASA Technical Reports Server (NTRS)

Goldstein, R. M.; Rumsey, H. C.

1972-01-01

Radar scans of Venus have yielded a brightness map of a large portion of the surface. The bright area in the south (alpha) and the twin such areas in the north (beta and delta) were first discovered by spectral analysis of radar echos. When range-gating is also applied, their shapes are revealed, and they are seen to be roundish and about 1000 km across. Although radar brightness can be the result of either intrinsic reflectivity or surface roughness, polarization studies show these features to be rough (to the scale of the wavelength, 12.5 cm). Dark, circular areas can also be seen, many with bright central spots. The dark areas are probably smooth. The blurring of the equatorial strip is an artifact of the range-Doppler geometry; all resolution disappears at the equator. Another artifact of the method is the 'ghost', in the south, of the images of beta and delta. Such ghosts appear only at the eastern and western extremes of the map.

An exact solution for a rotating black hole in modified gravity

NASA Astrophysics Data System (ADS)

Filippini, Francesco; Tasinato, Gianmassimo

2018-01-01

Exact solutions describing rotating black holes can offer important tests for alternative theories of gravity, motivated by the dark energy and dark matter problems. We present an analytic rotating black hole solution for a class of vector-tensor theories of modified gravity, valid for arbitrary values of the rotation parameter. The new configuration is characterised by parametrically large deviations from the Kerr-Newman geometry, controlled by non-minimal couplings between vectors and gravity. It has an oblate horizon in Boyer-Lindquist coordinates, and it can rotate more rapidly and have a larger ergosphere than black holes in General Relativity (GR) with the same asymptotic properties. We analytically investigate the features of the innermost stable circular orbits for massive objects on the equatorial plane, and show that stable orbits lie further away from the black hole horizon with respect to rotating black holes in GR. We also comment on possible applications of our findings for the extraction of rotational energy from the black hole.

ARC-1990-A91-2011

NASA Image and Video Library

1990-02-09

Range : 220,000 mi. (left)/350,000 mi. (right) These pictures of the Moon were taken by the Galileo spacecraft. Image on the right shows the dark Oceanus Procellarum in the upper center, with Mare Imbrium above it and the smaller circular Mare Humorum below. The Orientale Basin, with a small mare in its center, is on the lower left near the limb or edge. Between stretches the cratered highland terrain, with scattered bright young craters on highlands and maria alike. The left image shows the globe of the Moon rotated, putting Mare Imbrium on the eastern limb and moving the Orientale Basin almost to the center. The extent of the cratered highlands on tghe far side is very apparent., At lower left, near the limb, is the South-Pole-Aitken basin, similar to Orientale but very much older and some 1,200 miles in diameter. This feature was previously known as a large depression in the southern far side; this image shows its Orientale-like structure and darkness relative to surrounding highlands.

Propagation of partially coherent controllable dark hollow beams with various symmetries in turbulent atmosphere

NASA Astrophysics Data System (ADS)

Wang, Haiyan; Li, Xiangyin

2010-01-01

Normalized intensity distribution, the complex degree of coherence and power in the bucket for partially coherent controllable dark hollow beams (DHBs) with various symmetries propagating in atmospheric turbulence are derived using tensor method and investigated in detail. Analytical results show that, after sufficient propagation distance, partially coherent DHBs with various symmetries eventually become circular Gaussian beam (without dark hollow) in turbulent atmosphere, which is different from its propagation properties in free space. The partially coherent DHBs return to a circular Gaussian beam rapidly for stronger turbulence, higher coherence, lower beam order, smaller p or smaller beam waist width. Another interesting observation is that the profile of the complex degree of coherence attains a similar profile to that of the average intensity of the related beam propagating in a turbulent atmosphere. Besides the laser power focusablity of DHBs are better than that of Gaussian beam propagating in turbulent atmosphere.

Layers and Dark Dunes

NASA Image and Video Library

2015-04-08

The target of this observation as seen by ASA Mars Reconnaissance Orbiter is a circular depression in a dark-toned unit associated with a field of cones to the northeast. At the image scale of a Context Camera image, the depression appears to expose layers especially on the sides or walls of the depression, which are overlain by dark sands presumably associated with the dark-toned unit. HiRISE resolution, which is far higher than that of the Context Camera and its larger footprint, can help identify possible layers. http://photojournal.jpl.nasa.gov/catalog/PIA19358

Hyperspectral characterisation of the Martian south polar residual cap using CRISM

NASA Astrophysics Data System (ADS)

Campbell, J. D.; Sidiropoulos, P.; Muller, J.-P.

2017-09-01

We present our research on hyperspectral characterization of the Martian South Polar Residual Cap (SPRC), with a focus on the detection of organic signatures within the dust content of the ice. The SPRC exhibits unique CO2 ice sublimation features known colloquially as 'Swiss Cheese Terrain' (SCT). These flat floored, circular depressions are highly dynamic, and may expose dust particles previously trapped within the ice in the depression walls and partially on the floors. Here we identify suitable regions for potential dust exposure on the SPRC, and utilise data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on board NASA's Mars Reconnaissance Orbiter (MRO) satellite to examine infrared spectra of dark regions to establish their mineral composition, to eliminate the effects of ices on sub-pixel dusty features, and to assess whether ther might be signatures indicative of Polycyclic Aromatic Hydrocarbons (PAHs). Spectral mapping has identified compositional differences between depression rims and the majority of the SPRC and CRISM spectra have been corrected to minimise the influence of CO2 and H2O ice. Whilst no conclusive evidence for PAHs has been found, depression rims are shown to have higher water content than regions of featureless ice, and there are indications of magnesium carbonate within the dark, dusty regions.

Isabela Island, Galapagos Islands

NASA Image and Video Library

1996-01-20

STS072-732-072 (11-20 Jan. 1996) --- Three of the nineteen Galapagos Islands are visible in this image, photographed from the Earth-orbiting Space Shuttle Endeavour. The Galapagos Islands are located 600 miles (1,000 kilometers) to the west of Ecuador. The largest of the islands, Isabela, is at center (north is toward the upper right corner). The numerous circular features on the island, highlighted by clouds, are volcanoes. The Galapagos Islands owe their existence to a hot spot, or persistent heat source in the mantle, which also is located over a rift, or place where plates are separating and new crust is being created. The rift is located between the Cocos and Nazca Plates. The dark linear features on the islands are lava flows from past eruptions. The island to the left of Isabela is Fernandina, while the island to the right is San Salvador. The Galapagos Islands were visited by the English naturalist Charles Darwin in 1835.

Geologic analysis and evaluation of ERTS-A imagery for the State of New Mexico

NASA Technical Reports Server (NTRS)

Kottlowski, F. E. (Principal Investigator)

1974-01-01

The author has identified the following significant results. Many circular to elliptical features have been identified on the ERTS-1 images, only some of which can be accounted for by existing data. A small number of circular features are adjacent to existing ore deposits, but such relationships should not be emphasized unless other supporting data exists. Circular features may be tectonically or geomorphically controlled, or a combination of the two. A limited number are man-made. A preliminary listing of features which may have circular expression are listed. Photographic examples of identified and unidentified circular features will be included in the final report along with a thorough discussion and analysis. Comparisons will be made with existing gravity and magnetic data.

Effects of rat sex differences and lighting on locomotor exploration of a circular open field with free-standing central corners and without peripheral walls.

PubMed

Alstott, Jeff; Timberlake, William

2009-01-23

A typical open field consists of a square enclosure, bounded by four straight walls joined by identical corners. For decades behavioral researchers have used the open center and more sheltered perimeter of such fields to examine the effects of drugs, sex differences, and illumination on the behavioral expression of fear and anxiety. The present study "reversed" the relative security of the center and periphery of a circular field to re-examine the functional relation of open field behavior to experience, sex differences and lighting. Across six daily exposures, males in both the light and dark rapidly increased their preference for the center. Females in the light developed a similar pattern, though more slowly; females in the dark continued to spend the great majority of their time in the open periphery, including the edge of the field. The behavior of all groups, but especially the dark females, strongly supports the continued importance of environmental assessment in open field behavior.

Characteristics of circular features on comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Deller, J. F.; Güttler, C.; Tubiana, C.; Hofmann, M.; Sierks, H.

2017-09-01

Comet 67P/Churyumov-Gerasimenko shows a large variety of circular structures such as pits, elevated roundish features in Imhotep, and even a single occurrence of a plausible fresh impact crater. Imaging the pits in the Ma'at region, aiming to understand their structure and origin drove the design of the final descent trajectory of the Rosetta spacecraft. The high-resolution images obtained during the last mission phase allow us to study these pits as exemplary circular features. A complete catalogue of circular features gives us the possibility to compare and classify these structures systematically.

Neural dynamics for landmark orientation and angular path integration

PubMed Central

Seelig, Johannes D.; Jayaraman, Vivek

2015-01-01

Summary Many animals navigate using a combination of visual landmarks and path integration. In mammalian brains, head direction cells integrate these two streams of information by representing an animal's heading relative to landmarks, yet maintaining their directional tuning in darkness based on self-motion cues. Here we use two-photon calcium imaging in head-fixed flies walking on a ball in a virtual reality arena to demonstrate that landmark-based orientation and angular path integration are combined in the population responses of neurons whose dendrites tile the ellipsoid body — a toroidal structure in the center of the fly brain. The population encodes the fly's azimuth relative to its environment, tracking visual landmarks when available and relying on self-motion cues in darkness. When both visual and self-motion cues are absent, a representation of the animal's orientation is maintained in this network through persistent activity — a potential substrate for short-term memory. Several features of the population dynamics of these neurons and their circular anatomical arrangement are suggestive of ring attractors — network structures proposed to support the function of navigational brain circuits. PMID:25971509

Moon - 18 Image Mosaic

NASA Technical Reports Server (NTRS)

1992-01-01

This mosaic picture of the Moon was compiled from 18 images taken with a green filter by Galileo's imaging system during the spacecraft's flyby on December 7, 1992, some 11 hours before its Earth flyby at 1509 UTC (7:09 a.m. Pacific Standard Time) December 8. The north polar region is near the top part of the mosaic, which also shows Mare Imbrium, the dark area on the left; Mare Serenitatis at center; and Mare Crisium, the circular dark area to the right. Bright crater rim and ray deposits are from Copernicus, an impact crater 96 kilometers (60 miles) in diameter. Computer processing has exaggerated the brightness of poorly illuminated features near the day/night terminator in the polar regions, giving a false impression of high reflectivity there. The digital image processing was done by DLR the German aerospace research establishment near Munich, an international collaborator in the Galileo mission. The Galileo project, whose primary mission is the exploration of the Jupiter system in 1995-97, is managed for NASA's Office of Space Science and Applications by the Jet Propulsion Laboratory.

The growth and structure of dark matter haloes

NASA Astrophysics Data System (ADS)

Zhao, D. H.; Mo, H. J.; Jing, Y. P.; Börner, G.

2003-02-01

In this paper, we analyse in detail the mass-accretion histories and structural properties of dark haloes in high-resolution N-body simulations. We model the density distribution in individual haloes using the Navarro-Frenk-White (NFW) profile. For a given halo, there is a tight correlation between its inner-scale radius rs and the mass within it, Ms, for all its main progenitors. Using this correlation, one can predict quite well the structural properties of a dark halo at any time in its history from its mass-accretion history, implying that the structure properties and the mass-accretion history are closely correlated. The predicted growing rate of concentration c with time tends to increase with decreasing mass-accretion rate. The build-up of dark haloes in cold dark matter (CDM) models generally consists of an early phase of fast accretion (where the halo mass Mh increases with time much faster than the expansion rate of the Universe) and a late phase of slow accretion (where Mh increases with time approximately as the expansion rate). These two phases are separated at a time when c~ 4 and the typical binding energy of the halo is approximately equal to that of a singular isothermal sphere with the same circular velocity. Haloes in the two accretion phases show systematically different properties, for example, the circular velocity vh increases rapidly with time in the fast accretion phase but remains almost constant in the slow accretion phase, the inner properties of a halo, such as rs and Ms increase rapidly with time in the fast accretion phase but change only slowly in the slow accretion phase, the inner circular velocity vs is approximately equal to vh in the fast accretion phase but is larger in the slow accretion phase. The potential well associated with a halo is built up mainly in the fast accretion phase, while a large amount of mass can be accreted in the slow accretion phase without changing the potential well significantly. We discuss our results in connection with the formation of dark haloes and galaxies in hierarchical models.

Ulysses Patera

NASA Technical Reports Server (NTRS)

2002-01-01

[figure removed for brevity, see original site] (Released 18 July 2002) It is helpful to look at the context for this THEMIS image, which covers a large area over the summit of Ulysses Patera. Ulysses Patera is one of the many volcanoes that make up the giant Tharsis volcanic province, although Ulysses itself is fairly small in comparison to the other volcanoes in this area. In the context image, there are 3 circular features near the top of the volcano. The large, central feature is called a 'caldera', and is the result of volcanic activity at Ulysses. The other two circular features are impact craters. The THEMIS image primarily spans across the central caldera, but also covers a portion of the northernmost impact crater. We know that the large central caldera must have formed earlier than the two craters, because its circular form has been cut by the smaller crater rims. In the THEMIS image, there are stair-stepping plateaus in the northern portion of the image. These are part of the rim of the northern crater, and are caused by collapse or subsidence after the impact event. Just to the south of this crater, 'rayed' patterns can be seen on part of the caldera floor. The rayed pattern is most likely due to a landslide of material down the crater rim slope. Another possibility is that the impact that formed the northern crater caused material to be ejected radially, and then parts of the ejecta have either been buried or eroded away. Other signs of mass movement events in this image are dark streaks, caused by dust avalanches, visible in the caldera's northern wall. In the central portion of the image, there are two lobe-shaped features-one overlaps the other-that appear to have flowed westward. It is likely that these features are ejecta lobes, because they are located adjacent to the southeastern crater (see context image). The fluidized appearance of these ejecta lobes is probably due to a significant amount of ice or water being present in the soil at the time of impact. We know that the southeastern crater must have formed after the northern crater, because the fluidized ejecta lobe overlies the rayed pattern. A close-up look at the fluidized ejecta lobes reveals a different surface 'texture' than the surrounding caldera floor. This could be due to compressional features that formed during the lobe emplacement, or to contrasting surface properties that cause the flows to be eroded differently than the caldera floor. In the lower portion of the image, there is a cluster of small circular features in the southernmost part of the central caldera. These features may be layered material that has since been eroded into circular plateaus, or they may be degraded volcanic cones, which would indicate a later stage of smaller-scale volcanism within the caldera. Volcanic cones are common in many calderas on Earth, and are formed after the initial stage of volcanic activity in that caldera. Finally, in the southern wall of the caldera, there is classic 'spur-and-gully' morphology. This type of morphology is often formed on steep slopes, where variations in wall resistance cause the surface to be eroded more easily in some areas.

A search for polycyclic aromatic hydrocarbons over the Martian South Polar Residual Cap

NASA Astrophysics Data System (ADS)

Campbell, J. D.; Sidiropoulos, P.; Muller, J.-P.

2018-07-01

We present our research on compositional mapping of the Martian South Polar Residual Cap (SPRC), especially the detection of organic signatures within the dust content of the ice, based on hyperspectral data analysis. The SPRC is the main region of interest for this investigation, because of the unique CO2 ice sublimation features that cover the surface. These flat floored, circular depressions are highly dynamic, and we infer frequently expose dust particles previously trapped within the ice during the wintertime. Here we identify suitable regions for potential dust exposure on the SPRC, and utilise data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on board NASA's Mars Reconnaissance Orbiter (MRO) satellite to examine infrared spectra of dark regions assumed to be composed mainly of dust particles to establish their mineral composition, to eliminate the effects of ices on sub-pixel dusty features, and to look for signatures indicative of Polycyclic Aromatic Hydrocarbons (PAHs). Spectral mapping has identified compositional differences between depression rims and the majority of the SPRC and CRISM spectra have been corrected to minimise the influence of CO2 ice. Whilst no conclusive evidence for PAHs has been found within the detectability limits of the CRISM instrument, depression rims are shown to have higher water content than regions of featureless ice, and there are possible indications of magnesium carbonate within the dark, dusty regions.

Foods advertised in US weekly supermarket sales circulars over one year: a content analysis.

PubMed

Jahns, Lisa; Payne, Collin R; Whigham, Leah D; Johnson, LuAnn K; Scheett, Angela J; Hoverson, Bonita S; Kranz, Sibylle

2014-09-23

The nutritional content of Americans' shopping carts is suboptimal despite federal dietary guidance, in this case, the MyPlate consumer icon which displays desired proportions of vegetables, fruits, dairy, grains and protein foods for consumption. Consumers mention print advertising-such as weekly sales circulars-frequently as influencing their grocery shopping decisions. To examine and describe the relative proportions of advertised foods aggregated into the MyPlate food grouping system, a content analysis of 9 209 foods advertised in 52 weekly supermarket newspaper sales inserts in 2009 from a local grocery chain was conducted in a Midwestern community. Overall, the protein foods group was most often represented in sales circulars (25% of total items), followed by grains (18%); dairy (10%); vegetables (8%) and fruits (7%). Less than 3% of sales advertisements were for dark green and red & orange vegetables. Over twice as much whole fruit versus 100% fruit juice was advertised (70% vs. 30%, respectively; P < 0.001). Significantly fewer protein foods and more grains than expected were advertised in the fall, and slightly more dark green vegetables were advertised in winter and spring than in summer and fall (P = 0.05). The average American diet, including underconsumption of fruits and vegetables but overconsumption of protein foods, was reflected in the relative frequency of food groups advertised in weekly sales circulars. Modifying sales circulars to represent healthier food groups may preserve retail profits (considering these groups' higher profit margin) while promoting adherence to federal dietary guidance.

Stepwise dynamics of an anionic micellar film - Formation of crown lenses.

PubMed

Lee, Jongju; Nikolov, Alex; Wasan, Darsh

2017-06-15

We studied the stepwise thinning of a microscopic circular foam film formed from an anionic micellar solution of sodium dodecyl sulfate (SDS). The foam film formed from the SDS micellar solution thins in a stepwise manner by the formation and expansion of a dark spot(s) of one layer less than the film thickness. During the last stages of film thinning (e.g., a film with one micellar layer), the dark spot expansion occurs via two steps. Initially, a small dark circular spot inside a film of several microns in size is formed, which expands at a constant rate. Then, a ridge along the expanding spot is formed. As the ridge grows, it becomes unstable and breaks into regular crown lenses, which are seen as white spots in the reflected light at the border of the dark spot with the surrounding thicker film. The Rayleigh type of instability contributes to the formation of the lenses, which results in the increase of the dark spot expansion rate with time. We applied the two-dimensional micellar-vacancy diffusion model and took into consideration the effects of the micellar layering and film volume on the rate of the dark spot expansion [Lee et al., 2016] to predict the rate of the dark spot expansion for a 0.06M SDS film in the presence of lenses. We briefly discuss the Rayleigh type of instability in the case of a 0.06M SDS foam film. The goals of this study are to reveal why the crown lenses are formed during the foam film stratification and to elucidate their effect on the rate of spot expansion. Copyright © 2017 Elsevier Inc. All rights reserved.

Highest Resolution Image of Europa

NASA Technical Reports Server (NTRS)

1998-01-01

During its twelfth orbit around Jupiter, on Dec. 16, 1997, NASA's Galileo spacecraft made its closest pass of Jupiter's icy moon Europa, soaring 200 kilometers (124 miles) kilometers above the icy surface. This image was taken near the closest approach point, at a range of 560 kilometers (335 miles) and is the highest resolution picture of Europa that will be obtained by Galileo. The image was taken at a highly oblique angle, providing a vantage point similar to that of someone looking out an airplane window. The features at the bottom of the image are much closer to the viewer than those at the top of the image. Many bright ridges are seen in the picture, with dark material in the low-lying valleys. In the center of the image, the regular ridges and valleys give way to a darker region of jumbled hills, which may be one of the many dark pits observed on the surface of Europa. Smaller dark, circular features seen here are probably impact craters.

North is to the right of the picture, and the sun illuminates the surface from that direction. This image, centered at approximately 13 degrees south latitude and 235 degrees west longitude, is approximately 1.8 kilometers (1 mile) wide. The resolution is 6 meters (19 feet) per picture element. This image was taken on December 16, 1997 by the solid state imaging system camera on NASA's Galileo spacecraft.

The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/ galileo.

Cell-type specific features of circular RNA expression.

PubMed

Salzman, Julia; Chen, Raymond E; Olsen, Mari N; Wang, Peter L; Brown, Patrick O

2013-01-01

Thousands of loci in the human and mouse genomes give rise to circular RNA transcripts; at many of these loci, the predominant RNA isoform is a circle. Using an improved computational approach for circular RNA identification, we found widespread circular RNA expression in Drosophila melanogaster and estimate that in humans, circular RNA may account for 1% as many molecules as poly(A) RNA. Analysis of data from the ENCODE consortium revealed that the repertoire of genes expressing circular RNA, the ratio of circular to linear transcripts for each gene, and even the pattern of splice isoforms of circular RNAs from each gene were cell-type specific. These results suggest that biogenesis of circular RNA is an integral, conserved, and regulated feature of the gene expression program.

Shaping the beam profile of a partially coherent beam by a phase aperture

NASA Astrophysics Data System (ADS)

Wu, Gaofeng; Cai, Yangjian; Chen, Jun

2011-08-01

By use of a tensor method, an analytical formula for a partially coherent Gaussian Schell-model (GSM) beam truncated by a circular phase aperture propagating through a paraxial ABCD optical system is derived. The propagation properties of a GSM beam truncated by a circular phase aperture in free space are studied numerically. It is found that the circular phase aperture can be used to shape the beam profile of a GSM beam and generate partially coherent dark hollow or flat-topped beam, which is useful in many applications, e.g., optical trapping, free-space optical communication, and material thermal processing. The propagation factor of a GSM beam truncated by a circular phase aperture is also analyzed.

Dynamical Family Properties and Dark Halo Scaling Relations of Giant Elliptical Galaxies

NASA Astrophysics Data System (ADS)

Gerhard, Ortwin; Kronawitter, Andi; Saglia, R. P.; Bender, Ralf

2001-04-01

Based on a uniform dynamical analysis of the line-profile shapes of 21 mostly luminous, slowly rotating, and nearly round elliptical galaxies, we have investigated the dynamical family relations and dark halo properties of ellipticals. Our results include: (i) The circular velocity curves (CVCs) of elliptical galaxies are flat to within ~=10% for R>~0.2Re. (ii) Most ellipticals are moderately radially anisotropic; their dynamical structure is surprisingly uniform. (iii) Elliptical galaxies follow a Tully-Fisher (TF) relation with marginally shallower slope than spiral galaxies, and vmaxc~=300 km s-1 for an L*B galaxy. At given circular velocity, they are ~1 mag fainter in B and ~0.6 mag in R and appear to have slightly lower baryonic mass than spirals, even for the maximum M/LB allowed by the kinematics. (iv) The luminosity dependence of M/LB indicated by the tilt of the fundamental plane (FP) is confirmed. The tilt of the FP is not caused by dynamical or photometric nonhomology, although the latter might influence the slope of M/L versus L. It can also not be due only to an increasing dark matter fraction with L for the range of IMF currently discussed. It is, however, consistent with stellar population models based on published metallicities and ages. The main driver is therefore probably metallicity, and a secondary population effect is needed to explain the K-band tilt. (v) These results make it likely that elliptical galaxies have nearly maximal M/LB (minimal halos). (vi) Despite the uniformly flat CVCs, there is a spread in the luminous to dark matter ratio and in cumulative M/LB(r). Some galaxies have no indication for dark matter within 2Re, whereas for others we obtain local M/LB-values of 20-30 at 2Re. (vii) In models with maximum stellar mass, the dark matter contributes ~10%-40% of the mass within Re. Equal interior mass of dark and luminous matter is predicted at ~2-4Re. (viii) Even in these maximum stellar mass models, the halo core densities and phase-space densities are at least ~25 times larger and the halo core radii ~4 times smaller than in spiral galaxies of the same circular velocity. The increase in M/L sets in at ~10 times larger acceleration than in spirals. This could imply that elliptical galaxy halos collapsed at high redshifts or that some of the dark matter in ellipticals might be baryonic.

Cell-Type Specific Features of Circular RNA Expression

PubMed Central

Salzman, Julia; Chen, Raymond E.; Olsen, Mari N.; Wang, Peter L.; Brown, Patrick O.

2013-01-01

Thousands of loci in the human and mouse genomes give rise to circular RNA transcripts; at many of these loci, the predominant RNA isoform is a circle. Using an improved computational approach for circular RNA identification, we found widespread circular RNA expression in Drosophila melanogaster and estimate that in humans, circular RNA may account for 1% as many molecules as poly(A) RNA. Analysis of data from the ENCODE consortium revealed that the repertoire of genes expressing circular RNA, the ratio of circular to linear transcripts for each gene, and even the pattern of splice isoforms of circular RNAs from each gene were cell-type specific. These results suggest that biogenesis of circular RNA is an integral, conserved, and regulated feature of the gene expression program. PMID:24039610

Astrophysical uncertainties on the local dark matter distribution and direct detection experiments

NASA Astrophysics Data System (ADS)

Green, Anne M.

2017-08-01

The differential event rate in weakly interacting massive particle (WIMP) direct detection experiments depends on the local dark matter density and velocity distribution. Accurate modelling of the local dark matter distribution is therefore required to obtain reliable constraints on the WIMP particle physics properties. Data analyses typically use a simple standard halo model which might not be a good approximation to the real Milky Way (MW) halo. We review observational determinations of the local dark matter density, circular speed and escape speed and also studies of the local dark matter distribution in simulated MW-like galaxies. We discuss the effects of the uncertainties in these quantities on the energy spectrum and its time and direction dependence. Finally, we conclude with an overview of various methods for handling these astrophysical uncertainties.

Western hemisphere of the Moon taken by Galileo spacecraft

NASA Image and Video Library

1990-12-09

Galileo spacecraft image of the Moon recorded at 9:35 am Pacific Standard Time (PST), 12-09-90, after completing its first Earth Gravity Assist. Western hemisphere of the Moon was taken through a green filter at a range of about 350,000 miles. In the center is Orientale Basin, 600 miles in diameter, formed about 3.8 billion years ago by the impact of an asteroid-size body. Orientale's dark center is a small mare. To the right is the lunar near side with the great, dark Oceanus Procellarum above the small, circular, dark Mare Humorum below. Maria are broad plains formed mostly over 3 billion years ago as vast basaltic lava flows. To the left is the lunar far side with fewer maria, but, at lower left South-Pole-Aitken basin, about 1200 miles in diameter, which resembles Orientale but is much older and more weathered and battered by cratering. The intervening cratered highlands of both sides, as well as the maria, are dotted with bright young craters. This image was "reprojected" so as to center the Orientale Basin, and was filtered to enhance the visibility of small features. The digital image processing was done by DLR, the German Aerospace Research Establishment near Munich, an international collaborator in the Galileo mission. Photo was provided by Jet Propulsion Laboratory (JPL) with alternate number P-37327, 12-19-90.

Dark zone in the centre of the Arago-Poisson diffraction spot of a helical laser beam

NASA Astrophysics Data System (ADS)

Emile, O.; Voisin, A.; Niemiec, R.; Viaris de Lesegno, B.; Pruvost, L.; Ropars, G.; Emile, J.; Brousseau, C.

2013-03-01

We report on the diffraction of non-zero Laguerre Gaussian laser beams by an opaque disk. We observe a tiny circular dark zone at the centre of the usual Arago-Poisson diffraction bright spot. For such non-diffracting dark hollow beams, we have measured diameters as small as 20 μm on distances of the order of ten metres, without focalization. Diameters depend on the diffracting object size and on the topological charge of the input Laguerre Gaussian beam. These results are in good agreement with theoretical considerations. Potential applications are then discussed.

Optical pumping and negative luminescence polarization in charged GaAs quantum dots

NASA Astrophysics Data System (ADS)

Shabaev, Andrew; Stinaff, Eric A.; Bracker, Allan S.; Gammon, Daniel; Efros, Alexander L.; Korenev, Vladimir L.; Merkulov, Igor

2009-01-01

Optical pumping of electron spins and negative photoluminescence polarization are observed when interface quantum dots in a GaAs quantum well are excited nonresonantly by circularly polarized light. Both observations can be explained by the formation of long-lived dark excitons through hole spin relaxation in the GaAs quantum well prior to exciton capture. In this model, optical pumping of resident electron spins is caused by capture of dark excitons and recombination in charged quantum dots. Negative polarization results from accumulation of dark excitons in the quantum well and is enhanced by optical pumping. The dark exciton model describes the experimental results very well, including intensity and bias dependence of the photoluminescence polarization and the Hanle effect.

Moon - 2 Views of Orientale Basin

NASA Technical Reports Server (NTRS)

1990-01-01

These pictures of the Moon were taken by the Galileo spacecraft at (right photo) 6:47 p.m. PST Dec.8, 1990 from a distance of almost 220,000 miles, and at (left photo) 9:35 a.m. PST Dec. 9, 1990 at a range of more than 350,000 miles. The picture on the right shows the dark Oceanus Procellarum in the upper center, with Mare Imbrium above it and the smaller circular Mare Humorum below. The Orientale Basin, with a small mare in its center, is on the lower left near the limb or edge. Between stretches the cratered highland terrain, with scattered bright young craters on highlands and maria alike. The picture at left shows the globe of the Moon rotated, putting Mare Imbrium on the eastern limb and moving the Orientale Basin almost to the center. The extent of the cratered highlands on the far side is very apparent. At lower left, near the limb, is the South Pole Aitken basin, similar to Orientale but very much older and some 1,200 miles in diameter. This feature was previously known as a large depression in the southern far side; this image shows its Orientale like structure and darkness relative to surrounding highlands.

The dark side of galaxy colour

NASA Astrophysics Data System (ADS)

Hearin, Andrew P.; Watson, Douglas F.

2013-10-01

We present age distribution matching, a theoretical formalism for predicting how galaxies of luminosity L and colour C occupy dark matter haloes. Our model supposes that there are just two fundamental properties of a halo that determine the colour and brightness of the galaxy it hosts: the maximum circular velocity Vmax and the redshift zstarve that correlates with the epoch at which the star formation in the galaxy ceases. The halo property zstarve is intended to encompass physical characteristics of halo mass assembly that may deprive the galaxy of its cold gas supply and, ultimately, quench its star formation. The new, defining feature of the model is that, at fixed luminosity, galaxy colour is in monotonic correspondence with zstarve, with the larger values of zstarve being assigned redder colours. We populate an N-body simulation with a mock galaxy catalogue based on age distribution matching and show that the resulting mock galaxy distribution accurately describes a variety of galaxy statistics. Our model suggests that halo and galaxy assembly are indeed correlated. We make publicly available our low-redshift, Sloan Digital Sky Survey Mr < -19 mock galaxy catalogue, and main progenitor histories of all z = 0 haloes, at http://logrus.uchicago.edu/~aphearin

Mars Global Surveyor Approach Image

NASA Image and Video Library

1997-07-04

This image is the first view of Mars taken by the Mars Global Surveyor Orbiter Camera (MOC). It was acquired the afternoon of July 2, 1997 when the MGS spacecraft was 17.2 million kilometers (10.7 million miles) and 72 days from encounter. At this distance, the MOC's resolution is about 64 km per picture element, and the 6800 km (4200 mile) diameter planet is 105 pixels across. The observation was designed to show the Mars Pathfinder landing site at 19.4 N, 33.1 W approximately 48 hours prior to landing. The image shows the north polar cap of Mars at the top of the image, the dark feature Acidalia Planitia in the center with the brighter Chryse plain immediately beneath it, and the highland areas along the Martian equator including the canyons of the Valles Marineris (which are bright in this image owing to atmospheric dust). The dark features Terra Meridiani and Terra Sabaea can be seen at the 4 o`clock position, and the south polar hood (atmospheric fog and hazes) can be seen at the bottom of the image. Launched on November 7, 1996, Mars Global Surveyor will enter Mars orbit on Thursday, September 11 shortly after 6:00 PM PDT. After Mars Orbit Insertion, the spacecraft will use atmospheric drag to reduce the size of its orbit, achieving a circular orbit only 400 km (248 mi) above the surface in early March 1998, when mapping operations will begin. http://photojournal.jpl.nasa.gov/catalog/PIA00606

Arecibo radar imagery of Mars: The major volcanic provinces

NASA Astrophysics Data System (ADS)

Harmon, John K.; Nolan, Michael C.; Husmann, Diana I.; Campbell, Bruce A.

2012-08-01

We present Earth-based radar images of Mars obtained with the upgraded Arecibo S-band (λ = 12.6 cm) radar during the 2005-2012 oppositions. The imaging was done using the same long-code delay-Doppler technique as for the earlier (pre-upgrade) imaging but at a much higher resolution (˜3 km) and, for some regions, a more favorable sub-Earth latitude. This has enabled us to make a more detailed and complete mapping of depolarized radar reflectivity (a proxy for small-scale surface roughness) over the major volcanic provinces of Tharsis, Elysium, and Amazonis. We find that vast portions of these regions are covered by radar-bright lava flows exhibiting circular polarization ratios close to unity, a characteristic that is uncommon for terrestrial lavas and that is a likely indicator of multiple scattering from extremely blocky or otherwise highly disrupted flow surfaces. All of the major volcanoes have radar-bright features on their shields, although the brightness distribution on Olympus Mons is very patchy and the summit plateau of Pavonis Mons is entirely radar-dark. The older minor shields (paterae and tholi) are largely or entirely radar-dark, which is consistent with mantling by dust or pyroclastic material. Other prominent radar-dark features include: the "fan-shaped deposits", possibly glacial, associated with the three major Tharsis Montes shields; various units of the Medusae Fossae Formation; a region south and west of Biblis Patera where "Stealth" deposits appear to obscure Tharsis flows; and a number of "dark-halo craters" with radar-absorbing ejecta blankets deposited atop surrounding bright flows. Several major bright features in Tharsis are associated with off-shield lava flows; these include the Olympus Mons basal plains, volcanic fields east and south of Pavonis Mons, the Daedalia Planum flows south of Arsia Mons, and a broad expanse of flows extending east from the Tharsis Montes to Echus Chasma. The radar-bright lava plains in Elysium are concentrated mainly in Cerberus and include the fluvio-volcanic channels of Athabasca Valles, Grjotá Valles, and Marte Valles, as well as an enigmatic region at the southern tip of the Cerberus basin. Some of the Cerberus bright features correspond to the distinctive "platy-ridged" flows identified in orbiter images. The radar-bright terrain in Amazonis Planitia comprises two distinct but contiguous sections: a northern section formed of lavas and sediments debouched from Marte Valles and a southern section whose volcanics may derive, in part, from local sources. This South Amazonis region shows perhaps the most complex radar-bright structure on Mars and includes features that correspond to platy-ridged flows similar to those in Cerberus.

Effects of Different Viewing Conditions on Radiographic Interpretation

PubMed Central

Moshfeghi, Mahkameh; Shahbazian, Majid; Sajadi, Soodabeh Sadat; Sajadi, Sepideh; Ansari, Hossein

2015-01-01

Objectives: Optimum viewing conditions facilitate identification of radiographic details and decrease the need for retakes, patients’ costs and radiation dose. This study sought to evaluate the effects of different viewing conditions on radiographic interpretation. Materials and Methods: This diagnostic study was performed by evaluating radiograph of a 7mm-thick aluminum block, in which 10 holes with 2mm diameters were randomly drilled with depths ranging from 0.05 mm to 0.50mm. The radiograph was viewed by four oral radiologists independently under four viewing conditions, including a white light viewing light box in a lit room, yellow light viewing light box in a lit room, white light viewing light box in a dark room and yellow light viewing light box in a dark room. Number of circular shadows observed on the film was recorded. The data were analyzed by two-way ANOVA. Results: The mean number of detected circular shadows was 6.75, 7.5, 7.25 and 7.75 in white light viewing light box in a lit room, white light viewing light box in a dark room, yellow light viewing light box in a lit room and yellow light viewing light box in a dark room, respectively. Although the surrounding illumination had statistically significant effect on the radiographic details (P≤0.03), the light color of the viewing light box had no significant effect on visibility of the radiographic details. Conclusion: White and yellow light of the viewing light box had no significant effect on visibility of the radiographic details but more information was obtained in a dark room. PMID:27507997

Effects of Different Viewing Conditions on Radiographic Interpretation.

PubMed

Moshfeghi, Mahkameh; Shahbazian, Majid; Sajadi, Soodabeh Sadat; Sajadi, Sepideh; Ansari, Hossein

2015-11-01

Optimum viewing conditions facilitate identification of radiographic details and decrease the need for retakes, patients' costs and radiation dose. This study sought to evaluate the effects of different viewing conditions on radiographic interpretation. This diagnostic study was performed by evaluating radiograph of a 7mm-thick aluminum block, in which 10 holes with 2mm diameters were randomly drilled with depths ranging from 0.05 mm to 0.50mm. The radiograph was viewed by four oral radiologists independently under four viewing conditions, including a white light viewing light box in a lit room, yellow light viewing light box in a lit room, white light viewing light box in a dark room and yellow light viewing light box in a dark room. Number of circular shadows observed on the film was recorded. The data were analyzed by two-way ANOVA. The mean number of detected circular shadows was 6.75, 7.5, 7.25 and 7.75 in white light viewing light box in a lit room, white light viewing light box in a dark room, yellow light viewing light box in a lit room and yellow light viewing light box in a dark room, respectively. Although the surrounding illumination had statistically significant effect on the radiographic details (P≤0.03), the light color of the viewing light box had no significant effect on visibility of the radiographic details. White and yellow light of the viewing light box had no significant effect on visibility of the radiographic details but more information was obtained in a dark room.

Circles and Hexagons

NASA Image and Video Library

2017-10-09

Saturn's cloud belts generally move around the planet in a circular path, but one feature is slightly different. The planet's wandering, hexagon-shaped polar jet stream breaks the mold -- a reminder that surprises lurk everywhere in the solar system. This atmospheric feature was first observed by the Voyager mission in the early 1980s, and was dubbed "the hexagon." Cassini's visual and infrared mapping spectrometer was first to spy the hexagon during the mission, since it could see the feature's outline while the pole was still immersed in wintry darkness. The hexagon became visible to Cassini's imaging cameras as sunlight returned to the northern hemisphere. This view looks toward the northern hemisphere of Saturn -- in summer when this view was acquired -- from above 65 degrees north latitude. The image was taken with the Cassini spacecraft wide-angle camera on June 28, 2017 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers. The view was acquired at a distance of approximately 536,000 miles (862,000 kilometers) from Saturn. Image scale is 32 miles (52 kilometers) per pixel. The Cassini spacecraft ended its mission on Sept. 15, 2017. https://photojournal.jpl.nasa.gov/catalog/PIA21348

Triptych of the Moon

NASA Image and Video Library

1999-09-10

This composite image was made from NASA Cassini which captured a significant portion of the Moon during a Moon flyby imaging sequence.All three images have been scaled so that the brightness of Crisium basin, the dark circular region in the upper right,

Sample from Deep in Martian Crust: Marquette Island

NASA Image and Video Library

2010-01-21

Perched on a rippled Martian plain, a dark rock not much bigger than a basketball was the target of interest for NASA Opportunity during the past two months; Opportunity rock abrasion tool brushed dust out of the circular area.

ARC-1979-AC79-7095

NASA Image and Video Library

1979-07-11

Range : 312, 000 kilometers (195,000 miles) This photo of Ganymede (Ice Giant) was taken from Voyager 2 and shows features down to about 5 to 6 kilometers across. Different types of terrain common on Ganymede's surface are visible. The boundary of the largest region of dark ancient terrain on Ganymede can be seen to the east (right), revealing some of the light linear features which may be all that remains of a large ancient impact structure similar to the large ring structure on Callisto. The broad light regions running through the image are the typical grooved structures seen within another example of what might be evidence of large scale lateral motion in Ganymede's crust. The band of grooved terrain (about 100 kilometers wide) in this region appears to be offset by 50 kilometers or more on the left hand edge by a linear feature perpendicular to it. A feature similar to this one was previously discovered by Voyager 1. These are the first clear examples of strike-slip style faulting on any planet other than Earth. Many examples of craters of all ages can be seen in this image, ranging from fresh, bright ray craters to large, subdued circular markings thought to be the 'scars' of large ancient impacts that have been flatteded by glacier-like flows.

Propagation of various dark hollow beams through an apertured paraxial ABCD optical system

NASA Astrophysics Data System (ADS)

Cai, Yangjian; Ge, Di

2006-08-01

Propagation of a dark hollow beam (DHB) of circular, elliptical or rectangular symmetry through an apertured paraxial ABCD optical system is investigated. Approximate analytical formulas for various DHBs propagating through an apertured paraxial optical system are derived by expanding the hard-aperture function into a finite sum of complex Gaussian functions in terms of a tensor method. Some numerical results are given. Our formulas provide a convenient way for studying the propagation of various DHBs through an apertured paraxial optical system.

Circular Data Images for Directional Data

NASA Technical Reports Server (NTRS)

Morpet, William J.

2004-01-01

Directional data includes vectors, points on a unit sphere, axis orientation, angular direction, and circular or periodic data. The theoretical statistics for circular data (random points on a unit circle) or spherical data (random points on a unit sphere) are a recent development. An overview of existing graphical methods for the display of directional data is given. Cross-over occurs when periodic data are measured on a scale for the measurement of linear variables. For example, if angle is represented by a linear color gradient changing uniformly from dark blue at -180 degrees to bright red at +180 degrees, the color image will be discontinuous at +180 degrees and -180 degrees, which are the same location. The resultant color would depend on the direction of approach to the cross-over point. A new graphical method for imaging directional data is described, which affords high resolution without color discontinuity from "cross-over". It is called the circular data image. The circular data image uses a circular color scale in which colors repeat periodically. Some examples of the circular data image include direction of earth winds on a global scale, rocket motor internal flow, earth global magnetic field direction, and rocket motor nozzle vector direction vs. time.

Gravitational waves from dark first order phase transitions and dark photons

NASA Astrophysics Data System (ADS)

Addazi, Andrea; Marcianò, Antonino

2018-01-01

Cold Dark Matter particles may interact with ordinary particles through a dark photon, which acquires a mass thanks to a spontaneous symmetry breaking mechanism. We discuss a dark photon model in which the scalar singlet associated to the spontaneous symmetry breaking has an effective potential that induces a first order phase transition in the early Universe. Such a scenario provides a rich phenomenology for electron-positron colliders and gravitational waves interferometers, and may be tested in several different channels. The hidden first order phase transition implies the emission of gravitational waves signals, which may constrain the dark photon’s space of parameters. Compared limits from electron-positron colliders, astrophysics, cosmology and future gravitational waves interferometers such as eLISA, U-DECIGO and BBO are discussed. This highly motivates a cross-checking strategy of data arising from experiments dedicated to gravitational waves, meson factories, the International Linear Collider (ILC), the Circular Electron Positron Collider (CEPC) and other underground direct detection experiments of cold dark matter candidates. Supported by the Shanghai Municipality (KBH1512299) and Fudan University (JJH1512105)

Venus - Ovda Regio

NASA Image and Video Library

1996-08-13

This image covers much of Ovda Regio, which forms the western part of Aphrodite Terra. It covers an area about 2,250 kilometers (1,386 miles) wide by 1,300 kilometers (800 miles) north to south, and ranges in latitude from 8 degrees north to 12 degrees south and in longitude from 62 degrees east to 90 degrees east. Ovda Regio is a highland region that rises over 4 kilometers (2.5 miles) above the surrounding plain. Magellan images show a complex surface, with several generations of structures. A pervasive fabric of irregular broad domes and ridges and associated curvilinear valleys was flooded by lava, then fractured. The circular feature surrounded by dark lava flows in the western part of the image is a caldera, or large volcanic collapse pit. Late-stage extension created long graben, or fault-bounded valleys, is best seen near the center of the image. The northern boundary of Ovda Regio is a steep, curvilinear mountain belt made up of long, narrow, rounded ridges. These ridges are similar in appearance to folded mountain belts on Earth. Several impact craters, such as the circular features on the western margin of the image, are scattered across the area. The bright area in the southeast part of the image indicates the presence of a radar-reflective mineral such as pyrite. Most of the highland areas on Venus display a similar bright signal. Each pixel of this image covers an area on the surface 675 meters (2,215 feet) across, representing a 9- times reduction in resolution compared to full-scale resolution data. http://photojournal.jpl.nasa.gov/catalog/PIA00146

In vivo dark-field imaging of the retinal pigment epithelium cell mosaic

PubMed Central

Scoles, Drew; Sulai, Yusufu N.; Dubra, Alfredo

2013-01-01

Non-invasive reflectance imaging of the human RPE cell mosaic is demonstrated using a modified confocal adaptive optics scanning light ophthalmoscope (AOSLO). The confocal circular aperture in front of the imaging detector was replaced with a combination of a circular aperture 4 to 16 Airy disks in diameter and an opaque filament, 1 or 3 Airy disks thick. This arrangement reveals the RPE cell mosaic by dramatically attenuating the light backscattered by the photoreceptors. The RPE cell mosaic was visualized in all 7 recruited subjects at multiple retinal locations with varying degrees of contrast and cross-talk from the photoreceptors. Various experimental settings were explored for improving the visualization of the RPE cell boundaries including: pinhole diameter, filament thickness, illumination and imaging pupil apodization, unmatched imaging and illumination focus, wavelength and polarization. None of these offered an obvious path for enhancing image contrast. The demonstrated implementation of dark-field AOSLO imaging using 790 nm light requires low light exposures relative to light safety standards and it is more comfortable for the subject than the traditional autofluorescence RPE imaging with visible light. Both these factors make RPE dark-field imaging appealing for studying mechanisms of eye disease, as well as a clinical tool for screening and monitoring disease progression. PMID:24049692

Characterization of elliptic dark hollow beams

NASA Astrophysics Data System (ADS)

Gutiérrez-Vega, Julio C.

2008-08-01

A dark hollow beam (DHB) is designed in general as a ringed shaped light beam with a null intensity center on the beam axis. DHBs have interesting physical properties such as a helical wavefront, a center vortex singularity, doughnut-shaped transverse intensity distribution, they may carry and transfer orbital and spin angular momentum, and may also exhibit a nondiffracting behavior upon propagation. Most of the known theoretical models to describe DHBs consider axially symmetric transverse intensity distributions. However, in recent years there has been an increasing interest in developing models to describe DHBs with elliptic symmetry. DHBs with elliptic symmetry can be regarded as transition beams between circular and rectangular DHBs. For example, the high-order modes emitted from resonators with neither completely rectangular nor completely circular symmetry, but in between them, cannot be described by the known HermiteGaussian or LaguerreGaussian beams. In this work, we review the current state of research on elliptic DHBs, with particular emphasis in Mathieu and Ince-Gauss beams.

Revisiting the round bottom flask rainbow experiment

NASA Astrophysics Data System (ADS)

Selmke, Markus; Selmke, Sarah

2018-01-01

A popular demonstration experiment in optics uses a round-bottom flask filled with water to project a circular rainbow on a screen with a hole through which the flask is illuminated. We show how the vessel's wall shifts the first- and second-order bows towards each other and consequently reduces the width of Alexander's dark band. We address the challenge this introduces in observing Alexander's dark band, and explain the importance of a sufficient distance between the flask and the screen. The wall-effect also introduces a splitting of the bows that can easily be misinterpreted.

The geology of Hotei Regio, Titan: Correlation of Cassini VIMS and RADAR

USGS Publications Warehouse

Soderblom, L.A.; Brown, R.H.; Soderblom, J.M.; Barnes, J.W.; Kirk, R.L.; Sotin, Christophe; Jaumann, R.; MacKinnon, D.J.; Mackowski, D.W.; Baines, K.H.; Buratti, B.J.; Clark, R.N.; Nicholson, P.D.

2009-01-01

Joint Cassini VIMS and RADAR SAR data of ???700-km-wide Hotei Regio reveal a rich collection of geological features that correlate between the two sets of images. The degree of correlation is greater than anywhere else seen on Titan. Central to Hotei Regio is a basin filled with cryovolcanic flows that are anomalously bright in VIMS data (in particular at 5 ??m) and quite variable in roughness in SAR. The edges of the flows are dark in SAR data and appear to overrun a VIMS-bright substrate. SAR-stereo topography shows the flows to be viscous, 100-200 m thick. On its southern edge the basin is ringed by higher (???1 km) mountainous terrain. The mountains show mixed texture in SAR data: some regions are extremely rough, exhibit low and spectrally neutral albedo in VIMS data and may be partly coated with darker hydrocarbons. Around the southern margin of Hotei Regio, the SAR image shows several large, dendritic, radar-bright channels that flow down from the mountainous terrain and terminate in dark blue patches, seen in VIMS images, whose infrared color is consistent with enrichment in water ice. The patches are in depressions that we interpret to be filled with fluvial deposits eroded and transported by liquid methane in the channels. In the VIMS images the dark blue patches are encased in a latticework of lighter bands that we suggest to demark a set of circumferential and radial fault systems bounding structural depressions. Conceivably the circular features are tectonic structures that are remnant from an ancient impact structure. We suggest that impact-generated structures may have simply served as zones of weakness; no direct causal connection, such as impact-induced volcanism, is implied. We also speculate that two large dark features lying on the northern margin of Hotei Regio could be calderas. In summary the preservation of such a broad suite of VIMS infrared color variations and the detailed correlation with features in the SAR image and SAR topography evidence a complex set of geological processes (pluvial, fluvial, tectonic, cryovolcanic, impact) that have likely remained active up to very recent geological time (<104 year). That the cryovolcanic flows are excessively bright in the infrared, particularly at 5 ??m, might signal ongoing geological activity. One study [Nelson, R.M., and 28 colleagues, 2009. Icarus 199, 429-441] reported significant 2-??m albedo changes in VIMS data for Hotei Arcus acquired between 2004 and 2006, that were interpreted as evidence for such activity. However in our review of that work, we do not agree that such evidence has yet been found.

The cluster galaxy circular velocity function

NASA Astrophysics Data System (ADS)

Desai, V.; Dalcanton, J. J.; Mayer, L.; Reed, D.; Quinn, T.; Governato, F.

2004-06-01

We present galaxy circular velocity functions (GCVFs) for 34 low-redshift (z<~ 0.15) clusters identified in the Sloan Digital Sky Survey (SDSS), for 15 clusters drawn from dark matter simulations of hierarchical structure growth in a ΛCDM cosmology, and for ~22 000 SDSS field galaxies. We find that the simulations successfully reproduce the shape, amplitude and scatter in the observed distribution of cluster galaxy circular velocities. The power-law slope of the observed cluster GCVF is ~-2.4, independent of cluster velocity dispersion. The average slope of the simulated GCVFs is somewhat steeper, although formally consistent given the errors. We find that the effects of baryons on galaxy rotation curves is to flatten the simulated cluster GCVF into better agreement with observations. The cumulative GCVFs of the simulated clusters are very similar across a wide range of cluster masses, provided individual subhalo circular velocities are scaled by the circular velocities of the parent cluster. The scatter is consistent with that measured in the cumulative, scaled observed cluster GCVF. Finally, the observed field GCVF deviates significantly from a power law, being flatter than the cluster GCVF at circular velocities less than 200 km s-1.

37 CFR 201.39 - Notice to Libraries and Archives of Normal Commercial Exploitation or Availability at Reasonable...

Code of Federal Regulations, 2014 CFR

2014-07-01

... English (except for an original title, which may be in another language), typed or printed legibly in dark... information on Deposit Accounts, see Circular 5 on the U.S. Copyright Office's Web site, or request a copy at...

Photographer : JPL Range : 312, 000 kilometers (195,000 miles) This photo of Ganymede (Ice Giant)

NASA Technical Reports Server (NTRS)

1979-01-01

Photographer : JPL Range : 312, 000 kilometers (195,000 miles) This photo of Ganymede (Ice Giant) was taken from Voyager 2 and shows features down to about 5 to 6 kilometers across. Different types of terrain common on Ganymede's surface are visible. The boundary of the largest region of dark ancient terrain on Ganymede can be seen to the east (right), revealing some of the light linear features which may be all that remains of a large ancient impact structure similar to the large ring structure on Callisto. The broad light regions running through the image are the typical grooved structures seen within another example of what might be evidence of large scale lateral motion in Ganymede's crust. The band of grooved terrain (about 100 kilometers wide) in this region appears to be offset by 50 kilometers or more on the left hand edge by a linear feature perpendicular to it. A feature similar to this one was previously discovered by Voyager 1. These are the first clear examples of strike-slip style faulting on any planet other than Earth. Many examples of craters of all ages can be seen in this image, ranging from fresh, bright ray craters to large, subdued circular markings thought to be the 'scars' of large ancient impacts that have been flatteded by glacier-like flows.

Electron Spin Optical Orientation in Charged Quantum Dots

NASA Astrophysics Data System (ADS)

Shabaev, A.; Gershoni, D.; Korenev, V. L.

2005-03-01

We present a theory of nonresonant optical orientation of electron spins localized in quantum dots. This theory explains the negative circularly polarized photoluminescence of singlet trions localized in quantum dots previously observed in experiments where trion polarization changed to negative with time and where the degree of the negative polarization increased with intensity of pumping light. We have shown that this effect can be explained by the accumulation of dark excitons that occurs due to the spin blocking of the singlet trion formation - the major mechanism of dark exciton recombination. The accumulation of dark excitons results from a lack of electrons with a spin matching the exciton polarization. The electron spin lifetime is shortened by a transverse magnetic field or a temperature increase. This takes the block off the dark exciton recombination and restores the positive degree of trion polarization. The presented theory gives good agreement with experimental data.

Perceived Shrinkage of Motion Paths

ERIC Educational Resources Information Center

Sinico, Michele; Parovel, Giulia; Casco, Clara; Anstis, Stuart

2009-01-01

We show that human observers strongly underestimate a linear or circular trajectory that a luminous spot follows in the dark. At slow speeds, observers are relatively accurate, but, as the speed increases, the size of the path is progressively underestimated, by up to 35%. The underestimation imposes little memory load and does not require…

Reflective-emissive liquid-crystal displays constructed from AIE luminogens (Presentation Recording)

NASA Astrophysics Data System (ADS)

Tang, Ben Zhong; Zhao, Dongyu; Qin, Anjun

2015-10-01

The chiral nematic liquid crystal (N*-LC) has plenty of prospective applications in LC display (LCD) owing to the selective reflection and circular dichroism. The molecules in the N*-LC are aligned forming a helically twisted structure and the specific wavelength of incident light is reflected by the periodically varying refractive index in the N*-LC plane without the aid of a polarizer or color filter. However, N*-LC do not emit light which restricts its application in the dark environment. Moreover, the view angle of N*-LC display device was severe limited due to the strong viewing angle dependence of the structure color of the one dimensional photonic crystal of a N*-LC. In order to overcome these weaknesses, we have synthesized a luminescent liquid crystalline compound consisting of a tetraphenylethene (TPE) core, TPE-PPE, as a luminogen with mesogenic moieties. TPE-PPE exhibits both the aggregate-induced emission (AIE) and thermotropic liquid crystalline characteristics. By dissolving a little amount of TPE-PPE into N*-LC host, a circular polarized emission was obtained on the unidirectional orientated LC cell. Utilizing the circular polarized luminescence property of the LC mixture, we fabricated a photoluminescent liquid crystal display (PL-LCD) device which can work under both dark and sunlit conditions. This approach has simplified the device design, lowered the energy consumption and increased brightness and application of the LCD.

TIDAL STIRRING OF SATELLITES WITH SHALLOW DENSITY PROFILES PREVENTS THEM FROM BEING TOO BIG TO FAIL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tomozeiu, Mihai; Mayer, Lucio; Quinn, Thomas, E-mail: mihai@physik.uzh.ch

The “too big to fail” problem is revisited by studying the tidal evolution of populations of dwarf satellites with different density profiles. The high-resolution cosmological ΛCDM “ErisMod” set of simulations is used. These simulations can model both the stellar and dark matter components of the satellites, and their evolution under the action of the tides of a Milky Way (MW)-sized host halo at a force resolution better than 10 pc. The stronger tidal mass loss and re-shaping of the mass distribution induced in satellites with γ = 0.6 dark matter density distributions, as those resulting from the effect of feedbackmore » in hydrodynamical simulations of dwarf galaxy formation, are sufficient to bring the circular velocity profiles in agreement with the kinematics of MW’s dSphs. In contrast, in simulations in which the satellites retain cusps at z = 0 there are several “massive failures” with circular velocities in excess of the observational constraints. Various sources of deviations in the conventionally adopted relation between the circular velocity at the half-light radius and the one-dimensional line of sight velocity dispersions are found. Such deviations are caused by the response of circular velocity profiles to tidal effects, which also varies depending on the initially assumed inner density profile and by the complexity of the stellar kinematics, which include residual rotation and anisotropy. In addition, tidal effects naturally induce large deviations in the stellar mass–halo mass relation for halo masses below 10{sup 9} M {sub ⊙}, preventing any reliable application of the abundance matching technique to dwarf galaxy satellites.« less

CVF spectrophotometry of Pluto - Correlation of composition with albedo. [circularly variable filter

NASA Technical Reports Server (NTRS)

Marcialis, Robert L.; Lebofsky, Larry A.

1991-01-01

The present time-resolved, 0.96-2.65-micron spectrophotometry for the Pluto-Charon system indicates night-to-night variations in the depths of the methane absorptions such that the bands' equivalent width is near minimum light. The interpretation of these data in terms of a depletion of methane in dark regions of the planet, relative to bright ones, is consistent with the Buie and Fink (1987) observations. The near-IR spectrum of Pluto seems to be dominated by surface frost. It is suggested that the dark equatorial regions of Pluto are redder than those of moderate albedo.

Research on recognition of the geologic framework of porphyry copper deposits on ERTS-1 imagery. [New Guinea, Alaska, and Colorado

NASA Technical Reports Server (NTRS)

Wilson, J. C. (Principal Investigator)

1975-01-01

The author has identified the following significant results. Many new linear and circular features were found. These features prompted novel tectonic classification and analysis especially in the Ray and Ely areas. Tectonic analyses of the Ok Tedi, Tanacross, and Silvertone areas follow conventional interpretations. Circular features are mapped in many cases and are interpreted as exposed or covered intrusive centers. The small circular features reported in the Ok Tedi test area are valid and useful correlations with tertiary intrusion and volcanism in this remote part of New Guinea. Several major faults of regional dimensions, such as the Denali fault in Alaska and the Colorado mineral belt structures in Colorado are detected in the imagery. Many more faults and regional structures are found in the imagery than exist on present maps.

Algorithm for Detecting a Bright Spot in an Image

NASA Technical Reports Server (NTRS)

2009-01-01

An algorithm processes the pixel intensities of a digitized image to detect and locate a circular bright spot, the approximate size of which is known in advance. The algorithm is used to find images of the Sun in cameras aboard the Mars Exploration Rovers. (The images are used in estimating orientations of the Rovers relative to the direction to the Sun.) The algorithm can also be adapted to tracking of circular shaped bright targets in other diverse applications. The first step in the algorithm is to calculate a dark-current ramp a correction necessitated by the scheme that governs the readout of pixel charges in the charge-coupled-device camera in the original Mars Exploration Rover application. In this scheme, the fraction of each frame period during which dark current is accumulated in a given pixel (and, hence, the dark-current contribution to the pixel image-intensity reading) is proportional to the pixel row number. For the purpose of the algorithm, the dark-current contribution to the intensity reading from each pixel is assumed to equal the average of intensity readings from all pixels in the same row, and the factor of proportionality is estimated on the basis of this assumption. Then the product of the row number and the factor of proportionality is subtracted from the reading from each pixel to obtain a dark-current-corrected intensity reading. The next step in the algorithm is to determine the best location, within the overall image, for a window of N N pixels (where N is an odd number) large enough to contain the bright spot of interest plus a small margin. (In the original application, the overall image contains 1,024 by 1,024 pixels, the image of the Sun is about 22 pixels in diameter, and N is chosen to be 29.)

Propagation and coherence properties of higher order partially coherent dark hollow beams in turbulence

NASA Astrophysics Data System (ADS)

Eyyuboğlu, Halil Tanyer

2008-02-01

We formulate and evaluate in terms of graphical outputs, source and receiver plane expressions, the complex degree of coherence, beam size variation and power in bucket performance for higher order partially coherent dark hollow beams propagating in turbulent atmosphere. Our formulation is able to cover square, rectangular, circular, elliptical geometries for dark hollow and flat-topped beams in one single expression. From the graphical outputs of the receiver plane, it is observed that higher order partially coherent dark hollow beams will initially develop an outer ring around a central lobe, but will eventually evolve towards a Gaussian shape as the propagation distance is extended. It is further observed that stronger turbulence levels and greater partial coherence have similar effects on beam profile. During propagation, modulus of complex degree of coherence of partially coherent dark hollow beams appears to rise above that of the source plane values, reaching as high as near unity. Beam size analysis shows that, among the types examined, (nearly) flat-topped beam experiences the least beam expansion. Power in bucket analysis indicates that lowest order square fully coherent dark beam offers the best power capturing.

Generalized M-factor of hollow Gaussian beams through a hard-edge circular aperture

NASA Astrophysics Data System (ADS)

Deng, Dongmei

2005-06-01

Based on the generalized truncated second-order moments, the generalized M-factor (MG2-factor) of three-dimensional hollow Gaussian beams (HGBs) through a hard-edge circular aperture is studied in cylindrical coordinate system analytically and numerically. The closed-form expression for the MG2-factor of the truncated HGBs, which is dependent on the truncation parameter β and the beam order n, can be simplified to that of the truncated, the untruncated Gaussian beams and the untruncated HGBs. Also, the power fraction is demonstrated analytically and numerically, which shows that the area of the dark region across the HGBs increases as n increasing.

Indirect searches of dark matter via polynomial spectral features

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garcia-Cely, Camilo; Heeck, Julian

2016-08-11

We derive the spectra arising from non-relativistic dark matter annihilations or decays into intermediary particles with arbitrary spin, which subsequently produce neutrinos or photons via two-body decays. Our approach is model independent and predicts spectral features restricted to a kinematic box. The overall shape within that box is a polynomial determined by the polarization of the decaying particle. We illustrate our findings with two examples. First, with the neutrino spectra arising from dark matter annihilations into the massive Standard Model gauge bosons. Second, with the gamma-ray and neutrino spectra generated by dark matter annihilations into hypothetical massive spin-2 particles. Ourmore » results are in particular applicable to the 750 GeV diphoton excess observed at the LHC if interpreted as a spin-0 or spin-2 particle coupled to dark matter. We also derive limits on the dark matter annihilation cross section into this resonance from the non-observation of the associated gamma-ray spectral features by the H.E.S.S. telescope.« less

Unexpected features of the dark proteome.

PubMed

Perdigão, Nelson; Heinrich, Julian; Stolte, Christian; Sabir, Kenneth S; Buckley, Michael J; Tabor, Bruce; Signal, Beth; Gloss, Brian S; Hammang, Christopher J; Rost, Burkhard; Schafferhans, Andrea; O'Donoghue, Seán I

2015-12-29

We surveyed the "dark" proteome-that is, regions of proteins never observed by experimental structure determination and inaccessible to homology modeling. For 546,000 Swiss-Prot proteins, we found that 44-54% of the proteome in eukaryotes and viruses was dark, compared with only ∼14% in archaea and bacteria. Surprisingly, most of the dark proteome could not be accounted for by conventional explanations, such as intrinsic disorder or transmembrane regions. Nearly half of the dark proteome comprised dark proteins, in which the entire sequence lacked similarity to any known structure. Dark proteins fulfill a wide variety of functions, but a subset showed distinct and largely unexpected features, such as association with secretion, specific tissues, the endoplasmic reticulum, disulfide bonding, and proteolytic cleavage. Dark proteins also had short sequence length, low evolutionary reuse, and few known interactions with other proteins. These results suggest new research directions in structural and computational biology.

Cosmological simulations of decaying dark matter: implications for small-scale structure of dark matter haloes

NASA Astrophysics Data System (ADS)

Wang, Mei-Yu; Peter, Annika H. G.; Strigari, Louis E.; Zentner, Andrew R.; Arant, Bryan; Garrison-Kimmel, Shea; Rocha, Miguel

2014-11-01

We present a set of N-body simulations of a class of models in which an unstable dark matter particle decays into a stable dark matter particle and a non-interacting light particle with decay lifetime comparable to the Hubble time. We study the effects of the recoil kick velocity (Vk) received by the stable dark matter on the structures of dark matter haloes ranging from galaxy-cluster to Milky Way-mass scales. For Milky Way-mass haloes, we use high-resolution, zoom-in simulations to explore the effects of decays on Galactic substructure. In general, haloes with circular velocities comparable to the magnitude of kick velocity are most strongly affected by decays. We show that models with lifetimes Γ-1 ˜ H_0^{-1} and recoil speeds Vk ˜ 20-40 km s-1 can significantly reduce both the abundance of Galactic subhaloes and their internal densities. We find that decaying dark matter models that do not violate current astrophysical constraints can significantly mitigate both the `missing satellites problem' and the more recent `too big to fail problem'. These decaying models predict significant time evolution of haloes, and this implies that at high redshifts decaying models exhibit the similar sequence of structure formation as cold dark matter. Thus, decaying dark matter models are significantly less constrained by high-redshift phenomena than warm dark matter models. We conclude that models of decaying dark matter make predictions that are relevant for the interpretation of small galaxies observations in the Local Group and can be tested as well as by forthcoming large-scale surveys.

Theoretical implications of the galactic radial acceleration relation of McGaugh, Lelli, and Schombert

NASA Astrophysics Data System (ADS)

Nesbet, Robert K.

2018-05-01

Velocities in stable circular orbits about galaxies, a measure of centripetal gravitation, exceed the expected Kepler/Newton velocity as orbital radius increases. Standard Λ cold dark matter (ΛCDM) attributes this anomaly to galactic dark matter. McGaugh et al. have recently shown for 153 disc galaxies that observed radial acceleration is an apparently universal function of classical acceleration computed for observed galactic baryonic mass density. This is consistent with the empirical modified Newtonian dynamics (MOND) model, not requiring dark matter. It is shown here that suitably constrained ΛCDM and conformal gravity (CG) also produce such a universal correlation function. ΛCDM requires a very specific dark matter distribution, while the implied CG non-classical acceleration must be independent of galactic mass. All three constrained radial acceleration functions agree with the empirical baryonic v4 Tully-Fisher relation. Accurate rotation data in the nominally flat velocity range could distinguish between MOND, ΛCDM, and CG.

A new family of distribution functions for spherical galaxies

NASA Astrophysics Data System (ADS)

Gerhard, Ortwin E.

1991-06-01

The present study describes a new family of anisotropic distribution functions for stellar systems designed to keep control of the orbit distribution at fixed energy. These are quasi-separable functions of energy and angular momentum, and they are specified in terms of a circularity function h(x) which fixes the distribution of orbits on the potential's energy surfaces outside some anisotropy radius. Detailed results are presented for a particular set of radially anisotropic circularity functions h-alpha(x). In the scale-free logarithmic potential, exact analytic solutions are shown to exist for all scale-free circularity functions. Intrinsic and projected velocity dispersions are calculated and the expected properties are presented in extensive tables and graphs. Several applications of the quasi-separable distribution functions are discussed. They include the effects of anisotropy or a dark halo on line-broadening functions, the radial orbit instability in anisotropic spherical systems, and violent relaxation in spherical collapse.

Visual Circular Analysis of 266 Years of Sunspot Counts.

PubMed

Buelens, Bart

2016-06-01

Sunspots, colder areas that are visible as dark spots on the surface of the Sun, have been observed for centuries. Their number varies with a period of ∼11 years, a phenomenon closely related to the solar activity cycle. Recently, observation records dating back to 1749 have been reassessed, resulting in the release of a time series of sunspot numbers covering 266 years of observations. This series is analyzed using circular analysis to determine the periodicity of the occurrence of solar maxima. The circular analysis is combined with spiral graphs to provide a single visualization, simultaneously showing the periodicity of the series, the degree to which individual cycle lengths deviate from the average period, and differences in levels reached during the different maxima. This type of visualization of cyclic time series with varying cycle lengths in which significant events occur periodically is broadly applicable. It is aimed particularly at science communication, education, and public outreach.

Repeating firing fields of CA1 neurons shift forward in response to increasing angular velocity.

PubMed

Cowen, Stephen L; Nitz, Douglas A

2014-01-01

Self-motion information influences spatially-specific firing patterns exhibited by hippocampal neurons. Moreover, these firing patterns can repeat across similar subsegments of an environment, provided that there is similarity of path shape and head orientations across subsegments. The influence of self-motion variables on repeating fields remains to be determined. To investigate the role of path shape and angular rotation on hippocampal activity, we recorded the activity of CA1 neurons from rats trained to run on spiral-shaped tracks. During inbound traversals of circular-spiral tracks, angular velocity increases continuously. Under this condition, most neurons (74%) exhibited repeating fields across at least three adjacent loops. Of these neurons, 86% exhibited forward shifts in the angles of field centers relative to centers on preceding loops. Shifts were absent on squared-spiral tracks, minimal and less reliable on concentric-circle tracks, and absent on outward-bound runs on circular-spiral tracks. However, outward-bound runs on the circular-spiral track in the dark were associated with backward shifts. Together, the most parsimonious interpretation of the results is that continuous increases or decreases in angular velocity are particularly effective at shifting the center of mass of repeating fields, although it is also possible that a nonlinear integration of step counts contributes to the shift. Furthermore, the unexpected absence of field shifts during outward journeys in light (but not darkness) suggests visual cues around the goal location anchored the map of space to an allocentric reference frame.

Scintillation properties of dark hollow beams in a weak turbulent atmosphere

NASA Astrophysics Data System (ADS)

Chen, Y.; Cai, Y.; Eyyuboğlu, H. T.; Baykal, Y.

2008-01-01

The on-axis scintillation index for a circular dark hollow beam (DHB) propagating in a weak turbulent atmosphere is formulated, and the scintillation properties of a DHB are investigated in detail. The scintillation index for a DHB reduces to the scintillation index for a Gaussian beam, an annular beam and a flat-topped beam under certain conditions. It is found that the scintillation index of a DHB is closely related to the beam parameters and can be lower than that of a Gaussian beam, an annular beam and a flat-topped beam in a weak turbulent atmosphere at smaller waist sizes and longer propagation lengths.

Terrain and Rock Yogi

NASA Image and Video Library

1997-07-06

The left portion of this image, taken by the Imager for Mars Pathfinder (IMP) on July 5, 1997 (Sol 2), shows a portion of the large rock nicknamed "Yogi." Portions of a petal and deflated airbag are in the foreground. The dark circular object at right is a portion of the lander's high-gain antenna. http://photojournal.jpl.nasa.gov/catalog/PIA00630

Analysis of electroluminescence images in small-area circular CdTe solar cells

NASA Astrophysics Data System (ADS)

Bokalič, Matevž; Raguse, John; Sites, James R.; Topič, Marko

2013-09-01

The electroluminescence (EL) imaging process of small area solar cells is investigated in detail to expose optical and electrical effects that influence image acquisition and corrupt the acquired image. An approach to correct the measured EL images and to extract the exact EL radiation as emitted from the photovoltaic device is presented. EL images of circular cadmium telluride (CdTe) solar cells are obtained under different conditions. The power-law relationship between forward injection current and EL emission and a negative temperature coefficient of EL radiation are observed. The distributed Simulation Program with Integrated Circuit Emphasis (SPICE®) model of the circular CdTe solar cell is used to simulate the dark J-V curve and current distribution under the conditions used during EL measurements. Simulation results are presented as circularly averaged EL intensity profiles, which clearly show that the ratio between resistive parameters determines the current distribution in thin-film solar cells. The exact resistance values for front and back contact layers and for CdTe bulk layer are determined at different temperatures, and a negative temperature coefficient for the CdTe bulk resistance is observed.

Polarized excitons and optical activity in single-wall carbon nanotubes

NASA Astrophysics Data System (ADS)

Chang, Yao-Wen; Jin, Bih-Yaw

2018-05-01

The polarized excitons and optical activity of single-wall carbon nanotubes (SWNTs) are studied theoretically by π -electron Hamiltonian and helical-rotational symmetry. By taking advantage of the symmetrization, the single-particle energy and properties of a SWNT are characterized with the corresponding helical band structure. The dipole-moment matrix elements, magnetic-moment matrix elements, and the selection rules can also be derived. Based on different selection rules, the optical transitions can be assigned as the parallel-polarized, left-handed circularly-polarized, and right-handed circularly-polarized transitions, where the combination of the last two gives the cross-polarized transition. The absorption and circular dichroism (CD) spectra are simulated by exciton calculation. The calculated results are well comparable with the reported measurements. Built on the foundation, magnetic-field effects on the polarized excitons and optical activity of SWNTs are studied. Dark-bright exciton splitting and interband Faraday effect in the CD spectrum of SWNTs under an axial magnetic field are predicted. The Faraday rotation dispersion can be analyzed according to the selection rules of circular polarizations and the helical band structure.

Specific features of the circular dichroism of a chiral photonic crystal with a defect layer inside in the presence of a gain

NASA Astrophysics Data System (ADS)

Gevorgyan, A. H.

2017-01-01

The specific features of the circular dichroism (CD) spectra of a cholesteric liquid crystal (CLC) layer with a defect layer inside in the presence of gain have been investigated. The features of the dependence of CD on the parameter characterizing the gain on the defect mode are analyzed for two cases: (i) gain is present in the defect layer and is absent in the CLC sublayers and (ii) gain is absent in the defect layer but is present in the CLC sublayers. It is shown that these dependences significantly differ in the two aforementioned cases. The dependences of the reflection, transmission, and absorption on the defect mode on the gain parameter have been investigated for incident light with both circular polarizations.

Circles and Streaks

NASA Technical Reports Server (NTRS)

2003-01-01

MGS MOC Release No. MOC2-544, 14 November 2003

This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, acquired less than a week ago on 8 November 2003, shows a typical southern middle-to-high latitude scene at this time of year. It is summer in the southern hemisphere, and regions such as Promethei Terra, where this image was acquired, are being streaked by dust devils that remove or disrupt the coating of dust that was deposited over the region in the previous autumn or winter. While no active dust devils were captured in this scene, their tell-tale tracks are scratched all across the image. The circular features are the sites of buried meteor impact craters; their rims form dark rings; the material that fills the craters has become cracked. This picture is located near 68.1oS, 247.9oW. The area shown is approximately 3 km (1.9 mi) across and is illuminated by sunlight from the upper left.

Is the dark halo of the Milky Way prolate?

NASA Astrophysics Data System (ADS)

Bowden, A.; Evans, N. W.; Williams, A. A.

2016-07-01

We introduce the flattening equation, which relates the shape of the dark halo to the angular velocity dispersions and the density of a tracer population of stars. It assumes spherical alignment of the velocity dispersion tensor, as seen in the data on stellar halo stars in the Milky Way. The angular anisotropy and gradients in the angular velocity dispersions drive the solutions towards prolateness, whilst the gradient in the stellar density is a competing effect favouring oblateness. We provide an efficient numerical algorithm to integrate the flattening equation. Using tests on mock data, we show that there is a strong degeneracy between circular speed and flattening, which can be circumvented with informative priors. Therefore, we advocate the use of the flattening equation to test for oblateness or prolateness, though the precise value of q can only be measured with the addition of the radial Jeans equation. We apply the flattening equation to a sample extracted from the Sloan Digital Sky Survey of ˜15 000 halo stars with full phase space information and errors. We find that between Galactocentric radii of 5 and 10 kpc, the shape of the dark halo is prolate, whilst even mildly oblate models are disfavoured. Strongly oblate models are ruled out. Specifically, for a logarithmic halo model, if the asymptotic circular speed v0 lies between 210 and 250 km s-1, then we find the axis ratio of the equipotentials q satisfies 1.5 ≲ q ≲ 2.

Arecibo radar imagery of Mars: II. Chryse-Xanthe, polar caps, and other regions

NASA Astrophysics Data System (ADS)

Harmon, John K.; Nolan, Michael C.

2017-01-01

We conclude our radar imaging survey of Mars, which maps spatial variations in depolarized radar reflectivity using Arecibo S-band (λ12.6 cm) observations from 2005-2012. Whereas our earlier paper (Harmon et al., 2012, Arecibo radar imagery of Mars: the major volcanic provinces. Icarus 220, 990-1030) covered the volcanic regions of Tharsis, Elysium, and Amazonis, this paper includes non-volcanic regions where hydrologic and impact processes can be the dominant resurfacing agents affecting radar backscatter. Many of the more prominent and interesting radar-bright features outside the major volcanic provinces are located in and around Chryse Planitia and Xanthe Terra. These features are identified with: a basin in northeast Lunae Planum containing the combined deposits from Maja Vallis and Ganges Catena outflows; channel outwash plains in western and southern Chryse basin; plateaus bordering chasma/chaos zones, where surface modification may have resulted from hydrologic action associated with incipient chaos formation; and some bright-ejecta craters in Chryse basin, of a type otherwise rare on Mars. Dark-halo craters have also been identified in Chryse and elsewhere that are similar to those seen in the volcanic provinces. Although the cratered highlands are relatively radar-bland, they do exhibit some bright depolarized features; these include eroded crater rims, several unusual ejecta flows and impact melts, and terrain-softened plains. The rims of large impact basins (Hellas, Argyre, Isidis) show a variety of radar-bright features provisionally identified with massif slopes, erosion sediments, eroded pyroclastics, impact melts, and glacial deposits. The interiors of these basins are largely radar-dark, which is consistent with coverage by rock-free sediments. Tempe Terra and Acheron Fossae show bright features possibly associated with rift volcanism or eroded tectonic structures, and northwest Tempe Terra shows one very bright feature associated with glacial or other ice processes in the dichotomy boundary region. The first delay-Doppler images of the radar-bright features from the north and south polar icecaps are presented. Both poles show the circular polarization inversion and high reflectivity characteristic of coherent volume backscatter from relatively clean ice. The south polar feature is primarily backscatter from the residual CO2 icecap (with a lesser contribution from the polar layered deposits), whose finite optical depth probably accounts for the feature's strong S/X-band wavelength dependence. Conversely, the north polar radar feature appears to be mostly backscatter from the H2O-ice-rich polar layered deposits rather than from the thin residual H2O cap. The north polar region shows additional radar-bright features from Korolev Crater and a few other outlying circumpolar ice deposits.

Unexpected features of the dark proteome

PubMed Central

Perdigão, Nelson; Heinrich, Julian; Stolte, Christian; Sabir, Kenneth S.; Buckley, Michael J.; Tabor, Bruce; Signal, Beth; Gloss, Brian S.; Hammang, Christopher J.; Rost, Burkhard; Schafferhans, Andrea

2015-01-01

We surveyed the “dark” proteome–that is, regions of proteins never observed by experimental structure determination and inaccessible to homology modeling. For 546,000 Swiss-Prot proteins, we found that 44–54% of the proteome in eukaryotes and viruses was dark, compared with only ∼14% in archaea and bacteria. Surprisingly, most of the dark proteome could not be accounted for by conventional explanations, such as intrinsic disorder or transmembrane regions. Nearly half of the dark proteome comprised dark proteins, in which the entire sequence lacked similarity to any known structure. Dark proteins fulfill a wide variety of functions, but a subset showed distinct and largely unexpected features, such as association with secretion, specific tissues, the endoplasmic reticulum, disulfide bonding, and proteolytic cleavage. Dark proteins also had short sequence length, low evolutionary reuse, and few known interactions with other proteins. These results suggest new research directions in structural and computational biology. PMID:26578815

Coexistence of wave propagation and oscillation in the photosensitive Belousov-Zhabotinsky reaction on a circular route.

PubMed

Nakata, Satoshi; Morishima, Sayaka; Ichino, Takatoshi; Kitahata, Hiroyuki

2006-12-21

The photosensitive Belousov-Zhabotinsky (BZ) reaction was investigated on a circular ring, which was drawn using computer software and then projected on a film soaked with BZ solution using a liquid-crystal projector. Under the initial conditions, a chemical wave propagated with a constant velocity on the black ring under a bright background. When the background was rapidly changed to dark, coexistence of the oscillation on part of the ring and propagation of the chemical wave on the other part was observed. These experimental results are discussed in relation to the nature of the photosensitive BZ reaction and theoretically reproduced based on a reaction-diffusion system using the modified Oregonator model.

Evolution of Circular Polarization Ratio (CPR) Profiles of Kilometer-scale Craters on the Lunar Maria

NASA Technical Reports Server (NTRS)

King, I. R.; Fassett, C. I.; Thomson, B. J.; Minton, D. A.; Watters, W. A.

2017-01-01

When sufficiently large impact craters form on the Moon, rocks and unweathered materials are excavated from beneath the regolith and deposited into their blocky ejecta. This enhances the rockiness and roughness of the proximal ejecta surrounding fresh impact craters. The interior of fresh craters are typically also rough, due to blocks, breccia, and impact melt. Thus, both the interior and proximal ejecta of fresh craters are usually radar bright and have high circular polarization ratios (CPR). Beyond the proximal ejecta, radar-dark halos are observed around some fresh craters, suggesting that distal ejecta is finer-grained than background regolith. The radar signatures of craters fade with time as the regolith grows.

Coma Morphology Due to an Extended Active Region and Implications for the Spin State of Comet Hale-Bopp

NASA Technical Reports Server (NTRS)

Samarasinha, Nalin H.

2000-01-01

We show that the circular character of continuum structures observed in the coma of comet Hale-Bopp around the perihelion passage is most likely due to a dust jet from a large extended active region on the surface. Coma morphology due to a wide jet is different from that due to a narrow jet. The latter shows foreshortening effects due to observing geometry, wider jet produces more circular features. This circularization effect provides a self-consistent explanation for the evolution of near-perihelion coma morphology. No changes in the direction of the rotational angular momentum vector are required during this period in contrast to the models of Schleicher et al. This circularization effect also enables us to produce near-circular coma features in the S-E quadrant during 1997 late February and therefore questions the basic premise on which Sekanina bases his morphological arguments for a gravitationally bound satellite nucleus.

Magnetic annihilation of the dark mode in a strongly coupled bright-dark terahertz metamaterial.

PubMed

Manjappa, Manukumara; Turaga, Shuvan Prashant; Srivastava, Yogesh Kumar; Bettiol, Andrew Anthony; Singh, Ranjan

2017-06-01

Dark mode in metamaterials has become a vital component in determining the merit of the Fano type of interference in the system. Its strength dictates the enhancement and suppression in the amplitude and Q-factors of resulting resonance features. In this work, we experimentally probe the effect of strong near-field coupling on the strength of the dark mode in a concentrically aligned bright resonator and a dark split ring resonator (SRR) system exhibiting the classical analog of the electromagnetically induced transparency effect. An enhanced strong magnetic field between the bright-dark resonators destructively interferes with the inherent magnetic field of the dark mode to completely annihilate its effect in the coupled system. Moreover, the observed annihilation effect in the dark mode has a direct consequence on the disappearance of the SRR effect in the proposed system, wherein under the strong magnetic interactions, the LC resonance feature of the split ring resonator becomes invisible to the incident terahertz wave.

Skin - abnormally dark or light

MedlinePlus

... page: //medlineplus.gov/ency/article/003242.htm Abnormally dark or light skin To use the sharing features ... The bronze color can range from light to dark (in fair-skinned people) with the degree of ...

THE NUMBER OF TIDAL DWARF SATELLITE GALAXIES IN DEPENDENCE OF BULGE INDEX

DOE Office of Scientific and Technical Information (OSTI.GOV)

López-Corredoira, Martín; Kroupa, Pavel, E-mail: martinlc@iac.es, E-mail: pavel@astro.uni-bonn.de

We show that a significant correlation (up to 5σ) emerges between the bulge index, defined to be larger for a larger bulge/disk ratio, in spiral galaxies with similar luminosities in the Galaxy Zoo 2 of the Sloan Digital Sky Survey and the number of tidal-dwarf galaxies in the catalog by Kaviraj et al. In the standard cold or warm dark matter cosmological models, the number of satellite galaxies correlates with the circular velocity of the dark matter host halo. In generalized gravity models without cold or warm dark matter, such a correlation does not exist, because host galaxies cannot capture infalling dwarfmore » galaxies due to the absence of dark-matter-induced dynamical friction. However, in such models, a correlation is expected to exist between the bulge mass and the number of satellite galaxies because bulges and tidal-dwarf satellite galaxies form in encounters between host galaxies. This is not predicted by dark matter models in which bulge mass and the number of satellites are a priori uncorrelated because higher bulge/disk ratios do not imply higher dark/luminous ratios. Hence, our correlation reproduces the prediction of scenarios without dark matter, whereas an explanation is not found readily from the a priori predictions of the standard scenario with dark matter. Further research is needed to explore whether some application of the standard theory may explain this correlation.« less

Bars in dark-matter-dominated dwarf galaxy discs

NASA Astrophysics Data System (ADS)

Marasco, A.; Oman, K. A.; Navarro, J. F.; Frenk, C. S.; Oosterloo, T.

2018-05-01

We study the shape and kinematics of simulated dwarf galaxy discs in the APOSTLE suite of Λ cold dark matter (ΛCDM) cosmological hydrodynamical simulations. We find that a large fraction of these gas-rich, star-forming discs show weak bars in their stellar component, despite being dark-matter-dominated systems. The bar pattern shape and orientation reflect the ellipticity of the dark matter potential, and its rotation is locked to the slow figure rotation of the triaxial dark halo. The bar-like nature of the potential induces non-circular motions in the gas component, including strong bisymmetric flows that can be readily seen as m = 3 harmonic perturbations in the H I line-of-sight velocity fields. Similar bisymmetric flows are seen in many galaxies of The HI Nearby Galaxy Survey (THINGS) and Local Irregulars That Trace Luminosity Extremes THINGS (LITTLE THINGS), although on average their amplitudes are a factor of ˜2 weaker than in our simulated discs. Our results indicate that bar-like patterns may arise even when baryons are not dominant, and that they are common enough to warrant careful consideration when analysing the gas kinematics of dwarf galaxy discs.

Strong valley Zeeman effect of dark excitons in monolayer transition metal dichalcogenides in a tilted magnetic field

NASA Astrophysics Data System (ADS)

Van der Donck, M.; Zarenia, M.; Peeters, F. M.

2018-02-01

The dependence of the excitonic photoluminescence (PL) spectrum of monolayer transition metal dichalcogenides (TMDs) on the tilt angle of an applied magnetic field is studied. Starting from a four-band Hamiltonian we construct a theory which quantitatively reproduces the available experimental PL spectra for perpendicular and in-plane magnetic fields. In the presence of a tilted magnetic field, we demonstrate that the dark exciton PL peaks brighten due to the in-plane component of the magnetic field and split for light with different circular polarizations as a consequence of the perpendicular component of the magnetic field. This splitting is more than twice as large as the splitting of the bright exciton peaks in tungsten-based TMDs. We propose an experimental setup that will allow for accessing the predicted splitting of the dark exciton peaks in the PL spectrum.

k-essence model of inflation, dark matter, and dark energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bose, Nilok; Majumdar, A. S.

We investigate the possibility for k-essence dynamics to reproduce the primary features of inflation in the early universe, generate dark matter subsequently, and finally account for the presently observed acceleration. We first show that for a purely kinetic k-essence model the late-time energy density of the universe when expressed simply as a sum of a cosmological constant and a dark matter term leads to a static universe. We then study another k-essence model in which the Lagrangian contains a potential for the scalar field as well as a noncanonical kinetic term. We show that such a model generates the basicmore » features of inflation in the early universe, and also gives rise to dark matter and dark energy at appropriate subsequent stages. Observational constraints on the parameters of this model are obtained.« less

Influence of skin ageing features on Chinese women's perception of facial age and attractiveness.

PubMed

Porcheron, A; Latreille, J; Jdid, R; Tschachler, E; Morizot, F

2014-08-01

Ageing leads to characteristic changes in the appearance of facial skin. Among these changes, we can distinguish the skin topographic cues (skin sagging and wrinkles), the dark spots and the dark circles around the eyes. Although skin changes are similar in Caucasian and Chinese faces, the age of occurrence and the severity of age-related features differ between the two populations. Little is known about how the ageing of skin influences the perception of female faces in Chinese women. The aim of this study is to evaluate the contribution of the different age-related skin features to the perception of age and attractiveness in Chinese women. Facial images of Caucasian women and Chinese women in their 60s were manipulated separately to reduce the following skin features: (i) skin sagging and wrinkles, (ii) dark spots and (iii) dark circles. Finally, all signs were reduced simultaneously (iv). Female Chinese participants were asked to estimate the age difference between the modified and original images and evaluate the attractiveness of modified and original faces. Chinese women perceived the Chinese faces as younger after the manipulation of dark spots than after the reduction in wrinkles/sagging, whereas they perceived the Caucasian faces as the youngest after the manipulation of wrinkles/sagging. Interestingly, Chinese women evaluated faces with reduced dark spots as being the most attractive whatever the origin of the face. The manipulation of dark circles contributed to making Caucasian and Chinese faces being perceived younger and more attractive than the original faces, although the effect was less pronounced than for the two other types of manipulation. This is the first study to have examined the influence of various age-related skin features on the facial age and attractiveness perception of Chinese women. The results highlight different contributions of dark spots, sagging/wrinkles and dark circles to their perception of Chinese and Caucasian faces. © 2014 The Authors. International Journal of Cosmetic Science published by John Wiley & Sons Ltd on behalf of Society of Cosmetic Scientists and Societe Francaise de Cosmetologie.

Rhea's Surface: Ice Properties Measured by Radar.

NASA Astrophysics Data System (ADS)

Black, G.; Campbell, D.

2004-11-01

We obtained echoes from the leading and trailing hemispheres of Rhea in January 2004 using the Arecibo Observatory's 13-cm radar system. The transmitted signal was circularly polarized and strong echoes were received in both the opposite circular (OC) sense to that transmitted and the same circular (SC) sense. Rhea's mean total cross section normalized by projected area is 1.32±0.10 and the mean circular polarization ratio, the ratio of SC echo power to OC echo power, is 1.17±0.12. The reflectivity of the leading hemisphere may be slightly lower than that of the trailing hemisphere by about 10%, although the polarization ratio appears to vary less. The cross section and polarization ratio are similar to those of the icy Galilean satellites and closest to Ganymede's. For these bodies the high radar backscatter cross sections and high polarization ratios are due to an efficient multiple scattering mechanism in the cold, relatively clean water ice surfaces which have very low propagation loss at radio wavelengths. Rhea's surface appears to be exhibiting a similar effect. Rhea's echo spectra are broad, again similar to those of the icy Galilean satellites, and consistent with a multiple scattering mechanism. In contrast, the bright icy hemisphere of Rhea's sibling Iapetus is significantly more radar dark with a radar reflectivity roughly 10% of Rhea's (Black et al., Science, v304, 2004). On Iapetus this great reduction in scattering efficiency is most likely caused by a radar absorber in the ice, possibly ammonia compounds or buried non-ice material from its dark hemisphere. Rhea's surface ice must therefore be relatively free of contaminants, and have a purity similar to Ganymede's. These observations can constrain the concentration of ammonia in the near surface which would be a strong absorber even in amounts of only a few percent. We acknowledge support by NASA's PG&G program.

Etude expérimentale de la lamination des stromatolithes à Rivularia haematites en climat tempéré: édification des lamines micritiques

NASA Astrophysics Data System (ADS)

Caudwell, Christiane; Lang, Jacques; Pascal, André

1997-06-01

The lamination of Rivularia haematites stromatolites (D.C.) Agardh was studied experimentally for 7 years. Micritic laminae are found to form in three stages: biological formation of dark laminae during the wet season, microsparitic calcification of these laminae in the form of clearly individualized polycrystalline aggregates and, finally, micritization of the latter by bacterial action. These three stages develop over 2 to 3 years. The occurrence of transverse, longitudinal and circular microfibrils in the outer sheath is thought to explain the nucleation and the three-dimensional structure of the microsparitic crystals of the dark laminae and of the polycrystalline aggregates.

X-ray bright points and He I lambda 10830 dark points

NASA Technical Reports Server (NTRS)

Golub, L.; Harvey, K. L.; Herant, M.; Webb, D. F.

1989-01-01

Using near-simultaneous full disk Solar X-ray images and He I 10830 lambda, spectroheliograms from three recent rocket flights, dark points identified on the He I maps were compared with X-ray bright points identified on the X-ray images. It was found that for the largest and most obvious features there is a strong correlation: most He I dark points correspond to X-ray bright points. However, about 2/3 of the X-ray bright points were not identified on the basis of the helium data alone. Once an X-ray feature is identified it is almost always possible to find an underlying dark patch of enhanced He I absorption which, however, would not a priori have been selected as a dark point. Therefore, the He I dark points, using current selection criteria, cannot be used as a one-to-one proxy for the X-ray data. He I dark points do, however, identify the locations of the stronger X-ray bright points.

X-ray bright points and He I lambda 10830 dark points

NASA Technical Reports Server (NTRS)

Golub, L.; Harvey, K. L.; Herant, M.; Webb, D. F.

1989-01-01

Using near-simultaneous full disk Solar X-ray images and He I 10830 lambda, spectroheliograms from three recent rocket flights, dark points identified on the He I maps were compared with x-ray bright points identified on the X-ray images. It was found that for the largest and most obvious features there is a strong correlation: most He I dark points correspond to X-ray bright points. However, about 2/3 of the X-ray bright points were not identified on the basis of the helium data alone. Once an X-ray feature is identified it is almost always possible to find an underlying dark patch of enhanced He I absorption which, however, would not a priori have been selected as a dark point. Therefore, the He I dark points, using current selection criteria, cannot be used as a one-to-one proxy for the X-ray data. He I dark points do, however, identify the locations of the stronger X-ray bright points.

Circular RNA Expression: Its Potential Regulation and Function.

PubMed

Salzman, Julia

2016-05-01

In 2012, a new feature of eukaryotic gene expression emerged: ubiquitous expression of circular RNA (circRNA) from genes traditionally thought to express messenger or linear noncoding (nc)RNA only. CircRNAs are covalently closed, circular RNA molecules that typically comprise exonic sequences and are spliced at canonical splice sites. This feature of gene expression was first recognized in humans and mouse, but it quickly emerged that it was common across essentially all eukaryotes studied by molecular biologists. CircRNA abundance, and even which alternatively spliced circRNA isoforms are expressed, varies by cell type and can exceed the abundance of the traditional linear mRNA or ncRNA transcript. CircRNAs are enriched in the brain and increase in abundance during fetal development. Together, these features raise fundamental questions regarding the regulation of circRNA in cis and in trans, and its function. Copyright © 2016. Published by Elsevier Ltd.

A New Dark Vortex

NASA Astrophysics Data System (ADS)

Wong, Michael

2015-10-01

A bright, unusually long-lived outburst of cloud activity on Neptune was observed in 2015. This led to speculation about whether the clouds were convective in nature, or bright companions to an unseen dark vortex (similar to the Great Dark Spot studied in detail by Voyager 2). HST OPAL images at blue wavelengths finally answered this question by discovering a new dark vortex at 45 deg S. We call this feature SDS-2015, for southern dark spot discovered in 2015.Dark vortices on Neptune are rare; SDS-2015 is only the fifth ever seen. All five were diverse in terms of size and shape, the distribution of bright companion clouds, and horizontal motions (oscillations and drifts). The drift of these vortices is highly sensitive to horizontal and vertical wind shear, making them valuable probes into the structure of Neptune's atmospheric jets. We have traced oscillations in the longitudinal positions of bright companion clouds of SDS-2015, but a second epoch of HST imaging is needed to measure latitudinal motion of the dark vortex itself.Only HST can image dark vortices on Neptune. Ground-based facilities lack the resolution to detect these low-contrast features at blue optical wavelengths, while infrared observations don't detect the dark spots themselves, only their bright companion features. We propose observations of SDS-2015, in order to measure its size, drift rate, and aerosol structure, and to trace its temporal evolution. The observations will improve our understanding of the life cycle of neptunian vortices, of their influence on the surrounding atmosphere, and of the structure of planetary jets.

Detecting primordial gravitational waves with circular polarization of the redshifted 21 cm line. I. Formalism

NASA Astrophysics Data System (ADS)

Hirata, Christopher M.; Mishra, Abhilash; Venumadhav, Tejaswi

2018-05-01

We propose a new method to measure the tensor-to-scalar ratio r using the circular polarization of the 21 cm radiation from the pre-reionization epoch. Our method relies on the splitting of the F =1 hyperfine level of neutral hydrogen due to the quadrupole moment of the cosmic microwave background (CMB). We show that unlike the Zeeman effect, where MF=±1 have opposite energy shifts, the CMB quadrupole shifts MF=±1 together relative to MF=0 . This splitting leads to a small circular polarization of the emitted 21 cm radiation. In this paper (Paper I in a series on this effect), we present calculations on the microphysics behind this effect, accounting for all processes that affect the hyperfine transition. We conclude with an analytic formula for the circular polarization from the Dark Ages as a function of pre-reionization parameters and the value of the remote quadrupole of the CMB. We also calculate the splitting of the F =1 hyperfine level due to other anisotropic radiation sources and show that they are not dominant. In a companion paper (Paper II) we make forecasts for measuring the tensor-to-scalar ratio r using future radio arrays.

Optical activity in chiral stacks of 2D semiconductors

NASA Astrophysics Data System (ADS)

Poshakinskiy, Alexander V.; Kazanov, Dmitrii R.; Shubina, Tatiana V.; Tarasenko, Sergey A.

2018-03-01

We show that the stacks of two-dimensional semiconductor crystals with the chiral packing exhibit optical activity and circular dichroism. We develop a microscopic theory of these phenomena in the spectral range of exciton transitions that takes into account the spin-dependent hopping of excitons between the layers in the stack and the interlayer coupling of excitons via electromagnetic field. For the stacks of realistic two-dimensional semiconductors such as transition metal dichalcogenides, we calculate the rotation and ellipticity angles of radiation transmitted through such structures. The angles are resonantly enhanced at the frequencies of both bright and dark exciton modes in the stack. We also study the photoluminescence of chiral stacks and show that it is circularly polarized.

Planetarium Show on Dark Matter

DOE PAGES

Barnett, R. Michael

2016-05-31

We describe a new planetarium show about Dark Matter entitled “Phantom of the Universe”. When completed in late 2014, it will feature the exciting story of dark matter, from the Big Bang to its anticipated discovery at the Large Hadron Collider.

Dark matter phenomenology of high-speed galaxy cluster collisions

DOE PAGES

Mishchenko, Yuriy; Ji, Chueng-Ryong

2017-07-29

Here, we perform a general computational analysis of possible post-collision mass distributions in high-speed galaxy cluster collisions in the presence of self-interacting dark matter. Using this analysis, we show that astrophysically weakly self-interacting dark matter can impart subtle yet measurable features in the mass distributions of colliding galaxy clusters even without significant disruptions to the dark matter halos of the colliding galaxy clusters themselves. Most profound such evidence is found to reside in the tails of dark matter halos’ distributions, in the space between the colliding galaxy clusters. Such features appear in our simulations as shells of scattered dark mattermore » expanding in alignment with the outgoing original galaxy clusters, contributing significant densities to projected mass distributions at large distances from collision centers and large scattering angles of up to 90°. Our simulations indicate that as much as 20% of the total collision’s mass may be deposited into such structures without noticeable disruptions to the main galaxy clusters. Such structures at large scattering angles are forbidden in purely gravitational high-speed galaxy cluster collisions.Convincing identification of such structures in real colliding galaxy clusters would be a clear indication of the self-interacting nature of dark matter. Our findings may offer an explanation for the ring-like dark matter feature recently identified in the long-range reconstructions of the mass distribution of the colliding galaxy cluster CL0024+017.« less

Dark matter phenomenology of high-speed galaxy cluster collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishchenko, Yuriy; Ji, Chueng-Ryong

Here, we perform a general computational analysis of possible post-collision mass distributions in high-speed galaxy cluster collisions in the presence of self-interacting dark matter. Using this analysis, we show that astrophysically weakly self-interacting dark matter can impart subtle yet measurable features in the mass distributions of colliding galaxy clusters even without significant disruptions to the dark matter halos of the colliding galaxy clusters themselves. Most profound such evidence is found to reside in the tails of dark matter halos’ distributions, in the space between the colliding galaxy clusters. Such features appear in our simulations as shells of scattered dark mattermore » expanding in alignment with the outgoing original galaxy clusters, contributing significant densities to projected mass distributions at large distances from collision centers and large scattering angles of up to 90°. Our simulations indicate that as much as 20% of the total collision’s mass may be deposited into such structures without noticeable disruptions to the main galaxy clusters. Such structures at large scattering angles are forbidden in purely gravitational high-speed galaxy cluster collisions.Convincing identification of such structures in real colliding galaxy clusters would be a clear indication of the self-interacting nature of dark matter. Our findings may offer an explanation for the ring-like dark matter feature recently identified in the long-range reconstructions of the mass distribution of the colliding galaxy cluster CL0024+017.« less

Improved visualization of breast cancer features in multifocal carcinoma using phase-contrast and dark-field mammography: an ex vivo study.

PubMed

Grandl, Susanne; Scherer, Kai; Sztrókay-Gaul, Anikó; Birnbacher, Lorenz; Willer, Konstantin; Chabior, Michael; Herzen, Julia; Mayr, Doris; Auweter, Sigrid D; Pfeiffer, Franz; Bamberg, Fabian; Hellerhoff, Karin

2015-12-01

Conventional X-ray attenuation-based contrast is inherently low for the soft-tissue components of the female breast. To overcome this limitation, we investigate the diagnostic merits arising from dark-field mammography by means of certain tumour structures enclosed within freshly dissected mastectomy samples. We performed grating-based absorption, absolute phase and dark-field mammography of three freshly dissected mastectomy samples containing bi- and multifocal carcinoma using a compact, laboratory Talbot-Lau interferometer. Preoperative in vivo imaging (digital mammography, ultrasound, MRI), postoperative histopathological analysis and ex vivo digital mammograms of all samples were acquired for the diagnostic verification of our results. In the diagnosis of multifocal tumour growth, dark-field mammography seems superior to standard breast imaging modalities, providing a better resolution of small, calcified tumour nodules, demarcation of tumour boundaries with desmoplastic stromal response and spiculated soft-tissue strands extending from an invasive ductal breast cancer. On the basis of selected cases, we demonstrate that dark-field mammography is capable of outperforming conventional mammographic imaging of tumour features in both calcified and non-calcified tumours. Presuming dose optimization, our results encourage further studies on larger patient cohorts to identify those patients that will benefit the most from this promising additional imaging modality. • X-ray dark-field mammography provides significantly improved visualization of tumour features • X-ray dark-field mammography is capable of outperforming conventional mammographic imaging • X-ray dark-field mammography provides imaging sensitivity towards highly dispersed calcium grains.

A Circular Polarizer with Beamforming Feature Based on Frequency Selective Surfaces

NASA Astrophysics Data System (ADS)

Yin, Jia Yuan; Wan, Xiang; Ren, Jian; Cui, Tie Jun

2017-01-01

We propose a circular polarizer with beamforming features based on frequency selective surface (FSS), in which a modified anchor-shaped unit cell is used to reach the circular polarizer function. The beamforming characteristic is realized by a particular design of the unit-phase distribution, which is obtained by varying the scale of the unit cell. Instead of using plane waves, a horn antenna is designed to feed the phase-variant FSS. The proposed two-layer FSS is fabricated and measured to verify the design. The measured results show that the proposed structure can convert the linearly polarized waves to circularly polarized waves. Compared with the feeding horn antenna, the transmitted beam of the FSS-added horn is 14.43° broader in one direction, while 3.77° narrower in the orthogonal direction. To our best knowledge, this is the first time to realize circular polarizer with beamforming as the extra function based on FSS, which is promising in satellite and communication systems for potential applications due to its simple design and good performance.

Stabilization of gaze during circular locomotion in darkness. II. Contribution of velocity storage to compensatory eye and head nystagmus in the running monkey

NASA Technical Reports Server (NTRS)

Solomon, D.; Cohen, B.

1992-01-01

1. Yaw eye in head (Eh) and head on body velocities (Hb) were measured in two monkeys that ran around the perimeter of a circular platform in darkness. The platform was stationary or could be counterrotated to reduce body velocity in space (Bs) while increasing gait velocity on the platform (Bp). The animals were also rotated while seated in a primate chair at eccentric locations to provide linear and angular accelerations similar to those experienced while running. 2. Both animals had head and eye nystagmus while running in darkness during which slow phase gaze velocity on the body (Gb) partially compensated for body velocity in space (Bs). The eyes, driven by the vestibuloocular reflex (VOR), supplied high-frequency characteristics, bringing Gb up to compensatory levels at the beginning and end of the slow phases. The head provided substantial gaze compensation during the slow phases, probably through the vestibulocollic reflex (VCR). Synchronous eye and head quick phases moved gaze in the direction of running. Head movements occurred consistently only when animals were running. This indicates that active body and limb motion may be essential for inducing the head-eye gaze synergy. 3. Gaze compensation was good when running in both directions in one animal and in one direction in the other animal. The animals had long VOR time constants in these directions. The VOR time constant was short to one side in one animal, and it had poor gaze compensation in this direction. Postlocomotory nystagmus was weaker after running in directions with a long VOR time constant than when the animals were passively rotated in darkness. We infer that velocity storage in the vestibular system had been activated to produce continuous Eh and Hb during running and to counteract postrotatory afterresponses. 4. Continuous compensatory gaze nystagmus was not produced by passive eccentric rotation with the head stabilized or free. This indicates that an aspect of active locomotion, most likely somatosensory feedback, was responsible for activating velocity storage. 5. Nystagmus was compared when an animal ran in darkness and in light. the beat frequency of eye and head nystagmus was lower, and the quick phases were larger in darkness. The duration of head and eye quick phases covaried. Eye quick phases were larger when animals ran in darkness than when they were passively rotated. The maximum velocity and duration of eye quick phases were the same in both conditions. 6. The platform was counterrotated under one monkey in darkness while it ran in the direction of its long vestibular time constant.(ABSTRACT TRUNCATED AT 400 WORDS).

Circular RNA biogenesis can proceed through an exon-containing lariat precursor.

PubMed

Barrett, Steven P; Wang, Peter L; Salzman, Julia

2015-06-09

Pervasive expression of circular RNA is a recently discovered feature of eukaryotic gene expression programs, yet its function remains largely unknown. The presumed biogenesis of these RNAs involves a non-canonical 'backsplicing' event. Recent studies in mammalian cell culture posit that backsplicing is facilitated by inverted repeats flanking the circularized exon(s). Although such sequence elements are common in mammals, they are rare in lower eukaryotes, making current models insufficient to describe circularization. Through systematic splice site mutagenesis and the identification of splicing intermediates, we show that circular RNA in Schizosaccharomyces pombe is generated through an exon-containing lariat precursor. Furthermore, we have performed high-throughput and comprehensive mutagenesis of a circle-forming exon, which enabled us to discover a systematic effect of exon length on RNA circularization. Our results uncover a mechanism for circular RNA biogenesis that may account for circularization in genes that lack noticeable flanking intronic secondary structure.

New color-shifting security devices

NASA Astrophysics Data System (ADS)

Moia, Franco

2004-06-01

The unbroken global increase of forgery and counterfeiting of valuable documents and products steadily requires improved types of optical security devices. Hence, the "security world" is actively seeking for new features which meet high security standards, look attractively and allow easy recognition. One special smart security device created by ROLIC's technology represents a cholesteric device combined with a phase image. On tilting, such devices reveal strong color shifts which are clearly visible to the naked eye. The additional latent image is invisible under normal lighting conditions but can be revealed to human eyes by means of a simple, commercially available linear sheet polarizer. Based on our earlier work, first published in 1981, we now have developed phase change guest-host devices combined with dye-doped cholesteric material for application in new security features. ROLIC has developed sophisticated material systems of cross-linkable cholesteric liquid crystals and suitable cross-linkable dyes which allow to create outstanding cholesteric color-shifting effects not only on light absorbing dark backgrounds but also on bright or even white backgrounds preserving the circularly polarizing state. The new security devices combine unambiguously 1st and 2nd level inspection features and show brilliant colors on black as well as on white substrates. On tilting, the security devices exhibit remarkable color shifts while the integrated hidden images can be revealed by use of a sheet polarizer. Furthermore, due to its very thin material layers, even demanding applications, such as on banknotes can be considered.

Single-Layer Wire Routing.

DTIC Science & Technology

1987-08-01

techniques for routing and testing the rout- ability of designs. The design model is ill- suited for the developement of routing algorithms, but the...circular ordering of ca- bles at a feature endpoint. The arrows de - pict the circular ordering of cables at feature ’ 3 cables endpoints p and q. There can...Figure le -1, whose only proper realizations have size fQ(n 2 ). From a practical standpoint, however, the sketch algorithms do not seem as good. Most

Large quasi-circular features beneath frost on Triton

NASA Technical Reports Server (NTRS)

Helfenstein, Paul; Veverka, Joseph; Mccarthy, Derek; Lee, Pascal; Hillier, John

1992-01-01

Specially processed Voyager 2 images of Neptune's largest moon, Triton, reveal three large quasi-circular features ranging in diameter from 280 to 935 km within Triton's equatorial region. The largest of these features contains a central irregularly shaped area of comparatively low albedo about 380 km in diameter, surrounded by crudely concentric annuli of higher albedo materials. None of the features exhibit significant topographic expression, and all appear to be primarily albedo markings. The features are located within a broad equatorial band of anomalously transparent frost that renders them nearly invisible at the large phase angles (alpha greater than 90 deg) at which Voyager obtained its highest resolution coverage of Triton. The features can be discerned at smaller phase angles (alpha = 66 deg) at which the frost only partially masks underlying albedo contrasts. The origin of the features is uncertain but may have involved regional cryovolcanic activity.

Evidence of 3-D Reconnection at Null Point from the Observations of Circular Flares and Homologous Jets

NASA Astrophysics Data System (ADS)

Wang, Haimin; Liu, C.

2012-05-01

In recent studies by Pariat, Antiochos and DeVore (2009, 2010), fan-separatrix topology and magnetic reconnection at the null-point were simulated and found to produce homologous jets. This motivates us to search for axisymmetric magnetic structure and associated flaring/jetting activity. Using high-resolution ( 0.15" per pixel) and high-cadence ( 15 s) H-alpha center/offband observations obtained from the recently digitized films of Big Bear Solar Observatory, we were able to identify five large circular flares with associated surges. All the events exhibit a central parasite magnetic field surrounded by opposite polarity, forming a circular polarity inversion line (PIL). Consequently, a compact flare kernel at the center is surrounded by a circular ribbon, and together with the upward ejecting dark surge, these seem to depict a dome-like magnetic structure. Very interestingly, (1) the circular ribbon brightens sequentially rather than simultaneously, (2) the central compact flare kernel shows obvious motion, and (3) a remote elongated, co-temporal flare ribbon at a region with the same polarity as the central parasite site is seen in the series of four homologous events on 1991 March 17 and 18. The remote ribbon is 120" away from the jet location. Moreover, magnetic reconnection across the circular PIL is evident from the magnetic flux cancellation. These rarely observed homologous surges with circular as well as central and remote flare ribbons provide valuable evidence concerning the dynamics of magnetic reconnection in a null-point topology. This study is dedicated to Professor Hal Zirin, the founder of Big Bear Solar Observatory, who passed away on January 3, 2012.

Exploring the Surface of Titan with Cassini-Huygens

NASA Astrophysics Data System (ADS)

Turtle, E. P.; Barnes, J.; Buratti, B. J.; Collins, G.; Fussner, S.; Lopes, R.; Lorenz, R. D.; Lunine, J. I.; McCord, T. B.; McEwen, A. S.; Nelson, R.; Perry, J.; Porco, C. C.; Soderblom, L.; Sotin, C.; Wall, S. D.

2005-12-01

Over the past year, the Cassini-Huygens mission has returned a wealth of data about the surface of Saturn's satellite Titan. Cassini's Imaging Science Subsystem (ISS), RADAR, and Visual and Infrared Mapping Spectrometer (VIMS), and Huygens' Descent Imaging Spectral Radiometer (DISR) have revealed an intriguing surface that is at once familiar and alien. Although water-ice and liquid hydrocarbons play the roles that rock and water play on Earth, the surface appears to have been worked by a wide variety of processes resulting in a seemingly Earth-like balance of fluvial, aeolian, and volcanic features, with relatively few impact craters. There seem to be at least two classes of surface material: dark areas (at visible-IR wavelengths) that are spectrally consistent with contaminated water ice, and brighter areas of unknown composition which show greater variations. The expected bodies of liquids have yet to be definitively identified; however, circumstantial evidence for liquids having acted upon the surface in Titan's past is abundant, primarily in the form of channels, and possible ponds or lakes, which have been observed by multiple instruments. Other features suggest that wind redistributes some surface materials, most likely the detritus of the complex atmospheric chemistry, creating diffuse IR-bright deposits and long, narrow, radar-dark (2.2-cm) stripes, all of which trend generally east-west. Only two impact structures have been identified to date, although several other suspiciously circular features have been documented. A variety of the morphologies observed bear strong resemblances to volcanic structures. A number of other features remain mysterious and further co-analysis of these data sets, as well as the anticipated acquisition of more data, will be needed to fully understand the nature of Titan's surface, the albedo variations observed at different wavelengths, and the processes that have acted upon it (and may continue to). In addition to the Huygens descent, the Cassini orbiter has observed Titan on six close passes to date, and two more are planned for Fall 2005 which will increase both the spatial coverage, at various wavelengths, and the time base over which observations have been made as northern-hemisphere spring approaches. We will present observations of Titan's surface acquired by the complementary suite of instruments on board Cassini-Huygens, the combination of which is proving essential to interpreting Titan's geology.

The Mass Distribution in Disk Galaxies

NASA Astrophysics Data System (ADS)

Courteau, Stéphane; Dutton, Aaron A.

We present the relative fraction of baryons and dark matter at various radii in galaxies. For spiral galaxies, this fraction measured in a galaxy's inner parts is typically baryon-dominated (maximal) and dark-matter dominated (sub-maximal) in the outskirts. The transition from maximal to sub-maximal baryons occurs within the inner parts of low-mass disk galaxies (with V tot <= 200 km s-1) and in the outer disk for more massive systems. The mean mass fractions for late- and early-type galaxies vary significantly at the same fiducial radius and circular velocity, suggesting a range of galaxy formation mechanisms. A more detailed discussion, and resolution of the so-called ``maximal disk problem'', is presented in Courteau & Dutton, ApJL, 801, 20.

Life History and Environmental Requirements of Loggerhead Turtles

DTIC Science & Technology

1988-08-01

NOMENCLATURE/TAXONOMY/RANGE Scientific name ........ .................... Caretta caretta Preferred common name ........ ................. Loggerhead...Green 51-105 113-140 Broad, oval Olive , dark- White- Small round 15(90)’ (100)a brown mottled yellowish Loggerhead 79-125 77-140 Heart-shaped Reddish...Cream- Very large 25 (110)8 (105)8 brown yellow triangular Kemp’s ridey 59-73 36-45 Circular Olive -green Yellow Medium 13 (70)a (42)’ pointed

Mars Global Surveyor Approach Image

NASA Technical Reports Server (NTRS)

1997-01-01

This image is the first view of Mars taken by the Mars Global Surveyor Orbiter Camera (MOC). It was acquired the afternoon of July 2, 1997 when the MGS spacecraft was 17.2 million kilometers (10.7 million miles) and 72 days from encounter. At this distance, the MOC's resolution is about 64 km per picture element, and the 6800 km (4200 mile) diameter planet is 105 pixels across. The observation was designed to show the Mars Pathfinder landing site at 19.4 N, 33.1 W approximately 48 hours prior to landing. The image shows the north polar cap of Mars at the top of the image, the dark feature Acidalia Planitia in the center with the brighter Chryse plain immediately beneath it, and the highland areas along the Martian equator including the canyons of the Valles Marineris (which are bright in this image owing to atmospheric dust). The dark features Terra Meridiani and Terra Sabaea can be seen at the 4 o`clock position, and the south polar hood (atmospheric fog and hazes) can be seen at the bottom of the image. Launched on November 7, 1996, Mars Global Surveyor will enter Mars orbit on Thursday, September 11 shortly after 6:00 PM PDT. After Mars Orbit Insertion, the spacecraft will use atmospheric drag to reduce the size of its orbit, achieving a circular orbit only 400 km (248 mi) above the surface in early March 1998, when mapping operations will begin.

The Mars Global Surveyor is operated by the Mars Surveyor Operations Project managed for NASA by the Jet Propulsion Laboratory, Pasadena CA. The Mars Orbiter Camera is a duplicate of one of the six instruments originally developed for the Mars Observer mission. It was built and is operated under contract to JPL by an industry/university team led by Malin Space Science Systems, San Diego, CA.

The crystal structure of red fluorescent protein TagRFP-T reveals the mechanism of its superior photostability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Rui; Liang, Qing-Nan; Du, Shu-Qi

2016-08-19

The red fluorescent protein variant TagRFP-T has greatly improved photostability over its parent molecule, TagRFP, but the underlying mechanism leading to this improvement is to date unknown. The 1.95 Å resolution crystallographic structure of TagRFP-T showed that its chromophore exists as a mixture of cis and trans coplanar isomers in roughly equal proportions. Interestingly, both isomers are able to fluoresce, a property that has never been observed in any other fluorescent protein. We propose a “circular restoration model” for TagRFP-T to explain its superior photostability: There are four co-existing chromophore states (cis/trans protonated/ionized state) that can be driven by light tomore » transform from one state into another. This model also explains how TagRPF-T essentially eliminates the temporary dark state (reversible photobleaching). - Highlights: • The 1.95 Å resolution crystal structure of TagRFP-T was determined. • The chromophore of TagRFP-T contains a mixture of cis and trans coplanar isomers. • A “circular restoration model” was proposed to explain the superior photostability. • The chromophore can reversibly convert between cis/trans protonated/ionized states. • The light-driven conversion reduce the dark state (reversible photobleaching).« less

Nonintrusive measurement of the liquid refractive index by using properties of the cuvette wall.

PubMed

Xu, Ming; Ren, Junpeng; Miao, Runcai; Zhang, Zongquan

2016-10-01

We present a method of nonintrusive measurement of the refractive index of a liquid in a glass cuvette, which uses some optical properties of the cuvette wall and the principle of total internal reflection. By coating a transmission-scattering paint layer on the outer surface of the cuvette, we transform an incident laser beam into a transmitted scattered light. When the transmitted scattered light reaches the interface between the container wall and the liquid inside, the light beams satisfying the condition of total internal reflection are reflected to the coating layer, automatically forming a circular dark pattern that is related to the refractive index of the liquid. Based on an analytic relation between the diameter of the circular dark pattern and the refractive index of the liquid, we devised a method of in situ nonintrusive refractive index measurement. We tested the effect of several parameters on the measuring accuracy and found that the optimal thickness of the transmission-scattering layer is in the range of 50-70 μm, and the aperture of the diaphragm should be in the range of 0.7-1.0 mm. We measured the refractive indices of ethanol, Coca Cola, and red wine, and achieved an accuracy of ±3×10^-4  RIU (refractive index unit).

Chiral gravitational waves and baryon superfluid dark matter

NASA Astrophysics Data System (ADS)

Alexander, Stephon; McDonough, Evan; Spergel, David N.

2018-05-01

We develop a unified model of darkgenesis and baryogenesis involving strongly interacting dark quarks, utilizing the gravitational anomaly of chiral gauge theories. In these models, both the visible and dark baryon asymmetries are generated by the gravitational anomaly induced by the presence of chiral primordial gravitational waves. We provide a concrete model of an SU(2) gauge theory with two massless quarks. In this model, the dark quarks condense and form a dark baryon charge superfluid (DBS), in which the Higgs-mode acts as cold dark matter. We elucidate the essential features of this dark matter scenario and discuss its phenomenological prospects.

Dark energy and fate of the Universe

NASA Astrophysics Data System (ADS)

Li, XiaoDong; Wang, Shuang; Huang, QingGuo; Zhang, Xin; Li, Miao

2012-07-01

We explore the ultimate fate of the Universe by using a divergence-free parametrization for dark energy w( z)= w 0+ w a [ln(2 + z) / (1 + z) - ln 2]. Unlike the Chevallier-Polarski-Linder parametrization, this parametrization has well behaved, bounded behavior for both high redshifts and negative redshifts, and thus can genuinely cover many theoretical dark energy models. After constraining the parameter space of this parametrization by using the current cosmological observations, we find that, at the 95.4% confidence level, our Universe can still exist at least 16.7 Gyr before it ends in a big rip. Moreover, for the phantom energy dominated Universe, we find that a gravitationally bound system will be destroyed at a time {{t ˜eq Psqrt {2| {1 + 3w( - 1)} |} } {/ {{t ˜eq Psqrt {2| {1 + 3w( - 1)} |} } {[ {6π | {1 + w( - 1)} |} ]}}} . } {[ {6π | {1 + w( - 1)} |} ]}}, where P is the period of a circular orbit around this system, before the big rip.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ko, Sung Moon; Park, Jeong-Hyuck; Suh, Minwoo, E-mail: sinsmk2003@sogang.ac.kr, E-mail: park@sogang.ac.kr, E-mail: minsuh@usc.edu

Double Field Theory suggests to view the whole massless sector of closed strings as the gravitational unity. The fundamental symmetries therein, including the O( D , D ) covariance, can determine unambiguously how the Standard Model as well as a relativistic point particle should couple to the closed string massless sector. The theory also refines the notion of singularity. We consider the most general, spherically symmetric, asymptotically flat, static vacuum solution to D =4 Double Field Theory, which contains three free parameters and consequently generalizes the Schwarzschild geometry. Analyzing the circular geodesic of a point particle in string frame, wemore » obtain the orbital velocity as a function of R /( M {sub ∞} G ) which is the dimensionless radial variable normalized by mass. The rotation curve generically features a maximum and thus non-Keplerian over a finite range, while becoming asymptotically Keplerian at infinity, R /( M {sub ∞} G )→ ∞. The adoption of the string frame rather than Einstein frame is the consequence of the fundamental symmetry principle. Our result opens up a new scheme to solve the dark matter/energy problems by modifying General Relativity at 'short' range of R /( M {sub ∞} G ).« less

Moon taken by Galileo after completing its first Earth Gravity Assist

NASA Technical Reports Server (NTRS)

1990-01-01

Galileo spacecraft images of the Moon were taken at (right photo) 6:47 pm Pacific Standard Time (PST), 12-08-90, and at (left photo) 9:35 am PST, 12-09-90, at a range of more than 350,000 miles. The picture on the right shows the dark Oceanus Procellarum in the upper center, with Mare Imbrium above it and the smaller circular Mare Humorum below. The Orientale Basin, with a small mare in its center, is on the lower left near the limb or edge. Between stretches the cratered highland terrain, with scattered bright young craters on highlands and maria alike. The picture at left shows the globe of the Moon rotated, putting Mare Imbrium on the eastern limb and moving the Orientale Basin almost to the center. The extent of the cratered highlands on the far side is very apparent. At lower left, near the limb, is the South-Pole-Aitken basin, similar to Orientale but very much older and some 1,200 miles in diameter. This feature was previously known as a large depression in the southern far side

Mariner 9 views Ascraeus Lacus above the Martian Dust Storm

NASA Image and Video Library

2000-11-22

Oblique view of the crater complex near Ascraeus Lacus in the Tharsis region of Mars was taken by Mariner 9. It is the northernmost of the prominent dark spots observed by Mariner during its approach to the planet. The spot consists of several intersecting shallow crater-like depressions. The main crater is approximately 21 kilometers (13 miles) across, the whole complex about 40 kilometers (25 miles) across. The crater probably is in a relatively high area of the Martian surface, which accounts for its being visible above the dust storm. The faint circular features outside the crater are probably atmospheric. Mariner 9 was the first spacecraft to orbit another planet. The spacecraft was designed to continue the atmospheric studies begun by Mariners 6 and 7, and to map over 70% of the Martian surface from the lowest altitude (1500 kilometers [900 miles]) and at the highest resolutions (1 kilometer per pixel to 100 meters per pixel) of any previous Mars mission. Mariner 9 was launched on May 30, 1971 and arrived on November 14, 1971. http://photojournal.jpl.nasa.gov/catalog/PIA03100

Circular permutation of a WW domain: Folding still occurs after excising the turn of the folding-nucleating hairpin

PubMed Central

Kier, Brandon L.; Anderson, Jordan M.; Andersen, Niels H.

2014-01-01

A hyperstable Pin1 WW domain has been circularly permuted via excision of the fold-nucleating turn; it still folds to form the native three-strand sheet and hydrophobic core features. Multiprobe folding dynamics studies of the normal and circularly permuted sequences, as well as their constituent hairpin fragments and comparable-length β-strand-loop-β-strand models, indicate 2-state folding for all topologies. N-terminal hairpin formation is the fold nucleating event for the wild-type sequence; the slower folding circular permutant has a more distributed folding transition state. PMID:24350581

Possibility of testing the light dark matter hypothesis with the alpha magnetic spectrometer.

PubMed

Hooper, Dan; Xue, Wei

2013-01-25

The spectrum and morphology of gamma rays from the Galactic center and the spectrum of synchrotron emission observed from the Milky Way's radio filaments have each been interpreted as possible signals of ∼ 7-10 GeV dark matter particles annihilating in the inner Galaxy. In dark matter models capable of producing these signals, the annihilations should also generate significant fluxes of ∼ 7-10 GeV positrons which can lead to a distinctive bumplike feature in a local cosmic ray positron spectrum. In this Letter, we show that while such a feature would be difficult to detect with PAMELA, it would likely be identifiable by the currently operating Alpha Magnetic Spectrometer experiment. As no known astrophysical (i.e., nondark matter) sources or mechanisms are likely to produce such a sharp feature, the observation of a positron bump at around 7-10 GeV would significantly strengthen the case for a dark matter interpretation of the reported gamma-ray and radio anomalies.

Gamma-ray Signal from Dark Matter Annihilation Mediated by Mixing Slepton

NASA Astrophysics Data System (ADS)

Teng, Fei

2016-03-01

In order to reconcile the tension between the collider SUSY particle search and the dark matter relic density constraint, we free ourselves from the simplest CMSSM model and find a large parameter space in which a sub-TeV bino dark matter may comply with all the current experimental constraints. In this so-called incredible bulk region, dark matter mainly annihilates through the t channel exchange of a mixing slepton into a leptonic final state. We have explored this proposal and studied the resultant spectrum feature. We are going to show that the line signal produced by the γγ and γZ final state will give some indications to the mixing angle and CP-violation phase of the slepton sector. On the other hand, internal bremsstrahlung (IB) feature will be easier to get observed by future experiments, with sensitivity around 10-29cm3 /s . Unlike some other models, our IB signal is dominated by the collinear limit of the final state radiation amplitude and shows a bump-like feature.

THE CENTRAL SLOPE OF DARK MATTER CORES IN DWARF GALAXIES: SIMULATIONS VERSUS THINGS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oh, Se-Heon; De Blok, W. J. G.; Brook, Chris

2011-07-15

We make a direct comparison of the derived dark matter (DM) distributions between hydrodynamical simulations of dwarf galaxies assuming a {Lambda}CDM cosmology and the observed dwarf galaxies sample from the THINGS survey in terms of (1) the rotation curve shape and (2) the logarithmic inner density slope {alpha} of mass density profiles. The simulations, which include the effect of baryonic feedback processes, such as gas cooling, star formation, cosmic UV background heating, and most importantly, physically motivated gas outflows driven by supernovae, form bulgeless galaxies with DM cores. We show that the stellar and baryonic mass is similar to thatmore » inferred from photometric and kinematic methods for galaxies of similar circular velocity. Analyzing the simulations in exactly the same way as the observational sample allows us to address directly the so-called cusp/core problem in the {Lambda}CDM model. We show that the rotation curves of the simulated dwarf galaxies rise less steeply than cold dark matter rotation curves and are consistent with those of the THINGS dwarf galaxies. The mean value of the logarithmic inner density slopes {alpha} of the simulated galaxies' DM density profiles is {approx}-0.4 {+-} 0.1, which shows good agreement with {alpha} = -0.29 {+-} 0.07 of the THINGS dwarf galaxies. The effect of non-circular motions is not significant enough to affect the results. This confirms that the baryonic feedback processes included in the simulations are efficiently able to make the initial cusps with {alpha} {approx}-1.0 to -1.5 predicted by DM-only simulations shallower and induce DM halos with a central mass distribution similar to that observed in nearby dwarf galaxies.« less

Tidal stripping and the structure of dwarf galaxies in the Local Group

NASA Astrophysics Data System (ADS)

Fattahi, Azadeh; Navarro, Julio F.; Frenk, Carlos S.; Oman, Kyle A.; Sawala, Till; Schaller, Matthieu

2018-05-01

The shallow faint-end slope of the galaxy mass function is usually reproduced in Λ cold dark matter (ΛCDM) galaxy formation models by assuming that the fraction of baryons that turn into stars drops steeply with decreasing halo mass and essentially vanishes in haloes with maximum circular velocities Vmax < 20-30 km s-1. Dark-matter-dominated dwarfs should therefore have characteristic velocities of about that value, unless they are small enough to probe only the rising part of the halo circular velocity curve (i.e. half-mass radii, r1/2 ≪ 1 kpc). Many dwarfs have properties in disagreement with this prediction: they are large enough to probe their halo Vmax but their characteristic velocities are well below 20 km s-1. These `cold faint giants' (an extreme example is the recently discovered Crater 2 Milky Way satellite) can only be reconciled with our ΛCDM models if they are the remnants of once massive objects heavily affected by tidal stripping. We examine this possibility using the APOSTLE cosmological hydrodynamical simulations of the Local Group. Assuming that low-velocity-dispersion satellites have been affected by stripping, we infer their progenitor masses, radii, and velocity dispersions, and find them in remarkable agreement with those of isolated dwarfs. Tidal stripping also explains the large scatter in the mass discrepancy-acceleration relation in the dwarf galaxy regime: tides remove preferentially dark matter from satellite galaxies, lowering their accelerations below the amin ˜ 10-11 m s-2 minimum expected for isolated dwarfs. In many cases, the resulting velocity dispersions are inconsistent with the predictions from Modified Newtonian Dynamics, a result that poses a possibly insurmountable challenge to that scenario.

On the Evolution of High-redshift Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Mao, Jirong; Kim, Minsun

2016-09-01

We build a simple physical model to study the high-redshift active galactic nucleus (AGN) evolution within the co-evolution framework of central black holes (BHs) and their host galaxies. The correlation between the circular velocity of a dark halo V c and the velocity dispersion of a galaxy σ is used to link the dark matter halo mass and BH mass. The dark matter halo mass function is converted to the BH mass function for any given redshift. The high-redshift optical AGN luminosity functions (LFs) are constructed. At z˜ 4, the flattening feature is not shown at the faint end of the optical AGN LF. This is consistent with observational results. If the optical AGN LF at z˜ 6 can be reproduced in the case in which central BHs have the Eddington-limited accretion, it is possible for the AGN lifetime to have a small value of 2× {10}5 {{years}}. The X-ray AGN LFs and X-ray AGN number counts are also calculated at 2.0\\lt z\\lt 5.0 and z\\gt 3, respectively, using the same parameters adopted in the calculation for the optical AGN LF at z˜ 4. It is estimated that about 30 AGNs per {{{\\deg }}}2 at z\\gt 6 can be detected with a flux limit of 3× {10}-17 {erg} {{cm}}-2 {{{s}}}-1 in the 0.5-2 keV band. Additionally, the cosmic reionization is also investigated. The ultraviolet photons emitted from the high-redshift AGNs mainly contribute to the cosmic reionization, and the central BHs of the high-redshift AGNs have a mass range of {10}6{--}{10}8{M}⊙ . We also discuss some uncertainties in both the AGN LFs and AGN number counts originating from the {M}{{BH}}{--}σ relation, Eddington ratio, AGN lifetime, and X-ray attenuation in our model.

Circular RNA biogenesis can proceed through an exon-containing lariat precursor

PubMed Central

Barrett, Steven P; Wang, Peter L; Salzman, Julia

2015-01-01

Pervasive expression of circular RNA is a recently discovered feature of eukaryotic gene expression programs, yet its function remains largely unknown. The presumed biogenesis of these RNAs involves a non-canonical ‘backsplicing’ event. Recent studies in mammalian cell culture posit that backsplicing is facilitated by inverted repeats flanking the circularized exon(s). Although such sequence elements are common in mammals, they are rare in lower eukaryotes, making current models insufficient to describe circularization. Through systematic splice site mutagenesis and the identification of splicing intermediates, we show that circular RNA in Schizosaccharomyces pombe is generated through an exon-containing lariat precursor. Furthermore, we have performed high-throughput and comprehensive mutagenesis of a circle-forming exon, which enabled us to discover a systematic effect of exon length on RNA circularization. Our results uncover a mechanism for circular RNA biogenesis that may account for circularization in genes that lack noticeable flanking intronic secondary structure. DOI: http://dx.doi.org/10.7554/eLife.07540.001 PMID:26057830

Genome Features of “Dark-Fly”, a Drosophila Line Reared Long-Term in a Dark Environment

PubMed Central

Zhou, Jun; Sugiyama, Yuzo; Nishimura, Osamu; Aizu, Tomoyuki; Toyoda, Atsushi; Fujiyama, Asao; Agata, Kiyokazu

2012-01-01

Organisms are remarkably adapted to diverse environments by specialized metabolisms, morphology, or behaviors. To address the molecular mechanisms underlying environmental adaptation, we have utilized a Drosophila melanogaster line, termed “Dark-fly”, which has been maintained in constant dark conditions for 57 years (1400 generations). We found that Dark-fly exhibited higher fecundity in dark than in light conditions, indicating that Dark-fly possesses some traits advantageous in darkness. Using next-generation sequencing technology, we determined the whole genome sequence of Dark-fly and identified approximately 220,000 single nucleotide polymorphisms (SNPs) and 4,700 insertions or deletions (InDels) in the Dark-fly genome compared to the genome of the Oregon-R-S strain, a control strain. 1.8% of SNPs were classified as non-synonymous SNPs (nsSNPs: i.e., they alter the amino acid sequence of gene products). Among them, we detected 28 nonsense mutations (i.e., they produce a stop codon in the protein sequence) in the Dark-fly genome. These included genes encoding an olfactory receptor and a light receptor. We also searched runs of homozygosity (ROH) regions as putative regions selected during the population history, and found 21 ROH regions in the Dark-fly genome. We identified 241 genes carrying nsSNPs or InDels in the ROH regions. These include a cluster of alpha-esterase genes that are involved in detoxification processes. Furthermore, analysis of structural variants in the Dark-fly genome showed the deletion of a gene related to fatty acid metabolism. Our results revealed unique features of the Dark-fly genome and provided a list of potential candidate genes involved in environmental adaptation. PMID:22432011

Generation of Bright Phase-matched Circularly-polarized Extreme Ultraviolet High Harmonics

DTIC Science & Technology

2014-12-08

circularly-polarized laser pulses field-ionize a gas in a hollow - core waveguide. We use this new light source for magnetic circular dichroism...polarized with opposite helicity in a gas-filled hollow waveguide (see Supplementary Section 6 for details on the important features of this source...mJ/pulse) driving lasers are focused into a 150-µm-diameter, 2-cm-long gas-filled hollow waveguide using lenses with focal lengths of 50 cm and 75 cm

Kidney-Shaped Impact

NASA Technical Reports Server (NTRS)

2006-01-01

23 February 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an unusally-shaped (not circular) impact crater in the Elysium region of Mars. A dark-toned lava flow surface is seen in the southern (lower) portion of the image.

Location near: 5.9oN, 220.0oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Winter

An interdisciplinary analysis of multispectral satellite data for selected cover types in the Colorado mountains, using automatic data processing techniques

NASA Technical Reports Server (NTRS)

Hoffer, R. M. (Principal Investigator)

1974-01-01

The author has identified the following significant results. In the San Juan Mountains there exists a group of structural and topographic features which suggest a common origin. The relative positions of the San Juan Depression with the Silverton and Lake City Calderas indicate they are possibly on the edge of a large circular feature. Comparison with the 1:250,000 scale Durango Geologic Map reveals a series of radial and arcuate faults concentric with the major circular feature. Such a fracture pattern implies that the circular feature may represent the extent of a major domal uplift in the area. The uplift was very likely due to the sub-crustal emplacement of the parent magma of the San Juan volcanics and intrusives. The broad doming led to the formation of a zone of tensional ring fractures which acted as conduits of release for the magma and the eventual development of the various calderas. The ring fracturing was probably incomplete with hinging occurring in the southern and southwestern portions of the dome accounting for the lack of development of caldera structures in that portion of the area.

Cinematique et dynamique des galaxies spirales barrees

NASA Astrophysics Data System (ADS)

Hernandez, Olivier

The total mass (luminous and dark) of galaxies is derived from their circular velocities. Spectroscopic Fabry-Perot observations of the ionized gas component of spiral galaxies allow one to derive their kinematics. In the case of purely axisymmetric velocity fields--as in non-active and unbarred spirals galaxies-- the circular velocities can be derived directly. However, the velocity fields of barred galaxies (which constitute two thirds of the spirals) exhibit strong non-circular motions and need a careful analysis to retrieve the circular component. This thesis proposes the necessary steps to recover the axisymmetric component of barred spiral galaxies. The first step was to develop the best instrumentation possible for this work. [Special characters omitted.] , which is the most sensitive photon counting camera ever developed, was coupled to a Fabry-Perot interferometer. The observations of a sample of barred spiral galaxies--the BH a BAR sample--was assembled in order to obtain the most rigourous velocity fields. Then, the Tremaine-Weinberg method, which can determine the bar pattern speed and is usually used with the observations of stellar component, has been tested on the ionised gas and gave satisfactory results. Finally, all the above techniques have been applied to the BH a BAR sample in order to study the key parameters of the galaxies' evolution--bar pattern speeds, multiple stationary waves, resonances etc.--which will allow one to use N-body+SPH simulations to model properly the non-circular motions and determine the true total mass of barred spiral galaxies.

Chiral Templating of Self-Assembling Nanostructures by Circularly Polarized Light

PubMed Central

Yeom, Jihyeon; Yeom, Bongjun; Chan, Henry; Smith, Kyle W.; Dominguez-Medina, Sergio; Bahng, Joong Hwan; Zhao, Gongpu; Chang, Wei-Shun; Chang, Sung Jin; Chuvilin, Andrey; Melnikau, Dzmitry; Rogach, Andrey L.; Zhang, Peijun; Link, Stephan; Král, Petr; Kotov, Nicholas A.

2015-01-01

Chemical reactions affected by spin angular momenta of circularly polarized photons are rare and display low enantiomeric excess. High optical and chemical activity of nanoparticles (NPs) should facilitate the transfer of spin angular momenta of photons to nanoscale materials but such processes are unknown. Here we demonstrate that circularly polarized light (CPL) strongly affects self-assembly of racemic CdTe NPs. Illumination of NP dispersions with right- and left-handed CPL induces the formation of right- and left-handed twisted nanoribbons, respectively. Enantiomeric excess of such reactions exceeds 30% which is ~10 times higher than other CPL-induced reactions. Illumination with linearly polarized light and assembly in the dark led to straight nanoribbons. The mechanism of “templation” of NP assemblies by CPL is associated with selective photoactivation of chiral NPs and clusters followed by their photooxidation. Chiral anisotropy of interactions translates into chirality of the assembled ribbons. The ability of NPs to retain polarization information, or the “imprint” of incident photons opens new pathways for the synthesis of chiral photonic materials and allows for better understanding of the origins of biomolecular homochirality. PMID:25401922

Production of confluent hypergeometric beam by computer-generated hologram

NASA Astrophysics Data System (ADS)

Chen, Jiannong; Wang, Gang; Xu, Qinfeng

2011-02-01

Because of their spiral wave front, phase singularity, zero-intensity center and orbital angular momentum, dark hollow vortex beams have been found many applications in the field of atom optics such as atom cooling, atom transport and atom guiding. In this paper, a method for generating confluent hypergeometric beam by computer-generated hologram displayed on the spatial light modulator is presented. The hologram is formed by interference between a single ring Laguerre-Gaussian beam and a plane wave. The far-field Fraunhofer diffraction of this optical field transmitted from the hologram is the confluent hypergeometric beam. This beam is a circular symmetric beam which has a phase singularity, spiral wave front, zero-intensity center, and intrinsic orbital angular momentum. It is a new dark hollow vortex beam.

[The growth movements of moss protonemata under clinostatic and microgravity conditions

NASA Technical Reports Server (NTRS)

Demkiv, O. T.; Kordium, E. L.; Tairbekov, M. G.; Sack, F.; Kern, F.; Kardash, A. R.

1999-01-01

Populations of dark-grown protonemata of moss Ceratodon purpureus wt-4 (Germany) and wt-U (Ukraine) were rotated on clinostat or flown in space (experiment "Protonema" aboard Bion-11, December 24, 1996-January 7, 1997) to determine the effects of altered gravity on orientation of protonemata growing filaments. Protonemata had been cultivated 8 days in vertical stationary position at dark to be transported to microgravity or placed in clinostat for the period of 14 days. In the ground control, protonemata demonstrated the negatively gravitropic growth (straight upwards in a bundle of compact filaments). The horizontal or circular rotation in clinostat and exposure to microgravity made filaments grow every each way within the substrate plane but with an apparent trend to rightward curling resulting in "spiral galaxies".

South Polar Depression

NASA Technical Reports Server (NTRS)

2005-01-01

14 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a circular depression and a suite of eroding mesas of carbon dioxide. These features occur in the south polar residual cap of Mars. The eroding carbon dioxide creates landforms reminiscent of 'Swiss cheese.' The circular feature might indicate the location of a filled, buried impact crater.

Location near: 86.8oS, 111.0oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

Hyperion's Dark Material: Rotational Variation

NASA Technical Reports Server (NTRS)

Jarvis, K. S.; Vilas, F.; Buratti, B. J.; Hicks, M. D.; Gaffey, M. J.

2002-01-01

We present two new dark material spectra of Hyperion compared with previously published dark material spectra of Hyperion and Iapetus. A 0.67-micron absorption feature is seen in one of the two new spectra. This suggests possible mineralogical differences across the surface of this Saturnian satellite. Additional information is contained in the original extended abstract.

Thermal measurements of dark and bright surface features on Vesta as derived from Dawn/VIR

USGS Publications Warehouse

Tosi, Federico; Capria, Maria Teresa; De Sanctis, M.C.; Combe, J.-Ph.; Zambon, F.; Nathues, A.; Schröder, S.E.; Li, J.-Y.; Palomba, E.; Longobardo, A.; Blewett, D.T.; Denevi, B.W.; Palmer, E.; Capaccioni, F.; Ammannito, E.; Titus, Timothy N.; Mittlefehldt, D.W.; Sunshine, J.M.; Russell, C.T.; Raymond, C.A.; Dawn/VIR Team,

2014-01-01

Remote sensing data acquired during Dawn’s orbital mission at Vesta showed several local concentrations of high-albedo (bright) and low-albedo (dark) material units, in addition to spectrally distinct meteorite impact ejecta. The thermal behavior of such areas seen at local scale (1-10 km) is related to physical properties that can provide information about the origin of those materials. We use Dawn’s Visible and InfraRed (VIR) mapping spectrometer hyperspectral data to retrieve surface temperatures and emissivities, with high accuracy as long as temperatures are greater than 220 K. Some of the dark and bright features were observed multiple times by VIR in the various mission phases at variable spatial resolution, illumination and observation angles, local solar time, and heliocentric distance. This work presents the first temperature maps and spectral emissivities of several kilometer-scale dark and bright material units on Vesta. Results retrieved from the infrared data acquired by VIR show that bright regions generally correspond to regions with lower temperature, while dark regions correspond to areas with higher temperature. During maximum daily insolation and in the range of heliocentric distances explored by Dawn, i.e. 2.23-2.54 AU, the warmest dark unit found on Vesta rises to a temperature of 273 K, while bright units observed under comparable conditions do not exceed 266 K. Similarly, dark units appear to have higher emissivity on average compared to bright units. Dark-material units show a weak anticorrelation between temperature and albedo, whereas the relation is stronger for bright material units observed under the same conditions. Individual features may show either evanescent or distinct margins in the thermal images, as a consequence of the cohesion of the surface material. Finally, for the two categories of dark and bright materials, we were able to highlight the influence of heliocentric distance on surface temperatures, and estimate an average temperature rate change of 1% following a variation of 0.04 AU in the solar distance.

Compact waveguide circular polarizer

DOEpatents

Tantawi, Sami G.

2016-08-16

A multi-port waveguide is provided having a rectangular waveguide that includes a Y-shape structure with first top arm having a first rectangular waveguide port, a second top arm with second rectangular waveguide port, and a base arm with a third rectangular waveguide port for supporting a TE.sub.10 mode and a TE.sub.20 mode, where the end of the third rectangular waveguide port includes rounded edges that are parallel to a z-axis of the waveguide, a circular waveguide having a circular waveguide port for supporting a left hand and a right hand circular polarization TE.sub.11 mode and is coupled to a base arm broad wall, and a matching feature disposed on the base arm broad wall opposite of the circular waveguide for terminating the third rectangular waveguide port, where the first rectangular waveguide port, the second rectangular waveguide port and the circular waveguide port are capable of supporting 4-modes of operation.

HUBBLE FINDS NEW DARK SPOT ON NEPTUNE

NASA Technical Reports Server (NTRS)

2002-01-01

NASA's Hubble Space Telescope has discovered a new great dark spot, located in the northern hemisphere of the planet Neptune. Because the planet's northern hemisphere is now tilted away from Earth, the new feature appears near the limb of the planet. The spot is a near mirror-image to a similar southern hemisphere dark spot that was discovered in 1989 by the Voyager 2 probe. In 1994, Hubble showed that the southern dark spot had disappeared. Like its predecessor, the new spot has high altitude clouds along its edge, caused by gasses that have been pushed to higher altitudes where they cool to form methane ice crystal clouds. The dark spot may be a zone of clear gas that is a window to a cloud deck lower in the atmosphere. Planetary scientists don t know how long lived this new feature might be. Hubble's high resolution will allow astronomers to follow the spot's evolution and other unexpected changes in Neptune's dynamic atmosphere. The image was taken on November 2, 1994 with Hubble's Wide Field Planetary Camera 2, when Neptune was 2.8 billion miles (4.5 billion kilometers) from Earth. Hubble can resolve features as small as 625 miles (1,000 kilometers) across in Neptune's cloud tops. Credit: H. Hammel (Massachusetts Institute of Technology) and NASA

Degeneracy between nonadiabatic dark energy models and Λ CDM : Integrated Sachs-Wolfe effect and the cross correlation of CMB with galaxy clustering data

NASA Astrophysics Data System (ADS)

Velten, Hermano; Fazolo, Raquel Emy; von Marttens, Rodrigo; Gomes, Syrios

2018-05-01

As recently pointed out in [Phys. Rev. D 96, 083502 (2017), 10.1103/PhysRevD.96.083502] the evolution of the linear matter perturbations in nonadiabatic dynamical dark energy models is almost indistinguishable (quasidegenerated) to the standard Λ CDM scenario. In this work we extend this analysis to CMB observables in particular the integrated Sachs-Wolfe effect and its cross-correlation with large scale structure. We find that this feature persists for such CMB related observable reinforcing that new probes and analysis are necessary to reveal the nonadiabatic features in the dark energy sector.

Supersymmetric model for dark matter and baryogenesis motivated by the recent CDMS result.

PubMed

Allahverdi, Rouzbeh; Dutta, Bhaskar; Mohapatra, Rabindra N; Sinha, Kuver

2013-08-02

We discuss a supersymmetric model for cogenesis of dark and baryonic matter where the dark matter (DM) has mass in the 8-10 GeV range as indicated by several direct detection searches, including most recently the CDMS experiment with the desired cross section. The DM candidate is a real scalar field. Two key distinguishing features of the model are the following: (i) in contrast with the conventional weakly interacting massive particle dark matter scenarios where thermal freeze-out is responsible for the observed relic density, our model uses nonthermal production of dark matter after reheating of the Universe caused by moduli decay at temperatures below the QCD phase transition, a feature which alleviates the relic overabundance problem caused by small annihilation cross section of light DM particles and (ii) baryogenesis occurs also at similar low temperatures from the decay of TeV scale mediator particles arising from moduli decay. A possible test of this model is the existence of colored particles with TeV masses accessible at the LHC.

Fractal Simulations of African Design in Pre-College Computing Education

ERIC Educational Resources Information Center

Eglash, Ron; Krishnamoorthy, Mukkai; Sanchez, Jason; Woodbridge, Andrew

2011-01-01

This article describes the use of fractal simulations of African design in a high school computing class. Fractal patterns--repetitions of shape at multiple scales--are a common feature in many aspects of African design. In African architecture we often see circular houses grouped in circular complexes, or rectangular houses in rectangular…

Statistically based splicing detection reveals neural enrichment and tissue-specific induction of circular RNA during human fetal development.

PubMed

Szabo, Linda; Morey, Robert; Palpant, Nathan J; Wang, Peter L; Afari, Nastaran; Jiang, Chuan; Parast, Mana M; Murry, Charles E; Laurent, Louise C; Salzman, Julia

2015-06-16

The pervasive expression of circular RNA is a recently discovered feature of gene expression in highly diverged eukaryotes, but the functions of most circular RNAs are still unknown. Computational methods to discover and quantify circular RNA are essential. Moreover, discovering biological contexts where circular RNAs are regulated will shed light on potential functional roles they may play. We present a new algorithm that increases the sensitivity and specificity of circular RNA detection by discovering and quantifying circular and linear RNA splicing events at both annotated and un-annotated exon boundaries, including intergenic regions of the genome, with high statistical confidence. Unlike approaches that rely on read count and exon homology to determine confidence in prediction of circular RNA expression, our algorithm uses a statistical approach. Using our algorithm, we unveiled striking induction of general and tissue-specific circular RNAs, including in the heart and lung, during human fetal development. We discover regions of the human fetal brain, such as the frontal cortex, with marked enrichment for genes where circular RNA isoforms are dominant. The vast majority of circular RNA production occurs at major spliceosome splice sites; however, we find the first examples of developmentally induced circular RNAs processed by the minor spliceosome, and an enriched propensity of minor spliceosome donors to splice into circular RNA at un-annotated, rather than annotated, exons. Together, these results suggest a potentially significant role for circular RNA in human development.

Characterizing dark matter at the LHC in Drell-Yan events

NASA Astrophysics Data System (ADS)

Capdevilla, Rodolfo M.; Delgado, Antonio; Martin, Adam; Raj, Nirmal

2018-02-01

Spectral features in LHC dileptonic events may signal radiative corrections coming from new degrees of freedom, notably dark matter and mediators. Using simplified models, and under a set of simplifying assumptions, we show how these features can reveal the fundamental properties of the dark sector, such as self-conjugation, spin and mass of dark matter, and the quantum numbers of the mediator. Distributions of both the invariant mass mℓℓ and the Collins-Soper scattering angle cos θCS are studied to pinpoint these properties. We derive constraints on the models from LHC measurements of mℓℓ and cos θCS, which are competitive with direct detection and jets+MET searches. We find that in certain scenarios the cos θCS spectrum provides the strongest bounds, underlining the importance of scattering angle measurements for nonresonant new physics.

Thick, Dark Veins at Garden City, Mars

NASA Image and Video Library

2015-11-11

These images from the Chemistry and Camera (ChemCam) instrument on NASA's Curiosity Mars rover indicate similarly dark material, but with very different chemistries, in mineral veins at "Garden City." Each of the side-by-side circular images covers an area about 2 inches (5 centimeters) in diameter. The images were taken by ChemCam's Remote Micro-Imager. Researchers used ChemCam's laser, telescope and spectrometers to examine the chemistry of material in these veins. While both of these veins are dark, their chemistries are very different, indicating that they were formed by different fluids. One common aspect of the chemistry in the dark material is an iron content higher than nearby bedrock. Thus the dark appearance may be result of similar iron content. The dark maerial in the vein on the left is enriched in calcium and contains calcium fluorine. The dark material in the vein on the right is enriched in magnesium, but not in calcium or calcium fluorine. Thus, the veins were formed by different fluids that deposited minerals in rock fractures. The Remote Micro-Imager took the image on the left on March 27, 2015, during the 938th Martian day, or sol, of Curiosity's work on Mars. The next day, it took the image on the right. A broader view of the prominent mineral veins at Garden City is at PIA19161. ChemCam is one of 10 instruments in Curiosity's science payload. The U.S. Department of Energy's Los Alamos National Laboratory, in Los Alamos, New Mexico, developed ChemCam in partnership with scientists and engineers funded by the French national space agency (CNES), the University of Toulouse and the French national research agency (CNRS). More information about ChemCam is available at http://www.msl-chemcam.com. http://photojournal.jpl.nasa.gov/catalog/PIA19924

Are We Really Missing Small Galaxies?

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-02-01

One long-standing astrophysical puzzle is that of so-called missing dwarf galaxies: the number of small dwarf galaxies that we observe is far fewer than that predicted by theory. New simulations, however, suggest that perhaps theres no mystery after all.Missing DwarfsDark-matter cosmological simulations predict many small galaxy halos for every large halo that forms. [The Via Lactea project]Models of a lambda-cold-dark-matter (CDM) universe predict the distribution of galaxy halo sizes throughout the universe, suggesting there should be many more small galaxies than large ones. In what has become known as the missing dwarf problem, however, we find that while we observe the expected numbers of galaxies at the larger end of the scale, we dont see nearly enough small galaxies to match the predictions.Are these galaxies actually missing? Are our predictions wrong? Or are the galaxies there and were just not spotting them? A recent study led by Alyson Brooks (Rutgers University) uses new simulations to explore whatscausing the difference between theory and observation.The fraction of detectable halos as a function of velocity, according to the authors simulations. Below 35 km/s, the detectability of the galaxies drops precipitously. [Brooks et al. 2017]Simulating Galactic VelocitiesBecause we cant weigh a galaxy directly, one proxy used for galaxy mass is its circular velocity; the more massive a galaxy, the faster gas and stars rotate around its center. The discrepancy between models and observations lies in whats known as the galaxy velocity function, which describes the number density of galaxies for a given circular velocity. While theory and observations agree for galaxies with circular velocities above 100 km/s, theory predicts far more dwarfs below this velocity than we observe.To investigate this problem, Brooks and collaborators ran a series of cosmological simulations based on our understanding of a CDM universe. Instead of exploring the result using only dark matter, however, the team included baryons in their simulations. They then produced mock observations of the resulting galaxy velocities to see what an observed velocity function would look like for their simulated galaxies.No Problem After All?Comparison of theoretical velocity functions to observations. The black dashed line shows the original, dark-matter-only model predictions; the black solid line includes the effects of detectability. Blue lines show the authors new model, including the effects of detectability and inclusion of baryons. The red and teal data points from observations match this corrected model well. [Brooks et al. 2017]Based on their baryon-inclusive simulations, Brooks and collaborators argue that there are two main factors that have contributed to the seeming theory/observation mismatch of the missing dwarf problem:Galaxies with low velocities arent detectable by our current surveys.The authors found that the detectable fraction of their simulated galaxies plunges as soon as galaxy velocity drops below 35 km/s. They conclude that were probably unable to see a large fraction of the smallest galaxies.Were not correctly inferring the circular velocity of the galaxies.Circular velocity is usually measured by looking at the line width of a gas tracer like HI. The authors find that this doesnt trace the full potential wells of the dwarf galaxies, however, resulting in an incorrect interpretation of their velocities.The authors show that the inclusion of these effects in the theoretical model significantly changes the predicted shape of the galaxy velocity function. This new function beautifully matches observations, neatly eliminating the missing dwarf problem. Perhaps this long-standing mystery has been a problem of interpretation all along!CitationAlyson M. Brooks et al 2017 ApJ 850 97. doi:10.3847/1538-4357/aa9576

Imaging linear and circular polarization features in leaves with complete Mueller matrix polarimetry.

PubMed

Patty, C H Lucas; Luo, David A; Snik, Frans; Ariese, Freek; Buma, Wybren Jan; Ten Kate, Inge Loes; van Spanning, Rob J M; Sparks, William B; Germer, Thomas A; Garab, Győző; Kudenov, Michael W

2018-06-01

Spectropolarimetry of intact plant leaves allows to probe the molecular architecture of vegetation photosynthesis in a non-invasive and non-destructive way and, as such, can offer a wealth of physiological information. In addition to the molecular signals due to the photosynthetic machinery, the cell structure and its arrangement within a leaf can create and modify polarization signals. Using Mueller matrix polarimetry with rotating retarder modulation, we have visualized spatial variations in polarization in transmission around the chlorophyll a absorbance band from 650 nm to 710 nm. We show linear and circular polarization measurements of maple leaves and cultivated maize leaves and discuss the corresponding Mueller matrices and the Mueller matrix decompositions, which show distinct features in diattenuation, polarizance, retardance and depolarization. Importantly, while normal leaf tissue shows a typical split signal with both a negative and a positive peak in the induced fractional circular polarization and circular dichroism, the signals close to the veins only display a negative band. The results are similar to the negative band as reported earlier for single macrodomains. We discuss the possible role of the chloroplast orientation around the veins as a cause of this phenomenon. Systematic artefacts are ruled out as three independent measurements by different instruments gave similar results. These results provide better insight into circular polarization measurements on whole leaves and options for vegetation remote sensing using circular polarization. Copyright © 2018 The Author(s). Published by Elsevier B.V. All rights reserved.

Earth Observations taken by Expedition 30 crewmember

NASA Image and Video Library

2011-11-26

ISS030-E-005456 (26 Nov. 2011) --- Emi Koussi Volcano and Aorounga Impact Crater, Chad are featured in this image photographed by an Expedition 30 crew member on the International Space Station. This striking photograph features two examples of circular landscape features?labeled as craters?that were produced by very different geological processes. At left, the broad grey-green shield volcano of Emi Koussi is visible. The volcano is marked by three overlapping calderas formed by eruptions; these form a large oblong depression at the 3,415 meter ASL summit of the volcano. A smaller crater sits within the larger caldera depression. While volcanic activity has not been observed, nor is mentioned in the historical record, an active thermal area is located on the southern flank. The circular Aorounga Impact Crater is located approximately 110 kilometers to the southeast of Emi Koussi and has its origin in forces from above rather than eruptions from below. According to scientists, the Aorounga structure is thought to record a meteor impact approximately 345-370 million years ago. The circular feature visible at upper right may be only one of three impact craters formed by the same event ? the other two are buried by sand deposits. The linear features (lower right) that arc around Emi Koussi and overprint Aorounga and the surrounding bedrock are known as yardangs; these are rock ridges formed by wind erosion.

Axions and dark matter

NASA Astrophysics Data System (ADS)

Yang, Qiaoli

2017-05-01

Dark matter constitutes about 23% of the total energy density of the universe, but its properties are still little known besides that it should be composed by cold and weakly interacting particles. Many beyond Standard Model theories can provide proper candidates to serve as dark matter and the axion introduced to solve the strong CP problem turns out to be an attractive one. In this paper, we briefly review several important features of the axion and the axion dark matter.

The Gemini NICI Planet-Finding Campaign: asymmetries in the HD 141569 disc

NASA Astrophysics Data System (ADS)

Biller, Beth A.; Liu, Michael C.; Rice, Ken; Wahhaj, Zahed; Nielsen, Eric; Hayward, Thomas; Kuchner, Marc J.; Close, Laird M.; Chun, Mark; Ftaclas, Christ; Toomey, Douglas W.

2015-07-01

We report here the highest resolution near-IR imaging to date of the HD 141569A disc taken as part of the NICI (near infrared coronagraphic imager) Science Campaign. We recover four main features in the NICI images of the HD 141569 disc discovered in previous Hubble Space Telescope (HST) imaging: (1) an inner ring/spiral feature. Once deprojected, this feature does not appear circular. (2) An outer ring which is considerably brighter on the western side compared to the eastern side, but looks fairly circular in the deprojected image. (3) An additional arc-like feature between the inner and outer ring only evident on the east side. In the deprojected image, this feature appears to complete the circle of the west side inner ring and (4) an evacuated cavity from 175 au inwards. Compared to the previous HST imaging with relatively large coronagraphic inner working angles (IWA), the NICI coronagraph allows imaging down to an IWA of 0.3 arcsec. Thus, the inner edge of the inner ring/spiral feature is well resolved and we do not find any additional disc structures within 175 au. We note some additional asymmetries in this system. Specifically, while the outer ring structure looks circular in this deprojection, the inner bright ring looks rather elliptical. This suggests that a single deprojection angle is not appropriate for this system and that there may be an offset in inclination between the two ring/spiral features. We find an offset of 4 ± 2 au between the inner ring and the star centre, potentially pointing to unseen inner companions.

Diet Quality of Items Advertised in Supermarket Sales Circulars Compared to Diets of the US Population, as Assessed by the Healthy Eating Index-2010.

PubMed

Jahns, Lisa; Scheett, Angela J; Johnson, LuAnn K; Krebs-Smith, Susan M; Payne, Collin R; Whigham, Leah D; Hoverson, Bonita S; Kranz, Sibylle

2016-01-01

Supermarkets use sales circulars to highlight specific foods, usually at reduced prices. Resulting purchases help form the set of available foods within households from which individuals and families make choices about what to eat. The purposes of this study were to determine how closely foods featured in weekly supermarket sales circulars conform to dietary guidance and how diet quality compares with that of the US population's intakes. Food and beverage items (n=9,149) in 52 weekly sales circulars from a small Midwestern grocery chain in 2009 were coded to obtain food group and nutrient and energy content. Healthy Eating Index-2010 (HEI-2010) total and component scores were calculated using algorithms developed by the National Cancer Institute. HEI-2010 scores for the US population aged 2+ years were estimated using data from the 2009-2010 National Health and Nutrition Examination Survey. HEI-2010 scores of circulars and population intakes were compared using Student's t tests. Mean total (42.8 of 100) HEI-2010 scores of circulars were lower than that of the US population (55.4; P<0.001). Among individual components, Total Protein Foods was the only one for which 100% of the maximum score was met by both circulars and the population. The scores were also similar between the circulars and population for Whole Grains (22%; P=0.81) and Seafood and Plant Proteins (70% to 74%; P=0.33). Circular scores were lower than those of the population for Total and Whole Fruits, Total Vegetables and Greens and Beans, Dairy, Sodium, and Empty Calories (P<0.001); they were higher only for Fatty Acids (P=0.006) and Refined Grains (P<0.001). HEI-2010 total scores for these sales circulars were even lower than US population scores, which have been shown repeatedly to reflect low diet quality. Supermarkets could support improvements in consumer diets by weekly featuring foods that are more in concordance with food and nutrient recommendations. Copyright © 2016 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

Dynamical constraints on the dark matter distribution in the Milky Way

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pato, Miguel; Iocco, Fabio; Bertone, Gianfranco, E-mail: migpato@gmail.com, E-mail: fabio.iocco.astro@gmail.com, E-mail: g.bertone@uva.nl

2015-12-01

An accurate knowledge of the dark matter distribution in the Milky Way is of crucial importance for galaxy formation studies and current searches for particle dark matter. In this paper we set new dynamical constraints on the Galactic dark matter profile by comparing the observed rotation curve, updated with a comprehensive compilation of kinematic tracers, with that inferred from a wide range of observation-based morphologies of the bulge, disc and gas. The generalised Navarro-Frenk-White (NFW) and Einasto dark matter profiles are fitted to the data in order to determine the favoured ranges of local density, slope and scale radius. Formore » a representative baryonic model, a typical local circular velocity v{sub 0}=230 km/s and a distance of the Sun to the Galactic centre R{sub 0}=8 kpc, we find a local dark matter density ρ{sub 0} = 0.420{sup +0.021}{sub −0.018} (2σ) ± 0.025 GeV/cm{sup 3} (ρ{sub 0} = 0.420{sup +0.019}{sub −0.021} (2σ) ± 0.026 GeV/cm{sup 3}) for NFW (Einasto), where the second error is an estimate of the systematic due to baryonic modelling. Apart from the Galactic parameters, the main sources of uncertainty inside and outside the solar circle are baryonic modelling and rotation curve measurements, respectively. Upcoming astronomical observations are expected to reduce all these uncertainties substantially over the coming years.« less

Molecular orbital imaging via above-threshold ionization with circularly polarized pulses.

PubMed

Zhu, Xiaosong; Zhang, Qingbin; Hong, Weiyi; Lu, Peixiang; Xu, Zhizhan

2011-07-18

Above-threshold ionization (ATI) for aligned or orientated linear molecules by circularly polarized laser pulsed is investigated. It is found that the all-round structural information of the molecular orbital is extracted with only one shot by the circularly polarized probe pulse rather than with multi-shot detections in a linearly polarized case. The obtained photoelectron momentum spectrum directly depicts the symmetry and electron distribution of the occupied molecular orbital, which results from the strong sensitivity of the ionization probability to these structural features. Our investigation indicates that the circularly polarized probe scheme would present a simple method to study the angle-dependent ionization and image the occupied electronic orbital.

The tight focusing properties of Laguerre-Gaussian-correlated Schell-model beams

NASA Astrophysics Data System (ADS)

Xu, Hua-Feng; Zhang, Zhou; Qu, Jun; Huang, Wei

2016-08-01

Based on the Richards-Wolf vectorial diffraction theory, the tight focusing properties, including the intensity distribution, the degree of polarization and the degree of coherence, of the Laguerre-Gaussian-correlated Schell-model (LGSM) beams through a high-numerical-aperture (NA) focusing system are investigated in detail. It is found that the LGSM beam exhibits some extraordinary focusing properties, which is quite different from that of the GSM beam, and the tight focusing properties are closely related to the initial spatial coherence ? and the mode order n. The LGSM beam can form an elliptical focal spot, a circular focal spot or a doughnut-shaped dark hollow beam at the focal plane by choosing a suitable value of the initial spatial coherence ?, and the central dark size of the dark hollow beam increases with the increase of the mode order n. In addition, the influences of the initial spatial coherence ? and the mode order n on the degree of polarization and the degree of coherence are also analysed in detail, respectively. Our results may find applications in optical trapping.

Western hemisphere of the Moon taken by Galileo spacecraft

NASA Technical Reports Server (NTRS)

1990-01-01

Galileo spacecraft image of the Moon recorded at 9:35 am Pacific Standard Time (PST), 12-09-90, after completing its first Earth Gravity Assist. Western hemisphere of the Moon was taken through a green filter at a range of about 350,000 miles. In the center is Orientale Basin, 600 miles in diameter, formed about 3.8 billion years ago by the impact of an asteroid-size body. Orientale's dark center is a small mare. To the right is the lunar near side with the great, dark Oceanus Procellarum above the small, circular, dark Mare Humorum below. Maria are broad plains formed mostly over 3 billion years ago as vast basaltic lava flows. To the left is the lunar far side with fewer maria, but, at lower left South-Pole-Aitken basin, about 1200 miles in diameter, which resembles Orientale but is much older and more weathered and battered by cratering. The intervening cratered highlands of both sides, as well as the maria, are dotted with bright young craters. This image was 'reprojected' so as to

The Unique Geomorphology and Physical Properties of the Vestalia Terra Plateau

NASA Technical Reports Server (NTRS)

Buczkowski, D.L.; Wyrick, D.Y.; Toplis, M.; Yingst, R. A.; Williams, D. A.; Garry, W. B.; Mest, S.; Kneissl, T.; Scully, J. E. C.; Nathues, A.;

Survey of large circular and octagonal tanks operated at Norwegian commercial smolt and post-smolt sites

USDA-ARS?s Scientific Manuscript database

A survey was conducted to determine the geometry, operating parameters, and other key features of large circular or octagonal culture tanks used to produce Atlantic salmon smolt and post-smolt at six major Norwegian Atlantic salmon production companies. A total of 55 large tanks were reported at sev...

Effect of spatial coherence on the scintillation properties of a dark hollow beam in turbulent atmosphere

NASA Astrophysics Data System (ADS)

Yuan, Yangsheng; Chen, Yahong; Liang, Chunhao; Cai, Yangjian; Baykal, Yahya

2013-03-01

With the help of a tensor method, we derive an explicit expression for the on-axis scintillation index of a circular partially coherent dark hollow (DH) beam in weakly turbulent atmosphere. The derived formula can be applied to study the scintillation properties of a partially coherent Gaussian beam and a partially coherent flat-topped (FT) beam. The effect of spatial coherence on the scintillation properties of DH beam, FT beam and Gaussian beam is studied numerically and comparatively. Our results show that the advantage of a DH beam over a FT beam and a Gaussian beam for reducing turbulence-induced scintillation increases particularly at long propagation distances with the decrease of spatial coherence or the increase of the atmospheric turbulence, which will be useful for long-distance free-space optical communications.

Simulation of complex phenomena in optical fibres

NASA Astrophysics Data System (ADS)

Allington-Smith, Jeremy; Murray, Graham; Lemke, Ulrike

2012-12-01

Optical fibres are essential for many types of highly multiplexed and precision spectroscopy. The success of the new generation of multifibre instruments under construction to investigate fundamental problems in cosmology, such as the nature of dark energy, requires accurate modellization of the fibre system to achieve their signal-to-noise ratio (SNR) goals. Despite their simple construction, fibres exhibit unexpected behaviour including non-conservation of etendue (focal ratio degradation, FRD) and modal noise. Furthermore, new fibre geometries (non-circular or tapered) have become available to improve the scrambling properties that, together with modal noise, limit the achievable SNR in precision spectroscopy. These issues have often been addressed by extensive tests on candidate fibres and their terminations, but these are difficult and time-consuming. Modelling by ray tracing and wave analysis is possible with commercial software packages, but these do not address the more complex features, in particular FRD. We use a phase-tracking ray-tracing method to provide a practical description of FRD derived from our previous experimental work on circular fibres and apply it to non-standard fibres. This allows the relationship between scrambling and FRD to be quantified for the first time. We find that scrambling primarily affects the shape of the near-field pattern but has negligible effect on the barycentre. FRD helps to homogenize the near-field pattern but does not make it completely uniform. Fibres with polygonal cross-section improve scrambling without amplifying the FRD. Elliptical fibres, in conjunction with tapering, may offer an efficient means of image slicing to improve the product of resolving power and throughput, but the result is sensitive to the details of illumination. We also investigated the performance of fibres close to the limiting numerical aperture since this may affect the uniformity of the SNR for some prime focus fibre instrumentation.

Electromagnetic waves propagating in the string axiverse

NASA Astrophysics Data System (ADS)

Yoshida, Daiske; Soda, Jiro

2018-04-01

It is widely believed that axions are ubiquitous in string theory and could be dark matter. The peculiar features of axion dark matter are coherent oscillations and a coupling to the electromagnetic field through the Chern-Simons term. In this letter, we study the consequences of these two features of axions with mass in the range 10^{-13} eV to 103 eV. First, we study the parametric resonance of electromagnetic waves induced by the coherent oscillation of the axion. Since the resonance frequency is determined by the mass of the axion dark matter, if we detect this signal, we can get information on the mass of the axion dark matter. Second, we study the velocity of light in the background of the axion dark matter. In the presence of the Chern-Simons term, the dispersion relation is modified and the speed of light will oscillate in time. It turns out that the change in the speed of light would be difficult to observe. We argue that future radio wave observations of the resonance can give rise to a stronger constraint on the coupling constant and/or the density of the axion dark matter.

Dark matter in the coming decade: Complementary paths to discovery and beyond

DOE PAGES

Bauer, Daniel; Buckley, James; Cahill-Rowley, Matthew; ...

2015-05-27

Here, we summarize the many dark matter searches currently being pursued through four complementary approaches: direct detection, indirect detection, collider experiments, and astrophysical probes. The essential features of broad classes of experiments are described, each with their own strengths and weaknesses. Furthermore, we discuss the complementarity of the different dark matter searches qualitatively and illustrated quantitatively in two simple theoretical frameworks. Our primary conclusion is that the diversity of possible dark matter candidates requires a balanced program drawing from all four approaches.

Metazoan tRNA introns generate stable circular RNAs in vivo

PubMed Central

Lu, Zhipeng; Filonov, Grigory S.; Noto, John J.; Schmidt, Casey A.; Hatkevich, Talia L.; Wen, Ying; Jaffrey, Samie R.; Matera, A. Gregory

2015-01-01

We report the discovery of a class of abundant circular noncoding RNAs that are produced during metazoan tRNA splicing. These transcripts, termed tRNA intronic circular (tric)RNAs, are conserved features of animal transcriptomes. Biogenesis of tricRNAs requires anciently conserved tRNA sequence motifs and processing enzymes, and their expression is regulated in an age-dependent and tissue-specific manner. Furthermore, we exploited this biogenesis pathway to develop an in vivo expression system for generating “designer” circular RNAs in human cells. Reporter constructs expressing RNA aptamers such as Spinach and Broccoli can be used to follow the transcription and subcellular localization of tricRNAs in living cells. Owing to the superior stability of circular vs. linear RNA isoforms, this expression system has a wide range of potential applications, from basic research to pharmaceutical science. PMID:26194134

Lower-Dark-Current, Higher-Blue-Response CMOS Imagers

NASA Technical Reports Server (NTRS)

Pain, Bedabrata; Cunningham, Thomas; Hancock, Bruce

2008-01-01

Several improved designs for complementary metal oxide/semiconductor (CMOS) integrated-circuit image detectors have been developed, primarily to reduce dark currents (leakage currents) and secondarily to increase responses to blue light and increase signal-handling capacities, relative to those of prior CMOS imagers. The main conclusion that can be drawn from a study of the causes of dark currents in prior CMOS imagers is that dark currents could be reduced by relocating p/n junctions away from Si/SiO2 interfaces. In addition to reflecting this conclusion, the improved designs include several other features to counteract dark-current mechanisms and enhance performance.

Sterile neutrino dark matter with supersymmetry

NASA Astrophysics Data System (ADS)

Shakya, Bibhushan; Wells, James D.

2017-08-01

Sterile neutrino dark matter, a popular alternative to the WIMP paradigm, has generally been studied in non-supersymmetric setups. If the underlying theory is supersymmetric, we find that several interesting and novel dark matter features can arise. In particular, in scenarios of freeze-in production of sterile neutrino dark matter, its superpartner, the sterile sneutrino, can play a crucial role in early Universe cosmology as the dominant source of cold, warm, or hot dark matter, or of a subdominant relativistic population of sterile neutrinos that can contribute to the effective number of relativistic degrees of freedom Neff during big bang nucleosynthesis.

False Color View of Mercury

NASA Image and Video Library

2017-12-08

This colorful view of Mercury was produced by using images from the color base map imaging campaign during MESSENGER's primary mission. These colors are not what Mercury would look like to the human eye, but rather the colors enhance the chemical, mineralogical, and physical differences between the rocks that make up Mercury's surface. Young crater rays, extending radially from fresh impact craters, appear light blue or white. Medium- and dark-blue areas are a geologic unit of Mercury's crust known as the "low-reflectance material", thought to be rich in a dark, opaque mineral. Tan areas are plains formed by eruption of highly fluid lavas. The crater in the upper right whose rays stretch across the planet is Hokusai. To watch a movie of this colorful view of Mercury as a spinning globe go here: www.flickr.com/photos/gsfc/8497927473 Young crater rays, extending radially from fresh impact craters, appear light blue or white. Medium- and dark-blue areas are a geologic unit of Mercury's crust known as the "low-reflectance material", thought to be rich in a dark, opaque mineral. Tan areas are plains formed by eruption of highly fluid lavas. The giant Caloris basin is the large circular tan feature located just to the upper right of center of the image. The MESSENGER spacecraft is the first ever to orbit the planet Mercury, and the spacecraft's seven scientific instruments and radio science investigation are unraveling the history and evolution of the Solar System's innermost planet. Visit the Why Mercury? section of this website to learn more about the key science questions that the MESSENGER mission is addressing. During the one-year primary mission, MESSENGER acquired 88,746 images and extensive other data sets. MESSENGER is now in a yearlong extended mission, during which plans call for the acquisition of more than 80,000 additional images to support MESSENGER's science goals. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Dark-field imaging with the scanning transmission x-ray microscope

NASA Astrophysics Data System (ADS)

Morrison, G. R.; Browne, M. T.

1992-01-01

The King's College London scanning transmission x-ray microscope in use on beam line 5U2 at the SRS, SERC Daresbury Laboratory, has been modified to allow dark-field images to be formed using only the x rays scattered by the specimen. Experiments have been performed with a number of different detector geometries, and this has confirmed that the strongest scattering arises from edges or thickness gradients in the specimen. Although the dark-field signal is only a small fraction of the normal transmitted bright-field signal, features can be revealed with high contrast, and it has proved possible to detect the presence of features that are below the resolution limit of the microscope.

Variable features on Mars. VII - Dark filamentary markings on Mars

NASA Technical Reports Server (NTRS)

Veverka, J.

1976-01-01

The paper discusses the location, variability, and possible nature of well-developed patterns of dark filamentary markings in the Mariner 9 photographic records. Although not common on Mars, the markings are concentrated in at least two areas: Depressio Hellespontica and Cerberus/Trivium Charontis. In certain localities, strong winds are required to bring these markings into prominence. The dark filamentary markings seem to be true albedo features controlled by local topography, it being unlikely that they are free linear dunes. The distinctive criss-cross pattern seen in many of the pictures suggests that jointing provides the controlling topographic grid. At this stage it cannot be inferred whether the markings are erosional or depositional in character.

Dark matter in 3D

DOE PAGES

Alves, Daniele S. M.; El Hedri, Sonia; Wacker, Jay G.

2016-03-21

We discuss the relevance of directional detection experiments in the post-discovery era and propose a method to extract the local dark matter phase space distribution from directional data. The first feature of this method is a parameterization of the dark matter distribution function in terms of integrals of motion, which can be analytically extended to infer properties of the global distribution if certain equilibrium conditions hold. The second feature of our method is a decomposition of the distribution function in moments of a model independent basis, with minimal reliance on the ansatz for its functional form. We illustrate our methodmore » using the Via Lactea II N-body simulation as well as an analytical model for the dark matter halo. Furthermore, we conclude that O(1000) events are necessary to measure deviations from the Standard Halo Model and constrain or measure the presence of anisotropies.« less

Tachyon cosmology with non-vanishing minimum potential: a unified model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Huiquan, E-mail: hqli@ustc.edu.cn

2012-07-01

We investigate the tachyon condensation process in the effective theory with non-vanishing minimum potential and its implications to cosmology. It is shown that the tachyon condensation on an unstable three-brane described by this modified tachyon field theory leads to lower-dimensional branes (defects) forming within a stable three-brane. Thus, in the cosmological background, we can get well-behaved tachyon matter after tachyon inflation, (partially) avoiding difficulties encountered in the original tachyon cosmological models. This feature also implies that the tachyon inflated and reheated universe is followed by a Chaplygin gas dark matter and dark energy universe. Hence, such an unstable three-brane behavesmore » quite like our universe, reproducing the key features of the whole evolutionary history of the universe and providing a unified description of inflaton, dark matter and dark energy in a very simple single-scalar field model.« less

Surface features on Mars: Ground-based albedo and radar compared with Mariner 9 topography

NASA Technical Reports Server (NTRS)

Frey, H.

1973-01-01

Earth-based albedo maps of Mars were compared with Mariner 9 television data and ground-based radar profiles to investigate the nature of the bright and dark albedo features. Little correlation was found except at the boundaries of classical albedo features, where some topographic control is indicated. Wind-blown dust models for seasonal and secular albedo variations are supported, but it is not clear whether the fines are derived from bright or dark parent rock. Mars, like the Earth and Moon, has probably generated two distinct types of crustal material.

Conical refraction and formation of multiring focal image with Laguerre-Gauss light beams.

PubMed

Peet, Viktor

2011-08-01

For a light beam focused through a biaxial crystal along one of its optical axes, the effect of internal conical refraction in the crystal leads to the formation in the focal image plane of two bright rings separated by a dark ring. It is shown that, with circularly polarized Laguerre-Gauss LG(0)(ℓ) beams entering the crystal, this classical double-ring pattern is transformed into a multiring one consisting of ℓ+2 bright rings. © 2011 Optical Society of America

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grosso, G.; Nardin, G.; Morier-Genoud, F.

Exciton polaritons have been shown to be an optimal system in order to investigate the properties of bosonic quantum fluids. We report here on the observation of dark solitons in the wake of engineered circular obstacles and their decay into streets of quantized vortices. Our experiments provide a time-resolved access to the polariton phase and density, which allows for a quantitative study of instabilities of freely evolving polaritons. The decay of solitons is quantified and identified as an effect of disorder-induced transverse perturbations in the dissipative polariton gas.

Bright-dark and dark-dark solitons in coupled nonlinear Schrödinger equation with P T -symmetric potentials

NASA Astrophysics Data System (ADS)

Nath, Debraj; Gao, Yali; Babu Mareeswaran, R.; Kanna, T.; Roy, Barnana

2017-12-01

We explore different nonlinear coherent structures, namely, bright-dark (BD) and dark-dark (DD) solitons in a coupled nonlinear Schrödinger/Gross-Pitaevskii equation with defocusing/repulsive nonlinearity coefficients featuring parity-time ( P T )-symmetric potentials. Especially, for two choices of P T -symmetric potentials, we obtain the exact solutions for BD and DD solitons. We perform the linear stability analysis of the obtained coherent structures. The results of this linear stability analysis are well corroborated by direct numerical simulation incorporating small random noise. It has been found that there exists a parameter regime which can support stable BD and DD solitons.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bozorgnia, Nassim; Gelmini, Graciela B.; Gondolo, Paolo, E-mail: n.bozorgnia@uva.nl, E-mail: gelmini@physics.ucla.edu, E-mail: paolo@physics.utah.edu

Directional dark matter detection attempts to measure the direction of motion of nuclei recoiling after having interacted with dark matter particles in the halo of our Galaxy. Due to Earth's motion with respect to the Galaxy, the dark matter flux is concentrated around a preferential direction. An anisotropy in the recoil direction rate is expected as an unmistakable signature of dark matter. The average nuclear recoil direction is expected to coincide with the average direction of dark matter particles arriving to Earth. Here we point out that for a particular type of dark matter, inelastic exothermic dark matter, the meanmore » recoil direction as well as a secondary feature, a ring of maximum recoil rate around the mean recoil direction, could instead be opposite to the average dark matter arrival direction. Thus, the detection of an average nuclear recoil direction opposite to the usually expected direction would constitute a spectacular experimental confirmation of this type of dark matter.« less

Particle Dark Matter constraints: the effect of Galactic uncertainties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benito, Maria; Bernal, Nicolás; Iocco, Fabio

2017-02-01

Collider, space, and Earth based experiments are now able to probe several extensions of the Standard Model of particle physics which provide viable dark matter candidates. Direct and indirect dark matter searches rely on inputs of astrophysical nature, such as the local dark matter density or the shape of the dark matter density profile in the target in object. The determination of these quantities is highly affected by astrophysical uncertainties. The latter, especially those for our own Galaxy, are ill-known, and often not fully accounted for when analyzing the phenomenology of particle physics models. In this paper we present amore » systematic, quantitative estimate of how astrophysical uncertainties on Galactic quantities (such as the local galactocentric distance, circular velocity, or the morphology of the stellar disk and bulge) propagate to the determination of the phenomenology of particle physics models, thus eventually affecting the determination of new physics parameters. We present results in the context of two specific extensions of the Standard Model (the Singlet Scalar and the Inert Doublet) that we adopt as case studies for their simplicity in illustrating the magnitude and impact of such uncertainties on the parameter space of the particle physics model itself. Our findings point toward very relevant effects of current Galactic uncertainties on the determination of particle physics parameters, and urge a systematic estimate of such uncertainties in more complex scenarios, in order to achieve constraints on the determination of new physics that realistically include all known uncertainties.« less

New soliton solution to the longitudinal wave equation in a magneto-electro-elastic circular rod

NASA Astrophysics Data System (ADS)

Seadawy, Aly R.; Manafian, Jalil

2018-03-01

This paper examines the effectiveness of an integration scheme which called the extended trial equation method (ETEM) in exactly solving a well-known nonlinear equation of partial differential equations (PDEs). In this respect, the longitudinal wave equation (LWE) that arises in mathematical physics with dispersion caused by the transverse Poisson's effect in a magneto-electro-elastic (MEE) circular rod, which a series of exact traveling wave solutions for the aforementioned equation is formally extracted. Explicit new exact solutions are derived in different form such as dark solitons, bright solitons, solitary wave, periodic solitary wave, rational function, and elliptic function solutions of the longitudinal wave equation. The movements of obtained solutions are shown graphically, which helps to understand the physical phenomena of this longitudinal wave equation. Many other such types of nonlinear equations arising in non-destructive evaluation of structures made of the advanced MEE material can also be solved by this method.

Observation of macroscopic valley-polarized monolayer exciton-polaritons at room temperature

NASA Astrophysics Data System (ADS)

Lundt, N.; Stoll, S.; Nagler, P.; Nalitov, A.; Klembt, S.; Betzold, S.; Goddard, J.; Frieling, E.; Kavokin, A. V.; Schüller, C.; Korn, T.; Höfling, S.; Schneider, C.

2017-12-01

In this Rapid Communication, we address the chiral properties of valley exciton-polaritons in a monolayer of W S2 in the regime of strong light-matter coupling with a Tamm-plasmon resonance. We observe that the effect of valley polarization, which manifests in the circular polarization of the emitted photoluminescence as the sample is driven by a circularly polarized laser, is strongly enhanced in comparison to bare W S2 monolayers and can even be observed under strongly nonresonant excitation at ambient conditions. In order to explain this effect in more detail, we study the relaxation and decay dynamics of exciton-polaritons in our device, elaborate the role of the dark state, and present a microscopic model to explain the wave-vector-dependent valley depolarization by the linear polarization splitting inherent to the microcavity. We believe that our findings are crucial for designing novel polariton-valleytronic devices which can be operated at room temperature.

Circular RNA is expressed across the eukaryotic tree of life.

PubMed

Wang, Peter L; Bao, Yun; Yee, Muh-Ching; Barrett, Steven P; Hogan, Gregory J; Olsen, Mari N; Dinneny, José R; Brown, Patrick O; Salzman, Julia

2014-01-01

An unexpectedly large fraction of genes in metazoans (human, mouse, zebrafish, worm, fruit fly) express high levels of circularized RNAs containing canonical exons. Here we report that circular RNA isoforms are found in diverse species whose most recent common ancestor existed more than one billion years ago: fungi (Schizosaccharomyces pombe and Saccharomyces cerevisiae), a plant (Arabidopsis thaliana), and protists (Plasmodium falciparum and Dictyostelium discoideum). For all species studied to date, including those in this report, only a small fraction of the theoretically possible circular RNA isoforms from a given gene are actually observed. Unlike metazoans, Arabidopsis, D. discoideum, P. falciparum, S. cerevisiae, and S. pombe have very short introns (∼ 100 nucleotides or shorter), yet they still produce circular RNAs. A minority of genes in S. pombe and P. falciparum have documented examples of canonical alternative splicing, making it unlikely that all circular RNAs are by-products of alternative splicing or 'piggyback' on signals used in alternative RNA processing. In S. pombe, the relative abundance of circular to linear transcript isoforms changed in a gene-specific pattern during nitrogen starvation. Circular RNA may be an ancient, conserved feature of eukaryotic gene expression programs.

Circular RNA Is Expressed across the Eukaryotic Tree of Life

PubMed Central

Wang, Peter L.; Bao, Yun; Yee, Muh-Ching; Barrett, Steven P.; Hogan, Gregory J.; Olsen, Mari N.; Dinneny, José R.; Brown, Patrick O.; Salzman, Julia

2014-01-01

An unexpectedly large fraction of genes in metazoans (human, mouse, zebrafish, worm, fruit fly) express high levels of circularized RNAs containing canonical exons. Here we report that circular RNA isoforms are found in diverse species whose most recent common ancestor existed more than one billion years ago: fungi (Schizosaccharomyces pombe and Saccharomyces cerevisiae), a plant (Arabidopsis thaliana), and protists (Plasmodium falciparum and Dictyostelium discoideum). For all species studied to date, including those in this report, only a small fraction of the theoretically possible circular RNA isoforms from a given gene are actually observed. Unlike metazoans, Arabidopsis, D. discoideum, P. falciparum, S. cerevisiae, and S. pombe have very short introns (∼100 nucleotides or shorter), yet they still produce circular RNAs. A minority of genes in S. pombe and P. falciparum have documented examples of canonical alternative splicing, making it unlikely that all circular RNAs are by-products of alternative splicing or ‘piggyback’ on signals used in alternative RNA processing. In S. pombe, the relative abundance of circular to linear transcript isoforms changed in a gene-specific pattern during nitrogen starvation. Circular RNA may be an ancient, conserved feature of eukaryotic gene expression programs. PMID:24609083

Revealing the nonadiabatic nature of dark energy perturbations from galaxy clustering data

NASA Astrophysics Data System (ADS)

Velten, Hermano; Fazolo, Raquel

2017-10-01

We study structure formation using relativistic cosmological linear perturbation theory in the presence of intrinsic and relative (with respect to matter) nonadiabatic dark energy perturbations. For different dark energy models we assess the impact of nonadiabaticity on the matter growth promoting a comparison with growth rate data. The dark energy models studied lead to peculiar signatures of the (non)adiabatic nature of dark energy perturbations in the evolution of the f σ8(z ) observable. We show that nonadiabatic dark energy models become close to be degenerated with respect to the Λ CDM model at first order in linear perturbations. This would avoid the identification of the nonadiabatic nature of dark energy using current available data. Therefore, such evidence indicates that new probes are necessary to reveal the nonadiabatic features in the dark energy sector.

Analysis of Morphological Features of Benign and Malignant Breast Cell Extracted From FNAC Microscopic Image Using the Pearsonian System of Curves.

PubMed

Rajbongshi, Nijara; Bora, Kangkana; Nath, Dilip C; Das, Anup K; Mahanta, Lipi B

2018-01-01

Cytological changes in terms of shape and size of nuclei are some of the common morphometric features to study breast cancer, which can be observed by careful screening of fine needle aspiration cytology (FNAC) images. This study attempts to categorize a collection of FNAC microscopic images into benign and malignant classes based on family of probability distribution using some morphometric features of cell nuclei. For this study, features namely area, perimeter, eccentricity, compactness, and circularity of cell nuclei were extracted from FNAC images of both benign and malignant samples using an image processing technique. All experiments were performed on a generated FNAC image database containing 564 malignant (cancerous) and 693 benign (noncancerous) cell level images. The five-set extracted features were reduced to three-set (area, perimeter, and circularity) based on the mean statistic. Finally, the data were fitted to the generalized Pearsonian system of frequency curve, so that the resulting distribution can be used as a statistical model. Pearsonian system is a family of distributions where kappa (κ) is the selection criteria computed as functions of the first four central moments. For the benign group, kappa (κ) corresponding to area, perimeter, and circularity was -0.00004, 0.0000, and 0.04155 and for malignant group it was 1016942, 0.01464, and -0.3213, respectively. Thus, the family of distribution related to these features for the benign and malignant group were different, and therefore, characterization of their probability curve will also be different.

Structural geology and geological history of the Perrine and Nun Sulci Quadrangles (Jg-2 and Jg-5), Ganymede

NASA Technical Reports Server (NTRS)

Mcgill, George E.; Squyres, Steven W.

1991-01-01

Grooves are the dominant structural features on Ganymede. While single grooves are found in many areas, it is somewhat more common to find them grouped together in groove sets (groupings of grooves with common structural trends). It is generally believed that the grooves are extensional features. Their underlying geologic nature cannot be determined from Voyager images, however. It appears likely that they are grabens, but the images are insufficient to rule out the possibility that they are modified extension fractures or some kind of ductile necking features. The oldest materials within the Nun Sulci and Perrine quadrangles occur within the cratered dark materials unit, as is generally the case for all of Ganymede. This is the most widespread of the dark units mapped in these two quadrangles. Crater densities within cratered dark materials are consistent with an age on the order of several billion years, and thus cratered dark terrain probably represents crust that has survived from the end of the primordial intense bombardment phase of solar system history. The brief geologic history is greatly oversimplified as a result of the poor resolution and unfavorable viewing geometry of the images covering the area.

Chiral templating of self-assembling nanostructures by circularly polarized light

DOE PAGES

Yeom, Jihyeon; Yeom, Bongjun; Chan, Henry; ...

2014-11-17

Chemical reactions affected by spin angular momenta of circularly polarized photons are rare and display low enantiomeric excess. High optical and chemical activity of nanoparticles (NPs) should facilitate the transfer of spin angular momenta of photons to nanoscale materials but such processes are unknown. Here we demonstrate that circularly polarized light (CPL) strongly affects self-assembly of racemic CdTe NPs. Illumination of NP dispersions with right- and left-handed CPL induces the formation of right- and left-handed twisted nanoribbons, respectively. Enantiomeric excess of such reactions exceeds 30% which is ~10 times higher than other CPL-induced reactions. Illumination with linearly polarized light andmore » assembly in the dark led to straight nanoribbons. The mechanism of “templation” of NP assemblies by CPL is associated with selective photoactivation of chiral NPs and clusters followed by their photooxidation. Chiral anisotropy of interactions translates into chirality of the assembled ribbons. Lastly, the ability of NPs to retain polarization information, or the “imprint” of incident photons opens new pathways for the synthesis of chiral photonic materials and allows for better understanding of the origins of biomolecular homochirality.« less

Munitions related feature extraction from LIDAR data.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberts, Barry L.

2010-06-01

The characterization of former military munitions ranges is critical in the identification of areas likely to contain residual unexploded ordnance (UXO). Although these ranges are large, often covering tens-of-thousands of acres, the actual target areas represent only a small fraction of the sites. The challenge is that many of these sites do not have records indicating locations of former target areas. The identification of target areas is critical in the characterization and remediation of these sites. The Strategic Environmental Research and Development Program (SERDP) and Environmental Security Technology Certification Program (ESTCP) of the DoD have been developing and implementing techniquesmore » for the efficient characterization of large munitions ranges. As part of this process, high-resolution LIDAR terrain data sets have been collected over several former ranges. These data sets have been shown to contain information relating to former munitions usage at these ranges, specifically terrain cratering due to high-explosives detonations. The location and relative intensity of crater features can provide information critical in reconstructing the usage history of a range, and indicate areas most likely to contain UXO. We have developed an automated procedure using an adaptation of the Circular Hough Transform for the identification of crater features in LIDAR terrain data. The Circular Hough Transform is highly adept at finding circular features (craters) in noisy terrain data sets. This technique has the ability to find features of a specific radius providing a means of filtering features based on expected scale and providing additional spatial characterization of the identified feature. This method of automated crater identification has been applied to several former munitions ranges with positive results.« less

Modal analysis applied to circular, rectangular, and coaxial waveguides

NASA Technical Reports Server (NTRS)

Hoppe, D. J.

1988-01-01

Recent developments in the analysis of various waveguide components and feedhorns using Modal Analysis (Mode Matching Method) are summarized. A brief description of the theory is presented, and the important features of the method are pointed out. Specific examples in circular, rectangular, and coaxial waveguides are included, with comparisons between the theory and experimental measurements. Extensions to the methods are described.

Pancake Feature on Ceres

NASA Image and Video Library

2015-03-02

Some might see a pancake, and others a sand dollar, in this new image from NASA Dawn mission. Astronomers are puzzling over a mysterious large circular feature located south of the equator and slightly to the right of center in this view.

Parity–time-symmetric circular Bragg lasers: a proposal and analysis

PubMed Central

Gu, Jiahua; Xi, Xiang; Ma, Jingwen; Yu, Zejie; Sun, Xiankai

2016-01-01

We propose a new type of semiconductor lasers by implementing the concept of parity–time symmetry in a two-dimensional circular Bragg grating structure, where both the real and imaginary parts of the refractive index are modulated along the radial direction. The laser modal properties are analyzed with a transfer-matrix method and are verified with numerical simulation of a practical design. Compared with conventional distributed-feedback lasers with modulation of only the real part of refractive index, the parity–time-symmetric circular Bragg lasers feature reduced threshold and enhanced modal discrimination, which in combination with the intrinsic circularly symmetric, large emission aperture are clear advantages in applications that require mode-hop-free, high-power, single-mode laser operation. PMID:27892933

Earth Observations taken by Expedition 30 crewmember

NASA Image and Video Library

2012-02-21

ISS030-E-090918 (21 Feb. 2012) --- Agricultural fields in the Wadi As-Sirhan Basin in Saudi Arabia are featured in this image photographed by an Expedition 30 crew member on the International Space Station. Northern Saudi Arabia hosts some of the most extensive sand and gravel deserts in the world, but modern agricultural technology has changed the face of some of them. This photograph presents the almost surreal image of abundant green fields in the midst of a barren desert ? specifically the Wadi As-Sirhan Basin of northwestern Saudi Arabia. As recently as 1986 there was little to no agricultural activity in the area, but over the subsequent 26 years agricultural fields have been steadily developed, largely as a result of investment of oil industry revenues by the Saudi government. The fields use water pumped from subsurface aquifers and is distributed in rotation about a center point within a circular field ? a technique known as center-pivot agriculture. This technique affords certain benefits relative to more traditional surface irrigation such as better control of water use and application of fertilizers. The use of this so-called ?precision agriculture? is particularly important in regions subject to high evaporative water loss; by better controlling the amount and timing of water application, evaporative losses can be minimized. Crops grown in the area include fruits, vegetables, and wheat. For a sense of scale, agricultural fields in active use (dark green) and fallow (brown to tan), are approximately one kilometer in diameter. While much of the Wadi As-Sirhan Basin shown here is sandy (light tan to brown surfaces) and relatively flat, low hills and rocky outcrops (dark gray) of underlying sedimentary rocks are visible at left and right.

Testing Modified Gravity Theories via Wide Binaries and GAIA

NASA Astrophysics Data System (ADS)

Pittordis, Charalambos; Sutherland, Will

2018-06-01

The standard ΛCDM model based on General Relativity (GR) including cold dark matter (CDM) is very successful at fitting cosmological observations, but recent non-detections of candidate dark matter (DM) particles mean that various modified-gravity theories remain of significant interest. The latter generally involve modifications to GR below a critical acceleration scale ˜10-10 m s-2. Wide-binary (WB) star systems with separations ≳ 5 kAU provide an interesting test for modified gravity, due to being in or near the low-acceleration regime and presumably containing negligible DM. Here, we explore the prospects for new observations pending from the GAIA spacecraft to provide tests of GR against MOND or TeVes-like theories in a regime only partially explored to date. In particular, we find that a histogram of (3D) binary relative velocities, relative to equilibrium circular velocity predicted from the (2D) projected separation predicts a rather sharp feature in this distribution for standard gravity, with an 80th (90th) percentile value close to 1.025 (1.14) with rather weak dependence on the eccentricity distribution. However, MOND/TeVeS theories produce a shifted distribution, with a significant increase in these upper percentiles. In MOND-like theories without an external field effect, there are large shifts of order unity. With the external field effect included, the shifts are considerably reduced to ˜0.04 - 0.08, but are still potentially detectable statistically given reasonably large samples and good control of contaminants. In principle, followup of GAIA-selected wide binaries with ground-based radial velocities accurate to ≲ 0.03 { km s^{-1}} should be able to produce an interesting new constraint on modified-gravity theories.

Metazoan tRNA introns generate stable circular RNAs in vivo.

PubMed

Lu, Zhipeng; Filonov, Grigory S; Noto, John J; Schmidt, Casey A; Hatkevich, Talia L; Wen, Ying; Jaffrey, Samie R; Matera, A Gregory

2015-09-01

We report the discovery of a class of abundant circular noncoding RNAs that are produced during metazoan tRNA splicing. These transcripts, termed tRNA intronic circular (tric)RNAs, are conserved features of animal transcriptomes. Biogenesis of tricRNAs requires anciently conserved tRNA sequence motifs and processing enzymes, and their expression is regulated in an age-dependent and tissue-specific manner. Furthermore, we exploited this biogenesis pathway to develop an in vivo expression system for generating "designer" circular RNAs in human cells. Reporter constructs expressing RNA aptamers such as Spinach and Broccoli can be used to follow the transcription and subcellular localization of tricRNAs in living cells. Owing to the superior stability of circular vs. linear RNA isoforms, this expression system has a wide range of potential applications, from basic research to pharmaceutical science. © 2015 Lu et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

Hubble Finds New Dark Spot on Neptune

NASA Image and Video Library

1998-08-02

In 1995, NASA Hubble Space Telescope discovered a new great dark spot, located in the northern hemisphere of the planet Neptune. Because the planet northern hemisphere was tilted away from Earth, the new feature appeared near the limb of the planet.

Rotation invariant features for wear particle classification

NASA Astrophysics Data System (ADS)

Arof, Hamzah; Deravi, Farzin

1997-09-01

This paper investigates the ability of a set of rotation invariant features to classify images of wear particles found in used lubricating oil of machinery. The rotation invariant attribute of the features is derived from the property of the magnitudes of Fourier transform coefficients that do not change with spatial shift of the input elements. By analyzing individual circular neighborhoods centered at every pixel in an image, local and global texture characteristics of an image can be described. A number of input sequences are formed by the intensities of pixels on concentric rings of various radii measured from the center of each neighborhood. Fourier transforming the sequences would generate coefficients whose magnitudes are invariant to rotation. Rotation invariant features extracted from these coefficients were utilized to classify wear particle images that were obtained from a number of different particles captured at different orientations. In an experiment involving images of 6 classes, the circular neighborhood features obtained a 91% recognition rate which compares favorably to a 76% rate achieved by features of a 6 by 6 co-occurrence matrix.

Dark- and bright-rogue-wave solutions for media with long-wave-short-wave resonance.

PubMed

Chen, Shihua; Grelu, Philippe; Soto-Crespo, J M

2014-01-01

Exact explicit rogue-wave solutions of intricate structures are presented for the long-wave-short-wave resonance equation. These vector parametric solutions feature coupled dark- and bright-field counterparts of the Peregrine soliton. Numerical simulations show the robustness of dark and bright rogue waves in spite of the onset of modulational instability. Dark fields originate from the complex interplay between anomalous dispersion and the nonlinearity driven by the coupled long wave. This unusual mechanism, not available in scalar nonlinear wave equation models, can provide a route to the experimental realization of dark rogue waves in, for instance, negative index media or with capillary-gravity waves.

Investigations of dark, bright, combined dark-bright optical and other soliton solutions in the complex cubic nonlinear Schrödinger equation with δ-potential

NASA Astrophysics Data System (ADS)

Baskonus, Haci Mehmet; Sulaiman, Tukur Abdulkadir; Bulut, Hasan; Aktürk, Tolga

2018-03-01

In this study, using the extended sinh-Gordon equation expansion method, we construct the dark, bright, combined dark-bright optical, singular, combined singular solitons and singular periodic waves solutions to the complex cubic nonlinear Schrödinger equation with δ-potential. The conditions for the existence of the obtained solutions are given. To present the physical feature of the acquired result, the 2D and 3D graphs are plotted under the choice of suitable values of the parameters.

Probing light nonthermal dark matter at the LHC

NASA Astrophysics Data System (ADS)

Dutta, Bhaskar; Gao, Yu; Kamon, Teruki

2014-05-01

This paper investigates the collider phenomenology of a minimal nonthermal dark matter model with a 1-GeV dark matter candidate, which naturally explains baryogenesis. Since the light dark matter is not parity protected, it can be singly produced at the LHC. This leads to large missing energy associated with an energetic jet whose transverse momentum distribution is featured by a Jacobian-like shape. The monojet, dijet, paired dijet, and two jets + missing energy channels are studied. Currently existing data at the Tevatron and LHC offer significant bounds on our model.

High-Resolution Radar Imagery of Mars

NASA Astrophysics Data System (ADS)

Harmon, John K.; Nolan, M. C.

2009-09-01

We present high-resolution radar images of Mars obtained during the 2005 and 2007 oppositions. The images were constructed from long-code delay-Doppler observations made with the Arecibo S-band (13-cm) radar. The average image resolution of 3 km represented a better than order-of-magnitude improvement over pre-upgrade Arecibo imagery of the planet. Images of depolarized reflectivity (an indicator primarily of wavelength-scale surface roughness) show the same bright volcanic flow features seen in earlier imagery, but with much finer detail. A new image of the Elysium region shows fine detail in the radar-bright channels of Athabasca Vallis, Marte Vallis, and Grjota Vallis. The new images of Tharsis and Olympus Mons also show a complex array of radar-bright and radar-dark features. Southern Amazonis exhibits some of the most complex and puzzling radar-bright structure on the planet. Another curiosity is the Chryse/Xanthe/Channels region, where we find some radar-bright features in or adjacent to fluvial chaos structures. Chryse/Xanthe is also the only region of Mars showing radar-bright craters (which are rare on Mars but common on the Moon and Mercury). We also obtained the first delay-Doppler image showing the enhanced backscatter from the residual south polar ice cap. In addition to the depolarized imagery, we were able to make the first delay-Doppler images of the circular polarization ratio (an important diagnostic for surface roughness texture). We find that vast areas of the radar-bright volcanic regions have polarization ratios close to unity. Such high ratios are rare for terrestrial lava flows and only seen for extremely blocky surfaces giving high levels of multiple scattering.

ARC-1990-A90-3000

NASA Image and Video Library

1990-08-21

After traveling more than 1.5 billion km (948 million mi.), the Magellan spacecraft was inserted into orbit around Venus on Aug. 10, 1990. This mosaic consists of adjacent pieces of two magellan image strips obtained in the first radar test. The radar test was part of a planned In-Orbit Checkout sequence designed to prepare the magellan spacecraft and radar to begin mapping after Aug. 31. The strip on the left was returned to the Goldstone Deep Space Network station in California; the strip to the right was received at the DSN in Canberra, Australia. A third station that will be receiving Magellan data is locaterd near Madrid, Spain. Each image strip is 20 km (12 mi.) wide and 16,000 km (10,000 mi.) long. This mosaic is a small portion 80 km (50 mi.) long. This image is centered at 21 degrees north latitude and 286.8 degrees east longitude, southeast of a volcanic highland region called Beta Regio. The resolution of the image is about 120 meters (400 feet), 10 times better than revious images of the same area of Venus, revealing many new geologic features. The bright line trending northwest-southeast across the center of the image is a fracture or fault zone cutting the volcanic plains. In the upper lest corner of the image, a multiple-ring circular feature of probable volcanic origin can be seen, approx. 4.27 km (2.65 mi.) across. The bright and dark variations seen in the plains surrounding these features correspond to volcanic lava flows of varying ages. The volcanic lava flows in the southern half of the image have been cut by north-south trending faults. This area is similar geologically to volcanic deposits seen on Earth at Hawaii and the Snake River Plains in Idaho.

Comparison of Topographic Profiles Across Venus' Coronae and Craters: Implications for Corona Origin Hypothesis

NASA Astrophysics Data System (ADS)

Stoddard, P. R.; Jurdy, D. M.

2006-12-01

Venus' surface hosts nearly 1000 unambiguous impact craters, ranging in diameter from 1.5 to 280 km. Although the majority of these are pristine, slightly less than 200 have been modified by either volcanic or tectonic activity or both. In addition, numerous researchers have identified hundreds of ring-like features of varying morphology, termed "coronae." These have typically been thought of as having a diapiric or volcanic origin. Recently, however, based on the circular to quasi-circular nature of coronae, an alternative origin - impact - has been proposed. We compare the profiles across agreed-upon craters to several coronae that have been suggested as impact sites. For each feature, 36 profiles (taken every ten degrees) are aligned and then averaged together. For Mead, Cleopatra, Meitner, and Isabella craters, the profiles display the typical rim and basin structure expected for craters, but for Klenova crater the average is more domal, with only a few of the individual profiles looking crater-like. Among the "contested" coronae, the average profiles for Eurynome, Maya, and C21 appear crater-like, albeit with more variation among the individual profiles than seen in the agreed-upon craters. Anquet has a rim-and-basin structure, but unlike typical craters, the basin is elevated above the surrounding plains. Acrea appears to be a small hill in a large depression, again with a high degree of variability among the profiles. Ninhursag is clearly domal, and cannot be taken as a crater. A summary of the variability of the profiles - where 100% correlation would indicate perfect circular symmetry - indicates that, with the exception of Klenova, those features universally agreed-upon as craters have the highest correlation percentages - all at or above 80%. The disputed features are not as circular, although C21 is close. Based on this analysis, we conclude that Klenova has been mischaracterized as an impact crater, and that C21 and some other features previously classified as coronae may indeed be of impact origin. More careful analyses will be necessary to assess the origin of similar features.

Sequential two-photon double ionization of noble gases by circularly polarized XUV radiation

NASA Astrophysics Data System (ADS)

Gryzlova, E. V.; Grum-Grzhimailo, A. N.; Kuzmina, E. I.; Strakhova, S. I.

2014-10-01

Photoelectron angular distributions (PADs) and angular correlations between two emitted electrons in sequential two-photon double ionization (2PDI) of atoms by circularly polarized radiation are studied theoretically. In particular, the sequential 2PDI of the valence n{{p}6} shell in noble gas atoms (neon, argon, krypton) is analyzed, accounting for the first-order corrections to the dipole approximation. Due to different selection rules in ionization transitions, the circular polarization of photons causes some new features of the cross sections, PADs and angular correlation functions in comparison with the case of linearly polarized photons.

Dark-matter haloes and the M-σ relation for supermassive black holes

NASA Astrophysics Data System (ADS)

Larkin, Adam C.; McLaughlin, Dean E.

2016-10-01

We develop models of two-component spherical galaxies to establish scaling relations linking the properties of spheroids at z = 0 (total stellar masses, effective radii Re and velocity dispersions within Re) to the properties of their dark-matter haloes at both z = 0 and higher redshifts. Our main motivation is the widely accepted idea that the accretion-driven growth of supermassive black holes (SMBHs) in protogalaxies is limited by quasar-mode feedback and gas blow-out. The SMBH masses, MBH, should then be connected to the dark-matter potential wells at the redshift zqso of the blow-out. We specifically consider the example of a power-law dependence on the maximum circular speed in a protogalactic dark-matter halo: M_{BH}∝ V^4_{d,pk}, as could be expected if quasar-mode feedback were momentum-driven. For haloes with a given Vd,pk at a given zqso ≥ 0, our model scaling relations give a typical stellar velocity dispersion σap(Re) at z = 0. Thus, they transform a theoretical MBH-Vd,pk relation into a prediction for an observable MBH-σap(Re) relation. We find the latter to be distinctly non-linear in log-log space. Its shape depends on the generic redshift evolution of haloes in a Λ cold dark matter cosmology and the systematic variation of stellar-to-dark matter mass fraction at z = 0, in addition to any assumptions about the physics underlying the MBH-Vd,pk relation. Despite some clear limitations of the form we use for MBH versus Vd,pk, and even though we do not include any SMBH growth through dry mergers at low redshift, our results for MBH-σap(Re) compare well to data for local early types if we take zqso ˜ 2-4.

Attractiveness as a Function of Skin Tone and Facial Features: Evidence from Categorization Studies.

PubMed

Stepanova, Elena V; Strube, Michael J

2018-01-01

Participants rated the attractiveness and racial typicality of male faces varying in their facial features from Afrocentric to Eurocentric and in skin tone from dark to light in two experiments. Experiment 1 provided evidence that facial features and skin tone have an interactive effect on perceptions of attractiveness and mixed-race faces are perceived as more attractive than single-race faces. Experiment 2 further confirmed that faces with medium levels of skin tone and facial features are perceived as more attractive than faces with extreme levels of these factors. Black phenotypes (combinations of dark skin tone and Afrocentric facial features) were rated as more attractive than White phenotypes (combinations of light skin tone and Eurocentric facial features); ambiguous faces (combinations of Afrocentric and Eurocentric physiognomy) with medium levels of skin tone were rated as the most attractive in Experiment 2. Perceptions of attractiveness were relatively independent of racial categorization in both experiments.

Search for dark matter effects on gravitational signals from neutron star mergers

NASA Astrophysics Data System (ADS)

Ellis, John; Hektor, Andi; Hütsi, Gert; Kannike, Kristjan; Marzola, Luca; Raidal, Martti; Vaskonen, Ville

2018-06-01

Motivated by the recent detection of the gravitational wave signal emitted by a binary neutron star merger, we analyse the possible impact of dark matter on such signals. We show that dark matter cores in merging neutron stars may yield an observable supplementary peak in the gravitational wave power spectral density following the merger, which could be distinguished from the features produced by the neutron components.

Interpretation of a Landsat image of an unusual flood phenomenon in Australia

USGS Publications Warehouse

Robinove, Charles J.

1978-01-01

A Landsat image of part of the flooded area of Cooper Creek, Queensland, Australia, in February 1974, shows large dark areas within the flooded valley. The dark areas are believed to be wet, but unflooded, areas of dark alluvial soil. These striking features, which have not previously been identified on Landsat images, must be properly interpreted so as not to confuse them with clear water.

Exploring the dark foldable proteome by considering hydrophobic amino acids topology

PubMed Central

Bitard-Feildel, Tristan; Callebaut, Isabelle

2017-01-01

The protein universe corresponds to the set of all proteins found in all organisms. A way to explore it is by taking into account the domain content of the proteins. However, some part of sequences and many entire sequences remain un-annotated despite a converging number of domain families. The un-annotated part of the protein universe is referred to as the dark proteome and remains poorly characterized. In this study, we quantify the amount of foldable domains within the dark proteome by using the hydrophobic cluster analysis methodology. These un-annotated foldable domains were grouped using a combination of remote homology searches and domain annotations, leading to define different levels of darkness. The dark foldable domains were analyzed to understand what make them different from domains stored in databases and thus difficult to annotate. The un-annotated domains of the dark proteome universe display specific features relative to database domains: shorter length, non-canonical content and particular topology in hydrophobic residues, higher propensity for disorder, and a higher energy. These features make them hard to relate to known families. Based on these observations, we emphasize that domain annotation methodologies can still be improved to fully apprehend and decipher the molecular evolution of the protein universe. PMID:28134276

Dynamics with a Nonstandard Inertia-Acceleration Relation: An Alternative to Dark Matter in Galactic Systems

NASA Astrophysics Data System (ADS)

Milgrom, M.

1994-02-01

We investigate particle dynamics that is governed by a nonstandard kinetic action of a special form. We are guided by a phenomenological scheme-the modified dynamics (MOND)-that imputes the mass discrepancy, observed in galactic systems, not to the presence of dark matter, but to a departure from Newtonian dynamics below a certain scale of accelerations, a0. The particle's equation of motion in a potential φ is derived from an action, S, of the form S ~ Sk[r(t), a0] - ∫ φ dt. The limit a0 --> 0 corresponds to Newtonian dynamics, and there the kinetic action Sk must take the standard form. In the opposite limit, a0 --> ∞ we require Sk --> 0-and more specifically, for circular orbits Sk ~ a-10-in order to attain the phenomenological success of MOND. Galilei-invariant such theories must be strongly nonlocal. This is a blessing, as such theories need not suffer from the illnesses that are endemic to higher-derivative theories. We comment on the possibility that such a modified law of motion is an effective theory resulting from the elimination of degrees of freedom pertaining to the universe at large (the near equality a0 ≍ cH0 being a trace of that connection). We derive a general virial relation for bounded trajectories. Exact solutions are obtained for circular orbits, which pertain to rotation curves of disk galaxies. We also explore, in passing, theories that depart from the conventional Newtonian dynamics for very low frequencies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boehm, Céline; Degrande, Céline; Mattelaer, Olivier

The study of anomalous electromagnetic emission in the sky is the basis of indirect searches for dark matter. It is also a powerful tool to constrain the radiative decay of active neutrinos. Until now, quantitative analyses have focused on the flux and energy spectrum of such an emission; polarisation has never been considered. Here we show that we could be missing out on an essential piece of information. The radiative decay of neutrinos, as well as the interactions of dark matter and neutrinos with Standard Model particles can generate a circular polarisation signal in X-rays or γ-rays. If observed, thismore » could reveal important information about their spatial distribution and particle-antiparticle ratio, and could even reveal the nature of the high-energy particle physics processes taking place in astrophysical sites. The question of the observability of these polarised signatures and their separation from background astrophysical sources is left for future work.« less

Broadband Venetian-Blind Polarizer With Dual Vanes

NASA Technical Reports Server (NTRS)

Conroy, Bruce L.; Hoppe, Daniel J.

1995-01-01

Improved venetian-blind polarizer features optimized tandem, two-layer vane configuration reducing undesired reflections and deformation of radiation pattern below those of prior single-layer vane configuration. Consists of number of thin, parallel metal strips placed in path of propagating radio-frequency beam. Offers simple way to convert polarization from linear to circular or from circular to linear. Particularly useful for beam-wave-guide applications.

Holographic vortices in the presence of dark matter sector

NASA Astrophysics Data System (ADS)

Rogatko, Marek; Wysokinski, Karol I.

2015-12-01

The dark matter seem to be an inevitable ingredient of the total matter configuration in the Universe and the knowledge how the dark matter affects the properties of superconductors is of vital importance for the experiments aimed at its direct detection. The homogeneous magnetic field acting perpendicularly to the surface of (2+1) dimensional s-wave holographic superconductor in the theory with dark matter sector has been modeled by the additional U(1)-gauge field representing dark matter and coupled to the Maxwell one. As expected the free energy for the vortex configuration turns out to be negative. Importantly its value is lower in the presence of dark matter sector. This feature can explain why in the Early Universe first the web of dark matter appeared and next on these gratings the ordinary matter forming cluster of galaxies has formed.

Predicting Cortical Dark/Bright Asymmetries from Natural Image Statistics and Early Visual Transforms

PubMed Central

Cooper, Emily A.; Norcia, Anthony M.

2015-01-01

The nervous system has evolved in an environment with structure and predictability. One of the ubiquitous principles of sensory systems is the creation of circuits that capitalize on this predictability. Previous work has identified predictable non-uniformities in the distributions of basic visual features in natural images that are relevant to the encoding tasks of the visual system. Here, we report that the well-established statistical distributions of visual features -- such as visual contrast, spatial scale, and depth -- differ between bright and dark image components. Following this analysis, we go on to trace how these differences in natural images translate into different patterns of cortical input that arise from the separate bright (ON) and dark (OFF) pathways originating in the retina. We use models of these early visual pathways to transform natural images into statistical patterns of cortical input. The models include the receptive fields and non-linear response properties of the magnocellular (M) and parvocellular (P) pathways, with their ON and OFF pathway divisions. The results indicate that there are regularities in visual cortical input beyond those that have previously been appreciated from the direct analysis of natural images. In particular, several dark/bright asymmetries provide a potential account for recently discovered asymmetries in how the brain processes visual features, such as violations of classic energy-type models. On the basis of our analysis, we expect that the dark/bright dichotomy in natural images plays a key role in the generation of both cortical and perceptual asymmetries. PMID:26020624

The Jagged Shores of Pluto Highlands

NASA Image and Video Library

2016-06-09

This enhanced color view from NASA's New Horizons spacecraft zooms in on the southeastern portion of Pluto's great ice plains, where at lower right the plains border rugged, dark highlands informally named Krun Macula. Krun Macula -- Krun is the lord of the underworld in the Mandaean religion, and a macula is a dark feature on a planetary surface -- is believed to get its dark red color from tholins, complex molecules found across Pluto. Krun Macula rises 1.5 miles (2.5 kilometers) above the surrounding plain -- informally named Sputnik Planum -- and is scarred by clusters of connected, roughly circular pits that typically reach between 5 and 8 miles (8 and 13 kilometers) across, and up to 1.5 miles (2.5 kilometers) deep. At the boundary with Sputnik Planum, these pits form deep valleys reaching more than 25 miles (40 kilometers) long, 12.5 miles (20 kilometers) wide and almost 2 miles (3 kilometers) deep (almost twice as deep as the Grand Canyon in Arizona), and have floors covered with nitrogen ice. New Horizons scientists think these pits may have formed through surface collapse, although what may have prompted such a collapse is a mystery. This scene was created using three separate observations made by New Horizons in July 2015. The right half of the image is composed of 260 feet- (80 meter-) per-pixel data from the Long Range Reconnaissance Imager (LORRI), obtained at 9,850 miles (15,850 kilometers) from Pluto, about 23 minutes before New Horizons' closest approach. The left half is composed of 410 feet- (125 meter-) per-pixel LORRI data, obtained about six minutes earlier, with New Horizons 15,470 miles (24,900 kilometers) from Pluto. These data respectively represent portions of the highest- and second-highest-resolution observations obtained by New Horizons in the Pluto system. The entire scene was then colorized using 2230 feet- (680 meter-) per-pixel data from New Horizons' Ralph/Multispectral Visual Imaging Camera (MVIC), obtained at 21,100 miles (33,900 kilometers) from Pluto, about 45 minutes before closest approach. http://photojournal.jpl.nasa.gov/catalog/PIA20732

The Jagged Shores of Pluto Highlands

NASA Image and Video Library

2016-06-09

This enhanced color view from NASA's New Horizons spacecraft zooms in on the southeastern portion of Pluto's great ice plains, where at lower right the plains border rugged, dark highlands informally named Krun Macula. Krun Macula -- Krun is the lord of the underworld in the Mandaean religion, and a macula is a dark feature on a planetary surface -- is believed to get its dark red color from tholins, complex molecules found across Pluto. Krun Macula rises 1.5 miles (2.5 kilometers) above the surrounding plain -- informally named Sputnik Planum -- and is scarred by clusters of connected, roughly circular pits that typically reach between 5 and 8 miles (8 and 13 kilometers) across, and up to 1.5 miles (2.5 kilometers) deep. At the boundary with Sputnik Planum, these pits form deep valleys reaching more than 25 miles (40 kilometers) long, 12.5 miles (20 kilometers) wide and almost 2 miles (3 kilometers) deep (almost twice as deep as the Grand Canyon in Arizona), and have floors covered with nitrogen ice. New Horizons scientists think these pits may have formed through surface collapse, although what may have prompted such a collapse is a mystery. This scene was created using three separate observations made by New Horizons in July 2015. The right half of the image is composed of 260 feet- (80 meter-) per-pixel data from the Long Range Reconnaissance Imager (LORRI), obtained at 9,850 miles (15,850 kilometers) from Pluto, about 23 minutes before New Horizons' closest approach. The left half is composed of 410 feet- (125 meter-) per-pixel LORRI data, obtained about six minutes earlier, with New Horizons 15,470 miles (24,900 kilometers) from Pluto. These data respectively represent portions of the highest- and second-highest-resolution observations obtained by New Horizons in the Pluto system. The entire scene was then colorized using 2230 feet- (680 meter-) per-pixel data from New Horizons' Ralph/Multispectral Visual Imaging Camera (MVIC), obtained at 21,100 miles (33,900 kilometers) from Pluto, about 45 minutes before closest approach. http://photojournal.jpl.nasa.gov/catalog/PIA20733

Hunting dark matter gamma-ray lines with the Fermi LAT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vertongen, Gilles; Weniger, Christoph, E-mail: gilles.vertongen@desy.de, E-mail: weniger@mppmu.mpg.de

2011-05-01

Monochromatic photons could be produced in the annihilation or decay of dark matter particles. At high energies, the search for such line features in the cosmic gamma-ray spectrum is essentially background free because plausible astrophysical processes are not expected to produce such a signal. The observation of a gamma-ray line would hence be a 'smoking-gun' signature for dark matter, making the search for such signals particularly attractive. Among the different dark matter models predicting gamma-ray lines, the local supersymmetric extension of the standard model with small R-parity violation and gravitino LSP is of particular interest because it provides a frameworkmore » where primordial nucleosynthesis, gravitino dark matter and thermal leptogenesis are naturally consistent. Using the two-years Fermi LAT data, we present a dedicated search for gamma-ray lines coming from dark matter annihilation or decay in the Galactic halo. Taking into account the full detector response, and using a binned profile likelihood method, we search for significant line features in the energy spectrum of the diffuse flux observed in different regions of the sky. No evidence for a line signal at the 5σ level is found for photon energies between 1 and 300 GeV, and conservative bounds on dark matter decay rates and annihilation cross sections are presented. Implications for gravitino dark matter in presence of small R-parity violation are discussed, as well as the impact of our results on the prospect for seeing long-lived neutralinos or staus at the LHC.« less

Dissipative hidden sector dark matter

NASA Astrophysics Data System (ADS)

Foot, R.; Vagnozzi, S.

2015-01-01

A simple way of explaining dark matter without modifying known Standard Model physics is to require the existence of a hidden (dark) sector, which interacts with the visible one predominantly via gravity. We consider a hidden sector containing two stable particles charged under an unbroken U (1 )' gauge symmetry, hence featuring dissipative interactions. The massless gauge field associated with this symmetry, the dark photon, can interact via kinetic mixing with the ordinary photon. In fact, such an interaction of strength ε ˜10-9 appears to be necessary in order to explain galactic structure. We calculate the effect of this new physics on big bang nucleosynthesis and its contribution to the relativistic energy density at hydrogen recombination. We then examine the process of dark recombination, during which neutral dark states are formed, which is important for large-scale structure formation. Galactic structure is considered next, focusing on spiral and irregular galaxies. For these galaxies we modeled the dark matter halo (at the current epoch) as a dissipative plasma of dark matter particles, where the energy lost due to dissipation is compensated by the energy produced from ordinary supernovae (the core-collapse energy is transferred to the hidden sector via kinetic mixing induced processes in the supernova core). We find that such a dynamical halo model can reproduce several observed features of disk galaxies, including the cored density profile and the Tully-Fisher relation. We also discuss how elliptical and dwarf spheroidal galaxies could fit into this picture. Finally, these analyses are combined to set bounds on the parameter space of our model, which can serve as a guideline for future experimental searches.

Dark and Bright Terrains of Pluto

NASA Image and Video Library

2015-07-10

These circular maps shows the distribution of Pluto's dark and bright terrains as revealed by NASA's New Horizons mission prior to July 4, 2015. Each map is an azimuthal equidistant projection centered on the north pole, with latitude and longitude indicated. Both a gray-scale and color version are shown. The gray-scale version is based on 7 days of panchromatic imaging from the Long Range Reconnaissance Imager (LORRI), whereas the color version uses the gray-scale base and incorporates lower-resolution color information from the Multi-spectral Visible Imaging Camera (MVIC), part of the Ralph instrument. The color version is also shown in a simple cylindrical projection in PIA19700. In these maps, the polar bright terrain is surrounded by a somewhat darker polar fringe, one whose latitudinal position varies strongly with longitude. Especially striking are the much darker regions along the equator. A broad dark swath ("the whale") stretches along the equator from approximately 20 to 160 degrees of longitude. Several dark patches appear in a regular sequence centered near 345 degrees of longitude. A spectacular bright region occupies Pluto's mid-latitudes near 180 degrees of longitude, and stretches southward over the equator. New Horizons' closest approach to Pluto will occur near this longitude, which will permit high-resolution visible imaging and compositional mapping of these various regions. http://photojournal.jpl.nasa.gov/catalog/PIA19706

The Primordial Inflation Polarization Explorer: Science from Circular Polarization Measurements

NASA Astrophysics Data System (ADS)

Switzer, Eric; Ade, P.; Benford, D. J.; Bennett, C. L.; Chuss, D. T.; Dotson, J. L.; Eimer, J.; Fixsen, D. J.; Halpern, M.; Hinshaw, G. F.; Irwin, K.; Jhabvala, C.; Johnson, B.; Kogut, A. J.; Lazear, J.; Mirel, P.; Moseley, S. H.; Staguhn, J.; Tucker, C. E.; Weston, A.; Wollack, E.

2014-01-01

The Primordial Inflation Polarization Explorer (PIPER) is a balloon-borne CMB polarimeter designed to constrain the B-mode signature of cosmological inflation. Sequential one-day flights from Northern- and Southern- Hemisphere sites will yield maps of Stokes I, Q, U and V at 200, 270, 350 and 600 GHz over 85% of the sky. The full optical path is cooled to 1.5 K by liquid helium in the ARCADE bucket dewar, and a variable-delay polarization modulator (VPM) at the front of the optics modulates the polarization response. Independent Q and U cameras each have two 32x40 Transition Edge Sensor array receivers. In addition to its primary inflationary science goal, PIPER will also measure the circular (Stokes V) polarization to a depth similar to that of the primary linear polarization. The circular polarization has received relatively little attention in large-area surveys, with constraints from the 1980’s and recent results by the Milan Polarimeter. Astrophysical circular polarization is generally tied to the presence of magnetic fields, either in relativistic plasmas or Zeeman splitting of resonances. These effects are thought to be undetectable at PIPER's frequencies and resolution, despite the depth. The expectation of a null result makes the deep Stokes V map a good cross-check for experimental systematics. More fundamentally, the fact that the sky is expected to be dark in Stokes V makes it a sector sensitive to processes such as Lorentz-violating terms in the standard model or magnetic fields in the CMB era.

Lessons from the Auriga discs: the hunt for the Milky Way's ex situ disc is not yet over

NASA Astrophysics Data System (ADS)

Gómez, Facundo A.; Grand, Robert J. J.; Monachesi, Antonela; White, Simon D. M.; Bustamante, Sebastian; Marinacci, Federico; Pakmor, Rüdiger; Simpson, Christine M.; Springel, Volker; Frenk, Carlos S.

2017-12-01

We characterize the contribution from accreted material to the galactic discs of the Auriga Project, a set of high-resolution magnetohydrodynamic cosmological simulations of late-type galaxies performed with the moving-mesh code AREPO. Our goal is to explore whether a significant accreted (or ex situ) stellar component in the Milky Way disc could be hidden within the near-circular orbit population, which is strongly dominated by stars born in situ. One-third of our models shows a significant ex situ disc but this fraction would be larger if constraints on orbital circularity were relaxed. Most of the ex situ material (≳50 per cent) comes from single massive satellites (>6 × 1010 M⊙). These satellites are accreted with a wide range of infall times and inclination angles (up to 85°). Ex situ discs are thicker, older and more metal poor than their in situ counterparts. They show a flat median age profile, which differs from the negative gradient observed in the in situ component. As a result, the likelihood of identifying an ex situ disc in samples of old stars on near-circular orbits increases towards the outskirts of the disc. We show three examples that, in addition to ex situ discs, have a strongly rotating dark matter component. Interestingly, two of these ex situ stellar discs show an orbital circularity distribution that is consistent with that of the in situ disc. Thus, they would not be detected in typical kinematic studies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Behroozi, Peter S.; Wechsler, Risa H.; Lu, Yu

We find that infalling dark matter halos (i.e., the progenitors of satellite halos) begin losing mass well outside the virial radius of their eventual host halos. The peak mass occurs at a range of clustercentric distances, with median and 68th percentile range ofmore » $$1.8^{+2.3}_{-1.0} \\,R_\\mathrm{vir,host}$$ for progenitors of z = 0 satellites. The peak circular velocity for infalling halos occurs at significantly larger distances ($$3.7^{+3.3}_{-2.2} \\,R_\\mathrm{vir,host}$$ at z = 0). This difference arises because different physical processes set peak circular velocity (typically, ~1:5 and larger mergers which cause transient circular velocity spikes) and peak mass (typically, smooth accretion) for infalling halos. We find that infalling halos also stop having significant mergers well before they enter the virial radius of their eventual hosts. Mergers larger than a 1:40 ratio in halo mass end for infalling halos at similar clustercentric distances (~1.9 R vir, host) as the end of overall mass accretion. However, mergers larger than 1:3 typically end for infalling halos at more than four virial radial away from their eventual hosts. This limits the ability of mergers to affect quenching and morphology changes in clusters. We also note that the transient spikes which set peak circular velocity may lead to issues with abundance matching on that parameter, including unphysical galaxy stellar mass growth profiles near clusters; we propose a simple observational test to check if a better halo proxy for galaxy stellar mass exists.« less

Discrimination of Oil Slicks and Lookalikes in Polarimetric SAR Images Using CNN.

PubMed

Guo, Hao; Wu, Danni; An, Jubai

2017-08-09

Oil slicks and lookalikes (e.g., plant oil and oil emulsion) all appear as dark areas in polarimetric Synthetic Aperture Radar (SAR) images and are highly heterogeneous, so it is very difficult to use a single feature that can allow classification of dark objects in polarimetric SAR images as oil slicks or lookalikes. We established multi-feature fusion to support the discrimination of oil slicks and lookalikes. In the paper, simple discrimination analysis is used to rationalize a preferred features subset. The features analyzed include entropy, alpha, and Single-bounce Eigenvalue Relative Difference (SERD) in the C-band polarimetric mode. We also propose a novel SAR image discrimination method for oil slicks and lookalikes based on Convolutional Neural Network (CNN). The regions of interest are selected as the training and testing samples for CNN on the three kinds of polarimetric feature images. The proposed method is applied to a training data set of 5400 samples, including 1800 crude oil, 1800 plant oil, and 1800 oil emulsion samples. In the end, the effectiveness of the method is demonstrated through the analysis of some experimental results. The classification accuracy obtained using 900 samples of test data is 91.33%. It is here observed that the proposed method not only can accurately identify the dark spots on SAR images but also verify the ability of the proposed algorithm to classify unstructured features.

Discrimination of Oil Slicks and Lookalikes in Polarimetric SAR Images Using CNN

PubMed Central

An, Jubai

2017-01-01

Oil slicks and lookalikes (e.g., plant oil and oil emulsion) all appear as dark areas in polarimetric Synthetic Aperture Radar (SAR) images and are highly heterogeneous, so it is very difficult to use a single feature that can allow classification of dark objects in polarimetric SAR images as oil slicks or lookalikes. We established multi-feature fusion to support the discrimination of oil slicks and lookalikes. In the paper, simple discrimination analysis is used to rationalize a preferred features subset. The features analyzed include entropy, alpha, and Single-bounce Eigenvalue Relative Difference (SERD) in the C-band polarimetric mode. We also propose a novel SAR image discrimination method for oil slicks and lookalikes based on Convolutional Neural Network (CNN). The regions of interest are selected as the training and testing samples for CNN on the three kinds of polarimetric feature images. The proposed method is applied to a training data set of 5400 samples, including 1800 crude oil, 1800 plant oil, and 1800 oil emulsion samples. In the end, the effectiveness of the method is demonstrated through the analysis of some experimental results. The classification accuracy obtained using 900 samples of test data is 91.33%. It is here observed that the proposed method not only can accurately identify the dark spots on SAR images but also verify the ability of the proposed algorithm to classify unstructured features. PMID:28792477

Direct detection of light dark matter and solar neutrinos via color center production in crystals

NASA Astrophysics Data System (ADS)

Budnik, Ranny; Cheshnovsky, Ori; Slone, Oren; Volansky, Tomer

2018-07-01

We propose a new low-threshold direct-detection concept for dark matter and for coherent nuclear scattering of solar neutrinos, based on the dissociation of atoms and subsequent creation of color center type defects within a lattice. The novelty in our approach lies in its ability to detect single defects in a macroscopic bulk of material. This class of experiments features ultra-low energy thresholds which allows for the probing of dark matter as light as O (10) MeV through nuclear scattering. Another feature of defect creation in crystals is directional information, which presents as a spectacular signal and a handle on background reduction in the form of daily modulation of the interaction rate. We discuss the envisioned setup and detection technique, as well as background reduction. We further calculate the expected rates for dark matter and solar neutrinos in two example crystals for which available data exists, demonstrating the prospective sensitivity of such experiments.

ASI aurora search: an attempt of intelligent image processing for circular fisheye lens.

PubMed

Yang, Xi; Gao, Xinbo; Song, Bin; Wang, Nannan; Yang, Dong

2018-04-02

The circular fisheye lens exhibits an approximately 180° angular field-of-view (FOV), which is much larger than that of an ordinary lens. Thus, images captured with a circular fisheye lens are distributed non-uniformly with spherical deformation. Along with the fast development of deep neural networks for normal images, how to apply it to achieve intelligent image processing for a circular fisheye lens is a new task of significant importance. In this paper, we take the aurora images captured with all-sky-imagers (ASI) as a typical example. By analyzing the imaging principle of ASI and the magnetic characteristics of the aurora, a deformed region division (DRD) scheme is proposed to replace the region proposals network (RPN) in the advanced mask regional convolutional neural network (Mask R-CNN) framework. Thus, each image can be regarded as a "bag" of deformed regions represented with CNN features. After clustering all CNN features to generate a vocabulary, each deformed region is quantified to its nearest center for indexing. On the stage of an online search, a similarity score is computed by measuring the distances between regions in the query image and all regions in the data set, and the image with the highest value is outputted as the top rank search result. Experimental results show that the proposed method greatly improves the search accuracy and efficiency, demonstrating that it is a valuable attempt of intelligent image processing for circular fisheye lenses.

Lake Superior as seen from Skylab

NASA Image and Video Library

1974-01-06

SL4-139-3953 (7 Jan. 1974) --- An oblique view of a portion of the Middle West looking northeastward toward Lake Superior and Ontario, Canada, as seen from the Skylab space station in Earth orbit. This picture was taken by one of the Skylab 4 crewmen with a hand-held 70mm Hasselblad camera using a 100mm lens. Most of the land mass in the foreground is Wisconsin. Iowa is in the lower left corner. Minnesota is at left and upper left. Ontario is in the far right background. Michigan is at right center. Note the circular-shaped feature at center left which was first observed by the Skylab 4 crewmen. The feature is 85 kilometers (55 miles) in diameter, and it is centered near 91.5 degrees west longitude and 44.5 degrees north latitude. The Mississippi River Valley forms the southwest side of the circular feature. The City of La Crosse, Wisconsin, is just south of the near side of the circle, and the Black River completes the southern and eastern part. The City of Eau Claire is at the north edge of the circle. The most likely origin of circular features of this magnitude are (1) volcanic, (2) structural, or (3) meteorite impact. The feature is not volcanic -- the rocks are the wrong type. Possibly it is structural, formed by slight warping of layered rocks into a basin or dome, followed by erosion of all but the most subtle trace of the structure. The feature could be a severely eroded meteorite impact crater. If so, a thorough study of the area may yield evidence of the extreme pressure and temperature the rocks were subjected to by the shock of an impacting meteorite. Photo credit: NASA

Catching the Drift: Simulating Dark Spots and Bright Companions on the Ice Giants

NASA Astrophysics Data System (ADS)

LeBeau, R. P., Jr.; Koutas, N.; Palotai, C. J.; Bhure, S.; Hadland, N.; Sankar, R.

2017-12-01

Starting with the original Great Dark Spot (GDS-89) observed by Voyager 2, roughly a half-dozen large geophysical vortices have been observed on the Ice Giants, the most recent in 2015 on Neptune (Wong et al., 2016). While the presumption is that these Dark Spots are similar in structure to the large vortices on Jupiter, in some cases the Dark Spots exhibit dynamical motions such as the shape oscillations and latitudinal drift of GDS-89 (Smith et al., 1989) or the possible vortex drift underlying the "Berg" cloud feature on Uranus (de Pater et al., 2011). Others, like NGDS-1998, have remained largely stable across years of observation (Sromovsky et al., 2002). In addition, several of the vortices are linked with Bright Companion clouds which are presumed to be orographic features formed as the atmosphere rises over the vortex. The numerical simulation of these features has evolved with each new observation. Prior simulations have captured the forms if not all the specifics of observed Dark Spot dynamics (LeBeau and Dowling, 1998; LeBeau and Deng, 2006); likewise, numerical models have demonstrated the potential for orographic companion clouds (Stratman et al., 2001). However, as more knowledge of the Ice Giant atmospheres has been obtained, it has proven challenging to generate consistent dynamical models that capture the details of the Dark Spot variations and are physically consistent with known observations. In particular, current simulations indicate that the addition of a companion cloud can alter the vortex dynamics, both in terms of drift and oscillations. Given the impact of these clouds, a new parametric simulation study uses an updated microphysics model, implemented in the Explicit Planetary Isentropic Coordinate (EPIC) general circulation model (Dowling et al., 1998, 2006), to account for the condensation of methane and hydrogen sulfide (Palotai et al., 2016). Simulations of dark spots with varying sizes, strengths, and locations are conducted with different microphysical parameters such as the deep abundance and ambient supersaturation. Simulations are evaluated in terms of vortex stability and drift rate along with companion cloud formation with the goal of improving our understanding of the underlying physics driving the varying behaviors of the observed Dark Spots.

Asymmetric dark matter, baryon asymmetry and lepton number violation

NASA Astrophysics Data System (ADS)

Frandsen, Mads T.; Hagedorn, Claudia; Huang, Wei-Chih; Molinaro, Emiliano; Päs, Heinrich

2018-07-01

We study the effect of lepton number violation (LNV) on baryon asymmetry, generated in the early Universe, in the presence of a dark sector with a global symmetry U(1)X, featuring asymmetric dark matter (ADM). We show that in general LNV, observable at the LHC or in neutrinoless double beta decay experiments, cannot wash out a baryon asymmetry generated at higher scales, unlike in scenarios without such dark sector. An observation of LNV at the TeV scale may thus support ADM scenarios. Considering several models with different types of dark matter (DM), we find that the DM mass is of the order of a few GeV or below in our scenario.

Dark matter signals from Draco and Willman 1: prospects for MAGIC II and CTA

NASA Astrophysics Data System (ADS)

Bringmann, Torsten; Doro, Michele; Fornasa, Mattia

2009-01-01

The next generation of ground-based Imaging Air Cherenkov Telescopes will play an important role in indirect dark matter searches. In this article, we consider two particularly promising candidate sources for dark matter annihilation signals, the nearby dwarf galaxies Draco and Willman 1, and study the prospects of detecting such a signal for the soon-operating MAGIC II telescope system as well as for the planned installation of CTA, taking special care of describing the experimental features that affect the detectional prospects. For the first time in such studies, we fully take into account the effect of internal bremsstrahlung, which has recently been shown to considerably enhance, in some cases, the gamma-ray flux in the high energies domain where Atmospheric Cherenkov Telescopes operate, thus leading to significantly harder annihilation spectra than traditionally considered. While the detection of the spectral features introduced by internal bremsstrahlung would constitute a smoking gun signature for dark matter annihilation, we find that for most models the overall flux still remains at a level that will be challenging to detect, unless one adopts somewhat favorable descriptions of the smooth dark matter distribution in the dwarfs.

Dark Matter "Collider" from Inelastic Boosted Dark Matter.

PubMed

Kim, Doojin; Park, Jong-Chul; Shin, Seodong

2017-10-20

We propose a novel dark matter (DM) detection strategy for models with a nonminimal dark sector. The main ingredients in the underlying DM scenario are a boosted DM particle and a heavier dark sector state. The relativistic DM impinged on target material scatters off inelastically to the heavier state, which subsequently decays into DM along with lighter states including visible (standard model) particles. The expected signal event, therefore, accompanies a visible signature by the secondary cascade process associated with a recoiling of the target particle, differing from the typical neutrino signal not involving the secondary signature. We then discuss various kinematic features followed by DM detection prospects at large-volume neutrino detectors with a model framework where a dark gauge boson is the mediator between the standard model particles and DM.

Cold dark matter. 1: The formation of dark halos

NASA Technical Reports Server (NTRS)

Gelb, James M.; Bertschinger, Edmund

1994-01-01

We use numerical simulations of critically closed cold dark matter (CDM) models to study the effects of numerical resolution on observable quantities. We study simulations with up to 256(exp 3) particles using the particle-mesh (PM) method and with up to 144(exp 3) particles using the adaptive particle-particle-mesh (P3M) method. Comparisons of galaxy halo distributions are made among the various simulations. We also compare distributions with observations, and we explore methods for identifying halos, including a new algorithm that finds all particles within closed contours of the smoothed density field surrounding a peak. The simulated halos show more substructure than predicted by the Press-Schechter theory. We are able to rule out all omega = 1 CDM models for linear amplitude sigma(sub 8) greater than or approximately = 0.5 because the simulations produce too many massive halos compared with the observations. The simulations also produce too many low-mass halos. The distribution of halos characterized by their circular velocities for the P3M simulations is in reasonable agreement with the observations for 150 km/s less than or = V(sub circ) less than or = 350 km/s.

Analysis of Radar Images of Angkor, Cambodia

NASA Technical Reports Server (NTRS)

Freeman, Anthony; Hensley, Scott; Moore, Elizabeth

2000-01-01

During the 1996 AIRSAR Pacific Rim Deployment, data were collected over Angkor in Cambodia. The temples of Angkor date the succession of cities to the 9th-13th century AD, but little is known of its prehistoric habitation. A related area of archaeological debate has been the origin, spiritual meaning and use of the hydraulic constructions in the urban zone. The high resolution, multi-channel capability of AIRSAR, together with the unprecedentedly accurate topography provided by TOPSAR, offer identification and delineation of these features. Examples include previously unrecorded circular earthworks around circular village sites, detection of unrecorded earthwork dykes, reservoirs and canal features, and of temple sites located some distance from the main temple complex at Angkor.

Magnetic circular dichroism of chlorofullerenes: Experimental and computational study

NASA Astrophysics Data System (ADS)

Štěpánek, Petr; Straka, Michal; Šebestík, Jaroslav; Bouř, Petr

2016-03-01

Magnetic circular dichroism (MCD) spectra of C60Cl6, C70Cl10 and C60Cl24 were measured and interpreted using a sum-over-state (SOS) protocol exploiting time dependent density functional theory (TDDFT). Unlike for plain absorption, the MCD spectra exhibited easily recognizable features specific for each chlorinated molecule and appear as a useful tool for chlorofullerene identification. MCD spectrum of C60Cl24 was below 400 nm partially obscured due to scattering and low solubility. In all cases a finer vibrational structure of the electronic bands was observed at longer wavelengths. The TDDFT simulations provided a reasonable basis for interpretation of the most prominent spectral features.

An approach for traffic prohibition sign detection

NASA Astrophysics Data System (ADS)

Li, Qingquan; Xu, Dihong; Li, Bijun; Zeng, Zhe

2006-10-01

This paper presents an off-line traffic prohibition sign detection approach, whose core is based on combination with the color feature of traffic prohibition signs, shape feature and degree of circularity. Matlab-Image-processing toolbox is used for this purpose. In order to reduce the computational cost, a pre-processing of the image is applied before the core. Then, we employ the obvious redness attribute of prohibition signs to coarsely eliminate the non-redness image in the input data. Again, a edge-detection operator, Canny edge detector, is applied to extract the potential edge. Finally, Degree of circularity is used to verdict the traffic prohibition sign. Experimental results show that our systems offer satisfactory performance.

Northeast Arabia Terra

NASA Technical Reports Server (NTRS)

2004-01-01

9 September 2004 Northeastern Arabia Terra is a heavily eroded portion of the martian cratered highlands. Layered rock, containing filled and buried valleys and ancient impact craters, has been eroded such that these once-buried features are now partially exposed at the martian surface. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example of a field of circular and somewhat circular features that once were impact craters that were subsequently filled, buried, then exhumed to form the patterns exhibited here. The image is located near 25.6oN, 290.2oW. The image covers an area approximately 3 km (1.9 mi) across and is illuminated by sunlight from the lower left.

Neutrino mass and dark energy from weak lensing.

PubMed

Abazajian, Kevork N; Dodelson, Scott

2003-07-25

Weak gravitational lensing of background galaxies by intervening matter directly probes the mass distribution in the Universe. This distribution is sensitive to both the dark energy and neutrino mass. We examine the potential of lensing experiments to measure features of both simultaneously. Focusing on the radial information contained in a future deep 4000 deg(2) survey, we find that the expected (1-sigma) error on a neutrino mass is 0.1 eV, if the dark-energy parameters are allowed to vary. The constraints on dark-energy parameters are similarly restrictive, with errors on w of 0.09.

The DarkSide awakens

DOE PAGES

Davini, S.; Agnes, P.; Agostino, L.; ...

2016-06-09

Here, the DarkSide program at LNGS aims to perform background-free WIMP searches using two phase liquid argon time projection chambers, with the ultimate goal of covering all parameters down to the so-called neutrino floor. One of the distinct features of the program is the use of underground argon with has a reduced content of the radioactive 39Ar compared to atmospheric argon. The DarkSide Collaboration is currently operating the DarkSide-50 experiment, the first such WIMP detector using underground argon. Operations with underground argon indicate a suppression of 39Ar by a factor (1.4 ± 0.2) × 10 3 relative to atmospheric argon.more » The new results obtained with DarkSide-50 and the plans for the next steps of the DarkSide program, the 20t fiducial mass DarkSide-20k detector and the 200 t fiducial Argo, are reviewed in this proceedings.« less

The DarkSide awakens

NASA Astrophysics Data System (ADS)

Davini, S.; Agnes, P.; Agostino, L.; Albuquerque, I. F. M.; Alexander, T.; Alton, A. K.; Arisaka, K.; Back, H. O.; Baldin, B.; Biery, K.; Bonfini, G.; Bossa, M.; Bottino, B.; Brigatti, A.; Brodsky, J.; Budano, F.; Bussino, S.; Cadeddu, M.; Cadonati, L.; Cadoni, M.; Calaprice, F.; Canci, N.; Candela, A.; Cao, H.; Cariello, M.; Carlini, M.; Catalanotti, S.; Cavalcante, P.; Chepurnov, A.; Cocco, A. G.; Covone, G.; D'Angelo, D.; D'Incecco, M.; De Cecco, S.; De Deo, M.; De Vincenzi, M.; Derbin, A.; Devoto, A.; Di Eusanio, F.; Di Pietro, G.; Edkins, E.; Empl, A.; Fan, A.; Fiorillo, G.; Fomenko, K.; Foster, G.; Franco, D.; Gabriele, F.; Galbiati, C.; Giganti, C.; Goretti, A. M.; Granato, F.; Grandi, L.; Gromov, M.; Guan, M.; Guardincerri, Y.; Hackett, B. R.; Herner, K. R.; Hungerford, E. V.; Ianni, Aldo; Ianni, Andrea; James, I.; Jollet, C.; Keeter, K.; Kendziora, C. L.; Kobychev, V.; Koh, G.; Korablev, D.; Korga, G.; Kubankin, A.; Li, X.; Lissia, M.; Lombardi, P.; Luitz, S.; Ma, Y.; Machulin, I. N.; Mandarano, A.; Mari, S. M.; Maricic, J.; Marini, L.; Martoff, C. J.; Meregaglia, A.; Meyers, P. D.; Miletic, T.; Milincic, R.; Montanari, D.; Monte, A.; Montuschi, M.; Monzani, M. E.; Mosteiro, P.; Mount, B. J.; Muratova, V. N.; Musico, P.; Napolitano, J.; Orsini, M.; Ortica, F.; Pagani, L.; Pallavicini, M.; Pantic, E.; Parmeggiano, S.; Pelczar, K.; Pelliccia, N.; Perasso, S.; Pocar, A.; Pordes, S.; Pugachev, D. A.; Qian, H.; Randle, K.; Ranucci, G.; Razeto, A.; Reinhold, B.; Renshaw, A. L.; Romani, A.; Rossi, B.; Rossi, N.; Rountree, S. D.; Sablone, D.; Saggese, P.; Saldanha, R.; Sands, W.; Sangiorgio, S.; Savarese, C.; Segreto, E.; Semenov, D. A.; Shields, E.; Singh, P. N.; Skorokhvatov, M. D.; Smirnov, O.; Sotnikov, A.; Stanford, C.; Suvorov, Y.; Tartaglia, R.; Tatarowicz, J.; Testera, G.; Tonazzo, A.; Trinchese, P.; Unzhakov, E. V.; Vishneva, A.; Vogelaar, B.; Wada, M.; Walker, S.; Wang, H.; Wang, Y.; Watson, A. W.; Westerdale, S.; Wilhelmi, J.; Wojcik, M. M.; Xiang, X.; Xu, J.; Yang, C.; Yoo, J.; Zavatarelli, S.; Zec, A.; Zhong, W.; Zhu, C.; Zuzel, G.

2016-05-01

The DarkSide program at LNGS aims to perform background-free WIMP searches using two phase liquid argon time projection chambers, with the ultimate goal of covering all parameters down to the so-called neutrino floor. One of the distinct features of the program is the use of underground argon with has a reduced content of the radioactive 39Ar compared to atmospheric argon. The DarkSide Collaboration is currently operating the DarkSide-50 experiment, the first such WIMP detector using underground argon. Operations with underground argon indicate a suppression of 39Ar by a factor (1.4 ± 0.2) × 103 relative to atmospheric argon. The new results obtained with DarkSide-50 and the plans for the next steps of the DarkSide program, the 20t fiducial mass DarkSide-20k detector and the 200 t fiducial Argo, are reviewed in this proceedings.

Constraints on Leptophilic Dark Matter from the AMS-02 Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cavasonza, Leila Ali; Gast, Henning; Schael, Stefan

2017-04-10

The annihilation of dark matter particles in the Galactic halo of the Milky Way may lead to cosmic ray signatures that can be probed by the AMS-02 experiment, which has measured the composition and fluxes of charged cosmic rays with unprecedented precision. Given the absence of characteristic spectral features in the electron and positron fluxes measured by AMS-02, we derive upper limits on the dark matter annihilation cross section for leptophilic dark matter models. Our limits are based on a new background model that describes all recent measurements of the energy spectra of cosmic-ray positrons and electrons. For thermal darkmore » matter relics, we can exclude dark matter masses below about 100 GeV. We include the radiation of electroweak gauge bosons in the dark matter annihilation process and compute the antiproton signal that can be expected within leptophilic dark matter models.« less

Galaxy rotation curves via conformal factors

NASA Astrophysics Data System (ADS)

Sporea, Ciprian A.; Borowiec, Andrzej; Wojnar, Aneta

2018-04-01

We propose a new formula to explain circular velocity profiles of spiral galaxies obtained from the Starobinsky model in the Palatini formalism. It is based on the assumption that the gravity can be described by two conformally related metrics: one of them is responsible for the measurement of distances, while the other, the so-called dark metric, is responsible for a geodesic equation and therefore can be used for the description of the velocity profile. The formula is tested against a subset of galaxies taken from the HI Nearby Galaxy Survey (THINGS).

Soliton instabilities and vortex street formation in a polariton quantum fluid.

PubMed

Grosso, G; Nardin, G; Morier-Genoud, F; Léger, Y; Deveaud-Plédran, B

2011-12-09

Exciton polaritons have been shown to be an optimal system in order to investigate the properties of bosonic quantum fluids. We report here on the observation of dark solitons in the wake of engineered circular obstacles and their decay into streets of quantized vortices. Our experiments provide a time-resolved access to the polariton phase and density, which allows for a quantitative study of instabilities of freely evolving polaritons. The decay of solitons is quantified and identified as an effect of disorder-induced transverse perturbations in the dissipative polariton gas.

Dark plasmonic breathing modes in silver nanodisks.

PubMed

Schmidt, Franz-Philipp; Ditlbacher, Harald; Hohenester, Ulrich; Hohenau, Andreas; Hofer, Ferdinand; Krenn, Joachim R

2012-11-14

We map the complete plasmonic spectrum of silver nanodisks by electron energy loss spectroscopy and show that the mode which couples strongest to the electron beam has radial symmetry with no net dipole moment. Therefore, this mode does not couple to light and has escaped from observation in optical experiments. This radial breathing mode has the character of an extended two-dimensional surface plasmon with a wavenumber determined by the circular disk confinement. Its strong near fields can impact the hybridization in coupled plasmonic nanoparticles as well as couplings with nearby quantum emitters.

Galaxy rotation curves via conformal factors.

PubMed

Sporea, Ciprian A; Borowiec, Andrzej; Wojnar, Aneta

2018-01-01

We propose a new formula to explain circular velocity profiles of spiral galaxies obtained from the Starobinsky model in the Palatini formalism. It is based on the assumption that the gravity can be described by two conformally related metrics: one of them is responsible for the measurement of distances, while the other, the so-called dark metric, is responsible for a geodesic equation and therefore can be used for the description of the velocity profile. The formula is tested against a subset of galaxies taken from the HI Nearby Galaxy Survey (THINGS).

Detecting Circular RNAs by RNA Fluorescence In Situ Hybridization.

PubMed

Zirkel, Anne; Papantonis, Argyris

2018-01-01

Fluorescence in situ hybridization (FISH) coupled to high-resolution microscopy is a powerful method for analyzing the subcellular localization of RNA. However, the detection of circular RNAs (circRNAs) using microscopy is challenging because the only feature of a circRNA that can be used for the probe design is its junction. Circular RNAs are expressed at varying levels, and for their efficient monitoring by FISH, background fluorescence levels need to be kept low. Here, we describe a FISH protocol coupled to high-precision localizations using a single fluorescently labeled probe spanning the circRNA junction; this allows circRNA detection in mammalian cells with high signal-to-noise ratios.

Circular dichroism in photoelectron images from aligned nitric oxide molecules

DOE PAGES

Sen, Ananya; Pratt, S. T.; Reid, K. L.

2017-05-03

We have used velocity map photoelectron imaging to study circular dichroism of the photoelectron angular distributions (PADs) of nitric oxide following two-color resonanceenhanced two-photon ionization via selected rotational levels of the A 2Σ +, v' = 0 state. By using a circularly polarized pump beam and a counter-propagating, circularly polarized probe beam, cylindrical symmetry is preserved in the ionization process, and the images can be reconstructed using standard algorithms. The VMI set up enables individual ion rotational states to be resolved with excellent collection efficiency, rendering the measurements considerably simpler to perform than previous measurements conducted with a conventional photoelectronmore » spectrometer. The results demonstrate that circular dichroism is observed even when cylindrical symmetry is maintained, and serve as a reminder that dichroism is a general feature of the multiphoton ionization of atoms and molecules. Furthermore, the observed PADs are in good agreement with calculations based on parameters extracted from previous experimental results obtained by using a time-offlight electron spectrometer.« less

Circular dichroism in photoelectron images from aligned nitric oxide molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sen, Ananya; Pratt, S. T.; Reid, K. L.

We have used velocity map photoelectron imaging to study circular dichroism of the photoelectron angular distributions (PADs) of nitric oxide following two-color resonanceenhanced two-photon ionization via selected rotational levels of the A 2Σ +, v' = 0 state. By using a circularly polarized pump beam and a counter-propagating, circularly polarized probe beam, cylindrical symmetry is preserved in the ionization process, and the images can be reconstructed using standard algorithms. The VMI set up enables individual ion rotational states to be resolved with excellent collection efficiency, rendering the measurements considerably simpler to perform than previous measurements conducted with a conventional photoelectronmore » spectrometer. The results demonstrate that circular dichroism is observed even when cylindrical symmetry is maintained, and serve as a reminder that dichroism is a general feature of the multiphoton ionization of atoms and molecules. Furthermore, the observed PADs are in good agreement with calculations based on parameters extracted from previous experimental results obtained by using a time-offlight electron spectrometer.« less

Cerberus

NASA Technical Reports Server (NTRS)

2002-01-01

(Released 24 April 2002) The Science The Cerberus feature is a relatively dark region at the southeastern edge of the huge Elysium Mons volcanic complex. It was visible to early astronomers of Mars because it was a distinctive dark spot on a large bright region of the planet. Today we recognize that the Cerberus region encompasses a range of geologic terrains from relatively young and smooth lava flows to the very rugged, ancient eroded landscape seen in this THEMIS image. The Cerberus feature has also proven to be ephemeral. Compared to just 20 years ago when the Viking orbiter instruments viewed the planet, the Cerberus feature has shrunk down from its original length of roughly 1000 kilometers to just a few isolated dark splotches of just a few 100 kilometers. This is testament to the active eolian environment on Mars where global dust storms can lift and then later deposit significant amounts of dust, brightening formerly dark surfaces. The THEMIS image occurs in a portion of Cerberus that remains relatively dark and dust-free although in the bottommost portion of the image are faint, criss-crossing lines that likely are dust devil tracks. The abundant dune-like features covering many of the low, smooth surfaces are similar to those found in many places across the planet. They are evidence of the interaction of wind and movable particles at the surface but not necessarily in today's environment. In many other places on Mars they are clearly inactive; relicts of a different climate. The Story Hellhound of Greek mythology, Cerberus was the three-headed, dragon-tailed dog that stood guard at the opening to the underworld. This rough-and-tumble Mars terrain looks just as fierce and foreboding. At the edge of the huge Elysium Mons volcano complex, the Cerberus area appeared as a dark spot to early Mars astronomers in an otherwise bright region of the planet. If this dark area seems somewhat hellish to your imagination too, you'll be glad to know that the Martian wind has been brightening up the area. Just twenty years ago, the Viking orbiters reached Mars for the first long-term studies of Mars up close. The Cerberus feature was then almost 600 miles long, but has now been vanquished down to few small splotches about 60 miles long. Call that a triumph of lightness upon the surface, but don't think that the force bringing back the light is gentle and kind. The Martian wind can kick up a fierce global dust storm that lifts up the bright Martian dust into the air and then blankets the surface with the brighter material as it settles down again. The ancient, eroded terrain in this image is still rather dark and dust free, so you might say it's one area where a mythical Cerberus still guards its shrinking territory. The wind teases it, however, by kicking up small, whirling dust devils that leave long, dark, scratchy tracks upon the land. Fields of dunes wrinkle the surface in places as well, but they may be permanently cemented upon the surface now, no longer able to blow and drift as they did in their younger days.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwon, Jungmi; Tamura, Motohide; Hough, James H.

Near-infrared imaging polarimetry in the J , H , and K{sub s} bands was carried out for GGD 27 in the dark cloud Lynds 291. Details of an infrared reflection nebula associated with the optical nebulosity GGD 27 and the infrared nebula GGD 27 IRS are presented. Aperture photometry of 1263 point-like sources, detected in all three bands, was used to classify them based on a color–color diagram, and the linear polarization of several hundred sources was determined, with the latter used to map the magnetic field structure around GGD 27. This field, around GGD 27 IRS, appears to bemore » associated with the extended CO outflow of IRAS 18162–2048; however, there are partly distorted or bent components in the field. The Chandrasekhar–Fermi method gives an estimate of the magnetic field strength as ∼90 μ G. A region associated with GGD 27 IRS is discovered to have a circular polarization in the range of ∼2%–11% in the K{sub s} band. The circular polarization has an asymmetric positive/negative pattern and extends out to ∼ 120″ or 1.0 pc. The circular and linear polarization patterns are explained as resulting from a combination of dense inner and fainter outer lobes, suggesting episodic outflow.« less

Sourcing dark matter and dark energy from α-attractors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, Swagat S.; Sahni, Varun; Shtanov, Yuri, E-mail: swagat@iucaa.in, E-mail: varun@iucaa.in, E-mail: shtanov@bitp.kiev.ua

In [1], Kallosh and Linde drew attention to a new family of superconformal inflationary potentials, subsequently called α-attractors [2]. The α-attractor family can interpolate between a large class of inflationary models. It also has an important theoretical underpinning within the framework of supergravity. We demonstrate that the α-attractors have an even wider appeal since they may describe dark matter and perhaps even dark energy. The dark matter associated with the α-attractors, which we call α-dark matter (αDM), shares many of the attractive features of fuzzy dark matter, with V (φ) = ½ m {sup 2}φ{sup 2}, while having none ofmore » its drawbacks. Like fuzzy dark matter, αDM can have a large Jeans length which could resolve the cusp-core and substructure problems faced by standard cold dark matter. αDM also has an appealing tracker property which enables it to converge to the late-time dark matter asymptote, ( w ) ≅ 0, from a wide range of initial conditions. It thus avoids the enormous fine-tuning problems faced by the m {sup 2}φ{sup 2} potential in describing dark matter.« less

Jupiter's non-auroral Ionosphere and Thermosphere

NASA Astrophysics Data System (ADS)

Stallard, T.; Melin, H.; Burrell, A. G.; Hsu, V.; Johnson, R.; Moore, L.; O'Donoghue, J.; Thayer, J. P.

2017-12-01

Until recently, our understanding of the non-auroral ionosphere of Jupiter was very limited. However, with the arrival of the Juno spacecraft at Jupiter, we have begun to revise past observations of this region, as well as utilizing modern telescope facilities, in order to reveal a complex array of ionospheric features that show strong coupling with both the local magnetic field and dynamics within the underlying thermosphere. The first feature that was identified was an apparent `Great Dark Spot' in the sub-auroral ionosphere, almost as large as the Great Red Spot. This was observed well away from the northern magnetic pole, mapping to only 2.4 jovian radii. Spectra of the feature showed that it was produced by a 150K cooling in the thermosphere. However, images taken between 1995-2000 showed this feature was consistently observed over two decades at similar magnetic longitudes, but appeared to vary in size, morphology and exact location on a timescale of only days. This suggests that the Great Dark Spot is a large thermospheric vortex driven by auroral heating, similar to transitory features observed at Earth, forming in sub-auroral regions during periods of active aurora. Careful analysis of the Jupiter images then allowed us to measure ionospheric emission down to the equator. This revealed the location of Jupiter's magnetic equator for the first time, appearing as a dark sinusoidal ribbon. This feature appears to be produced as photo-electrons are pushed poleward of the equator when magnetic fields are parallel with the planet's surface, a different process than the dominant plasma fountain that drives Earth's equatorial anomaly. Also revealed were a series of dark spots. Recent Juno magnetometer measurements show that two of these spots appear in regions of high radial magnetic field, suggesting that these regions of the ionosphere are shielded, an inversion of the same process that drives higher ionization in the South Atlantic Anomaly.

Circular RNAs are abundant, conserved, and associated with ALU repeats

PubMed Central

Jeck, William R.; Sorrentino, Jessica A.; Wang, Kai; Slevin, Michael K.; Burd, Christin E.; Liu, Jinze; Marzluff, William F.; Sharpless, Norman E.

2013-01-01

Circular RNAs composed of exonic sequence have been described in a small number of genes. Thought to result from splicing errors, circular RNA species possess no known function. To delineate the universe of endogenous circular RNAs, we performed high-throughput sequencing (RNA-seq) of libraries prepared from ribosome-depleted RNA with or without digestion with the RNA exonuclease, RNase R. We identified >25,000 distinct RNA species in human fibroblasts that contained non-colinear exons (a “backsplice”) and were reproducibly enriched by exonuclease degradation of linear RNA. These RNAs were validated as circular RNA (ecircRNA), rather than linear RNA, and were more stable than associated linear mRNAs in vivo. In some cases, the abundance of circular molecules exceeded that of associated linear mRNA by >10-fold. By conservative estimate, we identified ecircRNAs from 14.4% of actively transcribed genes in human fibroblasts. Application of this method to murine testis RNA identified 69 ecircRNAs in precisely orthologous locations to human circular RNAs. Of note, paralogous kinases HIPK2 and HIPK3 produce abundant ecircRNA from their second exon in both humans and mice. Though HIPK3 circular RNAs contain an AUG translation start, it and other ecircRNAs were not bound to ribosomes. Circular RNAs could be degraded by siRNAs and, therefore, may act as competing endogenous RNAs. Bioinformatic analysis revealed shared features of circularized exons, including long bordering introns that contained complementary ALU repeats. These data show that ecircRNAs are abundant, stable, conserved and nonrandom products of RNA splicing that could be involved in control of gene expression. PMID:23249747

Propeller, Light and Dark

NASA Image and Video Library

2013-06-24

NASA Cassini spacecraft has been monitoring propeller features such as Bleriot since their discovery. The bright dash-like features are regions where a small moonlet has caused ring particles to cluster together more densely than normal.

Modulation of spectral intensity, polarization and coherence of a stochastic electromagnetic beam.

PubMed

Wu, Gaofeng; Cai, Yangjian

2011-04-25

Analytical formula for the cross-spectral density matrix of a stochastic electromagnetic Gaussian Schell-model (EGSM) beam truncated by a circular phase aperture propagating in free space is derived with the help of a tensor method, which provides a reliable and fast way for studying the propagation and transformation of a truncated EGSM beam. Statistics properties, such as the spectral intensity, the degree of coherence, the degree of polarization and the polarization ellipse of a truncated EGSM beam in free space are studied numerically. The propagation factor of a truncated EGSM beam is also analyzed. Our numerical results show that we can modulate the spectral intensity, the polarization, the coherence and the propagation factor of an EGSM beam by a circular phase aperture. It is found that the phase aperture can be used to shape the beam profile of an EGSM beam and generate electromagnetic partially coherent dark hollow or flat-topped beam, which is useful in some applications, such as optical trapping, material processing, free-space optical communications.

Crater-associated dark diffuse features on Venus: Properties of surficial deposits and their evolution

NASA Astrophysics Data System (ADS)

Bondarenko, N. V.; Head, J. W.

2009-03-01

In order to assess the nature of crater-associated radar-dark diffuse features (DDFs) on Venus and to understand their formation and evolution, we analyzed Magellan radar roughness, emissivity, and reflectivity data in the vicinity of craters accompanied by these features. Following others, we assumed that DDFs are deposits (mantles) of ejected material emplaced during formation of the impact crater. The majority of radar-dark parabolas (the youngest DDFs) are characterized by a smooth mantle-atmosphere interface having low root-mean-square (rms) slopes on scales of 1-100 m, as derived from Magellan altimeter data. Older DDFs also often have areas with low rms slopes, suggesting that the mantle rms slopes can be preserved for geologically long periods of time. Some parabolas and older DDFs have asymmetric small-scale (decimeter-scale) relief that is interpreted to be dunes that formed as a result of eolian processes. This implies that the mantle material is mobile and can saltate under the influence of wind action. On average, aging of these features is accompanied by a decrease of mantle material dielectric permittivity. The most efficient mechanism for parabola degradation seems to be the removal of mantle material from the site of initial deposition by subsequent winds. We found a few examples of features that could be interpreted to be the result of in situ modification of the primary mantle.

The composition of Martian aeolian sands: Thermal emissivity from Viking IRTM observations

NASA Technical Reports Server (NTRS)

Edgett, Kenneth S.; Christensen, Philip R.

1992-01-01

Aeolian sands provide excellent surfaces for the remote determination of the mineralogic composition of Martian materials, because such deposits consist of relatively well-sorted, uniform particle sizes and might consist of chemically unaltered, primary mineral grains derived from bedrock. Dark features on the floors of Martian craters are controlled by aeolian processes and many consist largely of unconsolidated, windblown sand. Measurement of the thermal emissivity of geologic materials provides a way to identify mid-infrared absorption bands, the strength and positions of which vary with mineral structure and composition. The Viking Infrared Thermal Mapper (IRTM) had four surface-sensing mid-IR bands, three of which, the 7, 9, and 11 micron channels, correspond to absorption features characteristic of carbonates, sialic, and mafic minerals, respectively. In this study, the highest quality IRTM data were constrained so as to avoid the effects of atmospheric dust, clouds, surface frosts, and particle size variations (the latter using data obtained between 7 and 9 H, and they were selected for dark intracrater features such that only data taken directly from the dark feature were used, so as to avoid thermal contributions from adjacent but unrelated materials. Three-point emissivity spectra of Martian dart intracrater features were compared with laboratory emission spectra of minerals and terrestrial aeolian sands convolved using the IRTM response function to the four IRTM spectral channels.

Automated Photoreceptor Cell Identification on Nonconfocal Adaptive Optics Images Using Multiscale Circular Voting.

PubMed

Liu, Jianfei; Jung, HaeWon; Dubra, Alfredo; Tam, Johnny

2017-09-01

Adaptive optics scanning light ophthalmoscopy (AOSLO) has enabled quantification of the photoreceptor mosaic in the living human eye using metrics such as cell density and average spacing. These rely on the identification of individual cells. Here, we demonstrate a novel approach for computer-aided identification of cone photoreceptors on nonconfocal split detection AOSLO images. Algorithms for identification of cone photoreceptors were developed, based on multiscale circular voting (MSCV) in combination with a priori knowledge that split detection images resemble Nomarski differential interference contrast images, in which dark and bright regions are present on the two sides of each cell. The proposed algorithm locates dark and bright region pairs, iteratively refining the identification across multiple scales. Identification accuracy was assessed in data from 10 subjects by comparing automated identifications with manual labeling, followed by computation of density and spacing metrics for comparison to histology and published data. There was good agreement between manual and automated cone identifications with overall recall, precision, and F1 score of 92.9%, 90.8%, and 91.8%, respectively. On average, computed density and spacing values using automated identification were within 10.7% and 11.2% of the expected histology values across eccentricities ranging from 0.5 to 6.2 mm. There was no statistically significant difference between MSCV-based and histology-based density measurements (P = 0.96, Kolmogorov-Smirnov 2-sample test). MSCV can accurately detect cone photoreceptors on split detection images across a range of eccentricities, enabling quick, objective estimation of photoreceptor mosaic metrics, which will be important for future clinical trials utilizing adaptive optics.

Dark mammoth trunks in the merging galaxy NGC 1316 and a mechanism of cosmic double helices

NASA Astrophysics Data System (ADS)

Carlqvist, Per

2010-06-01

NGC 1316 is a giant, elliptical galaxy containing a complex network of dark, dust features. The morphology of these features has been examined in some detail using a Hubble Space Telescope, Advanced Camera for Surveys image. It is found that most of the features are constituted of long filaments. There also exist a great number of dark structures protruding inwards from the filaments. Many of these structures are strikingly similar to elephant trunks in H ii regions in the Milky Way Galaxy, although much larger. The structures, termed mammoth trunks, generally are filamentary and often have shapes resembling the letters V or Y. In some of the mammoth trunks the stem of the Y can be resolved into two or more filaments, many of which showing signs of being intertwined. A model of the mammoth trunks, related to a recent theory of elephant trunks, is proposed. Based on magnetized filaments, the model is capable of giving an account of the various shapes of the mammoth trunks observed, including the twined structures.

Pupil size reflects the focus of feature-based attention.

PubMed

Binda, Paola; Pereverzeva, Maria; Murray, Scott O

2014-12-15

We measured pupil size in adult human subjects while they selectively attended to one of two surfaces, bright and dark, defined by coherently moving dots. The two surfaces were presented at the same location; therefore, subjects could select the cued surface only on the basis of its features. With no luminance change in the stimulus, we find that pupil size was smaller when the bright surface was attended and larger when the dark surface was attended: an effect of feature-based (or surface-based) attention. With the same surfaces at nonoverlapping locations, we find a similar effect of spatial attention. The pupil size modulation cannot be accounted for by differences in eye position and by other variables known to affect pupil size such as task difficulty, accommodation, or the mere anticipation (imagery) of bright/dark stimuli. We conclude that pupil size reflects not just luminance or cognitive state, but the interaction between the two: it reflects which luminance level in the visual scene is relevant for the task at hand. Copyright © 2014 the American Physiological Society.

Detecting features in the dark energy equation of state: a wavelet approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hojjati, Alireza; Pogosian, Levon; Zhao, Gong-Bo, E-mail: alireza_hojjati@sfu.ca, E-mail: levon@sfu.ca, E-mail: gong-bo.zhao@port.ac.uk

2010-04-01

We study the utility of wavelets for detecting the redshift evolution of the dark energy equation of state w(z) from the combination of supernovae (SNe), CMB and BAO data. We show that local features in w, such as bumps, can be detected efficiently using wavelets. To demonstrate, we first generate a mock supernovae data sample for a SNAP-like survey with a bump feature in w(z) hidden in, then successfully discover it by performing a blind wavelet analysis. We also apply our method to analyze the recently released ''Constitution'' SNe data, combined with WMAP and BAO from SDSS, and find weakmore » hints of dark energy dynamics. Namely, we find that models with w(z) < −1 for 0.2 < z < 0.5, and w(z) > −1 for 0.5 < z < 1, are mildly favored at 95% confidence level. This is in good agreement with several recent studies using other methods, such as redshift binning with principal component analysis (PCA) (e.g. Zhao and Zhang, arXiv: 0908.1568)« less

Oblique interaction of spatial dark-soliton stripes in nonlocal media.

PubMed

Fischer, Robert; Neshev, Dragomir N; Krolikowski, Wieslaw; Kivshar, Yuri S; Iturbe-Castillo, David; Chavez-Cerda, Sabino; Meneghetti, Mario R; Caetano, Dilson P; Hickman, Jandir M

2006-10-15

We report what we believe to be the first experimental observation of a large spatial lateral shift in the interaction of obliquely oriented spatial dark-soliton stripes. We demonstrate by numerical simulations that this new effect can be attributed to the specific features of optical media with a nonlocal nonlinear response.

Comparison of two satellite imaging platforms for evaluating quasi-circular vegetation patch in the Yellow River Delta, China

NASA Astrophysics Data System (ADS)

Liu, Qingsheng; Liang, Li; Liu, Gaohuan; Huang, Chong

2017-09-01

Vegetation often exists as patch in arid and semi-arid region throughout the world. Vegetation patch can be effectively monitored by remote sensing images. However, not all satellite platforms are suitable to study quasi-circular vegetation patch. This study compares fine (GF-1) and coarse (CBERS-04) resolution platforms, specifically focusing on the quasicircular vegetation patches in the Yellow River Delta (YRD), China. Vegetation patch features (area, shape) were extracted from GF-1 and CBERS-04 imagery using unsupervised classifier (K-Means) and object-oriented approach (Example-based feature extraction with SVM classifier) in order to analyze vegetation patterns. These features were then compared using vector overlay and differencing, and the Root Mean Squared Error (RMSE) was used to determine if the mapped vegetation patches were significantly different. Regardless of K-Means or Example-based feature extraction with SVM classification, it was found that the area of quasi-circular vegetation patches from visual interpretation from QuickBird image (ground truth data) was greater than that from both of GF-1 and CBERS-04, and the number of patches detected from GF-1 data was more than that of CBERS-04 image. It was seen that without expert's experience and professional training on object-oriented approach, K-Means was better than example-based feature extraction with SVM for detecting the patch. It indicated that CBERS-04 could be used to detect the patch with area of more than 300 m2, but GF-1 data was a sufficient source for patch detection in the YRD. However, in the future, finer resolution platforms such as Worldview are needed to gain more detailed insight on patch structures and components and formation mechanism.

Evidence for volcanism in NW Ishtar Terra, Venus

NASA Technical Reports Server (NTRS)

Gaddis, L.; Greeley, Ronald

1989-01-01

Venera 15/16 radar data for an area in NW Ishtar Terra, Venus, show an area with moderate radar return and a smooth textured surface which embays low lying areas of the surrounding mountainous terrain. Although this unit may be an extension of the lava plains of Lakshmi Planum to the southeast, detailed study suggests a separate volcanic center in NW Ishtar Terra. Lakshmi Planum, on the Ishtar Terra highland, exhibits major volcanic and tectonic features. On the Venera radar image radar brightness is influenced by slope and roughness; radar-facing slopes (east-facing) and rough surfaces (approx. 8 cm average relief) are bright, while west-facing slopes and smooth surfaces are dark. A series of semi-circular features, apparently topographic depressions, do not conform in orientation to major structural trends in this region of NW Ishtar Terra. The large depression in NW Ishtar Terra is similar to the calderas of Colette and Sacajawea Paterae, as all three structures are large irregular depressions. NW Ishtar Terra appears to be the site of a volcanic center with a complex caldera structure, possibly more than one eruptive vent, and associated lobed flows at lower elevations. The morphologic similarity between this volcanic center and those of Colette and Sacajawea suggests that centralized eruptions have been the dominant form of volcanism in Ishtar. The location of this volcanic center at the intersection of two major compressional mountain belts and the large size of the calders (with an inferred larg/deep magma source) support a crustal thickening/melting rather than a hot-spot origin for these magmas.

Evidence for volcanism in NW Ishtar Terra, Venus

NASA Astrophysics Data System (ADS)

Gaddis, L.; Greeley, Ronald

Venera 15/16 radar data for an area in NW Ishtar Terra, Venus, show an area with moderate radar return and a smooth textured surface which embays low lying areas of the surrounding mountainous terrain. Although this unit may be an extension of the lava plains of Lakshmi Planum to the southeast, detailed study suggests a separate volcanic center in NW Ishtar Terra. Lakshmi Planum, on the Ishtar Terra highland, exhibits major volcanic and tectonic features. On the Venera radar image radar brightness is influenced by slope and roughness; radar-facing slopes (east-facing) and rough surfaces (approx. 8 cm average relief) are bright, while west-facing slopes and smooth surfaces are dark. A series of semi-circular features, apparently topographic depressions, do not conform in orientation to major structural trends in this region of NW Ishtar Terra. The large depression in NW Ishtar Terra is similar to the calderas of Colette and Sacajawea Paterae, as all three structures are large irregular depressions. NW Ishtar Terra appears to be the site of a volcanic center with a complex caldera structure, possibly more than one eruptive vent, and associated lobed flows at lower elevations. The morphologic similarity between this volcanic center and those of Colette and Sacajawea suggests that centralized eruptions have been the dominant form of volcanism in Ishtar. The location of this volcanic center at the intersection of two major compressional mountain belts and the large size of the calders (with an inferred large/deep magma source) support a crustal thickening/melting rather than a hot-spot origin for these magmas.

Stability and tunneling dynamics of a dark-bright soliton pair in a harmonic trap

DOE PAGES

Karamatskos, E. T.; Stockhofe, J.; Kevrekidis, P. G.; ...

2015-04-30

In this study, we consider a binary repulsive Bose-Einstein condensate in a harmonic trap in one spatial dimension and investigate particular solutions consisting of two dark-bright solitons. There are two different stationary solutions characterized by the phase difference in the bright component, in-phase and out-of-phase states. We show that above a critical particle number in the bright component, a symmetry-breaking bifurcation of the pitchfork type occurs that leads to a new asymmetric solution whereas the parental branch, i.e., the out-of-phase state, becomes unstable. These three different states support different small amplitude oscillations, characterized by an almost stationary density of themore » dark component and a tunneling of the bright component between the two dark solitons. Within a suitable effective double-well picture, these can be understood as the characteristic features of a bosonic Josephson junction (BJJ), and we show within a two-mode approach that all characteristic features of the BJJ phase space are recovered. For larger deviations from the stationary states, the simplifying double-well description breaks down due to the feedback of the bright component onto the dark one, causing the solitons to move. In this regime we observe intricate anharmonic and aperiodic dynamics, exhibiting remnants of the BJJ phase space.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Behroozi, Peter S.; Wechsler, Risa H.; Lu, Yu

We find that infalling dark matter halos (i.e., the progenitors of satellite halos) begin losing mass well outside the virial radius of their eventual host halos. The peak mass occurs at a range of clustercentric distances, with median and 68th percentile range of 1.8{sub −1.0}{sup +2.3} R{sub vir,host} for progenitors of z = 0 satellites. The peak circular velocity for infalling halos occurs at significantly larger distances (3.7{sub −2.2}{sup +3.3} R{sub vir,host} at z = 0). This difference arises because different physical processes set peak circular velocity (typically, ∼1:5 and larger mergers which cause transient circular velocity spikes) and peakmore » mass (typically, smooth accretion) for infalling halos. We find that infalling halos also stop having significant mergers well before they enter the virial radius of their eventual hosts. Mergers larger than a 1:40 ratio in halo mass end for infalling halos at similar clustercentric distances (∼1.9 R {sub vir,} {sub host}) as the end of overall mass accretion. However, mergers larger than 1:3 typically end for infalling halos at more than four virial radial away from their eventual hosts. This limits the ability of mergers to affect quenching and morphology changes in clusters. We also note that the transient spikes which set peak circular velocity may lead to issues with abundance matching on that parameter, including unphysical galaxy stellar mass growth profiles near clusters; we propose a simple observational test to check if a better halo proxy for galaxy stellar mass exists.« less

Mergers and Mass Accretion for Infalling Halos Both End Well Outside Cluster Virial Radii

NASA Astrophysics Data System (ADS)

Behroozi, Peter S.; Wechsler, Risa H.; Lu, Yu; Hahn, Oliver; Busha, Michael T.; Klypin, Anatoly; Primack, Joel R.

2014-06-01

We find that infalling dark matter halos (i.e., the progenitors of satellite halos) begin losing mass well outside the virial radius of their eventual host halos. The peak mass occurs at a range of clustercentric distances, with median and 68th percentile range of 1.8^{+2.3}_{-1.0} \\,R_{vir,host} for progenitors of z = 0 satellites. The peak circular velocity for infalling halos occurs at significantly larger distances (3.7^{+3.3}_{-2.2} \\,R_{vir,host} at z = 0). This difference arises because different physical processes set peak circular velocity (typically, ~1:5 and larger mergers which cause transient circular velocity spikes) and peak mass (typically, smooth accretion) for infalling halos. We find that infalling halos also stop having significant mergers well before they enter the virial radius of their eventual hosts. Mergers larger than a 1:40 ratio in halo mass end for infalling halos at similar clustercentric distances (~1.9 R vir, host) as the end of overall mass accretion. However, mergers larger than 1:3 typically end for infalling halos at more than four virial radial away from their eventual hosts. This limits the ability of mergers to affect quenching and morphology changes in clusters. We also note that the transient spikes which set peak circular velocity may lead to issues with abundance matching on that parameter, including unphysical galaxy stellar mass growth profiles near clusters; we propose a simple observational test to check if a better halo proxy for galaxy stellar mass exists.

Influence of burner form and pellet type on domestic pellet boiler performance

NASA Astrophysics Data System (ADS)

Rastvorov, D. V.; Osintsev, K. V.; Toropov, E. V.

2017-10-01

The study presents combustion and emission results obtained using two serial pellet boilers of the same heating capacity 40 kW. These boilers have been designed by producers for domestic conditions of exploitation. The principal difference between boilers was the type of the burner. The study concerns the efficiency and ecological performance difference between burners of circular and rectangular forms. The features of the combustion process in both types of burners were studied when boiler operated with different sorts of pellets. The results suggest that the burner of circular form excels the rectangular form burner. However, there is some difference of NOx emission between circular and rectangular burners.

Circular RNAs Are the Predominant Transcript Isoform from Hundreds of Human Genes in Diverse Cell Types

PubMed Central

Wang, Peter Lincoln; Lacayo, Norman; Brown, Patrick O.

2012-01-01

Most human pre-mRNAs are spliced into linear molecules that retain the exon order defined by the genomic sequence. By deep sequencing of RNA from a variety of normal and malignant human cells, we found RNA transcripts from many human genes in which the exons were arranged in a non-canonical order. Statistical estimates and biochemical assays provided strong evidence that a substantial fraction of the spliced transcripts from hundreds of genes are circular RNAs. Our results suggest that a non-canonical mode of RNA splicing, resulting in a circular RNA isoform, is a general feature of the gene expression program in human cells. PMID:22319583

Helicity-selective phase-matching and quasi-phase matching of circularly polarized high-order harmonics: towards chiral attosecond pulses

DOE PAGES

Kfir, Ofer; Grychtol, Patrik; Turgut, Emrah; ...

2016-05-23

Phase matching of circularly polarized high-order harmonics driven by counter-rotating bi-chromatic lasers was recently predicted theoretically and demonstrated experimentally. In that work, phase matching was analyzed by assuming that the total energy, spin angular momentum and linear momentum of the photons participating in the process are conserved. Here we propose a new perspective on phase matching of circularly polarized high harmonics. We derive an extended phase matching condition by requiring a new propagation matching condition between the classical vectorial bi-chromatic laser pump and harmonics fields. This allows us to include the influence of the laser pulse envelopes on phase matching.more » Here, we find that the helicity dependent phase matching facilitates generation of high harmonics beams with a high degree of chirality. Indeed, we present an experimentally measured chiral spectrum that can support a train of attosecond pulses with a high degree of circular polarization. Moreover, while the degree of circularity of the most intense pulse approaches unity, all other pulses exhibit reduced circularity. Lastly, this feature suggests the possibility of using a train of attosecond pulses as an isolated attosecond probe for chiral-sensitive experiments.« less

Polarization optics of the Brewster's dark patch visible on water surfaces versus solar height and sky conditions: theory, computer modeling, photography, and painting.

PubMed

Takács, Péter; Barta, András; Pye, David; Horváth, Gábor

2017-10-20

When the sun is near the horizon, a circular band with approximately vertically polarized skylight is formed at 90° from the sun, and this skylight is only weakly reflected from the region of the water surface around the Brewster's angle (53° from the nadir). Thus, at low solar heights under a clear sky, an extended dark patch is visible on the water surface when one looks toward the north or south quarter perpendicular to the solar vertical. In this work, we study the radiance distribution of this so-called Brewster's dark patch (BDP) in still water as functions of the solar height and sky conditions. We calculate the pattern of reflectivity R of a water surface for a clear sky and obtain from this idealized situation the shape of the BDP. From three full-sky polarimetric pictures taken about a clear, a partly cloudy, and an overcast sky, we determine the R pattern and compose from that synthetic color pictures showing how the radiance distribution of skylight reflected at the water surface and the BDPs would look under these sky conditions. We also present photographs taken without a linearly polarizing filter about the BDP. Finally, we show a 19th century painting on which a river is seen with a dark region of the water surface, which can be interpreted as an artistic illustration of the BDP.

Where are the Fermi lines coming from?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rao, Kanishka; Whiteson, Daniel, E-mail: krao@uci.edu, E-mail: daniel@uci.edu

2013-03-01

We estimate the spatial locations of sources of the the observed features in the Fermi-LAT photon spectrum at E{sub γ} = 110 and E{sub γ} = 130 GeV. We determine whether they are consistent with emission from a single source, as would be expected in their interpretation as γγ and γZ lines from dark matter annhiliation, as well as whether they are consistent with a dark matter halo positioned at the center of the galaxy. We take advantage of the per-photon measured incident angle in reconstructing the line features. In addition, we use a data-driven background model rather than makingmore » the assumption of a feature-less background. We localize the sources of the features at 110 and 130 GeV. Assuming an Einasto (NFW) density model we find the 130 GeV line to be offset from the Galactic center by 285 (280) pc, the 110 GeV line by 60 (30) pc with a large relative separation of 220 (240) pc. However, we find this displacement of each source from the Galactic center, as well as their relative displacement to be statistically consistent with a single Einasto or NFW dark matter halo at the center of the galaxy.« less

Silver nano fabrication using leaf disc of Passiflora foetida Linn

NASA Astrophysics Data System (ADS)

Lade, Bipin D.; Patil, Anita S.

2017-06-01

The main purpose of the experiment is to develop a greener low cost SNP fabrication steps using factories of secondary metabolites from Passiflora leaf extract. Here, the leaf extraction process is omitted, and instead a leaf disc was used for stable SNP fabricated by optimizing parameters such as a circular leaf disc of 2 cm (1, 2, 3, 4, 5) instead of leaf extract and grade of pH (7, 8, 9, 11). The SNP synthesis reaction is tried under room temperature, sun, UV and dark condition. The leaf disc preparation steps are also discussed in details. The SNP obtained using (1 mM: 100 ml AgNO3+ singular leaf disc: pH 9, 11) is applied against featured room temperature and sun condition. The UV spectroscopic analysis confirms that sun rays synthesized SNP yields stable nano particles. The FTIR analysis confirms a large number of functional groups such as alkanes, alkyne, amines, aliphatic amine, carboxylic acid; nitro-compound, alcohol, saturated aldehyde and phenols involved in reduction of silver salt to zero valent ions. The leaf disc mediated synthesis of silver nanoparticles, minimizes leaf extract preparation step and eligible for stable SNP synthesis. The methods sun and room temperature based nano particles synthesized within 10 min would be use certainly for antimicrobial activity.

Light dark matter, naturalness, and the radiative origin of the electroweak scale

DOE PAGES

Altmannshofer, Wolfgang; Bardeen, William A.; Bauer, Martin; ...

2015-01-09

We study classically scale invariant models in which the Standard Model Higgs mass term is replaced in the Lagrangian by a Higgs portal coupling to a complex scalar field of a dark sector. We focus on models that are weakly coupled with the quartic scalar couplings nearly vanishing at the Planck scale. The dark sector contains fermions and scalars charged under dark SU(2) × U(1) gauge interactions. Radiative breaking of the dark gauge group triggers electroweak symmetry breaking through the Higgs portal coupling. Requiring both a Higgs boson mass of 125.5 GeV and stability of the Higgs potential up tomore » the Planck scale implies that the radiative breaking of the dark gauge group occurs at the TeV scale. We present a particular model which features a long-range abelian dark force. The dominant dark matter component is neutral dark fermions, with the correct thermal relic abundance, and in reach of future direct detection experiments. The model also has lighter stable dark fermions charged under the dark force, with observable effects on galactic-scale structure. Collider signatures include a dark sector scalar boson with mass ≲ 250 GeV that decays through mixing with the Higgs boson, and can be detected at the LHC. As a result, the Higgs boson, as well as the new scalar, may have significant invisible decays into dark sector particles.« less

A Near-Atomic Structure of the Dark Apoptosome Provides Insight into Assembly and Activation.

PubMed

Cheng, Tat Cheung; Akey, Ildikó V; Yuan, Shujun; Yu, Zhiheng; Ludtke, Steven J; Akey, Christopher W

2017-01-03

In Drosophila, the Apaf-1-related killer (Dark) forms an apoptosome that activates procaspases. To investigate function, we have determined a near-atomic structure of Dark double rings using cryo-electron microscopy. We then built a nearly complete model of the apoptosome that includes 7- and 8-blade β-propellers. We find that the preference for dATP during Dark assembly may be governed by Ser325, which is in close proximity to the 2' carbon of the deoxyribose ring. Interestingly, β-propellers in V-shaped domains of the Dark apoptosome are more widely separated, relative to these features in the Apaf-1 apoptosome. This wider spacing may be responsible for the lack of cytochrome c binding to β-propellers in the Dark apoptosome. Our structure also highlights the roles of two loss-of-function mutations that may block Dark assembly. Finally, the improved model provides a framework to understand apical procaspase activation in the intrinsic cell death pathway. Copyright © 2016 Elsevier Ltd. All rights reserved.

Self-Destructing Dark Matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grossman, Yuval; Harnik, Roni; Telem, Ofri

We present Self-Destructing Dark Matter (SDDM), a new class of dark matter models which are detectable in large neutrino detectors. In this class of models, a component of dark matter can transition from a long-lived state to a short-lived one by scattering off of a nucleus or an electron in the Earth. The short-lived state then decays to Standard Model particles, generating a dark matter signal with a visible energy of order the dark matter mass rather than just its recoil. This leads to striking signals in large detectors with high energy thresholds. We present a few examples of modelsmore » which exhibit self destruction, all inspired by bound state dynamics in the Standard Model. The models under consideration exhibit a rich phenomenology, possibly featuring events with one, two, or even three lepton pairs, each with a fixed invariant mass and a fixed energy, as well as non-trivial directional distributions. This motivates dedicated searches for dark matter in large underground detectors such as Super-K, Borexino, SNO+, and DUNE.« less

ON THE 2012 OCTOBER 23 CIRCULAR RIBBON FLARE: EMISSION FEATURES AND MAGNETIC TOPOLOGY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Kai; Guo, Yang; Ding, M. D., E-mail: guoyang@nju.edu.cn, E-mail: dmd@nju.edu.cn

2015-06-20

Circular ribbon flares are usually related to spine-fan type magnetic topology containing null points. In this paper, we investigate an X-class circular ribbon flare on 2012 October 23, using the multiwavelength data from the Solar Dynamics Observatory, Hinode, and RHESSI. In Ca ii H emission, the flare showed three ribbons with two highly elongated ones inside and outside a quasi-circular one, respectively. A hot channel was displayed in the extreme-ultraviolet emissions that infers the existence of a magnetic flux rope. Two hard X-ray (HXR) sources in the 12–25 keV energy band were located at the footpoints of this hot channel. Using amore » nonlinear force-free magnetic field extrapolation, we identify three topological structures: (1) a three-dimensional null point, (2) a flux rope below the fan of the null point, and (3) a large-scale quasi-separatrix layer (QSL) induced by the quadrupolar-like magnetic field of the active region. We find that the null point is embedded within the large-scale QSL. In our case, all three identified topological structures must be considered to explain all the emission features associated with the observed flare. Besides, the HXR sources are regarded as the consequence of the reconnection within or near the border of the flux rope.« less

Direct reconstruction of dark energy.

PubMed

Clarkson, Chris; Zunckel, Caroline

2010-05-28

An important issue in cosmology is reconstructing the effective dark energy equation of state directly from observations. With so few physically motivated models, future dark energy studies cannot only be based on constraining a dark energy parameter space. We present a new nonparametric method which can accurately reconstruct a wide variety of dark energy behavior with no prior assumptions about it. It is simple, quick and relatively accurate, and involves no expensive explorations of parameter space. The technique uses principal component analysis and a combination of information criteria to identify real features in the data, and tailors the fitting functions to pick up trends and smooth over noise. We find that we can constrain a large variety of w(z) models to within 10%-20% at redshifts z≲1 using just SNAP-quality data.

Cassini ISS observation of Saturn’s String of Pearls

NASA Astrophysics Data System (ADS)

Sayanagi, Kunio M.; Dyudina, Ulyana A.; Ewald, Shawn P.; Muro, Gabriel D.; Ingersoll, Andrew P.

2014-02-01

We present the dynamics of the String of Pearls (SoPs) feature observed by the Cassini spacecraft’s Imaging Science Subsystem (ISS) camera between 2007 and 2010. The SoPs was originally discovered in the 5 μm images captured by Cassini VIMS instrument, where it appeared as a chain of infrared-bright spots (Momary, T.W., et al. [2006]. The Zoology of Saturn: The Bizarre Features Unveiled by the 5 Micron Eyes of Cassini/VIMS. AAS/Division for Planetary Sciences Meeting Abstracts 38, 499). Using ISS images of Saturn, we found a chain of 23-26 dark spots at 33.2°N planetocentric latitude with characteristics that are consistent with those of SoPs. Our measurements imply that the feature propagated at -2.26 ± 0.02° day-1 in longitude (-22.27 ± 0.2 m s-1, negative values denote westward) during the observed period that spans three Earth years. Our measurements imply that the SoPs is a chain of cyclones, which we infer from the motion of clouds on the periphery of the individual pearls. We tracked the motion of 26 pearls for 6 months in 2008 and noted a few pearls appearing and disappearing, all near the east-west termini of the SoPs feature. During this period, a few of the pearls, varying between 6 and 10, harbored a small circular cloud at the center, which we call the central peaks. In general, a group of vortices with the same sign of vorticity tend to merge; however, our measurements did not detect merger of pearls. The interest in the feature was heightened when the latest planet-encircling storm erupted from the SoPs on December 5, 2010 (Sayanagi, K.M., Dyudina, U.A., Ewald, S.P., Fischer, G., Ingersoll, A.P., Kurth, W.S., Muro, G.D., Porco, C.C., West, R.A. [2013]. Icarus 223, 460-478). The storm severely disrupted the region; the SoPs was last seen on December 24, 2010 in the turbulent wake of the storm, and has not reappeared as of August 2013.

Search for a gamma-ray line feature from a group of nearby galaxy clusters with Fermi LAT Pass 8 data

NASA Astrophysics Data System (ADS)

Liang, Yun-Feng; Shen, Zhao-Qiang; Li, Xiang; Fan, Yi-Zhong; Huang, Xiaoyuan; Lei, Shi-Jun; Feng, Lei; Liang, En-Wei; Chang, Jin

2016-05-01

Galaxy clusters are the largest gravitationally bound objects in the Universe and may be suitable targets for indirect dark matter searches. With 85 months of Fermi LAT Pass 8 publicly available data, we analyze the gamma-ray emission in the direction of 16 nearby galaxy clusters with an unbinned likelihood analysis. No statistically or globally significant γ -ray line feature is identified and a tentative line signal may present at ˜43 GeV . The 95% confidence level upper limits on the velocity-averaged cross section of dark matter particles annihilating into double γ rays (i.e., ⟨σ v ⟩χχ →γ γ) are derived. Unless very optimistic boost factors of dark matter annihilation in these galaxy clusters have been assumed, such constraints are much weaker than the bounds set by the Galactic γ -ray data.

Hubble Finds New Dark Spot on Neptune

NASA Technical Reports Server (NTRS)

1995-01-01

NASA's Hubble Space Telescope has discovered a new great dark spot, located in the northern hemisphere of the planet Neptune. Because the planet's northern hemisphere is now tilted away from Earth, the new feature appears near the limb of the planet.

The spot is a near mirror-image to a similar southern hemisphere dark spot that was discovered in 1989 by the Voyager 2 probe. In 1994, Hubble showed that the southern dark spot had disappeared.

Like its predecessor, the new spot has high altitude clouds along its edge, caused by gasses that have been pushed to higher altitudes where they cool to form methane ice crystal clouds. The dark spot may be a zone of clear gas that is a window to a cloud deck lower in the atmosphere.

Planetary scientists don t know how long lived this new feature might be. Hubble's high resolution will allow astronomers to follow the spot's evolution and other unexpected changes in Neptune's dynamic atmosphere.

The image was taken on November 2, 1994 with Hubble's Wide Field Planetary Camera 2, when Neptune was 2.8 billion miles (4.5 billion kilometers) from Earth. Hubble can resolve features as small as 625 miles (1,000 kilometers) across in Neptune's cloud tops.

The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science.

This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

Explaining dark matter and B decay anomalies with an L μ - L τ model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Altmannshofer, Wolfgang; Gori, Stefania; Profumo, Stefano

We present a dark sector model based on gauging the L μ - L τ symmetry that addresses anomalies in b→ sμ +μ - decays and that features a particle dark matter candidate. The dark matter particle candidate is a vector-like Dirac fermion coupled to the Z' gauge boson of the L μ - L τ symmetry. We compute the dark matter thermal relic density, its pair-annihilation cross section, and the loop-suppressed dark matter-nucleon scattering cross section, and compare our predictions with current and future experimental results. We demonstrate that after taking into account bounds from Bs meson oscillations, darkmore » matter direct detection, and the CMB, the model is highly predictive: B physics anomalies and a viable particle dark matter candidate, with a mass of ~ (5 - 23) GeV, can be accommodated only in a tightly-constrained region of parameter space, with sharp predictions for future experimental tests. The viable region of parameter space expands if the dark matter is allowed to have L μ - L τ charges that are smaller than those of the SM leptons.« less

Explaining dark matter and B decay anomalies with an L μ - L τ model

DOE PAGES

Altmannshofer, Wolfgang; Gori, Stefania; Profumo, Stefano; ...

2016-12-20

We present a dark sector model based on gauging the L μ - L τ symmetry that addresses anomalies in b→ sμ +μ - decays and that features a particle dark matter candidate. The dark matter particle candidate is a vector-like Dirac fermion coupled to the Z' gauge boson of the L μ - L τ symmetry. We compute the dark matter thermal relic density, its pair-annihilation cross section, and the loop-suppressed dark matter-nucleon scattering cross section, and compare our predictions with current and future experimental results. We demonstrate that after taking into account bounds from Bs meson oscillations, darkmore » matter direct detection, and the CMB, the model is highly predictive: B physics anomalies and a viable particle dark matter candidate, with a mass of ~ (5 - 23) GeV, can be accommodated only in a tightly-constrained region of parameter space, with sharp predictions for future experimental tests. The viable region of parameter space expands if the dark matter is allowed to have L μ - L τ charges that are smaller than those of the SM leptons.« less

Moon Color Composite

NASA Technical Reports Server (NTRS)

1990-01-01

This color image of the Moon was taken by the Galileo spacecraft at 9:35 a.m. PST Dec. 9, 1990, at a range of about 350,000 miles. The color composite uses monochrome images taken through violet, red, and near-infrared filters. The concentric, circular Orientale basin, 600 miles across, is near the center; the nearside is to the right, the far side to the left. At the upper right is the large, dark Oceanus Procellarum; below it is the smaller Mare Humorum. These, like the small dark Mare Orientale in the center of the basin, formed over 3 billion years ago as basaltic lava flows. At the lower left, among the southern cratered highlands of the far side, is the South-Pole-Aitken basin, similar to Orientale but twice as great in diameter and much older and more degraded by cratering and weathering. The cratered highlands of the near and far sides and the Maria are covered with scattered bright, young ray craters.

The concentration dependence of the galaxy–halo connection: Modeling assembly bias with abundance matching

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lehmann, Benjamin V.; Mao, Yao -Yuan; Becker, Matthew R.

Empirical methods for connecting galaxies to their dark matter halos have become essential for interpreting measurements of the spatial statistics of galaxies. In this work, we present a novel approach for parameterizing the degree of concentration dependence in the abundance matching method. Furthermore, this new parameterization provides a smooth interpolation between two commonly used matching proxies: the peak halo mass and the peak halo maximal circular velocity. This parameterization controls the amount of dependence of galaxy luminosity on halo concentration at a fixed halo mass. Effectively this interpolation scheme enables abundance matching models to have adjustable assembly bias in the resulting galaxy catalogs. With the newmore » $$400\\,\\mathrm{Mpc}\\,{h}^{-1}$$ DarkSky Simulation, whose larger volume provides lower sample variance, we further show that low-redshift two-point clustering and satellite fraction measurements from SDSS can already provide a joint constraint on this concentration dependence and the scatter within the abundance matching framework.« less

The concentration dependence of the galaxy–halo connection: Modeling assembly bias with abundance matching

DOE PAGES

Lehmann, Benjamin V.; Mao, Yao -Yuan; Becker, Matthew R.; ...

2016-12-28

Empirical methods for connecting galaxies to their dark matter halos have become essential for interpreting measurements of the spatial statistics of galaxies. In this work, we present a novel approach for parameterizing the degree of concentration dependence in the abundance matching method. Furthermore, this new parameterization provides a smooth interpolation between two commonly used matching proxies: the peak halo mass and the peak halo maximal circular velocity. This parameterization controls the amount of dependence of galaxy luminosity on halo concentration at a fixed halo mass. Effectively this interpolation scheme enables abundance matching models to have adjustable assembly bias in the resulting galaxy catalogs. With the newmore » $$400\\,\\mathrm{Mpc}\\,{h}^{-1}$$ DarkSky Simulation, whose larger volume provides lower sample variance, we further show that low-redshift two-point clustering and satellite fraction measurements from SDSS can already provide a joint constraint on this concentration dependence and the scatter within the abundance matching framework.« less

The concept of geothermal exploration in west Java based on geophysical data

NASA Astrophysics Data System (ADS)

Gaffar, Eddy Z.

2018-02-01

Indonesia has the largest geothermal prospects in the world and most of them are concentrated in Java and Sumatera. The ones on Sumatra island are generally controlled by Sumatra Fault, either the main fault or the second and the third order fault. Geothermal in Java is still influenced by the subduction of oceanic plates from the south of Java island that forms the southern mountains extending from West Java to East Java. From a geophysical point of view, there is still no clue or concept that accelerates the process of geothermal exploration. The concept is that geothermal is located around the volcano (referred to the volcano as a host) and around the fault (fault as a host). There is another method from remote sensing analysis that often shows circular feature. In a study conducted by LIPI, we proposed a new concept for geothermal exploration which is from gravity analysis using Bouguer anomaly data from Java Island, which also show circular feature. The feature is supposed to be an "ancient crater" or a hidden caldera. Therefore, with this hypothesis, LIPI Geophysics team will try to prove whether this symptom can help accelerate the process of geothermal exploration on the island of West Java. Geophysical methods might simplify the exploration of geothermal prospect in West Java. Around the small circular feature, there are some large geothermal prospect areas such as Guntur, Kamojang, Drajat, Papandayan, Karaha Bodas, Patuha. The concept proposed by our team will try be applied to explore geothermal in Java Island for future work.

Dissipative dark matter and the rotation curves of dwarf galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Foot, R., E-mail: rfoot@unimelb.edu.au

2016-07-01

There is ample evidence from rotation curves that dark matter halos around disk galaxies have nontrivial dynamics. Of particular significance are: a) the cored dark matter profile of disk galaxies, b) correlations of the shape of rotation curves with baryonic properties, and c) Tully-Fisher relations. Dark matter halos around disk galaxies may have nontrivial dynamics if dark matter is strongly self interacting and dissipative. Multicomponent hidden sector dark matter featuring a massless 'dark photon' (from an unbroken dark U(1) gauge interaction) which kinetically mixes with the ordinary photon provides a concrete example of such dark matter. The kinetic mixing interactionmore » facilitates halo heating by enabling ordinary supernovae to be a source of these 'dark photons'. Dark matter halos can expand and contract in response to the heating and cooling processes, but for a sufficiently isolated halo could have evolved to a steady state or 'equilibrium' configuration where heating and cooling rates locally balance. This dynamics allows the dark matter density profile to be related to the distribution of ordinary supernovae in the disk of a given galaxy. In a previous paper a simple and predictive formula was derived encoding this relation. Here we improve on previous work by modelling the supernovae distribution via the measured UV and H α fluxes, and compare the resulting dark matter halo profiles with the rotation curve data for each dwarf galaxy in the LITTLE THINGS sample. The dissipative dark matter concept is further developed and some conclusions drawn.« less

Electromagnetic near-field coupling induced polarization conversion and asymmetric transmission in plasmonic metasurfaces

NASA Astrophysics Data System (ADS)

Peng, Yu-Xiang; Wang, Kai-Jun; He, Meng-Dong; Luo, Jian-Hua; Zhang, Xin-Min; Li, Jian-Bo; Tan, Shi-Hua; Liu, Jian-Qiang; Hu, Wei-Da; Chen, Xiaoshuang

2018-04-01

In this paper, we demonstrate the effect of polarization conversion in a plasmonic metasurface structure, in which each unit cell consists of a metal bar and four metal split-ring resonators (SRRs). Such effect is attributed to the fact that the dark plasmon mode of SRRs (bar), which radiates cross-polarized component, is induced by the bright plasmon mode of bar (SRRs) due to the electromagnetic near-field coupling between bar and SRRs. We find that there are two ways to achieve a large cross-polarized component in our proposed metasurface structure. The first way is realized when the dark plasmon mode of bar (SRRs) is in resonance, while at this time the bright plasmon mode of SRRs (bar) is not at resonant state. The second way is realized when the bright plasmon mode of SRRs (bar) is resonantly excited, while the dark plasmon mode of bar (SRRs) is at nonresonant state. It is also found that the linearly polarized light can be rotated by 56.50 after propagation through the metasurface structure. Furthermore, our proposed metasurface structure exhibits an asymmetric transmission for circularly polarized light. Our findings take a further step in developing integrated metasurface-based photonics devices for polarization manipulation and modulation.

Halo abundance matching: accuracy and conditions for numerical convergence

NASA Astrophysics Data System (ADS)

Klypin, Anatoly; Prada, Francisco; Yepes, Gustavo; Heß, Steffen; Gottlöber, Stefan

2015-03-01

Accurate predictions of the abundance and clustering of dark matter haloes play a key role in testing the standard cosmological model. Here, we investigate the accuracy of one of the leading methods of connecting the simulated dark matter haloes with observed galaxies- the halo abundance matching (HAM) technique. We show how to choose the optimal values of the mass and force resolution in large volume N-body simulations so that they provide accurate estimates for correlation functions and circular velocities for haloes and their subhaloes - crucial ingredients of the HAM method. At the 10 per cent accuracy, results converge for ˜50 particles for haloes and ˜150 particles for progenitors of subhaloes. In order to achieve this level of accuracy a number of conditions should be satisfied. The force resolution for the smallest resolved (sub)haloes should be in the range (0.1-0.3)rs, where rs is the scale radius of (sub)haloes. The number of particles for progenitors of subhaloes should be ˜150. We also demonstrate that the two-body scattering plays a minor role for the accuracy of N-body simulations thanks to the relatively small number of crossing-times of dark matter in haloes, and the limited force resolution of cosmological simulations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carlberg, R. G.; Grillmair, C. J., E-mail: carlberg@astro.utoronto.ca, E-mail: carl@ipac.caltech.edu

Measurements of velocity and density perturbations along stellar streams in the Milky Way provide a time-integrated measure of dark matter substructure at larger galactic radius than the complementary instantaneous inner-halo strong lensing detection of dark matter sub-halos in distant galaxies. An interesting case to consider is the proposed Phoenix–Hermus star stream, which is long, thin, and on a nearly circular orbit, making it a particular good target to study for velocity variations along its length. In the presence of dark matter sub-halos, the stream velocities are significantly perturbed in a manner that is readily understood with the impulse approximation. Amore » set of simulations shows that only sub-halos above a few 10{sup 7} M {sub ⊙} lead to reasonably long-lived observationally detectable velocity variations of amplitude of order 1 km s{sup −1}, with an average of about one visible hit per (two-armed) stream over a 3 Gyr interval. An implication is that globular clusters themselves will not have a visible impact on the stream. Radial velocities have the benefit of being completely insensitive to distance errors. Distance errors scatter individual star velocities perpendicular and tangential to the mean orbit, but their mean values remain unbiased. Calculations like these help build the quantitative case to acquire large, fairly deep, precision velocity samples of stream stars.« less

Assessment of tissue polarimetric properties using Stokes polarimetric imaging with circularly polarized illumination.

PubMed

Qi, Ji; He, Honghui; Lin, Jianyu; Dong, Yang; Chen, Dongsheng; Ma, Hui; Elson, Daniel S

2018-04-01

Tissue-depolarization and linear-retardance are the main polarization characteristics of interest for bulk tissue characterization, and are normally interpreted from Mueller polarimetry. Stokes polarimetry can be conducted using simpler instrumentation and in a shorter time. Here, we use Stokes polarimetric imaging with circularly polarized illumination to assess the circular-depolarization and linear-retardance properties of tissue. Results obtained were compared with Mueller polarimetry in transmission and reflection geometry, respectively. It is found that circular-depolarization obtained from these 2 methods is very similar in both geometries, and that linear-retardance is highly quantitatively similar for transmission geometry and qualitatively similar for reflection geometry. The majority of tissue circular-depolarization and linear-retardance image information (represented by local image contrast features) obtained from Mueller polarimetry is well preserved from Stokes polarimetry in both geometries. These findings can be referred to for further understanding tissue Stokes polarimetric data, and for further application of Stokes polarimetry under the circumstances where short acquisition time or low optical system complexity is a priority, such as polarimetric endoscopy and microscopy. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparative Study of Hand-Sutured versus Circular Stapled Anastomosis for Gastrojejunostomy in Laparoscopy Assisted Distal Gastrectomy.

PubMed

Seo, Su Hyun; Kim, Ki Han; Kim, Min Chan; Choi, Hong Jo; Jung, Ghap Joong

2012-06-01

Mechanical stapler is regarded as a good alternative to the hand sewing technique, when used in gastric reconstruction. The circular stapling method has been widely applied to gastrectomy (open orlaparoscopic), for gastric cancer. We illustrated and compared the hand-sutured method to the circular stapling method, for Billroth-II, in patients who underwent laparoscopy assisted distal gastrectomy for gastric cancer. Between April 2009 and May 2011, 60 patients who underwent laparoscopy assisted distal gastrectomy, with Billroth-II, were enrolled. Hand-sutured Billroth-II was performed in 40 patients (manual group) and circular stapler Billroth-II was performed in 20 patients (stapler group). Clinicopathological features and post-operative outcomes were evaluated and compared between the two groups. Nosignificant differences were observed in clinicopathologic parameters and post-operative outcomes, except in the operation times. Operation times and anastomosis times were significantly shorter in the stapler group (P=0.004 and P<0.001). Compared to the hand-sutured method, the circular stapling method can be applied safely and more efficiently, when performing Billroth-II anastomosis, after laparoscopy assisted distal gastrectomy in patients with gastric cancer.

Thermal dark matter from a highly decoupled sector

DOE PAGES

Berlin, Asher; Hooper, Dan; Krnjaic, Gordan

2016-11-17

It has recently been shown that if the dark matter is in thermal equilibrium with a sector that is highly decoupled from the Standard Model, it can freeze out with an acceptable relic abundance, even if the dark matter is as heavy as ~1–100 PeV. In such scenarios, both the dark and visible sectors are populated after inflation, but with independent temperatures. The lightest particle in the dark sector will be generically long-lived and can come to dominate the energy density of the Universe. Upon decaying, these particles can significantly reheat the visible sector, diluting the abundance of dark mattermore » and thus allowing for dark matter particles that are much heavier than conventional WIMPs. In this study, we present a systematic and pedagogical treatment of the cosmological history in this class of models, emphasizing the simplest scenarios in which a dark matter candidate annihilates into hidden sector particles which then decay into visible matter through the vector, Higgs, or lepton portals. In each case, we find ample parameter space in which very heavy dark matter particles can provide an acceptable thermal relic abundance. We also discuss possible extensions of models featuring these dynamics.« less

Thermal dark matter from a highly decoupled sector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berlin, Asher; Hooper, Dan; Krnjaic, Gordan

It has recently been shown that if the dark matter is in thermal equilibrium with a sector that is highly decoupled from the Standard Model, it can freeze out with an acceptable relic abundance, even if the dark matter is as heavy as ~1–100 PeV. In such scenarios, both the dark and visible sectors are populated after inflation, but with independent temperatures. The lightest particle in the dark sector will be generically long-lived and can come to dominate the energy density of the Universe. Upon decaying, these particles can significantly reheat the visible sector, diluting the abundance of dark mattermore » and thus allowing for dark matter particles that are much heavier than conventional WIMPs. In this study, we present a systematic and pedagogical treatment of the cosmological history in this class of models, emphasizing the simplest scenarios in which a dark matter candidate annihilates into hidden sector particles which then decay into visible matter through the vector, Higgs, or lepton portals. In each case, we find ample parameter space in which very heavy dark matter particles can provide an acceptable thermal relic abundance. We also discuss possible extensions of models featuring these dynamics.« less

Doppler effect on indirect detection of dark matter using dark matter only simulations

DOE PAGES

Powell, Devon; Laha, Ranjan; Ng, Kenny C. Y.; ...

2017-03-15

Indirect detection of dark matter is a major avenue for discovery. However, baryonic backgrounds are diverse enough to mimic many possible signatures of dark matter. In this work, we study the newly proposed technique of dark matter velocity spectroscopy. The nonrotating dark matter halo and the Solar motion produce a distinct longitudinal dependence of the signal which is opposite in direction to that produced by baryons. Using collisionless dark matter only simulations of Milky Way like halos, we show that this new signature is robust and holds great promise. We develop mock observations by a high energy resolution x-ray spectrometermore » on a sounding rocket, the Micro-X experiment, to our test case, the 3.5 keV line. We show that by using six different pointings, Micro-X can exclude a constant line energy over various longitudes at ≥ 3σ. As a result, the halo triaxiality is an important effect, and it will typically reduce the significance of this signal. We emphasize that this new smoking gun in motion signature of dark matter is general and is applicable to any dark matter candidate which produces a sharp photon feature in annihilation or decay.« less

Doppler effect on indirect detection of dark matter using dark matter only simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powell, Devon; Laha, Ranjan; Ng, Kenny C. Y.

Indirect detection of dark matter is a major avenue for discovery. However, baryonic backgrounds are diverse enough to mimic many possible signatures of dark matter. In this work, we study the newly proposed technique of dark matter velocity spectroscopy. The nonrotating dark matter halo and the Solar motion produce a distinct longitudinal dependence of the signal which is opposite in direction to that produced by baryons. Using collisionless dark matter only simulations of Milky Way like halos, we show that this new signature is robust and holds great promise. We develop mock observations by a high energy resolution x-ray spectrometermore » on a sounding rocket, the Micro-X experiment, to our test case, the 3.5 keV line. We show that by using six different pointings, Micro-X can exclude a constant line energy over various longitudes at ≥ 3σ. As a result, the halo triaxiality is an important effect, and it will typically reduce the significance of this signal. We emphasize that this new smoking gun in motion signature of dark matter is general and is applicable to any dark matter candidate which produces a sharp photon feature in annihilation or decay.« less

Dissipative dark matter halos: The steady state solution

NASA Astrophysics Data System (ADS)

Foot, R.

2018-02-01

Dissipative dark matter, where dark matter particle properties closely resemble familiar baryonic matter, is considered. Mirror dark matter, which arises from an isomorphic hidden sector, is a specific and theoretically constrained scenario. Other possibilities include models with more generic hidden sectors that contain massless dark photons [unbroken U (1 ) gauge interactions]. Such dark matter not only features dissipative cooling processes but also is assumed to have nontrivial heating sourced by ordinary supernovae (facilitated by the kinetic mixing interaction). The dynamics of dissipative dark matter halos around rotationally supported galaxies, influenced by heating as well as cooling processes, can be modeled by fluid equations. For a sufficiently isolated galaxy with a stable star formation rate, the dissipative dark matter halos are expected to evolve to a steady state configuration which is in hydrostatic equilibrium and where heating and cooling rates locally balance. Here, we take into account the major cooling and heating processes, and numerically solve for the steady state solution under the assumptions of spherical symmetry, negligible dark magnetic fields, and that supernova sourced energy is transported to the halo via dark radiation. For the parameters considered, and assumptions made, we were unable to find a physically realistic solution for the constrained case of mirror dark matter halos. Halo cooling generally exceeds heating at realistic halo mass densities. This problem can be rectified in more generic dissipative dark matter models, and we discuss a specific example in some detail.

Nearly Supersymmetric Dark Atoms

DOE PAGES

Behbahani, Siavosh R.; Jankowiak, Martin; Rube, Tomas; ...

2011-01-01

Theories of dark matter that support bound states are an intriguing possibility for the identity of the missing mass of the Universe. This article proposes a class of models of supersymmetric composite dark matter where the interactions with the Standard Model communicate supersymmetry breaking to the dark sector. In these models, supersymmetry breaking can be treated as a perturbation on the spectrum of bound states. Using a general formalism, the spectrum with leading supersymmetry effects is computed without specifying the details of the binding dynamics. The interactions of the composite states with the Standard Model are computed, and several benchmarkmore » models are described. General features of nonrelativistic supersymmetric bound states are emphasized.« less

SILICATES ON IAPETUS FROM CASSINI’S COMPOSITE INFRARED SPECTROMETER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Young, Cindy L.; Wray, James J.; Clark, Roger N.

We present the first spectral features obtained from Cassini’s Composite Infrared Spectrometer (CIRS) for any icy moon. The spectral region covered by CIRS focal planes (FP) 3 and 4 is rich in emissivity features, but previous studies at these wavelengths have been limited by low signal-to-noise ratios (S/Ns) for individual spectra. Our approach is to average CIRS FP3 spectra to increase the S/N and use emissivity spectra to constrain the composition of the dark material on Iapetus. We find an emissivity feature at ∼855 cm{sup −1} and a possible doublet at 660 and 690 cm{sup −1} that do not correspondmore » to any known instrument artifacts. We attribute the 855 cm{sup −1} feature to fine-grained silicates, similar to those found in dust on Mars and in meteorites, which are nearly featureless at shorter wavelengths. Silicates on the dark terrains of Saturn’s icy moons have been suspected for decades, but there have been no definitive detections until now. Serpentines reported in the literature at ambient temperature and pressure have features near 855 and 660 cm{sup −1}. However, peaks can shift depending on temperature and pressure, so measurements at Iapetus-like conditions are necessary for more positive feature identifications. As a first investigation, we measured muscovite at 125 K in a vacuum and found that this spectrum does match the emissivity feature near 855 cm{sup −1} and the location of the doublet. Further measurements are needed to robustly identify a specific silicate, which would provide clues regarding the origin and implications of the dark material.« less

Semi-automated algorithm for localization of dermal/epidermal junction in reflectance confocal microscopy images of human skin

NASA Astrophysics Data System (ADS)

Kurugol, Sila; Dy, Jennifer G.; Rajadhyaksha, Milind; Gossage, Kirk W.; Weissmann, Jesse; Brooks, Dana H.

2011-03-01

The examination of the dermis/epidermis junction (DEJ) is clinically important for skin cancer diagnosis. Reflectance confocal microscopy (RCM) is an emerging tool for detection of skin cancers in vivo. However, visual localization of the DEJ in RCM images, with high accuracy and repeatability, is challenging, especially in fair skin, due to low contrast, heterogeneous structure and high inter- and intra-subject variability. We recently proposed a semi-automated algorithm to localize the DEJ in z-stacks of RCM images of fair skin, based on feature segmentation and classification. Here we extend the algorithm to dark skin. The extended algorithm first decides the skin type and then applies the appropriate DEJ localization method. In dark skin, strong backscatter from the pigment melanin causes the basal cells above the DEJ to appear with high contrast. To locate those high contrast regions, the algorithm operates on small tiles (regions) and finds the peaks of the smoothed average intensity depth profile of each tile. However, for some tiles, due to heterogeneity, multiple peaks in the depth profile exist and the strongest peak might not be the basal layer peak. To select the correct peak, basal cells are represented with a vector of texture features. The peak with most similar features to this feature vector is selected. The results show that the algorithm detected the skin types correctly for all 17 stacks tested (8 fair, 9 dark). The DEJ detection algorithm achieved an average distance from the ground truth DEJ surface of around 4.7μm for dark skin and around 7-14μm for fair skin.

Modelling the magnetic activity and filtering radial velocity curves of young Suns : the weak-line T Tauri star LkCa 4

NASA Astrophysics Data System (ADS)

Donati, J.-F.; Hébrard, E.; Hussain, G.; Moutou, C.; Grankin, K.; Boisse, I.; Morin, J.; Gregory, S. G.; Vidotto, A. A.; Bouvier, J.; Alencar, S. H. P.; Delfosse, X.; Doyon, R.; Takami, M.; Jardine, M. M.; Fares, R.; Cameron, A. C.; Ménard, F.; Dougados, C.; Herczeg, G.; Matysse Collaboration

2014-11-01

We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri star LkCa 4 within the Magnetic Topologies of Young Stars and the Survival of close-in giant Exoplanets (MaTYSSE) programme, involving ESPaDOnS at the Canada-France-Hawaii Telescope. Despite an age of only 2 Myr and a similarity with prototypical classical T Tauri stars, LkCa 4 shows no evidence for accretion and probes an interesting transition stage for star and planet formation. Large profile distortions and Zeeman signatures are detected in the unpolarized and circularly polarized lines of LkCa 4 using Least-Squares Deconvolution (LSD), indicating the presence of brightness inhomogeneities and magnetic fields at the surface of LkCa 4. Using tomographic imaging, we reconstruct brightness and magnetic maps of LkCa 4 from sets of unpolarized and circularly polarized LSD profiles. The large-scale field is strong and mainly axisymmetric, featuring a ≃2 kG poloidal component and a ≃1 kG toroidal component encircling the star at equatorial latitudes - the latter making LkCa 4 markedly different from classical T Tauri stars of similar mass and age. The brightness map includes a dark spot overlapping the magnetic pole and a bright region at mid-latitudes - providing a good match to the contemporaneous photometry. We also find that differential rotation at the surface of LkCa 4 is small, typically ≃5.5 times weaker than that of the Sun, and compatible with solid-body rotation. Using our tomographic modelling, we are able to filter out the activity jitter in the radial velocity curve of LkCa 4 (of full amplitude 4.3 km s-1) down to an rms precision of 0.055 km s-1. Looking for hot Jupiters around young Sun-like stars thus appears feasible, even though we find no evidence for such planets around LkCa 4.

DESTINY, The Dark Energy Space Telescope

NASA Technical Reports Server (NTRS)

Pasquale, Bert A.; Woodruff, Robert A.; Benford, Dominic J.; Lauer, Tod

2007-01-01

We have proposed the development of a low-cost space telescope, Destiny, as a concept for the NASA/DOE Joint Dark Energy Mission. Destiny is a 1.65m space telescope, featuring a near-infrared (0.85-1.7m) survey camera/spectrometer with a moderate flat-field field of view (FOV). Destiny will probe the properties of dark energy by obtaining a Hubble diagram based on Type Ia supernovae and a large-scale mass power spectrum derived from weak lensing distortions of field galaxies as a function of redshift.

Chemical Composition of Diagenetic Features at Lower Aeolis Mons, Mars as Measured by Curiosity's APXS

NASA Astrophysics Data System (ADS)

Berger, J. A.; Schmidt, M. E.; Gellert, R.; Boyd, N.; Campbell, J. L.; Desouza, E.; Fisk, M. R.; Perrett, G. M.; Thompson, L. M.; VanBommel, S.; Yen, A. S.

2015-12-01

Curiosity's APXS investigation of the Murray Fm. (sols 755 - 950) at lower Aeolis Mons (Mt. Sharp) in Gale Crater, Mars has revealed (Mg, Ni)-sulfate diagenetic features and dark gray Ca-rich veins. The (Mg, Ni)-sulfate features occur as ~2 cm wide dendritic and botryoidal concretions that stand out in relief ~1 cm above the mudstone surface. APXS rasters over the features (Moenkopi, Mammoth, Morrison, Rosamond, Potatoe; sols 758 - 810) resulted in 1:1 molar variation of S and Mg consistent with a MgSO4 phase. The sulfate is not pure; the features are a mixture of 10 - 15% MgSO4 with the host mudstone. This mixture suggests the sulfates precipitated within pre-existing pore spaces, or were partially dissolved and replaced by sediment, preserving the crystal morphology. The sulfate features are enriched in Ni (2000 - 4250 ppm), indicating Ni-sulfate. The Murray Fm. mudstones that host the diagenetic features range to high SiO2 (60-73 wt%) and have bulk elemental signatures that are consistent with alteration by acid leaching. Low MgO (3.0 wt%) and low Ni (100 - 300 ppm) in the most apparently altered (highest SiO2) mudstones may link the acidic alteration with the fluids that formed the (Mg, Ni)-sulfates. Diagenetic Ca-sulfate-bearing veins that were abundant across Aeolis Palus persist at lower Aeolis Mons. A new vein type containing dark gray material as a separate crystalline phase within white Ca-sulfate veins was discovered in a cluster of veins in the Murray Fm. (Coalville, Alvord Mt., Amboy; sols 930 - 948). APXS rasters of the dark-toned material indicate high CaO (20 - 30 wt%) without concomitant increases in SO3. Ge (up to 650 ppm; 6.5X surrounding bedrock) and MnO (up to 1.0 wt%; 4X surrounding bedrock) are both enriched in the dark veins. These chemical observations are consistent with fluorite, although F (L.O.D. >5%) is not detectable in APXS spectra. The diagenetic features indicate that Ca, Mg, and Ni were mobilized with S in aqueous fluids, and that F may have played a role in the acidic alteration of the Murray Fm.

Boosted dark matter and its implications for the features in IceCube HESE data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacharya, Atri; Gandhi, Raj; Gupta, Aritra

2017-05-01

We study the implications of the premise that any new, relativistic, highly energetic neutral particle that interacts with quarks and gluons would create cascade-like events in the IceCube (IC) detector. Such events would be observationally indistinguishable from neutral current deep-inelastic (DIS) scattering events due to neutrinos. Consequently, one reason for deviations, breaks or excesses in the expected astrophysical power-law neutrino spectrum could be the flux of such a particle. Motivated by features in the recent 1347-day IceCube high energy starting event (HESE) data, we focus on particular boosted dark matter (χ) related realizations of this premise. Here, χ is assumedmore » to be much lighter than, and the result of, the slow decay of a massive scalar (φ ) which constitutes a major fraction of the Universe's dark matter (DM) . We show that this hypothesis, coupled with a standard power-law astrophysical neutrino flux is capable of providing very good fits to the present data, along with a possible explanation of other features in the HESE sample. These features include a) the paucity of events beyond ∼ 2 PeV b) a spectral feature resembling a dip or a spectral change in the 400 TeV–1 PeV region and c) an excess in the 50−100 TeV region. We consider two different boosted DM scenarios, and determine the allowed mass ranges and couplings for four different types of mediators (scalar, pseudoscalar, vector and axial-vector) which could connect the standard and dark sectors.We consider constraints from gamma-ray observations and collider searches. We find that the gamma-ray observations provide the most restrictive constraints, disfavouring the 1σ allowed parameter space from IC fits, while still being consistent with the 3σ allowed region. We also test our proposal and its implications against the (statistically independent) sample of six year through-going muon track data recently released by IceCube.« less

Mobius Molecules

ERIC Educational Resources Information Center

Eckert, J. M.

1973-01-01

Discusses formation of chemical molecules via Mobius strip intermediates, and concludes that many special physics-chemical properties of the fully closed circular form (1) of polyoma DNA are explainable by this topological feature. (CC)

The circular form of the linear superconducting machine for marine propulsion

NASA Astrophysics Data System (ADS)

Rakels, J. H.; Mahtani, J. L.; Rhodes, R. G.

1981-01-01

The superconducting linear synchronous machine (LSM) is an efficient method of propulsion of advanced ground transport systems and can also be used in marine engineering for the propulsion of large commercial vessels, tankers, and military ships. It provides high torque at low shaft speeds and ease of reversibility; a circular LSM design is proposed as a drive motor. The equipment is compared with the superconducting homopolar motors, showing flexibility in design, built in redundancy features, and reliability.

Pyrene-Containing ortho-Oligo(phenylene)ethynylene Foldamer as a Ratiometric Probe Based on Circularly Polarized Luminescence.

PubMed

Reiné, Pablo; Justicia, Jose; Morcillo, Sara P; Abbate, Sergio; Vaz, Belen; Ribagorda, María; Orte, Ángel; Álvarez de Cienfuegos, Luis; Longhi, Giovanna; Campaña, Araceli G; Miguel, Delia; Cuerva, Juan M

2018-04-20

In this manuscript, we report the first synthesis of an organic monomolecular emitter, which behaves as a circularly polarized luminescence (CPL)-based ratiometric probe. The enantiopure helical ortho-oligo(phenylene)ethynylene ( o-OPE) core has been prepared by a new and efficient macrocyclization reaction. The combination of such o-OPE helical skeleton and a pyrene couple leads to two different CPL emission features in a single structure whose ratio linearly responds to silver(I) concentration.

Spin-orbit optomechanics of optically levitated chiral Bragg microspheres

NASA Astrophysics Data System (ADS)

Tkachenko, Georgiy; Rafayelyan, Mushegh; Brasselet, Etienne

2017-05-01

We explore the spin-orbit nature of the optical torque exerted on chiral liquid-crystal microspheres exhibiting circular Bragg reflection. Experimental investigation relies on the direct optomechanical observation of spinning liquid-crystal droplets immersed in water and held in a circularly polarized laser levitator. More generally, we anticipate that the total angular momentum transfer per photon may depart from the commonly assumed spin-only ±2 ℏ contribution, when the topological features of the illuminated microsphere are taken into account.

PLASMAP: an interactive computational tool for storage, retrieval and device-independent graphic display of conventional restriction maps.

PubMed Central

Stone, B N; Griesinger, G L; Modelevsky, J L

1984-01-01

We describe an interactive computational tool, PLASMAP, which allows the user to electronically store, retrieve, and display circular restriction maps. PLASMAP permits users to construct libraries of plasmid restriction maps as a set of files which may be edited in the laboratory at any time. The display feature of PLASMAP quickly generates device-independent, artist-quality, full-color or monochrome, hard copies or CRT screens of complex, conventional circular restriction maps. PMID:6320096

Integrative analysis of Arabidopsis thaliana transcriptomics reveals intuitive splicing mechanism for circular RNA.

PubMed

Sun, Xiaoyong; Wang, Lin; Ding, Jiechao; Wang, Yanru; Wang, Jiansheng; Zhang, Xiaoyang; Che, Yulei; Liu, Ziwei; Zhang, Xinran; Ye, Jiazhen; Wang, Jie; Sablok, Gaurav; Deng, Zhiping; Zhao, Hongwei

2016-10-01

A new regulatory class of small endogenous RNAs called circular RNAs (circRNAs) has been described as miRNA sponges in animals. Using 16 Arabidopsis thaliana RNA-Seq data sets, we identified 803 circRNAs in RNase R-/non-RNase R-treated samples. The results revealed the following features: Canonical and noncanonical splicing can generate circRNAs; chloroplasts are a hotspot for circRNA generation; furthermore, limited complementary sequences exist not only in introns, but also in the sequences flanking splice sites. The latter finding suggests that multiple combinations between complementary sequences may facilitate the formation of the circular structure. Our results contribute to a better understanding of this novel class of plant circRNAs. © 2016 Federation of European Biochemical Societies.

Anisotropic Galaxy-Galaxy Lensing in the Illustris-1 Simulation

NASA Astrophysics Data System (ADS)

Brainerd, Tereasa G.

2017-06-01

In Cold Dark Matter universes, the dark matter halos of galaxies are expected to be triaxial, leading to a surface mass density that is not circularly symmetric. In principle, this "flattening" of the dark matter halos of galaxies should be observable as an anisotropy in the weak galaxy-galaxy lensing signal. The degree to which the weak lensing signal is observed to be anisotropic, however, will depend strongly on the degree to which mass (i.e., the dark matter) is aligned with light in the lensing galaxies. That is, the anisotropy will be maximized when the major axis of the projected mass distribution is well aligned with the projected light distribution of the lens galaxies. Observational studies of anisotropic galaxy-galaxy lensing have found an anisotropic weak lensing signal around massive, red galaxies. Detecting the signal around blue, disky galaxies has, however, been more elusive. A possible explanation for this is that mass and light are well aligned within red galaxies and poorly aligned within blue galaxies (an explanation that is supported by studies of the locations of satellites of large, relatively isolated galaxies). Here we compute the weak lensing signal of isolated central galaxies in the Illustris-1 simulation. We compute the anisotropy of the weak lensing signal using two definitions of the geometry: [1] the major axis of the projected dark matter mass distribution and [2] the major axis of the projected stellar mass. On projected scales less than 15% of the virial radius, an anisotropy of order 10% is found for both definitions of the geometry. On larger scales, the anisotropy computed relative to the major axis of the projected light distribution is less than the anisotropy computed relative to the major axis of the projected dark matter. On projected scales of order the virial radius, the anisotropy obtained when using the major axis of the light is an order of magnitude less than the anisotropy obtained when using the major axis of the dark matter. The suppression of the anisotropy when using the major axis of the light to define the geometry is indicative of a significant misalignment of mass and light in the Illustris-1 galaxies at large physical radii.

Detecting ultralight axion dark matter wind with laser interferometers

NASA Astrophysics Data System (ADS)

Aoki, Arata; Soda, Jiro

The ultralight axion with mass around 10-22eV is known as a candidate of dark matter. A peculiar feature of the ultralight axion is oscillating pressure in time, which produces oscillation of gravitational potentials. Since the solar system moves through the dark matter halo at the velocity of about v ˜ 300km/s = 10-3, there exists axion wind, which looks like scalar gravitational waves for us. Hence, there is a chance to detect ultralight axion dark matter with a wide mass range by using laser interferometer detectors. We calculate the detector signal induced by the oscillating pressure of the ultralight axion field, which would be detected by future laser interferometer experiments. We also argue that the detector signal can be enhanced due to the resonance in modified gravity theory explaining the dark energy.

Retinal identification based on an Improved Circular Gabor Filter and Scale Invariant Feature Transform.

PubMed

Meng, Xianjing; Yin, Yilong; Yang, Gongping; Xi, Xiaoming

2013-07-18

Retinal identification based on retinal vasculatures in the retina provides the most secure and accurate means of authentication among biometrics and has primarily been used in combination with access control systems at high security facilities. Recently, there has been much interest in retina identification. As digital retina images always suffer from deformations, the Scale Invariant Feature Transform (SIFT), which is known for its distinctiveness and invariance for scale and rotation, has been introduced to retinal based identification. However, some shortcomings like the difficulty of feature extraction and mismatching exist in SIFT-based identification. To solve these problems, a novel preprocessing method based on the Improved Circular Gabor Transform (ICGF) is proposed. After further processing by the iterated spatial anisotropic smooth method, the number of uninformative SIFT keypoints is decreased dramatically. Tested on the VARIA and eight simulated retina databases combining rotation and scaling, the developed method presents promising results and shows robustness to rotations and scale changes.

Retinal Identification Based on an Improved Circular Gabor Filter and Scale Invariant Feature Transform

PubMed Central

Meng, Xianjing; Yin, Yilong; Yang, Gongping; Xi, Xiaoming

2013-01-01

Retinal identification based on retinal vasculatures in the retina provides the most secure and accurate means of authentication among biometrics and has primarily been used in combination with access control systems at high security facilities. Recently, there has been much interest in retina identification. As digital retina images always suffer from deformations, the Scale Invariant Feature Transform (SIFT), which is known for its distinctiveness and invariance for scale and rotation, has been introduced to retinal based identification. However, some shortcomings like the difficulty of feature extraction and mismatching exist in SIFT-based identification. To solve these problems, a novel preprocessing method based on the Improved Circular Gabor Transform (ICGF) is proposed. After further processing by the iterated spatial anisotropic smooth method, the number of uninformative SIFT keypoints is decreased dramatically. Tested on the VARIA and eight simulated retina databases combining rotation and scaling, the developed method presents promising results and shows robustness to rotations and scale changes. PMID:23873409

Experimental study of contact edge roughness on sub-100 nm various circular shapes

NASA Astrophysics Data System (ADS)

Lee, Tae Y.; Ihm, Dongchul; Kang, Hyo C.; Lee, Jum B.; Lee, Byoung H.; Chin, Soo B.; Cho, Do H.; Song, Chang L.

2005-05-01

The measurement of edge roughness has become a hot issue in the semiconductor industry. Especially the contact roughness is being more critical as design rule shrinks. Major vendors offer a variety of features to measure the edge roughness in their CD-SEMs. For the line and space patterns, features such as Line Edge Roughness (LER) and Line Width Roughness (LWR) are available in current CD-SEMs. However the features currently available in commercial CD-SEM cannot provide a proper solution in monitoring the contact roughness. We had introduced a new parameter R, measurement algorithm and definition of contact edge roughness to quantify CER and CSR in previous paper. The parameter, R could provide an alternative solution to monitor contact or island pattern roughness. In this paper, we investigated to assess optimum number of CD measurement (1-D) and fitting method for CER or CSR. The study was based on a circular contact shape. Some new ideas to quantify CER or CSR were also suggested with preliminary experimental results.

Ultraviolet spectra of quenched carbonaceous composite derivatives: Comparison to the '217 nanometer' interstellar absorption feature

NASA Technical Reports Server (NTRS)

Sakata, Akira; Wada, Setsuko; Tokunaga, Alan T.; Narisawa, Takatoshi; Nakagawa, Hidehiro; Ono, Hiroshi

1994-01-01

QCCs (quenched carbonaceous composite) are amorphus carbonaceous material formed from a hydrocarbon plasma. We present the UV-visible spectra of 'filmy QCC; (obtained outside of the beam ejected from the hydrocarbon plasma) and 'dark QCC' (obtained very near to the beam) for comparison to the stellar extinction curve. When filmy QCC is heated to 500-700 C (thermally altered), the wavelength of the absorption maximum increases form 204 nm to 220-222 nm. The dark QCC has an absorption maximum at 217-222 nm. In addition, the thermally altered filmy QCC has a slope change at about 500 nm which resmbles that in the interstellar extinction curve. The resemblance of the extinction curve of the QCCs to that of the interstellar medium suggests that QCC derivatives may be representative of the type of interstellar material that produces the 217 nm interstellar medium feature. The peak extinction of the dark QCC is higher than the average interstellar extinction curve while that of the thermally altered filmy QCC is lower, so that a mixture of dark and thermally altered filmy QCC can match the peak extinction observed in the interstellar medium. It is shown from electron micrographs that most of the thermally altered flimy QCC is in the form of small grainy structure less than 4 nm in diameter. This shows that the structure unit causing the 217-222 nm feature in QCC is very small.

Venus 2004: east and west elongations and solar transit

NASA Astrophysics Data System (ADS)

McKim, R. J.; Blaxall, K.; Heath, A.

2007-04-01

The year 2004 was exceptional in producing the first solar transit of Venus since the late Victorian era. The bright aureole and atmospheric ring were re-observed, and the entire phenomenon was witnessed for the first time ever in hydrogen alpha light. Although routine observations throughout 2004 were unexceptional, patterns of visibility of bright and dark markings, cusp extensions and cusp-caps were recorded. No correlation was found between the latitude of the sub-Earth point and the visibility of either cusp-cap, with the S. cap predominating for most of the year. It was possible to accurately follow individual ultraviolet dark markings over many consecutive rotations, extending from the E. to W. elongations, and thereby to make a current measurement of the synodic atmospheric rotation period for the near-equatorial features: 3.996 ± 0.001 days. The true Ashen Light was reported visually on only a few occasions, but these correspond closely to times when infrared emission from the surface of the dark side was recorded in 1-micron waveband images. Some of the stable dark side albedo features were also visible upon the 1-micron images, and have been tentatively identified with known surface features. Infrared imaging at the same waveband showed little detail on the sunlit disk, but a few bright spots were sufficiently well observed to suggest a synodic rotation period close to 5.0 days, not atypical for the lower cloud decks.

Automated detection of new impact sites on Martian surface from HiRISE images

NASA Astrophysics Data System (ADS)

Xin, Xin; Di, Kaichang; Wang, Yexin; Wan, Wenhui; Yue, Zongyu

2017-10-01

In this study, an automated method for Martian new impact site detection from single images is presented. It first extracts dark areas in full high resolution image, then detects new impact craters within dark areas using a cascade classifier which combines local binary pattern features and Haar-like features trained by an AdaBoost machine learning algorithm. Experimental results using 100 HiRISE images show that the overall detection rate of proposed method is 84.5%, with a true positive rate of 86.9%. The detection rate and true positive rate in the flat regions are 93.0% and 91.5%, respectively.

Features in the spectra of gamma-ray bursts

NASA Technical Reports Server (NTRS)

Stanek, Krzysztof Z.; Paczynski, Bohdan; Goodman, Jeremy

1993-01-01

Gravitational lensing of cosmological gamma-ray bursts by objects in the mass range about 10 exp 17 to 10 exp 20 g (femtolensing) may introduce complicated interference patterns that might be interpreted as absorption or emission lines in the bursts' spectra. This phenomenon, if detected, may be used as a unique probe of dark matter in the universe. The BATSE spectral data should allow one to detect such spectral features or to put significant upper limits on the cosmic density of a dark matter component that may be in the femtolensing range. Software to generate theoretical spectra has been developed, and it is accessible over the computer network with anonymous ftp.

Longitudinal Variation and Waves in Jupiter's South Equatorial Wind Jet

NASA Technical Reports Server (NTRS)

Simon-Miller, A. A.; Rogers, John H.; Gierasch, Peter J.; Choi, David; Allison, Michael; Adamoli, Gianluigi; Mettig, Hans-Joerg

2012-01-01

We have conducted a detailed study of the cloud features in the strong southern equatorial wind jet near 7.5 S planetographic latitude. To understand the apparent variations in average zonal wind jet velocity at this latitude [e.g.. 1,2,3], we have searched for variations iIi both feature latitude and velocity with longitude and time. In particular, we focused on the repetitive chevron-shaped dark spots visible on most dates and the more transient large anticyclonic system known as the South Equatorial Disturbance (SED). These small dark spots are interpreted as cloud holes, and are often used as material tracers of the wind field.

Online Cost and Search Results: A Comparison of BRS After Dark and Knowledge Index.

ERIC Educational Resources Information Center

Cloud, Gayla Staples; Hambic, Jacqueline B.

1987-01-01

Reports the results of a study which examined costs and search results for 20 searchers conducted on both BRS After Dark and Knowledge Index. Various features of the two retrieval systems are reviewed, and advantages and disadvantages of each system are summarized. Data are presented in one table and several graphs. (24 references) (MES)

The DESI Experiment Part I: Science,Targeting, and Survey Design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aghamousa, Amir; et al.

DESI (Dark Energy Spectroscopic Instrument) is a Stage IV ground-based dark energy experiment that will study baryon acoustic oscillations (BAO) and the growth of structure through redshift-space distortions with a wide-area galaxy and quasar redshift survey. To trace the underlying dark matter distribution, spectroscopic targets will be selected in four classes from imaging data. We will measure luminous red galaxies up tomore » $z=1.0$. To probe the Universe out to even higher redshift, DESI will target bright [O II] emission line galaxies up to $z=1.7$. Quasars will be targeted both as direct tracers of the underlying dark matter distribution and, at higher redshifts ($ 2.1 < z < 3.5$), for the Ly-$$\\alpha$$ forest absorption features in their spectra, which will be used to trace the distribution of neutral hydrogen. When moonlight prevents efficient observations of the faint targets of the baseline survey, DESI will conduct a magnitude-limited Bright Galaxy Survey comprising approximately 10 million galaxies with a median $$z\\approx 0.2$$. In total, more than 30 million galaxy and quasar redshifts will be obtained to measure the BAO feature and determine the matter power spectrum, including redshift space distortions.« less

Defects Enable Dark Exciton Photoluminescence in Single-Walled Carbon Nanotubes

DOE PAGES

Amori, Amanda R.; Rossi, Jamie E.; Landi, Brian J.; ...

2018-01-24

Variable temperature photoluminescence excitation spectroscopy of three (n,m) species of single-walled carbon nanotubes revealed that at resonant S 22 excitation, in addition to allowed excitonic optical transitions, several sidebands that should be forbidden based on selection rules were observed and appeared to have a strong temperature dependence. In particular, we found that a sideband located approximately 130 meV away from the bright S 11 exciton peak relating to the K-momentum dark exciton state, called X 1, decreased in intensity five-fold as the samples were cooled. Direct optical excitation of this dark state is nominally forbidden, thus calling into question howmore » the state is populated, and why it is so prominent in the photoluminescence spectrum. Interestingly, the ratio of the integrated photoluminescence intensities of X 1 to S 11 scales with a Boltzmann factor unrelated to the phonon that is thought to be responsible for depopulating the K-momentum dark exciton state: an in-plane transverse optical phonon, A 1’. Furthermore, photoluminescence spectra from individual (7,5) nanotubes show that only a small fraction exhibit the X 1 feature, with varying oscillator strength, thus suggesting that intrinsic processes such as phonon scattering are not responsible for populating the dark state. Alternatively, we suggest that populating the K-momentum dark exciton state requires scattering from defects, which is consistent with the increased magnitude of the X 1 feature for samples with increased sample purification and processing. Thus, the presence of an X 1 peak in photoluminescence is an extremely sensitive spectroscopic indicator of defects on single-walled carbon nanotubes.« less

Defects Enable Dark Exciton Photoluminescence in Single-Walled Carbon Nanotubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amori, Amanda R.; Rossi, Jamie E.; Landi, Brian J.

Variable temperature photoluminescence excitation spectroscopy of three (n,m) species of single-walled carbon nanotubes revealed that at resonant S 22 excitation, in addition to allowed excitonic optical transitions, several sidebands that should be forbidden based on selection rules were observed and appeared to have a strong temperature dependence. In particular, we found that a sideband located approximately 130 meV away from the bright S 11 exciton peak relating to the K-momentum dark exciton state, called X 1, decreased in intensity five-fold as the samples were cooled. Direct optical excitation of this dark state is nominally forbidden, thus calling into question howmore » the state is populated, and why it is so prominent in the photoluminescence spectrum. Interestingly, the ratio of the integrated photoluminescence intensities of X 1 to S 11 scales with a Boltzmann factor unrelated to the phonon that is thought to be responsible for depopulating the K-momentum dark exciton state: an in-plane transverse optical phonon, A 1’. Furthermore, photoluminescence spectra from individual (7,5) nanotubes show that only a small fraction exhibit the X 1 feature, with varying oscillator strength, thus suggesting that intrinsic processes such as phonon scattering are not responsible for populating the dark state. Alternatively, we suggest that populating the K-momentum dark exciton state requires scattering from defects, which is consistent with the increased magnitude of the X 1 feature for samples with increased sample purification and processing. Thus, the presence of an X 1 peak in photoluminescence is an extremely sensitive spectroscopic indicator of defects on single-walled carbon nanotubes.« less

Risk factors associated with delayed gastric emptying after subtotal gastrectomy with Billroth-I anastomosis using circular stapler for early gastric cancer patients.

PubMed

Kim, Ki Han; Kim, Min Chan; Jung, Ghap Joong

2012-11-01

Gastric surgery may potentiate delayed gastric emptying. Billroth I gastroduodenostomy using a circular stapler is the most preferable reconstruction method. The purpose of this study is to analyze the risk factors associated with delayed gastric emptying after radical subtotal gastrectomy with Billroth I anastomosis using a stapler for early gastric cancer. Three hundred and seventy-eight patients who underwent circular stapled Billroth I gastroduodenostomy after subtotal gastrectomy due to early gastric cancer were analyzed retrospectively. One hundred and eighty-two patients had Billroth I anastomosis using a 25 mm diameter circular stapler, and 196 patients had anastomosis with a 28 or 29 mm diameter circular stapler. Clinicopathological features and postoperative outcomes were evaluated and compared between the two groups. Delayed gastric emptying was diagnosed by symptoms and simple abdomen X-ray with or without upper gastrointestinal series or endoscopy. Postoperative delayed gastric emptying was found in 12 (3.2%) of the 378 patients. Among all the variables, distal margin and circular stapler diameter were significantly different between the cases with delayed gastric emptying and no delayed gastric emptying. There were statistically significant differences in sex, body mass index, comorbidity, complication, and operation type according to circular stapler diameter. In both univariate and multivariate logistic regression analyses, only the stapler diameter was found to be a significant factor affecting delayed gastric emptying (P = 0.040). In this study, the circular stapler diameter was one of the most significant predictable factors of delayed gastric emptying for Billroth I gastroduodenostomy. The use of a 28 or 29 mm diameter circular stapler rather than a 25 mm diameter stapler in stapled gastroduodenostomy for early gastric cancer can reduce postoperative delayed gastric emptying associated with anastomosic stenosis or edema with relative safety.

A new astrophysical solution to the Too Big To Fail problem. Insights from the moria simulations

NASA Astrophysics Data System (ADS)

Verbeke, R.; Papastergis, E.; Ponomareva, A. A.; Rathi, S.; De Rijcke, S.

2017-10-01

Aims: We test whether or not realistic analysis techniques of advanced hydrodynamical simulations can alleviate the Too Big To Fail problem (TBTF) for late-type galaxies. TBTF states that isolated dwarf galaxy kinematics imply that dwarfs live in halos with lower mass than is expected in a Λ cold dark matter universe. Furthermore, we want to identify the physical mechanisms that are responsible for this observed tension between theory and observations. Methods: We use the moria suite of dwarf galaxy simulations to investigate whether observational effects are involved in TBTF for late-type field dwarf galaxies. To this end, we create synthetic radio data cubes of the simulated moria galaxies and analyse their H I kinematics as if they were real, observed galaxies. Results: We find that for low-mass galaxies, the circular velocity profile inferred from spatially resolved H I kinematics often underestimates the true circular velocity profile, as derived directly from the enclosed mass. Fitting the H I kinematics of moria dwarfs with a theoretical halo profile results in a systematic underestimate of the mass of their host halos. We attribute this effect to the fact that the interstellar medium of a low-mass late-type dwarf is continuously stirred by supernova explosions into a vertically puffed-up, turbulent state to the extent that the rotation velocity of the gas is simply no longer a good tracer of the underlying gravitational force field. If this holds true for real dwarf galaxies as well, it implies that they inhabit more massive dark matter halos than would be inferred from their kinematics, solving TBTF for late-type field dwarf galaxies.

Collider Interplay for Supersymmetry, Higgs and Dark Matter

DOE PAGES

Buchmueller, Oliver; Citron, M.; Ellis, J.; ...

2015-10-01

Here, we discuss the potential impacts on the CMSSM of future LHC runs and possible e +e – and higher-energy proton–proton colliders, considering searches for supersymmetry via /E T events, precision electroweak physics, Higgs measurements and dark matter searches. We validate and present estimates of the physics reach for exclusion or discovery of supersymmetry via /E T searches at the LHC, which should cover the low-mass regions of the CMSSM parameter space favoured in a recent global analysis. As we illustrate with a low-mass benchmark point, a discovery would make possible accurate LHC measurements of sparticle masses using the MT2more » variable, which could be combined with cross-section and other measurements to constrain the gluino, squark and stop masses and hence the soft supersymmetry-breaking parameters m 0,m 1/2 and A 0 of the CMSSM. Slepton measurements at CLIC would enable m 0 and m 1/2 to be determined with high precision. If supersymmetry is indeed discovered in the low-mass region, precision electroweak and Higgs measurements with a future circular e +e – collider (FCC-ee, also known as TLEP) combined with LHC measurements would provide tests of the CMSSM at the loop level. If supersymmetry is not discovered at the LHC, it is likely to lie somewhere along a focus-point, stop-coannihilation strip or direct-channel A / H resonance funnel. We discuss the prospects for discovering supersymmetry along these strips at a future circular proton–proton collider such as FCC-hh. Illustrative benchmark points on these strips indicate that also in this case FCC-ee could provide tests of the CMSSM at the loop level.« less

Space Radar Image of Moscow, Russia

NASA Image and Video Library

1999-05-01

This is a vertically polarized L-band image of the southern half of Moscow, an area which has been inhabited for 2,000 years. The image covers a diameter of approximately 50 kilometers (31 miles) and was taken on September 30, 1994 by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar aboard the space shuttle Endeavour. The city of Moscow was founded about 750 years ago and today is home to about 8 million residents. The southern half of the circular highway (a road that looks like a ring) can easily be identified as well as the roads and railways radiating out from the center of the city. The city was named after the Moskwa River and replaced Russia's former capital, St. Petersburg, after the Russian Revolution in 1917. The river winding through Moscow shows up in various gray shades. The circular structure of many city roads can easily be identified, although subway connections covering several hundred kilometers are not visible in this image. The white areas within the ring road and outside of it are buildings of the city itself and it suburban towns. Two of many airports are located in the west and southeast of Moscow, near the corners of the image. The Kremlin is located north just outside of the imaged city center. It was actually built in the 16th century, when Ivan III was czar, and is famous for its various churches. In the surrounding area, light gray indicates forests, while the dark patches are agricultural areas. The various shades from middle gray to dark gray indicate different stages of harvesting, ploughing and grassland. http://photojournal.jpl.nasa.gov/catalog/PIA01752

Automated Photoreceptor Cell Identification on Nonconfocal Adaptive Optics Images Using Multiscale Circular Voting

PubMed Central

Liu, Jianfei; Jung, HaeWon; Dubra, Alfredo; Tam, Johnny

2017-01-01

Purpose Adaptive optics scanning light ophthalmoscopy (AOSLO) has enabled quantification of the photoreceptor mosaic in the living human eye using metrics such as cell density and average spacing. These rely on the identification of individual cells. Here, we demonstrate a novel approach for computer-aided identification of cone photoreceptors on nonconfocal split detection AOSLO images. Methods Algorithms for identification of cone photoreceptors were developed, based on multiscale circular voting (MSCV) in combination with a priori knowledge that split detection images resemble Nomarski differential interference contrast images, in which dark and bright regions are present on the two sides of each cell. The proposed algorithm locates dark and bright region pairs, iteratively refining the identification across multiple scales. Identification accuracy was assessed in data from 10 subjects by comparing automated identifications with manual labeling, followed by computation of density and spacing metrics for comparison to histology and published data. Results There was good agreement between manual and automated cone identifications with overall recall, precision, and F1 score of 92.9%, 90.8%, and 91.8%, respectively. On average, computed density and spacing values using automated identification were within 10.7% and 11.2% of the expected histology values across eccentricities ranging from 0.5 to 6.2 mm. There was no statistically significant difference between MSCV-based and histology-based density measurements (P = 0.96, Kolmogorov-Smirnov 2-sample test). Conclusions MSCV can accurately detect cone photoreceptors on split detection images across a range of eccentricities, enabling quick, objective estimation of photoreceptor mosaic metrics, which will be important for future clinical trials utilizing adaptive optics. PMID:28873173

The vertical structure of gaseous galaxy discs in cold dark matter haloes

NASA Astrophysics Data System (ADS)

Benítez-Llambay, Alejandro; Navarro, Julio F.; Frenk, Carlos S.; Ludlow, Aaron D.

2018-01-01

We study the vertical structure of polytropic centrifugally supported gaseous discs embedded in cold dark matter (CDM) haloes. At fixed radius, R, the shape of the vertical density profile depends weakly on whether the disc is self-gravitating (SG) or non-self-gravitating (NSG). The disc 'characteristic' thickness, zH, set by the midplane sound speed and circular velocity, zNSG = (cs/Vc)R, in the NSG case, and by the sound speed and surface density, z_SG = c_s^2/GΣ, in SG discs, is smaller than zSG and zNSG. SG discs are typically Toomre unstable, NSG discs are stable. Exponential discs in CDM haloes with roughly flat circular velocity curves 'flare' outwards. Flares in mono abundance or coeval populations in galaxies like the Milky Way are thus not necessarily due to radial migration. For the polytropic equation of state of the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulations, discs that match observational constraints are NSG for Md < 3 × 109 M⊙ and SG at higher masses, if fully gaseous. We test these analytic results using a set of idealized smoothed particle hydrodynamic simulations and find excellent agreement. Our results clarify the role of the gravitational softening on the thickness of simulated discs, and on the onset of radial instabilities. EAGLE low-mass discs are NSG so the softening plays no role in their vertical structure. High-mass discs are expected to be SG and unstable, and may be artificially thickened and stabilized unless gravity is well resolved. Simulations with spatial resolution high enough to not compromise the vertical structure of a disc also resolve the onset of their instabilities, but the converse is not true.

ARC-1989-A89-7006

NASA Image and Video Library

1989-08-21

Range : 12 million km (7.5 million miles) Resolution 110 km (68 miles) per pixel. These 2 images of Neptune were taken by Voyager 2's narrow-angle camera. During the 17.6 hours between the left and right images, the Great Dark Spot, at 22 degrees south latitude (left of center), has completed a little less than one rotation of Neptune. The smaller dark spot, at 54 south, completed a little more than one rotation, as can be seen by comparing its relative positions in the two pictures. The Great Dark Spot and the smaller spot have a relative velocity of 100 meters per second (220 miles an hour). The light and dark bands circling Neptune indicate predominantly zonal (east-west) motion. The diffuse white feature north of the Great Dark Spot is near Neptune's equator, and rotates with about the same period as the Great Dark Spot. Streak of bright clouds at the south edge, and just east of the Great Dark Spot, are its constatnt companions, and change the details of their appearance, often within a few hours. Changing brightness of the cloud streaks could be a result of vertical mortions.

Ricci-Gauss-Bonnet holographic dark energy

NASA Astrophysics Data System (ADS)

Saridakis, Emmanuel N.

2018-03-01

We present a model of holographic dark energy in which the infrared cutoff is determined by both the Ricci and the Gauss-Bonnet invariants. Such a construction has the significant advantage that the infrared cutoff, and consequently the holographic dark energy density, does not depend on the future or the past evolution of the universe, but only on its current features, and moreover it is determined by invariants, whose role is fundamental in gravitational theories. We extract analytical solutions for the behavior of the dark energy density and equation-of-state parameters as functions of the redshift. These reveal the usual thermal history of the universe, with the sequence of radiation, matter and dark energy epochs, resulting in the future to a complete dark energy domination. The corresponding dark energy equation-of-state parameter can lie in the quintessence or phantom regime, or experience the phantom-divide crossing during the cosmological evolution, and its asymptotic value can be quintessencelike, phantomlike, or be exactly equal to the cosmological-constant value. Finally, we extract the constraints on the model parameters that arise from big bang nucleosynthesis.

Study of dark matter and QCD-charged mediators in the quasidegenerate regime

NASA Astrophysics Data System (ADS)

Davidson, Andrew; Kelso, Chris; Kumar, Jason; Sandick, Pearl; Stengel, Patrick

2017-12-01

We study a scenario in which the only light new particles are a Majorana fermion dark matter candidate and one or more QCD-charged scalars, which couple to light quarks. This scenario has several interesting phenomenological features if the new particles are nearly degenerate in mass. In particular, LHC searches for the light scalars have reduced sensitivity, since the visible and invisible products tend to be softer. Moreover, dark matter-scalar coannihilation can allow even relatively heavy dark matter candidates to be consistent thermal relics. Finally, the dark matter nucleon scattering cross section is enhanced in the quasidegenerate limit, allowing direct detection experiments to use both spin-independent and spin-dependent scattering to probe regions of parameter space beyond those probed by the LHC. Although this scenario has a broad application, we phrase this study in terms of the minimal supersymmetric standard model, in the limit where the only light sparticles are a binolike dark matter candidate and light-flavored squarks.

Oscillation of neutrinos produced by the annihilation of dark matter inside the Sun

DOE Office of Scientific and Technical Information (OSTI.GOV)

Esmaili, Arman; School of Physics, Institute for Research in Fundamental Sciences; Farzan, Yasaman

2010-06-01

The annihilation of dark matter particles captured by the Sun can lead to a neutrino flux observable in neutrino detectors. Considering the fact that these dark matter particles are nonrelativistic, if a pair of dark matter annihilates to a neutrino pair, the spectrum of neutrinos will be monochromatic. We show that in this case, even after averaging over the production point inside the Sun, the oscillatory terms of the oscillation probability do not average to zero. This leads to interesting observable features in the annual variation of the number of muon track events. We show that smearing of the spectrummore » due to thermal distribution of dark matter inside the Sun is too small to wash out this variation. We point out the possibility of studying the initial flavor composition of neutrinos produced by the annihilation of dark matter particles via measuring the annual variation of the number of {mu}-track events in neutrino telescopes.« less

Searching for dark matter-dark energy interactions: Going beyond the conformal case

NASA Astrophysics Data System (ADS)

van de Bruck, Carsten; Mifsud, Jurgen

2018-01-01

We consider several cosmological models which allow for nongravitational direct couplings between dark matter and dark energy. The distinguishing cosmological features of these couplings can be probed by current cosmological observations, thus enabling us to place constraints on these specific interactions which are composed of the conformal and disformal coupling functions. We perform a global analysis in order to independently constrain the conformal, disformal, and mixed interactions between dark matter and dark energy by combining current data from: Planck observations of the cosmic microwave background radiation anisotropies, a combination of measurements of baryon acoustic oscillations, a supernova type Ia sample, a compilation of Hubble parameter measurements estimated from the cosmic chronometers approach, direct measurements of the expansion rate of the Universe today, and a compilation of growth of structure measurements. We find that in these coupled dark-energy models, the influence of the local value of the Hubble constant does not significantly alter the inferred constraints when we consider joint analyses that include all cosmological probes. Moreover, the parameter constraints are remarkably improved with the inclusion of the growth of structure data set measurements. We find no compelling evidence for an interaction within the dark sector of the Universe.

Lunar pyroclastic deposits as seen by the Mini-SAR on Chandrayaan-1

NASA Astrophysics Data System (ADS)

Thomson, B. J.; Spudis, P.; Bussey, B.; Neisch, C.

2009-12-01

The principal objective of the Mini-SAR (synthetic aperture radar) instrument on the Chandrayaan-1 spacecraft is the investigation of permanently shadowed regions in the lunar polar regions. But additional radar observations have been made of selected non-polar targets for comparison with observations of polar targets, as well as for their own intrinsic scientific merit. These non-polar targets include former Apollo and other landing sites, lunar pyroclastic deposits, and select fresh and degraded impact craters. Here we focus on observations of a maar-type volcanic feature on the floor of Schrödinger Basin, which has been previously interpreted as a pyroclastic deposit [1]. Lunar pyroclastic deposits have a unique physical texture - glass spheres - resulting from their origin in fire fountains associated with basaltic eruptions. Schrödinger Basin is a 320 km diameter peak ring basin centered at 75°S, 138°E. Based on crater counts and superposition relationships, it appears to be only slightly older than the Orientale Basin, making it among the youngest and freshest lunar basins of its size [2]. Mini-SAR observations cover half of the basin closest to the south pole, including a portion of the central smooth plains material. Circular polarization ratio (CPR) values for the dark mantle deposits on the floor of Schrödinger are 0.2 to 0.3, which are lower than the median value of about 0.5 for the surrounding terrain. High CPR values can result from rough, rocky surfaces or from the presence of ice. Since the floor of Schrödinger is not in shadow, low CPR values here are likely indicative of a low abundance of scattering elements (e.g., rocks), consistent with the known properties of pyroclastic deposits. Comparisons of the radar return of the Schrödinger floor deposits with other dark mantle deposits are ongoing. [1] Shoemaker, E.M. et al. (1994) Science, 266, 1851-1854. [2] Wilhelms, D.E. (1987) USGS Prof Paper 1348, 302 pp.

False Color View of Mercury

NASA Image and Video Library

2017-12-08

This colorful view of Mercury was produced by using images from the color base map imaging campaign during MESSENGER's primary mission. These colors are not what Mercury would look like to the human eye, but rather the colors enhance the chemical, mineralogical, and physical differences between the rocks that make up Mercury's surface. To watch a movie of this colorful view of Mercury as a spinning globe go here: www.flickr.com/photos/gsfc/8497927473 Young crater rays, extending radially from fresh impact craters, appear light blue or white. Medium- and dark-blue areas are a geologic unit of Mercury's crust known as the "low-reflectance material", thought to be rich in a dark, opaque mineral. Tan areas are plains formed by eruption of highly fluid lavas. The giant Caloris basin is the large circular tan feature located just to the upper right of center of the image. The MESSENGER spacecraft is the first ever to orbit the planet Mercury, and the spacecraft's seven scientific instruments and radio science investigation are unraveling the history and evolution of the Solar System's innermost planet. Visit the Why Mercury? section of this website to learn more about the key science questions that the MESSENGER mission is addressing. During the one-year primary mission, MESSENGER acquired 88,746 images and extensive other data sets. MESSENGER is now in a yearlong extended mission, during which plans call for the acquisition of more than 80,000 additional images to support MESSENGER's science goals. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

The Surface Density Profile of the Galactic Disk from the Terminal Velocity Curve

NASA Astrophysics Data System (ADS)

McGaugh, Stacy S.

2016-01-01

The mass distribution of the Galactic disk is constructed from the terminal velocity curve and the mass discrepancy-acceleration relation. Mass models numerically quantifying the detailed surface density profiles are tabulated. For R0 = 8 kpc, the models have stellar mass 5 < M* < 6 × 1010 {M}⊙ , scale length 2.0 ≤ Rd ≤ 2.9 kpc, LSR circular velocity 222 ≤ Θ0 ≤ 233 {km} {{{s}}}-1, and solar circle stellar surface density 34 ≤ Σd(R0) ≤ 61 {M}⊙ {{pc}}-2. The present interarm location of the solar neighborhood may have a somewhat lower stellar surface density than average for the solar circle. The Milky Way appears to be a normal spiral galaxy that obeys scaling relations like the Tully-Fisher relation, the size-mass relation, and the disk maximality-surface brightness relation. The stellar disk is maximal, and the spiral arms are massive. The bumps and wiggles in the terminal velocity curve correspond to known spiral features (e.g., the Centaurus arm is a ˜50% overdensity). The rotation curve switches between positive and negative over scales of hundreds of parsecs. The rms amplitude {< {| {dV}/{dR}| }2> }1/2≈ 14 {km} {{{s}}}-1 {{kpc}}-1, implying that commonly neglected terms in the Jeans equations may be nonnegligible. The spherically averaged local dark matter density is ρ0,DM ≈ 0.009 {M}⊙ {{pc}}-3 (0.34 {GeV} {{cm}}-3). Adiabatic compression of the dark matter halo may help reconcile the Milky Way with the c-V200 relation expected in ΛCDM while also helping to mitigate the too-big-to-fail problem, but it remains difficult to reconcile the inner bulge/bar-dominated region with a cuspy halo. We note that NGC 3521 is a near twin to the Milky Way, having a similar luminosity, scale length, and rotation curve.

View of eastern coast of Sicily area

NASA Image and Video Library

1973-08-15

SL3-87-355 (July-September 1973) --- A vertical view of the eastern coast of Sicily area is seen in this Skylab 3 Earth Resources Experiments Package S190-B (five-inch earth terrain camera) infrared photograph taken from the Skylab space station in Earth orbit. Mount Etna, the highest volcano in Europe (10,958 feet), is still active as evidenced by the thin plume of smoke emanating from its crest. (The altitude is approximate because the height of the volcano changes with each eruption). On the flanks of Etna recent lava flows appear black in contrast to the older flows and volcanic debris that are red. Numerous small, circular cinder cones on the flanks represent sites of previous eruptions. Catania, on the Mediterranean coast south of Etna, is the largest of several cities and villages which appear as light-gray patches on the lower slopes of the volcano. Plano de Catania, south of the city of Catania, is outlined by polygonal light and dark agricultural tracts. Several lakes, the largest of which is Lake Pozzillo, show up as dark blue in the photograph. The unusual colors in the picture are due to the use of color infrared film in which vegetation appears red. This is very evident on the slopes of Etna, in the Monti Nebrodi area at upper let, and in the local areas in the lower part of the picture. Studies of Mount Etna and related volcanic features will be undertaken by Professor Roberto Cassinis of Servizio Geologio d?Italia, Rome. Federal agencies participating with NASA on the EREP project are the Departments of Agriculture, Commerce, Interior, the Environmental Protection Agency and the Corps of Engineers. All EREP photography is available to the public through the Department of Interior?s Earth Resources Observation Systems Data Center, Sioux Falls, South Dakota, 57198. Photo credit: NASA

A newly discovered impact crater in Titan's Senkyo: Cassini VIMS observations and comparison with other impact features

USGS Publications Warehouse

Buratti, B.J.; Sotin, Christophe; Lawrence, K.; Brown, R.H.; Le, Mouelic S.; Soderblom, J.M.; Barnes, J.; Clark, R.N.; Baines, K.H.; Nicholson, P.D.

2012-01-01

Senkyo is an equatorial plain on Titan filled with dunes and surrounded by hummocky plateaus. During the Titan targeted flyby T61 on August 25, 2009, the Cassini Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft observed a circular feature, centered at 5.4?? N and 341??W, that superimposes the dune fields and a bright plateau. This circular feature, which has been named Paxsi by the International Astronomical Union, is 120??10 km in diameter (measured from the outer edge of the crater rim) and exhibits a central bright area that can be interpreted as the central peak or pit of an impact crater. Although there are only a handful of certain impact craters on Titan, there are two other craters that are of similar size to this newly discovered feature and that have been studied by VIMS: Sinlap (Le Mou??lic et al, 2008) and Selk (Soderblom et al, 2010). Sinlap is associated with a large downwind, fan-like feature that may have been formed from an impact plume that rapidly expanded and deposited icy particles onto the surface. Although much of the surrounding region is covered with dunes, the plume region is devoid of dunes. The formation process of Selk also appears to have removed (or covered up) dunes from parts of the adjacent dune-filled terrain. The circular feature on Senkyo is quite different: there is no evidence of an ejecta blanket and the crater itself appears to be infilled with dune material. The rim of the crater appears to be eroded by fluvial processes; at one point the rim is breached. The rim is unusually narrow, which may be due to mass wasting on its inside and subsequent infill by dunes. Based on these observations, we interpret this newly discovered feature to be a more eroded crater than both Sinlap and Selk. Paxsi may have formed during a period when Titan was warmer and more ductile than it is currently. ?? 2011 Elsevier Ltd. All rights reserved.

The dark side of flipped trinification

NASA Astrophysics Data System (ADS)

Dong, P. V.; Huong, D. T.; Queiroz, Farinaldo S.; Valle, José W. F.; Vaquera-Araujo, C. A.

2018-04-01

We propose a model which unifies the Left-Right symmetry with the SU(3) L gauge group, called flipped trinification, and based on the SU(3) C ⊗ SU(3) L ⊗ SU(3) R ⊗ U(1) X gauge group. The model inherits the interesting features of both symmetries while elegantly explaining the origin of the matter parity, W P = (-1)3( B- L)+2 s , and dark matter stability. We develop the details of the spontaneous symmetry breaking mechanism in the model, determining the relevant mass eigenstates, and showing how neutrino masses are easily generated via the seesaw mechanism. Moreover, we introduce viable dark matter candidates, encompassing a fermion, scalar and possibly vector fields, leading to a potentially novel dark matter phenomenology.

Scalar dark matter in leptophilic two-Higgs-doublet model

NASA Astrophysics Data System (ADS)

Bandyopadhyay, Priyotosh; Chun, Eung Jin; Mandal, Rusa

2018-04-01

Two-Higgs-Doublet Model of Type-X in the large tan ⁡ β limit becomes leptophilic to allow a light pseudo-scalar A and thus provides an explanation of the muon g - 2 anomaly. Introducing a singlet scalar dark matter S in this context, one finds that two important dark matter properties, nucleonic scattering and self-annihilation, are featured separately by individual couplings of dark matter to the two Higgs doublets. While one of the two couplings is strongly constrained by direct detection experiments, the other remains free to be adjusted for the relic density mainly through the process SS → AA. This leads to the 4τ final states which can be probed by galactic gamma ray detections.

Stability of chirped bright and dark soliton-like solutions of the cubic complex Ginzburg Landau equation with variable coefficients

NASA Astrophysics Data System (ADS)

Fang, Fang; Xiao, Yan

2006-12-01

We consider an inhomogeneous optical fiber system described by the generalized cubic complex Ginzburg-Landau (CGL) equation with varying dispersion, nonlinearity, gain (loss), nonlinear gain (absorption) and the effect of spectral limitation. Exact chirped bright and dark soliton-like solutions of the CGL equation were found by using a suitable ansatz. Furthermore, we analyze the features of the solitons and consider the problem of stability of these soliton-like solutions under finite initial perturbations. It is shown by extensive numerical simulations that both bright and dark soliton-like solutions are stable in an inhomogeneous fiber system. Finally, the interaction between two chirped bright and dark soliton-like pulses is investigated numerically.

Richat Structure, Mauritania

NASA Image and Video Library

2004-06-17

This prominent circular feature, known as the Richat Structure, in the Sahara desert of Mauritania is often noted by astronauts because it forms a conspicuous bull-eye on the otherwise rather featureless expanse of the desert.

Digital amateur observations of Venus at 0.9μm

NASA Astrophysics Data System (ADS)

Kardasis, E.

2017-09-01

Venus atmosphere is extremely dynamic, though it is very difficult to observe any features on it in the visible and even in the near-IR range. Digital observations with planetary cameras in recent years routinely produce high-quality images, especially in the near-infrared (0.7-1μm), since IR wavelengths are less influenced by Earth's atmosphere and Venus's atmosphere is partially transparent in this spectral region. Continuous observations over a few hours may track dark atmospheric features in the dayside and determine their motion. In this work we will present such observations and some dark-feature motion measurements at 0.9μm. Ground-based observations at this wavelength are rare and are complementary to in situ observations by JAXA's Akatsuki orbiter, that studies the atmospheric dynamics of Venus also in this band with the IR1 camera.

View east over the Rocky Mountains and Great Plains

NASA Image and Video Library

1974-02-01

SL4-138-3875 (February 1974) --- A color oblique photograph looking east over the Rocky Mountains and Great Plains. This view covers a portion of the States of Colorado, Wyoming, and Nebraska. A Skylab 4 crewmen took this picture with a hand-held 70mm Hasselblad camera. This entire region, covered with a blanket of snow, depicts much of the structural and topographic features of the Rocky Mountain chain. Man's only apparent change to the snow pattern seen here is the (right center) metropolitan areas of Denver and Colorado Springs, Colorado, which can be observed along the eastern edge of the mountain front. Grand Junction, Colorado on the western slope of the Rocky Mountains is just off the photograph at left center bottom. The major inter-montane valleys of South Park (right center), Middle Park (center), and North Park (left center) are clearly visible and separate the Colorado Rockies Front Range from the high rugged mountains can be discovered such as Pikes Peak near right border (center), Mt. Cunnison region, circular feature accentuated by the Cunnison River (dark) in the right center (bottom) of the photograph. The snow covered peaks of Mts. Harvard, Princeton and Yale form the high region of the Collegiate Range which is the pronounced mountain area in the right center. Snow cover not only enhances mountain features but also the drainage patterns. East of Denver (right corner) the sinuous trace of the South Platte River (center) and its junction with the North Platte River near North Platte, Nebraska. Lake McConaughy in Nebraska is the body of water (black) near the river intersection. The trace of the Republic River in southern Nebraska is visible near the right corner of the photography. Geologic and hydro logic studies using this photograph will be conducted by Dr. Roger Morrison, U.S. Geological Survey. Photo credit: NASA

Automatic detection of diabetic retinopathy features in ultra-wide field retinal images

NASA Astrophysics Data System (ADS)

Levenkova, Anastasia; Sowmya, Arcot; Kalloniatis, Michael; Ly, Angelica; Ho, Arthur

2017-03-01

Diabetic retinopathy (DR) is a major cause of irreversible vision loss. DR screening relies on retinal clinical signs (features). Opportunities for computer-aided DR feature detection have emerged with the development of Ultra-WideField (UWF) digital scanning laser technology. UWF imaging covers 82% greater retinal area (200°), against 45° in conventional cameras3 , allowing more clinically relevant retinopathy to be detected4 . UWF images also provide a high resolution of 3078 x 2702 pixels. Currently DR screening uses 7 overlapping conventional fundus images, and the UWF images provide similar results1,4. However, in 40% of cases, more retinopathy was found outside the 7-field ETDRS) fields by UWF and in 10% of cases, retinopathy was reclassified as more severe4 . This is because UWF imaging allows examination of both the central retina and more peripheral regions, with the latter implicated in DR6 . We have developed an algorithm for automatic recognition of DR features, including bright (cotton wool spots and exudates) and dark lesions (microaneurysms and blot, dot and flame haemorrhages) in UWF images. The algorithm extracts features from grayscale (green "red-free" laser light) and colour-composite UWF images, including intensity, Histogram-of-Gradient and Local binary patterns. Pixel-based classification is performed with three different classifiers. The main contribution is the automatic detection of DR features in the peripheral retina. The method is evaluated by leave-one-out cross-validation on 25 UWF retinal images with 167 bright lesions, and 61 other images with 1089 dark lesions. The SVM classifier performs best with AUC of 94.4% / 95.31% for bright / dark lesions.

Terahertz Absorption and Circular Dichroism Spectroscopy of Solvated Biopolymers

NASA Astrophysics Data System (ADS)

Xu, Jing; Plaxco, Kevin; Allen, S. James

2006-03-01

Biopolymers are expected to exhibit broad spectral features in the terahertz frequency range, corresponding to their functionally relevant, global and sub-global collective vibrational modes with ˜ picosecond timescale. Recent advances in terahertz technology have stimulated researchers to employ terahertz absorption spectroscopy to directly probe these postulated collective modes. However, these pioneering studies have been limited to dry and, at best, moist samples. Successful isolation of low frequency vibrational activities of solvated biopolymers in their natural water environment has remained elusive, due to the overwhelming attenuation of the terahertz radiation by water. Here we have developed a terahertz absorption and circular dichroism spectrometer suitable for studying biopolymers in biologically relevant water solutions. We have precisely isolated, for the first time, the terahertz absorption of solvated prototypical proteins, Bovine Serum Albumin and Lysozyme, and made important direct comparison to the existing molecular dynamic simulations and normal mode calculations. We have also successfully demonstrated the magnetic circular dichroism in semiconductors, and placed upper bounds on the terahertz circular dichroism signatures of prototypical proteins in water solution.

Density Fluctuation in Asymmetric Nozzle Plumes and Correlation with Far Field Noise

NASA Technical Reports Server (NTRS)

Panda, J.; Zaman, K. B. M. Q.

2001-01-01

A comparative experimental study of air density fluctuations in the unheated plumes of a circular, 4-tabbed-circular, chevron-circular and 10-lobed rectangular nozzles was performed at a fixed Mach number of 0.95 using a recently developed Rayleigh scattering based technique. Subsequently, the flow density fluctuations are cross-correlated with the far field sound pressure fluctuations to determine sources for acoustics emission. The nearly identical noise spectra from the baseline circular and the chevron nozzles are found to be in agreement with the similarity in spreading, turbulence fluctuations, and flow-sound correlations measured in the plumes. The lobed nozzle produced the least low frequency noise, in agreement with the weakest overall density fluctuations and flow-sound correlation. The tabbed nozzle took an intermediate position in the hierarchy of noise generation, intensity of turbulent fluctuation and flow-sound correlation. Some of the features in the 4-tabbed nozzle are found to be explainable in terms of splitting of the jet in a central large core and 4 side jetlets.

Comprehensive asymmetric dark matter model

NASA Astrophysics Data System (ADS)

Lonsdale, Stephen J.; Volkas, Raymond R.

2018-05-01

Asymmetric dark matter (ADM) is motivated by the similar cosmological mass densities measured for ordinary and dark matter. We present a comprehensive theory for ADM that addresses the mass density similarity, going beyond the usual ADM explanations of similar number densities. It features an explicit matter-antimatter asymmetry generation mechanism, has one fully worked out thermal history and suggestions for other possibilities, and meets all phenomenological, cosmological and astrophysical constraints. Importantly, it incorporates a deep reason for why the dark matter mass scale is related to the proton mass, a key consideration in ADM models. Our starting point is the idea of mirror matter, which offers an explanation for dark matter by duplicating the standard model with a dark sector related by a Z2 parity symmetry. However, the dark sector need not manifest as a symmetric copy of the standard model in the present day. By utilizing the mechanism of "asymmetric symmetry breaking" with two Higgs doublets in each sector, we develop a model of ADM where the mirror symmetry is spontaneously broken, leading to an electroweak scale in the dark sector that is significantly larger than that of the visible sector. The weak sensitivity of the ordinary and dark QCD confinement scales to their respective electroweak scales leads to the necessary connection between the dark matter and proton masses. The dark matter is composed of either dark neutrons or a mixture of dark neutrons and metastable dark hydrogen atoms. Lepton asymmetries are generated by the C P -violating decays of heavy Majorana neutrinos in both sectors. These are then converted by sphaleron processes to produce the observed ratio of visible to dark matter in the universe. The dynamics responsible for the kinetic decoupling of the two sectors emerges as an important issue that we only partially solve.

Mineralogy of dark asteroids: Detection of phyllosilicate features in the mid-infrared

NASA Astrophysics Data System (ADS)

McAdam, Margaret; Sunshine , Jessica Sunshine M.; Kelley, Michael S.

2014-11-01

Dark asteroids (C- and related types) have been shown to have phyllosilicates on their surfaces by the presence of the 0.7-µm charge transfer band in the visible/near-infrared (VIS/NIR) spectral region (e.g. [1], [2]). Observations of asteroids in the 2.5-5-µm have also indicated the presence of water [3, 4] and phyllosilicates [5, 6]. Phyllosilicates also have spectral features in the 8-30-µm [7]. The results of a coordinated spectral-mineralogical study of aqueously altered meteorites [8] can be used to both remotely identify the presence of aqueous alteration and determine the degree of alteration on asteroids. Two main regions have strong features related to the mineralogy and degree of alteration: the 10-13-µm and the 16-25-µm region. Alteration features change continuously in these regions between less 60%) and highly 90%) altered meteorites. These features have been identified in the spectra of some dark asteroids [8, 9, 10]. Additionally, no trends are found between 0.7-µm charge transfer band and degree of alteration. While all meteorites with a 0.7-µm band have phyllosilicates, the absence of a 0.7-µm band is not indicative of the absence of alteration. Altered meteorites always exhibit MIR features that are directly related to their degree of alteration whether or not they have a 0.7-µm band. Here, we present preliminary results of a survey of archived Spitzer Space Telescope data of asteroids in the 10-13-µm region and the 16-25-µm region (where data is available) including comparisons to published VIS/NIR spectra of the same dark asteroids without VIS/NIR features. Possible effects in comparing laboratory measurements of meteorite powders under ambient conditions to telescopic spectra of asteroid regoliths are considered. [1] Vilas and Gaffey, (1989) Nature, 246, 790-792. [2] Barucci et al (1998) Icarus, 132, 388-396. [3] Campins et al., (2010), Nature Letters, 464, 1320-1321. [4] Rivkin & Emery (2010) Nature Letters, 464, 1322-1323. [5] Hargrove, et al. (2012), Icarus, 221, 453-455. [6] Takir and Emery (2012) Icarus, 219, 641-654. [7] Calvin & King, (1997), Met. & Plan. Sci., 32, 693-701. [8] McAdam et al, Icarus, in review. [9] McAdam, et al (2013) DPS abs. [10] McAdam et al, ACM abs.

Little composite dark matter.

PubMed

Balkin, Reuven; Perez, Gilad; Weiler, Andreas

2018-01-01

We examine the dark matter phenomenology of a composite electroweak singlet state. This singlet belongs to the Goldstone sector of a well-motivated extension of the Littlest Higgs with T -parity. A viable parameter space, consistent with the observed dark matter relic abundance as well as with the various collider, electroweak precision and dark matter direct detection experimental constraints is found for this scenario. T -parity implies a rich LHC phenomenology, which forms an interesting interplay between conventional natural SUSY type of signals involving third generation quarks and missing energy, from stop-like particle production and decay, and composite Higgs type of signals involving third generation quarks associated with Higgs and electroweak gauge boson, from vector-like top-partners production and decay. The composite features of the dark matter phenomenology allows the composite singlet to produce the correct relic abundance while interacting weakly with the Higgs via the usual Higgs portal coupling [Formula: see text], thus evading direct detection.

Little composite dark matter

NASA Astrophysics Data System (ADS)

Balkin, Reuven; Perez, Gilad; Weiler, Andreas

2018-02-01

We examine the dark matter phenomenology of a composite electroweak singlet state. This singlet belongs to the Goldstone sector of a well-motivated extension of the Littlest Higgs with T-parity. A viable parameter space, consistent with the observed dark matter relic abundance as well as with the various collider, electroweak precision and dark matter direct detection experimental constraints is found for this scenario. T-parity implies a rich LHC phenomenology, which forms an interesting interplay between conventional natural SUSY type of signals involving third generation quarks and missing energy, from stop-like particle production and decay, and composite Higgs type of signals involving third generation quarks associated with Higgs and electroweak gauge boson, from vector-like top-partners production and decay. The composite features of the dark matter phenomenology allows the composite singlet to produce the correct relic abundance while interacting weakly with the Higgs via the usual Higgs portal coupling λ _{ {DM}}˜ O(1%), thus evading direct detection.

Dynamics of Dark-Fly Genome Under Environmental Selections.

PubMed

Izutsu, Minako; Toyoda, Atsushi; Fujiyama, Asao; Agata, Kiyokazu; Fuse, Naoyuki

2015-12-04

Environmental adaptation is one of the most fundamental features of organisms. Modern genome science has identified some genes associated with adaptive traits of organisms, and has provided insights into environmental adaptation and evolution. However, how genes contribute to adaptive traits and how traits are selected under an environment in the course of evolution remain mostly unclear. To approach these issues, we utilize "Dark-fly", a Drosophila melanogaster line maintained in constant dark conditions for more than 60 years. Our previous analysis identified 220,000 single nucleotide polymorphisms (SNPs) in the Dark-fly genome, but did not clarify which SNPs of Dark-fly are truly adaptive for living in the dark. We found here that Dark-fly dominated over the wild-type fly in a mixed population under dark conditions, and based on this domination we designed an experiment for genome reselection to identify adaptive genes of Dark-fly. For this experiment, large mixed populations of Dark-fly and the wild-type fly were maintained in light conditions or in dark conditions, and the frequencies of Dark-fly SNPs were compared between these populations across the whole genome. We thereby detected condition-dependent selections toward approximately 6% of the genome. In addition, we observed the time-course trajectory of SNP frequency in the mixed populations through generations 0, 22, and 49, which resulted in notable categorization of the selected SNPs into three types with different combinations of positive and negative selections. Our data provided a list of about 100 strong candidate genes associated with the adaptive traits of Dark-fly. Copyright © 2016 Izutsu et al.

Dynamics of Dark-Fly Genome Under Environmental Selections

PubMed Central

Izutsu, Minako; Toyoda, Atsushi; Fujiyama, Asao; Agata, Kiyokazu; Fuse, Naoyuki

2015-01-01

Environmental adaptation is one of the most fundamental features of organisms. Modern genome science has identified some genes associated with adaptive traits of organisms, and has provided insights into environmental adaptation and evolution. However, how genes contribute to adaptive traits and how traits are selected under an environment in the course of evolution remain mostly unclear. To approach these issues, we utilize “Dark-fly”, a Drosophila melanogaster line maintained in constant dark conditions for more than 60 years. Our previous analysis identified 220,000 single nucleotide polymorphisms (SNPs) in the Dark-fly genome, but did not clarify which SNPs of Dark-fly are truly adaptive for living in the dark. We found here that Dark-fly dominated over the wild-type fly in a mixed population under dark conditions, and based on this domination we designed an experiment for genome reselection to identify adaptive genes of Dark-fly. For this experiment, large mixed populations of Dark-fly and the wild-type fly were maintained in light conditions or in dark conditions, and the frequencies of Dark-fly SNPs were compared between these populations across the whole genome. We thereby detected condition-dependent selections toward approximately 6% of the genome. In addition, we observed the time-course trajectory of SNP frequency in the mixed populations through generations 0, 22, and 49, which resulted in notable categorization of the selected SNPs into three types with different combinations of positive and negative selections. Our data provided a list of about 100 strong candidate genes associated with the adaptive traits of Dark-fly. PMID:26637434

A programmable light engine for quantitative single molecule TIRF and HILO imaging.

PubMed

van 't Hoff, Marcel; de Sars, Vincent; Oheim, Martin

2008-10-27

We report on a simple yet powerful implementation of objective-type total internal reflection fluorescence (TIRF) and highly inclined and laminated optical sheet (HILO, a type of dark-field) illumination. Instead of focusing the illuminating laser beam to a single spot close to the edge of the microscope objective, we are scanning during the acquisition of a fluorescence image the focused spot in a circular orbit, thereby illuminating the sample from various directions. We measure parameters relevant for quantitative image analysis during fluorescence image acquisition by capturing an image of the excitation light distribution in an equivalent objective backfocal plane (BFP). Operating at scan rates above 1 MHz, our programmable light engine allows directional averaging by circular spinning the spot even for sub-millisecond exposure times. We show that restoring the symmetry of TIRF/HILO illumination reduces scattering and produces an evenly lit field-of-view that affords on-line analysis of evanescnt-field excited fluorescence without pre-processing. Utilizing crossed acousto-optical deflectors, our device generates arbitrary intensity profiles in BFP, permitting variable-angle, multi-color illumination, or objective lenses to be rapidly exchanged.

Studies of outer planet satellites, Mercury and Uranus

NASA Technical Reports Server (NTRS)

Mckinnon, William B.; Schenk, Paul M.

1987-01-01

Arguments were made, based on geometry, for both an impact and an internal origin for the ancient, partially preserved furrow system of Ganymede. It was concluded that furrows were not concentric, but could be impact related if multiringed structures on icy satellites are initially noncircular. The geometry of the Valhalla ring structure on Callisto was examined in order to assess the circularity of an unmodified ring system. The Ganymede furrow system was remapped to make use of improvements in coordinate control. The least-squares center of curvature for all furrows in the Marius and Galileao Regio is -20.7, and 179.2 degrees. Furrows in Marius and Galileo Regio are reasonably concentric, and are much more circular than previously estimated. The perceived present nonalignment of the assumed originally concentric furrows were used to argue for large-scale lateral motion of dark terrain blocks in Ganymede's crust, presumably in association with bright terrain formation., The overall alignment of furrows as well as the inherent scatter in centers of curvature from subregions of Galileo and Marius do not support this hypothesis.

Can tonne-scale direct detection experiments discover nuclear dark matter?

NASA Astrophysics Data System (ADS)

Butcher, Alistair; Kirk, Russell; Monroe, Jocelyn; West, Stephen M.

2017-10-01

Models of nuclear dark matter propose that the dark sector contains large composite states consisting of dark nucleons in analogy to Standard Model nuclei. We examine the direct detection phenomenology of a particular class of nuclear dark matter model at the current generation of tonne-scale liquid noble experiments, in particular DEAP-3600 and XENON1T. In our chosen nuclear dark matter scenario distinctive features arise in the recoil energy spectra due to the non-point-like nature of the composite dark matter state. We calculate the number of events required to distinguish these spectra from those of a standard point-like WIMP state with a decaying exponential recoil spectrum. In the most favourable regions of nuclear dark matter parameter space, we find that a few tens of events are needed to distinguish nuclear dark matter from WIMPs at the 3 σ level in a single experiment. Given the total exposure time of DEAP-3600 and XENON1T we find that at best a 2 σ distinction is possible by these experiments individually, while 3 σ sensitivity is reached for a range of parameters by the combination of the two experiments. We show that future upgrades of these experiments have potential to distinguish a large range of nuclear dark matter models from that of a WIMP at greater than 3 σ.

Can tonne-scale direct detection experiments discover nuclear dark matter?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butcher, Alistair; Kirk, Russell; Monroe, Jocelyn

Models of nuclear dark matter propose that the dark sector contains large composite states consisting of dark nucleons in analogy to Standard Model nuclei. We examine the direct detection phenomenology of a particular class of nuclear dark matter model at the current generation of tonne-scale liquid noble experiments, in particular DEAP-3600 and XENON1T. In our chosen nuclear dark matter scenario distinctive features arise in the recoil energy spectra due to the non-point-like nature of the composite dark matter state. We calculate the number of events required to distinguish these spectra from those of a standard point-like WIMP state with amore » decaying exponential recoil spectrum. In the most favourable regions of nuclear dark matter parameter space, we find that a few tens of events are needed to distinguish nuclear dark matter from WIMPs at the 3 σ level in a single experiment. Given the total exposure time of DEAP-3600 and XENON1T we find that at best a 2 σ distinction is possible by these experiments individually, while 3 σ sensitivity is reached for a range of parameters by the combination of the two experiments. We show that future upgrades of these experiments have potential to distinguish a large range of nuclear dark matter models from that of a WIMP at greater than 3 σ .« less

Photographer : JPL Range : 862,200 km. ( 500,000 miles ) This photograph shows subspacecraft

NASA Technical Reports Server (NTRS)

1979-01-01

Photographer : JPL Range : 862,200 km. ( 500,000 miles ) This photograph shows subspacecraft longitude of approximately 146 degrees of Jupiter's moon Io. Circular features are seen that may be meteorite impact craters or features of internal origins. Irregular depressions are seen that indicate surface modifications. The bright irregular patches appear to be younger deposits masking the surface detail.

Terahertz circular dichroism spectroscopy of biomolecules

NASA Astrophysics Data System (ADS)

Xu, Jing; Galan, Jhenny; Ramian, Gerald; Savvidis, Pavlos; Scopatz, Anthony; Birge, Robert R.; Allen, S. James; Plaxco, Kevin

2004-02-01

Biopolymers such as proteins, DNA and RNA fold into large, macromolecular chiral structures. As charged macromolecules, they absorb strongly in the terahertz due to large-scale collective vibrational modes; as chiral objects, this absorption should be coupled with significant circular dichroism. Terahertz circular dichroism (TCD) is potentially important as a biospecific sensor, unobscured by spectral features related to abiological material. We have constructed atomistic simulations and elastic continuum models of TCD. These models estimate the magnitude of the TCD and the relation between TCD spectroscopic signatures (zero crossings) and the structure, charge distribution and mechanical properties of biomaterials. A broad band TCD spectrometer based on a polarizing interferometer is developed to explore TCD in biomolecules in aqueous solution. Preliminary results on TCD in lysozyme in water at several terahertz frequencies is presented.

Identification and characterization of circular RNAs in zebrafish.

PubMed

Shen, Yudong; Guo, Xianwu; Wang, Weimin

2017-01-01

Circular RNA (circRNA), a class of RNAs with circular structure, has received little attention until recently, when some new features and functions were discovered. In the present study, we sequenced circRNAs in zebrafish (Danio rerio) and identified 3868 circRNAs using three algorithms (find_circ, CIRI, segemehl). The analysis of microRNA target sites on circRNAs shows that some circRNAs may function as miRNA sponges. Furthermore, we identified the existence of reverse complementary sequences in the flanking regions of only 25 (2.64%) exonic circRNAs, indicating that the mechanism of zebrafish exonic circRNA biogenesis might be different from that in mammals. Moreover, 1122 (29%) zebrafish circRNA sequences showed homology with human, mouse and coelacanth circRNAs. © 2016 Federation of European Biochemical Societies.

Simulated cosmic microwave background maps at 0.5 deg resolution: Unresolved features

NASA Technical Reports Server (NTRS)

Kogut, A.; Hinshaw, G.; Bennett, C. L.

1995-01-01

High-contrast peaks in the cosmic microwave background (CMB) anisotropy can appear as unresolved sources to observers. We fit simluated CMB maps generated with a cold dark matter model to a set of unresolved features at instrumental resolution 0.5 deg-1.5 deg to derive the integral number density per steradian n (greater than absolute value of T) of features brighter than threshold temperature absolute value of T and compare the results to recent experiments. A typical medium-scale experiment observing 0.001 sr at 0.5 deg resolution would expect to observe one feature brighter than 85 micro-K after convolution with the beam profile, with less than 5% probability to observe a source brighter than 150 micro-K. Increasing the power-law index of primordial density perturbations n from 1 to 1.5 raises these temperature limits absolute value of T by a factor of 2. The MSAM features are in agreement with standard cold dark matter models and are not necessarily evidence for processes beyond the standard model.

Comparative Study of Hand-Sutured versus Circular Stapled Anastomosis for Gastrojejunostomy in Laparoscopy Assisted Distal Gastrectomy

PubMed Central

Seo, Su Hyun; Kim, Min Chan; Choi, Hong Jo; Jung, Ghap Joong

2012-01-01

Purpose Mechanical stapler is regarded as a good alternative to the hand sewing technique, when used in gastric reconstruction. The circular stapling method has been widely applied to gastrectomy (open orlaparoscopic), for gastric cancer. We illustrated and compared the hand-sutured method to the circular stapling method, for Billroth-II, in patients who underwent laparoscopy assisted distal gastrectomy for gastric cancer. Materials and Methods Between April 2009 and May 2011, 60 patients who underwent laparoscopy assisted distal gastrectomy, with Billroth-II, were enrolled. Hand-sutured Billroth-II was performed in 40 patients (manual group) and circular stapler Billroth-II was performed in 20 patients (stapler group). Clinicopathological features and post-operative outcomes were evaluated and compared between the two groups. Results Nosignificant differences were observed in clinicopathologic parameters and post-operative outcomes, except in the operation times. Operation times and anastomosis times were significantly shorter in the stapler group (P=0.004 and P<0.001). Conclusions Compared to the hand-sutured method, the circular stapling method can be applied safely and more efficiently, when performing Billroth-II anastomosis, after laparoscopy assisted distal gastrectomy in patients with gastric cancer. PMID:22792525

Ganymede - close up photos

NASA Technical Reports Server (NTRS)

1979-01-01

Two close-up photos of Ganymede, largest of Jupiter's 13 moons, were obtained on July 8 by Voyager 2 from 86,000 miles (top) and 192,000 miles. They show different views of the largest block of dark, heavily cratered terrain seen on the giant moon. The bottom image shows objects three to four miles across; has a resolution of about 1.5 miles. The light, linear stripes recurring across the dark region resemble the outer rings of the large ring structure on Callisto. If these features are in fact related to an ancient ring structure formed by a large impact, their small curvature suggests that the original structure was even larger than one seen on Callisto. There is no apparent trace now of the center of this suggested structure, which must have been destroyed by the resurfacing evident over most of Ganymede in the grooved terrain. Another interpretation is that these features are not impact-related rings but are internally produced fractures crossing the dark terrain, similar to the grooved bands.

Photographer : JPL Range : top- 86,000 miles bottom- 192,000 mi. These two close-ups of Ganymede,

NASA Technical Reports Server (NTRS)

1979-01-01

Photographer : JPL Range : top- 86,000 miles bottom- 192,000 mi. These two close-ups of Ganymede, the largest of Jupiter's 13 moons, show different views of the largest block of dark, heavily cratered terrain. The bottom image shows objects 3 or 4 miles across, with resolution of about 1.5 miles. The light, linear stripes recurring across the dark region resemble the outer rings of the large ring structure around Callisto. If these features are related to an ancient ring structure formed by a large impact, their small curvature suggests that the original structure was even larger than one seen on Callisto. There is no apparent trace now of the center of this suggested structure, which must have been destroyed by the resurfacing evident over most of Ganymede in the grooved terrain. Another interpretation is that these features are not impact-related rings, but rather internally produced fractures crossing the dark terrain, similiar to the grooved bands.

Airbag Tracks on Mars

NASA Technical Reports Server (NTRS)

2004-01-01

The circular shapes seen on the martian surface in these images are 'footprints' left by the Mars Exploration Rover Opportunity's airbags during landing as the spacecraft gently rolled to a stop. Opportunity landed at approximately 9:05 p.m. PST on Saturday, Jan. 24, 2004, Earth-received time. The circular region of the flower-like feature on the right is about the size of a basketball. Scientists are studying the prints for more clues about the makeup of martian soil. The images were taken at Meridiani Planum, Mars, by the panoramic camera on the Mars Exploration Rover Opportunity.

Aspects of vertebrate gustatory phylogeny: morphology and turnover of chick taste bud cells.

PubMed

Ganchrow, J R; Ganchrow, D; Royer, S M; Kinnamon, J C

1993-10-01

The taste bud is a receptor form observed across vertebrates. The present report compares chick taste buds to those of other vertebrates using light and electron microscopy. Unlike mammals, but common to many modern avians, the dorsal surface of chick anterior tongue lacks taste papillae and taste buds. Ultrastructurally, chick buds located in the anterior floor of the mouth (as in some reptiles and amphibians) and palate contain dark, intermediate, light, and basal cell types. Dark, intermediate, and light cells extend microvilli into intragemmal lumina and pores communicating with the oral cavity. As specialized features, dark cell apices lack dense granules and exhibit short microvilli relative to light and intermediate cells. Dark cell cytoplasmic fingers envelop intragemmal nerve fibers and cells as in other species, and sometimes contain abundant clear vesicles. Nerve profile expansions often are located adjacent to dark, intermediate, and light cell nuclei. Classical afferent synaptic contacts are rarely observed. Taste cell turnover is suggested by mitotic and degenerating figures in chick buds. In addition, tritiated thymidine injected into hatchlings, whose anterior mandibular oral taste bud population approximates that in adults, reveals a turnover rate of about 4.5 days. This is about half that observed in altricial mammals, reflecting a species difference or developmental factor in precocial avians. It is concluded that chick taste buds exhibit morphologic features common to other vertebrate buds with specializations reflecting the influences of niche, glandular relations, and/or age.

Galactic rings revisited. II. Dark gaps and the locations of resonances in early-to-intermediate-type disc galaxies

NASA Astrophysics Data System (ADS)

Buta, Ronald J.

2017-10-01

Dark gaps are commonly seen in early-to-intermediate-type barred galaxies having inner and outer rings or related features. In this paper, the morphologies of 54 barred and oval ringed galaxies have been examined with the goal of determining what the dark gaps are telling us about the structure and evolution of barred galaxies. The analysis is based mainly on galaxies selected from the Galaxy Zoo 2 data base and the Catalogue of Southern Ringed Galaxies. The dark gaps between inner and outer rings are of interest because of their likely association with the L4 and L5 Lagrangian points that would be present in the gravitational potential of a bar or oval. Since the points are theoretically expected to lie very close to the corotation resonance (CR) of the bar pattern, the gaps provide the possibility of locating corotation in some galaxies simply by measuring the radius rgp of the gap region and setting rCR=rgp. With the additional assumption of generally flat rotation curves, the locations of other resonances can be predicted and compared with observed morphological features. It is shown that this `gap method' provides remarkably consistent interpretations of the morphology of early-to-intermediate-type barred galaxies. The paper also brings attention to cases where the dark gaps lie inside an inner ring, rather than between inner and outer rings. These may have a different origin compared to the inner/outer ring gaps.

Why is Light Text Harder to Read Than Dark Text?

NASA Technical Reports Server (NTRS)

Scharff, Lauren V.; Ahumada, Albert J.

2005-01-01

Scharff and Ahumada (2002, 2003) measured text legibility for light text and dark text. For paragraph readability and letter identification, responses to light text were slower and less accurate for a given contrast. Was this polarity effect (1) an artifact of our apparatus, (2) a physiological difference in the separate pathways for positive and negative contrast or (3) the result of increased experience with dark text on light backgrounds? To rule out the apparatus-artifact hypothesis, all data were collected on one monitor. Its luminance was measured at all levels used, and the spatial effects of the monitor were reduced by pixel doubling and quadrupling (increasing the viewing distance to maintain constant angular size). Luminances of vertical and horizontal square-wave gratings were compared to assess display speed effects. They existed, even for 4-pixel-wide bars. Tests for polarity asymmetries in display speed were negative. Increased experience might develop full letter templates for dark text, while recognition of light letters is based on component features. Earlier, an observer ran all conditions at one polarity and then switched. If dark and light letters were intermixed, the observer might use component features on all trials and do worse on the dark letters, reducing the polarity effect. We varied polarity blocking (completely blocked, alternating smaller blocks, and intermixed blocks). Letter identification responses times showed polarity effects at all contrasts and display resolution levels. Observers were also more accurate with higher contrasts and more pixels per degree. Intermixed blocks increased the polarity effect by reducing performance on the light letters, but only if the randomized block occurred prior to the nonrandomized block. Perhaps observers tried to use poorly developed templates, or they did not work as hard on the more difficult items. The experience hypothesis and the physiological gain hypothesis remain viable explanations.

Finite Inflation, Holography, and Dark Matter Annihilation

NASA Astrophysics Data System (ADS)

Scacco, Andrew Joseph

This thesis covers work on theoretical cosmology relating to inflation, de Sitter space, dark matter annihilation, and holography. A unifying feature of all these topics is that all of them occur in de Sitter space or focus on epochs of the Universe when the spacetime was close to de Sitter and that all of them have some connection to holography. Chapter 1 provides a pedagogical introduction to the fundamentals of cosmology, inflation, de Sitter space, dark matter annihilation and entanglement entropy. Chapter 2 covers the impact on the causal entropic principle of dark matter annihilation that we find to have the greatest relevance at late times in the future when the dark energy has driven the universe to be asymptotically de Sitter. In this chapter we estimate holographically preferred dark matter properties for a range of assumptions. Chapter 3 covers holographic bounds in models of finite inflation, specifically the Banks-Fischler bound and de Sitter equilibrium. The assumptions in each of these models are explored in detail and some interesting new connections are presented. Chapter 4 tests models of inflation with a fast-roll start that happen to satisfy the holographic bounds in Chapter 3 against cosmic microwave background data from Planck. We find a slight preference for a feature at the scale predicted by the Banks-Fischler bound though this preference is not found to be statistically significant. Chapter 5 contains a numerical computation of the holographic mutual information for an annular configuration of regions on a conformal field theory in de Sitter space using the AdS/CFT correspondence. This computation shows that the de Sitter space CFT entanglement entropy matches what would be expected from a Minkowski CFT and shows that the HRT conjecture works for this case.

South Polar Surface

NASA Image and Video Library

2011-07-14

It is high summer as NASA 2001 Mars Odyssey spacecraft captures this image of the South Pole of Mars. The circular surface features may look like swiss cheese, but how they form, coalesce, and disappear is not fully understood.

Close-up View of Yavine Corona

NASA Image and Video Library

1998-06-03

The view from NASA's Magellan spacecraft shows Yavine Corona, looking northeast. Coronae are roughly circular, volcanic features believed to form over hot upwellings of magma within the Venusian mantle. http://photojournal.jpl.nasa.gov/catalog/PIA00098

A search for Potential Impact Sites in Southern Argentina

NASA Astrophysics Data System (ADS)

Rocca, M. C. L.

The Southern part of Argentina is composed of five Provinces; Tierra del Fuego, Santa Cruz, Chubut, Rio Negro and Neuquen. A search for potential impact sites was performed by the author through the examination of 76 color LANDSAT satellite images ( 1:250,000 - resolution = 250 meters ) at the Instituto Geografico Militar ( IGM ) of Buenos Aires city. When a potential candidate was found a more detailed study of the site was done. If available the radar X-SAR satellite images of the Deutsche Forschungsanstalt fur Luft-und Raumfahrt, (DLR), Berlin, Germany , were also examined. The final step was to perform a review of the available published geologic information of each site at the Servicio Geologico y Minero Argentino ( SEGEMAR ), ( =Geological Survey of Argentina ), in Buenos Aires. The resulting catalogue contains information about sites where possible simple crater or complex impact structures could be present. Each case demands future detailed and `in situ' research by an impact cratering specialist. --Tierra del Fuego: TF1 ) Ushuaia 5569-II, No 218. Cerro Taarsh, Estancia San Justo. Possible complex structure. Semi-circular area of concentric low ridges. Estimated diameter : 12 km. Probably very eroded. --Santa Cruz: SC1 ) Gobernador Gregores 4969-I, No 127. Estancia La Aragonesa Possible eroded complex structure. Circular area of low ridges, estimated diameter: 10 km.. Bull's eye like morphology. SC2 ) Gobernador Gregores 4969-I, No 127. Gran Altiplanicie Central. Possible simple crater in basalts. Diameter: 1 km.. SC3 ) Tres Lagos 4972-IV, No 106. Meseta del Bagual Chico. Possible perfectly circular simple crater in basalts. Diameter: 1.0 km.. SC4 )Paso Rio Bote 5172-II, No 20. Rio Pelque, Ruta Provincial No 5. A circular bowl-shaped structure is present on fluvial deposits of pleistocenic age. Diameter: 3.5 km.. SC5 ) Caleta Olivia 4769-II, No 28. North of Cerro Doce Grande. Possible complex structure of concentric circular rings of ridges. SC6 ) Caleta Olivia 4769-II, No 28. NW shore of Laguna Sirven. Possible simple crater of 2.5 km. Most probably, the circular crater is a basaltic caldera of upper Miocene's age. SC7 ) Destacamento La Maria 4769-II, No 188. Estancia Los Mellizos, Ruta Provincial No 39. Possible eroded and covered complex structure. In this site there is a semi-circular feature of ridges and low hills. Diameter: 15 km. Topographic map shows the same pattern. The DLR's X-SAR images show a clear semi-circular feature of ridges and hills in this site. SC8 ) Hipolito Irigoyen 4772-IV, No 116. Meseta del Lago Buenos Aires. Possible perfectly circular simple crater of 1 Km. Neuquen: N1 ) Picun Leufu 3969-III No 14. Meseta de la Barda Negra. Nice perfectly circular possible simple crater in black Miocene's ( 14-10 Ma ) basaltic plateau. Diameter: 1.5 km.. Possible raised rim. Fresh aspect. No visible lava flows .

CHILES Con Pol: Probing galaxy evolution, the dark Universe, and cosmic magnetism with a deep 1000 hour Jansky VLA survey

NASA Astrophysics Data System (ADS)

Hales, Christopher A.; Chiles Con Pol Collaboration

2014-04-01

We recently started a 1000 hour campaign to observe 0.2 square degrees of the COSMOS field in full polarization continuum at 1.4 GHz with the Jansky VLA, as part of a joint program with the spectral line COSMOS HI Large Extragalactic Survey (CHILES). When complete, we expect our CHILES Continuum Polarization (CHILES Con Pol) survey to reach an unprecedented SKA-era sensitivity of 0.7 uJy per 4 arcsecond FWHM beam. Here we present the key goals of CHILES Con Pol, which are to (i) produce a source catalog of legacy value to the astronomical community, (ii) measure differential source counts in total intensity, linear polarization, and circular polarization in order to constrain the redshift and luminosity distributions of source populations, (iii) perform a novel weak lensing study using radio polarization as an indicator of intrinsic alignment to better study dark energy and dark matter, and (iv) probe the unknown origin of cosmic magnetism by measuring the strength and structure of intergalactic magnetic fields in the filaments of large scale structure. The CHILES Con Pol source catalog will be a useful resource for upcoming wide-field surveys by acting as a training set for machine learning algorithms, which can then be used to identify and classify radio sources in regions lacking deep multiwavelength coverage.

Dissecting the evolution of dark matter subhaloes in the Bolshoi simulation

NASA Astrophysics Data System (ADS)

van den Bosch, Frank C.

2017-06-01

We present a comprehensive analysis of the evolution of dark matter subhaloes in the cosmological Bolshoi simulation. We identify a complete set of 12 unique evolution channels by which subhaloes evolve in between simulation outputs, and study their relative importance and demographics. We show that instantaneous masses and maximum circular velocities of individual subhaloes are extremely noisy, despite the use of a sophisticated, phase-space-based halo finder. We also show that subhaloes experience frequent penetrating encounters with other subhaloes (on average about one per dynamical time), and that subhaloes whose apo-centre lies outside the virial radius of their host (the 'ejected' or 'backsplash' haloes) experience tidal forces that modify their orbits. This results in an average fractional subhalo exchange rate among host haloes of ˜0.01 Gyr-1 (at the present time). In addition, we show that there are three distinct disruption channels; one in which subhaloes drop below the mass resolution limit of the simulation, one in which subhaloes 'merge' with their host halo largely driven by dynamical friction, and one in which subhaloes abruptly disintegrate. We estimate that roughly 80 per cent of all subhalo disruption in the Bolshoi simulation is numerical, rather than physical. This 'overmerging' is a serious road-block for the use of numerical simulations to interpret small-scale clustering, or for any other study that is sensitive to the detailed demographics of dark matter substructure.

Scalar-fluid interacting dark energy: Cosmological dynamics beyond the exponential potential

NASA Astrophysics Data System (ADS)

Dutta, Jibitesh; Khyllep, Wompherdeiki; Tamanini, Nicola

2017-01-01

We extend the dynamical systems analysis of scalar-fluid interacting dark energy models performed in C. G. Boehmer et al., Phys. Rev. D 91, 123002 (2015), 10.1103/PhysRevD.91.123002 by considering scalar field potentials beyond the exponential type. The properties and stability of critical points are examined using a combination of linear analysis, computational methods and advanced mathematical techniques, such as center manifold theory. We show that the interesting results obtained with an exponential potential can generally be recovered also for more complicated scalar field potentials. In particular, employing power law and hyperbolic potentials as examples, we find late time accelerated attractors, transitions from dark matter to dark energy domination with specific distinguishing features, and accelerated scaling solutions capable of solving the cosmic coincidence problem.

Stick-Shape, Rice-Size Features on Martian Rock "Haroldswick"

NASA Image and Video Library

2018-02-08

The dark, stick-shaped features clustered on this Martian rock are about the size of grains of rice. This is a focus-merged view from the Mars Hand Lens Imager (MAHLI) camera on NASA's Curiosity Mars rover. It covers an area about 2 inches (5 centimeters) across. The focus-merged product was generated autonomously by MAHLI combining the in-focus portions of a few separate images taken at different focus settings on Jan. 1, 2018, during the 1,922nd Martian day, or sol, of Curiosity's work on Mars. This rock target, called "Haroldswick," is near the southern, uphill edge of "Vera Rubin Ridge" on lower Mount Sharp. The origin of the stick-shaped features is uncertain. One possibility is that they are erosion-resistant bits of dark material from mineral veins cutting through rocks in this area. https://photojournal.jpl.nasa.gov/catalog/PIA22213

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karamatskos, E. T.; Stockhofe, J.; Kevrekidis, P. G.

In this study, we consider a binary repulsive Bose-Einstein condensate in a harmonic trap in one spatial dimension and investigate particular solutions consisting of two dark-bright solitons. There are two different stationary solutions characterized by the phase difference in the bright component, in-phase and out-of-phase states. We show that above a critical particle number in the bright component, a symmetry-breaking bifurcation of the pitchfork type occurs that leads to a new asymmetric solution whereas the parental branch, i.e., the out-of-phase state, becomes unstable. These three different states support different small amplitude oscillations, characterized by an almost stationary density of themore » dark component and a tunneling of the bright component between the two dark solitons. Within a suitable effective double-well picture, these can be understood as the characteristic features of a bosonic Josephson junction (BJJ), and we show within a two-mode approach that all characteristic features of the BJJ phase space are recovered. For larger deviations from the stationary states, the simplifying double-well description breaks down due to the feedback of the bright component onto the dark one, causing the solitons to move. In this regime we observe intricate anharmonic and aperiodic dynamics, exhibiting remnants of the BJJ phase space.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zackrisson, Erik; Rydberg, Claes-Erik; Oestlin, Goeran

The first stars in the history of the universe are likely to form in the dense central regions of {approx}10{sup 5}-10{sup 6} M{sub sun} cold dark matter halos at z {approx} 10-50. The annihilation of dark matter particles in these environments may lead to the formation of so-called dark stars, which are predicted to be cooler, larger, more massive, and potentially more long-lived than conventional population III stars. Here, we investigate the prospects of detecting high-redshift dark stars with the upcoming James Webb Space Telescope (JWST). We find that all dark stars with masses up to 10{sup 3} M{sub sun}more » are intrinsically too faint to be detected by JWST at z > 6. However, by exploiting foreground galaxy clusters as gravitational telescopes do, certain varieties of cool (T{sub eff} {<=} 30, 000 K) dark stars should be within reach at redshifts up to z {approx} 10. If the lifetimes of dark stars are sufficiently long, many such objects may also congregate inside the first galaxies. We demonstrate that this could give rise to peculiar features in the integrated spectra of galaxies at high redshifts, provided that dark stars make up at least {approx}1% of the total stellar mass in such objects.« less

Current Status of the dark matter experiment DarkSide-50

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marini, L.; Pagani, Ioanna; Agnes, P.

2016-07-12

DarkSide-50 is a dark matter direct search experiment at LNGS, searching for rare nuclear recoils possibly induced by WIMPs. It has two nested vetoes and a dual phase liquid argon TPC as dark matter detector. Key features of this experiment are the use of underground argon as radio-pure target and of muon and neutron active vetoes to suppress the background. The first data-taking campaign was running from November 2013 to April 2015 with an atmospheric argon target and a reduced efficiency neutron veto due to internal contamination. However, an upper limit on the WIMP-nucleon cross section of 6.1×10-44 cm2 atmore » 90% CL was obtained for a WIMP mass of 100 GeV/c2 and an exposure of (1422 ± 67) kg·d. At present DarkSide-50 started a 3 years run, intended to be background-free because the neutron veto was successfully recovered and underground argon replaced the atmospheric one. Additionally calibration campaigns for both the TPC and the neutron veto were completed. Thanks to the good performance of the background rejection, the results obtained so far suggest the scalability of DarkSide-50 to a ton-scale detector, which will play a key role into the dark matter search scenario.« less

Current status of the dark matter experiment DarkSide-50

NASA Astrophysics Data System (ADS)

Marini, L.; Pagani, L.; Agnes, P.; Alexander, T.; Alton, A.; Arisaka, K.; Back, H. O.; Baldin, B.; Biery, K.; Bonfini, G.; Bossa, M.; Brigatti, A.; Brodsky, J.; Budano, F.; Cadonati, L.; Calaprice, F.; Canci, N.; Candela, A.; Cao, H.; Cariello, M.; Cavalcante, P.; Chavarria, A.; Chepurnov, A.; Cocco, A. G.; D'Angelo, D.; D'Incecco, M.; Davini, S.; De Deo, M.; Derbin, A.; Devoto, A.; Di Eusanio, F.; Di Pietro, G.; Edkins, E.; Empl, A.; Fan, A.; Fiorillo, G.; Fomenko, K.; Forster, G.; Franco, D.; Gabriele, F.; Galbiati, C.; Goretti, A.; Grandi, L.; Gromov, M.; Guan, M. Y.; Guardincerri, Y.; Hackett, B.; Herner, K.; Humble, P.; Hungerford, E. V.; Ianni, Al.; Ianni, An.; Jollet, C.; Keeter, K.; Kendziora, C.; Kidner, S.; Kobychev, V.; Koh, G.; Korablev, D.; Korga, G.; Kurlej, A.; Li, P. X.; Lombardi, P.; Love, C.; Ludhova, L.; Luitz, S.; Ma, Y. Q.; Machulin, I.; Mandarano, A.; Mari, S.; Maricic, J.; Martoff, C. J.; Meregaglia, A.; Meroni, E.; Meyers, P. D.; Milincic, R.; Montanari, D.; Montuschi, M.; Monzani, M. E.; Mosteiro, P.; Mount, B.; Muratova, V.; Musico, P.; Nelson, A.; Odrowski, S.; Okounkova, M.; Orsini, M.; Ortica, F.; Pallavicini, M.; Pantic, E.; Papp, L.; Parmeggiano, S.; Parsells, R.; Pelczar, K.; Pelliccia, N.; Perasso, S.; Pocar, A.; Pordes, S.; Pugachev, D.; Qian, H.; Randle, K.; Ranucci, G.; Razeto, A.; Reinhold, B.; Renshaw, A.; Romani, A.; Rossi, B.; Rossi, N.; Rountree, S. D.; Sablone, D.; Saggese, P.; Saldanha, R.; Sands, W.; Sangiorgio, S.; Segreto, E.; Semenov, D.; Shields, E.; Skorokhvatov, M.; Smirnov, O.; Sotnikov, A.; Stanford, C.; Suvorov, Y.; Tartaglia, R.; Tatarowicz, J.; Testera, G.; Tonazzo, A.; Unzhakov, E.; Vogelaar, R. B.; Wada, M.; Walker, S.; Wang, H.; Wang, Y.; Watson, A.; Westerdale, S.; Wojcik, M.; Wright, A.; Xiang, X.; Xu, J.; Yang, C. G.; Yoo, J.; Zavatarelli, S.; Zec, A.; Zhu, C.; Zuzel, G.; DarkSide Collaboration

2016-01-01

DarkSide-50 is a dark matter direct search experiment at LNGS, searching for rare nuclear recoils possibly induced by WIMPs. It has two nested vetoes and a dual phase liquid argon TPC as dark matter detector. Key features of this experiment are the use of underground argon as radio-pure target and of muon and neutron active vetoes to suppress the background. The first data-taking campaign was running from November 2013 to April 2015 with an atmospheric argon target and a reduced efficiency neutron veto due to internal contamination. However, an upper limit on the WIMP-nucleon cross section of 6.1×10-44 cm2 at 90% CL was obtained for a WIMP mass of 100 GeV/c2 and an exposure of (1422±67) kg . d . At present DarkSide-50 started a 3 years run, intended to be background-free because the neutron veto was successfully recovered and underground argon replaced the atmospheric one. Additionally calibration campaigns for both the TPC and the neutron veto were completed. Thanks to the good performance of the background rejection, the results obtained so far suggest the scalability of DarkSide-50 to a ton-scale detector, which will play a key role into the dark matter search scenario.

The DarkSide experiment

NASA Astrophysics Data System (ADS)

Bottino, B.; Aalseth, C. E.; Acconcia, G.; Acerbi, F.; Agnes, P.; Agostino, L.; Albuquerque, I. F. M.; Alexander, T.; Alton, A.; Ampudia, P.; Ardito, R.; Arisaka, K.; Arnquist, I. J.; Asner, D. M.; Back, H. O.; Baldin, B.; Batignani, G.; Biery, K.; Bisogni, M. G.; Bocci, V.; Bondar, A.; Bonfini, G.; Bonivento, W.; Bossa, M.; Brigatti, A.; Brodsky, J.; Budano, F.; Bunker, R.; Bussino, S.; Buttafava, M.; Buzulutskov, A.; Cadeddu, M.; Cadoni, M.; Calandri, N.; Calaprice, F.; Calvo, J.; Campajola, L.; Canci, N.; Candela, A.; Cantini, C.; Cao, H.; Caravati, M.; Cariello, M.; Carlini, M.; Carpinelli, M.; Castellani, A.; Catalanotti, S.; Cavalcante, P.; Chepurnov, A.; Cicalò, C.; Citterio, M.; Cocco, A. G.; Corgiolu, S.; Covone, G.; Crivelli, P.; D'Angelo, D.; D'Incecco, M.; Daniel, M.; Davini, S.; De Cecco, S.; De Deo, M.; De Guido, G.; De Vincenzi, M.; Demontis, P.; Derbin, A.; Devoto, A.; Di Eusanio, F.; Di Pietro, G.; Dionisi, C.; Dolgov, A.; Dromia, I.; Dussoni, S.; Edkins, E.; Empl, A.; Fan, A.; Ferri, A.; Filip, C. O.; Fiorillo, G.; Fomenko, K.; Forster, G.; Franco, D.; Froudakis, G. E.; Gabriele, F.; Gabrieli, A.; Galbiati, C.; Gendotti, A.; Ghioni, M.; Ghisi, A.; Giagu, S.; Gibertoni, G.; Giganti, C.; Giorgi, M.; Giovannetti, G. K.; Gligan, M. L.; Gola, A.; Goretti, A.; Granato, F.; Grassi, M.; Grate, J. W.; Gromov, M.; Guan, M.; Guardincerri, Y.; Gulinatti, A.; Haaland, R. K.; Hackett, B.; Harrop, B.; Herner, K.; Hoppe, E. W.; Horikawa, S.; Hungerford, E.; Ianni, Al.; Ianni, An.; Ivashchuk, O.; James, I.; Johnson, T. N.; Jollet, C.; Keeter, K.; Kendziora, C.; Kobychev, V.; Koh, G.; Korablev, D.; Korga, G.; Kubankin, A.; Kuss, M. W.; Lissia, M.; Li, X.; Lodi, G. U.; Lombardi, P.; Longo, G.; Loverre, P.; Luitz, S.; Lussana, R.; Luzzi, L.; Ma, Y.; Machado, A. A.; Machulin, I.; Mais, L.; Mandarano, A.; Mapelli, L.; Marcante, M.; Mari, S.; Mariani, M.; Maricic, J.; Marinelli, M.; Marini, L.; Martoff, C. J.; Mascia, M.; Meregaglia, A.; Meyers, P. D.; Miletic, T.; Milincic, R.; Miller, J. D.; Moioli, S.; Monasterio, S.; Montanari, D.; Monte, A.; Montuschi, M.; Monzani, M. E.; Morrocchi, M.; Mosteiro, P.; Mount, B.; Mu, W.; Muratova, V. N.; Murphy, S.; Musico, P.; Napolitano, J.; Nelson, A.; Nosov, V.; Nurakhov, N. N.; Odrowski, S.; Oleinik, A.; Orsini, M.; Ortica, F.; Pagani, L.; Pallavicini, M.; Palmas, S.; Pantic, E.; Paoloni, E.; Parmeggiano, S.; Paternoster, G.; Pazzona, F.; Pelczar, K.; Pellegrini, L. A.; Pelliccia, N.; Perasso, S.; Peronio, P.; Perotti, F.; Perruzza, R.; Piemonte, C.; Pilo, F.; Pocar, A.; Pordes, S.; Pugachev, D.; Qian, H.; Radics, B.; Randle, K.; Ranucci, G.; Razeti, M.; Razeto, A.; Rech, I.; Regazzoni, V.; Regenfus, C.; Reinhold, B.; Renshaw, A.; Rescigno, M.; Ricotti, M.; Riffard, Q.; Rizzardini, S.; Romani, A.; Romero, L.; Rossi, B.; Rossi, N.; Rountree, D.; Rubbia, A.; Ruggeri, A.; Sablone, D.; Saggese, P.; Salatino, P.; Salemme, L.; Sands, W.; Sangiorgio, S.; Sant, M.; Santorelli, R.; Sanzaro, M.; Savarese, C.; Sechi, E.; Segreto, E.; Semenov, D.; Shchagin, A.; Shekhtman, L.; Shemyakina, E.; Shields, E.; Simeone, M.; Singh, P. N.; Skorokhvatov, M.; Smallcomb, M.; Smirnov, O.; Sokolov, A.; Sotnikov, A.; Stanford, C.; Suffritti, G. B.; Suvorov, Y.; Tamborini, D.; Tartaglia, R.; Tatarowicz, J.; Testera, G.; Tonazzo, A.; Tosi, A.; Trinchese, P.; Unzhakov, E.; Vacca, A.; Verducci, M.; Viant, T.; Villa, F.; Vishneva, A.; Vogelaar, B.; Wada, M.; Walker, S.; Wang, H.; Wang, Y.; Watson, A.; Westerdale, S.; Wilhelmi, J.; Wojcik, M.; Wu, S.; Xiang, X.; Xu, J.; Yang, C.; Yoo, J.; Zappa, F.; Zappalà, G.; Zavatarelli, S.; Zec, A.; Zhong, W.; Zhu, C.; Zullo, A.; Zullo, M.; Zuzel, G.

2017-01-01

DarkSide is a dark matter direct search experiment at Laboratori Nazionali del Gran Sasso (LNGS). DarkSide is based on the detection of rare nuclear recoils possibly induced by hypothetical dark matter particles, which are supposed to be neutral, massive (m>10{ GeV}) and weakly interactive (WIMP). The dark matter detector is a two-phase time projection chamber (TPC) filled with ultra-pure liquid argon. The TPC is placed inside a muon and a neutron active vetoes to suppress the background. Using argon as active target has many advantages, the key features are the strong discriminant power between nuclear and electron recoils, the spatial reconstruction and easy scalability to multi-tons size. At the moment DarkSide-50 is filled with ultra-pure argon, extracted from underground sources, and from April 2015 it is taking data in its final configuration. When combined with the preceding search with an atmospheric argon target, it is possible to set a 90% CL upper limit on the WIMP-nucleon spin-independent cross section of 2.0×10^{-44} cm ^2 for a WIMP mass of 100 GeV/ c^2 . The next phase of the experiment, DarkSide-20k, will be the construction of a new detector with an active mass of ˜20 tons.

WFC3/UVIS Dark Calibration: Monitoring Results and Improvements to Dark Reference Files

NASA Astrophysics Data System (ADS)

Bourque, M.; Baggett, S.

2016-04-01

The Wide Field Camera 3 (WFC3) UVIS detector possesses an intrinsic signal during exposures, even in the absence of light, known as dark current. A daily monitor program is employed every HST cycle to characterize and measure this current as well as to create calibration files which serve to subtract the dark current from science data. We summarize the results of the daily monitor program for all on-orbit data. We also introduce a new algorithm for generating the dark reference files that provides several improvements to their overall quality. Key features to the new algorithm include correcting the dark frames for Charge Transfer Efficiency (CTE) losses, using an anneal-cycle average value to measure the dark current, and generating reference files on a daily basis. This new algorithm is part of the release of the CALWF3 v3.3 calibration pipeline on February 23, 2016 (also known as "UVIS 2.0"). Improved dark reference files have been regenerated and re-delivered to the Calibration Reference Data System (CRDS) for all on-orbit data. Observers with science data taken prior to the release of CALWF3 v3.3 may request their data through the Mikulski Archive for Space Telescopes (MAST) to obtain the improved products.

Microbial Ecology of the Dark Ocean above, at, and below the Seafloor†

PubMed Central

Orcutt, Beth N.; Sylvan, Jason B.; Knab, Nina J.; Edwards, Katrina J.

2011-01-01

Summary: The majority of life on Earth—notably, microbial life—occurs in places that do not receive sunlight, with the habitats of the oceans being the largest of these reservoirs. Sunlight penetrates only a few tens to hundreds of meters into the ocean, resulting in large-scale microbial ecosystems that function in the dark. Our knowledge of microbial processes in the dark ocean—the aphotic pelagic ocean, sediments, oceanic crust, hydrothermal vents, etc.—has increased substantially in recent decades. Studies that try to decipher the activity of microorganisms in the dark ocean, where we cannot easily observe them, are yielding paradigm-shifting discoveries that are fundamentally changing our understanding of the role of the dark ocean in the global Earth system and its biogeochemical cycles. New generations of researchers and experimental tools have emerged, in the last decade in particular, owing to dedicated research programs to explore the dark ocean biosphere. This review focuses on our current understanding of microbiology in the dark ocean, outlining salient features of various habitats and discussing known and still unexplored types of microbial metabolism and their consequences in global biogeochemical cycling. We also focus on patterns of microbial diversity in the dark ocean and on processes and communities that are characteristic of the different habitats. PMID:21646433

Improving the Inventory of Large Lunar Basins: Using LOLA Data to Test Previous Candidates and Search for New Ones

NASA Technical Reports Server (NTRS)

Frey, H. V.; Meyer, H. M.; Romine, G. C.

2012-01-01

Topography and crustal thickness data from LOLA altimetry were used to test the validity of 98 candidate large lunar basins derived from photogeologic and earlier topographic and crustal thickness data, and to search for possible new candidates. We eliminate 23 previous candidates but find good evidence for 20 new candidates. The number of basins greater than 300 km diameter on the Moon is almost certainly a factor 2 (maybe 3?) larger than the number of named features having basin-like topography. Unified Lunar Control Net 2005 data [1] and model crustal thickness data [2] were previously used to search for possible previously unrecognized large lunar impact basins [3,4]. An inventory of 98 candidate topographic basins greater than 300 km in diameter was found [5]. This includes 33 named features (only those having basin-like topography) out of the 45 listed by Wilhelms [6], 38 additional Quasi-Circular Depressions (QCDs) found in the ULCN2005 topography, and 27 Circular Thin Areas (CTAs) found in model crustal thickness data [2]. Most named features and additional QCDs have strong CTA signatures, but there may be a class of CTAs that are not easily recognized in the old and low resolution ULCN2005 topography. Lunar Orbiter Laser Altimeter (LOLA) data have recently become publically available. We used these data to (a) refine the center and ring diameters of known basins, (b) test the viability of the candidate basins previously found (as described above), and (c) search for additional candidate basins not revealed by the earlier lower resolution data. We used the LOLA topography directly but also a recent new model crustal thickness data that includes Kaguya gravity data [7]. We repeated a Topographic Expression (TE) and a Crustal Thickness Expression (CTE) scoring exercise originally done with the basins found in ULCN and earlier model crustal thickness data [5]. Each candidate was scored on a scale from 0 (no topographic basin or circular thin area signature) to 5 (strong circular low or strong circular thin area signature). These were combined into a total score used to rank the probability for each candidate basin. We used the same GRIDVIEW software to stretch, contour and profile the LOLA and new crustal thickness data as was done with the ULCN2005 and older model crustal thickness data.

Characterization of Jupiter's Atmosphere from Galileo and Earth-Based Observations During the Ganymede-1 and Ganymede-2 Orbit Encounters

NASA Astrophysics Data System (ADS)

Orton, G.; Fisher, B.; Ortiz, J. L.; Yanamandra-Fisher, P.; Rages, K.; Howell, R.; Klebe, D.; Stencel, R.; Drossart, P.; Lecacheux, J.; Colas, F.; Frappa, E.; Hernandez, C.; Parker, D.; Miyazaki, I.; Stewart, S.; Stansberry, J.; Spencer, J.; Golisch, W.; Griep, D.; Hainaut, M.-C.; Joseph, R.; Kaminski, C.; Banjevic, M.; Connor, C.; Hinkley, S.; Marinova, M.; Marriage, B.; Dobrea, E. Noe

1996-09-01

Galileo remote sensing data are examined in the context of an extensive set of earth-based observations supporting the Ganymede-1 and Ganymede-2 encounters. Movies of the Great Red Spot (GRS) in reflected sunlight, show large-scale flow; for example, the circular feature northwest of the GRS during G1 was one of several high-altitude systems moving westward with respect to the GRS. The southern part of the clear band surrounding the GRS was narrower at 5 mu m than 8.57 mu m, suggesting more cloud cover at depth than at the NH_3 condensation level; this region was also warmer in the troposphere. High-altitude particles were found in the flow pattern ``trailing'' the GRS. The real-time NIMS G1 spectra sampled a region only moderately bright at 5-mu m, not a classical ``hot spot''. Synoptic middle-infrared spectra of this region complement NIMS spectra of the deep troposphere by constraining abundances of NH_3 and PH_3 at higher altitudes. The southern part of the North Equatorial Belt, observed by both NIMS spectra and PPR radiometry, was very active, generating classical bright ``plumes'' and dark ovals (``barges'') for the first time in many months. A long-term program will continue to observe potential targets for the Galileo's atmospheric investigation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Badran, Hussain Ali, E-mail: badran_hussein@yahoo.com; Ajeel, Khalid I.; Lazim, Haidar Gazy

Highlights: • Active layer (P3HT:PCBM) has been deposited on substrate type by spin coating at 1000 rpm. • The device was completed by evaporating a 60 nm thick, circular gold electrodes onto the P3HT:PCBM. • Nonlinear refractive indices of the three particle sizes are found to be of the order of 10{sup −7} cm{sup 2}/W - Abstract: Organic solar cells are based on (3-hexylthiophene):[6,6]-phenyl C61-butyric acid with methyl ester Bulk Heterojunction. An inverted structure has been fabricated using nano-anatase crystalline titanium dioxide, as the electron transport layer, which was prepared on either the Indium Tin Oxide coated glass (ITO—glass), ormore » Silicon wafer, as well as on glass substrates by the sol–gel method, at different spin speed, using the spin-coating system. The effect of thickness on the surface morphology and on the optical properties of TiO{sub 2} layer, was investigated using the Atomic Force Microscopy (AFM), X-ray diffraction, and UV–visible spectrophotometer. The samples were examined to feature currents and voltages, in the darkness and light extraction efficiency of the solar cell. The highest open-circuit voltage, V{sub oc}, and power conversion efficiency were 0.66% and 0.39%, fabricated with 90 nm, respectively. The non-linear optical properties of nano-anatase TiO{sub 2} sol–gel, were investigated at different particle sizes, using the z-scan technique.« less

Mars on 25 December 2003

NASA Technical Reports Server (NTRS)

2004-01-01

8 January 2004 This is how Mars appeared to the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) wide angle system on 25 December 2003, the day that Beagle 2 and Mars Express reached the red planet. The large, dark region just left of center is Syrtis Major, a persistent low albedo terrain known to astronomers for nearly four centuries before the first spacecraft went to Mars. Immediately to the right (east) of Syrtis Major is the somewhat circular plain, Isidis Planitia. Beagle 2 arrived in Isidis Planitia only about 18 minutes before Mars Global Surveyor flew over the region and acquired a portion of this global view. Relative to other global images of Mars acquired by MGS over the past several martian years, the surface features were not as sharp and distinct on 25 December 2003 because of considerable haze kicked up by large dust storms in the western and southern hemispheres during th previous two weeks. The picture is a composite of several MGS MOC red and blue daily global images that have been map-projected and digitally wrapped to a sphere. Although the effect here is minor, inspection of this mosaic shows zones that appear smudged or blurry. The high dust opacity on 25 December impacted MOC's oblique viewing geometry toward the edges of each orbit's daily global mapping image, thus emphasizing the 'blurry' zones between images acquired on successive orbits.

The value of specific MRI features in the evaluation of suspected placental invasion.

PubMed

Lax, Allison; Prince, Martin R; Mennitt, Kevin W; Schwebach, J Reid; Budorick, Nancy E

2007-01-01

The objective of this study was to determine imaging features that may help predict the presence of placenta accreta, placenta increta or placenta percreta on prenatal MRI scanning. A retrospective review of the prenatal MR scans of 10 patients with a diagnosis of placenta accreta, placenta increta or placenta percreta made by pathologic and clinical reports and of 10 patients without placental invasion was performed. Two expert MRI readers were blinded to the patients' true diagnosis and were asked to score a total of 17 MRI features of the placenta and adjacent structures. The interrater reliability was assessed using kappa statistics. The features with a moderate kappa statistic or better (kappa > .40) were then compared with the true diagnosis for each observer. Seven of the scored features had an interobserver reliability of kappa > .40: placenta previa (kappa = .83); abnormal uterine bulging (kappa = .48); intraplacental hemorrhage (kappa = .51); heterogeneity of signal intensity on T2-weighted (T2W) imaging (kappa = .61); the presence of dark intraplacental bands on T2W imaging (kappa = .53); increased placental thickness (kappa = .69); and visualization of the myometrium beneath the placenta on T2W imaging (kappa = .44). Using Fisher's two-sided exact test, there was a statistically significant difference between the proportion of patients with placental invasion and those without placental invasion for three of the features: abnormal uterine bulging (Rater 1, P = .005; Rater 2, P = .011); heterogeneity of T2W imaging signal intensity (Rater 1, P = .006; Rater 2, P = .010); and presence of dark intraplacental bands on T2W imaging (Rater 1, P = .003; Rater 2, P = .033). MRI can be a useful adjunct to ultrasound in diagnosing placenta accreta prenatally. Three features that are seen on MRI in patients with placental invasion appear to be useful for diagnosis: uterine bulging; heterogeneous signal intensity within the placenta; and the presence of dark intraplacental bands on T2W imaging.

A Computational Model of Afterimage Rotation in the Peripheral Drift Illusion Based on Retinal ON/OFF Responses

PubMed Central

Hayashi, Yuichiro; Ishii, Shin; Urakubo, Hidetoshi

2014-01-01

Human observers perceive illusory rotations after the disappearance of circularly repeating patches containing dark-to-light luminance. This afterimage rotation is a very powerful phenomenon, but little is known about the mechanisms underlying it. Here, we use a computational model to show that the afterimage rotation can be explained by a combination of fast light adaptation and the physiological architecture of the early visual system, consisting of ON- and OFF-type visual pathways. In this retinal ON/OFF model, the afterimage rotation appeared as a rotation of focus lines of retinal ON/OFF responses. Focus lines rotated clockwise on a light background, but counterclockwise on a dark background. These findings were consistent with the results of psychophysical experiments, which were also performed by us. Additionally, the velocity of the afterimage rotation was comparable with that observed in our psychophysical experiments. These results suggest that the early visual system (including the retina) is responsible for the generation of the afterimage rotation, and that this illusory rotation may be systematically misinterpreted by our high-level visual system. PMID:25517906

Galactic disks, infall, and the global value of Omega

NASA Technical Reports Server (NTRS)

Toth, G.; Ostriker, J. P.

1992-01-01

Stringent limits on the current rate of infall of satellite systems onto spiral galaxies are set on the basis of the thinness and coldness of Galactic disks. For infalling satellites on isotropically oriented circular orbits, it is shown that, due to scattering, the thermal energy gain of the disk exceeds the satellite energy loss from dynamical friction by a factor of 1.6, with 25 percent deposited in z motion and 75 percent in planar motions. It is found that no more than 4 percent of the Galactic mass inside the solar radius can have accreted within the last 5 billion years, or else its scale and its Toomre Q-parameter would exceed observed values. In standard cold-dark-matter-dominated models for the growth of structure with Omega sub tot of 1, the mass accreted in dark matter lumps rises faster than t exp 2/3 and would exceed 28 percent in the last 5 Gyr. It is proposed that heating from satellite infall accounts for a substantial fraction of the increase of velocity dispersion and scale height with age that is observed in the Galaxy.

Moon taken by Galileo after completing its first Earth Gravity Assist

NASA Technical Reports Server (NTRS)

1990-01-01

Color image of the Moon was taken by Galileo spacecraft at 9:35 am Pacific Standard Time (PST), 12-09-90, at a range of about 350,000 miles. The color composite uses monochrome images taken through violet, red, and near-infrared filters. The concentric, circular Orientale basin, 600 miles across, is near the center; the near side is to the right, the far side to the left. At the upper right is the large, dark Oceanus Procellarum; below it is the smaller Mare Humorum. These, like the small dark Mare Orientale in the center of the basin, formed over 3 billion years ago as basaltic lava flows. At the lower left, among the southern cratered highlands of the far side, is the South-Pole-Aitken basin, similar to Orientale but twice as great in diameter and much older and more degraded by cratering and weathering. The cratered highlands of the near and far sides and the Maria are covered with scattered bright, young ray craters. Photo provided by the Jet Propulsion Laboratory (JPL) with altern

Constraint on dark matter central density in the Eddington inspired Born-Infeld (EiBI) gravity with input from Weyl gravity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Potapov, Alexander A.; Mikolaychuk, Olga; Mikolaychuk, Nikolay

Recently, Harko et al. (2014) derived an approximate metric of the galactic halo in the Eddington inspired Born-Infeld (EiBI) gravity. In this metric, we show that there is an upper limit ρ {sub 0}{sup upper} on the central density ρ {sub 0} of dark matter such that stable circular orbits are possible only when the constraint ρ {sub 0}≤ ρ {sub 0}{sup upper} is satisfied in each galactic sample. To quantify different ρ {sub 0}{sup upper} for different samples, we follow the novel approach of Edery and Paranjape (1998), where we use as input the geometric halo radius R{sub WR} from Weyl gravity and equate itmore » with the dark matter radius R{sub DM} from EiBI gravity for the same halo boundary. This input then shows that the known fitted values of ρ {sub 0} obey the constraint ρ {sub 0}≤ ρ {sub 0}{sup upper}∝  (R{sub WR}){sup −2}. Using the mass-to-light ratios giving α , we shall also evaluate ρ {sub 0}{sup lower} ∝  (α −1)M{sub lum}R{sub WR}{sup −3} and the average dark matter density  ( ρ ) {sup lower}. Quantitatively, it turns out that the interval ρ {sub 0}{sup lower} ≤ ρ {sub 0}≤  ρ {sub 0}{sup upper} verifies reasonably well against many dark matter dominated low surface brightness (LSB) galaxies for which values of ρ {sub 0} are independently known. The interval holds also in the case of Milky Way galaxy. Qualitatively, the existence of a stability induced upper limit  ρ {sub 0}{sup upper} is a remarkable prediction of the EiBI theory.« less

Quantum entangled dark solitons formed by ultracold atoms in optical lattices.

PubMed

Mishmash, R V; Carr, L D

2009-10-02

Inspired by experiments on Bose-Einstein condensates in optical lattices, we study the quantum evolution of dark soliton initial conditions in the context of the Bose-Hubbard Hamiltonian. An extensive set of quantum measures is utilized in our analysis, including von Neumann and generalized quantum entropies, quantum depletion, and the pair correlation function. We find that quantum effects cause the soliton to fill in. Moreover, soliton-soliton collisions become inelastic, in strong contrast to the predictions of mean-field theory. These features show that the lifetime and collision properties of dark solitons in optical lattices provide clear signals of quantum effects.

Novel Drift Structures for Silicon and Compound Semiconductor X-Ray and Gamma-Ray Detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bradley E. Patt; Jan S. Iwanczyk

Recently developed silicon- and compound-semiconductor-based drift detector structures have produced excellent performance for charged particles, X rays, and gamma rays and for low-signal visible light detection. The silicon drift detector (SDD) structures that we discuss relate to direct X-ray detectors and scintillation photon detectors coupled with scintillators for gamma rays. Recent designs include several novel features that ensure very low dark current (both bulk silicon dark current and surface dark current) and hence low noise. In addition, application of thin window technology ensures a very high quantum efficiency entrance window on the drift photodetector.

Effects of the Sagittarius dwarf tidal stream on dark matter detectors.

PubMed

Freese, Katherine; Gondolo, Paolo; Newberg, Heidi Jo; Lewis, Matthew

2004-03-19

The Sagittarius dwarf tidal stream may be showering dark matter onto the solar neighborhood, which can change the results and interpretation of direct detection searches for weakly interacting massive particles (WIMPs). Stars in the stream may already have been detected in the solar neighborhood, and the dark matter in the stream is (0.3-25)% of the local density. Experiments should see an annually modulated steplike feature in the energy recoil spectrum that would be a smoking gun for WIMP detection. The total count rate in detectors is not a cosine curve in time and peaks at a different time of year than the standard case.

Venus - Impact Crater 'Jeanne

NASA Technical Reports Server (NTRS)

1991-01-01

This Magellan full-resolution image shows Jeanne crater, a 19.5 kilometer (12 mile) diameter impact crater. Jeanne crater is located at 40.0 degrees north latitude and 331.4 degrees longitude. The distinctive triangular shape of the ejecta indicates that the impacting body probably hit obliquely, traveling from southwest to northeast. The crater is surrounded by dark material of two types. The dark area on the southwest side of the crater is covered by smooth (radar-dark) lava flows which have a strongly digitate contact with surrounding brighter flows. The very dark area on the northeast side of the crater is probably covered by smooth material such as fine-grained sediment. This dark halo is asymmetric, mimicking the asymmetric shape of the ejecta blanket. The dark halo may have been caused by an atmospheric shock or pressure wave produced by the incoming body. Jeanne crater also displays several outflow lobes on the northwest side. These flow-like features may have formed by fine-grained ejecta transported by a hot, turbulent flow created by the arrival of the impacting object. Alternatively, they may have formed by flow of impact melt.

Monthly modulation in dark matter direct-detection experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Britto, Vivian; Meyers, Joel, E-mail: vivian.britto@mail.utoronto.ca, E-mail: jmeyers@cita.utoronto.ca

2015-11-01

The signals in dark matter direct-detection experiments should exhibit modulation signatures due to the Earth's motion with respect to the Galactic dark matter halo. The annual and daily modulations, due to the Earth's revolution about the Sun and rotation about its own axis, have been explored previously. Monthly modulation is another such feature present in direct detection signals, and provides a nearly model-independent method of distinguishing dark matter signal events from background. We study here monthly modulations in detail for both WIMP and WISP dark matter searches, examining both the effect of the motion of the Earth about the Earth-Moonmore » barycenter and the gravitational focusing due to the Moon. For WIMP searches, we calculate the monthly modulation of the count rate and show the effects are too small to be observed in the foreseeable future. For WISP dark matter experiments, we show that the photons generated by WISP to photon conversion have frequencies which undergo a monthly modulating shift which is detectable with current technology and which cannot in general be neglected in high resolution WISP searches.« less

A microwave applicator for uniform irradiation by circularly polarized waves in an anechoic chamber

NASA Astrophysics Data System (ADS)

Chiang, W. Y.; Wu, M. H.; Wu, K. L.; Lin, M. H.; Teng, H. H.; Tsai, Y. F.; Ko, C. C.; Yang, E. C.; Jiang, J. A.; Barnett, L. R.; Chu, K. R.

2014-08-01

Microwave applicators are widely employed for materials heating in scientific research and industrial applications, such as food processing, wood drying, ceramic sintering, chemical synthesis, waste treatment, and insect control. For the majority of microwave applicators, materials are heated in the standing waves of a resonant cavity, which can be highly efficient in energy consumption, but often lacks the field uniformity and controllability required for a scientific study. Here, we report a microwave applicator for rapid heating of small samples by highly uniform irradiation. It features an anechoic chamber, a 24-GHz microwave source, and a linear-to-circular polarization converter. With a rather low energy efficiency, such an applicator functions mainly as a research tool. This paper discusses the significance of its special features and describes the structure, in situ diagnostic tools, calculated and measured field patterns, and a preliminary heating test of the overall system.

A microwave applicator for uniform irradiation by circularly polarized waves in an anechoic chamber.

PubMed

Chiang, W Y; Wu, M H; Wu, K L; Lin, M H; Teng, H H; Tsai, Y F; Ko, C C; Yang, E C; Jiang, J A; Barnett, L R; Chu, K R

2014-08-01

Microwave applicators are widely employed for materials heating in scientific research and industrial applications, such as food processing, wood drying, ceramic sintering, chemical synthesis, waste treatment, and insect control. For the majority of microwave applicators, materials are heated in the standing waves of a resonant cavity, which can be highly efficient in energy consumption, but often lacks the field uniformity and controllability required for a scientific study. Here, we report a microwave applicator for rapid heating of small samples by highly uniform irradiation. It features an anechoic chamber, a 24-GHz microwave source, and a linear-to-circular polarization converter. With a rather low energy efficiency, such an applicator functions mainly as a research tool. This paper discusses the significance of its special features and describes the structure, in situ diagnostic tools, calculated and measured field patterns, and a preliminary heating test of the overall system.

The Advanced Light Source Elliptically Polarizing Undulator

NASA Astrophysics Data System (ADS)

Marks, Steve; Cortopassi, Christopher; Devries, Jan; Hoyer, Egon; Leinbach, Robert; Minamihara, Yoshi; Padmore, Howard; Pipersky, Paul; Plate, Dave; Schlueter, Ross; Young, Anthony

1997-05-01

An elliptically polarizing undulator for the Advanced Light Source has been designed and is currently under construction. The magnetic design is a four quadrant pure permanent magnet structure featuring moveable magnets to correct phase errors and on axis field integrals. The device is designed with a 5.0 cm period and will produce variably polarized light of any ellipticity, including pure circular and linear. The spectral range at 1.9 GeV for typical elliptical polarization with a degree of circular polarization greater than 0.8 will be from 100 eV to 1500 eV, using the third and fifth spectral harmonics. The device will be switchabe between left and right circular modes at a frequency of up to 0.1 Hz. The 1.95 m long overall length will allow two such devices in a single ALS straight sector.

Jovian Dark Spot

NASA Technical Reports Server (NTRS)

1998-01-01

A recently discovered black spot in Jupiter's clouds is darker than any feature ever before observed on the giant planet. The spot may be the result of a downward spiraling wind that blows away high clouds and reveals deeper, very dark cloud layers. These three panels depict the same area of Jupiter's atmosphere. A map of Jovian temperatures near 250 millibar pressure (top) panel is derived from the photopolarimeter-radiometer instrument on NASA's Galileo Jupiter orbiter. This map is compared with maps derived from images of the same area in visible light (middle panel)and thermal radiation sensitive to cloud-top temperatures (bottom panel).

The single downward-pointing arrow in the top panel indicates the location of a warm area that corresponds to the position of a so-called 'black spot'(shown in the middle panel), a feature that is about a year old. Features this dark are rare on Jupiter. The bottom panel, sensitive to temperatures at Jupiter's cloud tops, shows this feature as a bright object, meaning that upper-level cold clouds are missing - allowing us to see deeper into Jupiter's warmer interior. The dark visible appearance of the feature than most likely represents the color of very deep clouds. The warm temperatures and cloud-free conditions imply that this feature is a region where dry upper-atmospheric gas is being forced to converge, is warmed up and then forced to descend, clearing out clouds. It is the opposite of wet, upwelling gas in areas such as Jupiter's Great Red Spot or white ovals. On the other hand, it is unlike the dry and relatively cloudless feature into which the Galileo probe descended in 1995, because that region had the same temperatures as its surroundings and did not appear nearly as dark as this new spot.

The temperatures sampled by the photopolarimeter radiometer are near the top of Jupiter's troposphere, where wind motions control the atmosphere. The top row of arrows shows the location of temperature waves in a warm region of the atmosphere. These types of waves have never been seen before. What is interesting about these waves is both that they are 'channeled' within the warm band at the top of the panel, and that they appear to have no counterpart in the visible cloud structure. Thermal waves have already been seen in Jupiter that are independent of the cloud structure, but those waves were much larger in size. This is the first time Jupiter's temperatures have been mapped at a spatial resolution better than 2,000 kilometers (1,243 miles), allowing these waves to be detected.

These maps include an area on Jupiter between approximately the equator and 40 degrees south latitude, covering about 60 degrees of longitude. They were taken in late September during the spacecraft's 17th orbit.

The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC.

THE SPLASH SURVEY: SPECTROSCOPY OF 15 M31 DWARF SPHEROIDAL SATELLITE GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tollerud, Erik J.; Bullock, James S.; Yniguez, Basilio

2012-06-10

We present a resolved star spectroscopic survey of 15 dwarf spheroidal (dSph) satellites of the Andromeda galaxy (M31). We filter foreground contamination from Milky Way (MW) stars, noting that MW substructure is evident in this contaminant sample. We also filter M31 halo field giant stars and identify the remainder as probable dSph members. We then use these members to determine the kinematical properties of the dSphs. For the first time, we confirm that And XVIII, XXI, and XXII show kinematics consistent with bound, dark-matter-dominated galaxies. From the velocity dispersions for the full sample of dSphs we determine masses, which wemore » combine with the size and luminosity of the galaxies to produce mass-size-luminosity scaling relations. With these scalings we determine that the M31 dSphs are fully consistent with the MW dSphs, suggesting that the well-studied MW satellite population provides a fair sample for broader conclusions. We also estimate dark matter halo masses of the satellites and find that there is no sign that the luminosity of these galaxies depends on their dark halo mass, a result consistent with what is seen for MW dwarfs. Two of the M31 dSphs (And XV, XVI) have estimated maximum circular velocities smaller than 12 km s{sup -1} (to 1{sigma}), which likely places them within the lowest-mass dark matter halos known to host stars (along with Booetes I of the MW). Finally, we use the systemic velocities of the M31 satellites to estimate the mass of the M31 halo, obtaining a virial mass consistent with previous results.« less

Scaling Laws for Dark Matter Halos in Late-type and Dwarf Spheroidal Galaxies

NASA Astrophysics Data System (ADS)

Kormendy, John; Freeman, K. C.

2016-02-01

Dark matter (DM) halos of Sc-Im and dwarf spheroidal (dSph) galaxies satisfy scaling laws: halos in lower-luminosity galaxies have smaller core radii, higher central densities, and smaller velocity dispersions. These results are based on maximum-disk rotation curve decompositions for giant galaxies and Jeans equation analysis for dwarfs. (1) We show that spiral, Im, and Sph galaxies with absolute magnitudes MV > -18 form a sequence of decreasing baryon-to-DM surface density with decreasing luminosity. We suggest that this is a sequence of decreasing baryon retention versus supernova-driven losses or decreasing baryon capture after cosmological reionization. (2) The structural differences between S+Im and Sph galaxies are small. Both are affected mostly by the physics that controls baryon depletion. (3) There is a linear correlation between the maximum rotation velocities of baryonic disks and the outer circular velocities Vcirc of test particles in their DM halos. Baryons become unimportant at Vcirc = 42 ± 4 km s-1. Smaller galaxies are dim or dark. (4) We find that, absent baryon “depletion” and with all baryons converted into stars, dSph galaxies would be brighter by ˜4.6 mag and dIm galaxies would be brighter by ˜3.5 mag. Both have DM halos that are massive enough to help to solve the “too big to fail” problem with DM galaxy formation. (5) We suggest that there exist many galaxies that are too dark to be discovered by current techniques, as required by cold DM theory. (6) Central surface densities of DM halos are constant from MB ˜ -5 to -22. This implies a Faber-Jackson law with halo mass M ∝ (halo dispersion)4.

Evaluation of clustering algorithms at the < 1 GeV energy scale for the electromagnetic calorimeter of the PADME experiment

NASA Astrophysics Data System (ADS)

Leonardi, E.; Piperno, G.; Raggi, M.

2017-10-01

A possible solution to the Dark Matter problem postulates that it interacts with Standard Model particles through a new force mediated by a “portal”. If the new force has a U(1) gauge structure, the “portal” is a massive photon-like vector particle, called dark photon or A’. The PADME experiment at the DAΦNE Beam-Test Facility (BTF) in Frascati is designed to detect dark photons produced in positron on fixed target annihilations decaying to dark matter (e+e-→γA‧) by measuring the final state missing mass. One of the key roles of the experiment will be played by the electromagnetic calorimeter, which will be used to measure the properties of the final state recoil γ. The calorimeter will be composed by 616 21×21×230 mm3 BGO crystals oriented with the long axis parallel to the beam direction and disposed in a roughly circular shape with a central hole to avoid the pile up due to the large number of low angle Bremsstrahlung photons. The total energy and position of the electromagnetic shower generated by a photon impacting on the calorimeter can be reconstructed by collecting the energy deposits in the cluster of crystals interested by the shower. In PADME we are testing two different clustering algorithms, PADME-Radius and PADME-Island, based on two complementary strategies. In this paper we will describe the two algorithms, with the respective implementations, and report on the results obtained with them at the PADME energy scale (< 1 GeV), both with a GEANT4 based simulation and with an existing 5×5 matrix of BGO crystals tested at the DAΦNE BTF.

Risk factors associated with delayed gastric emptying after subtotal gastrectomy with Billroth-I anastomosis using circular stapler for early gastric cancer patients

PubMed Central

Kim, Ki Han; Jung, Ghap Joong

2012-01-01

Purpose Gastric surgery may potentiate delayed gastric emptying. Billroth I gastroduodenostomy using a circular stapler is the most preferable reconstruction method. The purpose of this study is to analyze the risk factors associated with delayed gastric emptying after radical subtotal gastrectomy with Billroth I anastomosis using a stapler for early gastric cancer. Methods Three hundred and seventy-eight patients who underwent circular stapled Billroth I gastroduodenostomy after subtotal gastrectomy due to early gastric cancer were analyzed retrospectively. One hundred and eighty-two patients had Billroth I anastomosis using a 25 mm diameter circular stapler, and 196 patients had anastomosis with a 28 or 29 mm diameter circular stapler. Clinicopathological features and postoperative outcomes were evaluated and compared between the two groups. Delayed gastric emptying was diagnosed by symptoms and simple abdomen X-ray with or without upper gastrointestinal series or endoscopy. Results Postoperative delayed gastric emptying was found in 12 (3.2%) of the 378 patients. Among all the variables, distal margin and circular stapler diameter were significantly different between the cases with delayed gastric emptying and no delayed gastric emptying. There were statistically significant differences in sex, body mass index, comorbidity, complication, and operation type according to circular stapler diameter. In both univariate and multivariate logistic regression analyses, only the stapler diameter was found to be a significant factor affecting delayed gastric emptying (P = 0.040). Conclusion In this study, the circular stapler diameter was one of the most significant predictable factors of delayed gastric emptying for Billroth I gastroduodenostomy. The use of a 28 or 29 mm diameter circular stapler rather than a 25 mm diameter stapler in stapled gastroduodenostomy for early gastric cancer can reduce postoperative delayed gastric emptying associated with anastomosic stenosis or edema with relative safety. PMID:23166886

The Spartan 1 Mission

DTIC Science & Technology

1989-07-11

this dark matter to be mea- sured. The special feature of the Spartan 1 instrument has been its ability to measure the density and temperature of the...required to create the potential well, because it exceeds by a large margin the mass we can account for as galaxies and gas. Some invisible (" dark ...34) matter of unknown origin pervades the cluster. Measurements of the radial density and temperature gradients in the hot gas allow the distribution of

DarkSide-50: A WIMP Search with a Two-phase Argon TPC

NASA Astrophysics Data System (ADS)

Meyers, P. D.; Agnes, P.; Alton, D.; Arisaka, K.; Back, H. O.; Baldin, B.; Biery, K.; Bonfini, G.; Bossa, M.; Brigatti, A.; Brodsky, J.; Budano, F.; Cadonati, L.; Calaprice, F.; Canci, N.; Candela, A.; Cao, H.; Cariello, M.; Cavalcante, P.; Chavarria, A.; Chepurnov, A.; Cocco, A. G.; Crippa, L.; DAngelo, D.; D'Incecco, M.; Davini, S.; De Deo, M.; Derbin, A.; Di Eusanio, F.; Di Pietro, G.; Edkins, E.; Empl, A.; Fan, A.; Fiorillo, G.; Fomenko, K.; Forster, G.; Franco, D.; Gabriele, F.; Galbiati, C.; Goretti, A.; Grandi, L.; Gromov, M.; Guan, M.; Guardincerri, Y.; Hackett, B.; Herner, K.; Humble, P.; Hungerford, E. V.; Ianni, Al.; Ianni, An.; Joliet, C.; Keeter, K.; Kendziora, C.; Kidner, S.; Kobychev, V.; Koh, G.; Korablev, D.; Korga, G.; Kurlej, A.; Li, P.; Loer, B.; Lombardi, P.; Love, C.; Ludhova, L.; Luitz, S.; Ma, Y.; Machulin, I.; Mandarano, A.; Mari, S.; Maricic, J.; Martoff, C. J.; Meregaglia, A.; Meroni, E.; Meyers, P. D.; Milincic, R.; Montanari, D.; Montuschi, M.; Monzani, M. E.; Mosteiro, P.; Mount, B.; Muratova, V.; Musico, P.; Nelson, A.; Okounkova, M.; Orsini, M.; Ortica, F.; Pagani, L.; Pallavicini, M.; Pantic, E.; Papp, L.; Parmeggiano, S.; Parsells, R.; Pelczar, K.; Pelliccia, N.; Perasso, S.; Perfetto, F.; Pocar, A.; Pordes, S.; Qian, H.; Randle, K.; Ranucci, G.; Razeto, A.; Reinhold, B.; Romani, A.; Rossi, B.; Rossi, N.; Rountree, S. D.; Sablone, D.; Saggese, P.; Saldanha, R.; Sands, W.; Segreto, E.; Semenov, D.; Shields, E.; Skorokhvatov, M.; Smirnov, O.; Sotnikov, A.; Suvarov, Y.; Tartaglia, R.; Tatarowicz, J.; Testera, G.; Tonazzo, A.; Unzhakov, E.; Vogelaar, R. B.; Wada, M.; Wang, H.; Wang, Y.; Watson, A.; Westerdale, R.; Wojcik, M.; Wright, A.; Xu, J.; Yang, C.; Yoo, J.; Zavatarelli, S.; Zuzel, G.

DarkSide-50 is a two phase argon TPC for direct dark matter detection which is installed at the Gran Sasso underground laboratory, Italy. DarkSide-50 has a 50-kg active volume and will make use of underground argon low in 39Ar. The TPC is installed inside an active neutron veto made with boron-loaded high radiopurity liquid scintillator. The neutron veto is installed inside a 1000 m3 water Cherenkov muon veto. The DarkSide-50 TPC and cryostat are assembled in two radon-free clean rooms to reduce radioactive contaminants. The overall design aims for a background free exposure after selection cuts are applied. The expected sensitivity for WIMP-nucleon cross section is of the order of 10-45 cm2 for WIMP masses around 100 GeV/c2. The commissioning and performance of the detector are described. Details of the low-radioactivity underground argon and other unique features of the projects are reported.

Ghost Dark Energy with Non-Linear Interaction Term

NASA Astrophysics Data System (ADS)

Ebrahimi, E.

2016-06-01

Here we investigate ghost dark energy (GDE) in the presence of a non-linear interaction term between dark matter and dark energy. To this end we take into account a general form for the interaction term. Then we discuss about different features of three choices of the non-linear interacting GDE. In all cases we obtain equation of state parameter, w D = p/ ρ, the deceleration parameter and evolution equation of the dark energy density parameter (Ω D ). We find that in one case, w D cross the phantom line ( w D < -1). However in two other classes w D can not cross the phantom divide. The coincidence problem can be solved in these models completely and there exist good agreement between the models and observational values of w D , q. We study squared sound speed {vs2}, and find that for one case of non-linear interaction term {vs2} can achieves positive values at late time of evolution.

Variable features on Mars - Preliminary Mariner 9 television results.

NASA Technical Reports Server (NTRS)

Sagan, C.; Veverka, J.; Fox, P.; Dubisch, R.; Lederberg, J.; Levinthal, E.; Quam, L.; Tucker, R.; Pollack, J. B.; Smith, B. A.

1972-01-01

Systematic Mariner 9 photography of a range of Martian surface features, observed with all three photometric angles approximately invariant, reveals three general categories of albedo variations: (1) an essentially uniform contrast enhancement due to the dissipation of the dust storm; (2) the appearance of splotches, irregular dark markings at least partially related to topography; and (3) the development of both bright and dark linear streaks, generally emanating from craters. Some splotches and streaks vary on characteristic timescales of about two weeks; they have characteristic dimensions of kilometers to tens of kilometers. The morphology and variability of streaks and splotches, and the resolution of at least one splotch into an extensive dune system, implicate windblown dust as the principal agent of Martian albedo differences and variability.

Self-frequency shift of dark solitons in optical fibers

NASA Astrophysics Data System (ADS)

Uzunov, Ivan M.; Gerdjikov, Vladimir S.

1993-02-01

An analytical description of the soliton self-frequency shift (SSFS) of dark solitons is presented, using the conservation laws of the nonlinear Schrödinger equation. It is shown that the influence of intrapulse Raman scattering on dark solitons crucially depends on the sign of soliton's velocity. Our analytical expressions qualitatively explain the main features of the SSFS of the dark solitons observed recently both in experiment [A. M. Weiner, R. N. Thurston, W. J. Tomlinson, J. P. Heritage, D. E. Leaird, E. M. Kirschner, and R. J. Hawkins, Opt. Lett. 14, 868 (1989)] and in numerical simulation [A. M. Weiner, R. N. Thurston, W. J. Tomlinson, J. P. Heritage, D. E. Leaird, E. M. Kirschner, and R. J. Hawkins, Opt. Lett. 14, 868 (1989); Yu. S. Kivshar and V. V. Afanasjev, ibid. 16, 285 (1991)].

Nova Superposed on Yavine Corona

NASA Image and Video Library

1998-06-04

The view from NASA's Magellan spacecraft shows a 100-km-wide nova superposed on Yavine Corona. Coronae are roughly circular, volcanic features believed to form over hot upwellings of magma within the Venusian mantle. http://photojournal.jpl.nasa.gov/catalog/PIA00150

Fourier transform vibrational circular dichroism of small pharmaceutical molecules

NASA Astrophysics Data System (ADS)

Long, Fujin; Freedman, Teresa B.; Nafie, Laurence A.

1998-06-01

Fourier transform vibrational circular dichroism (FT-VCD) spectra of the small pharmaceutical molecules propanolol, ibuprofen and naproxen have been measured in the hydrogen stretching and mid-infrared regions to obtain information on solution conformation and to identify markers for absolute configuration determination. Ab initio molecular orbital calculations of low energy conformations, vibrational frequencies and VCD intensities for fragments of the drugs were utilized in interpreting the spectra. Features characteristic of five conformers of propranolol were identified. The weak positive CH stretching VCD signal in ibuprofen and naproxen is characteristic of the S-configuration of the chiral center common to these two analgesics.

Polar POLICRYPS diffractive structures generate cylindrical vector beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alj, Domenico; Caputo, Roberto, E-mail: roberto.caputo@fis.unical.it; Umeton, Cesare

2015-11-16

Local shaping of the polarization state of a light beam is appealing for a number of applications. This can be achieved by employing devices containing birefringent materials. In this article, we present one such enables converting a uniformly circularly polarized beam into a cylindrical vector beam (CVB). This device has been fabricated by exploiting the POLICRYPS (POlymer-LIquid CRYstals-Polymer-Slices) photocuring technique. It is a liquid-crystal-based optical diffraction grating featuring polar symmetry of the director alignment. We have characterized the resulting CVB profile and polarization for the cases of left and right circularly polarized incoming beams.

Dark-field microscopic image stitching method for surface defects evaluation of large fine optics.

PubMed

Liu, Dong; Wang, Shitong; Cao, Pin; Li, Lu; Cheng, Zhongtao; Gao, Xin; Yang, Yongying

2013-03-11

One of the challenges in surface defects evaluation of large fine optics is to detect defects of microns on surfaces of tens or hundreds of millimeters. Sub-aperture scanning and stitching is considered to be a practical and efficient method. But since there are usually few defects on the large aperture fine optics, resulting in no defects or only one run-through line feature in many sub-aperture images, traditional stitching methods encounter with mismatch problem. In this paper, a feature-based multi-cycle image stitching algorithm is proposed to solve the problem. The overlapping areas of sub-apertures are categorized based on the features they contain. Different types of overlapping areas are then stitched in different cycles with different methods. The stitching trace is changed to follow the one that determined by the features. The whole stitching procedure is a region-growing like process. Sub-aperture blocks grow bigger after each cycle and finally the full aperture image is obtained. Comparison experiment shows that the proposed method is very suitable to stitch sub-apertures that very few feature information exists in the overlapping areas and can stitch the dark-field microscopic sub-aperture images very well.

Compositions of Low Albedo Intracrater Materials and Wind Streaks on Mars: Examination of MGS TES Data in Western Arabia Terra

NASA Technical Reports Server (NTRS)

Bandfield, J. L.; Wyatt, M. B.; Christensen, P.; McSween, H. Y., Jr.

2001-01-01

Basalt and andesite surface compositions are identified within individual low albedo intracrater features and adjacent dark wind streaks. High resolution mapping of compositional heterogeneities may help constrain origin hypotheses for these features. Additional information is contained in the original extended abstract.

IAU nomenclature for albedo features on the planet Mercury

NASA Technical Reports Server (NTRS)

Dollfus, A.; Chapman, C. R.; Davies, M. E.; Gingerich, O.; Goldstein, R.; Guest, J.; Morrison, D.; Smith, B. A.

1978-01-01

The International Astronomical Union has endorsed a nomenclature for the albedo features on Mercury. Designations are based upon the mythological names related to the god Hermes; they are expressed in Latin form. The dark-hued albedo features are associated with the generic term Solitudo. The light-hued areas are designated by a single name without generic term. The 32 names adopted are allocated on the Mercury map.

Indirect Detection Analysis: Wino Dark Matter Case Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hryczuk, Andrzej; Cholis, Ilias; Iengo, Roberto

2014-07-15

We perform a multichannel analysis of the indirect signals for the Wino Dark Matter, including one-loop electroweak and Sommerfeld enhancement corrections. We derive limits from cosmic ray antiprotons and positrons, from continuum galactic and extragalactic diffuse γ-ray spectra, from the absence of γ-ray line features at the galactic center above 500 GeV in energy, from γ-rays toward nearby dwarf spheroidal galaxies and galaxy clusters, and from CMB power-spectra. Additionally, we show the future prospects for neutrino observations toward the inner Galaxy and from antideuteron searches. For each of these indirect detection probes we include and discuss the relevance of themore » most important astrophysical uncertainties that can impact the strength of the derived limits. We find that the Wino as a dark matter candidate is excluded in the mass range bellow simeq 800 GeV from antiprotons and between 1.8 and 3.5 TeV from the absence of a γ-ray line feature toward the galactic center. Limits from other indirect detection probes confirm the main bulk of the excluded mass ranges.« less

Dark and vulnerable personality trait correlates of dimensions of criminal behavior among adult offenders.

PubMed

Edwards, Bethany G; Albertson, Emily; Verona, Edelyn

2017-10-01

Given the high-level impact of crime, empirical work is needed to identify personality traits, or overarching factors of personality pathology, that may leave individuals more prone to engage in criminal behaviors. This study empirically tested the distinction between the dark personality and vulnerable dark personality spectra (Miller et al., 2010) in a large offender sample and aimed to test how these personality factors relate to criminal dimensions and individual types of crime. Self-report and public record data verified criminal behaviors for 493 (34.7% women) adult offenders, and features of the 2 personality spectra were assessed using the Psychopathy Checklist: Screening Version, Narcissistic Personality Inventory-16, Hypersensitive Narcissism Scale, and Personality Assessment Inventory: Borderline Scale. Factor analyses supported the distinction between dark and vulnerable dark personality spectra and 3 dimensions of crime (i.e., crimes against property and persons, and drug-related crimes). Findings broadly pointed to trait vulnerabilities within the dark spectra (e.g., callousness) as relevant for criminal versatility and violent crimes against persons (e.g., assault, murder), and impulsive/reactive tendencies within the dark spectra (vulnerable dark) appeared to be particularly important for impulsive property crimes (e.g., theft, robbery) and drug offenses. Results may lend themselves well to refining offender intervention techniques and warrant further examination of the extent to which dark personality spectra coalesce as expected or similarly predict high-impact behaviors. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Three-dimensional axisymmetric sources for Majumdar-Papapetrou type spacetimes

NASA Astrophysics Data System (ADS)

García-Reyes, Gonzalo; Hernández-Gómez, Kevin A.

From Newtonian potential-density pairs, we construct three-dimensional axisymmetric relativistic sources for a Majumdar-Papapetrou type conformastatic spacetime. As simple examples, we build two families of relativistic thick disks from the first two Miyamoto-Nagai potential-density pairs used in Newtonian gravity to model flat galaxies, and a three-component relativistic model of galaxy (bulge, disk and dark matter halo). We study the equatorial circular motion of test particles around such structures. Also the stability of the orbits is analyzed for radial perturbation using an extension of the Rayleigh criterion. In all examples, the relativistic effects are analyzed and compared with the Newtonian approximation. The models are considered satisfying all the energy conditions.

Constructive polarization modulation for coherent population trapping clock

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yun, Peter, E-mail: enxue.yun@obspm.fr; Danet, Jean-Marie; Holleville, David

2014-12-08

We propose a constructive polarization modulation scheme for atomic clocks based on coherent population trapping (CPT). In this scheme, the polarization of a bichromatic laser beam is modulated between two opposite circular polarizations to avoid trapping the atomic populations in the extreme Zeeman sublevels. We show that if an appropriate phase modulation between the two optical components of the bichromatic laser is applied synchronously, the two CPT dark states which are produced successively by the alternate polarizations add constructively. Measured CPT resonance contrasts up to 20% in one-pulse CPT and 12% in two-pulse Ramsey-CPT experiments are reported, demonstrating the potentialmore » of this scheme for applications to high performance atomic clocks.« less

Crater dimensions from apollo data and supplemental sources

USGS Publications Warehouse

Pike, R.J.

1976-01-01

A catalog of crater dimensions that were compiled mostly from the new Apollo-based Lunar Topographic Orthophotomaps is presented in its entirety. Values of crater diameter, depth, rim height, flank width, circularity, and floor diameter (where applicable) are tabulated for a sample of 484 craters on the Moon and 22 craters on Earth. Systematic techniques of mensuration are detailed. The lunar craters range in size from 400 m to 300 km across and include primary impact craters of the main sequence, secondary impact craters, craterlets atop domes and cones, and dark-halo craters. The terrestrial craters are between 10 m and 22.5 km in diameter and were formed by meteorite impact. ?? 1976 D. Reidel Publishing Company.

The positron excess as a smoking gun for dynamical dark matter?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dienes, Keith R.; Kumar, Jason; Thomas, Brooks

One of the most puzzling aspects of recent data from the AMS-02 experiment is an apparent rise in the cosmic-ray positron fraction as a function of energy. This feature is observed out to energies of approximately 350 GeV. One explanation of these results interprets the extra positrons as arising from the decays of dark-matter particles. This in turn typically requires that such particles have rather heavy TeV-scale masses and not undergo simple two-body decays to leptons. In this talk, by contrast, we show that Dynamical Dark Matter (DDM) can not only match existing AMS-02 data on the positron excess, butmore » also accomplish this feat with significantly lighter dark-matter constituents undergoing simple two-body decays to leptons. We also demonstrate that the Dynamical Dark Matter framework makes a fairly robust prediction that the positron fraction should level off and then remain roughly constant out to approximately 1 TeV, without experiencing any sharp downturns. Thus, if we interpret the positron excess in terms of decaying dark matter, the existence of a plateau in the positron fraction at energies less than 1 TeV may be taken as a “smoking gun” of Dynamical Dark Matter.« less

Mimicking dark matter in Horndeski gravity

NASA Astrophysics Data System (ADS)

Rinaldi, Massimiliano

2017-06-01

Since the rediscovery of Horndeski gravity, a lot of work has been devoted to the exploration of its properties, especially in the context of dark energy. However, one sector of this theory, namely the one containing the coupling of the Einstein tensor to the kinetic term of the scalar field, shows some surprising features in the construction of black holes and neutron stars. Motivated by these new results, I explore the possibility that this sector of Horndeski gravity can mimic cold dark matter at cosmological level and also explain the flattening of galactic rotation curves. I will show that, in principle, it is possible to achieve both goals with at least two scalar fields and a minimal set of assumptions.

Resurrecting hot dark matter - Large-scale structure from cosmic strings and massive neutrinos

NASA Technical Reports Server (NTRS)

Scherrer, Robert J.

1988-01-01

These are the results of a numerical simulation of the formation of large-scale structure from cosmic-string loops in a universe dominated by massive neutrinos (hot dark matter). This model has several desirable features. The final matter distribution contains isolated density peaks embedded in a smooth background, producing a natural bias in the distribution of luminous matter. Because baryons can accrete onto the cosmic strings before the neutrinos, the galaxies will have baryon cores and dark neutrino halos. Galaxy formation in this model begins much earlier than in random-phase models. On large scales the distribution of clustered matter visually resembles the CfA survey, with large voids and filaments.

Review of the Functions of Archimedes’ Spiral Metallic Nanostructures

PubMed Central

Li, Zixiang; Zhang, Jingran; Guo, Kai; Shen, Fei; Zhou, Qingfeng; Zhou, Hongping

2017-01-01

Here, we have reviewed some typical plasmonic structures based on Archimedes’ spiral (AS) architectures, which can produce polarization-sensitive focusing phenomenon and generate plasmonic vortices (PVs) carrying controllable orbital angular momentum (OAM) because of the relation between the incident polarized states and the chiralities of the spiral structures. These features can be used to analyze different circular polarization states, which has been one of the rapidly developing researching topics in nanophotonics in recent years. Many investigations demonstrate that the multifunctional spiral-based plasmonic structures are excellent choices for chiral selection and generating the transmitted field with well-defined OAM. The circular polarization extinction ratio, as an evaluation criterion for the polarization selectivity of a designed structure, could be effectively improved by properly modulating the parameters of spiral structures. Such functional spiral plasmonic nanostructures are promising for applications in analyzing circular polarization light, full Stokes vector polarimetric sensors, near-field imaging, and so on. PMID:29165382

Detection of Frictional Heating on Faults Using Raman Spectra of Carbonaceous Material

NASA Astrophysics Data System (ADS)

Ito, K.; Ujiie, K.; Kagi, H.

2017-12-01

Raman spectra of carbonaceous material (RSCM) have been used as geothermometer in sedimentary and metamorphic rocks. However, it remains poorly understood whether RSCM are useful for detecting past frictional heating on faults. To detect increased heating during seismic slip, we examine the thrust fault in the Jurassic accretionary complex, central Japan. The thrust fault zone includes 10 cm-thick cataclasite and a few mm-thick dark layer. The cataclasite is characterized by fragments of black and gray chert in the black carbonaceous mudstone matrix. The dark layer is marked by intensely cracked gray chert fragments in the dark matrix of carbonaceous mudstone composition, which bounds the fractured gray chert above from the cataclasite below. The RSCM are analyzed for carbonaceous material in the cataclasite, dark layer, and host rock <10 mm from cataclasite and dark layer boundaries. The result indicates that there is no increased carbonization in the cataclasite. In contrast, the dark layer and part of host rocks <2 mm from the dark layer boundaries show prominent increase in carbonization. The absent of increased carbonization in the cataclasite could be attributed to insufficient frictional heating associated with distributed shear and/or faulting at low slip rates. The dark layer exhibits the appearance of fault and injection veins, and the dark layer boundaries are irregularly embayed or intensely cracked; these features have been characteristically observed in pseudotachylytes. Therefore, the increased carbonization in the dark layer is likely resulted from increased heating during earthquake faulting. The intensely cracked fragments in the dark layer and cracked wall rocks may reflect thermal fracturing in chert, which is caused by heat conduction from the molten zone. We suggest that RSCM are useful for the detection of increased heating on faults, particularly when the temperature is high enough for frictional melting and thermal fracturing.

Flies in the north: locomotor behavior and clock neuron organization of Drosophila montana.

PubMed

Kauranen, Hannele; Menegazzi, Pamela; Costa, Rodolfo; Helfrich-Förster, Charlotte; Kankainen, Annaliisa; Hoikkala, Anneli

2012-10-01

The circadian clock plays an important role in adaptation in time and space by synchronizing changes in physiological, developmental, and behavioral traits of organisms with daily and seasonal changes in their environment. We have studied some features of the circadian activity and clock organization in a northern Drosophila species, Drosophila montana, at both the phenotypic and the neuronal levels. In the first part of the study, we monitored the entrained and free-running locomotor activity rhythms of females in different light-dark and temperature regimes. These studies showed that D. montana flies completely lack the morning activity component typical to more southern Drosophila species in an entrained environment and that they are able to maintain their free-running locomotor activity rhythm better in constant light than in constant darkness. In the second part of the study, we traced the expression of the PDF neuropeptide and the CRY protein in the neurons of the brain in D. montana adults and found differences in the number and location of PDF- and CRY-expressing neurons compared with those described in Drosophila melanogaster. These differences could account, at least in part, for the lack of morning activity and the reduced circadian rhythmicity of D. montana flies in constant darkness, both of which are likely to be adaptive features during the long and dark winters occurring in nature.

Are Hyperion and Phoebe Linked to Iapetus?

NASA Technical Reports Server (NTRS)

Jarvis, Kandy S.; Vilas, Faith; Larson, Stephen M.; Gaffey, Michael J.

1999-01-01

Narrowband reflectance spectra of the Saturnian satellites S VII Hyperion and S IX Phoebe were obtained across the 0.4 - 0.8 micron spectral region. The spectrum of Phoebe is similar to the spectrum of a C-class asteroid, with an absorption feature centered near 0.43 micron superimposed on the UV/blue intervalence charge transfer transition present in the spectrum. The spectrum of Hyperion shows the strong spectral slope apparent in spectra of many outer Solar System materials and attributed to organics. We use a linear mixing model to separate the reflectance spectrum of the dark material on Hyperion from the icy material. A distinct absorption feature centered at 0.67 micron is present. A slight inflection near 0.4 - 0.6 micron and change in slope near 0.73 micron suggesting the lower wavelength edge of an absorption are also present. These absorptions are very similar to those identified in the spectrum of the dark material on the surface of Iapetus, suggesting that the dark material on these two satellites is compositionally similar and has a similar origin. These absorption features are attributed to the (6)A(sub 1) yields (4)T(sub 2)(G) and (6)A(sub 1) yields (4)T(sub 1)(G) ferric charge transfer transitions in iron alteration minerals such as goethite and hematite that are products of the aqueous alteration of anhydrous silicates.

Physical properties and dynamical relation of the circular depressions on comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Ip, W.-H.; Lai, I.-L.; Lee, J.-C.; Cheng, Y.-C.; Li, Y.; Lin, Z.-Y.; Vincent, J.-B.; Besse, S.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J.-L.; Bertini, I.; Bodewits, D.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hviid, S. F.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J.-R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Lowry, S.; Marchi, S.; Marzari, F.; Michalik, H.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Thomas, N.; Toth, E.; Tubiana, C.

2016-06-01

Aims: We aim to characterize the circular depressions of comet 67P/Churyumov-Gerasimenko and investigate whether such surface morphology of a comet nucleus is related to the cumulative sublimation effect since becoming a Jupiter family comet (JFC). Methods: The images from the Rosetta/OSIRIS science camera experiment are used to construct size frequency distributions of the circular depression structures on comet 67P and they are compared with those of the JFCs 81P/Wild 2, 9P/Tempel 1, and 103P/Hartley 2. The orbital evolutionary histories of these comets over the past 100 000 yr are analyzed statistically and compared with each other. Results: The global distribution of the circular depressions over the surface of 67P is charted and classified. Descriptions are given to the characteristics and cumulative size frequency distribution of the identified features. Orbital statistics of the JFCs visited by spacecraft are derived. Conclusions: The size frequency distribution of the circular depressions is found to have a similar power law distribution to those of 9P/Tempel 1 and 81P/Wild 2. This might imply that they could have been generated by the same process. Orbital integration calculation shows that the surface erosion histories of 81P/Wild 2, and 9P/Tempel 1 could be shorter than those of 67P, 103 P/Hartley 2 and 19P/Borrelly. From this point of view, the circular depressions could be dated back to the pre-JFC phase or the transneptunian phase of these comets. The north-south asymmetry in the distribution of the circular depressions could be associated with the heterogeneous structure of the nucleus of comet 67P and/or the solar insolation history.

Microlensing of an extended source by a power-law mass distribution

NASA Astrophysics Data System (ADS)

Congdon, Arthur B.; Keeton, Charles R.; Osmer, S. J.

2007-03-01

Microlensing promises to be a powerful tool for studying distant galaxies and quasars. As the data and models improve, there are systematic effects that need to be explored. Quasar continuum and broad-line regions may respond differently to microlensing due to their different sizes; to understand this effect, we study microlensing of finite sources by a mass function of stars. We find that microlensing is insensitive to the slope of the mass function but does depend on the mass range. For negative-parity images, diluting the stellar population with dark matter increases the magnification dispersion for small sources and decreases it for large sources. This implies that the quasar continuum and broad-line regions may experience very different microlensing in negative-parity lensed images. We confirm earlier conclusions that the surface brightness profile and geometry of the source have little effect on microlensing. Finally, we consider non-circular sources. We show that elliptical sources that are aligned with the direction of shear have larger magnification dispersions than sources with perpendicular alignment, an effect that becomes more prominent as the ellipticity increases. Elongated sources can lead to more rapid variability than circular sources, which raises the prospect of using microlensing to probe source shape.

Arecibo and Goldstone radar images of near-Earth Asteroid (469896) 2005 WC1

NASA Astrophysics Data System (ADS)

Lawrence, Kenneth J.; Benner, Lance A. M.; Brozovic, Marina; Ostro, Steven J.; Jao, Joseph S.; Giorgini, Jon D.; Slade, Martin A.; Jurgens, Raymond F.; Nolan, Michael C.; Howell, Ellen S.; Taylor, Patrick A.

2018-01-01

We report radar observations of near-Earth asteroid (469896) 2005 WC1 that were obtained at Arecibo (2380 MHz, 13 cm) and Goldstone (8560 MHz, 3.5 cm) on 2005 December 14-15 during the asteroid's approach within 0.020 au The asteroid was a strong radar target. Delay-Doppler images with resolutions as fine as 15 m/pixel were obtained with 2 samples per baud giving a correlated pixel resolution of 7.5 m. The radar images reveal an angular object with 100 m-scale surface facets, radar-dark regions, and an estimated diameter of 400 ± 50 m. The rotation of the facets in the images gives a rotation period of ∼2.6 h that is consistent with the estimated period of 2.582 h ± 0.002 h from optical lightcurves reported by Miles (private communication). 2005 WC1 has a circular polarization ratio of 1.12 ± 0.05 that is one of the highest values known, suggesting a structurally-complex near-surface at centimeter to decimeter spatial scales. It is the first asteroid known with an extremely high circular polarization ratio, relatively low optical albedo, and high radar albedo.

Abnormal dark-adapted electroretinogram in Best's vitelliform macular degeneration.

PubMed

Lachapelle, P; Quigley, M G; Polomeno, R C; Little, J M

1988-10-01

It is generally well accepted that in Best's vitelliform macular degeneration (BVMD) the electroretinogram (ERG) is normal whereas the electro-oculogram (EOG) is markedly abnormal. We describe a patient in whom BVMD was suspected on the basis of the clinical findings, EOG and family history (one of her daughters had the typical vitelliform lesion). However, her dark-adapted ERG was markedly abnormal. Similar anomalies were found in the dark-adapted ERG of the daughter. While the temporal features of the various ERG waves were well preserved, a substantial decrease in the amplitude of specific segments of the ERG signal was observed. A similar decrease in the amplitude of the oscillatory potentials was also found. We believe that this unusual combination of BVMD and abnormal dark-adapted ERG may be due to the reported reduced penetrance and variable expressivity of the BVMD gene(s).

Waveguide integrated low noise NbTiN nanowire single-photon detectors with milli-Hz dark count rate

PubMed Central

Schuck, Carsten; Pernice, Wolfram H. P.; Tang, Hong X.

2013-01-01

Superconducting nanowire single-photon detectors are an ideal match for integrated quantum photonic circuits due to their high detection efficiency for telecom wavelength photons. Quantum optical technology also requires single-photon detection with low dark count rate and high timing accuracy. Here we present very low noise superconducting nanowire single-photon detectors based on NbTiN thin films patterned directly on top of Si3N4 waveguides. We systematically investigate a large variety of detector designs and characterize their detection noise performance. Milli-Hz dark count rates are demonstrated over the entire operating range of the nanowire detectors which also feature low timing jitter. The ultra-low dark count rate, in combination with the high detection efficiency inherent to our travelling wave detector geometry, gives rise to a measured noise equivalent power at the 10−20 W/Hz1/2 level. PMID:23714696

Possible resonance effect of axionic dark matter in Josephson junctions.

PubMed

Beck, Christian

2013-12-06

We provide theoretical arguments that dark-matter axions from the galactic halo that pass through Earth may generate a small observable signal in resonant S/N/S Josephson junctions. The corresponding interaction process is based on the uniqueness of the gauge-invariant axion Josephson phase angle modulo 2π and is predicted to produce a small Shapiro steplike feature without externally applied microwave radiation when the Josephson frequency resonates with the axion mass. A resonance signal of so far unknown origin observed by C. Hoffmann et al. [Phys. Rev. B 70, 180503(R) (2004)] is consistent with our theory and can be interpreted in terms of an axion mass m(a)c2=0.11  meV and a local galactic axionic dark-matter density of 0.05  GeV/cm3. We discuss future experimental checks to confirm the dark-matter nature of the observed signal.

Venus - Impact Crater Jeanne

NASA Image and Video Library

1996-11-20

This full-resolution image from NASA Magellan spacecraft shows Jeanne crater, a 19.5 kilometer (12 mile) diameter impact crater. Jeanne crater is located at 40.0 degrees north latitude and 331.4 degrees longitude. The distinctive triangular shape of the ejecta indicates that the impacting body probably hit obliquely, traveling from southwest to northeast. The crater is surrounded by dark material of two types. The dark area on the southwest side of the crater is covered by smooth (radar-dark) lava flows which have a strongly digitate contact with surrounding brighter flows. The very dark area on the northeast side of the crater is probably covered by smooth material such as fine-grained sediment. This dark halo is asymmetric, mimicking the asymmetric shape of the ejecta blanket. The dark halo may have been caused by an atmospheric shock or pressure wave produced by the incoming body. Jeanne crater also displays several outflow lobes on the northwest side. These flow-like features may have formed by fine-grained ejecta transported by a hot, turbulent flow created by the arrival of the impacting object. Alternatively, they may have formed by flow of impact melt. http://photojournal.jpl.nasa.gov/catalog/PIA00472

Cytological diagnostic of lymphadenitis tuberculosis by eosinophilic material

NASA Astrophysics Data System (ADS)

Delyuzar; Amir, Z.; Kusumawati, L.

2018-03-01

AFB sputum and chest X-ray are used to identify patients with pulmonary TB. For extrapulmonary TB, fine needle aspiration cytology is needed, even though occasionally found not atypical feature in the form of eosinophilic material with dark brown particles, suspected as TB. This research was to show that eosinophilic material with dark brown particles is accurate as new criteria for the cytological diagnosis of TB. By performing fine needle aspiration biopsy stained with Giemsa, if an eosinophilic material with dark brown particles was encountered, we continued with Ziehl-Neelsen AFB stain and confirmed with PCR. To assess accuracy, we used a diagnostic test to evaluate sensitivity and specificity of eosinophilic material with dark brown particles by using AFB and PCR as the gold standard. The sensitivity and specificity of cytological diagnosis in tuberculosis of eosinophilic material with dark brown particles were 93.65% and 70.99%, respectively if confirmed with AFB. On the other hand, if confirmed with PCR using Mycobacterium tuberculosis DNA, the sensitivity and specificity were 98.95% and 96.79%, respectively. In conclusion, eosinophilic masses with dark brown particles is accurate as new criteria of TB diagnostic cytology with high sensitivity and specificity confirmed with AFB and PCR test.

Differentiating Dark Triad Traits Within and Across Interpersonal Circumplex Surfaces.

PubMed

Dowgwillo, Emily A; Pincus, Aaron L

2017-01-01

Recent discussions surrounding the Dark Triad (narcissism, psychopathy, and Machiavellianism) have centered on areas of distinctiveness and overlap. Given that interpersonal dysfunction is a core feature of Dark Triad traits, the current study uses self-report data from 562 undergraduate students to examine the interpersonal characteristics associated with narcissism, psychopathy, and Machiavellianism on four interpersonal circumplex (IPC) surfaces. The distinctiveness of these characteristics was examined using a novel bootstrapping methodology for computing confidence intervals around circumplex structural summary method parameters. Results suggest that Dark Triad traits exhibit distinct structural summary method parameters with narcissism characterized by high dominance, psychopathy characterized by a blend of high dominance and low affiliation, and Machiavellianism characterized by low affiliation on the problems, values, and efficacies IPC surfaces. Additionally, there was some heterogeneity in findings for different measures of psychopathy. Gender differences in structural summary parameters were examined, finding similar parameter values despite mean-level differences in Dark Triad traits. Finally, interpersonal information was integrated across different IPC surfaces to create profiles associated with each Dark Triad trait and to provide a more in-depth portrait of associated interpersonal dynamics. © The Author(s) 2016.

DISCOVERY OF A MAKEMAKEAN MOON

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, Alex H.; Buie, Marc W.; Grundy, Will M.

We describe the discovery of a satellite in orbit about the dwarf planet (136472) Makemake. This satellite, provisionally designated S/2015 (136472) 1, was detected in imaging data collected with the Hubble Space Telescope ’s Wide Field Camera 3 on UTC 2015 April 27 at 7.80 ± 0.04 mag fainter than Makemake and at a separation of 0.″57. It likely evaded detection in previous satellite searches due to a nearly edge-on orbital configuration, placing it deep within the glare of Makemake during a substantial fraction of its orbital period. This configuration would place Makemake and its satellite near a mutual eventmore » season. Insufficient orbital motion was detected to make a detailed characterization of its orbital properties, prohibiting a measurement of the system mass with the discovery data alone. Preliminary analysis indicates that if the orbit is circular, its orbital period must be longer than 12.4 days and must have a semimajor axis ≳21,000 km. We find that the properties of Makemake’s moon suggest that the majority of the dark material detected in the system by thermal observations may not reside on the surface of Makemake, but may instead be attributable to S/2015 (136472) 1 having a uniform dark surface. This “dark moon hypothesis” can be directly tested with future James Webb Space Telescope observations. We discuss the implications of this discovery for the spin state, figure, and thermal properties of Makemake and the apparent ubiquity of trans-Neptunian dwarf planet satellites.« less

Discovery of a Makemakean Moon

NASA Technical Reports Server (NTRS)

Parker, Alex H.; Buie, Marc W.; Grundy, Will M.; Noll, Keith S.

2016-01-01

We describe the discovery of a satellite in orbit about the dwarf planet (136472) Makemake. This satellite, provisionally designated S/2015 (136472) 1, was detected in imaging data collected with the Hubble Space Telescope's Wide Field Camera 3 on UTC 2015 April 27 at 7.80 +/- 0.04 mag fainter than Makemake and at a separation of 0farcs57. It likely evaded detection in previous satellite searches due to a nearly edge-on orbital configuration, placing it deep within the glare of Makemake during a substantial fraction of its orbital period. This configuration would place Makemake and its satellite near a mutual event season. Insufficient orbital motion was detected to make a detailed characterization of its orbital properties, prohibiting a measurement of the system mass with the discovery data alone. Preliminary analysis indicates that if the orbit is circular, its orbital period must be longer than 12.4 days and must have a semimajor axis > or approx. = 21,000 km. We find that the properties of Makemake's moon suggest that the majority of the dark material detected in the system by thermal observations may not reside on the surface of Makemake, but may instead be attributable to S/2015 (136472) 1 having a uniform dark surface. This dark moon hypothesis can be directly tested with future James Webb Space Telescope observations. We discuss the implications of this discovery for the spin state, figure, and thermal properties of Makemake and the apparent ubiquity of trans-Neptunian dwarf planet satellites.

Velocity variations of an Equatorial plume throughout a Jovian year

NASA Technical Reports Server (NTRS)

Reese, E.; Beebe, R. F.

1975-01-01

Features in the equatorial zone of Jupiter show that the equatorial plume reported by Pioneer 10 has existed for an 11-year interval. During this interval the plume has shown an acceleration which can be interpreted as a constant component of 3 x 10 to minus 8th power m/sq cm and a sinusoidal component which anticorrelates with the planetocentric declination of the sun, D sub s, and has an amplitude of -0.96 meters per second per degree change of D sub s. The sinusoidal component has been interpreted in terms of solar heating. Throughout this interval of time the equatorial zone has appeared abnormally dark and has contained many dark projections along the northern edge. When the plume approaches to within 25 to 30 deg of these features they are deflected in the direction of motion of the plume and then dissipate or become obscured as the plume passes. After passage of the plume normal features are again observed.

ARC-1990-AC91-2014

NASA Image and Video Library

1990-02-14

Range : 1.7 million miles This photo of Venus was taken by the Galileo spacecraft's Solid State Imaging System. A high-pass spatial filter has been applied in order to emphasize the smaller-scale cloud features, and the rendition has been colorized to a bluish hue in order to emphasize the subtle contrasts in the cloud markings and to indicate how it was taken through a violet filter. The sulfuric acid clouds indicate considerable convective activity, in the equatorial regions of the planet to the left and downwind of the subsolar point (afternoon on Venus), They are analogous to 'fair weather clouds' on Earth. The filamentary dark features visible in the colorized image are here revealed to be composed of several dark nodules, like strings on a bead, each about 60 miles across.

Tidal regime of intact planetoid capture model for the Earth-Moon system: Does it relate to the archean sedimentary rock record?

NASA Technical Reports Server (NTRS)

Malcuit, Robert J.; Winters, Ronald R.

1993-01-01

Regardless of one's favorite model for the origin of the Earth-Moon system (fission, coformation, tidal capture, giant-impact) the early history of lunar orbital evolution would produce significant thermal and earth and ocean tidal effects on the primitive earth. Three of the above lunar origin models (fission, coformation, giant-impact) feature a circular orbit which undergoes a progressive increase in orbital radius from the time of origin to the present time. In contrast, a tidal capture model places the moon in an elliptical orbit undergoing progressive circularization from the time of capture (for model purposes about 3.9 billion years ago) for at least a few 10(exp 8) years following the capture event. Once the orbit is circularized, the subsequent tidal history for a tidal capture scenario is similar to that for other models of lunar origin and features a progressive increase in orbital radius to the current state of the lunar orbit. This elliptical orbit phase, if it occurred, should have left a distinctive signature in the terrestrial and lunar rock records. Depositional events would be associated terrestrial shorelines characterized by abnormally high, but progressively decreasing, ocean tidal amplitudes and ranges associated with such an orbital evolution. Several rock units in the age range 3.6-2.5 billion years before present are reported to have a major tidal component. Examples are the Warrawoona, Fortescue, and Hamersley Groups of Western Australia and the Pangola and Witwatersand Supergroups of South Africa. Detailed study of the features of these tidal sequences may be helpful in deciphering the style of lunar orbital evolution during the Archean Eon.

High-resolution imaging of compact high-velocity clouds

NASA Astrophysics Data System (ADS)

Braun, R.; Burton, W. B.

2000-02-01

Six examples of the compact, isolated H i high-velocity clouds (CHVCs) identified by Braun & Burton (\\cite{brau99}), but only marginally resolved in single-dish data, have been imaged with the Westerbork Synthesis Radio Telescope. The 65 confirmed objects in this class define a dynamically cold system, with a global minimum for the velocity dispersion of only 70 km s-1, found in the Local Group Standard of Rest. The population is in-falling at 100 km s-1 toward the Local Group barycenter. These objects have a characteristic morphology, in which one or more compact cores is embedded in a diffuse halo. The compact cores typically account for 40% of the H i line flux while covering some 15% of the source area. The narrow line width of all core components allows unambiguous identification of these with the cool condensed phase of \\hi , the CNM, with kinetic temperature near 100 K, while the halos appear to represent a shielding column of warm diffuse \\hi , the WNM, with temperature near 8000 K. We detect a core with one of the narrowest H i emission lines ever observed, with intrinsic FWHM of no more than 2 km s-1 and 75 K brightness. From a comparison of column and volume densities for this feature we derive a distance in the range 0.5 to 1 Mpc. We determine a metallicity for this same object of 0.04 to 0.07 solar. Comparably high distances are implied by demanding the stability of objects with multiple cores, which show relative velocities as large as 70 km s-1 on 30 arcmin scales. Many of the compact cores show systematic velocity gradients along the major axis of their elliptical extent which are well-fit by circular rotation in a flattened disk system. Two out of three of the derived rotation curves are well-fit by Navarro, Frenk & White (1997) cold dark matter profiles. These kinematic signatures imply a high dark-to-visible mass ratio of 10-50, for D = 0.7 Mpc, which scales as 1/D. The implied dark matter halos dominate the mass volume density within the central 2 kpc (10 arcmin) of each source, providing a sufficent hydrostatic pressure to allow CNM condensation. The CHVC properties are similar in many respects to those of the Local Group dwarf irregular galaxies, excepting the presence of a high surface brightness stellar population.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peterson, John Russell

This grant funded the development and dissemination of the Photon Simulator (PhoSim) for the purpose of studying dark energy at high precision with the upcoming Large Synoptic Survey Telescope (LSST) astronomical survey. The work was in collaboration with the LSST Dark Energy Science Collaboration (DESC). Several detailed physics improvements were made in the optics, atmosphere, and sensor, a number of validation studies were performed, and a significant number of usability features were implemented. Future work in DESC will use PhoSim as the image simulation tool for data challenges used by the analysis groups.

Windblown Sand in Ganges Chasma

NASA Image and Video Library

2017-04-25

Dark, windblown sand covers intricate sedimentary rock layers in this image captured by NASA's Mars Reconnaissance Orbiter (MRO) from Ganges Chasma, a canyon in the Valles Marineris system. These features are at once familiar and unusual to those familiar with Earth's beaches and deserts. Most sand dunes on Earth are made of silica-rich sand, giving them a light color; these Martian dunes owe their dark color to the iron and magnesium-rich sand found in the region. https://photojournal.jpl.nasa.gov/catalog/PIA21600

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boehm, Celine; Ascasibar, Yago

In a previous work, it was found that the light dark matter scenario could be a possible explanation to the 511 keV emission line detected at the center of our galaxy. Here, we show that hints of this scenario may also have been discovered in particle physics experiments. This could explain the discrepancy between the measurement of the fine structure constant and the value referenced in the CODATA. Finally, our results indicate that some of the light dark matter features could be tested in accelerators. Their discovery might favor N=2 supersymmetry.

Dark matter in the outer solar system

NASA Technical Reports Server (NTRS)

Owen, T.; Cruikshank, D.; De Bergh, C.; Geballe, T.

1994-01-01

There are now a large number of small bodies in the outer solar system that are known to be covered with dark material. Attempts to identify that material have been thwarted by the absence of discrete absorption features in the reflection spectra of these planetesimals. An absorption at 2.2 micrometers that appeared to be present in several objects has not been confirmed by new observations. Three absorptions in the spectrum of the unusually red planetesimal 5145 Pholus are well-established, but their identity remains a mystery.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agnes, P.; et al.

The DarkSide-50 experiment, located at the “Laboratori Nazionali del Gran Sasso (INFN)”, is based on low-radioactivity argon double phase time projection chamber, surrounded by an active liquid scintillator veto, designed for the zero background achievement. The liquid argon features sufficient self shielding and easy scalability to multi-tons scale. The impressive reduction of the 39Ar isotope (compared to the atmospheric argon), along with the excellent pulse shape discrimination, make this technology a possible candidate for the forthcoming generation of multi-ton Dark Matter experiments.

Evolution of a Dark Anti-Cyclone on Saturn Associated with the Great Lightning Storm of 2010/2011 Through the Eyes of Cassini/VIMS

NASA Astrophysics Data System (ADS)

Momary, Thomas W.; Baines, K. H.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.; Sotin, C.

2012-10-01

A massive dark anti-cyclonic storm system on Saturn spanning some 7∘ of longitude and 2∘ of latitude was observed by Cassini/VIMS at a planetocentric latitude of 37∘ on 4 January 2012 and 26 January 2012. During this time, it drifted some 54∘ of longitude at a speed of 23.1 ± 0.2 m/s prograde, a drift speed which correlates well with the canonical Voyager (and VIMS) wind profiles for Saturn at this latitude. The spot also drifted northward during this time by 1∘ and became noticeably "squished" in morphology. Using this drift rate and extrapolating backward, we find that the position corresponds to the large (> 5,000 km) anti-cyclone observed by VIMS on 11 May 2011 at 35.4∘ latitude (pc) and 49.4∘ W. longitude. This would represent 8 months of observation of this titanic feature, which was associated with the major lightning storm of 2010-2011, following the spot as it changed in size and morphology and drifted northward. The spot underwent a dramatic shift in shape in the 3 weeks of January, changing from roughly oval to a highly elongated pancake shape as it apparently bumped up against the dark band at 40∘ latitude and experienced a powerful shear. The evolution suggests that we are watching the death throes of this feature in our most recent observations. Finally, the dark spot was darker than surrounding regions in May 2011 and maintained its dark color across all pseudo-continua from 1.0 to 4.0 μm between May 2011 and early January 2012.

Chiral-selective nonlinear optical generation and emission control with plasmonic metamaterials (Conference Presentation)

NASA Astrophysics Data System (ADS)

Cai, Wenshan

2016-09-01

Metamaterials can be designed to exhibit extraordinarily strong chiral responses. Here we present a chiral metamaterial that produces both distinguishable linear and nonlinear features in the visible to near-infrared range. In additional to the gigantic chiral effects in the linear regime, the metamaterial demonstrates a pronounced contrast between second harmonic responses from the two circular polarizations. Linear and nonlinear images probed with circularly polarized lights show strongly defined contrast. Moreover, the chiral centers of the nanometallic structures with enhanced hotspots can be purposely opened for direct access, where emitters occupying the light-confining regions produce chiral-selective enhancement of two-photon luminescence.

The multi-mode polarization modulation spectrometer: part 1: simultaneous detection of absorption, turbidity, and optical activity.

PubMed

Arvinte, Tudor; Bui, Tam T T; Dahab, Ali A; Demeule, Barthélemy; Drake, Alex F; Elhag, Dhia; King, Peter

2004-09-01

Circular dichroism (CD) is an important spectroscopic technique for monitoring chirality and biological macromolecule conformation. However, during a CD measurement, absorbance, light scattering/turbidity, and fluorescence can also be detected. The simultaneous measurement of these different spectral features for a single sample is the basis of a multi-mode optical spectrometer. This allows time-efficient gathering of complementary information and provides a scheme to ensure that CD measurements are reliable. Aspects of circular polarization differential light scattering, pH, and temperature variation of a protein (antibody) solution are described. A procedure to help ensure that CD measurements are reliable is described.

Detecting circular RNAs: bioinformatic and experimental challenges

PubMed Central

Szabo, Linda; Salzman, Julia

2017-01-01

The pervasive expression of circular RNAs (circRNAs) is a recently discovered feature of gene expression in highly diverged eukaryotes. Numerous algorithms that are used to detect genome-wide circRNA expression from RNA sequencing (RNA-seq) data have been developed in the past few years, but there is little overlap in their predictions and no clear gold-standard method to assess the accuracy of these algorithms. We review sources of experimental and bioinformatic biases that complicate the accurate discovery of circRNAs and discuss statistical approaches to address these biases. We conclude with a discussion of the current experimental progress on the topic. PMID:27739534

Sulfur "Bergs" and Sulfur Pools: Loki and Tupan Patera on Io

NASA Astrophysics Data System (ADS)

Howell, R. R.; Lopes, R. M.; Landis, C. E.; Allen, D. R.

2012-12-01

Loki and Tupan Patera on Io show numerous features related to the presence of volatiles. There are both striking similarities and distinct differences in the way the volatiles have acted at these two sites. At Loki numerous small bright features, colloquially known as sulfur "bergs", are distributed across the dark patera surface. We map their spatial distribution and spectral properties (Landis et al., this conference) and model sulfur vapor transport processes (Allen et al. this conference) to determine if those bright features are consistent with sulfur fumarole deposits. Alternatively, the "bergs" may represent topographic highs (kipukas) left un-resurfaced by the recurrent activity at Loki. To test this we examine Voyager, Galileo, and New Horizons images to determine if any changes in their spatial distribution have occurred over the 1979 through 2007 period. We also discuss further a statistical analysis of their size and spectral reflectance. Tupan shows an overall morphology similar to Loki, with a central island and one straight margin. It also shows linear features extending across the island. However instead of the dark eastern portion of the patera containing a myriad of small bright features like the Loki "bergs" which avoid the margins, Tupan shows higher albedo deposits concentrated at the margins. And in the higher albedo western portion of Tupan Patera numerous low albedo features can be interpreted as dark silicates erupting or eating through a volatile rich crust. Unlike Loki, these intra-patera features at Tupan clearly have sharply defined edges, indicating surface flow processes rather than possible vapor effects. However both outside the main Tupan Patera walls and on the island there are more diffuse patterns consistent with vapor transport. A detailed comparison of reflectance at violet through very near infrared wavelengths helps elucidate these effects. As also found at Loki, a low violet reflectance indicates that sulfur is abundant on many of the surfaces within the patera. That detailed comparison also helps highlight the vapor effects mentioned above. We discuss the insights into volatile processes gained from a detailed comparison of the Loki and Tupan images, and the implications those have for volcanism on Io.

Structural Concepts Study of Non-circular Fuselage Configurations

NASA Technical Reports Server (NTRS)

Mukhopadhyay, Vivel

1996-01-01

A preliminary study of structural concepts for noncircular fuselage configurations is presented. For an unconventional flying-wing type aircraft, in which the fuselage is inside the wing, multiple fuselage bays with non-circular sections need to be considered. In a conventional circular fuselage section, internal pressure is carried efficiently by a thin skin via hoop tension. If the section is non-circular, internal pressure loads also induce large bending stresses. The structure must also withstand additional bending and compression loads from aerodynamic and gravitational forces. Flat and vaulted shell structural configurations for such an unconventional, non-circular pressurized fuselage of a large flying-wing were studied. A deep honeycomb sandwich-shell and a ribbed double-wall shell construction were considered. Combinations of these structural concepts were analyzed using both analytical and simple finite element models of isolated sections for a comparative conceptual study. Weight, stress, and deflection results were compared to identify a suitable configuration for detailed analyses. The flat sandwich-shell concept was found preferable to the vaulted shell concept due to its superior buckling stiffness. Vaulted double-skin ribbed shell configurations were found to be superior due to their weight savings, load diffusion, and fail-safe features. The vaulted double-skin ribbed shell structure concept was also analyzed for an integrated wing-fuselage finite element model. Additional problem areas such as wing-fuselage junction and pressure-bearing spar were identified.

Rhodobacter capsulatus gains a competitive advantage from respiratory nitrate reduction during light-dark transitions.

PubMed

Ellington, M J K; Richardson, D J; Ferguson, S J

2003-04-01

Rhodobacter capsulatus N22DNAR(+) possesses a periplasmic nitrate reductase and is capable of reducing nitrate to nitrite under anaerobic conditions. In the absence of light this ability cannot support chemoheterotrophic growth in batch cultures. This study investigated the effect of nitrate reduction on the growth of R. capsulatus N22DNAR(+) during multiple light-dark cycles of anaerobic photoheterotrophic/dark chemoheterotrophic growth conditions in carbon-limited continuous cultures. The reduction of nitrate did not affect the photoheterotrophic growth yield of R. capsulatus N22DNAR(+). After a transition from photoheterotrophic to dark chemoheterotrophic growth conditions, the reduction of nitrate slowed the initial washout of a R. capsulatus N22DNAR(+) culture. Towards the end of a period of darkness nitrate-reducing cultures maintained higher viable cell counts than non-nitrate-reducing cultures. During light-dark cycling of a mixed culture, the strain able to reduce nitrate (N22DNAR(+)) outcompeted the strain which was unable to reduce nitrate (N22). The evidence indicates that the periplasmic nitrate reductase activity supports slow growth that retards the washout of a culture during anaerobic chemoheterotrophic conditions, and provides a protonmotive force for cell maintenance during the dark period before reillumination. This translates into a selective advantage during repeated light-dark cycles, such that in mixed culture N22DNAR(+) outcompetes N22. Exposure to light-dark cycles will be a common feature for R. capsulatus in its natural habitats, and this study shows that nitrate respiration may provide a selective advantage under such conditions.

Mapping all the mass in the universe (with weak gravitational lensing) - Oral Presentation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Everett, Spencer

Recent discoveries have shown that most of the universe is made of an exotic dark matter that behaves much differently than the normal matter that we experience in everyday life. As we cannot detect dark matter directly, we must infer its location in the universe by indirect effects, such as the distortion of light from distant galaxies as it travels through large clouds of dark matter. While the degree of distortion should be proportional to the amount of dark matter present, we don't know the original shape of the galaxy so the distortion is difficult to quantify. If we hadmore » a model of how dark matter is linked to galaxies, and thus be able predict the amount of distortion that should occur, we could apply the model to galaxy surveys to map out the dark matter in our universe. In this research, I attach a spherical 'halo' of dark matter to each galaxy in a simulated universe to approximate its known complex dark matter structure. I then predict how the halos distort the light from distant galaxies generated behind the halos. As the data is simulated, the true distortion of the light is known which is compared to the halo-predicted distortion. I find that, on average, the model under-predicts the degree of distortion on all scales and fails to capture distortions from large-scale dark matter structure. These issues are likely due to missing features in the model, as the halo model is a greatly simplified version of the actual distribution of dark matter. Potential improvements to the model for future work are discussed.« less

Iapetus Bright and Dark Terrains

NASA Technical Reports Server (NTRS)

1990-01-01

Saturn's outermost large moon, Iapetus, has a bright, heavily cratered icy terrain and a dark terrain, as shown in this Voyager 2 image taken on August 22, 1981. Amazingly, the dark material covers precisely the side of Iapetus that leads in the direction of orbital motion around Saturn (except for the poles), whereas the bright material occurs on the trailing hemisphere and at the poles. The bright terrain is made of dirty ice, and the dark terrain is surfaced by carbonaceous molecules, according to measurements made with Earth-based telescopes. Iapetus' dark hemisphere has been likened to tar or asphalt and is so dark that no details within this terrain were visible to Voyager 2. The bright icy hemisphere, likened to dirty snow, shows many large impact craters. The closest approach by Voyager 2 to Iapetus was a relatively distant 600,000 miles, so that our best images, such as this, have a resolution of about 12 miles. The dark material is made of organic substances, probably including poisonous cyano compounds such as frozen hydrogen cyanide polymers. Though we know a little about the dark terrain's chemical nature, we do not understand its origin. Two theories have been developed, but neither is fully satisfactory--(1) the dark material may be organic dust knocked off the small neighboring satellite Phoebe and 'painted' onto the leading side of Iapetus as the dust spirals toward Saturn and Iapetus hurtles through the tenuous dust cloud, or (2) the dark material may be made of icy-cold carbonaceous 'cryovolcanic' lavas that were erupted from Iapetus' interior and then blackened by solar radiation, charged particles, and cosmic rays. A determination of the actual cause, as well as discovery of any other geologic features smaller than 12 miles across, awaits the Cassini Saturn orbiter to arrive in 2004.

SPE analysis of high efficiency PMTs for the DEAP-3600 dark matter detector

NASA Astrophysics Data System (ADS)

Olsen, Kevin; Hallin, Aksel; DEAP/CLEAN Collaboration

2011-09-01

The Dark matter Experiment using Argon Pulse-shape discrimination is a collaborative effort to develop a next-generation, tonne-scale dark matter detector at SNOLAB. The detector will feature a single-phase liquid argon (LAr) target surrounded by an array of 266 photomultiplier tubes (PMTs). A new high-efficiency Hamamatsu R877-100 PMT has been delivered to the University of Alberta for evaluation by the DEAP collaboration. The increase in efficiency could lead to a much greater light yield, but other experiments have reported a slower rise time [1],[2]. We have placed the PMT in a small dark box and had a base and preamplifier designed to be used with either an oscilloscope or a multi-channel analyzer. With this setup we have demonstrated the PMT's ability to distinguish single photo-electrons (SPE) and characterized the PMT by measuring the SPE pulse height spectrum, the peak-to-valley ratio, the dark pulse rate, the baseline, time resolution and SPE efficiency for varying the high voltage supplied to the PMT.

Status and Prospects for Indirect Dark Matter Searches with the Fermi Large Area Telescope

NASA Astrophysics Data System (ADS)

Charles, Eric; Fermi-LAT Collaboration

2014-01-01

During the first five years of operation of the Fermi Large Area Telescope (LAT) the LAT collaboration has performed numerous searches for signatures of Dark Matter interactions in both gamma-ray and cosmic-ray data. These searches feature many different target types, including dwarf spheroidal galaxies, galaxy clusters, the Milky Way halo and inner Galaxy and unassociated LAT sources. They make use of a variety of techniques, and have been performed in both the spatial and spectral domains, as well as via less conventional strategies such as examining the potential Dark Matter contribution to both large scale and small scale anisotropies. To date no clear gamma-ray or cosmic-ray signal from dark matter annihilation or decay has been observed, and the deepest current limits for annihilation exclude many Dark Matter particle models with the canonical thermal relic cross section and masses up to 30 GeV. In this contribution we will briefly review the status of each of the searches by the LAT collaboration. We will also discuss the limiting factors for the various search strategies and examine the prospects for the future.

Mitigating direct detection bounds in non-minimal Higgs portal scalar dark matter models

NASA Astrophysics Data System (ADS)

Bhattacharya, Subhaditya; Ghosh, Purusottam; Maity, Tarak Nath; Ray, Tirtha Sankar

2017-10-01

The minimal Higgs portal dark matter model is increasingly in tension with recent results form direct detection experiments like LUX and XENON. In this paper we make a systematic study of simple extensions of the Z_2 stabilized singlet scalar Higgs portal scenario in terms of their prospects at direct detection experiments. We consider both enlarging the stabilizing symmetry to Z_3 and incorporating multipartite features in the dark sector. We demonstrate that in these non-minimal models the interplay of annihilation, co-annihilation and semi-annihilation processes considerably relax constraints from present and proposed direct detection experiments while simultaneously saturating observed dark matter relic density. We explore in particular the resonant semi-annihilation channel within the multipartite Z_3 framework which results in new unexplored regions of parameter space that would be difficult to constrain by direct detection experiments in the near future. The role of dark matter exchange processes within multi-component Z_3× Z_3^' } framework is illustrated. We make quantitative estimates to elucidate the role of various annihilation processes in the different allowed regions of parameter space within these models.

"Invisible" Galactic Halos.

ERIC Educational Resources Information Center

Lugt, Karel Vander

1993-01-01

Develops a simple core-halo model of a galaxy that exhibits the main features of observed rotation curves and quantitatively illustrates the need to postulate halos of dark matter. Uses only elementary mechanics. (Author/MVL)

Prospects for indirect dark matter searches with MeV photons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartels, Richard; Gaggero, Daniele; Weniger, Christoph, E-mail: r.t.bartels@uva.nl, E-mail: d.gaggero@uva.nl, E-mail: c.weniger@uva.nl

2017-05-01

Over the past decade, extensive studies have been undertaken to search for photon signals from dark matter annihilation or decay for dark matter particle masses above ∼1 GeV. However, due to the lacking sensitivity of current experiments at MeV–GeV energies, sometimes dubbed the 'MeV gap', dark matter models with MeV to sub-GeV particle masses have received little attention so far. Various proposed MeV missions (like, e.g., e-ASTROGAM or AMEGO) are aimed at closing this gap in the mid- or long-term future. This, and the absence of clear dark matter signals in the GeV–TeV range, makes it relevant to carefully reconsidermore » the expected experimental instrumental sensitivities in this mass range. The most common two-body annihilation channels for sub-GeV dark matter are to neutrinos, electrons, pions or directly to photons. Among these, only the electron channel has been extensively studied, and almost exclusively in the context of the 511 keV line. In this work, we study the prospects for detecting MeV dark matter annihilation in general in future MeV missions, using e-ASTROGAM as reference, and focusing on dark matter masses in the range 1 MeV–3 GeV. In the case of leptonic annihilation, we emphasise the importance of the often overlooked bremsstrahlung and in-flight annihilation spectral features, which in many cases provide the dominant gamma-ray signal in this regime.« less

Dark catalysis

NASA Astrophysics Data System (ADS)

Agrawal, Prateek; Cyr-Racine, Francis-Yan; Randall, Lisa; Scholtz, Jakub

2017-08-01

Recently it was shown that dark matter with mass of order the weak scale can be charged under a new long-range force, decoupled from the Standard Model, with only weak constraints from early Universe cosmology. Here we consider the implications of an additional charged particle C that is light enough to lead to significant dissipative dynamics on galactic times scales. We highlight several novel features of this model, which can be relevant even when the C particle constitutes only a small fraction of the number density (and energy density). We assume a small asymmetric abundance of the C particle whose charge is compensated by a heavy X particle so that the relic abundance of dark matter consists mostly of symmetric X and bar X, with a small asymmetric component made up of X and C. As the universe cools, it undergoes asymmetric recombination binding the free Cs into (XC) dark atoms efficiently. Even with a tiny asymmetric component, the presence of C particles catalyzes tight coupling between the heavy dark matter X and the dark photon plasma that can lead to a significant suppression of the matter power spectrum on small scales and lead to some of the strongest bounds on such dark matter theories. We find a viable parameter space where structure formation constraints are satisfied and significant dissipative dynamics can occur in galactic haloes but show a large region is excluded. Our model shows that subdominant components in the dark sector can dramatically affect structure formation.

Dark catalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agrawal, Prateek; Cyr-Racine, Francis-Yan; Randall, Lisa

Recently it was shown that dark matter with mass of order the weak scale can be charged under a new long-range force, decoupled from the Standard Model, with only weak constraints from early Universe cosmology. Here we consider the implications of an additional charged particle C that is light enough to lead to significant dissipative dynamics on galactic times scales. We highlight several novel features of this model, which can be relevant even when the C particle constitutes only a small fraction of the number density (and energy density). We assume a small asymmetric abundance of the C particle whosemore » charge is compensated by a heavy X particle so that the relic abundance of dark matter consists mostly of symmetric X and X-bar , with a small asymmetric component made up of X and C . As the universe cools, it undergoes asymmetric recombination binding the free C s into ( XC ) dark atoms efficiently. Even with a tiny asymmetric component, the presence of C particles catalyzes tight coupling between the heavy dark matter X and the dark photon plasma that can lead to a significant suppression of the matter power spectrum on small scales and lead to some of the strongest bounds on such dark matter theories. We find a viable parameter space where structure formation constraints are satisfied and significant dissipative dynamics can occur in galactic haloes but show a large region is excluded. Our model shows that subdominant components in the dark sector can dramatically affect structure formation.« less

Iron-absorption band analysis for the discrimination of iron-rich zones

NASA Technical Reports Server (NTRS)

Rowan, L. C. (Principal Investigator)

1973-01-01

The author has identified the following significant results. Study has concentrated on the two primary aspects of the project, structural analysis through evaluation of lineaments and circular features and spectral analyses through digital computer-processing techniques. Several previously unrecognized lineaments are mapped which may be the surface manifestations of major fault or fracture zones. Two of these, the Walker Lane and the Midas Trench lineament system, transect the predominantly NNE-NNW-trending moutain ranges for more than 500 km. Correlation of major lineaments with productive mining districts implies a genetic relationship, the 50 circular or elliptical features delineated suggest a related role for Tertiary volcanism. Color-ratio composites have been used to identify limonitic zones and to discriminate mafic and felsic rock by combing diazo color transparencies of three different ratios. EROS Data Center scene identification number for color composite in this report is ER 1 CC 500. Refinement of enhancement procedures for the ratio images is progressing. Fieldwork in coordination with both spectral and structural analyses is underway.

Universal ripper miner

DOEpatents

Morrell, Roger J.; Larson, David A.

1991-01-01

A universal ripper miner used to cut, collect and transfer material from an underground mine working face includes a cutter head that is vertically movable in an arcuate cutting cycle by means of drive members, such as hydraulically actuated pistons. The cutter head may support a circular cutter bit having a circular cutting edge that may be indexed to incrementally expose a fresh cutting edge. An automatic indexing system is disclosed wherein indexing occurs by means of a worm gear and indexing lever mechanism. The invention also contemplates a bi-directional bit holder enabling cutting to occur in both the upstroke and the downstroke cutting cycle. Another feature of the invention discloses multiple bits arranged in an in-line, radially staggered pattern, or a side-by-side pattern to increase the mining capacity in each cutting cycle. An on-board resharpening system is also disclosed for resharpening the cutting edge at the end of cutting stroke position. The aforementioned improvement features may be used either singly, or in any proposed combination with each other.

Exhuming Crater in Northeast Arabia

NASA Technical Reports Server (NTRS)

2003-01-01

MGS MOC Release No. MOC2-563, 3 December 2003

The upper crust of Mars is layered, and interbedded with these layers are old, filled and buried meteor impact craters. In a few places on Mars, such as Arabia Terra, erosion has re-exposed some of the filled and buried craters. This October 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example. The larger circular feature was once a meteor crater. It was filled with sediment, then buried beneath younger rocks. The smaller circular feature is a younger impact crater that formed in the surface above the rocks that buried the large crater. Later, erosion removed all of the material that covered the larger, buried crater, except in the location of the small crater. This pair of martian landforms is located near 17.6oN, 312.8oW. The image covers an area 3 km (1.9 mi) wide and is illuminated from the lower left.

Survival, growth and toxicity of Microcystis aeruginosa PCC 7806 in experimental conditions mimicking some features of the human gastro-intestinal environment.

PubMed

Stefanelli, Mara; Vichi, Susanna; Stipa, Giuseppe; Funari, Enzo; Testai, Emanuela; Scardala, Simona; Manganelli, Maura

2014-05-25

Cyanotoxins (CTX) are widely produced by several cyanobacteria (CB), increasingly spreading in most water bodies and terrestrial habitats, and represent a risk for human health. CB are prokaryotes, and although mostly autotrophic, several examples of heterotrophy in symbiotic relationship with different organisms have been described. In addition to the known routes of exposure, it has been hypothesized that CB might 'colonize' human intestine with relevant implications for human health. Colonization is a complex process and requires specific features of the possible invaders. Still, a short-term persistence as living and toxin-producing organisms within the intestinal lumen of the host could represent an 'internal' source of exposure to CTX. In this work we ran microcosm experiments (4-18days), looking at Microcystis aeruginosa PCC7806 resistance and cyanotoxin-producing capabilities in darkness, 37°C, pH 2, and subsequent recovery in a rich medium, in darkness, 37°C, in the presence of enteric bacteria, mimicking few important features of the gastrointestinal environment. We measured cyanobacterial populations and growth, microcystin (MC) production and the presence of mcyB gene. M. aeruginosa could grow in the dark at 37°C up to 17days, and survive at pH 2 at a rate between 30% and 70%, depending on the age and toxicity of the starting culture. Cell lysis resulted in a substantial amounts of MC released, not degraded at gastric pH. Following the acidic passage, still in the dark at 37°C, M. aeruginosa restarted to grow within 24h for the next 3-4days, independently on the presence of intestinal bacteria, maintaining the MC cell quota and mcyB gene. Our results show new features of CB: a significant resistance of M. aeruginosa in conditions far from its optimal one, that is an environment mimicking some of the important characteristics of human gastrointestinal tract, suggesting the possibility of an internal source of exposure to CTX, with implications for the risk assessment. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Structural, electrical and photovoltaic properties of CoS/Si heterojunction prepared by spray pyrolysis

NASA Astrophysics Data System (ADS)

El Radaf, I. M.; Nasr, Mahmoud; Mansour, A. M.

2018-01-01

Au/p-CoS/n-Si/Al heterojunction device was fabricated by spray pyrolysis technique. The structural and morphological features were examined by x-ray diffraction, scanning electron microscope and energy dispersive x-ray analysis. The capacitance-voltage characteristics of the prepared heterojunction were analyzed at room temperature in the dark. The current-voltage characteristics were examined under dark and different incident light intensities 20-100 mW cm-2. The rectification ratio, series resistance, shunt resistance, diode ideality factor and the effective barrier height were determined at dark and illumination conditions. The photovoltaic parameters such as short circuit current density, open circuit voltage, fill factor and power conversion efficiency were calculated at different incident light intensities.

Origin of Dark Material on VESTA from DAWN FC Data: Remnant Carbonaceous Chondrite Impators

NASA Technical Reports Server (NTRS)

Reddy, V.; LeCorre, L.; Nathues, A.; Mittlefehldt, David W.; Cloutis, E. A.; OBrien, D. P.; Durda, D. D.; Bottke, W. F.; Buczkowski, D.; Scully, J. E. C.;

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Jing; Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081; Yu, Hongwei, E-mail: hwyu@hunnu.edu.cn

We study the spontaneous excitation of a detector (modeled by a two-level atom) in circular motion coupled nonlinearly to vacuum massless Rarita–Schwinger fields in the ultrarelativistic limit and demonstrate that the spontaneous excitation occurs for ground-state atoms in circular motion in vacuum but the excitation rate is not of a pure thermal form as that of the atoms in linear uniform acceleration. An interesting feature is that terms of odd powers in acceleration appear in the excitation rate whereas in the linear acceleration case there are only terms of even powers present. On the other hand, what makes the presentmore » case unique in comparison to the atom’s coupling to other fields that are previously studied is the appearance of the terms proportional to the seventh and ninth powers of acceleration in the mean rate of change of atomic energy which are absent in the scalar, electromagnetic and Dirac field cases. -- Highlights: •Circular Unruh effect for detector coupled to Rarita–Schwinger field. •Nonlinear coupling between the detector and the fields. •Detector in circular motion does not feel pure thermal bath. •Excitation rate contains terms of odd powers in acceleration.« less