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Sample records for active south polar

  1. Present Day Activity of South Polar Gullies on Mars

    NASA Astrophysics Data System (ADS)

    Raack, J.; Reiss, D.; Ruesch, O.; Hiesinger, H.

    2012-04-01

    Here we report on clearly identified seasonal changes of gullies observed within the last two martian years (MY) on slopes of a south polar pit, which is located in a filled crater (diameter ~54 km) north of Sisyphi Cavi at ~68.5°S and ~1.5°E. Using new high-resolution imaging (High Resolution Imaging Science Experiment, HiRISE), temperature (Thermal Emission Spectrometer, TES) and spectral data (Compact Reconnaissance Imaging Spectrometer for Mars, CRISM; Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité, OMEGA), we analyzed the exact timing of changes of gullies and detect the possible medium (CO2, H2O or dry) and mechanism which initiate present day gully activity. Two locations in the study region with clear modifications of gullies were identified in MY 29 between LS 226° and LS 247° and between LS 209° and LS 247°. In MY 30 changes occur in both locations between LS 218° and LS 249°. Modifications are the formation of a new small apron and new deposits within the channel, both associated with the deposition of dark material. Erosion in gully alcoves or channels was not observed. TES data show temperatures between ~180 and ~240 K within the period of gully modifications. Maximum temperatures in the region rise up to ~285 K between LS ~270° and ~310°. Spectral data show a CO2-cover of the study region until LS 227°. CO2-ice free surface are spectrally observed for the first time at LS 249°. H2O was not spectrally detected in the study region and a mixture of CO2 and H2O as presented in [1] cannot be clearly detected. Unfortunately, there are no spectral data available between LS 227° and 249°. Modifications of gullies imply seasonal volatile activity. The activity can be narrowed down to occur between LS 226° and 247° at mean temperatures between ~180 and ~240 K. This is in the range of temperatures where CO2 sublimates back into the atmosphere. Based on the temperature range, the most likely candidate for the observed new

  2. Seasonal Activity of Gullies in South Polar Pits

    NASA Astrophysics Data System (ADS)

    Raack, Jan; Reiss, Dennis; Vincendon, Mathieu; Ruesch, Ottaviano; Appéré, Thomas; Hiesinger, Harald

    2013-04-01

    Seasonal activity of gullies under current climatic conditions on Mars was observed by [1-6]. These observations were made on mountain and/or crater slopes [2-4], on dune slopes at mid-latitudes [2,5,6], and on slopes of polar pits [1,2]. The suggested mechanisms to form new gully deposits are melting of H2O ice [3,5] or sublimation/removal of CO2 ice [2,4,6]. With high-resolution imaging, temperature, and spectral data we analyzed gully changes in a polar pit north of Sisyphi Cavi at ~68.5°S and ~1.5°E. One investigated gully shows dark material within the channel in martian years (MY) 28, 29, and 30. The dark material results to the formation of new dark deposits (dark flow-like features) at LS ~223° in MY 28, between LS 209° and 226° (beginning of spring) in MY 29, and between LS 218° and LS 249° in MY 30. We observed a new deposition of material at the channel termini, which shortens the channel by about 40 m in MY 29. Maximum surface temperature data of the area indicate that temperatures in autumn and winter are ~150 K. In mid-spring (between LS ~220° and ~250°) temperatures increase rapidly up to ~270 K due to solar insolation and ice sublimation. To better understand the temporal evolution of H2O and CO2, we processed near infrared spectral data and analyzed the strengths of absorption bands caused by these volatiles (ices). These investigations show that CO2 and H2O ices sublimate between LS ~225° and ~240°. This is also the time range when temperatures rise rapidly and when gully changes occurred. More detailed analyses show that the spectral signatures of ice are generally lower on the dark flow features within the gully channel / above the gully apron compared to the surrounding terrain. Our investigations either imply 1) a generally lower value of volatiles within gully channels due to non uniform volatile deposition on the slope, 2) a faster sublimation of volatiles within gully channels, or 3) deposition of debris above ice from the

  3. Mercury's South Polar Region

    NASA Video Gallery

    This animation shows 89 wide-angle camera (WAC) images of Mercury’s south polar region acquired by the Mercury Dual Imaging System (MDIS) over one complete Mercury solar day (176 Earth days). Thi...

  4. South Polar Scarps

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-438, 31 July 2003

    The terrain of the south polar residual ice cap, made up mostly of frozen carbon dioxide, has come to be known by many as 'swiss cheese terrain,' because many areas of the cap resemble slices of swiss cheese. However, not all of the south polar cap looks like a tasty lunch food. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a series of curving scarps formed by erosion and sublimation of carbon dioxide from the south polar cap. This area is located near 86.3oS, 51.2oW. The image is illuminated by sunlight from the upper left; the area is about 1.5 km (0.9 mi) wide.

  5. South Polar Variety

    NASA Technical Reports Server (NTRS)

    2005-01-01

    28 July 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a view of linear troughs and mesas formed in the frozen carbon dioxide of the martian south polar residual cap. This image, obtained in May 2005, is a reminder that not all of the south polar cap landscapes resemble 'swiss cheese.'

    Location near: 86.7oS, 24.8oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  6. South Polar Layers

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-516, 17 October 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows eroded, stair-stepped layers in the south polar region of Mars. These layers have been considered, for the past three decades, to consist of a mixture of dust and ice. The Mars Polar Lander (MPL) mission was designed to test this hypothesis. However, sadly, MPL was lost during descent in December 1999. This exposure of south polar layered material is located near 86.3oS, 187.7oW. The image covers an area 3 km (1.9 mi) wide and is illuminated by sunlight from the upper left.

  7. South Polar Details

    NASA Technical Reports Server (NTRS)

    2005-01-01

    22 September 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows details among some of the eroded layer outcrops of the martian south polar region. Much of the south polar region of Mars is covered by a thick unit of layered material. For decades, the layers have been assumed to consist of a mixture of dust and ice, but it is equally possible that the materials are sedimentary rocks. This image was captured during southern spring, at a time when some of the surface was still covered by seasonal carbon dioxide (CO2) frost.

    Location near: 86.5oS, 116.6oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  8. South Polar Polygons

    NASA Technical Reports Server (NTRS)

    2005-01-01

    4 July 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a polgyon-cracked surface, into which deep, somewhat kidney-bean-shaped pits have formed. These are landscapes of the martian south polar residual cap. This view was captured during May 2005.

    Location near: 86.9oS, 5.1oW Image width: 1.5 km (0.9 mi) Illumination from: upper left Season Southern Spring

  9. South Polar Scene

    NASA Technical Reports Server (NTRS)

    2004-01-01

    5 February 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of the south polar residual cap. Sunlight illuminates this scene from the upper left, thus the somewhat kidney bean-shaped features are pits, not mounds. These pits and their neighboring polygonal cracks are formed in a material composed mostly of carbon dioxide ice. The image is located near 87.0oS, 5.7oW, and covers an area 3 km (1.9 mi) wide.

  10. South Polar Erosion

    NASA Technical Reports Server (NTRS)

    2004-01-01

    24 June 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the results of erosion acting upon a layer of material in the south polar region of Mars. The elliptical pit in the lower left corner of the image was once buried beneath this eroding layer, as well. The processes that eroded the material, and the composition of the material, are unknown. The image is located near 80.7oS, 300.9oW, and covers an area about 3 km (1.9 mi) wide. Sunlight illuminates this scene from the top.

  11. 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

  12. South Polar 'Poodle'

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-422, 15 July 2003

    Have you ever stared up at the clouds in the sky and seen the shapes of animals, people, or objects? Sometimes when the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) team is looking at newly-returned pictures from Mars, the same thing happens. This is a picture of pits and scarps in the frozen south polar carbon dioxide ice cap. Sunlight illuminates the scene from the upper right. At the bottom of the picture is a feature that resembles a long, thin poodle; its head faces to the left, the tail to the right. This picture is located near 86.9oS, 55.8oW.

  13. South Polar Ice Cap

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-337, 21 April 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the 'swiss cheese' pattern of frozen carbon dioxide on the south polar residual cap. Observation of these materials over two Mars years has revealed that the scarps that bound the mesas and small buttes are retreating-the carbon dioxide ice is subliming away-at a rate of about 3 meters (3 yards) per Mars year in some places. The picture covers an area about 900 m (about 900 yards) wide near 87.1oS, 93.7oW. Sunlight illuminates the scene from the upper left.

  14. South Polar Landforms

    NASA Technical Reports Server (NTRS)

    2006-01-01

    8 February 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an area adjacent to the south polar residual cap that hosts several intricate fracture networks. Each network consists of multiple fractures radiating from a central location. Their origin is not understood -- some investigators have speculated that these are sites of release of carbon dioxide from beneath the ground, but this explanation seems inadequate to explain all attributes of the features. MOC images have shown that these features have not been changing from year to year during the course of the MGS mission.

    Location near: 87.1oS, 234.1oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  15. South Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released 28 May 2004 This image was collected February 29, 2004 during the end of southern summer season. The local time at the location of the image was about 2 pm. The image shows an area in the South Polar region.

    The THEMIS VIS camera is capable of capturing color images of the martian surface using its five different color filters. In this mode of operation, the spatial resolution and coverage of the image must be reduced to accommodate the additional data volume produced from the use of multiple filters. To make a color image, three of the five filter images (each in grayscale) are selected. Each is contrast enhanced and then converted to a red, green, or blue intensity image. These three images are then combined to produce a full color, single image. Because the THEMIS color filters don't span the full range of colors seen by the human eye, a color THEMIS image does not represent true color. Also, because each single-filter image is contrast enhanced before inclusion in the three-color image, the apparent color variation of the scene is exaggerated. Nevertheless, the color variation that does appear is representative of some change in color, however subtle, in the actual scene. Note that the long edges of THEMIS color images typically contain color artifacts that do not represent surface variation.

    Image information: VIS instrument. Latitude -84.7, Longitude 9.3 East (350.7 West). 38 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet

  16. Present-Day Seasonal Gully Activity in a South Polar Pit (Sisyphi Cavi) on Mars

    NASA Astrophysics Data System (ADS)

    Raack, Jan; Reiss, Dennis; Appéré, Thomas; Vincendon, Mathieu; Ruesch, Ottaviano; Hiesinger, Harald

    2014-05-01

    Seasonal activity of gullies under current climatic conditions on Mars was observed by [1-7]. Dundas et al. [2] reviewed the present-day activity of classical gullies (including the gully presented in this work), dune gullies, and other mass wasting processes in the southern hemisphere on Mars. Recent polar gullies in Sisyphi Cavi were also analyzed by [8], who estimated ages of about 20 ka to 20 Ma for the gullies. In this study we focus on a single gully in Sisyphi Cavi, located in the south polar region at 1.44° E and 68.54° S. The gully occurs on the gullied equator-facing slope of an isolated polar pit within an infilled impact crater. Multi-temporal high-resolution image data analyses show new deposits at the terminus of the gully channel and on the gully apron within spring (after solar longitudes of 236°) of martian years (MY) 29 and 31. In MY 29 deposition of material shortens the channel by about 40 m; in MY 31 a new deposit at the western flank of the gully apron with approximately 300-600 m3 of material is visible [3]. Our morphological investigations show that the identified new deposits were formed by dark flows through the entire gully deposited on top of the apron between LS ~218° and ~226°. Thermal data show a temperature increase between solar longitudes (LS) ~218° and ~226°. Near-infrared spectral data show relatively constant band strengths of CO2 ice and H2O ice in this time range. After the formation of the dark flows (after LS ~226°), temperatures increase rapidly from ~180 K to >~270 K at LS ~250°. At this time, spectral data indicate that all volatiles on the surface sublimated. However, an earlier beginning of sublimation when the dark flows were observed (between LS ~218° and ~226°) is likely, due to the fact that the instruments can only show the last phase of sublimation (decrease of volatile band strengths) [3]. Spectral modeling shows that from winter to mid-spring, the surface of the studied area is covered by CO2 slab

  17. South Polar Cap, Summer 2000

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This is the south polar cap of Mars as it appeared to the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) on April 17, 2000. In winter and early spring, this entire scene would be covered by frost. In summer, the cap shrinks to its minimum size, as shown here. Even though it is summer, observations made by the Viking orbiters in the 1970s showed that the south polar cap remains cold enough that the polar frost (seen here as white) consists of carbon dioxide. Carbon dioxide freezes at temperatures around -125o C (-193o F). Mid-summer afternoon sunlight illuminates this scene from the upper left from about 11.2o above the horizon. Soon the cap will experience sunsets; by June 2000, this pole will be in autumn, and the area covered by frost will begin to grow. Winter will return to the south polar region in December 2000. The polar cap from left to right is about 420 km (260 mi) across.

  18. Textures in south polar ice cap #2

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Textures of the south polar permanent residual ice cap and polar layered terrains. This 15 x 14 km area image (frame 7306) is centered near 87 degrees south, 341 degrees west.

    Figure caption from Science Magazine

  19. Textures in south polar ice cap #1

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Textures of the south polar permanent residual ice cap and polar layered terrains. This 30 x 29 km area image (frame 7709) is centered near 87 degrees south, 77 degrees west.

    Figure caption from Science Magazine

  20. More South Polar 'Swiss Cheese'

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This image is illuminated by sunlight from the upper left.

    Some of the surface of the residual south polar cap has a pattern that resembles that of sliced, swiss cheese. Shown here at the very start of southern spring is a frost-covered surface in which there are two layers evident--a brighter upper layer into which are set swiss cheese-like holes, and a darker, lower layer that lies beneath the 'swiss cheese' pattern. Nothing like this exists anywhere on Mars except within the south polar cap.

    This is a Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image acquired on August 2,1999. It is located near 84.8oS, 71.8oW, and covers an area 3 km across and about 6.1 km long (1.9 by 3.8 miles).

    Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  1. Semi-automatic measures of activity in selected south polar regions of Mars using morphological image analysis

    NASA Astrophysics Data System (ADS)

    Aye, Klaus-Michael; Portyankina, Ganna; Pommerol, Antoine; Thomas, Nicolas

    The High Resolution Imaging Science Experiment (HiRISE) onboard Mars Reconnaissance Orbiter (MRO) has been used to monitor the seasonal evolution of several regions at high southern latitudes. Of particular interest have been jet-like activities that may result from the process described by Kieffer (2007), involving translucent CO2 ice. These jets are assumed to create fan-shaped ground features, as studied e.g. in Hansen et.al. (2010) and Portyankina et.al. (2010). In Thomas et.al. (2009), a small region of interest (ROI) inside the south polar Inca City region (81° S, 296° E) was defined for which the seasonal change of the number of fans was determined. This ROI was chosen for its strong visual variability in ground features. The mostly manual counting work showed, that the number of apparent fans increases monotonously for a considerable amount of time from the beginning of the spring time observations at Ls of 178° until approx. 230° , following the increase of available solar energy for the aforementioned processes of the Kieffer model. This fact indicates that the number of visual fan features can be used as an activity measure for the seasonal evolution of this area, in addition to commonly used evolution studies of surface reflectance. Motivated by these results, we would like to determine the fan count evolution for more south polar areas like Ithaca, Manhattan, Giza and others. To increase the reproducibility of the results by avoiding potential variability in fan shape recognition by human eye and to increase the production efficiency, efforts are being undertaken to automise the fan counting procedure. The techniques used, cleanly separated in different stages of the procedure, the difficulties for each stage and an overview of the tools used at each step will be presented. After showing a proof of concept in Aye et.al. (2010), for a ROI that is comparable to the one previously used for manual counting in Thomas et.al. (2009), we now will show

  2. Titan's South Polar Vortex in Motion

    NASA Video Gallery

    This movie captured by NASA'S Cassini spacecraft shows a south polar vortex, or a swirling mass of gas around the pole in the atmosphere, at Saturn’s moon Titan. The swirling mass appears to exec...

  3. High-Resolution South Polar Cap Mosaics

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The layered terrains of the polar regions of Mars are among the most exotic planetary landscapes in our Solar System. The layers exposed in the south polar residual cap, vividly shown in the top view, are thought to contain detailed records of Mars' climate history over the last 100 million years or so. The materials that comprise the south polar layers may include frozen carbon dioxide, water ice, and fine dust. The bottom picture shows complex erosional patterns that have developed on the south polar cap, perhaps by a combination of sublimation, wind erosion, and ground-collapse. Because the south polar terrains are so strange and new to human eyes, no one (yet) has entirely adequate explanations as to what is being seen.

    These images were acquired by the Mars Orbiter Camera aboard the Mars Global Surveyor spacecraft during the southern spring season in October 1999. Each of these two pictures is a mosaic of many individual MOC images acquired at about 12 m/pixel scale that completely cover the highest latitude (87oS) visible to MOC on each orbital pass over the polar region. Both mosaics cover areas of about 10 x 4 kilometers (6.2 x 2.5 miles) near 87oS, 10oW in the central region of the permanent--or residual--south polar cap. They show features at the scale of a small house. Sunlight illuminates each scene from the left.'Gaps' at the upper and lower right of the second mosaic, above, are areas that were not covered by MOC in October 1999.

  4. South Pol: Revealing the polarized southern sky

    NASA Astrophysics Data System (ADS)

    Magalha~es, A. M.; de Oliveira, C. M.; Carciofi, A.; Costa, R.; Dal Pino, E. M. G.; Diaz, M.; Ferrari, T.; Fernandez, C.; Gomes, A. L.; Marrara, L.; Pereyrac, A.; Ribeiro, N. L.; Rodrigues, C. V.; Rubinho, M. S.; Seriacopi, D. B.; Taylor, K.

    2012-05-01

    SOUTH POL will be a survey of the Southern sky in optical polarized light. It will use a newly designed polarimetric module at an 80cm Robotic Telescope. Telescope and polarimeter will be installed at CTIO, Chile, in late 2012. The initial goal is to cover the sky south of declination -15° in two years of observing time, aiming at a polarimetric accuracy <~ 0.1% down to V=15, with a camera covering a field of about 2.0 square degrees. SOUTH POL will impact areas such as Cosmology, Extragalactic Astronomy, Interstellar Medium of the Galaxy and Magellanic Clouds, Star Formation, Stellar Envelopes, Stellar explosions and Solar System, among others.

  5. Active polarization descattering.

    PubMed

    Treibitz, Tali; Schechner, Yoav Y

    2009-03-01

    Vision in scattering media is important but challenging. Images suffer from poor visibility due to backscattering and attenuation. Most prior methods for scene recovery use active illumination scanners (structured and gated), which can be slow and cumbersome, while natural illumination is inapplicable to dark environments. The current paper addresses the need for a non-scanning recovery method, that uses active scene irradiance. We study the formation of images under widefield artificial illumination. Based on the formation model, the paper presents an approach for recovering the object signal. It also yields rough information about the 3D scene structure. The approach can work with compact, simple hardware, having active widefield, polychromatic polarized illumination. The camera is fitted with a polarization analyzer. Two frames of the scene are taken, with different states of the analyzer or polarizer. A recovery algorithm follows the acquisition. It allows both the backscatter and the object reflection to be partially polarized. It thus unifies and generalizes prior polarization-based methods, which had assumed exclusive polarization of either of these components. The approach is limited to an effective range, due to image noise and illumination falloff. Thus, the limits and noise sensitivity are analyzed. We demonstrate the approach in underwater field experiments. PMID:19147870

  6. South Polar Projection of Earth

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This view of the Earth shows a wonderfully unique but physically impossible view of the southern hemisphere and Antarctica. While a spacecraft could find itself directly over the Earth's pole, roughly half of the image should be in darkness! This view was created by mosaicing together several images taken by Galileo over a 24 hour period and projecting them as they would be seen from above the pole. The continents of South America, Africa, and Australia are respectively seen at the middle left, upper right, and lower right. The slightly bluish ice and snow of Antarctica include large ice shelves (upper left, lower middle), a broad fan of broken offshore pack ice (lower left and middle) and continental glaciers protruding into the sea (lower right). The regularly spaced weather systems are prominent.

    Most spacecraft traveling near the Earth's poles are in very low Earth orbit, and cannot acquire panoramic shots like this one. Galileo's view of the southern hemisphere, combined with the spacecraft's special spectral properties (four separate narrowband filters that measure the brightness of reflected light at specific infrared wavelengths), led to a number of unique observations. For example, Galileo's cameras distinguished between ice and high stratospheric clouds, allowing scientists to study the correlation between these clouds and growth of the ozone hole.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA'is Office of Space Science, Washington, DC.

    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://galileo.jpl.nasa.gov.

  7. Four Mars Years of South Polar Changes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] View in 1999View in 2001View in 2003View in 2005

    One of the most profound discoveries that would not have been possible if NASA's Mars Global Surveyor mission had not been extended beyond its primary mission of one Mars year (687 Earth days) is that of dramatic changes that take place in the south polar residual ice cap each martian year. To make this discovery, the Mars Orbiter Camera on the spacecraft had to be employed during a second Mars year to repeat images of sites on the south polar cap that had been imaged during the primary mission.

    The initial discovery was made in 2001, when the camera team repeated images of portions of the south polar cap that had already been imaged in 1999. The goal of these images was to obtain stereo views, which would allow investigators to see the topography of the cap in three dimensions and to measure the thickness of the polar ice layers.

    It was not possible to produce the desired 3-D views. To the team's surprise, the landforms of the south polar cap had changed.

    The south polar residual cap -- that is, the portion of the ice cap that remains bright and retains ice throughout the southern summer season -- was seen in 1997 and 1999 images to have a complex terrain of broad, relatively flat mesas, small buttes, and many pits and troughs. Pits are generally circular and in some areas visually resemble a stack of thin slices of Swiss cheese. Very early in the Mars Global Surveyor mission, the Mars Orbiter Camera team speculated that these landforms must be carved into frozen carbon dioxide, because they look so unfamiliar and because Viking orbiter infrared measurements indicated that the south polar cap is cold enough consist of frozen carbon dioxide, even in summer.

    The observations made by Mars Orbiter Camera in 2001, during the first part of the extended mission, showed that the scarps and pit walls of

  8. South Polar Cap Erosion and Aprons

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This scene is illuminated by sunlight from the upper left.

    While Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images have shown that the north and south polar cap surfaces are very different from each other, one thing that the two have in common is that they both seem to have been eroded. Erosion in the north appears mostly to come in the form of pits from which ice probably sublimed to vapor and was transported away from the polar cap by wind. Erosion in the south takes on a wider range of possible processes that include collapse, slumping and mass-movement on slopes, and probably sublimation. Among the landforms created by these process on the south polar cap are the 'aprons' that surround mesas and buttes of remnant layers such as the two almost triangular features in the lower quarter of this image. The upper slopes of the two triangular features show a stair-stepped pattern that suggest these hills are layered.

    This image shows part of the south polar residual cap near 86.9oS, 78.5oW, and covers an area approximately 1.2 by 1.0 kilometers (0.7 x 0.6 miles) in size. The image has a resolution of 2.2 meters per pixel. The picture was taken on September 11, 1999.

    Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  9. Mars South Polar Cap 'Fingerprint' Terrain

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This picture is illuminated by sunlight from the upper left.

    Some portions of the martian south polar residual cap have long, somewhat curved troughs instead of circular pits. These appear to form in a layer of material that may be different than that in which 'swiss cheese' circles and pits form, and none of these features has any analog in the north polar cap or elsewhere on Mars. This picture shows the 'fingerprint' terrain as a series of long, narrow depressions considered to have formed by collapse and widening by sublimation of ice. Unlike the north polar cap, the south polar region stays cold enough in summer to retain frozen carbon dioxide. Viking Orbiter observations during the late 1970s showed that very little water vapor comes off the south polar cap during summer, indicating that any frozen water that might be there remains solid throughout the year.

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image was obtained in early southern spring on August 4, 1999. It shows an area 3 x 5 kilometers (1.9 x 3.1 miles) at a resolution of about 7.3 meters (24 ft) per pixel. Located near 86.0oS, 53.9oW.

    Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  10. SOUTH POL: Revealing the Polarized Southern Sky

    NASA Astrophysics Data System (ADS)

    Magalhães, A. M.

    2014-10-01

    SOUTH POL will be a survey of the Southern sky in optical polarized light. It will use a newly designed polarimeter for an 80cm Robotic Telescope. Telescope and polarimeter will be installed at CTIO, Chile. The initial goal is to cover the sky south of declination -15° in about two years of observing time, aiming at a polarimetric accuracy ≤ 0.1% down to V=15, with a camera covering a field of about 2.0 square degrees. SOUTH POL will impact areas such as Cosmology, Extragalactic Astronomy, Interstellar Medium of the Galaxy and Magellanic Clouds, Star Formation, Stellar Envelopes, Stellar Explosions and Solar System, among others. The polarimeter is currently being built and its optics and electronics assembled. We will describe the current status of the project. This project is supported by FAPESP. AMM is also supported by CNPq.

  11. Interannual variability of Mars' south polar CAP

    NASA Astrophysics Data System (ADS)

    James, P. B.; Malolepszy, K. M.; Martin, L. J.

    1987-08-01

    Published observational data on the seasonal recession of the south polar cap on Mars (covering the period 1903-1977) are compiled in tables and graphs and analyzed statistically. The basic data set (photographic observations obtained at Lowell Observatory) of Fischbacher et al. (1960) and James and Lumme (1982) and the reduction procedures described by Baum and Martin (1973) are employed, and Viking data from 1977 are used for comparison; the early onset (relative to the mean) of the 1956 recession is characterized in detail. A list of photographically documented large dust storms is provided, and it is suggested that in years with early spring storms, recession may be slower than in years without such storms.

  12. Density of Mars' south polar layered deposits.

    PubMed

    Zuber, Maria T; Phillips, Roger J; Andrews-Hanna, Jeffrey C; Asmar, Sami W; Konopliv, Alexander S; Lemoine, Frank G; Plaut, Jeffrey J; Smith, David E; Smrekar, Suzanne E

    2007-09-21

    Both poles of Mars are hidden beneath caps of layered ice. We calculated the density of the south polar layered deposits by combining the gravity field obtained from initial results of radio tracking of the Mars Reconnaissance Orbiter with existing surface topography from the Mars Orbiter Laser Altimeter on the Mars Global Surveyor spacecraft and basal topography from the Mars Advanced Radar for Subsurface and Ionospheric Sounding on the Mars Express spacecraft. The results indicate a best-fit density of 1220 kilograms per cubic meter, which is consistent with water ice that has approximately 15% admixed dust. The results demonstrate that the deposits are probably composed of relatively clean water ice and also refine the martian surface-water inventory. PMID:17885129

  13. South Polar Cryptic Terrain in Early Spring

    NASA Technical Reports Server (NTRS)

    2007-01-01

    This image of the south polar region of Mars was taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) at 1557 UTC (10:57 a.m. EST) on Feb. 10, 2007, near 77.55 degrees south latitude, 131.98 degrees east longitude. CRISM's image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 30 meters (98 feet) across. The region covered is just over 9 kilometers (5.6 miles) wide at its narrowest point, and is one of several in which CRISM is monitoring the evaporation (or 'sublimation') of the seasonal frost cap.

    The Martian south polar seasonal cap consists of carbon dioxide ice and frost, whose sublimation in the Martian spring creates a variety of features unlike anything in Earth's circumpolar regions. Part of the cap known as the 'cryptic region' is so cold that it must be covered with carbon dioxide frost, but it is also unexpectedly low in brightness and exhibits a variety of unusual dark blotches. Many scientists believe that carbon dioxide gas trapped below the sublimating ice is released in bursts, which carry along dust that gradually darkens the ice. One idea is that geyser-like dust eruptions form the dark blotches, and that the blotches grow, coalesce, and eventually hide the frost under a thin layer of dust.

    This image was taken shortly after sunrise with the Sun only about five degrees above the horizon. The left version shows brightness of the surface at 1.3 micrometers. The right version shows strength of an absorption band due to carbon dioxide frost at 1.435 micrometers; brighter areas have a stronger absorption and more carbon dioxide frost. However, even the darkest areas still have frost. The correlation between brightness and carbon dioxide frost abundance is striking, supporting the idea that the frost is being darkened by dust. Frost in the upper right corner shows the expected dark blotches, whereas the frost over the rest of the image is more uniformly dark, hinting that another

  14. Curtain eruptions from Enceladus' south-polar terrain.

    PubMed

    Spitale, Joseph N; Hurford, Terry A; Rhoden, Alyssa R; Berkson, Emily E; Platts, Symeon S

    2015-05-01

    Observations of the south pole of the Saturnian moon Enceladus revealed large rifts in the south-polar terrain, informally called 'tiger stripes', named Alexandria, Baghdad, Cairo and Damascus Sulci. These fractures have been shown to be the sources of the observed jets of water vapour and icy particles and to exhibit higher temperatures than the surrounding terrain. Subsequent observations have focused on obtaining close-up imaging of this region to better characterize these emissions. Recent work examined those newer data sets and used triangulation of discrete jets to produce maps of jetting activity at various times. Here we show that much of the eruptive activity can be explained by broad, curtain-like eruptions. Optical illusions in the curtain eruptions resulting from a combination of viewing direction and local fracture geometry produce image features that were probably misinterpreted previously as discrete jets. We present maps of the total emission along the fractures, rather than just the jet-like component, for five times during an approximately one-year period in 2009 and 2010. An accurate picture of the style, timing and spatial distribution of the south-polar eruptions is crucial to evaluating theories for the mechanism controlling the eruptions. PMID:25951283

  15. Surface Texture Analysis of Enceladus' South Polar Region

    NASA Astrophysics Data System (ADS)

    Chang, J. P.; Buratti, B. J.; Hicks, M.; Mosher, J.; Landry, B.

    2009-12-01

    The Cassini spacecraft's discovery of active plumes at the south pole of Enceladus on its July 2006 flyby has sparked greater interest in both its internal and external physical and chemical properties. We choose to investigate the macroscopic surface texture of this active south polar region by implementing a surface roughness model developed by Buratti and Veverka (1985). The model requires intensity scans of Enceladus's surface and two unknown parameters: a scattering parameter A that indicates whether single or diffuse scattering is occurring, and a surface phase function f (α) that reflects changes in intensity due to various factors such as the single scattering albedo and the single particle phase function. The output is a quantitative description of surface roughness through a depth-to-radius ratio q. After fitting the model to the data, we find that plains north of the “tiger stripes” are fairly smooth, with preliminary values for q of around 0.08. Meanwhile, the stripes themselves are only slightly more rough, with preliminary values for q of around 0.10. These results strongly suggest in-filled coating of craters with water-ice throughout the entire south polar region of Enceladus. Furthermore, the model surface roughness of Enceladus does not appear to be sensitive to the choice of our photometric function, as changing A has little effect on q.

  16. Curtain eruptions from Enceladus' south-polar terrain

    NASA Astrophysics Data System (ADS)

    Spitale, Joseph N.; Hurford, Terry A.; Rhoden, Alyssa R.; Berkson, Emily E.; Platts, Symeon S.

    2015-05-01

    Observations of the south pole of the Saturnian moon Enceladus revealed large rifts in the south-polar terrain, informally called `tiger stripes', named Alexandria, Baghdad, Cairo and Damascus Sulci. These fractures have been shown to be the sources of the observed jets of water vapour and icy particles and to exhibit higher temperatures than the surrounding terrain. Subsequent observations have focused on obtaining close-up imaging of this region to better characterize these emissions. Recent work examined those newer data sets and used triangulation of discrete jets to produce maps of jetting activity at various times. Here we show that much of the eruptive activity can be explained by broad, curtain-like eruptions. Optical illusions in the curtain eruptions resulting from a combination of viewing direction and local fracture geometry produce image features that were probably misinterpreted previously as discrete jets. We present maps of the total emission along the fractures, rather than just the jet-like component, for five times during an approximately one-year period in 2009 and 2010. An accurate picture of the style, timing and spatial distribution of the south-polar eruptions is crucial to evaluating theories for the mechanism controlling the eruptions.

  17. A clathrate reservoir hypothesis for Enceladus' south polar plume.

    PubMed

    Kieffer, Susan W; Lu, Xinli; Bethke, Craig M; Spencer, John R; Marshak, Stephen; Navrotsky, Alexandra

    2006-12-15

    We hypothesize that active tectonic processes in the south polar terrain of Enceladus, the 500-kilometer-diameter moon of Saturn, are creating fractures that cause degassing of a clathrate reservoir to produce the plume documented by the instruments on the Cassini spacecraft. Advection of gas and ice transports energy, supplied at depth as latent heat of clathrate decomposition, to shallower levels, where it reappears as latent heat of condensation of ice. The plume itself, which has a discharge rate comparable to Old Faithful Geyser in Yellowstone National Park, probably represents small leaks from this massive advective system. PMID:17170301

  18. Photometric Properties of Enceladus' South Polar Terrain

    NASA Astrophysics Data System (ADS)

    Annex, Andrew; Verbiscer, A. J.; Helfenstein, P.

    2012-10-01

    Cassini images reveal in exquisite detail the complex and varied terrains within the geologically active south pole of Enceladus. The region is dominated by four parallel rifts or sulci, informally known as tiger stripes, from which plumes comprised primarily of water vapor erupt [1,2]. The rich data set of Cassini images acquired at high spatial resolution (< 0.5 km/pixel) and a variety of viewing and illumination geometries enables the quantitative analysis of surface scattering properties through disk-resolved photometry. Here we investigate the photometric properties of individual terrain units [3] through fits of the Hapke photometric model [4] to data acquired in the clear (CL1 CL2), UV3, GRN, and IR3 filters, centered at 0.61, 0.34, 0.57, and 0.93 μm, respectively. Terrain units include the tiger stripe smooth and platy plank formations, tiger stripe medial dorsum structures, relict tiger stripe structures, south pole funiscular (ropy) plains, south pole lateral fold-and-wedge formations, and the south pole reticulated plains. Despite the constant, ubiquitous infall of plume particles onto the surface, differences in scattering properties, texture, and albedo among terrain units can be discerned. Work supported by NASA's Cassini Data Analysis Program. [1] Porco et al. 2006 Science 311, 1393-1401. [2] Hansen et al. 2008 Nature 456, 477-479. [3] Spencer et al. 2009 in Saturn from Cassini-Huygens (M. K. Dougherty et al. Eds.) 683-724. [4] Hapke 2002 Icarus 157, 523-534.

  19. Mobile Lid Convection Beneath Enceladus' South Polar Terrain

    NASA Technical Reports Server (NTRS)

    Barr, Amy C.

    2008-01-01

    Enceladus' south polar region has a large heat flux, 55-110 milliwatts per square meter (or higher), that is spatially associated with cryovolcanic and tectonic activity. Tidal dissipation and vigorous convection in the underlying ice shell are possible sources of heat; however, prior predictions of the heat flux carried by stagnant lid convection range from F(sub conv) 15 to 30 milliwatts per square meter, too low to explain the observed heat flux. The high heat flux and increased cryovolcanic and tectonic activity suggest that near-surface ice in the region has become rheologically and mechanically weakened enough to permit convective plumes to reach close to the surface. If the yield strength of Enceladus' lithosphere is less than 1-10 kPa, convection may instead occur in the mobile lid" regime, which is characterized by large heat fluxes and large horizontal velocities in the near-surface ice. I show that model ice shells with effective surface viscosities between 10(exp 16) and 10(exp 17) Pa s and basal viscosities between 10(exp 13) and 10(exp 15) Pa s have convective heat fluxes comparable to that observed by the Cassini Composite Infrared Spectrometer. If this style of convection is occurring, the south polar terrain should be spreading horizontally with v1-10 millimeter per year and should be resurfaced in 0.1-10 Ma. On the basis of Cassini imaging data, the south polar terrain is 0.5 Ma old, consistent with the mobile lid hypothesis. Maxwell viscoelastic tidal dissipation in such ice shells is not capable of generating enough heat to balance convective heat transport. However, tidal heat may also be generated in the near-surface along faults as suggested by Nimmo et al. and/or viscous dissipation within the ice shell may occur by other processes not accounted for by the canonical Maxwell dissipation model.

  20. South Polar Region of Mars: Topography and Geology

    NASA Technical Reports Server (NTRS)

    Schenk, P. M.; Moore, J. M.

    1999-01-01

    The polar layered deposits of Mars represent potentially important volatile reservoirs and tracers for the planet's geologically recent climate history. Unlike the north polar cap, the uppermost surface of the bright residual south polar deposit is probably composed of carbon dioxide ice. It is unknown whether this ice extends through the entire thickness of the deposit. The Mars Polar Lander (MPL), launched in January 1999, is due to arrive in December 1999 to search for water and carbon dioxide on layered deposits near the south pole (SP) of Mars. Additional information is contained in the original extended abstract.

  1. Drawing the Curtain on Enceladus' South-Polar Eruptions

    NASA Astrophysics Data System (ADS)

    Spitale, Joseph N.; Hurford, Terry A.; Rhoden, Alyssa R.; Berkson, Emily E.; Platts, Symeon S.

    2015-11-01

    For a comprehensive description of Enceladus' south-polar eruptions observed at high resolution, they must be represented as broad curtains rather than discrete jets. Meanders in the fractures from which the curtains of material erupt give rise to optical illusions that look like discrete jets, even along fractures with no local variations in eruptive activity, implying that many features previously identified as "jets" are in fact phantoms. By comparing Cassini images with model curtain eruptions, we are able to obtain maps of eruptive activity that are not biased by the presence of those phantom jets. The average of our activity maps over all times agrees well with thermal maps produced by Cassini CIRS. We can best explain the observed curtains by assuming spreading angles with altitude of up to 14° and zenith angles of up to 8°, for curtains observed in geometries that are sensitive to those quantities.

  2. Transient surface liquid in Titan's south polar region from Cassini

    USGS Publications Warehouse

    Hayes, A.G.; Aharonson, O.; Lunine, J.I.; Kirk, R.L.; Zebker, H.A.; Wye, L.C.; Lorenz, R.D.; Turtle, E.P.; Paillou, P.; Mitri, G.; Wall, S.D.; Stofan, E.R.; Mitchell, K.L.; Elachi, C.

    2011-01-01

    Cassini RADAR images of Titan's south polar region acquired during southern summer contain lake features which disappear between observations. These features show a tenfold increases in backscatter cross-section between images acquired one year apart, which is inconsistent with common scattering models without invoking temporal variability. The morphologic boundaries are transient, further supporting changes in lake level. These observations are consistent with the exposure of diffusely scattering lakebeds that were previously hidden by an attenuating liquid medium. We use a two-layer model to explain backscatter variations and estimate a drop in liquid depth of approximately 1-m-per-year. On larger scales, we observe shoreline recession between ISS and RADAR images of Ontario Lacus, the largest lake in Titan's south polar region. The recession, occurring between June 2005 and July 2009, is inversely proportional to slopes estimated from altimetric profiles and the exponential decay of near-shore backscatter, consistent with a uniform reduction of 4 ± 1.3 m in lake depth. Of the potential explanations for observed surface changes, we favor evaporation and infiltration. The disappearance of dark features and the recession of Ontario's shoreline represents volatile transport in an active methane-based hydrologic cycle. Observed loss rates are compared and shown to be consistent with available global circulation models. To date, no unambiguous changes in lake level have been observed between repeat images in the north polar region, although further investigation is warranted. These observations constrain volatile flux rates in Titan's hydrologic system and demonstrate that the surface plays an active role in its evolution. Constraining these seasonal changes represents the first step toward our understanding of longer climate cycles that may determine liquid distribution on Titan over orbital time periods.

  3. Circular Polarization Characteristics of South Polar Lunar Craters using Chandrayaan-1 Mini-SAR and LRO Mini-RF

    NASA Astrophysics Data System (ADS)

    Calla, Om Prakash Narayan; Mathur, Shubhra; Jangid, Monika; Gadri, Kishan Lal

    2015-07-01

    The paper presents a case study of inconsistent behaviour of Chandrayaan-1 Mini-SAR and LRO Mini-RF data over south polar lunar craters. The paper includes analysis of Stokes parameters and characterization of received time-varying electromagnetic fields over the south pole lunar craters. For the study, Chandrayaan-1 Mini-SAR and LRO Mini-RF data at 2.38 GHz are used. Total five lunar craters in south polar region are analyzed to study the effect of various parameters on the polarization of the signal. We have compared linear horizontal (LH) and linear vertical (LV) polarization components of received radar signal over the same targets using two different SAR data. Ratios of received LH to LV components are also derived over the five craters. It is observed that Chandrayaan-1 Mini-SAR is receiving high LH component as compared to LV component. This is not consistent with the scattering theory (Fawwaz et al. in Microwave remote sensing active and passive, Artech House Inc., New York, 1981), which states that for incidence angle greater than 15°, the vertical polarized component of a received signal should be always high as compared to horizontal polarized component over rough surfaces. These inconsistent results of Chandrayaan-1 Mini-SAR are observed over all five craters. In the paper, various effects of sensor parameters like incident angle, ellipticity angle, orientation angle etc. on scattering mechanism are discussed to understand the inconsistent behaviour of two SAR data over same target.

  4. Frost streaks in the south polar cap of Mars

    NASA Technical Reports Server (NTRS)

    Thomas, P.; Veverka, J.; Campos-Marquetti, R.

    1979-01-01

    Viking Orbiter images of the annual south polar cap on Mars exhibit elongated bright features that are associated with craters and resemble wind streaks observed elsewhere on Mars. The study focuses on the well-documented frost streaks. The discussion covers the morphology of frost streaks, occurrence, seasonal behavior, thickness of frost in streak deposits, wind patterns inferred from frost streaks and other eolian features in the south polar region, formation of frost streaks, and other locales of preferential frost accumulation. The form and seasonal behavior of the bright elongated albedo markings which extend from the rims of many craters in the south polar cap suggest that they are accumulations of CO2 frost in the lee of craters. The frost streaks appear in the fall, increasing in length but not changing in direction during fall and winter. The frost streaks indicate a prograde circulation pattern of near-surface winds around the pole. Other details are also presented.

  5. The Residual South Polar Cap of Mars: Stable or Transitory?

    NASA Astrophysics Data System (ADS)

    Glenar, David A.; Bonev, B. P.; Hansen, G. B.; James, P. B.; Bjorkman, J. E.

    2006-09-01

    It remains uncertain whether the CO2 residual south polar cap (RSPC) is a permanent feature of the present Mars climate, or whether it occasionally sublimes completely during years marked by dramatic dust storm activity. While there is no firm evidence for complete disappearance of the cap in the past, observations show that the residual cap lost significant CO2 material in the spring / summer season prior to the Mariner 9 encounter. On the other hand, little interannual change has been observed in the RSPC during the MGS mission [1], despite the massive early-spring dust storm which occurred in 2001. We discuss whether a global dust storm beginning near perihelion could enhance the net CO2 sublimation sufficiently to completely remove the RSPC. We utilize a surface-plus-aerosol radiative transfer model under conditions of both modest and heavy atmospheric dust loading. The sublimination behavior depends critically on the extended (visible to thermal IR) albedo spectrum of the polar CO2 ice, which we have strongly constrained [2] from a combination of HST photometric imaging, ground based near-IR imaging spectroscopy and spectroscopic measurements by the Mars Express PFS. The extension of the cap spectrum to thermal IR wavelengths was accomplished by forward modeling using a semi-infinite grid of scattering grains. Results of this analysis depend on the strength of possible feedback mechanisms (increased surface dust content; exposure of water ice) as well as on the possibility of dust confinement by the polar vortex; but the general conclusion is that it would require multiple, intense dust storms in a given year in order to completely remove the CO2 ice veneer layer. This work has been supported by the NASA Planetary Astronomy and Mars Data Analysis Programs. [1] Benson and James, Icarus 174, 513, 2005; [2] Bonev et al., Planet Space Sci. 2006 (accepted).

  6. South polar craters as observed by LRO Mini-RF

    NASA Astrophysics Data System (ADS)

    Thomson, B. J.; Bussey, B.; Mini-RF Science Team

    2011-12-01

    Due to the Moon's low orbital inclination, impact craters near the lunar poles contain regions of permanent shadow. These shaded regions have correspondingly low temperatures and are thus potential sinks for lunar volatile species. Mini-RF is a dual-band synthetic aperture radar onboard the Lunar Reconnaissance Orbiter. Since radar provides its own illumination, Mini-RF is able to examine the interior of these craters and other locations not observable from Earth-based radar. As reported with similar but lower-resolution SAR data for the lunar north pole [1], numerous craters in the southern polar region exhibit anomalous polarization signatures. In particular, they contain modest interior CPR enhancements (circular polarization ratio), which is the ratio of same sense to opposite sense polarization. Such a signature is consistent with a mixture model of a few percent of water ice mixed with a dry silicate regolith. However, this scattering model assumes the target is a mixture of wavelength-scale (decimeter) chunks of ice and regolith, and thus may not be physically realistic. No empirical scattering models exist for potentially more realistic scenarios with smaller chunks of ice or ice disseminated as thin films around silicate grains. Our initial comparison south polar and non-polar craters indicate that shadowed polar craters record a distinctive and potentially unique polarization. We are currently building up a database of polar and non-polar craters to verify that the polarization signature of polar craters, regardless of origin, is unique to locations that lie in permanent shadow. [1] Spudis, P. D., et al., 2010. Initial results for the north pole of the Moon from Mini-SAR, Chandrayaan-1 mission. GRL 37, L06204.

  7. Effects of Atmospheric Dust on Residual South Polar Cap Stability

    NASA Technical Reports Server (NTRS)

    Bonrv, B. P.; Bjorkman, J. E.; Hansen, G. B.; James, P. B.; Wolff, M. J.

    2005-01-01

    The Martian polar caps have been studied from the time of Herschel. Neither polar cap normally disappears in summer. The Residual North Polar Cap (portion that remains through summer) is composed of a mixture of water ice and dust, and its interannual stability is due to its low sublimation rate at the summer temperatures in the North Polar Region. The Residual South Polar Cap (RSPC) is more enigmatic, surviving the relatively hot perihelic summer season despite being composed of much more volatile CO2. It is able to do so because of its unusually high albedo, which is larger than that of other bright regions in the seasonal cap (e.g. Mountains of Mitchel). The proximity of the albedo of the RSPC to the critical albedo for stability raises the question of whether the RSPC exists in every Martian year. The ground based record is somewhat ambivalent. Douglass and Lowell reported that RSPC suddenly vanished at Ls=297deg in 1894 and did not reappear until Ls=0deg [1], and Kuiper reported that it disappeared in 1956 [2]; but both observations were questioned by contemporaries, who tended to attribute them to obscuring dust. Barker [3] reported a large amount of water vapor over the south polar cap in 1969 that could be attributed to exposure of near surface water ice during partial removal of the CO2 in the RSPC in 1969.

  8. The nonuniform recession of the south polar cap of Mars

    NASA Technical Reports Server (NTRS)

    Veverka, J.; Goguen, J.

    1973-01-01

    The nature of the irregular springtime recession of the Martian polar caps is investigated, with particular reference to the southern polar cap. Our current knowledge about the composition of the caps is outlined, and the historical record of their springtime recession is reviewed. An attempt is made to correlate the irregularities of the recession pattern of the southern polar cap with the features of the terrain revealed by Mariner 9 photography at a time when the southern cap was at its minimum extent. The results are interpreted in terms of the physical and meteorological processes active in the polar regions.

  9. Monstrous Ice Cloud System in Titan's Present South Polar Stratosphere

    NASA Astrophysics Data System (ADS)

    Anderson, Carrie; Samuelson, Robert; McLain, Jason; Achterberg, Richard; Flasar, F. Michael; Milam, Stefanie

    2015-11-01

    During southern autumn when sunlight was still available, Cassini's Imaging Science Subsystem discovered a cloud around 300 km near Titan's south pole (West, R. A. et al., AAS/DPS Abstracts, 45, #305.03, 2013); the cloud was later determined by Cassini's Visible and InfraRed Mapping Spectrometer to contain HCN ice (de Kok et al., Nature, 514, pp 65-67, 2014). This cloud has proven to be only the tip of an extensive ice cloud system contained in Titan's south polar stratosphere, as seen through the night-vision goggles of Cassini's Composite InfraRed Spectrometer (CIRS). As the sun sets and the gloom of southern winter approaches, evidence is beginning to accumulate from CIRS far-IR spectra that a massive system of nitrile ice clouds is developing in Titan's south polar stratosphere. Even during the depths of northern winter, nothing like the strength of this southern system was evident in corresponding north polar regions.From the long slant paths that are available from limb-viewing CIRS far-IR spectra, we have the first definitive detection of the ν6 band of cyanoacetylene (HC3N) ice in Titan’s south polar stratosphere. In addition, we also see a strong blend of nitrile ice lattice vibration features around 160 cm-1. From these data we are able to derive ice abundances. The most prominent (and still chemically unidentified) ice emission feature, the Haystack, (at 220 cm-1) is also observed. We establish the vertical distributions of the ice cloud systems associated with both the 160 cm-1 feature and the Haystack. The ultimate aim is to refine the physical and possibly the chemical relationships between the two. Transmittance thin film spectra of nitrile ice mixtures obtained in our Spectroscopy for Planetary ICes Environments (SPICE) laboratory are used to support these analyses.

  10. Post-equinox evolution of Titan's south-polar stratosphere

    NASA Astrophysics Data System (ADS)

    Teanby, Nicholas A.; Vinatier, Sandrine; de Kok, Remco; Nixon, Conor A.; Irwin, Patrick GJ

    2015-11-01

    Since northern spring equinox in mid-2009, Titan's atmosphere has demonstrated dramatic changes in temperature (Achterberg et al 2014), composition (Teanby et al 2012, Vinatier et al 2015, Coustenis et al 2015), and aerosol/ice distribution (de Kok et al 2014, Jennings et al 2015, West et al 2015). Changes have been greatest at the southern winter pole, which continues to enter deeper into Titan's shadow following the 2009 equinox. Observational highlights include development of a south polar hot-spot, nitrile ice clouds, dense condensate clouds, and extreme trace gas concentrations.Here we use recent infrared spectral limb observations by Cassini/CIRS to determine the evolution of temperature and composition of the south polar region since equinox. Our observations show that the south polar hot-spot initially observed following equinox has now disappeared and been replaced by extremely low temperatures throughout the stratosphere, suspected to be due to enhanced radiative cooling. There also appears to be an unusual distribution of nitrile species, which suggests trace gases are now escaping the newly formed winter vortex. Thus providing clues to the underlying circulation. The new observations will be presented and implications for Titan's polar atmospheric dynamics discussed.Achterberg et al (2014), DPS46, 102.07, Tucson.Coustenis et al (2015), Icarus (in press).de Kok et al (2014), Nature, 514, 65-67.Jennings et al (2015), ApJL, 804, L34.Teanby et al (2012), Nature, 491, 732-735.Vinatier et al (2015), Icarus, 250, 95-115.West et al (2015), Icarus (in press).

  11. Imaging Enceladus' Exotic South Polar Regions: Imaging Science Team Results

    NASA Astrophysics Data System (ADS)

    Johnson, T.

    2005-12-01

    The Cassini spacecraft had a close (175 km altitute) encounter with Saturn's moon Enceladus on 14 July 2005, resulting in a major discovery: evidence from multiple experiments show that there is a large `plume' of water vapor and particles emanating from the satellite's south polar region. Infrared data from the CIRS instrument showed that this area is also anomalously warm, providing evidence for internal heat. High resolution images taken by the Imaging Science System during the encounter show that the warm region associated with water vapor venting is a unique area on this icy world. The region has very few if any detectable impact craters, making it the youngest surface seen on Enceladus, or any of the other icy Saturnian satellites; estimates from cratering models place its age at less than 10-100 million years. It is surrounded by tectonic features suggesting a global stress pattern that may be associated with a change in spin rate. Long, parallel fractures, informally dubbed `tiger stripes', cross the region and are correlated with at least some of the thermal anomalies, making them good candidates for the source regions of the water venting. Spectral data and photometric studies also show that the whole area and the tiger stripes in particular have fewer fine grained particles on the surface than most of the moon's surface, in agreement with a young surface and crystalinity and grain size interpretations of data from the Visual and Near Infrared Mapping Spectrometer experiment. Tidal forces and radioactive heating are probably responsible for the activity, although generating such intense internal heating is challenging for current models. Portions of this work were done at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.

  12. Condensation phase of the Martian south polar cap

    NASA Technical Reports Server (NTRS)

    Capuano, J.; Reed, M.; James, P. B.

    1992-01-01

    One type of database that can be useful in limiting models of the Mars surface-atmosphere system is the time dependent boundary of CO2 frost for the polar caps. Data acquired by the thermal infrared sensors on spacecraft are not limited by the lighting problems that hamper visual observations. The surface temperature of solid CO2 is limited by Clapeyron's equation as a function of the local partial pressure of CO2 gas. The growth was studied of the Martian south polar cap using the Viking IRTM dataset. These data are available in five bands, four of which should correspond to surface radiation in clear conditions; the 20 micron data was examined in the first phase.

  13. Stratigraphy of the south polar region of Ganymede

    NASA Technical Reports Server (NTRS)

    Dehon, R. A.

    1987-01-01

    A preliminary assessment is made of the stratigraphy and geology in the south polar region of the Jovian satellite, Ganymede. Geologic mapping is based on inspection of Voyager images and compilation on an airbrush base map at a scale of 1:5M. Illumination and resolution vary greatly in the region. Approximately half of the quadripole is beyond the terminator. Low angle illumination over a large part of the area precludes distinction of some units by albedo characteristics. Several types of grooved terrain and groove related terrain occur in the southern polar region. Grooves typically occur in straight to curvilinear sets or lanes. Bright lanes and grooved lanes intersect at high angles outlining polygons of dark cratered terrain. Groove sets exhibit a range of ages as shown by superposition or truncation and by crater superposition ages.

  14. Accumulation and erosion of Mars' south polar layered deposits.

    PubMed

    Seu, Roberto; Phillips, Roger J; Alberti, Giovanni; Biccari, Daniela; Bonaventura, Francesco; Bortone, Marco; Calabrese, Diego; Campbell, Bruce A; Cartacci, Marco; Carter, Lynn M; Catallo, Claudio; Croce, Anna; Croci, Renato; Cutigni, Marco; Di Placido, Antonio; Dinardo, Salvatore; Federico, Costanzo; Flamini, Enrico; Fois, Franco; Frigeri, Alessandro; Fuga, Oreste; Giacomoni, Emanuele; Gim, Yonggyu; Guelfi, Mauro; Holt, John W; Kofman, Wlodek; Leuschen, Carlton J; Marinangeli, Lucia; Marras, Paolo; Masdea, Arturo; Mattei, Stefania; Mecozzi, Riccardo; Milkovich, Sarah M; Morlupi, Antonio; Mouginot, Jérémie; Orosei, Roberto; Papa, Claudio; Paternò, Tobia; Persi del Marmo, Paolo; Pettinelli, Elena; Pica, Giulia; Picardi, Giovanni; Plaut, Jeffrey J; Provenziani, Marco; Putzig, Nathaniel E; Russo, Federica; Safaeinili, Ali; Salzillo, Giuseppe; Santovito, Maria Rosaria; Smrekar, Suzanne E; Tattarletti, Barbara; Vicari, Danilo

    2007-09-21

    Mars' polar regions are covered with ice-rich layered deposits that potentially contain a record of climate variations. The sounding radar SHARAD on the Mars Reconnaissance Orbiter mapped detailed subsurface stratigraphy in the Promethei Lingula region of the south polar plateau, Planum Australe. Radar reflections interpreted as layers are correlated across adjacent orbits and are continuous for up to 150 kilometers along spacecraft orbital tracks. The reflectors are often separated into discrete reflector sequences, and strong echoes are seen as deep as 1 kilometer. In some cases, the sequences are dipping with respect to each other, suggesting an interdepositional period of erosion. In Australe Sulci, layers are exhumed, indicating recent erosion. PMID:17885128

  15. Active Polymer Microfiber with Controlled Polarization Sensitivity

    PubMed Central

    Xia, Hongyan; Wang, Ruxue; Liu, Yingying; Cheng, Junjie; Zou, Gang; Zhang, Qijin; Zhang, Douguo; Wang, Pei; Ming, Hai; Badugu, Ramachandram; Lakowicz, Joseph R.

    2016-01-01

    Controlled Polarization Sensitivity of an active polymer microfiber has been proposed and realized with the electrospun method. The fluorescence intensity guiding through this active polymer microfiber shows high sensitivity to the polarization state of the excitation light. What is more, the fluorescence out-coupled from tip of the microfiber can be of designed polarization state. Principle of these phenomena lies on the ordered and controlled orientation of the polydiacetylene (PDA) main chains inside polymer microfiber. PMID:27099828

  16. Preliminary albedo map of the south polar region

    NASA Technical Reports Server (NTRS)

    Devaucouleurs, G.; Roth, J.; Mulholand, C.

    1973-01-01

    A preliminary albedo map of the Martian south polar region in stereographic projection was prepared mainly from mission test video system (MTVS) prints before rectified and gridded prints were received, but some adjustments were made to conform with a semi-controlled photomosaic. Wherever possible, use also was made of crater coordinates. Two versions of the map are presented: one with a coordinate grid overlay and one without it. The precision of the coordinates is generally within 1 deg in latitude and the corresponding are in longitude. The maps show both the albedo markings and, with subdued contrast, the craters and topographic features that are necessary to locate the former. The map covers the range of latitudes from - 65 deg to the south pole.

  17. Correlating Polar Stratospheric Cloud Occurrence at the South Pole with Transport and Polar Geopotential Height Anomalies

    NASA Astrophysics Data System (ADS)

    Campbell, J. R.; Sassen, K.

    2007-12-01

    In a recent paper, we describe the macrophysical and thermodynamic properties of polar stratospheric clouds (PSC) at the South Pole based on continuous eye-safe lidar measurements made over five seasons (2000, 2003-2006). In this paper, we describe the relationship between PSC occurrence and the propensity for transport within the austral polar vortex. The southern lower-stratospheric polar airmass may be approximated as a closed system from May to September. Saturation vapor pressures for background concentrations of sulfuric and nitric acid and water vapor are reached either through radiational cooling or isentropic lift. Once nucleated, PSC acquire fall-velocities that remove these compounds from these heights. Satellite measurements (e.g., MLS) depict the widening proximity of the depleted airmass through the polar night. Yet, our measurements show that PSC occurrence can occur up to 20 km late in the season, which suggests replenishment of these species in air originating near the edges of the vortex. We examine 120-h back-trajectories during July and August and temperature histories to identify conditions and circumstances favorable to this occurring. Furthermore, we describe geopotential height anomalies averaged along 60° - 90° S, and compared to a twenty-year mean, as a proxy for the dynamic character of the polar vortex. Negative/positive anomalies indicate a strong/weak and deep/shallow vortex where its circulation inhibits/promotes meridional transport, replenishment and the likelihood of PSC at South Pole. We test this hypothesis using our dataset and reach conclusions on the influence of the polar vortex on total PSC observed each season, which, in turn, may influence the severity of annual ozone losses.

  18. Seasonal recession of Mars' south polar cap in 1986

    NASA Technical Reports Server (NTRS)

    James, Philip B.; Martin, Leonard J.; Henson, Jean R.; Birch, Peter V.

    1990-01-01

    Photographs of Mars obtained during the 1986 opposition of the planet have been used to derive the regression curve for the south polar cap between Ls = 190 deg and Ls = 255 deg. The 1986 regression appears to have been unexceptional until after Ls = 230 deg, when it becomes retarded relative to the normal established by the 1971 and 1977 regressions. A study of the data as a function of the filter used suggests that circumpolar clouds were present in early spring, unlike the case in the 1977 recession.

  19. Implications of Martian North/South Polar Differences

    NASA Technical Reports Server (NTRS)

    Murray, Bruce C.

    2003-01-01

    Our first requirement was to create the specialized tools necessary to precisely co-locate at highest spatial resolution the rapidly growing MOC/NA and MOLA data sets in the polar regions. This meant promptly creating a very accurate Mars Polar GIs system (based on the commercial ArcView product) along with various other supporting routines. Later we extended its use to the THEMIS/VIS data. That customized GIS and integrated data system has enabled all of our polar research to date. We focused initially on a preliminary geological reconnaissance in the Ultimi Lobe region of the South Polar Layered Deposits, which also included the intended MPL landing site about which much remote sensing data and interpretations had been accumulated before the failed landing attempt on December 3, 1999. The most interesting findings from that effort were discoveries about the layering, faulting and contact relationships exposed along the bounding scarp. Those results were published in Icarus. We have had a priority interest in the cratering record of the polar layered deposits, starting with the first post-Viking survey based on MOLA shaded relief maps and crossing profiles. Those results, based primarily on craters < 1 km diameter, were published in JGR and showed that a portion of the SPLD exhibited a large crater population consistent with an exposure age of 30 million years or more. Those craters also exhibited remarkably low Depth to Diameter ratios, which Asmin Pathare, then at UCLA, subsequently interpreted as due to slow viscous flow in the ice-rich material composing the PLD. Our cratering study also recognized that the craters of less than 1 km diameter were many order of magnitudes too few compared to what the crater production function of the larger craters requires.

  20. Complete mitochondrial genome of the South Polar Skua Stercorarius maccormicki (Charadriiformes, Stercorariidae) in Antarctica.

    PubMed

    Han, Yeong-Deok; Baek, Ye-Seul; Kim, Jeong-Hoon; Choi, Han-Gu; Kim, Sanghee

    2016-05-01

    The South Polar Skua, gull-like seabirds is the most fascinating Antarctic seabirds that lay two eggs at sites free of snow and ice and predominantly hunt pelagic fish and penguins. Blood samples of the South Polar Skua Stercorarius maccormicki was collected during the summer activity near King Sejong station in Antarctica. The complete mitochondrial DNA sequence of S. maccormicki was 16,669 bp, showing conserved genome structure and orientation found in other avian species. The control region of S. maccormicki was 93- and 80 bp shorter compared to those of Chroicocephalus saundersi and Synthliboramphus antiquus respectively. Interestingly, there is a (CAACAAACAA)6 repeat sequence in the control region. Our results of S. maccormicki mt genome including the repeat sequence, may provide useful genetic information for phylogenetic and phylogeographic histories of the southern skua complex. PMID:25268998

  1. North-south asymmetry of eolian features in Martian polar regions - Analysis based on crater-related wind markers

    NASA Technical Reports Server (NTRS)

    Thomas, P.

    1981-01-01

    Crater-related wind markers in the north and south polar regions of Mars are analyzed in a study of possible north-south asymmetries in wind activity. Features including crater splotches and associated streaks, and depositional, erosional, frost and frost-sediment streaks were identified and analyzed as wind direction indicators on Viking Orbiter and Mariner 9 images of areas poleward of + or - 40 deg latitude. The wind streaks reveal eolian activity at present to be strongest in the north in winter and in the south in spring, due to the hemispherical asymmetry in climate. The alignment of the more massive intercrater dune fields with the presently strongest wind may reflect a longer-term asymmetry in spring flows, as the reorientation times of the dunes exceeded the period of climate asymmetry cycles. Finally, a wider distribution of dune latitudes in the southern polar region is noted to be suggestive of the greater effectiveness of windflow from the south pole.

  2. Potential vorticity of the south polar vortex of Venus

    NASA Astrophysics Data System (ADS)

    Garate-Lopez, I.; Hueso, R.; Sánchez-Lavega, A.; García Muñoz, A.

    2016-04-01

    Venus' atmosphere shows highly variable warm vortices over both of the planet's poles. The nature of the mechanism behind their formation and properties is still unknown. Potential vorticity is a conserved quantity when advective processes dominate over friction and diabatic heating and is a quantity frequently used to model balanced flows. As a step toward understanding the vortices' dynamics, we present maps of Ertel's potential vorticity (EPV) at Venus' south polar region. We analyze three configurations of the south polar vortex at the upper cloud level (P ~ 240 mbar; z ~ 58 km), based on our previous analyses of cloud motions and thermal structure from data acquired by the Visual and InfraRed Thermal Imaging Spectrometer instrument on board Venus Express. Additionally, we tentatively estimate EPV at the lower cloud level (P ~ 2200 mbar; z ~ 43 km), based on our previous wind measurements and on static stability data from Pioneer Venus and the Venus International Reference Atmosphere (VIRA) model. Values of EPV are on the order of 10-6 and 10-8 K m2 kg-1 s-1 at the upper and lower cloud levels, respectively, being 3 times larger than the estimated errors. The morphology observed in EPV maps is mainly determined by the structures of the vertical component of the relative vorticity. This is in contrast to the vortex's morphology observed in 3.8 or 5 µm images which are related to the thermal structure of the atmosphere at the cloud top. Some of the EPV maps point to a weak ringed structure in the upper cloud, while a more homogenous EPV field is found in the lower cloud.

  3. Complex Burial and Exhumation of South Polar Cap Pitted Terrain

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This image is illuminated by sunlight from the upper left. The two prominent bright stripes at the left/center of the image are covered with bright frost and thus create the illusion that they are sunlit from the lower left.

    The large pits, troughs, and 'swiss cheese' of the south polar residual cap appear to have been formed in the upper 4 or 5 layers of the polar material. Each layer is approximately 2 meters (6.6 feet) thick. Some Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images of this terrain show examples in which older pitted and eroded layers have been previously buried and are now being exhumed. The example shown here includes two narrow, diagonal slopes that trend from upper left toward lower right at the left/center portion of the frame. Along the bottoms of these slopes are revealed a layer that underlies them in which there are many more pits and troughs than in the upper layer. It is likely in this case that the lower layer formed its pits and troughs before it was covered by the upper layer. This observation suggests that the troughs, pits, and 'swiss cheese' features of the south polar cap are very old and form over long time scales.

    The picture is located near 84.6oS, 45.1oW, and covers an area 3 km by 5 km (1.9 x 3.1 mi) at a resolution of about 3.8 meters (12 ft) per pixel. The image was taken during southern spring on August 29, 1999.

    Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  4. The Changing South Polar Cap of Mars: 1999-2005

    NASA Technical Reports Server (NTRS)

    2005-01-01

    13 July 2005 The south polar residual cap of Mars is composed of layered, frozen carbon dioxide. In 1999, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) showed that the carbon dioxide layers have been eroded to form a variety of circular pits, arcuate scarps, troughs, buttes, and mesas. In 2001, MOC images designed to provide repeated views of the areas imaged in 1999 -- with the hope of creating stereo (3-D) images, so that the height of scarps and depth of pits could be measured -- showed that the scarps had retreated, pits enlarged, and buttes and mesas shrank. Only carbon dioxide is volatile enough in the martian environment to have caused such dramatic changes -- the scarps were seen to retreat at an average rate of 3 meters (about 3 yards) per Mars year. Most of the scarp retreat occurs during the southern summer season; in some areas the scarps move as much as 8 meters, in others, only 1 meter per Mars year.

    Three Mars years have now elapsed since MOC first surveyed the south polar cap in 1999. Over the past several months, MGS MOC has been re-imaging areas that were seen in 1999, 2001, and 2003, to develop a detailed look at how the landscape has been changing. This animated GIF provides an example of the dramatic changes that have occurred during the past three martian years. The first image, a sub-frame of M09-05244, was acquired on 21 November 1999. The second image, a sub-frame of S06-00973, was obtained on 11 May 2005. The animation shows the changes that have occurred between 1999 and 2005. Each summer, the cap has lost more carbon dioxide. This may mean that the carbon dioxide content of the martian atmosphere has been increasing, bit by very tiny little bit, each of the years that MGS has been orbiting the red planet. These observations also imply that there was once a time, in the not-too-distant past (because there are no impact craters on the polar cap), when the atmosphere was somewhat thinner and colder, to permit the layers

  5. South Polar Residual Cap Geomorphology and Inferred Environmental Changes

    NASA Astrophysics Data System (ADS)

    Byrne, S.; Ingersoll, A.; Pathare, A.

    2003-12-01

    The CO2 southern residual cap (SRC) both controls circulation patterns regionally and buffers the atmospheric pressure globally. In turn this CO2 deposit is affected by changes in environmental conditions wrought by external forces such as dust storm activity. Mars Global Surveyor data of this area have revealed a rich variety of geomorphic features (1) of which there are several distinct classes. These different classes may be end members of the same basic process of insolation driven ablation. We are currently investigating two types of SRC features. Swiss-cheese features (SCF) are depressions characterized by flat floors and steep walls, which retreat 1-3 meters each Martian year (2). In some regions they have a definite symmetry axis along the north-south direction (3). After the seasonal frost disappears the residual ice exposed in the walls has a lower albedo (4). Previously (5) we modeled the evolution and growth of these depressions as a hole in a layer of CO2 ice underlain by water ice, which best explains their morphologic and thermal properties. The observed thickness of the CO2 slab can be as high as 8 meters but in general is much lower. Larger SCF?s commonly possess a raised central island of CO2 surrounded by a moat that penetrates to the underlying water ice (3). The fast rate of wall retreat observed (2) combined with the small sizes of the SCF?s indicate that all SCF?s visible today were created geologically recently. Within a particular region the size distribution is quite narrow (3): no larger (older) or smaller (younger) features were seen indicating that some relatively abrupt change in environmental conditions initiated the growth of this particular population of features. Fingerprint terrain (1) are areas with evenly spaced parallel ridges, which are steeper on one side. These ridges may have small areas of water ice exposed in the intervening troughs. Their wavelength is on the order of 70-90m with the steep edges facing northeast although

  6. Mass Wasting Processes in Vesta's South Polar Region

    NASA Astrophysics Data System (ADS)

    Otto, K.; Jaumann, R.; Krohn, K.; Preusker, F.; Roatsch, T.; Stephan, K.; Sykes, M. V.; Schenk, P.; Raymond, C. A.; Russell, C. T.

    2012-12-01

    Images of Asteroid Vesta taken by the Dawn framing camera give insight to a wide range of geologic phenomena on Vesta's surface. In this abstract we focus on the evidence of different types of gravity-driven mass wasting that can be seen on Vesta with an emphasis on the south polar region where the formation of the giant impact basin of Rheasilvia (1, 2) caused significant mass movements and lateral displacement. During the formation of the impact basin various processes such as uplift and stretching moved material of the impact site (3). The remnant are fault scarps, ridges, and uplift features inside the Rheasilvia basin (2). Beside these mass movements, there are also three types of debris movement associated with the Rheasilvia impact basin: block slumping of solid material, granular landslides, and flow-like features. They all occur on the rim of the basin and the central peak with slopes varying from 10° to 40°. The movement, however, is in different directions. While the block slumping and landslides occur on the steep slopes of the crater wall facing inward, the flow-like movements go outward from the crater rim on less steep slopes. The block slumping is most prominent in the region between 80° and 120° east and 50° and 60° south (4). The slump blocks in a rotational movement showing multiple scarps and ridges. Landslides on the steep slopes inward of Rheasilvia have a length to height ratio of about 1. The flow-like features occur in the region between 50° and 90° east and 20° to 40° south. They are in a relatively young area and have a length to height ratio up to 35. Additionally, many small elongate depressions of about 1.5 km length can be found near the central peak of Rheasilvia. They are mainly arranged parallel to the slope with a slight curvature and are related to instability of granular material on a slope. References: (1) Jaumann et al., Science 336, 687 (2012); (2) Schenk et al., Science 336, 694 (2012); (3) Melosh, Impact Cratering

  7. A study of auroral activity in the nightside polar cap

    SciTech Connect

    Wu, Q.

    1989-01-01

    Using various ground observations at South Pole, Antarctica (invariant magnetic latitude -74{degree}) and its conjugate point, Frobisher Bay, Canada, the author has studied the following aspects of nightside polar cap auroral activity: the appearance and disappearance of polar cap auroras (diffuse and discrete) associated with substorms and interplanetary magnetic field (IMF) variations; auroral optical emission line intensities; and the seasonal variation of auroral conjugacy. The observations show that the polar cap auroras usually fade away before the expansive phase of a substorm and bright auroral arcs reach high latitude (-74{degree}) near the recovery phase. Just before the auroras fade away the discrete polar cap auroral arcs, which are usually on the poleward boundary of the diffuse aurora, intensify for 1 to 2 minutes. The observations also indicate the IMF may have stronger control over polar cap auroral activity than do substorms. A search for energy spectral variation of precipitating electrons using the intensities of 630.0 nm (0) and 427 nm (N{sub 2}{sup +}) auroral emission lines reveals no dramatic changes in the energy spectrum; instead, the data show possible atmospheric scattering and geometric effects on the photometric measurements while the bright auroral arc is moving into the polar cap. The conjugate observations show that the stormtime auroral electrojet current, which is associated with the bright auroral arc, in most cases reaches higher (lower) latitudes in the winter (summer) hemisphere. An asymmetric plasma sheet (with respect to the neutral sheet) is proposed, which expands deeper into the winter lobe, under a tilted geomagnetic dipole. Accordingly, the winter polar cap would have smaller area and the auroral electrojet would be at higher latitude.

  8. Study on the time difference of solar polar field reversal between the north and south hemisphere

    NASA Astrophysics Data System (ADS)

    Shukuya, D.; Kusano, K.

    2013-12-01

    Dynamo is a mechanism whereby the kinetic energy of plasma is converted to the magnetic energy. This mechanism works to generate and maintain the solar and stellar magnetic field. Since the sun is only a star whose magnetic field can be directly observed, the understanding of solar dynamo can provide clues to clarify dynamo mechanisms. On the other hand, because solar activities, which are caused by solar dynamo, can influence the Earth's climate, solar variability is an important issue also to understand long-term evolution of the Earth's climate. It is widely known that the polarity of the solar magnetic fields on the north and south poles periodically reverses at every sunspot maxima. It is also known that the reversal at one pole is followed by that on the other pole. The time difference of magnetic field reversal between the poles was first noted by Babcock (1959) from the very first observation of polar field. Recently, it was confirmed by detailed observations with the HINODE satellite (Shiota et al. 2012). Svalgaard and Kamide (2013) indicated that there is a relationship between the time difference of the polarity reversal and the hemispheric asymmetry of the sunspot activity. However, the mechanisms for the hemispheric asymmetry are still open to be revealed. In this paper, we study the asymmetric feature of the solar dynamo based on the flux transport dynamo model (Chatterjee et al. 2004) to explain the time difference of magnetic polarity reversal between the north and south poles. In order to calculate long-term variations of solar activities, we use the mean field kinematic dynamo model, which is derived from magnetohydrodynamics (MHD) equation through the mean field and other approximations. We carried out the mean field dynamo simulations using the updated SURYA code which was developed originally by Choudhuri and his collaborators (2004). We decomposed the symmetric and asymmetric components of magnetic field, which correspond respectively to the

  9. Intermittent turbulence in solar wind from the south polar hole

    NASA Technical Reports Server (NTRS)

    Ruzmaikin, A. A.; Feynman, J.; Goldstein, B. E.; Smith, E. J.; Balogh, A.

    1995-01-01

    The magnetic fields measured by the Ulysses spacecraft are used to study solar wind turbulence in the fast solar wind from the south polar hole. The spacecraft was at about 46 deg south latitude and 3.9 AU. For a magnetic field with a Gaussian distribution the power spectrum (second-order structure function) is sufficient to completely characterize the turbulence. However, the actual distribution is non-Gaussian so that the effects of intermittency must be taken into account. The observed spectral exponents include effects of intermittency and cannot be directly compared with the standard second-order spectral theories such as the Kolmogorov and Kraichnan theories. To permit a better comparison of the observations with the theoretical models, we study the structure characteristics of the data. We find the exponents of the second-order structure functions (power spectra) and the higher-order normalized structure functions for the components of the magnetic fields. We show that these sets of exponents can be approximately described by two basic numbers: the spectral exponent and the intermittency exponent. The intermittency exponent characterizes correlation properties of the energy cascade from large to small scales. Before comparing the observations to the theoretically expected values, a reduction must be made to the observed spectral exponent. The amount of the reduction depends on both the intermittency exponent and the model of the energy cascade assumed in the turbulence theory. We reduce the measured spectral indices according to a simple model for Alfven turbulence that is described here. We then compare our reduced spectral indices with second-order spectral theory. The reduced spectral indices for the period range of 1 min to about a half hour are remarkably constant and in good agreement with the value of 3/2. Thus our treatment is self-consistent. Our tentative conclusion is that the high-frequency turbulence appears to agree with the model of random

  10. CO_2 Frost Halos on the South Polar Residual Cap of Mars

    NASA Astrophysics Data System (ADS)

    Becerra, P.; Byrne, S.; HiRISE Team

    2012-03-01

    We present observational analysis, and a numerical model to explain the formation of bright CO_2 frost halos seen by HiRISE on the edges of scarps and "swiss cheese" features in the south polar residual cap of Mars.

  11. Evolution of sunspot activity and inversion of the Sun's polar magnetic field in the current cycle

    NASA Astrophysics Data System (ADS)

    Mordvinov, A. V.; Grigoryev, V. M.; Erofeev, D. V.

    2015-06-01

    A spatiotemporal analysis of the Sun's magnetic field was carried out to study the polar-field inversion in the current cycle in relation to sunspot activity. The causal relationship between these phenomena was demonstrated in a time-latitude aspect. After decay of long-lived activity complexes their magnetic fields were redistributed into the surrounding photosphere and formed unipolar magnetic regions which were transported to high latitudes. Zones of intense sunspot activity during 2011/2012 produced unipolar magnetic regions of the following polarities, whose poleward drift led to the inversion of the Sun's polar fields at the North and South Poles. At the North Pole the polar field reversal was completed by May 2013. It was demonstrated that mixed magnetic polarities near the North Pole resulted from violations of Joy's law at lower latitudes. Later sunspot activity in the southern hemisphere has led to a delay in magnetic polarity reversal at the South Pole. Thus, the north-south asymmetry of sunspot activity resulted in asynchronous polar field reversal in the current cycle.

  12. Internal structure of the Martian south polar layered deposits

    NASA Astrophysics Data System (ADS)

    Byrne, S.; Ivanov, A. B.

    2004-11-01

    We investigate the three-dimensional (3-D) stratigraphic structure of the south polar layered deposits (SPLD) on Mars. Prominent bench-forming layers exposed on SPLD scarps were observed and mapped in three dimensions using high-resolution topographic and imaging data sets. Using the 3-D location of exposures of one of these strata, we can accurately describe the shape of that layer using simple mathematical functions. Analysis of these functions and the surface topography can be used to reliably predict where on other scarps this layer is exposed. In general this bench-forming layer (and its surrounding strata) is not flat and is well approximated as a parabolic dome near the center of the SPLD. Its curvature indicates that when deposited it was draped over a topographic dome similar in size to that of the present day. The scarps in which this layer is exposed must have formed subsequently and have not been significantly modified by flow processes. The basement topography exercises some control over the shape of the interior strata in extreme cases. Our successful layer-fitting technique illustrates the regional uniformity in layer formation and the lack of major internal defects (such as faulting) within the SPLD. We have mapped exposures of what appear to be this layer in scarps farther from the center of the deposits. The position of these exposures can be used to modify the modeled parabolic shape at the periphery of the SPLD. These peripheral elevations provide constraints on the role of flow in the overall shaping of the SPLD.

  13. Spatial variability in the seasonal south polar CAP of Mars

    NASA Astrophysics Data System (ADS)

    Calvin, Wendy M.; Martin, Terry Z.

    1994-10-01

    The first comprehensive discussion of the south seasonal polar cap spectra obtained by the Mariner 7 infrared spectrometer in the short-wavelength region (2-4 microns) is presented. The infrared spectra is correlated with images acquired by the wide-angle camera. Significant spectral variation is noted in the cap interior and regions of varying water frost abundance, CO2 ice/frost cover, and CO2-ice path length can be distinguished. Many of these spectral variations correlate with heterogeneity noted in the camera images, but certain significant infrared spectral variations are not discernible in the visible. Simple reflectance models are used to classify the observed spectral variations into four regions. Region I is at the cap edge, where there is enhanced absorption beyond 3 microns inferred to be caused by an increased abundance of water frost. The increase in water abundance over that in the interior is on the level of a few parts per thousand or less. Region II is the typical cap interior characterized by spectral features of CO2 ice at grain sizes of several millimeters to centimeters. These spectra also indicate the presence of water frost at the parts per thousand level. A third, unusual region (III), is defined by three spectra in which weak CO2 absorption features are as much as twice as strong as in the average cap spectra and are assumed to be caused by an increased path length in the CO2. Such large paths are inconsistent with the high reflectance in the visible and at 2.2 microns and suggest layered structures or deposition conditions that are not accounted for in current reflectance models. The final region (IV) is an area of thinning frost coverage or transparent ice well in the interior of the seasonal cap. These spectra are a combination of CO2 and ground signatures.

  14. Continuous Lidar Monitoring of Polar Stratospheric Clouds at the South Pole

    NASA Technical Reports Server (NTRS)

    Campbell, James R.; Welton, Ellsworth J.; Spinhirne, James D

    2009-01-01

    Polar stratospheric clouds (PSC) play a primary role in the formation of annual ozone holes over Antarctica during the austral sunrise. Meridional temperature gradients in the lower stratosphere and upper troposphere, caused by strong radiative cooling, induce a broad dynamic vortex centered near the South Pole that decouples and insulates the winter polar airmass. PSC nucleate and grow as vortex temperatures gradually fall below equilibrium saturation and frost points for ambient sulfate, nitrate, and water vapor concentrations (generally below 197 K). Cloud surfaces promote heterogeneous reactions that convert stable chlorine and bromine-based molecules into photochemically active ones. As spring nears, and the sun reappears and rises, photolysis decomposes these partitioned compounds into individual halogen atoms that react with and catalytically destroy thousands of ozone molecules before they are stochastically neutralized. Despite a generic understanding of the ozone hole paradigm, many key components of the system, such as cloud occurrence, phase, and composition; particle growth mechanisms; and denitrification of the lower stratosphere have yet to be fully resolved. Satellite-based observations have dramatically improved the ability to detect PSC and quantify seasonal polar chemical partitioning. However, coverage directly over the Antarctic plateau is limited by polar-orbiting tracks that rarely exceed 80 degrees S. In December 1999, a NASA Micropulse Lidar Network instrument (MPLNET) was first deployed to the NOAA Earth Systems Research Laboratory (ESRL) Atmospheric Research Observatory at the Amundsen-Scott South Pole Station for continuous cloud and aerosol profiling. MPLNET instruments are eye-safe, capable of full-time autonomous operation, and suitably rugged and compact to withstand long-term remote deployment. With only brief interruptions during the winters of 2001 and 2002, a nearly continuous data archive exists to the present.

  15. Ir Spectral Mapping of the Martian South Polar Residual CAP Using Crism

    NASA Astrophysics Data System (ADS)

    Campbell, Jacqueline; Sidiropoulos, Panagiotis; Muller, Jan-Peter

    2016-06-01

    Polycyclic aromatic hydrocarbons (PAHs) are considered to be important in theories of abiogenesis (Allamandola, 2011) . There is evidence that PAHs have been detected on two icy Saturnian satellites using the Visual and Infrared Mapping Spectrometer (VIMS) on the Cassini spacecraft (Cruikshank et al., 2007). The hypothesised presence of PAHs in Mars south polar cap has not been systematically examined even though the Mars south polar cap may allow the preservation of organic molecules that are typically destroyed at the Martian surface by UV radiation (Dartnell et al. 2012). This hypothesis is supported by recent analyses of South Polar Residual Cap (SPRC) structural evolution (Thomas et al., 2009) that suggest the possibility that seasonal and long term sublimation may excavate dust particles from within the polar ice. Periodic sublimation is believed to be responsible for the formation of so-called "Swiss Cheese Terrain", a unique surface feature found only in the Martian south polar residual cap consisting of flat floored, circular depressions (Byrne, 2009). We show the first examples of work towards the detection of PAHs in Swiss Cheese Terrain, using data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), on board NASA's Mars Reconnaissance Orbiter (MRO). CRISM is designed to search for mineralogical indications of past and present water, thus providing extensive coverage of the south polar cap. In this work, we discuss whether CRISM infrared spectra can be used to detect PAHs in Swiss Cheese Terrain and demonstrate a number of maps showing shifts in spectral profiles over the SPRC.

  16. High Latitude Meridional Flow on the Sun May Explain North-South Polar Field Asymmetry

    NASA Technical Reports Server (NTRS)

    Kosak, Katie; Upton, Lisa; Hathaway, David

    2012-01-01

    We measured the flows of magnetic elements on the Sun at very high latitudes by analyzing magnetic images from the Helioseismic and Magnetic Imager (HMI) on the NASA Solar Dynamics Observatory (SDO) Mission. Magnetic maps constructed using a fixed, and north-south symmetric, meridional flow profile give weaker than observed polar fields in the North and stronger than observed polar fields in the South during the decline of Cycle 23 and rise of Cycle 24. Our measurements of the meridional flow at high latitudes indicate systematic north-south differences. In the fall of 2010 (when the North Pole was most visible), there was a strong flow in the North while in the spring of 2011 (when the South Pole was most visible) the flow there was weaker. With these results, we have a possible solution to this polar field asymmetry. The weaker flow in the South should keep the polar fields from becoming too strong while the stronger flow in the North should strengthen the field there. In order to gain a better understanding of the Solar Cycle and magnetic flux transport on the Sun, we need further observations and analyses of the Sun s polar regions in general and the polar meridional flow in particular.

  17. High Latitude Meridional Flow on the Sun May Explain North-South Polar Field Asymmetry

    NASA Technical Reports Server (NTRS)

    Kosak, Katie; Upton, Lisa; Hathaway, David

    2012-01-01

    We measured the flows of magnetic elements on the Sun at very high latitudes by analyzing magnetic images from the Helioseismic and Magnetic Imager (HMI) on the NASA Solar Dynamics Observatory (SDO) Mission. Magnetic maps constructed using a fixed, and north-south symmetric, meridional flow profile give weaker than observed polar fields in the North and stronger than observed polar fields in the South during the decline of Cycle 23 and rise of Cycle 24. Our measurements of the meridional flow at high latitudes indicate systematic north-south differences. There was a strong flow in the North while the flow in the South was weaker. With these results, we have a possible solution to the polar field asymmetry. The weaker flow in the South should keep the polar fields from becoming too strong while the stronger flow in the North should strengthen the field there. In order to gain a better understanding of the Solar Cycle and magnetic flux transport on the Sun, we need further observations and analyses of the Sun's polar regions in general and the polar meridonal flow in particular.

  18. High Latitude Meridional Flow on the Sun May Explain North-South Polar Field Asymmetry

    NASA Technical Reports Server (NTRS)

    Kosak, Katie; Upton, Lisa; Hathaway, David

    2012-01-01

    We measured the flows of magnetic elements on the Sun at very high latitudes by analyzing magnetic images from the Helioseismic and Magnetic Imager (HMI) on the NASA Solar Dynamics Observatory (SDO) Mission. Magnetic maps constructed using a fixed, and north ]south symmetric, meridional flow profile give weaker than observed polar fields in the North and stronger than observed polar fields in the South during the decline of Cycle 23 and rise of Cycle 24. Our measurements of the meridional flow at high latitudes indicate systematic north ]south differences. There was a strong flow in the North while the flow in the South was weaker. With these results, we have a possible solution to the polar field asymmetry. The weaker flow in the South should keep the polar fields from becoming too strong while the stronger flow in the North should strengthen the field there. In order to gain a better understanding of the Solar Cycle and magnetic flux transport on the Sun, we need further observations and analyses of the Sun fs polar regions in general and the polar meridional flow in particular

  19. Areas of permanent shadow in Mercury's south polar region ascertained by MESSENGER orbital imaging

    NASA Astrophysics Data System (ADS)

    Chabot, Nancy L.; Ernst, Carolyn M.; Denevi, Brett W.; Harmon, John K.; Murchie, Scott L.; Blewett, David T.; Solomon, Sean C.; Zhong, Ellen D.

    2012-05-01

    Radar-bright features near Mercury's poles have been postulated to be deposits of water ice trapped in cold, permanently shadowed interiors of impact craters. From its orbit about Mercury, MESSENGER repeatedly imaged the planet's south polar region over one Mercury solar day, providing a complete view of the terrain near the south pole and enabling the identification of areas of permanent shadow larger in horizontal extent than approximately 4 km. In Mercury's south polar region, all radar-bright features correspond to areas of permanent shadow. Application of previous thermal models suggests that the radar-bright deposits in Mercury's south polar cold traps are in locations consistent with a composition dominated by water ice provided that some manner of insulation, such as a thin layer of regolith, covers many of the deposits.

  20. Active Polar Two-Fluid Macroscopic Dynamics

    NASA Astrophysics Data System (ADS)

    Pleiner, Harald; Svensek, Daniel; Brand, Helmut R.

    2014-03-01

    We study the dynamics of systems with a polar dynamic preferred direction. Examples include the pattern-forming growth of bacteria (in a solvent, shoals of fish (moving in water currents), flocks of birds and migrating insects (flying in windy air). Because the preferred direction only exists dynamically, but not statically, the macroscopic variable of choice is the macroscopic velocity associated with the motion of the active units. We derive the macroscopic equations for such a system and discuss novel static, reversible and irreversible cross-couplings connected to this second velocity. We find a normal mode structure quite different compared to the static descriptions, as well as linear couplings between (active) flow and e.g. densities and concentrations due to the genuine two-fluid transport derivatives. On the other hand, we get, quite similar to the static case, a direct linear relation between the stress tensor and the structure tensor. This prominent ``active'' term is responsible for many active effects, meaning that our approach can describe those effects as well. In addition, we also deal with explicitly chiral systems, which are important for many active systems. In particular, we find an active flow-induced heat current specific for the dynamic chiral polar order.

  1. Actively Contracting Bundles of Polar Filaments

    NASA Astrophysics Data System (ADS)

    Kruse, K.; Jülicher, F.

    2000-08-01

    We introduce a phenomenological model to study the properties of bundles of polar filaments which interact via active elements. The stability of the homogeneous state, the attractors of the dynamics in the unstable regime, and the tensile stress generated in the bundle are discussed. We find that the interaction of parallel filaments can induce unstable behavior and is responsible for active contraction and tension in the bundle. The interaction between antiparallel filaments leads to filament sorting. Our model could apply to simple contractile structures in cells such as stress fibers.

  2. Magnetic Cloud Polarity and Geomagnetic Activities over Three Solar Cycles

    NASA Astrophysics Data System (ADS)

    Li, Y.; Luhmann, J.

    2006-12-01

    Interplanetary coronal mass ejections (ICMEs) that show fluxrope magnetic structures are named magnetic clouds (MCs). Majority of the MCs exhibit bipolar signature in their north-south component (Bz) in IMF measurements. The Bz component of a bipolar cloud is either NS (north first then turning south as the MC traverses the spacecraft) or SN. Studies show that the occurrence of these two types of MCs has some solar cycle dependence. However it appears to be a complex relationship as the switch between the two types of MCs is not concurrent with either the solar polar reversal or the time of the sunspot minimum when the new cycle sunspots start to appear. In this paper, we use ACE solar wind and IMF observations to obtain the most updated MC signatures and their temporal variation. In combination with our previously published results, we analyze MC polarity variations over the three solar cycles of 21, 22 and 23. Interpretations in terms of their solar sources will be attempted. On the other hand, the geomagnetic activities over the same solar cycles will be studied using geomagnetic indices. The geoeffectiveness of the MC will be evaluated in the aid of Dst indices.

  3. Pattern formation in Active Polar Fluids

    NASA Astrophysics Data System (ADS)

    Gopinath, Arvind; Hagan, Michael; Baskaran, Aparna

    2011-03-01

    Systems such as bacterial suspensions or cytoskeletal filaments and motility assays can be described within the paradigm of active polar fluids. These systems have been shown to exhibit pattern formation raging from asters and vortices to traveling stripes. A coarse-grained description of such a fluid is given by a scalar density field and a vector polarization field. We study such a macroscopic description of the system using weakly nonlinear analysis and numerical simulations to map out the emergent pattern formation as a function of the hydrodynamic parameters in the context of two specific microscopic models - a quasi-2D suspension of cytoskeletal filaments and motor proteins and a system of self propelled hard rods that interact through excluded volume interactions. The authors thank the Brandeis MRSEC center for financial support.

  4. Infrared and Visible Observations of South Polar Spots and Fans

    NASA Astrophysics Data System (ADS)

    Christensen, P. R.; Kieffer, H. H.; Titus, T. N.

    2005-12-01

    A variety of relatively low-albedo features that form in regions of the south polar cap during early spring have been previously reported. Four types of these dark features have been recognized: spots, fans, blotches, and halos. The spots are typically <15-50 m in diameter with typical spacings of several 100 m. Fans are 10's to 100's of m in length, 10-30 deg. in angular size, typically originate from a preexisting dark spot, and all point in a similar direction within a given area. Blotches are larger than spots, 100's of m to 10's of km in size, with less distinct boundaries, and, unlike most spots, have albedo patterns that match from winter to summer. Halos are roughly circularly symmetric annuli 10's to 100's of m in diameter surrounding spots. All of these features are only slightly darker than the surrounding ice, with TES-derived albedos of 0.22 versus 0.23 for the ice. We have observed these features with THEMIS in 100-m per pixel infrared and 18-m per pixel visible imaging, focusing intensely on a specific region (99 E, 86.2 S) where spot and fan formation was observed the previous Mars year. A few dark spots form before sunrise, with significant spot formation occurring immediately following sunrise. A large number of spots form fans within 10-20 days. All of these features are within 5 C of CO2 ice temperatures, indicating that they must be must be a very thin layer (<1 mm) that is on top of the CO2 ice, and do not represent surface defrosting. H. Kieffer initially developed a conceptual model to account for the observed observations of the spots, fans, and blotches. In this model relatively dark, granular material lies at the surface during summer. One to two meters of CO2 ice forms the residual cap during winter. This ice anneals to form a translucent slab, allowing sunlight to penetrate to the subsurface, and forming an impermeable layer. After sunrise, insolation reaches and heats the substrate, leading to sublimation of the CO2 ice from the base

  5. Why is the north polar cap on Mars different than the south polar cap?

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard Lee

    1994-01-01

    One of the most puzzling mysteries about the planet Mars is the hemispherical asymmetry in the polar caps. Every spring the seasonal polar cap of CO2 recedes until the end of summer, when only a small part, the residual polar cap, remains. During the year that Viking observed Mars, the residual polar cap was composed of water ice in the northern hemisphere but was primarily carbon dioxide ice in the southern hemisphere. Scientists have sought to explain this asymmetry by modeling observations of the latitudinal recession of the polar cap and seasonal variations in atmospheric pressure (since the seasonal polar caps are primarily frozen atmosphere, they are directly related to changes in atmospheric mass). These models reproduce most aspects of the observed annual variation in atmospheric pressure fairly accurately. Furthermore, the predicted latitudinal recession of the northern polar cap in the spring agrees well with observations, including the fact that the CO2 ice is predicted to completely sublime away. However, these models all predict that the carbon dioxide ice will also sublime away during the summer in the southern hemisphere, unlike what is observed. This paper will show how the radiative effects of ozone, clouds, airborne dust, light penetration into and through the polar cap, and the dependence of albedo on solar zenith angle affect CO2 ice formation and sublimation, and how they help explain the hemispherical asymmetry in the residual polar caps. These effects have not been studied with prior polar cap models.

  6. Different pathways of macrophage activation and polarization.

    PubMed

    Juhas, Ulana; Ryba-Stanisławowska, Monika; Szargiej, Patryk; Myśliwska, Jolanta

    2015-01-01

    Monocytes are short-lived cells and undergo spontaneous apoptosis every day. Inflammatory responses may induce dramatic up-regulation of monocyte survival and differentiation. When monocytes are recruited to an area of infection they may differentiate into macrophages. In different microenvironments macrophages polarize into two types. The M1 or classically activated macrophages are characterized by the high ability to produce pro-inflammatory cytokines and the production of NO through the induced synthesis of iNOS. The M2 or alternatively activated macrophages are divided into 3 subtypes, M2 a, b and c, and they have anti-inflammatory properties. Mediators of M1 macrophage TLR-dependent polarization include transcription factors such as NF-κB, AP-1, PU.1, CCAAT/enhancer-binding protein α (C/EBP-α), STAT1 as well as interferon regulatory factor 5 (IRF5), while the transcription factors which promote M2 activation include IRF4, C/EBP-β, Krüppel-like factor 4 (KLF4), STAT6 and PPARγ receptor. PMID:25983288

  7. Mars south polar spring and summer temperatures - A residual CO2 frost

    NASA Technical Reports Server (NTRS)

    Kieffer, H. H.

    1979-01-01

    Viking infrared thermal mapper (IRTM) energy measurements over the Mars south polar cap throughout the Martian spring and summer revealed complex spatial, spectral, and temporal variations. High albedos did not directly correspond with low temperatures, and as the cap shrank to its residual position, it maintained large differences in brightness temperature between the four IRTM surface-sensing bands at 7, 9, 11, and 20 microns. The late summer infrared spectral pattern can be matched by a surface consisting of CO2 frost with 20 micron emissivity of 0.8 and about 6% dark, warm soil under a dusty atmosphere of moderate infrared opacity and spectral properties similar to those measured for the Martian global dust storms. Low temperature, the absence of appreciable water vapor in the south polar atmosphere, and the absence of surface warming expected if H2O were to become exposed, all imply that the residual south polar cap was covered by solid CO2.

  8. North-south asymmetries in the polar thermosphere-ionosphere system: Solar cycle and seasonal influences

    NASA Astrophysics Data System (ADS)

    Cnossen, Ingrid; Förster, Matthias

    2016-01-01

    Previous studies have revealed that ion drift and neutral wind speeds at ~400 km in the polar cap (>80° magnetic latitude) are on average larger in the Northern Hemisphere (NH) than in the Southern Hemisphere, which is at least partly due to asymmetry in the geomagnetic field. Here we investigate for the first time how these asymmetries depend on season and on solar/geomagnetic activity levels. Ion drift measurements from the Cluster mission show little seasonal dependence in their north-south asymmetry when all data (February 2001-December 2013) are used, but the asymmetry disappears around June solstice for high solar activity and around December solstice for low solar activity. Neutral wind speeds in the polar cap obtained from the Challenging Minisatellite Payload spacecraft (January 2002-December 2008) are always larger in the summer hemisphere, regardless of solar activity, but the high-latitude neutral wind vortices at dawn and dusk tend to be stronger in the NH, except around December solstice, in particular, when solar activity is low. Simulations with the Coupled Magnetosphere-Ionosphere-Thermosphere (CMIT) more or less capture the behavior of the ion drift speeds, which can be explained as a superposition of seasonal and geomagnetic field effects, with the former being stronger for higher solar activity. The behavior of the neutral wind speed and vorticity is not accurately captured by the model. This is probably due to an incorrect seasonal cycle in plasma density around ~400 km in CMIT, which affects the ion drag force. This must be addressed in future work.

  9. Atmospheric Modeling of the Martian Polar Regions: CRISM EPF Coverage During the South Polar Spring Recession

    NASA Astrophysics Data System (ADS)

    Brown, A. J.; McGuire, P.; Wolff, M. J.

    2008-03-01

    We describe efforts to model dust and ice aerosols content and soils and icy surface reflectance in the Martian southern polar region during spring recession (Ls = 152-320) using CRISM emission phase function (EPF) observations.

  10. Possible recent and ancient glacial ice flow in the south polar region of Mars

    NASA Technical Reports Server (NTRS)

    Kargel, J. S.

    1992-01-01

    Martian polar science began almost as soon as small telescopes were trained on the planet. The seasonal expansion and contraction of the polar caps and their high albedoes led most astronomers to think that water ice is the dominant constituent. In 1911 Lowell perceived a bluish band around the retreating edge of the polar caps, and interpreted it as water from melting polar ice and seasonal snow. An alternative idea in his time was that the polar caps consist of frozen carbonic acid. Lowell rejected the carbonic acid hypothesis on account of his blue band. He also pointed out that carbonic acid would sublimate rather than melt at confining pressures near and below one bar, hence, carbonic acid could not account for the blue band. In comparing Lowell's theories with today's knowledge, it is recognized that (1) sublimation is mainly responsible for the growth and contraction of Mars' polar caps, (2) carbon dioxide is a major component of the southern polar cap, and (3) Lowell's blue band was probably seasonal dust and/or clouds. Geomorphic evidence that glacial ice and glacial melt waters once flowed over broad areas of the southern polar region. Two aspects of the south polar region suggest possible glacial processes during two distinct eras in Mars' history.

  11. Seasonal recession of Mars' south polar cap as seen by Viking

    NASA Technical Reports Server (NTRS)

    James, P. B.; Briggs, G.; Barnes, J.; Spruck, A.

    1979-01-01

    The spring-summer retreat of the south polar cap of Mars is portrayed in photomosaics obtained by Viking Orbiter 2 during 1977. Comparisons of these data to Mariner 9 photos and to the record of telescopic observations attest that the polar retreat viewed by Viking was significantly slower than those previously reported. A global dust storm which occurred at an unusually early season may have effected this retarded recession by introducing dust into the atmosphere of Mars which modified the polar energy balance through scattering of incident radiation. The composition of the south residual cap cannot be unambiguously determined at this time; however, some data suggest that CO2 or clathrate survived the entire summer viewed by Viking.

  12. Mariner 9 observations of the south polar cap of Mars - Evidence for residual CO2 frost

    NASA Technical Reports Server (NTRS)

    Paige, D. A.; Herkenhoff, K. E.; Murray, B. C.

    1990-01-01

    The first spacecraft observations of the south residual polar cap of Mars were obtained by the Mariner 9 orbiter during the Martian southern summer season, 1971-1972. Analyses of Viking orbiter observations obtained 3 Mars years later have shown that residual carbon dioxide frost was present at the south polar cap in 1977. In this study, Mariner 9 infrared interferometer spectrometer spectra and television camera images are used in conjuction with multispectral thermal emission models to constrain the temperatures of dark bare ground and bright frost regions within the south residual cap. The results provide strong evidence that carbon dioxide frost was present throughout the summer season despite the fact that the residual frost deposits observed by Mariner 9 were less extensive than those observed by Viking.

  13. Jupiter's north and south polar aurorae with IUE data

    NASA Technical Reports Server (NTRS)

    Livengood, T. A.; Moos, H. W.

    1990-01-01

    Observations of Jupiter's auroral H2 emissions with the IUE spacecraft, from 1978 through 1990, show that aurorae at the two poles are similar in several respects: (1) emission intensity is modulated with magnetic longitude, north peak emission at lambda (III) (1965) 200 deg, south peak at (1965) about 20 deg; (2) emission intensity and degree of modulation are comparable for both poles; and (3) attenuation by hydrocarbons varies in phase with the intensity, peak attenuation coinciding approximately with peak emission. Increases in the hydrocarbon column are an indicator of either enhanced penetration depth and, thus, energy of the auroral primaries, or of increases in the high-altitude hydrocarbon content caused by modification of the local atmosphere.

  14. Polarization rotator-splitters in standard active silicon photonics platforms.

    PubMed

    Sacher, Wesley D; Barwicz, Tymon; Taylor, Benjamin J F; Poon, Joyce K S

    2014-02-24

    We demonstrate various silicon-on-insulator polarization management structures based on a polarization rotator-splitter that uses a bi-level taper TM0-TE1 mode converter. The designs are fully compatible with standard active silicon photonics platforms with no new levels required and were implemented in the IME baseline and IME-OpSIS silicon photonics processes. We demonstrate a polarization rotator-splitter with polarization crosstalk < -13 dB over a bandwidth of 50 nm. Then, we improve the crosstalk to < -22 dB over a bandwidth of 80 nm by integrating the polarization rotator-splitter with directional coupler polarization filters. Finally, we demonstrate a polarization controller by integrating the polarization rotator-splitters with directional couplers, thermal tuners, and PIN diode phase shifters. PMID:24663698

  15. Bright Lower Echo in Radargram of South Polar Layered Deposits

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [figure removed for brevity, see original site] Annotated Version

    The upper image is a radargram from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS), showing data from the subsurface of Mars in the ice-rich layered deposits that surround the south pole. The lower image shows the position of the ground track (white line) on a topographic map of the area based on Mars Orbiter Laser Altimeter data. The images are 1,250 kilometers (775 miles) wide.

    The MARSIS echo trace splits into two traces on the left side of the image, at the point where the ground track crosses from the surrounding plains onto the elevated layered deposits. The upper trace is the echo from the surface of the deposits, while the lower trace is interpreted to be the boundary between the lower surface of the deposits and the underlying material. The strength of the lower echo suggests that the intervening material is nearly pure water ice. Near the image center, the bright lower echo abruptly disappears for unknown reasons. The time delay between the two echoes reaches a maximum of 42 microseconds left of center, corresponding to a thickness of 3.5 kilometers (2.2 miles) of ice. The total elevation difference shown in the topographic map is about 4 kilometers (2.5 miles) between the lowest surface (purple) and the highest (red).

    MARSIS is an instrument on the European Space Agency's Mars Express orbiter. NASA and the Italian Space Agency jointly funded the instrument. The Mars Orbiter Laser Altimeter flew on NASA's Mars Global Surveyor orbiter.

  16. Comparison Between North and South Near Polar Regions of Mars from HEND/Odyssey Data

    NASA Technical Reports Server (NTRS)

    Litvak, M. L.; Mitrofanov, I. G.; Kozyrev, A. S.; Sanin, A. B.; Tretyakov, V.; Boynton, W. V.; Hamara, D. K.; Shinohara, C.; Saunders, R. S.; Drake, D.

    2003-01-01

    It is known that North and South near polar regions are affected by global redistribution of atmospheric CO2. The maximal thickness of CO2 snow depth may be as high as 1 m at latitudes close to martian poles. It explains why neutron flux above martian poles significantly varies from summer to winter seasons. It occurs because CO2 frost hides upper surface layer from the orbit observations. This fact was used to estimate thickness of CO2 deposit at different latitudes. Here we suggest to make comparison between martian near polar regions in both ways as in terms of subsurface regolith structure as in terms of distribution of CO2 deposits.

  17. Unusual Polar Activity of the Sun in the Northern Hemisphere and Its Implications for Solar Cycle 25

    NASA Astrophysics Data System (ADS)

    Gopalswamy, Nat; Masuda, Satoshi; Yashiro, Seiji; Akiyama, Sachiko; Shibasaki, Kiyoto

    2016-07-01

    Polar field strength in one solar cycle is known to indicate the strength (e.g., Sunspot number) and phase of the next cycle. In particular the polar field strength (or its proxies such as the polar coronal hole area and microwave polar brightness) during the minimum phase of a given cycle seem to be well correlated with the maximum sunspot number of the next cycle. Polar prominence eruptions and coronal mass ejections have also been found to be indicators of low polar field; their cessation signals the time of polarity reversal. While these indicators are present in the current cycle, significant differences are found regarding the phase lag between the two hemispheres and the duration of polar eruptions. We use data from the Nobeyama Radioheliograph, the Solar Dynamics Observatory, SOLIS, and Wilcox Solar Observatory to highlight these differences. We find that the north polar region of the Sun has near-zero field strength for more than three years. This is unusually long and caused by surges of both polarities heading toward the north pole that prevent the buildup of the polar field. This seems to be due to anti-Hale active regions that appeared around the 2012 peak sunspot activity in the northern hemisphere. The unusual condition is consistent with (i) the continued high-latitude prominence eruption, (ii) the extended period of high tilt angle of the heliospheric current sheet, (iii) the weak microwave polar brightness, and (iv) the lack of north polar coronal hole. On the other hand, the south polar field has started building up and the coronal hole has appeared in early 2015 because of large active regions of the correct tilt in the southern hemisphere during the 2014 peak of sunspot activity. The extended period of near-zero field in the north polar region should result in very weak and delayed sunspot activity in the northern hemisphere in cycle 25. On the other hand the south polar field has already increased significantly, suggesting that the activity in

  18. Buried CO2 Ice traces in South Polar Layered Deposits of Mars detected by radar sounder

    NASA Astrophysics Data System (ADS)

    Castaldo, L.; Mège, D.; Orosei, R.; Séjourné, A.

    2014-12-01

    SHARAD (SHAllow RADar) is the subsurface sounding radar provided by the Italian Space Agency (ASI) as a facility instrument to NASA's 2005 Mars Reconnaissance Orbiter (MRO). The Reduced Data Record of SHARAD data covering the area of the South Polar Layered Deposits (SPLD), has been used. The elaboration and interpretation of the data, aimed to estimate electromagnetic properties of surface layers, has been performed in terms of permittivity. The theory of electromagnetic scattering from fractal surfaces, and the estimation of geometric parameters from topographic data by Mars Orbiter Laser Altimeter (MOLA) which was one of five instruments on board the Mars Global Surveyor (MGS) spacecraft, has been used. A deep analysis of inversion has been made on all Mars and extended to the South Polar Caps in order to extract the area with a permittivity constant of CO2 ice. Several corrections have been applied to the data, moreover the calibration of the signal requires the determination of a constant that takes into account the power gain due to the radar system and the surface in order to compensate the power losses due to the orbitographic phenomena. The determination of regions with high probability of buried CO2 ice in the first layer of the Martian surface, is obtained extracting the real part of the permittivity constant of the CO2 ice (~2), estimated by other means. The permittivity of CO2ice is extracted from the Global Permittivity Map of Mars using the global standard deviation of itself as following: ɛCO2ice=ɛCO2ice+ Σ (1)where Σ=±std(ɛMapMars)/2Figure 1(a) shows the south polar areas where the values of the permittivity point to the possibility of a CO2 ice layer. Figure 1(b) is the corresponding geologic map. The comparison between the two maps indicates that the area with probable buried CO2 overlaps Hesperian and Amazonian polar units (Hp, Hesperian plains-forming deposits marked by narrow sinuous, anabranching ridges and irregular depressions, and

  19. Large Grooves in the South Polar Layered Deposits: Insights from Spacecraft Data and Terrestrial Analogs

    NASA Technical Reports Server (NTRS)

    Bridges, N. T.; Herkenhoff, K. E.

    2000-01-01

    The Martian polar layered deposits (PLD) are probably the best source of information about the recent climate history of Mars, but their origin and the mechanisms of accumulation are still a mystery. The polar layers are sedimentary deposits that most planetary scientists believe are composed of water ice and varying amounts of wind-blown dust, although their composition is poorly constrained. Interpretation of the observed polar stratigraphy in terms of global climate changes is complicated by the significant difference in surface ages between the north and south PLD inferred from crater statistics. The study reported here was undertaken as part of the landing site selection effort for the Mars Polar Lander (MPL) and Deep Space 2 (DS2) missions that made use of all available data. We used Mariner 9, Viking, and Mars Global Surveyor images of the south PLD in the area accessible to MPL and DS2 to evaluate the topography and morphology of grooves, terraced layers, and other features. Here we report on results from grooves that appear to have been carved by strong winds. Because these features are found throughout the interior of the PLD, where MPL and DS2 were targeted to land, their topographic characteristics were judged as important input for landing site safety assessment. The characteristics of the grooves also provide constraints and insights into aeolian processes in the polar regions and the effects these have on PLD ablation. Our results indicate that these grooves do not represent landing hazards at the scale of the images (approx. 80 m/pixel). Their topography and shape do not seem correlated with south PLD layering. No Earth analog of suitable scale exists, although the grooves bear some resemblance to smaller terrestrial deflation hollows found in soft sediment and ice. Additional information is contained in original extended abstract.

  20. North-south asymmetry in the magnetic deflection of polar coronal hole jets

    NASA Astrophysics Data System (ADS)

    Nisticò, G.; Zimbardo, G.; Patsourakos, S.; Bothmer, V.; Nakariakov, V. M.

    2015-11-01

    Context. Measurements of the sunspots area, of the magnetic field in the interplanetary medium, and of the heliospheric current sheet (HCS) position, reveal a possible north-south (N-S) asymmetry in the magnetic field of the Sun. This asymmetry could cause the bending of the HCS of the order of 5-10 deg in the southward direction, and it appears to be a recurrent characteristic of the Sun during the minima of solar activity. Aims: We study the N-S asymmetry as inferred from measurements of the deflection of polar coronal hole jets when they propagate throughout the corona. Methods: Since the corona is an environment where the magnetic pressure is greater than the kinetic pressure (β ≪ 1), we can assume that the magnetic field controls the dynamics of plasma. On average, jets follow magnetic field lines during their propagation, highlighting their local direction. We measured the position angles at 1 R⊙ and at 2 R⊙ of 79 jets, based on the Solar TErrestrial RElations Observatory (STEREO) ultraviolet and white-light coronagraph observations during the solar minimum period March 2007-April 2008. The average jet deflection is studied both in the plane perpendicular to the line of sight and, for a reduced number of jets, in 3D space. The observed jet deflection is studied in terms of an axisymmetric magnetic field model comprising dipole (g1), quadrupole (g2), and esapole (g3) moments. Results: We found that the propagation of the jets is not radial, which is in agreement with the deflection due to magnetic field lines. Moreover, the amount of the deflection is different between jets over the north and those from the south pole. A comparison of jet deflections and field line tracing shows that a ratio g2/g1 ≃ -0.5 for the quadrupole and a ratio g3/g1 ≃ 1.6-2.0 for the esapole can describe the field. The presence of a non-negligible quadrupole moment confirms the N-S asymmetry of the solar magnetic field for the considered period. Conclusions: We find that the

  1. Color and albedo of the south polar layered deposits on Mars

    NASA Astrophysics Data System (ADS)

    Herkenhoff, K. E.; Murray, B. C.

    1990-02-01

    Five color/albedo units, including polar frost, have been recognized and mapped in the southern layered deposits on Mars. Atmospheric dust scattering was measured in shadows and modeled in order to remove the component of brightness in Mars images due to the atmosphere and quantify the albedo and color of the surface. The layered deposits appear to be mantled by red dust, except where eolian stripping has exposed the underlying bedrock. Dark material has been deposited in topographic depressions in much of the south polar region, including the layered deposits. The available observational data suggest that the layered deposits are composed of bright dust, ice, and a small amount of dark material. If the dark material is sand, a periodic change in polar winds seems required in order to transport the sand poleward into the layered terrain. In any case, the observations are not consistent with the layered deposits being composed only of bright dust and ice.

  2. Analysis of Properties of the North and South Polar Layered Deposits

    NASA Technical Reports Server (NTRS)

    Ivanov, A. B.; Byrne, S.; Richardson, M. I.; Vasavada, A. R.; Titus, T. N.; Bell, J. F.; McConnochie, T. H.; Christensen, P. R.

    2003-01-01

    One of the many questions of Martian exploration is to uncover the history of Mars, through analysis of the polar layered deposits (PLD). Martian polar ice caps hold most of the exposed water ice on the surface of Mars and yet their history and physical processes involved in their formation are unclear. We will attempt to contribute to our knowledge of the composition and stratigraphy of the PLD. In this work we present the latest imaging data acquired by the Mars Odyssey THermal EMission Imaging System (THEMIS) [1] and place it into context of the Mars Global Surveyor (MGS) data. We have discussed the North Polar data in [5]. This work concentrates on data acquired over the South pole of Mars and compares properties of North and South PLD. We are primarily interested in properties of the layers in both ice caps : their continuity, morphology and stratigraphy. These questions can be addressed by THEMIS VIS color images, along with MOC high resolution data and MOLA Digital Elevation Models (DEM). We will investigate thermophysical properties of the layered deposits employing THEMIS IR images. Based on the data obtained by the orbiting spacecraft and described here, we will attempt to expose major directions for modeling and further understanding of the physical processes involved in the formation of the polar layered terrain

  3. Integration of Lunar Polar Remote-Sensing Data Sets: Evidence for Ice at the Lunar South Pole

    NASA Technical Reports Server (NTRS)

    Nozette, Stewart; Spudis, Paul D.; Robinson, Mark S.; Bussey, D. B. J.; Lichtenberg, Chris; Bonner, Robert

    2001-01-01

    In order to investigate the feasibility of ice deposits at the lunar south pole, we have integrated all relevant lunar polar data sets. These include illumination data, Arecibo ground-based monostatic radar data, newly processed Clementine bistatic radar data, and Lunar Prospector neutron spectrometer measurements. The possibility that the lunar poles harbor ice deposits has important implications not only as a natural resource for future human lunar activity but also as a record of inner solar system volatiles (e.g., comets and asteroids) over the past billion years or more. We find that the epithermal neutron flux anomalies, measured by Lunar Prospector, are coincident with permanently shadowed regions at the lunar south pole, particularly those associated with Shackleton crater. Furthermore, these areas also correlate with the beta=0 circular polarization ratio (CPR) enhancements revealed by new processing of Clementine bistatic radar echoes, which in turn are colocated with areas of anomalous high CPR observed by Arecibo Observatory on the lower, Sun-shadowed wall of Shackleton crater. Estimates of the extent of high CPR from Arecibo Observatory and Clementine bistatic radar data independently suggest that approximately 10 square kilometers of ice may be present on the inner Earth-facing wall of Shackleton crater. None of the experiments that obtained the data presented here were ideally suited for definitively identifying ice in lunar polar regions. By assessing the relative merits of all available data, we find that it is plausible that ice does occur in cold traps at the lunar south pole and that future missions with instruments specifically designed to investigate these anomalies are worthy.

  4. Distinct water activation on polar/non-polar facets of ZnO nanoparticles

    SciTech Connect

    Zhang, He; Sun, Junming; Liu, Changjun; Wang, Yong

    2015-11-01

    ZnO nanoparticles with differing dominant facets were prepared and characterized by a complimentary of techniques such as X-ray diffraction, electron microscopy, temperature programmed desorption of H2O, and Fourier transform infrared spectroscopy analysis of adsorbed D2O. For the first time, water interaction/activation is compared on ZnO polar and non-polar facets. We report that non-polar facets exhibit high activity in water activation, which favors reactions such as ketonization and steam reforming in which dissociated water is involved. The distinct water dissociation on ZnO non-polar facets could be related to its facile formation of oxygen vacancies under realistic reaction conditions.

  5. Identifying Surface Changes on HRSC Images of the Mars South Polar Residual CAP (sprc)

    NASA Astrophysics Data System (ADS)

    Putri, Alfiah Rizky Diana; Sidiropoulos, Panagiotis; Muller, Jan-Peter

    2016-06-01

    The surface of Mars has been an object of interest for planetary research since the launch of Mariner 4 in 1964. Since then different cameras such as the Viking Visual Imaging Subsystem (VIS), Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC), and Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) and High Resolution Imaging Science Experiment (HiRISE) have been imaging its surface at ever higher resolution. The High Resolution Stereo Camera (HRSC) on board of the European Space Agency (ESA) Mars Express, has been imaging the Martian surface, since 25th December 2003 until the present-day. HRSC has covered 100 % of the surface of Mars, about 70 % of the surface with panchromatic images at 10-20 m/pixel, and about 98 % at better than 100 m/pixel (Neukum et. al., 2004), including the polar regions of Mars. The Mars polar regions have been studied intensively recently by analysing images taken by the Mars Express and MRO missions (Plaut et al., 2007). The South Polar Residual Cap (SPRC) does not change very much in volume overall but there are numerous examples of dynamic phenomena associated with seasonal changes in the atmosphere. In particular, we can examine the time variation of layers of solid carbon dioxide and water ice with dust deposition (Bibring, 2004), spider-like channels (Piqueux et al., 2003) and so-called Swiss Cheese Terrain (Titus et al., 2004). Because of seasonal changes each Martian year, due to the sublimation and deposition of water and CO2 ice on the Martian south polar region, clearly identifiable surface changes occur in otherwise permanently icy region. In this research, good quality HRSC images of the Mars South Polar region are processed based on previous identification as the optimal coverage of clear surfaces (Campbell et al., 2015). HRSC images of the Martian South Pole are categorized in terms of quality, time, and location to find overlapping areas, processed into high quality Digital Terrain

  6. Polarization insights for active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Antonucci, Robert

    Optical spectropolarimetry and broadband polarimetry in other wavebands has been a key to understanding many diverse aspects of AGN. In some cases polarization is due to synchrotron radiation, and in other cases it's due to scattering. Recognition of relativistically beamed optical synchrotron emission by polarization was vital for understanding blazars (BL Lacs and Optically Violently Variable quasars), both physically and geometrically. Radio polarimetry of quiescent AGN is equally important, again for both purposes. Scattering polarization was central to the Unified Model for Seyferts, Radio Galaxies and (high ionization) Ultraluminous Infrared Galaxies. It provides a periscope for viewing AGN from other directions. Finally, if we could understand its message, polarization would also provide major insights regarding the nature of the AGN "Featureless Continuum" and Broad (emission) Line Region. I point out that high ionization ULIRGs have all the exact right properties to the called Quasar 2s. Mid-IR observations generally don't penetrate to the nucleus, greatly reducing their ability to diagnose the energy source. In particular, LINER ULIRGs aren't necessarily starburst-dominated, as has been claimed.

  7. Enceladus's south polar thermal anomaly in light of weak thermal convection

    NASA Astrophysics Data System (ADS)

    Besserer, Jonathan; Golabek, Gregor J.; Rozel, Antoine; Tackley, Paul J.

    2014-05-01

    The south polar thermal anomaly of Enceladus, contrasting with older and colder northern regions, suggests an asymmetrical heat transfer in the satellite's ice shell. Most of the current models that explain such a distribution prescribe an a priori asymmetry by mean of a mechanical or topographical anomaly in or below the south polar ice shell. We present here a series of simulations with a 2D-spherical convection model to investigate the possibility of self-consistently generating a localized mechanical anomaly in the ice shell. We focus on the non-Newtonian character of ice rheology, and on the stability of a single-plume (i.e. localized convection) and low-degree convection regimes. We show that the non-Newtonian rheology favors a localized (tidally heated) convection surrounded by a conductive ice mantle, even with a global, liquid water ocean at the base of the ice shell. We find that the single-plume state is very unlikely to remain stable if the rheology is Newtonian. The proposed thermal regime for Enceladus's ice shell is therefore weak, single-plume thermal convection focused at the south pole (e.g., remnant of a formerly more vigorous convection). Such weak-to-sub-critical regimes may be important for icy satellites, as recently pointed out by Solomatov (2012, PEPI). We will discuss the effects of ice plasticity on heat focusing in Enceladus's South Polar Terrain, together with the possibility of an ice shell a factor ~2 thinner than previously thought (Hemingway et al., AGU 2013; Stevenson et al., AGU 2013).

  8. Perennial water ice identified in the south polar cap of Mars.

    PubMed

    Bibring, Jean-Pierre; Langevin, Yves; Poulet, François; Gendrin, Aline; Gondet, Brigitte; Berthé, Michel; Soufflot, Alain; Drossart, Pierre; Combes, Michel; Bellucci, Giancarlo; Moroz, Vassili; Mangold, Nicolas; Schmitt, Bernard

    2004-04-01

    The inventory of water and carbon dioxide reservoirs on Mars are important clues for understanding the geological, climatic and potentially exobiological evolution of the planet. From the early mapping observation of the permanent ice caps on the martian poles, the northern cap was believed to be mainly composed of water ice, whereas the southern cap was thought to be constituted of carbon dioxide ice. However, recent missions (NASA missions Mars Global Surveyor and Odyssey) have revealed surface structures, altimetry profiles, underlying buried hydrogen, and temperatures of the south polar regions that are thermodynamically consistent with a mixture of surface water ice and carbon dioxide. Here we present the first direct identification and mapping of both carbon dioxide and water ice in the martian high southern latitudes, at a resolution of 2 km, during the local summer, when the extent of the polar ice is at its minimum. We observe that this south polar cap contains perennial water ice in extended areas: as a small admixture to carbon dioxide in the bright regions; associated with dust, without carbon dioxide, at the edges of this bright cap; and, unexpectedly, in large areas tens of kilometres away from the bright cap. PMID:15024393

  9. Global tectonic of Enceladus driven by subsidence of South Polar Terrain

    NASA Astrophysics Data System (ADS)

    Czechowski, Leszek

    2016-07-01

    Enceladus is the smallest celestial body in the Solar System where volcanic and tectonic activities are observed. Every second, the mass of ~200 kg is ejected into space from the South Polar Terrain (SPT) - [1]. Our hypothesis states that this mass loss is the main driving mechanism of the tectonic processes. The hypothesis is presented in [2] and [3]. We find that the loss of the volatiles results in a void, an instability, and motion of solid matter to fill the void. The motion includes: (i) Subsidence of the 'lithosphere' of SPT. (ii) Flow of the matter in the mantle. (iii) Motion of plates adjacent to SPT towards the active region. The numerical model of the subsidence process is developed. It is based on the model of thermal convection in the mantle. Special boundary conditions are applied that could simulate subsidence of SPT. If emerging void is being filled by the subsidence of SPT only, then the velocity of subsidence is ~0.05 mm per yr. However, numerical calculations indicate that all three types of motion are usually important. The role of a given motion depends on the viscosity distribution. Generally, for most of the models the subsidence is ~0.02 mm per yr, but mantle flow and plates' motion also play a role in filling the void. The preliminary results of the numerical model indicate also that the velocity of adjacent plates could be ~0.02 mm per yr for the Newtonian rheology. The SPT is not compressed, so "tiger stripes" could exist for long time. Only after significant subsidence the regime of stresses changes to compression. It means the end of activity in a given region. The future region of activity is suggested. Acknowledgments This work was partially supported by the National Science Centre (grant 2011/01/B/ST10/06653). Computer resources of Interdisciplinary Centre for Mathematical and Computational Modeling of University of Warsaw were also used in the research References [1] Spencer, J. R., et al. (2009) Enceladus: An Active Cryovolcanic

  10. Survival, site and mate fidelity in south polar skuas Catharacta maccormicki at Anvers Island, Antarctica

    USGS Publications Warehouse

    Pietz, P.J.; Parmelee, D.F.

    1993-01-01

    In 1974-1975, 34 adult South Polar Skuas Catharacta maccormicki were colour-ringed on 18 nest territories at Bonaparte Point, Anvers Island, near Palmer Station along the Antarctic Peninsula. Subsequently, the area was searched for these birds during the austral summers of 1975-1976 to 1984-1985 and in 1987-1988 and 1989-1990. Fifty-three percent were seen in 1984-1985, 32% in 1987-1988 and 21% in 1989-1990. Annual survival rate averaged 95% from 1974-1975 to 1984-1985; no sexual differences were detected (n = 28 of known sex). Strong territory and mate fidelity were apparent; 34 skuas averaged 1.1 nest territories and 1.7 mates each in 16 years. Only 4 of 34 individuals (all females) were known to change territories, and each territory change involved a change of mates. Although males showed higher territory fidelity than females (P < 0.01), most females (four of five) retained their territories when previous mates failed to return. Seventeen of 34 birds changed mates a total of 24 times; at least 20 mate changes followed the death or disappearance of the former mate. Males showed slightly higher mate fidelity than females (P < 0.04). Female South Polar and Brown Skuas Catharacta lonnbergi did not differ in territory or mate fidelity. From 1974-1975 to 1984-1985, 120 South Polar Skua chicks were ringed on 18 nest territories on Bonaparte Point; 17 were resighted in the Palmer area when they were 3-10 years old. All 17 returnees were found within 3 km of their natal nest sites, and four of them occupied nest territories on Bonaparte Point.

  11. IR spectral properties of dust and ice at the Mars south polar cap

    NASA Astrophysics Data System (ADS)

    Titus, T. N.; Kieffer, H. H.

    2001-11-01

    Removal of atmospheric dust effects is required to derive surface IR spectral emissivity. Commonly, the atmospheric-surface separation is based on radiative transfer (RT) spectral inversion methods using nadir-pointing observations. This methodology depends on a priori knowledge of the spectral shape of each atmospheric aerosol (e.g. dust or water ice) and a large thermal contrast between the surface and atmosphere. RT methods fail over the polar caps due to low thermal contrast between the atmosphere and the surface. We have used multi-angle Emission Phase Function (EPF) observations to estimate the opacity spectrum of dust over the springtime south polar cap and the underlying surface radiance, and thus, the surface emissivity. We include a few EPFs from Hellas Basin as a basis for comparisons between the spectral shape of polar and non-polar dust. Surface spectral emissivities over the seasonal cap are compared to CO2 models. Our results show that the spectral shape of the polar dust opacity is not constant, but is a two-parameter family that can be characterized by the 9 um and 20 um opacities. The 9 um opacity varies from 0.15 to 0.45 and characterizes the overall atmospheric conditions. The 9 um to 20 um opacity ratio varies from 2.0 to 5.1, suggesting changes in dust size distribution over the polar caps. Derived surface temperatures from the EPFs confirm that the slightly elevated temperatures (relative to CO2 frost temperature) observed in ``cryptic'' regions are a surface effect, not atmospheric. Comparison of broad-band reflectivity and surface emissivities to model spectra suggest the bright regions (e.g. perennial cap, Mountains of Mitchell) have higher albedos due to a thin surface layer of fine-grain CO2 (perhaps either frost or fractured ice) with an underlying layer of either coarse grain or slab CO2 ice.

  12. A Sublimation Model for the Martian Polar Swiss-Cheese Features. Observational and Modeling Studies of the South Polar Residual Cap

    NASA Technical Reports Server (NTRS)

    Byrne, Shane; Ingersoll, Andrew P.

    2002-01-01

    In their pioneering work Leighton and Murray argued that the Mars atmosphere, which is 95 percent CO2 today, is controlled by vapor equilibrium with a much larger polar reservoir of solid CO2. Here we argue that the polar reservoir is small and cannot function as a long-term buffer to the more massive atmosphere. Our work is based on modeling the circular depressions (Swiss-cheese features) in the south polar cap. We argue that a solid CO2 layer approximately 8 meters thick is being etched away to reveal water ice underneath. Preliminary results from the THEMIS (Thermal Emission Imaging System) instrument seem to confirm our model.

  13. Massive CO2 Ice Deposits Sequestered in the South Polar Layered Deposits of Mars

    USGS Publications Warehouse

    Phillips, Roger J.; Davis, Brian J.; Tanaka, Kenneth L.; Byrne, Shane; Mellon, Michael T.; Putzig, Nathaniel E.; Haberle, Robert M.; Kahre, Melinda A.; Campbell, Bruce A.; Carter, Lynn M.; Smith, Isaac B.; Holt, John W.; Smrekar, Suzanne E.; Nunes, Daniel C.; Plaut, Jeffrey J.; Egan, Anthony F.; Titus, Timothy N.; Seu, Roberto

    2011-01-01

    Shallow Radar soundings from the Mars Reconnaissance Orbiter reveal a buried deposit of carbon dioxide (CO2) ice within the south polar layered deposits of Mars with a volume of 9500 to 12,500 cubic kilometers, about 30 times that previously estimated for the south pole residual cap. The deposit occurs within a stratigraphic unit that is uniquely marked by collapse features and other evidence of interior CO2 volatile release. If released into the atmosphere at times of high obliquity, the CO2 reservoir would increase the atmospheric mass by up to 80%, leading to more frequent and intense dust storms and to more regions where liquid water could persist without boiling.

  14. Massive CO₂ ice deposits sequestered in the south polar layered deposits of Mars.

    PubMed

    Phillips, Roger J; Davis, Brian J; Tanaka, Kenneth L; Byrne, Shane; Mellon, Michael T; Putzig, Nathaniel E; Haberle, Robert M; Kahre, Melinda A; Campbell, Bruce A; Carter, Lynn M; Smith, Isaac B; Holt, John W; Smrekar, Suzanne E; Nunes, Daniel C; Plaut, Jeffrey J; Egan, Anthony F; Titus, Timothy N; Seu, Roberto

    2011-05-13

    Shallow Radar soundings from the Mars Reconnaissance Orbiter reveal a buried deposit of carbon dioxide (CO(2)) ice within the south polar layered deposits of Mars with a volume of 9500 to 12,500 cubic kilometers, about 30 times that previously estimated for the south pole residual cap. The deposit occurs within a stratigraphic unit that is uniquely marked by collapse features and other evidence of interior CO(2) volatile release. If released into the atmosphere at times of high obliquity, the CO(2) reservoir would increase the atmospheric mass by up to 80%, leading to more frequent and intense dust storms and to more regions where liquid water could persist without boiling. PMID:21512003

  15. Some photometric properties of the Martian south polar cap region during the 1971 apparition

    NASA Technical Reports Server (NTRS)

    Lumme, K.; James, P. B.

    1984-01-01

    High-quality earth-based photographs from the Lowell Observatory Planetary Research Center collection have been analyzed to derive some photometric parameters for the Martian south polar cap region during the 1971 apparition. The optical thickness of the atmosphere above the cap varied with wavelength from 0.35 + or - 0.05 in red light to 0.58 + or 0.06 in UV light. The effective geometric albedo is calculated from the 30 deg phase data assuming isotropic scattering: it varies from 0.85 + or - 0.04 (in red light) to 0.63 + or 0.05 (in UV light).

  16. The Cratering Record of the South Polar Layered Deposits of Mars

    NASA Astrophysics Data System (ADS)

    Koutnik, M.; Byrne, S.; Murray, B.

    2001-11-01

    The Mars Orbiter Laser Altimeter (MOLA) and the Mars Orbiter Camera (MOC) instruments aboard the Mars Global Surveyor (MGS) were used in a detailed search of a selected part of the south polar layered deposits (SPLD) for impact craters. Impact craters were identified from the MOLA shaded relief map and validated using individual MOLA tracks and MOC narrow angle (NA) images. The resultant crater population is at least four times greater than the crater population previously recognized from Viking data [Plaut, et al., 1988]. The mean exposure age of the SPLD is estimated to be 30 to 100 Ma depending on the established production model isochrons used [Herkenhoff and Plaut, 2000; Hartmann, 1999]. All of the 0.8 to 5 km diameter craters are considerably shallower than other Martian craters in the same diameter range. The timescales postulated for layer formation modulated solely by deterministic astronomically driven climatic fluctuations of approximately 105 to 106 years [Ward, 1979] are much shorter than the high mean surface exposure age for the SPLD determined in this study. Thus the surface of the SPLD included in our study likely records some previously unrecognized event in polar history that marked the end of layer formation and erosion in that area. Hartmann, W.K., Martian Cratering VI: Crater count isochrons and evidence for recent volcanism from Mars Global Surveyor. Meteoritics & Planetary Science, 34, 167-177, 1999. Herkenhoff, K.E., and J.J. Plaut, Surface Ages and Resurfacing Rates of the Polar Layered Deposits on Mars, Icarus, 144, 243-253, 2000. Plaut, J.J., R. Kahn, E.A. Guiness, and R.E. Arvidson, Accumulation of Sedimentary Debris in the South Polar Region of Mars and Implications for Climate History, Icarus 75, 357-377, 1988. Ward, W.R., Present obliquity oscillations of Mars: Fourth-order accuracy in orbital e and I, J. Geophys. Res., 84, 237-241, 1979.

  17. Thermal and non-thermal fluctuations in active polar gels.

    PubMed

    Basu, A; Joanny, J F; Jülicher, F; Prost, J

    2008-10-01

    We discuss general features of noise and fluctuations in active polar gels close to and away from equilibrium. We use the single-component hydrodynamic theory of active polar gels built by Kruse and coworkers to describe the cytoskeleton in cells. Close to equilibrium, we calculate the response function of the gel to external fields and introduce Langevin forces in the constitutive equations with correlation functions respecting the fluctuation-dissipation theorem. We then discuss the breakage of the fluctuation-dissipation theorem due to an external field such as the activity of the motors. Active gels away from equilibrium are considered at the scaling level. As an example of application of the theory, we calculate the density correlation function (the dynamic structure factor) of a compressible active polar gel and discuss possible instabilities. PMID:18791871

  18. Zeno inhibition of polarization rotation in an optically active medium

    NASA Astrophysics Data System (ADS)

    Gonzalo, Isabel; Porras, Miguel A.; Luis, Alfredo

    2015-07-01

    We describe an experiment in which the rotation of the polarization of light propagating in an optically active water solution of D-fructose tends to be inhibited by frequent monitoring whether the polarization remains unchanged. This is an example of the Zeno effect that has remarkable pedagogical interest because of its conceptual simplicity, easy implementation, low cost, and because the same the Zeno effect holds at classical and quantum levels. An added value is the demonstration of the Zeno effect beyond typical idealized assumptions in a practical setting with real polarizers.

  19. Polarity establishment requires localized activation of Cdc42

    PubMed Central

    Woods, Benjamin; Kuo, Chun-Chen; Wu, Chi-Fang; Zyla, Trevin R.

    2015-01-01

    Establishment of cell polarity in animal and fungal cells involves localization of the conserved Rho-family guanosine triphosphatase, Cdc42, to the cortical region destined to become the “front” of the cell. The high local concentration of active Cdc42 promotes cytoskeletal polarization through various effectors. Cdc42 accumulation at the front is thought to involve positive feedback, and studies in the budding yeast Saccharomyces cerevisiae have suggested distinct positive feedback mechanisms. One class of mechanisms involves localized activation of Cdc42 at the front, whereas another class involves localized delivery of Cdc42 to the front. Here we show that Cdc42 activation must be localized for successful polarity establishment, supporting local activation rather than local delivery as the dominant mechanism in this system. PMID:26459595

  20. Polarization ray tracing in anisotropic optically active media

    NASA Technical Reports Server (NTRS)

    Mcclain, Stephen C.; Chipman, Russell A.

    1992-01-01

    Procedures for performing polarization ray tracing through birefringent media are presented in a form compatible with the standard methods of geometric ray tracing. The birefringent materials treated include the following: anisotropic optically active materials such as quartz, non-optically active uniaxial materials such as calcite, and isotropic optically active materials such as mercury sulfide or organic liquids. Refraction and reflection algorithms are presented which compute both ray directions and wave directions. Methods for computing polarization modes, refractive indices, optical path lengths, and Fresnel transmission and reflection coefficients are also specified.

  1. Composition and abundance of epibenthic-sledge catches in the South Polar Front of the Atlantic

    NASA Astrophysics Data System (ADS)

    Brandt, A.; Havermans, C.; Janussen, D.; Jörger, K. M.; Meyer-Löbbecke, A.; Schnurr, S.; Schüller, M.; Schwabe, E.; Brandão, S. N.; Würzberg, L.

    2014-10-01

    An epibenthic sledge (EBS) was deployed at seven different deep-sea stations along the South Polar Front of the Atlantic in order to explore the composition and abundance of macrofaunal organisms and to identify the most abundant taxa in this transition zone to the Southern Ocean. In total 3,130 specimens were sampled by means of the EBS on board of RV Polarstern during the expedition ANT-XXVIII/3 in the austral summer of 2012. Benthic and suprabenthic Crustacea occurred to be most frequent in the samples. Among those, copepods were by far most numerous, with 1,585 specimens followed by the peracarid taxa Isopoda (236 ind.), Amphipoda (103 ind.), Tanaidacea (78 ind.) and Cumacea (50 ind.). Annelida were represented by a high number of specimens belonging to different polychaete taxa (404 ind.). The molluscan fauna was clearly dominated by Bivalvia (255 ind.), followed in numbers of specimens by Gastropoda (47 ind.). The deep-sea benthos sampled along the Southern Polar Front occurred in surprisingly low abundances, contrasting the largely high surface productivity of the area. Numbers of specimens across different macrofaunal taxa and especially of peracarid crustaceans underscored by far those from South Ocean sites at higher latitudes in the Weddell Sea.

  2. Linking geomagnetic activity and polar surface air temperature variability

    NASA Astrophysics Data System (ADS)

    Seppala, Annika

    ERA-40 and ECMWF operational surface level air temperature (SAT) data sets from 1957 to 2006 were used to examine polar temperature variations during years with different levels of geomagnetic activity, as defined by the Ap index. Previous modelling work has suggested that NOx produced at high latitudes by energetic particle precipitation can eventually lead to detectable changes in polar SATs. We find that during winter months, ERA-40 and ECMWF polar SATs in years with high Ap index are different than in years with low Ap index; the differences are statistically significant at the 2-sigma level and range up to about ±4.5 K, de-pending on location. The temperature differences are larger when years with wintertime Sudden Stratospheric Warmings are excluded. Solar irradiance variations were taken into account in the analysis. Although using the re-analysis and operational data sets it was not possible to conclusively show that the polar SAT patterns are physically linked by geomagnetic activity, we conclude that geomagnetic activity likely plays a role in modulating polar wintertime surface air temperature patterns. The SAT results were tested against variation in the Quasi Biennial Oscillation (QBO), the El Niño Southern Oscillation (ENSO) and the Southern Annular Mode n (SAM). The results suggested that these were not driving the observed polar SAT variability. However, significant uncertainty is introduced by the Northern Annular Mode (NAM) and we could not robustly exclude a chance linkage between sea surface temperature (SST) variability and geomagnetic activity. Examining the physical link between geomagnetic activity and polar surface temperature variability patterns using atmospheric models is an ongoing task.

  3. Enzyme Activities in Polarized Cell Membranes

    PubMed Central

    Bass, L.; McIlroy, D. K.

    1968-01-01

    The theoretical pH dependence of enzyme activities in membranes of low dielectric constant is estimated. It is shown that in biological membranes some types of enzymes may attain a limiting pH sensitivity such that an increment of only 0.2 pH unit (sufficient to induce action potentials in squid axons) causes a relative activity change of over 25%. The transients of enzyme activity generated by membrane depolarization and by pH increments in the bathing solution are discussed in relation to the transients of nervous excitation. PMID:5641405

  4. Autonomous full-time lidar measurements of polar stratospheric clouds at the South Pole

    NASA Astrophysics Data System (ADS)

    Campbell, James R.

    Polar stratospheric clouds (PSC) are an artifact of extremely low temperatures in the lower-stratosphere caused by a lack of sunlight during winter. Their presence induces increased concentrations of chlorine and bromine radicals that drive catalytic ozone destruction upon the return of sunlight in spring. An eye-safe micropulse lidar (MPL; 0.23 mum) was installed at the Scott-Amundsen South Pole Station, Antarctica in December 1999 to collect continuous long-term measurements of polar clouds. A four-year data subset for analyzing PSC is derived from measurements for austral winters 2000 and 2003--2005. A statistical algorithm based on MPL signal uncertainties is designed to retrieve PSC boundary heights, attenuated scattering ratios and demonstrate instrument performance for low signal-to-noise measurements. The MPL measurements consist mostly of Type II PSC (i.e., ice). The likelihood for Type I measurements are described for specific conditions. Seasonal PSC macrophysical properties are examined relative to thermodynamic and chemical characteristics. The potential for dehumidification and denitrification of the lower Antarctic stratosphere is examined by comparing PSC observations to theoretical predictions for cloud based on common scenarios for water vapor and nitric acid concentrations. Conceptual models for seasonal PSC occurrence, denitrification and dehumidification and ozone loss are described. A linear relationship is established between total integrated PSC scattering and ozone loss, with high correlation. Polar vortex dynamics are investigated in relation to PSC occurrence, including synoptic-scale geopotential height anomalies, isentropic airmass trajectories and local-scale gravity waves. Moisture overrunning, from quasi-adiabatic cooling and transport along isentropic boundaries, is considered a primary mechanism for PSC occurrence. Middle and late-season PSC are found to be the result of mixing of moist air from the outer edges of the vortex that

  5. Dielectric Constant of Titan's South Polar Region from Cassini Radio Science Bistatic Scattering Observations

    NASA Astrophysics Data System (ADS)

    Marouf, E.; Rappaport, N.; French, R.; Simpson, R.; Kliore, A.; McGhee, C.; Schinder, P.; Anabtawi, A.

    2008-12-01

    (~ 23 minutes). The relatively more grazing incidence geometry (θ ~ 70-79°) caused the RCP component to dominate the LCP component, as expected. Nonetheless, the later was mostly detectable, allowing estimation of the corresponding polarization ratio and hence profiling of the variability of the dielectric constant along the ground track. The inferred dielectric constant ɛ appears to vary over the large surface region probed but falls generally in the range 2 to 2.5, suggesting solid hydrocarbons or hydrocarbon "sludge" surface composition close to Titan's south pole. The small observed spectral Doppler broadening suggests that the echoes originate from gently undulating surface regions with RMS slopes of order few degrees.

  6. Three-dimensional thermal structure of the South Polar Vortex of Venus

    NASA Astrophysics Data System (ADS)

    Hueso, Ricardo; Garate-Lopez, Itziar; Garcia-Muñoz, Antonio; Sánchez-Lavega, Agustín

    2014-11-01

    We have analyzed thermal infrared images provided by the VIRTIS-M instrument aboard Venus Express (VEX) to obtain high resolution thermal maps of the Venus south polar region between 55 and 85 km altitudes. The maps investigate three different dynamical configurations of the polar vortex including its classical dipolar shape, a regularly oval shape and a transition shape between the different configurations of the vortex. We apply the atmospheric model described by García Muñoz et al. (2013) and a variant of the retrieval algorithm detailed in Grassi et al. (2008) to obtain maps of temperature over the Venus south polar region in the quoted altitude range. These maps are discussed in terms of cloud motions and relative vorticity distribution obtained previously (Garate-Lopez et al. 2013). Temperature maps retrieved at 55 - 63 km show the same structures that are observed in the ~5 µm radiance images. This altitude range coincides with the optimal expected values of the cloud top altitude at polar latitudes and magnitudes derived from the analysis of ~5 µm images are measured at this altitude range. We also study the imprint of the vortex on the thermal field above the cloud level which extends up to 80 km. From the temperature maps, we also study the vertical stability of different atmospheric layers. The cold collar is clearly the most statically stable structure at polar latitudes, while the vortex and subpolar latitudes show lower stability values. Furthermore, the hot filaments present within the vortex at 55-63 km exhibit lower values of static stability than their immediate surroundings.ReferencesGarate-Lopez et al. Nat. Geosci. 6, 254-257 (2013).García Muñoz et al. Planet. Space Sci. 81, 65-73 (2013).Grassi, D. et al. J. Geophys. Res. 113, 1-12 (2008).AcknowledgementsWe thank ESA for supporting Venus Express, ASI, CNES and the other national space agencies supporting VIRTIS on VEX and their principal investigators G. Piccioni and P. Drossart. This work

  7. Instantaneous three-dimensional thermal structure of the South Polar Vortex of Venus

    NASA Astrophysics Data System (ADS)

    Garate-Lopez, I.; García Muñoz, A.; Hueso, R.; Sánchez-Lavega, A.

    2015-01-01

    The Venus thermal radiation spectrum exhibits the signature of CO2 absorption bands. By means of inversion techniques, those bands enable the retrieval of atmospheric temperature profiles. We have analyzed VIRTIS-M-IR night-side data obtaining high-resolution thermal maps of the Venus south polar region between 55 and 85 km altitudes. This analysis is specific to three Venus Express orbits where the vortex presents different dynamical configurations. The cold collar is clearly distinguishable centered at ∼62 km (∼100 mbar) altitude level. On average, the cold collar is more than 15 K colder than the pole, but its specific temperature varies with time. In the three orbits under investigation the South Polar Vortex appears as a vertically extended hot region close to the pole and squeezed by the cold collar between altitudes 55 and 67 km but spreading equatorwards at about 74 km. Both the instantaneous temperature maps and their zonal averages show that the top altitude limit of the thermal signature from the vortex is at ∼80 km altitude, at least on the night-side of the planet. The upper part of the atmosphere (67-85 km) is more homogeneous and has long-scale horizontal temperature differences of about 25 K over horizontal distances of ∼2000 km. The lower part (55-67 km) shows more fine-scale structure, creating the vortex morphology, with thermal differences of up to about 50 K over the same altitude range and ∼500 km horizontal distances. This lower part of the atmosphere is highly affected by the upper cloud deck, leading to stronger local temperature variations and larger uncertainties in the retrieval. From the temperature maps, we also study the vertical stability of different atmospheric layers for the three vortex configurations. The static stability is always positive (ST > 0) in the considered altitude range (55-85 km) and in the whole polar vortex. The cold collar is the most vertically stable structure at polar latitudes, while the vortex and

  8. Polar Mesospheric Cloud North/South Hemispheric differences: from SME (1982- present

    NASA Astrophysics Data System (ADS)

    Thomas, G. E.; DeLand, M. T.; Shettle, E. P.

    2011-12-01

    The Ultraviolet Spectrometer (UVS) on the Solar Mesosphere Explorer (SME) mission (1981-86) was designed to measure mesospheric ozone by limb sounding at pairs of UV wavelengths, and to establish its relationship with changes in solar spectral irradiance made by an accompanying solar experiment (Rottman, G. , this meeting). Because of its near-polar sun-synchronous orbit, it was anticipated that the overflights of the polar regions (up to 82 deg) would yield new information on transpolar mesospheric clouds, discovered earlier in 1969 by Donahue and colleagues. Known at lower latitudes as noctilucent clouds (NLC), the extensive ice layer was found in 1969 to grow in scattered brightness and occurrence frequency with latitude. SME was launched at a time when very little was known about the ice properties, their seasonal morphology, north/south differences, etc. SME in its five year lifetime over which atmospheric measurements were made established for the first time the seasonal morphology in the period (1981-86), constrained the particle sizes, described north/south differences, etc. The term PMC originated in the first publication of SME cloud data (Thomas, 1984). This paper describes the SME PMC data base, which has been updated extensively since the first publications. Its focus is on the question of north/south differences in PMC properties, and whether these properties have changed over the 30-year period from the SME era to the present. The quantity of interest is the north/south ratio (NSR) of ice water mass (IWC). The NSR has been reported to be greater than two, on the average, using Solar Backscatter Ultraviolet Spectrometer (SBUV) data by Stevens et al (2007). This earlier study applied to the years of the SME mission, and so provide a good comparison to the present results, with two differences: (1) we deal with the more sensitive SME data and thus a greater fraction of the IWC, and (2) use a new regression analysis which relates IWC to the scattered

  9. Polarized Raman optical activity of menthol and related molecules

    NASA Astrophysics Data System (ADS)

    Barron, L. D.; Hecht, L.; Blyth, S. M.

    1989-01-01

    Polarized and depolarized Raman optical activity spectra of menthol, menthyl chloride, neomenthol and neothiomenthol from 800 to 1500 cm -1 are reported. Despite axial symmetry in all the bonds, the presence of the heteroatoms O or S seems to induce large deviations from the expected ratio of 2:1 between the polarized and depolarized Raman optical activity intensities, but Cl does not. These deviations might originate in large electric quadrupole contributions induced by excited state interactions involving O or S Rydberg p orbitals and valence orbitals on other parts of the molecule. Such interactions appear to undermine the bond polarizability theory of Raman intensities.

  10. Cosmic ray density gradient and its dependence on the north-south asymmetry in solar activity

    NASA Technical Reports Server (NTRS)

    BADRUDDIN; Yadav, R. S.; Yadav, N. R.

    1985-01-01

    An analysis of the diurnal anisotropy on geomagnetically quiet days was performed using neutron monitor data at Deep River, Leeds, Rome and Tokyo, well distributed in latitude and longitude for the period 1964-79. The days were separated according to the polarity of IMF on that day. A significant difference in the amplitude and phase was found on towards and away polarity days, particularly during the years of high solar activity and large north-south asymmetry. These results (particularly time of maximum) on geomagnetically quiet days show some better relationship to the expected results as compared to the results obtained using all the days in a year.

  11. IRTM brightness temperature maps of the Martian south polar region during the polar night: The cold spots don't move

    NASA Technical Reports Server (NTRS)

    Paige, D. A.; Crisp, D.; Santee, M. L.; Richardson, M. I.

    1993-01-01

    A series of infrared thermal mapper (IRTM) south polar brightness temperature maps obtained by Viking Orbiter 2 during a 35-day period during the southern fall season in 1978 was examined. The maps show a number of phenomena that have been identified in previous studies, including day to day brightness temperature variations in individual low temperature regions and the tendency for IRTM 11-micron channel brightness temperatures to also decrease in regions where low 20-micron channel brightness temperatures are observed. The maps also show new phenomena, the most striking of which is a clear tendency for the low brightness temperature regions to occur at fixed geographic regions. During this season, the coldest low brightness temperatures appear to be concentrated in distinct regions, with spatial scales ranging from 50 to 300 km. There are approximately a dozen of these concentrations, with the largest centered near the location of the south residual polar cap. Other concentrations are located at Cavi Angusti and close to the craters Main, South, Lau, and Dana. Broader, less intense regions appear to be well correlated with the boundaries of the south polar layered deposits and the Mountains of Mitchell. No evidence for horizontal motion of any of these regions has been detected.

  12. Potential impacts of polar fronts on sedimentation processes at Abrolhos coral reef (South-West Atlantic Ocean/Brazil)

    NASA Astrophysics Data System (ADS)

    Segal, Bárbara; Evangelista, Heitor; Kampel, Milton; Gonçalves, Aldrey Costa; Polito, Paulo Simionatto; dos Santos, Elaine Alves

    2008-03-01

    Several reefs of the world have undergone changes in community due to sedimentation processes. It has been suggested that Abrolhos reefs (Brazil/South-West Atlantic) are subjected to a steady coastal influence, although there is still little information regarding this assumption. In this work, we have analyzed a set of environmental parameters concerning sedimentation characteristics at the Abrolhos reefs, near 18°S-39°W. The analysis included remote sensing, model and in situ data to provide a three-dimensional quantitative description of the processes that influence sediment apportionment to the reefs. Mineralogy and natural radioactivity of sediment trapped at three reef sites in a transect perpendicular to the coastline were used in conjunction with numerical weather prediction model and remote sensing databases. We have observed an increase of around 100% of sediment flux during the summer compared to the winter season. A comparison of regional rainfall regime, sediment plume dynamics and a year-around monitoring of polar fronts trajectories and surface wind showed that the wind-driven resedimentation due to polar front activity is the major contributor to the intensification of sedimentation processes at the offshore area of Abrolhos reefs, despite river runoff from mainland.

  13. How the geysers, tidal stresses, and thermal emission across the south polar terrain of enceladus are related

    SciTech Connect

    Porco, Carolyn; DiNino, Daiana; Nimmo, Francis

    2014-09-01

    We present the first comprehensive examination of the geysering, tidal stresses, and anomalous thermal emission across the south pole of Enceladus and discuss the implications for the moon's thermal history and interior structure. A 6.5 yr survey of the moon's south polar terrain (SPT) by the Cassini imaging experiment has located ∼100 jets or geysers erupting from four prominent fractures crossing the region. Comparing these results with predictions of diurnally varying tidal stresses and with Cassini low resolution thermal maps shows that all three phenomena are spatially correlated. The coincidence of individual jets with very small (∼10 m) hot spots detected in high resolution Cassini VIMS data strongly suggests that the heat accompanying the geysers is not produced by shearing in the upper brittle layer but rather is transported, in the form of latent heat, from a sub-ice-shell sea of liquid water, with vapor condensing on the near-surface walls of the fractures. Normal stresses modulate the geysering activity, as shown in the accompanying paper; we demonstrate here they are capable of opening water-filled cracks all the way down to the sea. If Enceladus' eccentricity and heat production are in steady state today, the currently erupting material and anomalous heat must have been produced in an earlier epoch. If regional tidal heating is occurring today, it may be responsible for some of the erupting water and heat. Future Cassini observations may settle the question.

  14. Subsidence of the South Polar Terrain and global tectonic of Enceladus

    NASA Astrophysics Data System (ADS)

    Czechowski, Leszek

    2016-04-01

    Introduction: Enceladus is the smallest celestial body in the Solar System where volcanic and tectonic activities are observed. Every second, the mass of ˜200 kg is ejected into space from the South Polar Terrain (SPT) - [1]. The loss of matter from the body's interior should lead to global compression of the crust (like on Mercury). Typical effects of compression are: thrust faults, folding and subduction. However, such forms are not dominant on Enceladus. We propose here special dynamical process that could explain this paradox. Our hypothesis states that the mass loss from SPT is the main driving mechanism of the following tectonic processes: subsidence of SPT, flow in the mantle and motion of adjacent tectonic plates. The hypothesis is presented in [2] and [3]. We suggest that the loss of the volatiles results in a void, an instability, and motion of solid matter to fill the void. The motion includes: Subsidence of the 'lithosphere' of SPT. Flow of the matter in the mantle. Motion of plates adjacent to SPT towards the active region. Methods and results: The numerical model of the subsidence process is developed. It is based on the model of thermal convection in the mantle. Special boundary conditions are applied, that could simulate subsidence of SPT. If emerging void is being filled by the subsidence of SPT only, then the velocity of subsidence is ˜0.05 mmṡyr‑1. However, numerical calculations indicate that all three types of motion are usually important. The role of a given motion depends on the viscosity distribution. Generally, for most of the models the subsidence is ˜0.02 mmṡyr‑1, but mantle flow and plates' motion also play a role in filling the void. The preliminary results of the numerical model indicate also that the velocity of adjacent plates could be ˜0.02 mmṡyr‑1 for the Newtonian rheology. Note that in our model the reduction of the crust area is not a result of compression but it is a result of the plate sinking. Therefore the

  15. Circularly polarized antennas for active holographic imaging through barriers

    SciTech Connect

    McMakin, Douglas L; Severtsen, Ronald H; Lechelt, Wayne M; Prince, James M

    2011-07-26

    Circularly-polarized antennas and their methods of use for active holographic imaging through barriers. The antennas are dielectrically loaded to optimally match the dielectric constant of the barrier through which images are to be produced. The dielectric loading helps to remove barrier-front surface reflections and to couple electromagnetic energy into the barrier.

  16. Geomagnetic activity and polar surface air temperature variability

    NASA Astrophysics Data System (ADS)

    Seppälä, A.; Randall, C. E.; Clilverd, M. A.; Rozanov, E.; Rodger, C. J.

    2009-10-01

    Here we use the ERA-40 and ECMWF operational surface level air temperature data sets from 1957 to 2006 to examine polar temperature variations during years with different levels of geomagnetic activity, as defined by the A p index. Previous modeling work has suggested that NO x produced at high latitudes by energetic particle precipitation can eventually lead to detectable changes in surface air temperatures (SATs). We find that during winter months, polar SATs in years with high A p index are different than in years with low A p index; the differences are statistically significant at the 2-sigma level and range up to about ±4.5 K, depending on location. The temperature differences are larger when years with wintertime Sudden Stratospheric Warmings (SSWs) are excluded. We take into account solar irradiance variations, unlike previous analyses of geomagnetic effects in ERA-40 and operational data. Although we cannot conclusively show that the polar SAT patterns are physically linked by geomagnetic activity, we conclude that geomagnetic activity likely plays a role in modulating wintertime surface air temperatures. We tested our SAT results against variation in the Quasi Biennial Oscillation, the El Niño Southern Oscillation and the Southern Annular Mode. The results suggested that these were not driving the observed polar SAT variability. However, significant uncertainty is introduced by the Northern Annular Mode, and we cannot robustly exclude a chance linkage between sea surface temperature variability and geomagnetic activity.

  17. Thermally activated delayed fluorescence with circularly polarized luminescence characteristics.

    PubMed

    Imagawa, Takuro; Hirata, Shuzo; Totani, Kenro; Watanabe, Toshiyuki; Vacha, Martin

    2015-09-01

    A metal-free aromatic compound with a chiral carbon sandwiched between a donor moiety and an acceptor moiety was designed. Under thermally activated delayed fluorescence, the compound displayed a photoluminescence quantum yield of 26%, and showed circularly polarized luminescence with a dissymmetry factor of 10(-3). PMID:26207648

  18. Stratigraphy and evolution of the buried CO2 deposit in the Martian south polar cap

    NASA Astrophysics Data System (ADS)

    Bierson, C. J.; Phillips, R. J.; Smith, I. B.; Wood, S. E.; Putzig, N. E.; Nunes, D.; Byrne, S.

    2016-05-01

    Observations by the Shallow Radar instrument on Mars Reconnaissance Orbiter reveal several deposits of buried CO2 ice within the south polar layered deposits. Here we present mapping that demonstrates this unit is 18% larger than previously estimated, containing enough mass to double the atmospheric pressure on Mars if sublimated. We find three distinct subunits of CO2 ice, each capped by a thin (10-60 m) bounding layer (BL). Multiple lines of evidence suggest that each BL is dominated by water ice. We model the history of CO2 accumulation at the poles based on obliquity and insolation variability during the last 1 Myr assuming a total mass budget consisting of the current atmosphere and the sequestered ice. Our model predicts that CO2 ice has accumulated over large areas several times during that period, in agreement with the radar findings of multiple periods of accumulation.

  19. The 1997 Spring Regression of the Martian South Polar Cap: Mars Orbiter Camera Observations

    NASA Astrophysics Data System (ADS)

    James, P. B.; Cantor, B. A.; Edgett, K.; Malin, M. C.

    1999-09-01

    The Mars Orbiter Cameras on Mars Global Surveyor observed the south polar cap of Mars during its spring recession in 1997. The images acquired by the Wide Angle Cameras reveal a pattern of recession that is qualitatively similar to that observed by Viking in 1977 but that does differ in at least two respects. The 1977 recession in the 0 deg to 120 deg longitude sector was accelerated relative to the 1997 observations after LS = 240 deg the Mountains of Mitchel also detached from the main cap earlier in 1997. Comparison of the MOC images with MOLA data shows that the Mountains of Mitchel feature is controlled by local topography. Relatively dark, low albedo regions well within the boundaries of the seasonal cap were observed to have red to violet ratios that characterize them as frost units rather than unfrosted or partially frosted ground; this suggests the possibility of regions covered by CO2 frost having different grain sizes.

  20. Frontier Science in the Polar Regions: Current Activities of the Polar Research Board

    NASA Astrophysics Data System (ADS)

    Brown, L. M.

    2011-12-01

    The National Academies (the umbrella term for the National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council) is a private, nonprofit organization chartered by Congress in 1863. The Polar Research Board (PRB) is the focal point within the Academies for providing advice on issues related to the Arctic, Antarctic, and cold regions in general. Tasks within the PRB mission include: providing a forum for the polar science community to address research needs and policy issues; conducting studies and workshops on emerging scientific and policy issues in response to requests from federal agencies and others; providing program reviews, guidance, and assessments of priorities; and facilitating communication on polar issues among academia, industry, and government. The PRB also serves as the US National Committee to two international, nongovernmental polar science organizations: the Scientific Committee on Antarctic Research (SCAR) and the International Arctic Science Committee (IASC). The polar regions are experiencing rapid changes in environment and climate, and the PRB has a number of completed and ongoing studies that will enhance scientific understanding of these issues. This poster will illustrate current PRB activities as well as results from two recently released reports: Frontiers in Understanding Climate Change and Polar Ecosystems and Future Science Opportunities in Antarctica and the Southern Ocean. In the former, a set of frontier research questions are developed to help scientists understand the impacts of climate change on polar ecosystems. The report builds on existing knowledge of climate change impacts and highlights the next big topics to be addressed in the coming decades. In addition, a number of methods and technologies are identified that will be useful to advance future research in polar ecosystem science. In the latter, changes to important science conducted on Antarctica and the surrounding

  1. Correlation between south polar cap composition from OMEGA/MEX data and geomorphologic units

    NASA Astrophysics Data System (ADS)

    Mangold, N.; Poulet, F.; Forget, F.; Gendrin, A.; Gondet, B.; Langevin, Y.; Schmitt, B.; Bibring, J.-P.; OMEGA, Team

    A series of observations covering the south polar cap and part of the surrounding terrains have been recorded in the first weeks of OMEGA operation. From these first observations nearly pure H2O ice has been discovered in several areas surrounding the bright cap on which CO2 ice is mainly concentrated. A strong correlation exists between these compositional units and geomorphic features observed on MOC images acquired during the summer of the south hemisphere. As postulated by previous studies using MOC and THEMIS data, CO2 ice is strongly correlated with the geomorphic features called swiss-cheese terrains characterized by quasi-circular depressions. H2O ice, devoid of any CO2 ice, is observed with OMEGA in the periphery of these these swiss-cheese terrains. These H2O ice terrains on MOC images are very smooth and only affected by polygonal cracks which likely result of thermal contraction. The CO2 ice is apparently superimposed on these H2O ice layers confirming that the CO2 ice cap is restricted to a thin layer of few meters thick. Outside of the bright cap, patches of H2O ice are observed with OMEGA in correlation with grooved homogeneous surfaces on MOC images. They represent part of an H2O ice cap devoid of any overlying CO2 units which suggests an extension of the cap far beyond the bright polar cap. Preliminary results of the modeling of the sublimation processes of these different ices units will be presented.

  2. Transient bright "halos" on the South Polar Residual Cap of Mars: Implications for mass-balance

    NASA Astrophysics Data System (ADS)

    Becerra, Patricio; Byrne, Shane; Brown, Adrian J.

    2015-05-01

    Spacecraft imaging of Mars' south polar region during mid-southern summer of Mars year 28 (2007) observed bright halo-like features surrounding many of the pits, scarps and slopes of the heavily eroded carbon dioxide ice of the South Polar Residual Cap (SPRC). These features had not been observed before, and have not been observed since. We report on the results of an observational study of these halos, and spectral modeling of the SPRC surface at the time of their appearance. Image analysis was performed using data from MRO's Context Camera (CTX), and High Resolution Imaging Science Experiment (HiRISE), as well as images from Mars Global Surveyor's (MGS) Mars Orbiter Camera (MOC). Data from MRO's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) were used for the spectral analysis of the SPRC ice at the time of the halos. These data were compared with a Hapke reflectance model of the surface to constrain their formation mechanism. We find that the unique appearance of the halos is intimately linked to a near-perihelion global dust storm that occurred shortly before they were observed. The combination of vigorous summertime sublimation of carbon dioxide ice from sloped surfaces on the SPRC and simultaneous settling of dust from the global storm, resulted in a sublimation wind that deflected settling dust particles away from the edges of these slopes, keeping these areas relatively free of dust compared to the rest of the cap. The fact that the halos were not exhumed in subsequent years indicates a positive mass-balance for flat portions of the SPRC in those years. A net accumulation mass-balance on flat surfaces of the SPRC is required to preserve the cap, as it is constantly being eroded by the expansion of the pits and scarps that populate its surface.

  3. Simultaneous ozone and polar stratospheric cloud observations at South Pole Station during winter and spring 1991

    SciTech Connect

    Rosen, J.M.; Kjome, N.T.; Oltmans, S.J.

    1993-07-20

    Simultaneous polar stratospheric cloud (PSC) and ozone measurements were made over South Pole Station using a two-wavelength backscattersonde. This instrument produces aerosol profiles similar to those obtained with a ground-based lidar system but with higher vertical resolution. In one sounding, depolarization of the PSCs was also measured. The backscattersondes were supplemented with occasional frost point soundings. The measurements made before the appearance of PSCs do not show clear evidence of particle deliquescence, suggesting that the background sulfate particles may be frozen solids rather than liquids. PSCs began appearing at {approximately}20 km when the temperature at that altitude dropped to {minus}80{degrees}C (193 K). Initially, there was apparent evidence of supersaturation (with respect to nitric acid trihydrate) associated with some type I PSCs, while other examples indicated that the condensation of nitric acid was in quantitative agreement with that expected from the saturation vapor pressure and available nitric acid vapor. The apparent supersaturated layers (which occurred within the first 2 weeks of the onset of PSCs) can alternatively be interpreted as denitrified regions. In the polarization sensitive sounding, two varieties of type I PSCs were observed, one of which exhibited significant depolarization and another which produced very little depolarization. This observation would be consistent with the classification of types Ia and Ib, respectively. At the precise time that sunlight was returning to the stratosphere near South Pole Station, a strong inverse correlation in the structure of PSCs and ozone mixing ratio was observed. Using trajectory analysis, it is argued that the effect is probably the result of chemical depletion rather than transport processes. This chance observation is consistent with enhanced ozone depletion occurring in association with sunlit PSCs during the early spring. 36 refs., 13 figs., 2 tabs.

  4. Comparisons of Na densities, Fe densities, and temperature measured over south polar cap with model predictions

    NASA Astrophysics Data System (ADS)

    Chu, X.; Gardner, C. S.; Vondrak, T.; Murray, B.; Plane, J. M.; Roble, R. G.; Espy, P. J.; Kawahara, T.

    Mesospheric Na and Fe layer densities and temperatures were measured by lidar systems at the South Pole, Syowa (69S, 39E), and Rothera (67.5S, 68.0W) during the past several years. Comparison of the wintertime temperatures measured above these sites with TIME-GCM predictions, suggests that the model over-estimates the compressional heating associated with downwelling. When simulating the winter Na and Fe densities at the pole using the UEA 1-D chemistry models, a 2-D general circulation model SOCRATES was used to predict the meridional and downward vertical transportation of O, H, etc. from the sunlit lower latitude into the polar vortex. However, the simulation indicates that the circulation, especially downward transport into the polar vortex, is overestimated by the general circulation model. Thus, the wintertime Na layer nearly disappears in the chemistry model, which does not agree with the maximum Na abundance observed in winter. In summer, the model correctly predicts the observed depletion of the metal atoms below 90 km. This results from the uptake of the metals onto ice particles, which seem to be a persistent feature of the summertime upper mesosphere at high latitudes. This paper will show that the observed seasonal behavior of the metal layers provides a rigorous test of general circulation models in the upper mesosphere.

  5. Year-to-year instability of the Mars south polar cap

    NASA Technical Reports Server (NTRS)

    Jakosky, Bruce M.; Haberle, Robert M.

    1990-01-01

    Models of the Mars polar cap energy balance suggest that the south cap has two possible configurations at the current epoch. It can be covered all year by CO2 frost, as was observed by the Viking spacecraft, or the CO2 frost can disappear at midsummer to expose an underlying surface. The difference between the two states depends on the role of energy conducted into the subsurface. If the cap was exposed the previous year, conducted energy will cause less CO2 frost to condense in winter, and the frost will disappear completely in summer. If the cap was covered the previous year, there will be no conducted energy, and it will stay covered again. Subtle effects in the atmosphere can perturb the cap energy balance sufficiently to cause the cap to jump between states. This behavior might provide an explanation for the large southern summer water vapor abundances observed in 1969. It also explains the observed differences between the north and the south residual caps as resulting in part from a difference in the role in the annual energy balance of energy conducted into the subsurface.

  6. The spatial coherence of Schumann activity in the polar cap

    NASA Astrophysics Data System (ADS)

    Holtham, P. M.; McAskill, B. J.

    1988-02-01

    The spatial coherence of the first two Schumann resonant modes has been studied at two locations in the polar cap separated by 1100 km. Measurements were made at Assistance Bay and Mould Bay, which have geomagnetic latitudes of 83 and 79 deg, respectively, and satellite time-keeping was employed to accurately synchronize the field stations. The coherence was found to be high, typically 95 percent for the first Schumann mode, and was unaffected by changes in Kp, a storm sudden commencement, or a solar flare event. Polarization rotations were observed between the two stations, which could most likely be attributed to the coastline effect. The results are consistent with a stable propagation of Schumann activity from midlatitudes to high latitudes that is relatively unaffected by changes in the polar cap ionosphere.

  7. Atmospheric Modeling of the Martian Polar Regions: One Mars Year of CRISM EPF Observations of the South Pole

    NASA Astrophysics Data System (ADS)

    Brown, A. J.; Wolff, M. J.

    2009-03-01

    We have used CRISM Emission Phase Function gimballed observations to investigate atmospheric dust/ice opacity and surface albedo in the south polar region for the first Mars year of MRO operations. This covers the MY28 "dust event" and cap recession.

  8. LSPECS: A Proposed Robotic Astronomy Mission to the Lunar South Polar Regions

    NASA Technical Reports Server (NTRS)

    Lowman, Paul D., Jr.

    2003-01-01

    This paper outlines a possible mission to emplace a robotic infrared/submillimeter wave interferometer array near the lunar south pole. This region has now been investigated by the Clementine and Lunar Prospector missions, and by Earth-based radar, and its topography and thermal environment are fairly well-known. The area would be exceptionally suitable for infrared/submillimeter astronomy because of the continually low temperatures, approaching that of liquid nitrogen (77K) in some places. The presence of ice has been inferred independently from Clementine and Lunar Prospector, providing another incentive for a south polar mission. A submillimeter spaceborne interferometer mission, Submillimeter Probe of the Evolution of the Cosmic Structure (SPECS) has been proposed by John Mather and others, covering the 40 - 500 micron region with 3 formation flying telescopes. The present paper proposes a lunar adaptation of the SPECS concept, LSPECS. This adaptation would involve landing 4 telescopes on the area north of Shackleton crater at zero degrees longitude. This is in nearly year round darkness but is continually radar visible from Earth. The landed payload of LSPECS would include a telerobotic rover, 4 three meter submm telescopes, a solar power array to be emplaced on the continually sunlit north rim of Shackleton crater, and an S-band antenna for data relay to Earth. Operation without the use of expendable cryogenics for cooling might be possible, trading long exposure time for instrument temperatures above that of liquid helium. The LSPECS would permit long-term study of an extremely wide range of cosmic and solar system phenomena in the southern celestial hemisphere. For complete sky coverage, a similar installation near the north pole would be required. The LSPECS site would also be suitable other types of observation, such as optical interferometry or centimeter wavelength radio astronomy. The lunar south pole is also of great interest because of its extensive

  9. Topography of the South Polar Cap and Layered Deposits of Mars: Viking Stereo Grametry at Regional and Local Scales

    NASA Astrophysics Data System (ADS)

    Schenk, P.; Moore, J.; Stoker, C.

    1998-01-01

    Layered deposits and residual polar caps on Mars may record the deposition of ice and sediment modulated by periodic climate change. Topographic information relating to layer thicknesses, erosional processes, and formation of dark spirals within these deposits has been sparce or unreliable until the arrival of MOLA in orbit in September 1997. To assist in evaluating these terrains prior to launch and to assess formation and erosion processes in the polar deposits, we have assembled Viking stereo mosaics of the region and have produced the first reliable DEM models of the south polar deposits using automated stereogrammetry tools. Here we report our preliminary topographic results, pending final image pointing updates. The maximum total thickness of the layered deposits in the south polar region is 2.5 km. The thick layered deposits consist of a series of megaterraces. Each terrace is several tens of kilometers wide and is flat or slopes very gently toward the pole. These terraces step downward from a central plateau near the south pole. Terraces are bounded by relatively steep scarps 100-500 meters high that face toward the equator. These scarps correspond to the pattern of dark spirals observed within the residual cap in southern summer, and are interpreted as ice or frost-free surfaces warmed by solar insolation. Several tongue-shaped troughs, with rounded cirquelike heads, are observed near the margins of the deposit. These troughs are 300-600 meters in deep and may be similar to troughs observed in the northern polar deposit.

  10. A Brunhes-Matuyama polarity transition record from anoxic sediments in the South Atlantic (Ocean Drilling Program Hole 1082C)

    NASA Astrophysics Data System (ADS)

    Yamazaki, T.; Oda, H.

    2001-08-01

    A paleomagnetic study was performed on Hole 1082C sediment cores taken during the Ocean Drilling Program (ODP) Leg 175 in the South Atlantic in order to obtain a high-resolution Brunhes-Matuyama (B/M) polarity transition record. An average sedimentation rate was as high as 10 cm/kyr. The cores consist of strongly anoxic sediments, which is common for the areas of large material supply. Anoxic sediments, which are geochemically quite active, were considered to be unsuitable for studies on detailed behavior of the geomagnetic field such as polarity transitions. For global site distribution, however, it is necessary to make efforts to retrieve paleomagnetic records from such sediments. A continuous record of directional changes around the transition was obtained from U-channel samples after cleaning by stepwise alternating-field (AF) demagnetization. Consistency of the record was checked using discrete samples taken from the other half of the cores. The coring-induced magnetic overprint of radial-inward direction, which has often been reported from ODP piston-cores, was negligibly small in our cores. Relative paleointensity variation was estimated from remanent intensities of the discrete samples normalized by artificial remanences. Our record shows following features of the B/M transition similar to those already reported by previous studies. A zone of large directional fluctuations with low paleointensities occurs just before the main transition (788 to 795 ka based on the oxygen-isotope stratigraphy), which would correspond to the "precursor" of Hartl and Tauxe (1996). The virtual geomagnetic poles (VGPs) at the precursor lie along the so-called preferred longitudinal bands over the north-south Americas and Australia-east Asia. After the main transition from the reversed to normal polarity, VGPs stayed in the middle-to-high latitudes over the North America with an intermediate paleointensity for about 5~kyrs, and then moved in the vicinity of the North Pole with

  11. Tidally-induced melting events as the origin of south-pole activity on Enceladus

    NASA Astrophysics Data System (ADS)

    Běhounková, Marie; Tobie, Gabriel; Choblet, Gaël; Čadek, Ondřej

    2012-06-01

    The intense activity at the south pole of Enceladus hints at an internal water reservoir. However, there is no direct evidence of liquid water at present and its long-term stability in the interior remains problematic. By modeling heat production and transfer in the ice shell in a spherical geometry, we show that tidal heating naturally leads to a concentration of convective hot upwellings in the south polar region, favoring the preservation of liquid water at depth. We show that large volumes of water are produced within the ice shell at the south pole during periods of elevated orbital eccentricity (3-5 times the present-day value). Strong lateral variations in the melt production and crystallization rates result in stress concentration in the south polar region, thus providing an explanation for the tectonic activity observed today. We predict that an internal ocean may be sustained over the long term as the consequence of repeated periods with elevated orbital eccentricity, leading to episodic melting and resurfacing events.

  12. Spontaneous motility of passive emulsion droplets in polar active gels.

    PubMed

    De Magistris, G; Tiribocchi, A; Whitfield, C A; Hawkins, R J; Cates, M E; Marenduzzo, D

    2014-10-21

    We study by computer simulations the dynamics of a droplet of passive, isotropic fluid, embedded in a polar active gel. The latter represents a fluid of active force dipoles, which exert either contractile or extensile stresses on their surroundings, modelling for instance a suspension of cytoskeletal filaments and molecular motors. When the polarisation of the active gel is anchored normal to the droplet at its surface, the nematic elasticity of the active gel drives the formation of a hedgehog defect; this defect then drives an active flow which propels the droplet forward. In an extensile gel, motility can occur even with tangential anchoring, which is compatible with a defect-free polarisation pattern. In this case, upon increasing activity the droplet first rotates uniformly, and then undergoes a discontinuous nonequilibrium transition into a translationally motile state, powered by bending deformations in the surrounding active medium. PMID:25156695

  13. Systematic High-Resolution Remote-Sensing Investigation of Martian South Polar Landforms: Thermal Contraction Polygons

    NASA Astrophysics Data System (ADS)

    van Gasselt, Stephan; Hao, Jingyan

    2015-04-01

    The Martian poles are geomorphologically highly diverse as orbital high-resolution imaging data have shown since the early 2000s [1]. Apart from an initially unexpected diversity and an abundance of different and exotic landform types, image and topography data presented evidence for seasonal changes, not only with respect to the seasonal extent of the polar-caps but also with respect to individual landforms that have later been addressed as cryptic material [2]. Most of these features are - though not exclusively - located within the seasonal CO2 cap and their changes imply not only seasonal but also potentially long-term climatic changes [3]. Today, plausible formation processes for some of these landforms have been proposed [7-9; 11-13] and modelled but despite a wealth of new data, systematic surveys are relatively rare [10]. For more than 13,500 images taken by the MGS Mars Orbiter Camera (MOC-NA) over the south-polar area (75'90°S) systematic mapping and classification of thermal contraction polygons have been conducted in previous work by the author and others [4-5], but seasonal changes were identified for few locations only due to limitations of image coverage. Reconstruction of thermal-contraction crack development suggests a complex interplay between seasonal H2O and CO2 ices [6] but image coverage was too sparse at that time to build a representative distribution model and to confirm formation models. Due to the small size of thermal contraction polygons (few tens of meters in diameter), data obtained by MEx/HRSC and MO/THEMIS could only marginally help to identify features and feature distributions. With the arrival of Mars Reconnaissance Orbiter, the Context Camera (CTX) provided new detailed insight into the seasonal behaviour of the south polar area of Mars and its landforms at geometric resolutions comparable to those of MOC. Four Martian years have been covered by now which allows us to reconstruct formation and analyse distribution of featured

  14. New Model Predicts Fire Activity in South America

    NASA Video Gallery

    UC Irvine scientist Jim Randerson discusses a new model that is able to predict fire activity in South America using sea surface temperature observations of the Pacific and Atlantic Ocean. The find...

  15. Cassini Observes the Active South Pole of Enceladus

    NASA Technical Reports Server (NTRS)

    Porco, C. C.; Helfenstein P.; Thomas, P. C.; Ingersoll, A. P.; Wisdom, J.; West, R.; Neukum, G.; Denk, T.; Wagner, R.; Roatsch, T.; Kieffer, S.; Turtle, E.; McEwen, A.; Johnson, T. V.; Rathbun, J.; Veverka, J.; Wilson, D.; Perry, J.; Spitale, J.; Brahic, A.; Burns, J. A.; DelGenio, A. D.; Dones, L.; Murray, C. D.; Squyres, S.

    2007-01-01

    Cassini has identified a geologically active province a the south pole of Saturn's moon Enceladus. The shape of Enceladus suggests a possible intense heating epoch in the past by capture into a 1:4 secondary spin/orbit resonance.

  16. Polarity Reversal of the Solar Photospheric Magnetic Field During Activity Cycle 24

    NASA Astrophysics Data System (ADS)

    Sun, Xudong; Hoeksema, Jon Todd; Liu, Yang; Zhao, Junwei

    2014-06-01

    The large-scale solar magnetic field reverses its polarity during the maximum phase of each activity cycle. As observed on the photosphere, active region (AR) magnetic flux migrates poleward in narrow, sheared streams resulted from large-scale flows and diffusion. A small net flux of the trailing sunspot polarity eventually aggregates at high latitudes, manifesting the poloidal field of the next cycle. We characterize this process for the ongoing cycle 24 based on four years' line-of-sight magnetograms from the Helioseismic and Magnetic Imager (HMI). The axial dipole component reversed sign in early 2012, but the poleward flux migration was grossly out of phase in the two hemispheres. As a proxy, the northern polar field (taken as mean above 70 degrees latitude) switched from negative to positive in late 2012, whereas the southern remained positive as of March 2014. Three factors that are in line with the surface flux transport model may have contributed. First, AR emergence started and peaked earlier in the north. Second, several ARs with small or inverse tilt angles (w.r.t. the Joy's law) emerged in the south in late 2010. Third, meridional flow speed inferred from helioseismology varied greatly prior to 2013; slower streams (compared to a three-year mean at the same latitude) appeared earlier in the north. We correlate HMI with the long-running Wilcox Solar Observatory (WSO) dataset, and compare the current cycle with the previous three.

  17. Basins and the South Polar Terrain of Enceladus: Hotspots vs. Coldspots, and More Evidence for Crustal Spreading and Convergence

    NASA Astrophysics Data System (ADS)

    McKinnon, William B.; Schenk, P. M.

    2009-09-01

    Stereo-derived topographic mapping of 50% of Enceladus reveals at least 6 large-scale, ovoid depressions (basins) 90-175 km across and 800-to-1500 m deep and uncorrelated with geologic boundaries (Schenk and McKinnon, GRL, in press). Their shape and scale are inconsistent with impact, geoid deflection, or with dynamically supported topography. Isostatic thinning of Enceladus’ ice shell associated with upwellings (and tidally-driven ice melting) can plausibly account for the basins. Thinning implies upwarping of the base of the shell of 10-20 km beneath the depressions, depending on total shell thickness; loss of near-surface porosity due to enhanced heat flow may also contribute to basin lows. Alternatively, the basins may overly cold, inactive, and hence denser ice, but thermal isostasy alone requires thermal expansion more consistent with clathrate hydrate than water ice. In contrast to the basins, the south polar depression (SPD) is larger ( 350 wide) and shallower ( 0.4-to-0.8 km deep) and correlates with the area of tectonic deformation and active resurfacing. The SPD also differs in that the floor is relatively flat (i.e., conforms roughly to the global triaxial shape, or geoid) with broad, gently sloping flanks. The relative flatness across the SPD suggests that it is in or near isostatic equilibrium, and underlain by denser material, supporting the polar sea hypothesis of Collins and Goodman [2007]. Near flatness is also predicted by a crustal spreading origin for the "tiger stripes” [e.g., Barr, 2008]; the extraordinary, high CIRS heat flows imply half-spreading rates in excess of 10 cm/yr, a very young surface age ( 250,000 yr), and a rather thin lithosphere (hence modest thermal topography). Topographic rises in places along the outer margin of the SPD correlate with parallel ridges and deformation along the edge of the resurfaced terrain, consistent with a compressional, imbricate thrust origin for these ridges, driven by the spreading.

  18. Reproductive performance and organochlorine pollutants in an Antarctic marine top predator: the south polar skua.

    PubMed

    Bustnes, Jan O; Tveraa, Torkild; Varpe, Øystein; Henden, John A; Skaare, Janneche U

    2007-10-01

    Despite low levels of organochlorine contaminants (OCs) in Antarctic biota, some compounds may exceed the levels in equivalent Arctic species, and previous studies have found biochemical evidence of pollutant exposure in south polar skuas (Catharacta maccormicki), a common marine top predator in the region. In this study we examined relationships between fitness components (fecundity and adult return rate between breeding seasons) and concentrations of OCs in this species. In 65 nests, both males and females were caught, and using principal component analyses (PCA) we produced composite measurements (PC1 and PC2) of six highly correlated OCs measured in blood samples. Although the concentrations of OC were below those documented to have reproductive effects in other aquatic birds, we found that the eggs of females with high levels of OCs in the blood hatched later, and their chicks were in poorer condition at hatching, than females with low OC levels. Thus OCs may delay reproduction and reduce foetal growth in the skuas. However, there was no relationship between the parents' OC residues and the occurrence of non-viable eggs, although the proportion of nests containing non-viable eggs was high (47%). Moreover, there were no significant relationships between OCs and reproductive variables in males, even if males had higher OC levels than females, and no associations between OCs and adult return rate between breeding seasons. PMID:17561256

  19. Albedo of Surface CO2 Deposits in Mars' Residual South Polar Cap

    NASA Astrophysics Data System (ADS)

    James, P. B.; Wolff, M. J.; Bonev, B.

    2014-12-01

    The albedo of surface CO2 deposits in the Residual South Polar Cap (RSPC) of Mars controls their net condensation / sublimation over a martian year and is therefore a crucial parameter in determining RSPC stability. The albedo used in previous analyses is obtained by dividing I/F, determined from radiometrically calibrated imaging data, by the cosine of the incidence angle. Because of atmospheric aerosols, the albedo calculated from I/F above the atmosphere is not the surface albedo that enters into stability considerations. In order to determine the surface albedo, we interpolate optical depths determined from CRISM EPF measurements to provide estimates of the dust and ice opacities over the RSPC (Wolff et al., 2009) and use these to determine the actual surface albedos from MARCI images using the radiative transport program DISORT (Stamnes et al., 1988). Assuming that dust is the only contributor to atmospheric opacity, the retrieved surface albedos for the longer wavelength MARCI filters in MY 28 and 29 are found to be consistent despite very different dust opacities in the two years (James et al., 2014). However, this model fails to reproduce the short wavelength behavior in early summer. We consider possible modifications of the dust only model that could explain the discrepancy.

  20. Albedo of surface CO2 deposits in Mars' Residual South Polar Cap

    NASA Astrophysics Data System (ADS)

    James, P. B.; Wolff, M. J.; Bonev, B.

    2013-12-01

    The albedo of surface CO2 deposits in the Residual South Polar Cap (RSPC) controls their net condensation / sublimation over a martian year and is therefore a crucial parameter in determining RSPC stability. The Lambert albedo used in previous analyses is obtained by dividing I/F, determined from radiometrically calibrated imaging data, by the cosine of the incidence angle. Because of atmospheric dust, this albedo calculated from I/F above the atmosphere is not the surface albedo that enters into stability considerations. In order to investigate the real surface albedo, we interpolate optical depths determined from CRISM EPF measurements to provide estimates of the opacites over the RSPC and use these to determine the actual surface albedos from MARCI images using the radiative transport program DISORT (Stamnes et al., 1988). The assumption that the surface is a Lambertian diffuse reflector can then also be tested. MARCI images acquired in one-day span a significant range of emission angles; the set of images acquired during one sol is similar to EPF observations except that diurnal opacity variations could be important.

  1. Gravitational spreading, bookshelf faulting, and tectonic evolution of the South Polar Terrain of Saturn's moon Enceladus

    NASA Astrophysics Data System (ADS)

    Yin, An; Pappalardo, Robert T.

    2015-11-01

    Despite a decade of intense research the mechanical origin of the tiger-stripe fractures (TSF) and their geologic relationship to the hosting South Polar Terrain (SPT) of Enceladus remain poorly understood. Here we show via systematic photo-geological mapping that the semi-squared SPT is bounded by right-slip, left-slip, extensional, and contractional zones on its four edges. Discrete deformation along the edges in turn accommodates translation of the SPT as a single sheet with its transport direction parallel to the regional topographic gradient. This parallel relationship implies that the gradient of gravitational potential energy drove the SPT motion. In map view, internal deformation of the SPT is expressed by distributed right-slip shear parallel to the SPT transport direction. The broad right-slip shear across the whole SPT was facilitated by left-slip bookshelf faulting along the parallel TSF. We suggest that the flow-like tectonics, to the first approximation across the SPT on Enceladus, is best explained by the occurrence of a transient thermal event, which allowed the release of gravitational potential energy via lateral viscous flow within the thermally weakened ice shell.

  2. Identification of tectonic deformations on the south polar surface of the moon

    NASA Astrophysics Data System (ADS)

    Mukherjee, Saumitra; Singh, Priyadarshini

    2015-07-01

    Recent extensional and contractional tectonic features present globally over the lunar surface have been studied to infer lunar crustal tectonism. Investigation of indicators of recent crustal tectonics, such as fault lines, thrust fault scarps, and dislocation of debris along the identified fault planes, primarily using data from the miniature-synthetic aperture radar (mini-SAR) aboard CHANDRAYAAN-1 mission and Narrow angle camera (NAC) images, are the focus of this study. Spatial orientation of these tectonic features helps to elucidate the change in the interior geological dynamics of any planetary body with time. The ability of microwave sensors to penetrate the lunar regolith, along with application of m-χ decomposition method on Mini-SAR data has been used to reveal unique features indicative of hidden tectonics. The m-χ decomposition derived radar images expose hidden lineaments and lobate scarps present within shadowed crater floors as well as over the illuminated regions of the lunar surface. The area around and within Cabeus B crater in the South Polar Region contains lobate scarps, hidden lineaments and debris avalanches (associated with the identified lineaments) indicative of relatively recent crustal tectonism.

  3. The 1997 Spring Regression of the Martian South Polar Cap: Mars Orbiter Camera Observations

    USGS Publications Warehouse

    James, P.B.; Cantor, B.A.; Malin, M.C.; Edgett, K.; Carr, M.H.; Danielson, G.E.; Ingersoll, A.P.; Davies, M.E.; Hartmann, W.K.; McEwen, A.S.; Soderblom, L.A.; Thomas, P.C.; Veverka, J.

    2000-01-01

    The Mars Orbiter cameras (MOC) on Mars Global Surveyor observed the south polar cap of Mars during its spring recession in 1997. The images acquired by the wide angle cameras reveal a pattern of recession that is qualitatively similar to that observed by Viking in 1977 but that does differ in at least two respects. The 1977 recession in the 0?? to 120?? longitude sector was accelerated relative to the 1997 observations after LS = 240??; the Mountains of Mitchel also detached from the main cap earlier in 1997. Comparison of the MOC images with Mars Orbiter Laser Altimeter data shows that the Mountains of Mitchel feature is controlled by local topography. Relatively dark, low albedo regions well within the boundaries of the seasonal cap were observed to have red-to-violet ratios that characterize them as frost units rather than unfrosted or partially frosted ground; this suggests the possibility of regions covered by CO2 frost having different grain sizes. ?? 2000 Academic Press.

  4. Barriers to Participation in Physical Activity Among South Sudanese Children in South Australia: Parents' Perspectives.

    PubMed

    Mude, William; Mwanri, Lillian

    2016-01-01

    Physical inactivity is one of the determinants of childhood obesity. Although its facilitators are well documented for the general community, limited evidence exists informing newly arrived and emerging migrant communities in Australia. To explore parents' perspectives of barriers to participation in physical activity among South Sudanese children in South Australia. Qualitative, face-to-face interviews were conducted with parents. Data were transcribed, coded, and analyzed thematically using NVivo software. Multiple and complex barriers to physical activity participation were described. Enabling and supportive programs are needed to improve physical activity participation and health outcomes of new migrants. PMID:27536934

  5. The Solar Non-activity Cycle of Polar Coronal Holes

    NASA Astrophysics Data System (ADS)

    Kirk, M. S.; Pesnell, W. D.; Young, C. A.

    2015-12-01

    After the unusually extended minimum in 2008 and 2009, solar cycle 24 continues to be an exceptionally weak cycle both in sunspot number and number of large magnetic storms. Coronal holes offer a direct measurement of the non-activity solar cycle, a missing link in our understanding of solar cycle progression. They are prevalent during solar minimum, non-axisymmetric, and are stable. Polar coronal holes are regularly observed capping the northern and southern solar poles in EUV images of the corona and are understood as the primary source of the fast solar wind. We make measurements of these features from 1996 through 2015 using four different NASA imagers: SOHO EIT, STEREO A and B EUVI, and SDO AIA. A measurement of the axial symmetry of the polar holes is seen to have clear solar cycle dependence. Polar coronal holes are aligned with the solar rotation axis during minimum and have a maximum asymmetry between holes of about 14 degrees in the declining phase of the current solar cycle.

  6. Research on the system scheme and experiment for the active laser polarization imaging

    NASA Astrophysics Data System (ADS)

    Fu, Qiang; Duan, Jin; Zhao, Rui; Li, Zheng; Zhang, Su; Zhan, Juntong; Zhu, Yong; Jiang, Hui-Lin

    2015-10-01

    The polarization imaging detection technology increased the polarization information on the basis of the intensity imaging, which is extensive application in the military and civil and other fields. The research present and development trend of polarization imaging detection technology was introduce, the system scheme of the active polarization imaging detection was put forward, and the key technologies such as the polarization information detection, optical system design, polarization radiation calibration and image fusion approach was analyzed. On this basis, detection system by existing equipment of laboratory was set up, and on the different materials such as wood, metal, plastic and goal was detected by polarization imaging to realize the active polarization imaging detection. The results show that image contrast of the metal and man-made objects is higher, the polarization effect is better, which provided the basis on the better performance of the polarization imaging instruments.

  7. Visco-elastic Dynamics of an Active Polar Dynamic System

    NASA Astrophysics Data System (ADS)

    Pleiner, Harald; Svensek, Daniel; Brand, Helmut R.

    2015-03-01

    We study the dynamics of systems with a polar dynamic preferred direction that are embedded in visco-elastic media. Examples include the pattern-forming growth of bacteria and molecular motors. Because the ordered state only exists dynamically, but not statically, the macroscopic variable of choice is the velocity of the active units. The passive visco-elastic medium is described by a relaxing strain tensor. We derive the macroscopic equations for such a system and discuss novel static, reversible and irreversible cross-couplings connected to this two-fluid (two-velocity) system. The dynamics is rather different compared to the case of passive, static polar order. In particular, we find a complicated normal mode structure that reflects the broken time-reversal symmetry due to the non-equilibrium situation, anisotropy of first sound and a possible second sound excitation due to the active velocity, and various manifestations of the visco-elastic relaxation. We discuss critically the role of the so-called active term in the stress tensor as well as the thermodynamically correct description of the hydrodynamic transport velocities.

  8. Treadmilling and length distributions of active polar filaments

    NASA Astrophysics Data System (ADS)

    Erlenkämper, C.; Kruse, K.

    2013-10-01

    The cytoskeleton is a network of filamentous proteins, notably, actin filaments and microtubules. These filaments are active as their assembly is driven by the hydrolysis of nucleotides bound to the constituting protomers. In addition, the assembly kinetics differs at the two respective ends, making them active polar filaments. Experimental evidence suggests, that, in vivo, actin filaments and microtubules can grow at one and shrink at the other end at the same rate, a state that is known as treadmilling. In this work, we use a generic discrete two-state model for active polar filaments to analyze the conditions leading to treadmilling. We find that a single filament can self-organize into the treadmilling state for a broad range of monomer concentrations. In this regime the corresponding length distribution has a pronounced maximum at a finite value. We then extend our description to consider specifically the dynamics of actin filaments. We show that actin treadmilling should be observable in vitro in the presence of appropriate depolymerization promoting factors.

  9. Post-Equinox Evolution of Titan’s Detached Haze and South Polar Vortex Cloud

    NASA Astrophysics Data System (ADS)

    West, Robert A.; Ovanessian, A.; Del Genio, A.; Turtle, E. P.; Perry, J.; NcEwen, A.; Ray, T.; Roy, M.

    2013-10-01

    Instruments on the Cassini spacecraft discovered new phenomena related to the (presumably) seasonal behavior of photochemical haze and formation of the winter polar vortex. West et al. 2011 (Geophys. Res. Lett. , 380 , L06204. doi: 10.1029/2011GL046843) described a ‘detached’ haze layer that dropped in altitude from about 500 km in 2005 to about 360 km by late 2010. New images from the Cassini ISS camera show that the appearance of a detached layer is produced by a gap in the haze vertical profile and it is the gap rather than a haze layer that drops in altitude. Intensity profiles from different epochs form an envelope when plotted on top of each other, and the downward movement of the gap can be most easily seen when plotted that way. The movement of a gap rather than movement of a layer of enhanced haze density was suspected in the earlier publication but now it is more apparent. In recent months the gap became very shallow and the limb intensity profiles at a pixel scale ~10 km/pixel evolved from one local maximum/minimum into two local minima/maxima of smaller amplitude and appear to be trending toward the disappearance of relative maxima and minima, leaving a smooth envelope. These observations will require new developments in coupled dynamical and haze microphysical models as none of the current models account for this behavior. Titan’s south polar vortex cloud was detected concurrently by the ISS, VIMS, and CIRS instruments on Cassini in May of 2012. It has an unusual color (more yellow than Titan’s main haze in ISS images), morphology and texture (suggestive of a condensate cloud experiencing open cell convection) and displays a spectral feature at 220 cm-1 (Jennings et al., 2012, Astrophys. J. Lett. 761, L15 DOI: 10.1088/2041-8205/761/1/L15). These attributes point to a condensate of unknown composition. The haze patch is seen in images up to the present (July, 2013), but the latest images suggest a ‘softening’ or more diffuse edge than the

  10. Limits on the Polarized Power Spectrum at 126 and 164 MHz from PAPER South Africa 32-Element Data

    NASA Astrophysics Data System (ADS)

    Aguirre, James E.; Moore, David; Paper Collaboration

    2015-01-01

    Faraday-rotated, polarized emission represents a potential contaminating foreground for measurements of the highly redshifted 21 cm power spectrum. There are few existing measurements of polarized foreground emission at meter wavelengths (e.g. Bernardi et al 2013, Jelic et al 2014) and its actual effect on the measured Stokes I spectrum from reionization is unclear. We present new limits on the power spectrum of Stokes Q, U, and V emission at 126 and 164 MHz using PAPER South Africa 32-element data, to supplement existing results for Stokes I (Parsons et al 2014, Jacobs et al 2014). We use upper limits on the Q power spectra to place upper limits on the average polarization fraction of point sources.

  11. Polarization aberrations in the solar activity measurements experiments (SAMEX) solar vector magnetograph

    NASA Technical Reports Server (NTRS)

    Mcguire, James P., Jr.; Chipman, Russell A.

    1989-01-01

    An optical design and polarization analysis of the Air Force/NASA Solar Activity Measurements Experiments solar vector magnetograph optical system is performed. Polarization aberration theory demonstrates that conventional telescope coating designs introduce unacceptably high levels of polarization aberrations into the optical system. Several ultralow polarization mirror and lens coatings designs for this instrument are discussed. Balancing of polarization aberrations at different surfaces is demonstrated.

  12. Topography of the Lunar South Polar Region: Implications for the Size and Location of Permanently Shaded Areas

    NASA Technical Reports Server (NTRS)

    Zuber, Maria T.; Smith, David E.

    1997-01-01

    We analyze Clementine altimetry to constrain the size and location of proposed permanently shadowed regions in the vicinity of the lunar south pole. Long and short wavelength topography in the vicinity of the pole, in combination with measurements of depths of well-preserved craters and basins and the lunar topographic power spectrum, have direct bearing on the nature of elevations in the south polar region. A criterion based on geometric considerations and altimetry demonstrates that the existence of permanent shadowing is not very sensitive to the elevation of the south pole. In addition, permanent shadowing cannot be a consequence of large structures such as the South Pole-Aitken Basin and/or a 300-km degraded polar basin. Perennially dark regions, if they exist, are most likely associated with craters or other axisymmetric features with diameters of at most 80 km centered at the pole. For structures displaced 2 deg from the pole the maximum allowable diameter decreases to approximately 30 km.

  13. Physical State of the ``Bright'' South Seasonal Polar Cap From OMEGA Observations

    NASA Astrophysics Data System (ADS)

    Doute, S.; Schmidt, F.; Schmitt, B.; Vincendon, M.; Langevin, Y.; Gondet, B.; Bibring, J.

    2009-12-01

    The composition, physical state and texture of the South Seasonal Polar Cap (SSPC) have important consequences on energy balance. The imaging spectrometer OMEGA on board Mars Express has acquired the most comprehensive set of observations to date in the near-infrared (0.93-5.1 microns) on the SSPC from mid-winter solstice (Ls=110° , December 2004) to the end of the recession at Ls=320° (November 2005) [1]. The time resolution is 3 days to one month and the spatial resolution ranges from 700m to 10 km/pixel. [1] showed that during southern spring and summer, there is a very complex evolution in terms of effective grain size of CO2 ice and contamination by dust or H2O ice. H2O ice does not play a significant role except close to the end of the recession. [2] systematically segmented the South Seasonal Polar Cap into different spectral units and tested diverse surface representations by the modeling of spectral end-members and average unit spectra. Here we focus on the “bright” part of the SSPC corresponding to spectral unit SSPC1 (I.b of [1]). Regions belonging to this unit have a very bright albedo (≈ 0.6-0.8) associated with strong CO2 ice absorption features. According to [1] such characteristics are compatible with granular CO2 deposits with grain size in the range of 5 cm implying an extremely low contamination by dust and water ice. Furthermore, from their study of a representative region at 34° E, 76° S, the albedo increases from Ls=223° up to a maximum at Ls=240° and then decreases until total disappearance of the ice. The albedo increase would require a decrease of grain size if the granular model is really relevant. However the mean free path within CO2 ice as well as its thermodynamic behavior would rather favor a porous CO2 slab model [3]. Then photometric effects could be expected that could explain the brightening. In this paper we propose to further study the physical state of the “bright” part of the SSPC and its evolution by

  14. Spectral-induced polarization characteristics of rocks from Shinyemi deposit in Northeastern South Korea

    NASA Astrophysics Data System (ADS)

    Park, Samgyu; Shin, Seung Wook; Son, Jeong-Sul; Kim, Changryol

    2016-04-01

    Contact metasomatism between carbonate and igneous rocks leads to the formation of skarn deposits, and ore minerals are abundant. Geophysical methods that visualize the distributions of physical properties have been utilized to determine lithological boundaries in ore deposits. In particular, spectral-induced polarization (SIP) is the most effective of those methods for mineral exploration because it can obtain not only the boundaries but also the abundance and grain size of ore minerals. It is crucial to characterize the SIP responses of in situ rocks for a more realistic interpretation. Thus, typical rocks composed of igneous rock, skarn rock, skarn ore, and carbonate rock were sampled from drilling cores in the Shinyemi deposit, which is one of the well-known skarn deposits in Northeastern South Korea. The purpose of this study was to characterize the SIP responses of rocks by laboratory measurements. The characterization was performed by evaluating spectra and IP parameters. The IP properties were acquired from equivalent circuit analysis using a circuit model based on the electrochemical theory, and the analysis results of this circuit model were relatively well fit compared with those of the traditional Dias and Cole-Cole models. The frequency responses below 100 Hz in the spectra and the chargeability values of the skarn rocks and ores containing magnetite were relatively strong and high, respectively, compared with those of non-mineralized igneous and carbonate rocks. Therefore, it is considered that these characteristics are dependent on the abundance of magnetite. In case of the skarn ores with high magnetite content, the resistivity values were significantly low and the relaxation time values were influenced by the grain size of magnetite. On the other hand, it is considered that the DC resistivity and the relaxation time values of the igneous and carbonate rocks are slightly related to the porosity and the grade of hydrothermal alteration, respectively.

  15. Some Activities with Polarized Light from a Laptop LCD Screen

    ERIC Educational Resources Information Center

    Fakhruddin, Hasan

    2008-01-01

    The LCD screen of a laptop computer provides a broad, bright, and extended source of polarized light. A number of demonstrations on the properties of polarized light from a laptop computer screens are presented here.

  16. Dynamics of Venus' Southern hemisphere and South Polar Vortex from VIRTIS data obtained during the Venus Expres Mission

    NASA Astrophysics Data System (ADS)

    Hueso, R.; Garate-Lopez, I.; Sanchez-Lavega, A.

    2011-12-01

    The VIRTIS instrument onboard Venus Express observes Venus in two channels (visible and infrared) obtaining spectra and multi-wavelength images of the planet. The images have been used to trace the motions of the atmosphere at different layers of clouds [1-3]. We review the VIRTIS cloud image data and wind results obtained by different groups [1-3] and we present new results concerning the morphology and evolution of the South Polar Vortex at the upper and lower cloud levels with data covering the first 900 days of the mission. We present wind measurements of the South hemisphere obtained by cloud tracking individual cloud features and higher-resolution wind results of the polar region covering the evolution of the South polar vortex. The later were obtained by an image correlation algorithm run under human supervision to validate the data. We present day-side data of the upper clouds obtained at 380 and 980 nm sensitive to altitudes of 66-70 km, night-side data in the near infrared at 1.74 microns of the lower cloud (45-50 km) and day and night-side data obtained in the thermal infrared (wavelengths of 3.8 and 5.1 microns) which covers the dynamical evolution of Venus South Polar vortex at the cloud tops (66-70 km). We explore the different dynamics associated to the varying morphology of the vortex, its dynamical structure at different altitudes, the variability of the global wind data of the southern hemisphere and the interrelation of the polar vortex dynamics with the wind dynamics at subpolar and mid-latitudes. Acknowledgements: Work funded by Spanish MICIIN AYA2009-10701 with FEDER support and Grupos Gobierno Vasco IT-464-07. References [1] A. Sánchez-Lavega et al., Geophys. Res. Lett. 35, L13204, (2008). [2] D. Luz et al., Science, 332, 577-580 (2011). [3] R. Hueso, et al., Icarus doi:10.1016/j.icarus.2011.04.020 (2011)

  17. Expansion of student activities in Africa: from south to north

    NASA Astrophysics Data System (ADS)

    Cherif, Rim; Ben Salem, Amine; Gueddana, Amor; Zghal, Mourad; Naidoo, Darryl; Forbes, Andrew; Heidt, Alexander M.; Rohwer, Erich G.

    2014-07-01

    Optics and photonics research in Africa has gradually grown in the past ten years with a very active optical community involved in state-of-the-art research. Despite relatively low resources, optics research in the continent is competitive with many international benchmarks and has had a significant impact within the African continent. In the past five years, a group of dynamic students have developed the student chapter network from Tunisia to South Africa. The first student chapters of the optical society of America (OSA) and the international society for optics and photonics (SPIE) were established in South Africa (in the Council for Scientific and Industrial Research (CSIR) and in the University of Stellenbosch), followed by a chapter in Tunisia (Engineering school of communications of Tunis, Sup'Com). In this paper, we will present the major activities of the student chapters of Tunisia and South Africa, and how they are promoting optics and photonics in Africa.

  18. Mass balance of Mars' residual south polar cap from CTX images and other data

    NASA Astrophysics Data System (ADS)

    Thomas, P. C.; Calvin, W.; Cantor, B.; Haberle, R.; James, P. B.; Lee, S. W.

    2016-04-01

    Erosion of pits in the residual south polar cap (RSPC) of Mars concurrent with deposition and fluctuating cap boundaries raises questions about the mass balance and long term stability of the cap. Determining a mass balance by measurement of a net gain or loss of atmospheric CO2 by direct pressure measurements (Haberle, R.M. et al. [2014]. Secular climate change on Mars: An update using one Mars year of MSL pressure data. American Geophysical Union (Fall). Abstract 3947), although perhaps the most direct method, has so far given ambiguous results. Estimating volume changes from imaging data faces challenges, and has previously been attempted only in isolated areas of the cap. In this study we use 6 m/pixel Context Imager (CTX) data from Mars year 31 to map all the morphologic units of the RSPC, expand the measurement record of pit erosion rates, and use high resolution images to place limits on vertical changes in the surface of the residual cap. We find the mass balance in Mars years 9-31 to be -6 to +4 km3/♂y, or roughly -0.039% to +0.026% of the mean atmospheric CO2 mass/♂y. The indeterminate sign results chiefly from uncertainty in the amounts of deposition or erosion on the upper surfaces of deposits (as opposed to scarp retreat). Erosion and net deposition in this period appear to be controlled by summertime planetary scale dust events, the largest occurring in MY 9, another, smaller one in MY 28. The rates of erosion and the deposition observed since MY 9 appear to be consistent with the types of deposits and erosional behavior found in most of the residual cap. However, small areas (<10%) of the cap are distinguished by their greater thickness, polygonal troughs, and embayed contacts with thinner units. These deposits may require extended periods (>100 ♂y) of depositional and/or erosional conditions different from those occurring in the period since MY 9, although these environmental differences could be subtle.

  19. Time scales of erosion and deposition recorded in the residual south polar cap of Mars

    NASA Astrophysics Data System (ADS)

    Thomas, P. C.; Calvin, W. M.; Gierasch, P.; Haberle, R.; James, P. B.; Sholes, S.

    2013-08-01

    The residual south polar cap (RSPC) of Mars has been subject to competing processes during recent Mars years of high resolution image coverage: continuing erosion of scarps while the maximum extent grows as well as shrinks (Piqueux, S., Christensen, P.R. [2008]. J. Geophys. Res. (Planets) 113, 2006; James, P.B., Thomas, P.C., Malin, M.C. [2010]. Icarus 208, 82-85). Additionally, the cap has a variety of morphologies and erosion (scarp retreat) rates (Thomas, P.C., James, P.B., Calvin, W.M., Haberle, R., Malin, M.C. [2009]. Icarus 203, 352-375). Do these different forms and competing processes indicate an aging and possibly disappearing cap, a growing cap, or a fluctuating cap, and is it possible to infer the timescales of the processes acting on the RSPC? Here we use the latest imaging data from Mars' southern summer in Mars year 30 (Calendar year 2011) to evaluate erosion rates of forms in the RSPC over 6 Mars years, and to map more fully features whose sizes can be used to predict deposit ages. Data through Mars year 30 show that scarp retreat rates in the RSPC have remained approximately the same for at least 6 Mars years and that these rates of erosion also apply approximately over the past 21 Mars years. The thicker units appear to have undergone changes in the locations of new pit formation about 30-50 Mars years ago. The thinner units have some areas that are possibly 80 Mars years old, with some younger materials having accumulated more than a meter in thickness since Mars year 9. Formation of the thicker units probably required over 100 Mars years. The upper surfaces of most areas, especially the thicker units, show little change at the few-cm level over the last 2 Mars years. This observation suggests that current conditions are substantially different from those when the thicker units were deposited. A prime characteristic of the evolution of the RSPC is that some changes are progressive, such as those involving scarp retreat, while others, such as the

  20. Lunar South Polar Hydrogen Concentrations in the Context of LRO/Diviner Results and Modeling

    NASA Astrophysics Data System (ADS)

    Elphic, R. C.; Paige, D. A.; Siegler, M. A.; Vasavada, A. R.; Lawrence, D. J.; James, M. R.; Bandfield, J. L.

    2009-12-01

    At the Moon, the leakage flux of cosmic ray-generated epithermal neutrons depends strongly on soil hydrogen content, and less strongly on other factors such as soil temperature [Lawrence et al., 2006]. For the lunar polar regions where warm sunlit features lie adjacent to permanently-shadowed (and very cold) areas, and where significant seasonal changes occur, it is important to take soil temperature into account. Here we investigate the effects of the subsurface soil temperature profile on epithermal leakage flux. As a starting point, we use a model of seasonally-averaged LRO/Diviner subsurface temperature to predict the effect on epithermal leakage flux. An isothermal depth profile is assumed. The relationship between Lunar Prospector epithermal detector count rates and surface temperature comes from Lawrence et al. [2006], and assumes the average soil near the south pole is of typical ferroan anorthosite highlands composition: epi = a + bT, where a = 19.65 counts/sec, b = 2.505x10-3 counts/sec/K, and T is the uniform soil temperature. We have adjusted the constant a to a value consistent with the epithermal measurements at lower latitudes. The temperature-dependent flux is convolved with the Lunar Prospector neutron spectrometer instrument spatial response for 30-km altitude to produce a map of predicted epithermal count rate that would be measured from orbit, in the absence of any soil hydrogen variations. We find that the predicted epithermal neutron count rates vary only over a narrow range: 19.85 to 20.1 counts/sec across a scene 600 x 600 km centered on the pole. The instrument-convolved prediction map shows a count rate low over the trio of large craters Faustini (87.2S, 89E), Shoemaker (88.5S, 50E), and Haworth (87.4S, 355E), and a separate low over Cabaeus (85.6S, 308.9E). The variation in predicted count rate is much smaller than what is observed in smoothed maps of the Lunar Prospector epithermal count rate. For example, the lowest epithermal count

  1. Broad-band linear polarization in late-type active dwarfs

    NASA Astrophysics Data System (ADS)

    Patel, Manoj K.; Pandey, Jeewan C.; Karmakar, Subhajeet; Srivastava, D. C.; Savanov, Igor S.

    2016-04-01

    We present recent polarimetric results of magnetically active late-type dwarfs. The polarization in these stars is found to be wavelength dependent, decreasing towards the longer wavelength. The average values of degree of polarization in these active dwarfs are found to be 0.16 ± 0.01, 0.080 ± 0.006, 0.056 ± 0.004 and 0.042 ± 0.003 per cent in B, V, R, and I bands, respectively. Present results indicate that polarization in the majority of active dwarfs are primarily due to sum of the polarization by magnetic intensification and scattering. However, supplementary sources of the polarization are also found to be present in some active stars. The correlations between the degree of polarization and various activity parameters like Rossby number, chromospheric activity indicator and coronal activity indicator are found to be stronger in B band and weaker in I band.

  2. A mechanism for cell motility by active polar gels

    PubMed Central

    Marth, W.; Praetorius, S.; Voigt, A.

    2015-01-01

    We analyse a generic motility model, with the motility mechanism arising by contractile stress due to the interaction of myosin and actin. A hydrodynamic active polar gel theory is used to model the cytoplasm of a cell and is combined with a Helfrich-type model to account for membrane properties. The overall model allows consideration of the motility without the necessity for local adhesion. Besides a detailed numerical approach together with convergence studies for the highly nonlinear free boundary problem, we also compare the induced flow field of the motile cell with that of classical squirmer models and identify the motile cell as a puller or pusher, depending on the strength of the myosin–actin interactions. PMID:25926698

  3. Active polarization imaging system to discriminate adaptively with diagonal Mueller matrix

    NASA Astrophysics Data System (ADS)

    Geng, Lixiang; Chen, Qian; Qian, Weixian; Gu, Guohua

    2015-11-01

    A promising method to optimize the polarization state of two-channel active polarization imaging system is presented. In this method, it is seminal that the detecting function of the imaging system is regarded as a discriminant projection of the observed objects' polarization features (elements of the Mueller matrix). The polarization state can be seen as a physical classifier which can be obtained by training samples. The image acquired with the system that has the designed optimal polarization state become discriminative results directly. The effectiveness of the proposed method and the discriminative ability of the optimal polarization state are demonstrated by the experimental results.

  4. Polar gravel beach-ridge systems as archive of climate variations (South Shetland Islands / Western Antarctic Peninsula)

    NASA Astrophysics Data System (ADS)

    Lindhorst, Sebastian; Schutter, Ilona; Betzler, Christian

    2014-05-01

    The architecture of polar gravel beach-ridge systems is presented and their potential as archive of past wave-climate conditions is evaluated. Raised beaches are common on paraglacial coasts which experienced a net uplift during the Holocene as the result of postglacial isostatic rebound. Ground-penetrating radar data obtained along the coasts of Potter Peninsula (King George Island) show that beach ridges unconformably overlie seaward-dipping strata of the strand plain. Whereas strand-plain progradation is the result of swash sedimentation at the beach face under enduring calm conditions, ridge construction reflects enhanced wave action at the beach as the result of increased storminess or reduced nearshore sea ice. The number of individual ridges which are preserved from a given time interval varies along the coast depending on the morphodynamic setting: Sheltered coasts are characterized by numerous small ridges, whereas fewer but larger ridges develop on exposed beaches. The sedimentary architecture of individual beach ridges is interpreted to reflect maximum wave-runup height during the time of ridge construction. Ridges at sheltered parts of the coast exhibit either seaward-dipping beds, interpreted to result from swash deposition, or an aggradational stacking pattern being the result of wave overtopping. At exposed beaches, larger ridges develop composed of seaward- as well as landward-dipping beds. Radiocarbon data indicate that the frequency of ridge building ranges from decades in low-energy settings to more than 1500 years under high-energy conditions. In the study area, beach ridges group into four distinct levels: up to 4 m, 5.5 m, 7.5 m, and 10 m above the present day storm beach. Hence, these levels are interpreted to reflect periods of increased wave activity in the area of the South Shetland Islands at about 4.3, 3.1, 1.9, and 0.35 ka cal BP.

  5. Resolution enhancement in active underwater polarization imaging with modulation transfer function analysis.

    PubMed

    Han, Jiefei; Yang, Kecheng; Xia, Min; Sun, Liying; Cheng, Zao; Liu, Hao; Ye, Junwei

    2015-04-10

    Active polarization imaging technology is a convenient and promising method for imaging in a scattering medium such as fog and turbid water. However, few studies have investigated the influence of polarization on the resolution in underwater imaging. This paper reports on the effects of polarization detection on the resolution of underwater imaging by using active polarization imaging technology. An experimental system is designed to determine the influence under various polarization and water conditions. The modulation transfer function is introduced to estimate the resolution variations at different spatial frequencies. Results show that orthogonal detection supplies the best resolution compared with other polarization directions in the turbid water. The performance of the circular polarization method is better than the linear process. However, if the light propagates under low scattering conditions, such as imaging in clean water or at small optical thickness, the resolution enhancement is not sensitive to the polarization angles. PMID:25967316

  6. Geomagnetic Polarity Reversal Model of Deeptow Magnetic Survey in the Southwest Subbasin of South China Sea Ridge

    NASA Astrophysics Data System (ADS)

    Qiu, N.; Sun, Z.; Lin, J.; Li, C. F.; Xu, X.

    2014-12-01

    South China Sea basin, which evolved from Cenozoic continental margin rifting and subsequent seafloor spreading, is a classic example of a marginal sea in Western Pacific. Since the early 1980's, several models have been proposed for the formation of this sea basin. The previous studies were based mainly on the distribution of magnetic anomaly lineation obtained from aerial and shipboard measurements. However, large water depth (over 4.5km) and thick sediment cover (up to 1km or more) make the magnetic anoamaly information not so well displayed in aerial and shipboard data. To better understand the evolution of the sea basin, we increased anomaly amplitudes by collecting magnetic data along deep-tow profiles over the magnetic lineations in the South China Sea oceanic area. The one across the southwest subsea basin was analyzed first. The total field magnetic measurements were processed through filtering, resampling, diurnal variation removal, continuation to a level datum, regional field correction, projection to a common azimuth, and deskewing. A magnetic polarity reversal timescale was constructed by matching deep-tow anomalies with a simple, rectangular block magnetization model with the expansion rate for oceanic crust. We analyzed the spreading duration, rate, asymmetry, and reversal events of Southwest subbasin, in reference to the recent GTS2012 geomagnetic polarity representative data and concluded that the Southwest subbasin opened from around 21.767 Ma and stopped around C5C at about 15.974Ma. The full spreading rate varied from 8 to 40 cm/yr. Spreading is usually asymmetric by showing alternate faster spreading rate in one slab than the other in different time periods. From the comparison, several small reversal were revealed in addition to the standard geomagnetic polarity. These findings helped to understand the evolution of the Southwest subbasin of South China Sea and will also help to establish new reversal discrimination.

  7. Asymmetry and polarity of the South Atlantic conjugated margins related to the presence of cratons: a numerical study

    NASA Astrophysics Data System (ADS)

    Andrés-Martínez, Miguel; Pérez-Gussinyé, Marta; de Monserrat Navarro, Albert; Morgan, Jason P.

    2015-04-01

    Tectonic asymmetry of conjugated passive margins, where one margin is much narrower than the conjugate one, is commonly observed at many passive margins world-wide. Conjugate margin asymmetry has been suggested to be a consequence of lateral changes in rheology, composition, temperature gradient or geometries of the crust and lithosphere. Here we use the South Atlantic margins (from Camamu/Gabon to North Santos/South Kwanza) as a natural laboratory to understand conjugate margin asymmetry. Along this margin sector the polarity of the asymmetry changes. To the North, the Brazilian margin developed in the strong Sao Francisco craton, and this constitutes the narrow side of the conjugate pair. To the South, the Brazilian margin developed in the Ribeira fold belt, and the margin is wide. The opposite is true for the African side. We have thus numerically analysed how the relative distance between the initial location of extension and the craton influences the symmetry/asymmetry and polarity of the conjugate margin system. Our numerical model is 2D visco-elasto-plastic and has a free surface, strain weakening and shear heating. The initial set-up includes a cratonic domain, a mobile belt and a transition area between both. We have run tests with different rheologies, thickness of the lithosphere, and weak seeds at different distances from the craton. Results show asymmetric conjugated margins, where the narrower margin is generally the closest to the craton. Our models also allow us to study how the polarity is controlled by the distance between the initial weakness and the craton, and help to understand how the presence of cratonic domains affects the final architecture of the conjugated margins.

  8. Sedimentation and polar order of active bottom-heavy particles.

    PubMed

    Wolff, Katrin; Hahn, Aljoscha M; Stark, Holger

    2013-04-01

    Self-propelled particles in an external gravitational field have been shown to display both an increased sedimentation length and polar order even without particle interactions. Here, we investigate self-propelled particles which additionally are bottom-heavy, that is they feel a torque aligning them to swim against the gravitational field. For bottom-heavy particles the gravitational field has the two opposite effects of i) sedimentation and ii) upward alignment of the particles' swimming direction. We perform a multipole expansion of the one-particle distribution of non-interacting particles with respect to orientation and derive expressions for sedimentation length and mean particle orientation which we check against Brownian Dynamics simulations. For large strength of gravity or small particle speeds and aligning torque, we observe sedimentation with increased sedimentation length compared with passive colloids but also active colloids without bottom-heaviness. Increasing, for example, swimming speed the sedimentation profile is inverted and the particles swim towards the top wall of the enclosing box. We find maximal orientational order at intermediate swimming speeds for both cases of particles with bottom-heaviness and those without. Ordering unsurprisingly is increased for the bottom-heavy particles, but this difference disappears at higher levels of activity and for very high activities ordering goes to zero in both cases. PMID:23612748

  9. Correlates of lifestyle: physical activity among South Asian Indian immigrants.

    PubMed

    Daniel, Manju; Wilbur, JoEllen; Fogg, Louis F; Miller, Arlene Michaels

    2013-01-01

    South Asian immigrants are at increased risk for cardiovascular disease and diabetes, but little is known about their physical activity patterns. In this cross-sectional study, 110 participants were recruited to describe lifestyle physical activity behavior of this at-risk population. Education (p = .042), global health (p = .045), and self-efficacy (p = .000) had significant positive independent effects on leisure-time physical activity. Depression (p = .035) and waist circumference (p = .012) had significant negative independent effects, and frequency of experiencing discrimination a significant positive independent effect (p = .007) on daily step counts. Culture-sensitive physical activity interventions need to target South Asian Indian immigrants who are less educated, in poor health, concerned about racial discrimination, and have low self-efficacy. PMID:24219639

  10. Modular activation of Rho1 by GPCR signalling imparts polarized myosin II activation during morphogenesis.

    PubMed

    Kerridge, Stephen; Munjal, Akankshi; Philippe, Jean-Marc; Jha, Ankita; de las Bayonas, Alain Garcia; Saurin, Andrew J; Lecuit, Thomas

    2016-03-01

    Polarized cell shape changes during tissue morphogenesis arise by controlling the subcellular distribution of myosin II. For instance, during Drosophila melanogaster gastrulation, apical constriction and cell intercalation are mediated by medial-apical myosin II pulses that power deformations, and polarized accumulation of myosin II that stabilizes these deformations. It remains unclear how tissue-specific factors control different patterns of myosin II activation and the ratchet-like myosin II dynamics. Here we report the function of a common pathway comprising the heterotrimeric G proteins Gα12/13, Gβ13F and Gγ1 in activating and polarizing myosin II during Drosophila gastrulation. Gα12/13 and the Gβ13F/γ1 complex constitute distinct signalling modules, which regulate myosin II dynamics medial-apically and/or junctionally in a tissue-dependent manner. We identify a ubiquitously expressed GPCR called Smog required for cell intercalation and apical constriction. Smog functions with other GPCRs to quantitatively control G proteins, resulting in stepwise activation of myosin II and irreversible cell shape changes. We propose that GPCR and G proteins constitute a general pathway for controlling actomyosin contractility in epithelia and that the activity of this pathway is polarized by tissue-specific regulators. PMID:26780298

  11. Towards a quantitative kinetic theory of polar active matter

    NASA Astrophysics Data System (ADS)

    Ihle, T.

    2014-06-01

    A recent kinetic approach for Vicsek-like models of active particles is reviewed. The theory is based on an exact Chapman- Kolmogorov equation in phase space. It can handle discrete time dynamics and "exotic" multi-particle interactions. A nonlocal mean-field theory for the one-particle distribution function is obtained by assuming molecular chaos. The Boltzmann approach of Bertin, et al., Phys. Rev. E 74, 022101 (2006) and J. Phys. A 42, 445001 (2009), is critically assessed and compared to the current approach. In Boltzmann theory, a collision starts when two particles enter each others action spheres and is finished when their distance exceeds the interaction radius. The average duration of such a collision, τ0, is measured for the Vicsek model with continuous time-evolution. If the noise is chosen to be close to the flocking threshold, the average time between collisions is found to be roughly equal to τ0 at low densities. Thus, the continuous-time Vicsek-model near the flocking threshold cannot be accurately described by a Boltzmann equation, even at very small density because collisions take so long that typically other particles join in, rendering Boltzmann's binary collision assumption invalid. Hydrodynamic equations for the phase space approach are derived by means of a Chapman-Enskog expansion. The equations are compared to the Toner-Tu theory of polar active matter. New terms, absent in the Toner-Tu theory, are highlighted. Convergence problems of Chapman-Enskog and similar gradient expansions are discussed.

  12. Diurnal patterns in lightning activity over South America

    NASA Astrophysics Data System (ADS)

    Ávila, Eldo E.; Bürgesser, Rodrigo E.; Castellano, Nesvit E.; Nicora, M. Gabriela

    2015-04-01

    Satellite observations of lightning flash distribution data are used to examine the diurnal cycle of lightning activity over the tropical and subtropical regions of South America. A harmonic analysis is used to study the spatial variations in the peak and strength of diurnal lightning activity across this area. Results show that in the northern and central regions of South America, the times of maxima in lightning activity was concentrated from late afternoon to evening hours (between 14:00 and 18:00 local time), which may be associated with the peaking of the local convective activity connected with heating of the surface caused by daytime insolation. In subtropical South America, particularly in the area limited by 25°S, 35°S of latitude and 70°W, 50°W of longitude, the time of maximum lightning activity was shifted to nocturnal hours, extending from close to midnight to early morning hours. This behavior can be associated to the peak in mesoscale convective systems in the region which occurs in the morning hours. The annual flash densities in the tropical and subtropical parts of the continent were found to have comparable magnitudes. However, the contribution of the continental tropics to the global electric circuit dominates over the continental subtropics contribution throughout all seasons, since the surface covered by the tropical region is more than twice the area covered by the subtropical region.

  13. Dust-Driven Halos on the Martian South Polar Residual CAP

    NASA Astrophysics Data System (ADS)

    Becerra, P.; Byrne, S.; Brown, A. J.

    2013-12-01

    The CO2 ice South Polar Residual Cap (SPRC) on Mars may be a sensitive indicator of inter-annual planetary climate variability. Imaging by HiRISE [1], and CTX [2] found that many scarps and pits in the 'Swiss cheese terrain' [3] of the SPRC exhibited a bright 'halo' around their edges. These halos appeared during Martian southern summer in Mars Year 28 (MY28, [4]), and have been observed in only one of eight mars years for which observations at high enough resolution exist. We hypothesize that the formation of these features is linked to the late-summer global dust storm of MY28 and report on observations and formation models. We surveyed HiRISE, CTX, and CRISM [5] data to constrain the optical properties and composition of the halos, as well as their time of appearance and location within the SPRC. The halos appeared throughout most of the surface area of the SPRC between Ls 280° and 330° in MY28. The widest portions of the halos occurred adjacent to north-facing walls, and the brightest parts adjacent to sun-facing walls, which points to a connection between insolation and halo appearance. CRISM spectral products rule out the presence of water ice as a factor in the halos' appearance. These data also imply larger CO2 ice grain sizes where the bright halos were seen, which are normally associated with lower, rather than higher, albedos [6]. Thus, we also ruled out CO2 ice grain size differences as the main cause for the halos. The remaining possibility is that the halos appeared due to differences in dust content between the terrain adjacent to the pit walls and the surrounding ice. To investigate this we made a Hapke [7] surface reflectance model in which the CO2 ice grain size, dust volumetric content and dust particle size were free parameters. We used the HiRISE and CRISM bandpass coefficients to simulate HiRISE I/F values and CRISM spectra, and attempted to match the HiRISE RED I/F, HiRISE BG/RED color ratio, and the CRISM 1.43 μm band depths. A self

  14. Influence of wave activity on the composition of the polar stratosphere

    NASA Astrophysics Data System (ADS)

    Smyshlyaev, S. P.; Pogoreltsev, A. I.; Galin, V. Ya.; Drobashevskaya, E. A.

    2016-01-01

    The planetary wave impact on the polar vortex stability, polar stratosphere temperature, and content of ozone and other gases was simulated with the global chemical-climatic model of the lower and middle atmosphere. It was found that the planetary waves propagating from the troposphere into the stratosphere differently affect the gas content of the Arctic and Antarctic stratosphere. In the Arctic region, the degree of wave activity critically affects the polar vortex formation, the appearance of polar stratospheric clouds, the halogen activation on their surface, and ozone anomaly formation. Ozone anomalies in the Arctic region as a rule are not formed at high wave activity and can be registered at low activity. In the Antarctic Regions, wave activity affects the stability of polar vortex and the depth of ozone holes, which are formed at almost any wave activity, and the minimal ozone values depend on the strong or weak wave activity that is registered in specific years.

  15. Rebuilding cytoskeleton roads: Active-transport-induced polarization of cells

    NASA Astrophysics Data System (ADS)

    Hawkins, R. J.; Bénichou, O.; Piel, M.; Voituriez, R.

    2009-10-01

    Many cellular processes require a polarization axis which generally initially emerges as an inhomogeneous distribution of molecular markers in the cell. We present a simple analytical model of a general mechanism of cell polarization taking into account the positive feedback due to the coupled dynamics of molecular markers and cytoskeleton filaments. We find that the geometry of the organization of cytoskeleton filaments, nucleated on the membrane (e.g., cortical actin) or from a center in the cytoplasm (e.g., microtubule asters), dictates whether the system is capable of spontaneous polarization or polarizes only in response to external asymmetric signals. Our model also captures the main features of recent experiments of cell polarization in two considerably different biological systems, namely, mating budding yeast and neuron growth cones.

  16. High Heat Flow from Enceladus' South Polar Region Measured using 10-600/cm(exp -1) Cassini/CIRS Data

    NASA Technical Reports Server (NTRS)

    Howett, C. J. A.; Spencer, J. R.; Pearl, J.; Segura, M.

    2011-01-01

    Analysis of 2008 Cassini Composite Infrared Spectrometer (CIRS) 10 to 600/cm thermal emission spectra of Enceladus shows that for reasonable assumptions about the spatial distribution of the emission and the thermophysical properties of the solar-heated background surface, which are supported by CIRS observations of background temperatures at the edge of the active region, the endogenic power of Enceladus' south polar terrain is 15.8 +/- 3.1 GW. This is significantly higher than the previous estimate of 5.8 +/- 1.9 GW. The new value represents an improvement over the previous one, which was derived from higher wave number data (600 to 1100/cm-I) and was thus only sensitive to high-temperature emission. The mechanism capable of producing such a high endogenic power remains a mystery and challenges the current models of proposed heat production.

  17. Interannual observations and quantification of summertime H2O ice deposition on the Martian CO2 ice south polar cap

    NASA Astrophysics Data System (ADS)

    Brown, Adrian J.; Piqueux, Sylvain; Titus, Timothy N.

    2014-11-01

    The spectral signature of water ice was observed on Martian south polar cap in 2004 by the Observatoire pour l'Mineralogie, l'Eau les Glaces et l'Activite (OMEGA) (Bibring et al., 2004). Three years later, the OMEGA instrument was used to discover water ice deposited during southern summer on the polar cap (Langevin et al., 2007). However, temporal and spatial variations of these water ice signatures have remained unexplored, and the origins of these water deposits remains an important scientific question. To investigate this question, we have used observations from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument on the Mars Reconnaissance Orbiter (MRO) spacecraft of the southern cap during austral summer over four Martian years to search for variations in the amount of water ice. We report below that for each year we have observed the cap, the magnitude of the H2O ice signature on the southern cap has risen steadily throughout summer, particularly on the west end of the cap. The spatial extent of deposition is in disagreement with the current best simulations of deposition of water ice on the south polar cap (Montmessin et al., 2007). This increase in water ice signatures is most likely caused by deposition of atmospheric H2O ice and a set of unusual conditions makes the quantification of this transport flux using CRISM close to ideal. We calculate a 'minimum apparent' amount of deposition corresponding to a thin H2O ice layer of 0.2 mm (with 70% porosity). This amount of H2O ice deposition is 0.6-6% of the total Martian atmospheric water budget. We compare our 'minimum apparent' quantification with previous estimates. This deposition process may also have implications for the formation and stability of the southern CO2 ice cap, and therefore play a significant role in the climate budget of modern day Mars.

  18. Comparison of the threshold of thermal-induced mode instabilities in polarization-maintaining and non-polarization-maintaining active fibers

    NASA Astrophysics Data System (ADS)

    Tao, Rumao; Ma, Pengfei; Wang, Xiaolin; Zhou, Pu; Liu, Zejin

    2016-06-01

    We present an investigation on the threshold of thermal-induced mode instability (MI) in ytterbium-doped polarization-maintaining and non-polarization-maintaining active fibers. By taking both electric fields along the two principal axes into consideration, we extend a previous steady-state theoretical model to analyze the polarization effect on MI. Based on the model, we analyzed whether maintaining the fiber’s polarization direction has an effect on the MI threshold, which showed that, for practical high power fiber laser systems, the MI threshold is nearly the same for polarization-maintaining and non-polarization-maintaining active fibers. Experimental validation of the theoretical analysis is presented with experimental results agreeing with the theoretical results, in which polarization-maintained and non-polarization-maintained fiber lasers with similar core/inner cladding diameters are employed.

  19. Astrobiological Journeys to and from the South Polar Sea of Enceladus - Bidirectional Interactions with the Saturn Magnetosphere

    NASA Technical Reports Server (NTRS)

    Cooper, John F.; Sittler, Edward C.; Lipatov, Alexander S.; Sturner, Steven J.

    2012-01-01

    The spectacularly cryovolcanic moon Enceladus is a major source of plasma for the Saturn magnetosphere via ionization of the ejected molecular species and ice grains. Field-aligned plasma flows from the Enceladus environment visibly impact the moon's magnetic footpoint in Saturn's polar auroral region, while water group and other ions from the moon emissions diffuse radially throughout the magnetosphere and may be the dominant source of oxygen for Titan's oxygen-poor upper atmosphere. But the moon-magnetosphere interaction is bidirectional in the sense that the moon surface is globally exposed to constant irradiation by the returning magnetospheric ions and by energetic electrons from the field-aligned and radially diffusing populations. The returning ion source operates both on global scales of the magnetosphere and locally for highly reactive species produced in the ejecta plume. All of these sources likely combine to produce a highly oxidized global surface layer. Since plasma electrons and ions are cooled by interaction with neutral gas and E-ring ice grains from Enceladus, the moon emissions have a governing effect on the seed populations of energetic particles that irradiate the surface. The proposed subsurface polar sea and transient crustal overturn in the south polar region could bring the polar surface oxidants into contact with hydrocarbons and ammonia to make oxidation product gases contributing to the cryovolcanic jets, a process first proposed by Cooper et al. (Plan. Sp. Sci., 2009). As has been previously suggested for Europa, the 'oxidants could contribute to enhanced astrobiological potential of Enceladus, perhaps even higher than for Europa where organic hydrocarbons have not yet been directly detected. Unlike Europa, Enceladus shows no sign of an oxygen-dominated exosphere that could otherwise be indicative of extreme surface and interior oxidation inhibiting the detectable survival and evolution of complex organics.

  20. Growth and Decay of the South Polar Residual Cap of Mars

    NASA Astrophysics Data System (ADS)

    Byrne, S.; McEwen, A.; HiRISE Team

    2008-12-01

    The southern residual ice cap (SRC) is composed of high-albedo solid CO2, is a few meters thick and has areas at its margins and in its interior where the underlying water ice of the polar layered deposits shows through. Previous observations show that pits within the SRC expose sections of layering in the CO2 ice (up to 10m thick) and are expanding by meters/year (Thomas et al., Icarus, 2005). The expansion of these pits is a problem as their spatial density and expansion rates indicate that there should be nothing left of the SRC within a century or so. Our analysis of pit expansion rates indicates that they increase during periods of dust-storm activity. The sensitivity of SRC evolution to climate indicates that its stratigraphy is likely also a valuable source of information about recent climate variability. We are using HiRISE data to constrain landscape evolution models of CO2 ice landscapes to quantify the history of the SRC and the connection of its stratigraphy to martian climate. Here we report on two investigations utilizing different models. 1. We use a landscape evolution model to simulate growth of an accumulating CO2 deposit. This model shows pits naturally form in this landscape, without any associated change in climate, due to increases in surface roughness with time and the feedback between slope and ice ablation. Comparison of model results with the current SRC indicates the thickest sections of stratigraphy likely represent up to 100 martian years of accumulation. 2. HiRISE data shows that some pits expand by faster retreat of the lower ice layers, undercutting of the upper bright ice and subsequent mass-wasting. A separate model that can handle topographic overhangs has been developed and is being used to investigate this behavior. Using this model to reproduce the non- circular aspects of the pit-shapes and their expansion rates (which HiRISE can measure as a function of azimuth) constrains properties of the lower CO2 ice layers such as

  1. Active display and encoding by integrated plasmonic polarizer on light-emitting-diode

    PubMed Central

    Wang, L.; Li, T.; Guo, R. Y.; Xia, W.; Xu, X. G.; Zhu, S. N.

    2013-01-01

    An electrical pumped microscopic active display with integration of plasmonic polarizer and light-emitting-diode is proposed. Thanks to the strong polarized emission through the rectangular nanoholes, well designed pixels with respect to different polarizations are engineered, which give rise to flexible and controllable active display. As results, polarization multiplexed letter encoding, single and double gray-scale images and animation movies are successfully realized. Our results demonstrate a new strategy in electro-optical integration and indicate potential applications in designing new type of microscopic electro-optical devices. PMID:24008314

  2. A measurement of the cosmic microwave background polarization with the south pole telescope

    NASA Astrophysics Data System (ADS)

    Crites, Abigail Tinney

    We present maps of the cosmic microwave background (CMB) polarization at 90 and 150 GHz measured with SPTpol and the first EE and TE CMB power spectrum measurements from SPTpol. We also describe the SPTpol instrument in detail. We discuss the development of the SPTpol camera including the cryogenic design and the transition edge sensor (TES) detectors developed at NIST and Argonne National Laboratory. The goals of the SPTpol project are to exploit the high resolution of the telescope (1 arcminute beam) and the high sensitivity afforded by the 1536 detector camera to measure the E-mode power spectrum of the CMB, characterize the B-mode polarization induced by the gravitational lensing of the primordial E-mode CMB polarization, and to detector set an upper limit on the level of the B-mode polarization from inflationary gravitational waves. This thesis is a first step toward accomplishing these goals. Measuring the E-mode power spectrum will allow us to improve constraints on parameters of the current cosmological models that are sensitive to the damping tail of the CMB.

  3. Dust aerosols above the south polar cap of Mars as seen by OMEGA

    NASA Astrophysics Data System (ADS)

    Vincendon, M.; Langevin, Y.; Poulet, F.; Bibring, J.-P.; Gondet, B.; Jouglet, D.; Omega Team

    2008-08-01

    The time evolution of atmospheric dust at high southern latitudes on Mars has been determined using observations of the south seasonal cap acquired in the near infrared (1-2.65 μm) by OMEGA/Mars Express in 2005. Observations at different solar zenith angles and one EPF sequence demonstrate that the reflectance in the 2.64 μm saturated absorption band of the surface CO 2 ice is mainly due to the light scattered by aerosols above most places of the seasonal cap. We have mapped the total optical depth of dust aerosols in the near-IR above the south seasonal cap of Mars from mid-spring to early summer with a time resolution ranging from one day to one week and a spatial resolution of a few kilometers. The optical depth above the south perennial cap is determined on a longer time range covering southern spring and summer. A constant set of optical properties of dust aerosols is consistent with OMEGA observations during the analyzed period. Strong variations of the optical depth are observed over small horizontal and temporal scales, corresponding in part to moving dust clouds. The late summer peak in dust opacity observed by Opportunity in 2005 propagated to the south pole contrarily to that observed in mid spring. This may be linked to evidence for dust scavenging by water ice-rich clouds circulating at high southern latitudes at this season.

  4. The chemokine system in diverse forms of macrophage activation and polarization.

    PubMed

    Mantovani, Alberto; Sica, Antonio; Sozzani, Silvano; Allavena, Paola; Vecchi, Annunciata; Locati, Massimo

    2004-12-01

    Plasticity and functional polarization are hallmarks of the mononuclear phagocyte system. Here we review emerging key properties of different forms of macrophage activation and polarization (M1, M2a, M2b, M2c), which represent extremes of a continuum. In particular, recent evidence suggests that differential modulation of the chemokine system integrates polarized macrophages in pathways of resistance to, or promotion of, microbial pathogens and tumors, or immunoregulation, tissue repair and remodeling. PMID:15530839

  5. Spin polarization and additional magneto-optical activity of nonmagnetic layers in Fe/Ag CMF

    NASA Astrophysics Data System (ADS)

    Xu, Y. B.; Zhai, H. R.; Lu, M.; Jin, Q. Y.; Miao, Y. Z.

    1992-08-01

    The experimental magneto-optical Kerr rotation spectra of Fe/Ag compositionally modulated films reported by Katayama et al. are studied theoretically. It is found that the free electrons of Ag are spin polarized. The magnitude of the polarization is about 1% with a direction opposite to that of Fe. The polarized Ag also gives rise to an additional magneto-optical activity as in Pt and Pd.

  6. Evaluation of antibacterial and anti-inflammatory activities of less polar ginsenosides produced from polar ginsenosides by heat-transformation.

    PubMed

    Wang, Lijun; Yang, Xiushi; Yu, Xiaona; Yao, Yang; Ren, Guixing

    2013-12-18

    Ginsenosides are the major active constituents in both white and red American ginseng (AG), and their pharmacological effects on central nervous, cardiovascular, and endocrine systems have been well elucidated. However, the anti-Propionibacterium acnes (P. acnes) activity of them is still unknown. In this study, 5 ginsenosides enriched fractions were obtained from the total ginsenosides extract of AG roots (TAG) by resin adsorption and heat-transformation. Resin purification decreased the total polyphenol (TP) content in the fractions. However, heat treatment increased the TP content and induced extensive conversion of the polar ginsenosides (Rg1, Re, Rb1, Rc, Rb2, Rd, and Gyp XVII) to less polar compounds (Rg2, Rg3, Rg6/F4, Rs3, and Rg5/Rk1). Only the heat-treated fraction from 65% methanol elution of the HP-20 column (HPHF) showed antibacterial activity against P. acnes (ATCC11827, MIC, 128 μg/mL; ATCC6919 MIC, 64 μg/mL), S. epidermidis (MIC, 4100 μg/mL) and S. aureus (MIC, 15000 μg/mL). In the anti-inflammatory activity assay, 10 μg/mL of HPHF significantly (P < 0.05) inhibited NO production in LPS-stimulated RAW264.7 cells. These results suggest that less polar ginsenosides enriched fraction HPHF obtained from AG might be useful to develop new types of antibacterial substances and new skin care cosmetics for acne prevention and therapy. PMID:24289140

  7. A STATISTICAL STUDY OF CORONAL ACTIVE EVENTS IN THE NORTH POLAR REGION

    SciTech Connect

    Sako, Nobuharu; Shimojo, Masumi; Watanabe, Tetsuya; Sekii, Takashi

    2013-09-20

    In order to study the relationship between characteristics of polar coronal active events and the magnetic environment in which such events take place, we analyze 526 X-ray jets and 1256 transient brightenings in the polar regions and in regions around the equatorial limbs. We calculate the occurrence rates of these polar coronal active events as a function of distance from the boundary of coronal holes, and find that most events in the polar quiet regions occur adjacent to and equatorward of the coronal hole boundaries, while events in the polar coronal holes occur uniformly within them. Based primarily on the background intensity, we define three categories of regions that produce activity: polar coronal holes, coronal hole boundary regions, and polar quiet regions. We then investigate the properties of the events produced in these regions. We find no significant differences in their characteristics, for example, length and lifetime, but there are differences in the occurrence rates. The mean occurrence rate of X-ray jets around the boundaries of coronal holes is higher than that in the polar quiet regions, equatorial quiet regions, and polar coronal holes. Furthermore, the mean occurrence rate of transient brightenings is also higher in these regions. We make comparison with the occurrence rates of emerging and canceling magnetic fields in the photosphere reported in previous studies, and find that they do not agree with the occurrence rates of transient brightenings found in this study.

  8. The polar wind: solar illumination, seasonal variations, and north-south asymmetry

    NASA Astrophysics Data System (ADS)

    Maes, Lukas; Maggiolo, Romain; André, Mats; Li, Kun; Eriksson, Anders; Haaland, Stein

    2016-04-01

    Solar illumination is the main driver of the polar wind. Since many of these outflowing ions can escape into the interplanetary medium - and contribute to atmospheric erosion - or end up in the plasma sheet - where they can affect magnetospheric dynamics - it is interesting to study the dependence of the polar wind flux on solar illumination. However, the bulk of these ions flowing out above the polar cap have very low energies and temperatures. This makes them very difficult to measure by a satellite crossing their path in the magnetospheric lobes. UV-radiation will cause the spacecraft to acquire a positive charge, repelling the ions, making those with too low energy invisible to the onboard detectors. An alternative method, using both of Cluster's electric field experiments, can exploit this fact to quantify the flux of the outflowing ions. This is done by André et al. [2015], and we use this data set in this study. It is extensive running over multiple years, during multiple months, with a large amount of measurements, allowing us to find effects of solar illumination despite the very large natural spread. We will show that solar illumination indeed has a strong control over the outflowing flux and that this results in seasonal variations. A difference between the flux from the northern and southern hemisphere is also found, which may be caused by an asymmetry in the magnetic field.

  9. Crustal Structure of the Caribbean-South American Diffuse Plate Boundary: Subduction Zone Migration and Polarity Reversal Along BOLIVAR Profile 64W

    NASA Astrophysics Data System (ADS)

    Clark, S. A.; Levander, A.; Magnani, M.; Zelt, C. A.; Sawyer, D. S.; Ave Lallemant, H. G.

    2005-12-01

    The BOLIVAR (Broadband Ocean-Land Investigation of Venezuela and the Antilles arc Region) project is an NSF funded, collaborative seismic experiment in the southeast Caribbean region. The purpose of the project is to understand the diffuse plate boundary created by the oblique collision between the Caribbean and South American plates. Profile 64W of the BOLIVAR experiment, a 450 km-long, N-S transect onshore and offshore Venezuela located at ~64°W longitude, images the deep crustal structures formed by this collision. The active source components of profile 64W include 300 km of MCS reflection data, 33 coincident OBSs, and 344 land seismic stations which recorded 7500 offshore airgun shots and 2 explosive land shots. Results from the reflection and refraction seismic data along 64W show complex crustal structure across the entire span of the diffuse plate boundary. The onshore portion of 64W crosses the fold and thrust belt of the Serrania del Interior, which formed at ~16 Ma by collision of the Caribbean forearc with the northern South American passive margin. Underlying the Serrania del Interior is a south-vergent, remnant Lesser Antillean subduction zone. As this Lesser Antilles subduction impinged on continental crust, it caused a polarity reversal and jump offshore to the north. Convergence was initially localized in the closure and inversion of the Grenada Basin. However, subduction could not develop because of the ~20-km-thick crust of the Aves Ridge; instead, north-vergent subduction initiated further to the north, where ~12-km-thick Caribbean oceanic crust of the Venezuela Basin began to subduct beneath the Aves Ridge in the Pliocene (~4 Ma) and appears to continue subducting today. Between the remnant subduction zone and the modern one, the El Pilar and Coche dextral strike-slip faults accommodate most of the transform motion of the plate boundary. From the Serrania del Interior to the Aves Ridge, ~260 km of accreted orogenic float comprises the diffuse

  10. SPT-3G: a next-generation cosmic microwave background polarization experiment on the South Pole telescope

    NASA Astrophysics Data System (ADS)

    Benson, B. A.; Ade, P. A. R.; Ahmed, Z.; Allen, S. W.; Arnold, K.; Austermann, J. E.; Bender, A. N.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Cho, H. M.; Cliche, J. F.; Crawford, T. M.; Cukierman, A.; de Haan, T.; Dobbs, M. A.; Dutcher, D.; Everett, W.; Gilbert, A.; Halverson, N. W.; Hanson, D.; Harrington, N. L.; Hattori, K.; Henning, J. W.; Hilton, G. C.; Holder, G. P.; Holzapfel, W. L.; Irwin, K. D.; Keisler, R.; Knox, L.; Kubik, D.; Kuo, C. L.; Lee, A. T.; Leitch, E. M.; Li, D.; McDonald, M.; Meyer, S. S.; Montgomery, J.; Myers, M.; Natoli, T.; Nguyen, H.; Novosad, V.; Padin, S.; Pan, Z.; Pearson, J.; Reichardt, C.; Ruhl, J. E.; Saliwanchik, B. R.; Simard, G.; Smecher, G.; Sayre, J. T.; Shirokoff, E.; Stark, A. A.; Story, K.; Suzuki, A.; Thompson, K. L.; Tucker, C.; Vanderlinde, K.; Vieira, J. D.; Vikhlinin, A.; Wang, G.; Yefremenko, V.; Yoon, K. W.

    2014-07-01

    We describe the design of a new polarization sensitive receiver, spt-3g, for the 10-meter South Pole Telescope (spt). The spt-3g receiver will deliver a factor of ~20 improvement in mapping speed over the current receiver, spt-pol. The sensitivity of the spt-3g receiver will enable the advance from statistical detection of B-mode polarization anisotropy power to high signal-to-noise measurements of the individual modes, i.e., maps. This will lead to precise (~0.06 eV) constraints on the sum of neutrino masses with the potential to directly address the neutrino mass hierarchy. It will allow a separation of the lensing and inflationary B-mode power spectra, improving constraints on the amplitude and shape of the primordial signal, either through spt-3g data alone or in combination with bicep2/keck, which is observing the same area of sky. The measurement of small-scale temperature anisotropy will provide new constraints on the epoch of reionization. Additional science from the spt-3g survey will be significantly enhanced by the synergy with the ongoing optical Dark Energy Survey (des), including: a 1% constraint on the bias of optical tracers of large-scale structure, a measurement of the differential Doppler signal from pairs of galaxy clusters that will test General Relativity on ~200Mpc scales, and improved cosmological constraints from the abundance of clusters of galaxies

  11. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap.

    PubMed

    Kieffer, Hugh H; Christensen, Philip R; Titus, Timothy N

    2006-08-17

    The martian polar caps are among the most dynamic regions on Mars, growing substantially in winter as a significant fraction of the atmosphere freezes out in the form of CO2 ice. Unusual dark spots, fans and blotches form as the south-polar seasonal CO2 ice cap retreats during spring and summer. Small radial channel networks are often associated with the location of spots once the ice disappears. The spots have been proposed to be simply bare, defrosted ground; the formation of the channels has remained uncertain. Here we report infrared and visible observations that show that the spots and fans remain at CO2 ice temperatures well into summer, and must be granular materials that have been brought up to the surface of the ice, requiring a complex suite of processes to get them there. We propose that the seasonal ice cap forms an impermeable, translucent slab of CO2 ice that sublimates from the base, building up high-pressure gas beneath the slab. This gas levitates the ice, which eventually ruptures, producing high-velocity CO2 vents that erupt sand-sized grains in jets to form the spots and erode the channels. These processes are unlike any observed on Earth. PMID:16915284

  12. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap

    USGS Publications Warehouse

    Kieffer, H.H.; Christensen, P.R.; Titus, T.N.

    2006-01-01

    The martian polar caps are among the most dynamic regions on Mars, growing substantially in winter as a significant fraction of the atmosphere freezes out in the form of CO2 ice. Unusual dark spots, fans and blotches form as the south-polar seasonal CO2 ice cap retreats during spring and summer. Small radial channel networks are often associated with the location of spots once the ice disappears. The spots have been proposed to be simply bare, defrosted ground; the formation of the channels has remained uncertain. Here we report infrared and visible observations that show that the spots and fans remain at CO2 ice temperatures well into summer, and must be granular materials that have been brought up to the surface of the ice, requiring a complex suite of processes to get them there. We propose that the seasonal ice cap forms an impermeable, translucent slab of CO2 ice that sublimates from the base, building up high-pressure gas beneath the slab. This gas levitates the ice, which eventually ruptures, producing high-velocity CO 2 vents that erupt sand-sized grains in jets to form the spots and erode the channels. These processes are unlike any observed on Earth. ?? 2006 Nature Publishing Group.

  13. Asters, Vortices, and Rotating Spirals in Active Gels of Polar Filaments

    NASA Astrophysics Data System (ADS)

    Kruse, K.; Joanny, J. F.; Jülicher, F.; Prost, J.; Sekimoto, K.

    2004-02-01

    We develop a general theory for active viscoelastic materials made of polar filaments. This theory is motivated by the dynamics of the cytoskeleton. The continuous consumption of a fuel generates a nonequilibrium state characterized by the generation of flows and stresses. Our theory applies to any polar system with internal energy consumption such as active chemical gels and cytoskeletal networks which are set in motion by active processes at work in cells.

  14. Mesosphere light scattering depolarization during the Perseids activity epoch by wide-angle polarization camera measurements

    NASA Astrophysics Data System (ADS)

    Ugolnikov, Oleg S.; Maslov, Igor A.

    2014-03-01

    The paper describes the study of scattered radiation field in the mesosphere basing on wide-angle polarization camera (WAPC) measurements of the twilight sky background and single scattering separation procedure. Mid-August observations in 2012 and 2013 show the decrease of single scattering polarization value probably related with Perseids meteor dust moderation in the upper mesosphere. Effect correlates with activity of tiny fraction of Perseids shower. Polarization and temperature analysis allows estimating the altitude of dust layer and character polarization of dust scattering.

  15. A Warmer Atmosphere on Mars Near the Noachian-Hesperian Boundary: Evidence from Basal Melting of the South Polar Ice Cap (Dorsa Argentea Formation)

    NASA Astrophysics Data System (ADS)

    Fastook, J. L.; Head, J. W.; Marchant, D. R.; Forget, F.; Madeleine, J.-B.

    2011-03-01

    Dorsa Argentea Formation (Noachian-Hesperian) eskers are evidence for basal melting. Ice-flow models show that the mean annual south polar temperature must be raised to -50° to -75°C, providing an independent estimate of elevated lower latitude surface temperature.

  16. Researcher and Educator Long Term Collaboration with NOAA ESRL Regarding Atmospheric Ozone Changes at the South Pole Through the NSF PolarTREC Program

    NASA Astrophysics Data System (ADS)

    Bergholz, E.; Johnson, B.; Hofmann, D.

    2008-12-01

    The NOAA/ESRL team at South Pole has been monitoring the development of the annual ozone hole over two decades using balloon-borne and ground-based instruments. Collaboration with educators has become an important aspect of NOAA/ESRL to educate the public about ozone loss and ozone hole formation. Researcher Bryan Johnson and educator Elke Bergholz worked together at South Pole in 1998/1999 as part of the NSF teacher outreach program called Teachers Experiencing Antarctica (TEA). It has been almost a decade when they collaborated again concerning the ozone changes at South Pole as part of the International Polar Year (IPY) and the PolarTREC (http://www.polartrec.com) teacher outreach program sponsored by NSF. The TEA and PolarTREC programs selected teachers to travel to polar locations to work with research scientists collecting data and running experiments at various Arctic and Antarctic field sites. While in the field, daily contact with classrooms and students around the globe was done through internet journals, answering emails from students, and webinars. This will be followed up with presentations to schools and the public relating Ms Bergholz's experience and new "hands-on" understanding of ozone measurements and ozone depletion over Antarctica, and discussing what changes in ozone we have seen at South Pole since the first outreach program nearly a decade ago.

  17. COMMENTS ON "MEASUREMENTS OF ATMOSPHERIC MERCURY SPECIES AT A COASTAL SITE IN THE ANTARCTIC AND OVER THE SOUTH ATLANTIC OCEAN DURING POLAR SUMMER"

    EPA Science Inventory

    Attached comment submitted to Environmental Science and Technology entitled, Comments on "Measurements of Atmospheric Mercury Species at a Costal Site in the Antarctic and over the South Atlantic Ocean during Polar Summer" by Temme et al. Environmental Science and Technology 37 (...

  18. Strong variable linear polarization in the cool active star II Peg

    NASA Astrophysics Data System (ADS)

    Rosén, Lisa; Kochukhov, Oleg; Wade, Gregg A.

    2014-08-01

    Magnetic fields of cool active stars are currently studied polarimetrically using only circular polarization observations. This provides limited information about the magnetic field geometry since circular polarization is only sensitive to the line-of-sight component of the magnetic field. Reconstructions of the magnetic field topology will therefore not be completely trustworthy when only circular polarization is used. On the other hand, linear polarization is sensitive to the transverse component of the magnetic field. By including linear polarization in the reconstruction the quality of the reconstructed magnetic map is dramatically improved. For that reason, we wanted to identify cool stars for which linear polarization could be detected at a level sufficient for magnetic imaging. Four active RS CVn binaries, II Peg, HR 1099, IM Peg, and σ Gem were observed with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope. Mean polarization profiles in all four Stokes parameters were derived using the multi-line technique of least-squares deconvolution (LSD). Not only was linear polarization successfully detected in all four stars in at least one observation, but also, II Peg showed an extraordinarily strong linear polarization signature throughout all observations. This qualifies II Peg as the first promising target for magnetic Doppler imaging in all four Stokes parameters and, at the same time, suggests that other such targets can possibly be identified.

  19. South Polar Ar Enhancement as a Tracer for Southern Winter Horizontal Meridional Mixing

    NASA Technical Reports Server (NTRS)

    Sprague, A. L.; Boynton, W. V.; Kim, K.; Reedy, R.; Kerry, K.; Janes, D.

    2004-01-01

    Measurements made by the Gamma Ray Spectrometer (GRS) on Mars Odyssey during 2002 and 2003 show an obvious increase in the gamma flux of 1294 keV gamma rays resulting from the decay of (41)Ar. (41)Ar is made by the capture of thermal neutrons by atmospheric (40)Ar. The increase measured above the southern polar region has permitted calculation of the increase in mixing ratio of Ar from L(sub s) 8 to 100 between latitudes 75 S and 90 S. The peak in Ar enhancement occurs about 200 Earth days after CO2 freeze-out has begun, indicating that up to this time equatorward meridional mixing is rapid enough to move enhanced Ar from the polar regions northward. Although the CO2 frost depth continues to increase from L(sub s) 110 deg to 190 deg, the Ar enhancement steadily decreases to its baseline value reached at about L(sub s) 200 deg. Our data permit an estimate of the horizontal eddy mixing coefficient useful for constraining equatorward meridional mixing during southern winter and a characteristic mixing time for the polar southern winter atmosphere. Also, using the drop in excess Ar measured by the GRS from L(sub s) 110 deg to 200 deg, we estimate an eddy coefficient appropriate for meridional mixing of the entire Ar excess back to the baseline value. The horizontal eddy mixing coefficients are derived using Ar as a tracer much as the vertical eddy mixing coefficient for the Earth's troposphere is derived using CH4 as a minor constituent tracer. The estimation of meridional mixing for high latitudes at Mars is important for constraining parameters used in atmospheric modeling and predicting seasonal and daily behavior. The calculations are order of magnitude estimates that should improve as the data set becomes more robust and improves our models.

  20. High Resolution North and South Polar Maps of the Moon with AMIE/SMART-1

    NASA Astrophysics Data System (ADS)

    Despan, Daniela; Erard, Stephane; Beauvivre, Stephane; Chevrel, Serge; Pinet, Patrick; Almeida, Miguel; Grieger, Bjoern; Cerroni, Priscilla; Barucci, M. A.; Josset, Jean-Luc; Koschny, Detlef; Foing, Bernard H.

    The northern and southern polar areas maps of the Moon are obtained by processing and mosaiking of the AMIE, SMART-1 images. The Advanced Moon micro-Imager Experiment (AMIE) on board the ESA lunar mission Smart-1 has performed colour imaging of the lunar surface using various filters in the visible and NIR. The low pericenter, polar orbit, allowed to obtain high resolution images in various locations at the surface. From the 300 km pericenter altitude, the field of view (5,3° x5,3° ) corresponds to a spatial resolution about 30 m. The 1024x1024 images are shared by the various filters, allowing to derive mosaics of the surface in up to 3 colors depending on pointing mode. Spot-pointing observations and multiple observations from different orbits have provided photometric sequences that allow to study the surface properties in restricted areas. Geometrical analysis of the AMIE images relies on the SPICE system: image coordinates are computed to get precise projection at the surface, and illumination angles are computed to analyze the photometric sequences. Images from various orbits are first identified for each selected region of interest. These images are then selected according to signal to noise ratio, spatial coverage, and spatial resolution. The best images obtained with the neutral filter are calibrated, and mosaicked using the coordinates of the image frames corners. In the polar areas, images are selected so as to provide the best possible viewing of surface topography, depending on solar illumination angle, while preserving images continuity in shadowed areas. The maps of other regions of interest are yielded: Marius Hills, the Gruitheisen Domes, Rumker Hills, Aristarchus Plateau. Eventually, this method will be applied in all regions where AMIE has provided high resolution observations of the surface, typically a factor of 3 higher than the Clementine UV-vis camera. These regions are essentially located at latitude ranging from 80 to 40° S, specially

  1. A hybrid particle-mesh method for incompressible active polar viscous gels

    NASA Astrophysics Data System (ADS)

    Ramaswamy, Rajesh; Bourantas, George; Jülicher, Frank; Sbalzarini, Ivo F.

    2015-06-01

    We present a hybrid particle-mesh method for numerically solving the hydrodynamic equations of incompressible active polar viscous gels. These equations model the dynamics of polar active agents, embedded in a viscous medium, in which stresses are induced through constant consumption of energy. The numerical method is based on Lagrangian particles and staggered Cartesian finite-difference meshes. We show that the method is second-order and first-order accurate with respect to grid and time-step sizes, respectively. Using the present method, we simulate the hydrodynamics in rectangular geometries, of a passive liquid crystal, of an active polar film and of active gels with topological defects in polarization. We show the emergence of spontaneous flow due to Fréedericksz transition, and transformation in the nature of topological defects by tuning the activity of the system.

  2. Researcher and Educator Long Term Collaboration with NOAA ESRL Regarding Atmospheric Ozone Changes at the South Pole Through the NSF PolarTREC Program

    NASA Astrophysics Data System (ADS)

    Bergholz, E. H.; Hofmann, D. J.; Johnson, B. J.

    2009-12-01

    The NOAA/ESRL team at South Pole has been monitoring the development of the annual ozone hole over two decades using balloon-borne and ground based instruments. Collaboration with educators has become an important aspect of NOAA/ESRL to educate the public about ozone loss and ozone hole formation. Researcher Bryan Johnson and educator Elke Bergholz worked together at South Pole in 1998/1999 as part of the NSF teacher outreach program called Teachers Experiencing Antarctica (TEA).It has been almost a decade when they collaborated again concerning the ozone changes at South Pole as part of the International Polar Year (IPY) and the PolarTREC ( http://wwpolartrec.com ) teacher outreach program sponsored by NSF. The TEA and PolarTREC programs selected teachers to travel to polar locations to work with research scientists collecting data and running experiments at various Arctic and Antarctic field sites, including Elke Bergholz working at the South Pole with the NOAA/ESRL team. While in the field, daily contact with classrooms and students around the globe was done through the internet journals, answering emails from students, and webinars. This has been followed up with presentations to schools and the public relating Ms. Bergholz’s experience and new “hands-on” understanding of ozone instruments and ozone depletion over Antarctica, and discussing what changes in the ozone we have seen at South Pole since the first outreach program nearly a decade ago. The lesson plans are available through the PolarTREC website or by contacting Elke Bergholz at ebergholz@unis.org.

  3. Lysophosphatidylcholine perpetuates macrophage polarization toward classically activated phenotype in inflammation.

    PubMed

    Qin, Xiaofei; Qiu, Chunguang; Zhao, Luosha

    2014-01-01

    Pro-inflammatory macrophages are involved in vascular inflammation and serve as the major effector cells in the pathophysiology of atherosclerosis. Phosphatidylcholine (PC) is a major phospholipid moiety affixed to oxidized low-density lipoprotein (oxLDL) and thought to play important roles in the development of atherosclerosis. In this study we described that a bioactive lipid derivative, lysophosphatidylcholine (lysoPC), generated from hydrolysis of the PC moiety of oxidized LDL, promoted and stabilized a strong M1 phenotype in macrophage polarization. Another derivative, 9-hydroxyoctadecadienoic acid (9-HODE), did not show the similar biological function. Blockade of G protein coupled receptor, G2A, which mediates the signal transduction of lysoPC, diminished the effects of lysoPC on the macrophage polarization toward M1 phenotype. The results provide insights into the new mechanism on how oxidized LDL participates in tissue inflammation in atherosclerosis. PMID:24841857

  4. Diviner Lunar Radiometer observations of cold traps in the Moon's south polar region.

    PubMed

    Paige, David A; Siegler, Matthew A; Zhang, Jo Ann; Hayne, Paul O; Foote, Emily J; Bennett, Kristen A; Vasavada, Ashwin R; Greenhagen, Benjamin T; Schofield, John T; McCleese, Daniel J; Foote, Marc C; DeJong, Eric; Bills, Bruce G; Hartford, Wayne; Murray, Bruce C; Allen, Carlton C; Snook, Kelly; Soderblom, Laurence A; Calcutt, Simon; Taylor, Fredric W; Bowles, Neil E; Bandfield, Joshua L; Elphic, Richard; Ghent, Rebecca; Glotch, Timothy D; Wyatt, Michael B; Lucey, Paul G

    2010-10-22

    Diviner Lunar Radiometer Experiment surface-temperature maps reveal the existence of widespread surface and near-surface cryogenic regions that extend beyond the boundaries of persistent shadow. The Lunar Crater Observation and Sensing Satellite (LCROSS) struck one of the coldest of these regions, where subsurface temperatures are estimated to be 38 kelvin. Large areas of the lunar polar regions are currently cold enough to cold-trap water ice as well as a range of both more volatile and less volatile species. The diverse mixture of water and high-volatility compounds detected in the LCROSS ejecta plume is strong evidence for the impact delivery and cold-trapping of volatiles derived from primitive outer solar system bodies. PMID:20966246

  5. Diviner lunar radiometer observations of cold traps in the moon's south polar region

    USGS Publications Warehouse

    Paige, D.A.; Siegler, M.A.; Zhang, J.A.; Hayne, P.O.; Foote, E.J.; Bennett, K.A.; Vasavada, A.R.; Greenhagen, B.T.; Schofield, J.T.; McCleese, D.J.; Foote, M.C.; DeJong, E.; Bills, B.G.; Hartford, W.; Murray, B.C.; Allen, C.C.; Snook, K.; Soderblom, L.A.; Calcutt, S.; Taylor, F.W.; Bowles, N.E.; Bandfield, J.L.; Elphic, R.; Ghent, R.; Glotch, T.D.; Wyatt, M.B.; Lucey, P.G.

    2010-01-01

    Diviner Lunar Radiometer Experiment surface-temperature maps reveal the existence of widespread surface and near-surface cryogenic regions that extend beyond the boundaries of persistent shadow. The Lunar Crater Observation and Sensing Satellite (LCROSS) struck one of the coldest of these regions, where subsurface temperatures are estimated to be 38 kelvin. Large areas of the lunar polar regions are currently cold enough to cold-trap water ice as well as a range of both more volatile and less volatile species. The diverse mixture of water and high-volatility compounds detected in the LCROSS ejecta plume is strong evidence for the impact delivery and cold-trapping of volatiles derived from primitive outer solar system bodies.

  6. Lifestyle Physical Activity Behavior among South Asian Indian Immigrants

    PubMed Central

    Daniel, Manju; Wilbur, JoEllen; Marquez, David; Farran, Carol

    2013-01-01

    Background Little is known of the physical activity behavior of South Asian Indian immigrants (SAIs), though they have more than twice the risk for cardiovascular disease (CVD) and diabetes than Whites. Methods A cross-sectional descriptive face-to-face survey design, comparing between men and women in leisure time (LTPA), household (HPA), and occupational physical activity (OPA). Participants also wore a Lifecorder EX (NL2200) accelerometer for seven days. Results Just over half (51.8%) of the participants met the recommended PA guidelines (≥150 minutes moderate-intensity or ≥75 minutes vigorous-intensity) through LTPA. The average number of daily steps was 6904.3, which is in the “low active” classification. Discussion Increasing lifestyle PA among SAIs is important; PA interventions appealing to gender and culture and with an aerobic component are needed. PMID:23686529

  7. GRAND MINIMA AND NORTH-SOUTH ASYMMETRY OF SOLAR ACTIVITY

    SciTech Connect

    Olemskoy, S. V.; Kitchatinov, L. L.

    2013-11-01

    A solar-type dynamo model in a spherical shell is developed with allowance for random dependence of the poloidal field generation mechanism on time and latitude. The model shows repeatable epochs of a strongly decreased amplitude of magnetic cycles similar to the Maunder minimum of solar activity. Random dependence of dynamo parameters on latitude breaks the equatorial symmetry of generated fields. The model shows the correlation of the occurrence of grand minima with deviations in the dynamo field from dipolar parity. An increased north-south asymmetry of magnetic activity can, therefore, be an indicator of transitions to grand minima. Qualitative interpretation of this correlation is suggested. Statistics of grand minima in the model are close to the Poisson random process, indicating that the onset of a grand minimum is statistically independent of preceding minima.

  8. Dependence of Quiet Time Geomagnetic Activity Seasonal Variation on the Solar Magnetic Polarity

    NASA Astrophysics Data System (ADS)

    Oh, Suyeon

    2013-03-01

    The geomagnetic activity shows the semiannual variation stronger in vernal and autumnal equinoxes than in summer and winter solstices. The semiannual variation has been explained by three main hypotheses such as Axial hypothesis, Equinoctial hypothesis, and Russell-McPherron Effect. Many studies using the various geomagnetic indices have done to support three main hypotheses. In recent, Oh & Yi (2011) examined the solar magnetic polarity dependency of the geomagnetic storm occurrence defined by Dst index. They reported that there is no dependency of the semiannual variation on the sign of the solar polar fields. This study examines the solar magnetic polarity dependency of quiet time geomagnetic activity. Using Dxt index (Karinen & Mursula 2005) and Dcx index (Mursula & Karinen 2005) which are recently suggested, in addition to Dst index, we analyze the data of three-year at each solar minimum for eight solar cycles since 1932. As a result, the geomagnetic activity is stronger in the period that the solar magnetic polarity is anti-parallel with the Earth's magnetic polarity. There exists the difference between vernal and autumnal equinoxes regarding the solar magnetic polarity dependency. However, the difference is not statistically significant. Thus, we conclude that there is no solar magnetic polarity dependency of the semiannual variation for quiet time geomagnetic activity.

  9. Active-polarization-controlled long-depth focus generated by orthogonal nanoslit array

    NASA Astrophysics Data System (ADS)

    Zhu, Lilin; Li, Yuanjie; Sun, Aihui; Xiong, Zhicheng; Liu, Cheng; Kong, Yan; Wang, Shouyu

    2016-08-01

    In order to realize long-range directional excitation and coupling, active-polarization-controlled Bessel beams with an orthogonal nanoslit array are proposed. Excited with left or right circular polarization light, long-depth focus from Bessel beams can be generated with different propagation directions. Moreover, multiple long-depth foci are also designed according to dual-conical phase settings. Proved with numerical simulations, it is considered that the active-polarization-controlled system can be potentially used in future logic photonic and plasmonic systems for optical switching and multichannel coupling.

  10. ASYMMETRIC SOLAR POLAR FIELD REVERSALS

    SciTech Connect

    Svalgaard, Leif; Kamide, Yohsuke

    2013-01-20

    The solar polar fields reverse because magnetic flux from decaying sunspots moves toward the poles, with a preponderance of flux from the trailing spots. If there is a strong asymmetry, in the sense that most activity is in the northern hemisphere, then that excess flux will move toward the north pole and reverse that pole first. If there is more activity in the south later on, then that flux will help to reverse the south pole. In this way, two humps in the solar activity and a corresponding difference in the time of reversals develop (in the ideal case). Such a difference was originally noted in the very first observation of polar field reversal just after the maximum of the strongly asymmetric solar cycle 19, when the southern hemisphere was most active before sunspot maximum and the south pole duly reversed first, followed by the northern hemisphere more than a year later, when that hemisphere became most active. Solar cycles since then have had the opposite asymmetry, with the northern hemisphere being most active before solar maximum. We show that polar field reversals for these cycles have all happened in the north first, as expected. This is especially noteworthy for the present solar cycle 24. We suggest that the association of two or more peaks of solar activity when separated by hemispheres with correspondingly different times of polar field reversals is a general feature of the cycle, and that asymmetric polar field reversals are simply a consequence of the asymmetry of solar activity.

  11. Nonequilibrium phase transitions, fluctuations and correlations in an active contractile polar fluid.

    PubMed

    Gowrishankar, Kripa; Rao, Madan

    2016-02-21

    We study the patterning, fluctuations and correlations of an active polar fluid consisting of contractile polar filaments on a two-dimensional substrate, using a hydrodynamic description. The steady states generically consist of arrays of inward pointing asters and show a continuous transition from a moving lamellar phase, a moving aster street, to a stationary aster lattice with no net polar order. We next study the effect of spatio-temporal athermal noise, parametrized by an active temperature TA, on the stability of the ordered phases. In contrast to its equilibrium counterpart, we find that the active crystal shows true long range order at low TA. On increasing TA, the asters dynamically remodel, concomitantly we find novel phase transitions characterized by bond-orientational and polar order upon "heating". PMID:26742682

  12. Paleomagnetism of the Santa Fé Group, central Brazil: Implications for the late Paleozoic apparent polar wander path for South America

    NASA Astrophysics Data System (ADS)

    Brandt, Daniele; Ernesto, Marcia; Rocha-Campos, Antonio Carlos; Dos Santos, Paulo Roberto

    2009-02-01

    Paleomagnetic and rockmagnetic data are reported for the Floresta Formation (Santa Fé Group) of the Sanfranciscana Basin, central Brazil. This formation represents the Permo-Carboniferous glacial record of the basin and comprises the Brocotó (diamictites and flow diamictites), Brejo do Arroz (red sandstones and shales with dropstones and invertebrate trails), and Lavado (red sandstones) members, which crop out near the cities of Santa Fé de Minas and Canabrava, Minas Gerais State. Both Brejo do Arroz and Lavado members were sampled in the vicinities of the two localities. Alternating field and thermal demagnetizations of 268 samples from 76 sites revealed reversed components of magnetization in all samples in accordance with the Permo-Carboniferous Reversed Superchron. The magnetic carriers are magnetite and hematite with both minerals exhibiting the same magnetization component, suggesting a primary origin for the remanence. We use the high-quality paleomagnetic pole for the Santa Fé Group (330.9°E 65.7°S; N = 60; α95 = 4.1°; k = 21) in a revised late Carboniferous to early Triassic apparent polar wander path for South America. On the basis of this result it is shown that an early Permian Pangea A-type fit is possible if better determined paleomagnetic poles become available.

  13. Mapping Vesta Mid-Latitude Quadrangle V-12EW: Mapping the Edge of the South Polar Structure

    NASA Astrophysics Data System (ADS)

    Hoogenboom, T.; Schenk, P.; Williams, D. A.; Hiesinger, H.; Garry, W. B.; Yingst, R.; Buczkowski, D.; McCord, T. B.; Jaumann, R.; Pieters, C. M.; Gaskell, R. W.; Neukum, G.; Schmedemann, N.; Marchi, S.; Nathues, A.; Le Corre, L.; Roatsch, T.; Preusker, F.; White, O. L.; DeSanctis, C.; Filacchione, G.; Raymond, C. A.; Russell, C. T.

    2011-12-01

    NASA's Dawn spacecraft arrived at the asteroid 4Vesta on July 15, 2011, and is now collecting imaging, spectroscopic, and elemental abundance data during its one-year orbital mission. As part of the geological analysis of the surface, a series of 15 quadrangle maps are being produced based on Framing Camera images (FC: spatial resolution: ~65 m/pixel) along with Visible & Infrared Spectrometer data (VIR: spatial resolution: ~180 m/pixel) obtained during the High-Altitude Mapping Orbit (HAMO). This poster presentation concentrates on our geologic analysis and mapping of quadrangle V-12EW. This quadrangle is dominated by the arcuate edge of the large 460+ km diameter south polar topographic feature first observed by HST (Thomas et al., 1997). Sparsely cratered, the portion of this feature covered in V-12EW is characterized by arcuate ridges and troughs forming a generalized arcuate pattern. Mapping of this terrain and the transition to areas to the north will be used to test whether this feature has an impact or other (e.g., internal) origin. We are also using FC stereo and VIR images to assess whether their are any compositional differences between this terrain and areas further to the north, and image data to evaluate the distribution and age of young impact craters within the map area. The authors acknowledge the support of the Dawn Science, Instrument and Operations Teams.

  14. Polar cap formation on Ganymede

    NASA Technical Reports Server (NTRS)

    Shaya, E. J.; Pilcher, C. B.

    1984-01-01

    It is argued that Ganymede's polar caps are the remnants of a more extensive covering of water ice that formed during a period in which the satellite was geologically active. It is inferred that the initial thickness of this covering was a significant fraction of the gardening depth since the covering formed. This suggests an initial thickness of at least a few meters over heavily cratered regions such as the south polar grooved terrain. The absence of similar polar caps on Callisto apparently reflects the absence of comparable geologic activity in the history of this satellite.

  15. The Spatial Distribution of Radiated Endogenic Power from Enceladus' South Polar Region

    NASA Astrophysics Data System (ADS)

    Howett, C.; Spencer, J. R.

    2014-12-01

    Estimates of the total power radiated by Enceladus' tiger stripes are constrained by Cassini CIRS observations of the thermal emission from the tiger stripe region. Unfortunately, these data have several limitations imposed by the nature of the CIRS instrument, and the very limited time available for high resolution observations of Enceladus' south pole. Short-wavelength (7 - 16 micron) maps have complete coverage with good spatial resolution, but do not capture the bulk of the radiated power, which is emitted at longer wavelengths. Long-wavelength (> 16 micron) maps which capture most of the emission have either very limited spatial coverage, or spatial resolution insufficient to separate the tiger stripes from background thermal emission. In Howett et al. (2011) we estimated ~16 GW of total endogenic heat flow based on low-resolution long-wavelength data. This estimate required model-dependent assumptions about passive background thermal emission, which was not directly separated spatially from the tiger stripes, but included potential inter-stripe endogenic background emission. Our recent much lower estimate of emission from the tiger stripes alone, ~4.5 GW (Spencer et al. 2013), uses high-resolution long-wavelength data to exclude both passive and possible endogenic inter-stripe emission, but is based on poorly-constrained extrapolations to the entire system of long-wavelength observations of small portions of the tiger stripes. We eagerly await the one remaining opportunity to extend long-wavelength, high spatial resolution, mapping to more of the tiger stripe system in Cassini's final close Enceladus flyby, in December 2015. In the meantime, existing long-wavelength data of intermediate spatial resolution provides intriguing additional clues about the true spatial distribution, and thus the total power, of the long-wavelength emission. In particular, a March 2008 scan of Damascus and Baghdad Sulci shows surprisingly bright 16 - 200 micron emission at the anti

  16. Macrophage activation and polarization: nomenclature and experimental guidelines.

    PubMed

    Murray, Peter J; Allen, Judith E; Biswas, Subhra K; Fisher, Edward A; Gilroy, Derek W; Goerdt, Sergij; Gordon, Siamon; Hamilton, John A; Ivashkiv, Lionel B; Lawrence, Toby; Locati, Massimo; Mantovani, Alberto; Martinez, Fernando O; Mege, Jean-Louis; Mosser, David M; Natoli, Gioacchino; Saeij, Jeroen P; Schultze, Joachim L; Shirey, Kari Ann; Sica, Antonio; Suttles, Jill; Udalova, Irina; van Ginderachter, Jo A; Vogel, Stefanie N; Wynn, Thomas A

    2014-07-17

    Description of macrophage activation is currently contentious and confusing. Like the biblical Tower of Babel, macrophage activation encompasses a panoply of descriptors used in different ways. The lack of consensus on how to define macrophage activation in experiments in vitro and in vivo impedes progress in multiple ways, including the fact that many researchers still consider there to be only two types of activated macrophages, often termed M1 and M2. Here, we describe a set of standards encompassing three principles-the source of macrophages, definition of the activators, and a consensus collection of markers to describe macrophage activation-with the goal of unifying experimental standards for diverse experimental scenarios. Collectively, we propose a common framework for macrophage-activation nomenclature. PMID:25035950

  17. Antiviral activity of some South American medicinal plants.

    PubMed

    Abad, M J; Bermejo, P; Sanchez Palomino, S; Chiriboga, X; Carrasco, L

    1999-03-01

    Folk medicinal plants are potential sources of useful therapeutic compounds including some with antiviral activities. Extracts prepared from 10 South American medicinal plants (Baccharis trinervis, Baccharis teindalensis, Eupatorium articulatum, Eupatorium glutinosum, Tagetes pusilla, Neurolaena lobata, Conyza floribunda, Phytolacca bogotensis, Phytolacca rivinoides and Heisteria acuminata) were screened for in vitro antiviral activity against herpes simplex type I (HSV-1), vesicular stomatitis virus (VSV) and poliovirus type 1. The most potent inhibition was observed with an aqueous extract of B. trinervis, which inhibited HSV-1 replication by 100% at 50-200 micrograms/mL, without showing cytotoxic effects. Good activities were also found with the ethanol extract of H. acuminata and the aqueous extract of E. articulatum, which exhibited antiviral effects against both DNA and RNA viruses (HSV-1 and VSV, respectively) at 125-250 micrograms/mL. The aqueous extracts of T. pusilla (100-250 micrograms/mL), B. teindalensis (50-125 micrograms/mL) and E. glutinosum (50-125 micrograms/mL) also inhibited the replication of VSV, but none of the extracts tested had any effect on poliovirus replication. PMID:10190189

  18. The International Polar Year 2007-2008: a Preliminary Overview of Proposed Research Activities.

    NASA Astrophysics Data System (ADS)

    Allison, I.; Beland, M.; Members, J.

    2005-05-01

    The International Polar Year 2007-2008 (IPY 2007-2008), co-sponsored by the International Council for Science and the World Meteorological Organization, will be an intensive and internationally coordinated campaign of high quality research and observations in the polar regions. It will have an interdisciplinary emphasis, with active inclusion of the social sciences as well as natural science. The IPY 2007-2008 is intended to lay the foundation for major scientific advances in knowledge and understanding of the polar regions and their role in the functioning of the planet. IPY 2007-2008 will address six broad research themes. These are the present environmental status of the polar regions; change in the polar regions; the links and interactions between polar regions and the rest of the globe; frontiers of science in the polar regions; the polar regions as a unique vantage point to observe processes from the interior of the Earth, to the Sun and the cosmos beyond; and the culture, history, and sociology of human societies in polar regions. Details of the IPY science plan and its implementation are available in the IPY Framework document at www.ipy.org, A large number of proposals for potential IPY activities were received in January 2005 in response to a preliminary call for "Expressions of Intent". Those projects meeting the IPY criteria have been identified and are presently being developed more fully and, where appropriate, consolidated into larger projects. This presentation will provide an outline of the major scientific initiatives that are developing under the IPY 2007-2008 vision. Opportunities for participation in the developing IPY projects will be noted, as will those projects seeking additional input from new collaborators.

  19. Active overbank deposition during the last century, South River, Virginia

    NASA Astrophysics Data System (ADS)

    Pizzuto, Jim; Skalak, Katherine; Pearson, Adam; Benthem, Adam

    2016-03-01

    We quantify rates of overbank deposition over decadal to centennial timescales along the South River in Virginia using four independent methods. Detailed mercury profiles sampled adjacent to the stream channel preserve the peak historic mercury concentration on suspended sediment dating from 1955 to 1961 and suggest sedimentation rates of 8 to 50 cm/100 years. Sediment accumulation over the roots of trees suggest rates of 0 to 100 cm/100 years, with significantly higher values on levees and lower values on floodplains farther from the channel. Profiles of 137Cs and 210Pb from two eroding streambanks are fit with an advection-diffusion model calibrated at an upland reference site; these methods suggest sedimentation rates of 44 to 73 cm/100 years. Mercury inventories from 107 floodplain cores, combined with a previously published reconstruction of the history of mercury concentration on suspended sediment, provide spatially comprehensive estimates of floodplain sedimentation: median sedimentation rates are 3.8 cm/100 years for the < 0.3-year floodplain, 1.37 cm/100 years for the 0.3- to 2-year floodplain, 0.4 cm/100 years for the 2- to 5-year floodplain, and 0.1 cm/100 years for the 5- to 62-year floodplain. While these sedimentation rates are relatively low, the total mass of sediment stored from 1930 to 2007 is 4.9 ± 1.7 (95% confidence interval) × 107 kg, corresponding to an average thickness of 2.5 cm (3.2 cm/100 years). These results demonstrate that floodplains of our 4.5-km-long study reach have stored 8 to 12% of the total suspended sediment supplied to the study reach of the South River. Hydrologic Engineering Center-River Analysis System (HEC-RAS) modeling demonstrates that the floodplain of the South River remains hydraulically connected to the channel: 56% of the 100-year floodplain is inundated every two years, and 83% of the floodplain is inundated every five years. These results, combined with previously published data, provide the basis for a

  20. Active imaging with the aids of polarization retrieve in turbid media system

    NASA Astrophysics Data System (ADS)

    Tao, Qiangqiang; Sun, Yongxuan; Shen, Fei; Xu, Qiang; Gao, Jun; Guo, Zhongyi

    2016-01-01

    We propose a novel active imaging based on the polarization retrieve (PR) method in turbid media system. In our simulations, the Monte Carlo (MC) algorithm has been used to investigate the scattering process between the incident photons and the scattering particles, and the visually concordant object but with different polarization characteristics in different regions, has been selected as the original target that is placed in the turbid media. Under linearly and circularly polarized illuminations, the simulation results demonstrate that the corresponding polarization properties can provide additional information for the imaging, and the contrast of the polarization image can also be enhanced greatly compared to the simplex intensity image in the turbid media. Besides, the polarization image adjusted by the PR method can further enhance the visibility and contrast. In addition, by PR imaging method, with the increasing particles' size in Mie's scale, the visibility can be enhanced, because of the increased forward scattering effect. In general, in the same circumstance, the circular polarization images can offer a better contrast and visibility than that of linear ones. The results indicate that the PR imaging method is more applicable to the scattering media system with relatively larger particles such as aerosols, heavy fog, cumulus, and seawater, as well as to biological tissues and blood media.

  1. Vertebrate records in polar sediments: Biological responses to past climate change and human activities

    NASA Astrophysics Data System (ADS)

    Sun, L. G.; Emslie, S. D.; Huang, T.; Blais, J. M.; Xie, Z. Q.; Liu, X. D.; Yin, X. B.; Wang, Y. H.; Huang, W.; Hodgson, D. A.; Smol, J. P.

    2013-11-01

    Biological responses to climate and environmental changes in remote polar regions are of increasing interest in global change research. Terrestrial and marine polar ecosystems have suffered from impacts of both rapid climate change and intense human activities, and large fluctuations in the population sizes of seabirds, seals, and Antarctic krill have been observed in the past decades. To understand the mechanisms driving these regime shifts in polar ecosystems, it is important to first distinguish the influences of natural forcing from anthropogenic activities. Therefore, investigations of past changes of polar ecosystems prior to human contact are relevant for placing recent human-induced changes within a long-term historical context. Here we focus our review on the fossil, sub-fossil, archaeological, and biogeochemical remains of marine vertebrates in polar sediments. These remains include well-preserved tissues such as bones, hairs and feathers, and biogeochemical markers and other proxy indicators, including deposits of guano and excrement, which can accumulate in lake and terrestrial sediments over thousands of years. Analyses of these remains have provided insight into both natural and anthropogenic impacts on marine vertebrates over millennia and have helped identify the causal agents for these impacts. Furthermore, land-based seabirds and marine mammals have been shown to play an important role as bio-vectors in polar environments as they transport significant amounts of nutrients and anthropogenic contaminants between ocean and terrestrial ecosystems.

  2. Correlation of Martian South Polar CO2 Seasonal Cap Retreat With Low Altitude Clouds: A Control On Annual Accumulation

    NASA Astrophysics Data System (ADS)

    Smith, Isaac; Spiga, Aymeric

    2014-05-01

    Both the north and south polar layered deposits (NPLD and SPLD) comprise the majority of surface ice on Mars and offer a historical record for understanding recent climate. Of importance, the deposits undergo seasonal variability, between winter (when CO2 ice frost covers the polar regions) and summer (when the CO2 ice has sublimed). Recent evidence has shown that winds and atmospheric deposition played major roles for forming the spiral troughs that cover the NPLD. Observations of low altitude clouds (or visible expressions of katabatic jumps), radar stratigraphy, and surface morphology, in combination with high resolution mesoscale simulations from the Laboratoire de Météorologie Dynamique, demonstrate that ice is transported across the NPLD by wind to form and modify the troughs [Smith et al., 2013]. We employ the same techniques on the SPLD to find that the processes affecting southern spiral troughs are very similar, although there is an additional seasonal component not detected on the NPLD. Clouds, as mechanisms of deposition, retreat pole-ward during southern spring and summer. The retreat is matched spatially to modeled high speed winds near the CO2 seasonal ice cap boundary. Our mesoscale simulations reveal that topographic heights of the SPLD primarily drive slope-wind (katabatic) circulations. This existing circulation is reinforced by an additional thermally-direct circulation driven by the retreating CO2 ice in proximity to nearby exposed low albedo deposits, explaining why enhanced winds (and trough clouds) are mostly found in the vicinity of the CO2 seasonal ice boundary. In one simulation, at Ls 290°, the ice line is located so that the slope winds produced by the SPLD topography are optimally enhanced (up to 20 ms-1) by thermally directed circulations caused by a nearly 100 K thermal contrast. This work, in combination with detailed stratigraphic analysis from ground penetrating radar indicates that sites of deposition and retention of ice on

  3. Anisotropy of thermoremanent magnetisation of Cryogenian glaciogenic and Ediacaran red beds, South Australia: Neoproterozoic apparent or true polar wander?

    NASA Astrophysics Data System (ADS)

    Schmidt, Phillip W.; Williams, George E.

    2013-11-01

    pole path for this period, for which true polar wander (TPW) has been inferred. However, until ages of Neoproterozoic strata in South Australia are better constrained uncertainty persists on whether the similarities of the Australian and North American pole paths reflect TPW.

  4. May the continuous trapping of atmospheric water on the permanent South polar cap affect the global atmospheric D/H ratio on Mars?

    NASA Astrophysics Data System (ADS)

    Chassefiere, E.; Montmessin, F.; Fouchet, T.; Forget, F.

    It is generally admitted that thermal escape is the only process responsible for hydrogen isotopic fractionation in Mars atmosphere (enrichment by a factor of 5.5 relative to SMOW value). The aim of the present paper is to show that thermodynamic processes (condensation/ sublimation) may potentially play a significant role in fractionating atmospheric H2O. The cycle of Martian H2O is complex. During northern summer, the North permanent water ice cap is assumed to release a few precipitable microns (pr. μ m), globally averaged, to the atmosphere. Part of this water vapor finally returns to North cap during northern winter, whereas a small fraction (<10%) is trapped in the South permanent carbonic ice cap, which acts as a permanent sink. Water vapor is probably cycled through regolith by adsorption/deposition and further sublimation/desorption. It is believed that the ultimate fate of water molecules released by the North water ice cap, and/or by the permafrost, is to stick to the South carbonic ice cap, with a time scale longer than one seasonal cycle. If so, a molecule released by the North cap must undergo a number of adsorption/desorption and deposition/sublimation cycles, through regolith and polar caps, before being trapped irreversibly in South cap carbonic ice. Recent IR observations of pure water ice on South polar cap by Mars-Express during southern spring show that water, migrating southward together with the edge of the retreating seasonal south CO2 cap, is finally deposited near cap edges in substantial amount. The fraction of this deposited water not released back to the atmosphere at later times (southern summer), therefore incorporated to carbonic ice, is not well known at present time. Because, during southern winter, water vapor above the South permanent cap is much depleted in deuterium, by at least a factor of 3 (Montmessin et al, AGU meeting, 2003), the polar cap tends to be depleted in deuterium (similarly to Earth's case), with a related

  5. Cassini ISS observations of Titan's surface and changes in its south-polar lakes

    NASA Astrophysics Data System (ADS)

    Turtle, Elizabeth; Perry, Jason; McEwen, Alfred; Hayes, Alexander; West, Robert

    Cassini's Imaging Science Subsystem (ISS) has been returning images of Titan since early 2004, continuing through the 65 close Titan encounters that have been performed to date. These ob-servations have been combined to produce a 938-nm albedo map of the surface with resolutions ranging from several kilometers to several hundred meters. The morphologies observed on Titan's surface reflect a wide variety of geological features [1]: roughly east-west streamlined shapes, suggestive of aeolian processes, consistent with Cassini RADAR observations of dunes at low latitudes [2]; narrow, curvilinear channels; dark lakes and seas at high latitudes [e.g., 3]; rare impact structures, further evidence for a geologically young surface; and possible tec-tonic and cryovolcanic structures. Changes have also been observed: a new large dark area appeared between July 2004 and June 2005 [3] and may have subsequently faded. Recent ISS observations of Ontario Lacus suggest that its shoreline may have receded as well [cf. 4]. Such changes are interpreted to be the result of precipitation and ponding of liquid methane and the subsequent infiltration into the subsurface or evaporation thereof [3]. No changes have been observed to date in the lakes and seas at high northern latitudes. We will present ISS' most recent map of Titan's surface, documenting changes that may have resulted from weather and seasonal changes and their implications for Titan's active methane cycle. References: [1] Porco et al. (2005) Nature 434, 159-168. [2] Lorenz et al. (2006) Science 312, 724-727. [3] Turtle et al. (2009) GRL 36, DOI 0.1029/2008GL036186. [4] Hayes et al. (2009) Eos Trans. AGU, 90, Abstract P54C-02.

  6. Non-polar organic compounds in marine aerosols over the northern South China Sea: Influence of continental outflow.

    PubMed

    Zhao, Yan; Zhang, Yingyi; Fu, Pingqing; Ho, Steven Sai Hang; Ho, Kin Fai; Liu, Fobang; Zou, Shichun; Wang, Shan; Lai, Senchao

    2016-06-01

    Filter samples of total suspended particle (TSP) collected during a cruise campaign over the northern South China Sea (SCS) from September to October 2013 were analyzed for non-polar organic compounds (NPOCs) as well as organic carbon (OC), elemental carbon (EC) and water-soluble ions. A total of 115 NPOCs species in groups of n-alkanes, polycyclic aromatic hydrocarbons (PAHs), iso-/antiso-alkanes, hopanes, steranes, methylalkanes, branched alkanes, cycloalkanes, alkenes and phthalates were detected. The characteristics of NPOCs in marine TSP samples were investigated to understand the sources from the Asian continent and other regions. The concentrations of total NPOCs ranged from 19.8 to 288.2 ng/m(3) with an average of 87.9 ng/m(3), which accounted for 0.8-1.7% (average 1.0%) of organic matter (OM). n-Alkanes was the predominant group, accounting for 43.1-79.5%, followed by PAHs (5.5-44.4%) and hopanes (1.6-11.4%). We found that primary combustion (biomass burning/fossil fuel combustion) was the dominant source for the majority of NPOCs (89.1%). Biomass burning in southern/southeastern China via long-range transport was proposed to be a major contributor of NPOCs in marine aerosols over the northern SCS, suggested by the significant correlations between nss-K(+) and NPOCs groups as well as the analysis of air mass back-trajectory and fire spots. For the samples with strong continental influence, the strong enhancement in concentrations of n-alkanes, PAHs, hopanes and steranes were attributed to fossil fuel (coal/petroleum) combustion. In addition, terrestrial plants waxes were another contributor to NPOCs. PMID:27023121

  7. Mars south polar spring and summer behavior observed by TES: seasonal cap evolution controlled by frost grain size

    USGS Publications Warehouse

    Kieffer, Hugh H.; Titus, Timothy N.; Mullins, Kevin F.; Christensen, Philip R.

    2000-01-01

    Thermal Emission Spectrometer (TES) observations of the recession phase of Mars' south polar cap are used to quantitatively map this recession in both thermal and visual appearance. Geographically nonuniform behavior interior to the cap is characterized by defining several small regions which exemplify the range of behavior. For most of the cap, while temperatures remain near the CO2 frost point, albedos slowly increase with the seasonal rise of the Sun, then drop rapidly as frost patches disappear over a period of ∼20 days. A “Cryptic” region remains dark and mottled throughout its cold period. TES observations are compared with first-order theoretical spectra of solid CO2 frost with admixtures of dust and H2O. The TES spectra indicate that the Cryptic region has much larger grained solid CO2 than the rest of the cap and that the solid CO2 here may be in the form of a slab. The Mountains of Mitchel remain cold and bright well after other areas at comparable latitude, apparently as a result of unusually small size of the CO2 frost grains; we found little evidence for a significant presence of H2O. Although CO2 grain size may be the major difference between these regions, incorporated dust is also required to match the observations; a self-cleaning process carries away the smaller dust grains. Comparisons with Viking observations indicate little difference in the seasonal cycle 12 Martian years later. The observed radiation balance indicates CO2 sublimation budgets of up to 1250 kg m−2. Regional atmospheric dust is common; localized dust clouds are seen near the edge of the cap prior to the onset of a regional dust storm and interior to the cap during the storm.

  8. Minimal model for spontaneous cell polarization and edge activity in oscillating, rotating and migrating cells

    NASA Astrophysics Data System (ADS)

    Raynaud, Franck; Ambühl, Mark E.; Gabella, Chiara; Bornert, Alicia; Sbalzarini, Ivo F.; Meister, Jean-Jacques; Verkhovsky, Alexander B.

    2016-04-01

    How cells break symmetry and organize activity at their edges to move directionally is a fundamental question in cell biology. Physical models of cell motility commonly incorporate gradients of regulatory proteins and/or feedback from the motion itself to describe the polarization of this edge activity. These approaches, however, fail to explain cell behaviour before the onset of polarization. We use polarizing and moving fish epidermal cells as a model system to bridge the gap between cell behaviours before and after polarization. Our analysis suggests a novel and simple principle of self-organizing cell activity, in which local cell-edge dynamics depends on the distance from the cell centre, but not on the orientation with respect to the front-back axis. We validate this principle with a stochastic model that faithfully reproduces a range of cell-migration behaviours. Our findings indicate that spontaneous polarization, persistent motion and cell shape are emergent properties of the local cell-edge dynamics controlled by the distance from the cell centre.

  9. Temperature thresholds for chlorine activation and ozone loss in the polar stratosphere

    NASA Astrophysics Data System (ADS)

    Drdla, K.; Müller, R.

    2012-07-01

    Low stratospheric temperatures are known to be responsible for heterogeneous chlorine activation that leads to polar ozone depletion. Here, we discuss the temperature threshold below which substantial chlorine activation occurs. We suggest that the onset of chlorine activation is dominated by reactions on cold binary aerosol particles, without the formation of polar stratospheric clouds (PSCs), i.e. without any significant uptake of HNO3 from the gas phase. Using reaction rates on cold binary aerosol in a model of stratospheric chemistry, a chlorine activation threshold temperature, TACL, is derived. At typical stratospheric conditions, TACL is similar in value to TNAT (within 1-2 K), the highest temperature at which nitric acid trihydrate (NAT) can exist. TNAT is still in use to parameterise the threshold temperature for the onset of chlorine activation. However, perturbations can cause TACL to differ from TNAT: TACL is dependent upon H2O and potential temperature, but unlike TNAT is not dependent upon HNO3. Furthermore, in contrast to TNAT, TACL is dependent upon the stratospheric sulfate aerosol loading and thus provides a means to estimate the impact on polar ozone of strong volcanic eruptions and some geo-engineering options, which are discussed. A parameterisation of TACL is provided here, allowing it to be calculated for low solar elevation (or high solar zenith angle) over a comprehensive range of stratospheric conditions. Considering TACL as a proxy for chlorine activation cannot replace a detailed model calculation, and polar ozone loss is influenced by other factors apart from the initial chlorine activation. However, TACL provides a more accurate description of the temperature conditions necessary for chlorine activation and ozone loss in the polar stratosphere than TNAT.

  10. Activation Layer Stabilization of High Polarization Photocathodes in Sub-Optimal RF Gun Environments

    SciTech Connect

    Gregory A. Mulhollan

    2010-11-16

    Specific activation recipes for bulk, 100 nm thick MBE grown and high polarization III-V photocathode material have been developed which mitigate the effects of exposure to background gasses. Lifetime data using four representative gasses were acquired for bulk GaAs, 100 nm unstrained GaAs and strained superlattice GaAs/GaAsP, all activated both with Cs and then Cs and Li (bi-alkali). Each photoemitter showed marked resilience improvement when activated using the bi-alkali recipe compared to the standard single alkali recipe. A dual alkali activation system at SLAC was constructed, baked and commissioned with the purpose of performing spin-polarization measurements on electrons emitted from the bi-alkali activated surfaces. An end station at SSRL was configured with the required sources for energy resolved photoemission measurements on the bi-alkali activated and CO2 dosed surfaces. The bi-alkali recipes were successfully implemented at SLAC/SSRL. Measurements at SLAC of the photoelectron spin-polarization from the modified activation surface showed no sign of a change in value compared to the standard activated material, i.e., no ill effects. Analysis of photoemission data indicates that the addition of Li to the activation layer results in a multi-layer structure. The presence of Li in the activation layer also acts as an inhibitor to CO2 absorption, hence better lifetimes in worse vacuum were achieved. The bi-alkali activation has been tested on O2 activated GaAs for comparison with NF3 activated surfaces. Comparable resilience to CO2 exposure was achieved for the O2 activated surface. An RF PECVD amorphous silicon growth system was modified to allow high temperature heat cleaning of GaAs substrates prior to film deposition. Growth versus thickness data were collected. Very thin amorphous silicon germanium layers were optimized to exhibit good behavior as an electron emitter. Growth of the amorphous silicon germanium films on the above substrates was fine tuned

  11. Telmisartan prevention of LPS-induced microglia activation involves M2 microglia polarization via CaMKKβ-dependent AMPK activation.

    PubMed

    Xu, Yuan; Xu, Yazhou; Wang, Yurong; Wang, Yunjie; He, Ling; Jiang, Zhenzhou; Huang, Zhangjian; Liao, Hong; Li, Jia; Saavedra, Juan M; Zhang, Luyong; Pang, Tao

    2015-11-01

    Brain inflammation plays an important role in the pathophysiology of many psychiatric and neurological diseases. During brain inflammation, microglia cells are activated, producing neurotoxic molecules and neurotrophic factors depending on their pro-inflammatory M1 and anti-inflammatory M2 phenotypes. It has been demonstrated that Angiotensin II type 1 receptor blockers (ARBs) ameliorate brain inflammation and reduce M1 microglia activation. The ARB telmisartan suppresses glutamate-induced upregulation of inflammatory genes in cultured primary neurons. We wished to clarify whether telmisartan, in addition, prevents microglia activation through polarization to an anti-inflammatory M2 phenotype. We found that telmisartan promoted M2 polarization and reduced M1 polarization in LPS-stimulated BV2 and primary microglia cells, effects partially dependent on PPARγ activation. The promoting effects of telmisartan on M2 polarization, were attenuated by an AMP-activated protein kinase (AMPK) inhibitor or AMPK knockdown, indicating that AMPK activation participates on telmisartan effects. Moreover, in LPS-stimulated BV2 cells, telmisartan enhancement of M2 gene expression was prevented by the inhibitor STO-609 and siRNA of calmodulin-dependent protein kinase kinase β (CaMKKβ), an upstream kinase of AMPK. Furthermore, telmisartan enhanced brain AMPK activation and M2 gene expression in a mouse model of LPS-induced neuroinflammation. In addition, telmisartan reduced the LPS-induced sickness behavior in this in vivo model, and this effect was prevented by prior administration of an AMPK inhibitor. Our results indicate that telmisartan can be considered as a novel AMPK activator, suppressing microglia activation by promoting M2 polarization. Telmisartan may provide a novel, safe therapeutic approach to treat brain disorders associated with enhanced inflammation. PMID:26188187

  12. Human and climate impacts on Holocene fire activity recorded in polar and mountain ice cores

    NASA Astrophysics Data System (ADS)

    Kehrwald, Natalie; Zennaro, Piero; Kirchgeorg, Torben; Li, Quanlian; Wang, Ninglian; Power, Mitchell; Zangrando, Roberta; Gabrielli, Paolo; Thompson, Lonnie; Gambaro, Andrea; Barbante, Carlo

    2014-05-01

    Fire is one of the major influences of biogeochemical change on local to hemispheric scales through emitting greenhouse gases, altering atmospheric chemistry, and changing primary productivity. Levoglucosan (1,6-anhydro-β-D-glucopyranose) is a specific molecular that can only be produced by cellulose burning at temperatures > 300°C, comprises a major component of smoke plumes, and can be transported across > 1000 km distances. Levoglucosan is deposited on and archived in glaciers over glacial interglacial cycles resulting in pyrochemical evidence for exploring interactions between fire, climate and human activity. Ice core records provide records of past biomass burning from regions of the world with limited paleofire data including polar and low-latitude, high-altitude regions. Here, we present Holocene fire activity records from the NEEM, Greenland (77° 27'N; 51° 3'W; 2454 masl), EPICA Dome C, Antarctica (75° 06'S; 123° 21'E; 3233 masl), Kilimanjaro, Tanzania (3° 05'S, 21.2° E, 5893 masl) and the Muztagh, China (87.17° E; 36.35° N; 5780 masl ice cores. The NEEM ice core reflects boreal fire activity from both North American and Eurasian sources. Temperature is the dominant control of NEEM levoglucosan flux over decadal to millennial time scales, while droughts influence fire activity over sub-decadal timescales. Our results demonstrate the prominence of Siberian fire sources during intense multiannual droughts. Unlike the NEEM core, which incorporates the largest land masses in the world as potential fire sources, EPICA Dome C is located far from any possible fire source. However, EPICA Dome C levoglucosan concentrations are consistently above detection limits and demonstrate a substantial 1000-fold increase in fire activity beginning approximately 800 years ago. This significant and sustained increase coincides with Maori arrival and dispersal in New Zealand augmented by later European arrival in Australia. The EPICA Dome C levoglucosan profile is

  13. Showdown over South Africa: The Second Coming of Student Activism.

    ERIC Educational Resources Information Center

    Fisher, Marc

    1979-01-01

    Student activists are charging that university investments are helping support South Africa's discriminatory practices. Confrontations between students and administrators and trustees are described, and instances of divestiture are reported. (LBH)

  14. Exhuming South Polar Crater

    NASA Technical Reports Server (NTRS)

    2004-01-01

    7 February 2004 The large, circular feature in this image is an old meteor impact crater. The crater is larger than the 3 kilometers-wide (1.9 miles-wide) Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, thus only part of the crater is seen. The bright mesas full of pits and holes--in some areas resembling swiss cheese--are composed of frozen carbon dioxide. In this summertime view, the mesa slopes and pit walls are darkened as sunlight causes some of the ice to sublime away. At one time in the past, the crater shown here may have been completely covered with carbon dioxide ice, but, over time, it has been exhumed as the ice sublimes a little bit more each summer. The crater is located near 86.8oS, 111.6oW. Sunlight illuminates this scene from the upper left.

  15. Broadband active tuning of unidirectional scattering from nanoantenna using combined radially and azimuthally polarized beams.

    PubMed

    Xi, Z; Wei, L; Adam, A J L; Urbach, H P

    2016-01-01

    We propose an approach to actively tune the scattering pattern of a Mie-type spherical antenna. The scheme is based on separate control over the induced electric dipole and induced magnetic dipole using two coherent focused beams of radial polarization and azimuthal polarization, respectively. By carefully tuning the amplitude and phase relation of the two beams, a broadband unidirectional scattering can be achieved, even at the antenna's resonant wavelength where the antenna scatters efficiently. By moving the focus of one beam, a drastic switch of the unidirectional scattering can be observed. Such a scheme enables the design of ultra-compact optical switches and directional couplers based on nanoantennas. PMID:26696151

  16. PPAR activation induces M1 macrophage polarization via cPLA₂-COX-2 inhibition, activating ROS production against Leishmania mexicana.

    PubMed

    Díaz-Gandarilla, J A; Osorio-Trujillo, C; Hernández-Ramírez, V I; Talamás-Rohana, P

    2013-01-01

    Defence against Leishmania depends upon Th1 inflammatory response and, a major problem in susceptible models, is the turnoff of the leishmanicidal activity of macrophages with IL-10, IL-4, and COX-2 upregulation, as well as immunosuppressive PGE2, all together inhibiting the respiratory burst. Peroxisome proliferator-activated receptors (PPAR) activation is responsible for macrophages polarization on Leishmania susceptible models where microbicide functions are deactivated. In this paper, we demonstrated that, at least for L. mexicana, PPAR activation, mainly PPAR γ , induced macrophage activation through their polarization towards M1 profile with the increase of microbicide activity against intracellular pathogen L. mexicana. PPAR activation induced IL-10 downregulation, whereas the production of proinflammatory cytokines such as TNF- α , IL-1 β , and IL-6 remained high. Moreover, PPAR agonists treatment induced the deactivation of cPLA2-COX-2-prostaglandins pathway together with an increase in TLR4 expression, all of whose criteria meet the M1 macrophage profile. Finally, parasite burden, in treated macrophages, was lower than that in infected nontreated macrophages, most probably associated with the increase of respiratory burst in these treated cells. Based on the above data, we conclude that PPAR agonists used in this work induces M1 macrophages polarization via inhibition of cPLA2 and the increase of aggressive microbicidal activity via reactive oxygen species (ROS) production. PMID:23555077

  17. Proliferative effects of apical, but not basal, matrix metalloproteinase-7 activity in polarized MDCK cells

    SciTech Connect

    Harrell, Permila C.; McCawley, Lisa J.; Fingleton, Barbara; McIntyre, J. Oliver; Matrisian, Lynn M. . E-mail: lynn.matrisian@vanderbilt.edu

    2005-02-15

    Matrix metalloproteinase-7 (MMP-7) is primarily expressed in glandular epithelium. Therefore, its mechanism of action may be influenced by its regulated vectorial release to either the apical and/or basolateral compartments, where it would act on its various substrates. To gain a better understanding of where MMP-7 is released in polarized epithelium, we have analyzed its pattern of secretion in polarized MDCK cells expressing stably transfected human MMP-7 (MDCK-MMP-7), and HCA-7 and Caco2 human colon cancer cell lines. In all cell lines, latent MMP-7 was secreted to both cellular compartments, but was 1.5- to 3-fold more abundant in the basolateral compartment as compared to the apical. However, studies in the MDCK system demonstrated that MMP-7 activity was 2-fold greater in the apical compartment of MDCK-MMP-7{sup HIGH}-polarized monolayers, which suggests the apical co-release of an MMP-7 activator. In functional assays, MMP-7 over-expression increased cell saturation density as a result of increased cell proliferation with no effect on apoptosis. Apical MMP-7 activity was shown to be responsible for the proliferative effect, which occurred, as demonstrated by media transfer experiments, through cleavage of an apical substrate and not through the generation of a soluble factor. Taken together, our findings demonstrate the importance of MMP-7 secretion in relation to its mechanism of action when expressed in a polarized epithelium.

  18. Search for correlations between the optical and radio polarization of active galactic nuclei - I. VLBA polarization data at 15 + 22 + 43 GHz

    NASA Astrophysics Data System (ADS)

    Algaba, J. C.; Gabuzda, D. C.; Smith, P. S.

    2011-02-01

    Although the continua of radio-loud active galactic nuclei (AGNs) are typically dominated by synchrotron radiation over virtually the entire spectrum, it is not clear whether the radio and higher frequency emission originates in the same or different parts of the jet. In some inhomogeneous synchrotron source models, the radio and ultraviolet-optical-infrared emission may be co-spatial, depending on the model parameters considered. Indeed, several different radio-optical correlations based on polarization data have been found recently, suggesting that the optical and radio polarization may be closely related in some AGNs, and that the corresponding emission regions may be co-spatial. Our joint analysis of optical and 15 + 22 + 43 GHz Very Long Baseline Array (VLBA) polarization data for a sample of about 40 AGNs shows that, after correction for the inferred VLBA core Faraday rotations, about 50-55 per cent of BL Lac objects and high-polarization quasars, and about 65 per cent of high-polarization quasars (LPQs) have aligned VLBA-core and optical polarization angles to within 20°; a considerable number of objects also show no obvious relationship between their VLBA-core and optical polarization angles. This may indicate that only some AGNs have co-spatial regions of optical and radio emission in their jets. However, another possibility is that some of the 15-43 GHz VLBA cores have Faraday rotations of the order of several tens of thousand of rad m-2, which were not properly fitted using our three-frequency data due to n×π ambiguities in the observed polarization angles, leading to inaccurate subtraction of the effects of the core Faraday rotation and so incorrect ‘zero-wavelength' radio polarization angles.

  19. Radiative recombination from dark excitons in nanocrystals: Activation mechanisms and polarization properties

    NASA Astrophysics Data System (ADS)

    Rodina, Anna V.; Efros, Alexander L.

    2016-04-01

    We analyze theoretically physical mechanisms responsible for the radiative recombination of the ground optically passive ("dark") exciton (DE), which dominates in photoluminescence (PL) of colloidal nanocrystals (NCs) at low temperatures. The DE becomes optically active due to its mixing with the bright excitons caused by an external magnetic field, dangling-bond spins or by acoustic and optical phonons. These activation mechanisms mix the DE with different bright excitons and, consequently, lead to different PL polarization properties, because they are determined by dipole orientations of the bright excitons, which the DE is coupled with. We show that the PL polarization properties of prolate and oblate shape NCs are different due to different activation mechanisms responsible for the DE recombination.

  20. Opposite-polarity motors activate one another to trigger cargo transport in live cells.

    PubMed

    Ally, Shabeen; Larson, Adam G; Barlan, Kari; Rice, Sarah E; Gelfand, Vladimir I

    2009-12-28

    Intracellular transport is typically bidirectional, consisting of a series of back and forth movements. Kinesin-1 and cytoplasmic dynein require each other for bidirectional transport of intracellular cargo along microtubules; i.e., inhibition or depletion of kinesin-1 abolishes dynein-driven cargo transport and vice versa. Using Drosophila melanogaster S2 cells, we demonstrate that replacement of endogenous kinesin-1 or dynein with an unrelated, peroxisome-targeted motor of the same directionality activates peroxisome transport in the opposite direction. However, motility-deficient versions of motors, which retain the ability to bind microtubules and hydrolyze adenosine triphosphate, do not activate peroxisome motility. Thus, any pair of opposite-polarity motors, provided they move along microtubules, can activate one another. These results demonstrate that mechanical interactions between opposite-polarity motors are necessary and sufficient for bidirectional organelle transport in live cells. PMID:20038680

  1. Opposite-polarity motors activate one another to trigger cargo transport in live cells

    PubMed Central

    Ally, Shabeen; Larson, Adam G.; Barlan, Kari; Rice, Sarah E.

    2009-01-01

    Intracellular transport is typically bidirectional, consisting of a series of back and forth movements. Kinesin-1 and cytoplasmic dynein require each other for bidirectional transport of intracellular cargo along microtubules; i.e., inhibition or depletion of kinesin-1 abolishes dynein-driven cargo transport and vice versa. Using Drosophila melanogaster S2 cells, we demonstrate that replacement of endogenous kinesin-1 or dynein with an unrelated, peroxisome-targeted motor of the same directionality activates peroxisome transport in the opposite direction. However, motility-deficient versions of motors, which retain the ability to bind microtubules and hydrolyze adenosine triphosphate, do not activate peroxisome motility. Thus, any pair of opposite-polarity motors, provided they move along microtubules, can activate one another. These results demonstrate that mechanical interactions between opposite-polarity motors are necessary and sufficient for bidirectional organelle transport in live cells. PMID:20038680

  2. Role of interfacial friction for flow instabilities in a thin polar-ordered active fluid layer.

    PubMed

    Sarkar, Niladri; Basu, Abhik

    2015-11-01

    We construct a generic coarse-grained dynamics of a thin inflexible planar layer of polar-ordered suspension of active particles that is frictionally coupled to an embedding isotropic passive fluid medium with a friction coefficient Γ. Being controlled by Γ, our model provides a unified framework to describe the long-wavelength behavior of a variety of thin polar-ordered systems, ranging from wet to dry active matter and free-standing active films. Investigations of the linear instabilities around a chosen orientationally ordered uniform reference state reveal generic moving and static instabilities in the system that can depend sensitively on Γ. Based on our results, we discuss estimation of bounds on Γ in experimentally accessible systems. PMID:26651694

  3. Role of interfacial friction for flow instabilities in a thin polar-ordered active fluid layer

    NASA Astrophysics Data System (ADS)

    Sarkar, Niladri; Basu, Abhik

    2015-11-01

    We construct a generic coarse-grained dynamics of a thin inflexible planar layer of polar-ordered suspension of active particles that is frictionally coupled to an embedding isotropic passive fluid medium with a friction coefficient Γ . Being controlled by Γ , our model provides a unified framework to describe the long-wavelength behavior of a variety of thin polar-ordered systems, ranging from wet to dry active matter and free-standing active films. Investigations of the linear instabilities around a chosen orientationally ordered uniform reference state reveal generic moving and static instabilities in the system that can depend sensitively on Γ . Based on our results, we discuss estimation of bounds on Γ in experimentally accessible systems.

  4. Seasonal, interannual, and long-term variabilities in biomass burning activity over South Asia.

    PubMed

    Bhardwaj, P; Naja, M; Kumar, R; Chandola, H C

    2016-03-01

    The seasonal, interannual, and long-term variations in biomass burning activity and related emissions are not well studied over South Asia. In this regard, active fire location retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS), the retrievals of aerosol optical depth (AOD) from MODIS Terra, and tropospheric column NO2 from Ozone Monitoring Instrument (OMI) are used to understand the effects of biomass burning on the tropospheric pollution loadings over South Asia during 2003-2013. Biomass burning emission estimates from Global Fire Emission Database (GFED) and Global Fire Assimilation System (GFAS) are also used to quantify uncertainties and regional discrepancies in the emissions of carbon monoxide (CO), nitrogen oxide (NOx), and black carbon (BC) due to biomass burning in South Asia. In the Asian continent, the frequency of fire activity is highest over Southeast Asia, followed by South Asia and East Asia. The biomass burning activity in South Asia shows a distinct seasonal cycle that peaks during February-May with some differences among four (north, central, northeast, and south) regions in India. The annual biomass burning activity in north, central, and south regions shows an increasing tendency, particularly after 2008, while a decrease is seen in northeast region during 2003-2013. The increase in fire counts over the north and central regions contributes 24 % of the net enhancement in fire counts over South Asia. MODIS AOD and OMI tropospheric column NO2 retrievals are classified into high and low fire activity periods and show that biomass burning leads to significant enhancement in tropospheric pollution loading over both the cropland and forest regions. The enhancement is much higher (110-176 %) over the forest region compared to the cropland (34-62 %) region. Further efforts are required to understand the implications of biomass burning on the regional air quality and climate of South Asia. PMID:26503008

  5. Comparative analysis of fecal microbiota and intestinal microbial metabolic activity in captive polar bears.

    PubMed

    Schwab, Clarissa; Gänzle, Michael

    2011-03-01

    The composition of the intestinal microbiota depends on gut physiology and diet. Ursidae possess a simple gastrointestinal system composed of a stomach, small intestine, and indistinct hindgut. This study determined the composition and stability of fecal microbiota of 3 captive polar bears by group-specific quantitative PCR and PCR-DGGE (denaturing gradient gel electrophoresis) using the 16S rRNA gene as target. Intestinal metabolic activity was determined by analysis of short-chain fatty acids in feces. For comparison, other Carnivora and mammals were included in this study. Total bacterial abundance was approximately log 8.5 DNA gene copies·(g feces)-1 in all 3 polar bears. Fecal polar bear microbiota was dominated by the facultative anaerobes Enterobacteriaceae and enterococci, and the Clostridium cluster I. The detection of the Clostridium perfringens α-toxin gene verified the presence of C. perfringens. Composition of the fecal bacterial population was stable on a genus level; according to results obtained by PCR-DGGE, dominant bacterial species fluctuated. The total short-chain fatty acid content of Carnivora and other mammals analysed was comparable; lactate was detected in feces of all carnivora but present only in trace amounts in other mammals. In comparison, the fecal microbiota and metabolic activity of captive polar bears mostly resembled the closely related grizzly and black bears. PMID:21358758

  6. Observations of the northern seasonal polar cap on Mars: I. Spring sublimation activity and processes

    NASA Astrophysics Data System (ADS)

    Hansen, C. J.; Byrne, S.; Portyankina, G.; Bourke, M.; Dundas, C.; McEwen, A.; Mellon, M.; Pommerol, A.; Thomas, N.

    2013-08-01

    Spring sublimation of the seasonal CO2 northern polar cap is a dynamic process in the current Mars climate. Phenomena include dark fans of dune material propelled out onto the seasonal ice layer, polygonal cracks in the seasonal ice, sand flow down slipfaces, and outbreaks of gas and sand around the dune margins. These phenomena are concentrated on the north polar erg that encircles the northern residual polar cap. The Mars Reconnaissance Orbiter has been in orbit for three Mars years, allowing us to observe three northern spring seasons. Activity is consistent with and well described by the Kieffer model of basal sublimation of the seasonal layer of ice applied originally in the southern hemisphere. Three typical weak spots have been identified on the dunes for escape of gas sublimed from the bottom of the seasonal ice layer: the crest of the dune, the interface of the dune with the interdune substrate, and through polygonal cracks in the ice. Pressurized gas flows through these vents and carries out material entrained from the dune. Furrows in the dunes channel gas to outbreak points and may be the northern equivalent of southern radially-organized channels ("araneiform" terrain), albeit not permanent. Properties of the seasonal CO2 ice layer are derived from timing of seasonal events such as when final sublimation occurs. Modification of dune morphology shows that landscape evolution is occurring on Mars today, driven by seasonal activity associated with sublimation of the seasonal CO2 polar cap.

  7. Observations of the northern seasonal polar cap on Mars: I. Spring sublimation activity and processes

    USGS Publications Warehouse

    Hansen, C.J.; Byrne, S.; Portyankina, G.; Bourke, M.; Dundas, C.; McEwen, A.; Mellon, M.; Pommerol, A.; Thomas, N.

    2013-01-01

    Spring sublimation of the seasonal CO2 northern polar cap is a dynamic process in the current Mars climate. Phenomena include dark fans of dune material propelled out onto the seasonal ice layer, polygonal cracks in the seasonal ice, sand flow down slipfaces, and outbreaks of gas and sand around the dune margins. These phenomena are concentrated on the north polar erg that encircles the northern residual polar cap. The Mars Reconnaissance Orbiter has been in orbit for three Mars years, allowing us to observe three northern spring seasons. Activity is consistent with and well described by the Kieffer model of basal sublimation of the seasonal layer of ice applied originally in the southern hemisphere. Three typical weak spots have been identified on the dunes for escape of gas sublimed from the bottom of the seasonal ice layer: the crest of the dune, the interface of the dune with the interdune substrate, and through polygonal cracks in the ice. Pressurized gas flows through these vents and carries out material entrained from the dune. Furrows in the dunes channel gas to outbreak points and may be the northern equivalent of southern radially-organized channels (“araneiform” terrain), albeit not permanent. Properties of the seasonal CO2 ice layer are derived from timing of seasonal events such as when final sublimation occurs. Modification of dune morphology shows that landscape evolution is occurring on Mars today, driven by seasonal activity associated with sublimation of the seasonal CO2 polar cap.

  8. Polar bear hepatic cytochrome P450: Immunochemical quantitation, EROD/PROD activity and organochlorines

    SciTech Connect

    Letcher, R.J.; Norstrom, R.J. |

    1994-12-31

    Polar bears (Ursus maritimus) are an ubiquitous mammal atop the arctic marine food chain and bioaccumulate lipophilic environmental contaminants. Antibodies prepared against purified rat liver cytochrome P450-1 Al, -1 A2, -2Bl and -3Al enzymes have been found to cross-react with structurally-related orthologues present in the hepatic microsomes of wild polar bears, immunochemically determined levels of P450-1 A and -2B proteins in polar bear liver relative to liver of untreated rats suggested enzyme induction, probably as a result of exposure to xenobiotic contaminants. Optical density quantitation of the most immunochemically responsive isozymes P450-I Al, -IA2 and -2Bi to polygonal rabbit anti-rat P450-IA/IA2 sera and -2BI antibodies in hepatic microsomes of 13 adult male polar bars from the Resolute Bay area of the Canadian Arctic is presented. Correlations with EROD and PROD catalytic activities and levels of organochlorines, such as polychlorinated biphenyls (PCBs), 1,1-dichloro-2,2-bis(4-chlorophenyl)ethene (p,p-DDE) and their methyl sulfone (MeSO2-) metabolites are made to determine if compound-specific enzyme induction linkages exist. Inter-species immunochemical quantitation of isozymic P450 cytochromes can serve as an indicator of exposure to biologically active contaminant.

  9. Is the South Pacific helium-3 plume dynamically active?

    NASA Astrophysics Data System (ADS)

    Stommel, Henry

    1982-11-01

    It is suggested that the hydrothermal vents of the South Pacific Rise produce a beta-governed circulation at mid-depth, and that perhaps the associated plume of excess 3He (Lupton and Craig [1]) points westward because of the dynamics of this circulation rather than as a passive tracer.

  10. Student Activism and Student Exclusions in South Africa

    ERIC Educational Resources Information Center

    Koen, Charlton; Cele, Mlungisi; Libhaber, Arial

    2006-01-01

    On average, about 25 percent of students leave higher education (HE) institutions annually in South Africa because they are excluded on academic and financial grounds. To resist such putouts, student boycotts and protests are common despite the fact that student organizations were incorporated into decision-making processes at HE institutions…

  11. The antibacterial activity, antioxidant activity and selectivity index of leaf extracts of thirteen South African tree species used in ethnoveterinary medicine to treat helminth infections

    PubMed Central

    2014-01-01

    Background Diseases caused by bacteria remain a major challenge globally and particularly in sub-Saharan Africa. The plants used in this study have been used in South Africa to treat helminth infections in livestock and humans. In a previous study we found a correlation between antifungal and anthelmintic activity in some cases. In this study we examined other potential uses of these thirteen plant species by determining the antibacterial and antioxidant activity of the leaf acetone extracts. The antibacterial activity was determined by using a serial microdilution method against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Enterococcus faecalis. Bioautography was used to determine the number of antibacterial compounds. The antioxidant activity was determined using the ABTS and DPPH methods. Results Maesa lanceolata and Leucosidea sericea with an MIC of 0.02 mg/ml had excellent antibacterial activity against Enterococcus faecalis and Pseudomonas aeruginosa. There was a poor correlation between antioxidant activity and antibacterial activity with R2 = 0.143. This is because antibacterial activity is mainly related to non-polar compounds and antioxidant activity to polar compounds. Maesa lanceolata extracts had a low cytotoxicity with a selectivity index of 5.2, 2.6, 2.6 and 1.3 for P. aeruginosa, E. faecalis, E. coli and S. aureus respectively. Strychnos mitis extracts had a therapeutic index of 1.1 for E. coli. Conclusions This study shows that plant extracts of some species used in ethnoveterinary medicine as anthelmintic may also have excellent antibacterial activity. PMID:24589020

  12. Active self-polarization of contractile cells in asymmetrically shaped domains.

    PubMed

    Zemel, A; Safran, S A

    2007-08-01

    Mechanical forces generated by contractile cells allow the cells to sense their environment and to interact with other cells. By locally pulling on their environment, cells can sense and respond to mechanical features such as the local stress (or strain), the shape of a cellular domain, and the surrounding rigidity; at the same time, they also modify the mechanical state of the system. This creates a mechanical feedback loop that can result in self-polarization of cells. In this paper, we present a quantitative mechanical model that predicts the self-polarization of cells in spheroidally shaped domains, comprising contractile cells and an elastic matrix, that are embedded in a three-dimensional, cell-free gel. The theory is based on a generalization of the known results for passive inclusions in solids to include the effects of cell activity. We use the active cellular susceptibility tensor presented by Zemel [Phys. Rev. Lett. 97, 128103 (2006)] to calculate the polarization response and hence the elastic stress field developed by the cells in the cellular domain. The cell polarization is analyzed as a function of the shape and the elastic moduli of the cellular domain compared with the cell-free surrounding material. Consistent with experiment, our theory predicts the development of a stronger contractile force for cells in a gel that is surrounded by a large, cell-free material whose elastic modulus is stiffer than that of the gel that contains the cells. This provides a quantitative explanation of the differences in the development of cellular forces as observed in free and fixed gels. In the case of an asymmetrically shaped (spheroidal) domain of cells, we show that the anisotropic elastic field within the domain leads to a spontaneous self-polarization of the cells along the long axis of the domain. PMID:17930063

  13. Comparison Between the Integrated Ion Outflow Fluxes from the North and South Hemispheres Under Sustained Geomagnetically Active Conditions

    NASA Astrophysics Data System (ADS)

    Barakat, A. R.; Schunk, R. W.; Eccles, J. V.

    2015-12-01

    The Generalized Polar Wind (GPW) model is used to simulate the polar ionosphere during the September/October 2002 storm. The simulation period is near equinox when the north and south hemispheres are similarly exposed to solar radiation. We present a model simulation of the eight day period 2002 September 27 (DOY 270) through October 4 (DOY 277). The first three days have relatively quiet magnetic activity as indicated by low Kp values. The fourth day (270) is moderately active, and over the last four days (1-4 October) a strong magnetic storm takes place where Kp reaches values greater than 7 and Dst reaches values below -170. The GPW model was utilized to simulate the behavior of the plasma outflow from both hemispheres over the eight-day period. This storm differs from idealized storm that was the subject of a number of previous studies by Schunk and coauthors in the following ways. First, the interplanetary magnetic field changed in a complex manner in contrast to the previous studies where the IMF remained in the negative z direction. Second, Kp variation is more complex than the previous investigations. Third, the simulation period of eight days is much longer than the previous simulations (less than 18 hours). Finally, both hemispheres are considered, in contrast to previous simulations that investigated the northern hemisphere only. This investigation focuses on the variation of the integrated flux (from the poles to 45 degrees of latitude). We discuss how the integrated flux depends on the ion species (O+ vs. H+) and on the hemisphere (north vs. south). We also investigated the integrated flux dependence on the physical conditions, e.g., Kp, Dst universal time, etc. This statistical approach helped extract important simple conclusions from the complex behavior of the ion outflow during real a storm.

  14. Tech Prep. South Dakota Career Activities for the Classroom, 4th Edition, 1998-1999.

    ERIC Educational Resources Information Center

    Kucker, Marsha, Comp.

    This document presents a sampling of projects and activities that have been implemented in Tech Prep training in South Dakota, or will be implemented during the upcoming school year. The projects and activities are categorized into 12 areas: career clusters; career units and activities; curriculum materials; employability skills; entrepreneurship;…

  15. Metal-VO2 hybrid grating structure for a terahertz active switchable linear polarizer

    NASA Astrophysics Data System (ADS)

    Shin, Jun-Hwan; Moon, Kiwon; Lee, Eui Su; Lee, Il-Min; Park, Kyung Hyun

    2015-08-01

    An active terahertz (THz) wave hybrid grating structure of Au/Ti metallic grating on VO2/Al2O3 (0001) was fabricated and evaluated. In our structure, it is shown that the metallic gratings on the VO2 layer strengthen the metallic characteristics to enhance the contrast of the metallic and dielectric phases of a VO2-based device. Especially, the metal grating-induced optical conductivity of the device is greatly enhanced, three times more than that of a metallic phase of bare VO2 films in the 0.1-2.0 THz spectral range. As an illustrative example, we fabricated an actively on/off switchable THz linear polarizer. The fabricated device has shown commercially comparable values in degree of polarization (DOP) and extinction ratio (ER). A high value of 0.89 in the modulation depth (MD) for the transmission field amplitude, superior to other THz wave modulators, is achieved. The experimental results show that the fabricated device can be highly useful in many applications, including active THz linear polarizers, THz wave modulators and variable THz attenuators.

  16. Metal-VO2 hybrid grating structure for a terahertz active switchable linear polarizer.

    PubMed

    Shin, Jun-Hwan; Moon, Kiwon; Lee, Eui Su; Lee, Il-Min; Park, Kyung Hyun

    2015-08-01

    An active terahertz (THz) wave hybrid grating structure of Au/Ti metallic grating on VO2/Al2O3 (0001) was fabricated and evaluated. In our structure, it is shown that the metallic gratings on the VO2 layer strengthen the metallic characteristics to enhance the contrast of the metallic and dielectric phases of a VO2-based device. Especially, the metal grating-induced optical conductivity of the device is greatly enhanced, three times more than that of a metallic phase of bare VO2 films in the 0.1-2.0 THz spectral range. As an illustrative example, we fabricated an actively on/off switchable THz linear polarizer. The fabricated device has shown commercially comparable values in degree of polarization (DOP) and extinction ratio (ER). A high value of 0.89 in the modulation depth (MD) for the transmission field amplitude, superior to other THz wave modulators, is achieved. The experimental results show that the fabricated device can be highly useful in many applications, including active THz linear polarizers, THz wave modulators and variable THz attenuators. PMID:26183858

  17. Passive bookshelf faulting driven by gravitational spreading as the cause of the tiger-stripe-fracture formation and development in the South Polar Terrain of Enceladus

    NASA Astrophysics Data System (ADS)

    Yin, A.; Pappalardo, R. T.

    2013-12-01

    Detailed photogeologic mapping of the tiger-stripe fractures in the South Polar Terrain (SPT) of Enceladus indicates that these structures are left-slip faults and terminate at hook-shaped fold-thrust zones and/or Y-shaped horsetail splay-fault zones. The semi-square-shaped tectonic domain that hosts the tiger-stripe faults is bounded by right-slip and left-slip faults on the north and south edges and fold-thrust and extensional zones on the western and eastern edges. We explain the above observations by a passive bookshelf-faulting model in which individual tiger-stripe faults are bounded by deformable wall rocks accommodating distributed deformation. Based on topographic data, we suggest that gravitational spreading had caused the SPT to spread unevenly from west to east. This process was accommodated by right-slip and left-slip faulting on the north and south sides and thrusting and extension along the eastern and southern margins of the tiger-stripe tectonic domain. The uneven spreading, expressed by a gradual northward increase in the number of extensional faults and thrusts/folds along the western and eastern margins, was accommodated by distributed right-slip simple shear across the whole tiger-stripe tectonic domain. This mode of deformation in turn resulted in the development of a passive bookshelf-fault system characterized by left-slip faulting on individual tiger-stripe fractures.

  18. Spin-wave activation by spin-polarized current pulse in magnetic nanopillars

    NASA Astrophysics Data System (ADS)

    Montoncello, Federico; Giovannini, Loris; Nizzoli, Fabrizio; Zivieri, Roberto; Consolo, Giancarlo; Gubbiotti, Gianluca

    2010-08-01

    We demonstrate the role of spin-polarized current pulse in activating only a subset of spin-wave normal modes in laterally confined magnetic systems. In order to derive selection rules based on geometrical considerations, the study was carried out by comparing the results of two different micromagnetic frameworks (a classical finite-difference time-domain scheme and the dynamical matrix method) and considering nanopillar devices of elliptical and circular cross-sections in different magnetic ground states (onion, S, and vortex states). The analogies and the differences existing between the mode activation process driven by spin-torque and that obtained by a magnetic field pulse are also addressed.

  19. Environmental contaminants activate human and polar bear (Ursus maritimus) pregnane X receptors (PXR, NR1I2) differently

    SciTech Connect

    Lille-Langøy, Roger; Goldstone, Jared V.; Rusten, Marte; Milnes, Matthew R.; Male, Rune; Stegeman, John J.; Blumberg, Bruce; Goksøyr, Anders

    2015-04-01

    Background: Many persistent organic pollutants (POPs) accumulate readily in polar bears because of their position as apex predators in Arctic food webs. The pregnane X receptor (PXR, formally NR1I2, here proposed to be named promiscuous xenobiotic receptor) is a xenobiotic sensor that is directly involved in metabolizing pathways of a wide range of environmental contaminants. Objectives: In the present study, we comparably assess the ability of 51 selected pharmaceuticals, pesticides and emerging contaminants to activate PXRs from polar bears and humans using an in vitro luciferase reporter gene assay. Results: We found that polar bear PXR is activated by a wide range of our test compounds (68%) but has a slightly more narrow ligand specificity than human PXR that was activated by 86% of the 51 test compounds. The majority of the agonists identified (70%) produces a stronger induction of the reporter gene via human PXR than via polar bear PXR, however with some notable and environmentally relevant exceptions. Conclusions: Due to the observed differences in activation of polar bear and human PXRs, exposure of each species to environmental agents is likely to induce biotransformation differently in the two species. Bioinformatics analyses and structural modeling studies suggest that amino acids that are not part of the ligand-binding domain and do not interact with the ligand can modulate receptor activation. - Highlights: • Comparative study of ligand activation of human and polar bear PXRs. • Polar bear PXR is a promiscuous ligand-activated nuclear receptor but less so than human PXR. • Environmental contaminants activate human and polar bear PXRs differently. • Expression and ligand promiscuity indicate that PXR is a xenosensor in polar bears.

  20. Macrophage activation and polarization modify P2X7 receptor secretome influencing the inflammatory process

    PubMed Central

    de Torre-Minguela, Carlos; Barberà-Cremades, Maria; Gómez, Ana I.; Martín-Sánchez, Fátima; Pelegrín, Pablo

    2016-01-01

    The activation of P2X7 receptor (P2X7R) on M1 polarized macrophages induces the assembly of the NLRP3 inflammasome leading to the release of pro-inflammatory cytokines and the establishment of the inflammatory response. However, P2X7R signaling to the NLRP3 inflammasome is uncoupled on M2 macrophages without changes on receptor activation. In this study, we analyzed P2X7R secretome in wild-type and P2X7R-deficient macrophages polarized either to M1 or M2 and proved that proteins released after P2X7R stimulation goes beyond caspase-1 secretome. The characterization of P2X7R-secretome reveals a new function of this receptor through a fine-tuning of protein release. We found that P2X7R stimulation in macrophages is able to release potent anti-inflammatory proteins, such as Annexin A1, independently of their polarization state suggesting for first time a potential role for P2X7R during resolution of the inflammation and not linked to the release of pro-inflammatory cytokines. These results are of prime importance for the development of therapeutics targeting P2X7R. PMID:26935289

  1. Influence of Polarity and Activation Energy in Microwave–Assisted Organic Synthesis (MAOS)

    PubMed Central

    Rodríguez, Antonio M; Prieto, Pilar; de la Hoz, Antonio; Díaz-Ortiz, Ángel; Martín, D Raúl; García, José I

    2015-01-01

    The aim of this work was to determine the parameters that have decisive roles in microwave-assisted reactions and to develop a model, using computational chemistry, to predict a priori the type of reactions that can be improved under microwaves. For this purpose, a computational study was carried out on a variety of reactions, which have been reported to be improved under microwave irradiation. This comprises six types of reactions. The outcomes obtained in this study indicate that the most influential parameters are activation energy, enthalpy, and the polarity of all the species that participate. In addition to this, in most cases, slower reacting systems observe a much greater improvement under microwave irradiation. Furthermore, for these reactions, the presence of a polar component in the reaction (solvent, reagent, susceptor, etc.) is necessary for strong coupling with the electromagnetic radiation. We also quantified that an activation energy of 20–30 kcal mol−1 and a polarity (μ) between 7–20 D of the species involved in the process is required to obtain significant improvements under microwave irradiation. PMID:26246993

  2. PLEKHG3 enhances polarized cell migration by activating actin filaments at the cell front.

    PubMed

    Nguyen, Trang Thi Thu; Park, Wei Sun; Park, Byung Ouk; Kim, Cha Yeon; Oh, Yohan; Kim, Jin Man; Choi, Hana; Kyung, Taeyoon; Kim, Cheol-Hee; Lee, Gabsang; Hahn, Klaus M; Meyer, Tobias; Heo, Won Do

    2016-09-01

    Cells migrate by directing Ras-related C3 botulinum toxin substrate 1 (Rac1) and cell division control protein 42 (Cdc42) activities and by polymerizing actin toward the leading edge of the cell. Previous studies have proposed that this polarization process requires a local positive feedback in the leading edge involving Rac small GTPase and actin polymerization with PI3K likely playing a coordinating role. Here, we show that the pleckstrin homology and RhoGEF domain containing G3 (PLEKHG3) is a PI3K-regulated Rho guanine nucleotide exchange factor (RhoGEF) for Rac1 and Cdc42 that selectively binds to newly polymerized actin at the leading edge of migrating fibroblasts. Optogenetic inactivation of PLEKHG3 showed that PLEKHG3 is indispensable both for inducing and for maintaining cell polarity. By selectively binding to newly polymerized actin, PLEKHG3 promotes local Rac1/Cdc42 activation to induce more local actin polymerization, which in turn promotes the recruitment of more PLEKHG3 to induce and maintain cell front. Thus, autocatalytic reinforcement of PLEKHG3 localization to the leading edge of the cell provides a molecular basis for the proposed positive feedback loop that is required for cell polarization and directed migration. PMID:27555588

  3. AgI microplate monocrystals with polar {0001} facets: spontaneous photocarrier separation and enhanced photocatalytic activity.

    PubMed

    Kuang, Qin; Zheng, Xiaoli; Yang, Shihe

    2014-02-24

    Elucidating the facet-dependent photocatalytic activity of semiconductor photocatalysts is important in improving the overall efficiency of photocatalysis. Furthermore, combining facet control with selective deposition of oxidation and/or reduction cocatalysts on specific faces of semiconductor photocatalysts is potentially an effective strategy to synergistically optimize the functionality of photocatalysts. In the present study, high-purity wurtzite-type β-AgI platelet microcrystals with polar {0001} facets were prepared by a facile polyvinylpyrrolidone-assisted precipitation reaction. The polar-faceted AgI microplates were used as archetypes to demonstrate preferential diametric migration (i.e., effective separation) of photogenerated electrons and holes along the c axis. Such vectorial electron-hole separation stems from the asymmetric surface structures, which give rise to distinct photoexcited reaction behaviors on the ±(0001) polar facets of wurtzite-type semiconductors. Furthermore, on selective deposition of Ag and MnOx (1.5activity of the AgI microplates in degrading organic pollutants was dramatically enhanced thanks to the broad light-absorption range, strong dye-adsorption ability, and effective spatial separation of photocarriers. PMID:24449437

  4. Effects of interplanetary magnetic field azimuth on auroral zone and polar cap magnetic activity

    NASA Technical Reports Server (NTRS)

    Burch, J. L.

    1972-01-01

    During relatively quiet times in the period 1964-1968, AE is found to be greater when the interplanetary magnetic field (b sub IMF) is directed toward the sun in Jan., Feb., and Apr., and when B sub IMF is directed away from the sun in Oct. to Dec. Using Murmansk hourly H values and the AE components, AU and AL, it is shown that this sector dependence is present only in the negative H deviations. This observation supports the idea that negative bay magnitudes are determined chiefly by particle-produced ionization, while positive bay magnitudes are rather insensitive to increases in particle precipitation. The ratio of DP2-type magnetic activity in the southern polar cap to that in the northern polar cap is found to be greater by a factor of about 1.75 for B sub IMF toward the sun.

  5. Summer declines in activity and body temperature offer polar bears limited energy savings

    USGS Publications Warehouse

    Whiteman, J.P.; Harlow, H.J.; Durner, George M.; Anderson-Sprecher, R.; Albeke, Shannon E.; Regehr, Eric V.; Amstrup, Steven C.; Ben-David, M.

    2015-01-01

    Polar bears (Ursus maritimus) summer on the sea ice or, where it melts, on shore. Although the physiology of “ice” bears in summer is unknown, “shore” bears purportedly minimize energy losses by entering a hibernation-like state when deprived of food. Such a strategy could partially compensate for the loss of on-ice foraging opportunities caused by climate change. However, here we report gradual, moderate declines in activity and body temperature of both shore and ice bears in summer, resembling energy expenditures typical of fasting, nonhibernating mammals. Also, we found that to avoid unsustainable heat loss while swimming, bears employed unusual heterothermy of the body core. Thus, although well adapted to seasonal ice melt, polar bears appear susceptible to deleterious declines in body condition during the lengthening period of summer food deprivation.

  6. Animal physiology. Summer declines in activity and body temperature offer polar bears limited energy savings.

    PubMed

    Whiteman, J P; Harlow, H J; Durner, G M; Anderson-Sprecher, R; Albeke, S E; Regehr, E V; Amstrup, S C; Ben-David, M

    2015-07-17

    Polar bears (Ursus maritimus) summer on the sea ice or, where it melts, on shore. Although the physiology of "ice" bears in summer is unknown, "shore" bears purportedly minimize energy losses by entering a hibernation-like state when deprived of food. Such a strategy could partially compensate for the loss of on-ice foraging opportunities caused by climate change. However, here we report gradual, moderate declines in activity and body temperature of both shore and ice bears in summer, resembling energy expenditures typical of fasting, nonhibernating mammals. Also, we found that to avoid unsustainable heat loss while swimming, bears employed unusual heterothermy of the body core. Thus, although well adapted to seasonal ice melt, polar bears appear susceptible to deleterious declines in body condition during the lengthening period of summer food deprivation. PMID:26185248

  7. Structural elucidation of olive pomace fed sea bass (Dicentrarchus labrax) polar lipids with cardioprotective activities.

    PubMed

    Nasopoulou, Constantina; Smith, Terry; Detopoulou, Maria; Tsikrika, Constantina; Papaharisis, Leonidas; Barkas, Dimitris; Zabetakis, Ioannis

    2014-02-15

    The purpose of this study was to structurally characterise the polar lipids of sea bass (Dicentrarchus labrax), fed with an experimental diet containing olive pomace (OP), that exhibit cardioprotective activities. OP has been added to conventional fish oil (FO) feed at 4% and this was the OP diet, having been supplemented as finishing diet to fish. Sea bass was aquacultured using either FO or OP diet. At the end of the dietary experiment, lipids in both samples of fish muscle were quantified and HPLC fractionated. The in vitro cardioprotective properties of the polar lipid fractions, using washed rabbit's platelets, have been assessed and the two most biologically active fractions were further analysed by mass spectrometry. The gas-chromatrograpy-mass spectrometric data shows that these two fractions contain low levels of myristic (14:0), oleic (18:1 cis ω-9) and linoleic acids (18:2 ω-6), but high levels of palmitic (16:0) and stearic acids (18:0) as well as eicosadienoic acid (20:2 ω-6). The first fraction (MS1) also contained significant levels of arachidonic acid (20:4 ω-6) and the omega-3 fatty acids: eicosapentaenoic acid (22:5) and docosahexaenoic acid (22:6). Electrospray-mass spectrometry elucidated that the lipid composition of the two fractions contained various diacyl-glycerophospholipids species, where the majority of them have either 18:0 or 18:1 fatty acids in the sn-1 position and either 22:6 or 20:2 fatty acids in the sn-2 position for MS1 and MS2, respectively. Our research focuses on the structure/function relationship of fish muscle polar lipids and cardiovascular diseases and structural data are given for polar lipid HPLC fractions with strong cardioprotective properties. PMID:24128590

  8. A New Polar Magnetic Index of Geomagnetic Activity and its Application to Monitoring Ionospheric Parameters

    NASA Technical Reports Server (NTRS)

    Lyatsky, Wladislaw; Khazanov, George V.

    2008-01-01

    For improving the reliability of Space Weather prediction, we developed a new, Polar Magnetic (PM) index of geomagnetic activity, which shows high correlation with both upstream solar wind data and related events in the magnetosphere and ionosphere. Similarly to the existing polar cap PC index, the new, PM index was computed from data from two near-pole geomagnetic observatories; however, the method for computing the PM index is different. The high correlation of the PM index with both solar wind data and events in Geospace environment makes possible to improve significantly forecasting geomagnetic disturbances and such important parameters as the cross-polar-cap voltage and global Joule heating in high latitude ionosphere, which play an important role in the development of geomagnetic, ionospheric and thermospheric disturbances. We tested the PM index for 10-year period (1995-2004). The correlation between PM index and upstream solar wind data for these years is very high (the average correlation coefficient R approximately equal to 0.86). The PM index also shows the high correlation with the cross-polar-cap voltage and hemispheric Joule heating (the correlation coefficient between the actual and predicted values of these parameters is approximately 0.9), which results in significant increasing the prediction reliability of these parameters. Using the PM index of geomagnetic activity provides a significant increase in the forecasting reliability of geomagnetic disturbances and related events in Geospace environment. The PM index may be also used as an important input parameter in modeling ionospheric, magnetospheric, and thermospheric processes.

  9. Lifestyles and routine activities of South African teenagers at risk of being trafficked for involuntary prostitution.

    PubMed

    Lutya, Thozama Mandisa

    2010-12-01

    The United Nations estimates that 79% of teenage girls trafficked globally every year are forced into involuntary prostitution. About 247 000 South African children work in exploitative conditions; about 40 000 South African female teenagers work as prostitutes. This paper investigates lifestyles and routine activities of teenagers at risk of being trafficked for involuntary prostitution. The key concepts involuntary prostitution, intergenerational sex and exploitative conditions are defined in relation to the lifestyles and routine activities of South African female teenagers. Human trafficking for involuntary prostitution is described, based on a literature review. Lifestyle exposure and routine activities theories help to explain the potential victimisation of these teenagers in human trafficking for involuntary prostitution. Actual lifestyle and routine activities of South African teenagers and risky behaviours (substance abuse, intergenerational sex and child prostitution) are discussed as factors that make teens vulnerable to such trafficking. This paper recommends that human trafficking prevention efforts (awareness programmes and information campaigns) be directed at places frequented by human traffickers and teenagers in the absence of a capable guardian to reduce victimisation, as traffickers analyse the lifestyles and routine activities of their targets. South Africa should also interrogate entrenched practices such as intergenerational sex. PMID:25859767

  10. First evidence of widespread active methane seepage in the Southern Ocean, off the sub-Antarctic island of South Georgia

    NASA Astrophysics Data System (ADS)

    Römer, M.; Torres, M.; Kasten, S.; Kuhn, G.; Graham, A. G. C.; Mau, S.; Little, C. T. S.; Linse, K.; Pape, T.; Geprägs, P.; Fischer, D.; Wintersteller, P.; Marcon, Y.; Rethemeyer, J.; Bohrmann, G.

    2014-10-01

    An extensive submarine cold-seep area was discovered on the northern shelf of South Georgia during R/V Polarstern cruise ANT-XXIX/4 in spring 2013. Hydroacoustic surveys documented the presence of 133 gas bubble emissions, which were restricted to glacially-formed fjords and troughs. Video-based sea floor observations confirmed the sea floor origin of the gas emissions and spatially related microbial mats. Effective methane transport from these emissions into the hydrosphere was proven by relative enrichments of dissolved methane in near-bottom waters. Stable carbon isotopic signatures pointed to a predominant microbial methane formation, presumably based on high organic matter sedimentation in this region. Although known from many continental margins in the world's oceans, this is the first report of an active area of methane seepage in the Southern Ocean. Our finding of substantial methane emission related to a trough and fjord system, a topographical setting that exists commonly in glacially-affected areas, opens up the possibility that methane seepage is a more widespread phenomenon in polar and sub-polar regions than previously thought.

  11. HiRISE Monitoring of Ongoing Activity in the North Polar Region of Mars

    NASA Astrophysics Data System (ADS)

    Herkenhoff, K. E.; Russell, P. S.; Byrne, S.; Banks, M. E.; Hansen, C. J.; HiRISE Team

    2010-12-01

    The High Resolution Imaging Science Experiment (HiRISE) [1] on the Mars Reconnaissance Orbiter (MRO) has observed the north polar region during 3 summer seasons on Mars. Here we summarize analyses of the north polar data, focusing on active and recent processes including evolution of frost streaks, the north polar residual cap (NPRC), frost avalanches, and scarp erosion. Bright and dark streaks have been observed at the periphery of the NPRC by previous Mars orbiters and were the target of several HiRISE observations. Some of these HiRISE images indicate that formation of the streaks involves processes more complex than the emplacement of dark veneers proposed by Rodriguez et al. [2]. Bright and dark streaks are seen to evolve during the northern summer, evidence for active eolian redistribution of frost and perhaps darker (non-volatile) dust or sand. Based on MRO Context imager observations of craters on the NPRC, accumulation rates are estimated to be 4-5 mm/yr within these craters, with lower rates likely on the intracrater NPRC surface [3]. The observed crater population probably accumulated during the last 20 ka or less. It is likely that NPRC resurfacing is episodic rather than continuous, and that annual changes may be detectable at HiRISE image resolutions. Therefore, a campaign of HiRISE observations of four NPRC targets near 87°N latitude (the maximum latitude of the MRO ground track) was initiated during the Martian northern summer of 2008 and continued during the summer of 2010. The images acquired during this campaign, with nearly nadir viewing geometry and similar solar azimuth, are being searched for evidence for current redistribution of NPRC material. Analyses are ongoing; no changes have been detected to date. We also conducted an early- to mid-spring 2010 survey of circumpolar scarps to monitor for falls and avalanches of CO2 frost and dust, of the type discovered on a scarp in northern spring 2008 [4]. The results confirm the restriction of

  12. Effect of habitat and foraging height on bat activity in the coastal plain of South Carolina.

    SciTech Connect

    Menzel, Jennifer, M.; Menzel, Michael A.; Kilgo, John C.; Ford, W. Mark; Edwards, John W.; McCracken, Gary F.

    2005-07-01

    A comparison of bat activity levels in the Coastal Plain of South Carolina among 5 habitat types: forested riparian areas, clearcuts, young pine plantations, mature pine plantations and pine savannas, using time expansion radio-microphones and integrated detectors to simultaneously monitor bat activity at three heights in each habitat type.

  13. Instabilities and boundary effects in a droplet of active polar liquid crystal

    NASA Astrophysics Data System (ADS)

    Whitfield, Carl; Hawkins, Rhoda

    2015-03-01

    Using the active gel theoretical framework, we have performed analytical calculations and numerical simulations of a droplet of active polar liquid crystal at low Reynolds number. This system is a simplified model of a cytoskeletal network that generates internal stresses by converting chemical energy (in the form of ATP) into mechanical work via molecular motors. A physical understanding of these systems can give an insight into the complex and varied dynamics of eukaryotic cell migration and division. We perform a linear stability analysis on the system by separating the behaviour into two limits. One where the internal polarisation is dominated by the shape of the boundary and one where it is deformed by the activity. We find that the two regimes show different instability thresholds for the activity parameter suggesting interesting behaviour both in and between these limits. We also simulate the system numerically and find the resulting steady state of the droplet for a range of parameters between these two limits.

  14. DOCK2 is a Rac activator that regulates motility and polarity during neutrophil chemotaxis.

    PubMed

    Kunisaki, Yuya; Nishikimi, Akihiko; Tanaka, Yoshihiko; Takii, Ryosuke; Noda, Mayuko; Inayoshi, Ayumi; Watanabe, Ken-ichi; Sanematsu, Fumiyuki; Sasazuki, Takehiko; Sasaki, Takehiko; Fukui, Yoshinori

    2006-08-28

    Neutrophils are highly motile leukocytes, and they play important roles in the innate immune response to invading pathogens. Neutrophil chemotaxis requires Rac activation, yet the Rac activators functioning downstream of chemoattractant receptors remain to be determined. We show that DOCK2, which is a mammalian homologue of Caenorhabditis elegans CED-5 and Drosophila melanogaster Myoblast City, regulates motility and polarity during neutrophil chemotaxis. Although DOCK2-deficient neutrophils moved toward the chemoattractant source, they exhibited abnormal migratory behavior with a marked reduction in translocation speed. In DOCK2-deficient neutrophils, chemoattractant-induced activation of both Rac1 and Rac2 were severely impaired, resulting in the loss of polarized accumulation of F-actin and phosphatidylinositol 3,4,5-triphosphate (PIP3) at the leading edge. On the other hand, we found that DOCK2 associates with PIP3 and translocates to the leading edge of chemotaxing neutrophils in a phosphatidylinositol 3-kinase (PI3K)-dependent manner. These results indicate that during neutrophil chemotaxis DOCK2 regulates leading edge formation through PIP3-dependent membrane translocation and Rac activation. PMID:16943182

  15. The Subarcsecond Mid-infrared View of Local Active Galactic Nuclei. III. Polar Dust Emission

    NASA Astrophysics Data System (ADS)

    Asmus, D.; Hönig, S. F.; Gandhi, P.

    2016-05-01

    Recent mid-infrared (MIR) interferometric observations have shown that in a few active galactic nuclei (AGNs) the bulk of the infrared emission originates from the polar region above the putative torus, where only a little dust should be present. Here, we investigate whether such strong polar dust emission is common in AGNs. Out of 149 Seyferts in the MIR atlas of local AGNs, 21 show extended MIR emission on single-dish images. In 18 objects, the extended MIR emission aligns with the position angle (PA) of the system axis, established by [O iii], radio, polarization, and maser-based PA measurements. The relative amount of resolved MIR emission is at least 40% and scales with the [O iv] fluxes, implying a strong connection between the extended continuum and [O iv] emitters. These results together with the radio-quiet nature of the Seyferts support the scenario that the bulk of MIR emission is emitted by dust in the polar region and not by the torus, which would demand a new paradigm for the infrared emission structure in AGNs. The current low detection rate of polar dust in the AGNs of the MIR atlas is explained by the lack of sufficient high-quality MIR data and the requirements on the orientation, strength of narrow-line region, and distance of the AGNs. The James Webb Space Telescope will enable much deeper nuclear MIR studies with comparable angular resolution, allowing us to resolve the polar emission and surroundings in most of the nearby AGNs. Based on European Southern Observatory (ESO) observing programmes 60.A-9242, 074.A-9016, 075.B-0182, 075.B-0621, 075.B-0631, 075.B-0727, 075.B-0791, 075.B-0844, 076.B-0194, 076.B-0468, 076.B-0599, 076.B-0621, 076.B-0656, 076.B-0696, 076.B-0743, 077.B-0060, 077.B-0135, 077.B-0137, 077.B-0728, 078.B-0020, 078.B-0173, 078.B-0255, 078.B-0303, 080.B-0240, 080.B-0860, 081.B-0182, 082.B-0299, 083.B-0239, 083.B-0452, 083.B-0536, 083.B-0592, 084.B-0366, 084.B-0606, 084.B-0974, 085.B-0251, 085.B-0639, 086.B-0242, 086.B-0257, 086

  16. Patterned dual-layer achromatic micro-quarter-wave-retarder array for active polarization imaging.

    PubMed

    Zhao, Xiaojin; Pan, Xiaofang; Fan, Xiaolei; Xu, Ping; Bermak, Amine; Chigrinov, Vladimir G

    2014-04-01

    In this paper, we present a liquid-crystal-polymer (LCP)-based dual-layer micro-quarter-wave-retarder (MQWR) array for active polarization image sensors. The proposed MQWRs, for the first time, enable the extraction of the incident light's circularly polarized components in the whole visible regime, which correspond to the fourth parameter of Stokes vector. Compared with the previous implementations, our proposed MQWRs feature high achromaticity, making their applications no longer limited to monochromatic illumination. In addition, the presented thin structure exhibits an overall thickness of 2.43μm, leading to greatly alleviated optical cross-talk between adjacent photo-sensing pixels. Moreover, the reported superior optical performance (e.g. minor transmittance, extinction ratio) validates our optical design and optimization of the proposed MQWRs. Furthermore, the demonstrated simple fabrication recipe offers a cost-effective solution for the monolithic integration between the proposed MQWR array and the commercial solid-state image sensors, which makes the multi-spectral full Stokes polarization imaging system on a single chip feasible. PMID:24718177

  17. Transcriptomic Analysis of Human Polarized Macrophages: More than One Role of Alternative Activation?

    PubMed Central

    Derlindati, Eleonora; Dei Cas, Alessandra; Montanini, Barbara; Spigoni, Valentina; Curella, Valentina; Aldigeri, Raffaella; Ardigò, Diego; Zavaroni, Ivana; Bonadonna, Riccardo C.

    2015-01-01

    Background Macrophages are a heterogeneous cell population which in response to the cytokine milieu polarize in either classically activated macrophages (M1) or alternatively activated macrophages (M2). This plasticity makes macrophages essential in regulating inflammation, immune response and tissue remodeling and a novel therapeutic target in inflammatory diseases such as atherosclerosis. The aim of the study was to describe the transcriptomic profiles of differently polarized human macrophages to generate new hypotheses on the biological function of the different macrophage subtypes. Methods and Results Polarization of circulating monocytes/macrophages of blood donors was induced in vitro by IFN-γ and LPS (M1), by IL-4 (M2a), and by IL-10 (M2c). Unstimulated cells (RM) served as time controls. Gene expression profile of M1, M2a, M2c and RM was assessed at 6, 12 and 24h after polarization with Whole Human Genome Agilent Microarray technique. When compared to RM, M1 significantly upregulated pathways involved in immunity and inflammation, whereas M2a did the opposite. Conversely, decreased and increased expression of mitochondrial metabolism, consistent with insulin resistant and insulin sensitive patterns, was seen in M1 and M2a, respectively. The time sequence in the expression of some pathways appeared to have some specific bearing on M1 function. Finally, canonical and non-canonical Wnt genes and gene groups, promoting inflammation and tissue remodeling, were upregulated in M2a compared to RM. Conclusion Our data in in vitro polarized human macrophages: 1. confirm and extend known inflammatory and anti-inflammatory gene expression patterns; 2. demonstrate changes in mitochondrial metabolism associated to insulin resistance and insulin sensitivity in M1 and M2a, respectively; 3. highlight the potential relevance of gene expression timing in M1 function; 4. unveil enhanced expression of Wnt pathways in M2a suggesting a potential dual (pro-inflammatory and anti

  18. NMAAP1 Expressed in BCG-Activated Macrophage Promotes M1 Macrophage Polarization

    PubMed Central

    Liu, Qihui; Tian, Yuan; Zhao, Xiangfeng; Jing, Haifeng; Xie, Qi; Li, Peng; Li, Dong; Yan, Dongmei; Zhu, Xun

    2015-01-01

    Macrophages are divided into two subpopulations: classically activated macrophages (M1) and alternatively activated macrophages (M2). BCG (Bacilli Calmette-Guérin) activates disabled naïve macrophages to M1 macrophages, which act as inflammatory, microbicidal and tumoricidal cells through cell-cell contact and/or the release of soluble factors. Various transcription factors and signaling pathways are involved in the regulation of macrophage activation and polarization. We discovered that BCG-activated macrophages (BAM) expressed a new molecule, and we named it Novel Macrophage Activated Associated Protein 1 (NMAAP1). The current study found that the overexpression of NMAAP1 in macrophages results in M1 polarization with increased expression levels of M1 genes, such as inducible nitric oxide synthase (iNOS), tumor necrosis factor alpha (TNF-α), Interleukin 6 (IL-6), Interleukin 12 (IL-12), Monocyte chemoattractant protein-1 (MCP-1) and Interleukin-1 beta (IL-1β), and decreased expression of some M2 genes, such as Kruppel-like factor 4 (KLF4) and suppressor of cytokine signaling 1 (SOCS1), but not other M2 genes, including arginase-1 (Arg-1), Interleukin (IL-10), transforming growth factor beta (TGF-β) and found in inflammatory zone 1 (Fizz1). Moreover, NMAAP1 overexpression in the RAW264.7 cell line increased cytotoxicity against MCA207 tumor cells, which depends on increased inflammatory cytokines rather than cell-cell contact. NMAAP1 also substantially enhanced the phagocytic ability of macrophages, which implies that NMAAP1 promoted macrophage adhesive and clearance activities. Our results indicate that NMAAP1 is an essential molecule that modulates macrophages phenotype and plays an important role in macrophage tumoricidal functions. PMID:26429502

  19. Universality for Moving Stripes: A Hydrodynamic Theory of Polar Active Smectics

    NASA Astrophysics Data System (ADS)

    Chen, Leiming; Toner, John

    2013-08-01

    We present a theory of moving stripes (“polar active smectics”), both with and without number conservation. The latter is described by a compact anisotropic Kardar-Parisi-Zhang equation, which implies smectic order is quasilong ranged in d=2 and long ranged in d=3. In d=2 the smectic disorders via a Kosterlitz-Thouless transition, which can be driven by either increasing the noise or varying certain nonlinearities. For the number-conserving case, giant number fluctuations are greatly suppressed by the smectic order, which is long ranged in d=3. Nonlinear effects become important in d=2.

  20. Nitroxyl (HNO) reduces endothelial and monocyte activation and promotes M2 macrophage polarization.

    PubMed

    Andrews, Karen L; Sampson, Amanda K; Irvine, Jennifer C; Shihata, Waled A; Michell, Danielle L; Lumsden, Natalie G; Lim, Chloe; Huet, Olivier; Drummond, Grant R; Kemp-Harper, Barbara K; Chin-Dusting, Jaye P F

    2016-09-01

    Nitroxyl anion (HNO) donors are currently being assessed for their therapeutic utility in several cardiovascular disorders including heart failure. Here, we examine their effect on factors that precede atherosclerosis including endothelial cell and monocyte activation, leucocyte adhesion to the endothelium and macrophage polarization. Similar to the NO donor glyceryl trinitrate (GTN), the HNO donors Angeli's salt (AS) and isopropylamine NONOate (IPA/NO) decreased leucocyte adhesion to activated human umbilical vein endothelial cells (HUVECs) and mouse isolated aorta. This reduction in adhesion was accompanied by a reduction in intercellular adhesion molecule-1 (ICAM-1) and the cytokines monocyte chemoattractant protein 1 (MCP-1) and interleukin 6 (IL-6) which was inhibitor of nuclear factor κB (NFκB) α (IκBα)- and subsequently NFκB-dependent. Intriguingly, the effects of AS on leucocyte adhesion, like those on vasodilation, were found to not be susceptible to pharmacological tolerance, unlike those observed with GTN. As well, HNO reduces monocyte activation and promotes polarization of M2 macrophages. Taken together, our data demonstrate that HNO donors can reduce factors that are associated with and which precede atherosclerosis and may thus be useful therapeutically. Furthermore, since the effects of the HNO donors were not subject to tolerance, this confers an additional advantage over NO donors. PMID:27231254

  1. Self-induced polar order of active Brownian particles in a harmonic trap.

    PubMed

    Hennes, Marc; Wolff, Katrin; Stark, Holger

    2014-06-13

    Hydrodynamically interacting active particles in an external harmonic potential form a self-assembled fluid pump at large enough Péclet numbers. Here, we give a quantitative criterion for the formation of the pump and show that particle orientations align in the self-induced flow field in surprising analogy to ferromagnetic order where the active Péclet number plays the role of inverse temperature. The particle orientations follow a Boltzmann distribution Φ(p) ∼ exp(Ap(z)) where the ordering mean field A scales with the active Péclet number and polar order parameter. The mean flow field in which the particles' swimming directions align corresponds to a regularized Stokeslet with strength proportional to swimming speed. Analytic mean-field results are compared with results from Brownian dynamics simulations with hydrodynamic interactions included and are found to capture the self-induced alignment very well. PMID:24972231

  2. Free energy, entropy and volume of activation for electron transfer reactions in a polar solvent

    SciTech Connect

    Manjari, Swati R.; Kim, Hyung J.

    2006-07-07

    A continuum theory with account of cavity size fluctuations is employed to study free energy, volume and entropy of activation for nonadiabatic electron transfer (ET) reactions in polar solvents. By using a two-sphere cavity description, model calculations are performed for charge separation and recombination processes in acetonitrile under ambient conditions. It is found that the cavity size at the transition state varies with the free energy of reaction as well as with the thermodynamic conditions. In contrast to the Marcus theory predictions, the volume and entropy of activation show a monotonic behavior with the free energy of reaction and a strong correlation with each other. For example, for a given ET process, the volume and entropy of activation have the same sign. Their values for the charge separation and recombination processes are opposite in sign. These findings are in good qualitative agreement with measurements.

  3. Lipase in aqueous-polar organic solvents: Activity, structure, and stability

    PubMed Central

    Kamal, Md Zahid; Yedavalli, Poornima; Deshmukh, Mandar V; Rao, Nalam Madhusudhana

    2013-01-01

    Studying alterations in biophysical and biochemical behavior of enzymes in the presence of organic solvents and the underlying cause(s) has important implications in biotechnology. We investigated the effects of aqueous solutions of polar organic solvents on ester hydrolytic activity, structure and stability of a lipase. Relative activity of the lipase monotonically decreased with increasing concentration of acetone, acetonitrile, and DMF but increased at lower concentrations (upto ∼20% v/v) of dimethylsulfoxide, isopropanol, and methanol. None of the organic solvents caused any appreciable structural change as evident from circular dichorism and NMR studies, thus do not support any significant role of enzyme denaturation in activity change. Change in 2D [15N, 1H]-HSQC chemical shifts suggested that all the organic solvents preferentially localize to a hydrophobic patch in the active-site vicinity and no chemical shift perturbation was observed for residues present in protein's core. This suggests that activity alteration might be directly linked to change in active site environment only. All organic solvents decreased the apparent binding of substrate to the enzyme (increased Km); however significantly enhanced the kcat. Melting temperature (Tm) of lipase, measured by circular dichroism and differential scanning calorimetry, altered in all solvents, albeit to a variable extent. Interestingly, although the effect of all organic solvents on various properties on lipase is qualitatively similar, our study suggest that magnitudes of effects do not appear to follow bulk solvent properties like polarity and the solvent effects are apparently dictated by specific and local interactions of solvent molecule(s) with the protein. PMID:23625694

  4. Transthyretin-binding activity of contaminants in blood from polar bear (Ursus maritimus) cubs.

    PubMed

    Bytingsvik, Jenny; Simon, Eszter; Leonards, Pim E G; Lamoree, Marja; Lie, Elisabeth; Aars, Jon; Derocher, Andrew E; Wiig, Oystein; Jenssen, Bjørn M; Hamers, Timo

    2013-05-01

    We determined the transthyretin (TTR)-binding activity of blood-accumulating contaminants in blood plasma samples of approximately 4-months-old polar bear (Ursus maritimus) cubs from Svalbard sampled in 1998 and 2008. The TTR-binding activity was measured as thyroxine (T4)-like equivalents (T4-EQMeas). Our findings show that the TTR-binding activity related to contaminant levels was significantly lower (45%) in 2008 than in 1998 (mean ± standard error of mean: 1998, 2265 ± 231 nM; 2008, 1258 ± 170 nM). Although we cannot exclude a potential influence of between-year differences in capture location and cub body mass, our findings most likely reflect reductions of TTR-binding contaminants or their precursors in the arctic environment (e.g., polychlorinated biphenyls [PCBs]). The measured TTR-binding activity correlated positively with the cubs' plasma levels of hydroxylated PCBs (OH-PCBs). No such association was found between TTR-binding activity and the plasma levels of perfluoroalkyl substances (PFASs). The OH-PCBs explained 60 ± 7% and 54 ± 4% of the TTR-binding activity in 1998 and 2008, respectively, and PFASs explained ≤1.2% both years. Still, almost half the TTR-binding activity could not be explained by the contaminants we examined. The considerable levels of TTR-binding contaminants warrant further effect directed analysis (EDA) to identify the contaminants responsible for the unexplained part of the observed TTR-binding activity. PMID:23551254

  5. Role of the active viscosity and self-propelling speed in channel flows of active polar liquid crystals.

    PubMed

    Yang, Xiaogang; Wang, Qi

    2016-01-28

    We study channel flows of active polar liquid crystals (APLCs) focusing on the role played by the active viscosity (β) and the self-propelling speed (ω) on the formation and long time evolution of spontaneous flows using a continuum model. First, we study the onset of spontaneous flows by carrying out a linear stability analysis on two special steady states subject to various physical boundary conditions. We identify a single parameter b1, proportional to a linear combination of the active viscosity and the self-propelling speed, and inversely proportional to a Frank elastic constant, the solvent viscosity, and the liquid crystal relaxation time. We show that the active viscosity and the self-propelling speed influence the onset of spontaneous flows through b1 in that for any fixed value of the bulk activity parameter ζ, large enough |b1| can suppress the spontaneous flow. We then follow spontaneous flows in long time to further investigate the role of β and ω on spatial-temporal structures in the nonlinear regime numerically. The numerical study demonstrates a strong correlation between the most unstable eigenfunction obtained from the linear analysis and the terminal steady state or the persistent, traveling wave structure, revealing the genesis of flow and orientational structures in the active matter system. In the nonlinear regime, a nonzero b1 facilitates the formation of traveling waves in the case of boundary anchoring (the Dirichlet boundary condition) so long as the linear stability analysis predicts an onset of spontaneous flows; in the case of the free boundary condition (the Neumann boundary condition), a stable, spatially homogeneous tilted state always emerges in the presence of two active effects. Finally, we note that various fully out-of-plane spatio-temporal structures can emerge in long time dynamics depending on the boundary condition as well as the initial state of the polarity vector field. PMID:26583506

  6. Polar Bear

    USGS Publications Warehouse

    Amstrup, S.D.; DeMaster

    1988-01-01

    Polar bears are long-lived, late-maturing carnivores that have relatively low rates of reproduction and natural mortality. Their populations are susceptible to disturbance from human activities, such as the exploration and development of mineral resources or hunting. Polar bear populations have been an important renewable resource available to coastal communities throughout the Arctic for thousands of years.

  7. The physical activity profiles of South Asian ethnic groups in England

    PubMed Central

    Bhatnagar, Prachi; Townsend, Nick; Shaw, Alison; Foster, Charlie

    2016-01-01

    Background To identify what types of activity contribute to overall physical activity in South Asian ethnic groups and how these vary according to sex and age. We used the White British ethnic group as a comparison. Methods Self-reported physical activity was measured in the Health Survey for England 1999 and 2004, a nationally representative, cross-sectional survey that boosted ethnic minority samples in these years. We merged the two survey years and analysed data from 19 476 adults. The proportions of total physical activity achieved through walking, housework, sports and DIY activity were calculated. We stratified by sex and age group and used analysis of variances to examine differences between ethnic groups, adjusted for the socioeconomic status. Results There was a significant difference between ethnic groups for the contributions of all physical activity domains for those aged below 55 years, with the exception of walking. In women aged 16–34 years, there was no significant difference in the contribution of walking to total physical activity (p=0.38). In the 35–54 age group, Bangladeshi males have the highest proportion of total activity from walking (30%). In those aged over 55 years, the proportion of activity from sports was the lowest in all South Asian ethnic groups for both sexes. Conclusions UK South Asians are more active in some ways that differ, by age and sex, from White British, but are similarly active in other ways. These results can be used to develop targeted population level interventions for increasing physical activity levels in adult UK South Asian populations. PMID:26677257

  8. Tumor cell-activated CARD9 signaling contributes to metastasis-associated macrophage polarization.

    PubMed

    Yang, M; Shao, J-H; Miao, Y-J; Cui, W; Qi, Y-F; Han, J-H; Lin, X; Du, J

    2014-08-01

    Macrophages are critical immune effector cells of the tumor microenvironment that promote seeding, extravasation and persistent growth of tumor cells in primary tumors and metastatic sites. Tumor progression and metastasis are affected by dynamic changes in the specific phenotypes of macrophage subpopulations; however, the mechanisms by which tumor cells modulate macrophage polarization remain incompletely understood. Caspase recruitment domain-containing protein 9 (CARD9) is a central adaptor protein of innate immune responses to extracellular pathogens. We report that increased CARD9 expression is primarily localized in infiltrated macrophages and significantly associated with advanced histopathologic stage and the presence of metastasis. Using CARD9-deficient (CARD9(-/-)) mice, we show that bone marrow-derived CARD9 promotes liver metastasis of colon carcinoma cells. Mechanistic studies reveal that CARD9 contributes to tumor metastasis by promoting metastasis-associated macrophage polarization through activation of the nuclear factor-kappa B signaling pathway. We further demonstrate that tumor cell-secreted vascular endothelial growth factor facilitates spleen tyrosine kinase activation in macrophages, which is necessary for formation of the CARD9-B-cell lymphoma/leukemia 10-mucosa-associated lymphoid tissue lymphoma translocation protein 1 complex. Taken together, our results indicating that CARD9 is a regulator of metastasis-associated macrophages will lead to new insights into evolution of the microenvironments supporting tumor metastasis, thereby providing targets for anticancer therapies. PMID:24722209

  9. Unexpected Levels of Biological Activity during the Polar Night Offer New Perspectives on a Warming Arctic.

    PubMed

    Berge, Jørgen; Daase, Malin; Renaud, Paul E; Ambrose, William G; Darnis, Gerald; Last, Kim S; Leu, Eva; Cohen, Jonathan H; Johnsen, Geir; Moline, Mark A; Cottier, Finlo; Varpe, Øystein; Shunatova, Natalia; Bałazy, Piotr; Morata, Nathalie; Massabuau, Jean-Charles; Falk-Petersen, Stig; Kosobokova, Ksenia; Hoppe, Clara J M; Węsławski, Jan Marcin; Kukliński, Piotr; Legeżyńska, Joanna; Nikishina, Daria; Cusa, Marine; Kędra, Monika; Włodarska-Kowalczuk, Maria; Vogedes, Daniel; Camus, Lionel; Tran, Damien; Michaud, Emma; Gabrielsen, Tove M; Granovitch, Andrei; Gonchar, Anya; Krapp, Rupert; Callesen, Trine A

    2015-10-01

    The current understanding of Arctic ecosystems is deeply rooted in the classical view of a bottom-up controlled system with strong physical forcing and seasonality in primary-production regimes. Consequently, the Arctic polar night is commonly disregarded as a time of year when biological activities are reduced to a minimum due to a reduced food supply. Here, based upon a multidisciplinary ecosystem-scale study from the polar night at 79°N, we present an entirely different view. Instead of an ecosystem that has entered a resting state, we document a system with high activity levels and biological interactions across most trophic levels. In some habitats, biological diversity and presence of juvenile stages were elevated in winter months compared to the more productive and sunlit periods. Ultimately, our results suggest a different perspective regarding ecosystem function that will be of importance for future environmental management and decision making, especially at a time when Arctic regions are experiencing accelerated environmental change [1]. PMID:26412132

  10. Active Mass Wasting of Ices in the North Polar Region of Mars

    NASA Astrophysics Data System (ADS)

    Russell, P. S.; Byrne, S.; Pathare, A.; Herkenhoff, K. E.

    2011-12-01

    The HiRISE camera on the Mars Reconnaissance Orbiter has discovered two forms of mass-wasting in the north-polar region. One is the scarpward retreat of bright layers of the north polar basal unit (BU, immediately underlying the north polar layered deposits, NPLD) and the overlying NPLD by fracture-controlled and undercutting-assisted piecewise failure of layer edges, resulting in rockfalls and rockslides, called blockfalls here. This is important as it suggests an alternative, significant mode of erosion in addition to sublimation which is traditionally held account-able for erosion of polar surfaces. The other form, caught in-action during imaging, comprises falls and avalanches of frost and dust over a few steep NPLD scarps during early spring. Here we report the latest findings in both of these dramatic and currently active processes and assess their role in the evolution and history of polar deposits. NPLD and BU mass wasting: Typical evidence of recent blockfall activity is in the form of blocks, flows, and debris on BU slopes. In a few cases, the appearance of new blocks in subsequent images proves this process is ongo-ing. In general, [likely] active outcrops have a higher overall MOLA-derived slope than [likely] quiescent outcrops (those with a lack of debris and abundance of sand on the BU). Furthermore, none of the NPLD peripheral scarps without BU exposure have slopes above 40°. This suggests BU exposure and this type of mass wasting play a role in maintaining and possibly creating over-steepened NPLD scarps (often 45°-65°, with sections approaching vertical). The lower-sloped NPLD scarps with no BU present also do not display the severe fracturing that characterizes steep NPLD cliffs directly above BU exposures. This may be due to fracture propagation from undercutting by the BU, thermal stresses induced by rapid and intense heating on steepened slopes with high solar incidence angles, or rapid uncovering of ice that was under compressive stresses

  11. Removal of highly polar micropollutants from wastewater by powdered activated carbon.

    PubMed

    Kovalova, Lubomira; Knappe, Detlef R U; Lehnberg, Kai; Kazner, Christian; Hollender, Juliane

    2013-06-01

    Due to concerns about ecotoxicological effects of pharmaceuticals and other micropollutants released from wastewater treatment plants, activated carbon adsorption is one of the few processes to effectively reduce the concentrations of micropollutants in wastewater. Although aimed mainly at apolar compounds, polar compounds are also simultaneously removed to a certain extent, which has rarely been studied before. In this study, adsorption isotherm and batch kinetic data were collected with two powdered activated carbons (PACs) to assess the removal of the polar pharmaceuticals 5-fluorouracil (5-Fu) and cytarabine (CytR) from ultrapure water and wastewater treatment plant effluent. At pH 7.8, single-solute adsorption isotherm data for the weak acid 5-Fu and the weak base CytR showed that their adsorption capacities were about 1 order of magnitude lower than those of the less polar endocrine disrupting chemicals bisphenol A (BPA) and 17-α-ethinylestradiol (EE2). To remove 90 % of the adsorbate from a single-solute solution 14, 18, 70, and 87 mg L(-1) of HOK Super is required for EE2, BPA, CytR, and 5-Fu, respectively. Effects of solution pH, ionic strength, temperature, and effluent organic matter (EfOM) on 5-Fu and CytR adsorption were evaluated for one PAC. Among the studied factors, the presence of EfOM had the highest effect, due to a strong competition on 5-Fu and CytR adsorption. Adsorption isotherm and kinetic data and their modeling with a homogeneous surface diffusion model showed that removal percentage in the presence of EfOM was independent on the initial concentration of the ionizable compounds 5-Fu and CytR. These results are similar to neutral organic compounds in the presence of natural organic matter. Overall, results showed that PAC doses sufficient to remove >90 % of apolar adsorbates were able to remove no more than 50 % of the polar adsorbates 5-Fu and CytR and that the contact time is a critical parameter. PMID:23299971

  12. Flagellar dynamics of a connected chain of active, polar, Brownian particles

    PubMed Central

    Chelakkot, Raghunath; Gopinath, Arvind; Mahadevan, L.; Hagan, Michael F.

    2014-01-01

    We show that active, self-propelled particles that are connected together to form a single chain that is anchored at one end can produce the graceful beating motions of flagella. Changing the boundary condition from a clamp to a pivot at the anchor leads to steadily rotating tight coils. Strong noise in the system disrupts the regularity of the oscillations. We use a combination of detailed numerical simulations, mean-field scaling analysis and first passage time theory to characterize the phase diagram as a function of the filament length, passive elasticity, propulsion force and noise. Our study suggests minimal experimental tests for the onset of oscillations in an active polar chain. PMID:24352670

  13. Flagellar dynamics of a connected chain of active, polar, Brownian particles.

    PubMed

    Chelakkot, Raghunath; Gopinath, Arvind; Mahadevan, L; Hagan, Michael F

    2014-03-01

    We show that active, self-propelled particles that are connected together to form a single chain that is anchored at one end can produce the graceful beating motions of flagella. Changing the boundary condition from a clamp to a pivot at the anchor leads to steadily rotating tight coils. Strong noise in the system disrupts the regularity of the oscillations. We use a combination of detailed numerical simulations, mean-field scaling analysis and first passage time theory to characterize the phase diagram as a function of the filament length, passive elasticity, propulsion force and noise. Our study suggests minimal experimental tests for the onset of oscillations in an active polar chain. PMID:24352670

  14. Investigations of electron helicity in optically active molecules using polarized beams of electrons and positrons

    NASA Technical Reports Server (NTRS)

    Gidley, D. W.; Rich, A.; Van House, J. C.; Zitzewitz, P. W.

    1981-01-01

    A positronium-formation experiment with a high sensitivity to a possible relation between the helicity of beta particles emitted in nuclear beta decay and the optical asymmetry of biological molecules is presented. The experiment is based on a mechanism in which the electrons in optically active molecules possess a helicity of less than 0.001, too weak to detect in radiolysis experiments, the sign of which depends on the chirality of the isomer. A helicity-dependent asymmetry is sought in the formation of the triplet ground state of positronium when a low-energy beam of polarized positrons of reversible helicity interacts with an optically active substance coating a channel electron multiplier. Asymmetries between positronium decays observed at positive and negative helicities for the same substance can thus be determined with a sensitivity of 0.0001, which represents a factor of 100 improvement over previous positronium experiments.

  15. 78 FR 16247 - Foreign-Trade Zone 38-Spartanburg County, South Carolina; Authorization of Production Activity...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-14

    ... Federal Register inviting public comment (77 FR 70992-70993, 11-28-2012). The FTZ Board has determined... On November 8, 2012, the South Carolina State Ports Authority, grantee of FTZ 38, submitted a notification of proposed production activity to the Foreign-Trade Zones (FTZ) Board on behalf of...

  16. Guidelines to Assist the Implementation of Differentiated Learning Activities in South African Secondary Schools

    ERIC Educational Resources Information Center

    de Jager, Thelma

    2013-01-01

    Despite previous research and recommendations in South Africa, secondary-school teachers still encounter economic, social and cultural challenges in implementing differentiated learning activities in the classroom. The diversity of learners with learning barriers inevitably leads to an increase in workload for the teachers. This article draws on…

  17. The Evolution of Student Activism and Its Influence on Tuition Fees in South Korean Universities

    ERIC Educational Resources Information Center

    Shin, Jung Cheol; Kim, Hoon-Ho; Choi, Hong-Sam

    2014-01-01

    This article briefly overviews the student movement working for political democratisation during the authoritarian governments in South Korea. The article focuses on how student activism has changed as a reflection of political developments from the dictatorship through to the civilian democratic governments. Further, it analyses how tuition-fee…

  18. Active-site motions and polarity enhance catalytic turnover of hydrated subtilisin dissolved in organic solvents.

    PubMed

    Hudson, Elton P; Eppler, Ross K; Beaudoin, Julianne M; Dordick, Jonathan S; Reimer, Jeffrey A; Clark, Douglas S

    2009-04-01

    The enzyme subtilisin Carlsberg was surfactant-solubilized into two organic solvents, isooctane and tetrahydrofuran, and hydrated through stepwise changes in the thermodynamic water activity, a(w). The apparent turnover number k(cat)(app) in these systems ranged from 0.2 to 80 s(-1) and increased 11-fold in isooctane and up to 50-fold in tetrahydrofuran with increasing a(w). (19)F NMR relaxation experiments employing an active-site inhibitor were used to assess the dependence of active-site motions on a(w). The rates of NMR-derived fast (k > 10(7) s(-1)) and slow (k < 10(4) s(-1)) active-site motions increased in both solvents upon hydration, but only the slow motions correlated with k(cat). The (19)F chemical shift was a sensitive probe of the local electronic environment and provided an empirical measure of the active-site dielectric constant epsilon(as), which increased with hydration to epsilon(as) approximately 13 in each solvent. In both solvents, the transition state free energy data and epsilon(as) followed Kirkwood's model for the continuum solvation of a dipole, indicating that water also enhanced catalysis by altering the active-site's electronic environment and increasing its polarity to better stabilize the transition state. These results reveal that favorable dynamic and electrostatic effects both contribute to accelerated catalysis by solubilized subtilisin Carlsberg upon hydration in organic solvents. PMID:19317505

  19. Active-site motions and polarity enhance catalytic turnover of hydrated subtilisin dissolved in organic solvents

    PubMed Central

    Hudson, Elton P; Eppler, Ross K; Beaudoin, Julianne M; Dordick, Jonathan S; Reimer, Jeffrey A; Clark, Douglas S

    2009-01-01

    The enzyme subtilisin Carlsberg was surfactant-solubilized into two organic solvents, isooctane and tetrahydrofuran, and hydrated through stepwise changes in the thermodynamic water activity, aw. The apparent turnover number kcatapp in these systems ranged from 0.2 to 80 s−1 and increased 11-fold in isooctane and up to 50-fold in tetrahydrofuran with increasing aw. 19F-NMR relaxation experiments employing an active-site inhibitor were used to assess the dependence of active-site motions on aw. The rates of NMR-derived fast (k > 107 s−1) and slow (k < 104 s−1) active-site motions increased in both solvents upon hydration, but only the slow motions correlated with kcat. The 19F chemical shift was a sensitive probe of the local electronic environment and provided an empirical measure of the active-site dielectric constant εas, which increased with hydration to εas ≈ 13 in each solvent. In both solvents the transition state free energy data and εas followed Kirkwood’s model for the continuum solvation of a dipole, indicating that water also enhanced catalysis by altering the active-site’s electronic environment and increasing its polarity to better stabilize the transition state. These results reveal that favorable dynamic and electrostatic effects both contribute to accelerated catalysis by solubilized subtilisin Carlsberg upon hydration in organic solvents. PMID:19317505

  20. Portugal and the International Polar Year: the role of researchers in promoting education and outreach activities to a wider audience

    NASA Astrophysics Data System (ADS)

    Mendes-Victor, L. A.; Xavier, J.; Vieira, G.; Canário, A.; Santos, C. R.

    2007-12-01

    Thanks to the International Polar Year (IPY), international programme of research and education, aiming to promote collaborative research in Polar regions in 2007-08, Portugal has been proposing to play an active role in various research disciplines. The main objectives, designed by the Portuguese Committee were: improving the knowledge in polar processes, implementing the capacity to detect climate change, assessing the global warming consequences in the preservation of marine and terrestrial biodiversity, and finally, attracting the people's attention to all these issues. Another one of the greatest objectives of the Portuguese Committee for the IPY, coordinated by Portuguese researchers, is to encourage activities and events related to Polar Regions, directed to the general public. The establishment of new collaborations with education institutions (e.g. Ministry of Education), schools, Universities and teacher associations has been already obtained. This presentation aims to show the educational programme "LATITUDE60!", that focuses on education and outreach activities (E&O) conducted in Portugal, emphasizing the various projects related to education for 2007- 2008, and focus on the importance of attracting the attention of the general public (from children to adults) to Portuguese activities and to the Science in the Polar Regions. It has been recognized internationally by taking the forefront of E&O within the International Polar Year. The work related to education and science outreach, during the IPY, has been coordinated in collaboration with the International Polar Year Education & Outreach Sub-Committee as well as with the International Youth Steering Committee for the International Polar Year.

  1. Peroxisome proliferator-activated receptor-gamma agonist rosiglitazone attenuates postincisional pain by regulating macrophage polarization

    SciTech Connect

    Hasegawa-Moriyama, Maiko; Ohnou, Tetsuya; Godai, Kohei; Kurimoto, Tae; Nakama, Mayo; Kanmura, Yuichi

    2012-09-14

    Highlights: Black-Right-Pointing-Pointer Rosiglitazone attenuated postincisional pain. Black-Right-Pointing-Pointer Rosiglitazone alters macrophage polarization to F4/80{sup +}CD206{sup +} M2 macrophages at the incisional sites. Black-Right-Pointing-Pointer Transplantation of rosiglitazone-treated macrophages produced analgesic effects. -- Abstract: Acute inflammation triggered by macrophage infiltration to injured tissue promotes wound repair and may induce pain hypersensitivity. Peroxisome proliferator-activated receptor {gamma} (PPAR){gamma} signaling is known to regulate heterogeneity of macrophages, which are often referred to as classically activated (M1) and alternatively activated (M2) macrophages. M1 macrophages have considerable antimicrobial activity and produce a wide variety of proinflammatory cytokines. In contrast, M2 macrophages are involved in anti-inflammatory and homeostatic functions linked to wound healing and tissue repair. Although it has been suggested that PPAR{gamma} agonists attenuate pain hypersensitivity, the molecular mechanism of macrophage-mediated effects of PPAR{gamma} signaling on pain development has not been explored. In this study, we investigated the link between the phenotype switching of macrophage polarization induced by PPAR{gamma} signaling and the development of acute pain hypersensitivity. Local administration of rosiglitazone significantly ameliorated hypersensitivity to heat and mechanical stimuli, and paw swelling. Consistent with the down-regulation of nuclear factor {kappa}B (NF{kappa}B) phosphorylation by rosiglitazone at the incisional sites, the number of F4/80{sup +}iNOS{sup +} M1 macrophages was decreased whereas numbers of F4/80{sup +}CD206{sup +} M2 macrophages were increased in rosiglitazone-treated incisional sites 24 h after the procedure. In addition, gene induction of anti-inflammatory M2-macrophage-associated markers such as arginase1, FIZZ1 and interleukin (IL)-10 were significantly increased, whereas

  2. Evaluation of wild herbivore faeces from South Africa as a potential source of hydrolytically active microorganisms.

    PubMed

    Ndlela, Luyanda L; Schmidt, Stefan

    2016-01-01

    This study assessed faecal matter from three indigenous South African herbivores-zebra, giraffe and impala-as a potential source for hydrolytically active aerobic and facultatively anaerobic bacteria. Herbivore droppings were collected freshly in a local nature reserve in Pietermaritzburg, South Africa. Soil samples adjacent to faecal collection sites and faeces from a domestic herbivore, the Nguni cow, were included as controls. Hydrolase and dehydrogenase activity in faecal matter and soil samples were measured by the fluorescein diacetate and the triphenyltetrazolium chloride assay. Viable counts and counts for amylase, cellulase, esterase and protease producers were established using plate count agar and solid media containing cellulose, skim milk, starch and Tween 80. Zebra droppings produced the highest hydrolase and dehydrogenase activity. Faecal matter of the three indigenous herbivores generally produced higher hydrolytic activity than Nguni cow faeces and soil controls, thereby confirming that these materials are potential targets for hydrolytic enzyme mining. PMID:26900540

  3. Nanoparticle-Aided Amplification of Fluorescence Polarization for Ultrasensitively Monitoring Activity of Telomerase.

    PubMed

    Gao, Yanfang; Xu, Jing; Li, Baoxin; Jin, Yan

    2016-06-01

    To realize facile and reliable analyzing telomerase activity in homogeneous, herein, for the first time, a fluorescent polarization (FP) strategy was developed for polymerase chain reaction (PCR) free monitoring activity of human telomerase at single-cell level ground on gold nanoparticle (GNP) enhancement of FP. First, thiolated telomerase substrate (TS) primer is modified to the surface of GNP via Au-S bond. In the presence of telomerase, TS primer was extended via adding hexamer repeats (GGGTTA), leading to the formation of a long elongation DNA. Several short carboxyfluorescein (FAM)-modified complementary DNA (F-cDNA) can hybridize with the hexamer repeats, resulting in a sharp increase in FP value. Because of the GNP enhancement and self-amplification of telomerase, telomerase activity accounting to one HeLa cell can be rapidly detected in homogeneous solution. Telomerase activities of various cell lines were also favorably estimated. Meanwhile, the inhibition efficiency of telomerase inhibitor was studied, which holds great potential in screening telomerase-targeted anticancer drugs as well. So, a facile method was put forward to reliably and ultrasensitively detect telomerase activity. PMID:27184230

  4. Protein binding mediation of biomaterial-dependent monocyte activation on a degradable polar hydrophobic ionic polyurethane.

    PubMed

    Battiston, Kyle G; Labow, Rosalind S; Santerre, J Paul

    2012-11-01

    Protein adsorption is an important phenomenon influencing the cellular response to biomaterials. Previous studies comparing monocyte activation on a degradable polar hydrophobic ionic polyurethane (D-PHI) indicated a reduced pro-inflammatory monocyte response relative to tissue culture polystyrene (TCPS) and poly(lactide-co-glycolide) (PLGA) substrates. The present study investigated the influence of protein binding in order to gain further insight into the observed differential monocyte activation. Several proteins, identified in different relative amounts within the bound protein layers on D-PHI vs. PLGA and TCPS, were evaluated for their effect on monocyte activation. It was found that, in general, both non-coated and protein pre-adsorbed D-PHI supported a reduced pro-inflammatory response relative to PLGA, as indicated by lower levels of tumor necrosis factor-α (TNF-α) release. An initial increase in TNF-α release occurred when α(2)-macroglobulin (A2M) was pre-adsorbed to D-PHI, which was shown to involve the α(2)-macroglobulin receptor and was active on D-PHI but not on the two other biomaterials. This response was not observed during competitive protein binding in the presence of fetal bovine serum (FBS), suggesting that a more complex arrangement of the bound proteins and their interactions with one another, as well as with the surface chemistry of the individual biomaterials, resulted in the low-activating character of D-PHI when interacting with human monocytes. PMID:22940217

  5. Separating planar cell polarity and Hippo pathway activities of the protocadherins Fat and Dachsous.

    PubMed

    Matakatsu, Hitoshi; Blair, Seth S

    2012-04-01

    The giant Drosophila protocadherin Fat (Ft) affects planar cell polarity (PCP). Ft also inhibits the overgrowth of imaginal discs via the Hippo pathway, repressing the activity of the transcription co-factor Yorkie (Yki). Much of Ft activity is likely to be mediated by its intracellular domain (Ft ICD). However, the links between the Ft ICD and either PCP or Hippo activity are poorly understood, and the role of the Hippo pathway in PCP is ambiguous. We have performed a structure-function analysis of the Ft ICD. We found that the effects of the Ft ICD on PCP and the Hippo pathway are largely separable. Surprisingly, the domains required for PCP and Hippo activities do not map to any of the previously identified protein interaction domains, nor, with one exception, to the regions that are highly conserved in mammalian Fat4. We also found that the extracellular domain of Ft can act independently of the Ft ICD in PCP and can trigger dominant-negative and boundary effects on Hippo activity, probably via binding to the protocadherin Dachsous. PMID:22399682

  6. The response of ionospheric convection in the polar cap to substorm activity

    NASA Technical Reports Server (NTRS)

    Lester, M.; Lockwood, M.; Yeoman, T. K.; Cowley, S. W. H.; Luehr, H.; Bunting, R.; Farrugia, C. J.

    1995-01-01

    We report multi-instrument observations during an isolated substorm on 17 October 1989. The European Incoherent Scatter (EISCAT) radar operated in the SP-UK-POLI mode measuring ionospheric convection at latitudes 71 deg Lambda - 78 deg Lambda. Sub-Auroral Magnetometer Network (SAMNET) and the EISCAT Magnetometer Cross provide information on the timing of substorm expansion phase onset and subsequent intensifications, as well as the location of the field aligned and ionospheric currents associated with the substorm current wedge. Interplanetary Monitoring Platform-8 (IMP-8) magnetic field data are also included. Evidence of a substorm growth phase is provided by the equatorward motion of a flow reversal boundary across the EISCAT radar field of view at 2130 MLT, following a southward turning of the interplanetary magnetic field (IMF). We infer that the polar cap expanded as a result of the addition of open magnetic flux in the tail lobes during this interval. The flow reversal boundary, which is a lower limit to the polar cap boundary, reached an invariant latitude equatorward of 71 deg Lambda by the time of the expansion phase onset. We conclude that the substorm onset region in the ionosphere, defined by the westward electrojet, mapped to a part of the tail radially earthward of the boundary between open and closed magnetic flux, the distant neutral line. Thus the substorm was not initiated at the distant neutral line, although there is evidence that it remained active during the expansion phase.

  7. PTK7 regulates myosin II activity to orient planar polarity in the mammalian auditory epithelium

    PubMed Central

    Lee, Jianyi; Andreeva, Anna; Sipe, Conor W.; Liu, Lixia; Cheng, Amy; Lu, Xiaowei

    2012-01-01

    Summary Background Planar Cell Polarity (PCP) signaling is a key regulator of epithelial morphogenesis, including neural tube closure and the orientation of inner ear sensory hair cells, and is mediated by a conserved noncanonical Wnt pathway. Ptk7 is a novel vertebrate-specific regulator of PCP, yet the mechanisms by which Ptk7 regulates mammalian epithelial PCP remain poorly understood. Results Here we show that, in the mammalian auditory epithelium, Ptk7 is not required for membrane recruitment of Dishevelled 2; Ptk7 and Frizzled3/Frizzled6 receptors act in parallel and have opposing effects on hair cell PCP. Mosaic analysis identified a requirement of Ptk7 in neighboring supporting cells for hair cell PCP. Ptk7 and the noncanonical Wnt pathway differentially regulate a contractile myosin II network near the apical surface of supporting cells. We provide evidence that this apical myosin II network exerts polarized contractile tension on hair cells to align their PCP, as revealed by asymmetric junctional recruitment of vinculin, a tension-sensitive actin binding protein. In Ptk7 mutants, compromised myosin II activity resulted in loss of planar asymmetry and reduced junctional localization of vinculin. By contrast, vinculin planar asymmetry and stereociliary bundle orientation were restored in Fz3−/−; Ptk7−/− double mutants. Conclusions These findings suggest that PTK7 acts in conjunction with the noncanonical Wnt pathway to orient epithelial PCP through modulation of myosin-II based contractile tension between supporting cells and hair cells. PMID:22560610

  8. Hyaluronan synthesis is necessary for autoreactive T-cell trafficking, activation, and Th1 polarization

    PubMed Central

    Kuipers, Hedwich F.; Rieck, Mary; Gurevich, Irina; Nagy, Nadine; Negrin, Robert S.; Wight, Thomas N.; Steinman, Lawrence; Bollyky, Paul L.

    2016-01-01

    The extracellular matrix polysaccharide hyaluronan (HA) accumulates at sites of autoimmune inflammation, including white matter lesions in multiple sclerosis (MS), but its functional importance in pathogenesis is unclear. We have evaluated the impact of 4-methylumbelliferone (4-MU), an oral inhibitor of HA synthesis, on disease progression in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS. Treatment with 4-MU decreases the incidence of EAE, delays its onset, and reduces the severity of established disease. 4-MU inhibits the activation of autoreactive T cells and prevents their polarization toward a Th1 phenotype. Instead, 4-MU promotes polarization toward a Th2 phenotpye and induction of Foxp3+ regulatory T cells. Further, 4-MU hastens trafficking of T cells through secondary lymphoid organs, impairs the infiltration of T cells into the CNS parenchyma, and limits astrogliosis. Together, these data suggest that HA synthesis is necessary for disease progression in EAE and that treatment with 4-MU may be a potential therapeutic strategy in CNS autoimmunity. Considering that 4-MU is already a therapeutic, called hymecromone, that is approved to treat biliary spasm in humans, we propose that it could be repurposed to treat MS. PMID:26787861

  9. Emissions of carbon species, organic polar compounds, potassium, and mercury from prescribed burning activities

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Obrist, D.; Zielinska, B.; Gerler, A.

    2012-04-01

    Biomass burning is an important emission source of pollutants to the atmosphere, but few studies have focused on the chemical composition of emissions from prescribed burning activities. Here we present results from a sampling campaign to quantify particulate-phase emissions from various types of prescribed fires including carbon species (Elemental Carbon: EC; Organic Carbon: OC; and Total Carbon: TC); polar organic compounds (12 different compounds and four functional classes); water-soluble potassium (K+); and mercury (Hg). We measured emissions from the following types of prescribed biomass burning in the Lake Tahoe basin located on the California/Nevada border: (i) log piles stacked and dried in the field; (ii) log piles along with green understory vegetation; and (iii) understory green vegetation and surface litter; further emissions were collected from burns conducted in a wood stove: (iv) dried wooden logs; (v) green foliage of understory vegetation collected from the field; and (vi) surface organic litter collected from the field; finally, samples were also taken from (vii) ambient air in residential areas during peak domestic wood combustion season. Results show that OC/EC ratios of prescribed burns in the field ranged from 4 to 10, but lower values (around 1) were observed in controlled stove fires. These results are consistent with an excess of OC emissions over EC found in wildfires. OC/EC ratios, however, showed clear separations between controlled wood stove combustion (higher EC) and prescribed burns in the field (lower EC). We attribute this difference to a higher combustion temperatures and dominance of flaming combustion in wood stove fires. OC positively and linearly correlated to the sum of polar organic compounds across all burn types (r2 of 0.82). The most prevalent group of polar compounds emitted during prescribed fires was resin acids (dehydroabietic, pimaric, and abietic acids), followed by levoglucosan plus mannositol. Negligible

  10. Correlation of Lunar South Polar Epithermal Neutron Maps: Lunar Exploration Neutron Detector and Lunar Prospector Neutron Detector

    NASA Technical Reports Server (NTRS)

    McClanahan, Timothy P.; Mitrofanov, I. G.; Boynton, W. V.; Sagdeev, R.; Trombka, J. I.; Starr, R. D.; Evans, L. G.; Litvak, M. L.; Chin, G.; Garvin, J.; Sanin, A. B.; Malakhov, A.; Milikh, G. M.; Harshman, K.; Finch, M. J.; Nandikotkur, G.

    2010-01-01

    The Lunar Reconnaissance Orbiter's (LRO), Lunar Exploration Neutron Detector (LEND) was developed to refine the lunar surface hydrogen (H) measurements generated by the Lunar Prospector Neutron Spectrometer. LPNS measurements indicated a approx.4,6% decrease in polar epithermal fluxes equivalent to (1.5+/-0,8)% H concentration and are direct geochemical evidence indicating water /high H at the poles. Given the similar operational and instrumental objectives of the LEND and LPNS systems, an important science analysis step for LEND is to test correlation with existing research including LPNS measurements. In this analysis, we compare corrected low altitude epithermal rate data from LPNS available via NASA's Planetary Data System (PDS) with calibrated LEND epithermal maps using a cross-correlation technique

  11. Environmental contaminants activate human and polar bear (Ursus maritimus) pregnane X receptors (PXR, NR1I2) differently

    PubMed Central

    Roger, Lille-Langøy; V, Goldstone Jared; Marte, Rusten; R, Milnes Matthew; Rune, Male; J, Stegeman John; Bruce, Blumberg; Anders, Goksøyr

    2015-01-01

    BACKGROUND Many persistent organic pollutants (POPs) accumulate readily in polar bears because of their position as apex predators in Arctic food webs. The pregnane X receptor (PXR, formally NR1I2, here proposed to be named promiscuous xenobiotic receptor) is a xenobiotic sensor that is directly involved in metabolizing pathways of a wide range of environmental contaminants. OBJECTIVES In the present study, we comparably assess the ability of 51 selected pharmaceuticals, pesticides and emerging contaminants to activate PXRs from polar bears and humans using an in vitro luciferase reporter gene assay. RESULTS We found that polar bear PXR is activated by a wide range of our test compounds (68%) but has a slightly more narrow ligand specificity than human PXR that was activated by 86% of the 51 test compounds. The majority of the agonists identified (70%) produces a stronger induction of the reporter gene via human PXR than via polar bear PXR, however with some notable and environmentally relevant exceptions. CONCLUSIONS Due to the observed differences in activation of polar bear and human PXRs, exposure of each species to environmental agents is likely to induce biotransformation differently in the two species. Bioinformatics analyses and structural modelling studies suggests that amino acids that are not part of the ligand-binding domain and do not interact with the ligand can modulate receptor activation. PMID:25680588

  12. Physical Activity in South Asians: An In-Depth Qualitative Study to Explore Motivations and Facilitators

    PubMed Central

    Jepson, Ruth; Harris, Fiona M.; Bowes, Alison; Robertson, Roma; Avan, Ghizala; Sheikh, Aziz

    2012-01-01

    Background People of South Asian backgrounds living in the UK have a five-fold increased risk of diabetes and a two-fold increased risk of heart disease when compared to the general population. Physical activity can reduce the risk of premature death from a range of conditions. The aim of the study was to explore the motivating and facilitating factors likely to increase physical activity for South Asian adults and their families, in order to develop successful interventions and services. Methodology/Principal Findings This was a qualitative study using focus groups and in-depth interviews. Participants were 59 purposively selected Bangladeshi-, Indian- and Pakistani-origin men and women with an additional 10 key informants. The setting was three urban areas of Scotland: Aberdeen, Glasgow and Edinburgh. We undertook a theoretically informed thematic analysis of data. Study participants described engaging in a range of physical activities, particularly football and the gym for men, and walking and swimming for women. The main motivators for taking part in physical activity were external motivators – i.e. undertaking physical activity as a means to an end, which included the opportunities that physical activity provided for social activity and enjoyment. The goals of weight reduction and improving mental and physical health and were also mentioned. Role models were seen as important to inspire and motivate people to undertake activities that they may otherwise lack confidence in. Few people undertook physical activity for its own sake (intrinsic motivation). Conclusions/Significance Attempts at promoting physical activity in people of South Asian origin need to take account of the social context of people's lives and the external motivators that encourage them to engage in physical activity. Undertaking group based physical activity is important and can be facilitated through religious, community, friendship or family networks. Role models may also prove

  13. Generation of stationary and moving vortices in active polar fluids in the planar Taylor-Couette geometry.

    PubMed

    Neef, M; Kruse, K

    2014-11-01

    We study the dynamics of an active polar fluid in the interstitial space between two fixed coaxial cylinders. For sufficiently large expansive or contractive active stresses, the fluid presents roll instabilities of axially symmetric states leading to the spontaneous formation of vortices in the flow field. These vortices are either stationary or travel around the inner cylinder. Increasing the activity further, our numerical solutions indicate the existence of active turbulence that coexists with regular vortex solutions. PMID:25493812

  14. THE EFFECTS OF POLARIZATION UPON THE STEEL WIRE-NITRIC ACID MODEL OF NERVE ACTIVITY.

    PubMed

    Bishop, G H

    1927-11-20

    The active process in a short length of steel wire passivated by 65 per cent nitric acid has been observed under the influence of a polarizing current, and the form of the potential recorded by the cathode ray oscillograph. In the passive wire, 80 per cent of the total potential drop takes place at the anode, 20 per cent at the cathode. The change from active to passive states, as measured by the potential change, is very abrupt compared to the duration of activity and the potential curve at a point on the wire is probably almost rectangular. The duration of the refractory state is decreased at the anode and increased at the cathode, as in nerve. This fact is against the idea that reactivity after passivation results from a partial reduction of an oxide layer. Soft iron wire passivated by anodal polarization repassivates after activation in acid of a dilution that fails to passivate it initially. It soon becomes rhythmic with a very short refractory phase, and then reacts continuously. Such a wire exhibits a very sharp alternation between a dark brown oxide coat during activity, and a bright clean surface during passivation. A passive steel wire in nitric acid shows many of the characteristics of an inert electrode such as platinum, and it may be inferred that, superposed upon the primary passivation potential, there exists an electrode or oxidation-reduction potential equilibrium between the effects of the various constituents of the solution. It is suggested that the phenomena of nerve-like reactivity in this system may involve an alternation between two protective coatings of the steel wire. During activity, the surface becomes mechanically coated with a brown oxide. If this coating does not adhere, due to gas convection or to rapid solution of the oxide, passivation does not result. Under sufficiently intense oxidizing conditions, a second oxide coat may form in the interstices of the first, and cover the surface as the first coating dissolves off. This

  15. Reduced polarization decay due to carrier in-scattering in a semiconductor active medium

    SciTech Connect

    Hughes, S.; Knorr, A.; Koch, S.W.; Chow, W.W.

    1996-07-01

    The in-scattering processes, which reduce the decay of the active medium polarization, should be included in a consistent treatment of semiconductor laser gain. The in-scattering processes affect the laser gain by decreasing the influence of the high k-states, which contribute absorption to the spectrum. A theory, based on the semiconductor-Bloch equations with the effects of carrier-carrier scattering treated at the level of the quantum kinetic equations in the Markov limit, predicts gain spectra that do not exhibit absorption below the renormalized band gap, in agreement with experiment. When compared to gain calculations where the in-scattering contribution is neglected, the theory predicts markedly different properties for intrinsic laser parameters, such as peak gain, gain bandwidth, differential gain and carrier density at transparency, especially at low carrier densities.

  16. Enhancing activity of N-glycosylation for constitutive proteins secretions in non-polarized cells

    SciTech Connect

    Akiyama, Nobutake; Ohno, Yuji; Fukuda, Takahiro; Manome, Yosinobu; Saito, Saburo

    2009-04-17

    Several fusion proteins of mouse Interleukins (mILs) and the enhanced green fluorescent protein (EGFP) were expressed in fibroblast and epithelial cells. Among these proteins, the mIL-31 derivative was the most efficiently secreted into the medium in a N-glycosylation-dependent manner. From the analysis of deletion mutants, the minimal structure for constitutive secretions consisted of a signal peptide and N-glycosylation. Introduction of the signal sequence from mIL-31 to human p53 protein failed to secrete the products, but further addition of the N-glycosylation site resulted in constitutive secretion of biologically active p53 protein into the medium in the N-glycosylated form. In this report, we showed the importance of N-glycosylation for constitutive protein secretions, especially using non-polarized cells.

  17. Active near infrared linear polarizer based on VO2 phase transition

    NASA Astrophysics Data System (ADS)

    Peng, Xiao-Yu; Wang, Bing; Teng, Jinghua; Kana Kana, J. B.; Zhang, Xinhai

    2013-10-01

    We demonstrate via the numerical simulation the modulation of the transmission of visible and near-infrared light through a hybrid grating structure containing a gold metallic wire-grid grating patterned on a thermochromic vanadium dioxide (VO2) thin film. We find that the transmission through the subwavelength slits of this hybrid device is significantly modulated in the near-infrared region due to the phase transition of VO2 film from insulator to metal when the temperature increases from 30 °C to 85 °C. By optimizing the hybrid-grating architecture parameters, the best switching efficiency of our hybrid grating at 1.5 μm reaches to 40%, and extinction ratio is larger than 1013. The capability of switching on/off and fine tuning of the thick hybrid grating parameters make our hybrid-grating structure a promising candidate of an active broadband linear polarizer with high switching efficiency and extinction ratio.

  18. Three-dimensional analysis of optical forces generated by an active tractor beam using radial polarization.

    PubMed

    Carretero, Luis; Acebal, Pablo; Blaya, Salvador

    2014-02-10

    We theoretically study the three-dimensional behavior of nanoparticles in an active optical conveyor. To do this, we solved the Langevin equation when the forces are generated by a focusing system at the near field. Analytical expressions for the optical forces generated by the optical conveyor were obtained by solving the Richards and Wolf vectorial diffraction integrals in an approximated form when a mask of two annular pupils is illuminated by a radially polarized Hermite-Gauss beam. Trajectories, in both the transverse plane and the longitudinal direction, are analyzed showing that the behavior of the optical conveyor can be optimized by conveniently choosing the configuration of the mask of the two annular pupils (inner and outer radius of the two rings) in order to trap and transport all particles at the focal plane. PMID:24663619

  19. Antarctic Polar Descent and Planetary Wave Activity Observed in ISAMS CO from April to July 1992

    NASA Technical Reports Server (NTRS)

    Allen, D. R.; Stanford, J. L.; Nakamura, N.; Lopez-Valverde, M. A.; Lopez-Puertas, M.; Taylor, F. W.; Remedios, J. J.

    2000-01-01

    Antarctic polar descent and planetary wave activity in the upper stratosphere and lower mesosphere are observed in ISAMS CO data from April to July 1992. CO-derived mean April-to-May upper stratosphere descent rates of 15 K/day (0.25 km/day) at 60 S and 20 K/day (0.33 km/day) at 80 S are compared with descent rates from diabatic trajectory analyses. At 60 S there is excellent agreement, while at 80 S the trajectory-derived descent is significantly larger in early April. Zonal wavenumber 1 enhancement of CO is observed on 9 and 28 May, coincident with enhanced wave 1 in UKMO geopotential height. The 9 May event extends from 40 to 70 km and shows westward phase tilt with height, while the 28 May event extends from 40 to 50 km and shows virtually no phase tilt with height.

  20. Polarization: A Key Difference between Man-made and Natural Electromagnetic Fields, in regard to Biological Activity

    NASA Astrophysics Data System (ADS)

    Panagopoulos, Dimitris J.; Johansson, Olle; Carlo, George L.

    2015-10-01

    In the present study we analyze the role of polarization in the biological activity of Electromagnetic Fields (EMFs)/Electromagnetic Radiation (EMR). All types of man-made EMFs/EMR - in contrast to natural EMFs/EMR - are polarized. Polarized EMFs/EMR can have increased biological activity, due to: 1) Ability to produce constructive interference effects and amplify their intensities at many locations. 2) Ability to force all charged/polar molecules and especially free ions within and around all living cells to oscillate on parallel planes and in phase with the applied polarized field. Such ionic forced-oscillations exert additive electrostatic forces on the sensors of cell membrane electro-sensitive ion channels, resulting in their irregular gating and consequent disruption of the cell’s electrochemical balance. These features render man-made EMFs/EMR more bioactive than natural non-ionizing EMFs/EMR. This explains the increasing number of biological effects discovered during the past few decades to be induced by man-made EMFs, in contrast to natural EMFs in the terrestrial environment which have always been present throughout evolution, although human exposure to the latter ones is normally of significantly higher intensities/energy and longer durations. Thus, polarization seems to be a trigger that significantly increases the probability for the initiation of biological/health effects.

  1. Polarization: A Key Difference between Man-made and Natural Electromagnetic Fields, in regard to Biological Activity

    PubMed Central

    Panagopoulos, Dimitris J.; Johansson, Olle; Carlo, George L.

    2015-01-01

    In the present study we analyze the role of polarization in the biological activity of Electromagnetic Fields (EMFs)/Electromagnetic Radiation (EMR). All types of man-made EMFs/EMR - in contrast to natural EMFs/EMR - are polarized. Polarized EMFs/EMR can have increased biological activity, due to: 1) Ability to produce constructive interference effects and amplify their intensities at many locations. 2) Ability to force all charged/polar molecules and especially free ions within and around all living cells to oscillate on parallel planes and in phase with the applied polarized field. Such ionic forced-oscillations exert additive electrostatic forces on the sensors of cell membrane electro-sensitive ion channels, resulting in their irregular gating and consequent disruption of the cell’s electrochemical balance. These features render man-made EMFs/EMR more bioactive than natural non-ionizing EMFs/EMR. This explains the increasing number of biological effects discovered during the past few decades to be induced by man-made EMFs, in contrast to natural EMFs in the terrestrial environment which have always been present throughout evolution, although human exposure to the latter ones is normally of significantly higher intensities/energy and longer durations. Thus, polarization seems to be a trigger that significantly increases the probability for the initiation of biological/health effects. PMID:26456585

  2. Polarization: A Key Difference between Man-made and Natural Electromagnetic Fields, in regard to Biological Activity.

    PubMed

    Panagopoulos, Dimitris J; Johansson, Olle; Carlo, George L

    2015-01-01

    In the present study we analyze the role of polarization in the biological activity of Electromagnetic Fields (EMFs)/Electromagnetic Radiation (EMR). All types of man-made EMFs/EMR - in contrast to natural EMFs/EMR - are polarized. Polarized EMFs/EMR can have increased biological activity, due to: 1) Ability to produce constructive interference effects and amplify their intensities at many locations. 2) Ability to force all charged/polar molecules and especially free ions within and around all living cells to oscillate on parallel planes and in phase with the applied polarized field. Such ionic forced-oscillations exert additive electrostatic forces on the sensors of cell membrane electro-sensitive ion channels, resulting in their irregular gating and consequent disruption of the cell's electrochemical balance. These features render man-made EMFs/EMR more bioactive than natural non-ionizing EMFs/EMR. This explains the increasing number of biological effects discovered during the past few decades to be induced by man-made EMFs, in contrast to natural EMFs in the terrestrial environment which have always been present throughout evolution, although human exposure to the latter ones is normally of significantly higher intensities/energy and longer durations. Thus, polarization seems to be a trigger that significantly increases the probability for the initiation of biological/health effects. PMID:26456585

  3. Seasonally active frost-dust avalanches on a north polar scarp of Mars captured by HiRISE

    USGS Publications Warehouse

    Russell, P.; Thomas, N.; Byrne, S.; Herkenhoff, K.; Fishbaugh, K.; Bridges, N.; Okubo, C.; Milazzo, M.; Daubar, I.; Hansen, C.; McEwen, A.

    2008-01-01

    North-polar temporal monitoring by the High Resolution Imaging Science Experiment (HiRISE) orbiting Mars has discovered new, dramatic examples that Mars1 CO2-dominated seasonal volatile cycle is not limited to quiet deposition and sublimation of frost. In early northern martian spring, 2008, HiRISE captured several cases of CO2 frost and dust cascading down a steep, polar scarp in discrete clouds. Analysis of morphology and process reveals these events to be similar to terrestrial powder avalanches, sluffs, and falls of loose, dry snow. Potential material sources and initiating mechanisms are discussed in the context of the Martian polar spring environment and of additional, active, aeolian processes observed on the plateau above the scarp. The scarp events are identified as a trigger for mass wasting of bright, fractured layers within the basal unit, and may indirectly influence the retreat rate of steep polar scarps in competing ways. Copyright 2008 by the American Geophysical Union.

  4. Alkaloid profiling and anticholinesterase activity of South American Lycopodiaceae species.

    PubMed

    Konrath, Eduardo Luis; Ortega, María Gabriela; de Loreto Bordignon, Sérgio; Apel, Miriam Anders; Henriques, Amélia Teresinha; Cabrera, José Luis

    2013-02-01

    The alkaloid extracts of four Huperzia and one Lycopodiella species, from Brazilian habitats, were tested for their in vitro anticholinesterase activities. IC(50) values showed a potent acetylcholinesterase inhibition for H. reflexa (0.11 ± 0.05 μg/mL), followed by H. quadrifariata (2.0 ± 0.3 μg/mL), H. acerosa (5.5 ± 0.9 μg/mL), H. heterocarpon (25.6 ± 2.7 μg/mL) and L. cernua (42.6 ± 1.5 μg/mL). A lower inhibition of butyrylcholinesterase was observed for all species with the exception of H. heterocarpon (8.3 ± 0.9 μg/mL), whose alkaloid extract presented a selectivity for pseudocholinesterase. Moreover, the chemical study of the bioactive extracts performed by GC-MS, revealed the presence of a number of Lycopodium alkaloids belonging to the lycopodane, flabellidane and cernuane groups. Surprisingly, the potent acetylcholinesterase inhibitors huperzines A and B were not detected in the extracts, suggesting that other alkaloids may be responsible for such an effect. PMID:22117191

  5. Vesta's north pole quadrangle Av-1 (Albana): Geologic map and the nature of the south polar basin antipodes

    NASA Astrophysics Data System (ADS)

    Blewett, David T.; Buczkowski, Debra L.; Ruesch, Ottaviano; Scully, Jennifer E.; O'Brien, David P.; Gaskell, Robert; Roatsch, Thomas; Bowling, Timothy J.; Ermakov, Anton; Hiesinger, Harald; Williams, David A.; Raymond, Carol A.; Russell, Christopher T.

    2014-12-01

    As part of systematic global mapping of Vesta using data returned by the Dawn spacecraft, we have produced a geologic map of the north pole quadrangle, Av-1 Albana. Extensive seasonal shadows were present in the north polar region at the time of the Dawn observations, limiting the ability to map morphological features and employ color or spectral data for determination of composition. The major recognizable units present include ancient cratered highlands and younger crater-related units (undivided ejecta, and mass-wasting material on crater floors). The antipode of Vesta's large southern impact basins, Rheasilvia and Veneneia, lie within or near the Av-1 quadrangle. Therefore it is of particular interest to search for evidence of features of the kind that are found at basin antipodes on other planetary bodies. Albedo markings known as lunar swirls are correlated with basin antipodes and the presence of crustal magnetic anomalies on the Moon, but lighting conditions preclude recognition of such albedo features in images of the antipode of Vesta's Rheasilvia basin. “Hilly and lineated terrain,” found at the antipodes of large basins on the Moon and Mercury, is not present at the Rheasilvia or Veneneia antipodes. We have identified small-scale linear depressions that may be related to increased fracturing in the Rheasilvia and Veneneia antipodal areas, consistent with impact-induced stresses (Buczkowski, D. et al. [2012b]. Analysis of the large scale troughs on Vesta and correlation to a model of giant impact into a differentiated asteroid. Geol. Soc. of America Annual Meeting. Abstract 152-4; Bowling, T.J. et al. [2013]. J. Geophys. Res. - Planets, 118. http://dx.doi.org/10.1002/jgre.20123). The general high elevation of much of the north polar region could, in part, be a result of uplift caused by the Rheasilvia basin-forming impact, as predicted by numerical modeling (Bowling, T.J. et al. [2013]. J. Geophys. Res. - Planets, 118. http://dx.doi.org/10.1002/jgre

  6. Melanogenesis and Antityrosinase Activity of Selected South African Plants

    PubMed Central

    Mapunya, Manyatja Brenda; Nikolova, Roumiana Vassileva; Lall, Namrita

    2012-01-01

    Melanin is the pigment that is responsible for the colour of eyes, hair, and skin in humans. Tyrosinase is known to be the key enzyme in melanin biosynthesis. Overactivity of this enzyme leads to dermatological disorders such as age spots, melanoma and sites of actinic damage. Ten plants belonging to four families (Asphodelaceae, Anacardiaceae, Oleaceae, and Rutaceae) were investigated for their effect on tyrosinase using both L-tyrosine and L-DOPA as substrates. Ethanol leaf extracts (500 μg/mL) of Aloe ferox, Aloe aculeata, Aloe pretoriensis, and Aloe sessiliflora showed 60%, 31%, 17%, and 13% inhibition of tyrosinase activity respectively, when L-tyrosine was used as a substrate. Harpephyllum caffrum (leaves) at a concentration of 500 μg/mL had an inhibitory effect of 70% on tyrosinase when L-DOPA was used as a substrate. The IC50 of Harpephyllum caffrum (leaves and bark) were found to be 51 ± 0.002 and 40 ± 0.035 μg/mL, respectively. Following the results obtained from the tyrosinase assay, extracts from Harpephyllum caffrum were selected for further testing on their effect on melanin production and their cytotoxicity on melanocytes in vitro. The IC50 of both extracts was found to be 6.25 μg/mL for melanocyte cells. Bark extract of Harpephyllum caffrum showed 26% reduction in melanin content of melanocyte cells at a concentration of 6.25 μg/mL. The leaf extract of this plant showed some toxicity on melanocyte cells. Therefore, the bark extract of Harpephyllum caffrum could be considered as an antityrosinase agent for dermatological disorders such as age spots and melasoma. PMID:22611429

  7. Should Physical Activity Recommendations for South Asian Adults Be Ethnicity-Specific? Evidence from a Cross-Sectional Study of South Asian and White European Men and Women

    PubMed Central

    Iliodromiti, Stamatina; Ghouri, Nazim; Celis-Morales, Carlos A.; Sattar, Naveed; Lumsden, Mary Ann; Gill, Jason M. R.

    2016-01-01

    International public health guidelines recommend that adults undertake at least 150 min.week−1 of moderate-intensity physical activity. However, the underpinning evidence has largely been obtained from studies of populations of white European descent. It is unclear whether these recommendations are appropriate for other ethnic groups, particularly South Asians, who have greater cardio-metabolic risk than white Europeans. The objective of our study was to determine the level of moderate-intensity physical activity required in South Asians adults to confer a similar cardio-metabolic risk profile to that observed in Europeans of similar age and body mass index (BMI) undertaking the currently recommended levels of 150 min.week−1. 148 South Asians and 163 white Europeans aged 18 to 70 years were recruited. Physical activity was measured objectively via vertical axis accelerations from hip-worn accelerometers. Factor analysis was used to summarize the measured risk biomarkers into a single underlying latent “factor” describing overall cardio-metabolic risk. Sex did not modify the association between physical activity and the cardio-metabolic risk factor, so data for both sexes were combined and models adjusted for age, sex, BMI and accelerometer wear time. We estimated that South Asian adults needed to undertake 232 (95% Confidence interval: 200 to 268) min.week−1 in order to obtain the same cardio-metabolic risk factor score as a white European undertaking 150 minutes of moderate-equivalent physical activity per week. The present findings suggest that South Asian men and women need to undertake ~230 minutes of moderate intensity physical activity per week. This equates to South Asians undertaking an extra 10–15 minutes of moderate intensity physical activity per day on top of existing recommendations. PMID:27529339

  8. Can Indian Ocean SST variability impact TC activity in the South Pacific? A Spatial Analysis

    NASA Astrophysics Data System (ADS)

    Magee, Andrew D.; Verdon-Kidd, Danielle C.; Kiem, Anthony S.

    2015-04-01

    Tropical Cyclones (TCs) represent a significant natural hazard to the 15 island nations and 2.7 million inhabitants of the South Pacific, accounting for 76% of reported disasters in the region since 1950. This vast area, dominated by the coupled ocean-atmosphere interactions of the South Pacific fuels the highly variable nature of TCs (both spatially and temporally), leading to difficulties in planning for and responding to these extreme events. While it is well known that the El Niño/Southern Oscillation (ENSO) plays a significant role in modulating the background state on which TCs form, there are other large-scale climate drivers operating on annual timescales or longer within the South Pacific (e.g. ENSO Modoki and the Interdecadal Pacific Oscillation) and outside the Pacific Basin (e.g. the Indian Ocean Dipole and the Southern Annular Mode) that may also influence TC formation. In response to this issue, the impact of these large-scale climate drivers upon the spatial characteristics of tropical cyclogenesis is assessed for the South Pacific region (5o-35oS, 145oE-130oW) over a 67-year period (1945-2011). It is shown, that in addition to the impact of 'Pacific-centric' climate drivers, eastern Indian Ocean sea surface temperatures significantly impact the spatial characteristics of tropical cyclogenesis in the South Pacific. In particular, warming (cooling) in the eastern Indian Ocean is found to result in an eastward (westward) shift in the average location of tropical cyclogenesis in the South Pacific (up to 712km between extreme phases). One mechanism that may account for this east/west modulation of TC activity in the South Pacific is the propagation of warmer water from the Timor Sea through the Coral Sea to the Pacific, resulting in a strengthening of the Pacific Warm Pool and associated meteorological characteristics connected with tropical cyclogenesis. Understanding how other large-scale climate modes interact with Indian Ocean processes is important

  9. Integrin adhesion drives the emergent polarization of active cytoskeletal stresses to pattern cell delamination

    PubMed Central

    Meghana, C.; Ramdas, Nisha; Hameed, Feroz Meeran; Rao, Madan; Shivashankar, G. V.; Narasimha, Maithreyi

    2011-01-01

    Tissue patterning relies on cellular reorganization through the interplay between signaling pathways and mechanical stresses. Their integration and spatiotemporal coordination remain poorly understood. Here we investigate the mechanisms driving the dynamics of cell delamination, diversely deployed to extrude dead cells or specify distinct cell fates. We show that a local mechanical stimulus (subcellular laser perturbation) releases cellular prestress and triggers cell delamination in the amnioserosa during Drosophila dorsal closure, which, like spontaneous delamination, results in the rearrangement of nearest neighbors around the delaminating cell into a rosette. We demonstrate that a sequence of “emergent cytoskeletal polarities” in the nearest neighbors (directed myosin flows, lamellipodial growth, polarized actomyosin collars, microtubule asters), triggered by the mechanical stimulus and dependent on integrin adhesion, generate active stresses that drive delamination. We interpret these patterns in the language of active gels as asters formed by active force dipoles involving surface and body stresses generated by each cell and liken delamination to mechanical yielding that ensues when these stresses exceed a threshold. We suggest that differential contributions of adhesion, cytoskeletal, and external stresses must underlie differences in spatial pattern. PMID:21571643

  10. Physical activity patterns among South-Asian adults: a systematic review

    PubMed Central

    2013-01-01

    Physical activity (PA) has many beneficial physical and mental health effects. Physical inactivity is considered the fourth leading risk factor for global mortality. At present there are no systematic reviews on PA patterns among South Asian adults residing in the region. The present study aims to systematically evaluate studies on PA patterns in South Asian countries. A five-staged comprehensive search of the literature was conducted in Medline, Web of Science and SciVerse Scopus using keywords ‘Exercise’, ‘Walking’, ‘Physical activity’, ‘Inactivity’, ‘Physical Activity Questionnaire’, ‘International Physical Activity Questionnaire’, ‘IPAQ’, ‘Global Physical Activity Questionnaire’ and ‘GPAQ’, combined with individual country names. The search was restricted to English language articles conducted in humans and published before 31st December 2012. To obtain additional data a manual search of the reference lists of articles was performed. Data were also retrieved from the search of relevant web sites and online resources. The total number of hits obtained from the initial search was 1,771. The total number of research articles included in the present review is eleven (India-8, Sri Lanka-2, Pakistan-1). In addition, eleven country reports (Nepal-3, Bangladesh-2, India-2, Sri Lanka-2, Bhutan-1, Maldives-1) of World Health Organization STEPS survey from the South-Asian countries were retrieved online. In the research articles the overall prevalence of inactivity was as follows; India (18.5%-88.4%), Pakistan (60.1%) and Sri Lanka (11.0%-31.8%). STEPS survey reports were available from all countries except Pakistan. Overall in majority of STEPS surveys females were more inactive compared to males. Furthermore, leisure related inactivity was >75% in studies reporting inactivity in this domain and people were more active in transport domain when compared with the other domains. In conclusion, our results show that there is a wide

  11. Modeling the reflectance of CO2 frost with new optical constants: Application to Martian south polar cap spectra

    NASA Technical Reports Server (NTRS)

    Hansen, Gary B.; Martin, Terry Z.

    1993-01-01

    New measurements of the absorption coefficients of CO2 ice, in most of the spectral range 0.2 to 3.9 microns where absorption coefficients are below 1.5 per cm, have recently been made. Although these measurements are preliminary, they contain spectral detail not seen previously in the literature. Therefore, it is useful to combine these new data with older data from spectral regions of stronger absorption and reformulate models of the albedo or reflectance of CO2 frost. These models can then be adjusted in an attempt to match measurements of Martian polar deposits, such as the set of spectra returned by the IRS instrument on Mariner 7 (1969). The new absorption coefficients of CO2 ice were measured on several samples of 41-mm thickness at 150-155 K. A portion of the spectrum from 1.9 to 3.9 microns wavelength is shown in the form of imaginary coefficient of refraction ( = linear absorption x wavelength / 4 pi). The data above 3x10(exp -5) are obtained from, except for the absorption line at 3.32 micrometers, which is extrapolated in a way that is consistent with laboratory frost measurements, but the peak level is still highly uncertain. This new imagary coefficient, combined with the real coefficient, can be immediately applied to the models for hemispherical albedo, resulting in markedly different results from those in that study. The results for an infinite optical depth layer and solar incidence of 60 degrees are plotted for a range of mean particle radii from 0.03 to 3 mm.

  12. Polar Stratospheric Cloud evolution and chlorine activation measured by CALIPSO and MLS, and modelled by ATLAS

    NASA Astrophysics Data System (ADS)

    Nakajima, H.; Wohltmann, I.; Wegner, T.; Takeda, M.; Pitts, M. C.; Poole, L. R.; Lehmann, R.; Santee, M. L.; Rex, M.

    2015-08-01

    We examined observations of polar stratospheric clouds (PSCs) by CALIPSO and of HCl, ClO and HNO3 by MLS along air mass trajectories to investigate the dependence of the inferred PSC composition on the temperature history of the air parcels, and the dependence of the level of chlorine activation on PSC composition. Several case studies based on individual trajectories from the Arctic winter 2009/10 were conducted, with the trajectories chosen such that the first processing of the air mass by PSCs in this winter occurred on the trajectory. Transitions of PSC composition classes were observed to be highly dependent on the temperature history. In cases of a gradual temperature decrease, nitric acid trihydrate (NAT) and super-cooled ternary solution (STS) mixture clouds were observed. In cases of rapid temperature decrease, STS clouds were first observed, followed by NAT/STS mixture clouds. When temperatures dropped below the frost point, ice clouds formed, and then transformed into NAT/STS mixture clouds when temperature increased above the frost point. The threshold temperature for rapid chlorine activation on PSCs is approximately 4 K below the NAT existence temperature, TNAT. Furthermore, simulations of the ATLAS chemistry and transport box model along the trajectories were used to corroborate the measurements and show good agreement with the observations. Rapid chlorine activation was observed when an airmass encountered PSCs. The observed and modelled dependence of the rate of chlorine activation on the PSC composition class was small. Usually, chlorine activation was limited by the amount of available ClONO2. Where ClONO2 was not the limiting factor, a large dependence on temperature was evident.

  13. Implementation of the ART approach in South Africa: an activity report.

    PubMed

    Mickenautsch, S; Rudolph, M J

    2001-07-01

    The Atraumatic Restorative Treatment (ART) approach has been adopted in public dental services in South Africa as an appropriate and economical means to provide basic restorative care in communities where it was not possible before. The approach also offers a less-traumatic treatment concept for fearful patients and children in the private dental practice. In 2000, the Division of Community Dentistry, University of the Witwatersrand, implemented a training, research and service programme in the ART approach. The aim of these activities was the promotion of ART at various levels within the oral health care system in the Republic of South Africa. The objectives of the programme were to initiate and provide training of oral health workers in ART, to evaluate the outcome of training and service programmes and to disseminate results. This paper describes the Division's ART activities in 2000, regarding public, private and refugee health services. PMID:11575117

  14. Active Landslide Erosion of Mars' North Polar Cliffs: Current Rates, Causes, and Implications

    NASA Astrophysics Data System (ADS)

    Russell, P. S.; Byrne, S.; Pathare, A.

    2014-12-01

    While the North Polar Layered Deposits (NPLD) have long been considered Mars' best climate record, only recently have some of the processes governing the evolution of the NPLD to their current form been discovered and even directly observed. MOC revealed outcrops of an interbedded ice and dark-sand "basal unit" (BU) below steep NPLD scarps. Some bright markings on the BU were suggested to be talus deposits of mass-wasted NPLD ice, caused by undercutting via removal of easily erodible BU sand. In previous work with HiRISE images that confirmed the origin of these deposits, we: detailed their meter-scale morphology, constituent features, and variability; identified fractures of BU ice layers and NPLD scarps as additional mass-wasting facilitators; and, based on inter- and inter-annual monitoring, discovered that new deposits appear over time, thereby establishing mass wasting (of both BU and NPLD ice) as a currently active process. Here, we advance from qualitative descriptions of new, active processes to quantification of the rates at which they are occurring. From ~4 years of HiRISE observations, we cataloged the location, volume, source, and timing constraints of >160 landslide events along ~ 20 km of BU-NPLD scarp. Average rates are ~44 events/yr and ~2000 m3/yr, although 7 large events account for ~3/4 of the volume; this is a very geologically dynamic environment. BU events are more frequent and smaller than NPLD events, reflecting the relative thickness of ice source deposits but also perhaps differing proportions of two causal mechanisms: sand-removal undercutting and thermal-stress induced expansion, contraction, and fracturing. BU events prefer summer over spring; NPLD events strongly prefer fall-winter over spring-summer. We compare this observational data with 1) thermal stress models of the ice scarp to assess consistency in timing of activity, and 2) sublimation models of the ice scarp to assess the relative contributions to scarp retreat - our

  15. Active polarization stabilization in optical fibers suitable for quantum key distribution.

    PubMed

    Chen, Jie; Wu, Guang; Li, Yao; Wu, E; Zeng, Heping

    2007-12-24

    Polarization feedback control of single-photon pulses has been achieved in long-distance fibers for more than 10 hours, which facilitated "one-way" polarization-encoded quantum key distribution with long-term stabilities. Experimental test of polarization encoding in 75 km fibers demonstrated that the single-photon polarization transformation in long-distance fibers could be controlled to provide a typical QBER of (3.9+/-1.5)% within a long-term operation of 620 minutes. PMID:19551088

  16. Cathodoluminescence study of Mg activation in non-polar and semi-polar faces of undoped/Mg-doped GaN core-shell nanorods

    NASA Astrophysics Data System (ADS)

    Hortelano, V.; Martínez, O.; Cuscó, R.; Artús, L.; Jiménez, J.

    2016-03-01

    Spectrally and spatially resolved cathodoluminescence (CL) measurements were carried out at 80 K on undoped/Mg-doped GaN core-shell nanorods grown by selective area growth metalorganic vapor phase epitaxy in order to investigate locally the optical activity of the Mg dopants. A study of the luminescence emission distribution over the different regions of the nanorods is presented. We have investigated the CL fingerprints of the Mg incorporation into the non-polar lateral prismatic facets and the semi-polar facets of the pyramidal tips. The amount of Mg incorporation/activation was varied by using several Mg/Ga flow ratios and post-growth annealing treatment. For lower Mg/Ga flow ratios, the annealed nanorods clearly display a donor-acceptor pair band emission peaking at 3.26-3.27 eV and up to 4 LO phonon replicas, which can be considered as a reliable indicator of effective p-type Mg doping in the nanorod shell. For higher Mg/Ga flow ratios, a substantial enhancement of the yellow luminescence emission as well as several emission subbands are observed, which suggests an increase of disorder and the presence of defects as a consequence of the excess Mg doping.

  17. Axi-symmetric patterns of active polar filaments on spherical and composite surfaces

    NASA Astrophysics Data System (ADS)

    Srivastava, Pragya; Rao, Madan

    2014-03-01

    Experiments performed on Fission Yeast cells of cylindrical and spherical shapes, rod-shaped bacteria and reconstituted cylindrical liposomes suggest the influence of cell geometry on patterning of cortical actin. A theoretical model based on active hydrodynamic description of cortical actin that includes curvature-orientation coupling predicts spontaneous formation of acto-myosin rings, cables and nodes on cylindrical and spherical geometries [P. Srivastava et al, PRL 110, 168104(2013)]. Stability and dynamics of these patterns is also affected by the cellular shape and has been observed in experiments performed on Fission Yeast cells of spherical shape. Motivated by this, we study the stability and dynamics of axi-symmetric patterns of active polar filaments on the surfaces of spherical, saddle shaped and conical geometry and classify the stable steady state patterns on these surfaces. Based on the analysis of the fluorescence images of Myosin-II during ring slippage we propose a simple mechanical model for ring-sliding based on force balance and make quantitative comparison with the experiments performed on Fission Yeast cells. NSF Grant DMR-1004789 and Syracuse Soft Matter Program.

  18. Polar stratospheric cloud evolution and chlorine activation measured by CALIPSO and MLS, and modeled by ATLAS

    NASA Astrophysics Data System (ADS)

    Nakajima, Hideaki; Wohltmann, Ingo; Wegner, Tobias; Takeda, Masanori; Pitts, Michael C.; Poole, Lamont R.; Lehmann, Ralph; Santee, Michelle L.; Rex, Markus

    2016-03-01

    We examined observations of polar stratospheric clouds (PSCs) by CALIPSO, and of HCl and ClO by MLS along air mass trajectories, to investigate the dependence of the inferred PSC composition on the temperature history of the air parcels and the dependence of the level of chlorine activation on PSC composition. Several case studies based on individual trajectories from the Arctic winter 2009/2010 were conducted, with the trajectories chosen such that the first processing of the air mass by PSCs in this winter occurred on the trajectory. Transitions of PSC composition classes were observed to be highly dependent on the temperature history. In cases of a gradual temperature decrease, nitric acid trihydrate (NAT) and super-cooled ternary solution (STS) mixture clouds were observed. In cases of rapid temperature decrease, STS clouds were first observed, followed by NAT/STS mixture clouds. When temperatures dropped below the frost point, ice clouds formed and then transformed into NAT/STS mixture clouds when temperature increased above the frost point. The threshold temperature for rapid chlorine activation on PSCs is approximately 4 K below the NAT existence temperature, TNAT. Furthermore, simulations of the ATLAS chemistry and transport box model along the trajectories were used to corroborate the measurements and show good agreement with the observations. Rapid chlorine activation was observed when an air mass encountered PSCs. Usually, chlorine activation was limited by the amount of available ClONO2. Where ClONO2 was not the limiting factor, a large dependence on temperature was evident.

  19. Mapping the polarity and stimulus density requirements for T-cell activation

    NASA Astrophysics Data System (ADS)

    Wei, Xunbin; Krasieva, Tatiana B.; Zhang, Zhanxiang; Negulescu, Paul A.; Sun, Chung-Ho; Berns, Michael W.; Cahalan, Michael D.; Tromberg, Bruce J.

    1998-08-01

    T-cell contact with antigen-presenting cells (APC) initiates an activation cascade which includes an increase in T-cell intracellular calcium [(Ca2+)i] and leads to T-cell proliferation and differentiation. Although T-cell/APC physical contact is required for an immune response, little is known about the patterns of cellular interaction and their relation to activation. We have combined fluorescence spectroscopy and imaging with optical manipulation to investigate the contact requirements for T-cell activation, using optical tweezers to control the orientation of T- cell/APC pairs and fluorescence microscopy to measure the subsequent (Ca2+)i response, detected as an emission shift from the combination of fura-red and oregon- green, two cytoplasmic (Ca2+) indicators. APCs or beads coated with antibodies to the T-cell receptor (TCR) are trapped with a near-infrared titanium-sapphire laser and placed at different locations along the T-cell, which has a polarized appearance defined by the shape and direction of crawling (2-5 micrometers /min). T cells contacted with antigen- presenting cells or antibody-coated beads entered a dynamic and reproducible program in the first 10 - 20 mins, including (Ca2+)i increase, changes in shape and motility, engulfment, and stable contact. T cells presented with antigen at the leading edge had a higher probability of responding (85%) and a shorter latency of response (50 secs) than those contacting APCs or beads with their trailing end (APCs: 30%, 150 secs; beads: 6%, 300 secs). Alterations in antibody density, quantified by FACS analysis, and bead size were used to determine the spatial requirements for T cell activation and the minimum number of receptors which must be engaged in order to transmit a positive signal. Preliminary data show that T cell responses [response percentage, latency and (Ca2+)i pattern] depend on both antibody density and bead size.

  20. Activation of the Wnt/Planar Cell Polarity Pathway Is Required for Pericyte Recruitment during Pulmonary Angiogenesis

    PubMed Central

    Yuan, Ke; Orcholski, Mark E.; Panaroni, Cristina; Shuffle, Eric M.; Huang, Ngan F.; Jiang, Xinguo; Tian, Wen; Vladar, Eszter K.; Wang, Lingli; Nicolls, Mark R.; Wu, Joy Y.; de Jesus Perez, Vinicio A.

    2016-01-01

    Pericytes are perivascular cells localized to capillaries that promote vessel maturation, and their absence can contribute to vessel loss. Whether impaired endothelial–pericyte interaction contributes to small vessel loss in pulmonary arterial hypertension (PAH) is unclear. Using 3G5-specific, immunoglobulin G–coated magnetic beads, we isolated pericytes from the lungs of healthy subjects and PAH patients, followed by lineage validation. PAH pericytes seeded with healthy pulmonary microvascular endothelial cells failed to associate with endothelial tubes, resulting in smaller vascular networks compared to those with healthy pericytes. After the demonstration of abnormal polarization toward endothelium via live-imaging and wound-healing studies, we screened PAH pericytes for abnormalities in the Wnt/planar cell polarity (PCP) pathway, which has been shown to regulate cell motility and polarity in the pulmonary vasculature. PAH pericytes had reduced expression of frizzled 7 (Fzd7) and cdc42, genes crucial for Wnt/PCP activation. With simultaneous knockdown of Fzd7 and cdc42 in healthy pericytes in vitro and in a murine model of angiogenesis, motility and polarization toward pulmonary microvascular endothelial cells were reduced, whereas with restoration of both genes in PAH pericytes, endothelial–pericyte association was improved, with larger vascular networks. These studies suggest that the motility and polarity of pericytes during pulmonary angiogenesis are regulated by Wnt/PCP activation, which can be targeted to prevent vessel loss in PAH. PMID:25447046

  1. On causes of the low seismic activity in the Earth's polar latitudes

    NASA Astrophysics Data System (ADS)

    Levin, Boris; Sasorova, Elena; Domanski, Andrei

    2016-04-01

    The irregularity of distribution of seismic activity in the world was observed at the beginning of the era of instrumental seismology (B. Gutenberg, C. Richter, K. Kasahara). At the same time, the global nature of the symmetry of this effect has been established only in this millennium, with the participation of authors (Levin B.W., Sasorova E.V., 2010). Analysis of the global earthquake catalogs showed that almost all seismic events over the last century occurred within a limited latitudinal band contained between the 65 N and 65 S. The seismic activity in the polar regions of the planet was manifested very weakly. The reasons for such features were found by following the analysis of the characteristics associated with the theory of the figure of the Earth. In the works of the French mathematician A. Veronne (1912) was the first to introduce the concept of "critical" latitudes (φ1 = ±35°15' 22″) wherein the radius of the ellipsoid of revolution is equal to the radius of the sphere of the same volume. Variation of the radius vector of the ellipsoid at this latitude is equal to zero. There is the boundary between the compressed areas of the polar zones and equatorial region, where the rocks of the Earth are dominated by tensile forces. Analysis of the specific characteristics of the gravity force distribution on the surface of the ellipsoid has shown that there is a distribution of the same character with a singular point at latitude φ2 = ±61° 52' 12″. In case of variations in the angular velocity of the planet's rotation the variation of gravity force at the latitude φ2 is negligible, compared with variations of gravity force on the equator and pole, which exceed the previous value by 3-4 orders. Attempted analysis of the model of the ellipsoid of revolution in the theory of axisymmetric elastic shells has allowed to establish that in the elastic shell of the planet must occur meridional and ring forces. The theory shows that when the flatness (or polar

  2. Evidence for exposed water ice in the Moon's south polar regions from Lunar Reconnaissance Orbiter ultraviolet albedo and temperature measurements

    NASA Astrophysics Data System (ADS)

    Hayne, Paul O.; Hendrix, Amanda; Sefton-Nash, Elliot; Siegler, Matthew A.; Lucey, Paul G.; Retherford, Kurt D.; Williams, Jean-Pierre; Greenhagen, Benjamin T.; Paige, David A.

    2015-07-01

    We utilize surface temperature measurements and ultraviolet albedo spectra from the Lunar Reconnaissance Orbiter to test the hypothesis that exposed water frost exists within the Moon's shadowed polar craters, and that temperature controls its concentration and spatial distribution. For locations with annual maximum temperatures Tmax greater than the H2O sublimation temperature of ∼110 K, we find no evidence for exposed water frost, based on the LAMP UV spectra. However, we observe a strong change in spectral behavior at locations perennially below ∼110 K, consistent with cold-trapped ice on the surface. In addition to the temperature association, spectral evidence for water frost comes from the following spectral features: (a) decreasing Lyman-α albedo, (b) decreasing "on-band" (129.57-155.57 nm) albedo, and (c) increasing "off-band" (155.57-189.57 nm) albedo. All of these features are consistent with the UV spectrum of water ice, and are expected for water ice layers >∼100 nm in thickness. High regolith porosity, which would darken the surface at all wavelengths, cannot alone explain the observed spectral changes at low temperatures. Given the observed LAMP off-band/on-band albedo ratios at a spatial scale of 250 m, the range of water ice concentrations within the cold traps with Tmax < 110 K is ∼0.1-2.0% by mass, if the ice is intimately mixed with dry regolith. If pure water ice is exposed instead, then up to ∼10% of the surface area on the 250-m scale of the measurements may be ice-covered. The observed distribution of exposed water ice is highly heterogeneous, with some cold traps <110 K having little to no apparent water frost, and others with a significant amount of water frost. As noted by Gladstone et al. (Gladstone, G.R. et al. [2012]. J. Geophys. Res.: Planets 117(E12)), this heterogeneity may be a consequence of the fact that the net supply rate of H2O molecules to the lunar poles is very similar to the net destruction rate within the cold

  3. A model for promoting physical activity among rural South African adolescent girls

    PubMed Central

    Kinsman, John; Norris, Shane A.; Kahn, Kathleen; Twine, Rhian; Riggle, Kari; Edin, Kerstin; Mathebula, Jennifer; Ngobeni, Sizzy; Monareng, Nester; Micklesfield, Lisa K.

    2015-01-01

    Background In South Africa, the expanding epidemic of non-communicable diseases is partly fuelled by high levels of physical inactivity and sedentary behaviour. Women especially are at high risk, and interventions promoting physical activity are urgently needed for girls in their adolescence, as this is the time when many girls adopt unhealthy lifestyles. Objective This qualitative study aimed to identify and describe facilitating factors and barriers that are associated with physical activity among adolescent girls in rural, north-eastern South Africa and, based on these, to develop a model for promoting leisure-time physical activity within this population. Design The study was conducted in and around three secondary schools. Six focus group discussions were conducted with adolescent girls from the schools, and seven qualitative interviews were held with sports teachers and youth leaders. The data were subjected to thematic analysis. Results Seven thematic areas were identified, each of which was associated with the girls’ self-reported levels of physical activity. The thematic areas are 1) poverty, 2) body image ideals, 3) gender, 4) parents and home life, 5) demographic factors, 6) perceived health effects of physical activity, and 7) human and infrastructural resources. More barriers to physical activity were reported than facilitating factors. Conclusions Analysis of the barriers found in the different themes indicated potential remedial actions that could be taken, and these were synthesised into a model for promoting physical activity among South African adolescent girls in resource-poor environments. The model presents a series of action points, seen both from the ‘supply-side’ perspective (such as the provision of resources and training for the individuals, schools, and organisations which facilitate the activities) and from the ‘demand-side’ perspective (such as the development of empowering messages about body image for teenage girls, and

  4. COMPUTATIONAL CHEMISTRY METHOD FOR PREDICTING VAPOR PRESSURES AND ACTIVITY COEFFICIENTS OF POLAR ORGANIC OXYGENATES IN PM2.5

    EPA Science Inventory

    Parameterizations of interactions of polar multifunctional organic oxygenates in PM2.5 must be included in aerosol chemistry models for evaluating control strategies for reducing ambient concentrations of PM2.5 compounds. Vapor pressures and activity coefficients of these compo...

  5. Polar Landforms

    NASA Technical Reports Server (NTRS)

    2005-01-01

    10 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows eroded remnants of carbon dioxide ice in the south polar residual cap of Mars. The scarps that outline each small mesa have retreated about 3 meters (10 feet) per Mars year since MGS began orbiting the red planet in 1997.

    Location near: 87.0oS, 31.9oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  6. Student activity: verification on Malus's law of polarization at low cost

    NASA Astrophysics Data System (ADS)

    Kadri, Shahrul; Chong, David; Wei, Bor; Jaafar, Rosly

    2014-07-01

    Polarization is the property of electromagnetic waves that describes the orientation of their field oscillation. Students face hard problem to visualize the important of the polarization in daily life. In common practice, students are taught with the help of sketch diagram. In this project, we describe both quantitative and qualitative ways of experimenting polarization using very low cost and easily available material: polarized sunglasses, PVC tubes, light-dependent resistors, LED, etc. With this set, the experiment of the Malus's Law verification of light polarization can be done without the need of expensive optical detector for quantitative measurement. Students will develop their own simple optical sensor if the set is developed as a project. This set of experiment integrates the concept of basic electricity. Therefore, students acquires the practical knowledge of electricity and optics in the easy way.

  7. Constraining the activity of waves on Titan's polar lakes and seas

    NASA Astrophysics Data System (ADS)

    Soderblom, Jason M.; Barnes, Jason W.; Brown, Robert H.; Soderblom, Laurence A.; Sotin, Christophe; Clark, Roger N.; Le Mouélic, Stéphane; Rodriguez, Sebastien; Baines, Kevin H.; Buratti, Bonnie J.; Nicholson, Philip D.

    2015-04-01

    Saturn's moon Titan has an active hydrological cycle in which the primary working fluid, methane, is thought to transport between poles on seasonal timescales, driving much of the observed meteorology. Surface winds play a critical role in determining the evaporation rates of methane from Titan's polar lakes and seas. Observational constraints on these winds, however, are limited. Aeolian landforms, in particular sand dunes, characterize Titan's mid latitudes, providing evidence that winds at these latitudes have, at least in the geologically recent past, exceeded the threshold for saltation (which recent work has shown might be higher than previously predicted). The shoreline morphology of Titan's lone large southern lake, Ontario Lacus, has been interpreted as evidence for wave erosion. Evidence for wave activity on Titan's lakes and seas, however, has been notably absent in Cassini observations. Explanations that have been forwarded to explain the lack of waves include the possibility that the liquids that comprise Titan's lakes and seas are highly viscous or that seasonal winds have not exceeded the threshold for capillary wave formation (Hayes et al., 2012, Icarus 225). Only recently have Cassini Visual and Infrared Mapping Spectrometer (VIMS) observations provided the first evidence of wave activity on Titan, in the north as Titan progresses towards northern summer (Barnes et al., 2014, Planetary Science 3). Herein, we use Cassini VIMS observations of the specular reflection of sunlight from Titan's lakes to infer the presence or absence of waves on Titan. We investigate observations acquired between 2012 and 2014. We find evidence for the presence of waves on Kraken Mare during a number of flybys, while specular reflections from the smaller Jingpo Lacus are more consistent with a smooth lake surface.

  8. Changing patterns of the long-term activity of the intermediate polar V1223 Sgr

    NASA Astrophysics Data System (ADS)

    Šimon, Vojtěch

    2014-11-01

    High and low states represent a large variety of features in the optical activity of some types of cataclysmic variables. Here, we examine them in the intermediate polar V1223 Sgr. We use the photographic observations from the Bamberg Observatory and from Garnavich and Szkody, and the CCD ASAS-3 and NSVS data. One plate or CCD image was usually obtained per night. These data span 78 years. We use the histograms of brightness to set the separation between the high and low states in V1223 Sgr at the level of 13.9 mag(B). The profile of this statistical distribution is dominated by a broad bump with the peak-to-peak amplitude of more than 1 mag(B). This is the result of co-adding various episodes of the high states, sometimes with the brightness varying on a timescale of months even during a single episode. The high state is not any uniquely defined level of brightness. Groups of the low states represent tails from such bumps rather than forming specific levels of brightness. The fuzzy boundaries of the bright side of the statistical distributions of brightness show that the system cannot find equilibrium of the mass transfer even in the high state. We show that V1223 Sgr underwent a large change of its high/low state activity; we ascribe it to the changes of the stellar activity of the donor. The episodes of the low states with mutually similar depth and profile were observed to recur with a cycle of 1092 days in the data mapping the years from 1999 to 2009; this behavior was discordant with the typical recurrence times present before. In our scenario, this cycle is driven by the changing aspect of some structure (e.g. a sequence of star spots migrating across the L1 point) on the donor. Because of the differential rotation of the donor, this configuration cyclically influences the mass flow to the accretion disk.

  9. Solubilization of active ingredients of different polarity in Pluronic® micellar solutions - Correlations between solubilizate polarity and solubilization site.

    PubMed

    Nguyen-Kim, Viet; Prévost, Sylvain; Seidel, Karsten; Maier, Walter; Marguerre, Ann-Kathrin; Oetter, Günter; Tadros, Tharwat; Gradzielski, Michael

    2016-09-01

    The solubilization of two pharmaceutically active ingredients (AI) with significantly different water solubility, namely carbamazepine and fenofibrate (solubility of 150ppm and 10ppm, respectively), has been investigated using a series of Pluronics® (Poloxamers) containing different ethylene oxide and propylene oxide (EO/PO) units in the molecule. The results show largely enhanced solubilization of fenofibrate by Pluronic® micelles that increases with the PPO chain length provided the temperature is above the critical micelle temperature (cmt). In contrast the more water-soluble carbamazepine only shows a moderate increase in solubilization upon addition of Pluronics®. Small angle neutron scattering (SANS) and pulsed field gradient (PFG) NMR experiments show that the solubilization of fenofibrate occurs in the core of the micelles, whereas carbamazepine shows no direct association with the micelles. These clearly different solubilization mechanisms for the two AIs were confirmed by Nuclear Overhauser Enhancement Spectroscopy (NOESY) experiments, which show that fenofibrate interacts only with the PPO core of the micelle, whereas carbamazepine interacts with both PPO and PEO similarly. Accordingly, the large enhancement of the solubilization of fenofibrate is related to the fact that it is solubilized within the PPO core of the Pluronic® micelles, while the much more moderate increase of carbamazepine solubility is attributed to the change of solvent quality due to the presence of the amphiphilic copolymer and the interaction with the EO and PO units in solution. PMID:27244594

  10. Effects of polarization induced by non-weak electric fields on the excitability of elongated neurons with active dendrites.

    PubMed

    Reznik, Robert I; Barreto, Ernest; Sander, Evelyn; So, Paul

    2016-02-01

    An externally-applied electric field can polarize a neuron, especially a neuron with elongated dendrites, and thus modify its excitability. Here we use a computational model to examine, predict, and explain these effects. We use a two-compartment Pinsky-Rinzel model neuron polarized by an electric potential difference imposed between its compartments, and we apply an injected ramp current. We vary three model parameters: the magnitude of the applied potential difference, the extracellular potassium concentration, and the rate of current injection. A study of the Time-To-First-Spike (TTFS) as a function of polarization leads to the identification of three regions of polarization strength that have different effects. In the weak region, the TTFS increases linearly with polarization. In the intermediate region, the TTFS increases either sub- or super-linearly, depending on the current injection rate and the extracellular potassium concentration. In the strong region, the TTFS decreases. Our results in the weak and strong region are consistent with experimental observations, and in the intermediate region, we predict novel effects that depend on experimentally-accessible parameters. We find that active channels in the dendrite play a key role in these effects. Our qualitative results were found to be robust over a wide range of inter-compartment conductances and the ratio of somatic to dendritic membrane areas. In addition, we discuss preliminary results where synaptic inputs replace the ramp injection protocol. The insights and conclusions were found to extend from our polarized PR model to a polarized PR model with I h dendritic currents. Finally, we discuss the degree to which our results may be generalized. PMID:26560333

  11. Objectively determined habitual physical activity in South African adolescents: the PAHL study

    PubMed Central

    2014-01-01

    Background There is limited data on objectively determined habitual physical activity (PA) in 16-year old South African adolescents. The purpose of this study was to objectively determine the habitual PA of adolescents from the North West Province of South Africa by race and gender. Methods Adolescents (137 girls, 89 boys) from the ongoing Physical Activity and Health Longitudinal Study (PAHL study), participated in the present study. Habitual PA was objectively recorded by means of the Actiheart® over a period of 7 days. Time spent in moderate-to-vigorous intensity physical activity (MVPA) was assessed. Results Average MVPA for the study sample was 50.9 ± 40.3 minutes/day. Girls were significantly more active than boys expending more time in MVPA (61.13 ± 52.2 minutes/day; p < 0.05) than boys (35.0 ± 32.9 minutes/day). Although white adolescents spent more time in MVPA than black adolescents, there was no significant difference in MVPA between black (47.87 ± 39.6 minutes/day; p = 0.58) and white adolescents (59.5 ± 41.8 minutes/day). Conclusion Physical activity varies by both gender and race in adolescents from the North West Province of South Africa. Objectively determined data from our study indicates that girls habitually spend more time in MVPA per day than boys, and that white adolescents habitually engage in more MVPA than black adolescents. Seeing as the average MVPA per day for the entire study sample falls below the recommended daily average of 60minutes/day, adolescents should be the foremost targets of interventions aimed at enhancing habitual PA. PMID:24885503

  12. Polarization of PI3K Activity Initiated by Ooplasmic Segregation Guides Nuclear Migration in the Mesendoderm.

    PubMed

    Takatori, Naohito; Oonuma, Kouhei; Nishida, Hiroki; Saiga, Hidetoshi

    2015-11-01

    Asymmetric localization of RNA is a widely observed mechanism of cell polarization. Using embryos of the ascidian, Halocynthia roretzi, we previously showed that mesoderm and endoderm fates are separated by localization of mRNA encoding a transcription factor, Not, to the future mesoderm-side cytoplasm of the mesendoderm cell through asymmetric positioning of the nucleus. Here, we investigated the mechanism that defines the direction of the nuclear migration. We show that localization of PtdIns(3,4,5)P3 to the future mesoderm region determines the direction of nuclear migration. Localization of PtdIns(3,4,5)P3 was dependent on the localization of PI3Kα to the future mesoderm region. PI3Kα was first localized at the 1-cell stage by the ooplasmic movement. Activity of localized PI3Kα at the 4-cell stage was required for the localization of PI3Kα up to the nuclear migration. Our results provide the scaffold for understanding the chain of causality leading to the separation of germ layer fates. PMID:26555053

  13. Functional demonstration of Na+-K+-2Cl- cotransporter activity in isolated, polarized choroid plexus cells.

    PubMed

    Wu, Q; Delpire, E; Hebert, S C; Strange, K

    1998-12-01

    The function of the apical Na+-K+-2Cl- cotransporter in mammalian choroid plexus (CP) is uncertain and controversial. To investigate cotransporter function, we developed a novel dissociated rat CP cell preparation in which single, isolated cells maintain normal polarized morphology. Immunofluorescence demonstrated that in isolated cells the Na+-K+-ATPase, Na+-K+-2Cl- cotransporter, and aquaporin 1 water channel remained localized to the brush border, whereas the Cl-/HCO-3 (anion) exchanger type 2 was confined to the basolateral membrane. We utilized video-enhanced microscopy and cell volume measurement techniques to investigate cotransporter function. Application of 100 microM bumetanide caused CP cells to shrink rapidly. Elevation of extracellular K+ from 3 to 6 or 25 mM caused CP cells to swell 18 and 33%, respectively. Swelling was blocked completely by Na+ removal or by addition of 100 microM bumetanide. Exposure of CP cells to 5 mM BaCl2 induced rapid swelling that was inhibited by 100 microM bumetanide. We conclude that the CP cotransporter is constitutively active and propose that it functions in series with Ba2+-sensitive K+ channels to reabsorb K+ from cerebrospinal fluid to blood. PMID:9843718

  14. A polyalanine peptide derived from polar fish with anti-infectious activities

    NASA Astrophysics Data System (ADS)

    Cardoso, Marlon H.; Ribeiro, Suzana M.; Nolasco, Diego O.; de La Fuente-Núñez, César; Felício, Mário R.; Gonçalves, Sónia; Matos, Carolina O.; Liao, Luciano M.; Santos, Nuno C.; Hancock, Robert E. W.; Franco, Octávio L.; Migliolo, Ludovico

    2016-02-01

    Due to the growing concern about antibiotic-resistant microbial infections, increasing support has been given to new drug discovery programs. A promising alternative to counter bacterial infections includes the antimicrobial peptides (AMPs), which have emerged as model molecules for rational design strategies. Here we focused on the study of Pa-MAP 1.9, a rationally designed AMP derived from the polar fish Pleuronectes americanus. Pa-MAP 1.9 was active against Gram-negative planktonic bacteria and biofilms, without being cytotoxic to mammalian cells. By using AFM, leakage assays, CD spectroscopy and in silico tools, we found that Pa-MAP 1.9 may be acting both on intracellular targets and on the bacterial surface, also being more efficient at interacting with anionic LUVs mimicking Gram-negative bacterial surface, where this peptide adopts α-helical conformations, than cholesterol-enriched LUVs mimicking mammalian cells. Thus, as bacteria present varied physiological features that favor antibiotic-resistance, Pa-MAP 1.9 could be a promising candidate in the development of tools against infections caused by pathogenic bacteria.

  15. Auxin efflux carrier activity and auxin accumulation regulate cell division and polarity in tobacco cells.

    PubMed

    Petrásek, Jan; Elckner, Miroslav; Morris, David A; Zazímalová, Eva

    2002-12-01

    Division and growth of most types of in vitro-cultured plant cells require an external source of auxin. In such cultures, the ratio of external to internal auxin concentration is crucial for the regulation of the phases of the standard growth cycle. In this report the internal concentration of auxin in suspension-cultured cells of Nicotiana tabacum L., strain VBI-0, was manipulated either (i) by increasing 10-fold the normal concentration of 1-naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid in the external medium; or (ii) by addition 1-N-naphthylphthalamic acid (NPA; an inhibitor of auxin efflux and of auxin efflux carrier traffic). Both treatments delayed the onset of cell division for 6-7 days without loss of cell viability. In both cases, cell division activity subsequently resumed coincident with a reduction in the ability of cells to accumulate [(3)H]NAA from an external medium. Following renewed cell division, a significant proportion of the NPA-treated cells but not those grown at high auxin concentration, exhibited changes in the orientation of new cell divisions and loss of polarity. We conclude that cell division, but not cell elongation, is prevented when the internal auxin concentration rises above a critical threshold value and that the directed traffic of auxin efflux carriers to the plasma membrane may regulate the orientation of cell divisions. PMID:12447544

  16. A polyalanine peptide derived from polar fish with anti-infectious activities

    PubMed Central

    Cardoso, Marlon H.; Ribeiro, Suzana M.; Nolasco, Diego O.; de la Fuente-Núñez, César; Felício, Mário R.; Gonçalves, Sónia; Matos, Carolina O.; Liao, Luciano M.; Santos, Nuno C.; Hancock, Robert E. W.; Franco, Octávio L.; Migliolo, Ludovico

    2016-01-01

    Due to the growing concern about antibiotic-resistant microbial infections, increasing support has been given to new drug discovery programs. A promising alternative to counter bacterial infections includes the antimicrobial peptides (AMPs), which have emerged as model molecules for rational design strategies. Here we focused on the study of Pa-MAP 1.9, a rationally designed AMP derived from the polar fish Pleuronectes americanus. Pa-MAP 1.9 was active against Gram-negative planktonic bacteria and biofilms, without being cytotoxic to mammalian cells. By using AFM, leakage assays, CD spectroscopy and in silico tools, we found that Pa-MAP 1.9 may be acting both on intracellular targets and on the bacterial surface, also being more efficient at interacting with anionic LUVs mimicking Gram-negative bacterial surface, where this peptide adopts α-helical conformations, than cholesterol-enriched LUVs mimicking mammalian cells. Thus, as bacteria present varied physiological features that favor antibiotic-resistance, Pa-MAP 1.9 could be a promising candidate in the development of tools against infections caused by pathogenic bacteria. PMID:26916401

  17. The Effects of Solvent Polarity on Hypoglycemic and Hypolipidemic Activities of Securigera Securidaca (L.) Seeds.

    PubMed

    Ahmadi, A; Khalili, M; Margedari, Sh; Nahri-Niknafs, B

    2016-03-01

    The search for indigenous natural antidiabetic and antilipidemec agents is still ongoing. Medicinal plants are widely used for this purpose. These herbs are very rich sources of bioactive compounds as flavonoids, polyphenols, tannins, alkaloids which have been reported as effective role to reduce blood glucose and lipid levels. Securigera securidaca seed is reputed in folk medicine for their value as antidiabetic and antilipidemec drugs. In this research, the effect of solvent polarity in bioactive extraction contents of this plant was evaluated by GC-MS analysis. Then antidiabetic and antilipidemic activies of different extracts were investigated in streptozotocine-induced diabetic rats and compared to glibenclamide as known chemical drug for diabetes.The results indicated that, carbon tetrachloride extract of Securigera securidaca seeds showed the best and significant hypoglycemic and hypolipidemic activities compared to other extracts because of its more sterols and fatty acids content with beta cells protecting effect from high glucose-induced apoptosis and also increasing in insulin level and sensitivity. PMID:26125283

  18. In vivo antileishmanial activity and chemical profile of polar extract from Selaginella sellowii

    PubMed Central

    Queiroz, Dayane Priscilla de Souza; Carollo, Carlos Alexandre; Kadri, Mônica Cristina Toffoli; Rizk, Yasmin Silva; de Araujo, Vanessa Carneiro Pereira; Monteiro, Paulo Eduardo de Oliveira; Rodrigues, Patrik Oening; Oshiro, Elisa Teruya; Matos, Maria de Fátima Cepa; de Arruda, Carla Cardozo Pinto

    2016-01-01

    The polar hydroethanolic extract from Selaginella sellowii(SSPHE) has been previously proven active on intracellular amastigotes (in vitro test) and now was tested on hamsters infected with Leishmania (Leishmania) amazonensis (in vivo test). SSPHE suppressed a 100% of the parasite load in the infection site and draining lymph nodes at an intralesional dose of 50 mg/kg/day × 5, which was similar to the results observed in hamsters treated with N-methylglucamine antimonate (Sb) (28 mg/Kg/day × 5). When orally administered, SSPHE (50 mg/kg/day × 20) suppressed 99.2% of the parasite load in infected footpads, while Sb suppressed 98.5%. SSPHE also enhanced the release of nitric oxide through the intralesional route in comparison to Sb. The chemical fingerprint of SSPHE by high-performance liquid chromatography with diode-array detection and tandem mass spectrometry showed the presence of biflavonoids and high molecular weight phenylpropanoid glycosides. These compounds may have a synergistic action in vivo. Histopathological study revealed that the intralesional treatment with SSPHE induced an intense inflammatory infiltrate, composed mainly of mononuclear cells. The present findings reinforce the potential of this natural product as a source of future drug candidates for American cutaneous leishmaniasis. PMID:26910353

  19. Active Upper-atmosphere Chemistry and Dynamics from Polar Circulation Reversal on Titan

    NASA Technical Reports Server (NTRS)

    Teanby, Nicholas A.; Irwin, Patrick Gerard Joseph; Nixon, Conor A.; DeKok, Remco; Vinatier, Sandrine; Coustenis, Athena; Sefton-Nash, Elliot; Calcutt, Simon B.; Flasar, Michael F.

    2012-01-01

    Saturn's moon Titan has a nitrogen atmosphere comparable to Earth's, with a surface pressure of 1.4 bar. Numerical models reproduce the tropospheric conditions very well but have trouble explaining the observed middle-atmosphere temperatures, composition and winds. The top of the middle-atmosphere circulation has been thought to lie at an altitude of 450 to 500 kilometres, where there is a layer of haze that appears to be separated from the main haze deck. This 'detached' haze was previously explained as being due to the colocation of peak haze production and the limit of dynamical transport by the circulation's upper branch. Herewe report a build-up of trace gases over the south pole approximately two years after observing the 2009 post-equinox circulation reversal, from which we conclude that middle-atmosphere circulation must extend to an altitude of at least 600 kilometres. The primary drivers of this circulation are summer-hemisphere heating of haze by absorption of solar radiation and winter-hemisphere cooling due to infrared emission by haze and trace gases; our results therefore imply that these effects are important well into the thermosphere (altitudes higher than 500 kilometres). This requires both active upper-atmosphere chemistry, consistent with the detection of high-complexity molecules and ions at altitudes greater than 950 kilometres, and an alternative explanation for the detached haze, such as a transition in haze particle growth from monomers to fractal structures.

  20. Induced polarization and self-potential geophysical signature of bacterial activity in porous media (Invited)

    NASA Astrophysics Data System (ADS)

    Revil, A.

    2013-12-01

    The first part of the presentation will be dedicated to the spectral induced polarization signature of bacteria in porous media. We developed a quantitative model to investigate frequency-domain induced polarization response of suspensions of bacteria and bacteria growth in porous media. Induced polarization of bacteria (alpha-polarization) is related to the properties of the electrical double layer of the bacteria. Surface conductivity and alpha-polarization are due to the Stern layer of counterions occurring in a brush of polymers coating the surface of the bacteria. These phenomena can be related to the cation exchange capacity of the bacteria. The mobility of the counterions in this Stern layer is found to be very small (4.7×10-10 m2s-1 V-1 at 25°C). This implies a very low relaxation frequency for the alpha-polarization of the bacteria cells (typically around 0.1 to 5 Hertz) in agreement with experimental observations. This new model can be coupled to reactive transport modeling codes in which the evolution of bacterial populations are usually described by Monod kinetics. We show that the growth rate and endogenous decay coefficients of bacteria in a porous sand can be inferred non-intrusively from time lapse frequency-domain induced polarization data. The second part of the presentation will concern the biogeobattery mechanism showing new data, the concept of transient biogeobattery and the influence of the concentration of the electron acceptors in the process.

  1. RoboPol: optical polarization-plane rotations and flaring activity in blazars

    NASA Astrophysics Data System (ADS)

    Blinov, D.; Pavlidou, V.; Papadakis, I. E.; Hovatta, T.; Pearson, T. J.; Liodakis, I.; Panopoulou, G. V.; Angelakis, E.; Baloković, M.; Das, H.; Khodade, P.; Kiehlmann, S.; King, O. G.; Kus, A.; Kylafis, N.; Mahabal, A.; Marecki, A.; Modi, D.; Myserlis, I.; Paleologou, E.; Papamastorakis, I.; Pazderska, B.; Pazderski, E.; Rajarshi, C.; Ramaprakash, A.; Readhead, A. C. S.; Reig, P.; Tassis, K.; Zensus, J. A.

    2016-04-01

    We present measurements of rotations of the optical polarization of blazars during the second year of operation of RoboPol, a monitoring programme of an unbiased sample of gamma-ray bright blazars specially designed for effective detection of such events, and we analyse the large set of rotation events discovered in two years of observation. We investigate patterns of variability in the polarization parameters and total flux density during the rotation events and compare them to the behaviour in a non-rotating state. We have searched for possible correlations between average parameters of the polarization-plane rotations and average parameters of polarization, with the following results: (1) there is no statistical association of the rotations with contemporaneous optical flares; (2) the average fractional polarization during the rotations tends to be lower than that in a non-rotating state; (3) the average fractional polarization during rotations is correlated with the rotation rate of the polarization plane in the jet rest frame; (4) it is likely that distributions of amplitudes and durations of the rotations have physical upper bounds, so arbitrarily long rotations are not realized in nature.

  2. Establishing a definition of polar bear (Ursus maritimus) health: a guide to research and management activities.

    PubMed

    Patyk, Kelly A; Duncan, Colleen; Nol, Pauline; Sonne, Christian; Laidre, Kristin; Obbard, Martyn; Wiig, Øystein; Aars, Jon; Regehr, Eric; Gustafson, Lori L; Atwood, Todd

    2015-05-01

    The meaning of health for wildlife and perspectives on how to assess and measure health, are not well characterized. For wildlife at risk, such as some polar bear (Ursus maritimus) subpopulations, establishing comprehensive monitoring programs that include health status is an emerging need. Environmental changes, especially loss of sea ice habitat, have raised concern about polar bear health. Effective and consistent monitoring of polar bear health requires an unambiguous definition of health. We used the Delphi method of soliciting and interpreting expert knowledge to propose a working definition of polar bear health and to identify current concerns regarding health, challenges in measuring health, and important metrics for monitoring health. The expert opinion elicited through the exercise agreed that polar bear health is defined by characteristics and knowledge at the individual, population, and ecosystem level. The most important threats identified were in decreasing order: climate change, increased nutritional stress, chronic physiological stress, harvest management, increased exposure to contaminants, increased frequency of human interaction, diseases and parasites, and increased exposure to competitors. Fifteen metrics were identified to monitor polar bear health. Of these, indicators of body condition, disease and parasite exposure, contaminant exposure, and reproductive success were ranked as most important. We suggest that a cumulative effects approach to research and monitoring will improve the ability to assess the biological, ecological, and social determinants of polar bear health and provide measurable objectives for conservation goals and priorities and to evaluate progress. PMID:25679818

  3. Establishing a definition of polar bear (Ursus maritimus) health: A guide to research and management activities

    USGS Publications Warehouse

    Patyk, Kelly A.; Duncan, Colleen G.; Nol, Pauline; Sonne, C.; Laidre, Kristin L.; Obbard, Martyn E.; Wiig, Øystein; Aars, Jon; Regehr, Eric V.; Gustafson, L.; Atwood, Todd C.

    2015-01-01

    The meaning of health for wildlife and perspectives on how to assess and measure health, are not well characterized. For wildlife at risk, such as some polar bear (Ursus maritimus) subpopulations, establishing comprehensive monitoring programs that include health status is an emerging need. Environmental changes, especially loss of sea ice habitat, have raised concern about polar bear health. Effective and consistent monitoring of polar bear health requires an unambiguous definition of health. We used the Delphi method of soliciting and interpreting expert knowledge to propose a working definition of polar bear health and to identify current concerns regarding health, challenges in measuring health, and important metrics for monitoring health. The expert opinion elicited through the exercise agreed that polar bear health is defined by characteristics and knowledge at the individual, population, and ecosystem level. The most important threats identified were in decreasing order: climate change, increased nutritional stress, chronic physiological stress, harvest management, increased exposure to contaminants, increased frequency of human interaction, diseases and parasites, and increased exposure to competitors. Fifteen metrics were identified to monitor polar bear health. Of these, indicators of body condition, disease and parasite exposure, contaminant exposure, and reproductive success were ranked as most important. We suggest that a cumulative effects approach to research and monitoring will improve the ability to assess the biological, ecological, and social determinants of polar bear health and provide measurable objectives for conservation goals and priorities and to evaluate progress.

  4. Vibrio cholerae porin OmpU mediates M1-polarization of macrophages/monocytes via TLR1/TLR2 activation.

    PubMed

    Khan, Junaid; Sharma, Praveen K; Mukhopadhaya, Arunika

    2015-11-01

    Polarization of the monocytes and macrophages toward the M1 and M2 states is important for hosts' defense against the pathogens. Moreover, it plays a crucial role to resolve the overwhelming inflammatory responses that can be harmful to the host. Polarization of macrophages/monocytes can be induced by pathogen-associated molecular patterns (PAMPs). PAMP-mediated monocyte/macrophage polarization is important during the infection, as pathogen can suppress host immune system by altering the polarization status of the macrophages/monocytes. OmpU, an outer membrane porin protein of Vibrio cholerae, possesses the ability to induce pro-inflammatory responses in monocytes/macrophages. It is also able to down-regulate the LPS-mediated activation of the monocytes/macrophages. Such observation leads us to believe that OmpU may induce a state that can be called as M1/M2-intermediate state. In the present study, we evaluated a set of M1 and M2 markers in RAW 264.7 murine macrophage cell line, and THP-1 human monocytic cell line, in response to the purified OmpU protein. We observed that OmpU, as a PAMP, induced M1-polarization by activating the Toll-like receptor (TLR) signaling pathway. OmpU induced formation of TLR1/TLR2-heterodimers. OmpU-mediated TLR-activation led to the MyD88 recruitment to the TLR1/TLR2 complex. MyD88, in turn, recruited IRAK1. Ultimately, OmpU-mediated signaling led to the activation and subsequent nuclear translocation of the NFκB p65 subunit. We also observed that blocking of the TLR1, TLR2, IRAK1, and NFκB affected OmpU-mediated production of M1-associated pro-inflammatory cytokines such as TNFα and IL-6. PMID:26093918

  5. Physical Activity and Sedentary Behavior in an Ethnically Diverse Group of South African School Children

    PubMed Central

    McVeigh, Joanne; Meiring, Rebecca

    2014-01-01

    Few studies have examined physical activity and inactivity levels in an urban South African setting across 12 years of formal schooling. This information is important for implementing strategies to curb increasing trends of physical inactivity and related negative consequences, especially in low to middle income countries facing multiple challenges on overburdened health care systems. We examined levels of physical activity and sedentary behaviour cross-sectionally over 12 school years from childhood to adolescence in Black, White and Indian boys and girls. The aim of our study was to describe gender and race related patterns of physical and sedentary activity levels in a sample of South African children and to determine whether there were associations between these variables and body mass status. Physical activity questionnaires, previously validated in a South African setting, were used to gather information about activity and sedentary behaviours among 767 Black, White and Indian children (5-18 years of age) across the 12 grades of formal schooling. Body mass and height were also measured. Time spent in moderate-vigorous physical activity declined over the school years for all race groups and was consistently lower for girls than boys (p = 0.03), while time spent in sedentary activity increased with increasing grade (p < 0.001) for boys and girls and across all race groups. Associations between physical activity and body mass were observed for White children (r = -0.22, p < 0.001), but not for Black and Indian children (p > 0.05) whereas time spent in sedentary activities was significantly and positively correlated with body mass across all race groups: Indian (r = 0.25, p < 0.001), White (r = 0.22, p < 0.001) and Black (r = 0.37, p = 0.001). The strength of the associations was similar for boys and girls. Black and Indian children were less physically active than their white peers (p < 0.05), and Black children also spent more time in sedentary activity (p < 0

  6. The seasonal succession of zooplankton in the Southern Ocean south of Australia, part II: The Sub-Antarctic to Polar Frontal Zones

    NASA Astrophysics Data System (ADS)

    Hunt, Brian P. V.; Hosie, Graham W.

    2006-07-01

    Between October 2001 and March 2002 six transects were completed at monthly intervals in the Sub-Antarctic Zone (SAZ) and Inter-Sub-Antarctic Front Zone (ISAFZ)/Polar Frontal Zone (PFZ) in the Southern Ocean south of Australia. Zooplankton were collected with a Continuous Plankton Recorder and NORPAC net and multivariate analysis was used to analyse the seasonal succession of communities. Despite strong, seasonally consistent, biogeographic differences between the SAZ and ISAFZ/PFZ, community structure in all zones was dominated by a suite of common taxa. These included the ubiquitous Oithona similis, foraminiferans and appendicularians (Core taxa), occurring in >97% of samples and contributing an average of 75% to total sample abundance, and Calanus simillimus, Rhincalanus gigas, Ctenocalanus citer, Clausocalanus brevipes, Clausocalanus laticeps, Oithona frigida, Limacina spp. and chaetognaths (Summer taxa), present in >57% of samples and occurring at seasonally high densities. Because of the dominance of the Core and Summer taxa, the seasonal succession was most clearly evident as a change in zooplankton densities. In October densities averaged <15 ind m -3, rising to 52 ind m -3 (max=92 ind m -3) in November, and subsequently increasing slowly through to January (ave=115 ind m -3; max=255 ind m -3). Densities peaked abruptly in February (ave=634 ind m -3; max=1593 ind m -3), and remained relatively high in March (ave=193 ind m -3; max=789 ind m -3). A latitudinal lag in seasonal development was observed with peak densities occurring first in the SAZ (February) and then in the ISAFZ/PFZ (March). The seasonal community succession was strongly influenced by species population cycles. The role of zooplankton in biogeochemical cycling in the SAZ and ISAFZ/PFZ was discussed in the light of past sediment trap data collected from the study area.

  7. Internal wave activity in the polar atmospheric regions during 2006 - 2009 revealed by COSMIC radio occultation data

    NASA Astrophysics Data System (ADS)

    Kirillovich, Ivan; Gubenko, Vladimir; Pavelyev, Alexander; Liou, Yuei-An

    The satellite mission Formosat-3/COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) consists of six micro-satellites, and each of them has four GPS-antennas. It was launched in April 2006, orbiting around the Earth at approximately 800 km. The primary scientific goal of the mission is to demonstrate the value of near-real-time radio occultation (RO) observations in improving operational numerical weather predictions (NWP). The goal is readily shown by assimilating the measurements of atmospheric parameters into used NWP-models. These parameters include density, temperature, pressure and relative humidity fields in the atmosphere. An analysis of their geographic and seasonal distributions is necessary to the understanding of the energy and momentum transfer and the reaction of the polar atmosphere in response to global warming. This task is especially important as the Polar Regions are very sensitive to the change in global temperature and it may be a major cause of global sea level rising. In this work, a statistical analysis of the internal gravity wave (IGW) activity in polar atmospheric regions (latitudes more than 60º) using Formosat-3/COSMIC RO temperature data collected from July 2006 to March 2009 has been performed. Geographic and seasonal distributions of the IGW potential energy (wave activity indicator) in the altitude interval from 15 to 35 km have been determined and analyzed. The obtained results show that the wave activity in the polar atmosphere is strong in winter and spring. The potential energy of IGWs in spring is largest in Antarctic atmospheric region, while it is largest in winter in Arctic region. The wave potential energy increases with altitude up to 35 km in the atmosphere of both Earth’s hemispheres. In Antarctic region, internal waves with high potential energy occur in the atmosphere over the Antarctic Peninsula. In Arctic region, a high wave activity is mainly observed over North Atlantic Ocean (Iceland

  8. Active Earth Display: Using Real-Time Data, Interactivity, and Storylines to Engage the Public in Polar Awareness

    NASA Astrophysics Data System (ADS)

    Schiffman, C. R.; Carroll, K. P.; Wilson, T. J.

    2008-12-01

    The Polar Earth Observation Network (POLENET) and UNAVCO are collaborating to develop new educational materials for the public focused on polar-based research. Polenet is a consortium that aims to dramatically improve the coverage of many different kinds of geophysical data sets across the polar regions of Earth. The data from Polenet will enable new research into the interaction between the atmosphere, oceans, polar ice-sheets, and the Earth's crust and mantle. It is important that this research is disseminated to the public in an engaging and accurate matter while avoiding oversimplification. The Incorporated Research Institutions for Seismology's (IRIS) Active Earth Display (AED), a touch screen web-based kiosk, was originally designed to highlight real-time seismic data, and therefore provides a useful format for showing real-time data from the poles. The new polar pages for the AED will highlight real-time data from Antarctica and Greenland, and provide a way for the public to learn about POLENET research. The polar AED pages aim to engage users through teaching about the importance of polar-based research using a rich interactive multimedia environment. The pages are organized around four storylines: equipment, ice movement through time, life on the ice, and what ice in Antarctica has to do with you. The pages present complex scientific concepts in a way that is accessible and engaging to the general public by using simplified text, real-time data, videos, interactive games, and a set of coherent storylines. For example, one interactive feature will be an energy game, where users adjust various sources to power a GPS unit through the polar night. Another interactive feature will be a map of Polar Regions with clickable hotspots that will show videos of calving glaciers and collapsing ice sheets from around the world. The AED maintains a constant Internet connection, so the storylines are flexible and can be changed to conform to the location of the kiosk and

  9. Aboveground activity rhythm in Arctic black-capped marmot ( Marmota camtschatica bungei Katschenko 1901) under polar day conditions

    NASA Astrophysics Data System (ADS)

    Semenov, Youri; Ramousse, Raymond; Le Berre, Michel; Vassiliev, Vladimir; Solomonov, Nikita

    2001-04-01

    Daily aboveground activity of wild black-capped marmots of Yakutia ( Marmota camtschatica bungei) was recorded under 'polar day' conditions at 71°56' N and 127°19' E (north of the Polar Circle). From the beginning of May until the end of August, the sun was permanently above or close to the horizon. However under this condition of continuous lighting, the aboveground activity of these arctic hibernating mammals was periodic. Onset and end of activity showed marked changes throughout the seasons. Activity time increased strongly from hibernation emergence until the end of July and then decreased slowly until onset of hibernation. Below daily mean temperatures of 5 °C, activity started when the sun was 35° above the horizon, and ended when it dropped below 28°. When daily mean temperatures were above 5 °C, activity onset was synchronised with a solar altitude around 17-18° and activity ended at 10°. Activity onset was more precise relative to the solar altitude than the end of activity. This may be explained by late feeding bouts, following a midday thermal stress. In absence of rapid natural light-dark (LD) transitions that occur at civil twilight, our results suggest that the activity pattern of black-capped marmots may be synchronised by the light cycle through the solar altitude and ambient temperature.

  10. Electrochemical Cathodic Polarization, a Simplified Method That Can Modified and Increase the Biological Activity of Titanium Surfaces: A Systematic Review

    PubMed Central

    2016-01-01

    Background The cathodic polarization seems to be an electrochemical method capable of modifying and coat biomolecules on titanium surfaces, improving the surface activity and promoting better biological responses. Objective The aim of the systematic review is to assess the scientific literature to evaluate the cellular response produced by treatment of titanium surfaces by applying the cathodic polarization technique. Data, Sources, and Selection The literature search was performed in several databases including PubMed, Web of Science, Scopus, Science Direct, Scielo and EBSCO Host, until June 2016, with no limits used. Eligibility criteria were used and quality assessment was performed following slightly modified ARRIVE and SYRCLE guidelines for cellular studies and animal research. Results Thirteen studies accomplished the inclusion criteria and were considered in the review. The quality of reporting studies in animal models was low and for the in vitro studies it was high. The in vitro and in vivo results reported that the use of cathodic polarization promoted hydride surfaces, effective deposition, and adhesion of the coated biomolecules. In the experimental groups that used the electrochemical method, cellular viability, proliferation, adhesion, differentiation, or bone growth were better or comparable with the control groups. Conclusions The use of the cathodic polarization method to modify titanium surfaces seems to be an interesting method that could produce active layers and consequently enhance cellular response, in vitro and in vivo animal model studies. PMID:27441840

  11. Web-based Tools for Educators: Outreach Activities of the Polar Radar for Ice Sheet Measurements (PRISM) Project

    NASA Astrophysics Data System (ADS)

    Braaten, D. A.; Holvoet, J. F.; Gogineni, S.

    2003-12-01

    The Radar Systems and Remote Sensing Laboratory at the University of Kansas (KU) has implemented extensive outreach activities focusing on Polar Regions as part of the Polar Radar for Ice Sheet Measurements (PRISM) project. The PRISM project is developing advanced intelligent remote sensing technology that involves radar systems, an autonomous rover, and communications systems to measure detailed ice sheet characteristics, and to determine bed conditions (frozen or wet) below active ice sheets in both Greenland and Antarctica. These measurements will provide a better understanding of the response of polar ice sheets to global climate change and the resulting impact the ice sheets will have on sea level rise. Many of the research and technological development aspects of the PRISM project, such as robotics, radar systems, climate change and exploration of harsh environments, can kindle an excitement and interest in students about science and technology. These topics form the core of our K-12 education and training outreach initiatives, which are designed to capture the imagination of young students, and prompt them to consider an educational path that will lead them to scientific or engineering careers. The K-12 PRISM outreach initiatives are being developed and implemented in a collaboration with the Advanced Learning Technology Program (ALTec) of the High Plains Regional Technology in Education Consortium (HPR*TEC). ALTec is associated with the KU School of Education, and is a well-established educational research center that develops and hosts web tools to enable teachers nationwide to network, collaborate, and share resources with other teachers. An example of an innovative and successful web interface developed by ALTec is called TrackStar. Teachers can use TrackStar over the Web to develop interactive, resource-based lessons (called tracks) on-line for their students. Once developed, tracks are added to the TrackStar database and can be accessed and modified

  12. PPAR Activation Induces M1 Macrophage Polarization via cPLA2-COX-2 Inhibition, Activating ROS Production against Leishmania mexicana

    PubMed Central

    Díaz-Gandarilla, J. A.; Osorio-Trujillo, C.; Hernández-Ramírez, V. I.; Talamás-Rohana, P.

    2013-01-01

    Defence against Leishmania depends upon Th1 inflammatory response and, a major problem in susceptible models, is the turnoff of the leishmanicidal activity of macrophages with IL-10, IL-4, and COX-2 upregulation, as well as immunosuppressive PGE2, all together inhibiting the respiratory burst. Peroxisome proliferator-activated receptors (PPAR) activation is responsible for macrophages polarization on Leishmania susceptible models where microbicide functions are deactivated. In this paper, we demonstrated that, at least for L. mexicana, PPAR activation, mainly PPARγ, induced macrophage activation through their polarization towards M1 profile with the increase of microbicide activity against intracellular pathogen L. mexicana. PPAR activation induced IL-10 downregulation, whereas the production of proinflammatory cytokines such as TNF-α, IL-1β, and IL-6 remained high. Moreover, PPAR agonists treatment induced the deactivation of cPLA2-COX-2-prostaglandins pathway together with an increase in TLR4 expression, all of whose criteria meet the M1 macrophage profile. Finally, parasite burden, in treated macrophages, was lower than that in infected nontreated macrophages, most probably associated with the increase of respiratory burst in these treated cells. Based on the above data, we conclude that PPAR agonists used in this work induces M1 macrophages polarization via inhibition of cPLA2 and the increase of aggressive microbicidal activity via reactive oxygen species (ROS) production. PMID:23555077

  13. Monitoring microbial growth and activity using spectral induced polarization and low-field nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Zhang, Chi; Keating, Kristina; Revil, Andre

    2015-04-01

    Microbes and microbial activities in the Earth's subsurface play a significant role in shaping subsurface environments and are involved in environmental applications such as remediation of contaminants in groundwater and oil fields biodegradation. Stimulated microbial growth in such applications could cause wide variety of changes of physical/chemical properties in the subsurface. It is critical to monitor and determine the fate and transportation of microorganisms in the subsurface during such applications. Recent geophysical studies demonstrate the potential of two innovative techniques, spectral induced polarization (SIP) and low-field nuclear magnetic resonance (NMR), for monitoring microbial growth and activities in porous media. The SIP measures complex dielectric properties of porous media at low frequencies of exciting electric field, and NMR studies the porous structure of geologic media and characterizes fluids subsurface. In this laboratory study, we examined both SIP and NMR responses from bacterial growth suspension as well as suspension mixed with silica sands. We focus on the direct contribution of microbes to the SIP and NMR signals in the absence of biofilm formation or biomineralization. We used Zymomonas mobilis and Shewanella oneidensis (MR-1) for SIP and NMR measurements, respectively. The SIP measurements were collected over the frequency range of 0.1 - 1 kHz on Z. mobilis growth suspension and suspension saturated sands at different cell densities. SIP data show two distinct peaks in imaginary conductivity spectra, and both imaginary and real conductivities increased as microbial density increased. NMR data were collected using both CPMG pulse sequence and D-T2 mapping to determine the T2-distribution and diffusion properties on S. oneidensis suspension, pellets (live and dead), and suspension mixed with silica sands. NMR data show a decrease in the T2-distribution in S. oneidensis suspension saturated sands as microbial density increase. A

  14. Multi-compound polarization by DNP allows simultaneous assessment of multiple enzymatic activities in vivo

    NASA Astrophysics Data System (ADS)

    Wilson, David M.; Keshari, Kayvan R.; Larson, Peder E. Z.; Chen, Albert P.; Hu, Simon; Van Criekinge, Mark; Bok, Robert; Nelson, Sarah J.; Macdonald, Jeffrey M.; Vigneron, Daniel B.; Kurhanewicz, John

    2010-07-01

    Methods for the simultaneous polarization of multiple 13C-enriched metabolites were developed to probe several enzymatic pathways and other physiologic properties in vivo, using a single intravenous bolus. A new method for polarization of 13C sodium bicarbonate suitable for use in patients was developed, and the co-polarization of 13C sodium bicarbonate and [1- 13C] pyruvate in the same sample was achieved, resulting in high solution-state polarizations (15.7% and 17.6%, respectively) and long spin-lattice relaxation times ( T1) (46.7 s and 47.7 s respectively at 3 T). Consistent with chemical shift anisotropy dominating the T1 relaxation of carbonyls, T1 values for 13C bicarbonate and [1- 13C] pyruvate were even longer at 3 T (49.7 s and 67.3 s, respectively). Co-polarized 13C bicarbonate and [1- 13C] pyruvate were injected into normal mice and a murine prostate tumor model at 3 T. Rapid equilibration of injected hyperpolarized 13C sodium bicarbonate with 13C CO 2 allowed calculation of pH on a voxel by voxel basis, and simultaneous assessment of pyruvate metabolism with cellular uptake and conversion of [1- 13C] pyruvate to its metabolic products. Initial studies in a Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) model demonstrated higher levels of hyperpolarized lactate and lower pH within tumor, relative to surrounding benign tissues and to the abdominal viscera of normal controls. There was no significant difference observed in the tumor lactate/pyruvate ratio obtained after the injection of co-polarized 13C bicarbonate and [1- 13C] pyruvate or polarized [1- 13C] pyruvate alone. The technique was extended to polarize four 13C labelled substrates potentially providing information on pH, metabolism, necrosis and perfusion, namely [1- 13C]pyruvic acid, 13C sodium bicarbonate, [1,4- 13C]fumaric acid, and 13C urea with high levels of solution polarization (17.5%, 10.3%, 15.6% and 11.6%, respectively) and spin-lattice relaxation values similar to those

  15. Screening of selected ethnomedicinal plants from South Africa for larvicidal activity against the mosquito Anopheles arabiensis

    PubMed Central

    2012-01-01

    Background This study was initiated to establish whether any South African ethnomedicinal plants (indigenous or exotic), that have been reported to be used traditionally to repel or kill mosquitoes, exhibit effective mosquito larvicidal properties. Methods Extracts of a selection of plant taxa sourced in South Africa were tested for larvicidal properties in an applicable assay. Thirty 3rd instar Anopheles arabiensis larvae were exposed to various extract types (dichloromethane, dichloromethane/methanol) (1:1), methanol and purified water) of each species investigated. Mortality was evaluated relative to the positive control Temephos (Mostop; Agrivo), an effective emulsifiable concentrate larvicide. Results Preliminary screening of crude extracts revealed substantial variation in toxicity with 24 of the 381 samples displaying 100% larval mortality within the seven day exposure period. Four of the high activity plants were selected and subjected to bioassay guided fractionation. The results of the testing of the fractions generated identified one fraction of the plant, Toddalia asiatica as being very potent against the An. arabiensis larvae. Conclusion The present study has successfully identified a plant with superior larvicidal activity at both the crude and semi pure fractions generated through bio-assay guided fractionation. These results have initiated further research into isolating the active compound and developing a malaria vector control tool. PMID:22963538

  16. The antimicrobial activities of processed Nigerian and South African black tea.

    PubMed

    Ojo, O A; Yunusa, A O; Akindele, S K; Vera, V N; Fowora, N

    2010-12-01

    The antibacterial activity of processed Nigerian Lipton Tea and South African 5 Roses Tea, extracted using distilled water, chloroform and 70% ethanol were determined against nine (9) enteropathogenic bacteria which includes; Bacillus subtilis, Proteus sp, Enterobacter sp., Klebsiella pneumoniae, Escherichia coli, Salmonella typhi, Salmonella paratyphi A, Salmonella arizona and Staphylococcus aureus. The 2 tea bags, Nigerian Lipton tea bag and the South African 5 Roses tea bag were extracted through Solvent extraction method using 3 extraction solvents; Distilled water, Chloroform and 70% Ethanol and then inoculated onto the Mueller-Hinton agar plates containing the standard isolates at 6 different points on each plate. The zones of inhibition of the bacterial isolates produced by each of these tea - extracts were determined while meaningful antibacterial activities against five (5) of the standard isolates; Enterobacter sp., K. pneumoniae, S. paratyphi A, B. subtilis and S. aureus were observed. Lipton tea water-extract was a more effective antibacterial agent than water-extract of 5 Roses tea. While the 70% ethanol-extract of 5 Roses tea had the greatest antibacterial activity of all the different tea-extract used for the study, the chloroform-extracts of the tea bags had no antimicrobial effect on all the test organisms used. PMID:22416657

  17. Melt-Triggered Seismic Response in Hydraulically-Active Polar Ice: Observations and Methods

    NASA Astrophysics Data System (ADS)

    Carmichael, Joshua D.

    occurrence at night relative to that in the day. Contrary to our expectations, we find that the timing of GPS-derived surface speeds do not clearly indicate this seismic activity on any given day. Rather, these icequakes are best explained by peaks in localized strain gradients that develop at night when decreased subglacial water flux likely increases variability in basal traction. Additionally, our results appear comprise the first detailed seismic observations targeted at an actively draining lake. Our last study addresses the apparent deficiency in observed basal icequakes detected from Greenland lake site. To explain the lack of deep icequakes, we compute thresholds on the magnitude of detectable basal events within the network and thereby illustrate that surficial icequakes with similar magnitudes and spectral content are more likely to be observed. By restricting our attention to seismic events that produce lower frequency waveforms, we find a population of nearly monochromatic, sub-1Hz, large magnitude ( M w ≤ 3) seismic events borne from remote glaciogenic sources. In contrast to surficial icequakes, these events occur without significant bias between day and/or night periods and are best explained as glacial earthquakes generated by sliding episodes or iceberg calving events in the vicinity of Jakobshavn Glacier. These events occur daily and not correlate with the presence of local, surficial seismicity. We conclude with three general assertions regarding melt-triggered response characteristics of polar ice. First, hydraulic connections established by fracture events do not necessarily result in seismogenic basal stick slip, and therefore cannot necessarily be observed with conventional GPS monitoring. This was demonstrated at Taylor Glacier. Here, meltwater input to a hydraulic pathway led to fracture growth deep within a cold glacier without any change in surface speed. Second, the presence of melt-triggered basal sliding does not necessarily induce a clear

  18. Loss of monocyte chemoattractant protein-1 alters macrophage polarization and reduces NFκB activation in the foreign body response.

    PubMed

    Moore, Laura Beth; Sawyer, Andrew J; Charokopos, Antonios; Skokos, Eleni A; Kyriakides, Themis R

    2015-01-01

    Implantation of biomaterials elicits a foreign body response characterized by fusion of macrophages to form foreign body giant cells and fibrotic encapsulation. Studies of the macrophage polarization involved in this response have suggested that alternative (M2) activation is associated with more favorable outcomes. Here we investigated this process in vivo by implanting mixed cellulose ester filters or polydimethylsiloxane disks in the peritoneal cavity of wild-type (WT) and monocyte chemoattractant protein-1 (MCP-1) knockout mice. We analyzed classical (M1) and alternative (M2) gene expression via quantitative polymerase chain reaction, immunohistochemistry and enzyme-linked immunosorbent assay in both non-adherent cells isolated by lavage and implant-adherent cells. Our results show that macrophages undergo unique activation that displays features of both M1 and M2 polarization including induction of tumor necrosis factor α (TNF), which induces the expression and nuclear translocation of p50 and RelA determined by immunofluorescence and Western blot. Both processes were compromised in fusion-deficient MCP-1 KO macrophages in vitro and in vivo. Furthermore, inclusion of BAY 11-7028, an inhibitor of NFκB activation, reduced nuclear translocation of RelA and fusion in WT macrophages. Our studies suggest that peritoneal implants elicit a unique macrophage polarization phenotype leading to induction of TNF and activation of the NFκB pathway. PMID:25242651

  19. Loss of MCP-1 alters macrophage polarization and reduces NFκB activation in the foreign body response

    PubMed Central

    Moore, Laura Beth; Sawyer, Andrew J.; Charokopos, Antonios; Skokos, Eleni A.; Kyriakides, Themis R.

    2014-01-01

    Implantation of biomaterials elicits a foreign body response characterized by fusion of macrophages to form foreign body giant cells and fibrotic encapsulation. Studies of macrophage polarization in this response have suggested that alternative (M2) activation is associated with more favorable outcomes. Here we investigated this process in vivo by implanting mixed cellulose ester filters or PDMS disks in the peritoneal cavity of WT and MCP-1 KO mice. We analyzed classical (M1) and alternative (M2) gene expression via Q-PCR, immunohistochemistry, and ELISA in both non-adherent cells isolated by lavage and implant-adherent cells. Our results show that macrophages undergo unique activation that displays features of both M1 and M2 polarization including induction of TNF, which induces the expression and nuclear translocation of p50 and RelA determined by immunofluorescence and western blot. Both processes were compromised in fusion-deficient MCP-1 KO macrophages in vitro and in vivo. Furthermore, inclusion of BAY 11-7028, an inhibitor of NFκB activation, reduced nuclear translocation of RelA and fusion in WT macrophages. Our studies suggest that peritoneal implants elicit a unique macrophage polarization phenotype leading to induction of TNF and activation of the NFκB pathway. PMID:25242651

  20. North-south asymmetry of different solar activity features during solar cycle 23

    NASA Astrophysics Data System (ADS)

    Bankoti, Neeraj Singh; Joshi, Navin Chandra; Pande, Seema; Pande, Bimal; Pandey, Kavita

    2010-08-01

    A study on north-south (N-S) asymmetry of different solar activity features (DSAF) such as solar proton events, solar active prominences [total, low (⩽40°) and high (⩾50°) latitudes], H α flare indices, soft X-ray flares, monthly mean sunspot areas and monthly mean sunspot numbers carried out from May 1996 to October 2008. Study shows a southern dominance of DSAF during this period. During the rising phase of the cycle 23 the number of DSAF approximately equals on both, the northern and the southern hemispheres. But these activities tend to shift from northern to southern hemisphere during the period 1998-1999. The statistical significance of the asymmetry time series using a χ2-test of goodness of fit indicates that in most of the cases the asymmetry is highly significant, meaning thereby that the asymmetry is a real feature in the N-S distribution of DSAF.

  1. Polar Textures

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03646 Polar Textures

    This VIS image shows part of the south polar region. The ejecta from the relatively young crater covers the rougher textured polar surface.

    Image information: VIS instrument. Latitude 81S, Longitude 54.5E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  2. Polarized Light Corridor Demonstrations.

    ERIC Educational Resources Information Center

    Davies, G. R.

    1990-01-01

    Eleven demonstrations of light polarization are presented. Each includes a brief description of the apparatus and the effect demonstrated. Illustrated are strain patterns, reflection, scattering, the Faraday Effect, interference, double refraction, the polarizing microscope, and optical activity. (CW)

  3. Ground Motion Polarization in the Damage Zone of the Active, Strike-Slip Mattinata Fault, Southern Italy

    NASA Astrophysics Data System (ADS)

    Pischiutta, M.; Cianfarra, P.; Anselmi, M.; Salvini, F.; Rovelli, A.

    2013-12-01

    We have recently observed the occurrence of directional amplification effects in fault zones using both earthquakes and ambient noise records. In several faults we have found that ground motion polarization tends to have a high angle to cleavages produced by the stress related to the kinematics in the fault damage zone. We thus interpret this effect as due to the higher compliance of the fractured rocks of the damage zone in a direction transversal to the cleavage strike. Here we have tested the technique of the wavefield polarization using ambient vibrations recorded across the seismically active Mattinata Fault, in the Gargano Promontory, Italy. This fault has been chosen for the high number of structural investigations led out so far. The Mattinata Fault outcrops for over 40 km and shows an ondulated trajectory that is characterized by a number of significant tectonic-related morphological features compatible with a general left-lateral strike-slip kinematics. These features include a pull-apart basin and a transpressional zone. The main associated cleavage consists of a marked array of disjunctive, spaced pressure-solution surfaces developed within the 200-300 m wide fault damage zone. In order to relate the orientation of cleavage to the ground motion polarization, we measured 20-50 min of ambient noise at about 30 sites chosen in the fault damage zone close to rock outcrops where also structural geological measurements were carried out. Ground motion polarization is assessed both in the frequency and time domain through the individual-station horizontal-to-vertical spectral ratio and covariance-matrix analysis, respectively. Two ambient noise measurements were performed close to permanent broadband stations of the Italian Seismic Telemetric Network. Results are consistent with those inferred on earthquake records at the two permanent stations, confirming that ambient noise yields results consistent with earthquake records as previously observed in other

  4. Ferroelectric polarization effect on surface chemistry and photo-catalytic activity: A review

    NASA Astrophysics Data System (ADS)

    Khan, M. A.; Nadeem, M. A.; Idriss, H.

    2016-03-01

    The current efficiency of various photocatalytic processes is limited by the recombination of photogenerated electron-hole pairs in the photocatalyst as well as the back-reaction of intermediate species. This review concentrates on the use of ferroelectric polarization to mitigate electron-hole recombination and back-reactions and therefore improve photochemical reactivity. Ferroelectric materials are considered as wide band gap polarizable semiconductors. Depending on the surface polarization, different regions of the surface experience different extents of band bending and promote different carriers to move to spatially different locations. This can lead to some interesting interactions at the surface such as spatially selective adsorption and surface redox reactions. This introductory review covers the fundamental properties of ferroelectric materials, effect of an internal electric field/polarization on charge carrier separation, effect of the polarization on the surface photochemistry and reviews the work done on the use of these ferroelectric materials for photocatalytic applications such as dye degradation and water splitting. The manipulation of photogenerated charge carriers through an internal electric field/surface polarization is a promising strategy for the design of improved photocatalysts.

  5. Upper Thermosphere Winds and Temperatures in the Geomagnetic Polar Cap: Solar Cycle, Geomagnetic Activity, and Interplanetary Magnetic Field Dependencies

    NASA Technical Reports Server (NTRS)

    Killeen, T. L.; Won, Y.-I.; Niciejewski, R. J.; Burns, A. G.

    1995-01-01

    Ground-based Fabry-Perot interferometers located at Thule, Greenland (76.5 deg. N, 69.0 deg. W, lambda = 86 deg.) and at Sondre Stromfjord, Greenland (67.0 deg. N, 50.9 deg. W, lambda = 74 deg.) have monitored the upper thermospheric (approx. 240-km altitude) neutral wind and temperature over the northern hemisphere geomagnetic polar cap since 1983 and 1985, respectively. The thermospheric observations are obtained by determining the Doppler characteristics of the (OI) 15,867-K (630.0-nm) emission of atomic oxygen. The instruments operate on a routine, automatic, (mostly) untended basis during the winter observing seasons, with data coverage limited only by cloud cover and (occasional) instrument failures. This unique database of geomagnetic polar cap measurements now extends over the complete range of solar activity. We present an analysis of the measurements made between 1985 (near solar minimum) and 1991 (near solar maximum), as part of a long-term study of geomagnetic polar cap thermospheric climatology. The measurements from a total of 902 nights of observations are compared with the predictions of two semiempirical models: the Vector Spherical Harmonic (VSH) model of Killeen et al. (1987) and the Horizontal Wind Model (HWM) of Hedin et al. (1991). The results are also analyzed using calculations of thermospheric momentum forcing terms from the Thermosphere-ionosphere General Circulation Model TGCM) of the National Center for Atmospheric Research (NCAR). The experimental results show that upper thermospheric winds in the geomagnetic polar cap have a fundamental diurnal character, with typical wind speeds of about 200 m/s at solar minimum, rising to up to about 800 m/s at solar maximum, depending on geomagnetic activity level. These winds generally blow in the antisunward direction, but are interrupted by episodes of modified wind velocity and altered direction often associated with changes in the orientation of the Interplanetary Magnetic Field (IMF). The

  6. A possible role of galactic cosmic rays in chlorine activation during polar night

    SciTech Connect

    Mueller, R.; Crutzen, P.J.

    1993-11-20

    The authors look at the concentration of HCl in the polar stratosphere, just at the end of the polar night in Antarctica, and conclude that heterogeneous reactions of HCl with ClONO{sub 2} and HOCl are not able to account for the observed decline in its density. They propose additional processing of HCl by reactions with N{sub 2}O{sub 5}, which could be formed by cosmic ray reactions which create NO radicals. OH radicals are also formed by cosmic ray reactions, and can also contribute to HCl processing. Including these type reactions they are able to predict an additional factor of 2 decrease in HCl densities following polar night.

  7. Polarization features of solar radio emission and possible existence of current sheets in active regions

    NASA Technical Reports Server (NTRS)

    Gopalswamy, N.; Zheleznyakov, V. V.; White, S. M.; Kundu, M. R.

    1994-01-01

    We show that it is possible to account for the polarization features of solar radio emission provided the linear mode coupling theory is properly applied and the presence of current sheets in the corona is taken into account. We present a schematic model, including a current sheet that can explain the polarization features of both the low frequency slowly varying component and the bipolar noise storm radiation; the two radiations face similar propagation conditions through a current sheet and hence display similar polarization behavior. We discuss the applications of the linear mode coupling theory to the following types of solar emission: the slowly varying component, the microwave radio bursts, metric type U bursts, and bipolar noise storms.

  8. β3 Integrin Promotes Long-Lasting Activation and Polarization of Vascular Endothelial Growth Factor Receptor 2 by Immobilized Ligand

    PubMed Central

    Ravelli, Cosetta; Grillo, Elisabetta; Corsini, Michela; Coltrini, Daniela

    2015-01-01

    Objective— During neovessel formation, angiogenic growth factors associate with the extracellular matrix. These immobilized factors represent a persistent stimulus for the otherwise quiescent endothelial cells (ECs), driving directional EC migration and proliferation and leading to new blood vessel growth. Vascular endothelial growth factor receptor 2 (VEGFR2) is the main mediator of angiogenesis. Although VEGFR2 signaling has been deeply characterized, little is known about its subcellular localization during neovessel formation. Aim of this study was the characterization and molecular determinants of activated VEGFR2 localization in ECs during neovessel formation in response to matrix-immobilized ligand. Approach and Results— Here we demonstrate that ECs stimulated by extracellular matrix–associated gremlin, a noncanonical VEGFR2 ligand, are polarized and relocate the receptor in close contact with the angiogenic factor–enriched matrix both in vitro and in vivo. GM1 (monosialotetrahexosylganglioside)-positive planar lipid rafts, β3 integrin receptors, and the intracellular signaling transducers focal adhesion kinase and RhoA (Ras homolog gene family, member A) cooperate to promote VEGFR2 long-term polarization and activation. Conclusions— A ligand anchored to the extracellular matrix induces VEGFR2 polarization in ECs. Long-lasting VEGFR2 relocation is closely dependent on lipid raft integrity and activation of β3 integrin pathway. The study of the endothelial responses to immobilized growth factors may offer insights into the angiogenic process in physiological and pathological conditions, including cancer, and for a better engineering of synthetic tissue scaffolds to blend with the host vasculature. PMID:26293466

  9. Antifungal and antibacterial activity and chemical composition of polar and non-polar extracts of Athrixia phylicoides determined using bioautography and HPLC

    PubMed Central

    2013-01-01

    Background Athrixia phylicoides DC. (Asteraceae) is used medicinally in South Africa to treat a plethora of ailments, including heart problems, diabetes, diarrhoea, sores and infected wounds. It is also prepared in the form of a tea (hot decoction) taken as a refreshing, pleasant-tasting beverage with commercialization potential. Methods Extracts of the dried ground aerial parts were prepared using organic solvents (diethyl ether, dichloromethane/methanol, ethyl acetate and ethanol) and water. These extracts were subjected to HPLC, TLC and bioautography analysis with the aim of linking a range of peaks visualized in HPLC chromatography profiles to antibacterial and antifungal activity of the same extracts. Results HPLC revealed a group of compounds extracted by more than one solvent. Compounds identified include inositol, caffeic acid, quercetin, kaempferol, apigenin, hymenoxin and oleanolic acid. The organic extracts displayed similar TLC profiles, and bioautography indicated approximately five antibacterial compounds, but only two antifungal compounds in these extracts. Bioautography indicated that cold water extracted the least antimicrobial compounds. Conclusions Several previously unknown compounds were identified in Athrixia phylicoides extracts, and bioautography indicated a number of antibacterial and antifungal compounds. There were notable differences in chemical composition and bioactivity between the organic and aqueous extracts. Further research is necessary to fully characterize the active components of the extracts. PMID:24330447

  10. Polar gravel beach-ridge systems: Sedimentary architecture, genesis, and implications for climate reconstructions (South Shetland Islands/Western Antarctic Peninsula)

    NASA Astrophysics Data System (ADS)

    Lindhorst, Sebastian; Schutter, Ilona

    2014-09-01

    The sedimentary architecture of polar gravel-beach ridges is presented and it is shown that ridge internal geometries reflect past wave-climate conditions. Ground-penetrating radar (GPR) data obtained along the coasts of Potter Peninsula (King George Island) show that beach ridges unconformably overlie the prograding strand plain. Development of individual ridges is seen to result from multiple storms in periods of increased storm-wave impact on the coast. Strand-plain progradation, by contrast, is the result of swash sedimentation at the beach-face under persistent calm conditions. The sedimentary architecture of beach ridges in sheltered parts of the coast is characterized by seaward-dipping prograding beds, being the result of swash deposition under stormy conditions, or aggrading beds formed by wave overtopping. By contrast, ridges exposed to high-energy waves are composed of seaward- as well as landward-dipping strata, bundled by numerous erosional unconformities. These erosional unconformities are the result of sediment starvation or partial reworking of ridge material during exceptional strong storms. The number of individual ridges which are preserved from a given time interval varies along the coast depending on the morphodynamic setting: sheltered coasts are characterized by numerous small ridges, whereas fewer but larger ridges develop on exposed beaches. The frequency of ridge building ranges from decades in the low-energy settings up to 1600 years under high-energy conditions. Beach ridges in the study area cluster at 9.5, 7.5, 5.5, and below 3.5 m above the present-day storm beach. Based on radiocarbon data, this is interpreted to reflect distinct periods of increased storminess and/or shortened annual sea-ice coverage in the area of the South Shetland Islands for the times around 4.3, c. 3.1, 1.9 ka cal BP, and after 0.65 ka cal BP. Ages further indicate that even ridges at higher elevations can be subject to later reactivation and reworking. A

  11. The Impact of Human Activities on Microbial Quality of Rivers in the Vhembe District, South Africa

    PubMed Central

    Traoré, Afsatou N.; Mulaudzi, Khodani; Chari, Gamuchirai J.E.; Foord, Stefan H.; Mudau, Lutendo S.; Barnard, Tobias G.; Potgieter, Natasha

    2016-01-01

    Background: Water quality testing is dictated by microbial agents found at the time of sampling in reference to their acceptable risk levels. Human activities might contaminate valuable water resources and add to the microbial load present in water bodies. Therefore, the effects of human activities on the microbial quality of rivers collected from twelve catchments in the Vhembe District in South Africa were investigated, with samples analyzed for total coliform (TC) and Eschericha coli (E. coli) contents. Methods: Physical parameters and various human activities were recorded for each sampling site. The Quanti-Tray® method was adopted for the assessment of TC and E. coli contents in the rivers over a two-year period. A multiplex polymerase chain (PCR) method was used to characterize the strains of E. coli found. Results: The microbial quality of the rivers was poor with both TC and E. coli contents found to be over acceptable limits set by the South African Department of Water and Sanitation (DWS). No significant difference (p > 0.05) was detected between TC and E. coli risks in dry and wet seasons. All six pathogenic E. coli strains were identified and Enteroaggregative E. coli (EAEC), atypical Enteropathogenic E. coli (a-EPEC) and Enterotoxigenic E. coli (ETEC) were the most prevalent E. coli strains detected (respectively, 87%, 86% and 83%). Conclusions: The study indicated that contamination in the majority of sampling sites, due to human activities such as car wash, animal grazing and farming, poses health risks to communities using the rivers for various domestic chores. It is therefore recommended that more education by the respective departments is done to avert pollution of rivers and prevent health risks to the communities in the Vhembe District. PMID:27529265

  12. Approach to theoretical estimation of the activation energy of particle aggregation taking ionic nonclassic polarization into account

    NASA Astrophysics Data System (ADS)

    Li, Qinyi; Tang, Ying; He, Xinhua; Li, Hang

    2015-10-01

    The activation energy of particle aggregation in suspensions is a very important kinetic parameter in a wide range of science and engineering applications. At present, however, there is no theory that can theoretically predict the activation energy. Because the activation energy is often less than 10 kT (where k is the Boltzmann constant and T is the temperature), it is difficult to experimentally measure. In this study, a theory for calculating the activation energy is established. Experimental measurements of the activation energy of montmorillonite aggregation were performed with different electrolyte and particle concentrations using the dynamic light scattering (DLS) technique. The validity of the theory was verified by the experiments. This study confirmed that both the method for activation energy measurements by DLS and the theory for its calculation can be applied to suspensions of polydisperse nonspherical particles. The average kinetic energy at the moment of particle collision in the aggregation process was found to be 0.2 kT, which is less than the instantaneous kinetic energy of a Brownian particle (0.5 kT) because of the viscous resistance of the water medium. This study also shows that adsorbed Na+ is strongly polarized in the electric field near the particle surface, and the polarization increases the effective charge of Na+ from +1 to +1.18.

  13. Career & Life Planning Portfolio Resource Book. Activities To Accompany the South Dakota Career and Life Planning Portfolio, 1999-2000.

    ERIC Educational Resources Information Center

    South Dakota State Dept. of Education, Pierre. Div. of Workforce and Career Preparation.

    This resource book provides several career development activities to accompany the South Dakota "My Career and Life Planning Portfolio," which is appended. The activities are arranged according to the following four folders found within the portfolio jacket: career and education planning; skills employers want; projects/work samples; and…

  14. 31 CFR 538.536 - Activities relating to the petroleum and petrochemical industries in the Republic of South Sudan.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 31 Money and Finance:Treasury 3 2013-07-01 2013-07-01 false Activities relating to the petroleum... Policy § 538.536 Activities relating to the petroleum and petrochemical industries in the Republic of... and transactions relating to the petroleum and petrochemical industries in the Republic of South...

  15. 31 CFR 538.536 - Activities relating to the petroleum and petrochemical industries in the Republic of South Sudan.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 31 Money and Finance:Treasury 3 2012-07-01 2012-07-01 false Activities relating to the petroleum... Policy § 538.536 Activities relating to the petroleum and petrochemical industries in the Republic of... and transactions relating to the petroleum and petrochemical industries in the Republic of South...

  16. 31 CFR 538.536 - Activities relating to the petroleum and petrochemical industries in the Republic of South Sudan.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 31 Money and Finance:Treasury 3 2014-07-01 2014-07-01 false Activities relating to the petroleum... Policy § 538.536 Activities relating to the petroleum and petrochemical industries in the Republic of... and transactions relating to the petroleum and petrochemical industries in the Republic of South...

  17. Association of syntenin-1 with M-RIP polarizes Rac-1 activation during chemotaxis and immune interactions.

    PubMed

    Sala-Valdés, Mónica; Gordón-Alonso, Mónica; Tejera, Emilio; Ibáñez, Anna; Cabrero, J Román; Ursa, Angeles; Mittelbrunn, María; Lozano, Francisco; Sánchez-Madrid, Francisco; Yáñez-Mó, María

    2012-03-01

    In this study, we describe that the PDZ protein syntenin-1 is a crucial element for the generation of signaling asymmetry during the cellular response to polarized extracellular cues. We analyze the role of syntenin-1 in the control of asymmetry in two independent models of T cell polarization--the migratory response to chemoattractants and the establishment of cognate interactions between T cells and antigen-presenting cells (APCs). A combination of mutant, biochemical and siRNA approaches demonstrate that syntenin-1 is vital for the generation of polarized actin structures such as the leading edge and the contact zone with APCs. We found that the mechanism by which syntenin-1 controls actin polymerization relies on its mandatory role for activation of the small GTPase Rac. Syntenin-1 controls Rac through a specific association with the myosin phosphatase Rho interacting protein (M-RIP), which occurs in response to phosphorylation of syntenin-1 by Src at Tyr4. Our data indicate the key role of syntenin-1 in the generation of functional asymmetry in T cells and provide a novel mechanistic link between receptor activation and actin polymerization and accumulation in response to extracellular stimulation. PMID:22349701

  18. Mouse macrophage polarity and ROCK1 activity depend on RhoA and non-apoptotic Caspase 3.

    PubMed

    Liu, Yianzhu; Minze, Laurie J; Mumma, Lindsay; Li, Xian C; Ghobrial, Rafik M; Kloc, Malgorzata

    2016-02-15

    The macrophages have different subtypes with different functions in immune response and disease. It has been generally accepted that M1 macrophages are responsible for stimulation of immune system and inflammation while M2 macrophages play a role in tissue repair. Irrespective of the type, macrophage functions depend on actin cytoskeleton, which is under the control of small GTPase RhoA pathway and its downstream effector ROCK1. We generated RhoA-deleted macrophages and compared the effect of RhoA deletion on M0, M1 and M2 macrophage phenotype. Our studies showed that, unexpectedly, the RhoA deletion did not eliminate macrophage ROCK1 expression and increased ROCK1 activity. The RhoA deletion effect on macrophage phenotype, structure and polarity was different for each subtype. Moreover, our study indicates that the up-regulation of ROCK1 activity in RhoA-deleted macrophages and macrophage phenotype/polarity are dependent on non-apoptotic Caspase-3 and are sensitive to Caspase-3 inhibition. These novel findings will revise/complement our understanding of RhoA pathway regulation of cell structure and polarity. PMID:26875770

  19. The F-BAR protein Hof1 tunes formin activity to sculpt actin cables during polarized growth

    PubMed Central

    Graziano, Brian R.; Yu, Hoi-Ying E.; Alioto, Salvatore L.; Eskin, Julian A.; Ydenberg, Casey A.; Waterman, David P.; Garabedian, Mikael; Goode, Bruce L.

    2014-01-01

    Asymmetric cell growth and division rely on polarized actin cytoskeleton remodeling events, the regulation of which is poorly understood. In budding yeast, formins stimulate the assembly of an organized network of actin cables that direct polarized secretion. Here we show that the Fer/Cip4 homology–Bin amphiphysin Rvs protein Hof1, which has known roles in cytokinesis, also functions during polarized growth by directly controlling the activities of the formin Bnr1. A mutant lacking the C-terminal half of Hof1 displays misoriented and architecturally altered cables, along with impaired secretory vesicle traffic. In vitro, Hof1 inhibits the actin nucleation and elongation activities of Bnr1 without displacing the formin from filament ends. These effects depend on the Src homology 3 domain of Hof1, the formin homology 1 (FH1) domain of Bnr1, and Hof1 dimerization, suggesting a mechanism by which Hof1 “restrains” the otherwise flexible FH1-FH2 apparatus. In vivo, loss of inhibition does not alter actin levels in cables but, instead, cable shape and functionality. Thus Hof1 tunes formins to sculpt the actin cable network. PMID:24719456

  20. No covariation between the geomagnetic activity and the incidence of acute myocardial infarction in the polar area of northern Sweden

    NASA Astrophysics Data System (ADS)

    Messner, T.; Häggström, I.; Sandahl, I.; Lundberg, V.

    2002-05-01

    This study was undertaken to investigate whether there was any relation between the aurora borealis (measured as the geomagnetic activity) and the number of acute myocardial infarctions (AMI) in the northern, partly polar, area of Sweden. The AMI cases were collected from The Northern Sweden MONICA (multinational MONItoring of trends and determinants of CArdiovascular disease) AMI registry between 1985 and 1998, inclusive, and the information on the geomagnetic activity from continuous measurements at the Swedish Institute of Space Physics, Kiruna. In the analyses, both the relation between the individual AMI case and ambient geomagnetic activity, and the relation between the mean daily K index and the daily number of AMI cases were tested. We found no statistically significant relation between the number of fatal or non-fatal AMI cases, the number of sudden deaths or the number of patients with chest pain without myocardial damage, and geomagnetic activity. Our data do not support a relation between the geomagnetic activity and AMI.

  1. Linear and nonlinear Faraday rotations of light polarization in a four-level active-Raman-gain medium

    NASA Astrophysics Data System (ADS)

    Zhu, Chengjie; Deng, L.; Hagley, E. W.

    2013-08-01

    We investigate linear and nonlinear Faraday effects in a room-temperature, coherently driven four-level active-Raman-gain (ARG) medium. By using the multiple-scale method, we derive two nonlinear coupled envelope equations governing the dynamics of left- and right-polarized components of a linearly polarized probe field. Under the weak probe field approximation, we demonstrate a factor of four increase of the Faraday rotation angle by the linear and nonlinear response of the ARG scheme without probe field loss. We further compare this ARG system with an M-type five-state electromagnetically induced transparency (EIT) scheme and demonstrate the superiority of the ARG scheme over the conventional EIT scheme.

  2. Investigating the effect of electro-active ion concentration on spectral induced polarization signatures arising from biomineralization pathways

    NASA Astrophysics Data System (ADS)

    Ntarlagiannis, D.; Slater, L. D.; Williams, K. H.; Hubbard, S. S.; Wu, Y.

    2010-12-01

    Spectral induced polarization (SIP) is a proven geophysical method for detecting biomineral formation with promising applications for monitoring biogeochemical products during microbial induced sequestration of heavy metals and radionuclides in soils. SIP has been used to monitor the evolution of bioremediation-induced end-products at the uranium-contaminated U.S. Department of Energy Rifle Integrated Field Research Challenge site in Colorado. Although a significant SIP response was detected, the quantitative interpretation is non-trivial as the polarization of metallic minerals depends both on the mineral surface properties and the electrolyte chemistry. In previous experiments SIP mechanisms were studied under complex environments and individual source mechanisms could not be evaluated. Here we examine the role of electrolyte chemistry by comparing the effect of redox active / inactive ions on metallic polarization. In these abiotic experiments magnetite was used as a proxy biomineral and dispersed within columns packed with sand. Parallel columns were saturated with solutions of different concentrations of active (Fe2+) and inactive (Ca2+) ions (0.01mM-10mM) and SIP measurements made (0.1-1000 Hz). Experimental results show small, but detectable, differences in the effect of active ion and inactive ion concentration on the SIP response. To better characterize the effect of electro-active ions on metallic minerals we used a Cole - Cole type relaxation model, to describe the SIP responses. In order to better resolve the relaxation model parameters, we followed a two-step approach whereby we started with a Bayesian based inversion to resolve for the initial parameter estimates, and subsequently used these estimates as a starting model for a deterministic solution. Our results suggest that changes in the active ion concentration, in the presence of magnetite, alone are unlikely to fully explain recent SIP monitoring data from the Rifle site.

  3. Geology of the area of induced seismic activity at Monticello Reservoir, South Carolina

    SciTech Connect

    Secor, D.T. Jr.; Smith, W.A.; Snoke, A.W.; Peck, L.S.; Pitcher, D.M.; Prowell, D.C.; Simpson, D.H.

    1982-08-10

    This study provides geological background information necessary for an evaluation of the earthquake hazard in an area of induced seismic activity at Monticello Reservoir, South Carolina. This region contains a thick stratified sequence of Proterozoic Z and Cambrian metasedimentary and metavolcanic rocks. In the early to middle Paleozoic, this sequence was recrystallized and deformed under metamorphic conditions that ranged from greenschist to amphibolite facies and experienced at least two episodes of folding. The region has been intruded by late kinematic to postkinematic granitoid plutons of Silurian and Carboniferous ages and by numerous northwest trending diabase diks of Late Traissic and Early Jurassic age. The region south of Monticello Reservoir in the Carolina slate belt experienced two episodes of faulting in the late Paleozoic and/or early to middle Mesozoic. The older group of faults trends approximately east, has only small displacements, and is characterized by extensive silicifiction of the fault zones. The younger group of faults trends approximately north has experienced dip slip displacements up to 1700 m and is characterized by carbonate mineralization in the fault zones. Both sets of faults are cut by an undeformed diabase dike of Late Triassic or Early Jurassic age. The induced seismic activity around Monticello Reservoir is occurring in a heterogeneous quartz monzonite pluton of Carboniferous age. The pluton contains large enclaves of country rock and is cut by numerous, diversely oriented small faults and joint. These local inhomogeneities in the pluton together with an irregular stress field are interpreted to control the diffuse seismic activity around the reservoir. In view of the apparent absence of lengthy faults it is unlikely that a large-magnitude earthquake will occur in response to the stress and pore pressure changes related to the impoundment of Monticello Reservoir.

  4. Polar Polygons

    NASA Technical Reports Server (NTRS)

    2004-01-01

    26 December 2003 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture displays polygons outlined by cracks in the martian south polar region. This southern summer view was acquired in October 2003 and is located near 86.9oS, 170.6oW. Polygons similar in size and shape to these are common in the arctic and antarctic regions of Earth. On Earth, they indicate the presence (or the past presence) of ground ice and the freeze-thaw cycles that accompany this ice. On Mars, whether ground ice was responsible for these landforms is uncertain, but their presence is suggestive that ground ice may exist or may once have existed in this region. The picture covers an area 3 km (1.9 mi) wide. Sunlight illuminates the scene from the upper left.

  5. Qualitative study exploring healthy eating practices and physical activity among adolescent girls in rural South Africa

    PubMed Central

    2014-01-01

    Background Dietary behaviours and physical activity are modifiable risk factors to address increasing levels of obesity among children and adolescents, and consequently to reduce later cardiovascular and metabolic disease. This paper explores perceptions, attitudes, barriers, and facilitators related to healthy eating and physical activity among adolescent girls in rural South Africa. Methods A qualitative study was conducted in the rural Agincourt subdistrict, covered by a health and sociodemographic surveillance system, in Mpumalanga province, South Africa. Semistructured “duo-interviews” were carried out with 11 pairs of adolescent female friends aged 16 to 19 years. Thematic content analysis was used. Results The majority of participants considered locally grown and traditional foods, especially fruits and vegetables, to be healthy. Their consumption was limited by availability, and these foods were often sourced from family or neighbourhood gardens. Female caregivers and school meal programmes facilitated healthy eating practices. Most participants believed in the importance of breakfast, even though for the majority, limited food within the household was a barrier to eating breakfast before going to school. The majority cited limited accessibility as a major barrier to healthy eating, and noted the increasing intake of “convenient and less healthy foods”. Girls were aware of the benefits of physical activity and engaged in various physical activities within the home, community, and schools, including household chores, walking long distances to school, traditional dancing, and extramural activities such as netball and soccer. Conclusions The findings show widespread knowledge about healthy eating and the benefits of consuming locally grown and traditional food items in a population that is undergoing nutrition transition. Limited access and food availability are strong barriers to healthy eating practices. School meal programmes are an important

  6. Recent advance in Asian polar science - Commemorating ten-year activities of the Asian Forum for Polar Sciences (AFoPS)

    NASA Astrophysics Data System (ADS)

    Watanabe, Kentaro; Doi, Koichiro; Ewe, Hong Tat; Krishnan, Kottekkatu Padinchati; Lee, Jae Il; Liu, Ruiyuan

    2015-12-01

    The Asian Forum for Polar Sciences (AFoPS) was established in 2004 to encourage and facilitate cooperation for the advance of polar sciences among countries in the Asian region. It commemorated tenth anniversary organizing the AFoPS Symposium on 7 October, 2014 in Port Dickson, Malaysia, hosted by the National Antarctic Research Center (NARC), University of Malaya. This second volume of AFoPS Special Issue includes those presentations submitted to the Symposium and scientific papers from AFoPS countries on wide variety of polar research. This publication is one of the excellent achievements of AFoPS.

  7. Use of polarization to improve signal to clutter ratio in an outdoor active imaging system

    NASA Astrophysics Data System (ADS)

    Fontoura, Patrick F.; Giles, Michael K.; Padilla, Denise D.

    2005-08-01

    This paper describes the methodology and presents the results of the design of a polarization-sensitive system used to increase the signal-to-clutter ratio in a robust outdoor structured lighting sensor that uses standard CCD camera technology. This lighting sensor is intended to be used on an autonomous vehicle, looking down to the ground and horizontal to obstacles in an 8 foot range. The kinds of surfaces to be imaged are natural and man-made, such as asphalt, concrete, dirt and grass. The main problem for an outdoor eye-safe laser imaging system is that the reflected energy from background clutter tends to be brighter than the reflected laser energy. A narrow-band optical filter does not reduce significantly the background clutter in bright sunlight, and problems also occur when the surface is highly absorptive, like asphalt. Therefore, most of applications are limited to indoor and controlled outdoor conditions. A series of measurements was made for each of the materials studied in order to find the best configuration for the polarizing system and also to find out the potential improvement in the signal-to-clutter ratio (STC). This process was divided into three parts: characterization of the reflected sunlight, characterization of the reflected laser light, and measurement of the improvement in the STC. The results show that by using polarization properties it is possible to design an optical system that is able to increase the signal-to-clutter ratio from approximately 30% to 100% in the imaging system, depending on the kind of surface and on the incidence angle of the sunlight. The technique was also analyzed for indoor use, with the background clutter being the room illumination. For this specific case, polarization did not improve the signal-to-clutter ratio.

  8. Unusual Polar Conditions in Solar Cycle 24 and Their Implications for Cycle 25

    NASA Astrophysics Data System (ADS)

    Gopalswamy, Nat; Yashiro, Seiji; Akiyama, Sachiko

    2016-05-01

    We report on the prolonged solar-maximum conditions until late 2015 at the north-polar region of the Sun indicated by the occurrence of high-latitude prominence eruptions (PEs) and microwave brightness temperature close to the quiet-Sun level. These two aspects of solar activity indicate that the polarity reversal was completed by mid-2014 in the south and late 2015 in the north. The microwave brightness in the south-polar region has increased to a level exceeding the level of the Cycle 23/24 minimum, but just started to increase in the north. The north–south asymmetry in the polarity reversal has switched from that in Cycle 23. These observations lead us to the hypothesis that the onset of Cycle 25 in the northern hemisphere is likely to be delayed with respect to that in the southern hemisphere. We find that the unusual condition in the north is a direct consequence of the arrival of poleward surges of opposite polarity from the active region belt. We also find that multiple rush-to-the-pole episodes were indicated by the PE locations that lined up at the boundary between opposite-polarity surges. The high-latitude PEs occurred in the boundary between the incumbent polar flux and the insurgent flux of opposite polarity.

  9. Longitudinal fecal hormone analysis for monitoring reproductive activity in the female polar bear (Ursus maritimus).

    PubMed

    Stoops, M A; MacKinnon, K M; Roth, T L

    2012-12-01

    The objective was to identify suitable enzyme immunoassays to monitor gonadal and placental function in the female polar bear. Immunoreactive progesterone, progesterone metabolite (PdG), estrogen, and androgen metabolite (T) concentrations were measured in fecal samples collected over 24 mo from captive female bears (N = 20). Whereas fecal extracts produced displacement curves parallel to the standard curve for each respective steroid, T and PdG more accurately reflected reproductive events. Concentrations of fecal T increased (P < 0.05) during the breeding season, and brief spikes were associated with estrus and mating. A postovulatory increase in PdG was not always detected, but sustained baseline T after mating appeared consistent with ovulation. Parturient bears excreted higher PdG concentrations (P < 0.05) during expected time of embryo implantation in Fall, and a late gestational rise in fecal T occurred 30 days prepartum. Many nonparturient bears also had a PdG rise in the Fall, suggesting they experienced either pregnancy loss or a pseudopregnancy. Differentiating pregnant and pseudopregnant states was not achieved using fecal PdG alone, but when combined with fecal T, comprehensive diagnoses could be made. Nonparturient bears demonstrated elevated (P < 0.05) fecal T during summer months, whereas parturient bears did not. In summary, noninvasive hormone monitoring techniques were established for the female polar bear. Although this study was directed at facilitating management and breeding efforts of captive polar bears, the methods could be applied to studies of reproductive function in wild populations. PMID:23040062

  10. Polar Markings

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA02155 Polar Markings

    These bright and dark markings occurred near the end of summer in the south polar region. The dark material is likely dust that has been freed of frost cover.

    Image information: VIS instrument. Latitude -76.3N, Longitude 84.9E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  11. Polar Layers

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA02153 Polar Layers

    This image of the south polar region shows layered material. It is not known if the layers are formed yearly or if they form over the period of 10s to 100s of years or more.

    Image information: VIS instrument. Latitude -80.3N, Longitude 296.2E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  12. Polar Ridges

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA03662 Polar Ridges

    This ridge system is located in the south polar region.

    Image information: VIS instrument. Latitude -81.7N, Longitude 296.5E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  13. Polar Textures

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03638 Polar Textures

    This image illustrates the variety of textures that appear in the south polar region during late summer.

    Image information: VIS instrument. Latitude 80.5S, Longitude 57.9E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  14. Polar Terrains

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03577 Polar Terrains

    The region surrounding the South Polar Cap contains many different terrain types. This image shows both etched terrain and a region of 'mounds'.

    Image information: VIS instrument. Latitude 75S, Longitude 286.5E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  15. Hypertension and Diabetes Mellitus: A Preliminary South African Health Promotion Activity Using Service-Learning Principles.

    PubMed

    Srinivas, Sunitha C; Paphitis, Sharli Anne

    2016-06-01

    A marked increase in the chronic non-communicable diseases such as hypertension and diabetes mellitus in the South African population is in concert with global trends. A health promotion activity carried out by pharmacy students for school learners during the Sasol National Festival of Science and Technology (SciFest) in South Africa was used as a service-learning opportunity. Pilot tested quizzes on hypertension and diabetes were used to determine the level of knowledge of attendees before and after taking the computer based quiz. Posters, information leaflets and interactive models on these two conditions were also used to reach out to the larger population. Of the 203 participants for the hypertension quiz, 169 completed both the pre- and post-intervention quizzes. Similarly, 86 of the 104 participants for the diabetes quiz, completed both the pre- and post-intervention quizzes. The results show that the post-intervention quiz resulted in a significant increase in the scores from 78.2 to 85.6 % in the case of Hypertension while a marginal increase from 94.2 to 95.5 % was obtained in the case of diabetes. The knowledge of the SciFest attendees with regard to both conditions is above average and improved further after the educational intervention. Health promotion activities which include interactive educational methods and culturally appropriate materials carried out by pharmacy students during service-learning courses are important for improving the awareness on the prevention of these chronic health conditions. Heath promotion service-learning courses can assist in addressing the health care gaps which arise because of a lack of co-ordinated efforts between NGO's and local Government to address the prevention and management of non-communicable diseases such as hypertension and diabetes mellitus. PMID:26659854

  16. Imidazole Alkaloids from the South China Sea Sponge Pericharax heteroraphis and Their Cytotoxic and Antiviral Activities.

    PubMed

    Gong, Kai-Kai; Tang, Xu-Li; Liu, Yi-Sheng; Li, Ping-Lin; Li, Guo-Qiang

    2016-01-01

    Marine sponges continue to serve as a rich source of alkaloids possessing interesting biological activities and often exhibiting unique structural frameworks. In the current study, chemical investigation on the marine sponge Pericharax heteroraphis collected from the South China Sea yielded one new imidazole alkaloid named naamidine J (1) along with four known ones (2-5). Their structures were established by extensive spectroscopic methods and comparison of their data with those of the related known compounds. All the isolates possessed a central 2-aminoimidazole ring, substituted by one or two functionalized benzyl groups in some combination of the C4 and C5 positions. The cytotoxicities against selected HL-60, HeLa, A549 and K562 tumor cell lines and anti-H1N1 (Influenza a virus (IAV)) activity for the isolates were evaluated. Compounds 1 and 2 exhibited cytotoxicities against the K562 cell line with IC50 values of 11.3 and 9.4 μM, respectively. Compound 5 exhibited weak anti-H1N1 (influenza a virus, IAV) activity with an inhibition ratio of 33%. PMID:26821008

  17. Energetic auroral and polar ion outflow at DE 1 altitudes Magnitude, composition, magnetic activity dependence, and long-term variations

    NASA Technical Reports Server (NTRS)

    Yau, A. W.; Lenchyshyn, L.; Shelley, E. G.; Peterson, W. K.

    1985-01-01

    Data acquired from the Dynamics Explorer I Energetic Ion Composition Spectrometer in the period from September 1981 to May 1984 are used to determine the magnitude of the terrestrial ion outflow in the 0.01-17 keV/el range. The data are also employed to investigate the mass composition and topology (local time and invariant latitude distributions) of the ion outflow, as well as the outflow's magnetic activity dependence and long-term variation. The relative importance of auroral versus polar cap upflowing ions as a source of energetic plasma for various parts of the magnetosphere is examined.

  18. Xenoestrogenic and dioxin-like activity in blood of East Greenland polar bears (Ursus maritimus).

    PubMed

    Erdmann, Simon E; Dietz, Rune; Sonne, Christian; Bechshøft, Thea Ø; Vorkamp, Katrin; Letcher, Robert J; Long, Manhai; Bonefeld-Jørgensen, Eva C

    2013-07-01

    The aims of the project were to (i) extract the lipophilic persistent organic pollutants (POPs) from the blood of 99 East Greenland polar bears and assess the combined mixture effect on the estrogen receptor (ER) and the aryl hydrocarbon receptor (AhR) mediated transactivity; (ii) To evaluate whether the receptor transactivities were associated with selected POP markers, and (iii) compare the receptor transactivities in polar bears with earlier studies on Greenlandic Inuit. Lipophilic POPs were extracted using a combination of solid-phase extraction (SPE) and high performance liquid chromatography (HPLC). ER mediated transactivity was determined using the ER luciferase reporter MVLN cell assay. The extracts were tested alone (XER) and together with 17β-estradiol (E2) as a physiological mimic (XERcomp). Dioxins and dioxin-like (DL) compounds were extracted by a combination of SPE and the Supelco Dioxin Prep System®. AhR mediated dioxin-like transactivity was determined using the AhR luciferase reporter Hepa 1.12cR cell assay. Agonistic ER transactivity was elicited by 19% of the samples, and a further increased E2 induced ER response was found for 52%, whereas 17% antagonized the E2 induced ER response. Positive correlations were found in subadult bears between XER and several POP biomarkers. XER and XERcomp correlated positively to each other. A total of 91% of the polar bear blood extracts elicited agonistic AhR transactivity. The AhR-TCDD equivalent (AhR-TEQ) median levels were higher among adult bears compared to subadult bears, but not significantly. PMID:23648332

  19. Proinflammatory-activated glioma cells induce a switch in microglial polarization and activation status, from a predominant M2b phenotype to a mixture of M1 and M2a/B polarized cells

    PubMed Central

    Lisi, Lucia; Stigliano, Egidio; Lauriola, Libero; Navarra, Pierluigi; Russo, Cinzia Dello

    2014-01-01

    Malignant gliomas are primary brain tumors characterized by morphological and genetic complexities, as well as diffuse infiltration into normal brain parenchyma. Within gliomas, microglia/macrophages represent the largest tumor-infiltrating cell population, contributing by at least one-third to the total tumor mass. Bi-directional interactions between glioma cells and microglia may therefore play an important role on tumor growth and biology. In the present study, we have characterized the influence of glioma-soluble factors on microglial function, comparing the effects of media harvested under basal conditions with those of media obtained after inducing a pro-inflammatory activation state in glioma cells. We found that microglial cells undergo a different pattern of activation depending on the stimulus; in the presence of activated glioma-derived factors, i.e. a condition mimicking the late stage of pathology, microglia presents as a mixture of polarization phenotypes (M1 and M2a/b), with up-regulation of iNOS (inducible nitric oxide synthase), ARG (arginase) and IL (interleukine)-10. At variance, microglia exposed to basal glioma-derived factors, i.e. a condition resembling the early stage of pathology, shows a more specific pattern of activation, with increased M2b polarization status and up-regulation of IL-10 only. As far as viability and cell proliferation are concerned, both LI-CM [LPS (lipopolysaccharide)–IFNγ (interferon γ) conditioned media] and C-CM (control-conditioned media) induce similar effects on microglial morphology. Finally, in human glioma tissue obtained from surgical resection of patients with IV grade glioblastoma, we detected a significant amount of CD68 positive cells, which is a marker of macrophage/microglial phagocytic activity, suggesting that in vitro findings presented here might have a relevance in the human pathology as well. PMID:24689533

  20. WRM-1 activates the LIT-1 protein kinase to transduce anterior/posterior polarity signals in C. elegans.

    PubMed

    Rocheleau, C E; Yasuda, J; Shin, T H; Lin, R; Sawa, H; Okano, H; Priess, J R; Davis, R J; Mello, C C

    1999-06-11

    During C. elegans development, Wnt/WG signaling is required for differences in cell fate between sister cells born from anterior/posterior divisions. A beta-catenin-related gene, wrm-1, and the lit-1 gene are effectors of this signaling pathway and appear to downregulate the activity of POP-1, a TCF/LEF-related protein, in posterior daughter cells. We show here that lit-1 encodes a serine/threonine protein kinase homolog related to the Drosophila tissue polarity protein Nemo. We demonstrate that the WRM-1 protein binds to LIT-1 in vivo and that WRM-1 can activate the LIT-1 protein kinase when coexpressed in vertebrate tissue culture cells. This activation leads to phosphorylation of POP-1 and to apparent changes in its subcellular localization. Our findings provide evidence for novel regulatory avenues for an evolutionarily conserved Wnt/WG signaling pathway. PMID:10380924

  1. Extending the X/Ka Celestial Reference Frame over the South Polar Cap: Results from combined NASA-ESA Deep Space Network baselines to Malargüe, Argentina

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.; de Vicente, J.; Dugast, M.; García-Miró, C.; Goodhart, C. E.; Horiuchi, S.; Lowe, S. T.; Maddè, R.; Mercolino, M.; Naudet, C. J.; Snedeker, L. G.; Sotuela, I.; White, L. A.

    2013-03-01

    In order to extend the X/Ka-band (8.4/32 GHz) Celestial Reference Frame coverage over the south polar cap region of declinations -45 to -90 deg, we developed a collaboration between the NASA and ESA Deep Space Networks. In particular ESA's new 35-meter X/Ka-band antenna in Malargüe, Argentina which became operational in January 2013 is now available for X/Ka VLBI baselines to NASA's antennas in Tidbinbilla, Australia; Goldstone, California; and Robledo, Spain. We report first fringes on baselines from Malargüe to Tidbinbilla, Goldstone, and Robledo using a semi-portable digital backend recording at 256 Mbps. To the best of our knowledge the Giga-lambda Malargüe-Tidbinbilla baseline is producing the highest resolution interferometry ever achieved over the south polar cap. We will present the distribution of Ka-band sources detected on this all-southern baseline. Lastly, we will discuss the prospects for using these new baselines to improve the astrometric accuracy of the X/Ka frame in the southern hemisphere.

  2. Counteractive Control of Polarized Morphogenesis during Mating by Mitogen-activated Protein Kinase Fus3 and G1 Cyclin-dependent Kinase

    PubMed Central

    Yu, Lu; Qi, Maosong; Sheff, Mark A.

    2008-01-01

    Cell polarization in response to external cues is critical to many eukaryotic cells. During pheromone-induced mating in Saccharomyces cerevisiae, the mitogen-activated protein kinase (MAPK) Fus3 induces polarization of the actin cytoskeleton toward a landmark generated by the pheromone receptor. Here, we analyze the role of Fus3 activation and cell cycle arrest in mating morphogenesis. The MAPK scaffold Ste5 is initially recruited to the plasma membrane in random patches that polarize before shmoo emergence. Polarized localization of Ste5 is important for shmooing. In fus3 mutants, Ste5 is recruited to significantly more of the plasma membrane, whereas recruitment of Bni1 formin, Cdc24 guanine exchange factor, and Ste20 p21-activated protein kinase are inhibited. In contrast, polarized recruitment still occurs in a far1 mutant that is also defective in G1 arrest. Remarkably, loss of Cln2 or Cdc28 cyclin-dependent kinase restores polarized localization of Bni1, Ste5, and Ste20 to a fus3 mutant. These and other findings suggest Fus3 induces polarized growth in G1 phase cells by down-regulating Ste5 recruitment and by inhibiting Cln/Cdc28 kinase, which prevents basal recruitment of Ste5, Cdc42-mediated asymmetry, and mating morphogenesis. PMID:18256288

  3. A simple method for the synthesis of a polar-embedded and polar-endcapped reversed-phase chromatographic packing with low activity of residue silanols.

    PubMed

    Liu, Hai-Yan; Li, Zhi-Yong; Liu, Dan; Xue, Ying-Wen; Shi, Zhi-Guo

    2016-04-22

    Octadecyl bonded silica (ODS) is the most popular packing for reversed-phase chromatography. However, it generally demonstrates bad resolution for polar analytes because of the residue silanols and its poor stability in aqueous mobile phase. To address the problem, a new reversed-phase packing containing both polar-embedded and polar-endcapped moieties was proposed. It was prepared by a very simple method, in which the epoxide addition reaction of 3-glycidoxypropyltrimethoxysilane with 1-octadecanethiol proceeded simultaneously with the reaction of silane coupling onto silica particles. By controlling the molecular ratio of 3-glycidoxypropyltrimethoxysilane to 1-octadecanethiol higher than 1.0 (1.56 for the present study), both polar-embedded and polar-endcapped moieties were achieved onto the packing. The performance of the packing was evaluated in detail. The results demonstrated that neutral, acidic and basic analytes were well separated on the packing. The column efficiency for phenanthrene was 34,200 theoretical plates per meter. In addition, four nucleotides can be separated in 100% phosphate buffered saline solution with good reproducibility, which indicates the packing has good stability in aqueous mobile phase. Amitriptyline, a typical basic analytes, was eluted out with relatively symmetric peak shape (asymmetry factor of 1.36), which implies that the packing has not suffered from the negative effect of residue silanols significantly. Good stability in buffer solution of pH ranging from 2.0 to 10.0 was also documented for the packing. PMID:27033982

  4. Human saccadic eye movements and tracking by active foveation in log polar space

    NASA Astrophysics Data System (ADS)

    Lim, Fee-Lee; Venkatesh, Svetha; West, Geoffrey A. W.

    1996-04-01

    One of the possible models of the human visual system (HVS) in the computer vision literature has a high resolution fovea and exponentially decreasing resolution periphery. The high resolution fovea is used to extract necessary information in order to solve a vision task and the periphery may be used to detect motion. To obtain the desired information, the fovea is guided by the contents of the scene and other knowledge to position the fovea over areas of interest. These eye movements are called saccades and corrective saccades. A two stage process has been implemented as a mechanism for changing foveation in log polar space. Initially, the open loop stage roughly foveates on the best interest feature and then the closed loop stage is invoked to accurately iteratively converge onto the foveation point. The open loop stage developed for the foveation algorithm is applied to saccadic eye movements and a tracking system. Log polar space is preferred over Cartesian space as: (1) it simultaneously provides high resolution and a wide viewing angle; and (2) feature invariance occurs in the fovea which simplifies the foveation process.

  5. Protest, Performance and Politics: The Use of "Nano-Media" in Social Movement Activism in South Africa

    ERIC Educational Resources Information Center

    Dawson, Marcelle C.

    2012-01-01

    Considering the lack of coverage in the mass media of certain kinds of social movement activity, many movements make use of smaller scale, independent media to publicise their struggles. From the vantage point of social movements in South Africa, this paper addresses what Mojca Pajnik and John Downing call "nano-media". Based on interviews with…

  6. Effect of Active Learning Techniques on Students' Choice of Approach to Learning in Dentistry: A South African Case Study

    ERIC Educational Resources Information Center

    Khan, S.

    2011-01-01

    The purpose of this article is to report on empirical work, related to a techniques module, undertaken with the dental students of the University of the Western Cape, South Africa. I will relate how a range of different active learning techniques (tutorials; question papers and mock tests) assisted students to adopt a deep approach to learning in…

  7. Out-of-School Activities and Achievement among Middle School Students in the U.S. and South Korea

    ERIC Educational Resources Information Center

    Won, Seoung Joun; Han, Seunghee

    2010-01-01

    This study examined the relationships between American and South Korean students' achievement and their time spent in out-of-school activities. Analyzing nationally representative data for 8,912 U.S. and 5,309 Korean middle school students from the Trends in International Mathematics and Science Study (TIMSS) 2003, we found differences in…

  8. Central and South America: Language Arts around the World, Volume II. Cross Curricular Activities for Grades 4-6.

    ERIC Educational Resources Information Center

    Fuchs, Lucy

    Suggesting that students in the intermediate grades can explore the world around them and practice valuable skills in spelling, reading, writing, communication, and language, this book presents cross-curricular units designed to integrate language-arts activities into the study of Central and South American cultures. The units in the book reach…

  9. Executive University Managers' Experiences of Strike and Protest Activity: A Qualitative Case Study of a South African University

    ERIC Educational Resources Information Center

    Dominguez-Whitehead, Y.

    2011-01-01

    Strike and protest activity at South African universities continues to be prevalent nearly two decades after the dismantling of apartheid, although there has been a shift away from directing strikes and protests against the government (during the apartheid era), to directing them against higher education institutions and management (since the…

  10. Active tectonics west of New Zealand's Alpine Fault: South Westland Fault Zone activity shows Australian Plate instability

    NASA Astrophysics Data System (ADS)

    De Pascale, Gregory P.; Chandler-Yates, Nicholas; Dela Pena, Federico; Wilson, Pam; May, Elijah; Twiss, Amber; Cheng, Che

    2016-04-01

    The 300 km long South Westland Fault Zone (SWFZ) is within the footwall of the Central Alpine Fault (<20 km away) and has 3500 m of dip-slip displacement, but it has been unknown if the fault is active. Here the first evidence for SWFZ thrust faulting in the "stable" Australian Plate is shown with cumulative dip-slip displacements up to 5.9 m (with 3 m throw) on Pleistocene and Holocene sediments and gentle hanging wall anticlinal folding. Cone penetration test (CPT) stratigraphy shows repeated sequences within the fault scarp (consistent with thrusting). Optically stimulated luminescence (OSL) dating constrains the most recent rupture post-12.1 ± 1.7 ka with evidence for three to four events during earthquakes of at least Mw 6.8. This study shows significant deformation is accommodated on poorly characterized Australian Plate structures northwest of the Alpine Fault and demonstrates that major active and seismogenic structures remain uncharacterized in densely forested regions on Earth.

  11. Protumoral TSP50 Regulates Macrophage Activities and Polarization via Production of TNF-α and IL-1β, and Activation of the NF-κB Signaling Pathway

    PubMed Central

    Yang, Cheng; Zhang, Dong-Mei; Song, Zhen-Bo; Hou, Ya-Qin; Bao, Yong-Li; Sun, Lu-Guo; Yu, Chun-Lei; Li, Yu-Xin

    2015-01-01

    Testes-specific protease 50 (TSP50) is abnormally overexpressed in many kinds of cancers and promotes cell proliferation and migration. However, whether TSP50 can influence the tumor microenvironment, especially the function of immune cells in the microenvironment, remains largely unknown. We demonstrated that exposure to the conditioned medium from TSP50-overexpressing cells, or co-culture with TSP50-overexpressing cells, enhanced the cytokine production and phagocytic activities of macrophages, and induced M2b polarization. Further investigation showed that production of TNF-α and IL-1β was strongly induced by TSP50 in TSP50-overexpressing cells. TSP50-induced TNF-α and IL-1β were main factors that mediated the effects of TSP50-overexpressing cells on macrophages. The NF-κB pathway could be activated in macrophages upon the treatment of conditioned medium of TSP50-overexpressing cells and its activation is necessary for the observed effects on macrophages. Taken together, our results suggested that oncogenic TSP50 expressed in cells could activate surrounding macrophages and induce M2b polarization, partly through inducing TNF-α/ IL-1β secretion and subsequent NF-κB pathway activation. This implies a potential mechanism by which oncogene TSP50 regulates tumor microenvironment to support tumor development. PMID:26684869

  12. Heightened free radical activity in blacks with chronic pancreatitis at Johannesburg, South Africa.

    PubMed

    Gut, A; Shiel, N; Kay, P M; Segal, I; Braganza, J M

    1994-10-31

    Four indices of free radical activity were measured in fasting serum/plasma samples from 14 consecutive blacks with clinically quiescent chronic pancreatitis and 15 outwardly healthy hospital personnel at Soweto, the township near Johannesburg in South Africa. The patients had higher serum levels than did controls of lipid isomerisation (P < 0.002) and peroxidation (P < 0.05) markers, with lower plasma levels of glutathione (P < 0.0001) and bioactive fraction of vitamin C (P < 0.002). Lipid peroxide and non-bioavailable vitamin C concentrations in Sowetan patients were significantly higher than in their counterparts from Manchester, UK (P < 0.0001, P < 0.0005, respectively). These differences mirrored those in controls in that outwardly healthy Sowetans had much higher serum lipid peroxide levels than Manchester controls (P < 0.001) and much lower plasma concentration of vitamin C (P < 0.001) and hence of the bioavailable fraction ascorbate (P < 0.0002). Heightened free radical activity is thus a common denominator in chronic pancreatitis irrespective of geography, or putative aetiological factors whether alcoholism or idiopathic, since that ratio was approximately 95:5 at Johannesburg and 50:50 at Manchester. The further finding of subclinical oxidative stress in Sowetan controls and the endemic nature of chronic pancreatitis in that area supports the hypothesis that oxidative stress may be involved in its pathogenesis. PMID:7834869

  13. Education and Public Outreach activities in Radio astronomy with the SKA South Africa

    NASA Astrophysics Data System (ADS)

    Oozeer, N.; Bassett, B. A.; de Boer, K.

    2014-10-01

    A Human Capital Development (HCD) program is a crucial part of any large organisation, and especially for large new research facilities such as the Square Kilometre Array (SKA) Africa. HCD provides a way of developing and channeling new minds into a very demanding field that ensures sustainability of the project and a multitude of spin-off benefits. Apart from educating learners at various levels, the HCD program must also inspire and educate the general public about the projects via an active outreach program. We highlight the various types of outreach activities that have been carried out in South Africa and the other SKA Africa partner countries. While there exist many teaching models we introduce and explore a novel concept of peer teaching for research known as the Joint Exchange Development Initiative (JEDI) and present some of its results. The JEDI workshops have resulted in a considerable number of learners embarking on advanced careers in science and research, and the demand is still growing.

  14. Neutrophils exposed to A. phagocytophilum under shear stress fail to fully activate, polarize, and transmigrate across inflamed endothelium.

    PubMed

    Schaff, U Y; Trott, K A; Chase, S; Tam, K; Johns, J L; Carlyon, J A; Genetos, D C; Walker, N J; Simon, S I; Borjesson, D L

    2010-07-01

    Anaplasma phagocytophilum is an obligate intracellular bacterium that has evolved mechanisms to hijack polymorphonuclear neutrophil (PMN) receptors and signaling pathways to bind, infect, and multiply within the host cell. E-selectin is upregulated during inflammation and is a requisite endothelial receptor that supports PMN capture, rolling, and activation of integrin-mediated arrest. Ligands expressed by PMN that mediate binding to endothelium via E-selectin include sialyl Lewis x (sLe(x))-expressing ligands such as P-selectin glycoprotein ligand-1 (PSGL-1) and other glycolipids and glycoproteins. As A. phagocytophilum is capable of binding to sLe(x)-expressing ligands expressed on PMN, we hypothesized that acute bacterial adhesion to PMN would subsequently attenuate PMN recruitment during inflammation. We assessed the dynamics of PMN recruitment and migration under shear flow in the presence of a wild-type strain of A. phagocytophilum and compared it with a strain of bacteria that binds to PMN independent of PSGL-1. Acute bacterial engagement with PMN resulted in transient PMN arrest and minimal PMN polarization. Although the wild-type pathogen also signaled activation of beta2 integrins and elicited a mild intracellular calcium flux, downstream signals including PMN transmigration and phosphorylation of p38 mitogen-activated protein kinase (MAPK) were inhibited. The mutant strain bound less well to PMN and failed to activate beta2 integrins and induce a calcium flux but did result in decreased PMN arrest and polarization that may have been partially mediated by a suppression of p38 MAPK activation. This model suggests that A. phagocytophilum binding to PMN under shear flow during recruitment to inflamed endothelium interferes with normal tethering via E-selectin and navigational signaling of transendothelial migration. PMID:20392928

  15. Combined Active and Passive Seismology to Study Continental Collision; Central South Island of New Zealand

    NASA Astrophysics Data System (ADS)

    Stern, T.; Okaya, D.; Baldock, G.; Scherwath, M.

    2005-12-01

    Central South Island of New Zealand is a continental region that has undergone both collision and strike-slip shear in the late Tertiary. From a tectonics, or rock-mechanics, view-point there is an interest in how the crust and mantle have been both thickened and sheared. The South Island Geophysical Transect (SIGHT) and the Southern Alps Passive Seismic Experiment (SAPSE) - both jointly funded US-NZ programs - studied these processes. Some of the most important findings came about by merging data from passive and active seismology. Three specific examples will be discussed: 1. Teleseismic P-wave delays from earthquakes in the Western Pacific are used to map a ~ 0.8-1 s speed-up in the mantle right beneath the region of thickest crust and highest topography of the collision zone. Forward modeling of this velocity anomaly shows that the amplitude of the anomaly can be explained by a 100 km-thick body that has a 7% in increase in P-wave speed. From the spatial pattern of the P-wave residuals we can also show that the high-speed body is about 80-100 km wide and roughly vertically disposed beneath the crustal root. The shape and position of the high-speed body beneath the seismically determined crustal root is consistent with it being thickened, and therefore cold, mantle lithosphere that has uniformly strained into a roughly symmetric root beneath the collision zone. 2. Pn anisotropy measurements from our onshore-offshore seismic shooting program allowed us to make mutually perpendicular determinations of Pn wave speeds at three localities. P-wave anisotropies of up to 11 ± 3%, 6.5 ± 2.5% and 0 ± 3%, were measured, depending on the distance of the measurement from the surface trace of the plate boundary (the Alpine Fault). These are necessarily minimum anisotropy values because it assumes that the two axes of measurement are those of minimum and maximum wave speed. Combining these results with SKS splitting values of ~ 2 s from passive seismology allowed us to make

  16. Polarization-independent actively tunable colour generation on imprinted plasmonic surfaces.

    PubMed

    Franklin, Daniel; Chen, Yuan; Vazquez-Guardado, Abraham; Modak, Sushrut; Boroumand, Javaneh; Xu, Daming; Wu, Shin-Tson; Chanda, Debashis

    2015-01-01

    Structural colour arising from nanostructured metallic surfaces offers many benefits compared to conventional pigmentation based display technologies, such as increased resolution and scalability of their optical response with structure dimensions. However, once these structures are fabricated their optical characteristics remain static, limiting their potential application. Here, by using a specially designed nanostructured plasmonic surface in conjunction with high birefringence liquid crystals, we demonstrate a tunable polarization-independent reflective surface where the colour of the surface is changed as a function of applied voltage. A large range of colour tunability is achieved over previous reports by utilizing an engineered surface which allows full liquid crystal reorientation while maximizing the overlap between plasmonic fields and liquid crystal. In combination with imprinted structures of varying periods, a full range of colours spanning the entire visible spectrum is achieved, paving the way towards dynamic pixels for reflective displays. PMID:26066375

  17. Polar [3 + 2] cycloaddition of ketones with electrophilically activated carbonyl ylides. Synthesis of spirocyclic dioxolane indolinones.

    PubMed

    Bentabed-Ababsa, Ghenia; Derdour, Aicha; Roisnel, Thierry; Sáez, Jose A; Domingo, Luis R; Mongin, Florence

    2008-09-01

    The [3 + 2] cycloaddition reaction between carbonyl ylides generated from epoxides and ketones (ethyl pyruvate, ethyl phenylglyoxylate, isatin, N-methylisatin and 5-chloroisatin) to give substituted dioxolanes and spirocyclic dioxolane indolinones was investigated. The effect of microwave irradiation on the outcome of the reaction was studied. The thermal reaction between 2,2-dicyano-3-phenyloxirane and N-methylisatin was theoretically studied using DFT methods. This reaction is a domino process that comprises two steps. The first is the thermal ring opening of the epoxide to yield a carbonyl ylide intermediate, whereas the second step is a polar [3 + 2] cycloaddition to yield the final spiro cycloadducts. The cycloaddition presents a low stereoselectivity and a large regio- and chemoselectivity. Analysis of the electrophilicity values and the Fukui functions of the reagents involved in the cycloaddition step allowed the chemical outcome to be explained. PMID:18698474

  18. Polarization-independent actively tunable colour generation on imprinted plasmonic surfaces

    PubMed Central

    Franklin, Daniel; Chen, Yuan; Vazquez-Guardado, Abraham; Modak, Sushrut; Boroumand, Javaneh; Xu, Daming; Wu, Shin-Tson; Chanda, Debashis

    2015-01-01

    Structural colour arising from nanostructured metallic surfaces offers many benefits compared to conventional pigmentation based display technologies, such as increased resolution and scalability of their optical response with structure dimensions. However, once these structures are fabricated their optical characteristics remain static, limiting their potential application. Here, by using a specially designed nanostructured plasmonic surface in conjunction with high birefringence liquid crystals, we demonstrate a tunable polarization-independent reflective surface where the colour of the surface is changed as a function of applied voltage. A large range of colour tunability is achieved over previous reports by utilizing an engineered surface which allows full liquid crystal reorientation while maximizing the overlap between plasmonic fields and liquid crystal. In combination with imprinted structures of varying periods, a full range of colours spanning the entire visible spectrum is achieved, paving the way towards dynamic pixels for reflective displays. PMID:26066375

  19. Wingless-type family member 3A triggers neuronal polarization via cross-activation of the insulin-like growth factor-1 receptor pathway

    PubMed Central

    Bernis, María E.; Oksdath, Mariana; Dupraz, Sebastián; Nieto Guil, Alvaro; Fernández, Marisa M.; Malchiodi, Emilio L.; Rosso, Silvana B.; Quiroga, Santiago

    2013-01-01

    Initial axonal elongation is essential for neuronal polarization and requires polarized activation of IGF-1 receptors (IGF-1r) and the phosphatidylinositol 3 kinase (PI3k) pathway. Wingless-type family growth factors (Wnts) have also been implied in the regulation of axonal development. It is not known, however, if Wnts have any participation in the regulation of initial axonal outgrowth and the establishment of neuronal polarity. We used cultured hippocampal neurons and growth cone particles (GCPs) isolated from fetal rat brain to show that stimulation with the wingless family factor 3A (Wnt3a) was sufficient to promote neuronal polarization in the absence of IGF-1 or high insulin. We also show that Wnt3a triggered a strong activation of IGF-1r, PI3k, and Akt in developmental Stage 2 neurons and that the presence of activatable IGF-1r and PI3k activation were necessary for Wnt3a polarizing effects. Surface plasmon resonance (SPR) experiments show that Wnt3a did not bind specifically to the IGF-1r. Using crosslinking and immuno-precipitation experiments, we show that stimulation with Wnt3a triggered the formation of a complex including IGF-1r-Wnt3a-Frizzled-7. We conclude that Wnt3a triggers polarization of neurons via cross-activation of the IGF-1r/PI3k pathway upon binding to Fz7. PMID:24298236

  20. DISCOVERY OF THE RECOMBINING PLASMA IN THE SOUTH OF THE GALACTIC CENTER: A RELIC OF THE PAST GALACTIC CENTER ACTIVITY?

    SciTech Connect

    Nakashima, S.; Nobukawa, M.; Uchida, H.; Tanaka, T.; Tsuru, T. G.; Koyama, K.; Murakami, H.; Uchiyama, H.

    2013-08-10

    We report Suzaku results for soft X-ray emission to the south of the Galactic center (GC). The emission (hereafter {sup G}C South{sup )} has an angular size of {approx}42' Multiplication-Sign 16' centered at (l, b) {approx} (0. Degree-Sign 0, - 1. Degree-Sign 4) and is located in the largely extended Galactic ridge X-ray emission (GRXE). The X-ray spectrum of GC South exhibits emission lines from highly ionized atoms. Although the X-ray spectrum of the GRXE can be well fitted with a plasma in collisional ionization equilibrium (CIE), that of GC South cannot be fitted with a plasma in CIE, leaving hump-like residuals at {approx}2.5 and 3.5 keV, which are attributable to the radiative recombination continua of the K-shells of Si and S, respectively. In fact, GC South spectrum is well fitted with a recombination-dominant plasma model; the electron temperature is 0.46 keV while atoms are highly ionized (kT = 1.6 keV) in the initial epoch, and the plasma is now in a recombining phase at a relaxation scale (plasma density Multiplication-Sign elapsed time) of 5.3 Multiplication-Sign 10{sup 11} s cm{sup -3}. The absorption column density of GC South is consistent with that toward the GC region. Thus, GC South is likely to be located in the GC region ({approx}8 kpc distance). The size of the plasma, the mean density, and the thermal energy are estimated to be {approx}97 pc Multiplication-Sign 37 pc, 0.16 cm{sup -3}, and 1.6 Multiplication-Sign 10{sup 51} erg, respectively. We discuss possible origins of the recombination-dominant plasma as a relic of past activity in the GC region.

  1. Activation Layer Stabilization of High Polarization Photocathodes in Sub-Optimal RF Gun Environments

    SciTech Connect

    Mulhollan, Gregory; /SLAC /Saxed Surface Science, Austin, TX

    2010-08-25

    We have developed an activation procedure by which the reactivity to CO{sub 2}, a principal cause of yield decay for GaAs photocathodes, is greatly reduced. The use of a second alkali in the activation process is responsible for the increased immunity of the activated surface. The best immunity was obtained by using a combination of Cs and Li without any loss in near bandgap yield. Optimally activated photocathodes have nearly equal quantities of both alkalis.

  2. Novel inhibitors for PRMT1 discovered by high-throughput screening using activity-based fluorescence polarization.

    PubMed

    Dillon, Myles B C; Bachovchin, Daniel A; Brown, Steven J; Finn, M G; Rosen, Hugh; Cravatt, Benjamin F; Mowen, Kerri A

    2012-07-20

    Protein arginine methyltransferases (PRMTs) catalyze the posttranslational methylation of arginine using S-adenosylmethionine (SAM) as a methyl-donor. The PRMT family is widely expressed and has been implicated in biological functions such as RNA splicing, transcriptional control, signal transduction, and DNA repair. Therefore, specific inhibitors of individual PRMTs have potentially significant research and therapeutic value. In particular, PRMT1 is responsible for >85% of arginine methyltransferase activity, but currently available inhibitors of PRMT1 lack specificity, efficacy, and bioavailability. To address this limitation, we developed a high-throughput screening assay for PRMT1 that utilizes a hyper-reactive cysteine within the active site, which is lacking in almost all other PRMTs. This assay, which monitors the kinetics of the fluorescence polarization signal increase upon PRMT1 labeling by a rhodamine-containing cysteine-reactive probe, successfully identified two novel inhibitors selective for PRMT1 over other SAM-dependent methyltransferases. PMID:22506763

  3. Mapping two-dimensional polar active fluids to two-dimensional soap and one-dimensional sandblasting

    NASA Astrophysics Data System (ADS)

    Chen, Leiming; Lee, Chiu Fan; Toner, John

    2016-07-01

    Active fluids and growing interfaces are two well-studied but very different non-equilibrium systems. Each exhibits non-equilibrium behaviour distinct from that of their equilibrium counterparts. Here we demonstrate a surprising connection between these two: the ordered phase of incompressible polar active fluids in two spatial dimensions without momentum conservation, and growing one-dimensional interfaces (that is, the 1+1-dimensional Kardar-Parisi-Zhang equation), in fact belong to the same universality class. This universality class also includes two equilibrium systems: two-dimensional smectic liquid crystals, and a peculiar kind of constrained two-dimensional ferromagnet. We use these connections to show that two-dimensional incompressible flocks are robust against fluctuations, and exhibit universal long-ranged, anisotropic spatio-temporal correlations of those fluctuations. We also thereby determine the exact values of the anisotropy exponent ζ and the roughness exponents χx,y that characterize these correlations.

  4. Mapping two-dimensional polar active fluids to two-dimensional soap and one-dimensional sandblasting.

    PubMed

    Chen, Leiming; Lee, Chiu Fan; Toner, John

    2016-01-01

    Active fluids and growing interfaces are two well-studied but very different non-equilibrium systems. Each exhibits non-equilibrium behaviour distinct from that of their equilibrium counterparts. Here we demonstrate a surprising connection between these two: the ordered phase of incompressible polar active fluids in two spatial dimensions without momentum conservation, and growing one-dimensional interfaces (that is, the 1+1-dimensional Kardar-Parisi-Zhang equation), in fact belong to the same universality class. This universality class also includes two equilibrium systems: two-dimensional smectic liquid crystals, and a peculiar kind of constrained two-dimensional ferromagnet. We use these connections to show that two-dimensional incompressible flocks are robust against fluctuations, and exhibit universal long-ranged, anisotropic spatio-temporal correlations of those fluctuations. We also thereby determine the exact values of the anisotropy exponent ζ and the roughness exponents χx,y that characterize these correlations. PMID:27452107

  5. Contribution of flavonoids to the overall radical scavenging activity of olive (Olea europaea L.) leaf polar extracts.

    PubMed

    Goulas, Vlassios; Papoti, Vassiliki T; Exarchou, Vassiliki; Tsimidou, Maria Z; Gerothanassis, Ioannis P

    2010-03-24

    The contribution of flavonoids to the overall radical scavenging activity of olive leaf polar extracts, known to be good sources of oleuropein related compounds, was examined. Off line and on line HPLC-DPPH(*) assays were employed, whereas flavonoid content was estimated colorimetrically. Individual flavonoid composition was first assessed by RP-HPLC coupled with diode array and fluorescence detectors and verified by LC-MS detection system. Olive leaf was found a robust source of flavonoids regardless sampling parameters (olive cultivar, leaf age or sampling date). Total flavonoids accounted for the 13-27% of the total radical scavenging activity assessed using the on line protocol. Luteolin 7-O-glucoside was one of the dominant scavengers (8-25%). Taking into consideration frequency of appearance the contribution of luteolin (3-13%) was considered important, too. Our findings support that olive leaf, except for oleuropein and related compounds, is also a stable source of bioactive flavonoids. PMID:20166722

  6. ΔF508 CFTR processing correction and activity in polarized airway and non-airway cell monolayers

    PubMed Central

    Rowe, SM; Pyle, LC; Jurkevante, A; Varga, K; Collawn, J; Sloane, PA; Woodworth, B; Mazur, M; Fulton, J; Fan, L; Li, Y; Fortenberry, J; Sorscher, EJ; Clancy, JP

    2010-01-01

    We examined the activity of ΔF508 cystic fibrosis transmembrane conductance regulator (CFTR) stably expressed in polarized cystic fibrosis bronchial epithelial cells (CFBE41o−) human airway cells and Fisher Rat Thyroid (FRT) cells following treatment with low temperature and a panel of small molecule correctors of ΔF508 CFTR misprocessing. Corr-4a increased ΔF508 CFTR-dependent Cl− conductance in both cell types, whereas treatment with VRT-325 or VRT-640 increased activity only in FRT cells. Total currents stimulated by forskolin and genistein demonstrated similar dose/response effects to Corr-4a treatment in each cell type. When examining the relative contribution of forskolin and genistein to total stimulated current, CFBE41o− cells had smaller forskolin-stimulated Isc following either low temperature or corr-4a treatment (10–30% of the total Isc produced by the combination of both CFTR agonists). In contrast, forskolin consistently contributed greater than 40% of total Isc in ΔF508 CFTR expressing FRT cells corrected with low temperature, and corr-4a treatment preferentially enhanced forskolin dependent currents only in FRT cells (60% of total Isc). ΔF508 CFTR cDNA transcript levels, ΔF508 CFTR C band levels, or cAMP signaling did not account for the reduced forskolin response in CFBE41o− cells. Treatment with non-specific inhibitors of phosphodiesterases (papaverine) or phosphatases (endothall) did not restore ΔF508 CFTR activation by forskolin in CFBE41o− cells, indicating that the Cl− transport defect in airway cells is distal to cAMP or its metabolism. The results identify important differences in ΔF508 CFTR activation in polarizing epithelial models of CF, and have important implications regarding detection of rescued of ΔF508 CFTR in vivo. PMID:20226262

  7. The 1968 Edcouch-Elsa High School Walkout: Chicano Student Activism in a South Texas Community

    ERIC Educational Resources Information Center

    Barrera, James B.

    2004-01-01

    A nonviolent school boycott by 192 Chicanola students in 1968 at Edcouch-Elsa high school in the Rio Grande Valley region of Deep South Texas is examined. This walkout was the first major Chicano student protest in South Texas, and was a product of the 1960s Chicano movement.

  8. EDs in the Midwest and South activate disaster plans as deadly tornadoes sweep through the region.

    PubMed

    2012-05-01

    Hospitals in the Midwest and South activated their disaster plans in early March to deal with a phalanx of powerful tornadoes that leveled several small towns and killed at least two dozen people. Some hospitals had to activate plans for both internal and external disasters as their own facilities were threatened. One small critical-access hospital in West Liberty, KY, sustained significant damage and had to evacuate its patients to another facility. All the hospitals credit their disaster plans and practice drills with helping them to manage the crisis as efficiently as possible. Morgan County ARH Hospital in West Liberty, KY, went for several days without an operational lab or radiology department, but staff kept the ED open for absolute emergencies. Margaret Mary Community Hospital (MMCH) in Batesville, IN, received six tornado victims, but it was prepared for many more. Administrators credit advanced warning of the storms with helping them to prepare effectively, as well as to coordinate their response with other hospitals in the area. As a level 1 trauma center, the University of Louisville Hospital in Louisville, KY, received all the most seriously injured patients in the region, even while the facility itself was under a tornado warning. Staff had to route families away from the glassed-in waiting room to the basement until the tornado warning had passed. At one point during the crisis, there were 90 patients in the hospital's ED even though the department is only equipped with 29 beds. Administrators at Huntsville Hospital in Huntsville, AL, encouraged colleagues to take advantage of smaller-scale emergencies to activate parts of their disaster plans, and to focus disaster preparation drills on their hospital's top hazard vulnerabilities. PMID:22545338

  9. Spontaneous flow in polar active fluids: the effect of a phenomenological self propulsion-like term.

    PubMed

    Bonelli, Francesco; Gonnella, Giuseppe; Tiribocchi, Adriano; Marenduzzo, Davide

    2016-01-01

    We present hybrid lattice Boltzmann simulations of extensile and contractile active fluids where we incorporate phenomenologically the tendency of active particles such as cell and bacteria, to move, or swim, along the local orientation. Quite surprisingly, we show that the interplay between alignment and activity can lead to completely different results, according to geometry (periodic boundary conditions or confinement between flat walls) and nature of the activity (extensile or contractile). An interesting generic outcome is that the alignment interaction can transform stationary active patterns into continuously moving ones: the dynamics of these evolving patterns can be oscillatory or chaotic according to the strength of the alignment term. Our results suggest that flow-polarisation alignment can have important consequences on the collective dynamics of active fluids and active gel. PMID:26769011

  10. Spatial and temporal variations in fault activity during early development of rift polarity within the offshore Corinth rift, central Greece

    NASA Astrophysics Data System (ADS)

    Nixon, C. W.; Moyle, A.; McNeill, L. C.; Bell, R. E.; Bull, J. M.; Henstock, T.

    2014-12-01

    The Corinth rift, Greece, is a young, highly active rift. A combined dense network of marine geophysical data and onshore exposure makes Corinth a natural laboratory for investigating early rift and fault formation. Rifts commonly develop a primary polarity during their formation resulting from a dominant fault set. However, how this occurs and develops is less clear. Here we characterise this process by establishing how a dominant fault set develops within the Corinth rift. Using a high spatio-temporal resolution chronostratigraphic and rift fault model, we investigate the variations in the distribution of displacement and faulting along and across the rift axis; focussing on the partitioning of deformation between N- and S-dipping faults, at a temporal resolution of ca. 100 kyr or less. Along-strike cumulative fault displacement profiles indicate overall equal distribution of strain between major S- and N-dipping faults over the last ca. 1.5 Myr. In detail, two peaks in cumulative displacement coincide with the early development of two discrete depocentres before ca. 600 ka. Since this time, displacement has become focussed on N-dipping faults with S-dipping faults becoming less active. Syn-rift isochore maps illuminate this change: a switch in rift polarity from a dominant N-thickening depocentre to a dominant S-thickening depocentre between ca. 530-420 kyr (a rapid change in rift structure and strain distribution). This change is accommodated by transfer of activity between major faults but also by formation of numerous non-basement cutting small faults. As major S-dipping faults decrease in slip rate from ca. 600 ka, they become segmented into smaller faults with variable slip rates. In contrast, N-dipping faults on the rift's southern margin, with increased activity post ~0.5-0.4 Ma, become kinematically and geometrically linked with almost equal slip rates along strike by ca. 130 kyr, controlling the single major depocentre of the present day. Our results

  11. The Polar Insulation Investigation

    ERIC Educational Resources Information Center

    Urban-Rich, Juanita

    2006-01-01

    In this article, the author developed an activity called "The Polar Insulation Investigation." This activity builds on students' natural interest in "things polar" and introduces them to animal adaptations in a unique way. The aim of the exploration is to determine the role of animal coverings (e.g., blubber, fur, and feathers) and to see which is…

  12. Models of Active Glacial Isostasy Roofing Warm Subduction: Case of the South Patagonian Ice Field

    NASA Technical Reports Server (NTRS)

    Klemann, Volker; Ivins, Erik R.; Martinec, Zdenek; Wolf, Detlef

    2007-01-01

    Modern geodetic techniques such as precise Global Positioning System (GPS) and high-resolution space gravity mapping (Gravity Recovery and Climate Experiment, GRACE) make it possible to measure the present-day rate of viscoelastic gravitational Earth response to present and past glacier mass changes. The Andes of Patagonia contain glacial environments of dramatic mass change. These mass load changes occur near a tectonically active boundary between the Antarctic and South American plates. The mechanical strength of the continental side of this boundary is influenced by Neogene ridge subduction and by the subduction of a youthful oceanic slab. A ridge of young volcanos parallels the Pacific coastline. Release of volatiles (such as water) at depth along this ridge creates a unique rheological environment. To assess the influence of this rheological ridge structure on the observational land uplift rate, we apply a two dimensional viscoelastic Earth model. A numerical study is presented which examines the sensitivity of the glacial loading-unloading response to the complex structure at depth related to the subducting slab, the viscous wedge between slab and continental lithosphere, and the increase of elastic thickness from oceanic to continental lithosphere. A key feature revealed by our numerical experiments is a continuum flow wherein the slab subdues the material transport toward oceanic mantle and crust. The restricted flow is sensitive to the details of slab mechanical strength and penetration into the upper mantle. The reduced viscosity within the mantle wedge, however, enhances the load-induced material transport everywhere within the asthenosphere.

  13. 9,11-Secosteroids with cytotoxic activity from the South China Sea gorgonian coral Subergorgia suberosa.

    PubMed

    Zhang, Jun; Liu, Ling-Li; Zhong, Ba-Lian; Liao, Xiao-Jian; Xu, Shi-Hai

    2015-06-01

    Nine new 9,11-secosterols (1-9), containing the same 3β,6α,11-trihydroxy-9,11-seco-5α-cholest-7-en-9-one steroidal nucleus, whereas possessing an array of structurally diverse side chains, along with fourteen known 9,11-secosterol compounds (10-23), were isolated from the South China Sea gorgonian coral Subergorgia suberosa, of which 3/4, 5/6, 7/8, and the known compounds 11/12, 20/21 were five pairs of inseparable C-24 epimers. Their structures were established by the extensive analyses of 1D and 2D NMR spectra, high-resolution chemical ionization mass spectrometry (HRCIMS), and by the comparison with literature data. Cytotoxic effect of these metabolites against the growth of HeLa cell lines was evaluated. The result showed that the inhibitory effect of compounds 1-23 varied considerably depending on the nature of the side chain in spite of sharing the same steroidal nucleus. Compound 19, featuring both the absence of hydroxyl group and the presence of double bond in the stigmasterol side chain, exhibited the most potent cytotoxicity with IC50 being 15.1 μM. The preliminary structure activity relationship studies identified some important structural features considerably influencing the biological effect deserved, providing valuable information for chemists and pharmacologists to design and synthesize more effective antitumor agents bearing the 9,11-secosteroid framework. PMID:25796549

  14. Concentrations and activity ratios of uranium isotopes in groundwater from Donana National Park, South of Spain

    SciTech Connect

    Bolivar, J. P.; Olias, M.; Gonzalez-Garcia, F.; Garcia-Tenorio, R.

    2008-08-07

    The levels and distribution of natural radionuclides in groundwaters from the unconfined Almonte-Marismas aquifer, upon which Donana National Park is located, have been analysed. Most sampled points were multiple piezometers trying to study the vertical distribution of the hydrogeochemical characteristics in the aquifer. Temperature, pH, electrical conductivity, dissolved oxygen and redox potential were determined in the field. A large number of parameters, physico-chemical properties, major and minor ions, trace elements and natural radionuclides (U-isotopes, Th-isotopes, Ra-isotopes and {sup 210}Po), were also analysed. In the southern zone, where aeolian sands crop out, water composition is of the sodium chloride type, and the lower U-isotopes concentrations have been obtained. As water circulates through the aquifer, bicarbonate and calcium concentrations increase slightly, and higher radionuclides concentrations were measured. Finally, we have demonstrated that {sup 234}U/{sup 238}U activity ratios can be used as markers of the type of groundwater and bedrock, as it has been the case for old waters with marine origin confined by a marsh in the south-east part of aquifer.

  15. No covariation between the geomagnetic activity and the incidence of acute myocardial infarction in the polar area of northern Sweden.

    PubMed

    Messner, T; Häggström, I; Sandahl, I; Lundberg, V

    2002-05-01

    This study was undertaken to investigate whether there was any relation between the aurora borealis (measured as the geomagnetic activity) and the number of acute myocardial infarctions (AMI) in the northern, partly polar, area of Sweden. The AMI cases were collected from The Northern Sweden MONICA (multinational MONItoring of trends and determinants of CArdiovascular disease) AMI registry between 1985 and 1998, inclusive, and the information on the geomagnetic activity from continuous measurements at the Swedish Institute of Space Physics, Kiruna. In the analyses, both the relation between the individual AMI case and ambient geomagnetic activity, and the relation between the mean daily K index and the daily number of AMI cases were tested. We found no statistically significant relation between the number of fatal or non-fatal AMI cases, the number of sudden deaths or the number of patients with chest pain without myocardial damage, and geomagnetic activity. Our data do not support a relation between the geomagnetic activity and AMI. PMID:12135204

  16. Nanostructured TiO2 surfaces promote polarized activation of microglia, but not astrocytes, toward a proinflammatory profile

    NASA Astrophysics Data System (ADS)

    de Astis, Silvia; Corradini, Irene; Morini, Raffaella; Rodighiero, Simona; Tomasoni, Romana; Lenardi, Cristina; Verderio, Claudia; Milani, Paolo; Matteoli, Michela

    2013-10-01

    Activation of glial cells, including astrocytes and microglia, has been implicated in the inflammatory responses underlying brain injury and neurodegenerative diseases including Alzheimer's and Parkinson's diseases. The classic activation state (M1) is characterized by high capacity to present antigens, high production of nitric oxide (NO) and reactive oxygen species (ROS) and proinflammatory cytokines. Classically activated cells act as potent effectors that drive the inflammatory response and may mediate detrimental effects on neural cells. The second phenotype (M2) is an alternative, apparently beneficial, activation state, more related to a fine tuning of inflammation, scavenging of debris, promotion of angiogenesis, tissue remodeling and repair. Specific environmental chemical signals are able to induce these different polarization states. We provide here evidence that nanostructured substrates are able, exclusively in virtue of their physical properties, to push microglia toward the proinflammatory activation phenotype, with an efficacy which reflects the graded nanoscale rugosity. The acquisition of a proinflammatory phenotype appears specific for microglia and not astrocytes, indicating that these two cell types, although sharing common innate immune responses, respond differently to external physical stimuli.

  17. Role of the Exposed Polar Facets in the Performance of Thermally and UV Activated ZnO Nanostructured Gas Sensors

    PubMed Central

    2013-01-01

    ZnO nanostructures with different morphologies (nanowires, nanodisks, and nanostars) were synthesized hydrothermally. Gas sensing properties of the as-grown nanostructures were investigated under thermal and UV activation. The performance of the ZnO nanodisk gas sensor was found to be superior to that of other nanostructures (Sg ∼ 3700% to 300 ppm ethanol and response time and recovery time of 8 and 13 s). The enhancement in sensitivity is attributed to the surface polarities of the different structures on the nanoscale. Furthermore, the selectivity of the gas sensors can be achieved by controlling the UV intensity used to activate these sensors. The highest sensitivity value for ethanol, isopropanol, acetone, and toluene are recorded at the optimal UV intensity of 1.6, 2.4, 3.2, and 4 mW/cm2, respectively. Finally, the UV activation mechanism for metal oxide gas sensors is compared with the thermal activation process. The UV activation of analytes based on solution processed ZnO structures pave the way for better quality gas sensors. PMID:24009781

  18. Chemical composition and biological activities of polar extracts and essential oil of rose-scented geranium, Pelargonium graveolens.

    PubMed

    Boukhris, Maher; Simmonds, Monique S J; Sayadi, Sami; Bouaziz, Mohamed

    2013-08-01

    Pelargonium graveolens (Geraniaceae) was characterized with respect to its chemical composition, antioxidant potential and antimicrobial activities. This is the first investigation focusing on the comparison of both essential oil and polar extracts from this species. The chemical composition of the essential oil of the aerial parts of P. graveolens was analyzed by gas chromatography/mass spectrometry. The main constituents of the oil were found to be β-citronellol (21.9%), citronellyl formate (13.2%), geraniol (11.1%), 10-epi-γ-eudesmol (7.9%), geranyl formate (6.2%) and (l)-linalool (5.6%). Nine flavonoids were identified by high-performance liquid chromatography-MS in leaf and flower extracts. Kaempferol 3-O-rhamnoside-glucoside, isorhamnetin aglycone, quercetin 3-O-glucoside, kaempferol 3,7-di-O-glucoside, quercetin 3-O-pentose and kaempferol 3-O-glucoside, quercetin 3-O-rhamnoside-glucoside, quercetin 3-O-pentoside-glucoside, myrisetin 3-O-glucoside-rhamnoside flavonoids were detected in methanolic and aqueous extracts, respectively. The total flavonoids ranged between 29.9 and 78.2 mg QE/g in flower water and methanol extracts, respectively, and 22.5 and 71.2 mg QE/g dry weight in leaf water and methanol extracts, respectively. The highest antioxidant activities using two methods of free radical scavenging capacities were obtained with the essential oil (9.16 mM of Trolox and 2.68 µg/ml). All P. graveolens essential oil and polar extracts were active against at least one bacterium. PMID:23027699

  19. Dynamics of the Polar Cusps for Active Solar Wind Conditions: Large-scale Modeling

    NASA Astrophysics Data System (ADS)

    Berchem, J.; Richard, R. L.; Escoubet, C. P.; Taylor, M. G.; Laakso, H. E.; Masson, A.; Dandouras, I. S.; Reme, H.; Pitout, F.; Lucek, E. A.

    2010-12-01

    The energy-latitude dispersion of precipitating particles observed by spacecraft near the high-latitude dayside magnetosphere offers a unique opportunity to investigate the large-scale topology and dynamics of the polar cusps. In particular, consecutive crossings of the cusps made by the Cluster spacecraft in a string of pearl configuration are particularly well suited for investigating the temporal and spatial evolution of precipitating particles as solar wind discontinuities interact with the dayside magnetopause. We present the results of large-scale simulation studies based on Cluster observations of ion dispersions following rapid changes in the direction of the interplanetary magnetic field (IMF). First, we use three-dimensional magnetohydrodynamic (MHD) simulations to follow the evolution of the global topology of the magnetic field during the events. Subsequently, the time-dependent electric and magnetic fields predicted by the MHD simulations are utilized to compute the trajectories of large samples of solar wind ions launched upstream of the bow shock. We assess the results of the studies by comparing Cluster ion measurements with ion dispersions calculated from the simulations along the spacecraft trajectories and discuss the temporal evolution and spatial extent of precipitating particles in the context of the reconnection process at the dayside magnetopause.

  20. Active normal faulting along the Mt. Morrone south-western slopes (central Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Gori, Stefano; Giaccio, Biagio; Galadini, Fabrizio; Falcucci, Emanuela; Messina, Paolo; Sposato, Andrea; Dramis, Francesco

    2011-01-01

    In the present work we analyse one of the active normal faults affecting the central Apennines, i.e. the Mt. Morrone normal fault system. This tectonic structure, which comprises two parallel, NW-SE trending fault segments, is considered as potentially responsible for earthquakes of magnitude ≥ 6.5 and its last activation probably occurred during the second century AD. Structural observations performed along the fault planes have allowed to define the mainly normal kinematics of the tectonic structure, fitting an approximately N 20° trending extensional deformation. Geological and geomorphological investigations performed along the whole Mt. Morrone south-western slopes permitted us to identify the displacement of alluvial fans, attributed to Middle and Late Pleistocene by means of tephro-stratigraphic analyses and geomorphological correlations with dated lacustrine sequences, along the western fault branch. This allowed to evaluate in 0.4 ± 0.07 mm/year the slip rate of this segment. On the other hand, the lack of synchronous landforms and/or deposits that can be correlated across the eastern fault segment prevented the definition of the slip rate related to this fault branch. Nevertheless, basing on a critical review of the available literature dealing with normal fault systems evolution, we hypothesised a total slip rate of the fault system in the range of 0.4 ± 0.07 to 0.8 ± 0.09 mm/year. Moreover, basing on the length at surface of the Mt. Morrone fault system (i.e. 22-23 km) we estimated the maximum expected magnitude of an earthquake that might originate along this tectonic structure in the order of 6.6-6.7.

  1. Perceived and Objectively Measured Physical Activity and Sedentary Time among South Asian Women in the UK

    PubMed Central

    Curry, Whitney Babakus; Duda, Joan L.; Thompson, Janice L.

    2015-01-01

    Introduction: Limited self-report data suggest that South Asian (SA) women fail to meet physical activity (PA) recommendations. Recent research using objective measures reveals SA women living in the UK have higher PA levels than previously reported, and a pattern of under-reporting PA and sedentary time (ST). There is limited research on SA women’s understanding and experiences of PA/ST, and the cultural contexts and conditions within which they occur. Therefore the aims of this mixed-methods study were to compare perceived PA and ST to objectively measured data and explore PA- and ST-specific contexts, experiences, and sources of PA and ST amongst SA women in the UK. Methods: 24 women were purposively sampled to participate in a semi-structured interview from a larger study of 140 women who wore an accelerometer for 7 days. Demographic and anthropometric data were also collected. Results: Notable qualitative themes on contextualisation were of adequate PA as “keeping busy” or “being healthy”, and of ST as “lazy” or “resting in old age”. Few participants reported being sedentary, and most believed they were sufficiently physically active. Objectively measured PA/ST indicated that 66% women were less active than perceived (with regard to duration and intensity), with none able to estimate duration of ST. Discussion: Findings suggest that overall, SA women have contextualisations of PA/ST that may not coincide with those of researchers, health professionals and policy makers, and lack awareness of the intensity of PA in which they engage and the health risks of high levels of ST. These findings highlight the need for objective measures of PA and ST in this population combined with in-depth qualitative assessments to provide more accurate assessments of these behaviours. This information can subsequently be used to develop health promotion messages and interventions focusing on increasing duration and/or intensity levels of daily activities (e