INTERFEROMETRIC MONITORING OF GAMMA-RAY BRIGHT AGNs. I. THE RESULTS OF SINGLE-EPOCH MULTIFREQUENCY OBSERVATIONS

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

Lee, Sang-Sung; Wajima, Kiyoaki; Algaba, Juan-Carlos

2016-11-01

We present results of single-epoch very long baseline interferometry (VLBI) observations of gamma-ray bright active galactic nuclei (AGNs) using the Korean VLBI Network (KVN) at the 22, 43, 86, and 129 GHz bands, which are part of a KVN key science program, Interferometric Monitoring of Gamma-Ray Bright AGNs. We selected a total of 34 radio-loud AGNs of which 30 sources are gamma-ray bright AGNs with flux densities of >6 × 10{sup −10} ph cm{sup −2} s{sup −1}. Single-epoch multifrequency VLBI observations of the target sources were conducted during a 24 hr session on 2013 November 19 and 20. All observed sources weremore » detected and imaged at all frequency bands, with or without a frequency phase transfer technique, which enabled the imaging of 12 faint sources at 129 GHz, except for one source. Many of the target sources are resolved on milliarcsecond scales, yielding a core-jet structure, with the VLBI core dominating the synchrotron emission on a milliarcsecond scale. CLEAN flux densities of the target sources are 0.43–28 Jy, 0.32–21 Jy, 0.18–11 Jy, and 0.35–8.0 Jy in the 22, 43, 86, and 129 GHz bands, respectively. Spectra of the target sources become steeper at higher frequency, with spectral index means of −0.40, −0.62, and −1.00 in the 22–43 GHz, 43–86 GHz and 86–129 GHz bands, respectively, implying that the target sources become optically thin at higher frequencies (e.g., 86–129 GHz).« less

Astrometry with the VLT Interferometer

NASA Astrophysics Data System (ADS)

Quirrenbach, Andreas

The VLTI was originally conceived as an imaging instrument, providing a resolution of a few milliarcseconds at near-infrared wavelengths for studies of stars, circumstellar matter, and extragalactic objects. However, following the pioneering work on interferometric narrow-angle astrometry by Shao and Colavita (1992) and Colavita (1994), it was proposed that the VLTI could also be used for astrometric planet detection (Quirrenbach 1995). It was envisaged that the astrometric mode of the VLTI could be implemented by taking advantage of the large unvignetted field-of-view foreseen at that time (von der Lühe, Quirrenbach, & Koehler 1995). The idea of using the VLTI for narrowangle astrometry was embraced by ESO's Interferometry Science Advisory Committee (Paresce et al. 1996), but the technical concept for the delay lines has changed. The current plan for narrow-angle astrometry is based on dual star feeds at the telescopes and comprehensive internal laser metrology, as described in the PRIMA (Phase-Referenced Imaging and Microarcsecond Astrometry) study (Quirrenbach et al. 1998).

First fringes with an integrated-optics beam combiner at 10 μm. A new step towards instrument miniaturization for mid-infrared interferometry

NASA Astrophysics Data System (ADS)

Labadie, L.; Martín, G.; Anheier, N. C.; Arezki, B.; Qiao, H. A.; Bernacki, B.; Kern, P.

2011-07-01

Context. Observations of milliarcsecond-resolution scales and high dynamic range hold a central place in the exploration of distant planetary systems in order to achieve, for instance, the spectroscopic characterization of exo-Earths or the detailed mapping of their protoplanetary disc birthplace. Multi-aperture infrared interferometry, either from the ground or from space, is a very powerful technique to tackle these goals. However, significant technical efforts still need to be undertaken to achieve a simplification of these instruments if we wish to recombine the light from a large number of telescopes. Integrated-optics concepts appear to be a suitable alternative to the current conventional designs, especially if their use can be extended to a higher number of astronomical bands. Aims: This article reports, for the first time to our knowledge, the experimental demonstration of the feasibility of an integrated-optics approach to mid-infrared beam combination for single-mode stellar interferometry. Methods: We fabricated a two-telescope beam combiner prototype integrated on a substrate of chalcogenide glass, a material transparent from ~1 μm to ~14 μm. We developed laboratory tools to characterize in the mid-infrared the modal properties and the interferometric capabilities of our device. Results: We obtain interferometric fringes at 10 μm and measure a mean contrast V = 0.981 ± 0.001 with high repeatability over one week and high stability over a time-period of ~5 h. We show experimentally - as well as on the basis of modeling considerations - that the component has a single-mode behavior at this wavelength, which is essential to achieve high-accuracy interferometry. From previous studies, the propagation losses are estimated to be 0.5 dB/cm for this type of component. We also discuss possible issues that may impact the interferometric contrast. Conclusions: The IO beam combiner performs well at the tested wavelength. We also anticipate the requirement of a closer matching between the numerical apertures of the component and the (de)coupling optics to optimize the total throughput. The next step foreseen is the achievement of wide-band interferograms.

Arcsecond positions for milliarcsecond VLBI nuclei of extragalactic radio sources. IV - Seventeen sources

NASA Technical Reports Server (NTRS)

Morabito, D. D.; Preston, R. A.; Linfield, R. P.; Slade, M. A.; Jauncey, D. L.

1986-01-01

VLBI measurements of time delay and delay rate at 2.29 and 8.42 GHz on baselines of 10,000 km have been used to determine the positions of the milliarcsecond nuclei in 17 extragalactic radio sources with estimated accuracies of 0.1 to 0.3 arcsec. The observed sources are part of an all-sky VLBI catalog of milliarcsecond radio sources. In addition, slightly improved positions are presented for 101 sources originally reported by Morabito et al. (1983). Arcsecond positions have now been determined for 836 sources.

Digital elevation model of King Edward VII Peninsula, West Antarctica, from SAR interferometry and ICESat laser altimetry

USGS Publications Warehouse

Baek, S.; Kwoun, Oh-Ig; Braun, Andreas; Lu, Z.; Shum, C.K.

2005-01-01

We present a digital elevation model (DEM) of King Edward VII Peninsula, Sulzberger Bay, West Antarctica, developed using 12 European Remote Sensing (ERS) synthetic aperture radar (SAR) scenes and 24 Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry profiles. We employ differential interferograms from the ERS tandem mission SAR scenes acquired in the austral fall of 1996, and four selected ICESat laser altimetry profiles acquired in the austral fall of 2004, as ground control points (GCPs) to construct an improved geocentric 60-m resolution DEM over the grounded ice region. We then extend the DEM to include two ice shelves using ICESat profiles via Kriging. Twenty additional ICESat profiles acquired in 2003-2004 are used to assess the accuracy of the DEM. After accounting for radar penetration depth and predicted surface changes, including effects due to ice mass balance, solid Earth tides, and glacial isostatic adjustment, in part to account for the eight-year data acquisition discrepancy, the resulting difference between the DEM and ICESat profiles is -0.57 ?? 5.88 m. After removing the discrepancy between the DEM and ICESat profiles for a final combined DEM using a bicubic spline, the overall difference is 0.05 ?? 1.35 m. ?? 2005 IEEE.

A direct localization of a fast radio burst and its host.

PubMed

Chatterjee, S; Law, C J; Wharton, R S; Burke-Spolaor, S; Hessels, J W T; Bower, G C; Cordes, J M; Tendulkar, S P; Bassa, C G; Demorest, P; Butler, B J; Seymour, A; Scholz, P; Abruzzo, M W; Bogdanov, S; Kaspi, V M; Keimpema, A; Lazio, T J W; Marcote, B; McLaughlin, M A; Paragi, Z; Ransom, S M; Rupen, M; Spitler, L G; van Langevelde, H J

2017-01-04

Fast radio bursts are astronomical radio flashes of unknown physical nature with durations of milliseconds. Their dispersive arrival times suggest an extragalactic origin and imply radio luminosities that are orders of magnitude larger than those of all known short-duration radio transients. So far all fast radio bursts have been detected with large single-dish telescopes with arcminute localizations, and attempts to identify their counterparts (source or host galaxy) have relied on the contemporaneous variability of field sources or the presence of peculiar field stars or galaxies. These attempts have not resulted in an unambiguous association with a host or multi-wavelength counterpart. Here we report the subarcsecond localization of the fast radio burst FRB 121102, the only known repeating burst source, using high-time-resolution radio interferometric observations that directly image the bursts. Our precise localization reveals that FRB 121102 originates within 100 milliarcseconds of a faint 180-microJansky persistent radio source with a continuum spectrum that is consistent with non-thermal emission, and a faint (twenty-fifth magnitude) optical counterpart. The flux density of the persistent radio source varies by around ten per cent on day timescales, and very long baseline radio interferometry yields an angular size of less than 1.7 milliarcseconds. Our observations are inconsistent with the fast radio burst having a Galactic origin or its source being located within a prominent star-forming galaxy. Instead, the source appears to be co-located with a low-luminosity active galactic nucleus or a previously unknown type of extragalactic source. Localization and identification of a host or counterpart has been essential to understanding the origins and physics of other kinds of transient events, including gamma-ray bursts and tidal disruption events. However, if other fast radio bursts have similarly faint radio and optical counterparts, our findings imply that direct subarcsecond localizations may be the only way to provide reliable associations.

Integrated optics prototype beam combiner for long baseline interferometry in the L and M bands

NASA Astrophysics Data System (ADS)

Tepper, J.; Labadie, L.; Diener, R.; Minardi, S.; Pott, J.-U.; Thomson, R.; Nolte, S.

2017-06-01

Context. Optical long baseline interferometry is a unique way to study astronomical objects at milli-arcsecond resolutions not attainable with current single-dish telescopes. Yet, the significance of its scientfic return strongly depends on a dense coverage of the uv-plane and a highly stable transfer function of the interferometric instrument. In the last few years, integrated optics (IO) beam combiners have facilitated the emergence of 4-telescope interferometers such as PIONIER or GRAVITY, boosting the imaging capabilities of the VLTI. However, the spectral range beyond 2.2 μm is not ideally covered by the conventional silica based IO. Here, we consider new laser-written IO prototypes made of gallium lanthanum sulfide (GLS) glass, a material that permits access to the mid-infrared spectral regime. Aims: Our goal is to conduct a full characterization of our mid-IR IO two-telescope coupler in order to measure the performance levels directly relevant for long-baseline interferometry. We focus in particular on the exploitation of the L and M astronomical bands. Methods: We use a dedicated Michelson-interferometer setup to perform Fourier transform spectroscopy on the coupler and measure its broadband interferometric performance. We also analyze the polarization properties of the coupler, the differential dispersion and phase degradation, as well as the modal behavior and the total throughput. Results: We measure broadband interferometric contrasts of 94.9% and 92.1% for unpolarized light in the L and M bands. Spectrally integrated splitting ratios are close to 50%, but show chromatic dependence over the considered bandwidths. Additionally, the phase variation due to the combiner is measured and does not exceed 0.04 rad and 0.07 rad across the L and M band, respectively. The total throughput of the coupler including Fresnel and injection losses from free-space is 25.4%. Furthermore, differential birefringence is low (<0.2 rad), in line with the high contrasts reported for unpolarized light. Conclusions: The laser-written IO GLS prototype combiners prove to be a reliable technological solution with promising performance for mid-infrared long-baseline interferometry. In the next steps, we will consider more advanced optical functions, as well as a fiber-fed input, and we will revise the optical design parameters in order to further enhance the total throughput and achromatic behavior.

Dual-Frequency VLBI Study of Centaurus A on Sub-Parsec Scales: The Highest-Resolution View of an Extragalactic Jet

NASA Technical Reports Server (NTRS)

Mueller, C.; Kadler, M.; Ojha, R.; Wilms, J.; Boeck, M.; Edwards, P.; Fromm, C. M.; Hase, H.; Horiuchi, S.; Katz, U.;

Witnessing Atmospheric Motions in Cool Evolved Stars with VLTI/Amber

NASA Astrophysics Data System (ADS)

Ohnaka, Keiichi

2018-04-01

Studies of the mass loss from stars in late evolutionary stages are of utmost importance for improving our understanding of not only stellar evolution but also the chemical enrichment of galaxies. Despite such importance, the mass loss from cool evolved stars is one of the long-standing problems in stellar astrophysics. Milliarcsecond resolution achieved by optical/infrared long-baseline interferometry provides a unique opportunity to spatially resolve this innermost key region. We have recently succeeded not only in imaging the surface of the red supergiant Antares in the 2.3 micron CO lines in unprecedented detail but also in witnessing, for the first time, the complex gas dynamics over the surface and atmosphere of the star. Our 2-D velocity field map of Antares reveals vigorous upwelling and downdrafting motions of large gas clumps in the atmosphere extending out to 1.7 stellar radii. This suggests that the mass loss in red supergiants may be launched in a turbulent, clumpy manner. We will also present preliminary results of the velocity-resolved imaging of an AGB star. Our work opens an entirely new window to observe stars just like in observations of the Sun.

Statistical Attitude Determination

NASA Technical Reports Server (NTRS)

Markley, F. Landis

2010-01-01

All spacecraft require attitude determination at some level of accuracy. This can be a very coarse requirement of tens of degrees, in order to point solar arrays at the sun, or a very fine requirement in the milliarcsecond range, as required by Hubble Space Telescope. A toolbox of attitude determination methods, applicable across this wide range, has been developed over the years. There have been many advances in the thirty years since the publication of Reference, but the fundamentals remain the same. One significant change is that onboard attitude determination has largely superseded ground-based attitude determination, due to the greatly increased power of onboard computers. The availability of relatively inexpensive radiation-hardened microprocessors has led to the development of "smart" sensors, with autonomous star trackers being the first spacecraft application. Another new development is attitude determination using interferometry of radio signals from the Global Positioning System (GPS) constellation. This article reviews both the classic material and these newer developments at approximately the level of, with emphasis on. methods suitable for use onboard a spacecraft. We discuss both "single frame" methods that are based on measurements taken at a single point in time, and sequential methods that use information about spacecraft dynamics to combine the information from a time series of measurements.

LSST Astrometric Science

NASA Astrophysics Data System (ADS)

Saha, A.; Monet, D.

2005-12-01

Continued acquisition and analysis for short-exposure observations support the preliminary conclusion presented by Monet et al. (BAAS v36, p1531, 2004) that a 10-second exposure in 1.0-arcsecond seeing can provide a differential astrometric accuracy of about 10 milliarcseconds. A single solution for mapping coefficients appears to be valid over spatial scales of up to 10 arcminutes, and this suggests that numerical processing can proceed on a per-sensor basis without the need to further divide the individual fields of view into several astrometric patches. Data from the Subaru public archive as well as from the LSST Cerro Pachon 2005 observing campaign and various CTIO and NOAO 4-meter engineering runs have been considered. Should these results be confirmed, the expected astrometric accuracy after 10 years of LSST observations should be around 1.0 milliarcseconds for parallax and 0.2 milliarcseconds/year for proper motions.

MASSIM, the Milli-Arc-Second Structure Imager

NASA Technical Reports Server (NTRS)

Skinner, Gerry

2008-01-01

The MASSIM (Milli-Arc-Second Structure Imager) mission will use a set of achromatic diffractive-refractive Fresnel lenses to achieve imaging in the X-ray band with unprecedented angular resolution. It has been proposed for study within the context of NASA's "Astrophysics Strategic Mission Concept Studies" program. Lenses on an optics spacecraft will focus 5-11 keV X-rays onto detectors on a second spacecraft flying in formation 1000 km away. It will have a point-source sensitivity comparable with that of the current generation of major X-ray observatories (Chandra, XMM-Newton) but an angular resolution some three orders of magnitude better. MASSIM is optimized for the study of jets and other phenomena that occur in the immediate vicinity of black holes and neutron stars. It can also be used for studying other phenomena on the milli-arc-second scale, such as those involving proto-stars, the surfaces and surroundings of nearby active stars and interacting winds.

Lunar occultation observations at the SAO RAS 6-m telescope

NASA Astrophysics Data System (ADS)

Dyachenko, V.; Richichi, A.; Balega, Yu; Beskakotov, A.; Maksimov, A.; Mitrofanova, A.; Rastegaev, D.

2018-06-01

We have initiated a program to systematically observe lunar occultations from the SAO RAS 6-m telescope (BTA). So far, twenty-five events have been recorded with some of them leading to accurate measurements of angular diameters in late-type stars and of binary stars. One interesting aspect is that the observations are carried out by the same group and with the same equipment dedicated also to speckle interferometry, so that many of the target objects are being investigated by two independent and complementary techniques almost simultaneously. This represents a novel approach with a potential to provide more complete and extended results than possible until now. In this paper we focus on a general description of the scientific aim and methods, and we provide an overview of the results including an assessment of the quantitative performance, showing that milliarcsecond resolution is achieved on sources as faint as ≈12 mag. Among the sources we discuss in detail are the binary stars SAO 98270 and μ Cet, and the resolved late-type stars 74 Gem, DE Psc and IRC+00213. Other stars with positive results are the subject of dedicated papers. We foresee to continue routine observations with this facility in the immediate future, and to coordinate with other observatories equipped with similar instrumentation.

Radio crickets: chirping jets from black hole binaries entering their gravitational wave inspiral

NASA Astrophysics Data System (ADS)

Kulkarni, Girish; Loeb, Abraham

2016-03-01

We study a novel electromagnetic signature of supermassive black hole (BH) binaries whose inspiral starts being dominated by gravitational wave (GW) emission. Recent simulations suggest that the binary's member BHs can continue to accrete gas from the circumbinary accretion disc in this phase of the binary's evolution, all the way until coalescence. If one of the binary members produces a radio jet as a result of accretion, the jet precesses along a biconical surface due to the binary's orbital motion. When the binary enters the GW phase of its evolution, the opening angle widens, the jet exhibits milliarcsecond-scale wiggles, and the conical surface of jet precession is twisted due to apparent superluminal motion. The rapidly increasing orbital velocity of the binary gives the jet an appearance of a `chirp'. This helical chirping morphology of the jet can be used to infer the binary parameters. For binaries with mass 107-1010 M⊙ at redshifts z < 0.5, monitoring these features in current and archival data will place a lower limit on sources that could be detected by Evolved Laser Interferometer Space Antenna and Pulsar Timing Arrays. In the future, microarcsecond interferometry with the Square Kilometre Array will increase the potential usefulness of this technique.

Multiwavelength and parsec-scale properties of extragalactic jets. Doctoral Thesis Award Lecture 2015

NASA Astrophysics Data System (ADS)

Müller, C.

2016-07-01

Extragalactic jets originating from the central supermassive black holes of active galaxies are powerful, highly relativistic plasma outflows, emitting light from the radio up to the γ-ray regime. The details of their formation, composition and emission mechanisms are still not completely clear. The combination of high-resolution observations using very long baseline interferometry (VLBI) and multiwavelength monitoring provides the best insight into these objects. Here, such a combined study of sources of the TANAMI sample is presented, investigating the parsec-scale and high-energy properties. The TANAMI program is a multiwavelength monitoring program of a sample of the radio and γ-ray brightest extragalactic jets in the southern sky, below -30o declination. We obtain the first-ever VLBI images for most of the sources, providing crucial information on the jet kinematics and brightness distribution at milliarcsecond resolution. Two particular sources are discussed in detail: PMN J1603-4904 , which can be classified either as an atypical blazar or a γ-ray loud (young) radio galaxy, and Centaurus A, the nearest radio-loud active galaxy. The VLBI kinematics of the innermost parsec of Centaurus A's jet result in a consistent picture of an accelerated jet flow with a spine-sheath like structure.

The Orbit and Distance of WR140

NASA Astrophysics Data System (ADS)

Dougherty, S. M.; Trenton, V.; Beasley, A. J.

2011-01-01

A campaign of 35 epochs of milli-arcsecond resolution VLBA observations of the archetype colliding-wind WR+O star binary system WR 140 show the wind-collision region (WCR) as a bow-shaped arc of emission that rotates as the highly eccentric orbit progresses. The observations comprise 21 epochs from the 1993-2001 orbit, discussed by Dougherty et al. (2005), and 14 epochs from the 2001-2009 orbit, and span orbital phase 0.43 to 0.95. Assuming the WCR is symmetric about the line-of-centres of the two stars and ``points'' at the WR star, this rotation shows the O star moving from SE to E of the WR star between these orbital phases. Using IR interferometry observations from IOTA that resolve both stellar components at phase 0.297 in conjunction with orbital parameters derived from radial velocity variations, the VLBA observations constrain the inclination of the orbit plane as 120°±4°, the longitude of the ascending node as 352°±2°, and the orbit semi-major axis as 9.0±0.1 mas. This leads to a distance estimate to WR 140 of 1.81±0.08 kpc. Further refinements of the orbit and distance await more IR interferometric observations of the stellar components directly.

Active galactic nuclei cores in infrared-faint radio sources. Very long baseline interferometry observations using the Very Long Baseline Array

NASA Astrophysics Data System (ADS)

Herzog, A.; Middelberg, E.; Norris, R. P.; Spitler, L. R.; Deller, A. T.; Collier, J. D.; Parker, Q. A.

2015-06-01

Context. Infrared-faint radio sources (IFRS) form a new class of galaxies characterised by radio flux densities between tenths and tens of mJy and faint or absent infrared counterparts. It has been suggested that these objects are radio-loud active galactic nuclei (AGNs) at significant redshifts (z ≳ 2). Aims: Whereas the high redshifts of IFRS have been recently confirmed based on spectroscopic data, the evidence for the presence of AGNs in IFRS is mainly indirect. So far, only two AGNs have been unquestionably confirmed in IFRS based on very long baseline interferometry (VLBI) observations. In this work, we test the hypothesis that IFRS contain AGNs in a large sample of sources using VLBI. Methods: We observed 57 IFRS with the Very Long Baseline Array (VLBA) down to a detection sensitivity in the sub-mJy regime and detected compact cores in 35 sources. Results: Our VLBA detections increase the number of VLBI-detected IFRS from 2 to 37 and provide strong evidence that most - if not all - IFRS contain AGNs. We find that IFRS have a marginally higher VLBI detection fraction than randomly selected sources with mJy flux densities at arcsec-scales. Moreover, our data provide a positive correlation between compactness - defined as the ratio of milliarcsec- to arcsec-scale flux density - and redshift for IFRS, but suggest a decreasing mean compactness with increasing arcsec-scale radio flux density. Based on these findings, we suggest that IFRS tend to contain young AGNs whose jets have not formed yet or have not expanded, equivalent to very compact objects. We found two IFRS that are resolved into two components. The two components are spatially separated by a few hundred milliarcseconds in both cases. They might be components of one AGN, a binary black hole, or the result of gravitational lensing.

Tectonic Evolution and Midplate Volcanism in the South Pacific

DTIC Science & Technology

1999-02-01

documented in the South- ern Austral Island region of the South Pacific. A twelve degree clock- wise change in Pacific-Farallon relative motion occurred...and spreading fabric orientation. At the southeastern end of the Cook-Austral Island chain, multiple episodes of volcanism have left a diverse...in the flexural moat of the Austral Islands , probably associated with Austral Islands volcanism, which may contribute a significant amount of

VLBA Observations of Low Luminosity Flat Spectrum Radio Galaxies and BL Lac Objects: Polarisation Properties

NASA Astrophysics Data System (ADS)

Bondi, M.; Dallacasa, D.; Stanghellini, C.; Marchã, M. J. M.

We obtained two-epoch VLBA observations at 5 GHz of a list of radio galaxies drawn from the 200 mJy sample (Marcha et al. 1996). The objects selected for milli-arcsecond scale observations are classified, on the basis of their optical spectroscopic and polarimetric properties, as BL Lac objects, normal weak line radio galaxies, broad line radio galaxies, and transition objects (those with intermediate properties). We present preliminary results on the radio polarization properties, on the milli-arcsecond scale, of objects with different optical properties and discuss structural variations detected from the two epochs.

Remote Sensing and Geologic Studies of Mare Australe: The North Australe Region

NASA Technical Reports Server (NTRS)

Lawrence, S. J.; Stopar, J. D.; Ostrach, L. R.; van der Bogert, C. H.; Hiesinger, H.; Jolliff, B. L.; Giguere, T. A.; Sato, H.; Robinson, M. S.

2017-01-01

A key goal of the Lunar Reconnaissance Orbiter (LRO) mission is to investigate volcanic processes at different temporal and physical scales, with one emphasis being the characterization of ancient (meaning, greater than 3.9 Ga) volcanic units. One such ancient volcanic terrain is Mare Australe, a loosely-circular collection of mare basalts centered at approximately 38.9 deg S, 93 deg E (Fig. 1). Mare Australe is a complex, extensive, and poorly understood volcanic region.

The Milli-Arc-Second Structure Imager, MASSIM: A New Concept for a High Angular Resolution X-ray Telescope

NASA Technical Reports Server (NTRS)

Skinner, Gerry; Arzoumanian, Z.; Cash, W.; Gehrels, N.; Gendreau, K.; Gorenstein, P.; Krizmanic, J.; Leitner, J.; Miller, M.; Reasenberg, R.;

Astrometric satellites

NASA Astrophysics Data System (ADS)

Lindegren, Lennart

2012-01-01

The launch of the Hipparcos satellite in 1989 and the Hubble Space Telescope in 1990 revolutionized astrometry. By no means does this imply that not much progress was made in the ground-based techniques used exclusively until then. On the contrary, the 1960s to 1980s saw an intense development of new or highly improved instruments, including photoelectric meridian circles, automated plate measuring machines, and the use of chargecoupled device (CCD) detectors for small-field differential astrometry (for a review of optical astrometry at the time, see Monet 1988). In the radio domain, very long baseline interferometry (VLBI) astrometry already provided an extragalactic reference frame accurate to about 1 milliarcsecond (mas) (Ma et al. 1990). Spectacular improvements were made in terms of accuracy, the faintness of the observed objects, and their numbers. However, there was a widening gulf between small-angle astrometry, where differential techniques could overcome atmospheric effects down to below 1 mas, and large-angle astrometry, where conventional instruments such as meridian circles seemed to have hit a barrier in the underlying systematic errors at about 100 mas. Though very precise, the small-angle measurements were of limited use for the determination of positions and proper motions, due to the lack of suitable reference objects in the small fields, and even for parallaxes the necessary correction for the mean parallax of background stars was highly non-trivial. Linking the optical observations to the accurate VLBI frame also proved extremely difficult.

Constraining the radio jet proper motion of the high-redshift quasar J2134-0419 at z = 4.3

NASA Astrophysics Data System (ADS)

Perger, Krisztina; Frey, Sándor; Gabányi, Krisztina É.; An, Tao; Britzen, Silke; Cao, Hong-Min; Cseh, Dávid; Dennett-Thorpe, Jane; Gurvits, Leonid I.; Hong, Xiao-Yu; Hook, Isobel M.; Paragi, Zsolt; Schilizzi, Richard T.; Yang, Jun; Zhang, Yingkang

2018-06-01

To date, PMN J2134-0419 (at a redshift z = 4.33) is the second most distant quasar known with a milliarcsecond-scale morphology permitting direct estimates of the jet proper motion. Based on two-epoch observations, we constrained its radio jet proper motion using the very long baseline interferometry (VLBI) technique. The observations were conducted with the European VLBI Network (EVN) at 5 GHz on 1999 November 26 and 2015 October 6. We imaged the central 10-pc scale radio jet emission and modelled its brightness distribution. By identifying a jet component at both epochs separated by 15.86 yr, a proper motion of μ = 0.035 ± 0.023 mas yr-1 is found. It corresponds to an apparent superluminal speed of βa = 4.1 ± 2.7 c. Relativistic beaming at both epochs suggests that the jet viewing angle with respect to the line of sight is smaller than 20°, with a minimum bulk Lorentz factor Γ = 4.3. The small value of the proper motion is in good agreement with the expectations from the cosmological interpretation of the redshift and the current cosmological model. Additionally we analysed archival Very Large Array observations of J2143-0419 and found indication of a bent jet extending to ˜30 kpc.

Interferometric Monitoring of Gamma-Ray Bright AGNs: S5 0716+714

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

Lee, Jee Won; Lee, Sang-Sung; Hodgson, Jeffrey A.

We present the results of very long baseline interferometry (VLBI) observations of gamma-ray bright blazar S5 0716+714 using the Korean VLBI Network (KVN) at the 22, 43, 86, and 129 GHz bands, as part of the Interferometric Monitoring of Gamma-ray Bright active galactic nuclei (iMOGABA) KVN key science program. Observations were conducted in 29 sessions from 2013 January 16 to 2016 March 1, with the source being detected and imaged at all available frequencies. In all epochs, the source was compact on the milliarcsecond scale, yielding a compact VLBI core dominating the synchrotron emission on these scales. Based on themore » multiwavelength data between 15 GHz (Owens Valley Radio Observatory) and 230 GHz (Submillimeter Array), we found that the source shows multiple prominent enhancements of the flux density at the centimeter (cm) and millimeter (mm) wavelengths, with mm enhancements leading cm enhancements by −16 ± 8 days. The turnover frequency was found to vary between 21 and 69 GHz during our observations. By assuming a synchrotron self-absorption model for the relativistic jet emission in S5 0716+714, we found the magnetic field strength in the mas emission region to be ≤5 mG during the observing period, yielding a weighted mean of 1.0 ± 0.6 mG for higher turnover frequencies (e.g., >45 GHz).« less

ON THE CONNECTION OF THE APPARENT PROPER MOTION AND THE VLBI STRUCTURE OF COMPACT RADIO SOURCES

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

Moor, A.; Frey, S.; Lambert, S. B.

2011-06-15

Many of the compact extragalactic radio sources that are used as fiducial points to define the celestial reference frame are known to have proper motions detectable with long-term geodetic/astrometric very long baseline interferometry (VLBI) measurements. These changes can be as high as several hundred microarcseconds per year for certain objects. When imaged with VLBI at milliarcsecond (mas) angular resolution, these sources (radio-loud active galactic nuclei) typically show structures dominated by a compact, often unresolved 'core' and a one-sided 'jet'. The positional instability of compact radio sources is believed to be connected with changes in their brightness distribution structure. For themore » first time, we test this assumption in a statistical sense on a large sample rather than on only individual objects. We investigate a sample of 62 radio sources for which reliable long-term time series of astrometric positions as well as detailed 8 GHz VLBI brightness distribution models are available. We compare the characteristic direction of their extended jet structure and the direction of their apparent proper motion. We present our data and analysis method, and conclude that there is indeed a correlation between the two characteristic directions. However, there are cases where the {approx}1-10 mas scale VLBI jet directions are significantly misaligned with respect to the apparent proper motion direction.« less

Mid-infrared interferometry towards the massive young stellar object CRL 2136: inside the dust rim

NASA Astrophysics Data System (ADS)

de Wit, W. J.; Hoare, M. G.; Oudmaijer, R. D.; Nürnberger, D. E. A.; Wheelwright, H. E.; Lumsden, S. L.

2011-02-01

Context. Establishing the importance of circumstellar disks and their properties is crucial to fully understand massive star formation. Aims: We aim to spatially resolve the various components that make-up the accretion environment of a massive young stellar object (⪉100 AU), and reproduce the emission from near-infrared to millimeter wavelengths using radiative transfer codes. Methods: We apply mid-infrared spectro-interferometry to the massive young stellar object CRL 2136. The observations were performed with the Very Large Telescope Interferometer and the MIDI instrument at a 42 m baseline probing angular scales of 50 milli-arcseconds. We model the observed visibilities in parallel with diffraction-limited images at both 24.5 μm and in the N-band (with resolutions of 0.6´´and 0.3´´, respectively), as well as the spectral energy distribution. Results: The arcsec-scale spatial information reveals the well-resolved emission from the dusty envelope. By simultaneously modelling the spatial and spectral data, we find that the bulk of the dust emission occurs at several dust sublimation radii (approximately 170 AU). This reproduces the high mid-infrared fluxes and at the same time the low visibilities observed in the MIDI data for wavelengths longward of 8.5 μm. However, shortward of this wavelength the visibility data show a sharp up-turn indicative of compact emission. We discuss various potential sources of this emission. We exclude a dust disk being responsible for the observed spectral imprint on the visibilities. A cool supergiant star and an accretion disk are considered and both shown to be viable origins of the compact mid-infrared emission. Conclusions: We propose that CRL 2136 is embedded in a dusty envelope, which truncates at several times the dust sublimation radius. A dust torus is manifest in the equatorial region. We find that the spectro-interferometric N-band signal can be reproduced by either a gaseous disk or a bloated central star. If the disk extends to the stellar surface, it accretes at a rate of 3.0 × 10-3 M⊙ yr-1. Based on observations with the VLTI, proposal 381.C-0607.

High-precision infra-red stellar interferometry

NASA Astrophysics Data System (ADS)

Lane, Benjamin F.

2003-08-01

This dissertation describes work performed at the Palomar Testbed Interferometer (PTI) during 1998 2002. Using PTI, we developed a method to measure stellar angular diameters in the 1 3 milli-arcsecond range with a precision of better than 5%. Such diameter measurements were used to measure the mass-radius relations of several lower main sequence stars and hence verify model predictions for these stars. In addition, by measuring the changes in Cepheid angular diameters during the pulsational cycle and applying a Baade-Wesselink analysis we are able to derive the distances to two galactic Cepheids (η Aql & ζ Gem) with a precision of ˜10%; such distance determinations provide an independent calibration of the Cepheid period- luminosity relations that underpin current estimates of cosmic distance scales. Second, we used PTI and the adaptive optics facility at the Keck Telescope on Mauna Kea to resolve the low mass binary systems BY Dra and GJ 569B, resulting in dynamical mass determinations for these systems. GJ 569B most likely contains at least one sub-stellar component, and as such represents the first dynamical mass determination of a brown dwarf. Finally, a new observing technique, dual star phase referencing, was developed and demonstrated at PTI. Phase referencing allows interferometric observations of stars previously too faint to observe, and is a prerequisite for large-scale interferometric astrometry programs such as the one planned for the Keck Interferometer; interferometric astrometry is a promising technique for the study of extra-solar planetary systems, particularly ones with long-period planets.

TESTING THE HYPOTHESIS THAT METHANOL MASER RINGS TRACE CIRCUMSTELLAR DISKS: HIGH-RESOLUTION NEAR-INFRARED AND MID-INFRARED IMAGING

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

De Buizer, James M.; Bartkiewicz, Anna; Szymczak, Marian, E-mail: jdebuizer@sofia.usra.edu

2012-08-01

Milliarcsecond very long baseline interferometry maps of regions containing 6.7 GHz methanol maser emission have lead to the recent discovery of ring-like distributions of maser spots and the plausible hypothesis that they may be tracing circumstellar disks around forming high-mass stars. We aimed to test this hypothesis by imaging these regions in the near- and mid-infrared at high spatial resolution and compare the observed emission to the expected infrared morphologies as inferred from the geometries of the maser rings. In the near-infrared we used the Gemini North adaptive optics system of ALTAIR/NIRI, while in the mid-infrared we used the combinationmore » of the Gemini South instrument T-ReCS and super-resolution techniques. Resultant images had a resolution of {approx}150 mas in both the near-infrared and mid-infrared. We discuss the expected distribution of circumstellar material around young and massive accreting (proto)stars and what infrared emission geometries would be expected for the different maser ring orientations under the assumption that the masers are coming from within circumstellar disks. Based upon the observed infrared emission geometries for the four targets in our sample and the results of spectral energy distribution modeling of the massive young stellar objects associated with the maser rings, we do not find compelling evidence in support of the hypothesis that methanol masers rings reside in circumstellar disks.« less

Radio Follow-up on All Unassociated Gamma-Ray Sources from the Third Fermi Large Area Telescope Source Catalog

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

Schinzel, Frank K.; Petrov, Leonid; Taylor, Gregory B.

The third Fermi Large Area Telescope γ -ray source catalog (3FGL) contains over 1000 objects for which there is no known counterpart at other wavelengths. The physical origin of the γ -ray emission from those objects is unknown. Such objects are commonly referred to as unassociated and mostly do not exhibit significant γ -ray flux variability. We performed a survey of all unassociated γ -ray sources found in 3FGL using the Australia Telescope Compact Array and Very Large Array in the range 4.0–10.0 GHz. We found 2097 radio candidates for association with γ -ray sources. The follow-up with very longmore » baseline interferometry for a subset of those candidates yielded 142 new associations with active galactic nuclei that are γ -ray sources, provided alternative associations for seven objects, and improved positions for another 144 known associations to the milliarcsecond level of accuracy. In addition, for 245 unassociated γ -ray sources we did not find a single compact radio source above 2 mJy within 3 σ of their γ -ray localization. A significant fraction of these empty fields, 39%, are located away from the Galactic plane. We also found 36 extended radio sources that are candidates for association with a corresponding γ -ray object, 19 of which are most likely supernova remnants or H ii regions, whereas 17 could be radio galaxies.« less

Resultados del relevamiento de HI en el Cielo Austral: 3. Relevamiento de Nubes de Alta Velocidad

NASA Astrophysics Data System (ADS)

Morras, R.; Bajaja, E.; Arnal, E. M.; Pöppel, W. G. L.

Los resultados del relevamiento de HI del Hemisferio Austral fueron reprocesados con el fin de incrementar su sensibilidad. Así, se utilizó esta nueva base de datos con el fin de obtener un nuevo relevamiento de Nubes de Alta Velocidad en el cielo austral. El ruido r.m.s. alcanzado es de 0.015-0.020 K, con una resolución espectral de 8 km/seg. El cubrimiento espacial del relevamiento mejora en un factor 16 al realizado por Bajaja et al (1985).

The unusual Samoan hotspot: A "hotspot highway" juxtaposed with a trench

NASA Astrophysics Data System (ADS)

Jackson, M. G.; Konter, J. G.; Koppers, A. A.

2011-12-01

Oceanic hotspots are fed by (relatively) stationary, upwelling mantle plumes that melt beneath mobile tectonic plates. This mechanism results in the generation of a linear chain of volcanoes exhibiting a clear age progression: the islands and seamounts should be increasingly older with increasing distance from the inferred location of the mantle plume. Located in the southwest Pacific, the Cook-Austral volcanic islands and seamounts were long thought to lack a clear age progression, and it has been argued that the Cook-Austral volcanic chain is an example of a hotspot not fed by a mantle plume. However, work by Chauvel et al (1997) showed that the Cook-Austral volcanoes have been generated by three distinct, co-linear mantle plumes spaced by ~1000 km, resulting in 3 overlapping hotspot tracks. Critically, the volcanoes generated by each hotspot exhibit a clear age progression that emerges from its respective plume. Using plate motion models, the reconstructed tracks of the three Cook-Austral hotspots backtrack through the region of the Pacific plate now occupied by the Samoan hotspot between 10 and 40 Ma (Konter et al., 2008). Owing to the unusual number of hotspots (Samoa is the fourth) that have been hosted in the region, we refer to this corridor of the Pacific plate as the "hotspot highway." The Samoan hotspot is burning through and thus crosscutting the trails of the older Cook-Austral hotspots. Consistent with this hypothesis, Jackson et al. (2010) reported volcanic features from the Cook-Austral hotspots in the Samoan region, including three seamounts and one atoll with geochemical affinities to the Cook-Austral hotspot. The Pacific lithosphere was likely "preconditioned" (metasomatized) by the three Cook-Australs hotspots before the arrival of the Samoan plume into the region, yet geochemical signatures associated with the Cook-Austral hotspot pedigrees are not evident in Samoan shield lavas. However, Samoan rejuvenated lavas exhibit a clear EMI (enriched mantle 1) signature that is not present in Samoan shield lavas (and thus not in the Samoan plume), but the EM1 signature is present in the most recent Cook-Austral hotspot (Rarotonga) to have contributed volcanism to the region of the Pacific plate occupied by Samoa. We suggest that the lithosphere beneath Samoa was underplated with (or impregnated by) material from the Rarotonga plume at ~10 Ma. The shield stage of Samoan volcanism does not sample melts of the lithosphere. However, the region of EM1-impregnated Pacific lithosphere once occupied by the Rarotonga hotspot (which has since been rafted into the Samoan region) is now located just ~100 km from the northern terminus of the Tonga trench. We suggest that plate flexure resulting from the tectonic regime near the trench has resulted in decompression melting of the metasomatized lithosphere, which yields the EM1-flavored melts observed in Samoan rejuvenated lavas.

Conditions leading to the unprecedented low Antarctic sea ice extent during the 2016 austral spring season

NASA Astrophysics Data System (ADS)

Stuecker, Malte F.; Bitz, Cecilia M.; Armour, Kyle C.

2017-09-01

The 2016 austral spring was characterized by the lowest Southern Hemisphere (SH) sea ice extent seen in the satellite record (1979 to present) and coincided with anomalously warm surface waters surrounding most of Antarctica. We show that two distinct processes contributed to this event: First, the extreme El Niño event peaking in December-February 2015/2016 contributed to pronounced extratropical SH sea surface temperature and sea ice extent anomalies in the eastern Ross, Amundsen, and Bellingshausen Seas that persisted in part until the following 2016 austral spring. Second, internal unforced atmospheric variability of the Southern Annular Mode promoted the exceptional low sea ice extent in November-December 2016. These results suggest that a combination of tropically forced and internal SH atmospheric variability contributed to the unprecedented sea ice decline during the 2016 austral spring, on top of a background of slow changes expected from greenhouse gas and ozone forcing.

The orbit and transit prospects for β pictoris b constrained with one milliarcsecond astrometry

DOE PAGES

Wang, Jason J.; Graham, James R.; Pueyo, Laurent; ...

2016-10-03

A principal scientific goal of the Gemini Planet Imager (GPI) is obtaining milliarcsecond astrometry to constrain exoplanet orbits. However, astrometry of directly imaged exoplanets is subject to biases, systematic errors, and speckle noise. Here, we describe an analytical procedure to forward model the signal of an exoplanet that accounts for both the observing strategy (angular and spectral differential imaging) and the data reduction method (Karhunen–Loève Image Projection algorithm). We use this forward model to measure the position of an exoplanet in a Bayesian framework employing Gaussian processes and Markov-chain Monte Carlo to account for correlated noise. In the case ofmore » GPI data on β Pic b, this technique, which we call Bayesian KLIP-FM Astrometry (BKA), outperforms previous techniques and yields 1σ errors at or below the one milliarcsecond level. We validate BKA by fitting a Keplerian orbit to 12 GPI observations along with previous astrometry from other instruments. The statistical properties of the residuals confirm that BKA is accurate and correctly estimates astrometric errors. Our constraints on the orbit of β Pic b firmly rule out the possibility of a transit of the planet at 10-σ significance. However, we confirm that the Hill sphere of β Pic b will transit, giving us a rare chance to probe the circumplanetary environment of a young, evolving exoplanet. As a result, we provide an ephemeris for photometric monitoring of the Hill sphere transit event, which will begin at the start of April in 2017 and finish at the end of January in 2018.« less

Rheum australe D. Don: a review of its botany, ethnobotany, phytochemistry and pharmacology.

PubMed

Rokaya, Maan Bahadur; Münzbergová, Zuzana; Timsina, Binu; Bhattarai, Krishna Ram

2012-06-14

Rheum australe D. Don (Polygonaceae) has been commonly used in traditional medicine for a wide range of ailments related to the circulatory, digestive, endocrine, respiratory and skeletal systems as well as to infectious diseases. To provide the up-to-date information that is available on the botany, traditional uses, phytochemistry, pharmacology and toxicology of Rheum australe. Additionally, to highlight the possible uses of this species to treat different diseases and to provide a basis for future research. The present review covers the literature available from 1980 to 2011. The information was collected from scientific journals, books, theses and reports via a library and electronic search (Google Scholar, Web of Science and ScienceDirect). Ethnomedical uses of Rheum australe have been recorded from China, India, Nepal and Pakistan for 57 different types of ailments. The phytochemical studies have shown the presence of many secondary metabolites belonging to anthraquinones, stilbenes, anthrones, oxantrone ethers and esters, chromones, flavonoids, carbohydrate, lignans, phenols and sterols. Crude extracts and isolated compounds from Rheum australe show a wide spectrum of pharmacological activities, such as antidiabetic, anti-inflammatory, antifungal, antimicrobial, antioxidant, anticancer, hepatoprotective and immune-enhancing activities, as well as a usefulness for improving renal function. Rheum australe has been widely used source of medicine for years without any adverse effects. Many studies have provided evidence for various traditional uses. However, there is a need for additional studies of the isolated compounds to validate the traditional uses in human models. The present review on the botany, traditional uses, phytochemistry and toxicity has provided preliminary information for further studies and commercial exploitations of the plant. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

The Impact of the AuScope VLBI Observations and the Regional AUSTRAL Sessions on the TRF

NASA Astrophysics Data System (ADS)

Plank, L.; Lovell, J.; McCallum, J.; Boehm, J.; Shabala, S.; Mayer, D.; Sun, J.; Titov, O.; Weston, S.; Quick, J.; Rastorgueva-Foi, E.

2014-12-01

The AuScope VLBI array was built with the purpose to improve the terrestrial (TRF) and celestial reference frames in the southern hemisphere. Since 2010 the three 12-m antennas in Hobart (Tasmania), Katherine (Northern Territory) and Yarragadee (Western Australia) heavily contribute to the global VLBI observations coordinated by the International VLBI Service for Geodesy and Astrometry. In 2011, the AUSTRAL VLBI program was started, with more than 40 sessions being observed so far. In the AUSTRALs, the three AuScope antennas observe together with the new 15-m dish in Hartebeesthoek (South Africa) and the 12-m antenna in Warkworth (New Zealand). Recently, the planned observations have been expanded again, with 50 additional sessions scheduled until mid-2015, along with 3 continuous campaigns covering 15 days each. All AUSTRALs are recorded with an increased data rate of 1 Gbps, allowing to compensate for the reduced sensitivity of the generally smaller dish size. We evaluate the positive impact of the AuScope VLBI program on the global TRF. This is due to the increased number of observations and the improved homogeneity of the global VLBI network. All data collected within this intense observing program is analysed and geodetic results are presented. This includes time series of baseline lengths and station coordinates of the contributing stations. We compare the results obtained within the regional AUSTRAL sessions with the ones of the classical global VLBI networks and identify superiorities and shortcomings of both. The high number of sessions gives high accuracies and good repeatabilities of the determined parameters. Additionally, remaining variations of baseline lengths can be identified and are compared against by default un-modelled station motions due to hydrology and atmosphere loading. Finally, we give an outlook on future plans for the AuScope antennas and the AUSTRAL observing program: on future operations, expected improvements through hardware upgrades as well as research on the use of sibling telescopes available at two sites within the AUSTRAL array (Hobart and Hartebeesthoek).

The in-flight calibration of the Hubble Space Telescope attitude sensors

NASA Technical Reports Server (NTRS)

Welter, Gary L.

1991-01-01

A detailed review of the in-flight calibration of the Hubble Space Telescope attitude sensors is presented. The review, which covers the period from the April 24, 1990, launch of the spacecraft until the time of this writing (June 1991), describes the calibrations required and accuracies achieved for the four principal attitude sensing systems on the spacecraft: the magnetometers, the fixed head star trackers, the gyroscopes, and the fine guidance sensors (FGS's). In contrast to the other three sensor groups, the Hubble Telecope's FGS's are unique in the precision and performance levels being attempted; spacecraft control and astrometric research at the near-milliarcsecond level are the ultimate goals. FGS calibration accuracies at the 20-milliarcsecond level have already been achieved, and plans for new data acquisitions and reductions that should substantially improve these results are in progress. A summary of the basic attributes of each of the four sensor groups with respect to its usage as an attitude measuring system is presented, followed by a discussion of the calibration items of interest for that group. The calibration items are as follows: for the magnetometers, the corrections for the spacecraft's static and time-varying magnetic fields; for the fixed-head star trackers, their relative alignments and use in performing onboard attitude updates; for the gyroscopes, their scale factors, alignments, and drift rate biases; and for the FGS's, their magnifications, optical distortions, and alignments. The discussion covers the procedures used for each calibration, as well as the order of the calibrations within the general flow of orbital verification activities. It also includes a synopsis of current plans for the eventual calibration of the FGS's to achieve their near-milliarcsecond design accuracy. The conclusions include a table indicating the current and predicted ultimate accuracies for each of the calibration items.

Flight demonstration of a milliarcsecond pointing system for direct exoplanet imaging.

PubMed

Mendillo, Christopher B; Chakrabarti, Supriya; Cook, Timothy A; Hicks, Brian A; Lane, Benjamin F

2012-10-10

We present flight results from the optical pointing control system onboard the Planetary Imaging Concept Testbed Using a Rocket Experiment (PICTURE) sounding rocket. PICTURE (NASA mission number: 36.225 UG) was launched on 8 October 2011, from White Sands Missile Range. It attempted to directly image the exozodiacal dust disk of ϵ Eridani (K2V, 3.22 pc) down to an inner radius of 1.5 AU using a visible nulling coronagraph. The rocket attitude control system (ACS) provided 627 milliarcsecond (mas) RMS body pointing (~2'' peak-to-valley). The PICTURE fine pointing system (FPS) successfully stabilized the telescope beam to 5.1 mas (0.02λ/D) RMS using an angle tracker camera and fast steering mirror. This level of pointing stability is comparable to that of the Hubble Space Telescope. We present the hardware design of the FPS, a description of the limiting noise sources and a power spectral density analysis of the FPS and rocket ACS in-flight performance.

Assessing host-parasite specificity through coprological analysis: a case study with species of Corynosoma (Acanthocephala: Polymorphidae) from marine mammals.

PubMed

Aznar, F J; Hernández-Orts, J; Suárez, A A; García-Varela, M; Raga, J A; Cappozzo, H L

2012-06-01

In this paper we report an investigation of the utility of coprological analysis as an alternative technique to study parasite specificity whenever host sampling is problematic; acanthocephalans from marine mammals were used as a model. A total of 252 scats from the South American sea lion, Otaria flavescens, and rectal faeces from 43 franciscanas, Pontoporia blainvillei, from Buenos Aires Province, were examined for acanthocephalans. Specimens of two species, i.e. Corynosoma australe and C. cetaceum, were collected from both host species. In sea lions, 78 out of 145 (37.9%) females of C. australe were gravid and the sex ratio was strongly female-biased. However, none of the 168 females of C. cetaceum collected was gravid and the sex ratio was not female-biased. Conversely, in franciscanas, 14 out of 17 (82.4%) females of C. cetaceum were gravid, but none of 139 females of C. australe was, and the sex ratio of C. cetaceum, but not that of C. australe, was female-biased. In putative non-hosts, the size of worms was similar to that from specimens collected from prey. Results suggest that both acanthocephalans contact sea lions and franciscanas regularly. However, C. australe and C. cetaceum cannot apparently reproduce, nor even grow, in franciscanas and sea lions, respectively. Coprological analysis may represent a useful supplementary method to investigate parasite specificity, particularly when host carcasses are difficult to obtain.

SHARP - V. Modelling gravitationally-lensed radio arcs imaged with global VLBI observations

NASA Astrophysics Data System (ADS)

Spingola, C.; McKean, J. P.; Auger, M. W.; Fassnacht, C. D.; Koopmans, L. V. E.; Lagattuta, D. J.; Vegetti, S.

2018-05-01

We present milliarcsecond (mas) angular resolution observations of the gravitationally lensed radio source MG J0751+2716 (at z = 3.2) obtained with global Very Long Baseline Interferometry (VLBI) at 1.65 GHz. The background object is highly resolved in the tangential and radial directions, showing evidence of both compact and extended structure across several gravitational arcs that are 200 to 600 mas in size. By identifying compact sub-components in the multiple images, we constrain the mass distribution of the foreground z = 0.35 gravitational lens using analytic models for the main deflector [power-law elliptical mass model; ρ(r)∝r-γ, where γ = 2 corresponds to isothermal] and for the members of the galaxy group. Moreover, our mass models with and without the group find an inner mass-density slope steeper than isothermal for the main lensing galaxy, with γ1 = 2.08 ± 0.02 and γ2 = 2.16 ± 0.02 at the 4.2σ level and 6.8σ level, respectively, at the Einstein radius (b1 = 0.4025 ± 0.0008 and b2 = 0.307 ± 0.002 arcsec, respectively). We find randomly distributed image position residuals of about 3 mas, which are much larger that the measurement errors (40 μas on average). This suggests that at the mas level, the assumption of a smooth mass distribution fails, requiring additional structure in the model. However, given the environment of the lensing galaxy, it is not clear whether this extra mass is in the form of sub-haloes within the lens or along the line of sight, or from a more complex halo for the galaxy group.

The Most Compact Bright Radio-loud AGNs. II. VLBA Observations of 10 Sources at 43 and 86 GHz

NASA Astrophysics Data System (ADS)

Cheng, X.-P.; An, T.; Hong, X.-Y.; Yang, J.; Mohan, P.; Kellermann, K. I.; Lister, M. L.; Frey, S.; Zhao, W.; Zhang, Z.-L.; Wu, X.-C.; Li, X.-F.; Zhang, Y.-K.

2018-01-01

Radio-loud active galactic nuclei (AGNs), hosting powerful relativistic jet outflows, provide an excellent laboratory for studying jet physics. Very long baseline interferometry (VLBI) enables high-resolution imaging on milli-arcsecond (mas) and sub-mas scales, making it a powerful tool to explore the inner jet structure, shedding light on the formation, acceleration, and collimation of AGN jets. In this paper, we present Very Long Baseline Array observations of 10 radio-loud AGNs at 43 and 86 GHz that were selected from the Planck catalog of compact sources and are among the brightest in published VLBI images at and below 15 GHz. The image noise levels in our observations are typically 0.3 and 1.5 mJy beam‑1 at 43 and 86 GHz, respectively. Compared with the VLBI data observed at lower frequencies from the literature, our observations with higher resolutions (with the highest resolution being up to 0.07 mas at 86 GHz and 0.18 mas at 43 GHz) and at higher frequencies detected new jet components at sub-parsec scales, offering valuable data for studies of the physical properties of the innermost jets. These include the compactness factor of the radio structure (the ratio of core flux density to total flux density), and core brightness temperature ({T}{{b}}). In all these sources, the compact core accounts for a significant fraction (> 60 % ) of the total flux density. Their correlated flux density at the longest baselines is higher than 0.16 Jy. The compactness of these sources make them good phase calibrators of millimeter-wavelength ground-based and space VLBI.

Correlation between SiO v = 3 J = 1 → 0 maser excitation and the light curve of a long-period variable star

NASA Astrophysics Data System (ADS)

Oyadomari, Miyako; Imai, Hiroshi; Nagayama, Takumi; Oyama, Tomoaki; Matsumoto, Naoko; Nakashima, Jun-ichi; Cho, Se-Hyung

2018-06-01

In order to understand the excitation mechanisms of silicon monoxide (SiO) masers around long-period variables (LPVs), we have investigated distributions of the SiO v = 2 and v = 3 J = 1 → 0 masers around 12 LPVs by very long baseline interferometry (VLBI) observations with the VLBI Exploration of Radio Astrometry (VERA) and the Nobeyama 45 m telescopes. VLBI fringes of the v = 3 maser emission were detected for five LPVs. The composite maps of the v = 2 and v = 3 masers were made for T Cep, W Hya, WX Psc, and R Leo using the spectral line phase-referencing technique. The v = 2 maser spots were distributed in a ring-like form around the central stars, while it is difficult to recognize any specific morphology in the v = 3 maser distributions due to the small number of v = 3 spots detected. However in T Cep, we find that the distribution of the v = 3 maser spots correlates well with the v = 2 masers within a few milliarcseconds (0.2-0.3 au) in position and 1 km s-1 in line-of-sight velocity at the light curve phase of ϕ = 0.28 (ϕ = 0.0 and 1.0 correspond to the visible light maxima). This correlation implies that the mechanism of line-overlapping between the mid-infrared lines of H2O and SiO molecules works in T Cep at ϕ = 0.28. We discuss the possibility that the line-overlapping may work at the limited duration from the maximum to the minimum of the stellar light curve.

Correlation between SiO v = 3 J = 1 → 0 maser excitation and the light curve of a long-period variable star

NASA Astrophysics Data System (ADS)

Oyadomari, Miyako; Imai, Hiroshi; Nagayama, Takumi; Oyama, Tomoaki; Matsumoto, Naoko; Nakashima, Jun-ichi; Cho, Se-Hyung

2018-03-01

In order to understand the excitation mechanisms of silicon monoxide (SiO) masers around long-period variables (LPVs), we have investigated distributions of the SiO v = 2 and v = 3 J = 1 → 0 masers around 12 LPVs by very long baseline interferometry (VLBI) observations with the VLBI Exploration of Radio Astrometry (VERA) and the Nobeyama 45 m telescopes. VLBI fringes of the v = 3 maser emission were detected for five LPVs. The composite maps of the v = 2 and v = 3 masers were made for T Cep, W Hya, WX Psc, and R Leo using the spectral line phase-referencing technique. The v = 2 maser spots were distributed in a ring-like form around the central stars, while it is difficult to recognize any specific morphology in the v = 3 maser distributions due to the small number of v = 3 spots detected. However in T Cep, we find that the distribution of the v = 3 maser spots correlates well with the v = 2 masers within a few milliarcseconds (0.2-0.3 au) in position and 1 km s-1 in line-of-sight velocity at the light curve phase of ϕ = 0.28 (ϕ = 0.0 and 1.0 correspond to the visible light maxima). This correlation implies that the mechanism of line-overlapping between the mid-infrared lines of H2O and SiO molecules works in T Cep at ϕ = 0.28. We discuss the possibility that the line-overlapping may work at the limited duration from the maximum to the minimum of the stellar light curve.

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

Cseh, David; Corbel, Stephane; Kaaret, Philip

We present new radio, optical, and X-ray observations of three ultraluminous X-ray sources (ULXs) that are associated with large-scale nebulae. We report the discovery of a radio nebula associated with the ULX IC 342 X-1 using the Very Large Array (VLA). Complementary VLA observations of the nebula around Holmberg II X-1, and high-frequency Australia Telescope Compact Array and Very Large Telescope spectroscopic observations of NGC 5408 X-1 are also presented. We study the morphology, ionization processes, and the energetics of the optical/radio nebulae of IC 342 X-1, Holmberg II X-1, and NGC 5408 X-1. The energetics of the optical nebulamore » of IC 342 X-1 is discussed in the framework of standard bubble theory. The total energy content of the optical nebula is 6 Multiplication-Sign 10{sup 52} erg. The minimum energy needed to supply the associated radio nebula is 9.2 Multiplication-Sign 10{sup 50} erg. In addition, we detected an unresolved radio source at the location of IC 342 X-1 at the VLA scales. However, our Very Long Baseline Interferometry (VLBI) observations using the European VLBI Network likely rule out the presence of any compact radio source at milliarcsecond (mas) scales. Using a simultaneous Swift X-ray Telescope measurement, we estimate an upper limit on the mass of the black hole in IC 342 X-1 using the 'fundamental plane' of accreting black holes and obtain M{sub BH} {<=} (1.0 {+-} 0.3) Multiplication-Sign 10{sup 3} M{sub Sun }. Arguing that the nebula of IC 342 X-1 is possibly inflated by a jet, we estimate accretion rates and efficiencies for the jet of IC 342 X-1 and compare with sources like S26, SS433, and IC 10 X-1.« less

Sources and levels of ambient ocean sound near the Antarctic Peninsula.

PubMed

Dziak, Robert P; Bohnenstiehl, DelWayne R; Stafford, Kathleen M; Matsumoto, Haruyoshi; Park, Minkyu; Lee, Won Sang; Fowler, Matt J; Lau, Tai-Kwan; Haxel, Joseph H; Mellinger, David K

2015-01-01

Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Peninsula region) from 2005 to 2009 to record ambient ocean sound at frequencies of up to 125 and 500 Hz. Icequakes, which are broadband, short duration signals derived from fracturing of large free-floating icebergs, are a prominent feature of the ocean soundscape. Icequake activity peaks during austral summer and is minimum during winter, likely following freeze-thaw cycles. Iceberg grounding and rapid disintegration also releases significant acoustic energy, equivalent to large-scale geophysical events. Overall ambient sound levels can be as much as ~10-20 dB higher in the open, deep ocean of the Scotia Sea compared to the relatively shallow Bransfield Strait. Noise levels become lowest during the austral winter, as sea-ice cover suppresses wind and wave noise. Ambient noise levels are highest during austral spring and summer, as surface noise, ice cracking and biological activity intensifies. Vocalizations of blue (Balaenoptera musculus) and fin (B. physalus) whales also dominate the long-term spectra records in the 15-28 and 89 Hz bands. Blue whale call energy is a maximum during austral summer-fall in the Drake Passage and Bransfield Strait when ambient noise levels are a maximum and sea-ice cover is a minimum. Fin whale vocalizations were also most common during austral summer-early fall months in both the Bransfield Strait and Scotia Sea. The hydrophone data overall do not show sustained anthropogenic sources (ships and airguns), likely due to low coastal traffic and the typically rough weather and sea conditions of the Southern Ocean.

Sources and Levels of Ambient Ocean Sound near the Antarctic Peninsula

PubMed Central

Dziak, Robert P.; Bohnenstiehl, DelWayne R.; Stafford, Kathleen M.; Matsumoto, Haruyoshi; Park, Minkyu; Lee, Won Sang; Fowler, Matt J.; Lau, Tai-Kwan; Haxel, Joseph H.; Mellinger, David K.

2015-01-01

Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Peninsula region) from 2005 to 2009 to record ambient ocean sound at frequencies of up to 125 and 500 Hz. Icequakes, which are broadband, short duration signals derived from fracturing of large free-floating icebergs, are a prominent feature of the ocean soundscape. Icequake activity peaks during austral summer and is minimum during winter, likely following freeze-thaw cycles. Iceberg grounding and rapid disintegration also releases significant acoustic energy, equivalent to large-scale geophysical events. Overall ambient sound levels can be as much as ~10–20 dB higher in the open, deep ocean of the Scotia Sea compared to the relatively shallow Bransfield Strait. Noise levels become lowest during the austral winter, as sea-ice cover suppresses wind and wave noise. Ambient noise levels are highest during austral spring and summer, as surface noise, ice cracking and biological activity intensifies. Vocalizations of blue (Balaenoptera musculus) and fin (B. physalus) whales also dominate the long-term spectra records in the 15–28 and 89 Hz bands. Blue whale call energy is a maximum during austral summer-fall in the Drake Passage and Bransfield Strait when ambient noise levels are a maximum and sea-ice cover is a minimum. Fin whale vocalizations were also most common during austral summer-early fall months in both the Bransfield Strait and Scotia Sea. The hydrophone data overall do not show sustained anthropogenic sources (ships and airguns), likely due to low coastal traffic and the typically rough weather and sea conditions of the Southern Ocean. PMID:25875205

MIGRATION PATTERNS, USE OF STOPOVER AREAS, AND AUSTRAL SUMMER MOVEMENTS OF SWAINSON'S HAWKS.

PubMed

Kochert, Michael N; Fuller, Mark R; Schueck, Linda S; Bond, Laura; Bechard, Marc J; Woodbridge, Brian; Holroyd, Geoff; Martell, Mark; Banasch, Ursula

From 1995-1998, we tracked movements of adult Swainson's Hawks ( Buteo swainsoni ) using satellite telemetry to characterize migration, important stopover areas, and austral summer movements. We tagged 46 hawks from July - September on their nesting grounds in seven U.S. states and two Canadian provinces. Swainson's Hawks basically followed three routes south on a broad front, converged along the east coast of central Mexico, and followed a concentrated corridor to a communal austral summer area in central Argentina. North of 20° N, southward and northward tracks differed little for individuals from east of the Continental Divide but differed greatly (up to 1700 km) for individuals from west of the Continental Divide. Hawks left the breeding grounds mid-August to mid-October; departure dates did not differ by location, year, or sex. South migration lasted 42 to 98 days, and north migration took 51 to 82 days. On south migration, 36% of the Swainson's Hawks departed the nesting grounds nearly 3 weeks earlier than the other radio marked hawks and made stopovers 9.0 - 26.0 days long in seven separate areas, mainly in the southern Great Plains, southern Arizona and New Mexico, and north-central Mexico. The austral period lasted 76 to 128 days. All Swainson's Hawks used a core area in central Argentina within 23% of the 738800 km 2 austral summer range where they frequently moved long distances (up to 1600 km). Conservation of Swainson's Hawks must be an international effort that considers habitats used during nesting and non-nesting seasons including migration stopovers.

Precipitation variability in the winter rainfall zone of South Africa during the last 1400 yr linked to the austral westerlies

NASA Astrophysics Data System (ADS)

Stager, J. C.; Mayewski, P. A.; White, J.; Chase, B. M.; Neumann, F. H.; Meadows, M. E.; King, C. D.; Dixon, D. A.

2011-12-01

The austral westerlies strongly influence precipitation and ocean circulation in the southern temperate zone, with important consequences for cultures and ecosystems. Global climate models anticipate poleward contraction of the austral westerlies with future warming, but the available paleoclimate records that might test these models have been largely limited to South America, are not fully consistent with each other, and may be complicated by influences from other climatic factors. Here we present the first fine-interval diatom and sedimentological records from the winter rainfall region of South Africa, representing precipitation during the last 1400 yr. Inferred rainfall increased ~1400-1200 cal yr BP and most notably during the Little Ice Age with pulses centered on ~600, 530, 470, 330, 200, and 90 cal yr BP. Synchronous fluctuations in Antarctic ice core chemistry strongly suggest that these variations are linked to changes in the westerlies. Partial inconsistencies among South African and South American records warn against the simplistic application of local-scale histories to the Southern Hemisphere as a whole. Nonetheless, these findings in general do support model projections of increasing aridity in austral winter rainfall zones with future warming.

Biodiversity of air-borne microorganisms at Halley Station, Antarctica.

PubMed

Pearce, David A; Hughes, K A; Lachlan-Cope, T; Harangozo, S A; Jones, A E

2010-03-01

A study of air-borne microbial biodiversity over an isolated scientific research station on an ice-shelf in continental Antarctica was undertaken to establish the potential source of microbial colonists. The study aimed to assess: (1) whether microorganisms were likely to have a local (research station) or distant (marine or terrestrial) origin, (2) the effect of changes in sea ice extent on microbial biodiversity and (3) the potential human impact on the environment. Air samples were taken above Halley Research Station during the austral summer and austral winter over a 2-week period. Overall, a low microbial biodiversity was detected, which included many sequence replicates. No significant patterns were detected in the aerial biodiversity between the austral summer and the austral winter. In common with other environmental studies, particularly in the polar regions, many of the sequences obtained were from as yet uncultivated organisms. Very few marine sequences were detected irrespective of the distance to open water, and around one-third of sequences detected were similar to those identified in human studies, though both of these might reflect prevailing wind conditions. The detected aerial microorganisms were markedly different from those obtained in earlier studies over the Antarctic Peninsula in the maritime Antarctic.

Photogrammetric determination of spatio-temporal velocity fields at Glaciar San Rafael in the Northern Patagonian Icefield

NASA Astrophysics Data System (ADS)

Maas, H.-G.; Casassa, G.; Schneider, D.; Schwalbe, E.; Wendt, A.

2010-11-01

Glaciar San Rafael in the Northern Patagonian Icefield, with a length of 46 km and an ice area of 722 km2, is the lowest latitude tidewater outlet glacier in the world and one of the fastest and most productive glaciers in southern South America in terms of iceberg flux. In a joint project of the TU Dresden and CECS, spatio-temporal velocity fields in the region of the glacier front were determined in a campaign in austral spring of 2009. Monoscopic terrestrial image sequences were recorded with an intervallometer mode high resolution digital camera over several days. In these image sequences, a large number of glacier surface points were tracked by subpixel accuracy feature tracking techniques. Scaling and georeferencing of the trajectories obtained from image space tracking was performed via a multi-station GPS-supported photogrammetric network. The technique allows for tracking hundreds of glacier surface points at a measurement accuracy in the order of one decimeter and an almost arbitrarily high temporary resolution. The results show velocities of up to 16 m per day. No significant tidal signals could be observed. Our velocities are in agreement with earlier measurements from theodolite and satellite interferometry performed in 1986-1994, suggesting that the current thinning of 3.5 m/y at the front is not due to dynamic thinning but rather by enhanced melting.

Quantitative Comparison of the in situ Microbial Communities in Different Biomes

DTIC Science & Technology

1995-09-01

70 60 50 40 [ a: 30 Ŕ ~ 20 10 o Neotrop. Neotrop_ Antartic . Antartic . -Deep Sea Deep Sea Austral. USA East West Surface 9·10 em...surface (n = 20) (21). ’" LL -’ a. " 2 𔃺 C w 2 ’" a. 60 50 40 30 20 10 o Neotrop. Neolrop. Antartic . Antartic . Deep Sea Deep Sea Austral

Combining and Comparing Astrometric Data from Different Epochs: A Case Study with Hipparcos and Nano-JASMINE

NASA Astrophysics Data System (ADS)

Michalik, D.; Lindegren, L.; Hobbs, D.; Lammers, U.; Yamada, Y.

2012-09-01

The Hipparcos mission (1989-1993) resulted in the first space-based stellar catalogue including measurements of positions, parallaxes and annual proper motions accurate to about one milli-arcsecond. More space astrometry missions will follow in the near future. The ultra-small Japanese mission Nano-JASMINE (launch in late 2013) will determine positions and annual proper motions with some milli-arcsecond accuracy. In mid 2013 the next-generation ESA mission Gaia will deliver some tens of micro-arcsecond accurate astrometric parameters. Until the final Gaia catalogue is published in early 2020 the best way of improving proper motion values is the combination of positions from different missions separated by long time intervals. Rather than comparing positions from separately reduced catalogues, we propose an optimal method to combine the information from the different data sets by making a joint astrometric solution. This allows to obtain good results even when each data set alone is insufficient for an accurate reduction. We demonstrate our method by combining Hipparcos and simulated Nano-JASMINE data in a joint solution. We show a significant improvement over the conventional catalogue combination.

Diffraction-limited Mid-infrared Integral Field Spectroscopy of Io's Volcanic Activity with ALES on the Large Binocular Telescope

NASA Astrophysics Data System (ADS)

Skrutskie, Michael F.; de Kleer, Katherine R.; Stone, Jordan; Conrad, Al; Davies, Ashley; de Pater, Imke; Leisenring, Jarron; Hinz, Philip; Skemer, Andrew; Veillet, Christian; Woodward, Charles E.; Ertel, Steve; Spalding, Eckhart

2017-10-01

The Arizona Lenslet for Exoplanet Spectroscopy (ALES) is an enhancement to the Large Binocular Telescope's mid-infrared imager, LMIRcam, that permits low-resolution (R~20) spectroscopy between 2.8 and 4.2 μm of every diffraction-limited resolution element in a 2.5"x2.5" field-of-view on a 2048x2048 HAWAII-2RG 5.2 μm-cutoff array. The 1" disk of Io, dotted with powerful self-luminous volcanic eruptions, provides an ideal target for ALES, where the single 8.4-meter aperture diffraction-limited scale for Io at opposition ranges from 240 kilometers (80 milliarcseconds) at 2.8 μm to 360 kilometers (120 milliarcseconds) at 4.2 μm. ALES provides the capability to assess the color temperature of each volcanic thermal emission site as well as map broadband absorbers such as SO2 frost. A monitoring campaign in the Spring 2017 semester provided two global snapshots of Io's volcanic activity with ALES as well as characterization of a new brightening episode at Loki Patera over four epochs between January and May 2017.

MIGRATION PATTERNS, USE OF STOPOVER AREAS, AND AUSTRAL SUMMER MOVEMENTS OF SWAINSON’S HAWKS

PubMed Central

Kochert, Michael N.; Fuller, Mark R.; Schueck, Linda S.; Bond, Laura; Bechard, Marc J.; Woodbridge, Brian; Holroyd, Geoff; Martell, Mark; Banasch, Ursula

2015-01-01

From 1995–1998, we tracked movements of adult Swainson’s Hawks (Buteo swainsoni) using satellite telemetry to characterize migration, important stopover areas, and austral summer movements. We tagged 46 hawks from July - September on their nesting grounds in seven U.S. states and two Canadian provinces. Swainson’s Hawks basically followed three routes south on a broad front, converged along the east coast of central Mexico, and followed a concentrated corridor to a communal austral summer area in central Argentina. North of 20° N, southward and northward tracks differed little for individuals from east of the Continental Divide but differed greatly (up to 1700 km) for individuals from west of the Continental Divide. Hawks left the breeding grounds mid-August to mid-October; departure dates did not differ by location, year, or sex. South migration lasted 42 to 98 days, and north migration took 51 to 82 days. On south migration, 36% of the Swainson’s Hawks departed the nesting grounds nearly 3 weeks earlier than the other radio marked hawks and made stopovers 9.0 – 26.0 days long in seven separate areas, mainly in the southern Great Plains, southern Arizona and New Mexico, and north-central Mexico. The austral period lasted 76 to 128 days. All Swainson’s Hawks used a core area in central Argentina within 23% of the 738800 km2 austral summer range where they frequently moved long distances (up to 1600 km). Conservation of Swainson’s Hawks must be an international effort that considers habitats used during nesting and non-nesting seasons including migration stopovers. PMID:26380528

From mammals back to birds: Host-switch of the acanthocephalan Corynosoma australe from pinnipeds to the Magellanic penguin Spheniscus magellanicus

PubMed Central

Brandão, Martha; Georgieva, Simona; Raga, Juan Antonio; Crespo, Enrique Alberto; Luque, José Luis

2017-01-01

Trophically-transmitted parasites are regularly exposed to potential new hosts through food web interactions. Successful colonization, or switching, to novel hosts, occur readily when ‘donor’ and ‘target’ hosts are phylogenetically related, whereas switching between distantly related hosts is rare and may result from stochastic factors (i.e. rare favourable mutations). This study investigates a host-switching event between a marine acanthocephalan specific to pinnipeds that is apparently able to reproduce in Magellanic penguins Spheniscus magellanicus from Brazil. Detailed analysis of morphological and morphometrical data from acanthocephalans from penguins indicates that they belong to Corynosoma australe Johnston, 1937. Partial fragments of the 28S rRNA and mitochondrial cox1 genes were amplified from isolates from penguins and two pinniped species (i.e. South American sea lion Otaria flavescens and South American fur seal Arctocephalus australis) to confirm this identification. Infection parameters clearly differ between penguins and the two pinniped species, which were significantly lower in S. magellanicus. The sex ratio of C. australe also differed between penguins and pinnipeds; in S. magellanicus was strongly biased against males, while in pinnipeds it was close to 1:1. Females of C. australe from O. flavescens were smaller than those from S. magellanicus and A. australis. However, fecundity (i.e. the proportion of fully developed eggs) was lower and more variable in females collected from S. magellanicus. At first glance, the occurrence of reproductive individuals of C. australe in Magellanic penguins could be interpreted as an adaptive colonization of a novel avian host through favourable mutations. However, it could also be considered, perhaps more likely, as an example of ecological fitting through the use of a plesimorphic (host) resource, since the ancestors of Corynosoma infected aquatic birds. PMID:28981550

Sources and levels of ambient ocean sound near the antarctic peninsula

DOE PAGES

Dziak, Robert P.; Bohnenstiehl, DelWayne R.; Stafford, Kathleen M.; ...

2015-04-14

Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Peninsula region) from 2005 to 2009 to record ambient ocean sound at frequencies of up to 125 and 500 Hz. Icequakes, which are broadband, short duration signals derived from fracturing of large free-floating icebergs, are a prominent feature of the ocean soundscape. Icequake activity peaks during austral summer and is minimum during winter, likely following freeze-thaw cycles. Iceberg grounding and rapid disintegration also releases significant acoustic energy, equivalent to large-scale geophysical events. Overall ambient sound levels can be as much as ~10–20 dB higher in the open,more » deep ocean of the Scotia Sea compared to the relatively shallow Bransfield Strait. Noise levels become lowest during the austral winter, as sea-ice cover suppresses wind and wave noise. Ambient noise levels are highest during austral spring and summer, as surface noise, ice cracking and biological activity intensifies. Vocalizations of blue ( Balaenoptera musculus) and fin ( B. physalus) whales also dominate the long-term spectra records in the 15–28 and 89 Hz bands. Blue whale call energy is a maximum during austral summer-fall in the Drake Passage and Bransfield Strait when ambient noise levels are a maximum and sea-ice cover is a minimum. Fin whale vocalizations were also most common during austral summer-early fall months in both the Bransfield Strait and Scotia Sea. The hydrophone data overall do not show sustained anthropogenic sources (ships and airguns), likely due to low coastal traffic and the typically rough weather and sea conditions of the Southern Ocean.« less

From mammals back to birds: Host-switch of the acanthocephalan Corynosoma australe from pinnipeds to the Magellanic penguin Spheniscus magellanicus.

PubMed

Hernández-Orts, Jesús Servando; Brandão, Martha; Georgieva, Simona; Raga, Juan Antonio; Crespo, Enrique Alberto; Luque, José Luis; Aznar, Francisco Javier

2017-01-01

Trophically-transmitted parasites are regularly exposed to potential new hosts through food web interactions. Successful colonization, or switching, to novel hosts, occur readily when 'donor' and 'target' hosts are phylogenetically related, whereas switching between distantly related hosts is rare and may result from stochastic factors (i.e. rare favourable mutations). This study investigates a host-switching event between a marine acanthocephalan specific to pinnipeds that is apparently able to reproduce in Magellanic penguins Spheniscus magellanicus from Brazil. Detailed analysis of morphological and morphometrical data from acanthocephalans from penguins indicates that they belong to Corynosoma australe Johnston, 1937. Partial fragments of the 28S rRNA and mitochondrial cox1 genes were amplified from isolates from penguins and two pinniped species (i.e. South American sea lion Otaria flavescens and South American fur seal Arctocephalus australis) to confirm this identification. Infection parameters clearly differ between penguins and the two pinniped species, which were significantly lower in S. magellanicus. The sex ratio of C. australe also differed between penguins and pinnipeds; in S. magellanicus was strongly biased against males, while in pinnipeds it was close to 1:1. Females of C. australe from O. flavescens were smaller than those from S. magellanicus and A. australis. However, fecundity (i.e. the proportion of fully developed eggs) was lower and more variable in females collected from S. magellanicus. At first glance, the occurrence of reproductive individuals of C. australe in Magellanic penguins could be interpreted as an adaptive colonization of a novel avian host through favourable mutations. However, it could also be considered, perhaps more likely, as an example of ecological fitting through the use of a plesimorphic (host) resource, since the ancestors of Corynosoma infected aquatic birds.

Galaxias australes con núcleo doble

NASA Astrophysics Data System (ADS)

Gimeno, G.; Díaz, R.; Carranza, G.

Se estudia una muestra de galaxias australes con núcleo doble a partir de una búsqueda extensiva en la literatura. Se analizan las características morfológicas, fotométricas y espectroscópicas de la muestra. Para algunas galaxias se han realizado observaciones con el espectrógrafo multifunción (EMF) de la Estación Astrofísica de Bosque Alegre a partir de las cuales se determinaron parámetros cinemáticos.

Spatial distribution of Salpa thompsoni in the high Antarctic area off Adélie Land, East Antarctica during the austral summer 2008

NASA Astrophysics Data System (ADS)

Ono, Atsushi; Moteki, Masato

2017-06-01

The salp Salpa thompsoni has the potential to alter the Southern Ocean ecosystem through competition with krill Euphausia superba. Information on the reproductive status of S. thompsoni in the high Southern Ocean is thus essential to understanding salp population growth and predicting changes in the Southern Ocean ecosystem. We carried out stratified and quantitative sampling from the surface to a depth of 2000 m during the austral summer of 2008 to determine the spatial distribution and population structure of S. thompsoni in the Southern Ocean off Adélie Land. We found two salp species, S. thompsoni and Ihlea racovitzai, with the former being dominant. S. thompsoni was distributed north of the continental slope area, while I. racovitzai was observed in the neritic zone. Mature aggregates and solitary specimens of S. thompsoni were found south of the Southern Boundary of the Antarctic Circumpolar Current, suggesting that S. thompsoni is able to complete its life cycle in high Antarctic waters during the austral summer. However, S. thompsoni was sparsely distributed in the continental slope area, and absent south of the Antarctic Slope Front, suggesting that it is less competitive with krill for food in the slope area off Adélie Land, where krill is densely distributed during the austral summer.

NGST fine guidance sensor

NASA Astrophysics Data System (ADS)

Rowlands, Neil; Hutchings, John; Murowinski, Richard G.; Alexander, Russ

2003-03-01

Instrumentation for the Next Generation Space Telescope (NGST) is currently in the Phase A definition stage. We have developed a concept for the NGST Fine Guidance Sensor or FGS. The FGS is a detector array based imager which resides in the NGST focal plane. We report here on tradeoff studies aimed at defining an overall configuration of the FGS which will meet the performance and interface requirements. A key performance requirement is a noise equivalent angle of 3 milli-arcseconds to be achieved with 95% probability for any pointing of the observatory in the celestial sphere. A key interface requirement is compatibility with the architecture of the Integrated Science Instrument Module (ISIM). The concept developed consists of two independent and redundant FGS modules, each with a 4' x 2' field of view covered by two 2048 x 2048 infrared detector arrays, providing 60 milli-arcsecond sampling. Performance modeling supporting the choice of this architecture and the trade space considered is presented. Each module has a set of readout electronics which perform star detection, pixel-by-pixel correction, and in fine guiding mode, centroid calculation. These readout electronics communicate with the ISIM Command &Data Handling Units where the FGS control software is based. Rationale for this choice of architecture is also presented.

A Starshade Petal Error Budget for Exo-Earth Detection and Characterization

NASA Technical Reports Server (NTRS)

Shaklan, Stuart B.; Marchen, Luis; Lisman, P. Douglas; Cady, Eric; Martin, Stefan; Thomson, Mark; Dumont, Philip; Kasdin, N. Jeremy

2011-01-01

We present a starshade error budget with engineering requirements that are well within the current manufacturing and metrology capabilities. The error budget is based on an observational scenario in which the starshade spins about its axis on timescales short relative to the zodi-limited integration time, typically several hours. The scatter from localized petal errors is smoothed into annuli around the center of the image plane, resulting in a large reduction in the background flux variation while reducing thermal gradients caused by structural shadowing. Having identified the performance sensitivity to petal shape errors with spatial periods of 3-4 cycles/petal as the most challenging aspect of the design, we have adopted and modeled a manufacturing approach that mitigates these perturbations with 1-meter-long precision edge segments positioned using commercial metrology that readily meets assembly requirements. We have performed detailed thermal modeling and show that the expected thermal deformations are well within the requirements as well. We compare the requirements for four cases: a 32 meter diameter starshade with a 1.5 meter telescope, analyzed at 75 and 90 milliarcseconds, and a 40 meter diameter starshade with a 4 meter telescope, analyzed at 60 and 75 milliarcseconds.

A direct gravitational lensing test for 10 exp 6 solar masses black holes in halos of galaxies

NASA Technical Reports Server (NTRS)

Wambsganss, Joachim; Paczynski, Bohdan

1992-01-01

We propose a method that will be able to detect or exclude the existence of 10 exp 6 solar masses black holes in the halos of galaxies. VLBA radio maps of two milliarcsecond jets of a gravitationally lensed quasar will show the signature of these black holes - if they exist. If there are no compact objects in this mass range along the line of sight, the two jets should be linear mappings of each other. If they are not, there must be compact objects of about 10 exp 6 solar masses in the halo of the galaxy that deform the images by gravitational deflection. We present numerical simulations for the two jets A and B of the double quasar 0957 + 561, but the method is valid for any gravitationally lensed quasar with structure on milliarcsecond scales. As a by-product from high-quality VLBA maps of jets A and B, one will be able to tell which features in the maps are intrinsic in the original jet and which are only an optical illusion, i.e., gravitational distortions by black holes along the line of sight.

Flight Demonstration of a Milli-Arcsecond Optical Pointing System for Direct Exoplanet Imaging

NASA Astrophysics Data System (ADS)

Mendillo, Christopher; Chakrabarti, S.; Cook, T.; Hicks, B.

2012-01-01

The PICTURE (Planetary Imaging Concept Testbed Using a Rocket Experiment) sounding rocket attempted to use a white-light nulling interferometer to image the exozodiacal dust disk of Epsilon Eridani (K2V, 3.22 pc) in reflected visible light down to an inner radius of 3 AU. PICTURE launched from White Sands Missile Range on October 8th, 2011. Unfortunately, the main science telemetry channel was lost seconds into flight and no science data was recovered. However, on-board diagnostic data does show that PICTURE successfully demonstrated a fast (200 Hz) optical tracking system that provided 2 milli-arcsecond in-flight pointing stability, a thousand-fold improvement over the raw pointing of the rocket's attitude control system (ACS). The PICTURE flight provides heritage for a technology that will be a key component for many future direct exoplanet imaging missions. We present a spectral analysis of the 200 Hz tracking data in comparison to the 50 Hz ACS gyro data and we provide a precise measurement of the true ACS performance at frequencies higher than 5 Hz where the ACS gyros become noise limited. This work is funded by NASA grant: NNG05WC17G.

Report of the Hydrographic Service Royal Australian Navy for the Year Ended 30th June 1989. Issue Number 25

DTIC Science & Technology

1989-06-30

charts 369 are Austral- ian and 44 British Admiralty. Australian charts represent 170 in imperial units and 199 in metric units: 92 in metric for...and operations advi(.e for the introduction into service of Vaisala Marwin Systems by the Royal Austral- ian Artiller,. 15 SURVEY INSTRUCTION, RAN... Maitland Pemberton Scott South Seringapatam Timor Trough Wilson Promontory Shark Bay BATHYMETRIC MANUSCRIPT AUSLIG Cove Blue Mud Ba Port Langdon Roper

Precipitation variability in the winter rainfall zone of South Africa during the last 1400 yr linked to the austral westerlies

NASA Astrophysics Data System (ADS)

Stager, J. C.; Mayewski, P. A.; White, J.; Chase, B. M.; Neumann, F. H.; Meadows, M. E.; King, C. D.; Dixon, D. A.

2012-05-01

The austral westerlies strongly influence precipitation and ocean circulation in the southern temperate zone, with important consequences for cultures and ecosystems. Global climate models anticipate poleward retreat of the austral westerlies with future warming, but the available paleoclimate records that might test these models have been limited to South America and New Zealand, are not fully consistent with each other and may be complicated by influences from other climatic factors. Here we present the first high-resolution diatom and sedimentological records from the winter rainfall region of South Africa, representing precipitation in the equatorward margin of the westerly wind belt during the last 1400 yr. Inferred rainfall was relatively high ∼1400-1200 cal yr BP, decreased until ∼950 cal yr BP, and rose notably through the Little Ice Age with pulses centred on ∼600, 530, 470, 330, 200, 90, and 20 cal yr BP. Synchronous fluctuations in Antarctic ice core chemistry strongly suggest that these variations were linked to changes in the westerlies. Equatorward drift of the westerlies during the wet periods may have influenced Atlantic meridional overturning circulation by restricting marine flow around the tip of Africa. Apparent inconsistencies among some aspects of records from South America, New Zealand and South Africa warn against the simplistic application of single records to the Southern Hemisphere as a whole. Nonetheless, these findings in general do support model projections of increasing aridity in the austral winter rainfall zones with future warming.

Physical and non-physical energy in scattered wave source-receiver interferometry.

PubMed

Meles, Giovanni Angelo; Curtis, Andrew

2013-06-01

Source-receiver interferometry allows Green's functions between sources and receivers to be estimated by means of convolution and cross-correlation of other wavefields. Source-receiver interferometry has been observed to work surprisingly well in practical applications when theoretical requirements (e.g., complete enclosing boundaries of other sources and receivers) are contravened: this paper contributes to explain why this may be true. Commonly used inter-receiver interferometry requires wavefields to be generated around specific stationary points in space which are controlled purely by medium heterogeneity and receiver locations. By contrast, application of source-receiver interferometry constructs at least kinematic information about physically scattered waves between a source and a receiver by cross-convolution of scattered waves propagating from and to any points on the boundary. This reduces the ambiguity in interpreting wavefields generated using source-receiver interferometry with only partial boundaries (as is standard in practical applications), as it allows spurious or non-physical energy in the constructed Green's function to be identified and ignored. Further, source-receiver interferometry (which includes a step of inter-receiver interferometry) turns all types of non-physical or spurious energy deriving from inter-receiver interferometry into what appears to be physical energy. This explains in part why source-receiver interferometry may perform relatively well compared to inter-receiver interferometry when constructing scattered wavefields.

A Very Small Astrometry Satellite, Nano-JASMINE: Its Telescope and Mission Goals

NASA Astrophysics Data System (ADS)

Hatsutori, Yoichi; Suganuma, Masahiro; Kobayashi, Yukiyasu; Gouda, Naoteru; Yano, Taihei; Yamada, Yoshiyuki; Yamauchi, Masahiro

This paper introduces a small astrometry satellite, Nano-JASMINE. Nano-JASMINE is mounted a 5-cm effective diameter telescope and aims to measure positions of ten or twenty thousands of stars of z ≤ 8 mag for all-sky with the accuracy of a few milli-arcseconds. The mission goals are clarified and the current status of development of the telescope is reported.

Seychelles coral record of changes in sea surface temperature bimodality in the western Indian Ocean from the Mid-Holocene to the present

NASA Astrophysics Data System (ADS)

Zinke, J.; Pfeiffer, M.; Park, W.; Schneider, B.; Reuning, L.; Dullo, W.-Chr.; Camoin, G. F.; Mangini, A.; Schroeder-Ritzrau, A.; Garbe-Schönberg, D.; Davies, G. R.

2014-08-01

We report fossil coral records from the Seychelles comprising individual time slices of 14-20 sclerochronological years between 2 and 6.2 kyr BP to reconstruct changes in the seasonal cycle of western Indian Ocean sea surface temperature (SST) compared to the present (1990-2003). These reconstructions allowed us to link changes in the SST bimodality to orbital changes, which were causing a reorganization of the seasonal insolation pattern. Our results reveal the lowest seasonal SST range in the Mid-Holocene (6.2-5.2 kyr BP) and around 2 kyr BP, while the highest range is observed around 4.6 kyr BP and between 1990 and 2003. The season of maximum temperature shifts from austral spring (September to November) to austral autumn (March to May), following changes in seasonal insolation over the past 6 kyr. However, the changes in SST bimodality do not linearly follow the insolation seasonality. For example, the 5.2 and 6.2 kyr BP corals show only subtle SST differences in austral spring and autumn. We use paleoclimate simulations of a fully coupled atmosphere-ocean general circulation model to compare with proxy data for the Mid-Holocene around 6 kyr BP. The model results show that in the Mid-Holocene the austral winter and spring seasons in the western Indian Ocean were warmer while austral summer was cooler. This is qualitatively consistent with the coral data from 6.2 to 5.2 kyr BP, which shows a similar reduction in the seasonal amplitude compared to the present day. However, the pattern of the seasonal SST cycle in the model appears to follow the changes in insolation more directly than indicated by the corals. Our results highlight the importance of ocean-atmosphere interactions for Indian Ocean SST seasonality throughout the Holocene. In order to understand Holocene climate variability in the countries surrounding the Indian Ocean, we need a much more comprehensive analysis of seasonally resolved archives from the tropical Indian Ocean. Insolation data alone only provides an incomplete picture.

Galaxies as High-resolution Telescopes

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

Barnacka, Anna, E-mail: abarnacka@cfa.harvard.edu

Recent observations show a population of active galaxies with milliarcsecond offsets between optical and radio emission. Such offsets can be an indication of extreme phenomena associated with supermassive black holes including relativistic jets, binary supermassive black holes, or even recoiling supermassive black holes. However, the multi-wavelength structure of active galaxies at a few milliarcseconds cannot be resolved with direct observations. We propose using strong gravitational lensing to elucidate the multi-wavelength structure of sources. When sources are located close to the caustic of a lensing galaxy, even a small offset in the position of the sources results in a drastic differencemore » in the position and magnification of mirage images. We show that the angular offset in the position of the sources can be amplified more than 50 times in the observed position of mirage images. We find that at least 8% of the observed gravitationally lensed quasars will be in the caustic configuration. The synergy between SKA and Euclid will provide an ideal set of observations for thousands of gravitationally lensed sources in the caustic configuration, which will allow us to resolve the multi-wavelength structure for a large ensemble of sources and to study the physical origin of radio emissions, their connection to supermassive black holes, and their cosmic evolution.« less

Are we close to putting the anomalous perihelion precessions from Verlinde's emergent gravity to the test?

NASA Astrophysics Data System (ADS)

Iorio, Lorenzo

2017-03-01

In the framework of the emergent gravity scenario by Verlinde, it was recently observed by Liu and Prokopec that, among other things, an anomalous pericenter precession would affect the orbital motion of a test particle orbiting an isolated central body. Here, it is shown that, if it were real, its expected magnitude for the inner planets of the Solar System would be at the same level of the present-day accuracy in constraining any possible deviations from their standard perihelion precessions as inferred from long data records spanning about the last century. The most favorable situation for testing the Verlinde-type precession seems to occur for Mars. Indeed, according to recent versions of the EPM and INPOP planetary ephemerides, non-standard perihelion precessions, of whatsoever physical origin, which are larger than some ≈ 0.02-0.11 milliarcseconds per century are not admissible, while the putative precession predicted by Liu and Prokopec amounts to 0.09 milliarcseconds per century. Other potentially interesting astronomical and astrophysical scenarios like, e.g., the Earth's LAGEOS II artificial satellite, the double pulsar system PSR J0737-3039A/B and the S-stars orbiting the Supermassive Black Hole in Sgr A^* are, instead, not viable because of the excessive smallness of the predicted precessions for them.

Linking Deep Astrometric Standards to the ICRF

NASA Astrophysics Data System (ADS)

Frey, S.; Platais, I.; Fey, A. L.

2007-07-01

The next-generation large aperature and large field-of-view telescopes will address fundamantal questions of astrophysica and cosmology such as the nature of dark matter and dark energy. For a variety of applications, the CCD mosaic detectors in the focal plane arrays require astronomic calibrationat the milli-arcsecond (mas) level. The existing optical reference frames are insufficient to support such calibrations. To address this problem, deep optical astronomic fields are being established near the Galactic plane. In order to achiev a 5-10-mas or better positional accuracyfor the Deepp Astrometric Standards (DAS), and to obtain bsolute stellar proper motions for the study of Galactic structure, it is crucial to link these fields to the International Celestial Reference Frame (ICRF). To this end, we selected 15 candidate compact extragalactic radio sources in the Gemini-Orion-Taurus (GOT) field. These sources were observed with the European VLBI Network (EVN) at 5 GHz in phase-reference mode. The bright compact calibrator source J0603+2159 and seven other sources were detected and imaged at the angular resolution of -1.5-8 mas. Relative astrometric positions were derived for these sources at a milli-arcsecond accuracy level. The detection of the optical counterparts of these extragalactic radio sources will allow us to establish a direct link to the ICRF locally in the GOT field.

Three-genome mosses: complex double allopolyploid origins for triploid gametophytes in Sphagnum.

PubMed

Karlin, Eric F; Boles, S B; Ricca, M; Temsch, E M; Greilhuber, J; Shaw, A J

2009-04-01

This paper documents the occurrence of allotriploidy (having three differentiated genomes) in gametophytes of two Southern Hemisphere Sphagnum species (S. australe, S. falcatulum). The pattern of microsatellite alleles indicates that both species are composed of a complex of allodiploid and allotriploid gametophytes, with the latter resulting from two allopolyploidization events. No haploid (n = x) gametophytes were found for either species. The ploidal levels suggested by the pattern of microsatellite alleles were confirmed by flow cytometry and Feulgen DNA image densitometry. For both S. australe and S. falcatulum, the respective allodiploid plants (or their ancestors) are one of the parent species of the allotriploid plants. This is the first report of triploidy in Sphagnum gametophytes occurring in nature and also the first report of the presence of three differentiated genomes in any bryophyte. It is also the first report of intersectional allopolyploidy in Sphagnum, with S. australe appearing to have parental species from Sphagnum sections Rigida and Sphagnum, and S. falcatulum having parental species from Sphagnum sections Cuspidata and Subsecunda. In both species, the allotriploid cytotypes were the most prevalent cytotype on the South Island of New Zealand. The pattern of microsatellite alleles shows the presence of two genetically distinct populations of allodiploid S. australe, possibly indicating multiple origins of polyploidy for that allodiploid cytotype. Morphological evidence is also highly indicative of recurrent polyploidy in the allotriploid cytotype of S. falcatulum. Allopolyploidy has clearly played a major evolutionary role in these two Southern Hemisphere taxa. This study, in conjunction with other recent research, indicates that allopolyploidy is a common, if not the predominant, form of polyploidy in Sphagnum.

Migration patterns, use of stopover areas, and austral summer movements of Swainson's hawks

USGS Publications Warehouse

Kocher, Michael N.; Fuller, Mark R.; Schueck, Linda S.; Bond, Laura; Bechard, Marc J.; Woodbridge, Brian; Holroyd, Geoff L.; Martell, Mark S.; Banasch, Ursula

2011-01-01

from 1995 to 1998, we tracked movements of adult Swainson's Hawks (Buteo swainsoni), using satellite telemetry to characterize migration, important stopover areas, and movements in the austral summer. we tagged 46 hawks from July to September on their nesting grounds in seven U.S. states and two Canadian provinces. Swainson's Hawks followed three basic routes south on a broad front, converged along the east coast of cen-tral Mexico, and followed a concentrated corridor to a communal area in central Argentina for the austral summer. North of 20° N, southward and northward tracks differed little for individuals from east of the continental divide but differed greatly (up to 1700 km) for individuals from west of the continental divide. Hawks left the breeding grounds mid-August to mid-October; departure dates did not differ by location, year, or sex. Southbound migra-tion lasted 42 to 98 days, northbound migration 51 to 82 days. Southbound, 36% of the Swainson's Hawks departed the nesting grounds nearly 3 weeks earlier than the other radio-marked hawks and made stopovers 9.0–26.0 days long in seven separate areas, mainly in the southern great Plains, southern Arizona and New Mexico, and north-central Mexico. The birds stayed in their nonbreeding range for 76 to 128 days. All used a core area in central Ar-gentina within 23% of the 738 800-km2 austral summer range, where they frequently moved long distances (up to 1600 km). Conservation of Swainson's Hawks must be an international effort that considers habitats used during nesting and non-nesting seasons, including migration stopovers.

Multi-locus phylogenetics, lineage sorting, and reticulation in Pinus subsection Australes.

PubMed

Gernandt, David S; Aguirre Dugua, Xitlali; Vázquez-Lobo, Alejandra; Willyard, Ann; Moreno Letelier, Alejandra; Pérez de la Rosa, Jorge A; Piñero, Daniel; Liston, Aaron

2018-04-23

Both incomplete lineage sorting and reticulation have been proposed as causes of phylogenetic incongruence. Disentangling these factors may be most difficult in long-lived, wind-pollinated plants with large population sizes and weak reproductive barriers. We used solution hybridization for targeted enrichment and massive parallel sequencing to characterize low-copy-number nuclear genes and high-copy-number plastomes (Hyb-Seq) in 74 individuals of Pinus subsection Australes, a group of ~30 New World pine species of exceptional ecological and economic importance. We inferred relationships using methods that account for both incomplete lineage sorting and reticulation. Concatenation- and coalescent-based trees inferred from nuclear genes mainly agreed with one another, but they contradicted the plastid DNA tree in recovering the Attenuatae (the California closed-cone pines) and Oocarpae (the egg-cone pines of Mexico and Central America) as monophyletic and the Australes sensu stricto (the southern yellow pines) as paraphyletic to the Oocarpae. The plastid tree featured some relationships that were discordant with morphological and geographic evidence and species limits. Incorporating gene flow into the coalescent analyses better fit the data, but evidence supporting the hypothesis that hybridization explains the non-monophyly of the Attenuatae in the plastid tree was equivocal. Our analyses document cytonuclear discordance in Pinus subsection Australes. We attribute this discordance to ancient and recent introgression and present a phylogenetic hypothesis in which mostly hierarchical relationships are overlain by gene flow. © 2018 The Authors. American Journal of Botany is published by Wiley Periodicals, Inc. on behalf of the Botanical Society of America.

Land-atmosphere-ocean interactions in the southeastern Atlantic: interannual variability

NASA Astrophysics Data System (ADS)

Sun, Xiaoming; Vizy, Edward K.; Cook, Kerry H.

2018-02-01

Land-atmosphere-ocean interactions in the southeastern South Atlantic and their connections to interannual variability are examined using a regional climate model coupled with an intermediate-level ocean model. In austral summer, zonal displacements of the South Atlantic subtropical high (SASH) can induce variations of mixed-layer currents in the Benguela upwelling region through surface wind stress curl anomalies near the Namibian coast, and an eastward shifted SASH is related to the first Pacific-South American mode. When the SASH is meridionally displaced, mixed layer vertically-integrated Ekman transport anomalies are mainly a response to the change of alongshore surface wind stress. The latitudinal shift of the SASH tends to dampen the anomalous alongshore wind by modulating the land-sea thermal contrast, while opposed by oceanic diffusion. Although the position of the SASH is closely linked to the phase of El Niño-Southern Oscillation (ENSO) and the southern annular mode (SAM) in austral summer, an overall relationship between Benguela upwelling strength and ENSO or SAM is absent. During austral winter, variations of the mixed layer Ekman transport in the Benguela upwelling region are connected to the strength of the SASH through its impact on both coastal wind stress curl and alongshore surface wind stress. Compared with austral summer, low-level cloud cover change plays a more important role. Although wintertime sea surface temperature fluctuations in the equatorial Atlantic are strong and may act to influence variability over the northern Benguela area, the surface heat budget analysis suggests that local air-sea interactions dominate.

A review of recent work in sub-nanometre displacement measurement using optical and X-ray interferometry.

PubMed

Peggs, G N; Yacoot, A

2002-05-15

This paper reviews recent work in the field of displacement measurement using optical and X-ray interferometry at the sub-nanometre level of accuracy. The major sources of uncertainty in optical interferometry are discussed and a selection of recent designs of ultra-precise, optical-interferometer-based, displacement measuring transducers presented. The use of X-ray interferometry and its combination with optical interferometry is discussed.

Bibliography of spatial interferometry in optical astronomy

NASA Technical Reports Server (NTRS)

Gezari, Daniel Y.; Roddier, Francois; Roddier, Claude

1990-01-01

The Bibliography of Spatial Interferometry in Optical Astronomy is a guide to the published literature in applications of spatial interferometry techniques to astronomical observations, theory and instrumentation at visible and infrared wavelengths. The key words spatial and optical define the scope of this discipline, distinguishing it from spatial interferometry at radio wavelengths, interferometry in the frequency domain applied to spectroscopy, or more general electro-optics theoretical and laboratory research. The main bibliography is a listing of all technical articles published in the international scientific literature and presented at the major international meetings and workshops attended by the spatial interferometry community. Section B summarizes publications dealing with the basic theoretical concepts and algorithms proposed and applied to optical spatial interferometry and imaging through a turbulent atmosphere. The section on experimental techniques is divided into twelve categories, representing the most clearly identified major areas of experimental research work. Section D, Observations, identifies publications dealing specifically with observations of astronomical sources, in which optical spatial interferometry techniques have been applied.

Speckle interferometry of asteroids

NASA Technical Reports Server (NTRS)

Drummond, Jack

1988-01-01

This final report for NASA Contract NAGw-867 consists of abstracts of the first three papers in a series of four appearing in Icarus that were funded by the preceding contract NAGw-224: (1) Speckle Interferometry of Asteroids I. 433 Eros; (2) Speckle Interferometry of Asteroids II. 532 Herculina; (3) Speckle Interferometry of Asteroids III. 511 Davida and its Photometry; and the fourth abstract attributed to NAGw-867, (4) Speckle Interferometry of Asteroids IV. Reconstructed images of 4 Vesta; and a review of the results from the asteroid interferometry program at Steward Observatory prepared for the Asteroids II book, (5) Speckle Interferometry of Asteroids. Two papers on asteroids, indirectly related to speckle interferometry, were written in part under NAGw-867. One is in press and its abstract is included here: Photometric Geodesy of Main-Belt Asteroids. II. Analysis of Lightcurves for Poles, Periods and Shapes; and the other paper, Triaxial Ellipsoid Dimensions and Rotational Pole of 2 Pallas from Two Stellar Occultations, is included in full.

Influence of the preceding austral summer Southern Hemisphere annular mode on the amplitude of ENSO decay

NASA Astrophysics Data System (ADS)

Zheng, Fei; Li, Jianping; Ding, Ruiqiang

2017-11-01

There is increasing evidence of the possible role of extratropical forcing in the evolution of ENSO. The Southern Hemisphere Annular Mode (SAM) is the dominant mode of atmospheric circulation in the Southern Hemisphere extratropics. This study shows that the austral summer (December-January-February; DJF) SAM may also influence the amplitude of ENSO decay during austral autumn (March-April-May; MAM). The mechanisms associated with this SAM-ENSO relationship can be briefly summarized as follows: The SAM is positively (negatively) correlated with SST in the Southern Hemisphere middle (high) latitudes. This dipole-like SST anomaly pattern is referred to as the Southern Ocean Dipole (SOD). The DJF SOD, caused by the DJF SAM, could persist until MAM and then influence atmospheric circulation, including trade winds, over the Niño3.4 area. Anomalous trade winds and SST anomalies over the Niño3.4 area related to the DJF SAM are further developed through the Bjerkness feedback, which eventually results in a cooling (warming) over the Niño3.4 area followed by the positive (negative) DJF SAM.

Studies towards the stabilisation of a mushroom phytase produced by submerged cultivation.

PubMed

Spier, Michele Rigon; Behsnilian, Diana; Zielinski, Acácio; Konietzny, Ursula; Greiner, Ralf

2015-10-01

A novel phytase from Ganoderma australe G24 was produced by submerged cultivation and recovery. Liquid and solid forms of phytase were developed; both types of product were formulated using different additives. Ganoderma australe G24 phytase was very stable in liquid form with NaCl and sodium acetate buffer. Solid form products were obtained by spray-drying using different polymers to encapsulate the phytase and the capsules obtained were analyzed by electron microscopy. Micrographs confirmed micro and nanoparticles formed with maltodextrin (300 nm to 7-8 µm) without the presence of agglomerates. The use of maltodextrin for solid formulation of G. australe G24 phytase is recommended, and resulted in good stability after the drying process and during storage (shelf life). Kinetic models of phytase inactivation in the microencapsulated powders over time were proposed for the different stabilizing additives. Inactivation rate constants, half-lives and D values (decimal reduction time) were obtained. Phytase encapsulated with maltodextrin remained stable after 90 days, with k 0.0019 day(-1) and a half-life (t1/2) of 367.91 days(-1).

Cardenolide glycosides from Elaeodendron australe var. integrifolium.

PubMed

Butler, Mark S; Towerzey, Leanne; Pham, Ngoc B; Hyde, Edward; Wadi, Sao Khemar; Guymer, Gordon P; Quinn, Ronald J

2014-02-01

Extracts from dried leaf and stems of Elaeodendron australe var. integrifolium (Celastraceae) collected in South East Queensland, Australia, were active in an assay that measured Ca(2+) driven expression of IL-2/luciferase designed to identify inhibitors of the ICRAC channel. Bioassay-guided isolation using C18 and polyamide column chromatography, HPLC (Phenyl and C18) and centrifugal partition chromatography (CPC) led to the isolation of digitoxigenin (1) and three cardenolide glycosides, glucoside 2, quinovoside 3 and the new natural product xyloside 4, as the active components with low nM activity in the reporter assay. Copyright © 2013 Elsevier Ltd. All rights reserved.

Doppler synthetic aperture radar interferometry: a novel SAR interferometry for height mapping using ultra-narrowband waveforms

NASA Astrophysics Data System (ADS)

Yazıcı, Birsen; Son, Il-Young; Cagri Yanik, H.

2018-05-01

This paper introduces a new and novel radar interferometry based on Doppler synthetic aperture radar (Doppler-SAR) paradigm. Conventional SAR interferometry relies on wideband transmitted waveforms to obtain high range resolution. Topography of a surface is directly related to the range difference between two antennas configured at different positions. Doppler-SAR is a novel imaging modality that uses ultra-narrowband continuous waves (UNCW). It takes advantage of high resolution Doppler information provided by UNCWs to form high resolution SAR images. We introduce the theory of Doppler-SAR interferometry. We derive an interferometric phase model and develop the equations of height mapping. Unlike conventional SAR interferometry, we show that the topography of a scene is related to the difference in Doppler frequency between two antennas configured at different velocities. While the conventional SAR interferometry uses range, Doppler and Doppler due to interferometric phase in height mapping; Doppler-SAR interferometry uses Doppler, Doppler-rate and Doppler-rate due to interferometric phase in height mapping. We demonstrate our theory in numerical simulations. Doppler-SAR interferometry offers the advantages of long-range, robust, environmentally friendly operations; low-power, low-cost, lightweight systems suitable for low-payload platforms, such as micro-satellites; and passive applications using sources of opportunity transmitting UNCW.

The VLTI Roadmap

NASA Astrophysics Data System (ADS)

Mérand, A.

2018-03-01

ESO's Very Large Telescope Interferometer (VLTI) was a unique facility when it was conceived more than 30 years ago, and it remains competitive today in the field of milli-arcsecond angular resolution astronomy. Over the past decade, while the VLTI matured into an operationally efficient facility, it became limited by its first-generation instruments. As the second generation of VLTI instrumentation achieves first light, further developments for this unique facility are being planned and are described here.

The Joint Milli-Arcsecond Pathfinder Survey (J-MAPS) Mission: Application for Space Situational Awareness

DTIC Science & Technology

2008-09-01

One implication of this is that the instrument can physically resolve satellites at smaller separations than current and existing optical SSA assets...with the potential for 24/7 taskability and near-real time capability. By optimizing an instrument to perform position measurement rather than...sensors. The J-MAPS baseline also includes a novel filter-grating wheel, of interest in the area of non- resolved object characterization. We discuss the

Seasonal changes in the tropospheric carbon monoxide profile over the remote Southern Hemisphere evaluated using multi-model simulations and aircraft observations

NASA Astrophysics Data System (ADS)

Fisher, J. A.; Wilson, S. R.; Zeng, G.; Williams, J. E.; Emmons, L. K.; Langenfelds, R. L.; Krummel, P. B.; Steele, L. P.

2014-11-01

We use aircraft observations from the 1991-2000 Cape Grim Overflight Program and the 2009-2011 HIAPER Pole-to-Pole Observations (HIPPO), together with output from four chemical transport and chemistry-climate models, to better understand the vertical distribution of carbon monoxide (CO) in the remote Southern Hemisphere. Observed CO vertical gradients at Cape Grim vary from 1.6 ppbv km-1 in austral autumn to 2.2 ppbv km-1 in austral spring. CO vertical profiles from Cape Grim are remarkably consistent with those observed over the southern mid-latitudes Pacific during HIPPO, despite major differences in time periods, flight locations, and sampling strategies between the two datasets. Using multi-model simulations from the Southern Hemisphere Model Intercomparison Project (SHMIP), we find that observed CO vertical gradients in austral winter-spring are well-represented in models and can be attributed to primary CO emissions from biomass burning. In austral summer-autumn, inter-model variability in simulated gradients is much larger, and two of the four SHMIP models significantly underestimate the Cape Grim observations. Sensitivity simulations show that CO vertical gradients at this time of year are driven by long-range transport of secondary CO of biogenic origin, implying a large sensitivity of the remote Southern Hemisphere troposphere to biogenic emissions and chemistry. Inter-model variability in summer-autumn gradients can be explained by differences in both the chemical mechanisms that drive secondary production of CO from biogenic sources and the vertical transport that redistributes this CO throughout the Southern Hemisphere. This suggests that the CO vertical gradient in the remote Southern Hemisphere provides a sensitive test of the chemistry and transport processes that define the chemical state of the background atmosphere.

Arago Seamount: The missing hotspot found in the Austral Islands

NASA Astrophysics Data System (ADS)

Bonneville, Alain; Le Suavé, Raymond; Audin, Laurence; Clouard, Valérie; Dosso, Laure; Yves Gillot, Pierre; Janney, Philip; Jordahl, Kelsey; Maamaatuaiahutapu, Keitapu

2002-11-01

The Austral archipelago, on the western side of the South Pacific superswell, is composed of several volcanic chains, corresponding to distinct events from 35 Ma to the present, and lies on oceanic crust created between 60 and 85 Ma. In 1982, Turner and Jarrard proposed that the two distinct volcanic stages found on Rurutu Island and dated as 12 Ma and 1 Ma could be due to two different hotspots, but no evidence of any recent aerial or submarine volcanic source has ever been found. In July 1999, expedition ZEPOLYF2 aboard the R/V L'Atalante conducted a geophysical survey of the northern part of the Austral volcanic archipelago. Thirty seamounts were mapped for the first time, including a very shallow one (<27 m below sea level), located at lat 23°26.4‧S, long 150°43.8‧W, ˜120 km southeast of Rurutu. A nepheline-rich scoriaceous basalt sample from pillow lavas dredged on the newly mapped seamount's western flank gave a K-Ar age of 230 ± 0.004 ka obtained on pure selected nepheline. We propose that this seamount, already called Arago Seamount after a French Navy ship that discovered its summit in 1993, is the missing hotspot in the Cook-Austral history. This interpretation adds a new hotspot to the already complicated geologic history of this region. We suggest that several hotspots have been active simultaneously on a region of the seafloor that does not exceed 2000 km in diameter and that each of them had a short lifetime (<20 m.y.). These short-lived and closely spaced hotspots cannot be the result of discrete deep-mantle plumes and are likely due to more local upwelling in the upper mantle strongly influenced by weaknesses in the lithosphere.

LISA Long-Arm Interferometry

NASA Technical Reports Server (NTRS)

Thorpe, James I.

2009-01-01

An overview of LISA Long-Arm Interferometry is presented. The contents include: 1) LISA Interferometry; 2) Constellation Design; 3) Telescope Design; 4) Constellation Acquisition; 5) Mechanisms; 6) Optical Bench Design; 7) Phase Measurement Subsystem; 8) Phasemeter Demonstration; 9) Time Delay Interferometry; 10) TDI Limitations; 11) Active Frequency Stabilization; 12) Spacecraft Level Stabilization; 13) Arm-Locking; and 14) Embarassment of Riches.

Space Interferometry Science Working Group

NASA Astrophysics Data System (ADS)

Ridgway, Stephen T.

1992-12-01

Decisions taken by the astronomy and astrophysics survey committee and the interferometry panel which lead to the formation of the Space Interferometry Science Working Group (SISWG) are outlined. The SISWG was formed by the NASA astrophysics division to provide scientific and technical input from the community in planning for space interferometry and in support of an Astrometric Interferometry Mission (AIM). The AIM program hopes to measure the positions of astronomical objects with a precision of a few millionths of an arcsecond. The SISWG science and technical teams are described and the outcomes of its first meeting are given.

Robust interferometry against imperfections based on weak value amplification

NASA Astrophysics Data System (ADS)

Fang, Chen; Huang, Jing-Zheng; Zeng, Guihua

2018-06-01

Optical interferometry has been widely used in various high-precision applications. Usually, the minimum precision of an interferometry is limited by various technical noises in practice. To suppress such kinds of noises, we propose a scheme which combines the weak measurement with the standard interferometry. The proposed scheme dramatically outperforms the standard interferometry in the signal-to-noise ratio and the robustness against noises caused by the optical elements' reflections and the offset fluctuation between two paths. A proof-of-principle experiment is demonstrated to validate the amplification theory.

VizieR Online Data Catalog: Pulsation model data for delta Cep and eta Aql (Merand+, 2015)

NASA Astrophysics Data System (ADS)

Merand, A.; Kervella, P.; Breitfelder, J.; Gallenne, A.; Coude du Foresto, V.; ten Brummelaar, T. A.; McAlister, H. A.; Ridgway, S.; Sturmann, L.; Sturmann, J.; Turner, N. H.

2015-09-01

FITS files containing the stars' (delta Cep and eta Aql) data and model presented in the paper. Each fits file has 3 HDU: 1- primary HDU: contains no data apart from the header. The header has the parameters of the model (keywords 'HIERARCH PARAM') as well as some other quantities derived from the modeling (keywords 'HIERARCH MODEL'). These quantities are aimed at people who would like to reproduce or compare their results with us. 2- 'DATA' HDU: this contains the data used for the fit. Each line is a scalar measurement described as follow: col1='MJD' (E) modified Julian date of the observations col2='OBS' (A50) description of the data point: the string before ";" defines the type, after ";" is the source. after | are anciliary data: for diam, UDdiam: [wavelengthum, interfbaseline_m] for mag: photometric band for color: photometric band1 - photometric band2 col3='MEAS' (E) the actual measurements. units are km/s for Vpuls or Vrad (which includes the p-factor correction), and mas (milli-arcseconds) for diameters (diam of UDdiam). col4='ERR' (E) the uncertainty on the measurement. col5='MODEL' (E) corresponding value predicted by the model col6='PHASE' (E) pulsation phase computed from the model ranges from 0 to 1. col7='PERIOD' (E) pulsation period computed from the model in days 3- 'MODEL' HDU: a tabulation of the pulsation model, as a function of pulsation phase. col1='PHASE' (E) phase from 0 to 1. col2='Vpuls' (E) pulsation velocity, in km/s. col3='Vrad' (E) radial velocity, in km/s. It is Vpuls/p-factor + Vgamma. col4='diam' (E) Rosseland angular diameter, in milliarcseconds (mas). col5='Teff' (E) effective temperature, in Kelvin. col6='Lum' (E) Luminosity in solar luminosities. col7='logg' (E) surface gravity, in log_10(cm/s2). col8,9,10='diamK xxxm' (E) biased angular diameters measured by an interferometer at baselines xxx (in m), for xxx=[100, 200, 300]. In milliarcseconds col>=11= 'MAG ...' or 'COLOR ...' (E) reddenned magnitudes or colors in various bands, depending on the data entry. '...' is the name of band for magnitudes, and pair of bands for colors. (6 data files).

The influence of sea ice, wind speed and marine mammals on Southern Ocean ambient sound.

PubMed

Menze, Sebastian; Zitterbart, Daniel P; van Opzeeland, Ilse; Boebel, Olaf

2017-01-01

This paper describes the natural variability of ambient sound in the Southern Ocean, an acoustically pristine marine mammal habitat. Over a 3-year period, two autonomous recorders were moored along the Greenwich meridian to collect underwater passive acoustic data. Ambient sound levels were strongly affected by the annual variation of the sea-ice cover, which decouples local wind speed and sound levels during austral winter. With increasing sea-ice concentration, area and thickness, sound levels decreased while the contribution of distant sources increased. Marine mammal sounds formed a substantial part of the overall acoustic environment, comprising calls produced by Antarctic blue whales ( Balaenoptera musculus intermedia ), fin whales ( Balaenoptera physalus ), Antarctic minke whales ( Balaenoptera bonaerensis ) and leopard seals ( Hydrurga leptonyx ). The combined sound energy of a group or population vocalizing during extended periods contributed species-specific peaks to the ambient sound spectra. The temporal and spatial variation in the contribution of marine mammals to ambient sound suggests annual patterns in migration and behaviour. The Antarctic blue and fin whale contributions were loudest in austral autumn, whereas the Antarctic minke whale contribution was loudest during austral winter and repeatedly showed a diel pattern that coincided with the diel vertical migration of zooplankton.

The influence of sea ice, wind speed and marine mammals on Southern Ocean ambient sound

NASA Astrophysics Data System (ADS)

Menze, Sebastian; Zitterbart, Daniel P.; van Opzeeland, Ilse; Boebel, Olaf

2017-01-01

This paper describes the natural variability of ambient sound in the Southern Ocean, an acoustically pristine marine mammal habitat. Over a 3-year period, two autonomous recorders were moored along the Greenwich meridian to collect underwater passive acoustic data. Ambient sound levels were strongly affected by the annual variation of the sea-ice cover, which decouples local wind speed and sound levels during austral winter. With increasing sea-ice concentration, area and thickness, sound levels decreased while the contribution of distant sources increased. Marine mammal sounds formed a substantial part of the overall acoustic environment, comprising calls produced by Antarctic blue whales (Balaenoptera musculus intermedia), fin whales (Balaenoptera physalus), Antarctic minke whales (Balaenoptera bonaerensis) and leopard seals (Hydrurga leptonyx). The combined sound energy of a group or population vocalizing during extended periods contributed species-specific peaks to the ambient sound spectra. The temporal and spatial variation in the contribution of marine mammals to ambient sound suggests annual patterns in migration and behaviour. The Antarctic blue and fin whale contributions were loudest in austral autumn, whereas the Antarctic minke whale contribution was loudest during austral winter and repeatedly showed a diel pattern that coincided with the diel vertical migration of zooplankton.

The Joint Milli-Arcsecond Pathfinder Survey (JMAPS): Mission Overview and Attitude Sensing Applications

DTIC Science & Technology

2009-01-01

employs a set of reference targets such as asteroids that are relatively numer- ous, more or less uniformly distributed around the Sun, and relatively...point source-like. Just such a population exists—90 km-class asteroids . There are about 100 of these objects with relatively well-know orbits...These are main belt objects that are approximately evenly distributed around the sun. They are large enough to be quasi-spherical in nature, and as a

TDRS orbit determination by radio interferometry

NASA Technical Reports Server (NTRS)

Pavloff, Michael S.

1994-01-01

In support of a NASA study on the application of radio interferometry to satellite orbit determination, MITRE developed a simulation tool for assessing interferometry tracking accuracy. The Orbit Determination Accuracy Estimator (ODAE) models the general batch maximum likelihood orbit determination algorithms of the Goddard Trajectory Determination System (GTDS) with the group and phase delay measurements from radio interferometry. ODAE models the statistical properties of tracking error sources, including inherent observable imprecision, atmospheric delays, clock offsets, station location uncertainty, and measurement biases, and through Monte Carlo simulation, ODAE calculates the statistical properties of errors in the predicted satellites state vector. This paper presents results from ODAE application to orbit determination of the Tracking and Data Relay Satellite (TDRS) by radio interferometry. Conclusions about optimal ground station locations for interferometric tracking of TDRS are presented, along with a discussion of operational advantages of radio interferometry.

Application of Hybrid Along-Track Interferometry/Displaced Phase Center Antenna Method for Moving Human Target Detection in Forest Environments

DTIC Science & Technology

2016-10-01

ARL-TR-7846 ● OCT 2016 US Army Research Laboratory Application of Hybrid Along-Track Interferometry/ Displaced Phase Center...Research Laboratory Application of Hybrid Along-Track Interferometry/ Displaced Phase Center Antenna Method for Moving Human Target Detection...TYPE Technical Report 3. DATES COVERED (From - To) 2015–2016 4. TITLE AND SUBTITLE Application of Hybrid Along-Track Interferometry/ Displaced

Optical Interferometry Motivation and History

NASA Technical Reports Server (NTRS)

Lawson, Peter

2006-01-01

A history and motivation of stellar interferometry is presented. The topics include: 1) On Tides, Organ Pipes, and Soap Bubbles; 2) Armand Hippolyte Fizeau (1819-1896); 3) Fizeau Suggests Stellar Interferometry 1867; 4) Edouard Stephan (1837-1923); 5) Foucault Refractor; 6) Albert A. Michelson (1852-1931); 7) On the Application of Interference Methods to Astronomy (1890); 8) Moons of Jupiter (1891); 9) Other Applications in 19th Century; 10) Timeline of Interferometry to 1938; 11) 30 years goes by; 12) Mount Wilson Observatory; 13) Michelson's 20 ft Interferometer; 14) Was Michelson Influenced by Fizeau? 15) Work Continues in the 1920s and 30s; 16) 50 ft Interferometer (1931-1938); 17) Light Paths in the 50 ft Interferometer; 18) Ground-level at the 50 ft; 19) F.G. Pease (1881-1938); 20) Timeline of Optical Interferometry to 1970; 21) A New Type of Stellar Interferometer (1956); 22) Intensity Interferometer (1963- 1976; 23) Robert Hanbury Brown; 24) Interest in Optical Interferometry in the 1960s; 25) Interferometry in the Early 1970s; and 26) A New Frontier is Opened up in 1974.

Feasibility of satellite interferometry for surveillance, navigation, and traffic control

NASA Technical Reports Server (NTRS)

Gopalapillai, S.; Ruck, G. T.; Mourad, A. G.

1976-01-01

The feasibility of using a satellite borne interferometry system for surveillance, navigation, and traffic control applications was investigated. The evaluation was comprised of: (1) a two part systems analysis (software and hardware); (2) a survey of competitive navigation systems (both experimental and planned); (3) a comparison of their characteristics and capabilities with those of an interferometry system; and (4) a limited survey of potential users to determine the variety of possible applications for the interferometry system and the requirements which it would have to meet. Five candidate or "strawman" interferometry systems for various applications with various capabilities were configured (on a preliminary basis) and were evaluated. It is concluded that interferometry in conjunction with a geostationary satellite has an inherent ability to provide both a means for navigation/position location and communication. It offers a very high potential for meeting a large number of user applications and requirements for navigation and related functions.

Spectroastrometric Study of Ro-vibrational CO Emission from the Herbig Ae Star HD 179218 with ISHELL on the NASA Infrared Telescope Facility

NASA Astrophysics Data System (ADS)

Brittain, Sean D.; Carr, John S.; Najita, Joan R.

2018-07-01

We present analysis of commissioning M-band data acquired with the infrared echelle spectrograph (iSHELL) on NASA’s Infrared Telescope Facility. In this paper we describe the delivered performance of the instrument for these M-band observations and the data reduction process. The feasibility of using iSHELL for spectro-astrometry is tested on the Herbig Ae/Be star HD 179218 and we show that sub-milliarcsecond fidelity is achievable..

Development of a very small telescope for a milli-arcsec space astrometry

NASA Astrophysics Data System (ADS)

Suganuma, M.; Kobayashi, Y.; Gouda, N.; Yano, T.; Yamada, Y.; Takato, N.; Yamauchi, M.

2008-07-01

We are preparing a reflecting telescope for Nano-JASMINE, a very small satellite for global space astrometry of milli-arcsecond accuracy. The telescope has a 5-cm diameter primary mirror and a beam-combiner in front of it. It occupies only about 12x12x17cm and is entirely made out of aluminum alloy. The telescope and its surrounding structures are carefully designed for thermal stability of the optics, especially to control changes in the relative angle of the beam-combiner.

The Fast Rotating Star 51 Oph Probed by VEGA/CHARA

NASA Astrophysics Data System (ADS)

Jamialahmadi, N.; Berio, P.; Meilland, A.; Perraut, K.; Mourard, D.; Lopez, B.; Stee, P.; Nardetto, N.; Pichon, B.; Clausse, J. M.; Spang, A.; McAlister, H.; ten Brummelaar, T.

2015-12-01

Stellar rotation is a key in our understanding of both mass-loss and evolution of intermediate and massive stars. It can lead to anisotropic mass-loss in the form of radiative wind or an excretion disk. We used the VEGA visible beam combiner installed on the CHARA array that reaches a sub milliarcsecond resolution. We derived, for the first time, the extension and flattening of 51 Oph photosphere. We found an elongated ratio of 1.45 ± 0.12.

22 GHz VLBI Survey: Status Report and Preliminary Results

NASA Technical Reports Server (NTRS)

Moellenbrock, G.; Fujisawa, K.; Preston, R.; Gurvits, L.; Dewey, R.; Hirabayashi, H.; Inoue, M.; Jauncey, D.; Migenes, V.; Roberts, D.;

Joint Milli-Arcsecond Pathfinder Survey (JMAPS): Overview and Application to NWO Mission

DTIC Science & Technology

2009-03-11

degrade
 at
a
much
reduced
rate
over
 time 
when
compared
with
the
Hipparcos
catalog.
 JMAPS
will
accomplish
this
with
a
relatively
modest
aperture...collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources...JMAPS
instrument
is
operated
in
a
fashion
similar
to
standard
star
trackers.

A
 star
field
is
imaged—in
the
case
of
JMAPS,
integration
 times 
of
1

Comparing Laser Interferometry and Atom Interferometry Approaches to Space-Based Gravitational-Wave Measurement

NASA Technical Reports Server (NTRS)

Baker, John; Thorpe, Ira

2012-01-01

Thoroughly studied classic space-based gravitational-wave missions concepts such as the Laser Interferometer Space Antenna (LISA) are based on laser-interferometry techniques. Ongoing developments in atom-interferometry techniques have spurred recently proposed alternative mission concepts. These different approaches can be understood on a common footing. We present an comparative analysis of how each type of instrument responds to some of the noise sources which may limiting gravitational-wave mission concepts. Sensitivity to laser frequency instability is essentially the same for either approach. Spacecraft acceleration reference stability sensitivities are different, allowing smaller spacecraft separations in the atom interferometry approach, but acceleration noise requirements are nonetheless similar. Each approach has distinct additional measurement noise issues.

L'aléa tsunami en Polynésie française : apports de la simulation numérique

NASA Astrophysics Data System (ADS)

Sladen, Anthony; Hébert, Hélène; Schindelé, François; Reymond, Dominique

2007-04-01

French Polynesia is frequently struck by transoceanic tsunamis originating from around the Pacific. The numerical modelling of five scenarios defined among threatening source areas has been performed on seven Polynesian sites. The results show that the Marquesian bays are consistently most affected, while the sites in Tahiti and Rurutu are significantly exposed, though less heavily. The tsunami hazard has been then mapped for whole Polynesia. Major tsunamis are expected to hit Marquesas, and Rurutu (Australes), but less frequently. An elevated hazard level is defined for the other Australes and for several Society Islands (especially Tahiti). Tuamotu atolls and other Society Islands are only moderately exposed.

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.

Holographic analysis as an inspection method for welded thin-wall tubing

NASA Technical Reports Server (NTRS)

Brooks, Lawrence; Mulholland, John; Genin, Joseph; Matthews, Larryl

1990-01-01

The feasibility of using holographic interferometry for locating flaws in welded tubing is explored. Two holographic techniques are considered: traditional holographic interferometry and electronic speckle pattern interferometry. Several flaws including cold laps, discontinuities, and tube misalignments are detected.

Phase-Shift Interferometry with a Digital Photocamera

ERIC Educational Resources Information Center

Vannoni, Maurizio; Trivi, Marcelo; Molesini, Giuseppe

2007-01-01

A phase-shift interferometry experiment is proposed, working on a Twyman-Green optical configuration with additional polarization components. A guideline is provided to modern phase-shift interferometry, using concepts and laboratory equipment at the level of undergraduate optics courses. (Contains 5 figures.)

The influence of sea ice, wind speed and marine mammals on Southern Ocean ambient sound

PubMed Central

van Opzeeland, Ilse; Boebel, Olaf

2017-01-01

This paper describes the natural variability of ambient sound in the Southern Ocean, an acoustically pristine marine mammal habitat. Over a 3-year period, two autonomous recorders were moored along the Greenwich meridian to collect underwater passive acoustic data. Ambient sound levels were strongly affected by the annual variation of the sea-ice cover, which decouples local wind speed and sound levels during austral winter. With increasing sea-ice concentration, area and thickness, sound levels decreased while the contribution of distant sources increased. Marine mammal sounds formed a substantial part of the overall acoustic environment, comprising calls produced by Antarctic blue whales (Balaenoptera musculus intermedia), fin whales (Balaenoptera physalus), Antarctic minke whales (Balaenoptera bonaerensis) and leopard seals (Hydrurga leptonyx). The combined sound energy of a group or population vocalizing during extended periods contributed species-specific peaks to the ambient sound spectra. The temporal and spatial variation in the contribution of marine mammals to ambient sound suggests annual patterns in migration and behaviour. The Antarctic blue and fin whale contributions were loudest in austral autumn, whereas the Antarctic minke whale contribution was loudest during austral winter and repeatedly showed a diel pattern that coincided with the diel vertical migration of zooplankton. PMID:28280544

Sleep and Mood During A Winter in Antarctica

NASA Technical Reports Server (NTRS)

Palinkas, Lawrence A.; Houseal, Matt; Miller, Christopher

2000-01-01

Seasonal variations in sleep characteristics and their association with changes in mood were examined in 91 American men and women also who spent the 1991 austral winter at three different research stations in Antarctica. Measures of total hours of sleep over a 24-hr period, duration of longest (i.e.,"nighttime") sleep event, number of sleep events, time of sleep onset, and quality of sleep remained unchanged over the course of the austral winter (March through October). However, exposure to total darkness based on station latitude was significantly associated with total hours of sleep, duration of are longest sleep event, time of sleep onset, and quality of sleep. Reported vigor the previous month was a significant independent predictor of changes in all five sleep measures; previous month's measures of all six POMS subscales were significant independent predictors of sleep quality. Sleep characteristics were significant independent predictors of vigor and confusion the following month; total sleep, longest sleep event, sleep onset and sleep quality were significant independent predictors of tension-anxiety and depression. Changes in mood during the austral winter are preceded by changes in sleep characteristics, but prolonged exposure to the photoperiodicity characteristic of the high latitudes appears to be associated with improved sleep. In turn, mood changes appear to affect certain sleep characteristics, especially sleep quality.

Aerosol Transport Over Equatorial Africa

NASA Technical Reports Server (NTRS)

Gatebe, C. K.; Tyson, P. D.; Annegarn, H. J.; Kinyua, A. M.; Piketh, S.; King, M.; Helas, G.

1999-01-01

Long-range and inter-hemispheric transport of atmospheric aerosols over equatorial Africa has received little attention so far. Most aerosol studies in the region have focussed on emissions from rain forest and savanna (both natural and biomass burning) and were carried out in the framework of programs such as DECAFE (Dynamique et Chimie Atmospherique en Foret Equatoriale) and FOS (Fires of Savanna). Considering the importance of this topic, aerosols samples were measured in different seasons at 4420 meters on Mt Kenya and on the equator. The study is based on continuous aerosol sampling on a two stage (fine and coarse) streaker sampler and elemental analysis by Particle Induced X-ray Emission. Continuous samples were collected for two seasons coinciding with late austral winter and early austral spring of 1997 and austral summer of 1998. Source area identification is by trajectory analysis and sources types by statistical techniques. Major meridional transports of material are observed with fine-fraction silicon (31 to 68 %) in aeolian dust and anthropogenic sulfur (9 to 18 %) being the major constituents of the total aerosol loading for the two seasons. Marine aerosol chlorine (4 to 6 %), potassium (3 to 5 %) and iron (1 to 2 %) make up the important components of the total material transport over Kenya. Minimum sulfur fluxes are associated with recirculation of sulfur-free air over equatorial Africa, while maximum sulfur concentrations are observed following passage over the industrial heartland of South Africa or transport over the Zambian/Congo Copperbelt. Chlorine is advected from the ocean and is accompanied by aeolian dust recirculating back to land from mid-oceanic regions. Biomass burning products are transported from the horn of Africa. Mineral dust from the Sahara is transported towards the Far East and then transported back within equatorial easterlies to Mt Kenya. This was observed during austral summer and coincided with the dying phase of 1997/98 El Nino.

Thermochronological constraints on the Cambrian to recent geological evolution of the Argentina passive continental margin

NASA Astrophysics Data System (ADS)

Kollenz, Sebastian; Glasmacher, Ulrich A.; Rossello, Eduardo A.; Stockli, Daniel F.; Schad, Sabrina; Pereyra, Ricardo E.

2017-10-01

Passive continental margins are geo-archives that store information from the interplay of endogenous and exogenous forces related to continental rifting, post-breakup history, and climate changes. The recent South Atlantic passive continental margins (SAPCMs) in Brazil, Namibia, and South Africa are partly high-elevated margins ( 2000 m a.s.l.), and the recent N-S-trending SAPCM in Argentina and Uruguay is of low elevation. In Argentina, an exception in elevation is arising from the higher topography (> 1000 m a.s.l.) of the two NW-SE-trending mountain ranges Sierras Septentrionales and Sierras Australes. Precambrian metamorphic and intrusive rocks, and siliciclastic rocks of Ordovician to Permian age represent the geological evolution of both areas. The Sierras Australes have been deformed and metamorphosed (incipient - greenschist) during the Gondwanides Orogeny. The low-temperature thermochronological (LTT) data (< 240 °C) indicated that the Upper Jurassic to Lower Cretaceous opening of the South Atlantic has not completely thermally reset the surface rocks. The LTT archives apatite and zircon still revealed information on the pre- to post-orogenic history of the Gondwanides and the Mesozoic and Cenozoic South Atlantic geological evolution. Upper Carboniferous zircon (U-Th/He)-ages (ZHe) indicate the earliest cooling below 180 °C/1 Ma. Most of the ZHe-ages are of Upper Triassic to Jurassic age. The apatite fission-track ages (AFT) of Sierras Septentrionales and the eastern part of Sierras Australes indicate the South Atlantic rifting and, thereafter. AFT-ages of Middle to Upper Triassic on the western side of the Sierras Australes are in contrast, indicating a Triassic exhumation caused by the eastward thrusting along the Sauce Grande wrench. The corresponding t-T models report a complex subsidence and exhumation history with variable rates since the Ordovician. Based on the LTT-data and the numerical modelling we assume that the NW-SE-trending mountain ranges received their geographic NW-SE orientation during the syn- to post-orogenic history of the Gondwanides.

SAIP2014, the 59th Annual Conference of the South African Institute of Physics

NASA Astrophysics Data System (ADS)

Engelbrecht, Chris; Karataglidis, Steven

2015-04-01

The International Celestial Reference Frame (ICRF) was adopted by the International Astronomical Union (IAU) in 1997. The current standard, the ICRF-2, is based on Very Long Baseline Interferometric (VLBI) radio observations of positions of 3414 extragalactic radio reference sources. The angular resolution achieved by the VLBI technique is on a scale of milliarcsecond to sub-milliarcseconds and defines the ICRF with the highest accuracy available at present. An ideal reference source used for celestial reference frame work should be unresolved or point-like on these scales. However, extragalactic radio sources, such as those that definevand maintain the ICRF, can exhibit spatially extended structures on sub-milliarsecond scalesvthat may vary both in time and frequency. This variability can introduce a significant error in the VLBI measurements thereby degrading the accuracy of the estimated source position. Reference source density in the Southern celestial hemisphere is also poor compared to the Northern hemisphere, mainly due to the limited number of radio telescopes in the south. In order to dene the ICRF with the highest accuracy, observational efforts are required to find more compact sources and to monitor their structural evolution. In this paper we show that the astrometric VLBI sessions can be used to obtain source structure information and we present preliminary imaging results for the source J1427-4206 at 2.3 and 8.4 GHz frequencies which shows that the source is compact and suitable as a reference source.

Digital Holographic Interferometry for Airborne Particle Characterization

DTIC Science & Technology

2015-03-19

Interferometry and polarimetry for aerosol particle characterization, Bioaerosols: Characterization and Environmental Impact, Austin, TX (2014) [organizer...and conference chair]. 6. Invited talk: Holographic Interferometry and polarimetry for aerosol particle characterization, Optical...Stokes parameters, NATO Advanced Science Institute on Special Detection Technique ( Polarimetry ) and Remote Sensing, Kyiv, Ukraine (2010). (c

Accessing High Spatial Resolution in Astronomy Using Interference Methods

ERIC Educational Resources Information Center

Carbonel, Cyril; Grasset, Sébastien; Maysonnave, Jean

2018-01-01

In astronomy, methods such as direct imaging or interferometry-based techniques (Michelson stellar interferometry for example) are used for observations. A particular advantage of interferometry is that it permits greater spatial resolution compared to direct imaging with a single telescope, which is limited by diffraction owing to the aperture of…

Intellectual property in holographic interferometry

NASA Astrophysics Data System (ADS)

Reingand, Nadya; Hunt, David

2006-08-01

This paper presents an overview of patents and patent applications on holographic interferometry, and highlights the possibilities offered by patent searching and analysis. Thousands of patent documents relevant to holographic interferometry were uncovered by the study. The search was performed in the following databases: U.S. Patent Office, European Patent Office, Japanese Patent Office and Korean Patent Office for the time frame from 1971 through May 2006. The patent analysis unveils trends in patent temporal distribution, patent families formation, significant technological coverage within the market of system that employ holographic interferometry and other interesting insights.

Determination of thin hydrodynamic lubricating film thickness using dichromatic interferometry.

PubMed

Guo, L; Wong, P L; Guo, F; Liu, H C

2014-09-10

This paper introduces the application of dichromatic interferometry for the study of hydrodynamic lubrication. In conventional methods, two beams with different colors are projected consecutively on a static object. By contrast, the current method deals with hydrodynamic lubricated contacts under running conditions and two lasers with different colors are projected simultaneously to form interference images. Dichromatic interferometry incorporates the advantages of monochromatic and chromatic interferometry, which are widely used in lubrication research. This new approach was evaluated statically and dynamically by measuring the inclination of static wedge films and the thickness of the hydrodynamic lubricating film under running conditions, respectively. Results show that dichromatic interferometry can facilitate real-time determination of lubricating film thickness and is well suited for the study of transient or dynamic lubricating problems.

The Path to Interferometry in Space

NASA Technical Reports Server (NTRS)

Rinehart, S. A.; Savini, G.; Holland, W.; Absil, O.; Defrere, D.; Spencer, L.; Leisawitz, D.; Rizzo, M.; Juanola-Parramon, R.; Mozurkewich, D.

2016-01-01

For over two decades, astronomers have considered the possibilities for interferometry in space. The first of these missions was the Space Interferometry Mission (SIM), but that was followed by missions for studying exoplanets (e.g Terrestrial Planet Finder, Darwin), and then far-infrared interferometers (e.g. the Space Infrared Interferometric Telescope, the Far-Infrared Interferometer). Unfortunately, following the cancellation of SIM, the future for space-based interferometry has been in doubt, and the interferometric community needs to reevaluate the path forward. While interferometers have strong potential for scientific discovery, there are technological developments still needed, and continued maturation of techniques is important for advocacy to the broader astronomical community. We review the status of several concepts for space-based interferometry, and look for possible synergies between missions oriented towards different science goals.

Mode-resolved frequency comb interferometry for high-accuracy long distance measurement

PubMed Central

van den Berg, Steven. A.; van Eldik, Sjoerd; Bhattacharya, Nandini

2015-01-01

Optical frequency combs have developed into powerful tools for distance metrology. In this paper we demonstrate absolute long distance measurement using a single femtosecond frequency comb laser as a multi-wavelength source. By applying a high-resolution spectrometer based on a virtually imaged phased array, the frequency comb modes are resolved spectrally to the level of an individual mode. Having the frequency comb stabilized against an atomic clock, thousands of accurately known wavelengths are available for interferometry. From the spectrally resolved output of a Michelson interferometer a distance is derived. The presented measurement method combines spectral interferometry, white light interferometry and multi-wavelength interferometry in a single scheme. Comparison with a fringe counting laser interferometer shows an agreement within <10−8 for a distance of 50 m. PMID:26419282

Sentinel-1 TOPS interferometry for along-track displacement measurement

NASA Astrophysics Data System (ADS)

Jiang, H. J.; Pei, Y. Y.; Li, J.

2017-02-01

The European Space Agency’s Sentinel-1 mission, a constellation of two C-band synthetic aperture radar (SAR) satellites, utilizes terrain observation by progressive scan (TOPS) antenna beam steering as its default operation mode to achieve wide-swath coverage and short revisit time. The beam steering during the TOPS acquisition provides a means to measure azimuth motion by using the phase difference between forward and backward looking interferograms within regions of burst overlap. Hence, there are two spectral diversity techniques for along-track displacement measurement, including multi-aperture interferometry (MAI) and “burst overlap interferometry”. This paper analyses the measurement accuracies of MAI and burst overlap interferometry. Due to large spectral separation in the overlap region, burst overlap interferometry is a more sensitive measurement. We present a TOPS interferometry approach for along-track displacement measurement. The phase bias caused by azimuth miscoregistration is first estimated by burst overlap interferometry over stationary regions. After correcting the coregistration error, the MAI phase and the interferometric phase difference between burst overlaps are recalculated to obtain along-track displacements. We test the approach with Sentinel-1 TOPS interferometric data over the 2015 Mw 7.8 Nepal earthquake fault. The results prove the feasibility of our approach and show the potential of joint estimation of along-track displacement with burst overlap interferometry and MAI.

Occurrence of Magellanic penguins along the Northeast Brazilian coast during 2008 Austral winter.

PubMed

da Silva, Renato Ramos; Pereira, Janini; Tanajura, Clemente A S; Lentini, Carlos A D; Cirano, Mauro; Boersma, P Dee; Rodrigues, Regina R

2012-01-01

During the austral winter of 2008, thousands of penguins traveled to low latitudes along the South Atlantic coast of South America. The atmospheric and oceanic conditions from April to July 2008 may account for the penguins' unusual geographic distribution. During that period, South Atlantic coastal waters were cooler; the wind anomalies had northward and onshore components; the ocean's coastal region presented northward currents that favored the penguins to travel toward lower latitudes. This anomalous climate regime resulted from extreme meteorological frontal systems that occurred mainly during June 2008. Three consecutive extreme midlatitude cyclones produced strong wind shear that resulted in the northward oceanic flow along the South American eastern shoreline favoring the penguins to be spotted in northern tropical waters.

The austral peregrine falcon: Color variation, productivity, and pesticides

USGS Publications Warehouse

Ellis, D.H.

1985-01-01

The austral peregrine falcon (Falco peregrinus cassini) was studied in the Andean foot- hills and across the Patagonian steppe from November to December 1981. The birds under study (18 pairs) were reproducing at or near normal (pre-DDT) levels for other races. Pesticide residues, while elevated, were well below the values associated with reproductive failure in other populations. With one exception, eggshells were not abnormally thin. The peregrine falcon in Patagonia exhibits extreme color variation. Pallid birds are nearly pure white below (light cream as juveniles), whereas normally pigmented birds are black-crowned and conspicuously barred with black ventrally. Rare individuals of the Normal Phase display black heads, broad black ventral barring, and warm reddish-brown ventral background coloration.

Magnetostriction Measured by Holographic Interferometry with the Simple and Inexpensive "Arrowhead" Setup

ERIC Educational Resources Information Center

Ladera, Celso L.; Donoso, Guillermo; Contreras, Johnny H.

2012-01-01

Double-exposure holographic interferometry is applied to measure the "linear" or "longitudinal" magnetostriction constant of a soft-ferrite rod. This high-accuracy measurement is done indirectly, by measuring the small rotations of a lever in contact with the rod using double-exposure holographic interferometry implemented with a robust…

Development and applications of optical interferometric micrometrology in the Angstrom and subangstrom range

NASA Technical Reports Server (NTRS)

Lauer, James L.; Abel, Phillip B.

1988-01-01

The characteristics of the scanning tunneling microscope and atomic force microscope (AFM) are briefly reviewed, and optical methods, mainly interferometry, of sufficient resolution to measure AFM deflections are discussed. The methods include optical resonators, laser interferometry, multiple-beam interferometry, and evanescent wave detection. Experimental results using AFM are reviewed.

Spatial interferometry in optical astronomy

NASA Technical Reports Server (NTRS)

Gezari, Daniel Y.; Roddier, Francois; Roddier, Claude

1990-01-01

A bibliographic guide is presented to publications of spatial interferometry techniques applied to optical astronomy. Listings appear in alphabetical order, by first author, as well as in specific subject categories listed in chronological order, including imaging theory and speckle interferometry, experimental techniques, and observational results of astronomical studies of stars, the Sun, and the solar system.

Differential interferometry for measurement of density fluctuations and fluctuation-induced transport (invited)

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

Lin, L.; Ding, W. X.; Brower, D. L.

2010-10-15

Differential interferometry employs two parallel laser beams with a small spatial offset (less than beam width) and frequency difference (1-2 MHz) using common optics and a single mixer for a heterodyne detection. The differential approach allows measurement of the electron density gradient, its fluctuations, as well as the equilibrium density distribution. This novel interferometry technique is immune to fringe skip errors and is particularly useful in harsh plasma environments. Accurate calibration of the beam spatial offset, accomplished by use of a rotating dielectric wedge, is required to enable broad application of this approach. Differential interferometry has been successfully used onmore » the Madison Symmetric Torus reversed-field pinch plasma to directly measure fluctuation-induced transport along with equilibrium density profile evolution during pellet injection. In addition, by combining differential and conventional interferometry, both linear and nonlinear terms of the electron density fluctuation energy equation can be determined, thereby allowing quantitative investigation of the origin of the density fluctuations. The concept, calibration, and application of differential interferometry are presented.« less

The Wide-Field Imaging Interferometry Testbed: Recent Progress

NASA Technical Reports Server (NTRS)

Rinehart, Stephen A.

2010-01-01

The Wide-Field Imaging Interferometry Testbed (WIIT) at NASA's Goddard Space Flight Center was designed to demonstrate the practicality and application of techniques for wide-field spatial-spectral ("double Fourier") interferometry. WIIT is an automated system, and it is now producing substantial amounts of high-quality data from its state-of-the-art operating environment, Goddard's Advanced Interferometry and Metrology Lab. In this paper, we discuss the characterization and operation of the testbed and present the most recent results. We also outline future research directions. A companion paper within this conference discusses the development of new wide-field double Fourier data analysis algorithms.

The mechanical design of CHARIS: an exoplanet IFS for the Subaru Telescope

NASA Astrophysics Data System (ADS)

Galvin, Michael B.; Carr, Michael A.; Groff, Tyler D.; Kasdin, N. Jeremy; Fagan, Radford; Hayashi, Masahiko; Takato, Naruhisa

2014-07-01

Princeton University is designing and building an integral field spectrograph (IFS), the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS), for integration with the Subaru Corona Extreme Adaptive Optics (SCExAO) system and the AO188 adaptive optics system on the Subaru Telescope. CHARIS and SCExAO will measure spectra of hot, young Jovian planets in a coronagraphic image across J, H, and K bands down to an 80 milliarcsecond inner working angle. Here we present the current status of the mechanical design of the CHARIS instrument.

Coseismic Displacement Analysis of the 12 November 2017 MW 7.3 Sarpol-E Zahab (iran) Earthquake from SAR Interferometry, Burst Overlap Interferometry and Offset Tracking

NASA Astrophysics Data System (ADS)

Vajedian, Sanaz; Motagh, Mahdi

2018-04-01

Interferometric wide-swath mode of Sentinel-1, which is implemented by Terrain Observation by Progressive Scan (TOPS) technique, is the main mode of SAR data acquisition in this mission. It aims at global monitoring of large areas with enhanced revisit frequency of 6 days at the expense of reduced azimuth resolution, compared to classical ScanSAR mode. TOPS technique is equipped by steering the beam from backward to forward along the heading direction for each burst, in addition to the steering along the range direction, which is the only sweeping direction in standard ScanSAR mode. This leads to difficulty in measuring along-track displacement by applying the conventional method of multi-aperture interferometry (MAI), which exploits a double difference interferometry to estimate azimuth offset. There is a possibility to solve this issue by a technique called "Burst Overlap Interferometry" which focuses on the region of burst overlap. Taking advantage of large squint angle diversity of 1° in burst overlapped area leads to improve the accuracy of ground motion measurement especially in along-track direction. We investigate the advantage of SAR Interferometry (InSAR), burst overlap interferometry and offset tracking to investigate coseismic deformation and coseismic-induced landslide related to 12 November 2017 Mw 7.3 Sarpol-e Zahab earthquake in Iran.

Seasonal and Inter-Annual Changes in the Distribution of Dominant Phytoplancton Groups in the Global Ocean

NASA Astrophysics Data System (ADS)

Severine, A.; Cyril, M.; Yves, D.; Laurent, B.; Hubert, L.

2006-12-01

The fate of fixed organic carbon in the ocean strongly varies with the phytoplankton group that makes photosynthesis. The monitoring of phytoplankton groups in the global ocean is thus of primary importance to evaluate and improve ocean carbon models. A new method (PHYSAT; Alvain et al., 2005) enables to distinguish between four different groups from space using SeaWiFS ocean color measurements. In addition to these four initial phytoplankton groups, which are diatoms, Prochlorococcus, Synecochoccus and haptophytes, we show that PHYSAT is also capable of identifying blooms of phaeocystis and coccolithophorids. Daily global SeaWiFS level-3 data from September 1997 to December 2004 were processed using PHYSAT. We present here the first monthly mean global climatology of the dominant phytoplankton groups. The seasonal cycle is discussed, with particular emphasis on the succession of phytoplankton groups during the North Atlantic spring bloom and on the coexistence of large phaeocystis and diatoms blooms during winter in the Austral Ocean. We also present the inter-annual variability for the 1998-2004 period. The contribution of diatoms to the total chlorophyll is highly variable (up to a factor of two) from one year to the other in both Atlantic and Austral Oceans, suggesting a significant variability in organic carbon export by diatoms in these regions. On the opposite, the phaeocystis contribution is less variable in the Austral Ocean.

Understanding Madden-Julian-Induced sea surface temperature variations in the North Western Australian Basin

NASA Astrophysics Data System (ADS)

Vialard, J.; Drushka, K.; Bellenger, H.; Lengaigne, M.; Pous, S.; Duvel, J. P.

2013-12-01

The strongest large-scale intraseasonal (30-110 day) sea surface temperature (SST) variations in austral summer in the tropics are found in the eastern Indian Ocean between Australia and Indonesia (North-Western Australian Basin, or NWAB). TMI and Argo observations indicate that the temperature signal (std. ~0.4 °C) is most prominent within the top 20 m. This temperature signal appears as a standing oscillation with a 40-50 day timescale within the NWAB, associated with ~40 Wm-2 net heat fluxes (primarily shortwave and latent) and ~0.02 Nm-2 wind stress perturbations. This signal is largely related to the Madden-Julian Oscillation. A slab ocean model with climatological observed mixed-layer depth and an ocean general circulation model both accurately reproduce the observed intraseasonal SST oscillations in the NWAB. Both indicate that most of the intraseasonal SST variations in the NWAB in austral winter are related to surface heat flux forcing, and that intraseasonal SST variations are largest in austral summer because the mixed-layer is shallow (~20 m) and thus more responsive during that season. The general circulation model indicates that entrainment cooling plays little role in intraseasonal SST variations. The larger intraseasonal SST variations in the NWAB as compared to the widely-studied thermocline-ridge of the Indian Ocean region is explained by the larger convective and air-sea heat flux perturbations in the NWAB.

Variability of the extent of the Hadley circulation in the southern hemisphere: a regional perspective

NASA Astrophysics Data System (ADS)

Nguyen, H.; Hendon, H. H.; Lim, E.-P.; Boschat, G.; Maloney, E.; Timbal, B.

2018-01-01

In order to understand the regional impacts of variations in the extent of the Hadley circulation in the Southern Hemisphere, regional Hadley circulations are defined in three sectors centered on the main tropical heat sources over Africa, Asia-Pacific (Maritime Continent) and the Americas. These regional circulations are defined by computing a streamfunction from the divergent component of the meridional wind. A major finding from this study is that year-to-year variability in the extent of the hemispheric Hadley circulation in the Southern Hemisphere is primarily governed by variations of the extent of the Hadley circulation in the Asia-Pacific sector, especially during austral spring and summer when there is little co-variability with the African sector, and the American sector exhibits an out of phase behavior. An expanded Hadley circulation in the Southern Hemisphere (both hemispherically and in the Asia-Pacific sector) is associated with La Niña conditions and a poleward expansion of the tropical wet zone in the Asia-Pacific sector. While La Niña also promotes expansion in the American and African sectors during austral winter, these tropical conditions tend to promote contraction in the two sectors during austral summer as a result of compensating convergence over the Americas and Africa sectors: a process driven by variations in the Walker circulation and Rossby wave trains emanating from the tropical Indian Ocean.

The Impact of Warm Pool El Nino Events on Antarctic Ozone

NASA Technical Reports Server (NTRS)

Hurwitz, Margaret M.; Newman, P. A.; Song, In-Sun; Frith, Stacey M.

2011-01-01

Warm pool El Nino (WPEN) events are characterized by positive sea surface temperature (SST) anomalies in the central equatorial Pacific in austral spring and summer. Previous work found an enhancement in planetary wave activity in the South Pacific in austral spring, and a warming of 3-5 K in the Antarctic lower stratosphere during austral summer, in WPEN events as compared with ENSO neutral. In this presentation, we show that weakening of the Antarctic vortex during WPEN affects the structure and magnitude of high-latitude total ozone. We use total ozone data from TOMS and OMI, as well as station data from Argentina and Antarctica, to identify shifts in the longitudinal location of the springtime ozone minimum from its climatological position. In addition, we examine the sensitivity of the WPEN-related ozone response to the phase of the quasi-biennial oscillation (QBO). We then compare the observed response to WPEN events with Goddard Earth Observing System chemistry-climate model, version 2 (GEOS V2 CCM) simulations. Two, 50-year time-slice simulations are forced by annually repeating SST and sea ice climatologies, one set representing observed WPEN events and the second set representing neutral ENSO events, in a present-day climate. By comparing the two simulations, we isolate the impact of WPEN events on lower stratospheric ozone, and furthermore, examine the sensitivity of the WPEN ozone response to the phase of the QBO.

Atom Interferometry for Fundamental Physics and Gravity Measurements in Space

NASA Technical Reports Server (NTRS)

Kohel, James M.

2012-01-01

Laser-cooled atoms are used as freefall test masses. The gravitational acceleration on atoms is measured by atom-wave interferometry. The fundamental concept behind atom interferometry is the quantum mechanical particle-wave duality. One can exploit the wave-like nature of atoms to construct an atom interferometer based on matter waves analogous to laser interferometers.

Bidensmeyeri (Asteraceae, Coreopsideae): a new critically endangered species from Rapa, Austral Islands.

PubMed

Funk, Vicki A; Wood, Kenneth R

2014-01-01

Bidensmeyeri (Asteraceae/Compositae) is described and illustrated from Rapa, Austral Islands, (French Polynesia). This new species is presumed to be most closely related to Bidenssaint-johniana from nearby Marotiri Island. Bidensmeyeri may be distinguished from Bidenssaint-johniana based on the length of the peduncle (3 cm versus 10 cm), apex of the inner involucral bracts (glabrous vs. puberulent), smaller leaves (2.0-2.3 cm vs. 5-6 cm), and the general smaller size of the new species. Known from less than 50 individuals and restricted to one remote location, Bidensmeyeri falls into the IUCN Critically Endangered (CR) category. The new species is named in honor of Dr. Jean-Yves Meyer, Délégation à la Recherche, Polynésie Française.

A Data Exchange Standard for Optical (Visible/IR) Interferometry

NASA Astrophysics Data System (ADS)

Pauls, T. A.; Young, J. S.; Cotton, W. D.; Monnier, J. D.

2005-11-01

This paper describes the OI (Optical Interferometry) Exchange Format, a standard for exchanging calibrated data from optical (visible/infrared) stellar interferometers. The standard is based on the Flexible Image Transport System (FITS) and supports the storage of optical interferometric observables, including squared visibility and closure phase-data products not included in radio interferometry standards such as UV-FITS. The format has already gained the support of most currently operating optical interferometer projects, including COAST, NPOI, IOTA, CHARA, VLTI, PTI, and the Keck Interferometer, and is endorsed by the IAU Working Group on Optical Interferometry. Software is available for reading, writing, and the merging of OI Exchange Format files.

Application of deconvolution interferometry with both Hi-net and KiK-net data

NASA Astrophysics Data System (ADS)

Nakata, N.

2013-12-01

Application of deconvolution interferometry to wavefields observed by KiK-net, a strong-motion recording network in Japan, is useful for estimating wave velocities and S-wave splitting in the near surface. Using this technique, for example, Nakata and Snieder (2011, 2012) found changed in velocities caused by Tohoku-Oki earthquake in Japan. At the location of the borehole accelerometer of each KiK-net station, a velocity sensor is also installed as a part of a high-sensitivity seismograph network (Hi-net). I present a technique that uses both Hi-net and KiK-net records for computing deconvolution interferometry. The deconvolved waveform obtained from the combination of Hi-net and KiK-net data is similar to the waveform computed from KiK-net data only, which indicates that one can use Hi-net wavefields for deconvolution interferometry. Because Hi-net records have a high signal-to-noise ratio (S/N) and high dynamic resolution, the S/N and the quality of amplitude and phase of deconvolved waveforms can be improved with Hi-net data. These advantages are especially important for short-time moving-window seismic interferometry and deconvolution interferometry using later coda waves.

Interferometry as a tool for evaluating effects of antimicrobial doses on Mycobacterium bovis growth.

PubMed

Machado, Rachel R P; Dutra, Rafael C; Raposo, Nádia R B; Lesche, Bernhard; Gomes, Marlei S; Duarte, Rafael S; Soares, Geraldo Luiz G; Kaplan, Maria Auxiliadora C

2015-12-01

Interferometry was used together with the conventional microplate resazurin assay to evaluate the antimycobacterial properties of essential oil (EO) from fruits of Pterodon emarginatus and also of rifampicin against Mycobacterium bovis. The aim of this work is not only to investigate the potential antimycobacterial activity of this EO, but also to test the interferometric method in comparison with the conventional one. The Minimum Inhibitory Concentration (MIC) values of EO (625 μg/mL) and rifampicin (4 ng/mL) were firstly identified with the microplate method. These values were used as parameters in Drug Susceptibility Tests (DST) with interferometry. The interferometry confirmed the MIC value of EO identified with microplate and revealed a bacteriostatic behavior for this concentration. At 2500 μg/mL interferometry revealed bactericidal activity of the EO. Mycobacterial growth was detected with interferometry at 4 ng/mL of rifampicin and even at higher concentrations. One important difference is that the interferometric method preserves the sample, so that after weeks of quantitative observation, the sample can be used to evaluate the bactericidal activity of the tested drug. Copyright © 2015 Elsevier Ltd. All rights reserved.

Diversity of moderate El Niño events evolution: role of air-sea interactions in the eastern tropical Pacific

NASA Astrophysics Data System (ADS)

Dewitte, Boris; Takahashi, Ken

2017-12-01

In this paper we investigate the evolution of moderate El Niño events during their developing phase with the objective to understand why some of them did not evolve as extreme events despite favourable conditions for the non-linear amplification of the Bjerknes feedback (i.e. warm SST in Austral winter in the eastern equatorial Pacific). Among the moderate events, two classes are considered consisting in the Eastern Pacific (EP) El Niño events and Central Pacific (CP) events. We first show that the observed SST variability across moderate El Niño events (i.e. inter-event variability) is largest in the far eastern Pacific (east of 130°W) in the Austral winter prior to their peak, which is associated to either significant warm anomaly (moderate EP El Niño) or an anomaly between weak warm and cold (moderate CP El Niño) as reveals by the EOF analysis of the SST anomaly evolution during the development phase of El Niño across the El Niño years. Singular value decomposition (SVD) analysis of SST and wind stress anomalies across the El Niño years further indicates that the inter-event SST variability is associated with an air-sea mode explaining 31% of the covariance between SST and wind stress. The associated SST pattern consists in SST anomalies developing along the coast of Ecuador in Austral fall and expanding westward as far as 130°W in Austral winter. The associated wind stress pattern features westerlies (easterlies) west of 130°W along the equator peaking around June-August for EP (CP) El Niño events. This air-sea mode is interpreted as resulting from a developing seasonal Bjerknes feedback for EP El Niño events since it is shown to be associated to a Kelvin wave response at its peak phase. However equatorial easterlies east of 130°W emerge in September that counters the growing SST anomalies associated to the air-sea mode. These have been particularly active during both the 1972 and the 2015 El Niño events. It is shown that the easterlies are connected to an off-equatorial southerly wind off the coast of Peru and Ecuador. The southerly wind is a response to the coastal SST anomalies off Peru developing from Austral fall. Implications of our results for the understanding of the seasonal ENSO dynamics and diversity are discussed in the light of the analysis of two global climate models simulating realistically ENSO diversity (GFDL_CM2.1 and CESM).

Very Long Baseline Array Imaging of Type-2 Seyferts with Double-peaked Narrow Emission Lines: Searches for Sub-kpc Dual AGNs and Jet-powered Outflows

NASA Astrophysics Data System (ADS)

Liu, Xin; Lazio, T. Joseph W.; Shen, Yue; Strauss, Michael A.

2018-02-01

This paper presents Very Long Baseline Array (VLBA) observations of 13 double-peaked [O III] emission-line type-2 active galactic nuclei (AGNs) at redshifts 0.06 < z < 0.41 (with a median redshift of z ∼ 0.15) identified in the Sloan Digital Sky Survey. Such double-peaked emission-line objects may result from jets or outflows from the central engine or from a dual AGN. The VLBA provides an angular resolution of ≲10 pc at the distance of many of these galaxies, sufficient to resolve the radio emission from extremely close dual AGNs and to contribute to understanding the origin of double-peaked [O III] emission lines. Of the 13 galaxies observed at 3.6 cm (8.4 GHz), we detect six at a 1σ sensitivity level of ∼0.15 mJy beam‑1, two of which show clear jet structures on scales ranging from a few milliarcseconds to tens of milliarcseconds (corresponding to a few pc to tens of pc at a median redshift of 0.15). We suggest that radio-loud, double-peaked emission-line type-2 AGNs may be indicative of jet produced structures, but a larger sample of double-peaked [O III] AGNs with high angular resolution radio observations will be required to confirm this suggestion. Based, in part, on observations made with the Very Long Baseline Array, obtained at the Long Baseline Observatory. The Long Baseline Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Does Newton’s gravitational constant vary sinusoidally with time? Orbital motions say no

NASA Astrophysics Data System (ADS)

Iorio, Lorenzo

2016-02-01

A sinusoidally time-varying pattern of the values of Newton’s constant of gravitation G measured in Earth-based laboratories over the last few decades has been recently reported in the literature. We put to the test the hypothesis that the aforementioned harmonic variation may pertain to G itself in a direct and independent way. We numerically integrated the ad hoc modified equations of motion of the major bodies of the Solar System, finding that the orbits of the planets would be altered by an unacceptably larger amount in view of the present-day high accuracy astrometric measurements. In the case of Saturn, its geocentric right ascension α, declination δ and range ρ would be affected by up to {10}4-{10}5 milliarcseconds and 105 km, respectively; the present-day residuals of such observables are as little as about 4 milliarcseconds and 10-1 km, respectively. We analytically calculated the long-term orbital effects induced by the putative harmonic variation of G at hand, finding non-zero rates of change for the semimajor axis a, the eccentricity e and the argument of pericenter ω of a test particle. For the LAGEOS satellite, an orbital increase as large as 3.9 m yr-1 is predicted, in contrast with the observed decay of -0.203 ± 0.035 m yr-1. An anomalous perihelion precession as large as 14 arcseconds per century is implied for Saturn, while latest observations constrain it to the 10-4 arcseconds per century level. The rejection level provided by the Mercury’s perihelion rate is of the same order of magnitude.

On-sky Closed-loop Correction of Atmospheric Dispersion for High-contrast Coronagraphy and Astrometry

NASA Astrophysics Data System (ADS)

Pathak, P.; Guyon, O.; Jovanovic, N.; Lozi, J.; Martinache, F.; Minowa, Y.; Kudo, T.; Kotani, T.; Takami, H.

2018-02-01

Adaptive optic (AO) systems delivering high levels of wavefront correction are now common at observatories. One of the main limitations to image quality after wavefront correction comes from atmospheric refraction. An atmospheric dispersion compensator (ADC) is employed to correct for atmospheric refraction. The correction is applied based on a look-up table consisting of dispersion values as a function of telescope elevation angle. The look-up table-based correction of atmospheric dispersion results in imperfect compensation leading to the presence of residual dispersion in the point spread function (PSF) and is insufficient when sub-milliarcsecond precision is required. The presence of residual dispersion can limit the achievable contrast while employing high-performance coronagraphs or can compromise high-precision astrometric measurements. In this paper, we present the first on-sky closed-loop correction of atmospheric dispersion by directly using science path images. The concept behind the measurement of dispersion utilizes the chromatic scaling of focal plane speckles. An adaptive speckle grid generated with a deformable mirror (DM) that has a sufficiently large number of actuators is used to accurately measure the residual dispersion and subsequently correct it by driving the ADC. We have demonstrated with the Subaru Coronagraphic Extreme AO (SCExAO) system on-sky closed-loop correction of residual dispersion to <1 mas across H-band. This work will aid in the direct detection of habitable exoplanets with upcoming extremely large telescopes (ELTs) and also provide a diagnostic tool to test the performance of instruments which require sub-milliarcsecond correction.

Maintenance and Variations of Atmospheric Subsidence in the Southeast Pacific

NASA Astrophysics Data System (ADS)

Wang, C.; Lee, S.; Mechoso, C. R.; Enfield, D. B.

2010-12-01

The southeastern tropical Pacific (SEP) is characterized by large-scale subsidence, extensive and persistent stratocumulus cloud, and cold SST. The subtropical high in the South Pacific and subsidence over the SEP during the austral summer are related to the monsoonal heating over South America. Previous studies demonstrate that during the austral summer, Rossby wave response to heating associated with the South American monsoon system interacting with the midlatitude westerlies produces descending motion to the west of the South American heating, i.e., over the SEP. The Sverdrup balance demands the existence of equatorward flow beneath the region of descent, closing off the South Pacific subtropical anticyclone on its eastern flank. During seasons other than the austral summer, when convective activity over South America is weaker, other processes must be responsible for maintaining and varying the subsidence over the SEP. This paper shows that the Atlantic warm pool (AWP) is responsible for the subsidence in the SEP during the austral winter and spring. The AWP is a large body of warm water comprising the Gulf of Mexico, the Caribbean Sea, and the western tropical North Atlantic. AWP variability occurs on seasonal, interannual, and multidecadal timescales. The AWP reaches its maximum size in the boreal late summer and early fall, with large AWPs being almost three times larger than small ones. The warm pool alternates with South America as the seasonal heating source for the Hadley circulation in the Western Hemisphere. During the boreal summer and fall, a strong Hadley circulation emanates from the AWP and forks into the subsidence region of the SEP. The anomalous warm pool index is positively correlated with rainfall anomalies over the SEP where the drizzle under the stratus cloud deck appears. Large (small) warm pools strengthen (weaken) the summer Hadley circulation that emanates from the region of the warm pool into the SEP. This will change the subsidence over the SEP and thus the stratus cloud and drizzle. Atmospheric GCM and simple models are further used to demonstrate the remote and inter-hemispheric response of the AWP to the SEP; that is, the AWP contributes to sinking over the SEP and hence the stratus cloud in the region.

Seasonal and annual variability of coastal sulphur plumes in the northern Benguela upwelling system.

PubMed

Ohde, Thomas; Dadou, Isabelle

2018-01-01

We investigated the seasonal and annual variability of surface sulphur plumes in the northern Benguela upwelling system off Namibia because of their significant impacts on the marine ecosystem, fishing industry, aquaculture farming and tourism due to their toxic properties. We identified the sulphur plumes in ocean colour satellite data of the medium resolution imaging spectrometer (MERIS) for the 2002-2012 time period using the differences in the spectral properties of Namibian Benguela optical water types. The sulphur events have a strong seasonal cycle with pronounced main and off-seasons forced by local and remote-driven processes. The main peak season is in late austral summer and early austral autumn at the beginning of the annual upwelling cycle caused by increasing equatorwards alongshore winds. The sulphur plume activity is high between February and April during the seasonal oxygen minimum associated with the seasonal reduction of cross-shore ventilation of the bottom waters, the seasonal southernmost position of the Angola Benguela Frontal Zone, the seasonal maximum of water mass fractions of South Atlantic and Angola Gyre Central Waters as well as the seasonal arrival of the downwelling coastal trapped waves. The off-season is in austral spring and early austral summer during increased upwelling intensity and enhanced oxygen supply. The annual variability of sulphur events is characterized by very high activities in years 2004, 2005 and 2010 interrupted by periods of lower activity in years 2002 to 2003, 2006 to 2009 and 2011 to 2012. This result can be explained by the relative contributions or adding effects of local and remote-driven forces (from the equatorial area). The probability for the occurrence of sulphur plumes is enhanced in years with a lower annual mean of upwelling intensity, decreased oxygen supply associated with decreased lateral ventilation of bottom waters, more southern position of the Angola Benguela Frontal Zone, increased mass fraction of South Atlantic Central Water and stronger downwelling coastal trapped waves. Understanding of the variability and forcing processes of the toxic sulphur events will help in the future to monitor and forecast them as well as to manage their social and economic consequences in the northern Benguela upwelling system off Namibia.

Hydrological differentiation and spatial distribution of high altitude wetlands in a semi-arid Andean region derived from satellite data

NASA Astrophysics Data System (ADS)

Otto, M.; Scherer, D.; Richters, J.

2011-05-01

High Altitude Wetlands of the Andes (HAWA) belong to a unique type of wetland within the semi-arid high Andean region. Knowledge about HAWA has been derived mainly from studies at single sites within different parts of the Andes at only small time scales. On the one hand, HAWA depend on water provided by glacier streams, snow melt or precipitation. On the other hand, they are suspected to influence hydrology through water retention and vegetation growth altering stream flow velocity. We derived HAWA land cover from satellite data at regional scale and analysed changes in connection with precipitation over the last decade. Perennial and temporal HAWA subtypes can be distinguished by seasonal changes of photosynthetically active vegetation (PAV) indicating the perennial or temporal availability of water during the year. HAWA have been delineated within a region of 12 800 km2 situated in the Northwest of Lake Titicaca. The multi-temporal classification method used Normalized Differenced Vegetation Index (NDVI) and Normalized Differenced Infrared Index (NDII) data derived from two Landsat ETM+ scenes at the end of austral winter (September 2000) and at the end of austral summer (May 2001). The mapping result indicates an unexpected high abundance of HAWA covering about 800 km2 of the study region (6 %). Annual HAWA mapping was computed using NDVI 16-day composites of Moderate Resolution Imaging Spectroradiometer (MODIS). Analyses on the relation between HAWA and precipitation was based on monthly precipitation data of the Tropical Rain Measurement Mission (TRMM 3B43) and MODIS Eight Day Maximum Snow Extent data (MOD10A2) from 2000 to 2010. We found HAWA subtype specific dependencies on precipitation conditions. A strong relation exists between perennial HAWA and snow fall (r2: 0.82) in dry austral winter months (June to August) and between temporal HAWA and precipitation (r2: 0.75) during austral summer (March to May). Annual changes in spatial extend of perennial HAWA indicate alterations in annual water supply generated from snow melt.

Hydrological differentiation and spatial distribution of high altitude wetlands in a semi-arid Andean region derived from satellite data

NASA Astrophysics Data System (ADS)

Otto, M.; Scherer, D.; Richters, J.

2011-01-01

High Altitude Wetlands of the Andes (HAWA) are unique types of wetlands within the semi-arid high Andean region. Knowledge about HAWA has been derived mainly from studies at single sites within different parts of the Andes at only small time scales. On the one hand HAWA depend on water provided by glacier streams, snow melt or precipitation. On the other hand, they are suspected to influence hydrology through water retention and vegetation growth altering stream flow velocity. We derived HAWA land cover from satellite data at regional scale and analysed changes in connection with precipitation over the last decade. Perennial and temporal HAWA subtypes can be distinguished by seasonal changes of photosynthetically active vegetation (PAV) indicating the perennial or temporal availability of water during the year. HAWA have been delineated within a region of 11 000 km2 situated in the Northwest of Lake Titicaca. The multi temporal classification method used Normalized Differenced Vegetation Index (NDVI) and Normalized Differenced Infrared Index (NDII) data derived from two Landsat ETM+ scenes at the end of austral winter (September 2000) and at the end of austral summer (May 2001). The mapping result indicates an unexpected high abundance of HAWA covering about 800 km2 of the study region (6%). Annual HAWA mapping was computed using NDVI 16-day composites of Moderate Resolution Imaging Spectroradiometer (MODIS). Analyses on the reletation between HAWA and precipitation was based on monthly precipitation data of the Tropical Rain Measurement Mission (TRMM 3B43) and MODIS Eight Day Maximum Snow Extent data (MOD10A2) from 2000 to 2010. We found HAWA subtype specific dependencies to precipitation conditions. Strong relation exists between perennial HAWA and snow fall (r2: 0.82) in dry austral winter months (June to August) and between temporal HAWA and precipitation (r2: 0.75) during austral summer (March to May). Annual spatial patterns of perennial HAWA indicated spatial alteration of water supply for PAV up to several hundred metres at a single HAWA site.

Very Long Baseline Interferometry Applied to Polar Motion, Relativity and Geodesy. Ph.D. Thesis - Maryland Univ.

NASA Technical Reports Server (NTRS)

Ma, C.

1978-01-01

The causes and effects of diurnal polar motion are described. An algorithm is developed for modeling the effects on very long baseline interferometry observables. Five years of radio-frequency very long baseline interferometry data from stations in Massachusetts, California, and Sweden are analyzed for diurnal polar motion. It is found that the effect is larger than predicted by McClure. Corrections to the standard nutation series caused by the deformability of the earth have a significant effect on the estimated diurnal polar motion scaling factor and the post-fit residual scatter. Simulations of high precision very long baseline interferometry experiments taking into account both measurement uncertainty and modeled errors are described.

Beam shuttering interferometer and method

DOEpatents

Deason, V.A.; Lassahn, G.D.

1993-07-27

A method and apparatus resulting in the simplification of phase shifting interferometry by eliminating the requirement to know the phase shift between interferograms or to keep the phase shift between interferograms constant. The present invention provides a simple, inexpensive means to shutter each independent beam of the interferometer in order to facilitate the data acquisition requirements for optical interferometry and phase shifting interferometry. By eliminating the requirement to know the phase shift between interferograms or to keep the phase shift constant, a simple, economical means and apparatus for performing the technique of phase shifting interferometry is provide which, by thermally expanding a fiber optical cable changes the optical path distance of one incident beam relative to another.

Beam shuttering interferometer and method

DOEpatents

Deason, Vance A.; Lassahn, Gordon D.

1993-01-01

A method and apparatus resulting in the simplification of phase shifting interferometry by eliminating the requirement to know the phase shift between interferograms or to keep the phase shift between interferograms constant. The present invention provides a simple, inexpensive means to shutter each independent beam of the interferometer in order to facilitate the data acquisition requirements for optical interferometry and phase shifting interferometry. By eliminating the requirement to know the phase shift between interferograms or to keep the phase shift constant, a simple, economical means and apparatus for performing the technique of phase shifting interferometry is provide which, by thermally expanding a fiber optical cable changes the optical path distance of one incident beam relative to another.

Status of holographic interferometry at Wright Patterson Air Force Base

NASA Technical Reports Server (NTRS)

Seibert, George

1987-01-01

At Wright Patterson AFB, holographic interferometry has been used for nearly 15 years in a variety of supersonic and hypersonic wind tunnels. Specifically, holographic interferometry was used to study boundary layers, shock boundary layer interaction, and general flow diagnostics. Although a considerable amount of quantitative work was done, the difficulty of reducing data severely restricted this. In the future, it is of interest to use holographic interferometry in conjunction with laser Doppler velocimetry to do more complete diagnostics. Also, there is an interest to do particle field diagnostics in the combustion research facility. Finally, there are efforts in nondestructive testing where automated fringe readout and analysis would be extremely helpful.

Theoretical Properties of Acoustical Speckle Interferometry.

DTIC Science & Technology

1980-09-01

an obvious one , since it was first performed in the acoustical holography. An acoustical speckle interferometry study has been demonstrated to be a...experiments in which pulses were used to study the propagation of the circumferential waves on aluminum cylinders immersed in water. In 1969, Bunney...destructive Testing SB. ABTRACT aCdo as revers. NW ass a" Id by block numb") Acoustical speckle interferometry is based locally on the elastodynamic response

Algorithms and Array Design Criteria for Robust Imaging in Interferometry

DTIC Science & Technology

2016-04-01

Interferometry 1.1 Chapter Overview In this Section, we introduce the physics -based principles of optical interferometry, thereby providing a foundation for...particular physical structure (i.e. the existence of a certain type of loop in the interferometric graph), and provide a simple algorithm for identifying...mathematical conditions for wrap invariance to a physical condition on aperture placement is more intuitive when considering the raw phase measurements as

Ocean Remote Sensing Using Ambient Noise

DTIC Science & Technology

2015-09-30

and other adaptive array processing methods. OBJECTIVES Work on this project has focused on noise interferometry – the process by which an...measured at xA and xB. In that context, our objective is to investigate and identify the limitations of noise interferometry for remote sensing...and 6 is ongoing. 1. Demonstration of noise interferometry at 10 km range in a shallow water environment Recently conducted experiments in the

A Possible Future for Space-Based Interferometry

NASA Technical Reports Server (NTRS)

Labadie, L.; Leger, A.; Malbet, F.; Danchi, William C.; Lopez, B.

2013-01-01

We address the question of space interferometry following the recent outcome of the science themes selection by ESA for the L2/L3 missions slots. We review the current context of exoplanetary sciences and its impact for an interferometric mission. We argue that space interferometry will make a major step forward when the scientific communities interested in this technique will merge their efforts into a coherent technology development plan.

Very long baseline interferometry applied to polar motion, relativity, and geodesy. Ph. D. thesis

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

Ma, C.

1978-01-01

The causes and effects of diurnal polar motion are described. An algorithm was developed for modeling the effects on very long baseline interferometry observables. A selection was made between two three-station networks for monitoring polar motion. The effects of scheduling and the number of sources observed on estimated baseline errors are discussed. New hardware and software techniques in very long baseline interferometry are described.

Seasonal variation in the range areas of the diurnal rodent Octodon degus

PubMed Central

Quirici, Verónica; Castro, Rodrigo A.; Ortiz-Tolhuysen, Liliana; Chesh, Adrian S.; Burger, Joseph Robert; Miranda, Eduardo; Cortés, Arturo; Hayes, Loren D.; Ebensperger, Luis A.

2012-01-01

Both breeding activity and abundance and quality of available food are expected to influence daily movements of animals. Animals are predicted to range over large areas to meet high energy demands associated with reproduction (females) or to increase mating success (males). However, animals should expand their range areas whenever food conditions deteriorate. To examine the extent to which breeding activity versus food availability influence space use, we compared the size and location of range areas (home ranges) of the degu (Octodon degus), a diurnal rodent from semiarid environments of north-central Chile, during the austral winter and summer seasons. Degus produce young during the austral spring (September–October) when high-quality food is readily available. In contrast, degus do not breed during the austral summer (January–March) when food is scarce and of low quality. We predicted that degus would range over smaller areas in winter if the availability of food has a greater influence on space than breeding activity. Individuals were radiotracked in winter and the following summer over a 3-year period. Surveys of herbaceous cover were conducted during winter and summer to determine seasonal changes in the abundance and quality of primary food. In summer degus expanded and moved the location of their range areas to locations with available food. Given that preferred food was less abundant in summer than winter, we suggest that degu range areas are strongly influenced by food conditions. PMID:22328788

Seasonal variation in the range areas of the diurnal rodent Octodon degus.

PubMed

Quirici, Verónica; Castro, Rodrigo A; Ortiz-Tolhuysen, Liliana; Chesh, Adrian S; Burger, Joseph Robert; Miranda, Eduardo; Cortés, Arturo; Hayes, Loren D; Ebensperger, Luis A

2010-01-01

Both breeding activity and abundance and quality of available food are expected to influence daily movements of animals. Animals are predicted to range over large areas to meet high energy demands associated with reproduction (females) or to increase mating success (males). However, animals should expand their range areas whenever food conditions deteriorate. To examine the extent to which breeding activity versus food availability influence space use, we compared the size and location of range areas (home ranges) of the degu (Octodon degus), a diurnal rodent from semiarid environments of north-central Chile, during the austral winter and summer seasons. Degus produce young during the austral spring (September-October) when high-quality food is readily available. In contrast, degus do not breed during the austral summer (January-March) when food is scarce and of low quality. We predicted that degus would range over smaller areas in winter if the availability of food has a greater influence on space than breeding activity. Individuals were radiotracked in winter and the following summer over a 3-year period. Surveys of herbaceous cover were conducted during winter and summer to determine seasonal changes in the abundance and quality of primary food. In summer degus expanded and moved the location of their range areas to locations with available food. Given that preferred food was less abundant in summer than winter, we suggest that degu range areas are strongly influenced by food conditions.

Why the Australian Monsoon Strengthened During the Cold Last Glacial Maximum?

NASA Astrophysics Data System (ADS)

Yan, M.; Wang, B.; Liu, J.; Ning, L.

2017-12-01

The multi-model ensemble simulation suggests that the global monsoon and most sub-monsoons are weakened during the Last Glacial Maximum (LGM) due to the lower green-house gases concentration, the presence of the ice-sheets and the weakened seasonal distribution of insolation. In contrast, the Australian monsoon is strengthened during the LGM. The precipitation there increases in austral summer and decreases in austral winter, so that the annual range or monsoonality increases. The strengthened monsoonality is mainly due to the decreased precipitation in austral winter, which is primarily caused by circulation changes, although the reduced atmospheric water vapor also has a moderate contribution. On the other hand, the strengthened Australian summer monsoon rainfall is likely caused by the change of land-sea thermal contrast due to the alteration of land-sea configuration and by the asymmetric change in sea surface temperature (SST) over Indo-Pacific warm pool region. The strengthened land-sea thermal contrast and Western Pacific-Eastern Indian Ocean thermal gradients in the pre-summer monsoon season triggers a cyclonic wind anomaly that is maintained to the monsoon season, thereby increasing summer precipitation. The increased summer precipitation is associated with the increased cloud cover over the land and decreased cloud cover over the ocean. This may weaken the land-sea thermal contrast, which agrees with the paleoclimate reconstruction. The biases between different models are likely related to the different responses of SST over the North Atlantic Ocean in the pre-summer monsoon season.

Spectral interferometry for morphological imaging in in vitro fertilization (IVF) (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zhu, Yizheng; Li, Chengshuai

2016-03-01

Morphological assessment of spermatozoa is of critical importance for in vitro fertilization (IVF), especially intracytoplasmic sperm injection (ICSI)-based IVF. In ICSI, a single sperm cell is selected and injected into an egg to achieve fertilization. The quality of the sperm cell is found to be highly correlated to IVF success. Sperm morphology, such as shape, head birefringence and motility, among others, are typically evaluated under a microscope. Current observation relies on conventional techniques such as differential interference contrast microscopy and polarized light microscopy. Their qualitative nature, however, limits the ability to provide accurate quantitative analysis. Here, we demonstrate quantitative morphological measurement of sperm cells using two types of spectral interferometric techniques, namely spectral modulation interferometry and spectral multiplexing interferometry. Both are based on spectral-domain low coherence interferometry, which is known for its exquisite phase determination ability. While spectral modulation interferometry encodes sample phase in a single spectrum, spectral multiplexing interferometry does so for sample birefringence. Therefore they are capable of highly sensitive phase and birefringence imaging. These features suit well in the imaging of live sperm cells, which are small, dynamic objects with only low to moderate levels of phase and birefringence contrast. We will introduce the operation of both techniques and demonstrate their application to measuring the phase and birefringence morphology of sperm cells.

Cryo Cooler Induced Micro-Vibration Disturbances to the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Jedrich, Nick; Zimbelman, Darrell; Turczyn, Mark; Sills, Joel; Voorhees, Carl; Clapp, Brian; Brumfield, Mark (Technical Monitor)

2002-01-01

This paper presents an overview of the Hubble Space Telescope (HST) Near Infrared Camera and Multi-Object Spectrometer (NICMOS) Cryo Cooler (MCC) system, a description of the micro-vibration characterization testing performed, and a discussion of the simulated performance. The NCC is a reverse Brayton cycle system that employs micro turbo-machinery to provide cooling to the NICMOS instrument. Extensive testing was conducted to quantify the expected on-orbit disturbances caused by the micro turbo-machinery and provide input to a flexible-body dynamic simulation to demonstrate compliance with the HST 7 milli-arcsecond root mean square jitter requirement.

Flaw Detection and Evaluation of Composite Cylinders Using Laser Speckle Interferometry and Holography

DTIC Science & Technology

1979-11-23

Entered) ACKNOWLEDGMENTS The author hereby expresses his appreciation to Mr. J. A. Schaeffel Jr. for his guidance on interferometry and the computer...were collected by an automated laser speckle interferometry displacement contour analyzer developed by John A. Schaeffel , Jr. [3]. The new method of 10...Fringe Patterns, US Army Missile Command, Redstone Arsenal, Alabama, Technical Report RL-76-18, 20 April 1976. 3. Schaeffel , J. A., Automated Laser

Beam-modulation methods in quantitative and flow visualization holographic interferometry

NASA Technical Reports Server (NTRS)

Decker, A.

1986-01-01

This report discusses heterodyne holographic interferometry and time-average holography with a frequency shifted reference beam. Both methods will be used for the measurement and visualization of internal transonic flows, where the target facility is a flutter cascade. The background and experimental requirements for both methods are reviewed. Measurements using heterodyne holographic interferometry are presented. The performance of the laser required for time-average holography of time-varying transonic flows is discussed.

Beam-modulation methods in quantitative and flow-visualization holographic interferometry

NASA Technical Reports Server (NTRS)

Decker, Arthur J.

1986-01-01

Heterodyne holographic interferometry and time-average holography with a frequency shifted reference beam are discussed. Both methods will be used for the measurement and visualization of internal transonic flows where the target facility is a flutter cascade. The background and experimental requirements for both methods are reviewed. Measurements using heterodyne holographic interferometry are presented. The performance of the laser required for time-average holography of time-varying transonic flows is discussed.

Fringe formation in dual-hologram interferometry

NASA Technical Reports Server (NTRS)

Burner, A. W.

1990-01-01

Reference-fringe formation in nondiffuse dual-hologram interferometry is described by combining a first-order geometrical hologram treatment with interference fringes generated by two point sources. The first-order imaging relationships can be used to describe reference-fringe patterns for the geometry of the dual-hologram interferometry. The process can be completed without adjusting the two holograms when the reconstructing wavelength is less than the exposing wavelength, and the process is found to facilitate basic intereferometer adjustments.

Measurement of Three-dimensional Density Distributions by Holographic Interferometry and Computer Tomography

NASA Technical Reports Server (NTRS)

Vest, C. M.

1982-01-01

The use of holographic interferometry to measure two and threedimensional flows and the interpretation of multiple-view interferograms with computer tomography are discussed. Computational techniques developed for tomography are reviewed. Current research topics are outlined including the development of an automated fringe readout system, optimum reconstruction procedures for when an opaque test model is present in the field, and interferometry and tomography with strongly refracting fields and shocks.

Simultaneous immersion Mirau interferometry.

PubMed

Lyulko, Oleksandra V; Randers-Pehrson, Gerhard; Brenner, David J

2013-05-01

A novel technique for label-free imaging of live biological cells in aqueous medium that is insensitive to ambient vibrations is presented. This technique is a spin-off from previously developed immersion Mirau interferometry. Both approaches utilize a modified Mirau interferometric attachment for a microscope objective that can be used both in air and in immersion mode, when the device is submerged in cell medium and has its internal space filled with liquid. While immersion Mirau interferometry involves first capturing a series of images, the resulting images are potentially distorted by ambient vibrations. Overcoming these serial-acquisition challenges, simultaneous immersion Mirau interferometry incorporates polarizing elements into the optics to allow simultaneous acquisition of two interferograms. The system design and production are described and images produced with the developed techniques are presented.

Multitechnique Testing of the Viscous Decretion Disk Model. 1. The Stable and Tenuous Disk of the Late-Type Be Star Beta CMi

DTIC Science & Technology

2015-10-05

photometry covering the interval between optical and radio wavelengths, optical polarimetry , and optical and near-IR (spectro)interferometry. Results. A...covering the interval between optical and radio wavelengths, optical polarimetry , and optical and near-IR (spectro)interferometry. Results. A... polarimetry , and near-infrared (IR) interferometry of ζ Tau, providing firm evi- dence that the V/R oscillations are an effect of one-armed den- sity

A Novel Femtosecond-gated, High-resolution, Frequency-shifted Shearing Interferometry Technique for Probing Pre-plasma Expansion in Ultra-intense Laser Experiments

DTIC Science & Technology

2014-07-17

frequency-shifted shearing interferometry technique for probing pre-plasma expansion in ultra-intense laser experimentsa) Ultra-intense laser -matter...interaction experiments (>1018 W/cm2) with dense targets are highly sensitive to the effect of laser “noise” (in the form of pre-pulses) preceding the...interferometry technique for probing pre- plasma expansion in ultra-intense laser experimentsa) Report Title Ultra-intense laser -matter interaction

Potential of the McMath-Pierce 1.6-Meter Solar Telescope for Speckle Interferometry

NASA Astrophysics Data System (ADS)

Harshaw, Richard; Jones, Gregory; Wiley, Edward; Boyce, Patrick; Branston, Detrick; Rowe, David; Genet, Russell

2015-09-01

We explored the aiming and tracking accuracy of the McMath-Pierce 1.6 m solar telescope at Kitt Peak National Observatory as part of an investigation of using this telescope for speckle interferometry of close visual double stars. Several slews of various lengths looked for hysteresis in the positioning system (we found none of significance) and concluded that the 1.6 m telescope would make a useful telescope for speckle interferometry.

Tunable-optical-filter-based white-light interferometry for sensing.

PubMed

Yu, Bing; Wang, Anbo; Pickrell, Gary; Xu, Juncheng

2005-06-15

We describe tunable-optical-filter-based white-light interferometry for sensor interrogation. By introducing a tunable optical filter into a white-light interferometry system, one can interrogate an interferometer with either quadrature demodulation or spectral-domain detection at low cost. To demonstrate the feasibility of effectively demodulating various types of interferometric sensor, experiments have been performed using an extrinsic Fabry-Perot tunable filter to interrogate two extrinsic Fabry-Perot interferometric temperature sensors and a diaphragm-based pressure sensor.

Interferometry science center

NASA Technical Reports Server (NTRS)

Sargent, A. I.

2002-01-01

The Interferometry Science Center (ISC) is operated jointly by Caltech and JPL and is part of NASA's Navigator Program. The ISC has been created to facilitate the timely and successful execution of scientific investigations within the Navigator program, particularly those that rely on observations from NASA's interferometer projects. Currently, ISC is expected to provide full life cycle support for the Keck Interferometer, the Starlight mission, the Space Interferometry Mission, and the Terrestrial Planet Finder Mission. The nature and goals of ISc will be described.

Extracting DEM from airborne X-band data based on PolInSAR

NASA Astrophysics Data System (ADS)

Hou, X. X.; Huang, G. M.; Zhao, Z.

2015-06-01

Polarimetric Interferometric Synthetic Aperture Radar (PolInSAR) is a new trend of SAR remote sensing technology which combined polarized multichannel information and Interferometric information. It is of great significance for extracting DEM in some regions with low precision of DEM such as vegetation coverage area and building concentrated area. In this paper we describe our experiments with high-resolution X-band full Polarimetric SAR data acquired by a dual-baseline interferometric airborne SAR system over an area of Danling in southern China. Pauli algorithm is used to generate the double polarimetric interferometry data, Singular Value Decomposition (SVD), Numerical Radius (NR) and Phase diversity (PD) methods are used to generate the full polarimetric interferometry data. Then we can make use of the polarimetric interferometric information to extract DEM with processing of pre filtering , image registration, image resampling, coherence optimization, multilook processing, flat-earth removal, interferogram filtering, phase unwrapping, parameter calibration, height derivation and geo-coding. The processing system named SARPlore has been exploited based on VC++ led by Chinese Academy of Surveying and Mapping. Finally compared optimization results with the single polarimetric interferometry, it has been observed that optimization ways can reduce the interferometric noise and the phase unwrapping residuals, and improve the precision of DEM. The result of full polarimetric interferometry is better than double polarimetric interferometry. Meanwhile, in different terrain, the result of full polarimetric interferometry will have a different degree of increase.

Comparison of immersion ultrasound, partial coherence interferometry, and low coherence reflectometry for ocular biometry in cataract patients.

PubMed

Montés-Micó, Robert; Carones, Francesco; Buttacchio, Antonietta; Ferrer-Blasco, Teresa; Madrid-Costa, David

2011-09-01

To compare ocular biometry parameters measured with immersion ultrasound, partial coherence interferometry, and low coherence reflectometry in cataract patients. Measurements of axial length and anterior chamber depth were analyzed and compared using immersion ultrasound, partial coherence interferometry, and low coherence reflectometry. Keratometry (K), flattest axis, and white-to-white measurements were compared between partial coherence interferometry and low coherence reflectometry. Seventy-eight cataract (LOCS II range: 1 to 3) eyes of 45 patients aged between 42 and 90 years were evaluated. A subanalysis as a function of cataract degree was done for axial length and anterior chamber depth between techniques. No statistically significant differences were noted for the study cohort or within each cataract degree among the three techniques for axial length and anterior chamber depth (P>.05, ANOVA test). Measurements between techniques were highly correlated for axial length (R=0.99) and anterior chamber depth (R=0.90 to 0.96) for all methods. Keratometry, flattest axis, and white-to-white measurements were comparable (paired t test, P>.1) and correlated well between partial coherence interferometry and low coherence reflectometry (K1 [R=0.95), K2 [R=0.97], flattest axis [R=0.95], and white-to-white [R=0.92]). Immersion ultrasound, partial coherence interferometry, and low coherence reflectometry provided comparable ocular biometry measurements in cataractous eyes. Copyright 2011, SLACK Incorporated.

Polar stratospheric clouds and ozone depletion

NASA Technical Reports Server (NTRS)

Toon, Owen B.; Turco, Richard P.

1991-01-01

A review is presented of investigations into the correlation between the depletion of ozone and the formation of polar stratospheric clouds (PSCs). Satellite measurements from Nimbus 7 showed that over the years the depletion from austral spring to austral spring has generally worsened. Approximately 70 percent of the ozone above Antarctica, which equals about 3 percent of the earth's ozone, is lost during September and October. Various hypotheses for ozone depletion are discussed including the theory suggesting that chlorine compounds might be responsible for the ozone hole, whereby chlorine enters the atmosphere as a component of chlorofluorocarbons produced by humans. The three types of PSCs, nitric acid trihydrate, slowly cooling water-ice, and rapidly cooling water-ice clouds act as important components of the Antarctic ozone depletion. It is indicated that destruction of the ozone will be more severe each year for the next few decades, leading to a doubling in area of the Antarctic ozone hole.

Conservation challenges for the Austral and Neotropical America section.

PubMed

Ceballos, Gerardo; Vale, Mariana M; Bonacic, Cristian; Calvo-Alvarado, Julio; List, Rurik; Bynum, Nora; Medellín, Rodrigo A; Simonetti, Javier A; Rodríguez, Jon Paul

2009-08-01

The Austral and Neotropical America (ANA) section of the Society for Conservation Biology includes a vast territory with some of the largest relatively pristine ecosystems in the world. With more than 573 million people, the economic growth of the region still depends strongly on natural resource exploitation and still has high rates of environmental degradation and biodiversity loss. A survey among the ANA section membership, with more than 700 members, including most of the section's prominent ecologists and conservationists, indicates that lack of capacity building for conservation, corruption, and threats such as deforestation and illegal trade of species, are among the most urgent problems that need to be addressed to improve conservation in the region. There are, however, strong universities and ecology groups taking the lead in environmental research and conservation, a most important issue to enhance the ability of the region to solve conservation and development conflicts.

Satellite Detection of Orographic Gravity-wave Activity in the Winter Subtropical Stratosphere over Australia and Africa

NASA Technical Reports Server (NTRS)

Eckermann, S. D.; Wu, D. L.

2012-01-01

Orographic gravity-wave (OGW) parameterizations in models produce waves over subtropical mountain ranges in Australia and Africa that propagate into the stratosphere during austral winter and deposit momentum, affecting weather and climate. Satellite sensors have measured stratospheric GWs for over a decade, yet find no evidence of these waves. So are parameterizations failing here? Here we argue that the short wavelengths of subtropical OGWs place them near or below the detection limits of satellite sensors. To test this hypothesis, we reanalyze nine years of stratospheric radiances from the Atmospheric Infrared Sounder (AIRS) on NASA's Aqua satellite during austral winter, applying new averaging techniques to maximize signal-to-noise and improve thresholds for OGW detection. Deep climatological enhancements in stratospheric OGW variance over specific mountain ranges in Australia and southern Africa are revealed for the first time, which exhibit temporal and vertical variations consistent with predicted OGW responses to varying background winds.

The Beauty and Limitations of 10 Micron Heterodyne Interferometry (ISI)

NASA Technical Reports Server (NTRS)

Danchi, William C.

2003-01-01

Until recently, heterodyne interferometry at 10 microns has been the only successful technique for stellar interferometry in the very difficult atmospheric window from 9-12 microns. For most of its operational lifetime the U.C. Berkeley Infrared Spatial Interferometer was a single-baseline two telescope (1.65 m aperture) system using CO2 lasers as local oscillators. This instrument was designed and constructed from 1983-1988, and first fringes were obtained at Mt. Wilson in June 1988. During the past few years, a third telescope was constructed and just recently the first closure phases were obtained at 11.15 microns. We discuss the history, physics and technology of heterodyne interferometry in the mid-infrared, and some key astronomical results that have come from this unique instrument.

Infrasonic interferometry of stratospherically refracted microbaroms--a numerical study.

PubMed

Fricke, Julius T; El Allouche, Nihed; Simons, Dick G; Ruigrok, Elmer N; Wapenaar, Kees; Evers, Läslo G

2013-10-01

The atmospheric wind and temperature can be estimated through the traveltimes of infrasound between pairs of receivers. The traveltimes can be obtained by infrasonic interferometry. In this study, the theory of infrasonic interferometry is verified and applied to modeled stratospherically refracted waves. Synthetic barograms are generated using a raytracing model and taking into account atmospheric attenuation, geometrical spreading, and phase shifts due to caustics. Two types of source wavelets are implemented for the experiments: blast waves and microbaroms. In both numerical experiments, the traveltimes between the receivers are accurately retrieved by applying interferometry to the synthetic barograms. It is shown that microbaroms can be used in practice to obtain the traveltimes of infrasound through the stratosphere, which forms the basis for retrieving the wind and temperature profiles.

The Wide-Field Imaging Interferometry Testbed: Enabling Techniques for High Angular Resolution Astronomy

NASA Technical Reports Server (NTRS)

Rinehart, S. A.; Armstrong, T.; Frey, Bradley J.; Jung, J.; Kirk, J.; Leisawitz, David T.; Leviton, Douglas B.; Lyon, R.; Maher, Stephen; Martino, Anthony J.;

Simultaneous immersion Mirau interferometry

PubMed Central

Lyulko, Oleksandra V.; Randers-Pehrson, Gerhard; Brenner, David J.

2013-01-01

A novel technique for label-free imaging of live biological cells in aqueous medium that is insensitive to ambient vibrations is presented. This technique is a spin-off from previously developed immersion Mirau interferometry. Both approaches utilize a modified Mirau interferometric attachment for a microscope objective that can be used both in air and in immersion mode, when the device is submerged in cell medium and has its internal space filled with liquid. While immersion Mirau interferometry involves first capturing a series of images, the resulting images are potentially distorted by ambient vibrations. Overcoming these serial-acquisition challenges, simultaneous immersion Mirau interferometry incorporates polarizing elements into the optics to allow simultaneous acquisition of two interferograms. The system design and production are described and images produced with the developed techniques are presented. PMID:23742552

High-Speed Digital Interferometry

NASA Technical Reports Server (NTRS)

De Vine, Glenn; Shaddock, Daniel A.; Ware, Brent; Spero, Robert E.; Wuchenich, Danielle M.; Klipstein, William M.; McKenzie, Kirk

2012-01-01

Digitally enhanced heterodyne interferometry (DI) is a laser metrology technique employing pseudo-random noise (PRN) codes phase-modulated onto an optical carrier. Combined with heterodyne interferometry, the PRN code is used to select individual signals, returning the inherent interferometric sensitivity determined by the optical wavelength. The signal isolation arises from the autocorrelation properties of the PRN code, enabling both rejection of spurious signals (e.g., from scattered light) and multiplexing capability using a single metrology system. The minimum separation of optical components is determined by the wavelength of the PRN code.

Infrared Speckle Interferometry with 2-D Arrays

NASA Technical Reports Server (NTRS)

Harvey, P. M.; Balkum, S. L.; Monin, J. L.

1994-01-01

We describe results from a program of speckle interferometry with two-dimensional infrared array detectors. Analysis of observations of eta Carinae made with 58 x 62 InSb detector are discussed. The data have been analyzed with both the Labeyrie autocorrelation, a deconvolution of shift-and-add data, and a phase restoration process. Development of a new camera based on a much lower noise HgCdTe detector will lead to a significant improvement i limiting magnitude for IR speckle interferometry.

Application of virtual phase-shifting speckle-interferometry for detection of polymorphism in the Chlamydia trachomatis omp1 gene

NASA Astrophysics Data System (ADS)

Feodorova, Valentina A.; Saltykov, Yury V.; Zaytsev, Sergey S.; Ulyanov, Sergey S.; Ulianova, Onega V.

2018-04-01

Method of phase-shifting speckle-interferometry has been used as a new tool with high potency for modern bioinformatics. Virtual phase-shifting speckle-interferometry has been applied for detection of polymorphism in the of Chlamydia trachomatis omp1 gene. It has been shown, that suggested method is very sensitive to natural genetic mutations as single nucleotide polymorphism (SNP). Effectiveness of proposed method has been compared with effectiveness of the newest bioinformatic tools, based on nucleotide sequence alignment.

Infrared Spectro-Interferometry of Massive Stars: Disks, Winds, Outflows, and Stellar Multiplicity

NASA Astrophysics Data System (ADS)

Kraus, Stefan

2007-06-01

Interferometry is the ultimate technology for overcoming the limitations which diffraction and the atmosphere-induced seeing impose on the resolution achievable with ground-based telescopes. The latest generation of long-baseline interferometric instruments (in particular VLTI/AMBER and VLTI/MIDI), combines the high spatial resolution (typically a few milliarcseconds) with spectroscopic capabilities, allowing one to characterize the geometry of a continuum-emitting region over a wide spectral range or to spatially resolve the emitting region of Doppler-broadened spectral lines in many velocity channels. One branch of astrophysics which might particularly benefit from these advances in technology is the study of massive (O-B type) stars. In order to characterize these stars and their companions and to study accretion and outflow processes in their vicinity with unprecedented angular resolution, we have performed interferometric studies on four key objects, representing the still most enigmatic evolutionary phases of massive stars; namely the pre-main-sequence (MWC 147, NGC 7538 IRS1, Theta 1 Orionis C) and the post-main-sequence phase (Eta Carinae). MWC 147: As indicated by its strong infrared excess, this young Herbig Be star (B6-type) is still associated with residual material from its formation; maybe arranged in a circumstellar disk. In order to investigate the geometry of the material, we combined, for the first time, long-baseline spectro-interferometric observations at near- (NIR) and mid-infrared (MIR) wavelengths (using VLTI/AMBER, VLTI/MIDI, and archival PTI data). Fitting analytic models to the obtained interferometric data revealed a significant elongation of the continuum-emitting region. For a physical interpretation, we modeled the geometry of the dust distribution using 2-D radiative transfer simulations of Keplerian disks with and without a puffed-up inner rim, simultaneously fitting the wavelength-dependent visibilities and the SED, which we complemented with archival Spitzer/IRS spectra. Surprisingly, we found that passive disk models, which can reproduce the SED well, are in strong conflict with the interferometric data. However, when including emission from an optically thick inner gaseous disk, good quantitative agreement was found for all observables, suggesting that MWC 147 harbours a still actively accreting disk. NGC 7538 IRS1/2: NGC 7538 IRS1 is a high-mass (O7-type) protostar with a CO outflow, an associated ultracompact H II region, and a linear methanol maser structure, which might trace a Keplerian-rotating circumstellar disk. We investigated the NIR morphology of the source with unprecedented resolution using NIR bispectrum speckle interferometry obtained at the BTA 6 m and the MMT 6.5 m telescopes. Our high-dynamic range images show fan-shaped outflow structures, in which we detected 18 stars and several blobs of diffuse emission. Complementary archival Spitzer/IRAC images were used to relate the detected structures with the outflow at larger scales. We found a misalignment of various outflow axes and interpreted this in the context of a disk precession model, also using molecular hydrodynamic simulations. As a possible triggering mechanism, we identified non-coplanar tidal interaction of an (yet undiscovered) close companion with the circumbinary disk. Finally, our observations resolved the nearby massive protostar NGC 7538 IRS2 as a close binary with a separation of 195 mas, finding indications for shock interaction between the outflows from IRS1 and IRS2. Theta 1 Orionis C/D: Located in the Orion Trapezium Cluster, Theta 1 C is one of the youngest and nearest high-mass (O5-O7) stars. The star is also known to be a close binary system. We traced the orbital motion from 1997.8 to 2004.8 using visual and NIR bispectrum speckle interferometry at the BTA 6 m telescope. In 2005.9, we obtained first IOTA long-baseline interferometry on the Theta 1 C system, allowing us to derive preliminary solutions for the dynamical orbit and the dynamical mass. Taking the measured flux ratio and the derived location in the HR-diagram into account, we estimated the spectral types and masses of Theta 1 Ori C1 and C2 to be O5.5 (M=34.0 M_sun) and O9.5 (M=15.5 M_sun), respectively. Thus, the companion C2 appears to be much more massive than previously thought, suggesting strong wind-wind interaction during the periastron passage, which we predict for epoch 2007.5 with a small physical separation of only approx. 1.5 AU. From the IOTA data on Theta 1 Ori C, we reconstructed the first optical aperture synthesis image of a young star. We also obtained IOTA data for Theta 1 Ori D, which appears resolved, perhaps indicating the presence of a close, faint companion. Eta Carinae: Using VLTI/AMBER, we performed the first NIR spectro-interferometry of the Luminous Blue Variable (LBV) Eta Car, simultaneously obtaining high spatial and spectral resolutions (R=1,500 and 12,000). The measured wavelength-dependent visibilities, differential phases, and closure phases were used to constrain the geometry of the continuum-emitting region, as well as the Br Gamma 2.166 micron and He I 2.059 micron line-emitting region. We compared the measured visibilities with predictions of the radiative transfer model of Hillier et al. (2001), finding good agreement. For the interpretation of the non-zero differential and closure phases measured within the Br Gamma line, we present a simple geometric model of an inclined, latitude-dependent wind zone. Thus, our observations support theoretical models of anisotropic winds from fast-rotating, luminous hot stars with enhanced high-velocity mass loss near the polar regions. In the He I line, we measured non-zero phases as well, indicating asymmetries in the brightness distribution, which we discuss in the context of wind-wind interaction between Eta Car and its hypothetical hot binary companion. Using simulations, we examined the possibility to directly detect this companion in future observations. Besides these astrophysical results of my dissertation, I present work related to methodological and technical aspects of infrared interferometry. The principles of a data reduction software developed for IOTA/IONIC3 and a pipeline for VLTI/AMBER are discussed. Furthermore, I summarize comparative studies which aim to evaluate the performance of different image reconstruction algorithms in order to explore the prospects and limitations of optical aperture synthesis imaging.

Holograph and Interferometry.

ERIC Educational Resources Information Center

Altman, Thomas C.

1992-01-01

Describes a method to create holograms for use in different interferometry techniques. Students utilize these techniques in experiments to study the structural integrity of a clarinet reed and the effects of temperature on objects. (MDH)

Fringe Formation in Dual-Hologram Interferometry

NASA Technical Reports Server (NTRS)

Burner, A. W.

1989-01-01

A first order geometrical optics treatment of holograms combined with the generation of interference fringes by two point sources is used to describe reference fringe formation in non-diffuse dual-hologram interferometry.

Frontolysis by surface heat flux in the Agulhas Return Current region with a focus on mixed layer processes: observation and a high-resolution CGCM

NASA Astrophysics Data System (ADS)

Ohishi, Shun; Tozuka, Tomoki; Komori, Nobumasa

2016-12-01

Detailed mechanisms for frontogenesis/frontolysis of the Agulhas Return Current (ARC) Front, defined as the maximum of the meridional sea surface temperature (SST) gradient at each longitude within the ARC region (40°-50°E, 55°-35°S), are investigated using observational datasets. Due to larger (smaller) latent heat release to the atmosphere on the northern (southern) side of the front, the meridional gradient of surface net heat flux (NHF) is found throughout the year. In austral summer, surface warming is weaker (stronger) on the northern (southern) side, and thus the NHF tends to relax the SST front. The weaker (stronger) surface warming, at the same time, leads to the deeper (shallower) mixed layer on the northern (southern) side. This enhances the frontolysis, because deeper (shallower) mixed layer is less (more) sensitive to surface warming. In austral winter, stronger (weaker) surface cooling on the northern (southern) side contributes to the frontolysis. However, deeper (shallower) mixed layer is induced by stronger (weaker) surface cooling on the northern (southern) side and suppresses the frontolysis, because the deeper (shallower) mixed layer is less (more) sensitive to surface cooling. Therefore, the frontolysis by the NHF becomes stronger (weaker) through the mixed layer processes in austral summer (winter). The cause of the meridional gradient of mixed layer depth is estimated using diagnostic entrainment velocity and the Monin-Obukhov depth. Furthermore, the above mechanisms obtained from the observation are confirmed using outputs from a high-resolution coupled general circulation model. Causes of model biases are also discussed.

Causes of Interannual Variability over the Southern Hemispheric Tropospheric Ozone Maximum

NASA Technical Reports Server (NTRS)

Liu, Junhua; Rodriguez, Jose M.; Steenrod, Stephen D.; Douglass, Anne R.; Logan, Jennifer A.; Olsen, Mark A.; Wargan, Krzysztog; Ziemke, Jerald R.

2017-01-01

We examine the relative contribution of processes controlling the interannual variability (IAV) of tropospheric ozone over four sub-regions of the southern hemispheric tropospheric ozone maximum (SHTOM) over a 20-year period. Our study is based on hindcast simulations from the National Aeronautics and Space Administration Global Modeling Initiative chemistry transport model (NASA GMI-CTM) of tropospheric and stratospheric chemistry, driven by assimilated Modern Era Retrospective Analysis for Research and Applications (MERRA) meteorological fields. Our analysis shows that over SHTOM region, the IAV of the stratospheric contribution is the most important factor driving the IAV of upper tropospheric ozone (270 hectopascals), where ozone has a strong radiative effect. Over the South Atlantic region, the contribution from surface emissions to the IAV of ozone exceeds that from stratospheric input at and below 430 hectopascals. Over the South Indian Ocean, the IAV of stratospheric ozone makes the largest contribution to the IAV of ozone with little or no influence from surface emissions at 270 and 430 hectopascals in austral winter. Over the tropical South Atlantic region, the contribution from IAV of stratospheric input dominates in austral winter at 270 hectopascals and drops to less than half but is still significant at 430 hectopascals. Emission contributions are not significant at these two levels. The IAV of lightning over this region also contributes to the IAV of ozone in September and December. Over the tropical southeastern Pacific, the contribution of the IAV of stratospheric input is significant at 270 and 430 hectopascals in austral winter, and emissions have little influence.

Causes of interannual variability over the southern hemispheric tropospheric ozone maximum

NASA Astrophysics Data System (ADS)

Liu, Junhua; Rodriguez, Jose M.; Steenrod, Stephen D.; Douglass, Anne R.; Logan, Jennifer A.; Olsen, Mark A.; Wargan, Krzysztof; Ziemke, Jerald R.

2017-03-01

We examine the relative contribution of processes controlling the interannual variability (IAV) of tropospheric ozone over four sub-regions of the southern hemispheric tropospheric ozone maximum (SHTOM) over a 20-year period. Our study is based on hindcast simulations from the National Aeronautics and Space Administration Global Modeling Initiative chemistry transport model (NASA GMI-CTM) of tropospheric and stratospheric chemistry, driven by assimilated Modern Era Retrospective Analysis for Research and Applications (MERRA) meteorological fields. Our analysis shows that over SHTOM region, the IAV of the stratospheric contribution is the most important factor driving the IAV of upper tropospheric ozone (270 hPa), where ozone has a strong radiative effect. Over the South Atlantic region, the contribution from surface emissions to the IAV of ozone exceeds that from stratospheric input at and below 430 hPa. Over the South Indian Ocean, the IAV of stratospheric ozone makes the largest contribution to the IAV of ozone with little or no influence from surface emissions at 270 and 430 hPa in austral winter. Over the tropical South Atlantic region, the contribution from IAV of stratospheric input dominates in austral winter at 270 hPa and drops to less than half but is still significant at 430 hPa. Emission contributions are not significant at these two levels. The IAV of lightning over this region also contributes to the IAV of ozone in September and December. Over the tropical southeastern Pacific, the contribution of the IAV of stratospheric input is significant at 270 and 430 hPa in austral winter, and emissions have little influence.

Improved atmosphere-ocean coupled modeling in the tropics for climate prediction

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

Zhang, Minghua

2015-01-01

We investigated the initial development of the double ITCZ in the Community Climate System Model (CCSM Version 3) in the central Pacific. Starting from a resting initial condition of the ocean in January, the model developed a warm bias of sea-surface temperature (SST) in the central Pacific from 5oS to 10oS in the first three months. We found this initial bias to be caused by excessive surface shortwave radiation that is also present in the standalone atmospheric model. The initial bias is further amplified by biases in both surface latent heat flux and horizontal heat transport in the upper ocean.more » These biases are caused by the responses of surface winds to SST bias and the thermocline structure to surface wind curls. We also showed that the warming biases in surface solar radiation and latent heat fluxes are seasonally offset by cooling biases from reduced solar radiation after the austral summer due to cloud responses and in the austral fall due to enhanced evaporation when the maximum SST is closest to the equator. The warming biases from the dynamic heat transport by ocean currents however stay throughout all seasons once they are developed, which are eventually balanced by enhanced energy exchange and penetration of solar radiation below the mixed layer. Our results also showed that the equatorial cold tongue develops after the warm biases in the south central Pacific, and the overestimation of surface shortwave radiation recurs in the austral summer in each year.« less

Last light: Sunset at the South Pole | National Oceanic and Atmospheric

Science.gov Websites

Observatory, Sunday March 20 marks the start of the austral autumn, the last time they see the sun for six months. The National Science Foundation's Atmospheric Research Observatory illuminated by the sun

Timing and rates of long-term landscape evolution in Southern Argentina

NASA Astrophysics Data System (ADS)

Kollenz, S.; Glasmacher, P. A.

2013-12-01

The eastern Argentina South Atlantic passive continental margin is distinguished by a very flat topography. Out of the so called Pampean flat two mountain ranges are arising. These mountain ranges, the Sierras Australes and the Sierras Septentrionales, are located in the State of Buenos Aires south of the capital Buenos Aires. North of the Sierras Septentrionales the Salado basin is located. The Sierras Septentrionales and the Sierras Australes are also divided by a smaller intracratonic basin. Further in the South the Colorado basin is located. The Sierras Australes is a variscian fold belt originated by strong phases of metamorphosis, but till now it is unclear by how many tectonic phases the area was influenced (Tomezzoli & Vilas, 1999). It consists of Proterozoic to Paleozoic rocks. The Sierras Septentrionales consists mainly of Precambrian crystalline rocks. The Precambrian sequences are overlain by younger Sediments (Cingolani, 2010). The aim is to understand the long-term landscape evolution of the area by quantifiying erosion- and exhumation-rates and by dating ancient rock-uplift-events. Another goal is to find out how the opening of the south atlantic took effect on this region. To fulfill this goal, thermochronological techniques, such as fission-track dating and (U-Th-Sm)/He dating has been applied to samples from the region. Because there was no low- temperature thermochronology done in this area, both techniques were applied on apatites and zircons. Furthermore, numerical modeling of the cooling history has provided the data base for the quantification of the exhumation rates. The data-set shows clusters of different ages which can be linked to tectonic activities during late Paleozoic times. Also the thermokinematic modeling is leading to new insights of the evolution of both mountain ranges and shows patterns of ongoing tectonic processes in this region. Caltculated exhumation rates show also varying cooling historys and the influence of tectonics throughout the research area. References: Renata Nela Tomezzoli and Juan Francisco Vilas (1999): Palaeomagnetic constraints on the age of deformation of the Sierras Australes thrust and fold belt, Argentina. Geophys. J. Int. (1999) 138, 857-870 Carlos A. Cingolani (2010): The Tandilia System of Argentina as a southern extension of the Rio de la Plata craton: an overview, Int. J. Earth. Sci. (Geol. Rundsch.) (2011) 100, 221-242

Seasonal and annual variability of coastal sulphur plumes in the northern Benguela upwelling system

PubMed Central

Dadou, Isabelle

2018-01-01

We investigated the seasonal and annual variability of surface sulphur plumes in the northern Benguela upwelling system off Namibia because of their significant impacts on the marine ecosystem, fishing industry, aquaculture farming and tourism due to their toxic properties. We identified the sulphur plumes in ocean colour satellite data of the medium resolution imaging spectrometer (MERIS) for the 2002–2012 time period using the differences in the spectral properties of Namibian Benguela optical water types. The sulphur events have a strong seasonal cycle with pronounced main and off-seasons forced by local and remote-driven processes. The main peak season is in late austral summer and early austral autumn at the beginning of the annual upwelling cycle caused by increasing equatorwards alongshore winds. The sulphur plume activity is high between February and April during the seasonal oxygen minimum associated with the seasonal reduction of cross-shore ventilation of the bottom waters, the seasonal southernmost position of the Angola Benguela Frontal Zone, the seasonal maximum of water mass fractions of South Atlantic and Angola Gyre Central Waters as well as the seasonal arrival of the downwelling coastal trapped waves. The off-season is in austral spring and early austral summer during increased upwelling intensity and enhanced oxygen supply. The annual variability of sulphur events is characterized by very high activities in years 2004, 2005 and 2010 interrupted by periods of lower activity in years 2002 to 2003, 2006 to 2009 and 2011 to 2012. This result can be explained by the relative contributions or adding effects of local and remote-driven forces (from the equatorial area). The probability for the occurrence of sulphur plumes is enhanced in years with a lower annual mean of upwelling intensity, decreased oxygen supply associated with decreased lateral ventilation of bottom waters, more southern position of the Angola Benguela Frontal Zone, increased mass fraction of South Atlantic Central Water and stronger downwelling coastal trapped waves. Understanding of the variability and forcing processes of the toxic sulphur events will help in the future to monitor and forecast them as well as to manage their social and economic consequences in the northern Benguela upwelling system off Namibia. PMID:29420587

Seismo-stratigraphic evolution of the northern Austral Basin and its possible relation to the Andean tectonics, onshore Argentina.

NASA Astrophysics Data System (ADS)

Sachse, Victoria; Anka, Zahie; Pagan, Facundo; Kohler, Guillermina; Cagnolatti, Marcelo; di Primio, Rolando; Rodriguez, Jorge

2013-04-01

The Austral Basin is situated in a formerly and recently high active tectonic zone in southern Argentina. The opening of the South Atlantic to the east, the opening of the Drake Passage in the south, and the subduction related to the rise of the Andes to the west, had major influence on the study area. To identify the impact of the tectonic events on basin geometry, sediment thickness and depocenter migration through time, 2D seismic interpretation was performed for an area of approx. 180.000 km² covering the onshore northern Austral Basin. A total of 10 seismic horizons were mapped and tied to the stratigraphy from well reports, representing 9 syn- and post- rift sequences. The main units are: Basement (U1), Jurassic Tobifera Formation (U2), Early Cretaceous (U3), Late Cretaceous (U4), sub-unit Campanian (U4A), Paleocene (U5), Eocene (U6), Oligocene (U7), Miocene (U8), and Plio-Pleistocene (U9). Main tectonic events are identified representing the break-up phase forming graben systems and the evolution from the ancient backarc Rocas Verdes Basin to the foreland Austral Basin. Inversion and changes in the tectonic regime are concomitant with onlapping and thinning of the base of the Upper Cretaceous to Campanian sediments, while the Top of the Upper Cretaceous represents a Maastrichtian unconformity. Units depth maps show a triangular geometry since the Jurassic, tracing the north-eastern basement high and deepening to the south. Since the Campanian the former geometry of basin fill changed and deepening to the south stopped. Beginning of the foreland phase is assigned to this time as well as changes in the stress regime. Paleogene times are marked by a relatively high sedimentation rate coupled with enduring thermal subsidence, on-going rise of the Andes and changes in the convergence rates of the Nazca relative to the South American plate. Onset of sediment supply from the Andes (Incaic phase) resulted in enhanced sedimentation rates during the Paleocene, coupled with important basin subsidence at Andes foothills. An E-W transpressive deformation occurred during late Oligocene and Miocene, initiated by significant changes of plate motion between Nazca and South American plate, driving the Quechua phase of the Andean uplift. Hence, enhanced sedimentation from the rising Andes was renewed since a late Miocene unconformity.

Phase shifting white light interferometry using colour CCD for optical metrology and bio-imaging applications

NASA Astrophysics Data System (ADS)

Upputuri, Paul Kumar; Pramanik, Manojit

2018-02-01

Phase shifting white light interferometry (PSWLI) has been widely used for optical metrology applications because of their precision, reliability, and versatility. White light interferometry using monochrome CCD makes the measurement process slow for metrology applications. WLI integrated with Red-Green-Blue (RGB) CCD camera is finding imaging applications in the fields optical metrology and bio-imaging. Wavelength dependent refractive index profiles of biological samples were computed from colour white light interferograms. In recent years, whole-filed refractive index profiles of red blood cells (RBCs), onion skin, fish cornea, etc. were measured from RGB interferograms. In this paper, we discuss the bio-imaging applications of colour CCD based white light interferometry. The approach makes the measurement faster, easier, cost-effective, and even dynamic by using single fringe analysis methods, for industrial applications.

Developing Wide-Field Spatio-Spectral Interferometry for Far-Infrared Space Applications

NASA Technical Reports Server (NTRS)

Leisawitz, David; Bolcar, Matthew R.; Lyon, Richard G.; Maher, Stephen F.; Memarsadeghi, Nargess; Rinehart, Stephen A.; Sinukoff, Evan J.

2012-01-01

Interferometry is an affordable way to bring the benefits of high resolution to space far-IR astrophysics. We summarize an ongoing effort to develop and learn the practical limitations of an interferometric technique that will enable the acquisition of high-resolution far-IR integral field spectroscopic data with a single instrument in a future space-based interferometer. This technique was central to the Space Infrared Interferometric Telescope (SPIRIT) and Submillimeter Probe of the Evolution of Cosmic Structure (SPECS) space mission design concepts, and it will first be used on the Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII). Our experimental approach combines data from a laboratory optical interferometer (the Wide-field Imaging Interferometry Testbed, WIIT), computational optical system modeling, and spatio-spectral synthesis algorithm development. We summarize recent experimental results and future plans.

Satellite radar interferometry measures deformation at Okmok Volcano

USGS Publications Warehouse

Lu, Zhong; Mann, Dorte; Freymueller, Jeff

1998-01-01

The center of the Okmok caldera in Alaska subsided 140 cm as a result of its February– April 1997 eruption, according to satellite data from ERS-1 and ERS-2 synthetic aperture radar (SAR) interferometry. The inferred deflationary source was located 2.7 km beneath the approximate center of the caldera using a point source deflation model. Researchers believe this source is a magma chamber about 5 km from the eruptive source vent. During the 3 years before the eruption, the center of the caldera uplifted by about 23 cm, which researchers believe was a pre-emptive inflation of the magma chamber. Scientists say such measurements demonstrate that radar interferometry is a promising spaceborne technique for monitoring remote volcanoes. Frequent, routine acquisition of images with SAR interferometry could make near realtime monitoring at such volcanoes the rule, aiding in eruption forecasting.

Interferometry in the Era of Very Large Telescopes

NASA Technical Reports Server (NTRS)

Barry, Richard K.

2010-01-01

Research in modern stellar interferometry has focused primarily on ground-based observatories, with very long baselines or large apertures, that have benefited from recent advances in fringe tracking, phase reconstruction, adaptive optics, guided optics, and modern detectors. As one example, a great deal of effort has been put into development of ground-based nulling interferometers. The nulling technique is the sparse aperture equivalent of conventional coronography used in filled aperture telescopes. In this mode the stellar light itself is suppressed by a destructive fringe, effectively enhancing the contrast of the circumstellar material located near the star. Nulling interferometry has helped to advance our understanding of the astrophysics of many distant objects by providing the spatial resolution necessary to localize the various faint emission sources near bright objects. We illustrate the current capabilities of this technique by describing the first scientific results from the Keck Interferometer Nuller that combines the light from the two largest optical telescopes in the world including new, unpublished measurements of exozodiacal dust disks. We discuss prospects in the near future for interferometry in general, the capabilities of secondary masking interferometry on very large telescopes, and of nulling interferometry using outriggers on very large telescopes. We discuss future development of a simplified space-borne NIR nulling architecture, the Fourier-Kelvin Stellar Interferometer, capable of detecting and characterizing an Earth twin in the near future and how such a mission would benefit from the optical wavelength coverage offered by large, ground-based instruments.

Late Paleozoic transpression in Buenos Aires and northeast Patagonia ranges, Argentina

NASA Astrophysics Data System (ADS)

Rossello, E. A.; Massabie, A. C.; López-Gamundí, O. R.; Cobbold, P. R.; Gapais, D.

1997-12-01

Paleozoic sediments are present in three regions in eastern central Argentina: (1) the Sierras Australes of Buenos Aires, (2) Sierras Septentrionales of Buenos Aires and (3) Northeast Patagonia. All of these deposits share a common deformational imprint imparted by late Paleozoic Gondwanan deformation. Exposures of these rocks are scattered, variably deformed, and isolated by younger sediments deposited in basins related to the Mesozoic through Tertiary opening of the South Atlantic such as the offshore Colorado Basin. The Sierras Australes of Buenos Aires outcrops are the best preserved. They are mostly located along the Sierras Australes foldbelt, with minor outliers distributed in the adjacent Claromec-basin. The Tunas Formation (early-early late? Permian) is the uppermost unit of the Pillahuincó Group (late Carboniferous-Permian) and is crucial to the understanding of the tectono-sedimentary evolution of the region during the late Paleozoic. The underlying units of the Pillahuincó Group (Sauce Grande, Piedra Azul and Bonete Formations) exhibit a depositional and compositional history characterized by glaciomarine sedimentation and postglacial transgression. They are also characterized by rather uniform quartz-rich compositions indicative of a cratonic provenance from the La Plata craton to the NE. In contrast, the sandstone-rich Tunas Formation has low quartz contents, and abundant volcanic and metasedimentary fragments; paleocurrents are consistently from the SW. Glassrich tuffs are interbedded with sandstone in the upper half of the Tunas Formation. The age of the deformation in the Sierras Australes is Permian and early-middle Triassic. This is based on metamorphic events indicated by formation of illite at 282 ± 3 Ma, 273 ± 8 Ma, 265 ± 3 Ma, and 260 ± 3 Ma ( {K}/{Ar} illite) in the Silurian Curamalal Group. Evidence of syntectonic magmatism is provided by a radiometric date of 245 ± 12 Ma ( {K}/{Ar} hornblende) for the López Lecube Granite, immediately west of the Sierras Australes. In the Sierras Septentrionales of Buenos Aires, Precambrian through early Paleozoic deposits of La Tinta, Sierras Bayas, Las Aguilas and Balcarce Formations rest on Precambrian crystalline basement of the La Plata craton. These exposed rocks are affected by subordinate, right lateral wrench faulting; some thrusting indicates tectonic transport toward the NE. In northeast Patagonia (Sierra Grande region) synkinematic deformation of early Permian (261 ± 5 Ma, {Rb}/{Sr} whole rock) age has been identified in Silurian metasediments of the Sierra Grande Formation. Bands of deformation in Sierra Grande quartzites indicate right lateral wrenching in a N-S direction. Contraction in a NE-SW direction is evidenced by folding. Three stages of tectonic evolution can be discerned for the above regions: (1) Early Paleozoic platform sedimentation, punctuated by episodes of accelerated subsidence during the Silurian and early Devonian, as shown by transgressive episodes, (2) late Paleozoic sedimentation and deformation, and (3) Meso-Cenozoic extensional inversion due to the South Atlantic opening. The late Paleozoic sedimentation and deformation (stage 2) includes late Carboniferous-earliest Permian glacial deposits of the Sierras Australes and Colorado offshore basin, deposited during an initial phase of extension, and cratonward foreland subsidence triggered sedimentation of the synorogenic deposits of the Permian Tunas Formation. Tuffs are intercalated in the upper half of this unit. These tuffs are associated with the silicic volcanism along the Andes and Patagonia (Choiyoi magmatic province) that peaked between the late early Permian and late Permian. Likewise, the first widespread appearance of tuffs in the Karoo basin is in the Whitehill Formation, of late early Permian (260 Ma) age. The deformation described in this paper can be considered as part of a large scale intracontinental deformation in SW Gondwanaland inboard of an Andean-type compressive margin. This deformation is characterized by transpression (right lateral wrenching) combined with overthrusting to the NE and N-S horizontal contraction.

Resolving the dusty circumstellar environment of the A[e] supergiant HD 62623 with the VLTI/MIDI

NASA Astrophysics Data System (ADS)

Meilland, A.; Kanaan, S.; Borges Fernandes, M.; Chesneau, O.; Millour, F.; Stee, Ph.; Lopez, B.

2010-03-01

Context. B[e] stars are hot stars surrounded by circumstellar gas and dust which is responsible for the presence of emission lines and IR-excess in their spectra. How dust can be formed in this highly illuminated and diluted environment remains an open issue. Aims: HD 62623 is one of the very few A-type supergiants showing the B[e] phenomenon. We studied the geometry of its circumstellar envelope in the mid-infrared using long-baseline interferometry, which is the only observing technique able to spatially resolve objects smaller than a few tens of milliarcseconds. Methods: We obtained nine calibrated visibility measurements between October 2006 and January 2008 using the VLTI/MIDI instrument in SCI-PHOT mode and PRISM spectral dispersion mode with projected baselines ranging from 13 to 71 m and with various position angles (PA). We used geometrical models and physical modeling with a radiative transfer code to analyze these data. Results: The dusty circumstellar environment of HD 62623 is partially resolved by the VLTI/MIDI, even with the shortest baselines. The environment is flattened (a/b~1.3±0.1) and can be separated into two components: a compact one whose extension grows from 17 mas at 8 μm to 30 mas at 9.6 μm and stays almost constant up to 13 μm, and a more extended one that is over-resolved even with the shortest baselines. Using the radiative transfer code MC3D, we managed to model HD 62623's circumstellar environment as a dusty disk with an inner radius of 3.85±0.6 AU, an inclination angle of 60±10°, and a mass of 2 × 10-7 M_⊙. Conclusions: It is the first time that the dusty disk inner rim of a supergiant star exhibiting the B[e] phenomenon is significantly constrained. The inner gaseous envelope likely contributes up to 20% to the total N band flux and acts like a reprocessing disk. Finally, the hypothesis of a stellar wind deceleration by the companion's gravitational effects remains the most probable case since the bi-stability mechanism does not seem to be efficient for this star. Based on observations made with ESO Telescopes at Paranal Observatory under programs 078.D-O511 and 080.D.0181.

Higher-dimensional phase imaging

NASA Astrophysics Data System (ADS)

Huntley, Jonathan M.

2010-04-01

Traditional full-field interferometric techniques (speckle, moiré, holography etc) provide 2-D phase images, which encode the surface deformation state of the object under test. Over the past 15 years, the use of additional spatial or temporal dimensions has been investigated by a number of research groups. Early examples include the measurement of 3-D surface profiles by temporally-varying projected fringe patterns, and dynamic speckle interferometry. More recently (the past 5 years) a family of related techniques (Wavelength Scanning Interferometry, Phase Contrast Spectral Optical Coherence Tomography (OCT), and Tilt Scanning Interferometry) has emerged that provides the volume deformation state of the object. The techniques can be thought of as a marriage between the phase sensing capabilities of Phase Shifting Interferometry and the depth-sensing capabilities of OCT. Finally, in the past 12 months a technique called Hyperspectral Interferometry has been proposed in which absolute optical path distributions are obtained in a single shot through the spectral decomposition of a white light interferogram, and for which the additional dimension therefore corresponds to the illumination wavenumber. An overview of these developments, and the related issue of robust phase unwrapping of noisy 3-D wrapped phase volumes, is presented in this paper.

Spatial phase-shift dual-beam speckle interferometry.

PubMed

Gao, Xinya; Yang, Lianxiang; Wang, Yonghong; Zhang, Boyang; Dan, Xizuo; Li, Junrui; Wu, Sijin

2018-01-20

The spatial phase-shift technique has been successfully applied to an out-of-plane speckle interferometry system. Its application to a pure in-plane sensitive system has not been reported yet. This paper presents a novel optical configuration that enables the application of the spatial phase-shift technique to pure in-plane sensitive dual-beam speckle interferometry. The new spatial phase-shift dual-beam speckle interferometry (SPS-DBSP) uses a dual-beam in-plane electronic speckle pattern interferometry configuration with individual aperture shears, avoiding the interference in the object plane by the use of a low-coherence source, and different optical paths. The measured object is illuminated by two incoherent beams that are generated by a delay line, which is larger than the coherence length of the laser. The two beams reflected from the object surface interfere with each other at the CCD plane because of different optical paths. A spatial phase shift is introduced by the angle between the two apertures when they are mapped to the same optical axis. The phase of the in-plane deformation can directly be extracted from the speckle patterns by the Fourier transform method. The capability of SPS-DBSI is demonstrated by theoretical discussion as well as experiments.

Kitt Peak Speckle Interferometry of Close Visual Binary Stars (Abstract)

NASA Astrophysics Data System (ADS)

Gener, R.; Rowe, D.; Smith, T. C.; Teiche, A.; Harshaw, R.; Wallace, D.; Weise, E.; Wiley, E.; Boyce, G.; Boyce, P.; Branston, D.; Chaney, K.; Clark, R. K.; Estrada, C.; Estrada, R.; Frey, T.; Green, W. L.; Haurberg, N.; Jones, G.; Kenney, J.; Loftin, S.; McGieson, I.; Patel, R.; Plummer, J.; Ridgely, J.; Trueblood, M.; Westergren, D.; Wren, P.

2014-12-01

(Abstract only) Speckle interferometry can be used to overcome normal seeing limitations by taking many very short exposures at high magnification and analyzing the resulting speckles to obtain the position angles and separations of close binary stars. A typical speckle observation of a close binary consists of 1,000 images, each 20 milliseconds in duration. The images are stored as a multi-plane FITS cube. A portable speckle interferometry system that features an electron-multiplying CCD camera was used by the authors during two week-long observing runs on the 2.1-meter telescope at Kitt Peak National Observatory to obtain some 1,000 data cubes of close binaries selected from a dozen different research programs. Many hundreds of single reference stars were also observed and used in deconvolution to remove undesirable atmospheric and telescope optical effects. The database of well over one million images was reduced with the Speckle Interferometry Tool of platesolve3. A few sample results are provided. During the second Kitt Peak run, the McMath-Pierce 1.6- and 0.8-meter solar telescopes were evaluated for nighttime speckle interferometry, while the 0.8-meter Coude feed was used to obtain differential radial velocities of short arc binaries.

Kitt Peak Speckle Interferometry of Close Visual Binary Stars

NASA Astrophysics Data System (ADS)

Genet, Russell M.; Rowe, David; Smith, Thomas C.; Teiche, Alex; Harshaw, Richard; Wallace, Daniel; Weise, Eric; Wiley, Edward; Boyce, Grady; Boyce, Patrick; Branston, Detrick; Chaney, Kayla; Clark, R. Kent; Estrada, Chris; Frey, Thomas; Estrada, Reed; Green, Wayne; Haurberg, Nathalie; Kenney, John; Jones, Greg; Loftin, Sheri; McGieson, Izak; Patel, Rikita; Plummer, Josh; Ridgely, John; Trueblood, Mark; Westergren, Donald; Wren, Paul

2015-09-01

Speckle interferometry can be used to overcome normal seeing limitations by taking many very short exposures at high magnification and analyzing the resulting speckles to obtain the position angles and separations of close binary stars. A typical speckle observation of a close binary consists of 1000 images, each 20 milliseconds in duration. The images are stored as a multi-plane FITS cube. A portable speckle interferometry system that features an electronmultiplying CCD camera was used by the authors during two week-long observing runs on the 2.1-meter telescope at Kitt Peak National Observatory to obtain some 1000 data cubes of close binaries selected from a dozen different research programs. Many hundreds of single reference stars were also observed and used in deconvolution to remove undesirable atmospheric and telescope optical effects. The data base of well over one million images was reduced with the Speckle Interferometry Tool of PlateSolve 3. A few sample results are provided. During the second Kitt Peak run, the McMath-Pierce 1.6- and 0.8-meter solar telescopes were evaluated for nighttime speckle interferometry, while the 0.8-meter Coude feed was used to obtain differential radial velocities of short arc binaries.

Analyzing refractive index profiles of confined fluids by interferometry.

PubMed

Kienle, Daniel F; Kuhl, Tonya L

2014-12-02

This work describes an interferometry data analysis method for determining the optical thickness of thin films or any variation in the refractive index of a fluid or film near a surface. In particular, the method described is applied to the analysis of interferometry data taken with a surface force apparatus (SFA). The technique does not require contacting or confining the fluid or film. By analyzing interferometry data taken at many intersurface separation distances out to at least 300 nm, the properties of a film can be quantitatively determined. The film can consist of material deposited on the surface, like a polymer brush, or variation in a fluid's refractive index near a surface resulting from, for example, a concentration gradient, depletion in density, or surface roughness. The method is demonstrated with aqueous polyethylenimine (PEI) adsorbed onto mica substrates, which has a large concentration and therefore refractive index gradient near the mica surface. The PEI layer thickness determined by the proposed method is consistent with the thickness measured by conventional SFA methods. Additionally, a thorough investigation of the effects of random and systematic error in SFA data analysis and modeling via simulations of interferometry is described in detail.

Performance Evaluation of Nano-JASMINE

NASA Astrophysics Data System (ADS)

Hatsutori, Y.; Kobayashi, Y.; Gouda, N.; Yano, T.; Murooka, J.; Niwa, Y.; Yamada, Y.

We report the results of performance evaluation of the first Japanese astrometry satellite, Nano-JASMINE. It is a very small satellite and weighs only 35 kg. It aims to carry out astrometry measurement of nearby bright stars (z ≤ 7.5 mag) with an accuracy of 3 milli-arcseconds. Nano-JASMINE will be launched by Cyclone-4 rocket in August 2011 from Brazil. The current status is in the process of evaluating the performances. A series of performance tests and numerical analysis were conducted. As a result, the engineering model (EM) of the telescope was measured to be achieving a diffraction-limited performance and confirmed that it has enough performance for scientific astrometry.

Small-Grid Dithers for the JWST Coronagraphs

NASA Technical Reports Server (NTRS)

Lajoie, Charles-Philippe; Soummer, Remi; Pueyo, Laurent; Hines, Dean C.; Nelan, Edmund P.; Perrin, Marshall; Clampin, Mark; Isaacs, John C.

2016-01-01

We discuss new results of coronagraphic simulations demonstrating a novel mode for JWST that utilizes sub-pixel dithered reference images, called Small-Grid Dithers, to optimize coronagraphic PSF subtraction. These sub-pixel dithers are executed with the Fine Steering Mirror under fine guidance, are accurate to approx.2-3 milliarcseconds (1-s/axis), and provide ample speckle diversity to reconstruct an optimized synthetic reference PSF using LOCI or KLIP. We also discuss the performance gains of Small-Grid Dithers compared to the standard undithered scenario, and show potential contrast gain factors for the NIRCam and MIRI coronagraphs ranging from 2 to more than 10, respectively.

Radio Imaging of Envelopes of Evolved Stars

NASA Astrophysics Data System (ADS)

Cotton, Bill

2018-04-01

This talk will cover imaging of stellar envelopes using radio VLBI techniques; special attention will be paid to the technical differences between radio and optical/IR interferomery. Radio heterodyne receivers allow a straightforward way to derive spectral cubes and full polarization observations. Milliarcsecond resolution of very bright, i.e. non thermal, emission of molecular masers in the envelopes of evolved stars can be achieved using VLBI techniques with baselines of thousands of km. Emission from SiO, H2O and OH masers are commonly seen at increasing distance from the photosphere. The very narrow maser lines allow accurate measurements of the velocity field within the emitting region.

Generalized parametric down conversion, many particle interferometry, and Bell's theorem

NASA Technical Reports Server (NTRS)

Choi, Hyung Sup

1992-01-01

A new field of multi-particle interferometry is introduced using a nonlinear optical spontaneous parametric down conversion (SPDC) of a photon into more than two photons. The study of SPDC using a realistic Hamiltonian in a multi-mode shows that at least a low conversion rate limit is possible. The down converted field exhibits many stronger nonclassical phenomena than the usual two photon parametric down conversion. Application of the multi-particle interferometry to a recently proposed many particle Bell's theorem on the Einstein-Podolsky-Rosen problem is given.

A far-infrared spatial/spectral Fourier interferometry laboratory-based testbed instrument

NASA Astrophysics Data System (ADS)

Spencer, Locke D.; Naylor, David A.; Scott, Jeremy P.; Weiler, Vince F.; MacCrimmon, Roderick K.; Sitwell, Geoffrey R. H.; Ade, Peter A. R.

2016-07-01

We describe the current status, including preliminary design, characterization efforts, and recent progress, in the development of a spatial/spectral double Fourier laboratory-based interferometer testbed instrument within the Astronomical Instrumentation Group (AIG) laboratories at the University of Lethbridge, Canada (UL). Supported by CRC, CFI, and NSERC grants, this instrument development will provide laboratory demonstration of spatial-spectral interferometry with a concentration of furthering progress in areas including the development of spatial/spectral interferometry observation, data processing, characterization, and analysis techniques in the Far-Infrared (FIR) region of the electromagnetic spectrum.

Optical long baseline intensity interferometry: prospects for stellar physics

NASA Astrophysics Data System (ADS)

Rivet, Jean-Pierre; Vakili, Farrokh; Lai, Olivier; Vernet, David; Fouché, Mathilde; Guerin, William; Labeyrie, Guillaume; Kaiser, Robin

2018-06-01

More than sixty years after the first intensity correlation experiments by Hanbury Brown and Twiss, there is renewed interest for intensity interferometry techniques for high angular resolution studies of celestial sources. We report on a successful attempt to measure the bunching peak in the intensity correlation function for bright stellar sources with 1 meter telescopes (I2C project). We propose further improvements of our preliminary experiments of spatial interferometry between two 1 m telescopes, and discuss the possibility to export our method to existing large arrays of telescopes.

Optics in engineering measurement; Proceedings of the Meeting, Cannes, France, December 3-6, 1985

NASA Technical Reports Server (NTRS)

Fagan, William F. (Editor)

1986-01-01

The present conference on optical measurement systems considers topics in the fields of holographic interferometry, speckle techniques, moire fringe and grating methods, optical surface gaging, laser- and fiber-optics-based measurement systems, and optics for engineering data evaluation. Specific attention is given to holographic NDE for aerospace composites, holographic interferometry of rotating components, new developments in computer-aided holography, electronic speckle pattern interferometry, mass transfer measurements using projected fringes, nuclear reactor photogrammetric inspection, a laser Doppler vibrometer, and optoelectronic measurements of the yaw angle of projectiles.

SPIPS: Spectro-Photo-Interferometry of Pulsating Stars

NASA Astrophysics Data System (ADS)

Mérand, Antoine

2017-10-01

SPIPS (Spectro-Photo-Interferometry of Pulsating Stars) combines radial velocimetry, interferometry, and photometry to estimate physical parameters of pulsating stars, including presence of infrared excess, color excess, Teff, and ratio distance/p-factor. The global model-based parallax-of-pulsation method is implemented in Python. Derived parameters have a high level of confidence; statistical precision is improved (compared to other methods) due to the large number of data taken into account, accuracy is improved by using consistent physical modeling and reliability of the derived parameters is strengthened by redundancy in the data.

Laser Interferometry Method as a Novel Tool in Endotoxins Research.

PubMed

Arabski, Michał; Wąsik, Sławomir

2017-01-01

Optical properties of chemical substances are widely used at present for assays thereof in a variety of scientific disciplines. One of the measurement techniques applied in physical sciences, with a potential for novel applications in biology, is laser interferometry. This method enables to record the diffusion properties of chemical substances. Here we describe the novel application of laser interferometry in chitosan interactions with lipopolysaccharide by detection of colistin diffusion. The proposed model could be used in simple measurements of polymer interactions with endotoxins and/or biological active compounds, like antibiotics.

Heterodyne Interferometry in InfraRed at OCA-Calern Observatory in the seventies

NASA Astrophysics Data System (ADS)

Gay, J.; Rabbia, Y.

2014-04-01

We report on various works carried four decades ago, so as to develop Heterodyne Interferometry in InfraRed (10 μm) at Calern Observatory (OCA, France), by building an experiment, whose the acronym "SOIRDETE" means "Synthese d'Ouverture en InfraRouge par Detection hETErodyne". Scientific and technical contexts by this time are recalled, as well as basic principles of heterodyne interferometry. The preliminary works and the SOIRDETE experiment are briefly described. Short comments are given in conclusion regarding the difficulties which have prevented the full success of the SOIRDETE experiment.

Local earthquake interferometry of the IRIS Community Wavefield Experiment, Grant County, Oklahoma

NASA Astrophysics Data System (ADS)

Eddy, A. C.; Harder, S. H.

2017-12-01

The IRIS Community Wavefield Experiment was deployed in Grant County, located in north central Oklahoma, from June 21 to July 27, 2016. Data from all nodes were recorded at 250 samples per second between June 21 and July 20 along three lines. The main line was 12.5 km long oriented east-west and consisted of 129 nodes. The other two lines were 5.5 km long north-south oriented with 49 nodes each. During this time, approximately 150 earthquakes of magnitude 1.0 to 4.4 were recorded in the surrounding counties of Oklahoma and Kansas. Ideally, sources for local earthquake interferometry should be near surface events that produce high frequency body waves. Unlike ambient noise seismic interferometry (ANSI), which uses days, weeks, or even months of continuously recorded seismic data, local earthquake interferometry uses only short segments ( 2 min.) of data. Interferometry in this case is based on the cross-correlation of body wave surface multiples where the event source is translated to a reference station in the array, which acts as a virtual source. Multiples recorded between the reference station and all other stations can be cross-correlated to produce a clear seismic trace. This process will be repeated with every node acting as the reference station for all events. The resulting shot gather will then be processed and analyzed for quality and accuracy. Successful application of local earthquake interferometry will produce a crustal image with identifiable sedimentary and basement reflectors and possibly a Moho reflection. Economically, local earthquake interferometry could lower the time and resource cost of active and passive seismic surveys while improving subsurface image quality in urban settings or areas of limited access. The applications of this method can potentially be expanded with the inclusion of seismic events with a magnitude of 1.0 or lower.

State-of-the-art of photorefractive holographic interferometry and potentialities for space applications

NASA Astrophysics Data System (ADS)

Georges, Marc; Lemaire, Philippe; Pauliat, Gilles; Launay, Jean-Claude; Roosen, Gérald

2018-04-01

This paper, "State-of-the-art of photorefractive holographic interferometry and potentialities for space applications," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.

Theoretical investigations on dual-beam illumination electronic speckle pattern interferometry

NASA Astrophysics Data System (ADS)

Goudemand, Nicolas

2006-07-01

Contrary to what is found in most of the existing scientific literature, where a specific frame is developed, the theory of speckle interferometry is (conveniently) presented here as a particular case of the more general theory of holographic interferometry. In addition to the intellectual benefit of dealing with a single unified theory, this brings about many advantages when it comes to discuss fundamental topics such as the three-dimensional evolution of the complex amplitude of the diffuse optical wavefronts, the degree of approximation of the leading formulas, the loss of fringe contrast, the decorrelation effects, the real influence of the terms generally neglected in out-of-focus regions. In the same way, the statistical properties of the speckle fields, usually treated as a separate subject matter, are also integrated in the theory, thus providing a comprehensive knowledge of the qualitative features of speckle interferometry methods, otherwise difficult to understand.

The mid-IR and near-IR interferometry of AGNs: key results and their implications

NASA Astrophysics Data System (ADS)

Kishimoto, M.

2015-09-01

Infrared interferometry has been very productive in directly probing the structure of AGNs at sub-pc scales. With tens of objects already probed in the mid-IR and near-IR, I will summarize the key results and im- plications from this direct exploration. The Keck interferometry in the near-IR and VLTI in the mid-IR shaped the luminosity dependence of the torus size and structure, while the latter also revealed an equatorial structure at several Rsub (dust sublimation radius), and a polar-elongated region at a few tens of Rsub. Notably, this polar component seems to dominate the compact mid-IR flux. This component can persuasively be attributed to a polar outflow. However, interferometry, through emissivity estimations, also indicates that it is not a UV-optically-thin cloud but participating in the obscuration of the nucleus. I will discuss how to accommodate all these facts to build a consistent picture.

Essential features of residual stress determination in thin-walled plane structures in a base of whole field interferometric measurements

NASA Astrophysics Data System (ADS)

Pisarev, Vladimir S.; Odintsev, I.; Balalov, V.; Apalkov, A.

2003-05-01

Sophisticated technique for reliable quantitative deriving residual stress values from initial experimental data, which are inherent in combined implementing the hole drilling method with both holographic and speckle interferometry, is described in detail. The approach developed includes both possible ways of obtaining initial experimental information. The first of them consists of recording a set of required interference fringe patterns, which are resulted from residual stress energy release after through hole drilling, in two orthogonal directions that coincide with principal strain directions. The second way is obtaining a series of interrelated fringe patterns when a direction of either observation in reflection hologram interferometry or dual-beam illumination in speckle interferometry lies arbitrary with respect to definite principal strain direction. A set of the most typical both actual and analogous reference fringe patterns, which are related to both reflection hologram and dual-beam speckle interferometry, are presented.

Absolute marine gravimetry with matter-wave interferometry.

PubMed

Bidel, Y; Zahzam, N; Blanchard, C; Bonnin, A; Cadoret, M; Bresson, A; Rouxel, D; Lequentrec-Lalancette, M F

2018-02-12

Measuring gravity from an aircraft or a ship is essential in geodesy, geophysics, mineral and hydrocarbon exploration, and navigation. Today, only relative sensors are available for onboard gravimetry. This is a major drawback because of the calibration and drift estimation procedures which lead to important operational constraints. Atom interferometry is a promising technology to obtain onboard absolute gravimeter. But, despite high performances obtained in static condition, no precise measurements were reported in dynamic. Here, we present absolute gravity measurements from a ship with a sensor based on atom interferometry. Despite rough sea conditions, we obtained precision below 10 -5  m s -2 . The atom gravimeter was also compared with a commercial spring gravimeter and showed better performances. This demonstration opens the way to the next generation of inertial sensors (accelerometer, gyroscope) based on atom interferometry which should provide high-precision absolute measurements from a moving platform.

Threshold secret sharing scheme based on phase-shifting interferometry.

PubMed

Deng, Xiaopeng; Shi, Zhengang; Wen, Wei

2016-11-01

We propose a new method for secret image sharing with the (3,N) threshold scheme based on phase-shifting interferometry. The secret image, which is multiplied with an encryption key in advance, is first encrypted by using Fourier transformation. Then, the encoded image is shared into N shadow images based on the recording principle of phase-shifting interferometry. Based on the reconstruction principle of phase-shifting interferometry, any three or more shadow images can retrieve the secret image, while any two or fewer shadow images cannot obtain any information of the secret image. Thus, a (3,N) threshold secret sharing scheme can be implemented. Compared with our previously reported method, the algorithm of this paper is suited for not only a binary image but also a gray-scale image. Moreover, the proposed algorithm can obtain a larger threshold value t. Simulation results are presented to demonstrate the feasibility of the proposed method.

A publication database for optical long baseline interferometry

NASA Astrophysics Data System (ADS)

Malbet, Fabien; Mella, Guillaume; Lawson, Peter; Taillifet, Esther; Lafrasse, Sylvain

2010-07-01

Optical long baseline interferometry is a technique that has generated almost 850 refereed papers to date. The targets span a large variety of objects from planetary systems to extragalactic studies and all branches of stellar physics. We have created a database hosted by the JMMC and connected to the Optical Long Baseline Interferometry Newsletter (OLBIN) web site using MySQL and a collection of XML or PHP scripts in order to store and classify these publications. Each entry is defined by its ADS bibcode, includes basic ADS informations and metadata. The metadata are specified by tags sorted in categories: interferometric facilities, instrumentation, wavelength of operation, spectral resolution, type of measurement, target type, and paper category, for example. The whole OLBIN publication list has been processed and we present how the database is organized and can be accessed. We use this tool to generate statistical plots of interest for the community in optical long baseline interferometry.

Aberration correction in wide-field fluorescence microscopy by segmented-pupil image interferometry.

PubMed

Scrimgeour, Jan; Curtis, Jennifer E

2012-06-18

We present a new technique for the correction of optical aberrations in wide-field fluorescence microscopy. Segmented-Pupil Image Interferometry (SPII) uses a liquid crystal spatial light modulator placed in the microscope's pupil plane to split the wavefront originating from a fluorescent object into an array of individual beams. Distortion of the wavefront arising from either system or sample aberrations results in displacement of the images formed from the individual pupil segments. Analysis of image registration allows for the local tilt in the wavefront at each segment to be corrected with respect to a central reference. A second correction step optimizes the image intensity by adjusting the relative phase of each pupil segment through image interferometry. This ensures that constructive interference between all segments is achieved at the image plane. Improvements in image quality are observed when Segmented-Pupil Image Interferometry is applied to correct aberrations arising from the microscope's optical path.

Resolving microstructures in Z pinches with intensity interferometry

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

Apruzese, J. P.; Kroupp, E.; Maron, Y.

2014-03-15

Nearly 60 years ago, Hanbury Brown and Twiss [R. Hanbury Brown and R. Q. Twiss, Nature 178, 1046 (1956)] succeeded in measuring the 30 nrad angular diameter of Sirius using a new type of interferometry that exploited the interference of photons independently emitted from different regions of the stellar disk. Its basis was the measurement of intensity correlations as a function of detector spacing, with no beam splitting or preservation of phase information needed. Applied to Z pinches, X pinches, or laser-produced plasmas, this method could potentially provide spatial resolution under one micron. A quantitative analysis based on the workmore » of Purcell [E. M. Purcell, Nature 178, 1449 (1956)] reveals that obtaining adequate statistics from x-ray interferometry of a Z-pinch microstructure would require using the highest-current generators available. However, using visible light interferometry would reduce the needed photon count and could enable its use on sub-MA machines.« less

Real-Time and Meter-Scale Absolute Distance Measurement by Frequency-Comb-Referenced Multi-Wavelength Interferometry.

PubMed

Wang, Guochao; Tan, Lilong; Yan, Shuhua

2018-02-07

We report on a frequency-comb-referenced absolute interferometer which instantly measures long distance by integrating multi-wavelength interferometry with direct synthetic wavelength interferometry. The reported interferometer utilizes four different wavelengths, simultaneously calibrated to the frequency comb of a femtosecond laser, to implement subwavelength distance measurement, while direct synthetic wavelength interferometry is elaborately introduced by launching a fifth wavelength to extend a non-ambiguous range for meter-scale measurement. A linearity test performed comparatively with a He-Ne laser interferometer shows a residual error of less than 70.8 nm in peak-to-valley over a 3 m distance, and a 10 h distance comparison is demonstrated to gain fractional deviations of ~3 × 10 -8 versus 3 m distance. Test results reveal that the presented absolute interferometer enables precise, stable, and long-term distance measurements and facilitates absolute positioning applications such as large-scale manufacturing and space missions.

Optical aperture synthesis with electronically connected telescopes

PubMed Central

Dravins, Dainis; Lagadec, Tiphaine; Nuñez, Paul D.

2015-01-01

Highest resolution imaging in astronomy is achieved by interferometry, connecting telescopes over increasingly longer distances and at successively shorter wavelengths. Here, we present the first diffraction-limited images in visual light, produced by an array of independent optical telescopes, connected electronically only, with no optical links between them. With an array of small telescopes, second-order optical coherence of the sources is measured through intensity interferometry over 180 baselines between pairs of telescopes, and two-dimensional images reconstructed. The technique aims at diffraction-limited optical aperture synthesis over kilometre-long baselines to reach resolutions showing details on stellar surfaces and perhaps even the silhouettes of transiting exoplanets. Intensity interferometry circumvents problems of atmospheric turbulence that constrain ordinary interferometry. Since the electronic signal can be copied, many baselines can be built up between dispersed telescopes, and over long distances. Using arrays of air Cherenkov telescopes, this should enable the optical equivalent of interferometric arrays currently operating at radio wavelengths. PMID:25880705

A real-time interferometer technique for compressible flow research

NASA Technical Reports Server (NTRS)

Bachalo, W. D.; Houser, M. J.

1984-01-01

Strengths and shortcomings in the application of interferometric techniques to transonic flow fields are examined and an improved method is elaborated. Such applications have demonstrated the value of interferometry in obtaining data for compressible flow research. With holographic techniques, interferometry may be applied in large scale facilities without the use of expensive optics or elaborate vibration isolation equipment. Results obtained using holographic interferometry and other methods demonstrate that reliable qualitative and quantitative data can be acquired. Nevertheless, the conventional method can be difficult to set up and apply, and it cannot produce real-time data. A new interferometry technique is investigated that promises to be easier to apply and can provide real-time information. This single-beam technique has the necessary insensitivity to vibration for large scale wind tunnel operations. Capabilities of the method and preliminary tests on some laboratory scale flow fluids are described.

Real-Time and Meter-Scale Absolute Distance Measurement by Frequency-Comb-Referenced Multi-Wavelength Interferometry

PubMed Central

Tan, Lilong; Yan, Shuhua

2018-01-01

We report on a frequency-comb-referenced absolute interferometer which instantly measures long distance by integrating multi-wavelength interferometry with direct synthetic wavelength interferometry. The reported interferometer utilizes four different wavelengths, simultaneously calibrated to the frequency comb of a femtosecond laser, to implement subwavelength distance measurement, while direct synthetic wavelength interferometry is elaborately introduced by launching a fifth wavelength to extend a non-ambiguous range for meter-scale measurement. A linearity test performed comparatively with a He–Ne laser interferometer shows a residual error of less than 70.8 nm in peak-to-valley over a 3 m distance, and a 10 h distance comparison is demonstrated to gain fractional deviations of ~3 × 10−8 versus 3 m distance. Test results reveal that the presented absolute interferometer enables precise, stable, and long-term distance measurements and facilitates absolute positioning applications such as large-scale manufacturing and space missions. PMID:29414897

The use of holographic interferometry and electron speckle pattern interferometry for diffusion measurement in biochemical and pharmaceutical engineering applications

NASA Astrophysics Data System (ADS)

Axelsson, Anders; Marucci, Mariagrazia

2008-12-01

In this review holographic interferometry and electron speckle pattern interferometry are discussed as efficient techniques for diffusion measurements in biochemical and pharmaceutical applications. Transport phenomena can be studied, quantitatively and qualitatively, in gels, liquids and membranes. Detailed information on these phenomena is required to design effective chromatography bioseparation processes using gel beads or ultrafiltration membranes, and in the design of controlled-release pharmaceuticals using membrane-coated pellets or tablets. The influence of gel concentration, ion strength in the liquid and the size of diffusing protein molecules can easily be studied with good accuracy. When studying membranes, the resistance can be quantified, and it is also possible to discriminate between permeable and semi-permeable membranes. In this review the influence of temperature, natural convection and light deflection on the accuracy of the diffusion measurements is also discussed.

Study of the location of testing area in residual stress measurement by Moiré interferometry combined with hole-drilling method

NASA Astrophysics Data System (ADS)

Qin, Le; Xie, HuiMin; Zhu, RongHua; Wu, Dan; Che, ZhiGang; Zou, ShiKun

2014-04-01

This paper investigates the effect of the location of testing area in residual stress measurement by Moiré interferometry combined with hole-drilling method. The selection of the location of the testing area is analyzed from theory and experiment. In the theoretical study, the factors which affect the surface released radial strain ɛ r were analyzed on the basis of the formulae of the hole-drilling method, and the relations between those factors and ɛ r were established. By combining Moiré interferometry with the hole-drilling method, the residual stress of interference-fit specimen was measured to verify the theoretical analysis. According to the analysis results, the testing area for minimizing the error of strain measurement is determined. Moreover, if the orientation of the maximum principal stress is known, the value of strain will be measured with higher precision by the Moiré interferometry method.

Experimental determination of release fields in cut railroad car wheels

DOT National Transportation Integrated Search

1999-02-01

A new approach to the measurement of residual stresses in railroad wheels is investigated using a saw cut method of releasing stresses in the structure. High-sensitivity moire interferometry combined with Michelson interferometry provides full-field ...

Experimental Study of Residual Stresses in Rail by Moire Interferometry

DOT National Transportation Integrated Search

1993-09-01

The residual stresses in rails produced by rolling cycles are studied experimentally by moire interferometry. The dissection technique is adopted for this investigation. The basic principle of the dissection technique is that the residual stress is r...

Year-round record of Dry Valley soil CO2 flux provides insights into Antarctic soil dynamics

NASA Astrophysics Data System (ADS)

Risk, D. A.; Lee, C.; Macintyre, C. M.; Cary, C.

2012-12-01

The McMurdo Dry Valleys of Antarctica host extreme soil microbial communities that have been extensively studied within the past decade. Activity of microbial communities is routinely measured via soil CO2 flux, and some useful Antarctic measurements have been made during short Austral summers. These studies are mostly spatial in nature, but temporal patterns are also valuable and may provide insights into critical thresholds and the interplay between various mechanisms that drive CO2 flux and its variation. New membrane-based Forced Diffusion (FD) soil efflux techniques offer promise for this application. The purpose of this study was to use a specially designed FD instrument in Hidden Valley of the Antarctic Dry Valleys to evaluate hardware performance in year-round deployments, and to identify features of interest with respect to soil CO2 flux variation. Overall, the deployment was successful. Small but sustained positive fluxes were present only twice during the year. The first such event was small but consistent and of long duration, occurring in the Austral winter. The second was more volatile and likely of microbial origin, and appeared for roughly a month at the end of the calendar year within the Austral summer. The observed patterns suggest that Hidden Valley soil CO2 fluxes are not solely biological in nature, but likely modulated by a combination of biological, geological, and physical processes, which will be discussed in this presentation. In future studies, additional measurement locations, and simultaneous subsurface and lower atmospheric gradient concentration measurements (power-permitting) would be extremely valuable for interpreting measured fluxes, to help identify advective depletion events, the depth source of fluxes, and changes in soil and atmospheric diffusivities.

Phylogeography of Pinus subsection Australes in the Caribbean Basin

PubMed Central

Jardón-Barbolla, Lev; Delgado-Valerio, Patricia; Geada-López, Gretel; Vázquez-Lobo, Alejandra; Piñero, Daniel

2011-01-01

Background and Aims Four species of Pinus subsection Australes occur in the Caribbean Basin: P. caribaea, P. cubensis, P. maestrensis and P. occidentalis. This study analyses the phylogeography of these species to assess possible colonization events from Central America to the islands and subsequent population expansions during glacial periods driven by both drier climate and larger emerged land areas. Methods Allele size data were obtained for plastid microsatellites for 314 individuals from 24 populations, covering the distribution range of subsection Australes in the Caribbean Basin. Key Results In total, 113 plastid haplotypes were identified. The highest genetic diversity was found in populations of P. caribaea. Overall, Caribbean Basin populations fit the isolation by distance model. Significant phylogeographical structure was found (RST = 0·671 > permuted RST = 0·101; P < 0·0001). The haplotype network and a Bayesian analysis of population structure (BAPS) indicated different Central American origins for P. caribaea var. bahamensis and P. caribaea var. caribaea plastids, with Central America populations in northern and south-eastern groups. Sudden expansion times for BAPS clusters were close to three glacial maxima. Conclusions Central America contains ancestral plastid haplotypes. Population expansion has played a major role in the distribution of genetic diversity in P. caribaea var. hondurensis. Two colonization events gave rise to the P. caribaea var. bahamensis and P. caribaea var. caribaea lineages. Plastid variation in the eastern species (P. cubensis, P. maestrensis and P. occidentalis) evolved independently from that in P. caribaea var. caribaea. Incomplete lineage sorting between P. cubensis and P. maestrensis is apparent. Inferred expansion times for P. caribaea var. bahamensis and for the eastern lineages correspond to glacial maxima, whereas those for P. caribaea var. hondurensis correspond to the beginning of the temperature decrease that led to Marine Isotope Stage 8. PMID:21118838

Direct Contribution of the Stratosphere to Recent West Antarctic Warming in Austral Spring

NASA Astrophysics Data System (ADS)

Nicolas, J. P.; Bromwich, D. H.

2015-12-01

The causes of the rapid warming of West Antarctica in recent decades are not yet fully understood. Thus far, investigations of the phenomenon have emphasized the role of tropospheric teleconnections originating from the Tropics in austral winter, but have had less success in explaining the strong warming in austral spring (SON). Here, we further explore the mechanisms behind the SON warming by focusing on September, the month during which atmospheric temperature and circulation trends in and around West Antarctica largely account for the 3-month average SON trends. We show that the tropospheric trends toward lower pressures/heights (more cyclonic) over the South Pacific sector of the Southern Ocean previously reported extend vertically well into the stratosphere. In the lower troposphere, these circulation changes, by steering more warm air toward West Antarctica, have likely contributed to the warming of the region. In the stratosphere, we provide evidence that the cyclonic trends are associated with a very prominent stratospheric warming in the Australian sector, believed to be the result of increased tropically-forced planetary wave activity and wave breaking. Through thermal wind balance, this regional stratospheric warming has led to a poleward displacement of the polar-night jet south of Australia, leading to enhanced cyclonic motion and potential vorticity (PV) downwind over the Amundsen Sea region. Finally, we establish, through the PV inversion framework, a causal link between stratospheric and tropospheric changes, whereby large PV anomalies in the stratosphere induce consistent geopotential height anomalies down in the troposphere. Our results highlight not only the important and largely overlooked role played by the stratosphere in recent West Antarctic climate change, but also a new pathway for tropical climate variability to influence Antarctic climate.

The Tunas Formation (Permian) in the Sierras Australes foldbelt, east central Argentina: evidence for syntectonic sedimentation in a foreland basin

NASA Astrophysics Data System (ADS)

Lopez-Gamundi, O. R.; Conaghan, P. J.; Rossello, E. A.; Cobbold, P. R.

1995-04-01

The Tunas Formation, extensively exposed in the Sierras Australes foldbelt of eastern central Argentina, completes the sedimentation of the Gondwanan (Late Carboniferous-Permian) sequence, locally known as the Pillahuincó Group. The underlying units of the Group show an integrated depositional history which can be explained in terms of glaciomarine sedimentation (Sauce Grande Formation) and postglacial transgression (Piedra Azul and Bonete Formations). This succession also has a rather uniform quartz-rich, sand-sized composition indicative of a cratonic provenance from the Tandilia Massif to the northeast. Early to Late Permian deformation folded and thrusted the southwestern basin margin (Sierras Australes) and triggered the deposition of a 1,500 m — thick, synorogenic prograding wedge, the Tunas Formation, in the adjacent foreland basin (Sauce Grande or Claromecó Basin). Sandstone detrital modes for the Tunas deposits show moderate to low contents of quartz and abundant lithics, mostly of volcanic and metasedimentary origin. Paleocurrents are consistently from the SW. Tuffs interbedded with sandstones in the upper half of Tunas Formation (Early — early Late? Permian) are interpreted as being derived from volcanic glass-rich tuffs settled in a body of water. Extensive rhyolitic ignimbrites and consanguineous airborne tuffaceous material erupted in the northern Patagonian region during that period. The age constraints and similarities in composition between these volcanics and the tuffaceous horizons present in the Sauce Grande, Parana and Karoo Basins suggest a genetic linkage between these two episodes. The intimate relationship between volcanic activity inboard of the paleo-Pacific margin, deformation in the adjacent orogenic belt and subsidence and sedimentation in the contiguous foreland basin constitutes a common motif in the Sauce Grande and Karoo Basins of southwestern Gondwana.

Using continuous microbarom recordings for probing peri-Antarctica's atmosphere

NASA Astrophysics Data System (ADS)

Ceranna, Lars; Le Pichon, Alexis; Blanc, Elisabeth

2010-05-01

Germany is operating one of the four Antarctic infrasound stations to fulfil the compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). IS27 is a nine element array which is in continuous operation since its deployment in January 2003. Using the PMCC detection algorithm coherent signals are observed in the frequency range from 0.0002 to 4.0 Hz covering a large variety of infrasound sources such as low frequent mountain-associated wave or high frequency ice-quakes. The most prominent signals are related to microbaroms (mb) generated by the strong peri-Antarctic ocean swells. These continuous signals with a dominant period of 5 s show a clear trend in the direction of their detection being well correlated to the prevailing stratospheric winds. For mb-signals a strong increase in trace velocity along with a decrease in the number of detections were observed during the Austral summer 2006 indicating strong variations in the troposphere and the stratospheric wave duct. However, ECMWF wind speed profiles at the station give no evidence for such an anomaly. Nevertheless, a smaller El-Nino event during Austral winter 2006 together with cooling in the upper stratosphere caused by eruption of the Manam volcano in Indonesia provide a potential explanation for the abnormal ducting conditions. This will be demonstrated with a statistical approach for the dominating ray-parameter launched from the estimated source regions towards IS27 (based on NOAA wave watch III). An increase in gravity wave activity is considered for Austral summer 2006 since a comparison of ECMWF profiles and measured radiosonde data has revealed a cleaning of the numerical profiles with respect to turbulences in the troposphere and lower stratosphere.

A New Synthetic Allotetraploid (A1A1G2G2) between Gossypium herbaceum and G. australe: Bridging for Simultaneously Transferring Favorable Genes from These Two Diploid Species into Upland Cotton

PubMed Central

Chen, Yu; Wang, Yingying; Chen, Jinjin; Zhang, Tianzhen; Zhou, Baoliang

2015-01-01

Gossypium herbaceum, a cultivated diploid cotton species (2n = 2x = 26, A1A1), has favorable traits such as excellent drought tolerance and resistance to sucking insects and leaf curl virus. G. australe, a wild diploid cotton species (2n = 2x = 26, G2G2), possesses numerous economically valuable characteristics such as delayed pigment gland morphogenesis (which is conducive to the production of seeds with very low levels of gossypol as a potential food source for humans and animals) and resistance to insects, wilt diseases and abiotic stress. Creating synthetic allotetraploid cotton from these two species would lay the foundation for simultaneously transferring favorable genes into cultivated tetraploid cotton. Here, we crossed G. herbaceum (as the maternal parent) with G. australe to produce an F1 interspecific hybrid and doubled its chromosome complement with colchicine, successfully generating a synthetic tetraploid. The obtained tetraploid was confirmed by morphology, cytology and molecular markers and then self-pollinated. The S1 seedlings derived from this tetraploid gradually became flavescent after emergence of the fifth true leaf, but they were rescued by grafting and produced S2 seeds. The rescued S1 plants were partially fertile due to the existence of univalents at Metaphase I of meiosis, leading to the formation of unbalanced, nonviable gametes lacking complete sets of chromosomes. The S2 plants grew well and no flavescence was observed, implying that interspecific incompatibility, to some extent, had been alleviated in the S2 generation. The synthetic allotetraploid will be quite useful for polyploidy evolutionary studies and as a bridge for transferring favorable genes from these two diploid species into Upland cotton through hybridization. PMID:25879660

The annual cycle of nitrate and net community production in surface waters of the Southern Ocean observed with SOCCOM profiling floats

NASA Astrophysics Data System (ADS)

Johnson, K. S.; Plant, J. N.; Sakamoto, C.; Coletti, L. J.; Sarmiento, J. L.; Riser, S.; Talley, L. D.

2016-12-01

Sixty profiling floats with ISUS and SUNA nitrate sensors have been deployed in the Southern Ocean (south of 30 degrees S) as part of the SOCCOM (Southern Ocean Carbon and Climate Observations and Modeling) program and earlier efforts. These floats have produced detailed records of the annual cycle of nitrate concentration throughout the region from the surface to depths near 2000 m. In surface waters, there are clear cycles in nitrate concentration that result from uptake of nitrate during austral spring and summer. These changes in nitrate concentration were used to compute the annual net community production over this region. NCP was computed using a simplified version of the approach detailed by Plant et al. (2016, Global Biogeochemical Cycles, 30, 859-879, DOI: 10.1002/2015GB005349). At the time the abstract was written 41 complete annual cycles were available from floats deployed before the austral summer of 2015/2016. After filtering the data to remove floats that crossed distinct frontal boundaries, floats with other anomalies, and floats in sub-tropical waters, 23 cycles were available. A preliminary assessment of the data yields an NCP of 2.8 +/- 0.95 (1 SD) mol C/m2/y after integrating to 100 m depth and converting nitrate uptake to carbon using the Redfield ratio. This preliminary assessment ignores vertical transport across the nitracline and is, therefore, a minimum estimate. The number of cycles available for analysis will increase rapidly, as 32 of the floats were deployed in the austral summer of 2015/2016 and have not yet been analyzed.

Does coupled ocean enhance ozone-hole-induced Southern Hemisphere circulation changes?

NASA Astrophysics Data System (ADS)

Son, S. W.; Han, B. R.; Kim, S. Y.; Park, R.

2017-12-01

The ozone-hole-induced Southern Hemisphere (SH) circulation changes, such as poleward shift of westerly jet and Hadley cell widening, have been typically explored with either coupled general circulation models (CGCMs) prescribing stratospheric ozone or chemistry-climate models (CCMs) prescribing surface boundary conditions. Only few studies have utilized ocean-coupled CCMs with a relatively coarse resolution. To better quantify the role of interactive chemistry and coupled ocean in the ozone-hole-induced SH circulation changes, the present study examines a set of CGCM and CCM simulations archived for the Coupled Model Intercomparison Project phase 5 (CMIP5) and CCM initiative (CCMI). Although inter-model spread of Antarctic ozone depletion is substantially large especially in the austral spring, both CGCMs with relatively simple ozone chemistry and CCMs with fully interactive comprehensive chemistry reasonably well reproduce long-term trends of Antarctic ozone and the associated polar-stratospheric temperature changes. Most models reproduce a poleward shift of SH jet and Hadley-cell widening in the austral summer in the late 20th century as identified in reanalysis datasets. These changes are quasi-linearly related with Antarctic ozone changes, confirming the critical role of Antarctic ozone depletion in the austral-summer zonal-mean circulation changes. The CGCMs with simple but still interactive ozone show slightly stronger circulation changes than those with prescribed ozone. However, the long-term circulation changes in CCMs are largely insensitive to the coupled ocean. While a few models show the enhanced circulation changes when ocean is coupled, others show essentially no changes or even weakened circulation changes. This result suggests that the ozone-hole-related stratosphere-troposphere coupling in the late 20th century may be only weakly sensitive to the coupled ocean.

LEA polypeptide profiling of recalcitrant and orthodox legume seeds reveals ABI3-regulated LEA protein abundance linked to desiccation tolerance.

PubMed

Delahaie, Julien; Hundertmark, Michaela; Bove, Jérôme; Leprince, Olivier; Rogniaux, Hélène; Buitink, Julia

2013-11-01

In contrast to orthodox seeds that acquire desiccation tolerance during maturation, recalcitrant seeds are unable to survive drying. These desiccation-sensitive seeds constitute an interesting model for comparative analysis with phylogenetically close species that are desiccation tolerant. Considering the importance of LEA (late embryogenesis abundant) proteins as protective molecules both in drought and in desiccation tolerance, the heat-stable proteome was characterized in cotyledons of the legume Castanospermum australe and it was compared with that of the orthodox model legume Medicago truncatula. RNA sequencing identified transcripts of 16 homologues out of 17 LEA genes for which polypeptides are detected in M. truncatula seeds. It is shown that for 12 LEA genes, polypeptides were either absent or strongly reduced in C. australe cotyledons compared with M. truncatula seeds. Instead, osmotically responsive, non-seed-specific dehydrins accumulated to high levels in the recalcitrant cotyledons compared with orthodox seeds. Next, M. truncatula mutants of the abscisic acid insensitive3 (ABI3) gene were characterized. Mature Mtabi3 seeds were found to be desiccation sensitive when dried below a critical water content of 0.4 g H2O g DW(-1). Characterization of the LEA proteome of the Mtabi3 seeds revealed a subset of LEA proteins with severely reduced abundance that were also found to be reduced or absent in C. australe cotyledons. Transcripts of these genes were indeed shown to be ABI3 responsive. The results highlight those LEA proteins that are critical to desiccation tolerance and suggest that comparable regulatory pathways responsible for their accumulation are missing in both desiccation-sensitive genotypes, revealing new insights into the mechanistic basis of the recalcitrant trait in seeds.

LEA polypeptide profiling of recalcitrant and orthodox legume seeds reveals ABI3-regulated LEA protein abundance linked to desiccation tolerance

PubMed Central

Hundertmark, Michaela; Buitink, Julia

2013-01-01

In contrast to orthodox seeds that acquire desiccation tolerance during maturation, recalcitrant seeds are unable to survive drying. These desiccation-sensitive seeds constitute an interesting model for comparative analysis with phylogenetically close species that are desiccation tolerant. Considering the importance of LEA (late embryogenesis abundant) proteins as protective molecules both in drought and in desiccation tolerance, the heat-stable proteome was characterized in cotyledons of the legume Castanospermum australe and it was compared with that of the orthodox model legume Medicago truncatula. RNA sequencing identified transcripts of 16 homologues out of 17 LEA genes for which polypeptides are detected in M. truncatula seeds. It is shown that for 12 LEA genes, polypeptides were either absent or strongly reduced in C. australe cotyledons compared with M. truncatula seeds. Instead, osmotically responsive, non-seed-specific dehydrins accumulated to high levels in the recalcitrant cotyledons compared with orthodox seeds. Next, M. truncatula mutants of the ABSCISIC ACID INSENSITIVE3 (ABI3) gene were characterized. Mature Mtabi3 seeds were found to be desiccation sensitive when dried below a critical water content of 0.4g H2O g DW–1. Characterization of the LEA proteome of the Mtabi3 seeds revealed a subset of LEA proteins with severely reduced abundance that were also found to be reduced or absent in C. australe cotyledons. Transcripts of these genes were indeed shown to be ABI3 responsive. The results highlight those LEA proteins that are critical to desiccation tolerance and suggest that comparable regulatory pathways responsible for their accumulation are missing in both desiccation-sensitive genotypes, revealing new insights into the mechanistic basis of the recalcitrant trait in seeds. PMID:24043848

Hinge-line Migration of Petermann Gletscher, North Greenland, Detected Using Satellite Radar Interferometry

NASA Technical Reports Server (NTRS)

Rignot, Eric

1998-01-01

The synthetic-aperture radar interferometry technique is used to detect the migration of the limit of tidal flexing, or hinge line, of the floating ice tongue of Petermann Gletscher, a major outlet glacier of north Greenland.

Integrated optics applied to astronomical aperture synthesis III: simulation of components optimized for astronomical interferometry

NASA Astrophysics Data System (ADS)

Nabias, Laurent; Schanen, Isabelle; Berger, Jean-Philippe; Kern, Pierre; Malbet, Fabien; Benech, Pierre

2018-04-01

This paper, "Integrated optics applied to astronomical aperture synthesis III: simulation of components optimized for astronomical interferometry," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.

Interferometry correlations in central p+Pb collisions

NASA Astrophysics Data System (ADS)

Bożek, Piotr; Bysiak, Sebastian

2018-01-01

We present results on interferometry correlations for pions emitted in central p+Pb collisions at √{s_{NN}}=5.02 TeV in a 3+1-dimensional viscous hydrodynamic model with initial conditions from the Glauber Monte Carlo model. The correlation function is calculated as a function of the pion pair rapidity. The extracted interferometry radii show a weak rapidity dependence, reflecting the lack of boost invariance of the pion distribution. A cross term between the out and long directions is found to be nonzero. The results obtained in the hydrodynamic model are in fair agreement with recent data of the ATLAS Collaboration.

Altimetry Using GPS-Reflection/Occultation Interferometry

NASA Technical Reports Server (NTRS)

Cardellach, Estel; DeLaTorre, Manuel; Hajj, George A.; Ao, Chi

2008-01-01

A Global Positioning System (GPS)- reflection/occultation interferometry was examined as a means of altimetry of water and ice surfaces in polar regions. In GPS-reflection/occultation interferometry, a GPS receiver aboard a satellite in a low orbit around the Earth is used to determine the temporally varying carrier- phase delay between (1) one component of a signal from a GPS transmitter propagating directly through the atmosphere just as the GPS transmitter falls below the horizon and (2) another component of the same signal, propagating along a slightly different path, reflected at glancing incidence upon the water or ice surface.

Global astrometry with the space interferometry mission

NASA Technical Reports Server (NTRS)

Boden, A.; Unwin, S.; Shao, M.

1997-01-01

The prospects for global astrometric measurements with the space interferometry mission (SIM) are discussed. The SIM mission will perform four microarcsec astrometric measurements on objects as faint as 20 mag using the optical interferometry technique with a 10 m baseline. The SIM satellite will perform narrow angle astrometry and global astrometry by means of an astrometric grid. The sensitivities of the SIM global astrometric performance and the grid accuracy versus instrumental parameters and sky coverage schemes are reported on. The problems in finding suitable astrometric grid objects to support microarcsec astrometry, and related ground-based observation programs are discussed.

Recent New Ideas and Directions for Space-Based Nulling Interferometry

NASA Technical Reports Server (NTRS)

Serabyn, Eugene (Gene)

2004-01-01

This document is composed of two viewgraph presentations. The first is entitled "Recent New Ideas and Directions for Space-Based Nulling Interferometry." It reviews our understanding of interferometry compared to a year or so ago: (1) Simpler options identified, (2) A degree of flexibility is possible, allowing switching (or degradation) between some options, (3) Not necessary to define every component to the exclusion of all other possibilities and (4) MIR fibers are becoming a reality. The second, entitled "The Fiber Nuller," reviews the idea of Combining beams in a fiber instead of at a beamsplitter.

Measurement of energy contrast of amplified ultrashort pulses using cross-polarized wave generation and spectral interferometry.

PubMed

Iliev, Marin; Meier, Amanda K; Galloway, Benjamin; Adams, Daniel E; Squier, Jeff A; Durfee, Charles G

2014-07-28

We present a method using spectral interferometry (SI) to characterize a pulse in the presence of an incoherent background such as amplified spontaneous emission (ASE). The output of a regenerative amplifier is interfered with a copy of the pulse that has been converted using third-order cross-polarized wave generation (XPW). The ASE shows as a pedestal background in the interference pattern. The energy contrast between the short-pulse component and the ASE is retrieved. The spectra of the interacting beams are obtained through an improvement to the self-referenced spectral interferometry (SRSI) analysis.

Highly sensitive atomic based MW interferometry.

PubMed

Shylla, Dangka; Nyakang'o, Elijah Ogaro; Pandey, Kanhaiya

2018-06-06

We theoretically study a scheme to develop an atomic based micro-wave (MW) interferometry using the Rydberg states in Rb. Unlike the traditional MW interferometry, this scheme is not based upon the electrical circuits, hence the sensitivity of the phase and the amplitude/strength of the MW field is not limited by the Nyquist thermal noise. Further, this system has great advantage due to its much higher frequency range in comparision to the electrical circuit, ranging from radio frequency (RF), MW to terahertz regime. In addition, this is two orders of magnitude more sensitive to field strength as compared to the prior demonstrations on the MW electrometry using the Rydberg atomic states. Further, previously studied atomic systems are only sensitive to the field strength but not to the phase and hence this scheme provides a great opportunity to characterize the MW completely including the propagation direction and the wavefront. The atomic based MW interferometry is based upon a six-level loopy ladder system involving the Rydberg states in which two sub-systems interfere constructively or destructively depending upon the phase between the MW electric fields closing the loop. This work opens up a new field i.e. atomic based MW interferometry replacing the conventional electrical circuit in much superior fashion.

Study of nanometer-level precise phase-shift system used in electronic speckle shearography and phase-shift pattern interferometry

NASA Astrophysics Data System (ADS)

Jing, Chao; Liu, Zhongling; Zhou, Ge; Zhang, Yimo

2011-11-01

The nanometer-level precise phase-shift system is designed to realize the phase-shift interferometry in electronic speckle shearography pattern interferometry. The PZT is used as driving component of phase-shift system and translation component of flexure hinge is developed to realize micro displacement of non-friction and non-clearance. Closed-loop control system is designed for high-precision micro displacement, in which embedded digital control system is developed for completing control algorithm and capacitive sensor is used as feedback part for measuring micro displacement in real time. Dynamic model and control model of the nanometer-level precise phase-shift system is analyzed, and high-precision micro displacement is realized with digital PID control algorithm on this basis. It is proved with experiments that the location precision of the precise phase-shift system to step signal of displacement is less than 2nm and the location precision to continuous signal of displacement is less than 5nm, which is satisfied with the request of the electronic speckle shearography and phase-shift pattern interferometry. The stripe images of four-step phase-shift interferometry and the final phase distributed image correlated with distortion of objects are listed in this paper to prove the validity of nanometer-level precise phase-shift system.

Phase-Shifted Laser Feedback Interferometry

NASA Technical Reports Server (NTRS)

Ovryn, Benjie

1999-01-01

Phase-shifted, laser feedback interferometry is a new diagnostic tool developed at the NASA Lewis Research Center under the Advanced Technology Development (ATD) Program directed by NASA Headquarters Microgravity Research Division. It combines the principles of phase-shifting interferometry (PSI) and laser-feedback interferometry (LFI) to produce an instrument that can quantify both optical path length changes and sample reflectivity variations. In a homogenous medium, the optical path length between two points is the product of the index of refraction and the geometric distance between the two points. LFI differs from other forms of interferometry by using the laser as both the source and the phase detector. In LFI, coherent feedback of the incident light either reflected directly from a surface or reflected after transmission through a region of interest will modulate the output intensity of the laser. The combination of PSI and LFI has produced a robust instrument, based on a low-power helium-neon (HeNe) gas laser, with a high dynamic range that can be used to measure either static or oscillatory changes of the optical path length. Small changes in optical path length are limited by the fraction of a fringe that can be measured; we can measure nonoscillatory changes with a root mean square (rms) error of the wavelength/1000 without averaging.

Biological activities of ophiobolin K and 6-epi-ophiobolin K produced by the endophytic fungus Aspergillus calidoustus

USDA-ARS?s Scientific Manuscript database

The endophytic fungus, Aspergillus calidoustus, was isolated from the plant species Acanthospermum australe (Asteraceae). A dichloromethane extract of the fungus displayed antifungal, antiprotozoal, and cytotoxic activities. Aspergillus calidoustus was identified using molecular, physiological and m...

Modulation of the Seasonal Cycle of Antarctic Sea Ice Extent Related to the Southern Annular Mode

NASA Astrophysics Data System (ADS)

Doddridge, Edward W.; Marshall, John

2017-10-01

Through analysis of remotely sensed sea surface temperature (SST) and sea ice concentration data, we investigate the impact of winds related to the Southern Annular Mode (SAM) on sea ice extent around Antarctica. We show that positive SAM anomalies in the austral summer are associated with anomalously cold SSTs that persist and lead to anomalous ice growth in the following autumn, while negative SAM anomalies precede warm SSTs and a reduction in sea ice extent during autumn. The largest effect occurs in April, when a unit change in the detrended summertime SAM is followed by a 1.8±0.6 ×105 km2 change in detrended sea ice extent. We find no evidence that sea ice extent anomalies related to the summertime SAM affect the wintertime sea ice extent maximum. Our analysis shows that the wind anomalies related to the negative SAM during the 2016/2017 austral summer contributed to the record minimum Antarctic sea ice extent observed in March 2017.

Relevamiento de HI en el Hemisferio Austral

NASA Astrophysics Data System (ADS)

Arnal, E. M.; Bajaja, E.; Morras, R.; Pöppel, W. G. L.

Un nuevo relevamiento de HI de todo el Hemisferio Austral, comprendido entre -90o <= δ <= -25o, está siendo observado con la antena I del IAR. El mismo es realizado con alta sensibilidad (r.m.s.<= 0.07 K) y alta resolución espectral (1 Km/s). Un total de ~50000 posiciones en el cielo serán observadas, espaciadas en una grilla (lxb) de (0.5o x 0.5o). El intervalo de velocidades cubierto en este relevamiento abarca el rango -450 km/s a +450 km/s en el sistema LSR. Esta base de datos será corregida por efectos de ``stray radiation''. Al presente se ha observado ~70% del total del relevamiento. El mismo es complementario de uno similar realizado en el Hemisferio Norte por Hartman y Burton (1996), con cubrimiento espacial, sensibilidad, resoluciones espaciales y en velocidad, similares a los del IAR. El objetivo final de ambos relevamientos es disponer de una base de datos uniforme en todo el cielo.

Gravity field of the Western Weddell Sea: Comparison of airborne gravity and Geosat derived gravity

NASA Technical Reports Server (NTRS)

Bell, R. E.; Brozena, J. M.; Haxby, W. F.; Labrecque, J. L.

1989-01-01

Marine gravity surveying in polar regions was typically difficult and costly, requiring expensive long range research vessels and ice-breakers. Satellite altimetry can recover the gravity field in these regions where it is feasible to survey with a surface vessel. Unfortunately, the data collected by the first global altimetry mission, Seasat, was collected only during the austral winter, producing a very poor quality gravitational filed for the southern oceans, particularly in the circum-Antarctic regions. The advent of high quality airborne gravity (Brozena, 1984; Brozena and Peters, 1988; Bell, 1988) and the availability of satellite altimetry data during the austral summer (Sandwell and McAdoo, 1988) has allowed the recovery of a free air gravity field for most of the Weddell Sea. The derivation of the gravity field from both aircraft and satellite measurements are briefly reviewed, before presenting along track comparisons and shaded relief maps of the Weddell Sea gravity field based on these two data sets.

Air- Sea Interactions in the Southwest Tropical Indian Ocean

NASA Astrophysics Data System (ADS)

Burns, J. M.; Bulusu, S.

2016-12-01

The Southwest Tropical Indian Ocean (SWTIO) features a unique, seasonal upwelling of the thermocline also known as the Seychelles-Chagos Thermocline Ridge (SCTR; 55°E-65°E, 5°S-12°S). Past research provides evidence for more tropical cyclone days over the SWTIO during austral summer with a deep thermocline ridge than in austral summer with a shallow thermocline ridge. Normally more cyclones form over the SWTIO when the thermocline is deeper, which has a positive relation to the arrival of downwelling Rossby waves originating in the southeast tropical Indian Ocean due to the anomalous effects of the Indian Ocean Dipole (IOD) and El Niño. With a particular focus on 2012/2013, this study reveals the dynamic properties of the SCTR that play an important role in the modulation of tropical cycles in the SWTIO. In addition to influencing cyclogeneis in the SCTR region, remote processes such as IOD and ENSO are also primary drivers of the SCTR interannual variability with respect to both ocean temperature and salinity.

Statistical characteristics of austral summer cyclones in Southern Ocean

NASA Astrophysics Data System (ADS)

Liu, Na; Fu, Gang; Kuo, Ying-Hwa

2012-06-01

Characteristics of cyclones and explosively developing cyclones (or `bombs') over the Southern Ocean in austral summer (December, January and February) from 2004 to 2008 are analyzed by using the Final Analysis (FNL) data produced by the National Centers for Environmental Prediction (NCEP) of the United States. Statistical results show that both cyclones and explosively developing cyclones frequently develop in January, and most of them occur within the latitudinal zone between 55°S and 70°S. These cyclones gradually approach the Antarctic Continent from December to February. Generally cyclones and bombs move east-southeastward with some exceptions of northeastward movement. The lifetime of cyclones is around 2-6 d, and the horizontal scale is about 1000 km. Explosive cyclones have the lifetime of about 1 week with the horizontal scale reaching up to 3000 km. Compared with cyclones developed in the Northern Hemisphere, cyclones over the southern ocean have much higher occurrence frequency, lower central pressure and larger horizontal scale, which may be caused by the unique geographical features of the Southern Hemisphere.

Speckle interferometry applied to asteroids and other solar system objects

NASA Technical Reports Server (NTRS)

Drummond, J. D.; Hege, E. K.

1985-01-01

The application of speckle interferometry to asteroids and other solar system objects is discussed. The assumption of a triaxial ellipsoid rotating about its shortest axis is the standard model. Binary asteroids, 433 Eros, 532 Herculina, 511 Davida, and Pallas are discussed.

An Atomic Clock with 10 (exp -18) Instability

DTIC Science & Technology

2013-09-13

experimental tools to address exciting topics in cosmology and gravitational physics such as Hawking radiation (13) or Unruh effect (27). References...long baseline interferometry), secure communication, and interferometry and can possibly lead to a re definition of the SI second (9). References and

Detection of deoxynivalenol using biolayer interferometry

USDA-ARS?s Scientific Manuscript database

Biolayer interferometry allows for the real time monitoring of the interactions between molecules without the need for reagents with enzymatic, fluorescent, or radioactive labels. The technology is based upon the changes in interference pattern of light reflected from the surface of an optical fiber...

Study on a multi-delay spectral interferometry for stellar radial velocity measurement

NASA Astrophysics Data System (ADS)

Zhang, Kai; Jiang, Haijiao; Tang, Jin; Ji, Hangxin; Zhu, Yongtian; Wang, Liang

2014-08-01

High accuracy radial velocity measurement isn't only one of the most important methods for detecting earth-like Exoplanets, but also one of the main developing fields of astronomical observation technologies in future. Externally dispersed interferometry (EDI) generates a kind of particular interference spectrum through combining a fixed-delay interferometer with a medium-resolution spectrograph. It effectively enhances radial velocity measuring accuracy by several times. Another further study on multi-delay interferometry was gradually developed after observation success with only a fixed-delay, and its relative instrumentation makes more impressive performance in near Infrared band. Multi-delay is capable of giving wider coverage from low to high frequency in Fourier field so that gives a higher accuracy in radial velocity measurement. To study on this new technology and verify its feasibility at Guo Shoujing telescope (LAMOST), an experimental instrumentation with single fixed-delay named MESSI has been built and tested at our lab. Another experimental study on multi-delay spectral interferometry given here is being done as well. Basically, this multi-delay experimental system is designed in according to the similar instrument named TEDI at Palomar observatory and the preliminary test result of MESSI. Due to existence of LAMOST spectrograph at lab, a multi-delay interferometer design actually dominates our work. It's generally composed of three parts, respectively science optics, phase-stabilizing optics and delay-calibrating optics. To switch different fixed delays smoothly during observation, the delay-calibrating optics is possibly useful to get high repeatability during switching motion through polychromatic interferometry. Although this metrology is based on white light interferometry in theory, it's different that integrates all of interference signals independently obtained by different monochromatic light in order to avoid dispersion error caused by broad band in big optical path difference (OPD).

From a structural average to the conformational ensemble of a DNA bulge

PubMed Central

Shi, Xuesong; Beauchamp, Kyle A.; Harbury, Pehr B.; Herschlag, Daniel

2014-01-01

Direct experimental measurements of conformational ensembles are critical for understanding macromolecular function, but traditional biophysical methods do not directly report the solution ensemble of a macromolecule. Small-angle X-ray scattering interferometry has the potential to overcome this limitation by providing the instantaneous distance distribution between pairs of gold-nanocrystal probes conjugated to a macromolecule in solution. Our X-ray interferometry experiments reveal an increasing bend angle of DNA duplexes with bulges of one, three, and five adenosine residues, consistent with previous FRET measurements, and further reveal an increasingly broad conformational ensemble with increasing bulge length. The distance distributions for the AAA bulge duplex (3A-DNA) with six different Au-Au pairs provide strong evidence against a simple elastic model in which fluctuations occur about a single conformational state. Instead, the measured distance distributions suggest a 3A-DNA ensemble with multiple conformational states predominantly across a region of conformational space with bend angles between 24 and 85 degrees and characteristic bend directions and helical twists and displacements. Additional X-ray interferometry experiments revealed perturbations to the ensemble from changes in ionic conditions and the bulge sequence, effects that can be understood in terms of electrostatic and stacking contributions to the ensemble and that demonstrate the sensitivity of X-ray interferometry. Combining X-ray interferometry ensemble data with molecular dynamics simulations gave atomic-level models of representative conformational states and of the molecular interactions that may shape the ensemble, and fluorescence measurements with 2-aminopurine-substituted 3A-DNA provided initial tests of these atomistic models. More generally, X-ray interferometry will provide powerful benchmarks for testing and developing computational methods. PMID:24706812

Evaluation of the Surface Characteristics of Various Implant Abutment Materials Using Confocal Microscopy and White Light Interferometry.

PubMed

Park, Jun-Beom; Yang, Seung-Min; Ko, Youngkyung

2015-12-01

The purpose of this study was to evaluate the surface characteristics of various implant abutment materials, such as of titanium alloy (Ti6Al4V; Ma), machined cobalt-chrome-molybdenum alloy (CCM), titanium nitride coating on a titanium alloy disc (TiN), anodic oxidized titanium alloy disc (AO), composite resin coating on a titanium alloy disc (Res), and zirconia disc (Zr), using confocal microscopy and white light interferometry. Measurements from the 2 methods were evaluated to see if these methods would give equivalent results. The precision of measurements were evaluated by the coefficient of variation. Five discs each of Ma, CCM, TiN, AO, Res, and Zr were used. The surface roughness was evaluated by confocal laser microscopy and white light interferometry. Confocal microscopy showed that the Res group showed significantly greater Ra, Rq, Rz, Sa, Sq, and Sz values compared with those of the Ma group (P < 0.05). The white light interferometry results showed that the Res group had significantly higher Ra, Rq, Rz, Rt, Sa, Sq, Sz, and Sdr values compared with the Ma group (P < 0.05). All the roughness parameters obtained from the 2 methods differed, and the Sa values of the Zr group from confocal microscopy were greater by 0.163 μm than those obtained by white light interferometry. Least difference was seen in the TiN group where the difference was 0.058 μm. Roughness parameters of different abutment materials varied significantly. Precision of measurement differed according to the characteristics of the material used. White light interferometry could be recommended for measurement of TiN and AO. Confocal microscopy gave more precise measurements for Ma and CCM groups. The optical characteristics of the surface should be considered before choosing the examination method.

Review of ASTM Symposium on Surface Crack Growth: Models, Experiments, and Structures

DTIC Science & Technology

1990-11-01

34 Extraction of Stress-Intensity Factor from In-Plane Displacements Measured by Holographic Interferometry--J.W. Dally, C.A. Sciammarella , and I...results and finite elements and find that they are essentially equivalent. Dally, Sciammarella , and Shareef use holographic interferometry and

An examination of along-track interferometry for detecting ground moving targets

NASA Technical Reports Server (NTRS)

Chen, Curtis W.; Chapin, Elaine; Muellerschoen, Ron; Hensley, Scott

2005-01-01

Along-track interferometry (ATI) is an interferometric synthetic aperture radar technique primarily used to measure Earth-surface velocities. We present results from an airborne experiment demonstrating phenomenology specific to the context of observing discrete ground targets moving admidst a stationary clutter background.

Interferometry using subnanosecond pulses from TEA nitrogen lasers.

PubMed

Schmidt, H; Salzmann, H; Strohwald, H

1975-09-01

The applicability of TEA nitrogen lasers emitting at 3371 A for high speed optical plasma interferometry of short lived plasmas is demonstrated. Interferograms of the dense phase of a 30-kJ plasma focus are obtained with an exposure time of less than 500 psec.

Advanced technology development multi-color holography

NASA Technical Reports Server (NTRS)

Vikram, Chandra S.

1993-01-01

This is the final report of the Multi-color Holography project. The comprehensive study considers some strategic aspects of multi-color holography. First, various methods of available techniques for accurate fringe counting are reviewed. These are heterodyne interferometry, quasi-heterodyne interferometry, and phase-shifting interferometry. Phase-shifting interferometry was found to be the most suitable for multi-color holography. Details of experimentation with a sugar solution are also reported where better than 1/200 of a fringe order measurement capability was established. Rotating plate glass phase shifter was used for the experimentation. The report then describes the possible role of using more than two wavelengths with special reference-to-object beam intensity ratio needs in multicolor holography. Some specific two- and three-color cases are also described in detail. Then some new analysis methods of the reconstructed wavefront are considered. These are deflectometry, speckle metrology, confocal optical signal processing, and phase shifting technique related applications. Finally, design aspects of an experimental breadboard are presented.

The use of holographic interferometry for measurements of temperature in a rectangular heat pipe. M.S. Thesis

NASA Technical Reports Server (NTRS)

Marn, Jure

1989-01-01

Holographic interferometry is a nonintrusive method and as such possesses considerable advantages such as not disturbing the velocity and temperature field by creating obstacles which would alter the flow field. These optical methods have disadvantages as well. Holography, as one of the interferometry methods, retains the accuracy of older methods, and at the same time eliminates the system error of participating components. The holographic interferometry consists of comparing the objective beam with the reference beam and observing the difference in lengths of optical paths, which can be observed during the propagation of the light through a medium with locally varying refractive index. Thus, change in refractive index can be observed as a family of nonintersecting surfaces in space (wave fronts). The object of the investigation was a rectangular heat pipe. The goal was to measure temperatures in the heat pipe, which yields data for computer code or model assessment. The results were obtained by calculating the temperatures by means of finite fringes.

LISA pathfinder optical interferometry

NASA Astrophysics Data System (ADS)

Braxmaier, Claus; Heinzel, Gerhard; Middleton, Kevin F.; Caldwell, Martin E.; Konrad, W.; Stockburger, H.; Lucarelli, S.; te Plate, Maurice B.; Wand, V.; Garcia, A. C.; Draaisma, F.; Pijnenburg, J.; Robertson, D. I.; Killow, Christian; Ward, Harry; Danzmann, Karsten; Johann, Ulrich A.

2004-09-01

The LISA Technology Package (LTP) aboard of LISA pathfinder mission is dedicated to demonstrate and verify key technologies for LISA, in particular drag free control, ultra-precise laser interferometry and gravitational sensor. Two inertial sensor, the optical interferometry in between combined with the dimensional stable Glass ceramic Zerodur structure are setting up the LTP. The validation of drag free operation of the spacecraft is planned by measuring laser interferometrically the relative displacement and tilt between two test masses (and the optical bench) with a noise levels of 10pm/√Hz and 10 nrad/√Hz between 3mHz and 30mHz. This performance and additionally overall environmental tests was currently verified on EM level. The OB structure is able to support two inertial sensors (≍17kg each) and to withstand 25 g design loads as well as 0...40°C temperature range. Optical functionality was verified successfully after environmental tests. The engineering model development and manufacturing of the optical bench and interferometry hardware and their verification tests will be presented.

Development of Speckle Interferometry Algorithm and System

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

Shamsir, A. A. M.; Jafri, M. Z. M.; Lim, H. S.

2011-05-25

Electronic speckle pattern interferometry (ESPI) method is a wholefield, non destructive measurement method widely used in the industries such as detection of defects on metal bodies, detection of defects in intergrated circuits in digital electronics components and in the preservation of priceless artwork. In this research field, this method is widely used to develop algorithms and to develop a new laboratory setup for implementing the speckle pattern interferometry. In speckle interferometry, an optically rough test surface is illuminated with an expanded laser beam creating a laser speckle pattern in the space surrounding the illuminated region. The speckle pattern is opticallymore » mixed with a second coherent light field that is either another speckle pattern or a smooth light field. This produces an interferometric speckle pattern that will be detected by sensor to count the change of the speckle pattern due to force given. In this project, an experimental setup of ESPI is proposed to analyze a stainless steel plate using 632.8 nm (red) wavelength of lights.« less

A portable magneto-optical trap with prospects for atom interferometry in civil engineering

NASA Astrophysics Data System (ADS)

Hinton, A.; Perea-Ortiz, M.; Winch, J.; Briggs, J.; Freer, S.; Moustoukas, D.; Powell-Gill, S.; Squire, C.; Lamb, A.; Rammeloo, C.; Stray, B.; Voulazeris, G.; Zhu, L.; Kaushik, A.; Lien, Y.-H.; Niggebaum, A.; Rodgers, A.; Stabrawa, A.; Boddice, D.; Plant, S. R.; Tuckwell, G. W.; Bongs, K.; Metje, N.; Holynski, M.

2017-06-01

The high precision and scalable technology offered by atom interferometry has the opportunity to profoundly affect gravity surveys, enabling the detection of features of either smaller size or greater depth. While such systems are already starting to enter into the commercial market, significant reductions are required in order to reach the size, weight and power of conventional devices. In this article, the potential for atom interferometry based gravimetry is assessed, suggesting that the key opportunity resides within the development of gravity gradiometry sensors to enable drastic improvements in measurement time. To push forward in realizing more compact systems, techniques have been pursued to realize a highly portable magneto-optical trap system, which represents the core package of an atom interferometry system. This can create clouds of 107 atoms within a system package of 20 l and 10 kg, consuming 80 W of power. This article is part of the themed issue 'Quantum technology for the 21st century'.

The correction of vibration in frequency scanning interferometry based absolute distance measurement system for dynamic measurements

NASA Astrophysics Data System (ADS)

Lu, Cheng; Liu, Guodong; Liu, Bingguo; Chen, Fengdong; Zhuang, Zhitao; Xu, Xinke; Gan, Yu

2015-10-01

Absolute distance measurement systems are of significant interest in the field of metrology, which could improve the manufacturing efficiency and accuracy of large assemblies in fields such as aircraft construction, automotive engineering, and the production of modern windmill blades. Frequency scanning interferometry demonstrates noticeable advantages as an absolute distance measurement system which has a high precision and doesn't depend on a cooperative target. In this paper , the influence of inevitable vibration in the frequency scanning interferometry based absolute distance measurement system is analyzed. The distance spectrum is broadened as the existence of Doppler effect caused by vibration, which will bring in a measurement error more than 103 times bigger than the changes of optical path difference. In order to decrease the influence of vibration, the changes of the optical path difference are monitored by a frequency stabilized laser, which runs parallel to the frequency scanning interferometry. The experiment has verified the effectiveness of this method.

A portable magneto-optical trap with prospects for atom interferometry in civil engineering

PubMed Central

Perea-Ortiz, M.; Winch, J.; Briggs, J.; Freer, S.; Moustoukas, D.; Powell-Gill, S.; Squire, C.; Lamb, A.; Rammeloo, C.; Stray, B.; Voulazeris, G.; Zhu, L.; Kaushik, A.; Lien, Y.-H.; Niggebaum, A.; Rodgers, A.; Stabrawa, A.; Boddice, D.; Plant, S. R.; Tuckwell, G. W.; Bongs, K.; Metje, N.; Holynski, M.

2017-01-01

The high precision and scalable technology offered by atom interferometry has the opportunity to profoundly affect gravity surveys, enabling the detection of features of either smaller size or greater depth. While such systems are already starting to enter into the commercial market, significant reductions are required in order to reach the size, weight and power of conventional devices. In this article, the potential for atom interferometry based gravimetry is assessed, suggesting that the key opportunity resides within the development of gravity gradiometry sensors to enable drastic improvements in measurement time. To push forward in realizing more compact systems, techniques have been pursued to realize a highly portable magneto-optical trap system, which represents the core package of an atom interferometry system. This can create clouds of 107 atoms within a system package of 20 l and 10 kg, consuming 80 W of power. This article is part of the themed issue ‘Quantum technology for the 21st century’. PMID:28652493

A portable magneto-optical trap with prospects for atom interferometry in civil engineering.

PubMed

Hinton, A; Perea-Ortiz, M; Winch, J; Briggs, J; Freer, S; Moustoukas, D; Powell-Gill, S; Squire, C; Lamb, A; Rammeloo, C; Stray, B; Voulazeris, G; Zhu, L; Kaushik, A; Lien, Y-H; Niggebaum, A; Rodgers, A; Stabrawa, A; Boddice, D; Plant, S R; Tuckwell, G W; Bongs, K; Metje, N; Holynski, M

2017-08-06

The high precision and scalable technology offered by atom interferometry has the opportunity to profoundly affect gravity surveys, enabling the detection of features of either smaller size or greater depth. While such systems are already starting to enter into the commercial market, significant reductions are required in order to reach the size, weight and power of conventional devices. In this article, the potential for atom interferometry based gravimetry is assessed, suggesting that the key opportunity resides within the development of gravity gradiometry sensors to enable drastic improvements in measurement time. To push forward in realizing more compact systems, techniques have been pursued to realize a highly portable magneto-optical trap system, which represents the core package of an atom interferometry system. This can create clouds of 10 7 atoms within a system package of 20 l and 10 kg, consuming 80 W of power.This article is part of the themed issue 'Quantum technology for the 21st century'. © 2017 The Author(s).

Elastic rebound following the Kocaeli earthquake, Turkey, recorded using synthetic aperture radar interferometry

USGS Publications Warehouse

Mayer, Larry; Lu, Zhong

2001-01-01

A basic model incorporating satellite synthetic aperture radar (SAR) interferometry of the fault rupture zone that formed during the Kocaeli earthquake of August 17, 1999, documents the elastic rebound that resulted from the concomitant elastic strain release along the North Anatolian fault. For pure strike-slip faults, the elastic rebound function derived from SAR interferometry is directly invertible from the distribution of elastic strain on the fault at criticality, just before the critical shear stress was exceeded and the fault ruptured. The Kocaeli earthquake, which was accompanied by as much as ∼5 m of surface displacement, distributed strain ∼110 km around the fault prior to faulting, although most of it was concentrated in a narrower and asymmetric 10-km-wide zone on either side of the fault. The use of SAR interferometry to document the distribution of elastic strain at the critical condition for faulting is clearly a valuable tool, both for scientific investigation and for the effective management of earthquake hazard.

Accessing High Spatial Resolution in Astronomy Using Interference Methods

NASA Astrophysics Data System (ADS)

Carbonel, Cyril; Grasset, Sébastien; Maysonnave, Jean

2018-04-01

In astronomy, methods such as direct imaging or interferometry-based techniques (Michelson stellar interferometry for example) are used for observations. A particular advantage of interferometry is that it permits greater spatial resolution compared to direct imaging with a single telescope, which is limited by diffraction owing to the aperture of the instrument as shown by Rueckner et al. in a lecture demonstration. The focus of this paper, addressed to teachers and/or students in high schools and universities, is to easily underline both an application of interferometry in astronomy and stress its interest for resolution. To this end very simple optical experiments are presented to explain all the concepts. We show how an interference pattern resulting from the combined signals of two telescopes allows us to measure the distance between two stars with a resolution beyond the diffraction limit. Finally this work emphasizes the breathtaking resolution obtained in state-of-the-art instruments such as the VLTi (Very Large Telescope interferometer).

Double-path acquisition of pulse wave transit time and heartbeat using self-mixing interferometry

NASA Astrophysics Data System (ADS)

Wei, Yingbin; Huang, Wencai; Wei, Zheng; Zhang, Jie; An, Tong; Wang, Xiulin; Xu, Huizhen

2017-06-01

We present a technique based on self-mixing interferometry for acquiring the pulse wave transit time (PWTT) and heartbeat. A signal processing method based on Continuous Wavelet Transform and Hilbert Transform is applied to extract potentially useful information in the self-mixing interference (SMI) signal, including PWTT and heartbeat. Then, some cardiovascular characteristics of the human body are easily acquired without retrieving the SMI signal by complicated algorithms. Experimentally, the PWTT is measured on the finger and the toe of the human body using double-path self-mixing interferometry. Experimental statistical data show the relation between the PWTT and blood pressure, which can be used to estimate the systolic pressure value by fitting. Moreover, the measured heartbeat shows good agreement with that obtained by a photoplethysmography sensor. The method that we demonstrate, which is based on self-mixing interferometry with significant advantages of simplicity, compactness and non-invasion, effectively illustrates the viability of the SMI technique for measuring other cardiovascular signals.

Modulation of Polarization for Phase Extraction in Holographic Interferometry with Two References

NASA Astrophysics Data System (ADS)

Rodriguez-Zurita, G.; Vázquez-Castillo, J.-F.; Toto-Arellano, N.-I.; Meneses-Fabian, C.; Jiménez-Montero, L.-E.

2010-04-01

Heterodyne holographic interferometry allows high accuracy for phase-difference extraction between two wave fronts, especially when they are previously recorded in the same recording medium. In part, this is because the wave fronts can be affected by the recording process in a very similar way. The double reconstruction of a double-exposure hologram with two independent references results in a two-beam holographic interferometer with an arm conveying a wave modulated in frequency when using heterodyne techniques. The heterodyne frequency has been usually introduced with a plane mirror attached to a piezo-electric stack driven with a suitable variable power supply. For holographic interferometry, however, less attention has been devoted to alternative phase retrieval variants as, for example, phase-shifting with modulation of polarization or Fourier methods. In this work, we propose and demonstrate the basic capabilities of modulation of polarization performing as a phase-shifting technique for holographic interferometry with two references in a phase-stepping scheme. Experimental results are provided.

Austral echoes of Shklovsky

NASA Astrophysics Data System (ADS)

Edwards, P. G.

On the occasion of the 100th anniversary of the birth of Iosif Shklovsky, this paper reviews a number of his contributions to astrophysics. As a means of considering the impact of these contributions, the diverse and ongoing connections that these have to current research activities in Australia are examined.

The Fraser Gyre: A cyclonic eddy off the coast of eastern Australia

NASA Astrophysics Data System (ADS)

Azis Ismail, Mochamad Furqon; Ribbe, Joachim; Karstensen, Johannes; Lemckert, Charles; Lee, Serena; Gustafson, Johann

2017-06-01

This paper examines the on-shelf circulation of the eastern Australian continental shelf for a region off southeast Queensland. We identify a characteristic seasonally reoccurring wind-driven cyclonic flow. It influences the cross-shelf exchange with the East Australian Current (EAC), which is the western boundary current of the South Pacific Ocean. We refer to this cyclonic circulation as the Fraser Gyre. It is located south of Fraser Island between about 25 °S and 27 °S. The region is adjacent to the intensification zone of the EAC where the current accelerates and establishes a swift, albeit seasonally variable southward boundary flow. Through the analysis of several data sets including remotely sensed sea surface temperature and sea surface height anomaly, satellite tracked surface drifters, ocean and atmospheric reanalysis data as well as geostrophic currents from altimetry, we find that the on-shelf Fraser Gyre develops during the southern hemisphere autumn and winter months. The gyre is associated with a longshore near-coast northward flow. Maximum northward on-shelf depth averaged velocities are estimated with about 0.15-0.26 ms-1. The flow turns eastward just to the south of Fraser Island and joins the persistent southward EAC flow along the shelf break. The annual mean net cross-shelf outward and inward flow associated with the gyre is about -1.17 ± 0.23 Sv in the north and 0.23 ± 0.13 Sv (1 Sv = 106 m3s-1) in the south. Mean seasonal water renewal time scales of the continental shelf are longest during austral winter with an average of about 3.3 days due to the Fraser Gyre retaining water over the shelf, however, monthly estimates range from 2 to 8 days with the longer timescale during the austral autumn and winter. The southerly wind during austral autumn and winter is identified as controlling the on shelf circulation and is the principal driver of the seasonally appearing Fraser Gyre. The conceptual model of the Fraser Gyre is consistent with general physical principals of the coastal shelf circulation. A southerly wind is associated with surface layer flow toward the coast, a near coast positive SSHa with a current in the direction of the wind, down-welling and export of shelf water. The Fraser Gyre influenced cross-shelf exchanges are possibly facilitating the offshore transport of fish larvae, sediments, nutrients, river discharges, and other properties across the shelf break and into the southward flowing EAC during the austral autumn and winter.

The CHARA Array Database

NASA Astrophysics Data System (ADS)

Jones, Jeremy; Schaefer, Gail; ten Brummelaar, Theo; Gies, Douglas; Farrington, Christopher

2018-01-01

We are building a searchable database for the CHARA Array data archive. The Array consists of six telescopes linked together as an interferometer, providing sub-milliarcsecond resolution in the optical and near-infrared. The Array enables a variety of scientific studies, including measuring stellar angular diameters, imaging stellar shapes and surface features, mapping the orbits of close binary companions, and resolving circumstellar environments. This database is one component of an NSF/MSIP funded program to provide open access to the CHARA Array to the broader astronomical community. This archive goes back to 2004 and covers all the beam combiners on the Array. We discuss the current status of and future plans for the public database, and give directions on how to access it.

Digitally Enhanced Heterodyne Interferometry

NASA Technical Reports Server (NTRS)

Shaddock, Daniel; Ware, Brent; Lay, Oliver; Dubovitsky, Serge

2010-01-01

Spurious interference limits the performance of many interferometric measurements. Digitally enhanced interferometry (DEI) improves measurement sensitivity by augmenting conventional heterodyne interferometry with pseudo-random noise (PRN) code phase modulation. DEI effectively changes the measurement problem from one of hardware (optics, electronics), which may deteriorate over time, to one of software (modulation, digital signal processing), which does not. DEI isolates interferometric signals based on their delay. Interferometric signals are effectively time-tagged by phase-modulating the laser source with a PRN code. DEI improves measurement sensitivity by exploiting the autocorrelation properties of the PRN to isolate only the signal of interest and reject spurious interference. The properties of the PRN code determine the degree of isolation.

[Foot arch shape in children aged 2-5 years according to the data of plantography and holographic interferometry].

PubMed

bol'shakov, O P; Kotov, I R; Poliakova, E L

2014-01-01

25 children aged 2 to 5 years were examined orthopedically using the methods of plantometry and holographic interferometry of three-dimensional casts of footprints. The computer maps of the foot arch surface were obtained and the graphic reconstruction of the arch shape was performed in normal cases and in children with flatfoot. Most significant deviations of the foot arch shape, probably associated with the development delay, were detected in 4-5-year-old children under the dynamic load. Some additional advantages of holographic interferometry for the early diagnosis of flatfoot in children were demonstrated.

Speckle interferometry of asteroids

NASA Technical Reports Server (NTRS)

Drummond, Jack D.; Hege, E. Keith

1989-01-01

Steward Observatory's two-dimensional power spectrum signature analysis of speckle interferometry observations is summarized. Results for six asteroids are presented. The poles and triaxial ellipsoid dimensions of 4 Vesta, 433 Eros, 511 Davida, and 532 Herculina have been previously reported. New results for 2 Pallas and 29 Amphitrite are given, as well as further results for Vesta. Image reconstruction is ultimately required to minimize biasing effects of asteroid surface features on the simpler power spectrum analysis. Preliminary imaging results have been achieved for Vesta and Eros, and images for these two are displayed. Speckle interferometry and radiometry diameters are compared, and diameters from the two occultations of Pallas are addressed.

The Wide-Field Imaging Interferometry Testbed (WIIT): Recent Progress and Results

NASA Technical Reports Server (NTRS)

Rinehart, Stephen A.; Frey, Bradley J.; Leisawitz, David T.; Lyon, Richard G.; Maher, Stephen F.; Martino, Anthony J.

2008-01-01

Continued research with the Wide-Field Imaging Interferometry Testbed (WIIT) has achieved several important milestones. We have moved WIIT into the Advanced Interferometry and Metrology (AIM) Laboratory at Goddard, and have characterized the testbed in this well-controlled environment. The system is now completely automated and we are in the process of acquiring large data sets for analysis. In this paper, we discuss these new developments and outline our future research directions. The WIIT testbed, combined with new data analysis techniques and algorithms, provides a demonstration of the technique of wide-field interferometric imaging, a powerful tool for future space-borne interferometers.

Optical interferometry study of film formation in lubrication of sliding and/or rolling contacts

NASA Technical Reports Server (NTRS)

Stejskal, E. O.; Cameron, A.

1972-01-01

Seventeen fluids of widely varying physical properties and molecular structure were chosen for study. Film thickness and traction were measured simultaneously in point contacts by interferometry, from which a new theory of traction was proposed. Film thickness was measured in line contacts by interferometry and electrical capacitance to establish correlation between these two methods. An interferometric method for the absolute determination of refractive index in the contact zone was developed and applied to point contact fluid entrapments. Electrical capacitance was used to study the thickness and properties of the soft surface film which sometimes forms near a metal-fluid interface.

Optical fiber Fabry-Perot interferometry

NASA Astrophysics Data System (ADS)

Wang, Anbo

2014-06-01

Fiber Fabry-Perot (FP) interferometry is one of the most important tools for harsh environment sensing because of its great flexibility of sensor material selection, superior long-­-term stability, and nature of remote passive operation. Virginia Tech's Center for Photonics Technology has been involved in the research of this field for many years. After a quick review of the typical methods for the construction of F-P sensors, emphasis will be placed on the whitelight interferometry, which is perhaps the most robust interferometric sensor demodulation technique today. The recent discovery of an additional phase will be presented and its significance to the sensor demodulation will be discussed.

Modulated Source Interferometry with Combined Amplitude and Frequency Modulation

NASA Technical Reports Server (NTRS)

Gutierrez, Roman C. (Inventor)

1998-01-01

An improved interferometer is produced by modifying a conventional interferometer to include amplitude and/or frequency modulation of a coherent light source at radio or higher frequencies. The phase of the modulation signal can be detected in an interfering beam from an interferometer and can be used to determine the actual optical phase of the beam. As such, this improvement can be adapted to virtually any two-beam interferometer, including: Michelson, Mach-Zehnder, and Sagnac interferometers. The use of an amplitude modulated coherent tight source results in an interferometer that combines the wide range advantages of coherent interferometry with the precise distance measurement advantages of white light interferometry.

The Path to Far-IR Interferometry in Space: Recent Developments, Plans, and Prospects

NASA Technical Reports Server (NTRS)

Leisawitz, David T.; Rinehart, Stephen A.

2012-01-01

The far-IR astrophysics community is eager to follow up Spitzer and Herschel observations with sensitive, highresolution imaging and spectroscopy, for such measurements are needed to understand merger-driven star formation and chemical enrichment in galaxies, star and planetary system formation, and the development and prevalence of waterbearing planets. The community is united in its support for a space-based interferometry mission. Through concerted efforts worldwide, the key enabling technologies are maturing. Two balloon-borne far-IR interferometers are presently under development. This paper reviews recent technological and programmatic developments, summarizes plans, and offers a vision for space-based far-IR interferometry involving international collaboration.

Amplitude and intensity spatial interferometry; Proceedings of the Meeting, Tucson, AZ, Feb. 14-16, 1990

NASA Technical Reports Server (NTRS)

Breckinridge, Jim B. (Editor)

1990-01-01

Attention is given to such topics as ground interferometers, space interferometers, speckle-based and interferometry-based astronomical observations, adaptive and atmospheric optics, speckle techniques, and instrumentation. Particular papers are presented concerning recent progress on the IR Michelson array; the IOTA interferometer project; a space interferometer concept for the detection of extrasolar earth-like planets; IR speckle imaging at Palomar; optical diameters of stars measured with the Mt. Wilson Mark III interferometer; the IR array camera for interferometry with the cophased Multiple Mirror Telescope; optimization techniques appliesd to the bispectrum of one-dimensional IR astronomical speckle data; and adaptive optical iamging for extended objects.

Synthetic aperture imaging in astronomy and aerospace: introduction.

PubMed

Creech-Eakman, Michelle J; Carney, P Scott; Buscher, David F; Shao, Michael

2017-05-01

Aperture synthesis methods allow the reconstruction of images with the angular resolutions exceeding that of extremely large monolithic apertures by using arrays of smaller apertures together in combination. In this issue we present several papers with techniques relevant to amplitude interferometry, laser radar, and intensity interferometry applications.

Mask Design for the Space Interferometry Mission Internal Metrology

NASA Technical Reports Server (NTRS)

Marx, David; Zhao, Feng; Korechoff, Robert

2005-01-01

This slide presentation reviews the mask design used for the internal metrology of the Space Interferometry Mission (SIM). Included is information about the project, the method of measurements with SIM, the internal metrology, numerical model of internal metrology, wavefront examples, performance metrics, and mask design

Systemic errors calibration in dynamic stitching interferometry

NASA Astrophysics Data System (ADS)

Wu, Xin; Qi, Te; Yu, Yingjie; Zhang, Linna

2016-05-01

The systemic error is the main error sauce in sub-aperture stitching calculation. In this paper, a systemic error calibration method is proposed based on pseudo shearing. This method is suitable in dynamic stitching interferometry for large optical plane. The feasibility is vibrated by some simulations and experiments.

Signal Processing in Cold Atom Interferometry-Based INS

DTIC Science & Technology

2014-03-27

INTERFEROMETRY-BASED INS Kara M. Willis, BS Civilian, DAF Approved: //signed// Meir Pachter, PhD (Chairman) //signed// Maj Marshall Haker , PhD (Member) //signed...matter mentors, Maj Marshall Haker and Dr Kyle Kauffman, for their insights and unwavering encouragement. Kara M. Willis v Table of Contents Page

Seismic interferometry by crosscorrelation and by multidimensional deconvolution: a systematic comparison

NASA Astrophysics Data System (ADS)

Wapenaar, Kees; van der Neut, Joost; Ruigrok, Elmer; Draganov, Deyan; Hunziker, Jürg; Slob, Evert; Thorbecke, Jan; Snieder, Roel

2011-06-01

Seismic interferometry, also known as Green's function retrieval by crosscorrelation, has a wide range of applications, ranging from surface-wave tomography using ambient noise, to creating virtual sources for improved reflection seismology. Despite its successful applications, the crosscorrelation approach also has its limitations. The main underlying assumptions are that the medium is lossless and that the wavefield is equipartitioned. These assumptions are in practice often violated: the medium of interest is often illuminated from one side only, the sources may be irregularly distributed, and losses may be significant. These limitations may partly be overcome by reformulating seismic interferometry as a multidimensional deconvolution (MDD) process. We present a systematic analysis of seismic interferometry by crosscorrelation and by MDD. We show that for the non-ideal situations mentioned above, the correlation function is proportional to a Green's function with a blurred source. The source blurring is quantified by a so-called interferometric point-spread function which, like the correlation function, can be derived from the observed data (i.e. without the need to know the sources and the medium). The source of the Green's function obtained by the correlation method can be deblurred by deconvolving the correlation function for the point-spread function. This is the essence of seismic interferometry by MDD. We illustrate the crosscorrelation and MDD methods for controlled-source and passive-data applications with numerical examples and discuss the advantages and limitations of both methods.

Pines

Treesearch

C. Dana Nelson; Gary F. Peter; Steven E. McKeand; Eric J. Jokela; Robert B. Rummer; Les Groom; Kurt H. Johnsen

2013-01-01

The southern pines (yellow or hard pines, Genus Pinus Sub-genus Pinus Section Pinus Subsection Australes) occupy an immense land-base in the southeastern region of the United States (Little and Critchfield, 1969). In addition, they are planted and managed for wood production on millions of hectares worldwide including China, Brazil, Argentina, and Australia. The...

Dehydration, rehydration and overhydration alter patterns of gene expression in the Antarctic midge, Belgica antarctica

USDA-ARS?s Scientific Manuscript database

We investigated molecular responses elicited by three types of dehydration (fast, slow and cryoprotective), rehydration and overhydration in larvae of the Antarctic midge, Belgica antarctica. The larvae spend most the year encased in ice but during the austral summer are vulnerable to summer storms,...

From East Gondwana to Central America: Historical biogeography of the Alstroemeriaceae

USDA-ARS?s Scientific Manuscript database

Southern South America and Australia/New Zealand share some 15 plant families more or less restricted to them. Understanding these Austral floristic links requires extensive sampling in both regions. For the Alstroemeriaceae, with 189 species in three South American genera, two in an Australian/Tasm...

Reference karyotype and cytomolecular map for loblolly pine (Pinus taeda L.)

Treesearch

M. Nurul Islam-faridi; C. Dana Nelson; Thomas L. Kubisiak

2007-01-01

A reference karyotype is presented for loblolly pine (Pinus taeda L., subgenus Pinus , section Pinus, subsection Australes), based on fluorescent in situ hybridization (FISH), using 18s-28s rDNA, 5s rDNA, and Arabidopsis-type telomere repeat sequence (A-type TRS). Well...

Analysis of the principal component algorithm in phase-shifting interferometry.

PubMed

Vargas, J; Quiroga, J Antonio; Belenguer, T

2011-06-15

We recently presented a new asynchronous demodulation method for phase-sampling interferometry. The method is based in the principal component analysis (PCA) technique. In the former work, the PCA method was derived heuristically. In this work, we present an in-depth analysis of the PCA demodulation method.

The Spatially Resolved H(alpha)-Emitting Wind Structure of P Cygni

DTIC Science & Technology

2010-06-01

using radio and optical interferometry, as well as direct imaging with adaptive optics (AO). Radio interferometric observations detect the nebula around...to structures in the nebula of P Cyg that are more than an order of magnitude smaller. Therefore, optical interferometry provides a unique window of

The Compact and Inexpensive "Arrowhead" Setup for Holographic Interferometry

ERIC Educational Resources Information Center

Ladera, Celso L.; Donoso, Guillermo

2011-01-01

Hologram recording and holographic interferometry are intrinsically sensitive to phase changes, and therefore both are easily perturbed by minuscule optical path perturbations. It is therefore very convenient to bank on holographic setups with a reduced number of optical components. Here we present a compact off-axis holographic setup that…

Milk matrix effects on antibody binding analyzed by elisa and biolayer interferometry

USDA-ARS?s Scientific Manuscript database

Biolayer interferometry (BLI) was employed to study the impact of the milk matrix on the binding of ricin to asialofetuin (ASF) and to antibodies. This optical sensing platform utilized ligands immobilized covalently or via biotin-streptavidin linkage, and the results were compared to those obtained...

TOPSAT: Global space topographic mission

NASA Technical Reports Server (NTRS)

Vetrella, Sergio

1993-01-01

Viewgraphs on TOPSAT Global Space Topographic Mission are presented. Topics covered include: polar region applications; terrestrial ecosystem applications; stereo electro-optical sensors; space-based stereoscopic missions; optical stereo approach; radar interferometry; along track interferometry; TOPSAT-VISTA system approach; ISARA system approach; topographic mapping laser altimeter; and role of multi-beam laser altimeter.

Multiple Beam Interferometry in Elementary Teaching

ERIC Educational Resources Information Center

Tolansky, S.

1970-01-01

Discusses a relatively simple technique for demonstrating multiple beam interferometry. The technique can be applied to measuring (1) radii of curvature of lenses, (2) surface finish of glass, and (3) differential phase change on reflection. Microtopographies, modulated fringe systems and opaque objects may also be observed by this technique.…

Vision: A Six-telescope Fiber-fed Visible Light Beam Combiner for the Navy Precision Optical Interferometer

DTIC Science & Technology

2016-05-01

Visible-light long baseline interferometry holds the promise of advancing a number of important applications in fundamental astronomy, including the...advance the field of visible-light interferometry requires development of instruments capable of combing light from 15 baselines (6 telescopes

Optical Biosensing: Kinetics of Protein A-IGG Binding Using Biolayer Interferometry

ERIC Educational Resources Information Center

Wilson, Jo Leanna; Scott, Israel M.; McMurry, Jonathan L.

2010-01-01

An undergraduate biochemistry laboratory experiment has been developed using biolayer interferometry (BLI), an optical biosensing technique similar to surface plasmon resonance (SPR), in which students obtain and analyze kinetic data for a protein-protein interaction. Optical biosensing is a technique of choice to determine kinetic and affinity…

Polarimetric Interferometry - Remote Sensing Applications

DTIC Science & Technology

2007-02-01

This lecture is mainly based on the work of S.R. Cloude and presents examples for remote sensing applications Polarimetric SAR Interferometry...PolInSAR). PolInSAR has its origins in remote sensing and was first developed for applications in 1997 using SIRC L-Band data [1,2]. In its original form it

Accurate free and forced rotational motions of rigid Venus

NASA Astrophysics Data System (ADS)

Cottereau, L.; Souchay, J.; Aljbaae, S.

2010-06-01

Context. The precise and accurate modelling of a terrestrial planet like Venus is an exciting and challenging topic, all the more interesting because it can be compared with that of Earth for which such a modelling has already been achieved at the milli-arcsecond level. Aims: We aim to complete a previous study, by determining the polhody at the milli-arcsecond level, i.e. the torque-free motion of the angular momentum axis of a rigid Venus in a body-fixed frame, as well as the nutation of its third axis of figure in space, which is fundamental from an observational point of view. Methods: We use the same theoretical framework as Kinoshita (1977, Celest. Mech., 15, 277) did to determine the precession-nutation motion of a rigid Earth. It is based on a representation of the rotation of a rigid Venus, with the help of Andoyer variables and a set of canonical equations in Hamiltonian formalism. Results: In a first part we computed the polhody, we showed that this motion is highly elliptical, with a very long period of 525 cy compared with 430 d for the Earth. This is due to the very small dynamical flattening of Venus in comparison with our planet. In a second part we precisely computed the Oppolzer terms, which allow us to represent the motion in space of the third Venus figure axis with respect to the Venus angular momentum axis under the influence of the solar gravitational torque. We determined the corresponding tables of the nutation coefficients of the third figure axis both in longitude and in obliquity due to the Sun, which are of the same order of amplitude as for the Earth. We showed that the nutation coefficients for the third figure axis are significantly different from those of the angular momentum axis on the contrary of the Earth. Our analytical results have been validated by a numerical integration, which revealed the indirect planetary effects.

Fine pointing control for a Next-Generation Space Telescope

NASA Astrophysics Data System (ADS)

Mosier, Gary E.; Femiano, Michael; Ha, Kong; Bely, Pierre Y.; Burg, Richard; Redding, David C.; Kissil, Andrew; Rakoczy, John; Craig, Larry

1998-08-01

The Next Generation Space Telescope will provide at least ten times the collecting area of the Hubble Space Telescope in a package that fits into the shroud of an expendable launch vehicle. The resulting large, flexible structure provides a challenge to the design of a pointing control system for which the requirements are at the milli-arcsecond level. This paper describes a design concept in which pointing stability is achieved by means of a nested-loop design involving an inertial attitude control system (ACS) and a fast steering mirror (FSM). A key to the integrated control design is that the ACS controllers has a bandwidth well below known structural modes and the FSM uses a rotationally balanced mechanism which should not interact with the flexible modes that are within its control bandwidth. The ACS controller provides stable pointing of the spacecraft bus with star trackers and gyros. This low bandwidth loop uses nearly co-located sensors and actuators to slew and acquire faint guide stars in the NIR camera. This controller provides a payload reference stable to the arcsecond level. Low-frequency pointing errors due to sensor noise and dynamic disturbances are suppressed by a 2-axis gimbaled FSM locate din the instrument module. The FSM servo bandwidth of 6 Hz is intended to keep the guide star position stable in the NIR focal plane to the required milli-arcsecond level. The mirror is kept centered in its range of travel by a low-bandwidth loop closed around the ACS. This paper presents the result of parametric trade studies designed to assess the performance of this control design in the presence of modeled reaction wheel disturbances, assumed to be the principle source of vibration for the NGST, and variations in structural dynamics. Additionally, requirements for reaction wheel disturbance levels and potential vibration isolation subsystems were developed.

Revealing H I gas in emission and absorption on pc to kpc scales in a galaxy at z ˜ 0.017

NASA Astrophysics Data System (ADS)

Gupta, N.; Srianand, R.; Farnes, J. S.; Pidopryhora, Y.; Vivek, M.; Paragi, Z.; Noterdaeme, P.; Oosterloo, T.; Petitjean, P.

2018-05-01

We present a detailed study of the quasar-galaxy pair: J1243+4043-UGC 07904. The sight line of the background quasar ( zq = 1.5266) passes through a region of the galaxy (zg = 0.0169) at an impact parameter of 6.9 kpc with high metallicity (0.5 Z⊙) and negligible dust extinction. We detect H I 21-cm absorption from the foreground galaxy at arcsecond and milliarcsecond scales. For typical cold neutral medium (CNM) temperatures in the Milky Way, this 21-cm absorber can be classified as a damped Lyα absorber (DLA). We infer the harmonic mean spin temperature of the gas to be ˜400 K and for a simple two-phase medium we estimate the CNM fraction to be fCNM = 0.27. This is remarkably consistent with the CNM fraction observed in the Galaxy and less than that of high-redshift DLAs. The quasar exhibits a core-jet morphology on milliarcsecond scales, corresponding to an overall extent of ˜9 pc at zg. We show that the size of CNM absorbing clouds associated with the foreground galaxy is >5 pc and they may be part of cold gas structures that extend beyond ˜35 pc. Interestingly, the rotation measure of quasar J1243+4043 is higher than any other source in samples of quasars with high-z DLAs. However, we do not find any detectable differences in rotation measures and polarization fraction of sight lines with or without high-z (z ≥ 2) DLAs or low-z (z ≤ 0.3) 21-cm absorbers. Finally, the foreground galaxy UGC 07904 is also part of a galaxy group. We serendipitously detect H I 21-cm emission from four members of the group, and an ˜80 kpc long H I bridge connecting two of the other members. The latter, together with the properties of the group members, suggests that the group is a highly interactive environment.

Stellar Imager

NASA Technical Reports Server (NTRS)

Carpenter, Kenneth

2007-01-01

The Stellar Imager (SI) is one of NASA's "Vision Missions" - concepts for future, space-based, strategic missions that could enormously increase our capabilities for observing the Cosmos. SI is designed as a UV/Optical Interferometer which will enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and, via asteroseismology, stellar interiors and of the Universe in general. The ultra-sharp images of the Stellar Imager will revolutionize our view of many dynamic astrophysical processes by transforming point sources into extended sources, and snapshots into evolving views. SI, with a characteristic angular resolution of 0.1 milli-arcseconds at 2000 Angstroms, represents an advance in image detail of several hundred times over that provided by the Hubble Space Telescope. The Stellar Imager will zoom in on what today-with few exceptions - we only know as point sources, revealing processes never before seen, thus providing a tool as fundamental to astrophysics as the microscope is to the study of life on Earth. SI's science focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. It's prime goal is to enable long-term forecasting of solar activity and the space weather that it drives, in support of the Living With a Star program in the Exploration Era. SI will also revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magneto-hydrodynamically controlled processes in the Universe. Stellar Imager is included as a "Flagship and Landmark Discovery Mission" in the 2005 Sun Solar System Connection (SSSC) Roadmap and as a candidate for a "Pathways to Life Observatory" in the Exploration of the Universe Division (EUD) Roadmap (May, 2005) and as such is a candidate mission for the 2025-2030 timeframe. An artist's drawing of the current "baseline" concept for SI is presented.

Plasmas with an index of refraction greater than 1.

PubMed

Nilsen, Joseph; Scofield, James H

2004-11-15

Over the past decade, x-ray lasers in the wavelength range 14-47 nm have been used for interferometry of plasmas. As in optical interferometry of plasmas, the experimental analysis assumed that the index of refraction is due only to free electrons. This makes the index of refraction less than 1. Recent experiments in A1 plasmas have shown fringe lines bending the wrong way as though the electron density were negative. We show how the bound electrons can dominate the index of refraction in many plasmas and make the index greater than 1 or enhance the index such that one would greatly overestimate the density of the plasma using interferometry.

Threshold multi-secret sharing scheme based on phase-shifting interferometry

NASA Astrophysics Data System (ADS)

Deng, Xiaopeng; Wen, Wei; Shi, Zhengang

2017-03-01

A threshold multi-secret sharing scheme is proposed based on phase-shifting interferometry. The K secret images to be shared are firstly encoded by using Fourier transformation, respectively. Then, these encoded images are shared into many shadow images based on recording principle of the phase-shifting interferometry. In the recovering stage, the secret images can be restored by combining any 2 K + 1 or more shadow images, while any 2 K or fewer shadow images cannot obtain any information about the secret images. As a result, a (2 K + 1 , N) threshold multi-secret sharing scheme can be implemented. Simulation results are presented to demonstrate the feasibility of the proposed method.

Laser interferometry for the determination of thickness distributions of low absorbing films and their spatial and thickness resolutions.

PubMed

Mishima, T; Kao, K C

1982-03-15

New laser interferometry has been developed, based on the principle that a 2-D fringe pattern can be produced by interference of spatially coherent light beams. To avoid the effect of reflection from the back surface of the substrate, the Brewster angle of incidence is adopted; to suppress the effect of diffraction, a lens or a lens system is used. This laser interferometry is an efficient nondestructive technique for the determination of thickness distributions or uniformities of low absorbing films on transparent substrates over a large area without involving laborious computations. The limitation of spatial resolution, thickness resolution, and visibility of fringes is fully analyzed.

Dual-hologram shearing interferometry with regulated sensitivity

NASA Astrophysics Data System (ADS)

Toker, Gregory R.; Levin, Daniel

1998-07-01

A novel optical diagnostic technique, namely, a dual hologram shearing interferometry with regulated sensitivity, is proposed for visualization and measuring the density gradients of compressible flows in wind tunnels. It has advantages over conventional shearing interferometry in both accuracy and sensitivity. The method is especially useful for strong turbulent or unsteady regions of the flows including shock flows. The interferometer proved to be insensitive to mechanical vibrations and allowed to record holograms during the noisy wind tunnel run. The proposed approach was demonstrated by its application to a supersonic flow over spherically blunted and sharp nose cone/cylinder models. It is believed that the technique will become an effective tool for receiving optical data in many flow facilities.

Freeform metrology using subaperture stitching interferometry

NASA Astrophysics Data System (ADS)

Supranowitz, Chris; Lormeau, Jean-Pierre; Maloney, Chris; Murphy, Paul; Dumas, Paul

2016-11-01

As applications for freeform optics continue to grow, the need for high-precision metrology is becoming more of a necessity. Currently, coordinate measuring machines (CMM) that implement touch probes or optical probes can measure the widest ranges of shapes of freeform optics, but these measurement solutions often lack sufficient lateral resolution and accuracy. Subaperture stitching interferometry (SSI™) extends traditional Fizeau interferometry to provide accurate, high-resolution measurements of flats, spheres, and aspheres, and development is currently on-going to enable measurements of freeform surfaces. We will present recent freeform metrology results, including repeatability and cross-test data. We will also present MRF® polishing results where the stitched data was used as the input "hitmap" to the deterministic polishing process.

Measurements of 427 Double Stars With Speckle Interferometry: The Winter/Spring 2017 Observing Program at Brilliant Sky Observatory, Part 1

NASA Astrophysics Data System (ADS)

Harshaw, Richard

2018-04-01

In the winter and spring of 2017, an aggressive observing program of measuring close double stars with speckle interferometry and CCD imaging was undertaken at Brilliant Sky Observatory, my observing site in Cave Creek, Arizona. A total of 596 stars were observed, 8 of which were rejected for various reasons, leaving 588 pairs. Of these, 427 were observed and measured with speckle interferometry, while the remaining 161 were measured with a CCD. This paper reports the results of the observations of the 427 speckle cases. A separate paper in this issue will report the CCD measurements of the 161 other pairs.

Interferometry

NASA Astrophysics Data System (ADS)

Totzeck, Michael

The intention of this chapter is to provide a fast and comprehensive overview of the principles of interferometry and the various types of interferometer, including interferogram evaluation and applications. Due to the age and the importance of the subject, you can find a number of monographs [16.1,2,3,4] and book chapters [16.5] in the literature. The number of original papers on optical interferometry is far too large to even attempt complete coverage in this chapter. Whenever possible, review papers are cited. Original papers are cited according to their aptness as starting points into the subject. This, however, reflects my personal judgment. Even if you do not share my opinion, you should find the references therein useful.

Optical Distortion Evaluation in Large Area Windows using Interferometry

NASA Technical Reports Server (NTRS)

Youngquist, Robert C.; Skow, Miles; Nurge, Mark A.

2015-01-01

It is important that imagery seen through large area windows, such as those used on space vehicles, not be substantially distorted. Many approaches are described in the literature for measuring the distortion of an optical window, but most suffer from either poor resolution or processing difficulties. In this paper a new definition of distortion is presented, allowing accurate measurement using an optical interferometer. This new definition is shown to be equivalent to the definitions provided by the military and the standards organizations. In order to determine the advantages and disadvantages of this new approach the distortion of an acrylic window is measured using three different methods; image comparison, Moiré interferometry, and phase-shifting interferometry.

A recent history of science cases for optical interferometry

NASA Astrophysics Data System (ADS)

Defrère, Denis; Aerts, Conny; Kishimoto, Makoto; Léna, Pierre

2018-04-01

Optical long-baseline interferometry is a unique and powerful technique for astronomical research. Since the 1980's (with I2T, GI2T, Mark I to III, SUSI, ...), optical interferometers have produced an increasing number of scientific papers covering various fields of astrophysics. As current interferometric facilities are reaching their maturity, we take the opportunity in this paper to summarize the conclusions of a few key meetings, workshops, and conferences dedicated to interferometry. We present the most persistent recommendations related to science cases and discuss some key technological developments required to address them. In the era of extremely large telescopes, optical long-baseline interferometers will remain crucial to probe the smallest spatial scales and make breakthrough discoveries.

Hologram interferometry in automotive component vibration testing

NASA Astrophysics Data System (ADS)

Brown, Gordon M.; Forbes, Jamie W.; Marchi, Mitchell M.; Wales, Raymond R.

1993-02-01

An ever increasing variety of automotive component vibration testing is being pursued at Ford Motor Company, U.S.A. The driving force for use of hologram interferometry in these tests is the continuing need to design component structures to meet more stringent functional performance criteria. Parameters such as noise and vibration, sound quality, and reliability must be optimized for the lightest weight component possible. Continually increasing customer expectations and regulatory pressures on fuel economy and safety mandate that vehicles be built from highly optimized components. This paper includes applications of holographic interferometry for powertrain support structure tuning, body panel noise reduction, wiper system noise and vibration path analysis, and other vehicle component studies.

An Experimental Weight Function Method for Stress Intensity Factor Calibration.

DTIC Science & Technology

1980-04-01

in accuracy to the ones obtained by Macha (Reference 10) for the laser interferometry technique. The values of KI from the interpolating polynomial...Measurement. Air Force Material Laboratories, AFML-TR-74-75, July 1974. 10. D. E. Macha , W. N. Sharpe Jr., and A. F. Grandt Jr., A Laser Interferometry

Multi-scale Computational Electromagnetics for Phenomenology and Saliency Characterization in Remote Sensing

DTIC Science & Technology

2014-06-12

interferometry and polarimetry . In the paper, the model was used to simulate SAR data for Mangrove (tropical) and Nezer (temperate) forests for P-band and...Scattering Model Applied to Radiometry, Interferometry, and Polarimetry at P- and L-Band. IEEE Transactions on Geoscience and Remote Sensing 44(4): 849

Autonomous formation flying sensor for the Star Light Mission

NASA Technical Reports Server (NTRS)

Aung, M.; Purcell, G.; Tien, J.; Young, L.; Srinivasan, J.; Ciminera, M. A.; Chong, Y. J.; Amaro, L. R.; Young, L. E.

2002-01-01

The StarLight Mission, an element of NASA's Origins Program, was designed for first-time demonstration of two technologies: formation flying optical interferometry between spacecraft and autonomous precise formation flying of an array of spacecraft to support optical interferometry. The design overview and results of the technology effort are presented in this paper.

Radar Interferometry Detection of Hinge Line Migration on Rutford Ice Stream and Carlson Inlet, Antarctica

NASA Technical Reports Server (NTRS)

Rignot, Eric

1997-01-01

Satellite synthetic-aperture radar (SAR) Interferometry is employed to map the hinge line, or limit of tidal flexing, of Rutford Ice Stream and Carlson Inlet, Antarctica, and detect its migration between 1992 and 1996. The hinge line is mapped using a model fit from an elastic beam theory.

Appendix to theory of radio-frequency interferometry in geophysical subsurface probing, numerical results

NASA Technical Reports Server (NTRS)

Kong, J. A.; Tsang, L.

1974-01-01

A series of interference and radiation patterns are presented for radio interferometry in subsurface probing. The interference patterns are due both to a vertical magnetic dipole and to a horizontal electric dipole. Mode solutions are also presented for layer thickness equal to 1 wavelength, as well as for thin layers.

Performance analysis of an integrated GPS/inertial attitude determination system. M.S. Thesis - MIT

NASA Technical Reports Server (NTRS)

Sullivan, Wendy I.

1994-01-01

The performance of an integrated GPS/inertial attitude determination system is investigated using a linear covariance analysis. The principles of GPS interferometry are reviewed, and the major error sources of both interferometers and gyroscopes are discussed and modeled. A new figure of merit, attitude dilution of precision (ADOP), is defined for two possible GPS attitude determination methods, namely single difference and double difference interferometry. Based on this figure of merit, a satellite selection scheme is proposed. The performance of the integrated GPS/inertial attitude determination system is determined using a linear covariance analysis. Based on this analysis, it is concluded that the baseline errors (i.e., knowledge of the GPS interferometer baseline relative to the vehicle coordinate system) are the limiting factor in system performance. By reducing baseline errors, it should be possible to use lower quality gyroscopes without significantly reducing performance. For the cases considered, single difference interferometry is only marginally better than double difference interferometry. Finally, the performance of the system is found to be relatively insensitive to the satellite selection technique.

A programmable broadband low frequency active vibration isolation system for atom interferometry.

PubMed

Tang, Biao; Zhou, Lin; Xiong, Zongyuan; Wang, Jin; Zhan, Mingsheng

2014-09-01

Vibration isolation at low frequency is important for some precision measurement experiments that use atom interferometry. To decrease the vibrational noise caused by the reflecting mirror of Raman beams in atom interferometry, we designed and demonstrated a compact stable active low frequency vibration isolation system. In this system, a digital control subsystem is used to process and feedback the vibration measured by a seismometer. A voice coil actuator is used to control and cancel the motion of a commercial passive vibration isolation platform. With the help of field programmable gate array-based control subsystem, the vibration isolation system performed flexibly and accurately. When the feedback is on, the intrinsic resonance frequency of the system will change from 0.8 Hz to about 0.015 Hz. The vertical vibration (0.01-10 Hz) measured by the in-loop seismometer is reduced by an additional factor of up to 500 on the basis of a passive vibration isolation platform, and we have proved the performance by adding an additional seismometer as well as applying it in the atom interferometry experiment.

An investigation of CO2 laser scleral buckling using moiré interferometry.

PubMed

Maswadi, Saher M; Dyer, Peter E; Verma, Dinesh; Jalabi, Wadah; Dave, Dinesh

2002-01-01

To demonstrate suitability of moiré interferometry to assess and quantify laser-induced shrinkage of scleral collagen for buckling procedures. Scleral buckling of human cadaver eyes was investigated using a Coherent Ultrapulse CO2 laser. Projection moiré interferometry was employed to determine the out-of plane displacement produced by laser exposure, and in-situ optical microscopy of reference markers on the eye was used to measure in-plane shrinkage. Measurements based on moiré interferometry allow a three dimensional view of shape changes in the eye surface as laser treatment proceeds. Out-of-plane displacement reaches up to 1.5 mm with a single laser spot exposure. In-plane shrinkage reached a maximum of around 30%, which is similar to that reported by Sasoh et al (Ophthalmic Surg Lasers. 1998;29:410) for a Tm:YAG laser. The moiré technique is found to be suitable for quantifying the effects of CO2 laser scleral shrinkage and buckling. This can be further developed to provide a standardized method for experimental investigations of other laser sources for scleral shrinkage.

Master-slave interferometry for parallel spectral domain interferometry sensing and versatile 3D optical coherence tomography.

PubMed

Podoleanu, Adrian Gh; Bradu, Adrian

2013-08-12

Conventional spectral domain interferometry (SDI) methods suffer from the need of data linearization. When applied to optical coherence tomography (OCT), conventional SDI methods are limited in their 3D capability, as they cannot deliver direct en-face cuts. Here we introduce a novel SDI method, which eliminates these disadvantages. We denote this method as Master - Slave Interferometry (MSI), because a signal is acquired by a slave interferometer for an optical path difference (OPD) value determined by a master interferometer. The MSI method radically changes the main building block of an SDI sensor and of a spectral domain OCT set-up. The serially provided signal in conventional technology is replaced by multiple signals, a signal for each OPD point in the object investigated. This opens novel avenues in parallel sensing and in parallelization of signal processing in 3D-OCT, with applications in high- resolution medical imaging and microscopy investigation of biosamples. Eliminating the need of linearization leads to lower cost OCT systems and opens potential avenues in increasing the speed of production of en-face OCT images in comparison with conventional SDI.

Development of phase detection schemes based on surface plasmon resonance using interferometry.

PubMed

Kashif, Muhammad; Bakar, Ahmad Ashrif A; Arsad, Norhana; Shaari, Sahbudin

2014-08-28

Surface plasmon resonance (SPR) is a novel optical sensing technique with a unique ability to monitor molecular binding in real-time for biological and chemical sensor applications. Interferometry is an excellent tool for accurate measurement of SPR changes, the measurement and comparison is made for the sensitivity, dynamic range and resolution of the different analytes using interferometry techniques. SPR interferometry can also employ phase detection in addition to the amplitude of the reflected light wave, and the phase changes more rapidly compared with other approaches, i.e., intensity, angle and wavelength. Therefore, the SPR phase interferometer offers the advantages of spatial phase resolution and high sensitivity. This work discusses the advancements in interferometric SPR methods to measure the phase shifts due to refractive index changes. The main application areas of SPR sensors are demonstrated, i.e., the Fabry-Perot interferometer, Michelson interferometer and Mach-Zehnder interferometer, with different configurations. The three interferometers are discussed in detail, and solutions are suggested to enhance the performance parameters that will aid in future biological and chemical sensors.

Development of Phase Detection Schemes Based on Surface Plasmon Resonance Using Interferometry

PubMed Central

Kashif, Muhammad; Bakar, Ahmad Ashrif A.; Arsad, Norhana; Shaari, Sahbudin

2014-01-01

Surface plasmon resonance (SPR) is a novel optical sensing technique with a unique ability to monitor molecular binding in real-time for biological and chemical sensor applications. Interferometry is an excellent tool for accurate measurement of SPR changes, the measurement and comparison is made for the sensitivity, dynamic range and resolution of the different analytes using interferometry techniques. SPR interferometry can also employ phase detection in addition to the amplitude of the reflected light wave, and the phase changes more rapidly compared with other approaches, i.e., intensity, angle and wavelength. Therefore, the SPR phase interferometer offers the advantages of spatial phase resolution and high sensitivity. This work discusses the advancements in interferometric SPR methods to measure the phase shifts due to refractive index changes. The main application areas of SPR sensors are demonstrated, i.e., the Fabry-Perot interferometer, Michelson interferometer and Mach-Zehnder interferometer, with different configurations. The three interferometers are discussed in detail, and solutions are suggested to enhance the performance parameters that will aid in future biological and chemical sensors. PMID:25171117

Application of Radar Data to Remote Sensing and Geographical Information Systems

NASA Technical Reports Server (NTRS)

vanZyl, Jakob J.

2000-01-01

The field of synthetic aperture radar changed dramatically over the past decade with the operational introduction of advance radar techniques such as polarimetry and interferometry. Radar polarimetry became an operational research tool with the introduction of the NASA/JPL AIRSAR system in the early 1980's, and reached a climax with the two SIR-C/X-SAR flights on board the space shuttle Endeavour in April and October 1994. Radar interferometry received a tremendous boost when the airborne TOPSAR system was introduced in 1991 by NASA/JPL, and further when data from the European Space Agency ERS-1 radar satellite became routinely available in 1991. Several airborne interferometric SAR systems are either currently operational, or are about to be introduced. Radar interferometry is a technique that allows one to map the topography of an area automatically under all weather conditions, day or night. The real power of radar interferometry is that the images and digital elevation models are automatically geometrically resampled, and could be imported into GIS systems directly after suitable reformatting. When combined with polarimetry, a technique that uses polarization diversity to gather more information about the geophysical properties of the terrain, a very rich multi-layer data set is available to the remote sensing scientist. This talk will discuss the principles of radar interferometry and polarimetry with specific application to the automatic categorization of land cover. Examples will include images acquired with the NASA/JPL AIRSAR/TOPSAR system in Australia and elsewhere.

Monitoring the englacial fracture state using virtual-reflector seismology

NASA Astrophysics Data System (ADS)

Lindner, F.; Weemstra, C.; Walter, F.; Hadziioannou, C.

2017-12-01

Fracturing and changes in the englacial macroscopic water content change the elastic bulk properties of ice bodies. Small seismic velocity variations, resulting from such changes, can be measured using a technique called coda-wave interferometry. Here, coda refers to the later-arriving, multiply scattered waves. Often, this technique is applied to so-called virtual-source responses, which can be obtained using seismic interferometry (a simple crosscorrelation process). Compared to other media (e.g., the Earth's crust), however, ice bodies exhibit relatively little scattering. This complicates the application of coda-wave interferometry to the retrieved virtual-source responses. In this work, we therefore investigate the applicability of coda-wave interferometry to virtual-source responses obtained using two alternative seismic interferometric techniques, namely, seismic interferometry by multidimensional deconvolution (SI by MDD), and virtual-reflector seismology (VRS). To that end, we use synthetic data, as well as active-source glacier data acquired on Glacier de la Plaine Morte, Switzerland. Both SI by MDD and VRS allow the retrieval of more accurate virtual-source responses. In particular, the dependence of the retrieved virtual-source responses on the illumination pattern is reduced. We find that this results in more accurate glacial phase-velocity estimates. In addition, VRS introduces virtual reflections from a receiver contour (partly) enclosing the medium of interest. By acting as a sort of virtual reverberation, the coda resulting from the application of VRS significantly increases seismic monitoring capabilities, in particular in cases where natural scattering coda is not available.

Star Scheduling Mode—A New Observing Strategy for Monitoring Weak Southern Radio Sources with the AuScope VLBI Array

NASA Astrophysics Data System (ADS)

McCallum, Lucia; Mayer, David; Le Bail, Karine; Schartner, Matthias; McCallum, Jamie; Lovell, Jim; Titov, Oleg; Shu, Fengchun; Gulyaev, Sergei

2017-11-01

The International Celestial Reference Frame suffers from significantly less observations in the southern hemisphere compared to the northern one. One reason for this is the historically low number of very long baseline interferometry radio telescopes in the south. The AuScope very long baseline interferometry array with three new telescopes on the Australian continent and an identical antenna in New Zealand were built to address this issue. While the overall number of observations in the south has greatly improved since then, a closer look reveals that this improvement is only true for strong radio sources (source flux densities >0.6 Jy). The new array of small very long baseline interferometry antennas has a relatively low baseline sensitivity so that only strong sources can be observed within a short integration time. A new observing strategy, the star scheduling mode, was developed to enable efficient observations of weak sources during geodetic sessions, through the addition of a single more sensitive antenna to the network. This scheduling mode was implemented in the Vienna very long baseline interferometry Software and applied in four 24-h sessions in 2016. These observations provide updated positions and source flux densities for 42 weak southern radio sources and significantly reduce the formal uncertainties for these sources. The star scheduling mode now allows the AuScope very long baseline interferometry array to undertake greater responsibility in monitoring sources in the southern sky, without significantly weakening the session for geodetic purposes.

Seismic interferometry of the Bighorn Mountains: Using virtual source gathers to increase fold in sparse-source, dense-receiver data

NASA Astrophysics Data System (ADS)

Plescia, S. M.; Sheehan, A. F.; Haines, S. S.; Cook, S. W.; Worthington, L. L.

2016-12-01

The Bighorn Arch Seismic Experiment (BASE) was a combined active- and passive-source seismic experiment designed to image deep structures including the Moho beneath a basement-involved foreland arch. In summer 2010, over 1800 Texan receivers, with 4.5 Hz vertical component geophones, were deployed at 100-m to 1-km spacing in a region spanning the Bighorn Arch and the adjacent Bighorn and Powder River Basins. Twenty explosive sources were used to create seismic energy during a two-week acquisition period. Teleseismic earthquakes and mine blasts were also recorded during this time period. We utilize both virtual source interferometry and traditional reflection processing to better understand the deep crustal features of the region and the Moho. The large number of receivers, compared to the limited, widely spaced (10 - 30 km) active-source shots, makes the data an ideal candidate for virtual source seismic interferometry to increase fold. Virtual source interferometry results in data representing a geometry where receiver locations act as if they were seismic source positions. A virtual source gather, the product of virtual source interferometry, is produced by the cross correlation of one receiver's recording, the reference trace, with the recordings of all other receivers in a given shot gather. The cross correlation is repeated for all shot gathers and the resulting traces are stacked. This process is repeated until a virtual source gather has been determined for every real receiver location. Virtual source gathers can be processed with a standard reflection seismic processing flow to yield a reflection section. Improper static corrections can be detrimental to effective stacking, and determination of proper statics is often difficult in areas of significant contrast such as between basin and mountain areas. As such, a natural synergy exists between virtual source interferometry and modern industry reflection seismic processing, with its emphasis on detailed static correction and dense acquisition geometries.

Genetic analysis of Israel Acute Paralysis Virus: distinct clusters are circulating into the United States.

USDA-ARS?s Scientific Manuscript database

Israel acute paralysis virus (IAPV) is associated with colony collapse disorder of honey bees. Nonetheless, its role in the pathogenesis of the disorder and its geographic distribution are unclear. Here, we report phylogenetic analysis of IAPV obtained from bees in the United States, Canada, Austral...

Antarctica: Arena for South American Cooperation or Conflict.

ERIC Educational Resources Information Center

Child, Jack

A number of converging circumstances suggest that Antarctica may be a major object of geopolitical attention in South America in the decade to come. The Malvinas/Falklands crisis focused geopolitical attention on the South Atlantic and the chain of Southern (Austral) Islands which link the southern tip of South America to the Antarctic Peninsula.…

Honors in Chile: New Engagements in the Higher Education System

ERIC Educational Resources Information Center

Skewes, Juan Carlos; Sampaio, Carlos Alberto Cioce; Conway, Frederick J.

2012-01-01

Honors programs are rare in Latin America, and in Chile they were unknown before 2003. At the Universidad Austral de Chile, an interdisciplinary group of scholars linked to environmental studies put forward a pilot project for implementing a new experience in higher education. Challenged by an educational environment where (i) apathy and…

Pleistocene Refugia for Longleaf and Loblolly Pines

Treesearch

Ronald C. Schmidtling; V. Hipkins; E. Carroll

2000-01-01

Longleaf pine (P. palustris Mill.) and loblolly pine (P. taeda L.) are two species that are common to the coastal plain of the southeastern United States. The current natural range of the two species is largely overlapping. Loblolly pine occurs in 13 southeastern states. Longleaf pine is the more austral of the two species,...

Applying the seismic interferometry method to vertical seismic profile data using tunnel excavation noise as source

NASA Astrophysics Data System (ADS)

Jurado, Maria Jose; Teixido, Teresa; Martin, Elena; Segarra, Miguel; Segura, Carlos

2013-04-01

In the frame of the research conducted to develop efficient strategies for investigation of rock properties and fluids ahead of tunnel excavations the seismic interferometry method was applied to analyze the data acquired in boreholes instrumented with geophone strings. The results obtained confirmed that seismic interferometry provided an improved resolution of petrophysical properties to identify heterogeneities and geological structures ahead of the excavation. These features are beyond the resolution of other conventional geophysical methods but can be the cause severe problems in the excavation of tunnels. Geophone strings were used to record different types of seismic noise generated at the tunnel head during excavation with a tunnelling machine and also during the placement of the rings covering the tunnel excavation. In this study we show how tunnel construction activities have been characterized as source of seismic signal and used in our research as the seismic source signal for generating a 3D reflection seismic survey. The data was recorded in vertical water filled borehole with a borehole seismic string at a distance of 60 m from the tunnel trace. A reference pilot signal was obtained from seismograms acquired close the tunnel face excavation in order to obtain best signal-to-noise ratio to be used in the interferometry processing (Poletto et al., 2010). The seismic interferometry method (Claerbout 1968) was successfully applied to image the subsurface geological structure using the seismic wave field generated by tunneling (tunnelling machine and construction activities) recorded with geophone strings. This technique was applied simulating virtual shot records related to the number of receivers in the borehole with the seismic transmitted events, and processing the data as a reflection seismic survey. The pseudo reflective wave field was obtained by cross-correlation of the transmitted wave data. We applied the relationship between the transmission response and the reflection response for a 1D multilayer structure, and next 3D approach (Wapenaar 2004). As a result of this seismic interferometry experiment the 3D reflectivity model (frequencies and resolution ranges) was obtained. We proved also that the seismic interferometry approach can be applied in asynchronous seismic auscultation. The reflections detected in the virtual seismic sections are in agreement with the geological features encountered during the excavation of the tunnel and also with the petrophysical properties and parameters measured in previous geophysical borehole logging. References Claerbout J.F., 1968. Synthesis of a layered medium from its acoustic transmision response. Geophysics, 33, 264-269 Flavio Poletto, Piero Corubolo and Paolo Comeli.2010. Drill-bit seismic interferometry whith and whitout pilot signals. Geophysical Prospecting, 2010, 58, 257-265. Wapenaar, K., J. Thorbecke, and D. Draganov, 2004, Relations between reflection and transmission responses of three-dimensional inhomogeneous media: Geophysical Journal International, 156, 179-194.

Caldera unrest detected with seawater temperature anomalies at Deception Island, Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Berrocoso, M.; Prates, G.; Fernández-Ros, A.; Peci, L. M.; de Gil, A.; Rosado, B.; Páez, R.; Jigena, B.

2018-04-01

Increased thermal activity was detected to coincide with the onset of volcano inflation in the seawater-filled caldera at Deception Island. This thermal activity was manifested in pulses of high water temperature that coincided with ocean tide cycles. The seawater temperature anomalies were detected by a thermometric sensor attached to the tide gauge (bottom pressure sensor). This was installed where the seawater circulation and the locations of known thermal anomalies, fumaroles and thermal springs, together favor the detection of water warmed within the caldera. Detection of the increased thermal activity was also possible because sea ice, which covers the entire caldera during the austral winter months, insulates the water and thus reduces temperature exchange between seawater and atmosphere. In these conditions, the water temperature data has been shown to provide significant information about Deception volcano activity. The detected seawater temperature increase, also observed in soil temperature readings, suggests rapid and near-simultaneous increase in geothermal activity with onset of caldera inflation and an increased number of seismic events observed in the following austral summer.

Morphology and metamorphosis of Eupsophus calcaratus tadpoles (Anura: Leptodactylidae).

PubMed

Vera Candioti, M F; Ubeda, C; Lavilla, E O

2005-05-01

Eupsophus calcaratus, a leptodactyloid frog from the austral Andean forests of Argentina and Chile, has endotrophic, nidicolous tadpoles. We studied a metamorphic series from Stages 31 to 46 of Gosner's developmental table (1960). Other than the scarce pigmentation, proportionately large eyes, and massive developing hindlimbs, the remaining external characters are similar to those of generalized, exotrophic larvae. At the same time, internal morphology does not reveal any character state attributable to the endotrophic-nidicolous way of life; conversely, structures such as the hyobranchial skeleton and the mandibular cartilages are similar to those of exotrophic-macrophagous tadpoles. The metamorphic process is characterized by the delayed development of diverse structures (e.g., ethmoid region, palatoquadrate, and hyobranchial apparatus), and the retention of some larval characters (e.g., parietal fenestrae, overall absence of ossification) with the absence of development of some "juvenile" characters (e.g., adult otic process, several bones) in metamorphosed individuals. These heterochronic processes and truncation of larval development are related to a shorter larval life (when compared to other species of the austral Andean region) and to the small size at metamorphosis. 2004 Wiley-Liss, Inc.

Community structure of copepods in the oceanic and neritic waters off Adélie and George V Land, East Antarctica, during the austral summer of 2008

NASA Astrophysics Data System (ADS)

Tachibana, Aiko; Watanabe, Yuko; Moteki, Masato; Hosie, Graham W.; Ishimaru, Takashi

2017-06-01

Copepods are one of the most important components of the Southern Ocean food web, and are widely distributed from surface to deeper waters. We conducted discrete depth sampling to clarify the community structure of copepods from the epi- to bathypelagic layers of the oceanic and neritic waters off Adélie and George V Land, East Antarctica, in the austral summer of 2008. Notably high diversity and species numbers were observed in the meso- and bathypelagic layers. Cluster analysis based on the similarity of copepod communities identified seven cluster groups, which corresponded well with water masses. In the epi- and upper- mesopelagic layers of the oceanic zone, the SB (Southern Boundary of the Antarctic Circumpolar Current) divided copepod communities. Conversely, in the lower meso- and bathypelagic layers (500-2000 m depth), communities were consistent across the SB. In these layers, the distributions of copepod species were separated by habitat depth ranges and feeding behaviour. The different food webs occur in the epipelagic layer with habitat segregation by zooplankton in their horizontal distribution ranges.

Absorption and fluorescence properties of colored dissolved organic matter in the Ross Sea during austral summer

NASA Astrophysics Data System (ADS)

D'Sa, E. J.; Kim, H. C.; Ha, S. Y.

2016-12-01

Colored dissolved organic matter (CDOM) spectral absorption and excitation-emission matrix (EEMs) fluorescence with parallel factor analysis (PARAFAC) were examined in the Ross Sea during a survey conducted on board the R/V Araon in the austral summer of 14/15. CDOM absorption at 355 nm ranged from 0.06 to 1.14 m-1 while spectral slope S calculated between 275-295 nm wavelength ranged from 18.83 to 33.32 µm-1 with water masses playing an important role in its variability. Spectral slope S decreased with increasing CDOM absorption indicating the strong role of photo-oxidation on CDOM abundance during the summer. PARAFAC analysis of EEM data identified two humic-like (terrestrial and marine-like) and a protein-like (tryptophan-like) component. The two humic-like components were well correlated with little variability spatially and across the water column ( 0-100 m) likely indicating more refractory material. The protein-like fluorescent component was relatively quite variable supporting the autochthonous production of this fluorescent component in the highly productive Ross Sea waters.

Spatial and temporal distribution of aliphatic hydrocarbons and linear alkylbenzenes in the particulate phase from a subtropical estuary (Guaratuba Bay, SW Atlantic) under seasonal population fluctuation.

PubMed

Dauner, Ana Lúcia L; Martins, César C

2015-12-01

Guaratuba Bay, a subtropical estuary located in the SW Atlantic, is under variable anthropogenic pressure throughout the year. Samples of surficial suspended particulate matter (SPM) were collected at 22 sites during three different periods to evaluate the temporal and spatial variability of aliphatic hydrocarbons (AHs) and linear alkylbenzenes (LABs). These compounds were determined by gas chromatography with flame ionization detection (GC-FID) and mass spectrometry (GC/MS). The spatial distributions of both compound classes were similar and varied among the sampling campaigns. Generally, the highest concentrations were observed during the austral summer, highlighting the importance of the increased human influence during this season. The compound distributions were also affected by the natural geochemical processes of organic matter accumulation. AHs were associated with petroleum, derived from boat and vehicle traffic, and biogenic sources, related to mangrove forests and autochthonous production. The LAB composition evidenced preferential degradation processes during the austral summer. Copyright © 2015 Elsevier B.V. All rights reserved.

Decoupling of monsoon activity across the northern and southern Indo-Pacific during the Late Glacial

NASA Astrophysics Data System (ADS)

Denniston, R. F.; Asmerom, Y.; Polyak, V. J.; Wanamaker, A. D.; Ummenhofer, C. C.; Humphreys, W. F.; Cugley, J.; Woods, D.; Lucker, S.

2017-11-01

Recent studies of stalagmites from the Southern Hemisphere tropics of Indonesia reveal two shifts in monsoon activity not apparent in records from the Northern Hemisphere sectors of the Austral-Asian monsoon system: an interval of enhanced rainfall at ∼19 ka, immediately prior to Heinrich Stadial 1, and a sharp increase in precipitation at ∼9 ka. Determining whether these events are site-specific or regional is important for understanding the full range of sensitivities of the Austral-Asian monsoon. We present a discontinuous 40 kyr carbon isotope record of stalagmites from two caves in the Kimberley region of the north-central Australian tropics. Heinrich stadials are represented by pronounced negative carbon isotopic anomalies, indicative of enhanced rainfall associated with a southward shift of the intertropical convergence zone and consistent with hydroclimatic changes observed across Asia and the Indo-Pacific. Between 20 and 8 ka, however, the Kimberley stalagmites, like the Indonesian record, reveal decoupling of monsoon behavior from Southeast Asia, including the early deglacial wet period (which we term the Late Glacial Pluvial) and the abrupt strengthening of early Holocene monsoon rainfall.

The Formation each Winter of the Circumpolar Wave in the Sea Ice around Antarctica

NASA Technical Reports Server (NTRS)

Gloersen, Per; White, Warren B.

1999-01-01

Seeking to improve upon the visualization of the Antarctic Circumpolar Wave (ACW) , we compare a 16-year sequence of 6-month winter averages of Antarctic sea ice extents and concentrations with those of adjacent sea surface temperatures (SSTs). Here we follow SSTs around the globe along the maximum sea ice edge rather than in a zonal band equatorward of it. The results are similar to the earlier ones, but the ACWs do not propagate with equal amplitude or speed. Additionally in a sequence of 4 polar stereographic plots of these SSTs and sea ice concentrations, we find a remarkable correlation between SST minima and sea ice concentration maxima, even to the extent of matching contours across the ice-sea boundary, in the sector between 900E and the Palmer Peninsula. Based on these observations, we suggest that the memory of the ACW in the sea ice is carried from one Austral winter to the next by the neighboring SSTS, since the sea ice is nearly absent in the Austral summer.

UVER and UV index at high altitude in Northwestern Argentina.

PubMed

Utrillas, M P; Marín, M J; Esteve, A R; Salazar, G; Suarez, H; Castillo, J; Martínez-Lozano, J A

2016-10-01

Measurements of ultraviolet erythemal radiation (UVER) made during two years at three sites located at altitudes over 1000ma.s.l. in Northwestern Argentina (Salta, San Carlos, and El Rosal) have been used to estimate and analyze the UV Index (UVI) and the cumulative doses at these locations. For the UVER irradiance, data of January (maximum values) and June (minimum values) have been analyzed as representative of the year for all locations. The UVI reaches extreme (>11) values in >20% of the analyzed days in Salta (1190ma.s.l.), while these are reached in San Carlos (1611ma.s.l.) and El Rosal (3355ma.s.l.) in >40% of the analyzed days. Finally, the cumulative doses over an average year have also been studied for each location. The doses received during austral summer and autumn are of the same order, and represent one third of the annual dose, while the doses received during austral winter and spring represent one sixth of the annual dose approximately. Copyright © 2016 Elsevier B.V. All rights reserved.

The impact of the eruptions of Mt. Pinatubo and Cerro Hudson on Antarctic aerosol levels during the 1991 Austral spring

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

Pitts, M.C.; Thomason, L.W.

1993-11-19

At the beginning of 1991 Austral spring, volcanic aerosols from Mt. Pinatubo and Cerro Hudson were present in the polar stratosphere of the Southern Hemisphere. Satellite observations of aerosol extinction were used to identify and track the movement of these aerosols in the vicinity of the Antarctic vortex during August through November 1991. A layer of mature Mt. Pinatubo aerosols was identified near 21 km and a layer of fresh Cerro Hudson aerosols was identified near 12 km. This altitude separation of the Mt. Pinatubo and Cerro Hudson aerosols was observed throughout the period. Below 15 km, the polar stratospheremore » was subject to episodes of strong wave activity which transported the Cerro Hudson aerosols poleward and, after the middle of September, they became a persistent feature beneath the vortex. Above 15 km, signatures of Mt. Pinatubo aerosols were observed near the vortex boundary, but significant portions of the vortex interior remained free of any detectable intrusions of Mt. Pinatubo aerosols until the final warming in mid-November. 13 refs., 4 figs.« less

Ideal-observer detectability in photon-counting differential phase-contrast imaging using a linear-systems approach

PubMed Central

Fredenberg, Erik; Danielsson, Mats; Stayman, J. Webster; Siewerdsen, Jeffrey H.; Åslund, Magnus

2012-01-01

Purpose: To provide a cascaded-systems framework based on the noise-power spectrum (NPS), modulation transfer function (MTF), and noise-equivalent number of quanta (NEQ) for quantitative evaluation of differential phase-contrast imaging (Talbot interferometry) in relation to conventional absorption contrast under equal-dose, equal-geometry, and, to some extent, equal-photon-economy constraints. The focus is a geometry for photon-counting mammography. Methods: Phase-contrast imaging is a promising technology that may emerge as an alternative or adjunct to conventional absorption contrast. In particular, phase contrast may increase the signal-difference-to-noise ratio compared to absorption contrast because the difference in phase shift between soft-tissue structures is often substantially larger than the absorption difference. We have developed a comprehensive cascaded-systems framework to investigate Talbot interferometry, which is a technique for differential phase-contrast imaging. Analytical expressions for the MTF and NPS were derived to calculate the NEQ and a task-specific ideal-observer detectability index under assumptions of linearity and shift invariance. Talbot interferometry was compared to absorption contrast at equal dose, and using either a plane wave or a spherical wave in a conceivable mammography geometry. The impact of source size and spectrum bandwidth was included in the framework, and the trade-off with photon economy was investigated in some detail. Wave-propagation simulations were used to verify the analytical expressions and to generate example images. Results: Talbot interferometry inherently detects the differential of the phase, which led to a maximum in NEQ at high spatial frequencies, whereas the absorption-contrast NEQ decreased monotonically with frequency. Further, phase contrast detects differences in density rather than atomic number, and the optimal imaging energy was found to be a factor of 1.7 higher than for absorption contrast. Talbot interferometry with a plane wave increased detectability for 0.1-mm tumor and glandular structures by a factor of 3–4 at equal dose, whereas absorption contrast was the preferred method for structures larger than ∼0.5 mm. Microcalcifications are small, but differ from soft tissue in atomic number more than density, which is favored by absorption contrast, and Talbot interferometry was barely beneficial at all within the resolution limit of the system. Further, Talbot interferometry favored detection of “sharp” as opposed to “smooth” structures, and discrimination tasks by about 50% compared to detection tasks. The technique was relatively insensitive to spectrum bandwidth, whereas the projected source size was more important. If equal photon economy was added as a restriction, phase-contrast efficiency was reduced so that the benefit for detection tasks almost vanished compared to absorption contrast, but discrimination tasks were still improved close to a factor of 2 at the resolution limit. Conclusions: Cascaded-systems analysis enables comprehensive and intuitive evaluation of phase-contrast efficiency in relation to absorption contrast under requirements of equal dose, equal geometry, and equal photon economy. The benefit of Talbot interferometry was highly dependent on task, in particular detection versus discrimination tasks, and target size, shape, and material. Requiring equal photon economy weakened the benefit of Talbot interferometry in mammography. PMID:22957600

Radio interferometry: Techniques for Geodesy. [conference

NASA Technical Reports Server (NTRS)

1980-01-01

Progress in the development and application of radio interferometry as a tool for geophysical research is reported and discussed. Among the topics reviewed are: Surveys of is the Seventies, Movements, Terrestrial and Celestial, Degrees Kelvin and Degrees of Phase, the Mark 3 VLBI System, Waves of the Future and other Emissions, and Adherence and Coherence in Networks, and Plans.

Proceedings of the Annual Gaseous Electronics Conference (40th) Held in Atlanta Georgia on 13-16 October 1987

DTIC Science & Technology

1988-07-01

BURNING PLASMA ARC BY A COMBINATION OF HOLOGRAPHIC INTERFEROMETRY AND EMISSION SPECTROSCOPY A. Shah, M. S. Dassanayake and K. Etemadi 5:03 - 5:16 NB...Free- burning Plasma Arc by a Combination of Holo- graphic Interferometry and Emission Spectros- copy, A. SHAH, M. S. DASSANAYAKE,AND K. ETEMA- DI

Measurement of spatio-temporal field distribution of THz pulses in electro-optic crystal by interferometry method

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

Chizhov, P A; Ushakov, A A; Bukin, V V

2015-05-31

We propose a scheme for measuring the spatial distribution of the THz pulse electric field strength in an electro-optic crystal using optical interferometry. The resulting images of the field distribution from a test source with a spherical wave front are presented. (extreme light fields and their applications)

Design and fabrication of a brassboard optical bench structure for space interferometry mission

NASA Technical Reports Server (NTRS)

Buck, Stephanie

2006-01-01

The Space Interferometry Mission (SIM), consisting of an orbiting pair of telescopes, will be used for characterization of extrasolar planetary systems and for associated astrophysics research. To maximize the capabilities of this instrument, extensive technology development has been performed, much of it to understand and verify the performance of precision structures.

Apparatus and method for laser velocity interferometry

DOEpatents

Stanton, Philip L.; Sweatt, William C.; Crump, Jr., O. B.; Bonzon, Lloyd L.

1993-09-14

An apparatus and method for laser velocity interferometry employing a fixed interferometer cavity and delay element. The invention permits rapid construction of interferometers that may be operated by those non-skilled in the art, that have high image quality with no drift or loss of contrast, and that have long-term stability even without shock isolation of the cavity.

Chaoticity parameter λ in two-pion interferometry in an expanding boson gas model

DOE PAGES

Liu, Jie; Ru, Peng; Zhang, Wei-Ning; ...

2014-10-15

We investigate the chaoticity parameter λ in two-pion interferometry in an expanding boson gas model. The degree of Bose-Einstein condensation of identical pions, density distributions, and Hanbury-Brown-Twiss (HBT) correlation functions are calculated for the expanding gas within the mean-field description with a harmonic oscillator potential. The results indicate that a sources with thousands of identical pions may exhibit a degree of Bose-Einstein condensation at the temperatures during the hadronic phase in relativistic heavy-ion collisions. This finite condensation may decrease the chaoticity parameter λ in the two-pion interferometry measurements at low pion pair momenta, but influence only slightly the λ valuemore » at high pion pair momentum.« less

Correlation of scanning microwave interferometry and digital X-ray images for damage detection in ceramic composite armor

NASA Astrophysics Data System (ADS)

Schmidt, Karl F.; Goitia, Ryan M.; Ellingson, William A.; Green, William

2012-05-01

Application of non-contact, scanning, microwave interferometry for inspection of ceramic-based composite armor facilitates detection of defects which may occur in manufacturing or in service. Non-contact, one-side access permits inspection of panels while on the vehicle. The method was applied as a base line inspection and post-damage inspection of composite ceramic armor containing artificial defects, fiduciaries, and actual damage. Detection, sizing, and depth location capabilities were compared using microwave interferometry system and micro-focus digital x-ray imaging. The data demonstrates corroboration of microwave interference scanning detection of cracks and laminar features. The authors present details of the system operation, descriptions of the test samples used, and recent results obtained.

Precision Geodesy via Radio Interferometry.

PubMed

Hinteregger, H F; Shapiro, I I; Robertson, D S; Knight, C A; Ergas, R A; Whitney, A R; Rogers, A E; Moran, J M; Clark, T A; Burke, B F

1972-10-27

Very-long-baseline interferometry experiments, involving observations of extragalactic radio sources, were performed in 1969 to determine the vector separations between antenna sites in Massachusetts and West Virginia. The 845.130-kilometer baseline was estimated from two separate experiments. The results agreed with each other to within 2 meters in all three components and with a special geodetic survey to within 2 meters in length; the differences in baseline direction as determined by the survey and by interferometry corresponded to discrepancies of about 5 meters. The experiments also yielded positions for nine extragalactic radio sources, most to within 1 arc second, and allowed the hydrogen maser clocks at the two sites to be synchronized a posteriori with an uncertainty of only a few nanoseconds.

Fast and economic signal processing technique of laser diode self-mixing interferometry for nanoparticle size measurement

NASA Astrophysics Data System (ADS)

Wang, Huarui; Shen, Jianqi

2014-05-01

The size of nanoparticles is measured by laser diode self-mixing interferometry, which employs a sensitive, compact, and simple optical setup. However, the signal processing of the interferometry is slow or expensive. In this article, a fast and economic signal processing technique is introduced, in which the self-mixing AC signal is transformed into DC signals with an analog circuit consisting of 16 channels. These DC signals are obtained as a spectrum from which the size of nanoparticles can be retrieved. The technique is examined by measuring the standard nanoparticles. Further experiments are performed to compare the skimmed milk and whole milk, and also the fresh skimmed milk and rotten skimmed milk.

Phase gradient algorithm based on co-axis two-step phase-shifting interferometry and its application

NASA Astrophysics Data System (ADS)

Wang, Yawei; Zhu, Qiong; Xu, Yuanyuan; Xin, Zhiduo; Liu, Jingye

2017-12-01

A phase gradient method based on co-axis two-step phase-shifting interferometry, is used to reveal the detailed information of a specimen. In this method, the phase gradient distribution can only be obtained by calculating both the first-order derivative and the radial Hilbert transformation of the intensity difference between two phase-shifted interferograms. The feasibility and accuracy of this method were fully verified by the simulation results for a polystyrene sphere and a red blood cell. The empirical results demonstrated that phase gradient is sensitive to changes in the refractive index and morphology. Because phase retrieval and tedious phase unwrapping are not required, the calculation speed is faster. In addition, co-axis interferometry has high spatial resolution.

A LISA Interferometry Primer

NASA Technical Reports Server (NTRS)

Thorpe, James Ira

2010-01-01

A key challenge for all gravitational wave detectors in the detection of changes in the fractional difference between pairs of test masses with sufficient precision to measure astrophysical strains with amplitudes on the order of approx.10(exp -21). ln the case of the five million km arms of LISA, this equates to distance measurements on the ten picometer level. LISA interferometry utilizes a decentralized topology, in which each of the sciencecraft houses its own light sources, detectors, and electronics. The measurements made at each of the sciencecraft are then telemetered to ground and combined to extract the strain experienced by the constellation as a whole. I will present an overview of LISA interferometry and highlight some of the key components and technologies that make it possible.

Biolayer Interferometry: A Novel Method to Elucidate Protein-Protein and Protein-DNA Interactions in the Mitochondrial DNA Replisome.

PubMed

Ciesielski, Grzegorz L; Hytönen, Vesa P; Kaguni, Laurie S

2016-01-01

A lack of effective treatment for mitochondrial diseases prompts scientists to investigate the molecular processes that underlie their development. The major cause of mitochondrial diseases is dysfunction of the sole mitochondrial DNA polymerase, DNA polymerase γ (Pol γ). The development of treatment strategies will require a detailed characterization of the molecular properties of Pol γ. A novel technique, biolayer interferometry, allows one to monitor molecular interactions in real time, thus providing an insight into the kinetics of the process. Here, we present an application of the biolayer interferometry technique to characterize the fundamental reactions that Pol γ undergoes during the initiation phase of mitochondrial DNA replication: holoenzyme formation and binding to the primer-template.

Biolayer Interferometry: A Novel Method to Elucidate Protein–Protein and Protein–DNA Interactions in the Mitochondrial DNA Replisome

PubMed Central

Ciesielski, Grzegorz L.; Hytönen, Vesa P.; Kaguni, Laurie S.

2015-01-01

A lack of effective treatment for mitochondrial diseases prompts scientists to investigate the molecular processes that underlie their development. The major cause of mitochondrial diseases is dysfunction of the sole mitochondrial DNA polymerase, DNA polymerase γ (Pol γ). The development of treatment strategies will require a detailed characterization of the molecular properties of Pol γ. A novel technique, biolayer interferometry, allows one to monitor molecular interactions in real time, thus providing an insight into the kinetics of the process. Here, we present an application of the biolayer interferometry technique to characterize the fundamental reactions that Pol γ undergoes during the initiation phase of mitochondrial DNA replication: holoenzyme formation and binding to the primer-template. PMID:26530686

Recent Experiments Conducted with the Wide-Field Imaging Interferometry Testbed (WIIT)

NASA Technical Reports Server (NTRS)

Leisawitz, David T.; Juanola-Parramon, Roser; Bolcar, Matthew; Iacchetta, Alexander S.; Maher, Stephen F.; Rinehart, Stephen A.

2016-01-01

The Wide-field Imaging Interferometry Testbed (WIIT) was developed at NASA's Goddard Space Flight Center to demonstrate and explore the practical limitations inherent in wide field-of-view double Fourier (spatio-spectral) interferometry. The testbed delivers high-quality interferometric data and is capable of observing spatially and spectrally complex hyperspectral test scenes. Although WIIT operates at visible wavelengths, by design the data are representative of those from a space-based far-infrared observatory. We used WIIT to observe a calibrated, independently characterized test scene of modest spatial and spectral complexity, and an astronomically realistic test scene of much greater spatial and spectral complexity. This paper describes the experimental setup, summarizes the performance of the testbed, and presents representative data.

Absolute distance measurement by dual-comb interferometry with multi-channel digital lock-in phase detection

NASA Astrophysics Data System (ADS)

Yang, Ruitao; Pollinger, Florian; Meiners-Hagen, Karl; Krystek, Michael; Tan, Jiubin; Bosse, Harald

2015-08-01

We present a dual-comb-based heterodyne multi-wavelength absolute interferometer capable of long distance measurements. The phase information of the various comb modes is extracted in parallel by a multi-channel digital lock-in phase detection scheme. Several synthetic wavelengths of the same order are constructed and the corresponding phases are averaged to deduce the absolute lengths with significantly reduced uncertainty. Comparison experiments with an incremental HeNe reference interferometer show a combined relative measurement uncertainty of 5.3 × 10-7 at a measurement distance of 20 m. Combining the advantage of synthetic wavelength interferometry and dual-comb interferometry, our compact and simple approach provides sufficient precision for many industrial applications.

Measurement of the surface morphology of plasma facing components on the EAST tokamak by a laser speckle interferometry approach

NASA Astrophysics Data System (ADS)

Hongbei, WANG; Xiaoqian, CUI; Yuanbo, LI; Mengge, ZHAO; Shuhua, LI; Guangnan, LUO; Hongbin, DING

2018-03-01

The laser speckle interferometry approach provides the possibility of an in situ optical non-contacted measurement for the surface morphology of plasma facing components (PFCs), and the reconstruction image of the PFC surface morphology is computed by a numerical model based on a phase unwrapping algorithm. A remote speckle interferometry measurement at a distance of three meters for real divertor tiles retired from EAST was carried out in the laboratory to simulate a real detection condition on EAST. The preliminary surface morphology of the divertor tiles was well reproduced by the reconstructed geometric image. The feasibility and reliability of this approach for the real-time measurement of PFCs have been demonstrated.

Investigation of a complete sample of flat spectrum radio sources from the S5 survey

NASA Astrophysics Data System (ADS)

Eckart, A.; Witzel, A.; Biermann, P.; Johnston, K. J.; Simon, R.; Schalinski, C.; Kuhr, H.

1986-11-01

An analysis of 13 extragalactic sources of the S5 survey with flux densities greater than or equal to 1 Jy at 4990 MHz, mapped with milliarcsecond resolution at 1.6 and 5 GHz by means of VLBI, is presented. All sources appear to display multiple components dominated in flux density at 6 cm by a core component which is self-absorbed at 18 cm. Comparison of the measured to predicted X-ray flux density of the core radio components suggests that all sources should display bulk relativistic motion with small angles to the line of sight, and four sources show rapid changes in their radio structures which can be interpreted as apparent superliminal motion.

CCD centroiding analysis for Nano-JASMINE observation data

NASA Astrophysics Data System (ADS)

Niwa, Yoshito; Yano, Taihei; Araki, Hiroshi; Gouda, Naoteru; Kobayashi, Yukiyasu; Yamada, Yoshiyuki; Tazawa, Seiichi; Hanada, Hideo

2010-07-01

Nano-JASMINE is a very small satellite mission for global space astrometry with milli-arcsecond accuracy, which will be launched in 2011. In this mission, centroids of stars in CCD image frames are estimated with sub-pixel accuracy. In order to realize such a high precision centroiding an algorithm utilizing a least square method is employed. One of the advantages is that centroids can be calculated without explicit assumption of the point spread functions of stars. CCD centroiding experiment has been performed to investigate whether this data analysis is available, and centroids of artificial star images on a CCD are determined with a precision of less than 0.001 pixel. This result indicates parallaxes of stars within 300 pc from Sun can be observed in Nano-JASMINE.

WFIRST: Managing Telescope Wavefront Stability to Meet Coronagraph Performance

NASA Astrophysics Data System (ADS)

Noecker, Martin; Poberezhskiy, Ilya; Kern, Brian; Krist, John; WFIRST System Engineering Team

2018-01-01

The WFIRST coronagraph instrument (CGI) needs a stable telescope and active wavefront control to perform coronagraph science with an expected sensitivity of 8x10-9 in the exoplanet-star flux ratio (SNR=10) at 200 milliarcseconds angular separation. With its subnanometer requirements on the stability of its input wavefront error (WFE), the CGI employs a combination of pointing and wavefront control loops and thermo-mechanical stability to meet budget allocations for beam-walk and low-order WFE, which enable stable starlight speckles on the science detector that can be removed by image subtraction. We describe the control strategy and the budget framework for estimating and budgeting the elements of wavefront stability, and the modeling strategy to evaluate it.

Hardware development for Gravity Probe-B

NASA Technical Reports Server (NTRS)

Bardas, D.; Cheung, W. S.; Gill, D.; Hacker, R.; Keiser, G. M.

1986-01-01

Gravity Probe-B (GP-B), also known as the Stanford Relativity Gyroscope Experiment, will test two fundamental predictions of Einstein's General Theory of Relativity by precise measurement of the precessions of nearly perfect gyroscopes in earth orbit. This endeavor embodies state-of-the-art technologies in many fields, including gyroscope fabrication and readout, cryogenics, superconductivity, magnetic shielding, precision optics and alignment methods, and satellite control systems. These technologies are necessary to enable measurement of the predicted precession rates to the milliarcsecond/year level, and to reduce to 'near zero' all non-General Relativistic torques on the gyroscopes. This paper provides a brief overview of the experiment followed by descriptions of several specific hardware items with highlights on progress to date and plans for future development and tests.

Not drowning, (hand)waving? Molecular phylogenetics, biogeography and evolutionary tempo of the 'Gondwanan' midge Stictocladius Edwards (Diptera: Chironomidae).

PubMed

Krosch, Matt; Cranston, Peter S

2013-09-01

Many insect clades, especially within the Diptera (true flies), have been considered classically 'Gondwanan', with an inference that distributions derive from vicariance of the southern continents. Assessing the role that vicariance has played in the evolution of austral taxa requires testing the location and tempo of diversification and speciation against the well-established predictions of fragmentation of the ancient super-continent. Several early (anecdotal) hypotheses that current austral distributions originate from the breakup of Gondwana derive from studies of taxa within the family Chironomidae (non-biting midges). With the advent of molecular phylogenetics and biogeographic analytical software, these studies have been revisited and expanded to test such conclusions better. Here we studied the midge genus Stictocladius Edwards, from the subfamily Orthocladiinae, which contains austral-distributed clades that match vicariance-based expectations. We resolve several issues of systematic relationships among morphological species and reveal cryptic diversity within many taxa. Time-calibrated phylogenetic relationships among taxa accorded partially with the predicted tempo from geology. For these apparently vagile insects, vicariance-dated patterns persist for South America and Australia. However, as often found, divergence time estimates for New Zealand at c. 50 mya post-date separation of Zealandia from Antarctica and the remainder of Gondwana, but predate the proposed Oligocene 'drowning' of these islands. We detail other such 'anomalous' dates and suggest a single common explanation rather than stochastic processes. This could involve synchronous establishment following recovery from 'drowning' and/or deleteriously warming associated with the mid-Eocene climatic optimum (hence 'waving', which refers to cycles of drowning events) plus new availability of topography providing of cool running waters, or all these factors in combination. Alternatively a vicariance explanation remains available, given the uncertain duration of connectivity of Zealandia to Australia-Antarctic-South America via the Lord Howe and Norfolk ridges into the Eocene. Copyright © 2013 Elsevier Inc. All rights reserved.

Water or sediment? Partitioning the role of water column and sediment chemistry as drivers of macroinvertebrate communities in an austral South African stream.

PubMed

Dalu, Tatenda; Wasserman, Ryan J; Tonkin, Jonathan D; Mwedzi, Tongayi; Magoro, Mandla L; Weyl, Olaf L F

2017-12-31

Water pollution is a critical management issue, with many rivers and streams draining urban areas being polluted by the disposal of untreated solid waste and wastewater discharge, storm water and agricultural runoff. This has implications for biodiversity, and many rivers in the developing world are now considered compromised. We investigated benthic macroinvertebrate community structure and composition in relation to physico-chemical conditions of the water column and sediments. The study was conducted in an Austral catchment subject to both urban and agricultural pollutants in two different seasons. We assessed whether sediment characteristics were more important drivers of macroinvertebrate community composition than water column characteristics. We expected clear differences in macroinvertebrate community composition and in the associated community metrics due to distinct flow conditions between the two seasons. A combination of multivariate analyses (canonical correspondence analysis (CCA)) and biological indicator analysis were used to examine these patterns. Chironomidae was the most abundant family (>60%) in the upper mainstem river and stream sites. Stream sites were positively associated with CCA axis 2, being characterised by high turbidity and lower pH, salinity, phosphate concentration, channel width and canopy cover. Canopy cover, channel width, substrate embeddedness, phosphate concentration, pH, salinity and turbidity all had a significant effect on macroinvertebrate community composition. Using CCA variation partitioning, water quality was, however, a better predictor of benthic macroinvertebrate composition than sediment chemical conditions. Furthermore, our results suggest that seasonality had little effect on structuring benthic macroinvertebrate communities in this south-eastern zone of South Africa, despite clear changes in sediment chemistry. This likely reflects the relative lack of major variability in water chemistry compared to sediment chemistry between seasons and the relatively muted variability in precipitation between seasons than the more classic Austral temperate climates. Copyright © 2017 Elsevier B.V. All rights reserved.

Seasonal variations in physical characteristics of aerosol particles at the King Sejong Station, Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Kim, Jaeseok; Yoon, Young Jun; Gim, Yeontae; Kang, Hyo Jin; Choi, Jin Hee; Park, Ki-Tae; Lee, Bang Yong

2017-11-01

Seasonal variability in the physical characteristics of aerosol particles sampled from the King Sejong Station in the Antarctic Peninsula was investigated over the period between March 2009 and February 2015. Clear seasonal cycles for the total particle concentration (CN) were observed. The mean monthly concentration of particles larger than 2.5 nm (CN2.5) was highest during the austral summer, with an average value of 1080.39 ± 595.05 cm-3, and lowest during the austral winter, with a mean value of 197.26 ± 71.71 cm-3. The seasonal patterns in the concentrations of cloud condensation nuclei (CCN) and CN coincide, with both concentrations being at a minimum in winter and maximum in summer. The measured CCN spectra were approximated by fitting a power-law function relating the number of CCN for a given supersaturation (SS) to each SS value, with fitting coefficients C and kT. The values for C varied from 6.35 to 837.24 cm-3, with a mean of 171.48 ± 62.00 cm-3. The values for kT ranged from 0.07 to 2.19, with a mean of 0.41 ± 0.10. In particular, the kT values during the austral summer were higher than those during the winter, indicating that aerosol particles are more sensitive to SS changes during summer. Furthermore, the annual mean hygroscopicity parameter, κ, was estimated as 0.15 ± 0.05, for a SS of 0.4 %. The effects of the origin and pathway travelled by the air mass on the physical characteristics of the aerosol particles were also determined. The modal diameter of aerosol particles originating in the South Pacific Ocean showed a seasonal variation varying from 0.023 µm in winter to 0.034 µm in summer for the Aitken mode, and from 0.086 µm in winter to 0.109 µm in summer for the accumulation mode.

Influence of aerosol-cloud interaction on austral summer precipitation over Southern Africa during ENSO events

NASA Astrophysics Data System (ADS)

Ruchith, R. D.; Sivakumar, V.

2018-04-01

In the present study, we are investigating the role of aerosols-and clouds in modulating the austral summer precipitation (December-February) during ENSO events over southern Africa region for the period from 2002 to2012 by using satellite and complimentary data sets. Aerosol radiative forcing (ARF) and Cloud radiative forcing (CRF) shows distinct patterns for El-Nina and La-Nina years. Further analysis were carried out by selecting the four Southern Africa regions where the precipitation shows remarkable difference during El-Nino and La-Nina years. These regions are R1 (33°S-24°S, 18°E-30°E), R2 (17°S-10°S, 24°E-32°E), R3 (19°S-9°S, 33°E-41°E) and R4 (7°S-0°S, 27°E-36°E). Aerosol Optical depth (AOD) shows considerable differences during these events. In region R1, R2 and R3 AOD shows more abundance in El-Nino years as compared to La-Nina years where as in R4 the AOD shows more abundance in La-Nina years. Cloud Droplet Effective radius (CDER) shows higher values during La-Nina years over R1, R2 and R3 regions but in R4 region CDER shows higher values in El-Nino years. Aerosol indirect effect (AIE) is estimated both for fixed cloud liquid water path (CLWP) and for fixed cloud ice path (CIP) bins, ranging from 1 to 300 gm -2 at 25 gm -2 interval over all the selected regions for El-Nino and La-Nina years. The results indicate more influence of positive indirect effect (Twomey effect) over R1 and R3 region during El-Nino years as compared to La-Nina years. This analysis reveals the important role of aerosol on cloud-precipitation interaction mechanism illustrating the interlinkage between dynamics and microphysics during austral summer season over southern Africa.

Intestinal helminth fauna of the South American sea lion Otaria flavescens and fur seal Arctocephalus australis from northern Patagonia, Argentina.

PubMed

Hernández-Orts, J S; Montero, F E; Juan-García, A; García, N A; Crespo, E A; Raga, J A; Aznar, F J

2013-09-01

We report on the intestinal helminth fauna of 56 South American sea lions, Otaria flavescens, and 5 South American fur seals, Arctocephalus australis, from northern Patagonia, Argentina. A total of 97,325 helminth specimens were collected from sea lions. Gravid individuals were represented by 6 species of parasites: 1 digenean (Ascocotyle (Ascocotyle) patagoniensis), 1 cestode (Diphyllobothrium spp.), 3 nematodes (Uncinaria hamiltoni, Contracaecum ogmorhini s.s., Pseudoterranova cattani) and 1 acanthocephalan (Corynosoma australe). In addition, third-stage larvae of 2 nematodes (Contracaecum sp. and Anisakis sp. type I) and 3 juvenile acanthocephalans (Andracantha sp., Profilicollis chasmagnathi and Corynosoma cetaceum) were also collected. Andracantha sp., C. ogmorhini s.s. and P. chasmagnathi represent new host records. A total of 1516 helminth specimens were collected from fur seals. Gravid individuals were represented by three species of parasites, namely, Diphyllobothrium spp., C. ogmorhini s.s. and C. australe. In addition, larvae of Contracaecum sp. and P. cattani, juveniles of C. cetaceum and immature cestodes (Tetrabothriidae gen. sp.) were also collected. Corynosoma australe was the most prevalent and abundant parasite in both hosts, accounting for >90% of all specimens. Sea lions and furs seals from northern Patagonia harbour the intestinal helminth communities that could be predicted for otariids, i.e. the combination of species of the genera Corynosoma, Diphyllobothrium, Pseudoterranova, Contracaecum and, in pups, Uncinaria. Additionally, both species of otariid are apparently unsuitable hosts (i.e. non-hosts) for as many as five parasite taxa. The inclusion or exclusion of these species affects estimation of species richness at both component community (11 versus 6 species in sea lions; 7 versus 3 species in fur seals) and infracommunity (mean: 3.1 versus 2.6 in sea lions; 2.2 versus 1.7 species) levels. Information about the reproductive status of helminth species is often lacking in parasitological surveys on otariids and other marine vertebrates, but it is of significance to improve precision in parascript studies or ecological meta-analyses.

ENSO related SST anomalies and relation with surface heat fluxes over south Pacific and Atlantic

NASA Astrophysics Data System (ADS)

Chatterjee, S.; Nuncio, M.; Satheesan, K.

2017-07-01

The role of surface heat fluxes in Southern Pacific and Atlantic Ocean SST anomalies associated with El Nino Southern Oscillation (ENSO) is studied using observation and ocean reanalysis products. A prominent dipole structure in SST anomaly is found with a positive (negative) anomaly center over south Pacific (65S-45S, 120W-70W) and negative (positive) one over south Atlantic (50S-30S, 30W-0E) during austral summer (DJF) of El Nino (LaNina). During late austral spring-early summer (OND) of El Nino (LaNina), anomalous northerly (southerly) meridional moisture transport and a positive (negative) sea level pressure anomaly induces a suppressed (enhanced) latent heat flux from the ocean surface over south Pacific. This in turn results in a shallower than normal mixed layer depth which further helps in development of the SST anomaly. Mixed layer thins further due to anomalous shortwave radiation during summer and a well developed SST anomaly evolves. The south Atlantic pole exhibits exactly opposite characteristics at the same time. The contribution from the surface heat fluxes to mixed layer temperature change is found to be dominant over the advective processes over both the basins. Net surface heat fluxes anomaly is also found to be maximum during late austral spring-early summer period, with latent heat flux having a major contribution to it. The anomalous latent heat fluxes between atmosphere and ocean surface play important role in the growth of observed summertime SST anomaly. Sea-surface height also shows similar out-of-phase signatures over the two basins and are well correlated with the ENSO related SST anomalies. It is also observed that the magnitude of ENSO related anomalies over the southern ocean are weaker in LaNina years than in El Nino years, suggesting an intensified tropics-high latitude tele-connection during warm phases of ENSO.

Immunological response of the Sub-Antarctic Notothenioid fish Eleginops maclovinus injected with two strains of Piscirickettsia salmonis.

PubMed

Martínez, D; Díaz-Ibarrola, D; Vargas-Lagos, C; Oyarzún, R; Pontigo, J P; Muñoz, J L P; Yáñez, A J; Vargas-Chacoff, L

2018-04-01

Eleginops maclovinus is an endemic fish to Chile that lives in proximity to salmonid culture centers, feeding off of uneaten pellet and salmonid feces. Occurring in the natural environment, this interaction between native and farmed fish could result in the horizontal transmission of pathogens affecting the aquaculture industry. The aim of this study was to evaluate the innate and adaptive immune responses of E. maclovinus challenged with P. salmonis. Treatment injections (in duplicate) were as follows: control (100 μL of culture medium), wild type LF-89 strain (100 μL, 1 × 10 8 live bacteria), and antibiotic resistant strain Austral-005 (100 μL, 1 × 10 8 live bacteria). The fish were sampled at various time-points during the 35-day experimental period. The gene expression of TLRs (1, 5, and 8), NLRCs (3 and 5), C3, IL-1β, MHCII, and IgMs were significantly modulated during the experimental period in both the spleen and gut (excepting TLR1 and TLR8 spleen expressions), with tissue-specific expression profiles and punctual differences between the injected strains. Anti-P. salmonis antibodies increased in E. maclovinus serum from day 14-28 for the LF-89 strain and from day 14-35 for the Austral-005 strain. These results suggest temporal activation of the innate and adaptive immune responses in E. maclovinus tissues when injected by distinct P. salmonis strains. The Austral-005 strain did not always cause the greatest increases/decreases in the number of transcripts, so the magnitude of the observed immune response (mRNA) may not be related to antibiotic resistance. This is the first immunological study to relate a pathogen widely studied in salmonids with a native fish. Copyright © 2018 Elsevier Ltd. All rights reserved.

Response of the Antarctic Stratosphere to Warm Pool EI Nino Events in the GEOS CCM

NASA Technical Reports Server (NTRS)

Hurwitz, Margaret M.; Song, In-Sun; Oman, Luke D.; Newman, Paul A.; Molod, Andrea M.; Frith, Stacey M.; Nielsen, J. Eric

2011-01-01

A new type of EI Nino event has been identified in the last decade. During "warm pool" EI Nino (WPEN) events, sea surface temperatures (SSTs) in the central equatorial Pacific are warmer than average. The EI Nino signal propagates poleward and upward as large-scale atmospheric waves, causing unusual weather patterns and warming the polar stratosphere. In austral summer, observations show that the Antarctic lower stratosphere is several degrees (K) warmer during WPEN events than during the neutral phase of EI Nino/Southern Oscillation (ENSO). Furthermore, the stratospheric response to WPEN events depends of the direction of tropical stratospheric winds: the Antarctic warming is largest when WPEN events are coincident with westward winds in the tropical lower and middle stratosphere i.e., the westward phase of the quasi-biennial oscillation (QBO). Westward winds are associated with enhanced convection in the subtropics, and with increased poleward wave activity. In this paper, a new formulation of the Goddard Earth Observing System Chemistry-Climate Model, Version 2 (GEOS V2 CCM) is used to substantiate the observed stratospheric response to WPEN events. One simulation is driven by SSTs typical of a WPEN event, while another simulation is driven by ENSO neutral SSTs; both represent a present-day climate. Differences between the two simulations can be directly attributed to the anomalous WPEN SSTs. During WPEN events, relative to ENSO neutral, the model simulates the observed increase in poleward planetary wave activity in the South Pacific during austral spring, as well as the relative warming of the Antarctic lower stratosphere in austral summer. However, the modeled response to WPEN does not depend on the phase of the QBO. The modeled tropical wind oscillation does not extend far enough into the lower stratosphere and upper troposphere, likely explaining the model's insensitivity to the phase of the QBO during WPEN events.

Estimation of austral summer net community production in the Amundsen Sea: Self-organizing map analysis approach

NASA Astrophysics Data System (ADS)

Park, K.; Hahm, D.; Lee, D. G.; Rhee, T. S.; Kim, H. C.

2014-12-01

The Amundsen Sea, Antarctica, has been known for one of the most susceptible region to the current climate change such as sea ice melting and sea surface temperature change. In the Southern Ocean, a predominant amount of primary production is occurring in the continental shelf region. Phytoplankton blooms take place during the austral summer due to the limited sunlit and sea ice cover. Thus, quantifying the variation of summer season net community production (NCP) in the Amundsen Sea is essential to analyze the influence of climate change to the variation of biogeochemical cycle in the Southern Ocean. During the past three years of 2011, 2012 and 2014 in austral summer, we have conducted underway observations of ΔO2/Ar and derived NCP of the Amundsen Sea. Despite the importance of NCP for understanding biological carbon cycle of the ocean, the observations are rather limited to see the spatio-temporal variation in the Amundsen Sea. Therefore, we applied self-organizing map (SOM) analysis to expand our observed data sets and estimate the NCP during the summer season. SOM analysis, a type of artificial neural network, has been proved to be a useful method for extracting and classifying features in geoscience. In oceanography, SOM has applied for the analysis of various properties of the seawater such as sea surface temperature, chlorophyll concentration, pCO2, and NCP. Especially it is useful to expand a spatial coverage of direct measurements or to estimate properties whose satellite observations are technically or spatially limited. In this study, we estimate summer season NCP and find a variables set which optimally delineates the NCP variation in the Amundsen Sea as well. Moreover, we attempt to analyze the interannual variation of the Amundsen Sea NCP by taking climatological factors into account for the SOM analysis.

Role of the Southwest Tropical Indian Ocean on the Modulation of Tropical Cyclones

NASA Astrophysics Data System (ADS)

Burns, J. M.; Bulusu, S.

2016-02-01

The Seychelles-Chagos Thermocline Ridge (SCTR), located in the Indian Ocean and bound by 55°E-65°E and 5°S-12°S, is a key region for air-sea interaction. This feature inhabits one of the seven ocean basins where tropical cyclones regularly form and is unique in that the variability of the subsurface can influence cyclogenesis. Tropical cyclone days for this region span from November through April, with peaks in the months of January and February. The influence of thermocline variation is particularly strong during the months of December through May and it is known that a high correlation exists between the depth of the thermocline and sea surface temperature (key ingredient for cyclogenesis). Past research provides evidence that more tropical cyclone days are observed in Southwest Tropical Indian Ocean (SWTIO) during austral summers with a deep thermocline ridge than in austral summers when a shallow thermocline ridge exists. The formation and thickness of the Barrier layer (BL) have also been shown to impact tropical cyclones in this region. BL formation is an important parameter for surface heat exchange. The amount of salt in the boundary layer may also effect heat exchange and thus cyclones. Other ocean basins have verified that salt-stratified barrier layers influence the intensification of tropical cyclones, however, the role that salinity in SWTIO plays in the modulation of tropical cycles has still yet to be explored. This study further explores how the dynamic properties of the SCTR influence the modulation of cyclones. Primarily Argo observations of salinity and temperature along with Soil Moisture Ocean Salinity (SMOS) and Aquarius salinity, and Hybrid Coordinate Ocean Model (HYCOM) simulations are used to examine this influence of the BL and salinity on cyclone formation and intensity in this region. This study is progressed with a particular focus on the austral summer of 2012/2013 when seven tropical cyclones developed in the region.

Field Investigation of Surface-Lake Processes on Ice Shelves: Results of the 2015/16 Field Campaign on McMurdo Ice Shelf, Antarctica

NASA Astrophysics Data System (ADS)

MacAyeal, Doug; Banwell, Alison; Willis, Ian; Macdonald, Grant

2016-04-01

Ice-shelf instability and breakup of the style exhibited by Larsen B Ice Shelf in 2002 remains the most difficult glaciological process of consequence to observe in detail. It is, however, vital to do so because ice-shelf breakup has the potential to influence the buttressing controls on inland ice discharge, and thus to affect sea level. Several mechanisms enabling Larsen B style breakup have been proposed, including the ability of surface lakes to introduce ice-shelf fractures when they fill and drain, thereby changing the surface loads the ice-shelf must adjust to. Our model suggest that these fractures resulted in a chain-reaction style drainage of >2750 surface lakes on the Larsen B in the days prior to its demise. To validate this and other models, we began a field project on the McMurdo Ice Shelf (MIS) during the 2015/16 austral summer. Advantages of the MIS study site are: there is considerable surface melting during 3-6 weeks of the summer season, the ice is sufficiently thin (< 30 m in places) to allow observable viscoelastic responses to relatively small loads, and it is close to a center of logistical support (McMurdo Station). Here we show initial results from the field campaign, including GPS and water-depth observations of a lake that has filled and drained over multiple week timescales in previous austral summers. We also report on the analysis of high-resolution WorldView satellite imagery from several summers that reveals the complexity of surface meltwater movement in channels and subsurface void spaces. Initial reconnaissance of the largest surface-lake features reveal that they have a central circular depression surrounded by an uplifted ring, which supports one of the central tenets of our ice-shelf flexure theory. A second field season is anticipated for the 2016/17 austral summer.

Infrasonic interferometry applied to synthetic and measured data

NASA Astrophysics Data System (ADS)

Fricke, Julius T.; Evers, Läslo G.; Ruigrok, Elmer; Wapenaar, Kees; Simons, Dick G.

2013-04-01

The estimation of the traveltime of infrasound through the atmosphere is interesting for several applications. For example, it could be used to determine temperature and wind of the atmosphere, since the traveltime depends on these atmospheric conditions (Haney, 2009). In this work the traveltime is estimated with infrasonic interferometry. In other words, we calculate the crosscorrelations of data of spatially distributed receivers. With this method the traveltime between two receivers is determined without the need for ground truth events. In a first step, we crosscorrelate synthetic data, which are generated by a raytracing model. This model takes into account the traveltime along the rays, the attenuation of the different atmospheric layers, the spreading of the rays and the influence of caustics. In these numerical experiments we show that it is possible to determine the traveltime through infrasonic interferometry. We present the results of infrasonic interferometry applied to measured data. Microbaroms are used in the crosscorrelation approach. Microbaroms are caused by ocean waves and are measured by the 'Large Aperture Infrasound Array' (LAIA). LAIA is being installed by the Royal Netherlands Meteorological Institute (KNMI) in the framework of the radio-astronomical 'Low Frequency Array' (LOFAR) initiative. LAIA consists currently of around twenty receivers (microbarometers) with an aperture of around 100 km, allowing for several inter-station distances. Here, we show the results of crosscorrelations as a function of receivers distance, to assess the signal coherency. This research is made possible by the support of the 'Netherlands Organization for Scientific Research' (NWO). Haney, M., 2009. Infrasonic ambient noise interferometry from correlations of microbaroms, Geophysical Research Letters, 36, L19808

Grounding line migration of Petermann Gletscher, north Greenland, detected using satellite radar interferometry

NASA Technical Reports Server (NTRS)

Rignot, Eric

1997-01-01

Ice Sheet grounding lines are sensitive indicator of changes in ice thickness, sea level or elevation of the sea bed. Here, we use the synthetic-aperture radar interferometry technique to detect the migration of thel imit of tidal flexing, or hinge line, of Petermann Gletscher, a major outlet glacier of north Greenland which develops an extensive floating tongue.

Development of a femtosecond micromachining workstation by use of spectral interferometry.

PubMed

Bera, Sudipta; Sabbah, A J; Durfee, Charles G; Squier, Jeff A

2005-02-15

A workstation that permits real-time measurement of ablation depth while micromachining with femtosecond laser pulses is demonstrated. This method incorporates the unamplified pulse train that is available in a chirped-pulse amplification system as the probe in an arrangement that uses spectral interferometry to measure the ablation depth while cutting with the amplified pulse in thin metal films.

Polarimetry and Interferometry Applications

DTIC Science & Technology

2007-02-01

crown. Since for the traditional SAR interferometry only the total phase center of all scattering effects is relevant, the estimated height would be...the tree trunks and ground level. This contribution has its scattering phase center on the ground and is not present in the cross-polar channels...also the phase relations between the polarizations contain valuable information about the backscattering process. From the azimuth slices presented

Polarimetry and Interferometry Applications

DTIC Science & Technology

2005-02-01

contribution of the backscattering is occurring in the crown. Since for the traditional SAR interferometry only the total phase center of all scattering...double bounce scattering mechanism between the tree trunks and ground level. This contribution has its scattering phase center on the ground and is not...polarizations shows several differences. But addi- tionally to these amplitude images also the phase relations between the polarizations contain

Spatial heterodyne interferometry of VY Canis Major's, alpha Orionis, alpha Scorpii, and R leonis at 11 microns

NASA Technical Reports Server (NTRS)

Sutton, E. C.; Storey, J. W. V.; Betz, A. L.; Townes, C. H.; Spears, D. L.

1977-01-01

Using the technique of heterodyne interferometry, measurements were made of the spatial distribution of 11 micron radiation from four late type stars. The circumstellar shells surrounding VY Canis Majoris, alpha Orionis, and alpha Scorpii were resolved, whereas that of R Leonis was only partially resolved at a fringe spacing of 0.4 sec.

Defect Depth Measurement Using White Light Interferometry

NASA Technical Reports Server (NTRS)

Parker, Don; Starr, Stan

2009-01-01

The objectives of the White Light Interferometry project are the following: (1) Demonstrate a small hand-held instrument capable of performing inspections of identified defects on Orbiter outer pane window surfaces. (2) Build and field-test a prototype device using miniaturized optical components. (3) Modify the instrument based on field testing and begin the conversion of the unit to become a certified shop-aid.

Present and Future Airborne and Space-borne Systems

DTIC Science & Technology

2007-02-01

Present and Future Airborne and Space-borne Systems Wolfgang Keydel Microwaves and Radar Institute German Aerospace Research Centre (DLR...airborne and space-borne SAR systems with polarimetric interferometry capability, their technological, system technical and application related...interferometry accuracies in the cm range have been obtained. In order to reach these values an exact system calibration is indispensable. The calibration of

The Mount Wilson optical interferometer: The first automated instrument and the prospects for lunar interferometry

NASA Technical Reports Server (NTRS)

Johnston, Ken J.; Mozurkewich, D.; Simon, R. S.; Shao, Michael; Colavita, M.

1992-01-01

Before contemplating an optical interferometer on the Moon one must first review the accomplishments achieved by this technology in scientific applications for astronomy. This will be done by presenting the technical status of optical interferometry as achieved by the Mount Wilson Optical Interferometer. The further developments needed for a future lunar-based interferometer are discussed.

Kinematic Slip Model for 12 May 2008 Wenchuan-Beichuan Mw 7.9 Earthquake from Joint Inversion of ALOS, Envisat, and Teleseismic Data

NASA Technical Reports Server (NTRS)

Fielding, Eric; Sladen, Anthony; Avouac, Jean-Philippe; Li, Zhenhong; Ryder, Isabelle; Burgmann, Roland

2008-01-01

The presentations explores kinematics of the Wenchaun-Beichuan earthquake using data from ALOS, Envisat, and teleseismic recordings. Topics include geomorphic mapping, ALOS PALSAR range offsets, ALOS PALSAR interferometry, Envisat IM interferometry, Envisat ScanSAR, Joint GPS-InSAR inversion, and joint GPS-teleseismic inversion (static and kinematic).

Far infrared diagnostics of electron concentration in combustion MHD plasmas using interferometry and Faraday rotation

NASA Astrophysics Data System (ADS)

Kuzmenko, P. J.

1985-12-01

The plasma electrical conductivity is a key parameter in determining the efficiency of an magnetohydrodynamic (MHD) generator. Electromagnetic waves offer an accurate, non-intrusive probe. The electron concentration and mobility may be deduced from the refractive index and absorption coefficient measured with an interferometer. The first experiment used an HCOOH laser at 393.6 microns feeding a Michelson interferometer mounted around a combustor duct with open ports. Simultaneous measurements of positive ion density and plasma temperature made with a Langmuir probe and line reversal apparatus verified the operation of the interferometer. With a magnetic field present, measurement of the polarization rotation and induced ellipticity in a wave traveling along the field provides information on the plasma conductivity. Compared to interferometry, diagnostic apparatus based on Faraday rotation offers simpler optics and requires far less stringent mechanical stability at a cost of lower sensitivity. An advanced detection scheme, using a polarizing beam splitter improved the sensitivity to be comparable to that of interferometry. Interferometry is the preferred technique for small scale, high accuracy measurements, with Faraday rotation reserved for large systems or measurements within a working generator.

From master slave interferometry to complex master slave interferometry: theoretical work

NASA Astrophysics Data System (ADS)

Rivet, Sylvain; Bradu, Adrian; Maria, Michael; Feuchter, Thomas; Leick, Lasse; Podoleanu, Adrian

2018-03-01

A general theoretical framework is described to obtain the advantages and the drawbacks of two novel Fourier Domain Optical Coherence Tomography (OCT) methods denoted as Master/Slave Interferometry (MSI) and its extension denoted as Complex Master/Slave Interferometry (CMSI). Instead of linearizing the digital data representing the channeled spectrum before a Fourier transform can be applied to it (as in OCT standard methods), channeled spectrum is decomposed on the basis of local oscillations. This replaces the need for linearization, generally time consuming, before any calculation of the depth profile in the range of interest. In this model two functions, g and h, are introduced. The function g describes the modulation chirp of the channeled spectrum signal due to nonlinearities in the decoding process from wavenumber to time. The function h describes the dispersion in the interferometer. The utilization of these two functions brings two major improvements to previous implementations of the MSI method. The paper details the steps to obtain the functions g and h, and represents the CMSI in a matrix formulation that enables to implement easily this method in LabVIEW by using parallel programming with multi-cores.

The application of satellite differential SAR interferometry-derived ground displacements in hydrogeology

USGS Publications Warehouse

Galloway, D.L.; Hoffmann, J.

2007-01-01

The application of satellite differential synthetic aperture radar (SAR) interferometry, principally coherent (InSAR) and to a lesser extent, persistent-scatterer (PSI) techniques to hydrogeologic studies has improved capabilities to map, monitor, analyze, and simulate groundwater flow, aquifer-system compaction and land subsidence. A number of investigations over the previous decade show how the spatially detailed images of ground displacements measured with InSAR have advanced hydrogeologic understanding, especially when a time series of images is used in conjunction with histories of changes in water levels and management practices. Important advances include: (1) identifying structural or lithostratigraphic boundaries (e.g. faults or transitional facies) of groundwater flow and deformation; (2) defining the material and hydraulic heterogeneity of deforming aquifer-systems; (3) estimating system properties (e.g. storage coefficients and hydraulic conductivities); and (4) constraining numerical models of groundwater flow, aquifer-system compaction, and land subsidence. As a component of an integrated approach to hydrogeologic monitoring and characterization of unconsolidated alluvial groundwater basins differential SAR interferometry contributes unique information that can facilitate improved management of groundwater resources. Future satellite SAR missions specifically designed for differential interferometry will enhance these contributions. ?? Springer-Verlag 2006.

During air cool process aerosol absorption detection with photothermal interferometry

NASA Astrophysics Data System (ADS)

Li, Baosheng; Xu, Limei; Huang, Junling; Ma, Fei; Wang, Yicheng; Li, Zhengqiang

2014-11-01

This paper studies the basic principle of laser photothermal interferometry method of aerosol particles absorption coefficient. The photothermal interferometry method with higher accuracy and lower uncertainty can directly measure the absorption coefficient of atmospheric aerosols and not be affected by scattered light. With Jones matrix expression, the math expression of a special polarization interferometer is described. This paper using folded Jamin interferometer, which overcomes the influence of vibration on measuring system. Interference come from light polarization beam with two orthogonal and then combine to one beam, finally aerosol absorption induced refractive index changes can be gotten with four beam of phase orthogonal light. These kinds of styles really improve the stability of system and resolution of the system. Four-channel detections interact with interference fringes, to reduce the light intensity `zero drift' effect on the system. In the laboratory, this device typical aerosol absorption index, it shows that the result completely agrees with actual value. After heated by laser, cool process of air also show the process of aerosol absorption. This kind of instrument will be used to monitor ambient aerosol absorption and suspended particulate matter chemical component. Keywords: Aerosol absorption coefficient; Photothermal interferometry; Suspended particulate matter.

[Analysis of antibiotic diffusion from agarose gel by spectrophotometry and laser interferometry methods].

PubMed

Arabski, Michał; Wasik, Sławomir; Piskulak, Patrycja; Góźdź, Natalia; Slezak, Andrzej; Kaca, Wiesław

2011-01-01

The aim of this study was to analysis of antibiotics (ampicilin, streptomycin, ciprofloxacin or colistin) release from agarose gel by spectrophotmetry and laser interferometry methods. The interferometric system consisted of a Mach-Zehnder interferometer with a He-Ne laser, TV-CCD camera, computerised data acquisition system and a gel system. The gel system under study consists of two cuvettes. We filled the lower cuvette with an aqueous 1% agarose solution with the antibiotics at initial concentration of antibiotics in the range of 0.12-2 mg/ml for spectrophotmetry analysis or 0.05-0.5 mg/ml for laser interferometry methods, while in the upper cuvette there was pure water. The diffusion was analysed from 120 to 2400 s with a time interval of deltat = 120 s by both methods. We observed that 0.25-1 mg/ml and 0,05 mg/ml are minimal initial concentrations detected by spectrophotometric and laser interferometry methods, respectively. Additionally, we observed differences in kinetic of antibiotic diffusion from gel measured by both methods. In conclusion, the laser interferometric method is a useful tool for studies of antibiotic release from agarose gel, especially for substances are not fully soluble in water, for example: colistin.

Wideband optical sensing using pulse interferometry.

PubMed

Rosenthal, Amir; Razansky, Daniel; Ntziachristos, Vasilis

2012-08-13

Advances in fabrication of high-finesse optical resonators hold promise for the development of miniaturized, ultra-sensitive, wide-band optical sensors, based on resonance-shift detection. Many potential applications are foreseen for such sensors, among them highly sensitive detection in ultrasound and optoacoustic imaging. Traditionally, sensor interrogation is performed by tuning a narrow linewidth laser to the resonance wavelength. Despite the ubiquity of this method, its use has been mostly limited to lab conditions due to its vulnerability to environmental factors and the difficulty of multiplexing - a key factor in imaging applications. In this paper, we develop a new optical-resonator interrogation scheme based on wideband pulse interferometry, potentially capable of achieving high stability against environmental conditions without compromising sensitivity. Additionally, the method can enable multiplexing several sensors. The unique properties of the pulse-interferometry interrogation approach are studied theoretically and experimentally. Methods for noise reduction in the proposed scheme are presented and experimentally demonstrated, while the overall performance is validated for broadband optical detection of ultrasonic fields. The achieved sensitivity is equivalent to the theoretical limit of a 6 MHz narrow-line width laser, which is 40 times higher than what can be usually achieved by incoherent interferometry for the same optical resonator.

A low cost method for hard x-ray grating interferometry.

PubMed

Du, Yang; Lei, Yaohu; Liu, Xin; Huang, Jianheng; Zhao, Zhigang; Guo, Jinchuan; Li, Ji; Niu, Hanben

2016-12-07

Grating interferometry is advantageous over conventional x-ray absorption imaging because it enables the detection of samples constituted by low atomic number elements (low-Z materials). Therefore, it has a potential application in biological science and medical diagnostics. The grating interferometry has some critical optics components such as absorption gratings which are conventionally manufactured by the lithography, electroplating, and molding (LIGA) technique and employing gold as the absorbent material in it. However, great challenge lies in its implementations for practical applications because of the cost and difficulty to achieve high aspect ratio absorbing grating devices. In this paper, we present a low-cost approach that involves using the micro-casting technique with bismuth (Bi) as the absorber in source grating and as well as filling cesium iodide thallium(CsI:Tl) in a periodically structured scintillator. No costly facilities as synchrotron radiation are required and cheap material is used in our approach. Our experiment using these components shows high quality complementary images can be obtained with contrast of absorption, phase and visibility. This alternative method conquers the limitation of costly grating devices for a long time and stands an important step towards the further practical application of grating interferometry.

Modulating the amplitude and phase of the complex spectral degree of coherence with plasmonic interferometry

NASA Astrophysics Data System (ADS)

Li, Dongfang; Pacifici, Domenico

The spectral degree of coherence describes the correlation of electromagnetic fields, which plays a key role in many applications, including free-space optical communications and speckle-free bioimaging. Recently, plasmonic interferometry, i.e. optical interferometry that employs surface plasmon polaritons (SPPs), has enabled enhanced light transmission and high-sensitivity biosensing, among other applications. It offers new ways to characterize and engineer electromagnetic fields using nano-structured thin metal films. Here, we employ plasmonic interferometry to demonstrate full control of spatial coherence at length scales comparable to the wavelength of the incident light. Specifically, by measuring the diffraction pattern of several double-slit plasmonic structures etched on a metal film, the amplitude and phase of the degree of spatial coherence is determined as a function of slit-slit separation distance and incident wavelength. When the SPP contribution is turned on (i.e., by changing the polarization of the incident light from TE to TM illumination mode), strong modulation of both amplitude and phase of the spatial coherence is observed. These findings may help design compact modulators of optical spatial coherence and other optical elements to shape the light intensity in the far-field.

Characterization methods of integrated optics for mid-infrared interferometry

NASA Astrophysics Data System (ADS)

Labadie, Lucas; Kern, Pierre Y.; Schanen-Duport, Isabelle; Broquin, Jean-Emmanuel

2004-10-01

his article deals with one of the important instrumentation challenges of the stellar interferometry mission IRSI-Darwin of the European Space Agency: the necessity to have a reliable and performant system for beam combination has enlightened the advantages of an integrated optics solution, which is already in use for ground-base interferometry in the near infrared. Integrated optics provides also interesting features in terms of filtering, which is a main issue for the deep null to be reached by Darwin. However, Darwin will operate in the mid infrared range from 4 microns to 20 microns where no integrated optics functions are available on-the-shelf. This requires extending the integrated optics concept and the undergoing technology in this spectral range. This work has started with the IODA project (Integrated Optics for Darwin) under ESA contract and aims to provide a first component for interferometry. In this paper are presented the guidelines of the characterization work that is implemented to test and validate the performances of a component at each step of the development phase. We present also an example of characterization experiment used within the frame of this work, is theoretical approach and some results.

Double-sideband frequency scanning interferometry for long-distance dynamic absolute measurement

NASA Astrophysics Data System (ADS)

Mo, Di; Wang, Ran; Li, Guang-zuo; Wang, Ning; Zhang, Ke-shu; Wu, Yi-rong

2017-11-01

Absolute distance measurements can be achieved by frequency scanning interferometry which uses a tunable laser. The main drawback of this method is that it is extremely sensitive to the movement of targets. In addition, since this method is limited to the linearity of frequency scanning, it is commonly used for close measurements within tens of meters. In order to solve these problems, a double-sideband frequency scanning interferometry system is presented in the paper. It generates two opposite frequency scanning signals through a fixed frequency laser and a Mach-Zehnder modulator. And the system distinguishes the two interference fringe patterns corresponding to the two signals by IQ demodulation (i.e., quadrature detection) of the echo. According to the principle of double-sideband modulation, the two signals have the same characteristics. Therefore, the error caused by the target movement can be effectively eliminated, which is similar to dual-laser frequency scanned interferometry. In addition, this method avoids the contradiction between laser frequency stability and swept performance. The system can be applied to measure the distance of the order of kilometers, which profits from the good linearity of frequency scanning. In the experiment, a precision about 3 μm was achieved for a kilometer-level distance.

Influence of OPD in wavelength-shifting interferometry

NASA Astrophysics Data System (ADS)

Wang, Hongjun; Tian, Ailing; Liu, Bingcai; Dang, Juanjuan

2009-12-01

Phase-shifting interferometry is a powerful tool for high accuracy optical measurement. It operates by change the optical path length in the reference arm or test arm. This method practices by move optical device. So it has much problem when the optical device is very large and heavy. For solve this problem, the wavelength-shifting interferometry was put forwarded. In wavelength-shifting interferometry, the phase shifting angle was achieved by change the wavelength of optical source. The phase shifting angle was decided by wavelength and OPD (Optical Path Difference) between test and reference wavefront. So the OPD is an important factor to measure results. But in measurement, because the positional error and profile error of under testing optical element is exist, the phase shifting angle is different in different test point when wavelength scanning, it will introduce phase shifting angle error, so it will introduce optical surface measure error. For analysis influence of OPD on optical surface error, the relation between surface error and OPD was researched. By simulation, the relation between phase shifting error and OPD was established. By analysis, the error compensation method was put forward. After error compensation, the measure results can be improved to great extend.

Influence of OPD in wavelength-shifting interferometry

NASA Astrophysics Data System (ADS)

Wang, Hongjun; Tian, Ailing; Liu, Bingcai; Dang, Juanjuan

2010-03-01

Phase-shifting interferometry is a powerful tool for high accuracy optical measurement. It operates by change the optical path length in the reference arm or test arm. This method practices by move optical device. So it has much problem when the optical device is very large and heavy. For solve this problem, the wavelength-shifting interferometry was put forwarded. In wavelength-shifting interferometry, the phase shifting angle was achieved by change the wavelength of optical source. The phase shifting angle was decided by wavelength and OPD (Optical Path Difference) between test and reference wavefront. So the OPD is an important factor to measure results. But in measurement, because the positional error and profile error of under testing optical element is exist, the phase shifting angle is different in different test point when wavelength scanning, it will introduce phase shifting angle error, so it will introduce optical surface measure error. For analysis influence of OPD on optical surface error, the relation between surface error and OPD was researched. By simulation, the relation between phase shifting error and OPD was established. By analysis, the error compensation method was put forward. After error compensation, the measure results can be improved to great extend.

Workshop on Functional and Structural Relationships and Factor Analysis (1983). Summary of Research Interests of Participants.

DTIC Science & Technology

1983-01-01

J. Amer. Statist. Assoc. 75, 687-692. Dahm, P. F., Helton, B. and Fuller, W. A. (1983), Generalized least squares estimation of the genotypic ...with applications to -"insect development times". Austral. J. Statist. 23, 204-213. [2] Angus , J.F., R. Morton and C. Schafer. (1981). "Phasic

A demonstration of an independent-station radio interferometry system with 4-cm precision on a 16-km base line. [for geodesy

NASA Technical Reports Server (NTRS)

Thomas, J. B.; Fanselow, J. L.; Macdoran, P. F.; Skjerve, L. J.; Spitzmesser, D. J.; Fliegel, H. F.

1976-01-01

Radio interferometry promises eventually to measure directly, with accuracies of a few centimeters, both whole earth motions and relative crustal motions with respect to an 'inertial' reference frame. Interferometry measurements of arbitrarily long base lines require, however, the development of new techniques for independent-station observation. In connection with the development of such techniques, a series of short base line demonstration experiments has been conducted between two antennas. The experiments were related to a program involving the design of independent-station instrumentation capable of making three-dimensional earth-fixed base line measurements with an accuracy of a few centimeters. Attention is given to the instrumentation used in the experiments, aspects of data analysis, and the experimental results.

2D image of local density and magnetic fluctuations from line-integrated interferometry-polarimetry measurements.

PubMed

Lin, L; Ding, W X; Brower, D L

2014-11-01

Combined polarimetry-interferometry capability permits simultaneous measurement of line-integrated density and Faraday effect with fast time response (∼1 μs) and high sensitivity. Faraday effect fluctuations with phase shift of order 0.05° associated with global tearing modes are resolved with an uncertainty ∼0.01°. For physics investigations, local density fluctuations are obtained by inverting the line-integrated interferometry data. The local magnetic and current density fluctuations are then reconstructed using a parameterized fit of the polarimetry data. Reconstructed 2D images of density and magnetic field fluctuations in a poloidal cross section exhibit significantly different spatial structure. Combined with their relative phase, the magnetic-fluctuation-induced particle transport flux and its spatial distribution are resolved.

Scanning fiber angle-resolved low coherence interferometry

PubMed Central

Zhu, Yizheng; Terry, Neil G.; Wax, Adam

2010-01-01

We present a fiber-optic probe for Fourier-domain angle-resolved low coherence interferometry for the determination of depth-resolved scatterer size. The probe employs a scanning single-mode fiber to collect the angular scattering distribution of the sample, which is analyzed using the Mie theory to obtain the average size of the scatterers. Depth sectioning is achieved with low coherence Mach–Zehnder interferometry. In the sample arm of the interferometer, a fixed fiber illuminates the sample through an imaging lens and a collection fiber samples the backscattered angular distribution by scanning across the Fourier plane image of the sample. We characterize the optical performance of the probe and demonstrate the ability to execute depth-resolved sizing with subwavelength accuracy by using a double-layer phantom containing two sizes of polystyrene microspheres. PMID:19838271

Holographic interferometry applied to the measurement of displacements of the interior points of transparent bodies.

PubMed

Sciammarella, C A; Gilbert, J A

1976-09-01

Utilizing the light scattering property of transparent media, holographic interferometry is applied to the measurement of displacement at the interior planes of three dimensional bodies. The use of a double beam illumination and the introduction of a fictitious displacement make it feasible to obtain information corresponding to components of displacement projected on the scattering plane. When the proposed techniques are invoked, it is possible to eliminate the use of a matching index of refraction fluid in many problems involving symmetrically loaded prismatic bodies. Scattered light holographic interferometry is limited in its use to small changes in the index of refraction and to low values of relative retardation. In spite of these restrictions, a large number of technical problems in both statics and dynamics can be solved.

Optical interferometry and Gaia parallaxes for a robust calibration of the Cepheid distance scale

NASA Astrophysics Data System (ADS)

Kervella, Pierre; Mérand, Antoine; Gallenne, Alexandre; Trahin, Boris; Borgniet, Simon; Pietrzynski, Grzegorz; Nardetto, Nicolas; Gieren, Wolfgang

2018-04-01

We present the modeling tool we developed to incorporate multi-technique observations of Cepheids in a single pulsation model: the Spectro-Photo-Interferometry of Pulsating Stars (SPIPS). The combination of angular diameters from optical interferometry, radial velocities and photometry with the coming Gaia DR2 parallaxes of nearby Galactic Cepheids will soon enable us to calibrate the projection factor of the classical Parallax-of-Pulsation method. This will extend its applicability to Cepheids too distant for accurate Gaia parallax measurements, and allow us to precisely calibrate the Leavitt law's zero point. As an example application, we present the SPIPS model of the long-period Cepheid RS Pup that provides a measurement of its projection factor, using the independent distance estimated from its light echoes.

Comparison of the results of refractometric measurements in the process of diffusion, obtained by means of the backgroundoriented schlieren method and the holographic interferometry method

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

Kraiskii, A V; Mironova, T V

2015-08-31

The results of the study of interdiffusion of two liquids, obtained using the holographic recording scheme with a nonstationary reference wave with the frequency linearly varying in space and time are compared with the results of correlation processing of digital photographs, made with a random background screen. The spatio-temporal behaviour of the signal in four basic representations ('space – temporal frequency', 'space – time', 'spatial frequency – temporal frequency' and 'spatial frequency – time') is found in the holographic experiment and calculated (in the appropriate coordinates) based on the background-oriented schlieren method. Practical coincidence of the results of the correlationmore » analysis and the holographic double-exposure interferometry is demonstrated. (interferometry)« less

A three-image algorithm for hard x-ray grating interferometry.

PubMed

Pelliccia, Daniele; Rigon, Luigi; Arfelli, Fulvia; Menk, Ralf-Hendrik; Bukreeva, Inna; Cedola, Alessia

2013-08-12

A three-image method to extract absorption, refraction and scattering information for hard x-ray grating interferometry is presented. The method comprises a post-processing approach alternative to the conventional phase stepping procedure and is inspired by a similar three-image technique developed for analyzer-based x-ray imaging. Results obtained with this algorithm are quantitatively comparable with phase-stepping. This method can be further extended to samples with negligible scattering, where only two images are needed to separate absorption and refraction signal. Thanks to the limited number of images required, this technique is a viable route to bio-compatible imaging with x-ray grating interferometer. In addition our method elucidates and strengthens the formal and practical analogies between grating interferometry and the (non-interferometric) diffraction enhanced imaging technique.

2D image of local density and magnetic fluctuations from line-integrated interferometry-polarimetry measurements

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

Lin, L., E-mail: lianglin@ucla.edu; Ding, W. X.; Brower, D. L.

2014-11-15

Combined polarimetry-interferometry capability permits simultaneous measurement of line-integrated density and Faraday effect with fast time response (∼1 μs) and high sensitivity. Faraday effect fluctuations with phase shift of order 0.05° associated with global tearing modes are resolved with an uncertainty ∼0.01°. For physics investigations, local density fluctuations are obtained by inverting the line-integrated interferometry data. The local magnetic and current density fluctuations are then reconstructed using a parameterized fit of the polarimetry data. Reconstructed 2D images of density and magnetic field fluctuations in a poloidal cross section exhibit significantly different spatial structure. Combined with their relative phase, the magnetic-fluctuation-induced particlemore » transport flux and its spatial distribution are resolved.« less

Angular-domain scattering interferometry.

PubMed

Shipp, Dustin W; Qian, Ruobing; Berger, Andrew J

2013-11-15

We present an angular-scattering optical method that is capable of measuring the mean size of scatterers in static ensembles within a field of view less than 20 μm in diameter. Using interferometry, the method overcomes the inability of intensity-based models to tolerate the large speckle grains associated with such small illumination areas. By first estimating each scatterer's location, the method can model between-scatterer interference as well as traditional single-particle Mie scattering. Direct angular-domain measurements provide finer angular resolution than digitally transformed image-plane recordings. This increases sensitivity to size-dependent scattering features, enabling more robust size estimates. The sensitivity of these angular-scattering measurements to various sizes of polystyrene beads is demonstrated. Interferometry also allows recovery of the full complex scattered field, including a size-dependent phase profile in the angular-scattering pattern.

Measurement of a density profile of a hot-electron plasma in RT-1 with three-chord interferometry

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

Saitoh, H.; Yano, Y.; Yoshida, Z.

2015-02-15

The electron density profile of a plasma in a magnetospheric dipole field configuration was measured with a multi-chord interferometry including a relativistic correction. In order to improve the accuracy of density reconstruction, a 75 GHz interferometer was installed at a vertical chord of the Ring Trap 1 (RT-1) device in addition to previously installed ones at tangential and another vertical chords. The density profile was calculated by using the data of three-chord interferometry including relativistic effects for a plasma consisting of hot and cold electrons generated by electron cyclotron resonance heating (ECH). The results clearly showed the effects of density peakingmore » and magnetic mirror trapping in a strongly inhomogeneous dipole magnetic field.« less

Spectrally controlled interferometry for measurements of flat and spherical optics

NASA Astrophysics Data System (ADS)

Salsbury, Chase; Olszak, Artur G.

2017-10-01

Conventional interferometry is widely used to measure spherical and at surfaces with nanometer level precision but is plagued by back reflections. We describe a new method of isolating the measurement surface by controlling spectral properties of the source (Spectrally Controlled Interferometry - SCI). Using spectral modulation of the interferometer's source enables formation of localized fringes where the optical path difference is non-zero. As a consequence it becomes possible to form white-light like fringes in common path interferometers, such as the Fizeau. The proposed setup does not require mechanical phase shifting, resulting in simpler instruments and the ability to upgrade existing interferometers. Furthermore, it allows absolute measurement of distance, including radius of curvature of lenses in a single setup with possibility of improving the throughput and removing some modes of failure.

Application of SPM interferometry in MEMS vibration measurement

NASA Astrophysics Data System (ADS)

Tang, Chaowei; He, Guotian; Xu, Changbiao; Zhao, Lijuan; Hu, Jun

2007-12-01

The resonant frequency measurement of cantilever has an important position in MEMS(Micro Electro Mechanical Systems) research. Meanwhile the SPM interferometry is a high-precision optical measurement technique, which can be used in physical quantity measurement of vibration, displacement, surface profile. Hence, in this paper we propose to apply SPM(SPM) interferometry in measuring the vibration of MEMS cantilever and in the experiment the vibration of MEMS cantilever was driven by light source. Then this kind of vibration was measured in nm precision. Finally the relational characteristics of MEMS cantilever vibration under optical excitation can be gotten and the measurement principle is analyzed. This method eliminates the influence on the measuring precision caused by external interference and light intensity change through feedback control loop. Experiment results prove that this measurement method has a good effect.

Phase-Sensitive Surface Plasmon Resonance Sensors: Recent Progress and Future Prospects

PubMed Central

Deng, Shijie; Wang, Peng; Yu, Xinglong

2017-01-01

Surface plasmon resonance (SPR) is an optical sensing technique that is capable of performing real-time, label-free and high-sensitivity monitoring of molecular interactions. SPR biosensors can be divided according to their operating principles into angle-, wavelength-, intensity- and phase-interrogated devices. With their complex optical configurations, phase-interrogated SPR sensors generally provide higher sensitivity and throughput, and have thus recently emerged as prominent biosensing devices. To date, several methods have been developed for SPR phase interrogation, including heterodyne detection, polarimetry, shear interferometry, spatial phase modulation interferometry and temporal phase modulation interferometry. This paper summarizes the fundamentals of phase-sensitive SPR sensing, reviews the available methods for phase interrogation of these sensors, and discusses the future prospects for and trends in the development of this technology. PMID:29206182

Parsimonious surface wave interferometry

NASA Astrophysics Data System (ADS)

Li, Jing; Hanafy, Sherif; Schuster, Gerard T.

2018-03-01

To decrease the recording time of a 2-D seismic survey from a few days to one hour or less, we present a parsimonious surface wave interferometry method. Interferometry allows for the creation of a large number of virtual shot gathers from just two reciprocal shot gathers by crosscoherence of trace pairs. Then, the virtual surface waves can be inverted for the S-wave velocity model by wave-equation dispersion inversion (WD). Synthetic and field data tests suggest that parsimonious WD (PWD) gives S-velocity tomograms that are comparable to those obtained from a conventional survey with a shot at each receiver. The limitation of PWD is that the virtual data lose some information so that the resolution of the S-velocity tomogram can be modestly lower than that of the S-velocity tomogram inverted from a conventional survey.

Multi-function optical characterization and inspection of MEMS components using stroboscopic coherence scanning interferometry

NASA Astrophysics Data System (ADS)

Tapilouw, Abraham Mario; Chen, Liang-Chia; Xuan-Loc, Nguyen; Chen, Jin-Liang

2014-08-01

A Micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and automotive industries. However, effective inspection systems are also needed to ensure the functional reliability of MEMS. This study developed a stroboscopic coherence scanning Interferometry (SCSI) technique for measuring key characteristics typically used as criteria in MEMS inspections. Surface profiles of MEMS both static and dynamic conditions were measured by means of coherence scanning Interferometry (CSI). Resonant frequencies of vibrating MEMS were measured by deformation of interferogram fringes for out-of-plane vibration and by image correlation for in-plane vibration. The measurement bandwidth of the developed system can be tuned up to three megahertz or higher for both in-plane and out-of-plane measurement of MEMS.

Development of realtime connected element interferometry at the Goldstone Deep Space Communications Complex

NASA Technical Reports Server (NTRS)

Edwards, C. D.

1990-01-01

Connected-element interferometry (CEI) has the potential to provide high-accuracy angular spacecraft tracking on short baselines by making use of the very precise phase delay observable. Within the Goldstone Deep Space Communications Complex (DSCC), one of three tracking complexes in the NASA Deep Space Network, baselines of up to 21 km in length are available. Analysis of data from a series of short-baseline phase-delay interferometry experiments are presented to demonstrate the potential tracking accuracy on these baselines. Repeated differential observations of pairs of angularly close extragalactic radio sources were made to simulate differential spacecraft-quasar measurements. Fiber-optic data links and a correlation processor are currently being developed and installed at Goldstone for a demonstration of real-time CEI in 1990.

Neutron interferometry: The pioneering contributions of Samuel A. Werner

NASA Astrophysics Data System (ADS)

Klein, A. G.

2006-11-01

In 1975, Sam Werner, while on the staff of the Scientific Laboratory of the Ford Motor Company, and his collaborators from Purdue University, Roberto Colella and Albert Overhauser, carried out one of the pioneering experiments in neutron interferometry at the 2 MW University of Michigan research reactor. It was the famous COW Experiment [Colella et al., Phys. Rev. Lett. 34 (1975) 1472] on gravitationally induced quantum interference. Shortly thereafter he moved to the University of Missouri in Columbia, to set up a program of neutron scattering research, including neutron interferometry. In the 25 years until his retirement a large number of beautiful experiments have been performed by Sam, with his group, his numerous students and many international collaborators. This work and its history are briefly reviewed in this paper.

Modeling of Compaction Wave Behavior in Confined Granular Energetic Material

DTIC Science & Technology

1990-08-01

Compacted 65% TMD Aggregate Melamine Compaction Wave Microwave DIAGNOSTICS: Interferometry (a) Microwave Interferometry (b) 3 Wall-Mounted Pressure...involved 65% TMD melamine but was run very recently (Dec 1989) The value of compaction wave speed (from the microwave data) just after impact is...47 B. Simulation of PDC-M34 / 65% TMD Melamine (Inert Material) ........ 54 C. Influence of Energy Release / PDC Experiment

Using Optical Interferometry for GEO Satellites Imaging: An Update

DTIC Science & Technology

2016-05-27

of a geostationary satellite using the Navy Precision Optical Inter- ferometer (NPOI) during the glint season of March 2015. We succeeded in detecting...night. These baseline lengths correspond to a resolution of ∼4 m at geostationary altitude. This is the first multiple-baseline interferometric...detection of a satellite. Keywords: geostationary satellites, optical interferometry, imaging, telescope arrays 1. INTRODUCTION Developing the ability to

Measurement of picometre non-linearity in an optical grating encoder using x-ray interferometry

NASA Astrophysics Data System (ADS)

Yacoot, Andrew; Cross, Nigel

2003-01-01

X-ray interferometry has been used to characterize the non-linearity in an optical encoder displacement measuring system. Traceable measurements of the non-linearity have been made and an estimation of the uncertainty associated with the measurements is given. Cyclic errors with a magnitude of up to 50 pm and periodicity of the encoder system (128 nm) have been recorded.

Synchronous Stroboscopic Electronic Speckle Pattern Interferometry

NASA Astrophysics Data System (ADS)

Soares, Oliverio D. D.

1986-10-01

Electronic Speckle Pattern Interferometry (E.S.P.I) oftenly called Electronic Holography is a practical powerful technique in non-destructive testing. Practical capabilities of the technique have been improved by fringe betterment and the control of analysis in the time domain, in particular, the scanning of the vibration cycle, with introduction of: synchronized amplitude and phase modulated pulse illumination, microcomputer control, fibre optics design, and moire evaluation techniques.

Multi-object investigation using two-wavelength phase-shift interferometry guided by an optical frequency comb

NASA Astrophysics Data System (ADS)

Ibrahim, Dahi Ghareab Abdelsalam; Yasui, Takeshi

2018-04-01

Two-wavelength phase-shift interferometry guided by optical frequency combs is presented. We demonstrate the operation of the setup with a large step sample simultaneously with a resolution test target with a negative pattern. The technique can investigate multi-objects simultaneously with high precision. Using this technique, several important applications in metrology that require high speed and precision are demonstrated.

Measuring the Dispersion in Laser Cavity Mirrors using White-Light Interferometry

DTIC Science & Technology

2008-03-01

mirrors. Two AlGaInP (aluminum gallium indium phosphide ) diode lasers are aligned such that one is polarized vertically while one is polarized...linear crystals, where the index of refraction depends on beam intensity. Short pulses with high peak intensities are well 14 suited to induce the...MEASURING THE DISPERSION OF LASER CAVITY MIRRORS USING WHITE-LIGHT INTERFEROMETRY THESIS Allison S

Geological Interpretations of the Topography of Selected Regions of Venus from Arecibo to Goldstone Radar Interferometry

NASA Technical Reports Server (NTRS)

Jurgens, R. F.; Margot, J-L.; Simons, M.; Pritchard, M. E.; Slade, M. A.

2002-01-01

Radar interferometry using Arecibo to transmit and three antennas at the Goldstone to receive was conducted on 14 dates in Spring, 2001. This data has been used so far to generate DEMs (digital elevation models) for several of the dates with pixel resolution of 0.5-1.0 km. Additional information is contained in the original extended abstract.

Precise signal amplitude retrieval for a non-homogeneous diagnostic beam using complex interferometry approach

NASA Astrophysics Data System (ADS)

Krupka, M.; Kalal, M.; Dostal, J.; Dudzak, R.; Juha, L.

2017-08-01

Classical interferometry became widely used method of active optical diagnostics. Its more advanced version, allowing reconstruction of three sets of data from just one especially designed interferogram (so called complex interferogram) was developed in the past and became known as complex interferometry. Along with the phase shift, which can be also retrieved using classical interferometry, the amplitude modifications of the probing part of the diagnostic beam caused by the object under study (to be called the signal amplitude) as well as the contrast of the interference fringes can be retrieved using the complex interferometry approach. In order to partially compensate for errors in the reconstruction due to imperfections in the diagnostic beam intensity structure as well as for errors caused by a non-ideal optical setup of the interferometer itself (including the quality of its optical components), a reference interferogram can be put to a good use. This method of interferogram analysis of experimental data has been successfully implemented in practice. However, in majority of interferometer setups (especially in the case of the ones employing the wavefront division) the probe and the reference part of the diagnostic beam would feature different intensity distributions over their respective cross sections. This introduces additional error into the reconstruction of the signal amplitude and the fringe contrast, which cannot be resolved using the reference interferogram only. In order to deal with this error it was found that additional separately recorded images of the intensity distribution of the probe and the reference part of the diagnostic beam (with no signal present) are needed. For the best results a sufficient shot-to-shot stability of the whole diagnostic system is required. In this paper, efficiency of the complex interferometry approach for obtaining the highest possible accuracy of the signal amplitude reconstruction is verified using the computer generated complex and reference interferograms containing artificially introduced intensity variations in the probe and the reference part of the diagnostic beam. These sets of data are subsequently analyzed and the errors of the signal amplitude reconstruction are evaluated.

Seismic interferometry by crosscorrelation and by multidimensional deconvolution: a systematic comparison

NASA Astrophysics Data System (ADS)

Wapenaar, Kees; van der Neut, Joost; Ruigrok, Elmer; Draganov, Deyan; Hunziker, Juerg; Slob, Evert; Thorbecke, Jan; Snieder, Roel

2010-05-01

In recent years, seismic interferometry (or Green's function retrieval) has led to many applications in seismology (exploration, regional and global), underwater acoustics and ultrasonics. One of the explanations for this broad interest lies in the simplicity of the methodology. In passive data applications a simple crosscorrelation of responses at two receivers gives the impulse response (Green's function) at one receiver as if there were a source at the position of the other. In controlled-source applications the procedure is similar, except that it involves in addition a summation along the sources. It has also been recognized that the simple crosscorrelation approach has its limitations. From the various theoretical models it follows that there are a number of underlying assumptions for retrieving the Green's function by crosscorrelation. The most important assumptions are that the medium is lossless and that the waves are equipartitioned. In heuristic terms the latter condition means that the receivers are illuminated isotropically from all directions, which is for example achieved when the sources are regularly distributed along a closed surface, the sources are mutually uncorrelated and their power spectra are identical. Despite the fact that in practical situations these conditions are at most only partly fulfilled, the results of seismic interferometry are generally quite robust, but the retrieved amplitudes are unreliable and the results are often blurred by artifacts. Several researchers have proposed to address some of the shortcomings by replacing the correlation process by deconvolution. In most cases the employed deconvolution procedure is essentially 1-D (i.e., trace-by-trace deconvolution). This compensates the anelastic losses, but it does not account for the anisotropic illumination of the receivers. To obtain more accurate results, seismic interferometry by deconvolution should acknowledge the 3-D nature of the seismic wave field. Hence, from a theoretical point of view, the trace-by-trace process should be replaced by a full 3-D wave field deconvolution process. Interferometry by multidimensional deconvolution is more accurate than the trace-by-trace correlation and deconvolution approaches but the processing is more involved. In the presentation we will give a systematic analysis of seismic interferometry by crosscorrelation versus multi-dimensional deconvolution and discuss applications of both approaches.

Hybrid shearing and phase-shifting point diffraction interferometer

DOEpatents

Goldberg, Kenneth Alan; Naulleau, Patrick P.

2003-06-03

A new interferometry configuration combines the strengths of two existing interferometry methods, improving the quality and extending the dynamic range of both. On the same patterned mask, placed near the image-plane of an optical system under test, patterns for phase-shifting point diffraction interferometry and lateral shearing interferometry coexist. The former giving verifiable high accuracy for the measurement of nearly diffraction-limited optical systems. The latter enabling the measurement of optical systems with more than one wave of aberration in the system wavefront. The interferometry configuration is a hybrid shearing and point diffraction interferometer system for testing an optical element that is positioned along an optical path including: a source of electromagnetic energy in the optical path; a first beam splitter that is secured to a device that includes means for maneuvering the first beam splitter in a first position wherein the first beam splitter is in the optical path dividing light from the source into a reference beam and a test beam and in a second position wherein the first beam splitter is outside the optical path: a hybrid mask which includes a first section that defines a test window and at least one reference pinhole and a second section that defines a second beam splitter wherein the hybrid mask is secured to a device that includes means for maneuvering either the first section or the second section into the optical path positioned in an image plane that is created by the optical element, with the proviso that the first section of the hybrid mask is positioned in the optical path when first beam splitter is positioned in the optical path; and a detector positioned after the hybrid mask along the optical path.

Quantitative measurement of thin phase objects: comparison of speckle deflectometry and defocus-variant lateral shear interferometry.

PubMed

Sjodahl, Mikael; Amer, Eynas

2018-05-10

The two techniques of lateral shear interferometry and speckle deflectometry are analyzed in a common optical system for their ability to measure phase gradient fields of a thin phase object. The optical system is designed to introduce a shear in the frequency domain of a telecentric imaging system that gives a sensitivity of both techniques in proportion to the defocus introduced. In this implementation, both techniques successfully measure the horizontal component of the phase gradient field. The response of both techniques scales linearly with the defocus distance, and the precision is comparative, with a random error in the order of a few rad/mm. It is further concluded that the precision of the two techniques relates to the transverse speckle size in opposite ways. While a large spatial coherence width, and correspondingly a large lateral speckle size, makes lateral shear interferometry less susceptible to defocus, a large lateral speckle size is detrimental for speckle correlation. The susceptibility for the magnitude of the defocus is larger for the lateral shear interferometry technique as compared to the speckle deflectometry technique. The two techniques provide the same type of information; however, there are a few fundamental differences. Lateral shear interferometry relies on a special hardware configuration in which the shear angle is intrinsically integrated into the system. The design of a system sensitive to both in-plane phase gradient components requires a more complex configuration and is not considered in this paper. Speckle deflectometry, on the other hand, requires no special hardware, and both components of the phase gradient field are given directly from the measured speckle deformation field.

Narrow-linewidth tunable laser working at 633 nm suitable for industrial interferometry

NASA Astrophysics Data System (ADS)

Minh, Tuan Pham; Hucl, Václav; Čížek, Martin; Mikel, Břetislav; Hrabina, Jan; Řeřucha, Šimon; Číp, Ondřej; Lazar, Josef

2015-05-01

Semiconductor lasers found a foothold in many fields of human activities, mainly thanks to its small size, low cost and high energy efficiency. Recent methods for accurate distance measurement in industrial practice use principles of laser interferometry, which are based on lasers operating in the visible spectrum. When the laser beam is visible the alignment of the industrial interferometer makes the measuring process easier. Traditional lasers for these purposes for many decades - HeNe gas laser - have superb coherence properties but small tunable range. On the other hand laser diodes are very useful lasers but only if the active layer of the semiconductor equips with a passive selective element that will increase the quality of their own resonator and also prevents the structure of its higher longitudinal modes. The main aim of the work is a design of the laser source based on a new commercial available laser diode with Distributed Bragg Reflector structure, butterfly package and fibre coupled output. The ultra-low noise injection current source, stable temperature controller and supply electronic equipment were developed with us and experimentally tested with this laser for the best performances required of the industrial interferometry field. The work also performs a setup for frequency noise properties investigation with an unbalanced fibre based Mach-Zehnder interferometer and 10 m long fibre spool inserted in the reference arm. The work presents the way to developing the narrow-linewidth operation the DBR laser with the wide tunable range up to more than 1 nm of the operation wavelength at the same time. Both capabilities predetermine this complex setup for the industrial interferometry application as they are the long distance surveying or absolute scale interferometry.

Deformations and strains in adhesive joints by moire interferometry

NASA Technical Reports Server (NTRS)

Post, D.; Czarnek, R.; Wood, J.; John, D.; Lubowinski, S.

1984-01-01

Displacement fields in a thick adherend lap joint and a cracked lap shear specimen were measured by high sensitivity moire interferometry. Contour maps of in-plane U and V displacements were obtained across adhesive and adherent surfaces. Loading sequences ranged from modest loads to near-failure loads. Quantitative results are given for displacements and certain strains in the adhesive and along the adhesive/adherend boundary lines. The results show nonlinear displacements and strains as a function of loads or stresses and they show viscoelastic or time-dependent response. Moire interferometry is an excellent method for experimental studies of adhesive joint performance. Subwavelength displacement resolution of a few micro-inches, and spatial resolution corresponding to 1600 fringes/inch (64 fringes/mm), were obtained in these studies. The whole-field contour maps offer insights not available from local measurements made by high sensitivity gages.

Stitching interferometry of a full cylinder without using overlap areas

NASA Astrophysics Data System (ADS)

Peng, Junzheng; Chen, Dingfu; Yu, Yingjie

2017-08-01

Traditional stitching interferometry requires finding out the overlap correspondence and computing the discrepancies in the overlap regions, which makes it complex and time-consuming to obtain the 360° form map of a cylinder. In this paper, we develop a cylinder stitching model based on a new set of orthogonal polynomials, termed Legendre Fourier (LF) polynomials. With these polynomials, individual subaperture data can be expanded as a composition of the inherent form of a partial cylinder surface and additional misalignment parameters. Then the 360° form map can be acquired by simultaneously fitting all subaperture data with the LF polynomials. A metal shaft was measured to experimentally verify the proposed method. In contrast to traditional stitching interferometry, our technique does not require overlapping of adjacent subapertures, thus significantly reducing the measurement time and making the stitching algorithm simple.

Laser holographic interferometry for an unsteady airfoil in dynamic stall

NASA Technical Reports Server (NTRS)

Lee, G.; Buell, D. A.; Licursi, J. P.; Craig, J. E.

1983-01-01

Laser holographic interferometry was used to study a two-dimensional NACA 0012 airfoil undergoing dynamic stall. The airfoil, fabricated from graphite fiber and epoxy, was tested at Mach numbers of 0.3 to 0.6, at Reynolds numbers of 500,000-2,000,000, at reduced frequencies of 0.015 to 0.15, and at mean angles of attack of 0-10 deg with amplitudes of 10 deg. Density and pressure fields were obtained from dual-plate interferograms. Double-pulse interferograms, which seemed to show the wake boundaries better, were also taken. Comparisons of pressures with orifice pressures were good for the attached flow cases. For the separated flow cases, which had a vortex enbedded in the flow, the comparisons were poor. Vortices, wake structures, and the dynamic stall process can be seen by holographic interferometry.

Actively stabilized optical fiber interferometry technique for online/in-process surface measurement.

PubMed

Wang, Kaiwei; Martin, Haydn; Jiang, Xiangqian

2008-02-01

In this paper, we report the recent progress in optical-beam scanning fiber interferometry for potential online nanoscale surface measurement based on the previous research. It attempts to generate a robust and miniature measurement device for future development into a multiprobe array measurement system. In this research, both fiber-optic-interferometry and the wavelength-division-multiplexing techniques have been used, so that the optical probe and the optical interferometer are well spaced and fast surface scanning can be carried out, allowing flexibility for online measurement. In addition, this system provides a self-reference signal to stabilize the optical detection with high common-mode noise suppression by adopting an active phase tracking and stabilization technique. Low-frequency noise was significantly reduced compared with unstabilized result. The measurement of a sample surface shows an attained repeatability of 3.3 nm.

Spectro-Interferometry Studies of Velocity-Related Phenomena at the Surface of Stars: Pulsation and Rotation

NASA Astrophysics Data System (ADS)

Mérand, Antoine; Patru, Fabien; Aufdenberg, Jason

We illustrate here two applications of spectro-interferometry to the study of velocity fields at the surface of stars: pulsation and rotation. Stellar pulsation has been resolved spectroscopically for a long time, and interferometry has resolved stellar diameters variations due to pulsation. Combining the two provides unique insights to the study of Cepheids, in particular regarding the structure of the photosphere or investigating the infamous projection factor which biases distances measured by the Baade-Wesselink method. On the other hand, resolving the surface velocity field of rotating stars offers a unique opportunity to potentially study differential rotation in other cases than for the Sun. We also present the model we have implemented recently, as well as two applications to VLTI/AMBER Data: the pulsation of Cepheids and the rotation of intermediate mass main sequence stars.

Kinetic Titration Series with Biolayer Interferometry

PubMed Central

Frenzel, Daniel; Willbold, Dieter

2014-01-01

Biolayer interferometry is a method to analyze protein interactions in real-time. In this study, we illustrate the usefulness to quantitatively analyze high affinity protein ligand interactions employing a kinetic titration series for characterizing the interactions between two pairs of interaction patterns, in particular immunoglobulin G and protein G B1 as well as scFv IC16 and amyloid beta (1–42). Kinetic titration series are commonly used in surface plasmon resonance and involve sequential injections of analyte over a desired concentration range on a single ligand coated sensor chip without waiting for complete dissociation between the injections. We show that applying this method to biolayer interferometry is straightforward and i) circumvents problems in data evaluation caused by unavoidable sensor differences, ii) saves resources and iii) increases throughput if screening a multitude of different analyte/ligand combinations. PMID:25229647

Digitally enhanced homodyne interferometry.

PubMed

Sutton, Andrew J; Gerberding, Oliver; Heinzel, Gerhard; Shaddock, Daniel A

2012-09-24

We present two variations of a novel interferometry technique capable of simultaneously measuring multiple targets with high sensitivity. The technique performs a homodyne phase measurement by application of a four point phase shifting algorithm, with pseudo-random switching between points to allow multiplexed measurement based upon propagation delay alone. By multiplexing measurements and shifting complexity into signal processing, both variants realise significant complexity reductions over comparable methods. The first variant performs a typical coherent detection with a dedicated reference field and achieves a displacement noise floor 0.8 pm/√Hz above 50 Hz. The second allows for removal of the dedicated reference, resulting in further simplifications and improved low frequency performance with a 1 pm/√Hz noise floor measured down to 20 Hz. These results represent the most sensitive measurement performed using this style of interferometry whilst simultaneously reducing the electro-optic footprint.

Nanoscale optical interferometry with incoherent light

PubMed Central

Li, Dongfang; Feng, Jing; Pacifici, Domenico

2016-01-01

Optical interferometry has empowered an impressive variety of biosensing and medical imaging techniques. A widely held assumption is that devices based on optical interferometry require coherent light to generate a precise optical signature in response to an analyte. Here we disprove that assumption. By directly embedding light emitters into subwavelength cavities of plasmonic interferometers, we demonstrate coherent generation of surface plasmons even when light with extremely low degrees of spatial and temporal coherence is employed. This surprising finding enables novel sensor designs with cheaper and smaller light sources, and consequently increases accessibility to a variety of analytes, such as biomarkers in physiological fluids, or even airborne nanoparticles. Furthermore, these nanosensors can now be arranged along open detection surfaces, and in dense arrays, accelerating the rate of parallel target screening used in drug discovery, among other high volume and high sensitivity applications. PMID:26880171

Photoacoustic tomography based on the Green's function retrieval with ultrasound interferometry for sample partially behind an acoustically scattering layer

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

Yin, Jie; Department of Automation, Nanjing Polytechnic Institute, 210048 Nanjing; Tao, Chao, E-mail: taochao@nju.edu.cn

2015-06-08

Acoustically inhomogeneous mediums with multiple scattering are often the nightmare of photoacoustic tomography. In order to break this limitation, a photoacoustic tomography scheme combining ultrasound interferometry and time reversal is proposed to achieve images in acoustically scattering medium. An ultrasound interferometry is developed to determine the unknown Green's function of strong scattering tissue. Using the determined Greens' function, a time-reversal process is carried out to restore images behind an acoustically inhomogeneous layer from the scattering photoacoustic signals. This method effectively decreases the false contrast, noise, and position deviation of images induced by the multiple scattering. Phantom experiment is carried outmore » to validate the method. Therefore, the proposed method could have potential value in extending the biomedical applications of photoacoustic tomography in acoustically inhomogeneous tissue.« less

A method for monitoring mass concentration of black carbon particulate matter using photothermal interferometry.

PubMed

Li, Baosheng; Wang, Yicheng; Li, Zhengqiang

2016-03-01

A method for measurements of mass concentration of black carbon particulate matter (PM) is proposed based on photothermal interferometry (PTI). A folded Jamin photothermal interferometer was used with a laser irradiation of particles deposited on a filter paper. The black carbon PM deposited on the filter paper was regarded as a film while the quartz filter paper was regarded as a substrate to establish a mathematical model for measuring the mass concentration of PM using a photothermal method. The photothermal interferometry system was calibrated and used to measure the atmospheric PM concentration corresponding to different dust-treated filter paper. The measurements were compared to those obtained using β ray method and were found consistent. This method can be particularly relevant to polluted atmospheres where PM is dominated by black carbon.

Relative astrometry of compact flaring structures in Sgr A* with polarimetric very long baseline interferometry

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

Johnson, Michael D.; Doeleman, Sheperd S.; Fish, Vincent L.

2014-10-20

We demonstrate that polarimetric interferometry can be used to extract precise spatial information about compact polarized flares of Sgr A*. We show that, for a faint dynamical component, a single interferometric baseline suffices to determine both its polarization and projected displacement from the quiescent intensity centroid. A second baseline enables two-dimensional reconstruction of the displacement, and additional baselines can self-calibrate using the flare, enhancing synthesis imaging of the quiescent emission. We apply this technique to simulated 1.3 mm wavelength observations of a 'hot spot' embedded in a radiatively inefficient accretion disk around Sgr A*. Our results indicate that, even withmore » current sensitivities, polarimetric interferometry with the Event Horizon Telescope can achieve ∼5 μas relative astrometry of compact flaring structures near Sgr A* on timescales of minutes.« less

Kinetic titration series with biolayer interferometry.

PubMed

Frenzel, Daniel; Willbold, Dieter

2014-01-01

Biolayer interferometry is a method to analyze protein interactions in real-time. In this study, we illustrate the usefulness to quantitatively analyze high affinity protein ligand interactions employing a kinetic titration series for characterizing the interactions between two pairs of interaction patterns, in particular immunoglobulin G and protein G B1 as well as scFv IC16 and amyloid beta (1-42). Kinetic titration series are commonly used in surface plasmon resonance and involve sequential injections of analyte over a desired concentration range on a single ligand coated sensor chip without waiting for complete dissociation between the injections. We show that applying this method to biolayer interferometry is straightforward and i) circumvents problems in data evaluation caused by unavoidable sensor differences, ii) saves resources and iii) increases throughput if screening a multitude of different analyte/ligand combinations.

Nanoscale optical interferometry with incoherent light.

PubMed

Li, Dongfang; Feng, Jing; Pacifici, Domenico

2016-02-16

Optical interferometry has empowered an impressive variety of biosensing and medical imaging techniques. A widely held assumption is that devices based on optical interferometry require coherent light to generate a precise optical signature in response to an analyte. Here we disprove that assumption. By directly embedding light emitters into subwavelength cavities of plasmonic interferometers, we demonstrate coherent generation of surface plasmons even when light with extremely low degrees of spatial and temporal coherence is employed. This surprising finding enables novel sensor designs with cheaper and smaller light sources, and consequently increases accessibility to a variety of analytes, such as biomarkers in physiological fluids, or even airborne nanoparticles. Furthermore, these nanosensors can now be arranged along open detection surfaces, and in dense arrays, accelerating the rate of parallel target screening used in drug discovery, among other high volume and high sensitivity applications.

Development of a force sensor using atom interferometry to constrain theories on dark matter and dark energy

NASA Astrophysics Data System (ADS)

Schlupf, Chandler; Niederriter, Robert; Bohr, Eliot; Khamis, Sami; Park, Youna; Szwed, Erik; Hamilton, Paul

2017-04-01

Atom interferometry has been used in many precision measurements such as Newton's gravitational constant, the fine structure constant, and tests of the equivalence principle. We will perform atom interferometry in an optical lattice to measure the force felt by an atom due to a test mass in search of new forces suggested by dark matter and dark energy theories. We will be developing a new apparatus using laser-cooled ytterbium to continuously measure this force by observing their Bloch oscillations. Interfering atoms in an optical lattice allows continuous measurements in a small volume over a long period of time, enabling our device to be sensitive to time-varying forces while minimizing vibrational noise. We present the details of this experiment and the progress on it thus far.

Dynamical measurement of refractive index distribution using digital holographic interferometry based on total internal reflection.

PubMed

Zhang, Jiwei; Di, Jianglei; Li, Ying; Xi, Teli; Zhao, Jianlin

2015-10-19

We present a method for dynamically measuring the refractive index distribution in a large range based on the combination of digital holographic interferometry and total internal reflection. A series of holograms, carrying the index information of mixed liquids adhered on a total reflection prism surface, are recorded with CCD during the diffusion process. Phase shift differences of the reflected light are reconstructed exploiting the principle of double-exposure holographic interferometry. According to the relationship between the reflection phase shift difference and the liquid index, two dimensional index distributions can be directly figured out, assuming that the index of air near the prism surface is constant. The proposed method can also be applied to measure the index of solid media and monitor the index variation during some chemical reaction processes.

Gravity Probe B: final results of a space experiment to test general relativity.

PubMed

Everitt, C W F; DeBra, D B; Parkinson, B W; Turneaure, J P; Conklin, J W; Heifetz, M I; Keiser, G M; Silbergleit, A S; Holmes, T; Kolodziejczak, J; Al-Meshari, M; Mester, J C; Muhlfelder, B; Solomonik, V G; Stahl, K; Worden, P W; Bencze, W; Buchman, S; Clarke, B; Al-Jadaan, A; Al-Jibreen, H; Li, J; Lipa, J A; Lockhart, J M; Al-Suwaidan, B; Taber, M; Wang, S

2011-06-03

Gravity Probe B, launched 20 April 2004, is a space experiment testing two fundamental predictions of Einstein's theory of general relativity (GR), the geodetic and frame-dragging effects, by means of cryogenic gyroscopes in Earth orbit. Data collection started 28 August 2004 and ended 14 August 2005. Analysis of the data from all four gyroscopes results in a geodetic drift rate of -6601.8±18.3  mas/yr and a frame-dragging drift rate of -37.2±7.2  mas/yr, to be compared with the GR predictions of -6606.1  mas/yr and -39.2  mas/yr, respectively ("mas" is milliarcsecond; 1  mas=4.848×10(-9)  rad).

Hubble Space Telescope Reduced-Gyro Control Law Design, Implementation, and On-Orbit Performance

NASA Technical Reports Server (NTRS)

Clapp, Brian R.; Ramsey, Patrick R.; Wirzburger, John H.; Smith, Daniel C.; VanArsadall, John C.

2008-01-01

Following gyro failures in April 2001 and April 2003, HST Pointing Control System engineers designed reduced-gyro control laws to extend the spacecraft science mission. The Two-Gyro Science (TGS) and One-Gyro Science (OGS) control laws were designed and implemented using magnetometers, star trackers, and Fine Guidance Sensors in succession to control vehicle rate about the missing gyro axes. Both TGS and OGS have demonstrated on-orbit pointing stability of 7 milli-arcseconds or less, which depends upon the guide star magnitude used by the Fine Guidance Sensor. This paper describes the design, implementation, and on-orbit performance of the TGS and OGS control law fine-pointing modes using Fixed Head Star Trackers and Fine Guidance Sensors, after successfully achieving coarse-pointing control using magnetometers.

Amplitude-dependent relationship between the Southern Annular Mode and the El Niño Southern Oscillation in austral summer

NASA Astrophysics Data System (ADS)

Kim, Baek-Min; Choi, Hyesun; Kim, Seong-Joong; Choi, Wookap

2017-02-01

Co-variability between the Southern Annular Mode (SAM) and the El Niño Southern Oscillation (ENSO) during the austral summer is examined, and it is found that there exists an apparent co-variability of a negative (positive) SAM during the mature period of El Niño (La Niña). However, this co-variability is largely controlled by the small number of strong ENSO cases. When strong ENSO cases are excluded, the correlation becomes non-significant. This behavior in the relationship between SAM and ENSO is supported by a series of general circulation model experiments with prescribed sea surface temperature boundary conditions that represent the incremental strengthening of El Niño (La Niña) conditions. The modeled Antarctic sub-polar jet exhibits similar behavior to that identified through observational analysis. Marked changes in both the magnitude and position of the sub-polar jet are largely controlled by particularly strong transient eddy forcing. Planetary wave forcing plays only a minor role in the co-variability, but it can explain in part the asymmetric response of the sub-polar jet between El Niño and La Niña.

Life in the sea of plenty: Seasonal and regional comparison of physiological performance of Euphausia hanseni in the northern Benguela upwelling system

NASA Astrophysics Data System (ADS)

Werner, Thorsten; Buchholz, Cornelia; Buchholz, Friedrich

2015-09-01

Variability in upwelling events may lead to periods of constrained food availability in the northern Benguela upwelling system (NBUS), thereby affecting the physiological state and metabolic activity of euphausiids. Most attention has so far been paid to seasonal effects but little is known about regional variability. Metabolic activity (expressed by respiration and excretion rates) and physiological state (expressed by reproductive effort and moult activity) in Euphausia hanseni were examined at different stations during austral summer (minimum upwelling) and austral winter (maximum upwelling). Overall, regional differences in physiological state, influencing metabolic activity, were greater than seasonal ones, indicating favourable conditions for growth and reproduction year-round. Higher respiration rates were found for females in more advanced stages of sexual development. Moult stage did not affect oxygen consumption rates, however. The physiological state of E. hanseni at the time of capture may serve as a meaningful indicator of the associated hydrographic conditions in the NBUS, to be further used in eco-system analysis on seasonal or long-term time scales. A latitudinal comparison of species highlights the extraordinary physiological plasticity of euphausiids.

DNA barcoding as an aid for species identification in austral black flies (Insecta: Diptera: Simuliidae).

PubMed

Hernández-Triana, Luis M; Montes De Oca, Fernanda; Prosser, Sean W J; Hebert, Paul D N; Gregory, T Ryan; McMurtrie, Shelley

2017-04-01

In this paper, the utility of a partial sequence of the COI gene, the DNA barcoding region, for the identification of species of black flies in the austral region was assessed. Twenty-eight morphospecies were analyzed: eight of the genus Austrosimulium (four species in the subgenus Austrosimulium s. str., three species in the subgenus Novaustrosimulium, and one species unassigned to subgenus), two of the genus Cnesia, eight of Gigantodax, three of Paracnephia, one of Paraustrosimulium, and six of Simulium (subgenera Morops, Nevermannia, and Pternaspatha). The neighbour-joining tree derived from the DNA barcode sequences grouped most specimens according to species or species groups recognized by morphotaxonomic studies. Intraspecific sequence divergences within morphologically distinct species ranged from 0% to 1.8%, while higher divergences (2%-4.2%) in certain species suggested the presence of cryptic diversity. The existence of well-defined groups within S. simile revealed the likely inclusion of cryptic diversity. DNA barcodes also showed that specimens identified as C. dissimilis, C. nr. pussilla, and C. ornata might be conspecific, suggesting possible synonymy. DNA barcoding combined with a sound morphotaxonomic framework would provide an effective approach for the identification of black flies in the region.

Variation in the biomass density and demography of Antarctic krill in the vicinity of the South Shetland Islands during the 1999/2000 austral summer

NASA Astrophysics Data System (ADS)

Hewitt, R. P.; Kim, S.; Naganobu, M.; Gutierrez, M.; Kang, D.; Takao, Y.; Quinones, J.; Lee, Y.-H.; Shin, H.-C.; Kawaguchi, S.; Emery, J. H.; Demer, D. A.; Loeb, V. J.

2004-06-01

Vessels from Japan, Peru, and the USA conducted four sequential surveys designed to estimate the biomass density and demography of Antarctic krill in the vicinity of the South Shetland Islands between late December 1999 and early March 2000. The surveys were conducted during the same austral summer as the CCAMLR 2000 Survey in the Scotia Sea (Watkins et al., Deep-Sea Research, II, this issue [doi: 10.1016/j.dsr2.2004.06.010]), and the data were analyzed in a similar manner. Biomass densities were not significantly different between the surveys and averaged 49 g m -2. Maps of krill biomass indicate three areas of consistently high density: one near the eastern end of Elephant Island, one mid-way between Elephant Island and King George Island, and one near Cape Shirreff on the north side of Livingston Island. The areas of highest krill density appeared to move closer to the shelf break as the season progressed. This apparent movement was accompanied by a change in the demographic structure of the population, with smaller krill absent and a larger proportion of sexually mature animals present in late summer.

Internal habitat quality determines the effects of fragmentation on austral forest climbing and epiphytic angiosperms.

PubMed

Magrach, Ainhoa; Larrinaga, Asier R; Santamaría, Luis

2012-01-01

Habitat fragmentation has become one of the major threats to biodiversity worldwide, particularly in the case of forests, which have suffered enormous losses during the past decades. We analyzed how changes in patch configuration and habitat quality derived from the fragmentation of austral temperate rainforests affect the distribution of six species of forest-dwelling climbing and epiphytic angiosperms. Epiphyte and vine abundance is primarily affected by the internal characteristics of patches (such as tree size, the presence of logging gaps or the proximity to patch edges) rather than patch and landscape features (such as patch size, shape or connectivity). These responses were intimately related to species-specific characteristics such as drought- or shade-tolerance. Our study therefore suggests that plant responses to fragmentation are contingent on both the species' ecology and the specific pathways through which the study area is being fragmented, (i.e. extensive logging that shaped the boundaries of current forest patches plus recent, unregulated logging that creates gaps within patches). Management practices in fragmented landscapes should therefore consider habitat quality within patches together with other spatial attributes at landscape or patch scales.

Conflict amongst chloroplast DNA sequences obscures the phylogeny of a group of Asplenium ferns.

PubMed

Shepherd, Lara D; Holland, Barbara R; Perrie, Leon R

2008-07-01

A previous study of the relationships amongst three subgroups of the Austral Asplenium ferns found conflicting signal between the two chloroplast loci investigated. Because organelle genomes like those of chloroplasts and mitochondria are thought to be non-recombining, with a single evolutionary history, we sequenced four additional chloroplast loci with the expectation that this would resolve these relationships. Instead, the conflict was only magnified. Although tree-building analyses favoured one of the three possible trees, one of the alternative trees actually had one more supporting site (six versus five) and received greater support in spectral and neighbor-net analyses. Simulations suggested that chance alone was unlikely to produce strong support for two of the possible trees and none for the third. Likelihood permutation tests indicated that the concatenated chloroplast sequence data appeared to have experienced recombination. However, recombination between the chloroplast genomes of different species would be highly atypical, and corollary supporting observations, like chloroplast heteroplasmy, are lacking. Wider taxon sampling clarified the composition of the Austral group, but the conflicting signal meant analyses (e.g., morphological evolution, biogeographic) conditional on a well-supported phylogeny could not be performed.

A Mini-Surge on theRyder Glacier, Greenland Observed via Satelite Radar Interferometry

NASA Technical Reports Server (NTRS)

Joughin, I.; Tulaczyk, S.; Fahnestock, M.; Kwok, R.

1996-01-01

A dramatic short term speed up of the Ryder glacier has been detected using satellite radar interferometry. The accelerated flow represents a substantial, though short-lived, change in the ice discharge from this basin. We believe that meltwater was involved in this event, either as an active participant, as meltwater-filled lakes on the surface of the glacier drained during the period of rapid motion.

Optical measurement methods in thermogasdynamics

NASA Technical Reports Server (NTRS)

Stursberg, K.; Erhardt, K.; Krahr, W.; Becker, M.

1978-01-01

A review is presented of a number of optical methods of flow measurements. Consideration is given to such spectroscopic methods as emission and absorption techniques, electron beam-stimulated fluorescence, and light scattering - Rayleigh, Raman and Mie - methods. The following visualization methods are also discussed: shadow photography, schlieren photography, interferometry, holographic interferometry, laser anemometry, particle holography, and electron-excitation imaging. A large bibliography is presented and the work is copiously illustrated with figures and photographs.

Interferometry

NASA Technical Reports Server (NTRS)

Ridgway, Stephen; Wilson, Robert W.; Begelman, Mitchell C.; Bender, Peter; Burke, Bernard F.; Cornwell, Tim; Drever, Ronald; Dyck, H. Melvin; Johnston, Kenneth J.; Kibblewhite, Edward

1991-01-01

The following recommended programs are reviewed: (1) infrared and optical interferometry (a ground-based and space programs); (2) compensation for the atmosphere with adaptive optics (a program for development and implementation of adaptive optics); and (3) gravitational waves (high frequency gravitational wave sources (LIGO), low frequency gravitational wave sources (LAGOS), a gravitational wave observatory program, laser gravitational wave observatory in space, and technology development during the 1990's). Prospects for international collaboration and related issues are also discussed.

Algorithms and Array Design Criteria for Robust Imaging in Interferometry

DTIC Science & Technology

2016-04-01

Chapter 1 Fundamentals of Optical Interferometry 1.1 Chapter Overview In this chapter, we introduce the physics -based principles of optical...particular physical structure (i.e. the existence of a certain type of loop in the interferometric graph), and provide a simple algorithm for... physical condition on aperture placement is more intuitive when considering the raw phase measurements as opposed to their closures. For this reason

Normal and Differential SAR Interferometry

DTIC Science & Technology

2005-02-01

incorporating the use of a rough DEM. [ Adragna 1995]. The same technique is also used for flat Earth removal, and for differential interferometry (Cap.5...and F. Adragna , 1994. Radar Interferometric Mapping of Deformation in the Year After the Landers Earthquake, Nature, Vol. 369, pp. 227-230 Massonnet...D., M. Rossi, C. Carmona, F. Adragna , G. Peltzer, K. Feigi, and T. Rabaute, 1993. The Displacement Field of the Landers Earthquake Mapped by Radar

Very long baseline interferometry using a communication satellite

NASA Technical Reports Server (NTRS)

Swenson, G. W., Jr.

1975-01-01

A planned experiment is discussed in long-baseline interferometry, using the Communications Technology Satellite to transmit the base-band signal from one telescope to another for real-time correlation. A 20 megabit data rate is planned, calling for a delay-line of 10 MHz bandwidth and controllable delay up to 275 milliseconds. A number of sources will be studied on baselines from Ontario to West Virginia and California.

Applications of Polarimetric and Interferometric SAR to Environmental Remote Sensing and its Activities: Recent Advances in Extrawideband Polarimetry, Interferometry and Polarimetric Interferometry in Synthetic Aperture Remote Sensing and its Applications

DTIC Science & Technology

2007-02-01

January 2003. [69] EUSAR 2000 Proceedings, VDE Verlag, Offenbach, ISBN: 3-8007-2544-4, Munich, Germany, May 2000. [70] EUSAR 2002 Proceedings... VDE Verlag, Offenbach, ISBN: 3-8007-2697-1, Cologne, Germany, June 2002. [71] Ferro-Famil, L. and E. Pottier, 2000, "Description of Dual Frequency

Digital Holographic Interferometry and Speckle Correlation

NASA Astrophysics Data System (ADS)

Yamaguchi, Ichirou

2010-04-01

Relations and combinations between holographic interferometry and speckle correlation in contouring by phase-shifting digital holography are discussed. Three-dimensional distributions of correlations of the complex amplitudes and intensities before and after the laser wavelength shift are calculated in numerical simulations where a rough surface is modeled with random numbers. Fringe localization related to speckle displacement as well as speckle suppression in phase analysis are demonstrated for general surface shape and recording conditions.

Holographic interferometry of transparent media using light scattered by embedded test objects

NASA Technical Reports Server (NTRS)

Prikryl, I.; Vest, C. M.

1982-01-01

Fringe formation and localization in holographic interferometry of transparent media are discussed for configurations in which light enters the medium and is scattered back through it by an embedded diffuse object. Fringe order numbers are doubled, and the fringe localization region is translated and compressed by a factor of two. The results are applicable to tomographic reconstruction of aerodynamic density fields around opaque test objects.

Numerical simulation of time delay Interferometry for LISA with one arm dysfunctional

NASA Astrophysics Data System (ADS)

Ni, Wei-Tou; Dhurandhar, Sanjeev V.; Nayak, K. Rajesh; Wang, Gang

In order to attain the requisite sensitivity for LISA, laser frequency noise must be suppressed below the secondary noises such as the optical path noise, acceleration noise etc. In a previous paper(a), we have found an infinite family of second generation analytic solutions of time delay interferometry and estimated the laser noise due to residual time delay semi-analytically from orbit perturbations due to earth. Since other planets and solar-system bodies also perturb the orbits of LISA spacecraft and affect the time delay interferometry, we simulate the time delay numerically in this paper. To conform to the actual LISA planning, we have worked out a set of 10-year optimized mission orbits of LISA spacecraft using CGC3 ephemeris framework(b). Here we use this numerical solution to calculate the residual errors in the second generation solutions upto n 3 of our previous paper, and compare with the semi-analytic error estimate. The accuracy of this calculation is better than 1 m (or 30 ns). (a) S. V. Dhurandhar, K. Rajesh Nayak and J.-Y. Vinet, time delay Interferometry for LISA with one arm dysfunctional (b) W.-T. Ni and G. Wang, Orbit optimization for 10-year LISA mission orbit starting at 21 June, 2021 using CGC3 ephemeris framework

Terahertz reflection interferometry for automobile paint layer thickness measurement

NASA Astrophysics Data System (ADS)

Rahman, Aunik; Tator, Kenneth; Rahman, Anis

2015-05-01

Non-destructive terahertz reflection interferometry offers many advantages for sub-surface inspection such as interrogation of hidden defects and measurement of layers' thicknesses. Here, we describe a terahertz reflection interferometry (TRI) technique for non-contact measurement of paint panels where the paint is comprised of different layers of primer, basecoat, topcoat and clearcoat. Terahertz interferograms were generated by reflection from different layers of paints on a metallic substrate. These interferograms' peak spacing arising from the delay-time response of respective layers, allow one to model the thicknesses of the constituent layers. Interferograms generated at different incident angles show that the interferograms are more pronounced at certain angles than others. This "optimum" angle is also a function of different paint and substrate combinations. An automated angular scanning algorithm helps visualizing the evolution of the interferograms as a function of incident angle and also enables the identification of optimum reflection angle for a given paint-substrate combination. Additionally, scanning at different points on a substrate reveals that there are observable variations from one point to another of the same sample over its entire surface area. This ability may be used as a quality control tool for in-situ inspection in a production line. Keywords: Terahertz reflective interferometry, Paint and coating layers, Non-destructive

Dynamic Deformation of ETNA Volcano Observed by GPS and SAR Interferometry

NASA Technical Reports Server (NTRS)

Lundgren, P.; Rosen, P.; Webb, F.; Tesauro, M.; Lanari, R.; Sansosi, E.; Puglisi, G.; Bonforte, A.; Coltelli, M.

1999-01-01

Synthetic aperture radar (SAR) interferometry and GPS have shown that during the quiescent period from 1993-1995 Mt. Etna volcano, Italy, inflated. Since the initiation of eruptive activity since late 1995 the deformation has been more contentious. We will explore the detailed deformation during the period from 1995-1996 spanning the late stages of inflation and the beginning of eruptive activity. We use SAR interferometry and GPS data to measure the volcano deformation. We invert the observed deformation for both simple point source. le crack elastic sources or if warranted for a spheroidal pressure So In particular, we will examine the evolution of the inflation and the transition to a lesser deflation observed at the end of 1995. We use ERS-1/2 SAR data from both ascending and descending passes to allow for dense temporal 'sampling of the deformation and to allow us to critically assess atmospheric noise. Preliminary results from interferometry suggest that the inflation rate accelerated prior to resumption of activity in 1995, while GPS data suggest a more steady inflation with some fluctuation following the start of activity. This study will compare and contrast the interferometric SAR and GPS results and will address the strengths and weaknesses of each technique towards volcano deformation studies.

Development of a Hybrid Atomic Force Microscopic Measurement System Combined with White Light Scanning Interferometry

PubMed Central

Guo, Tong; Wang, Siming; Dorantes-Gonzalez, Dante J.; Chen, Jinping; Fu, Xing; Hu, Xiaotang

2012-01-01

A hybrid atomic force microscopic (AFM) measurement system combined with white light scanning interferometry for micro/nanometer dimensional measurement is developed. The system is based on a high precision large-range positioning platform with nanometer accuracy on which a white light scanning interferometric module and an AFM head are built. A compact AFM head is developed using a self-sensing tuning fork probe. The head need no external optical sensors to detect the deflection of the cantilever, which saves room on the head, and it can be directly fixed under an optical microscopic interferometric system. To enhance the system’s dynamic response, the frequency modulation (FM) mode is adopted for the AFM head. The measuring data can be traceable through three laser interferometers in the system. The lateral scanning range can reach 25 mm × 25 mm by using a large-range positioning platform. A hybrid method combining AFM and white light scanning interferometry is proposed to improve the AFM measurement efficiency. In this method, the sample is measured firstly by white light scanning interferometry to get an overall coarse morphology, and then, further measured with higher resolution by AFM. Several measuring experiments on standard samples demonstrate the system’s good measurement performance and feasibility of the hybrid measurement method. PMID:22368463

Assessing tear film on soft contact lenses with lateral shearing interferometry.

PubMed

Szczesna, Dorota H

2011-11-01

Evaluating precorneal tear film is one of important clinical measurements for assessing health of anterior eye. Contact lens wear is known to influence the quality of tear film. The aim was to evaluate the applicability of lateral shearing interferometry technique in the noninvasive assessment of the effects of contact lens replacement modality and its water content on tear film stability. Sixteen regular soft contact lens wearers took place in the study. Lateral shearing interferometry measurements, in suppressed blinking conditions, were taken in the mornings and afternoons, after a minimum of 5 hours of lens wear for the daily lenses, and after 2 weeks and 1 month for the fortnightly and monthly lens replacement modalities, respectively. Significant differences (paired bootstrap-based Behrens-Fisher test, P < 0.05) in the tear film surface quality were found between all considered pairs of replacement modalities except for the daily and fortnightly lenses measured in the afternoon of the first day of wear. Significant worsening (paired bootstrap-based Behrens-Fisher test, P < 0.001) of tear film quality was found for the low water content materials. Lateral shearing interferometry is a powerful method for the noninvasive assessment of tear film surface quality on soft contact lenses that may find, in future, its use in the clinical assessment of anterior eye's health.

Interferometric Dynamic Measurement: Techniques Based on High-Speed Imaging or a Single Photodetector

PubMed Central

Fu, Yu; Pedrini, Giancarlo

2014-01-01

In recent years, optical interferometry-based techniques have been widely used to perform noncontact measurement of dynamic deformation in different industrial areas. In these applications, various physical quantities need to be measured in any instant and the Nyquist sampling theorem has to be satisfied along the time axis on each measurement point. Two types of techniques were developed for such measurements: one is based on high-speed cameras and the other uses a single photodetector. The limitation of the measurement range along the time axis in camera-based technology is mainly due to the low capturing rate, while the photodetector-based technology can only do the measurement on a single point. In this paper, several aspects of these two technologies are discussed. For the camera-based interferometry, the discussion includes the introduction of the carrier, the processing of the recorded images, the phase extraction algorithms in various domains, and how to increase the temporal measurement range by using multiwavelength techniques. For the detector-based interferometry, the discussion mainly focuses on the single-point and multipoint laser Doppler vibrometers and their applications for measurement under extreme conditions. The results show the effort done by researchers for the improvement of the measurement capabilities using interferometry-based techniques to cover the requirements needed for the industrial applications. PMID:24963503

Development of a hybrid atomic force microscopic measurement system combined with white light scanning interferometry.

PubMed

Guo, Tong; Wang, Siming; Dorantes-Gonzalez, Dante J; Chen, Jinping; Fu, Xing; Hu, Xiaotang

2012-01-01

A hybrid atomic force microscopic (AFM) measurement system combined with white light scanning interferometry for micro/nanometer dimensional measurement is developed. The system is based on a high precision large-range positioning platform with nanometer accuracy on which a white light scanning interferometric module and an AFM head are built. A compact AFM head is developed using a self-sensing tuning fork probe. The head need no external optical sensors to detect the deflection of the cantilever, which saves room on the head, and it can be directly fixed under an optical microscopic interferometric system. To enhance the system's dynamic response, the frequency modulation (FM) mode is adopted for the AFM head. The measuring data can be traceable through three laser interferometers in the system. The lateral scanning range can reach 25 mm × 25 mm by using a large-range positioning platform. A hybrid method combining AFM and white light scanning interferometry is proposed to improve the AFM measurement efficiency. In this method, the sample is measured firstly by white light scanning interferometry to get an overall coarse morphology, and then, further measured with higher resolution by AFM. Several measuring experiments on standard samples demonstrate the system's good measurement performance and feasibility of the hybrid measurement method.

Selected aspects of wide-field stellar interferometry

NASA Astrophysics Data System (ADS)

D'Arcio, Luigi Arsenio

1999-11-01

In Michelson stellar interferometry, the high-resolution information about the source structure is detected by performing observations with widely separated telescopes, interconnected to form an interferometer. At optical wavelengths, this method provides a technically viable approach for achieving angular resolutions in the milliarcsecond range, comparable to those of a 100 m diameter telescope, whose realization is beyond the immediate engineering capabilities. Considerable efforts are currently devoted to the definition of dedicated interferometric instruments, which will allow to address ambitious astronomical tasks such as high-resolution imaging, astrometry at microarcsecond level, and the direct detection of exoplanets. Astrometry and related techniques employ the so-called wide field-of-view interferometric mode, where phase measurements are performed simultaneously at two (or more) sources; often, the actual observable is the instantaneous phase difference of the two object signals. The future success of wide-field interferometry critically depends on the development of techniques for the accurate control of field-dependent (anisoplanatic) phase errors. In this thesis, we address two aspects of this problem in detail. The first one is theoretical in nature. For ground-based measurements, atmospheric turbulence is the largest source of random phase fluctuations between the on- and the off-axis fringes. We developed a model of the temporal power spectrum of this disturbance, whose validity is not limited to low frequencies only, as it is the case with earlier models. This extension opens the possibility of the analysis of dynamic issues, such as the determination of the allowable coherent integration time T for the off-axis fringes. The spectrum turns out to be well approximated by a sequences of four power-law branches. In first instance, its overall form is determined by the values of the baseline length, telescope diameter, and average beam separation in the atmosphere. Due to the rapid decorrelation of the on- and off-axis phases for increasing star separation theta, the useful field for wide-field interferometry is limited to about |theta|<1', the so-called very narrow angle regime. For high-accuracy applications, this range decreases to a few arcseconds. We estimated that for the VLTI along baselines operating at lambda=2.2 mu, a turbulence-related error of less than lambda/10 rms is only available for field angles smaller than 7.3'' and 5.8'', for UT-UT and AT-AT pairs respectively. The bulk of the spectral power is confined at relatively low frequencies, typically below 1 Hz. Both smaller star separations and larger telescope sizes contribute in lowering the spectral content at hight frequencies. We found that in general, as compared to blind observations, wide-field measurements can make use of significantly longer off-axis integration times T, even at rather big star separations. For the long UT-UT baseline operating at lambda=2.2 mu, we have calculated a 5 % fringe visibility loss is reached for T=740 ms, 2.1 s and 12.7 s for star separations of 30'', 10'', and 5'', respectively. These figures are about 2, 5 and 32 times higher than for a blind observation. Finally, we point out that for large telescopes a significant fraction of the total phase error due to anisoplanatic turbulence is contributed by wavefront modes higher than piston. Therefore, we generalized the formalism used in out study to the analysis of (Zernike) wavefront modes of arbitrary order. This thesis also addresses an instrumental aspect of the problem of the control of anisoplanatic phase errors. A Michelson interferometric imager is suitable for wide-field operation only if the configuration of the pupil images forms a scaled replica of the total array aperture. This implies the factual coincidence of the magnification factors M and pupil rotations phi of all interferometric arms: for the VLTI, the matching accuracy requirements are as severe as dM< 1.9e-3, dphi < 3.8''. We addressed the problem of measuring dM, dphi, to the accuracies expressed here above. In the selected approach, this is done by measuring the difference of the star separation vectors for the two interferometer arms, as measured at the corresponding pupil images. Variations of M and phi affect this quantity in orthogonal directions, which allows the simultaneous determination of both unknowns. The measurement makes use of two two-axis tilt sensors, that determine the angular separation vectors of the on- and off-axis beams, respectively, from the two interferometric arms. A 0.0075'' single-axis accuracy is required, together with a sufficiently high sensitivity for astronomical applications. This led to the choice of implementing the sensors as pupil plane devices, using the same interferometric tilt-detection principle as applied in Fine Guidance Sensors of the Hubble Space Telescope. The main challenge was to ensure equal responses for the two sensors, to within 0.0075''. Test measurements have shown that we succeeded in controlling mismatches between the sensors (including their mutual orientations, electronic gain and phase, linearity and signal normalization) a the 0.004'' level, and in performing beam recombination without introducing errors exceeding 0.006''. Pupil rotation alignment runs confirmed a 2'' overall measurement uncertainty for dphi, about half the 3.8'' calibration requirement. Finally, in this thesis we also developed a near-filed propagation method, intended for the diffraction-based analysis of optical systems with extremely high accuracy requirements (typically 1 deg in phase and 1.e-3 in field amplitude). Examples thereof are the nulling optics for planet detection and, outside the field of stellar interferometry, systems for the determination of the shape of mirrors for extreme-UV lithographic projection systems. The method is based on the local Fresnel approximation of the propagation integral, that we have solved analytically for rectangular domains and for triangular ones with an arched hypotenuse. This allows for an accurate computation of the field diffracted at the edges of complicated aperture shapes, without having to recur to time-consuming numerical quadrature techniques. The method has shown the ability to provide complex amplitude estimates that are consistently accurate to the specifications given above, and this in reasonable times. In a series of comparative tests, our method outperformed the Hopkins algorithm by typically a factor of fifty with respect to the computational speed.

The Spatially Resolved H(alpha)-Emitting Wind Structure of P Cygni

DTIC Science & Technology

2010-06-01

using radio and optical interferometry, as well as direct imaging with adaptive optics (AO). Radio interferometric observations detect the nebula around...to structures in the nebula of P Cyg that are more than an order of magnitude smaller. Therefore, optical interferometry provides a unique window of...resolved the outer Hα-emitting region of the extended envelope, but detected signatures of clumping. Although, the angular scales sampled with a 1.52 m

Grazing Incidence Optics for X-rays Interferometry

NASA Technical Reports Server (NTRS)

Shipley, Ann; Zissa, David; Cash, Webster; Joy, Marshall

1999-01-01

Grazing incidence mirror parameters and constraints for x-ray interferometry are described. We present interferometer system tolerances and ray trace results used to define mirror surface accuracy requirements. Mirror material, surface figure, roughness, and geometry are evaluated based on analysis results. We also discuss mirror mount design constraints, finite element analysis, environmental issues, and solutions. Challenges associated with quantifying high accuracy mirror surface quality are addressed and test results are compared with theoretical predictions.

Interferometry theory for the block 2 processor

NASA Technical Reports Server (NTRS)

Thomas, J. B.

1987-01-01

Presented is the interferometry theory for the Block 2 processor, including a high-level functional description and a discussion of data structure. The analysis covers the major processing steps: cross-correlation, fringe counter-rotation, transformation to the frequency domain, phase calibration, bandwidth synthesis, and extraction of the observables of amplitude, phase, phase rate, and delay. Also included are analyses for fractional bitshift correction, station clock error, ionosphere correction, and effective frequencies for the observables.

Mapping Ocean Surface Topography with a Synthetic-Aperture Interferometry Radar

NASA Technical Reports Server (NTRS)

Fu, Lee-Lueng; Rodriguez, Ernesto

2006-01-01

We propose to apply the technique of synthetic aperture radar interferometry to the measurement of ocean surface topography at spatial resolution approaching 1 km. The measurement will have wide ranging applications in oceanography, hydrology. and marine geophysics. The oceanographic and related societal applications are briefly discussed in the paper. To meet the requirements for oceanographic applications, the instrument must be flown in an orbit with proper sampling of ocean tides.

Proposed satellite laser ranging and very long baseline interferometry sites for crustal dynamics investigations

NASA Technical Reports Server (NTRS)

Lowman, P. D.; Allenby, R. J.; Frey, H. V.

1979-01-01

Recommendations are presented for a global network of 125 sites for geodetic measurements by satellite laser ranging and very long baseline interferometry. The sites were proposed on the basis of existing facilities and scientific value for investigation of crustal dynamics as related to earthquake hazards. Tectonic problems are discussed for North America peripheral regions and for the world. The sites are presented in tables and maps, with bibliographic references.