Constraints on the outer radius of the broad emission line region of active galactic nuclei

NASA Astrophysics Data System (ADS)

Landt, Hermine; Ward, Martin J.; Elvis, Martin; Karovska, Margarita

2014-03-01

Here we present observational evidence that the broad emission line region (BELR) of active galactic nuclei (AGN) generally has an outer boundary. This was already clear for sources with an obvious transition between the broad and narrow components of their emission lines. We show that the narrow component of the higher-order Paschen lines is absent in all sources, revealing a broad emission line profile with a broad, flat top. This indicates that the BELR is kinematically separate from the narrow emission line region. We use the virial theorem to estimate the BELR outer radius from the flat top width of the unblended profiles of the strongest Paschen lines, Paα and Paβ, and find that it scales with the ionizing continuum luminosity roughly as expected from photoionization theory. The value of the incident continuum photon flux resulting from this relationship corresponds to that required for dust sublimation. A flat-topped broad emission line profile is produced by both a spherical gas distribution in orbital motion and an accretion disc wind if the ratio between the BELR outer and inner radius is assumed to be less than ˜100-200. On the other hand, a pure Keplerian disc can be largely excluded, since for most orientations and radial extents of the disc the emission line profile is double-horned.

Deformation of the Tonga Slab: Evidence for Interaction with a Small-scale Secondary Plume in the Transition Zone

NASA Astrophysics Data System (ADS)

Billen, M. I.; Bikoba, J. Z.; Tarlow, S.

2015-12-01

Magali I. Billen and John Z. BikobaThe Tonga Slab is the most seismically active subduction zone providing a uniquely detailed picture of the internal deformation of the slab, with apparent warping and folding, from the surface through the transition zone. Here, we investigate the dynamical origin of a irregular feature in the seismicity within the transition zone located at 21-28oS, using 3D visualization and analysis of the seismicity and compression/tension (P/T) axis from the moment tensor solutions to characterize the geometry of, and the orientation of forces acting on, the slab. This irregular feature can be described as narrow region of upward deflection of the slab, with a gap in seismicity beyond (down-dip of) the deflected region, and flanked by two narrow V-shaped gaps in seismicity suggestive of tearing of the slab. The P/T axis show a dominate down-dip orientation of the P axis above the deflection point, which rotate to a nearly vertical orientation within the central region of the deflected slab. The adjacent attached regions (down-dip of the two flanking slab gaps) also have rotated and more heterogeneous P/T axis orientations. In contrast, the adjacent section of the slab to the north of 21oS has continuous seismicity throughout the transition zone, with a roughly uniform planar shape, and generally down-dip orientation of the P axis. We explore three possible hypothesis for the observed deformation including: 1) deflection due to a buoyant metastable olivine wedge, 2) a buckling feature in the slab as previously proposed by Myhill (GJI., 2013), and interaction with a small-scale, secondary plume upwelling below the slab. If the newly-observed gaps in seismicity indicate physical gaps or significant thinning of the slab, then these observations are not consistent with the buckling hypothesis. The lack of significant along-strike variation in slab age or subduction rate also suggests that a localized region of metastable olivine is unlikely. Therefore, we test the third hypothesis using a simple 3D geodynamical model of a planar dipping slab overlying a localized buoyant upwelling (radius < 150 km). We present comparisons of the observations to the model predictions for the subsequent deformation of the slab and orientations of principal stress axis within the slab.

Metal-insulator transition and superconductivity induced by Rh doping in the binary pnictides RuPn (Pn=P, As, Sb)

NASA Astrophysics Data System (ADS)

Hirai, Daigorou; Takayama, Tomohiro; Hashizume, Daisuke; Takagi, Hidenori

2012-04-01

Binary ruthenium pnictides, RuP and RuAs, with an orthorhombic MnP structure, were found to show a metal to a nonmagnetic insulator transition at TMI = 270 and 200 K, respectively. In the metallic region above TMI, a structural phase transition, accompanied with a weak anomaly in the resistivity and the magnetic susceptibility, indicative of a pseudogap formation, was identified at Ts = 330 and 280 K, respectively. These two transitions were suppressed by substituting Ru with Rh. We found superconductivity with a maximum Tc = 3.7 and 1.8 K in a narrow composition range around the critical point for the pseudogap phase, Rh content xc = 0.45 and 0.25 for Ru1-xRhxP and Ru1-xRhxAs, respectively, which may provide us with a nonmagnetic route to superconductivity at a quantum critical point.

Homogeneous spectral spanning of terahertz semiconductor lasers with radio frequency modulation.

PubMed

Wan, W J; Li, H; Zhou, T; Cao, J C

2017-03-08

Homogeneous broadband and electrically pumped semiconductor radiation sources emitting in the terahertz regime are highly desirable for various applications, including spectroscopy, chemical sensing, and gas identification. In the frequency range between 1 and 5 THz, unipolar quantum cascade lasers employing electron inter-subband transitions in multiple-quantum-well structures are the most powerful semiconductor light sources. However, these devices are normally characterized by either a narrow emission spectrum due to the narrow gain bandwidth of the inter-subband optical transitions or an inhomogeneous broad terahertz spectrum from lasers with heterogeneous stacks of active regions. Here, we report the demonstration of homogeneous spectral spanning of long-cavity terahertz semiconductor quantum cascade lasers based on a bound-to-continuum and resonant phonon design under radio frequency modulation. At a single drive current, the terahertz spectrum under radio frequency modulation continuously spans 330 GHz (~8% of the central frequency), which is the record for single plasmon waveguide terahertz lasers with a bound-to-continuum design. The homogeneous broadband terahertz sources can be used for spectroscopic applications, i.e., GaAs etalon transmission measurement and ammonia gas identification.

Homogeneous spectral spanning of terahertz semiconductor lasers with radio frequency modulation

PubMed Central

Wan, W. J.; Li, H.; Zhou, T.; Cao, J. C.

2017-01-01

Homogeneous broadband and electrically pumped semiconductor radiation sources emitting in the terahertz regime are highly desirable for various applications, including spectroscopy, chemical sensing, and gas identification. In the frequency range between 1 and 5 THz, unipolar quantum cascade lasers employing electron inter-subband transitions in multiple-quantum-well structures are the most powerful semiconductor light sources. However, these devices are normally characterized by either a narrow emission spectrum due to the narrow gain bandwidth of the inter-subband optical transitions or an inhomogeneous broad terahertz spectrum from lasers with heterogeneous stacks of active regions. Here, we report the demonstration of homogeneous spectral spanning of long-cavity terahertz semiconductor quantum cascade lasers based on a bound-to-continuum and resonant phonon design under radio frequency modulation. At a single drive current, the terahertz spectrum under radio frequency modulation continuously spans 330 GHz (~8% of the central frequency), which is the record for single plasmon waveguide terahertz lasers with a bound-to-continuum design. The homogeneous broadband terahertz sources can be used for spectroscopic applications, i.e., GaAs etalon transmission measurement and ammonia gas identification. PMID:28272492

Solar CIV Vacuum-Ultraviolet Fabry-Perot Interferometers

NASA Technical Reports Server (NTRS)

Gary, G. Allen; West, Edward A.; Rees, David; McKay, Jack A.; Zukic, Maumer; Herman, Peter

2006-01-01

Aims: A tunable, high spectral resolution, high effective finesse, vacuum ultraviolet (VUV) Fabry-Perot interferometer (PPI) is designed for obtaining narrow-passband images, magnetograms, and Dopplergrams of the transition region emission line of CIV (155 nm). Methods: The integral part of the CIV narrow passband filter package (with a 2-10 pm FWHM) consists of a multiple etalon system composed of a tunable interferometer that provides high-spectral resolution and a static low-spectral resolution interferometer that allows a large effective free spectral range. The prefilter for the interferometers is provided by a set of four mirrors with dielectric high-reflective coatings. A tunable interferometer, a VUV piezoelectric-control etalon, has undergone testing using the surrogate F2 eximer laser line at 157 nm for the CIV line. We present the results of the tests with a description of the overall concept for a complete narrow-band CIV spectral filter. The static interferometer of the filter is envisioned as being hudt using a set of fixed MgF2 plates. The four-mirror prefilter is designed to have dielectric multilayer n-stacks employing the design concept used in the Ultraviolet Imager of NASA's Polar Spacecraft. A dual etalon system allows the effective free spectral range to be commensurate with the prefilter profile. With an additional etalon, a triple etalon system would allow a spectrographic resolution of 2 pm. The basic strategy has been to combine the expertise of spaceflight etalon manufacturing with VUV coating technology to build a VUV FPI which combines the best attributes of imagers and spectrographs into a single compact instrument. Results. Spectro-polarimetry observations of the transition region CIV emission can be performed to increase the understanding of the magnetic forces, mass motion, evolution, and energy release within the solar atmosphere at the base of the corona where most of the magnetic field is approximately force-free. The 2D imaging of the full vector magnetic field at the height of maximum magnetic influence (minimum plasma beta) can be accomplished, albeit difficult, by measuring the Zeeman splitting of the CIV resonance pair. Designs of multiple VUV FPIs can be developed for integration into future orbiting solar observatories to obtain rapid cadence, spectral imaging of the transition region.

17 CFR 41.14 - Transition period for indexes that cease being narrow-based security indexes.

Code of Federal Regulations, 2014 CFR

2014-04-01

... day tolerance provision. An index that is a narrow-based security index that becomes a broad-based... than forty-five days. An index that is a narrow-based security index that becomes a broad-based...

Plasma Reflection in Multigrain Layers of Narrow-Bandgap Semiconductors

NASA Astrophysics Data System (ADS)

Zhukov, N. D.; Shishkin, M. I.; Rokakh, A. G.

2018-04-01

Qualitatively similar spectral characteristics of plasma-resonance reflection in the region of 15-25 μm were obtained for layers of electrodeposited submicron particles of InSb, InAs, and GaAs and plates of these semiconductors ground with M1-grade diamond powder. The most narrow-bandgap semiconductor InSb (intrinsic absorption edge ˜7 μm) is characterized by an absorption band at 2.1-2.3 μm, which is interpreted in terms of the model of optical excitation of electrons coupled by the Coulomb interaction. The spectra of a multigrain layer of chemically deposited PbS nanoparticles (50-70 nm) exhibited absorption maxima at 7, 10, and 17 μm, which can be explained by electron transitions obeying the energy-quantization rules for quantum dots.

First Results of Exoplanet Observations with the Gran Telescopio Canarias: Narrow-Band Transit Photometry Capable of Detecting Super-Earth-size Planets

NASA Astrophysics Data System (ADS)

Ford, Eric B.; Colon, K. D.; Blake, C.; Lee, B.; Mahadevan, S.

2010-01-01

We present the first exoplanet observations from the Gran Telescopio Canarias (GTC) using the OSIRIS tunable filter imager. Our narrow-band transit follow-up observations set a new record for ground-based, narrow-band photometric precision of an exoplanet transit. The demonstrated precision would allow the detection of a transiting super-Earth-sized planet at near-infrared wavelengths. Such high-precision follow-up observations could significantly improve measurements of the size and orbit of transiting super-Earth and Earth-like planets to be discovered by the CoRoT and Kepler space missions (Colon & Ford 2009). OSIRIS is one of two first light instruments for the GTC and features a tunable filter imaging mode. We observed the planet's host star along with several nearby reference stars during each transit, rapidly alternating observations between multiple narrow band-passes. The GTC's large aperture results in small photon noise and minimal scintillation noise, so care must be taken to minimize other potential systematic noise sources. The use of a narrow bandpass (2nm) reduces the effects of differential extinction, and we chose bandpasses that minimize atmospheric absorption and variability. We measure the flux of the target star relative to an ensemble of reference stars, using an aperture photometry algorithm adapted to allow for: 1) the center of the band-pass varying across the field and resulting in sky rings, and 2) a significant defocus to reduce flat fielding uncertainties and increase observing efficiency. We present results from the first tunable filter observations of an exoplanet transit and outline the exciting prospects for future GTC/OSIRIS observations to study super-Earth planets and the atmospheres of giant planets via occultation photometry. Based on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, in the island of La Palma.

Is Perceptual Narrowing Too Narrow?

ERIC Educational Resources Information Center

Cashon, Cara H.; Denicola, Christopher A.

2011-01-01

There is a growing list of examples illustrating that infants are transitioning from having earlier abilities that appear more "universal," "broadly tuned," or "unconstrained" to having later abilities that appear more "specialized," "narrowly tuned," or "constrained." Perceptual narrowing, a well-known phenomenon related to face, speech, and…

17 CFR 41.14 - Transition period for indexes that cease being narrow-based security indexes.

Code of Federal Regulations, 2011 CFR

2011-04-01

... provision. An index that is a narrow-based security index that becomes a broad-based security index for no...-five days. An index that is a narrow-based security index that becomes a broad-based security index for...

17 CFR 41.14 - Transition period for indexes that cease being narrow-based security indexes.

Code of Federal Regulations, 2010 CFR

2010-04-01

... provision. An index that is a narrow-based security index that becomes a broad-based security index for no...-five days. An index that is a narrow-based security index that becomes a broad-based security index for...

17 CFR 41.14 - Transition period for indexes that cease being narrow-based security indexes.

Code of Federal Regulations, 2013 CFR

2013-04-01

... provision. An index that is a narrow-based security index that becomes a broad-based security index for no...-five days. An index that is a narrow-based security index that becomes a broad-based security index for...

17 CFR 41.14 - Transition period for indexes that cease being narrow-based security indexes.

Code of Federal Regulations, 2012 CFR

2012-04-01

... provision. An index that is a narrow-based security index that becomes a broad-based security index for no...-five days. An index that is a narrow-based security index that becomes a broad-based security index for...

Poiseuille flow of soft glasses in narrow channels: from quiescence to steady state.

PubMed

Chaudhuri, Pinaki; Horbach, Jürgen

2014-10-01

Using numerical simulations, the onset of Poiseuille flow in a confined soft glass is investigated. Starting from the quiescent state, steady flow sets in at a time scale which increases with a decrease in applied forcing. At this onset time scale, a rapid transition occurs via the simultaneous fluidization of regions having different local stresses. In the absence of steady flow at long times, creep is observed even in regions where the local stress is larger than the bulk yielding threshold. Finally, we show that the time scale to attain steady flow depends strongly on the history of the initial state.

Observation of coherently enhanced tunable narrow-band terahertz transition radiation from a relativistic sub-picosecond electron bunch train

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

Piot, P.; Sun, Y. -E; Maxwell, T. J.

2011-06-27

We experimentally demonstrate the production of narrow-band (δf/f ~ =20% at f ~ = 0.5 THz) THz transition radiation with tunable frequency over [0.37, 0.86] THz. The radiation is produced as a train of sub-picosecond relativistic electron bunches transits at the vacuum-aluminum interface of an aluminum converter screen. In addition, we show a possible application of modulated beams to extend the dynamical range of a popular bunch length diagnostic technique based on the spectral analysis of coherent radiation.

Strike-Slip Faulting Processes on Ganymede: Global Morphological Mapping and Structural Interpretation of Grooved and Transitional Terrains

NASA Astrophysics Data System (ADS)

Burkhard, L. M.; Cameron, M. E.; Smith-Konter, B. R.; Seifert, F.; Pappalardo, R. T.; Collins, G. C.

2015-12-01

Ganymede's fractured surface reveals many large-scale, morphologically distinct regions of inferred distributed shear and strike-slip faulting that may be important to the structural development of its surface and in the transition from dark to light (grooved) materials. To better understand the role of strike-slip tectonism in shaping Ganymede's complex icy surface, we perform a detailed mapping of key examples of strike-slip morphologies (i.e., en echelon structures, strike-slip duplexes, laterally offset pre-existing features, and possible strained craters) from Galileo and Voyager images. We focus on complex structures associated with grooved terrain (e.g. Nun Sulcus, Dardanus Sulcus, Tiamat Sulcus, and Arbela Sulcus) and terrains transitional from dark to light terrain (e.g. the boundary between Nippur Sulcus and Marius Regio, including Byblus Sulcus and Philus Sulcus). Detailed structural interpretations suggest strong evidence of strike-slip faulting in some regions (i.e., Nun and Dardanus Sulcus); however, further investigation of additional strike-slip structures is required of less convincing regions (i.e., Byblus Sulcus). Where applicable, these results are synthesized into a global database representing an inferred sense of shear for many of Ganymede's fractures. Moreover, when combined with existing observations of extensional features, these results help to narrow down the range of possible principal stress directions that could have acted at the regional or global scale to produce grooved terrain on Ganymede.

Systematic study of vortex pinning and liquid-glass phase transition in BaFe2-x Ni x As2 single crystals

NASA Astrophysics Data System (ADS)

Vlasenko, V. A.; Sobolevskiy, O. A.; Sadakov, A. V.; Pervakov, K. S.; Gavrilkin, S. Yu.; Dik, A. V.; Eltsev, Yu. F.

2018-01-01

The vortex pinning and liquid-glass transition have been studied in BaFe2-x Ni x As2 single crystals with different doping levels (x = 0.065; 0.093; 0.1; 0.14; 0.18). We found that Ni-doped Ba-122 has rather narrow vortex-liquid state region. Our results show that the temperature dependence of the resistivity as well as I-V characteristics of Ni-doped Ba-122 is consistent with 3D vortex-glass model. It was found that δl-pinning gives the main contribution to overall pinning in 122 Ni-doped system. The vortex phase diagrams for different doping levels were built based on the obtained data of temperature of the vortex-glass transition T g and the upper critical magnetic field H c2.

Controls of inherited lithospheric heterogeneity on rift linkage: Numerical and analog models of interaction between the Kenyan and Ethiopian rifts across the Turkana depression

NASA Astrophysics Data System (ADS)

Brune, Sascha; Corti, Giacomo; Ranalli, Giorgio

2017-09-01

Inherited rheological structures in the lithosphere are expected to have large impact on the architecture of continental rifts. The Turkana depression in the East African Rift connects the Main Ethiopian Rift to the north with the Kenya rift in the south. This region is characterized by a NW-SE trending band of thinned crust inherited from a Mesozoic rifting event, which is cutting the present-day N-S rift trend at high angle. In striking contrast to the narrow rifts in Ethiopia and Kenya, extension in the Turkana region is accommodated in subparallel deformation domains that are laterally distributed over several hundred kilometers. We present both analog experiments and numerical models that reproduce the along-axis transition from narrow rifting in Ethiopia and Kenya to a distributed deformation within the Turkana depression. Similarly to natural observations, our models show that the Ethiopian and Kenyan rifts bend away from each other within the Turkana region, thus forming a right-lateral step over and avoiding a direct link to form a continuous N-S depression. The models reveal five potential types of rift linkage across the preexisting basin: three types where rifts bend away from the inherited structure connecting via a (1) wide or (2) narrow rift or by (3) forming a rotating microplate, (4) a type where rifts bend towards it, and (5) straight rift linkage. The fact that linkage type 1 is realized in the Turkana region provides new insights on the rheological configuration of the Mesozoic rift system at the onset of the recent rift episode.

Some aspects of unsteady separation

NASA Technical Reports Server (NTRS)

Smith, C. R.; Walker, J. D. A.

1992-01-01

Unsteady separation can be forced in a variety of ways and in this presentation two fundamental means will be considered: (1) the introduction of convected vorticular disturbances into the flow; and (2) the influence of a specific type of three-dimensional geometry. In both situations a response of the viscous flow near the wall is provoked wherein the fluid near the surface abruptly focuses into a narrow region that erupts from the surface into the mainstream. In two-dimensional flows, the eruption takes the form of a narrow, explosively-growing spike, while in three-dimensional situations, examples are presented which indicate that the eruption is along a narrow zone in the shape of a crescent-shaped plume. The nature of the three-dimensional flow near a circular cylinder, which is mounted normal to a flat plate, is also examined in this study. Here the three-dimensional geometry induces complex three-dimensional separations periodically. The dynamics of the generation process is studied experimentally in a water channel using hydrogen bubble wires and a laser sheet, and the main features of the laminar regime through to transition are documented.

Phase transition in lithium ammonium sulphate doped with cesium metal ions

NASA Astrophysics Data System (ADS)

Gaafar, M.; Kassem, M. E.; Kandil, S. H.

2000-07-01

Effects of doped cesium (C s+) metal ions (with different molar ratios n) on the phase transition of lithium ammonium sulphate LiNH 4SO 4 system have been studied by measuring the specific heat Cp( T) of the doped systems in the temperature range from 400 to 480 K. The study shows a peculiar phase transition of the pure system ( n=0) characterized by double distinct peaks, changed to a single sharp and narrow one as a result of the doping process. The measurements exhibit different effects of enhanced molar ratios of dopants on the phase transition behaviour of this system. At low dopant content ( n≤3%), the excess specific heat (Δ Cp) max at the transition temperature T1 decreases till a minimum value at n=0.8%, then it increases gradually. In this case, Δ Cp( T) behaviour is varied quantitatively and not modified. Enhanced dopant content ( n>3%) has a pronounced effect on the critical behaviour, which is significantly changed and considerably modified relative to the pure system. In addition, broadening of the critical temperature region, and decrease of (Δ Cp) max associated with changes of the Landau expansion coefficients are obtained and discussed. The study deals with the contribution of the thermally excited dipoles to the specific heat in the ferroelectric region and shows that their energy depends on doping.

Tunable, high-sensitive measurement of inter-dot transition via tunneling induced absorption

NASA Astrophysics Data System (ADS)

Peng, Yandong; Yang, Aihong; Chen, Bing; Li, Lei; Liu, Shande; Guo, Hongju

2016-10-01

A tunable, narrow absorption spectrum induced by resonant tunneling is demonstrated and proposed for measuring interdot tunneling. Tunneling-induced absorption (TIA) arises from constructive interference between different transition paths, and the large nonlinear TIA significantly enhances the total absorption. The narrow nonlinear TIA spectrum is sensitive to inter-dot tunneling, and its sensor characteristics, including sensitivity and bandwidth, are investigated in weak-coupling and strong-coupling regimes, respectively.

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

Costa, Fatima Rubio da; Petrosian, Vahé; Kleint, Lucia

Spectroscopic observations of solar flares provide critical diagnostics of the physical conditions in the flaring atmosphere. Some key features in observed spectra have not yet been accounted for in existing flare models. Here we report a data-driven simulation of the well-observed X1.0 flare on 2014 March 29 that can reconcile some well-known spectral discrepancies. We analyzed spectra of the flaring region from the Interface Region Imaging Spectrograph ( IRIS ) in Mg ii h and k, the Interferometric BIdimensional Spectropolarimeter at the Dunn Solar Telescope (DST/IBIS) in H α 6563 Å and Ca ii 8542 Å, and the Reuven Ramatymore » High Energy Solar Spectroscope Imager ( RHESSI ) in hard X-rays. We constructed a multithreaded flare loop model and used the electron flux inferred from RHESSI data as the input to the radiative hydrodynamic code RADYN to simulate the atmospheric response. We then synthesized various chromospheric emission lines and compared them with the IRIS and IBIS observations. In general, the synthetic intensities agree with the observed ones, especially near the northern footpoint of the flare. The simulated Mg ii line profile has narrower wings than the observed one. This discrepancy can be reduced by using a higher microturbulent velocity (27 km s{sup −1}) in a narrow chromospheric layer. In addition, we found that an increase of electron density in the upper chromosphere within a narrow height range of ≈800 km below the transition region can turn the simulated Mg ii line core into emission and thus reproduce the single peaked profile, which is a common feature in all IRIS flares.« less

World Oil Transit Chokepoints

EIA Publications

2014-01-01

The U.S. Energy Information Administration (EIA) defines world oil chokepoints as narrow channels along widely-used global sea routes, some so narrow that restrictions are placed on the size of the vessel that can navigate through them. Chokepoints are a critical part of global energy security because of the high volume of petroleum and other liquids transported through their narrow straits.

Experimental investigation of self-induced transparency and pulse delay in ruby.

NASA Technical Reports Server (NTRS)

Asher, I. M.

1972-01-01

We have investigated the self-induced transparency effect in ruby over a range of input energies which range from linear absorption to full transparency. The transmission, pulse delay, and pulse broadening were studied as a function of input energy. The transition region is narrower than that found in similar studies of the CO2/SF6 system; this is consistent with predictions based on ensembles of two-level systems. Included are the first pulse-delay and pulse-broadening curves to be obtained for the ruby system.

Fluctuations and symmetry energy in nuclear fragmentation dynamics.

PubMed

Colonna, M

2013-01-25

Within a dynamical description of nuclear fragmentation, based on the liquid-gas phase transition scenario, we explore the relation between neutron-proton density fluctuations and nuclear symmetry energy. We show that, along the fragmentation path, isovector fluctuations follow the evolution of the local density and approach an equilibrium value connected to the local symmetry energy. Higher-density regions are characterized by smaller average asymmetry and narrower isotopic distributions. This dynamical analysis points out that fragment final state isospin fluctuations can probe the symmetry energy of the density domains from which fragments originate.

Observation of coherently enhanced tunable narrow-band terahertz transition radiation from a relativistic sub-picosecond electron bunch train

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

Piot, P.; Maxwell, T. J.; Accelerator Physics Center, Fermi National Accelerator Laboratory, Batavia, Illinois 60510

2011-06-27

We experimentally demonstrate the production of narrow-band ({delta}f/f{approx_equal}20% at f{approx_equal}0.5THz) transition radiation with tunable frequency over [0.37, 0.86] THz. The radiation is produced as a train of sub-picosecond relativistic electron bunches transits at the vacuum-aluminum interface of an aluminum converter screen. The bunch train is generated via a transverse-to-longitudinal phase space exchange technique. We also show a possible application of modulated beams to extend the dynamical range of a popular bunch length diagnostic technique based on the spectral analysis of coherent radiation.

High-Pressure Study of Perovskite-Like Organometal Halide: Band-Gap Narrowing and Structural Evolution of [NH 3 -(CH 2 ) 4 -NH 3 ]CuCl 4

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

Li, Qian; Li, Shourui; Wang, Kai

Searching for nontoxic and stable perovskite-like alternatives to lead-based halide perovskites for photovoltaic application is one urgent issue in photoelectricity science. Such exploration inevitably requires an effective method to accurately control both the crystalline and electronic structures. This work applies high pressure to narrow the band gap of perovskite-like organometal halide, [NH 3-(CH 2) 4-NH 3]CuCl 4 (DABCuCl4), through the crystalline-structure tuning. The band gap keeps decreasing below ~12 GPa, involving the shrinkage and distortion of CuCl 4 2–. Inorganic distortion determines both band-gap narrowing and phase transition between 6.4 and 10.5 GPa, and organic chains function as the springmore » cushion, evidenced by the structural transition at ~0.8 GPa. The supporting function of organic chains protects DABCuCl 4 from phase transition and amorphization, which also contributes to the sustaining band-gap narrowing. This work combines crystal structure and macroscopic property together and offers new strategies for the further design and synthesis of hybrid perovskite-like alternatives.« less

The effect of silver on the optical, spectral-luminescent, and crystallization properties of bromide photo-thermo-refractive glasses

NASA Astrophysics Data System (ADS)

Oreshkina, K. V.; Dubrovin, V. D.; Ignat'ev, A. I.; Nikonorov, N. V.

2017-10-01

The effect of silver on the optical, spectral-luminescent, and crystallization properties of bromide photo-thermo-refractive glasses is studied. Multicomponent photosensitive glasses of the Na2O-ZnO-Al2O3-SiO2 system with photosensitizing agents (cerium, antimony, silver) and halogenides (fluorine and bromine) are synthesized. Ultraviolet irradiation and thermal treatment below the glass-transition temperature of the glasses cause the formation of silver molecular clusters, which exhibit luminescence in the visible and infrared regions. UV irradiation and thermal treatment of glasses above the glass-transition temperature lead to the growth of silver nanoparticles with plasmon resonance peak in the region of 420 nm. Further thermal treatment of glasses above the glass-transition temperature shifts the plasmon-resonance maximum by 70 nm to longer wavelengths, which is related to the growth of a crystalline shell consisting of mixed silver and sodium bromides on nanoparticles. This formation of a crystalline phase on colloidal centers results in a local increase in the refractive index of the irradiated region by +Δ n 900 ppm compared to the nonirradiated region. Photo-thermo-refractive glasses with increased silver concentration are promising photosensitive materials for creating holographic optical elements and devices for line narrowing and stabilizing filters, spectral beam combiners, and filters for increasing the spectral brightness of laser diodes. A positive change in the refractive index of Photo-thermo-refractive glasses provides the possibility of recording in them 3D waveguide and integrated-optical structures.

Development of a sensor for temperature and water concentration in combustion gases using a single tunable diode laser

NASA Astrophysics Data System (ADS)

Zhou, Xin; Liu, Xiang; Jeffries, Jay B.; Hanson, R. K.

2003-08-01

The water vapour spectrum in the 1-2 µm near-infrared region is systematically analysed to find the best absorption transitions for sensitive measurement of H2O concentration and temperature in combustion environments using a single tunable diode laser with typical distributed feedback single-mode scanning range (1 cm-1). The use of a single laser, even with relatively narrow tuning range, can offer distinct advantages over wavelength-multiplexing techniques. The strategy and spectroscopic criteria for selecting optimum wavelength regions and absorption line combinations are discussed. It should be stressed that no single figure of merit can be derived to simplify the selection process, and the optimum line pair should be chosen case by case. Our investigation reveals that the 1.8 µm spectral region is especially promising, and we have identified 10 of the best water line pairs in this spectral region for temperature measurements in flames. Based on these findings, a pair of H2O transitions near 1.8 µm was targeted for the design and development of an initial single-laser sensor for simultaneously measuring H2O concentration and temperature in atmospheric-pressure flames. As part of the sensor development effort, fundamental spectroscopic parameters including the line strength, line-centre frequency and lower state energies of the probed transitions were measured experimentally to improve the current databases. We conclude with demonstration results in a steady and a forced atmospheric-pressure laboratory combustor.

The phi-meson and Chiral-mass-meson production in heavy-ion collisions as potential probes of quark-gluon-plasma and Chiral symmetry transitions

NASA Technical Reports Server (NTRS)

Takahashi, Y.; Eby, P. B.

1985-01-01

Possibilities of observing abundances of phi mesons and narrow hadronic pairs, as results of QGP and Chiral transitions, are considered for nucleus-nucleus interactions. Kinematical requirements in forming close pairs are satisfied in K+K decays of S(975) and delta (980) mesons with small phi, and phi (91020) mesons with large PT, and in pi-pi decays of familiar resonance mesons only in a partially restored chiral symmetry. Gluon-gluon dominance in QGP can enhance phi meson production. High hadronization rates of primordial resonance mesons which form narrow hadronic pairs are not implausible. Past cosmic ray evidences of anomalous phi production and narrow pair abundances are considered.

Experimental observation of phase-flip transitions in the brain

NASA Astrophysics Data System (ADS)

Dotson, Nicholas M.; Gray, Charles M.

2016-10-01

The phase-flip transition has been demonstrated in a host of coupled nonlinear oscillator models, many pertaining directly to understanding neural dynamics. However, there is little evidence that this phenomenon occurs in the brain. Using simultaneous microelectrode recordings in the nonhuman primate cerebral cortex, we demonstrate the presence of phase-flip transitions between oscillatory narrow-band local field potential signals separated by several centimeters. Specifically, we show that sharp transitions between in-phase and antiphase synchronization are accompanied by a jump in synchronization frequency. These findings are significant for two reasons. First, they validate predictions made by model systems. Second, they have potentially far reaching implications for our understanding of the mechanisms underlying corticocortical communication, which are thought to rely on narrow-band oscillatory synchronization with specific relative phase relationships.

A clock transition in a solid-state system

NASA Astrophysics Data System (ADS)

Edge, G. J. A.; Potnis, S.; Vutha, A. C.

2017-04-01

With the impending redefinition of the SI second based on optical frequency standards, new secondary frequency standards are needed in order to form clock ensembles. Ideally such secondary standards will offer enhanced robustness, portability and high signal-to-noise ratios (SNR), to enable rapid and precise comparisons to be made against primary standards. A clock based on a narrow optical transition, in atoms that are doped into a solid-state host, offers the experimental simplicity and large SNR to satisfy these requirements. The intra-configuration 7F0 ->5D0 transition, in Sm2+ ions doped into a host crystal, is an attractive candidate for such secondary standards due to its low susceptibility to perturbations from the crystal environment. We present results from the interrogation of this clock transition with a narrow linewidth laser.

High resolution emission Fourier transform infrared spectra of the 4p-5s and 5p-6s bands of ArH.

PubMed

Baskakov, O I; Civis, S; Kawaguchi, K

2005-03-15

In the 2500-8500 cm(-1) region several strong emission bands of (40)ArH were observed by Fourier transform spectroscopy through a dc glow discharge in a mixture of argon and hydrogen. Rotational-electronic transitions of the two previously unstudied 4p-5s and 5p-6s,v = 0-0, bands of (40)ArH were measured and assigned in the 6060 and 3770 cm(-1) regions, respectively. A simultaneous fit of the emission transitions of the 4p-5s and 5p-6s bands and an extended set of transitions of the 6s-4p band observed by Dabrowski, Tokaryk, and Watson [J. Mol. Spectrosc. 189, 95 (1998)] and remeasured in the present work yielded consistent values of the spectroscopic parameters of the electronic states under investigation. In the branch of the 4p-5s band with transitions of type (Q)Q(f(3)e) we observed a narrowing in the linewidths with increasing rotational quantum number N. The rotational dependence of the linewidth is caused by predissociation of the 5s state by the repulsive ground 4s state through homogeneous coupling and changes in overlap integrals of the vibrational wave functions with the rotational level. Analysis was based on the Fermi's golden rule approximation model. In the 4p-5s band region a vibrational sequence ofv(')-v(")=1-1, 2-2, and 3-3 were recorded and a number of transitions belonging to the strongest (Q)Q(f(3)e) form branch of the 1-1 band were analyzed.

Evaluation of the economic viability of narrow-gauge local rail systems

DOT National Transportation Integrated Search

2001-11-01

The purpose of this project is to investigate and determine whether narrow-gauge local rail is a viable transportation alternative in Florida. A number of proposals for transit greenways have been developed for various communities throughout Florida....

Twisted MoSe 2 bilayers with variable local stacking and interlayer coupling revealed by low-frequency Raman spectroscopy

DOE PAGES

Puretzky, Alexander A.; Liang, Liangbo; Li, Xufan; ...

2016-01-14

Unique twisted bilayers of MoSe 2 with multiple stacking orientations and interlayer couplings in the narrow range of twist angles, 60 ± 3°, are revealed by low-frequency Raman spectroscopy and theoretical analysis. The slight deviation from 60 allows the concomitant presence of patches featuring all three high-symmetry stacking configurations (2H or AA', AB', A'B) in one unique bilayer system. In this case, the periodic arrangement of the patches and their size strongly depend on the twist angle. Ab initio modeling predicts significant changes in frequencies and intensities of low-frequency modes versus stacking and twist angle. Experimentally, the variable stacking andmore » coupling across the interface is revealed by the appearance of two breathing modes corresponding to the mixture of the high-symmetry stacking configurations and unaligned regions of monolayers. Only one breathing mode is observed outside the narrow range of twist angles. This indicates a stacking transition to unaligned monolayers with mismatched atom registry without the in-plane restoring force required to generate a shear mode. As a result, the variable interlayer coupling and spacing in transition metal dichalcogenide bilayers revealed in this study may provide a new platform for optoelectronic applications of these materials.« less

Twisted MoSe 2 bilayers with variable local stacking and interlayer coupling revealed by low-frequency Raman spectroscopy

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

Puretzky, Alexander A.; Liang, Liangbo; Li, Xufan

Unique twisted bilayers of MoSe 2 with multiple stacking orientations and interlayer couplings in the narrow range of twist angles, 60 ± 3°, are revealed by low-frequency Raman spectroscopy and theoretical analysis. The slight deviation from 60 allows the concomitant presence of patches featuring all three high-symmetry stacking configurations (2H or AA', AB', A'B) in one unique bilayer system. In this case, the periodic arrangement of the patches and their size strongly depend on the twist angle. Ab initio modeling predicts significant changes in frequencies and intensities of low-frequency modes versus stacking and twist angle. Experimentally, the variable stacking andmore » coupling across the interface is revealed by the appearance of two breathing modes corresponding to the mixture of the high-symmetry stacking configurations and unaligned regions of monolayers. Only one breathing mode is observed outside the narrow range of twist angles. This indicates a stacking transition to unaligned monolayers with mismatched atom registry without the in-plane restoring force required to generate a shear mode. As a result, the variable interlayer coupling and spacing in transition metal dichalcogenide bilayers revealed in this study may provide a new platform for optoelectronic applications of these materials.« less

Multiple mantle upwellings through the transition zone beneath the Afar Depression?

NASA Astrophysics Data System (ADS)

Hammond, J. O.; Kendall, J. M.; Stuart, G. W.; Thompson, D. A.; Ebinger, C. J.; Keir, D.; Ayele, A.; Goitom, B.; Ogubazghi, G.

2012-12-01

Previous seismic studies using regional deployments of sensors in East-Africa show that low seismic velocities underlie Africa, but their resolution is limited to the top 200-300km of the Earth. Thus, the connection between the low velocities in the uppermost mantle and those imaged in global studies in the lower mantle is unclear. We have combined new data from Afar, Ethiopia with 7 other regional experiments and global network stations across Kenya, Ethiopia, Eritrea, Djibouti and Yemen, to produce high-resolution models of upper mantle P- and S-wave velocities to the base of the transition zone. Relative travel time tomographic inversions show that within the transition zone two focussed sharp-sided low velocity regions exist: one beneath the Western Ethiopian plateau outside the rift valley, and the other beneath the Afar depression. Estimates of transition zone thickness suggest that this is unlikely to be an artefact of mantle discontinuity topography as a transition zone of normal thickness underlies the majority of Afar and surrounding regions. However, a low velocity layer is evident directly above the 410 discontinuity, co-incident with some of the lowest seismic velocities suggesting that smearing of a strong low velocity layer of limited depth extent may contribute to the tomographic models in north-east Afar. The combination of seismic constraints suggests that small low temperature (<50K) upwellings may rise from a broader low velocity plume-like feature in the lower mantle. This interpretation is supported by numerical and analogue experiments that suggest the 660km phase change and viscosity jump may impede flow from the lower to upper mantle creating a thermal boundary layer at the base of the transition zone. This allows smaller, secondary upwellings to initiate and rise to the surface. These, combined with possible evidence of melt above the 410 discontinuity can explain the seismic velocity models. Our images of secondary upwellings suggest that there is no evidence for a plume in the classical sense (i.e. a narrow conduit). Instead, we propose that secondary upwellings rise from the base of the transition zone and connect with the northeast flowing African superswell in the upper mantle.

Molecular Diagnostics of Diffusive Boundary Layers

NASA Astrophysics Data System (ADS)

Rawlings, J. M. C.; Hartquist, T. W.

1995-11-01

We have assessed the role of diffusion in determining chemical abundances in molecular interface regions. Chemical models have been developed which include the appropriate diffusion terms and that are appropriate to a narrow diffusion region (˜0.01pc) that may exist at the interface between a dark core and a hot, shocked T-Tauri wind. We have assumed pressure balance throughout and have calculated the chemical abundances as functions of time and position through the interface. The results show that significant enhancements of detectable molecules/transitions are expected (e.g. CO J=6→5, OH and CH). Using a realistic value of the diffusion coefficient a diffusive region of dimension 0.01pc may be established within about 104 years. In general it seems likely that diffusion processes are highly significant on these and smaller lengthscales.

Exhaustive Classification of the Invariant Solutions for a Specific Nonlinear Model Describing Near Planar and Marginally Long-Wave Unstable Interfaces for Phase Transition

NASA Astrophysics Data System (ADS)

Ahangari, Fatemeh

2018-05-01

Problems of thermodynamic phase transition originate inherently in solidification, combustion and various other significant fields. If the transition region among two locally stable phases is adequately narrow, the dynamics can be modeled by an interface motion. This paper is devoted to exhaustive analysis of the invariant solutions for a modified Kuramoto-Sivashinsky equation in two spatial and one temporal dimensions is presented. This nonlinear partial differential equation asymptotically characterizes near planar interfaces, which are marginally long-wave unstable. For this purpose, by applying the classical symmetry method for this model the classical symmetry operators are attained. Moreover, the structure of the Lie algebra of symmetries is discussed and the optimal system of subalgebras, which yields the preliminary classification of group invariant solutions is constructed. Mainly, the Lie invariants corresponding to the infinitesimal symmetry generators as well as associated similarity reduced equations are also pointed out. Furthermore, the nonclassical symmetries of this nonlinear PDE are also comprehensively investigated.

Switch over to the high frequency rf systems near transition

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

Brennan, J.M.; Wei, J.

1988-01-01

The purpose of this note is to point out that since bunch narrowing naturally occurs in the acceleration process in the vicinity of transition, it should be possible to switch over to the high frequency system close to transition when the bunch has narrowed enough to fit directly into the high frequency bucket. The advantage of this approach is the simplicity, no extra components or gymnastics are required of the low frequency system. The disadvantage, of course, is for protons which do not go through transition. But on the other hand, there is no shortage of intensity for protons andmore » so it should be possible to keep the phase space area low for protons, and then matching to the high frequency bucket should be easily accomplished by adiabatic compression. 3 refs., 7 figs.« less

Laminar-Turbulent Transition Behind Discrete Roughness Elements in a High-Speed Boundary Layer

NASA Technical Reports Server (NTRS)

Choudhari, Meelan M.; Li, Fei; Wu, Minwei; Chang, Chau-Lyan; Edwards, Jack R., Jr.; Kegerise, Michael; King, Rudolph

2010-01-01

Computations are performed to study the flow past an isolated roughness element in a Mach 3.5, laminar, flat plate boundary layer. To determine the effects of the roughness element on the location of laminar-turbulent transition inside the boundary layer, the instability characteristics of the stationary wake behind the roughness element are investigated over a range of roughness heights. The wake flow adjacent to the spanwise plane of symmetry is characterized by a narrow region of increased boundary layer thickness. Beyond the near wake region, the centerline streak is surrounded by a pair of high-speed streaks with reduced boundary layer thickness and a secondary, outer pair of lower-speed streaks. Similar to the spanwise periodic pattern of streaks behind an array of regularly spaced roughness elements, the above wake structure persists over large distances and can sustain strong enough convective instabilities to cause an earlier onset of transition when the roughness height is sufficiently large. Time accurate computations are performed to clarify additional issues such as the role of the nearfield of the roughness element during the generation of streak instabilities, as well as to reveal selected details of their nonlinear evolution. Effects of roughness element shape on the streak amplitudes and the interactions between multiple roughness elements aligned along the flow direction are also investigated.

A Search for Phosphine in Circumstellar Envelopes: PH3 in IRC +10216 and CRL 2688?

NASA Astrophysics Data System (ADS)

Tenenbaum, E. D.; Ziurys, L. M.

2008-06-01

We present the results of a search for the JK = 10→ 00 transition of PH3 (phosphine) at 267 GHz toward several circumstellar envelopes using the Arizona Radio Observatory 10 m Submillimeter Telescope (SMT). In the carbon-rich shells of IRC +10216 and CRL 2688, we have detected emission lines exactly at the PH3 frequency. Toward the oxygen-rich supergiant VY Canis Majoris, only an upper limit was obtained, while in the evolved carbon-rich proto-planetary nebula CRL 618, the transition is contaminated by vibrationally excited HC3N (ν7 = 4). The line shape in IRC +10216 appears to consist of two distinct components: a flat-topped profile with a width of ~28 km s-1, as is typical for this source, and a narrower feature approximately 4 km s-1 wide. The narrow component likely arises from the inner envelope (r < 8R*) where the gas has not reached the terminal expansion velocity, or it is nonthermal emission. Based on the broader component, the abundance of PH3 with respect to H2 is estimated to be 5 × 10-8 in a region with a radius of r < 150R*. If the narrower component is thermal, it implies a phosphine abundance of ~5 × 10-7 close to the stellar photosphere (r < 8R*). In CRL 2688, the PH3 abundance is less constrained, with plausible values ranging from 3 × 10-8 to 4 × 10-7, assuming a spherical distribution. Phosphine appears to be present in large concentrations in the inner envelope of C-rich AGB stars, and thus may function as a parent molecule for other phosphorus species.

Absolute frequency of cesium 6S-8S 822 nm two-photon transition by a high-resolution scheme.

PubMed

Wu, Chien-Ming; Liu, Tze-Wei; Wu, Ming-Hsuan; Lee, Ray-Kuang; Cheng, Wang-Yau

2013-08-15

We present an alternative scheme for determining the frequencies of cesium (Cs) atom 6S-8S Doppler-free transitions. With the use of a single electro-optical crystal, we simultaneously narrow the laser linewidth, lock the laser frequency, and resolve a narrow spectrum point by point. The error budget for this scheme is presented, and we prove that the transition frequency obtained from the Cs cell at room temperature and with one-layer μ-metal shielding is already very near that for the condition of zero collision and zero magnetic field. We point out that a sophisticated linewidth measurement could be a good guidance for choosing a suitable Cs cell for better frequency accuracy.

Comet giacobini-zinner: plasma description.

PubMed

Bame, S J; Anderson, R C; Asbridge, J R; Baker, D N; Feldman, W C; Fuselier, S A; Gosling, J T; McComas, D J; Thomsen, M F; Young, D T; Zwickl, R D

1986-04-18

A strong interaction between the solar wind and comet Giacobini-Zinner was observed oh 11 September 1985 with the Los Alamos plasma electron experiment on the International Cometary Explorer (ICE) spacecraft. As ICE approached an intercept point 7800 kilometers behind the nucleus from the south and receded to the north, upstream phenomena due to the comet were observed. Periods of enhanced electron heat flux from the comet as well as almost continuous electron density fluctuations were measured. These effects are related to the strong electron heating observed in the cometary interaction region and to cometary ion pickup by the solar wind, respectively. No evidence for a conventional bow shock was found as ICE entered and exited the regions of strongest interaction of the solar wind with the cometary environment. The outer extent of this strong interaction zone was a transition region in which the solar wind plasma was heated, compressed, and slowed. Inside the inner boundary of the transition region was a sheath that enclosed a cold intermediate coma. In the transition region and sheath, small-scale enhancements in density were observed. These density spikes may be due to an instability associated with cometary ion pickup or to the passage of ICE through cometary ray structures. In the center of the cold intermediate coma a narrow, high-density core of plasma, presumably the developing plasma tail was found. In some ways this tail can be compared to the plasma sheet in Earth's magnetotail and to the current sheet in the tail at Venus. This type of configuration is expected in the double-lobe magnetic topology detected at the comet, possibly caused by the theoretically expected draping of the interplanetary magnetic field around its ionosphere.

Genomic analyses of primitive, wild and cultivated citrus provide insights into asexual reproduction.

PubMed

Wang, Xia; Xu, Yuantao; Zhang, Siqi; Cao, Li; Huang, Yue; Cheng, Junfeng; Wu, Guizhi; Tian, Shilin; Chen, Chunli; Liu, Yan; Yu, Huiwen; Yang, Xiaoming; Lan, Hong; Wang, Nan; Wang, Lun; Xu, Jidi; Jiang, Xiaolin; Xie, Zongzhou; Tan, Meilian; Larkin, Robert M; Chen, Ling-Ling; Ma, Bin-Guang; Ruan, Yijun; Deng, Xiuxin; Xu, Qiang

2017-05-01

The emergence of apomixis-the transition from sexual to asexual reproduction-is a prominent feature of modern citrus. Here we de novo sequenced and comprehensively studied the genomes of four representative citrus species. Additionally, we sequenced 100 accessions of primitive, wild and cultivated citrus. Comparative population analysis suggested that genomic regions harboring energy- and reproduction-associated genes are probably under selection in cultivated citrus. We also narrowed the genetic locus responsible for citrus polyembryony, a form of apomixis, to an 80-kb region containing 11 candidate genes. One of these, CitRWP, is expressed at higher levels in ovules of polyembryonic cultivars. We found a miniature inverted-repeat transposable element insertion in the promoter region of CitRWP that cosegregated with polyembryony. This study provides new insights into citrus apomixis and constitutes a promising resource for the mining of agriculturally important genes.

Precision Measurements with a Molecular Clock

NASA Astrophysics Data System (ADS)

Grier, Andrew; McDonald, Mickey; McGuyer, Bart; Iwata, Geoffrey; Apfelbeck, Florian; Tarallo, Marco; Zelevinsky, Tanya

2015-05-01

We report on recent results obtained with photoassociated Sr2 molecules confined in a lattice. Sr2 has a range of electronically excited bound states which are readily accessible with optical wavelengths using the narrow 1S0->3P1 intercombination line. As in Nat. Phys. 11, 32, we measure the lifetimes of the narrow, deeply-bound subradiant states in the 1g (1S0+3P1 dissociative limit) potential, allowing for coherent control of molecules and a comparison with theoretical predictions of the lifetimes and transition strengths of these states. Next, we study ultracold photodissociation of Sr2 molecules through abortion of one and two photons near the atomic intercombination line. This allows us to observe the vector character of transition elements through the angular dissociation pattern and to directly measure barrier heights in the excited state potentials. Finally, as shown in PRL 114, 023001, we demonstrate that in a non-magic lattice, a narrow transition can be used to measure the trapped gas temperature through the linewidth of the spectral feature corresponding to the carrier transitions. We use this technique to measure the temperature of Sr2 molecules to 10x higher precision than with standard techniques. We discuss future prospects with this molecular lattice clock. Funding from NIST, ARO, and NSF IGERT.

Millimeter-wave Spectroscopy of NGC1068 With Z-Spec

NASA Astrophysics Data System (ADS)

Kamenetzky, Julia; Aguirre, J. E.; Bock, J. J.; Bradford, M.; Earle, L.; Glenn, J.; Maloney, P.; Matsuhara, H.; Naylor, B.; Nguyen, H. T.; Zmuidzinas, J.

2009-05-01

NGC1068 is commonly cited as the prototypical Seyfert 2 galaxy. Both the central and extended regions have been studied extensively across the electromagnetic spectrum, revealing many different astrophysical phenomena, such as a bright central region, radio jet knots, and a conical narrow-line region. Significantly, evidence has been found that the active galactic nucleus is shrouded by a dusty molecular disk, which could support the theory that viewing angle will unify Seyfert 1 and 2 galaxies. We observed NGC1068 with Z-Spec, a broadband (185-305 GHz) millimeter-wave grating spectrometer, at the Caltech Submillimeter Observatory. Its large bandwidth allows us to simultaneously observe multiple molecular rotational transitions along with the underlying continuum. The detector array is composed of 160 silicon-nitride micromesh bolometers cooled to 60 mK by an adiabatic demagnetization refrigerator (ADR) and a closed-cycle 3He refrigerator. Z-Spec's compact design is achieved via a WaFIRS (Waveguide Far IR Spectrometer) design utilizing a parallel-plate waveguide and curved diffraction grating. Z-Spec's spectral resolution is approximately 900 MHz at the band center. We obtained a high signal-to-noise ratio spectrum of NGC1068 in late January 2007. Key observable transitions in Z-Spec's bandpass include CO , 13CO, and C18O (J = 2 - 1), HCN, HNC, and HCO+ (J = 3 - 2), and multiple CS transitions. We are modeling the NGC1068 spectrum using these data and other transitions of these molecules from the literature to probe the physical characteristics of its interstellar medium, such as temperature, density, dense gas fraction, and the extent of the AGN's contribution to the molecular gas excitation. We will present preliminary results of the analysis.

Random pinning elucidates the nature of melting transition in two-dimensional core-softened potential system

NASA Astrophysics Data System (ADS)

Tsiok, E. N.; Fomin, Y. D.; Ryzhov, V. N.

2018-01-01

Despite about forty years of investigations, the nature of the melting transition in two dimensions is not completely clear. In the framework of the most popular Berezinskii-Kosterlitz-Thouless-Halperin-Nelson-Young (BKTHNY) theory, 2D systems melt through two continuous Berezinskii-Kosterlitz-Thouless (BKT) transitions with intermediate hexatic phase. The conventional first-order transition is also possible. On the other hand, recently on the basis of computer simulations the new melting scenario was proposed with continuous BKT type solid-hexatic transition and first order hexatic-liquid transition. However, in the simulations the hexatic phase is extremely narrow that makes its study difficult. In the present paper, we propose to apply the random pinning to investigate the hexatic phase in more detail. The results of molecular dynamics simulations of two dimensional system having core-softened potentials with narrow repulsive step which is similar to the soft disk system are outlined. The system has a small fraction of pinned particles giving quenched disorder. Random pinning widens the hexatic phase without changing the melting scenario and gives the possibility to study the behavior of the diffusivity and order parameters in the vicinity of the melting transition and inside the hexatic phase.

Nature of the narrow optical band in H*-aggregates: Dozy-chaos–exciton coupling

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

Egorov, Vladimir V., E-mail: egorov@photonics.ru

2014-07-15

Dozy chaos emerges as a combined effect of the collective chaotic motion of electrons and nuclei, and their chaotic electromagnetic interactions in the transient state of molecules experiencing quantum transitions. Following earlier discussions of the well-known Brönsted relations for proton-transfer reactions; the temperature-dependent electron transfer in Langmuir–Blodgett films; the shape of the optical bands of polymethine dye monomers, their dimers, and J-aggregates, this paper reports one more application of the dozy-chaos theory of molecular quantum transitions. The qualitative and quantitative explanations for shape of a narrow and blue-shifted optical absorption band in H{sup *}-aggregates is given on the basis ofmore » the dozy-chaos theory by taking into account the dozy-chaos–exciton coupling effect. It is emphasized that in the H{sup *}-aggregate chromophore (dimer of cyclic bis-thiacarbocyanines) there is a competition between two Frenkel exciton transitions through the chaotic reorganization motion of nuclear environment. As a result, the highly organized quantum transition to the upper exciton state becomes an exciton-induced source of dozy chaos for the low organized transition to the lower exciton state. This manifests itself in appearing the narrow peak and broad wing in the optical spectrum pattern of H{sup *}-aggregates. A similar enhancement in the H{sup *}-effect caused by the strengthening of the exciton coupling in H{sup *}-dimers, which could be achieved by synthesizing tertiary and quarternary thiacarbocyanine monomers, is predicted.« less

Seismically imaging the Afar plume

NASA Astrophysics Data System (ADS)

Hammond, J. O.; Kendall, J. M.; Bastow, I. D.; Stuart, G. W.; Keir, D.; Ayele, A.; Ogubazghi, G.; Ebinger, C. J.; Belachew, M.

2011-12-01

Plume related flood basalt volcanism in Ethiopia has long been cited to have instigated continental breakup in northeast Africa. However, to date seismic images of the mantle beneath the region have not produced conclusive evidence of a plume-like structure. As a result the nature and even existence of a plume in the region and its role in rift initiation and continental rupture are debated. Previous seismic studies using regional deployments of sensors in East-Africa show that low seismic velocities underlie northeast Africa, but their resolution is limited to the top 200-300km of the Earth. Thus, the connection between the low velocities in the uppermost mantle and those imaged in global studies in the lower mantle is unclear. We have combined new data from Afar, Ethiopia with 6 other regional experiments and global network stations across Ethiopia, Eritrea, Djibouti and Yemen, to produce high-resolution models of upper mantle P- and S- wave velocities to the base of the transition zone. Relative travel time tomographic inversions show that the top 100km is dominated by focussed low velocity zones, likely associated with melt in the lithosphere/uppermost asthenosphere. Below these depths a broad SW-NE oriented sheet like upwelling extends down to the top of the transition zone. Within the transition zone two focussed sharp-sided low velocity regions exist: one beneath the Western Ethiopian plateau outside the rift valley, and the other beneath the Afar depression. The nature of the transition zone anomalies suggests that small upwellings may rise from a broader low velocity plume-like feature in the lower mantle. This interpretation is supported by numerical and analogue experiments that suggest the 660km phase change and viscosity jump may impede flow from the lower to upper mantle creating a thermal boundary layer at the base of the transition zone. This allows smaller, secondary upwellings to initiate and rise to the surface. Our images of secondary upwellings suggest that there is no evidence for a plume in the classical sense (i.e. a narrow conduit). Instead, we propose that secondary upwellings rise from the base of the transition zone and connect in the upper mantle. This coupled with measurements of seismic anisotropy suggest that mantle material flows northeast towards Arabia, and may be responsible for the dramatic dynamic topography observed in northeast Africa and western Arabia.

Crystallization of Deformable Spherical Colloids

NASA Astrophysics Data System (ADS)

Batista, Vera M. O.; Miller, Mark A.

2010-08-01

We introduce and characterize a first-order model for a generic class of colloidal particles that have a preferred spherical shape but can undergo deformations while always maintaining hard-body interactions. The model consists of hard spheres that can continuously change shape at fixed volume into prolate or oblate ellipsoids of revolution, subject to an energetic penalty. The severity of this penalty is specified by a single parameter that determines the flexibility of the particles. The deformable hard spheres crystallize at higher packing fractions than rigid hard spheres, have a narrower solid-fluid coexistence region and can reach high densities by a second transition to an orientationally ordered crystal.

The impact of swidden decline on livelihoods and ecosystem services in Southeast Asia: A review of the evidence from 1990 to 2015.

PubMed

Dressler, Wolfram H; Wilson, David; Clendenning, Jessica; Cramb, Rob; Keenan, Rodney; Mahanty, Sango; Bruun, Thilde Bech; Mertz, Ole; Lasco, Rodel D

2017-04-01

Global economic change and policy interventions are driving transitions from long-fallow swidden (LFS) systems to alternative land uses in Southeast Asia's uplands. This study presents a systematic review of how these transitions impact upon livelihoods and ecosystem services in the region. Over 17 000 studies published between 1950 and 2015 were narrowed, based on relevance and quality, to 93 studies for further analysis. Our analysis of land-use transitions from swidden to intensified cropping systems showed several outcomes: more households had increased overall income, but these benefits came at significant cost such as reductions of customary practice, socio-economic wellbeing, livelihood options, and staple yields. Examining the effects of transitions on soil properties revealed negative impacts on soil organic carbon, cation-exchange capacity, and aboveground carbon. Taken together, the proximate and underlying drivers of the transitions from LFS to alternative land uses, especially intensified perennial and annual cash cropping, led to significant declines in pre-existing livelihood security and the ecosystem services supporting this security. Our results suggest that policies imposing land-use transitions on upland farmers so as to improve livelihoods and environments have been misguided; in the context of varied land uses, swidden agriculture can support livelihoods and ecosystem services that will help buffer the impacts of climate change in Southeast Asia.

Electron impact excitation of Kr XXXII

NASA Astrophysics Data System (ADS)

Aggarwal, K. M.; Keenan, F. P.; Lawson, K. D.

2009-09-01

Collision strengths (Ω) have been calculated for all 7750 transitions among the lowest 125 levels belonging to the 2s2p,2s2p,2p,2s3ℓ,2s2p3ℓ, and 2p3ℓ configurations of boron-like krypton, Kr XXXII, for which the Dirac Atomic R-matrix Code has been adopted. All partial waves with angular momentum J⩽40 have been included, sufficient for the convergence of Ω for forbidden transitions. For allowed transitions, a top-up has been included in order to obtain converged values of Ω up to an energy of 500 Ryd. Resonances in the thresholds region have been resolved in a narrow energy mesh, and results for effective collision strengths (ϒ) have been obtained after averaging the values of Ω over a Maxwellian distribution of electron velocities. Values of ϒ are reported over a wide temperature range below 107.3K, and the accuracy of the results is assessed. Values of ϒ are also listed in the temperature range 7.3⩽logTe(K)⩽9.0, obtained from the nonresonant collision strengths from the Flexible Atomic Code.

Direct observation of a Γ -X energy spectrum transition in narrow AlAs quantum wells

NASA Astrophysics Data System (ADS)

Khisameeva, A. R.; Shchepetilnikov, A. V.; Muravev, V. M.; Gubarev, S. I.; Frolov, D. D.; Nefyodov, Yu. A.; Kukushkin, I. V.; Reichl, C.; Tiemann, L.; Dietsche, W.; Wegscheider, W.

2018-03-01

Spectra of magnetoplasma excitations have been investigated in two-dimensional electron systems in AlAs quantum wells (QWs) of different widths. The magnetoplasma spectrum has been found to change profoundly when the quantum well width becomes thinner than 5.5 nm, indicating a drastic change in the conduction electron energy spectrum. The transformation can be interpreted in terms of transition from the in-plane strongly anisotropic Xx-Xy valley occupation to the out-of-plane isotropic Xz valley in the QW plane. Strong enhancement of the cyclotron effective mass over the band value in narrow AlAs QWs is reported.

Investigation of narrow-band thermal emission from intersubband transitions in quantum wells

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

De Zoysa, M.; Hakubi Center, Kyoto University, Yoshida, Kyoto 606-8501; Asano, T.

2015-09-14

We investigate thermal emission from n-doped GaAs/AlGaAs quantum wells (QWs). Emission peaks with Lorentzian shapes (linewidth 11∼19 meV) that reflect transitions between the first and second conduction subbands are observed in the mid-infrared range. It is demonstrated that the emission characteristics can be tuned by modifying the QW parameters. The peak emissivity is increased from 0.3 to 0.9 by modifying the doping density, and the peak wavelength is tuned from 6 to 10 μm by changing the well width. The obtained results are useful for the design of narrow-band thermal emitters.

A potassium Faraday anomalous dispersion optical filter

NASA Technical Reports Server (NTRS)

Yin, B.; Shay, T. M.

1992-01-01

The characteristics of a potassium Faraday anomalous dispersion optical filter operating on the blue and near infrared transitions are calculated. The results show that the filter can be designed to provide high transmission, very narrow pass bandwidth, and low equivalent noise bandwidth. The Faraday anomalous dispersion optical filter (FADOF) provides a narrow pass bandwidth (about GHz) optical filter for laser communications, remote sensing, and lidar. The general theoretical model for the FADOF has been established in our previous paper. In this paper, we have identified the optimum operational conditions for a potassium FADOF operating on the blue and infrared transitions. The signal transmission, bandwidth, and equivalent noise bandwidth (ENBW) are also calculated.

Aspects of the Solar Tachocline

NASA Technical Reports Server (NTRS)

Elliott, J. R.

1997-01-01

The splitting of the frequencies of p-mode multiplets enables information to be gained about the internal rotation of the sun. Such data have revealed a transition at the base of the convection zone from differential rotation similar to that observed at the surface to almost solid-body rotation in the radiative interior. This transition region, known as the tachocline, has been found to be relatively narrow and centered below the base of the convection zone. In this paper, the evolution of the transition region is investigated numerically. Without a large anisotropic viscosity, the depth to which it would spread in one solar age, under the assumption of a constant prescribed differential rotation at the base of the convection zone, is found to be greater than its extent as inferred from helioseismology. In the second part of the paper a highly anisotropic turbulent viscosity with a large horizontal component, as suggested by Spiegel & Zahn (1992), is assumed. In this case, a steady tachocline is formed in which the advection of angular momentum balances the Reynolds stresses. The horizontal component of turbulent viscosity required to match the thickness of the tachocline to that obtained by helioseismology, is estimated to be 5 x 1O sq cm/s The transport of helium is studied in this case and is found to yield a sound-speed increase similar to that required by helioseismology.

Temperature Measurements in the Solar Transition Region Using N III Line Intensity Ratios

NASA Technical Reports Server (NTRS)

Doron, R.; Doschek, G. A.; Laming, J. M.; Feldman, U.; Bhatia, A. K.

2003-01-01

UV emission from B-like N and O ions a rather rare opportunity for recording spectral lines in a narrow wavelength range that can potentially be used to derive temperatures relevant to the solar transition region. In these ions, the line intensity ratios of the type (2s2p(sup 2) - 2p(sup 3)) / (2s(sup 2)2p - 2s2p(sup 2)) are very sensitive to the electron temperature. Additionally, the lines involving the ratios fall within a range of only - 12 A; in N III the lines fall in the 980 - 992 A range and in O IV in the 780 - 791 A range. In this work, we explore the use of these atomic systems, primarily in N III, for temperature diagnostics of the transition region by analyzing UV spectra obtained by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer flown on the Solar and Heliospheric Observatory (SOHO). The N III temperature-sensitive line ratios are measured in more than 60 observations. Most of the measured ratios correspond to temperatures in the range 5.7x10(exp 4) - 6.7x10(exp 4) K. This range is considerably lower than the calculated temperature of maximum abundance of N III, which is approx. 7.6x10(exp 4) K. Detailed analysis of the spectra further indicates that the measured ratios are probably somewhat overestimated due to resonant scattering effects in the 2s(sup 2)2p - 2s2p(sup 2) lines and small blends in the 2s2p(sup 2) - 2p3 lines. Actual lower ratios would only increase the disagreement between the ionization balance calculations and present temperature measurements based on a collisional excitation model. In the case of the O IV spectra, we determined that due to the close proximity in wavelength of the weak line (2s2p(sup 2)-2p3 transitions) to a strong Ne VIII line, sufficiently accurate ratio measurements cannot be obtained. Subject headings: atomic data --- atomic processes --- Sun: transition region --- Sun: U V radiation --- techniques: spectroscopic

Transition to complete synchronization and global intermittent synchronization in an array of time-delay systems.

PubMed

Suresh, R; Senthilkumar, D V; Lakshmanan, M; Kurths, J

2012-07-01

We report the nature of transitions from the nonsynchronous to a complete synchronization (CS) state in arrays of time-delay systems, where the systems are coupled with instantaneous diffusive coupling. We demonstrate that the transition to CS occurs distinctly for different coupling configurations. In particular, for unidirectional coupling, locally (microscopically) synchronization transition occurs in a very narrow range of coupling strength but for a global one (macroscopically) it occurs sequentially in a broad range of coupling strength preceded by an intermittent synchronization. On the other hand, in the case of mutual coupling, a very large value of coupling strength is required for local synchronization and, consequently, all the local subsystems synchronize immediately for the same value of the coupling strength and, hence, globally, synchronization also occurs in a narrow range of the coupling strength. In the transition regime, we observe a type of synchronization transition where long intervals of high-quality synchronization which are interrupted at irregular times by intermittent chaotic bursts simultaneously in all the systems and which we designate as global intermittent synchronization. We also relate our synchronization transition results to the above specific types using unstable periodic orbit theory. The above studies are carried out in a well-known piecewise linear time-delay system.

Numerical Treatment of the Boltzmann Equation for Self-Propelled Particle Systems

NASA Astrophysics Data System (ADS)

Thüroff, Florian; Weber, Christoph A.; Frey, Erwin

2014-10-01

Kinetic theories constitute one of the most promising tools to decipher the characteristic spatiotemporal dynamics in systems of actively propelled particles. In this context, the Boltzmann equation plays a pivotal role, since it provides a natural translation between a particle-level description of the system's dynamics and the corresponding hydrodynamic fields. Yet, the intricate mathematical structure of the Boltzmann equation substantially limits the progress toward a full understanding of this equation by solely analytical means. Here, we propose a general framework to numerically solve the Boltzmann equation for self-propelled particle systems in two spatial dimensions and with arbitrary boundary conditions. We discuss potential applications of this numerical framework to active matter systems and use the algorithm to give a detailed analysis to a model system of self-propelled particles with polar interactions. In accordance with previous studies, we find that spatially homogeneous isotropic and broken-symmetry states populate two distinct regions in parameter space, which are separated by a narrow region of spatially inhomogeneous, density-segregated moving patterns. We find clear evidence that these three regions in parameter space are connected by first-order phase transitions and that the transition between the spatially homogeneous isotropic and polar ordered phases bears striking similarities to liquid-gas phase transitions in equilibrium systems. Within the density-segregated parameter regime, we find a novel stable limit-cycle solution of the Boltzmann equation, which consists of parallel lanes of polar clusters moving in opposite directions, so as to render the overall symmetry of the system's ordered state nematic, despite purely polar interactions on the level of single particles.

Deformation processes and weakening mechanisms within the frictional viscous transition zone of major crustal-scale faults: insights from the Great Glen Fault Zone, Scotland

NASA Astrophysics Data System (ADS)

Stewart, M.; Holdsworth, R. E.; Strachan, R. A.

2000-05-01

The Great Glen Fault Zone (GGFZ), Scotland, is a typical example of a crustal-scale, reactivated strike-slip fault within the continental crust. Analysis of intensely strained fault rocks from the core of the GGFZ near Fort William provides a unique insight into the nature of deformation associated with the main phase of (sinistral) movements along the fault zone. In this region, an exhumed sequence of complex mid-crustal deformation textures that developed in the region of the frictional-viscous transition (ca. 8-15 km depth) is preserved. Fault rock fabrics vary from mylonitic in quartzites to cataclastic in micaceous shear zones and feldspathic psammites. Protolith mineralogy exerted a strong control on the initial textural development and distribution of the fault rocks. At lower strains, crystal-plastic deformation occurred in quartz-dominated lithologies to produce mylonites simultaneously with widespread fracturing and cataclasis in feldspar- and mica-dominated rocks. At higher strains, shearing appears to increasingly localise into interconnected networks of cataclastic shear zones, many of which are strongly foliated. Textures indicative of fluid-assisted diffusive mass transfer mechanisms are widespread in such regions and suggest that a hydrous fluid-assisted, grainsize-controlled switch in deformation behaviour followed the brittle comminution of grains. The fault zone textural evolution implies that a strain-induced, fluid-assisted shallowing and narrowing of the frictional-viscous transition occurred with increasing strain. It is proposed that this led to an overall weakening of the fault zone and that equivalent processes may occur along many other long-lived, crustal-scale dislocations.

Mesoporous transition metal oxides quasi-nanospheres with enhanced electrochemical properties for supercapacitor applications.

PubMed

Wang, Lu; Duan, Guorong; Zhu, Junwu; Chen, Shen-Ming; Liu, Xiao-Heng; Palanisamy, Selvakumar

2016-12-01

In this report, we obtain mesoporous transition metal oxides quasi-nanospheres (includes MnO2, NiO, and Co3O4) by utilizing mesoporous silica nanospheres as a template for high-performance supercapacitor electrodes. All samples have a large specific surface area of approximately 254-325m(2)g(-1) and a relatively narrow pore size distribution in the region of 7nm. Utilization of a nanosized template resulted in a product with a relative uniform morphology and a small particle diameter in the region of 50-100nm. As supercapacitor electrodes, MnO2, NiO, and Co3O4 exhibit an outstanding capacity as high as 838-1185Fg(-1) at 0.5Ag(-1) and a superior long-term stability with minimal loss of 3-7% after 6000 cycles at 1Ag(-1). Their excellent electrochemical performances are attributed to favorable morphologies with a large surface area and a uniform architecture with abundant pores. The associated enhancement of electrolyte ion circulation within the electrode facilitates a significant increase in availability of Faradic reaction electroactive sites. Copyright © 2016 Elsevier Inc. All rights reserved.

Where is the exact origin of narrow premature ventricular contractions manifesting qR in inferior wall leads?

PubMed

Zheng, Cheng; Li, Jin; Lin, Jia-Xuan; Wang, Lu-Ping; Lin, Jia-Feng

2016-04-04

In recent years, radiofrequency catheter ablation(RFCA) has been established as an effective therapy for idiopathic premature ventricular contractions (PVCs), however, its effect on the narrow PVCs (QRS duration < 130 msec) with qR pattern in inferior leads, may not been fully concluded. Characteristics of 12-lead electrocardiogram (ECG) and electrophysiologic recordings were analyzed in 40 patients with symptomatic PVCs manifesting narrow QRS complex with qR pattern in inferior leads. The procedure of RFCA was performed based on pace mapping and activation mapping. Among the 40 patients with narrow PVCs, complete elimination of PVCs was achieved by RFCA in 35 patients during a median follow-up period of 23 months. Successful ablation was achieved on 19 patients at the sites where earliest Purkinje potentials were recorded in left ventricular anterosuperior septum, thus PVCs arising from left anterior fascicle (LAF) were confirmed, for these PVCs, the QRS morphology were right bundle branch and left posterior fascicle block (RBBB + LPFB) with rightward axis, the average QRS duration 116.07 ± 7.96 ms, R or rsR'in lead V1,with transition zone ahead of lead V1 in precordial leads. Another 16 successful RFCA were achieved by energy delivery at interleaflet triangle(ILT) between right coronary cusp(RCC) and left coronary cusp(LCC) where no Purkinje potentials were recorded, for narrow PVCs arising from the L-RCC ILT, the QRS morphology were similar to the PVCs arising from LAF but much narrower in QRS duration (100.44 ± 3.49 vs. 116.07 ± 7.96 ms, p < 0.05), they were also R or Rs in lead V1 with the transition zone ahead of lead V1. For 5 symptomatic narrow PVCs failed to the procedure of RFCA, their electrocardiographic characteristics showed that the narrowest QRS duration (91.80 ± 6.94 vs. 100.44 ± 3.49, 116.07 ± 7.96 ms, p < 0.05), rs or rS (r/s or r/S≦1) morphology in lead V1 with the precordial transition zone behind lead V3. Most of idiopathic PVCs of narrow QRS duration (<130 msec) with qR pattern in inferior leads can be cured by the procedure of RFCA. On the basis of our study, we proposed that for narrow PVCs presenting qR pattern in inferior leads, when the ablation procedure failed at proximity of LAF within left anterosuperior septum, mapping and ablation in L-RCC ILT can be tried. The present findings can be helpful for planning catheter ablation for narrow PVCs manifesting qR in inferior leads.

Diode laser measurements of linestrength and temperature-dependent lineshape parameters of H2O-, CO2-, and N2-perturbed H2O transitions near 2474 and 2482 nm

NASA Astrophysics Data System (ADS)

Goldenstein, Christopher S.; Jeffries, Jay B.; Hanson, Ronald K.

2013-11-01

Absorption lineshapes for two unresolved H2O doublets near 4029.52 and 4041.92 cm-1 were measured at high-resolution in a heated static cell using two distributed-feedback diode lasers. Measurements were acquired for H2O, CO2, and N2 perturbers over a temperature and pressure range of 650-1325 K and 2-760 Torr, respectively. Strong collisional narrowing effects were observed in CO2 and N2, but not in pure H2O. The Galatry profile was used to infer collisional-broadening and -narrowing coefficients and their respective temperature dependence for CO2 and N2 perturbers. The collisional-broadening and -narrowing coefficients for CO2 perturbers were found to decrease with increasing temperature in a similar manner. For N2 perturbers, the collisional-broadening coefficients increased with temperature while the collisional-narrowing coefficients decreased with increasing temperature. Self-broadening coefficients were inferred from Voigt profile fits and are compared with HITEMP 2010. The linestrengths of 17 H2O transitions are also reported.

Observation of the spin-orbit components of the 3B 2g( 3A 2g) ground state in the system Ni 2+:MgF 2 by fluorescence line narrowing

NASA Astrophysics Data System (ADS)

Tonucci, R. J.; Jacobsen, S. M.; Yen, W. M.

1990-10-01

Using a tunable narrow-band infrared laser, we demonstrate for the first time infrared-fluorescnece line narrowing in the system Ni 2+:MgF 2. High-resolution emission spectra were obtained by pumping the lowest spin-orbit component B 3 ( 3T 2g) (orthorhombic notation with octahedral notation in parentheses) of the 3T 2g multiplet and observing the B 3( 3T 2g)→B 1, A, B 2( 3A 2g) luminescent transitions at low temperature. By tuning the narrow-band laser over the B 3( 3T 2g) band, resonant and non-resonant fluorescence were obtained which narrowed with respect to the inhomogeneously broadened profile, and additional lines were observed. The spectra can be understood in terms of a simultaneous excitation of two different subsets of Ni 2+ ions which have their B 2( 3A 2g)→B 3( 3T 2g) and A( 3A 2g)→B 3( 3T 2g) transitions in resonance with the laser. The A( 3A 2g) and B 1( 3A 2g) spin-orbit components of the ground-state multiplet lie 1.9 cm -1 and 6.5 cm -1 above the B 2( 3A 2g) ground state, respectively, at 2 K.

The orthorhombic to high-P monoclinic phase transition in Mg-Fe Pyroxenes: Can it produce a seismic discontinuity?

NASA Astrophysics Data System (ADS)

Woodland, Alan B.

The orthorhombic to high-P monoclinic phase transition in (Mg,Fe)SiO3 pyroxene with a mantle-relevant composition (XFs = 0.1) is expected to occur at ˜300 km depth [Woodland and Angel, 1997]. However, the divariant nature of the phase transition in the Mg-Fe system leaves the question open as to whether this transition occurs over a narrow enough pressure interval to cause a seismic discontinuity. New experimental results with binary Mg-Fe pyroxenes constrain the divariant loop to be 0.2 GPa wide at the composition of XFs = 0.4 and on the order of 0.15 GPa for a mantle-relevant composition. This implies that the phase transition will be complete over a depth interval of about 5-6 km in the mantle and it is concluded that the divariant loop of the orthorhombic to high-P monoclinic phase transition in (Mg,Fe)SiO3 pyroxene is indeed narrow enough to produce a “jump” in seismic velocities. The experimentally observed metastable behavior of orthopyroxene could further reduce the effective depth interval of this phase transition. The expected location of this phase transition coincides with a small magnitude seismic discontinuity, the “X-discontinuity”, occasionally observed in seismic profiles at ˜300 km depth, and thus provides a viable petrologic explanation for the origin of this discontinuity, if it truly exists.

Gardner Transition in Physical Dimensions

NASA Astrophysics Data System (ADS)

Hicks, C. L.; Wheatley, M. J.; Godfrey, M. J.; Moore, M. A.

2018-06-01

The Gardner transition is the transition that at mean-field level separates a stable glass phase from a marginally stable phase. This transition has similarities with the de Almeida-Thouless transition of spin glasses. We have studied a well-understood problem, that of disks moving in a narrow channel, which shows many features usually associated with the Gardner transition. We show that some of these features are artifacts that arise when a disk escapes its local cage during the quench to higher densities. There is evidence that the Gardner transition becomes an avoided transition, in that the correlation length becomes quite large, of order 15 particle diameters, even in our quasi-one-dimensional system.

Pressure dependence of transverse acoustic phonon energy in ferropericlase across the spin transition.

PubMed

Fukui, Hiroshi; Baron, Alfred Q R; Ishikawa, Daisuke; Uchiyama, Hiroshi; Ohishi, Yasuo; Tsuchiya, Taku; Kobayashi, Hisao; Matsuzaki, Takuya; Yoshino, Takashi; Katsura, Tomoo

2017-06-21

We investigated transverse acoustic (TA) phonons in iron-bearing magnesium oxide (ferropericlase) up to 56 GPa using inelastic x-ray scattering (IXS). The results show that the energy of the TA phonon far from the Brillouin zone center suddenly increases with increasing pressure above the spin transition pressure of ferropericlase. Ab initio calculations revealed that the TA phonon energy far from the Brillouin zone center is higher in the low-spin state than in the high spin state; that the TA phonon energy depend weakly on pressure; and that the energy gap between the TA and the lowest-energy-optic phonons is much narrower in the low-spin state than in the high-spin state. This allows us to conclude that the anomalous behavior of the TA mode in the present experiments is the result of gap narrowing due to the spin transition and explains contradictory results in previous experimental studies.

Ruling out unresolved binaries in five transitional disks. VLT/NACO deep 2.12 and 1.75 μm narrow-band imaging

NASA Astrophysics Data System (ADS)

Vicente, S.; Merín, B.; Hartung, M.; Bouy, H.; Huélamo, N.; Artigau, E.; Augereau, J.-C.; van Dishoeck, E.; Olofsson, J.; Oliveira, I.; Prusti, T.

2011-09-01

Context. The presence of unresolved binaries on sub-arsecond scales could explain the existence of optically thin inner holes or gaps in circumstellar disks, which are commonly referred to as "transitional" or "cold" disks, and it is the first scenario to check before making any other assumptions. Aims: We aim at detecting the presence of companions inside the inner hole/gap region of a sample of five well known transitional disks using spatially-resolved imaging in the near-IR with the VLT/NACO/S13 camera, which probes projected distances from the primary of typically 0.1 to 7 arcsec. The sample includes the stars DoAr 21, HD 135344B (SAO 206462), HR 4796A, T Cha, and TW Hya, spanning ages of less than 1 to 10 Myr, spectral types of A0 to K7, and hole/gap outer radii of 4 to 100 AU. Methods: In order to enhance the contrast and to avoid saturation at the core of the point-spread function (PSF), we use narrow-band filters at 1.75 and 2.12 μm. The "locally optimized combination of images" (LOCI) algorithm is applied for an optimal speckle noise removal and PSF subtraction, providing an increase of 0.5-1.5 mag in contrast over the classic method. Results: With the proviso that we could have missed companions owing to unfavorable projections, the VLT/NACO observations rule out the presence of unresolved companions down to an inner radius of about 0.1 arcsec from the primary in all five transitional disks and with a detection limit of 2 to 5 mag in contrast. In the disk outer regions the detection limits typically reach 8 to 9 mag in contrast and 4.7 mag for T Cha. Hence, the NACO images resolve part of the inner hole/gap region of all disks with the exception of TW Hya, for which the inner hole is only 4 AU. The 5σ sensitivity profiles, together with a selected evolutionary model, allow to discard stellar companions within the inner hole/gap region of T Cha, and down to the substellar regime for HD 135344B and HR 4796A. DoAr 21 is the only object from the sample of five disks for which the NACO images are sensitive enough for a detection of objects less massive than ~13 MJup that is, potential giant planets or low-mass brown dwarfs at radii larger than ~76 AU (0.63 arcsec). Conclusions: These new VLT/NACO observations further constrain the origin of the inner opacity cavities to be owing to closer or lower-mass companions or other mechanisms such as giant planet formation, efficient grain growth, and photoevaporation (for DoAr 21 and HR 4796A).

Boundary-layer mantle flow under the Dead Sea transform fault inferred from seismic anisotropy.

PubMed

Rümpker, Georg; Ryberg, Trond; Bock, Günter

2003-10-02

Lithospheric-scale transform faults play an important role in the dynamics of global plate motion. Near-surface deformation fields for such faults are relatively well documented by satellite geodesy, strain measurements and earthquake source studies, and deeper crustal structure has been imaged by seismic profiling. Relatively little is known, however, about deformation taking place in the subcrustal lithosphere--that is, the width and depth of the region associated with the deformation, the transition between deformed and undeformed lithosphere and the interaction between lithospheric and asthenospheric mantle flow at the plate boundary. Here we present evidence for a narrow, approximately 20-km-wide, subcrustal anisotropic zone of fault-parallel mineral alignment beneath the Dead Sea transform, obtained from an inversion of shear-wave splitting observations along a dense receiver profile. The geometry of this zone and the contrast between distinct anisotropic domains suggest subhorizontal mantle flow within a vertical boundary layer that extends through the entire lithosphere and accommodates the transform motion between the African and Arabian plates within this relatively narrow zone.

Growth of nanostructures with controlled diameter

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

Pfefferle, Lisa; Haller, Gary; Ciuparu, Dragos

2009-02-03

Transition metal-substituted MCM-41 framework structures with a high degree of structural order and a narrow pore diameter distribution were reproducibly synthesized by a hydrothermal method using a surfactant and an anti-foaming agent. The pore size and the mesoporous volume depend linearly on the surfactant chain length. The transition metals, such as cobalt, are incorporated substitutionally and highly dispersed in the silica framework. Single wall carbon nanotubes with a narrow diameter distribution that correlates with the pore diameter of the catalytic framework structure were prepared by a Boudouard reaction. Nanostructures with a specified diameter or cross-sectional area can therefore be predictablymore » prepared by selecting a suitable pore size of the framework structure.« less

Solar flare microwave observations with high spectral resolution

NASA Astrophysics Data System (ADS)

Bruggmann, G.; Magun, A.; Benz, A. O.; Stehling, W.

1990-12-01

The solar flare radio emission in the 6-8 GHz range was observed with a high resolution spectrometer. The observed band corresponds to the plasma frequencies and gyrofrequencies of the transition region and the lowest part of the corona in active regions. Most of the emissions were found to be broadbanded, as expected from the gyrosynchrotron mechanism. In eight out of 46 observed events, spectral structures of three types were detected: spikes below the time resolution of 100 ms, slowly drifting broadband structures, and a narrow bandwidth patch of continuum emission. These first narrowband bursts spectrally recorded in the 6-8 GHz range are generally weak. Slowly drifting structures are the only type compatible with the gyrosynchrotron emission mechanism. A simple argument based on free-free absorption shows that plasma emission can only be propagated if the radiation originates in a dense region with a small density-scale length. The same holds for maser emission at a low harmonic of the electron gyrofrequency. Possible emission mechanisms and diagnostic capabilities are discussed.

Population differentiation decreases with depth in deep-sea gastropods

NASA Astrophysics Data System (ADS)

Etter, Ron J.; Rex, Michael A.

1990-08-01

The evolutionary processes that have generated the rich and highly endemic deep-sea benthic invertebrate fauna remain largely unstudied. Patterns of geographic variation constitute the most basic and essential information for understanding speciation and adaptive radiation. Here we present a multivariate analysis of phenotypic distance to quantify geographic variation in shell form among populations of eight deep-sea gastropod species distributed along a depth gradient in the western North Atlantic. Our primary aim is to identify regions within the deep sea that may promote population differentiation. The degree of interpopulation divergence is highest at the shelf-slope transition (200 m), and then decreases dramatically with increasing depth across the bathyal region (200-4000 m) to the abyssal plain (>4000 m). Phenotypic change parallels faunal change along the depth gradient, suggesting that the selective regime becomes more uniform with increasing depth. Results indicate that the potential for gastropod radiation within the deep-sea environment (>200 m) varies geographically and is highest in the narrow upper bathyal region.

Direct simulation of flat-plate boundary layer with mild free-stream turbulence

NASA Astrophysics Data System (ADS)

Wu, Xiaohua; Moin, Parviz

2014-11-01

Spatially evolving direct numerical simulation of the flat-plate boundary layer has been performed. The momentum thickness Reynolds number develops from 80 to 3000 with a free-stream turbulence intensity decaying from 3 percent to 0.8 percent. Predicted skin-friction is in agreement with the Blasius solution prior to breakdown, follows the well-known T3A bypass transition data during transition, and agrees with the Erm and Joubert Melbourne wind-tunnel data after the completion of transition. We introduce the concept of bypass transition in the narrow sense. Streaks, although present, do not appear to be dynamically important during the present bypass transition as they occur downstream of infant turbulent spots. For the turbulent boundary layer, viscous scaling collapses the rate of dissipation profiles in the logarithmic region at different Reynolds numbers. The ratio of Taylor microscale and the Kolmogorov length scale is nearly constant over a large portion of the outer layer. The ratio of large-eddy characteristic length and the boundary layer thickness scales very well with Reynolds number. The turbulent boundary layer is also statistically analyzed using frequency spectra, conditional-sampling, and two-point correlations. Near momentum thickness Reynolds number of 2900, three layers of coherent vortices are observed: the upper and lower layers are distinct hairpin forests of large and small sizes respectively; the middle layer consists of mostly fragmented hairpin elements.

Fluorosilicate and fluorophosphate superfluorescent multicore optical fibers co-doped with Nd3+/Yb3+

NASA Astrophysics Data System (ADS)

Kochanowicz, M.; Zmojda, J.; Dorosz, D.

2014-06-01

In the paper spectroscopic properties of two fluorosilicate and fluorophosphate glass systems co-doped with Nd3+/Yb3+ ions are investigated. As a result of optical excitation at the wavelength of 808 nm strong and wide emission in the 1 μm region corresponding to the superposition of optical transitions 4F3/2 → 4I11/2 (Nd3+) and 2F5/2 → 2F7/2 (Yb3+) can be observed. The optimization of Nd3+ → Yb3+ energy transfer in both glasses allows to manufacture multicore optical fibers with narrowing and red-shifting of amplified spontaneous emission (ASE) at 1.1 μm.

Effective Hamiltonians for correlated narrow energy band systems and magnetic insulators: Role of spin-orbit interactions in metal-insulator transitions and magnetic phase transitions

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

Chakraborty, Subrata; Vijay, Amrendra, E-mail: avijay@iitm.ac.in

Using a second-quantized many-electron Hamiltonian, we obtain (a) an effective Hamiltonian suitable for materials whose electronic properties are governed by a set of strongly correlated bands in a narrow energy range and (b) an effective spin-only Hamiltonian for magnetic materials. The present Hamiltonians faithfully include phonon and spin-related interactions as well as the external fields to study the electromagnetic response properties of complex materials and they, in appropriate limits, reduce to the model Hamiltonians due to Hubbard and Heisenberg. With the Hamiltonian for narrow-band strongly correlated materials, we show that the spin-orbit interaction provides a mechanism for metal-insulator transition, whichmore » is distinct from the Mott-Hubbard (driven by the electron correlation) and the Anderson mechanism (driven by the disorder). Next, with the spin-only Hamiltonian, we demonstrate the spin-orbit interaction to be a reason for the existence of antiferromagnetic phase in materials which are characterized by a positive isotropic spin-exchange energy. This is distinct from the Néel-VanVleck-Anderson paradigm which posits a negative spin-exchange for the existence of antiferromagnetism. We also find that the Néel temperature increases as the absolute value of the spin-orbit coupling increases.« less

Crystal nucleation and metastable bcc phase in charged colloids: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Ji, Xinqiang; Sun, Zhiwei; Ouyang, Wenze; Xu, Shenghua

2018-05-01

The dynamic process of homogenous nucleation in charged colloids is investigated by brute-force molecular dynamics simulation. To check if the liquid-solid transition will pass through metastable bcc, simulations are performed at the state points that definitely lie in the phase region of thermodynamically stable fcc. The simulation results confirm that, in all of these cases, the preordered precursors, acting as the seeds of nucleation, always have predominant bcc symmetry consistent with Ostwald's step rule and the Alexander-McTague mechanism. However, the polymorph selection is not straightforward because the crystal structures formed are not often determined by the symmetry of intermediate precursors but have different characters under different state points. The region of the state point where bcc crystal structures of large enough size are formed during crystallization is narrow, which gives a reasonable explanation as to why the metastable bcc phase in charged colloidal suspensions is rarely detected in macroscopic experiments.

Thermodynamics and Structural Evolution during a Reversible Vesicle-Micelle Transition of a Vitamin-Derived Bolaamphiphile Induced by Sodium Cholate.

PubMed

Tian, Jun-Nan; Ge, Bing-Qiang; Shen, Yun-Feng; He, Yu-Xuan; Chen, Zhong-Xiu

2016-03-09

Interaction of endogenous sodium cholate (SC) with dietary amphiphiles would induce structural evolution of the self-assembled aggregates, which inevitably affects the hydrolysis of fat in the gut. Current work mainly focused on the interaction of bile salts with classical double-layered phospholipid vesicles. In this paper, the thermodynamics and structural evolution during the interaction of SC with novel unilamellar vesicles formed from vitamin-derived zwitterionic bolaamphiphile (DDO) were characterized. It was revealed that an increased temperature and the presence of NaCl resulted in narrowed micelle-vesicle coexistence and enlarged the vesicle region. The coexistence of micelles and vesicles mainly came from the interaction of monomeric SC with DDO vesicles, whereas micellar SC contributed to the total solubilization of DDO vesicles. This research may enrich the thermodynamic mechanism behind the structure transition of the microaggregates formed by amphiphiles in the gut. It will also contribute to the design of food formulation and drug delivery system.

Challenges Faced by Faculty Who Transition to Post-Secondary Online Education

ERIC Educational Resources Information Center

Chester, Maryanne Christine

2012-01-01

Online education has provided the opportunity for many learners to pursue higher education. However, training is crucial for instructors who may be hesitant to transition to online teaching, unaware of online teaching strategies, and lack support from educational institutions. The purpose of this qualitative case study was to narrow the knowledge…

78 FR 69524 - Preparation of an Environmental Impact Statement for High Capacity Transit Improvements for the...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-19

... intervening high-density residential and commercial areas of northeastern and central Marion County. This is... of 10th Street where the street is narrow and eastbound traffic volumes are low. The transit lanes... impact areas include: land use, zoning, potential displacements, parkland, economic development...

Narrow-line laser cooling by adiabatic transfer

NASA Astrophysics Data System (ADS)

Norcia, Matthew A.; Cline, Julia R. K.; Bartolotta, John P.; Holland, Murray J.; Thompson, James K.

2018-02-01

We propose and demonstrate a novel laser cooling mechanism applicable to particles with narrow-linewidth optical transitions. By sweeping the frequency of counter-propagating laser beams in a sawtooth manner, we cause adiabatic transfer back and forth between the ground state and a long-lived optically excited state. The time-ordering of these adiabatic transfers is determined by Doppler shifts, which ensures that the associated photon recoils are in the opposite direction to the particle’s motion. This ultimately leads to a robust cooling mechanism capable of exerting large forces via a weak transition and with reduced reliance on spontaneous emission. We present a simple intuitive model for the resulting frictional force, and directly demonstrate its efficacy for increasing the total phase-space density of an atomic ensemble. We rely on both simulation and experimental studies using the 7.5 kHz linewidth 1S0 to 3P1 transition in 88Sr. The reduced reliance on spontaneous emission may allow this adiabatic sweep method to be a useful tool for cooling particles that lack closed cycling transitions, such as molecules.

Method of making an improved superconducting quantum interference device

DOEpatents

Wu, Cheng-Teh; Falco, Charles M.; Kampwirth, Robert T.

1977-01-01

An improved superconducting quantum interference device is made by sputtering a thin film of an alloy of three parts niobium to one part tin in a pattern comprising a closed loop with a narrow region, depositing a thin film of a radiation shield such as copper over the niobium-tin, scribing a narrow line in the copper over the narrow region, exposing the structure at the scribed line to radiation and removing the deposited copper.

Morphology of AGN Emission Line Regions in SDSS-IV MaNGA Survey

NASA Astrophysics Data System (ADS)

He, Zhicheng; Sun, Ai-Lei; Zakamska, Nadia L.; Wylezalek, Dominika; Kelly, Michael; Greene, Jenny E.; Rembold, Sandro B.; Riffel, Rogério; Riffel, Rogemar A.

2018-05-01

Extended narrow-line regions (NLRs) around active galactic nuclei (AGN) are shaped by the distribution of gas in the host galaxy and by the geometry of the circumnuclear obscuration, and thus they can be used to test the AGN unification model. In this work, we quantify the morphologies of the narrow-line regions in 308 nearby AGNs (z = 0 - 0.14, Lbol˜1042.4 - 44.1 erg s-1) from the MaNGA survey. Based on the narrow-line region maps, we find that a large fraction (81%) of these AGN have bi-conical NLR morphology. The distribution of their measured opening angles suggests that the intrinsic opening angles of the ionization cones has a mean value of 85-98° with a finite spread of 39-44° (1-σ). Our inferred opening angle distribution implies a number ratio of type I to type II AGN of 1:1.6-2.3, consistent with other measurements of the type I / type II ratio at low AGN luminosities. Combining these measurements with the WISE photometry data, we find that redder mid-IR color (lower effective temperature of dust) corresponds to stronger and narrower photo-ionized bicones. This relation is in agreement with the unification model that suggests that the bi-conical narrow-line regions are shaped by a toroidal dusty structure within a few pc from the AGN. Furthermore, we find a significant alignment between the minor axis of host galaxy disks and AGN ionization cones. Together, these findings suggest that obscuration on both circumnuclear (˜pc) and galactic (˜ kpc) scales are important in shaping and orienting the AGN narrow-line regions.

The crustal structure along the 1999 Izmit/Düzce rupture of the North-Anatolian Fault

NASA Astrophysics Data System (ADS)

Sebastian, Rost; David, Cornwell; David, Thompson; Greg, Houseman; Metin, Kahraman; Ugur, Teoman; Selda, Altuncu-Poyraz; Niyazi, Turkelli; Andrew, Frederiksen; Stephane, Rondenay; Tim, Wright

2015-04-01

Deformation along continental strike-slip faults is localized onto narrow fault zones at the surface, which may slip suddenly and catastrophically in earthquakes. On the other hand, strain in the upper mantle is more broadly distributed and is thought to occur by continuous ductile creep. The transition between these two states is poorly understood although it controls the behaviour of the fault zone during the earthquake loading cycle. To understand the structure of and strain distribution across the North-Anatolian Fault Zone (NAFZ) we deployed temporary seismic stations in the region of the 1999 Izmit (M7.5) and Düzce (M7.2) earthquakes. The rectangular array consisted of 66 seismic stations with a nominal station spacing of 7 km and seven additional stations forming a semi-circular ring towards the east (Dense Array for Northern Anatolia - DANA). Using this very dense seismic dataset and a combination of established (e.g. H-k stacking and common conversion point migration) and novel (scattering migration and scattering inversion) seismic processing techniques allows unprecedented resolution of the crustal structure in this region. This study resolves sharp changes in crustal structure across and along the surface expression of the two branches of the NAFZ at scale lengths less than 10 km at mid to lower-crustal depths. The results indicate that the northern NAFZ branch depth extent varies from the mid-crust to the upper mantle and it is likely to be less than 5 km wide throughout the crust. We furthermore resolve a high velocity lower crust and a region of crustal underthrusting that might add strength to a heterogeneous crust and may play a role in dictating the variation in faulting style and postseismic deformation in this region of the NAFZ. The results are consistent with a narrow fault zone accommodating postseismic deformation in the lower crust, as opposed to a broad ductile region below the seismogenic region of the fault.

Anomalous mantle transition zone beneath the Yellowstone hotspot track

NASA Astrophysics Data System (ADS)

Zhou, Ying

2018-06-01

The origin of the Yellowstone and Snake River Plain volcanism has been strongly debated. The mantle plume model successfully explains the age-progressive volcanic track, but a deep plume structure has been absent in seismic imaging. Here I apply diffractional tomography to receiver functions recorded at USArray stations to map high-resolution topography of mantle transition-zone discontinuities. The images reveal a trail of anomalies that closely follow the surface hotspot track and correlate well with a seismic wave-speed gap in the subducting Farallon slab. This observation contradicts the plume model, which requires anomalies in the mid mantle to be confined in a narrow region directly beneath the present-day Yellowstone caldera. I propose an alternative interpretation of the Yellowstone volcanism. About 16 million years ago, a section of young slab that had broken off from a subducted spreading centre in the mantle first penetrated the 660 km discontinuity beneath Oregon and Idaho, and pulled down older stagnant slab. Slab tearing occurred along pre-existing fracture zones and propagated northeastward. This reversed-polarity subduction generated passive upwellings from the lower mantle, which ascended through a water-rich mantle transition zone to produce melting and age-progressive volcanism.

Turbulent spots and scalar flashes in pipe transition

NASA Astrophysics Data System (ADS)

Adrian, Ronald; Wu, Xiaohua; Moin, Parviz

2017-11-01

Recent study (Wu et al., PNAS, 1509451112, 2015) demonstrated the feasibility and accuracy of direct computation of the Osborne Reynolds' pipe transition experiment without the unphysical axially periodic boundary condition. Here we use this approach to address three questions: (1) What are the dynamics of turbulent spot generation in pipe transition? (2) How is the succession of scalar flashes, as observed and sketched by Osborne Reynolds, created? (3) What happens to the succession of flashes further downstream? In this study, the inlet disturbance is of radial-mode type imposed through a narrow, three-degree numerical wedge; and the simulation Reynolds number is 6500. Numerical dye is introduced at the inlet plane locally very close to the pipe axis, similar to the needle injection by O. Reynolds. Inception of infant turbulent spots occurs when normal, forward inclined hairpin packets form near the walls from the debris of the inlet perturbations. However, the young and mature turbulent spots consist almost exclusively of reverse, backward leaning hairpin vortices. Scalar flashes appear successively downstream and persist well into the fully-developed turbulent region. Their creation mechanism is addressed. RJA gratefully acknowledges support of the National Science Foundation with NSF Award CBET-0933848.

Electron impact excitation of Kr XXVIII

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

Aggarwal, K.M., E-mail: K.Aggarwal@qub.ac.u; Keenan, F.P.; Lawson, K.D.

2011-05-15

Collision strengths ({Omega}) are calculated for all 6328 transitions among the lowest 113 levels belonging to the 2s{sup 2}2p{sup 5},2s2p{sup 6},2s{sup 2}2p{sup 4}3l,2s2p{sup 5}3l, and 2p{sup 6}3l configurations of fluorine-like krypton, Kr XXVIII, using the Dirac Atomic R-matrix Code. All partial waves with angular momentum J{<=}40 are included, sufficient for the convergence of {Omega} for forbidden transitions. For allowed transitions a top-up is employed to obtain converged values of {Omega} up to an energy of 400 Ryd. Resonances in the thresholds region are resolved on a narrow energy mesh, and results for effective collision strengths (Y) are obtained after averagingmore » the values of {Omega} over a Maxwellian distribution of electron velocities. Values of Y are reported over a wide temperature range below 10{sup 7.1}K, and the accuracy of the results is assessed. In addition, effective collision strengths are listed for the temperature range 7.0{<=}logT{sub e}(K){<=}9.0, obtained from non-resonant collision strengths generated with the FAC code.« less

Photoluminescence from narrow InAs-AlSb quantum wells

NASA Technical Reports Server (NTRS)

Brar, Berinder; Kroemer, Herbert; Ibbetson, James; English, John H.

1993-01-01

We report on photoluminescence spectra from narrow InAs-AlSb quantum wells. Strong, clearly resolved peaks for well widths from 2 to 8 monolayers were observed. Transmission electron micrographs show direct evidence for the structural quality of the quantum well structures. The transition energies of the narrowest wells suggest a strong influence of the AlSb X-barrier on the electronic states in the conduction band.

Subseasonal forecast skills and biases of global summer monsoons in the NCEP Climate Forecast System version 2

NASA Astrophysics Data System (ADS)

Liu, Xiangwen; Yang, Song; Li, Qiaoping; Kumar, Arun; Weaver, Scott; Liu, Shi

2014-03-01

Subseasonal forecast skills and biases of global summer monsoons are diagnosed using daily data from the hindcasts of 45-day integrations by the NCEP Climate Forecast System version 2. Predictions for subseasonal variability of zonal wind and precipitation are generally more skillful over the Asian and Australian monsoon regions than other monsoon regions. Climatologically, forecasts for the variations of dynamical monsoon indices have high skills at leads of about 2 weeks. However, apparent interannual differences exist, with high skills up to 5 weeks in exceptional cases. Comparisons for the relationships of monsoon indices with atmospheric circulation and precipitation patterns between skillful and unskillful forecasts indicate that skills for subseasonal variability of a monsoon index depend partially on the degree to which the observed variability of the index attributes to the variation of large-scale circulation. Thus, predictions are often more skillful when the index is closely linked to atmospheric circulation over a broad region than over a regional and narrow range. It is also revealed that, the subseasonal variations of biases of winds, precipitation, and surface temperature over various monsoon regions are captured by a first mode with seasonally independent biases and a second mode with apparent phase transition of biases during summer. The first mode indicates the dominance of overall weaker-than-observed summer monsoons over major monsoon regions. However, at certain stages of monsoon evolution, these underestimations are regionally offset or intensified by the time evolving biases portrayed by the second mode. This feature may be partially related to factors such as the shifts of subtropical highs and intertropical convergence zones, the reversal of biases of surface temperature over some monsoon regions, and the transition of regional circulation system. The significant geographical differences in bias growth with increasing lead time reflect the distinctions of initial memory capability of the climate system over different monsoon regions.

Arabian Plate Deformation: The role of inherited structures in the localization of strain in the Red Sea extensional system

NASA Astrophysics Data System (ADS)

Aldaajani, T.; Furlong, K.; Malservisi, R.

2017-12-01

The Red Sea rift structural architecture changes dramatically along strike from narrow localized spreading (with creation of new oceanic crust) in the south to asymmetrical diffuse extension north of 21 ° latitude. The region of diffuse extension falls within a triangle that is bounded to the east by the Sarhan graben, (a Cenozoic failed rift), to the west by the northern Red Sea Rift, and to the south by the Makkah-Madinah-Nafud (MMN) volcanic line. Geological observations appear to show that tectonic stresses acting on inherited structures within the NW Arabian margin are associated with the region of diffuse extension. In contrast, in the southern Red Sea, a single strong block within the SW Arabian margin led to localize the extension there. Using current velocities from more than 30 GNSS stations distributed within the Arabian plate, we are able to map its rigidity and the distribution of strain along the plate margin. The data show that the transition between the two styles of extension within the Red Sea (crustal accretion vs crustal extension) corresponds with a transition between rigid behavior and diffuse extension within the Arabian Plate. This suggests that the preexisting structures within the Arabian plate play a significant role in the style of extension along the Red Sea margin.

Complex dynamics induced by strong confinement - From tracer diffusion in strongly heterogeneous media to glassy relaxation of dense fluids in narrow slits

NASA Astrophysics Data System (ADS)

Mandal, Suvendu; Spanner-Denzer, Markus; Leitmann, Sebastian; Franosch, Thomas

2017-08-01

We provide an overview of recent advances of the complex dynamics of particles in strong confinements. The first paradigm is the Lorentz model where tracers explore a quenched disordered host structure. Such systems naturally occur as limiting cases of binary glass-forming systems if the dynamics of one component is much faster than the other. For a certain critical density of the host structure the tracers undergo a localization transition which constitutes a critical phenomenon. A series of predictions in the vicinity of the transition have been elaborated and tested versus computer simulations. Analytical progress is achieved for small obstacle densities. The second paradigm is a dense strongly interacting liquid confined to a narrow slab. Then the glass transition depends nonmonotonically on the separation of the plates due to an interplay of local packing and layering. Very small slab widths allow to address certain features of the statics and dynamics analytically.

Active Faraday optical frequency standard.

PubMed

Zhuang, Wei; Chen, Jingbiao

2014-11-01

We propose the mechanism of an active Faraday optical clock, and experimentally demonstrate an active Faraday optical frequency standard based on narrow bandwidth Faraday atomic filter by the method of velocity-selective optical pumping of cesium vapor. The center frequency of the active Faraday optical frequency standard is determined by the cesium 6 (2)S(1/2) F=4 to 6 (2)P(3/2) F'=4 and 5 crossover transition line. The optical heterodyne beat between two similar independent setups shows that the frequency linewidth reaches 281(23) Hz, which is 1.9×10(4) times smaller than the natural linewidth of the cesium 852-nm transition line. The maximum emitted light power reaches 75 μW. The active Faraday optical frequency standard reported here has advantages of narrow linewidth and reduced cavity pulling, which can readily be extended to other atomic transition lines of alkali and alkaline-earth metal atoms trapped in optical lattices at magic wavelengths, making it useful for new generation of optical atomic clocks.

OUTFLOWS AND DARK BANDS AT ARCADE-LIKE ACTIVE REGION CORE BOUNDARIES

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

Scott, J. T.; Martens, P. C. H.; Tarr, L.

Observations from the EUV Imaging Spectrometer (EIS) on board Hinode have revealed outflows and non-thermal line broadening in low intensity regions at the edges of active regions (ARs). We use data from Hinode's EIS, Solar Dynamic Observatory's Atmospheric Imaging Assembly and Helioseismic and Magnetic Imager, and the Transition Region and Coronal Explorer instrument to investigate the boundaries of arcade-like AR cores for NOAA ARs 11112, 10978, and 9077. A narrow, low intensity region that is observed at the core's periphery as a dark band shows outflows and increased spectral line broadening. This dark band is found to exist for daysmore » and appears between the bright coronal loop structures of different coronal topologies. We find a case where the dark band region is formed between the magnetic field from emerging flux and the field of the pre-existing flux. A magnetic field extrapolation indicates that this dark band is coincident with the spine lines or magnetic separatrices in the extrapolated field. This occurs over unipolar regions where the brightened coronal field is separated in connectivity and topology. This separation does not appear to be infinitesimal and an initial estimate of the minimum distance of separation is found to be Almost-Equal-To 1.5-3.5 Mm.« less

The first transition Wolf-Rayet WN/C star in M31

NASA Astrophysics Data System (ADS)

Shara, Michael M.; Mikołajewska, Joanna; Caldwell, Nelson; Iłkiewicz, Krystian; Drozd, Katarzyna; Zurek, David

2016-02-01

Three decades of searches have revealed 154 Wolf-Rayet (WR) stars in M31, with 62 of WC type, 92 of WN type and zero of transition-type WN/C or WC/N. In apparent contrast, about two per cent of the WR stars in the Galaxy, the LMC and M33 simultaneously display strong lines of carbon and nitrogen, I.e. they are transition-type WN/C or WC/N stars. We report here the serendipitous discovery of M31 WR 84-1, the first transition star in M31, located at RA = 00h43m43{^s.}61 Dec. = +41°45'27{^''.}95 (J2000). We present its spectrum, classify it as WN5/WC6, and compare it with other known transition stars. The star is unresolved in Hubble Space Telescope narrow-band and broad-band images, while its spectrum displays strong, narrow emission lines of hydrogen, [N II], [S II] and [O III]; this indicates a nebula surrounding the star. The radial velocity of the nebular lines is consistent with that of gas at the same position in the disc of M31. The metallicity at the 11.8 kpc galactocentric distance of M31 WR 84-1 is approximately solar, consistent with other known transition stars. We suggest that modest numbers of reddened WR stars remain to be found in M31.

Wedge-shaped potential and Airy-function electron localization in oxide superlattices.

PubMed

Popovic, Z S; Satpathy, S

2005-05-06

Oxide superlattices and microstructures hold the promise for creating a new class of devices with unprecedented functionalities. Density-functional studies of the recently fabricated, lattice-matched perovskite titanates (SrTiO3)n/(LaTiO3)m reveal a classic wedge-shaped potential well for the monolayer (m = 1) structure, originating from the Coulomb potential of a two-dimensional charged La sheet. The potential in turn confines the electrons in the Airy-function-localized states. Magnetism is suppressed for the monolayer structure, while in structures with a thicker LaTiO3 part, bulk antiferromagnetism is recovered, with a narrow transition region separating the magnetic LaTiO3 and the nonmagnetic SrTiO3.

Laboratory Rotational Spectra of Silyl Isocyanide

NASA Astrophysics Data System (ADS)

Lee, K. L. K.; Gottlieb, C. A.; McCarthy, M. C.

2018-06-01

The rotational spectrum of silyl isocyanide (SiH3NC), an isomer of the well-studied silyl cyanide (SiH3CN), has been detected in the laboratory in a supersonic molecular beam, and the identification was confirmed by observations of the corresponding rotational transitions in the rare isotopic species {SiH}}3}15{NC} and SiH3N13C. Spectroscopic constants derived from 19 transitions between 11 and 35 GHz in the three lowest harmonically related rotational transitions in the K = 0 and 1 ladders of the normal isotopic species including the nitrogen nuclear quadrupole hyperfine constant allow the principal astronomical transitions of SiH3NC to be calculated to an uncertainty of about 4 km s‑1 in equivalent radial velocity, or within the FWHM of narrow spectral features in the inner region of IRC+10216 near 200 GHz. The concentration of SiH3NC in our molecular beam is three times less than SiH3CN, or about the same as the corresponding ratio of the isomeric pair SiNC and SiCN produced under similar conditions. Silyl isocyanide is an excellent candidate for astronomical detection, because the spectroscopic and chemical properties are very similar to SiH3CN, which was recently identified in the circumstellar envelope of IRC+10216 by Cernicharo et al. and of SiNC and SiCN in the same source.

GTC OSIRIS transiting exoplanet atmospheric survey: detection of sodium in XO-2b from differential long-slit spectroscopy

NASA Astrophysics Data System (ADS)

Sing, D. K.; Huitson, C. M.; Lopez-Morales, M.; Pont, F.; Désert, J.-M.; Ehrenreich, D.; Wilson, P. A.; Ballester, G. E.; Fortney, J. J.; Lecavelier des Etangs, A.; Vidal-Madjar, A.

2012-10-01

We present two transits of the hot-Jupiter exoplanet XO-2b using the Gran Telescopio Canarias (GTC). The time series observations were performed using long-slit spectroscopy of XO-2 and a nearby reference star with the Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) instrument, enabling differential spectrophotometric transit light curves capable of measuring the exoplanet's transmission spectrum. Two optical low-resolution grisms were used to cover the optical wavelength range from 3800 to 9300 Å. We find that sub-mmag-level slit losses between the target and reference star prevent full optical transmission spectra from being constructed, limiting our analysis to differential absorption depths over ˜1000 Å regions. Wider long slits or multi-object grism spectroscopy with wide masks will likely prove effective in minimizing the observed slit-loss trends. During both transits, we detect significant absorption in the planetary atmosphere of XO-2b using a 50-Å bandpass centred on the Na I doublet, with absorption depths of Δ(Rpl/R★)2 = 0.049 ± 0.017 per cent using the R500R grism and 0.047 ± 0.011 per cent using the R500B grism (combined 5.2σ significance from both transits). The sodium feature is unresolved in our low-resolution spectra, with detailed modelling also likely ruling out significant line-wing absorption over an ˜800 Å region surrounding the doublet. Combined with narrow-band photometric measurements, XO-2b is the first hot Jupiter with evidence for both sodium and potassium present in the planet's atmosphere. Based on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, in the island of La Palma, and part of the large European Southern Observatory (ESO) programme 182.C-2018.

Broad- versus Narrow-Spectrum Oral Antibiotic Transition and Outcomes in Health Care-associated Pneumonia.

PubMed

Buckel, Whitney R; Stenehjem, Edward; Sorensen, Jeff; Dean, Nathan; Webb, Brandon

2017-02-01

Guidelines recommend a switch from intravenous to oral antibiotics once patients who are hospitalized with pneumonia achieve clinical stability. However, little evidence guides the selection of an oral antibiotic for patients with health care-associated pneumonia, especially where no microbiological diagnosis is made. To compare outcomes between patients who were transitioned to broad- versus narrow-spectrum oral antibiotics after initially receiving broad-spectrum intravenous antibiotic coverage. We performed a secondary analysis of an existing database of adults with community-onset pneumonia admitted to seven Utah hospitals. We identified 220 inpatients with microbiology-negative health care-associated pneumonia from 2010 to 2012. After excluding inpatient deaths and treatment failures, 173 patients remained in which broad-spectrum intravenous antibiotics were transitioned to an oral regimen. We classified oral regimens as broad-spectrum (fluoroquinolone) versus narrow-spectrum (usually a β-lactam). We compared demographic and clinical characteristics between groups. Using a multivariable regression model, we adjusted outcomes by severity (electronically calculated CURB-65), comorbidity (Charlson Index), time to clinical stability, and length of intravenous therapy. Age, severity, comorbidity, length of intravenous therapy, and clinical response were similar between the two groups. Observed 30-day readmission (11.9 vs. 21.4%; P = 0.26) and 30-day all-cause mortality (2.3 vs. 5.3%; P = 0.68) were also similar between the narrow and broad oral antibiotic groups. In multivariable analysis, we found no statistically significant differences for adjusted odds of 30-day readmission (adjusted odds ratio, 0.56; 95% confidence interval, 0.06-5.2; P = 0.61) or 30-day all-cause mortality (adjusted odds ratio, 0.55; 95% confidence interval, 0.19-1.6; P = 0.26) between narrow and broad oral antibiotic groups. On the basis of analysis of a limited number of patients observed retrospectively, our findings suggest that it may be safe to switch from broad-spectrum intravenous antibiotic coverage to a narrow-spectrum oral antibiotic once clinical stability is achieved for hospitalized patients with health care-associated pneumonia when no microbiological diagnosis is made. A larger retrospective study with propensity matching or regression-adjusted test of equivalence or ideally a prospective comparative effectiveness study will be necessary to confirm our observations.

Proton spin-lattice relaxation in low-dimensional ferromagnetic copper halides (abstract)

NASA Astrophysics Data System (ADS)

Marzke, R. F.; Haines, D. N.; Raffaelle, D. P.; Chamberlin, R. V.; Ramakrishna, B. L.

1991-04-01

1H spin-lattice relaxation times have been measured as functions of temperature and frequency in powder samples of the two-dimensional ferromagnetic compound (CH3NH3)2CuCl4 and in single crystals of the one-dimensional ferromagnets (C6H11NH3)CuB3 (CHAB), (C6H11NH3)CuCl3 (CHAC), and (C4H12N)CuCl3 (TMCuC). Sample temperatures were varied between 4.2 and 298 K, and NMR frequencies ranging from 12.6 to 54.0 MHz were used. Widths and shapes of the lines, typically several hundred Gauss broad at low temperatures, were recorded. The dependence of T1 upon magnetic field orientation was measured for the one-dimensional (1D) single crystal samples. Each compound showed basically two temperature regimes of different spin-lattice relaxation behavior, separated by a narrow transition temperature region. From 4.2 K, T1 in the compounds decreased strongly as the temperature was raised, a behavior expected for second-order Raman processes [K. M. Kopinga, A. M. C. Tinus, W. J. M. de Jonge, and G. C. de Vries, Phys. Rev. B 36, 5398 (1987)]. At the transition temperature region the decrease of T1 ceased, and T1 began to increase weakly and quasilinearly to 300 K. In the three 1D compounds, the transition regions occurred well below temperatures corresponding to 1D exchange interaction strengths in CHAC (˜70 K), CHAB (˜55 K), and TMCuC (˜30 K), and also above the compounds' 3D ordering temperatures (˜1.5 K and below). We noted a correlation between the T1 transition temperatures and temperatures at which spin dimensionality ``crossovers'' are observed in magnetic susceptibilities, going from Heisenberg to non-Heisenberg behavior as the temperature is decreased. The latter occur at approximately 10 K in CHAC. TMCuC, which has the most isotropic J tensor of these compounds and also the lowest weak-strong T1 transition, does not show a spin dimensionality crossover in susceptibility down to 2 K, but based on our NMR results one would be expected at or below this temperature. Further theoretical work appears to be necessary in order to elucidate the role of magnons and solitons in the transition behavior of the temperature dependence of T1.

Searching for the influence radius of AGN in nearby narrow emission-line galaxies using the CALIFA survey

NASA Astrophysics Data System (ADS)

Robleto-Orús, A. C.; Torres-Papaqui, J. P.; Coziol, R.; Morales-Vargas, A.; Romero-Cruz, F. J.; Ortega-Minakata, R. A.; Chow-Martinez, M.; Trejo-Alonso, J. J.

2017-07-01

In narrow emission-line galaxies, one important problem consists in discriminating gas ionization due to an AGN and gas ionization due to OB stars in active star-forming regions. This problem becomes more acute in case of AGNs classified as transition-type objects (TO), where star formation is relatively intense, and for LINERs, where the AGN is very weak. Thanks to the integral field spectroscopy, we have a new way to attack this problem. By definition, OB stars ionize a definite portion of space, the Strömgren's sphere, which size depends on the total luminosity of the star, its temperature, and the density of the surrounding gas. Therefore one expects gas ionized by OB stars to cover limited areas in a galaxy. On the other hand, due to the huge amount of ionizing photons emitted by an AGN, its "influence radius" is expected do be much more extended, in the order of kpc. Using a sample of galaxies from included in the CALIFA survey DR3, we will test a new way to measure the characteristic "influence radius" of AGN with different intensities.

Impurity-induced photoconductivity of narrow-gap Cadmium–Mercury–Telluride structures

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

Kozlov, D. V., E-mail: dvkoz@impras.ru; Rumyantsev, V. V.; Morozov, S. V.

2015-12-15

The photoconductivity (PC) spectra of CdHgTe (MCT) solid solutions with a Cd fraction of 17 and 19% are measured. A simple model for calculating the states of doubly charged acceptors in MCT solid solutions, which makes it possible to describe satisfactorily the observed photoconductivity spectra, is proposed. The found lines in the photoconductivity spectra of narrow-gap MCT structures are associated with transitions between the states of both charged and neutral acceptor centers.

Turboprop and rotary-wing aircraft flight parameter estimation using both narrow-band and broadband passive acoustic signal-processing methods.

PubMed

Ferguson, B G; Lo, K W

2000-10-01

Flight parameter estimation methods for an airborne acoustic source can be divided into two categories, depending on whether the narrow-band lines or the broadband component of the received signal spectrum is processed to estimate the flight parameters. This paper provides a common framework for the formulation and test of two flight parameter estimation methods: one narrow band, the other broadband. The performances of the two methods are evaluated by applying them to the same acoustic data set, which is recorded by a planar array of passive acoustic sensors during multiple transits of a turboprop fixed-wing aircraft and two types of rotary-wing aircraft. The narrow-band method, which is based on a kinematic model that assumes the source travels in a straight line at constant speed and altitude, requires time-frequency analysis of the acoustic signal received by a single sensor during each aircraft transit. The broadband method is based on the same kinematic model, but requires observing the temporal variation of the differential time of arrival of the acoustic signal at each pair of sensors that comprises the planar array. Generalized cross correlation of each pair of sensor outputs using a cross-spectral phase transform prefilter provides instantaneous estimates of the differential times of arrival of the signal as the acoustic wavefront traverses the array.

Structural phase transition, narrow band gap, and room-temperature ferromagnetism in [KNbO{sub 3}]{sub 1−x}[BaNi{sub 1/2}Nb{sub 1/2}O{sub 3−δ}]{sub x} ferroelectrics

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

Zhou, Wenliang; Yang, Pingxiong, E-mail: pxyang@ee.ecnu.edu.cn; Chu, Junhao

2014-09-15

Structural phase transition, narrow band gap (E{sub g}), and room-temperature ferromagnetism (RTFM) have been observed in the [KNbO{sub 3}]{sub 1−x}[BaNi{sub 1/2}Nb{sub 1/2}O{sub 3−δ}]{sub x} (KBNNO) ceramics. All the samples have single phase perovskite structure, but exhibit a gradual transition behaviour from the orthorhombic to a cubic structure with the increase of x. Raman spectroscopy analysis not only corroborates this doping-induced change in normal structure but also shows the local crystal symmetry for x ≥ 0.1 compositions to deviate from the idealized cubic perovskite structure. A possible mechanism for the observed specific changes in lattice structure is discussed. Moreover, it ismore » noted that KBNNO with compositions x = 0.1–0.3 have quite narrow E{sub g} of below 1.5 eV, much smaller than the 3.2 eV band gap of parent KNbO{sub 3} (KNO), which is due to the increasing Ni 3d electronic states within the gap of KNO. Furthermore, the KBNNO materials present RTFM near a tetragonal to cubic phase boundary. With increasing x from 0 to 0.3, the magnetism of the samples develops from diamagnetism to ferromagnetism and paramagnetism, originating from the ferromagnetic–antiferromagnetic competition. These results are helpful in the deeper understanding of phase transitions, band gap tunability, and magnetism variations in perovskite oxides and show the potential role, such materials can play, in perovskite solar cells and multiferroic applications.« less

Dynamics of magnetic single domain particles embedded in a viscous liquid

NASA Astrophysics Data System (ADS)

Usadel, K. D.; Usadel, C.

2015-12-01

Kinetic equations for magnetic nano particles dispersed in a viscous liquid are developed and analyzed numerically. Depending on the amplitude of an applied oscillatory magnetic field, the particles orient their time averaged anisotropy axis perpendicular to the applied field for low magnetic field amplitudes and nearly parallel to the direction of the field for high amplitudes. The transition between these regions takes place in a narrow field interval. In the low field region, the magnetic moment is locked to some crystal axis and the energy absorption in an oscillatory driving field is dominated by viscous losses associated with particle rotation in the liquid. In the opposite limit, the magnetic moment rotates within the particle while its easy axis being nearly parallel to the external field direction oscillates. The kinetic equations are generalized to include thermal fluctuations. This leads to a significant increase of the power absorption in the low and intermediate field regions with a pronounced absorption peak as function of particle size. In the high field region, on the other hand, the inclusion of thermal fluctuations reduces the power absorption. The illustrative numerical calculations presented are performed for magnetic parameters typical for iron oxide.

A cost-effective strategy for nonoscillatory convection without clipping

NASA Technical Reports Server (NTRS)

Leonard, B. P.; Niknafs, H. S.

1990-01-01

Clipping of narrow extrema and distortion of smooth profiles is a well known problem associated with so-called high resolution nonoscillatory convection schemes. A strategy is presented for accurately simulating highly convective flows containing discontinuities such as density fronts or shock waves, without distorting smooth profiles or clipping narrow local extrema. The convection algorithm is based on non-artificially diffusive third-order upwinding in smooth regions, with automatic adaptive stencil expansion to (in principle, arbitrarily) higher order upwinding locally, in regions of rapidly changing gradients. This is highly cost effective because the wider stencil is used only where needed-in isolated narrow regions. A recently developed universal limiter assures sharp monotonic resolution of discontinuities without introducing artificial diffusion or numerical compression. An adaptive discriminator is constructed to distinguish between spurious overshoots and physical peaks; this automatically relaxes the limiter near local turning points, thereby avoiding loss of resolution in narrow extrema. Examples are given for one-dimensional pure convection of scalar profiles at constant velocity.

Ultrafast Silicon-based Modulators using Optical Switching of Vanadium Dioxide

DTIC Science & Technology

2014-12-04

demonstrated by using photothermal heating to induce the VO2 semiconductor-to- metal phase transition and modulate the transmitted optical signal...speeds. By utilizing the sub-picosecond semiconductor-to- metal transition (SMT) in VO2 as the active switching mechanism that enables direct... metallic phases. The steep slope, high contrast, and relatively narrow hysteresis exhibited by these reflectivity measurements indicate the high quality

Electrical Switching in Semiconductor-Metal Self-Assembled VO2 Disordered Metamaterial Coatings

PubMed Central

Kumar, Sunil; Maury, Francis; Bahlawane, Naoufal

2016-01-01

As a strongly correlated metal oxide, VO2 inspires several highly technological applications. The challenging reliable wafer-scale synthesis of high quality polycrystalline VO2 coatings is demonstrated on 4” Si taking advantage of the oxidative sintering of chemically vapor deposited VO2 films. This approach results in films with a semiconductor-metal transition (SMT) quality approaching that of the epitaxial counterpart. SMT occurs with an abrupt electrical resistivity change exceeding three orders of magnitude with a narrow hysteresis width. Spatially resolved infrared and Raman analyses evidence the self-assembly of VO2 disordered metamaterial, compresing monoclinic (M1 and M2) and rutile (R) domains, at the transition temperature region. The M2 mediation of the M1-R transition is spatially confined and related to the localized strain-stabilization of the M2 phase. The presence of the M2 phase is supposed to play a role as a minor semiconducting phase far above the SMT temperature. In terms of application, we show that the VO2 disordered self-assembly of M and R phases is highly stable and can be thermally triggered with high precision using short heating or cooling pulses with adjusted strengths. Such a control enables an accurate and tunable thermal control of the electrical switching. PMID:27883052

Magnetostratigraphy, paleomagnetic correlation, and deformation of pleistocene deposits in the south central Puget Lowland, Washington

USGS Publications Warehouse

Hagstrum, J.T.; Booth, D.B.; Troost, K.G.; Blakely, R.J.

2002-01-01

Paleomagnetic results from Pleistocene sedimentary deposits in the central Puget Lowland indicate that the region has experienced widespread deformation within the last 780 kyr. Three oriented samples were collected from unaltered fine-grained sediments mostly at sea level to determine the magnetostratigraphy at 83 sites. Of these, 47 have normal, 18 have reversed, and 18 have transitional (8 localities) polarities. Records of reversed- to normal-polarity transitions of the geomagnetic field were found in thick sections of silt near the eastern end of the Tacoma Narrows Bridge, and again at Wingehaven Park near the northern tip of Vashon Island. The transitional horizons, probably related to the Bruhnes-Matuyama reversal, apparently fall between previously dated Pleistocene sediments at the Puyallup Valley type section (all reversed-polarity) to the south and the Whidbey Island type section (all normal-polarity) to the north. The samples, in general, are of sufficient quality to record paleosecular variation (PSV) of the geomagnetic field, and a statistical technique is used to correlate horizons with significant agreement in their paleomagnetic directions. Our data are consistent with the broad structures of the Seattle uplift inferred at depth from seismic reflection, gravity, and aeromagnetic profiles, but the magnitude of vertical adjustments is greatly subdued in the Pleistocene deposits.

IDA Gamma-Ray Laser Annual Summary Report (1985). Investigation of the Feasibility of Developing a Laser Using Nuclear Transitions. Revised.

DTIC Science & Technology

1986-06-01

beams of coherent radiation whose short wavelengths would permit greater penetration of matter than is possible with current laser sources. With that...nuclear linewidth. It is claimed that the time required for any narrowing is at least as long as the inverse of the linewidth achieved, no matter what...with the re- quired narrow line can be prepared is a different matter . The point is that the previous uncertainty principle does not forbid the

Design and Simulation of Optically Actuated Bistable MEMS

NASA Astrophysics Data System (ADS)

Lucas, Thomas; Moiseeva, Evgeniya; Harnett, Cindy

2012-02-01

In this project, bistable three-dimensional MEMS actuators are designed to be optically switched between stable states for biological research applications. The structure is a strained rectangular frame created with stress-mismatched metal-oxide bilayers. The devices curl into an arc in one of two directions tangent to the substrate, and can switch orientation when regions are selectively heated. The heating is powered by infrared laser, and localized with patterned infrared-resonant gold nanoparticles on critical regions. The enhanced energy absorption on selected areas provides switching control and heightened response to narrow-band infrared light. Coventorware has been used for finite element analysis of the system. The numerical simulations indicate that it has two local minimum states with extremely rapid transition time (<<0.1 s) when the structure is thermally deformed. Actuation at laser power and thermal limits compatible with physiological applications will enable microfluidic pumping elements and fundamental studies of tissue response to three-dimensional mechanical stimuli, artificial-muscle based pumps and other biomedical devices triggered by tissue-permeant infrared light.

Probing the conditions within Photo-dissociation Regions with high resolution near-infrared spectroscopy of UV-excited molecular hydrogen

NASA Astrophysics Data System (ADS)

Kaplan, Kyle; Dinerstein, Harriet L.; Jaffe, Daniel Thomas

2017-01-01

UV radiation regulates the energetics, ionization, and chemistry in much of the ISM. Regions between hot ionized and cool molecular gas where non-ionizing far-UV radiation dominates the state of the gas are called Photo-Dissociation or Photon-Dominated Regions (PDRs). PDRs are found in regions of high-mass star formation, planetary nebulae, and other environments that contain strong far-UV radiation fields. Hydrogen molecules (H2) are pumped by far-UV photons into excited rotational-vibrational levels of the ground electronic state, which give rise to a rich array of transitions in the near to mid-infrared. These transitions make an excellent probe of the physical conditions within a PDR. I will present near-IR spectra taken with the Immersion GRating Infrared Spectrometer (IGRINS; Park et al. 2014, Proc. SPIE, 9147), a novel, sensitive spectrometer with high spectral resolving power (R~45000) and instantaneous broad wavelength coverage (1.45-2.45 μm). Using IGRINS, I obtained deep spectra and measured up to 100 H2 rotational-vibrational transitions in the well-studied Orion Bar PDR, four other star formation complexes, and over a dozen planetary nebulae. Measurements of many lines from a wide range of vibrational states (v=1 to 13), rotational states (J=1 to 13), and excitation energies provides leverage for constraining the overall level populations and discerning the state of and physical processes within the gas. This combination of high spectral and spatial resolution enables us to distinguish previously unresolved spatio-kinematical components with distinct intrinsic spectra and excitation mechanisms (e.g. shocks vs. radiative excitation) within some individual planetary nebulae. I use the plasma simulation code Cloudy (Ferland et al. 2013, ApJ, 757, 79) as a tool for interpreting the observed H2 line ratios. Some sources are well fit by models with a single temperature and density, consistent with emission from a narrow region of the overall PDR structure. Populations of certain levels are more sensitive than others to specific physical parameters such as gas kinetic temperature or density.I acknowledge support from the following grants: NSF 1229522, NSF 0708245, and JPL RSA 1427884.

Current driven transition from Abrikosov-Josephson to Josephson-like vortex in mesoscopic lateral S/S’/S superconducting weak links

PubMed Central

Carapella, G.; Sabatino, P.; Barone, C.; Pagano, S.; Gombos, M.

2016-01-01

Vortices are topological defects accounting for many important effects in superconductivity, superfluidity, and magnetism. Here we address the stability of a small number of such excitations driven by strong external forces. We focus on Abrikosov-Josephson vortex that appears in lateral superconducting S/S’/S weak links with suppressed superconductivity in S’. In such a system the vortex is nucleated and confined in the narrow S’ region by means of a small magnetic field and moves under the effect of a force proportional to an applied electrical current with a velocity proportional to the measured voltage. Our numerical simulations show that when a slow moving Abrikosov-Josephson vortex is driven by a strong constant current it becomes unstable with respect to a faster moving excitation: the Josephon-like vortex. Such a current-driven transition explains the structured dissipative branches that we observe in the voltage-current curve of the weak link. When vortex matter is strongly confined phenomena as magnetoresistance oscillations and reentrance of superconductivity can possibly occur. We experimentally observe these phenomena in our weak links. PMID:27752137

Three-Dimensional Rheological Structure of North China Craton Determined by Integration of Multiple observations: Controlling Role for Lithospheric Rifting

NASA Astrophysics Data System (ADS)

Xiong, X.; Shan, B.; Li, Y.

2017-12-01

The North China Craton (NCC) has undergone significant lithospheric rejuvenation in late Mesozoic and Cenozoic, one feature of which is the widespread extension and rifting. The extension is distinct between the two parts of NCC: widespread rifting in the eastern NCC and localized narrow rifting in the west. The mechanism being responsible for this difference is uncertain and highly debated. Since lithospheric deformation can be regarded as the response of lithosphere to various dynamic actions, the rheological properties of lithosphere must have a fundamental influence on its tectonics and deformation behavior. In this study, we investigated the 3D thermal and rheological structure of NCC by developing a model integrating several geophysical observables (such as surface heatflow, regional elevation, gravity and geoid anomalies, and seismic tomography models). The results exhibit obvious lateral variation in rheological structure between the eastern and western NCC. The overall lithospheric strength is higher in the western NCC than in the east. Despite of such difference in rheology, both parts of NCC are characterized by mantle dominated strength regime, which facilitates the development of narrow rifting. Using ancient heatflow derived from mantle xenoliths studies, and taking the subduction-related dehydration reactions during Mesozoic into account, we constructed the thermal and rheological structure of NCC in Ordovician, early Cretaceous and early Cenozoic. Combining the evidence from numerical simulations, we proposed an evolution path of the rifting in NCC. The lithosphere of NCC in Ordovician was characterized by a normal craton features: low geotherm, high strength and mantle dominated regime. During Jurassic and Cretaceous, the mantle lithosphere in the eastern NCC was hydrated by fluid released by the suduction of the Pacific plate, resulting in weakening of the lithosphere and a transition from mantle dominated to crust dominated regime, which facilitated the development of metamorphic core complex extension. The rifting in eastern NCC experienced a further transition to the wide rifting style under a low strain rate environment during early Cenozoic. In contrast, the western NNC has been kept mantle dominated regime, leading to a localized narrow rifting.

Microstructure and Mechanical Properties of Narrow Gap Laser-Arc Hybrid Welded 40 mm Thick Mild Steel.

PubMed

Zhang, Chen; Li, Geng; Gao, Ming; Zeng, XiaoYan

2017-01-26

Both laser-arc hybrid welding and narrow gap welding have potential for the fabrication of thick sections, but their combination has been seldom studied. In this research, 40 mm thick mild steel was welded by narrow gap laser-arc hybrid welding. A weld with smooth layer transition, free of visible defects, was obtained by nine passes at a 6 mm width narrow gap. The lower part of the weld has the lowest mechanical properties because of the lowest amount of acicular ferrite, but its ultimate tensile strength and impact absorbing energy is still 49% and 60% higher than those of base metal, respectively. The microhardness deviation of all filler layers along weld thickness direction is no more than 15 HV 0.2 , indicating that no temper softening appeared during multiple heat cycles. The results provide an alternative technique for improving the efficiency and quality of welding thick sections.

Microstructure and Mechanical Properties of Narrow Gap Laser-Arc Hybrid Welded 40 mm Thick Mild Steel

PubMed Central

Zhang, Chen; Li, Geng; Gao, Ming; Zeng, XiaoYan

2017-01-01

Both laser-arc hybrid welding and narrow gap welding have potential for the fabrication of thick sections, but their combination has been seldom studied. In this research, 40 mm thick mild steel was welded by narrow gap laser-arc hybrid welding. A weld with smooth layer transition, free of visible defects, was obtained by nine passes at a 6 mm width narrow gap. The lower part of the weld has the lowest mechanical properties because of the lowest amount of acicular ferrite, but its ultimate tensile strength and impact absorbing energy is still 49% and 60% higher than those of base metal, respectively. The microhardness deviation of all filler layers along weld thickness direction is no more than 15 HV0.2, indicating that no temper softening appeared during multiple heat cycles. The results provide an alternative technique for improving the efficiency and quality of welding thick sections. PMID:28772469

Narrowband diode laser pump module for pumping alkali vapors.

PubMed

Rotondaro, M D; Zhdanov, B V; Shaffer, M K; Knize, R J

2018-04-16

We describe a method of line narrowing and frequency-locking a diode laser stack to an alkali atomic line for use as a pump module for Diode Pumped Alkali Lasers. The pump module consists of a 600 W antireflection coated diode laser stack configured to lase using an external cavity. The line narrowing and frequency locking is accomplished by introducing a narrowband polarization filter based on magneto-optical Faraday effect into the external cavity, which selectively transmits only the frequencies that are in resonance with the 6 2 S 1/2 → 6 2 P 3/2 transition of Cs atoms. The resulting pump module has demonstrated that a diode laser stack, which lases with a line width of 3 THz without narrowbanding, can be narrowed to 10 GHz. The line narrowed pump module produced 518 Watts that is 80% of the power generated by the original broadband diode laser stack.

Spontaneous emission near the edge of a photonic band gap

NASA Astrophysics Data System (ADS)

John, Sajeev; Quang, Tran

1994-08-01

The spectral and dynamical features of spontaneous emission from two and three-level atoms in which one transition frequency lay near the edge of a photonic band gap (PBG) were derived. These features included temporal oscillations, fractionalized steady-state atomic population on the excited state, spectral splitting and subnatural bandwidth. The effect of N-1 unexcited atoms were also taken into account. The direct consequences of photon localization as embodied in the photon-atom bound state were observed. One feasible experimental accomplishment of these effects may ensue from laser-cooled atoms in the void regions of a PBG medium. Another option is the application of an organic impurity molecule such as pentacene. Such molecules were known to show extremely narrow linewidths when placed in fitting solid hosts.

Neutron detection using a current biased kinetic inductance detector

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

Shishido, Hiroaki, E-mail: shishido@pe.osakafu-u.ac.jp; Miyajima, Shigeyuki; Ishida, Takekazu

2015-12-07

We demonstrate neutron detection using a solid state superconducting current biased kinetic inductance detector (CB-KID), which consists of a superconducting Nb meander line of 1 μm width and 40 nm thickness. {sup 10}B-enriched neutron absorber layer of 150 nm thickness is placed on top of the CB-KID. Our neutron detectors are able to operate in a wide superconducting region in the bias current–temperature diagram. This is in sharp contrast with our preceding current-biased transition edge detector, which can operate only in a narrow range just below the superconducting critical temperature. The full width at half maximum of the signals remains of the ordermore » of a few tens of ns, which confirms the high speed operation of our detectors.« less

The red edge in arid region vegetation: 340-1060 nm spectra

NASA Technical Reports Server (NTRS)

Ray, Terrill W.; Murray, Bruce C.; Chehbouni, A.; Njoku, Eni

1993-01-01

The remote sensing study of vegetated regions of the world has typically been focused on the use of broad-band vegetation indices such as NDVI. Various modifications of these indices have been developed in attempts to minimize the effect of soil background, e.g., SAVI, or to reduce the effect of the atmosphere, e.g., ARVI. Most of these indices depend on the so-called 'red edge,' the sharp transition between the strong absorption of chlorophyll pigment in visible wavelengths and the strong scattering in the near-infrared from the cellular structure of leaves. These broadband indices tend to become highly inaccurate as the green canopy cover becomes sparse. The advent of high spectral resolution remote sensing instrument such as the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) has allowed the detection of narrow spectral features in vegetation and there are reports of detection of the red edge even for pixels with very low levels of green vegetation cover by Vane et al. and Elvidge et al., and to characterize algal biomass in coastal areas. Spectral mixing approaches similar to those of Smith et al. can be extended into the high spectral resolution domain allowing for the analysis of more endmembers, and potentially, discrimination between material with narrow spectral differences. Vegetation in arid regions tends to be sparse, often with small leaves such as the creosote bush. Many types of arid region vegetation spend much of the year with their leaves in a senescent state, i.e., yellow, with lowered chlorophyll pigmentation. The sparseness of the leaves of many arid region plants has the dual effect of lowering the green leaf area which can be observed and of allowing more of the sub-shrub soil to be visible which further complicates the spectrum of a region covered with arid region vegetation. Elvidge examined the spectral characteristics of dry plant materials showing significant differences in the region of the red edge and the diagnostic ligno-cellulose absorptions at 2090 nm and 2300 nm. Ray et al. detected absorption at 2100 nm in AVIRIS spectra of an abandoned field known to be covered by a great deal of dead plant litter. In order to better study arid region vegetation remote sensing data, it is necessary to better characterize the reflectance spectra of in situ, living, arid region plants.

Prospects for a Measurement of Parity-Violating Photoproduction of π^± on the Δ-resonance Using the G^0 Spectrometer

NASA Astrophysics Data System (ADS)

Martin, Jeffery W.

2002-04-01

Recent calculations of parity-violating (PV) electroproduction asymmetries for the NarrowΔ transition and for quasi-elastic electron scattering on the deuteron have led theorists to consider the photoproduction limit of these processes. In the case of the NarrowΔ transition, it has been proposed that the PV π^± photoproduction asymmetry A_γ^± might be of order 10-6, from a model based on hyperon weak radiative decays. An accurate measurement of A_γ^± would tightly constrain that model, at the same time reducing the dominant theoretical uncertainty in calculations of the PV NarrowΔ asymmetry at non-zero Q^2. Estimates for the G^0 experiment at Jefferson Lab for a measurement of A_γ^± will be presented. A measurement of π^- production from deuterium should yield a 47% measurement of A_γ^±, assuming the best theory estimate for A_γ^±. This measurement would be parasitic to a low-energy run that is already planned. Improvements to this accuracy would require tuning the spectrometer for maximum acceptance of pions and/or luminosity upgrades for photoproduction. Possibilities for such improvements will be discussed.

Magnetic states, correlation effects and metal-insulator transition in FCC lattice

NASA Astrophysics Data System (ADS)

Timirgazin, M. A.; Igoshev, P. A.; Arzhnikov, A. K.; Irkhin, V. Yu

2016-12-01

The ground-state magnetic phase diagram (including collinear and spiral states) of the single-band Hubbard model for the face-centered cubic lattice and related metal-insulator transition (MIT) are investigated within the slave-boson approach by Kotliar and Ruckenstein. The correlation-induced electron spectrum narrowing and a comparison with a generalized Hartree-Fock approximation allow one to estimate the strength of correlation effects. This, as well as the MIT scenario, depends dramatically on the ratio of the next-nearest and nearest electron hopping integrals {{t}\\prime}/t . In contrast with metallic state, possessing substantial band narrowing, insulator one is only weakly correlated. The magnetic (Slater) scenario of MIT is found to be superior over the Mott one. Unlike simple and body-centered cubic lattices, MIT is the first order transition (discontinuous) for most {{t}\\prime}/t . The insulator state is type-II or type-III antiferromagnet, and the metallic state is spin-spiral, collinear antiferromagnet or paramagnet depending on {{t}\\prime}/t . The picture of magnetic ordering is compared with that in the standard localized-electron (Heisenberg) model.

Characterization of adsorbed water in MIL-53(Al) by FTIR spectroscopy and ab-initio calculations.

PubMed

Salazar, J M; Weber, G; Simon, J M; Bezverkhyy, I; Bellat, J P

2015-03-28

Here, we report ab-initio calculations developed with a twofold purpose: understand how adsorbed water molecules alter the infrared spectrum of the metal-organic framework MIL-53(Al) and to investigate which are the associated physico-chemical processes. The analyzed structures are the two anhydrous narrow (np⊘) and large (lp⊘) pore forms and the hydrated narrow pore form (np-H2O) of the MIL-53(Al). For these structures, we determined their corresponding infrared spectra (FTIR) and we identified the vibrational modes associated to the dominant spectral lines. We show that wagging and scissoring modes of CO2 give flexibility to the structure for facilitating the lp⊘- np⊘ transition. In our studies, this transition is identified by eight vibrational modes including the δCH(18a) vibrational mode currently used to identify the mentioned transition. We report an exhaustive band identification of the infrared spectra associated to the analyzed structures. Moreover, the FTIR for the np-H2O structure allowed us to identify four types of water molecules linked to the host structure by one to three hydrogen bonds.

Amplitude equation and long-range interactions in underwater sand ripples in one dimension

NASA Astrophysics Data System (ADS)

Schnipper, Teis; Mertens, Keith; Ellegaard, Clive; Bohr, Tomas

2008-10-01

We present an amplitude equation for sand ripples under oscillatory flow in a situation where the sand is moving in a narrow channel and the height profile is practically one dimensional. The equation has the form ht=-γ(h- hmacr )+((hx)2-1)hxx-hxxxx+δ((hx)2)xx which, due to the first term, is neither completely local (it has long-range coupling through the average height hmacr ) nor has local sand conservation. We argue that this is reasonable and show that the equation compares well with experimental observations in narrow channels. We focus in particular on the so-called doubling transition, a secondary instability caused by the sudden decrease in the amplitude of the water motion, leading to the appearance of a new ripple in each trough. This transition is well reproduced for sufficiently large δ (asymmetry between trough and crest). We finally present surprising experimental results showing that long-range coupling is indeed seen in the initial details of the doubling transition, where in fact two small ripples are initially formed, followed by global symmetry breaking removing one of them.

Hierarchical Bayesian calibration of tidal orbit decay rates among hot Jupiters

NASA Astrophysics Data System (ADS)

Collier Cameron, Andrew; Jardine, Moira

2018-05-01

Transiting hot Jupiters occupy a wedge-shaped region in the mass ratio-orbital separation diagram. Its upper boundary is eroded by tidal spiral-in of massive, close-in planets and is sensitive to the stellar tidal dissipation parameter Q_s^'. We develop a simple generative model of the orbital separation distribution of the known population of transiting hot Jupiters, subject to tidal orbital decay, XUV-driven evaporation and observational selection bias. From the joint likelihood of the observed orbital separations of hot Jupiters discovered in ground-based wide-field transit surveys, measured with respect to the hyperparameters of the underlying population model, we recover narrow posterior probability distributions for Q_s^' in two different tidal forcing frequency regimes. We validate the method using mock samples of transiting planets with known tidal parameters. We find that Q_s^' and its temperature dependence are retrieved reliably over five orders of magnitude in Q_s^'. A large sample of hot Jupiters from small-aperture ground-based surveys yields log _{10} Q_s^' }=(8.26± 0.14) for 223 systems in the equilibrium-tide regime. We detect no significant dependence of Q_s^' on stellar effective temperature. A further 19 systems in the dynamical-tide regime yield log _{10} Q_s^' }=7.3± 0.4, indicating stronger coupling. Detection probabilities for transiting planets at a given orbital separation scale inversely with the increase in their tidal migration rates since birth. The resulting bias towards younger systems explains why the surface gravities of hot Jupiters correlate with their host stars' chromospheric emission fluxes. We predict departures from a linear transit-timing ephemeris of less than 4 s for WASP-18 over a 20-yr baseline.

Upside-Down Subduction of the Farallon Slab and the Origin of Yellowstone Volcanism from Finite-Frequency Tomography of USArray Receiver Functions

NASA Astrophysics Data System (ADS)

Zhou, Y.

2017-12-01

The origin of the Yellowstone and Snake River Plain volcanic track stretching over 600 km from Northwest Wyoming to the Idaho-Oregon border has been strongly debated. The most widely accepted interpretation involves the North America plate moving over a stationary narrow plume of hot materials rising up from the lowermost mantle. The plume model successfully explains the age-progressive volcanic track and high ratios of Helium-3/Helium-4 isotope observed in the basaltic volcanism but such a deep mantle plume has been long missing in seismic imaging. In this study, we apply a newly developed finite-frequency imaging method to receiver functions recorded at USArray stations to map the topography of two seismic discontinuities in the mantle, the 410-km and the 660-km discontinuity. The new images reveal a trail of anomalies within a previously imaged wavespeed slab gap and closely follow the surface volcanic track. This observation contradicts the plume model which requires anomalies at those depths to be confined in a narrow region directly beneath the present-day Yellowstone caldera. We propose an alternative interpretation of the Yellowstone volcanism as a result of an upside-down subduction of the stagnant oceanic Farallon plate in the Western US. This upside-down episode of subduction started about 16 million years ago in the mantle transition zone, where the younger slab beneath Oregon and Idaho penetrated the 660-km discontinuity, pulling down older stagnant slab. The upside-down subduction propagated north-westward and generated passive upwellings from the lower mantle, ascending through a water-rich mantle transition zone, producing melting and age-progressive volcanism.

Autosomal and X-linked single nucleotide polymorphisms reveal a steep Asian-Melanesian ancestry cline in eastern Indonesia and a sex bias in admixture rates.

PubMed

Cox, Murray P; Karafet, Tatiana M; Lansing, J Stephen; Sudoyo, Herawati; Hammer, Michael F

2010-05-22

The geographical region between mainland Asia and New Guinea is characterized by numerous small islands with isolated human populations. Phenotypically, groups in the west are similar to their neighbours in mainland Southeast Asia, eastern groups near New Guinea are similar to Melanesians, and intervening populations are intermediate in appearance. A long-standing question is whether this pattern primarily reflects mixing between groups with distinct origins or whether natural selection has shaped this range of variation by acting differentially on populations across the region. To address this question, we genotyped a set of 37 single nucleotide polymorphisms that are evolutionarily independent, putatively neutral and highly informative for Asian-Melanesian ancestry in 1430 individuals from 60 populations spanning mainland Asia to Melanesia. Admixture analysis reveals a sharp transition from Asian to Melanesian genetic variants over a narrow geographical region in eastern Indonesia. Interestingly, this admixture cline roughly corresponds to the human phenotypic boundary noted by Alfred Russell Wallace in 1869. We conclude that this phenotypic gradient probably reflects mixing of two long-separated ancestral source populations-one descended from the initial Melanesian-like inhabitants of the region, and the other related to Asian groups that immigrated during the Paleolithic and/or with the spread of agriculture. A higher frequency of Asian X-linked markers relative to autosomal markers throughout the transition zone suggests that the admixture process was sex-biased, either favouring a westward expansion of patrilocal Melanesian groups or an eastward expansion of matrilocal Asian immigrants. The matrilocal marriage practices that dominated early Austronesian societies may be one factor contributing to this observed sex bias in admixture rates.

Autosomal and X-linked single nucleotide polymorphisms reveal a steep Asian–Melanesian ancestry cline in eastern Indonesia and a sex bias in admixture rates

PubMed Central

Cox, Murray P.; Karafet, Tatiana M.; Lansing, J. Stephen; Sudoyo, Herawati; Hammer, Michael F.

2010-01-01

The geographical region between mainland Asia and New Guinea is characterized by numerous small islands with isolated human populations. Phenotypically, groups in the west are similar to their neighbours in mainland Southeast Asia, eastern groups near New Guinea are similar to Melanesians, and intervening populations are intermediate in appearance. A long-standing question is whether this pattern primarily reflects mixing between groups with distinct origins or whether natural selection has shaped this range of variation by acting differentially on populations across the region. To address this question, we genotyped a set of 37 single nucleotide polymorphisms that are evolutionarily independent, putatively neutral and highly informative for Asian–Melanesian ancestry in 1430 individuals from 60 populations spanning mainland Asia to Melanesia. Admixture analysis reveals a sharp transition from Asian to Melanesian genetic variants over a narrow geographical region in eastern Indonesia. Interestingly, this admixture cline roughly corresponds to the human phenotypic boundary noted by Alfred Russell Wallace in 1869. We conclude that this phenotypic gradient probably reflects mixing of two long-separated ancestral source populations—one descended from the initial Melanesian-like inhabitants of the region, and the other related to Asian groups that immigrated during the Paleolithic and/or with the spread of agriculture. A higher frequency of Asian X-linked markers relative to autosomal markers throughout the transition zone suggests that the admixture process was sex-biased, either favouring a westward expansion of patrilocal Melanesian groups or an eastward expansion of matrilocal Asian immigrants. The matrilocal marriage practices that dominated early Austronesian societies may be one factor contributing to this observed sex bias in admixture rates. PMID:20106848

Design and Test of Passively Operated Heat Switches for 0.2 to 15 K

NASA Technical Reports Server (NTRS)

DiPirro, M. J.; Shirron, P. J.; Canavan, E. R.; Francis, J. J.; Tuttle, J. G.

2003-01-01

Heat switches have many uses in cryogenics, from regulating heat flow between refrigeration stages to thermally isolating components once they have cooled to low temperature. Among the techniques one can use for thermal switching, the gas-gap technique has the advantages of wide operating temperature range, high switching ratio, and no moving parts. The traditional gas-gap switch uses copper conductors separated by a small gap and an external getter. The switch is activated by heating and cooling the getter by moving gas into and out of the gap, turning the switch on and off. We have designed, built and tested heat switches that use an internal getter to passively turn off at temperatures between 0.2 and 15 K. The getter is thermally anchored to one side of the switch, and when that side of the switch cools through a transition region, gas adsorbs onto the getter and the switch turns off. The challenges are to make the transition region very narrow and tailorable to a wide range of applications, and to achieve high gas conductance when the switch is on. We have made switches using He-3, He-4, hydrogen, and neon gas, and have used charcoal and various metal substrates as getters. Switching ratios range from 1000 to over 10,000. Design and performance of these switches will be discussed in detail.

Narrow Networks on the Individual Marketplace in 2017.

PubMed

Polski, Daniel; Weiner, Janet; Zhang, Yuehan

2017-09-01

This Issue Brief describes the breadth of physician networks on the ACA marketplaces in 2017. We find that the overall rate of narrow networks is 21%, which is a decline since 2014 (31%) and 2016 (25%). Narrow networks are concentrated in plans sold on state-based marketplaces, at 42%, compared to 10% of plans on federally-facilitated marketplaces. Issuers that have traditionally offered Medicaid coverage have the highest prevalence of narrow network plans at 36%, with regional/local plans and provider-based plans close behind at 27% and 30%. We also find large differences in narrow networks by state and by plan type.

Small airway obstruction in COPD: new insights based on micro-CT imaging and MRI imaging.

PubMed

Hogg, James C; McDonough, John E; Suzuki, Masaru

2013-05-01

The increase in total cross-sectional area in the distal airways of the human lung enhances the mixing of each tidal breath with end-expiratory gas volume by slowing bulk flow and increasing gas diffusion. However, this transition also favors the deposition of airborne particulates in this region because they diffuse 600 times slower than gases. Furthermore, the persistent deposition of toxic airborne particulates stimulates a chronic inflammatory immune cell infiltration and tissue repair and remodeling process that increases the resistance in airways <2 mm in diameter four to 40-fold in COPD. This increase was originally attributed to lumen narrowing because it increases resistance in proportion to the change in lumen radius raised to the fourth power. In contrast, removal of one-half the number of tubes arranged in parallel is required to double their resistance, and approximately 90% need to be removed to explain the increase in resistance measured in COPD. However, recent reexamination of this problem based on micro-CT imaging indicates that terminal bronchioles are both narrowed and reduced to 10% of the control values in the centrilobular and 25% in the panlobular emphysematous phenotype of very severe (GOLD [Global Initiative for Chronic Obstructive Lung Disease] grade IV) COPD. These new data indicate that both narrowing and reduction in numbers of terminal bronchioles contribute to the rapid decline in FEV₁ that leads to severe airway obstruction in COPD. Moreover, the observation that terminal bronchiolar loss precedes the onset of emphysematous destruction suggests this destruction begins in the very early stages of COPD.

Small Airway Obstruction in COPD

PubMed Central

McDonough, John E.; Suzuki, Masaru

2013-01-01

The increase in total cross-sectional area in the distal airways of the human lung enhances the mixing of each tidal breath with end-expiratory gas volume by slowing bulk flow and increasing gas diffusion. However, this transition also favors the deposition of airborne particulates in this region because they diffuse 600 times slower than gases. Furthermore, the persistent deposition of toxic airborne particulates stimulates a chronic inflammatory immune cell infiltration and tissue repair and remodeling process that increases the resistance in airways <2 mm in diameter four to 40-fold in COPD. This increase was originally attributed to lumen narrowing because it increases resistance in proportion to the change in lumen radius raised to the fourth power. In contrast, removal of one-half the number of tubes arranged in parallel is required to double their resistance, and approximately 90% need to be removed to explain the increase in resistance measured in COPD. However, recent reexamination of this problem based on micro-CT imaging indicates that terminal bronchioles are both narrowed and reduced to 10% of the control values in the centrilobular and 25% in the panlobular emphysematous phenotype of very severe (GOLD [Global Initiative for Chronic Obstructive Lung Disease] grade IV) COPD. These new data indicate that both narrowing and reduction in numbers of terminal bronchioles contribute to the rapid decline in FEV1 that leads to severe airway obstruction in COPD. Moreover, the observation that terminal bronchiolar loss precedes the onset of emphysematous destruction suggests this destruction begins in the very early stages of COPD. PMID:23648907

Metastable State during Melting and Solid-Solid Phase Transition of [CnMim][NO3] (n = 4-12) Ionic Liquids by Molecular Dynamics Simulation.

PubMed

Cao, Wudi; Wang, Yanting; Saielli, Giacomo

2018-01-11

We simulate the heating process of ionic liquids [C n Mim][NO 3 ] (n = 4, 6, 8, 10, 12), abbreviated as C n , by means of molecular dynamics (MD) simulation starting from a manually constructed triclinic crystal structure composed of polar layers containing anions and cationic head groups and nonpolar regions in between containing cationic alkyl side chains. During the heating process starting from 200 K, each system undergoes first a solid-solid phase transition at a lower temperature, and then a melting phase transition at a higher temperature to an isotropic liquid state (C 4 , C 6 , and C 8 ) or to a liquid crystal state (C 10 and C 12 ). After the solid-solid phase transition, all systems keep the triclinic space symmetry, but have a different set of lattice constants. C 4 has a more significant structural change in the nonpolar regions which narrows the layer spacing, while the layer spacings of other systems change little, which can be qualitatively understood by considering that the contribution of the effective van der Waals interaction in the nonpolar regions (abbreviated as EF1) to free energy becomes stronger with increasing side-chain length, and at the same time the contribution of the effective electrostatic interaction in the polar layers (abbreviated as EF2) to free energy remains almost the same. The melting phase transitions of all systems except C 6 are found to be a two-step process with an intermediate metastable state appeared during the melting from the crystal state to the liquid or liquid crystal state. Because the contribution of EF2 to the free energy is larger than EF1, the metastable state of C 4 has the feature of having higher ordered polar layers and lower ordered side-chain orientation. By contrast, C 8 -C 12 have the feature of having lower ordered polar layers and higher ordered side-chain orientation, because for these systems, the contribution of EF2 to the free energy is smaller than EF1. No metastable state is found for C 6 because the free-energy contribution of EF1 is balanced with EF2.

Squeezing on Momentum States for Atom Interferometry.

PubMed

Salvi, Leonardo; Poli, Nicola; Vuletić, Vladan; Tino, Guglielmo M

2018-01-19

We propose and analyze a method that allows for the production of squeezed states of the atomic center-of-mass motion that can be injected into an atom interferometer. Our scheme employs dispersive probing in a ring resonator on a narrow transition in order to provide a collective measurement of the relative population of two momentum states. We show that this method is applicable to a Bragg diffraction-based strontium atom interferometer with large diffraction orders. This technique can be extended also to small diffraction orders and large atom numbers N by inducing atomic transparency at the frequency of the probe field, reaching an interferometer phase resolution scaling Δϕ∼N^{-3/4}. We show that for realistic parameters it is possible to obtain a 20 dB gain in interferometer phase estimation compared to the standard quantum limit. Our method is applicable to other atomic species where a narrow transition is available or can be synthesized.

X-ray frequency combs from optically controlled resonance fluorescence

NASA Astrophysics Data System (ADS)

Cavaletto, Stefano M.; Harman, Zoltán; Buth, Christian; Keitel, Christoph H.

2013-12-01

An x-ray pulse-shaping scheme is put forward for imprinting an optical frequency comb onto the radiation emitted on a driven x-ray transition, thus producing an x-ray frequency comb. A four-level system is used to describe the level structure of N ions driven by narrow-bandwidth x rays, an optical auxiliary laser, and an optical frequency comb. By including many-particle enhancement of the emitted resonance fluorescence, a spectrum is predicted consisting of equally spaced narrow lines which are centered on an x-ray transition energy and separated by the same tooth spacing as the driving optical frequency comb. Given an x-ray reference frequency, our comb could be employed to determine an unknown x-ray frequency. While relying on the quality of the light fields used to drive the ensemble of ions, the model has validity at energies from the 100 eV to the keV range.

Anatomy, feeding ecology, and ontogeny of a transitional baleen whale: a new genus and species of Eomysticetidae (Mammalia: Cetacea) from the Oligocene of New Zealand

PubMed Central

Fordyce, R. Ewan

2015-01-01

The Eocene history of cetacean evolution is now represented by the expansive fossil record of archaeocetes elucidating major morphofunctional shifts relating to the land to sea transition, but the change from archaeocetes to modern cetaceans is poorly established. New fossil material of the recently recognized family Eomysticetidae from the upper Oligocene Otekaike Limestone includes a new genus and species, Waharoa ruwhenua, represented by skulls and partial skeletons of an adult, juvenile, and a smaller juvenile. Ontogenetic status is confirmed by osteohistology of ribs. Waharoa ruwhenua is characterized by an elongate and narrow rostrum which retains vestigial alveoli and alveolar grooves. Palatal foramina and sulci are present only on the posterior half of the palate. The nasals are elongate, and the bony nares are positioned far anteriorly. Enormous temporal fossae are present adjacent to an elongate and narrow intertemporal region with a sharp sagittal crest. The earbones are characterized by retaining inner and outer posterior pedicles, lacking fused posterior processes, and retaining a separate accessory ossicle. Phylogenetic analysis supports inclusion of Waharoa ruwhenua within a monophyletic Eomysticetidae as the earliest diverging clade of toothless mysticetes. This eomysticetid clade also included Eomysticetus whitmorei, Micromysticetus rothauseni, Tohoraata raekohao, Tokarahia kauaeroa, Tokarahia lophocephalus, and Yamatocetus canaliculatus. Detailed study of ontogenetic change demonstrates postnatal elaboration of the sagittal and nuchal crests, elongation of the intertemporal region, inflation of the zygomatic processes, and an extreme proportional increase in rostral length. Tympanic bullae are nearly full sized during early postnatal ontogeny indicating precocial development of auditory structures, but do increase slightly in size. Positive allometry of the rostrum suggests an ontogenetic change in feeding ecology, from neonatal suckling to a more specialized adult feeding behaviour. Possible absence of baleen anteriorly, a delicate temporomandibular joint with probable synovial capsule, non-laterally deflected coronoid process, and anteroposteriorly expanded palate suggests skim feeding as likely mode of adult feeding for zooplankton. Isotopic data in concert with preservation of young juveniles suggests the continental shelf of Zealandia was an important calving ground for latitudinally migrating Oligocene baleen whales. PMID:26380800

Anatomy, feeding ecology, and ontogeny of a transitional baleen whale: a new genus and species of Eomysticetidae (Mammalia: Cetacea) from the Oligocene of New Zealand.

PubMed

Boessenecker, Robert W; Fordyce, R Ewan

2015-01-01

The Eocene history of cetacean evolution is now represented by the expansive fossil record of archaeocetes elucidating major morphofunctional shifts relating to the land to sea transition, but the change from archaeocetes to modern cetaceans is poorly established. New fossil material of the recently recognized family Eomysticetidae from the upper Oligocene Otekaike Limestone includes a new genus and species, Waharoa ruwhenua, represented by skulls and partial skeletons of an adult, juvenile, and a smaller juvenile. Ontogenetic status is confirmed by osteohistology of ribs. Waharoa ruwhenua is characterized by an elongate and narrow rostrum which retains vestigial alveoli and alveolar grooves. Palatal foramina and sulci are present only on the posterior half of the palate. The nasals are elongate, and the bony nares are positioned far anteriorly. Enormous temporal fossae are present adjacent to an elongate and narrow intertemporal region with a sharp sagittal crest. The earbones are characterized by retaining inner and outer posterior pedicles, lacking fused posterior processes, and retaining a separate accessory ossicle. Phylogenetic analysis supports inclusion of Waharoa ruwhenua within a monophyletic Eomysticetidae as the earliest diverging clade of toothless mysticetes. This eomysticetid clade also included Eomysticetus whitmorei, Micromysticetus rothauseni, Tohoraata raekohao, Tokarahia kauaeroa, Tokarahia lophocephalus, and Yamatocetus canaliculatus. Detailed study of ontogenetic change demonstrates postnatal elaboration of the sagittal and nuchal crests, elongation of the intertemporal region, inflation of the zygomatic processes, and an extreme proportional increase in rostral length. Tympanic bullae are nearly full sized during early postnatal ontogeny indicating precocial development of auditory structures, but do increase slightly in size. Positive allometry of the rostrum suggests an ontogenetic change in feeding ecology, from neonatal suckling to a more specialized adult feeding behaviour. Possible absence of baleen anteriorly, a delicate temporomandibular joint with probable synovial capsule, non-laterally deflected coronoid process, and anteroposteriorly expanded palate suggests skim feeding as likely mode of adult feeding for zooplankton. Isotopic data in concert with preservation of young juveniles suggests the continental shelf of Zealandia was an important calving ground for latitudinally migrating Oligocene baleen whales.

Role of spontaneous emission through operating transition in probe-field spectroscopy of two-level systems

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

Saprykin, E. G.; Chernenko, A. A., E-mail: chernen@isp.nsc.ru; Shalagin, A. M.

Analytical and numerical investigations are carried out of the effect of spontaneous decay through operating transition on the shape of a resonance in the work of a probe field under a strong field applied to the transition. A narrow nonlinear resonance arising on transitions with long-living lower level in the work of a probe field can manifest itself in the form of a traditional minimum and a peak as a function of the first Einstein coefficient for the operating transition. The transformation of the resonance from a minimum to a peak is attributed to the specific character of relaxation ofmore » lower-level population beatings on a closed or almost closed transition (the decay of the upper level occurs completely or almost completely through the operating transition).« less

A VLT VIMOS study of the anomalous BCD Mrk996: mapping the ionized gas kinematics and abundances

NASA Astrophysics Data System (ADS)

James, B. L.; Tsamis, Y. G.; Barlow, M. J.; Westmoquette, M. S.; Walsh, J. R.; Cuisinier, F.; Exter, K. M.

2009-09-01

A study of the blue compact dwarf (BCD) galaxy Mrk996 based on high-resolution optical Very Large Telescope Visible Multi-Object Spectrograph integral field unit spectroscopy is presented. Mrk996 displays multicomponent line emission, with most line profiles consisting of a narrow, central Gaussian [full width at half-maximum (FWHM) ~ 110kms-1] with an underlying broad component (FWHM ~ 400kms-1). The broad HI Balmer component splits into two separate broad components inside a 1.5-arcsec radius from the nucleus; these are attributed to a two-armed minispiral. This spiral-like nucleus rotates in the same sense as the extended narrow line ionized gas but is offset by ~50kms-1 from the systemic velocity of the galaxy. The rotation curve of Mrk996 derived from the Hα narrow component yields a total mass of 5 × 108Msolar within a radius of 3kpc. From the Hα luminosity we infer a global star formation rate of ~2Msolaryr-1. The high excitation energy, high critical density [OIII] λ4363 and [NII] λ5755 lines are only detected from the inner region and exist purely in broad component form, implying unusual excitation conditions. Surface brightness, radial velocity and FWHM maps for several emission components are presented. A separate physical analysis of the broad and narrow emission line regions is undertaken. We derive an upper limit of 10000K for the electron temperature of the narrow line gas, together with an electron density of 170cm-3, typical of normal HII regions. For the broad line component, measured [OIII] and [FeIII] diagnostic line ratios are consistent with a temperature of 11000K and an electron density of 107cm-3. The broad line emission regions show N/H and N/O enrichment factors of ~20 relative to the narrow line regions, but no He/H, O/H, S/H or Ar/H enrichment is inferred. Previous studies indicated that Mrk996 showed anomalously high N/O ratios compared with BCDs of a similar metallicity. Our multicomponent analysis yields a revised metallicity of >=0.5Zsolar (12 + logO/H = 8.37) for both the narrow and broad gas components, significantly higher than previous studies. As a result the narrow line region's N/O ratio is now typical for the galaxy's metallicity. The narrow line component's N/O ratio peaks outside the core region, spatially correlating with ~3-Myr-old stellar populations. The dominant line excitation mechanism is photoionization by the ~3000 Wolf-Rayet stars and ~150000 O-type stars estimated to be present in the core. This is indeed a peculiar BCD, with extremely dense zones of gas in the core, through which stellar outflows and possible shock fronts permeate contributing to the excitation of the broad line emission. Based on observations made with ESO telescopes at the Paranal Observatory under programme ID 078.B-0353(A). E-mail: bj@star.ucl.ac.uk (BLJ); tsamis@iaa.es (YGT)

The size-luminosity relationship of quasar narrow-line regions

NASA Astrophysics Data System (ADS)

Dempsey, Ross; Zakamska, Nadia L.

2018-07-01

The presence of an active galactic nucleus (AGN) can strongly affect its host. Due to the copious radiative power of the nucleus, the effects of radiative feedback can be detected over the entire host galaxy and sometimes well into the intergalactic space. In this paper we model the observed size-luminosity relationship of the narrow-line regions (NLRs) of AGN. We model the NLR as a collection of clouds in pressure equilibrium with the ionizing radiation, with each cloud producing line emission calculated by Cloudy. The sizes of the NLRs of powerful quasars are reproduced without any free parameters, as long as they contain massive (105-107 M⊙) ionization-bounded clouds. At lower AGN luminosities the observed sizes are larger than the model sizes, likely due to additional unmodeled sources of ionization (e.g. star formation). We find that the observed saturation of sizes at ˜10 kpc which is observed at high AGN luminosities (Lion ≃ 1046 erg s-1) is naturally explained by optically thick clouds absorbing the ionizing radiation and preventing illumination beyond a critical distance. Using our models in combination with observations of the [O III]/IR ratio and the [O III] size-IR luminosity relationship, we calculate the covering factor of the obscuring torus (and therefore the type 2 fraction within the quasar population) to be f = 0.5, though this is likely an upper bound. Finally, because the gas behind the ionization front is invisible in ionized gas transitions, emission-based NLR mass calculations underestimate the mass of the NLR and therefore of the energetics of ionized-gas winds.

The Size-Luminosity Relationship of Quasar Narrow-Line Regions

NASA Astrophysics Data System (ADS)

Dempsey, Ross; Zakamska, Nadia L.

2018-04-01

The presence of an active galactic nucleus (AGN) can strongly affect its host. Due to the copious radiative power of the nucleus, the effects of radiative feedback can be detected over the entire host galaxy and sometimes well into the intergalactic space. In this paper we model the observed size-luminosity relationship of the narrow-line regions (NLRs) of AGN. We model the NLR as a collection of clouds in pressure equilibrium with the ionizing radiation, with each cloud producing line emission calculated by Cloudy. The sizes of the NLRs of powerful quasars are reproduced without any free parameters, as long as they contain massive (105M⊙ to 107M⊙) ionization-bounded clouds. At lower AGN luminosities the observed sizes are larger than the model sizes, likely due to additional unmodeled sources of ionization (e.g., star formation). We find that the observed saturation of sizes at ˜10kpc which is observed at high AGN luminosities (Lion ≃ 1046erg/s) is naturally explained by optically thick clouds absorbing the ionizing radiation and preventing illumination beyond a critical distance. Using our models in combination with observations of the [O III]/IR ratio and the [O III] size - IR luminosity relationship, we calculate the covering factor of the obscuring torus (and therefore the type 2 fraction within the quasar population) to be f = 0.5, though this is likely an upper bound. Finally, because the gas behind the ionization front is invisible in ionized gas transitions, emission-based NLR mass calculations underestimate the mass of the NLR and therefore of the energetics of ionized-gas winds.

Faraday anomalous dispersion optical filters

NASA Technical Reports Server (NTRS)

Shay, T. M.; Yin, B.

1992-01-01

The present calculations of the performance of Faraday anomalous dispersion optical filters (FADOF) on IR transitions indicate that such filters may furnish high transmission, narrow-pass bandwidth, and low equivalent noise bandwidth under optimum operating conditions. A FADOF consists of an atomic vapor cell between crossed polarizers that are subject to a dc magnetic field along the optical path; when linearly polarized light travels along the direction of the magnetic field through the dispersive atomic vapor, a polarization rotation occurs. If FADOF conditions are suitably adjusted, a maximum transmission with very narrow bandwidth is obtained.

Spin Crossover and the Magnetic P- T Phase Diagram of Hematite at High Hydrostatic Pressures and Cryogenic Temperatures

NASA Astrophysics Data System (ADS)

Gavriliuk, A. G.; Struzhkin, V. V.; Mironovich, A. A.; Lyubutin, I. S.; Troyan, I. A.; Chow, P.; Xiao, Y.

2018-02-01

The magnetic properties of the α-Fe2O3 hematite at a high hydrostatic pressure have been studied by synchrotron Mössbauer spectroscopy (nuclear forward scattering (NFS)) on iron nuclei. Time-domain NFS spectra of hematite have been measured in a diamond anvil cell in the pressure range of 0-72 GPa and the temperature range of 36-300 K in order to study the magnetic properties at a phase transition near a critical pressure of 50 GPa. In addition, Raman spectra at room temperature have been studied in the pressure range of 0-77 GPa. Neon has been used as a pressure-transmitting medium. The appearance of an intermediate electronic state has been revealed at a pressure of 48 GPa. This state is probably related to the spin crossover in Fe3+ ions at their transition from the high-spin state (HS, S = 5/2) to a low-spin one (LS, S = 1/2). It has been found that the transient pressure range of the HS-LS crossover is extended from 48 to 55 GPa and is almost independent of the temperature. This surprising result differs fundamentally from other cases of the spin crossover in Fe3+ ions observed in other crystals based on iron oxides. The transition region of spin crossover appears because of thermal fluctuations between HS and LS states in the critical pressure range and is significantly narrowed at cooling because of the suppression of thermal excitations. The magnetic P- T phase diagram of α-Fe2O3 at high pressures and low temperatures in the spin crossover region has been constructed according to the results of measurements.

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

Kraus, Stefan; Espaillat, Catherine; Wilner, David J.

Pre-transitional disks are protoplanetary disks with a gapped disk structure, potentially indicating the presence of young planets in these systems. In order to explore the structure of these objects and their gap-opening mechanism, we observed the pre-transitional disk V1247 Orionis using the Very Large Telescope Interferometer, the Keck Interferometer, Keck-II, Gemini South, and IRTF. This allows us to spatially resolve the AU-scale disk structure from near- to mid-infrared wavelengths (1.5-13 {mu}m), tracing material at different temperatures and over a wide range of stellocentric radii. Our observations reveal a narrow, optically thick inner-disk component (located at 0.18 AU from the star)more » that is separated from the optically thick outer disk (radii {approx}> 46 AU), providing unambiguous evidence for the existence of a gap in this pre-transitional disk. Surprisingly, we find that the gap region is filled with significant amounts of optically thin material with a carbon-dominated dust mineralogy. The presence of this optically thin gap material cannot be deduced solely from the spectral energy distribution, yet it is the dominant contributor at mid-infrared wavelengths. Furthermore, using Keck/NIRC2 aperture masking observations in the H, K', and L' bands, we detect asymmetries in the brightness distribution on scales of {approx}15-40 AU, i.e., within the gap region. The detected asymmetries are highly significant, yet their amplitude and direction changes with wavelength, which is not consistent with a companion interpretation but indicates an inhomogeneous distribution of the gap material. We interpret this as strong evidence for the presence of complex density structures, possibly reflecting the dynamical interaction of the disk material with sub-stellar mass bodies that are responsible for the gap clearing.« less

Structural control on arc volcanism: The Caviahue Copahue complex, Central to Patagonian Andes transition (38°S)

NASA Astrophysics Data System (ADS)

Melnick, Daniel; Folguera, Andrés; Ramos, Victor A.

2006-11-01

This paper describes the volcanostratigraphy, structure, and tectonic implications of an arc volcanic complex in an oblique subduction setting: the Caviahue caldera Copahue volcano (CAC) of the Andean margin. The CAC is located in a first-order morphotectonic transitional zone, between the low and narrow Patagonian and the high and broad Central Andes. The evolution of the CAC started at approximately 4-3 Ma with the opening of the 20 × 15 km Caviahue pull-apart caldera; Las Mellizas volcano formed inside the caldera and collapsed at approximately 2.6 Ma; and the Copahue volcano evolved in three stages: (1) 1.2-0.7 Ma formed the approximately 1 km thick andesitic edifice, (2) 0.7-0.01 Ma erupted andesitic-dacitic subglacial pillow lavas, and (3) 0.01-0 Ma erupted basaltic-andesites and pyroclastic flows from fissures, aligned cones, and summit craters. Magma ascent has occurred along planes perpendicular to the least principal horizontal stress, whereas hydrothermal activity and hot springs also occur along parallel planes. At a regional scale, Quaternary volcanism concentrates along the NE-trending, 90 km long Callaqui-Copahue-Mandolegüe lineament, the longest of the southern volcanic zone, which is here interpreted as an inherited crustal-scale transfer zone from a Miocene rift basin. At a local scale within the CAC, effusions are controlled by local structures that formed at the intersection of regional fault systems. The Central to Patagonian Andes transition occurs at the Callaqui-Copahue-Mandolegüe lineament, which decouples active deformation from the intra-arc strike-slip Liquiñe-Ofqui fault zone to the south and the backarc Copahue-Antiñir thrust system.

Experimental study of H2O spectroscopic parameters in the near-IR (6940 7440 cm-1) for gas sensing applications at elevated temperature

NASA Astrophysics Data System (ADS)

Liu, Xiang; Zhou, Xin; Jeffries, Jay B.; Hanson, Ronald K.

2007-02-01

Tunable diode laser (TDL) absorption sensors of water vapor are attractive for temperature, gas composition, velocity, pressure, and mass flux measurements in a variety of practical applications including hydrocarbon-fueled combustion systems. Optimized design of these sensors requires a complete catalog of the assigned transitions with accurate spectroscopic data; our particular interest has been in the 2ν1, 2ν3, and ν1+ν3 bands in the near-IR where telecommunications diode lasers are available. In support of this need, fully resolved absorption spectra of H2O vapor in the spectral range of 6940 7440 cm-1 (1344 1441 nm) have been measured as a function of temperature (296 1000 K) and pressure (1 800 Torr), and quantitative spectroscopic parameters inferred from these spectra compared to published data from Toth, HITRAN 2000 and HITRAN 2004. The peak absorbances were measured for more than 100 strong transitions at 296 and 828 K, and linestrengths determined for 47 strong lines in this region. In addition to reference linestrengths S(296 K), the air-broadening coefficients γair(296 K) and temperature exponents n were inferred for strong transitions in five narrow regions, near 7185.60, 7203.89, 7405.11, 7426.14 and 7435.62 cm-1 that had been targeted as attractive for future diagnostics applications. Most of the measured results, determined within an accuracy of 5%, are found to be in better agreement with HITRAN 2004 than with earlier editions of this database. Large discrepancies (>10%) between measurements and HITRAN 2004 database are identified for some of the probed transitions. These new spectroscopic data for H2O provide a useful test of the sensor design capabilities of HITRAN 2004 for combustion and other applications at elevated temperatures.

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

Harilal, Sivanandan S.; LaHaye, Nicole L.; Phillips, Mark C.

We used a CW laser as a narrow-band (~50kHz) tunable LIF excitation source to probe absorption from selected atomic transitions (Al, U etc. ) in a ns laser ablation plume. A comparison of fluorescence signal with respect to emission spectroscopy show significant increase in the magnitude and persistence from selected Al and U transitions in a LIBS plume. The high spectral resolution provided by the LIF measurement allows peaks to be easily separated even if they overlap in the emission spectra.

Determination of the vinyl fluoride line intensities by TDL spectroscopy: the object oriented approach of Visual Line Shape Fitting Program to line profile analysis

NASA Astrophysics Data System (ADS)

Tasinato, Nicola; Pietropolli Charmet, Andrea; Stoppa, Paolo; Giorgianni, Santi

2010-03-01

In this work the self-broadening coefficients and the integrated line intensities for a number of ro-vibrational transitions of vinyl fluoride have been determined for the first time by means of TDL spectroscopy. The spectra recorded in the atmospheric window around 8.7 µm appear very crowded with a density of about 90 lines per cm-1. In order to fit these spectral features a new fitting software has been implemented. The program, which is designed for laser spectroscopy, can fit many lines simultaneously on the basis of different theoretical profiles (Doppler, Lorentz, Voigt, Galatry and Nelkin-Ghatak). Details of the object oriented implementation of the application are given. The reliability of the program is demonstrated by determining the line parameters of some ro-vibrational lines of sulphur dioxide in the ν1 band region around 9 µm. Then the software is used for the line profile analysis of vinyl fluoride. The experimental line shapes show deviations from the Voigt profile, which can be well modelled by using a Dicke narrowed line shape function. This leads to the determination of the self-narrowing coefficient within the framework of the strong collision model.

Buttressing and stability of marine Ice sheets

NASA Astrophysics Data System (ADS)

Goldberg, D.; Holland, D. M.; Schoof, C.

2009-04-01

The West Antarctic Ice Sheet is marine in nature, meaning most of its base is below sea level. At the grounding line (where it becomes thin enough to float), its outlet streams flow into large ice shelves. Gravitational stress in the shelf is transmitted back to the grounding line, and largely balanced by basal friction in the transition zone. The details of this force balance control the evolution of both the thickness and grounded extent of the ice sheet, and can lead to Weertman's (1974) Marine Instability for a foredeepened bedrock (one that deepens inland). However, the presence of rigid sidewalls and locally grounded regions in the shelf can reduce the longitudinal stresses felt at the grounding line (a phenomenon called buttressing). Thomas (1979) and others pointed out that Marine Instability may be lessened or reversed by ice shelf buttressing. When modelling marine ice sheets numerically, the physics of the grounded-to-floating transition must be represented and the associated small length scales must be resolved (Schoof, 2007). Failing to do so can result in nonphysical or numerically inconsistent behavior (Vieli and Payne, 2005). While several methods have been developed to treat these issues (Vieli and Payne, 2005; Pattyn et al, 2006; Schoof, 2007) they are limited to flowline models. We present a model that represents the physics of the grounded-to-floating transition in a time-dependent three-dimensional marine ice sheet, using mesh adaption to resolve the transition zone. We show that in the special case of a two-dimensional sheet our model reproduces the theoretical results of the MISMIP experiments, and that it produces robust results when both horizontal dimensions are resolved. In idealized experiments in a channel with rigid sidewalls and a foredeepened bed, we narrow the channel to determine whether buttressing is sufficient to reverse instability. We find that for strong beds (high friction coefficients), while the timescales and dynamics are affected greatly by buttressing, true stability reversal is still not seen even as the channel becomes quite narrow. However, for weaker beds, stability is seen, though it can be shown that sufficient ocean melting can still cause collapse. Experiments with more complicated bed topography show that locally grounded areas (ice rises) have similar dynamic effects to rigid sidewalls.

Are rapid transitions between invasive and native species caused by alternative stable states, and does it matter?

PubMed

Hansen, Gretchen J A; Ives, Anthony R; Vander Zanden, M Jake; Carpenter, Stephen R

2013-10-01

Rapid transitions in ecosystem structure, or regime shifts, are a hallmark of alternative stable states (ASS). However, regime shifts can occur even when feedbacks are not strong enough to cause ASS. We investigated the potential for ASS to explain transitions between dominance of an invasive species, rusty crayfish (Orconectes rusticus), and native sunfishes (Lepomis spp.) in northern Wisconsin (USA) lakes. A rapid transition from Lepomis to rusty crayfish dominance occurred as rusty crayfish invaded Trout Lake, and the reverse transition resulted from an eight-year experimental removal of rusty crayfish from Sparkling Lake. We fit a stage-structured population model of species interactions to 31 years of time-series data from each lake. The model identified water level as an important driver, with drought conditions reducing rusty crayfish recruitment and allowing Lepomis dominance. The maximum-likelihood parameter estimates of the negative interaction between rusty crayfish and Lepomis led to ASS in the model, where each species was capable of excluding the other within a narrow range of environmental conditions. However, uncertainty in parameter estimates made it impossible to exclude the potential that rapid transitions were caused by a simpler threshold response lacking alternative equilibria. Simulated forward and backward transitions between species dominance occurred at different environmental conditions (i.e., hysteresis), even when the parameters used for simulation did not predict ASS as a result of slow species responses to environmental drivers. Thus, ASS are possible, but by no means certain, explanations for rapid transitions in this system, and our results highlight the difficulties associated with distinguishing ASS from other types of threshold responses. However, whether regime shifts are caused by ASS may be relatively unimportant in this system, as the range of conditions over which transitions occur is narrow, and under most conditions, the system is predicted to exist in only a single state.

Light effects in the atomic-motion-induced Ramsey narrowing of dark resonances in wall-coated cells

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

Breschi, E.; Schori, C.; Di Domenico, G.

2010-12-15

We report on light shift and broadening in the atomic-motion-induced Ramsey narrowing of dark resonances prepared in alkali-metal vapors contained in wall-coated cells without buffer gas. The atomic-motion-induced Ramsey narrowing is due to the free motion of the polarized atomic spins in and out of the optical interaction region before spin relaxation. As a consequence of this effect, we observe a narrowing of the dark resonance linewidth as well as a reduction of the ground states' light shift when the volume of the interaction region decreases at constant optical intensity. The results can be intuitively interpreted as a dilution ofmore » the intensity effect similar to a pulsed interrogation due to the atomic motion. Finally the influence of this effect on the performance of compact atomic clocks is discussed.« less

The transition from diffuse to focused extension: Modeled evolution of the West Antarctic Rift system

NASA Astrophysics Data System (ADS)

Huerta, Audrey D.; Harry, Dennis L.

2007-03-01

Two distinct stages of extension are recognized in the West Antarctic Rift system (WARS). During the first stage, beginning in the Late Cretaceous, extension was broadly distributed throughout much of West Antarctica. A second stage of extension in the late Paleogene was focused primarily in the Victoria Land Basin, near the boundary with the East Antarctic craton. The transition to focused extension was roughly coeval with volcanic activity and strike-slip faulting in the adjacent Transantarctic Mountains. This spatial and temporal correspondence suggests that the transition in extensional style could be the result of a change in plate motions or impingement of a plume. Here we use finite element models to study the processes and conditions responsible for the two-stage evolution of rifting in the WARS. Model results indicate that the transition from a prolonged period of broadly distributed extension to a later period of focused rifting did not require a change in the regional stress regime (changes in plate motion), or deep mantle thermal state (impingement of a plume). Instead, we attribute the transition from diffuse to focused extension to an early stage dominated by the initially weak accreted lithosphere of West Antarctica, and a later stage that concentrated around a secondary weakness located at the boundary between the juvenile West Antarctica lithosphere and Precambrian East Antarctic craton. The modeled transition in extension from the initially weak West Antarctica region to the secondary weakness at the West Antarctic-East Antarctic boundary is precipitated by strengthening of the West Antarctica lithosphere during syn-extensional thinning and cooling. The modeled syn-extensional strengthening of the WARS lithosphere promotes a wide-rift mode of extension between 105 and ˜ 65 Ma. By ˜ 65 Ma most of the extending WARS region becomes stronger than the area immediately adjacent to the East Antarctic craton and extension becomes concentrated near the East Antarctic/West Antarctic boundary, forming the Victoria Land Basin region. Mantle necking in this region leads to syn-extensional weakening that promotes a narrow-rift mode of extension that becomes progressively more focused with time, resulting in formation of the Terror Rift in the western Victoria Land Basin. The geodynamic models demonstrate that the transition from diffuse to focused extension occurs only under a limited set of initial and boundary conditions, and is particularly sensitive to the pre-rift thermal state of the crust and upper mantle. Models that predict diffuse extension in West Antarctica followed by localization of rifting near the boundary between East and West Antarctica require upper mantle temperatures of 730 ± 50 °C and sufficient concentration of heat producing elements in the crust to account for ˜ 50% of the upper mantle temperature. Models with upper mantle temperatures < ca. 680 °C and/or less crustal heat production initially undergo diffuse extension in West Antarctica, and quickly develop a lithospheric neck at the model edge furthest from East Antarctica. Models with upper mantle temperatures > ca. 780 °C do not develop focused rifts, and predict indefinite diffuse extension in West Antarctica.

LETTER TO THE EDITOR: Green emission and bandgap narrowing due to two-photon excitation in thin film CdS formed by spray pyrolysis

NASA Astrophysics Data System (ADS)

Ullrich, B.; Schroeder, R.

2001-08-01

Thin (10 µm) film CdS on Pyrex® formed by spray pyrolysis is excited below the gap at 804 nm with 200 fs laser pulses at room temperature. Excitation intensities up to 250 GW cm-2 evoke green bandgap emission due to two-photon transitions. This two-photon photoluminescence does not show a red emission contribution in contrast to the single-photon excited emission, which is dominated by broad emission in the red spectral range. It is demonstrated that two-photon excitation causes photo-induced bandgap narrowing due to Debye screening. At 250 GW cm-2 bandgap narrowing of 47 meV is observed, which corresponds to an excited electron density of 1.6×1018 cm-3.

Role of zonal flow predator-prey oscillations in triggering the transition to H-mode confinement.

PubMed

Schmitz, L; Zeng, L; Rhodes, T L; Hillesheim, J C; Doyle, E J; Groebner, R J; Peebles, W A; Burrell, K H; Wang, G

2012-04-13

Direct evidence of zonal flow (ZF) predator-prey oscillations and the synergistic roles of ZF- and equilibrium E×B flow shear in triggering the low- to high-confinement (L- to H-mode) transition in the DIII-D tokamak is presented. Periodic turbulence suppression is first observed in a narrow layer at and just inside the separatrix when the shearing rate transiently exceeds the turbulence decorrelation rate. The final transition to H mode with sustained turbulence and transport reduction is controlled by equilibrium E×B shear due to the increasing ion pressure gradient.

Polaronic and dressed molecular states in orbital Feshbach resonances

NASA Astrophysics Data System (ADS)

Xu, Junjun; Qi, Ran

2018-04-01

We consider the impurity problem in an orbital Feshbach resonance (OFR), with a single excited clock state | e ↑⟩ atom immersed in a Fermi sea of electronic ground state | g ↓⟩. We calculate the polaron effective mass and quasi-particle residue, as well as the polaron to molecule transition. By including one particle-hole excitation in the molecular state, we find significant correction to the transition point. This transition point moves toward the BCS side for increasing particle densities, which suggests that the corresponding many-body physics is similar to a narrow resonance.

Photon transitions in {psi}(2S) decays to {chi}{sub cJ}(1P) and {eta}{sub c}(1S)

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

Athar, S.B.; Avery, P.; Breva-Newell, L.

2004-12-01

We have studied the inclusive photon spectrum in {psi}(2S) decays using the CLEO III detector. We present the most precise measurements of electric dipole (E1) photon transition rates for {psi}(2S){yields}{gamma}{chi}{sub cJ}(1P) (J=0,1,2). We also confirm the hindered magnetic dipole (M1) transition, {psi}(2S){yields}{gamma}{eta}{sub c}(1S). However, the direct M1 transition {psi}(2S){yields}{gamma}{eta}{sub c}(2S) observed by the Crystal Ball as a narrow peak at a photon energy of 91 MeV is not found in our data.

Influence of annealing temperature on optical properties of the photonic-crystal structures obtained by self-organization of colloidal microspheres of polystyrene and silica

NASA Astrophysics Data System (ADS)

Mikhnev, L. V.; Bondarenko, E. A.; Chapura, O. M.; Skomorokhov, A. A.; Kravtsov, A. A.

2018-01-01

The influence of annealing temperature on the transmission spectra of photonic crystals composed of polystyrene and silicon dioxide microspheres was studied. It was found that annealing of photonic crystals based on polystyrene and silica leads to a shift in the photonic band gap to the short-wavelength region. Based on the results of optical studies, the dependences of the structural parameters of the obtained opal-like crystals on annealing temperature were obtained. In the case of polystyrene photonic crystals, the displacement of the photonic band gap is observed in a narrow temperature range above the glass transition temperature. For SiO2 photonic crystals, it was found that the process of microspheres sintering is complex and involves three stages of structural modification.

Assessment of forest degradation in Vietnam using Landsat time series data

USGS Publications Warehouse

Vogelmann, James; Van Khoa, Phung; Xuan Lan, Do; Shermeyer, Jacob S.; Shi, Hua; Wimberly, Michael C.; Tat Duong, Hoang; Van Huong, Le

2017-01-01

Landsat time series data were used to characterize forest degradation in Lam Dong Province, Vietnam. We conducted three types of image change analyses using Landsat time series data to characterize the land cover changes. Our analyses concentrated on the timeframe of 1973–2014, with much emphasis on the latter part of that range. We conducted a field trip through Lam Dong Province to develop a better understanding of the ground conditions of the region, during which we obtained many photographs of representative forest sites with Global Positioning System locations to assist us in our image interpretations. High-resolution Google Earth imagery and Landsat data of the region were used to validate results. In general, our analyses indicated that many land-use changes have occurred throughout Lam Dong Province, including gradual forest to non-forest transitions. Recent changes are most marked along the relatively narrow interfaces between agricultural and forest areas that occur towards the boundaries of the province. One important observation is that the most highly protected national reserves in the region have not changed much over the entire Landsat timeframe (1972–present). Spectral changes within these regions have not occurred at the same levels as those areas adjacent to the reserves. 

Environmental niche conservatism explains the accumulation of species richness in Mediterranean-hotspot plant genera.

PubMed

Skeels, Alexander; Cardillo, Marcel

2017-03-01

The causes of exceptionally high plant diversity in Mediterranean-climate biodiversity hotspots are not fully understood. We asked whether a mechanism similar to the tropical niche conservatism hypothesis could explain the diversity of four large genera (Protea, Moraea, Banksia, and Hakea) with distributions within and adjacent to the Greater Cape Floristic Region (South Africa) or the Southwest Floristic Region (Australia). Using phylogenetic and spatial data we estimated the environmental niche of each species, and reconstructed the mode and dynamics of niche evolution, and the geographic history, of each genus. For three genera, there were strong positive relationships between the diversity of clades within a region and their inferred length of occupation of that region. Within genera, there was evidence for strong evolutionary constraint on niche axes associated with climatic seasonality and aridity, with different niche optima for hotspot and nonhotspot clades. Evolutionary transitions away from hotspots were associated with increases in niche breadth and elevated rates of niche evolution. Our results point to a process of "hotspot niche conservatism" whereby the accumulation of plant diversity in Mediterranean-type ecosystems results from longer time for speciation, with dispersal away from hotspots limited by narrow and phylogenetically conserved environmental niches. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

Density Affects the Nature of the Hexatic-Liquid Transition in Two-Dimensional Melting of Soft-Core Systems

NASA Astrophysics Data System (ADS)

Zu, Mengjie; Liu, Jun; Tong, Hua; Xu, Ning

2016-08-01

We find that both continuous and discontinuous hexatic-liquid transitions can happen in the melting of two-dimensional solids of soft-core disks. For three typical model systems, Hertzian, harmonic, and Gaussian-core models, we observe the same scenarios. These systems exhibit reentrant crystallization (melting) with a maximum melting temperature Tm happening at a crossover density ρm. The hexatic-liquid transition at a density smaller than ρm is discontinuous. Liquid and hexatic phases coexist in a density interval, which becomes narrower with increasing temperature and tends to vanish approximately at Tm. Above ρm, the transition is continuous, in agreement with the Kosterlitz-Thouless-Halperin-Nelson-Young theory. For these soft-core systems, the nature of the hexatic-liquid transition depends on density (pressure), with the melting at ρm being a plausible transition point from discontinuous to continuous hexatic-liquid transition.

Electromagnetically-induced-absorption resonance with high contrast and narrow width in the Hanle configuration

NASA Astrophysics Data System (ADS)

Brazhnikov, D. V.; Taichenachev, A. V.; Tumaikin, A. M.; Yudin, V. I.

2014-12-01

The method for observing the high-contrast and narrow-width resonances of electromagnetically induced absorption (EIA) in the Hanle configuration under counter-propagating pump and probe light waves is proposed. Here, as an example, we study a ‘dark’ type of atomic dipole transition {{F}\\text{g}}={1}\\to {{F}\\text{e}}={1} in D1 line of 87Rb, where usually the electromagnetically induced transparency can be observed. To obtain the EIA signal one should properly choose the polarizations of light waves and intensities. In contrast to regular schemes for observing EIA signals (under a single traveling light wave in the Hanle configuration or under a bichromatic light field consisting of two traveling waves), the proposed scheme allows one to use buffer gas for significantly improving the properties of the resonance. Also the dramatic influence of atomic transition openness on the contrast of the resonance is revealed, which is advantageous in comparison with cyclic atomic transitions. The nonlinear resonances in a probe-wave transmitted signal with contrast close to 100% and sub-kHz widths can be obtained. The results are interesting in high-resolution spectroscopy, nonlinear and magneto-optics.

Narrow band noise response of a Belleville spring resonator.

PubMed

Lyon, Richard H

2013-09-01

This study of nonlinear dynamics includes (i) an identification of quasi-steady states of response using equivalent linearization, (ii) the temporal simulation of the system using Heun's time step procedure on time domain analytic signals, and (iii) a laboratory experiment. An attempt has been made to select material and measurement parameters so that nearly the same systems are used and analyzed for all three parts of the study. This study illustrates important features of nonlinear response to narrow band excitation: (a) states of response that the system can acquire with transitions of the system between those states, (b) the interaction between the noise source and the vibrating load in which the source transmits energy to or draws energy from the load as transitions occur; (c) the lag or lead of the system response relative to the source as transitions occur that causes the average frequencies of source and response to differ; and (d) the determination of the state of response (mass or stiffness controlled) by observation of the instantaneous phase of the influence function. These analyses take advantage of the use of time domain analytic signals that have a complementary role to functions that are analytic in the frequency domain.

Planar heterostructures of single-layer transition metal dichalcogenides: Composite structures, Schottky junctions, tunneling barriers, and half metals

NASA Astrophysics Data System (ADS)

Aras, Mehmet; Kılıç, ćetin; Ciraci, S.

2017-02-01

Planar composite structures formed from the stripes of transition metal dichalcogenides joined commensurately along their zigzag or armchair edges can attain different states in a two-dimensional (2D), single-layer, such as a half metal, 2D or one-dimensional (1D) nonmagnetic metal and semiconductor. Widening of stripes induces metal-insulator transition through the confinements of electronic states to adjacent stripes, that results in the metal-semiconductor junction with a well-defined band lineup. Linear bending of the band edges of the semiconductor to form a Schottky barrier at the boundary between the metal and semiconductor is revealed. Unexpectedly, strictly 1D metallic states develop in a 2D system along the boundaries between stripes, which pins the Fermi level. Through the δ doping of a narrow metallic stripe one attains a nanowire in the 2D semiconducting sheet or narrow band semiconductor. A diverse combination of constituent stripes in either periodically repeating or finite-size heterostructures can acquire critical fundamental features and offer device capacities, such as Schottky junctions, nanocapacitors, resonant tunneling double barriers, and spin valves. These predictions are obtained from first-principles calculations performed in the framework of density functional theory.

Dynamical heterogeneities and mechanical non-linearities: Modeling the onset of plasticity in polymer in the glass transition.

PubMed

Masurel, R J; Gelineau, P; Lequeux, F; Cantournet, S; Montes, H

2017-12-27

In this paper we focus on the role of dynamical heterogeneities on the non-linear response of polymers in the glass transition domain. We start from a simple coarse-grained model that assumes a random distribution of the initial local relaxation times and that quantitatively describes the linear viscoelasticity of a polymer in the glass transition regime. We extend this model to non-linear mechanics assuming a local Eyring stress dependence of the relaxation times. Implementing the model in a finite element mechanics code, we derive the mechanical properties and the local mechanical fields at the beginning of the non-linear regime. The model predicts a narrowing of distribution of relaxation times and the storage of a part of the mechanical energy --internal stress-- transferred to the material during stretching in this temperature range. We show that the stress field is not spatially correlated under and after loading and follows a Gaussian distribution. In addition the strain field exhibits shear bands, but the strain distribution is narrow. Hence, most of the mechanical quantities can be calculated analytically, in a very good approximation, with the simple assumption that the strain rate is constant.

Turbulent Transition in Electromagnetically Levitated Drops

NASA Technical Reports Server (NTRS)

Hyers, Robert W.; Trapaga, G.; Abedian, B.; Matson, D. M.; Rose, M. Franklin (Technical Monitor)

2000-01-01

Electromagnetic levitation (EML) is an important tool in materials research. Because a sample can be processed without contact with a container, experiments may be performed on high temperature, highly reactive, and undercooled liquid metals. Many of these experiments are affected by fluid flow in the sample, driven by the electromagnetic positioning force. Despite the importance of convection in these experiments, the transition to turbulence is not well understood in this system. However, we have observed a transition from laminar to turbulent flow in EML droplets in the course of microgravity experiments in TEMPUS on the Space Shuttle (STS-94). The transition occurs repeatably and over a narrow range of conditions. These experimental observations are compared with two competing theories about the transition to turbulence. Also, the results of a particle tracking study of the instabilities leading up to the transition to turbulence are presented.

Biomechanics of Tetrahymena escaping from dead ends

NASA Astrophysics Data System (ADS)

Ishikawa, Takuji; Kikuchi, Kenji

2017-11-01

Behaviors of swimming microorganisms in complex environments are important in understanding cells' distribution in nature and in industries. Although cell's swimming and spreading in an infinite fluid has been intensively investigated, that in a narrow region bounded by walls is still unclear. Thus, in this study, we used Tetrahymena thermophila as a model microorganism, and experimentally investigated its behavior between flat plates with an angle. The results showed that the cells tended to escape from the narrow region, and the swimming velocity and the radius of curvature of the trajectories decreased as they swam narrower region. We then developed a computational model of swimming Tetrahymena. The results showed that the escaping behavior could be well explained by fluid mechanics. The obtained knowledge is useful in understanding cells' behaviors in complex environments, such as in porous media and in a granular matter. This research was supported by JSPS KAKENHI Grants, numbers 25000008 and 17H00853.

Using 15-minute acoustic data to analyze suspended-sediment dynamics in the Rio Grande in the Big Bend Region

USGS Publications Warehouse

Dean, David; Topping, David; Griffiths, Ronald; Sabol, Thomas; Schmidt, John C.; Bennett, Jeffery B.

2015-01-01

The Rio Grande in the Big Bend region is subject to rapid geomorphic change consisting of channel narrowing during years of low flow, and channel widening during rare, large, long duration floods. Since the 1940s, there have been large declines in mean and peak stream flow, and the channel has progressively narrowed. Large, channel widening floods are infrequent and have failed to widen the channel to widths measured prior to the onset of channel narrowing in the 1940s. Before the most recent channel-widening flood in September 2008, the Rio Grande in the Big Bend was more than 50 percent narrower than measured in the 1940s. Channel narrowing results in increased flood frequency and flood magnitude due to the loss of channel capacity and flood conveyance (Dean and Schmidt, 2011). Channel narrowing also results in the loss of important aquatic habitats such as backwaters and side-channels, because these habitats accumulate sediment and are converted to floodplains. Environmental managers are attempting to construct an environmental flow program for the purposes of minimizing channel narrowing during low flow years such that channel capacity, flood conveyance, and important aquatic habitats are maintained. Effective mitigation of channel narrowing processes requires an in-depth understanding of the predominant sediment source areas, the quantity of sediment input from those source areas, the parts of the flow regime responsible for the greatest sediment deposition, and the effect of managed flows in ameliorating the sediment loading that occurs within the channel. Here, we analyze data collected with acoustic instrumentation at high temporal resolution to quantify suspended-sediment transport during a variety of flood types. We also investigate the effect of long duration managed flows in promoting sediment export and minimizing channel narrowing.

Investigations of α-helix↔β-sheet transition pathways in a miniprotein using the finite-temperature string method

PubMed Central

Ovchinnikov, Victor; Karplus, Martin

2014-01-01

A parallel implementation of the finite-temperature string method is described, which takes into account the invariance of coordinates with respect to rigid-body motions. The method is applied to the complex α-helix↔β-sheet transition in a β-hairpin miniprotein in implicit solvent, which exhibits much of the complexity of conformational changes in proteins. Two transition paths are considered, one derived from a linear interpolant between the endpoint structures and the other derived from a targeted dynamics simulation. Two methods for computing the conformational free energy (FE) along the string are compared, a restrained method, and a tessellation method introduced by E. Vanden-Eijnden and M. Venturoli [J. Chem. Phys. 130, 194103 (2009)]. It is found that obtaining meaningful free energy profiles using the present atom-based coordinates requires restricting sampling to a vicinity of the converged path, where the hyperplanar approximation to the isocommittor surface is sufficiently accurate. This sampling restriction can be easily achieved using restraints or constraints. The endpoint FE differences computed from the FE profiles are validated by comparison with previous calculations using a path-independent confinement method. The FE profiles are decomposed into the enthalpic and entropic contributions, and it is shown that the entropy difference contribution can be as large as 10 kcal/mol for intermediate regions along the path, compared to 15–20 kcal/mol for the enthalpy contribution. This result demonstrates that enthalpic barriers for transitions are offset by entropic contributions arising from the existence of different paths across a barrier. The possibility of using systematically coarse-grained representations of amino acids, in the spirit of multiple interaction site residue models, is proposed as a means to avoid ad hoc sampling restrictions to narrow transition tubes. PMID:24811667

Investigations of α-helix↔β-sheet transition pathways in a miniprotein using the finite-temperature string method

NASA Astrophysics Data System (ADS)

Ovchinnikov, Victor; Karplus, Martin

2014-05-01

A parallel implementation of the finite-temperature string method is described, which takes into account the invariance of coordinates with respect to rigid-body motions. The method is applied to the complex α-helix↔β-sheet transition in a β-hairpin miniprotein in implicit solvent, which exhibits much of the complexity of conformational changes in proteins. Two transition paths are considered, one derived from a linear interpolant between the endpoint structures and the other derived from a targeted dynamics simulation. Two methods for computing the conformational free energy (FE) along the string are compared, a restrained method, and a tessellation method introduced by E. Vanden-Eijnden and M. Venturoli [J. Chem. Phys. 130, 194103 (2009)]. It is found that obtaining meaningful free energy profiles using the present atom-based coordinates requires restricting sampling to a vicinity of the converged path, where the hyperplanar approximation to the isocommittor surface is sufficiently accurate. This sampling restriction can be easily achieved using restraints or constraints. The endpoint FE differences computed from the FE profiles are validated by comparison with previous calculations using a path-independent confinement method. The FE profiles are decomposed into the enthalpic and entropic contributions, and it is shown that the entropy difference contribution can be as large as 10 kcal/mol for intermediate regions along the path, compared to 15-20 kcal/mol for the enthalpy contribution. This result demonstrates that enthalpic barriers for transitions are offset by entropic contributions arising from the existence of different paths across a barrier. The possibility of using systematically coarse-grained representations of amino acids, in the spirit of multiple interaction site residue models, is proposed as a means to avoid ad hoc sampling restrictions to narrow transition tubes.

Modified Kelvin Equations for Capillary Condensation in Narrow and Wide Grooves

NASA Astrophysics Data System (ADS)

Malijevský, Alexandr; Parry, Andrew O.

2018-03-01

We consider the location and order of capillary condensation transitions occurring in deep grooves of width L and depth D . For walls that are completely wet by liquid (contact angle θ =0 ) the transition is continuous and its location is not sensitive to the depth of the groove. However, for walls that are partially wet by liquid, where the transition is first order, we show that the pressure at which it occurs is determined by a modified Kelvin equation characterized by an edge contact angle θE describing the shape of the meniscus formed at the top of the groove. The dependence of θE on the groove depth D relies, in turn, on whether corner menisci are formed at the bottom of the groove in the low density gaslike phase. While for macroscopically wide grooves these are always present when θ <45 ° we argue that their formation is inhibited in narrow grooves. This has a number of implications including that the local pinning of the meniscus and location of the condensation transition is different depending on whether the contact angle is greater or less than a universal value θ*≈31 °. Our arguments are supported by detailed microscopic density functional theory calculations that show that the modified Kelvin equation remains highly accurate even when L and D are of the order of tens of molecular diameters.

Experimental realization of extraordinary acoustic transmission using Helmholtz resonators

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

Crow, Brian C.; Cullen, Jordan M.; McKenzie, William W.

2015-02-15

The phenomenon of extraordinary acoustic transmission through a solid barrier with an embedded Helmholtz resonator (HR) is demonstrated. The Helmholtz resonator consists of an embedded cavity and two necks that protrude, one on each side of the barrier. Extraordinary transmission occurs for a narrow spectral range encompassing the resonant frequency of the Helmholtz resonator. We show that an amplitude transmission of 97.5% is achieved through a resonator whose neck creates an open area of 6.25% of the total barrier area. In addition to the enhanced transmission, we show that there is a smooth, continuous phase transition in the transmitted soundmore » as a function of frequency. The frequency dependent phase transition is used to experimentally realize slow wave propagation for a narrow-band Gaussian wave packet centered at the maximum transmission frequency. The use of parallel pairs of Helmholtz resonators tuned to different resonant frequencies is experimentally explored as a means of increasing the transmission bandwidth. These experiments show that because of the phase transition, there is always a frequency between the two Helmholtz resonant frequencies at which destructive interference occurs whether the resonances are close or far apart. Finally, we explain how the phase transition associated with Helmholtz-resonator-mediated extraordinary acoustic transmission can be exploited to produce diffractive acoustic components including sub-wavelength thickness acoustic lenses.« less

Practical applications of the bioinformatics toolbox for narrowing quantitative trait loci.

PubMed

Burgess-Herbert, Sarah L; Cox, Allison; Tsaih, Shirng-Wern; Paigen, Beverly

2008-12-01

Dissecting the genes involved in complex traits can be confounded by multiple factors, including extensive epistatic interactions among genes, the involvement of epigenetic regulators, and the variable expressivity of traits. Although quantitative trait locus (QTL) analysis has been a powerful tool for localizing the chromosomal regions underlying complex traits, systematically identifying the causal genes remains challenging. Here, through its application to plasma levels of high-density lipoprotein cholesterol (HDL) in mice, we demonstrate a strategy for narrowing QTL that utilizes comparative genomics and bioinformatics techniques. We show how QTL detected in multiple crosses are subjected to both combined cross analysis and haplotype block analysis; how QTL from one species are mapped to the concordant regions in another species; and how genomewide scans associating haplotype groups with their phenotypes can be used to prioritize the narrowed regions. Then we illustrate how these individual methods for narrowing QTL can be systematically integrated for mouse chromosomes 12 and 15, resulting in a significantly reduced number of candidate genes, often from hundreds to <10. Finally, we give an example of how additional bioinformatics resources can be combined with experiments to determine the most likely quantitative trait genes.

Preferred gait and walk-run transition speeds in ostriches measured using GPS-IMU sensors.

PubMed

Daley, Monica A; Channon, Anthony J; Nolan, Grant S; Hall, Jade

2016-10-15

The ostrich (Struthio camelus) is widely appreciated as a fast and agile bipedal athlete, and is a useful comparative bipedal model for human locomotion. Here, we used GPS-IMU sensors to measure naturally selected gait dynamics of ostriches roaming freely over a wide range of speeds in an open field and developed a quantitative method for distinguishing walking and running using accelerometry. We compared freely selected gait-speed distributions with previous laboratory measures of gait dynamics and energetics. We also measured the walk-run and run-walk transition speeds and compared them with those reported for humans. We found that ostriches prefer to walk remarkably slowly, with a narrow walking speed distribution consistent with minimizing cost of transport (CoT) according to a rigid-legged walking model. The dimensionless speeds of the walk-run and run-walk transitions are slower than those observed in humans. Unlike humans, ostriches transition to a run well below the mechanical limit necessitating an aerial phase, as predicted by a compass-gait walking model. When running, ostriches use a broad speed distribution, consistent with previous observations that ostriches are relatively economical runners and have a flat curve for CoT against speed. In contrast, horses exhibit U-shaped curves for CoT against speed, with a narrow speed range within each gait for minimizing CoT. Overall, the gait dynamics of ostriches moving freely over natural terrain are consistent with previous lab-based measures of locomotion. Nonetheless, ostriches, like humans, exhibit a gait-transition hysteresis that is not explained by steady-state locomotor dynamics and energetics. Further study is required to understand the dynamics of gait transitions. © 2016. Published by The Company of Biologists Ltd.

Controlling the optical parameters of self-assembled silver films with wetting layers and annealing

NASA Astrophysics Data System (ADS)

Ciesielski, Arkadiusz; Skowronski, Lukasz; Trzcinski, Marek; Szoplik, Tomasz

2017-11-01

We investigated the influence of presence of Ni and Ge wetting layers as well as annealing on the permittivity of Ag films with thicknesses of 20, 35 and 65 nm. Most of the research on thin silver films deals with very small (<20 nm) or relatively large (≥50 nm) thicknesses. We studied the transition region (around 30 nm) from charge percolation pathways to fully continuous films and compared the values of optical parameters among silver layers with at least one fixed attribute (thickness, wetting and capping material, post-process annealing). Our study, based on atomic force microscopy, ellipsometric and X-ray photoelectron spectroscopy measurements, shows that utilizing a wetting layer is comparable to increasing the thickness of the silver film. Both operations decrease the roughness-to-thickness ratio, thus decreasing the scattering losses and both narrow the Lorentz-shaped interband transition peak. However, while increasing silver thickness increases absorption on the free carriers, the use of wetting layers influences the self-assembled internal structure of silver films in such a way, that the free carrier absorption decreases. Wetting layers also introduce additional contributions from effects like segregation or diffusion, which evolve in time and due to annealing.

The Heliopause Electrostatic Rapid Transit System (HERTS) Design, Trades, and Analyses Performed in the First Year of a Two Year Investigation

NASA Technical Reports Server (NTRS)

Wiegmann, Bruce M.

2016-01-01

The Heliopause Electrostatic Rapid Transit System (HERTS)1 was one of the seven total Phase II NASA Innovative Advanced Concepts (NIAC) that was down-selected in 2015 for continued funding and research. In Phase I we learned that a spacecraft propelled by an Electric Sail (E-Sail) can travel great astronomical distances, such as to the Heliopause region of the solar system (approx.100 to 120 AU) in approximately one quarter of the time (10 years) versus the time it took the Voyager spacecraft launched in 1977 (36 years). The current work within the Phase II NIAC effort builds upon the work that was done in the Phase I NIAC and is focused on: 1) Testing of plasma interaction with a charged wire in a unique MSFC test chamber, 2) Development of a Particle-in-Cell (PIC) models that are validated in the plasma testing and used to extrapolate to the E-Sail propulsion system design. 3) Further down select of a wire deployment and control approach from those narrowed down in the Phase I effort. This paper will document the findings to date (June, 2016) of the above focused areas.

Computational Prediction of Excited-State Carbon Tunneling in the Two Steps of Triplet Zimmerman Di-π-Methane Rearrangement.

PubMed

Li, Xin; Liao, Tao; Chung, Lung Wa

2017-11-22

The photoinduced Zimmerman di-π-methane (DPM) rearrangement of polycyclic molecules to form synthetically useful cyclopropane derivatives was found experimentally to proceed in a triplet excited state. We have applied state-of-the-art quantum mechanical methods, including M06-2X, DLPNO-CCSD(T) and variational transition-state theory with multidimensional tunneling corrections, to an investigation of the reaction rates of the two steps in the triplet DPM rearrangement of dibenzobarrelene, benzobarrelene and barrelene. This study predicts a high probability of carbon tunneling in regions around the two consecutive transition states at 200-300 K, and an enhancement in the rates by 104-276/35-67% with carbon tunneling at 200/300 K. The Arrhenius plots of the rate constants were found to be curved at low temperatures. Moreover, the computed 12 C/ 13 C kinetic isotope effects were affected significantly by carbon tunneling and temperature. Our predictions of electronically excited-state carbon tunneling and two consecutive carbon tunneling are unprecedented. Heavy-atom tunneling in some photoinduced reactions with reactive intermediates and narrow barriers can be potentially observed at relatively low temperature in experiments.

Correlation of Positive and Negative Reciprocity Fails to Confer an Evolutionary Advantage: Phase Transitions to Elementary Strategies

NASA Astrophysics Data System (ADS)

Szolnoki, Attila; Perc, Matjaž

2013-10-01

Economic experiments reveal that humans value cooperation and fairness. Punishing unfair behavior is therefore common, and according to the theory of strong reciprocity, it is also directly related to rewarding cooperative behavior. However, empirical data fail to confirm that positive and negative reciprocity are correlated. Inspired by this disagreement, we determine whether the combined application of reward and punishment is evolutionarily advantageous. We study a spatial public goods game, where in addition to the three elementary strategies of defection, rewarding, and punishment, a fourth strategy that combines the latter two competes for space. We find rich dynamical behavior that gives rise to intricate phase diagrams where continuous and discontinuous phase transitions occur in succession. Indirect territorial competition, spontaneous emergence of cyclic dominance, as well as divergent fluctuations of oscillations that terminate in an absorbing phase are observed. Yet, despite the high complexity of solutions, the combined strategy can survive only in very narrow and unrealistic parameter regions. Elementary strategies, either in pure or mixed phases, are much more common and likely to prevail. Our results highlight the importance of patterns and structure in human cooperation, which should be considered in future experiments.

Recent Line-Shape and Doppler Thermometry Studies Involving Transitions in the ν1 +ν3 Band of Acetylene

NASA Astrophysics Data System (ADS)

Hashemi, Robab; Rozario, Hoimonti; Povey, Chad; Garber, Jolene; Derksen, Mark; Predoi-Cross, Adriana

2014-06-01

The line positions for transitions in the ν1 +ν3 band are often used as a frequency standard by the telecom industry and also needed for planetary atmospheric studies. Four relevant studies have been recently carried out in our group and will be discussed briefly below. (1) N2-broadened line widths and N2-pressure induced line shifts have been measured for transitions in the ν1 +ν3 band of acetylene at seven temperatures in the range 213333K to obtain the temperature dependences of broadening and shift coefficients. The Voigt and hard-collision line profile models were used to retrieve the line parameters. This study has been published in Molecular Physics, 110 Issue 21/22 (2012) 2645-2663. (2) Six nitrogen perturbed transitions of acetylene within the ν1 +ν3 absorption band have been recorded using a 3-channel diode laser spectrometer. We have examined C2H2 spectra using a hard collision (Rautian) profile over a range of five temperatures (213 K-333 K). From these fits we have obtained the N2-broadening and narrowing coefficients of C2H2 and examined their temperature dependence. The experimentally measured narrowing coefficients have been used to estimate the nitrogen diffusion coefficients. The broadening coefficients and corresponding temperature dependence exponents have also been compared to that of calculations completed using a classical impact approach on an ab initio potential energy surface. We have observed a good agreement between our theoretical and experimental results. This study was published in Canadian Journal of Physics 91(11) 896-905 (2013). (3) An extension of the previous study was to analyze the room temperature for the same six transitions using the Voigt, Rautian, Galatry, RautianGalatry and Correlated Rautian profiles. For the entire pressure range, we have tested the applicability of these line-shape models. Except for Voigt profile, Dicke narrowing effect has been considered in all mentioned line-shape models. The experimental results for the narrowing parameters have been compared with calculated values based on the theory of diffusion. This study is in press in press in the Journal of Quantitative Spectroscopy and Radiative Transfer. (4) In this paper we present accurate measurements of the fundamental Boltzmann constant based on a lineshape analysis of acetylene spectra in the ν1 +ν3 band recorded using a tunable diode laser. Experimental spectra recorded at low pressures have been analyzed using both the Voigt model and the Speed Dependent Voigt model that takes into account the molecular speed dependence effects. These line-shape models reproduces the experimental data with high accuracy and allow us to determine precise line-shape parameters for the transitions used, the Doppler-width and then determined the Boltzmann constant, kB. This study has been submitted for publication in the Journal of Chemical Physics. 1 1 Research described in this work was funded by NSERC, Canada.

High Work Output Ni-Ti-Pt High Temperature Shape Memory Alloys and Associated Processing Methods

NASA Technical Reports Server (NTRS)

Noebe, Ronald D. (Inventor); Draper, Susan L. (Inventor); Nathal, Michael V. (Inventor); Garg, Anita (Inventor)

2009-01-01

According to the invention, compositions of Ni-Ti-Pt high temperature, high force, shape memory alloys are disclosed that have transition temperatures above 100 C.; have narrow hysteresis; and produce a high specific work output.

Transition from magma dominant to magma poor rifting along the Nova Scotia Continental Margin

NASA Astrophysics Data System (ADS)

Lau, K. H.; Louden, K. E.; Nedimović, M. R.; Whitehead, M.; Farkas, A.; Watremez, L.; Dehler, S. A.

2011-12-01

Passive margins have been characterized as magma-dominant (volcanic) or magma-poor (non-volcanic). However, the conditions under which margins might switch states are not well understood as they typically have been studied as end member examples in isolation to each other. The Nova Scotia (NS) continental margin, however, offers an opportunity to study the nature of such a transition between the magma-dominant US East Coast margin to the south and the magma-poor Newfoundland margin to the north within a single rift segment. This transition is evidenced by a clear along-strike reduction in features characteristic of syn-rift volcanism from south-to-north along the NS margin, such as the weakening of the East Coast Magnetic Anomaly (ECMA) and the coincident disappearance of seaward dipping reflector sequences (SDRS) on multichannel seismic (MCS) reflection profiles. Results from recent industry MCS profiles along and across the margin suggest a potentially narrow magma-dominant to magma-poor along-strike transition between the southern and the central NS margin. Such a transition is broadly consistent with results of several widely-spaced, across-strike ocean bottom seismometer (OBS) wide-angle profiles. In the southern region, the crustal structure exhibits a narrow (~120-km wide) ocean-continent transition (OCT) with a high velocity (7.2 km/s) lower crust, interpreted as a gabbro-rich underplated melt, beneath the SDRS and the ECMA, similar to crustal models across the US East Coast. In contrast, profiles across the central and northern margin contain a much wider OCT (150-200-km wide) underlain by a low velocity mantle layer (7.3-7.9 km/s), interpreted as partially serpentinized olivine, which is similar to the magma-poor Newfoundland margin to the north. However, the central-to-northern OBS profiles also exhibit significant variations within the OCT and the along-strike continuity of these OCT structures is not yet clear. In November 2010, we acquired, in the OCTOPUS survey, wide-angle seismic data along a 240-km-long margin parallel profile extending from the central to the northern margin segments along an existing industry MCS profile (Ion/GX Technology NovaSPAN 5100). Twenty OBSs at 10-km spacing were analysed. A preliminary p-wave velocity model along the profile indicates that the cross-strike structures are continuous within the OCT. However, a substantial anisotropy in velocity (~8% lower parallel to the margin) is observed within the OCT. This result is consistent with an interpretation of partially serpentinized mantle that flowed perpendicular to the margin during its extension. In addition, along strike variations are also observed along the profile, which suggest a higher degree of volcanism and a thinner layer of serpentinized mantle to the southwest. These results provide a framework for future studies to the southwest to further investigate the transition to a magma-dominant regime towards the US East Coast.

Simple effective rule to estimate the jamming packing fraction of polydisperse hard spheres.

PubMed

Santos, Andrés; Yuste, Santos B; López de Haro, Mariano; Odriozola, Gerardo; Ogarko, Vitaliy

2014-04-01

A recent proposal in which the equation of state of a polydisperse hard-sphere mixture is mapped onto that of the one-component fluid is extrapolated beyond the freezing point to estimate the jamming packing fraction ϕJ of the polydisperse system as a simple function of M1M3/M22, where Mk is the kth moment of the size distribution. An analysis of experimental and simulation data of ϕJ for a large number of different mixtures shows a remarkable general agreement with the theoretical estimate. To give extra support to the procedure, simulation data for seventeen mixtures in the high-density region are used to infer the equation of state of the pure hard-sphere system in the metastable region. An excellent collapse of the inferred curves up to the glass transition and a significant narrowing of the different out-of-equilibrium glass branches all the way to jamming are observed. Thus, the present approach provides an extremely simple criterion to unify in a common framework and to give coherence to data coming from very different polydisperse hard-sphere mixtures.

Bathymetric controls on sediment transport in the Hudson River estuary: Lateral asymmetry and frontal trapping

USGS Publications Warehouse

Ralston, David K.; Geyer, W. Rockwell; Warner, John C.

2012-01-01

Analyses of field observations and numerical model results have identified that sediment transport in the Hudson River estuary is laterally segregated between channel and shoals, features frontal trapping at multiple locations along the estuary, and varies significantly over the spring-neap tidal cycle. Lateral gradients in depth, and therefore baroclinic pressure gradient and stratification, control the lateral distribution of sediment transport. Within the saline estuary, sediment fluxes are strongly landward in the channel and seaward on the shoals. At multiple locations, bottom salinity fronts form at bathymetric transitions in width or depth. Sediment convergences near the fronts create local maxima in suspended-sediment concentration and deposition, providing a general mechanism for creation of secondary estuarine turbidity maxima at bathymetric transitions. The lateral bathymetry also affects the spring-neap cycle of sediment suspension and deposition. In regions with broad, shallow shoals, the shoals are erosional and the channel is depositional during neap tides, with the opposite pattern during spring tides. Narrower, deeper shoals are depositional during neaps and erosional during springs. In each case, the lateral transfer is from regions of higher to lower bed stress, and depends on the elevation of the pycnocline relative to the bed. Collectively, the results indicate that lateral and along-channel gradients in bathymetry and thus stratification, bed stress, and sediment flux lead to an unsteady, heterogeneous distribution of sediment transport and trapping along the estuary rather than trapping solely at a turbidity maximum at the limit of the salinity intrusion.

CHEERS Results from NGC 3393. II. Investigating the Extended Narrow-line Region Using Deep Chandra Observations and Hubble Space Telescope Narrow-line Imaging

NASA Astrophysics Data System (ADS)

Maksym, W. Peter; Fabbiano, Giuseppina; Elvis, Martin; Karovska, Margarita; Paggi, Alessandro; Raymond, John; Wang, Junfeng; Storchi-Bergmann, Thaisa

2017-07-01

The CHandra Extended Emission Line Region Survey (CHEERS) is an X-ray study of nearby active galactic nuclei (AGNs) designed to take full advantage of Chandra's unique angular resolution by spatially resolving feedback signatures and effects. In the second paper of a series on CHEERS target NGC 3393, we examine deep high-resolution Chandra images and compare them with Hubble Space Telescope narrow-line images of [O III], [S II], and Hα, as well as previously unpublished mid-ultraviolet (MUV) images. The X-rays provide unprecedented evidence that the S-shaped arms that envelope the nuclear radio outflows extend only ≲0.″2 (≲50 pc) across. The high-resolution multiwavelength data suggest that the extended narrow-line region is a complex multiphase structure in the circumnuclear interstellar medium (ISM). Its ionization structure is highly stratified with respect to outflow-driven bubbles in the bicone and varies dramatically on scales of ˜10 pc. Multiple findings show likely contributions from shocks to the feedback in regions where radio outflows from the AGN most directly influence the ISM. These findings include Hα evidence for gas compression and extended MUV emission and are in agreement with existing STIS kinematics. Extended filamentary structure in the X-rays and optical suggests the presence of an undetected plasma component, whose existence could be tested with deeper radio observations.

A simplified scheme for generating narrow-band mid-ultraviolet laser radiation

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

Almog, G.; Ludwig-Maximilians-Universität, Geschwister-Scholl-Platz 1, 80539 München; Scholz, M., E-mail: Matthias.Scholz@toptica.com

2015-03-15

We report on the development and characterization of continuous, narrow-band, and tunable laser systems that use direct second-harmonic generation from blue and green diode lasers with an output power level of up to 11.1 mW in the mid-ultraviolet. One of our laser systems was tuned to the mercury 6{sup 1}S{sub 0} → 6{sup 3}P{sub 1} intercombination line at 253.7 nm. We could perform Doppler-free saturation spectroscopy on this line and were able to lock our laser to the transition frequency on long time scales.

A new method suitable for calculating accurately wetting temperature over a wide range of conditions: Based on the adaptation of continuation algorithm to classical DFT

NASA Astrophysics Data System (ADS)

Zhou, Shiqi

2017-11-01

A new scheme is put forward to determine the wetting temperature (Tw) by utilizing the adaptation of arc-length continuation algorithm to classical density functional theory (DFT) used originally by Frink and Salinger, and its advantages are summarized into four points: (i) the new scheme is applicable whether the wetting occurs near a planar or a non-planar surface, whereas a zero contact angle method is considered only applicable to a perfectly flat solid surface, as demonstrated previously and in this work, and essentially not fit for non-planar surface. (ii) The new scheme is devoid of an uncertainty, which plagues a pre-wetting extrapolation method and originates from an unattainability of the infinitely thick film in the theoretical calculation. (iii) The new scheme can be similarly and easily applied to extreme instances characterized by lower temperatures and/or higher surface attraction force field, which, however, can not be dealt with by the pre-wetting extrapolation method because of the pre-wetting transition being mixed with many layering transitions and the difficulty in differentiating varieties of the surface phase transitions. (iv) The new scheme still works in instance wherein the wetting transition occurs close to the bulk critical temperature; however, this case completely can not be managed by the pre-wetting extrapolation method because near the bulk critical temperature the pre-wetting region is extremely narrow, and no enough pre-wetting data are available for use of the extrapolation procedure.

Phase equilibrium in argon films stabilized by homogeneous surfaces and thermodynamics of two-stage melting transition.

PubMed

Ustinov, E A

2014-02-21

Freezing of gases adsorbed on open surfaces (e.g., graphite) and in narrow pores is a widespread phenomenon which is a subject of a large number of publications. Modeling of the gas/liquid-solid transition is usually accomplished with a molecular simulation technique. However, quantitative analysis of the gas/liquid-solid coexistence and thermodynamic properties of the solid layer still encounters serious difficulties. This is mainly due to the effect of simulation box size on the lattice constant. Since the lattice constant is a function of loading and temperature, once the ordering transition has occurred, the simulation box size must be corrected in the course of simulation according to the Gibbs-Duhem equation. A significant problem is also associated with accurate prediction of the two-dimensional liquid-solid coexistence because of a small difference in densities of coexisting phases. The aim of this study is thermodynamic analysis of the two-dimensional phase coexistence in systems involving crystal-like free of defects layers in narrow slit pores. A special attention was paid to the determination of triple point temperatures. It is shown that intrinsic properties of argon monolayer adsorbed on the graphite surface are similar to those of isolated monolayer accommodated in the slit pore having width of two argon collision diameters. Analysis of the latter system is shown to be clearer and less time-consuming than the former one, which has allowed for explanation of the experimentally observed two-stage melting transition of argon monolayer on graphite without invoking the periodic surface potential modulation and orientational transition.

Phase equilibrium in argon films stabilized by homogeneous surfaces and thermodynamics of two-stage melting transition

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

Ustinov, E. A., E-mail: eustinov@mail.wplus.net

Freezing of gases adsorbed on open surfaces (e.g., graphite) and in narrow pores is a widespread phenomenon which is a subject of a large number of publications. Modeling of the gas/liquid–solid transition is usually accomplished with a molecular simulation technique. However, quantitative analysis of the gas/liquid–solid coexistence and thermodynamic properties of the solid layer still encounters serious difficulties. This is mainly due to the effect of simulation box size on the lattice constant. Since the lattice constant is a function of loading and temperature, once the ordering transition has occurred, the simulation box size must be corrected in the coursemore » of simulation according to the Gibbs–Duhem equation. A significant problem is also associated with accurate prediction of the two-dimensional liquid–solid coexistence because of a small difference in densities of coexisting phases. The aim of this study is thermodynamic analysis of the two-dimensional phase coexistence in systems involving crystal-like free of defects layers in narrow slit pores. A special attention was paid to the determination of triple point temperatures. It is shown that intrinsic properties of argon monolayer adsorbed on the graphite surface are similar to those of isolated monolayer accommodated in the slit pore having width of two argon collision diameters. Analysis of the latter system is shown to be clearer and less time-consuming than the former one, which has allowed for explanation of the experimentally observed two-stage melting transition of argon monolayer on graphite without invoking the periodic surface potential modulation and orientational transition.« less

Femoral neck-shaft angle in humans: variation relating to climate, clothing, lifestyle, sex, age and side.

PubMed

Gilligan, Ian; Chandraphak, Supichya; Mahakkanukrauh, Pasuk

2013-08-01

The femoral neck-shaft angle (NSA) varies among modern humans but measurement problems and sampling limitations have precluded the identification of factors contributing to its variation at the population level. Potential sources of variation include sex, age, side (left or right), regional differences in body shape due to climatic adaptation, and the effects of habitual activity patterns (e.g. mobile and sedentary lifestyles and foraging, agricultural, and urban economies). In this study we addressed these issues, using consistent methods to assemble a global NSA database comprising over 8000 femora representing 100 human groups. Results from the analyses show an average NSA for modern humans of 127° (markedly lower than the accepted value of 135°); there is no sex difference, no age-related change in adults, but possibly a small lateral difference which could be due to right leg dominance. Climatic trends consistent with principles based on Bergmann's rule are evident at the global and continental levels, with the NSA varying in relation to other body shape indices: median NSA, for instance, is higher in warmer regions, notably in the Pacific (130°), whereas lower values (associated with a more stocky body build) are found in regions where ancestral populations were exposed to colder conditions, in Europe (126°) and the Americas (125°). There is a modest trend towards increasing NSA with the economic transitions from forager to agricultural and urban lifestyles and, to a lesser extent, from a mobile to a sedentary existence. However, the main trend associated with these transitions is a progressive narrowing in the range of variation in the NSA, which may be attributable to thermal insulation provided by improved cultural buffering from climate, particularly clothing. © 2013 Anatomical Society.

TRANSITION-REGION/CORONAL SIGNATURES AND MAGNETIC SETTING OF SUNSPOT PENUMBRAL JETS: HINODE (SOT/FG), Hi-C, AND SDO/AIA OBSERVATIONS

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

Tiwari, Sanjiv K.; Moore, Ronald L.; Winebarger, Amy R.

2016-01-10

Penumbral microjets (PJs) are transient narrow bright features in the chromosphere of sunspot penumbrae, first characterized by Katsukawa et al. using the Ca ii H-line filter on Hinode's Solar Optical Telescope (SOT). It was proposed that the PJs form as a result of reconnection between two magnetic components of penumbrae (spines and interspines), and that they could contribute to the transition region (TR) and coronal heating above sunspot penumbrae. We propose a modified picture of formation of PJs based on recent results on the internal structure of sunspot penumbral filaments. Using data of a sunspot from Hinode/SOT, High Resolution Coronalmore » Imager, and different passbands of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, we examine whether PJs have signatures in the TR and corona. We find hardly any discernible signature of normal PJs in any AIA passbands, except for a few of them showing up in the 1600 Å images. However, we discovered exceptionally stronger jets with similar lifetimes but bigger sizes (up to 600 km wide) occurring repeatedly in a few locations in the penumbra, where evidence of patches of opposite-polarity fields in the tails of some penumbral filaments is seen in Stokes-V images. These tail PJs do display signatures in the TR. Whether they have any coronal-temperature plasma is unclear. We infer that none of the PJs, including the tail PJs, directly heat the corona in active regions significantly, but any penumbral jet might drive some coronal heating indirectly via the generation of Alfvén waves and/or braiding of the coronal field.« less

Femoral neck-shaft angle in humans: variation relating to climate, clothing, lifestyle, sex, age and side

PubMed Central

Gilligan, Ian; Chandraphak, Supichya; Mahakkanukrauh, Pasuk

2013-01-01

The femoral neck-shaft angle (NSA) varies among modern humans but measurement problems and sampling limitations have precluded the identification of factors contributing to its variation at the population level. Potential sources of variation include sex, age, side (left or right), regional differences in body shape due to climatic adaptation, and the effects of habitual activity patterns (e.g. mobile and sedentary lifestyles and foraging, agricultural, and urban economies). In this study we addressed these issues, using consistent methods to assemble a global NSA database comprising over 8000 femora representing 100 human groups. Results from the analyses show an average NSA for modern humans of 127° (markedly lower than the accepted value of 135°); there is no sex difference, no age-related change in adults, but possibly a small lateral difference which could be due to right leg dominance. Climatic trends consistent with principles based on Bergmann's rule are evident at the global and continental levels, with the NSA varying in relation to other body shape indices: median NSA, for instance, is higher in warmer regions, notably in the Pacific (130°), whereas lower values (associated with a more stocky body build) are found in regions where ancestral populations were exposed to colder conditions, in Europe (126°) and the Americas (125°). There is a modest trend towards increasing NSA with the economic transitions from forager to agricultural and urban lifestyles and, to a lesser extent, from a mobile to a sedentary existence. However, the main trend associated with these transitions is a progressive narrowing in the range of variation in the NSA, which may be attributable to thermal insulation provided by improved cultural buffering from climate, particularly clothing. PMID:23781912

Wigner time-delay distribution in chaotic cavities and freezing transition.

PubMed

Texier, Christophe; Majumdar, Satya N

2013-06-21

Using the joint distribution for proper time delays of a chaotic cavity derived by Brouwer, Frahm, and Beenakker [Phys. Rev. Lett. 78, 4737 (1997)], we obtain, in the limit of the large number of channels N, the large deviation function for the distribution of the Wigner time delay (the sum of proper times) by a Coulomb gas method. We show that the existence of a power law tail originates from narrow resonance contributions, related to a (second order) freezing transition in the Coulomb gas.

Localized-to-extended-states transition below the Fermi level

NASA Astrophysics Data System (ADS)

Tito, M. A.; Pusep, Yu. A.

2018-05-01

Time-resolved photoluminescence is employed to examine a transition from localized to extended electron states below the Fermi level in multiple narrow quantum well GaAs/AlGaAs heterostructures, where disorder was generated by interface roughness. Such a transition resembles the metal-insulator transition profoundly investigated by electric transport measurements. An important distinction distinguishes the localized-to-extended-states transition studied here: it takes place below the Fermi level in an electron system with a constant concentration, which implies unchanging Coulomb correlations. Moreover, for such a localized-to-extended-states transition the temperature is shown to be irrelevant. In the insulating regime the magnetic field was found to cause an additional momentum relaxation which considerably enhanced the recombination rate. Thus, we propose a method to explore the evolution of the localized electron states in a system with a fixed disorder and Coulomb interaction.

The Structure of A Pacific Narrow Cold Frontal Rainband

NASA Technical Reports Server (NTRS)

Jorgensen, David P.; Pu, Zhaoxia; Persson, Ola; Tao, Wei-Kuo; Starr, David OC. (Technical Monitor)

2002-01-01

A NOAA P-3 instrumented aircraft observed an intense, fast-moving narrow cold frontal Farmhand as it approached the Pacific Northwest coast on 19 February 2001 during the Pacific Coastal Jets Experiment. Pseudo-dual-Doppler analyses performed on the airborne Doppler radar data while the frontal system was well offshore indicated that a narrow ribbon of very high radar reflectively convective cores characterized the Farmhand at low levels with echo tops to approximately 4-5 km. The NCFR exhibited gaps in its narrow ribbon of high reflectively, probably as a result of hydrodynamic instability all no its advancing cold pool leading edge. In contrast to some earlier studies of cold frontal rainbands, density current theory described well the motion of the overall front. The character of the updraft structure associated with the heavy rainfall at its leading edge varied across the gap region. The vertical shear of the cross-frontal low-level ambient flow exerted a strong influence on the updraft character, consistent with theoretical arguments developed for squall lines describing the balance of vorticity at the leading edge. In short regions south of the gaps the vertical wind shear was strongest with the updrafts and rain shafts more intense, narrower, and more erect or even downshear tilted. North of the gaps the wind shear weakened with less intense Dihedrals which tilted upshear with a broader band of rainfall. Simulations using a nonhydrostatic mesoscale nested grid model are used to investigate the gap regions, particularly the balance of cold pool induced to pre-frontal ambient shears at the leading edge. Observations confirm the model results that the updraft character depends on the balance of vorticity at the leading edge. Downshear-tilted updrafts imply that convection south of the gap regions would weaken with time relative to the frontal segments north of the gaps since inflow air would be affected by passage through the heavy rain region before ascent, suggesting a mechanism for gap filling.

Zero-gap semiconductor to excitonic insulator transition in Ta2NiSe5

PubMed Central

Lu, Y. F.; Kono, H.; Larkin, T. I.; Rost, A. W.; Takayama, T.; Boris, A. V.; Keimer, B.; Takagi, H.

2017-01-01

The excitonic insulator is a long conjectured correlated electron phase of narrow-gap semiconductors and semimetals, driven by weakly screened electron–hole interactions. Having been proposed more than 50 years ago, conclusive experimental evidence for its existence remains elusive. Ta2NiSe5 is a narrow-gap semiconductor with a small one-electron bandgap EG of <50 meV. Below TC=326 K, a putative excitonic insulator is stabilized. Here we report an optical excitation gap Eop ∼0.16 eV below TC comparable to the estimated exciton binding energy EB. Specific heat measurements show the entropy associated with the transition being consistent with a primarily electronic origin. To further explore this physics, we map the TC–EG phase diagram tuning EG via chemical and physical pressure. The dome-like behaviour around EG∼0 combined with our transport, thermodynamic and optical results are fully consistent with an excitonic insulator phase in Ta2NiSe5. PMID:28205553

Superconductivity in the Narrow Gap Semiconductor RbBi 11/3Te 6

DOE PAGES

Malliakas, Christos D.; Chung, Duck Young; Claus, Helmut; ...

2016-10-16

Superconductivity was discovered in the layered compound RbBi 11/3Te 6, featuring Bi vacancies and a narrow band gap of 0.25(2) eV at room temperature. In addition, a sharp superconducting transition at similar to 3.2 K was observed in polycrystalline ingots. The superconducting volume fraction of oriented single crystals is almost 100%, confirming bulk superconductivity. Systematic Se and Sb substitutions in RbBi 11/3-ySb ySe xTe 6-x, revealed a dependence of the superconducting transition on composition that can increase the T c up to similar to 10%. The RbBi 11/3Te 6 system is the first member of the new homologous series Rb[Bimore » 2n+11/3Te 3n+6] with infinite Bi 2Te 3-like layers. Lastly, the large degree of chemical tunability of the electronic structure of the homology via doping and/or substitution gives rise to a new family of superconductors.« less

Adhesive micro-line periodicity determines guidance of axonal outgrowth†

PubMed Central

Huang, Yu; Fothergill, Thomas; Lumbard, Derek C.; Dent, Erik W.; Williams, Justin C.

2014-01-01

Adhesive micro-lines of various sub-cellular geometries were created using a non-traditional micro stamping technique. This technique employed the use of commercially available diffraction gratings as the molds for the micro stamps, a method which is quick and inexpensive, and which could easily be adopted as a patterning tool in a variety of research efforts. The atypical saw-tooth profile of the micro stamps enabled a unique degree of control and flexibility over patterned line and gap widths. Cortical neurons cultured on patterned poly-lysine micro-lines on PDMS exhibit a startling transition in axonal guidance: From the expected parallel guidance to an unexpected perpendicular guidance that becomes dominant as patterned lines and gaps become sufficiently narrow. This transition is most obvious when the lines are narrow relative to gaps, while the periodicity of the pattern is reduced. Axons growing perpendicular to micro-lines exhibited ‘vinculated’ growth, a unique morphological phenotype consisting of periodic orthogonal extensions along the axon. PMID:23250489

Pulse Shaped 8-PSK Bandwidth Efficiency and Spectral Spike Elimination

NASA Technical Reports Server (NTRS)

Tao, Jian-Ping

1998-01-01

The most bandwidth-efficient communication methods are imperative to cope with the congested frequency bands. Pulse shaping methods have excellent effects on narrowing bandwidth and increasing band utilization. The position of the baseband filters for the pulse shaping is crucial. Post-modulation pulse shaping (a low pass filter is located after the modulator) can change signals from constant envelope to non-constant envelope, and non-constant envelope signals through non-linear device (a SSPA or TWT) can further spread the power spectra. Pre-modulation pulse shaping (a filter is located before the modulator) will have constant envelope. These two pulse shaping methods have different effects on narrowing the bandwidth and producing bit errors. This report studied the effect of various pre-modulation pulse shaping filters with respect to bandwidth, spectral spikes and bit error rate. A pre-modulation pulse shaped 8-ary Phase Shift Keying (8PSK) modulation was used throughout the simulations. In addition to traditional pulse shaping filters, such as Bessel, Butterworth and Square Root Raised Cosine (SRRC), other kinds of filters or pulse waveforms were also studied in the pre-modulation pulse shaping method. Simulations were conducted by using the Signal Processing Worksystem (SPW) software package on HP workstations which simulated the power spectral density of pulse shaped 8-PSK signals, end to end system performance and bit error rates (BERS) as a function of Eb/No using pulse shaping in an AWGN channel. These results are compared with the post-modulation pulse shaped 8-PSK results. The simulations indicate traditional pulse shaping filters used in pre-modulation pulse shaping may produce narrower bandwidth, but with worse BER than those in post-modulation pulse shaping. Theory and simulations show pre- modulation pulse shaping could also produce discrete line power spectra (spikes) at regular frequency intervals. These spikes may cause interference with adjacent channel and reduce power efficiency. Some particular pulses (filters), such as trapezoid and pulses with different transits (such as weighted raised cosine transit) were found to reduce bandwidth and not generate spectral spikes. Although a solid state power amplifier (SSPA) was simulated in the non-linear (saturation) region, output power spectra did not spread due to the constant envelope 8-PSK signals.

Narrowing of the Upwelling Branch of the Brewer-Dobson Circulation and Hadley Cell in Chemistry-Climate Model Simulations of the 21st Century

NASA Technical Reports Server (NTRS)

Li, Feng; Stolarski, Richard S.; Pawson, Steven; Newman, Paul A.; Waugh, Darryn

2010-01-01

Changes in the width of the upwelling branch of the Brewer-Dobson circulation and Hadley cell in the 21st Century are investigated using simulations from a coupled chemistry-climate model. In these model simulations the tropical upwelling region narrows in the troposphere and lower stratosphere. The narrowing of the Brewer-Dobson circulation is caused by an equatorward shift of Rossby wave critical latitudes and Eliassen-Palm flux convergence in the subtropical lower stratosphere. In the troposphere, the model projects an expansion of the Hadley cell's poleward boundary, but a narrowing of the Hadley rising branch. Model results suggest that the narrowing of the Hadley cell ascent is also eddy-driven.

New Geologic Map of the Argyre Region of Mars: Deciphering the Geologic History Through Mars Global Surveyor, Mars Odyssey, and Mars Express Data

NASA Technical Reports Server (NTRS)

Dohm, J. M.; Banks, M.; Buczkowski, D.

2010-01-01

The primary objective of the mapping effort is to produce a geologic map of the Argyre basin and surrounding region at 1:5,000,000 scale in both digital and print formats that will detail the stratigraphic and crosscutting relations among rock materials and landforms (30 deg. S to 65 deg. S, 290 deg. E to 340 deg E). There has not been a detailed geologic map produced of the Argyre region since the Viking-era mapping investigation. The mapping tasks include stratigraphic mapping, crater counting, feature mapping, quantitative landform analysis, and spectroscopic/ stratigraphic investigation feature mapping. The regional geologic mapping investigation includes the Argyre basin floor and rim materials, the transition zone that straddles the Thaumasia plateau, which includes Argyre impactrelated modification, and the southeast margin of the Thaumasia plateau using important new data sets from the Mars Global Surveyor, Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter. The geologic information unfolded by this new mapping project will be useful to the community for constraining the regional geology, paleohydrology, and paleoclimate, which includes but is not limited to the assessment of: (1) whether the Argyre basin contained lakes, (2) the extent of reported flooding and glaciation, (3) existing interpretations of the origin of the narrow ridges located in the southeast part of the basin floor, and (4) the extent of Argyre-related tectonism and its influence on the surrounding regions.

Bose-Einstein condensation in an ultra-hot gas of pumped magnons.

PubMed

Serga, Alexander A; Tiberkevich, Vasil S; Sandweg, Christian W; Vasyuchka, Vitaliy I; Bozhko, Dmytro A; Chumak, Andrii V; Neumann, Timo; Obry, Björn; Melkov, Gennadii A; Slavin, Andrei N; Hillebrands, Burkard

2014-03-11

Bose-Einstein condensation of quasi-particles such as excitons, polaritons, magnons and photons is a fascinating quantum mechanical phenomenon. Unlike the Bose-Einstein condensation of real particles (like atoms), these processes do not require low temperatures, since the high densities of low-energy quasi-particles needed for the condensate to form can be produced via external pumping. Here we demonstrate that such a pumping can create remarkably high effective temperatures in a narrow spectral region of the lowest energy states in a magnon gas, resulting in strikingly unexpected transitional dynamics of Bose-Einstein magnon condensate: the density of the condensate increases immediately after the external magnon flow is switched off and initially decreases if it is switched on again. This behaviour finds explanation in a nonlinear 'evaporative supercooling' mechanism that couples the low-energy magnons overheated by pumping with all the other thermal magnons, removing the excess heat, and allowing Bose-Einstein condensate formation.

Broadband observations of the naked-eye gamma-ray burst GRB 080319B.

PubMed

Racusin, J L; Karpov, S V; Sokolowski, M; Granot, J; Wu, X F; Pal'shin, V; Covino, S; van der Horst, A J; Oates, S R; Schady, P; Smith, R J; Cummings, J; Starling, R L C; Piotrowski, L W; Zhang, B; Evans, P A; Holland, S T; Malek, K; Page, M T; Vetere, L; Margutti, R; Guidorzi, C; Kamble, A P; Curran, P A; Beardmore, A; Kouveliotou, C; Mankiewicz, L; Melandri, A; O'Brien, P T; Page, K L; Piran, T; Tanvir, N R; Wrochna, G; Aptekar, R L; Barthelmy, S; Bartolini, C; Beskin, G M; Bondar, S; Bremer, M; Campana, S; Castro-Tirado, A; Cucchiara, A; Cwiok, M; D'Avanzo, P; D'Elia, V; Valle, M Della; de Ugarte Postigo, A; Dominik, W; Falcone, A; Fiore, F; Fox, D B; Frederiks, D D; Fruchter, A S; Fugazza, D; Garrett, M A; Gehrels, N; Golenetskii, S; Gomboc, A; Gorosabel, J; Greco, G; Guarnieri, A; Immler, S; Jelinek, M; Kasprowicz, G; La Parola, V; Levan, A J; Mangano, V; Mazets, E P; Molinari, E; Moretti, A; Nawrocki, K; Oleynik, P P; Osborne, J P; Pagani, C; Pandey, S B; Paragi, Z; Perri, M; Piccioni, A; Ramirez-Ruiz, E; Roming, P W A; Steele, I A; Strom, R G; Testa, V; Tosti, G; Ulanov, M V; Wiersema, K; Wijers, R A M J; Winters, J M; Zarnecki, A F; Zerbi, F; Mészáros, P; Chincarini, G; Burrows, D N

2008-09-11

Long-duration gamma-ray bursts (GRBs) release copious amounts of energy across the entire electromagnetic spectrum, and so provide a window into the process of black hole formation from the collapse of massive stars. Previous early optical observations of even the most exceptional GRBs (990123 and 030329) lacked both the temporal resolution to probe the optical flash in detail and the accuracy needed to trace the transition from the prompt emission within the outflow to external shocks caused by interaction with the progenitor environment. Here we report observations of the extraordinarily bright prompt optical and gamma-ray emission of GRB 080319B that provide diagnostics within seconds of its formation, followed by broadband observations of the afterglow decay that continued for weeks. We show that the prompt emission stems from a single physical region, implying an extremely relativistic outflow that propagates within the narrow inner core of a two-component jet.

Mesoscale Particle-Based Model of Electrophoretic Deposition

DOE PAGES

Giera, Brian; Zepeda-Ruiz, Luis A.; Pascall, Andrew J.; ...

2016-12-20

In this paper, we present and evaluate a semiempirical particle-based model of electrophoretic deposition using extensive mesoscale simulations. We analyze particle configurations in order to observe how colloids accumulate at the electrode and arrange into deposits. In agreement with existing continuum models, the thickness of the deposit increases linearly in time during deposition. Resulting colloidal deposits exhibit a transition between highly ordered and bulk disordered regions that can give rise to an appreciable density gradient under certain simulated conditions. The overall volume fraction increases and falls within a narrow range as the driving force due to the electric field increasesmore » and repulsive intercolloidal interactions decrease. We postulate ordering and stacking within the initial layer(s) dramatically impacts the microstructure of the deposits. Finally, we find a combination of parameters, i.e., electric field and suspension properties, whose interplay enhances colloidal ordering beyond the commonly known approach of only reducing the driving force.« less

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

Tyson, T. A.; Gao, W.; Chen, Y. -S.

Solar cells based on hybrid perovskites have shown high efficiency while possessing simple processing methods. To gain a fundamental understanding of their properties on an atomic level, we investigate single crystals of CH 3NH 3PbI 3 with a narrow transition (~5 K) near 327 K. Temperature dependent structural measurements reveal a persistent tetragonal structure with smooth changes in the atomic displacement parameters (ADPs) on crossing T*. We show that the ADPs for I ions yield extended flat regions in the potential wells consistent with the measured large thermal expansion parameter. Molecular dynamics simulations reveal that this material exhibits significant asymmetriesmore » in the Pb-I pair distribution functions. We also show that the intrinsically enhanced freedom of motion of the iodine atoms enables large deformations. This flexibility (softness) of the atomic structure results in highly localized atomic relaxation about defects and hence accounts for both the high carrier mobility as well as the structural instability.« less

The excitation and distribution of CO (J = 6-5) emission in the Orion Nebula

NASA Technical Reports Server (NTRS)

Buhl, D.; Chin, G.; Fetterman, H. R.; Koepf, G. A.; Peck, D. D.

1982-01-01

Observations of the 691-GHz (J = 6-5) transition of CO in the BN/KL region of Orion obtained in February 1981, at the IR Telescope Facility at Mauna Kea are reported. The system employs a heterodyne receiver with an overall noise temperature of 3900 K DSB at 432 microns, 64 5-MHz IF-filter-bank channels, and a chopping secondary with 120-arcsec excursion, and has 35-arcsec resolution. Sample data are presented graphically and analyzed using a rate equation and a kinetic model. A 35 x 45-arcsec core with hot broad plateau emission (antenna temperature 180 + or - 36 K) surrounded by an area of strong narrow-line 120-K emission is found. It is suggested that the plateau emission originates in a wide thin sheet after a shock wave, with H2 density at least 10 to the 6th/cu cm and gas kinetic temperature greater than 500 K.

Property Analysis of the Real-Time Uncalibrated Phase Delay Product Generated by Regional Reference Stations and Its Influence on Precise Point Positioning Ambiguity Resolution

PubMed Central

Zhang, Yong; Wang, Qing; Jiang, Xinyuan

2017-01-01

The real-time estimation of the wide-lane and narrow-lane Uncalibrated Phase Delay (UPD) of satellites is realized by real-time data received from regional reference station networks; The properties of the real-time UPD product and its influence on real-time precise point positioning ambiguity resolution (RTPPP-AR) are experimentally analyzed according to real-time data obtained from the regional Continuously Operating Reference Stations (CORS) network located in Tianjin, Shanghai, Hong Kong, etc. The results show that the real-time wide-lane and narrow-lane UPD products differ significantly from each other in time-domain characteristics; the wide-lane UPDs have daily stability, with a change rate of less than 0.1 cycle/day, while the narrow-lane UPDs have short-term stability, with significant change in one day. The UPD products generated by different regional networks have obvious spatial characteristics, thus significantly influencing RTPPP-AR: the adoption of real-time UPD products employing the sparse stations in the regional network for estimation is favorable for improving the regional RTPPP-AR up to 99%; the real-time UPD products of different regional networks slightly influence PPP-AR positioning accuracy. After ambiguities are successfully fixed, the real-time dynamic RTPPP-AR positioning accuracy is better than 3 cm in the plane and 8 cm in the upward direction. PMID:28534844

Property Analysis of the Real-Time Uncalibrated Phase Delay Product Generated by Regional Reference Stations and Its Influence on Precise Point Positioning Ambiguity Resolution.

PubMed

Zhang, Yong; Wang, Qing; Jiang, Xinyuan

2017-05-19

The real-time estimation of the wide-lane and narrow-lane Uncalibrated Phase Delay (UPD) of satellites is realized by real-time data received from regional reference station networks; The properties of the real-time UPD product and its influence on real-time precise point positioning ambiguity resolution (RTPPP-AR) are experimentally analyzed according to real-time data obtained from the regional Continuously Operating Reference Stations (CORS) network located in Tianjin, Shanghai, Hong Kong, etc. The results show that the real-time wide-lane and narrow-lane UPD products differ significantly from each other in time-domain characteristics; the wide-lane UPDs have daily stability, with a change rate of less than 0.1 cycle/day, while the narrow-lane UPDs have short-term stability, with significant change in one day. The UPD products generated by different regional networks have obvious spatial characteristics, thus significantly influencing RTPPP-AR: the adoption of real-time UPD products employing the sparse stations in the regional network for estimation is favorable for improving the regional RTPPP-AR up to 99%; the real-time UPD products of different regional networks slightly influence PPP-AR positioning accuracy. After ambiguities are successfully fixed, the real-time dynamic RTPPP-AR positioning accuracy is better than 3 cm in the plane and 8 cm in the upward direction.

Influence of the narrow {111} planes on axial and planar ion channeling.

PubMed

Motapothula, M; Dang, Z Y; Venkatesan, T; Breese, M B H; Rana, M A; Osman, A

2012-05-11

We report channeling patterns where clearly resolved effects of the narrow {111} planes are observed in axial and planar alignments for 2 MeV protons passing through a 55 nm [001] silicon membrane. At certain axes, such as <213> and <314>, the offset in atomic rows forming the narrow {111} planes results in shielding from the large potential at the wide {111} planes, producing a region of shallow, asymmetric potential from which axial channeling patterns have no plane of symmetry. At small tilts from such axes, different behavior is observed from the wide and narrow {111} planes. At planar alignment, distinctive channeling effects due to the narrow planes are observed. As a consequence of the shallow potential well at the narrow planes, incident protons suffer dechanneled trajectories which are excluded from channeling within the wide planes, resulting in an anomalously large scattered beam at {111} alignment.

A large-scale structure traced by [O II] emitters hosting a distant cluster at z= 1.62

NASA Astrophysics Data System (ADS)

Tadaki, Ken-ichi; Kodama, Tadayuki; Ota, Kazuaki; Hayashi, Masao; Koyama, Yusei; Papovich, Casey; Brodwin, Mark; Tanaka, Masayuki; Iye, Masanori

2012-07-01

We present a panoramic narrow-band imaging survey of [O II] emitters in and around the ClG J0218.3-0510 cluster at z= 1.62 with Suprime-Cam on Subaru Telescope. 352 [O II] emitters were identified on the basis of narrow-band excesses and photometric redshifts. We discovered a huge filamentary structure with some clumps traced by [O II] emitters and found that the ClG J0218.3-0510 cluster is embedded in an even larger superstructure than the one reported previously. 31 [O II] emitters were spectroscopically confirmed with the detection of Hα and/or [O III] emission lines by Fibre Multi Object Spectrograph observations. In the high-density regions such as cluster core and clumps, star-forming [O II] emitters show a high overdensity by a factor of more than 10 compared to the field region. Interestingly, the relative fraction of [O II] emitters in photo-z selected sample does not depend significantly on the local density. Although the star formation activity is very high even in the cluster core, some massive quiescent galaxies also exist at the same time. Furthermore, the properties of the individual [O II] emitters, such as star formation rates (SFRs), stellar masses and specific SFRs, do not show a significant dependence on the local density, either. Such a lack of environmental dependence is consistent with our earlier result by Hayashi et al. on a z= 1.5 cluster and its surrounding region. The fact that the star-forming activity of galaxies in the cluster core is as high as that in the field at z˜ 1.6 may suggest that the star-forming galaxies are probably just in a transition phase from a starburst mode to a quiescent mode, and are thus showing comparable level of star formation rates to those in lower density environments. We may be witnessing the start of the reversal of the local SFR-density relation due to the 'biased' galaxy formation and evolution in high-density regions at this high redshift, beyond which massive galaxies would be forming vigorously in a more biased way in protocluster cores.

Standoff Spectroscopy via Remote Generation of a Backward-Propagating Laser Beam

DTIC Science & Technology

2011-02-04

nighttime probing of stratospheric ozone and measurements in polar and equatorial regions. Appl Opt 28:3616–3624. 2. Bisson SE, Goldsmith JEM, Mitchell...MG (1999) Narrow-band, narrow-field-of-view Raman Lidar with combined day and night capability for tropospheric water-vapor profile measurements. Appl

CHEERS Results from NGC 3393. II. Investigating the Extended Narrow-line Region Using Deep Chandra Observations and Hubble Space Telescope Narrow-line Imaging

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

Maksym, W. Peter; Fabbiano, Giuseppina; Elvis, Martin

The CHandra Extended Emission Line Region Survey (CHEERS) is an X-ray study of nearby active galactic nuclei (AGNs) designed to take full advantage of Chandra 's unique angular resolution by spatially resolving feedback signatures and effects. In the second paper of a series on CHEERS target NGC 3393, we examine deep high-resolution Chandra images and compare them with Hubble Space Telescope narrow-line images of [O iii], [S ii], and H α , as well as previously unpublished mid-ultraviolet (MUV) images. The X-rays provide unprecedented evidence that the S-shaped arms that envelope the nuclear radio outflows extend only ≲0.″2 (≲50 pc)more » across. The high-resolution multiwavelength data suggest that the extended narrow-line region is a complex multiphase structure in the circumnuclear interstellar medium (ISM). Its ionization structure is highly stratified with respect to outflow-driven bubbles in the bicone and varies dramatically on scales of ∼10 pc. Multiple findings show likely contributions from shocks to the feedback in regions where radio outflows from the AGN most directly influence the ISM. These findings include H α evidence for gas compression and extended MUV emission and are in agreement with existing STIS kinematics. Extended filamentary structure in the X-rays and optical suggests the presence of an undetected plasma component, whose existence could be tested with deeper radio observations.« less

PROBING THE PHYSICS OF NARROW LINE REGIONS IN ACTIVE GALAXIES. II. THE SIDING SPRING SOUTHERN SEYFERT SPECTROSCOPIC SNAPSHOT SURVEY (S7)

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

Dopita, Michael A.; Davies, Rebecca; Kewley, Lisa

2015-03-15

Here we describe the Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7) and present results on 64 galaxies drawn from the first data release. The S7 uses the Wide Field Spectrograph mounted on the ANU 2.3 m telescope located at the Siding Spring Observatory to deliver an integral field of 38 × 25 arcsec at a spectral resolution of R = 7000 in the red (530–710 nm), and R = 3000 in the blue (340–560 nm). From these data cubes we have extracted the narrow-line region spectra from a 4 arcsec aperture centered on the nucleus. We also determine themore » Hβ and [O iii] λ5007 fluxes in the narrow lines, the nuclear reddening, the reddening-corrected relative intensities of the observed emission lines, and the Hβ and [O iii] λ5007 luminosities determined from spectra for which the stellar continuum has been removed. We present a set of images of the galaxies in [O iii] λ5007, [N ii] λ6584, and Hα, which serve to delineate the spatial extent of the extended narrow-line region and also to reveal the structure and morphology of the surrounding H ii regions. Finally, we provide a preliminary discussion of those Seyfert 1 and Seyfert 2 galaxies that display coronal emission lines in order to explore the origin of these lines.« less

Consequences of narrow cyclotron emission from Hercules X-1

NASA Technical Reports Server (NTRS)

Weaver, R. P.

1978-01-01

The implications of the recent observations of a narrow cyclotron line in the hard X-ray spectrum of Hercules X-1 are studied. A Monte Carlo code is used to simulate the X-ray transfer of an intrinsically narrow feature at approximately 56 keV through an opaque, cold magnetospheric shell. The results of this study indicate that if a narrow line can be emitted by the source region, then only about 10% of the photons remain in a narrow feature after scattering through the shell. The remaining photons are scattered into a broad feature (FWHM approximately 30 keV) that peaks near 20 keV. Thus, these calculations indicate that the intrinsic source luminosity of the cyclotron line is at least an order of magnitude greater than the observed luminosity.

Attachment reaction of rat uterine luminal epithelium. II. The effect of progesterone on the morphology of the uterine glands and the luminal epithelium of the spayed, virgin rat.

PubMed

Ljungkvist, I

1971-01-01

Ovariosalpingectomized rat uterine glands and luminal epithelium were examined by electron microscopy and in serial cross sections under light microscopy after up to 8 days of treatment with 5 mg progesterone daily. Under light microscopy, the gland lumen was narrow or absent in many epon sections, but wide in many paraffin sections, filled with toluidine blue stained secretion, and serial sections showed that the openings were closed, allowing no connection between the gland lumen and the uterus. In electron micrographs, only those glands without an opening appeared altered by progesterone. The most notable differences in the glandular epithelium were microvilli, condensed ribosome-free cytoplasm next to the lumen, numerous vesicles, sacs and dilated Golgi cisternae in the apical cytoplasm, and more giant mitrochondria in the basal cytoplasm than usually seen in controls. In the luminal epithelium, there were 3 distinct regions: the apical region had condensed cytoplasm often extruded into the lumen, with close-packed, smooth, empty vesicles; the middle region had granular endoplasmic reticulum, mitrochondria, dense bodies, multivesicular bodies, and lipid granules; the basal region contained the nucleus, granular endoplasmic reticulum, mitrochondria and dense abodies. These observations were interpreted as indicative of a transitional state from secretion to absorption, especially since without an opening, secretion would be of little significance.

Narrowband noise study of sliding charge density waves in NbSe3 nanoribbons

NASA Astrophysics Data System (ADS)

Onishi, Seita; Jamei, Mehdi; Zettl, Alex

2017-02-01

Transport properties (dc electrical resistivity, threshold electric field, and narrow-band noise) are reported for nanoribbon specimens of NbSe3 with thicknesses as low as 18 nm. As the sample thickness decreases, the resistive anomalies characteristic of the charge density wave (CDW) state are suppressed and the threshold fields for nonlinear CDW conduction apparently diverge. Narrow-band noise measurements allow determination of the concentration of carriers condensed in the CDW state n c , reflective of the CDW order parameter Δ. Although the CDW transition temperatures are relatively independent of sample thickness, in the lower CDW state Δ decreases dramatically with decreasing sample thickness.

Along-strike variations in seismic structure of the locked-sliding transition on the plate boundary beneath the southern part of Kii Peninsula, southwestern Japan

NASA Astrophysics Data System (ADS)

Kurashimo, E.; Iidaka, T.; Iwasaki, T.; Saiga, A.; Umeyama, E.; Tsumura, N.; Sakai, S.; Hirata, N.

2013-12-01

The Nankai trough region, where the Philippine Sea Plate (PHS) subducts beneath the SW Japan arc, is a well-known seismogenic zone of interplate earthquakes. A narrow zone of nonvolcanic tremor has been found in the SW Japan fore-arc, along strike of the arc (Obara, 2002). The epicentral distribution of tremor corresponds to the locked-sliding transition estimated from thermal and deformation models (Hyndman et al., 1995). The spatial distribution of the tremor is not homogeneous in a narrow belt but is spatially clustered. Obara [2002] suggested fluids as a source for tremor because of the long duration and the mobility of the tremor activity. The behavior of fluids at the plate interface is a key factor in understanding fault slip processes. Seismic reflection characteristics and seismic velocity variations can provide important information on the fluid-related heterogeneity of structure around plate interface. However, little is known about the deeper part of the plate boundary, especially the transition zone on the subducting plate. To reveal the seismic structure of the transition zone, we conducted passive and active seismic experiments in the southern part of Kii Peninsula, SW Japan. Sixty 3-component portable seismographs were installed on a 60-km-long line (SM-line) nearly perpendicular to the direction of the subduction of the PHS with approximately 1 km spacing. To improve accuracy of hypocenter locations, we additionally deployed six 3-component seismic stations around the survey line. Waveforms were continuously recorded during a five-month period from December, 2009. In October of 2010, a deep seismic profiling was also conducted. 290 seismometers were deployed on the SM-line with about 200 m spacing, on which five explosives shots were fired as controlled seismic sources. Arrival times of local earthquakes and explosive shots were used in a joint inversion for earthquake locations and 3-D Vp and Vp/Vs structures, using the iterative damped least-squares algorithm, simul2000 (Thurber and Eberhart-Phillips, 1999). To obtain the detailed structure image of the transition zone on the subducting plate, the explosive shot data recorded on the SM-line were processed using the seismic reflection technique. Seismic reflection image shows the lateral variation of the reflectivity along the top of the PHS. A clear reflection band is present where the clustered tremors occurred. The depth section of Vp/Vs structure shows the lateral variation of the Vp/Vs values along the top of the PHS. Clustered tremors are located in and around the high Vp/Vs zone. These results suggest the occurrence of the tremors may be associated with fluids dehydrated from the subducted oceanic lithosphere.

A recent deep earthquake doublet in light of long-term evolution of Nazca subduction

NASA Astrophysics Data System (ADS)

Zahradník, J.; Čížková, H.; Bina, C. R.; Sokos, E.; Janský, J.; Tavera, H.; Carvalho, J.

2017-03-01

Earthquake faulting at ~600 km depth remains puzzling. Here we present a new kinematic interpretation of two Mw7.6 earthquakes of November 24, 2015. In contrast to teleseismic analysis of this doublet, we use regional seismic data providing robust two-point source models, further validated by regional back-projection and rupture-stop analysis. The doublet represents segmented rupture of a ˜30-year gap in a narrow, deep fault zone, fully consistent with the stress field derived from neighbouring 1976-2015 earthquakes. Seismic observations are interpreted using a geodynamic model of regional subduction, incorporating realistic rheology and major phase transitions, yielding a model slab that is nearly vertical in the deep-earthquake zone but stagnant below 660 km, consistent with tomographic imaging. Geodynamically modelled stresses match the seismically inferred stress field, where the steeply down-dip orientation of compressive stress axes at ˜600 km arises from combined viscous and buoyant forces resisting slab penetration into the lower mantle and deformation associated with slab buckling and stagnation. Observed fault-rupture geometry, demonstrated likelihood of seismic triggering, and high model temperatures in young subducted lithosphere, together favour nanometric crystallisation (and associated grain-boundary sliding) attending high-pressure dehydration as a likely seismogenic mechanism, unless a segment of much older lithosphere is present at depth.

Toward a Unified Componential Theory of Human Reasoning. Technical Report No. 4.

ERIC Educational Resources Information Center

Sternberg, Robert J.

The unified theory described in this paper characterizes human reasoning as an information processing system with a hierarchical sequence of components and subtheories that account for performance on successively narrower tasks. Both deductive and inductive theories are subsumed in the unified componential theory, including transitive chain theory…

Transitions in Students' Epistemic Framing along Two Axes

ERIC Educational Resources Information Center

Irving, Paul W.; Martinuk, Mathew Sandy; Sayre, Eleanor C.

2013-01-01

We use epistemological framing to interpret participants' behavior during group problem-solving sessions in an intermediate mechanics course. We are interested in how students frame discussion and in how the groups shift discussion framings. Our analysis includes two framing axes, expansive vs narrow and serious vs silly, which together…

33 CFR 165.1710 - Port Valdez and Valdez Narrows, Valdez, Alaska-security zones.

Code of Federal Regulations, 2010 CFR

2010-07-01

... following areas are security zones: (1) Trans-Alaska Pipeline (TAPS) Valdez Terminal complex (Terminal), Valdez, Alaska and TAPS tank vessels. All waters enclosed within a line beginning on the southern... TAPS tank vessel maneuvering to approach, moor, unmoor or depart the TAPS Terminal or transiting...

Possibility of Recombination Gain Increase in CV Ions at 4.0 nm Via Coherence

NASA Astrophysics Data System (ADS)

Luo, Y.; Morozov, A.; Gordon, D.; Sprangle, P.; Svidzinsky, A.; Xia, H.; Scully, M.; Suckewer, S.

This paper is about the recent experimental results on amplification of the CV line in the "water window" at 4.03 nm from resonance transition to the ground level of He-like ions in recombination scheme. The indication of the amplification of the CV line has been observed when an elongated narrow plasma channel was created, where high intensity 100 fs beams, optimal for creating CV ions in high density plasma, was propagated up to 0.5-0.6 mm. Without channeling the effective plasma length was much shorter and there was no indication of amplification.The large interest in gain generation in He-like ions in the transition to ground state is due to the possibility of applying a recently developed theory of Lasing Without Inversion (LWI) in XUV and X-ray regions to largely increase the gain for such transitions. The presented results of the indication of CV line amplifications are being discussed from the point of view of using LWI as a superradiance gain increase, hence to construct a very compact soft X-ray laser in the "water window".The last part of the paper is related to the application of the ultra-intensive fs plasma laser, which is currently in the process of development by using stimulated Raman backscattering (SRBS) to create a plasma amplifier and compressor, as the pump for compact laser operating in the "water window" and also at shorter wavelengths.

THERMALLY DRIVEN ATMOSPHERIC ESCAPE: TRANSITION FROM HYDRODYNAMIC TO JEANS ESCAPE

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

Volkov, Alexey N.; Johnson, Robert E.; Tucker, Orenthal J.

2011-03-10

Thermally driven escape from planetary atmospheres changes in nature from an organized outflow (hydrodynamic escape) to escape on a molecule-by-molecule basis (Jeans escape) with increasing Jeans parameter, {lambda}, the ratio of the gravitational to thermal energy of the atmospheric molecules. This change is described here for the first time using the direct simulation Monte Carlo method. When heating is predominantly below the lower boundary of the simulation region, R{sub 0}, and well below the exobase of a single-component atmosphere, the nature of the escape process changes over a surprisingly narrow range of Jeans parameters, {lambda}{sub 0}, evaluated at R{sub 0}.more » For an atomic gas, the transition occurs over {lambda}{sub 0} {approx} 2-3, where the lower bound, {lambda}{sub 0} {approx} 2.1, corresponds to the upper limit for isentropic, supersonic outflow. For {lambda}{sub 0} > 3 escape occurs on a molecule-by-molecule basis and we show that, contrary to earlier suggestions, for {lambda}{sub 0} > {approx}6 the escape rate does not deviate significantly from the familiar Jeans rate. In a gas composed of diatomic molecules, the transition shifts to {lambda}{sub 0} {approx} 2.4-3.6 and at {lambda}{sub 0} > {approx}4 the escape rate increases a few tens of percent over that for the monatomic gas. Scaling by the Jeans parameter and the Knudsen number, these results can be applied to thermally induced escape of the major species from solar and extrasolar planets.« less

Linear variable narrow bandpass optical filters in the far infrared (Conference Presentation)

NASA Astrophysics Data System (ADS)

Rahmlow, Thomas D.

2017-06-01

We are currently developing linear variable filters (LVF) with very high wavelength gradients. In the visible, these filters have a wavelength gradient of 50 to 100 nm/mm. In the infrared, the wavelength gradient covers the range of 500 to 900 microns/mm. Filter designs include band pass, long pass and ulta-high performance anti-reflection coatings. The active area of the filters is on the order of 5 to 30 mm along the wavelength gradient and up to 30 mm in the orthogonal, constant wavelength direction. Variation in performance along the constant direction is less than 1%. Repeatable performance from filter to filter, absolute placement of the filter relative to a substrate fiducial and, high in-band transmission across the full spectral band is demonstrated. Applications include order sorting filters, direct replacement of the spectrometer and hyper-spectral imaging. Off-band rejection with an optical density of greater than 3 allows use of the filter as an order sorting filter. The linear variable order sorting filters replaces other filter types such as block filters. The disadvantage of block filters is the loss of pixels due to the transition between filter blocks. The LVF is a continuous gradient without a discrete transition between filter wavelength regions. If the LVF is designed as a narrow band pass filter, it can be used in place of a spectrometer thus reducing overall sensor weight and cost while improving the robustness of the sensor. By controlling the orthogonal performance (smile) the LVF can be sized to the dimensions of the detector. When imaging on to a 2 dimensional array and operating the sensor in a push broom configuration, the LVF spectrometer performs as a hyper-spectral imager. This paper presents performance of LVF fabricated in the far infrared on substrates sized to available detectors. The impact of spot size, F-number and filter characterization are presented. Results are also compared to extended visible LVF filters.

Explosive Events in the Quiet Sun: Extreme Ultraviolet Imaging Spectroscopy Instrumentation and Observations

NASA Astrophysics Data System (ADS)

Rust, Thomas Ludwell

Explosive event is the name given to slit spectrograph observations of high spectroscopic velocities in solar transition region spectral lines. Explosive events show much variety that cannot yet be explained by a single theory. It is commonly believed that explosive events are powered by magnetic reconnection. The evolution of the line core appears to be an important indicator of which particular reconnection process is at work. The Multi-Order Solar Extreme Ultraviolet Spectrograph (MOSES) is a novel slitless spectrograph designed for imaging spectroscopy of solar extreme ultraviolet (EUV) spectral lines. The spectrograph design forgoes a slit and images instead at three spectral orders of a concave grating. The images are formed simultaneously so the resulting spatial and spectral information is co-temporal over the 20' x 10' instrument field of view. This is an advantage over slit spectrographs which build a field of view one narrow slit at a time. The cost of co-temporal imaging spectroscopy with the MOSES is increased data complexity relative to slit spectrograph data. The MOSES data must undergo tomographic inversion for recovery of line profiles. I use the unique data from the MOSES to study transition region explosive events in the He ii 304 A spectral line. I identify 41 examples of explosive events which include 5 blue shifted jets, 2 red shifted jets, and 10 bi-directional jets. Typical doppler speeds are approximately 100kms-1. I show the early development of one blue jet and one bi-directional jet and find no acceleration phase at the onset of the event. The bi-directional jets are interesting because they are predicted in models of Petschek reconnection in the transition region. I develop an inversion algorithm for the MOSES data and test it on synthetic observations of a bi-directional jet. The inversion is based on a multiplicative algebraic reconstruction technique (MART). The inversion successfully reproduces synthetic line profiles. I then use the inversion to study the time evolution of a bi-directional jet. The inverted line profiles show fast doppler shifted components and no measurable line core emission. The blue and red wings of the jet show increasing spatial separation with time.

Rifting the continental lithosphere: case studies of the lithosphere-asthenosphere system in rifted settings across the western U.S. and in the southern East African Rift

NASA Astrophysics Data System (ADS)

Hopper, E.; Gaherty, J. B.; Shillington, D. J.

2016-12-01

Continental extension comes in many guises, often described in terms of two endmembers. Narrow rifting is typified by a rift valley narrower than lithospheric thickness (50-100 km), presumed to result in steep lateral changes in crustal and lithospheric topography; wide rifting by a broad zone (<1000 km) of normal faulting associated with much smaller topographic gradients. A type example for the former is the East African Rift Valley; for the latter, the Basin and Range in the western U.S.A. An important control on rift development is the state of the lithosphere: for example, its strength and thickness. We analyse common conversion point stacked Sp converted wave images of the lithosphere beneath rift systems in the contiguous U.S., both the wide Basin and Range, and narrow rift systems such as the Rio Grande Rift and Salton Trough. We use Sp waves recorded by EarthScope's Transportable Array and other available permanent and temporary broadband stations. Beneath the Basin and Range, we observe a very strong, shallow velocity decrease (the lithosphere-asthenosphere boundary, or LAB) that is relatively uniform over 100s of km. The strength of this feature indicates melt has ponded at this transition. We have not observed a clear relationship between lithospheric thickness beneath the Basin and Range, and total degree of extension, current extension rate, or age since surface volcanism. Beneath narrow rifts in the western U.S., however, more localised thinning of the lithosphere has been observed. We also compare these observations with seismic images of the Malawi Rift, at the southern end of the Western Branch of the East African Rift System, using broadband data acquired as part of the Study of Extension and MaGmatism in Malawi aNd Tanzania (SEGMeNT) experiment. The Malawi Rift is extending slowly in a magma-poor region of relatively strong lithosphere. We constrain the pattern of plate-scale extension by observations of crustal thinning, and image complex variations in deeper lithospheric structure.

Rifting the continental lithosphere: case studies of the lithosphere-asthenosphere system in rifted settings across the western U.S. and in the southern East African Rift

NASA Astrophysics Data System (ADS)

Hopper, E.; Gaherty, J. B.; Shillington, D. J.

2017-12-01

Continental extension comes in many guises, often described in terms of two endmembers. Narrow rifting is typified by a rift valley narrower than lithospheric thickness (50-100 km), presumed to result in steep lateral changes in crustal and lithospheric topography; wide rifting by a broad zone (<1000 km) of normal faulting associated with much smaller topographic gradients. A type example for the former is the East African Rift Valley; for the latter, the Basin and Range in the western U.S.A. An important control on rift development is the state of the lithosphere: for example, its strength and thickness. We analyse common conversion point stacked Sp converted wave images of the lithosphere beneath rift systems in the contiguous U.S., both the wide Basin and Range, and narrow rift systems such as the Rio Grande Rift and Salton Trough. We use Sp waves recorded by EarthScope's Transportable Array and other available permanent and temporary broadband stations. Beneath the Basin and Range, we observe a very strong, shallow velocity decrease (the lithosphere-asthenosphere boundary, or LAB) that is relatively uniform over 100s of km. The strength of this feature indicates melt has ponded at this transition. We have not observed a clear relationship between lithospheric thickness beneath the Basin and Range, and total degree of extension, current extension rate, or age since surface volcanism. Beneath narrow rifts in the western U.S., however, more localised thinning of the lithosphere has been observed. We also compare these observations with seismic images of the Malawi Rift, at the southern end of the Western Branch of the East African Rift System, using broadband data acquired as part of the Study of Extension and MaGmatism in Malawi aNd Tanzania (SEGMeNT) experiment. The Malawi Rift is extending slowly in a magma-poor region of relatively strong lithosphere. We constrain the pattern of plate-scale extension by observations of crustal thinning, and image complex variations in deeper lithospheric structure.

Spectra of 42S1/2→32D5/2 Transitions of a Single Trapped 40Ca+ Ion

NASA Astrophysics Data System (ADS)

Gong, Shi-Jie; Zhou, Fei; Wu, Hao-Yu; Wan, Wei; Chen, Liang; Feng, Mang

2015-01-01

We investigate the spectra of the electric quadrupole 42S1/2→32D5/2 transitions in a single 40Ca+ ion confined in a home-built linear trap. We probe the transitions with an ultra-narrow bandwidth laser at 729 nm. In a weak magnetic field, the quadrupole transition splits into ten components with the maximal line strength proportional to their squared Clebsch—Gordan factors. In a magnetic field of the order of Gauss, the observed equidistant sideband reflects the Zeeman substructure modulated by the quantized oscillation due to the secular motion in the trap. The temperature of the trapped ion can be determined by the envelope of the sideband spectrum. We also demonstrate the Rabi oscillation in a carrier transition after the ion has been Doppler cooled, which can be fitted by the model with the thermal state of motion.

Inhomogeneous and homogeneous linewidths in Er 3+-doped chalcogenide glasses

NASA Astrophysics Data System (ADS)

Bigot, L.; Jurdyc, A.-M.; Jacquier, B.; Adam, J.-L.

2003-10-01

The erbium 4I 13/2- 4I 15/2 transition around 1.5 μm is of prim interest for telecommunications and depends on the erbium ions surrounding. In glasses, the broadening of a transition comes from two contributions: inhomogeneous (due to the disorder) and homogeneous (due to the electron phonon interaction) broadening. Resonant Fluorescence Line Narrowing (RFLN) is a useful tool to separate this two parameters. We will show in this paper that the 4I 13/2- 4I 15/2 transition in chalcogenide glass (GeGaSSb) presents a strong homogeneous character and a smaller inhomogeneous contribution compared to aluminosilicate and fluoride glasses. Consequences on gain saturation will also be discussed.

Imaging AGN Feedback in NGC 3393 with CHEERS

NASA Astrophysics Data System (ADS)

Maksym, W. Peter; Fabbiano, Giuseppina; Elvis, Martin; Karovska, Margarita; Paggi, Alessandro; Wang, Junfeng; Storchi-Bergmann, Thaisa

2016-01-01

The CHandra Extended Emission-line Region Survey (CHEERS) is the 'ultimate' resolution X-ray imaging survey of nearby far-IR selected AGN. By comparing deep Chandra observations with complementary HST and radio data, we investigate the morphology of the extended narrow-line region on scales of <100 pc. We present new results on the gas surrounding the compton-thick AGN NGC 3393. The luminous extended narrow-line X-ray emission from this gas allows us to study the role and extent of AGN feedback as sub-kpc jets interact with the surrounding ISM.

Imaging AGN Feedback in NGC 3393 with CHEERS

NASA Astrophysics Data System (ADS)

Paggi, Alessandro; Maksym, W. Peter; Fabbiano, Giuseppina; Elvis, Martin; Karovska, Margarita; Wang, Junfeng; Storchi-Bergmann, Thaisa

2016-04-01

The CHandra Extended Emission-line Region Survey (CHEERS) is the 'ultimate' resolution X-ray imaging survey of nearby far-IR selected AGN. By comparing deep Chandra observations with complementary HST and radio data, we investigate the morphology of the extended narrow-line region on scales of <100 pc. We present new results on the gas surrounding the compton-thick AGN NGC 3393. The luminous extended narrow-line X-ray emission from this gas allows us to study the role and extent of AGN feedback as sub-kpc jets interact with the surrounding ISM.

The Lyman Imaging Telescope Experiment (LITE)

NASA Technical Reports Server (NTRS)

Siegmund, O. H. W.

1997-01-01

The scientific aim of the LITE mission is to carry out the first set of very high spatial resolution (0.2 arc sec), wide field of view (10 arc minute), pointed astronomical observations in several narrow wavelength bands in the far ultraviolet region of the spectrum (900-1600 A). Two wavelength regions in the far UV were chosen to be of prime scientific importance for the LITE mission: 1030A and 1240A. It was therefore decided to design and test novel, narrow band, high reflectance multilayer filters for these observations.

Frequency stability measurement of pulsed superradiance from strontium

NASA Astrophysics Data System (ADS)

Norcia, Matthew; Cline, Julia; Robinson, John; Ye, Jun; Thompson, James

2017-04-01

Superradiant laser light from an ultra-narrow optical transition holds promise as a next-generation of active frequency references. We have recently demonstrated pulsed lasing on the milliHertz linewidth clock transition in strontium. Here, we present the first frequency comparisons between such a superradiant source and a state of the art stable laser system. We characterize the stability of the superradiant system, and demonstrate a reduction in sensitivity to cavity frequency fluctuations of nearly five orders of magnitude compared to a conventional laser. DARPA QUASAR, NIST, NSF PFC.

Electron transport in some transition metal di-chalcogenides: MoS2 and WS2

NASA Astrophysics Data System (ADS)

Ferry, D. K.

2017-08-01

The transition metal di-chalcogenides are promising single monolayer materials that hold promise for applications in several fields, including nanoelectronics. Here, I study the transport of electrons in two of these materials, MoS2 and WS2. While the low-field behavior shows very low mobility, due mostly to impurity scattering, the high-field behavior shows a relatively high saturated velocity and a high breakdown field. Complications arise due to the relative narrowness of the conduction band, and the effect of this on the transport is discussed.

The Radio-Loud Narrow-Line Quasar SDSS J172206.03+565451.6

NASA Astrophysics Data System (ADS)

Komossa, Stefanie; Voges, Wolfgang; Adorf, Hans-Martin; Xu, Dawei; Mathur, Smita; Anderson, Scott F.

2006-03-01

We report identification of the radio-loud narrow-line quasar SDSS J172206.03+565451.6, which we found in the course of a search for radio-loud narrow-line active galactic nuclei (AGNs). SDSS J172206.03+565451.6 is only about the fourth securely identified radio-loud narrow-line quasar and the second-most radio loud, with a radio index R1.4~100-700. Its black hole mass, MBH~=(2-3)×107 Msolar estimated from Hβ line width and 5100 Å luminosity, is unusually small given its radio loudness, and the combination of mass and radio index puts SDSS J172206.03+565451.6 in a scarcely populated region of MBH-R diagrams. SDSS J172206.03+565451.6 is a classical narrow-line Seyfert 1-type object with FWHMHβ~=1490 km s-1, an intensity ratio of [O III]/Hβ~=0.7, and Fe II emission complexes with Fe II λ4570/Hβ~=0.7. The ionization parameter of its narrow-line region, estimated from the line ratio [O II]/[O III], is similar to Seyferts, and its high ratio of [Ne V]/[Ne III] indicates a strong EUV-to-soft X-ray excess. We advertise the combined usage of [O II]/[O III] and [Ne V]/[Ne III] diagrams as a useful diagnostic tool to estimate ionization parameters and to constrain the EUV-soft X-ray continuum shape relatively independently from other parameters.

The Narrow-Line Region of Narrow-Line Seyfert 1 Galaxies

NASA Astrophysics Data System (ADS)

Rodríguez-Ardila, A.; Binette, Luc; Pastoriza, Miriani G.; Donzelli, Carlos J.

2000-08-01

This work studies the optical emission-line properties and physical conditions of the narrow-line region (NLR) of seven narrow-line Seyfert 1 galaxies (NLS1's) for which high signal-to-noise ratio spectroscopic observations were available. The resolution is 340 km s-1 (at Hα) over the wavelength interval 3700-9500 Å, enabling us to separate the broad and narrow components of the permitted emission lines. Our results show that the flux carried out by the narrow component of Hβ is, on average, 50% of the total line flux. As a result, the [O III] λ5007/Hβ ratio emitted in the NLR varies from 1 to 5, instead of the universally adopted value of 10. This has strong implications for the required spectral energy distribution that ionizes the NLR gas. Photoionization models that consider a NLR composed of a combination of matter-bounded and ionization-bounded clouds are successful at explaining the low [O III] λ5007/Hβ ratio and the weakness of low-ionization lines of NLS1's. Variation of the relative proportion of these two type of clouds nicely reproduces the dispersion of narrow-line ratios found among the NLS1 sample. Assuming similar physical model parameters of both NLS1's and the normal Seyfert 1 galaxy NGC 5548, we show that the observed differences of emission-line ratios between these two groups of galaxies can be explained, to a first approximation, in terms of the shape of the input ionizing continuum. Narrow emission-line ratios of NLS1's are better reproduced by a steep power-law continuum in the EUV-soft X-ray region, with spectral index α~-2. Flatter spectral indices (α~-1.5) match the observed line ratios of NGC 5548 but are unable to provide a good match to the NLS1 ratios. This result is consistent with ROSAT observations of NLS1's, which show that these objects are characterized by steeper power-law indices than those of Seyfert 1 galaxies with strong broad optical lines. Based on observations made at CASLEO. Complejo Astronómico El Leoncito (CASLEO) is operated under agreement between the Consejo Nacional de Investigaciones Científicas y técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juán.

Gated access to the pore of a P2X receptor: structural implications for closed-open transitions.

PubMed

Kracun, Sebastian; Chaptal, Vincent; Abramson, Jeff; Khakh, Baljit S

2010-03-26

P2X receptors are ligand-gated cation channels that transition from closed to open states upon binding ATP. The crystal structure of the closed zebrafish P2X4.1 receptor directly reveals that the ion-conducting pathway is formed by three transmembrane domain 2 (TM2) alpha-helices, each being provided by the three subunits of the trimer. However, the transitions in TM2 that accompany channel opening are incompletely understood and remain unresolved. In this study, we quantified gated access to Cd(2+) at substituted cysteines in TM2 of P2X2 receptors in the open and closed states. Our data for the closed state are consistent with the zebrafish P2X4.1 structure, with isoleucines and threonines (Ile-332 and Thr-336) positioned one helical turn apart lining the channel wall on approach to the gate. Our data for the open state reveal gated access to deeper parts of the pore (Thr-339, Val-343, Asp-349, and Leu-353), suggesting the closed channel gate is between Thr-336 and Thr-339. We also found unexpected interactions between native Cys-348 and D349C that result in tight Cd(2+) binding deep within the intracellular vestibule in the open state. Interpreted with a P2X2 receptor structural model of the closed state, our data suggest that the channel gate opens near Thr-336/Thr-339 and is accompanied by movement of the pore-lining regions, which narrow toward the cytosolic end of TM2 in the open state. Such transitions would relieve the barrier to ion flow and render the intracellular vestibule less splayed during channel opening in the presence of ATP.

The Visibility of Earth Transits

NASA Technical Reports Server (NTRS)

Castellano, Tim; DeVincenzi, Donald L. (Technical Monitor)

2000-01-01

The recent detection of planetary transits of the solar-like star HD 209458 at a distance of 47 parsecs suggest that transits can reveal the presence of Jupiter-size planetary companions in the solar neighborhood. Recent space-based transit searches have achieved photometric precision within an order of magnitude of that required to detect the much smaller transit signal of an earth-size planet around a solar-size star. Laboratory experiments in the presence of realistic noise sources have shown that CCDs can achieve photometric precision adequate to detect the 9.6 E-5 dimming, of the Sun due to a transit of the Earth. Space-based solar irradiance monitoring has shown that the intrinsic variability of the Sun would not preclude such a detection. Transits of the Sun by the Earth would be detectable by observers that reside within a narrow band of sky positions near the ecliptic plane, if the observers possess current Earth epoch levels of technology and astronomical expertise. A catalog of candidate target stars, their properties, and simulations of the photometric Earth transit signal detectability at each target is presented.

The Visibility of Earth Transits

NASA Technical Reports Server (NTRS)

Castellano, Timothy P.; Doyle, Laurance; McIntosh, Dawn; DeVincenzi, Donald (Technical Monitor)

2000-01-01

The recent photometric detection of planetary transits of the solar-like star HD 209458 at a distance of 47 parsecs suggest that transits can reveal the presence of Jupiter-size planetary companions in the solar neighborhood. Recent space-based transit searches have achieved photometric precision within an order of magnitude of that required to detect the much smaller transit signal of an earth-size planet across a solar-size star. Laboratory experiments in the presence of realistic noise sources have shown that CCDs can achieve photometric precision adequate to detect the 9.6 E-5 dimming of the Sun due to a transit of the Earth. Space-based solar irradiance monitoring has shown that the intrinsic variability of the Sun would not preclude such a detection. Transits of the Sun by the Earth would be detectable by observers that reside within a narrow band of sky positions near the ecliptic plane, if the observers possess current Earth epoch levels of technology and astronomical expertise. A catalog of solar-like stars that satisfy the geometric condition for Earth transit visibility are presented.

3D Thermal/Mechanical Evolution Of The Plate Boundary Corner In SE Alaska

NASA Astrophysics Data System (ADS)

Barker, A.; Koons, P.; Upton, P.; Pavlis, T.; Chapman, J.

2007-12-01

The St Elias orogen of southeast Alaska forms part of an actively deforming plate boundary corner. The corner accommodates the transition from a strike-slip lateral boundary to a convergent normal boundary. Oblique convergence of the Yakutat microplate into the corner generates early stage tectonic characteristics associated with other corner systems (e.g. Himalayan Eastern Syntaxis). In combination with the high relief, the extreme erosive processes of the region redistribute crustal material, partition tectonic strain, and influence the advection of deep crustal material. The evolution of the convergent corner is investigated using 3D numerical models and sandbox analog models. Preliminary model results indicate the deformation partitions into a narrow two-sided orogen along the lateral boundary. The pattern transitions into a wider zone of shortening bounded by inboard and outboard directed thrusts along the frontal boundary. The inclusion of erosion boundary conditions leads to nascent tectonic aneurysm behavior, involving increased strain localization and focused vertical advection of deep crustal material. Thermal models, using the 3D velocity field from these mechanical solutions, show a vertical deflection (towards the surface) of isotherms beneath the eroding region. Sensitivity of the aneurysm behavior is related to the efficiency of the imposed erosion rate (i.e. greater erosion rates led to greater bedrock uplift rates). Higher erosion rates are localized within zones containing major glacier systems in SE Alaska: Bering Glacier, Bagley Icefield, Malaspina Glacier, and Seward Glacier. Combined thermal/mechanical solutions identify the glacier valleys as rheological weakspots, defined by localized strain and differential advection of deep crustal material.

Two-dimensional simulation of red blood cell motion near a wall under a lateral force

NASA Astrophysics Data System (ADS)

Hariprasad, Daniel S.; Secomb, Timothy W.

2014-11-01

The motion of a red blood cell suspended in a linear shear flow adjacent to a fixed boundary subject to an applied lateral force directed toward the boundary is simulated. A two-dimensional model is used that represents the viscous and elastic properties of normal red blood cells. Shear rates in the range of 100 to 600 s-1 are considered, and the suspending medium viscosity is 1 cP. In the absence of a lateral force, the cell executes a tumbling motion. With increasing lateral force, a transition from tumbling to tank-treading is predicted. The minimum force required to ensure tank-treading increases nonlinearly with the shear rate. Transient swinging motions occur when the force is slightly larger than the transition value. The applied lateral force is balanced by a hydrodynamic lift force resulting from the positive orientation of the long axis of the cell with respect to the wall. In the case of cyclic tumbling motions, the orientation angle takes positive values through most of the cycle, resulting in lift generation. These results are used to predict the motion of a cell close to the outer edge of the cell-rich core region that is generated when blood flows in a narrow tube. In this case, the lateral force is generated by shear-induced dispersion, resulting from cell-cell interactions in a region with a concentration gradient. This force is estimated using previous data on shear-induced dispersion. The cell is predicted to execute tank-treading motions at normal physiological hematocrit levels, with the possibility of tumbling at lower hematocrit levels.

Spectral Simulations and Abundance Determinations in the Interstellar Medium of Active Galaxies

NASA Astrophysics Data System (ADS)

Ferguson, Jason W.

The narrow emission line spectra of gas illuminated by the nuclear region of active galaxies cannot be described by models involving simple photoionization calculations. In this project we develop the numerical tools necessary to accurately simulate observed spectra from such regions. We begin by developing a compact model hydrogen atom, and show that a moderate number of atomic levels can reproduce the emission of much larger, definitive calculations. We discuss the excitation mechanism of the gas, that is, whether the emission we see is a result of either local shock excitation or direct photoionization by the central source. We show that photoionization plus continuum fluorescence can mimic excitation by shocks, and we suggest an observational test to distinguish between photoionization due to shocks and the central source. We extend to the narrow line region of active galaxies the 'locally optimally-emitting cloud' (LOC) model, wherein the observed spectra are predominantly determined by a simple, yet powerful selection effect. Namely, nature provides the emitting line region with clouds of a vast ensemble of properties, and we observe emission lines from those clouds that are most efficient at emitting them. We have calculated large grids of photoionization models of narrow line clouds for a wide range of gas density and distances from the ionizing source. We show that when coupled to a simple Keplerian velocity field, the LOC naturally reproduces the line width - critical density correlation observed in many narrow line objects. In addition, we calculate classical diagnostic line ratios and use simple LOC integrations over gas density to simulate the radial emission of the narrow lines and compare with observations. The effects of including dust in the simulations is discussed and we show that the more neutral gas is likely to be dusty, while the more highly ionized gas is dust-free. This implies a variety of cloud origins.

Mantle transition zone input to kimberlite magmatism near a subduction zone: Origin of anomalous Nd-Hf isotope systematics at Lac de Gras, Canada

NASA Astrophysics Data System (ADS)

Tappe, Sebastian; Graham Pearson, D.; Kjarsgaard, Bruce A.; Nowell, Geoff; Dowall, David

2013-06-01

Late Cretaceous-Eocene kimberlites from the Lac de Gras area, central Slave craton, show the most extreme Nd-Hf isotope decoupling observed for kimberlites worldwide. They are characterized by a narrow range of moderately enriched Nd isotope compositions (ɛNd(i)=-0.4 to -3.5) that contrasts strongly with their moderately depleted to highly enriched ɛHf(i) values (+3.9 to -9.9). Although digestion of cratonic mantle material in proto-kimberlite melt can theoretically produce steep arrays in Nd-Hf isotope space, the amount of contaminant required to explain the Lac de Gras data is unrealistic. Instead, it is more plausible that mixing of compositionally discrete melt components within an isotopically variable source region is responsible for the steep Nd-Hf isotope array. As development of strongly negative ΔɛHf requires isotopic aging of a precursor material with Sm/Nd≫Lu/Hf for billion-year timescales, a number of models have been proposed where ancient MORB crust trapped in the mantle transition zone is the ultimate source of the extreme Hf isotope signature. However, we provide a conceptual modification and demonstrate that OIB-type domains within ancient subducted oceanic lithosphere can produce much stronger negative ΔɛHf during long-term isolation. Provided that these OIB-type domains have lower melting points compared with associated MORB crust, they are among the first material to melt within the transition zone during thermal perturbations. The resulting hydrous alkali silicate melts react strongly with depleted peridotite at the top of the transition zone and transfer negative ΔɛHf signatures to less dense materials, which can be more easily entrained within upward flowing mantle. Once these entrained refertilized domains rise above 300 km depth, they may become involved in CO2- and H2O-fluxed redox melting of upper mantle peridotite beneath a thick cratonic lid. We argue that incorporation of ancient transition zone material, which includes ultradeep diamonds, into the convecting upper mantle source region of Lac de Gras kimberlites was due to vigorous mantle return flow. This occurred in direct response to fast and complex subduction along the western margin of North America during the Late Cretaceous.

Revealing Stellar Surface Structure Behind Transiting Exoplanets

NASA Astrophysics Data System (ADS)

Dravins, Dainis

2018-04-01

During exoplanet transits, successive stellar surface portions become hidden and differential spectroscopy between various transit phases provide spectra of small surface segments temporarily hidden behind the planet. Line profile changes across the stellar disk offer diagnostics for hydrodynamic modeling, while exoplanet analyses require stellar background spectra to be known along the transit path. Since even giant planets cover only a small fraction of any main-sequence star, very precise observations are required, as well as averaging over numerous spectral lines with similar parameters. Spatially resolved Fe I line profiles across stellar disks have now been retrieved for HD209458 (G0V) and HD189733A (K1V), using data from the UVES and HARPS spectrometers. Free from rotational broadening, spatially resolved profiles are narrower and deeper than in integrated starlight. During transit, the profiles shift towards longer wavelengths, illustrating both stellar rotation at the latitude of transit and the prograde orbital motion of the exoplanets. This method will soon become applicable to more stars, once additional bright exoplanet hosts have been found.

Size-dependent phase diagrams of metallic alloys: A Monte Carlo simulation study on order–disorder transitions in Pt–Rh nanoparticles

PubMed Central

Stahl, Christian; Albe, Karsten

2012-01-01

Summary Nanoparticles of Pt–Rh were studied by means of lattice-based Monte Carlo simulations with respect to the stability of ordered D022- and 40-phases as a function of particle size and composition. By thermodynamic integration in the semi-grand canonical ensemble, phase diagrams for particles with a diameter of 7.8 nm, 4.3 nm and 3.1 nm were obtained. Size-dependent trends such as the lowering of the critical ordering temperature, the broadening of the compositional stability range of the ordered phases, and the narrowing of the two-phase regions were observed and discussed in the context of complete size-dependent nanoparticle phase diagrams. In addition, an ordered surface phase emerges at low temperatures and low platinum concentration. A decrease of platinum surface segregation with increasing global platinum concentration was observed, when a second, ordered phase is formed inside the core of the particle. The order–disorder transitions were analyzed in terms of the Warren–Cowley short-range order parameters. Concentration-averaged short-range order parameters were used to remove the surface segregation bias of the conventional short-range order parameters. Using this procedure, it was shown that the short-range order in the particles at high temperatures is bulk-like. PMID:22428091

FURTHER CONSTRAINTS ON THE OPTICAL TRANSMISSION SPECTRUM OF HAT-P-1b

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

Montalto, M.; Santos, N. C.; Martins, J. H. C.

We report on novel observations of HAT-P-1 aimed at constraining the optical transmission spectrum of the atmosphere of its transiting hot-Jupiter exoplanet. Ground-based differential spectrophotometry was performed over two transit windows using the DOLORES spectrograph at the Telescopio Nazionale Galileo. Our measurements imply an average planet to star radius ratio equal to R{sub p}/R{sub *} = (0.1159 ± 0.0005). This result is consistent with the value obtained from recent near-infrared measurements of this object, but differs from previously reported optical measurements, being lower by around 4.4 exoplanet scale heights. Analyzing the data over five different spectral bins of ∼600 Åmore » wide, we observed a single peaked spectrum (3.7 σ level) with a blue cutoff corresponding to the blue edge of the broad absorption wing of sodium and an increased absorption in the region in-between 6180 and 7400 Å. We also infer that the width of the broad absorption wings due to alkali metals is likely narrower than the one implied by solar abundance clear atmospheric models. We interpret the result as evidence that HAT-P-1b has a partially clear atmosphere at optical wavelengths with a more modest contribution from an optical absorber than previously reported.« less

Further Constraints on the Optical Transmission Spectrum of HAT-P-1b

NASA Astrophysics Data System (ADS)

Montalto, M.; Iro, N.; Santos, N. C.; Desidera, S.; Martins, J. H. C.; Figueira, P.; Alonso, R.

2015-09-01

We report on novel observations of HAT-P-1 aimed at constraining the optical transmission spectrum of the atmosphere of its transiting hot-Jupiter exoplanet. Ground-based differential spectrophotometry was performed over two transit windows using the DOLORES spectrograph at the Telescopio Nazionale Galileo. Our measurements imply an average planet to star radius ratio equal to Rp/R* = (0.1159 ± 0.0005). This result is consistent with the value obtained from recent near-infrared measurements of this object, but differs from previously reported optical measurements, being lower by around 4.4 exoplanet scale heights. Analyzing the data over five different spectral bins of ∼600 Å wide, we observed a single peaked spectrum (3.7 σ level) with a blue cutoff corresponding to the blue edge of the broad absorption wing of sodium and an increased absorption in the region in-between 6180 and 7400 Å. We also infer that the width of the broad absorption wings due to alkali metals is likely narrower than the one implied by solar abundance clear atmospheric models. We interpret the result as evidence that HAT-P-1b has a partially clear atmosphere at optical wavelengths with a more modest contribution from an optical absorber than previously reported.

Integrated multi-stratigraphic study of the Coll de Terrers late Permian-Early Triassic continental succession from the Catalan Pyrenees (NE Iberian Peninsula): A geologic reference record for equatorial Pangaea

NASA Astrophysics Data System (ADS)

Mujal, Eudald; Fortuny, Josep; Pérez-Cano, Jordi; Dinarès-Turell, Jaume; Ibáñez-Insa, Jordi; Oms, Oriol; Vila, Isabel; Bolet, Arnau; Anadón, Pere

2017-12-01

The most severe biotic crisis on Earth history occurred during the Permian-Triassic (PT) transition around 252 Ma. Whereas in the marine realm such extinction event is well-constrained, in terrestrial settings it is still poorly known, mainly due to the lack of suitable complete sections. This is utterly the case along the Western Tethys region, located at Pangaea's equator, where terrestrial successions are typically build-up of red beds often characterised by a significant erosive gap at the base of the Triassic strata. Henceforth, documenting potentially complete terrestrial successions along the PT transition becomes fundamental. Here, we document the exceptional Coll de Terrers area from the Catalan Pyrenees (NE Iberian Peninsula), for which a multidisciplinary research is conducted along the PT transition. The red-bed succession, located in a long E-W extended narrow rift system known as Pyrenean Basin, resulted from a continuous sedimentary deposition evolving from meandering (lower Upper Red Unit) to playa-lake/ephemeral lacustrine (upper Upper Red Unit) and again to meandering settings (Buntsandstein facies). Sedimentary continuity is suggested by preliminary cyclostratigraphic analysis that warrants further analysis. Our combined sedimentological, mineralogical and geochemical data infer a humid-semiarid-humid climatic trend across the studied succession. The uppermost Permian strata, deposited under an orbitally controlled monsoonal regime, yields a relatively diverse ichnoassemblage mainly composed of tetrapod footprints and arthropod trace fossils. Such fossils indicate appropriate life conditions and water presence in levels that also display desiccation structures. These levels alternate with barren intervals formed under dry conditions, being thus indicative of strong seasonality. All these features are correlated with those reported elsewhere in Gondwana and Laurasia, and suggest that the Permian-Triassic boundary might be recorded somewhere around the Buntsandstein base. Consequently, Coll de Terrers and the whole Catalan Pyrenees become key regions to investigate in detail the Permian extinction event and the Triassic ecosystems recovery.

A Quasi-Classical Model of the Hubbard Gap in Lightly Compensated Semiconductors

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

Poklonski, N. A.; Vyrko, S. A.; Kovalev, A. I.

2016-03-15

A quasi-classical method for calculating the narrowing of the Hubbard gap between the A{sup 0} and A{sup +} acceptor bands in a hole semiconductor or the D{sup 0} and D{sup –} donor bands in an electron semiconductor is suggested. This narrowing gives rise to the phenomenon of a semiconductor transition from the insulator to metal state with an increase in doping level. The major (doping) impurity can be in one of three charge states (–1, 0, or +1), while the compensating impurity can be in states (+1) or (–1). The impurity distribution over the crystal is assumed to be randommore » and the width of Hubbard bands (levels), to be much smaller than the gap between them. It is shown that narrowing of the Hubbard gap is due to the formation of electrically neutral acceptor (donor) states of the quasicontinuous band of allowed energies for holes (electrons) from excited states. This quasicontinuous band merges with the top of the valence band (v band) for acceptors or with the bottom of the conduction band (c band) for donors. In other words, the top of the v band for a p-type semiconductor or the bottom of the c band for an n-type semiconductor is shifted into the band gap. The value of this shift is determined by the maximum radius of the Bohr orbit of the excited state of an electrically neutral major impurity atom, which is no larger than half the average distance between nearest impurity atoms. As a result of the increasing dopant concentration, the both Hubbard energy levels become shallower and the gap between them narrows. Analytical formulas are derived to describe the thermally activated hopping transition of holes (electrons) between Hubbard bands. The calculated gap narrowing with increasing doping level, which manifests itself in a reduction in the activation energy ε{sub 2} is consistent with available experimental data for lightly compensated p-Si crystals doped with boron and n-Ge crystals doped with antimony.« less

Semiconducting-metallic transition of singlecrystalline ferromagnetic Hf-doped CuCr2Se4 spinels

NASA Astrophysics Data System (ADS)

Maciążek, E.; Malicka, E.; Gągor, A.; Stokłosa, Z.; Groń, T.; Sawicki, B.; Duda, H.; Gudwański, A.

2017-09-01

Chalcogenide spinels show a variety of physical properties and are very good candidates for electronic and high-frequency applications. We report the measurements of magnetic susceptibility, magnetic isotherm, electrical conductivity, thermoelectric power and calculations of the superexchange and double-exchange integrals made for singlecrystalline Cu[CrxHfy]Se4 spinels. The results showed a ferromagnetic order of magnetic moments below the Curie temperatures of 390 K and, an increase in the splitting of the zero-field cooled and field cooled susceptibilities with increasing Hf-content below the room temperature suggesting a slight spin-frustration and a rapid transition from semiconducting to metallic state at room temperature. A quantitative evaluation of the exchange Hamiltonian showed that the total hopping integral rapidly decreased and the bandwidth of the 3d t2g band due to Cr3+ and Cr4+ ions strongly narrowed from 0.76 eV for y = 0 to 0.28 eV for y = 0.14. The narrowing of this band appears to be responsible for semiconducting properties of the Hf-doped CuCr2Se4 spinels below the room temperature.

Analysis of high-efficiency widely-tunable N-resonances in Cs vapor

NASA Astrophysics Data System (ADS)

Krasteva, A.; Gateva, S.; Tzvetkov, S.; Ghosh, P. N.; Sargsyan, A.; Cartaleva, S.

2018-03-01

The narrow-band coherent N-type resonance, promising for the development of advanced atomic clocks, can be considered as a type of three-photon resonance, where a two-photon Raman excitation is combined with a resonant optical pumping field. In this communication, we present an experimental study and a theoretical analysis related to three-photon, bi-chromatic excitation of Cs atomic vapor contained in an 8-mm long cell with 20 Torr of neon. If a coupling laser is fixed at a frequency that is lower by several GHz than the position of the absorption profile of the Fg = 4 set of transitions, and a probe laser is tuned over the D2 line (λ = 852 nm), a narrow high-contrast enhanced absorption N-resonance will be observed in the probe light profile, superimposed on the absorption profile of the Fg = 4 set of transitions. We present theoretical modeling aimed to clarify the processes behind the efficiency of the N-resonance preparation for different frequency positions of the coupling laser within the D2 line of Cs.

Zero-gap semiconductor to excitonic insulator transition in Ta2NiSe5.

PubMed

Lu, Y F; Kono, H; Larkin, T I; Rost, A W; Takayama, T; Boris, A V; Keimer, B; Takagi, H

2017-02-16

The excitonic insulator is a long conjectured correlated electron phase of narrow-gap semiconductors and semimetals, driven by weakly screened electron-hole interactions. Having been proposed more than 50 years ago, conclusive experimental evidence for its existence remains elusive. Ta 2 NiSe 5 is a narrow-gap semiconductor with a small one-electron bandgap E G of <50 meV. Below T C =326 K, a putative excitonic insulator is stabilized. Here we report an optical excitation gap E op ∼0.16 eV below T C comparable to the estimated exciton binding energy E B . Specific heat measurements show the entropy associated with the transition being consistent with a primarily electronic origin. To further explore this physics, we map the T C -E G phase diagram tuning E G via chemical and physical pressure. The dome-like behaviour around E G ∼0 combined with our transport, thermodynamic and optical results are fully consistent with an excitonic insulator phase in Ta 2 NiSe 5 .

The continent-ocean transition on the northwestern South China Sea

NASA Astrophysics Data System (ADS)

Cameselle, Alejandra L.; Ranero, César R.; Franke, Dieter; Barckhausen, Udo

2015-04-01

Rifted margins are created as a result of stretching and breakup of continental lithosphere that eventually leads to oceanic spreading and formation of a new oceanic basin. A cornerstone for understanding how rift characteristics vary along strike in the same system and what processes control the final transition to seafloor spreading is the continent-ocean transition (COT). We use four regional multichannel seismic profiles and published magnetic lineations to study the structure and variability of COT on the northwest subbasin (NWSB) of the South China Sea and to discern continental from oceanic domains. The continental domain is characterized by tilted fault blocks overlaid by thick syn-rift sedimentary units and fairly continuous Moho reflections typically at 8-10 s twtt. Thickness of the continental crust changes from ~20-25 km under the uppermost slope to ~9-6 km under the lower slope. The oceanic domain is interpreted where a highly reflective top of basement, little faulting, no syntectonic strata, and fairly constant thickness basement (4-8 km) occur. The COT is imaged as a ~5-10 km wide zone where oceanic-type features abut continental-type structures. The South China margin is deformed by abundant normal faults dissecting the continental crust, whereas the conjugate Macclesfield Bank margin displays comparatively abrupt thinning and little faulting. Seismic profiles show an along-strike variation in the tectonic structure of the continental margin. The NE-most lines display ~20-40 km wide segments of intense faulting under the slope and associated continental-crust thinning. Towards the SW, faulting and thinning of the continental crust occurs across a ~100-110 km wide segment. We interpret this 3D structural variability and the narrow COT as a consequence of the abrupt termination of continental rifting tectonics by the NE to SW propagation of a spreading center. We suggest that breakup occurred by spreading center propagation to a larger degree than by lithospheric thinning during continental rifting. Based on the sedimentary successions overlying the oceanic crust, we propose a kinematic evolution for the oceanic domain of the NWSB consisting of a southward spreading center propagation followed by a first narrow ridge jump to the north, and then a younger larger jump to the SW into the east subbasin.

Analysis of metal transfer in gas metal arc welding

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

Kim, Y.S.; Eager, T.W.

1993-06-01

Droplet sizes produced in GMAW are predicted using both the static force balance theory and the pinch instability theory as a function of welding current, and the results are compared with experimental measurements. The causes for the deviation of predicted droplet size from measured size are discussed with suggestions for modification of the theories in order to more accurately model metal transfer in GMAW. The mechanism of repelled metal transfer is also discussed. The transition of metal transfer mode has been considered as a critical phenomenon which changes dramatically over a narrow range of welding current. This transition has beenmore » investigated experimentally using high-speed videography which shows that the transition is much more gradual than is generally believed. The mechanism of the transition is discussed using a modified static force balance theory.« less

Modeling the transition region

NASA Technical Reports Server (NTRS)

Singer, Bart A.

1993-01-01

The current status of transition-region models is reviewed in this report. To understand modeling problems, various flow features that influence the transition process are discussed first. Then an overview of the different approaches to transition-region modeling is given. This is followed by a detailed discussion of turbulence models and the specific modifications that are needed to predict flows undergoing laminar-turbulent transition. Methods for determining the usefulness of the models are presented, and an outlook for the future of transition-region modeling is suggested.

The acoustical bright spot and mislocalization of tones by human listeners.

PubMed

Macaulay, Eric J; Hartmann, William M; Rakerd, Brad

2010-03-01

Listeners attempted to localize 1500-Hz sine tones presented in free field from a loudspeaker array, spanning azimuths from 0 degrees (straight ahead) to 90 degrees (extreme right). During this task, the tone levels and phases were measured in the listeners' ear canals. Because of the acoustical bright spot, measured interaural level differences (ILD) were non-monotonic functions of azimuth with a maximum near 55 degrees . In a source-identification task, listeners' localization decisions closely tracked the non-monotonic ILD, and thus became inaccurate at large azimuths. When listeners received training and feedback, their accuracy improved only slightly. In an azimuth-discrimination task, listeners decided whether a first sound was to the left or to the right of a second. The discrimination results also reflected the confusion caused by the non-monotonic ILD, and they could be predicted approximately by a listener's identification results. When the sine tones were amplitude modulated or replaced by narrow bands of noise, interaural time difference (ITD) cues greatly reduced the confusion for most listeners, but not for all. Recognizing the important role of the bright spot requires a reevaluation of the transition between the low-frequency region for localization (mainly ITD) and the high-frequency region (mainly ILD).

A 700 V narrow channel nJFET with low pinch-off voltage and suppressed drain-induced barrier lowering effect

NASA Astrophysics Data System (ADS)

Mao, Kun; Qiao, Ming; Zhang, WenTong; Zhang, Bo; Li, Zhaoji

2014-11-01

This paper proposes a 700 V narrow channel region triple-RESURF (reduced surface field) n-type junction field-effect transistor (NCT-nJFET). Compared to traditional structures, low pinch-off voltage (VP) with unobvious drain-induced barrier lowering (DIBL) effect and large saturated current (IDsat) are achieved. This is because p-type buried layer (Pbury) and PWELL are introduced to shape narrow n-type channel in JFET channel region. DIBL sensitivity (SDIBL) is firstly introduced in this paper to analyze the DIBL effect of high-voltage long-channel JFET. Ultra-high breakdown voltage is obtained by triple RESURF technology. Experimental results show that proposed NCT-nJFET achieves 24-V VP, 3.5% SDIBL, 2.3-mA IDsat, 800-V OFF-state breakdown voltage (OFF-BV) and 650-V ON-state breakdown voltage when VGS equals 0 V (ON-BV).

Magnetic penetration depth and flux dynamics in single-crystal Bi2Sr2CaCu2O8+δ

NASA Astrophysics Data System (ADS)

Harshman, D. R.; Kleiman, R. N.; Inui, M.; Espinosa, G. P.; Mitzi, D. B.; Kapitulnik, A.; Pfiz, T.; Williams, D. Ll.

1991-11-01

The muon-spin-relaxation technique has been used to study vortex dynamics in single-phase superconducting single crystals of Bi2Sr2CaCu2O8+δ (Tc~=90 K). The data indicate motional narrowing of the internal field distribution due to vortex motion (on a time scale comparable to the muon lifetime). A field-dependent lattice transition is also observed at Tx~30 K, as evidenced by the onset of an asymmetric line shape below Tx. Narrowing arising from disordering of the vortices along [001] is also discussed with reference to its effect on the measured penetration depth.

Observation of narrow isotopic optical magnetic resonances in individual emission spectral lines of neon

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

Saprykin, E G; Sorokin, V A; Shalagin, A M

Narrow resonances are observed in the course of recording the individual emission lines of the glow discharge in the mixture of isotopes {sup 20}Ne and {sup 22}Ne, depending on the strength of the longitudinal magnetic field. The position of resonances in the magnetic scale corresponds to the compensation of the isotopic shift for certain spectral lines due to the Zeeman effect. It is found that the contrast of the resonances is higher for the transitions between the highly excited energy levels, and the resonances themselves are formed in the zone of longitudinal spatial nonuniformity of the magnetic field. (laser applicationsmore » and other topics in quantum electronics)« less

Narrowband noise study of sliding charge density waves in NbSe 3 nanoribbons

DOE PAGES

Onishi, Seita; Jamei, Mehdi; Zettl, Alex

2017-01-12

Transport properties (dc electrical resistivity, threshold electric field, and narrow-band noise) are reported for nanoribbon specimens of NbSe 3 with thicknesses as low as 18 nm. As the sample thickness decreases, the resistive anomalies characteristic of the charge density wave (CDW) state are suppressed and the threshold fields for nonlinear CDW conduction apparently diverge. Narrow-band noise measurements allow determination of the concentration of carriers condensed in the CDW state n c , reflective of the CDW order parameter Δ. Although the CDW transition temperatures are relatively independent of sample thickness, in the lower CDW state Δ decreases dramatically with decreasingmore » sample thickness.« less

Sedimentology of the mid-Carboniferous fill of the Olta paleovalley, eastern Paganzo Basin, Argentina: Implications for glaciation and controls on diachronous deglaciation in western Gondwana during the late Paleozoic Ice Age

NASA Astrophysics Data System (ADS)

Moxness, Levi D.; Isbell, John L.; Pauls, Kathryn N.; Limarino, Carlos O.; Schencman, Jazmin

2018-07-01

Both global and regional climate drivers contributed to glaciation during the late Paleozoic Ice Age (LPIA). However, the transition from icehouse to greenhouse conditions was asynchronous across Gondwana suggesting that, in some cases, regional controls played a significant role in deglaciation. Of particular interest to understanding changing LPIA climatic conditions, is the eastern Paganzo Basin. This region was flanked by ice centers in the Precordilleran and Sierras Pampeanas regions of Argentina on the west, and major ice sheets in the Paraná, Chaco-Paraná, and Sauce Grande basins to the east, all of which resided between ∼40 and 65° S latitude. Hypotheses on the occurrence of ice in the eastern Paganzo Basin are based on interpretations of the narrow, steep-walled, Olta-Malanzán paleovalley as carved by an alpine glacier or by an outlet glacier draining an eastern ice sheet, and that glaciers deposited coarse clastics within the paleovalley. However, we found no evidence for glaciation. Rather, gravel from prograding alluvial fans/fan deltas and rock falls ponded drainage resulting in lacustrine activity in the eastern end of the valley. A transition from either subaerially or shallow subaqueously deposited sandstones to marine mudstones in the western end of the Olta paleovalley suggest a marine transgression, which, in turn, was overlain by deposits of prograding Gilbert-type deltas. Dropstones were from rock falls off valley walls and rafting by lake ice rather than from icebergs. Therefore, we conclude that the climate in western Argentina resulted from uplift induced glaciation in the Precordilleran region and along the western margin of the Paganzo Basin, and the occurrence of a precipitation shadow to the east. The disappearance of the western glaciers during the mid-Carboniferous, prior to deglaciation elsewhere at the same paleolatitude, resulted from a westward shift in the position of the active margin, collapse of the glaciated upland(s), and an expansion of the precipitation shadow across the whole of western Argentina.

Flow regimes of adiabatic gas-liquid two-phase under rolling conditions

NASA Astrophysics Data System (ADS)

Yan, Chaoxing; Yan, Changqi; Sun, Licheng; Xing, Dianchuan; Wang, Yang; Tian, Daogui

2013-07-01

Characteristics of adiabatic air/water two-phase flow regimes under vertical and rolling motion conditions were investigated experimentally. Test sections are two rectangular ducts with the gaps of 1.41 and 10 mm, respectively, and a circular tube with 25 mm diameter. Flow regimes were recorded by a high speed CCD-camera and were identified by examining the video images. The experimental results indicate that the characteristics of flow patterns in 10 mm wide rectangular duct under vertical condition are very similar to those in circular tube, but different from the 1.41 mm wide rectangular duct. Channel size has a significant influence on flow pattern transition, boundary of which in rectangular channels tends asymptotically towards that in the circular tube with increasing the width of narrow side. Flow patterns in rolling channels are similar to each other, nevertheless, the effect of rolling motion on flow pattern transition are significantly various. Due to the remarkable influences of the friction shear stress and surface tension in the narrow gap duct, detailed flow pattern maps of which under vertical and rolling conditions are indistinguishable. While for the circular tube with 25 mm diameter, the transition from bubbly to slug flow occurs at a higher superficial liquid velocity and the churn flow covers more area on the flow regime map as the rolling period decreases.

An Examination of the Mixing of Low-Lying Excited 0+ States in 116Sn

NASA Astrophysics Data System (ADS)

Pore, Jennifer Louise

The even-even tin isotopes are known to exhibit shape coexistence, the phenomenon where multiple shapes coexist in a narrow energy region at relatively lowlying levels of the nucleus. These nuclei have a 0+ spherical ground state and multiple excited 0+ states, one of which is a band head for a deformed rotational band, caused by the promotion of two protons across the Z=50 shell gap. Experimental and theoretical investigations have been performed on 116Sn to describe the nature of the mixing that occurs between the vibrational phonon levels and the deformed rotational band by probing the character of the excited 0+ states. At the time it was thought that the 0+ states showed almost equal mixing of rotational and vibrational character, but this result was based on an indirect observation and fit of the intensity of a weak 85 keV transition. The current work, a high-statistics 116Sn measurement, demonstrates unequal mixing of character between the two excited 0+ states based on a direct measurement of the intensity of the 85 keV transition. These new results might prompt a new interpretation of the structure of 116Sn. The experiment to investigate the low-lying structure of 116Sn was conducted at TRIUMF, Canada's National Laboratory for Nuclear and Particle Physics. A highintensity and high-purity beam of 116In was used to populate states in 116Sn via beta decay. The resulting gamma rays were observed with the 8th detector array, which consists of twenty high-purity Compton-suppressed germanium detectors coupled to a suite of ancillary detectors for beta particle detection and conversion electron spectroscopy. From this high-statistics measurement 57 gamma-ray transitions were observed, with 4 new transitions that depopulate the 3096 keV level observed for the first time with energies of 101 keV, 296 keV, 447 keV, and 871 keV. Branching ratios were determined for all of the observed transitions. For the 57 transitions observed, a relative intensity had not been reported for 17 of them, and a branching ratio had not been reported for 12 of them. Transition rates were determined for 25 transitions that depopulate levels with previously reported lifetimes, and 2 of these transition rates had not been previously observed.

Ground-state ordering of the J1-J2 model on the simple cubic and body-centered cubic lattices

NASA Astrophysics Data System (ADS)

Farnell, D. J. J.; Götze, O.; Richter, J.

2016-06-01

The J1-J2 Heisenberg model is a "canonical" model in the field of quantum magnetism in order to study the interplay between frustration and quantum fluctuations as well as quantum phase transitions driven by frustration. Here we apply the coupled cluster method (CCM) to study the spin-half J1-J2 model with antiferromagnetic nearest-neighbor bonds J1>0 and next-nearest-neighbor bonds J2>0 for the simple cubic (sc) and body-centered cubic (bcc) lattices. In particular, we wish to study the ground-state ordering of these systems as a function of the frustration parameter p =z2J2/z1J1 , where z1 (z2) is the number of nearest (next-nearest) neighbors. We wish to determine the positions of the phase transitions using the CCM and we aim to resolve the nature of the phase transition points. We consider the ground-state energy, order parameters, spin-spin correlation functions, as well as the spin stiffness in order to determine the ground-state phase diagrams of these models. We find a direct first-order phase transition at a value of p =0.528 from a state of nearest-neighbor Néel order to next-nearest-neighbor Néel order for the bcc lattice. For the sc lattice the situation is more subtle. CCM results for the energy, the order parameter, the spin-spin correlation functions, and the spin stiffness indicate that there is no direct first-order transition between ground-state phases with magnetic long-range order, rather it is more likely that two phases with antiferromagnetic long range are separated by a narrow region of a spin-liquid-like quantum phase around p =0.55 . Thus the strong frustration present in the J1-J2 Heisenberg model on the sc lattice may open a window for an unconventional quantum ground state in this three-dimensional spin model.

Narrowing the wingless-2 mutation to a 227 kb candidate region on chicken chromosome 12

PubMed Central

Webb, A E; Youngworth, I A; Kaya, M; Gitter, C L; O’Hare, E A; May, B; Cheng, H H; Delany, M E

2018-01-01

ABSTRACT Wingless-2 (wg-2) is an autosomal recessive mutation in chicken that results in an embryonic lethal condition. Affected individuals exhibit a multisystem syndrome characterized by absent wings, truncated legs, and craniofacial, kidney, and feather malformations. Previously, work focused on phenotype description, establishing the autosomal recessive pattern of Mendelian inheritance and placing the mutation on an inbred genetic background to create the congenic line UCD Wingless-2.331. The research described in this paper employed the complementary tools of breeding, genetics, and genomics to map the chromosomal location of the mutation and successively narrow the size of the region for analysis of the causative element. Specifically, the wg-2 mutation was initially mapped to a 7 Mb region of chromosome 12 using an Illumina 3 K SNP array. Subsequent SNP genotyping and exon sequencing combined with analysis from improved genome assemblies narrowed the region of interest to a maximum size of 227 kb. Within this region, 3 validated and 3 predicted candidate genes are found, and these are described. The wg-2 mutation is a valuable resource to contribute to an improved understanding of the developmental pathways involved in chicken and avian limb development as well as serving as a model for human development, as the resulting syndrome shares features with human congenital disorders. PMID:29562287

Relationship between Pulmonary Airflow and Resistance in Patients with Airway Narrowing Using An 1-D Network Resistance and Compliance Model

NASA Astrophysics Data System (ADS)

Choi, Sanghun; Choi, Jiwoong; Hoffman, Eric; Lin, Ching-Long

2016-11-01

To predict the proper relationship between airway resistance and regional airflow, we proposed a novel 1-D network model for airway resistance and acinar compliance. First, we extracted 1-D skeletons at inspiration images, and generated 1-D trees of CT unresolved airways with a volume filling method. We used Horsfield order with random heterogeneity to create diameters of the generated 1-D trees. We employed a resistance model that accounts for kinetic energy and viscous dissipation (Model A). The resistance model is further coupled with a regional compliance model estimated from two static images (Model B). For validation, we applied both models to a healthy subject. The results showed that Model A failed to provide airflows consistent with air volume change, whereas Model B provided airflows consistent with air volume change. Since airflows shall be regionally consistent with air volume change in patients with normal airways, Model B was validated. Then, we applied Model B to severe asthmatic subjects. The results showed that regional airflows were significantly deviated from air volume change due to airway narrowing. This implies that airway resistance plays a major role in determining regional airflows of patients with airway narrowing. Support for this study was provided, in part, by NIH Grants U01 HL114494, R01 HL094315, R01 HL112986, and S10 RR022421.

Narrow polarized components in the OH 1612-MHz maser emission from supergiant OH-IR sources

NASA Technical Reports Server (NTRS)

Cohen, R. J.; Downs, G.; Emerson, R.; Grimm, M.; Gulkis, S.; Stevens, G.

1987-01-01

High-resolution (300 Hz) OH 1612-MHz spectra of the supergiant OH-IR sources VY CMa, VX Sgr, IRC 10420, and NML Cyg are presented. Linewidths as small as 550 Hz (0.1 km/s) are found for narrow components in the spectra. The present results are consistent with current models for maser line-narrowing and for the physical properties in the OH maser regions. A significant degree of circular polarization is noted in many of the narrow components. The circular polarization suggests the presence of magnetic fields of about 1 mG in the circumstellar envelopes which would be strong enough to influence the outflow from the stars, and which may explain asymmetries found in the circumstellar envelopes.

Interplay of Cu and oxygen vacancy in optical transitions and screening of excitons in ZnO:Cu films

NASA Astrophysics Data System (ADS)

Darma, Yudi; Seng Herng, Tun; Marlina, Resti; Fauziah, Resti; Ding, Jun; Rusydi, Andrivo

2014-02-01

We study room temperature optics and electronic structures of ZnO:Cu films as a function of Cu concentration using a combination of spectroscopic ellipsometry, photoluminescence, and ultraviolet-visible absorption spectroscopy. Mid-gap optical states, interband transitions, and excitons are observed and distinguishable. We argue that the mid-gap states are originated from interactions of Cu and oxygen vacancy (Vo). They are located below conduction band (Zn4s) and above valence band (O2p) promoting strong green emission and narrowing optical band gap. Excitonic states are screened and its intensities decrease upon Cu doping. Our results show the importance of Cu and Vo driving the electronic structures and optical transitions in ZnO:Cu films.

Metal-insulator transition in a doubly orbitally degenerate model with correlated hopping

NASA Astrophysics Data System (ADS)

Didukh, L.; Skorenkyy, Yu.; Dovhopyaty, Yu.; Hankevych, V.

2000-03-01

In the present paper, we propose a doubly orbitally degenerate narrow-band model with correlated hopping. The peculiarity of the model is taking into account the matrix element of electron-electron interaction, which describes intersite hoppings of electrons. In particular, this leads to the concentration dependence of the effective hopping integral. The cases of the strong and weak Hund's coupling are considered. By means of a generalized mean-field approximation the single-particle Green function and quasiparticle energy spectrum are calculated. Metal-insulator transition is studied in the model at different integer values of the electron concentration. With the help of the obtained energy spectrum, we find energy gap width and criteria of metal-insulator transition.

Optical transitions in highly charged californium ions with high sensitivity to variation of the fine-structure constant.

PubMed

Berengut, J C; Dzuba, V A; Flambaum, V V; Ong, A

2012-08-17

We study electronic transitions in highly charged Cf ions that are within the frequency range of optical lasers and have very high sensitivity to potential variations in the fine-structure constant, α. The transitions are in the optical range despite the large ionization energies because they lie on the level crossing of the 5f and 6p valence orbitals in the thallium isoelectronic sequence. Cf(16+) is a particularly rich ion, having several narrow lines with properties that minimize certain systematic effects. Cf(16+) has very large nuclear charge and large ionization energy, resulting in the largest α sensitivity seen in atomic systems. The lines include positive and negative shifters.

Metal-Insulator Transition of strained SmNiO3 Thin Films: Structural, Electrical and Optical Properties

PubMed Central

Torriss, B.; Margot, J.; Chaker, M.

2017-01-01

Samarium nickelate (SmNiO3) thin films were successfully synthesized on LaAlO3 and SrTiO3 substrates using pulsed-laser deposition. The Mott metal-insulator (MI) transition of the thin films is sensitive to epitaxial strain and strain relaxation. Once the strain changes from compressive to tensile, the transition temperature of the SmNiO3 samples shifts to slightly higher values. The optical conductivity reveals the strong dependence of the Drude spectral weight on the strain relaxation. Actually, compressive strain broadens the bandwidth. In contrast, tensile strain causes the effective number of free carriers to reduce which is consistent with the d-band narrowing. PMID:28098240

A TDDFT study of the ruthenium(II) polyazaaromatic complex [Ru(dppz)(phen) 2] 2+ in solution

NASA Astrophysics Data System (ADS)

Fantacci, Simona; De Angelis, Filippo; Sgamellotti, Antonio; Re, Nazzareno

2004-09-01

DFT/TDDFT calculations were performed to investigate the structural, electronic and optical properties of the [Ru(dppz)(phen) 2] 2+ complex in solution. TDDFT calculations in water show two groups of metal-to-ligand charge transfer (MLCT) transitions at ≈450 and 415 nm whose superposition gives account of the broad absorption band experimentally characterized at 440 nm. Also, a group of almost coincident MLCT transitions partially mixed with dppz intraligand π-π ∗ transitions centered at ≈380 nm is found to give rise to the narrow absorption band experimentally found at 380 nm. Our results provide insight into the hypochromic shifts experimentally characterized upon intercalation of the title complex into DNA.

Examination of Regional Transit Service Under Contracting : A Case Study in the Greater New Orleans Region

DOT National Transportation Integrated Search

2011-04-01

Many local governments and transit agencies in the United States face financial difficulties in providing adequate public transit service in individual systems, and in providing sufficient regional coordination to accommodate transit trips involving ...

Imaging Extended Emission-Line Regions of Obscured AGN with the Subaru Hyper Suprime-Cam Survey

NASA Astrophysics Data System (ADS)

Sun, Ai-Lei; Greene, Jenny E.; Zakamska, Nadia L.; Goulding, Andy; Strauss, Michael A.; Huang, Song; Johnson, Sean; Kawaguchi, Toshihiro; Matsuoka, Yoshiki; Marsteller, Alisabeth A.; Nagao, Tohru; Toba, Yoshiki

2018-05-01

Narrow-line regions excited by active galactic nuclei (AGN) are important for studying AGN photoionization and feedback. Their strong [O III] lines can be detected with broadband images, allowing morphological studies of these systems with large-area imaging surveys. We develop a new broad-band imaging technique to reconstruct the images of the [O III] line using the Subaru Hyper Suprime-Cam (HSC) Survey aided with spectra from the Sloan Digital Sky Survey (SDSS). The technique involves a careful subtraction of the galactic continuum to isolate emission from the [O III]λ5007 and [O III]λ4959 lines. Compared to traditional targeted observations, this technique is more efficient at covering larger samples without dedicated observational resources. We apply this technique to an SDSS spectroscopically selected sample of 300 obscured AGN at redshifts 0.1 - 0.7, uncovering extended emission-line region candidates with sizes up to tens of kpc. With the largest sample of uniformly derived narrow-line region sizes, we revisit the narrow-line region size - luminosity relation. The area and radii of the [O III] emission-line regions are strongly correlated with the AGN luminosity inferred from the mid-infrared (15 μm rest-frame) with a power-law slope of 0.62^{+0.05}_{-0.06}± 0.10 (statistical and systematic errors), consistent with previous spectroscopic findings. We discuss the implications for the physics of AGN emission-line regions and future applications of this technique, which should be useful for current and next-generation imaging surveys to study AGN photoionization and feedback with large statistical samples.

Electrochemical deposition of copper decorated titania nanotubes and its visible light photocatalytic performance

NASA Astrophysics Data System (ADS)

Lim, Y. C.; Siti, A. S.; Nur Amiera, P.; Devagi, K.; Lim, Y. P.

2017-09-01

Coupling of titania with narrow band gap materials has been a promising strategy in preparing visible light responsive photocatalyst. In this work, self-organized copper decorated TiO2 nanotube (Cu/TNT) was prepared via electrodeposition of Cu onto highly ordered titania nanotube arrays (TNT). The catalysts were characterized by X-ray diffraction, diffuse reflectance spectroscopy (DRS), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX). The DRS studies clearly show the extended absorption of Cu/TNT into the visible region and present a red shift of band gap to 2.1 eV. FESEM analysis has shown the dispersion of cubic-like Cu particles upon electrodeposition and EDX analysis supports the presence of copper species on the nanotubes surface. The photocatalytic ability of Cu/TNT was evaluated by the degradation of methyl orange from aqueous solution under low power visible light illumination. Compared to TNT, an appreciable improvement in methyl orange removal was observed for Cu/TNT and the highest removal efficiency of 80% was achieved. The effects of catalyst loading and samples repeatability were investigated and under optimum conditions, the removal efficiency of methyl orange over Cu/TNT had further increased to 93.4%. This work has demonstrated a feasible and simple way to introduce narrow band gap transition metal into nanotube arrays, which could create novel properties for functionalized nanotube arrays as well as promise a wide range of applications.

Large Eddy Simulation and Reynolds-Averaged Navier-Stokes modeling of flow in a realistic pharyngeal airway model: an investigation of obstructive sleep apnea.

PubMed

Mihaescu, Mihai; Murugappan, Shanmugam; Kalra, Maninder; Khosla, Sid; Gutmark, Ephraim

2008-07-19

Computational fluid dynamics techniques employing primarily steady Reynolds-Averaged Navier-Stokes (RANS) methodology have been recently used to characterize the transitional/turbulent flow field in human airways. The use of RANS implies that flow phenomena are averaged over time, the flow dynamics not being captured. Further, RANS uses two-equation turbulence models that are not adequate for predicting anisotropic flows, flows with high streamline curvature, or flows where separation occurs. A more accurate approach for such flow situations that occur in the human airway is Large Eddy Simulation (LES). The paper considers flow modeling in a pharyngeal airway model reconstructed from cross-sectional magnetic resonance scans of a patient with obstructive sleep apnea. The airway model is characterized by a maximum narrowing at the site of retropalatal pharynx. Two flow-modeling strategies are employed: steady RANS and the LES approach. In the RANS modeling framework both k-epsilon and k-omega turbulence models are used. The paper discusses the differences between the airflow characteristics obtained from the RANS and LES calculations. The largest discrepancies were found in the axial velocity distributions downstream of the minimum cross-sectional area. This region is characterized by flow separation and large radial velocity gradients across the developed shear layers. The largest difference in static pressure distributions on the airway walls was found between the LES and the k-epsilon data at the site of maximum narrowing in the retropalatal pharynx.

Structure and Formation Mechanism of Black TiO 2 Nanoparticles

DOE PAGES

Tian, Mengkun; Mahjouri-Samani, Masoud; Eres, Gyula; ...

2015-10-27

The remarkable properties of black TiO 2 are due to its disordered surface shell surrounding a crystalline core. However, the chemical composition and the atomic and electronic structure of the disordered shell and its relationship to the core remain poorly understood. Using advanced transmission electron microscopy methods, we show that the outermost layer of black TiO 2 nanoparticles consists of a disordered Ti 2O 3 shell. The measurements show a transition region that connects the disordered Ti 2O 3 shell to the perfect rutile core consisting first of four to five monolayers of defective rutile, containing clearly visible Ti interstitialmore » atoms, followed by an ordered reconstruction layer of Ti interstitial atoms. Our data suggest that this reconstructed layer presents a template on which the disordered Ti 2O 3 layers form by interstitial diffusion of Ti ions. In contrast to recent reports that attribute TiO 2 band-gap narrowing to the synergistic action of oxygen vacancies and surface disorder of nonspecific origin, our results point to Ti 2O 3, which is a narrow-band-gap semiconductor. In conclusion, as a stoichiometric compound of the lower oxidation state Ti 3+ it is expected to be a more robust atomic structure than oxygen-deficient TiO 2 for preserving and stabilizing Ti 3+ surface species that are the key to the enhanced photocatalytic activity of black TiO 2.« less

Bilateral primary xanthoma of the humeri with pathologic fractures: A case report

PubMed Central

Ali, Sayed; Fedenko, Alex; Syed, Ali B; Matcuk, George; Patel, Dakshesh; Gottsegen, Chris; White, Eric

2013-01-01

Xanthomas are rare bone tumors that occur more often in the appendicular skeleton and typically appear radiographically benign, with a narrow zone of transition and a sclerotic rim. We report the case of a 57-year-old woman with hyperlipidemia presenting with bilateral shoulder pain after minor trauma. Radiographic and histopathologic investigation demonstrated intraosseous xanthoma with atypical features, including multifocality, a wide zone of transition and pathologic fractures-characteristics more commonly associated with aggressive lesions such as multiple myeloma or metastasis. The diagnosis, imaging, and histological appearance of xanthoma of bone are reviewed. PMID:24198913

Enhanced effect of temporal variation of the fine structure constant and the strong interaction in 229Th.

PubMed

Flambaum, V V

2006-09-01

The relative effects of the variation of the fine structure constant alpha = e2/variant Planck's over 2pi c and the dimensionless strong interaction parameter m(q)/LambdaQCD are enhanced by 5-6 orders of magnitude in a very narrow ultraviolet transition between the ground and the first excited states in the 229Th nucleus. It may be possible to investigate this transition with laser spectroscopy. Such an experiment would have the potential of improving the sensitivity to temporal variation of the fundamental constants by many orders of magnitude.

New insight into enhanced superconductivity in metals near the metal-insulator transition.

PubMed

Osofsky, M S; Soulen, R J; Claassen, J H; Trotter, G; Kim, H; Horwitz, J S

2001-11-05

We have studied the transport properties of disordered WSi films near the metal/insulator transition (MIT) and we have also reviewed the data for several other disordered materials near their MIT. In all cases, we found the presence of enhanced superconductivity. We constructed a superconductivity "phase diagram" (i.e., T(c) versus sigma) for each system, which reveals a striking correlation: In all cases, T(c) values are significantly enhanced only for samples whose conductivities lie within a narrow range on the metallic side of, and moderately near, the MIT. We present a heuristic model to explain this phenomenon.

High Interfacial Barriers at Narrow Carbon Nanotube-Water Interfaces.

PubMed

Varanasi, Srinivasa Rao; Subramanian, Yashonath; Bhatia, Suresh K

2018-06-26

Water displays anomalous fast diffusion in narrow carbon nanotubes (CNTs), a behavior that has been reproduced in both experimental and simulation studies. However, little is reported on the effect of bulk water-CNT interfaces, which is critical to exploiting the fast transport of water across narrow carbon nanotubes in actual applications. Using molecular dynamics simulations, we investigate here the effect of such interfaces on the transport of water across arm-chair CNTs of different diameters. Our results demonstrate that diffusion of water is significantly retarded in narrow CNTs due to bulk regions near the pore entrance. The slowdown of dynamics can be attributed to the presence of large energy barriers at bulk water-CNT interfaces. The presence of such intense barriers at the bulk-CNT interface arises due to the entropy contrast between the bulk and confined regions, with water molecules undergoing high translational and rotational entropy gain on entering from the bulk to the CNT interior. The intensity of such energy barriers decreases with increase in CNT diameter. These results are very important for emerging technological applications of CNTs and other nanoscale materials, such as in nanofluidics, water purification, nanofiltration, and desalination, as well as for biological transport processes.

Transition Heat Transfer Modeling Based on the Characteristics of Turbulent Spots

NASA Technical Reports Server (NTRS)

Simon, Fred; Boyle, Robert

1998-01-01

While turbulence models are being developed which show promise for simulating the transition region on a turbine blade or vane, it is believed that the best approach with the greatest potential for practical use is the use of models which incorporate the physics of turbulent spots present in the transition region. This type of modeling results in the prediction of transition region intermittency which when incorporated in turbulence models give a good to excellent prediction of the transition region heat transfer. Some models are presented which show how turbulent spot characteristics and behavior can be employed to predict the effect of pressure gradient and Mach number on the transition region. The models predict the spot formation rate which is needed, in addition to the transition onset location, in the Narasimha concentrated breakdown intermittency equation. A simplified approach is taken for modeling turbulent spot growth and interaction in the transition region which utilizes the turbulent spot variables governing transition length and spot generation rate. The models are expressed in terms of spot spreading angle, dimensionless spot velocity, dimensionless spot area, disturbance frequency and Mach number. The models are used in conjunction with a computer code to predict the effects of pressure gradient and Mach number on the transition region and compared with VKI experimental turbine data.

Narrowing the Distance: Bridging the Gap between Teaching Online and Faculty Development

ERIC Educational Resources Information Center

Rochefort, Beth A.

2013-01-01

Online education is a steadily growing industry, and financial pressure at institutions, combined with the rising demand for online education, have caused many universities and colleges to rely on adjunct faculty to staff their online courses For instructors, the transition to teaching online can pose a variety of barriers not the least of which…

A Possible Pathway for High School Science in a STEM World

ERIC Educational Resources Information Center

Sneider, Cary

2011-01-01

Today's high school science teachers find themselves in a period of transition. For the past decade there have been calls for replacing a narrow focus on science education--the traditional courses in physics, chemistry, biology, and Earth and space science--with a broader curriculum on STEM (that is, the four allied fields of science, technology,…

High School Students with Asperger Syndrome: A Career Path Binder Project

ERIC Educational Resources Information Center

Hurlbutt, Karen S.; Handler, Beth R.

2010-01-01

Graduating from high school and moving to the next phase of life can be difficult for any student but is particularly so for those with Asperger syndrome (AS). Social skill difficulties; sensory concerns; and narrow, restricted interest areas all have an impact on this transition. This article describes an activity that can be used with students…

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

Bai, X. Y.; Liu, S. Q.; Su, J. T.

We report a subarcsecond penumbral transient brightening event with the high-spatial resolution observations from the 1.6 m New Solar Telescope (NST), Interface Region Imaging Spectrograph ( IRIS ), and the Solar Dynamics Observatory . The transient brightening, whose thermal energy is in the range of nanoflares, has signatures in the chromosphere, the transient region, and the corona. NST's H α channel reveals the fine structure of the event with a width as narrow as 101 km (0.″14), which is much smaller than the width from the previous observation. The transient brightening lasts for about 3 minutes. It is associated withmore » a redshift of about 17 km s{sup −1}, found in the Si iv 1402.77 Å line and exhibits an inward motion to the umbra with a speed of 87 km s{sup −1}. The small-scale energy released from the event has a multi-temperature component. Spectral analysis of the brightening region from IRIS shows that not only the transition region lines such as Si iv 1402.77 Å and C ii 1334.53 Å, but also the chromospheric Mg ii k 2796.35 Å line are significantly enhanced and broadened. In addition, the event can be found in all the extreme-ultraviolet passbands of the Atmospheric Imaging Assembly and the derived differential emission measure profile increases between 4 and 15 MK (or 6.6 ≤ log T ≤ 7.2) in the transient brightening phase. It is possible that the penumbral transient brightening event is caused by magnetic reconnection.« less

Quantifying the Variation in Shear Zone Character with Depth: a Case Study from the Simplon Shear Zone, Central Alps

NASA Astrophysics Data System (ADS)

Cawood, T. K.; Platt, J. P.

2017-12-01

A widely-accepted model for the rheology of crustal-scale shear zones states that they comprise distributed strain at depth, in wide, high-temperature shear zones, which narrow to more localized, high-strain zones at lower temperature and shallower crustal levels. We test and quantify this model by investigating how the width, stress, temperature and deformation mechanisms change with depth in the Simplon Shear Zone (SSZ). The SSZ marks a major tectonic boundary in the central Alps, where normal-sense motion and rapid exhumation of the footwall have preserved evidence of older, deeper deformation in rocks progressively further into the currently-exposed footwall. As such, microstructures further from the brittle fault (which represents the most localized, most recently-active part of the SSZ) represent earlier, higher- temperature deformation from deeper crustal levels, while rocks closer to the fault have been overprinted by successively later, cooler deformation at shallower depths. This study uses field mapping and microstructural studies to identify zones representing deformation at various crustal levels, and characterize each in terms of zone width (representing width of the shear zone at that time and depth) and dominant deformation mechanism. In addition, quartz- (by Electron Backscatter Diffraction, EBSD) and feldspar grain size (measured optically) piezometry are used to calculate the flow stress for each zone, while the Ti-in-quartz thermometer (TitaniQ) is used to calculate the corresponding temperature of deformation. We document the presence of a broad zone in which quartz is recrystallized by the Grain Boundary Migration (GBM) mechanism and feldspar by Subgrain Rotation (SGR), which represents the broad, deep zone of deformation occurring at relatively high temperatures and low stresses. In map view, this transitions to successively narrower zones, respectively characterized by quartz SGR and feldspar Bulge Nucleation (BLG); quartz BLG and brittle deformation of feldspar; and finally, a zone of generally brittle deformation. These zones represent deformation in progressively narrower regions at shallower depths, under lower temperatures and higher stresses.

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

Wang, Wei, E-mail: wang_wei_310@163.com; Lu, Yonghao, E-mail: lu_yonghao@mater.ustb.edu.cn; Ding, Xianfei, E-mail: xfding@ustb.edu.cn

Microstructures and microhardness at fusion boundary of a weld joint were investigated in a 316 stainless steel/Inconel 182 dissimilar weldment. The results showed that there were two alternately distributed typical fusion boundaries, a narrow random boundary (possessed 15% in length) with a clear sharp interface and an epitaxial fusion one with (100){sub BM}//(100){sub WM} at the joint interface. The composition transition, microstructure and hardness across the fusion boundary strongly depended on the type of the fusion boundary. For the random boundary, there was a clear sharp interface and the composition transition with a width of 100 μm took place symmetricallymore » across the grain boundary. For the epitaxial fusion one, however, there were Type-I and Type-II grain boundaries perpendicular and parallel to the epitaxial fusion boundary, respectively. The composition transition took place in the Inconel 182 weld side. Σ3 boundaries in the HAZ of 316SS side and Σ5 grain boundaries in weld metal were usually observed, despite the type of fusion boundary, however the former was much more in epitaxial fusion boundary. Microhardness was continuously decreased across the random fusion boundary from the side of Inconel 182 to 316SS, but a hardening phenomenon appeared in the epitaxial fusion boundary zone because of its fine cellular microstructure. - Highlights: • Two typical fusion boundaries alternately distributed in the fusion interface • The microstructure, composition and hardness across fusion boundary depended on its type. • Different regions in welded joint have different special CSL value boundaries. • Hardening phenomenon only appeared in the epitaxial fusion boundary.« less

Seasonal cross-shelf distribution of major zooplankton taxa on the northern Gulf of Alaska shelf relative to water mass properties, species depth preferences and vertical migration behavior

NASA Astrophysics Data System (ADS)

Coyle, Kenneth O.; Pinchuk, Alexei I.

2005-01-01

The cross-shelf distribution of major zooplankton species was examined on the northern Gulf of Alaska (GOA) shelf during the production season for four years, between October 1997 and October 2001. The zooplankton community on the northern GOA shelf consisted of oceanic and neritic species of the North Pacific subarctic species complex. Cross-shelf distribution of the major zooplankton species was influenced by their depth preferences, vertical migration behavior, salinity-temperature preferences, and by cross-shelf water-mass distribution and movement. The neritic community, dominated by Pseudocalanus spp., Metridia pacifica and Calanus marshallae, had highest abundances on the inner shelf, in the Alaska Coastal Current, and in the adjacent fjords in late spring and early summer. The oceanic community, which contained primarily Neocalanus cristatus and Eucalanus bungii, was observed in the Alaskan Stream and adjacent waters near the shelf break. A mid-shelf transition zone contained a mixture of oceanic and neritic species. Prince William Sound (PWS) contained a unique species complex of large mesopelagic copepods, amphipods and shrimp. Neocalanus flemingeri and Oithona similis were abundant in all four regions during spring and early summer. The transition zone commonly crossed much of the shelf between the shelf break and the ACC, but satellite images and CTD data indicate that occasionally a narrow shelf-break front can form, in which case distinct zooplankton species groups are observed on either side of the front. Satellite data also revealed numerous large and small eddies, which probably contribute to cross-shelf mixing in the transition zone.

Scalable hydrothermal synthesis of free-standing VO₂ nanowires in the M1 phase.

PubMed

Horrocks, Gregory A; Singh, Sujay; Likely, Maliek F; Sambandamurthy, G; Banerjee, Sarbajit

2014-09-24

VO2 nanostructures derived from solution-phase methods are often plagued by broadened and relatively diminished metal-insulator transitions and adventitious doping due to imperfect control of stoichiometry. Here, we demonstrate a stepwise scalable hydrothermal and annealing route for obtaining VO2 nanowires exhibiting almost 4 orders of magnitude abrupt (within 1 °C) metal-insulator transitions. The prepared nanowires have been characterized across their structural and electronic phase transitions using single-nanowire Raman microprobe analysis, ensemble differential scanning calorimetry, and single-nanowire electrical transport measurements. The electrical band gap is determined to be 600 meV and is consistent with the optical band gap of VO2, and the narrowness of differential scanning calorimetry profiles indicates homogeneity of stoichiometry. The preparation of high-quality free-standing nanowires exhibiting pronounced metal-insulator transitions by a solution-phase process allows for scalability, further solution-phase processing, incorporation within nanocomposites, and integration onto arbitrary substrates.

Experimental investigation on the heat transfer characteristics and flow pattern in vertical narrow channels heated from one side

NASA Astrophysics Data System (ADS)

Huang, Lihao; Li, Gang; Tao, Leren

2016-07-01

Experimental investigation for the flow boiling of water in a vertical rectangular channel was conducted to reveal the boiling heat transfer mechanism and flow patterns map aspects. The onset of nucleate boiling went upward with the increasing of the working fluid mass flow rate or the decreasing of the inlet working fluid temperature. As the vapour quality was increased, the local heat transfer coefficient increased first, then decreased, followed by various flow patterns. The test data from other researchers had a similar pattern transition for the bubble-slug flow and the slug-annular flow. Flow pattern transition model analysis was performed to make the comparison with current test data. The slug-annular and churn-annular transition models showed a close trend with current data except that the vapor phase superficial velocity of flow pattern transition was much higher than that of experimental data.

Clogging Transition of Vibration-Driven Vehicles Passing through Constrictions.

PubMed

Patterson, G A; Fierens, P I; Sangiuliano Jimka, F; König, P G; Garcimartín, A; Zuriguel, I; Pugnaloni, L A; Parisi, D R

2017-12-15

We report experimental results on the competitive passage of elongated self-propelled vehicles rushing through a constriction. For the chosen experimental conditions, we observe the emergence of intermittencies similar to those reported previously for active matter passing through narrow doors. Noteworthy, we find that, when the number of individuals crowding in front of the bottleneck increases, there is a transition from an unclogged to a clogged state characterized by a lack of convergence of the mean clog duration as the measuring time increases. It is demonstrated that this transition-which was reported previously only for externally vibrated systems such as colloids or granulars-appears also for self-propelled agents. This suggests that the transition should also occur for the flow through constrictions of living agents (e.g., humans and sheep), an issue that has been elusive so far in experiments due to safety risks.

The Evolution of Transition Region Loops Using IRIS and AIA

NASA Technical Reports Server (NTRS)

Winebarger, Amy R.; DePontieu, Bart

2014-01-01

Over the past 50 years, the model for the structure of the solar transition region has evolved from a simple transition layer between the cooler chromosphere to the hotter corona to a complex and diverse region that is dominated by complete loops that never reach coronal temperatures. The IRIS slitjaw images show many complete transition region loops. Several of the "coronal" channels in the SDO AIA instrument include contributions from weak transition region lines. In this work, we combine slitjaw images from IRIS with these channels to determine the evolution of the loops. We develop a simple model for the temperature and density evolution of the loops that can explain the simultaneous observations. Finally, we estimate the percentage of AIA emission that originates in the transition region.

Phase transitions in traffic flow on multilane roads.

PubMed

Kerner, Boris S; Klenov, Sergey L

2009-11-01

Based on empirical and numerical analyses of vehicular traffic, the physics of spatiotemporal phase transitions in traffic flow on multilane roads is revealed. The complex dynamics of moving jams observed in single vehicle data measured by video cameras on American highways is explained by the nucleation-interruption effect in synchronized flow, i.e., the spontaneous nucleation of a narrow moving jam with the subsequent jam dissolution. We find that (i) lane changing, vehicle merging from on-ramps, and vehicle leaving to off-ramps result in different traffic phases-free flow, synchronized flow, and wide moving jams-occurring and coexisting in different road lanes as well as in diverse phase transitions between the traffic phases; (ii) in synchronized flow, the phase transitions are responsible for a non-regular moving jam dynamics that explains measured single vehicle data: moving jams emerge and dissolve randomly at various road locations in different lanes; (iii) the phase transitions result also in diverse expanded general congested patterns occurring at closely located bottlenecks.

Narrowing the harvest: Increasing sickle investment and the rise of domesticated cereal agriculture in the Fertile Crescent

NASA Astrophysics Data System (ADS)

Maeda, Osamu; Lucas, Leilani; Silva, Fabio; Tanno, Ken-Ichi; Fuller, Dorian Q.

2016-08-01

For the first time we integrate quantitative data on lithic sickles and archaeobotanical evidence for domestication and the evolution of plant economies from sites dated to the terminal Pleistocene and Early Holocene (ca. 12000-5000 cal. BCE) from throughout the Fertile Crescent region of Southwest Asia. We find a strong correlation in some regions, throughout the Levant, for increasing investment in sickles that tracks the evidence for increasing reliance on cereal crops, while evidence for morphological domestication in wheats (Triticum monococcum and Triticum dicoccum) and barley (Hordeum vulgare) was delayed in comparison to sickle use. These data indicate that while the co-increase of sickle blades and cereal crops support the protracted development of agricultural practice, sickles did not drive the initial stages of the domestication process but rather were a cultural adaptation to increasing reliance on cereals that were still undergoing selection for morphological change. For other regions, such as the Eastern Fertile Crescent and Cyprus such correlations are weaker or non-existent suggesting diverse cultural trajectories to cereal domestication. We conclude that sickles were an exaptation transferred to cereal harvesting and important in signalling a new cultural identity of "farmers". Furthermore, the protracted process of technological and agricultural evolution calls into question hypotheses that the transition to agriculture was caused by any particular climatic event.

Driving Solar Spicules and Jets with Magnetohydrodynamic Turbulence: Testing a Persistent Idea

NASA Astrophysics Data System (ADS)

Cranmer, Steven R.; Woolsey, Lauren N.

2015-10-01

The solar chromosphere contains thin, highly dynamic strands of plasma known as spicules. Recently, it has been suggested that the smallest and fastest (Type II) spicules are identical to intermittent jets observed by the Interface Region Imaging Spectrograph. These jets appear to expand out along open magnetic field lines rooted in unipolar network regions of coronal holes. In this paper we revisit a thirty-year-old idea that spicules may be caused by upward forces associated with Alfvén waves. These forces involve the conversion of transverse Alfvén waves into compressive acoustic-like waves that steepen into shocks. The repeated buffeting due to upward shock propagation causes nonthermal expansion of the chromosphere and a transient levitation of the transition region (TR). Some older models of wave-driven spicules assumed sinusoidal wave inputs, but the solar atmosphere is highly turbulent and stochastic. Thus, we model this process using the output of a time-dependent simulation of reduced magnetohydrodynamic turbulence. The resulting mode-converted compressive waves are strongly variable in time, with a higher TR occurring when the amplitudes are large and a lower TR when the amplitudes are small. In this picture, the TR bobs up and down by several Mm on timescales less than a minute. These motions produce narrow, intermittent extensions of the chromosphere that have similar properties as the observed jets and Type II spicules.

Prevalence, cause, and location of palatal fistula in operated complete unilateral cleft lip and palate: retrospective study.

PubMed

de Agostino Biella Passos, Vivian; de Carvalho Carrara, Cleide Felício; da Silva Dalben, Gisele; Costa, Beatriz; Gomide, Marcia Ribeiro

2014-03-01

To evaluate the prevalence of fistulas after palate repair and analyze their location and association with possible causal factors. Retrospective analysis of patient records and evaluation of preoperative initial photographs. Tertiary craniofacial center. Five hundred eighty-nine individuals with complete unilateral cleft lip and palate that underwent palate repair at the age of 12 to 36 months by the von Langenbeck technique, in a single stage, by the plastic surgery team of the hospital, from January 2003 to July 2007. The cleft width was visually classified by a single examiner as narrow, regular, or wide. The following regions of the palate were considered for the location: anterior, medium, transition (between hard and soft palate), and soft palate. Descriptive statistics and analysis of association between the occurrence of fistula and the different parameters were evaluated. Palatal fistulas were observed in 27% of the sample, with a greater proportion at the anterior region (37.11%). The chi-square statistical test revealed statistically significant association (P ≤ .05) between the fistulas and initial cleft width (P = .0003), intraoperative problems (P = .0037), and postoperative problems (P = .00002). The prevalence of palatal fistula was similar to mean values reported in the literature. Analysis of causal factors showed a positive association between palatal fistulas with wide and regular initial cleft width and intraoperative and postoperative problems. The anterior region presented the greatest occurrence of fistulas.

DRIVING SOLAR SPICULES AND JETS WITH MAGNETOHYDRODYNAMIC TURBULENCE: TESTING A PERSISTENT IDEA

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

Cranmer, Steven R.; Woolsey, Lauren N.

The solar chromosphere contains thin, highly dynamic strands of plasma known as spicules. Recently, it has been suggested that the smallest and fastest (Type II) spicules are identical to intermittent jets observed by the Interface Region Imaging Spectrograph. These jets appear to expand out along open magnetic field lines rooted in unipolar network regions of coronal holes. In this paper we revisit a thirty-year-old idea that spicules may be caused by upward forces associated with Alfvén waves. These forces involve the conversion of transverse Alfvén waves into compressive acoustic-like waves that steepen into shocks. The repeated buffeting due to upwardmore » shock propagation causes nonthermal expansion of the chromosphere and a transient levitation of the transition region (TR). Some older models of wave-driven spicules assumed sinusoidal wave inputs, but the solar atmosphere is highly turbulent and stochastic. Thus, we model this process using the output of a time-dependent simulation of reduced magnetohydrodynamic turbulence. The resulting mode-converted compressive waves are strongly variable in time, with a higher TR occurring when the amplitudes are large and a lower TR when the amplitudes are small. In this picture, the TR bobs up and down by several Mm on timescales less than a minute. These motions produce narrow, intermittent extensions of the chromosphere that have similar properties as the observed jets and Type II spicules.« less

Local homogeneity of cell cycle length in developing mouse cortex

NASA Technical Reports Server (NTRS)

Cai, L.; Hayes, N. L.; Nowakowski, R. S.

1997-01-01

We have measured the amount of variation in the length of the cell cycle for cells in the pseudostratified ventricular epithelium (PVE) of the developing cortex of mice on embryonic day 14. Our measurements were made in three cortical regions (i.e., the neocortex, archicortex, and periarchicortex) using three different methods: the cumulative labeling method (CLM), the percent labeled mitoses (PLM) method, and a comparison of the time needed for the PLM to ascend from 0 to 100% with the time needed for the PLM to descend from 100 to 0%. These 3 different techniques provide different perspectives on the cytokinetic parameters. Theoretically, CLM gives an estimate for a maximum value of the total length of the cell cycle (TC), whereas PLM gives an estimate of a minimum value of TC. The difference between these two estimates indicates that the range for TC is +/-1% of the mean TC for periarchicortex, +/-7% for neocortex, and +/-8% for archicortex. This was confirmed by a lengthening of the PLM descent time in comparison with its ascent time. The sharpness of the transitions and the flatness of the plateau of the PLM curves indicate that 99% of the proliferating cells are within this narrow estimated range for TC; hence, only approximately 1% deviate outside of a relatively restricted range from the average TC of the population. In the context of the possible existence within the cortical PVE of two populations with markedly dissimilar cell cycle kinetics from the mean, one such population must comprise approximately 99% of the total population, and the other, if it exists, is only approximately 1% of the total. This seems to be true for all three cortical regions. The narrow range of TC indicates a homogeneity in the cell cycle length for proliferating cells in three different cortical regions, despite the fact that progenitor cells of different lineages may be present. It further predicts the existence of almost synchronous interkinetic nuclear movements of the proliferating cells in the ventricular zone during early development of the cerebral cortex.

The first optical spectra of Wolf-Rayet stars in M101 revealed with Gemini/GMOS

NASA Astrophysics Data System (ADS)

Pledger, J. L.; Shara, M. M.; Wilde, M.; Crowther, P. A.; Long, K. S.; Zurek, D.; Moffat, A. F. J.

2018-01-01

Deep narrow-band Hubble Space Telescope (HST) imaging of the iconic spiral galaxy M101 has revealed over a thousand new Wolf-Rayet (WR) candidates. We report spectrographic confirmation of 10 He II-emission line sources hosting 15 WR stars. We find WR stars present at both sub- and super-solar metallicities with WC stars favouring more metal-rich regions compared to WN stars. We investigate the association of WR stars with H II regions using archival HST imaging and conclude that the majority of WR stars are in or associated with H II regions. Of the 10 emission lines sources, only one appears to be unassociated with a star-forming region. Our spectroscopic survey provides confidence that our narrow-band photometric candidates are in fact bona fide WR stars, which will allow us to characterize the progenitors of any core-collapse supernovae that erupt in the future in M101.

Sudden Thickening in Flowing Soap Films

NASA Astrophysics Data System (ADS)

Goldburg, Walter; Steers, Stanley; Hartman, Nikolaus

2007-11-01

There is no difficulty in creating soap films that flow vertically downward under gravity at speeds of the order of a m/s. If the height of the film L0 is of the order of 1 m or less, the film thickness h(x) is a few microns (The coordinate x increases downward below the injection point at x = 0.) However if L0 is of the order of 2 m, one finds that h abruptly increases at a sharply defined value of x =L. In the experiments to be described, L ˜ =.9 m. As expected, the vertical film velocity vx(x) correspondingly drops to a small fraction of its upstream value at x ˜L. In the narrow transition region from thin to thick film at x=L, both h(x) and the vx(x) oscillate at a well-defined frequency of the order of 1 Hz. The abrupt thickening is expected on the basis of singular perturbation theory (T. Tran, following paper).

Resistive MHD Stability Analysis in Near Real-time

NASA Astrophysics Data System (ADS)

Glasser, Alexander; Kolemen, Egemen

2017-10-01

We discuss the feasibility of a near real-time calculation of the tokamak Δ' matrix, which summarizes MHD stability to resistive modes, such as tearing and interchange modes. As the operational phase of ITER approaches, solutions for active feedback tokamak stability control are needed. It has been previously demonstrated that an ideal MHD stability analysis is achievable on a sub- O (1 s) timescale, as is required to control phenomena comparable with the MHD-evolution timescale of ITER. In the present work, we broaden this result to incorporate the effects of resistive MHD modes. Such modes satisfy ideal MHD equations in regions outside narrow resistive layers that form at singular surfaces. We demonstrate that the use of asymptotic expansions at the singular surfaces, as well as the application of state transition matrices, enable a fast, parallelized solution to the singular outer layer boundary value problem, and thereby rapidly compute Δ'. Sponsored by US DOE under DE-SC0015878 and DE-FC02-04ER54698.

Large Thermal Motion in Halide Perovskites

DOE PAGES

Tyson, T. A.; Gao, W.; Chen, Y. -S.; ...

2017-08-24

Solar cells based on hybrid perovskites have shown high efficiency while possessing simple processing methods. To gain a fundamental understanding of their properties on an atomic level, we investigate single crystals of CH 3NH 3PbI 3 with a narrow transition (~5 K) near 327 K. Temperature dependent structural measurements reveal a persistent tetragonal structure with smooth changes in the atomic displacement parameters (ADPs) on crossing T*. We show that the ADPs for I ions yield extended flat regions in the potential wells consistent with the measured large thermal expansion parameter. Molecular dynamics simulations reveal that this material exhibits significant asymmetriesmore » in the Pb-I pair distribution functions. We also show that the intrinsically enhanced freedom of motion of the iodine atoms enables large deformations. This flexibility (softness) of the atomic structure results in highly localized atomic relaxation about defects and hence accounts for both the high carrier mobility as well as the structural instability.« less

Resonance-enhanced two-photon excitation of CaI

NASA Astrophysics Data System (ADS)

Casero-Junquera, Elena; Lawruszczuk, Rafal; Rostas, Joëlle; Taieb, Guy

1994-07-01

Induced fluorescence following visible (620-655 nm) laser excitation of the CaI radical has been detected not only in the same region (B, A-X transitions), but also in the UV (315-330 nm). The UV two-photon excitation spectrum consists of narrow bands appearing at laser frequencies located within certain bands of the Δ v = 1, 0 sequences of the B 2Σ +-X 2Σ + and A 2Π 1/2-X 2Σ + systems. The main peaks are tentatively assigned to resonance-enhanced excitation of a single vibrational level of the lowest Rydberg D 2Σ + state from successive vibrational levels of the ground state. The excitation process is a one-color two-photon optical—optical-double-resonance via B 2Σ + and A 2Π 1/2 intermediate levels. This analysis is supported by the absorption spectrum observed long ago by Walters and Barratt. The absorption and laser excitation complementary data have been used to derive approximate molecular constants for the D state.

Near-Resonant Raman Amplification in the Rotational Quantum Wave Packets of Nitrogen Molecular Ions Generated by Strong Field Ionization

NASA Astrophysics Data System (ADS)

Liu, Zhaoxiang; Yao, Jinping; Chen, Jinming; Xu, Bo; Chu, Wei; Cheng, Ya

2018-02-01

The generation of laserlike narrow bandwidth emissions from nitrogen molecular ions (N2+ ) generated in intense near- and mid infrared femtosecond laser fields has aroused much interest because of the mysterious physics underlying such a phenomenon. Here, we perform a pump-probe measurement on the nonlinear interaction of rotational quantum wave packets of N2+ generated in midinfrared (e.g., at a wavelength centered at 1580 nm) femtosecond laser fields with an ultrashort probe pulse whose broad spectrum overlaps both P - and R -branch rotational transition lines between the electronic states N2+(B2Σu+,v'=0 ) and N2+(X2Σg+,v =0 ) . The results indicate the occurrence of highly efficient near-resonant stimulated Raman scattering in the quantum wave packets of N2+ ions generated in strong laser fields in the midinfrared region, of which the underlying mechanism is different from that of the air lasers generated in atmospheric environment when pumping with 800 nm intense pulses.

Geothermal energy prospectivity of the Torrens Hinge Zone: evidence from new heat flow data

NASA Astrophysics Data System (ADS)

Matthews, Chris

2009-09-01

The Torrens Hinge Zone is a long but narrow (up to 40km wide) geological transition zone between the relatively stable Eastern Gawler Craton `Olympic Domain' to the west, and the sedimentary basin known as the Adelaide Geosyncline to the east. The author hypothesised from first principles that the Torrens Hinge Zone should be prospective for high geothermal gradients due to the likely presence of high heat flow and insulating cover rocks. A method to test this hypothesis was devised, which involved the determination of surface heat flow on a pattern grid using purpose-drilled wells, precision temperature logging and detailed thermal conductivity measurements. The results of this structured test have validated the hypothesis, with heat flow values over 90mW/m2 recorded in five of six wells drilled. With several kilometres thickness of moderate conductivity sediments overlying the crystalline basement in this region, predicted temperature at 5000m ranges between 200 and 300°C.

Atomically thin noble metal dichalcogenide: a broadband mid-infrared semiconductor.

PubMed

Yu, Xuechao; Yu, Peng; Wu, Di; Singh, Bahadur; Zeng, Qingsheng; Lin, Hsin; Zhou, Wu; Lin, Junhao; Suenaga, Kazu; Liu, Zheng; Wang, Qi Jie

2018-04-18

The interest in mid-infrared technologies surrounds plenty of important optoelectronic applications ranging from optical communications, biomedical imaging to night vision cameras, and so on. Although narrow bandgap semiconductors, such as Mercury Cadmium Telluride and Indium Antimonide, and quantum superlattices based on inter-subband transitions in wide bandgap semiconductors, have been employed for mid-infrared applications, it remains a daunting challenge to search for other materials that possess suitable bandgaps in this wavelength range. Here, we demonstrate experimentally for the first time that two-dimensional (2D) atomically thin PtSe 2 has a variable bandgap in the mid-infrared via layer and defect engineering. Here, we show that bilayer PtSe 2 combined with defects modulation possesses strong light absorption in the mid-infrared region, and we realize a mid-infrared photoconductive detector operating in a broadband mid-infrared range. Our results pave the way for atomically thin 2D noble metal dichalcogenides to be employed in high-performance mid-infrared optoelectronic devices.

Tunable picosecond infrared pulses generated by stimulated electronic Raman scattering of a mode-locked Ti:Sapphire laser in potassium vapor

NASA Astrophysics Data System (ADS)

Ohde, H.; Lin, S.; Minoh, A.; Shimizu, F. O.; Aono, M.; Suzuki, T.

1996-01-01

A down-conversion to the mid-infrared region by using Stimulated Electronic Raman Scattering (SERS) in potassium vapor is described. The pump radiation is a frequency-doubled regeneratively amplified Ti:Sapphire laser with a pulse duration of 2 ps, pulse energy of 0.2 mJ, and repetition rate of 10 Hz. With the pumping frequency tuned around the potassium 4 s-5 p transition, nearly transform-limited infrared radiation tunable between 2.2 and 3.4 μm has been generated with a peak infrared energy of 12 µJ, corresponding to a quantum efficiency of 17%, and with a pulse duration of 2 ps. The present tuning range could be extended by extending the tuning range of the pump laser. In comparison, intense infrared radiation of 90 µJ energy but with a very narrow tunability around 2.9 μm has also been generated by SERS in barium vapor.

Universality and Quantum Criticality of the One-Dimensional Spinor Bose Gas

NASA Astrophysics Data System (ADS)

PâÅ£u, Ovidiu I.; Klümper, Andreas; Foerster, Angela

2018-06-01

We investigate the universal thermodynamics of the two-component one-dimensional Bose gas with contact interactions in the vicinity of the quantum critical point separating the vacuum and the ferromagnetic liquid regime. We find that the quantum critical region belongs to the universality class of the spin-degenerate impenetrable particle gas which, surprisingly, is very different from the single-component case and identify its boundaries with the peaks of the specific heat. In addition, we show that the compressibility Wilson ratio, which quantifies the relative strength of thermal and quantum fluctuations, serves as a good discriminator of the quantum regimes near the quantum critical point. Remarkably, in the Tonks-Girardeau regime, the universal contact develops a pronounced minimum, reflected in a counterintuitive narrowing of the momentum distribution as we increase the temperature. This momentum reconstruction, also present at low and intermediate momenta, signals the transition from the ferromagnetic to the spin-incoherent Luttinger liquid phase and can be detected in current experiments with ultracold atomic gases in optical lattices.

Remarkable optical red shift and extremely high optical absorption coefficient of V-Ga co-doped TiO2

NASA Astrophysics Data System (ADS)

Deng, Quanrong; Han, Xiaoping; Gao, Yun; Shao, Guosheng

2012-07-01

A first attempt has been made to study the effect of codoping of transition metal and sp metal on the electronic structure and associated optical properties of TiO2, through V-Ga codoped thin films. V-Ga codoped rutile TiO2 films were fabricated on fused quartz substrates using pulsed laser ablation, followed by heat treatment at high temperatures. Gigantic redshift in the optical absorption edge was observed in V-Ga co-doped TiO2 materials, from UV to infrared region with high absorption coefficient. Through combined structural characterization and theoretical modeling, this is attributed to the p-d hybridization between the two metals. This leads to additional energy bands to overlap with the minimum of the conduction band, leading to remarkably narrowed band gap free of mid-gap states. The direct-gap of the co-doped phase is key to the remarkably high optical absorption coefficient of the coped titania.

Structure of micro-instabilities in tokamak plasmas: Stiff transport or plasma eruptions?

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

Dickinson, D., E-mail: dd502@york.ac.uk; EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB; Roach, C. M.

2014-01-15

Solutions to a model 2D eigenmode equation describing micro-instabilities in tokamak plasmas are presented that demonstrate a sensitivity of the mode structure and stability to plasma profiles. In narrow regions of parameter space, with special plasma profiles, a maximally unstable mode is found that balloons on the outboard side of the tokamak. This corresponds to the conventional picture of a ballooning mode. However, for most profiles, this mode cannot exist, and instead, a more stable mode is found that balloons closer to the top or bottom of the plasma. Good quantitative agreement with a 1D ballooning analysis is found, providedmore » the constraints associated with higher order profile effects, often neglected, are taken into account. A sudden transition from this general mode to the more unstable ballooning mode can occur for a critical flow shear, providing a candidate model for why some experiments observe small plasma eruptions (Edge Localised Modes, or ELMs) in place of large Type I ELMs.« less

Along-strike supply of volcanic rifted margins: Implications for plume-influenced rifting and sudden along-strike transitions between volcanic and non-volcanic rifted margins

NASA Astrophysics Data System (ADS)

Ranero, C. R.; Phipps Morgan, J.

2006-12-01

The existence of sudden along-strike transitions between volcanic and non-volcanic rifted margins is an important constraint for conceptual models of rifting and continental breakup. We think there is a promising indirect approach to infer the maximum width of the region of upwelling that exists beneath a rifted margin during the transition from rifting to seafloor-spreading. We infer this width of ~30km from the minimum length of the ridge-offsets that mark the limits of the `region of influence' of on-ridge plumes on the axial relief, axial morphology, and crustal thickness along the ridge and at the terminations of fossil volcanic rifted margins. We adopt Vogt's [1972] hypothesis for along-ridge asthenospheric flow in a narrow vertical slot beneath the axis of plume-influenced `macro-segments' and volcanic rifted margins. We find that: (1) There is a threshold distance to the lateral offsets that bound plume-influenced macrosegments; all such `barrier offsets' are greater than ~30km, while smaller offsets do not appear to be a barrier to along-axis flow. This pattern is seen in the often abrupt transitions between volcanic and non-volcanic rifted margins; these transitions coincide with >30km ridge offsets that mark the boundary between the smooth seafloor morphology and thick crust of a plume- influenced volcanic margin and a neighboring non-volcanic margin, as recorded in 180Ma rifting of the early N. Atlantic, the 42Ma rifting of the Kerguelen-Broken Ridge, and the 66Ma Seychelles-Indian rifting in the Indian Ocean. (2) A similar pattern is seen in the often abrupt transitions between `normal' and plume-influenced mid- ocean ridge segments, which is discussed in a companion presentation by Phipps Morgan and Ranero (this meeting). (3) The coexistance of adjacent volcanic and non-volcanic rifted margin segments is readily explained in this conceptual framework. If the volcanic margin macrosegment is plume-fed by hot asthenosphere along an axial ridge slot, while adjacent non-volcanic margin segments stretch and upwell ambient cooler subcontinental mantle, then there will be a sudden transition from volcanic to non-volcanic margins across a transform offset. (4) A 30km width for the region of ridge upwelling and melting offers a simple conceptual explanation for the apparent 30km threshold length for the existence of strike-slip transform faults and the occurrence of non-transform offsets at smaller ridge offset-distances. (5) The conceptual model leads to the interpretation of the observed characteristic ~1000km-2000km-width of plume-influenced macro- segments as a measure of the maximum potential plume supply into a subaxial slot of 5-10 cubic km per yr. (6) If asthenosphere consumption by plate-spreading is less than plume-supply into a macro-segment, then the shallow seafloor and excess gravitational spreading stresses associated with a plume-influenced ridge can lead to growth of the axial slot by ridge propagation. We think this is a promising conceptual framework with which to understand the differences between volcanic and non-volcanic rifted margins.

SHOCK-ENHANCED C{sup +} EMISSION AND THE DETECTION OF H{sub 2}O FROM THE STEPHAN'S QUINTET GROUP-WIDE SHOCK USING HERSCHEL

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

Appleton, P. N.; Lord, S.; Lu, N.

2013-11-01

We present the first Herschel spectroscopic detections of the [O I] 63 μm and [C II] 158 μm fine-structure transitions, and a single para-H{sub 2}O line from the 35 × 15 kpc{sup 2} shocked intergalactic filament in Stephan's Quintet. The filament is believed to have been formed when a high-speed intruder to the group collided with a clumpy intergroup gas. Observations with the PACS spectrometer provide evidence for broad (>1000 km s{sup –1}) luminous [C II] line profiles, as well as fainter [O I] 63 μm emission. SPIRE FTS observations reveal water emission from the p-H{sub 2}O (1{sub 11}-0{sub 00})more » transition at several positions in the filament, but no other molecular lines. The H{sub 2}O line is narrow and may be associated with denser intermediate-velocity gas experiencing the strongest shock-heating. The [C II]/PAH{sub tot} and [C II]/FIR ratios are too large to be explained by normal photo-electric heating in photodissociation regions. H II region excitation or X-ray/cosmic-ray heating can also be ruled out. The observations lead to the conclusion that a large fraction the molecular gas is diffuse and warm. We propose that the [C II], [O I], and warm H{sub 2} line emission is powered by a turbulent cascade in which kinetic energy from the galaxy collision with the intergalactic medium is dissipated to small scales and low velocities, via shocks and turbulent eddies. Low-velocity magnetic shocks can help explain both the [C II]/[O I] ratio, and the relatively high [C II]/H{sub 2} ratios observed. The discovery that [C II] emission can be enhanced, in large-scale turbulent regions in collisional environments, has implications for the interpretation of [C II] emission in high-z galaxies.« less

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

Harilal, Sivanandan S.; LaHaye, Nicole L.; Phillips, Mark C.

We use a two-dimensional laser-induced fluorescence spectroscopy technique to measure the coupled absorption and emission properties of atomic species in plasmas produced via laser ablation of solid aluminum targets at atmospheric pressure. Emission spectra from the Al I 394.4 nm and Al I 396.15 nm transitions are measured while a frequency-doubled, continuous-wave, Ti:Sapphire laser is tuned across the Al I 396.15 nm transition. The resulting two-dimensional spectra show the energy coupling between the two transitions via increased emission intensity for both transitions during resonant absorption of the continuous-wave laser at one transition. Time-delayed and gated detection of the emission spectrummore » is used to isolate the resonantly-excited fluorescence emission from the thermally-excited emission from the plasma. In addition, the tunable continuous-wave laser measures the absorption spectrum of the Al transition with ultra-high resolution after the plasma has cooled, resulting in narrower spectral linewidths than observed in emission spectra. Our results highlight that fluorescence spectroscopy employing continuous-wave laser re-excitation after pulsed laser ablation combines benefits of both traditional emission and absorption spectroscopic methods.« less

Unravelling the mechanisms for plant survival on gypsum soils: an analysis of the chemical composition of gypsum plants from Turkey.

PubMed

Bolukbasi, A; Kurt, L; Palacio, S

2016-03-01

Depending on their specificity to gypsum, plants can be classified as gypsophiles (gypsum exclusive) and gypsovags (non-exclusive). The former may further be segregated into wide and narrow gypsophiles, depending on the breadth of their distribution area. Narrow gypsum endemics have a putative similar chemical composition to plants non-exclusive to gypsum (i.e. gypsovags), which may indicate their similar ecological strategy as stress-tolerant plant refugees on gypsum. However, this hypothesis awaits testing in different regions of the world. We compared the chemical composition of four narrow gypsum endemics, one widely distributed gypsophile and six gypsovags from Turkey. Further, we explored the plasticity in chemical composition of Turkish gypsovags growing on high- and low-gypsum content soils. Differences were explored with multivariate analyses (RDA) and mixed models (REML). Narrow gypsum endemics segregated from gypsovags in their chemical composition according to RDAs (mainly due to higher K and ash content in the former). Nevertheless, differences were small and disappeared when different nutrients were analysed individually. All the gypsovags studied accumulated more S and ash when growing on high-gypsum than on low-gypsum soils. Similar to narrow gypsum endemics from other regions of the world, most local gypsum endemics from Turkey show a similar chemical composition to gypsovags. This may indicate a shared ecological strategy as stress-tolerant plants not specifically adapted to gypsum. Nevertheless, the narrow gypsum endemic Gypsophila parva showed a chemical composition typical of gypsum specialists, indicating that various strategies are feasible within narrowly distributed gypsophiles. © 2015 German Botanical Society and The Royal Botanical Society of the Netherlands.

Structural analysis and molecular modelling of the Cu/Zn-SOD from fungal strain Humicola lutea 103

NASA Astrophysics Data System (ADS)

Dolashka, Pavlina; Moshtanska, Vesela; Dolashki, Aleksander; Velkova, Lyudmila; Rao, Gita Subba; Angelova, Maria; Betzel, Christian; Voelter, Wolfgang; Atanasov, Boris

2011-12-01

The native form of Cu/Zn-superoxide dismutase, isolated from fungal strain Humicola lutea 103 is a homodimer that coordinates one Cu(2+) and one Zn(2+) per monomer. Cu(2+) and Zn(2+) ions play crucial roles in enzyme activity and structural stability, respectively. It was established that HLSOD shows high pH and temperature stability. Thermostability of the glycosylated enzyme Cu/Zn-SOD, isolated from fungal strain H. lutea 103, was determined by CD spectroscopy. Determination of reversibility toward thermal denaturation for HLSOD allowed several thermodynamic parameters to be calculated. In this communication we report the conditions under which reversible denaturation of HLSOD exists. The narrow range over which the system is reversible has been determined using the strongest test of two important thermodynamic independent variables (T and pH). Combining both these variables, the "phase diagram" was determined, as a result of which the real thermodynamic parameters (Δ Cp, ΔHexp°, and ΔGexp°) was established. Because very narrow pH-interval of transitions we assume they are as result of overlapping of two simple transitions. It was found that Δ Ho is independent from pH with a value of 1.3 kcal/mol and 2.8 kcal/mol for the first and the second transition, respectively. Δ Go was pH-dependent in all studied pH-interval. This means that the transitions are entropically driven, these. Based on this, these processes can be described as hydrophobic rearrangement of the quaternary structure. It was also found that glycosylation does not influence the stability of the enzyme because the carbohydrate chain is exposed on the surface of the molecule.

Evidence for hot clumpy accretion flow in the transitional millisecond pulsar PSR J1023+0038

NASA Astrophysics Data System (ADS)

Shahbaz, T.; Dallilar, Y.; Garner, A.; Eikenberry, S.; Veledina, A.; Gandhi, P.

2018-06-01

We present simultaneous optical and near-infrared (IR) photometry of the millisecond pulsar PSR J1023+0038 during its low-mass X-ray binary phase. The r΄- and Ks-band light curves show rectangular, flat-bottomed dips, similar to the X-ray mode-switching (active-passive state transitions) behaviour observed previously. The cross-correlation function (CCF) of the optical and near-IR data reveals a strong, broad negative anticorrelation at negative lags, a broad positive correlation at positive lags, with a strong, positive narrow correlation superimposed. The shape of the CCF resembles the CCF of black hole X-ray binaries but the time-scales are different. The features can be explained by reprocessing and a hot accretion flow close to the neutron star's magnetospheric radius. The optical emission is dominated by the reprocessed component, whereas the near-IR emission contains the emission from plasmoids in the hot accretion flow and a reprocessed component. The rapid active-passive state transition occurs when the hot accretion flow material is channelled on to the neutron star and is expelled from its magnetosphere. During the transition the optical reprocessing component decreases resulting in the removal of a blue spectral component. The accretion of clumpy material through the magnetic barrier of the neutron star produces the observed near-IR/optical CCF and variability. The dip at negative lags corresponds to the suppression of the near-IR synchrotron component in the hot flow, whereas the broad positive correlation at positive lags is driven by the increased synchrotron emission of the outflowing plasmoids. The narrow peak in the CCF is due to the delayed reprocessed component, enhanced by the increased X-ray emission.

Large Format Narrow-Band, Multi-Band, and Broad-Band LWIR QWIP Focal Planes for Space and Earth Science Applications

NASA Technical Reports Server (NTRS)

Gunapala, S. D.; Bandara, S. V.

2004-01-01

A 640x512 pixel, long-wavelength cutoff, narrow-band (delta(lambda)/approx. 10%) quantum well infrared photodetector (QWIP) focal plane array (FPA), a four-band QWIP FPA in the 4-16 m spectral region, and a broad-band (delta(lambda)/approx. 42%) QWIP FPA having 15.4 m cutoff have been demonstrated.

Venus - Complex Network of Narrow Fractures Near Hestia Rupes Region

NASA Image and Video Library

1996-10-23

This image from NASA Magellan spacecraft covers region near Hestia Rupes on the northwestern corner of Aphrodite Terra. The complex network of narrow (<1 kilometer) fractures in the center of the image extends for approximately 50 kilometers (31 miles). This network exhibits tributary-like branches similar to those observed in river systems on Earth. However, the angular intersections of tributaries suggest tectonic control. These features appear to be due to drainage of lava along preexisting fractures and subsequent collapse of the surface. The underlying tectonic fabric can be observed in the northeast trending ridges which predate the plains. http://photojournal.jpl.nasa.gov/catalog/PIA00469

Line Narrowing of Excited-State Transitions in Nonlinear Polarization Spectroscopy: Application to Water-Soluble Chlorophyll-Binding Protein

NASA Astrophysics Data System (ADS)

Schoth, Mario; Richter, Marten; Knorr, Andreas; Renger, Thomas

2012-04-01

The homogeneous linewidth of dye aggregates like photosynthetic light-harvesting complexes contains important information about energy transfer and relaxation times that is, however, masked by inhomogeneous broadening caused by static disorder. Whereas there exist line narrowing techniques for the study of low-energy exciton states, the homogeneous linewidth of the high-energy states is not so easy to decipher. Here we present a microscopic theory for nonlinear polarization spectroscopy in the frequency domain that contains a dynamic aggregate selection revealing the homogeneous linewidth of these states. The theory is applied to the water-soluble chlorophyll-binding protein for which the high-energy exciton state was predicted to exhibit a sub-100-fs lifetime.

Investigations of glass structure using fluorescence line narrowing and moleuclar dynamics simulations

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

Weber, M.J.; Brawer, S.A.

1982-07-02

The local structure at individual ion sites in simple and multicomponent glasses is simulated using methods of molecular dynamics. Computer simulations of fluoroberyllate glasses predict a range of ion separations and coordination numbers that increases with increasing complexity of the glass composition. This occurs at both glass forming and glass modifying cation sites. Laser-induced fluorescence line-narrowing techniques provide a unique probe of the local environments of selected subsets of ions and are used to measure site to site variations in the electronic energy levels and transition probabilities of rare earth ions. These and additional results from EXAFS, neutron and x-raymore » diffraction, and NMR experiments are compared with simulated glass structures.« less

Crustal tomographic imaging of a transitional continental rift: the Ethiopian rift

NASA Astrophysics Data System (ADS)

Daly, E.; Keir, D.; Ebinger, C. J.; Stuart, G. W.; Bastow, I. D.; Ayele, A.

2008-03-01

In this study we image crustal structure beneath a magmatic continental rift to understand the interplay between crustal stretching and magmatism during the late stages of continental rifting: the Main Ethiopian Rift (MER). The northern sector of this region marks the transition from continental rifting in the East African Rift to incipient seafloor spreading in the southern Red Sea and western Gulf of Aden. Our local tomographic inversion exploits 172 broad-band instruments covering an area of 250 × 350 km of the rift and adjacent plateaux. The instruments recorded a total of 2139 local earthquakes over a 16-month period. Several synthetic tests show that resolution is good between 12 and 25 km depth (below sea level), but some horizontal velocity smearing is evident along the axis of the Main Ethiopian Rift below 16 km. We present a 3-D P-wave velocity model of the mid-crust and present the first 3-D Vp/Vs model of the region. Our models show high P-wave velocities (6.5 km s-1) beneath the axis of the rift at a depth of 12-25 km. The presence of high Vp/Vs ratios (1.81-1.84) at the same depth range suggest that they are cooled mafic intrusions. The high Vp/Vs values, along with other geophysical evidence, suggest that dyking is pervasive beneath the axis of the rift from the mid-crustal depths to the surface and that some portion of partial melt may exist at lower crustal depths. Although the crustal stretching factor across the Main Ethiopian Rift is ~1.7, our results indicate that magma intrusion in narrow zones accommodates a large proportion of extensional strain, with similarities to slow-spreading mid-ocean ridge processes.

Fine structure of the transitional zone of the rat seminiferous tubule.

PubMed

Nykänen, M

1979-05-25

An electron microscopic study was made on the structure of the testicular transitional zone (TZ) in the adult rat. The TZ proper consists of modified Sertoli cellss, with only a few spermatogonia and macrophages, surrounding distally a very narrow lumen. The TZ Sertoli cells have nuclei with a somewhat coarser matrix and more peripheral heterochromatin than Sertoli cell nuclei of the nearby seminiferous tubules, and the electron density of the cytoplasm varies from cell to cell. Smooth endoplasmic reticulum is abundant, but usually there are also scattered ribosomal rosettes and an occasional profile of rough endoplasmic reticulum. Microtubules are very numerous in the columnar portion of the cell, and laminar structures seemingly joining the cell surfaces are sometimes seen. Lipid droplets and lysosmal structures are frequent cellular components in proximal TZ Sertoli cells. Empty intracellular vacuoles are abundant, sometimes arranged around areas of smooth endoplasmic reticulum. Occasionally, membrane-limited fine granules and vacuoles are seen within Sertoli cells and also in the TZ lumen, suggesting a possible secretory activity by these cells. The apical processes of the Sertoli cells form large vacuolar structures, and in the basal parts of the epithelium vacuoles with capillary-like appearance are frequently seen. Phagocytosis of germinal cells by the Sertoli cells occurs in the proximal region of the TZ. Round waste bodies in contact with the Sertoli cell apices protruding into the tubulus rectus, are also common. The tunica propria of the TZ is thickened and somewhat wrinkled, and in the proximal region the myoid cell layer loses its continuity and is replaced by fibroblasts. The epithelium of the tubulus rectus adjacent to the TZ consists of several overlapping epithelial cells. The typical junctional complexes between TZ Sertoli cells appear to be impermeable to the lanthanum tracer.

Influence of spin and charge fluctuations on spectra of the two-dimensional Hubbard model

NASA Astrophysics Data System (ADS)

Sherman, A.

2018-05-01

The influence of spin and charge fluctuations on spectra of the two-dimensional fermionic Hubbard model is considered using the strong coupling diagram technique. Infinite sequences of diagrams containing ladder inserts, which describe the interaction of electrons with these fluctuations, are summed, and obtained equations are self-consistently solved for the ranges of Hubbard repulsions , temperatures and electron concentrations with t the intersite hopping constant. For all considered U the system exhibits a transition to the long-range antiferromagnetic order at . At the same time no indication of charge ordering is observed. Obtained solutions agree satisfactorily with results of other approaches and obey moments sum rules. In the considered region of the U-T plane, the curve separating metallic solutions passes from at the highest temperatures to U  =  2t at for half-filling. If only short-range fluctuations are allowed for the remaining part of this region is occupied by insulating solutions. Taking into account long-range fluctuations leads to strengthening of maxima tails, which transform a part of insulating solutions into bad-metal states. For low T, obtained results allow us to trace the gradual transition from the regime of strong correlations with the pronounced four-band structure and well-defined Mott gap for to the Slater regime of weak correlations with the spectral intensity having a dip along the boundary of the magnetic Brillouin zone due to an antiferromagnetic ordering for . For and doping leads to the occurrence of a pseudogap near the Fermi level, which is a consequence of the splitting out of a narrow band from a Hubbard subband. Obtained spectra feature waterfalls and Fermi arcs, which are similar to those observed in hole-doped cuprates.

Genetic Consideration of Schizotypal Traits: A Review

PubMed Central

Walter, Emma E.; Fernandez, Francesca; Snelling, Mollie; Barkus, Emma

2016-01-01

Schizotypal traits are of interest and importance in their own right and also have theoretical and clinical associations with schizophrenia. These traits comprise attenuated psychotic symptoms, social withdrawal, reduced cognitive capacity, and affective dysregulation. The link between schizotypal traits and psychotic disorders has long since been debated. The status of knowledge at this point is such schizotypal traits are a risk for psychotic disorders, but in and of themselves only confer liability, with other risk factors needing to be present before a transition to psychosis occurs. Investigation of schizotypal traits also has the possibility to inform clinical and research pursuits concerning those who do not make a transition to psychotic disorders. A growing body of literature has investigated the genetic underpinnings of schizotypal traits. Here, we review association, family studies and describe genetic disorders where the expression of schizotypal traits has been investigated. We conducted a thorough review of the existing literature, with multiple search engines, references, and linked articles being searched for relevance to the current review. All articles and book chapters in English were sourced and reviewed for inclusion. Family studies demonstrate that schizotypal traits are elevated with increasing genetic proximity to schizophrenia and some chromosomal regions have been associated with schizotypy. Genes associated with schizophrenia have provided the initial start point for the investigation of candidate genes for schizotypal traits; neurobiological pathways of significance have guided selection of genes of interest. Given the chromosomal regions associated with schizophrenia, some genetic disorders have also considered the expression of schizotypal traits. Genetic disorders considered all comprise a profile of cognitive deficits and over representation of psychotic disorders compared to the general population. We conclude that genetic variations associated with schizotypal traits require further investigation, perhaps with targeted phenotypes narrowed to assist in refining the clinical end point of significance. PMID:27895608

Infrared Spectra of He-, Ne-, and Ar-C_2D_2 Complexes

NASA Astrophysics Data System (ADS)

Rezai, M.; Moazzen-Ahmadi, N.; McKellar, A. R. W.; Fernandez, Berta; Farrelly, David

2012-06-01

Remarkably, there are no previously published experimental spectra of the helium-acetylene van der Waals complex. Apparently, infrared spectra of He-C_2H_2 were recorded around 1990 in Roger Miller's lab, but a detailed rotational assignment was not possible even with the help of two extensive sets of theoretical predictions. Here, we study rare gas-C_2D_2 complexes in the νb{3} region (˜2439 wn) using a rapid-scan tuneable diode laser spectrometer to probe a pulsed supersonic slit-jet expansion. The He-C_2D_2 assignment problem is readily apparent: most of the absorption is piled-up in a very narrow region around 2440.85 wn, close to the R(0) line of the C_2D_2 monomer. This pile-up is a signature of very weak anisotropy in the helium-acetylene intermolecular potential, leading to almost free internal rotation of the C_2D_2. We are able to achieve a convincing rotational assignment with the help of theoretical energy level calculations based on the intermolecular potential surface of Munteanu and Fernández. So far the results are limited to He-C_2D_2 transitions which correlate with the monomer R(0) transition. Ne-C_2D_2 also shows a free-rotation pile-up of lines near R(0) which makes assignment tricky. In contrast, Ar-C_2D_2 exhibits more conventional behavior and a normal asymmetric rotor analysis is possible. [1] T. Slee, R.J. Le Roy, and C.E. Chuaqui, Mol. Phys. 77, 111 (1992); R. Moszynski, P.E.S. Wormer, and A. van der Avoird, J. Chem. Phys. 102, 8385 (1995). [2] R. Munteanu and B. Fernández, J. Chem. Phys. 123, 014309 (2005).

DISSECTING THE POWER SOURCES OF LOW-LUMINOSITY EMISSION-LINE GALAXY NUCLEI VIA COMPARISON OF HST-STIS AND GROUND-BASED SPECTRA

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

Constantin, Anca; Castillo, Christopher A.; Shields, Joseph C.

Using a sample of ∼100 nearby line-emitting galaxy nuclei, we have built the currently definitive atlas of spectroscopic measurements of Hα and neighboring emission lines at subarcsecond scales. We employ these data in a quantitative comparison of the nebular emission in Hubble Space Telescope (HST) and ground-based apertures, which offer an order-of-magnitude difference in contrast, and provide new statistical constraints on the degree to which transition objects and low-ionization nuclear emission-line regions (LINERs) are powered by an accreting black hole at ≲10 pc. We show that while the small-aperture observations clearly resolve the nebular emission, the aperture dependence in themore » line ratios is generally weak, and this can be explained by gradients in the density of the line-emitting gas: the higher densities in the more nuclear regions potentially flatten the excitation gradients, suppressing the forbidden emission. The transition objects show a threefold increase in the incidence of broad Hα emission in the high-resolution data, as well as the strongest density gradients, supporting the composite model for these systems as accreting sources surrounded by star-forming activity. The narrow-line LINERs appear to be the weaker counterparts of the Type 1 LINERs, where the low accretion rates cause the disappearance of the broad-line component. The enhanced sensitivity of the HST observations reveals a 30% increase in the incidence of accretion-powered systems at z ≈ 0. A comparison of the strength of the broad-line emission detected at different epochs implies potential broad-line variability on a decade-long timescale, with at least a factor of three in amplitude.« less

Upper mantle anisotropy beneath Peru from SKS splitting: Constraints on flat slab dynamics and interaction with the Nazca Ridge

NASA Astrophysics Data System (ADS)

Eakin, Caroline M.; Long, Maureen D.; Wagner, Lara S.; Beck, Susan L.; Tavera, Hernando

2015-02-01

The Peruvian flat slab is by far the largest region of flat subduction in the world today, but aspects of its structure and dynamics remain poorly understood. In particular, questions remain over whether the relatively narrow Nazca Ridge subducting beneath southern Peru provides dynamic support for the flat slab or it is just a passive feature. We investigate the dynamics and interaction of the Nazca Ridge and the flat slab system by studying upper mantle seismic anisotropy across southern Peru. We analyze shear wave splitting of SKS, sSKS, and PKS phases at 49 stations distributed across the area, primarily from the PerU Lithosphere and Slab Experiment (PULSE). We observe distinct spatial variations in anisotropic structure along strike, most notably a sharp transition from coherent splitting in the north to pervasive null (non-split) arrivals in the south, with the transition coinciding with the northern limit of the Nazca Ridge. For both anisotropic domains there is evidence for complex and multi-layered anisotropy. To the north of the ridge our *KS splitting measurements likely reflect trench-normal mantle flow beneath the flat slab. This signal is then modified by shallower anisotropic layers, most likely in the supra-slab mantle, but also potentially from within the slab. To the south the sub-slab mantle is similarly anisotropic, with a trench-oblique fast direction, but widespread nulls appear to reflect dramatic heterogeneity in anisotropic structure above the flat slab. Overall the regional anisotropic structure, and thus the pattern of deformation, appears to be closely tied to the location of the Nazca Ridge, which further suggests that the ridge plays a key role in the mantle dynamics of the Peruvian flat slab system.

Contribution of the 2(1)Ag state to the third-order optical nonlinearity in a squaraine dye.

PubMed

Andrews, J H; Khaydarov, J D; Singer, K D

1994-07-01

We have measured the third-harmonic response, gamma, of a centrosymmetric squaraine dye (ISQ) in chloroform at a range of frequencies for which the third harmonic is above the strong, narrow peak in the dye's linear absorption spectrum but below the UV absorption band. By fitting the experimental dispersion of gamma using a four-level model, we determine the strength, location, and width of the lowest-lying two-photon transition. We find that the 2(1)Ag state appears just above the 1(1)Bu state in energy and that the 1(1)Bu-2(1)Ag transition moment is somewhat smaller than the transition moment between the ground state and the 1(1)Bu state but much larger than previously predicted for comparable squaraine dyes.

Competitive behavior of photons contributing to junction voltage jump in narrow band-gap semiconductor multi-quantum-well laser diodes at lasing threshold

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

Feng, Liefeng, E-mail: fengliefeng@tju.edu.cn, E-mail: lihongru@nankai.edu.cn; Yang, Xiufang; Wang, Cunda

2015-04-15

The junction behavior of different narrow band-gap multi-quantum-well (MQW) laser diodes (LDs) confirmed that the jump in the junction voltage in the threshold region is a general characteristic of narrow band-gap LDs. The relative change in the 1310 nm LD is the most obvious. To analyze this sudden voltage change, the threshold region is divided into three stages by I{sub th}{sup l} and I{sub th}{sup u}, as shown in Fig. 2; I{sub th}{sup l} is the conventional threshold, and as long as the current is higher than this threshold, lasing exists and the IdV/dI-I plot drops suddenly; I{sub th}{sup u}more » is the steady lasing point, at which the separation of the quasi-Fermi levels of electron and holes across the active region (V{sub j}) is suddenly pinned. Based on the evolutionary model of dissipative structure theory, the rate equations of the photons in a single-mode LD were deduced in detail at I{sub th}{sup l} and I{sub th}{sup u}. The results proved that the observed behavior of stimulated emission suddenly substituting for spontaneous emission, in a manner similar to biological evolution, must lead to a sudden increase in the injection carriers in the threshold region, which then causes the sudden increase in the junction voltage in this region.« less

Very large array and green bank telescope observations of Orion B (NGC 2024, W12): photodissociation region properties and magnetic field

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

Roshi, D. Anish; Goss, W. M.; Jeyakumar, S., E-mail: aroshi@nrao.edu, E-mail: mgoss@nrao.edu, E-mail: sjk@astro.ugto.mx

We present images of C110α and H110α radio recombination line (RRL) emission at 4.8 GHz and images of H166α, C166α, and X166α RRL emission at 1.4 GHz, observed toward the star-forming region NGC 2024. The 1.4 GHz image with angular resolution ∼70'' is obtained using Very Large Array (VLA) data. The 4.8 GHz image with angular resolution ∼17'' is obtained by combining VLA and Green Bank Telescope data in order to add the short and zero spacing data in the uv plane. These images reveal that the spatial distributions of C110α line emission is confined to the southern rim ofmore » the H II region close to the ionization front whereas the C166α line emission is extended in the north-south direction across the H II region. The LSR velocity of the C110α line is 10.3 km s{sup –1} similar to that of lines observed from molecular material located at the far side of the H II region. This similarity suggests that the photodissociation region (PDR) responsible for C110α line emission is at the far side of the H II region. The LSR velocity of C166α is 8.8 km s{sup –1}. This velocity is comparable with the velocity of molecular absorption lines observed from the foreground gas, suggesting that the PDR is at the near side of the H II region. Non-LTE models for carbon line-forming regions are presented. Typical properties of the foreground PDR are T {sub PDR} ∼ 100 K, n{sub e}{sup PDR}∼5 cm{sup –3}, n {sub H} ∼ 1.7 × 10{sup 4} cm{sup –3}, and path length l ∼ 0.06 pc, and those of the far side PDR are T {sub PDR} ∼ 200 K, n{sub e}{sup PDR}∼ 50 cm{sup –3}, n {sub H} ∼ 1.7 × 10{sup 5} cm{sup –3}, and l ∼ 0.03 pc. Our modeling indicates that the far side PDR is located within the H II region. We estimate the magnetic field strength in the foreground PDR to be 60 μG and that in the far side PDR to be 220 μG. Our field estimates compare well with the values obtained from OH Zeeman observations toward NGC 2024. The H166α spectrum shows narrow (1.7 km s{sup –1}) and broad (33 km s{sup –1}) line features. The narrow line has spatial distribution and central velocity (∼9 km s{sup –1}) similar to that of the foreground carbon line emission, suggesting that they are associated. Modeling the narrow H166α emission provides physical properties T {sub PDR} ∼ 50 K, n{sub e}{sup PDR}∼4 cm{sup –3}, and l ∼ 0.01 pc and implies an ionization fraction of ∼10{sup –4}. The broad H166α line originates from the H II region. The X166α line has a different spatial distribution compared to other RRLs observed toward NGC 2024 and is probably associated with cold dust clouds. Based on the expected low depletion of sulfur in such clouds and the –8.1 km s{sup –1} velocity separation between the X166α and C166α lines, we interpret that the X166α transition arises from sulfur.« less

Slab and Plume Morphology in the Transition Zone and Below: a Comparison of Images From Recent P and S Velocity Models

NASA Astrophysics Data System (ADS)

Salmi, L. M.; French, S. W.; Romanowicz, B. A.

2014-12-01

Resolving subduction zones in the shallow upper mantle using global shear velocity tomography has long been a challenge, likely due to the rather narrow signature of the slabs down to ~400 km depth compared to the wavelength of fundamental mode and overtone surface waves, on which resolution of Vs at these depths often relies. On the other hand, models based on P wave travel times exhibit higher resolution in subduction zone regions, owing to both the higher frequencies of the P waves as well as an optimal illumination geometry. Conversely, the global Vs models typically have better resolution near the CMB, because of constraints provided by Sdiff and multiple ScS phases. Here we compare the morphology of subducted slabs throughout the mantle, as imaged by both a recent Vp model (GAP_P4, Fukao and Obayashi, 2013) and a new Vs model (SEMUCB-WM1, French and Romanowicz, GJI, in revision). The latter model was developed by inverting body (to 32s) and fundamental and overtone surface (to 60s) waveforms, with the forward seismic wavefield computed using the spectral element method. While the S velocity model is still "fuzzier" than the Vp model, it tracks the behavior of slabs trapped in the transition zone, and those ponding around 1000 km depth. We quantify the high correlation of the region of fast Vp and Vs anomalies, and thus derive a robust estimate of the R=dlnVs/dlnVp ratio as a function of depth in regions of faster than average velocity. We compare these results with estimates obtained with other combinations of available P and S models, as well as theoretical values from mineral physical calculations. Estimating R in slow velocity regions is more difficult, as resolution varies more among models. Here we compare slow velocity images in SEMUCB-WM1 with those of other recent Vs and Vp models and attempt to estimate R in those regions as well. Interestingly, we note that, in the SEMUCB-WM1 model, some of the columnar, lower than average velocity regions "rising" from the CMB through the lower mantle appear to be deflected horizontally at ~1000 km depth. This observation suggests that whatever mechanism causes the resistance to downward flow in subduction zones at this depth may also affect upwellings.

Shell stability and conditions analyzed using a new method of extracting shell areal density maps from spectrally resolved images of direct-drive inertial confinement fusion implosions

DOE PAGES

Johns, H. M.; Mancini, R. C.; Nagayama, T.; ...

2016-01-25

In warm target direct-drive inertial confinement fusion implosion experiments performed at the OMEGA laser facility, plastic micro-balloons doped with a titanium tracer layer in the shell and filled with deuterium gas were imploded using a low-adiabat shaped laser pulse. Continuum radiation emitted in the core is transmitted through the tracer layer and the resulting spectrum recorded with a gated multi-monochromatic x-ray imager (MMI). Titanium K-shell line absorption spectra observed in the data are due to transitions in L-shell titanium ions driven by the backlighting continuum. The MMI data consist of an array of spectrally resolved images of the implosion. Thesemore » 2-D space-resolved titanium spectral features constrain the plasma conditions and areal density of the titanium doped region of the shell. The MMI data were processed to obtain narrow-band images and space resolved spectra of titanium spectral features. Shell areal density maps, ρL(x,y), extracted using a new method using both narrow-band images and space resolved spectra are confirmed to be consistent within uncertainties. We report plasma conditions in the titanium-doped region of electron temperature (Te) = 400 ± 28 eV, electron number density (N e) = 8.5 × 10 24 ± 2.5 × 10 24 cm –3, and average areal density = 86 ± 7 mg/cm 2. Fourier analysis of areal density maps reveals shell modulations caused by hydrodynamic instability growth near the fuel-shell interface in the deceleration phase. We observe significant structure in modes l = 2–9, dominated by l = 2. We extract a target breakup fraction of 7.1 ± 1.5% from our Fourier analysis. Furthermore, a new method for estimating mix width is evaluated against existing literature and our target breakup fraction. We estimate a mix width of 10.5 ±1 μm.« less

The importance of costoclavicular space on possible compression of the subclavian artery in the thoracic outlet region: a radio-anatomical study.

PubMed

Kaplan, Tevfik; Comert, Ayhan; Esmer, Ali Firat; Ataç, Gökçe Kaan; Acar, Halil Ibrahim; Ozkurt, Bulent; Tekdemir, Ibrahim; Han, Serdar

2018-04-16

The purposes of this study were to identify possible compression points along the transit route of the subclavian artery and to provide a detailed anatomical analysis of areas that are involved in the surgical management of the thoracic outlet syndrome (TOS). The results of the current study are based on measurements from cadavers, computed tomography (CT) scans and dry adult first ribs. The width and length of the interscalene space and the width of the costoclavicular passage were measured on 18 cervical dissections in 9 cadavers, on 50 dry first ribs and on CT angiography sections from 15 patients whose conditions were not related to TOS. The average width and length of the interscalene space in cadavers were 15.28 ± 1.94 mm and 15.98 ± 2.13 mm, respectively. The widths of the costoclavicular passage (12.42 ± 1.43 mm) were significantly narrower than the widths and lengths of the interscalene space in cadavers (P < 0.05). The average width and length of the interscalene space (groove for the subclavian artery) in 50 dry ribs were 15.53 ± 2.12 mm and 16.12 ± 1.95 mm, respectively. In CT images, the widths of the costoclavicular passage were also significantly narrower than those of the interscalene space (P < 0.05). The measurements from cadavers, dry first ribs and CT images were not significantly different (P > 0.05). Our results showed that the costoclavicular width was the narrowest space along the passage route of the subclavian artery. When considering the surgical decompression of the subclavian artery for TOS, this narrowest area should always be kept in mind. Since measurements from CT images and cadavers were significantly similar, CT measurements may be used to evaluate the thoracic outlet region in patients with TOS.

33 CFR 165.163 - Safety Zones; Port of New York/New Jersey Fleet Week.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Safety Zones; Port of New York... § 165.163 Safety Zones; Port of New York/New Jersey Fleet Week. (a) The following areas are established... parade vessels as it transits the Port of New York and New Jersey from the Verrazano Narrows Bridge to...

An observation of direct-gap electroluminescence in GaAs structures with Ge quantum wells

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

Aleshkin, V. Ya.; Dikareva, N. V.; Dubinov, A. A., E-mail: sanya@ipm.sci-nnov.ru

2015-02-15

A light-emitting diode structure based on GaAs with eight narrow Ge quantum wells is grown by laser sputtering. An electroluminescence line polarized predominately in the plane parallel to the constituent layers of the structure is revealed. The line corresponds to the direct optical transitions in momentum space in the Ge quantum wells.

Polarization and Out-of-Plane Observables in the γ^*NarrowΔ Transition

NASA Astrophysics Data System (ADS)

Kaloskamis, N. I.

1998-10-01

The H(e,e^' p)π^0, H(e,e^' p)π^0 and H(e,e^' π^+)n reactions have been studied at Bates during the past three years. Polarization observables have been measured for the first time in order to extract the Coulomb quadrupole amplitude of the γ^*NarrowΔ transition, by isolating it from that due to background processes. The detection equipment included a focal plane polarimeter (FPP) in the first experiment, and out-of-plane spectrometers (OOPS) in the second. Measurements were made at Q^2=0.127 (GeV/c)^2, invariant masses of W=1170, 1232, 1294 MeV and angles θ_pq^cm of up to 61^o. Data will be presented for the total cross section and the proton recoil polarization (P_n). Combined with sequencial measurements of the space asymmetry (A_LT), they provide clear discrimination among available electroproduction models and do not confirm a recent reportfootnote F. Kalleicher et al., Z. Phys. A359, 201 (1997) of a large Coulomb quadrupole amplitude. Preliminary data of the helicity asymmetry (A_LT^'), measured simultaneously using two OOPS modules, will also be presented.

Specific features of the spectra and relaxation kinetics of long-wavelength photoconductivity in narrow-gap HgCdTe epitaxial films and heterostructures with quantum wells

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

Rumyantsev, V. V., E-mail: rumyantsev@ipmras.ru; Ikonnikov, A. V.; Antonov, A. V.

2013-11-15

The spectra and relaxation kinetics of interband photoconductivity are investigated in narrow-gap Hg{sub 1-x}Cd{sub x}Te epitaxial films with x = 0.19-0.23 and in structures with HgCdTe-based quantum wells (QWs), having an interband-transition energy in the range of 30-90 meV, grown by molecular-beam epitaxy on GaAs (013) substrates. A long-wavelength sensitivity band caused by impurities or defects is found in the spectra of the structures with quantum wells in addition to the interband photoconductivity. It is shown that the lifetimes of nonequilibrium carriers in the structures with QWs is less than in bulk samples at the same optical-transition energy. From themore » measured carrier lifetimes, the ampere-watt responsivity and the equivalent noise power for a film with x = 0.19 at a wavelength of 19 {mu}m are estimated. When investigating the relaxation kinetics of the photoconductivity at 4.2 K in high excitation regime, it is revealed that radiative recombination is dominant over other mechanisms of nonequilibrium-carrier recombination.« less

Intensity dependence narrowing of electromagnetically induced absorption in a Doppler-broadened medium

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

Dimitrijevic, J.; Arsenovic, D.; Jelenkovic, B. M.

In this paper, we present a theoretical model for studying the interaction between linearly polarized laser light and near-degenerated Zeeman sublevels for a multiple V-type atomic system of {sup 2}S{sub 1/2}F{sub g}=2{yields}{sup 2}P{sub 3/2}F{sub e}=3 transition in {sup 87}Rb. We have calculated the laser absorption in a Hanle configuration, as well as the amplitudes and the widths of electromagnetically induced absorption (EIA) in the range of laser intensities from 0.01 to 40 mW/cm{sup 2}. Our results, showing nonvanishing EIA amplitude, a nonmonotonic increase of the EIA width for the increase of laser intensity, and pronounced shape differences of the Hanlemore » EIA curves at different laser intensities, are in good agreement with recent experimental results. We have found that the EIA behaves differently than the electromagnetically induced transparency (EIT) as a function of the laser intensity. Both the amplitude and width of the EIA have narrow maximums at 1 to 2 mW/cm{sup 2}. We have shown the strong influence of Doppler broadening of atomic transition on Hanle resonances and have suggested the explanation of it.« less

Effects of gap width on droplet transfer behavior in ultra-narrow gap laser welding of high strength aluminum alloys

NASA Astrophysics Data System (ADS)

Song, Chaoqun; Dong, Shiyun; Yan, Shixing; He, Jiawu; Xu, Binshi; He, Peng

2017-10-01

Ultra-narrow gap laser welding is a novel method for thick high strength aluminum alloy plate for its lower heat input, less deformation and higher efficiency. To obtain a perfect welding quality, it is vital to control the more complex droplet transfer behavior under the influence of ultra-narrow gap groove. This paper reports the effects of gap width of groove on droplet transfer behavior in ultra-narrow gap laser welding of 7A52 aluminum alloy plates by a high speed camera, using an ER 5356 filler wire. The results showed that the gap width had directly effects on droplet transfer mode and droplet shape. The droplet transfer modes were, in order, both-sidewall transfer, single-sidewall transfer, globular droplet transfer and bridging transfer, with different droplet shape and transition period, as the gap width increased from 2 mm to 3.5mm. The effect of gap width on lack of fusion was also studied to analyze the cause for lack of fusion at the bottom and on the sidewall of groove. Finally, with a 2.5 mm U-type parallel groove, a single-pass joint with no lack of fusion and other macro welding defects was successfully obtained in a single-sidewall transfer mode.

Disentangling flows in the solar transition region

NASA Astrophysics Data System (ADS)

Zacharias, P.; Hansteen, V. H.; Leenaarts, J.; Carlsson, M.; Gudiksen, B. V.

2018-06-01

Context. The measured average velocities in solar and stellar spectral lines formed at transition region temperatures have been difficult to interpret. The dominant redshifts observed in the lower transition region naturally leads to the question of how the upper layers of the solar (and stellar) atmosphere can be maintained. Likewise, no ready explanation has been made for the average blueshifts often found in upper transition region lines. However, realistic three-dimensional radiation magnetohydrodynamics (3D rMHD) models of the solar atmosphere are able to reproduce the observed dominant line shifts and may thus hold the key to resolve these issues. Aims: These new 3D rMHD simulations aim to shed light on how mass flows between the chromosphere and corona and on how the coronal mass is maintained. These simulations give new insights into the coupling of various atmospheric layers and the origin of Doppler shifts in the solar transition region and corona. Methods: The passive tracer particles, so-called corks, allow the tracking of parcels of plasma over time and thus the study of changes in plasma temperature and velocity not only locally, but also in a co-moving frame. By following the trajectories of the corks, we can investigate mass and energy flows and understand the composition of the observed velocities. Results: Our findings show that most of the transition region mass is cooling. The preponderance of transition region redshifts in the model can be explained by the higher percentage of downflowing mass in the lower and middle transition region. The average upflows in the upper transition region can be explained by a combination of both stronger upflows than downflows and a higher percentage of upflowing mass. The most common combination at lower and middle transition region temperatures are corks that are cooling and traveling downward. For these corks, a strong correlation between the pressure gradient along the magnetic field line and the velocity along the magnetic field line has been observed, indicating a formation mechanism that is related to downward propagating pressure disturbances. Corks at upper transition region temperatures are subject to a rather slow and highly variable but continuous heating process. Conclusions: Corks are shown to be an essential tool in 3D rMHD models in order to study mass and energy flows. We have shown that most transition region plasma is cooling after having been heated slowly to upper transition region temperatures several minutes before. Downward propagating pressure disturbances are identified as one of the main mechanisms responsible for the observed redshifts at transition region temperatures. The movie associated to Fig. 3 is available at http://www.aanda.org

The role of feedback mechanisms in historic channel changes of the lower Rio Grande in the Big Bend region

NASA Astrophysics Data System (ADS)

Dean, David J.; Schmidt, John C.

2011-03-01

Over the last century, large-scale water development of the upper Rio Grande in the U.S. and Mexico, and of the Rio Conchos in Mexico, has resulted in progressive channel narrowing of the lower Rio Grande in the Big Bend region. We used methods operating at multiple spatial and temporal scales to analyze the rate, magnitude, and processes responsible for channel narrowing. These methods included: hydrologic analysis of historic stream gage data, analysis of notes of measured discharges, historic oblique and aerial photograph analysis, and stratigraphic and dendrogeomorphic analysis of inset floodplain deposits. Our analyses indicate that frequent large floods between 1900 and the mid-1940s acted as a negative feedback mechanism and maintained a wide, sandy, multi-threaded river. Declines in mean and peak flow in the mid-1940s resulted in progressive channel narrowing. Channel narrowing has been temporarily interrupted by occasional large floods that widened the channel, however, channel narrowing has always resumed. After large floods in 1990 and 1991, the active channel width of the lower Rio Grande has narrowed by 36-52%. Narrowing has occurred by the vertical accretion of fine-grained deposits on top of sand and gravel bars, inset within natural levees. Channel narrowing by vertical accretion occurred simultaneously with a rapid invasion of non-native riparian vegetation ( Tamarix spp., Arundo donax) which created a positive feedback and exacerbated the processes of channel narrowing and vertical accretion. In two floodplain trenches, we measured 2.75 and 3.5 m of vertical accretion between 1993 and 2008. In some localities, nearly 90% of bare, active channel bars were converted to vegetated floodplain during the same period. Upward shifts of stage-discharge relations occurred resulting in over-bank flooding at lower discharges, and continued vertical accretion despite a progressive reduction in stream flow. Thus, although the magnitude of the average annual flood was reduced between 40 and 50%, over-bank flooding continued. These changes reflect a shift in the geomorphic nature of the Rio Grande from a wide, laterally unstable, multi-thread river, to a laterally stable, single-thread channel with cohesive, vertical banks, and few active in-channel bars.

Transitioning a Large Scale HIV/AIDS Prevention Program to Local Stakeholders: Findings from the Avahan Transition Evaluation

PubMed Central

Bennett, Sara; Singh, Suneeta; Rodriguez, Daniela; Ozawa, Sachiko; Singh, Kriti; Chhabra, Vibha; Dhingra, Neeraj

2015-01-01

Background Between 2009–2013 the Bill and Melinda Gates Foundation transitioned its HIV/AIDS prevention initiative in India from being a stand-alone program outside of government, to being fully government funded and implemented. We present an independent prospective evaluation of the transition. Methods The evaluation drew upon (1) a structured survey of transition readiness in a sample of 80 targeted HIV prevention programs prior to transition; (2) a structured survey assessing institutionalization of program features in a sample of 70 targeted intervention (TI) programs, one year post-transition; and (3) case studies of 15 TI programs. Findings Transition was conducted in 3 rounds. While the 2009 transition round was problematic, subsequent rounds were implemented more smoothly. In the 2011 and 2012 transition rounds, Avahan programs were well prepared for transition with the large majority of TI program staff trained for transition, high alignment with government clinical, financial and managerial norms, and strong government commitment to the program. One year post transition there were significant program changes, but these were largely perceived positively. Notable negative changes were: limited flexibility in program management, delays in funding, commodity stock outs, and community member perceptions of a narrowing in program focus. Service coverage outcomes were sustained at least six months post-transition. Interpretation The study suggests that significant investments in transition preparation contributed to a smooth transition and sustained service coverage. Notwithstanding, there were substantive program changes post-transition. Five key lessons for transition design and implementation are identified. PMID:26327591

Noise Assessment of the Greater Cleveland Regional Transit Authority Heavy Rail Transit Authority

DOT National Transportation Integrated Search

1978-10-01

The report describes the noise climate on and near the Greater Cleveland Regional Transit Authority (RTA), formerly the Cleveland Transit System (CTS), Airport Line. The RTA urban rail transit line has approximately 19 miles of two-way revenue track ...

Region IV Transit Workshop: Harnessing the Private Sector

DOT National Transportation Integrated Search

1988-09-01

This Report constitutes the Proceedings of the Region IV Transit Workshop: : Harnessing the Private Sector. Included in this document is a general report of : the activities of the Workshop. : The purpose ot the Region IV Transit Workshop: Harnessing...

AT THE SOURCE OF AN EXTRAGALACTIC JET

NASA Technical Reports Server (NTRS)

2002-01-01

Artist's concept of the formation region of M87's jet. An accretion disk (red-yellow) surrounds the black hole, and its magnetic field lines twist tightly to channel the outpouring subatomic particles into a narrow jet. The jet opens widely near the black hole, then is shaped into a narrower beam within a light-year of the black hole. Credit: NASA and Ann Feild (Space Telescope Science Institute)

Rotational spectroscopy with an optical centrifuge.

PubMed

Korobenko, Aleksey; Milner, Alexander A; Hepburn, John W; Milner, Valery

2014-03-07

We demonstrate a new spectroscopic method for studying electronic transitions in molecules with extremely broad range of angular momentum. We employ an optical centrifuge to create narrow rotational wave packets in the ground electronic state of (16)O2. Using the technique of resonance-enhanced multi-photon ionization, we record the spectrum of multiple ro-vibrational transitions between X(3)Σg(-) and C(3)Πg electronic manifolds of oxygen. Direct control of rotational excitation, extending to rotational quantum numbers as high as N ≳ 120, enables us to interpret the complex structure of rotational spectra of C(3)Πg beyond thermally accessible levels.

Improved mechanical properties of thermoelectric (Bi 0.2Sb 0.8) 2Te 3 by nanostructuring

DOE PAGES

Lavrentev, M. G.; Osvenskii, V. B.; Parkhomenko, Yu. N.; ...

2016-06-01

Temperature-dependent strength of Bi-Sb-Te under uniaxial compression is investigated. Bi-Sb-Te samples were produced by three methods: vertical zone-melting, hot extrusion, and spark plasma sintering (SPS). For zone-melted and extruded samples, the brittle-ductile transition occurs over a temperature range of 200-350 °C. In nanostructured samples produced via SPS, the transition is observed in a narrower temperature range of 170-200 °C. At room temperature, the strength of the nanostructured samples is higher than that of zone-melted and extruded samples, but above 300 °C, all samples decrease to roughly the same strength.

Improved mechanical properties of thermoelectric (Bi 0.2Sb 0.8) 2Te 3 by nanostructuring

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

Lavrentev, M. G.; Osvenskii, V. B.; Parkhomenko, Yu. N.

Temperature-dependent strength of Bi-Sb-Te under uniaxial compression is investigated. Bi-Sb-Te samples were produced by three methods: vertical zone-melting, hot extrusion, and spark plasma sintering (SPS). For zone-melted and extruded samples, the brittle-ductile transition occurs over a temperature range of 200-350 °C. In nanostructured samples produced via SPS, the transition is observed in a narrower temperature range of 170-200 °C. At room temperature, the strength of the nanostructured samples is higher than that of zone-melted and extruded samples, but above 300 °C, all samples decrease to roughly the same strength.

Population Switching and Charge Sensing in Quantum Dots: A Case for a Quantum Phase Transition

NASA Astrophysics Data System (ADS)

Goldstein, Moshe; Berkovits, Richard; Gefen, Yuval

2010-06-01

A broad and a narrow level of a quantum dot connected to two external leads may swap their respective occupancies as a function of an external gate voltage. By mapping this problem onto a multiflavored Coulomb gas we show that such population switching is not abrupt. However, trying to measure it by adding a third electrostatically coupled lead may render this switching an abrupt first order quantum phase transition. This is related to the interplay of the Mahan mechanism versus the Anderson orthogonality catastrophe, in similitude to the Fermi edge singularity. A concrete setup for experimental observation of this effect is also suggested.

Intracavity absorption with a continuous wave dye laser - Quantification for a narrowband absorber

NASA Technical Reports Server (NTRS)

Brobst, William D.; Allen, John E., Jr.

1987-01-01

An experimental investigation of the dependence of intracavity absorption on factors including transition strength, concentration, absorber path length, and pump power is presented for a CW dye laser with a narrow-band absorber (NO2). A Beer-Lambert type relationship is found over a small but useful range of these parameters. Quantitative measurement of intracavity absorption from the dye laser spectral profiles showed enhancements up to 12,000 (for pump powers near lasing threshold) when compared to extracavity measurements. The definition of an intracavity absorption coefficient allowed the determination of accurate transition strength ratios, demonstrating the reliability of the method.

Observation of the L-H confinement bifurcation triggered by a turbulence-driven shear flow in a tokamak plasma.

PubMed

Yan, Z; McKee, G R; Fonck, R; Gohil, P; Groebner, R J; Osborne, T H

2014-03-28

Comprehensive 2D turbulence and eddy flow velocity measurements on DIII-D demonstrate a rapidly increasing turbulence-driven shear flow that develops ∼100  μs prior to the low-confinement (L mode) to high-confinement (H mode) transition and appears to trigger it. These changes are localized to a narrow layer 1-2 cm inside the magnetic boundary. Increasing heating power increases the Reynolds stress, the energy transfer from turbulence to the poloidal flow, and the edge flow shearing rate that then exceeds the decorrelation rate, suppressing turbulence and triggering the transition.

Prospective CO 2 saline resource estimation methodology: Refinement of existing US-DOE-NETL methods based on data availability

DOE PAGES

Goodman, Angela; Sanguinito, Sean; Levine, Jonathan S.

2016-09-28

Carbon storage resource estimation in subsurface saline formations plays an important role in establishing the scale of carbon capture and storage activities for governmental policy and commercial project decision-making. Prospective CO 2 resource estimation of large regions or subregions, such as a basin, occurs at the initial screening stages of a project using only limited publicly available geophysical data, i.e. prior to project-specific site selection data generation. As the scale of investigation is narrowed and selected areas and formations are identified, prospective CO 2 resource estimation can be refined and uncertainty narrowed when site-specific geophysical data are available. Here, wemore » refine the United States Department of Energy – National Energy Technology Laboratory (US-DOE-NETL) methodology as the scale of investigation is narrowed from very large regional assessments down to selected areas and formations that may be developed for commercial storage. In addition, we present a new notation that explicitly identifies differences between data availability and data sources used for geologic parameters and efficiency factors as the scale of investigation is narrowed. This CO 2 resource estimation method is available for screening formations in a tool called CO 2-SCREEN.« less

Prospective CO 2 saline resource estimation methodology: Refinement of existing US-DOE-NETL methods based on data availability

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

Goodman, Angela; Sanguinito, Sean; Levine, Jonathan S.

Carbon storage resource estimation in subsurface saline formations plays an important role in establishing the scale of carbon capture and storage activities for governmental policy and commercial project decision-making. Prospective CO 2 resource estimation of large regions or subregions, such as a basin, occurs at the initial screening stages of a project using only limited publicly available geophysical data, i.e. prior to project-specific site selection data generation. As the scale of investigation is narrowed and selected areas and formations are identified, prospective CO 2 resource estimation can be refined and uncertainty narrowed when site-specific geophysical data are available. Here, wemore » refine the United States Department of Energy – National Energy Technology Laboratory (US-DOE-NETL) methodology as the scale of investigation is narrowed from very large regional assessments down to selected areas and formations that may be developed for commercial storage. In addition, we present a new notation that explicitly identifies differences between data availability and data sources used for geologic parameters and efficiency factors as the scale of investigation is narrowed. This CO 2 resource estimation method is available for screening formations in a tool called CO 2-SCREEN.« less

How A Black Hole Lights Up Its Surroundings

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-10-01

How do the supermassive black holes that live at the centers of galaxies influence their environments? New observations of a distant active galaxy offer clues about this interaction.Signs of CoevolutionPlot demonstrating the m-sigma relation, the empirical correlation between the stellar velocity dispersion of a galactic bulge and the mass of the supermassive black hole at its center. [Msigma]We know that the centers of active galaxies host supermassive black holes with masses of millions to billions of suns. One mystery surrounding these beasts is that they are observed to evolve simultaneously with their host galaxies for instance, an empirical relationship is seen between the growth of a black hole and the growth of its host galaxys bulge. This suggests that there must be a feedback mechanism through which the evolution of a black hole is linked to that of its host galaxy.One proposed source of this coupling is the powerful jets emitted from the poles of these supermassive black holes. These jets are thought to be produced as some of the material accreting onto the black hole is flung out, confined by surrounding gas and magnetic fields. Because the jets of hot gas and radiation extend outward through the host galaxy, they provide a means for the black hole to influence the gas and dust of its surroundings.In our current model of a radio-loud active galactic nuclei,a region of hot, ionized gas the narrow-line region lies beyond the sphere of influence of the supermassive black hole. [C.M. Urry and P. Padovani]Clues in the Narrow-Line RegionThe region of gas thought to sit just outside of the black holes sphere of influence (at a distance of perhaps a thousand to a few thousand light-years) is known as the narrow line region so named because we observe narrow emission lines from this gas. Given its hot, ionized state, this gas must somehow be being pummeled with energy. In the canonical picture, radiation from the black hole heats the gas directly in a process called photoionization. But could jets also be involved?In a recent study led by kos Bogdn, a team of scientists at the Harvard-Smithsonian Center for Astrophysics used X-ray observations of a galaxys nucleus to explore the possibility that its narrow-line region is heated and ionized not only by radiation, but also by the shocks produced as radio jets collide with their surrounding environment.Heating from JetsChandra X-ray data for Mrk 3, with radio contours overplotted. Both wavelengths show S-shaped morphology of the jets, with the X-ray emission enveloping the radio emission. A strong shock is present in the west and a weaker shock toward the east. [Bogdn et al. 2017]Bogdn and collaborators analyzed deep Chandra X-ray observations of the center of Mrk 3, an early-type galaxy located roughly 200 million light-years away. Chandras imaging and high-resolution spectroscopy of the galaxys narrow-line region allowed the team to build a detailed picture of the hot gas, demonstrating that it shows similar S-shaped morphology to the gas emitting at radio wavelengths, but its more broadly distributed.The authors demonstrate the presence of shocks in the X-ray gas both toward the west and toward the east of the nucleus. These shocks, combined with the broadening of the X-ray emission and other signs, strongly support the idea that collisions of the jets with the surrounding environment heat the narrow-line-region gas, contributing to its ionization. The authors argue that, given how common small-scale radio jets are in galaxies such as Mrk 3, its likely that collisional ionization plays an important role in how the black holes in these galaxies impart energy to their surrounding environments.Citationkos Bogdn et al 2017 ApJ 848 61. doi:10.3847/1538-4357/aa8c76

Self-Sustained Mode-3 Tear Controls Dynamics of Narrow Retreating Subduction Zones

NASA Astrophysics Data System (ADS)

Munch, J.; Gerya, T.; Ueda, K.

2017-12-01

The Caribbean oroclinal basin exhibits several narrow retreating slabs in an oceanic domain. The slabs show a curved shape associated to a bent topography (trench). We propose that the curvature of the topography depends on slab retreat mechanisms following mode-3 tearing at the edges of the slab (out of the plane fracture propagation). While first-order characteristics have been principally reproduced in self-sustained subduction initiation models (Gerya et al., 2015, Nature, 527, 221-225), the relevant observations have not been quantified and the exact mechanism is not understood. In this work, we study the long-term 3D evolution of narrowing oceanic subduction zones during retreat, and investigate the link between mode-3 tear and orocline formation. Numerical experiments are carried out with a thermo-mechanical 3D finite-difference code. To allow the observation of developing topography, the precise location of the internal surface and its evolution by material diffusion is tracked. Retreating subduction is facilitated via a strong age contrast between a young lithosphere window enclosed by shear zones and the surrounding lithosphere. By varying the length and thickness of the shear zones and location of the age transition, the influence of these parameters on the tearing process and the development of topography is assessed. Experiments trigger subduction initiation and slab retreat via fracture zone collapse and spontaneous paired mode-3 tear propagation within the oceanic plate interior. Narrow retreating subducting slabs form as a natural result of the spontaneous paired tearing process. A curved trench forms along with slab retreat. Topography evolution and tearing trajectory appear to be dependent on the initial shear zones and young window dimensions. We also note a strong narrowing of the slab during the retreat (several tens of kilometers over 800 km of retreat). Overall, results indicate that narrowing of retreating slabs is a self-consistent consequence of tear propagation dynamics. This plate tearing mechanism may control dynamics of other narrow retreating subduction zones worldwide.

Determination of 20Ne(p ,γ )21Na cross sections from Ep=500 -2000 keV

NASA Astrophysics Data System (ADS)

Lyons, S.; Görres, J.; deBoer, R. J.; Stech, E.; Chen, Y.; Gilardy, G.; Liu, Q.; Long, A. M.; Moran, M.; Robertson, D.; Seymour, C.; Vande Kolk, B.; Wiescher, M.; Best, A.

2018-06-01

Background: The reaction 20Ne(p ,γ )21Na influences the nucleosynthesis of Ne, Na, and Mg isotopes while contributing to hydrogen burning in several stellar sites, such as red giants, asymptotic giant branch (AGB) stars, massive stars, and oxygen-neon (ONe) novae. In the relevant temperature range for these environments (T = 0.05-0.5 GK), the main contributions to this reaction rate are from the direct capture process as well as the high-energy tail of a subthreshold resonance in the ground-state transition at Ex = 2425 keV in the 21Na compound nucleus. Purpose: The previous measurement of this reaction reports cross sections with large uncertainties for the ground-state transition. At higher energies, where the subthreshold resonance makes a smaller contribution to the total cross section, only upper limits are provided. This work aims to reduce the uncertainty in the cross section where direct capture dominates, as well as provide cross-section data in previously unmeasured regions. Method: The 20Ne(p ,γ )21Na reaction was measured over a wide proton energy range (Ep = 0.5-2.0 MeV) at θlab = 90∘. Transitions to the ground state and to the 332 and 2425 keV excited states were observed. The primary transitions to these three bound states were utilized in an R -matrix analysis to determine the contributions of the direct capture and the subthreshold resonance to the total cross section. Results: The cross sections of the present measurements have been found to be in good agreement with the previous data at low energy. Significantly improved cross-section measurements have been obtained over the Ep = 1300-1900 keV region. The narrow resonance at Ec.m. = 1113 keV (Ex = 3544.3 keV) has also been remeasured and its strength has been found to be in good agreement with previous measurements. Conclusions: An extrapolation of the S factor of 20Ne(p ,γ )21Na has been made to low energies using the R -matrix fit. The reaction rate from the subthreshold resonance was found to be the main contributor to the reaction rate at temperatures below about 0.1 GK. The present rate is lower in the temperature range of interest than those presented in current reaction rate libraries by up to 20%.

Nucleolar organizer regions in Sittasomus griseicapillus and Lepidocolaptes angustirostris (Aves, Dendrocolaptidae): Evidence of a chromosome inversion.

PubMed

de Oliveira Barbosa, Marcelo; da Silva, Rubens Rodrigues; de Sena Correia, Vanessa Carolina; Dos Santos, Luana Pereira; Garnero, Analía Del Valle; Gunski, Ricardo José

2013-03-01

Cytogenetic studies in birds are still scarce compared to other vertebrates. Woodcreepers (Dendrocolaptidae) are part of a highly specialized group within the Suboscines of the New World. They are forest birds exclusive to the Neotropical region and similar to woodpeckers, at a comparable evolutionary stage. This paper describes for the first time the karyotypes of the Olivaceous and the Narrow-billed Woodcreeper using conventional staining with Giemsa and silver nitrate staining of the nucleolar organizer regions (Ag-NORs). Metaphases were obtained by fibular bone marrow culture. The chromosome number of the Olivaceous Woodcreeper was 2n = 82 and of the Narrow-billed Woodcreeper, 2n = 82. Ag-NORs in the largest macrochromosome pair and evidence of a chromosome inversion are described herein for the first time for this group.

Self-gravity, Resonances, and Orbital Diffusion in Stellar Disks

NASA Astrophysics Data System (ADS)

Fouvry, Jean-Baptiste; Binney, James; Pichon, Christophe

2015-06-01

Fluctuations in a stellar system's gravitational field cause the orbits of stars to evolve. The resulting evolution of the system can be computed with the orbit-averaged Fokker-Planck equation once the diffusion tensor is known. We present the formalism that enables one to compute the diffusion tensor from a given source of noise in the gravitational field when the system's dynamical response to that noise is included. In the case of a cool stellar disk we are able to reduce the computation of the diffusion tensor to a one-dimensional integral. We implement this formula for a tapered Mestel disk that is exposed to shot noise and find that we are able to explain analytically the principal features of a numerical simulation of such a disk. In particular the formation of narrow ridges of enhanced density in action space is recovered. As the disk's value of Toomre's Q is reduced and the disk becomes more responsive, there is a transition from a regime of heating in the inner regions of the disk through the inner Lindblad resonance to one of radial migration of near-circular orbits via the corotation resonance in the intermediate regions of the disk. The formalism developed here provides the ideal framework in which to study the long-term evolution of all kinds of stellar disks.

Limb Spicules from the Ground and from Space

NASA Astrophysics Data System (ADS)

Pasachoff, Jay M.; Jacobson, William A.; Sterling, Alphonse C.

2009-11-01

We amassed statistics for quiet-sun chromosphere spicules at the limb using ground-based observations from the Swedish 1-m Solar Telescope on La Palma and simultaneously from NASA’s Transition Region and Coronal Explorer (TRACE) spacecraft. The observations were obtained in July 2006. With the 0.2 arcsecond resolution obtained after maximizing the ground-based resolution with the Multi-Object Multi-Frame Blind Deconvolution (MOMFBD) program, we obtained specific statistics for sizes and motions of over two dozen individual spicules, based on movies compiled at 50-second cadence for the series of five wavelengths observed in a very narrow band at Hα, on-band and at ± 0.035 nm and ± 0.070 nm (10 s at each wavelength) using the SOUP filter, and had simultaneous observations in the 160 nm EUV continuum from TRACE. The MOMFBD restoration also automatically aligned the images, facilitating the making of Dopplergrams at each off-band pair. We studied 40 Hα spicules, and 14 EUV spicules that overlapped Hα spicules; we found that their dynamical and morphological properties fit into the framework of several previous studies. From a preliminary comparison with spicule theories, our observations are consistent with a reconnection mechanism for spicule generation, and with UV spicules being a sheath region surrounding the Hα spicules.

The acoustical bright spot and mislocalization of tones by human listeners

PubMed Central

Macaulay, Eric J.; Hartmann, William M.; Rakerd, Brad

2010-01-01

Listeners attempted to localize 1500-Hz sine tones presented in free field from a loudspeaker array, spanning azimuths from 0° (straight ahead) to 90° (extreme right). During this task, the tone levels and phases were measured in the listeners’ ear canals. Because of the acoustical bright spot, measured interaural level differences (ILD) were non-monotonic functions of azimuth with a maximum near 55°. In a source-identification task, listeners’ localization decisions closely tracked the non-monotonic ILD, and thus became inaccurate at large azimuths. When listeners received training and feedback, their accuracy improved only slightly. In an azimuth-discrimination task, listeners decided whether a first sound was to the left or to the right of a second. The discrimination results also reflected the confusion caused by the non-monotonic ILD, and they could be predicted approximately by a listener’s identification results. When the sine tones were amplitude modulated or replaced by narrow bands of noise, interaural time difference (ITD) cues greatly reduced the confusion for most listeners, but not for all. Recognizing the important role of the bright spot requires a reevaluation of the transition between the low-frequency region for localization (mainly ITD) and the high-frequency region (mainly ILD). PMID:20329844

The use of transition region characteristics to improve the numerical simulation of heat transfer in bypass transitional flows

NASA Technical Reports Server (NTRS)

Simon, Frederick F.

1993-01-01

A method is presented for improving the numerical prediction of bypass transition heat transfer on a flat plate in a high-disturbance environment with zero or favorable pressure gradient. The method utilizes low Reynolds number k-epsilon turbulence models in combination with the characteristic parameters of the transition region. The parameters representing the characteristics of the transition region used are the intermittency, transition length and turbulent spot properties. An analysis is made of the transition length in terms of turbulent spot variables. The nondimensional spot formation rate, required for the prediction of the transition length, is shown by the analysis to be a function of the spot spreading angle, the dimensionless spot velocity ratio and the dimensionless spot area ratio. The intermittency form of the k-epsilon equations were derived from conditionally averaged equations which have been shown to be an improvement over global-time-averaged equations for the numerical calculation of the transition region. The numerical predictions are in general good agreement with the experimental data and indicate the potential use of the method in accelerating flows. Turbulence models of the k-epsilon type are known to underpredict the transition length. The present work demonstrates how incorporating transition region characteristics improves the ability of two-equation turbulence models to simulate bypass transition for flat plates with potential application to turbine vanes and blades.

Lunar Reconnaissance Orbiter Camera (LROC) instrument overview

USGS Publications Warehouse

Robinson, M.S.; Brylow, S.M.; Tschimmel, M.; Humm, D.; Lawrence, S.J.; Thomas, P.C.; Denevi, B.W.; Bowman-Cisneros, E.; Zerr, J.; Ravine, M.A.; Caplinger, M.A.; Ghaemi, F.T.; Schaffner, J.A.; Malin, M.C.; Mahanti, P.; Bartels, A.; Anderson, J.; Tran, T.N.; Eliason, E.M.; McEwen, A.S.; Turtle, E.; Jolliff, B.L.; Hiesinger, H.

2010-01-01

The Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) and Narrow Angle Cameras (NACs) are on the NASA Lunar Reconnaissance Orbiter (LRO). The WAC is a 7-color push-frame camera (100 and 400 m/pixel visible and UV, respectively), while the two NACs are monochrome narrow-angle linescan imagers (0.5 m/pixel). The primary mission of LRO is to obtain measurements of the Moon that will enable future lunar human exploration. The overarching goals of the LROC investigation include landing site identification and certification, mapping of permanently polar shadowed and sunlit regions, meter-scale mapping of polar regions, global multispectral imaging, a global morphology base map, characterization of regolith properties, and determination of current impact hazards.

11 W narrow linewidth laser source at 780nm for laser cooling and manipulation of Rubidium

NASA Astrophysics Data System (ADS)

Sané, S. S.; Bennetts, S.; Debs, J. E.; Kuhn, C. C. N.; McDonald, G. D.; Altin, P. A.; Close, J. D.; Robins, N. P.

2012-04-01

We present a narrow linewidth continuous laser source with over 11 Watts of output power at 780nm, based on single-pass frequency doubling of an amplified 1560nm fibre laser with 36% efficiency. This source offers a combination of high power, simplicity, mode quality and stability. Without any active stabilization, the linewidth is measured to be below 10kHz. The fibre seed is tunable over 60GHz, which allows access to the D2 transitions in 87Rb and 85Rb, providing a viable high-power source for laser cooling as well as for large-momentum-transfer beamsplitters in atom interferometry. Sources of this type will pave the way for a new generation of high flux, high duty-cycle degenerate quantum gas experiments.

Demonstration of a neonlike argon soft-x-ray laser with a picosecond-laser-irradiated gas puff target.

PubMed

Fiedorowicz, H; Bartnik, A; Dunn, J; Smith, R F; Hunter, J; Nilsen, J; Osterheld, A L; Shlyaptsev, V N

2001-09-15

We demonstrate a neonlike argon-ion x-ray laser, using a short-pulse laser-irradiated gas puff target. The gas puff target was formed by pulsed injection of gas from a high-pressure solenoid valve through a nozzle in the form of a narrow slit and irradiated with a combination of long, 600-ps and short, 6-ps high-power laser pulses with a total of 10 J of energy in a traveling-wave excitation scheme. Lasing was observed on the 3p (1)S(0)?3s (1)P(1) transition at 46.9 nm and the 3d (1)P(1)?3p (1)P(1) transition at 45.1 nm. A gain of 11 cm(-1) was measured on these transitions for targets up to 0.9 cm long.

2017 Total Solar Eclipse - ISS Transit - (NHQ201708210203)

NASA Image and Video Library

2017-08-21

2017 Total Solar Eclipse - ISS Transit - (NHQ201708210203) In this video captured at 1,500 frames per second with a high-speed camera, the International Space Station, with a crew of six onboard, is seen in silhouette as it transits the sun at roughly five miles per second during a partial solar eclipse, Monday, Aug. 21, 2017 near Banner, Wyoming. Onboard as part of Expedition 52 are: NASA astronauts Peggy Whitson, Jack Fischer, and Randy Bresnik; Russian cosmonauts Fyodor Yurchikhin and Sergey Ryazanskiy; and ESA (European Space Agency) astronaut Paolo Nespoli. A total solar eclipse swept across a narrow portion of the contiguous United States from Lincoln Beach, Oregon to Charleston, South Carolina. A partial solar eclipse was visible across the entire North American continent along with parts of South America, Africa, and Europe. Photo Credit: (NASA/Joel Kowsky)

Gradient structure-induced temperature responsiveness in styrene/methyl methacrylate gradient copolymers micelles.

PubMed

Zheng, Chao; Huang, Haiying; He, Tianbai

2014-02-01

In this work, micelles are formed by gradient copolymer of styrene and methyl methacrylate in acetone-water mixture and their temperature responsiveness is investigated in a narrow range near room temperature. Three different kinds of structural transitions could be induced by temperature: unimers to micelle transition, shrinkage/stretching of micelles, and morphological transition from spherical micelles to vesicles. In addition, a model analysis on the interface of gradient copolymer micelle is made to better understand these phenomena. It is found that both position and composition of the interface could alter in response to the change in temperature. According to the experiments and model analysis, it is proposed that temperature responsiveness might be an intrinsic and universal property of gradient copolymer micelles, which only originates from the gradient structure. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Detroit regional transit study : a study of factors that enable and inhibit effective regional transit.

DOT National Transportation Integrated Search

2014-03-01

An interdisciplinary team of six faculty members and six students at the University of Detroit Mercy (UDM) conducted a : comprehensive study of the factors enabling or inhibiting development of effective regional transit. Focusing on Metro Detroit an...

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

Li, Zhaoyi; Zhou, You; Qi, Hao

The electron-doping-induced phase transition of a prototypical perovskite SmNiO 3 induces a large and non-volatile optical refractive-index change and has great potential for active-photonic-device applications. Strong optical modulation from the visible to the mid-infrared is demonstrated using thin-film SmNiO 3. Finally, modulation of a narrow band of light is demonstrated in this paper using plasmonic metasurfaces integrated with SmNiO 3.

Endogenously generated gamma-band oscillations in early visual cortex: A neurofeedback study.

PubMed

Merkel, Nina; Wibral, Michael; Bland, Gareth; Singer, Wolf

2018-04-26

Human subjects were trained with neurofeedback (NFB) to enhance the power of narrow-band gamma oscillations in circumscribed regions of early visual cortex. To select the region and the oscillation frequency for NFB training, gamma oscillations were induced with locally presented drifting gratings. The source and frequency of these induced oscillations were determined using beamforming methods. During NFB training the power of narrow band gamma oscillations was continuously extracted from this source with online beamforming and converted into the pitch of a tone signal. We found that seven out of ten subjects were able to selectively increase the amplitude of gamma oscillations in the absence of visual stimulation. One subject however failed completely and two subjects succeeded to manipulate the feedback signal by contraction of muscles. In all subjects the attempts to enhance visual gamma oscillations were associated with an increase of beta oscillations over precentral/frontal regions. Only successful subjects exhibited an additional marked increase of theta oscillations over precentral/prefrontal and temporal regions whereas unsuccessful subjects showed an increase of alpha band oscillations over occipital regions. We argue that spatially confined networks in early visual cortex can be entrained to engage in narrow band gamma oscillations not only by visual stimuli but also by top down signals. We interpret the concomitant increase in beta oscillations as indication for an engagement of the fronto-parietal attention network and the increase of theta oscillations as a correlate of imagery. Our finding support the application of NFB in disease conditions associated with impaired gamma synchronization. © 2018 Wiley Periodicals, Inc.

A multi-wavelength investigation of Seyfert 1.8 and 1.9 galaxies

NASA Astrophysics Data System (ADS)

Trippe, Margaret L.

We focus on determining the underlying physical cause of a Seyfert galaxy's appearance as type a 1.8 or 1.9. Are these "intermediate" Seyfert types typical Seyfert 1 nuclei reddened by central dusty tori or by nuclear dust lanes/spirals in the narrow-line region? Or, are they similar to NGC 2992, objects that have intrinsically weak continua and weak broad emission lines? Our study compares measurements of the reddenings of the narrow and broad-line regions with each other and with the X-ray column derived from XMM Newton 0.5--10 keV spectra to determine the presence and location of dust in the line of sight for a sample of 35 Seyfert 1.8s and 1.9s. From this, we find that Seyfert 1.9s are an almost equal mix of low-flux objects with unreddened broad line regions, and objects with broad line regions reddened by an internal dust source, either the torus or dust structures on the same size scale as the narrow line region. The 1.9s that recieved this designation due to a low continuum flux state showed variable type classifications. All three of the Seyfert 1.8s in our study are probably in low continuum states. Many objects have been misclassified as Seyfert 1.8/1.9s in the past, probably due to improper [N II]/Halpha deconvolution leading to a false detection of weak broad Halpha. INDEX WORDS: Active galaxies, Seyfert galaxies, Optical spectroscopy, X-ray spectroscopy, Astronomical dust

Planning for transit-supportive development : a practitioner's guide. Section 3 : regional vision planning and transit-supportive development.

DOT National Transportation Integrated Search

2014-06-01

Planning for Transit-Supportive Development: A Practitioners Guide is a toolkit of practical and innovative measures to help : Metropolitan Planning Organizations (MPOs), regional planners, transit agencies, and local government elected o...

Focus on Teacher Salaries: Update for 1998-99.

ERIC Educational Resources Information Center

Gaines, Gale F.

For the third consecutive year, Southern Regional Education Board (SREB) states narrowed the gap between national average teacher salaries and the region's average. The regional average for 1998-99 was 88.2 percent of the national average. A year earlier, it was 87.3 percent of the national average. The average increase for SREB states was 4…

Structural and photoluminescence properties of stannate based displaced pyrochlore-type red phosphors: Ca(3-x)Sn₃Nb₂O₁₄:xEu³⁺.

PubMed

Sreena, T S; Prabhakar Rao, P; Francis, T Linda; Raj, Athira K V; Babu, Parvathi S

2015-05-14

New stannate based displaced pyrochlore-type red phosphors, Ca(3-x)Sn3Nb2O14:xEu(3+), were prepared via a conventional solid state method. The influence of partial occupancy of Sn in both A and B sites of the pyrochlore-type oxides on the photoluminescence properties was studied using powder X-ray diffraction, FT-Raman, transmission electron microscopy, scanning electron microscopy with energy dispersive spectrometry, UV-visible absorption spectroscopy, and photoluminescence excitation and emission spectra with lifetime measurements. The structural analysis establishes that these oxides belong to a cubic displaced pyrochlore type structure with a space group Fd3̄m. These phosphors exhibit strong absorptions at near UV and blue wavelength regions and emit intense multiband emissions due to Eu(3+ 5)D0-(7)F(0, 1, 2) transitions. The absence of characteristic MD transition splitting points out that local cation disorder exists in this type of displaced pyrochlores, reducing the D(3d) inversion symmetry, which is not evidenced by such disorder in the X-ray diffraction analysis. The unusual forbidden intense sharp (5)D0-(7)F0 transition indicates single site occupancy of Eu(3+) with a narrower range of bonding environment, preventing the cluster formation. This is supported by the stable (5)D0 lifetime with Eu(3+) concentration. The Judd-Ofelt intensity parameter assessment corroborates these results. The CIE color coordinates of these phosphors were found to be (0.60, 0.40), which are close to the NTSC standard values (0.67, 0.33) for a potential red phosphor.

Interface-induced superconductivity at ∼25 K at ambient pressure in undoped CaFe2As2 single crystals

PubMed Central

Zhao, Kui; Lv, Bing; Deng, Liangzi; Huyan, Shu-Yuan; Xue, Yu-Yi; Chu, Ching-Wu

2016-01-01

Superconductivity has been reversibly induced/suppressed in undoped CaFe2As2 (Ca122) single crystals through proper thermal treatments, with Tc at ∼25 K at ambient pressure and up to 30 K at 1.7 GPa. We found that Ca122 can be stabilized in two distinct tetragonal (T) phases at room temperature and ambient pressure: PI with a nonmagnetic collapsed tetragonal (cT) phase at low temperature and PII with an antiferromagnetic orthorhombic (O) phase at low temperature, depending on the low-temperature annealing condition. Neither phase at ambient pressure is superconducting down to 2 K. However, systematic annealing for different time periods at 350 °C on the as-synthesized crystals, which were obtained by quenching the crystal ingot from 850 °C, reveals the emergence of superconductivity over a narrow time window. Whereas the onset Tc is insensitive to the anneal time, the superconductive volume fraction evolves with the time in a dome-shaped fashion. Detailed X-ray diffraction profile analyses further reveal mesoscopically stacked layers of the PI and the PII phases. The deduced interface density correlates well with the superconducting volume measured. The transport anomalies of the T–cT transition, which is sensitive to lattice strain, and the T–O transition, which is associated with the spin-density-wave (SDW) transition, are gradually suppressed over the superconductive region, presumably due to the interface interactions between the nonmagnetic metallic cT phase and the antiferromagnetic O phase. The results provide the most direct evidence to date for interface-enhanced superconductivity in undoped Ca122, consistent with the recent theoretical prediction. PMID:27799564

Cathodoluminescence emission of REE (Dy, Pr and Eu) doped LaAlO3 phosphors

NASA Astrophysics Data System (ADS)

Boronat, C.; Rivera, T.; Garcia-Guinea, J.; Correcher, V.

2017-01-01

Luminescence emission from rare earth (REE) ions doped materials are being of interest since can be employed as scintillators, catalysts, battery and magnetic materials, etc. We herein report on the preliminary results obtained from the cathodoluminescence (CL) properties of undoped LaAlO3 (LAO) and LaAlO3: REE3+ (REE=Dy3+, Pr3+ and Eu3+) samples synthesized by a sol-gel process based on the Pechini's method with a spray-drying technique. The samples, previously characterized by means of Environmental Scanning Electron Microscopy and Energy Dispersive X-Ray Analysis Spectrometry, display CL spectra with well-defined peaks that could specifically be associated with the LAO structure (in the range of 300-450 nm) and point defects (from 450 to 800 nm) spectral regions. The observed wavebands are as follows: (i) 480 and 570 from the Dy-doped LAO correspond respectively to 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions, (ii) 490-638 from the Pr-doped LAO is linked to 3P0→3H4, 1D2→3H4 transitions and (iii) 590 and 620 where the dopant Eu3+ gives rise to 5D0→7F1 and 5D0→7F2 transitions and (iv) a UV-blue broad band is associated with NBHOC in undoped LAO. Such emissions are due to the presence of the 4f electrons of rare earth ions that are shielded by the outer 5s and 5p electrons, the intra-4f emission spectra of REE that induce sharp and narrow wavebands.

Spatially Directed Proteomics of the Human Lens Outer Cortex Reveals an Intermediate Filament Switch Associated With the Remodeling Zone

PubMed Central

Wenke, Jamie L.; McDonald, W. Hayes; Schey, Kevin L.

2016-01-01

Purpose To quantify protein changes in the morphologically distinct remodeling zone (RZ) and adjacent regions of the human lens outer cortex using spatially directed quantitative proteomics. Methods Lightly fixed human lens sections were deparaffinized and membranes labeled with fluorescent wheat germ agglutinin (WGA-TRITC). Morphology directed laser capture microdissection (LCM) was used to isolate tissue from four distinct regions of human lens outer cortex: differentiating zone (DF), RZ, transition zone (TZ), and inner cortex (IC). Liquid chromatography-tandem mass spectrometry (LC-MS/MS) of the plasma membrane fraction from three lenses (21-, 22-, and 27-year) revealed changes in major cytoskeletal proteins including vimentin, filensin, and phakinin. Peptides from proteins of interest were quantified using multiple reaction monitoring (MRM) mass spectrometry and isotopically-labeled internal peptide standards. Results Results revealed an intermediate filament switch from vimentin to beaded filament proteins filensin and phakinin that occurred at the RZ. Several other cytoskeletal proteins showed significant changes between regions, while most crystallins remained unchanged. Targeted proteomics provided accurate, absolute quantification of these proteins and confirmed vimentin, periplakin, and periaxin decrease from the DF to the IC, while filensin, phakinin, and brain acid soluble protein 1 (BASP1) increase significantly at the RZ. Conclusions Mass spectrometry-compatible fixation and morphology directed laser capture enabled proteomic analysis of narrow regions in the human lens outer cortex. Results reveal dramatic cytoskeletal protein changes associated with the RZ, suggesting that one role of these proteins is in membrane deformation and/or the establishment of ball and socket joints in the human RZ. PMID:27537260

Aggregate-cement paste transition zone properties affecting the salt-frost damage of high-performance concretes

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

Cwirzen, Andrzej; Penttala, Vesa

2005-04-01

The influence of the cement paste-aggregate interfacial transition zone (ITZ) on the frost durability of high-performance silica fume concrete (HPSFC) has been studied. Investigation was carried out on eight non-air-entrained concretes having water-to-binder (W/B) ratios of 0.3, 0.35 and 0.42 and different additions of condensed silica fume. Studies on the microstructure and composition of the cement paste have been made by means of environmental scanning electron microscope (ESEM)-BSE, ESEM-EDX and mercury intrusion porosimetry (MIP) analysis. The results showed that the transition zone initiates and accelerates damaging mechanisms by enhancing movement of the pore solution within the concrete during freezing andmore » thawing cycles. Cracks filled with ettringite were primarily formed in the ITZ. The test concretes having good frost-deicing salt durability featured a narrow transition zone and a decreased Ca/Si atomic ratio in the transition zone compared to the bulk cement paste. Moderate additions of silica fume seemed to densify the microstructure of the ITZ.« less

Vibronic transitions of trivalent Er and Ce in BaY2F8 single crystals

NASA Astrophysics Data System (ADS)

Baraldi, A.; Capelletti, R.; Mazzera, M.; Ponzoni, A.; Sani, E.; Tonelli, M.

2003-01-01

High resolution (0.02 cm(-1)) Fourier transform spectroscopy was applied in the 9-300 K and 100-24,000 cm(-1) ranges, respectively, to detect in Er3+ and Ce3+ doped Bay(2)F(8) single crystals (1) the narrow line spectra due to the intraconfigurational 4f-->4f transitions of the rare earths (RE) and (2) the possible vibronic tails accompanying the zero-phonon lines. The F-2(5/2) --> F-2(7/2) transition was monitored for the Ce3+-doping and the crystal field splitting of the initial and final manifold was determined. Weak vibronic spectra accompanying six among the nine investigated 4f-->4f transitions of Er3+ and the F-2(5/2) --> F-2(7/2) transition of Ce3+ were detected. The vibronic spectra amplitude was found to scale with the RE contents. On the basis of the IR- and Raman-active vibrational modes, either measured or quoted in the literature, most of the vibronic lines could be successfully assigned to the lattice modes. Violations of the selection rules were envisaged and discussed.

Echolocation by the harbour porpoise: life in coastal waters.

PubMed

Miller, Lee A; Wahlberg, Magnus

2013-01-01

The harbor porpoise is one of the smallest and most widely spread of all toothed whales. They are found abundantly in coastal waters all around the northern hemisphere. They are among the 11 species known to use high frequency sonar of relative narrow bandwidth. Their narrow biosonar beam helps isolate echoes from prey among those from unwanted items and noise. Obtaining echoes from small objects like net mesh, net floats, and small prey is facilitated by the very high peak frequency around 130 kHz with a wavelength of about 12 mm. We argue that such echolocation signals and narrow band auditory filters give the harbor porpoise a selective advantage in a coastal environment. Predation by killer whales and a minimum noise region in the ocean around 130 kHz may have provided selection pressures for using narrow bandwidth high frequency biosonar signals.

Echolocation by the harbour porpoise: life in coastal waters

PubMed Central

Miller, Lee A.; Wahlberg, Magnus

2013-01-01

The harbor porpoise is one of the smallest and most widely spread of all toothed whales. They are found abundantly in coastal waters all around the northern hemisphere. They are among the 11 species known to use high frequency sonar of relative narrow bandwidth. Their narrow biosonar beam helps isolate echoes from prey among those from unwanted items and noise. Obtaining echoes from small objects like net mesh, net floats, and small prey is facilitated by the very high peak frequency around 130 kHz with a wavelength of about 12 mm. We argue that such echolocation signals and narrow band auditory filters give the harbor porpoise a selective advantage in a coastal environment. Predation by killer whales and a minimum noise region in the ocean around 130 kHz may have provided selection pressures for using narrow bandwidth high frequency biosonar signals. PMID:23596420

NGC 3393: multi-component AGN feedback as seen by CHEERS

NASA Astrophysics Data System (ADS)

Maksym, W. Peter; Fabbiano, Giuseppina; Elvis, Martin; Karovska, Margarita; Raymond, John C.; Storchi-Bergmann, Thaisa; Paggi, Alessandro; Wang, Junfeng; Risaliti, Guido

2017-01-01

Due to its low density, moderate ionization, and weak kinematics, the narrow line region (NLR) of active galactic nuclei (AGN) provides poweful diagnostics for investigating AGN feedback. The CHandra Extended Emission line Region Survey (CHEERS) is the ultimate investigation into resolved feedback in the NLR. We present results from our CHEERS investigations of NGC 3393. By imaging extended X-ray line emission of NGC 3393 with Chandra and optical line emission with Hubble's narrow-band filters, we are able to map out the simultaneous impact of photoionization, jets and an AGN disk-wind. When resolved on scales of ~10s of parsecs, the NLR of NGC 3393 shows a complex multi-component medium. Diagnostic line mapping indicates a Low-ionization Emmision Line Region (LINER) cocoon surrounding the outflow-evacuated cavities (in optical) and surrounding the supports the presence of collisional plasma (in X-rays). These physically distinct constituent regions can only be resolved by the high-resolution imaging that Chandra and HST enable.

Synthesis of Caffeine/Maleic Acid Co-crystal by Ultrasound-assisted Slurry Co-crystallization.

PubMed

Apshingekar, Prafulla P; Aher, Suyog; Kelly, Adrian L; Brown, Elaine C; Paradkar, Anant

2017-01-01

A green approach has been used for co-crystallization of noncongruent co-crystal pair of caffeine/maleic acid using water. Ultrasound is known to affect crystallization; hence, the effect of high power ultrasound on the ternary phase diagram has been investigated in detail using a slurry co-crystallization approach. A systematic investigation was performed to understand how the accelerated conditions during ultrasound-assisted co-crystallization will affect different regions of the ternary phase diagram. Application of ultrasound showed considerable effect on the ternary phase diagram, principally on caffeine/maleic acid 2:1 (disappeared) and 1:1 co-crystal (narrowed) regions. Also, the stability regions for pure caffeine and maleic acid in water were narrowed in the presence of ultrasound, expanding the solution region. The observed effect of ultrasound on the phase diagram was correlated with solubility of caffeine and maleic acid and stability of co-crystal forms in water. Copyright © 2016. Published by Elsevier Inc.

Perfect narrow band absorber for sensing applications.

PubMed

Luo, Shiwen; Zhao, Jun; Zuo, Duluo; Wang, Xinbing

2016-05-02

We design and numerically investigate a perfect narrow band absorber based on a metal-metal-dielectric-metal structure which consists of periodic metallic nanoribbon arrays. The absorber presents an ultra narrow absorption band of 1.11 nm with a nearly perfect absorption of over 99.9% in the infrared region. For oblique incidence, the absorber shows an absorption more than 95% for a wide range of incident angles from 0 to 50°. Structure parameters to the influence of the performance are investigated. The structure shows high sensing performance with a high sensitivity of 1170 nm/RIU and a large figure of merit of 1054. The proposed structure has great potential as a biosensor.

The role of media and public opinion efforts in the transit field : the Detroit region case study.

DOT National Transportation Integrated Search

2014-03-01

This study, one of seven comprising the report Factors that Inhibit and Enable Effective Regional Transit in Southeastern : Michigan, explores the role of media and public opinion efforts in developing support for regional transit initiatives. The go...

A metal-insulator transition study of VO 2 thin films grown on sapphire substrates

DOE PAGES

Yu, Shifeng; Wang, Shuyu; Lu, Ming; ...

2017-12-15

In this paper, vanadium thin films were deposited on sapphire substrates by DC magnetron sputtering and then oxidized in a tube furnace filled with oxygen under different temperatures and oxygen flow rates. The significant influence of the oxygen flow rate and oxidation temperature on the electrical and structural properties of the vanadium oxide thin films were investigated systematically. It shows the pure vanadium dioxide (VO 2) state can only be obtained in a very narrow temperature and oxygen flow rate range. The resistivity change during the metal-insulator transition varies from 0.2 to 4 orders of magnitude depending on the oxidationmore » condition. Large thermal hysteresis during the metal-insulator phase transition was observed during the transition compared to the results in literature. Proper oxidation conditions can significantly reduce the thermal hysteresis. Finally, the fabricated VO 2 thin films showed the potential to be applied in the development of electrical sensors and other smart devices.« less

The E3Σ1+ (63S1)←A3Π0+(53P1) transition in CdAr revisited: The spectrum and new analysis of the E3Σ1+ Rydberg state interatomic potential.

PubMed

Urbańczyk, T; Krośnicki, M; Kędziorski, A; Koperski, J

2018-05-05

Revisited study of the E 3 Σ 1 + (6 3 S 1 )←A 3 Π 0+ (5 3 P 1 ) transition in CdAr using both theoretical and experimental approach is presented. Systematic detection of the E 3 Σ 1 + in ,υ'←A 3 Π 0+ ,υ″=6 transition frequencies with higher accuracy and spectrally narrower laser extended and improved analysis and simulation of the LIF excitation spectrum. More consistent characterization of the E 3 Σ 1 + in -Rydberg state inner well using inversed perturbation approach methodology was achieved. Free←bound transitions in the E 3 Σ 1 + in ←A 3 Π 0+ ,υ″=6 excitation were taken into account in the analysis and simulation of the recorded spectrum. The updated spectroscopic characterization of the A 3 Π 0+ state was also revisited. Copyright © 2018 Elsevier B.V. All rights reserved.

Theoretical studies on effective metal-to-ligand charge transfer characteristics of novel ruthenium dyes for dye sensitized solar cells.

PubMed

Wang, Huei-Tang; Taufany, Fadlilatul; Nachimuthu, Santhanamoorthi; Jiang, Jyh-Chiang

2014-05-01

The development of ruthenium dye-sensitizers with highly effective metal-to-ligand charge transfer (MLCT) characteristics and narrowed transition energy gaps are essential for the new generation of dye-sensitized solar cells. Here, we designed a novel anchoring ligand by inserting the cyanovinyl-branches inside the anchoring ligands of selected highly efficient dye-sensitizers and studied their intrinsic optical properties using theoretical methods. Our calculated results show that the designed ruthenium dyes provide good performances as sensitizers compared to the selected efficient dyes, because of their red-shift in the UV-visible absorption spectra with an increase in the absorption intensity, smaller energy gaps and thereby enhancing MLCT transitions. We found that, the designed anchoring ligand acts as an efficient "electron-acceptor" which boosts electron-transfer from a -NCS ligand to this ligand via a Ru-bridge, thus providing a way to lower the transition energy gap and enhance the MLCT transitions.

Pressure induced metallization with absence of structural transition in layered molybdenum diselenide

PubMed Central

Zhao, Zhao; Zhang, Haijun; Yuan, Hongtao; Wang, Shibing; Lin, Yu; Zeng, Qiaoshi; Xu, Gang; Liu, Zhenxian; Solanki, G. K.; Patel, K. D.; Cui, Yi; Hwang, Harold Y.; Mao, Wendy L.

2015-01-01

Layered transition-metal dichalcogenides have emerged as exciting material systems with atomically thin geometries and unique electronic properties. Pressure is a powerful tool for continuously tuning their crystal and electronic structures away from the pristine states. Here, we systematically investigated the pressurized behavior of MoSe2 up to ∼60 GPa using multiple experimental techniques and ab-initio calculations. MoSe2 evolves from an anisotropic two-dimensional layered network to a three-dimensional structure without a structural transition, which is a complete contrast to MoS2. The role of the chalcogenide anions in stabilizing different layered patterns is underscored by our layer sliding calculations. MoSe2 possesses highly tunable transport properties under pressure, determined by the gradual narrowing of its band-gap followed by metallization. The continuous tuning of its electronic structure and band-gap in the range of visible light to infrared suggest possible energy-variable optoelectronics applications in pressurized transition-metal dichalcogenides. PMID:26088416

The E3Σ1+ (63S1) ← A3Π0+(53P1) transition in CdAr revisited: The spectrum and new analysis of the E3Σ1+ Rydberg state interatomic potential

NASA Astrophysics Data System (ADS)

Urbańczyk, T.; Krośnicki, M.; Kędziorski, A.; Koperski, J.

2018-05-01

Revisited study of the E3Σ1+ (63S1) ← A3Π0+(53P1) transition in CdAr using both theoretical and experimental approach is presented. Systematic detection of the E3Σ1+in,υ' ← A3Π0+,υ″ = 6 transition frequencies with higher accuracy and spectrally narrower laser extended and improved analysis and simulation of the LIF excitation spectrum. More consistent characterization of the E3Σ1+in-Rydberg state inner well using inversed perturbation approach methodology was achieved. Free ← bound transitions in the E3Σ1+in ← A3Π0+,υ″ = 6 excitation were taken into account in the analysis and simulation of the recorded spectrum. The updated spectroscopic characterization of the A3Π0+ state was also revisited.

Pressure induced metallization with absence of structural transition in layered molybdenum diselenide

DOE PAGES

Zhao, Zhao; Zhang, Haijun; Yuan, Hongtao; ...

2015-06-19

Layered transition-metal dichalcogenides have emerged as exciting material systems with atomically thin geometries and unique electronic properties. Pressure is a powerful tool for continuously tuning their crystal and electronic structures away from the pristine states. Here, we systematically investigated the pressurized behavior of MoSe 2 up to ~60 GPa using multiple experimental techniques and ab-initio calculations. MoSe 2 evolves from an anisotropic two-dimensional layered network to a three-dimensional structure without a structural transition, which is a complete contrast to MoS 2. The role of the chalcogenide anions in stabilizing different layered patterns is underscored by our layer sliding calculations. MoSemore » 2 possesses highly tunable transport properties under pressure, determined by the gradual narrowing of its band-gap followed by metallization. The continuous tuning of its electronic structure and band-gap in the range of visible light to infrared suggest possible energy-variable optoelectronics applications in pressurized transition-metal dichalcogenides.« less

Structure, phonon properties, and order-disorder transition in the metal formate framework of [NH4][Mg(HCOO)3].

PubMed

Mączka, Mirosław; Pietraszko, Adam; Macalik, Bogusław; Hermanowicz, Krzysztof

2014-01-21

We report the synthesis, crystal structure, thermal, dielectric, IR, and Raman studies of [NH4][Mg(HCOO)3] formate. Single-crystal X-ray diffraction shows that it crystallizes in the hexagonal space group P6322, with orientationally disordered NH4(+) ions located in the cages of the network. Upon cooling, [NH4][Mg(HCOO)3] undergoes a phase transition at around 255 K to the ferroelectric P63 structure. Raman and IR spectra show a strong increase in intensity of the N-H stretching bands as well as narrowing of the bands related to the NH4(+) ions upon cooling. These changes indicate that the phase transition is due to orientational ordering of the NH4(+) ions. Analysis of the Raman data show, however, that the rotational and translational motions of NH4(+) do not freeze completely at the phase transition but exhibit further slowing down below 255 K, and the motional freezing becomes nearly complete below 140 K.

Precursor of superfluidity in a strongly interacting Fermi gas with negative effective range

NASA Astrophysics Data System (ADS)

Tajima, Hiroyuki

2018-04-01

We investigate theoretically the effects of pairing fluctuations in an ultracold Fermi gas near a Feshbach resonance with a negative effective range. By employing a many-body T -matrix theory with a coupled fermion-boson model, we show that the single-particle density of states exhibits the so-called pseudogap phenomenon, which is a precursor of superfluidity induced by strong pairing fluctuations. We clarify the region where strong pairing fluctuations play a crucial role in single-particle properties, from the broad-resonance region to the narrow-resonance limit at the divergent two-body scattering length. We also extrapolate the effects of pairing fluctuations to the positive-effective-range region from our results near the narrow Feshbach resonance. Results shown in this paper are relevant to the connection between ultracold Fermi gases and low-density neutron matter from the viewpoint of finite-effective-range corrections.

InGaP Heterojunction Barrier Solar Cells

NASA Technical Reports Server (NTRS)

Welser, Roger E. (Inventor)

2014-01-01

A new solar cell structure called a heterojunction barrier solar cell is described. As with previously reported quantum-well and quantum-dot solar cell structures, a layer of narrow band-gap material, such as GaAs or indium-rich InGaP, is inserted into the depletion region of a wide band-gap PN junction. Rather than being thin, however, the layer of narrow band-gap material is about 400-430 nm wide and forms a single, ultrawide well in the depletion region. Thin (e.g., 20-50 nm), wide band-gap InGaP barrier layers in the depletion region reduce the diode dark current. Engineering the electric field and barrier profile of the absorber layer, barrier layer, and p-type layer of the PN junction maximizes photogenerated carrier escape. This new twist on nanostructured solar cell design allows the separate optimization of current and voltage to maximize conversion efficiency.

Performance characteristics according to the radial position of gas distributor holes in a low-power cylindrical Hall thruster

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

Gao, Yuanyuan; Liu, Hui; Hu, Peng

The effect of radial position of gas holes in the distributor on the performance of cylindrical Hall thruster was investigated. A series of gas distributors with different radial positions (R{sub g}) of holes were designed in the experiment. The results show that the larger R{sub g} leads to the higher ion current and electron current; meanwhile, the beam angle in plume is narrowed. Nevertheless, the peak energy in ion energy distribution function increases, together with the narrowing of ion energy distribution function. As a result, the overall performance is enhanced. It is suggested that the growing of R{sub g} couldmore » lead to the movement of the main ionization region towards anode, which could promote ion velocity and the clearer separation of acceleration region from ionization region. This work can provide some optimal design ideas to improve the performance of the thruster.« less

Low lower crustal velocity across Ethiopia: Is the Main Ethiopian Rift a narrow rift in a hot craton?

NASA Astrophysics Data System (ADS)

Keranen, Katie M.; Klemperer, Simon L.; Julia, Jordi; Lawrence, Jesse F.; Nyblade, Andy A.

2009-05-01

The Main Ethiopian Rift (MER) is a classic narrow rift that developed in hot, weak lithosphere, not in the initially cold, thick, and strong lithosphere that would be predicted by common models of rift mode formation. Our new 1-D seismic velocity profiles from Rayleigh wave/receiver function joint inversion across the MER and the Ethiopian Plateau indicate that hot lower crust and upper mantle are present throughout the broad region affected by Oligocene flood basalt volcanism, including both the present rift and the adjacent Ethiopian Plateau hundreds of kilometers from the rift valley. The region of hot lithosphere closely corresponds to the region of flood basalt volcanism, and we interpret that the volcanism and thermal perturbation were jointly caused by impingement of the Afar plume head. Across the affected region, Vs is 3.6-3.8 km/s in the lowermost crust and ≤4.3 km/s in the uppermost mantle, both ˜0.3 km/s lower than in the eastern and western branches of the East African Rift System to the south. We interpret the low Vs in the lower crust and upper mantle as indicative of hot lithosphere with partial melt. Our results lead to a hybrid rift mode, in which the brittle upper crust has developed as a narrow rift along the Neoproterozoic suture between East and West Gondwana, while at depth lithospheric deformation is distributed over the broad region (˜400 km wide) thermally perturbed by the broad thermal upwelling associated with the Afar plume head. Development of both the East African Rift System to the south (in cold, strong lithosphere) and the MER to the north (in hot, weak lithosphere) as narrow rifts, despite their vastly different initial thermal states and depth-integrated lithospheric strength, indicates that common models of rift mode formation that focus only on temperature, thickness, and vertical strength profiles do not apply to these classic continental rifts. Instead, inherited structure and associated lithospheric weaknesses are the primary control on the mode of extension.

Low lower crustal velocity across Ethiopia: Is the Main Ethiopian Rift a narrow rift in a hot craton?

USGS Publications Warehouse

Keranen, K.M.; Klemperer, S.L.; Julia, J.; Lawrence, J. F.; Nyblade, A.A.

2009-01-01

[1] The Main Ethiopian Rift (MER) is a classic narrow rift that developed in hot, weak lithosphere, not in the initially cold, thick, and strong lithosphere that would be predicted by common models of rift mode formation. Our new 1-D seismic velocity profiles from Rayleigh wave/receiver function joint inversion across the MER and the Ethiopian Plateau indicate that hot lower crust and upper mantle are present throughout the broad region affected by Oligocene flood basalt volcanism, including both the present rift and the adjacent Ethiopian Plateau hundreds of kilometers from the rift valley. The region of hot lithosphere closely corresponds to the region of flood basalt volcanism, and we interpret that the volcanism and thermal perturbation were jointly caused by impingement of the Afar plume head. Across the affected region, Vs is 3.6-3.8 km/s in the lowermost crust and ???4.3 km/s in the uppermost mantle, both ??0.3 km/s lower than in the eastern and western branches of the East African Rift System to the south. We interpret the low Vs in the lower crust and upper mantle as indicative of hot lithosphere with partial melt. Our results lead to a hybrid rift mode, in which the brittle upper crust has developed as a narrow rift along the Neoproterozoic suture between East and West Gondwana, while at depth lithospheric deformation is distributed over the broad region (??400 km wide) thermally perturbed by the broad thermal upwelling associated with the Afar plume head. Development of both the East African Rift System to the south (in cold, strong lithosphere) and the MER to the north (in hot, weak lithosphere) as narrow rifts, despite their vastly different initial thermal states and depth-integrated lithospheric strength, indicates that common models of rift mode formation that focus only on temperature, thickness, and vertical strength profiles do not apply to these classic continental rifts. Instead, inherited structure and associated lithospheric weaknesses are the primary control on the mode of extension. ?? 2009 by the American Geophysical Union.

Correspondence between solar fine-scale structures in the corona, transition region, and lower atmosphere from collaborative observations

NASA Technical Reports Server (NTRS)

Moses, J. Daniel; Cook, J. W.; Bartoe, J.-D. F.; Brueckner, G. E.; Dere, K. P.; Webb, D. F.; Davis, John M.; Recely, F.; Martin, S. F.; Zirin, H.

1989-01-01

The Soft X-Ray Imaging Payload and the High Resolution Telescope and Spectrograph (HRTS) instrument were launched from White Sands on 11 December 1987 in coordinated sounding rocket flights to investigate the correspondence of coronal and transition region structures, especially the relationship between X-ray bright points (XBPs) and transition region small spatial scale energetic events. The coaligned data from X-ray images are presented along with maps of sites of transition region energetic events observed in C IV (100,000 K), HRTS 1600 A spectroheliograms of the T sub min region and ground based magnetogram and He I 10830 A images.

Heating the sun's lower transition region with fine-scale electric currents

NASA Technical Reports Server (NTRS)

Rabin, D.; Moore, R.

1984-01-01

Analytical and observational data are presented to show that the lower transition zone, a 100 km thick region at 10,000-200,000 K between the solar chromosphere and corona, is heated by local electric currents. The study was spurred by correlations between the enhanced atmospheric heating and magnetospheric flux in the chromospheric network and active regions. Field aligned current heated flux loops are asserted to mainly reside in and make up most of the transition region. It is shown that thermal conduction from the sides of hot gas columns generated by the current dissipation is the source of the observed temperature distribution in the transition regions.

Anatomy of the pubovisceral muscle origin: Macroscopic and microscopic findings within the injury zone.

PubMed

Kim, Jinyong; Betschart, Cornelia; Ramanah, Rajeev; Ashton-Miller, James A; DeLancey, John O L

2015-11-01

The levator ani muscle (LA) injury associated with vaginal birth occurs in a characteristic site of injury on the inner surface of the pubic bone to the pubovisceral portion of the levator ani muscle's origin. This study investigated the gross and microscopic anatomy of the pubic origin of the LA in this region. Pubic origin of the levator ani muscle was examined in situ then harvested from nine female cadavers (35-98 years). A combination of targeted feature sampling and sequential sampling was used where each specimen was cut sequentially in approximately 5 mm thick slices apart in the area of known LA injury. Histological sections were stained with Masson's trichrome. The pubovisceral origin is transparent and thin as it attaches tangentially to the pubic periosteum, with its morphology changing from medial to lateral regions. Medially, fibers of the thick muscle belly coalesce toward multiple narrow points of bony attachment for individual fascicles. In the central portion there is an aponeurosis and the distance between muscle and periosteum is wider (∼3 mm) than in the medial region. Laterally, the LA fibers attach to the levator arch where the transition from pubovisceral muscle to the iliococcygeal muscle occurs. The morphology of the levator ani origin varies from the medial to lateral margin. The medial origin is a rather direct attachment of the muscle, while lateral origin is made through the levator arch. © 2014 Wiley Periodicals, Inc.

Thick-skinned tectonics closing the Rifian Corridor

NASA Astrophysics Data System (ADS)

Capella, Walter; Matenco, Liviu; Dmitrieva, Evelina; Roest, Wilmer M. J.; Hessels, Suzanne; Hssain, Mohamed; Chakor-Alami, Abdelwahid; Sierro, Francisco J.; Krijgsman, Wout

2017-07-01

Tectonic processes in the Gibraltar region are associated with Africa-Iberia convergence and the formation of the Betic-Rif orogenic system. The Late Miocene shortening recorded in the Rif orogen resulted in gradual shallowing and eventual closure of the Rifian Corridor, a narrow marine gateway connecting the Atlantic Ocean with the Mediterranean Sea. This closure is associated with paleoenvironmental changes that ultimately led to the Mediterranean Messinian Salinity Crisis. Here we present a structural analysis based on a combination of field kinematic data and interpretation of reflection seismic lines acquired for petroleum exploration to understand the deformational phases associated with the closure of the Rifian Corridor. We show the succession of three Late Miocene to present day events, an initial thin-skinned nappe thrusting, followed by regional subsidence and continued by thick-skinned contraction. The transition from in sequence thin-skinned tectonics during subduction to thick-skinned contraction during continental collision resulted in significant acceleration of tectonic uplift and associated exhumation. This is related to a change in the regional deformation linked to plate convergence, but possibly also coupled with deep lithospheric or dynamic topography processes. Such a mechanism is also common for other Mediterranean orogens during late stages of slab retreat, where accelerated tectonics resulted in rapid sedimentation and associated basins evolution. We conclude that the thick-skinned contraction in the Rif orogeny initiated in the late Tortonian, has created a cumulative uplift in the order of 1 km, and provided high enough uplift rates to close the Rifian Corridor.

Procedures for offline grid nesting in regional ocean models

NASA Astrophysics Data System (ADS)

Mason, Evan; Molemaker, Jeroen; Shchepetkin, Alexander F.; Colas, Francois; McWilliams, James C.; Sangrà, Pablo

One-way offline nesting of a primitive-equation regional ocean numerical model (ROMS) is investigated, with special attention to the boundary forcing file creation process. The model has a modified open boundary condition which minimises false wave reflections, and is optimised to utilise high-frequency boundary updates. The model configuration features a previously computed solution which supplies boundary forcing data to an interior domain with an increased grid resolution. At the open boundaries of the interior grid (the child) the topography is matched to that of the outer grid (the parent), over a narrow transition region. A correction is applied to the normal baroclinic and barotropic velocities at the open boundaries of the child to ensure volume conservation. It is shown that these steps, together with a carefully constructed interpolation of the parent data, lead to a high-quality child solution, with minimal artifacts such as persistent rim currents and wave reflections at the boundaries. Sensitivity experiments provide information about the robustness of the model open boundary condition to perturbations in the surface wind stress forcing field, to the perturbation of the volume conservation enforcement in the boundary forcing, and to perturbation of the vertical density structure in the boundary forcing. This knowledge is important when extending the nesting technique to include external data from alien sources, such as ocean models with physics and/or numerics different from ROMS, or from observed climatologies of temperature, salinity and sea level.

Dynamic properties of the haptenic site of lipid haptens in phosphatidylcholine membranes. Their relation to the phase transition of the host lattice.

PubMed Central

Takeshita, K.; Utsumi, H.; Hamada, A.

1987-01-01

The relation between the dynamic properties of the haptenic site of lipid haptens and the phase transition of the host lattice was investigated using head group spin-labeled phosphatidylethanolamines, that is, spin-label lipid haptens (Brûlet, P., and H. M. McConnell, 1976, Proc. Natl. Acad. Sci. USA., 73:2977-2981; Brûlet, P., and H. M. McConnell, 1977, Biochemistry, 16:1209-1217). The electron spin resonance (ESR) spectra of the lipid haptens in liposomal membranes showed three narrow resonance lines, whose widths and hyperfine splitting values suggested that the haptenic site, i.e., the spin-label moiety, should be exposed in the water phase. The line width of each peak depended on the host lipid species and on the incubation temperature. A temperature study using dipalmitoylphosphatidylcholine (DPPC) liposomes showed that the dynamic properties of the haptenic site were related to the main phase transition and the subphase transition of the host lattice but not to the prephase transition. The angular amplitudes of the tumbling motion of the haptenic site were estimated using oriented multibilayer systems. The angular amplitude of dipalmitoyl-phosphatidyl-N-[[N-(1-oxyl-2,2,6, 6-tetramethyl-4-piperidinyl)-carbamoyl]-methyl]-ethanolamine in DPPC membranes was 63 degrees at 2 degrees C, and it increased slightly with an increase in temperature regardless of the phase transition of the host lattice. The value for egg phosphatidylcholine (PC) at 25 degrees C was the same as for DPPC above its main phase transition temperature. Rotational correlation time analysis showed that the axial rotation of the haptenic site was preferable to the tumbling motion of the rotational axis, and the predominance depended on the phase transition, Lc----L beta' and P beta'----L alpha. Elongation of the spacer arm between the haptenic site and phosphate increased the angular amplitude of the tumbling motion but reduced the effect of the host lattice. Spin-label lipid haptens with unsaturated fatty acyl chains were distributed heterogeneously in DPPC membranes, whereas those with the same fatty acyl chain as the host lattice were distributed randomly. The ESR spectrum of a lipid hapten under its prephase transition temperature showed two components, broad and narrow. This suggests that at least two different domains, a hapten-rich domain and a hapten-poor one, may coexist in membranes. ESR measurements at various temperatures suggested that the haptenic site fraction in the hapten-rich domain decreased in part during the phase transition from L beta' to P beta', and disappeared completely in the La phase. The spatial mobility and lateral diffusion of lipid haptens will be discussed in greater detail. PMID:2822160

A 1.1-1.9 GHz SETI Survey of the Kepler Field. I. A Search for Narrow-band Emission from Select Targets

NASA Astrophysics Data System (ADS)

Siemion, Andrew P. V.; Demorest, Paul; Korpela, Eric; Maddalena, Ron J.; Werthimer, Dan; Cobb, Jeff; Howard, Andrew W.; Langston, Glen; Lebofsky, Matt; Marcy, Geoffrey W.; Tarter, Jill

2013-04-01

We present a targeted search for narrow-band (<5 Hz) drifting sinusoidal radio emission from 86 stars in the Kepler field hosting confirmed or candidate exoplanets. Radio emission less than 5 Hz in spectral extent is currently known to only arise from artificial sources. The stars searched were chosen based on the properties of their putative exoplanets, including stars hosting candidates with 380 K > T eq > 230 K, stars with five or more detected candidates or stars with a super-Earth (R p < 3 R ⊕) in a >50 day orbit. Baseband voltage data across the entire band between 1.1 and 1.9 GHz were recorded at the Robert C. Byrd Green Bank Telescope between 2011 February and April and subsequently searched offline. No signals of extraterrestrial origin were found. We estimate that fewer than ~1% of transiting exoplanet systems host technological civilizations that are radio loud in narrow-band emission between 1 and 2 GHz at an equivalent isotropically radiated power (EIRP) of ~1.5 × 1021 erg s-1, approximately eight times the peak EIRP of the Arecibo Planetary Radar, and we limit the number of 1-2 GHz narrow-band-radio-loud Kardashev type II civilizations in the Milky Way to be {<}10^{-6}\\ M^{-1}_\\odot. Here we describe our observations, data reduction procedures and results.

Water Dynamics and Dewetting Transitions in the Small Mechanosensitive Channel MscS

PubMed Central

Anishkin, Andriy; Sukharev, Sergei

2004-01-01

The dynamics of confined water in capillaries and nanotubes suggests that gating of ion channels may involve not only changes of the pore geometry, but also transitions between water-filled and empty states in certain locations. The recently solved heptameric structure of the small mechanosensitive channel of Escherichia coli, MscS, has revealed a relatively wide (7–15 Å) yet highly hydrophobic transmembrane pore. Continuum estimations based on the properties of pore surface suggest low conductance and a thermodynamic possibility of dewetting. To test the predictions we performed molecular dynamics simulations of MscS filled with flexible TIP3P water. Irrespective to the initial conditions, several independent 6-ns simulations converged to the same stable state with the pore water-filled in the wider part, but predominantly empty in the narrow hydrophobic part, displaying intermittent vapor-liquid transitions. The polar gain-of-function substitution L109S in the constriction resulted in a stable hydration of the entire pore. Steered passages of Cl− ions through the narrow part of the pore consistently produced partial ion dehydration and required a force of 200–400 pN to overcome an estimated barrier of 10–20 kcal/mole, implying negligibly low conductance. We conclude that the crystal structure of MscS does not represent an open state. We infer that MscS gate, which is similar to that of the nicotinic ACh receptor, involves a vapor-lock mechanism where limited changes of geometry or surface polarity can locally switch the regime between water-filled (conducting) and empty (nonconducting) states. PMID:15111405

Color Tuning in Garnet Oxides: The Role of Tetrahedral Coordination Geometry for 3 d Metal Ions and Ligand-Metal Charge Transfer (Band-Gap Manipulation).

PubMed

Bhim, Anupam; Laha, Sourav; Gopalakrishnan, Jagannatha; Natarajan, Srinivasan

2017-10-18

We explored garnet-structured oxide materials containing 3d transition-metal ions (e.g., Co 2+ , Ni 2+ , Cu 2+ , and Fe 3+ ) for the development of new inorganic colored materials. For this purpose, we synthesized new garnets, Ca 3 Sb 2 Ga 2 ZnO 12 (I) and Ca 3 Sb 2 Fe 2 ZnO 12 (II), that were isostructural with Ca 3 Te 2 Zn 3 O 12 . Substitution of Co 2+ , Ni 2+ , and Cu 2+ at the tetrahedral Zn 2+ sites in I and II gave rise to brilliantly colored materials (different shades of blue, green, turquoise, and red). The materials were characterized by optical absorption spectroscopy and CIE chromaticity diagrams. The Fe 3+ -containing oxides showed band-gap narrowing (owing to strong sp-d exchange interactions between Zn 2+ and the transition-metal ion), and this tuned the color of these materials uniquely. We also characterized the color and optical absorption properties of Ca 3 Te 2 Zn 3-x Co x O 12 (0

Mapping Antarctic Crustal Thickness using Gravity Inversion and Comparison with Seismic Estimates

NASA Astrophysics Data System (ADS)

Kusznir, Nick; Ferraccioli, Fausto; Jordan, Tom

2017-04-01

Using gravity anomaly inversion, we produce comprehensive regional maps of crustal thickness and oceanic lithosphere distribution for Antarctica and the Southern Ocean. Crustal thicknesses derived from gravity inversion are consistent with seismic estimates. We determine Moho depth, crustal basement thickness, continental lithosphere thinning (1-1/β) and ocean-continent transition location using a 3D spectral domain gravity inversion method, which incorporates a lithosphere thermal gravity anomaly correction (Chappell & Kusznir 2008). The gravity anomaly contribution from ice thickness is included in the gravity inversion, as is the contribution from sediments which assumes a compaction controlled sediment density increase with depth. Data used in the gravity inversion are elevation and bathymetry, free-air gravity anomaly, the Bedmap 2 ice thickness and bedrock topography compilation south of 60 degrees south and relatively sparse constraints on sediment thickness. Ocean isochrons are used to define the cooling age of oceanic lithosphere. Crustal thicknesses from gravity inversion are compared with independent seismic estimates, which are still relatively sparse over Antarctica. Our gravity inversion study predicts thick crust (> 45 km) under interior East Antarctica, which is penetrated by narrow continental rifts featuring relatively thinner crust. The largest crustal thicknesses predicted from gravity inversion lie in the region of the Gamburtsev Subglacial Mountains, and are consistent with seismic estimates. The East Antarctic Rift System (EARS), a major Permian to Cretaceous age rift system, is imaged by our inversion and appears to extend from the continental margin at the Lambert Rift to the South Pole region, a distance of 2500 km. Offshore an extensive region of either thick oceanic crust or highly thinned continental crust lies adjacent to Oates Land and north Victoria Land, and also off West Antarctica around the Amundsen Ridges. Thin crust is predicted under the Ross Sea and beneath the West Antarctic Ice Sheet and delineates the regional extent of the broad West Antarctic Rift System (WARS). Substantial regional uplift is required under Marie Byrd Land to reconcile gravity and seismic estimates. A mantle dynamic uplift origin of the uplift is preferred to a thermal anomaly from a very young rift. The new maps produced by this study support the hypothesis that one branch of the WARS links through to the De Gerlache sea-mounts and Peter I Island in the Bellingshausen Sea region, while another branch may link to the George V Sound Rift in the Antarctic Peninsula region. Crustal thickness and lithosphere thinning derived from gravity inversion also allows the determination of circum-Antarctic ocean-continent transition structure and the mapping of continent-ocean boundary location. Superposition of illuminated satellite gravity data onto crustal thickness maps from gravity inversion provides improved determination of Southern Ocean rift orientation, pre-breakup rifted margin conjugacy and continental breakup trajectory. The continental lithosphere thinning distribution, used to define the initial thermal model temperature perturbation, is derived from the gravity inversion and uses no a priori isochron information; as a consequence the gravity inversion method provides a prediction of ocean-continent transition location, which is independent of ocean isochron information.

Hell and High Water: Diminished Septic System Performance in Coastal Regions Due to Climate Change

PubMed Central

Cooper, Jennifer A.; Loomis, George W.; Amador, Jose A.

2016-01-01

Climate change may affect the ability of soil-based onsite wastewater treatment systems (OWTS) to treat wastewater in coastal regions of the Northeastern United States. Higher temperatures and water tables can affect treatment by reducing the volume of unsaturated soil and oxygen available for treatment, which may result in greater transport of pathogens, nutrients, and biochemical oxygen demand (BOD5) to groundwater, jeopardizing public and aquatic ecosystem health. The soil treatment area (STA) of an OWTS removes contaminants as wastewater percolates through the soil. Conventional STAs receive wastewater from the septic tank, with infiltration occurring deeper in the soil profile. In contrast, shallow narrow STAs receive pre-treated wastewater that infiltrates higher in the soil profile, which may make them more resilient to climate change. We used intact soil mesocosms to quantify the water quality functions of a conventional and two types of shallow narrow STAs under present climate (PC; 20°C) and climate change (CC; 25°C, 30 cm elevation in water table). Significantly greater removal of BOD5 was observed under CC for all STA types. Phosphorus removal decreased significantly from 75% (PC) to 66% (CC) in the conventional STA, and from 100% to 71–72% in shallow narrow STAs. No fecal coliform bacteria (FCB) were released under PC, whereas up to 17 and 20 CFU 100 mL-1 were released in conventional and shallow narrow STAs, respectively, under CC. Total N removal increased from 14% (PC) to 19% (CC) in the conventional STA, but decreased in shallow narrow STAs, from 6–7% to less than 3.0%. Differences in removal of FCB and total N were not significant. Leaching of N in excess of inputs was also observed in shallow narrow STAs under CC. Our results indicate that climate change can affect contaminant removal from wastewater, with effects dependent on the contaminant and STA type. PMID:27583363

Hell and High Water: Diminished Septic System Performance in Coastal Regions Due to Climate Change.

PubMed

Cooper, Jennifer A; Loomis, George W; Amador, Jose A

2016-01-01

Climate change may affect the ability of soil-based onsite wastewater treatment systems (OWTS) to treat wastewater in coastal regions of the Northeastern United States. Higher temperatures and water tables can affect treatment by reducing the volume of unsaturated soil and oxygen available for treatment, which may result in greater transport of pathogens, nutrients, and biochemical oxygen demand (BOD5) to groundwater, jeopardizing public and aquatic ecosystem health. The soil treatment area (STA) of an OWTS removes contaminants as wastewater percolates through the soil. Conventional STAs receive wastewater from the septic tank, with infiltration occurring deeper in the soil profile. In contrast, shallow narrow STAs receive pre-treated wastewater that infiltrates higher in the soil profile, which may make them more resilient to climate change. We used intact soil mesocosms to quantify the water quality functions of a conventional and two types of shallow narrow STAs under present climate (PC; 20°C) and climate change (CC; 25°C, 30 cm elevation in water table). Significantly greater removal of BOD5 was observed under CC for all STA types. Phosphorus removal decreased significantly from 75% (PC) to 66% (CC) in the conventional STA, and from 100% to 71-72% in shallow narrow STAs. No fecal coliform bacteria (FCB) were released under PC, whereas up to 17 and 20 CFU 100 mL-1 were released in conventional and shallow narrow STAs, respectively, under CC. Total N removal increased from 14% (PC) to 19% (CC) in the conventional STA, but decreased in shallow narrow STAs, from 6-7% to less than 3.0%. Differences in removal of FCB and total N were not significant. Leaching of N in excess of inputs was also observed in shallow narrow STAs under CC. Our results indicate that climate change can affect contaminant removal from wastewater, with effects dependent on the contaminant and STA type.

Anisotropic ionizing radiation in Seyfert galaxies. I - The extended narrow-line region in Markarian 573

NASA Technical Reports Server (NTRS)

Tsvetanov, Zlatan; Walsh, J. R.

1992-01-01

The morphology, kinematics, and ionization state of the nuclear extended narrow-line region (ENLR) of the Seyfert 2 galaxy Mrk 573 are studied using narrow-band images of a grid of long-slit spectra. The entire ENLR is mapped spectroscopically, and velocity structure is studied. The velocity field map shows a typical galactic rotation picture with some important deviations. A simple geometric model, in accordance with the 'unified schemes', is employed to study the effects of various parameters of the observed picture. The best match is achieved when a biconical radiation field illuminates the ISM of the host galaxy that takes part in a normal galaxy rotation but also has radial motions close to the nucleus. The emission-line images reveal an ENLR elongated along the radio axis in the northwest-southeast direction, but a map of the flux ratio forbidden O III 5007/(H-alpha + forbidden N II) shows a different structure, with the highest excitation peak offset by about 4 arcsec along the radio axis to the southeast.

Searching for Variability of NV Intrinsic Narrow Absorption Line Systems

NASA Astrophysics Data System (ADS)

Rodruck, Michael; Charlton, Jane; Ganguly, Rajib

2018-01-01

The majority of quasar absorption line systems with NV detected are found within the associated region (within 5000 km/s of the quasar redshift) and many/most are believed to be related to the quasar accretion disk wind or outflows. The most definite evidence that these NV absorbers are "intrinsic" is partial covering of the quasar continuum source and/or broad line region. Over 75 quasars containing NV narrow absorption lines have observations obtained at different times with the Keck/HIRES and the VLT/UVES spectrographs at high resolution. The interval between these observations range from months to a decade in the quasar rest frame. While variability is common for intrinsic broad and mini-broad absorption lines, intrinsic narrow absorption lines have been found to be less likely to vary, though systematic studies with large, high quality datasets have been limited. The variability timescales are useful for deriving gas densities and thus the distances from the central engines. This is important in mapping the quasar surroundings, understanding the accretion disk wind mechanism, and assessing the effect the wind has on the galaxy surroundings. We report on the results of a systematic study of variability of NV NALs, exploiting the overlap of targets for observations in the archives of Keck and VLT, and discuss the consequences for interpretation of the origin of intrinsic narrow absorption lines.

Rheological observation of glassy dynamics of dilute polymer solutions near the coil-stretch transition in elongational flows.

PubMed

Sridhar, T; Nguyen, D A; Prabhakar, R; Prakash, J Ravi

2007-04-20

It has long been conjectured that the macroscopic dynamics of dilute polymer solutions may exhibit a glasslike slowdown caused by ergodicity breaking, in the vicinity of the coil-stretch transition in elongational flows. We report experimental observations using a filament stretching rheometer that confirm the existence of such glassy states. It is observed that different time-dependent elongational strain-rate profiles lead to a pronounced history dependence and aging effects within a narrow range of strain rates. The results have a direct bearing on the analysis and design of processes employing dilute polymer solutions, such as ink-jet printing, surface coating, and turbulent-drag reduction.

2017 Total Solar Eclipse - ISS Transit

NASA Image and Video Library

2017-08-21

The International Space Station, with a crew of six onboard, is seen in silhouette as it transits the Sun at roughly five miles per second during a partial solar eclipse, Monday, Aug. 21, 2017 near Banner, Wyoming. Onboard as part of Expedition 52 are: NASA astronauts Peggy Whitson, Jack Fischer, and Randy Bresnik; Russian cosmonauts Fyodor Yurchikhin and Sergey Ryazanskiy; and ESA (European Space Agency) astronaut Paolo Nespoli. A total solar eclipse swept across a narrow portion of the contiguous United States from Lincoln Beach, Oregon to Charleston, South Carolina. A partial solar eclipse was visible across the entire North American continent along with parts of South America, Africa, and Europe. Photo Credit: (NASA/Joel Kowsky)

2017 Total Solar Eclipse - ISS Transit

NASA Image and Video Library

2017-08-21

This composite image, made from seven frames, shows the International Space Station, with a crew of six onboard, as it transits the Sun at roughly five miles per second during a partial solar eclipse, Monday, Aug. 21, 2017 near Banner, Wyoming. Onboard as part of Expedition 52 are: NASA astronauts Peggy Whitson, Jack Fischer, and Randy Bresnik; Russian cosmonauts Fyodor Yurchikhin and Sergey Ryazanskiy; and ESA (European Space Agency) astronaut Paolo Nespoli. A total solar eclipse swept across a narrow portion of the contiguous United States from Lincoln Beach, Oregon to Charleston, South Carolina. A partial solar eclipse was visible across the entire North American continent along with parts of South America, Africa, and Europe. Photo Credit: (NASA/Joel Kowsky)

Observation of interlayer excitons in MoSe2 single crystals

NASA Astrophysics Data System (ADS)

Horng, Jason; Stroucken, Tineke; Zhang, Long; Paik, Eunice Y.; Deng, Hui; Koch, Stephan W.

2018-06-01

Interlayer excitons with direct optical transitions are observed coexisting with intralayer excitons in the same K valleys in bilayer, few-layer, and bulk MoSe2 single crystals by confocal reflection contrast spectroscopy. Quantitative analysis using the Dirac-Bloch equations provides unambiguous state assignment of all the measured resonances. The interlayer excitons in bilayer MoSe2 have a large binding energy of 153 meV and a narrow linewidth of 20 meV. Their spectral weight is comparable to the commonly studied higher-order intralayer excitons. At the same time, the interlayer excitons are characterized by distinct transition energies and permanent dipole moments, providing a promising high temperature and optically accessible platform for dipolar exciton physics.

New results on thermalization of electrons in GaAs

NASA Astrophysics Data System (ADS)

Hannak, Reinhard M.; Ruehle, Wolfgang W.

1994-05-01

The transition from a nonthermal into a thermal distribution of electrons at low densities (< 1014 cm-3) is traced on a picosecond time-scale by the time evolution of a band-to-acceptor transition in GaAs:Be. Two narrow, nonthermal electron distributions are detected during the first picoseconds originating from the heavy- and light-hole valence band, respectively. Measurements with circular polarization of excitation and luminescence confirm this assignment. The variation of their energetic peak-positions with excitation energy allows the experimental determination of the valence band dispersions for very small wave vectors near k equals 0, where only parabolic energy terms contribute to the dispersions. The results are consistent with the commonly used effective hole masses.

2017 Total Solar Eclipse - ISS Transit

NASA Image and Video Library

2017-08-21

The International Space Station, with a crew of six onboard, is seen in silhouette as it transits the Sun at roughly five miles per second during a partial solar eclipse, Monday, Aug. 21, 2017 from Ross Lake, Northern Cascades National Park, Washington. Onboard as part of Expedition 52 are: NASA astronauts Peggy Whitson, Jack Fischer, and Randy Bresnik; Russian cosmonauts Fyodor Yurchikhin and Sergey Ryazanskiy; and ESA (European Space Agency) astronaut Paolo Nespoli. A total solar eclipse swept across a narrow portion of the contiguous United States from Lincoln Beach, Oregon to Charleston, South Carolina. A partial solar eclipse was visible across the entire North American continent along with parts of South America, Africa, and Europe. Photo Credit: (NASA/Bill Ingalls)

Electromagnetically induced absorption and transparency in degenerate two level systems of metastable Kr atoms and measurement of Landé g-factor

NASA Astrophysics Data System (ADS)

Kale, Y. B.; Tiwari, V. B.; Mishra, S. R.; Singh, S.; Rawat, H. S.

2016-12-01

We report electromagnetically induced absorption (EIA) and transparency (EIT) resonances of sub-natural linewidth in degenerate two level systems (DTLSs) of metastable 84Kr (84Kr*) and 83Kr (83Kr*) atoms. Using the spectrally narrow EIA signals obtained corresponding to the closed hyperfine transition 4p55s[3/2]2(F=13/2) to 4p55p[5/2]3(F‧ = 15 / 2) in 83Kr* atom, we have measured the Landé g-factor (gF) for the lower hyperfine level involved in this transition by application of small values of magnetic field of few Gauss.

High-Latitude Scintillation Morphology, Alaskan Sector

DTIC Science & Technology

1979-10-01

region. Localized nighttime scintillation enhancements within the scin - tillation boundary have been associated with active auroral arcs. This list...thus ideally located for measuring scin - tillation phenomena associated with the nighttime auroral oval. The Wideband satellite orbit is such that...1000 UT). The region of enhanced phase scin - tillation between 0952 and 0955 is associated with a narrow region of enhanced energetic particle

Evaluation of the tripolar electrode stimulation method by numerical analysis and animal experiments for cochlear implants.

PubMed

Miyoshi, S; Sakajiri, M; Ifukube, T; Matsushima, J

1997-01-01

We have proposed the Tripolar Electrode Stimulation Method (TESM) which may enable us to narrow the stimulation region and to move continuously the stimulation site for the cochlear implants. We evaluated whether or not TESM works according to a theory based on numerical analysis using the auditory nerve fiber model. In this simulation, the sum of the excited model fibers were compared with the compound actions potentials obtained from animal experiments. As a result, this experiment showed that TESM could narrow a stimulation region by controlling the sum of the currents emitted from the electrodes on both sides, and continuously move a stimulation site by changing the ratio of the currents emitted from the electrodes on both sides.

Identification of transitional disks in Chamaeleon with Herschel

NASA Astrophysics Data System (ADS)

Ribas, Á.; Merín, B.; Bouy, H.; Alves de Oliveira, C.; Ardila, D. R.; Puga, E.; Kóspál, Á.; Spezzi, L.; Cox, N. L. J.; Prusti, T.; Pilbratt, G. L.; André, Ph.; Matrà, L.; Vavrek, R.

2013-04-01

Context. Transitional disks are circumstellar disks with inner holes that in some cases are produced by planets and/or substellar companions in these systems. For this reason, these disks are extremely important for the study of planetary system formation. Aims: The Herschel Space Observatory provides an unique opportunity for studying the outer regions of protoplanetary disks. In this work we update previous knowledge on the transitional disks in the Chamaeleon I and II regions with data from the Herschel Gould Belt Survey. Methods: We propose a new method for transitional disk classification based on the WISE 12 μm - PACS 70 μm color, together with inspection of the Herschel images. We applied this method to the population of Class II sources in the Chamaeleon region and studied the spectral energy distributions of the transitional disks in the sample. We also built the median spectral energy distribution of Class II objects in these regions for comparison with transitional disks. Results: The proposed method allows a clear separation of the known transitional disks from the Class II sources. We find six transitional disks, all previously known, and identify five objects previously thought to be transitional as possibly non-transitional. We find higher fluxes at the PACS wavelengths in the sample of transitional disks than those of Class II objects. Conclusions: We show the Herschel 70 μm band to be a robust and efficient tool for transitional disk identification. The sensitivity and spatial resolution of Herschel reveals a significant contamination level among the previously identified transitional disk candidates for the two regions, which calls for a revision of previous samples of transitional disks in other regions. The systematic excess found at the PACS bands could be either a result of the mechanism that produces the transitional phase, or an indication of different evolutionary paths for transitional disks and Class II sources. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendix A is available in electronic form at http://www.aanda.org

Preparation of nitrogen-doped carbon tubes

DOEpatents

Chung, Hoon Taek; Zelenay, Piotr

2015-12-22

A method for synthesizing nitrogen-doped carbon tubes involves preparing a solution of cyanamide and a suitable transition metal-containing salt in a solvent, evaporating the solvent to form a solid, and pyrolyzing the solid under an inert atmosphere under conditions suitable for the production of nitrogen-doped carbon tubes from the solid. Pyrolyzing for a shorter period of time followed by rapid cooling resulted in a tubes with a narrower average diameter.

Power and polarization dependences of ultra-narrow electromagnetically induced absorption (EIA) spectra of 85 Rb atoms in degenerate two-level system

NASA Astrophysics Data System (ADS)

Qureshi, Muhammad Mohsin; Rehman, Hafeez Ur; Noh, Heung-Ryoul; Kim, Jin-Tae

2016-05-01

We have investigated ultra-narrow EIA spectral features with respect to variations of polarizations and powers of pump laser beam in a degenerate two-level system of the transition of 85 Rb D2 transition line. Polarizations of the probe laser beam in two separate experiments were fixed at right circular and horizontal linear polarizations, respectively while the polarizations of the pump lasers were varied from initial polarizations same as the probe laser beams to orthogonal to probe polarizations. One homemade laser combined with AOMs was used to the pump and probe laser beams instead of two different lasers to overcome broad linewidths of the homemade lasers. Theoretically, probe absorption coefficients have been calculated from optical Bloch equations of the degenerate two level system prepared by a pump laser beam. In the case of the circular polarization, EIA signal was obtained as expected theoretically although both pump and probe beams have same polarization. The EIA signal become smaller as power increases and polarizations of the pump and probe beams were same. When the polarization of the pump beam was linear polarization, maximum EIA signal was obtained theoretically and experimentally. Experimental EIA spectral shapes with respect to variations of the pump beam polarization shows similar trends as the theoretical results.

Transition from intelligence cycle to intelligence process: the network-centric intelligence in narrow seas

NASA Astrophysics Data System (ADS)

Büker, Engin

2015-05-01

The defence technologies which have been developing and changing rapidly, today make it difficult to be able to foresee the next environment and spectrum of warfare. When said change and development is looked in specific to the naval operations, it can be said that the possible battlefield and scenarios to be developed in the near and middle terms (5-20 years) are more clarified with compare to other force components. Network Centric Naval Warfare Concept that was developed for the floating, diving and flying fleet platforms which serves away from its own mainland for miles, will keep its significance in the future. Accordingly, Network Centric Intelligence structure completely integrating with the command and control systems will have relatively more importance. This study will firstly try to figure out the transition from the traditional intelligence cycle that is still used in conventional war to Network Centric Intelligence Production Process. In the last part, the use of this new approach on the base of UAV that is alternative to satellite based command control and data transfer systems in the joint operations in narrow seas will be examined, a model suggestion for the use of operative and strategic UAVs which are assured within the scope of the NATO AGS2 for this aim will be brought.

Strain-induced formation of ultra-coherent CDW in quasi one-dimensional conductors

NASA Astrophysics Data System (ADS)

Zybtsev, S. G.; Pokrovskii, V. Ya.

2015-03-01

We have developed techniques for stretching whiskers up to 1.5-3%, including those of nanometer cross-section. An exceptionally high coherence of the CDW transport for TaS3 and NbS3 has been observed under the uniaxial strain, ε. For TaS3 samples with transverse dimensions ∼0.1-1 μm for ε approaching εс the CDW coherence falls down and a new, ultra-coherent, CDW phase begins to form. At ε εс the two phases coexist within a very narrow range δε 2×10-4. Further stretching results in a complete vanishing of the transport of the incoherent CDW. The threshold fields, Et, of the ultra-coherent CDW, as well as the dissipation, appear by an order of magnitude lower; giant negative differential resistance is observed. The narrow-band noise shows up to 10 harmonics of the fundamental frequency. RF irradiation results in complete synchronization of the CDW sliding. The CDW transformation shows features of the 1st order transition. We also report hysteresis of resistance vs. ε, from which we conclude that the transition cannot be associated with the lock-in of the CDW: the strain draws the CDW away from 4-fold commensurability with the lattice.

Precision Spectroscopy on Single Cold Trapped Molecular Nitrogen Ions

NASA Astrophysics Data System (ADS)

Hegi, Gregor; Najafian, Kaveh; Germann, Matthias; Sergachev, Ilia; Willitsch, Stefan

2016-06-01

The ability to precisely control and manipulate single cold trapped particles has enabled spectroscopic studies on narrow transitions of ions at unprecedented levels of precision. This has opened up a wide range of applications, from tests of fundamental physical concepts, e.g., possible time-variations of fundamental constants, to new and improved frequency standards. So far most of these experiments have concentrated on atomic ions. Recently, however, attention has also been focused on molecular species, and molecular nitrogen ions have been identified as promising candidates for testing a possible time-variation of the proton/electron mass ratio. Here, we report progress towards precision-spectroscopic studies on dipole-forbidden vibrational transitions in single trapped N2+ ions. Our approach relies on the state-selective generation of single N2+ ions, subsequent infrared excitation using high intensity, narrow-band quantum-cascade lasers and a quantum-logic scheme for non-destructive state readout. We also characterize processes limiting the state lifetimes in our experiment, which impair the measurement fidelity. P. O. Schmidt et. al., Science 309 (2005), 749. M. Kajita et. al., Phys. Rev. A 89 (2014), 032509 M. Germann , X. Tong, S. Willitsch, Nature Physics 10 (2014), 820. X. Tong, A. Winney, S. Willitsch, Phys. Rev. Lett. 105 (2010), 143001

Infrared Spectroscopy of Pa-beta and [Fe II] Emission in NGC 4151

NASA Technical Reports Server (NTRS)

Knop, R. A.; Armus, L.; Larkin, J. E.; Matthews, K.; Shupe, D. L.; Soifer, B. T.

1996-01-01

We present spatially resolved 1.24-1.30 micron spectroscopy with a resolution of 240 km/s of the Seyfert 1.5 galaxy NGC 4151. Broad Pa-beta, narrow Pa-beta, and narrow [Fe II] (lambda = 1.2567 micron) emission lines are identified in the spectrum. Additionally, a spatially unresolved narrow component probably due to [S ix] (lambda = 1.25235 micron) is observed on the nucleus. The narrow Pa-beta and [Fe II] lines are observed to be extended over a scale of 5 sec. The spatial variation of the velocity centers of the Pa-beta and [Fe II] lines show remarkable similarity, and additionally show similarities to the velocity structure previously observed in ground based spectroscopy of [O III] emission in NGC 4151. This leads to the conclusion that the [Fe II] emission arises in clouds in the Seyfert narrow line region that are physically correlated with those narrow line clouds responsible for the optical emission. The [Fe II] emission line, however, is significantly wider than the Pa-beta emission line along the full spatial extent of the observed emission. This result suggests that despite the correlation between the bulk kinematics of Pa-beta and [Fe II], there is an additional process, perhaps fast shocks from a wind in the Seyfert nucleus, contributing to the [Fe II] emission.

Sub-natural width resonances in Cs vapor confined in micrometric thickness optical cell

NASA Astrophysics Data System (ADS)

Cartaleva, S.; Krasteva, A.; Sargsyan, A.; Sarkisyan, D.; Slavov, D.; Vartanyan, T.

2013-03-01

We present here the behavior of Electromagnetically Induced Transparency (EIT), Velocity Selective Optical Pumping (VSOP) resonances and Velocity Selective Excitation (VSE) resonances observed in Cs vapor confined in а micrometric optical cell (MC) with thickness L = 6λ, λ = 852nm. For comparison of behavior of VSE resonance another conventional optical cell with thickness L=2.5 cm is used. Cells are irradiated in orthogonal to their windows directions by probe beam scanned on the Fg = 4 → Fe= 3, 4, 5 set of transitions and pump beam fixed at the Fg = 3 → Fe = 4 transition, on the D2 line of Cs. The enhanced absorption (fluorescence) narrow VSOP resonance at the closed transition transforms into reduced absorption (fluorescence) one with small increase of atomic concentration or light intensity. A striking difference appears between the VSE resonance broadening in L = 6λ and conventional L = 2.5cm cells.

Tegotae-based decentralised control scheme for autonomous gait transition of snake-like robots.

PubMed

Kano, Takeshi; Yoshizawa, Ryo; Ishiguro, Akio

2017-08-04

Snakes change their locomotion patterns in response to the environment. This ability is a motivation for developing snake-like robots with highly adaptive functionality. In this study, a decentralised control scheme of snake-like robots that exhibited autonomous gait transition (i.e. the transition between concertina locomotion in narrow aisles and scaffold-based locomotion on unstructured terrains) was developed. Additionally, the control scheme was validated via simulations. A key insight revealed is that these locomotion patterns were not preprogrammed but emerged by exploiting Tegotae, a concept that describes the extent to which a perceived reaction matches a generated action. Unlike local reflexive mechanisms proposed previously, the Tegotae-based feedback mechanism enabled the robot to 'selectively' exploit environments beneficial for propulsion, and generated reasonable locomotion patterns. It is expected that the results of this study can form the basis to design robots that can work under unpredictable and unstructured environments.

Selective Hydrogen Isotope Separation via Breathing Transition in MIL-53(Al).

PubMed

Kim, Jin Yeong; Zhang, Linda; Balderas-Xicohténcatl, Rafael; Park, Jaewoo; Hirscher, Michael; Moon, Hoi Ri; Oh, Hyunchul

2017-12-13

Breathing of MIL-53(Al), a flexible metal-organic framework (MOF), leads to dynamic changes as narrow pore (np) transitions to large pore (lp). During the flexible and reversible transition, the pore apertures are continuously adjusted, thus providing the tremendous opportunity to separate mixtures of similar-sized and similar-shaped molecules that require precise pore tuning. Herein, for the first time, we report a strategy for effectively separating hydrogen isotopes through the dynamic pore change during the breathing of MIL-53(Al), a representative of flexible MOFs. The experiment shows that the selectivity for D 2 over H 2 is strongly related to the state of the pore structure of MIL-53(Al). The highest selectivity (S D 2 /H 2 = 13.6 at 40 K) was obtained by optimizing the exposure temperature, pressure, and time to systematically tune the pore state of MIL-53(Al).

High-resolution two-photon spectroscopy of a 5 p56 p ←5 p6 transition of xenon

NASA Astrophysics Data System (ADS)

Altiere, Emily; Miller, Eric R.; Hayamizu, Tomohiro; Jones, David J.; Madison, Kirk W.; Momose, Takamasa

2018-01-01

We report high-resolution Doppler-free two-photon excitation spectroscopy of Xe from the ground state to the 5 p5(P 3 /2 2 ) 6 p [3 /2 ] 2 2 electronic excited state. This is a first step to developing a comagnetometer using polarized 129Xe atoms for planned neutron electric dipole moment measurements at TRIUMF. Narrow linewidth radiation at 252.5 nm produced by a continuous wave laser was built up in an optical cavity to excite the two-photon transition, and the near-infrared emission from the 5 p56 p excited state to the 5 p56 s intermediate electronic state was used to detect the two-photon transition. Hyperfine constants and isotope shift parameters were evaluated and compared with previously reported values. In addition, the detected photon count rate was estimated from the observed intensities.

Observation and investigation of narrow optical transitions of 167Er3+ ions in femtosecond laser printed waveguides in 7LiYF4 crystal

NASA Astrophysics Data System (ADS)

Minnegaliev, M. M.; Dyakonov, I. V.; Gerasimov, K. I.; Kalinkin, A. A.; Kulik, S. P.; Moiseev, S. A.; Saygin, M. Yu; Urmancheev, R. V.

2018-04-01

We produced optical waveguides in the 167Er3+:7 LiYF4 crystal with diameters ranging from 30 to 100 μm by using the depressed-cladding approach with femtosecond laser. Stationary and coherent spectroscopy was performed on the 809 nm optical transitions between the hyperfine sublevels of 4I15/2 and 4I9/2 multiplets of 167Er3+ ions both inside and outside of waveguides. It was found that the spectra of 167Er3+ were slightly broadened and shifted inside the waveguides compared to the bulk crystal spectra. We managed to observe a two-pulse photon echo on this transition and determined phase relaxation times for each waveguide. The experimental results show that the created crystal waveguides doped by rare-earth ions can be used in optical quantum memory and integrated quantum schemes.

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

Yu, Shifeng; Wang, Shuyu; Lu, Ming

In this paper, vanadium thin films were deposited on sapphire substrates by DC magnetron sputtering and then oxidized in a tube furnace filled with oxygen under different temperatures and oxygen flow rates. The significant influence of the oxygen flow rate and oxidation temperature on the electrical and structural properties of the vanadium oxide thin films were investigated systematically. It shows the pure vanadium dioxide (VO 2) state can only be obtained in a very narrow temperature and oxygen flow rate range. The resistivity change during the metal-insulator transition varies from 0.2 to 4 orders of magnitude depending on the oxidationmore » condition. Large thermal hysteresis during the metal-insulator phase transition was observed during the transition compared to the results in literature. Proper oxidation conditions can significantly reduce the thermal hysteresis. Finally, the fabricated VO 2 thin films showed the potential to be applied in the development of electrical sensors and other smart devices.« less

Precision ESR measurements of transverse anisotropy in the single-molecule magnet Ni4

NASA Astrophysics Data System (ADS)

Collett, Charles A.; Allão Cassaro, Rafael A.; Friedman, Jonathan R.

2016-12-01

We present a method for precisely measuring the tunnel splitting in single-molecule magnets (SMMs) using electron-spin resonance, and use these measurements to precisely and independently determine the underlying transverse anisotropy parameter, given a certain class of transitions. By diluting samples of the SMM Ni4 via cocrystallization in a diamagnetic isostructural analog we obtain markedly narrower resonance peaks than are observed in undiluted samples. Using custom loop-gap resonators we measure the transitions at several frequencies, allowing a precise determination of the tunnel splitting. Because the transition under investigation occurs at zero field, and arises due to a first-order perturbation from the transverse anisotropy, we can determine the magnitude of this anisotropy independent of any other Hamiltonian parameters. This method can be applied to other SMMs with tunnel splittings arising from first-order transverse anisotropy perturbations.

Clogging Transition of Vibration-Driven Vehicles Passing through Constrictions

NASA Astrophysics Data System (ADS)

Patterson, G. A.; Fierens, P. I.; Sangiuliano Jimka, F.; König, P. G.; Garcimartín, A.; Zuriguel, I.; Pugnaloni, L. A.; Parisi, D. R.

2017-12-01

We report experimental results on the competitive passage of elongated self-propelled vehicles rushing through a constriction. For the chosen experimental conditions, we observe the emergence of intermittencies similar to those reported previously for active matter passing through narrow doors. Noteworthy, we find that, when the number of individuals crowding in front of the bottleneck increases, there is a transition from an unclogged to a clogged state characterized by a lack of convergence of the mean clog duration as the measuring time increases. It is demonstrated that this transition—which was reported previously only for externally vibrated systems such as colloids or granulars—appears also for self-propelled agents. This suggests that the transition should also occur for the flow through constrictions of living agents (e.g., humans and sheep), an issue that has been elusive so far in experiments due to safety risks.

Radioluminescence and photoluminescence of Th:CaF2 crystals

PubMed Central

Stellmer, Simon; Schreitl, Matthias; Schumm, Thorsten

2015-01-01

We study thorium-doped CaF2 crystals as a possible platform for optical spectroscopy of the 229Th nuclear isomer transition. We anticipate two major sources of background signal that might cover the nuclear spectroscopy signal: VUV-photoluminescence, caused by the probe light, and radioluminescence, caused by the radioactive decay of 229Th and its daughters. We find a rich photoluminescence spectrum at wavelengths above 260 nm, and radioluminescence emission above 220 nm. This is very promising, as fluorescence originating from the isomer transition, predicted at a wavelength shorter than 200 nm, could be filtered spectrally from the crystal luminescence. Furthermore, we investigate the temperature-dependent decay time of the luminescence, as well as thermoluminescence properties. Our findings allow for an immediate optimization of spectroscopy protocols for both the initial search for the nuclear transition using synchrotron radiation, as well as future optical clock operation with narrow-linewidth lasers. PMID:26502749

On-demand semiconductor source of 780-nm single photons with controlled temporal wave packets

NASA Astrophysics Data System (ADS)

Béguin, Lucas; Jahn, Jan-Philipp; Wolters, Janik; Reindl, Marcus; Huo, Yongheng; Trotta, Rinaldo; Rastelli, Armando; Ding, Fei; Schmidt, Oliver G.; Treutlein, Philipp; Warburton, Richard J.

2018-05-01

We report on a fast, bandwidth-tunable single-photon source based on an epitaxial GaAs quantum dot. Exploiting spontaneous spin-flip Raman transitions, single photons at 780 nm are generated on demand with tailored temporal profiles of durations exceeding the intrinsic quantum dot lifetime by up to three orders of magnitude. Second-order correlation measurements show a low multiphoton emission probability [g2(0 ) ˜0.10 -0.15 ] at a generation rate up to 10 MHz. We observe Raman photons with linewidths as low as 200 MHz, which is narrow compared to the 1.1-GHz linewidth measured in resonance fluorescence. The generation of such narrow-band single photons with controlled temporal shapes at the rubidium wavelength is a crucial step towards the development of an optimized hybrid semiconductor-atom interface.

Spin-injection optical pumping of molten cesium salt and its NMR diagnosis

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

Ishikawa, Kiyoshi

2015-07-15

Nuclear spin polarization of cesium ions in the salt was enhanced during optical pumping of cesium vapor at high magnetic field. Significant motional narrowing and frequency shift of NMR signals were observed by intense laser heating of the salt. When the hyperpolarized salt was cooled by blocking the heating laser, the signal width and frequency changed during cooling and presented the phase transition from liquid to solid. Hence, we find that the signal enhancement is mostly due to the molten salt and nuclear spin polarization is injected into the salt efficiently in the liquid phase. We also show that opticalmore » pumping similarly induces line narrowing in the solid phase. The use of powdered salt provided an increase in effective surface area and signal amplitude without glass wool in the glass cells.« less

The molecular gas content of the Pipe Nebula. I. Direct evidence of outflow-generated turbulence in B59?

NASA Astrophysics Data System (ADS)

Duarte-Cabral, A.; Chrysostomou, A.; Peretto, N.; Fuller, G. A.; Matthews, B.; Schieven, G.; Davis, G. R.

2012-07-01

Context. Star forming regions may share many characteristics, but the specific interplay between gravity, magnetic fields, large-scale dynamics, and protostellar feedback will have an impact on the star formation history of each region. The importance of feedback from outflows is a particular subject to debate, as we are yet to understand the details of their impact on clouds and star formation. Aims: The Pipe Nebula is a nearby molecular cloud hosting the B59 region as its only active star-forming clump. This paper focuses on the global dynamics of B59, its temperature structure, and its outflowing gas, with the goal of revealing the local and global impact of the protostellar outflows. Methods: Using HARP at the James Clerk Maxwell Telescope, we have mapped the B59 region in the J = 3 → 2 transition of 12CO to study the kinematics and energetics of the outflows, and the same transitions of 13CO and C18O to study the overall dynamics of the ambient cloud, the physical properties of the gas, and the hierarchical structure of the region. Results: The B59 region has a total of ~30 M⊙ of cold and quiescent material, mostly gravitationally bound, with narrow line widths throughout. Such low levels of turbulence in the non-star-forming regions within B59 are indicative of the intrinsic initial conditions of the cloud. On the other hand, close to the protostars the impact of the outflows is observed as a localised increase of both C18O line widths from ~0.3 km s-1 to ~1 km s-1, and 13CO excitation temperatures by ~2-3 K. The impact of the outflows is also evident in the low column density material which shows signs of being shaped by the outflow bow shocks as they pierce their way out of the cloud. Much of this structure is readily apparent in a dendrogram analysis of the cloud and demonstrates that when decomposing clouds using such techniques a careful interpretation of the results is needed. Conclusions: The low mass of B59 together with its intrinsically quiescent gas and small number of protostars, allows the identification of specific regions where the outflows from the embedded sources interact the dense gas. Our study suggests that outflows are an important mechanism for injecting and sustaining supersonic turbulence at sub-parsec size scales. We find that less than half of the outflow energy is deposited as turbulent energy of the gas, however this turbulent energy is sufficient to slow down the collapse of the region.

Saturn's F Ring Core: Calm in the Midst of Chaos

NASA Technical Reports Server (NTRS)

Cuzzi, J. N.; Whizin, A. D.; Hogan, R. C.; Dobrovolskis, A. R.; Dones, L.; Showalter. M. R.; Colwell, J. E.; Scargle, J. D.

2013-01-01

The long-term stability of the narrow F Ring core has been hard to understand. Instead of acting as "shepherds", Prometheus and Pandora together stir the vast preponderance of the region into a chaotic state, consistent with the orbits of newly discovered objects like S/2004S6. We show how a comb of very narrow radial locations of high stability in semimajor axis is embedded within this otherwise chaotic region. The stability of these semimajor axes relies fundamentally on the unusual combination of rapid apse precession and long synodic period which characterizes the region. This situation allows stable "antiresonances" to fall on or very close to traditional Lindblad resonances which, under more common circumstances, are destabilizing. We present numerical integrations of tens of thousands of test particles over tens of thousands of Prometheus orbits that map out the effect. The stable antiresonance zones are most stable in a subset of the region where Prometheus first-order resonances are least cluttered by Pandora resonances. This region of optimum stability is paradoxically closer to Prometheus than a location more representative of "torque balance", helping explain a longstanding paradox. One stable zone corresponds closely to the currently observed semimajor axis of the F Ring core. While the model helps explain the stability of the narrow F Ring core, it does not explain why the F Ring material all shares a common apse longitude; we speculate that collisional damping at the preferred semimajor axis (not included in the current simulations) may provide that final step. Essentially, we find that the F Ring core is not confined by a combination of Prometheus and Pandora, but a combination of Prometheus and precession.

Scintigraphic measurement of regional gut transit in idiopathic constipation

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

Stivland, T.; Camilleri, M.; Vassallo, M.

1991-07-01

In this study, total gut transit and regional colonic transit in patients with idiopathic constipation were measured scintigraphically. Eight patients with severe constipation were studied, none of whom had evidence of abnormal function of the pelvic floor. 99mTc-radiolabeled Amberlite resin particles with a mixed meal were used to assess gastric emptying and small bowel transit; similar particles labeled with 111In were ingested in a coated capsule that dispersed in the ileocecal region. These were used to quantify colonic transit. Five healthy volunteers were also studied. Two patients showed delayed gastric emptying and two had slow small bowel transit. Seven ofmore » the eight patients had slow colonic transit. In five, delay affected the whole colon (pancolonic inertia); in two, transit in the ascending and transverse colon was normal, but solids moved through the left colon slowly. Mean colonic transit was also measured using radiopaque markers; this technique identified the patients with slow transit, as shown by measurements of overall colonic transit by simultaneous scintigraphy. However, estimated transit through the ascending and transverse colons was considerably shorter by the radiopaque marker technique. In conclusion, idiopathic constipation is characterized by either exaggerated reservoir functions of the ascending and transverse colons and/or impairment of propulsive function in the descending colon. Particle size may influence the result of regional colonic transit tests. Transit delays in other parts of the gut suggest that, in some patients, the condition may be a more generalized motor dysfunction.« less

Comparison of Antarctic Crustal Thickness from Gravity Inversion and Seismology: Evidence for Mantle Dynamic Uplift under Marie Byrd Land

NASA Astrophysics Data System (ADS)

Ferraccioli, F.; Kusznir, N. J.; Jordan, T. A.

2017-12-01

Using gravity anomaly inversion, we produce comprehensive regional maps of crustal thickness and oceanic lithosphere distribution for Antarctica and the Southern Ocean. Antarctic crustal thicknesses derived from gravity inversion are compared with seismic estimates from Baranov (2011) and An et al. (2015). We determine Moho depth, crustal basement thickness, continental lithosphere thinning (1-1/) and ocean-continent transition location using a 3D spectral domain gravity inversion method, which incorporates a lithosphere thermal gravity anomaly correction (Chappell & Kusznir 2008). Data used in the gravity inversion are elevation and bathymetry, free-air gravity anomaly, the Bedmap 2 ice thickness and bedrock topography compilation south of 60 degrees south and relatively sparse constraints on sediment thickness. Our gravity inversion study predicts thick crust (> 45 km) under interior East Antarctica, which is penetrated by narrow continental rifts featuring relatively thinner crust. The largest crustal thicknesses predicted from gravity inversion lie in the region of the Gamburtsev Subglacial Mountains, and are consistent with seismic estimates. The East Antarctic Rift System (EARS), a major Permian to Cretaceous age rift system, is imaged by our inversion and appears to extend from the continental margin at the Lambert Rift (LR) to the South Pole region, a distance of 2500 km. Thin crust is predicted under the Ross Sea and beneath the West Antarctic Ice Sheet and delineates the regional extent of the broad West Antarctic Rift System (WARS). Substantial regional uplift is required under Marie Byrd Land to reconcile gravity and seismic estimates. A mantle dynamic uplift origin of the uplift is preferred to a thermal anomaly from a very young rift. The new crustal thickness map produced by this gravity inversion study support the hypothesis that one branch of the WARS links through to the De Gerlache sea-mounts (DG) and Peter I Island (PI) in the Bellingshausen Sea region, while another branch may link to the George V Sound Rift in the Antarctic Peninsula region.

Narrow-band microwave radiation from a biased single-Cooper-pair transistor.

PubMed

Naaman, O; Aumentado, J

2007-06-01

We show that a single-Cooper-pair transistor (SCPT) electrometer emits narrow-band microwave radiation when biased in its subgap region. Photoexcitation of quasiparticle tunneling in a nearby SCPT is used to spectroscopically detect this radiation in a configuration that closely mimics a qubit-electrometer integrated circuit. We identify emission lines due to Josephson radiation and radiative transport processes in the electrometer and argue that a dissipative superconducting electrometer can severely disrupt the system it attempts to measure.

Observations of Hall Reconnection Physics Far Downstream of the X Line.

PubMed

Mistry, R; Eastwood, J P; Haggerty, C C; Shay, M A; Phan, T D; Hietala, H; Cassak, P A

2016-10-28

Observations made using the Wind spacecraft of Hall magnetic fields in solar wind reconnection exhausts are presented. These observations are consistent with the generation of Hall fields by a narrow ion inertial scale current layer near the separatrix, which is confirmed with an appropriately scaled particle-in-cell simulation that shows excellent agreement with observations. The Hall fields are observed thousands of ion inertial lengths downstream from the reconnection X line, indicating that narrow regions of kinetic dynamics can persist extremely far downstream.

Magnetic susceptibility and relation to initial 87Sr/86Sr for granitoids of the central Sierra Nevada, California

USGS Publications Warehouse

Bateman, P.C.; Dodge, F.C.W.; Kistler, R.W.

1991-01-01

Measurement of the magnetic susceptibility of more than 6000 samples of granitic rock from the Mariposa 1?? by 2?? quadrangle, which crosses the central part of the Sierra Nevada batholith between 37?? and 38??N latitude, shows that magnetic susceptibility values are above 10-2 SI units in the east and central parts of the batholith and drop abruptly to less than 10-3 SI units in the western foothills. In a narrow transitional zone, intermediate values (10-3 to 10-2) prevail. Magnetic susceptibility appears to decrease slightly westward within the zones of both high and low values. Magnetic susceptibility in plutonic rocks is chiefly a function of the abundance of magnetite, which depends, in turn, on the total iron content of the rocks and their oxidation ratio. Correlations of magnetic susceptibility with initial 87Sr/86Sr suggest that oxidation ratios have been inherited from the source regions for the magmas from which the rocks crystallized. Reduction of Fe3+ to Fe2+ by organic carbon or other reducing substances may also have affected magnetic susceptibility. -from Authors

Structure of the Espanola Basin, Rio Grande Rift, New Mexico, from SAGE seismic and gravity data

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

Ferguson, J.F.; Baldridge, W.S.; Braile, L.W.

1995-04-01

Seismic and gravity data, acquired by the SAGE program over the past twelve years, are used to define the geometry of the Espanola basin and the extent of pre-Tertiary sedimentary rocks. The Paleozoic and Mesozoic units have been thinned and removed during Laramide uplift in an area now obscured by the younger rift basin. The Espanola basin is generally a shallow, asymmetric transitional structure between deeper, better developed basins to the northeast and southwest. The gravity data indicate the presence of three narrow, but deep, structural lows arrayed along the Embudo/Pajarito fault system. These sub-basins seem to be younger thanmore » the faults on the basin margins. This apparent focussing of deformation in the later history of the basin may be a response to changes in regional stress or more local accommodation of the rift extension. Future work is planned to develop seismic data over one of these sub-basins, the Velarde graben, and to better define the gravity map in order to facilitate three-dimensional modeling.« less

Observation and Manipulation of Visible Edge Plasmons in Bi2Te3 Nanoplates.

PubMed

Lu, Xiaowei; Hao, Qunqing; Cen, Mengjia; Zhang, Guanhua; Sun, Julong; Mao, Libang; Cao, Tun; Zhou, Chuanyao; Jiang, Peng; Yang, Xueming; Bao, Xinhe

2018-05-09

Noble metals, like Ag and Au, are the most intensively studied plasmonic materials in the visible range. Plasmons in semiconductors, however, are usually believed to be in the infrared wavelength region due to the intrinsic low carrier concentrations. Herein, we observe the edge plasmon modes of Bi 2 Te 3 , a narrow-band gap semiconductor, in the visible spectral range using photoemission electron microscopy (PEEM). The Bi 2 Te 3 nanoplates excited by 400 nm femtosecond laser pulses exhibit strong photoemission intensities along the edges, which follow a cos 4 dependence on the polarization state of incident beam. Because of the phase retardation effect, plasmonic response along different edges can be selectively exited. The thickness-dependent photoemission intensities exclude the spin-orbit induced surface states as the origin of these plasmonic modes. Instead, we propose that the interband transition-induced nonequilibrium carriers might play a key role. Our results not only experimentally demonstrate the possibility of visible plasmons in semiconducting materials but also open up a new avenue for exploring the optical properties of topological insulator materials using PEEM.

Strong temperature-dependent crystallization, phase transition, optical and electrical characteristics of p-type CuAlO2 thin films.

PubMed

Liu, Suilin; Wu, Zhiheng; Zhang, Yake; Yao, Zhiqiang; Fan, Jiajie; Zhang, Yiqiang; Hu, Junhua; Zhang, Peng; Shao, Guosheng

2015-01-07

We report here a reliable and reproducible single-step (without post-annealing) fabrication of phase-pure p-type rhombohedral CuAlO2 (r-CuAlO2) thin films by reactive magnetron sputtering. The dependence of crystallinity and phase compositions of the films on the growth temperature was investigated, revealing that highly-crystallized r-CuAlO2 thin films could be in situ grown in a narrow temperature window of ∼940 °C. Optical and electrical property studies demonstrate that (i) the films are transparent in the visible light region, and the bandgaps of the films increased to ∼3.86 eV with the improvement of crystallinity; (ii) the conductance increased by four orders of magnitude as the film was evolved from the amorphous-like to crystalline structure. The predominant role of crystallinity in determining CuAlO2 film properties was demonstrated to be due to the heavy anisotropic characteristics of the O 2p-Cu 3d hybridized valence orbitals.

Dislocation blocking by AlGaN hot electron injecting layer in the epitaxial growth of GaN terahertz Gunn diode

NASA Astrophysics Data System (ADS)

Li, Liang; Yang, Lin'an; Zhang, Jincheng; Hao, Yue

2013-09-01

This paper reports an efficient method to improve the crystal quality of GaN Gunn diode with AlGaN hot electron injecting layer (HEI). An evident reduction of screw dislocation and edge dislocation densities is achieved by the strain management and the enhanced lateral growth in high temperature grown AlGaN HEI layer. Compared with the top hot electron injecting layer (THEI) structure, the bottom hot electron injecting layer (BHEI) structure enhances the crystal quality of transit region due to the growth sequence modulation of HEI layer. A high Hall mobility of 2934 cm2/Vs at 77 K, a nearly flat downtrend of Hall mobility at the temperature ranging from 300 to 573 K, a low intensity of ratio of yellow luminescence band to band edge emission, a narrow band edge emission line-width, and a smooth surface morphology are observed for the BHEI structural epitaxy of Gunn diode, which indicates that AlGaN BHEI structure is a promising candidate for fabrication of GaN Gunn diodes in terahertz regime.

Sensing charges of the Ciona intestinalis voltage-sensing phosphatase.

PubMed

Villalba-Galea, Carlos A; Frezza, Ludivine; Sandtner, Walter; Bezanilla, Francisco

2013-11-01

Voltage control over enzymatic activity in voltage-sensitive phosphatases (VSPs) is conferred by a voltage-sensing domain (VSD) located in the N terminus. These VSDs are constituted by four putative transmembrane segments (S1 to S4) resembling those found in voltage-gated ion channels. The putative fourth segment (S4) of the VSD contains positive residues that likely function as voltage-sensing elements. To study in detail how these residues sense the plasma membrane potential, we have focused on five arginines in the S4 segment of the Ciona intestinalis VSP (Ci-VSP). After implementing a histidine scan, here we show that four arginine-to-histidine mutants, namely R223H to R232H, mediate voltage-dependent proton translocation across the membrane, indicating that these residues transit through the hydrophobic core of Ci-VSP as a function of the membrane potential. These observations indicate that the charges carried by these residues are sensing charges. Furthermore, our results also show that the electrical field in VSPs is focused in a narrow hydrophobic region that separates the extracellular and intracellular space and constitutes the energy barrier for charge crossing.

Photoluminescent spectroscopy measurements in nanocrystalline praseodymium doped zirconia powders

NASA Astrophysics Data System (ADS)

Ramos-Brito, F.; Murrieta S, H.; Hernández A, J.; Camarillo, E.; García-Hipólito, M.; Martínez-Martínez, R.; Álvarez-Fragoso, O.; Falcony, C.

2006-05-01

Praseodymium doped zirconia powder (ZrO2: (0.53 at%) Pr3+) was prepared by a co-precipitation technique and annealed in air at a temperature Ta = 950 °C. The x-ray diffraction pattern shows a nanocrystalline structure composed of 29.6% monoclinic and 70.4% cubic-tetragonal phases. Medium infrared and Raman analysis confirms the monoclinic/cubic-tetragonal crystalline structure and proves the absence of praseodymium aggregates in the material. Photoluminescent spectroscopy over excitations of 457.9 and 514.9 nm (at 20 K), shows two emission spectra composed of many narrow peaks in the visible-near infrared region (VIS-NIR) of the electromagnetic spectrum, associated with 4f inter-level electronic transitions in praseodymium ions incorporated in the zirconia. Excitation and emission spectra show the different mechanisms of the direct and non-direct excitation of the dopant ion (Pr3+), and the preferential relaxation of the material by charge transfer from the host (zirconia) to the 4f5d band and the 4f inter-level of the dopant ion (Pr3+). No evidence of energy transfer from the host to the dopant was observed.

Quantum state engineering with ultra-short-period (AlN)m/(GaN)n superlattices for narrowband deep-ultraviolet detection.

PubMed

Gao, Na; Lin, Wei; Chen, Xue; Huang, Kai; Li, Shuping; Li, Jinchai; Chen, Hangyang; Yang, Xu; Ji, Li; Yu, Edward T; Kang, Junyong

2014-12-21

Ultra-short-period (AlN)m/(GaN)n superlattices with tunable well and barrier atomic layer numbers were grown by metal-organic vapour phase epitaxy, and employed to demonstrate narrowband deep ultraviolet photodetection. High-resolution transmission electron microscopy and X-ray reciprocal space mapping confirm that superlattices containing well-defined, coherently strained GaN and AlN layers as thin as two atomic layers (∼ 0.5 nm) were grown. Theoretical and experimental results demonstrate that an optical absorption band as narrow as 9 nm (210 meV) at deep-ultraviolet wavelengths can be produced, and is attributable to interband transitions between quantum states along the [0001] direction in ultrathin GaN atomic layers isolated by AlN barriers. The absorption wavelength can be precisely engineered by adjusting the thickness of the GaN atomic layers because of the quantum confinement effect. These results represent a major advance towards the realization of wavelength selectable and narrowband photodetectors in the deep-ultraviolet region without any additional optical filters.

The anomalous C 4 intensity ratio in symbiotic stars

NASA Technical Reports Server (NTRS)

Michalitsianos, A. G.; Kafatos, M.; Fahey, R. P.

1988-01-01

The C IV lambda lambda 1548.2,1550.8 resonance doublet in a symbiotic stars was shown to exhibit anomalous line intensity ratios in which I (lambda 1548.2)/I(lambda 1550.8) less than 1, or less than the optically-thick limit of unity. The R Aquarii-central HII region and RX Puppis exhibit this phenomena. The I(lambda 1548.2)/I(lambda 1550.8) ratio in RX Puppis is found to vary inversely with the total C IV line intensity, and with the FES-visual light, as the object declined over a 5 yr period following a brightening in UV and optical emission which peaked in 1982. This doublet intensity behavior could be explained by a wind which has a narrow velocity range of 600 approx. less than sup v wind approx. less than 1000 km/sec, or by the pumping of the Fe II (mul. 45.01) transition a sup 4 F sub 9/2 - y sup 4 H(o) sub 11/2 by C IV lambda 1548.2, which effectively scatters C IV photons into the Fe II spectrum in these objects.

Spatially resolved images of reactive ions in the Orion Bar

NASA Astrophysics Data System (ADS)

Goicoechea, Javier R.; Cuadrado, Sara; Pety, Jérôme; Bron, Emeric; Black, John H.; Cernicharo, José; Chapillon, Edwige; Fuente, Asunción; Gerin, Maryvonne

2017-05-01

We report high angular resolution (4.9'' × 3.0'') images of reactive ions SH+, HOC+, and SO+ toward the Orion Bar photodissociation region (PDR). We used ALMA-ACA to map several rotational lines at 0.8 mm, complemented with multi-line observations obtained with the IRAM 30 m telescope. The SH+ and HOC+ emission is restricted to a narrow layer of 2''- to 10''-width (≈800 to 4000 AU depending on the assumed PDR geometry) that follows the vibrationally excited H emission. Both ions efficiently form very close to the H/H2 transition zone, at a depth of AV ≲ 1 mag into the neutral cloud, where abundant C+, S2* coexist. SO+ peaks slightly deeper into the cloud. The observed ions have low rotational temperatures (Trot ≈ 10-30 K ≪ Tk) and narrow line-widths ( 2-3 km s-1), a factor of ≃2 narrower that those of the lighter reactive ion CH+. This is consistent with the higher reactivity and faster radiative pumping rates of CH+ compared to the heavier ions, which are driven relatively more quickly toward smaller velocity dispersion by elastic collisions and toward lower Trot by inelastic collisions. We estimate column densities and average physical conditions from an excitation model (n(H2) ≈ 105-106 cm-3, n(e-) ≈ 10 cm-3, and Tk ≈ 200 K). Regardless of the excitation details, SH+ and HOC+ clearly trace the most exposed layers of the UV-irradiated molecular cloud surface, whereas SO+ arises from slightly more shielded layers. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2012.1.00352.S. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada), and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ.Includes IRAM 30 m telescope observations. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).

Emission-line studies of young stars. 4: The optical forbidden lines

NASA Astrophysics Data System (ADS)

Hamann, Fred

1994-08-01

Optical forbidden line strengths and profiles are discussed for a sample of 30 T Tauri stars and 12 Herbig Ae-Be stars. Transitions of (C I), (N II), (O I), (O II), (S II), (Ca II), (Cr II), (Fe II), and (Ni II) are detected. Profile variability occurred in DG Tau and probably other sources. The ensemble profiles can be divided into four generic components that may represent distinct emitting regions; (1) narrow rest-velocity lines, (2) 'low'-velocity lines (peaking at less than or approximately +/- 50 km s-1), (3) 'high'-velocity (usually greater than or approximately +/- 100 km s-1) blueshifted peaks or wings, and (4) high-velocity redshifted peaks. Among T Tauri stars, the rest-velocity lines appear most often in sources with weak and narrow permitted lines, such as the Ca II triplet. The low- and high-velocity blueshifted components usually appear together in sources with strong and broad Ca II triplet lines. If the velocity-shifted lines form in jets, the smallest (full) opening angles required by the profiles are less than or approximately 20 deg for the narrow, blueshifted (Ca II) lines of DG Tau and HL Tau. Other lines in DG Tau are much broader, implying larger opening angles or greater velocity dispersions. The variability in DG Tau also implies significant changes in the collimation or velocity coherence on timescales of a few years. RW Aur and AS 353A have blue- and redshifted line peaks that could form in oppositely directed jets. The strong (S II) lambda 6716 and lambda 6731 lines in RW Aur are exclusively redshifted and require opening angles less than or approximately 60 deg. Measurements of different profiles in the same spectrum show that the physical conditions change with the line-of-sight velocities. The most persistent trends are for more (N II) and (O II) and less (O I) lambda 5577 flux at high velocities. Constraints on the physical conditions are derived by modeling the emission lines via multilevel ions in 'coronal ionization equilibrium.' A single temperature and density cannot fully describe the line spectra in any velocity interval. Temperatures in the (O I) region are 9000 less than or approximately Te less than 14,000 K, and the ionization fraction (of H) is less than 35%. The densities derived from (O I) include ne less than or approximately 5 x 105 to approximately 107 cm-3, but ne greater than or approximately 106 cm-3 obtains only at low velocities. In the (S II) regions the densities are lower, 103 less than or approximately ne less than or approximately 7 x 104 cm-3, and the temperatures are probably higher, Te greater than or approximately 13,000 K. At high velocities (only) there is additional hot gas that produces (N II) and (O II), possibly most of the (S II), and little (O I). This region is characterized by Te greater than or approximately 15,000 K, ne less than or approximately 105 cm-3, and an ionization fraction greater than or approximately 50%.

Emission-line studies of young stars. 4: The optical forbidden lines

NASA Technical Reports Server (NTRS)

Hamann, Fred

1994-01-01

Optical forbidden line strengths and profiles are discussed for a sample of 30 T Tauri stars and 12 Herbig Ae-Be stars. Transitions of (C I), (N II), (O I), (O II), (S II), (Ca II), (Cr II), (Fe II), and (Ni II) are detected. Profile variability occurred in DG Tau and probably other sources. The ensemble profiles can be divided into four generic components that may represent distinct emitting regions; (1) narrow rest-velocity lines, (2) 'low'-velocity lines (peaking at less than or approximately +/- 50 km s(exp -1)), (3) 'high'-velocity (usually greater than or approximately +/- 100 km s(exp -1)) blueshifted peaks or wings, and (4) high-velocity redshifted peaks. Among T Tauri stars, the rest-velocity lines appear most often in sources with weak and narrow permitted lines, such as the Ca II triplet. The low- and high-velocity blueshifted components usually appear together in sources with strong and broad Ca II triplet lines. If the velocity-shifted lines form in jets, the smallest (full) opening angles required by the profiles are less than or approximately 20 deg for the narrow, blueshifted (Ca II) lines of DG Tau and HL Tau. Other lines in DG Tau are much broader, implying larger opening angles or greater velocity dispersions. The variability in DG Tau also implies significant changes in the collimation or velocity coherence on timescales of a few years. RW Aur and AS 353A have blue- and redshifted line peaks that could form in oppositely directed jets. The strong (S II) lambda 6716 and lambda 6731 lines in RW Aur are exclusively redshifted and require opening angles less than or approximately 60 deg. Measurements of different profiles in the same spectrum show that the physical conditions change with the line-of-sight velocities. The most persistent trends are for more (N II) and (O II) and less (O I) lambda 5577 flux at high velocities. Constraints on the physical conditions are derived by modeling the emission lines via multilevel ions in 'coronal ionization equilibrium.' A single temperature and density cannot fully describe the line spectra in any velocity interval. Temperatures in the (O I) region are 9000 less than or approximately T(sub e) less than 14,000 K, and the ionization fraction (of H) is less than 35%. The densities derived from (O I) include n(sub e) less than or approximately 5 x 10(exp 5) to approximately 10(exp 7) cm(exp -3), but n(sub e) greater than or approximately 10(exp 6) cm(exp -3) obtains only at low velocities. In the (S II) regions the densities are lower, 10(exp 3) less than or approximately n(sub e) less than or approximately 7 x 10(exp 4) cm(exp -3), and the temperatures are probably higher, T(sub e) greater than or approximately 13,000 K. At high velocities (only) there is additional hot gas that produces (N II) and (O II), possibly most of the (S II), and little (O I). This region is characterized by T(sub e) greater than or approximately 15,000 K, n(sub e) less than or approximately 10(exp 5) cm(exp -3), and an ionization fraction greater than or approximately 50%. When combined with the spatially segregated emitting regions observed by others by spectral imaging, these results suggest decreasing n(sub e) and increasing T(sub e) away from the star in at least the high velocity gas.

Convective heat transfer in a high aspect ratio minichannel heated on one side

DOE PAGES

Forrest, Eric C.; Hu, Lin -Wen; Buongiorno, Jacopo; ...

2015-10-21

Experimental results are presented for single-phase heat transfer in a narrow rectangular minichannel heated on one side. The aspect ratio and gap thickness of the test channel were 29:1 and 1.96 mm, respectively. Friction pressure drop and Nusselt numbers are reported for the transition and fully turbulent flow regimes, with Prandtl numbers ranging from 2.2 to 5.4. Turbulent friction pressure drop for the high aspect ratio channel is well-correlated by the Blasius solution when a modified Reynolds number, based upon a laminar equivalent diameter, is utilized. The critical Reynolds number for the channel falls between 3500 and 4000, with Nusseltmore » numbers in the transition regime being reasonably predicted by Gnielinski's correlation. The dependence of the heat transfer coefficient on the Prandtl number is larger than that predicted by circular tube correlations, and is likely a result of the asymmetric heating. The problem of asymmetric heating condition is approached theoretically using a boundary layer analysis with a two-region wall layer model, similar to that originally proposed by Prandtl. The analysis clarifies the influence of asymmetric heating on the Nusselt number and correctly predicts the experimentally observed trend with Prandtl number. Furthermore, a semi-analytic correlation is derived from the analysis that accounts for the effect of aspect ratio and asymmetric heating, and is shown to predict the experimental results of this study with a mean absolute error (MAE) of less than 5% for 4000 < Re < 70,000.« less

Positron annihilation studies of Bi 2CaSr 2Cu 2O x and Bi 1.6Pb 0.4Ca 2Sr 2Cu 3O y in the region of the superconducting transition

NASA Astrophysics Data System (ADS)

Pujari, P. K.; Datta, T.; Manohar, S. B.; Prakash, Satya; Sastry, P. V. P. S. S.; Yakhmi, J. V.; Iyer, R. M.

1990-03-01

Doppler broadened annihilation radiation (DBAR) spectral parameters have been reported- for the first time- between 77 K and 300 K, for several Bi-based oxide superconductors, viz. A: single phase (2122) Bi 2CaSr 2Cu 2O x with Tc=85 K (R=0), B: a mixed phase lead doped sample containing both 2122 and 2223 with a nominal composition Bi 1.6Pb 0.4Ca 2Sr 2Cu 3O y, and, C: another 2122+2223 sample with same nominal composition as that of B but synthesised under a different heat-treatment schedule so as to yield a Tc=85 K (R=0). Analyses of these spectra using PAACFIT program yielded two components, of which the intensity of the narrow component, I N, and, the width of the broad component, T B, were seen to be the only temperature dependent parameters. At the onset of superconducting transition both T B and I N were seen to increase to a maximum value and decrease on further cooling. A double peak structure in T B vs temperature profile were observed in sample B and C, similar to one reported by us in Tl-Ca-Ba-Cu-O systems. In addition, presence of a magnetic field (1 KG) yielded no significant change in the DBAR spectral parameters. The results are discussed.

Physics with charmonium - Highlights of BESIII and PANDA

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

Messchendorp, Johan

2014-11-11

The physics of the strong interaction is undoubtedly one of the most challenging areas of modern science. Quantum ChromoDynamics (QCD) is reproducing successfully the physics phenomena at distances much shorter than the size of the nucleon, where perturbation theory can be used yielding results of high precision and predictive power. At larger distance scales, however, perturbative methods cannot be applied anymore, although spectacular phenomena, such as the generation of hadron masses and quark confinement, occur. Studies using charmed quarks and gluon-rich matter have the potential to connect the perturbative and the non-perturbative QCD region. The annihilation of matter with antimattermore » in the mass regime of charmonium is an ideal environment to discover new states or transitions that could reveal the secrets of the strong interaction. Hadronic and electromagnetic transitions between charmonium states and their decays have been measured with a world-record in precision with the BESIII spectrometer at the electron-positron collider at IHEP Beijing, China. Moreover, unconventional narrow charmonium-rich states have been discovered recently in an energy regime above the open-charm threshold, thereby, possibly initiating a new era in charmonium spectroscopy. The near future experiment, PANDA, at the research facility FAIR in Germany, Darmstadt, will exploit the annihilation of cooled anti-protons with protons to perform charmonium spectroscopy with an incredible precision. I will present the most promising results that have been recently obtained with BESIII together with the future perspectives of PANDA in the field of charmonium spectroscopy.« less

Collapse transition in polymer models with multiple monomers per site and multiple bonds per edge

NASA Astrophysics Data System (ADS)

Rodrigues, Nathann T.; Oliveira, Tiago J.

2017-12-01

We present results from extensive Monte Carlo simulations of polymer models where each lattice site can be visited by up to K monomers and no restriction is imposed on the number of bonds on each lattice edge. These multiple monomer per site (MMS) models are investigated on the square and cubic lattices, for K =2 and 3, by associating Boltzmann weights ω0=1 , ω1=eβ1 , and ω2=eβ2 to sites visited by 1, 2, and 3 monomers, respectively. Two versions of the MMS models are considered for which immediate reversals of the walks are allowed (RA) or forbidden (RF). In contrast to previous simulations of these models, we find the same thermodynamic behavior for both RA and RF versions. In three dimensions, the phase diagrams, in space β2×β1 , are featured by coil and globule phases separated by a line of Θ points, as thoroughly demonstrated by the metric νt, crossover ϕt, and entropic γt exponents. The existence of the Θ lines is also confirmed by the second virial coefficient. This shows that no discontinuous collapse transition exists in these models, in contrast to previous claims based on a weak bimodality observed in some distributions, which indeed exists in a narrow region very close to the Θ line when β1<0 . Interestingly, in two dimensions, only a crossover is found between the coil and globule phases.

Physics with charmonium - Highlights of BESIII and PANDA

NASA Astrophysics Data System (ADS)

Messchendorp, Johan

2014-11-01

The physics of the strong interaction is undoubtedly one of the most challenging areas of modern science. Quantum ChromoDynamics (QCD) is reproducing successfully the physics phenomena at distances much shorter than the size of the nucleon, where perturbation theory can be used yielding results of high precision and predictive power. At larger distance scales, however, perturbative methods cannot be applied anymore, although spectacular phenomena, such as the generation of hadron masses and quark confinement, occur. Studies using charmed quarks and gluon-rich matter have the potential to connect the perturbative and the non-perturbative QCD region. The annihilation of matter with antimatter in the mass regime of charmonium is an ideal environment to discover new states or transitions that could reveal the secrets of the strong interaction. Hadronic and electromagnetic transitions between charmonium states and their decays have been measured with a world-record in precision with the BESIII spectrometer at the electron-positron collider at IHEP Beijing, China. Moreover, unconventional narrow charmonium-rich states have been discovered recently in an energy regime above the open-charm threshold, thereby, possibly initiating a new era in charmonium spectroscopy. The near future experiment, PANDA, at the research facility FAIR in Germany, Darmstadt, will exploit the annihilation of cooled anti-protons with protons to perform charmonium spectroscopy with an incredible precision. I will present the most promising results that have been recently obtained with BESIII together with the future perspectives of PANDA in the field of charmonium spectroscopy.

Extended Narrow-Line Region in Seyfert Galaxies

NASA Astrophysics Data System (ADS)

Congiu, Enrico; Contini, Marcella.; Ciroi, Stefano; Cracco, Valentina; Di Mille, Francesco; Berton, Marco; Frezzato, Michele; La Mura, Giovanni; Rafanelli, Piero

2017-10-01

We present our recent results about the extended narrow-line region (ENLR) of two nearby Seyfert 2 galaxies (IC 5063 and NGC 7212) obtained by modelling the observed line profiles and spectra with composite models (photoionization+shocks) in the different regions surrounding the AGN. Then, we compare the Seyfert 2 ENLRs with the very extended one recently discovered in the narrow-line Seyfert 1 (NLS1) galaxy Mrk 783. We have found several evidences of interaction between the ISM of the galaxies and their radio jets, such as a) the contribution of shocks in ionizing the high velocity gas, b) the complex kinematics showed by the profile of the emission lines, c) the high fragmentation of matter, etc. The results suggest that the ENLR of IC 5063 have a hollow bi-conical shape, with one edge aligned to the galaxy disk, which may cause some kind of dependence on velocity of the ionization parameter. Regarding the Mrk 783 properties, it is found that the extension of the optical emission is almost twice the size of the radio one and it seems due to the AGN activity, although there is contamination by star formation around 12 arcsec from the nucleus. Diagnostic diagrams excluded the contribution of star formation in IC 5063 and NGC 7212, while the shock contribution was used to explain the spectra emitted by their high velocity gas.

Narrowing down the region of the Vf locus for scab resistance in apple using AFLP-derived SCARs.

PubMed

Huaracha, E; Xu, M; Korban, S S

2004-01-01

A narrow-down strategy to restrict the Vf region, which controls resistance to the fungal disease apple scab in apple, to a genetic distance of 0.4 cM is presented. Using 11 AFLP-derived SCARs and three RAPD-derived SCARs, all linked to the Vf gene, we subjected 1,412 scab-resistant individuals from 16 mapping populations to genotype analysis. Eleven recombinant individuals were identified within a genetic distance of 0.9 cM around the Vf gene. Using these 11 recombinants, we achieved fine-resolution of several AFLP-derived SCAR markers surrounding the Vf gene, resulting in the following genetic linkage map: ACS-6 and ACS are located left of the Vf gene at genetic distances of 0.2 cM and 0.1 cM, respectively; ACS-7 and ACS-9 are inseparable from the Vf gene; ACS-8, ACS-10, and ACS-4 are located to the right of the Vf gene at genetic distances of 0.1 cM, 0.4 cM, and 0.5 cM, respectively; the remaining five SCARs-ACS-11, ACS-5, ACS-2, ACS-1, and AL07-are inseparable and are located right of the Vf gene at a genetic distance of 0.7 cM. By integrating this linkage data with our previous physical map, we generated a revised map of the narrowed-down region of Vf.

Flat tensile specimen design for advanced composites

NASA Technical Reports Server (NTRS)

Worthem, Dennis W.

1990-01-01

Finite element analyses of flat, reduced gage section tensile specimens with various transition region contours were performed. Within dimensional constraints, such as maximum length, tab region width, gage width, gage length, and minimum tab length, a transition contour radius of 41.9 cm produced the lowest stress values in the specimen transition region. The stresses in the transition region were not sensitive to specimen material properties. The stresses in the tab region were sensitive to specimen composite and/or tab material properties. An evaluation of stresses with different specimen composite and tab material combinations must account for material nonlinearity of both the tab and the specimen composite. Material nonlinearity can either relieve stresses in the composite under the tab or elevate them to cause failure under the tab.

Energy balance in the solar transition region. II - Effects of pressure and energy input on hydrostatic models

NASA Technical Reports Server (NTRS)

Fontenla, J. M.; Avrett, E. H.; Loeser, R.

1991-01-01

The radiation of energy by hydrogen lines and continua in hydrostatic energy-balance models of the transition region between the solar chromosphere and corona is studied using models which assume that mechanical or magnetic energy is dissipated in the hot corona and is then transported toward the chromosphere down the steep temperature gradient of the transition region. These models explain the average quiet sun and also the entire range of variability of the Ly-alpha lines. The relations between the downward energy flux, the pressure of the transition region, and the different hydrogen emission are described.

Mechanical heating in the transition region

NASA Technical Reports Server (NTRS)

Withbroe, G.

1981-01-01

Attention is focused on the energy balance in the transition region and the role that mechanical heating plays in determining the temperature density structure of this region in a stellar atmosphere. Because of its role as the interface layer through which mass and energy flow between the chromospheres and corona, direct deposition of mechanical energy is a relatively unimportant factor in the overall energy balance in the transition region, except in the uppermost layers where the temperature approaches coronal values.

Edge-induced Schottky barrier modulation at metal contacts to exfoliated molybdenum disulfide flakes

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

Nouchi, Ryo, E-mail: r-nouchi@21c.osakafu-u.ac.jp

2016-08-14

Ultrathin two-dimensional semiconductors obtained from layered transition-metal dichalcogenides such as molybdenum disulfide (MoS{sub 2}) are promising for ultimately scaled transistors beyond Si. Although the shortening of the semiconductor channel is widely studied, the narrowing of the channel, which should also be important for scaling down the transistor, has been examined to a lesser degree thus far. In this study, the impact of narrowing on mechanically exfoliated MoS{sub 2} flakes was investigated according to the channel-width-dependent Schottky barrier heights at Cr/Au contacts. Narrower channels were found to possess a higher Schottky barrier height, which is ascribed to the edge-induced band bendingmore » in MoS{sub 2}. The higher barrier heights degrade the transistor performance as a higher electrode-contact resistance. Theoretical analyses based on Poisson's equation showed that the edge-induced effect can be alleviated by a high dopant impurity concentration, but this strategy should be limited to channel widths of roughly 0.7 μm because of the impurity-induced charge-carrier mobility degradation. Therefore, proper termination of the dangling bonds at the edges should be necessary for aggressive scaling with layered semiconductors.« less

Health transition in Brazil: regional variations and divergence/convergence in mortality.

PubMed

Borges, Gabriel Mendes

2017-08-21

This study analyzes the main characteristics of the health transition in Brazil and its five major regions, using a framework that accounts for regional inequalities in mortality trends. The regional mortality divergence/convergence process is described and discussed by considering the specific contributions of age groups and causes of death in life expectancy variations. Results show that mortality change in Brazil has follow the epidemiologic transition theory to some extent during the period under analysis - for instance, the sharp decline in infant mortality in all regions (first from infectious and parasitic diseases and then from causes associated with the perinatal period) and the increase in the participation of chronic and degenerative diseases as the main cause of death. However, some features of Brazilian transition have not followed the linear and unidirectional pattern proposed by the epidemiologic transition theory, which helps to understand the periods of regional divergence in life expectancy, despite the long-term trends showing reducing regional inequalities. The emergence of HIV/AIDS, the persistence of relatively high levels of other infections and parasitic diseases, the regional differences in the unexpected mortality improvements from cardiovascular diseases, and the rapid and strong variations in mortality from external causes are some of the examples.

Increased impedance near cut-off in plasma-like media leading to emission of high-power, narrow-bandwidth radiation

PubMed Central

Hur, M. S.; Ersfeld, B.; Noble, A.; Suk, H.; Jaroszynski, D. A.

2017-01-01

Ultra-intense, narrow-bandwidth, electromagnetic pulses have become important tools for exploring the characteristics of matter. Modern tuneable high-power light sources, such as free-electron lasers and vacuum tubes, rely on bunching of relativistic or near-relativistic electrons in vacuum. Here we present a fundamentally different method for producing narrow-bandwidth radiation from a broad spectral bandwidth current source, which takes advantage of the inflated radiation impedance close to cut-off in a medium with a plasma-like permittivity. We find that by embedding a current source in this cut-off region, more than an order of magnitude enhancement of the radiation intensity is obtained compared with emission directly into free space. The method suggests a simple and general way to flexibly use broadband current sources to produce broad or narrow bandwidth pulses. As an example, we demonstrate, using particle-in-cell simulations, enhanced monochromatic emission of terahertz radiation using a two-colour pumped current source enclosed by a tapered waveguide. PMID:28071681

Increased impedance near cut-off in plasma-like media leading to emission of high-power, narrow-bandwidth radiation

NASA Astrophysics Data System (ADS)

Hur, M. S.; Ersfeld, B.; Noble, A.; Suk, H.; Jaroszynski, D. A.

2017-01-01

Ultra-intense, narrow-bandwidth, electromagnetic pulses have become important tools for exploring the characteristics of matter. Modern tuneable high-power light sources, such as free-electron lasers and vacuum tubes, rely on bunching of relativistic or near-relativistic electrons in vacuum. Here we present a fundamentally different method for producing narrow-bandwidth radiation from a broad spectral bandwidth current source, which takes advantage of the inflated radiation impedance close to cut-off in a medium with a plasma-like permittivity. We find that by embedding a current source in this cut-off region, more than an order of magnitude enhancement of the radiation intensity is obtained compared with emission directly into free space. The method suggests a simple and general way to flexibly use broadband current sources to produce broad or narrow bandwidth pulses. As an example, we demonstrate, using particle-in-cell simulations, enhanced monochromatic emission of terahertz radiation using a two-colour pumped current source enclosed by a tapered waveguide.

Phase relations in a harzburgite composition: implications for splitting of 660-km seismic discontinuity and seismic velocities in mantle transition zone

NASA Astrophysics Data System (ADS)

Nishiyama, N.; Kato, T.; Kinoshita, Y.; Irifune, T.

2011-12-01

Subducting slab is composed of chemically differentiated rocks: The top layer is MORB, which is underlain by harzburgite, and the bottom part is undifferentiated mantle rock, pyrolite. Harzburgite is the residual of melting at mid oceanic ridge and is depleted in Al, Ca, and Fe. One of the roles of slab subduction is transportation of chemically differentiated rocks, MORB and harzburgite into the earth's interior. Seismic tomographic images show that slab stagnation at mantle transition zone (MTZ) occurs in many subduction zones, which implies that harzbrugite component exits in MTZ. We studied phase relations in a harzbugite composition at pressures between 16 and 25 GPa and at temperatures between 1673 and 1873 K. At 16.5 GPa, a mineral assemblage of wadsleyite (Wd) + clinopyroxene (CPx) + garnet (Gt) was observed, whereas, at 17.5 GPa, Wd + Gt + stishovite (St) was stabilized, which indicates that MgSiO3-rich component transforms into Wd + St at about 17 GPa (500 km depth). At about 18 GPa, we observed a phase transition from Wd to ringwoodite (Rw). The mineral assemblage, Rw + St + Gt, is stable between 18 and 21 GPa (520-600 km depth). At 22 GPa, the non-olivine component transforms into akimotoite (Ak) with minor Gt. The stability field of Ak is narrow and Ak to MgSiO3-rich perovskite (Pv) transition occurs at 22. 5 GPa, which indicates that Rw coexists with Pv at the bottom of MTZ in harzburgite. At 24 GPa, postspinel transition occurs in olivine component. In the Al-poor system, harzburgite, the Pv-forming transition in non-olivine component occurs at a pressure below the post-spinel transition. In general, harzburgite is less dense than the surrounding pyrolite because of the low Fe content, but, between 630 and 660 km depth, harzburgite with a mineral assemblage of Rw + Pv + Gt is denser than the surrounding pyrolite, which consists of Rw + Gt + Ca-perovskite. The high density of harzburgite at the bottom of MTZ is originated by the presence of a high density phase, Pv, and can cause the accumulation of harzburgite component at the base of MTZ. We calculated seismic velocities, Vp and Vs, of harzburgite using thermoelastic parameters determined in previous studies. Harzburgite is faster than pyrolite and 1D earth models, like PREM, at the lower half of MTZ (between 500 and 660 km depth) because of presence of St, Ak, and Pv in addition to the lower density caused by the low-Fe content. It has been demonstrated that pyrolite is slower than the 1D earth models in this region because of low velocity of majorite garnet. Mechanical mixture of pyrolite and harzgurgite can explain 1D earth models, which strongly indicates that harzburgite is accumulated and stagnant at the base of the MTZ. In addition, harzburgite can produce many seismic discontinuities in the non-olivine component, like Ak-Pv transition at 630 km depth, which are superimposed on phase transitions in olivine. Thus, presence of harzburgite in MTZ may explain regionally observed splitting of seismic discontinuities. The splitting of the seismic discontinuities may be caused by chemical heterogeneity, presence of harzburgite.

Linkage Disequilibrium Mapping in Domestic Dog Breeds Narrows the Progressive Rod-Cone Degeneration (prcd) Interval and Identifies Ancestral Disease Transmitting Chromosome

PubMed Central

Goldstein, Orly; Zangerl, Barbara; Pearce-Kelling, Sue; Sidjanin, Duska J.; Kijas, James W.; Felix, Jeanette; Acland, Gregory M; Aguirre, Gustavo D.

2014-01-01

Canine progressive rod-cone degeneration (prcd) is a retinal disease previously mapped to a broad, gene-rich centromeric region of canine chromosome 9. As allelic disorders are present in multiple breeds, we used linkage disequilibrium (LD) to narrow the ∼6.4 Mb interval candidate region. Multiple dog breeds, each representing genetically isolated populations, were typed for SNPs and other polymorphisms identified from BACs. The candidate region was initially localized to a 1.5 Mb zero recombination interval between growth factor receptor-bound protein 2 (GRB2) and SEC14-like 1 (SEC14L). A fine-scale haplotype of the region was developed which reduced the LD interval to 106 Kb, and identified a conserved haplotype of 98 polymorphisms present in all prcd-affected chromosomes from 14 different dog breeds. The findings strongly suggest that a common ancestor transmitted the prcd disease allele to many of the modern dog breeds, and demonstrate the power of LD approach in the canine model. PMID:16859891

Exploratory Investigation of Failure Mechanisms in Transition Regions between Solid Laminates and X-cor(registered tm) Truss Sandwich

NASA Technical Reports Server (NTRS)

OBrien, T. Kevin; Paris, Isabelle L.

2004-01-01

Small sub-component specimens consisting of solid laminates at the ends that transition to X-cor(R) truss sandwich in the center, were tested in a combination of three point bending, uni-axial tension, and combined tension and bending. The failure process in the transition region was documented for each loading using digital video and high-resolution cameras. For the 3-point bending tests, most of the deformation occurred in the solid laminate regions on either end of the specimen. Some pin debonding from the skin of the X-cor(R) truss sandwich was observed in the transition region and was accompanied by audible "pings" throughout the loading. Tension loaded specimens failed in the sandwich skin in the middle of the gage length, accompanied by separation of the sandwich core from the back skin and by delamination between the top skin and bottom skin at the transition region. The pinging associated with pin debonding occurred as the load was increased. However, the frequency of the pinging exceeded any visual observations of pin debonding in the video of the transition region. For specimens tested in combined tension and bending, the greatest amount of pinging occurred during initial application of the axial load. High-resolution images in the transition region indicated that the pinging corresponded to pins debonding and buckling due to the through-thickness Poisson contraction of the specimen. This buckling continued to a much smaller extent as the transverse load was applied.

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

Dodson-Robinson, Sarah E.; Salyk, Colette, E-mail: sdr@astro.as.utexas.edu

Although there has yet been no undisputed discovery of a still-forming planet embedded in a gaseous protoplanetary disk, the cleared inner holes of transitional disks may be signposts of young planets. Here, we show that the subset of accreting transitional disks with wide, optically thin inner holes of 15 AU or more can only be sculpted by multiple planets orbiting inside each hole. Multiplanet systems provide two key ingredients for explaining the origins of transitional disks. First, multiple planets can clear wide inner holes where single planets open only narrow gaps. Second, the confined, non-axisymmetric accretion flows produced by multiplemore » planets provide a way for an arbitrary amount of mass transfer to occur through an apparently optically thin hole without overproducing infrared excess flux. Rather than assuming that the gas and dust in the hole are evenly and axisymmetrically distributed, one can construct an inner hole with apparently optically thin infrared fluxes by covering a macroscopic fraction of the hole's surface area with locally optically thick tidal tails. We also establish that other clearing mechanisms, such as photoevaporation, cannot explain our subset of accreting transitional disks with wide holes. Transitional disks are therefore high-value targets for observational searches for young planetary systems.« less

Structure of siderite FeCO[subscript 3] to 56 GPa and hysteresis of its spin-pairing transition

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

Lavina, Barbara; Dera, Przemyslaw; Downs, Robert T.

2010-09-17

The structure of siderite, FeCO{sub 3}, was determined to 56 GPa, beyond the spin-pairing transition of its iron d electrons. Fe{sup 2+} in the siderite structure is in the high-spin state at low pressures and transforms to the low-spin (LS) state over a narrow pressure range, 44 to 45 GPa, that is concomitant with a shrinkage of the octahedral bond distance by 4%, and a volume collapse of 10%. The structural rearrangements associated with the electronic transition are nearly isotropic in contrast with other properties of siderite, which mostly are highly anisotropic. Robust refinements of the crystal structure from single-crystalmore » x-ray diffraction data were performed at small pressure intervals in order to accurately evaluate the variation in the interatomic distances and to define the geometry of the carbonate hosting LS-Fe{sup 2+}. Thermal vibrations are remarkably lowered in the LS-Sd as shown by atomic displacement parameters. The formation of like-spin domains at the transition shows a hysteresis of more than 3 GPa, compatible with a strong cooperative contribution of neighboring clusters to the transition.« less

Generative rules of Drosophila locomotor behavior as a candidate homology across phyla.

PubMed

Gomez-Marin, Alex; Oron, Efrat; Gakamsky, Anna; Dan Valente; Benjamini, Yoav; Golani, Ilan

2016-06-08

The discovery of shared behavioral processes across phyla is a significant step in the establishment of a comparative study of behavior. We use immobility as an origin and reference for the measurement of fly locomotor behavior; speed, walking direction and trunk orientation as the degrees of freedom shaping this behavior; and cocaine as the parameter inducing progressive transitions in and out of immobility. We characterize and quantify the generative rules that shape Drosophila locomotor behavior, bringing about a gradual buildup of kinematic degrees of freedom during the transition from immobility to normal behavior, and the opposite narrowing down into immobility. Transitions into immobility unfold via sequential enhancement and then elimination of translation, curvature and finally rotation. Transitions out of immobility unfold by progressive addition of these degrees of freedom in the opposite order. The same generative rules have been found in vertebrate locomotor behavior in several contexts (pharmacological manipulations, ontogeny, social interactions) involving transitions in-and-out of immobility. Recent claims for deep homology between arthropod central complex and vertebrate basal ganglia provide an opportunity to examine whether the rules we report also share common descent. Our approach prompts the discovery of behavioral homologies, contributing to the elusive problem of behavioral evolution.

Coherently Coupled ZnO and VO2 Interface studied by Photoluminescence and electrical transport across a phase transition

NASA Astrophysics Data System (ADS)

Srivastava, Amar; Saha, S.; Annadi, A.; Zhao, Y. L.; Gopinadhan, K.; Wang, X.; Naomi, N.; Liu, Z. Q.; Dhar, S.; Herng, T. S.; Nina, Bao; Ariando, -; Ding, Jun; Venkatesan, T.

2012-02-01

In this work we report a study of a coherently coupled interface consisting of a ZnO layer grown on top of an oriented VO2 layer on sapphire by photoluminescence and electrical transport measurements across the VO2 metal insulator phase transition (MIT). The photoluminescence of the ZnO layer showed a broad hysteresis induced by the phase transition of VO2 while the width of the electrical hysteresis was narrow and unaffected by the over layer. The enhanced width of the PL hysteresis was due to the formation of defects during the MIT as evidenced by a broad hysteresis in the opposite direction to that of the band edge PL in the defect luminescense. Unlike VO2 the defects in ZnO did not fully recover across the phase transition. From the defect luminescence data, oxygen interstitials were found to be the predominant defects in ZnO mediated by the strain from the VO2 phase transition. Such coherently coupled interfaces could be of use in characterizing the stability of a variety of interfaces and also for novel device application.

X-linked infantile spinal muscular atrophy: clinical definition and molecular mapping.

PubMed

Dressman, Devin; Ahearn, Mary Ellen; Yariz, Kemal O; Basterrecha, Hugo; Martínez, Francisco; Palau, Francesc; Barmada, M Michael; Clark, Robin Dawn; Meindl, Alfons; Wirth, Brunhilde; Hoffman, Eric P; Baumbach-Reardon, Lisa

2007-01-01

X-linked infantile spinal-muscular atrophy (XL-SMA) is a rare disorder, which presents with the clinical characteristics of hypotonia, areflexia, and multiple congenital contractures (arthrogryposis) associated with loss of anterior horn cells and death in infancy. We have previously reported a single family with XL-SMA that mapped to Xp11.3-q11.2. Here we report further clinical description of XL-SMA plus an additional seven unrelated (XL-SMA) families from North America and Europe that show linkage data consistent with the same region. We first investigated linkage to the candidate disease gene region using microsatellite repeat markers. We further saturated the candidate disease gene region using polymorphic microsatellite repeat markers and single nucleotide polymorphisms in an effort to narrow the critical region. Two-point and multipoint linkage analysis was performed using the Allegro software package. Linkage analysis of all XL-SMA families displayed linkage consistent with the original XL-SMA region. The addition of new families and new markers has narrowed the disease gene interval for a XL-SMA locus between SNP FLJ22843 near marker DXS 8080 and SNP ARHGEF9 which is near DXS7132 (Xp11.3-Xq11.1).

Coupled channels description of the α-decay fine structure

NASA Astrophysics Data System (ADS)

Delion, D. S.; Ren, Zhongzhou; Dumitrescu, A.; Ni, Dongdong

2018-05-01

We review the coupled channels approach of α transitions to excited states. The α-decaying states are identified as narrow outgoing Gamow resonances in an α-daughter potential. The real part of the eigenvalue corresponds to the Q-value, while the imaginary part determines the half of the total α-decay width. We first review the calculations describing transitions to rotational states treated by the rigid rotator model, in even–even, odd-mass and odd–odd nuclei. It is found that the semiclassical method overestimates the branching ratios to excited 4+ for some even–even α-emitters and fails in explaining the unexpected inversion of branching ratios of some odd-mass nuclei, while the coupled-channels results show good agreement with the experimental data. Then, we review the coupled channels method for α-transitions to 2+ vibrational and transitional states. We present the results of the Coherent State Model that describes in a unified way the spectra of vibrational, transitional and rotational nuclei. We evidence general features of the α-decay fine structure, namely the linear dependence between α-intensities and excitation energy, the linear correlation between the strength of the α-core interaction and spectroscopic factor, and the inverse correlation between the nuclear collectivity, given by electromagnetic transitions, and α-clustering.

Magnetic field-induced modification of selection rules for Rb D 2 line monitored by selective reflection from a vapor nanocell

NASA Astrophysics Data System (ADS)

Klinger, Emmanuel; Sargsyan, Armen; Tonoyan, Ara; Hakhumyan, Grant; Papoyan, Aram; Leroy, Claude; Sarkisyan, David

2017-08-01

Magnetic field-induced giant modification of the probabilities of five transitions of 5S1 / 2,Fg = 2 → 5P3 / 2,Fe = 4 of 85Rb and three transitions of 5S1 / 2,Fg = 1 → 5P3 / 2,Fe = 3 of 87Rb forbidden by selection rules for zero magnetic field has been observed experimentally and described theoretically for the first time. For the case of excitation with circularly-polarized (σ+) laser radiation, the probability of Fg = 2,mF = - 2 → Fe = 4,mF = - 1 transition becomes the largest among the seventeen transitions of 85Rb Fg = 2 → Fe = 1,2,3,4 group, and the probability of Fg = 1, mF = - 1 → Fe = 3,mF = 0 transition becomes the largest among the nine transitions of 87Rb Fg = 1 → Fe = 0,1,2,3 group, in a wide range of magnetic field 200-1000 G. Complete frequency separation of individual Zeeman components was obtained by implementation of derivative selective reflection technique with a 300 nm-thick nanocell filled with Rb, allowing formation of narrow optical resonances. Possible applications are addressed. The theoretical model is well consistent with the experimental results.

Eta Carinae across the 2003.5 Minimum: Analysis in the Visible and Near Infrared Spectral Region

NASA Technical Reports Server (NTRS)

Nielsen, K. E.; Kober, G. Vieira; Weis, K.; Gull, T.; Stahl, O.; Bomans, D. J.

2008-01-01

We present analysis of the visible through near infrared spectrum of eta Car and its ejecta obtained during the 'eta Car Campaign with the Ultraviolet Visual Echelle Spectrograph (UVES) at the ESO Very Large Telescope (VLT)'. This is a part of larger effort to present a complete eta Car spectrum, and extends the previously presented analyses with the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) in the UV (1240-3159 A) to 10,430 A. The spectrum in the mid and near UV is characterized by the ejecta absorption. At longer wavelengths, stellar wind features from the central source and narrow emission lines from the Weigelt condensations dominate the spectrum. However, narrow absorption lines from the circumstellar shells are present. This paper provides a description of the spectrum between 3060 and 10,430 A, including line identifications of the ejecta absorption spectrum, the emission spectrum from the Weigelt condensations and the P-Cygni stellar wind features. The high spectral resolving power of VLT/UVES enables equivalent width measurements of atomic and molecular absorption lines for elements with no transitions at the shorter wavelengths. However, the ground based seeing and contributions of nebular scattered radiation prevent direct comparison of measured equivalent widths in the VLT/UVES and HST/STIS spectra. Fortunately, HST/STIS and VLT/UVES have a small overlap in wavelength coverage which allows us to compare and adjust for the difference in scattered radiation entering the instruments apertures. This paper provide a complete online VLT/UVES spectrum with line identifications and a spectral comparison between HST/STIS and VLT/UVES between 3060 and 3160 A.

Eta Carinae across the 2003.5 Minimum: Analysis in the Visible and Near Infrared Spectral Region

NASA Technical Reports Server (NTRS)

Nielsen, K. E.; Kober, G. Vieira; Weis, K.; Gull, T. R.; Stahl, O.; Bomans, D. J.

2009-01-01

We present an analysis of the visible through near infrared spectrum of Eta Car and its ejecta obtained during the "Eta Car Campaign with the Ultraviolet and Visual Echelle Spectrograph (UVES) at the ESO Very Large Telescope (VLT)". This is a part of the larger effort to present a complete Eta Car spectrum, and extends the previously presented analyses with the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) in the UV (1240-3159 Angstrom) to 10,430 Angstrom. The spectrum in the mid and near UV is characterized by the ejecta absorption. At longer wavelengths, stellar wind features from the central source and narrow emission lines from the Weigelt condensations dominate the spectrum. However, narrow absorption lines from the circumstellar shells are present. This paper provides a description of the spectrum between 3060 and 10,430 Angstroms, including line identifications of the ejecta absorption spectrum, the emission spectrum from the Weigelt condensations and the P-Cygni stellar wind features. The high spectral resolving power of VLT/UVES enables equivalent width measurements of atomic and molecular absorption lines for elements with no transitions at the shorter wavelengths. However, the ground based seeing and contributions of nebular scattered radiation prevent direct comparison of measured equivalent widths in the VLT/UVES and HST/STIS spectra. Fortunately, HST/STIS and VLT/UVES have a small overlap in wavelength coverage which allows us to compare and adjust for the difference in scattered radiation entering the instruments' apertures. This paper provides a complete online VLT/UVES spectrum with line identifications and a spectral comparison between HST/STIS and VLT/UVES between 3060 and 3160 Angstroms.