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Sample records for neutral wind structures

  1. Sq Currents and Neutral Winds

    NASA Astrophysics Data System (ADS)

    Yamazaki, Y.

    2015-12-01

    The relationship between ionospheric dynamo currents and neutral winds is examined using the Thermosphere Ionosphere Mesosphere Electrodynamic General Circulation Model (TIME-GCM). The simulation is run for May and June 2009 with variable neutral winds but with constant solar and magnetospheric energy inputs, which ensures that day-to-day changes in the solar quiet (Sq) current system arise only from lower atmospheric forcing. The intensity and focus position of the simulated Sq current system exhibit large day-to-day variability, as is also seen in ground magnetometer data. We show how the day-to-day variation of the Sq current system relate to variable winds at various altitudes, latitudes, and longitudes.

  2. Neutral wind results from TIMED Doppler interferometer

    NASA Astrophysics Data System (ADS)

    Killeen, T.; Gablehouse, R.; Gell, D.; Johnson, R.; Niciejewski, R.; Ortland, D.; Wu, Q.; Skinner, W.; Solomon, S.; Kafkalidis, J.

    2003-04-01

    Since the launch of the NASA Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite in December 2001, the TIMED Doppler Interferometer (TIDI) has been collecting lower thermosphere and mesospheric data for over a year. After adjustments to the spectral sampling scheme and operational mode, the instrument has been optimized. Efforts have also been made to improve the instrument performance. Preliminary neutral winds from O2 (0-0) have been analyzed. Tidal features and their seasonal variation are shown clearly in the wind data, which are quantitatively consistent with model prediction. We will report our progress on these efforts.

  3. Neutral wind estimation from 4-D ionospheric electron density images

    NASA Astrophysics Data System (ADS)

    Datta-Barua, S.; Bust, G. S.; Crowley, G.; Curtis, N.

    2009-06-01

    We develop a new inversion algorithm for Estimating Model Parameters from Ionospheric Reverse Engineering (EMPIRE). The EMPIRE method uses four-dimensional images of global electron density to estimate the field-aligned neutral wind ionospheric driver when direct measurement is not available. We begin with a model of the electron continuity equation that includes production and loss rate estimates, as well as E × B drift, gravity, and diffusion effects. We use ion, electron, and neutral species temperatures and neutral densities from the Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIMEGCM-ASPEN) for estimating the magnitude of these effects. We then model the neutral wind as a power series at a given longitude for a range of latitudes and altitudes. As a test of our algorithm, we have input TIMEGCM electron densities to our algorithm. The model of the neutral wind is computed at hourly intervals and validated by comparing to the “true” TIMEGCM neutral wind fields. We show results for a storm day: 10 November 2004. The agreement between the winds derived from EMPIRE versus the TIMEGCM “true” winds appears to be time-dependent for the day under consideration. This may indicate that the diurnal variation in certain driving processes impacts the accuracy of our neutral wind model. Despite the potential temporal and spatial limits on accuracy, estimating neutral wind speed from measured electron density fields via our algorithm shows great promise as a complement to the more sparse radar and satellite measurements.

  4. Modeling of the coupled magnetospheric and neutral wind dynamos

    NASA Technical Reports Server (NTRS)

    Thayer, Jeffrey P.

    1994-01-01

    This report summarizes the progress made in the first year of NASA Grant No. NAGW-3508 entitled 'Modeling of the Coupled Magnetospheric and Neutral Wind Dynamos.' The approach taken has been to impose magnetospheric boundary conditions with either pure voltage or current characteristics and solve the neutral wind dynamo equation under these conditions. The imposed boundary conditions determine whether the neutral wind dynamo will contribute to the high-latitude current system or the electric potential. The semi-annual technical report, dated December 15, 1993, provides further detail describing the scientific and numerical approach of the project. The numerical development has progressed and the dynamo solution for the case when the magnetosphere acts as a voltage source has been evaluated completely using spectral techniques. The simulation provides the field-aligned current distribution at high latitudes due to the neutral wind dynamo. A number of geophysical conditions can be simulated to evaluate the importance of the neutral wind dynamo contribution to the field-aligned current system. On average, field-aligned currents generated by the neutral wind dynamo contributed as much as 30 percent to the large-scale field-aligned current system driven by the magnetosphere. A term analysis of the high-latitude neutral wind dynamo equation describing the field aligned current distribution has also been developed to illustrate the important contributing factors involved in the process. The case describing the neutral dynamo response for a magnetosphere acting as a pure current generator requires the existing spectral code to be extended to a pseudo-spectral method and is currently under development.

  5. Neutral wind effects on ion outflow at Mars

    NASA Astrophysics Data System (ADS)

    Andersson, L.; Ergun, R. E.

    2012-02-01

    This paper evaluates the influence of neutral winds on ions using the CAPIT (Combined Atmospheric Photochemistry and Ion Tracking) code, which includes ionospheric photochemistry and plasma wave energization. Based on two different wind profiles, ion outflow is, to first order, not sensitive to neutral winds. However, the ion density profiles are clearly affected by neutral winds at the exobase. For example, the direction of a strong neutral wind will dramatically change the location of the highest ion densities. This finding suggests that strongly varying neutral winds at the exobase complicate the analysis of in-situ observations. To evaluate dynamic effects of the different magnetic field configurations, crustal fields are included in the simulation domain. The outflow of O2 + ions is the most dynamic, partly because the photochemical production is almost a factor of two larger than the photochemical loss so loss to space is important (for other ions, this ratio is closer to one and loss to space is small compared to photochemical production). Since the photochemical production rate of O2 + is relatively slow, it takes time to replenish O2 + that is lost to space, so loss to space over long periods should be relatively constant.

  6. Wind Turbine Structural Dynamics

    NASA Technical Reports Server (NTRS)

    Miller, D. R. (Editor)

    1978-01-01

    A workshop on wind turbine structural dynamics was held to review and document current United States work on the dynamic behavior of large wind turbines, primarily of the horizontal-axis type, and to identify and discuss other wind turbine configurations that may have lower cost and weight. Information was exchanged on the following topics: (1) Methods for calculating dynamic loads; (2) Aeroelasticity stability (3) Wind loads, both steady and transient; (4) Critical design conditions; (5) Drive train dynamics; and (6) Behavior of operating wind turbines.

  7. Modeling of the coupled magnetospheric and neutral wind dynamos

    NASA Technical Reports Server (NTRS)

    Thayer, Jeff P.

    1993-01-01

    The solar wind interaction with the earth's magnetosphere generates electric fields and currents that flow from the magnetosphere to the ionosphere at high latitudes. Consequently, the neutral atmosphere is subject to the dissipation and conversion of this electrical energy to thermal and mechanical energy through Joule heating and Lorentz forcing. As a result of the mechanical energy stored within the neutral wind (caused in part by Lorentz--and pressure gradient--forces set up by the magnetospheric flux of electrical energy), electric currents and fields can be generated in the ionosphere through the neutral wind dynamo mechanism. At high latitudes this source of electrical energy has been largely ignored in past studies, owing to the assumed dominance of the solar wind/magnetospheric dynamo as an electrical energy source to the ionosphere. However, other researchers have demonstrated that the available electrical energy provided by the neutral wind is significant at high latitudes, particularly in the midnight sector of the polar cap and in the region of the magnetospheric convection reversal. As a result, the conclusions of a number of broad ranging high-latitude investigations may be modified if the neutral-wind contribution to high-latitude electrodynamics is properly accounted for. These include the following: studies assessing solar wind-magnetospheric coupling by comparing the cross polar cap potential with solar wind parameters; research based on the alignment of particle precipitation with convection or field aligned current boundaries; and synoptic investigations attributing seasonal variations in the observed electric field and current patterns to external sources. These research topics have been initiated by satellite and ground-based observations and have been attributed to magnetospheric causes. However, the contribution of the neutral wind to the high-latitude electric field and current systems and their seasonal and local time dependence has yet

  8. Day-To-Night Ionosphere Transport by Neutral Winds

    NASA Astrophysics Data System (ADS)

    Grebowsky, J. M.; Bougher, S. W.; Benna, M.

    2015-12-01

    Nightside low altitude nightside ionosphere production sources for the terrestrial planets are either transport from the dayside and production due to energetic particle impacts. The transport can be driven by ion coupling to the neutral atmosphere motions as part of the general atmospheric global circulation patterns and/or by ionosphere density gradients near the terminators produced as a result of a dayside source of ionization (photoionization) and a nightside sink (chemical losses). The day to night transport of ionization at high altitudes on Venus (during solar max and at Earth maintains the ionosphere throughout the night. This is not the case for Mars, where the dense ionosphere carried from the day does not extend much further than ~120 degrees solar zenith angle. Although predicted neutral wind speeds in the lower thermosphere of Mars are comparable to those on Earth and Venus, the winds at Mars can have larger impacts on horizontal transport since the planet's circumference is much smaller. One prominent effect of the winds is indicated by the observed rapid global dispersal of long-lived metal ions associated following the short, localized impact of the meteor storm associated with Comet Siding Spring . This paper will explore wind control of the low altitude Mars ionosphere ion composition measurements across the terminator from day into night, using the Neutral Gas Ion Mass Spectrometer instrument on MAVEN with the wind patterns predicted by the Mars Global Ionosphere-Thermosphere Model (M-GITM).

  9. Solar Wind - Mars Interactions: Energetic Neutral Atom Production

    NASA Astrophysics Data System (ADS)

    Friedrich, Erena; Yau, Andrew; Brackbill, Jerry

    2012-10-01

    We study the energetic neutral atoms (ENAs) that are formed by charge exchange between solar wind ions and neutral particles in the Martian atmosphere. Mars Global Surveyor has shown that Mars has no notable global intrinsic magnetic field. Consequently, the neutral particles in the Martian atmosphere are unshielded from the flow of energetic solar wind protons. There results extensive production of energetic neutral hydrogen atoms (H-ENAs). In our study, we use a 3D hybrid (kinetic ions, fluid electrons), quasi-neutral, particle-in-cell (PIC) plasma simulation to investigate the production of H-ENAs due to collisions with neutral oxygen (O, O) and nitrogen (N) molecules in the near-space environment of Mars. A detailed chemical model that comprises multi-species reactions, such as ionization by photons, electron recombination, particle collisions, and charge exchange, is self-consistently included in the simulation. These chemical interactions, which take place between ions, atoms, and molecules in the martian exosphere and ionosphere, control the production of the H-ENAs. What is presented is a ``work in progress'' highlighting the ionospheric chemical and physical model as we work towards our goal of computing the flux of escaping H-ENAs due to charge exchange.

  10. Compact Ion and Neutral Mass Spectrometer with Ion Drifts, Temperatures and Neutral Winds

    NASA Astrophysics Data System (ADS)

    Paschalidis, Nikolaos

    2016-07-01

    In situ measurements of atmospheric neutral and ion composition and density, temperatures, ion drifts and neutral winds, are in high demand to study the dynamics of the ionosphere-theremosphere-mesosphere system. This paper presents a compact Ion and Neutral Mass Spectrometer (INMS) with impended ion drifts and temperature, and neutral winds capability for in situ measurements of ions and neutrals H, He, N, O, N2, O2. The mass resolution M/dM is approximately 10 at an incoming energy range of 0-20eV. The goal is to resolve ion drifts in the range 0 to 3000m/sec with a resolution better than 50m/sec, and neutral winds in the range of 0 to 1000m/sec with similar resolution. For temperatures the goal is to cover a dynamic range of 0 to 5000K. The INMS is based on front end optics for ions and neutrals, pre acceleration, gated time of flight, top hat ESA, MCP detectors and compact electronics. The instrument is redundant for ions and neutrals with the ion and neutral sensor heads on opposite sides and with full electronics in the middle. The ion front end includes RPA for temperature scanning and neutral front end includes angular modulation and thermionic ionization and ion blocking grids. The electronics include fast electric gating, TOF electronics, TOF binning and C&DH digital electronics. The data package includes 400 mass bins each for ions and neutrals and key housekeeping data for instrument health and calibration. The data sampling can be commanded from 0.1 to 10 sec with 1sec nominal setting. The instrument has significant onboard storage capability and a data compression scheme. The mass spectrometer version of the instrument has been flown on the Exocube mission. The instrument occupied 1.5U volume, weighed only 560 g and required nominal power of 1.6W The ExoCube mission was designed to acquire global knowledge of in-situ densities of [H], [He], [O] and H+, He+, O+ in the upper ionosphere and lower exosphere in combination with incoherent scatter radar and

  11. Modeling of the Coupled Magnetospheric and Neutral Wind Dynamos

    NASA Technical Reports Server (NTRS)

    Thayer, Jeffrey P.

    1997-01-01

    Over the past four years of funding, SRI, in collaboration with the University of Texas at Dallas, has been involved in assessing the influence of thermospheric neutral winds on the electric field and current systems at high latitudes. The initial direction of the project was to perform a set of numerical experiments concerning the contribution of the magnetospheric and neutral wind dynamo processes, under specific boundary conditions, to the polarization electric field and/or the field-aligned current distribution at high latitudes. To facilitate these numerical experiments we developed a numerical scheme that relied on using output from the NCAR Thermosphere-Ionosphere General Circulation Model (NCAR-TIGCM), expanding them in the form of spherical harmonics and solving the dynamo equations spectrally. Once initial calculations were completed, it was recognized that the neutral wind contribution could be significant but its actual contribution to the electric field or currents depended strongly on the generator properties of the magnetosphere. Solutions to this problem are not unique because of the unknown characteristics of the magnetospheric generator, therefore the focus was on two limiting cases. One limiting case was to consider the magnetosphere as a voltage generator delivering a fixed voltage to the high-latitude ionosphere and allowing for the neutral wind dynamo to contribute only to the current system. The second limiting case was to consider the magnetosphere as a current generator and allowing for the neutral wind dynamo to contribute only to the generation of polarization electric fields. This work was completed and presented at the l994 Fall AGU meeting. The direction of the project then shifted to applying the Poynting flux concept to the high-latitude ionosphere. This concept was more attractive as it evaluated the influence of neutral winds on the high-latitude electrodynamics without actually having to determine the generator characteristics of

  12. First Thermospheric Winds and Neutral Temperatures statistics Over Oukaimeden Observatory

    NASA Astrophysics Data System (ADS)

    Kaab, Mohamed; Benkhaldoun, Zouhair; Fisher, Daniel J.; Harding, Brian; Makela, Jonathan J.; Bounhir, Aziza; Lazrek, Mohamed; Lagheryeb, Amine; Daassou, Ahmed; Khalifa, Malki

    2015-08-01

    In order to study the thermospheric-ionospheric coupling and to gain a better understanding of thermospheric neutral winds and temperatures by providing measurements over the African sector, we have deployed a new suite of instruments in Morocco: a high-resolution Fabry-Perot interferometer (FPI) and a wide-angle ionospheric imaging system. In this work, we present the statistical results from the first year of observation of thermospheric winds and neutral temperatures made at Oukaimeden Observatory, located 75 km south of Marrakesh 7° 51' W / 31° 12' N. The available data is based on the FPI measurements of Doppler shift and Doppler broadening of the 630.0-nm spectral emission caused by the dissociative recombination of O2+. Viewing the profile of trends of the winds and neutral temperatures shows that the zonal winds are eastward in the early night just after sunset with a speed of 50 m.s-1 up to 150 m.s-1, reducing over the course of the night and switching to westward flow before sunrise. The meridional winds tend to move towards the equator in the summer with speeds exceeding 150 m.s-1, while in the winter they tend to move towards the north pole with a relatively low speed that does not exceed 50 m.s-1. The neutral temperatures show a maximum around ˜1100 K at the beginning of the night and decrease as the night continues until reaching minimum values of ˜700 K before sunrise. The 630.0 nm emission intensity was relatively dim during most of the year, with the exception of a few days in late January and early February when there was a significant increase in the emission's brightness. In this paper, we discuss the instrumentation as well as the variability of these parameters day-to-day, monthly, and seasonally.

  13. Satellite Studies of Ionospheric Electric Fields and Neutral Winds

    NASA Technical Reports Server (NTRS)

    Fejer, Bela G.

    2002-01-01

    We have studied mid- and low-latitude electrodynamic and neutral thermospheric dynamic processes using measurements on board the AE-E, DE-2, and UARS (Upper Atmosphere Research Satellite) satellites, and global convection and general circulation models. These studies have determined the morphology of the equatorial zonal electric fields, the response of equatorial plasma irregularities to magnetospheric disturbances, and the time dependent response of the mid- and low latitude electric fields to magnetospheric disturbances. We have also used extensive F region zonal and meridional wind data obtained by Wind Imaging Interferometer (WINDII) instrument on board the UARS to study the latitudinal dependence of daytime disturbance winds during magnetically disturbed periods and the general characteristics of the global thermospheric disturbance wind system during geomagnetically active periods. This project has supported the PhD thesis research of John Emmert.

  14. TIDI Neutral Winds From O2 P Branch Broadband Filter

    NASA Astrophysics Data System (ADS)

    Wu, Q.; Killeen, T.; Gablehouse, R.; Johnson, R.; Solomon, S.; Skinner, W.; Niciejewski, R.; Ortland, D.; Gell, D.

    A new operational mode for the instrument has been designed to incorporate a broadband filter, which allows most of the O2 (0-0) P branch to pass through. The broadband filter data increases the signal level by an order of magnitude, which greatly increases the accuracy of the neutral wind allowing more detailed analysis of the migrating and non-migrating tide in the MLT region. Already the new wind data have shown strong non-migrating tide component. Comparisons with ground-based radar measurements show a much better consistency. We will report these new data and tidal analysis results

  15. Propagation of large amplitude Alfven waves in the solar wind neutral sheet

    NASA Technical Reports Server (NTRS)

    Malara, F.; Primavera, L.; Veltri, P.

    1995-01-01

    Analysis of solar wind fluctuation data show that the correlation between velocity and magnetic field fluctuations decreases when going farther away from the Sun. This decorrelation can be attributed either to the time evolution of the fluctuations, carried away by the solar wind, or to the interaction between the solar wind neutral sheet and Alfven waves. To check this second hypothesis we have numerically studied the propagation of Alfven waves in the solar wind neutral sheet. The initial conditions have been set up in order to guarantee B(exp 2) = const, so that the following numerical evolution is only due to the inhomogeneity in the background magnetic field. The analysis of the results shows that compressive structures are formed, mainly in the neutral sheet where they have been identified as pressure balanced structures, i.e., tangential discontinuities. Fast perturbations, which are also produced, have a tendency to leave the simulation domain, propagating also perpendicularly to the mean magnetic field. For this reason the level of fast perturbations is always smaller with respect to the previously cited plasma balanced structures, which are slow mode perturbations. A comparison between the numerical results and some particular observational issues is also presented.

  16. Modeling of the coupled magnetospheric and neutral wind dynamos

    NASA Technical Reports Server (NTRS)

    Thayer, J. P.; Vickrey, J. F.; Heelis, R. A.; Gary, J. B.

    1995-01-01

    Work at SRI involved modeling the exchange of electromagnetic energy between the ionosphere and magnetosphere to help interpret the DE-B Poynting flux observations. To describe the electrical properties of the high-latitude ionosphere, we constructed a numerical model, from the framework provided by the Vector Spherical Harmonic (VSH) model, that determines the ionospheric currents, conductivities, and electric fields including both magnetospheric inputs and neutral wind dynamo effects. This model development grew from the earlier question of whether an electrical energy source in the ionosphere was capable of providing an upward Poynting flux. The model solves the steady-state neutral wind dynamo equations and the Poynting flux equation to provide insight into the electrodynamic role of the neutral winds. The modeling effort to determine the high-latitude energy flux has been able to reproduce many of the large-scale features observed in the Poynting flux measurements made by DE-2. Because the Poynting flux measurement is an integrated result of energy flux into or out of the ionosphere, we investigated the ionospheric properties that may contribute to the observed flux of energy measured by the spacecraft. During steady state the electromagnetic energy flux, or DC Poynting flux, is equal to the Joule heating rate and the mechanical energy transfer rate in the high-latitude ionosphere. Although the Joule heating rate acts as an energy sink, transforming electromagnetic energy into thermal or internal energy of the gas, the mechanical energy transfer rate may be either a sink or source of electromagnetic energy. In the steady state, it is only the mechanical energy transfer rate that can generate electromagnetic energy and result in a DC Poynating flux that is directed out of the ionosphere.

  17. On the contribution of the thermospheric neutral wind to high-latitude energetics

    NASA Technical Reports Server (NTRS)

    Thayer, J. P.; Vickrey, J. F.

    1992-01-01

    The significance of the neutral wind dynamo as a contributor to ionospheric energetics at high latitudes is addressed by determining separately the electrical energy flux from the magnetospheric dynamo and the maximum electrical energy flux available due to the neutral wind dynamo, neglecting the natural feedback processes between the two. The neutral wind dynamo is found to contribute significantly to the flux of energy exchanged between the magnetosphere and thermosphere, particularly in the central polar cap. In the region of the magnetospheric convection reversal, the amount of available energy flux from the neutral wind dynamo can exceed that provided by the magnetospheric dynamo making the neutrals a dominant contributor to local electrodynamics.

  18. The Climatology of Neutral Winds in the MLT Region as Observed From Orbit

    NASA Astrophysics Data System (ADS)

    Niciejewski, R.; Skinner, W.; Gell, D.; Cooper, M.; Marsh, A.; Killeen, T.; Wu, Q.; Solomon, S.; Ortland, D.; Drob, D.; Emmert, J.

    2005-12-01

    Unique observations of the horizontal neutral winds in the altitude range 70 to 115 km have been performed from satellite platforms by HRDI and WINDII (UARS) and by TIDI (TIMED), the former since September 1991 and the latter since January 2002. All three experiments observed airglow on the terrestrial limb and derived vertical wind profiles of geophysical quantities by inverting altitude scans of Doppler shifted emission spectra. As a result, the global mesosphere / lower thermosphere region has been sampled for 14 years by a common technique resulting in an unparalleled neutral wind database. This database will be one of the key contributions to an improved Horizontal Wind Model (HWM). This paper will describe results from the first long term climatological study of the MLT region based on satellite wind measurements. The basic dynamic structure in the MLT is a tide, which also has long-term variation that has similar periods to the 27-month QBO (quasi-biennial oscillation) and the SAO (semi-annual oscillation). Signatures of ultra-long variability require analysis of the full wind database.

  19. Ion-neutral coupling effects on low-latitude thermospheric evening winds

    NASA Astrophysics Data System (ADS)

    Evonosky, W.; Richmond, A. D.; Fang, T.-W.; Maute, A.

    2016-05-01

    We examine the forces that determine zonal wind structure in the low-latitude evening thermosphere and its relation with ion-neutral coupling. These winds drive the evening F region dynamo that affects the equatorial ionization anomaly (EIA) and the generation of plasma irregularities. Forces are calculated using the Thermosphere-Ionosphere-Electrodynamics General Circulation Model coupled with the Global Ionosphere-Plasmasphere model. At 19 LT, the horizontal pressure gradient dominates the net acceleration of neutral winds below ˜220 km, while it tends to be offset by ion drag and viscosity higher up. The eastward pressure-gradient acceleration above 200 km increases approximately linearly with height and tends to be similar for different latitudes and different levels of solar activity. The pressure-gradient and ion-drag forces in the central F region approximately balance for field lines that pass through the EIA. Viscosity is an important additional force at non-EIA latitudes and in the bottomside and topside EIA ionosphere. An increase in E region drag on plasma convection due to increased nighttime ionization causes both the ion and neutral velocities in the F region to decrease, while the velocity difference tends to be maintained. The presence of a low-latitude evening time vertical shear in the zonal wind is associated primarily with a strong eastward pressure-gradient acceleration at high altitude that reverses the daytime westward wind and a weak low-altitude pressure-gradient acceleration of either eastward or westward direction that fails to reverse the low-altitude westward wind present in the afternoon.

  20. Meridional neutral winds in the thermosphere at Arecibo Simultaneous incoherent scatter and airglow observations

    NASA Astrophysics Data System (ADS)

    Burnside, R. G.; Walker, J. C. G.; Behnke, R. A.

    1983-04-01

    The possibility of using incoherent scatter radar measurements to calculate the meridional neutral wind velocity at Arecibo, Puerto Rico, has been demonstrated by Behnke and Harper (1973) and Behnke and Kohl (1974). The present study extends this earlier work, whose calculations were restricted to the height of the F layer peak. The study is restricted to the nighttime and covers the region from 250 to 480 km. Sufficient data have been obtained to demonstrate clearly seasonal variations in the meridional neutral wind velocity. Attention is given to incoherent scatter measurements, neutral wind measurements, the diffusion calculation, a diffusion velocity comparison, and vertical profiles of the meridional wind.

  1. On the contribution of the thermospheric neutral wind to high-latitude energetics

    SciTech Connect

    Thayer, J.P.; Vickrey, J.F. )

    1992-02-07

    Although the neutral wind's contribution to ionospheric electrodynamics is well-established at low latitudes, this electrical energy source has been largely ignored at high latitudes, owing to the assumed dominance of the magnetospheric dynamo contribution. Yet, the potential for exchange of electrical energy between the neutral wind dynamo and the magnetospheric dynamo is a direct consequence of the coupling magnetic field lines. The integral nature of this coupling precludes the direct separation of the neutral wind and solar wind contributions to the observed electrodynamics. Therefore, to gain some insight into their relative importance, the authors have performed a simple numerical experiment in which the two dynamos are individually connected to a fixed load and their energetics evaluated separately. To determine the electric energy flux supplied by the magnetosphere, they treat is a voltage generator and the ionosphere as a resistive load. The available electrical energy flux generated by the neutral wind dynamo is determined from the mechanical energy stored within an established neutral wind field. This exercise has led to a number of conclusions, including: (1) the neutral wind dynamo contributes significantly to high-latitude energetics, particularly in the central polar cap; and (2) in the region near the plasma convection reversal boundary, the amount of energy flux available from the neutral wind dynamo can exceed that provided by the magnetospheric dynamo.

  2. Optical remote sensing of penetration into the lower thermosphere of neutral wind and composition perturbations driven by magnetospheric forcing

    NASA Astrophysics Data System (ADS)

    Conde, M. G.; Anderson, C.; Hecht, J. H.

    2011-12-01

    Numerous observations of thermospheric neutral winds at altitudes of 240 km and higher clearly show wind structures occurring at auroral latitudes in response to magnetospheric forcing. It is also known from observations that magnetospheric forcing is not a major driver of winds down at mesopause heights and below. Because it is difficult to measure winds in the intervening "transition region" between these height regimes, very little is known about how deeply the magnetospherically driven neutral wind structures penetrate into the lower thermosphere, what factors affect this penetration, and what consequences it may have for transport of chemical species. Here we will show neutral wind maps obtained at F-region and E-region heights in the auroral zone using Fabry-Perot Doppler spectroscopy of the 630 nm and 558 nm optical emissions. Although thermospheric neutral winds are smoothed by viscosity and inertia, observed responses to magnetospheric forcing still include wind responses on time scales as short as 10 minutes or less, and on length scales shorter than 100 km horizontally and 5 km vertically. The data also show that the degree of penetration of magnetospheric forcing into the lower thermospheric wind field is highly variable from day to day. Signatures of magnetospheric forcing are sometimes seen at altitudes as low as 120 km, whereas at other times the E-region does not seem to respond at all. Possible links will be explored between this variability and the day to day differences seen in the column integrated thermospheric [O]/[N2] ratio over Alaska.

  3. Wind turbine wakes in forest and neutral plane wall boundary layer large-eddy simulations

    NASA Astrophysics Data System (ADS)

    Schröttle, Josef; Piotrowski, Zbigniew; Gerz, Thomas; Englberger, Antonia; Dörnbrack, Andreas

    2016-09-01

    Wind turbine wake flow characteristics are studied in a strongly sheared and turbulent forest boundary layer and a neutral plane wall boundary layer flow. The reference simulations without wind turbine yield similar results as earlier large-eddy simulations by Shaw and Schumann (1992) and Porte-Agel et al. (2000). To use the fields from the homogeneous turbulent boundary layers on the fly as inflow fields for the wind turbine wake simulations, a new and efficient methodology was developed for the multiscale geophysical flow solver EULAG. With this method fully developed turbulent flow fields can be achieved upstream of the wind turbine which are independent of the wake flow. The large-eddy simulations reproduce known boundary-layer statistics as mean wind profile, momentum flux profile, and eddy dissipation rate of the plane wall and the forest boundary layer. The wake velocity deficit is more asymmetric above the forest and recovers faster downstream compared to the velocity deficit in the plane wall boundary layer. This is due to the inflection point in the mean streamwise velocity profile with corresponding turbulent coherent structures of high turbulence intensity in the strong shear flow above the forest.

  4. Study of The MLT Neutral Wind Tide Using The TIMED Doppler Interferometer (TIDI)

    NASA Astrophysics Data System (ADS)

    Killeen, T.; Wu, Q.; Solomon, S.; Skinner, W.; Ortland, D.; Niciejewski, R.; Johnson, R.; Gablehouse, R.; Gell, D.

    Using the TIDI neutral wind data, we will examine the migrating tide and non-migrating tide variations. TIDI instrument samples four local times at latitudes between 60N and 60S during one day. The instrument monitors winds from 70 to 105 km altitude range during the day and 80 to 100 km during the night. The orbital precessing rate of TIMED satellite is 3 degree/day. It will take 60 days (one yaw period) for TIDI to sample all 24-hour local times. We will examine the possibility of extracting tidal wave features using data period less than 60 days. TIDI can provide a global view of the tidal structure. We also compare the tidal amplitudes and phases obtained from the satellite data and ground based data

  5. Satellite accelerometer measurements of neutral density and winds during geomagnetic storms

    NASA Technical Reports Server (NTRS)

    Marcos, F. A.; Forbes, J. M.

    1986-01-01

    A new thermospheric wind measurement technique is reported which is based on a Satellite Electrostatic Triaxial Accelerometer (SETA) system capable of accurately measuring accelerations in the satellite's in-track, cross-track and radial directions. Data obtained during two time periods are presented. The first data set describes cross-track winds measured between 170 and 210 km during a 5-day period (25 to 29 March 1979) of mostly high geomagnetic activity. In the second data set, cross-track winds and neutral densities from SETA and exospheric temperatures from the Millstone Hill incoherent scatter radar are examined during an isolated magnetic substorm occurring on 21 March 1979. A polar thermospheric wind circulation consisting of a two cell horizontal convection pattern is reflected in both sets of cross-track acceleration measurements. The density response is highly asymmetric with respect to its day/night behavior. Latitude structures of the density response at successive times following the substorm peak suggest the equatorward propagation of a disturbance with a phase speed between 300 and 600 m/s. A deep depression in the density at high latitudes (less than 70 deg) is evident in conjunction with this phenomenon. The more efficient propagation of the disturbance to lower latitudes during the night is probably due to the midnight surge effect.

  6. Assimilating Storm-time Neutral Winds in Ionospheric-Thermospheric State Estimation

    NASA Astrophysics Data System (ADS)

    Datta-Barua, S.; Miladinovich, D.; Makela, J. J.; Bust, G. S.

    2015-12-01

    During geomagnetic storms at mid-latitudes both electrodynamic disturbances and neutral composition variations contribute to time evolving and localized variations in the plasma content of the ionosphere. While the most plentiful data are typically Global Navigation Satellite System (GNSS) based measurements of total electron content (TEC), assimilation of measurements of the ionospheric-thermospheric state itself, i.e., neutral winds, can improve the fidelity of the result. Fabry-Perot interferometers (FPIs) measure emissions of thermospheric oxygen, giving line-of-sight wind speeds. During storm-times however, these FPI measurements may also detect a non-thermal oxygen source, yielding a measurement that is not strictly of the thermospheric wind [Makela et al., 2014]. The sign of non-thermal oxygen is in the apparent large 50 to 100 m/s vertical winds. This raises the question: what happens when we try to assimilate direct measurements of the wind but some of those measurements are "contaminated" by a non-thermal source? We present results of a Kalman Filtered data assimilative experiment ingesting neutral wind measurements made by a 630.0 nm FPI sited in the mid-latitude U.S. during the geomagnetic storm of October 25, 2011. Ionospheric Data Assimilation 4-Dimensional (IDA4D) estimates time-varying plasma densities from GNSS TEC. These densities are ingested without, and with, respectively, FPI neutral wind data into Estimating Model Parameters with Ionospheric Reverse Engineering (EMPIRE). EMPIRE uses background electric potential and neutral wind models, to produce an optimized estimate of both ExB drift and neutral wind based on the data ingested. We compare the estimated horizontal neutral wind at the FPI measurement locations at about 250 km altitude, first using electron densities without ingesting FPI data. Then plasma densities plus half the FPI data are ingested to estimate neutral winds. These wind estimates are then compared to the FPI data that were

  7. Detailed Atomic Structure of Neutral and Near-Neutral Systems

    SciTech Connect

    Oliver, Paul; Hibbert, Alan

    2011-05-11

    This paper highlights the issues which need to be addressed in undertaking accurate calculations of multi-electron atoms and ions, particularly at or near the neutral end of an isoelectronic sequence. We illustrate the processes through two calculations--of transitions in Cl I and Sn II--and discuss the convergence of our results as well as updating previous work. In particular, in the case of Cl I, we propose new identifications of the levels involved in certain transitions which are important in determining the abundance of chlorine in the inter-stellar medium (ISM), while in singly ionised tin, our calculations suggest a re-evaluation of the the abundance of tin in the ISM. We also confirm recent identification of Sn II lines seen in tokamak plasmas.

  8. Neutral winds derived from IRI parameters and from the HWM87 wind model for the sundial campaign of September, 1986

    NASA Technical Reports Server (NTRS)

    Miller, K. L.; Hedin, A. E.; Wilkinson, P. J.; Torr, D. G.; Richards, P. G.

    1990-01-01

    Meridional neutral winds derived from the height of the maximum ionization of the F2 layer are compared with values from results of the HWM87 empirical neutral wind model. The time period considered is the SUNDIAL-2 campaign, 21 Sept. through 5 Oct. 1986. Winds were derived from measurements by a global network of ionosondes, as well as from similar quantities generated by the International Reference Ionosphere. Global wind patterns from the three sources are similar. Differences tend to be the result of local or transient phenomena that are either too rapid to be described by the order of harmonics of the empirical models, or are the result of temporal changes not reproduced by models based on average conditions.

  9. Local scale structures in Earth's thermospheric winds and their consequences for wind driven transport

    NASA Astrophysics Data System (ADS)

    Dhadly, Manbharat Singh

    In the traditional picture of Earth's upper thermosphere (~190--300 km), it is widely presumed that its convective stability and enormous kinematic viscosity attenuate wind gradients, and hence smooth out any structure present in the wind over scale size of several hundreds of kilometers. However, several independent experimental studies have shown that observed upper thermospheric wind fields at high latitudes contain stronger than expected local-scale spatial structures. The motivation of this dissertation is to investigate how the resulting local-scale gradients would distort neutral air masses and complicate thermospheric wind transport. To achieve this goal, we examined the behavior of a simple parameter that we refer to as the "distortion gradient". It incorporates all of the wind field's departures from uniformity, and is thus capable of representing all resulting contributions to the distortion or mixing of air masses. Climatological analysis of the distortion gradient using 2010, 2011, and 2012 wind data from the All-sky Scanning Doppler Imager (SDI) located at Poker Flat (65.12N, 147.47W) revealed the diurnal and seasonal trends in distortion of thermospheric masses. Distortion was observed to be dependent on geomagnetic activity and orientation of the interplanetary magnetic field. To understand the time-cumulative influence of these local-scale non-uniformities on thermospheric wind driven transport, time-resolved two-dimensional maps of the thermospheric vector wind fields were used to infer forward and backward air parcel trajectories. Tracing air parcel trajectories through a given geographic location indicates where they came from previously, and where they will go in the future. Results show that wind driven transport is very sensitive to small-scale details of the wind field. Any local-scale spatial wind gradients can significantly complicate air parcel trajectories. Transport of thermospheric neutral species in the presence of the local

  10. First E region observations of mesoscale neutral wind interaction with auroral arcs

    NASA Astrophysics Data System (ADS)

    Kosch, M. J.; Anderson, C.; Makarevich, R. A.; Carter, B. A.; Fiori, R. A. D.; Conde, M.; Dyson, P. L.; Davies, T.

    2010-02-01

    We report the first observations of E region neutral wind fields and their interaction with auroral arcs at mesoscale spatial resolution during geomagnetically quiet conditions at Mawson, Antarctica. This was achieved by using a scanning Doppler imager, which can observe thermospheric neutral line-of-sight winds and temperatures simultaneously over a wide field of view. In two cases, the background E region wind field was perpendicular to an auroral arc, which when it appeared caused the wind direction within ˜50 km of the arc to rotate parallel along the arc, reverting to the background flow direction when the arc disappeared. This was observed under both westward and eastward plasma convection. The wind rotations occurred within 7-16 min. In one case, as an auroral arc propagated from the horizon toward the local zenith, the background E region wind field became significantly weaker but remained unaffected where the arc had not passed through. We demonstrate through modeling that these effects cannot be explained by height changes in the emission layer. The most likely explanation seems to be the greatly enhanced ion drag associated with the increased plasma density and localized ionospheric electric field associated with auroral arcs. In all cases, the F region neutral wind appeared less affected by the auroral arc, although its presence is clear in the data.

  11. First E-region observations of meso-scale neutral wind interaction with auroral arcs

    NASA Astrophysics Data System (ADS)

    Kosch, M.; Anderson, C.; Makarevitch, R.; Carter, B.; Fiori, R. A.; Conde, M. G.; Dyson, P. L.; Davies, T.

    2009-12-01

    We report the first observations of E-region neutral wind fields and their interaction with auroral arcs at meso-scale spatial resolution during geomagnetically quiet conditions at Mawson, Antarctica. This was achieved by using a scanning Doppler imager, which can observe thermospheric neutral line-of-sight winds and temperatures simultaneously over a wide field of view. In two cases, the background E-region wind field was perpendicular to an auroral arc, which when it appeared caused the wind direction within ~50 km of the arc to rotate parallel along the arc, reverting to the background flow direction when the arc disappeared. This was observed under both westward and eastward ion convection. The wind rotations occurred within 7-16 min. In another case, as an auroral arc propagated from the horizon toward the local zenith, the background E-region wind field became significantly weaker but remained unaffected where the arc had not passed through. We demonstrate through modelling that these effects cannot be explained by height changes in the emission layer. The most likely explanation seems to be greatly enhanced ion drag associated with the increased plasma density and localised ionospheric electric field associated with auroral arcs. In all cases, the F-region neutral wind appeared only slightly affected by the auroral arc, although its presence is clear in the data.

  12. Protein structure and neutral theory of evolution.

    PubMed

    Ptitsyn, O B; Volkenstein, M V

    1986-08-01

    The neutral theory of evolution is extended to the origin of protein molecules. Arguments are presented which suggest that the amino acid sequences of many globular proteins mainly represent "memorized" random sequences while biological evolution reduces to the "editing" these random sequences. Physical requirements for a functional globular protein are formulated and it is shown that many of these requirement do not involve strategical selection of amino acid sequences during biological evolution but are inherent also for typical random sequences. In particular, it is shown that random sequences of polar and amino acid residues can form alpha-helices and beta-strand with lengths and arrangement along the chain similar to those in real globular proteins. These alpha- and beta-regions in random sequences can form three-dimensional folding patterns also similar to those in proteins. The arguments are presented suggesting that even the tight packing of side groups inside protein core do not require very strong biological selection of amino acid sequences either. Thus many structural features of real proteins can exist also in random sequences and the biological selection is needed mainly for the creation of active site of protein and for their stability under physiological conditions.

  13. Neutral wind acceleration in the polar lower E-region during an intense electric-field

    NASA Astrophysics Data System (ADS)

    Tsuda, Takuo T.; Buchert, Stephan C.; Nozawa, Satonori; Oyama, Shin-ichiro; Ogawa, Yasunobu; Fujii, Ryoichi

    2016-04-01

    The Joule heating and ion drag effects are considered as important factors in the neutral wind dynamics in the polar E-region. However, quantitative evaluations for these effects are insufficient for correct understanding, particularly, in the lower E-region (100-110 km heights) where the anomalous heating effect, related with the electron Pedersen currents, can occur during the intense electric field. In the present study, using EISCAT Svalbard radar data, we have investigated, for the first time, the normal and anomalous heating effects to the neutral wind acceleration in the lower E-region.

  14. Calculation of meridional neutral winds in the middle latitudes from the Irkutsk incoherent scatter radar

    NASA Astrophysics Data System (ADS)

    Shcherbakov, A. A.; Medvedev, A. V.; Kushnarev, D. S.; Tolstikov, M. V.; Alsatkin, S. S.

    2015-12-01

    This paper presents a consistent technique for velocity determination of meridional neutral winds from the Irkutsk incoherent scatter radar (IISR.) We calculated plasma drift velocity based on phase analysis of an autocorrelation function of an incoherent scatter signal. We also preliminary tested the described technique by determining several low-orbit satellite velocities. Midlatitude meridional neutral winds were calculated using a "three-beam" technique from the IISR velocity with taking into account motions due to electric fields across magnetic field lines in both meridional and zonal directions. It has been shown that an underestimated impact of the motions generated by electric fields can seriously interfere in determining wind velocities. The results obtained were compared with the modeled wind values.

  15. Ion and neutral polar winds for northward interplanetary magnetic field conditions

    NASA Astrophysics Data System (ADS)

    Gardner, Larry C.; Schunk, Robert W.

    2006-08-01

    The coupling of the ionosphere/magnetosphere system at high-latitudes is dependent in part upon the transport of neutral atoms from the ionosphere to the magnetosphere, and visa versa. The neutral atoms that flow between the ionosphere and the magnetosphere are neutral stream atoms that are produced in charge exchange reactions between the ions in the polar wind and the background thermal and geocoronal atoms. The characteristics of these neutral stream particles are highly dependent upon the ions in the polar cap. The ions are convected across the polar cap due to convection electric fields, and thus the neutral stream particles are also indirectly affected by the convection electric fields due to charge exchange. The horizontal flow of neutral stream particles, therefore, shows a general anti-sunward motion during periods of southward interplanetary magnetic field (IMF), and a general sunward flow across the magnetic pole during times of northward IMF. The vertical fluxes of these neutral stream particles depend upon several processes, including the heat input due to precipitating electrons, the vertical velocity of the ions involved in the charge exchange reactions that produce the neutral stream particles, and the time history of neutral stream particles in the high-latitude region.

  16. Thermal Coupling of Protons and Neutral Hydrogen in the Fast Solar Wind

    NASA Astrophysics Data System (ADS)

    Allen, L.; Habbal, S. R.

    1997-05-01

    Motivated by the recent Spartan and UVCS observations [Kohl et al. 1996] of hot protons with temperatures exceeding 4 x 10(6) K below 3.5 R_s in coronal holes, as inferred from the measured broadening of the Lyman alpha spectral line profile, we studied the thermal coupling of neutral hydrogen to protons in the presence of Alfven waves in the solar wind. The approach used is adopted from Olsen et al. [1994] in which the neutral hydrogen atoms are treated as test particles in a background electron-proton solar wind. The model computations show that an anisotropy in the neutral hydrogen temperature in the directions parallel and perpendicular to the magnetic field develops in the inner corona well below 5 R_s for background solar wind solutions consistent with observational constraints of the high speed wind. In particular, we find that the neutral hydrogen temperature parallel to the magnetic field direction remains strongly coupled to the proton temperature, T_p, while the perpendicular neutral hydrogen temperature exceeds this by ~ 10(6) K for a wide range of proton flow speeds, densities and temperatures for a spectrum of Alfven waves. The neutral hydrogen effective temperature, T_{H(eff)}(perpendicular to ) , incorporating both random thermal motion and wave motion of the particles, is found to be independent of frequency and significantly less than the proton effective temperature, T_{p(eff)}, in the inner corona. Thus, without additional information about the waves, which would allow T_H(perpendicular to ) and T_p to be extracted from the models, T_{H(eff)}(perpendicular to ) provides an upper limit on T_p and a lower limit on T_{p(eff)}. However, with increasing proton temperature, the anisotropy in the inner corona decreases, with a temperature difference of < 8 x 10(5) K between the protons and neutrals below 3 R_s when the latter reach 6 x 10(6) K.

  17. Synthetic thermosphere winds based on CHAMP neutral and plasma density measurements

    NASA Astrophysics Data System (ADS)

    Gasperini, F.; Forbes, J. M.; Doornbos, E. N.; Bruinsma, S. L.

    2016-04-01

    Meridional winds in the thermosphere are key to understanding latitudinal coupling and thermosphere-ionosphere coupling, and yet global measurements of this wind component are scarce. In this work, neutral and electron densities measured by the Challenging Minisatellite Payload (CHAMP) satellite at solar low and geomagnetically quiet conditions are converted to pressure gradient and ion drag forces, which are then used to solve the horizontal momentum equation to estimate low latitude to midlatitude zonal and meridional "synthetic" winds. We validate the method by showing that neutral and electron densities output from National Center for Atmospheric Research (NCAR) Thermosphere Ionosphere Mesosphere Electrodynamics-General Circulation Model (TIME-GCM) can be used to derive solutions to the momentum equations that replicate reasonably well (over 85% of the variance) the winds self-consistently calculated within the TIME-GCM. CHAMP cross-track winds are found to share over 65% of the variance with the synthetic zonal winds, providing further reassurance that this wind product should provide credible results. Comparisons with the Horizontal Wind Model 14 (HWM14) show that the empirical model largely underestimates wind speeds and does not reproduce much of the observed variability. Additionally, in this work we reveal the longitude, latitude, local time, and seasonal variability in the winds; show evidence of ionosphere-thermosphere (IT) coupling, with enhanced postsunset eastward winds due to depleted ion drag; demonstrate superrotation speeds of ˜27 m/s at the equator; discuss vertical wave coupling due the diurnal eastward propagating tide with zonal wave number 3 and the semidiurnal eastward propagating tide with zonal wave number 2.

  18. Project CONDOR: Middle atmosphere wind structure obtained with lightweight inflatable spheres near the equatorial electrojet

    NASA Technical Reports Server (NTRS)

    Schmidlin, F. J.

    1987-01-01

    Observed correlations between the atmospheric electric field and the neutral wind were studied using additional atmospheric measurements during Project CONDOR. Project CONDOR obtained measurements near the equatorial electrojet (12 S) during March 1983. Neutral atmosphere wind measurements were obtained using lightweight inflatable spheres and temperatures were obtained using a datasonde. The lightweight sphere technology, the wind structure, and temperature structure are described. Results show that the lightweight sphere gives higher vertical resolution of winds below 75 km compared with the standard sphere, but gives little or no improvement above 80 km, and no usable temperature and density data.

  19. A case study of the thermospheric neutral wind response to geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Jiang, Guoying; Zhang, Shunrong; Wang, Wenbin; Yuan, Wei; Wu, Qian; Xu, Jiyao

    A minor geomagnetic storm (Kp=5) occurred on March 27-28, 2012. The response of the thermospheric neutral wind at ~ 250 km to this storm was investigated by the 630.0 nm nightglow measurements of Fabry-Perot interferometers (FPIs) over Xinglong (geographic location: 40.2N, 117.4E; geomagnetic location: 29.8N, 193.2E) and Millstone Hill (geographic location: 42.6N, 71.5W; geomagnetic location: 53.1N, 65.1W). Our results show that the minor storm on March 27-28, 2012 obviously effected on the thermospheric neutral winds over Xinglong and Millstone Hill, especially Millstone Hill had larger response because of its higher geomagnetic latitude. Another interesting result is that a small variation in geomagnetic activity (Kp=2.7) could enough introduce a clear disturbance in the nighttime thermospheric neutral wind over Millstone hill. NCAR-TIME-GCM (National Center for Atmospheric Research-Thermosphere Ionosphere Mesosphere Electrodynamics-General Circulation Model) was employed to study the evolution and mechanism of the thermospheric neutral wind response.

  20. Wind farm performance in conventionally neutral atmospheric boundary layers with varying inversion strengths

    NASA Astrophysics Data System (ADS)

    Allaerts, Dries; Meyers, Johan

    2014-06-01

    In this study we consider large wind farms in a conventionally neutral atmospheric boundary layer. In large wind farms the energy extracted by the turbines is dominated by downward vertical turbulent transport of kinetic energy from the airflow above the farm. However, atmospheric boundary layers are almost always capped by an inversion layer which slows down the entrainment rate and counteracts boundary layer growth. In a suite of large eddy simulations the effect of the strength of the capping inversion on the boundary layer and on the performance of a large wind farm is investigated. For simulations with and without wind turbines the results indicate that the boundary layer growth is effectively limited by the capping inversion and that the entrainment rate depends strongly on the inversion strength. The power output of wind farms is shown to decrease for increasing inversions.

  1. Thermal coupling between neutral hydrogen and protons in the fast solar wind: Models and inferences

    NASA Astrophysics Data System (ADS)

    Allen, Lorraine Ann

    2001-10-01

    In response to the recent Spartan and UVCS/SOHO observations of Ly α spectral line profiles in the inner corona implying large temperature anisotropies and proton temperatures as high as 6 × 106 K [ Kohl et al., 1996, 1997]1, we investigate the thermal coupling between neutral hydrogen atoms and protons in the fast solar wind. We include charge exchange between neutrals and protons, radiative recombination, collisional ionization of the neutrals, and the effects of Alfvén waves, described by a single frequency or a spectrum. We follow the approach developed by Olsen et al. [1994]2 to incorporate the collisional interaction between the neutrals and protons and the resulting wave motion of the neutrals. A fluid approach is used in which the neutrals are treated as test particles in a background electron- proton solar wind driven out from the Sun by thermal and Alfvén wave pressure against gravity. Coulomb collisions and thermal conductivity of the electrons and protons are included, as well as the allowance for non- radially expanding flow tubes and additional heating to the electrons and protons. We study the behavior of the neutral hydrogen in the solar wind for cases with isotropic and anisotropic proton temperatures. Our model solutions show, and we confirm by analytical calculation, that the effective temperature, T⊥H(eff) , incorporating both random and wave motions of the neutral hydrogen, is independent of Alfvén wave frequency. We find that for solutions with either isotropic or anisotropic proton temperatures the proton and neutral hydrogen effective temperatures and outflow velocities are comparable, with a temperature difference less than 5 × 105 K, below 3 Rs. For plasma conditions typical of the fast solar wind, these results imply that the measured Ly α spectral line profiles, from which the neutral hydrogen temperature, anisotropy ratio, and outflow velocity are inferred, are equivalent to measurements of protons below 3 R s. To relate our

  2. Interaction of the solar wind with interstellar neutral hydrogen - Three-fluid model

    NASA Technical Reports Server (NTRS)

    Isenberg, P. A.

    1986-01-01

    It is commonly assumed in models of the solar wind-interstellar neutral hydrogen interaction that the ionized interstellar particles are quickly assimilated into the solar wind proton population and 'become indistinguishable' from the original solar wind. This assumption leads to the prediction that the solar wind proton temperature should increase with radius in the outer heliosphere. This temperature increase has not been observed. It is pointed out that assimilation of the interstellar particles to the point of indistinguishability takes place on the very long Coulomb collision time scale, and is not expected to occur within the heliosphere. Results are presented of a three-fluid model of the solar wind which consists of comoving thermal populations of protons of solar origin, protons produced by ionization of interstellar hydrogen, and electrons. The steady-state results yield a solar wind with a 'core' proton distribution which cools adiabatically, and a 'halo' of interstellar pickup protons which is maintained near 10 to the 7th K by the energy input of continued ionization and pickup. Such a distribution will not be observed to manifest the temperature increase at large heliocentric distances which is predicted from a one-fluid analysis. Further time-dependent calculations show a strong correlation between the densities of the solar wind and the interstellar pickup protons. It is suggested that the interstellar pickup population may be observable by the Voyager plasma instruments in low resolution mode during periods of high solar wind density and low solar wind temperature.

  3. Colliding planetary and stellar winds: charge exchange and transit spectroscopy in neutral hydrogen

    NASA Astrophysics Data System (ADS)

    Tremblin, Pascal; Chiang, Eugene

    2013-01-01

    When transiting their host stars, hot Jupiters absorb about 10 per cent of the light in the wings of the stellar Lyman α emission line. The absorption occurs at wavelengths Doppler-shifted from line centre by ±100 km s-1 - larger than the thermal speeds with which partially neutral, ˜104 K hydrogen escapes from hot Jupiter atmospheres. It has been proposed that the absorption arises from ˜106 K hydrogen from the host stellar wind, made momentarily neutral by charge exchange with planetary H i. The ±100 km s-1 velocities would then be attributed to the typical velocity dispersions of protons in the stellar wind - as inferred from spacecraft measurements of the solar wind. To test this proposal, we perform 2D hydrodynamic simulations of colliding hot Jupiter and stellar winds, augmented by a chemistry module to compute the amount of hot neutral hydrogen produced by charge exchange. We observe the contact discontinuity where the two winds meet to be Kelvin-Helmholtz unstable. The Kelvin-Helmholtz instability mixes the two winds; in the mixing layer, charge exchange reactions establish, within tens of seconds, a chemical equilibrium in which the neutral fraction of hot stellar hydrogen equals the neutral fraction of cold planetary hydrogen (about 20 per cent). In our simulations, enough hot neutral hydrogen is generated to reproduce the transit observations, and the amount of absorption converges with both spatial resolution and time. Our calculations support the idea that charge transfer between colliding winds correctly explains the Lyman α transit observations - modulo the effects of magnetic fields, which we do not model but which may suppress mixing. Other neglected effects include, in order of decreasing importance, rotational forces related to orbital motion, gravity and stellar radiation pressure; we discuss quantitatively the errors introduced by our approximations. How hot stellar hydrogen cools when it collides with cold planetary hydrogen is also

  4. Emergence of structural patterns in neutral trophic networks.

    PubMed

    Canard, Elsa; Mouquet, Nicolas; Marescot, Lucile; Gaston, Kevin J; Gravel, Dominique; Mouillot, David

    2012-01-01

    Interaction networks are central elements of ecological systems and have very complex structures. Historically, much effort has focused on niche-mediated processes to explain these structures, while an emerging consensus posits that both niche and neutral mechanisms simultaneously shape many features of ecological communities. However, the study of interaction networks still lacks a comprehensive neutral theory. Here we present a neutral model of predator-prey interactions and analyze the structural characteristics of the simulated networks. We find that connectance values (complexity) and complexity-diversity relationships of neutral networks are close to those observed in empirical bipartite networks. High nestedness and low modularity values observed in neutral networks fall in the range of those from empirical antagonist bipartite networks. Our results suggest that, as an alternative to niche-mediated processes that induce incompatibility between species ("niche forbidden links"), neutral processes create "neutral forbidden links" due to uneven species abundance distributions and the low probability of interaction between rare species. Neutral trophic networks must be seen as the missing endpoint of a continuum from niche to purely stochastic approaches of community organization. PMID:22899987

  5. The Wind and Temperature Spectrometer (WTS) in the Atmospheric Neutral Density Experiment (ANDE) Satellite

    NASA Technical Reports Server (NTRS)

    Herrero, F. A.; Vancil, B.; Nicholas, A.; Zaruba, C.; Beasley, L.

    2004-01-01

    Miniaturization efforts in new spectrometers for ionosphere/thermosphere investigations of the ion-drifts and neutral winds and corresponding temperatures make possible very light (about 250 g) packages consuming less than 0.4 W. Previously described, our approach measures the angular and energy distributions of neutral atoms and molecules (or ions) in two perpendicular planes; using those distributions to determine the full wind vector, the temperature and the relative densities of O and N2, as required for the ANDE mission. The measurements require two separate electron impact ion sources each with its own electron beam cathode. We have developed a low-temperature thermionic emission cathode that delivers 1 mA electron current at 80 mW power, making it possible to operate neutral wind-temperature experiments for the first time with powers less than 0.5 W. Advances in the ion optics of the energy-angle spectrometer enhance the energy resolution-aperture product more than a factor of 3 to enable energy resolutions of a few percent with large apertures. With these technology improvements it is now possible to obtain the full neutral wind vector, temperature and O/N2, density ratio once per second in a 250g/0.4W package with sensitivity up to about 500 km altitude in the thermosphere. We will describe the WTS as deployed in ANDE and show simulated data with the non-linear least squares analysis to illustrate expected performance of the WTS in the estimated errors in the three components of the wind, the temperature, and the relative densities.

  6. Thermospheric neutral wind signatures dependent on the east-west component of the interplanetary magnetic field for Northern and Southern Hemispheres as measured from Dynamics Explorer-2

    NASA Technical Reports Server (NTRS)

    Thayer, J. P.; Killeen, T. L.; Mccormac, F. G.; Tschan, C. R.; Ponthieu, J.-J.; Spencer, N. W.

    1987-01-01

    DE-2 neutral-wind measurements obtained between November and January 1981-1982 and 1982-1983 were analyzed to investigate the effect of the sign of the IMF By component on neutral thermosphere dynamics at F-region altitudes. Maps of the mean neutral circulation for the northern (winter) and southern (summer) polar regions were derived for By positive and negative using polar geomagnetic coordinates. The mean neutral winds demonstrate clear By-dependent neutral wind signatures in both hemispheres.

  7. Characteristics of satellite accelerometer measurements of thermospheric neutral winds at high latitudes

    NASA Astrophysics Data System (ADS)

    Doornbos, E.; Ridley, A. J.; Cnossen, I.; Aruliah, A. L.; Foerster, M.

    2015-12-01

    Thermospheric neutral winds play an important part in the coupled thermosphere-ionosphere system at high latitudes. Neutral wind speeds have been derived from the CHAMP and GOCE satellites, which carried precise accelerometers in low Earth orbits. Due to the need to simultaneously determine thermosphere neutral density from the accelerometer in-track measurements, only information on the wind component in the cross-track direction, perpendicular to the flight direction can be derived. However, contrary to ground-based Fabry-Perot interferometer and scanning Doppler imager observations of the thermosphere wind, these satellite-based measurements provide equally distributed coverage over both hemispheres. The sampling of seasonal and local time variations depend on the precession rate of the satellite's orbital plane, with CHAMP covering about 28 cycles of 24-hour local solar time coverage, during its 10 year mission (2000-2010), while the near sun-synchronous orbit of GOCE resulted in a much more limited local time coverage ranging from 6:20 to 8:00 (am and pm), during a science mission duration of 4 years (2009-2013). For this study, the wind data from both CHAMP and GOCE have been analysed in terms of seasonal variations and geographic and geomagnetic local solar time and latitude coordinates, in order to make statistical comparisons for both the Northern and Southern polar areas. The wind data from both satellites were studied independently and in combination, in order to investigate how the strengths and weaknesses of the instruments and orbit parameters of these missions affect investigations of interhemispheric differences. Finally, the data have been compared with results from coupled ionosphere-thermosphere models and from ground-based FPI and SDI measurements.

  8. The TIMED Doppler Interferometer (TIDI) Neutral Wind Data From The O2 P Branch Broadband Filter

    NASA Astrophysics Data System (ADS)

    Killeen, T. L.; Wu, Q.; Gablehouse, R. D.; Johnson, R. J.; Solomon, S. C.; Skinner, W. R.; Ortland, D. A.; Niciejewski, R. J.; Gell, D. A.

    2004-05-01

    A new operational mode for the instrument has been designed to incorporate a broadband filter, which allows most of the O2 (0-0) P branch to pass through. The broadband filter data increases the signal level by an order of magnitude, which greatly increases the accuracy of the neutral wind allowing more detailed analysis of the migrating and non-migrating tide in the MLT region. Already the new wind data have shown strong non-migrating tide component. Comparisons with ground-based radar measurements show a much better consistency. We will report these new data and tidal analysis results.

  9. Global and Meso-scale Thermospheric Neutral Wind Response to Geomagnetic Storm

    NASA Astrophysics Data System (ADS)

    Lu, G.; Conde, M.; Doornbos, E.

    2015-12-01

    This paper presents a case study of thermospheric response to the 5 April 2010 geomagnetic storm. The NCAR Thermosphere-Ionosphere-Mesosphere Electrodynamic General Circulation Model (TIMEGCM) is used to investigate thermospheric neutral wind variations during the storm, and the model results are validated through comparison with ground and space based observations. More specifically, we conduct detailed inter-comparison of the winds observed by scanning Doppler imagers (SDI) in Alaska with those derived from the TIMEGCM simulations in order to assess model's ability in reproducing the observed meso-scale wind field. The thermospheric winds obtained from the accelerometers on board the GOCE satellite are also used to validate the simulation results on a global scale. While globally the wind velocity tends to be smaller than ion drift velocity, locally the winds can exceed ion drifts and also blow in the different direction than the ions. We will discuss how the thermospheric winds affect the energetic coupling of the magnetosphere-ionosphere-thermosphere system in terms of Joule heating and field-aligned currents.

  10. Modeling large wind farms in conventionally neutral atmospheric boundary layers under varying initial conditions

    NASA Astrophysics Data System (ADS)

    Allaerts, Dries; Meyers, Johan

    2014-05-01

    Atmospheric boundary layers (ABL) are frequently capped by an inversion layer limiting the entrainment rate and boundary layer growth. Commonly used analytical models state that the entrainment rate is inversely proportional to the inversion strength. The height of the inversion turns out to be a second important parameter. Conventionally neutral atmospheric boundary layers (CNBL) are ABLs with zero surface heat flux developing against a stratified free atmosphere. In this regime the inversion-filling process is merely driven by the downward heat flux at the inversion base. As a result, CNBLs are strongly dependent on the heating history of the boundary layer and strong inversions will fail to erode during the course of the day. In case of large wind farms, the power output of the farm inside a CNBL will depend on the height and strength of the inversion above the boundary layer. On the other hand, increased turbulence levels induced by wind farms may partially undermine the rigid lid effect of the capping inversion, enhance vertical entrainment of air into the farm, and increase boundary layer growth. A suite of large eddy simulations (LES) is performed to investigate the effect of the capping inversion on the conventionally neutral atmospheric boundary layer and on the wind farm performance under varying initial conditions. For these simulations our in-house pseudo-spectral LES code SP-Wind is used. The wind turbines are modelled using a non-rotating actuator disk method. In the absence of wind farms, we find that a decrease in inversion strength corresponds to a decrease in the geostrophic angle and an increase in entrainment rate and geostrophic drag. Placing the initial inversion base at higher altitudes further reduces the effect of the capping inversion on the boundary layer. The inversion can be fully neglected once it is situated above the equilibrium height that a truly neutral boundary layer would attain under the same external conditions such as

  11. Neutral thermospheric dynamics observed with two scanning Doppler imagers: 3. Horizontal wind gradients

    NASA Astrophysics Data System (ADS)

    Anderson, C.; Conde, M.; McHarg, M. G.

    2012-05-01

    This is the third and final article in a series of papers reporting on observations of the 630.0 nm thermospheric airglow emission by two spatially separated scanning Doppler imagers (SDI's) in Alaska. In this article, bistatic winds derived from the combined measurements of both instruments in a region of field-of-view overlap were used to derive local-scale maps of horizontal neutral wind gradients. Averaged over the bistatic ‘field-of-view’, these gradient estimates were compared with the monostatic gradient estimates routinely produced by the two SDI's. The key findings to emerge from this study include: 1) the bistatic gradient estimate agreed very well with monostatic estimates for the majority of the time which, given the very different methods involved in each technique, gives us great confidence in our ability to measure F-region neutral wind gradients; 2) the strongest gradient was that which describes the magnetic meridional shear of the zonal wind, which is driven by momentum deposition from convecting ions; 3) vortical flow was more often observed than divergent flow, and both types of flow showed systematic variations with magnetic local time; 4) viscous heating due to non-negligible gradients was on the order of 10-11 Wm-3 which, while small compared to typical F-region Joule heating rates, may be comparable to particle heating, and in a time-integrated sense may be an appreciable source of heating.

  12. Ionosonde and optical determinations of thermospheric neutral winds over the Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Foppiano, A. J.; Won, Y.-I.; Torres, X. A.; Flores, P. A.; Veloso, A. Daniel; Arriagada, M. A.

    2016-11-01

    Ionosonde observations have been made at Great Wall station (62.22°S; 58.97°W), King George Island, and at further south Vernadsky station (65.25°S; 64.27°W), Argentine Islands, for many years. For several days at the two locations the magnetic meridional component of the thermospheric neutral wind has also been derived using three different algorithms with ionosonde data input. At King Sejong station (62.22°S; 58.78°W), close to Great Wall, almost simultaneous thermospheric winds were measured with a Fabry-Perot Interferometer (FPI) during a few days in 1997. All days correspond to intervals of low solar and geomagnetic activity levels and for different seasons. Here, the geographic meridional FPI winds measured at the geographic south pointing location are compared with the magnetic meridional component of the wind derived from ionosonde observations at Vernadsky. Also, the magnetic meridian FPI winds measured using all four cardinal pointing locations are compared with the magnetic meridional component of the wind derived from ionosonde observations at Great Wall. The patterns of the diurnal variations of the magnetic meridional component of ionosonde derived winds using the three different techniques are similar in most cases. However, the amplitudes of these variations and some individual values can differ by more than 150 m/s depending on season, particularly during daytime. Comparison of the autumn FPI with the ionosonde winds for Vernadsky and Great Wall shows that they coincide within observation uncertainties. Results for other seasons are not so good. Some of the discrepancies are discussed in relation to the hour-to-hour variability of ionosonde based winds and the latitudinal gradients of ionospheric characteristics. Other discrepancies need to be further explained. Recently reported FPI mean winds for tens of days in different seasons for Palmer (64.77°S; 64.05°W), Anvers Island, are found to be particularly close to ionosonde derived mean

  13. Structural basis of hepatitis C virus neutralization by broadly neutralizing antibody HCV1

    SciTech Connect

    Kong, Leopold; Giang, Erick; Robbins, Justin B.; Stanfield, Robyn L.; Burton, Dennis R.; Wilson, Ian A.; Law, Mansun

    2012-10-29

    Hepatitis C virus (HCV) infects more than 2% of the global population and is a leading cause of liver cirrhosis, hepatocellular carcinoma, and end-stage liver diseases. Circulating HCV is genetically diverse, and therefore a broadly effective vaccine must target conserved T- and B-cell epitopes of the virus. Human mAb HCV1 has broad neutralizing activity against HCV isolates from at least four major genotypes and protects in the chimpanzee model from primary HCV challenge. The antibody targets a conserved antigenic site (residues 412-423) on the virus E2 envelope glycoprotein. Two crystal structures of HCV1 Fab in complex with an epitope peptide at 1.8-{angstrom} resolution reveal that the epitope is a {beta}-hairpin displaying a hydrophilic face and a hydrophobic face on opposing sides of the hairpin. The antibody predominantly interacts with E2 residues Leu{sup 413} and Trp{sup 420} on the hydrophobic face of the epitope, thus providing an explanation for how HCV isolates bearing mutations at Asn{sup 415} on the same binding face escape neutralization by this antibody. The results provide structural information for a neutralizing epitope on the HCV E2 glycoprotein and should help guide rational design of HCV immunogens to elicit similar broadly neutralizing antibodies through vaccination.

  14. Large-scale wind turbine structures

    NASA Technical Reports Server (NTRS)

    Spera, David A.

    1988-01-01

    The purpose of this presentation is to show how structural technology was applied in the design of modern wind turbines, which were recently brought to an advanced stage of development as sources of renewable power. Wind turbine structures present many difficult problems because they are relatively slender and flexible; subject to vibration and aeroelastic instabilities; acted upon by loads which are often nondeterministic; operated continuously with little maintenance in all weather; and dominated by life-cycle cost considerations. Progress in horizontal-axis wind turbines (HAWT) development was paced by progress in the understanding of structural loads, modeling of structural dynamic response, and designing of innovative structural response. During the past 15 years a series of large HAWTs was developed. This has culminated in the recent completion of the world's largest operating wind turbine, the 3.2 MW Mod-5B power plane installed on the island of Oahu, Hawaii. Some of the applications of structures technology to wind turbine will be illustrated by referring to the Mod-5B design. First, a video overview will be presented to provide familiarization with the Mod-5B project and the important components of the wind turbine system. Next, the structural requirements for large-scale wind turbines will be discussed, emphasizing the difficult fatigue-life requirements. Finally, the procedures used to design the structure will be presented, including the use of the fracture mechanics approach for determining allowable fatigue stresses.

  15. Large-scale wind turbine structures

    NASA Astrophysics Data System (ADS)

    Spera, David A.

    1988-05-01

    The purpose of this presentation is to show how structural technology was applied in the design of modern wind turbines, which were recently brought to an advanced stage of development as sources of renewable power. Wind turbine structures present many difficult problems because they are relatively slender and flexible; subject to vibration and aeroelastic instabilities; acted upon by loads which are often nondeterministic; operated continuously with little maintenance in all weather; and dominated by life-cycle cost considerations. Progress in horizontal-axis wind turbines (HAWT) development was paced by progress in the understanding of structural loads, modeling of structural dynamic response, and designing of innovative structural response. During the past 15 years a series of large HAWTs was developed. This has culminated in the recent completion of the world's largest operating wind turbine, the 3.2 MW Mod-5B power plane installed on the island of Oahu, Hawaii. Some of the applications of structures technology to wind turbine will be illustrated by referring to the Mod-5B design. First, a video overview will be presented to provide familiarization with the Mod-5B project and the important components of the wind turbine system. Next, the structural requirements for large-scale wind turbines will be discussed, emphasizing the difficult fatigue-life requirements. Finally, the procedures used to design the structure will be presented, including the use of the fracture mechanics approach for determining allowable fatigue stresses.

  16. High-latitude lower thermospheric neutral winds at EISCAT and Sondrestrom during LTCS 1

    SciTech Connect

    Johnson, R.M. ); Virdi, T.S. )

    1991-02-01

    The incoherent scatter radar located at Soendre Stroemfjord, Greenland (67{degree}N, 51{degree}W, 74.5{degree}{Lambda}) and the EISCAT incoherent scatter facility located in northern Scandinavia (69.5{degree}N, 19{degree}E, 66.3{degree}{Lambda}) both obtained E and F region measurements during the first campaign of the Lower Thermosphere Coupling Study (LTCS 1, September 21-25, 1987). Neutral winds deduced from these measurements have been analyzed for their mean flow and tidal components. A number of the altitude profiles for the mean winds and the diurnal and semidiurnal wave components at the two radar locations show similar variations with height, indicating that latitudinal rather than longitudinal effects are dominant in determining the observed wind field. Diurnal tidal amplitudes and phases are reasonably well represented by theoretical model results (Forbes, 1982). The semidiurnal amplitudes and phases, although somewhat consistent between the two radars, are not well represented in equinox tidal model results (Forbes and Vial, this issue). Results from both radars indicate a vertical wavelength for the zonal semidiurnal oscillation of approximately 60 km. During a period of impulsive magnetospheric forcing (September 22-23), winds deduced from measurements at both radars show enhanced eastward flows near midnight accompanied by equatorward winds at Sondrestrom. Comparison with the results of a National Center for Atmospheric Research thermosphere-ionosphere general circulation model (TIGCM) simulation of the LTCS 1 interval shows generally better agreement with the observations at EISCAT than at Sondrestrom.

  17. Feedbacks of Composition and Neutral Density Changes on the Structure of the Cusp Density Anomaly

    NASA Astrophysics Data System (ADS)

    Brinkman, D. G.; Walterscheid, R. L.; Clemmons, J. H.

    2015-12-01

    The Earth's magnetospheric cusp provides direct access of energetic particles to the thermosphere. These particles produce ionization and kinetic (particle) heating of the atmosphere. The increased ionization coupled with enhanced electric fields in the cusp produces increased Joule heating and ion drag forcing. These energy inputs cause large wind and temperature changes in the cusp region. Measurements by the CHAMP satellite (460-390- km altitude) have shown strongly enhanced density in the cusp region. The Streak mission (325-123 km), on the other hand, showed a relative depletion. The atmospheric response in the cusp can be sensitive to composition and neutral density changes. In response to heating in the cusp, air of heavier mean molecular weight is brought up from lower altitudes significantly affecting pressure gradients. This opposes the effects of temperature change due to heating and in-turn affects the density and winds produced in the cusp. Also changes in neutral density change the interaction between precipitating particles and the atmosphere and thus change heating rates and ionization in the region affected by cusp precipitation. In this study we assess the sensitivity of the wind and neutral density structure in the cusp region to changes in the mean molecular weight induced by neutral dynamics, and the changes in particle heating rates and ionization which result from changes in neutral density. We use a high resolution two-dimensional time-dependent nonhydrostatic nonlinear dynamical model where inputs can be systematically altered. The resolution of the model allows us to examine the complete range of cusp widths. We compare the current simulations to observations by CHAMP and Streak. Acknowledgements: This research was supported by The Aerospace Corporation's Technical Investment program

  18. Wind velocity measurements in the neutral boundary layer above hilly prairie

    NASA Technical Reports Server (NTRS)

    Sugita, Michiaki; Brutsaert, Wilfried

    1990-01-01

    The Flint Hills region in eastern Kansas is characterized by a strongly dissected rolling to hilly terrain with an average about 25 m of relief between steep ridges and valleys, and with ridges typically separated by distances of the order of 600 m. Intensive radiosonde observations during summer and fall of 1987 allowed the determination of some aspects of the wind regime in the region. For an assumed ground-surface reference of 330 m above sea level (asl), analysis of neutral profiles yielded a value z(0) of about 1.05 m, approximately. Good agreement was obtained between the values of friction velocity derived from wind profiles and values determined independently from the corresponding humidity profiles.

  19. Investigation and validation of wake model combinations for large wind farm modelling in neutral atmospheric boundary layers

    NASA Astrophysics Data System (ADS)

    Tromeur, E.; Puygrenier, S.; Sanquer, S.

    2016-09-01

    This study is focused on assessing the ability of two refined large wind farm models to describe the disturbance of the neutral atmospheric flow caused by large offshore wind farms. Sensitivity studies of internal boundary layer parameters are carried out. An optimum large wind farm correction is then proposed and combined with two different standard single wake models, the Park and EVM models. The large wind farm wake effect is evaluated and validated against measurements of two offshore wind farms at Horns Rev and Nysted and four standard wake models by computing velocity deficit and normalized power. All large wind farm models proposed were able to capture wake width to some degree and the decrease of power output moving through the wind farm. Despite some uncertainties, this very promising model combinations allows us to take into account the slowdown in large wind farms.

  20. Watershed Scale Shear Stress From Tethersonde Wind Profile Measurements Under Near Neutral and Unstable Atmospheric Stability

    NASA Astrophysics Data System (ADS)

    Parlange, M. B.; Katul, G. G.

    1995-04-01

    Mean wind speed profiles were measured in the atmospheric surface layer, using a tethersonde system, above the Ojai Valley Watershed in southern California. The valley is mainly planted with mature avocado and orange trees. The surface shear stress and latent and sensible heat fluxes were measured above the trees which are up to 9 m in height. Near-neutral wind speed profile measurements allowed the determination of the watershed surface roughness (z0 = 1.4 m) and the momentum displacement height (d0 = 7.0 m). The wind speed measurements obtained under unstable atmospheric stability were analyzed using Monin-Obukhov similarity theory. New stability correction functions proposed based on theory and experiments of Kader-Yaglom as well as the now classic Businger-Dyer type functions were tested. The watershed shear stress values calculated using the surface layer wind speed profiles with the new Monin-Obukhov stability functions were found to be improved in comparison with the values obtained with the Businger-Dyer functions under strongly unstable stability conditions. The Monin-Obukhov model with the Businger-Dyer stability correction function underpredicted the momentum flux by 25% under strongly unstable stability conditions, while the new Kader-Yaglom formulation compared well on average (R2 = 0.77) with the surface eddy correlation measurements for all atmospheric stability conditions. The unstable 100-m drag coefficient was found to be u*2/V1002 = 0.0182.

  1. A modelling study of the effects of neutral air winds on electron content at mid-latitudes in winter

    NASA Astrophysics Data System (ADS)

    Sethia, G. C.; Hargreaves, J. K.; Bailey, G. J.; Moffett, R. J.

    1984-05-01

    A modelling study of the effects of neutral air winds on the electron content of the mid-latitude ionosphere protonosphere in winter has been made. The theoretical models are based on solutions of time dependent momentum and continuity equations for oxygen and hydrogen ions. The computations are compared with results from slant path observations of the ATS-6 radio beacon made at Lancaster (U.K.) and Boulder, Colorado (U.S.A.). It is found that the magnitude of the poleward neutral air wind velocity has a strong effect on the general magnitude of the electron content, but that the daily pattern of electron content variation is relatively insensitive to changes in the magnitude and phase of the wind pattern. These results are in contrast with the behavior reported previously (Sethia et al., 1983) for summer conditions. However, the night-time electron content is increased by advancing the phase of the neutral air wind and decreased by retarding it. It appears that day-to-day variations in the electron content pattern in winter cannot be explained as effects of changing neutral air winds, which again contrasts with the findings for summer. As in summer, the wind has a major effect on the filling of the protonosphere, but in opposite sense. It is argued that the effect of the neutral air wind on the ionospheric and the protonospheric electron contents depends on the duration of the poleward wind in relation to daylight and on whether or not the wind reverses direction whilst the ionosphere is sunlit.

  2. The interaction between the solar wind and the heterogeneous neutral gas coma of comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Rubin, Martin; Toth, Gabor; Tenishev, Valeriy; Fougere, Nicolas; Huang, Zhenguang

    2016-07-01

    Comets are surrounded by an extended gas and dust coma. Neutral particles are continuously ionized by solar irradiation and then picked-up by the solar wind. This leads to a complex interaction between the neutral gas coma and the solar wind, which changes over the course of the comet's orbit around the Sun. The European Space Agency's Rosetta spacecraft has been in orbit around comet 67P/Churyumov-Gerasimenko since August 2014. Rosetta carries several instruments to investigate the comet's nucleus and surrounding neutral gas coma and plasma. Part of the payload is the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) that consists of two mass spectrometers and a pressure sensor. ROSINA was designed to measure the neutral gas abundance and composition and low energy ions in the coma in situ. ROSINA observations have shown that the coma is very heterogeneous both in total density and composition of the neutral gas. This heterogeneity is driven in large part by the complex shape of the nucleus and the varying illumination conditions associated with the comet's rotation. In this presentation we will show the time-dependent distribution of the major volatiles around the comet constrained by ROSINA observations. Furthermore we will investigate the impact of the highly non-symmetric neutral gas coma on the interaction of the solar wind with the comet.

  3. Modeling of the coupled magnetospheric and neutral wind dynamos. Semiannual technical status report No. 1, 1 April- 31 October 1993

    SciTech Connect

    Thayer, J.P.

    1993-12-01

    The solar wind interaction with the earth`s magnetosphere generates electric fields and currents that flow from the magnetosphere to the ionosphere at high latitudes. Consequently, the neutral atmosphere is subject to the dissipation and conversion of this electrical energy to thermal and mechanical energy through Joule heating and Lorentz forcing. As a result of the mechanical energy stored within the neutral wind (caused in part by Lorentz--and pressure gradient--forces set up by the magnetospheric flux of electrical energy), electric currents and fields can be generated in the ionosphere through the neutral wind dynamo mechanism. At high latitudes this source of electrical energy has been largely ignored in past studies, owing to the assumed dominance of the solar wind/magnetospheric dynamo as an electrical energy source to the ionosphere. However, other researchers have demonstrated that the available electrical energy provided by the neutral wind is significant at high latitudes, particularly in the midnight sector of the polar cap and in the region of the magnetospheric convection reversal. As a result, the conclusions of a number of broad ranging high-latitude investigations may be modified if the neutral-wind contribution to high-latitude electrodynamics is properly accounted for. These include the following: studies assessing solar wind-magnetospheric coupling by comparing the cross polar cap potential with solar wind parameters; research based on the alignment of particle precipitation with convection or field aligned current boundaries; and synoptic investigations attributing seasonal variations in the observed electric field and current patterns to external sources. These research topics have been initiated by satellite and ground-based observations and have been attributed to magnetospheric causes.

  4. Analysis of Solar Wind Samples Returned by Genesis Using Laser Post Ionization Secondary Neutral Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Veryovkin, I. V.; Calaway, W. F.; Tripa, C. E.; Pellin, M. J.; Burnett, D. S.

    2005-12-01

    A new secondary neutral mass spectrometry (SNMS) instrument implementing laser post ionization (LPI) of ion sputtered and laser desorbed neutral species has been developed and constructed for the specific purpose of quantitative analysis of metallic elements at ultra trace levels in solar wind collector samples returned to Earth by the Genesis Discovery mission. The first LPI SNMS measurements are focusing on determining Al, Ca, Cr, and Mg in these samples. These measurements provide the first concentration and isotopic abundances determinations for several key metallic elements and also elucidate possible fractionation effects between the photosphere and the solar wind compositions. It is now documented that Genesis samples suffered surface contamination both during flight and during the breach of the Sample Return Capsule when it crashed. Since accurate quantitative analysis is compromised by sample contamination, several features have been built into the new LPI SNMS instrument to mitigate this difficulty. A normally-incident, low-energy (<500 eV) ion beam combined with a keV energy ion beam and a desorbing laser beam (both microfocused) enables dual beam analyses. The low-energy ion beam can be used to remove surface contaminant by sputtering with minimum ion beam mixing. This low-energy beam also will be used to perform ion beam milling, while either the microfocused ion or laser beam probes the solar wind elemental compositions as a function of sample depth. Because of the high depth resolution of dual beam analyses, such depth profiles clearly distinguish between surface contaminants and solar wind implanted atoms. In addition, in-situ optical and electron beam imaging for observing and avoiding particulates and scratches on solar wind sample surfaces is incorporated in the new LPI SNMS instrument to further reduce quantification problems. The current status of instrument tests and analyses will be presented. This work is supported by the U. S. Department of

  5. Thermospheric neutral wind profile in moonlit midnight by Lithium release experiments in Japan

    NASA Astrophysics Data System (ADS)

    Yamamoto, M. Y.; Watanabe, S.; Abe, T.; Kakinami, Y.; Habu, H.; Yamamoto, M.

    2015-12-01

    Neutral wind profiles were observed in lower thermosphere at about between 90 km and 130 km altitude by using resonance scattering light of moonlit Lithium (Li) vapor released from sounding rockets in midnight (with almost full-moon condition) in 2013 in Japan. As a target of the Daytime Dynamo campaign, Li release experiment was operated at Wallops Flight Facility (WFF) of NASA, U.S.A. in July, 2013 (Pfaff et al., 2015, this meeting), while the same kind of rocket-ground observation campaign in midnight was carried out by using S-520-27/S-310-42 sounding rockets in Uchinoura Space Center (USC) of JAXA, Kagoshima, Japan, also in July 2013.Since imaging signal-to-noise (S/N) condition of the experiment was so severe, we conducted to apply airborne observation for imaging the faint moonlit Li tracers so as to reduce the illuminating intensity of the background skies as an order of magnitude. Two independent methods for calculating the wind profile were applied to the Lithium emission image sequences successfully obtained by the airborne imaging by special Li imagers aboard the airplanes in order to derive precise information of Li tracers motion under the condition of single observation site on a moving aircraft along its flight path at about 12 km altitude in lower stratosphere. Slight attitude-feedback motion of the aircraft's 3-axes attitude changes (rolling, yawing and pitching) was considered for obtaining precise coordinates on each snapshot. Another approach is giving a simple mathematic function for wind profile to resolve the shape displacement of the imaged Li tracers. As a result, a wind profile in moonlit thermosphere was calculated in a range up to about 150 m/s with some fluctuated parts possibly disturbed by wind shears. In the same experiment, another sounding rocket S-310-42 with a TMA canister was also launched from USC/JAXA at about 1 hour before the rocket with carrying the Lithium canisters, thus, we can derive the other 2 profiles determined by

  6. Atmospheric response in aurora experiment: Observations of E and F region neutral winds in a region of postmidnight diffuse aurora

    NASA Technical Reports Server (NTRS)

    Larsen, M. F.; Marshall, T. R.; Mikkelsen, I. S.; Emery, B. A.; Christensen, A.; Kayser, D.; Hecht, J.; Lyons, L.; Walterscheid, R.

    1995-01-01

    The goal of the Atmospheric Response in Aurora (ARIA) experiment carried out at Poker Flat, Alaska, on March 3, 1992, was to determine the response of the neutral atmosphere to the long-lived, large-scale forcing that is characteristic of the diffuse aurora in the post midnight sector. A combination of chemical release rocket wind measurements, instrumented rocket composition measurements, and ground-based optical measurements were used to characterize the response of the neutral atmosphere. The rocket measurements were made at the end of a 90-min period of strong Joule heating. We focus on the neutral wind measurements made with the rocket. The forcing was determined by running the assimilated mapping of ionospheric electrodynamics (AMIE) analysis procedure developed at the National Center for Atmospheric Research. The winds expected at the latitude and longitude of the experiment were calculated using the spectral thermospheric general circulation model developed at the Danish Meteorological Institute. Comparisons of the observations and the model suggest that the neutral winds responded strongly in two height ranges. An eastward wind perturbation of approximately 100 m/s developed between 140 and 200 km altitude with a peak near 160 km. A southwestward wind with peak magnitude of approximately 150 m/s developed near 115 km altitude. The large amplitude winds at the lower altitude are particularly surprising. They appear to be associated with the upward propagating semidiurnal tide. However, the amplitude is much larger than predicted by any of the tidal models, and the shear found just below the peak in the winds was nominally unstable with a Richardson number of approximately 0.08.

  7. EFFECT OF SOLAR CHROMOSPHERIC NEUTRALS ON EQUILIBRIUM FIELD STRUCTURES

    SciTech Connect

    Arber, T. D.; Botha, G. J. J.; Brady, C. S. E-mail: G.J.J.Botha@warwick.ac.u

    2009-11-10

    Solar coronal equilibrium fields are often constructed by nonlinear force-free field (NLFFF) extrapolation from photospheric magnetograms. It is well known that the photospheric field is not force-free and the correct lower boundary for NLFFF construction ought to be the top of the chromosphere. To compensate for this, pre-filtering algorithms are often applied to the photospheric data to remove the non-force-free components. Such pre-filtering models, while physically constrained, do not address the mechanisms that may be responsible for the field becoming force-free. The chromospheric field can change through, for example, field expansion due to gravitational stratification, reconnection, or flux emergence. In this paper, we study and quantify the effect of the chromospheric neutrals on equilibrium field structures. It is shown that, depending on the degree to which the photospheric field is not force-free, the chromosphere will change the structure of the equilibrium field. This is quantified to give an estimate of the change in alpha profiles one might expect due to neutrals in the chromosphere. Simple scaling of the decay time of non-force-free components of the magnetic field due to chromospheric neutrals is also derived. This is used to quantify the rate at which, or equivalent at which height, the chromosphere is expected to become force-free.

  8. Coronal structure and the solar wind

    NASA Technical Reports Server (NTRS)

    Roelof, E. C.

    1974-01-01

    Aspects concerning the open coronal structure and geomagnetic disturbances are considered along with the general coronal emission characteristics and relations between the open coronal structure and the interplanetary field. The nonstatistical indicators of coronal structure are examined and questions are investigated regarding the accuracy obtained in the determination of the emission latitude and longitude in the high corona for plasma, fields, and particles. Attention is given to the problem of particle population organization by low-coronal neutral line structures in the absence of a high coronal polarity structure.

  9. Structure and dynamics of supercooled water in neutral confinements

    NASA Astrophysics Data System (ADS)

    Klameth, F.; Vogel, M.

    2013-04-01

    We perform molecular dynamics simulations to study the structure and dynamics of liquid water in neutral nanopores, which are generated by pinning a suitable subset of water molecules in an equilibrium configuration of a bulk system. It is found that such neutral confinement does not disturb the structure of water, in particular, the local tetrahedral order, while it imposes a pronounced spatial inhomogeneity on the dynamics of water. Specifically, when the pore wall is approached, hopping motion sets in and water dynamics slows down. We show that the logarithm of the correlation time is an exponential function of the distance to the wall, indicating a tremendous gradient of water mobility across the confinement. Upon cooling, the length scale associated with this exponential distance dependence and, thus, the range of the wall effect increases, at least down to the critical temperature of mode coupling theory, Tc. Also, the temperature dependence of water dynamics varies across the pore, i.e., fragility is high in the pore center, while it is low near the pore wall. Due to all these effects, time-temperature superposition is violated. Our observations for a neutral confinement reveal that specific interactions at hydrophilic or hydrophobic walls are not the main cause of spatially inhomogeneous dynamics of confined water. In view of similarities with the behavior of Lennard-Jones liquids in neutral confinements, one may rather speculate that the effects observed for confined water are general and result from the existence of a static contribution to the energy landscape, which is imprinted by an immobile environment.

  10. Wind loads for bar-truss structures

    NASA Technical Reports Server (NTRS)

    Katow, M. S.

    1981-01-01

    An analysis method developed to calculate the wind loads on the nodes or joints of the truss type support structure of the 64 meter antenna is described. The method uses the CBAR element and GRID coordinate cards of the NASTRAN or IDEAS structural analysis programs as inputs to the computer model of the structure. Cross flow principles and vector analysis are also used in the analysis. The algorithms used are described and probable accuracy of the solution is discussed.

  11. Structural basis for the antibody neutralization of Herpes simplex virus

    SciTech Connect

    Lee, Cheng-Chung; Lin, Li-Ling; Chan, Woan-Eng; Ko, Tzu-Ping; Lai, Jiann-Shiun; Wang, Andrew H.-J.

    2013-10-01

    The gD–E317-Fab complex crystal revealed the conformational epitope of human mAb E317 on HSV gD, providing a molecular basis for understanding the viral neutralization mechanism. Glycoprotein D (gD) of Herpes simplex virus (HSV) binds to a host cell surface receptor, which is required to trigger membrane fusion for virion entry into the host cell. gD has become a validated anti-HSV target for therapeutic antibody development. The highly inhibitory human monoclonal antibody E317 (mAb E317) was previously raised against HSV gD for viral neutralization. To understand the structural basis of antibody neutralization, crystals of the gD ectodomain bound to the E317 Fab domain were obtained. The structure of the complex reveals that E317 interacts with gD mainly through the heavy chain, which covers a large area for epitope recognition on gD, with a flexible N-terminal and C-terminal conformation. The epitope core structure maps to the external surface of gD, corresponding to the binding sites of two receptors, herpesvirus entry mediator (HVEM) and nectin-1, which mediate HSV infection. E317 directly recognizes the gD–nectin-1 interface and occludes the HVEM contact site of gD to block its binding to either receptor. The binding of E317 to gD also prohibits the formation of the N-terminal hairpin of gD for HVEM recognition. The major E317-binding site on gD overlaps with either the nectin-1-binding residues or the neutralizing antigenic sites identified thus far (Tyr38, Asp215, Arg222 and Phe223). The epitopes of gD for E317 binding are highly conserved between two types of human herpesvirus (HSV-1 and HSV-2). This study enables the virus-neutralizing epitopes to be correlated with the receptor-binding regions. The results further strengthen the previously demonstrated therapeutic and diagnostic potential of the E317 antibody.

  12. Imaging the heliosphere using neutral atoms from solar wind energy down to 15 eV

    SciTech Connect

    Galli, A.; Wurz, P.; Fuselier, S. A.; McComas, D. J.; Bzowski, M.; Sokół, J. M.; Kubiak, M. A.; Möbius, E.

    2014-11-20

    We study the spatial and temporal distribution of hydrogen energetic neutral atoms (ENAs) from the heliosheath observed with the IBEX-Lo sensor of the Interstellar Boundary EXplorer (IBEX) from solar wind energies down to the lowest available energy (15 eV). All available IBEX-Lo data from 2009 January until 2013 June were included. The sky regions imaged when the spacecraft was outside of Earth's magnetosphere and when the Earth was moving toward the direction of observation offer a sufficient signal-to-noise ratio even at very low energies. We find that the ENA ribbon—a 20° wide region of high ENA intensities—is most prominent at solar wind energies whereas it fades at lower energies. The maximum emission in the ribbon is located near the poles for 2 keV and closer to the ecliptic plane for energies below 1 keV. This shift is an evidence that the ENA ribbon originates from the solar wind. Below 0.1 keV, the ribbon can no longer be identified against the globally distributed ENA signal. The ENA measurements in the downwind direction are affected by magnetospheric contamination below 0.5 keV, but a region of very low ENA intensities can be identified from 0.1 keV to 2 keV. The energy spectra of heliospheric ENAs follow a uniform power law down to 0.1 keV. Below this energy, they seem to become flatter, which is consistent with predictions. Due to the subtraction of local background, the ENA intensities measured with IBEX agree with the upper limit derived from Lyα observations.

  13. Imaging the Heliosphere Using Neutral Atoms from Solar Wind Energy Down to 15 eV

    NASA Astrophysics Data System (ADS)

    Galli, A.; Wurz, P.; Fuselier, S. A.; McComas, D. J.; Bzowski, M.; Sokół, J. M.; Kubiak, M. A.; Möbius, E.

    2014-11-01

    We study the spatial and temporal distribution of hydrogen energetic neutral atoms (ENAs) from the heliosheath observed with the IBEX-Lo sensor of the Interstellar Boundary EXplorer (IBEX) from solar wind energies down to the lowest available energy (15 eV). All available IBEX-Lo data from 2009 January until 2013 June were included. The sky regions imaged when the spacecraft was outside of Earth's magnetosphere and when the Earth was moving toward the direction of observation offer a sufficient signal-to-noise ratio even at very low energies. We find that the ENA ribbon—a 20° wide region of high ENA intensities—is most prominent at solar wind energies whereas it fades at lower energies. The maximum emission in the ribbon is located near the poles for 2 keV and closer to the ecliptic plane for energies below 1 keV. This shift is an evidence that the ENA ribbon originates from the solar wind. Below 0.1 keV, the ribbon can no longer be identified against the globally distributed ENA signal. The ENA measurements in the downwind direction are affected by magnetospheric contamination below 0.5 keV, but a region of very low ENA intensities can be identified from 0.1 keV to 2 keV. The energy spectra of heliospheric ENAs follow a uniform power law down to 0.1 keV. Below this energy, they seem to become flatter, which is consistent with predictions. Due to the subtraction of local background, the ENA intensities measured with IBEX agree with the upper limit derived from Lyα observations.

  14. The collapse of the midnight ionosphere and behavior of meridional neutral winds at Townsville over a full solar cycle

    NASA Astrophysics Data System (ADS)

    Dandenault, P. B.; Richards, P. G.

    2015-11-01

    This paper investigates the causes of the sudden descent (midnight collapse) of the ionosphere at Townsville, Australia, during the equinox periods of years between 1970 and 1980. The collapse of hmF2 at midnight is found to occur on 89% of the 330 equinox nights that are investigated, and the mean magnitude of the midnight collapse is 84 km in the March equinox periods and 99 km in the September equinox periods. Observations of hmF2 are used to determine equivalent meridional neutral winds using a first principles physics model. Harmonic analysis of these derived winds reveals the existence of significant diurnal (24 h), semidiurnal (12 h), and terdiurnal (8 h) tidal components. The contribution of wind harmonics to the midnight collapse is determined by band-pass filtering the winds to only allow certain tides and then modeling their effect on hmF2 near midnight. The results indicate that the diurnal, semidiurnal, and terdiurnal components of the meridional neutral wind all play a significant role at various times, but the effect of the 6 h wind component is minimal. The spectral analysis also reveals that the terdiurnal wind component becomes dominant during solar maximum. Electric fields do not appear to be responsible for the midnight hmF2 collapse because it is seldom seen at the near-conjugate station of Akita, Japan.

  15. Highly Structured Wind in Vela X-1

    NASA Technical Reports Server (NTRS)

    Kreykenbohm, Ingo; Wilms, Joern; Kretschmar, Peter; Torrejon, Jose Miguel; Pottschmidt, Katja; Hanke, Manfred; Santangelo, Andrea; Ferrigno, Carlo; Staubert, Ruediger

    2008-01-01

    We present an in-depth analysis of the spectral and temporal behavior of a long almost uninterrupted INTEGRAL observation of Vela X-1 in Nov/Dec 2003. In addition to an already high activity level, Vela X-1 exhibited several very intense flares with a maximum intensity of more than 5 Crab in the 20 40 keV band. Furthermore Vela X-1 exhibited several off states where the source became undetectable with ISGRI. We interpret flares and off states as being due to the strongly structured wind of the optical companion: when Vela X-1 encounters a cavity in the wind with strongly reduced density, the flux will drop, thus potentially triggering the onset of the propeller effect which inhibits further accretion, thus giving rise to the off states. The required drop in density to trigger the propeller effect in Vela X-1 is of the same order as predicted by theoretical papers for the densities in the OB star winds. The same structured wind can give rise to the giant flares when Vela X-1 encounters a dense blob in the wind. Further temporal analysis revealed that a short lived QPO with a period of 6800 sec is present. The part of the light curve during which the QPO is present is very close to the off states and just following a high intensity state, thus showing that all these phenomena are related.

  16. PULSAR WIND NEBULAE WITH THICK TOROIDAL STRUCTURE

    SciTech Connect

    Chevalier, Roger A.; Reynolds, Stephen P. E-mail: reynolds@ncsu.edu

    2011-10-10

    We investigate a class of pulsar wind nebulae that show synchrotron emission from a thick toroidal structure. The best studied such object is the small radio and X-ray nebula around the Vela pulsar, which can be interpreted as the result of interaction of a mildly supersonic inward flow with the recent pulsar wind. Such a flow near the center of a supernova remnant can be produced in a transient phase when the reverse shock reaches the center of the remnant. Other nebulae with a thick toroidal structure are G106.6+2.9 and G76.9+1.0. Their structure contrasts with young pulsar nebulae like the Crab Nebula and 3C 38, which show a more chaotic, filamentary structure in the synchrotron emission. In both situations, a torus-jet structure is present where the pulsar wind passes through a termination shock, indicating the flow is initially toroidal. We suggest that the difference is due to the Rayleigh-Taylor instability that operates when the outer boundary of the nebula is accelerating into freely expanding supernova ejecta. The instability gives rise to mixing in the Crab and related objects, but is not present in the nebulae with thick toroidal regions.

  17. High time and height resolution neutral wind profile measurements across the mesosphere/lower thermosphere region using the Arecibo incoherent scatter radar

    NASA Astrophysics Data System (ADS)

    Hysell, D. L.; Larsen, M. F.; Sulzer, M. P.

    2014-03-01

    A method for estimating the vector neutral wind profiles in the mesosphere and lower thermosphere (MALT) region of the upper atmosphere from Arecibo dual-beam incoherent scatter radar data is presented. The method yields continuous estimates of both the altitude-averaged F region plasma drifts and all three components of the altitude-resolved neutral wind profiles in the MALT using data taken while the Arecibo feed system swings in azimuth. The problem is mixed determined, and its solution is not inherently unique. Second-order Tikhonov regularization is used to find solutions consistent with the available data while being minimally structured, additional structure being unsupported by the data. The solution is found using the method of conjugate gradient least squares and sparse matrix mathematics. Example data acquired during an interval of midlatitude spread F are used to illustrate the method. The estimated wind profiles exhibit characteristics broadly consistent with gravity waves but are impulsive, with features that generally persist for less than one and a half wave periods.

  18. Spatial-temporal analysis of coherent offshore wind field structures measured by scanning Doppler-lidar

    NASA Astrophysics Data System (ADS)

    Valldecabres, L.; Friedrichs, W.; von Bremen, L.; Kühn, M.

    2016-09-01

    An analysis of the spatial and temporal power fluctuations of a simplified wind farm model is conducted on four offshore wind fields data sets, two from lidar measurements and two from LES under unstable and neutral atmospheric conditions. The integral length scales of the horizontal wind speed computed in the streamwise and the cross-stream direction revealed the elongation of the structures in the direction of the mean flow. To analyse the effect of the structures on the power output of a wind turbine, the aggregated equivalent power of two wind turbines with different turbine spacing in the streamwise and cross-stream direction is analysed at different time scales under 10 minutes. The fact of considering the summation of the power of two wind turbines smooths out the fluctuations of the power output of a single wind turbine. This effect, which is stronger with increasing spacing between turbines, can be seen in the aggregation of the power of two wind turbines in the streamwise direction. Due to the anti-correlation of the coherent structures in the cross-stream direction, this smoothing effect is stronger when the aggregated power is computed with two wind turbines aligned orthogonally to the mean flow direction.

  19. Structural health monitoring of wind turbines

    SciTech Connect

    Simmermacher, T.; James, G.H. III.; Hurtado, J.E.

    1997-09-01

    To properly determine what is needed in a structural health monitoring system, actual operational structures need to be studied. We have found that to effectively monitor the structural condition of an operational structure four areas must be addressed: determination of damage-sensitive parameters, test planning, information condensation, and damage identification techniques. In this work, each of the four areas has been exercised on an operational structure. The structures studied were all be wind turbines of various designs. The experiments are described and lessons learned will be presented. The results of these studies include a broadening of experience in the problems of monitoring actual structures as well as developing a process for implementing such monitoring systems.

  20. The neutral wind in ionospheric modeling: the month-long ISR campaign at Millstone Hill, October 2002

    NASA Astrophysics Data System (ADS)

    David, M.; Sojka, J. J.; Schunk, R. W.; Holt, J. M.

    2013-12-01

    The thermospheric wind is one of the most important inputs in modeling the mid-latitude ionosphere; unfortunately the currently available models do not seem to provide a very accurate representation of it. When running an ionospheric model, such as Utah State University's TDIM, the neutral wind input has a large effect on both the peak density of the F-layer (NmF2) as well as the height of the layer (hmF2). The month-long campaign of the Incoherent Scatter Radar at Millstone Hill provides an excellent base for the comparison of model runs to observations, to determine what sort of neutral wind is needed to provide a match with the height and peak density of the F layer. The data base shows a marked degree of day-to-day variability in two regards: the value of NmF2 (or TEC) at the time of sunrise (approximately 1100 hrs UT), and the rate at which the value of TEC increases during the morning sunlit hours. In a previous study we showed that this day-to-day variability could be accounted for by variations in either a neutral wind, or a penetrating electric field. Recent work has indicated that in this case the electric field will not account for the variation, therefore we look to the neutral wind. Total Electron Content (TEC) at Millstone Hill during the month-long ISR campaign of October 2002. Notice the day-to-day variability in the TEC value at the time of sunrise (about 1100 UT) as well as the rate at which TEC increases during the morning hours.

  1. Structural Dynamic Behavior of Wind Turbines

    NASA Technical Reports Server (NTRS)

    Thresher, Robert W.; Mirandy, Louis P.; Carne, Thomas G.; Lobitz, Donald W.; James, George H. III

    2009-01-01

    The structural dynamicist s areas of responsibility require interaction with most other members of the wind turbine project team. These responsibilities are to predict structural loads and deflections that will occur over the lifetime of the machine, ensure favorable dynamic responses through appropriate design and operational procedures, evaluate potential design improvements for their impact on dynamic loads and stability, and correlate load and control test data with design predictions. Load prediction has been a major concern in wind turbine designs to date, and it is perhaps the single most important task faced by the structural dynamics engineer. However, even if we were able to predict all loads perfectly, this in itself would not lead to an economic system. Reduction of dynamic loads, not merely a "design to loads" policy, is required to achieve a cost-effective design. The two processes of load prediction and structural design are highly interactive: loads and deflections must be known before designers and stress analysts can perform structural sizing, which in turn influences the loads through changes in stiffness and mass. Structural design identifies "hot spots" (local areas of high stress) that would benefit most from dynamic load alleviation. Convergence of this cycle leads to a turbine structure that is neither under-designed (which may result in structural failure), nor over-designed (which will lead to excessive weight and cost).

  2. Helicoidal structures, useful as wind turbines

    SciTech Connect

    Krolick, R.S.; Storey, J.S.; Le Fever, R.E.

    1987-11-24

    A wind-responsive structure is described comprising, in combination: an elongated sheet of flexible material which is substantially impervious to the wind and which has oppositely-disposed ends; bracing means attached to and extending throughout the length of the sheet, the bracing means being disposed on the sheet to permit the sheet to be collapsed into a folded compact condition and to position the sheet into a helical configuration upon the application of a pulling force to the oppositely disposed ends of the sheet, the bracing means comprising at least one elongated member, and attachment means at the oppositely-disposed ends of the sheet for attaching the sheet to respective associated supporting structures.

  3. Using IBEX data to constrain the heliosphere's large-scale structure: interstellar neutral gas and the Warm Breeze

    NASA Astrophysics Data System (ADS)

    Bzowski, Maciej; McComas, David; Galli, Andre; Kucharek, Harald; Wurz, Peter; Sokol, Justyna M.; Schwadron, Nathan; Heirtzler, David M.; Kubiak, M. Marzena A.; Möbius, Eberhard; Fuselier, Stephen; Swaczyna, Paweł; Leonard, Trevor; Park, Jeewoo

    2016-07-01

    The large-scale structure of the heliosphere is governed by the interaction of the partly ionized, magnetized interstellar gas and the magnetized, fully ionized solar wind, structured in heliolatitude. Determining factors of this interaction are the density and flow velocity of interstellar gas relative to the Sun, the Mach number of this flow and the strength and inclination of the interstellar magnetic field to the flow vector at the interstellar side, and the magnitude of dynamic pressure of solar wind and the strength of its embedded magnetic field at the solar side. As a result of charge exchange interactions operating in the boundary region between the heliosphere and interstellar matter, a new population of neutral atoms is created, in addition to the population of unperturbed interstellar neutral gas. Both of these populations penetrate deep inside the heliosphere, where they can be sampled by the first space probe dedicated to observations of the heliosphere and its immediate surroundings by means of neutral atoms: the Interstellar Boundary Explorer (IBEX). Due to distortion of the heliosphere from axial symmetry, the secondary population of interstellar neutrals, created via charge exchange between the plasma flowing past the heliopause and the unperturbed pristine neutral interstellar gas, appears to be coming from a different direction than the unperturbed interstellar neutral flow. These two directions should be coplanar with the plane defined by the local interstellar magnetic field and the flow direction of the unperturbed gas. IBEX provides an unprecedented opportunity to study and interpret these relations. The IBEX science team have recently accomplished important milestones in researching the primary and secondary populations of interstellar gas and their relation to the local interstellar magnetic fields. First, the temperature and velocity vector of the inflowing interstellar neutral gas has been determined with unprecedented robustness based

  4. Evidence of active region imprints on the solar wind structure

    NASA Technical Reports Server (NTRS)

    Hick, P.; Jackson, B. V.

    1995-01-01

    A common descriptive framework for discussing the solar wind structure in the inner heliosphere uses the global magnetic field as a reference: low density, high velocity solar wind emanates from open magnetic fields, with high density, low speed solar wind flowing outward near the current sheet. In this picture, active regions, underlying closed magnetic field structures in the streamer belt, leave little or no imprint on the solar wind. We present evidence from interplanetary scintillation measurements of the 'disturbance factor' g that active regions play a role in modulating the solar wind and possibly contribute to the solar wind mass output. Hence we find that the traditional view of the solar wind, though useful in understanding many features of solar wind structure, is oversimplified and possibly neglects important aspects of solar wind dynamics

  5. Coherent structures in the Es layer and neutral middle atmosphere

    NASA Astrophysics Data System (ADS)

    Mošna, Zbyšek; Knížová, Petra Koucká; Potužníková, Kateřina

    2015-12-01

    The present paper shows results from the summer campaign performed during geomagnetically quiet period from June 1 to August 31, 2009. Within time-series of stratospheric and mesospheric temperatures at pressure levels 10-0.1 hPa, mesospheric winds measured in Collm, Germany, and the sporadic E-layer parameters foEs and hEs measured at the Pruhonice station we detected specific coherent wave-bursts in planetary wave domain. Permanent wave-like activity is observed in all analyzed data sets. However, the number of wave-like structures persistent in large range of height from the stratosphere to lower ionosphere is limited. The only coherent modes that are detected on consequent levels of the atmosphere are those corresponding to eigenmodes of planetary waves.

  6. Large eddy simulation of a large wind-turbine array in a conventionally neutral atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Allaerts, Dries; Meyers, Johan

    2015-06-01

    Under conventionally neutral conditions, the boundary layer is frequently capped by an inversion layer, which counteracts vertical entrainment of kinetic energy. Very large wind farms are known to depend on vertical entrainment to transport energy from above the farm towards the turbines. In this study, large eddy simulations of an infinite wind-turbine array in a conventionally neutral atmospheric boundary layer are performed. By carefully selecting the initial potential-temperature profile, the influence of the height and the strength of a capping inversion on the power output of a wind farm is investigated. Results indicate that both the height and the strength have a significant effect on the boundary layer flow, and that the height of the neutral boundary layer is effectively controlled by the capping inversion. In addition, it is shown that the vertical entrainment rate decreases for increasing inversion strength or height. In our infinite wind-farm simulations, varying the inversion characteristics leads to differences in power extraction on the order of 13% ± 0.2% (for increasing the strength from 2.5 to 10 K), and 31% ± 0.4% (for increasing the height from 500 to 1500 m). A detailed analysis of the mean kinetic-energy equation is included, showing that the variation in power extraction originates from the work done by the driving pressure gradient related to the boundary layer height and the geostrophic angle, while entrainment of kinetic energy from the free atmosphere does not play a significant role. Also, the effect of inversion strength on power extraction is energetically not related to different amounts of energy entrained, but explained by a difference in boundary layer growth, leading to higher boundary layers for lower inversion strengths. We further present a simple analytical model that allows to obtain wind-farm power output and driving power for the fully developed regime as function of Rossby number and boundary layer height.

  7. The interaction between an impact-produced neutral gas cloud and the solar wind at the lunar surface

    NASA Technical Reports Server (NTRS)

    Lindeman, R. A.; Vondrak, R. R.; Freeman, J. W.; Snyder, C. W.

    1974-01-01

    On Apr. 15, 1970, the Apollo 13 S-IVB stage impacted the nighttime lunar surface. Beginning 20 sec after impact, the Suprathermal Ion Detector Experiment and the Solar Wind Spectrometer observed a large flux of positive ions (maximum flux of about 3 x 10 to the 8th ions/sq cm/sec/ster) and electrons. Two separate streams of ions were observed: a horizontal flux that appeared to be deflected solar wind ions and a smaller vertical flux of predominantly heavy ions (greater than 10 amu), which probably were material vaporized from the S-IVB stage. An examination of the data shows that collisions between neutral molecules and hot electrons (50 eV) were probably an important ionization mechanism in the impact-produced neutral gas cloud. These electrons, which were detected by the Solar Wind Spectrometer, are thought to have been energized in a shock front or some form of intense interaction region between the cloud and the solar wind. Thus strong ionization and acceleration are seen under conditions approaching a collisionless state.

  8. Determining the power-law wind-profile exponent under near-neutral stability conditions at sea

    NASA Technical Reports Server (NTRS)

    Hsu, S. A.; Meindl, Eric A.; Gilhousen, David B.

    1994-01-01

    On the basis of 30 samples from near-simultaneous overwater measurements by pairs of anemometers located at different heights in the Gulf of Mexico and off the Chesapeake Bay, Virginia, the mean and standard deviation for the exponent of the power-law wind profile over the ocean under near-neutral atmospheric stability conditions were determined to be 0.11 +/- 0.03. Because this mean value is obtained from both deep and shallow water environments, it is recommended for use at sea to adjust the wind speed measurements at different heights to the standard height of 10 m above the mean sea surface. An example to apply this P value to estimate the momentum flux or wind stress is provided.

  9. Solar wind compressible structures at ion scales

    NASA Astrophysics Data System (ADS)

    Perrone, D.; Alexandrova, O.; Rocoto, V.; Pantellini, F. G. E.; Zaslavsky, A.; Maksimovic, M.; Issautier, K.; Mangeney, A.

    2014-12-01

    In the solar wind turbulent cascade, the energy partition between fluid and kinetic degrees of freedom, in the vicinity of plasma characteristic scales, i.e. ion and electron Larmor radius and inertial lengths, is still under debate. In a neighborhood of the ion scales, it has been observed that the spectral shape changes and fluctuations become more compressible. Nowadays, a huge scientific effort is directed to the comprehension of the link between macroscopic and microscopic scales and to disclose the nature of compressive fluctuations, meaning that if space plasma turbulence is a mixture of quasi-linear waves (as whistler or kinetic Alfvèn waves) or if turbulence is strong with formation of coherent structures responsible for dissipation. Here we present an automatic method to identify compressible coherent structures around the ion spectral break, using Morlet wavelet decomposition of magnetic signal from Cluster spacecraft and reconstruction of magnetic fluctuations in a selected scale range. Different kind of coherent structures have been detected: from soliton-like one-dimensional structures to current sheet- or wave-like two-dimensional structures. Using a multi-satellite analysis, in order to characterize 3D geometry and propagation in plasma rest frame, we recover that these structures propagate quasi-perpendicular to the mean magnetic field, with finite velocity. Moreover, without using the Taylor hypothesis, the spatial scales of coherent structures have been estimated. Our observations in the solar wind can provide constraints on theoretical modeling of small scale turbulence and dissipation in collisionless magnetized plasmas.

  10. Neutral thermospheric dynamics observed with two scanning Doppler imagers: 1. Monostatic and bistatic winds

    NASA Astrophysics Data System (ADS)

    Anderson, C.; Conde, M.; McHarg, M. G.

    2012-03-01

    Doppler-shift measurements of the thermospheric 630.0 nm emission recorded by two spatially separated imaging Fabry-Perot spectrometers in Alaska have been combined to infer F region horizontal wind vectors at approximately 75 locations across their overlapping fields-of-view. These “bistatic” horizontal wind estimates rely only on an assumption regarding the local vertical wind (and assume a common observing volume), and thus represent a more direct measurement of the wind than do the monostatic (single-station) vector wind fields routinely inferred by these instruments. Here we present comparisons between both the independently derived monostatic wind fields from each instrument and the bistatic wind estimates inferred in their common observing volumes. Data are presented from observations on three nights during 2010. Two principal findings have emerged from this study. First, the monostatic technique was found to be capable of estimating the actual large-scale wind field reliably under a large range of geophysical conditions, and is well suited to applications requiring only a large-scale, ‘big picture’ approximation of the wind flow. Secondly, the bistatic (or tristatic) technique is essential for applications requiring detailed knowledge of the small-scale behavior of the wind, as for example is required when searching for gravity waves.

  11. Modeling of the coupled magnetospheric and neutral wind dynamos. Annual Technical status report No. 1, 1 April 1993-30 March 1994

    SciTech Connect

    Thayer, J.P.

    1994-03-01

    This report summarizes the progress made in the first year of NASA Grant No. NAGW-3508 entitled Modeling of the Coupled Magnetospheric and Neutral Wind Dynamos.' The approach taken has been to impose magnetospheric boundary conditions with either pure voltage or current characteristics and solve the neutral wind dynamo equation under these conditions. The imposed boundary conditions determine whether the neutral wind dynamo will contribute to the high-latitude current system or the electric potential. The semi-annual technical report, dated December 15, 1993, provides further detail describing the scientific and numerical approach of the project. The numerical development has progressed and the dynamo solution for the case when the magnetosphere acts as a voltage source has been evaluated completely using spectral techniques. The simulation provides the field-aligned current distribution at high latitudes due to the neutral wind dynamo. A number of geophysical conditions can be simulated to evaluate the importance of the neutral wind dynamo contribution to the field-aligned current system. On average, field-aligned currents generated by the neutral wind dynamo contributed as much as 30 percent to the large-scale field-aligned current system driven by the magnetosphere. A term analysis of the high-latitude neutral wind dynamo equation describing the field aligned current distribution has also been developed to illustrate the important contributing factors involved in the process. The case describing the neutral dynamo response for a magnetosphere acting as a pure current generator requires the existing spectral code to be extended to a pseudo-spectral method and is currently under development.

  12. Crystal structures of ricin toxin's enzymatic subunit (RTA) in complex with neutralizing and non-neutralizing single-chain antibodies.

    PubMed

    Rudolph, Michael J; Vance, David J; Cheung, Jonah; Franklin, Matthew C; Burshteyn, Fiana; Cassidy, Michael S; Gary, Ebony N; Herrera, Cristina; Shoemaker, Charles B; Mantis, Nicholas J

    2014-08-26

    Ricin is a select agent toxin and a member of the RNA N-glycosidase family of medically important plant and bacterial ribosome-inactivating proteins. In this study, we determined X-ray crystal structures of the enzymatic subunit of ricin (RTA) in complex with the antigen binding domains (VHH) of five unique single-chain monoclonal antibodies that differ in their respective toxin-neutralizing activities. None of the VHHs made direct contact with residues involved in RTA's RNA N-glycosidase activity or induced notable allosteric changes in the toxin's subunit. Rather, the five VHHs had overlapping structural epitopes on the surface of the toxin and differed in the degree to which they made contact with prominent structural elements in two folding domains of the RTA. In general, RTA interactions were influenced most by the VHH CDR3 (CDR, complementarity-determining region) elements, with the most potent neutralizing antibody having the shortest and most conformationally constrained CDR3. These structures provide unique insights into the mechanisms underlying toxin neutralization and provide critically important information required for the rational design of ricin toxin subunit vaccines. PMID:24907552

  13. Turbulent kinetics of a large wind farm and their impact in the neutral boundary layer

    SciTech Connect

    Na, Ji Sung; Koo, Eunmo; Munoz-Esparza, Domingo; Jin, Emilia Kyung; Linn, Rodman; Lee, Joon Sang

    2015-12-28

    High-resolution large-eddy simulation of the flow over a large wind farm (64 wind turbines) is performed using the HIGRAD/FIRETEC-WindBlade model, which is a high-performance computing wind turbine–atmosphere interaction model that uses the Lagrangian actuator line method to represent rotating turbine blades. These high-resolution large-eddy simulation results are used to parameterize the thrust and power coefficients that contain information about turbine interference effects within the wind farm. Those coefficients are then incorporated into the WRF (Weather Research and Forecasting) model in order to evaluate interference effects in larger-scale models. In the high-resolution WindBlade wind farm simulation, insufficient distance between turbines creates the interference between turbines, including significant vertical variations in momentum and turbulent intensity. The characteristics of the wake are further investigated by analyzing the distribution of the vorticity and turbulent intensity. Quadrant analysis in the turbine and post-turbine areas reveals that the ejection motion induced by the presence of the wind turbines is dominant compared to that in the other quadrants, indicating that the sweep motion is increased at the location where strong wake recovery occurs. Regional-scale WRF simulations reveal that although the turbulent mixing induced by the wind farm is partly diffused to the upper region, there is no significant change in the boundary layer depth. The velocity deficit does not appear to be very sensitive to the local distribution of turbine coefficients. However, differences of about 5% on parameterized turbulent kinetic energy were found depending on the turbine coefficient distribution. Furthermore, turbine coefficients that consider interference in the wind farm should be used in wind farm parameterization for larger-scale models to better describe sub-grid scale turbulent processes.

  14. Turbulent kinetics of a large wind farm and their impact in the neutral boundary layer

    DOE PAGES

    Na, Ji Sung; Koo, Eunmo; Munoz-Esparza, Domingo; Jin, Emilia Kyung; Linn, Rodman; Lee, Joon Sang

    2015-12-28

    High-resolution large-eddy simulation of the flow over a large wind farm (64 wind turbines) is performed using the HIGRAD/FIRETEC-WindBlade model, which is a high-performance computing wind turbine–atmosphere interaction model that uses the Lagrangian actuator line method to represent rotating turbine blades. These high-resolution large-eddy simulation results are used to parameterize the thrust and power coefficients that contain information about turbine interference effects within the wind farm. Those coefficients are then incorporated into the WRF (Weather Research and Forecasting) model in order to evaluate interference effects in larger-scale models. In the high-resolution WindBlade wind farm simulation, insufficient distance between turbines createsmore » the interference between turbines, including significant vertical variations in momentum and turbulent intensity. The characteristics of the wake are further investigated by analyzing the distribution of the vorticity and turbulent intensity. Quadrant analysis in the turbine and post-turbine areas reveals that the ejection motion induced by the presence of the wind turbines is dominant compared to that in the other quadrants, indicating that the sweep motion is increased at the location where strong wake recovery occurs. Regional-scale WRF simulations reveal that although the turbulent mixing induced by the wind farm is partly diffused to the upper region, there is no significant change in the boundary layer depth. The velocity deficit does not appear to be very sensitive to the local distribution of turbine coefficients. However, differences of about 5% on parameterized turbulent kinetic energy were found depending on the turbine coefficient distribution. Furthermore, turbine coefficients that consider interference in the wind farm should be used in wind farm parameterization for larger-scale models to better describe sub-grid scale turbulent processes.« less

  15. Structure of wind-shear turbulence

    NASA Technical Reports Server (NTRS)

    Trevino, G.; Laituri, T. R.

    1988-01-01

    The statistical characteristics of wind-shear turbulence are modelled. Isotropic turbulence serves as the basis of comparison for the anisotropic turbulence which exists in wind shear. The question of how turbulence scales in a wind shear is addressed from the perspective of power spectral density.

  16. IUE's View of Callisto: Detection of an SO2 Absorption Correlated to Possible Torus Neutral Wind Alterations

    NASA Technical Reports Server (NTRS)

    Lane, Arthur L.; Domingue, Deborah L.

    1997-01-01

    Observations taken with the International Ultraviolet Explorer (IUE) detected a 0.28 micron absorption feature on Callisto's leading and Jupiter-facing hemispheres. This feature is similar to Europa's 0.28 micron feature, however it shows no correlation with magnetospheric ion bombardment. The strongest 0.28 micron signature is seen in the region containing the Valhalla impact. This absorption feature also shows some spatial correlation to possible neutral wind interactions, suggestive of S implantation (rather than S(sub x)) into Callisto's water ice surface, Indications of possible temporal variations (on the 10% level) are seen at other wavelengths between the 1984-1986 and the 1996 observations.

  17. Effects of the geomagnetic asymmetry of flux-tube integrated neutral winds to the Rayleigh-Taylor instability in equatorial ionosphere

    NASA Astrophysics Data System (ADS)

    Luo, Weihua; Xu, Jisheng; Tian, Mao

    Neutral winds play an important role in the develop-ment of Rayleigh-Taylor instability which is very associated with the occurrence of irregularities in the equatorial and low-latitude regions. For example, eastward winds would make for the development of R-T instability and meridional winds suppress the development of R-T insta-bility. In this work, we investigate effects of the geomagnetic asymmetry of neutral winds to the flux-tube integrated R-T instability in equatorial ionosphere. The flux-tube integrated lin-ear growth rate of R-T instability were estimated and considering the ambient electric fields and asymmetry of neutral winds between North-South hemispheres, and the integrated growth rates were compared which were get with and without the neutral wind, including the zonal and meridional wind. Effects of the longitudinal distribution of the meridional winds on the inte-grated growth rate are investigated also. It is shown that the zonal and meridional wind could significantly affect the growth rates and the meridional winds could decrease the integrated growth rate, respectively. The longitudinal variation of occurrence of irregularities would be related with the global distribution of meridional wind. Reference: Sultan, P.J., Linear theory and modeling of the Rayleigh-Taylor instability leading to the occurrence of equatorial spread F, J. Geophys. Res., 1996, 101(A12), 26875-26891 Basu, B., On the linear theory of equato-rial plasma instability: Comparison of different descriptions, J. Geophys. Res., 2002, 107(A8), 1199, doi: 10.1029/2001JA000317

  18. Flow structure inside and above a variable wind farm: A wind tunnel study.

    NASA Astrophysics Data System (ADS)

    Chamorro, Leonardo; Porte-Agel, Fernando

    2010-05-01

    Wind turbine wakes are known to have important effects on both power generation and fatigue loads in wind farms. Wake characteristics are expected to depend on the incoming atmospheric boundary layer flow statistics (e.g., mean velocity, turbulence intensity and turbulent fluxes), and vertical transport, which is affected by the relative position of the turbines in the wind farm. In this study, wind-tunnel experiments were carried out at the St. Anthony Falls Laboratory atmospheric boundary layer wind tunnel using a 10 by 3 model wind turbine array placed inside a neutrally stratified boundary layer developed over a smooth surface. Different turbine layouts (aligned and staggered farm with different inter-turbine spacing) were considered. Cross-wire anemometry and Particle Image Velocimetry (PIV) were used to characterize the mean velocity, turbulence intensity and turbulent stress at different locations in the wind farm. Results suggest that the turbulent flow can be divided into two main regions. The first, located below the turbine top tip height, has a direct effect on the performance of the turbines. Here the mean flow statistics appear to reach equilibrium as close as 3-4 turbines downwind from the edge of the wind farm. In the second region, located immediately above the first region, the flow adjustment is slower. Here, two distinct layers were found: and internal boundary layer where the flow starts to adjust to the new farm conditions but is still affected by the upwind condition; and an equilibrium layer, where the flow statistics are fully adjusted to the wind farm conditions. The high-resolution spatial and temporal information obtained in the laboratory experiments is being used to test and guide the development of improved parameterizations of wind turbines in high-resolution numerical models, such as large-eddy simulations (LES).

  19. Flow structure inside and above a variable wind farm: A wind tunnel study.

    NASA Astrophysics Data System (ADS)

    Chamorro, L.; Porte-Agel, F.

    2010-09-01

    Wind turbine wakes are known to have important effects on both power generation and fatigue loads in wind farms. Wake characteristics are expected to depend on the incoming atmospheric boundary layer flow statistics (e.g., mean velocity, turbulence intensity and turbulent fluxes), and vertical transport, which is affected by the relative position of the turbines in the wind farm. In this study, wind-tunnel experiments were carried out at the St. Anthony Falls Laboratory atmospheric boundary layer wind tunnel using a 10 by 3 model wind turbine array placed inside a neutrally stratified boundary layer developed over a smooth surface. Different turbine layouts of aligned wind turbines were considered. Cross-wire anemometry was used to characterize the mean velocity, turbulence intensity and turbulent stress at different locations in the wind farm. Results suggest that the turbulent flow can be divided into two main regions. The first, located below the turbine top tip height, has a direct effect on the performance of the turbines. Here the mean flow statistics appear to reach equilibrium as close as 3-4 turbines downwind from the edge of the wind farm. In the second region, located immediately above the first region, the flow adjustment is slower. Here, two distinct layers were found: and internal boundary layer where the flow starts to adjust to the new farm conditions and an equilibrium layer, where the flow statistics are fully adjusted. The high-resolution spatial and temporal information obtained in the laboratory experiments is being used to test and guide the development of improved parameterizations of wind turbines in high-resolution numerical models, such as large-eddy simulations (LES).

  20. Correcting the Record on the Analysis of IBEX and STEREO Data Regarding Variations in the Neutral Interstellar Wind

    NASA Astrophysics Data System (ADS)

    Frisch, P. C.; Bzowski, M.; Drews, C.; Leonard, T.; Livadiotis, G.; McComas, D. J.; Möbius, E.; Schwadron, N.; Sokół, J. M.

    2015-03-01

    The journey of the Sun through space carries the solar system through a dynamic interstellar environment that is presently characterized by a Mach ~1 motion between the heliosphere and the surrounding warm partially ionized interstellar cloud. The interaction between the heliosphere and interstellar medium is an evolving process due to variable solar wind properties and the turbulent nature of the interstellar cloud that surrounds the heliosphere. Frisch et al. presented a meta-analysis of the historical data on the interstellar wind flowing through the heliosphere and concluded that temporal changes in the ecliptic longitude of the flow direction with time were statistically indicated by the data available in the refereed literature at the time of that writing. Lallement & Bertaux disagree with this result, and suggested, for instance, that a key instrumental response function of IBEX-Lo was incorrect and that the STEREO pickup ion data are unsuitable for diagnosing the flow of interstellar neutrals through the heliosphere. In this paper we first show that temporal variations in the interstellar wind through the heliosphere are consistent with our knowledge of the very local interstellar medium. The statistical analysis of the helium wind data is revisited, and a recent correction of a typographical error in the literature is incorporated into the new fits. With this correction, and including no newer IBEX results, these combined data still indicate that a change in the longitude of the interstellar neutral wind of λ = 5.°6 ± 2.°4 over the past forty years remains statistically likely, but an constant flow longitude is now statistically possible. Other scenarios for the selection of subsets of these data used in the fitting process produce similar conclusions. We show that the speculations made by Lallement & Bertin about the IBEX instrumental response function are incorrect, and that their other objections to the data used in the meta-analysis are either

  1. Dynamic Wind Loads and Vortex Structures in the Wake of a Wind Turbine

    NASA Astrophysics Data System (ADS)

    Hu, Hui; Yang, Zifeng; Sarkar, Partha

    2010-11-01

    We report an experimental study to characterize the dynamic wind loads and evolution of wake vortex flow structures downstream of a horizontal axis wind turbine (HAWT). The experiments were conducted in a wind tunnel with a wind turbine model placed in a boundary layer flow developed over rough and smooth surfaces in order to study the effects of roughness and the resulting velocity and turbulence fields on the wake characteristics and fatigue loads acting on the wind turbine. In addition to measuring dynamic wind loads (both aerodynamic forces and moments) acting on the wind turbine model using a six-component load cell, a high-resolution Particle Image Velocimetry (PIV) system was used to make phase-locked flow field measurements to quantify the time-evolution of the wake vortex and turbulence flow structures shedding from wind turbine blades. The detailed flow field measurements were correlated with the wind load measurements to elucidate the underlying physics associated with turbine power generation and fatigue loads acting on wind turbines.

  2. Neutral thermospheric dynamics observed with two scanning Doppler imagers: 2. Vertical winds

    NASA Astrophysics Data System (ADS)

    Anderson, C.; Conde, M.; McHarg, M. G.

    2012-03-01

    This article is the second in a series of three papers reporting on observations of the 630.0 nm thermospheric airglow emission by two spatially separated scanning Doppler imagers (SDI’s) in Alaska. In this article, line-of-sight wind measurements from these instruments in four common-volume regions lying along the great circle joining the two observatories have been used to derive estimates of the vertical wind in those common-volumes. These estimates are combined with the vertical winds measured directly in each of the station zeniths to resolve both the spatial and temporal variations of the vertical wind field. Data from four nights are presented as examples of the wave-like oscillations and frequently high spatial correlations that are observed. A statistical study of data from the full 19-night data set showed that the frequency of observing statistically significant correlation between vertical winds measured at separate locations decreased linearly with increasing separation. A linear fit to this trend indicated that for this particular location and orientation the largest separation over which statistically significant correlation would be expected to occur is approximately 540 km.

  3. Nonlinear regression method for estimating neutral wind and temperature from Fabry-Perot interferometer data.

    PubMed

    Harding, Brian J; Gehrels, Thomas W; Makela, Jonathan J

    2014-02-01

    The Earth's thermosphere plays a critical role in driving electrodynamic processes in the ionosphere and in transferring solar energy to the atmosphere, yet measurements of thermospheric state parameters, such as wind and temperature, are sparse. One of the most popular techniques for measuring these parameters is to use a Fabry-Perot interferometer to monitor the Doppler width and breadth of naturally occurring airglow emissions in the thermosphere. In this work, we present a technique for estimating upper-atmospheric winds and temperatures from images of Fabry-Perot fringes captured by a CCD detector. We estimate instrument parameters from fringe patterns of a frequency-stabilized laser, and we use these parameters to estimate winds and temperatures from airglow fringe patterns. A unique feature of this technique is the model used for the laser and airglow fringe patterns, which fits all fringes simultaneously and attempts to model the effects of optical defects. This technique yields accurate estimates for winds, temperatures, and the associated uncertainties in these parameters, as we show with a Monte Carlo simulation. PMID:24514183

  4. Nonlinear regression method for estimating neutral wind and temperature from Fabry-Perot interferometer data.

    PubMed

    Harding, Brian J; Gehrels, Thomas W; Makela, Jonathan J

    2014-02-01

    The Earth's thermosphere plays a critical role in driving electrodynamic processes in the ionosphere and in transferring solar energy to the atmosphere, yet measurements of thermospheric state parameters, such as wind and temperature, are sparse. One of the most popular techniques for measuring these parameters is to use a Fabry-Perot interferometer to monitor the Doppler width and breadth of naturally occurring airglow emissions in the thermosphere. In this work, we present a technique for estimating upper-atmospheric winds and temperatures from images of Fabry-Perot fringes captured by a CCD detector. We estimate instrument parameters from fringe patterns of a frequency-stabilized laser, and we use these parameters to estimate winds and temperatures from airglow fringe patterns. A unique feature of this technique is the model used for the laser and airglow fringe patterns, which fits all fringes simultaneously and attempts to model the effects of optical defects. This technique yields accurate estimates for winds, temperatures, and the associated uncertainties in these parameters, as we show with a Monte Carlo simulation.

  5. Structural comparison of four different antibodies interacting with human papillomavirus 16 and mechanisms of neutralization

    SciTech Connect

    Guan, Jian; Bywaters, Stephanie M.; Brendle, Sarah A.; Lee, Hyunwook; Ashley, Robert E.; Makhov, Alexander M.; Conway, James F.; Christensen, Neil D.; Hafenstein, Susan

    2015-09-15

    Cryo-electron microscopy (cryo-EM) was used to solve the structures of human papillomavirus type 16 (HPV16) complexed with fragments of antibody (Fab) from three different neutralizing monoclonals (mAbs): H16.1A, H16.14J, and H263.A2. The structure-function analysis revealed predominantly monovalent binding of each Fab with capsid interactions that involved multiple loops from symmetry related copies of the major capsid protein. The residues identified in each Fab-virus interface map to a conformational groove on the surface of the capsomer. In addition to the known involvement of the FG and HI loops, the DE loop was also found to constitute the core of each epitope. Surprisingly, the epitope mapping also identified minor contributions by EF and BC loops. Complementary immunological assays included mAb and Fab neutralization. The specific binding characteristics of mAbs correlated with different neutralizing behaviors in pre- and post-attachment neutralization assays. - Highlights: • We present HPV16-Fab complexes from neutralizing mAbs: H16.1A, H16.14J, and H263.A2. • The structure-function analysis revealed predominantly monovalent binding of each mAb. • Capsid–Fab interactions involved multiple loops from symmetry related L1 proteins. • Besides the known FG and HI loops, epitope mapping also identified DE, EF, and BC loops. • Neutralizing assays complement the structures to show multiple neutralization mechanisms.

  6. Testing the thermospheric neutral wind suppression mechanism for day-to-day variability of equatorial spread F

    NASA Astrophysics Data System (ADS)

    Mendillo, Michael; Meriwether, John; Biondi, Manfred

    2001-03-01

    The determination of the physical processes that cause the day-to-day variability of equatorial spread F (ESF) has long been one of the outstanding problems in terrestrial space physics. Within the context of the Rayleigh-Taylor instability model for ESF, mechanisms that either enhance or inhibit the growth of a seed perturbation offer potential sources of variability that can be tested. In this study the hypothesis that enhanced thermospheric meridional winds play a critical role in suppressing ESF is examined during the Multi-Instrumented Studies of Equatorial Thermospheric Aeronomy (MISETA) campaign of September 1998. New, high-time-resolution Fabry-Perot interferometer (FPI) observations at 6300-Å nightglow made at Arequipa (Peru) provided the neutral wind measurements during the critical postsunset hours that had been sampled only sparsely in earlier morphology studies. Evidence of local ESF activity was obtained using GPS-based observations of phase fluctuations (Fp) and 6300-Å all-sky optical images from the same site. Additional GPS measurements of Fp and total electron content (TEC) from Bogota (Colombia) and Santiago (Chile) were used to determine the full flux tube development of ESF plumes and to characterize the F region morphology of the interhemispheric Appleton anomaly. Correlative studies between the nightly magnitudes of the meridional winds (Um), ESF activity (Fp), and indices describing the strength (Is) and asymmetry (Ia) of the Appleton anomaly offered no convincing evidence for the wind suppression mechanism. The best available precursor for premidnight ESF appeared to be the strength of the electrodynamically driven Appleton anomaly pattern at sunset. If one assumes that the required seed perturbation for ESF onset is essentially always available, then for all practical purposes, the magnitude of the eastward electric field that causes upward drift is both the necessary and sufficient parameter to forecast ESF with reasonable success

  7. Damage tolerance and structural monitoring for wind turbine blades

    PubMed Central

    McGugan, M.; Pereira, G.; Sørensen, B. F.; Toftegaard, H.; Branner, K.

    2015-01-01

    The paper proposes a methodology for reliable design and maintenance of wind turbine rotor blades using a condition monitoring approach and a damage tolerance index coupling the material and structure. By improving the understanding of material properties that control damage propagation it will be possible to combine damage tolerant structural design, monitoring systems, inspection techniques and modelling to manage the life cycle of the structures. This will allow an efficient operation of the wind turbine in terms of load alleviation, limited maintenance and repair leading to a more effective exploitation of offshore wind. PMID:25583858

  8. Damage tolerance and structural monitoring for wind turbine blades.

    PubMed

    McGugan, M; Pereira, G; Sørensen, B F; Toftegaard, H; Branner, K

    2015-02-28

    The paper proposes a methodology for reliable design and maintenance of wind turbine rotor blades using a condition monitoring approach and a damage tolerance index coupling the material and structure. By improving the understanding of material properties that control damage propagation it will be possible to combine damage tolerant structural design, monitoring systems, inspection techniques and modelling to manage the life cycle of the structures. This will allow an efficient operation of the wind turbine in terms of load alleviation, limited maintenance and repair leading to a more effective exploitation of offshore wind.

  9. Damage tolerance and structural monitoring for wind turbine blades.

    PubMed

    McGugan, M; Pereira, G; Sørensen, B F; Toftegaard, H; Branner, K

    2015-02-28

    The paper proposes a methodology for reliable design and maintenance of wind turbine rotor blades using a condition monitoring approach and a damage tolerance index coupling the material and structure. By improving the understanding of material properties that control damage propagation it will be possible to combine damage tolerant structural design, monitoring systems, inspection techniques and modelling to manage the life cycle of the structures. This will allow an efficient operation of the wind turbine in terms of load alleviation, limited maintenance and repair leading to a more effective exploitation of offshore wind. PMID:25583858

  10. Measurements from the Daytime Dynamo Sounding Rocket missions: Altitude Profiles of Neutral Temperature, Density, Winds, and Con Composition

    NASA Astrophysics Data System (ADS)

    Clemmons, J. H.; Bishop, R. L.; Pfaff, R. F., Jr.; Rowland, D. E.; Larsen, M. F.

    2015-12-01

    Results from the two Daytime Dynamo sounding rocket missions launched from Wallops Island, Virginia, in July 2011 and July 2013 are presented and discussed. Measurements returned by the rockets' multiple-sensor ionization gauge instrumentation are used to derive profiles vs. altitude of neutral temperature, density, and, using a new technique, winds. The techniques used are described in detail and the resulting profiles discussed in the context of the daytime atmospheric dynamo. The profiles are also compared to those of established models. Also presented are measurements returned by the high-speed ion mass spectrometer on the 2011 flight. The measurements show the dominance of NO+ ions up to apogee at 160 km, but also reveal a significant admixture of O2+ ions below an intense daytime sporadic-E layer observed at 100.5 km.

  11. Structure of Rotavirus Outer-Layer Protein VP7 Bound with a Neutralizing Fab

    SciTech Connect

    Aoki, Scott T.; Settembre, Ethan C.; Trask, Shane D.; Greenberg, Harry B.; Harrison, Stephen C.; Dormitzer, Philip R.

    2009-06-17

    Rotavirus outer-layer protein VP7 is a principal target of protective antibodies. Removal of free calcium ions (Ca{sup 2+}) dissociates VP7 trimers into monomers, releasing VP7 from the virion, and initiates penetration-inducing conformational changes in the other outer-layer protein, VP4. We report the crystal structure at 3.4 angstrom resolution of VP7 bound with the Fab fragment of a neutralizing monoclonal antibody. The Fab binds across the outer surface of the intersubunit contact, which contains two Ca{sup 2+} sites. Mutations that escape neutralization by other antibodies suggest that the same region bears the epitopes of most neutralizing antibodies. The monovalent Fab is sufficient to neutralize infectivity. We propose that neutralizing antibodies against VP7 act by stabilizing the trimer, thereby inhibiting the uncoating trigger for VP4 rearrangement. A disulfide-linked trimer is a potential subunit immunogen.

  12. Estimate of Low/Mid-Latitude Conductances, Electric Potential and Neutral Winds using IDA4D and EMPIRE

    NASA Astrophysics Data System (ADS)

    Bust, G. S.; Makela, J. J.; Harding, B. J.; Heelis, R. A.; Bishop, R. L.

    2015-12-01

    In this talk we will focus on the current ability of the ionosphere-thermosphere data assimilative models, Ionospheric Data Assimilation Four Dimensional (IDA4D) and Estimating Model Parameters from Ionospheric Reverse Engineering (EMPIRE), to estimate low and mid latitude ionosphere-thermosphere (IT) state variables at altitudes of 200 km and less. In particular we focus on the estimation of Pederson and Hall conductances, equatorial electric potential, and neutral winds. We will characterize the current state of IDA4D and EMPIRE in terms of data available to be assimilated and geophysical conditions. We will discuss the accuracy expected for given conditions, current limitations, and to what degree data assimilative models can be used to advance our understanding of the low/mid latitude physics at 200 km and below. We will use three case study events to help elucidate the current capabilities of IDA4D and EMPIRE: The March, 2013 storm, the March 2015 storm, and the March 2014 time period, which was relatively quiet. In additional to the normal data sets ingested by IDA4D and EMPIRE we intend to ingest observation from the C/NOFS satellite including radio occultations, in-situ measurements of plasma density and ion drifts. We will also ingest other measurements related to electric fields from coherent scatter radars and magnetometers when available. Finally, we will ingest neutral wind measurements from FPI's. We will conclude with a discussion of the future of IT data assimilation algorithms, the advantages of coupling to first principle models, and what future satellite missions such as ICON, GOLD and COSMIC 2 will contribute to improved IT data assimilation estimates.

  13. Electrospray neutralization process and apparatus for generation of nano-aerosol and nano-structured materials

    DOEpatents

    Bailey, Charles L.; Morozov, Victor; Vsevolodov, Nikolai N.

    2010-08-17

    The claimed invention describes methods and apparatuses for manufacturing nano-aerosols and nano-structured materials based on the neutralization of charged electrosprayed products with oppositely charged electrosprayed products. Electrosprayed products include molecular ions, nano-clusters and nano-fibers. Nano-aerosols can be generated when neutralization occurs in the gas phase. Neutralization of electrospan nano-fibers with molecular ions and charged nano-clusters may result in the formation of fibrous aerosols or free nano-mats. Nano-mats can also be produced on a suitable substrate, forming efficient nano-filters.

  14. Neutral Buoyancy Simulator - NB32 - Large Space Structure

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The Hubble Space Telescope (HST) is a cooperative program of the European Space Agency (ESA) and the National Aeronautical and Space Administration (NASA) to operate a long-lived space-based observatory; it was the flagship mission of NASA's Great Observatories program. The HST program began as an astronomical dream in the 1940s. During the 1970s and 1980s, HST was finally designed and built; and it finally became operational in the 1990s. HST was deployed into a low-Earth orbit on April 25, 1990 from the cargo bay of the Space Shuttle Discovery (STS-31). The design of the HST took into consideration its length of service and the necessity of repairs and equipment replacement by making the body modular. In doing so, subsequent shuttle missions could recover the HST, replace faulty or obsolete parts and be re-released. MSFC's Neutral Buoyancy Simulator served as the training facility for shuttle astronauts for Hubble related missions. Shown is astronaut Sharnon Lucid having her life support system being checked prior to entering the NBS to begin training on the space telescope axial scientific instrument changeout.

  15. Structural basis of respiratory syncytial virus neutralization by motavizumab

    SciTech Connect

    McLellan, Jason S.; Chen, Man; Kim, Albert; Yang, Yongping; Graham, Barney S.; Kwong, Peter D.

    2010-04-13

    Motavizumab is {approx}tenfold more potent than its predecessor, palivizumab (Synagis), the FDA-approved monoclonal antibody used to prevent respiratory syncytial virus (RSV) infection. The structure of motavizumab in complex with a 24-residue peptide corresponding to its epitope on the RSV fusion (F) glycoprotein reveals the structural basis for this greater potency. Modeling suggests that motavizumab recognizes a different quaternary configuration of the F glycoprotein than that observed in a homologous structure.

  16. Spiropyran salts and their neutral precursors: synthesis, crystal structure, photochromic transformations in solutions and solid state

    NASA Astrophysics Data System (ADS)

    Yurieva, E. A.; Aldoshin, S. M.

    2015-06-01

    This review covers investigations of spiropyran iodides with N-substituted indoline fragment, and with the pyran cycle being annelated to N-methylated pyridine ring. The schemes of synthesis of iodides and their neutral precursors, as well as results of X-ray analysis and photochemical study of the crystals of the obtained compounds are presented. Based on our and literature data, the relationship between the structure and photochromic properties has been discussed for a series of salts and neutral pyridospiropyrans.

  17. An Empirical Reference Model of the Quiet-Time Thermospheric Neutral Wind

    NASA Astrophysics Data System (ADS)

    Drob, D. P.

    2014-12-01

    The Horizontal Wind Model (HWM) provides a framework for summarizing five decades of satellite, rocket, and ground-based observations. The development of a statistical consensus of these data provided the means to accurately specify the climatological spatiotemporal variability of upper atmospheric winds as function of day-of-year, time-of-day, latitude, longitude, and altitude. HWM includes representations of annual and semi-annual variations of the general circulation patterns and migrating tides via Fourier modulated vector spherical harmonics, B-splines, and 17,4000 optimally estimated coefficients. The approach works well for the thermosphere which is dominated by forced periodic oscillations driven by in-situ solar heating under the influence of the earths rotation, tilt, and orbit around the sun. Where average climatological specification are adequate for basic research and engineering applications HWM provides a readily accessible observationally based alternative to the need to compute them from first principles. Results from the newly updated version of the model (HWM14) are presented. In this update new satellite- and ground-based observations fill data gaps in the prior observational database of the 250 km altitude region. Additional changes where made to the model formulation to rectify problems near the poles. The model parameter estimation procedure was also improved. In the new approach all 17,400 unknown model parameters are simultaneously estimated using error-weighted sequential optimal estimation theory. This mitigates difficulties from local-time aliasing of synoptically sampled single satellite datasets; however the utilization of multiple satellite- and ground-based datasets is essential. Construction of the reference model also provides the opportunity to inter-compare the new measurements. Results are presented highlighting important aspects of; 1) the thermosphere zonal mean general circulation, 2) equatorial local time variations, 3) the

  18. Wind Turbine Blade Design System - Aerodynamic and Structural Analysis

    NASA Astrophysics Data System (ADS)

    Dey, Soumitr

    2011-12-01

    The ever increasing need for energy and the depletion of non-renewable energy resources has led to more advancement in the "Green Energy" field, including wind energy. An improvement in performance of a Wind Turbine will enhance its economic viability, which can be achieved by better aerodynamic designs. In the present study, a design system that has been under development for gas turbine turbomachinery has been modified for designing wind turbine blades. This is a very different approach for wind turbine blade design, but will allow it to benefit from the features inherent in the geometry flexibility and broad design space of the presented system. It starts with key overall design parameters and a low-fidelity model that is used to create the initial geometry parameters. The low-fidelity system includes the axisymmetric solver with loss models, T-Axi (Turbomachinery-AXIsymmetric), MISES blade-to-blade solver and 2D wing analysis code XFLR5. The geometry parameters are used to define sections along the span of the blade and connected to the CAD model of the wind turbine blade through CAPRI (Computational Analysis PRogramming Interface), a CAD neutral API that facilitates the use of parametric geometry definition with CAD. Either the sections or the CAD geometry is then available for CFD and Finite Element Analysis. The GE 1.5sle MW wind turbine and NERL NASA Phase VI wind turbine have been used as test cases. Details of the design system application are described, and the resulting wind turbine geometry and conditions are compared to the published results of the GE and NREL wind turbines. A 2D wing analysis code XFLR5, is used for to compare results from 2D analysis to blade-to-blade analysis and the 3D CFD analysis. This kind of comparison concludes that, from hub to 25% of the span blade to blade effects or the cascade effect has to be considered, from 25% to 75%, the blade acts as a 2d wing and from 75% to the tip 3D and tip effects have to be taken into account

  19. Structure of Respiratory Syncytial Virus Fusion Glycoprotein in the Postfusion Conformation Reveals Preservation of Neutralizing Epitopes

    SciTech Connect

    McLellan, Jason S.; Yang, Yongping; Graham, Barney S.; Kwong, Peter D.

    2011-09-16

    Respiratory syncytial virus (RSV) invades host cells via a type I fusion (F) glycoprotein that undergoes dramatic structural rearrangements during the fusion process. Neutralizing monoclonal antibodies, such as 101F, palivizumab, and motavizumab, target two major antigenic sites on the RSV F glycoprotein. The structures of these sites as peptide complexes with motavizumab and 101F have been previously determined, but a structure for the trimeric RSV F glycoprotein ectodomain has remained elusive. To address this issue, we undertook structural and biophysical studies on stable ectodomain constructs. Here, we present the 2.8-{angstrom} crystal structure of the trimeric RSV F ectodomain in its postfusion conformation. The structure revealed that the 101F and motavizumab epitopes are present in the postfusion state and that their conformations are similar to those observed in the antibody-bound peptide structures. Both antibodies bound the postfusion F glycoprotein with high affinity in surface plasmon resonance experiments. Modeling of the antibodies bound to the F glycoprotein predicts that the 101F epitope is larger than the linear peptide and restricted to a single protomer in the trimer, whereas motavizumab likely contacts residues on two protomers, indicating a quaternary epitope. Mechanistically, these results suggest that 101F and motavizumab can bind to multiple conformations of the fusion glycoprotein and can neutralize late in the entry process. The structural preservation of neutralizing epitopes in the postfusion state suggests that this conformation can elicit neutralizing antibodies and serve as a useful vaccine antigen.

  20. Structure and composition of the neutral upper atmosphere of Mars from the MAVEN NGIMS investigation

    PubMed Central

    Benna, M.; Elrod, M.; Yelle, R. V.; Bougher, S. W.; Stone, S. W.; Jakosky, B. M.

    2015-01-01

    Abstract The Mars Atmosphere and Volatile EvolutioN (MAVEN) Neutral Gas and Ion Mass Spectrometer (NGIMS) provides sensitive detections of neutral gas and ambient ion composition. NGIMS measurements of nine atomic and molecular neutral species, and their variation with altitude, latitude, and solar zenith angle are reported over several months of operation of the MAVEN mission. Sampling NGIMS signals from multiple neutral species every several seconds reveals persistent and unexpectedly large amplitude density structures. The scale height temperatures are mapped over the course of the first few months of the mission from high down to midlatitudes. NGIMS measurements near the homopause of 40Ar/N2 ratios agree with those reported by the Sample Analysis at Mars investigation and allow the altitude of the homopause for the most abundant gases to be established. PMID:27667873

  1. Structure and composition of the neutral upper atmosphere of Mars from the MAVEN NGIMS investigation

    PubMed Central

    Benna, M.; Elrod, M.; Yelle, R. V.; Bougher, S. W.; Stone, S. W.; Jakosky, B. M.

    2015-01-01

    Abstract The Mars Atmosphere and Volatile EvolutioN (MAVEN) Neutral Gas and Ion Mass Spectrometer (NGIMS) provides sensitive detections of neutral gas and ambient ion composition. NGIMS measurements of nine atomic and molecular neutral species, and their variation with altitude, latitude, and solar zenith angle are reported over several months of operation of the MAVEN mission. Sampling NGIMS signals from multiple neutral species every several seconds reveals persistent and unexpectedly large amplitude density structures. The scale height temperatures are mapped over the course of the first few months of the mission from high down to midlatitudes. NGIMS measurements near the homopause of 40Ar/N2 ratios agree with those reported by the Sample Analysis at Mars investigation and allow the altitude of the homopause for the most abundant gases to be established.

  2. Turbulence structures in wind turbine wake: Effects of atmospheric stratification

    NASA Astrophysics Data System (ADS)

    Bhaganagar, Kiran

    2014-11-01

    Turbulence structure in the wake behind full-scale horizontal-axis WT under the influence of realistic atmospheric turbulent flow conditions has been investigated using actuator-line-model based large-eddy-simulations. Wind turbine simulations have revealed that, in addition to wind shear and ABL turbulence, height-varying wind angle and low-level jets are ABL metrics that influence the structure of turbine wake. Turbulent mixing layer forms downstream of the WT, the strength and size of which decreases with increasing stability. Height dependent wind angle and turbulence are the ABL metrics influencing the lateral wake expansion. Further, ABL metrics strongly impact the evolution of tip and root vortices formed behind the rotor. Two factors play an important role in wake meandering: tip vortex merging due to the mutual inductance form of instability and the corresponding instability of the turbulent mixing layer. NSF CBET Energy for Sustainability.

  3. Coherent structure and Intermittent Turbulence in the Solar Wind Plasma

    NASA Astrophysics Data System (ADS)

    Sondhiya, Deepak Kumar; Gwal, Ashok Kumar; Kasde, Satish Kumar

    2016-07-01

    We analyze the coherent structures and intermittent turbulence in the solar wind plasma using measurements from the Wind spacecraft. Previously established novel wavelet and higher order statistics are used in this work. We analyze the wavelet power spectrum of various solar wind plasma parameters. We construct a statistical significance level in the wavelet power spectrum to quantify the interference effects arising from filling missing data in the time series, allowing extraction of significant power from the measured data. We analyze each wavelet power spectra for transient coherency, and global periodicities resulting from the superposition of repeating coherent structures. Furthermore, these coherent structures are preferentially found in plasma unstable to the mirror and firehose instabilities. These results offer a new understanding of various processes in a turbulent regime. Finally, we discuss the implications of our results for current theories of solar wind generation and describe future work for determining the relationship between the coherent structures in our ionic composition data and the structure of the coronal magnetic field. Keywords: Wavelet Power Spectrum, Coherent structure and Solar wind plasma

  4. Field-aligned neutral wind bias correction scheme for global ionospheric modeling at midlatitudes by assimilating FORMOSAT-3/COSMIC hmF2 data under geomagnetically quiet conditions

    NASA Astrophysics Data System (ADS)

    Sun, Yang-Yi; Matsuo, Tomoko; Maruyama, Naomi; Liu, Jann-Yenq

    2015-04-01

    This study demonstrates the usage of a data assimilation procedure, which ingests the FORMOSAT-3/COSMIC (F3/C) hmF2 observations to correct the model wind biases to enhance the capability of the new global Ionosphere Plasmasphere Electrodynamics (IPE) model under geomagnetically quiet conditions. The IPE model is built upon the field line interhemispheric plasma model with a realistic geomagnetic field model and empirical model drivers. The hmF2 observed by the F3/C radio occultation technique is utilized to adjust global thermospheric field-aligned neutral winds (i.e., a component of the thermospheric neutral wind parallel to the magnetic field) at midlatitudes according to a linear relationship between time differentials of the field-aligned wind and hmF2. The adjusted winds are further applied to drive the IPE model. The comparison of the modeled electron density with the observations of F3/C and ground-based GPS receivers at the 2012 March equinox suggests that the modeled electron density can be significantly improved in the midlatitude regions of the Southern Hemisphere, if the wind correction scheme is applied. Moreover, the F3/C observation, the IPE model, and the wind bias correction scheme are applied to study the 2012 Southern Hemisphere Midlatitude Summer Nighttime Anomaly (southern MSNA)/Weddell Sea Anomaly (WSA) event at December solstice for examining the role of the neutral winds in controlling the longitudinal variation of the southern MSNA/WSA behavior. With the help of the wind bias correction scheme, the IPE model better tracks the F3/C-observed eastward movement of the southern MSNA/WSA feature. The apparent eastward movement of the southern MSNA/WSA features in the local time coordinate is primarily caused by the longitudinal variation in the declination angle of the geomagnetic field that controls the field-aligned projection of both geographic meridional and zonal components of the neutral wind. Both the IPE simulations and the F3/C

  5. The electronic structure of the neutral isoalloxazine semiquinone within Anabaena flavodoxin: New insights from HYSCORE experiments

    NASA Astrophysics Data System (ADS)

    Martínez, Jesús I.; Alonso, Pablo J.; Medina, Milagros

    2012-05-01

    A complete study of Anabaena flavodoxin in the neutral semiquinone state by means of the EPR pulse technique HYSCORE is here presented. The results provide new information about the hyperfine interactions of the unpaired electronic spin and the nuclei in the isoalloxazine ring. This allows a better knowledge of the electronic structure of the neutral flavin radical within the protein. Combination of these results with other previously obtained by using other EPR related techniques allowed producing a very precise mapping of the flavin spin distribution in the neutral semiquinone state. This information can be very useful for determining the relationship between the electronic structure and mechanisms in flavoproteins. An experimental protocol for measuring the electronic structure details available to date is suggested.

  6. The structure of the solar wind in the inner heliosphere

    NASA Astrophysics Data System (ADS)

    Lee, Christina On-Yee

    2010-12-01

    This dissertation is devoted to expanding our understanding of the solar wind structure in the inner heliosphere and variations therein with solar activity. Using spacecraft observations and numerical models, the origins of the large-scale structures and long-term trends of the solar wind are explored in order to gain insights on how our Sun determines the space environments of the terrestrial planets. I use long term measurements of the solar wind density, velocity, interplanetary magnetic field, and particles, together with models based on solar magnetic field data, to generate time series of these properties that span one solar rotation (˜27 days). From these time series, I assemble and obtain the synoptic overviews of the solar wind properties. The resulting synoptic overviews show that the solar wind around Mercury, Venus, Earth, and Mars is a complex co-rotating structure with recurring features and occasional transients. During quiet solar conditions, the heliospheric current sheet, which separates the positive interplanetary magnetic field from the negative, usually has a remarkably steady two- or four-sector structure that persists for many solar rotations. Within the sector boundaries are the slow and fast speed solar wind streams that originate from the open coronal magnetic field sources that map to the ecliptic. At the sector boundaries, compressed high-density and the related high-dynamic pressure ridges form where streams from different coronal source regions interact. High fluxes of energetic particles also occur at the boundaries, and are seen most prominently during the quiet solar period. The existence of these recurring features depends on how long-lived are their source regions. In the last decade, 3D numerical solar wind models have become more widely available. They provide important scientific tools for obtaining a more global view of the inner heliosphere and of the relationships between conditions at Mercury, Venus, Earth, and Mars. When

  7. Wind/seismic comparisons for upgrading existing structures

    SciTech Connect

    Giller, R.A. )

    1989-10-01

    This paper depicts the analysis procedures and methods used to evaluate three existing building structures for extreme wind loads. The three structures involved in this evaluation are located at the US Department of Energy's Hanford Site near Richland, Washington. This site is characterized by open flat grassland with few surrounding obstructions and has extreme winds in lieu of tornados as a design basis accident condition. This group of buildings represents a variety of construction types, including a concrete stack, a concrete load-bearing wall structure, and a rigid steel-frame building. The three structures included in this group have recently been evaluated for response to the design basis earthquake that included non-linear time history effects. The resulting loads and stresses from the wind analyses were compared to the loads and stresses resulting from seismic analyses. This approach eliminated the need to prepare additional capacity calculations that were already contained in the seismic evaluations. 4 refs., 5 figs., 5 tabs.

  8. Coherent structures in rotating non-neutral plasma

    NASA Astrophysics Data System (ADS)

    Lund, Steven M.; Ramos, Jesus J.; Davidson, Ronald C.

    1993-01-01

    Nonaxisymmetric (∂/∂θ≠0) rotating equilibria are investigated theoretically for strongly magnetized, low-density (ωpe2/ωce2≪1) pure electron plasmas confined in cylindrical geometry. These two-dimensional equilibria are also called rotating coherent structures, and are stationary (time independent) in a frame of reference rotating with angular velocity ωr=const about the cylinder axis (r=0). Radial confinement of the pure electron plasma is provided by a uniform axial magnetic field B0ez, and a grounded, perfectly conducting, cylindrical wall is located at radius r=rw. The analysis is based on a nonrelativistic, guiding-center model in the cold-fluid limit (the continuity and Poisson equations) that treats the electrons as a massless fluid (me→0) with E×B flow velocity Ve=-(c/B0)∇φ×ez. Within this model, general rotating equilibria with electron density ne≡nR(r,θ-ωrt) and electrostatic potential φ≡φR(r,θ-ωrt) have the property that the electron density is functionally related to the streamfunction ψR=-eφR+ωr(eB0/2c)r2 by nR=nR(ψR). The streamfunction ψR satisfies the nonlinear equilibrium equation ∇2ψR=-4πe2nR(ψR)+2ωreB0/c with ψR=ωr(eB0/2c)rw2≡ψw=const on the cylindrical wall at r=rw. Following a general discussion of rotating equilibria, an integral equation formulation of the nonlinear equilibrium equation is developed to investigate equilibria with ``waterbag'' (step-function) density profiles. In this investigation, a numerical method is formulated that can be used to construct diverse classes of highly nonlinear waterbag equilibria. This method is employed to investigate two classes of nonaxisymmetric equilibria that are nonlinear extrapolations of well-known small-amplitude equilibria. These two classes of rotating equilibria bear strong similarities to coherent structures observed experimentally by Driscoll and Fine [Phys. Fluids B 2, 1359 (1990)].

  9. Focused Evolution of HIV-1 Neutralizing Antibodies Revealed by Structures and Deep Sequencing

    SciTech Connect

    Wu, Xueling; Zhou, Tongqing; Zhu, Jiang; Zhang, Baoshan; Georgiev, Ivelin; Wang, Charlene; Chen, Xuejun; Longo, Nancy S.; Louder, Mark; McKee, Krisha; O’Dell, Sijy; Perfetto, Stephen; Schmidt, Stephen D.; Shi, Wei; Wu, Lan; Yang, Yongping; Yang, Zhi-Yong; Yang, Zhongjia; Zhang, Zhenhai; Bonsignori, Mattia; Crump, John A.; Kapiga, Saidi H.; Sam, Noel E.; Haynes, Barton F.; Simek, Melissa; Burton, Dennis R.; Koff, Wayne C.; Doria-Rose, Nicole A.; Connors, Mark; Mullikin, James C.; Nabel, Gary J.; Roederer, Mario; Shapiro, Lawrence; Kwong, Peter D.; Mascola, John R.

    2013-03-04

    Antibody VRC01 is a human immunoglobulin that neutralizes about 90% of HIV-1 isolates. To understand how such broadly neutralizing antibodies develop, we used x-ray crystallography and 454 pyrosequencing to characterize additional VRC01-like antibodies from HIV-1-infected individuals. Crystal structures revealed a convergent mode of binding for diverse antibodies to the same CD4-binding-site epitope. A functional genomics analysis of expressed heavy and light chains revealed common pathways of antibody-heavy chain maturation, confined to the IGHV1-2*02 lineage, involving dozens of somatic changes, and capable of pairing with different light chains. Broadly neutralizing HIV-1 immunity associated with VRC01-like antibodies thus involves the evolution of antibodies to a highly affinity-matured state required to recognize an invariant viral structure, with lineages defined from thousands of sequences providing a genetic roadmap of their development.

  10. Solar wind stream structure at large heliocentric distances Pioneer observations

    NASA Technical Reports Server (NTRS)

    Gazis, P. R.

    1987-01-01

    Time profiles and histograms of plasma data from Pioneers 10 and 11 are examined for the period between 1975 and 1983. During this time, Pioneer 10 traveled between a heliocentric distance of 8.7 and 30.4 AU. The velocity structure of the solar wind at these heliocentric distances is found to have one of two distinct forms: approximately 70 percent of the time the solar wind has a nearly flat velocity profile. Occasionally, this flat velocity profile is accompanied by quasi-periodic variations in density and in thermal speed consistent with the concept that the 'corotating interaction regions' which are produced by the interaction of high- and low-speed streams at intermediate heliocentric distances are replaced by 'pressure regions' in the outer heliosphere. The remaining 30 percent of the time the solar wind is marked by large (50-200 km/s) long-term (30-120 days) shifts in the average solar wind velocity.

  11. On the relationship between wind profiles and the STS ascent structural loads

    NASA Technical Reports Server (NTRS)

    Smith, Orvel E.; Adelfang, Stanley I.; Whitehead, Douglas S.

    1989-01-01

    The response of STS ascent structural load indicators to the wind profile is analyzed. The load indicator values versus Mach numbers are calculated with algorithms using trajectory information. The ascent load minimum margin concept is used to show that the detailed wind profile structure measured by the Jimsphere wind system is not needed to assess the STS rigid body structural wind loads.

  12. Structural Constraints of Vaccine-Induced Tier-2 Autologous HIV Neutralizing Antibodies Targeting the Receptor-Binding Site.

    PubMed

    Bradley, Todd; Fera, Daniela; Bhiman, Jinal; Eslamizar, Leila; Lu, Xiaozhi; Anasti, Kara; Zhang, Ruijung; Sutherland, Laura L; Scearce, Richard M; Bowman, Cindy M; Stolarchuk, Christina; Lloyd, Krissey E; Parks, Robert; Eaton, Amanda; Foulger, Andrew; Nie, Xiaoyan; Karim, Salim S Abdool; Barnett, Susan; Kelsoe, Garnett; Kepler, Thomas B; Alam, S Munir; Montefiori, David C; Moody, M Anthony; Liao, Hua-Xin; Morris, Lynn; Santra, Sampa; Harrison, Stephen C; Haynes, Barton F

    2016-01-01

    Antibodies that neutralize autologous transmitted/founder (TF) HIV occur in most HIV-infected individuals and can evolve to neutralization breadth. Autologous neutralizing antibodies (nAbs) against neutralization-resistant (Tier-2) viruses are rarely induced by vaccination. Whereas broadly neutralizing antibody (bnAb)-HIV-Envelope structures have been defined, the structures of autologous nAbs have not. Here, we show that immunization with TF mutant Envs gp140 oligomers induced high-titer, V5-dependent plasma neutralization for a Tier-2 autologous TF evolved mutant virus. Structural analysis of autologous nAb DH427 revealed binding to V5, demonstrating the source of narrow nAb specificity and explaining the failure to acquire breadth. Thus, oligomeric TF Envs can elicit autologous nAbs to Tier-2 HIVs, but induction of bnAbs will require targeting of precursors of B cell lineages that can mature to heterologous neutralization.

  13. Structural Basis for Recognition of Human Enterovirus 71 by a Bivalent Broadly Neutralizing Monoclonal Antibody.

    PubMed

    Ye, Xiaohua; Fan, Chen; Ku, Zhiqiang; Zuo, Teng; Kong, Liangliang; Zhang, Chao; Shi, Jinping; Liu, Qingwei; Chen, Tan; Zhang, Yingyi; Jiang, Wen; Zhang, Linqi; Huang, Zhong; Cong, Yao

    2016-03-01

    Enterovirus 71 (EV71) is the main pathogen responsible for hand, foot and mouth disease with severe neurological complications and even death in young children. We have recently identified a highly potent anti-EV71 neutralizing monoclonal antibody, termed D5. Here we investigated the structural basis for recognition of EV71 by the antibody D5. Four three-dimensional structures of EV71 particles in complex with IgG or Fab of D5 were reconstructed by cryo-electron microscopy (cryo-EM) single particle analysis all at subnanometer resolutions. The most critical EV71 mature virion-Fab structure was resolved to a resolution of 4.8 Å, which is rare in cryo-EM studies of virus-antibody complex so far. The structures reveal a bivalent binding pattern of D5 antibody across the icosahedral 2-fold axis on mature virion, suggesting that D5 binding may rigidify virions to prevent their conformational changes required for subsequent RNA release. Moreover, we also identified that the complementary determining region 3 (CDR3) of D5 heavy chain directly interacts with the extremely conserved VP1 GH-loop of EV71, which was validated by biochemical and virological assays. We further showed that D5 is indeed able to neutralize a variety of EV71 genotypes and strains. Moreover, D5 could potently confer protection in a mouse model of EV71 infection. Since the conserved VP1 GH-loop is involved in EV71 binding with its uncoating receptor, the scavenger receptor class B, member 2 (SCARB2), the broadly neutralizing ability of D5 might attribute to its inhibition of EV71 from binding SCARB2. Altogether, our results elucidate the structural basis for the binding and neutralization of EV71 by the broadly neutralizing antibody D5, thereby enhancing our understanding of antibody-based protection against EV71 infection. PMID:26938634

  14. Relative roles of niche and neutral processes in structuring a soil microbial community.

    PubMed

    Dumbrell, Alex J; Nelson, Michaela; Helgason, Thorunn; Dytham, Calvin; Fitter, Alastair H

    2010-03-01

    Most attempts to identify the processes that structure natural communities have focused on conspicuous macroorganisms whereas the processes responsible for structuring microbial communities remain relatively unknown. Two main theories explaining these processes have emerged; niche theory, which highlights the importance of deterministic processes, and neutral theory, which focuses on stochastic processes. We examined whether neutral or niche-based mechanisms best explain the composition and structure of communities of a functionally important soil microbe, the arbuscular mycorrhizal (AM) fungi. Using molecular techniques, we surveyed AM fungi from 425 individual plants of 28 plant species along a soil pH gradient. There was evidence that both niche and neutral processes structured this community. Species abundances fitted the zero-sum multinomial distribution and there was evidence of dispersal limitation, both indicators of neutral processes. However, we found stronger support that niche differentiation based on abiotic soil factors, primarily pH, was structuring the AM fungal community. Host plant species affected AM fungal community composition negligibly compared to soil pH. We conclude that although niche partitioning was the primary mechanism regulating the composition and diversity of natural AM fungal communities, these communities are also influenced by stochastic-neutral processes. This study represents one of the most comprehensive investigations of community-level processes acting on soil microbes; revealing a community that although influenced by stochastic processes, still responded in a predictable manner to a major abiotic niche axis, soil pH. The strong response to environmental factors of this community highlights the susceptibility of soil microbes to environmental change.

  15. Structural Basis for Recognition of Human Enterovirus 71 by a Bivalent Broadly Neutralizing Monoclonal Antibody

    PubMed Central

    Ku, Zhiqiang; Zuo, Teng; Kong, Liangliang; Zhang, Chao; Shi, Jinping; Liu, Qingwei; Chen, Tan; Zhang, Yingyi; Jiang, Wen; Zhang, Linqi; Huang, Zhong; Cong, Yao

    2016-01-01

    Enterovirus 71 (EV71) is the main pathogen responsible for hand, foot and mouth disease with severe neurological complications and even death in young children. We have recently identified a highly potent anti-EV71 neutralizing monoclonal antibody, termed D5. Here we investigated the structural basis for recognition of EV71 by the antibody D5. Four three-dimensional structures of EV71 particles in complex with IgG or Fab of D5 were reconstructed by cryo-electron microscopy (cryo-EM) single particle analysis all at subnanometer resolutions. The most critical EV71 mature virion-Fab structure was resolved to a resolution of 4.8 Å, which is rare in cryo-EM studies of virus-antibody complex so far. The structures reveal a bivalent binding pattern of D5 antibody across the icosahedral 2-fold axis on mature virion, suggesting that D5 binding may rigidify virions to prevent their conformational changes required for subsequent RNA release. Moreover, we also identified that the complementary determining region 3 (CDR3) of D5 heavy chain directly interacts with the extremely conserved VP1 GH-loop of EV71, which was validated by biochemical and virological assays. We further showed that D5 is indeed able to neutralize a variety of EV71 genotypes and strains. Moreover, D5 could potently confer protection in a mouse model of EV71 infection. Since the conserved VP1 GH-loop is involved in EV71 binding with its uncoating receptor, the scavenger receptor class B, member 2 (SCARB2), the broadly neutralizing ability of D5 might attribute to its inhibition of EV71 from binding SCARB2. Altogether, our results elucidate the structural basis for the binding and neutralization of EV71 by the broadly neutralizing antibody D5, thereby enhancing our understanding of antibody-based protection against EV71 infection. PMID:26938634

  16. Density, Velocity and Ionization Structure in Accretion-Disc Winds

    NASA Technical Reports Server (NTRS)

    Sonneborn, George (Technical Monitor); Long, Knox

    2004-01-01

    This was a project to exploit the unique capabilities of FUSE to monitor variations in the wind- formed spectral lines of the luminous, low-inclination, cataclysmic variables(CV) -- RW Sex. (The original proposal contained two additional objects but these were not approved.) These observations were intended to allow us to determine the relative roles of density and ionization state changes in the outflow and to search for spectroscopic signatures of stochastic small-scale structure and shocked gas. By monitoring the temporal behavior of blue-ward extended absorption lines with a wide range of ionization potentials and excitation energies, we proposed to track the changing physical conditions in the outflow. We planned to use a new Monte Carlo code to calculate the ionization structure of and radiative transfer through the CV wind. The analysis therefore was intended to establish the wind geometry, kinematics and ionization state, both in a time-averaged sense and as a function of time.

  17. Some Notes on the Determination of the Stick-Free Neutral Point from Wind-Tunnel Data

    NASA Technical Reports Server (NTRS)

    Schuldenfrei, Marvin

    1944-01-01

    Two graphical methods are presented for determining the stick-free neutral point, and they are extensions of the methods commonly used to determine the stick-free neutral point. A mathematical formula for computing the stick-free neutral point is also given. These methods may be applied to determine approximately the increase in tail size necessary to shift the neutral point (stick fixed or free) to any desired location on an airplane having inadequate longitudinal stability.

  18. Structural Basis for Broad and Potent Neutralization of HIV-1 by Antibody VRC01

    SciTech Connect

    Zhou, Tongqing; Georgiev, Ivelin; Wu, Xueling; Yang, Zhi-Yong; Dai, Kaifan; Finzi, Andrés; Kwon, Young Do; Scheid, Johannes F.; Shi, Wei; Xu, Ling; Yang, Yongping; Zhu, Jiang; Nussenzweig, Michel C.; Sodroski, Joseph; Shapiro, Lawrence; Nabel, Gary J.; Mascola, John R.; Kwong, Peter D.

    2010-08-26

    During HIV-1 infection, antibodies are generated against the region of the viral gp120 envelope glycoprotein that binds CD4, the primary receptor for HIV-1. Among these antibodies, VRC01 achieves broad neutralization of diverse viral strains. We determined the crystal structure of VRC01 in complex with a human immunodeficiency virus HIV-1 gp120 core. VRC01 partially mimics CD4 interaction with gp120. A shift from the CD4-defined orientation, however, focuses VRC01 onto the vulnerable site of initial CD4 attachment, allowing it to overcome the glycan and conformational masking that diminishes the neutralization potency of most CD4-binding-site antibodies. To achieve this recognition, VRC01 contacts gp120 mainly through immunoglobulin V-gene regions substantially altered from their genomic precursors. Partial receptor mimicry and extensive affinity maturation thus facilitate neutralization of HIV-1 by natural human antibodies.

  19. The molecular clock of neutral evolution can be accelerated or slowed by asymmetric spatial structure.

    PubMed

    Allen, Benjamin; Sample, Christine; Dementieva, Yulia; Medeiros, Ruben C; Paoletti, Christopher; Nowak, Martin A

    2015-02-01

    Over time, a population acquires neutral genetic substitutions as a consequence of random drift. A famous result in population genetics asserts that the rate, K, at which these substitutions accumulate in the population coincides with the mutation rate, u, at which they arise in individuals: K = u. This identity enables genetic sequence data to be used as a "molecular clock" to estimate the timing of evolutionary events. While the molecular clock is known to be perturbed by selection, it is thought that K = u holds very generally for neutral evolution. Here we show that asymmetric spatial population structure can alter the molecular clock rate for neutral mutations, leading to either Ku. Our results apply to a general class of haploid, asexually reproducing, spatially structured populations. Deviations from K = u occur because mutations arise unequally at different sites and have different probabilities of fixation depending on where they arise. If birth rates are uniform across sites, then K ≤ u. In general, K can take any value between 0 and Nu. Our model can be applied to a variety of population structures. In one example, we investigate the accumulation of genetic mutations in the small intestine. In another application, we analyze over 900 Twitter networks to study the effect of network topology on the fixation of neutral innovations in social evolution.

  20. A Review of Wind Project Financing Structures in the USA

    SciTech Connect

    Bolinger, Mark A; Harper, John; Karcher, Matthew

    2008-09-24

    The rapid pace of wind power development in the U.S. over the last decade has outstripped the ability of most project developers to provide adequate equity capital and make efficient use of project-related tax benefits. In response, the sector has created novel project financing structures that feature varying combinations of equity capital from project developers and third-party tax-oriented investors, and in some cases commercial debt. While their origins stem from variations in the financial capacity and business objectives of wind project developers, as well as the risk tolerances and objectives of equity and debt providers, each structure is, at its core, designed to manage project risk and allocate federal tax incentives to those entities that can use them most efficiently. This article surveys the six principal financing structures through which most new utility-scale wind projects (excluding utility-owned projects) in the U.S. have been financed from 1999 to the present. These structures include simple balance-sheet finance, several varieties of all-equity special allocation partnership 'flip' structures, and two leveraged structures. In addition to describing each structure's mechanics, the article also discusses its rationale for use, the types of investors that find it appealing and why, and its relative frequency of use in the market. The article concludes with a generalized summary of how a developer might choose one structure over another.

  1. Understanding the structural transformation, stability of medium-sized neutral and charged silicon clusters

    PubMed Central

    Ding, Li Ping; Zhang, Fang Hui; Zhu, Yong Sheng; Lu, Cheng; Kuang, Xiao Yu; Lv, Jian; Shao, Peng

    2015-01-01

    The structural and electronic properties for the global minimum structures of medium-sized neutral, anionic and cationic Sinμ (n = 20–30, μ = 0, −1 and +1) clusters have been studied using an unbiased CALYPSO structure searching method in conjunction with first-principles calculations. A large number of low-lying isomers are optimized at the B3PW91/6-311 + G* level of theory. Harmonic vibrational analysis has been performed to assure that the optimized geometries are stable. The growth behaviors clearly indicate that a structural transition from the prolate to spherical-like geometries occurs at n = 26 for neutral silicon clusters, n = 27 for anions and n = 25 for cations. These results are in good agreement with the available experimental and theoretical predicted findings. In addition, no significant structural differences are observed between the neutral and cation charged silicon clusters with n = 20–24, both of them favor prolate structures. The HOMO-LUMO gaps and vertical ionization potential patterns indicate that Si22 is the most chemical stable cluster, and its dynamical stability is deeply discussed by the vibrational spectra calculations. PMID:26526519

  2. Visualising the electron density structure of blobs and studying its possible effect on neutral turbulence

    NASA Astrophysics Data System (ADS)

    de la Cal, E.; The TJ-II Team

    2016-10-01

    The electron density n e of turbulent coherent structures (blobs) has been measured at the edge plasma of the TJ-II stellarator using the helium line ratio technique. A spectroscopic high-speed camera set-up allowed 2D imaging of n e with spatial resolutions of a few millimetres and exposure times down to 15 µs. The turbulent plasma density structures have been compared with the raw helium emission structures, which in principle should be similar due to the expected relation between both, and although generally positive (negative) emission structures correspond to n e blobs (holes), we see that the shape is different and that in some cases there is even no correspondence at all. A possible explanation could be that the neutral distribution, which relates the intensity emission with the n e, varies on the same spatio-temporal scale as the plasma turbulence. This would be the case if the local n e variations of blobs and holes regulated the neutral density through ionisation, making it also turbulent within our experimental frequency (<100 kHz) and spatial scale (>1 cm). To study this point we simulate the neutrals with a simple transport model to reconstruct the corresponding measured emission profiles using the experimentally obtained n e and T e radial profiles. We do this for two cases: one where the neutral distribution is stationary and another where the atoms respond to the measured n e blob and get locally depleted through ionisation. Comparing the simulated and experimental emission profiles and looking at the characteristic ionisation times we find clear indications that point to the fact that slow thermal neutrals could react to the plasma fluctuations in the 10-100 kHz frequency range, also becoming turbulent.

  3. Effects of solar wind speed on the secondary energetic neutral source of the Interstellar Boundary Explorer ribbon

    NASA Astrophysics Data System (ADS)

    Zirnstein, E. J.; Funsten, H. O.; Heerikhuisen, J.; McComas, D. J.

    2016-02-01

    The Interstellar Boundary EXplorer (IBEX) ribbon is an intense energetic neutral atom (ENA) emission feature encircling the sky, spanning energies ≤0.5-6 keV. The ribbon may be produced by the "secondary ENA" mechanism, where ENAs emitted from a source plasma population inside the heliosphere propagate outside the heliopause, undergo two charge-exchange events, and become secondary ENAs that may be directed back toward Earth and detected by IBEX. In this scenario, the source plasma population is governed by the interaction of the solar wind (SW) with the interstellar medium and is thus sensitive to the global SW properties. Moreover, this scenario predicts that the distance to the source of secondary ENAs depends on the ENA energy and SW speed, which in turn may affect the shape of the ribbon. In this paper, we use a computational model of the heliosphere with simplified SW boundary conditions to analyze the influence of ENA energy and SW speed, independent of time and latitude, on the global spatial and geometric properties of the ribbon. We find a strong dependence of the simulated ribbon energy spectrum and spatial symmetry on SW speed and ENA energy, and only a slight dependence on ribbon geometry. Our results suggest a significant number of primary ENAs from the inner heliosheath may contribute to the pickup ion source population outside the heliopause, depending on the ENA energy and SW speed. The lack of variation in the simulated ribbon center as a function of ENA energy and SW speed, in contrast to the observations, implies that the asymmetry of the SW plays an important role in determining the position of the ribbon. Comparisons to the IBEX data also signify the ribbon's dependence on the properties of the local interstellar medium, particularly the interstellar magnetic field.

  4. Stapled HIV-1 Peptides Recapitulate Antigenic Structures and Engage Broadly Neutralizing Antibodies

    PubMed Central

    Bird, Gregory H.; Irimia, Adriana; Ofek, Gilad; Kwong, Peter D.; Wilson, Ian A.; Walensky, Loren D.

    2014-01-01

    Hydrocarbon stapling can restore bioactive, α-helical structure to natural peptides, yielding research tools and prototype therapeutics to dissect and target protein interactions. Here, we explore the capacity of peptide stapling to generate high fidelity, protease-resistant mimics of antigenic structures for vaccine development. HIV-1 has been refractory to vaccine technologies thus far, although select human antibodies can broadly neutralize HIV-1 by targeting sequences of the gp41 juxtamembrane fusion apparatus. To develop candidate HIV-1 immunogens, we generated and characterized stabilized α-helices of the membrane proximal external region (SAH-MPER) of gp41. SAH-MPER peptides were remarkably protease-resistant and bound to the broadly neutralizing 4E10 and 10E8 antibodies with high affinity, recapitulating the structure of the MPER epitope when differentially engaged by the two anti-HIV Fabs. Thus, stapled peptides may provide a new opportunity to develop chemically-stabilized antigens for vaccination. PMID:25420104

  5. Structural comparison of four different antibodies interacting with human papillomavirus 16 and mechanisms of neutralization.

    PubMed

    Guan, Jian; Bywaters, Stephanie M; Brendle, Sarah A; Lee, Hyunwook; Ashley, Robert E; Makhov, Alexander M; Conway, James F; Christensen, Neil D; Hafenstein, Susan

    2015-09-01

    Cryo-electron microscopy (cryo-EM) was used to solve the structures of human papillomavirus type 16 (HPV16) complexed with fragments of antibody (Fab) from three different neutralizing monoclonals (mAbs): H16.1A, H16.14J, and H263.A2. The structure-function analysis revealed predominantly monovalent binding of each Fab with capsid interactions that involved multiple loops from symmetry related copies of the major capsid protein. The residues identified in each Fab-virus interface map to a conformational groove on the surface of the capsomer. In addition to the known involvement of the FG and HI loops, the DE loop was also found to constitute the core of each epitope. Surprisingly, the epitope mapping also identified minor contributions by EF and BC loops. Complementary immunological assays included mAb and Fab neutralization. The specific binding characteristics of mAbs correlated with different neutralizing behaviors in pre- and post-attachment neutralization assays.

  6. Structural comparison of four different antibodies interacting with human papillomavirus 16 and mechanisms of neutralization.

    PubMed

    Guan, Jian; Bywaters, Stephanie M; Brendle, Sarah A; Lee, Hyunwook; Ashley, Robert E; Makhov, Alexander M; Conway, James F; Christensen, Neil D; Hafenstein, Susan

    2015-09-01

    Cryo-electron microscopy (cryo-EM) was used to solve the structures of human papillomavirus type 16 (HPV16) complexed with fragments of antibody (Fab) from three different neutralizing monoclonals (mAbs): H16.1A, H16.14J, and H263.A2. The structure-function analysis revealed predominantly monovalent binding of each Fab with capsid interactions that involved multiple loops from symmetry related copies of the major capsid protein. The residues identified in each Fab-virus interface map to a conformational groove on the surface of the capsomer. In addition to the known involvement of the FG and HI loops, the DE loop was also found to constitute the core of each epitope. Surprisingly, the epitope mapping also identified minor contributions by EF and BC loops. Complementary immunological assays included mAb and Fab neutralization. The specific binding characteristics of mAbs correlated with different neutralizing behaviors in pre- and post-attachment neutralization assays. PMID:25996608

  7. Inrush Current Simulation of Two Windings Power Transformer using Machine Parameters Estimated by Design Procedure of Winding Structure

    NASA Astrophysics Data System (ADS)

    Tokunaga, Yoshitaka; Kubota, Kunihiro

    This paper presents estimation techniques of machine parameters for two windings power transformer using design procedure of winding structure. Especially, it is very difficult to obtain machine parameters for transformers in customers' facilities. Using estimation techniques, machine parameters could be calculated from the only nameplate data of these transformers. Subsequently, EMTP-ATP simulation of the inrush current was carried out using machine parameters estimated by design procedure of winding structure and simulation results were reproduced measured waveforms.

  8. Structural testing of the North Wind 250 composite rotor joint

    SciTech Connect

    Musial, W; Link, H; Coleman, C

    1994-05-01

    The North Wind 250 wind turbine is under development at Northern Power Systems (NPS) in Moretown, VT. The turbine uses a unique, flow-through, teetered-rotor design. This design eliminates structural discontinuities at the blade/hub interface by fabricating the rotor as one continuous structural element. To accomplish this, the two blade spars are joined at the center of the rotor using a proprietary bonding technique. Fatigue tests were conducted on the full-scale rotor joint at the National Renewable Energy Laboratory (NREL). Subsequent tests are now underway to test the full-scale rotor and hub assembly to verify the design assumptions. The test articles were mounted in dedicated test fixtures. For the joint test, a constant moment was generated across the joint and parent material. Hydraulic actuators applied sinusoidal loading to the test article at levels equivalent to 90% of the extreme wind load for over one million cycles. When the loading was increased to 112% of the extreme wind load, the joint failed by buckling. Strain levels were monitored at 14 locations inside and outside of the blade joint during the test. The tests were used to qualify this critical element of the rotor for field testing and to provide information needed to improve the structural design of the joint.

  9. Simultaneous Observations of Electric Fields, Current Density, Plasma Density, and Neutral Winds During Two Sounding Rocket Experiments Launched from Wallops Island into Strong Daytime Dynamo Currents

    NASA Astrophysics Data System (ADS)

    Pfaff, R. F., Jr.; Rowland, D. E.; Klenzing, J.; Freudenreich, H. T.; Martin, S. C.; Abe, T.; Habu, H.; Yamamoto, M. Y.; Watanabe, S.; Yamamoto, M.; Yokoyama, T.; Kakinami, Y.; Yamazaki, Y.; Larsen, M. F.; Hurd, L.; Clemmons, J. H.; Bishop, R. L.; Walterscheid, R. L.; Fish, C. S.; Bullett, T. W.; Mabie, J. J.; Murphy, N.; Angelopoulos, V.; Leinweber, H. K.; Bernal, I.; Chi, P. J.

    2015-12-01

    To investigate the ion-neutral coupling that creates the global electrical daytime "dynamo" currents in the mid-latitude, lower ionosphere, NASA carried out two multiple sounding rocket experiments from Wallops Island, VA on July 10, 2011 (14:00 UT, 10:00 LT) and July 4, 2013 (14:31 UT, 10:31 LT). The rockets were launched in the presence of well-defined, westward Hall currents observed on the ground with ΔH values of ­-25 nT and -30 nT, respectively, as well as a well-defined, daytime ionospheric density observed by the VIPIR ionosonde at Wallops. During the 2011 experiment, a narrow, intense sporadic-E layer was observed near 102 km. Each experiment consisted of a pair of rockets launched 15 sec apart. The first rocket of each pair carried instruments to measure DC electric and magnetic fields, as well as the ambient plasma and neutral gases and attained apogees of 158 km and 135 km in the 2011 and 2013 experiments, respectively. The second rocket of each pair carried canisters which released a lithium vapor trail along the upleg to illuminate neutral winds in the upper atmosphere. This daytime vapor trail technology was developed jointly by researchers at JAXA and Clemson University. In the second experiment, the lithium release was clearly visible in cameras with infrared filters operated by US and Japanese researchers in a NASA airplane at 9.6 km altitude. The observed wind profiles reached speeds of 100 m/s with strong shears with respect to altitude and were consistent with an independent derivation of the wind from the ionization gauge sensor suite on the instrumented rocket. The "vapor trail" rockets, which also included a falling sphere, attained apogees of 150 km and 143 km in the 2011 and 2013 experiments, respectively. By measuring the current density, conductivity, DC electric fields, and neutral winds, we solve the dynamo equation as a function of altitude, revealing the different contributions to the lower E-region currents. We find that the DC

  10. Structural integrity of wind tunnel wooden fan blades

    NASA Technical Reports Server (NTRS)

    Young, Clarence P., Jr.; Wingate, Robert T.; Rooker, James R.; Mort, Kenneth W.; Zager, Harold E.

    1991-01-01

    Information is presented which was compiled by the NASA Inter-Center Committee on Structural Integrity of Wooden Fan Blades and is intended for use as a guide in design, fabrication, evaluation, and assurance of fan systems using wooden blades. A risk assessment approach for existing NASA wind tunnels with wooden fan blades is provided. Also, state of the art information is provided for wooden fan blade design, drive system considerations, inspection and monitoring methods, and fan blade repair. Proposed research and development activities are discussed, and recommendations are provided which are aimed at future wooden fan blade design activities and safely maintaining existing NASA wind tunnel fan blades. Information is presented that will be of value to wooden fan blade designers, fabricators, inspectors, and wind tunnel operations personnel.

  11. Effects of structure flexibility on horizontal axis wind turbine performances

    NASA Astrophysics Data System (ADS)

    Coiro, D. P.; Daniele, E.; Scherillo, F.

    2013-10-01

    This work illustrates the effects of flexibility of rotor blades and turbine tower on the performances of an horizontal axis wind turbine (HAWT) designed by our ADAG research group, by means of several example applied on a recent project for a active pitch controlled upwind 60 kW HAWT. The influence of structural flexibility for blade only, tower only and blade coupled with tower configuration is investigated using an aero-elastic computer-aided engineering (CAE) tool for horizontal axis wind turbines named FAST developed at National Renewable Energy Laboratory (NREL) of USA. For unsteady inflow conditions in front of the isolated HAWT the performances in rigid and flexible operation mode are computed and compared in order to illustrate the limitation included within a classical rigid body approach to wind turbine simulation.

  12. FORMATION OF COLD FILAMENTARY STRUCTURE FROM WIND-BLOWN SUPERBUBBLES

    SciTech Connect

    Ntormousi, Evangelia; Burkert, Andreas; Fierlinger, Katharina; Heitsch, Fabian

    2011-04-10

    The expansion and collision of two wind-blown superbubbles is investigated numerically. Our models go beyond previous simulations of molecular cloud formation from converging gas flows by exploring this process with realistic flow parameters, sizes, and timescales. The superbubbles are blown by time-dependent winds and supernova explosions, calculated from population synthesis models. They expand into a uniform or turbulent diffuse medium. We find that dense, cold gas clumps and filaments form naturally in the compressed collision zone of the two superbubbles. Their shapes resemble the elongated, irregular structure of observed cold, molecular gas filaments, and clumps. At the end of the simulations, between 65% and 80% of the total gas mass in our simulation box is contained in these structures. The clumps are found in a variety of physical states, ranging from pressure equilibrium with the surrounding medium to highly underpressured clumps with large irregular internal motions and structures which are rotationally supported.

  13. Spatial structure of morphological and neutral genetic variation in Brook Trout

    USGS Publications Warehouse

    Kazyak, David C.; Hilderbrand, Robert H.; Keller, Stephen R.; Colaw, Mark C.; Holloway, Amanda E.; Morgan, Raymond P.; King, Timothy L.

    2015-01-01

    Brook Trout Salvelinus fontinalis exhibit exceptional levels of life history variation, remarkable genetic variability, and fine-scale population structure. In many cases, neighboring populations may be highly differentiated from one another to an extent that is comparable with species-level distinctions in other taxa. Although genetic samples have been collected from hundreds of populations and tens of thousands of individuals, little is known about whether differentiation at neutral markers reflects phenotypic differences among Brook Trout populations. We compared differentiation in morphology and neutral molecular markers among populations from four geographically proximate locations (all within 24 km) to examine how genetic diversity covaries with morphology. We found significant differences among and/or within streams for all three morphological axes examined and identified the source stream of many individuals based on morphology (52.3% classification efficiency). Although molecular and morphological differentiation among streams ranged considerably (mean pairwise FST: 0.023–0.264; pairwise PST: 0.000–0.339), the two measures were not significantly correlated. While in some cases morphological characters appear to have diverged to a greater extent than expected by neutral genetic drift, many traits were conserved to a greater extent than were neutral genetic markers. Thus, while Brook Trout exhibit fine-scale spatial patterns in both morphology and neutral genetic diversity, these types of biological variabilities are being structured by different ecological and evolutionary processes. The relative influences of genetic drift versus selection and phenotypic plasticity in shaping morphology appear to vary among populations occupying nearby streams.

  14. Wind turbine design codes: A comparison of the structural response

    SciTech Connect

    Buhl, M.L. Jr.; Wright, A.D.; Pierce, K.G.

    2000-03-01

    The National Wind Technology Center (NWTC) of the National Renewable Energy Laboratory is continuing a comparison of several computer codes used in the design and analysis of wind turbines. The second part of this comparison determined how well the programs predict the structural response of wind turbines. In this paper, the authors compare the structural response for four programs: ADAMS, BLADED, FAST{_}AD, and YawDyn. ADAMS is a commercial, multibody-dynamics code from Mechanical Dynamics, Inc. BLADED is a commercial, performance and structural-response code from Garrad Hassan and Partners Limited. FAST{_}AD is a structural-response code developed by Oregon State University and the University of Utah for the NWTC. YawDyn is a structural-response code developed by the University of Utah for the NWTC. ADAMS, FAST{_}AD, and YawDyn use the University of Utah's AeroDyn subroutine package for calculating aerodynamic forces. Although errors were found in all the codes during this study, once they were fixed, the codes agreed surprisingly well for most of the cases and configurations that were evaluated. One unresolved discrepancy between BLADED and the AeroDyn-based codes was when there was blade and/or teeter motion in addition to a large yaw error.

  15. Neutral Hydrogen Structures Trace Dust Polarization Angle: Implications for Cosmic Microwave Background Foregrounds.

    PubMed

    Clark, S E; Hill, J Colin; Peek, J E G; Putman, M E; Babler, B L

    2015-12-11

    Using high-resolution data from the Galactic Arecibo L-Band Feed Array HI (GALFA-Hi) survey, we show that linear structure in Galactic neutral hydrogen (Hi) correlates with the magnetic field orientation implied by Planck 353 GHz polarized dust emission. The structure of the neutral interstellar medium is more tightly coupled to the magnetic field than previously known. At high Galactic latitudes, where the Planck data are noise dominated, the Hi data provide an independent constraint on the Galactic magnetic field orientation, and hence the local dust polarization angle. We detect strong cross-correlations between template maps constructed from estimates of dust intensity combined with either Hi-derived angles, starlight polarization angles, or Planck 353 GHz angles. The Hi data thus provide a new tool in the search for inflationary gravitational wave B-mode polarization in the cosmic microwave background, which is currently limited by dust foreground contamination. PMID:26705622

  16. Structural and electronic properties of neutral and charged Ca 8C 12 metal carbides

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Peng, Qi; Kawazoe, Yoshiyuki

    2011-05-01

    This Letter reports our detailed first-principles study on neutral and charged Ca8C12 clusters. Except a compact structure owning geometrical characters of the CaC2 bulk, all the other low-lying structures within 0.2 eV in relative total energy are hollow configurations. Most of the low-lying structures are calculated to be magnetic. The ground states are a D3d flat structure, a compact structure, and a D3d hollow cage-like structure for Ca8C12, Ca8C12-, and Ca8C12+ clusters, respectively. The net charge on Ca ion, except the dangling one of the compact structure, is calculated to be around +1.4e.

  17. Structural repertoire of HIV-1-neutralizing antibodies targeting the CD4 supersite in 14 donors

    PubMed Central

    Zhou, Tongqing; Lynch, Rebecca M.; Chen, Lei; Acharya, Priyamvada; Wu, Xueling; Doria-Rose, Nicole A.; Joyce, M. Gordon; Lingwood, Daniel; Soto, Cinque; Bailer, Robert T.; Ernandes, Michael J.; Kong, Rui; Longo, Nancy S.; Louder, Mark K.; McKee, Krisha; O’Dell, Sijy; Schmidt, Stephen D.; Tran, Lillian; Yang, Zhongjia; Druz, Aliaksandr; Luongo, Timothy S.; Moquin, Stephanie; Srivatsan, Sanjay; Yang, Yongping; Zhang, Baoshan; Zheng, Anqi; Pancera, Marie; Kirys, Tatsiana; Georgiev, Ivelin S.; Gindin, Tatyana; Peng, Hung-Pin; Yang, An-Suei; Mullikin, James C.; Gray, Matthew D.; Stamatatos, Leonidas; Burton, Dennis R.; Koff, Wayne C.; Cohen, Myron S.; Haynes, Barton F.; Casazza, Joseph P.; Connors, Mark; Corti, Davide; Lanzavecchia, Antonio; Sattentau, Quentin J.; Weiss, Robin A.; West, Anthony P.; Bjorkman, Pamela J.; Scheid, Johannes F.; Nussenzweig, Michel C.; Shapiro, Lawrence; Mascola, John R.; Kwong, Peter D.

    2015-01-01

    The site on the HIV-1 gp120 glycoprotein that binds the CD4 receptor is recognized by broadly reactive antibodies, several of which neutralize over 90% of HIV-1 strains. To understand how antibodies achieve such neutralization, we isolated CD4-binding-site (CD4bs) antibodies and analyzed 16 co-crystal structures –8 determined here– of CD4bs antibodies from 14 donors. The 16 antibodies segregated by recognition mode and developmental ontogeny into two types: CDR H3-dominated and VH-gene-restricted. Both could achieve greater than 80% neutralization breadth, and both could develop in the same donor. Although paratope chemistries differed, all 16 gp120-CD4bs antibody complexes showed geometric similarity, with antibody-neutralization breadth correlating with antibody-angle of approach relative to the most effective antibody of each type. The repertoire for effective recognition of the CD4 supersite thus comprises antibodies with distinct paratopes arrayed about two optimal geometric orientations, one achieved by CDR H3 ontogenies and the other achieved by VH-gene-restricted ontogenies. PMID:26004070

  18. Stochastic Demography and the Neutral Substitution Rate in Class-Structured Populations

    PubMed Central

    Lehmann, Laurent

    2014-01-01

    The neutral rate of allelic substitution is analyzed for a class-structured population subject to a stationary stochastic demographic process. The substitution rate is shown to be generally equal to the effective mutation rate, and under overlapping generations it can be expressed as the effective mutation rate in newborns when measured in units of average generation time. With uniform mutation rate across classes the substitution rate reduces to the mutation rate. PMID:24594520

  19. Hyperfine structure and isotope shifts of transitions in neutral and singly ionized ytterbium

    NASA Technical Reports Server (NTRS)

    Berends, R. W.; Maleki, L.

    1992-01-01

    The present experimental investigation of the hyperfine structure and isotopic shifts of transitions in neutral and singly-ionized Yb, which constitute a system of some interest to microwave-frequency standards, used counterpropagating pump and probe laser beams directed through a hollow-cathode discharge lamp. The results obtained are in agreement with previous measurements except in the case of the Yb-173(+) 6 2P0 sub 3/2 state, which is more accurately determined.

  20. Adaptive and neutral markers both show continent-wide population structure of mountain pine beetle (Dendroctonus ponderosae).

    PubMed

    Batista, Philip D; Janes, Jasmine K; Boone, Celia K; Murray, Brent W; Sperling, Felix A H

    2016-09-01

    Assessments of population genetic structure and demographic history have traditionally been based on neutral markers while explicitly excluding adaptive markers. In this study, we compared the utility of putatively adaptive and neutral single-nucleotide polymorphisms (SNPs) for inferring mountain pine beetle population structure across its geographic range. Both adaptive and neutral SNPs, and their combination, allowed range-wide structure to be distinguished and delimited a population that has recently undergone range expansion across northern British Columbia and Alberta. Using an equal number of both adaptive and neutral SNPs revealed that adaptive SNPs resulted in a stronger correlation between sampled populations and inferred clustering. Our results suggest that adaptive SNPs should not be excluded prior to analysis from neutral SNPs as a combination of both marker sets resulted in better resolution of genetic differentiation between populations than either marker set alone. These results demonstrate the utility of adaptive loci for resolving population genetic structure in a nonmodel organism. PMID:27648243

  1. Adaptive and neutral markers both show continent-wide population structure of mountain pine beetle (Dendroctonus ponderosae).

    PubMed

    Batista, Philip D; Janes, Jasmine K; Boone, Celia K; Murray, Brent W; Sperling, Felix A H

    2016-09-01

    Assessments of population genetic structure and demographic history have traditionally been based on neutral markers while explicitly excluding adaptive markers. In this study, we compared the utility of putatively adaptive and neutral single-nucleotide polymorphisms (SNPs) for inferring mountain pine beetle population structure across its geographic range. Both adaptive and neutral SNPs, and their combination, allowed range-wide structure to be distinguished and delimited a population that has recently undergone range expansion across northern British Columbia and Alberta. Using an equal number of both adaptive and neutral SNPs revealed that adaptive SNPs resulted in a stronger correlation between sampled populations and inferred clustering. Our results suggest that adaptive SNPs should not be excluded prior to analysis from neutral SNPs as a combination of both marker sets resulted in better resolution of genetic differentiation between populations than either marker set alone. These results demonstrate the utility of adaptive loci for resolving population genetic structure in a nonmodel organism.

  2. THE MULTIPHASE STRUCTURE AND POWER SOURCES OF GALACTIC WINDS IN MAJOR MERGERS

    SciTech Connect

    Rupke, David S. N.; Veilleux, Sylvain

    2013-05-01

    Massive, galaxy-scale outflows are known to be ubiquitous in major mergers of disk galaxies in the local universe. In this paper, we explore the multiphase structure and power sources of galactic winds in six ultraluminous infrared galaxies (ULIRGs) at z < 0.06 using deep integral field spectroscopy with the Gemini Multi-Object Spectrograph (GMOS) on Gemini North. We probe the neutral, ionized, and dusty gas phases using Na I D, strong emission lines ([O I], H{alpha}, and [N II]), and continuum colors, respectively. We separate outflow motions from those due to rotation and tidal perturbations, and find that all of the galaxies in our sample host high-velocity flows on kiloparsec scales. The properties of these outflows are consistent with multiphase (ionized, neutral, and dusty) collimated bipolar winds emerging along the minor axis of the nuclear disk to scales of 1-2 kpc. In two cases, these collimated winds take the form of bipolar superbubbles, identified by clear kinematic signatures. Less collimated (but still high-velocity) flows are also present on scales up to 5 kpc in most systems. The three galaxies in our sample with obscured QSOs host higher velocity outflows than those in the three galaxies with no evidence for an active galactic nucleus. The peak outflow velocity in each of the QSOs is in the range 1450-3350 km s{sup -1}, and the highest velocities (2000-3000 km s{sup -1}) are seen only in ionized gas. The outflow energy and momentum in the QSOs are difficult to produce from a starburst alone, but are consistent with the QSO contributing significantly to the driving of the flow. Finally, when all gas phases are accounted for, the outflows are massive enough to provide negative feedback to star formation.

  3. Structural and physical properties of collagen extracted from moon jellyfish under neutral pH conditions.

    PubMed

    Miki, Ayako; Inaba, Satomi; Baba, Takayuki; Kihira, Koji; Fukada, Harumi; Oda, Masayuki

    2015-01-01

    We extracted collagen from moon jellyfish under neutral pH conditions and analyzed its amino acid composition, secondary structure, and thermal stability. The content of hydroxyproline was 4.3%, which is lower than that of other collagens. Secondary structure analysis using circular dichroism (CD) showed a typical collagen helix. The thermal stability of this collagen at pH 3.0 was lower than those from fish scale and pig skin, which also correlates closely with jellyfish collagen having lower hydroxyproline content. Because the solubility of jellyfish collagen used in this study at neutral pH was quite high, it was possible to analyze its structural and physical properties under physiological conditions. Thermodynamic analysis using CD and differential scanning calorimetry showed that the thermal stability at pH 7.5 was higher than at pH 3.0, possibly due to electrostatic interactions. During the process of unfolding, fibrillation would occur only at neutral pH. PMID:26011511

  4. Structural and physical properties of collagen extracted from moon jellyfish under neutral pH conditions.

    PubMed

    Miki, Ayako; Inaba, Satomi; Baba, Takayuki; Kihira, Koji; Fukada, Harumi; Oda, Masayuki

    2015-01-01

    We extracted collagen from moon jellyfish under neutral pH conditions and analyzed its amino acid composition, secondary structure, and thermal stability. The content of hydroxyproline was 4.3%, which is lower than that of other collagens. Secondary structure analysis using circular dichroism (CD) showed a typical collagen helix. The thermal stability of this collagen at pH 3.0 was lower than those from fish scale and pig skin, which also correlates closely with jellyfish collagen having lower hydroxyproline content. Because the solubility of jellyfish collagen used in this study at neutral pH was quite high, it was possible to analyze its structural and physical properties under physiological conditions. Thermodynamic analysis using CD and differential scanning calorimetry showed that the thermal stability at pH 7.5 was higher than at pH 3.0, possibly due to electrostatic interactions. During the process of unfolding, fibrillation would occur only at neutral pH.

  5. Functional and structural characterization of neutralizing epitopes of measles virus hemagglutinin protein.

    PubMed

    Tahara, Maino; Ito, Yuri; Brindley, Melinda A; Ma, Xuemin; He, Jilan; Xu, Songtao; Fukuhara, Hideo; Sakai, Kouji; Komase, Katsuhiro; Rota, Paul A; Plemper, Richard K; Maenaka, Katsumi; Takeda, Makoto

    2013-01-01

    Effective vaccination programs have dramatically reduced the number of measles-related deaths globally. Although all the available data suggest that measles eradication is biologically feasible, a structural and biochemical basis for the single serotype nature of measles virus (MV) remains to be provided. The hemagglutinin (H) protein, which binds to two discrete proteinaceous receptors, is the major neutralizing target. Monoclonal antibodies (MAbs) recognizing distinct epitopes on the H protein were characterized using recombinant MVs encoding the H gene from different MV genotypes. The effects of various mutations on neutralization by MAbs and virus fitness were also analyzed, identifying the location of five epitopes on the H protein structure. Our data in the present study demonstrated that the H protein of MV possesses at least two conserved effective neutralizing epitopes. One, which is a previously recognized epitope, is located near the receptor-binding site (RBS), and thus MAbs that recognize this epitope blocked the receptor binding of the H protein, whereas the other epitope is located at the position distant from the RBS. Thus, a MAb that recognizes this epitope did not inhibit the receptor binding of the H protein, rather interfered with the hemagglutinin-fusion (H-F) interaction. This epitope was suggested to play a key role for formation of a higher order of an H-F protein oligomeric structure. Our data also identified one nonconserved effective neutralizing epitope. The epitope has been masked by an N-linked sugar modification in some genotype MV strains. These data would contribute to our understanding of the antigenicity of MV and support the global elimination program of measles. PMID:23115278

  6. Structure and Composition of the Neutral Upper Atmosphere of Mars from the MAVEN NGIMS Investigation

    NASA Astrophysics Data System (ADS)

    Mahaffy, P. R.; Benna, M.; Yelle, R. V.; Stone, S. W.; Elrod, M. K.; Fox, J. L.

    2015-12-01

    The Neutral Gas and Ion Mass Spectrometer (NGIMS) on the MAVEN mission is designed to characterize the state of the upper atmosphere and its response to perturbations from the sun and from lower atmosphere. These measurements complement other instruments on the MAVEN spacecraft and support the MAVEN science goal [Jakosky et al., 2015] of understanding atmospheric escape and over the course of martian history. We report NGIMS measurements of the neutral composition of multiple atomic and molecular species over hundreds of orbits since the science phase of this mission began late in 2014. Ion measurements from NGIMS are reported separately in other contributions to this session. The wide dynamic range, the high temporal resolution, and the use of two different ion source configurations of the NGIMS instrument [Mahaffy et al., 2014] allows neutral density structure and its variability to be characterized in detail. Large amplitude wave structure is observed on the lowest altitude portion of many orbits that dissipates at higher altitudes. Although this structure puts scatter in the retrieval of scale height temperatures these are nevertheless robustly secured by averaging over several orbits. The variability of the upper atmosphere temperature with latitude and local solar time is reported. The deep dip campaign approach to the homopause allows the mixing ratio of the major gases in the lower atmosphere to be measured. We compare these mixing ratios with those reported by the Sample Analysis at Mars investigation and previous Viking measurements. Jakosky, B. M., et al. (2015), The Mars Atmosphere and Volatile Evolution (MAVEN) Mission, Space Sci Rev, 21. Mahaffy, P. R., et al. (2014), The Neutral Gas and Ion Mass Spectrometer on the Mars Atmosphere and Volatile Evolution Mission, Space Sci Rev, 185, DOI: 10.1007/s11214-11014-10091-11211.

  7. Relationships between adaptive and neutral genetic diversity and ecological structure and functioning: a meta-analysis.

    PubMed

    Whitlock, Raj

    2014-07-01

    Understanding the effects of intraspecific genetic diversity on the structure and functioning of ecological communities is a fundamentally important part of evolutionary ecology and may also have conservation relevance in identifying the situations in which genetic diversity coincides with species-level diversity.Early studies within this field documented positive relationships between genetic diversity and ecological structure, but recent studies have challenged these findings. Conceptual synthesis has been hampered because studies have used different measures of intraspecific variation (phenotypically adaptive vs. neutral) and have considered different measures of ecological structure in different ecological and spatial contexts. The aim of this study is to strengthen conceptual understanding by providing an empirical synthesis quantifying the relationship between genetic diversity and ecological structure.Here, I present a meta-analysis of the relationship between genetic diversity within plant populations and the structure and functioning of associated ecological communities (including 423 effect sizes from 70 studies). I used Bayesian meta-analyses to examine (i) the strength and direction of this relationship, (ii) the extent to which phenotypically adaptive and neutral (molecular) measures of diversity differ in their association with ecological structure and (iii) variation in outcomes among different measures of ecological structure and in different ecological contexts.Effect sizes measuring the relationship between adaptive diversity (genotypic richness) and both community- and ecosystem-level ecological responses were small, but significantly positive. These associations were supported by genetic effects on species richness and productivity, respectively.There was no overall association between neutral genetic diversity and measures of ecological structure, but a positive correlation was observed under a limited set of demographic conditions. These

  8. Relationships between adaptive and neutral genetic diversity and ecological structure and functioning: a meta-analysis

    PubMed Central

    Whitlock, Raj

    2014-01-01

    Understanding the effects of intraspecific genetic diversity on the structure and functioning of ecological communities is a fundamentally important part of evolutionary ecology and may also have conservation relevance in identifying the situations in which genetic diversity coincides with species-level diversity.Early studies within this field documented positive relationships between genetic diversity and ecological structure, but recent studies have challenged these findings. Conceptual synthesis has been hampered because studies have used different measures of intraspecific variation (phenotypically adaptive vs. neutral) and have considered different measures of ecological structure in different ecological and spatial contexts. The aim of this study is to strengthen conceptual understanding by providing an empirical synthesis quantifying the relationship between genetic diversity and ecological structure.Here, I present a meta-analysis of the relationship between genetic diversity within plant populations and the structure and functioning of associated ecological communities (including 423 effect sizes from 70 studies). I used Bayesian meta-analyses to examine (i) the strength and direction of this relationship, (ii) the extent to which phenotypically adaptive and neutral (molecular) measures of diversity differ in their association with ecological structure and (iii) variation in outcomes among different measures of ecological structure and in different ecological contexts.Effect sizes measuring the relationship between adaptive diversity (genotypic richness) and both community- and ecosystem-level ecological responses were small, but significantly positive. These associations were supported by genetic effects on species richness and productivity, respectively.There was no overall association between neutral genetic diversity and measures of ecological structure, but a positive correlation was observed under a limited set of demographic conditions. These

  9. Community investment in wind farms: funding structure effects in wind energy infrastructure development.

    PubMed

    Beery, Joshua A; Day, Jennifer E

    2015-03-01

    Wind energy development is an increasingly popular form of renewable energy infrastructure in rural areas. Communities generally perceive socioeconomic benefits accrue and that community funding structures are preferable to corporate structures, yet lack supporting quantitative data to inform energy policy. This study uses the Everpower wind development, to be located in Midwestern Ohio, as a hypothetical modeling environment to identify and examine socioeconomic impact trends arising from corporate, community and diversified funding structures. Analysis of five National Renewable Energy Laboratory Jobs and Economic Development Impact models incorporating local economic data and review of relevant literature were conducted. The findings suggest that community and diversified funding structures exhibit 40-100% higher socioeconomic impact levels than corporate structures. Prioritization of funding sources and retention of federal tax incentives were identified as key elements. The incorporation of local shares was found to mitigate the negative effects of foreign private equity, local debt financing increased economic output and opportunities for private equity investment were identified. The results provide the groundwork for energy policies focused to maximize socioeconomic impacts while creating opportunities for inclusive economic participation and improved social acceptance levels fundamental to the deployment of renewable energy technology.

  10. Community investment in wind farms: funding structure effects in wind energy infrastructure development.

    PubMed

    Beery, Joshua A; Day, Jennifer E

    2015-03-01

    Wind energy development is an increasingly popular form of renewable energy infrastructure in rural areas. Communities generally perceive socioeconomic benefits accrue and that community funding structures are preferable to corporate structures, yet lack supporting quantitative data to inform energy policy. This study uses the Everpower wind development, to be located in Midwestern Ohio, as a hypothetical modeling environment to identify and examine socioeconomic impact trends arising from corporate, community and diversified funding structures. Analysis of five National Renewable Energy Laboratory Jobs and Economic Development Impact models incorporating local economic data and review of relevant literature were conducted. The findings suggest that community and diversified funding structures exhibit 40-100% higher socioeconomic impact levels than corporate structures. Prioritization of funding sources and retention of federal tax incentives were identified as key elements. The incorporation of local shares was found to mitigate the negative effects of foreign private equity, local debt financing increased economic output and opportunities for private equity investment were identified. The results provide the groundwork for energy policies focused to maximize socioeconomic impacts while creating opportunities for inclusive economic participation and improved social acceptance levels fundamental to the deployment of renewable energy technology. PMID:25621885

  11. Predicting community structure in snakes on Eastern Nearctic islands using ecological neutral theory and phylogenetic methods.

    PubMed

    Burbrink, Frank T; McKelvy, Alexander D; Pyron, R Alexander; Myers, Edward A

    2015-11-22

    Predicting species presence and richness on islands is important for understanding the origins of communities and how likely it is that species will disperse and resist extinction. The equilibrium theory of island biogeography (ETIB) and, as a simple model of sampling abundances, the unified neutral theory of biodiversity (UNTB), predict that in situations where mainland to island migration is high, species-abundance relationships explain the presence of taxa on islands. Thus, more abundant mainland species should have a higher probability of occurring on adjacent islands. In contrast to UNTB, if certain groups have traits that permit them to disperse to islands better than other taxa, then phylogeny may be more predictive of which taxa will occur on islands. Taking surveys of 54 island snake communities in the Eastern Nearctic along with mainland communities that have abundance data for each species, we use phylogenetic assembly methods and UNTB estimates to predict island communities. Species richness is predicted by island area, whereas turnover from the mainland to island communities is random with respect to phylogeny. Community structure appears to be ecologically neutral and abundance on the mainland is the best predictor of presence on islands. With regard to young and proximate islands, where allopatric or cladogenetic speciation is not a factor, we find that simple neutral models following UNTB and ETIB predict the structure of island communities. PMID:26609083

  12. Structure of HCMV glycoprotein B in the postfusion conformation bound to a neutralizing human antibody

    PubMed Central

    Chandramouli, Sumana; Ciferri, Claudio; Nikitin, Pavel A.; Caló, Stefano; Gerrein, Rachel; Balabanis, Kara; Monroe, James; Hebner, Christy; Lilja, Anders E.; Settembre, Ethan C.; Carfi, Andrea

    2015-01-01

    Human cytomegalovirus (HCMV) poses a significant threat to immunocompromised individuals and neonates infected in utero. Glycoprotein B (gB), the herpesvirus fusion protein, is a target for neutralizing antibodies and a vaccine candidate due to its indispensable role in infection. Here we show the crystal structure of the HCMV gB ectodomain bound to the Fab fragment of 1G2, a neutralizing human monoclonal antibody isolated from a seropositive subject. The gB/1G2 interaction is dominated by aromatic residues in the 1G2 heavy chain CDR3 protruding into a hydrophobic cleft in the gB antigenic domain 5 (AD-5). Structural analysis and comparison with HSV gB suggest the location of additional neutralizing antibody binding sites on HCMV gB. Finally, immunoprecipitation experiments reveal that 1G2 can bind to HCMV virion gB suggesting that its epitope is exposed and accessible on the virus surface. Our data will support the development of vaccines and therapeutic antibodies against HCMV infection. PMID:26365435

  13. Predicting community structure in snakes on Eastern Nearctic islands using ecological neutral theory and phylogenetic methods.

    PubMed

    Burbrink, Frank T; McKelvy, Alexander D; Pyron, R Alexander; Myers, Edward A

    2015-11-22

    Predicting species presence and richness on islands is important for understanding the origins of communities and how likely it is that species will disperse and resist extinction. The equilibrium theory of island biogeography (ETIB) and, as a simple model of sampling abundances, the unified neutral theory of biodiversity (UNTB), predict that in situations where mainland to island migration is high, species-abundance relationships explain the presence of taxa on islands. Thus, more abundant mainland species should have a higher probability of occurring on adjacent islands. In contrast to UNTB, if certain groups have traits that permit them to disperse to islands better than other taxa, then phylogeny may be more predictive of which taxa will occur on islands. Taking surveys of 54 island snake communities in the Eastern Nearctic along with mainland communities that have abundance data for each species, we use phylogenetic assembly methods and UNTB estimates to predict island communities. Species richness is predicted by island area, whereas turnover from the mainland to island communities is random with respect to phylogeny. Community structure appears to be ecologically neutral and abundance on the mainland is the best predictor of presence on islands. With regard to young and proximate islands, where allopatric or cladogenetic speciation is not a factor, we find that simple neutral models following UNTB and ETIB predict the structure of island communities.

  14. Structural basis of potent Zika-dengue virus antibody cross-neutralization.

    PubMed

    Barba-Spaeth, Giovanna; Dejnirattisai, Wanwisa; Rouvinski, Alexander; Vaney, Marie-Christine; Medits, Iris; Sharma, Arvind; Simon-Lorière, Etienne; Sakuntabhai, Anavaj; Cao-Lormeau, Van-Mai; Haouz, Ahmed; England, Patrick; Stiasny, Karin; Mongkolsapaya, Juthathip; Heinz, Franz X; Screaton, Gavin R; Rey, Félix A

    2016-08-01

    Zika virus is a member of the Flavivirus genus that had not been associated with severe disease in humans until the recent outbreaks, when it was linked to microcephaly in newborns in Brazil and to Guillain-Barré syndrome in adults in French Polynesia. Zika virus is related to dengue virus, and here we report that a subset of antibodies targeting a conformational epitope isolated from patients with dengue virus also potently neutralize Zika virus. The crystal structure of two of these antibodies in complex with the envelope protein of Zika virus reveals the details of a conserved epitope, which is also the site of interaction of the envelope protein dimer with the precursor membrane (prM) protein during virus maturation. Comparison of the Zika and dengue virus immunocomplexes provides a lead for rational, epitope-focused design of a universal vaccine capable of eliciting potent cross-neutralizing antibodies to protect simultaneously against both Zika and dengue virus infections.

  15. Mirror mode structures ahead of dipolarization front near the neutral sheet observed by Cluster

    NASA Astrophysics Data System (ADS)

    Wang, G. Q.; Zhang, T. L.; Volwerk, M.; Schmid, D.; Baumjohann, W.; Nakamura, R.; Pan, Z. H.

    2016-09-01

    Magnetic compressional structures ahead of a dipolarization front (DF) on 30 August 2002 are investigated by using Cluster data. Our findings are as follows: (1) the structures, observed near the neutral sheet, are mainly compressional and dominant in BZ; (2) they are almost nonpropagating relative to the local ion bulk flow and their lengths are several local proton gyroradius; (3) the ion density increases when BT decreases; (4) ions are partially trapped by the structures with parallel and perpendicular velocities varying in antiphase; and (5) local conditions are favorable for excitation of the mirror instability, and we suggest that these structures are mirror mode-like. Our findings also suggest that local conditions ahead of the DF are viable for exciting the mirror instability to generate mirror mode waves or structures.

  16. Global Structure of HIV-1 Neutralizing Antibody IgG1 b12 is Asymmetric

    SciTech Connect

    Ashish, F.; Solanki, A; Boone, C; Krueger, J

    2010-01-01

    Human antibody IgG1 b12 is one of the four antibodies known to neutralize a broad range of human immunodeficiency virus-1. The crystal structure of this antibody displayed an asymmetric disposition of the Fab arms relative to its Fc portion. Comparison of structures solved for other IgG1 antibodies led to a notion that crystal packing forces entrapped a 'snap-shot' of different conformations accessible to this antibody. To elucidate global structure of this unique antibody, we acquired small-angle X-ray scattering data from its dilute solution. Data analysis indicated that b12 adopts a bilobal globular structure in solution with a radius of gyration and a maximum linear dimension of {approx}54 and {approx}180 {angstrom}, respectively. Extreme similarity between its solution and crystal structure concludes that non-flexible, asymmetric shape is an inherent property of this rare antibody.

  17. Structural Bases of Coronavirus Attachment to Host Aminopeptidase N and Its Inhibition by Neutralizing Antibodies

    PubMed Central

    Mudgal, Gaurav; Ordoño, Desiderio; Enjuanes, Luis; Casasnovas, José M.

    2012-01-01

    The coronaviruses (CoVs) are enveloped viruses of animals and humans associated mostly with enteric and respiratory diseases, such as the severe acute respiratory syndrome and 10–20% of all common colds. A subset of CoVs uses the cell surface aminopeptidase N (APN), a membrane-bound metalloprotease, as a cell entry receptor. In these viruses, the envelope spike glycoprotein (S) mediates the attachment of the virus particles to APN and subsequent cell entry, which can be blocked by neutralizing antibodies. Here we describe the crystal structures of the receptor-binding domains (RBDs) of two closely related CoV strains, transmissible gastroenteritis virus (TGEV) and porcine respiratory CoV (PRCV), in complex with their receptor, porcine APN (pAPN), or with a neutralizing antibody. The data provide detailed information on the architecture of the dimeric pAPN ectodomain and its interaction with the CoV S. We show that a protruding receptor-binding edge in the S determines virus-binding specificity for recessed glycan-containing surfaces in the membrane-distal region of the pAPN ectodomain. Comparison of the RBDs of TGEV and PRCV to those of other related CoVs, suggests that the conformation of the S receptor-binding region determines cell entry receptor specificity. Moreover, the receptor-binding edge is a major antigenic determinant in the TGEV envelope S that is targeted by neutralizing antibodies. Our results provide a compelling view on CoV cell entry and immune neutralization, and may aid the design of antivirals or CoV vaccines. APN is also considered a target for cancer therapy and its structure, reported here, could facilitate the development of anti-cancer drugs. PMID:22876187

  18. Structural bases of coronavirus attachment to host aminopeptidase N and its inhibition by neutralizing antibodies.

    PubMed

    Reguera, Juan; Santiago, César; Mudgal, Gaurav; Ordoño, Desiderio; Enjuanes, Luis; Casasnovas, José M

    2012-01-01

    The coronaviruses (CoVs) are enveloped viruses of animals and humans associated mostly with enteric and respiratory diseases, such as the severe acute respiratory syndrome and 10-20% of all common colds. A subset of CoVs uses the cell surface aminopeptidase N (APN), a membrane-bound metalloprotease, as a cell entry receptor. In these viruses, the envelope spike glycoprotein (S) mediates the attachment of the virus particles to APN and subsequent cell entry, which can be blocked by neutralizing antibodies. Here we describe the crystal structures of the receptor-binding domains (RBDs) of two closely related CoV strains, transmissible gastroenteritis virus (TGEV) and porcine respiratory CoV (PRCV), in complex with their receptor, porcine APN (pAPN), or with a neutralizing antibody. The data provide detailed information on the architecture of the dimeric pAPN ectodomain and its interaction with the CoV S. We show that a protruding receptor-binding edge in the S determines virus-binding specificity for recessed glycan-containing surfaces in the membrane-distal region of the pAPN ectodomain. Comparison of the RBDs of TGEV and PRCV to those of other related CoVs, suggests that the conformation of the S receptor-binding region determines cell entry receptor specificity. Moreover, the receptor-binding edge is a major antigenic determinant in the TGEV envelope S that is targeted by neutralizing antibodies. Our results provide a compelling view on CoV cell entry and immune neutralization, and may aid the design of antivirals or CoV vaccines. APN is also considered a target for cancer therapy and its structure, reported here, could facilitate the development of anti-cancer drugs. PMID:22876187

  19. Influence of spin-orbit effects on structures and dielectric properties of neutral lead clusters

    SciTech Connect

    Götz, D. A. Shayeghi, A.; Schäfer, R.; Johnston, R. L.; Schwerdtfeger, P.

    2014-04-28

    Combining molecular beam electric deflection experiments and global optimization techniques has proven to be a powerful tool for resolving equilibrium structures of neutral metal and semiconductor clusters. Herein, we present electric molecular beam deflection experiments on Pb{sub N} (N = 7–18) clusters. Promising structures are generated using the unbiased Birmingham Cluster Genetic Algorithm approach based on density functional theory. The structures are further relaxed within the framework of two-component density functional theory taking scalar relativistic and spin orbit effects into account. Quantum chemical results are used to model electric molecular beam deflection profiles based on molecular dynamics calculations. Comparison of measured and simulated beam profiles allows the assignment of equilibrium structures for the most cluster sizes in the examined range for the first time. Neutral lead clusters adopt mainly spherical geometries and resemble the structures of lead cluster cations apart from Pb{sub 10}. Their growth pattern deviates strongly from the one observed for tin and germanium clusters.

  20. Modeling of the coupled magnetospheric and neutral wind dynamos. Annual Technical status report No. 2, 1 April 1994-30 March1995

    SciTech Connect

    Thayer, J.P.; Vickrey, J.F.; Heelis, R.A.; Gary, J.B.

    1995-03-01

    Work at SRI involved modeling the exchange of electromagnetic energy between the ionosphere and magnetosphere to help interpret the DE-B Poynting flux observations. To describe the electrical properties of the high-latitude ionosphere, the authors constructed a numerical model, from the framework provided by the Vector Spherical Harmonic (VSH) model, that determines the ionospheric currents, conductivities, and electric fields including both magnetospheric inputs and neutral wind dynamo effects. This model development grew from the earlier question of whether an electrical energy source in the ionosphere was capable of providing an upward Poynting flux. The model solves the steady-state neutral wind dynamo equations and the Poynting flux equation to provide insight into the electrodynamic role of the neutral winds. The modeling effort to determine the high-latitude energy flux has been able to reproduce many of the large-scale features observed in the Poynting flux measurements made by DE-2. Because the Poynting flux measurement is an integrated result of energy flux into or out of the ionosphere, the authors investigated the ionospheric properties that may contribute to the observed flux of energy measured by the spacecraft. During steady state the electromagnetic energy flux, or DC Poynting flux, is equal to the Joule heating rate and the mechanical energy transfer rate in the high-latitude ionosphere. Although the Joule heating rate acts as an energy sink, transforming electromagnetic energy into thermal or internal energy of the gas, the mechanical energy transfer rate may be either a sink or source of electromagnetic energy. In the steady state, it is only the mechanical energy transfer rate that can generate electromagnetic energy and result in a DC Poynating flux that is directed out of the ionosphere.

  1. Crystal Structures of Ricin Toxin’s Enzymatic Subunit (RTA) in Complex with Neutralizing and Non-neutralizing Single Chain Antibodies

    PubMed Central

    Rudolph, Michael J.; Vance, David J.; Cheung, Jonah; Franklin, Matthew C.; Burshteyn, Fiana; Cassidy, Michael S.; Gary, Ebony N.; Herrera, Cristina; Shoemaker, Charles B.; Mantis, Nicholas J.

    2014-01-01

    Ricin is a Select Agent Toxin and a member of the RNA N-glycosidase family of medically important plant and bacterial ribosome-inactivating proteins (RIPs). In this study, we determined x-ray crystal structures of the enzymatic subunit of ricin (RTA) in complex with the antigen binding domains (VHH) of five unique single-chain monoclonal antibodies that differ in their respective toxin-neutralizing activities. None of the VHHs made direct contact with residues involved in RTA’s RNA N-glycosidase activity or induced notable allosteric changes in the toxin’s subunit. Rather, the five VHHs had overlapping structural epitopes on the surface of the toxin and differed in the degree to which they made contact with prominent structural elements in two folding domains of the RTA. In general, RTA interactions were influenced most by the VHH CDR3 elements, with the most potent neutralizing antibody having the shortest and most conformationally constrained CDR3. These structures provide unique insights into the mechanisms underlying toxin neutralization and provide critically important information required for the rational design of ricin toxin subunit vaccines. PMID:24907552

  2. Relationship of the quaternary structure of human secretory IgA to neutralization of influenza virus.

    PubMed

    Suzuki, Tadaki; Kawaguchi, Akira; Ainai, Akira; Tamura, Shin-ichi; Ito, Ryo; Multihartina, Pretty; Setiawaty, Vivi; Pangesti, Krisna Nur Andriana; Odagiri, Takato; Tashiro, Masato; Hasegawa, Hideki

    2015-06-23

    Secretory IgA (S-IgA) antibodies, the major contributors to humoral mucosal immunity to influenza virus infection, are polymeric Igs present in many external secretions. In the present study, the quaternary structures of human S-IgA induced in nasal mucosa after administration of intranasal inactivated influenza vaccines were characterized in relation to neutralization potency against influenza A viruses. Human nasal IgA antibodies have been shown to contain at least five quaternary structures. Direct and real-time visualization of S-IgA using high-speed atomic force microscopy (AFM) demonstrated that trimeric and tetrameric S-IgA had six and eight antigen-binding sites, respectively, and that these structures exhibited large-scale asynchronous conformational changes while capturing influenza HA antigens in solution. Furthermore, trimeric, tetrameric, and larger polymeric structures, which are minor fractions in human nasal IgA, displayed increased neutralizing potency against influenza A viruses compared with dimeric S-IgA, suggesting that the larger polymeric than dimeric forms of S-IgA play some important roles in protection against influenza A virus infection in the human upper respiratory tract.

  3. Structural analyses at pseudo atomic resolution of Chikungunya virus and antibodies show mechanisms of neutralization.

    PubMed

    Sun, Siyang; Xiang, Ye; Akahata, Wataru; Holdaway, Heather; Pal, Pankaj; Zhang, Xinzheng; Diamond, Michael S; Nabel, Gary J; Rossmann, Michael G

    2013-04-02

    A 5.3 Å resolution, cryo-electron microscopy (cryoEM) map of Chikungunya virus-like particles (VLPs) has been interpreted using the previously published crystal structure of the Chikungunya E1-E2 glycoprotein heterodimer. The heterodimer structure was divided into domains to obtain a good fit to the cryoEM density. Differences in the T = 4 quasi-equivalent heterodimer components show their adaptation to different environments. The spikes on the icosahedral 3-fold axes and those in general positions are significantly different, possibly representing different phases during initial generation of fusogenic E1 trimers. CryoEM maps of neutralizing Fab fragments complexed with VLPs have been interpreted using the crystal structures of the Fab fragments and the VLP structure. Based on these analyses the CHK-152 antibody was shown to stabilize the viral surface, hindering the exposure of the fusion-loop, likely neutralizing infection by blocking fusion. The CHK-9, m10 and m242 antibodies surround the receptor-attachment site, probably inhibiting infection by blocking cell attachment. DOI:http://dx.doi.org/10.7554/eLife.00435.001.

  4. Relationship of the quaternary structure of human secretory IgA to neutralization of influenza virus

    PubMed Central

    Suzuki, Tadaki; Kawaguchi, Akira; Ainai, Akira; Tamura, Shin-ichi; Ito, Ryo; Multihartina, Pretty; Setiawaty, Vivi; Pangesti, Krisna Nur Andriana; Odagiri, Takato; Tashiro, Masato; Hasegawa, Hideki

    2015-01-01

    Secretory IgA (S-IgA) antibodies, the major contributors to humoral mucosal immunity to influenza virus infection, are polymeric Igs present in many external secretions. In the present study, the quaternary structures of human S-IgA induced in nasal mucosa after administration of intranasal inactivated influenza vaccines were characterized in relation to neutralization potency against influenza A viruses. Human nasal IgA antibodies have been shown to contain at least five quaternary structures. Direct and real-time visualization of S-IgA using high-speed atomic force microscopy (AFM) demonstrated that trimeric and tetrameric S-IgA had six and eight antigen-binding sites, respectively, and that these structures exhibited large-scale asynchronous conformational changes while capturing influenza HA antigens in solution. Furthermore, trimeric, tetrameric, and larger polymeric structures, which are minor fractions in human nasal IgA, displayed increased neutralizing potency against influenza A viruses compared with dimeric S-IgA, suggesting that the larger polymeric than dimeric forms of S-IgA play some important roles in protection against influenza A virus infection in the human upper respiratory tract. PMID:26056267

  5. The extended interacting wind structure of Eta Carinae

    NASA Astrophysics Data System (ADS)

    Gull, T. R.; Nielsen, K. E.; Corcoran, M. F.; Madura, T. I.; Owocki, S. P.; Russell, C. M. P.; Hillier, D. J.; Hamaguchi, K.; Kober, G. V.; Weis, K.; Stahl, O.; Okazaki, A. T.

    2009-07-01

    The highly eccentric binary system, η Car, provides clues to the transition of massive stars from hydrogen-burning via the CNO cycle to a helium-burning evolutionary state. The fast-moving wind of η Car B creates a cavity in η Car A's slower, but more massive, stellar wind, providing an in situ probe. The Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS), with its high spatial and spectral resolutions, is well matched to follow temporal spatial and velocity variations of multiple wind features. We use observations obtained across 1998-2004 to produce a rudimentary three-dimensional model of the wind interaction in the η Car system. Broad (+/-500 km s-1) [FeII] emission line structures extend 0.7arcsec (~1600 au) from the stellar core. In contrast, [FeIII], [ArIII], [NeIII] and [SIII] lines extend only 0.3arcsec (700 au) from NE to SW and are blue shifted from -500 to +200 km s-1. All observed spectral features vary with the 5.54-year orbital period. The highly ionized, forbidden emission disappears during the low state, associated with periastron passage. The high-ionization emission originates in the outer wind interaction region that is directly excited by the far-ultraviolet radiation from η Car B. The HST/STIS spectra reveal a time-varying, distorted paraboloidal structure, caused by the interaction of the massive stellar winds. The model and observations are consistent with the orbital plane aligned with the skirt of the Homunculus. However, the axis of the distorted paraboloid, relative to the major axis of the binary orbit, is shifted in a prograde rotation along the plane, which projected on the sky is from NE to NW. Based on observations made with the National Aeronautics and Space Agency/European Space Agency (NASA/ESA) HST. Support for Programme numbers 7302, 8036, 8483, 8619, 9083, 9337, 9420, 9973, 10957 and 11273 was provided by NASA directly to the Space Telescope Imaging Spectrograph Science Team and through grants from the

  6. THREE-DIMENSIONAL STRUCTURE OF SOLAR WIND TURBULENCE

    SciTech Connect

    Chen, C. H. K.; Bale, S. D.; Mallet, A.; Schekochihin, A. A.; Horbury, T. S.; Wicks, R. T.

    2012-10-20

    We present a measurement of the scale-dependent, three-dimensional structure of the magnetic field fluctuations in inertial range solar wind turbulence with respect to a local, physically motivated coordinate system. The Alfvenic fluctuations are three-dimensionally anisotropic, with the sense of this anisotropy varying from large to small scales. At the outer scale, the magnetic field correlations are longest in the local fluctuation direction, consistent with Alfven waves. At the proton gyroscale, they are longest along the local mean field direction and shortest in the direction perpendicular to the local mean field and the local field fluctuation. The compressive fluctuations are highly elongated along the local mean field direction, although axially symmetric perpendicular to it. Their large anisotropy may explain why they are not heavily damped in the solar wind.

  7. Simulation of the atmospheric boundary layer in the wind tunnel for modeling of wind loads on low-rise structures

    NASA Technical Reports Server (NTRS)

    Tieleman, H. W.; Reinhold, T. A.; Marshall, R. D.

    1976-01-01

    The lower part of the atmospheric boundary layer (strong wind conditions) was simulated in low speed wind tunnel for the modeling of wind loads on low-rise structures. The turbulence characteristics of the turbulent boundary layer in the wind tunnel are compared with full scale measurements and with measurements made at NASA Wallops Flight Center. Wind pressures measured on roofs of a 1:70 scale model of a small single family dwelling were compared with results obtained from full scale measurements. The results indicate a favorable comparison between full scale and model pressure data as far as mean, r.m.s. and peak pressures are concerned. In addition, results also indicate that proper modeling of the turbulence is essential for proper simulation of the wind pressures.

  8. Vertical structure of the ionosphere and upper neutral atmosphere of saturn from the pioneer radio occultation.

    PubMed

    Kliore, A J; Lindal, G F; Patel, I R; Sweetnam, D N; Hotz, H B; McDonough, T R

    1980-01-25

    Radio occultation measurements at S band (2.293 gigahertz) of the ionosphere and upper neutral atmosphere of Saturn were obtained during the flyby of the Pioneer 11 Saturn spacecraft on 5 September 1979. Preliminary analysis of the occultation exit data taken at a latitude of 9.5 degrees S and a solar zenith angle of 90.6 degrees revealed the presence of a rather thin ionosphere, having a main peak electron density of about 9.4 x 10/(3) per cubic centimeter at an altitude of about 2800 above the level of a neutral number density of 10(19) per cubic centimeter and a lower peak of about 7 x 10(3) per cubic centimeter at 2200 kilometers. Data in the neutral atmosphere were obtained to a pressure level of about 120 millibars. The temperature structure derived from these data is consistent with the results of the Pioneer 11 Saturn infrared radiometer experiment (for a helium fraction of 15 percent) and with models derived from Earth-based observations for a helium fraction by number of about 4 to 10 percent. The helium fraction will be further defined by mutual iteration with the infrared radiometer team.

  9. Quantification of the relative roles of niche and neutral processes in structuring gastrointestinal microbiomes

    PubMed Central

    Jeraldo, Patricio; Sipos, Maksim; Chia, Nicholas; Brulc, Jennifer M.; Dhillon, A. Singh; Konkel, Michael E.; Larson, Charles L.; Nelson, Karen E.; Qu, Ani; Schook, Lawrence B.; Yang, Fang; White, Bryan A.; Goldenfeld, Nigel

    2012-01-01

    The theoretical description of the forces that shape ecological communities focuses around two classes of models. In niche theory, deterministic interactions between species, individuals, and the environment are considered the dominant factor, whereas in neutral theory, stochastic forces, such as demographic noise, speciation, and immigration, are dominant. Species abundance distributions predicted by the two classes of theory are difficult to distinguish empirically, making it problematic to deduce ecological dynamics from typical measures of diversity and community structure. Here, we show that the fusion of species abundance data with genome-derived measures of evolutionary distance can provide a clear indication of ecological dynamics, capable of quantifying the relative roles played by niche and neutral forces. We apply this technique to six gastrointestinal microbiomes drawn from three different domesticated vertebrates, using high-resolution surveys of microbial species abundance obtained from carefully curated deep 16S rRNA hypervariable tag sequencing data. Although the species abundance patterns are seemingly well fit by the neutral theory of metacommunity assembly, we show that this theory cannot account for the evolutionary patterns in the genomic data; moreover, our analyses strongly suggest that these microbiomes have, in fact, been assembled through processes that involve a significant nonneutral (niche) contribution. Our results demonstrate that high-resolution genomics can remove the ambiguities of process inference inherent in classic ecological measures and permits quantification of the forces shaping complex microbial communities. PMID:22615407

  10. Synthesis, molecular structure, and properties of a neutral Schiff base phenolic complex of magnesium

    SciTech Connect

    Polyakov, V.R.; Sharma, V.; Crankshaw, C.L.; Piwnica-Worms, D.

    1998-09-07

    Multidrug resistance (MDR) in cancer mediated by the MDR1 P-glycoprotein (Pgp), a 140--180 kDa plasma membrane protein, renders chemotherapeutic treatment ineffective by pumping a variety of natural product cytotoxic agents and xenobiotic compounds out of cancer cells. Pgp has been a major target for synthesis and development of both therapeutic antagonists that block its transport function and diagnostic radiopharmaceuticals that are transported by the protein for use in functional imaging of Pgp transport activity in tumors in vivo. Most, but not all, compounds that interact with Pgp are hydrophobic and cationic at physiological pH. To further understand the Pgp targeting properties, the authors sought to directly evaluate the effect of charge of the complex on Pgp interactions. This could be done by comparing the cytotoxicity profile of a neutral complex to that of an identical, but positively charged, complex in both drug-sensitive and multidrug-resistant cancer cells. Thus, a neutral analogue of the Ga(III) and Fe(III) complexes was desired. Herein the authors describe the synthesis and structure of a novel neutral Schiff base Mg complex and evaluate its cytotoxic potency in human drug-sensitive KB-3-1 and multi-drug-resistant KB-8-5 tumor cells.

  11. Spherical Particles of Zirconia-Titania of Hexagonal Structure from a Neutral Amine Route.

    PubMed

    de Farias RF; Airoldi

    1999-12-15

    Through the sol-gel process, using the so-called neutral amine route, spherical particles of 1:1 zirconia-titania were synthesized from zirconium(IV) and titanium(IV) butoxides as well as 1,12-diaminododecane as precursor species. The obtained product exhibited a hexagonal structure, as determinated by X-ray diffraction data. The obtained material was also characterized by thermogravimetry, differential scanning calorimetry, infrared spectroscopy, scanning electron microscopy, and surface area measurements. Despite the release of template molecules on heating, the spherical morphology was retained up to about 1200 degrees C, at which the disruption of the spheres took place. Copyright 1999 Academic Press.

  12. Vortex-core structure in neutral fermion superfluids with population imbalance.

    PubMed

    Takahashi, M; Mizushima, T; Ichioka, M; Machida, K

    2006-11-01

    Quantized vortex-core structure is theoretically investigated in fermion superfluids with population imbalance for two atom species of neutral atom clouds near a Feshbach resonance. In contrast with the vortex core in balance case where the quantum depletion makes a vortex visible through the density profile measurement, the vortex core is filled in and becomes less visible because the quantized discrete bound states are occupied exclusively by the majority species. Yet it is shown that the core can be visible through the minority density profile experiment using phase contrast imaging, revealing an interesting opportunity to examine low-lying fermionic core bound states unexplored so far.

  13. The Photoevaporation of a Neutral Structure by an EUV+FUV Radiation Field

    NASA Astrophysics Data System (ADS)

    Lora, Veronica; Vasconcelos, M. J.; Raga, A. C.; Cerqueira, A. H.; Esquivel, A.

    The expansion of an HII region into a surrounding inhomogeneous molecular cloud, leads to the formation of elongated "elephant trunk" structures. The EUV photo-ionising radiation and FUV dissociating radiation from newly born stars photo-evaporate their parental neutral cloud, leading to the formation of dense clumps in the tips of elephant trunks, that could in principle eventually form stars. We study th effects of including a photo-dissociating FUV flux in models of fragmentation of a photo-evaporating, self-gravitating molecular cloud.

  14. Structure of adeno-associated virus-2 in complex with neutralizing monoclonal antibody A20

    SciTech Connect

    McCraw, Dustin M.; O'Donnell, Jason K.; Taylor, Kenneth A.; Stagg, Scott M.; Chapman, Michael S.

    2012-09-15

    The use of adeno-associated virus (AAV) as a gene therapy vector is limited by the host neutralizing immune response. The cryo-electron microscopy (EM) structure at 8.5 A resolution is determined for a complex of AAV-2 with the Fab' fragment of monoclonal antibody (MAb) A20, the most extensively characterized AAV MAb. The binding footprint is determined through fitting the cryo-EM reconstruction with a homology model following sequencing of the variable domain, and provides a structural basis for integrating diverse prior epitope mappings. The footprint extends from the previously implicated plateau to the side of the spike, and into the conserved canyon, covering a larger area than anticipated. Comparison with structures of binding and non-binding serotypes indicates that recognition depends on a combination of subtle serotype-specific features. Separation of the neutralizing epitope from the heparan sulfate cell attachment site encourages attempts to develop immune-resistant vectors that can still bind to target cells.

  15. Structural Insights into the Neutralization Properties of the Fully Human, Anti-interferon Monoclonal Antibody Sifalimumab.

    PubMed

    Oganesyan, Vaheh; Peng, Li; Woods, Robert M; Wu, Herren; Dall'Acqua, William F

    2015-06-12

    We report the three-dimensional structure of human interferon α-2A (IFN-α2A) bound to the Fab fragment of a therapeutic monoclonal antibody (sifalimumab; IgG1/κ). The structure of the corresponding complex was solved at a resolution of 3.0 Å using molecular replacement and constitutes the first reported structure of a human type I IFN bound to a therapeutic antibody. This study revealed the major contribution made by the first complementarity-determining region in each of sifalimumab light and heavy chains. These data also provided the molecular basis for sifalimumab mechanism of action. We propose that its interferon-neutralizing properties are the result of direct competition for IFN-α2A binding to the IFN receptor subunit 1 (IFNAR1) and do not involve inhibiting IFN-α2A binding to the IFN receptor subunit 2 (IFNAR2). PMID:25925951

  16. Remote Structural Health Monitoring and Advanced Prognostics of Wind Turbines

    SciTech Connect

    Douglas Brown; Bernard Laskowski

    2012-05-29

    The prospect of substantial investment in wind energy generation represents a significant capital investment strategy. In order to maximize the life-cycle of wind turbines, associated rotors, gears, and structural towers, a capability to detect and predict (prognostics) the onset of mechanical faults at a sufficiently early stage for maintenance actions to be planned would significantly reduce both maintenance and operational costs. Advancement towards this effort has been made through the development of anomaly detection, fault detection and fault diagnosis routines to identify selected fault modes of a wind turbine based on available sensor data preceding an unscheduled emergency shutdown. The anomaly detection approach employs spectral techniques to find an approximation of the data using a combination of attributes that capture the bulk of variability in the data. Fault detection and diagnosis (FDD) is performed using a neural network-based classifier trained from baseline and fault data recorded during known failure conditions. The approach has been evaluated for known baseline conditions and three selected failure modes: pitch rate failure, low oil pressure failure and a gearbox gear-tooth failure. Experimental results demonstrate the approach can distinguish between these failure modes and normal baseline behavior within a specified statistical accuracy.

  17. The Response of the Ionospheric Cusp to the Solar Wind Through Two Perspectives: Low Energy Charged Particle In-Situ Measurements and Low-Energy Neutral Atom Imaging

    NASA Technical Reports Server (NTRS)

    Coffey, V. N.; Moore, T. E.; Chandler, M. O.; Giles, B. L.; Craven, P. D.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    The Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) mission provides a new perspective on the study of the response of the magnetosphere/ionosphere system to changing solar wind conditions, particularly the variability of ion outflow. Learning to interpret this new type of data becomes an essential step in the process of melding these results with the wealth of in-situ charged particle observations obtained over the past 25 years. In order to understand how the in-situ data correspond to and contrast with IMAGE results we will perform a conjunctive study of event data from two instruments to shed light on the coupling of the solar wind and ionosphere from these different perspectives. We will use the Low Energy Neutral Atom instrument (LENA) which images energetic neutral atom emissions from upward flowing ionospheric ions and the Thermal Ion Dynamics Instrument (TIDE) on the Polar satellite which measures in-situ ion outflow from 0.3-300 eV. Our primary goal will be to understand how comparing the imaging and in-situ perspectives can aid in the analysis of both data sets.

  18. Structural health and prognostics management for offshore wind turbines :

    SciTech Connect

    Myrent, Noah J.; Kusnick, Joshua F.; Barrett, Natalie C.; Adams, Douglas E.; Griffith, Daniel

    2013-04-01

    Operations and maintenance costs for offshore wind plants are significantly higher than the current costs for land-based (onshore) wind plants. One way to reduce these costs would be to implement a structural health and prognostic management (SHPM) system as part of a condition based maintenance paradigm with smart load management and utilize a state-based cost model to assess the economics associated with use of the SHPM system. To facilitate the development of such a system a multi-scale modeling approach developed in prior work is used to identify how the underlying physics of the system are affected by the presence of damage and faults, and how these changes manifest themselves in the operational response of a full turbine. This methodology was used to investigate two case studies: (1) the effects of rotor imbalance due to pitch error (aerodynamic imbalance) and mass imbalance and (2) disbond of the shear web; both on a 5-MW offshore wind turbine in the present report. Based on simulations of damage in the turbine model, the operational measurements that demonstrated the highest sensitivity to the damage/faults were the blade tip accelerations and local pitching moments for both imbalance and shear web disbond. The initial cost model provided a great deal of insight into the estimated savings in operations and maintenance costs due to the implementation of an effective SHPM system. The integration of the health monitoring information and O&M cost versus damage/fault severity information provides the initial steps to identify processes to reduce operations and maintenance costs for an offshore wind farm while increasing turbine availability, revenue, and overall profit.

  19. Wind turbine wake structure and yawed effect analysis

    NASA Astrophysics Data System (ADS)

    Ge, Yuntian

    In this research, the three-dimensional CFD simulation of the complex flow around a two-bladed rotor based on NREL Phase VI Experiment is presented. Its accuracy is demonstrated by comparing torque, thrust, power and power coefficient with experimental data. Then the wake structure behind the rotor is analyzed by showing the vorticity contour and comparing the velocity distribution behind the rotor with previous studies. Furthermore, a triangle relationship among power, upstream wind speed and yaw angle is given by setting control groups simulation. Reasonable explanations to the simulation results are presented. Finally, a linear relationship between power output and cosine value of yaw angle is found and analyzed.

  20. The Origins of Magnetic Structure in the Corona and Wind

    NASA Technical Reports Server (NTRS)

    Antiochos, Spiro K.

    2010-01-01

    One of the most important and most puzzling features of the coronal magnetic field is that it appears to have smooth magnetic structure with little evidence for non-potentiality except at two special locations: photospheric polarity inversions lines. (non-potentiality observed as a filament channel) and coronal hole boundaries, (observed as the slow solar wind). This characteristic feature of the closed-field corona is highly unexpected given that its magnetic field is continuously tangled by photospheric motions. Although reconnection can eliminate some of the injected structure, it cannot destroy the helicity, which should build up to produce observable complexity. I propose that an inverse cascade process transports the injected helicity from the interior of closed flux regions to their boundaries inversion lines and coronal holes, creating both filament channels and the slow wind. We describe how the helicity is injected and transported and calculate the relevant rates. I argue that one process, helicity transport, can explain both the observed lack and presence of structure in the coronal magnetic field. This work has been supported by the NASA HTP, SR&T, and LWS programs.

  1. Effects of magnetospheric electric fields and neutral winds on the low-middle latitude ionosphere during the March 20-21, 1990, Storm

    SciTech Connect

    Buonsanto, M.J.; Foster, J.C.

    1993-11-01

    During the geomagnetic storm of March 20-21, 1990, substorm activity is clearly evident in magnetometer data collected during the night at the middle- and low-latitude stations Fredericksburg (38.2{degrees}N, 282.6{degrees}E) and San Juan (18.1{degrees}N, 293.8{degrees}E). At the same time, incoherent scatter radars at Millstone Hill (42.6{degrees}N, 288.5{degrees}E) and Arecibo (18.3{degrees}N, 293.25{degrees}E) observed ionospheric storm effects, which included the penetration of magnetospheric electric fields and disturbance neutral winds to the latitude of Arecibo. The eastward electric fields associated with the substorm disturbances result in increases in the F2 peak height (hmF2) at Arecibo. Decreases in hmF2 follow as a result of increased downward diffusion and/or the effects of an ion drag induced poleward wind. During the intervals between the electric field penetration events, equatorward surges in the neutral wind result in westward electric fields by the disturbance dynamo mechanism. At these times the horizontal ionization drifts are not as strong as the neutral winds, apparently because of a partial shorting out of the dynamo electric fields as a result of some E region conductivity. The anticorrelation between the components of ion drift parallel (V{sub {parallel}}) and perpendicular to the magnetic field in the northward direction (V{sub {perpendicular}}N) results in approximately horizontal (constant altitude) ion drift motion throughout the interval. Calculations of spatial gradients in the electron density and in the components of the ion velocity are carried out using the multi-directional incoherent scatter observations at Arecibo. The results show that the variations in electron density during the disturbed interval follow closely the motion term in the F2 region continuity equation, with both advection of spatial gradients and divergence of the ion flow important at times. 28 refs., 8 figs.

  2. Structural basis for the inhibition of the essential Plasmodium falciparum M1 neutral aminopeptidase.

    PubMed

    McGowan, Sheena; Porter, Corrine J; Lowther, Jonathan; Stack, Colin M; Golding, Sarah J; Skinner-Adams, Tina S; Trenholme, Katharine R; Teuscher, Franka; Donnelly, Sheila M; Grembecka, Jolanta; Mucha, Artur; Kafarski, Pawel; Degori, Ross; Buckle, Ashley M; Gardiner, Donald L; Whisstock, James C; Dalton, John P

    2009-02-24

    Plasmodium falciparum parasites are responsible for the major global disease malaria, which results in >2 million deaths each year. With the rise of drug-resistant malarial parasites, novel drug targets and lead compounds are urgently required for the development of new therapeutic strategies. Here, we address this important problem by targeting the malarial neutral aminopeptidases that are involved in the terminal stages of hemoglobin digestion and essential for the provision of amino acids used for parasite growth and development within the erythrocyte. We characterize the structure and substrate specificity of one such aminopeptidase, PfA-M1, a validated drug target. The X-ray crystal structure of PfA-M1 alone and in complex with the generic inhibitor, bestatin, and a phosphinate dipeptide analogue with potent in vitro and in vivo antimalarial activity, hPheP[CH(2)]Phe, reveals features within the protease active site that are critical to its function as an aminopeptidase and can be exploited for drug development. These results set the groundwork for the development of antimalarial therapeutics that target the neutral aminopeptidases of the parasite.

  3. The global structure of hot star winds: Constraints from spectropolarimetry

    NASA Astrophysics Data System (ADS)

    Eversberg, Thomas

    2000-11-01

    Chapter 1. We present time-series of ultra-high S/N, high resolution spectra of the He II λ 4686 Å emission line in the O4I(n)f supergiant ζ Puppis, the brightest early-type O-star in the sky. These reveal stochastic, variable substructures in the line, which tend to move away from the line-center with time. Similar scaled-up features are well established in the strong winds of Wolf-Rayet stars (the presumed descendants of O stars), where they are explained by outward moving inhomogeneities (e.g., blobs, clumps, shocks) in the winds. If all hot-star winds are clumped like that of ζ Pup, as is plausible, then mass-low rates based on recombination-line intensities will have to be revised downwards. Using a standard `β' velocity law we deduce a value of β = 1.0-1.2 to account for the kinematics of these structures in the wind of ζ Pup. In addition to the small-scale stochastic variations we also find a slow systematic variation of the mean central absorption reversal. Chapter 2. We introduce a new polarimeter unit which, mounted at the Cassegrain focus of any telescope and fiber-connected to a fixed CCD spectrograph, is able to measure all Stokes parameters I, Q, U and V across spectral lines of bright stellar targets and other point sources in a quasi-simultaneous manner. Applying standard reduction techniques for linearly and circularly polarized light we are able to obtain photon-noise limited line polarization. We briefly outline the technical design of the polarimeter unit and the linear algebraic Mueller calculus for obtaining polarization parameters of any point source. In addition, practical limitations of the optical elements are outlined. We present first results obtained with our spectropolarimeter for four bright, hot-star targets: We confirm previous results for Hα in the bright Be star γ Cas and find linear depolarization features across the emission line complex C III/C IV (λ 5696/λ 5808 Å) of the WR+O binary γ2 Vel. We also find circular

  4. Wind structure and small-scale wind variability in the stratosphere and mesosphere during the November 1980 Energy Budget Campaign

    NASA Technical Reports Server (NTRS)

    Schmidlin, F. J.; Carlson, M.; Rees, D.; Offermann, D.; Philbrick, C. R.; Widdel, H. U.

    1982-01-01

    Rocket observations made from two sites in northern Scandinavia between November 6 and December 1, 1980, as part of the Energy Budget Campaign are discussed. It was found that significant vertical and temporal changes in the wind structure were present and that they coincided with different geomagnetic conditions, that is, quiet and enhanced. Before November 16, the meridional wind component above 60 km was found to be positive (southerly), whereas the magnitude of the zonal wind component increased with altitude. After November 16 the meridional component became negative (northerly), and the magnitude of the zonal wind component was observed to decrease with altitude. Time sections of the perturbations of the zonal wind reveal the presence of vertically propagating waves, suggesting gravity wave activity. The waves are found to increase in wavelength from 3-4 km near 40 km to more than 12 km near 80 km. The observational techniques made use of chaff foil, chemical trails, inflatable spheres, and parachutes.

  5. How to bet on the location of the termination shock - A summary overview of the Symposium. [study of solar wind and structure of outer heliosphere

    NASA Technical Reports Server (NTRS)

    Lee, Martin A.

    1993-01-01

    This paper loosely summarizes the Symposium in the context of estimating the distance to the solar wind termination shock. Thus the major constituents of the heliosphere are first reviewed including the solar wind and its shocks, magnetic structure and stream structure, the interstellar neutral gas and its daughters, the interstellar pickup ions and the cosmic ray anomalous component, and the galactic cosmic rays. Then a direct calculation of the distance to the termination shock is presented, which yields 80 AU but with large error bars. Finally information carried by messengers from the termination shock and heliosheath (the kHz radio bursts observed by Voyager, galactic cosmic rays, the cosmic ray anomalous component, and the interstellar neutral gas and backscattered photons) is assessed and interpreted. The paper concludes that 80 AU is the best bet.

  6. Advanced Fluid--Structure Interaction Techniques in Application to Horizontal and Vertical Axis Wind Turbines

    NASA Astrophysics Data System (ADS)

    Korobenko, Artem

    During the last several decades engineers and scientists put significant effort into developing reliable and efficient wind turbines. As a wind power production demands grow, the wind energy research and development need to be enhanced with high-precision methods and tools. These include time-dependent, full-scale, complex-geometry advanced computational simulations at large-scale. Those, computational analysis of wind turbines, including fluid-structure interaction simulations (FSI) at full scale is important for accurate and reliable modeling, as well as blade failure prediction and design optimization. In current dissertation the FSI framework is applied to most challenging class of problems, such as large scale horizontal axis wind turbines and vertical axis wind turbines. The governing equations for aerodynamics and structural mechanics together with coupled formulation are explained in details. The simulations are performed for different wind turbine designs, operational conditions and validated against field-test and wind tunnel experimental data.

  7. Structural analysis of wind turbine rotors for NSF-NASA Mod-0 wind power system

    NASA Technical Reports Server (NTRS)

    Spera, D. A.

    1976-01-01

    Preliminary estimates are presented of vibratory loads and stresses in hingeless and teetering rotors for the proposed NSF-NASA Mod-0 wind power system. Preliminary blade design utilizes a tapered tubular aluminum spar which supports nonstructural aluminum ribs and skin and is joined to the rotor hub by a steel shank tube. Stresses in the shank of the blade are calculated for static, rated, and overload operating conditions. Blade vibrations were limited to the fundamental flapping modes, which were elastic cantilever bending for hingeless rotor blades and rigid-body rotation for teetering rotor blades. The MOSTAB-C computer code was used to calculate aerodynamic and mechanical loads. The teetering rotor has substantial advantages over the hingeless rotor with respect to shank stresses, fatigue life, and tower loading. The hingeless rotor analyzed does not appear to be structurally stable during overloads.

  8. Structural basis of potent Zika-dengue virus antibody cross-neutralization.

    PubMed

    Barba-Spaeth, Giovanna; Dejnirattisai, Wanwisa; Rouvinski, Alexander; Vaney, Marie-Christine; Medits, Iris; Sharma, Arvind; Simon-Lorière, Etienne; Sakuntabhai, Anavaj; Cao-Lormeau, Van-Mai; Haouz, Ahmed; England, Patrick; Stiasny, Karin; Mongkolsapaya, Juthathip; Heinz, Franz X; Screaton, Gavin R; Rey, Félix A

    2016-08-01

    Zika virus is a member of the Flavivirus genus that had not been associated with severe disease in humans until the recent outbreaks, when it was linked to microcephaly in newborns in Brazil and to Guillain-Barré syndrome in adults in French Polynesia. Zika virus is related to dengue virus, and here we report that a subset of antibodies targeting a conformational epitope isolated from patients with dengue virus also potently neutralize Zika virus. The crystal structure of two of these antibodies in complex with the envelope protein of Zika virus reveals the details of a conserved epitope, which is also the site of interaction of the envelope protein dimer with the precursor membrane (prM) protein during virus maturation. Comparison of the Zika and dengue virus immunocomplexes provides a lead for rational, epitope-focused design of a universal vaccine capable of eliciting potent cross-neutralizing antibodies to protect simultaneously against both Zika and dengue virus infections. PMID:27338953

  9. Charge Neutral Fermionic States and Current Oscillation in a Graphene-Superconductor Hybrid Structure

    NASA Astrophysics Data System (ADS)

    Duan, Wenye; Wang, Wei; Zhang, Chao; Jin, Kuijuan; Ma, Zhongshui

    2016-10-01

    The proximity properties of edge currents in the vicinity of the interface between the graphene and superconductor in the presence of magnetic field are investigated. It is shown that the edge states introduced by Andreev reflection at the graphene-superconductor (G/S) interface give rise to the charge neutral states in all Landau levels. We note that in a topological insulator-superconductor (TI/S) hybrid structure, only N = 0 Landau level can support this type of charge neutral states. The different interface states of a G/S hybrid and a TI/S hybrid is due to that graphene consists of two distinct sublattices. The armchair edge consists of two inequivalent atoms. This gives rise to unique electronic properties of edge states when connected to a superconductor. A direct consequence of zero charge states in all Landau levels is that the current density approaches zero at interface. The proximity effect leads to quantum magnetic oscillation of the current density in the superconductor region. The interface current density can also be tuned with a finite interface potential. For sharp δ-type interface potential, the derivative of the wavefunction is discontinuous. As a result, we found that there is current density discontinuity at the interface. The step of the current discontinuity is proportional to the strength of the interface potential.

  10. Structural health and prognostics management for offshore wind turbines :

    SciTech Connect

    Griffith, Daniel; Resor, Brian Ray; White, Jonathan Randall; Paquette, Joshua A.; Yoder, Nathanael C.

    2012-12-01

    Operations and maintenance costs for offshore wind plants are expected to be significantly higher than the current costs for onshore plants. One way in which these costs may be able to be reduced is through the use of a structural health and prognostic management system as part of a condition based maintenance paradigm with smart load management. To facilitate the creation of such a system a multiscale modeling approach has been developed to identify how the underlying physics of the system are affected by the presence of damage and how these changes manifest themselves in the operational response of a full turbine. The developed methodology was used to investigate the effects of a candidate blade damage feature, a trailing edge disbond, on a 5-MW offshore wind turbine and the measurements that demonstrated the highest sensitivity to the damage were the local pitching moments around the disbond. The multiscale method demonstrated that these changes were caused by a local decrease in the blades torsional stiffness due to the disbond, which also resulted in changes in the blades local strain field. Full turbine simulations were also used to demonstrate that derating the turbine power by as little as 5% could extend the fatigue life of a blade by as much as a factor of 3. The integration of the health monitoring information, conceptual repair cost versus damage size information, and this load management methodology provides an initial roadmap for reducing operations and maintenance costs for offshore wind farms while increasing turbine availability and overall profit.

  11. Ion-Neutral Coupling in Solar Prominence

    NASA Technical Reports Server (NTRS)

    Gilbert, H.; DeVore, C. R.; Karpen, J.; Kucera, T.; Antiochos, S.; Kawashima, R.

    2011-01-01

    Coupling between ions and neutrals in magnetized plasmas is fundamentally important to many aspects of heliophysics, including our ionosphere, the solar chromosphere, the solar wind interaction with planetary atmospheres, and the interface between the heliosphere and the interstellar medium. Ion-neutral coupling also plays a major role in the physics of solar prominences. By combining theory, modeling, and observations we are working toward a better understanding of the structure and dynamics of partially ionized prominence plasma. Two key questions are addressed in the present work: 1) what physical mechanism(s) sets the cross-field scale of prominence threads? 2) Are ion-neutral interactions responsible for the vertical flows and structure in prominences? We present initial results from a study investigating what role ion-neutral interactions play in prominence dynamics and structure. This research was supported by NASA.

  12. An Experimental Field Dataset with Buoyant, Neutral, and Dense Gas Atmospheric Releases and Model Comparisons in Low-Wind Speed (Diffusion) Conditions

    SciTech Connect

    Veronica E. Wannberg, Gustavious Williams, Patrick Sawyer, and Richard Venedam

    2010-09-01

    Aunique field dataset from a series of low–wind speed experiments, modeling efforts using three commonly used models to replicate these releases, and statistical analysis of how well these models were able to predict the plume concentrations is presented. The experiment was designed to generate a dataset to describe the behavior of gaseous plumes under low-wind conditions and the ability of current, commonly used models to predict these movements. The dataset documents the release and transport of three gases: ammonia (buoyant), ethylene (neutral), and propylene (dense) in low–wind speed (diffusion) conditions. Release rates ranged from 1 to 20 kg h21. Ammonia and ethylene had five 5-min releases each to represent puff releases and five 20-min releases each to represent plume releases. Propylene had five 5-min puffs, six 20-min plumes, and a single 30-min plume. Thirty-two separate releases ranging from 6 to 47 min were conducted, of which only 30 releases generated useful data. The data collected included release rates, atmospheric concentrations to 100 m from the release point, and local meteorological conditions. The diagnostics included nine meteorological stations on 100-m centers and 36 photoionization detectors in a radial pattern. Three current stateof- the-practice models, Aerial locations of Hazardous Atmospheres (ALOHA), Emergency Prediction Information code (EPIcode), and Second-Order Closure Integrated Puff (SCIPUFF), were used to try to duplicate the measured field results. Low wind speeds are difficult to model, and all of the models had difficulty replicating the field measurements. However, the work does show that these models, if used correctly, are conservative (overpredict concentrations) and can be used for safety and emergency planning.

  13. ON THE APPARENT ASSOCIATIONS BETWEEN INTERSTELLAR NEUTRAL HYDROGEN STRUCTURE AND (WMAP) HIGH-FREQUENCY CONTINUUM EMISSION

    SciTech Connect

    Verschuur, Gerrit L.

    2010-03-10

    Galactic neutral hydrogen (H I) within a few hundred parsecs of the Sun contains structure with an angular distribution that is similar to small-scale structure observed by the Wilkinson Microwave Anisotropy Probe (WMAP). A total of 108 associated pairs of associated H I and WMAP features have now been cataloged using H I data mapped in 2 km s{sup -1} intervals and these pairs show a typical offset of 0.{sup 0}8. A large-scale statistical test for a direct association is carried out that casts little additional light on whether the these small offsets are merely coincidental or carry information. To pursue the issue further, the nature of several of the features within the foreground H I most closely associated with WMAP structure is examined in detail and it is shown that the cross-correlation coefficient for well-matched pairs of structures is of order unity. It is shown that free-free emission from electrons in unresolved density enhancements in interstellar space could theoretically produce high-frequency radio continuum radiation at the levels observed by WMAP and that such emission will appear nearly flat across the WMAP frequency range. Evidence for such structure in the interstellar medium already exists in the literature. Until higher angular resolution observations of the high-frequency continuum emission structure as well as the apparently associated H I structure become available, it may be difficult to rule out the possibility that some if not all the small-scale structure usually attributed to the cosmic microwave background may have a galactic origin.

  14. TNF neutralization results in disseminated disease during acute and latent M. tuberculosis infection with normal granuloma structure

    PubMed Central

    Lin, Philana Ling; Myers, Amy; Smith, Le’Kneitah; Bigbee, Carolyn; Bigbee, Matthew; Fuhrman, Carl; Grieser, Heather; Chiosea, Ion; Voitenek, Nikolai N.; Capuano, Saverio V.; Klein, Edwin; Flynn, JoAnne L.

    2010-01-01

    An increased risk of tuberculosis has been documented in humans treated with tumor necrosis factor alpha (TNF) neutralizing agents. In murine models, impaired signaling by TNF caused exacerbation of both acute and chronic infection associated with aberrant granuloma formation and maintenance. The non-human primate model of tuberculosis provides an opportunity to study immune modulation in the setting of TNF neutralization during primary and latent tuberculosis. Administration of TNF neutralizing agents prior to M. tuberculosis infection resulted in fulminant and disseminated disease by 8 weeks post-infection. Neutralization of TNF in latently infected cynomolgus macaques caused reactivation in a majority of animals as determined by gross pathology and bacterial burden. A spectrum of dissemination was noted including extrapulmonary disease. Surprisingly, monkeys who developed primary and reactivation tuberculosis after TNF neutralization had similar granuloma structure and composition compared to active control monkeys. TNF neutralization was associated with increased IL-12, decreased CCL4, increased chemokine receptor expression and reduced mycobacteria-specific IFN-γ production in blood but not to the affected mediastinal lymph nodes. Finally, the first signs of reactivation often occurred in thoracic lymph nodes. These findings have important clinical implications for determining the mechanism of TNF-neutralization-related tuberculosis. PMID:20112395

  15. Exploring Vertical Turbulence Structure in Neutrally and Stably Stratified Flows Using the Weather Research and Forecasting-Large-Eddy Simulation (WRF-LES) Model

    NASA Astrophysics Data System (ADS)

    Udina, Mireia; Sun, Jielun; Kosović, Branko; Soler, Maria Rosa

    2016-11-01

    Following Sun et al. (J Atmos Sci 69(1):338-351, 2012), vertical variations of turbulent mixing in stably stratified and neutral environments as functions of wind speed are investigated using the large-eddy simulation capability in the Weather Research and Forecasting model. The simulations with a surface cooling rate for the stable boundary layer (SBL) and a range of geostrophic winds for both stable and neutral boundary layers are compared with observations from the Cooperative Atmosphere-Surface Exchange Study 1999 (CASES-99). To avoid the uncertainty of the subgrid scheme, the investigation focuses on the vertical domain when the ratio between the subgrid and the resolved turbulence is small. The results qualitatively capture the observed dependence of turbulence intensity on wind speed under neutral conditions; however, its vertical variation is affected by the damping layer used in absorbing undesirable numerical waves at the top of the domain as a result of relatively large neutral turbulent eddies. The simulated SBL fails to capture the observed temperature variance with wind speed and the observed transition from the SBL to the near-neutral atmosphere with increasing wind speed, although the vertical temperature profile of the simulated SBL resembles the observed profile. The study suggests that molecular thermal conduction responsible for the thermal coupling between the surface and atmosphere cannot be parameterized through the Monin-Obukhov bulk relation for turbulent heat transfer by applying the surface radiation temperature, as is common practice when modelling air-surface interactions.

  16. Exploring Vertical Turbulence Structure in Neutrally and Stably Stratified Flows Using the Weather Research and Forecasting-Large-Eddy Simulation (WRF-LES) Model

    NASA Astrophysics Data System (ADS)

    Udina, Mireia; Sun, Jielun; Kosović, Branko; Soler, Maria Rosa

    2016-07-01

    Following Sun et al. (J Atmos Sci 69(1):338-351, 2012), vertical variations of turbulent mixing in stably stratified and neutral environments as functions of wind speed are investigated using the large-eddy simulation capability in the Weather Research and Forecasting model. The simulations with a surface cooling rate for the stable boundary layer (SBL) and a range of geostrophic winds for both stable and neutral boundary layers are compared with observations from the Cooperative Atmosphere-Surface Exchange Study 1999 (CASES-99). To avoid the uncertainty of the subgrid scheme, the investigation focuses on the vertical domain when the ratio between the subgrid and the resolved turbulence is small. The results qualitatively capture the observed dependence of turbulence intensity on wind speed under neutral conditions; however, its vertical variation is affected by the damping layer used in absorbing undesirable numerical waves at the top of the domain as a result of relatively large neutral turbulent eddies. The simulated SBL fails to capture the observed temperature variance with wind speed and the observed transition from the SBL to the near-neutral atmosphere with increasing wind speed, although the vertical temperature profile of the simulated SBL resembles the observed profile. The study suggests that molecular thermal conduction responsible for the thermal coupling between the surface and atmosphere cannot be parameterized through the Monin-Obukhov bulk relation for turbulent heat transfer by applying the surface radiation temperature, as is common practice when modelling air-surface interactions.

  17. An integrated structural strength analysis method for Spar type floating wind turbine

    NASA Astrophysics Data System (ADS)

    Hu, Zhi-qiang; Liu, Yi; Wang, Jin

    2016-04-01

    An integrated structural strength analysis method for a Spar type floating wind turbine is proposed in this paper, and technical issues related to turbine structure modeling and stress combination are also addressed. The NREL-5MW "Hywind" Spar type wind turbine is adopted as study object. Time-domain dynamic coupled simulations are performed by a fully-coupled aero-hydro-servo-elastic tool, FAST, on the purpose of obtaining the dynamic characteristics of the floating wind turbine, and determining parameters for design load cases of finite element calculation. Then design load cases are identified, and finite element analyses are performed for these design load cases. The structural stresses due to wave-induced loads and wind-induced loads are calculated, and then combined to assess the structural strength of the floating wind turbine. The feasibility of the proposed structural strength analysis method for floating wind turbines is then validated.

  18. Structure determination of the neutral exopolysaccharide produced by Lactobacillus delbrueckii subsp. bulgaricus OLL1073R-1.

    PubMed

    Van Calsteren, Marie-Rose; Gagnon, Fleur; Nishimura, Junko; Makino, Seiya

    2015-09-01

    The neutral exopolysaccharide (NPS) of Lactobacillus delbrueckii subsp. bulgaricus strain OLL1073R-1 was purified and characterized. The molecular mass was 5.0×10(6) g/mol. Sugar and absolute configuration analyses gave the following composition: d-Glc, 1; d-Gal, 1.5. The NPS was also submitted to periodate oxidation followed by borohydride reduction and Smith degradation. Sugar and methylation analyses, (1)H and (13)C nuclear magnetic resonance, and mass spectrometry of the NPS or of its specifically modified products allowed determining the repeating unit sequence: {2)Glc(α1-3)Glc(β1-3)[Gal(β1-4)]Gal(β1-4)Gal(α1-}n. The structure is compared to that of exopolysaccharides produced by other Lactobacillus bulgaricus strains.

  19. Structural investigation of a neutral extracellular glucan from Lactobacillus reuteri SK24.003.

    PubMed

    Miao, Ming; Ma, Yajun; Jiang, Bo; Huang, Chao; Li, Xiaohui; Cui, Steve W; Zhang, Tao

    2014-06-15

    The structural features of a neutral extracellular glucan derived from Lactobacillus reuteri SK24.003 were investigated. Colonies of the strain SK24.003 exhibited a creamy and slimy morphological appearance on MRS solid medium and were identified as L. reuteri via 16S rDNA sequence analysis. The exopolysaccharide produced from sucrose was composed exclusively of glucose, and the weight-average molecular weight was 4.31 × 10(7)g/mol. The polysaccharide exhibited an α-(1→4) backbone with an α-(1→6) branch at every fourth residue, as deduced from both NMR and GC-MS data. The exopolysaccharide acted as a natural steel corrosion inhibitor. The results suggested that a novel α-glucan produced by L. reuteri SK24.00 could be broadly used in food and material field.

  20. Neutral hydrogen associated with shells and other fine structure in NGC 2865: A dynamically young elliptical?

    NASA Technical Reports Server (NTRS)

    Schiminovich, D.; Van Gorkom, J. H.; Van Der Hulst, J. M.; Malin, D. F.

    1995-01-01

    We report the discovery of neutral hydrogen in a second elliptical galaxy with shells, NGC 2865. Very Large Array (VLA) images reveal an association between the neutral hydrogen (H I) and the fine structure (shells, tails, and loops) in the galaxy. Similar to what we previously observed in NGC 5128 (Centaurus A), most of the 6 x 10(exp 8)/h(exp 2) solar mass of cold gas is found in a broken ring in the outer regions of NGC 2865 (beyond 0.5D(sub 25)) and is displaced to the outside of the shells and loops. The measured velocities cover a range of 500 km/s around the systematic velocity. The velocity field of the outer H I has the same sense and magnitude (and line of nodes) as that of the stars in the elliptical body. Although NGC 2865 appears to be a relaxed elliptical galaxy, deep images, photometry, and spectroscopy suggest that the galaxy might be the recent (less than 7 Gyr) product of a major disk-disk merger -- a 'dynamically young elliptical.' Our H I data support this hypothesis. Nevertheless, the association between gas and stellar fine structure, with gas displaced outward from the stars in projected position, implies gas motions not predicted by any of the current merger scenarios. Using the H I ring and assuming nearly circular motion, we measure M/L(sub B) at large radii (4 x 0.5D(sub 25)). We find M/L(sub B) = 33 +/- 4 h, a factor of 5 greater than the value of M/L(sub B) found for the central regions, indicating the presence of a dark halo.

  1. Structure of Respiratory Syncytial Virus Fusion Glycoprotein in the Postfusion Conformation Reveals Preservation of Neutralizing Epitopes▿†

    PubMed Central

    McLellan, Jason S.; Yang, Yongping; Graham, Barney S.; Kwong, Peter D.

    2011-01-01

    Respiratory syncytial virus (RSV) invades host cells via a type I fusion (F) glycoprotein that undergoes dramatic structural rearrangements during the fusion process. Neutralizing monoclonal antibodies, such as 101F, palivizumab, and motavizumab, target two major antigenic sites on the RSV F glycoprotein. The structures of these sites as peptide complexes with motavizumab and 101F have been previously determined, but a structure for the trimeric RSV F glycoprotein ectodomain has remained elusive. To address this issue, we undertook structural and biophysical studies on stable ectodomain constructs. Here, we present the 2.8-Å crystal structure of the trimeric RSV F ectodomain in its postfusion conformation. The structure revealed that the 101F and motavizumab epitopes are present in the postfusion state and that their conformations are similar to those observed in the antibody-bound peptide structures. Both antibodies bound the postfusion F glycoprotein with high affinity in surface plasmon resonance experiments. Modeling of the antibodies bound to the F glycoprotein predicts that the 101F epitope is larger than the linear peptide and restricted to a single protomer in the trimer, whereas motavizumab likely contacts residues on two protomers, indicating a quaternary epitope. Mechanistically, these results suggest that 101F and motavizumab can bind to multiple conformations of the fusion glycoprotein and can neutralize late in the entry process. The structural preservation of neutralizing epitopes in the postfusion state suggests that this conformation can elicit neutralizing antibodies and serve as a useful vaccine antigen. PMID:21613394

  2. Facilitating wind development: the importance of electric industry structure

    SciTech Connect

    Kirby, Brendan; Milligan, Michael

    2008-04-15

    ISOs and RTOs, with their day-ahead and real-time markets, large geographies to aggregate diverse wind resources, large loads to aggregate with wind, large generation pools that tap conventional-generator flexibility, and regional transmission planning efforts, offer the best environments for wind generation to develop. (author)

  3. Structural fatigue test results for large wind turbine blade sections

    NASA Technical Reports Server (NTRS)

    Faddoul, J. R.; Sullivan, T. L.

    1982-01-01

    In order to provide quantitative information on the operating life capabilities of wind turbine rotor blade concepts for root-end load transfer, a series of cantilever beam fatigue tests was conducted. Fatigue tests were conducted on a laminated wood blade with bonded steel studs, a low cost steel spar (utility pole) with a welded flange, a utility pole with additional root-end thickness provided by a swaged collar, fiberglass spars with both bonded and nonbonded fittings, and, finally, an aluminum blade with a bolted steel fitting (Lockheed Mod-0 blade). Photographs, data, and conclusions for each of these tests are presented. In addition, the aluminum blade test results are compared to field failure information; these results provide evidence that the cantilever beam type of fatigue test is a satisfactory method for obtaining qualitative data on blade life expectancy and for identifying structurally underdesigned areas (hot spots).

  4. Structures and Intermittency in Small Scales Solar Wind Turbulence

    SciTech Connect

    Sahraoui, Fouad; Goldstein, Melvyn

    2010-03-25

    Several observations in space plasmas have reported the presence of coherent structures at different plasma scales. Structure formation is believed to result from nonlinear interactions between the plasma modes, which depend strongly on their phase synchronization. Despite this important role of the phases in turbulence, very limited work has been devoted to study the phases as potential tracers of nonlinearities in comparison with the wealth of literature on power spectra of turbulence where phases are totally missed. The reason why the phases are seldom used is probably because they usually appear to be completely mixed (due to their dependence on an arbitrary time origin and to 2pi periodicity). To handle the phases properly, a new method based on using surrogate data has been developed recently to detect coherent structures in magnetized plasmas [Sahraoui, PRE, 2008]. Here, we show new applications of the technique to study the nature (weak vs strong, self-similar vs intermittent) of the small scale turbulence in the solar wind using the Cluster observations.

  5. The Energy-Dependent Position of the IBEX Ribbon Due to the Solar Wind Structure

    NASA Astrophysics Data System (ADS)

    Swaczyna, Paweł; Bzowski, Maciej; Sokół, Justyna M.

    2016-08-01

    Observations of energetic neutral atoms (ENAs) allow for remote studies of the condition of plasma in the heliosphere and the neighboring local interstellar medium. The first results from the Interstellar Boundary Explorer (IBEX) revealed an arc-like enhancement of the ENA intensity in the sky, known as the ribbon. The ribbon was not expected from the heliospheric models prior to the launch of IBEX. One proposed explanation for the ribbon is the mechanism of secondary ENA emission. The ribbon reveals energy-dependent structure in the relative intensity along its circumference and in its position. That is, the geometric center of the ribbon varies systematically by about 10° in the energy range 0.7-4.3 keV. Here, we show by analytical modeling that this effect is a consequence of the helio-latitudinal structure of the solar wind reflected in the secondary ENAs. Along with a recently measured distance to the ribbon’s source just beyond the heliopause, our findings support the connection of the ribbon with the local interstellar magnetic field by the mechanism of secondary ENA emission. However, the magnitude of the center shift in the highest IBEX energy channel is much larger in the observations than expected from the modeling. This may be due to another, not currently recognized, process of ENA generation.

  6. The Energy-Dependent Position of the IBEX Ribbon Due to the Solar Wind Structure

    NASA Astrophysics Data System (ADS)

    Swaczyna, Paweł; Bzowski, Maciej; Sokół, Justyna M.

    2016-08-01

    Observations of energetic neutral atoms (ENAs) allow for remote studies of the condition of plasma in the heliosphere and the neighboring local interstellar medium. The first results from the Interstellar Boundary Explorer (IBEX) revealed an arc-like enhancement of the ENA intensity in the sky, known as the ribbon. The ribbon was not expected from the heliospheric models prior to the launch of IBEX. One proposed explanation for the ribbon is the mechanism of secondary ENA emission. The ribbon reveals energy-dependent structure in the relative intensity along its circumference and in its position. That is, the geometric center of the ribbon varies systematically by about 10° in the energy range 0.7–4.3 keV. Here, we show by analytical modeling that this effect is a consequence of the helio-latitudinal structure of the solar wind reflected in the secondary ENAs. Along with a recently measured distance to the ribbon’s source just beyond the heliopause, our findings support the connection of the ribbon with the local interstellar magnetic field by the mechanism of secondary ENA emission. However, the magnitude of the center shift in the highest IBEX energy channel is much larger in the observations than expected from the modeling. This may be due to another, not currently recognized, process of ENA generation.

  7. The effect of neutral helper lipids on the structure of cationic lipid monolayers

    PubMed Central

    Dabkowska, A. P.; Barlow, D. J.; Hughes, A. V.; Campbell, R. A.; Quinn, P. J.; Lawrence, M. J.

    2012-01-01

    Successful drug delivery via lipid-based systems has often been aided by the incorporation of ‘helper lipids’. While these neutral lipids enhance the effectiveness of cationic lipid-based delivery formulations, many questions remain about the nature of their beneficial effects. The structure of monolayers of the cationic lipid dimethyldioctadecylammonium bromide (DODAB) alone, and mixed with a neutral helper lipid, either diolelyphosphatidylethanolamine or cholesterol at a 1 : 1 molar ratio was investigated at the air–water interface using a combination of surface pressure–area isotherms, Brewster angle microscopy (BAM) and specular neutron reflectivity in combination with contrast variation. BAM studies showed that while pure DODAB and DODAB with cholesterol monolayers showed fairly homogeneous surfaces, except in the regions of phase transition, monolayers of DODAB with diolelyphosphatidylethanolamine were, in contrast, inhomogeneous exhibiting irregular bean-shaped domains throughout. Neutron reflectivity data showed that while the thickness of the DODAB monolayer increased from 17 to 24 Å as it was compressed from a surface pressure of 5–40 mN m−1, the thickness of the helper lipid-containing monolayers, over the same range of surface pressures, was relatively invariant at between 25 and 27 Å. In addition, the monolayers containing diolelyphosphatidylethanolamine were found to be more heavily hydrated than the monolayers of cationic lipid, alone or in combination with cholesterol, with hydration levels of 18 molecules of water per molecule of lipid being recorded for the diolelyphosphatidylethanolamine-containing monolayers at a surface pressure of 30 mN m−1 compared with only six and eight molecules of water per molecule of lipid for the pure DODAB monolayer and the cholesterol-containing DODAB monolayer, respectively. PMID:21831895

  8. Neutral Buoyancy Simulator: MSFC-Langley joint test of large space structures component assembly:

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Once the United States' space program had progressed from Earth's orbit into outerspace, the prospect of building and maintaining a permanent presence in space was realized. To accomplish this feat, NASA launched a temporary workstation, Skylab, to discover the effects of low gravity and weightlessness on the human body, and also to develop tools and equipment that would be needed in the future to build and maintain a more permanent space station. The structures, techniques, and work schedules had to be carefully designed to fit this unique construction site. The components had to be lightweight for transport into orbit, yet durable. The station also had to be made with removable parts for easy servicing and repairs by astronauts. All of the tools necessary for service and repairs had to be designed for easy manipulation by a suited astronaut. And construction methods had to be efficient due to limited time the astronauts could remain outside their controlled environment. In lieu of all the specific needs for this project, an environment on Earth had to be developed that could simulate a low gravity atmosphere. A Neutral Buoyancy Simulator (NBS) was constructed by NASA Marshall Space Flight Center (MSFC) in 1968. Since then, NASA scientists have used this facility to understand how humans work best in low gravity and also provide information about the different kinds of structures that can be built. With the help of the NBS, building a space station became more of a reality. In a joint venture between NASA/Langley Research Center in Hampton, VA and MSFC, the Assembly Concept for Construction of Erectable Space Structures (ACCESS) was developed and demonstrated at MSFC's NBS. The primary objective of this experiment was to test the ACCESS structural assembly concept for suitability as the framework for larger space structures and to identify ways to improve the productivity of space construction. Pictured is a demonstration of ACCESS.

  9. Structural basis for immunization with postfusion respiratory syncytial virus fusion F glycoprotein (RSV F) to elicit high neutralizing antibody titers

    SciTech Connect

    Swanson, Kurt A.; Settembre, Ethan C.; Shaw, Christine A.; Dey, Antu K.; Rappuoli, Rino; Mandl, Christian W.; Dormitzer, Philip R.; Carfi, Andrea

    2012-02-07

    Respiratory syncytial virus (RSV), the main cause of infant bronchiolitis, remains a major unmet vaccine need despite more than 40 years of vaccine research. Vaccine candidates based on a chief RSV neutralization antigen, the fusion (F) glycoprotein, have foundered due to problems with stability, purity, reproducibility, and potency. Crystal structures of related parainfluenza F glycoproteins have revealed a large conformational change between the prefusion and postfusion states, suggesting that postfusion F antigens might not efficiently elicit neutralizing antibodies. We have generated a homogeneous, stable, and reproducible postfusion RSV F immunogen that elicits high titers of neutralizing antibodies in immunized animals. The 3.2-{angstrom} X-ray crystal structure of this substantially complete RSV F reveals important differences from homology-based structural models. Specifically, the RSV F crystal structure demonstrates the exposure of key neutralizing antibody binding sites on the surface of the postfusion RSV F trimer. This unanticipated structural feature explains the engineered RSV F antigen's efficiency as an immunogen. This work illustrates how structural-based antigen design can guide the rational optimization of candidate vaccine antigens.

  10. Observed wind and wave field structures from multi-sensor satellite measurements

    SciTech Connect

    Queffeulou, P.; Bentamy, A.

    1994-12-31

    Sea surface wind speed and wave data are presently available from various sensors in flight on several satellites. The wind speed and direction are available from the wind scatterometer of ERS-1. The wind speed can also be inferred from altimeters on board ERS-1 and TOPEX POSEIDON, and from the Special Microwave Imager on the satellites of the Defense Meteorological Space Program. These data are merged and used to investigate sea surface wind and wave field structure. One application study presently in progress, concerning the Mistral, is presented.

  11. Lewis Structures Technology, 1988. Volume 3: Structural Integrity Fatigue and Fracture Wind Turbines HOST

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The charter of the Structures Division is to perform and disseminate results of research conducted in support of aerospace engine structures. These results have a wide range of applicability to practioners of structural engineering mechanics beyond the aerospace arena. The specific purpose of the symposium was to familiarize the engineering structures community with the depth and range of research performed by the division and its academic and industrial partners. Sessions covered vibration control, fracture mechanics, ceramic component reliability, parallel computing, nondestructive evaluation, constitutive models and experimental capabilities, dynamic systems, fatigue and damage, wind turbines, hot section technology (HOST), aeroelasticity, structural mechanics codes, computational methods for dynamics, structural optimization, and applications of structural dynamics, and structural mechanics computer codes.

  12. Electrostatic solitary structures in the solar wind plasma

    NASA Astrophysics Data System (ADS)

    Singh, Satyavir; Singh Lakhina, Gurbax; Rubia, R.

    2016-07-01

    Recent observations have shown the existence of coherent electrostatic structures observed in the solar wind at 1 AU which could accelerate the charged particles. Electrostatic solitary waves are studied in a homogeneous, collisionless, and magnetized three-component plasma model relevant to the solar wind plasma. The theoretical model consists of hot protons, hot heavier ions (doubly charged helium ions) and suprathermal electrons having kappa distribution. Sagdeev pseudopotential technique is used to study the arbitrary amplitude ion-acoustic solitary wave. The study shows that when the heavier ion temperature is not exactly 4 times the proton temperature, we observe a new slow ion-acoustic mode in addition to the usual fast ion-acoustic mode. It is found that fast ion-acoustic mode supports only positive potential solitons. However, slow ion-acoustic mode is found to support both positive and negative potential solitons/double layers. The effect of various parameters such as the spectral index, κ, Mach number, temperature and number density of ions is studied on the evolution of ion-acoustic solitary waves as well as their existence domains. It is found that the limitation on the attainable amplitudes of fast ion-acoustic solitons is attributed to, that the number density of protons should remain real valued. While, for the slow ion-acoustic solitons the upper limit is provided by the requirement that the number density of heavier ion should remain real. In the presence of the double layers, the occurrence of the double layer limits the attainable amplitudes of the slow ion-acoustic solitons.

  13. Crystal Structure of PG16 and Chimeric Dissection with Somatically Related PG9: Structure-Function Analysis of Two Quaternary-Specific Antibodies That Effectively Neutralize HIV-1

    SciTech Connect

    Pancera, Marie; McLellan, Jason S.; Wu, Xueling; Zhu, Jiang; Changela, Anita; Schmidt, Stephen D.; Yang, Yongping; Zhou, Tongqing; Phogat, Sanjay; Mascola, John R.; Kwong, Peter D.

    2010-11-03

    HIV-1 resists neutralization by most antibodies. Two somatically related human antibodies, PG9 and PG16, however, each neutralize 70 to 80% of circulating HIV-1 isolates. Here we present the structure of the antigen-binding fragment of PG16 in monoclinic and orthorhombic lattices at 2.4 and 4.0 {angstrom}, respectively, and use a combination of structural analysis, paratope dissection, and neutralization assessment to determine the functional relevance of three unusual PG9/PG16 features: N-linked glycosylation, extensive affinity maturation, and a heavy chain-third complementarity-determining region (CDR H3) that is one of the longest observed in human antibodies. Glycosylation extended off the side of the light chain variable domain and was not required for neutralization. The CDR H3 formed an axe-shaped subdomain, which comprised 42% of the CDR surface, with the axe head looming {approx}20 {angstrom} above the other combining loops. Comprehensive sets of chimeric swaps between PG9 and PG16 of light chain, heavy chain, and CDR H3 were employed to decipher structure-function relationships. Chimeric swaps generally complemented functionally, with differences in PG9/PG16 neutralization related primarily to residue differences in CDR H3. Meanwhile, chimeric reversions to genomic V genes showed isolate-dependent effects, with affinity maturation playing a significant role in augmenting neutralization breadth (P = 0.036) and potency (P < 0.0001). The structural and functional details of extraordinary CDR H3 and extensive affinity maturation provide insights into the neutralization mechanism of and the elicitation pathway for broadly neutralizing antibodies like PG9 and PG16.

  14. Nonlinear stability theorem for rotating coherent structures in a non-neutral plasma column

    NASA Astrophysics Data System (ADS)

    Davidson, Ronald C.; Lund, Steven M.

    1991-09-01

    A nonlinear stability theorem is developed for arbitrary-amplitude, two-dimensional coherent structures, nR(θ - ωr t) and φR(θ - ωr t), in a strongly magnetized, low-density (ω2pe/ω2ce ≪ 1) non-neutral plasma column confined radially by a uniform axial magnetic field B0êz. Here, a grounded, perfectly conducting, cylindrical wall is located at radius r = rw, and ωr = const is the angular rotation velocity of the coherent structures about the cylinder axis (r=0). A cold-fluid guiding-center model based on the continuity-Poisson equations is used to describe the nonlinear evolution of the electron density ne(r,θ,t) = nR + δne and electrostatic potential φ(r,θ,t) = φR + δφ. Making use of global (spatially averaged) nonlinear conservation constraints, it is shown that ∂nR(ψR)/∂ψR ≤ 0 is a sufficient condition for nonlinear stability of the rotating equilibrium state (φR,nR) to arbitrary-amplitude perturbations δne and δφ. Here, ψR(r,θ - ωr t) = -eφR(r,θ - ωr t) + ωr(eB0/2c)r 2 is an effective streamfunction, and the stability theorem is valid no matter how complex the radial and azimuthal structure of φR(r,θ - ωr t) and nR(r,θ - ωr t).

  15. Structure of a Major Antigenic Site on the Respiratory Syncytial Virus Fusion Glycoprotein in Complex with Neutralizing Antibody 101F

    SciTech Connect

    McLellan, Jason S.; Chen, Man; Chang, Jung-San; Yang, Yongping; Kim, Albert; Graham, Barney S.; Kwong, Peter D.

    2010-11-19

    Respiratory syncytial virus (RSV) is a major cause of pneumonia and bronchiolitis in infants and elderly people. Currently there is no effective vaccine against RSV, but passive prophylaxis with neutralizing antibodies reduces hospitalizations. To investigate the mechanism of antibody-mediated RSV neutralization, we undertook structure-function studies of monoclonal antibody 101F, which binds a linear epitope in the RSV fusion glycoprotein. Crystal structures of the 101F antigen-binding fragment in complex with peptides from the fusion glycoprotein defined both the extent of the linear epitope and the interactions of residues that are mutated in antibody escape variants. The structure allowed for modeling of 101F in complex with trimers of the fusion glycoprotein, and the resulting models suggested that 101F may contact additional surfaces located outside the linear epitope. This hypothesis was supported by surface plasmon resonance experiments that demonstrated 101F bound the peptide epitope {approx}16,000-fold more weakly than the fusion glycoprotein. The modeling also showed no substantial clashes between 101F and the fusion glycoprotein in either the pre- or postfusion state, and cell-based assays indicated that 101F neutralization was not associated with blocking virus attachment. Collectively, these results provide a structural basis for RSV neutralization by antibodies that target a major antigenic site on the fusion glycoprotein.

  16. Infrared Action Spectroscopy of Low-Temperature Neutral Gas-Phase Molecules of Arbitrary Structure.

    PubMed

    Yatsyna, Vasyl; Bakker, Daniël J; Salén, Peter; Feifel, Raimund; Rijs, Anouk M; Zhaunerchyk, Vitali

    2016-09-01

    We demonstrate a technique for IR action spectroscopy that enables measuring IR spectra in a background-free fashion for low-temperature neutral gas-phase molecules of arbitrary structure. The method is exemplified experimentally for N-methylacetamide molecules in the mid-IR spectral range of 1000-1800  cm^{-1}, utilizing the free electron laser FELIX. The technique involves the resonant absorption of multiple mid-IR photons, which induces molecular dissociation. The dissociation products are probed with 10.49 eV vacuum ultraviolet photons and analyzed with a mass spectrometer. We also demonstrate the capability of this method to record, with unprecedented ease, mid-IR spectra for the molecular associates, such as clusters and oligomers, present in a molecular beam. In this way the mass-selected spectra of low-temperature gas-phase dimers and trimers of N-methylacetamide are measured in the full amide I-III range.

  17. Synthesis, structural characterisation and antibacterial activity of Ag+-doped fluorapatite nanomaterials prepared by neutralization method

    NASA Astrophysics Data System (ADS)

    Stanić, Vojislav; Radosavljević-Mihajlović, Ana S.; Živković-Radovanović, Vukosava; Nastasijević, Branislav; Marinović-Cincović, Milena; Marković, Jelena P.; Budimir, Milica D.

    2015-05-01

    Silver doped fluorapatite nanopowders were synthesised by neutralization method, which consists of dissolving Ag2O in solution of HF and H3PO4 and addition to suspension of Ca(OH)2. The powder XRD, SEM and FTIR studies indicated the formation of a fluorapatite nanomaterials with average length of the particles is about 80 nm and a width of about 15 nm. The FTIR studies show that carbonate content in samples is very small and carbonte ions substitute both phosphate and hydroxyl groups in the crystal structure of samples, forming AB-type fluorapatite. Antibacterial studies have demonstrated that all Ag+-doped fluorapatite samples exhibit bactericidal effect against pathogens: Staphylococcus aureus, Micrococcus luteus and Kllebsiela pneumoniae. Antibacterial activity increased with the increase of Ag+ in the samples. The atomic force microscopy studies revealed extensive damage to the bacterial cell envelops in the presence of Ag+-doped fluorapatite particles which may lead to their death. The synthesized Ag+-doped fluorapatite nanomaterials are promising as antibacterial biomaterials in orthopedics and dentistry.

  18. Infrared Action Spectroscopy of Low-Temperature Neutral Gas-Phase Molecules of Arbitrary Structure.

    PubMed

    Yatsyna, Vasyl; Bakker, Daniël J; Salén, Peter; Feifel, Raimund; Rijs, Anouk M; Zhaunerchyk, Vitali

    2016-09-01

    We demonstrate a technique for IR action spectroscopy that enables measuring IR spectra in a background-free fashion for low-temperature neutral gas-phase molecules of arbitrary structure. The method is exemplified experimentally for N-methylacetamide molecules in the mid-IR spectral range of 1000-1800  cm^{-1}, utilizing the free electron laser FELIX. The technique involves the resonant absorption of multiple mid-IR photons, which induces molecular dissociation. The dissociation products are probed with 10.49 eV vacuum ultraviolet photons and analyzed with a mass spectrometer. We also demonstrate the capability of this method to record, with unprecedented ease, mid-IR spectra for the molecular associates, such as clusters and oligomers, present in a molecular beam. In this way the mass-selected spectra of low-temperature gas-phase dimers and trimers of N-methylacetamide are measured in the full amide I-III range. PMID:27661721

  19. Mosaic of Water Orientation Structures at a Neutral Zwitterionic Lipid/Water Interface Revealed by Molecular Dynamics Simulations.

    PubMed

    Re, Suyong; Nishima, Wataru; Tahara, Tahei; Sugita, Yuji

    2014-12-18

    Ordering of water structures near the surface of biological membranes has been recently extensively studied using interface-selective techniques like vibrational sum frequency generation (VSFG) spectroscopy. The detailed structures of interface water have emerged for charged lipids, but those for neutral zwitterionic lipids remain obscure. We analyze an all-atom molecular dynamics (MD) trajectory of a hydrated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayer to characterize the orientation of interface waters in different chemical environments. The structure and dynamics of interfacial waters strongly depend on both their vertical position along the bilayer normal as well as vicinal lipid charged groups. Water orientation in the vicinity of phosphate groups is opposite to that around choline groups. The results are consistent with observed VSFG spectra and demonstrate that a mosaic of water orientation structures exists on the surface of a neutral zwitterionic phospholipid bilayer, reflecting rapid water exchange and the influence of local chemical environments. PMID:26273985

  20. Extreme winds and tornadoes: design and evaluation of buildings and structures

    SciTech Connect

    McDonald, J.R.

    1985-01-01

    The general provisions of ANSI A58.1-1982 are explained in detail. As mentioned above, these procedures may be used to determine design wind loads on structures from extreme winds, hurricane and tornado winds. Treatment of atmospheric pressure change loads are discussed, including recommendations for venting a building, if necessary, and the effects of rate of pressure change on HVAC systems. Finally, techniques for evaluating existing facilities are described.

  1. Structure and chain conformation of a neutral intracellular heteropolysaccharide from mycelium of Paecilomyces cicadae.

    PubMed

    Wei, Chao-yang; Li, Wei-qi; Shao, Shuang-shuang; He, Liang; Cheng, Junwen; Han, Sufang; Liu, Yu

    2016-01-20

    A neutral heteropolysaccharide (PCIPS2) was isolated and purified from mycelium of Paecilomyces cicadae, which was investigated to be mainly composed of D-mannose, L-rhamnose, 3-O-methyl-D-galactose, D-glucose and D-galactose with a molar ratio of 47.9:3.1:6.4:0.9:0.8. It had a backbone of 1,4-linked α-L-Rhap residues and 1,6-linked α-D-Manp residues with branches at O-3 of α-D-Manp residues. Its side chain was comprised of minor terminal β-D-glucose and 1,4-linked α-3-O-Me-D-Galp residues terminated by α-D-galactose. Furthermore, its chain information on the values of weight-average molar mass (Mw), root mean square radius ([Formula: see text]), hydrodynamic radius (Rh) and intrinsic viscosity ([η]) for PCIPS2 were analyzed to be 3.09 × 10(4)g/mol, 7.8 nm, 3.6 nm and 8.5 mL/g, respectively. The structural exponent α of 0.57 indicated that PCIPS2 existed as a flexible chain conformation with a coil-like structure in 0.1M NaNO3 at 25 °C. In terms of known theory for worm-like chains, the model parameters for PCIPS2 were as following: molar mass per unit contour length (ML) = 379 nm(-1), persistence length (q) = 0.74 nm and hydrodynamic diameter of cylinder (d) = 0.82 nm, which were further evidenced by atomic force microscopy (AFM). PMID:26572406

  2. Neutral Buoyancy Simulator: MSFC-Langley joint test of large space structures component assembly:

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Once the United States' space program had progressed from Earth's orbit into outerspace, the prospect of building and maintaining a permanent presence in space was realized. To accomplish this feat, NASA launched a temporary workstation, Skylab, to discover the effects of low gravity and weightlessness on the human body, and also to develop tools and equipment that would be needed in the future to build and maintain a more permanent space station. The structures, techniques, and work schedules had to be carefully designed to fit this unique construction site. The components had to be lightweight for transport into orbit, yet durable. The station also had to be made with removable parts for easy servicing and repairs by astronauts. All of the tools necessary for service and repairs had to be designed for easy manipulation by a suited astronaut. And construction methods had to be efficient due to limited time the astronauts could remain outside their controlled environment. In lieu of all the specific needs for this project, an environment on Earth had to be developed that could simulate a low gravity atmosphere. A Neutral Buoyancy Simulator (NBS) was constructed by NASA Marshall Space Flight Center (MSFC) in 1968. Since then, NASA scientists have used this facility to understand how humans work best in low gravity and also provide information about the different kinds of structures that can be built. Another facet of the space station would be electrical cornectors which would be used for powering tools the astronauts would need for construction, maintenance and repairs. Shown is an astronaut training during an underwater electrical connector test in the NBS.

  3. Structural Basis of Differential Neutralization of DENV-1 Genotypes by an Antibody that Recognizes a Cryptic Epitope

    PubMed Central

    Austin, S. Kyle; Dowd, Kimberly A.; Shrestha, Bimmi; Nelson, Christopher A.; Edeling, Melissa A.; Johnson, Syd; Pierson, Theodore C.; Diamond, Michael S.; Fremont, Daved H.

    2012-01-01

    We previously developed a panel of neutralizing monoclonal antibodies against Dengue virus (DENV)-1, of which few exhibited inhibitory activity against all DENV-1 genotypes. This finding is consistent with reports observing variable neutralization of different DENV strains and genotypes using serum from individuals that experienced natural infection or immunization. Herein, we describe the crystal structures of DENV1-E111 bound to a novel CC′ loop epitope on domain III (DIII) of the E protein from two different DENV-1 genotypes. Docking of our structure onto the available cryo-electron microscopy models of DENV virions revealed that the DENV1-E111 epitope was inaccessible, suggesting that this antibody recognizes an uncharacterized virus conformation. While the affinity of binding between DENV1-E111 and DIII varied by genotype, we observed limited correlation with inhibitory activity. Instead, our results support the conclusion that potent neutralization depends on genotype-dependent exposure of the CC′ loop epitope. These findings establish new structural complexity of the DENV virion, which may be relevant for the choice of DENV strain for induction or analysis of neutralizing antibodies in the context of vaccine development. PMID:23055922

  4. Structural evolution and stabilities of neutral and anionic clusters of lead sulfide: joint anion photoelectron and computational studies.

    PubMed

    Koirala, Pratik; Kiran, Boggavarapu; Kandalam, Anil K; Fancher, Charles A; de Clercq, Helen L; Li, Xiang; Bowen, Kit H

    2011-10-01

    The geometric and electronic structures of both neutral and negatively charged lead sulfide clusters, (PbS)(n)/(PbS)(n)(-) (n = 2-10) were investigated in a combined anion photoelectron spectroscopy and computational study. Photoelectron spectra provided vertical detachment energies (VDEs) for the cluster anions and estimates of electron affinities (EA) for their neutral cluster counterparts, revealing a pattern of alternating EA and VDE values in which even n clusters exhibited lower EA and VDE values than odd n clusters up until n = 8. Computations found neutral lead sulfide clusters with even n to be thermodynamically more stable than their immediate (odd n) neighbors, with a consistent pattern also being found in their HOMO-LUMO gaps. Analysis of neutral cluster dissociation energies found the Pb(4)S(4) cube to be the preferred product of the queried fragmentation processes, consistent with our finding that the lead sulfide tetramer exhibits enhanced stability; it is a magic number species. Beyond n = 10, computational studies showed that neutral (PbS)(n) clusters in the size range, n = 11-15, prefer two-dimensional stacking of face-sharing lead sulfide cubical units, where lead and sulfur atoms possess a maximum of five-fold coordination. The preference for six-fold coordination, which is observed in the bulk, was not observed at these cluster sizes. Taken together, the results show a preference for the formation of slightly distorted, fused cuboids among small lead sulfide clusters.

  5. Neutral Atmospheres

    NASA Astrophysics Data System (ADS)

    Mueller-Wodarg, I. C. F.; Strobel, D. F.; Moses, J. I.; Waite, J. H.; Crovisier, J.; Yelle, R. V.; Bougher, S. W.; Roble, R. G.

    This paper summarizes the understanding of aeronomy of neutral atmospheres in the solar system, discussing most planets as well as Saturn's moon Titan and comets. The thermal structure and energy balance is compared, highlighting the principal reasons for discrepancies amongst the atmospheres, a combination of atmospheric composition, heliocentric distance and other external energy sources not common to all. The composition of atmospheres is discussed in terms of vertical structure, chemistry and evolution. The final section compares dynamics in the upper atmospheres of most planets and highlights the importance of vertical dynamical coupling as well as magnetospheric forcing in auroral regions, where present. It is shown that a first order understanding of neutral atmospheres has emerged over the past decades, thanks to the combined effects of spacecraft and Earth-based observations as well as advances in theoretical modeling capabilities. Key gaps in our understanding are highlighted which ultimately call for a more comprehensive programme of observation and laboratory measurements.

  6. Neutral Atmospheres

    NASA Astrophysics Data System (ADS)

    Mueller-Wodarg, I. C. F.; Strobel, D. F.; Moses, J. I.; Waite, J. H.; Crovisier, J.; Yelle, R. V.; Bougher, S. W.; Roble, R. G.

    2008-08-01

    This paper summarizes the understanding of aeronomy of neutral atmospheres in the solar system, discussing most planets as well as Saturn’s moon Titan and comets. The thermal structure and energy balance is compared, highlighting the principal reasons for discrepancies amongst the atmospheres, a combination of atmospheric composition, heliocentric distance and other external energy sources not common to all. The composition of atmospheres is discussed in terms of vertical structure, chemistry and evolution. The final section compares dynamics in the upper atmospheres of most planets and highlights the importance of vertical dynamical coupling as well as magnetospheric forcing in auroral regions, where present. It is shown that a first order understanding of neutral atmospheres has emerged over the past decades, thanks to the combined effects of spacecraft and Earth-based observations as well as advances in theoretical modeling capabilities. Key gaps in our understanding are highlighted which ultimately call for a more comprehensive programme of observation and laboratory measurements.

  7. Structural basis for type VI secreted peptidoglycan DL-endopeptidase function, specificity and neutralization in Serratia marcescens.

    PubMed

    Srikannathasan, Velupillai; English, Grant; Bui, Nhat Khai; Trunk, Katharina; O'Rourke, Patrick E F; Rao, Vincenzo A; Vollmer, Waldemar; Coulthurst, Sarah J; Hunter, William N

    2013-12-01

    Some Gram-negative bacteria target their competitors by exploiting the type VI secretion system to extrude toxic effector proteins. To prevent self-harm, these bacteria also produce highly specific immunity proteins that neutralize these antagonistic effectors. Here, the peptidoglycan endopeptidase specificity of two type VI secretion-system-associated effectors from Serratia marcescens is characterized. These small secreted proteins, Ssp1 and Ssp2, cleave between γ-D-glutamic acid and L-meso-diaminopimelic acid with different specificities. Ssp2 degrades the acceptor part of cross-linked tetratetrapeptides. Ssp1 displays greater promiscuity and cleaves monomeric tripeptides, tetrapeptides and pentapeptides and dimeric tetratetra and tetrapenta muropeptides on both the acceptor and donor strands. Functional assays confirm the identity of a catalytic cysteine in these endopeptidases and crystal structures provide information on the structure-activity relationships of Ssp1 and, by comparison, of related effectors. Functional assays also reveal that neutralization of these effectors by their cognate immunity proteins, which are called resistance-associated proteins (Raps), contributes an essential role to cell fitness. The structures of two immunity proteins, Rap1a and Rap2a, responsible for the neutralization of Ssp1 and Ssp2-like endopeptidases, respectively, revealed two distinct folds, with that of Rap1a not having previously been observed. The structure of the Ssp1-Rap1a complex revealed a tightly bound heteromeric assembly with two effector molecules flanking a Rap1a dimer. A highly effective steric block of the Ssp1 active site forms the basis of effector neutralization. Comparisons with Ssp2-Rap2a orthologues suggest that the specificity of these immunity proteins for neutralizing effectors is fold-dependent and that in cases where the fold is conserved sequence differences contribute to the specificity of effector-immunity protein interactions.

  8. Wind structure and small-scale wind variability in the stratosphere and mesosphere during the November 1980 energy budget campaign

    NASA Astrophysics Data System (ADS)

    Schmidlin, F. J.; Carlson, M.; Rees, D.; Offermann, D.; Philbrick, C. R.; Widdel, H. U.

    Between November 6 and December 1, 1980, a series of rocket observations obtained from two sites in northern Scandinavia as part of the Energy Budget Campaign indicated that significant vertical and temporal changes in the wind structure were present and were noted to coincide with different geomagnetic conditions, i.e., quiet and enhanced. This series of observations represents for the first time the largest amount of data ever gathered at high latitudes over such a short interval of time. It is observed that prior to November 16, the meridional wind component above 60 kilometers was found to be positive (southerly) while the magnitude of the zonal wind component increased with altitude. After November 16 the meridional component became negative (northerly) and the magnitude of the zonal wind component was noted to decrease with altitude. Time-sections of the perturbations of the zonal wind show the presence of vertically propagating waves which suggest gravity wave activity. These waves increase in wavelength from 3-4 kilometers near 40 kilometers to over 12 kilometers near 80 kilometers. The observational techniques employed at Andoya, Norway, and ESRANGE in Sweden, consisted of chaff foil, chemical trails, inflatable spheres, and parachutes.

  9. Numerical simulation of tornado wind loading on structures

    NASA Technical Reports Server (NTRS)

    Maiden, D. E.

    1976-01-01

    A numerical simulation of a tornado interacting with a building was undertaken in order to compare the pressures due to a rotational unsteady wind with that due to steady straight winds used in design of nuclear facilities. The numerical simulations were performed on a two-dimensional compressible hydrodynamics code. Calculated pressure profiles for a typical building were then subjected to a tornado wind field and the results were compared with current quasisteady design calculations. The analysis indicates that current design practices are conservative.

  10. Reconstruction of Helio-Latitudinal Structure of the Solar Wind Proton Speed and Density

    NASA Astrophysics Data System (ADS)

    Sokół, Justyna M.; Swaczyna, Paweł; Bzowski, Maciej; Tokumaru, Munetoshi

    2015-09-01

    The modeling of the heliosphere requires continuous three-dimensional solar wind data. The in-situ out-of-ecliptic measurements are very rare, so that other methods of solar wind detection are needed. We use the remote-sensing data of the solar wind speed from observations of interplanetary scintillation (IPS) to reconstruct spatial and temporal structures of the solar wind proton speed from 1985 to 2013. We developed a method of filling the data gaps in the IPS observations to obtain continuous and homogeneous solar wind speed records. We also present a method to retrieve the solar wind density from the solar wind speed, utilizing the invariance of the solar wind dynamic pressure and energy flux with latitude. To construct the synoptic maps of the solar wind speed we use the decomposition into spherical harmonics of each of the Carrington rotation map. To fill the gaps in time we apply the singular spectrum analysis to the time series of the coefficients of spherical harmonics. We obtained helio-latitudinal profiles of the solar wind proton speed and density over almost three recent solar cycles. The accuracy in the reconstruction is, due to computational limitations, about 20 %. The proposed methods allow us to improve the spatial and temporal resolution of the model of the solar wind parameters presented in our previous paper (Sokół et al., Solar Phys. 285, 167, 2013) and give a better insight into the time variations of the solar wind structure. Additionally, the solar wind density is reconstructed more accurately and it fits better to the in-situ measurements from Ulysses.

  11. Modeling Neutral Hydrogen in the Heliospheric Interface

    NASA Astrophysics Data System (ADS)

    Heerikhuisen, J.; Pogorelov, N.

    2009-05-01

    Observational data of neutral atoms provides us with a 1 AU picture of the neutral atom flux in the heliosphere. The large mean free paths of neutrals allow us to infer properties of their distant source, as well as the properties of the intermediary medium. Energetic neutral hydrogen, for example, travels on almost straight trajectories, so that the particles observed coming from a particular direction were created from energetic protons along that line of sight. Similarly, low energy interstellar atoms are attenuated and deflected as they enter the heliosphere, and this deflection tells us something about the structure of the heliospheric interface. Of course, to infer quantitative features of the global heliosphere from neutral atom observations at 1 AU, we need accurate models that capture the 3D structure of the heliosphere. We will present an advanced MHD-neutral model of the heliosphere which is 3D, employs kinetic neutral Hydrogen, and incorporates a suprathermal tail on the solar wind proton distribution to approximate pick-up ions. We will demonstrate that with the help of such a model, we can test various hypotheses regarding the heliospheric boundary via forward modeling and comparison with data.

  12. Modeling Neutral Hydrogen in the Heliospheric Interface

    NASA Astrophysics Data System (ADS)

    Heerikhuisen, Jacob; Pogorelov, Nikolai; Brand, Pontus

    2010-03-01

    Observational data of neutral atoms provides us with a 1 AU picture of the neutral atom flux in the heliosphere. The large mean free paths of neutrals allow us to infer properties of their distant source, as well as the properties of the intermediary medium. Energetic neutral hydrogen, for example, travels on almost straight trajectories, so that the particles observed coming from a particular direction were created from energetic protons along that line of sight. Similarly, low energy interstellar atoms are attenuated and deflected as they enter the heliosphere, and this deflection tells us something about the structure of the heliospheric interface. Of course, to infer quantitative features of the global heliosphere from neutral atom observations at 1 AU, we need accurate models that capture the 3D structure of the heliosphere. In this paper we present our MHD-plasma/kinetic-neutral model of the heliospheric interface that uses a Lorentzian distribution function to approximate a suprathermal tail on the solar wind proton distribution due to pick-up ions. We investigate the effect the k parameter of the Lorentzian function has on the overall solution and the flux of energetic neutral atoms (ENAs). ENA fluxes are also compared to ``pre-IBEX'' spacecraft data.

  13. The measurement of the ground wind structure at Wallops Island

    NASA Technical Reports Server (NTRS)

    Tielman, H. W.

    1981-01-01

    The mean and turbulence characteristics of the surface wind measured near the Atlantic coast were measured. The experimental data were acquired from a 76 meter tall instrumented micrometeorological tower. Mean wind and turbulence measurements were made with two types of instrumentation consisting of cup vane and temperature probes, primarily used for mean profile measurements of velocity and temperature respectively. The second system, a hot film and thermocouple system, was used for measurement of turbulence variances and covariances and spectra. The cup vane system was used to acquire data from all wind directions, while the hot film system was primarily used for turbulence measurements from the two prevailing wind directions, south and northwest. The micrometeorological tower is a self standing nonguyed tower with five working platforms at 15.2m (50 ft.) intervals, with cup vane and aspirated temperature probes mounted at each platform.

  14. Lawn Structured Triboelectric Nanogenerators for Scavenging Sweeping Wind Energy on Rooftops.

    PubMed

    Zhang, Lei; Zhang, Binbin; Chen, Jun; Jin, Long; Deng, Weili; Tang, Junfeng; Zhang, Haitao; Pan, Hong; Zhu, Minhao; Yang, Weiqing; Wang, Zhong Lin

    2016-02-24

    A novel triboelectric nanogenerator (TENG) is designed, based on flexible and transparent vertical-strip arrays, for environmental wind-energy harvesting. Given the low cost, simple structure, and wide applicability, the TENGs present a green alternative to traditional methods used for large-scale wind-energy harvesting. PMID:26669627

  15. Lawn Structured Triboelectric Nanogenerators for Scavenging Sweeping Wind Energy on Rooftops.

    PubMed

    Zhang, Lei; Zhang, Binbin; Chen, Jun; Jin, Long; Deng, Weili; Tang, Junfeng; Zhang, Haitao; Pan, Hong; Zhu, Minhao; Yang, Weiqing; Wang, Zhong Lin

    2016-02-24

    A novel triboelectric nanogenerator (TENG) is designed, based on flexible and transparent vertical-strip arrays, for environmental wind-energy harvesting. Given the low cost, simple structure, and wide applicability, the TENGs present a green alternative to traditional methods used for large-scale wind-energy harvesting.

  16. Al and Ge simultaneous oxidation using neutral beam post-oxidation for formation of gate stack structures

    SciTech Connect

    Ohno, Takeo; Nakayama, Daiki; Samukawa, Seiji

    2015-09-28

    To obtain a high-quality Germanium (Ge) metal–oxide–semiconductor structure, a Ge gate stacked structure was fabricated using neutral beam post-oxidation. After deposition of a 1-nm-thick Al metal film on a Ge substrate, simultaneous oxidation of Al and Ge was carried out at 300 °C, and a Ge oxide film with 29% GeO{sub 2} content was obtained by controlling the acceleration bias power of the neutral oxygen beam. In addition, the fabricated AlO{sub x}/GeO{sub x}/Ge structure achieved a low interface state density of less than 1 × 10{sup 11 }cm{sup −2 }eV{sup −1} near the midgap.

  17. The fossil wind structures of Eta Carinae: changes across one 5.54-yr cycle

    NASA Astrophysics Data System (ADS)

    Gull, Theodore R.; Madura, Thomas I.; Teodoro, Mairan; Clementel, Nicola; Corcoran, Michael; Damineli, Augusto; Groh, Jose H.; Hamaguchi, Kenji; Hillier, D. John; Moffat, Anthony F. J.; Richardson, Noel D.; Weigelt, Gerd; Lindler, Don; Feggans, Keith

    2016-11-01

    Eta Carinae, the closest, active, massive binary containing a highly unstable Luminous Blue Variable, exhibits expanding, compressed wind shells, seen in emission, that are spatially and spectrally resolved by Hubble Space Telescope/Space Telescope Imaging Spectrograph. Starting in 2009 June, these structures were mapped across its 5.54-yr, highly elliptical, binary orbit to follow temporal changes in the light of [Fe III] 4659 Å and [Fe II] 4815 Å. The emissions trace portions of fossil wind shells, that were formed by wind-wind interactions across each cycle. Over the high-ionization state, dense arcs, photoionized by far-ultraviolet radiation from the hot secondary, are seen in [Fe III]. Other arcs, ionized by mid-ultraviolet radiation from the primary star, are seen in [Fe II]. The [Fe III] structures tend to be interior to [Fe II] structures that trace extensive, less disturbed primary wind. During the brief periastron passage when the secondary plunges deep into the primary's extremely dense wind, on the far side of primary star, high-ionization [Fe III] structures fade and reappear in [Fe II]. Multiple fossil wind structures were traced across the 5.7-yr monitoring interval. The strong similarity of the expanding [Fe II] shells suggests that the wind and photoionization properties of the massive binary have not changed substantially from one orbit to the next over the past several orbital cycles. These observations trace structures that can be used to test 3D hydrodynamical and radiative-transfer models of massive, interacting winds. They also provide a baseline for following future changes in η Car, especially of its winds and photoionization properties.

  18. Considering changing temporal structures in the construction of scenario-neutral runoff response surfaces

    NASA Astrophysics Data System (ADS)

    Vormoor, Klaus; Rössler, Ole; Bürger, Gerd; Weingartner, Rolf; Bronstert, Axel

    2016-04-01

    Climate change impact studies are usually based on traditional top-down approaches in which post-processed climate model data serves as input into some kind of impact model. Parallel to these traditional approaches, scenario-neutral bottom-up approaches have been developed as an alternative methodology which assesses the intrinsic vulnerability of a system towards climate change. Such bottom-approaches perform a sensitivity analysis of an impact model towards systematically 'user-defined' changes in the climate system and summarize its response in a two-dimensional matrix: the response surface. The climate change signal is obtained by perturbing observed time series, which serve as inputs into the impact models. The impact model is then run with all possible combinations of perturbed input data series and the result of each combination (i.e. the impact) is plotted as one single realization (i.e. one pixel) of possible climate change impacts over the two dimensional domain. Although the complexity of existing perturbation methods varies, the temporal structure (i.e. the seasonal- and day-to-day-variability) of these time series often remains the same, which is critical, in particular for the simulations of extremes. In this study, we present standardized response surfaces (SRS) that are based on impact simulations using both perturbed climate observations and projections which are scaled to a common domain. We apply this approach within the field of hydrology and estimate different aspects of runoff response, covering mean runoff as well as extremes like low flows and floods in a Nordic catchment with a mixed snowmelt/rainfall regime. Climate observations and projections from eight GCM-RCM combinations, downscaled by two different methods, are used for the perturbation which results in 17 different SRS. A series of linear regression- and linear mixed-effects models is applied to quantify the different effects of perturbing the climate input data and of the varying

  19. Structural analysis of wind turbine rotors for NSF-NASA Mod-0 wind power system

    NASA Technical Reports Server (NTRS)

    Spera, D. A.

    1975-01-01

    Preliminary estimates of vibratory loads and stresses in hingeless and teetering rotors for the proposed 100-kW wind power system are presented. Stresses in the shank areas of the 19-m (62.5-ft) blades are given for static, rated, and overload conditions. The teetering rotor has substantial advantages over the hingeless rotor with respect to shank stresses, fatigue life, and tower loading. A teetering rotor will probably be required in order to achieve a long service life in a large wind turbine exposed to periodic overload conditions.

  20. Structure of magnetic field in the solar wind

    NASA Technical Reports Server (NTRS)

    Chertkov, A. D.

    1995-01-01

    This work is concerned with empirical data on magnetic field in the solar wind in frame of a concept of dissipative solar wind, developed in papers (Solar Wind 7 Conf., Pergamon Press, 1992, 165 and 1992 STEP/5th COSPAR Coll. Pergamon Press, 1994, 117; 235; 803). Interplanetary magnetic fields should be classified with respect to their origin. It is very important for all the theoretical problems from the necessity to specify correctly boundary and initial conditions: the magnetic field must be sewed with its source. One should select the field, connected directly with the Sun (stretched out from it), and the field of moving electric currents. It occured central in discussion about the velocity of Alfven waves, probably warming up the solar wind, relative to the Sun, the magnetic field and solar wind plasma. The selection problem corresponds to an inverse problem and obviously has no single solution. The dissipative model of the solar wind introduce the slipping and leakage of plasma relative to magnetic field. There are no 'interplanetary current sheets' in it. But temporal fluctuations from the filamentation of electric currents play the key role. As a whole, the new concept requires the re-interpretation of main objects in the interplanetary magnetic field.

  1. Wind Energy's New Role in Supplying the World's Energy: What Role Will Structural Health Monitoring Play?

    SciTech Connect

    Butterfield, S.; Sheng, S.; Oyague, F.

    2009-12-01

    Wind energy installations are leading all other forms of new energy installations in the United States and Europe. In Europe, large wind plants are supplying as much as 25% of Denmark's energy needs and 8% of the electric needs for Germany and Spain, who have more ambitious goals on the horizon. Although wind energy only produces about 2% of the current electricity demand in the United States, the U.S. Department of Energy, in collaboration with wind industry experts, has drafted a plan that would bring the U.S. installed wind capacity up to 20% of the nation's total electrical supply. To meet these expectations, wind energy must be extremely reliable. Structural health monitoring will play a critical role in making this goal successful.

  2. Dynamics of neutralized electrons and the focusability of intenseion beams in HIF accelerating structures

    SciTech Connect

    Lifschitz, A.F.; Maynard, G.; Vay, J.-V.

    2005-01-18

    In most of the proposals for HIF reactors, beams propagate ballistically through the containment chamber. To get the required final radius ({approx} 3 mm), the charge of the beam must be neutralized to some extent. Several neutralization schemes are possible, as co-injection of negative-ions beams, inclusion of external sources of electrons, or it can be provided by electrons coming from ionization of the background gas. In this work, we study the role of the electron dynamic on the neutralization and final radius of the beam. This is done by performing fully-electromagnetic PIC simulations of the beam ballistic transport using the BPIC code[1]. In agreement with previous works we found that the evolution of an isolated beam is well described as a bidimensional adiabatic compression, and the beam neutralization degree and final radius can be estimated from the initial electron transversal temperature. When a background gas is present the evolution differs significantly from an adiabatic compression. Even for low gas densities, the continuous electrons flow coming from gas ionization limits efficiently the compressional heating, thus reducing the final radius. Aspects of beam neutralization by background gas ionization are discussed.

  3. The plasma structure of coronal hole solar wind: Origins and evolution

    NASA Astrophysics Data System (ADS)

    Borovsky, Joseph E.

    2016-06-01

    Whereas slow solar wind is known to be highly structured, the fast (coronal hole origin) wind is usually considered to be homogeneous. Using measurements from Helios 1 + 2, ACE, Wind, and Ulysses, structure in the coronal hole origin solar wind is examined from 0.3 AU to 2.3 AU. Care is taken to collect and analyze intervals of "unperturbed coronal hole plasma." In these intervals, solar wind structure is seen in the proton number density, proton temperature, proton specific entropy, magnetic field strength, magnetic field to density ratio, electron heat flux, helium abundance, heavy-ion charge-state ratios, and Alfvenicity. Typical structure amplitudes are factors of 2, far from homogeneous. Variations are also seen in the solar wind radial velocity. Using estimates of the motion of the solar wind origin footpoint on the Sun for the various spacecraft, the satellite time series measurements are converted to distance along the photosphere. Typical variation scale lengths for the solar wind structure are several variations per supergranule. The structure amplitude and structure scale sizes do not evolve with distance from the Sun from 0.3 to 2.3 AU. An argument is quantified that these variations are the scale expected for solar wind production in open magnetic flux funnels in coronal holes. Additionally, a population of magnetic field foldings (switchbacks, reversals) in the coronal hole plasma is examined: this population evolves with distance from the Sun such that the magnetic field is mostly Parker spiral aligned at 0.3 AU and becomes more misaligned with distance outward.

  4. Chromospheric Structure and Wind Acceleration in Zeta Aur Stars

    NASA Astrophysics Data System (ADS)

    Bennett, Philip D.

    2001-11-01

    This NASA grant supported an analysis of the variability of the wind of the supergiant primary star (K4 Ib) in the eclipsing binary Zeta Aurigae (Zeta Aur). In the ultraviolet, the main-sequence companion star (B5 V) dominates the observed flux, and therefore serves as a convenient probe of the cool supergiant's wind. This study utilized the extensive set of (100+) ultraviolet spectroscopic observations obtained with the International Ultraviolet Explorer (IUE) satellite over its operational lifetime of 1978-1995. Although the resolution of IUE is limited (about 25 km/s), it is adequate to resolve variability in the wind features in Zeta Aur's ultraviolet spectrum, which are blueshifted 70 km/s from line center. Our analysis used the tau-v technique of Cardelli and Savage, which makes full use of the available line profile information. We find that the wind column densities vary by up to an order of magnitude over time. These results are being written up for submission to the Astrophysical Journal as the third paper of a series on the chromosphere and wind of Zeta Aurigae. The first two papers report on the construction of mean chromosphere and wind models respectively, based on HST/GHRS observations and funded by STScI. The third paper - this research - reports on variability of the Zeta Aur wind as determined from our analysis of the long IUE time series. This paper will be completed within the next three months; the delay in publication was to allow the completion of Papers 1 and 2, which logically precede the present work. Therefore, an additional no-cost extension was requested in order to ensure budgeted funds remain available for publication of this work. Unfortunately, this request was denied, and so I am forced to write this final report before publication of Paper 3. Regardless, this paper will be submitted for publication within the next three months.

  5. Chromospheric Structure and Wind Acceleration in Zeta Aur Stars

    NASA Technical Reports Server (NTRS)

    Bennett, Philip D.

    2001-01-01

    This NASA grant supported an analysis of the variability of the wind of the supergiant primary star (K4 Ib) in the eclipsing binary Zeta Aurigae (Zeta Aur). In the ultraviolet, the main-sequence companion star (B5 V) dominates the observed flux, and therefore serves as a convenient probe of the cool supergiant's wind. This study utilized the extensive set of (100+) ultraviolet spectroscopic observations obtained with the International Ultraviolet Explorer (IUE) satellite over its operational lifetime of 1978-1995. Although the resolution of IUE is limited (about 25 km/s), it is adequate to resolve variability in the wind features in Zeta Aur's ultraviolet spectrum, which are blueshifted 70 km/s from line center. Our analysis used the tau-v technique of Cardelli and Savage, which makes full use of the available line profile information. We find that the wind column densities vary by up to an order of magnitude over time. These results are being written up for submission to the Astrophysical Journal as the third paper of a series on the chromosphere and wind of Zeta Aurigae. The first two papers report on the construction of mean chromosphere and wind models respectively, based on HST/GHRS observations and funded by STScI. The third paper - this research - reports on variability of the Zeta Aur wind as determined from our analysis of the long IUE time series. This paper will be completed within the next three months; the delay in publication was to allow the completion of Papers 1 and 2, which logically precede the present work. Therefore, an additional no-cost extension was requested in order to ensure budgeted funds remain available for publication of this work. Unfortunately, this request was denied, and so I am forced to write this final report before publication of Paper 3. Regardless, this paper will be submitted for publication within the next three months.

  6. Crystal structure of the HIV neutralizing antibody 2G12 in complex with a bacterial oligosaccharide analog of mammalian oligomannose

    PubMed Central

    Stanfield, Robyn L; De Castro, Cristina; Marzaioli, Alberto M; Wilson, Ian A; Pantophlet, Ralph

    2015-01-01

    Human immunodeficiency virus-1 (HIV-1) is a major public health threat that continues to infect millions of people worldwide each year. A prophylactic vaccine remains the most cost-effective way of globally reducing and eliminating the spread of the virus. The HIV envelope spike, which is the target of many vaccine design efforts, is densely mantled with carbohydrate and several potent broadly neutralizing antibodies to HIV-1 recognize carbohydrate on the envelope spike as a major part of their epitope. However, immunizing with recombinant forms of the envelope glycoprotein does not typically elicit anti-carbohydrate antibodies. Thus, studies of alternative antigens that may serve as a starting point for carbohydrate-based immunogens are of interest. Here, we present the crystal structure of one such anti-carbohydrate HIV neutralizing antibody (2G12) in complex with the carbohydrate backbone of the lipooligosaccharide from Rhizobium radiobacter strain Rv3, which exhibits a chemical structure that naturally mimics the core high-mannose carbohydrate epitope of 2G12 on HIV-1 gp120. The structure described here provides molecular evidence of the structural homology between the Rv3 oligosaccharide and highly abundant carbohydrates on the surface of HIV-1 and raises the potential for the design of novel glycoconjugates that may find utility in efforts to develop immunogens for eliciting carbohydrate-specific neutralizing antibodies to HIV. PMID:25380763

  7. The Structure of the Solar Wind at Large Heliocentric Distances: CIRs and their Successors

    NASA Technical Reports Server (NTRS)

    Gazis, P. R.

    1997-01-01

    Co-rotating interaction regions (CIRs) and their associated shock pairs are dominant structures in the solar wind between the heliocentric distances of 2 and 8 AU. At larger heliocentric distances, these structures undergo a qualitative change. Shocks decay to a point where they are often difficult to detect, and may have little influence on the dynamics of the solar wind. Interaction regions spread and merge, though they appear to retain their identity to surprisingly large distances from the Sun. Solar wind and IMF data from the Pioneer 10, Pioneer 11, and Voyager 2 spacecraft were used to conduct a comprehensive survey of CIRs and their successors between heliocentric distances of 1 and 55 AU over the last two solar cycles. The structure of the solar wind varied in a consistent fashion with heliocentric distance. Similar structures were observed at similar heliocentric distances by all three spacecraft during different portions of the solar cycle.

  8. The Structure of the Solar Wind at Large Heliocentric Distances: CIRs and their Successors

    NASA Technical Reports Server (NTRS)

    Gazis, P. R.

    1999-01-01

    Co-rotating interaction regions (CIRs) and their associated shock pairs are dominant structures in the solar wind between the heliocentric distances of 2 and 8 AU. At larger heliocentric distances, these structures undergo a qualitative change. Shocks decay to a point where they are often difficult to detect, and may have little influence on the dynamics of the solar wind. Interaction regions spread and merge, though they appear to retain their identity to surprisingly large distances from the Sun. Solar wind and IMF data from the Pioneer 10, Pioneer 11, and Voyager 2 spacecraft were used to conduct a comprehensive survey of CIRs and their successors between heliocentric distances of 1 and 55 AU over the last two solar cycles. The structure of the solar wind varied in a consistent fashion with heliocentric distance. Similar structures were observed at similar heliocentric distances by all three spacecraft during different portions of the solar cycle.

  9. Observations of the properties of the water surface roughness structure under the action of wind and waves

    NASA Technical Reports Server (NTRS)

    Long, Steven R.; Huang, Norden E.

    1988-01-01

    The statistical properties of a water surface roughness structure subjected to wind and waves are analyzed in a laboratory wind wave channel. The surface slope is derived using elevation measurements and the pitot tube is employed to measure wind speed. The transient responses of the surface slope to a calm condition and low, medium, and high wind conditions are studied. Two methods for determining a critical wind speed range are described.

  10. Interplanetary shock waves and the structure of solar wind disturbances

    NASA Technical Reports Server (NTRS)

    Hundhausen, A. J.

    1972-01-01

    Observations and theoretical models of interplanetary shock waves are reviewed, with emphasis on the large-scale characteristics of the associated solar wind disturbances and on the relationship of these disturbances to solar activity. The sum of observational knowledge indicates that shock waves propagate through the solar wind along a broad, roughly spherical front, ahead of plasma and magnetic field ejected from solar flares. Typically, the shock front reaches 1 AU about two days after its flare origin, and is of intermediate strength. Not all large flares produce observable interplanetary shock waves; the best indicator of shock production appears to be the generation of both type 2 and type 4 radio bursts by a flare. Theoretical models of shock propagation in the solar wind can account for the typically observed shock strength, transit time, and shape.

  11. Plasma and field observation of the structures in the polar solar wind

    NASA Technical Reports Server (NTRS)

    McComas, D. J.; Barraclough, B. L.; Gosling, J. T.; Hammond, C. M.; Phillips, J. L.; Neugebauer, M.; Balogh, A.; Forsyth, R. J.

    1995-01-01

    Since passing essentially continuously into regions of solar wind from the southern polar coronal hole at approximately 36 deg S, Ulysses has observed frequent structures lasting from several hours to several days. In addition to Alfven waves and coronal mass ejections, which have been discussed by previous authors, two other sorts of structures are routinely evident. This paper provides the first report of these structures in the high latitude solar wind: (1) small scale compressional structures, and (2) pressure balance structures. The compressional structures are driven by faster solar wind overtaking the slower solar wind ahead of it and exhibit the plasma and field properties expected for compressions. However, unlike large scale stream interaction regions observed in and near the ecliptic plane, these structures are much smaller scale and are transient, not recurring from one rotation to the next. The pressure balance structures are indicated by roughly equal increases in the plasma pressure and decreases in the magnetic field pressure. These structures, which are several degrees across, are more dense and have higher plasma pressures and betas than the surrounding solar wind. These pressure balance structures seem to be likely manifestations of 'polar plumes.'

  12. The structure of the Venus neutral atmosphere from the Radio Science Experiment VeRa on Venus Express

    NASA Astrophysics Data System (ADS)

    Tellmann, Silvia; Bird, Mike; Verweyen, Alice; Haeusler, Bernd; Paetzold, Martin; Tyler, G. L.

    The Venus Express Radio Science Experiment VeRa uses one-way radio signals at X-band and S-band for the sounding of the Venus neutral atmosphere and ionosphere. An Ultrastable Oscillator (USO) provides a high quality onboard frequency reference source for this one-way radio link. Simultaneous, coherent measurements at two wavelengths allow separation of dispersive media effects from the classical Doppler shift. Electron density profiles of the ionosphere and profiles of pressure, temperature and neutral number density of the neutral atmosphere can be derived via an Abel transform with an altitude resolution of only a few hundred metres in the altitude range between about 40 and 100 km. Three occultation seasons could be covered during the nominal mission of Venus Express resulting in a data set of about 140 profiles of the neutral atmosphere. Another three occultation seasons are planned during the extended mission. The polar orbit of Venus Express provides the opportunity to study the atmosphere at all planetocentric latitudes under varying illumination conditions. Day-night and latitudinal variations of the thermal structure, the high variability of the atmosphere above the troposphere and signal absorption effects caused by the H2SO4 vapour can be investigated with the resulting data set.

  13. The Structure of the Venus Neutral Atmosphere from the Radio Science Experiment VeRa on Venus Express

    NASA Astrophysics Data System (ADS)

    Tellmann, S. A.; Häusler, B.; Pätzold, M.; Bird, M. K.; Tyler, G. L.

    2007-12-01

    The Venus Express Radio Science Experiment VeRa is sounding the Venus neutral atmosphere and ionosphere using the spacecraft radio subsystem in the oneway radio link mode. An Ultrastable Oscillator (USO) provides a high quality onboard frequency reference source for the derivation of electron density profiles in the ionosphere and profiles of pressure, temperature and neutral number density of the neutral atmosphere. The measurement configuration allows an altitude resolution of only a few hundred metres from the cloud deck at about 40 km to approximately 100 km. Three occultation seasons could be covered in the first two years of the Venus Express mission resulting in a data set of about 140 profiles of the neutral atmosphere. The polar orbit of Venus Express provides the opportunity to study the atmosphere at all planetocentric latitudes under varying illumination conditions. Special attention will be given to day-night variations of the thermal structure and the temperature distribution at high polar latitudes on both hemispheres ("cold collar region") and signal absorption effects caused by the H2SO4 vapour.

  14. Freezing and Melting of 3D Complex Plasma Structures under Microgravity Conditions Driven by Neutral Gas Pressure Manipulation

    SciTech Connect

    Khrapak, S. A.; Klumov, B. A.; Huber, P.; Thomas, H. M.; Ivlev, A. V.; Morfill, G. E.; Molotkov, V. I.; Lipaev, A. M.; Naumkin, V. N.; Petrov, O. F.; Fortov, V. E.; Malentschenko, Yu.; Volkov, S.

    2011-05-20

    Freezing and melting of large three-dimensional complex plasmas under microgravity conditions is investigated. The neutral gas pressure is used as a control parameter to trigger the phase changes: Complex plasma freezes (melts) by decreasing (increasing) the pressure. The evolution of complex plasma structural properties upon pressure variation is studied. Theoretical estimates allow us to identify the main factors responsible for the observed behavior.

  15. Wavelet analysis of the structure of microstreams in the polar solar wind

    SciTech Connect

    Neugebauer, M.; Ruzmaikin, A.; McComas, D.J.

    1997-01-01

    The fluctuations in solar-wind velocity measured by the Ulysses spacecraft above the polar regions of the Sun are organized into structures called microstreams. The application of wavelet transformations to the Ulysses data reveals the scales and positions of the microstreams and their association with variations in the helium content of the solar wind. It is concluded that the microstreams must have their origin in solar structures associated with the acceleration of the solar wind with little modification resulting from interplanetary phenomena. {copyright} {ital 1997 American Institute of Physics.}

  16. Line profiles variations from atmospheric eclipses: Constraints on the wind structure in Wolf-Rayet stars

    NASA Technical Reports Server (NTRS)

    Auer, L. H.; Koenigsberger, G.

    1994-01-01

    Binary systems in which one of the components has a stellar wind may present a phenomenon known as 'wind' or 'atmospheric eclipse', in which that wind occults the luminous disk of the companion. The enhanced absorption profile, relative to the spectrum at uneclipsed orbital phases, can be be modeled to yield constraints on the spatial structure of the eclipsing wind. A new, very efficient approach to the radiative transfer problem, which makes no requirements with respect to monotonicity of the velocity gradient or size of that gradient, is presented. The technique recovers both the comoving frame calculation and the Sobolev approximation in the appropiate limits. Sample computer simulations of the line profile variations induced by wind eclipses are presented. It is shown that the location of the wind absorption features in frequency is a diagnostic tool for identifying the size of the wind acceleration region. Comparison of the model profile variations with the observed variations in the Wolf-Rayet (W-R)+6 binary system V444 Cyg illustrate how the method can be used to derive information on the structure of the wind of the W-R star constrain the size of the W-R core radius.

  17. Aspects of structural health and condition monitoring of offshore wind turbines.

    PubMed

    Antoniadou, I; Dervilis, N; Papatheou, E; Maguire, A E; Worden, K

    2015-02-28

    Wind power has expanded significantly over the past years, although reliability of wind turbine systems, especially of offshore wind turbines, has been many times unsatisfactory in the past. Wind turbine failures are equivalent to crucial financial losses. Therefore, creating and applying strategies that improve the reliability of their components is important for a successful implementation of such systems. Structural health monitoring (SHM) addresses these problems through the monitoring of parameters indicative of the state of the structure examined. Condition monitoring (CM), on the other hand, can be seen as a specialized area of the SHM community that aims at damage detection of, particularly, rotating machinery. The paper is divided into two parts: in the first part, advanced signal processing and machine learning methods are discussed for SHM and CM on wind turbine gearbox and blade damage detection examples. In the second part, an initial exploration of supervisor control and data acquisition systems data of an offshore wind farm is presented, and data-driven approaches are proposed for detecting abnormal behaviour of wind turbines. It is shown that the advanced signal processing methods discussed are effective and that it is important to adopt these SHM strategies in the wind energy sector. PMID:25583864

  18. Aspects of structural health and condition monitoring of offshore wind turbines

    PubMed Central

    Antoniadou, I.; Dervilis, N.; Papatheou, E.; Maguire, A. E.; Worden, K.

    2015-01-01

    Wind power has expanded significantly over the past years, although reliability of wind turbine systems, especially of offshore wind turbines, has been many times unsatisfactory in the past. Wind turbine failures are equivalent to crucial financial losses. Therefore, creating and applying strategies that improve the reliability of their components is important for a successful implementation of such systems. Structural health monitoring (SHM) addresses these problems through the monitoring of parameters indicative of the state of the structure examined. Condition monitoring (CM), on the other hand, can be seen as a specialized area of the SHM community that aims at damage detection of, particularly, rotating machinery. The paper is divided into two parts: in the first part, advanced signal processing and machine learning methods are discussed for SHM and CM on wind turbine gearbox and blade damage detection examples. In the second part, an initial exploration of supervisor control and data acquisition systems data of an offshore wind farm is presented, and data-driven approaches are proposed for detecting abnormal behaviour of wind turbines. It is shown that the advanced signal processing methods discussed are effective and that it is important to adopt these SHM strategies in the wind energy sector. PMID:25583864

  19. Wind turbine control systems: Dynamic model development using system identification and the fast structural dynamics code

    SciTech Connect

    Stuart, J.G.; Wright, A.D.; Butterfield, C.P.

    1996-10-01

    Mitigating the effects of damaging wind turbine loads and responses extends the lifetime of the turbine and, consequently, reduces the associated Cost of Energy (COE). Active control of aerodynamic devices is one option for achieving wind turbine load mitigation. Generally speaking, control system design and analysis requires a reasonable dynamic model of {open_quotes}plant,{close_quotes} (i.e., the system being controlled). This paper extends the wind turbine aileron control research, previously conducted at the National Wind Technology Center (NWTC), by presenting a more detailed development of the wind turbine dynamic model. In prior research, active aileron control designs were implemented in an existing wind turbine structural dynamics code, FAST (Fatigue, Aerodynamics, Structures, and Turbulence). In this paper, the FAST code is used, in conjunction with system identification, to generate a wind turbine dynamic model for use in active aileron control system design. The FAST code is described and an overview of the system identification technique is presented. An aileron control case study is used to demonstrate this modeling technique. The results of the case study are then used to propose ideas for generalizing this technique for creating dynamic models for other wind turbine control applications.

  20. Aspects of structural health and condition monitoring of offshore wind turbines.

    PubMed

    Antoniadou, I; Dervilis, N; Papatheou, E; Maguire, A E; Worden, K

    2015-02-28

    Wind power has expanded significantly over the past years, although reliability of wind turbine systems, especially of offshore wind turbines, has been many times unsatisfactory in the past. Wind turbine failures are equivalent to crucial financial losses. Therefore, creating and applying strategies that improve the reliability of their components is important for a successful implementation of such systems. Structural health monitoring (SHM) addresses these problems through the monitoring of parameters indicative of the state of the structure examined. Condition monitoring (CM), on the other hand, can be seen as a specialized area of the SHM community that aims at damage detection of, particularly, rotating machinery. The paper is divided into two parts: in the first part, advanced signal processing and machine learning methods are discussed for SHM and CM on wind turbine gearbox and blade damage detection examples. In the second part, an initial exploration of supervisor control and data acquisition systems data of an offshore wind farm is presented, and data-driven approaches are proposed for detecting abnormal behaviour of wind turbines. It is shown that the advanced signal processing methods discussed are effective and that it is important to adopt these SHM strategies in the wind energy sector.

  1. The structure and strength of public attitudes towards wind farm development

    NASA Astrophysics Data System (ADS)

    Bidwell, David Charles

    A growing social science literature seeks to understand why, despite broad public support for wind energy, proposals for specific projects are often met with strong local opposition. This gap between general and specific attitudes is viewed as a significant obstacle to the deployment of wind energy technologies. This dissertation applies theoretical perspectives and methodological tools from social psychology to provide insights on the structure and strength of attitudes towards the potential development of commercial wind farm in three coastal areas of Michigan. A survey of attitudes was completed by 375 residents in these communities and structural equation modeling was used to explore the relationship among variables. The analysis found that attitudes towards wind farm development are shaped by anticipated economic benefits to the community, but expectations of economic benefit are driven by personal values. Social psychology has long recognized that all attitudes are not created equal. Weak attitudes are fleeting and prone to change, while strong attitudes are stable over time and resistant to change. There are two fundamental paths to strong attitudes: repeated experience with an attitude object or the application of deeply held principles or values to that object. Structural equation models were also used to understand the strength of attitudes among the survey respondents. Both the anticipated effects of wind farm development and personal values were found to influence the strength of attitudes towards wind farms. However, while expectations that wind farm development will have positive effects on the economy bolster two measures of attitude strength (collective identity and importance), these expectations are associated with a decline in a third measure (confidence). A follow-up survey asking identical questions was completed by completed by 187 respondents to the initial survey. Linear regressions models were used to determine the effects of attitude

  2. Modified Adaptive Control for Region 3 Operation in the Presence of Wind Turbine Structural Modes

    NASA Technical Reports Server (NTRS)

    Frost, Susan Alane; Balas, Mark J.; Wright, Alan D.

    2010-01-01

    Many challenges exist for the operation of wind turbines in an efficient manner that is reliable and avoids component fatigue and failure. Turbines operate in highly turbulent environments resulting in aerodynamic loads that can easily excite turbine structural modes, possibly causing component fatigue and failure. Wind turbine manufacturers are highly motivated to reduce component fatigue and failure that can lead to loss of revenue due to turbine down time and maintenance costs. The trend in wind turbine design is toward larger, more flexible turbines that are ideally suited to adaptive control methods due to the complexity and expense required to create accurate models of their dynamic characteristics. In this paper, we design an adaptive collective pitch controller for a high-fidelity simulation of a utility-scale, variable-speed horizontal axis wind turbine operating in Region 3. The objective of the adaptive pitch controller is to regulate generator speed, accommodate wind gusts, and reduce the excitation of structural modes in the wind turbine. The control objective is accomplished by collectively pitching the turbine blades. The adaptive collective pitch controller for Region 3 was compared in simulations with a baseline classical Proportional Integrator (PI) collective pitch controller. The adaptive controller will demonstrate the ability to regulate generator speed in Region 3, while accommodating gusts, and reducing the excitation of certain structural modes in the wind turbine.

  3. Identification of minute damage in composite bridge structures equipped with fiber optic sensors using the location of neutral axis and finite element analysis

    NASA Astrophysics Data System (ADS)

    Li, Xi; Glisic, Branko

    2016-04-01

    By definition, the neutral axis of a loaded composite beam structure is the curve along which the section experiences zero bending strain. When no axial loading is present, the location of the neutral axis passes through the centroid of stiffness of the beam cross-section. In the presence of damage, the centroid of stiffness, as well as the neutral axis, shift from the healthy position. The concept of neutral axis can be widely applied to all beam-like structures. According to literature, a change in location of the neutral axis can be associated with damage in the corresponding cross-section. In this paper, the movement of neutral axis near locations of minute damage in a composite bridge structure was studied using finite element analysis and experimental results. The finite element model was developed based on a physical scale model of a composite simply-supported structure with controlled minute damage in the reinforced concrete deck. The structure was equipped with long-gauge fiber optic strain and temperature sensors at a healthy reference location as well as two locations of damage. A total of 12 strain sensors were installed during construction and used to monitor the structure during various loading events. This paper aims to explain previous experimental results which showed that the observed positions of neutral axis near damage locations were higher than the predicted healthy locations in some loading events. Analysis has shown that finite element analysis has potential to simulate and explain the physical behavior of the test structure.

  4. Fading Coronal Structure and the Onset of Turbulence in the Young Solar Wind

    NASA Astrophysics Data System (ADS)

    DeForest, C. E.; Matthaeus, W. H.; Viall, N. M.; Cranmer, S. R.

    2016-09-01

    Above the top of the solar corona, the young, slow solar wind transitions from low-β, magnetically structured flow dominated by radial structures to high-β, less structured flow dominated by hydrodynamics. This transition, long inferred via theory, is readily apparent in the sky region close to 10° from the Sun in processed, background-subtracted solar wind images. We present image sequences collected by the inner Heliospheric Imager instrument on board the Solar-Terrestrial Relations Observatory (STEREO/HI1) in 2008 December, covering apparent distances from approximately 4° to 24° from the center of the Sun and spanning this transition in the large-scale morphology of the wind. We describe the observation and novel techniques to extract evolving image structure from the images, and we use those data and techniques to present and quantify the clear textural shift in the apparent structure of the corona and solar wind in this altitude range. We demonstrate that the change in apparent texture is due both to anomalous fading of the radial striae that characterize the corona and to anomalous relative brightening of locally dense puffs of solar wind that we term “flocculae.” We show that these phenomena are inconsistent with smooth radial flow, but consistent with the onset of hydrodynamic or magnetohydrodynamic instabilities leading to a turbulent cascade in the young solar wind.

  5. Cellular porous anodic alumina grown in neutral organic electrolyte. 1. Structure, composition, and properties of the films

    SciTech Connect

    Liu, Y.; Alwitt, R.S.; Shimizu, K.

    2000-04-01

    Anodic alumina films with cellular porous structure grow in neutral organic electrolytes with low water content and containing ethylene glycol and a large dicarboxylic acid. An Al carboxylate precipitates in the pore and is extruded from the coating. The porous structure develops even though the current efficiency for film formation is near 95%. The coating matrix contains substantial organic material, 15 wt % by thermal analysis. It is an oxide/organic composite with higher field strength and lower dielectric constant than pure anodic alumina.

  6. Structural basis for type VI secreted peptidoglycan dl-endopeptidase function, specificity and neutralization in Serratia marcescens

    SciTech Connect

    Srikannathasan, Velupillai; English, Grant; Bui, Nhat Khai; Trunk, Katharina; O’Rourke, Patrick E. F.; Rao, Vincenzo A.; Vollmer, Waldemar; Coulthurst, Sarah J. Hunter, William N.

    2013-12-01

    Crystal structures of type VI secretion system-associated immunity proteins, a peptidoglycan endopeptidase and a complex of the endopeptidase and its cognate immunity protein are reported together with assays of endopeptidase activity and functional assessment. Some Gram-negative bacteria target their competitors by exploiting the type VI secretion system to extrude toxic effector proteins. To prevent self-harm, these bacteria also produce highly specific immunity proteins that neutralize these antagonistic effectors. Here, the peptidoglycan endopeptidase specificity of two type VI secretion-system-associated effectors from Serratia marcescens is characterized. These small secreted proteins, Ssp1 and Ssp2, cleave between γ-d-glutamic acid and l-meso-diaminopimelic acid with different specificities. Ssp2 degrades the acceptor part of cross-linked tetratetrapeptides. Ssp1 displays greater promiscuity and cleaves monomeric tripeptides, tetrapeptides and pentapeptides and dimeric tetratetra and tetrapenta muropeptides on both the acceptor and donor strands. Functional assays confirm the identity of a catalytic cysteine in these endopeptidases and crystal structures provide information on the structure–activity relationships of Ssp1 and, by comparison, of related effectors. Functional assays also reveal that neutralization of these effectors by their cognate immunity proteins, which are called resistance-associated proteins (Raps), contributes an essential role to cell fitness. The structures of two immunity proteins, Rap1a and Rap2a, responsible for the neutralization of Ssp1 and Ssp2-like endopeptidases, respectively, revealed two distinct folds, with that of Rap1a not having previously been observed. The structure of the Ssp1–Rap1a complex revealed a tightly bound heteromeric assembly with two effector molecules flanking a Rap1a dimer. A highly effective steric block of the Ssp1 active site forms the basis of effector neutralization. Comparisons with Ssp2–Rap2

  7. Structure of colloidal complexes obtained from neutral/poly- electrolyte copolymers and oppositely charged surfactants

    NASA Astrophysics Data System (ADS)

    Berret, J.-F.; Cristobal, G.; Hervé, P.; Oberdisse, J.; Grillo, I.

    2002-11-01

    We report on the phase behavior and scattering properties of colloidal complexes made from block copolymers and surfactants. The copolymer is poly(sodium acrylate)-b-poly(acrylamide), hereafter abbreviated as PANa-PAM, with molecular weight 5000 g/mol for the first block and 30000 g/mol for the second. In aqueous solutions and neutral pH, poly(sodium acrylate) is a weak polyelectrolyte, whereas poly(acrylamide) is neutral and in good-solvent conditions. The surfactant is dodecyltrimethylammonium bromide (DTAB) and is of opposite charge with respect to the polyelectrolyte block. Combining dynamical light scattering and small-angle neutron scattering, we show that in aqueous solutions PANa-PAM diblocks and DTAB associate into colloidal complexes. For surfactant-to-polymer charge ratios Z lower than a threshold (Z_C sim 0.3), the complexes are single surfactant micelles decorated by few copolymers. Above the threshold, the colloidal complexes reveal an original core-shell microstructure. We have found that the core of typical radius 100 200 Å is constituted from densely packed surfactant micelles connected by the polyelectrolyte blocks. The outer part of the colloidal complex is a corona and is made from the neutral poly(acrylamide) chains. Typical hydrodynamic sizes for the whole aggregate are around 1000 Å. The aggregation numbers expressed in terms of numbers of micelles and copolymers per complex are determined and found to be comprised between 100 400, depending on the charge ratio Z and on the total concentration. We have also shown that the sizes of the complexes depend on the exact procedure of the sample preparation. We propose that the driving mechanism for the complex formation is similar to that involved in the phase separation of homopolyelectrolyte/surfactant systems. With copolymers, the presence of the neutral blocks prevents the macroscopic phase separation from occurring.

  8. Model structure of a cosmic-ray mediated stellar or solar wind

    NASA Technical Reports Server (NTRS)

    Lee, M. A.; Axford, W. I.

    1988-01-01

    An idealized hydrodynamic model is presented for the mediation of a free-streaming stellar wind by galactic cosmic rays or energetic particles accelerated at the stellar wind termination shock. The spherically-symmetric stellar wind is taken to be cold; the only body force is the cosmic ray pressure gradient. The cosmic rays are treated as a massless fluid with an effective mean diffusion coefficient k proportional to radial distance r. The structure of the governing equations is investigated both analytically and numerically. Solutions for a range of values of k are presented which describe the deceleration of the stellar wind and a transition to nearly incompressible flow and constant cosmic ray pressure at large r. In the limit of small k the transition steepens to a strong stellar wind termination shock. For large k the stellar wind is decelerated gradually with no shock transition. It is argued that the solutions provide a simple model for the mediation of the solar wind by interstellar ions as both pickup ions and the cosmic ray anomalous component which together dominate the pressure of the solar wind at large r.

  9. Structural changes in lower ionosphere wind trends at midlatitudes

    NASA Astrophysics Data System (ADS)

    Jacobi, C.; Merzlyakov, E. G.; Liu, R. Q.; Solovjova, T. V.; Portnyagin, Y. I.

    2010-10-01

    Long-term variability of the mesosphere/lower thermosphere (lower E region ionosphere) since 1970 has been analyzed using wind data series obtained at Collm (52° N, 15° E) using the LF drift method and at Obninsk (55° N, 37° E) applying VHF meteor radar. Applying piecewise linear trend analysis with a priori unknown number and positions of breakpoints shows that trend models with breakpoints are generally to be preferred against straight lines. There is a strong indication for a change of trends in wind parameters around 1975-1980. Similar changes are also found in the lower atmosphere, e.g., in tropospheric temperatures. This indicates a coupling between atmospheric layers at time scales of decades.

  10. Coronal sources of the intrastream structure of the solar wind

    NASA Technical Reports Server (NTRS)

    Sullivan, J. D.; Bridge, H. S.

    1983-01-01

    Short time scale changes in the bulk speed were found not to coincide with X-ray transients near the sub-earth point nor with the number of X-ray bright points within a coronal hole and near the equator. The changes in bulk speed, it is shown, are associated with changes in light areas in a hole which may be associated with the opening or closing of magnetic field lines within the coronal hole. That there is a causal connection between these sudden changes (apperance or disappearance) in light area and sudden changes in the bulk speed of the solar wind is further evidenced by the spatial proximity on the Sun of these changing light regions to the source position of stream lines from Levine's model that connect into the same solar wind streams.

  11. Titan's Temperature and Zonal Wind Structure and Seasonal Behavior

    NASA Astrophysics Data System (ADS)

    Flasar, F.; Achterberg, Richard; Schinder, Paul

    2016-06-01

    Titan's atmosphere near 80 km (20 mbar) marks the transition between large radiative damping times at lower altitudes, where seasonal variations are muted, and small damping times higher up, where temperatures and winds vary significantly over the year. Cassini CIRS and Radio-Occultation measurements obtained in 2004-2016 have tracked the evolution of temperatures and winds in Titan's atmosphere from early northern winter to late spring. In winter, the northern hemisphere was characterized by cold temperatures at high latitudes in the lower stratosphere and a strong circumpolar vortex that extended to subtropical northern latitudes. At high altitudes over the north pole, there was an elevated stratopause with a temperature roughly 30 K above the seasonal average, associated with subsidence and adiabatic warming. As the northern hemisphere has moved toward summer the dissolution of the circumpolar vortex has been gradual, and there is no evidence of rapid distortion and disruption forced by planetary waves like that seen on Earth. During this time, the southern hemisphere has cooled fairly abruptly at high latitudes. A circumpolar vortex has formed in the stratosphere, but it is more compact than seen in the north, with maximum winds at 60°S. Potential vorticity maps now indicate steep meridional gradients at high southern latitudes, implying a barrier to efficient mixing between the polar region and lower latitudes. One of the curious features of Titan's temperatures has been the destabilization seen in the winter north polar region, where negative temperature gradients were observed between 80 and 100 km. As the southern hemisphere moves toward winter, temperatures retrieved from radio occultation soundings have shown the early development this phenomenon at high southernlatitudes. The cause of the destabilization in winter may be associated with a cloud of organic ices. However, the transition region near 80 km is also where the zonal winds exhibit a sharp

  12. An acoustic-array based structural health monitoring technique for wind turbine blades

    NASA Astrophysics Data System (ADS)

    Aizawa, Kai; Poozesh, Peyman; Niezrecki, Christopher; Baqersad, Javad; Inalpolat, Murat; Heilmann, Gunnar

    2015-04-01

    This paper proposes a non-contact measurement technique for health monitoring of wind turbine blades using acoustic beamforming techniques. The technique works by mounting an audio speaker inside a wind turbine blade and observing the sound radiated from the blade to identify damage within the structure. The main hypothesis for the structural damage detection is that the structural damage (cracks, edge splits, holes etc.) on the surface of a composite wind turbine blade results in changes in the sound radiation characteristics of the structure. Preliminary measurements were carried out on two separate test specimens, namely a composite box and a section of a wind turbine blade to validate the methodology. The rectangular shaped composite box and the turbine blade contained holes with different dimensions and line cracks. An acoustic microphone array with 62 microphones was used to measure the sound radiation from both structures when the speaker was located inside the box and also inside the blade segment. A phased array beamforming technique and CLEAN-based subtraction of point spread function from a reference (CLSPR) were employed to locate the different damage types on both the composite box and the wind turbine blade. The same experiment was repeated by using a commercially available 48-channel acoustic ring array to compare the test results. It was shown that both the acoustic beamforming and the CLSPR techniques can be used to identify the damage in the test structures with sufficiently high fidelity.

  13. High-R Walls for New Construction Structural Performance: Wind Pressure Testing

    SciTech Connect

    DeRenzis, A.; Kochkin, V.

    2013-01-01

    This technical report is focused primarily on laboratory testing that evaluates wind pressure performance characteristics for wall systems constructed with exterior insulating sheathing. This research and test activity will help to facilitate the ongoing use of non-structural sheathing options and provide a more in-depth understanding of how wall system layers perform in response to high wind perturbations normal to the surface.

  14. High-R Walls for New Construction Structural Performance. Wind Pressure Testing

    SciTech Connect

    DeRenzis, A.; Kochkin, V.

    2013-01-01

    This technical report is focused primarily on laboratory testing that evaluates wind pressure performance characteristics for wall systems constructed with exterior insulating sheathing. This research and test activity will help to facilitate the ongoing use of non-structural sheathing options and provide a more in-depth understanding of how wall system layers perform in response to high wind perturbations normal to the surface.

  15. Multiple Eyewall Structure and its Wind Features in 2012 Typhoon Bolaven

    NASA Astrophysics Data System (ADS)

    Origuchi, S.

    2015-12-01

    Typhoon 'Bolaven' passed the Okinawa Main Island at about 1200 UTC 26 August 2012, while moving northwestward. The radar images showed that 'Bolaven' had the multiple eyewall structure. The surface observation data at Nago of Okinawa showed that the precipitation and surface wind velocity in the typhoon's central region were weaker than those of the Japan Meteorological Agency (JMA)'s operational forecast. Cloud-resolving ensemble simulations were performed to investigate the relations between the multiple eyewall structure and the wind features in the typhoon's central regions. The ensemble simulations reproduced double eyewall structures in several members. To evaluate the reproducibility of multiple eyewall structures, the multi-eye index (MEI) was defined in this study. Compared with the members in which the typhoon had the spiral rainband structures, the pressure gradients in the typhoon's central region of the small MEI (multiple eyewall) members were weak. The precipitation and surface wind velocity were also weaker than those of the typhoons with spiral rainbands. In case of the multiple eyewall typhoon, the gentle pressure gradients and the associated weaker surface inflows suppressed convections in the inner eyewall. The statistical analysis was performed based on the ensemble prediction. A clear positive correlation was indicated between the MEI and the wind velocity (tangential wind and inward radial wind) in the typhoon's central region. This result explains the reason why the actual wind velocity was weaker than that of the original JMA's forecast. The relationship between the atmospheric environmental factors around the typhoon (e.g., level of free convection and convective available potential energy) and MEI was investigated from the outputs of ensemble simulations. The results indicated that there were no strong relations between them. This suggests that the formation of the multiple eyewall structures is not simply determined by the atmospheric

  16. The Structure of the Venus Neutral Atmosphere from the Radio Science Experiment VeRa on Venus Express

    NASA Astrophysics Data System (ADS)

    Tellmann, S.; Häusler, B.; Pätzold, M.; Bird, M.; Tyler, G. L.

    2007-08-01

    The Venus Express Radio Science Experiment VeRa uses one-way radio signals at X-band and S-band for the sounding of the Venus neutral atmosphere and ionosphere. An Ultrastable Oscillator (USO) provides a high quality onboard frequency reference source for this dual-frequency one-way radio link. Simultaneous, coherent measurements at two wavelengths allow separation of dispersive media effects from the classical Doppler shift. Electron density profiles of the ionosphere and profiles of pressure, temperature and neutral number density of the neutral atmosphere can be derived via an Abel transform with an altitude resolution of only a few hundred metres from the cloud deck to ~ 100 km. Two occultation seasons took place in the first year of observation. A total number of 42 profiles occultation experiments were conducted. The polar orbit of Venus Express provides the opportunity to study the atmosphere at all planetocentric latitudes under varying illumination conditions. Special attention will be given to day-night variations of the atmospheric structure and the temperature distribution at high polar latitudes on both hemispheres ("cold collar region") and signal absorption effects caused by the H2SO4 vapour.

  17. Structural and anti-inflammatory characterization of a novel neutral polysaccharide from North American ginseng (Panax quinquefolius).

    PubMed

    Wang, Lijun; Yu, Xiaona; Yang, Xiushi; Li, Yi; Yao, Yang; Lui, Edmund Man King; Ren, Guixing

    2015-03-01

    Neutral polysaccharides are one of the active components in the American ginseng roots. Recently, the studies about American ginseng polysaccharides are mainly centered on acidic polysaccharides, while there is relatively limited research that explores neutral polysaccharides. In this study a novel neutral polysaccharide (PPQN) was isolated from American ginseng roots and its structure and anti-inflammatory activity were investigated. The average molecular weight (Mw) of PPQN was 3.1 kDa. Monosaccharide components' analysis indicated that PPQN was composed of glucose (Glc) and galactose (Gal) in a molar ratio of 1:1.15. Secretions of nitric oxide (NO), TNF-α, IL-6, and IL-1β after lipopolysaccharide (LPS) stimulation were detected in PPQN pre-treatment RAW264.7 macrophages. PPQN (150 μg/mL) exhibited more effective inhibition of TNF-α, IL-1β, and IL-6 secretions, followed by NO production with respective values of 40.5%, 41.1%, 34.4%, and 11.1% suppression. These results indicated that PPQN may have therapeutic implications in treatment of inflammation and inflammatory-related diseases.

  18. Flow around new wind fence with multi-scale fractal structure in an atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    McClure, Sarah; Lee, Sang-Joon; Zhang, Wei

    2015-11-01

    Understanding and controlling atmospheric boundary-layer flows with engineered structures, such as porous wind fences or windbreaks, has been of great interest to the fluid mechanics and wind engineering community. Previous studies found that the regular mono-scale grid fence of 50% porosity and a bottom gap of 10% of the fence height are considered to be optimal over a flat surface. Significant differences in turbulent flow structure have recently been noted behind multi-scale fractal wind fences, even with the same porosity. In this study, wind-tunnel tests on the turbulent flow and the turbulence kinetic energy transport of 1D and 2D multi-scale fractal fences under atmospheric boundary-layer were conducted. Velocity fields around the fractal fences were systematically measured using Particle Image Velocimetry to uncover effects of key parameters on turbulent flows around the fences at a Reynolds number of approximately 3.6x104 based on the free-stream speed and fence height. The turbulent flow structures induced by specific 1D/2D multi-scale fractal wind fences were compared to those of a conventional grid fence. The present results would contribute to the design of new-generation wind fences to reduce snow/sand deposition on critical infrastructure such as roads and bridges.

  19. Augmented Adaptive Control of a Wind Turbine in the Presence of Structural Modes

    NASA Technical Reports Server (NTRS)

    Frost, Susan A.; Balas, Mark J.; Wright, Alan D.

    2010-01-01

    Wind turbines operate in highly turbulent environments resulting in aerodynamic loads that can easily excite turbine structural modes, potentially causing component fatigue and failure. Two key technology drivers for turbine manufacturers are increasing turbine up time and reducing maintenance costs. Since the trend in wind turbine design is towards larger, more flexible turbines with lower frequency structural modes, manufacturers will want to develop methods to operate in the presence of these modes. Accurate models of the dynamic characteristics of new wind turbines are often not available due to the complexity and expense of the modeling task, making wind turbines ideally suited to adaptive control. In this paper, we develop theory for adaptive control with rejection of disturbances in the presence of modes that inhibit the controller. We use this method to design an adaptive collective pitch controller for a high-fidelity simulation of a utility-scale, variable-speed wind turbine operating in Region 3. The objective of the adaptive pitch controller is to regulate generator speed, accommodate wind gusts, and reduce the interference of certain structural modes in feedback. The control objective is accomplished by collectively pitching the turbine blades. The adaptive pitch controller for Region 3 is compared in simulations with a baseline classical Proportional Integrator (PI) collective pitch controller.

  20. Structural Health Monitoring challenges on the 10-MW offshore wind turbine model

    NASA Astrophysics Data System (ADS)

    Di Lorenzo, E.; Kosova, G.; Musella, U.; Manzato, S.; Peeters, B.; Marulo, F.; Desmet, W.

    2015-07-01

    The real-time structural damage detection on large slender structures has one of its main application on offshore Horizontal Axis Wind Turbines (HAWT). The renewable energy market is continuously pushing the wind turbine sizes and performances. This is the reason why nowadays offshore wind turbines concepts are going toward a 10 MW reference wind turbine model. The aim of the work is to perform operational analyses on the 10-MW reference wind turbine finite element model using an aeroelastic code in order to obtain long-time-low- cost simulations. The aeroelastic code allows simulating the damages in several ways: by reducing the edgewise/flapwise blades stiffness, by adding lumped masses or considering a progressive mass addiction (i.e. ice on the blades). The damage detection is then performed by means of Operational Modal Analysis (OMA) techniques. Virtual accelerometers are placed in order to simulate real measurements and to estimate the modal parameters. The feasibility of a robust damage detection on the model has been performed on the HAWT model in parked conditions. The situation is much more complicated in case of operating wind turbines because the time periodicity of the structure need to be taken into account. Several algorithms have been implemented and tested in the simulation environment. They are needed in order to carry on a damage detection simulation campaign and develop a feasible real-time damage detection method. In addition to these algorithms, harmonic removal tools are needed in order to dispose of the harmonics due to the rotation.

  1. Approximate method for calculating free vibrations of a large-wind-turbine tower structure

    NASA Technical Reports Server (NTRS)

    Das, S. C.; Linscott, B. S.

    1977-01-01

    A set of ordinary differential equations were derived for a simplified structural dynamic lumped-mass model of a typical large-wind-turbine tower structure. Dunkerley's equation was used to arrive at a solution for the fundamental natural frequencies of the tower in bending and torsion. The ERDA-NASA 100-kW wind turbine tower structure was modeled, and the fundamental frequencies were determined by the simplified method described. The approximate fundamental natural frequencies for the tower agree within 18 percent with test data and predictions analyzed.

  2. Modal testing of a very flexible 110 m wind turbine structure

    SciTech Connect

    Carne, T.G.; Lauffer, J.P.; Gomez, A.J.; Benjannet, Hassine

    1988-01-01

    Modal Testing of immense and very flexible structures poses a number of problems. It requires innovative excitation techniques since the modal frequencies of these stuctures can be quite low. Also, substantial energy must be input to the structure to obtain reasonable levels of response. In this paper, results are presented from a modal test of the 110 m tall EOLE wind turbine which had four modal frequencies below 1.0 Hz. Step-relaxation and wind were used to excite the structure. 5 refs., 14 figs., 2 tabs.

  3. Neutralizer optimization

    NASA Technical Reports Server (NTRS)

    Patterson, Michael J.; Mohajeri, Kayhan

    1991-01-01

    The preliminary results of a test program to optimize a neutralizer design for 30 cm xenon ion thrusters are discussed. The impact of neutralizer geometry, neutralizer axial location, and local magnetic fields on neutralizer performance is discussed. The effect of neutralizer performance on overall thruster performance is quantified, for thruster operation in the 0.5-3.2 kW power range. Additionally, these data are compared to data published for other north-south stationkeeping (NSSK) and primary propulsion xenon ion thruster neutralizers.

  4. Structural and Functional Characterization of Anti-A33 Antibodies Reveal a Potent Cross-Species Orthopoxviruses Neutralizer

    PubMed Central

    Matho, Michael H.; Schlossman, Andrew; Meng, Xiangzhi; Benhnia, Mohammed Rafii-El-Idrissi; Kaever, Thomas; Buller, Mark; Doronin, Konstantin; Parker, Scott; Peters, Bjoern; Crotty, Shane; Xiang, Yan; Zajonc, Dirk M.

    2015-01-01

    Vaccinia virus A33 is an extracellular enveloped virus (EEV)-specific type II membrane glycoprotein that is essential for efficient EEV formation and long-range viral spread within the host. A33 is a target for neutralizing antibody responses against EEV. In this study, we produced seven murine anti-A33 monoclonal antibodies (MAbs) by immunizing mice with live VACV, followed by boosting with the soluble A33 homodimeric ectodomain. Five A33 specific MAbs were capable of neutralizing EEV in the presence of complement. All MAbs bind to conformational epitopes on A33 but not to linear peptides. To identify the epitopes, we have adetermined the crystal structures of three representative neutralizing MAbs in complex with A33. We have further determined the binding kinetics for each of the three antibodies to wild-type A33, as well as to engineered A33 that contained single alanine substitutions within the epitopes of the three crystallized antibodies. While the Fab of both MAbs A2C7 and A20G2 binds to a single A33 subunit, the Fab from MAb A27D7 binds to both A33 subunits simultaneously. A27D7 binding is resistant to single alanine substitutions within the A33 epitope. A27D7 also demonstrated high-affinity binding with recombinant A33 protein that mimics other orthopoxvirus strains in the A27D7 epitope, such as ectromelia, monkeypox, and cowpox virus, suggesting that A27D7 is a potent cross-neutralizer. Finally, we confirmed that A27D7 protects mice against a lethal challenge with ectromelia virus. PMID:26325270

  5. THE SPATIALLY RESOLVED H{alpha}-EMITTING WIND STRUCTURE OF P CYGNI

    SciTech Connect

    Balan, Aurelian; Tycner, C.; Zavala, R. T.; Benson, J. A.; Hutter, D. J.; Templeton, M. E-mail: c.tycner@cmich.ed E-mail: jbenson@nofs.navy.mi E-mail: matthewt@aavso.or

    2010-06-15

    High spatial resolution observations of the H{alpha}-emitting wind structure associated with the luminous blue variable star P Cygni were obtained with the Navy Prototype Optical Interferometer. These observations represent the most comprehensive interferometric data set on P Cyg to date. We demonstrate how the apparent size of the H{alpha}-emitting region of the wind structure of P Cyg compares between the 2005, 2007, and 2008 observing seasons and how this relates to the H{alpha} line spectroscopy. Using the data sets from 2005, 2007, and 2008 observing seasons, we fit a circularly symmetric Gaussian model to the interferometric signature from the H{alpha}-emitting wind structure of P Cyg. Based on our results, we conclude that the radial extent of the H{alpha}-emitting wind structure around P Cyg is stable at the 10% level. We also show how the radial distribution of the H{alpha} flux from the wind structure deviates from a Gaussian shape, whereas a two-component Gaussian model is sufficient to fully describe the H{alpha}-emitting region around P Cyg.

  6. Examining Periodic Solar-Wind Density Structures Observed in the SECCHI Heliospheric Imagers

    NASA Technical Reports Server (NTRS)

    Viall, Nicholeen M.; Spence, Harlan E.; Vourlidas, Angelos; Howard, Russell

    2010-01-01

    We present an analysis of small-scale, periodic, solar-wind density enhancements (length scales as small as approximately equals 1000 Mm) observed in images from the Heliospheric Imager (HI) aboard STEREO-A. We discuss their possible relationship to periodic fluctuations of the proton density that have been identified at 1 AU using in-situ plasma measurements. Specifically, Viall, Kepko, and Spence examined 11 years of in-situ solar-wind density measurements at 1 AU and demonstrated that not only turbulent structures, but also nonturbulent, periodic density structures exist in the solar wind with scale sizes of hundreds to one thousand Mm. In a subsequent paper, Viall, Spence, and Kasper analyzed the alpha-to-proton solar-wind abundance ratio measured during one such event of periodic density structures, demonstrating that the plasma behavior was highly suggestive that either temporally or spatially varying coronal source plasma created those density structures. Large periodic density structures observed at 1 AU, which were generated in the corona, can be observable in coronal and heliospheric white-light images if they possess sufficiently high density contrast. Indeed, we identify such periodic density structures as they enter the HI field of view and follow them as they advect with the solar wind through the images. The smaller, periodic density structures that we identify in the images are comparable in size to the larger structures analyzed in-situ at 1 AU, yielding further evidence that periodic density enhancements are a consequence of coronal activity as the solar wind is formed.

  7. Structural basis for the binding of the neutralizing antibody, 7D11, to the poxvirus L1 protein

    SciTech Connect

    Su, Hua-Poo; Golden, Joseph W.; Gittis, Apostolos G.; Hooper, Jay W.; Garboczi, David N.

    2007-11-25

    Medical countermeasures to prevent or treat smallpox are needed due to the potential use of poxviruses as biological weapons. Safety concerns with the currently available smallpox vaccine indicate a need for research on alternative poxvirus vaccine strategies. Molecular vaccines involving the use of proteins and/or genes and recombinant antibodies are among the strategies under current investigation. The poxvirus L1 protein, encoded by the L1R open reading frame, is the target of neutralizing antibodies and has been successfully used as a component of both protein subunit and DNA vaccines. L1-specific monoclonal antibodies (e.g., mouse monoclonal antibody mAb-7D11, mAb-10F5) with potent neutralizing activity bind L1 in a conformation-specific manner. This suggests that proper folding of the L1 protein used in molecular vaccines will affect the production of neutralizing antibodies and protection. Here, we co-crystallized the Fab fragment of mAb-7D11 with the L1 protein. The crystal structure of the complex between Fab-7D11 and L1 reveals the basis for the conformation-specific binding as recognition of a discontinuous epitope containing two loops that are held together by a disulfide bond. The structure of this important conformational epitope of L1 will contribute to the development of molecular poxvirus vaccines and also provides a novel target for anti-poxvirus drugs. In addition, the sequence and structure of Fab-7D11 will contribute to the development of L1-targeted immunotherapeutics.

  8. Structures in the polar solar wind: Plasma and field observations from Ulysses

    SciTech Connect

    McComas, D.J.; Barraclough, B.L.; Gosling, J.T.; Hammond, C.M.; Phillips, J.L.; Neugebauer, M.; Balogh, A.; Forsyth, R.J.

    1996-07-01

    The Ulysses measurements of the solar wind plasma and magnetic fields for the 36-69 deg.south latitude are analyzed. The plasma compressional structures and pressure balance structures are identified in addition to Alfven waves and coronal mass ejection. {copyright} {bold 1997 American Institute of Physics.}

  9. The Solar Wind

    NASA Technical Reports Server (NTRS)

    Goldstein, B. E.

    1998-01-01

    The first evidence of the solar wind was provided through observations of comet tail deflections by L. Biermann in 1951. A cometary ion tail is oriented along the difference between the cometary and solar wind velocities, whereas the dust tail is in the antisunward direction; the ion tail directions demonstrated the existence of an outflow of ionized gas from the Sun (the solar wind) and allowed estimates of solar wind speed. Spacecraft observations have now established that at 1 AU the solar wind has a typical ion number density of about 7 /cc and is composed by number of about 95% protons and 5% Helium, with other minor ions also present. The solar wind as observed at 1 AU in the ecliptic has speeds typically in the range 300-700 km/ s. At such speeds ions travel from the Sun to 1 AU in from 2.5 to 6 days. The impact of the solar wind on planets with magnetic fields (Earth, Jupiter, Saturn, Uranus, Neptune) causes phenomena such as magnetospheres, aurorae, and geomagnetic storms, whereas at objects lacking magnetospheres (Mars, Venus, comets), atmospheric neutrals undergo charge exchange and are picked up by the solar wind flow. The solar wind also shields the Earth from low energy cosmic rays, and is responsible for the existence of the anomalous component of the cosmic rays a low energy component that is created locally rather than in the galaxy. Presented here is a brief introduction to the solar wind and a description of some current topics of research. Solar wind properties vary a great deal due to the changing magnetic structure on the Sun.

  10. Gas-phase structures and thermochemistry of neutral histidine and its conjugated acid and base.

    PubMed

    Riffet, Vanessa; Bouchoux, Guy

    2013-04-28

    Extensive exploration of the conformational space of neutral, protonated and deprotonated histidine has been conducted at the G4MP2 level. Theoretical protonation and deprotonation thermochemistry as well as heats of formation of gaseous histidine and its ionized forms have been calculated at the G4 level considering either the most stable conformers or an equilibrium population of conformers at 298 K. These theoretical results were compared to evaluated experimental determinations. Recommended proton affinity and protonation entropy deduced from these comparisons are PA(His) = 980 kJ mol(-1) and ΔpS(His) ∼ 0 J mol(-1) K(-1), thus leading to a gas-phase basicity value of GB(His) = 947.5 kJ mol(-1). Similarly, gas phase acidity parameters are ΔacidH(o)(His) = 1373 kJ mol(-1), ΔacidS(His) ∼ 10 J mol(-1) K(-1) and ΔacidG(o)(His) = 1343 kJ mol(-1). Computed G4 heats of formation values are equal to -290, 265 and -451 kJ mol(-1) for gaseous neutral histidine and its protonated and deprotonated forms, respectively. The present computational data correct, and complete, previous thermochemical parameter estimates proposed for gas-phase histidine and its acido-basic properties.

  11. Crystal structure of a 3B3 variant - A broadly neutralizing HIV-1 scFv antibody

    SciTech Connect

    Clark, K. Reed; Walsh, Scott T.R.

    2009-12-10

    We present the crystal structure determination of an anti-HIV-1 gp120 single-chain variable fragment antibody variant, 3B3, at 2.5 {angstrom} resolution. This 3B3 variant was derived from the b12 antibody, using phage display and site-directed mutagenesis of the variable heavy chain (V{sub H}) complementary-determining regions (CDRs). 3B3 exhibits enhanced binding affinity and neutralization activity against several cross-clade primary isolates of HIV-1 by interaction with the recessed CD4-binding site on the gp120 envelope protein. Comparison with the structures of the unbound and bound forms of b12, the 3B3 structure closely resembles these structures with minimal differences with two notable exceptions. First, there is a reorientation of the CDR-H3 of the V{sub H} domain where the primary sequences evolved from b12 to 3B3. The structural changes in CDR-H3 of 3B3, in light of the b12-gp120 complex structure, allow for positioning an additional Trp side chain in the binding interface with gp120. Finally, the second region of structural change involves two peptide bond flips in CDR-L3 of the variable light (VL) domain triggered by a point mutation in CDR-H3 of Q100eY resulting in changes in the intramolecular hydrogen bonding patterning between the VL and VH domains. Thus, the enhanced binding affinities and neutralization capabilities of 3B3 relative to b12 probably result from higher hydrophobic driving potential by burying more aromatic residues at the 3B3-gp120 interface and by indirect stabilization of intramolecular contacts of the core framework residues between the VL and VH domains possibly through more favorable entropic effect through the expulsion of water.

  12. 3D printing meets computational astrophysics: deciphering the structure of η Carinae's inner colliding winds

    NASA Astrophysics Data System (ADS)

    Madura, T. I.; Clementel, N.; Gull, T. R.; Kruip, C. J. H.; Paardekooper, J.-P.

    2015-06-01

    We present the first 3D prints of output from a supercomputer simulation of a complex astrophysical system, the colliding stellar winds in the massive (≳120 M⊙), highly eccentric (e ˜ 0.9) binary star system η Carinae. We demonstrate the methodology used to incorporate 3D interactive figures into a PDF (Portable Document Format) journal publication and the benefits of using 3D visualization and 3D printing as tools to analyse data from multidimensional numerical simulations. Using a consumer-grade 3D printer (MakerBot Replicator 2X), we successfully printed 3D smoothed particle hydrodynamics simulations of η Carinae's inner (r ˜ 110 au) wind-wind collision interface at multiple orbital phases. The 3D prints and visualizations reveal important, previously unknown `finger-like' structures at orbital phases shortly after periastron (φ ˜ 1.045) that protrude radially outwards from the spiral wind-wind collision region. We speculate that these fingers are related to instabilities (e.g. thin-shell, Rayleigh-Taylor) that arise at the interface between the radiatively cooled layer of dense post-shock primary-star wind and the fast (3000 km s-1), adiabatic post-shock companion-star wind. The success of our work and easy identification of previously unrecognized physical features highlight the important role 3D printing and interactive graphics can play in the visualization and understanding of complex 3D time-dependent numerical simulations of astrophysical phenomena.

  13. Syntheses and structural characterization of mercury (II) coordination polymers with neutral bidentate flexible pyrazole-based ligands

    NASA Astrophysics Data System (ADS)

    Lalegani, Arash; Khaledi Sardashti, Mohammad; Salavati, Hossein; Asadi, Amin; Gajda, Roman; Woźniak, Krzysztof

    2016-03-01

    Mercury(II) coordination compounds [Hg(μ-bbd)(μ-SCN)4]n(1) and [Hg(bpp)(SCN)2] (2) were synthesized by using the neutral flexible bidentate N-donor ligands 1,4-bis(3,5-dimethypyrazol-1-yl)butane (bbd) and 1,3-bis(3,5-dimethylpyrazolyl)propane (bpp), NCS- ligand and appropriate mercury(II) salts. Compound 1 forms a polymeric network with moieties which are connected by SCN groups and the mercury ions present as HgN3S2 trigonal bipyramides. The crystal structure of 2 is build of monomers and the mercury(II) ion adopts an HgN2S2 tetrahedral geometry. In the complex 1, each bbd acts as bridging ligand connecting Hg(μ-SCN)4 ions, while in the complex 2, the bpp ligand is coordinated to an mercury(II) ion in a cyclic-bidentate fashion forming an eight-membered metallocyclic ring. Moreover, in the tetrahedral structure of 2, the neutral molecules form a 1D chain structure through the C-H···N hydrogen bonds, whereas in 1 no hydrogen bonds are observed. Coordination compounds 1 and 2 have been characterized by infrared spectroscopy, elemental analyses and single-crystal X-ray diffraction.

  14. Structure of HIV-1 gp120 V1/V2 domain with broadly neutralizing antibody PG9

    SciTech Connect

    McLellan, Jason S.; Pancera, Marie; Carrico, Chris; Gorman, Jason; Julien, Jean-Philippe; Khayat, Reza; Louder, Robert; Pejchal, Robert; Sastry, Mallika; Dai, Kaifan; O’Dell, Sijy; Patel, Nikita; Shahzad-ul-Hussan, Syed; Yang, Yongping; Zhang, Baoshan; Zhou, Tongqing; Zhu, Jiang; Boyington, Jeffrey C.; Chuang, Gwo-Yu; Diwanji, Devan; Georgiev, Ivelin; Kwon, Young Do; Lee, Doyung; Louder, Mark K.; Moquin, Stephanie; Schmidt, Stephen D.; Yang, Zhi-Yong; Bonsignori, Mattia; Crump, John A.; Kapiga, Saidi H.; Sam, Noel E.; Haynes, Barton F.; Burton, Dennis R.; Koff, Wayne C.; Walker, Laura M.; Phogat, Sanjay; Wyatt, Richard; Orwenyo, Jared; Wang, Lai-Xi; Arthos, James; Bewley, Carole A.; Mascola, John R.; Nabel, Gary J.; Schief, William R.; Ward, Andrew B.; Wilson, Ian A.; Kwong, Peter D.

    2012-12-13

    Variable regions 1 and 2 (V1/V2) of human immunodeficiency virus-1 (HIV-1) gp120 envelope glycoprotein are critical for viral evasion of antibody neutralization, and are themselves protected by extraordinary sequence diversity and N-linked glycosylation. Human antibodies such as PG9 nonetheless engage V1/V2 and neutralize 80% of HIV-1 isolates. Here we report the structure of V1/V2 in complex with PG9. V1/V2 forms a four-stranded {beta}-sheet domain, in which sequence diversity and glycosylation are largely segregated to strand-connecting loops. PG9 recognition involves electrostatic, sequence-independent and glycan interactions: the latter account for over half the interactive surface but are of sufficiently weak affinity to avoid autoreactivity. The structures of V1/V2-directed antibodies CH04 and PGT145 indicate that they share a common mode of glycan penetration by extended anionic loops. In addition to structurally defining V1/V2, the results thus identify a paradigm of antibody recognition for highly glycosylated antigens, which - with PG9 - involves a site of vulnerability comprising just two glycans and a strand.

  15. Structure of HIV-1 gp120 V1/V2 domain with broadly neutralizing antibody PG9

    PubMed Central

    McLellan, Jason S.; Pancera, Marie; Carrico, Chris; Gorman, Jason; Julien, Jean-Philippe; Khayat, Reza; Louder, Robert; Pejchal, Robert; Sastry, Mallika; Dai, Kaifan; O’Dell, Sijy; Patel, Nikita; Shahzad-ul-Hussan, Syed; Yang, Yongping; Zhang, Baoshan; Zhou, Tongqing; Zhu, Jiang; Boyington, Jeffrey C.; Chuang, Gwo-Yu; Diwanji, Devan; Georgiev, Ivelin; Kwon, Young Do; Lee, Doyung; Louder, Mark K.; Moquin, Stephanie; Schmidt, Stephen D.; Yang, Zhi-Yong; Bonsignori, Mattia; Crump, John A.; Kapiga, Saidi H.; Sam, Noel E.; Haynes, Barton F.; Burton, Dennis R.; Koff, Wayne C.; Walker, Laura M.; Phogat, Sanjay; Wyatt, Richard; Orwenyo, Jared; Wang, Lai-Xi; Arthos, James; Bewley, Carole A.; Mascola, John R.; Nabel, Gary J.; Schief, William R.; Ward, Andrew B.; Wilson, Ian A.; Kwong, Peter D.

    2012-01-01

    Variable regions 1 and 2 (V1/V2) of human immunodeficiency virus-1 (HIV-1) gp120 envelope glycoprotein are critical for viral evasion of antibody neutralization, and are themselves protected by extraordinary sequence diversity and N-linked glycosylation. Human antibodies such as PG9 nonetheless engage V1/V2 and neutralize 80% of HIV-1 isolates. Here we report the structure of V1/V2 in complex with PG9. V1/V2 forms a four-stranded β-sheet domain, in which sequence diversity and glycosylation are largely segregated to strand-connecting loops. PG9 recognition involves electrostatic, sequence-independent and glycan interactions: the latter account for over half the interactive surface but are of sufficiently weak affinity to avoid autoreactivity. The structures of V1/V2-directed antibodies CH04 and PGT145 indicate that they share a common mode of glycan penetration by extended anionic loops. In addition to structurally defining V1/V2, the results thus identify a paradigm of antibody recognition for highly glycosylated antigens, which—with PG9—involves a site of vulnerability comprising just two glycans and a strand. PMID:22113616

  16. NREL Wind Turbine Blade Structural Testing of the Modular Wind Energy MW45 Blade: Cooperative Research and Development Final Report, CRADA Number CRD-09-354

    SciTech Connect

    Hughes, S.

    2012-05-01

    This CRADA was a purely funds-in CRADA with Modular Wind Energy (MWE). MWE had a need to perform full-scale testing of a 45-m wind turbine blade. NREL/NWTC provided the capabilities, facilities, and equipment to test this large-scale MWE wind turbine blade. Full-scale testing is required to demonstrate the ability of the wind turbine blade to withstand static design load cases and demonstrate the fatigue durability. Structural testing is also necessary to meet international blade testing certification requirements. Through this CRADA, MWE would obtain test results necessary for product development and certification, and NREL would benefit by working with an industrial partner to better understand the unique test requirements for wind turbine blades with advanced structural designs.

  17. Models of Solar Wind Structures and Their Interaction with the Earth's Space Environment

    NASA Astrophysics Data System (ADS)

    Watermann, J.; Wintoft, P.; Sanahuja, B.; Saiz, E.; Poedts, S.; Palmroth, M.; Milillo, A.; Metallinou, F.-A.; Jacobs, C.; Ganushkina, N. Y.; Daglis, I. A.; Cid, C.; Cerrato, Y.; Balasis, G.; Aylward, A. D.; Aran, A.

    2009-11-01

    The discipline of “Space Weather” is built on the scientific foundation of solar-terrestrial physics but with a strong orientation toward applied research. Models describing the solar-terrestrial environment are therefore at the heart of this discipline, for both physical understanding of the processes involved and establishing predictive capabilities of the consequences of these processes. Depending on the requirements, purely physical models, semi-empirical or empirical models are considered to be the most appropriate. This review focuses on the interaction of solar wind disturbances with geospace. We cover interplanetary space, the Earth’s magnetosphere (with the exception of radiation belt physics), the ionosphere (with the exception of radio science), the neutral atmosphere and the ground (via electromagnetic induction fields). Space weather relevant state-of-the-art physical and semi-empirical models of the various regions are reviewed. They include models for interplanetary space, its quiet state and the evolution of recurrent and transient solar perturbations (corotating interaction regions, coronal mass ejections, their interplanetary remnants, and solar energetic particle fluxes). Models of coupled large-scale solar wind-magnetosphere-ionosphere processes (global magnetohydrodynamic descriptions) and of inner magnetosphere processes (ring current dynamics) are discussed. Achievements in modeling the coupling between magnetospheric processes and the neutral and ionized upper and middle atmospheres are described. Finally we mention efforts to compile comprehensive and flexible models from selections of existing modules applicable to particular regions and conditions in interplanetary space and geospace.

  18. OBSERVATIONAL EVIDENCE OF A CORONAL MASS EJECTION DISTORTION DIRECTLY ATTRIBUTABLE TO A STRUCTURED SOLAR WIND

    SciTech Connect

    Savani, N. P.; Owens, M. J.; Forsyth, R. J.; Rouillard, A. P.; Davies, J. A.

    2010-05-01

    We present the first observational evidence of the near-Sun distortion of the leading edge of a coronal mass ejection (CME) by the ambient solar wind into a concave structure. On 2007 November 14, a CME was observed by coronagraphs onboard the STEREO-B spacecraft, possessing a circular cross section. Subsequently the CME passed through the field of view of the STEREO-B Heliospheric Imagers where the leading edge was observed to distort into an increasingly concave structure. The CME observations are compared to an analytical flux rope model constrained by a magnetohydrodynamic solar wind solution. The resultant bimodal speed profile is used to kinematically distort a circular structure that replicates the initial shape of the CME. The CME morphology is found to change rapidly over a relatively short distance. This indicates an approximate radial distance in the heliosphere where the solar wind forces begin to dominate over the magnetic forces of the CME influencing the shape of the CME.

  19. Laser neutralization

    SciTech Connect

    Peterson, O.G.

    1986-06-17

    Laser photodetachment of the excess electron to neutralize relativistic ions offers many advantages over the more conventional collisional methods using gases or thin foils as the neutralization agents. Probably the two most important advantages of laser photodetachment are the generation of a compact and low divergence beam, and the production of intense neutral beams at very high efficiency (approximately 90%). The high intensities or high current densities of the neutral beam result from the fixed maximum divergence that can be added to the beam by photodetachment of the charge using laser intensity of fixed wavelength and incident angle. The high neutralization efficiency is possible because there is no theoretical maximum to the neutralization efficiency, although higher efficiencies require higher laser powers and, therefore, costs. Additional advantages include focusability of the laser light onto the ion beam to maximize its efficacy. There certainly is no residual gas left in the particle beam path as is typical with gas neutralizers. The photodetachment process leaves the neutral atoms in the ground state so there is no excited state fluorescence to interfere with the subsequent beam sensing. Finally, since the beams to be neutralized are very high powered, for a large range of neutralization efficiencies the neutral beam can be increased more by increasing the power to the laser neutralizer than by adding an equal amount of power to the primary accelerator. 26 figs.

  20. The Structure of Magnetocentrifugal Jets and Winds I. Steady Mass Loading

    SciTech Connect

    Anderson, J.

    2004-12-15

    We present the results of a series of time-dependent numerical simulations of cold, magnetocentrifugally launched winds from accretion disks. The goal of this study is to determine how the mass loading from the disk affects the structure and dynamics of the wind for a given distribution of magnetic field. Our simulations span four and half decades of mass loading; in the context of a disk with a launching region from 0.1 AU to 1.0 AU around a 1M{circle_dot} star and a field strength of about 20 G at the inner disk edge, this amounts to mass loss rates of 1 x 10{sup -9} - 3 x 10{sup -5} M{circle_dot} yr{sup -1} from each side of the disk. We find that, as expected intuitively, the degree of collimation of the wind increases with mass loading; however even the ''lightest'' wind simulated is significantly collimated compared with the force-free magnetic configuration of the same magnetic flux distribution at the launching surface, which becomes radial at large distances. The implication is that for flows from young stellar objects a radial field approximation is inappropriate. Surprisingly, the terminal velocity of the wind and the magnetic lever arm are still well-described by the analytical solutions for a radial field geometry. We also find that the isodensity contours and Alfven surface are very nearly self-similar in mass loading. The wind becomes unsteady above some critical mass loading rate. The exact value of the critical rate depends on the (small) velocity with which we inject the material into the wind. For a small enough injection speed, we are able to obtain the first examples of a class of heavily-loaded magnetocentrifugal winds with magnetic fields completely dominated by the toroidal component all the way to the launching surface. The stability of such toroidally dominated winds in 3D will be the subject of a future investigation.

  1. Structural basis of clade-specific HIV-1 neutralization by humanized anti-V3 monoclonal antibody KD-247

    PubMed Central

    Kirby, Karen A.; Ong, Yee Tsuey; Hachiya, Atsuko; Laughlin, Thomas G.; Chiang, Leslie A.; Pan, Yun; Moran, Jennifer L.; Marchand, Bruno; Singh, Kamalendra; Gallazzi, Fabio; Quinn, Thomas P.; Yoshimura, Kazuhisa; Murakami, Toshio; Matsushita, Shuzo; Sarafianos, Stefan G.

    2015-01-01

    Humanized monoclonal antibody KD-247 targets the Gly312-Pro313-Gly314-Arg315 arch of the third hypervariable (V3) loop of the HIV-1 surface glycoprotein. It potently neutralizes many HIV-1 clade B isolates, but not of other clades. To understand the molecular basis of this specificity, we solved a high-resolution (1.55 Å) crystal structure of the KD-247 antigen binding fragment and examined the potential interactions with various V3 loop targets. Unlike most antibodies, KD-247 appears to interact with its target primarily through light chain residues. Several of these interactions involve Arg315 of the V3 loop. To evaluate the role of light chain residues in the recognition of the V3 loop, we generated 20 variants of KD-247 single-chain variable fragments with mutations in the antigen-binding site. Purified proteins were assessed for V3 loop binding using AlphaScreen technology and for HIV-1 neutralization. Our data revealed that recognition of the clade-specificity defining residue Arg315 of the V3 loop is based on a network of interactions that involve TyrL32, TyrL92, and AsnL27d that directly interact with Arg315, thus elucidating the molecular interactions of KD-247 with its V3 loop target.—Kirby, K. A., Ong, Y. T., Hachiya, A., Laughlin, T. G., Chiang, L. A., Pan, Y., Moran, J. L., Marchand, B., Singh, K., Gallazzi, F., Quinn, T. P., Yoshimura, K., Murakami, T., Matsushita, S., Sarafianos, S. G. Structural basis of clade-specific HIV-1 neutralization by humanized anti-V3 monoclonal antibody KD-247. PMID:25351987

  2. Elastic dynamics of a complete wind turbine structure: Theoretical development

    NASA Astrophysics Data System (ADS)

    Lobitz, D. W.; Arguello, J. G.; Veers, P. S.

    A pseudo-linear formulation of the equations of motion for analyzing elastic bodies which undergo large rotations relative to one another with an emphasis on its application to horizontal axis wind turbines (HAWT) is developed. This procedure greatly simplifies the computational aspects of the solution algorithm over the nonlinear alternatives and should yield a significant improvement in computer speed. Additional speed can be achieved by ordering the nodes such that a minimum bandwidth can be realized (leading to approximately 64 multiplications per degree of freedom per solution step). The formulation utilizes a set of nested moving coordinate systems, each of which is loosely tied to one of the elastic bodies such that the displacements in the body relative to its coordinate system remain small. The formulation also includes a scheme for handling the nonlinear geometric stiffness that occurs in the blades as a result of the centrifugal loads in a pseudo-linear fashion.

  3. Structural and molecular basis for Ebola virus neutralization by protective human antibodies.

    PubMed

    Misasi, John; Gilman, Morgan S A; Kanekiyo, Masaru; Gui, Miao; Cagigi, Alberto; Mulangu, Sabue; Corti, Davide; Ledgerwood, Julie E; Lanzavecchia, Antonio; Cunningham, James; Muyembe-Tamfun, Jean Jacques; Baxa, Ulrich; Graham, Barney S; Xiang, Ye; Sullivan, Nancy J; McLellan, Jason S

    2016-03-18

    Ebola virus causes hemorrhagic fever with a high case fatality rate for which there is no approved therapy. Two human monoclonal antibodies, mAb100 and mAb114, in combination, protect nonhuman primates against all signs of Ebola virus disease, including viremia. Here, we demonstrate that mAb100 recognizes the base of the Ebola virus glycoprotein (GP) trimer, occludes access to the cathepsin-cleavage loop, and prevents the proteolytic cleavage of GP that is required for virus entry. We show that mAb114 interacts with the glycan cap and inner chalice of GP, remains associated after proteolytic removal of the glycan cap, and inhibits binding of cleaved GP to its receptor. These results define the basis of neutralization for two protective antibodies and may facilitate development of therapies and vaccines.

  4. Estimation of the refractive index structure characteristic of air from coherent Doppler wind lidar data.

    PubMed

    Banakh, V A; Smalikho, I N; Rahm, S

    2014-08-01

    A technique is proposed for estimating the refractive index structure characteristic of air from data of a coherent Doppler wind lidar. The proposed technique is tested in atmospheric experiments. Time profiles of the structure characteristic in the atmospheric surface layer are obtained and compared with the time profiles of the dissipation rate of the kinetic energy of turbulence obtained from the same lidar data. It is shown in this way that coherent lidars can be used for investigating not only wind turbulence, but also temperature turbulence.

  5. Study on steady state wind and turbulence environments. [structure of wakes near buildings

    NASA Technical Reports Server (NTRS)

    Brundidge, K. C.

    1977-01-01

    The structure of wakes and how this structure is related to the size and shape of buildings and other obstacles, and to ambient winds, was investigated. Mean values of natural atmospheric flow were obtained and used in conjunction with theoretical relationships developed by dimensional analysis to establish a model of the flow in the wake. Results indicate that conventional and V/STOL aircraft passing through the wake during takeoff and landing would experience not only a change in turbulence level, but also a change in mean wind speed of a magnitude roughly equivalent to that of the eddy components.

  6. A complete tropical cyclone radial wind structure model and comprehensive comparison with observations

    NASA Astrophysics Data System (ADS)

    Chavas, D. R.; Emanuel, K.; Lin, N.

    2014-12-01

    This work develops a simple model for the complete radial structure of the tropical cyclone wind field at the top of the boundary layer. The model is constructed by mathematically merging existing theoretical solutions for the radial wind structure in the inner convecting and outer non-convecting regions. The model is then evaluated against three observational datasets. First, the outer solution is tested against a global database from the QuikSCAT satellite (1999-2009) and found to reproduce the characteristic wind structure of tropical cyclones at large radii where convection is absent, suggesting that it successfully captures the physics of this region. Second, the inner solution is tested against the HWind database (2004-2012) for the Atlantic and East Pacific basins and are shown to credibly represent the inner-core structure but substantially underestimate wind speeds at large radii. The complete model is then shown to largely rectify this underestimation, particularly at higher intensities. Finally, model variability is compared with the Extended Best Track dataset (1988-2013). The complete model exhibits two modes of variability corresponding to the independent variations in storm size and in inner structure that mirror that observed in nature, including the independent variability of the inner and outer regions of tropical cyclones. More broadly, the model provides insight into clear definitions of the terms "size" and "structure" and their respective, independent variabilities.

  7. Structural basis for diverse N-glycan recognition by HIV-1-neutralizing V1-V2-directed antibody PG16.

    PubMed

    Pancera, Marie; Shahzad-Ul-Hussan, Syed; Doria-Rose, Nicole A; McLellan, Jason S; Bailer, Robert T; Dai, Kaifan; Loesgen, Sandra; Louder, Mark K; Staupe, Ryan P; Yang, Yongping; Zhang, Baoshan; Parks, Robert; Eudailey, Joshua; Lloyd, Krissey E; Blinn, Julie; Alam, S Munir; Haynes, Barton F; Amin, Mohammed N; Wang, Lai-Xi; Burton, Dennis R; Koff, Wayne C; Nabel, Gary J; Mascola, John R; Bewley, Carole A; Kwong, Peter D

    2013-07-01

    HIV-1 uses a diverse N-linked-glycan shield to evade recognition by antibody. Select human antibodies, such as the clonally related PG9 and PG16, recognize glycopeptide epitopes in the HIV-1 V1-V2 region and penetrate this shield, but their ability to accommodate diverse glycans is unclear. Here we report the structure of antibody PG16 bound to a scaffolded V1-V2, showing an epitope comprising both high mannose-type and complex-type N-linked glycans. We combined structure, NMR and mutagenesis analyses to characterize glycan recognition by PG9 and PG16. Three PG16-specific residues, arginine, serine and histidine (RSH), were critical for binding sialic acid on complex-type glycans, and introduction of these residues into PG9 produced a chimeric antibody with enhanced HIV-1 neutralization. Although HIV-1-glycan diversity facilitates evasion, antibody somatic diversity can overcome this and can provide clues to guide the design of modified antibodies with enhanced neutralization.

  8. Crystal structure of the Hendra virus attachment G glycoprotein bound to a potent cross-reactive neutralizing human monoclonal antibody.

    PubMed

    Xu, Kai; Rockx, Barry; Xie, Yihu; DeBuysscher, Blair L; Fusco, Deborah L; Zhu, Zhongyu; Chan, Yee-Peng; Xu, Yan; Luu, Truong; Cer, Regina Z; Feldmann, Heinz; Mokashi, Vishwesh; Dimitrov, Dimiter S; Bishop-Lilly, Kimberly A; Broder, Christopher C; Nikolov, Dimitar B

    2013-01-01

    The henipaviruses, represented by Hendra (HeV) and Nipah (NiV) viruses are highly pathogenic zoonotic paramyxoviruses with uniquely broad host tropisms responsible for repeated outbreaks in Australia, Southeast Asia, India and Bangladesh. The high morbidity and mortality rates associated with infection and lack of licensed antiviral therapies make the henipaviruses a potential biological threat to humans and livestock. Henipavirus entry is initiated by the attachment of the G envelope glycoprotein to host cell membrane receptors. Previously, henipavirus-neutralizing human monoclonal antibodies (hmAb) have been isolated using the HeV-G glycoprotein and a human naïve antibody library. One cross-reactive and receptor-blocking hmAb (m102.4) was recently demonstrated to be an effective post-exposure therapy in two animal models of NiV and HeV infection, has been used in several people on a compassionate use basis, and is currently in development for use in humans. Here, we report the crystal structure of the complex of HeV-G with m102.3, an m102.4 derivative, and describe NiV and HeV escape mutants. This structure provides detailed insight into the mechanism of HeV and NiV neutralization by m102.4, and serves as a blueprint for further optimization of m102.4 as a therapeutic agent and for the development of entry inhibitors and vaccines.

  9. Cryo-EM structures elucidate neutralizing mechanisms of anti-chikungunya human monoclonal antibodies with therapeutic activity

    PubMed Central

    Long, Feng; Fong, Rachel H.; Austin, Stephen K.; Chen, Zhenguo; Klose, Thomas; Fokine, Andrei; Liu, Yue; Porta, Jason; Sapparapu, Gopal; Akahata, Wataru; Doranz, Benjamin J.; Crowe, James E.; Diamond, Michael S.; Rossmann, Michael G.

    2015-01-01

    Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that causes severe acute and chronic disease in humans. Although highly inhibitory murine and human monoclonal antibodies (mAbs) have been generated, the structural basis of their neutralizing activity remains poorly characterized. Here, we determined the cryo-EM structures of chikungunya virus-like particles complexed with antibody fragments (Fab) of two highly protective human mAbs, 4J21 and 5M16, that block virus fusion with host membranes. Both mAbs bind primarily to sites within the A and B domains, as well as to the B domain’s β-ribbon connector of the viral glycoprotein E2. The footprints of these antibodies on the viral surface were consistent with results from loss-of-binding studies using an alanine scanning mutagenesis-based epitope mapping approach. The Fab fragments stabilized the position of the B domain relative to the virus, particularly for the complex with 5M16. This finding is consistent with a mechanism of neutralization in which anti-CHIKV mAbs that bridge the A and B domains impede movement of the B domain away from the underlying fusion loop on the E1 glycoprotein and therefore block the requisite pH-dependent fusion of viral and host membranes. PMID:26504196

  10. Structural basis for diverse N-glycan recognition by HIV-1-neutralizing V1-V2-directed antibody PG16

    SciTech Connect

    Pancera, Marie; Shahzad-ul-Hussan, Syed; Doria-Rose, Nicole A.; McLellan, Jason S.; Bailer, Robert T.; Dai, Kaifan; Loesgen, Sandra; Louder, Mark K.; Staupe, Ryan P.; Yang, Yongping; Zhang, Baoshan; Parks, Robert; Eudailey, Joshua; Lloyd, Krissey E.; Blinn, Julie; Alam, S. Munir; Haynes, Barton F.; Amin, Mohammed N.; Wang, Lai-Xi; Burton, Dennis R.; Koff, Wayne C.; Nabel, Gary J.; Mascola, John R.; Bewley, Carole A; Kwong, Peter D.

    2013-08-05

    HIV-1 uses a diverse N-linked-glycan shield to evade recognition by antibody. Select human antibodies, such as the clonally related PG9 and PG16, recognize glycopeptide epitopes in the HIV-1 V1–V2 region and penetrate this shield, but their ability to accommodate diverse glycans is unclear. Here we report the structure of antibody PG16 bound to a scaffolded V1–V2, showing an epitope comprising both high mannose–type and complex-type N-linked glycans. We combined structure, NMR and mutagenesis analyses to characterize glycan recognition by PG9 and PG16. Three PG16-specific residues, arginine, serine and histidine (RSH), were critical for binding sialic acid on complex-type glycans, and introduction of these residues into PG9 produced a chimeric antibody with enhanced HIV-1 neutralization. Although HIV-1–glycan diversity facilitates evasion, antibody somatic diversity can overcome this and can provide clues to guide the design of modified antibodies with enhanced neutralization.

  11. Cryo-EM structures elucidate neutralizing mechanisms of anti-chikungunya human monoclonal antibodies with therapeutic activity.

    PubMed

    Long, Feng; Fong, Rachel H; Austin, Stephen K; Chen, Zhenguo; Klose, Thomas; Fokine, Andrei; Liu, Yue; Porta, Jason; Sapparapu, Gopal; Akahata, Wataru; Doranz, Benjamin J; Crowe, James E; Diamond, Michael S; Rossmann, Michael G

    2015-11-10

    Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that causes severe acute and chronic disease in humans. Although highly inhibitory murine and human monoclonal antibodies (mAbs) have been generated, the structural basis of their neutralizing activity remains poorly characterized. Here, we determined the cryo-EM structures of chikungunya virus-like particles complexed with antibody fragments (Fab) of two highly protective human mAbs, 4J21 and 5M16, that block virus fusion with host membranes. Both mAbs bind primarily to sites within the A and B domains, as well as to the B domain's β-ribbon connector of the viral glycoprotein E2. The footprints of these antibodies on the viral surface were consistent with results from loss-of-binding studies using an alanine scanning mutagenesis-based epitope mapping approach. The Fab fragments stabilized the position of the B domain relative to the virus, particularly for the complex with 5M16. This finding is consistent with a mechanism of neutralization in which anti-CHIKV mAbs that bridge the A and B domains impede movement of the B domain away from the underlying fusion loop on the E1 glycoprotein and therefore block the requisite pH-dependent fusion of viral and host membranes. PMID:26504196

  12. Full-scale tests of wind effects on a long span roof structure

    NASA Astrophysics Data System (ADS)

    Fu, Jiyang; Zheng, Qingxing; Wu, Jiurong; Xu, An

    2015-06-01

    Full-scale measurements are regarded as the most reliable method to evaluate wind effects on large buildings and structures. Some selected results are presented in this paper from the full-scale measurement of wind effects on a long-span steel roof structure during the passage of Typhoon Fanapi. Some field data, including wind speed and direction, acceleration responses, etc., were continuously and simultaneously recorded during the passage of the typhoon. Comprehensive analysis of the measured data is conducted to evaluate the typhoon-generated wind characteristics and its effects on a long-span steel roof. The first four natural frequencies and their vibration mode shapes of the Guangzhou International Sports Arena (GISA) roof are evaluated by the stochastic subspace identification (SSI) method and comparisons with those from finite element (FE) analysis are made. Meanwhile, damping ratios of the roof are also identified by the SSI method and compared with those identified by the random decrement method; the amplitude-dependent damping behaviors are also discussed. The fullscale measurement results are further compared with the corresponding wind tunnel test results to evaluate its reliability. The results obtained from this study are valuable for academic and professional engineers involved in the design of large-span roof structures.

  13. Structural effects of unsteady aerodynamic forces on horizontal-axis wind turbines

    SciTech Connect

    Miller, M.S.; Shipley, D.E.

    1994-08-01

    Due to its renewable nature and abundant resources, wind energy has the potential to fulfill a large portion of this nation`s energy needs. The simplest means of utilizing wind energy is through the use of downwind, horizontal-axis wind turbines (HAWT) with fixed-pitch rotors. This configuration regulates the peak power by allowing the rotor blade to aerodynamically stall. The stall point, the point of maximum coefficient of lift, is currently predicted using data obtained from wind tunnel tests. Unfortunately, these tests do not accurately simulate conditions encountered in the field. Flow around the tower and nacelle coupled with inflow turbulence and rotation of the turbine blades create unpredicted aerodynamic forces. Dynamic stall is hypothesized to occur. Such aerodynamic loads are transmitted into the rotor and tower causing structural resonance that drastically reduces the design lifetime of the wind turbine. The current method of alleviating this problem is to structurally reinforce the tower and blades. However, this adds unneeded mass and, therefore, cost to the turbines. A better understanding of the aerodynamic forces and the manner in which they affect the structure would allow for the design of more cost effective and durable wind turbines. Data compiled by the National Renewable Energy Laboratory (NREL) for a downwind HAWT with constant chord, untwisted, fixed-pitch rotors is analyzed. From these data, the actual aerodynamic characteristics of the rotor are being portrayed and the potential effects upon the structure can for the first time be fully analyzed. Based upon their understanding, solutions to the problem of structural resonance are emerging.

  14. Structural effects of unsteady aerodynamic forces on horizontal-axis wind turbines

    NASA Astrophysics Data System (ADS)

    Miller, M. S.; Shipley, D. E.

    1994-08-01

    Due to its renewable nature and abundant resources, wind energy has the potential to fulfill a large portion of this nation's energy needs. The simplest means of utilizing wind energy is through the use of downwind, horizontal-axis wind turbines (HAWT) with fixed-pitch rotors. This configuration regulates the peak power by allowing the rotor blade to aerodynamically stall. The stall point, the point of maximum coefficient of lift, is currently predicted using data obtained from wind tunnel tests. Unfortunately, these tests do not accurately simulate conditions encountered in the field. Flow around the tower and nacelle coupled with inflow turbulence and rotation of the turbine blades create unpredicted aerodynamic forces. Dynamic stall is hypothesized to occur. Such aerodynamic loads are transmitted into the rotor and tower causing structural resonance that drastically reduces the design lifetime of the wind turbine. The current method of alleviating this problem is to structurally reinforce the tower and blades. However, this adds unneeded mass and, therefore, cost to the turbines. A better understanding of the aerodynamic forces and the manner in which they affect the structure would allow for the design of more cost effective and durable wind turbines. Data compiled by the National Renewable Energy Laboratory (NREL) for a downwind HAWT with constant chord, untwisted, fixed-pitch rotors is analyzed. From these data, the actual aerodynamic characteristics of the rotor are being portrayed and the potential effects upon the structure can for the first time be fully analyzed. Based upon their understanding, solutions to the problem of structural resonance are emerging.

  15. Large fog collectors: New strategies for collection efficiency and structural response to wind pressure

    NASA Astrophysics Data System (ADS)

    Holmes, Robert; Rivera, Juan de Dios; de la Jara, Emilio

    2015-01-01

    Most studies of large fog collectors (LFC) have focused on the collection efficiency, the amount of water collected, or economic and social aspects, but have not addressed the effects of strong winds on the system. Wind pressure is directly related to fog water collection efficiency but on the other hand may cause serious damage on the structure of LFCs. This study focuses in the effects of wind pressure on the components of the LFC as an integral system, and the ways to face strong winds with no significant damage. For this purpose we analysed cases of mechanical failure of LFCs both in our experimental station at Peña Blanca in Chile and elsewhere. The effects of wind pressure can be described as a sequence of physical processes, starting with the mesh deformation as a way of adapting to the induced stresses. For a big enough pressure, local stress concentrations generate a progressive rupture of the mesh. In cases where the mesh is sufficiently strong the wind force causes the partial or total collapse of the structure. Usually the weakest part is the mesh, especially close to where it is attached to the structure. The way the mesh is attached to the frame or cable of the structure is particularly important since it can induce significant stress concentrations. Mesh failure before the structure failure may be considered as a mechanical fuse, since it is cheaper to repair. However, more practical mechanical fuses can be conceived. In relation to structural performance and water collection efficiency, we propose a new design strategy that considers a three-dimensional spatial display of the collection screen, oblique incidence angle of wind on mesh and small mesh area between the supporting frame. The proposed design strategies consider both the wind pressure on mesh and structure and the collection efficiency as an integral solution for the LFC. These new design strategies are the final output of this research. Applying these strategies a multi-funnel LFC is

  16. DENGUE VIRUS. Cryo-EM structure of an antibody that neutralizes dengue virus type 2 by locking E protein dimers.

    PubMed

    Fibriansah, Guntur; Ibarra, Kristie D; Ng, Thiam-Seng; Smith, Scott A; Tan, Joanne L; Lim, Xin-Ni; Ooi, Justin S G; Kostyuchenko, Victor A; Wang, Jiaqi; de Silva, Aravinda M; Harris, Eva; Crowe, James E; Lok, Shee-Mei

    2015-07-01

    There are four closely-related dengue virus (DENV) serotypes. Infection with one serotype generates antibodies that may cross-react and enhance infection with other serotypes in a secondary infection. We demonstrated that DENV serotype 2 (DENV2)-specific human monoclonal antibody (HMAb) 2D22 is therapeutic in a mouse model of antibody-enhanced severe dengue disease. We determined the cryo-electron microscopy (cryo-EM) structures of HMAb 2D22 complexed with two different DENV2 strains. HMAb 2D22 binds across viral envelope (E) proteins in the dimeric structure, which probably blocks the E protein reorganization required for virus fusion. HMAb 2D22 "locks" two-thirds of or all dimers on the virus surface, depending on the strain, but neutralizes these DENV2 strains with equal potency. The epitope defined by HMAb 2D22 is a potential target for vaccines and therapeutics. PMID:26138979

  17. Ascent structural wind loads for the National Space Transportation System (NSTS)

    NASA Technical Reports Server (NTRS)

    Smith, O. E.; Adelfang, S. I.; Brown, R. P.

    1988-01-01

    An aerospace vehicle must withstand the design ascent structural load or be within any flight constraint to safely reach orbit. For the NSTS an assessment for flight readiness is made for each mission. This assessment for ascent loads and performance parameters is stated in terms of launch probability derived from samples of Jimsphere wind profiles. For the day of launch operations an allowance is made for the ascent load variability due to the wind profile variability over a 3.5-hour period. This is the current time period required to obtain a Jimsphere measurement and perform a complete load simulation prior to launch time. The load variability is derived from a sample of 3.5-hour Jimsphere wind profile pairs. It is applied as a conditional percentile value given the wind load at 3.5 hours prior to launch time. Probability models are used for these analyses. Application of the univariate, bivariate and conditional forms of the extreme value (Gumbel) probability distribution to the analysis of extreme wind speeds, wind shears and vehicle loads is described.

  18. Structural damage identification in wind turbine blades using piezoelectric active sensing with ultrasonic validation

    SciTech Connect

    Claytor, Thomas N; Ammerman, Curtt N; Park, Gyu Hae; Farinholt, Kevin M; Farrar, Charles R; Atterbury, Marie K

    2010-01-01

    This paper gives a brief overview of a new project at LANL in structural damage identification for wind turbines. This project makes use of modeling capabilities and sensing technology to understand realistic blade loading on large turbine blades, with the goal of developing the technology needed to automatically detect early damage. Several structural health monitoring (SHM) techniques using piezoelectric active materials are being investigated for the development of wireless, low power sensors that interrogate sections of the wind turbine blade using Lamb wave propagation data, frequency response functions (FRFs), and time-series analysis methods. The modeling and sensor research will be compared with extensive experimental testing, including wind tunnel experiments, load and fatigue tests, and ultrasonic scans - on small- to mid-scale turbine blades. Furthermore, this study will investigate the effect of local damage on the global response of the blade by monitoring low-frequency response changes.

  19. Coherent structures and turbulent spectrum in solar wind plasmas

    SciTech Connect

    Sharma, R. P.; Yadav, N.; Kumari, Anju

    2013-08-15

    The present paper investigates the localization of a uniform plane kinetic Alfvén wave (KAW) due to the coupling with the density/magnetic field fluctuations associated with a magnetosonic wave propagating in the transverse direction, i.e., perpendicular to the background magnetic field. To gain the physical insight into this evolution, a simplified analytical model based on the Mathieu equation has also been studied. Numerical method has also been used to analyse the evolution of KAW. The magnetic fluctuation spectrum follows Kolmogorovian scaling above the proton gyroradius scalelength, which is regarded as the inertial range. Below this scale, a steepened spectrum has been obtained in the dispersive range with power law index ∼−2.5, which continues up to the dissipation range. Our results reveal that the proposed mechanism may be an interesting physical mechanism for transferring the energy from larger lengthscales to smaller lengthscales in the solar wind plasmas. Relevance of the present study with Cluster spacecraft observations has also been discussed.

  20. Cassini Ion and Neutral Mass Spectrometer: Enceladus Plume Composition and Structure

    NASA Astrophysics Data System (ADS)

    Waite, J. Hunter; Combi, Michael R.; Ip, Wing-Huen; Cravens, Thomas E.; McNutt, Ralph L.; Kasprzak, Wayne; Yelle, Roger; Luhmann, Janet; Niemann, Hasso; Gell, David; Magee, Brian; Fletcher, Greg; Lunine, Jonathan; Tseng, Wei-Ling

    2006-03-01

    The Cassini spacecraft passed within 168.2 kilometers of the surface above the southern hemisphere at 19:55:22 universal time coordinated on 14 July 2005 during its closest approach to Enceladus. Before and after this time, a substantial atmospheric plume and coma were observed, detectable in the Ion and Neutral Mass Spectrometer (INMS) data set out to a distance of over 4000 kilometers from Enceladus. INMS data indicate that the atmospheric plume and coma are dominated by water, with significant amounts of carbon dioxide, an unidentified species with a mass-to-charge ratio of 28 daltons (either carbon monoxide or molecular nitrogen), and methane. Trace quantities (<1%) of acetylene and propane also appear to be present. Ammonia is present at a level that does not exceed 0.5%. The radial and angular distributions of the gas density near the closest approach, as well as other independent evidence, suggest a significant contribution to the plume from a source centered near the south polar cap, as distinct from a separately measured more uniform and possibly global source observed on the outbound leg of the flyby.

  1. Cassini ion and neutral mass spectrometer: Enceladus plume composition and structure.

    PubMed

    Waite, J Hunter; Combi, Michael R; Ip, Wing-Huen; Cravens, Thomas E; McNutt, Ralph L; Kasprzak, Wayne; Yelle, Roger; Luhmann, Janet; Niemann, Hasso; Gell, David; Magee, Brian; Fletcher, Greg; Lunine, Jonathan; Tseng, Wei-Ling

    2006-03-10

    The Cassini spacecraft passed within 168.2 kilometers of the surface above the southern hemisphere at 19:55:22 universal time coordinated on 14 July 2005 during its closest approach to Enceladus. Before and after this time, a substantial atmospheric plume and coma were observed, detectable in the Ion and Neutral Mass Spectrometer (INMS) data set out to a distance of over 4000 kilometers from Enceladus. INMS data indicate that the atmospheric plume and coma are dominated by water, with significant amounts of carbon dioxide, an unidentified species with a mass-to-charge ratio of 28 daltons (either carbon monoxide or molecular nitrogen), and methane. Trace quantities (<1%) of acetylene and propane also appear to be present. Ammonia is present at a level that does not exceed 0.5%. The radial and angular distributions of the gas density near the closest approach, as well as other independent evidence, suggest a significant contribution to the plume from a source centered near the south polar cap, as distinct from a separately measured more uniform and possibly global source observed on the outbound leg of the flyby.

  2. A New Structural Technique for Examining Ion-Neutral Association in Aqueous Solution

    PubMed Central

    Mason, Philip E.; Neilson, George W.; Price, David L.; Saboungi, Marie-Louise; Brady, John W.

    2013-01-01

    The method of intramolecular coordination number concentration invariance (ICNCI) is used on neutron diffraction with isotopic substitution (NDIS) measurements of aqueous solutions to separate the intra- and intermolecular contributions to the total intensities. Molecular dynamics simulations of corresponding systems are then used to interpret the ICNCI function. It is found that the ICNCI function (characterized by two concentration measurements) is sensitive specifically to intermolecular association and that the molecular dynamics can successfully replicate this function in the cases of the neutral species xylose and pyridine in aqueous solution. ICNCI functions can also be obtained by the addition of a cosolute (such as adding GdmCl or Gdm2SO4 to pyridine solutions). In that case it is found that molecular dynamics can replicate the ICNCI function for the addition of GdmCl to pyridine, but fails to successfully replicate the same function for the addition of Gdm2SO4. This result implies that the interaction of pyridine with guanidinium sulfate is over-estimated in MD these simulations, and is of significant importance to the use of molecular dynamics simulations to elucidate an atomic level understanding of the Hofmeister series. PMID:23795499

  3. Damage estimates from long-term structural analysis of a wind turbine in a US wind farm environment

    SciTech Connect

    Kelley, N.D.; Sutherland, H.J.

    1996-10-01

    Time-domain simulations of the loads on wind energy conversion systems have been hampered in the past by the relatively long computational times for nonlinear structural analysis codes. However, recent advances in both the level of sophistication and computational efficiency of available computer hardware and the codes themselves now permit long-term simulations to be conducted in reasonable times. Thus, these codes provide a unique capability to evaluate the spectral content of the fatigue loads on a turbine. To demonstrate these capabilities, a Micon 65/13 turbine is analyzed using the YawDyn and the ADAMS dynamic analysis codes. The SNLWIND-3D simulator and measured boundary conditions are used to simulate the inflow environment that can be expected during a single, 24-hour period by a turbine residing in Row 41 of a wind farm located in San Gorgonio Pass, California. Also, long-term simulations (up to 8 hours of simulated time) with constant average inflow velocities are used to better define the characteristics of the fatigue load on the turbine. Damage calculations, using the LIFE2 fatigue analysis code and the MSU/DOE fatigue data base for composite materials, are then used to determine minimum simulation times for consistent estimates of service lifetimes.

  4. A 100-kW wind turbine blade dynamics analysis, weight-balance, and structural test results

    NASA Technical Reports Server (NTRS)

    Anderson, W. D.

    1975-01-01

    The results of dynamic analyses, weight and balance tests, static stiffness tests, and structural vibration tests on the 60-foot-long metal blades for the ERDA-NASA 100-kW wind turbine are presented. The metal blades are shown to be free from structural or dynamic resonance at the wind turbine design speed. Aeroelastic instabilities are unlikely to occur within the normal operating range of the wind turbine.

  5. NWTC Researchers Field-Test Advanced Control Turbine Systems to Increase Performance, Decrease Structural Loading of Wind Turbines and Plants

    SciTech Connect

    2015-08-01

    Researchers at the National Renewable Energy Laboratory's (NREL's) National Wind Technology Center (NWTC) are studying component controls, including new advanced actuators and sensors, for both conventional turbines as well as wind plants. This research will help develop innovative control strategies that reduce aerodynamic structural loads and improve performance. Structural loads can cause damage that increase maintenance costs and shorten the life of a turbine or wind plant.

  6. Vertical and Horizontal Wind Structure Prior to and During the 1997/1998 ENSO Event

    NASA Technical Reports Server (NTRS)

    Adamec, David

    1998-01-01

    Analyses of ECMWF and satellite wind products are used to investigate low frequency fluctuations in the wind fields immediately preceding and during the 1997/1998 ENSO event. An extended EOF analysis of the horizontal and vertical wind structure that allows for the study of propagating features indicates that the dominant mode of variability established in the lower levels of the atmosphere is a convergence in the central tropical Pacific. At mid-levels, the westerlies increase with time over most of the equatorial Pacific, and there are closed cyclonic features on either side of the equator. At upper levels, the flow tends to become divergent across the equatorial Pacific, and there is a strong flow from the northwest Pacific across Indonesia that then turns to the west along the equator in the Indian Ocean. The addition of satellite data for improved surface wind estimates reveal that the Indian Ocean winds were anomalously strong during the winter preceding the initiation of the ENSO event. An analysis of the momentum convergence flux at the surface indicates a very strong anomaly 9 months prior to the ENSO event that begins in the western Indian Ocean and propagates to the east, arriving over the Pacific warm pool area coincident with the beginning of the El Nino. Changes in the near surface thermal and water vapor structure over the Indian Ocean during this period will also be discussed.

  7. Statistical Evaluation of the Identified Structural Parameters of an idling Offshore Wind Turbine

    NASA Astrophysics Data System (ADS)

    Kramers, Hendrik C.; van der Valk, Paul L. C.; van Wingerden, Jan-Willem

    2016-09-01

    With the increased need for renewable energy, new offshore wind farms are being developed at an unprecedented scale. However, as the costs of offshore wind energy are still too high, design optimization and new innovations are required for lowering its cost. The design of modern day offshore wind turbines relies on numerical models for estimating ultimate and fatigue loads of the turbines. The dynamic behavior and the resulting structural loading of the turbines is determined for a large part by its structural properties, such as the natural frequencies and damping ratios. Hence, it is important to obtain accurate estimates of these modal properties. For this purpose stochastic subspace identification (SSI), in combination with clustering and statistical evaluation methods, is used to obtain the variance of the identified modal properties of an installed 3.6MW offshore wind turbine in idling conditions. It is found that one is able to obtain confidence intervals for the means of eigenfrequencies and damping ratios of the fore-aft and side-side modes of the wind turbine.

  8. Investigation of the adhesive bonding technology for the insulator structure of EAST neutral beam injector

    SciTech Connect

    Wei, Jiang-Long Li, Jun; Hu, Chun-Dong; Xie, Ya-Hong; Jing, Hao

    2014-07-15

    A key issue on the development of EAST ion source was the junction design of insulator structure, which consists of three insulators and four supporting flanges of electrode grid. Because the ion source is installed on the vertical plane, the insulator structure has to withstand large bending and shear stress due to the gravity of whole ion source. Through a mechanical analysis, it was calculated that the maximum bending normal stress was 0.34 MPa and shear stress was 0.23 MPa on the insulator structure. Due to the advantages of simplicity and high strength, the adhesive bonding technology was applied to the junction of insulator structure. A tensile testing campaign of different junction designs between insulator and supporting flange was performed, and a junction design of stainless steel and fiber enhanced epoxy resin with epoxy adhesive was determined. The insulator structure based on the determined design can satisfy both the requirements of high-voltage holding and mechanical strength.

  9. Simulation of wind effects on tall structures by finite element method

    NASA Astrophysics Data System (ADS)

    Ebrahimi, Masood

    2016-06-01

    In the present study finite element method is used to predict the wind forces on a tall structure. The governing equations of mass and momentum with boundary conditions are solved. The κ- ɛ turbulence model is utilized to calculate the turbulence viscosity. The results are independent from the generated mesh. The numerical results are validated with American Society of Civil Engineering standards.

  10. Influence of coherent mesoscale structures on satellite-based Doppler lidar wind measurements

    NASA Technical Reports Server (NTRS)

    Emmitt, G. D.

    1985-01-01

    The influence of coherent mesoscale structures on satellite based Doppler lidar wind measurements was investigated. Range dependent weighting functions and the single shot SNR of scan angle are examined and a space shuttle lidar experiment which used a fixed beam and rotating shuttle is simulated.

  11. Improvement of neutral beam injection heating efficiency with magnetic field well structures in a tokamak with a low magnetic field

    NASA Astrophysics Data System (ADS)

    Kim, S. K.; Na, D. H.; Lee, J. W.; Yoo, M. G.; Kim, H.-S.; Hwang, Y. S.; Hahm, T. S.; Na, Yong-Su

    2016-10-01

    Magnetic well structures are introduced as an effective means to reduce the prompt loss of fast ions, the so-called first orbit loss from neutral beam injection (NBI), which is beneficial to tokamaks with a low magnetic field strength such as small spherical torus devices. It is found by single-particle analysis that this additional field structure can modify the gradient of the magnetic field to reduce the shift of the guiding center trajectory of the fast ion. This result is verified by a numerical calculation of following the fast ion’s trajectory. We apply this concept to the Versatile Experiment Spherical Torus [1], where NBI is under design for the purpose of achieving high-performance plasma, to evaluate the effect of the magnetic well structure on NBI efficiency. A 1D NBI analysis code and the NUBEAM code are employed for detailed NBI calculations. The simulation results show that the orbit loss can be reduced by 70%-80%, thereby improving the beam efficiency twofold compared with the reference case without the well structure. The well-shaped magnetic field structure in the low-field side can significantly decrease orbit loss by broadening the non-orbit loss region and widening the range of the velocity direction, thus improving the heating efficiency. It is found that this magnetic well can also improve orbit loss during the slowing down process.

  12. Structural characterization of wind-sheared turbulent flow using self-organized mapping

    NASA Astrophysics Data System (ADS)

    Scott, Nicholas V.; Handler, Robert A.

    2016-05-01

    A nonlinear cluster analysis algorithm is used to characterize the spatial structure of a wind-sheared turbulent flow obtained from the direct numerical simulation (DNS) of the three-dimensional temperature and momentum fields. The application of self-organizing mapping to DNS data for data reduction is utilized because of the dimensional similitude in structure between DNS data and remotely sensed hyperspectral and multispectral data where the technique has been used extensively. For the three Reynolds numbers of 150, 180, and 220 used in the DNS, self-organized mapping is successful in the extraction of boundary layer streaky structures from the turbulent temperature and momentum fields. In addition, it preserves the cross-wind scale structure of the streaks exhibited in both fields which loosely scale with the inverse of the Reynolds number. Self-organizing mapping of the along wind component of the helicity density shows a layer of the turbulence field which is spotty suggesting significant direct coupling between the large and small-scale turbulent structures. The spatial correlation of the temperature and momentum fields allows for the possibility of the remote extrapolation of the momentum structure from thermal structure.

  13. An extended structure-function model and its application to the analysis of solar wind intermittency

    NASA Technical Reports Server (NTRS)

    Tu, C.-Y.; Marsch, E.; Rosenbauer, H.

    1995-01-01

    An extended structure-function model is developed by including the new effect in the p-model of Meneveau and Sreenivasan (1987a), i.e., that the averaged energy cascade rate changes with scale, a situation which has been found to prevail in non-fully-developed turbulence in the inner solar wind. This model is useful for the small-scale fluctuations in the inner heliosphere, where the turbulence is not fully developed and cannot be explained quantitatively by any of the previous intermittency turbulence models. With two model parameters, the intrinsic index of the energy spectrum, alpha and the fragmentation fraction p, the model can fit, for the first time, all the observed scaling exponents of the structure functions, which are calculated for time lags ranging from 81 seconds to 0.7 hours from the Helios solar wind data. From the cases we studied we can establish for p neither a clear radial evolution trend, nor a solar-wind-speed, or stream-structure dependence, or a systematic anisotropy for both the flow velocity and magnetic field component fluctuations. Generally, p has values between 0. 7 and 0.8. However, in some cases in low-speed wind p has somewhat higher values for the magnetic components, especially for the radial component. In high-speed wind, the inferred intrinsic spectral indices (alpha) of the velocity and magnetic field components are about equal, while the experimental spectral indices derived from the observed power spectra differ. The magnetic index is somewhat larger than the index of the velocity spectrum. For magnetic fluctuations in both high- and low-speed winds, the intrinsic exponent alpha has values which are near 1.5, while the observed spectral exponent has much higher values.

  14. General asymmetric neutral networks and structure design by genetic algorithms: A learning rule for temporal patterns

    SciTech Connect

    Bornholdt, S.; Graudenz, D.

    1993-07-01

    A learning algorithm based on genetic algorithms for asymmetric neural networks with an arbitrary structure is presented. It is suited for the learning of temporal patterns and leads to stable neural networks with feedback.

  15. Multi-spacecraft observations of heliographic latitude-longitude structure in the solar wind

    NASA Technical Reports Server (NTRS)

    Rhodes, E. J., Jr.; Smith, E. J.

    1981-01-01

    The heliographic latitude-longitude structure of high speed solar winds observed prior to the maximum of sunspot cycle 20 is investigated by multi-spacecraft comparisons. It is shown that differences in solar wind structures are due to two different kinds of spatial structures. One structure is found to be consistent with the simultaneous existence of a single, broad stream at latitudes above 7 deg N and a series of narrow streams at lower latitudes, while the other is consistent with the existence of a latitudinally sloping stream boundary near the solar equator. For latitude separations less than 3.5 deg, cross-correlations of Explorer-Mariner velocities show only previously reported systematic increases in velocity with latitude, and for latitude separations from 3.5 to 6.2 deg, differences in high speed streams shift in longitude and/or amplitude are also identified on a timescale of one solar rotation.

  16. Teaching Technology-Structure Contingencies by "Harnessing the Wind"

    ERIC Educational Resources Information Center

    Miller, Lynn E.

    2007-01-01

    This article describes a role-playing simulation that demonstrates how organizational structure is influenced by organizational and departmental technologies. Students act as employees of firms that must manufacture either a range of innovative products or a large number of standardized products. The simulation can be used in organizational…

  17. A search for rotationally-modulated wind-structure in Wolf-Rayet star WR 137

    NASA Astrophysics Data System (ADS)

    Harries, Tim J.

    1999-08-01

    We wish to obtain high signal-to-noise, moderate dispersion time- series spectroscopy of the dust-producting Wolf-Rayet star WR 137. These data will be used to examine the frequency, life-times, and velocity distributions of density inhomogeneities within the wind, and to search for periodic modulation of the line-profile morphology indicative of large-scale azimuthal structure. Evidence for rotational modulation will provide strong support for the hypothesis that WR 137 has an equatorially-compressed wind as a result of rapid rotation, and that it is a carbon-sequence analogue of WRs 6 and 134.

  18. Wind energy systems

    NASA Technical Reports Server (NTRS)

    Stewart, H. J.

    1978-01-01

    A discussion on wind energy systems involved with the DOE wind energy program is presented. Some of the problems associated with wind energy systems are discussed. The cost, efficiency, and structural design of wind energy systems are analyzed.

  19. Structure-Based Design of a Protein Immunogen that Displays an HIV-1 gp41 Neutralizing Epitope

    SciTech Connect

    Stanfield, Robyn L.; Julien, Jean-Philippe; Pejchal, Robert; Gach, Johannes S.; Zwick, Michael B.; Wilson, Ian A.

    2012-06-27

    Antibody Z13e1 is a relatively broadly neutralizing anti-human immunodeficiency virus type 1 antibody that recognizes the membrane-proximal external region (MPER) of the human immunodeficiency virus type 1 envelope glycoprotein gp41. Based on the crystal structure of an MPER epitope peptide in complex with Z13e1 Fab, we identified an unrelated protein, interleukin (IL)-22, with a surface-exposed region that is structurally homologous in its backbone to the gp41 Z13e1 epitope. By grafting the gp41 Z13e1 epitope sequence onto the structurally homologous region in IL-22, we engineered a novel protein (Z13-IL22-2) that contains the MPER epitope sequence for use as a potential immunogen and as a reagent for the detection of Z13e1-like antibodies. The Z13-IL22-2 protein binds Fab Z13e1 with a K{sub d} of 73 nM. The crystal structure of Z13-IL22-2 in complex with Fab Z13e1 shows that the epitope region is faithfully replicated in the Fab-bound scaffold protein; however, isothermal calorimetry studies indicate that Fab binding to Z13-IL22-2 is not a lock-and-key event, leaving open the question of whether conformational changes upon binding occur in the Fab, in Z13-IL-22, or in both.

  20. Comparison of Ring Current and Radiation Belt Responses during Transient Solar Wind Structures

    NASA Astrophysics Data System (ADS)

    Mulligan, T. L.; Roeder, J. L.; Lemon, C.; Fennell, J. F.

    2013-12-01

    The analysis of radiation belt dynamics provides insight into the physical mechanisms of trapping, energization, and loss of energetic particles in the magnetosphere. It is well known that the storm-time ring current response to solar wind drivers changes the magnetic field in the inner magnetosphere, which modifies radiation belt particle trajectories as well as the magnetopause and geomagnetic cutoff locations. What is not well known is the detailed space-time structure of solar wind transient features that drive the dynamics of the ring-current and radiation belt response. We compare observed responses of the ring current and radiation belts during two geomagnetic storms of similar intensity on 15 November 2012 and 29 June 2013. Using the self-consistent ring current model RCM-Equilibrium (RCM-E), which ensures a force-balanced ring-current response at each time step, we generate a simulated ring current in response to the changing conditions as the storm evolves on a timescale of hours. Observations of the plasma sheet particles, fields, and solar wind parameters are used to specify the dynamic boundary conditions as the storm evolves. This allows more realistic magnetospheric field and plasma dynamics during solar wind transients than can be obtained from existing empirical models. Using a spatial mapping algorithm developed by Mulligan et al., (2012) we create two-dimensional contour maps of the solar wind bulk plasma parameters using ACE, Wind, Geotail, and THEMIS data to quantitatively follow upstream spatial variations in the radial and azimuthal dimensions driving the storm. We perform a comparison of how the structure and impact angle of the solar wind transients affect the intensity and duration of energization of the ring current and radiation belt at various energies. We also investigate how the varying geomagnetic conditions determined by the solar wind affect dominant loss mechanisms such as magnetopause shadowing. Comparison of energetic particle

  1. Smart Sensor System for Structural Condition Monitoring of Wind Turbines: 30 May 2002--30 April 2006

    SciTech Connect

    Schulz, M. J.; Sundaresan, M. J.

    2006-08-01

    This report describes the efforts of the University of Cincinnati, North Carolina A&T State University, and NREL to develop a structural neural system for structural health monitoring of wind turbine blades.

  2. Diurnal Evolution of Three-Dimensional Wind and Temperature Structure in California's Central Valley

    SciTech Connect

    Zhong, Shiyuan; Whiteman, Charles D.; Bian, Xindi

    2004-11-01

    The diurnal evolution of the three-dimensional summer season mean wind and temperature structure in California’s Sacramento and San Joaquin Valleys (collectively called the Central Valley) are investigated using data from 22 radar wind profiler/Radio Acoustic Sounding Systems (RASS) operated as part of the Central California Ozone Study in 2000. The profiler network revealed, for the first time, that the persistent summer season flow pattern documented by surface observations extends 800-1000 m above the surface. At most locations, up-valley winds persist both day and night except at the upper ends of the valleys and close to the valley sidewalls where diurnal wind reversals occur. Wind speeds exhibit pronounced diurnal oscillations, with amplitudes decreasing with height. A low-level wind maximum occurs in the lowest 300 m, with a sharp decrease in speed above the maximum. Especially well-defined nocturnal low-level jets occur at sites in the southern San Joaquin Valley, where maximum speeds of 10 m s-1 or more occur 1-2 h before midnight at heights near 300 m. The afternoon mixed layer, generally deeper than 1000 m, increases in depth with up-valley distance in both valleys. At night, temperature inversions develop in the lowest several hundred meters with near-isothermal layers above. Mean temperatures in the lowest 500 m of the valleys are always warmer than at the same altitude over the coast, and temperature increases from the lower to upper valleys. The diurnal oscillation of the coast-valley and along-valley temperature and pressure difference reach a maximum in late afternoon and a minimum in early morning. These oscillations are in phase with the diurnal variation of westerly onshore flows. The along-valley wind maxima, however, occur 1-2 h before midnight while the pressure gradient maxima are usually found just before sunset.

  3. A NASTRAN-based computer program for structural dynamic analysis of Horizontal Axis Wind Turbines

    NASA Technical Reports Server (NTRS)

    Lobitz, Don W.

    1995-01-01

    This paper describes a computer program developed for structural dynamic analysis of horizontal axis wind turbines (HAWT's). It is based on the finite element method through its reliance on NASTRAN for the development of mass, stiffness, and damping matrices of the tower end rotor, which are treated in NASTRAN as separate structures. The tower is modeled in a stationary frame and the rotor in one rotating at a constant angular velocity. The two structures are subsequently joined together (external to NASTRAN) using a time-dependent transformation consistent with the hub configuration. Aerodynamic loads are computed with an established flow model based on strip theory. Aeroelastic effects are included by incorporating the local velocity and twisting deformation of the blade in the load computation. The turbulent nature of the wind, both in space and time, is modeled by adding in stochastic wind increments. The resulting equations of motion are solved in the time domain using the implicit Newmark-Beta integrator. Preliminary comparisons with data from the Boeing/NASA MOD2 HAWT indicate that the code is capable of accurately and efficiently predicting the response of HAWT's driven by turbulent winds.

  4. Fluid-structure coupling for wind turbine blade analysis using OpenFOAM

    NASA Astrophysics Data System (ADS)

    Dose, Bastian; Herraez, Ivan; Peinke, Joachim

    2015-11-01

    Modern wind turbine rotor blades are designed increasingly large and flexible. This structural flexibility represents a problem for the field of Computational Fluid Dynamics (CFD), which is used for accurate load calculations and detailed investigations of rotor aerodynamics. As the blade geometries within CFD simulations are considered stiff, the effect of blade deformation caused by aerodynamic loads cannot be captured by the common CFD approach. Coupling the flow solver with a structural solver can overcome this restriction and enables the investigation of flexible wind turbine blades. For this purpose, a new Finite Element (FE) solver was implemented into the open source CFD code OpenFOAM. Using a beam element formulation based on the Geometrically Exact Beam Theory (GEBT), the structural model can capture geometric non-linearities such as large deformations. Coupled with CFD solvers of the OpenFOAM package, the new framework represents a powerful tool for aerodynamic investigations. In this work, we investigated the aerodynamic performance of a state of the art wind turbine. For different wind speeds, aerodynamic key parameters are evaluated and compared for both, rigid and flexible blade geometries. The present work is funded within the framework of the joint project Smart Blades (0325601D) by the German Federal Ministry for Economic Affairs and Energy (BMWi) under decision of the German Federal Parliament.

  5. A NASTRAN-based computer program for structural dynamic analysis of Horizontal Axis Wind Turbines

    NASA Astrophysics Data System (ADS)

    Lobitz, Don W.

    1995-05-01

    This paper describes a computer program developed for structural dynamic analysis of horizontal axis wind turbines (HAWT's). It is based on the finite element method through its reliance on NASTRAN for the development of mass, stiffness, and damping matrices of the tower end rotor, which are treated in NASTRAN as separate structures. The tower is modeled in a stationary frame and the rotor in one rotating at a constant angular velocity. The two structures are subsequently joined together (external to NASTRAN) using a time-dependent transformation consistent with the hub configuration. Aerodynamic loads are computed with an established flow model based on strip theory. Aeroelastic effects are included by incorporating the local velocity and twisting deformation of the blade in the load computation. The turbulent nature of the wind, both in space and time, is modeled by adding in stochastic wind increments. The resulting equations of motion are solved in the time domain using the implicit Newmark-Beta integrator. Preliminary comparisons with data from the Boeing/NASA MOD2 HAWT indicate that the code is capable of accurately and efficiently predicting the response of HAWT's driven by turbulent winds.

  6. Forced vibration analysis of rotating structures with application to vertical axis wind turbines

    NASA Astrophysics Data System (ADS)

    Lobitz, D. W.

    Predictive methods for the dynamic analysis of wind turbine systems are important for assessing overall structural integrity and fatigue life. For the former, the identification of resonance points (spectral analysis) is of primary concern. For the latter forced vibration analysis is necessary. These analyses are complicated by the fact that, for a spinning turbine, the stress-producing deformations take place in both fixed and rotating reference systems simultaneously. As an example, the tower of a horizontal axis wind turbine (HAWT) must be analyzed in a fixed frame, and the rotor in a rotating one. Forced vibration analysis is further complicated in that accurate models need to be developed for aeroload prediction. Methods which are available for forced vibration analysis of both horizontal and vertical axis machines are identified and the method which was developed for vertical axis wind turbines is emphasized, with some comparisons of the predictions to experimental data.

  7. Wind tunnel measurements in the wake of a simple structure in a simulated atmospheric flow

    NASA Technical Reports Server (NTRS)

    Hansen, A. C.; Peterka, J. A.; Cermak, J. E.

    1975-01-01

    Measurements of longitudinal mean velocity and turbulence intensity were made in the wake of a rectangular model building in a simulated atmospheric boundary-layer wind. The model building was a 1:50 scale model of a structure used in a wake measurement program at the George C. Marshall Space Flight Center 8-tower boundary-layer facility. The approach wind profile and measurement locations were chosen to match the field site conditions. The wakes of the building in winds from azimuths of 0 and 47 degrees referenced to the normal to the building long axis were examined. The effect of two lines of trees upwind of the building on the wake and the importance of the ratio of the building height to boundary-layer thickness on the extent of the wake were determined.

  8. Wind Turbine Model and Observer in Takagi-Sugeno Model Structure

    NASA Astrophysics Data System (ADS)

    Georg, Sören; Müller, Matthias; Schulte, Horst

    2014-12-01

    Based on a reduced-order, dynamic nonlinear wind turbine model in Takagi- Sugeno (TS) model structure, a TS state observer is designed as a disturbance observer to estimate the unknown effective wind speed. The TS observer model is an exact representation of the underlying nonlinear model, obtained by means of the sector-nonlinearity approach. The observer gain matrices are obtained by means of a linear matrix inequality (LMI) design approach for optimal fuzzy control, where weighting matrices for the individual system states and outputs are included. The observer is tested in simulations with the aero-elastic code FAST for the NREL 5 MW reference turbine, where it shows a stable behaviour in turbulent wind simulations.

  9. Longitudinal structure in atomic oxygen concentrations observed with WINDII on UARS. [Wind Imaging Interferometer

    NASA Technical Reports Server (NTRS)

    Shepherd, G. G.; Thuillier, G.; Solheim, B. H.; Chandra, S.; Cogger, L. L.; Duboin, M. L.; Evans, W. F. J.; Gattinger, R. L.; Gault, W. A.; Herse, M.

    1993-01-01

    WINDII, the Wind Imaging Interferometer on the Upper Atmosphere Research Satellite, began atmospheric observations on September 28, 1991 and since then has been collecting data on winds, temperatures and emissions rates from atomic, molecular and ionized oxygen species, as well as hydroxyl. The validation of winds and temperatures is not yet complete, and scientific interpretation has barely begun, but the dominant characteristic of these data so far is the remarkable structure in the emission rate from the excited species produced by the recombination of atomic oxygen. The latitudinal and temporal variability has been noted before by many others. In this preliminary report on WINDII results we draw attention to the dramatic longitudinal variations of planetary wave character in atomic oxygen concentration, as reflected in the OI 557.7 nm emission, and to similar variations seen in the Meine1 hydroxyl band emission.

  10. Disentangling niche and neutral influences on community assembly: assessing the performance of community phylogenetic structure tests.

    PubMed

    Kembel, Steven W

    2009-09-01

    Patterns of phylogenetic relatedness within communities have been widely used to infer the importance of different ecological and evolutionary processes during community assembly, but little is known about the relative ability of community phylogenetics methods and null models to detect the signature of processes such as dispersal, competition and filtering under different models of trait evolution. Using a metacommunity simulation incorporating quantitative models of trait evolution and community assembly, I assessed the performance of different tests that have been used to measure community phylogenetic structure. All tests were sensitive to the relative phylogenetic signal in species metacommunity abundances and traits; methods that were most sensitive to the effects of niche-based processes on community structure were also more likely to find non-random patterns of community phylogenetic structure under dispersal assembly. When used with a null model that maintained species occurrence frequency in random communities, several metrics could detect niche-based assembly when there was strong phylogenetic signal in species traits, when multiple traits were involved in community assembly, and in the presence of environmental heterogeneity. Interpretations of the causes of community phylogenetic structure should be modified to account for the influence of dispersal.

  11. Sulfate templated assembly of neutral receptors in aqueous DMSO - orthogonal versus biplane structures.

    PubMed

    Bąk, Krzysztof M; Chmielewski, Michał J

    2014-02-01

    Simple, easily available diamidocarbazoles form robust 2 : 1 complexes with SO4(2-) even in the presence of a large excess of water. An appropriate choice of side arms directs the assembly towards the formation of either an orthogonal or a biplane structure, both in solution and in the solid state.

  12. The average solar wind in the inner heliosphere: Structures and slow variations

    NASA Technical Reports Server (NTRS)

    Schwenn, R.

    1983-01-01

    Measurements from the HELIOS solar probes indicated that apart from solar activity related disturbances there exist two states of the solar wind which might result from basic differences in the acceleration process: the fast solar wind (v 600 kms(-)1) emanating from magnetically open regions in the solar corona and the "slow" solar wind (v 400 kms(-)1) correlated with the more active regions and its mainly closed magnetic structures. In a comprehensive study using all HELIOS data taken between 1974 and 1982 the average behavior of the basic plasma parameters were analyzed as functions of the solar wind speed. The long term variations of the solar wind parameters along the solar cycle were also determined and numerical estimates given. These modulations appear to be distinct though only minor. In agreement with earlier studies it was concluded that the major modulations are in the number and size of high speed streams and in the number of interplanetary shock waves caused by coronal transients. The latter ones usually cause huge deviations from the averages of all parameters.

  13. Wind structure and variability in the middle atmosphere during the November 1980 energy budget campaign

    NASA Astrophysics Data System (ADS)

    Schmidlin, F. J.; Carlson, M.; Rees, D.; Offermann, D.; Philbrick, C. R.; Widdel, H. U.

    1985-03-01

    Between November 6 and December 1, 1980 series of rocket observations were obtained from two sites in northern Scandinavia (68 deg N) as part of the Energy Budget Campaign, revealing the presence of significant vertical and temporal changes in the wind structure. These changes coincided with different geomagnetic conditions, i.e. quiet and enhanced. Large amounts of rocket data were gathered from high latitudes over such a short interval of time. Prior to November 16 the meridional wind component above 60 km was found to be positive (southerly), while the magnitude of the zonal wind component incresed with altitude. After November 16 the meridional component became negative (northerly) and the magnitude of the zonal wind component was noted to decrease with altitude. Time-sections of the perturbations of the zonal wind show the presence of vertically propagating waves, which suggest gravity wave activity. These waves increase in length from 1 km near 30 km to over 12 km near 80 km. The observational techniques employed Andoya (69 deg N), Norway, and Esrange (67.9 deg N), Sweden, consisted of chaff foil, instrumented rigid spheres, chemical trails, inflatable spheres and parachutes.

  14. Wind structure and variability in the middle atmosphere during the November 1980 energy budget campaign

    NASA Technical Reports Server (NTRS)

    Schmidlin, F. J.; Carlson, M.; Rees, D.; Offermann, D.; Philbrick, C. R.; Widdel, H. U.

    1985-01-01

    Between November 6 and December 1, 1980 series of rocket observations were obtained from two sites in northern Scandinavia (68 deg N) as part of the Energy Budget Campaign, revealing the presence of significant vertical and temporal changes in the wind structure. These changes coincided with different geomagnetic conditions, i.e. quiet and enhanced. Large amounts of rocket data were gathered from high latitudes over such a short interval of time. Prior to November 16 the meridional wind component above 60 km was found to be positive (southerly), while the magnitude of the zonal wind component incresed with altitude. After November 16 the meridional component became negative (northerly) and the magnitude of the zonal wind component was noted to decrease with altitude. Time-sections of the perturbations of the zonal wind show the presence of vertically propagating waves, which suggest gravity wave activity. These waves increase in length from 1 km near 30 km to over 12 km near 80 km. The observational techniques employed Andoya (69 deg N), Norway, and Esrange (67.9 deg N), Sweden, consisted of chaff foil, instrumented rigid spheres, chemical trails, inflatable spheres and parachutes.

  15. HARLIE Aerosol and Cloud Structure and Wind Observations during HARGLO and IHOP

    NASA Technical Reports Server (NTRS)

    Schwemmer, Geary K.; Miller, David O.; Wilkersorf, Thomas D.

    2003-01-01

    The Holographic Airborne Rotating Lidar Instrument Experiment (HARLIE) is a conical-scanning, 1-micron wavelength lidar that has been adapted for ground-based applications and used to infer horizontal wind information by tracking the motions of aerosol and cloud scattering structures. In addition, HARLIE's rapid continuous scanning enables boundary layer statistics and a new cloud lidar data product that gives cloud coverage as a function of altitude with high temporal resolution. HARLIE has been used in several field campaigns while developing the techniques for wind, boundary layer (BL), and cloud data products. These campaigns involved a variety of wind measuring instruments including rawindsondes, cloud-tracked winds from video imagery, Doppler lidars and Doppler radars. HARGLO-2 was one of these campaigns and was dedicated to wind profile intercomparisons over a 1-week period in November of 2001. The most recent of these campaigns was the International H20 Project (IHOP) located in the Southern Great Plains of the US during May and June of 2002.

  16. Structural Load Analysis of a Wind Turbine under Pitch Actuator and Controller Faults

    NASA Astrophysics Data System (ADS)

    Etemaddar, Mahmoud; Gao, Zhen; Moan, Torgeir

    2014-12-01

    In this paper, we investigate the characteristics of a wind turbine under blade pitch angle and shaft speed sensor faults as well as pitch actuator faults. A land-based NREL 5MW variable speed pitch reg- ulated wind turbine is considered as a reference. The conventional collective blade pitch angle controller strategy with independent pitch actuators control is used for load reduction. The wind turbine class is IEC-BII. The main purpose is to investigate the severity of end effects on structural loads and responses and consequently identify the high-risk components according to the type and amplitude of fault using a servo-aero-elastic simulation code, HAWC2. Both transient and steady state effects of faults are studied. Such information is useful for wind turbine fault detection and identification as well as system reliability analysis. Results show the effects of faults on wind turbine power output and responses. Pitch sensor faults mainly affects the vibration of shaft main bearing, while generator power and aerodynamic thrust are not changed significantly, due to independent pitch actuator control of three blades. Shaft speed sensor faults can seriously affect the generator power and aerodynamic thrust. Pitch actuator faults can result in fully pitching of the blade, and consequently rotor stops due to negative aerodynamic torque.

  17. Probing the structures of neutral boron clusters using infrared/vacuum ultraviolet two color ionization: B11, B16, and B17.

    PubMed

    Romanescu, Constantin; Harding, Dan J; Fielicke, André; Wang, Lai-Sheng

    2012-07-01

    The structures of neutral boron clusters, B(11), B(16), and B(17), have been investigated using vibrational spectroscopy and ab initio calculations. Infrared absorption spectra in the wavelength range of 650 to 1550 cm(-1) are obtained for the three neutral boron clusters from the enhancement of their near-threshold ionization efficiency at a fixed UV wavelength of 157 nm (7.87 eV) after resonant absorption of the tunable infrared photons. All three clusters, B(11), B(16), and B(17), are found to possess planar or quasi-planar structures, similar to their corresponding anionic counterparts (B(n) (-)), whose global minima were found previously to be planar, using photoelectron spectroscopy and theoretical calculations. Only minor structural changes are observed between the neutral and the anionic species for these three boron clusters.

  18. Probing the structures of neutral boron clusters using infrared/vacuum ultraviolet two color ionization: B11, B16, and B17

    NASA Astrophysics Data System (ADS)

    Romanescu, Constantin; Harding, Dan J.; Fielicke, André; Wang, Lai-Sheng

    2012-07-01

    The structures of neutral boron clusters, B11, B16, and B17, have been investigated using vibrational spectroscopy and ab initio calculations. Infrared absorption spectra in the wavelength range of 650 to 1550 cm-1 are obtained for the three neutral boron clusters from the enhancement of their near-threshold ionization efficiency at a fixed UV wavelength of 157 nm (7.87 eV) after resonant absorption of the tunable infrared photons. All three clusters, B11, B16, and B17, are found to possess planar or quasi-planar structures, similar to their corresponding anionic counterparts (Bn-), whose global minima were found previously to be planar, using photoelectron spectroscopy and theoretical calculations. Only minor structural changes are observed between the neutral and the anionic species for these three boron clusters.

  19. Microtraps for neutral atoms using superconducting structures in the critical state

    SciTech Connect

    Emmert, A.; Brune, M.; Raimond, J.-M.; Nogues, G.; Lupascu, A.; Haroche, S.

    2009-12-15

    Recently demonstrated superconducting atom chips provide a platform for trapping atoms and coupling them to solid-state quantum systems. Controlling these devices requires a full understanding of the supercurrent distribution in the trapping structures. For type-II superconductors, this distribution is hysteretic in the critical state due to the partial penetration of the magnetic field in the thin superconducting film through pinned vortices. We report here an experimental observation of this memory effect. Our results are in good agreement with the predictions of the Bean model of the critical state without adjustable parameters. The memory effect allows to write and store permanent currents in micron-sized superconducting structures and paves the way toward engineered trapping potentials.

  20. Measurements of internal magnetic structures from neutral beam emission spectra in KSTAR

    NASA Astrophysics Data System (ADS)

    Ko, J.; Chung, J.; Song, M.; You, K. I.

    2012-10-01

    The magnetic pitch angle and the magnitude from magnetically confined fusion devices are measured by fitting the beam emission spectra under the motional Stark effect (MSE). Initial values for the free parameters in the complicated raw spectra are obtained from and constrained by the MSE model in the Atomic Data and Analysis Structure (ADAS) which uses a collisional-radiative model with level populations nlm-resolved up to n = 4 and a simple born approximation for ion-impact cross sections. This technique is examined for the MSE spectra taken from the KSTAR plasma discharges and its validity and applicability are discussed to directly infer the internal magnetic field structure with a wide range of pitch angles. The sensitivity of EFIT reconstruction on these internal magnetic data is also discussed.

  1. Structural basis for Marburg virus neutralization by a cross-reactive human antibody.

    PubMed

    Hashiguchi, Takao; Fusco, Marnie L; Bornholdt, Zachary A; Lee, Jeffrey E; Flyak, Andrew I; Matsuoka, Rei; Kohda, Daisuke; Yanagi, Yusuke; Hammel, Michal; Crowe, James E; Saphire, Erica Ollmann

    2015-02-26

    The filoviruses, including Marburg and Ebola, express a single glycoprotein on their surface, termed GP, which is responsible for attachment and entry of target cells. Filovirus GPs differ by up to 70% in protein sequence, and no antibodies are yet described that cross-react among them. Here, we present the 3.6 Å crystal structure of Marburg virus GP in complex with a cross-reactive antibody from a human survivor, and a lower resolution structure of the antibody bound to Ebola virus GP. The antibody, MR78, recognizes a GP1 epitope conserved across the filovirus family, which likely represents the binding site of their NPC1 receptor. Indeed, MR78 blocks binding of the essential NPC1 domain C. These structures and additional small-angle X-ray scattering of mucin-containing MARV and EBOV GPs suggest why such antibodies were not previously elicited in studies of Ebola virus, and provide critical templates for development of immunotherapeutics and inhibitors of entry. PMID:25723165

  2. Hydrophobic End-Modulated Amino-Acid-Based Neutral Hydrogelators: Structure-Specific Inclusion of Carbon Nanomaterials.

    PubMed

    Choudhury, Pritam; Mandal, Deep; Brahmachari, Sayanti; Das, Prasanta Kumar

    2016-04-01

    Hydrophobic end-modulated l-phenylalanine-containing triethylene glycol monomethyl ether tagged neutral hydrogelators (1-4) are developed. Investigations determine the gelators' structure-dependent inclusion of carbon nanomaterials (CNMs) in the self-assembled fibrillar network (SAFIN). The gelators (1, 3, and 4) can immobilize water and aqueous buffer (pH 3-7) with a minimum gelator concentration of 10-15 mg mL(-1). The hydrophobic parts of the gelators are varied from a long chain (C-16) to an extended aromatic pyrenyl moiety, and their abilities to integrate 1 D and 2 D allotropes of carbon (i.e., single-walled carbon nanotubes (SWNTs) and graphene oxide (GO), respectively) within the gel are investigated. Gelator 1, containing a long alkyl chain (C-16), can include SWNTs, whereas the pyrene-containing 4 can include both SWNTs and GO. Gelator 3 fails to incorporate SWNTs or GO owing to its slow rate of gelation and possibly a mismatch between the aggregated structure and CNMs. The involvement of various forces in self-aggregated gelation and physicochemical changes occurring through CNM inclusion are examined by spectroscopic and microscopic techniques. The distinctive pattern of self-assembly of gelators 1 and 4 through J- and H-type aggregation might facilitate the structure-specific CNM inclusion. Inclusion of SWNTs/GO within the hydrogel matrix results in a reinforcement in mechanical stiffness of the composites compared with that of the native hydrogels.

  3. Structural characterization of neutral oligosaccharides with blood-group A and H activity isolated from bovine submaxillary mucin.

    PubMed Central

    Savage, A V; D'Arcy, S M; Donoghue, C M

    1991-01-01

    In this study we investigated the structures of 11 neutral oligosaccharides released from bovine submaxillary mucin by alkaline borohydride treatment and isolated by h.p.l.c. One hexa-, one penta-, three tetra-, four tri- and two di-saccharides containing core types 1, 2, 3 or 4 were obtained. We report their structures, determined by a combination of one- and two-dimensional 1H n.m.r. spectroscopy at 270 MHz and methylation analysis involving g.l.c.-m.s., along with their approximate molar ratios. Only three of these oligosaccharides have previously been reported in this source. Of the new oligosaccharides, one contains the blood-group-A antigenic determinant, two contain the blood-group-H type 2 determinant, while another contains the blood-group-H type 3 determinant. The oligosaccharide GlcNAc beta (1----6)[GlcNAc beta (1----3)]GalNAcol, although previously found as a core structure, has been isolated here as a novel trisaccharide. PMID:1718265

  4. Solar Wind Speed Structure in the Inner Corona at 3-12 Ro

    NASA Technical Reports Server (NTRS)

    Woo, Richard

    1995-01-01

    Estimates of solar wind speed obtained by Armstrong et al. [1986] based on 1983 VLA multiple-station intensity scintillation measurements inside 12 R(sub o) have been correlated with the electron density structure observed in white-light coronagraph measurements. The observed large- scale and apparently systematic speed variations are found to depend primarily on changes in heliographic latitude and longitude, which leads to the first results on large-scale speed structure in the acceleration region of the solar wind. Over an equatorial hole, solar wind speed is relatively steady, with peak-to-peak variations of 50 km/s and an average of 230 km/s. In contrast, the near-Sun flow speed across the streamer belt shows regular large-scale variations in the range of 100-300 km/s. Based on four groups of data, the gradient is 36 km/s per degree in heliocentric coordinates (corresponding to a rise of 260 km/s over a spatial distance on the Sun of two arcmin) with a standard deviation of 2.4 km/s per degree. The lowest speeds most likely coincide with the stalks of coronal streamers observed in white-light measurements. The detection of significant wind shear over the streamer belt is consistent with in situ and scintillation measurements showing that the density spectrum has a power-law form characteristic of fully developed turbulence over a much broader range of scales than in neighboring regions.

  5. The structure and appearance of winds from supercritical accretion disks. I - Numerical models

    NASA Technical Reports Server (NTRS)

    Meier, D. L.

    1979-01-01

    Equations for the structure and appearance of supercritical accretion disks and the radiation-driven winds which emanate from them are derived and solved by a steady-state hydrodynamic computer code with a relaxation technique used in stellar structure problems. The present model takes into account the mass of the accreting star, the total accretion rate, a generalization of the disk alpha parameter which accounts for heating by processes in addition to viscosity, and the ratio of the total luminosity to the Eddington luminosity. Solutions indicate that for accretion onto a hard-surfaced star, steady, optically thick winds result for even slightly supercritical accretion, and the object will appear as a supergiant star with a high mass loss rate and a nonblackbody spectrum. Winds from black hole accretion disks are expected to depend on the form of the accretion interior to the critical radius, possibly consisting of no ejection at all, a wind similar to that of a hard-surfaced star, or a column of material ejected from a hole in the accretion disk.

  6. Electronic Structure Determination of Pyridine N-Heterocyclic Carbene Iron Dinitrogen Complexes and Neutral Ligand Derivatives

    PubMed Central

    2015-01-01

    The electronic structures of pyridine N-heterocyclic dicarbene (iPrCNC) iron complexes have been studied by a combination of spectroscopic and computational methods. The goal of these studies was to determine if this chelate engages in radical chemistry in reduced base metal compounds. The iron dinitrogen example (iPrCNC)Fe(N2)2 and the related pyridine derivative (iPrCNC)Fe(DMAP)(N2) were studied by NMR, Mössbauer, and X-ray absorption spectroscopy and are best described as redox non-innocent compounds with the iPrCNC chelate functioning as a classical π acceptor and the iron being viewed as a hybrid between low-spin Fe(0) and Fe(II) oxidation states. This electronic description has been supported by spectroscopic data and DFT calculations. Addition of N,N-diallyl-tert-butylamine to (iPrCNC)Fe(N2)2 yielded the corresponding iron diene complex. Elucidation of the electronic structure again revealed the CNC chelate acting as a π acceptor with no evidence for ligand-centered radicals. This ground state is in contrast with the case for the analogous bis(imino)pyridine iron complexes and may account for the lack of catalytic [2π + 2π] cycloaddition reactivity. PMID:25328270

  7. An interoperable, data-structure-neutral component for mesh query and manipulation.

    SciTech Connect

    Ollivier-Gooch, C.; Diachin, L.; Shephard, M. S.; Tautges, T.; Kraftcheck, J.; Leung, V.; Luo, X.; Miller, M.

    2010-01-01

    Much of the effort required to create a new simulation code goes into developing infrastructure for mesh data manipulation, adaptive refinement, design optimization, and so forth. This infrastructure is an obvious target for code reuse, except that implementations of these functionalities are typically tied to specific data structures. In this article, we describe a software component---an abstract data model and programming interface---designed to provide low-level mesh query and manipulation support for meshing and solution algorithms. The component's data model provides a data abstraction, completely hiding all details of how mesh data is stored, while its interface defines how applications can interact with that data. Because the component has been carefully designed to be general purpose and efficient, it provides a practical platform for implementing high-level mesh operations independently of the underlying mesh data structures. After describing the data model and interface, we provide several usage examples, each of which has been used successfully with multiple implementations of the interface functionality. The overhead due to accessing mesh data through the interface rather than directly accessing the underlying mesh data is shown to be acceptably small.

  8. Structural characterization of poorly-crystalline scorodite, iron(III)-arsenate co-precipitates and uranium mill neutralized raffinate solids using X-ray absorption fine structure spectroscopy

    SciTech Connect

    Chen, N; Jiang, D T; Cutler, J; Kotzer, T; Jia, Y F; Demopoulos, G P; Rowson, J W

    2009-12-01

    X-ray absorption fine structure (XAFS) is used to characterize the mineralogy of the iron(III)-arsenate(V) precipitates produced during the raffinate (aqueous effluent) neutralization process at the McClean Lake uranium mill in northern Saskatchewan, Canada. To facilitate the structural characterization of the precipitated solids derived from the neutralized raffinate, a set of reference compounds were synthesized and analyzed. The reference compounds include crystalline scorodite, poorly-crystalline scorodite, iron(III)-arsenate co-precipitates obtained under different pH conditions, and arsenate-adsorbed on goethite. The poorly-crystalline scorodite (prepared at pH 4 with Fe/As = 1) has similar As local structure as that of crystalline scorodite. Both As and Fe K-edge XAFS of poorly-crystalline scorodite yield consistent results on As-Fe (or Fe-As) shell. From As K-edge analysis the As-Fe shell has an inter-atomic distance of 3.33 ± 0.02 Å and coordination number of 3.2; while from Fe K-edge analysis the Fe-As distance and coordination number are 3.31 ± 0.02 Å and 3.8, respectively. These are in contrast with the typical arsenate adsorption on bidentate binuclear sites on goethite surfaces, where the As-Fe distance is 3.26 ± 0.03 Å and coordination number is close to 2. A similar local structure identified in the poorly-crystalline scorodite is also found in co-precipitation solids (Fe(III)/As(V) = 3) when precipitated at the same pH (pH = 4): As-Fe distance 3.30 ± 0.03 Å and coordination number 3.9; while at pH = 8 the co-precipitate has As-Fe distance of 3.27 ± 0.03 Å and coordination number about 2, resembling more closely the adsorption case. The As local structure in the two neutralized raffinate solid series (precipitated at pH values up to 7) closely resembles that in the poorly-crystalline scorodite. All of the raffinate solids have the same As-Fe inter-atomic distance as that in the poorly-crystalline scorodite, and a systematic decrease in the

  9. Compressive Coherent Structures at Ion Scales in the Slow Solar Wind

    NASA Astrophysics Data System (ADS)

    Perrone, D.; Alexandrova, O.; Mangeney, A.; Maksimovic, M.; Lacombe, C.; Rakoto, V.; Kasper, J. C.; Jovanovic, D.

    2016-08-01

    We present a study of magnetic field fluctuations in a slow solar wind stream, close to ion scales, where an increase of the level of magnetic compressibility is observed. Here, the nature of these compressive fluctuations is found to be characterized by coherent structures. Although previous studies have shown that current sheets can be considered the principal cause of intermittency at ion scales, here we show for the first time that, in the case of the slow solar wind, a large variety of coherent structures contributes to intermittency at proton scales, and current sheets are not the most common. Specifically, we find compressive (δ {b}\\parallel \\gg δ {b}\\perp ), linearly polarized structures in the form of magnetic holes, solitons, and shock waves. Examples of Alfvénic structures (δ {b}\\perp \\gt δ {b}\\parallel ) are identified as current sheets and vortex-like structures. Some of these vortices have δ {b}\\perp \\gg δ {b}\\parallel , as in the case of Alfvén vortices, but the majority of them are characterized by δ {b}\\perp ≳ δ {b}\\parallel . Thanks to multi-point measurements by the Cluster spacecraft, for about 100 structures we could determine the normal, the propagation velocity, and the spatial scale along this normal. Independently of the nature of the structures, the normal is always perpendicular to the local magnetic field, meaning that k ⊥ ≫ k ∥. The spatial scales of the studied structures are found to be between two and eight times the proton gyroradius. Most of them are simply convected by the wind, but 25% propagate in the plasma frame. Possible interpretations of the observed structures and the connection with plasma heating are discussed.

  10. Quaternary structure defines a large class of amyloid-β oligomers neutralized by sequestration

    PubMed Central

    Liu, Peng; Reed, Miranda N.; Kotilinek, Linda A.; Grant, Marianne K.O.; Forster, Colleen L.; Qiang, Wei; Shapiro, Samantha L.; Reichl, John H.; Chiang, Angie C.A.; Jankowsky, Joanna L.; Wilmot, Carrie M.; Cleary, James P.; Zahs, Kathleen R.; Ashe, Karen H.

    2015-01-01

    Summary The accumulation of amyloid-β (Aβ) as amyloid fibrils and toxic oligomers is an important step in the development of Alzheimer's disease (AD). However, there are numerous potentially toxic oligomers and little is known about their neurological effects when generated in the living brain. Here, we show that Aβ oligomers can be assigned to one of at least two classes (Type 1 and Type 2) based on their temporal, spatial and structural relationships to amyloid fibrils. The Type 2 oligomers are related to amyloid fibrils and represent the majority of oligomers generated in vivo, but remain confined to the vicinity of amyloid plaques and do not impair cognition at levels relevant to AD. Type 1 oligomers are unrelated to amyloid fibrils and may have greater potential to cause global neural dysfunction in AD because they are dispersed. These results refine our understanding of the pathogenicity of Aβ oligomers in vivo. PMID:26051935

  11. On the Launching and Structure of Radiatively Driven Winds in Wolf–Rayet Stars

    NASA Astrophysics Data System (ADS)

    Ro, Stephen; Matzner, Christopher D.

    2016-04-01

    Hydrostatic models of Wolf–Rayet (WR) stars typically contain low-density outer envelopes that inflate the stellar radii by a factor of several and are capped by a denser shell of gas. Inflated envelopes and density inversions are hallmarks of envelopes that become super-Eddington as they cross the iron-group opacity peak, but these features disappear when mass loss is sufficiently rapid. We re-examine the structures of steady, spherically symmetric wind solutions that cross a sonic point at high optical depth, identifying the physical mechanism through which the outflow affects the stellar structure, and provide an improved analytical estimate for the critical mass-loss rate above which extended structures are erased. Weak-flow solutions below this limit resemble hydrostatic stars even in supersonic zones; however, we infer that these fail to successfully launch optically thick winds. WR envelopes will therefore likely correspond to the strong, compact solutions. We also find that wind solutions with negligible gas pressure are stably stratified at and below the sonic point. This implies that convection is not the source of variability in WR stars, as has been suggested; however, acoustic instabilities provide an alternative explanation. Our solutions are limited to high optical depths by our neglect of Doppler enhancements to the opacity, and do not account for acoustic instabilities at high Eddington factors; yet, they do provide useful insights into WR stellar structures.

  12. On the Launching and Structure of Radiatively Driven Winds in Wolf-Rayet Stars

    NASA Astrophysics Data System (ADS)

    Ro, Stephen; Matzner, Christopher D.

    2016-04-01

    Hydrostatic models of Wolf-Rayet (WR) stars typically contain low-density outer envelopes that inflate the stellar radii by a factor of several and are capped by a denser shell of gas. Inflated envelopes and density inversions are hallmarks of envelopes that become super-Eddington as they cross the iron-group opacity peak, but these features disappear when mass loss is sufficiently rapid. We re-examine the structures of steady, spherically symmetric wind solutions that cross a sonic point at high optical depth, identifying the physical mechanism through which the outflow affects the stellar structure, and provide an improved analytical estimate for the critical mass-loss rate above which extended structures are erased. Weak-flow solutions below this limit resemble hydrostatic stars even in supersonic zones; however, we infer that these fail to successfully launch optically thick winds. WR envelopes will therefore likely correspond to the strong, compact solutions. We also find that wind solutions with negligible gas pressure are stably stratified at and below the sonic point. This implies that convection is not the source of variability in WR stars, as has been suggested; however, acoustic instabilities provide an alternative explanation. Our solutions are limited to high optical depths by our neglect of Doppler enhancements to the opacity, and do not account for acoustic instabilities at high Eddington factors; yet, they do provide useful insights into WR stellar structures.

  13. Forest structure and light regimes following moderate wind storms: implications for multi-cohort management.

    PubMed

    Hanson, Jacob J; Lorimer, Craig G

    2007-07-01

    Moderate-severity disturbances appear to be common throughout much of North America, but they have received relatively little detailed study compared to catastrophic disturbances and small gap dynamics. In this study, we examined the immediate impact of moderate-intensity wind storms on stand structure, opening sizes, and light regimes in three hemlock-hardwood forests of northeastern Wisconsin. These were compared to three stands managed by single-tree and group selection, the predominant forest management system for northern hardwoods in the region. Wind storms removed an average of 41% of the stand basal area, compared to 27% removed by uneven-aged harvests, but both disturbances removed trees from a wide range of size classes. The removal of nearly half of the large trees by wind in two old-growth stands caused partial retrogression to mature forest structure, which has been hypothesized to be a major disturbance pathway in the region. Wind storms resulted in residual stand conditions that were much more heterogeneous than in managed stands. Gap sizes ranged from less than 10 m2 up to 5000 m2 in wind-disturbed stands, whereas the largest opening observed in managed stands was only 200 m2. Wind-disturbed stands had, on average, double the available solar radiation at the forest floor compared to managed stands. Solar radiation levels were also more heterogeneous in wind-disturbed stands, with six times more variability at small scales (0.1225 ha) and 15 times more variability at the whole-stand level. Modification of uneven-aged management regimes to include occasional harvests of variable intensity and spatial pattern may help avoid the decline in species diversity that tends to occur after many decades of conventional uneven-aged management. At the same time, a multi-cohort system with these properties would retain a high degree of average crown cover, promote structural heterogeneity typical of old-growth forests, and maintain dominance by late

  14. Effects of precipitation on the thermodynamic structure of the trade wind boundary layer

    NASA Technical Reports Server (NTRS)

    Albrecht, Bruce A.

    1993-01-01

    A model of the thermodynamic structure of the trade wind boundary layer is formulated to include the parameterization of precipitation in relatively shallow clouds. Although the area-averaged simulated precipitation rates are relatively small (less than 1 mm/day), the inclusion of precipitation has an appreciable effect on the predicted thermodynamic structure. The cloud layer structure simulated with precipitation is warmer, drier, and more stable than that simulated without precipitation. The simulated inversion height is lowered by as much as 60 mbar when precipitation is included.

  15. Integrated Layout and Support Structure Optimization for Offshore Wind Farm Design

    NASA Astrophysics Data System (ADS)

    Ashuri, T.; Ponnurangam, C.; Zhang, J.; Rotea, M.

    2016-09-01

    This paper develops a multidisciplinary design optimization framework for integrated design optimization of offshore wind farm layout and support structure. A computational model is developed to characterize the physics of the wind farm wake, aerodynamic and hydrodynamic loads, response of the support structure to these loads, soil- structure interaction, as well as different cost elements. Levelized cost of energy is introduced as the objective function. The design constraints are the farm external boundary, and support structure buckling, first modal-frequency, fatigue damage and ultimate stresses. To evaluate the effectiveness of the proposed approach, four optimization scenarios are considered: a feasible baseline design, optimization of layout only, optimization of support structure only, and integrated design of the layout and support structure. Compared to the baseline design, the optimization results show that the isolated support structure design reduces the levelized cost of energy by 0.6%, the isolated layout design reduces the levelized cost of energy by 2.0%, and the integrated layout and support structure design reduces the levelized cost of energy by 2.6%.

  16. Structure and spectroscopic properties of neutral and cationic tetratomic [C,H,N,Zn] isomers: A theoretical study

    SciTech Connect

    Redondo, Pilar; Largo, Antonio; Vega-Vega, Álvaro; Barrientos, Carmen

    2015-05-14

    The structure and spectroscopic parameters of the most relevant [C,H,N,Zn] isomers have been studied employing high-level quantum chemical methods. For each isomer, we provide predictions for their molecular structure, thermodynamic stabilities as well as vibrational and rotational spectroscopic parameters which could eventually help in their experimental detection. In addition, we have carried out a detailed study of the bonding situations by means of a topological analysis of the electron density in the framework of the Bader’s quantum theory of atoms in molecules. The analysis of the relative stabilities and spectroscopic parameters suggests two linear isomers of the neutral [C,H,N,Zn] composition, namely, cyanidehydridezinc HZnCN ({sup 1}Σ) and hydrideisocyanidezinc HZnNC ({sup 1}Σ), as possible candidates for experimental detections. For the cationic [C,H,N,Zn]{sup +} composition, the most stable isomers are the ion-molecule complexes arising from the direct interaction of the zinc cation with either the nitrogen or carbon atom of either hydrogen cyanide or hydrogen isocyanide, namely, HCNZn{sup +} ({sup 2}Σ) and HCNZn{sup +} ({sup 2}Σ)

  17. Structure and spectroscopic properties of neutral and cationic tetratomic [C,H,N,Zn] isomers: A theoretical study.

    PubMed

    Redondo, Pilar; Largo, Antonio; Vega-Vega, Álvaro; Barrientos, Carmen

    2015-05-14

    The structure and spectroscopic parameters of the most relevant [C,H,N,Zn] isomers have been studied employing high-level quantum chemical methods. For each isomer, we provide predictions for their molecular structure, thermodynamic stabilities as well as vibrational and rotational spectroscopic parameters which could eventually help in their experimental detection. In addition, we have carried out a detailed study of the bonding situations by means of a topological analysis of the electron density in the framework of the Bader's quantum theory of atoms in molecules. The analysis of the relative stabilities and spectroscopic parameters suggests two linear isomers of the neutral [C,H,N,Zn] composition, namely, cyanidehydridezinc HZnCN ((1)Σ) and hydrideisocyanidezinc HZnNC ((1)Σ), as possible candidates for experimental detections. For the cationic [C,H,N,Zn](+) composition, the most stable isomers are the ion-molecule complexes arising from the direct interaction of the zinc cation with either the nitrogen or carbon atom of either hydrogen cyanide or hydrogen isocyanide, namely, HCNZn(+) ((2)Σ) and HCNZn(+) ((2)Σ).

  18. Structural basis of the broadly neutralizing anti-interferon-α antibody rontalizumab.

    PubMed

    Maurer, Brigitte; Bosanac, Ivan; Shia, Steven; Kwong, Mandy; Corpuz, Racquel; Vandlen, Richard; Schmidt, Kerstin; Eigenbrot, Charles

    2015-09-01

    Interferons-alpha (IFN-α) are the expressed gene products comprising thirteen type I interferons with protein pairwise sequence similarities in the 77-96% range. Three other widely expressed human type I interferons, IFN-β, IFN-κ and IFN-ω have sequences 29-33%, 29-32% and 56-60% similar to the IFN-αs, respectively. Type I interferons act on immune cells by producing subtly different immune-modulatory effects upon binding to the extracellular domains of a heterodimeric cell-surface receptor composed of IFNAR1 and IFNAR2, most notably anti-viral effects. IFN-α has been used to treat infection by hepatitis-virus type C (HCV) and a correlation between hyperactivity of IFN-α-induced signaling and systemic lupus erythematosis (SLE), or lupus, has been noted. Anti-IFN-α antibodies including rontalizumab have been under clinical study for the treatment of lupus. To better understand the rontalizumab mechanism of action and specificity, we determined the X-ray crystal structure of the Fab fragment of rontalizumab bound to human IFN-α2 at 3Å resolution and find substantial overlap of the antibody and IFNA2 epitopes on IFN-α2.

  19. Structural Analysis of Human and Macaque Monoclonal Antibodies 2909 and 2.5B: Implications for the Configuration of the Quaternary Neutralizing Epitope of HIV-1 gp120

    SciTech Connect

    B Spurrier; J Sampson; M Totrov; H Li; T ONeal; C Williams; J Robinson; M Gorny; S Zolla-Pazner; X Kong

    2011-12-31

    The quaternary neutralizing epitope (QNE) of HIV-1 gp120 is preferentially expressed on the trimeric envelope spikes of intact HIV virions, and QNE-specific monoclonal antibodies (mAbs) potently neutralize HIV-1. Here, we present the crystal structures of the Fabs of human mAb 2909 and macaque mAb 2.5B. Both mAbs have long beta hairpin CDR H3 regions >20 {angstrom} in length that are each situated at the center of their respective antigen-binding sites. Computational analysis showed that the paratopes include the whole CDR H3, while additional CDR residues form shallow binding pockets. Structural modeling suggests a way to understand the configuration of QNEs and the antigen-antibody interaction for QNE mAbs. Our data will be useful in designing immunogens that may elicit potent neutralizing QNE Abs.

  20. Structural Analysis of Human and Macaque Monoclonal Antibodies 2909 and 2.5B: Implications for the Configuration of the Quaternary Neutralizing Epitope of HIV-1 gp120

    PubMed Central

    Spurrier, Brett; Sampson, Jared M.; Totrov, Maxim; Li, Huiguang; O'Neal, Timothy; Williams, Constance; Robinson, James; Gorny, Miroslaw K.; Zolla-Pazner, Susan; Kong, Xiang-Peng

    2011-01-01

    Summary The quaternary neutralizing epitope (QNE) of HIV-1 gp120 is preferentially expressed on the trimeric envelope spikes of intact HIV virions, and QNE-specific monoclonal antibodies (mAbs) potently neutralize HIV-1. Here we present the crystal structures of the Fabs of human mAb 2909 and macaque mAb 2.5B. Both mAbs have long beta hairpin CDR H3 regions >20Å in length that are each situated at the center of their respective antigen-binding sites. Computational analysis showed that the paratopes include the whole CDR H3, while additional CDR residues form shallow binding pockets. Structural modeling suggests a way to understand the configuration of QNEs and the antigen antibody interaction for QNE mAbs. Our data will be useful in designing immunogens that may elicit potent neutralizing QNE Abs. PMID:21565703

  1. Structure of relativistic shocks in pulsar winds: A model of the wisps in the Crab Nebula

    NASA Technical Reports Server (NTRS)

    Gallant, Yves A.; Arons, Jonathan

    1994-01-01

    We propose a model of a optical 'wisps' of the Crab Nebula, features observed in the nebular synchrotron surface brightness near the central pulsar, as manifestations of the internal structure of the shock terminating the pulsar wind. We assume that this wind is composed of ions and a much denser plasma of electrons and positrons, frozen together to a toroidal magnetic field and flowing relativistically. We construct a form of solitary wave model of the shock structure in which we self-consistently solve for the ion orbits and the dynamics of the relativistically hot, magnetized e(+/-) background flow. We ignore dispersion in the ion energies, and we treat the pairs as an adiabatic fluid. The synchrotron emission enhancements, observed as the wisps, are then explained as the regions where reflection of the ions in the self-consistent magnetic field causes compressions of the e(+/-).

  2. Understanding the Global Structure and Evolution of Coronal Mass Ejections in the Solar Wind

    NASA Technical Reports Server (NTRS)

    Riley, Pete

    2004-01-01

    This report summarizes the technical progress made during the first six months of the second year of the NASA Living with a Star program contract Understanding the global structure and evolution of coronal mass ejections in the solar wind, between NASA and Science Applications International Corporation, and covers the period November 18, 2003 - May 17,2004. Under this contract SAIC has conducted numerical and data analysis related to fundamental issues concerning the origin, intrinsic properties, global structure, and evolution of coronal mass ejections in the solar wind. During this working period we have focused on a quantitative assessment of 5 flux rope fitting techniques. In the following sections we summarize the main aspects of this work and our proposed investigation plan for the next reporting period. Thus far, our investigation has resulted in 6 refereed scientific publications and we have presented the results at a number of scientific meetings and workshops.

  3. Structural Load Alleviation Applied to Next Generation Aircraft and Wind Turbines

    NASA Technical Reports Server (NTRS)

    Frost, Susan

    2011-01-01

    Reducing the environmental impact of aviation is a goal of the Subsonic Fixed Wing Project under the Fundamental Aeronautics Program of NASAs Aeronautics Research Mission Directorate. Environmental impact of aviation is being addressed by novel aircraft configurations and materials that reduce aircraft weight and increase aerodynamic efficiency. NASA is developing tools to address the challenges of increased airframe flexibility created by wings constructed with reduced structural material and novel light-weight materials. This talk will present a framework and demonstration of a flight control system using optimal control allocation with structural load feedback and constraints to achieve safe aircraft operation. As wind turbines age, they become susceptible to many forms of blade degradation. Results will be presented on work in progress that uses adaptive contingency control for load mitigation in a wind turbine simulation with blade damage progression modeled.

  4. Solar wind suprathermal electron Stahl widths across high-speed stream structures

    SciTech Connect

    Skoug, Ruth M; Steinberg, John T; Goodrich, Katherine A; Anderson, Brett R

    2011-01-03

    Suprathermal electrons (100-1500 eV) observed in the solar wind typically show a strahl distribution, that is, a beam directed away from the Sun along the magnetic field direction. The strahl width observed at 1 AU is highly variable, ranging from 10-70 degrees. The obsenred finite width of the strahl results from the competition between beam focusing as the interplanetary magnetic field strength drops with distance from the Sun, and pitch-angle scattering as the beam interacts with the solar wind plasma in transit from the sun. Here we examine strahl width, observed with ACE SWEPAM across high-speed stream structures to investigate variations in electron scattering as a function of local plasma characteristics. We find that narrow strahls (less than 20 degrees wide), indicating reduced scattering, are observed within high-speed streams. Narrow strahls are also observed in both very low temperature solar wind, in association with ICMEs. Case studies of high-speed streams typically show the strahl narrowing at the leading edge of the stream. In some cases, the strahl narrows at the reverse shock or pressure wave, in other cases at the stream interface. The narrowing can either occur discontinuously or gradually over a period of hours. Within the high-speed wind, the strahl remains narrow for a period of hours to days, and then gradually broadens. The strahl width is roughly constant at all energies across these structures. For some fraction of high-speed streams, counterstreaming is associated with passage of the corotating interaction region. In these cases, we find the widths of the two counterstreaming beams frequently differ by more than 40 degrees. This dramatic difference in strahl width contrasts with observations in the solar wind as a whole, in which counterstreaming strahls typically differ in width by less than 20 degrees.

  5. The nature of stream-stream interaction in the large-scale structure of the solar wind

    NASA Technical Reports Server (NTRS)

    Lee, T. S.

    1972-01-01

    The stream-stream interaction between a slow solar wind and its leading faster solar wind is considered. A hydrodynamic model comprising double-layered rarefactions and recompressions is proposed toward understanding the observed large-scale structure near the trailing portion of a high-speed stream.

  6. Spatial differences in thermal structure and variability within a small bay: Interplay of diurnal winds and tides

    NASA Astrophysics Data System (ADS)

    Bonicelli, Jessica; Moffat, Carlos; Navarrete, Sergio A.; Largier, John L.; Tapia, Fabian J.

    2014-10-01

    We characterize diurnal and semidiurnal temporal variability of the spring and summer near-shore hydrographic structure and circulation in Cartagena Bay, a small open bay in central Chile, and assess the relative role of diurnal wind and semidiurnal tide as forcing mechanisms of that variability. Our results highlight that the relative importance of these forcing mechanisms and the thermal structure can vary over small spatial scales within the bay. The water column at the southern and most wind-sheltered study site within the Bay (CTGN) was stratified all day despite the sea breeze. Throughout the water column, temperature variability at CTGN was strongly associated with the semidiurnal tide. At the northern site (ECIM), which was relatively more exposed to wind forcing, surface layer temperature fluctuations were principally diurnal and tightly associated with diurnal wind variability. The wind effect weakened near the bottom, where temperature variability was also correlated with the semidiurnal tide. At ECIM, we observed a vertically sheared cross-shore current structure, with onshore surface flow and offshore flow at mid-depth during strong winds. The diurnal variability in cross-shore flows matched diurnal variability in winds, suggesting that this vertical circulation could be directly forced by the wind. The diurnal circulation and the spatial differences in thermal structure across the bay are likely to be important for larval dispersal and material transport in and out of the Bay, as well as between near-shore waters and the shoreline.

  7. Breaking wave impact forces on truss support structures for offshore wind turbines

    NASA Astrophysics Data System (ADS)

    Cieślikiewicz, Witold; Gudmestad, Ove T.; Podrażka, Olga

    2014-05-01

    Due to depletion of the conventional energy sources, wind energy is becoming more popular these days. Wind energy is being produced mostly from onshore farms, but there is a clear tendency to transfer wind farms to the sea. The foundations of offshore wind turbines may be truss structures and might be located in shallow water, where are subjected to highly varying hydrodynamic loads, particularly from plunging breaking waves. There are models for impact forces prediction on monopiles. Typically the total wave force on slender pile from breaking waves is a superposition of slowly varying quasi-static force, calculated from the Morison equation and additional dynamical, short duration force due to the impact of the breaker front or breaker tongue. There is not much research done on the truss structures of wind turbines and there are still uncertainties on slamming wave forces, due to plunging breaking waves on those structures. Within the WaveSlam (Wave slamming forces on truss structures in shallow water) project the large scale tests were carried out in 2013 at the Large Wave Flume in Forschungszentrum Küste (FZK) in Hannover, Germany. The following institutions participated in this initiative: the University of Stavanger and the Norwegian University of Science and Technology (project management), University of Gdańsk, Poland, Hamburg University of Technology and the University of Rostock, Germany and Reinertsen AS, Norway. This work was supported by the EU 7th Framework Programme through the grant to the budget of the Integrating Activity HYDRALAB IV. The main aim of the experiment was to investigate the wave slamming forces on truss structures, development of new and improvement of existing methods to calculate forces from the plunging breakers. The majority of the measurements were carried out for regular waves with specified frequencies and wave heights as well as for the irregular waves based on JONSWAP spectrum. The truss structure was equipped with both

  8. Thermospheric Neutral Wind Observations from Three Antarctic Sites Compared with Data from Two Near-Conjugate Sites in the Northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Conde, M. G.; Wu, Q.; Anderson, C.; Aruliah, A. L.; Noto, J.; Yiu, I.; Dyson, P. L.; Davies, T.; Kosch, M.

    2011-12-01

    The 2010/2011 austral summer season saw a new narrow-field Fabry-Perot Doppler spectrometer installed at Palmer station, while an existing all-sky instrument at Mawson station was returned to service by replacing an EMCCD camera that had failed two years earlier. E-region and F-region thermospheric winds recorded in 2011 by these two instruments will be presented, together with observations from a third (narrow-field) Antarctic Fabry-Perot spectrometer that has been running at Davis station since 2004. Combined observations from these three sites characterize the large-scale thermospheric circulation over Antarctica, whereas the all-sky data from Mawson also resolves small-scale features such as divergence, shear, and gravity waves. Hemispheric differences in thermospheric winds will be examined by comparing these data with corresponding northern hemisphere winds recorded by Fabry-Perot instruments located at Millstone Hill (which is approximately conjugate to Palmer) and Longyearbyen (which is approximately conjugate to Davis and Mawson.) Inter-hemispheric comparisons will consider both the average wind patterns observed from the southern and northern sites, and case studies of individual days during the March equinox when both hemispheres were in darkness.

  9. Structure and function of broadly reactive antibody PG16 reveal an H3 subdomain that mediates potent neutralization of HIV-1

    SciTech Connect

    Pejchal, Robert; Walker, Laura M.; Stanfield, Robyn L.; Phogat, Sanjay K.; Koff, Wayne C.; Poignard, Pascal; Burton, Dennis R.; Wilson, Ian A.

    2010-11-15

    Development of an effective vaccine against HIV-1 will likely require elicitation of broad and potent neutralizing antibodies against the trimeric surface envelope glycoprotein (Env). Monoclonal antibodies (mAbs) PG9 and PG16 neutralize {approx}80% of HIV-1 isolates across all clades with extraordinary potency and target novel epitopes preferentially expressed on Env trimers. As these neutralization properties are ideal for a vaccine-elicited antibody response to HIV-1, their structural basis was investigated. The crystal structure of the antigen-binding fragment (Fab) of PG16 at 2.5 {angstrom} resolution revealed its unusually long, 28-residue, complementarity determining region (CDR) H3 forms a unique, stable subdomain that towers above the antibody surface. A 7-residue 'specificity loop' on the 'hammerhead' subdomain was identified that, when transplanted from PG16 to PG9 and vice versa, accounted for differences in the fine specificity and neutralization of these two mAbs. The PG16 electron density maps also revealed that a CDR H3 tyrosine was sulfated, which was confirmed for both PG9 (doubly) and PG16 (singly) by mass spectral analysis. We further showed that tyrosine sulfation plays a role in binding and neutralization. An N-linked glycan modification is observed in the variable light chain, but not required for antigen recognition. Further, the crystal structure of the PG9 light chain at 3.0 {angstrom} facilitated homology modeling to support the presence of these unusual features in PG9. Thus, PG9 and PG16 use unique structural features to mediate potent neutralization of HIV-1 that may be of utility in antibody engineering and for high-affinity recognition of a variety of therapeutic targets.

  10. Study of compressible coherent structures, close to ion scales, in solar wind turbulence using Cluster data

    NASA Astrophysics Data System (ADS)

    Perrone, Denise; Alexandrova, Olga; Mangeney, André; Maksimovic, Milan; Rocoto, Virgile; Pantellini, Filippo; Zaslavsky, Arnaud; Issautier, Karine

    2015-04-01

    The interplanetary medium, a weakly collisional and fully turbulent medium, can be considered the best natural laboratory to study the dynamical behavior of turbulent plasmas. A fundamental question in solar wind plasma physics is whether, space plasma turbulence can be considered as a mixture of quasi-linear waves or if the turbulence is strong with formation of coherent structures responsible for the dissipation. Here we present an automatic method to identify compressible coherent structures using Morlet wavelet decomposition of magnetic signal from Cluster spacecraft and reconstruction of magnetic fluctuations in a selected scale range (0.033-0.2 Hz). Different kind of coherent structures have been detected: from soliton-like compressible structures to current sheet- or vortex-like alfvenic structures. A multi-satellite analysis, in order to characterize 3D geometry and propagation in plasma rest frame, reveals that these structures propagate quasi-perpendicular to the mean magnetic field, with finite velocity. Moreover, the spatial scales of coherent structures have been estimated: for the selected frequency range, the distribution of spatial scales is picked around ~30 ion Larmor radius or ion inertial length (~1200 km). Our observations in the solar wind can provide constraints on theoretical modeling of small-scale turbulence and dissipation in collisionless magnetized plasmas.

  11. The changing wind structure of the WR/LBV star in HD 5980

    NASA Astrophysics Data System (ADS)

    Koenigsberger, Gloria

    2013-10-01

    HD 5980 is an extraordinary system of massive stars that is located in the Small Magellanic Cloud. It contains an eclipsing binary {P=19.3 d} consisting of a luminous blue variable {LBV} and its Wolf-Rayet {WR} companion. The LBV underwent a major eruptive event in 1994 during which its bolometric luminosity increased by a factor of 5 and it is currently approaching its minimum state of activity. The primary objective of this proposal is to determine the wind velocity and mass-loss rate of the LBV in its current state. With these observations and our earlier observations and analyses, HD 5980 offers the unprecedented opportunity of deriving all the fundamental parameters of an LBV system throughout its activity cycle, parameters which are required in order to constrain the sources of the instabilities that lead to the eruptive phenomena. To accomplish these goals, we request 2 HST orbits to observe HD 5980 with STIS in order to obtain one set of FUV MAMA and CCD spectra at the eclipse, when the LBV occults its WR companion.The study of HD 5980 and the UV spectrum that we propose to acquire are relevant to a broad range of problems including wind-wind collision phenomena, the formation of circumstellar structures powered by stellar winds and the evolution of supernova progenitors.

  12. Inverse structure functions in the canonical wind turbine array boundary layer

    NASA Astrophysics Data System (ADS)

    Viggiano, Bianca; Gion, Moira; Ali, Naseem; Tutkun, Murat; Cal, Raúl Bayoán

    2015-11-01

    Insight into the statistical behavior of the flow past an array of wind turbines is useful in determining how to improve power extraction from the overall available energy. Considering a wind tunnel experiment, hot-wire anemometer velocity signals are obtained at the centerline of a 3 x 3 canonical wind turbine array boundary layer. Two downstream locations are considered referring to the near- and far-wake, and 21 vertical points were acquired per profile. Velocity increments are used to quantify the ordinary and inverse structure functions at both locations and their relationship between the scaling exponents is noted. It is of interest to discern if there is evidence of an inverted scaling. The inverse structure functions will also be discussed from the standpoint of the proximity to the array. Observations will also address if inverted scaling exponents follow a power law behavior and furthermore, extended self-similarity of the second moment is used to obtain the scaling exponent of other moments. Inverse structure functions of moments one through eight are tested via probability density functions and the behavior of the negative moment is investigated as well. National Science Foundation-CBET-1034581.

  13. THz Limb Sounder (TLS) for Lower Thermospheric Wind, Oxygen Density, and Temperature

    NASA Technical Reports Server (NTRS)

    Wu, Dong L.; Yee, Jeng-Hwa; Schlecht, Erich; Mehdi, Imran; Siles, Jose; Drouin, Brian J.

    2016-01-01

    Neutral winds are one of the most critical measurements in the lower thermosphere and E region ionosphere (LTEI) for understanding complex electrodynamic processes and ion-neutral interactions. We are developing a high-sensitivity, low-power, noncryogenic 2.06 THz Schottky receiver to measure wind profiles at 100-140 km. The new technique, THz limb sounder (TLS), aims to measure LTEI winds by resolving the wind-induced Doppler shift of 2.06 THz atomic oxygen (OI) emissions. As a transition between fine structure levels in the ground electronic state, the OI emission is in local thermodynamic equilibrium(LTE) at altitudes up to 350km. This LTE property, together with day-and-night capability and small line-of-sight gradient, makes the OI limb sounding a very attractive technique for neutral wind observations. In addition to the wind measurement, TLS can also retrieve [OI] density and neutral temperature in the LTEI region. TLS leverages rapid advances in THz receiver technologies including subharmonically pumped (SHP)mixers and Schottky-diode-based power multipliers. Current SHP Schottky receivers have produced good sensitivity for THz frequencies at ambient environment temperatures (120-150 K), which are achievable through passively cooling in spaceflight. As an emerging technique, TLS can fill the critical data gaps in the LTEI neutral wind observations to enable detailed studies on the coupling and dynamo processes between charged and neutral molecules.

  14. THz limb sounder (TLS) for lower thermospheric wind, oxygen density, and temperature

    NASA Astrophysics Data System (ADS)

    Wu, Dong L.; Yee, Jeng-Hwa; Schlecht, Erich; Mehdi, Imran; Siles, Jose; Drouin, Brian J.

    2016-07-01

    Neutral winds are one of the most critical measurements in the lower thermosphere and E region ionosphere (LTEI) for understanding complex electrodynamic processes and ion-neutral interactions. We are developing a high-sensitivity, low-power, noncryogenic 2.06 THz Schottky receiver to measure wind profiles at 100-140 km. The new technique, THz limb sounder (TLS), aims to measure LTEI winds by resolving the wind-induced Doppler shift of 2.06 THz atomic oxygen (OI) emissions. As a transition between fine structure levels in the ground electronic state, the OI emission is in local thermodynamic equilibrium (LTE) at altitudes up to 350 km. This LTE property, together with day-and-night capability and small line-of-sight gradient, makes the OI limb sounding a very attractive technique for neutral wind observations. In addition to the wind measurement, TLS can also retrieve [OI] density and neutral temperature in the LTEI region. TLS leverages rapid advances in THz receiver technologies including subharmonically pumped (SHP) mixers and Schottky-diode-based power multipliers. Current SHP Schottky receivers have produced good sensitivity for THz frequencies at ambient environment temperatures (120-150 K), which are achievable through passively cooling in spaceflight. As an emerging technique, TLS can fill the critical data gaps in the LTEI neutral wind observations to enable detailed studies on the coupling and dynamo processes between charged and neutral molecules.

  15. Associations between Small-scale Structure in Local Galactic Neutral Hydrogen and in the Cosmic Microwave Background Observed by PLANCK

    NASA Astrophysics Data System (ADS)

    Verschuur, Gerrit L.

    2015-11-01

    High-resolution galactic neutral hydrogen (HI) data obtained with the Green Bank Telescope (GBT) over 56 square degrees of sky around l = 132°, b = 25° are compared with small-scale structure in the Cosmic Microwave Background observed by PLANCK, specifically at 143 and 857 GHz, as well as with 100 μm observations from the IRIS survey. The analysis uses data in 13 2° × 2° sub-areas found in the IRSA database at IPAC. The results confirm what has been reported previously; nearby galactic HI features and high-frequency continuum sources believed to be cosmological are in fact clearly associated. While several attempts strongly suggest that the associations are statistically significant, the key to understanding the phenomenon lies in the fact that in any given area HI is associated with cirrus dust at certain HI velocities and with 143 GHz features at different velocities. At the same time, for the 13 sub-areas studied, there is very little overlap between the dust and 143 GHz features. The data do not imply that the HI itself gives rise to the high-frequency continuum emission. Rather, they appear to indicate undiagnosed brightness enhancements indirectly associated with the HI. If low density interstellar electrons concentrated into clumps, or observed in directions where their integrated line-of-sight column densities are greater than the background in a manner similar to the phenomena that give rise to structure in diffuse HI structure, they will profoundly affect attempts to create a foreground electron mask used for processing PLANCK as well as WMAP data.

  16. Structures of complexes formed by H5 influenza hemagglutinin with a potent broadly neutralizing human monoclonal antibody

    PubMed Central

    Xiong, Xiaoli; Corti, Davide; Liu, Junfeng; Pinna, Debora; Foglierini, Mathilde; Calder, Lesley J.; Martin, Stephen R.; Lin, Yi Pu; Walker, Philip A.; Collins, Patrick J.; Monne, Isabella; Suguitan, Amorsolo L.; Santos, Celia; Temperton, Nigel J.; Subbarao, Kanta; Lanzavecchia, Antonio; Gamblin, Steven J.; Skehel, John J.

    2015-01-01

    H5N1 avian influenza viruses remain a threat to public health mainly because they can cause severe infections in humans. These viruses are widespread in birds, and they vary in antigenicity forming three major clades and numerous antigenic variants. The most important features of the human monoclonal antibody FLD194 studied here are its broad specificity for all major clades of H5 influenza HAs, its high affinity, and its ability to block virus infection, in vitro and in vivo. As a consequence, this antibody may be suitable for anti-H5 therapy and as a component of stockpiles, together with other antiviral agents, for health authorities to use if an appropriate vaccine was not available. Our mutation and structural analyses indicate that the antibody recognizes a relatively conserved site near the membrane distal tip of HA, near to, but distinct from, the receptor-binding site. Our analyses also suggest that the mechanism of infectivity neutralization involves prevention of receptor recognition as a result of steric hindrance by the Fc part of the antibody. Structural analyses by EM indicate that three Fab fragments are bound to each HA trimer. The structure revealed by X-ray crystallography is of an HA monomer bound by one Fab. The monomer has some similarities to HA in the fusion pH conformation, and the monomer’s formation, which results from the presence of isopropanol in the crystallization solvent, contributes to considerations of the process of change in conformation required for membrane fusion. PMID:26170284

  17. ASSOCIATIONS BETWEEN SMALL-SCALE STRUCTURE IN LOCAL GALACTIC NEUTRAL HYDROGEN AND IN THE COSMIC MICROWAVE BACKGROUND OBSERVED BY PLANCK

    SciTech Connect

    Verschuur, Gerrit L.

    2015-11-01

    High-resolution galactic neutral hydrogen (HI) data obtained with the Green Bank Telescope (GBT) over 56 square degrees of sky around l = 132°, b = 25° are compared with small-scale structure in the Cosmic Microwave Background observed by PLANCK, specifically at 143 and 857 GHz, as well as with 100 μm observations from the IRIS survey. The analysis uses data in 13 2° × 2° sub-areas found in the IRSA database at IPAC. The results confirm what has been reported previously; nearby galactic HI features and high-frequency continuum sources believed to be cosmological are in fact clearly associated. While several attempts strongly suggest that the associations are statistically significant, the key to understanding the phenomenon lies in the fact that in any given area HI is associated with cirrus dust at certain HI velocities and with 143 GHz features at different velocities. At the same time, for the 13 sub-areas studied, there is very little overlap between the dust and 143 GHz features. The data do not imply that the HI itself gives rise to the high-frequency continuum emission. Rather, they appear to indicate undiagnosed brightness enhancements indirectly associated with the HI. If low density interstellar electrons concentrated into clumps, or observed in directions where their integrated line-of-sight column densities are greater than the background in a manner similar to the phenomena that give rise to structure in diffuse HI structure, they will profoundly affect attempts to create a foreground electron mask used for processing PLANCK as well as WMAP data.

  18. A site of varicella-zoster virus vulnerability identified by structural studies of neutralizing antibodies bound to the glycoprotein complex gHgL.

    PubMed

    Xing, Yi; Oliver, Stefan L; Nguyen, TuongVi; Ciferri, Claudio; Nandi, Avishek; Hickman, Julie; Giovani, Cinzia; Yang, Edward; Palladino, Giuseppe; Grose, Charles; Uematsu, Yasushi; Lilja, Anders E; Arvin, Ann M; Carfí, Andrea

    2015-05-12

    Varicella-zoster virus (VZV), of the family Alphaherpesvirinae, causes varicella in children and young adults, potentially leading to herpes zoster later in life on reactivation from latency. The conserved herpesvirus glycoprotein gB and the heterodimer gHgL mediate virion envelope fusion with cell membranes during virus entry. Naturally occurring neutralizing antibodies against herpesviruses target these entry proteins. To determine the molecular basis for VZV neutralization, crystal structures of gHgL were determined in complex with fragments of antigen binding (Fabs) from two human monoclonal antibodies, IgG-94 and IgG-RC, isolated from seropositive subjects. These structures reveal that the antibodies target the same site, composed of residues from both gH and gL, distinct from two other neutralizing epitopes identified by negative-stain electron microscopy and mutational analysis. Inhibition of gB/gHgL-mediated membrane fusion and structural comparisons with herpesvirus homologs suggest that the IgG-RC/94 epitope is in proximity to the site on VZV gHgL that activates gB. Immunization studies proved that the anti-gHgL IgG-RC/94 epitope is a critical target for antibodies that neutralize VZV. Thus, the gHgL/Fab structures delineate a site of herpesvirus vulnerability targeted by natural immunity.

  19. A site of varicella-zoster virus vulnerability identified by structural studies of neutralizing antibodies bound to the glycoprotein complex gHgL

    PubMed Central

    Xing, Yi; Oliver, Stefan L.; Nguyen, TuongVi; Ciferri, Claudio; Nandi, Avishek; Hickman, Julie; Giovani, Cinzia; Yang, Edward; Palladino, Giuseppe; Grose, Charles; Uematsu, Yasushi; Lilja, Anders E.; Arvin, Ann M.; Carfí, Andrea

    2015-01-01

    Varicella-zoster virus (VZV), of the family Alphaherpesvirinae, causes varicella in children and young adults, potentially leading to herpes zoster later in life on reactivation from latency. The conserved herpesvirus glycoprotein gB and the heterodimer gHgL mediate virion envelope fusion with cell membranes during virus entry. Naturally occurring neutralizing antibodies against herpesviruses target these entry proteins. To determine the molecular basis for VZV neutralization, crystal structures of gHgL were determined in complex with fragments of antigen binding (Fabs) from two human monoclonal antibodies, IgG-94 and IgG-RC, isolated from seropositive subjects. These structures reveal that the antibodies target the same site, composed of residues from both gH and gL, distinct from two other neutralizing epitopes identified by negative-stain electron microscopy and mutational analysis. Inhibition of gB/gHgL-mediated membrane fusion and structural comparisons with herpesvirus homologs suggest that the IgG-RC/94 epitope is in proximity to the site on VZV gHgL that activates gB. Immunization studies proved that the anti-gHgL IgG-RC/94 epitope is a critical target for antibodies that neutralize VZV. Thus, the gHgL/Fab structures delineate a site of herpesvirus vulnerability targeted by natural immunity. PMID:25918416

  20. A site of varicella-zoster virus vulnerability identified by structural studies of neutralizing antibodies bound to the glycoprotein complex gHgL.

    PubMed

    Xing, Yi; Oliver, Stefan L; Nguyen, TuongVi; Ciferri, Claudio; Nandi, Avishek; Hickman, Julie; Giovani, Cinzia; Yang, Edward; Palladino, Giuseppe; Grose, Charles; Uematsu, Yasushi; Lilja, Anders E; Arvin, Ann M; Carfí, Andrea

    2015-05-12

    Varicella-zoster virus (VZV), of the family Alphaherpesvirinae, causes varicella in children and young adults, potentially leading to herpes zoster later in life on reactivation from latency. The conserved herpesvirus glycoprotein gB and the heterodimer gHgL mediate virion envelope fusion with cell membranes during virus entry. Naturally occurring neutralizing antibodies against herpesviruses target these entry proteins. To determine the molecular basis for VZV neutralization, crystal structures of gHgL were determined in complex with fragments of antigen binding (Fabs) from two human monoclonal antibodies, IgG-94 and IgG-RC, isolated from seropositive subjects. These structures reveal that the antibodies target the same site, composed of residues from both gH and gL, distinct from two other neutralizing epitopes identified by negative-stain electron microscopy and mutational analysis. Inhibition of gB/gHgL-mediated membrane fusion and structural comparisons with herpesvirus homologs suggest that the IgG-RC/94 epitope is in proximity to the site on VZV gHgL that activates gB. Immunization studies proved that the anti-gHgL IgG-RC/94 epitope is a critical target for antibodies that neutralize VZV. Thus, the gHgL/Fab structures delineate a site of herpesvirus vulnerability targeted by natural immunity. PMID:25918416

  1. A novel structure of transmission line pulse transformer with mutually coupled windings.

    PubMed

    Yu, Binxiong; Su, Jiancang; Li, Rui; Zhao, Liang; Zhang, Xibo; Wang, Junjie

    2014-03-01

    A novel structure of transmission line transformer (TLT) with mutually coupled windings is described in this paper. All transmission lines except the first stage of the transformer are wound on a common ferrite core for the TLT with this structure. A referral method was introduced to analyze the TLT with this structure, and an analytic expression of the step response was derived. It is shown that a TLT with this structure has a significantly slower droop rate than a TLT with other winding structures and the number of ferrite cores needed is largely reduced. A four-stage TLT with this structure was developed, whose input and output impedance were 4.2 Ω and 67.7 Ω, respectively. A frequency response test of the TLT was carried out. The test results showed that pulse response time of the TLT is several nanoseconds. The TLT described in this paper has the potential to be used as a rectangle pulse transformer with very fast response time.

  2. Structural Basis of HIV-1 Neutralization by Affinity Matured Fabs Directed against the Internal Trimeric Coiled-Coil of gp41

    SciTech Connect

    Gustchina, Elena; Li, Mi; Louis, John M.; Anderson, D.Eric; Lloyd, John; Frisch, Christian; Bewley, Carole A.; Gustchina, Alla; Wlodawer, Alexander; Clore, G.Marius

    2010-12-03

    The conserved internal trimeric coiled-coil of the N-heptad repeat (N-HR) of HIV-1 gp41 is transiently exposed during the fusion process by forming a pre-hairpin intermediate, thus representing an attractive target for the design of fusion inhibitors and neutralizing antibodies. In previous studies we reported a series of broadly neutralizing mini-antibodies derived from a synthetic naive human combinatorial antibody library by panning against a mimetic of the trimeric N-HR coiled coil, followed by affinity maturation using targeted diversification of the CDR-H2 loop. Here we report crystal structures of the N-HR mimetic 5-Helix with two Fabs that represent the extremes of this series: Fab 8066 is broadly neutralizing across a wide panel of B and C type HIV-1 viruses, whereas Fab 8062 is non-neutralizing. The crystal structures reveal important differences in the conformations of the CDR-H2 loops in the complexes that propagate into other regions of the antigen-antibody interface, and suggest that both neutralization properties and affinity for the target can be attributed, at least in part, to the differences in the interactions of the CDR-H2 loops with the antigen. Furthermore, modeling of the complex of an N-HR trimer with three Fabs suggests that the CDR-H2 loop may be involved in close intermolecular contacts between neighboring antibody molecules, and that such contacts may hinder the formation of complexes between the N-HR trimer and more than one antibody molecule depending on the conformation of the bound CDR-H2 loop which is defined by its interactions with antigen. Comparison with the crystal structure of the complex of 5-Helix with another neutralizing monoclonal antibody known as D5, derived using an entirely different antibody library and panning procedure, reveals remarkable convergence in the optimal sequence and conformation of the CDR-H2 loop.

  3. Computation of wind-induced vibrations of flexible shells and membranous structures

    NASA Astrophysics Data System (ADS)

    Glück, M.; Breuer, M.; Durst, F.; Halfmann, A.; Rank, E.

    2003-04-01

    A partitioned coupling approach for time-dependent fluid-structure interactions is applied to thin shells and membranous structures with large displacements. The frame algorithm connects a three-dimensional, finite volume-based multi-block flow solver for incompressible fluids with a finite element code for geometrically nonlinear structural problems using a commercial coupling interface. Thus a high modularity is achieved and the whole range of opportunities with these two powerful codes - each of them highly adapted to its specific field of application - can be used also for coupled simulations. Two completely different configurations were investigated. First, the coupling algorithm was applied to an academic test configuration consisting of one, two, and three flexible L-shaped plates being loaded by a steady far-field flow. Various investigations were carried out at different Reynolds numbers /(Re=50,200, and 500) in order to study phenomena such as vortex shedding, resonance, influence of the interaction between several flexible plates, whereas the second and third plates were placed in the wake of the first. The second part of the paper shows that in principle the coupling procedure can also deal with real-life structures as they occur in civil engineering. A membranous roof of glass-fiber synthetics with a complex shape was exposed to a time-dependent wind gust from diagonally above which was superimposed on a constant basic wind flow parallel to the ground. The structural model contains the pre-stressed textile roof including the taut cables at its circumference which are fastened at the pylons. As a structural response, the wind gust led to a displacement of the textile roof which disappeared again when the gust subsided. With the coupled algorithm proposed in the paper it is possible to study dynamic interactions for engineering applications.

  4. Vibronic coupling effects on the structure and spectroscopy of neutral and charged TiO2 clusters

    NASA Astrophysics Data System (ADS)

    Taylor, Daniel J.; Paterson, Martin J.

    2012-10-01

    We present a detailed computational study of the structure of small (TiO2)n nanoclusters including neutral closed-shell, radical cation, and radical anion species. We show that the geometries can be rationalised in terms of the pseudo-Jahn-Teller effect. A variety of methods are employed including CASSCF, DFT (and TD-DFT), EOM-CCSD, and Bruekner doubles (BD). The CASSCF method uses symmetry restrictions on analytical Hessians and can be seen as benchmark results for the smallest systems. Using these for calibration we then show that in general the B3LYP functional in conjunction with a reasonably large all electron basis is reasonably accurate, and in conjunction with TD-B3LYP can give a qualitative picture of the underlying pseudo-Jahn-Teller vibronic coupling effects. We do however show that artificial symmetry breaking does occur for some radical clusters, and that different DFT functionals unfortunately display this in a non-systematic manner.

  5. Structures of HIV-1-Env V1V2 with broadly neutralizing antibodies reveal commonalities that enable vaccine design

    PubMed Central

    Gorman, Jason; Soto, Cinque; Yang, Max M.; Davenport, Thaddeus M.; Guttman, Miklos; Bailer, Robert T.; Chambers, Michael; Chuang, Gwo-Yu; DeKosky, Brandon J.; Doria-Rose, Nicole A.; Druz, Aliaksandr; Ernandes, Michael J.; Georgiev, Ivelin S.; Jarosinski, Marissa C.; Joyce, M. Gordon; Lemmin, Thomas M.; Leung, Sherman; Louder, Mark K.; McDaniel, Jonathan R.; Narpala, Sandeep; Pancera, Marie; Stuckey, Jonathan; Wu, Xueling; Yang, Yongping; Zhang, Baoshan; Zhou, Tongqing; Mullikin, James C.; Baxa, Ulrich; Georgiou, George; McDermott, Adrian B.; Bonsignori, Mattia; Haynes, Barton F.; Moore, Penny L.; Morris, Lynn; Lee, Kelly K.; Shapiro, Lawrence; Mascola, John R.; Kwong, Peter D.

    2016-01-01

    Broadly neutralizing antibodies (bNAbs) against HIV-1-Env V1V2 arise in multiple donors. However, atomic-level interactions had only been determined with antibodies from a single donor, making commonalities in recognition uncertain. Here we report the co-crystal structure of V1V2 with antibody CH03 from a second donor and model Env interactions of antibody CAP256-VRC26 from a third. These V1V2-directed bNAbs utilized strand-strand interactions between a protruding antibody loop and a V1V2 strand, but differed in their N-glycan recognition. Ontogeny analysis indicated protruding loops to develop early, with glycan interactions maturing over time. Altogether, the multidonor information suggested V1V2-directed bNAbs to form an ‘extended class’, for which we engineered ontogeny-specific antigens: Env trimers with chimeric V1V2s that interacted with inferred ancestor and intermediate antibodies. The ontogeny-based design of vaccine antigens described here may provide a general means for eliciting antibodies of a desired class. PMID:26689967

  6. Differential Velocity between Solar Wind Protons and Alpha Particles in Pressure Balance Structures

    NASA Technical Reports Server (NTRS)

    Yamauchi, Yohei; Suess, Steven T.; Steinberg, John T.; Sakurai, Takashi

    2004-01-01

    Pressure balance structures (PBSs) are a common high-plasma beta feature in high-latitude, high-speed solar wind. They have been proposed as remnants of coronal plumes. If true, they should reflect the observation that plumes are rooted in unipolar magnetic flux concentrations in the photosphere and are heated as oppositely directed flux is advected into and reconnects with the flux concentration. A minimum variance analysis (MVA) of magnetic discontinuities in PBSs showed there is a larger proportion of tangential discontinuities than in the surrounding high-speed wind, supporting the hypothesis that plasmoids or extended current sheets are formed during reconnection at the base of plumes. To further evaluate the character of magnetic field discontinuities in PBSs, differential streaming between alpha particles and protons is analyzed here for the same sample of PBSs used in the MVA. Alpha particles in high-speed wind generally have a higher radial flow speed than protons. However, if the magnetic field is folded back on itself, as in a large-amplitude Alfven wave, alpha particles will locally have a radial flow speed less than protons. This characteristic is used here to distinguish between folded back magnetic fields (which would contain rotational discontinuities) and tangential discontinuities using Ulysses high-latitude, high-speed solar wind data. The analysis indicates that almost all reversals in the radial magnetic field in PBSs are folded back field lines. This is found to also be true outside PBSs, supporting existing results for typical high-speed, high-latitude wind. There remains a small number of cases that appear not to be folds in the magnetic field and which may be flux tubes with both ends rooted in the Sun. The distinct difference in MVA results inside and outside PBSs remains unexplained.

  7. Wind Structure and Luminosity Variations in the Wolf-Rayet/Luminous Blue Variable HD 5980

    NASA Astrophysics Data System (ADS)

    Georgiev, Leonid; Koenigsberger, Gloria; Hillier, D. John; Morrell, Nidia; Barbá, Rodolfo; Gamen, Roberto

    2011-12-01

    Over the past 40 years, the massive luminous blue variable/Wolf-Rayet system HD 5980 in the Small Magellanic Cloud (SMC) has undergone a long-term S Doradus-type variability cycle and two brief and violent eruptions in 1993 and 1994. In this paper we analyze a collection of UV and optical spectra obtained between 1979 and 2009 and perform CMFGEN model fits to spectra of 1994, 2000, 2002, and 2009. The results are as follows: (1) the long-term S Dor-type variability is associated with changes of the hydrostatic radius; (2) the 1994 eruption involved changes in its bolometric luminosity and wind structure; (3) the emission-line strength, the wind velocity, and the continuum luminosity underwent correlated variations in the sense that a decreasing V ∞ is associated with increasing emission line and continuum levels; and (4) the spectrum of the third star in the system (Star C) is well fit by a T eff = 32 K model atmosphere with SMC chemical abundances. For all epochs, the wind of the erupting star is optically thick at the sonic point and is thus driven mainly by the continuum opacity. We speculate that the wind switches between two stable regimes driven by the "hot" (during the eruption) and the "cool" (post-eruption) iron opacity bumps as defined by Lamers & Nugis and Gräfener & Hamann, and thus the wind may undergo a bi-stability jump of a different nature from that which occurs in OB stars. Based on data obtained with HST, IUE, FUSE, and the 6.5 m Magellan telescopes at Las Campanas Observatory in Chile.

  8. Propagation of the 12 May 1997 interplanetary coronal mass ejection in evolving solar wind structures

    NASA Astrophysics Data System (ADS)

    Odstrcil, D.; Pizzo, V. J.; Arge, C. N.

    2005-02-01

    Recently, we simulated the 12 May 1997 coronal mass ejection (CME) event with a numerical three-dimensional magnetohydrodynamic model (Odstrcil et al., 2004), in which the background solar wind was determined from the Science Applications International Corporation (SAIC) coronal model (Riley et al., 2001) and the transient disturbance was determined from the cone model (Zhao et al., 2002). Although we reproduced with some fidelity the arrival of the shock and interplanetary CME at Earth, detailed analysis of the simulations showed a poorly defined shock and discrepancies in the standoff distance between the shock and the driving ejecta and in the inclination of the shock with respect to the Sun-Earth line. In this paper, we investigate these problems in more detail. First, we use an alternative coronal outflow model, the so-called Wang-Sheeley-Arge-Mount Wilson Observatory (WSA-MWO) model (Arge and Pizzo, 2000; Arge et al., 2002; Arge et al., 2004), to assess the effect of using synoptic, full rotation coronal maps that differ in method of preparation. Second, we investigate how differences in the presumed evolution of the coronal stream structure affect the propagation of the disturbance. We incorporate two time-dependent boundary conditions for the ambient solar wind as determined by the WSA model, one derived from pseudo daily updated maps and one derived from artificially modified full rotation maps. Numerical results from these different scenarios are compared with solar wind observations at Earth. We find that heliospheric simulations with the SAIC and WSA full rotation models provide qualitatively similar parameters of the background solar wind and transient disturbances at Earth. Improved agreement with the observations is achieved by artificially modified maps that simulate the rapid displacement of the coronal hole boundary after the CME eruption. We also consider how multipoint temporal profiles of solar wind parameters and multiperspective synthetic

  9. Distortion of thermospheric air masses by horizontal neutral winds over Poker Flat Alaska measured using an all-sky scanning Doppler imager

    NASA Astrophysics Data System (ADS)

    Dhadly, M. S.; Conde, M.

    2016-01-01

    An air mass transported by a wind field will become distorted over time by any gradients present in the wind field. To study this effect in Earth's thermosphere, we examine the behavior of a simple parameter that we describe here as the "distortion gradient." It incorporates all of the wind field's departures from uniformity and is thus capable of representing all contributions to the distortion or mixing of air masses. The distortion gradient is defined such that it is always positive, so averaging over time and/or space does not suppress small-scale features. Conventional gradients, by contrast, are signed quantities that would often average to zero. To analyze the climatological behavior of this distortion gradient, we used three years (2010, 2011, and 2012) of thermospheric F region wind observations from a high-latitude ground-based all-sky wavelength scanning Doppler Fabry-Perot interferometer located at Poker Flat Alaska. Climatological averaging of the distortion gradient allowed us to investigate its diurnal and seasonal (annual) behaviors at our observing location. Distortion was observed to be higher before local magnetic midnight and to be seasonally dependent. While maximum distortion occurred before local magnetic midnight under all geomagnetic conditions, the peak distortion occurred earlier under moderate geomagnetic conditions as compared to the quiet geomagnetic conditions and even earlier still when geomagnetic conditions were active. Peak distortion was stronger and appeared earlier when interplanetary magnetic field (IMF) was southward compared to northward. By contrast, we could not resolve any time-shift effect due to the IMF component tangential to Earth's orbit.

  10. Surface solitary waves and solitons. [in solar atmosphere and solar wind magnetic structure

    NASA Technical Reports Server (NTRS)

    Hollweg, J. V.; Roberts, B.

    1984-01-01

    The solar atmosphere and solar wind are magnetically structured. The structuring can include tangential discontinuities, which can support surface waves. Such waves can be dispersive. This means that dispersion and nonlinearity can balance in such a way that solitary waves (or solitons) can result. This general point is illustrated by a two-dimensional nonlinear analysis which explicitly demonstrates the presence of long-wavelength solitary waves propagating on tangential discontinuities. If the waves are only weakly nonlinear, then they obey the Korteweg-de Vries equation and are true solitons.

  11. Fabrication of low cost composite tooling for filament winding large structures

    NASA Astrophysics Data System (ADS)

    Miller, Timothy S.; Fortin, Christopher J.

    A TQM/concurrent engineering approach has been used to create a low cost filament-winding mandrel for large launch-vehicle structure fabrication. The process involves the fabrication of a low cost/low temperature master model, followed by the building of the mandrel and its backup structure within the master. Mandrels fabricated by these means are able to maintain full vacuum integrity and dimensional stability throughout high-temperature cure cycles; the reduced thermal mass of the mandrel results in part-cure cycles that are shorter than those associated with conventional mandrel materials.

  12. Interception of spray drift by border structures. Part 1: wind tunnel experiments.

    PubMed

    De Schampheleire, M; Nuyttens, D; Dekeyser, D; Verboven, P; Cornelis, W; Gabriels, D; Spanoghe, P

    2008-01-01

    This research investigated the drift-intercepting potential of structures surrounding the field borders, like artificial screens and crops, which are not yet a part of the drift mitigation measures for field crop sprayers in Belgium. Drift-interception experiments were performed in the wind tunnel of the International Centre for Eremology (Ghent University, Belgium) with various interception structures: Artificial screens with heights of 0.5, 0.75 and 1 m and screen open areas of 16, 36 and 63%; a row of plastic Christmas trees with heights of 0.5 and 0.75 m; and a potato canopy. The interception structure was positioned at 1 m from the field border. From the results it was found that type of border structure has a pronounced effect on the drift interception, while the height of the border structure had no significant effect.

  13. Learning the Relationship between the Primary Structure of HIV Envelope Glycoproteins and Neutralization Activity of Particular Antibodies by Using Artificial Neural Networks

    PubMed Central

    Buiu, Cătălin; Putz, Mihai V.; Avram, Speranta

    2016-01-01

    The dependency between the primary structure of HIV envelope glycoproteins (ENV) and the neutralization data for given antibodies is very complicated and depends on a large number of factors, such as the binding affinity of a given antibody for a given ENV protein, and the intrinsic infection kinetics of the viral strain. This paper presents a first approach to learning these dependencies using an artificial feedforward neural network which is trained to learn from experimental data. The results presented here demonstrate that the trained neural network is able to generalize on new viral strains and to predict reliable values of neutralizing activities of given antibodies against HIV-1. PMID:27727189

  14. A numerical investigation of the wake structure of vertical axis wind turbines

    NASA Astrophysics Data System (ADS)

    Balaras, Elias; Posa, Antonio; Leftwich, Megan

    2014-11-01

    Recent field-testing has shown that vertical axis wind turbines (VAWT) in wind farm configurations have the potential to reach higher power densities, when compared to the more widespread horizontal axis turbines. A critical component in achieving this goal is a good understanding of the wake structure and how it is influenced by operating conditions. In the present study the Large-Eddy Simulation technique is adopted to characterize the wake of a small vertical axis wind turbine and to explore its dependence on the value of its Tip Speed Ratio (TSR). It will be shown that its wake significantly differs from that of a spinning cylinder, often adopted to model this typology of machines: the displacement of the momentum deficit towards the windward side follows the same behavior, but turbulence is higher on the leeward side. An initial increase of the momentum deficit is observed moving downstream, with central peaks in the core of the near wake for both momentum and turbulent kinetic energy, especially at lower TSRs. No back-flow is produced downstream of the turbine. The interaction between blades is stronger at higher values of the TSR, while the production of coherent structures is enhanced at lower TSRs, with large rollers populating the leeward side of the wake.

  15. Seismic analysis of offshore wind turbines on bottom-fixed support structures.

    PubMed

    Alati, Natale; Failla, Giuseppe; Arena, Felice

    2015-02-28

    This study investigates the seismic response of a horizontal axis wind turbine on two bottom-fixed support structures for transitional water depths (30-60 m), a tripod and a jacket, both resting on pile foundations. Fully coupled, nonlinear time-domain simulations on full system models are carried out under combined wind-wave-earthquake loadings, for different load cases, considering fixed and flexible foundation models. It is shown that earthquake loading may cause a significant increase of stress resultant demands, even for moderate peak ground accelerations, and that fully coupled nonlinear time-domain simulations on full system models are essential to capture relevant information on the moment demand in the rotor blades, which cannot be predicted by analyses on simplified models allowed by existing standards. A comparison with some typical design load cases substantiates the need for an accurate seismic assessment in sites at risk from earthquakes.

  16. Seismic analysis of offshore wind turbines on bottom-fixed support structures.

    PubMed

    Alati, Natale; Failla, Giuseppe; Arena, Felice

    2015-02-28

    This study investigates the seismic response of a horizontal axis wind turbine on two bottom-fixed support structures for transitional water depths (30-60 m), a tripod and a jacket, both resting on pile foundations. Fully coupled, nonlinear time-domain simulations on full system models are carried out under combined wind-wave-earthquake loadings, for different load cases, considering fixed and flexible foundation models. It is shown that earthquake loading may cause a significant increase of stress resultant demands, even for moderate peak ground accelerations, and that fully coupled nonlinear time-domain simulations on full system models are essential to capture relevant information on the moment demand in the rotor blades, which cannot be predicted by analyses on simplified models allowed by existing standards. A comparison with some typical design load cases substantiates the need for an accurate seismic assessment in sites at risk from earthquakes. PMID:25583865

  17. The use of long term monitoring data for the extension of the service duration of existing wind turbine support structures

    NASA Astrophysics Data System (ADS)

    Loraux, C.; Brühwiler, E.

    2016-09-01

    Actual wind energy converter (WEC) are designed for a relatively short service life of 20 years and the limiting criterion is the fatigue safety. However, effective fatigue loading endured by the structural components of the wind turbines (WT) is likely to be much below design assumptions provided by current codes. This paper describes a simple but efficient long term monitoring system that allows owners to verify the fatigue safety of their existing WTs. The monitored data will also help to drastically extend the service life of existing wind turbine support structure and will thus reduce the global environmental footprint of WTs.

  18. The neutral surface layer above rough surfaces

    NASA Astrophysics Data System (ADS)

    Smedman, Ann-Sofi; Sahlee, Erik

    2014-05-01

    It is generally accepted that turbulent fluxes (momentum and scalar fluxes) are approx. constant with height above horizontal surfaces with low roughness. But what will happen when the roughness sub-layer is large as found over cities, forests and rough seas? In a study of the kinematic structure of the near neutral atmospheric surface layer, Högström, Hunt and Smedman, 2002, it was demonstrated that a model with detached eddies from above the surface layer impinging on to the surface (Hunt and Morison, 2000) could explain some of the observed features in the neutral atmospheric boundary layer. Thus the detached eddy model proved successful in explaining the dynamic structure of the near neutral atmospheric surface layer, especially the shape of the spectra of the wind components and scalars and corresponding fluxes. Here we make the hypothesis that the detached-eddy model can also be used to explain the experimental results related to the 3-dimensional turbulence structure above rough surfaces. Measurements are taken both over land (grass and forest) and over sea (Baltic Sea and hurricane Fabian in the Atlantic) above the roughness sub-layer. Analysis of the turbulence structure shows a striking similarity between the different sites. Hunt, J.C.R and Morrison, J.F., 2000: Eddy structure in turbulent boundary layers, Euro. J. Mech. B-Fluids, 19, 673-694. Högström, U., Hunt, J.C.R., and Smedman, A., 2002: Theory and measurements for turbulence spectra and variances in the atmospheric neutral surface layer, Bound.-Layer Meteorol., 103,101-124.

  19. Influence of electron-neutral collisions on the Compton scattering cross section and the Salpeter structure factor in warm collisional plasmas

    SciTech Connect

    Song, Mi-Young; Yoon, Jung-Sik; Jung, Young-Dae

    2015-03-15

    The electron-neutral collision effects on the Compton scattering process are investigated in warm collisional plasmas. The Compton scattering cross section in warm collisional plasmas is obtained by the Salpeter structure factor with the fluctuation-dissipation theorem and the plasma dielectric function as a function of the electron-neutral collision frequency, Debye length, and wave number. It is shown that the influence of electron-neutral collision strongly suppresses the Compton scattering cross section in warm collisional plasmas. It is also found that the electron-neutral collision effect on the differential Compton scattering cross section is more significant in forward scattering directions. We show that the differential Compton scattering cross section has a maximum at the scattering angle φ=π/2. In addition, we find that the electron-neutral collision effect on the total Compton scattering cross section increases with increasing Debye length and wave number. The variation of the Compton scattering cross section due to the change of collision frequency and plasma parameters is also discussed.

  20. The impact of forest edge structure on longitudinal patterns of deposition, wind speed, and turbulence

    NASA Astrophysics Data System (ADS)

    Wuyts, Karen; Verheyen, Kris; De Schrijver, An; Cornelis, Wim M.; Gabriels, Donald

    The impact of forest edge structure on edge patterns of wind speed, turbulence, and atmospheric deposition was studied by means of a model forest in a wind tunnel. Tests were conducted with eight structure configurations, encompassing combinations of stem densities, crown depths, and edge transitions (steep or gradual edge). Mean wind speed and its standard deviation (as a measure for turbulence) were determined within and at the top of the canopy; deposition was simulated using Cl - aerosols. Edge patterns of wind speed, turbulence, and deposition were closely related and were significantly affected by stem density and, particularly, by edge transition. In the dense forests, the edge effect on deposition extended less deeply into the forest than in the sparse forests, so the deposition in the forest edge zone was lowered with 40%. Gradual edges were able to limit the level by which deposition is enhanced at the edge in comparison with the forest interior deposition, and consequently, they reduced the deposition in the forest edge zone with 66%. Even when the deposition on the trees of the gradually ascending vegetation in front of the forest edge was taken into account, gradual edges were still advantageous in comparison with steep edges. A lower crown depth decreased the enhancement of deposition at the edge relative to the interior, but only at steep edges. We conclude that an adjusted layout of forest edges should be able to mitigate the edge effects on atmospheric deposition, through reducing the deposition enhancement at the edge or the penetration depth of the edge effect.

  1. Sensitivities of eyewall replacement cycle to model physics, vortex structure, and background winds in numerical simulations of tropical cyclones

    NASA Astrophysics Data System (ADS)

    Zhu, Zhenduo; Zhu, Ping

    2015-01-01

    series of sensitivity experiments by the Weather Research and Forecasting (WRF) model is used to investigate the impact of model physics, vortex axisymmetric radial structure, and background wind on secondary eyewall formation (SEF) and eyewall replacement cycle (ERC) in three-dimensional full physics numerical simulations. It is found that the vertical turbulent mixing parameterization can substantially affect the concentric ring structure of tangential wind associated with SEF through a complicated interaction among eyewall and outer rainband heating, radial inflow in the boundary layer, surface layer processes, and shallow convection in the moat. Large snow terminal velocity can substantially change the vertical distribution of eyewall diabatic heating to result in a strong radial inflow in the boundary layer, and thus, favors the development of shallow convection in the moat allowing the outer rainband convection to move closer to the inner eyewall, which may leave little room both temporally and spatially for a full development of a secondary maximum of tangential wind. Small radius of maximum wind (RMW) of a vortex and small potential vorticity (PV) skirt outside the RMW tend to generate double-eyewall replacement and may lead to an ERC without a clean secondary concentric maximum of tangential wind. A sufficiently large background wind can smooth out an ERC that would otherwise occur without background wind for a vortex with a small or moderate PV skirt. However, background wind does not appear to have an impact on an ERC if the vortex has a sufficiently large PV skirt.

  2. Multivariate QST-FST comparisons: a neutrality test for the evolution of the g matrix in structured populations.

    PubMed

    Martin, Guillaume; Chapuis, Elodie; Goudet, Jérôme

    2008-12-01

    Neutrality tests in quantitative genetics provide a statistical framework for the detection of selection on polygenic traits in wild populations. However, the existing method based on comparisons of divergence at neutral markers and quantitative traits (Q(st)-F(st)) suffers from several limitations that hinder a clear interpretation of the results with typical empirical designs. In this article, we propose a multivariate extension of this neutrality test based on empirical estimates of the among-populations (D) and within-populations (G) covariance matrices by MANOVA. A simple pattern is expected under neutrality: D = 2F(st)/(1 - F(st))G, so that neutrality implies both proportionality of the two matrices and a specific value of the proportionality coefficient. This pattern is tested using Flury's framework for matrix comparison [common principal-component (CPC) analysis], a well-known tool in G matrix evolution studies. We show the importance of using a Bartlett adjustment of the test for the small sample sizes typically found in empirical studies. We propose a dual test: (i) that the proportionality coefficient is not different from its neutral expectation [2F(st)/(1 - F(st))] and (ii) that the MANOVA estimates of mean square matrices between and among populations are proportional. These two tests combined provide a more stringent test for neutrality than the classic Q(st)-F(st) comparison and avoid several statistical problems. Extensive simulations of realistic empirical designs suggest that these tests correctly detect the expected pattern under neutrality and have enough power to efficiently detect mild to strong selection (homogeneous, heterogeneous, or mixed) when it is occurring on a set of traits. This method also provides a rigorous and quantitative framework for disentangling the effects of different selection regimes and of drift on the evolution of the G matrix. We discuss practical requirements for the proper application of our test in empirical

  3. Periodic Density Structures and the Origin of the Slow Solar Wind

    NASA Technical Reports Server (NTRS)

    Viall-Kepko, Nicholeen M.; Vourlidas, Angelos

    2015-01-01

    The source of the slow solar wind has challenged scientists for years. Periodic density structures (PDSs), observed regularly in the solar wind at 1 AU (Astronomical Unit), can be used to address this challenge. These structures have length scales of hundreds to several thousands of megameters and frequencies of tens to hundreds of minutes. Two lines of evidence indicate that PDSs are formed in the solar corona as part of the slow solar wind release and/or acceleration processes. The first is corresponding changes in compositional data in situ, and the second is PDSs observed in the inner Heliospheric Imaging data on board the Solar Terrestrial Relations Observatory (STEREO)/Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) suite. The periodic nature of these density structures is both a useful identifier as well as an important physical constraint on their origin. In this paper, we present the results of tracking periodic structures identified in the inner Heliospheric Imager in SECCHI back in time through the corresponding outer coronagraph (COR2) images. We demonstrate that the PDSs are formed around or below 2.5 solar radii-the inner edge of the COR2 field of view. We compute the occurrence rates of PDSs in 10 days of COR2 images both as a function of their periodicity and location in the solar corona, and we find that this set of PDSs occurs preferentially with a periodicity of approximately 90 minutes and occurs near streamers. Lastly, we show that their acceleration and expansion through COR2 is self-similar, thus their frequency is constant at distances beyond 2.5 solar radii.

  4. Periodic Density Structures and the Origin of the Slow Solar Wind

    NASA Astrophysics Data System (ADS)

    Viall, Nicholeen M.; Vourlidas, Angelos

    2015-07-01

    The source of the slow solar wind has challenged scientists for years. Periodic density structures (PDSs), observed regularly in the solar wind at 1 AU, can be used to address this challenge. These structures have length scales of hundreds to several thousands of megameters and frequencies of tens to hundreds of minutes. Two lines of evidence indicate that PDSs are formed in the solar corona as part of the slow solar wind release and/or acceleration processes. The first is corresponding changes in compositional data in situ, and the second is PDSs observed in the inner Heliospheric Imaging data on board the Solar Terrestrial Relations Observatory (STEREO)/Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) suite. The periodic nature of these density structures is both a useful identifier as well as an important physical constraint on their origin. In this paper, we present the results of tracking periodic structures identified in the inner Heliospheric Imager in SECCHI back in time through the corresponding outer coronagraph (COR2) images. We demonstrate that the PDSs are formed around or below 2.5 solar radii—the inner edge of the COR2 field of view. We compute the occurrence rates of PDSs in 10 days of COR2 images both as a function of their periodicity and location in the solar corona, and we find that this set of PDSs occurs preferentially with a periodicity of ˜90 minutes and occurs near streamers. Lastly, we show that their acceleration and expansion through COR2 is self-similar, thus their frequency is constant at distances beyond 2.5 solar radii.

  5. Diffusion in the vicinity of standard-design nuclear power plants--I. Wind-tunnel evaluation of diffusive characteristics of a simulated suburban neutral atmospheric boundary layer.

    PubMed

    Payne, A W; Snyder, W H; Binkowski, F S; Watson, J E

    1982-12-01

    A large meteorological wind tunnel was used to simulate a suburban atmospheric boundary layer. The model-prototype scale was 1:300 and the roughness length was approximately 1.0 m full scale. The model boundary layer simulated full scale dispersion from ground-level and elevated release points over surfaces of comparable roughness length. This information should prove useful in a variety of transport and diffusion studies over short to moderate downwind distances. It will be used in Part II as the baseline data set with which to compare diffusion downwind of standard-design nuclear power plants.

  6. Morphology of solar wind fluctuations and structure in the vicinity of the Sun from radio propagation measurements

    NASA Technical Reports Server (NTRS)

    Woo, R.

    1995-01-01

    Radio propagation measurements represent a powerful means for remote probing of electron density and solar wind speed in the acceleration region of the solar wind not yet explored by in situ measurements. Recent investigations based on radio propagation measurements have led to considerable progress in our knowledge of the general morphology of solar wind fluctuations and structure, especially in terms of their relationship to solar wind properties that have been observed directly by fields and particles measurements, and to coronal features observed in white-light measurements. The purpose of this paper is to present an overview of the latest results on quasi-stationary structure covering the large scale variation of solar wind speed over the streamer belt and coronal hole regions, coronal streamers (source of slow solar wind) and their associated small-scale electron density structure, plumes, density and fractional or relative density fluctuations, and the spectral characteristics of the electron density fluctuations. The radio propagation measurements not only reveal new information on the structure near the Sun, but also show that the structure appears to undergo substantial evolution on its way to 0.3 AU, the closest radial distance for which direct in situ spacecraft measurements are available.

  7. Structural health and prognostics management for the enhancement of offshore wind turbine operations and maintenance strategies

    DOE PAGES

    Griffith, D. Todd; Yoder, Nathanael C.; Resor, Brian; White, Jonathan; Paquette, Joshua

    2013-09-19

    Offshore wind turbines are an attractive source for clean and renewable energy for reasons including their proximity to population centers and higher capacity factors. One obstacle to the more widespread installation of offshore wind turbines in the USA, however, is that recent projections of offshore operations and maintenance costs vary from two to five times the land-based costs. One way in which these costs could be reduced is through use of a structural health and prognostics management (SHPM) system as part of a condition-based maintenance paradigm with smart loads management. Our paper contributes to the development of such strategies bymore » developing an initial roadmap for SHPM, with application to the blades. One of the key elements of the approach is a multiscale simulation approach developed to identify how the underlying physics of the system are affected by the presence of damage and how these changes manifest themselves in the operational response of a full turbine. A case study of a trailing edge disbond is analysed to demonstrate the multiscale sensitivity of damage approach and to show the potential life extension and increased energy capture that can be achieved using simple changes in the overall turbine control and loads management strategy. Finally, the integration of health monitoring information, economic considerations such as repair costs versus state of health, and a smart loads management methodology provides an initial roadmap for reducing operations and maintenance costs for offshore wind farms while increasing turbine availability and overall profit.« less

  8. Structural health and prognostics management for the enhancement of offshore wind turbine operations and maintenance strategies

    SciTech Connect

    Griffith, D. Todd; Yoder, Nathanael C.; Resor, Brian; White, Jonathan; Paquette, Joshua

    2013-09-19

    Offshore wind turbines are an attractive source for clean and renewable energy for reasons including their proximity to population centers and higher capacity factors. One obstacle to the more widespread installation of offshore wind turbines in the USA, however, is that recent projections of offshore operations and maintenance costs vary from two to five times the land-based costs. One way in which these costs could be reduced is through use of a structural health and prognostics management (SHPM) system as part of a condition-based maintenance paradigm with smart loads management. Our paper contributes to the development of such strategies by developing an initial roadmap for SHPM, with application to the blades. One of the key elements of the approach is a multiscale simulation approach developed to identify how the underlying physics of the system are affected by the presence of damage and how these changes manifest themselves in the operational response of a full turbine. A case study of a trailing edge disbond is analysed to demonstrate the multiscale sensitivity of damage approach and to show the potential life extension and increased energy capture that can be achieved using simple changes in the overall turbine control and loads management strategy. Finally, the integration of health monitoring information, economic considerations such as repair costs versus state of health, and a smart loads management methodology provides an initial roadmap for reducing operations and maintenance costs for offshore wind farms while increasing turbine availability and overall profit.

  9. Economics of online structural health monitoring of wind turbines: Cost benefit analysis

    NASA Astrophysics Data System (ADS)

    Van Dam, Jeremy; Bond, Leonard J.

    2015-03-01

    Operations and maintenance (O&M) costs have an average share over the lifetime of the turbine of approximately 20%-25% of the total levelized cost per kWh of electricity produced. Online structural health monitoring (OSHM) and condition-based maintenance (CBM) of wind turbine blades has the potential to reduce O&M costs and hence reduce the overall cost of wind energy. OSHM and CBM offer the potential to improve turbine blade life cycle management, limit the number of physical inspections, and reduce the potential for missed significant defects. An OSHM system would reduce the need for physical inspections, and have inspections occur only after problem detection takes place. In the economics of wind energy, failures and unplanned outages can cause significant downtime, particularly while waiting for the manufacturing and shipping of major parts. This paper will report a review and assessment of SHM technologies and a cost benefit analysis, which will examine whether the added costs associated with an OSHM system will give an adequate return on the investment. One method in which OSHM reduces costs is, in part, by converting corrective maintenance to preventative maintenance. This paper shows that under both best and worse conditions implementing an OSHM system is cost effective in more than 50% of the trials, which have been performed. Opportunities appear to exist to improve the economic justification for implementing OSHM.

  10. Composite Structural Analysis of Flat-Back Shaped Blade for Multi-MW Class Wind Turbine

    NASA Astrophysics Data System (ADS)

    Kim, Soo-Hyun; Bang, Hyung-Joon; Shin, Hyung-Ki; Jang, Moon-Seok

    2014-06-01

    This paper provides an overview of failure mode estimation based on 3D structural finite element (FE) analysis of the flat-back shaped wind turbine blade. Buckling stability, fiber failure (FF), and inter-fiber failure (IFF) analyses were performed to account for delamination or matrix failure of composite materials and to predict the realistic behavior of the entire blade region. Puck's fracture criteria were used for IFF evaluation. Blade design loads applicable to multi-megawatt (MW) wind turbine systems were calculated according to the Germanischer Lloyd (GL) guideline and the International Electrotechnical Commission (IEC) 61400-1 standard, under Class IIA wind conditions. After the post-processing of final load results, a number of principal load cases were selected and converted into applied forces at the each section along the blade's radius of the FE model. Nonlinear static analyses were performed for laminate failure, FF, and IFF check. For buckling stability, linear eigenvalue analysis was performed. As a result, we were able to estimate the failure mode and locate the major weak point.

  11. The solar wind interaction with Venus - Pioneer Venus observations of bow shock location and structure

    NASA Astrophysics Data System (ADS)

    Slavin, J. A.; Elphic, R. C.; Russell, C. T.; Scarf, F. L.; Wolfe, J. H.; Mihalov, J. D.; Intriligator, D. S.; Brace, L. H.; Taylor, H. A.; Daniell, R. E.

    1980-12-01

    Pioneer Venus observations are used in carrying out a study of the location and structure of the Venus bow shock. The trace of the shock in the solar wind aberrated terminator plane is almost circular at an altitude of 1.38 Venus radii independent of interplanetary magnetic field orientation with an extrapolated subsolar height of 0.38 Venus radii. Gas dynamic relations and scaling of the terrestrial analogue are used in determining the effective impenetrable obstacle altitude from the mean shock surface with the conclusion that it lies beneath the observed height of the ionopause. The short-term variability in shock position is similar to that found at the earth; over the long-term bow shock, altitude varies by up to approximately 35% in phase with the solar cycle for reasons other than changing solar wind Mach number. In contrast to ionopause position, which is shown to be well determined by external pressure measurements, it is found that bow shock altitude is only weakly dependent on ionopause height and solar wind dynamic pressure.

  12. Effect of coherent structures on energetic particle intensity in the solar wind

    NASA Astrophysics Data System (ADS)

    Tessein, Jeffrey A.

    Solar energetic particles in the solar wind are accelerated in both solar flares and shocks assocated with fast coronal mass ejections. They follow the interplanetary magnetic field and, upon reaching Earth, have implications for space weather. Space weather affects astronaut health and orbiting equipment through radiation hazard and electrical infrastructure on the ground with ground induced currents. Economic im- pacts include disruption of GPS and redirection of commercial polar flights due to a dangerous radiation environment over the poles. By studying how these particles interact with the magnetic fields we can better predict onset times and diffusion of these events. We find, using superposed epoch analysis and conditional statisitics from spacecraft observations that there is a strong association between energetic particles in the solar wind and magnetic discontinuities. This may be related to turbulent dissipa- tion mechanisms in which coherent structures in the solar wind seem to be preferred sites of heating, plasma instabilites and dissipation. In the case of energetic particles, magnetic reconnection and transport in flux tubes are likely to play a role. Though we focus on data away from large shocks, trapping can occur in the downstream region of shocks due to the preponderance of compressive turbulence in these areas. This thesis lays the ground work for the results described above with an intro- duction to solar wind and heliospheric physics in Chapter 1. Chapter 2 is an intro- duction to the acceleration mechanisms that give rise to observed energetic particle events. Chapter 3 describes various data analysis techniques and statistics that are bread and butter when analyzing spacecraft data for turbulence and energetic particle studies. Chapter 4 is a digression that covers preliminary studies that were done on the side; scale dependent kurtosis, ergodic studies and initial conditions for simulations. Chapter 5 contains that central published

  13. Structure of Turbulence in Katabatic Flows Below and Above the Wind-Speed Maximum

    NASA Astrophysics Data System (ADS)

    Grachev, Andrey A.; Leo, Laura S.; Sabatino, Silvana Di; Fernando, Harindra J. S.; Pardyjak, Eric R.; Fairall, Christopher W.

    2016-06-01

    Measurements of small-scale turbulence made in the atmospheric boundary layer over complex terrain during the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program are used to describe the structure of turbulence in katabatic flows. Turbulent and mean meteorological data were continuously measured on four towers deployed along the east lower slope (2-4°) of Granite Mountain near Salt Lake City in Utah, USA. The multi-level (up to seven) observations made during a 30-day long MATERHORN field campaign in September-October 2012 allowed the study of temporal and spatial structure of katabatic flows in detail, and herein we report turbulence statistics (e.g., fluxes, variances, spectra, and cospectra) and their variations in katabatic flow. Observed vertical profiles show steep gradients near the surface, but in the layer above the slope jet the vertical variability is smaller. It is found that the vertical (normal to the slope) momentum flux and horizontal (along-slope) heat flux in a slope-following coordinate system change their sign below and above the wind maximum of a katabatic flow. The momentum flux is directed downward (upward) whereas the along-slope heat flux is downslope (upslope) below (above) the wind maximum. This suggests that the position of the jet-speed maximum can be obtained by linear interpolation between positive and negative values of the momentum flux (or the along-slope heat flux) to derive the height where the flux becomes zero. It is shown that the standard deviations of all wind-speed components (and therefore of the turbulent kinetic energy) and the dissipation rate of turbulent kinetic energy have a local minimum, whereas the standard deviation of air temperature has an absolute maximum at the height of wind-speed maximum. We report several cases when the destructive effect of vertical heat flux is completely cancelled by the generation of turbulence due to the along-slope heat flux. Turbulence above the wind

  14. Broadening of the Interplanetary Helium Cone Structure Due to Elastic Collisions of LISM Helium Atoms with Solar Wind Ions

    NASA Technical Reports Server (NTRS)

    Fahr, H. J.; Nass, H. U.; Rucinski, D.

    1984-01-01

    Neutral interstellar particles penetrating into the heliosphere, besides being subject there to specific loss processes, suffer elastic collisions with KeV-solar wind ions. The momentum transfer to the neutrals connected with these collisions leads to a loss of angular momentum with respect to the Sun and to a fractional compensation of the effective solar gravity. The dynamical particle trajectories hence are changed into non-Keplerians leading to density and temperature distributions differing from those calculated in the past. This is found from a solution of the Boltzmann equation that linearizes the effect of this additional force. It is shown that the HeI-584A resonance glow of the heliospheric helium cone lead to substantially lower interstellar helium temperatures if re-interpreted on the basis of this revised theory. These temperatures now seem to be in accordance with the derived temperatures for interstellar hydrogen.

  15. Broadening of the interplanetary helium cone structure due to elastic collisions of LISM helium atoms with solar wind ions

    NASA Astrophysics Data System (ADS)

    Fahr, H. J.; Nass, H. U.; Rucinski, D.

    1984-11-01

    Neutral interstellar particles penetrating into the heliosphere, besides being subject there to specific loss processes, suffer elastic collisions with KeV-solar wind ions. The momentum transfer to the neutrals connected with these collisions leads to a loss of angular momentum with respect to the Sun and to a fractional compensation of the effective solar gravity. The dynamical particle trajectories hence are changed into non-Keplerians leading to density and temperature distributions differing from those calculated in the past. This is found from a solution of the Boltzmann equation that linearizes the effect of this additional force. It is shown that the HeI-584A resonance glow of the heliospheric helium cone lead to substantially lower interstellar helium temperatures if re-interpreted on the basis of this revised theory. These temperatures now seem to be in accordance with the derived temperatures for interstellar hydrogen.

  16. Development of Self-Powered Wireless Structural Health Monitoring (SHM) for Wind Turbine Blades

    NASA Astrophysics Data System (ADS)

    Lim, Dong-Won

    Wind turbine blade failure can lead to unexpected power interruptions. Monitoring wind turbine blades is important to ensure seamless electricity delivery from power generation to consumers. Structural health monitoring (SHM) enables early recognition of structural problems so that the safety and reliability of operation can be enhanced. This dissertation focuses on the development of a wireless SHM system for wind turbine blades. The sensor is comprised of a piezoelectric energy harvester (EH) and a telemetry unit. The sensor node is mounted on the blade surface. As the blade rotates, the blade flexes, and the energy harvester captures the strain energy on the blade surface. Once sufficient electricity is captured, a pulse is sent from the sensing node to a gateway. Then, a central monitoring algorithm processes a series of pulses received from all three blades. This wireless SHM, which uses commercially available components, can be retrofitted to existing turbines. The harvested energy for sensing can be estimated in terms of two factors: the available strain energy and conversion efficiency. The available strain energy was evaluated using the FAST (Fatigue, Aerodynamics, Structures, and Turbulence) simulator. The conversion efficiency was studied analytically and experimentally. An experimental set-up was designed to mimic the expected strain frequency and amplitude for rotor blades. From a series of experiments, the efficiency of a piezoelectric EH at a typical rotor speed (0.2 Hz) was approximately 0.5%. The power requirement for sending one measurement (280 muJ) can be achieved in 10 minutes. Designing a detection algorithm is challenging due to this low sampling rate. A new sensing approach-the timing of pulses from the transmitter-was introduced. This pulse timing, which is tied to the charging time, is indicative of the structural health. The SHM system exploits the inherent triple redundancy of the three blades. The timing data of the three blades are

  17. Structural and functional plasticity specific to musical training with wind instruments.

    PubMed

    Choi, Uk-Su; Sung, Yul-Wan; Hong, Sujin; Chung, Jun-Young; Ogawa, Seiji

    2015-01-01

    Numerous neuroimaging studies have shown structural and functional changes resulting from musical training. Among these studies, changes in primary sensory areas are mostly related to motor functions. In this study, we looked for some similar functional and structural changes in other functional modalities, such as somatosensory function, by examining the effects of musical training with wind instruments. We found significant changes in two aspects of neuroplasticity, cortical thickness, and resting-state neuronal networks. A group of subjects with several years of continuous musical training and who are currently playing in university wind ensembles showed differences in cortical thickness in lip- and tongue-related brain areas vs. non-music playing subjects. Cortical thickness in lip-related brain areas was significantly thicker and that in tongue-related areas was significantly thinner in the music playing group compared with that in the non-music playing group. Association analysis of lip-related areas in the music playing group showed that the increase in cortical thickness was caused by musical training. In addition, seed-based correlation analysis showed differential activation in the precentral gyrus and supplementary motor areas (SMA) between the music and non-music playing groups. These results suggest that high-intensity training with specific musical instruments could induce structural changes in related anatomical areas and could also generate a new functional neuronal network in the brain.

  18. Structural and functional plasticity specific to musical training with wind instruments

    PubMed Central

    Choi, Uk-Su; Sung, Yul-Wan; Hong, Sujin; Chung, Jun-Young; Ogawa, Seiji

    2015-01-01

    Numerous neuroimaging studies have shown structural and functional changes resulting from musical training. Among these studies, changes in primary sensory areas are mostly related to motor functions. In this study, we looked for some similar functional and structural changes in other functional modalities, such as somatosensory function, by examining the effects of musical training with wind instruments. We found significant changes in two aspects of neuroplasticity, cortical thickness, and resting-state neuronal networks. A group of subjects with several years of continuous musical training and who are currently playing in university wind ensembles showed differences in cortical thickness in lip- and tongue-related brain areas vs. non-music playing subjects. Cortical thickness in lip-related brain areas was significantly thicker and that in tongue-related areas was significantly thinner in the music playing group compared with that in the non-music playing group. Association analysis of lip-related areas in the music playing group showed that the increase in cortical thickness was caused by musical training. In addition, seed-based correlation analysis showed differential activation in the precentral gyrus and supplementary motor areas (SMA) between the music and non-music playing groups. These results suggest that high-intensity training with specific musical instruments could induce structural changes in related anatomical areas and could also generate a new functional neuronal network in the brain. PMID:26578939

  19. Wind tunnel investigation of the effect of high relative velocities on the structural integrity of birds

    NASA Technical Reports Server (NTRS)

    Bresnahan, D. L.

    1972-01-01

    An experimental investigation was conducted in a supersonic wind tunnel to determine the effect a sudden high velocity headwind had on the physical deformation and structural breakup characteristics of birds. Several sizes of recently killed birds were dropped into the test section at free-stream Mach numbers ranging from 0.2 to 0.8 and photographed with high-speed motion-picture cameras. These conditions simulated flow conditions encountered when birds are ingested into the inlets of high speed aircraft, thereby constituting a safety hazard to the aircraft and its occupants. The investigation shows that, over the range of headwind conditions tested, the birds remained structurally intact and did not suffer any appreciable deformation or structural breakup.

  20. Inverse Load Calculation of Wind Turbine Support Structures - A Numerical Verification Using the Comprehensive Simulation Code FAST: Preprint (Revised)

    SciTech Connect

    Pahn, T.; Jonkman, J.; Rolges, R.; Robertson, A.

    2012-11-01

    Physically measuring the dynamic responses of wind turbine support structures enables the calculation of the applied loads using an inverse procedure. In this process, inverse means deriving the inputs/forces from the outputs/responses. This paper presents results of a numerical verification of such an inverse load calculation. For this verification, the comprehensive simulation code FAST is used. FAST accounts for the coupled dynamics of wind inflow, aerodynamics, elasticity and turbine controls. Simulations are run using a 5-MW onshore wind turbine model with a tubular tower. Both the applied loads due to the instantaneous wind field and the resulting system responses are known from the simulations. Using the system responses as inputs to the inverse calculation, the applied loads are calculated, which in this case are the rotor thrust forces. These forces are compared to the rotor thrust forces known from the FAST simulations. The results of these comparisons are presented to assess the accuracy of the inverse calculation. To study the influences of turbine controls, load cases in normal operation between cut-in and rated wind speed, near rated wind speed and between rated and cut-out wind speed are chosen. The presented study shows that the inverse load calculation is capable of computing very good estimates of the rotor thrust. The accuracy of the inverse calculation does not depend on the control activity of the wind turbine.

  1. Waves of 3D marine structures slamming at different initial poses in complex wind-wave-flow environments

    NASA Astrophysics Data System (ADS)

    Zhu, Liang-sheng; Yu, Long-fei

    2016-10-01

    Aimed at the hydrodynamic response for marine structures slamming into water, based on the mechanism analysis to the slamming process, and by combining 3D N-S equation and k- ɛ turbulent kinetic equation with structure fully 6DOF motion equation, a mathematical model for the wind-fluid-solid interaction is established in 3D marine structure slamming wave at free poses and wind-wave-flow complex environments. Compared with the results of physical model test, the numerical results from the slamming wave well correspond with the experimental results. Through the mathematical model, the wave-making issue of 3D marine structure at initial pose falls into water in different complex wind, wave and flow environments is investigated. The research results show that various kinds of natural factors and structure initial poses have different influence on the slamming wave, and there is an obvious rule in this process.

  2. Structural and thermotropic properties of calcium-dimyristoylphosphatidic acid complexes at acidic and neutral pH conditions.

    PubMed Central

    Takahashi, H.; Yasue, T.; Ohki, K.; Hatta, I.

    1995-01-01

    Two kinds of calcium-dimyristoylphosphatidic acid (DMPA) complexes at acidic and neutral pH conditions were prepared in the following ways. The complex at pH 4 was obtained by adding Ca2+ to DMPA dispersion in pure water. On the other hand, the complex at pH 7.4 was obtained by adding Ca2+ to DMPA dispersion in the presence of NaOH. The stoichiometries of Ca2+ ion to DMPA molecule are 0.5-0.67 and approximately 1 for the complexes at pH 4 and 7.4, respectively. Static x-ray diffraction shows that the hydrocarbon chains of the Ca(2+)-DMPA complex at pH 4 at 20 degrees C are more tightly packed than those of the complex at pH 7.4 at 20 degrees C. Furthermore, the complex at pH 4 at 20 degrees C gives rise to several reflections that might be related to the ordered arrangement of the Ca2+ ions. These results indicate that the structure of the complex at pH 4 is crystalline-like. In the differential scanning calorimetry (DSC) thermogram, the complex at pH 7.4 undergoes no phase transition in a temperature range between 30 and 80 degrees C. On the other hand, in the DSC thermogram for the complex at pH 4, a peak appears at 65.8 degrees C in the first heating scan. In the successive second heating scan, a transition peak appears at 63.5 degrees C. In connection with the DSC results, the structural changes associated with these phase transitions were studied with temperature-scan x-ray diffraction. In the first heating scan, although a peak appears at 65.80C in the DSC thermogram, the hydrocarbon chain packing gradually converts from an orthorhombic lattice to a hexagonal lattice near 52 degree C, and successively the chain melting phase transition occurs near 670C. In the second heating scan, the hydrocarbon chains are packed in a hexagonal lattice over the whole temperature range and the chain melting phase transition occurs near 63.5 degree C. Therefore,the Ca2+-DMPA complex at pH 4 has a metastable state. The metastable state transforms to a stable state by

  3. Multiple damage identification on a wind turbine blade using a structural neural system

    NASA Astrophysics Data System (ADS)

    Kirikera, Goutham R.; Schulz, Mark J.; Sundaresan, Mannur J.

    2007-04-01

    A large number of sensors are required to perform real-time structural health monitoring (SHM) to detect acoustic emissions (AE) produced by damage growth on large complicated structures. This requires a large number of high sampling rate data acquisition channels to analyze high frequency signals. To overcome the cost and complexity of having such a large data acquisition system, a structural neural system (SNS) was developed. The SNS reduces the required number of data acquisition channels and predicts the location of damage within a sensor grid. The sensor grid uses interconnected sensor nodes to form continuous sensors. The combination of continuous sensors and the biomimetic parallel processing of the SNS tremendously reduce the complexity of SHM. A wave simulation algorithm (WSA) was developed to understand the flexural wave propagation in composite structures and to utilize the code for developing the SNS. Simulation of AE responses in a plate and comparison with experimental results are shown in the paper. The SNS was recently tested by a team of researchers from University of Cincinnati and North Carolina A&T State University during a quasi-static proof test of a 9 meter long wind turbine blade at the National Renewable Energy Laboratory (NREL) test facility in Golden, Colorado. Twelve piezoelectric sensor nodes were used to form four continuous sensors to monitor the condition of the blade during the test. The four continuous sensors are used as inputs to the SNS. There are only two analog output channels of the SNS, and these signals are digitized and analyzed in a computer to detect damage. In the test of the wind turbine blade, multiple damages were identified and later verified by sectioning of the blade. The results of damage identification using the SNS during this proof test will be shown in this paper. Overall, the SNS is very sensitive and can detect damage on complex structures with ribs, joints, and different materials, and the system

  4. A bow-shaped thermal structure traveling upstream of the zonal wind flow of Venus atmosphere

    NASA Astrophysics Data System (ADS)

    Taguchi, Makoto; Fukuhara, Tetsuya; Imamura, Takeshi; Kouyama, Toru; Nakamura, Masato; Sato, Takao M.; Ueno, Munetaka; Suzuki, Makoto; Iwagami, Naomoto; Sato, Mitsuteru; Hashimoto, George L.; Takagi, Seiko; Akatsuki Science Team

    2016-10-01

    The Longwave Infrared Camera (LIR) onboard the Japanese Venus orbiter Akatsuki acquires a snap shot of Venus in the middle infrared region, and provides a brightness temperature distribution at the cloud-top altitudes of about 65 km. Hundreds of images taken by LIR have been transferred to the ground since the successful Venus orbit insertion of Akatsuki on Dec. 7, 2015. Here we report that a bow shaped thermal structure extending from the northern high latitudes to the southern high latitudes was found in the brightness temperature map on Dec. 7, 2015, and that it lasted for four days at least surprisingly at almost same geographical position. The bow shape structure looks symmetrical with the equator, and consists of a high temperature region in east or upstream of the background strong westward wind or the super rotation of the Venus atmosphere followed by a low temperature region in west with an amplitude of 5 K. It appeared close to the evening terminator in the dayside, and seems not to have stayed in the same local time rather to have co-rotated with the slowly rotating ground where the western part of Aphrodite Continent was below the center of the bow shape. Meridionally aligned dark filaments similar to the bow shape structure in shape but in much smaller scale were also identified in the brightness temperature map on Dec. 7, and they propagated upstream of the zonal wind as well. The bow shape structure disappeared when LIR observed the same local time and longitude in the earliest opportunity on Jan. 16, 2016. Similar events, though their amplitudes were less than 1 K, were found on Apr. 15 and 26, 2016, but they appeared in different local times and longitudes. A simulation of a gravity wave generated in the lower atmosphere and propagating upward reproduces the observed bow shape structure. The bow shape structure could be a signature of transferring momentum from the ground to the upper atmosphere.

  5. Analysis of the thermal structure of the "Ora del Garda" wind from airborne and surface measurements

    NASA Astrophysics Data System (ADS)

    Laiti, L.; Zardi, D.; de Franceschi, M.

    2010-09-01

    Systems of daily-periodic valley winds typically develop in the Alps, driven by the interaction between the thermally forced motion of air masses and the complex orographic configuration. The occurrence of large lakes can mark these phenomena with local peculiarities. This study investigates a well known valley/lake breeze phenomenon, the so-called Ora del Garda. The latter is a diurnal wind originating in the late morning of sunny days on the northern shores of Lake Garda, channelling into the Sarca River Valley and the Lakes Valley nearby, and reaching, on days of greater intensity, the Adige River Valley, where it gets mixed with the local up-valley winds and produces a strong and gusty local flow. The Ora blows very regularly on sunny days under fair weather conditions, from late spring to early autumn, and marks local weather conditions in the area. In order to explore how the development of this wind affects the boundary layer processes in the valleys, and in particular temperature and humidity structures, three measurements campaigns were performed in 1998-1999, including flights of an instrumented light airplane. Each flight trajectory explored three or four sections along the valley at specific locations (namely over the lake coast, at half valley, at the end of the valley). By following spiralling paths on vertical planes oriented either along or cross valley, data allowing detailed pictures of atmospheric structure on these sections were collected. At the same time data from surface weather stations located both on the valley floor and on the sidewall slopes were collected and analysed. In particular measurements from radiometers allowed to monitor the evolution of the radiation forcing the valley wind. For each single section suitable analytical expressions for mean vertical temperature and humidity profiles were first inferred to determine the dominating vertical structure. Then the characteristic spatial scales of variability of local deviations from

  6. Structural health monitoring of wind turbine blades : SE 265 Final Project.

    SciTech Connect

    Barkley, W. C.; Jacobs, Laura D.; Rutherford, A. C.; Puckett, Anthony

    2006-03-23

    ACME Wind Turbine Corporation has contacted our dynamic analysis firm regarding structural health monitoring of their wind turbine blades. ACME has had several failures in previous years. Examples are shown in Figure 1. These failures have resulted in economic loss for the company due to down time of the turbines (lost revenue) and repair costs. Blade failures can occur in several modes, which may depend on the type of construction and load history. Cracking and delamination are some typical modes of blade failure. ACME warranties its turbines and wishes to decrease the number of blade failures they have to repair and replace. The company wishes to implement a real time structural health monitoring system in order to better understand when blade replacement is necessary. Because of warranty costs incurred to date, ACME is interested in either changing the warranty period for the blades in question or predicting imminent failure before it occurs. ACME's current practice is to increase the number of physical inspections when blades are approaching the end of their fatigue lives. Implementation of an in situ monitoring system would eliminate or greatly reduce the need for such physical inspections. Another benefit of such a monitoring system is that the life of any given component could be extended since real conditions would be monitored. The SHM system designed for ACME must be able to operate while the wind turbine is in service. This means that wireless communication options will likely be implemented. Because blade failures occur due to cyclic stresses in the blade material, the sensing system will focus on monitoring strain at various points.

  7. Brillouin Corrosion Expansion Sensors for Steel Reinforced Concrete Structures Using a Fiber Optic Coil Winding Method

    PubMed Central

    Zhao, Xuefeng; Gong, Peng; Qiao, Guofu; Lu, Jie; Lv, Xingjun; Ou, Jinping

    2011-01-01

    In this paper, a novel kind of method to monitor corrosion expansion of steel rebars in steel reinforced concrete structures named fiber optic coil winding method is proposed, discussed and tested. It is based on the fiber optical Brillouin sensing technique. Firstly, a strain calibration experiment is designed and conducted to obtain the strain coefficient of single mode fiber optics. Results have shown that there is a good linear relationship between Brillouin frequency and applied strain. Then, three kinds of novel fiber optical Brillouin corrosion expansion sensors with different fiber optic coil winding packaging schemes are designed. Sensors were embedded into concrete specimens to monitor expansion strain caused by steel rebar corrosion, and their performance was studied in a designed electrochemical corrosion acceleration experiment. Experimental results have shown that expansion strain along the fiber optic coil winding area can be detected and measured by the three kinds of sensors with different measurement range during development the corrosion. With the assumption of uniform corrosion, diameters of corrosion steel rebars were obtained using calculated average strains. A maximum expansion strain of 6,738 με was monitored. Furthermore, the uniform corrosion analysis model was established and the evaluation formula to evaluate mass loss rate of steel rebar under a given corrosion rust expansion rate was derived. The research has shown that three kinds of Brillouin sensors can be used to monitor the steel rebar corrosion expansion of reinforced concrete structures with good sensitivity, accuracy and monitoring range, and can be applied to monitor different levels of corrosion. By means of this kind of monitoring technique, quantitative corrosion expansion monitoring can be carried out, with the virtues of long durability, real-time monitoring and quasi-distribution monitoring. PMID:22346672

  8. Vertical structure of cross-shore currents from wind-induced setup

    USGS Publications Warehouse

    Gelfenbaum, Guy

    1991-01-01

    Most of the storm surge models presented in the literature are vertically averaged and calculate only the sea-surface elevation and mean flow. Whereas these models may be adequate for predicting storm surge heights for flooding purposes, they neglect the vertical structure of the flow and the boundary shear stress, which are both critical for predicting cross-shore sediment transport. The steady and horizontally uniform equations of motion are used here to compute the sea-surface slope, the vertical structure of the cross-shore currents, and the boundary shear stress in a shallow wind dominated environment. The steady state model developed here balances the pressure gradient and the stress divergence, resulting in sea-surface slope and associated pressure gradient in the opposite direction of the wind, thus inducing a reversal in the currents near the bed. The Reynolds stress is modeled with a depth-dependent turbulent diffusion coefficient so that both the boundary shear stress and the velocity field are calculated, avoiding the need to set a bottom drag coefficient. Input parameters for this model are simply the wind stress, the water depth, and z0, the bed roughness parameter. A sensitivity test of the model results to various values of z0 indicates that large changes in z0 cause only minor differences in the surface slope, and moderate differences in the velocity field and boundary shear stress. Given the sediment size distribution and the small scale morphology of the bed, a reasonable estimate of z0 may be obtained and the above uncertainty will be nearly eliminated.

  9. Simulations of Atmospheric Neutral Wave Coupling to the Ionosphere

    NASA Astrophysics Data System (ADS)

    Siefring, C. L.; Bernhardt, P. A.

    2005-12-01

    The densities in the E- and F-layer plasmas are much less than the density of background neutral atmosphere. Atmospheric neutral waves are primary sources of plasma density fluctuations and are the sources for triggering plasma instabilities. The neutral atmosphere supports acoustic waves, acoustic gravity waves, and Kelvin Helmholtz waves from wind shears. These waves help determine the structure of the ionosphere by changes in neutral density that affect ion-electron recombination and by neutral velocities that couple to the plasma via ion-neutral collisions. Neutral acoustic disturbances can arise from thunderstorms, chemical factory explosions and intentional high-explosive tests. Based on conservation of energy, acoustic waves grow in amplitude as they propagate upwards to lower atmospheric densities. Shock waves can form in an acoustic pulse that is eventually damped by viscosity. Ionospheric effects from acoustic waves include transient perturbations of E- and F-Regions and triggering of E-Region instabilities. Acoustic-gravity waves affect the ionosphere over large distances. Gravity wave sources include thunderstorms, auroral region disturbances, Space Shuttle launches and possibly solar eclipses. Low frequency acoustic-gravity waves propagate to yield traveling ionospheric disturbances (TID's), triggering of Equatorial bubbles, and possible periodic structuring of the E-Region. Gravity wave triggering of equatorial bubbles is studied numerically by solving the equations for plasma continuity and ion velocity along with Ohms law to provide an equation for the induced electric potential. Slow moving gravity waves provide density depressions on bottom of ionosphere and a gravitational Rayleigh-Taylor instability is initiated. Radar scatter detects field aligned irregularities in the resulting plasma bubble. Neutral Kelvin-Helmholtz waves are produced by strong mesospheric wind shears that are also coincident with the formation of intense E-layers. An

  10. Structural damage detection in wind turbine blades based on time series representations of dynamic responses

    NASA Astrophysics Data System (ADS)

    Hoell, Simon; Omenzetter, Piotr

    2015-03-01

    The development of large wind turbines that enable to harvest energy more efficiently is a consequence of the increasing demand for renewables in the world. To optimize the potential energy output, light and flexible wind turbine blades (WTBs) are designed. However, the higher flexibilities and lower buckling capacities adversely affect the long-term safety and reliability of WTBs, and thus the increased operation and maintenance costs reduce the expected revenue. Effective structural health monitoring techniques can help to counteract this by limiting inspection efforts and avoiding unplanned maintenance actions. Vibration-based methods deserve high attention due to the moderate instrumentation efforts and the applicability for in-service measurements. The present paper proposes the use of cross-correlations (CCs) of acceleration responses between sensors at different locations for structural damage detection in WTBs. CCs were in the past successfully applied for damage detection in numerical and experimental beam structures while utilizing only single lags between the signals. The present approach uses vectors of CC coefficients for multiple lags between measurements of two selected sensors taken from multiple possible combinations of sensors. To reduce the dimensionality of the damage sensitive feature (DSF) vectors, principal component analysis is performed. The optimal number of principal components (PCs) is chosen with respect to a statistical threshold. Finally, the detection phase uses the selected PCs of the healthy structure to calculate scores from a current DSF vector, where statistical hypothesis testing is performed for making a decision about the current structural state. The method is applied to laboratory experiments conducted on a small WTB with non-destructive damage scenarios.

  11. Cosmic ray decreases and particle acceleration in 1978-1982 and the associated solar wind structures

    NASA Technical Reports Server (NTRS)

    Cane, H. V.; Richardson, I. G.; Von Rosenvinge, T. T.

    1993-01-01

    Results of a study of the time histories of particles in the energy range 1 MeV to 1 GeV at the times of greater than 3-percent cosmic ray decreases in the years 1978-1982 are presented. The intensity-time profiles of the particles are used to separate the cosmic ray decreases into four classes which are subsequently associated with three types of solar wind structures. Decreases in class 1 (15 events) and class 2 (26 events) are associated with shocks driven by energetic coronal mass ejections. For class 1 events, the ejecta are detected at 1 AU, whereas this is not usually the case for class 2 events. The shock must therefore play a dominant role in producing the cosmic ray depression in class 2 events. It is argued that since energetic particles (from MEV to GeV energies) seen at earth may respond to solar wind structures which are not detected at earth, consideration of particle observations over a wide range of energies is necessary for a full understanding of cosmic ray decreases.

  12. Wireless monitoring of structural components of wind turbines including tower and foundations

    NASA Astrophysics Data System (ADS)

    Wondra, B.; Botz, M.; Grosse, C. U.

    2016-09-01

    Only few large wind turbines contain an extensive structural health monitoring (SHM) system. Such SHM systems could provide deeper insight into the real load history of a wind turbine along its standard lifetime of 20 years and support a justified extension of operation beyond the original intended period. This paper presents a new concept of a wireless SHM system based on acceleration measurement sensor nodes to permanently record acceleration of the tower structure at different heights. Exploitation of acceleration data and its referring position on the turbine tower enables calculation of vibration frequencies, their amplitudes and subsequently eigenmodes. Tower heights of 100 m and more are within the transmission range of wireless nodes, enabling a complete surveillance of the tower in three dimensions without the need for long cabling or electric signal amplification. Mounting of the sensor nodes on the tower is not limited to a few positions by the presence of an electric cable anymore. Still a comparison between data recorded by wireless sensors and data recorded by high-resolution wire-based sensors shows that the present resolution of the wireless sensors has to be improved to record accelerations more accurately and thus analyze vibration frequencies more precisely.

  13. Rotor anisotropy as a blade damage indicator for wind turbine structural health monitoring systems

    NASA Astrophysics Data System (ADS)

    Tcherniak, Dmitri

    2016-06-01

    Structural damage of a rotor blade causes structural anisotropy of the rotor. In rotor dynamic, the anisotropy affects the symmetry of the rotor mode shapes, and the latter can be utilized to detect the blade damage. The mode shape symmetry can be characterized by relative blades' magnitude and phase. The study examines the potential use of these parameters as rotor damage indicators. Firstly the indicators are studied analytically using a simple 6 degrees-of-freedom model of a rotating rotor. Floquet analysis is used due to the time periodic nature of the considered system. Floquet analysis allows one to perform analytical modal decomposition of the system and study the sensitivity of the damage indicators to the amount of damage. Secondly, operational modal analysis (OMA) is involved to extract the same damage indicators from simulated experimental data, which was synthesized via numerical simulations. Finally, the same procedure was applied to operating Vestas V27 wind turbine, first using the simulated experimental data obtained by using aeroelastic simulation code HAWC2 and then using the data acquired during the measurement campaign on a real wind turbine. The study demonstrates that the proposed damage indicators are significantly more sensitive than the commonly used changes in natural frequency, and in contrast to the latter, can also pinpoint the faulty blade. It is also demonstrated that these indicators can be derived from blades vibration data obtained from real life experiment.

  14. Leonardo's branching rule in trees: How self-similar structures resist wind

    NASA Astrophysics Data System (ADS)

    Eloy, Christophe

    2011-11-01

    In his notebooks, Leonardo da Vinci observed that ``all the branches of a tree at every stage of its height when put together are equal in thickness to the trunk,'' which means that the total cross-sectional area of branches is conserved across branching nodes. The usual explanation for this rule involves vascular transport of sap, but this argument is questionable because the portion of wood devoted to transport varies across species and can be as low as 5%. It is proposed here that Leonardo's rule is a consequence of the tree skeleton having a self-similar structure and the branch diameters being adjusted to resist wind-induced loads. To address this problem, a continuous model is first considered by neglecting the geometrical details of branching and wind incident angles. The robustness of this analytical model is then assessed with numerical simulations on tree skeletons generated with a simple branching rule producing self-similar structures. This study was supported by the European Union through the fellowship PIOF-GA-2009-252542.

  15. A Study of the Structure of the Source Region of the Solar Wind in Support of a Solar Probe Mission

    NASA Technical Reports Server (NTRS)

    Habbal , Shadia R.

    1998-01-01

    Despite the richness of the information about the physical properties and the structure of the solar wind provided by the Ulysses and SOHO observations, fundamental questions regarding the nature of the coronal heating mechanisms, their source, and the manifestations of the fast and slow solar wind, still remain unanswered. The last unexplored frontier to establish the connection between the structure and dynamics of the solar atmosphere, its extension into interplanetary space, and the mechanisms responsible for the evolution of the solar wind, is the corona between 1 and 30 R(sub s). A Solar Probe mission offers an unprecedented opportunity to explore this frontier. The uniqueness of this mission stems from its trajectory in a plane perpendicular to the ecliptic which reaches within 9 R(sub s), of the solar surface over the poles and 3 - 9 R(sub s), at the equator. With a complement of simultaneous in situ and remote sensing observations, this mission is destined to have a significant impact on our understanding of the fundamental processes that heat the corona and drive the solar wind. The Solar Probe should be able to detect remnants and signatures of the processes which heat the corona and accelerate the solar wind. The primary objective of this proposal was to explore the structure of the different source regions of the solar wind through complementary observational and theoretical studies in support of a Solar Probe mission.

  16. Structural Basis of Neutralization of the Major Toxic Component from the Scorpion Centruroides noxius Hoffmann by a Human-derived Single-chain Antibody Fragment

    SciTech Connect

    Canul-Tec, Juan Carlos; Riaño-Umbarila, Lidia; Rudiño-Piñera, Enrique; Becerril, Baltazar; Possani, Lourival D.; Torres-Larios, Alfredo

    2011-08-09

    It has previously been reported that several single-chain antibody fragments of human origin (scFv) neutralize the effects of two different scorpion venoms through interactions with the primary toxins of Centruroides noxius Hoffmann (Cn2) and Centruroides suffusus suffusus (Css2). Here we present the crystal structure of the complex formed between one scFv (9004G) and the Cn2 toxin, determined in two crystal forms at 2.5 and 1.9 {angstrom} resolution. A 15-residue span of the toxin is recognized by the antibody through a cleft formed by residues from five of the complementarity-determining regions of the scFv. Analysis of the interface of the complex reveals three features. First, the epitope of toxin Cn2 overlaps with essential residues for the binding of {beta}-toxins to its Na+ channel receptor site. Second, the putative recognition of Css2 involves mainly residues that are present in both Cn2 and Css2 toxins. Finally, the effect on the increase of affinity of previously reported key residues during the maturation process of different scFvs can be inferred from the structure. Taken together, these results provide the structural basis that explain the mechanism of the 9004G neutralizing activity and give insight into the process of directed evolution that gave rise to this family of neutralizing scFvs.

  17. Structure of Antibody F425-B4e8 in Complex With a V3 Peptide Reveals a New Binding Mode for Hiv-1 Neutralization

    SciTech Connect

    Bell, C.H.; Pantophlet, R.; Schiefner, A.; Cavacini, L.A.; Stanfield, R.L.; Burton, D.R.; Wilson, I.A.

    2009-05-11

    F425-B4e8 (B4e8) is a monoclonal antibody isolated from a human immunodeficiency virus type 1 (HIV-1)-infected individual that recognizes the V3 variable loop on the gp120 subunit of the viral envelope spike. B4e8 neutralizes a subset of HIV-1 primary isolates from subtypes B, C and D, which places this antibody among the very few human anti-V3 antibodies with notable cross-neutralizing activity. Here, the crystal structure of the B4e8 Fab fragment in complex with a 24-mer V3 peptide (RP142) at 2.8 A resolution is described. The complex structure reveals that the antibody recognizes a novel V3 loop conformation, featuring a five-residue alpha-turn around the conserved GPGRA apex of the beta-hairpin loop. In agreement with previous mutagenesis analyses, the Fab interacts primarily with V3 through side-chain contacts with just two residues, Ile(P309) and Arg(P315), while the remaining contacts are to the main chain. The structure helps explain how B4e8 can tolerate a certain degree of sequence variation within V3 and, hence, is able to neutralize an appreciable number of different HIV-1 isolates.

  18. A combined tvd-lax-friedrichs scheme and its application in multi-streamer structure solar wind modeling

    NASA Astrophysics Data System (ADS)

    Feng, X.; Wei, F.; Wu, S.; Fan, Q.

    By employing a modified Lax-Friedrichs scheme for the fluid part and MacCormack II scheme for the magnetic induction part in MHD equations and taking consideration of large-scale structure of solar-terrestrial simulation, a combined TVD type numerical model is introduced for solar wind m deling. To show theo validation of this new model, its ability of modeling solar wind background with multi-streamer structures is investigated here, showing strong robustness and stability without any artificial diffusion added. Numerical results are in agreement with former widely accepted ones by giving fine structures.

  19. Formation of Coherent Structures and Impact on Turbulence Scaling in Solar-Wind Plasma

    NASA Astrophysics Data System (ADS)

    Nandal, P.; Sharma, Swati; Yadav, N.; Sharma, R. P.

    2016-10-01

    The governing dynamical equations of the right-handed circularly polarized dispersive Alfvén wave (DAW), which becomes dispersive owing to the finite frequency of the wave, and the slow Alfvén wave have been obtained using a two-fluid model. The wave localization at different instants of time and its power spectrum have been investigated. The ponderomotive force associated with the pump wave results in intense localized structures. The steepening of spectra is observed from the inertial range to the dispersive range. The results imply that the DAW may play a significant role in solar-wind turbulence. In addition, the formation of DAW localized structures is further examined considering two primary approaches, parametric instability (filamentation) and the reconnection-based model, to study the impact on the turbulent spectrum in more detail.

  20. Development of Ultrasonic Surface Wave Sensors for Structural Health Monitoring of Composite Wind Turbine Blades

    NASA Astrophysics Data System (ADS)

    Druffner, C.; Nalladega, V.; Na, J. K.

    2011-06-01

    To increase the power generating capacity of a wind turbine composite turbine blade manufacturers have been increasing the size of blades. Current utility-scale windmills are equipped with blades ranging from 40 m (130 ft) to 90 m (300 ft) in their sweep diameter. The increased blade size brings greater structural and safety demands. Recent blade recalls and field failures highlights the market need for sensors capable of part quality inspections on manufacturing line and for structural health monitoring (SHM) of the composites in service. An ultrasonic surface wave sensor technology based on interdigitization transduction (IDT) has been developed that can inspect and detect defects in the composite blades. The current work covers the design, fabrication, and characterization of the IDT sensors. The sensor characterization, coverage area, and detection capability for a variety of defects such as impact, cracking and delamination will be discussed.