Energetics of the terrestrial bow shock

NASA Astrophysics Data System (ADS)

Hamrin, Maria; Gunell, Herbert; Norqvist, Patrik

2017-04-01

The solar wind is the primary energy source for the magnetospheric energy budget. Energy can enter through the magnetopause both as kinetic energy (plasma entering via e.g. magnetic reconnection and impulsive penetration) and as electromagnetic energy (e.g. by the conversion of solar wind kinetic energy into electromagnetic energy in magnetopause generators). However, energy is extracted from the solar wind already at the bow shock, before it encounters the terrestrial magnetopause. At the bow shock the supersonic solar wind is slowed down and heated, and the region near the bow shock is known to host many complex processes, including the accelerating of particles and the generation of waves. The processes at and near the bow shock can be discussed in terms of energetics: In a generator (load) process kinetic energy is converted to (from) electromagnetic energy. Bow shock regions where the solar wind is decelerated correspond to generators, while regions where particles are energized (accelerated and heated) correspond to loads. Recently, it has been suggested that currents from the bow shock generator should flow across the magnetosheath and connect to the magnetospause current systems [Siebert and Siscoe, 2002; Lopez et al., 2011]. In this study we use data from the Magnetospheric MultiScale (MMS) mission to investigate the energetics of the bow shock and the current closure, and we compare with the MHD simulations of Lopez et al., 2011.

Large amplitude MHD waves upstream of the Jovian bow shock

NASA Technical Reports Server (NTRS)

Goldstein, M. L.; Smith, C. W.; Matthaeus, W. H.

1983-01-01

Observations of large amplitude magnetohydrodynamics (MHD) waves upstream of Jupiter's bow shock are analyzed. The waves are found to be right circularly polarized in the solar wind frame which suggests that they are propagating in the fast magnetosonic mode. A complete spectral and minimum variance eigenvalue analysis of the data was performed. The power spectrum of the magnetic fluctuations contains several peaks. The fluctuations at 2.3 mHz have a direction of minimum variance along the direction of the average magnetic field. The direction of minimum variance of these fluctuations lies at approximately 40 deg. to the magnetic field and is parallel to the radial direction. We argue that these fluctuations are waves excited by protons reflected off the Jovian bow shock. The inferred speed of the reflected protons is about two times the solar wind speed in the plasma rest frame. A linear instability analysis is presented which suggests an explanation for many of the observed features of the observations.

Bow Shocks in Space

NASA Image and Video Library

2016-01-05

Bow shocks thought to mark the paths of massive, speeding stars are highlighted in these images from NASA's Spitzer Space Telescope and Wide-field Infrared Survey Explorer, or WISE. Cosmic bow shocks occur when massive stars zip through space, pushing material ahead of them in the same way that water piles up in front of a race boat. The stars also produce high-speed winds that smack into this compressed material. The end result is pile-up of heated material that glows in infrared light. In these images, infrared light has been assigned the colored red. Green shows wispy dust in the region and blue shows stars. The two images at left are from Spitzer, and the one on the right is from WISE. The speeding stars thought to be creating the bow shocks can be seen at the center of each arc-shaped feature. The image at right actually consists of two bow shocks and two speeding stars. All the speeding stars are massive, ranging from about 8 to 30 times the mass of our sun. http://photojournal.jpl.nasa.gov/catalog/PIA20062

Characterizing the X-ray Emission From Stellar Bow Shocks and Their Driving Stars with the Chandra Archive

NASA Astrophysics Data System (ADS)

Binder, Breanna

2017-09-01

We propose an archival study of 2.8 Msec of ACIS images to search for X-ray emission from stellar-wind bow shocks and to characterize the X-ray properties of their driving stars. Bow shocks, particularly those produced by runaway OB stars, are theorized to up-scatter IR photons via inverse Compton scattering, and may produce a significant fraction of high-energy photons in our Galaxy. However, their low X-ray luminosity makes direct detection difficult. By stacking 106 archival observations containing >100 bow shocks, we will create the deepest X-ray exposure of bow shocks to date. We will perform the first detailed comparison of bow shock driving stars to the general massive star population.

Observations of low-energy electrons upstream of the earth's bow shock

NASA Technical Reports Server (NTRS)

Reasoner, D. L.

1974-01-01

Observations of electron fluxes with a lunar-based electron spectrometer when the moon was upstream of the earth have shown that a subset of observed fluxes are strongly controlled by the interplanetary magnetic field direction. The fluxes occur only when the IMF lines connect back to the earth's bow shock. Observed densities and temperatures were in the ranges 2-4 x 0,001/cu cm and 1.7-2.8 x 1,000,000 K. It is shown that these electrons can account for increases in effective solar wind electron temperatures on bow-shock connected field lines which have been observed previously by other investigators. It is further shown that if a model of the bow shock with an electrostatic potential barrier is assumed, the potential can be estimated to be 500 volts.

46 CFR 42.20-70 - Minimum bow height.

Code of Federal Regulations, 2012 CFR

2012-10-01

... Freeboards § 42.20-70 Minimum bow height. (a) The bow height defined as the vertical distance at the forward... 46 Shipping 2 2012-10-01 2012-10-01 false Minimum bow height. 42.20-70 Section 42.20-70 Shipping... less than 0.68. (b) Where the bow height required in paragraph (a) of this section is obtained by sheer...

46 CFR 42.20-70 - Minimum bow height.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Freeboards § 42.20-70 Minimum bow height. (a) The bow height defined as the vertical distance at the forward... 46 Shipping 2 2011-10-01 2011-10-01 false Minimum bow height. 42.20-70 Section 42.20-70 Shipping... less than 0.68. (b) Where the bow height required in paragraph (a) of this section is obtained by sheer...

46 CFR 42.20-70 - Minimum bow height.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Freeboards § 42.20-70 Minimum bow height. (a) The bow height defined as the vertical distance at the forward... 46 Shipping 2 2014-10-01 2014-10-01 false Minimum bow height. 42.20-70 Section 42.20-70 Shipping... less than 0.68. (b) Where the bow height required in paragraph (a) of this section is obtained by sheer...

46 CFR 42.20-70 - Minimum bow height.

Code of Federal Regulations, 2013 CFR

2013-10-01

... Freeboards § 42.20-70 Minimum bow height. (a) The bow height defined as the vertical distance at the forward... 46 Shipping 2 2013-10-01 2013-10-01 false Minimum bow height. 42.20-70 Section 42.20-70 Shipping... less than 0.68. (b) Where the bow height required in paragraph (a) of this section is obtained by sheer...

46 CFR 42.20-70 - Minimum bow height.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Freeboards § 42.20-70 Minimum bow height. (a) The bow height defined as the vertical distance at the forward... 46 Shipping 2 2010-10-01 2010-10-01 false Minimum bow height. 42.20-70 Section 42.20-70 Shipping... less than 0.68. (b) Where the bow height required in paragraph (a) of this section is obtained by sheer...

Evolution of Bow-Tie Architectures in Biology

PubMed Central

Friedlander, Tamar; Mayo, Avraham E.; Tlusty, Tsvi; Alon, Uri

2015-01-01

Bow-tie or hourglass structure is a common architectural feature found in many biological systems. A bow-tie in a multi-layered structure occurs when intermediate layers have much fewer components than the input and output layers. Examples include metabolism where a handful of building blocks mediate between multiple input nutrients and multiple output biomass components, and signaling networks where information from numerous receptor types passes through a small set of signaling pathways to regulate multiple output genes. Little is known, however, about how bow-tie architectures evolve. Here, we address the evolution of bow-tie architectures using simulations of multi-layered systems evolving to fulfill a given input-output goal. We find that bow-ties spontaneously evolve when the information in the evolutionary goal can be compressed. Mathematically speaking, bow-ties evolve when the rank of the input-output matrix describing the evolutionary goal is deficient. The maximal compression possible (the rank of the goal) determines the size of the narrowest part of the network—that is the bow-tie. A further requirement is that a process is active to reduce the number of links in the network, such as product-rule mutations, otherwise a non-bow-tie solution is found in the evolutionary simulations. This offers a mechanism to understand a common architectural principle of biological systems, and a way to quantitate the effective rank of the goals under which they evolved. PMID:25798588

Statistics of bow shock nonuniformity.

NASA Technical Reports Server (NTRS)

Greenstadt, E. W.

1973-01-01

The statistical occurrence of pulsation or oblique structure about the earth's generally nonuniform bow shock is estimated at selected points by combining a three-dimensional distribution of interplanetary field directions obtained for a six-day solar wind sector with an index of local pulsation geometry. The result, obtained with a pulsation index of 1.6, is a set of distribution patterns showing the dependence of the pulsation index on the field orientation at the selected shock loci for this value of the index.

Magnetic Fields and Bow Shocks Illustration

NASA Image and Video Library

2013-02-19

This illustration shows quasi-parallel top and quasi-perpendicular bottom magnetic field conditions at a planetary bow shock. Bow shocks are shockwaves created when the solar wind blows on a planet magnetic field.

Proper motions of five OB stars with candidate dusty bow shocks in the Carina Nebula

NASA Astrophysics Data System (ADS)

Kiminki, Megan M.; Smith, Nathan; Reiter, Megan; Bally, John

2017-06-01

We constrain the proper motions of five OB stars associated with candidate stellar wind bow shocks in the Carina Nebula using Hubble Space Telescope ACS imaging over 9-10 yr baselines. These proper motions allow us to directly compare each star's motion to the orientation of its candidate bow shock. Although these stars are saturated in our imaging, we assess their motion by the shifts required to minimize residuals in their airy rings. The results limit the direction of each star's motion to sectors less than 90° wide. None of the five stars are moving away from the Carina Nebula's central clusters as runaway stars would be, confirming that a candidate bow shock is not necessarily indicative of a runaway star. Two of the five stars are moving tangentially relative to the orientation of their candidate bow shocks, both of which point at the OB cluster Trumpler 14. In these cases, the large-scale flow of the interstellar medium, powered by feedback from the cluster, appears to dominate over the motion of the star in producing the observed candidate bow shock. The remaining three stars all have some component of motion towards the central clusters, meaning that we cannot distinguish whether their candidate bow shocks are indicators of stellar motion, of the flow of ambient gas or of density gradients in their surroundings. In addition, these stars' lack of outward motion hints that the distributed massive-star population in Carina's South Pillars region formed in place, rather than migrating out from the association's central clusters.

Linear modal stability analysis of bowed-strings.

PubMed

Debut, V; Antunes, J; Inácio, O

2017-03-01

Linearised models are often invoked as a starting point to study complex dynamical systems. Besides their attractive mathematical simplicity, they have a central role for determining the stability properties of static or dynamical states, and can often shed light on the influence of the control parameters on the system dynamical behaviour. While the bowed string dynamics has been thoroughly studied from a number of points of view, mainly by time-domain computer simulations, this paper proposes to explore its dynamical behaviour adopting a linear framework, linearising the friction force near an equilibrium state in steady sliding conditions, and using a modal representation of the string dynamics. Starting from the simplest idealisation of the friction force given by Coulomb's law with a velocity-dependent friction coefficient, the linearised modal equations of the bowed string are presented, and the dynamical changes of the system as a function of the bowing parameters are studied using linear stability analysis. From the computed complex eigenvalues and eigenvectors, several plots of the evolution of the modal frequencies, damping values, and modeshapes with the bowing parameters are produced, as well as stability charts for each system mode. By systematically exploring the influence of the parameters, this approach appears as a preliminary numerical characterisation of the bifurcations of the bowed string dynamics, with the advantage of being very simple compared to sophisticated numerical approaches which demand the regularisation of the nonlinear interaction force. To fix the idea about the potential of the proposed approach, the classic one-degree-of-freedom friction-excited oscillator is first considered, and then the case of the bowed string. Even if the actual stick-slip behaviour is rather far from the linear description adopted here, the results show that essential musical features of bowed string vibrations can be interpreted from this simple approach

Control wafer bow of InGaP on 200 mm Si by strain engineering

NASA Astrophysics Data System (ADS)

Wang, Bing; Bao, Shuyu; Made, Riko I.; Lee, Kwang Hong; Wang, Cong; Eng Kian Lee, Kenneth; Fitzgerald, Eugene A.; Michel, Jurgen

2017-12-01

When epitaxially growing III-V compound semiconductors on Si substrates the mismatch of coefficients of thermal expansion (CTEs) between III-V and Si causes stress and wafer bow. The wafer bow is deleterious for some wafer-scale processing especially when the wafer size is large. Strain engineering was applied in the epitaxy of InGaP films on 200 mm silicon wafers having high quality germanium buffers. By applying compressive strain in the InGaP films to compensate the tensile strain induced by CTE mismatch, wafer bow was decreased from about 100 μm to less than 50 μm. X-ray diffraction studies show a clear trend between the decrease of wafer bow and the compensation of CTE mismatch induced tensile strain in the InGaP layers. In addition, the anisotropic strain relaxation in InGaP films resulted in anisotropic wafer bow along two perpendicular (110) directions. Etch pit density and plane-view transmission electron microscopy characterizations indicate that threading dislocation densities did not change significantly due to the lattice-mismatch applied in the InGaP films. This study shows that strain engineering is an effective method to control wafer bow when growing III-V semiconductors on large size Si substrates.

The earth's foreshock, bow shock, and magnetosheath

NASA Technical Reports Server (NTRS)

Onsager, T. G.; Thomsen, M. F.

1991-01-01

Studies directly pertaining to the earth's foreshock, bow shock, and magnetosheath are reviewed, and some comparisons are made with data on other planets. Topics considered in detail include the electron foreshock, the ion foreshock, the quasi-parallel shock, the quasi-perpendicular shock, and the magnetosheath. Information discussed spans a broad range of disciplines, from large-scale macroscopic plasma phenomena to small-scale microphysical interactions.

True versus apparent shapes of bow shocks

NASA Astrophysics Data System (ADS)

Tarango-Yong, Jorge A.; Henney, William J.

2018-06-01

Astrophysical bow shocks are a common result of the interaction between two supersonic plasma flows, such as winds or jets from stars or active galaxies, or streams due to the relative motion between a star and the interstellar medium. For cylindrically symmetric bow shocks, we develop a general theory for the effects of inclination angle on the apparent shape. We propose a new two-dimensional classification scheme for bow shapes, which is based on dimensionless geometric ratios that can be estimated from observational images. The two ratios are related to the flatness of the bow's apex, which we term planitude, and the openness of its wings, which we term alatude. We calculate the expected distribution in the planitude-alatude plane for a variety of simple geometrical and physical models: quadrics of revolution, wilkinoids, cantoids, and ancantoids. We further test our methods against numerical magnetohydrodynamical simulations of stellar bow shocks and find that the apparent planitude and alatude measured from infrared dust continuum maps serve as accurate diagnostics of the shape of the contact discontinuity, which can be used to discriminate between different physical models. We present an algorithm that can determine the planitude and alatude from observed bow shock emission maps with a precision of 10 to 20 per cent.

BOWS (bioinformatics open web services) to centralize bioinformatics tools in web services.

PubMed

Velloso, Henrique; Vialle, Ricardo A; Ortega, J Miguel

2015-06-02

Bioinformaticians face a range of difficulties to get locally-installed tools running and producing results; they would greatly benefit from a system that could centralize most of the tools, using an easy interface for input and output. Web services, due to their universal nature and widely known interface, constitute a very good option to achieve this goal. Bioinformatics open web services (BOWS) is a system based on generic web services produced to allow programmatic access to applications running on high-performance computing (HPC) clusters. BOWS intermediates the access to registered tools by providing front-end and back-end web services. Programmers can install applications in HPC clusters in any programming language and use the back-end service to check for new jobs and their parameters, and then to send the results to BOWS. Programs running in simple computers consume the BOWS front-end service to submit new processes and read results. BOWS compiles Java clients, which encapsulate the front-end web service requisitions, and automatically creates a web page that disposes the registered applications and clients. Bioinformatics open web services registered applications can be accessed from virtually any programming language through web services, or using standard java clients. The back-end can run in HPC clusters, allowing bioinformaticians to remotely run high-processing demand applications directly from their machines.

46 CFR 45.69 - Correction for bow height.

Code of Federal Regulations, 2014 CFR

2014-10-01

... consideration by the Commandant. (e) The bow height is defined as the vertical distance at the forward... 46 Shipping 2 2014-10-01 2014-10-01 false Correction for bow height. 45.69 Section 45.69 Shipping... § 45.69 Correction for bow height. (a) The minimum summer freeboard of all manned vessels must be...

46 CFR 45.69 - Correction for bow height.

Code of Federal Regulations, 2012 CFR

2012-10-01

... consideration by the Commandant. (e) The bow height is defined as the vertical distance at the forward... 46 Shipping 2 2012-10-01 2012-10-01 false Correction for bow height. 45.69 Section 45.69 Shipping... § 45.69 Correction for bow height. (a) The minimum summer freeboard of all manned vessels must be...

46 CFR 45.69 - Correction for bow height.

Code of Federal Regulations, 2013 CFR

2013-10-01

... consideration by the Commandant. (e) The bow height is defined as the vertical distance at the forward... 46 Shipping 2 2013-10-01 2013-10-01 false Correction for bow height. 45.69 Section 45.69 Shipping... § 45.69 Correction for bow height. (a) The minimum summer freeboard of all manned vessels must be...

H2 emission from non-stationary magnetized bow shocks

NASA Astrophysics Data System (ADS)

Tram, L. N.; Lesaffre, P.; Cabrit, S.; Gusdorf, A.; Nhung, P. T.

2018-01-01

When a fast moving star or a protostellar jet hits an interstellar cloud, the surrounding gas gets heated and illuminated: a bow shock is born that delineates the wake of the impact. In such a process, the new molecules that are formed and excited in the gas phase become accessible to observations. In this paper, we revisit models of H2 emission in these bow shocks. We approximate the bow shock by a statistical distribution of planar shocks computed with a magnetized shock model. We improve on previous works by considering arbitrary bow shapes, a finite irradiation field and by including the age effect of non-stationary C-type shocks on the excitation diagram and line profiles of H2. We also examine the dependence of the line profiles on the shock velocity and on the viewing angle: we suggest that spectrally resolved observations may greatly help to probe the dynamics inside the bow shock. For reasonable bow shapes, our analysis shows that low-velocity shocks largely contribute to H2 excitation diagram. This can result in an observational bias towards low velocities when planar shocks are used to interpret H2 emission from an unresolved bow. We also report a large magnetization bias when the velocity of the planar model is set independently. Our 3D models reproduce excitation diagrams in BHR 71 and Orion bow shocks better than previous 1D models. Our 3D model is also able to reproduce the shape and width of the broad H2 1-0S(1) line profile in an Orion bow shock (Brand et al. 1989).

A Single Deformed Bow Shock for Titan-Saturn System

NASA Astrophysics Data System (ADS)

Sulaiman, A. H.; Omidi, N.; Kurth, W. S.; Madanian, H.; Cravens, T.; Sergis, N.; Dougherty, M. K.; Edberg, N. J. T.

2017-12-01

During periods of high solar wind pressure, Saturn's bow shock is pushed inside Titan's orbit exposing the moon and its ionosphere to the supersonic solar wind. The Cassini spacecraft's T96 encounter with Titan occurred during such a period and is the subject of this presentation. The observations during this encounter show evidence for the presence of outbound and inbound shock crossings associated with Saturn and Titan. They also reveal the presence of two foreshocks: one between the outbound Kronian and inbound Titan bow shocks (foreshock-1) and the other between the outbound Titan and inbound Kronian bow shocks (foreshock-2). Using electromagnetic hybrid (kinetic ions, fluid electrons) simulations and Cassini observations we show that the origin of foreshock-1 is tied to the formation of a single deformed bow shock for the Titan-Saturn system. We also report for the first time, the observations of spontaneous hot flow anomalies (SHFAs) in foreshock-1 making Saturn the fourth planet this phenomenon has been observed and indicating its universal nature. The results of hybrid simulations also show the generation of oblique fast magnetosonic waves upstream of the outbound Titan bow shock in agreement with the observations of large amplitude magnetosonic pulsations in foreshock-2. The formation of a single deformed bow shock results in unique foreshock-bow shock or foreshock-foreshock geometries. For example, the presence of Saturn's foreshock upstream of Titan's quasi-perpendicular bow shock result in ion acceleration through a combination of shock drift and Fermi processes. We also discuss the implications of a single deformed bow shock for Saturn's magnetopause and magnetosphere.

CPR methodology with new steady-state criterion and more accurate statistical treatment of channel bow

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

Baumgartner, S.; Bieli, R.; Bergmann, U. C.

2012-07-01

An overview is given of existing CPR design criteria and the methods used in BWR reload analysis to evaluate the impact of channel bow on CPR margins. Potential weaknesses in today's methodologies are discussed. Westinghouse in collaboration with KKL and Axpo - operator and owner of the Leibstadt NPP - has developed an optimized CPR methodology based on a new criterion to protect against dryout during normal operation and with a more rigorous treatment of channel bow. The new steady-state criterion is expressed in terms of an upper limit of 0.01 for the dryout failure probability per year. This ismore » considered a meaningful and appropriate criterion that can be directly related to the probabilistic criteria set-up for the analyses of Anticipated Operation Occurrences (AOOs) and accidents. In the Monte Carlo approach a statistical modeling of channel bow and an accurate evaluation of CPR response functions allow the associated CPR penalties to be included directly in the plant SLMCPR and OLMCPR in a best-estimate manner. In this way, the treatment of channel bow is equivalent to all other uncertainties affecting CPR. Emphasis is put on quantifying the statistical distribution of channel bow throughout the core using measurement data. The optimized CPR methodology has been implemented in the Westinghouse Monte Carlo code, McSLAP. The methodology improves the quality of dryout safety assessments by supplying more valuable information and better control of conservatisms in establishing operational limits for CPR. The methodology is demonstrated with application examples from the introduction at KKL. (authors)« less

Modeling of direct wafer bonding: Effect of wafer bow and etch patterns

NASA Astrophysics Data System (ADS)

Turner, K. T.; Spearing, S. M.

2002-12-01

Direct wafer bonding is an important technology for the manufacture of silicon-on-insulator substrates and microelectromechanical systems. As devices become more complex and require the bonding of multiple patterned wafers, there is a need to understand the mechanics of the bonding process. A general bonding criterion based on the competition between the strain energy accumulated in the wafers and the surface energy that is dissipated as the bond front advances is developed. The bonding criterion is used to examine the case of bonding bowed wafers. An analytical expression for the strain energy accumulation rate, which is the quantity that controls bonding, and the final curvature of a bonded stack is developed. It is demonstrated that the thickness of the wafers plays a large role and bonding success is independent of wafer diameter. The analytical results are verified through a finite element model and a general method for implementing the bonding criterion numerically is presented. The bonding criterion developed permits the effect of etched features to be assessed. Shallow etched patterns are shown to make bonding more difficult, while it is demonstrated that deep etched features can facilitate bonding. Model results and their process design implications are discussed in detail.

The return of the bow shock

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

Scherer, K.; Fichtner, H., E-mail: kls@tp4.rub.de, E-mail: hf@tp4.rub.de

2014-02-10

Recently, whether a bow shock ahead of the heliospheric stagnation region exists or not has been a topic of discussion. This was triggered by measurements indicating that the Alfvén speed and the speed of fast magnetosonic waves are higher than the flow speed of the local interstellar medium (LISM) relative to the heliosphere and resulted in the conclusion that either a bow wave or a slow magnetosonic shock might exist. We demonstrate here that including the He{sup +} component of the LISM yields both an Alfvén and fast magnetosonic wave speed lower than the LISM flow speed. Consequently, the scenariomore » of a bow shock in front of the heliosphere, as modeled in numerous simulations of the interaction of the solar wind with the LISM, remains valid.« less

Reversal of Direct Oral Anticoagulants: Current Status and Future Directions.

PubMed

Weitz, Jeffrey I

2017-02-01

Direct oral anticoagulants (DOACs) are increasingly used for prevention and treatment of venous thromboembolism and for prevention of stroke in patients with nonvalvular atrial fibrillation. In phase III clinical trials that included more than 100,000 patients, the DOACs were at least as effective as vitamin K antagonists (VKAs) and were associated with less serious bleeding, particularly less intracranial bleeding. Real-world evidence supports these outcomes. Despite this, some physicians and patients are concerned about serious bleeding or emergencies unless specific reversal agents for the DOACs are available. However, in clinical trials performed without reversal agents, the outcome of major bleeds was similar or better in patients receiving DOACs than in those taking VKAs. Because of their short half-lives, supportive measures are sufficient to manage most bleeds in patients receiving DOACs. Anticoagulant reversal should only be considered with life-threatening bleeds, with bleeds that fail to respond to usual measures and in patients requiring urgent surgery. Idarucizumab is licensed for dabigatran reversal and andexanet alfa is likely to be soon licensed for reversal of rivaroxaban, apixaban, and edoxaban. To ensure responsible use of these agents, every hospital needs a bleeding management algorithm that identifies patients eligible for reversal and outlines appropriate dosing regimens. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Mach 5 bow shock control by a nanosecond pulse surface dielectric barrier discharge

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

Nishihara, M.; Takashima, K.; Rich, J. W.

2011-06-15

Bow shock perturbations in a Mach 5 air flow, produced by low-temperature, nanosecond pulse, and surface dielectric barrier discharge (DBD), are detected by phase-locked schlieren imaging. A diffuse nanosecond pulse discharge is generated in a DBD plasma actuator on a surface of a cylinder model placed in air flow in a small scale blow-down supersonic wind tunnel. Discharge energy coupled to the actuator is 7.3-7.8 mJ/pulse. Plasma temperature inferred from nitrogen emission spectra is a few tens of degrees higher than flow stagnation temperature, T = 340 {+-} 30 K. Phase-locked Schlieren images are used to detect compression waves generatedmore » by individual nanosecond discharge pulses near the actuator surface. The compression wave propagates upstream toward the baseline bow shock standing in front of the cylinder model. Interaction of the compression wave and the bow shock causes its displacement in the upstream direction, increasing shock stand-off distance by up to 25%. The compression wave speed behind the bow shock and the perturbed bow shock velocity are inferred from the Schlieren images. The effect of compression waves generated by nanosecond discharge pulses on shock stand-off distance is demonstrated in a single-pulse regime (at pulse repetition rates of a few hundred Hz) and in a quasi-continuous mode (using a two-pulse sequence at a pulse repetition rate of 100 kHz). The results demonstrate feasibility of hypersonic flow control by low-temperature, repetitive nanosecond pulse discharges.« less

Electron velocity distributions near the earth's bow shock

NASA Technical Reports Server (NTRS)

Feldman, W. C.; Anderson, R. C.; Bame, S. J.; Gary, S. P.; Gosling, J. T.; Mccomas, D. J.; Thomsen, M. F.; Paschmann, G.; Hoppe, M. M.

1983-01-01

New information is presented on the general characteristics of electron distribution functions upstream, within, and downstream of the earth's bow shock, thereby providing new insights into the instabilities in collisionless shocks. The results presented are from a survey of electron velocity distributions measured near the earth's bow shock between October 1977 and December 1978 using the Los Alamos/Garching plasma instrumentation aboard ISEE 2. A wide variety of distribution shapes is found within the different plasma regions in close proximity to the bow shock. It is found that these shapes can be classified into general types that are characteristic of three different plasma regions, namely the upstream region or electron foreshock, the shock proper where most of the heating occurs, and the downstream region or the magnetosheath. Evidence is provided that field-aligned, rather than cross-field, instabilities are the major source of electron dissipation in the earth's bow shock.

Dependence of sound characteristics on the bowing position in a violin

NASA Astrophysics Data System (ADS)

Roh, YuJi; Kim, Young H.

2014-12-01

A quantitative analysis of violin sounds produced for different bowing positions over the full length of a violin string has been carried out. An automated bowing machine was employed in order to keep the bowing parameters constant. A 3-dimensional profile of the frequency spectrum was introduced in order to characterize the violin's sound. We found that the fundamental frequency did not change for different bowing positions, whereas the frequencies of the higher harmonics were different. Bowing the string at 30 mm from the bridge produced musical sounds. The middle of the string was confirmed to be a dead zone, as reported in previous works. In addition, the quarter position was also found to be a dead zone. Bowing the string 90 mm from the bridge dominantly produces a fundamental frequency of 864 Hz and its harmonics.

Transient bow shock around a cylinder in a supersonic dusty plasma

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

Meyer, John K.; Merlino, Robert L.

2013-07-15

Visual observations of the formation of a bow shock in the transient supersonic flow of a dusty plasma incident on a biased cylinder are presented. The bow shock formed when the advancing front of a streaming dust cloud was reflected by the obstacle. After its formation, the density jump of the bow shock increased as it moved upstream of the obstacle. A physical picture for the formation of the electrohydrodynamic bow shock is discussed.

Bow-tie diagrams for risk management in anaesthesia.

PubMed

Culwick, M D; Merry, A F; Clarke, D M; Taraporewalla, K J; Gibbs, N M

2016-11-01

Bow-tie analysis is a risk analysis and management tool that has been readily adopted into routine practice in many high reliability industries such as engineering, aviation and emergency services. However, it has received little exposure so far in healthcare. Nevertheless, its simplicity, versatility, and pictorial display may have benefits for the analysis of a range of healthcare risks, including complex and multiple risks and their interactions. Bow-tie diagrams are a combination of a fault tree and an event tree, which when combined take the shape of a bow tie. Central to bow-tie methodology is the concept of an undesired or 'Top Event', which occurs if a hazard progresses past all prevention controls. Top Events may also occasionally occur idiosyncratically. Irrespective of the cause of a Top Event, mitigation and recovery controls may influence the outcome. Hence the relationship of hazard to outcome can be viewed in one diagram along with possible causal sequences or accident trajectories. Potential uses for bow-tie diagrams in anaesthesia risk management include improved understanding of anaesthesia hazards and risks, pre-emptive identification of absent or inadequate hazard controls, investigation of clinical incidents, teaching anaesthesia risk management, and demonstrating risk management strategies to third parties when required.

Laboratory studies of stagnating plasma flows with applications to inner solar system and stellar bow shocks

NASA Astrophysics Data System (ADS)

Weber, T. E.; Smith, R. J.; Hsu, S. C.

2016-10-01

Supercritical magnetized collisionless shocks are thought to play a dominant role in the overall partition of energy throughout the universe by converting flow kinetic energy to other forms such as thermal and supra-thermal populations, magnetic field enhancement, turbulence, and energetic particles. The Magnetized Shock Experiment (MSX) at LANL creates conditions similar to those of inner solar system and stellar bow shocks by accelerating hot (100s of eV during translation) dense (1022 - 1023 m-3) Field Reversed Configuration (FRC) plasmoids to 100s of km/s; resulting in β 1, collisionless plasma flows with Msonic and MAlfvén 10. The drifting FRC can be made to impinge upon a variety of static obstacles including: a strong mirror or cusp magnetic field (mimicking magnetically excited shocks such as the Earth's bow shock), plasma pileup from a solid obstacle (similar to the bow shocks of Mercury and the Moon), and a neural gas puff (bow shocks of Venus or the comets). Characteristic shock length and time scales that are both large enough to observe yet small enough to fit within the experiment, enabling study of the complex interplay of kinetic and fluid processes that mediate cosmic shocks and can generate non-thermal distributions, produce density and magnetic field enhancements much greater than predicted by fluid theory, and accelerate particles. An overview of the experimental program will be presented, including recent results. This work is supported by the U.S. DOE, Office of Science, Office of Fusion Energy Sciences under Contract No. DE-AC52-06NA25369.

The density of cometary protons upstream of Comet Halley's bow shock

NASA Astrophysics Data System (ADS)

Neugebauer, M.; Goldstein, B. E.; Balsiger, H.; Neubauer, F. M.; Schwenn, R.; Shelley, E. G.

1989-02-01

Cometary protons picked up by the solar wind were detected by the high energy range spectrometer of the Giotto ion mass spectrometer starting at a cometocentric distance of about 12 million km. On the average, the density of cometary protons varied approximately as the inverse square of the cometocentric distance, reaching a value of 0.11/cu cm just outside the bow shock. The data can be successfully fit to models that include substantial amounts of both slow (1 km/s) and fast (8 km/s or greater) H atoms beyond the bow shock. Large local variations in the density of picked-up protons can be explained on the basis of variations in the direction of the interplanetary magnetic field in upstream regions where pitch angle scattering was weak.

Ion distributions in the Earth's foreshock upstream from the bow shock

NASA Technical Reports Server (NTRS)

Fuselier, S. A.

1995-01-01

A variety of suprathermal and energetic ion distributions are found upstream from shocks. Some distributions, such as field-aligned beams, are generated directly at the shock either through reflection processes or through leakage from the hotter downstream region. Other distributions, such as intermediate distributions, evolve from these parent distributions through wave-particle interactions. This paper reviews our current understanding of the creation and evolution of suprathermal distributions at shocks. Examples of suprathermal ion distributions are taken from observations at the Earth's bow shock. Particular emphasis is placed on the creation of field-aligned beams and specularly reflected ion distributions and on the evolution of these distributions in the Earth's ion foreshock. However, the results from this heavily studied region are applicable to interplanetary shocks, bow shocks at other planets, and comets.

Direct and reverse secret-key capacities of a quantum channel.

PubMed

Pirandola, Stefano; García-Patrón, Raul; Braunstein, Samuel L; Lloyd, Seth

2009-02-06

We define the direct and reverse secret-key capacities of a memoryless quantum channel as the optimal rates that entanglement-based quantum-key-distribution protocols can reach by using a single forward classical communication (direct reconciliation) or a single feedback classical communication (reverse reconciliation). In particular, the reverse secret-key capacity can be positive for antidegradable channels, where no forward strategy is known to be secure. This property is explicitly shown in the continuous variable framework by considering arbitrary one-mode Gaussian channels.

Flow performance of highly loaded axial fan with bowed rotor blades

NASA Astrophysics Data System (ADS)

Chen, L.; Liu, X. J.; Yang, A. L.; Dai, R.

2013-12-01

In this paper, a partial bowed rotor blade was proposed for a newly designed high loaded axial fan. The blade was positively bowed 30 degrees from hub to 30 percent spanwise position. Flows of radial blade and bowed blade fans were numerically compared for various operation conditions. Results show that the fan's performance is improved. At the designed condition with flow coefficient of 0.52, the efficiency of the bowed blade fan is increased 1.44% and the static pressure rise is increased 11%. Comparing the flow structures, it can be found that the separated flow in the bowed fan is reduced and confined within 20 percent span, which is less than the 35 percent in the radial fan. It means that the bowed blade generates negative blade force and counteracts partial centrifugal force. It is alleviates the radial movements of boundary layers in fan's hub region. Flow losses due to 3D mixing are reduced in the rotor. Inlet flow to downstream stator is also improved.

46 CFR 45.69 - Correction for bow height.

Code of Federal Regulations, 2010 CFR

2010-10-01

... least 15 percent of the length of the vessel measured from the forward perpendicular. (c) Where the bow... point at least 0.06 L abaft the forward perpendicular. (d) Vessels which, to suit exceptional... consideration by the Commandant. (e) The bow height is defined as the vertical distance at the forward...

46 CFR 45.69 - Correction for bow height.

Code of Federal Regulations, 2011 CFR

2011-10-01

... least 15 percent of the length of the vessel measured from the forward perpendicular. (c) Where the bow... point at least 0.06 L abaft the forward perpendicular. (d) Vessels which, to suit exceptional... consideration by the Commandant. (e) The bow height is defined as the vertical distance at the forward...

PLANETARY EMBRYO BOW SHOCKS AS A MECHANISM FOR CHONDRULE FORMATION

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

Mann, Christopher R.; Boley, Aaron C.; Morris, Melissa A.

2016-02-20

We use radiation hydrodynamics with direct particle integration to explore the feasibility of chondrule formation in planetary embryo bow shocks. The calculations presented here are used to explore the consequences of a Mars-size planetary embryo traveling on a moderately excited orbit through the dusty, early environment of the solar system. The embryo’s eccentric orbit produces a range of supersonic relative velocities between the embryo and the circularly orbiting gas and dust, prompting the formation of bow shocks. Temporary atmospheres around these embryos, which can be created via volatile outgassing and gas capture from the surrounding nebula, can non-trivially affect thermalmore » profiles of solids entering the shock. We explore the thermal environment of solids that traverse the bow shock at different impact radii, the effects that planetoid atmospheres have on shock morphologies, and the stripping efficiency of planetoidal atmospheres in the presence of high relative winds. Simulations are run using adiabatic and radiative conditions, with multiple treatments for the local opacities. Shock speeds of 5, 6, and 7 km s{sup −1} are explored. We find that a high-mass atmosphere and inefficient radiative conditions can produce peak temperatures and cooling rates that are consistent with the constraints set by chondrule furnace studies. For most conditions, the derived cooling rates are potentially too high to be consistent with chondrule formation.« less

IRC -10414: a bow-shock-producing red supergiant star

NASA Astrophysics Data System (ADS)

Gvaramadze, V. V.; Menten, K. M.; Kniazev, A. Y.; Langer, N.; Mackey, J.; Kraus, A.; Meyer, D. M.-A.; Kamiński, T.

2014-01-01

Most runaway OB stars, like the majority of massive stars residing in their parent clusters, go through the red supergiant (RSG) phase during their lifetimes. Nonetheless, although many dozens of massive runaways were found to be associated with bow shocks, only two RSG bow-shock-producing stars, Betelgeuse and μ Cep, are known to date. In this paper, we report the discovery of an arc-like nebula around the late M-type star IRC -10414 using the SuperCOSMOS H-alpha Survey. Our spectroscopic follow-up of IRC -10414 with the Southern African Large Telescope (SALT) showed that it is a M7 supergiant, which supports previous claims on the RSG nature of this star based on observations of its maser emission. This was reinforced by our new radio- and (sub)millimetre-wavelength molecular line observations made with the Atacama Pathfinder Experiment 12-m telescope and the Effelsberg 100-m radio telescope, respectively. The SALT spectrum of the nebula indicates that its emission is the result of shock excitation. This finding along with the arc-like shape of the nebula and an estimate of the space velocity of IRC -10414 (≈70 ± 20 km s-1) imply the bow shock interpretation for the nebula. Thus, IRC -10414 represents the third case of a bow-shock-producing RSG and the first one with a bow shock visible at optical wavelengths. We discuss the smooth appearance of the bow shocks around IRC -10414 and Betelgeuse and propose that one of the necessary conditions for stability of bow shocks generated by RSGs is the ionization of the stellar wind. Possible ionization sources of the wind of IRC -10414 are proposed and discussed.

Asymmetries in the location of the Venus and Mars bow shock

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

Zhang, T.L.; Schwingenschuh, K.; Russell, C.T.

1991-02-01

An examination of observations of the position of the terminator bow shock at Venus and Mars shows that the terminator bow shock varies with the angle between the local bow shock normal and the upstream magnetic field, {theta}{sub BN}. The part of the shock on the quasi-parallel side is closer to the planet than the part on the quasi-perpendicular side, a result which had been sggested by an earlier computer simulation by Thomas and Winske (1990). This bow shock asymmetry is observed to be larger at Mars than at Venus.

Tibial Bowing and Pseudarthrosis in Neurofibromatosis Type 1

DTIC Science & Technology

2014-04-01

Neurofibromatosis Type 1 PRINCIPAL INVESTIGATOR: Dr. David Stevenson CONTRACTING ORGANIZATION: University of Utah SALT LAKE CITY...COVERED 1 April 2013 - 31 March 2014 4. TITLE AND SUBTITLE Tibial Bowing and Pseudarthrosis in Neurofibromatosis Type 1 5a. CONTRACT NUMBER...SUPPLEMENTARY NOTES 14. ABSTRACT Anterolateral tibial bowing is a morbid skeletal manifestation observed in 5% of children with neurofibromatosis

Underwater laser weld bowing distortion behavior and mechanism of thin 304 stainless steel plates

NASA Astrophysics Data System (ADS)

Huang, ZunYue; Luo, Zhen; Ao, Sansan; Cai, YangChuan

2018-10-01

Underwater laser weld bowing distortion behavior and mechanism of thin 304 stainless steel plates are studied in the paper. The influence of underwater laser welding parameters (such as laser power, welding speed, defocusing distance and gas flow rate) on weld bowing distortion was investigated through central composite rotatable design and an orthogonal test. A quadratic response model was established to evaluate the underwater laser weld bowing distortion by central composite rotatable design and the order of the impacts of the welding parameters on weld bowing distortion was studied by an orthogonal test. The weld bowing distortion after welding was determined by the digital image correlation technique. The weld bowing distortion of in-air laser welding and underwater laser welding were compared and it revealed that the shape of the in-air and underwater laser welded specimens are the same, but the weld bowing distortion amount of in-air welding is larger than that of underwater welding. Weld bowing distortion mechanism was studied by the digital image correlation technique, and it was demonstrated that weld bowing distortion is associated with the welding plate temperature gradient during laser welding. The wider weld width also resulted in larger weld bowing distortion.

Data Recorded as Juno Crossed Jovian Bow Shock

NASA Image and Video Library

2016-06-30

This chart presents data that the Waves investigation on NASA's Juno spacecraft recorded as the spacecraft crossed the bow shock just outside of Jupiter's magnetosphere on June 24, 2016, while approaching Jupiter. Audio accompanies the animation, with volume and pitch correlated to the amplitude and frequency of the recorded waves. The graph is a frequency-time spectrogram with color coding to indicate wave amplitudes as a function of wave frequency (vertical axis, in hertz) and time (horizontal axis, with a total elapsed time of two hours). During the hour before Juno reached the bow shock, the Waves instrument was detecting mainly plasma oscillations just below 10,000 hertz (10 kilohertz). The frequency of these oscillations is related to the local density of electrons; the data yield an estimate of approximately one electron per cubic centimeter (about 16 per cubic inch) in this region just outside Jupiter's bow shock. The broadband burst of noise marked "Bow Shock" is the region of turbulence where the supersonic solar wind is heated and slowed by encountering the Jovian magnetosphere. The shock is analogous to a sonic boom generated in Earth's atmosphere by a supersonic aircraft. The region after the shock is called the magnetosheath. The vertical bar to the right of the chart indicates the color coding of wave amplitude, in decibels (dB) above the background level detected by the Waves instrument. Each step of 10 decibels marks a tenfold increase in wave power. When Juno collected these data, the distance from the spacecraft to Jupiter was about 5.56 million miles (8.95 million kilometers), indicated on the chart as 128 times the radius of Jupiter. Jupiter's magnetic field is tilted about 10 degrees from the planet's axis of rotation. The note of 22 degrees on the chart indicates that at the time these data were recorded, the spacecraft was 22 degrees north of the magnetic-field equator. The "LT" notation is local time on Jupiter at the longitude of the

Cometary compact H II regions are stellar-wind bow shocks

NASA Technical Reports Server (NTRS)

Van Buren, Dave; Mac Low, Mordecai-Mark; Wood, Douglas O. S.; Churchwell, ED

1990-01-01

Comet-shaped H II regions, like G34.3 + 0.2, are easily explained as bow shocks created by wind-blowing massive stars moving supersonically through molecular clouds. The required velocities of the stars through dense clumps are less than about 10 km/s, comparable to the velocity dispersion of stars in OB associations. An analytic model of bow shocks matches the gross characteristics seen in the radio continuum and the velocity structure inferred from hydrogen recombination and molecular line observations. The champagne flow model cannot account for these structures. VLBI observations of masers associated with the shells of cometary compact H II regions should reveal tailward proper motions predominantly parallel to the shell, rather than perpendicular. It is predicted that over a decade baseline, high signal-to-noise VLA observations of this class of objects will show headward pattern motion in the direction of the symmetry axis, but not expansion. Finally, shock-generated and coronal infrared lines are also predicted.

75 FR 39201 - MedBow-Routt Resource Advisory Committee

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-08

... DEPARTMENT OF AGRICULTURE Forest Service MedBow-Routt Resource Advisory Committee AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The MedBow-Routt Resource Advisory Committee will meet... and Community Self-Determination Act (Pub. L. 110-343) and in compliance with the Federal Advisory...

75 FR 52304 - MedBow-Routt Resource Advisory Committee

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-25

... DEPARTMENT OF AGRICULTURE Forest Service MedBow-Routt Resource Advisory Committee AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The MedBow-Routt Resource Advisory Committee will meet... Community Self-Determination Act (Pub. L. 110- 343) and in compliance with the Federal Advisory Committee...

76 FR 12016 - MedBow-Routt Resource Advisory Committee

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-04

... DEPARTMENT OF AGRICULTURE Forest Service MedBow-Routt Resource Advisory Committee AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The MedBow-Routt Resource Advisory Committee will meet... Community Self-Determination Act (Pub. L. 110- 343) and in compliance with the Federal Advisory Committee...

Distance and direction, but not light cues, support response reversal learning.

PubMed

Wright, S L; Martin, G M; Thorpe, C M; Haley, K; Skinner, D M

2018-03-05

Across three experiments, we examined the cuing properties of metric (distance and direction) and nonmetric (lighting) cues in different tasks. In Experiment 1, rats were trained on a response problem in a T-maze, followed by four reversals. Rats that experienced a change in maze orientation (Direction group) or a change in the length of the start arm (Distance group) across reversals showed facilitation of reversal learning relative to a group that experienced changes in room lighting across reversals. In Experiment 2, rats learned a discrimination task more readily when distance or direction cues were used than when light cues were used as the discriminative stimuli. In Experiment 3, performance on a go/no-go task was equivalent using both direction and lighting cues. The successful use of both metric and nonmetric cues in the go/no-go task indicates that rats are sensitive to both types of cues and that the usefulness of different cues is dependent on the nature of the task.

EVAPORATION OF ICY PLANETESIMALS DUE TO BOW SHOCKS

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

Tanaka, Kyoko K.; Yamamoto, Tetsuo; Tanaka, Hidekazu

2013-02-20

We present the novel concept of evaporation of planetesimals as a result of bow shocks associated with planetesimals orbiting with supersonic velocities relative to the gas in a protoplanetary disk. We evaluate the evaporation rates of the planetesimals based on a simple model describing planetesimal heating and evaporation by the bow shock. We find that icy planetesimals with radius {approx}>100 km evaporate efficiently even outside the snow line in the stage of planetary oligarchic growth, where strong bow shocks are produced by gravitational perturbations from protoplanets. The obtained results suggest that the formation of gas giant planets is suppressed owingmore » to insufficient accretion of icy planetesimals onto the protoplanet within the {approx}<5 AU disk region.« less

2. VIEW NORTH OF BOW OF JFK IN DRYDOCK NO. ...

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

2. VIEW NORTH OF BOW OF JFK IN DRYDOCK NO. 5; NOTE BOW ANCHOR AT TOP CENTER. - Naval Base Philadelphia-Philadelphia Naval Shipyard, Dry Dock No. 5, League Island, Philadelphia, Philadelphia County, PA

Astronomy In Denver: Polarization of Stellar Wind Bow Shocks

NASA Astrophysics Data System (ADS)

Lin, Austin A.; Shrestha, Manisha; Wolfe, Tristan; Stencel, Robert E.; Hoffman, Jennifer L.

2018-06-01

When a star with stellar wind moves through the interstellar medium (ISM) at a relative supersonic velocity, an arch like structure known as a stellar wind bow shock is formed. Studying the characteristics of these structures can further our understanding of evolved stellar winds and the composition of the ISM. Observations of these structures have been performed for some time, but the recent discovery of many bow shock structures have opened more ways to study them. These stellar wind bow shocks display aspherical shapes, which cause light scattering through the dense shock material to become polarized. We selected a target star for observation using a catalog compiled from previous studies and observed it in polarized light with the University of Denver’s DUSTPol instrument. Our group has also simulated the polarization of stellar wind bow shocks using a Monte Carlo radiative transfer code. We present the data from our observations and compare them with the simulations. We also discuss the contribution of interstellar polarization to the data.

Simulation of the oscillation regimes of bowed bars: a non-linear modal approach

NASA Astrophysics Data System (ADS)

Inácio, Octávio; Henrique, Luís.; Antunes, José

2003-06-01

It is still a challenge to properly simulate the complex stick-slip behavior of multi-degree-of-freedom systems. In the present paper we investigate the self-excited non-linear responses of bowed bars, using a time-domain modal approach, coupled with an explicit model for the frictional forces, which is able to emulate stick-slip behavior. This computational approach can provide very detailed simulations and is well suited to deal with systems presenting a dispersive behavior. The effects of the bar supporting fixture are included in the model, as well as a velocity-dependent friction coefficient. We present the results of numerical simulations, for representative ranges of the bowing velocity and normal force. Computations have been performed for constant-section aluminum bars, as well as for real vibraphone bars, which display a central undercutting, intended to help tuning the first modes. Our results show limiting values for the normal force FN and bowing velocity ẏbow for which the "musical" self-sustained solutions exist. Beyond this "playability space", double period and even chaotic regimes were found for specific ranges of the input parameters FN and ẏbow. As also displayed by bowed strings, the vibration amplitudes of bowed bars also increase with the bow velocity. However, in contrast to string instruments, bowed bars "slip" during most of the motion cycle. Another important difference is that, in bowed bars, the self-excited motions are dominated by the system's first mode. Our numerical results are qualitatively supported by preliminary experimental results.

The Reversal of Direct Oral Anticoagulants in Animal Models

PubMed Central

Honickel, Markus; Akman, Necib; Grottke, Oliver

2017-01-01

ABSTRACT Several direct oral anticoagulants (DOACs), including direct thrombin and factor Xa inhibitors, have been approved as alternatives to vitamin K antagonist anticoagulants. As with any anticoagulant, DOAC use carries a risk of bleeding. In patients with major bleeding or needing urgent surgery, reversal of DOAC anticoagulation may be required, presenting a clinical challenge. The optimal strategy for DOAC reversal is being refined, and may include use of hemostatic agents such as prothrombin complex concentrates (PCCs; a source of concentrated clotting factors), or DOAC-specific antidotes (which bind their target DOAC to abrogate its activity). Though promising, most specific antidotes are still in development. Preclinical animal research is the key to establishing the efficacy and safety of potential reversal agents. Here, we summarize published preclinical animal studies on reversal of DOAC anticoagulation. These studies (n = 26) were identified via a PubMed search, and used rodent, rabbit, pig, and non-human primate models. The larger of these animals have the advantages of similar blood volume/hemodynamics to humans, and can be used to model polytrauma. We find that in addition to varied species being used, there is variability in the models and assays used between studies; we suggest that blood loss (bleeding volume) is the most clinically relevant measure of DOAC anticoagulation-related bleeding and its reversal. The studies covered indicate that both PCCs and specific reversal agents have the potential to be used as part of a clinical strategy for DOAC reversal. For the future, we advocate the development and use of standardized, clinically, and pharmacologically relevant animal models to study novel DOAC reversal strategies. PMID:28471371

Runaways and weathervanes: The shape of stellar bow shocks

NASA Astrophysics Data System (ADS)

Henney, W. J.; Tarango-Yong, J. A.

2017-11-01

Stellar bow shocks are the result of the supersonic interaction between a stellar wind and its environment. Some of these are "runaways": high-velocity stars that have been ejected from a star cluster. Others are "weather vanes", where it is the local interstellar medium itself that is moving, perhaps as the result of a champagne flow of ionized gas from a nearby HII region. We propose a new two-dimensional classification scheme for bow shapes, which is based on dimensionless geometric ratios that can be estimated from observational images. The two ratios are related to the flatness of the bow’s apex, which we term "planitude" and the openness of its wings, which we term "alatude". We calculate the inclination-dependent tracks on the planitude-alatude plane that are predicted by simple models for the bow shock shape. We also measure the shapes of bow shocks from three different observational datasets: mid-infrared arcs around hot main-sequence stars, far-infrared arcs around luminous cool stars, and emission-line arcs around proplyds and other young stars in the Orion Nebula. Clear differences are found between the different datasets in their distributions on the planitude-alatude plane, which can be used to constrain the physics of the bow shock interaction and emission mechanisms in the different classes of object.

The bowing potential of granitic rocks: rock fabrics, thermal properties and residual strain

NASA Astrophysics Data System (ADS)

Siegesmund, S.; Mosch, S.; Scheffzük, Ch.; Nikolayev, D. I.

2008-10-01

The bowing of natural stone panels is especially known for marble slabs. The bowing of granite is mainly known from tombstones in subtropical humid climate. Field inspections in combination with laboratory investigations with respect to the thermal expansion and the bowing potential was performed on two different granitoids (Cezlak granodiorite and Flossenbürg granite) which differ in the composition and rock fabrics. In addition, to describe and explain the effect of bowing of granitoid facade panels, neutron time-of-flight diffraction was applied to determine residual macro- and microstrain. The measurements were combined with investigations of the crystallographic preferred orientation of quartz and biotite. Both samples show a significant bowing as a function of panel thickness and destination temperature. In comparison to marbles the effect of bowing is more pronounced in granitoids at temperatures of 120°C. The bowing as well as the thermal expansion of the Cezlak sample is also anisotropic with respect to the rock fabrics. A quantitative estimate was performed based on the observed textures. The effect of the locked-in stresses may also have a control on the bowing together with the thermal stresses related to the different volume expansion of the rock-forming minerals.

The heliosphere's interstellar interaction: no bow shock.

PubMed

McComas, D J; Alexashov, D; Bzowski, M; Fahr, H; Heerikhuisen, J; Izmodenov, V; Lee, M A; Möbius, E; Pogorelov, N; Schwadron, N A; Zank, G P

2012-06-08

As the Sun moves through the local interstellar medium, its supersonic, ionized solar wind carves out a cavity called the heliosphere. Recent observations from the Interstellar Boundary Explorer (IBEX) spacecraft show that the relative motion of the Sun with respect to the interstellar medium is slower and in a somewhat different direction than previously thought. Here, we provide combined consensus values for this velocity vector and show that they have important implications for the global interstellar interaction. In particular, the velocity is almost certainly slower than the fast magnetosonic speed, with no bow shock forming ahead of the heliosphere, as was widely expected in the past.

DOUBLE BOW SHOCKS AROUND YOUNG, RUNAWAY RED SUPERGIANTS: APPLICATION TO BETELGEUSE

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

Mackey, Jonathan; Mohamed, Shazrene; Neilson, Hilding R.

2012-05-20

A significant fraction of massive stars are moving supersonically through the interstellar medium (ISM), either due to disruption of a binary system or ejection from their parent star cluster. The interaction of their wind with the ISM produces a bow shock. In late evolutionary stages these stars may undergo rapid transitions from red to blue and vice versa on the Hertzsprung-Russell diagram, with accompanying rapid changes to their stellar winds and bow shocks. Recent three-dimensional simulations of the bow shock produced by the nearby runaway red supergiant (RSG) Betelgeuse, under the assumption of a constant wind, indicate that the bowmore » shock is very young (<30, 000 years old), hence Betelgeuse may have only recently become an RSG. To test this possibility, we have calculated stellar evolution models for single stars which match the observed properties of Betelgeuse in the RSG phase. The resulting evolving stellar wind is incorporated into two-dimensional hydrodynamic simulations in which we model a runaway blue supergiant (BSG) as it undergoes the transition to an RSG near the end of its life. We find that the collapsing BSG wind bubble induces a bow shock-shaped inner shell around the RSG wind that resembles Betelgeuse's bow shock, and has a similar mass. Surrounding this is the larger-scale retreating bow shock generated by the now defunct BSG wind's interaction with the ISM. We suggest that this outer shell could explain the bar feature located (at least in projection) just in front of Betelgeuse's bow shock.« less

Bow and Oblique Shock Formation in Soap Film

NASA Astrophysics Data System (ADS)

Kim, Ildoo; Mandre, Shreyas; Sane, Aakash

2015-11-01

In recent years, soap films have been exploited primarily to approximate two-dimensional flows while their three-dimensional character is relatively unattended. An example of the three-dimensional character of the flow in a soap film is the observed Marangoni shock wave when the flow speed exceeds the wave speed. In this study, we investigated the formation of bow and oblique shocks in soap films generated by wedges with different deflection angles. When the wedge deflection angle is small and the film flows fast, oblique shocks are observed. When the oblique shock cannot exists, bow shock is formed upstream the wedge. We characterized the oblique shock angle as a function of the wedge deflection angle and the flow speed, and we also present the criteria for transition between bow and oblique Marangoni shocks in soap films.

Study of the relation between Pc 3 micropulsations and magnetosheath fluctuations and of the multisatellite, multimeasurement investigation of the earth's bow shock

NASA Technical Reports Server (NTRS)

1976-01-01

The structure and direction of bow shock waves and the occurence of Pc 3, 4 micropulsations were investigated. An observational description is given of a quasi-parallel structure in a plasma parameter regime. The use of approximation to estimate the thickness of thin, nearly perpendicular bow shocks at supralaminar Mach numbers is discussed. The pattern of energies of backstreaming protons in the foreshock are predicted.

Acceleration of Particles Near Earth's Bow Shock

NASA Astrophysics Data System (ADS)

Sandroos, A.

2012-12-01

Collisionless shock waves, for example, near planetary bodies or driven by coronal mass ejections, are a key source of energetic particles in the heliosphere. When the solar wind hits Earth's bow shock, some of the incident particles get reflected back towards the Sun and are accelerated in the process. Reflected ions are responsible for the creation of a turbulent foreshock in quasi-parallel regions of Earth's bow shock. We present first results of foreshock macroscopic structure and of particle distributions upstream of Earth's bow shock, obtained with a new 2.5-dimensional self-consistent diffusive shock acceleration model. In the model particles' pitch angle scattering rates are calculated from Alfvén wave power spectra using quasilinear theory. Wave power spectra in turn are modified by particles' energy changes due to the scatterings. The new model has been implemented on massively parallel simulation platform Corsair. We have used an earlier version of the model to study ion acceleration in a shock-shock interaction event (Hietala, Sandroos, and Vainio, 2012).

BOW SHOCK FRAGMENTATION DRIVEN BY A THERMAL INSTABILITY IN LABORATORY ASTROPHYSICS EXPERIMENTS

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

Suzuki-Vidal, F.; Lebedev, S. V.; Pickworth, L. A.

The role of radiative cooling during the evolution of a bow shock was studied in laboratory-astrophysics experiments that are scalable to bow shocks present in jets from young stellar objects. The laboratory bow shock is formed during the collision of two counterstreaming, supersonic plasma jets produced by an opposing pair of radial foil Z-pinches driven by the current pulse from the MAGPIE pulsed-power generator. The jets have different flow velocities in the laboratory frame, and the experiments are driven over many times the characteristic cooling timescale. The initially smooth bow shock rapidly develops small-scale nonuniformities over temporal and spatial scalesmore » that are consistent with a thermal instability triggered by strong radiative cooling in the shock. The growth of these perturbations eventually results in a global fragmentation of the bow shock front. The formation of a thermal instability is supported by analysis of the plasma cooling function calculated for the experimental conditions with the radiative packages ABAKO/RAPCAL.« less

Earth's Bow Shock: Elapsed-Time Observations by Two Closely Spaced Satellites.

PubMed

Greenstadt, E W; Green, I M; Colburn, D S

1968-11-22

Coordinated observations of the earth's bow shock were made as Vela 3A and Explorer 33 passed within 6 earth radii of each other. Elapsed time measurements of shock motion give directly determined velocities in the range 1 to 10 kilometers per second and establish the existence of two regions, one of large amplitude magnetic "shock" oscillations and another of smaller, sunward, upstream oscillations. Each region is as thick as 1 earth radius, or more.

A new technique to characterize CT scanner bow-tie filter attenuation and applications in human cadaver dosimetry simulations

PubMed Central

Li, Xinhua; Shi, Jim Q.; Zhang, Da; Singh, Sarabjeet; Padole, Atul; Otrakji, Alexi; Kalra, Mannudeep K.; Xu, X. George; Liu, Bob

2015-01-01

Purpose: To present a noninvasive technique for directly measuring the CT bow-tie filter attenuation with a linear array x-ray detector. Methods: A scintillator based x-ray detector of 384 pixels, 307 mm active length, and fast data acquisition (model X-Scan 0.8c4-307, Detection Technology, FI-91100 Ii, Finland) was used to simultaneously detect radiation levels across a scan field-of-view. The sampling time was as short as 0.24 ms. To measure the body bow-tie attenuation on a GE Lightspeed Pro 16 CT scanner, the x-ray tube was parked at the 12 o’clock position, and the detector was centered in the scan field at the isocenter height. Two radiation exposures were made with and without the bow-tie in the beam path. Each readout signal was corrected for the detector background offset and signal-level related nonlinear gain, and the ratio of the two exposures gave the bow-tie attenuation. The results were used in the geant4 based simulations of the point doses measured using six thimble chambers placed in a human cadaver with abdomen/pelvis CT scans at 100 or 120 kV, helical pitch at 1.375, constant or variable tube current, and distinct x-ray tube starting angles. Results: Absolute attenuation was measured with the body bow-tie scanned at 80–140 kV. For 24 doses measured in six organs of the cadaver, the median or maximum difference between the simulation results and the measurements on the CT scanner was 8.9% or 25.9%, respectively. Conclusions: The described method allows fast and accurate bow-tie filter characterization. PMID:26520720

Primary bowing tremor: a task-specific movement disorder of string instrumentalists.

PubMed

Lederman, Richard J

2012-12-01

Fear of a tremulous or unsteady bow is widespread among string instrumentalists. Faulty technique and performance anxiety have generally been blamed. The cases of 4 high-level violinists and 1 violist, 3 women and 2 men, with uncontrollable bow tremor are presented. Age at onset was from 16 to 75 years, and symptom duration 8 months to 20 years at the time of neurological evaluation. The degree of tremor varied with type of bow stroke and even the portion of the bow contacting the string. Only 1 patient had a slight postural tremor of the opposite limb. In 3 of 5 the tremor was task-specific; the other 2 had mild and nontroubling tremor with other activities. The tremor appeared to worsen over time but then seemed to stabilize. The characteristics of this tremor appear to be distinguishable from the features of both essential tremor and focal dystonia; comparison is made with representative string players afflicted by these other disorders. Analogy of this tremor is made with primary writing tremor, a well-defined task-specific movement disorder also sharing at least some features with both essential tremor and writers' cramp, a focal dystonia. Hence, it was decided to call this primary bowing tremor. Clinical features, family history, diagnostic studies, and responsiveness to treatment of primary writing tremor are discussed to emphasize the similarity to primary bowing tremor. This appears to represent a previously unreported form of task-specific movement disorder of string instrumentalists.

Glacial Meltwater Contirbutions to the Bow River, Alberta, Canada

NASA Astrophysics Data System (ADS)

Bash, E. A.; Marshall, S. J.; White, E. C.

2009-12-01

Assessment of glacial melt is critical for water resource management in areas which rely on glacier-fed rivers for agricultural and municipal uses. Changes in precipitation patterns coupled with current glacial retreat are altering the glacial contribution to river flow in areas such as the Andes of South America and the high ranges of Asia, as well as the Rockies of Western Canada. Alberta’s Bow River has its headwaters in the eastern slopes of the Canadian Rockies and contributes to the Nelson drainage system feeding into Hudson Bay. The Bow River basin contains several population centers, including the City of Calgary, and is heavily taxed for agricultural use. The combined effects of rapid glacial retreat in the Canadian Rockies, higher drought frequency, and increased demand are likely to heighten water stress in Southern Alberta. However, there has been little focus to date on the extent and importance of glacial meltwater in the Bow River. The Bow River contains 74.5 km2 of glacier ice, which amounts to only 0.29% of the basin. While this number is not high compared to some glacierized areas, Hopkinson and Young (1998) report that in dry years, glacier melt can provide up to 50% of late summer flows at a station in the upper reaches of the river system. We extend this work with an assessment of monthly and annual glacial contributions to the Bow River farther downstream in Calgary. Our analysis is based on mass balance, meteorological, and hydrological data that has been collected at the Haig Glacier since 2001. This data is used in conjunction with glacier coverage and hypsometric data for the remainder of the basin to estimate seasonal snow and glacial meltwater contributions to the Bow River from the glacierized fraction of the catchment. The results of this study show the percentage of total flow attributed to glacial melt to be highly variable. Glacier runoff contributes up to an order of magnitude more water to the Bow River per unit area of

Systematic search for high-energy gamma-ray emission from bow shocks of runaway stars

DOE PAGES

Schulz, A.; Ackermann, M.; Buehler, R.; ...

2014-05-01

Context. It has been suggested that the bow shocks of runaway stars are sources of high-energy gamma rays (E > 100 MeV). Theoretical models predicting high-energy gamma-ray emission from these sources were followed by the first detection of non-thermal radio emission from the bow shock of BD+43°3654 and non-thermal X-ray emission from the bow shock of AE Aurigae. Aims. We perform the first systematic search for MeV and GeV emission from 27 bow shocks of runaway stars using data collected by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope (Fermi). Methods. We analysed 57 months of Fermi-LATmore » data at the positions of 27 bow shocks of runaway stars extracted from the Extensive stellar BOw Shock Survey catalogue (E-BOSS). A likelihood analysis was performed to search for gamma-ray emission that is not compatible with diffuse background or emission from neighbouring sources and that could be associated with the bow shocks. Results. None of the bow shock candidates is detected significantly in the Fermi-LAT energy range. We therefore present upper limits on the high-energy emission in the energy range from 100MeV to 300 GeV for 27 bow shocks of runaway stars in four energy bands. For the three cases where models of the high-energy emission are published we compare our upper limits to the modelled spectra. Our limits exclude the model predictions for ζ Ophiuchi by a factor ≈ 5.« less

Compositional bowing of band energies and their deformation potentials in strained InGaAs ternary alloys: A first-principles study

NASA Astrophysics Data System (ADS)

Khomyakov, Petr A.; Luisier, Mathieu; Schenk, Andreas

2015-08-01

Using first-principles calculations, we show that the conduction and valence band energies and their deformation potentials exhibit a non-negligible compositional bowing in strained ternary semiconductor alloys such as InGaAs. The electronic structure of these compounds has been calculated within the framework of local density approximation and hybrid functional approach for large cubic supercells and special quasi-random structures, which represent two kinds of model structures for random alloys. We find that the predicted bowing effect for the band energy deformation potentials is rather insensitive to the choice of the functional and alloy structural model. The direction of bowing is determined by In cations that give a stronger contribution to the formation of the InxGa1-xAs valence band states with x ≳ 0.5, compared to Ga cations.

HIGH-TEMPERATURE PROCESSING OF SOLIDS THROUGH SOLAR NEBULAR BOW SHOCKS: 3D RADIATION HYDRODYNAMICS SIMULATIONS WITH PARTICLES

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

Boley, A. C.; Morris, M. A.; Desch, S. J.

2013-10-20

A fundamental, unsolved problem in solar system formation is explaining the melting and crystallization of chondrules found in chondritic meteorites. Theoretical models of chondrule melting in nebular shocks have been shown to be consistent with many aspects of thermal histories inferred for chondrules from laboratory experiments; but, the mechanism driving these shocks is unknown. Planetesimals and planetary embryos on eccentric orbits can produce bow shocks as they move supersonically through the disk gas, and are one possible source of chondrule-melting shocks. We investigate chondrule formation in bow shocks around planetoids through three-dimensional radiation hydrodynamics simulations. A new radiation transport algorithmmore » that combines elements of flux-limited diffusion and Monte Carlo methods is used to capture the complexity of radiative transport around bow shocks. An equation of state that includes the rotational, vibrational, and dissociation modes of H{sub 2} is also used. Solids are followed directly in the simulations and their thermal histories are recorded. Adiabatic expansion creates rapid cooling of the gas, and tail shocks behind the embryo can cause secondary heating events. Radiative transport is efficient, and bow shocks around planetoids can have luminosities ∼few× 10{sup –8} L{sub ☉}. While barred and radial chondrule textures could be produced in the radiative shocks explored here, porphyritic chondrules may only be possible in the adiabatic limit. We present a series of predicted cooling curves that merit investigation in laboratory experiments to determine whether the solids produced by bow shocks are represented in the meteoritic record by chondrules or other solids.« less

Measurement of bow tie profiles in CT scanners using a real-time dosimeter

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

Whiting, Bruce R., E-mail: whitingbrucer@gmail.com; Evans, Joshua D.; Williamson, Jeffrey F.

2014-10-15

Purpose: Several areas of computed tomography (CT) research require knowledge about the intensity profile of the x-ray fan beam that is introduced by a bow tie filter. This information is considered proprietary by CT manufacturers, so noninvasive measurement methods are required. One method using real-time dosimeters has been proposed in the literature. A commercially available dosimeter was used to apply that method, and analysis techniques were developed to extract fan beam profiles from measurements. Methods: A real-time ion chamber was placed near the periphery of an empty CT gantry and the dose rate versus time waveform was recorded as themore » x-ray source rotated about the isocenter. In contrast to previously proposed analysis methods that assumed a pointlike detector, the finite-size ion chamber received varying amounts of coverage by the collimated x-ray beam during rotation, precluding a simple relationship between the source intensity as a function of fan beam angle and measured intensity. A two-parameter model for measurement intensity was developed that included both effective collimation width and source-to-detector distance, which then was iteratively solved to minimize the error between duplicate measurements at corresponding fan beam angles, allowing determination of the fan beam profile from measured dose-rate waveforms. Measurements were performed on five different scanner systems while varying parameters such as collimation, kVp, and bow tie filters. On one system, direct measurements of the bow tie profile were collected for comparison with the real-time dosimeter technique. Results: The data analysis method for a finite-size detector was found to produce a fan beam profile estimate with a relative error between duplicate measurement intensities of <5%. It was robust over a wide range of collimation widths (e.g., 1–40 mm), producing fan beam profiles that agreed with a relative error of 1%–5%. Comparison with a direct measurement

A survey for Hα pulsar bow shocks

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

Brownsberger, Sasha; Romani, Roger W., E-mail: rwr@astro.stanford.edu, E-mail: sashab@stanford.edu

2014-04-01

We report on a survey for Hα bow shock emission around nearby γ-detected energetic pulsars. This survey adds three Balmer-dominated neutron star bow shocks to the six previously confirmed examples. In addition to the shock around Fermi pulsar PSR J1741–2054, we now report Hα structures around two additional γ-ray pulsars, PSR J2030+4415 and PSR J1509–5850. These are the first known examples of Hα nebulae with pre-ionization halos. With new measurements, we show that a simple analytic model can account for the angular size and flux of the bow shocks' apices. The latter, in particular, provides a new pulsar probe andmore » indicates large moments of inertia and smaller distances than previously assumed in several cases. In particular, we show that the re-measured PSR J0437–4715 shock flux implies I = (1.7 ± 0.2) × 10{sup 45}/(f {sub HI}sin i) g cm{sup 2}. We also derive a distance d ≈ 0.72 kpc for the γ-ray only pulsar PSR J2030+4415 and revised distances for PSRs J1959+2048 (1.4 kpc) and J2555+6535 (∼1 kpc), smaller than the conventional DM-estimated values. Finally, we report upper limits for 94 additional LAT pulsars. An estimate of the survey sensitivity indicates that for a warm neutral medium filling factor φ{sub WNM} ∼ 0.3 there should be a total of approximately nine Hα bow shocks in our LAT-targeted survey; given that seven such objects are now known, a much larger φ{sub WNM} seems problematic.« less

On the stability of bow shocks generated by red supergiants: the case of IRC -10414

NASA Astrophysics Data System (ADS)

Meyer, D. M.-A.; Gvaramadze, V. V.; Langer, N.; Mackey, J.; Boumis, P.; Mohamed, S.

2014-03-01

In this Letter, we explore the hypothesis that the smooth appearance of bow shocks around some red supergiants (RSGs) might be caused by the ionization of their winds by external sources of radiation. Our numerical simulations of the bow shock generated by IRC -10414 (the first-ever RSG with an optically detected bow shock) show that the ionization of the wind results in its acceleration by a factor of 2, which reduces the difference between the wind and space velocities of the star and makes the contact discontinuity of the bow shock stable for a range of stellar space velocities and mass-loss rates. Our best-fitting model reproduces the overall shape and surface brightness of the observed bow shock and suggests that the space velocity and mass-loss rate of IRC -10414 are ≈50 km s-1 and ≈10-6 M⊙ yr-1, respectively, and that the number density of the local interstellar medium is ≈3 cm-3. It also shows that the bow shock emission comes mainly from the shocked stellar wind. This naturally explains the enhanced nitrogen abundance in the line-emitting material, derived from the spectroscopy of the bow shock. We found that photoionized bow shocks are ≈15-50 times brighter in optical line emission than their neutral counterparts, from which we conclude that the bow shock of IRC -10414 must be photoionized.

Global Explicit Particle-in-cell Simulations of the Nonstationary Bow Shock and Magnetosphere

NASA Astrophysics Data System (ADS)

Yang, Zhongwei; Huang, Can; Liu, Ying D.; Parks, George K.; Wang, Rui; Lu, Quanming; Hu, Huidong

2016-07-01

We carry out two-dimensional global particle-in-cell simulations of the interaction between the solar wind and a dipole field to study the formation of the bow shock and magnetosphere. A self-reforming bow shock ahead of a dipole field is presented by using relatively high temporal-spatial resolutions. We find that (1) the bow shock and the magnetosphere are formed and reach a quasi-stable state after several ion cyclotron periods, and (2) under the B z southward solar wind condition, the bow shock undergoes a self-reformation for low β I and high M A . Simultaneously, a magnetic reconnection in the magnetotail is found. For high β I and low M A , the shock becomes quasi-stationary, and the magnetotail reconnection disappears. In addition, (3) the magnetopause deflects the magnetosheath plasmas. The sheath particles injected at the quasi-perpendicular region of the bow shock can be convected downstream of an oblique shock region. A fraction of these sheath particles can leak out from the magnetosheath at the wings of the bow shock. Hence, the downstream situation is more complicated than that for a planar shock produced in local simulations.

BowMapCL: Burrows-Wheeler Mapping on Multiple Heterogeneous Accelerators.

PubMed

Nogueira, David; Tomas, Pedro; Roma, Nuno

2016-01-01

The computational demand of exact-search procedures has pressed the exploitation of parallel processing accelerators to reduce the execution time of many applications. However, this often imposes strict restrictions in terms of the problem size and implementation efforts, mainly due to their possibly distinct architectures. To circumvent this limitation, a new exact-search alignment tool (BowMapCL) based on the Burrows-Wheeler Transform and FM-Index is presented. Contrasting to other alternatives, BowMapCL is based on a unified implementation using OpenCL, allowing the exploitation of multiple and possibly different devices (e.g., NVIDIA, AMD/ATI, and Intel GPUs/APUs). Furthermore, to efficiently exploit such heterogeneous architectures, BowMapCL incorporates several techniques to promote its performance and scalability, including multiple buffering, work-queue task-distribution, and dynamic load-balancing, together with index partitioning, bit-encoding, and sampling. When compared with state-of-the-art tools, the attained results showed that BowMapCL (using a single GPU) is 2 × to 7.5 × faster than mainstream multi-threaded CPU BWT-based aligners, like Bowtie, BWA, and SOAP2; and up to 4 × faster than the best performing state-of-the-art GPU implementations (namely, SOAP3 and HPG-BWT). When multiple and completely distinct devices are considered, BowMapCL efficiently scales the offered throughput, ensuring a convenient load-balance of the involved processing in the several distinct devices.

Correlation of bow shock plasma wave turbulence with solar wind parameters

NASA Technical Reports Server (NTRS)

Rodriguez, P.; Gurnett, D. A.

1975-01-01

The r.m.s. field strengths of electrostatic and electromagnetic turbulence in the earth's bow shock, measured in the frequency range 20 Hz to 200 kHz with IMP-6 satellite, are found to correlate with specific solar wind parameters measured upstream of the bow shock.

Polarization properties of bow shock sources close to the Galactic centre

NASA Astrophysics Data System (ADS)

Zajaček, M.; Karas, V.; Hosseini, E.; Eckart, A.; Shahzamanian, B.; Valencia-S., M.; Peissker, F.; Busch, G.; Britzen, S.; Zensus, J. A.

2017-12-01

Several bow shock sources were detected and resolved in the innermost parsec from the supermassive black hole in the Galactic centre. They show several distinct characteristics, including an excess towards mid-infrared wavelengths and a significant linear polarization as well as a characteristic prolonged bow-shock shape. These features give hints about the presence of a non-spherical dusty envelope generated by the bow shock. The Dusty S-cluster Object (also denoted as G2) shows similar characteristics and it is a candidate for the closest bow shock with a detected proper motion in the vicinity of Sgr A*, with the pericentre distance of only approx. 2000 Schwarzschild radii. However, in the continuum emission it is a point-like source and hence we use Monte Carlo radiative transfer modeling to reveal its possible three-dimensional structure. Alongside the spectral energy distribution, the detection of polarized continuum emission in the near-infrared Ks-band (2.2 micrometers) puts additional constraints on the geometry of the source.

Magnetosheath Filamentary Structures Formed by Ion Acceleration at the Quasi-Parallel Bow Shock

NASA Technical Reports Server (NTRS)

Omidi, N.; Sibeck, D.; Gutynska, O.; Trattner, K. J.

2014-01-01

Results from 2.5-D electromagnetic hybrid simulations show the formation of field-aligned, filamentary plasma structures in the magnetosheath. They begin at the quasi-parallel bow shock and extend far into the magnetosheath. These structures exhibit anticorrelated, spatial oscillations in plasma density and ion temperature. Closer to the bow shock, magnetic field variations associated with density and temperature oscillations may also be present. Magnetosheath filamentary structures (MFS) form primarily in the quasi-parallel sheath; however, they may extend to the quasi-perpendicular magnetosheath. They occur over a wide range of solar wind Alfvénic Mach numbers and interplanetary magnetic field directions. At lower Mach numbers with lower levels of magnetosheath turbulence, MFS remain highly coherent over large distances. At higher Mach numbers, magnetosheath turbulence decreases the level of coherence. Magnetosheath filamentary structures result from localized ion acceleration at the quasi-parallel bow shock and the injection of energetic ions into the magnetosheath. The localized nature of ion acceleration is tied to the generation of fast magnetosonic waves at and upstream of the quasi-parallel shock. The increased pressure in flux tubes containing the shock accelerated ions results in the depletion of the thermal plasma in these flux tubes and the enhancement of density in flux tubes void of energetic ions. This results in the observed anticorrelation between ion temperature and plasma density.

Effect of bow-type initial imperfection on reliability of minimum-weight, stiffened structural panels

NASA Technical Reports Server (NTRS)

Stroud, W. Jefferson; Krishnamurthy, Thiagaraja; Sykes, Nancy P.; Elishakoff, Isaac

1993-01-01

Computations were performed to determine the effect of an overall bow-type imperfection on the reliability of structural panels under combined compression and shear loadings. A panel's reliability is the probability that it will perform the intended function - in this case, carry a given load without buckling or exceeding in-plane strain allowables. For a panel loaded in compression, a small initial bow can cause large bending stresses that reduce both the buckling load and the load at which strain allowables are exceeded; hence, the bow reduces the reliability of the panel. In this report, analytical studies on two stiffened panels quantified that effect. The bow is in the shape of a half-sine wave along the length of the panel. The size e of the bow at panel midlength is taken to be the single random variable. Several probability density distributions for e are examined to determine the sensitivity of the reliability to details of the bow statistics. In addition, the effects of quality control are explored with truncated distributions.

Bow shock formation in a complex plasma.

PubMed

Saitou, Y; Nakamura, Y; Kamimura, T; Ishihara, O

2012-02-10

A bow shock is observed in a two-dimensional supersonic flow of charged microparticles in a complex plasma. A thin conducting needle is used to make a potential barrier as an obstacle for the particle flow in the complex plasma. The flow is generated and the flow velocity is controlled by changing a tilt angle of the device under the gravitational force. A void, microparticle-free region, is formed around the potential barrier surrounding the obstacle. The flow is bent around the leading edge of the void and forms an arcuate structure when the flow is supersonic. The structure is characterized by the bow shock as confirmed by a polytropic hydrodynamic theory as well as numerical simulation.

GLOBAL EXPLICIT PARTICLE-IN-CELL SIMULATIONS OF THE NONSTATIONARY BOW SHOCK AND MAGNETOSPHERE

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

Yang, Zhongwei; Liu, Ying D.; Wang, Rui

2016-07-01

We carry out two-dimensional global particle-in-cell simulations of the interaction between the solar wind and a dipole field to study the formation of the bow shock and magnetosphere. A self-reforming bow shock ahead of a dipole field is presented by using relatively high temporal-spatial resolutions. We find that (1) the bow shock and the magnetosphere are formed and reach a quasi-stable state after several ion cyclotron periods, and (2) under the B{sub z} southward solar wind condition, the bow shock undergoes a self-reformation for low β{sub i} and high M{sub A}. Simultaneously, a magnetic reconnection in the magnetotail is found.more » For high β{sub i} and low M{sub A}, the shock becomes quasi-stationary, and the magnetotail reconnection disappears. In addition, (3) the magnetopause deflects the magnetosheath plasmas. The sheath particles injected at the quasi-perpendicular region of the bow shock can be convected downstream of an oblique shock region. A fraction of these sheath particles can leak out from the magnetosheath at the wings of the bow shock. Hence, the downstream situation is more complicated than that for a planar shock produced in local simulations.« less

Interplanetary magnetic field control of the Mars bow shock: Evidence for Venuslike interaction

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

Zhang, T.L.; Schwingenschuh, K.; Lichtenegger, H.

1991-07-01

The Mars bow shock location and shape have been determined by examining the PHOBOS spacecraft magnetometer data. Observations show that the position of the terminator bow shock varies with interplanetary magnetic field orientation in the same way as at Venus. The shock is farthest from Mars in the direction of the interplanetary electric field, consistent with the idea that mass loading plays an important role in the solar wind interaction with Mars. The authors also find that the shock cross section at the terminator plane is asymmetric and is controlled by the interplanetary magnetic field as expected from the asymmetricmore » propagation velocity of the fast magnetosonic wave. Comparing with earlier mission data, they show that the Mars shock location varies with solar activity. The shock is farther from Mars during solar maximum. Thus the solar wind interaction with Mars appears to be Venuslike, with a magnetic moment too small to affect significantly the solar wind interaction.« less

AOTV bow shock location

NASA Technical Reports Server (NTRS)

Desautel, D.

1985-01-01

Hypersonic bow-shock location and geometry are of central importance to the aerodynamics and aerothermodynamics of aeroassisted orbital transfer vehicles (AOTVs), but they are difficult to predict for a given vehicle configuration. This paper reports experimental measurements of shock standoff distance for the 70 deg cone AOTV configuration in shock-tunnel-test flows at Mach numbers of 3.8 to 7.9 and for angles of attack from 0 deg to 20 deg. The controlling parameter for hypersonic bow-shock standoff distance (for a given forebody shape) is the mean normal-shock density ratio. Values for this parameter in the tests reported are in the same range as those of the drag-brake AOTV perigee regime. Results for standoff distance are compared with those previously reported in the literature for this AOTV configuration. It is concluded that the AOTV shock standoff distance for the conical configuration, based on frustrum (base) radius, is equivalent to that of a sphere with a radius about 35 percent greater than that of the cone; the distance is, therefore, much less than reported in previous studies. Some reasons for the discrepancies between the present and previous are advanced. The smaller standoff distance determined here implies there will be less radiative heat transfer than was previously expected.

MMS Observations of Parallel Electric Fields During a Quasi-Perpendicular Bow Shock Crossing

NASA Astrophysics Data System (ADS)

Goodrich, K.; Schwartz, S. J.; Ergun, R.; Wilder, F. D.; Holmes, J.; Burch, J. L.; Gershman, D. J.; Giles, B. L.; Khotyaintsev, Y. V.; Le Contel, O.; Lindqvist, P. A.; Strangeway, R. J.; Russell, C.; Torbert, R. B.

2016-12-01

Previous observations of the terrestrial bow shock have frequently shown large-amplitude fluctuations in the parallel electric field. These parallel electric fields are seen as both nonlinear solitary structures, such as double layers and electron phase-space holes, and short-wavelength waves, which can reach amplitudes greater than 100 mV/m. The Magnetospheric Multi-Scale (MMS) Mission has crossed the Earth's bow shock more than 200 times. The parallel electric field signatures observed in these crossings are seen in very discrete packets and evolve over time scales of less than a second, indicating the presence of a wealth of kinetic-scale activity. The high time resolution of the Fast Particle Instrument (FPI) available on MMS offers greater detail of the kinetic-scale physics that occur at bow shocks than ever before, allowing greater insight into the overall effect of these observed electric fields. We present a characterization of these parallel electric fields found in a single bow shock event and how it reflects the kinetic-scale activity that can occur at the terrestrial bow shock.

Mesoscale Surface Pressure and Temperature Features Associated with Bow Echoes

DTIC Science & Technology

2010-01-01

contain several bowing segments. These multiple segments could occur at the same time and be located within the same bow, such as the serial derecho ...Examination of derecho environments using proximity soundings. Wea. Forecasting, 16, 329–342. Fovell, R. G., 2002: Upstream influence of numerically...Se- vere Local Storms, Hyannis, MA, Amer. Meteor. Soc., 4.6. Johns, R. H., and W. D. Hirt, 1987: Derechos : Widespread con- vectively induced

Investigating the Function of Play Bows in Dog and Wolf Puppies (Canis lupus familiaris, Canis lupus occidentalis).

PubMed

Byosiere, Sarah-Elizabeth; Espinosa, Julia; Marshall-Pescini, Sarah; Smuts, Barbara; Range, Friederike

2016-01-01

Animals utilize behavioral signals across a range of different contexts in order to communicate with others and produce probable behavioral outcomes. During play animals frequently adopt action patterns used in other contexts. Researchers have therefore hypothesized that play signals have evolved to clarify communicative intent. One highly stereotyped play signal is the canid play bow, but its function remains contested. In order to clarify how canid puppies use play bows, we used data on play bows in immature wolves (ages 2.7-7.8 months) and dogs (ages 2 to 5 months) to test hypotheses evaluated in a previous study of adult dogs. We found that young dogs used play bows similarly to adult dogs; play bows most often occurred after a brief pause in play followed by complementary highly active play states. However, while the relative number of play bows and total observation time was similar between dog and wolf puppies, wolves did not follow this behavioral pattern, as play bows were unsuccessful in eliciting further play activity by the partner. While some similarities for the function of play bows in dog and wolf puppies were documented, it appears that play bows may function differently in wolf puppies in regards to re-initiating play.

GYROSURFING ACCELERATION OF IONS IN FRONT OF EARTH's QUASI-PARALLEL BOW SHOCK

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

Kis, Arpad; Lemperger, Istvan; Wesztergom, Viktor

2013-07-01

It is well known that shocks in space plasmas can accelerate particles to high energies. However, many details of the shock acceleration mechanism are still unknown. A critical element of shock acceleration is the injection problem; i.e., the presence of the so called seed particle population that is needed for the acceleration to work efficiently. In our case study, we present for the first time observational evidence of gyroresonant surfing acceleration in front of Earth's quasi-parallel bow shock resulting in the appearance of the long-suspected seed particle population. For our analysis, we use simultaneous multi-spacecraft measurements provided by the Clustermore » spacecraft ion (CIS), magnetic (FGM), and electric field and wave instrument (EFW) during a time period of large inter-spacecraft separation distance. The spacecraft were moving toward the bow shock and were situated in the foreshock region. The results show that the gyroresonance surfing acceleration takes place as a consequence of interaction between circularly polarized monochromatic (or quasi-monochromatic) transversal electromagnetic plasma waves and short large amplitude magnetic structures (SLAMSs). The magnetic mirror force of the SLAMS provides the resonant conditions for the ions trapped by the waves and results in the acceleration of ions. Since wave packets with circular polarization and different kinds of magnetic structures are very commonly observed in front of Earth's quasi-parallel bow shock, the gyroresonant surfing acceleration proves to be an important particle injection mechanism. We also show that seed ions are accelerated directly from the solar wind ion population.« less

76 FR 65717 - City of Broken Bow, OK; Notice of Availability of Final Environmental Assessment

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-24

... application for an Original Major License for the Broken Bow Re-Regulation Dam Hydropower Project (FERC Project No. 12470-001). The Broken Bow Re-Regulation Dam Project is proposed to be located on the Mountain Fork River in McCurtain County, Oklahoma, at the U.S. Army Corps of Engineers' Broken Bow Re-Regulation...

Astronomy in Denver: Polarization of bow shock nebulae around massive stars

NASA Astrophysics Data System (ADS)

Shrestha, Manisha; Hoffman, Jennifer L.; Ignace, Richard; Neilson, Hilding; Richard Ignace

2018-06-01

Stellar wind bow shocks are structures created when stellar winds with supersonic relative velocities interact with the local interstellar medium (ISM). They can be studied to understand the properties of stars as well as the ISM. Since bow shocks are asymmetric, light becomes polarized by scattering in the regions of enhanced density they create. We use a Monte Carlo radiative transfer code calle SLIP to simulate the polarization signatures produced by both resolved and unresolved bow shocks with analytically derived shapes and density structures. When electron scattering is the polarizing mechanism, we find that optical depth plays an important role in the polarization signatures. While results for low optical depths reproduce theoretical predictions, higher optical depths produce higher polarization and position angle rotations at specific viewing angles. This is due to the geometrical properties of the bow shock along with multiple scattering effects. For dust scattering, we find that the polarization signature is strongly affected by wavelength, dust size, dust composition, and viewing angle. Depending on the viewing angle, the polarization magnitude may increase or decrease as a function of wavelength. We will present results from these simulations and preliminary comparisons with observational data.

First observations and simulations of specularly reflected He++ at Earth's quasi-perpendicular bow shock

NASA Astrophysics Data System (ADS)

Broll, J. M.; Fuselier, S. A.; Trattner, K. J.; Giles, B. L.; Anderson, B. J.; Burch, J. L.

2017-12-01

Proton specular reflection at quasi-perpendicular shocks provides dissipation in cases where the upstream Mach number is too high for fluid dissipation mechanisms alone - as is almost always the case at Earth's bow shock. Some evidence of He++ specular reflection was found in reduced particle distributions measured by previous spacecraft at the bow shock. However, due to resolution constraints it was not possible to confirm that the bow shock was capable of reflecting solar wind He++. We present MMS observations of quasi-perpendicular bow shock crossing that are consistent with He++ specular reflection. These observations are supported by 1D particle-in- cell simulations demonstrating that a small amount of He++ can be turned back despite having twice the mass-per-charge of the protons.

Sedentism, social change, warfare, and the bow in the ancient Pueblo Southwest.

PubMed

Reed, Paul F; Geib, Phil R

2013-01-01

In the ancient American Southwest, use of the bow developed relatively rapidly among Pueblo people by the fifth century AD. This new technology replaced the millennia-old atlatl and dart weaponry system. Roughly 150 years later in the AD 600s, Pueblo socioeconomic organization began to evolve rapidly, as many groups adopted a much more sedentary life. Multiple factors converged to allow this sedentary pattern to emerge, but the role of the bow in this process has not been fully explored. In this paper, we trace the development of the bow and discuss its role as sedentism emerged and social changes occurred in ancient Puebloan society from the fifth through seventh centuries AD. Copyright © 2013 Wiley Periodicals, Inc.

The Milky Way Project: A Citizen Science Catalog of Infrared Bow Shock Nebulae

NASA Astrophysics Data System (ADS)

Dixon, Don; Jayasinghe, Tharindu; Povich, Matthew S.

2017-01-01

We present preliminary results from the first citizen-science search for infrared stellar-wind bow shock candidates. This search uses the Milky Way project, hosted by the Zooniverse, an online platform with over 1 million volunteer citizen scientists. Milky Way Project volunteers examine 77,000 randomly-distributed Spitzer image cutouts at varying zoom levels. Volunteers mark the infrared arc of potential bow shock candidates as well as the star likely driving the nebula. We produce lists of candidates from bow shocks flagged by multiple volunteers, which after merging and final visual review form the basis for our catalog. Comparing our new catalog to a recently-published catalog of 709 infrared bow shock candidates identified by a small team of (primarily undergraduate) researchers will allow us to assess the effectiveness of citizen science for this type of search and should yield a more complete catalog. Planned studies using these large catalogs will improve constraints on the mass-loss rates for the massive stars that create these bow shock nebulae. Mass-loss rates are highly uncertain but are a critical component of evolutionary models for massive stars. This work is supported by the National Science Foundation under grants CAREER-1454334, AST-1411851 (RUI) and AST-1412845.

Systematic search for very-high-energy gamma-ray emission from bow shocks of runaway stars

NASA Astrophysics Data System (ADS)

H.E.S.S. Collaboration; Abdalla, H.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Andersson, T.; Angüner, E. O.; Arakawa, M.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Büchele, M.; Bulik, T.; Capasso, M.; Carr, J.; Casanova, S.; Cerruti, M.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Chrétien, M.; Coffaro, M.; Colafrancesco, S.; Cologna, G.; Condon, B.; Conrad, J.; Cui, Y.; Davids, I. D.; Decock, J.; Degrange, B.; Deil, C.; Devin, J.; deWilt, P.; Dirson, L.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O.'C.; Dutson, K.; Dyks, J.; Edwards, T.; Egberts, K.; Eger, P.; Ernenwein, J.-P.; Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Funk, S.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goyal, A.; Grondin, M.-H.; Hahn, J.; Haupt, M.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holler, M.; Horns, D.; Ivascenko, A.; Iwasaki, H.; Jacholkowska, A.; Jamrozy, M.; Janiak, M.; Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jogler, T.; Jouvin, L.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katsuragawa, M.; Katz, U.; Kerszberg, D.; Khangulyan, D.; Khélifi, B.; Kieffer, M.; King, J.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lees, J.-P.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; López-Coto, R.; Lypova, I.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Morå, K.; Moulin, E.; Murach, T.; Nakashima, S.; de Naurois, M.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Öttl, S.; Ohm, S.; Ostrowski, M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Pekeur, N. W.; Pelletier, G.; Perennes, C.; Petrucci, P.-O.; Peyaud, B.; Piel, Q.; Pita, S.; Poon, H.; Prokhorov, D.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Richter, S.; Rieger, F.; Romoli, C.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Saito, S.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer, S.; Seglar-Arroyo, M.; Settimo, M.; Seyffert, A. S.; Shafi, N.; Shilon, I.; Simoni, R.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stycz, K.; Sushch, I.; Takahashi, T.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tibaldo, L.; Tiziani, D.; Tluczykont, M.; Trichard, C.; Tsuji, N.; Tuffs, R.; Uchiyama, Y.; van der Walt, D. J.; van Eldik, C.; van Rensburg, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zanin, R.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Żywucka, N.

2018-04-01

Context. Runaway stars form bow shocks by ploughing through the interstellar medium at supersonic speeds and are promising sources of non-thermal emission of photons. One of these objects has been found to emit non-thermal radiation in the radio band. This triggered the development of theoretical models predicting non-thermal photons from radio up to very-high-energy (VHE, E ≥ 0.1 TeV) gamma rays. Subsequently, one bow shock was also detected in X-ray observations. However, the data did not allow discrimination between a hot thermal and a non-thermal origin. Further observations of different candidates at X-ray energies showed no evidence for emission at the position of the bow shocks either. A systematic search in the Fermi-LAT energy regime resulted in flux upper limits for 27 candidates listed in the E-BOSS catalogue. Aim. Here we perform the first systematic search for VHE gamma-ray emission from bow shocks of runaway stars. Methods: Using all available archival H.E.S.S. data we search for very-high-energy gamma-ray emission at the positions of bow shock candidates listed in the second E-BOSS catalogue release. Out of the 73 bow shock candidates in this catalogue, 32 have been observed with H.E.S.S. Results: None of the observed 32 bow shock candidates in this population study show significant emission in the H.E.S.S. energy range. Therefore, flux upper limits are calculated in five energy bins and the fraction of the kinetic wind power that is converted into VHE gamma rays is constrained. Conclusions: Emission from stellar bow shocks is not detected in the energy range between 0.14 and 18 TeV.The resulting upper limits constrain the level of VHE gamma-ray emission from these objects down to 0.1-1% of the kinetic wind energy.

First Detection of a Pulsar Bow Shock Nebula in Far-UV: PSR J0437-4715

NASA Astrophysics Data System (ADS)

Rangelov, Blagoy; Pavlov, George G.; Kargaltsev, Oleg; Durant, Martin; Bykov, Andrei M.; Krassilchtchikov, Alexandre

2016-11-01

Pulsars traveling at supersonic speeds are often accompanied by cometary bow shocks seen in Hα. We report on the first detection of a pulsar bow shock in the far-ultraviolet (FUV). We detected it in FUV images of the nearest millisecond pulsar J0437-4715 obtained with the Hubble Space Telescope. The images reveal a bow-like structure positionally coincident with part of the previously detected Hα bow shock, with an apex at 10″ ahead of the moving pulsar. Its FUV luminosity, L(1250{--}2000 \\mathringA )≈ 5 × {10}28 erg s-1, exceeds the Hα luminosity from the same area by a factor of 10. The FUV emission could be produced by the shocked interstellar medium matter or, less likely, by relativistic pulsar wind electrons confined by strong magnetic field fluctuations in the bow shock. In addition, in the FUV images we found a puzzling extended (≃3″ in size) structure overlapping with the limb of the bow shock. If related to the bow shock, it could be produced by an inhomogeneity in the ambient medium or an instability in the bow shock. We also report on a previously undetected X-ray emission extending for about 5″ ahead of the pulsar, possibly a pulsar wind nebula created by shocked pulsar wind, with a luminosity L(0.5-8 keV) ˜ 3 × 1028 erg s-1. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO 12917 and GO 10568.

Visualization of interaction of Mach waves with a bow shock

NASA Astrophysics Data System (ADS)

Pavlov, Al.; Golubev, M.; Kosinov, A.; Pavlov, A.

2017-10-01

The work presents results of investigation of couple weak waves with a bow shock at Mach number M = 2. The waves produced by a small 2D roughness installed on the nozzle inset or side wall of working section. Hot-wire measurements revealed profile of the waves to be similar to N-wave. The visualization was done by means of schlieren technique and interferential AVT SA method. The inclination angle change of the Mach waves at free-stream section and bow shock section was found.

Polarized bow shocks reveal features of the winds and environments of massive stars

NASA Astrophysics Data System (ADS)

Shrestha, Manisha

2018-01-01

Massive stars strongly affect their surroundings through their energetic stellar winds and deaths as supernovae. The bow shock structures created by fast-moving massive stars contain important information about the winds and ultimate fates of these stars as well as their local interstellar medium (ISM). Since bow shocks are aspherical, the light scattered in the dense shock material becomes polarized. Analyzing this polarization reveals details of the bow shock geometry as well as the composition, velocity, density, and albedo of the scattering material. With these quantities, we can constrain the properties of the stellar wind and thus the evolutionary state of the star, as well as the dust composition of the local ISM.In my dissertation research, I use a Monte Carlo radiative transfer code that I optimized to simulate the polarization signatures produced by both resolved and unresolved stellar wind bow shocks (SWBS) illuminated by a central star and by shock emission. I derive bow shock shapes and densities from published analytical calculations and smooth particle hydrodynamic (SPH) models. In the case of the analytical SWBS and electron scattering, I find that higher optical depths produce higher polarization and position angle rotations at specific viewing angles compared to theoretical predictions for low optical depths. This is due to the geometrical properties of the bow shock combined with multiple scattering effects. For dust scattering, the polarization signature is strongly affected by wavelength, dust grain properties, and viewing angle. The behavior of the polarization as a function of wavelength in these cases can distinguish among different dust models for the local ISM. In the case of SPH density structures, I investigate how the polarization changes as a function of the evolutionary phase of the SWBS. My dissertation compares these simulations with polarization data from Betelgeuse and other massive stars with bow shocks. I discuss the

The Neural Substrates for Letter String Readings in The Normal and Reverse Directions: An fMRI Study

NASA Astrophysics Data System (ADS)

Ge, Sheng; Saito, Takashi; Wu, Jing-Long; Ogasawara, Jun-Ichi; Yamauchi, Shuichi; Matsunaga, Naofumi; Iramina, Keiji

In order to investigate the difference in cortical activations between reading letter strings in the normal direction and the reverse direction, an fMRI study was conducted. In this study, the cortical activations elicited by Japanese letter string reading and Chinese letter string reading were investigated. The subjects performed the normal direction reading task (read letter strings from left to right), and the reverse direction reading task (read letter strings from right to left). According to the experimental results, the activated brain regions during the normal and the reverse direction reading tasks were compared. It was found that visuospatial transformation was involved in the reverse direction reading task, while this function was not significant during the normal direction reading task. Furthermore, we found that there was no significant difference in cortical activation between Japanese and Chinese letter string readings.

Curvature and bow of bulk GaN substrates

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

Foronda, Humberto M.; Young, Erin C.; Robertson, Christian A.

2016-07-21

We investigate the bow of free standing (0001) oriented hydride vapor phase epitaxy grown GaN substrates and demonstrate that their curvature is consistent with a compressive to tensile stress gradient (bottom to top) present in the substrates. The origin of the stress gradient and the curvature is attributed to the correlated inclination of edge threading dislocation (TD) lines away from the [0001] direction. A model is proposed and a relation is derived for bulk GaN substrate curvature dependence on the inclination angle and the density of TDs. The model is used to analyze the curvature for commercially available GaN substratesmore » as determined by high resolution x-ray diffraction. The results show a close correlation between the experimentally determined parameters and those predicted from theoretical model.« less

Annual variations in the Martian bow shock location as observed by the Mars Express mission

NASA Astrophysics Data System (ADS)

Hall, B. E. S.; Lester, M.; Sánchez-Cano, B.; Nichols, J. D.; Andrews, D. J.; Edberg, N. J. T.; Opgenoorth, H. J.; Fränz, M.; Holmström, M.; Ramstad, R.; Witasse, O.; Cartacci, M.; Cicchetti, A.; Noschese, R.; Orosei, R.

2016-11-01

The Martian bow shock distance has previously been shown to be anticorrelated with solar wind dynamic pressure but correlated with solar extreme ultraviolet (EUV) irradiance. Since both of these solar parameters reduce with the square of the distance from the Sun, and Mars' orbit about the Sun increases by ˜0.3 AU from perihelion to aphelion, it is not clear how the bow shock location will respond to variations in these solar parameters, if at all, throughout its orbit. In order to characterize such a response, we use more than 5 Martian years of Mars Express Analyser of Space Plasma and EneRgetic Atoms (ASPERA-3) Electron Spectrometer measurements to automatically identify 11,861 bow shock crossings. We have discovered that the bow shock distance as a function of solar longitude has a minimum of 2.39RM around aphelion and proceeds to a maximum of 2.65RM around perihelion, presenting an overall variation of ˜11% throughout the Martian orbit. We have verified previous findings that the bow shock in southern hemisphere is on average located farther away from Mars than in the northern hemisphere. However, this hemispherical asymmetry is small (total distance variation of ˜2.4%), and the same annual variations occur irrespective of the hemisphere. We have identified that the bow shock location is more sensitive to variations in the solar EUV irradiance than to solar wind dynamic pressure variations. We have proposed possible interaction mechanisms between the solar EUV flux and Martian plasma environment that could explain this annual variation in bow shock location.

Severe lateral tibial bowing with short stature in two siblings--a provisionally novel syndrome.

PubMed

Zitano, Lia; Loder, Randall T; Cohen, Mervyn D; Weaver, David D

2012-09-01

In this report, we describe two siblings with short stature and severe lateral tibial bowing. In the younger sibling, the bowing was bilateral, while in the older sib, it was unilateral. However, both showed bilateral abnormalities of the distal tibial epiphyses and growth plates. Pseudoarthrosis of the left distal tibial metaphysis and subsequent spontaneous resolution of the abnormality occurred in the younger sibling. The fibulas of both children were of normal diameter and were straight, except for the distal ends. Surgery has almost completely corrected the lower leg bowing in both patients. The type of tibial bowing seen in these children can be associated with a number of syndromes, such as neurofibromatosis type I, Weismann-Netter syndrome, and a variety of environmental caused disorders, such as vitamin D deficient rickets. However, the severity of the bowing present in our patients and the absence of other clinical features differentiates this condition from those reported in the literature. We posit that the condition in the children presented here represents an as yet undescribed syndrome, which is likely to be of genetic origin. Copyright © 2012 Wiley Periodicals, Inc.

First simultaneous measurements of waves generated at the bow shock in the solar wind, the magnetosphere and on the ground

NASA Astrophysics Data System (ADS)

Clausen, L. B. N.; Yeoman, T. K.; Fear, R. C.; Behlke, R.; Lucek, E. A.; Engebretson, M. J.

2009-01-01

On 5 September 2002 the Geotail satellite observed the cone angle of the Interplanetary Magnetic Field (IMF) change to values below 30° during a 56 min interval between 18:14 and 19:10 UT. This triggered the generation of upstream waves at the bow shock, 13 RE downstream of the position of Geotail. Upstream generated waves were subsequently observed by Geotail between 18:30 and 18:48 UT, during times the IMF cone angle dropped below values of 10°. At 18:24 UT all four Cluster satellites simultaneously observed a sudden increase in wave power in all three magnetic field components, independent of their position in the dayside magnetosphere. We show that the 10 min delay between the change in IMF direction as observed by Geotail and the increase in wave power observed by Cluster is consistent with the propagation of the IMF change from the Geotail position to the bow shock and the propagation of the generated waves through the bow shock, magnetosheath and magnetosphere towards the position of the Cluster satellites. We go on to show that the wave power recorded by the Cluster satellites in the component containing the poloidal and compressional pulsations was broadband and unstructured; the power in the component containing toroidal oscillations was structured and shows the existence of multi-harmonic Alfvénic continuum waves on field lines. Model predictions of these frequencies fit well with the observations. An increase in wave power associated with the change in IMF direction was also registered by ground based magnetometers which were magnetically conjunct with the Cluster satellites during the event. To the best of our knowledge we present the first simultaneous observations of waves created by backstreaming ions at the bow shock in the solar wind, the dayside magnetosphere and on the ground.

The absent bow tie sign in bucket-handle tears of the menisci in the knee.

PubMed

Helms, C A; Laorr, A; Cannon, W D

1998-01-01

Bucket-handle tears of the menisci are one of the most frequently missed diagnoses in MR examinations of the knee. This article describes the "absent bow tie sign," which can be used to identify bucket-handle tears on routine MR examinations of the knee. The arthroscopic surgical reports (n = 350) from a single orthopedic surgeon's practice during a 24-month period were examined for patients who had a diagnosis of bucket-handle tear and who underwent MR imaging before surgery (n = 32). The MR examinations were retrospectively evaluated for the presence of a bow tie sign. The bow tie sign was considered normal when two sagittal images showed the body segment (a bow tie appearance). The bow tie sign was considered abnormal, consistent with a bucket-handle tear, when only one or no body segment was seen (the absent bow tie sign). Coronal images were evaluated for a truncated meniscus. Also, each MR examination was scrutinized for a displaced fragment and a double posterior cruciate ligament (PCL) sign. Thirty-three bucket-handle tears were found at arthroscopy in 32 patients. One patient had tears of the medial and lateral menisci. The absent bow tie sign was seen in 32 of the 33 cases (sensitivity, 97%) and correlated with the medial or lateral meniscus that was reported torn at arthroscopy. The single false-negative result occurred in a patient with a nondisplaced bucket-handle tear. The findings in 31 contralateral normal menisci were all negative for an absent bow tie sign (specificity, 100%). A displaced fragment was found in 30 (94%) of 32 cases. The coronal images showed a truncated meniscus in 21 (64%) of 33 cases. A double PCL sign was seen in 10 (30%) of 33 cases. The absent bow tie sign is an easily applied finding that can be used with good sensitivity to diagnose bucket-handle tears of the menisci on MR imaging. This sign has a higher accuracy rate than other findings common with bucket-handle tears, such as displaced fragments, a truncated appearance of

Finite element method (FEM) analysis of the force systems produced by asymmetric inner headgear bows.

PubMed

Geramy, Allahyar; Kizilova, Natalya; Terekhov, Leonid

2011-11-01

Extra-oral traction appliances were introduced more than a century ago and continue to be used to produce orthopaedic and/or dental changes in the maxilla. While force systems produced by asymmetric outer bows have been studied extensively, the force systems produced by asymmetric inner bows have been overlooked. To analyse the forces acting on the maxillary first molars: when the size of one bayonet bend is increased; when the point of application of the distalising force on the inner bow is moved to one side; when one molar is displaced palatally. Four FEM models of cervical headgear attached to maxillary first molars were designed in SolidWorks 2010 and transferred to an ANSYS Workbench Ver. 12.1. Model 1, each molar was 23 mm from the midpalatal line and the inner bow was symmetrical; Model 2, the left molar was displaced 4 mm towards the midpalatal line and the inner bow was symmetrical; Model 3, the molars were equidistant (23 mm) from the midpalatal line, but the left molar was engaged by a 2 mm larger bayonet bend; Model 4, the molars were equidistant (23 mm) from the midpalatal line but the join between the inner and outer bows was displaced 2 mm towards the left molar. In all FEM models, a 2N force was applied to the inner bow at the join between inner and outer bows and the energy transmitted to the teeth and the von Mises stresses on the molar PDLs were assessed. There were marked differences in the strain energy on the teeth and the von Mises stresses on their PDLs. A 14 to 20 per cent increase in energy and force was produced on the tooth closer to the symmetric plane of the headgear. In addition, the increase in energy produced a 30 to 62 per cent increase in the von Mises stresses within the PDLs. Small asymmetries in molar position, the size of a bayonet bend and the point of application of a force on an inner bow resulted in asymmetrical forces on the molars. These forces were higher on the molar closer to the symmetric plane of the headgear.

Two-dimensional steady bow waves in water of finite depth

NASA Astrophysics Data System (ADS)

Kao, John

1998-12-01

In this study, the two-dimensional steady bow flow in water of arbitrary finite depth has been investigated. The two-dimensional bow is assumed to consist of an inclined flat plate connected downstream to a horizontal semi-infinite draft plate. The bottom of the channel is assumed to be a horizontal plate; the fluid is assumed to be inviscid, incompressible; and the flow irrotational. For the angle of incidence α (held by the bow plate) lying between 0o and 60o, the local flow analysis near the stagnation point shows that the angle lying between the free surface and the inclined plate, β, must always be equal to 120o, otherwise no solution can exist. Moreover, we further find that the local flow solution does not exist if /alpha > 60o, and that on the inclined plate there exists a negative pressure region adjacent to the stagnation point for /alpha < 30o. Singularities at the stagnation point and the upstream infinity are found to have multiple branch-point singularities of irrational orders. A fully nonlinear theoretical model has been developed in this study for evaluating the incompressible irrotational flow satisfying the free-surface conditions and two constraint equations. To solve the bow flow problem, successive conformal mappings are first used to transform the flow domain into the interior of a unit semi-circle in which the unknowns can be represented as the coefficients of an infinite series. A total error function equivalent to satisfying the Bernoulli equation is defined and solved by minimizing the error function and applying the method of Lagrange's multiplier. Smooth solutions with monotonic free surface profiles have been found and presented here for the range of 35o < /alpha < 60o, a draft Froude number Frd less than 0.5, and a water-depth Froude number Frh less than 0.4. The dependence of the solution on these key parameters is examined. Our results may be useful in designing the optimum bow shape.

Research on bulbous bow optimization based on the improved PSO algorithm

NASA Astrophysics Data System (ADS)

Zhang, Sheng-long; Zhang, Bao-ji; Tezdogan, Tahsin; Xu, Le-ping; Lai, Yu-yang

2017-08-01

In order to reduce the total resistance of a hull, an optimization framework for the bulbous bow optimization was presented. The total resistance in calm water was selected as the objective function, and the overset mesh technique was used for mesh generation. RANS method was used to calculate the total resistance of the hull. In order to improve the efficiency and smoothness of the geometric reconstruction, the arbitrary shape deformation (ASD) technique was introduced to change the shape of the bulbous bow. To improve the global search ability of the particle swarm optimization (PSO) algorithm, an improved particle swarm optimization (IPSO) algorithm was proposed to set up the optimization model. After a series of optimization analyses, the optimal hull form was found. It can be concluded that the simulation based design framework built in this paper is a promising method for bulbous bow optimization.

Determining the standoff distance of the bow shock: Mach number dependence and use of models

NASA Technical Reports Server (NTRS)

Farris, M. H.; Russell, C. T.

1994-01-01

We explore the factors that determine the bow shock standoff distance. These factors include the parameters of the solar wind, as well as the size and shape of the obstacle. In this report we develop a semiempirical Mach number relation for the bow shock standoff distance in order to take into account the shock's behavior at low Mach numbers. This is done by determining which properties of the shock are most important in controlling the standoff distance and using this knowledge to modify the current Mach number relation. While the present relation has proven useful at higher Mach numbers, it has lacked effectiveness at the low Mach number limit. We also analyze the bow shock dependence upon the size and shape of the obstacle, noting that it is most appropriate to compare the standoff distance of the bow shock to the radius of curvature of the obstacle, as opposed to the distance from the focus of the object to the nose. Last, we focus our attention on the use of bow shock models in determining the standoff distance. We note that the physical behavior of the shock must correctly be taken into account, specifically the behavior as a function of solar wind dynamic pressure; otherwise, erroneous results can be obtained for the bow shock standoff distance.

Can postural modification reduce kinetic and kinematic loading during the bowing postures of Islamic prayer?

PubMed

AbouHassan, J; Milosavljevic, S; Carman, A

2010-12-01

As stooped postures are known to increase kinematic and kinetic loading on the lumbar spine they can be problematic for people with low back pain and postural task modification is often recommended. For the Muslim with low back pain, the bowing postures during prayer can aggravate low back symptoms. The aims of this study were to describe lumbo-sacral and pelvic tilt kinematics and lumbo-sacral kinetics during the standard bowing postures of Islam and to compare these to kinematic and kinetic data gathered during a clinically recommended modified bowing posture. The study was a repeated measures within subject cross-over design with 33 healthy male Muslim participants. 3-D motion analysis data were gathered to calculate body joint angles during the two bowing postures. A 3-D biomechanical model was then used to calculate spinal loads. Paired t-test analyses showed that the use of the modified posture resulted in significantly less pelvic tilt range of motion and anterior shear force and compressive force L5/S1, at stages 1 and 5 of bowing. Although this study was conducted with healthy young Muslim males, the use of this modified bent knee posture is recommended for all Muslims with low back pain. Clinical trials are being considered to determine the clinical utility of this postural manoeuvre as an intervention. STATEMENT OF RELEVANCE: The presence of low back pain may hinder a Muslim's ability to use the traditional Islamic bowing posture. Muslims who have low back pain may benefit from adopting a modification to the traditional bowing posture, which has been found to reduce the loads and postural demands on the lower back.

Sociopolitical effects of bow and arrow technology in prehistoric coastal California.

PubMed

Kennett, Douglas J; Lambert, Patricia M; Johnson, John R; Culleton, Brendan J

2013-01-01

Bow and arrow technology spread across California between ∼AD 250 and 1200, first appearing in the intermountain deserts of the Great Basin and later spreading to the coast. We critically evaluate the available data for the initial spread in bow and arrow technology and examine its societal effects on the well-studied Northern Channel Islands off the coast of Southern California. The introduction of this technology to these islands between AD 650 and 900 appears to predate the appearance of hereditary inequality between AD 900 and 1300. We conclude, based on the available data, that this technology did not immediately trigger intergroup warfare. We argue that the introduction of the bow and arrow contributed to sociopolitical instabilities that were on the rise within the context of increasing population levels and unstable climatic conditions, which stimulated intergroup conflict and favored the development of hereditary inequality. Population aggregation and economic intensification did occur with the introduction of the bow and arrow. This observation is consistent with the hypothesis that social coercion via intra-group "law enforcement" contributed to changes in societal scale that ultimately resulted in larger groups that were favored in inter-group conflict. We argue that the interplay between intra-group "law enforcement" and inter-group warfare were both essential for the ultimate emergence of social inequality between AD 900 and 1300. Copyright © 2013 Wiley Periodicals, Inc.

Fuzzy Bayesian Network-Bow-Tie Analysis of Gas Leakage during Biomass Gasification

PubMed Central

Yan, Fang; Xu, Kaili; Yao, Xiwen; Li, Yang

2016-01-01

Biomass gasification technology has been rapidly developed recently. But fire and poisoning accidents caused by gas leakage restrict the development and promotion of biomass gasification. Therefore, probabilistic safety assessment (PSA) is necessary for biomass gasification system. Subsequently, Bayesian network-bow-tie (BN-bow-tie) analysis was proposed by mapping bow-tie analysis into Bayesian network (BN). Causes of gas leakage and the accidents triggered by gas leakage can be obtained by bow-tie analysis, and BN was used to confirm the critical nodes of accidents by introducing corresponding three importance measures. Meanwhile, certain occurrence probability of failure was needed in PSA. In view of the insufficient failure data of biomass gasification, the occurrence probability of failure which cannot be obtained from standard reliability data sources was confirmed by fuzzy methods based on expert judgment. An improved approach considered expert weighting to aggregate fuzzy numbers included triangular and trapezoidal numbers was proposed, and the occurrence probability of failure was obtained. Finally, safety measures were indicated based on the obtained critical nodes. The theoretical occurrence probabilities in one year of gas leakage and the accidents caused by it were reduced to 1/10.3 of the original values by these safety measures. PMID:27463975

Magnetohydrodynamic and gasdynamic theories for planetary bow waves

NASA Technical Reports Server (NTRS)

Spreiter, John R.; Stahara, Stephen S.

1985-01-01

A bow wave was previously observed in the solar wind upstream of each of the first six planets. The observed properties of these bow waves and the associated plasma flows are outlined, and those features identified that can be described by a continuum magnetohydrodynamic flow theory. An account of the fundamental concepts and current status of the magnetohydrodynamic and gas dynamic theories for solar wind flow past planetary bodies is provided. This includes a critical examination of: (1) the fundamental assumptions of the theories; (2) the various simplifying approximations introduced to obtain tractable mathematical problems; (3) the limitations they impose on the results; and (4) the relationship between the results of the simpler gas dynamic-frozen field theory and the more accurate but less completely worked out magnetohydrodynamic theory. Representative results of the various theories are presented and compared.

Magnetohydrodynamic and gasdynamic theories for planetary bow waves

NASA Technical Reports Server (NTRS)

Spreiter, J. R.; Stahara, S. S.

1983-01-01

A bow wave was previously observed in the solar wind upstream of each of the first six planets. The observed properties of these bow waves and the associated plasma flows are outlined, and those features identified that can be described by a continuum magnetohydrodynamic flow theory. An account of the fundamental concepts and current status of the magnetohydrodynamic and gas dynamic theories for solar wind flow past planetary bodies is provided. This includes a critical examination of: (1) the fundamental assumptions of the theories; (2) the various simplifying approximations introduced to obtain tractable mathematical problems; (3) the limitations they impose on the results; and (4) the relationship between the results of the simpler gas dynamic-frozen field theory and the more accurate but less completely worked out magnetohydrodynamic theory. Representative results of the various theories are presented and compared.

Demographic noise can reverse the direction of deterministic selection

PubMed Central

Constable, George W. A.; Rogers, Tim; McKane, Alan J.; Tarnita, Corina E.

2016-01-01

Deterministic evolutionary theory robustly predicts that populations displaying altruistic behaviors will be driven to extinction by mutant cheats that absorb common benefits but do not themselves contribute. Here we show that when demographic stochasticity is accounted for, selection can in fact act in the reverse direction to that predicted deterministically, instead favoring cooperative behaviors that appreciably increase the carrying capacity of the population. Populations that exist in larger numbers experience a selective advantage by being more stochastically robust to invasions than smaller populations, and this advantage can persist even in the presence of reproductive costs. We investigate this general effect in the specific context of public goods production and find conditions for stochastic selection reversal leading to the success of public good producers. This insight, developed here analytically, is missed by the deterministic analysis as well as by standard game theoretic models that enforce a fixed population size. The effect is found to be amplified by space; in this scenario we find that selection reversal occurs within biologically reasonable parameter regimes for microbial populations. Beyond the public good problem, we formulate a general mathematical framework for models that may exhibit stochastic selection reversal. In this context, we describe a stochastic analog to r−K theory, by which small populations can evolve to higher densities in the absence of disturbance. PMID:27450085

Reversed stereo depth and motion direction with anti-correlated stimuli.

PubMed

Read, J C; Eagle, R A

2000-01-01

We used anti-correlated stimuli to compare the correspondence problem in stereo and motion. Subjects performed a two-interval forced-choice disparity/motion direction discrimination task for different displacements. For anti-correlated 1d band-pass noise, we found weak reversed depth and motion. With 2d anti-correlated stimuli, stereo performance was impaired, but the perception of reversed motion was enhanced. We can explain the main features of our data in terms of channels tuned to different spatial frequencies and orientation. We suggest that a key difference between the solution of the correspondence problem by the motion and stereo systems concerns the integration of information at different orientations.

Anterior Femoral Bow and Possible Effect on the Stifle Joint: A Comparison between Humans and Dogs.

PubMed

Ocal, M K; Sabanci, S S; Cobanoglu, M; Enercan, M

2017-08-01

The aim of the study was to compare the anterior bow of the femur between dogs and humans in terms of the possible impact on the stifle joint. The femoral radiographs obtained retrospectively were used to determine the angles and positions of the anterior bow in both dogs (n = 135) and humans (n = 57). Descriptive statistics and Pearson's correlation analysis were used for the statistical analyses of the variables. The mean anterior bow angle (ABA) was 18.3 ± 2.02° and 4.88 ± 1.24° in dogs and humans, respectively. The bow position was at the distal shaft in dogs (64.9 ± 2.04%) and almost at the mid-shaft of the bone (46.5 ± 5.52%) in humans. The ABA was related to the bow position in both humans and dogs. Additionally, the angle correlated with age in humans, while it was correlated with weight and breed in dogs. In conclusion, it is suggested that the anterior bow should be used as a landmark on the femoral axis for the biomechanical research of stifle joint, and dog stifle could be used as a suitable model for human knee in experimental studies for clinicians, while making sure that ethical principles are fully respected. © 2017 Blackwell Verlag GmbH.

75 FR 33290 - City of Broken Bow, OK; Notice of Availability of Environmental Assessment

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-11

... application for an Original Major License for the Broken Bow Re-Regulation Dam Hydropower Project. The project would be located at the United States Army Corps of Engineers' (Corps) Broken Bow Re-Regulation Dam on... http://www.ferc.gov , using the ``eLibrary'' link. Enter the docket number excluding the last three...

A numerical study on bow shocks around the lightning return stroke channel

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

Chen, Qiang, E-mail: cq0405@126.com; Chen, Bin, E-mail: emcchen@163.com; Yi, Yun

2015-03-15

Bow shock structures are important to various hydrodynamics and magnetohydrodynamics (MHD) phenomena in geophysics and astrophysics. The formation and propagation of bow shocks around the lightning return stroke channel are investigated based on the self-similar motion theory and simulated with a two-dimensional Eulerian finite volume resistive radiation MHD code. In this framework, as verification of theoretical models, the evolving structures of many quantities, such as the plasma density, temperature, pressure, shock velocity, and magnetic field, can be obtained, which present all the characteristics of bow shocks in the lightning return stroke processes. The evolution characteristics and the configuration of themore » curved return stroke channels, e.g., the non-ideal effects and the scaling laws, are discussed in detail. The results may have applications for some observed features of the return stroke channels and other phenomena in the lightning discharge plasmas.« less

Optimal trajectories for solar bow shock mission

NASA Astrophysics Data System (ADS)

Pizzurro, S.; Circi, C.

2012-11-01

This paper deals a Solar Bow Shock mission, a phenomenon of interaction between the solar wind and the interstellar medium, due to the relative motion of our star with respect to the enormous interstellar matter cloud that contains it. This phenomenon occurs at boundary of the solar system (200 AU), and it is preferable a mission in situ that could examine in detail what actually happens on-the-spot, to understand its effect on the planets of the solar system. Voyager 1 & 2 reached the area where the phenomenon takes place after 30 years. The target is to arrive there optimizing both the transfer time, and the propellant mass consumption. Therefore, the trajectory will be optimized using different propulsion systems and appropriate flyby sequences.. The approach techniques that will be used foresee executions of impulsive or ballistic gravity assists with the utilisation of high thrust engine only, or low thrust engine only, or both engines in two different phases of the mission. By comparing all the solutions obtained imposing different initial conditions the optimal trajectory to arrive at Solar Bow Shock is presented.

Mechanisms of Amplified Arteriogenesis in Collateral Artery Segments Exposed to Flow Direction Reversal

PubMed Central

Heuslein, Joshua L.; Meisner, Joshua K.; Li, Xuanyue; Song, Ji; Vincentelli, Helena; Leiphart, Ryan J.; Ames, Elizabeth G.; Price, Richard J.

2015-01-01

Objective Collateral arteriogenesis, the growth of existing arterial vessels to a larger diameter, is a fundamental adaptive response that is often critical for the perfusion and survival of tissues downstream of chronic arterial occlusion(s). Shear stress regulates arteriogenesis; however, the arteriogenic significance of flow direction reversal, occurring in numerous collateral artery segments after femoral artery ligation (FAL), is unknown. Our objective was to determine if flow direction reversal in collateral artery segments differentially regulates endothelial cell signaling and arteriogenesis. Approach and Results Collateral segments experiencing flow reversal after FAL in C57BL/6 mice exhibit increased pericollateral macrophage recruitment, amplified arteriogenesis (30% diameter and 2.8-fold conductance increases), and remarkably permanent (12 weeks post-FAL) remodeling. Genome-wide transcriptional analyses on HUVECs exposed to flow reversal conditions mimicking those occurring in-vivo yielded 10-fold more significantly regulated transcripts, as well as enhanced activation of upstream regulators (NFκB, VEGF, FGF2, TGFβ) and arteriogenic canonical pathways (PKA, PDE, MAPK). Augmented expression of key pro-arteriogenic molecules (KLF2, ICAM-1, eNOS) was also verified by qRT-PCR, leading us to test whether ICAM-1 and/or eNOS regulate amplified arteriogenesis in flow-reversed collateral segments in-vivo. Interestingly, enhanced pericollateral macrophage recruitment and amplified arteriogenesis was attenuated in flow-reversed collateral segments after FAL in ICAM-1−/− mice; however, eNOS−/− mice showed no such differences. Conclusions Flow reversal leads to a broad amplification of pro-arteriogenic endothelial signaling and a sustained ICAM-1-dependent augmentation of arteriogenesis. Further investigation of the endothelial mechanotransduction pathways activated by flow reversal may lead to more effective and durable therapeutic options for arterial

Enhanced model of photovoltaic cell/panel/array considering the direct and reverse modes

NASA Astrophysics Data System (ADS)

Zegaoui, Abdallah; Boutoubat, Mohamed; Sawicki, Jean-Paul; Kessaissia, Fatma Zohra; Djahbar, Abdelkader; Aillerie, Michel

2018-05-01

This paper presents an improved generalized physical model for photovoltaic, PV cells, panels and arrays taking into account the behavior of these devices when considering their biasing existing in direct and reverse modes. Existing PV physical models generally are very efficient for simulating influence of irradiation changes on the short circuit current but they could not visualize the influences of temperature changes. The Enhanced Direct and Reverse Mode model, named EDRM model, enlightens the influence on the short-circuit current of both temperature and irradiation in the reverse mode of the considered PV devices. Due to its easy implementation, the proposed model can be a useful power tool for the development of new photovoltaic systems taking into account and in a more exhaustive manner, environmental conditions. The developed model was tested on a marketed PV panel and it gives a satisfactory results compared with parameters given in the manufacturer datasheet.

Asymmetric Outer Bow Length and Cervical Headgear Force System: 3D Analysis Using Finite Element Method.

PubMed

Geramy, Allahyar; Hassanpour, Mehdi; Emadian Razavi, Elham Sadat

2015-03-01

This study sought to assess distal and lateral forces and moments of asymmetric headgears by variable outer bow lengths. Four 3D finite element method (FEM) models of a cervical headgear attached to the maxillary first molars were designed in SolidWorks 2010 software and transferred to ANSYS Workbench ver. 11 software. Models contained the first molars, their periodontal ligament (PDL), cancellous and cortical bones, a mesiodistal slice of the maxillae and the headgear. Models were the same except for the outer bow length in headgears. The headgear was symmetric in model 1. In models 2 to 4, the headgears were asymmetric in length with differences of 5mm, 10mm and 15mm, respectively. A 2.5 N force in horizontal plane was applied and the loading manner of each side of the outer bow was calculated trigonometrically using data from a volunteer. The 15mm difference in outer bow length caused the greatest difference in lateral (=0.21 N) and distal (= 1.008 N) forces and also generated moments (5.044 N.mm). As the difference in outer bow length became greater, asymmetric effects increased. Greater distal force in the longer arm side was associated with greater lateral force towards the shorter arm side and more net yawing moment. A difference range of 1mm to 15 mm of length in cervical headgear can be considered as a safe length of outer bow shortening in clinical use.

Global MHD Simulations of the Earth's Bow Shock Shape and Motion Under Variable Solar Wind Conditions

NASA Astrophysics Data System (ADS)

Mejnertsen, L.; Eastwood, J. P.; Hietala, H.; Schwartz, S. J.; Chittenden, J. P.

2018-01-01

Empirical models of the Earth's bow shock are often used to place in situ measurements in context and to understand the global behavior of the foreshock/bow shock system. They are derived statistically from spacecraft bow shock crossings and typically treat the shock surface as a conic section parameterized according to a uniform solar wind ram pressure, although more complex models exist. Here a global magnetohydrodynamic simulation is used to analyze the variability of the Earth's bow shock under real solar wind conditions. The shape and location of the bow shock is found as a function of time, and this is used to calculate the shock velocity over the shock surface. The results are compared to existing empirical models. Good agreement is found in the variability of the subsolar shock location. However, empirical models fail to reproduce the two-dimensional shape of the shock in the simulation. This is because significant solar wind variability occurs on timescales less than the transit time of a single solar wind phase front over the curved shock surface. Empirical models must therefore be used with care when interpreting spacecraft data, especially when observations are made far from the Sun-Earth line. Further analysis reveals a bias to higher shock speeds when measured by virtual spacecraft. This is attributed to the fact that the spacecraft only observes the shock when it is in motion. This must be accounted for when studying bow shock motion and variability with spacecraft data.

Polarization simulations of stellar wind bow-shock nebulae - I. The case of electron scattering

NASA Astrophysics Data System (ADS)

Shrestha, Manisha; Neilson, Hilding R.; Hoffman, Jennifer L.; Ignace, Richard

2018-06-01

Bow shocks and related density enhancements produced by the winds of massive stars moving through the interstellar medium provide important information regarding the motions of the stars, the properties of their stellar winds, and the characteristics of the local medium. Since bow-shock nebulae are aspherical structures, light scattering within them produces a net polarization signal even if the region is spatially unresolved. Scattering opacity arising from free electrons and dust leads to a distribution of polarized intensity across the bow-shock structure. That polarization encodes information about the shape, composition, opacity, density, and ionization state of the material within the structure. In this paper, we use the Monte Carlo radiative transfer code SLIP to investigate the polarization created when photons scatter in a bow-shock-shaped region of enhanced density surrounding a stellar source. We present results for electron scattering, and investigate the polarization behaviour as a function of optical depth, temperature, and source of photons for two different cases: pure scattering and scattering with absorption. In both regimes, we consider resolved and unresolved cases. We discuss the implications of these results as well as their possible use along with observational data to constrain the properties of observed bow-shock systems. In different situations and under certain assumptions, our simulations can constrain viewing angle, optical depth and temperature of the scattering region, and the relative luminosities of the star and shock.

Geminga's tails: a pulsar bow shock probing the interstellar medium.

PubMed

Caraveo, P A; Bignami, G F; DeLuca, A; Mereghetti, S; Pellizzoni, A; Mignani, R; Tur, A; Becker, W

2003-09-05

We report the X-ray Multimirror Mission-Newton European Photon Imaging Camera observation of two elongated parallel x-ray tails trailing the pulsar Geminga. They are aligned with the object's supersonic motion, extend for approximately 2', and have a nonthermal spectrum produced by electron-synchrotron emission in the bow shock between the pulsar wind and the surrounding medium. Electron lifetime against synchrotron cooling matches the source transit time over the x-ray features' length. Such an x-ray detection of a pulsar bow shock (with no Halpha emission) allows us to gauge the pulsar electron injection energy and the shock magnetic field while constraining the angle of Geminga's motion and the local matter density.

X-RAY EMISSION LINE PROFILES FROM WIND CLUMP BOW SHOCKS IN MASSIVE STARS

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

Ignace, R.; Waldron, W. L.; Cassinelli, J. P.

2012-05-01

The consequences of structured flows continue to be a pressing topic in relating spectral data to physical processes occurring in massive star winds. In a preceding paper, our group reported on hydrodynamic simulations of hypersonic flow past a rigid spherical clump to explore the structure of bow shocks that can form around wind clumps. Here we report on profiles of emission lines that arise from such bow shock morphologies. To compute emission line profiles, we adopt a two-component flow structure of wind and clumps using two 'beta' velocity laws. While individual bow shocks tend to generate double-horned emission line profiles,more » a group of bow shocks can lead to line profiles with a range of shapes with blueshifted peak emission that depends on the degree of X-ray photoabsorption by the interclump wind medium, the number of clump structures in the flow, and the radial distribution of the clumps. Using the two beta law prescription, the theoretical emission measure and temperature distribution throughout the wind can be derived. The emission measure tends to be power law, and the temperature distribution is broad in terms of wind velocity. Although restricted to the case of adiabatic cooling, our models highlight the influence of bow shock effects for hot plasma temperature and emission measure distributions in stellar winds and their impact on X-ray line profile shapes. Previous models have focused on geometrical considerations of the clumps and their distribution in the wind. Our results represent the first time that the temperature distribution of wind clump structures are explicitly and self-consistently accounted for in modeling X-ray line profile shapes for massive stars.« less

Unilateral Outer Bow Expanded Cervical Headgear Force System: 3D Analysis Using Finite Element Method.

PubMed

Geramy, Allahyar; Mortezai, Omid; Esmaily, Masomeh; Darvishpour, Hojat

2015-04-01

Headgears are among the effective orthodontic appliances to achieve treatment goals. Unilateral molar distal movement is sometimes needed during an orthodontic treatment, which can be achieved by an asymmetric headgear. Different unilateral headgears have been introduced. The main goal of this study was to analyze the force system of unilateral expanded outer bow asymmetric headgears by the finite element method (FEM). Six 3D finite element models of a mesiodistal slice of the maxilla containing upper first molars, their periodontal ligaments (PDLs), cancellous bone, cortical bone, and a cervical headgear with expanded outer bow attached to maxillary first molars were designed in SolidWorks 2010 and meshed in ANSYS Workbench ver. 12.1. The models were the same except for the degree of outer bow expansion. The outer bow ends were loaded with 2 N force. The distal driving force and the net moment were evaluated. A decrease in the distalizing force in the normal side molar from 1.69 N to 1.37 N was shown by increasing the degree of unilateral expansion. At the same time, the force increased from 2.19 N to 2.49 N in the expanded side molar. A net moment increasing from 2.26 N.mm to 4.64 N.mm was also shown. Unilateral outer bow expansion can produce different distalizing forces in molars, which increase by increasing the expansion.

76 FR 2710 - Pitney Bowes, Inc., Mailing Solutions Management Division Including On-Site Leased Workers of...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-14

...., Mailing Solutions Management Division Including On-Site Leased Workers of Guidant Group, and Teleworkers... Bowes, Inc., Mailing Solutions Management Division, Engineering Quality Assurance, Shelton, Connecticut... identity of the subject worker group. The worker group consists of workers of Pitney Bowes, Inc., the...

Asymmetric Outer Bow Length and Cervical Headgear Force System: 3D Analysis Using Finite Element Method

PubMed Central

Geramy, Allahyar; Hassanpour, Mehdi; Emadian Razavi, Elham sadat

2015-01-01

Objectives: This study sought to assess distal and lateral forces and moments of asymmetric headgears by variable outer bow lengths. Materials and Methods: Four 3D finite element method (FEM) models of a cervical headgear attached to the maxillary first molars were designed in SolidWorks 2010 software and transferred to ANSYS Workbench ver. 11 software. Models contained the first molars, their periodontal ligament (PDL), cancellous and cortical bones, a mesiodistal slice of the maxillae and the headgear. Models were the same except for the outer bow length in headgears. The headgear was symmetric in model 1. In models 2 to 4, the headgears were asymmetric in length with differences of 5mm, 10mm and 15mm, respectively. A 2.5 N force in horizontal plane was applied and the loading manner of each side of the outer bow was calculated trigonometrically using data from a volunteer. Results: The 15mm difference in outer bow length caused the greatest difference in lateral (=0.21 N) and distal (= 1.008 N) forces and also generated moments (5.044 N.mm). Conclusion: As the difference in outer bow length became greater, asymmetric effects increased. Greater distal force in the longer arm side was associated with greater lateral force towards the shorter arm side and more net yawing moment. Clinical Relevance: A difference range of 1mm to 15 mm of length in cervical headgear can be considered as a safe length of outer bow shortening in clinical use. PMID:26622275

THEMIS Observations of Unusual Bow Shock Motion, Attending a Transient Magnetospheric Event

NASA Technical Reports Server (NTRS)

Korotova, Galina; Sibeck, David; Omidi, N.; Angelopoulos, V.

2013-01-01

We present a multipoint case study of solar wind and magnetospheric observations during a transient magnetospheric compression at 2319 UT on October 15, 2008. We use high-time resolution magnetic field and plasma data from the THEMIS and GOES-11/12 spacecraft to show that this transient event corresponded to an abrupt rotation in the IMF orientation, a change in the location of the foreshock, and transient outward bow shock motion. We employ results from a global hybrid code model to reconcile the observations indicating transient inward magnetopause motion with the outward bow shock motion.

41. BOW SPACES (YN OFFICES, AYN OFFICES & DECK SHOP, ...

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

41. BOW SPACES (YN OFFICES, AYN OFFICES & DECK SHOP, LAUNDRY & BOS'N STORES), WITH HATCH TO PAINT LOCKER AT LEFT. - U.S. Coast Guard Cutter WHITE HEATH, USGS Integrated Support Command Boston, 427 Commercial Street, Boston, Suffolk County, MA

Propagation direction reversal of ionization zones in the transition between high and low current magnetron sputtering

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

School of Materials Science and Engineering, State Key Lab for Materials Processing and Die & Mold Technology, Huazhong University of Science and Technology, Wuhan 430074, China; Department of Physics, University of California Berkeley, Berkeley, California 94720, USA; Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA

2014-12-11

Past research has revealed the propagation of dense, asymmetric ionization zones in both high and low current magnetron discharges. Here we report about the direction reversal of ionization zone propagation as observed with fast cameras. At high currents, zones move in the E B direction with velocities of 103 to 104 m/s. However at lower currents, ionization zones are observed to move in the opposite, the -E B direction, with velocities ~;; 103 m/s. It is proposed that the direction reversal is associated with the local balance of ionization and supply of neutrals in the ionization zone.

Forest resources of the Medicine Bow National Forest

Treesearch

Jim Steed

2008-01-01

The Interior West Forest Inventory and Analysis (IWFIA) Program of the USDA Forest Service, Rocky Mountain Research Station, as part of our National Forest System cooperative inventories, conducted a forest resource inventory on the Medicine Bow National Forest using a nationally standardized mapped-plot design (for more details see "Inventory methods"...

Fiber-Based Measurement of Bow-Shock Spectra for Reentry Flight Testing

NASA Technical Reports Server (NTRS)

Schott, Timothy D.; Herring, Gregory C.; Munk, Michelle M.; Grinstead, Jay H.; Prabbu, Dinesh K.

2010-01-01

We demonstrated a fiber-based approach for obtaining optical spectra of a glowing bow shock in a high-enthalpy air flow. The work was performed in a ground test with the NASA Ames Aerodynamic Heating Facility (AHF) that is used for atmospheric reentry simulation. The method uses a commercial fiber optic that is embedded in the nose of an ablating bluntbody model and provides a line-of-sight view in the streamwise direction - directly upstream into the hot post-shock gas flow. Both phenolic impregnated carbon ablator (PICA) and phenolic carbon (PhenCarb 28) materials were used as thermal protection systems. Results show that the fibers survive the intense heat and operate sufficiently well during the first several seconds of a typical AHF run (20 MJ/kg). This approach allowed the acquisition of optical spectra, enabling a Boltzmann-based electronic excitation temperature measurement from Cu atom impurities (averaged over a line-of-sight through the gas cap, with a 0.04 sec integration time).

Direct and reverse pollen-mediated gene flow between GM rice and red rice weed

PubMed Central

Serrat, X.; Esteban, R.; Peñas, G.; Català, M. M.; Melé, E.; Messeguer, J.

2013-01-01

Potential risks of genetically modified (GM) crops must be identified before their commercialization, as happens with all new technologies. One of the major concerns is the proper risk assessment of adventitious presence of transgenic material in rice fields due to cross-pollination. Several studies have been conducted in order to quantify pollen-mediated gene flow from transgenic rice (Oryza sativa) to both conventional rice and red rice weed (O. sativa f. spontanea) under field conditions. Some of these studies reported GM pollen-donor rice transferring GM traits to red rice. However, gene flow also occurs in the opposite direction, in a phenomenon that we have called reverse gene flow, resulting in transgenic seeds that have incorporated the traits of wild red rice. We quantified reverse gene flow using material from two field trials. A molecular analysis based on amplified fragment length polymorphisms was carried out, being complemented with a phenotypic identification of red rice traits. In both field trials, the reverse gene flow detected was greater than the direct gene flow. The rate of direct gene flow varied according to the relative proportions of the donor (GM rice) and receptor (red rice) plants and was influenced by wind direction. The ecological impact of reverse gene flow is limited in comparison with that of direct gene flow because non-shattered and non-dormant seeds would be obtained in the first generation. Hybrid seed would remain in the spike and therefore most of it would be removed during harvesting. Nevertheless, this phenomenon must be considered in fields used for elite seed production and in developing countries where farmers often keep some seed for planting the following year. In these cases, there is a higher risk of GM red rice weed infestation increasing from year to year and therefore a proper monitoring plan needs to be established.

Unilateral Outer Bow Expanded Cervical Headgear Force System: 3D Analysis Using Finite Element Method

PubMed Central

Mortezai, Omid; Esmaily, Masomeh; Darvishpour, Hojat

2015-01-01

Objectives: Headgears are among the effective orthodontic appliances to achieve treatment goals. Unilateral molar distal movement is sometimes needed during an orthodontic treatment, which can be achieved by an asymmetric headgear. Different unilateral headgears have been introduced. The main goal of this study was to analyze the force system of unilateral expanded outer bow asymmetric headgears by the finite element method (FEM). Materials and Methods: Six 3D finite element models of a mesiodistal slice of the maxilla containing upper first molars, their periodontal ligaments (PDLs), cancellous bone, cortical bone, and a cervical headgear with expanded outer bow attached to maxillary first molars were designed in SolidWorks 2010 and meshed in ANSYS Workbench ver. 12.1. The models were the same except for the degree of outer bow expansion. The outer bow ends were loaded with 2 N force. The distal driving force and the net moment were evaluated. Results: A decrease in the distalizing force in the normal side molar from 1.69 N to 1.37 N was shown by increasing the degree of unilateral expansion. At the same time, the force increased from 2.19 N to 2.49 N in the expanded side molar. A net moment increasing from 2.26 N.mm to 4.64 N.mm was also shown. Conclusion: Unilateral outer bow expansion can produce different distalizing forces in molars, which increase by increasing the expansion. PMID:26622282

RADIO POLARIZATION OBSERVATIONS OF G319.9-0.7: A BOW-SHOCK NEBULA WITH AN AZIMUTHAL MAGNETIC FIELD POWERED BY PULSAR J1509-5850

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

Ng, C.-Y.; Gaensler, B. M.; Chatterjee, S.

2010-03-20

We report radio polarization observations of G319.9-0.7 (MSC 319.9-0.7) at 3 and 6 cm obtained with the Australia Telescope Compact Array. The source shows a highly elongated morphology with the energetic pulsar J1509-5850 located at the tip. We found a flat radio spectrum of index alpha = -0.26 +- 0.04 and a high degree of linear polarization. These results confirm G319.9-0.7 as a bow-shock pulsar wind nebula. The polarization maps suggest a helical magnetic field trailing the pulsar, with the symmetry axis parallel to the system's inferred direction of motion. This is the first time such a field geometry hasmore » been seen in a bow-shock nebula, and it may be the result of an alignment between the pulsar spin axis and its space velocity. Compared to other bow-shock examples, G319.9-0.7 exhibits very different properties in the field structure and surface brightness distribution, illustrating the large diversity of the population.« less

Observational test of shock drift and Fermi acceleration on a seed particle population upstream of earth's bow shock

NASA Technical Reports Server (NTRS)

Anagnostopoulos, G. C.; Sarris, E. T.; Krimigis, S. M.

1988-01-01

The efficiency of proposed shock acceleration mechanisms as they operate at the bow shock in the presence of a seed energetic particle population was examined using data from simultaneous observations of energetic solar-origin protons, carried out by the IMP 7 and 8 spacecraft in the vicinity of the quasi-parallel (dawn) and quasi-perpendicular (dusk) regions of the earth's bow shock, respectively. The results of observations (which include acceleration effects in the intensities of the energetic protons with energies as high as 4 MeV observed at the vicinity of the dusk bow shock, but no evidence for any particle acceleration at the energy equal to or above 50 keV at the dawn side of the bow shock) indicate that the acceleration of a seed particle population occurs only at the quasi-perpendicular bow shock through shock drift acceleration and that the major source of observed upstream ion populations is the leakage of magnetospheric ions of energies not less than 50 keV, rather than in situ acceleration.

40. BOW SPACES (YN OFFICES, AYN OFFICES & DECK SHOP, ...

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

40. BOW SPACES (YN OFFICES, AYN OFFICES & DECK SHOP, LAUNDRY & BOS'N STORES), WITH HATCH TO PAINT LOCKER AT LEFT. - U.S. Coast Guard Cutter WHITE LUPINE, U.S. Coast Guard Station Rockland, east end of Tillson Avenue, Rockland, Knox County, ME

Reverse pupillary block associated with pigment dispersion syndrome after in-the-bag intraocular lens implantation.

PubMed

Itagaki, Hideo; Kunikata, Toshio; Hiratsuka, Kentaro; Saito, Junichiro; Oshika, Tetsuro

2013-12-01

A 61-year-old man with high myopia who had received a systemic α1A-adrenoceptor antagonist had phacoemulsification and in-the-bag intraocular lens implantation in the right eye. One day postoperatively, marked pigment dispersion in the anterior chamber, posterior bowing of the iris, and iridodonesis were noted associated with a subsequent elevation in intraocular pressure (IOP). Pharmacological pupil dilation was effective in reducing pigment dispersion and IOP, and laser peripheral iridotomy was performed to alleviate posterior bowing of the iris. We hypothesize that dynamic changes in the aqueous humor flow by cataract surgery and latent flaccidity of the iris due to the systemic α1A-adrenoceptor antagonist caused reverse pupillary block. High myopia may be another risk factor for this complication. Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

The Radial Bow following Square Nailing in Radius and Ulna Shaft Fractures in Adults and its Relation to Disability and Function.

PubMed

Dave, M B; Parmar, K D; Sachde, B A

2016-07-01

One of the points made against nailing in radius and ulna shaft fractures has been the loss of radial bow and its impact on function. The aims of the study were to assess the change in magnitude and location of the radial bow in radius and ulna shaft fractures treated with intramedullary square nails and to assess the impact of this change on functional outcome, patient reported disability and the range of motion of the forearm. We measured the magnitude of radial bow and its location in the operated extremity and compared it to the uninjured side in 32 adult patients treated with intramedullary square nailing for radius and ulna shaft fractures at our institute. The mean loss of magnitude of maximum radial bow was 2.18 mm which was statistically significant by both student-T test and Mann-Whitney U test with p value less than 0.01. The location of maximum radial bow shifted distally but was statistically insignificant. The magnitude of maximum radial bow had a negative correlation with DASH score that was statistically insignificant (R=- 0.22, p=0.21). It had a positive, statistically significant correlation to the extent of supination in the operated extremity (R = 0.66, p = 0.0004). A loss of up to 2mm of radial bow did not influence the functional outcome as assessed by criteria reported by Anderson et al. The magnitude of radial bow influenced the supination of the forearm but not the final disability as measured by DASH score. Intramedullary nailing did decrease the magnitude of radial bow but a reduction of up to 2mm did not influence the functional outcome.

Differential Binding Models for Direct and Reverse Isothermal Titration Calorimetry.

PubMed

Herrera, Isaac; Winnik, Mitchell A

2016-03-10

Isothermal titration calorimetry (ITC) is a technique to measure the stoichiometry and thermodynamics from binding experiments. Identifying an appropriate mathematical model to evaluate titration curves of receptors with multiple sites is challenging, particularly when the stoichiometry or binding mechanism is not available. In a recent theoretical study, we presented a differential binding model (DBM) to study calorimetry titrations independently of the interaction among the binding sites (Herrera, I.; Winnik, M. A. J. Phys. Chem. B 2013, 117, 8659-8672). Here, we build upon our DBM and show its practical application to evaluate calorimetry titrations of receptors with multiple sites independently of the titration direction. Specifically, we present a set of ordinary differential equations (ODEs) with the general form d[S]/dV that can be integrated numerically to calculate the equilibrium concentrations of free and bound species S at every injection step and, subsequently, to evaluate the volume-normalized heat signal (δQ(V) = δq/dV) of direct and reverse calorimetry titrations. Additionally, we identify factors that influence the shape of the titration curve and can be used to optimize the initial concentrations of titrant and analyte. We demonstrate the flexibility of our updated DBM by applying these differentials and a global regression analysis to direct and reverse calorimetric titrations of gadolinium ions with multidentate ligands of increasing denticity, namely, diglycolic acid (DGA), citric acid (CIT), and nitrilotriacetic acid (NTA), and use statistical tests to validate the stoichiometries for the metal-ligand pairs studied.

DETAIL VIEW, WINDOW BOW IN EAST WALL. (NOTE THE OPENING ...

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

DETAIL VIEW, WINDOW BOW IN EAST WALL. (NOTE THE OPENING FOR THE CRYPTOPORTICUS TO THE BOW’S RIGHT. THIS EXTERIOR FEATURE EXTENDS BENEATH THE NORTH TERRACE - The Woodlands, 4000 Woodlands Avenue, Philadelphia, Philadelphia County, PA

17. SAME ROOMVIEW SOUTH TOWARDS TWO SKIFFS UNDER CONSTRUCTION (BOW ...

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

17. SAME ROOM-VIEW SOUTH TOWARDS TWO SKIFFS UNDER CONSTRUCTION (BOW VIEW SHOWING CLAMPING JIG MOUNTED TO BEAMS ABOVE/PROFILE VIEW IN BACKGROUND SHOWING JIG). - Lowell's Boat Shop, 459 Main Street, Amesbury, Essex County, MA

A "reverse direction" technique of single-port left upper pulmonary resection.

PubMed

Zhang, Min; Sihoe, Alan D L; Du, Ming

2016-08-01

Single-port video-assisted thoracoscopic surgery (VATS) left upper lobectomy is difficult amongst all the lobes. At the beginning of single-port lobectomies, the upper lobes were believed not to be amenable for single-port approach due to the difficult angulation for staplers. Gonzalez reported the first single-port VATS left upper lobectomy in 2011. We report a new technique of single-port VATS left upper lobectomy with the concept of "reverse direction". We divide the apical-anterior arterial trunk with upper vein in the last. The procedure sequence is described as follows: posterior artery, lingular artery, bronchus and finally upper vein & apical-anterior arterial trunk. This method could overcome the angular limitations frequently encountered in single-port VATS procedures; reduce the risk of injuries to pulmonary artery; broaden the indications of single-port the upper lobe of the left lung (LUL) to include hypoplastic lung fissures. Limitations of this new practice include the enlargement or severe calcifications of hilar and bronchial lymph nodes. A "reverse direction" technique of single-port left upper pulmonary resection is feasible and safe.

19. DETAIL VIEW OF SKIFF BOW WITH OAK STEM AND ...

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

19. DETAIL VIEW OF SKIFF BOW WITH OAK STEM AND FRAMES PLANKED IN CEDAR USING COPPER CLINCH NAILS. TRANSOM OF SECOND SKIFF CAN BE SEEN BACKGROUND. - Lowell's Boat Shop, 459 Main Street, Amesbury, Essex County, MA

Influence of wheelchair front caster wheel on reverse directional stability.

PubMed

Guo, Songfeng; Cooper, Rory A; Corfman, Tom; Ding, Dan; Grindle, Garrett

2003-01-01

The purpose of this research was to study directional stability during reversing of rear-wheel drive, electric powered wheelchairs (EPW) under different initial front caster orientations. Specifically, the weight distribution differences caused by certain initial caster orientations were examined as a possible mechanism for causing directional instability that could lead to accidents. Directional stability was quantified by measuring the drive direction error of the EPW by a motion analysis system. The ground reaction forces were collected to determine the load on the front casters, as well as back-emf data to attain the speed of the motors. The drive direction error was found to be different for various initial caster orientations. Drive direction error was greatest when both casters were oriented 90 degrees to the left or right, and least when both casters were oriented forward. The results show that drive direction error corresponds to the loading difference on the casters. The data indicates that loading differences may cause asymmetric drag on the casters, which in turn causes unbalanced torque load on the motors. This leads to a difference in motor speed and drive direction error.

Whistler mode waves observed by MGF search coil magnetometer -Polarization and wave normal features of upstream waves near the bow-shock

NASA Astrophysics Data System (ADS)

Hayashi, K.; Matsui, H.; Kawano, H.; Yamamoto, T.; Kokubun, S.

1994-12-01

Whistler mode waves observed in the upstream region very close to the bow-shock is focused from the initial survey for magnetic fed data in a frequency range between 1Hz and 50Hz observed by the search coil magnetometer on board the Geotail satellite. Based on the three component wave form data polarization and wave-normal characteristics of foreshock waves is first shown as dynamic spectra for the whole Fourier components of the 50 Hz band width. Intense whistler mode waves generated in the foot region of the bow-shock are found strongly controlled in the observed polarization dependent on the angle between directions of the wave propagation and the solar wind flow but not very dependent on frequency. Our simple scheme to derive the ware characteristics which is effective to survey large amount of data continuously growing is also introduced.

Atmospheric helium and geomagnetic field reversals.

NASA Technical Reports Server (NTRS)

Sheldon, W. R.; Kern, J. W.

1972-01-01

The problem of the earth's helium budget is examined in the light of recent work on the interaction of the solar wind with nonmagnetic planets. It is proposed that the dominant mode of helium (He4) loss is ion pumping by the solar wind during geomagnetic field reversals, when the earth's magnetic field is very small. The interaction of the solar wind with the earth's upper atmosphere during such a period is found to involve the formation of a bow shock. The penetration altitude of the shock-heated solar plasma is calculated to be about 700 km, and ionization rates above this level are estimated for a cascade ionization (electron avalanche) process to average 10 to the 9th power ions/sq cm/sec. The calculated ionization rates and the capacity of the solar wind to remove ionized helium (He4) from the upper atmosphere during geomagnetic dipole reversals are sufficient to yield a secular equilibrium over geologic time scales. The upward transport of helium from the lower atmosphere under these conditions is found to be adequate to sustain the proposed loss rate.

3. VIEW NORTHEAST OF PORT BOW OF JFK IN DRYDOCK ...

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

3. VIEW NORTHEAST OF PORT BOW OF JFK IN DRYDOCK NO. 5; PAINTERS WORKING APPLYING ANTI-FOULING PAINT BELOW WATER LINE. - Naval Base Philadelphia-Philadelphia Naval Shipyard, Dry Dock No. 5, League Island, Philadelphia, Philadelphia County, PA

Terahertz-wave near-field imaging with subwavelength resolution using surface-wave-assisted bow-tie aperture

NASA Astrophysics Data System (ADS)

Ishihara, Kunihiko; Ohashi, Keishi; Ikari, Tomofumi; Minamide, Hiroaki; Yokoyama, Hiroyuki; Shikata, Jun-ichi; Ito, Hiromasa

2006-11-01

We demonstrate the terahertz-wave near-field imaging with subwavelength resolution using a bow-tie shaped aperture surrounded by concentric periodic structures in a metal film. A subwavelength aperture with concentric periodic grooves, which are known as a bull's eye structure, shows extremely large enhanced transmission beyond the diffraction limit caused by the resonant excitation of surface waves. Additionally, a bow-tie aperture exhibits extraordinary field enhancement at the sharp tips of the metal, which enhances the transmission and the subwavelength spatial resolution. We introduced a bow-tie aperture to the bull's eye structure and achieved high spatial resolution (˜λ/17) in the near-field region. The terahertz-wave near-field image of the subwavelength metal pattern (pattern width=20μm) was obtained for the wavelength of 207μm.

Asymmetry of nonlinear interactions of solar MHD discontinuities with the bow shock

NASA Astrophysics Data System (ADS)

Grib, S. A.; Pushkar, E. A.

2006-07-01

Oblique interaction between the solar fast shock wave, which is a typical nonstationary strong discontinuity in the interplanetary space, and the bow shock front upstream of an Earth-type planetary magnetosphere is studied. Attention has been paid to the qualitative and quantitative (with respect to the proton density distribution) dawn-dusk (or morning-evening) asymmetry of the discontinuities refracted into the magnetosheath, which originates in the ecliptic plane on different sides of the Sun-Earth line. The results under discussion have been corroborated experimentally by the gas-kinetic pattern of the bow-shock front and the WIND and ISEE 3 spacecraft measurements of the plasma density.

Possible Ceres bow shock surfaces based on fluid models

NASA Astrophysics Data System (ADS)

Jia, Y.-D.; Villarreal, M. N.; Russell, C. T.

2017-05-01

The hot electron beams that Dawn detected at Ceres can be explained by fast-Fermi acceleration at a temporary bow shock. A shock forms when the solar wind encounters a temporary atmosphere, similar to a cometary coma. We use a magnetohydrodynamic model to quantitatively reproduce the 3-D shock surface at Ceres and deduce the atmosphere characteristics that are required to create such a shock. Our most simple model requires about 1.8 kg/s, or 6 × 1025/s water vapor production rate to form such a shock. Such an estimate relies on characteristics of the solar wind-Ceres interaction. We present several case studies to show how these conditions affect our estimate. In addition, we contrast these cases with the smaller and narrower shock caused by a subsurface induction. Our multifluid model reveals the asymmetry introduced by the large gyroradius of the heavy pickup ions and further constrains the IMF direction during the events.

6. VIEW OF BOW OF VESSEL FROM STARBOARD SIDE, SHOWING ...

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

6. VIEW OF BOW OF VESSEL FROM STARBOARD SIDE, SHOWING DOCKING CREW PREPARING TO REMOVE FOREFOOT FROM VESSEL'S STEM IN ORDER TO DRAW VESSEL OFF LIFT DOCK - Bugeye "Louise Travers", Intersection of Routes 2 & 4, Solomons, Calvert County, MD

Electron distributions upstream of the Comet Halley bow shock - Evidence for adiabatic heating

NASA Technical Reports Server (NTRS)

Larson, D. E.; Anderson, K. A.; Lin, R. P.; Carlson, C. W.; Reme, H.; Glassmeier, K. H.; Neubauer, F. M.

1992-01-01

Three-dimensional plasma electron (22 eV to 30 keV) observations upstream of Comet Halley bow shock, obtained by the RPA-1 COPERNIC (Reme Plasma Analyzer - Complete Positive Ion, Electron and Ram Negative Ion Measurements near Comet Halley) experiment on the Giotto spacecraft are reported. Besides electron distributions typical of the undisturbed solar wind and backstreaming electrons observed when the magnetic field line intersects the cometary bow shock, a new type of distribution, characterized by enhanced low energy (less than 100 eV) flux which peaks at 90-deg pitch angles is found. These are most prominent when the spacecraft is on field lines which pass close to but are not connected to the bow shock. The 90-deg pitch angle electrons appear to have been adiabatically heated by the increase in the magnetic field strength resulting from the compression of the upstream solar wind plasma by the cometary mass loading. A model calculation of this effect which agrees qualitatively with the observed 90-deg flux enhancements is presented.

Bow shock data analysis

NASA Astrophysics Data System (ADS)

Zipf, Edward C.; Erdman, Peeter W.

1994-08-01

The University of Pittsburgh Space Physics Group in collaboration with the Army Research Office (ARO) modeling team has completed a systematic organization of the shock and plume spectral data and the electron temperature and density measurements obtained during the BowShock I and II rocket flights which have been submitted to the AEDC Data Center, has verified the presence of CO Cameron band emission during the Antares engine burn and for an extended period of time in the post-burn plume, and have adapted 3-D radiation entrapment codes developed by the University of Pittsburgh to study aurora and other atmospheric phenomena that involve significant spatial effects to investigate the vacuum ultraviolet (VUV) and extreme ultraviolet (EUV) envelope surrounding the re-entry that create an extensive plasma cloud by photoionization.

126. AERIAL FORWARD VIEW OF ENCLOSED HURRICANE BOW WITH FLIGHT ...

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

126. AERIAL FORWARD VIEW OF ENCLOSED HURRICANE BOW WITH FLIGHT DECK GUN MOUNTS REMOVED AND ANGLED FLIGHT DECK. 1 OCTOBER 1956. (NATIONAL ARCHIVES NO. 80-G-1001445) - U.S.S. HORNET, Puget Sound Naval Shipyard, Sinclair Inlet, Bremerton, Kitsap County, WA

Bow shocks as tracers of the environment and stellar outflows near the supermassive black hole.

NASA Astrophysics Data System (ADS)

Stofanova, L.; Zajaček, M.; Karas, V.

2017-10-01

Bow shocks develop near stars in the supersonic motion with respect to the surrounding interstellar environment. In particular, extended shocks emerge due to the interaction of stars with strong winds. We discuss the expected shape and orientation of bow shocks in the context of fast moving stars near a supermassive black hole (SMBH) embedded within Bondi-type accretion flow (Zajaček et al. 2016, MNRAS; Štofanová 2016, BSc. Thesis). We present models which take into account different velocities of the probe star and also consider various scenarios for the ambient medium near the vicinity of the black hole such as an inflow/outflow of the material towards/outwards SMBH or a model which considers inflow and outflow at the same time. Under suitable circumstances, a bow shock structure can be detected in infrared domain and their properties can trace the environment of the Galactic center. On the other hand, if density of the ambient medium is determined from mm/radio observations, bow shocks can be used to constrain mass-loss rates of massive OB/WR stars. X-rays can supplement the spectral evidence, though, the structures are below the angular resolution of the current instruments even in the most favourable case of the Milky Way's SMBH (Sgr A*).

ASYMPTOTIC STEADY-STATE SOLUTION TO A BOW SHOCK WITH AN INFINITE MACH NUMBER

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

Yalinewich, Almog; Sari, Re’em

2016-08-01

The problem of a cold gas flowing past a stationary obstacle is considered. We study the bow shock that forms around the obstacle and show that at large distances from the obstacle the shock front forms a parabolic solid of revolution. The profiles of the hydrodynamic variables in the interior of the shock are obtained by solution of the hydrodynamic equations in parabolic coordinates. The results are verified with a hydrodynamic simulation. The drag force on the obstacle is also calculated. Finally, we use these results to model the bow shock around an isolated neutron star.

Bilateral Carpus Valgus with Cranial Bowing of the Distal Radius in a Foal

PubMed Central

Caron, J. P.; Fretz, P. B.; Pharr, J. W.; Bailey, J. V.

1986-01-01

Bilateral carpus valgus with concomitant outward rotation and cranial bowing of the distal radii was diagnosed in a crossbred foal. The foal was not lame on admission and showed no radiographic evidence of carpal bone abnormalities. Surgery was limited to the most severely affected leg, and consisted of a combination of growth promotion (periosteal transection and stripping) and temporary physeal retardation (transphyseal bridging) procedures. Correction of the valgus deformity was nearly complete in the operated limb and substantial improvement was observed in the cranial bowing and outward rotation in both limbs, five months postoperatively. ImagesFigure 1.Figure 2. PMID:17422668

Wrist muscle activity of khatrah approach in Mameluke technique using traditional bow archery

NASA Astrophysics Data System (ADS)

Ariffin, Muhammad Shahimi; Rambely, Azmin Sham; Ariff, Noratiqah Mohd

2018-04-01

An investigation of khatrah technique in archery was carried out. An electromyography (EMG) experiment was conducted towards six wrist muscles which are flexor carpi radialis, extensor carpi ulnaris and extensor digitorum communis for both arms. The maximum voluntary contraction (MVC) and activity data were recorded. The bow arm produced a higher muscle force compared to draw arm muscles during release phase. However, the muscle forces produced by bow arm had a consistency in term of pattern throughout the phases. In conclusion, the forces generated by the professional archer produced a force benchmark at the wrist joint to alleviate the risk of injury.

4. DETAIL VIEW, LOOKING SOUTH, ACROSS HULL NEAR BOW END, ...

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

4. DETAIL VIEW, LOOKING SOUTH, ACROSS HULL NEAR BOW END, TOP OF FORWARD STARBOARD CARGO HATCH IN FOREGROUND, OPENING FOR PORT HATCH BEYOND Edward Larrabee, photographer, November 1984 - Shooters Island, Ships Graveyard, Vessel No. 54, Newark Bay, Staten Island (subdivision), Richmond County, NY

STEREO and Wind Observations of Intense Cyclotron Harmonic Waves at the Earth's Bow Shock and Inside the Magnetosheath

NASA Technical Reports Server (NTRS)

Breneman, A. W.; Cattell, C.

2013-01-01

We present the first observations of electron cyclotron harmonic waves at the Earth's bow shock from STEREO and Wind burst waveform captures. These waves are observed at magnetic field gradients at a variety of shock geometries ranging from quasi-parallel to nearly perpendicular along with whistler mode waves, ion acoustic waves, and electrostatic solitary waves. Large amplitude cyclotron harmonic waveforms are also observed in the magnetosheath in association with magnetic field gradients convected past the bow shock. Amplitudes of the cyclotron harmonic waves range from a few tens to more than 500 millivolts/meter peak-peak. A comparison between the short (15 meters) and long (100 meters) Wind spin plane antennas shows a similar response at low harmonics and a stronger response on the short antenna at higher harmonics. This indicates that wavelengths are not significantly larger than 100 meters, consistent with the electron cyclotron radius. Waveforms are broadband and polarizations are distinctively comma-shaped with significant power both perpendicular and parallel to the magnetic field. Harmonics tend to be more prominent in the perpendicular directions. These observations indicate that the waves consist of a combination of perpendicular Bernstein waves and field-aligned waves without harmonics. A likely source is the electron cyclotron drift instability which is a coupling between Bernstein and ion acoustic waves. These waves are the most common type of high-frequency wave seen by STEREO during bow shock crossings and magnetosheath traversals and our observations suggest that they are an important component of the high-frequency turbulent spectrum in these regions.

The Contemplative Bow in Teaching and Learning Pastoral Care

ERIC Educational Resources Information Center

Koppel, Michael S.

2013-01-01

This article elucidates theoretical underpinnings for the use of one's self in the pastoral theological classroom. The contemplative bow is developed as a capacious metaphor to describe appropriate self use and its necessary importance in the teaching and learning of pastoral arts in a theological curriculum. Central to the argument is the…

Automated bow shock and radiation belt edge identification methods and their application for Cluster, THEMIS/ARTEMIS and Van Allen Probes data

NASA Astrophysics Data System (ADS)

Facsko, Gabor; Sibeck, David; Balogh, Tamas; Kis, Arpad; Wesztergom, Viktor

2017-04-01

The bow shock and the outer rim of the outer radiation belt are detected automatically by our algorithm developed as a part of the Boundary Layer Identification Code Cluster Active Archive project. The radiation belt positions are determined from energized electron measurements working properly onboard all Cluster spacecraft. For bow shock identification we use magnetometer data and, when available, ion plasma instrument data. In addition, electrostatic wave instrument electron density, spacecraft potential measurements and wake indicator auxiliary data are also used so the events can be identified by all Cluster probes in highly redundant way, as the magnetometer and these instruments are still operational in all spacecraft. The capability and performance of the bow shock identification algorithm were tested using known bow shock crossing determined manually from January 29, 2002 to February 3,. The verification enabled 70% of the bow shock crossings to be identified automatically. The method shows high flexibility and it can be applied to observations from various spacecraft. Now these tools have been applied to Time History of Events and Macroscale Interactions during Substorms (THEMIS)/Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) magnetic field, plasma and spacecraft potential observations to identify bow shock crossings; and to Van Allen Probes supra-thermal electron observations to identify the edges of the radiation belt. The outcomes of the algorithms are checked manually and the parameters used to search for bow shock identification are refined.

Relationship between Lateral Femoral Bowing and Varus Knee Deformity Based on Two-Dimensional Assessment of Side-to-Side Differences.

PubMed

Cho, Myung-Rae; Lee, Young Sik; Choi, Won-Kee

2018-03-01

The objective was to evaluate the relationship between side-to-side differences of lateral femoral bowing and varus knee deformity based on two-dimensional (2D) assessment in unilateral total knee arthroplasty (TKA). A total of 143 patients with varus knee osteoarthritis who underwent unilateral TKA were enrolled. We evaluated the side-to-side differences of the frontal lower limb alignment by assessing lateral femoral bowing, anatomical medial distal femoral angle, and anatomical medial proximal tibial angle (aMPTA). The average values of all anatomical indices were significantly different between the operated side and the non-operated side (p＜0.05). The side-to-side difference in hip knee ankle (HKA) angle had a statistically significant correlation with that in lateral femoral bowing (intraclass correlation coefficient, 0.259; p=0.002) and that in aMPTA. Linear regression analysis showed 0.199° of side-to-side difference in lateral femoral bowing was associated with 1° of side-to-side difference in bilateral HKA angle. The side-to-side difference in lateral femoral bowing showed a tendency to increase in proportion to varus knee deformity based on 2D assessment in unilateral TKA patients.

Ionospheric Bow Wave Induced by the Moon Shadow Ship Over the Continent of United States on 21 August 2017

NASA Astrophysics Data System (ADS)

Sun, Yang-Yi; Liu, Jann-Yenq; Lin, Charles Chien-Hung; Lin, Chi-Yen; Shen, Ming-Hsueh; Chen, Chieh-Hung; Chen, Chia-Hung; Chou, Min-Yang

2018-01-01

A moon shadow of the total solar eclipse swept through the continent of United States (CONUS) from west to east on 21 August 2017. Massive total electron content (integration of electron density from 0 km to 20,200 km altitude) observations from 2,255 ground-based Global Navigation Satellite System receivers show that the moon shadow ship generates a great ionospheric bow wave front which extends 1,500 km away from the totality path covering the entire CONUS. The bow wave front consists of the acoustic shock wave due to the supersonic/near-supersonic moon shadow ship and the significant plasma recombination due to the reduction in solar irradiation within the shadow area. The deep bow wave trough (-0.02 total electron content unit (1 TECU = 1016 el m-2) area) nearly coincides with the 100% obscuration moving along the totality path over the CONUS through the entire eclipse period. The supersonic moon shadow ship induces a bow wave crest in front of the ship ( 80% obscuration). It is the first time to find the acoustic shock wave-formed bow wave trough and crest near the totality.

The research on medical image classification algorithm based on PLSA-BOW model.

PubMed

Cao, C H; Cao, H L

2016-04-29

With the rapid development of modern medical imaging technology, medical image classification has become more important for medical diagnosis and treatment. To solve the existence of polysemous words and synonyms problem, this study combines the word bag model with PLSA (Probabilistic Latent Semantic Analysis) and proposes the PLSA-BOW (Probabilistic Latent Semantic Analysis-Bag of Words) model. In this paper we introduce the bag of words model in text field to image field, and build the model of visual bag of words model. The method enables the word bag model-based classification method to be further improved in accuracy. The experimental results show that the PLSA-BOW model for medical image classification can lead to a more accurate classification.

Observations and simulations of specularly reflected He++ at Earth's quasiperpendicular bow shock

NASA Astrophysics Data System (ADS)

Broll, J. M.; Fuselier, S. A.; Trattner, K. J.; Anderson, B. J.; Burch, J. L.; Giles, B. L.

2016-12-01

Specular reflection of protons at Earth's quasiperpendicular bow shock is an important process for supercritical shock dissipation. Previous studies have found evidence of He++ specular reflection from reduced particle distributions downstream from the shock, but confirmation of the process for heavier ions in the shock foot was not possible due to time resolution constraints. We present He++ distributions, observed by MMS in a quasiperpendicular bow shock crossing, that are consistent with specularly reflected He++. We also investigate the He++ dynamics with test-particle simulations in a simulated shock based on this crossing and we conduct wave analysis to determine what processes lead to separate gyrotropization timescales for the transmitted and reflected populations.

[Development Of 25-Year Imp 8 Bow Shock Crossing "List, Ingestion Of This List To Cdaweb, & Enhancement"

NASA Technical Reports Server (NTRS)

Merka, J.; Szabo, A.; Narock, T. W.; King, J. H.; Paularena, K. I.; Richardson, J. D.

2003-01-01

The MIT portion of this project was to use the plasma data from IMP 8 to identify bow shock crossings for construction of a bow shock data base. In collaboration with Goddard, we determined which shock parameters would be included in the catalog and developed a set of flags for characterizing the data. IMP 8 data from 1973-2001 were surveyed for bow shock crossings; the crossings apparent in the plasma data were compared to a list of crossing chosen in the magnetometer data by Goddard. Differences were reconciled to produce a single list. The data were then provided to the NSSDC for archiving. All the work ascribed to MIT in the proposal was completed.

Upstream energetic ions and electrons - Bow shock-associated or magnetospheric origin

NASA Technical Reports Server (NTRS)

Scholer, M.; Hovestadt, D.; Ipavich, F. M.; Gloeckler, G.

1981-01-01

An analysis is made of 35 proton bursts observed with the Max-Planck-Institut/University of Maryland sensor system on ISEE 3 far upstream of the earth's bow shock. These upstream bursts are found to fall into two distinctive groups. The first is accompanied by energetic electrons (more than about 75 keV), and the proton spectrum extends up to energies greater than about 300 keV and higher and bends over toward lower energies (less than about 30 keV). The second group, which is unaccompanied by energetic electron bursts, exhibits spectra which can be represented extremely well by exponentials in energy with a mean e-folding energy of approximately 15 keV. The first group is thought to be of a magnetospheric origin, and the second to be bow-shock associated.

Heliospheric structure. The bow wave and the hydrogen wall

DOE PAGES

Zank, G. P.; Heerikhuisen, J.; Wood, B. E.; ...

2012-12-28

Some recent IBEX observations indicate that the local interstellar medium (LISM) flow speed is less than previously thought (23.2 km s -1 rather than 26 km s -1). Reasonable LISM plasma parameters indicate that the LISM flow may be either marginally super-fast magnetosonic or sub-fast magnetosonic. This raises two challenging questions: (1) Can a LISM model that is barely super-fast or sub-fast magnetosonic account for Lyα observations that rely critically on the additional absorption provided by the hydrogen wall (H-wall)? and (2) If the LISM flow is weakly super-fast magnetosonic, does the transition assume the form of a traditional shockmore » or does neutral hydrogen (H) mediate shock dissipation and hence structure through charge exchange? Both questions are addressed using three three-dimensional self-consistently coupled magnetohydrodynamic plasma—kinetic H models with different LISM magnetic field strengths (2, 3, and 4 μG) as well as plasma and neutral H number densities. The 2 and 3 μG models are fast magnetosonic far upwind of the heliopause whereas the 4 μG model is fully subsonic. The 2 μG model admits a broad (~50-75 AU) bow-shock-like structure. The 3 μG model has a smooth super-fast-sub-fast magnetosonic transition that resembles a very broad, ~200 AU thick, bow wave. A theoretical analysis shows that the transition from a super-fast to a sub-fast magnetosonic downstream state is due to the charge exchange of fast neutral H and hot neutral H created in the supersonic solar wind and hot inner heliosheath, respectively. For both the 2 μG and the 3 μG models, the super-fast magnetosonic LISM flow passes through a critical point located where the fast magnetosonic Mach number M = 1 and Qe = γ/(γ - 1)UQm , where Qe and Qm are the plasma energy and momentum source terms due to charge exchange, U is the LISM flow speed, and γ is the plasma adiabatic index. Because the Mach number is only barely super-fast magnetosonic in the 3 μG case, the

Suprathermal Electrons at Saturn's Bow Shock

NASA Astrophysics Data System (ADS)

Masters, A.; Sulaiman, A. H.; Sergis, N.; Stawarz, L.; Fujimoto, M.; Coates, A. J.; Dougherty, M. K.

2016-07-01

The leading explanation for the origin of galactic cosmic rays is particle acceleration at the shocks surrounding young supernova remnants (SNRs), although crucial aspects of the acceleration process are unclear. The similar collisionless plasma shocks frequently encountered by spacecraft in the solar wind are generally far weaker (lower Mach number) than these SNR shocks. However, the Cassini spacecraft has shown that the shock standing in the solar wind sunward of Saturn (Saturn's bow shock) can occasionally reach this high-Mach number astrophysical regime. In this regime Cassini has provided the first in situ evidence for electron acceleration under quasi-parallel upstream magnetic conditions. Here we present the full picture of suprathermal electrons at Saturn's bow shock revealed by Cassini. The downstream thermal electron distribution is resolved in all data taken by the low-energy electron detector (CAPS-ELS, <28 keV) during shock crossings, but the higher energy channels were at (or close to) background. The high-energy electron detector (MIMI-LEMMS, >18 keV) measured a suprathermal electron signature at 31 of 508 crossings, where typically only the lowest energy channels (<100 keV) were above background. We show that these results are consistent with the theory in which the “injection” of thermal electrons into an acceleration process involves interaction with whistler waves at the shock front, and becomes possible for all upstream magnetic field orientations at high Mach numbers like those of the strong shocks around young SNRs. A future dedicated study will analyze the rare crossings with evidence for relativistic electrons (up to ˜1 MeV).

30. View of main deck at bow (looking aft from ...

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

30. View of main deck at bow (looking aft from samson post, upper deck removed), showing anchor windlass (left foreground), head (right foregound), and forward deckhouse; weather canopy overhead not an original or permanent feature - Schooner WAWONA, 1018 Valley Street, Seattle, King County, WA

Lunar Surface Potential Increases during Terrestrial Bow Shock Traversals

NASA Technical Reports Server (NTRS)

Collier, Michael R.; Stubbs, Timothy J.; Hills, H. Kent; Halekas, Jasper; Farrell, William M.; Delory, Greg T.; Espley, Jared; Freeman, John W.; Vondrak, Richard R.; Kasper, Justin

2009-01-01

Since the Apollo era the electric potential of the Moon has been a subject of interest and debate. Deployed by three Apollo missions, Apollo 12, Apollo 14 and Apollo 15, the Suprathermal Ion Detector Experiment (SIDE) determined the sunlit lunar surface potential to be about +10 Volts using the energy spectra of lunar ionospheric thermal ions accelerated toward the Moon. We present an analysis of Apollo 14 SIDE "resonance" events that indicate the lunar surface potential increases when the Moon traverses the dawn bow shock. By analyzing Wind spacecraft crossings of the terrestrial bow shock at approximately this location and employing current balancing models of the lunar surface, we suggest causes for the increasing potential. Determining the origin of this phenomenon will improve our ability to predict the lunar surface potential in support of human exploration as well as provide models for the behavior of other airless bodies when they traverse similar features such as interplanetary shocks, both of which are goals of the NASA Lunar Science Institute's Dynamic Response of the Environment At the Moon (DREAM) team.

Intermediate shocks in three-dimensional magnetohydrodynamic bow-shock flows with multiple interacting shock fronts

PubMed

De Sterck H; Poedts

2000-06-12

Simulation results of three-dimensional (3D) stationary magnetohydrodynamic (MHD) bow-shock flows around perfectly conducting spheres are presented. For strong upstream magnetic field a new complex bow-shock flow topology arises consisting of two consecutive interacting shock fronts. It is shown that the leading shock front contains a segment of intermediate 1-3 shock type. This is the first confirmation in 3D that intermediate shocks, which were believed to be unphysical for a long time, can be formed and can persist for small-dissipation MHD in a realistic flow configuration.

Risk analysis of urban gas pipeline network based on improved bow-tie model

NASA Astrophysics Data System (ADS)

Hao, M. J.; You, Q. J.; Yue, Z.

2017-11-01

Gas pipeline network is a major hazard source in urban areas. In the event of an accident, there could be grave consequences. In order to understand more clearly the causes and consequences of gas pipeline network accidents, and to develop prevention and mitigation measures, the author puts forward the application of improved bow-tie model to analyze risks of urban gas pipeline network. The improved bow-tie model analyzes accident causes from four aspects: human, materials, environment and management; it also analyzes the consequences from four aspects: casualty, property loss, environment and society. Then it quantifies the causes and consequences. Risk identification, risk analysis, risk assessment, risk control, and risk management will be clearly shown in the model figures. Then it can suggest prevention and mitigation measures accordingly to help reduce accident rate of gas pipeline network. The results show that the whole process of an accident can be visually investigated using the bow-tie model. It can also provide reasons for and predict consequences of an unfortunate event. It is of great significance in order to analyze leakage failure of gas pipeline network.

Sequential Polarity-Reversing Circuit

NASA Technical Reports Server (NTRS)

Labaw, Clayton C.

1994-01-01

Proposed circuit reverses polarity of electric power supplied to bidirectional dc motor, reversible electro-mechanical actuator, or other device operating in direction depending on polarity. Circuit reverses polarity each time power turned on, without need for additional polarity-reversing or direction signals and circuitry to process them.

INTERIOR VIEW, WINDOW BOW IN EAST WALL OF SERVANTS’ HALL. ...

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

INTERIOR VIEW, WINDOW BOW IN EAST WALL OF SERVANTS’ HALL. THE STEEL BEAMS (COLORED WHITE) EXTENDING ACROSS THE SPACE UNDER THE JOISTS WERE PART OF A RECENT INTERVENTION TO COUNTERACT DEFLECTION IN THE FLOORS OF THE PRINCIPAL STORY - The Woodlands, 4000 Woodlands Avenue, Philadelphia, Philadelphia County, PA

Transonic flow past a wedge profile with detached bow wave

NASA Technical Reports Server (NTRS)

Vincenti, Walter G; Wagoner, Cleo B

1952-01-01

A theoretical study has been made of the aerodynamic characteristics at zero angle of attack of a thin, doubly symmetrical double-wedge profile in the range of supersonic flight speed in which the bow wave is detached. The analysis utilizes the equations of the transonic small-disturbance theory and involves no assumptions beyond those implicit in this theory. The mixed flow about the front half of the profile is calculated by relaxation solution of boundary conditions along the shock polar and sonic line. The purely subsonic flow about the rear of the profile is found by means of the method of characteristics specialized to the transonic small-disturbance theory. Complete calculations were made for four values of the transonic similarity parameter. These were found sufficient to bridge the gap between the previous results of Guderley and Yoshihara at a Mach number of 1 and the results which are readily obtained when the bow wave is attached and the flow is completely supersonic.

Short wavelength ion waves upstream of the earth's bow shock

NASA Technical Reports Server (NTRS)

Fuselier, S. A.; Gurnett, D. A.

1984-01-01

The identification and explanation of short wavelength antenna interference effects observed in spacecraft plasma wave data have provided an important new method of determining limits on the wavelength, direction of propagation, and Doppler shift of short wavelength electrostatic waves. Using the ISEE-1 wideband electric field data, antenna interference effects have been identified in the ion waves upstream of the earth's bow shock. This identification implies that wavelengths of the upstream ion waves are shorter than the antenna length. The interference effects also provide new measurements of the direction of propagation of the ion waves. The new measurements show that the wave vectors of the ion waves are not parallel to the interplanetary magnetic field (IMF) as previously reported. The direction of propagation does not appear to be controlled by the IMF. In addition, analysis of the Doppler shift of the short wavelength ion waves has provided a measurement of the dispersion relation. The upper limit of the rest frame frequency was found to be on the order of the ion plasma frequency. At this frequency, the wavelength is on the order of a few times the Debye length. The results of this study now provide strong evidence that the ion waves in the upstream region are Doppler-shifted ion acoustic waves. Previously announced in STAR as N83-36328

MMS Observation of Shock-Reflected He++ at Earth's Quasi-Perpendicular Bow Shock

NASA Astrophysics Data System (ADS)

Broll, Jeffrey Michael; Fuselier, S. A.; Trattner, K. J.; Schwartz, S. J.; Burch, J. L.; Giles, B. L.; Anderson, B. J.

2018-01-01

Specular reflection of protons at Earth's supercritical quasi-perpendicular bow shock has long been known to lead to the thermalization of solar wind particles by velocity-space dispersion. The same process has been proposed for He++ but could not be confirmed previously due to insufficient time resolution for velocity distribution measurements. We present observations and simulations of a bow shock crossing by the Magnetospheric Multiscale (MMS) mission on 20 November 2015 indicating that a very similar reflection process for He++ is possible, and further that the part of the incoming distribution with the highest probability of reflecting is the same for H+ and He++. However, the reflection process for He++ is accomplished by deeper penetration into the downstream magnetic fields.

TRANSPORT OF SOLAR WIND H{sup +} AND He{sup ++} IONS ACROSS EARTH’S BOW SHOCK

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

Parks, G. K.; Lin, N.; Lee, E.

2016-07-10

We have investigated the dependence of mass, energy, and charge of solar wind (SW) transport across Earth’s bow shock. An examination of 111 crossings during quiet SW in both quasi-perpendicular and quasi-parallel shock regions shows that 64 crossings had various degrees of heating and thermalization of SW. We found 22 crossings where the SW speed was <400 km s{sup −1}. The shock potential of a typical supercritical quasi-perpendicular shock estimated from deceleration of the SW and cutoff energy of electron flat top distribution is ∼50 Volts. We find that the temperatures of H{sup +} and He{sup ++} beams that penetratemore » the shock can sometimes be nearly the same in the upstream and downstream regions, indicating little or no heating had occurred crossing the bow shock. None of the models predict that the SW can cross the bow shock without heating. Our observations are important constraints for new models of collisionless shocks.« less

Specific and reversible DNA-directed self-assembly of oil-in-water emulsion droplets

PubMed Central

Hadorn, Maik; Boenzli, Eva; Sørensen, Kristian T.; Fellermann, Harold; Eggenberger Hotz, Peter; Hanczyc, Martin M.

2012-01-01

Higher-order structures that originate from the specific and reversible DNA-directed self-assembly of microscopic building blocks hold great promise for future technologies. Here, we functionalized biotinylated soft colloid oil-in-water emulsion droplets with biotinylated single-stranded DNA oligonucleotides using streptavidin as an intermediary linker. We show the components of this modular linking system to be stable and to induce sequence-specific aggregation of binary mixtures of emulsion droplets. Three length scales were thereby involved: nanoscale DNA base pairing linking microscopic building blocks resulted in macroscopic aggregates visible to the naked eye. The aggregation process was reversible by changing the temperature and electrolyte concentration and by the addition of competing oligonucleotides. The system was reset and reused by subsequent refunctionalization of the emulsion droplets. DNA-directed self-assembly of oil-in-water emulsion droplets, therefore, offers a solid basis for programmable and recyclable soft materials that undergo structural rearrangements on demand and that range in application from information technology to medicine. PMID:23175791

HELIOSPHERIC STRUCTURE: THE BOW WAVE AND THE HYDROGEN WALL

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

Zank, G. P.; Heerikhuisen, J.; Pogorelov, N. V.

2013-01-20

Recent IBEX observations indicate that the local interstellar medium (LISM) flow speed is less than previously thought (23.2 km s{sup -1} rather than 26 km s{sup -1}). Reasonable LISM plasma parameters indicate that the LISM flow may be either marginally super-fast magnetosonic or sub-fast magnetosonic. This raises two challenging questions: (1) Can a LISM model that is barely super-fast or sub-fast magnetosonic account for Ly{alpha} observations that rely critically on the additional absorption provided by the hydrogen wall (H-wall)? and (2) If the LISM flow is weakly super-fast magnetosonic, does the transition assume the form of a traditional shock ormore » does neutral hydrogen (H) mediate shock dissipation and hence structure through charge exchange? Both questions are addressed using three three-dimensional self-consistently coupled magnetohydrodynamic plasma-kinetic H models with different LISM magnetic field strengths (2, 3, and 4 {mu}G) as well as plasma and neutral H number densities. The 2 and 3 {mu}G models are fast magnetosonic far upwind of the heliopause whereas the 4 {mu}G model is fully subsonic. The 2 {mu}G model admits a broad ({approx}50-75 AU) bow-shock-like structure. The 3 {mu}G model has a smooth super-fast-sub-fast magnetosonic transition that resembles a very broad, {approx}200 AU thick, bow wave. A theoretical analysis shows that the transition from a super-fast to a sub-fast magnetosonic downstream state is due to the charge exchange of fast neutral H and hot neutral H created in the supersonic solar wind and hot inner heliosheath, respectively. For both the 2 {mu}G and the 3 {mu}G models, the super-fast magnetosonic LISM flow passes through a critical point located where the fast magnetosonic Mach number M = 1 and Q{sub e} = {gamma}/({gamma} - 1)UQ{sub m} , where Q{sub e} and Q{sub m} are the plasma energy and momentum source terms due to charge exchange, U is the LISM flow speed, and {gamma} is the plasma adiabatic index. Because the

SUPRATHERMAL ELECTRONS AT SATURN'S BOW SHOCK

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

Masters, A.; Dougherty, M. K.; Sulaiman, A. H.

2016-07-20

The leading explanation for the origin of galactic cosmic rays is particle acceleration at the shocks surrounding young supernova remnants (SNRs), although crucial aspects of the acceleration process are unclear. The similar collisionless plasma shocks frequently encountered by spacecraft in the solar wind are generally far weaker (lower Mach number) than these SNR shocks. However, the Cassini spacecraft has shown that the shock standing in the solar wind sunward of Saturn (Saturn's bow shock) can occasionally reach this high-Mach number astrophysical regime. In this regime Cassini has provided the first in situ evidence for electron acceleration under quasi-parallel upstream magneticmore » conditions. Here we present the full picture of suprathermal electrons at Saturn's bow shock revealed by Cassini . The downstream thermal electron distribution is resolved in all data taken by the low-energy electron detector (CAPS-ELS, <28 keV) during shock crossings, but the higher energy channels were at (or close to) background. The high-energy electron detector (MIMI-LEMMS, >18 keV) measured a suprathermal electron signature at 31 of 508 crossings, where typically only the lowest energy channels (<100 keV) were above background. We show that these results are consistent with the theory in which the “injection” of thermal electrons into an acceleration process involves interaction with whistler waves at the shock front, and becomes possible for all upstream magnetic field orientations at high Mach numbers like those of the strong shocks around young SNRs. A future dedicated study will analyze the rare crossings with evidence for relativistic electrons (up to ∼1 MeV).« less

On the generation of magnetosheath high-speed jets by bow shock ripples

PubMed Central

Hietala, H; Plaschke, F

2013-01-01

[1]The terrestrial magnetosheath is embedded with coherent high-speed jets of about 1RE in scale, predominantly during quasi-radial interplanetary magnetic field (IMF). When these high dynamic pressure (Pdyn) jets hit the magnetopause, they cause large indentations and further magnetospheric effects. The source of these jets has remained controversial. One of the proposed mechanisms is based on ripples of the quasi-parallel bow shock. In this paper, we combine for the first time, 4 years of subsolar magnetosheath observations from the Time History of Events and Macroscale Interactions during Substorms mission and corresponding NASA/OMNI solar wind conditions with model calculations of a rippled bow shock. Concentrating on the magnetosheath close to the shock during intervals when the angle between the IMF and the Sun-Earth line was small, we find that (1) 97% of the observed jets can be produced by local ripples of the shock under the observed upstream conditions; (2) the coherent jets form a significant fraction of the high Pdyn tail of the magnetosheath flow distribution; (3) the magnetosheath Pdyn distribution matches the flow from a bow shock with ripples that have a dominant amplitude to wavelength ratio of about 9% (∼0.1RE/1RE) and are present ∼12% of the time at any given location. PMID:26167426

On the generation of magnetosheath high-speed jets by bow shock ripples.

PubMed

Hietala, H; Plaschke, F

2013-11-01

[1]The terrestrial magnetosheath is embedded with coherent high-speed jets of about 1 R E in scale, predominantly during quasi-radial interplanetary magnetic field (IMF). When these high dynamic pressure ( P dyn ) jets hit the magnetopause, they cause large indentations and further magnetospheric effects. The source of these jets has remained controversial. One of the proposed mechanisms is based on ripples of the quasi-parallel bow shock. In this paper, we combine for the first time, 4 years of subsolar magnetosheath observations from the Time History of Events and Macroscale Interactions during Substorms mission and corresponding NASA/OMNI solar wind conditions with model calculations of a rippled bow shock. Concentrating on the magnetosheath close to the shock during intervals when the angle between the IMF and the Sun-Earth line was small, we find that (1) 97% of the observed jets can be produced by local ripples of the shock under the observed upstream conditions; (2) the coherent jets form a significant fraction of the high P dyn tail of the magnetosheath flow distribution; (3) the magnetosheath P dyn distribution matches the flow from a bow shock with ripples that have a dominant amplitude to wavelength ratio of about 9% (∼0.1 R E /1 R E ) and are present ∼12 % of the time at any given location.

RADIO SYNCHROTRON EMISSION FROM A BOW SHOCK AROUND THE GAS CLOUD G2 HEADING TOWARD THE GALACTIC CENTER

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

Narayan, Ramesh; Sironi, Lorenzo; Oezel, Feryal

2012-10-01

A dense ionized cloud of gas has been recently discovered to be moving directly toward the supermassive black hole, Sgr A*, at the Galactic center. In 2013 June, at the pericenter of its highly eccentric orbit, the cloud will be approximately 3100 Schwarzschild radii from the black hole and will move supersonically through the ambient hot gas with a velocity of v{sub p} Almost-Equal-To 5400 km s{sup -1}. A bow shock is likely to form in front of the cloud and could accelerate electrons to relativistic energies. We estimate via particle-in-cell simulations the energy distribution of the accelerated electrons andmore » show that the non-thermal synchrotron emission from these electrons might exceed the quiescent radio emission from Sgr A* by a factor of several. The enhanced radio emission should be detectable at GHz and higher frequencies around the time of pericentric passage and in the following months. The bow shock emission is expected to be displaced from the quiescent radio emission of Sgr A* by {approx}33 mas. Interferometric observations could resolve potential changes in the radio image of Sgr A* at wavelengths {approx}< 6 cm.« less

Reproduction accuracy of articulator mounting with an arbitrary face-bow vs. average values-a controlled, randomized, blinded patient simulator study.

PubMed

Ahlers, M Oliver; Edelhoff, Daniel; Jakstat, Holger A

2018-06-21

The benefit from positioning the maxillary casts with the aid of face-bows has been questioned in the past. Therefore, the aim of this study was to investigate the reliability and validity of arbitrary face-bow transfers compared to a process solely based on the orientation by means of average values. For optimized validity, the study was conducted using a controlled, randomized, anonymized, and blinded patient simulator study design. Thirty-eight undergraduate dental students were randomly divided into two groups; both groups were applied to both methods, in opposite sequences. Investigated methods were the transfer of casts using an arbitrary face-bow in comparison to the transfer using average values based on Bonwill's triangle and the Balkwill angle. The "patient" used in this study was a patient simulator. All casts were transferred to the same individual articulator, and all the transferred casts were made using type IV special hard stone plaster; for the attachment into the articulator, type II plaster was used. A blinded evaluation was performed based on three-dimensional measurements of three reference points. The results are presented three-dimensionally in scatterplots. Statistical analysis indicated a significantly smaller variance (Student's t test, p < 0.05) for the transfer using a face-bow, applicable for all three reference points. The use of an arbitrary face-bow significantly improves the transfer reliability and hence the validity. To simulate the patient situation in an individual articulator correctly, casts should be transferred at least by means of an arbitrary face-bow.

Vocal Fold Bowing in Elderly Male Monozygotic Twins: A Case Study

PubMed Central

Tanner, Kristine; Sauder, Cara; Thibeault, Susan L.; Dromey, Christopher; Smith, Marshall E.

2009-01-01

Objectives This study examined case histories, diagnostic features, and treatment response in two 79-year-old male monozygotic (identical) twins with vocal fold bowing, exploring both genetic and environmental factors. Study Design Case study. Methods DNA concordance was examined via cheek swab. Case histories, videostroboscopy, auditory- and visual-perceptual assessment, electromyography, acoustic measures, and Voice Handicap ratings were undertaken. Both twins underwent surgical intervention and subsequent voice therapy. Results Monozygosity was confirmed for DNA polymorphisms, with 10 of 10 concordance for STR DNA markers. For both twins, auditory and visual-perceptual assessments indicated severe bowing, hoarseness and breathiness, although Twin 1 was judged to be extremely severe. Differences in RMS amplitudes were observed for TA and LCA muscles, with smaller relative amplitudes observed for the Twin 1 versus Twin 2. No consistent voice improvement was observed following surgical intervention(s), despite improved mid-membranous vocal fold closure. Marked reductions in Voice Handicap Index total scores were observed following behavioral voice therapy, coinciding with increased mid-membranous and posterior laryngeal (interarytenoid) glottal closure. No substantive differences in acoustic measures were observed. Conclusions Vocal fold bowing was more severe for Twin 1 versus Twin 2 despite identical heritability factors. Overall voice improvement with treatment was greater for Twin 2 than Twin 1. Environmental factors might partially account for the differences observed between the twins, including variability in their responsiveness to behavioral voice therapy. Voice therapy was useful in improving mid-membranous and posterior laryngeal closure, although dysphonia remained severe in both cases. PMID:19664899

THE ROLE OF PICKUP IONS ON THE STRUCTURE OF THE VENUSIAN BOW SHOCK AND ITS IMPLICATIONS FOR THE TERMINATION SHOCK

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

Lu Quanming; Shan Lican; Zhang Tielong

2013-08-20

The recent crossing of the termination shock by Voyager 2 has demonstrated the important role of pickup ions (PUIs) in the physics of collisionless shocks. The Venus Express (VEX) spacecraft orbits Venus in a 24 hr elliptical orbit that crosses the bow shock twice a day. VEX provides a unique opportunity to investigate the role of PUIs on the structure of collisionless shocks more generally. Using VEX observations, we find that the strength of the Venusian bow shock is weaker when solar activity is strong. We demonstrate that this surprising anti-correlation is due to PUIs mediating the Venusian bow shock.

The solar cycle dependence of the location and shape of the Venus bow shock

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

Zhang, T.L.; Luhmann, J.G.; Russell, C.T.

1990-09-01

From initial Pioneer Venus observations during the maximum of solar cycle 21 it was evident that the position of the Venus bow shock varies with solar activity. The bow shock radius in the terminator plane changed from 2.4 R{sub v} to 2.1 R{sub v} as solar activity went from maximum to minimum and, as activity has increased in cycle 22, it has increased again. The recent studies of the subsolar region show that the altitude of the nose of the bow shock varies from 1,600 km at solar minimum to 2,200 km at intermediate solar activity in concert with themore » terminator altitude so that the shape remains constant and only the size varies during the solar cycle. Using a gas dynamic model and the observed bow shock location, the authors infer the variation in the size of the effective obstacle during the solar cycle. At solar maximum, the effective obstacle is larger than the ionopause as if a magnetic barrier exists in the inner magnetosheath. This magnetic barrier acts as the effective obstacle deflecting the magnetosheath plasma about 500 km above the surface of Venus. However, at solar minimum the effective obstacle is well below the subsolar ionopause, and some absorption of the solar wind plasma by the Venus neutral atmosphere is suggested by these observations. The dependence of the solar cycle variation of the shock position on the orientation of the interplanetary magnetic field reinforces the idea that planetary ion pickup is important in the interaction of the solar wind with Venus.« less

10. VIEW TOWARD PORT BOW IN THE FOC'S'LE OF THE ...

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

10. VIEW TOWARD PORT BOW IN THE FOC'S'LE OF THE EVELINA M. GOULART. OBJECT IN THE FOREGROUND IS A FOLDING MESS TABLE LOCATED BETWEEN THE TIERS OF BUNKS. - Auxiliary Fishing Schooner "Evelina M. Goulart", Essex Shipbuilding Museum, 66 Main Street, Essex, Essex County, MA

Bow Shock Leads the Way for a Speeding Hot Jupiter

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2015-09-01

As hot Jupiters whip around their host stars, their speeds can exceed the speed of sound in the surrounding material, theoretically causing a shock to form ahead of them. Now, a study has reported the detection of such a shock ahead of transiting exoplanet HD 189733b, providing a potential indicator of the remarkably strong magnetic field of the planet.Rushing PlanetsDue to their proximity to their hosts, hot Jupiters move very quickly through the stellar wind and corona surrounding the star. When this motion is supersonic, the material ahead of the planet can be compressed by a bow shock and for a transiting hot Jupiter, this shock will cross the face of the host star in advance of the planets transit.In a recent study, a team of researchers by Wilson Cauley of Wesleyan University report evidence of just such a pre-transit. The teams target is exoplanet HD 189733b, one of the closest hot Jupiters to our solar system. When the authors examined high-resolution transmission spectra of this system, they found that prior to the optical transit of the planet, there was a large dip in the transmission of the first three hydrogen Balmer lines. This could well be the absorption of an optically-thick bow shock as it moves past the face of the star.Tremendous MagnetismOperating under this assumption, the authors create a model of the absorption expected from a hot Jupiter transiting with a bow shock ahead of it. Using this model, they show that a shock leading the planet at a distance of 12.75 times the planets radius reproduces the key features of the transmission spectrum.This stand-off distance is surprisingly large. Assuming that the location of the bow shock is set by the point where the planets magnetospheric pressure balances the pressure of the stellar wind or corona that it passes through, the planetary magnetic field would have to be at least 28 Gauss. This is seven times the strength of Jupiters magnetic field!Understanding the magnetic fields of exoplanets is

Discovery Of An Infrared Bow Shock Associated With Delta Cephei

NASA Astrophysics Data System (ADS)

Remage Evans, Nancy; Marengo, M.; Barmby, P.; Matthews, L. D.; Bono, G.; Welch, D. L.; Romaniello, M.; Huelsman, D.; Su, K. Y. L.; Fazio, G.

2010-05-01

We have obtained Spitzer Infrared Array Camera (IRAC) and Multiband Infrared Photometer for Spitzer (MIPS) observations of a sample of classical Cepheids both to derive infrared Leavitt Laws (Period-Luminosity Relations) and to look for evidence of mass loss in the spectral energy distributions. The MIPS 24 and 70 micron images of Delta Cep were particularly striking, since they show an arc of emission offset about an arcmin from Delta Cep. The emission is shaped like a bow shock and is aligned with the space motion of the Cepheid, implying it is physically related to the star. Bow shock structures of this kind can be formed when ram pressure of the ambient ISM balances the wind from a mass-losing star, raising the intriguing possibility that delta Cep is undergoing mass-loss during the Cepheid phase. Circumstellar emission is not a general feature of our Cepheid observations, but 2 unusual circumstances may make it visible around Delta Cep. If the Cepheid was already surrounded by interstellar matter, mass loss from the star could have created the bow shock. Second, Delta Cep has a physical companion 40" to the South, HD 213317, itself a binary. This B7-8 III-IV star is hot enough that it may produce infrared emission by heating dust within the ejected material. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. P. B. and D. W. both acknowledge research support through Discovery Grants from the Natural Sciences and Engineering Research Council of Canada. N. R. E. acknowledges support from the Chandra X-Ray Center grant NAS8-03060.

On the role of the quasi-parallel bow shock in ion pickup - A lesson from Venus?

NASA Technical Reports Server (NTRS)

Luhmann, J. G.; Russell, C. T.; Phillips, J. L.; Barnes, A.

1987-01-01

Previous observations at Venus show convincing evidence of planetary O(+) ion pickup by the largescale motional -V x B electric field in the magnetosheath when the interplanetary magnetic field is perpendicular to the solar wind flow. However, the presence of magnetic field fluctuations in the magnetosheath downstream from the quasi-parallel bow shock should allow pickup to occur even when the upstream magnetic field B and plasma velocity V are practically coaligned. Single-particle calculations are used to demonstrate the convecting magnetic field fluctuations similar to those observed in the Venus magnetosheath when the subsolar bow shock is quasi-parallel can efficiently accelerate cold planetary ions by means of the electric field associated with their transverse components. This ion pickup process, which is characterized by a spatial dependence determined by the bow shock shape and the orientation of the upstream magnetic field, is likely also to occur at Mars and may be effective at comets.

77 FR 19661 - City of Broken Bow, OK; Notice of Technical Conference

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-02

... for the Broken Bow Re-Regulation Dam Hydroelectric Project No. 12470. This conference will be held on... Liberty at (202) 502-6862 or [email protected]gov by April 5, 2012, to RSVP. Nathaniel J. Davis, Sr...

Defense Modernization Plans Through the 2020s: Addressing the Bow Wave

DTIC Science & Technology

2016-04-30

qÜáêíÉÉåíÜ=^ååì~ä= ^Åèìáëáíáçå=oÉëÉ~êÅÜ= póãéçëáìã= qÜìêëÇ~ó=pÉëëáçåë= sçäìãÉ=ff= = Defense Modernization Plans Through the 2020s : Addressing the Bow Wave...Strategic International Studies Defense Modernization Plans Through the 2020s : Addressing the Bow Wave Todd Harrison, Director, Defense Budget Analysis...Scientist, RAND ^Åèìáëáíáçå=oÉëÉ~êÅÜ=mêçÖê~ãW= `êÉ~íáåÖ=póåÉêÖó=Ñçê=fåÑçêãÉÇ=`Ü~åÖÉ= - 136 - Defense Modernization Plans Through the 2020s

16. Detail, northeast facade, operator's bow window and tower; note ...

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

16. Detail, northeast facade, operator's bow window and tower; note condition of slates on tower skirt roof, missing section of gutter at left side of skirt roof, missing window panes; note also knee braces carried on masonry ancons; view to southwest, 90mm lens. - Southern Pacific Depot, 559 El Camino Real, San Carlos, San Mateo County, CA

Electron temperature and de Hoffmann-Teller potential change across the Earth's bow shock: New results from ISEE 1

NASA Astrophysics Data System (ADS)

Hull, A. J.; Scudder, J. D.; Fitzenreiter, R. J.; Ogilvie, K. W.; Newbury, J. A.; Russell, C. T.

We present a survey of the trends between the electron temperature increase ΔTe and the de Hoffmann-Teller frame (HTF) electrostatic potential jump ΔΦHT and their correlation with other parameters that characterize the shock transition using a new ISEE 1 database of 129 Earth bow shock crossings. A fundamental understanding of the HTF potential is central to distinguishing the reversible and irreversible changes to electron temperature across collisionless shocks. The HTF potential is estimated using three different techniques: (1) integrating the steady state, electron fluid momentum equation across the shock layer using high time resolution plasma and field data from ISEE 1, (2) using the steady state, electron fluid energy equation, and (3) using an electron polytrope approximation. We find that ΔΦHT and ΔTe are strongly and positively correlated with |Δ(mpUn2/2)|, which is in good qualitative agreement with earlier experimental surveys [Thomsen et al., 1987b; Schwartz et al., 1988] that used bow shock model normals and used the flow in the spacecraft frame. There is a strong linear organization of the ΔTe with ΔΦHT, which suggests an average effective electron polytropic index of <γe>~2. In addition, ΔTe and ΔΦHT are organized by βe, although our results may be biased by our limited sampling of shock conditions. Comparisons indicate that the differentials in the HTF potential δΦHT are proportional to the differentials in the magnetic field intensity δB across the shock, with a proportionality constant κ that is a fixed constant for a given shock crossing.

Posterior inferior cerebellar artery to posterior inferior cerebellar artery in situ bypass for the treatment of Bow hunter's-type dynamic ischemia in holovertebral dissection.

PubMed

Kan, Peter; Yashar, Parham; Langer, David J; Siddiqui, Adnan H; Levy, Elad I

2012-11-01

Bow hunter's syndrome is a rare cause of vertebrobasilar insufficiency arising from mechanical compression of the vertebral artery (VA) during rotation of the head. Surgical treatment usually involves direct decompression of the VA at the site of compression. We describe what is to our knowledge the first reported case of a posterior inferior cerebellar artery (PICA)-to-PICA in situ bypass for treatment of Bow hunter's-type ischemia in a patient with a VA dissection. The patient was a 41-year-old man who developed disabling symptoms of vertebrobasilar insufficiency after trauma when he rotated his head to the right. Dynamic angiography demonstrated a chronic dissection and stasis of flow in the right VA when his head was rotated to the right, with no obvious site of focal compression. The right VA ended in the PICA and the left VA was of good caliber. A single-photon emission computed tomography study with acetazolamide challenge confirmed brainstem ischemia and poor cerebrovascular reserve. He ultimately underwent a PICA-to-PICA in situ bypass to revascularize his right PICA territory with complete symptom resolution. The PICA-to-PICA in situ bypass is a useful option in the treatment of Bow hunter's-type ischemia in the absence of focal structural compression of the VA or VA stenosis. Copyright © 2012 Elsevier Inc. All rights reserved.

Astrophysically relevant radiatively cooled hypersonic bow shocks in nested wire arrays

NASA Astrophysics Data System (ADS)

Ampleford, David

2009-11-01

We have performed laboratory experiments which introduce obstructions into hypersonic plasma flows to study the formation of shocks. Astrophysical observations have demonstrated many examples of equivalent radiatively cooled bow shocks, for example the head of protostellar jets or supernova remnants passing through the interstellar medium or between discrete clumps in jets. Wire array z-pinches allow us to study quasi-planar radiatively cooled flows in the laboratory. The early stage of a wire array z-pinch implosion consists of a steady flow of the wire material towards the axis. Given a high rate of radiative cooling, these flows reach high sonic- Mach numbers, typically up to 5. The 2D nature of this configuration allows the insertion of obstacles into the flow, such as a concentric ``inner'' wire array, as has previously been studied for ICF research. Here we study the application of such a nested array to laboratory astrophysics where the inner wires act as obstructions perpendicular to the flow, and induce bow shocks. By varying the wire array material (W/Al), the significance of radiative cooling on these shocks can be controlled, and is shown to change the shock opening angle. As multiple obstructions are present, the experiments show the interaction of multiple bow shocks. It is also possible to introduce a magnetic field around the static object, increasing the opening angle of the shocks. Further experiments can be designed to control the flow density, magnetic field structure and obstruction locations. In collaboration with: S.V. Lebedev, M.E. Cuneo, C.A. Jennings, S.N. Bland, J.P. Chittenden, A. Ciardi, G.N. Hall, S.C. Bott, M. Sherlock, A. Frank, E. Blackman

Comparison of theory with atomic oxygen 130.4 nm radiation data from the Bow Shock ultraviolet 2 rocket flight

NASA Technical Reports Server (NTRS)

Levin, Deborah A.; Candler, Graham V.; Collins, Robert J.; Howlett, Carl L.; Espy, Patrick; Whiting, Ellis; Park, Chul

1993-01-01

Comparison is made between the results obtained from a state-of-the-art flow and radiative model and bow shock vacuum ultraviolet (VUV) data obtained the recent Bow Shock 2 Flight Experiment. An extensive data set was obtained from onboard rocket measurements at a reentry speed of 5 km/sec between the altitudes of approximately 65-85 km. A description of the NO photoionization cell used, the data, and the interpretation of the data will be presented. The primary purpose of the analyses is to assess the utility of the data and to propose a radiation model appropriate to the flight conditions of Bow Shock 2. Theoretical predictions based on flow modeling discussed in earlier work and a new radiation model are compared with data.

The cometary H II regions of DR 21: Bow shocks or champagne flows or both?

NASA Astrophysics Data System (ADS)

Immer, K.; Cyganowski, C.; Reid, M. J.; Menten, K. M.

2014-03-01

We present deep Very Large Array H66α radio recombination line (RRL) observations of the two cometary H II regions in DR 21. With these sensitive data, we test the "hybrid" bow shock/champagne flow model previously proposed for the DR 21 H II regions. The ionized gas down the tail of the southern H II region is redshifted by up to ~30 km s-1 with respect to the ambient molecular gas, as expected in the hybrid scenario. The RRL velocity structure, however, reveals the presence of two velocity components in both the northern and southern H II regions. This suggests that the ionized gas is flowing along cone-like shells, swept-up by stellar winds. The observed velocity structure of the well-resolved southern H II region is most consistent with a picture that combines a stellar wind with stellar motion (as in bow shock models) along a density gradient (as in champagne flow models). The direction of the implied density gradient is consistent with that suggested by maps of dust continuum and molecular line emission in the DR 21 region. The image cubes are only available as a FITS file at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/563/A39Table 2, Fig. 4, and Appendices A and B are available in electronic form at http://www.aanda.org

A Prospective Evaluation of Duplex Ultrasound for Thoracic Outlet Syndrome in High-Performance Musicians Playing Bowed String Instruments

PubMed Central

Adam, Garret; Wang, Kevin; Demaree, Christopher J.; Jiang, Jenny S.; Cheung, Mathew; Bechara, Carlos F.

2018-01-01

Thoracic outlet syndrome (TOS) is a neurovascular condition involving the upper extremity, which is known to occur in individuals who perform chronic repetitive upper extremity activities. We prospectively evaluate the incidence of TOS in high-performance musicians who played bowed string musicians. Sixty-four high-performance string instrument musicians from orchestras and professional musical bands were included in the study. Fifty-two healthy volunteers formed an age-matched control group. Bilateral upper extremity duplex scanning for subclavian vessel compression was performed in all subjects. Provocative maneuvers including Elevated Arm Stress Test (EAST) and Upper Limb Tension Test (ULTT) were performed. Abnormal ultrasound finding is defined by greater than 50% subclavian vessel compression with arm abduction, diminished venous waveforms, or arterial photoplethysmography (PPG) tracing with arm abduction. Bowed string instruments performed by musicians in our study included violin (41%), viola (33%), and cello (27%). Positive EAST or ULTT test in the musician group and control group were 44%, and 3%, respectively (p = 0.03). Abnormal ultrasound scan with vascular compression was detected in 69% of musicians, in contrast to 15% of control subjects (p = 0.03). TOS is a common phenomenon among high-performance bowed string instrumentalists. Musicians who perform bowed string instruments should be aware of this condition and its associated musculoskeletal symptoms. PMID:29370085

Multicentre randomised double bind crossover trial on contamination of conventional ties and bow ties in routine obstetric and gynaecological practice.

PubMed Central

Biljan, M M; Hart, C A; Sunderland, D; Manasse, P R; Kingsland, C R

1993-01-01

OBJECTIVE--To assess level of contamination of neckwear worn by gynaecologists and obstetricians during routine working week. DESIGN--Multicentre randomised double blind crossover trial. Participants wore the same conventional ties for three days in one week and bow ties for the same period in second week. SETTING--Two teaching and three district general hospitals in the midlands, Wales, and north England. SUBJECTS--15 registrars and senior registrars. INTERVENTIONS--A swab soaked in sterile saline was taken from specific area on ties at end of first and third working days and sent in transport medium for culture on chocolatised blood and MacConkey agar for 48 hours. MAIN OUTCOME MEASURES--Level of bacteriological growth assessed semiquantitatively (0 for no contamination; for heavy contamination) after swabs had been cultured. At end of study the participants completed a questionnaire to assess their attitude toward wearing different types of necktie. RESULTS--12 doctors (80%) completed the study. Although bow ties were significantly less contaminated at end of first working day (z = -2.354, p = 0.019), this difference was not maintained; there was no difference in level of contamination on third day. Level of contamination did not increase between first and third day of wearing the same garment. One of the 10 doctors who returned the questionnaire found the bow tie very uncomfortable. All participants would consider wearing a bow tie if it proved to be less contaminated than a conventional tie. CONCLUSIONS--Although a significant difference in contamination was established between conventional and bow ties on first day of study, this difference was not confirmed on third day and there is unlikely to be any real association between tie type and bacterial contamination. Because of its negative image and difficulty to tie, the bow tie will probably remain a minority fashion. Images p1583-a PMID:8292945

Lunar Surface Potential Changes Possible Associated with Traversals of the Bow Shock

NASA Technical Reports Server (NTRS)

Collier, M. R.; Stubbs, T. J.; Hills, H. K.

2008-01-01

We report an analysis of seven Apollo 14 Apollo Lunar Surface Experiments Package (ALSEP) Suprathermal Ion Detector Experiment (SIDE) "resonance" events from January 1972 through January 1973. The events appear to be associated with traversals of the Moon through the terrestrial bow shock.

AE AURIGAE: FIRST DETECTION OF NON-THERMAL X-RAY EMISSION FROM A BOW SHOCK PRODUCED BY A RUNAWAY STAR

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

Lopez-Santiago, J.; Pereira, V.; De Castro, E.

2012-09-20

Runaway stars produce shocks when passing through interstellar medium at supersonic velocities. Bow shocks have been detected in the mid-infrared for several high-mass runaway stars and in radio waves for one star. Theoretical models predict the production of high-energy photons by non-thermal radiative processes in a number sufficiently large to be detected in X-rays. To date, no stellar bow shock has been detected at such energies. We present the first detection of X-ray emission from a bow shock produced by a runaway star. The star is AE Aur, which was likely expelled from its birthplace due to the encounter ofmore » two massive binary systems and now is passing through the dense nebula IC 405. The X-ray emission from the bow shock is detected at 30'' northeast of the star, coinciding with an enhancement in the density of the nebula. From the analysis of the observed X-ray spectrum of the source and our theoretical emission model, we confirm that the X-ray emission is produced mainly by inverse Compton upscattering of infrared photons from dust in the shock front.« less

Conduction of thermal energy in the neighborhood of the earth's bow shock

NASA Technical Reports Server (NTRS)

Hohlfeld, R. G.

1976-01-01

The Rankine-Hugoniot equations for MHD shocks are generalized by the addition of a term to the energy conservation equation representing a nonzero heat flow in the plasma in the neighborhood of the shock. This generalization is found to be compatible with the assumption of infinite electrical conductivity. The effects of plasma waves in this treatment are of the order of the reciprocal Alfvenic Mach number squared and hence are neglected. The effect of alpha particles in the solar wind is discussed. Seven crossings of the earth's bow shock by Explorer 35 in lunar orbit are analyzed. Sufficient data are available so that the determination of a dimensionless parameter, psi, characterizing the heat-flow difference across the bow shock is possible. The values of psi indicate energy-flux densities due to heat flow which are a nonnegligible fraction of the total energy flux. Two possible interpretations of psi are discussed.

Serendipitous discovery of an infrared bow shock near PSR J1549–4848 with Spitzer

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

Wang, Zhongxiang; Kaplan, David L.; Slane, Patrick

2013-06-01

We report on the discovery of an infrared cometary nebula around PSR J1549–4848 in our Spitzer survey of a few middle-aged radio pulsars. Following the discovery, multi-wavelength imaging and spectroscopic observations of the nebula were carried out. We detected the nebula in Spitzer Infrared Array Camera 8.0, Multiband Imaging Photometer for Spitzer 24 and 70 μm imaging, and in Spitzer IRS 7.5-14.4 μm spectroscopic observations, and also in the Wide-field Infrared Survey Explorer all-sky survey at 12 and 22 μm. These data were analyzed in detail, and we find that the nebula can be described with a standard bow shockmore » shape, and that its spectrum contains polycyclic aromatic hydrocarbon and H{sub 2} emission features. However, it is not certain which object drives the nebula. We analyze the field stars and conclude that none of them can be the associated object because stars with a strong wind or mass ejection that usually produce bow shocks are much brighter than the field stars. The pulsar is approximately 15'' away from the region in which the associated object is expected to be located. In order to resolve the discrepancy, we suggest that a highly collimated wind could be emitted from the pulsar and produce the bow shock. X-ray imaging to detect the interaction of the wind with the ambient medium- and high-spatial resolution radio imaging to determine the proper motion of the pulsar should be carried out, which will help verify the association of the pulsar with the bow shock nebula.« less

Can the magnetic field in the Orion arm inhibit the growth of instabilities in the bow shock of Betelgeuse?

NASA Astrophysics Data System (ADS)

van Marle, A. J.; Decin, L.; Meliani, Z.

2014-01-01

Context. Many evolved stars travel through space at supersonic velocities, which leads to the formation of bow shocks ahead of the star where the stellar wind collides with the interstellar medium (ISM). Herschel observations of the bow shock of α-Orionis show that the shock is almost free of instabilities, despite being, at least in theory, subject to both Kelvin-Helmholtz and Rayleigh-Taylor instabilities. Aims: A possible explanation for the lack of instabilities lies in the presence of an interstellar magnetic field. We wish to investigate whether the magnetic field of the ISM in the Orion arm can inhibit the growth of instabilities in the bow shock of α-Orionis. Methods: We used the code MPI-AMRVAC to make magneto-hydrodynamic simulations of a circumstellar bow shock, using the wind parameters derived for α-Orionis and interstellar magnetic field strengths of B = 1.4, 3.0, and 5.0 μG, which fall within the boundaries of the observed magnetic field strength in the Orion arm of the Milky Way. Results: Our results show that even a relatively weak magnetic field in the ISM can suppress the growth of Rayleigh-Taylor and Kelvin-Helmholtz instabilities, which occur along the contact discontinuity between the shocked wind and the shocked ISM. Conclusions: The presence of even a weak magnetic field in the ISM effectively inhibits the growth of instabilities in the bow shock. This may explain the absence of such instabilities in the Herschel observations of α-Orionis. Appendix A and associated movies are available in electronic form at http://www.aanda.org

Investigation of radiative bow-shocks in magnetically accelerated plasma flows

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

Bott-Suzuki, S. C., E-mail: sbottsuzuki@ucsd.edu; Caballero Bendixsen, L. S.; Cordaro, S. W.

2015-05-15

We present a study of the formation of bow shocks in radiatively cooled plasma flows. This work uses an inverse wire array to provide a quasi-uniform, large scale hydrodynamic flow accelerated by Lorentz forces to supersonic velocities. This flow impacts a stationary object placed in its path, forming a well-defined Mach cone. Interferogram data are used to determine a Mach number of ∼6, which may increase with radial position suggesting a strongly cooling flow. Self-emission imaging shows the formation of a thin (<60 μm) strongly emitting shock region, where T{sub e} ∼ 40–50 eV, and rapid cooling behind the shock. Emission is observed upstreammore » of the shock position which appears consistent with a radiation driven phenomenon. Data are compared to 2-dimensional simulations using the Gorgon MHD code, which show good agreement with the experiments. The simulations are also used to investigate the effect of magnetic field in the target, demonstrating that the bow-shocks have a high plasma β, and the influence of B-field at the shock is small. This consistent with experimental measurement with micro bdot probes.« less

Optical Hydrogen Absorption Consistent with a Thin Bow Shock Leading the Hot Jupiter HD 189733b

NASA Astrophysics Data System (ADS)

Cauley, P. Wilson; Redfield, Seth; Jensen, Adam G.; Barman, Travis; Endl, Michael; Cochran, William D.

2015-09-01

Bow shocks are ubiquitous astrophysical phenomena resulting from the supersonic passage of an object through a gas. Recently, pre-transit absorption in UV metal transitions of the hot Jupiter (HJ) exoplanets HD 189733b and WASP12-b have been interpreted as being caused by material compressed in a planetary bow shock. Here we present a robust detection of a time-resolved pre-transit, as well as in-transit absorption signature around the HJ exoplanet HD 189733b using high spectral resolution observations of several hydrogen Balmer lines. The line shape of the pre-transit feature and the shape of the timeseries absorption provide the strongest constraints on the morphology and physical characteristics of extended structures around an exoplanet. The in-transit measurements confirm the previous exospheric Hα detection, although the absorption depth measured here is ∼50% lower. The pre-transit absorption feature occurs 125 minutes before the predicted optical transit, a projected linear distance from the planet to the stellar disk of 7.2 Rp. The absorption strength observed in the Balmer lines indicates an optically thick, but physically small, geometry. We model this signal as the early ingress of a planetary bow shock. If the bow shock is mediated by a planetary magnetosphere, the large standoff distance derived from the model suggests a large planetary magnetic field strength of Beq = 28 G. Better knowledge of exoplanet magnetic field strengths is crucial to understanding the role these fields play in planetary evolution and the potential development of life on planets in the habitable zone.

Band gap bowing and crossing of BxGa1-xN alloy investigated by hybrid functional method

NASA Astrophysics Data System (ADS)

Jiaping, Jiang; Yanqin, Gai; Gang, Tang

2016-02-01

The electronic properties of zinc-blende BxGa1-xN alloys are comparatively investigated by employing both the Perdewe-Burkee-Ernzerhof generalized-gradient approximation (PBE-GGA) and the Heyd-Scuseria-Ernzerhof screened hybrid functional methods (HSE06). HSE06 reproduced much closer ground-state properties to experiments. Large and composition-dependent bowing parameters bγ for the direct band gaps were obtained from both PBE and HSE06. The crossover composition where alloy switches from direct to indirect was predicted to occur at very similar x from PBE and HSE06. We can obtain direct gap BxGa1-xN with a gap value much larger than that of GaN by alloying x < 0.557 boron into GaN. Project supported by the Fundamental Research Funds for the Central Universities (No. 2010LKWL03), the Special Fund for Theoretical Physics (No. 11047130), and the National Natural Science Foundation of China (No. 11104345).

The solar wind interaction with Mars - Mariner 4, Mars 2, Mars 3, Mars 5, and Phobos 2 observations of bow shock position and shape

NASA Technical Reports Server (NTRS)

Slavin, J. A.; Schwingenschuh, K.; Riedler, W.; Eroshenko, E.

1991-01-01

An aggregate Mars bow shock data set using Mariner 4, Mars 2, Mars 3, Mars 5, and Phobos 2 observations has been analyzed. The results support the earlier conclusion that the mean distance to the subsolar shock at Mars is nearly 1.5 planetary radii, from which gas dynamic models predict an obstacle altitude of 500 km. The Martian bow shock does not appear to vary significantly in shape or altitude with the phase of the solar cycle. The unusually distant dayside bow shock crossings reported by Mars 2 and 3 also appear in the Phobos 3 observations, suggesting that the dayside obstacle can on rare occasions reach altitudes over 1000 km. The Martian bow shock differs from that of Venus in that its mean altitude is greater, it lacks a strong solar cycle variation, and its location is far more variable, including the occurrence of strong bow shocks over the dayside hemisphere at distances at least as great as the orbit of Phobos 2, i.e., 2.8 Mars radii.

In-situ wafer bowing measurements of GaN grown on Si (111) substrate by reflectivity mapping in metal organic chemical vapor deposition system

NASA Astrophysics Data System (ADS)

Yang, Yi-Bin; Liu, Ming-Gang; Chen, Wei-Jie; Han, Xiao-Biao; Chen, Jie; Lin, Xiu-Qi; Lin, Jia-Li; Luo, Hui; Liao, Qiang; Zang, Wen-Jie; Chen, Yin-Song; Qiu, Yun-Ling; Wu, Zhi-Sheng; Liu, Yang; Zhang, Bai-Jun

2015-09-01

In this work, the wafer bowing during growth can be in-situ measured by a reflectivity mapping method in the 3×2″ Thomas Swan close coupled showerhead metal organic chemical vapor deposition (MOCVD) system. The reflectivity mapping method is usually used to measure the film thickness and growth rate. The wafer bowing caused by stresses (tensile and compressive) during the epitaxial growth leads to a temperature variation at different positions on the wafer, and the lower growth temperature leads to a faster growth rate and vice versa. Therefore, the wafer bowing can be measured by analyzing the discrepancy of growth rates at different positions on the wafer. Furthermore, the wafer bowings were confirmed by the ex-situ wafer bowing measurement. High-resistivity and low-resistivity Si substrates were used for epitaxial growth. In comparison with low-resistivity Si substrate, GaN grown on high-resistivity substrate shows a larger wafer bowing caused by the highly compressive stress introduced by compositionally graded AlGaN buffer layer. This transition of wafer bowing can be clearly in-situ measured by using the reflectivity mapping method. Project supported by the National Natural Science Foundation of China (Grant Nos. 61274039 and 51177175), the National Basic Research Program of China (Grant No. 2011CB301903), the Ph.D. Programs Foundation of Ministry of Education of China (Grant No. 20110171110021), the International Science and Technology Collaboration Program of China (Grant No. 2012DFG52260), the International Science and Technology Collaboration Program of Guangdong Province, China (Grant No. 2013B051000041), the Science and Technology Plan of Guangdong Province, China (Grant No. 2013B010401013), the National High Technology Research and Development Program of China (Grant No. 2014AA032606), and the Opened Fund of the State Key Laboratory on Integrated Optoelectronics, China (Grant No. IOSKL2014KF17).

PSR J2124-3358: A Bow Shock Nebula with an X-ray Tail

NASA Astrophysics Data System (ADS)

Chatterjee, S.; Gaensler, B. M.; Vigelius, M.; Cordes, J. M.; Arzoumanian, Z.; Stappers, B.; Ghavamian, P.; Melatos, A.

2005-12-01

As neutron stars move supersonically through the interstellar medium, their relativistic winds are confined by the ram pressure of the interstellar medium. The outer shocked layers may emit in Hα , producing a visible bow shock nebula, while the confined relativistic wind may produce radio or X-ray emission. The Hα bow shock nebula powered by the recycled pulsar J2124-3358 is asymmetric about the velocity vector and shows a marked kink. In recent observations with the Chandra X-ray Observatory, we have detected a long, curved X-ray tail associated with the pulsar. The tail is not aligned with the pulsar velocity, but is confined within the optical bow shock. The X-ray spectrum of the tail is well-fit by a power law, consistent with synchrotron emission from the wind termination shock and the post-shock flow. The presence of Hα and X-ray emission allows us to trace both the external ambient medium and the confined wind. In magnetohydrodynamic simulations, we verify that a bulk flow and non-uniformities in the ambient medium can produce the observed shape of the nebula, possibly in combination with an anisotropic pulsar wind. Support for this work was provided by the National Aeronautics and Space Administration through Chandra Award Number GO5-6075X issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration under contract NAS8-03060.

Synoptic analysis and hindcast of an intense bow echo in Western Europe: The 09 June 2014 storm

NASA Astrophysics Data System (ADS)

Mathias, Luca; Ermert, Volker; Kelemen, Fanni D.; Ludwig, Patrick; Pinto, Joaquim G.

2017-04-01

On Pentecost Monday of 09 June 2014, a severe mesoscale convective system (MCS) hit Belgium and Western Germany. This storm was one of the most severe thunderstorms in Germany for decades. The synoptic-scale and mesoscale characteristics of this storm are analyzed based on remote sensing data and in-situ measurements. Moreover, the forecast potential of the storm is evaluated using sensitivity experiments with a regional climate model. The key ingredients for the development of the Pentecost storm were the concurrent presence of low-level moisture, atmospheric conditional instability and wind shear. The synoptic and mesoscale analysis shows that the outflow of a decaying MCS above northern France triggered the storm, which exhibited the typical features of a bow echo like a mesovortex and rear inflow jet. This resulted in hurricane-force wind gusts (reaching 40 m/s) along a narrow swath in the Rhine-Ruhr region leading to substantial damage. Operational numerical weather predictions models mostly failed to forecast the storm, but high-resolution regional model hindcasts enable a realistic simulation of the storm. The model experiments reveal that the development of the bow echo is particularly sensitive to the initial wind field and the lower tropospheric moisture content. Correct initial and boundary conditions are therefore necessary for realistic numerical forecasts of such a bow echo event. We conclude that the Pentecost storm exhibited a comparable structure and a similar intensity to the observed bow echo systems in the United States.

Preliminary report on radioactive conglomerates of Middle Precambrian age in the Sierra Madre and Medicine Bow Mountains of southeastern Wyoming

USGS Publications Warehouse

Houston, Robert Stroud; Graff, P.J.; Karlstrom, K.E.; Root, Forrest

1977-01-01

Middle Precambrian miogeosynclinal metasedimentary rocks o# the Sierra Madre and Medicine Bow Mountains of southeastern Wyoming contain radioactive quartz-pebble conglomerates of possible economic interest. These conglomerates do not contain ore-grade uranium in surface outcrops, but an earlier report on the geochemistry of the Arrastre Lake area of the Medicine Bow Mountains shows that ore-grade deposits may be present in the subsurface. This report describes the stratigraphy of the host metasedimentary rocks and the stratigraphic setting of the radioactive conglomerates in both the Sierra Madre and Medicine Bow Mountains, and compares these rock units with those of the Blind River-Elliot Lake uranium district in Canada. The location of radioactive .conglomerates is given so that further exploration may be undertaken by interested parties.

Superfund Explanation of Significant Difference for the Record of Decision (EPA Region 8): Silver Bow Creek/Butte Area, Silver Bow and Deer Lodge, MT, August 31, 1998

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

Not Available

1998-12-01

This document presents an Explanation of Significant Differences from the Record of Decision (ROD) for one Streamside Tailings Operable Unit (SSTOU) of the Silver Bow Creek/Butte Area National Priorities List (NPL) Site. The significant differences discussed in this ESD are: An increase in the volume of tailings/impacted soil in the operable unit; Modifications to the alignment of Silver Bow Creek and the channel profile (i.e., elevation profile); Use of a temporary stream diversion during and after construction to facilitate dewatering and excavation of near-stream tailings and to enhance floodplain and streambank revegetation efforts; Changes in the criteria for in-stream sedimentmore » removal as a result of other design changes; Modifications to the mine waste relocation repository (MWRR) design; The inclusion of sediment basins to contain contaminated overland flow run-on from off-site mine waste sources; Elimination of treatment wetlands as the end land use in Subarea 1; Changes in the estimated schedule to implement the SSTOU remedy; and An increase in the estimated cost of the SSTOU remedy.« less

The Geomagnetic Field During a Reversal

NASA Technical Reports Server (NTRS)

Heirtzler, James R.

2003-01-01

By modifying the IGRF it is possible to learn what may happen to the geomagnetic field during a geomagnetic reversal. If the entire IGRF reverses then the declination and inclination only reverse when the field strength is zero. If only the dipole component of the IGRF reverses a large geomagnetic field remains when the dipole component is zero and he direction of the field at the end of the reversal is not exactly reversed from the directions at the beginning of the reversal.

16-channel bow tie antenna transceiver array for cardiac MR at 7.0 tesla.

PubMed

Oezerdem, Celal; Winter, Lukas; Graessl, Andreas; Paul, Katharina; Els, Antje; Weinberger, Oliver; Rieger, Jan; Kuehne, Andre; Dieringer, Matthias; Hezel, Fabian; Voit, Dirk; Frahm, Jens; Niendorf, Thoralf

2016-06-01

To design, evaluate, and apply a bow tie antenna transceiver radiofrequency (RF) coil array tailored for cardiac MRI at 7.0 Tesla (T). The radiofrequency (RF) coil array comprises 16 building blocks each containing a bow tie shaped λ/2-dipole antenna. Numerical simulations were used for transmission field homogenization and RF safety validation. RF characteristics were examined in a phantom study. The array's suitability for high spatial resolution two-dimensional (2D) CINE imaging and for real time imaging of the heart was examined in a volunteer study. The arrays transmission fields and RF characteristics are suitable for cardiac MRI at 7.0T. The coil performance afforded a spatial resolution as good as (0.8 × 0.8 × 2.5) mm(3) for segmented 2D CINE MRI at 7.0T which is by a factor of 12 superior versus standardized protocols used in clinical practice at 1.5T. The proposed transceiver array supports 1D acceleration factors of up to R = 6 without impairing image quality significantly. The 16-channel bow tie antenna transceiver array supports accelerated and high spatial resolution cardiac MRI. The array is compatible with multichannel transmission and provides a technological basis for future clinical assessment of parallel transmission techniques at 7.0 Tesla. Magn Reson Med 75:2553-2565, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Reversal of radial glow distribution in helicon plasma induced by reversed magnetic field

NASA Astrophysics Data System (ADS)

Wang, Y.; Zhao, G.; Niu, C.; Liu, Z. W.; Ouyang, J. T.; Chen, Q.

2017-02-01

In this work, the reversal of radial glow distribution induced by reversed magnetic field is reported. Based on the Boswell antenna which is symmetric and insensitive to the magnetic field direction, it seems such a phenomenon in theory appears impossible. However, according to the diagnostic of the helicon waves by magnetic probe, it is found that the direction of magnetic field significantly affects the propagation characteristic of helicon waves, i.e., the interchange of the helicon waves at the upper and the lower half of tube was caused by reversing the direction of magnetic field. It is suggested that the variation of helicon wave against the direction of magnetic field causes the reversed radial glow distribution. The appearance of the traveling wave does not only improve the discharge strength, but also determines the transition of the discharge mode.

Reverse transcription of phage RNA and its fragment directed by synthetic heteropolymeric primers

PubMed Central

Frolova, L. Yu.; Metelyev, V. G.; Ratmanova, K. I.; Smirnov, V. D.; Shabarova, Z. A.; Prokofyev, M. A.; Berzin, V. M.; Jansone, I. V.; Gren, E. J.; Kisselev, L. L.

1977-01-01

DNA synthesis catalysed by RNA-directed DNA-polymerase (reverse transcriptase) was found to proceed on the RNA template of an MS2 phage in the presence of heteropolymeric synthetic octa- and nonadeoxyribonucleotide primers complementary to the intercistronic region (coat protein binding site) and the region of the coat protein cistron, respectively. The product of synthesis consists of discrete DNA fractions of different length, including transcripts longer than 1,000 nucleotides. The coat protein inhibits DNA synthesis if it is initiated at its binding site, but has no effect on DNA synthesis initiated at the coat protein cistron. It has been suggested that, in this system, the initiation of DNA synthesis by synthetic primers is topographically specific. The MS2 coat protein binding site (an RNA fragment of 59 nucleotides) serves as a template for polydeoxyribonucleotide synthesis in the presence of octanucleotide primer and reverse transcriptase. The product of synthesis is homogenous and its length corresponds to the length of the template. The effective and complete copying of the fragment having a distinct secondary structure proves that the secondary structure does not interfere, in principle, with RNA being a template in the system of reverse transcription. PMID:71713

Direct visualization of polarization reversal of organic ferroelectric memory transistor by using charge modulated reflectance imaging

NASA Astrophysics Data System (ADS)

Otsuka, Takako; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

2017-11-01

By using the charge modulated reflectance (CMR) imaging technique, charge distribution in the pentacene organic field-effect transistor (OFET) with a ferroelectric gate insulator [P(VDF-TrFE)] was investigated in terms of polarization reversal of the P(VDF-TrFE) layer. We studied the polarization reversal process and the carrier spreading process in the OFET channel. The I-V measurement showed a hysteresis behavior caused by the spontaneous polarization of P(VDF-TrFE), but the hysteresis I-V curve changes depending on the applied drain bias, possibly due to the gradual shift of the polarization reversal position in the OFET channel. CMR imaging visualized the gradual shift of the polarization reversal position and showed that the electrostatic field formed by the polarization of P(VDF-TrFE) contributes to hole and electron injection into the pentacene layer and the carrier distribution is significantly dependent on the direction of the polarization. The polarization reversal position in the channel region is governed by the electrostatic potential, and it happens where the potential reaches the coercive voltage of P(VDF-TrFE). The transmission line model developed on the basis of the Maxwell-Wagner effect element analysis well accounts for this polarization reversal process in the OFET channel.

Discovery of a Bow Shock around VELA X-1: Erratum

NASA Astrophysics Data System (ADS)

Kaper, L.; van Loon, J. Th.; Augusteijn, T.; Goudfrooij, P.; Patat, F.; Waters, L. B. F. M.; Zijlstra, A. A.

1997-04-01

In the Letter Discovery of a Bow Shock around Vela X-1 by L. Kaper, J. Th. van Loon, T. Augusteijn, P. Goudfrooij, F. Patat, L. B. F. M. Waters, and A. A. Zijlstra (ApJ, 475, L37 [1997]), Figure 1 (Plate L7) was printed without its axis labels, as the result of a printer's error. The corrected figure appears in this issue as Plate L12.

Giotto magnetic field observations at the outbound quasi-parallel bow shock of Comet Halley

NASA Technical Reports Server (NTRS)

Neubauer, F. M.; Glassmeier, K. H.; Acuna, M. H.; Mariani, F.; Musmann, G.

1990-01-01

The investigation of the outbound bow shock of Comet Halley using Giotto magnetometer data leads to the following results: the shock is characterized by strong magnetic turbulence associated with an increasing background magnetic field and a change in direction by 60 deg as one goes inward. In HSE-coordinates, the observed normal turned out to be (0.544, - 0.801, 0.249). The thickness of the quasi-parallel shock was 120,000 km. The shock is shown to be a new type of shock transition called a 'draping shock'. In a draping shock with high beta in the transonic transition region, the transonic region is characterized by strong directional variations of the magnetic field. The magnetic turbulence ahead of the shock is characterized by k-vectors parallel or antiparallel to the average field (and, therefore, also to the normal of the quasi-parallel shock) and almost isotropic magnetic turbulence in the shock transition region. A model of the draping shock is proposed which also includes a hypothetical subshock in which the supersonic-subsonic transition is accomplished.

OPTICAL HYDROGEN ABSORPTION CONSISTENT WITH A THIN BOW SHOCK LEADING THE HOT JUPITER HD 189733B

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

Cauley, P. Wilson; Redfield, Seth; Jensen, Adam G.

Bow shocks are ubiquitous astrophysical phenomena resulting from the supersonic passage of an object through a gas. Recently, pre-transit absorption in UV metal transitions of the hot Jupiter (HJ) exoplanets HD 189733b and WASP12-b have been interpreted as being caused by material compressed in a planetary bow shock. Here we present a robust detection of a time-resolved pre-transit, as well as in-transit absorption signature around the HJ exoplanet HD 189733b using high spectral resolution observations of several hydrogen Balmer lines. The line shape of the pre-transit feature and the shape of the timeseries absorption provide the strongest constraints on themore » morphology and physical characteristics of extended structures around an exoplanet. The in-transit measurements confirm the previous exospheric Hα detection, although the absorption depth measured here is ∼50% lower. The pre-transit absorption feature occurs 125 minutes before the predicted optical transit, a projected linear distance from the planet to the stellar disk of 7.2 R{sub p}. The absorption strength observed in the Balmer lines indicates an optically thick, but physically small, geometry. We model this signal as the early ingress of a planetary bow shock. If the bow shock is mediated by a planetary magnetosphere, the large standoff distance derived from the model suggests a large planetary magnetic field strength of B{sub eq} = 28 G. Better knowledge of exoplanet magnetic field strengths is crucial to understanding the role these fields play in planetary evolution and the potential development of life on planets in the habitable zone.« less

Dissipation Mechanisms and Particle Acceleration at the Earth's Bow Shock

NASA Astrophysics Data System (ADS)

Desai, M. I.; Burch, J. L.; Fuselier, S. A.; Genestreti, K. J.; Torbert, R. B.; Ergun, R.; Russell, C.; Wei, H.; Phan, T.; Giles, B. L.; Chen, L. J.; Mauk, B.

2016-12-01

Collisionless shocks are a major producer of suprathermal and energetic particles throughout space and astrophysical plasma environments. Theoretical studies combined with in-situ observations during the space age have significantly advanced our understanding of how such shocks are formed, the manner in which they evolve and dissipate their energy, and the physical mechanisms by which they heat the local plasma and accelerate the energetic particles. Launched in March 2015, NASA's Magnetospheric Multiscale (MMS) mission has four spacecraft separated between 10-40 km and equipped with identical state-of-the-art instruments that acquire magnetic and electric field, plasma wave, and particle data at unprecedented temporal resolution to study the fundamental physics of magnetic reconnection in the Earth's magnetosphere. Serendipitously, during Phase 1a, the MMS mission also encountered and crossed the Earth's bow shock more than 300 times. In this paper, we combine and analyze the highest available time resolution MMS burst data during 140 bow shock crossings from October 2015 through December 31, 2015 to shed new light on key open questions regarding the formation, evolution, dissipation, and particle injection and energization at collisionless shocks. In particular, we compare and contrast the differences in shock dissipation and particle acceleration mechanisms at quasi-parallel and quasi-perpendicular shocks.

Dissipation Mechanisms and Particle Acceleration at the Earth's Bow Shock

NASA Astrophysics Data System (ADS)

Desai, M. I.; Burch, J. L.; Broll, J. M.; Genestreti, K.; Torbert, R. B.; Ergun, R.; Wei, H.; Giles, B. L.; Russell, C. T.; Phan, T.; Chen, L. J.; Lai, H.; Wang, S.; Schwartz, S. J.; Allen, R. C.; Mauk, B.; Gingell, I.

2017-12-01

NASA's Magnetospheric Multiscale (MMS) mission has four spacecraft equipped with identical state-of-the-art instruments that acquire magnetic and electric field, plasma wave, and particle data at unprecedented temporal resolution to study the fundamental physics of magnetic reconnection in the Earth's magnetosphere. During Phase 1a, MMS also encountered and crossed the Earth's bow shock more than 300 times. We use burst data during 2 bow shock crossings to shed new light on key open questions regarding the formation, evolution, and dissipation mechanisms at collisionless shocks. Specifically, we focus on two events that exhibit clear differences in the ion and electron properties, the associated wave activity, and, therefore in the nature of the dissipation. In the case of a quasi-perpendicular, low beta shock crossing, we find that the dissipation processes are most likely associated with field-aligned electron beams that are coincident with high frequency electrostatic waves. On the other hand, the dissipation processes at an oblique, high beta shock crossing are largely governed by the quasi-static electric field and generation of magnetosonic whistler waves that result in perpendicular temperature anisotropy for the electrons. We also discuss the implications of these results for ion heating, reflection, and particle acceleration.

Reversing the direction of galvanotaxis with controlled increases in boundary layer viscosity

NASA Astrophysics Data System (ADS)

Kobylkevich, Brian M.; Sarkar, Anyesha; Carlberg, Brady R.; Huang, Ling; Ranjit, Suman; Graham, David M.; Messerli, Mark A.

2018-05-01

Weak external electric fields (EFs) polarize cellular structure and direct most migrating cells (galvanotaxis) toward the cathode, making it a useful tool during tissue engineering and for healing epidermal wounds. However, the biophysical mechanisms for sensing weak EFs remain elusive. We have reinvestigated the mechanism of cathode-directed water flow (electro-osmosis) in the boundary layer of cells, by reducing it with neutral, viscous polymers. We report that increasing viscosity with low molecular weight polymers decreases cathodal migration and promotes anodal migration in a concentration dependent manner. In contrast, increased viscosity with high molecular weight polymers does not affect directionality. We explain the contradictory results in terms of porosity and hydraulic permeability between the polymers rather than in terms of bulk viscosity. These results provide the first evidence for controlled reversal of galvanotaxis using viscous agents and position the field closer to identifying the putative electric field receptor, a fundamental, outside-in signaling receptor that controls cellular polarity for different cell types.

Reversing the direction of galvanotaxis with controlled increases in boundary layer viscosity.

PubMed

Kobylkevich, Brian M; Sarkar, Anyesha; Carlberg, Brady R; Huang, Ling; Ranjit, Suman; Graham, David M; Messerli, Mark A

2018-03-09

Weak external electric fields (EFs) polarize cellular structure and direct most migrating cells (galvanotaxis) toward the cathode, making it a useful tool during tissue engineering and for healing epidermal wounds. However, the biophysical mechanisms for sensing weak EFs remain elusive. We have reinvestigated the mechanism of cathode-directed water flow (electro-osmosis) in the boundary layer of cells, by reducing it with neutral, viscous polymers. We report that increasing viscosity with low molecular weight polymers decreases cathodal migration and promotes anodal migration in a concentration dependent manner. In contrast, increased viscosity with high molecular weight polymers does not affect directionality. We explain the contradictory results in terms of porosity and hydraulic permeability between the polymers rather than in terms of bulk viscosity. These results provide the first evidence for controlled reversal of galvanotaxis using viscous agents and position the field closer to identifying the putative electric field receptor, a fundamental, outside-in signaling receptor that controls cellular polarity for different cell types.

Atypical Femoral Shaft Fractures in Female Bisphosphonate Users Were Associated with an Increased Anterolateral Femoral Bow and a Thicker Lateral Cortex: A Case-Control Study.

PubMed

Jang, Seung Pil; Yeo, Ingwon; So, Sang-Yeon; Kim, Keunbyuel; Moon, Young-Wan; Park, Youn-Soo; Lim, Seung-Jae

2017-01-01

The purpose of our study was to investigate the radiographic characteristics of atypical femoral shaft fractures (AFSFs) in females with a particular focus on femoral bow and cortical thickness. We performed a fracture location-, age-, gender-, and ethnicity-matched case-control study. Forty-two AFSFs in 29 patients and 22 typical osteoporotic femoral shaft fractures in 22 patients were enrolled in AFSF group and control group, respectively. With comparing demographics between two groups, radiographically measured femoral bow and cortical thicknesses of AFSF group were compared with control group. All AFSF patients were females with a mean age of 74.4 years (range, 58-85 years). All had a history of bisphosphonate (BP) use with a mean duration of 7.3 years (range 1-17 years). Femoral bow of AFSF group was significantly higher than control group on both anteroposterior (AP) and lateral radiographs after age correction. Mean femoral bow on an AP radiograph was 12.39° ± 5.38° in AFSF group and 3.97 ± 3.62° in control group ( P < 0.0001). Mean femoral bow on the lateral radiograph was 15.71° ± 5.62° in AFSF group and 10.72° ± 4.61° in control group (after age correction P = 0.003). And cortical thicknesses of AFSF group demonstrated marked disparity between tensile and compressive side of bowed femurs in this study. An adjusted lateral cortical thickness was 10.5 ± 1.4 mm in AFSF group and 8.1 ± 1.3 mm in control group (after age correction P < 0.0001) while medial cortical thickness of AFSF group was not statistically different from control group. Correlation analysis showed that the lateral femoral bow on the AP radiograph was solely related to lateral CTI ( R = 0.378, P = 0.002). AFSFs in female BP users were associated with an increased anterolateral femoral bow and a thicker lateral cortex of femurs.

Study of relation between Pc 3 micropulsations and magnetosheath fluctuations, and multisatellite investigation of earth's bow shock

NASA Technical Reports Server (NTRS)

Greenstadt, E. W.

1975-01-01

The validity is investigated of a suggested model according to which Pc 3 and/or Pc 4 micropulsations are excited by magnetosheath field (and plasma) fluctuations arising in the quasi-parallel structure of the subsolar bow shock. The influence of solar wind plasma parameters on local shock structure and on the configuration of the entire bow shock system is included. Simultaneous data from two or more spacecraft and from multiple diagnostics is used to evaluate the geometrical factor, field-to-shock normal angle, or its B-X equivalent, and the principal plasma parameters. Results are presented and discussed.

The solar wind interaction with Mars: Mariner 4, Mars 2, Mars 3, Mars 5, and Phobos 2 observations of bow shock position and shape

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

Slavin, J.A.; Schwingenschuh, K.; Riedler, W.

1991-07-01

Observations taken by Mariner 4, Mars 2, Mars 3, Mars 5, and Phobos 2 are used to model the shape, position, and variability of the Martian bow shock for the purpose of better understanding the interaction of this planet with the solar wind. Emphasis is placed upon comparisons with the results of similar analyses at Venus, the only planet known to have no significant intrinsic magnetic field. Excellent agreement is found between Mars bow shock models derived from the earlier Mariner-Mars data set (24 crossings in 1964-1974) and the far more extensive observations recently returned by Phobos 2 (94 crossingsmore » in 1989). The best fit model to the aggregate data set locates the subsolar bow shock at a planetocentric distance of 1.56 {plus minus} 0.04 R{sub M}. Mapped into the terminator plane, the average distance to the Martian bow shock is 2.66 {plus minus} 0.05 R{sub M}. Compared with Venus, the bow wave at Mars is significantly more distant in the terminator plane, 2.7 R{sub M} versus 2.4 R{sub V}, and over twice as variable in location with a standard deviation of 0.49 R{sub M} versus 0.21 R{sub V} at Venus. The Mars 2, 3, and 5 and Phobos 2 data also contain a small number of very distant dayside shock crossings with inferred subsolar obstacle radii derived from gasdynamic modeling of 2,000 to 4,000 km. Such distant bow shock occurrences do not appear to take place at Venus and may be associated with the expansion of a small Martian magnetosphere under the influence of unusually low wind pressure. Finally, the altitude of the Venus bow shock has a strong solar cycle dependence believed to be due to the effect of solar EUV on the neutral atmosphere and mass loading. Comparison of the Phobos 2 shock observations near solar maximum (R{sub z} = 141) with the Mariner-Mars measurements taken much farther from solar maximum (R{sub z} = 59) indicates that the Martian bow shock location is independent of solar cycle phase and, hence, solar EUV flux.« less

Venusian ion populations and bow shock as seen by the ASPERA-4 ion instrument on Venus Express

NASA Astrophysics Data System (ADS)

Grande, M.; Whittaker, I.; Guymer, G.; Barabash, S.

2008-09-01

Introduction We examine ion populations at Venus. Previous models use magnetic crossing points to derive the bow shock position. The current work uses data from the ASPERA-4 (Analyser of Space Plasmas and Energetic Atoms) [1] instrument to measure ion populations and derive a bow shock position at Venus. Instrumentation The ASPERA-4 instrument flies onboard Venus Express (VEX) and is comprised of five different detectors (Barabash et al 2006 [1]). A neutral particle detector and analyser, an electron spectrometer and the Ion Mass Analyser (IMA) (ref). This paper uses the IMA instrument for all its data and an explanation of the specifications is required. The instrument is a top hat electrostatic analyser; it runs through voltages to scan look angles and also acceptance energies. In one look direction it scans through 96 different energy values before changing to the next. A full scan of all look directions and energies takes 192 seconds. Data Collection All data is weighed dependant upon its probability of the spacecraft measuring at a particular point and when fitted produces a value of 1.24 RV, somewhat closer distance for the sub solar point than previous authors - see figure 1. We separate the data according to slow or fast solar wind and not the similarities and differences in the results derived. The inbound and outbound bow shock crossings were taken by inspection of 106 orbits between November 2006 and February 2007. Any orbits where the crossing point was not clear or with data missing were ignored. The occupational probability is found from orbital mechanics. By setting up a grid and deriving the amount of time it takes to cross each square the probability as a whole can then be determined. Ion distribution plots Two dimensional maps of the ions are produced and the bow shock model overplotted to verify its accuracy, as shown in figure 3. The test of the bow shock is to place it upon real data and examine the fit. To do this ion distribution plots are

Predictions of lithium interactions with earth's bow shock in the presence of wave activity

NASA Technical Reports Server (NTRS)

Decker, R. B.; Lui, A. T. Y.; Vlahos, L.

1984-01-01

The results of a test-particle simulation studying the movement of a lithium tracer ion injected upstream of the bow shock are reported. Wave activity consists of parallel and antiparallel propagating Alfven waves characterized by a frequency power spectrum within a frequency or range of amplitudes defined separately in the upstream and downstream regions. The results show that even a moderate level of wave activity can substantially change the results obtained in the absence of waves. Among the effects observed are: (1) increased ion transmission; (2) both the average energy gain and spread about the average are increased for transmitted and reflected particles; (3) the average final pitch angle for transmitted particles tends to 90 deg, and the spread of reflected particles is reduced; and (4) the spatial dispersion of the ions on the bow shock after a single encounter is increased.

Numerical modeling of a glow discharge through a supersonic bow shock in air

NASA Astrophysics Data System (ADS)

Rassou, S.; Packan, D.; Elias, P.-Q.; Tholin, F.; Chemartin, L.; Labaune, J.

2017-03-01

The interaction between a glow discharge and the bow shock of a Mach 3 air flow around a truncated conical model with a central spike is modeled, and comparison is made with prior experimental results. The KRONOS workflow for plasma modeling in flow fields, which has recently been developed at ONERA, was used for the modeling. Based on the quasi-neutral approximation, it couples hypersonic and reactive flow fields with electron chemistry, including the effect of non-Maxwellian electron energy distribution function. The model used for the discharge involves 12 species and 82 reactions, including ionization, electronic and vibrational excitation, and attachment. The simulations reproduce the main features of the discharge observed experimentally well, in particular, the very recognizable topology of the discharge. It was found from the simulations that behind the bow shock, in the afterglow, the negative ion flow ensures the electrical conduction and the establishment of the glow discharge. The influence of kinetic rates on the voltage-current characteristics is discussed.

Process of forming compounds using reverse micelle or reverse microemulsion systems

DOEpatents

Linehan, John C.; Fulton, John L.; Bean, Roger M.

1998-01-01

The present invention is directed to a process for producing a nanometer-sized metal compound. The process comprises forming a reverse micelle or reverse microemulsion system comprising a polar fluid in a non-polar or low-polarity fluid. A first reactant comprising a multi-component, water-soluble metal compound is introduced into the polar fluid in a non-polar or low-polarity fluid. This first reactant can be introduced into the reverse micelle or reverse microemulsion system during formation thereof or subsequent to the formation of the reverse micelle or microemulsion system. The water-soluble metal compound is then reacted in the reverse micelle or reverse microemulsion system to form the nanometer-sized metal compound. The nanometer-sized metal compound is then precipitated from the reverse micelle or reverse microemulsion system.

Joint High Speed Sealift (JHSS) Baseline Shaft & Strut (Model 5653) Series 1: Bare Hull Resistance, Appended Resistance, and Alternative Bow Evaluations

DTIC Science & Technology

2007-08-01

individually for each of the four candidate bows in Appendix B, Figures B13- Bl6 , and collectively in Table B 18. Wave Traces Wave traces along the JHSS BSS... B16 B7. JHSS: BSS, GB, BH, displacement variations, PE test comparisons ............................... B19 B8. JHSS: BSS, bow variations, BH, DES, PE...BSS, EB, dynamic sinkage and pitch ................................................................... B33 B16 . JHSS: BSS, GB, dynamic sinkage and pitch

Bimanual coordination of bowing and fingering in violinists--effects of position changes and string changes.

PubMed

Kazennikov, Oleg; Wiesendanger, Mario

2009-07-01

Music performance is based on demanding motor control with much practice from young age onward. We have chosen to investigate basic bimanual movements played by violin amateurs and professionals. We posed the question whether position and string changes, two frequent mechanisms, may influence the time interval bowing (right)-fingering (left) coordination. The objective was to measure bimanual coordination, i.e., with or without position changes and string changes. The tendency was that the bimanual coordination was statistically only slightly increased or even unchanged but not perceptible. We conclude that the coordination index is limited up to 100 ms intervals, without any erroneous perception. Although the mentioned position changes and string changes are movements with their timing, they are executed in parallel rather than in series with the bow-fingering coordination.

Numerical Simulation of the Fluid-Structure Interaction of a Surface Effect Ship Bow Seal

NASA Astrophysics Data System (ADS)

Bloxom, Andrew L.

Numerical simulations of fluid-structure interaction (FSI) problems were performed in an effort to verify and validate a commercially available FSI tool. This tool uses an iterative partitioned coupling scheme between CD-adapco's STAR-CCM+ finite volume fluid solver and Simulia's Abaqus finite element structural solver to simulate the FSI response of a system. Preliminary verification and validation work (V&V) was carried out to understand the numerical behavior of the codes individually and together as a FSI tool. Verification and Validation work that was completed included code order verification of the respective fluid and structural solvers with Couette-Poiseuille flow and Euler-Bernoulli beam theory. These results confirmed the 2 nd order accuracy of the spatial discretizations used. Following that, a mixture of solution verifications and model calibrations was performed with the inclusion of the physics models implemented in the solution of the FSI problems. Solution verifications were completed for fluid and structural stand-alone models as well as for the coupled FSI solutions. These results re-confirmed the spatial order of accuracy but for more complex flows and physics models as well as the order of accuracy of the temporal discretizations. In lieu of a good material definition, model calibration is performed to reproduce the experimental results. This work used model calibration for both instances of hyperelastic materials which were presented in the literature as validation cases because these materials were defined as linear elastic. Calibrated, three dimensional models of the bow seal on the University of Michigan bow seal test platform showed the ability to reproduce the experimental results qualitatively through averaging of the forces and seal displacements. These simulations represent the only current 3D results for this case. One significant result of this study is the ability to visualize the flow around the seal and to directly measure the

Asymmetric Thrust Reversers

NASA Technical Reports Server (NTRS)

Chandler, Jesse M. (Inventor); Suciu, Gabriel L. (Inventor)

2018-01-01

An aircraft includes a propulsion supported within an aft portion of a fuselage A thrust reverser is mounted in the aft portion of the fuselage proximate the propulsion system for directing thrust in a direction to slow the aircraft. The thrust reverser includes an upper blocker door movable about a first pivot axis to a deployed position and a lower blocker door movable about a second pivot axis not parallel to the first pivot axis.

Nonthermal ions and associated magnetic field behavior at a quasi-parallel earth's bow shock

NASA Technical Reports Server (NTRS)

Wilkinson, W. P.; Pardaens, A. K.; Schwartz, S. J.; Burgess, D.; Luehr, H.; Kessel, R. L.; Dunlop, M.; Farrugia, C. J.

1993-01-01

Attention is given to ion and magnetic field measurements at the earth's bow shock from the AMPTE-UKS and -IRM spacecraft, which were examined in high time resolution during a 45-min interval when the field remained closely aligned with the model bow shock normal. Dense ion beams were detected almost exclusively in the midst of short-duration periods of turbulent magnetic field wave activity. Many examples of propagation at large elevation angles relative to the ecliptic plane, which is inconsistent with reflection in the standard model shock configuration, were discovered. The associated waves are elliptically polarized and are preferentially left-handed in the observer's frame of reference, but are less confined to the maximum variance plane than other previously studied foreshock waves. The association of the wave activity with the ion beams suggests that the former may be triggered by an ion-driven instability, and possible candidates are discussed.

Chondrule Formation in Bow Shocks around Eccentric Planetary Embryos

NASA Astrophysics Data System (ADS)

Morris, Melissa A.; Boley, Aaron C.; Desch, Steven J.; Athanassiadou, Themis

2012-06-01

Recent isotopic studies of Martian meteorites by Dauphas & Pourmand have established that large (~3000 km radius) planetary embryos existed in the solar nebula at the same time that chondrules—millimeter-sized igneous inclusions found in meteorites—were forming. We model the formation of chondrules by passage through bow shocks around such a planetary embryo on an eccentric orbit. We numerically model the hydrodynamics of the flow and find that such large bodies retain an atmosphere with Kelvin-Helmholtz instabilities allowing mixing of this atmosphere with the gas and particles flowing past the embryo. We calculate the trajectories of chondrules flowing past the body and find that they are not accreted by the protoplanet, but may instead flow through volatiles outgassed from the planet's magma ocean. In contrast, chondrules are accreted onto smaller planetesimals. We calculate the thermal histories of chondrules passing through the bow shock. We find that peak temperatures and cooling rates are consistent with the formation of the dominant, porphyritic texture of most chondrules, assuming a modest enhancement above the likely solar nebula average value of chondrule densities (by a factor of 10), attributable to settling of chondrule precursors to the midplane of the disk or turbulent concentration. We calculate the rate at which a planetary embryo's eccentricity is damped and conclude that a single planetary embryo scattered into an eccentric orbit can, over ~105 years, produce ~1024 g of chondrules. In principle, a small number (1-10) of eccentric planetary embryos can melt the observed mass of chondrules in a manner consistent with all known constraints.

On the failure behaviour to striking bow penetration of impacted marine-steel structures

NASA Astrophysics Data System (ADS)

Prabowo, Aditya Rio; Muttaqie, Teguh; Sohn, Jung Min; Bae, Dong Myung; Setiyawan, Agus

2018-04-01

Demands for water transportation modes are continuously increasing as rapid economic and industrial growths in the recent decade. Ship as representative of the water transportation is generally needed to carry various products from one location to another. Besides as product carrier, ship also acts as public facility to transport human across islands for number of reasons, such as tourism and vehicle. Considering its importance, structural damage due to accidental loads or so-called impact can cause unacceptable casualties which threat ship passenger, shipping industry and maritime environment in same time. The most frequent impact phenomena occur in forms of collision and grounding, which are targeting side structure and double bottom consecutively. However, since responses of the impacts on structure are highly nonlinear and vary due to development of ship structures, sustainable analysis as an update of pioneer calculation can be beneficial as rational reference for improving safety and navigational instruments. This work aims to assess failures of the side structures subjected to penetration of striking bow in ship-ship collision scenario. Locations of impact are idealized to happen on after-end, midsection and fore-end to provide complete assessment. Striking bow is to be deployed by varying input velocity to observe significance of the fractures on the side structure. This configuration is implemented on the designed collision scenario, and later calculated using nonlinear finite element method (NLFEM). Summary of the solution indicated that the midsection produced the highest resistance against side collision. Breaching of the inner shell was successfully avoided on the fore-end, but the critical damage to the cargo was observed during bow penetration to the after-end region. This location was recommended to be added by longitudinal framing to increase its resistance against ship collision.

Collisionless dissipation in quasi-perpendicular shocks. [in terresrial bow waves

NASA Technical Reports Server (NTRS)

Forslund, D. W.; Quest, K. B.; Brackbill, J. U.; Lee, K.

1984-01-01

Microscopic dissipation processes in quasi-perpendicular shocks are studied by two-dimensional plasma simulations in which electrons and ions are treated as particles moving in self-consistent electric and magnetic fields. Cross-field currents induce substantial turbulence at the shock front reducing the reflected ion fraction, increasing the bulk ion temperature behind the shock, doubling the average magnetic ramp thickness, and enhancing the upstream field aligned electron heat flow. The short scale length magnetic fluctuations observed in the bow shock are probably associated with this turbulence.

76 FR 13666 - Pitney Bowes, Inc., Mailing Solutions Management, Global Engineering Group, Including On-Site...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-14

...., Mailing Solutions Management, Global Engineering Group, Including On-Site Leased Workers From Guidant... workers and former workers of Pitney Bowes, Inc., Mailing Solutions Management Division, Engineering... reviewed the certification to clarify the subject worker group's identity. Additional information revealed...

Kaguya observations of the lunar wake in the terrestrial foreshock: Surface potential change by bow-shock reflected ions

NASA Astrophysics Data System (ADS)

Nishino, Masaki N.; Harada, Yuki; Saito, Yoshifumi; Tsunakawa, Hideo; Takahashi, Futoshi; Yokota, Shoichiro; Matsushima, Masaki; Shibuya, Hidetoshi; Shimizu, Hisayoshi

2017-09-01

There forms a tenuous region called the wake behind the Moon in the solar wind, and plasma entry/refilling into the wake is a fundamental problem of the lunar plasma science. High-energy ions and electrons in the foreshock of the Earth's magnetosphere were detected at the lunar surface in the Apollo era, but their effects on the lunar night-side environment have never been studied. Here we show the first observation of bow-shock reflected protons by Kaguya (SELENE) spacecraft in orbit around the Moon, confirming that solar wind plasma reflected at the terrestrial bow shock can easily access the deepest lunar wake when the Moon stays in the foreshock (We name this mechanism 'type-3 entry'). In a continuous type-3 event, low-energy electron beams from the lunar night-side surface are not obvious even though the spacecraft location is magnetically connected to the lunar surface. On the other hand, in an intermittent type-3 entry event, the kinetic energy of upward-going field-aligned electron beams decreases from ∼ 80 eV to ∼ 20 eV or electron beams disappear as the bow-shock reflected ions come accompanied by enhanced downward electrons. According to theoretical treatment based on electric current balance at the lunar surface including secondary electron emission by incident electron and ion impact, we deduce that incident ions would be accompanied by a few to several times higher flux of an incident electron flux, which well fits observed downward fluxes. We conclude that impact by the bow-shock reflected ions and electrons raises the electrostatic potential of the lunar night-side surface.

Nickel-hydrogen cell reversal characteristics

NASA Technical Reports Server (NTRS)

Lurie, Charles

1994-01-01

Nickel-hydrogen cell reversal characteristics are being studied as part of a TRW program directed towards development of a high current battery cell bypass switch. The following are discussed: cell bypass switch; nickel-hydrogen cell reversal characteristics; and nickel-hydrogen cell chemistry: discharge/reversal and overdischarge (reversal) with nickel and hydrogen precharge.

Wave and ion evolution downstream of quasi-perpendicular bow shocks

NASA Technical Reports Server (NTRS)

Mckean, M. E.; Omidi, N.; Krauss-Varban, D.

1995-01-01

Distribution functions of ions heated in quasi-perpendicular bow shocks have a large perpendicular temperature anisotropy that provides free energy for the growth of Alfven ion cyclotron (AIC) waves and mirror waves. Both types of waves have been observed in the Earth's magnetosheath downstream of quasi-perpendicular shocks. We use a two-dimensional hybrid simulations to give a self-consistent description of the evolution of the wave spectra downstream of quasi-perpendicular shocks. Both mirror and AIC waves are identified in the simulated magnetosheath. They are generated at or near the shock front and convected away from it by the sheath plasma. Near the shock, the waves have a broad spectrum, but downstream of the shock, shorter-wavelength modes are heavily damped and only longer-wavelength modes persist. The characteristics of these surviving modes can be predicted with reasonable accuracy by linear kinetic theory appropriate for downstream conditions. We also follow the evolution of the ion distribution function. The shocked ions that provide the free energy for wave growth have a two-component distribution function. The halo is initially gyrophase-bunched and extremely anisotropic. Within a relatively short distance downstream of the shock (of the order of 10 ion inertial lengths), wave-particle interactions remove these features from the halo and reduce the anisotropy of the distribution to near-threshold levels for the mirror and AIC instabilities. A similar evolution has been observed for ions at the Earth's bow shock.

Extremely rapid directional change during Matuyama-Brunhes geomagnetic polarity reversal

NASA Astrophysics Data System (ADS)

Sagnotti, Leonardo; Scardia, Giancarlo; Giaccio, Biagio; Liddicoat, Joseph C.; Nomade, Sebastien; Renne, Paul R.; Sprain, Courtney J.

2014-11-01

We report a palaeomagnetic investigation of the last full geomagnetic field reversal, the Matuyama-Brunhes (M-B) transition, as preserved in a continuous sequence of exposed lacustrine sediments in the Apennines of Central Italy. The palaeomagnetic record provides the most direct evidence for the tempo of transitional field behaviour yet obtained for the M-B transition. 40Ar/39Ar dating of tephra layers bracketing the M-B transition provides high-accuracy age constraints and indicates a mean sediment accumulation rate of about 0.2 mm yr-1 during the transition. Two relative palaeointensity (RPI) minima are present in the M-B transition. During the terminus of the upper RPI minimum, a directional change of about 180 ° occurred at an extremely fast rate, estimated to be less than 2 ° per year, with no intermediate virtual geomagnetic poles (VGPs) documented during the transit from the southern to northern hemisphere. Thus, the entry into the Brunhes Normal Chron as represented by the palaeomagnetic directions and VGPs developed in a time interval comparable to the duration of an average human life, which is an order of magnitude more rapid than suggested by current models. The reported investigation therefore provides high-resolution integrated palaeomagnetic and radioisotopic data that document the fine details of the anatomy and tempo of the M-B transition in Central Italy that in turn are crucial for a better understanding of Earth's magnetic field, and for the development of more sophisticated models that are able to describe its global structure and behaviour.

The existence and nature of the interstellar bow shock

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

Ben-Jaffel, Lotfi; Strumik, M.; Ratkiewicz, R.

2013-12-20

We report a new diagnosis of two different states of the local interstellar medium (LISM) near our solar system by using a sensitivity study constrained by several distinct and complementary observations of the LISM, solar wind, and inner heliosphere. Assuming the Interstellar Boundary Explorer (IBEX) He flow parameters for the LISM, we obtain a strength of ∼2.7 ± 0.2 μG and a direction pointing away from galactic coordinates (28, 52) ± 3° for the interstellar magnetic field as a result of fitting Voyager 1 and Voyager 2 in situ plasma measurements and IBEX energetic neutral atoms ribbon. When using Ulyssesmore » parameters for the LISM He flow, we recently reported the same direction but with a strength of 2.2 ± 0.1 μG. First, we notice that with Ulysses He flow, our solution is in the expected hydrogen deflection plane (HDP). In contrast, for the IBEX He flow, the solution is ∼20° away from the corresponding HDP plane. Second, the long-term monitoring of the interplanetary H I flow speed shows a value of ∼26 km s{sup –1} measured upwind from the Doppler shift in the strong Lyα sky background emission line. All elements of the diagnosis seem therefore to support Ulysses He flow parameters for the interstellar state. In that frame, we argue that reliable discrimination between superfast, subfast, or superslow states of the interstellar flow should be based on most existing in situ and remote observations used together with global modeling of the heliosphere. For commonly accepted LISM ionization rates, we show that a fast interstellar bow shock should be standing off upstream of the heliopause.« less

Violin Pedagogy and the Physics of the Bowed String

NASA Astrophysics Data System (ADS)

McLeod, Alexander Rhodes

The paper describes the mechanics of violin tone production using non-specialist language, in order to present a scientific understanding of tone production accessible to a broad readership. As well as offering an objective understanding of tone production, this model provides a powerful tool for analyzing the technique of string playing. The interaction between the bow and the string is quite complex. Literature reviewed for this study reveals that scientific investigations have provided important insights into the mechanics of string playing, offering explanations for factors which both contribute to and limit the range of tone colours and dynamics that stringed instruments can produce. Also examined in the literature review are significant works of twentieth century violin pedagogy exploring tone production on the violin, based on the practical experience of generations of teachers and performers. Hermann von Helmholtz described the stick-slip cycle which drives the string in 1863, which replaced earlier ideas about the vibration of violin strings. Later, scientists such as John Schelleng and Lothar Cremer were able to demonstrate how the mechanics of the bow-string interaction can create different tone colours. Recent research by Anders Askenfelt, Knut Guettler, and Erwin Schoonderwaldt have continued to refine earlier research in this area. The writings of Lucien Capet, Leopold Auer, Carl Flesch, Paul Rolland, Kato Havas, Ivan Galamian, and Simon Fischer are examined and analyzed. Each author describes a different approach to tone production on the violin, representing a different understanding of the underlying mechanism. Analyzing these writings within the context of a scientific understanding of tone production makes it possible to compare these approaches more consistently, and to synthesize different concepts drawn from the diverse sources evaluated.

Measurement of large parallel and perpendicular electric fields on electron spatial scales in the terrestrial bow shock.

PubMed

Bale, S D; Mozer, F S

2007-05-18

Large parallel (bow shock by the vector electric field experiment on the Polar satellite. These are the first reported direct measurements of parallel electric fields in a collisionless shock. These fields exist on spatial scales comparable to or less than the electron skin depth (a few kilometers) and correspond to magnetic-field-aligned potentials of tens of volts and perpendicular potentials up to a kilovolt. The perpendicular fields are amongst the largest ever measured in space, with energy densities of epsilon0E2/nkBTe of the order of 10%. The measured parallel electric field implies that the electrons are demagnetized, which may result in stochastic (rather than coherent) electron heating.

26 CFR 48.4161(b)-1 - Imposition and rates of tax; bows and arrows.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 26 Internal Revenue 16 2010-04-01 2010-04-01 true Imposition and rates of tax; bows and arrows. 48.4161(b)-1 Section 48.4161(b)-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) MISCELLANEOUS EXCISE TAXES MANUFACTURERS AND RETAILERS EXCISE TAXES Sporting Goods § 48.4161(b)-1...

Enhanced Scattering of Diffuse Ions on Front of the Earth's Quasi-Parallel Bow Shock: a Case Study

NASA Astrophysics Data System (ADS)

Kis, A.; Matsukiyo, S.; Otsuka, F.; Hada, T.; Lemperger, I.; Dandouras, I. S.; Barta, V.; Facsko, G. I.

2017-12-01

In the analysis we present a case study of three energetic upstream ion events at the Earth's quasi-parallel bow shock based on multi-spacecraft data recorded by Cluster. The CIS-HIA instrument onboard Cluster provides partial energetic ion densities in 4 energy channels between 10 and 32 keV.The difference of the partial ion densities recorded by the individual spacecraft at various distances from the bow shock surface makes possible the determination of the spatial gradient of energetic ions.Using the gradient values we determined the spatial profile of the energetic ion partial densities as a function of distance from the bow shock and we calculated the e-folding distance and the diffusion coefficient for each event and each ion energy range. Results show that in two cases the scattering of diffuse ions takes place in a normal way, as "by the book", and the e-folding distance and diffusion coefficient values are comparable with previous results. On the other hand, in the third case the e-folding distance and the diffusion coefficient values are significantly lower, which suggests that in this case the scattering process -and therefore the diffusive shock acceleration (DSA) mechanism also- is much more efficient. Our analysis provides an explanation for this "enhanced" scattering process recorded in the third case.

Theoretical study of the transonic lift of a double-wedge profile with detached bow wave

NASA Technical Reports Server (NTRS)

Vincenti, Walter G; Wagoner, Cleo B

1954-01-01

A theoretical study is described of the aerodynamic characteristics at small angle of attack of a thin, double-wedge profile in the range of supersonic flight speed in which the bow wave is detached. The analysis is carried out within the framework of the transonic (nonlinear) small-disturbance theory, and the effects of angle of attack are regarded as a small perturbation on the flow previously calculated at zero angle. The mixed flow about the front half of the profile is calculated by relaxation solution of a suitably defined boundary-value problem for transonic small-disturbance equation in the hodograph plane (i.e., the Tricomi equation). The purely supersonic flow about the rear half is found by an extension of the usual numerical method of characteristics. Analytical results are also obtained, within the framework of the same theory, for the range of speed in which the bow wave is attached and the flow is completely supersonic.

Historic range of variability for upland vegetation in the Medicine Bow National Forest, Wyoming

Treesearch

Gregory K. Dillon; Dennis H. Knight; Carolyn B. Meyer

2005-01-01

An approach for synthesizing the results of ecological research pertinent to land management is the analysis of the historic range of variability (HRV) for key ecosystem variables that are affected by management activities. This report provides an HRV analysis for the upland vegetation of the Medicine Bow National Forest in southeastern Wyoming. The variables include...

Ground-state magnetic phase diagram of bow-tie graphene nanoflakes in external magnetic field

NASA Astrophysics Data System (ADS)

Szałowski, Karol

2013-12-01

The magnetic phase diagram of a ground state is studied theoretically for graphene nanoflakes of bow-tie shape and various sizes in external in-plane magnetic field. The tight-binding Hamiltonian supplemented with Hubbard term is used to model the electronic structure of the systems in question. The existence of the antiferromagnetic phase with magnetic moments localized at the sides of the bow-tie is found for low field and a field-induced spin-flip transition to ferromagnetic state is predicted to occur in charge-undoped structures. For small nanoflake doped with a single charge carrier, the low-field phase is ferrimagnetic and a metamagnetic transition to ferromagnetic ordering can be forced by the field. The critical field is found to decrease with increasing size of the nanoflake. The influence of diagonal and off-diagonal disorder on the mentioned magnetic properties is studied. The effect of off-diagonal disorder is found to be more important than that of diagonal disorder, leading to significantly widened distribution of critical fields for disordered population of nanoflakes.

Surface Plasmon-Coupled Directional Enhanced Raman Scattering by Means of the Reverse Kretschmann Configuration.

PubMed

Huo, Si-Xin; Liu, Qian; Cao, Shuo-Hui; Cai, Wei-Peng; Meng, Ling-Yan; Xie, Kai-Xin; Zhai, Yan-Yun; Zong, Cheng; Yang, Zhi-Lin; Ren, Bin; Li, Yao-Qun

2015-06-04

Surface-enhanced Raman scattering (SERS) is a unique analytical technique that provides fingerprint spectra, yet facing the obstacle of low collection efficiency. In this study, we demonstrated a simple approach to measure surface plasmon-coupled directional enhanced Raman scattering by means of the reverse Kretschmann configuration (RK-SPCR). Highly directional and p-polarized Raman scattering of 4-aminothiophenol (4-ATP) was observed on a nanoparticle-on-film substrate at 46° through the prism coupler with a sharp angle distribution (full width at half-maximum of ∼3.3°). Because of the improved collection efficiency, the Raman scattering signal was enhanced 30-fold over the conventional SERS mode; this was consistent with finite-difference time-domain simulations. The effect of nanoparticles on the coupling efficiency of propagated surface plasmons was investigated. Possessing straightforward implementation and directional enhancement of Raman scattering, RK-SPCR is anticipated to simplify SERS instruments and to be broadly applicable to biochemical assays.

Mapping the Structure of Directed Networks: Beyond the Bow-Tie Diagram

NASA Astrophysics Data System (ADS)

Timár, G.; Goltsev, A. V.; Dorogovtsev, S. N.; Mendes, J. F. F.

2017-02-01

We reveal a hierarchical, multilayer organization of finite components—i.e., tendrils and tubes—around the giant connected components in directed networks and propose efficient algorithms allowing one to uncover the entire organization of key real-world directed networks, such as the World Wide Web, the neural network of Caenorhabditis elegans, and others. With increasing damage, the giant components decrease in size while the number and size of tendril layers increase, enhancing the susceptibility of the networks to damage.

Character Reversal in Children: The Prominent Role of Writing Direction

ERIC Educational Resources Information Center

Fischer, Jean-Paul

2017-01-01

Recent research has established that 5- to 6-year-old typically developing children in a left-right writing culture spontaneously reverse left-oriented characters (e.g., they write a [reversed J] instead of J) when they write single characters. Thus, children seem to implicitly apply a right-writing rule (RWR: see Fischer & Koch, 2016a). In…

Long-term reversal of diabetes in non-obese diabetic mice by liver-directed gene therapy.

PubMed

Ren, Binhai; O'Brien, Bronwyn A; Byrne, Michelle R; Ch'ng, Edwin; Gatt, Prudence N; Swan, M Anne; Nassif, Najah T; Wei, Ming Q; Gijsbers, Rik; Debyser, Zeger; Simpson, Ann M

2013-01-01

Type 1 diabetes (T1D) results from an autoimmune attack against the insulin-producing β-cells of the pancreas. The present study aimed to reverse T1D by gene therapy. We used a novel surgical technique, which involves isolating the liver from the circulation before the delivery of a lentiviral vector carrying furin-cleavable human insulin (INS-FUR) or empty vector to the livers of diabetic non-obese diabetic mice (NOD). This was compared with the direct injection of the vector into the portal circulation. Mice were monitored for body weight and blood glucose. Intravenous glucose tolerance tests were performed. Expression of insulin and pancreatic transcription factors was determined by the reverse transcriptase-polymerase chain reaction and immunohistochemistry and immunoelectron microscopy was used to localise insulin. Using the novel surgical technique, we achieved long-term transduction (42% efficiency) of hepatocytes, restored normoglycaemia for 150 days (experimental endpoint) and re-established normal glucose tolerance. We showed the expression of β-cell transcription factors, murine insulin, glucagon and somatostatin, and hepatic storage of insulin in granules. The expression of hepatic markers, C/EBP-β, G6PC, AAT and GLUI was down-regulated in INS-FUR-treated livers. Liver function tests remained normal, with no evidence of intrahepatic inflammation or autoimmune destruction of the insulin-secreting liver tissue. By comparison, direct injection of INS-FUR reduced blood glucose levels, and no pancreatic transdifferentiation or normal glucose tolerance was observed. This gene therapy protocol has, for the first time, permanently reversed T1D with normal glucose tolerance in NOD mice and, as such, represents a novel therapeutic strategy for the treatment of T1D. Copyright © 2013 John Wiley & Sons, Ltd.

Reconsidering the process for bow-stave removal from juniper trees in the Great Basin

Treesearch

Constance I. Millar; Kevin T. Smith

2017-01-01

We question the growth arrestment hypothesis for bow stave removal used by indigenous people in the western Great Basin. Using modern understanding of tree growth and wound response, we suggest that growth would not be arrested by one or two transverse notches along a juniper stem. Rather these would trigger compartmentalization, which limits cambial death to within 10...

The Reverse Ludloff Osteotomy for Bunionette Deformity.

PubMed

Waizy, Hazibullah; Jastifer, James R; Stukenborg-Colsman, Christina; Claassen, Leif

2016-08-01

Background The typical bunionette deformity often presents as pain over the lateral margin of the fifth metatarsal head. There have been numerous operative treatments described for this pathology. The purpose of this study was to evaluate the results after a reverse Ludloff osteotomy in cases of severe bunionette deformities. Methods Between 2008 and 2012, 16 patients received a reverse Ludloff osteotomy of the fifth metatarsal due to a symptomatic type II or III bunionette that failed nonoperative treatment. We retrospectively reviewed charts, radiographic images, postoperative AOFAS (American Orthopaedic Foot and Ankle Society) lesser toe scores, and the EQ-5D at a mean of 41.9 months (range, 31-74 months) of follow-up. Additionally, limitation in activities of daily living, pain, and patient satisfaction were assessed. Results At latest follow-up, the mean AOFAS lesser toe score was 86.6 points and the mean EQ-5D score was 14.1. Fifteen patients had no or only little limitations. Fifteen out of 16 patients were satisfied or predominantly satisfied. Radiographic analysis showed for type II deformities a correction of the lateral bowing from 8.1° down to 0.67° (P < .001). The fourth-fifth intermetatarsal angle (4-5 IMA) improved from a mean of 13.2° to a mean of 5.2° (P < .001). The length of the fifth metatarsal was unchanged (P > .05). There were no observed complications, and no revision was necessary. Conclusion In the present study, the reverse Ludloff osteotomy had a high satisfaction rate and no complications. It provided radiographic correction of the deformity and may be considered in the surgical treatment of severe bunionette deformities. Therapeutic, Level IV: Case series. © 2016 The Author(s).

Hybrid simulation techniques applied to the earth's bow shock

NASA Technical Reports Server (NTRS)

Winske, D.; Leroy, M. M.

1985-01-01

The application of a hybrid simulation model, in which the ions are treated as discrete particles and the electrons as a massless charge-neutralizing fluid, to the study of the earth's bow shock is discussed. The essentials of the numerical methods are described in detail; movement of the ions, solution of the electromagnetic fields and electron fluid equations, and imposition of appropriate boundary and initial conditions. Examples of results of calculations for perpendicular shocks are presented which demonstrate the need for a kinetic treatment of the ions to reproduce the correct ion dynamics and the corresponding shock structure. Results for oblique shocks are also presented to show how the magnetic field and ion motion differ from the perpendicular case.

O+ pickup ions outside of Venus' bow shock: Venus Express observation

NASA Astrophysics Data System (ADS)

Wei, Y.; Fraenz, M.; Dubinin, E.; Zhang, T. L.; Wan, W.; Barabash, S.; Woch, J.; Lundin, R.

2012-09-01

Pickup ions are ions of planetary origin that become assimilated into the solar wind flow through their interaction with the solar wind magnetic and electric field. The speed of pickup ions varies between zero and twice the underlying plasma flow component perpendicular to magnetic field vector. For the unmagnetized planet Venus and Mars, oxygen (O+) pickup ions are known to be important because they can modify the global configuration of planetary plasma environment and significantly contribute to the atmospheric O+ loss [1]. Since the kinetic energy of an O+ pickup ion can reach 64 times that of a co-moving proton, an instrument must be able to measure O+ ions with energy of at least tens of keV to investigate the O+ pickup ion distribution from planetary ionosphere to solar wind. The in-situ observations and simulations at Mars have shown that the energy of O+ pickup ions can be 55-72 keV outside of the bow shock [2]. For Venus case, the plasma analyzer (OPA) onboard Pioneer Venus Orbiter (PVO), which was designed for solar wind monitoring, has an 8 keV energy limit for O+ detection and the limited sampling and data rate [3]. Therefore, OPA can only measure the O+ pickup ions in the sheath flow or inside the induced magnetosphere where the speed of ambient plasma flow is significantly lower than that of the unshocked solar wind outside of the bow shock. The Ion Mass Analyzer (IMA), included in the Analyzer of Space Plasma and Energetic Atoms (ASPERA-4) package on board Venus Express (VEX), determines the composition, energy, and angular distribution of ions in the energy range ~10 eV/q to 30 keV/q. Note that an O+ ion moving at the typical solar wind speed 400 km/s has kinetic energy 13.4 keV. Therefore, IMA has ability to measure the O+ pickup ions outside of Venus' bow shock. We have examined the IMA data during the solar minimum period 2006-2010, and identified about ten cases with clear signature of O+ pickup ion. With these observations, we will determine

Electron Scattering by High-Frequency Whistler Waves at Earth's Bow Shock

NASA Technical Reports Server (NTRS)

Oka, M.; Wilson, L. B., III; Phan, T. D.; Hull, A. J.; Amano, T.; Hoshino, M.; Argall, M. R.; Le Contel, O.; Agapitov, O.; Gersham, D. J.;

Photo series for quantifying forest residues in managed lands of the Medicine Bow National Forest

Treesearch

John B. Popp; John E. Lundquist

2006-01-01

This photo series presents a visual representation of a range of fuel loading conditions specifically found on the Medicine Bow National Forest. The photos are grouped by forest type and past management practices. This field guide describes the distribution of different types of woody fuels and includes some vegetation data.

Tibial Geometry in Individuals with Neurofibromatosis Type 1 without Anterolateral Bowing of the Lower Leg Using Peripheral Quantitative Computed Tomography

PubMed Central

Stevenson, David A.; Viskochil, David H.; Carey, John C.; Slater, Hillarie; Murray, Mary; Sheng, Xiaoming; D’Astous, Jacques; Hanson, Heather; Schorry, Elizabeth; Moyer-Mileur, Laurie J.

2008-01-01

Introduction Lower leg bowing with tibial pseudarthrosis is associated with neurofibromatosis type 1 (NF1). The objective of the study is to determine if the geometry of the lower limb in individuals with neurofibromatosis type 1 (NF1) differs from controls, and to characterize the osseous components of the tibia in NF1. Methods Peripheral quantitative computed tomography (pQCT) of the lower limb was performed (90 individuals with NF1 without tibial and/or fibular dysplasia: 474 healthy individuals without NF1). Subjects were 4–18 years of age. Individuals with NF1 were compared to controls using an analysis-of-covariance with a fixed set of covariates (age, weight, height, Tanner stage, and gender). Results Using pQCT, NF1 individuals without bowing of the lower leg have smaller periosteal circumferences (p<0.0001), smaller cortical area (p<0.0001), and decreased tibial cortical and trabecular bone mineral content (BMC) (p<0.0001) compared to controls. Discussion Individuals with NF1 have a different geometry of the lower leg compared to healthy controls suggesting that NF1 haploinsufficiency impacts bone homeostasis although not resulting in overt anterolateral bowing of the lower leg. PMID:19118659

Population genetic structure and direct observations reveal sex-reversed patterns of dispersal in a cooperative bird.

PubMed

Harrison, Xavier A; York, Jennifer E; Young, Andrew J

2014-12-01

Sex-biased dispersal is pervasive and has diverse evolutionary implications, but the fundamental drivers of dispersal sex biases remain unresolved. This is due in part to limited diversity within taxonomic groups in the direction of dispersal sex biases, which leaves hypothesis testing critically dependent upon identifying rare reversals of taxonomic norms. Here, we use a combination of observational and genetic data to demonstrate a rare reversal of the avian sex bias in dispersal in the cooperatively breeding white-browed sparrow weaver (Plocepasser mahali). Direct observations revealed that (i) natal philopatry was rare, with both sexes typically dispersing locally to breed, and (ii), unusually for birds, males bred at significantly greater distances from their natal group than females. Population genetic analyses confirmed these patterns, as (i) corrected Assignment index (AIc), FST tests and isolation-by-distance metrics were all indicative of longer dispersal distances among males than females, and (ii) spatial autocorrelation analysis indicated stronger within-group genetic structure among females than males. Examining the spatial scale of extra-group mating highlighted that the resulting 'sperm dispersal' could have acted in concert with individual dispersal to generate these genetic patterns, but gamete dispersal alone cannot account entirely for the sex differences in genetic structure observed. That leading hypotheses for the evolution of dispersal sex biases cannot readily account for these sex-reversed patterns of dispersal in white-browed sparrow weavers highlights the continued need for attention to alternative explanations for this enigmatic phenomenon. We highlight the potential importance of sex differences in the distances over which dispersal opportunities can be detected. © 2014 The Authors. Molecular Ecology Published by John Wiley & Sons Ltd.

Structural basis of reverse nucleotide polymerization

PubMed Central

Nakamura, Akiyoshi; Nemoto, Taiki; Heinemann, Ilka U.; Yamashita, Keitaro; Sonoda, Tomoyo; Komoda, Keisuke; Tanaka, Isao; Söll, Dieter; Yao, Min

2013-01-01

Nucleotide polymerization proceeds in the forward (5′-3′) direction. This tenet of the central dogma of molecular biology is found in diverse processes including transcription, reverse transcription, DNA replication, and even in lagging strand synthesis where reverse polymerization (3′-5′) would present a “simpler” solution. Interestingly, reverse (3′-5′) nucleotide addition is catalyzed by the tRNA maturation enzyme tRNAHis guanylyltransferase, a structural homolog of canonical forward polymerases. We present a Candida albicans tRNAHis guanylyltransferase-tRNAHis complex structure that reveals the structural basis of reverse polymerization. The directionality of nucleotide polymerization is determined by the orientation of approach of the nucleotide substrate. The tRNA substrate enters the enzyme’s active site from the opposite direction (180° flip) compared with similar nucleotide substrates of canonical 5′-3′ polymerases, and the finger domains are on opposing sides of the core palm domain. Structural, biochemical, and phylogenetic data indicate that reverse polymerization appeared early in evolution and resembles a mirror image of the forward process. PMID:24324136

Reversible vector ratchets for skyrmion systems

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

Ma, Xiu; Reichhardt, Cynthia Jane Olson; Reichhardt, Charles

In this paper, we show that ac driven skyrmions interacting with an asymmetric substrate provide a realization of a class of ratchet system which we call a vector ratchet that arises due to the effect of the Magnus term on the skyrmion dynamics. In a vector ratchet, the dc motion induced by the ac drive can be described as a vector that can be rotated clockwise or counterclockwise relative to the substrate asymmetry direction. Up to a full 360° rotation is possible for varied ac amplitudes or skyrmion densities. In contrast to overdamped systems, in which ratchet motion is alwaysmore » parallel to the substrate asymmetry direction, vector ratchets allow the ratchet motion to be in any direction relative to the substrate asymmetry. It is also possible to obtain a reversal in the direction of rotation of the vector ratchet, permitting the creation of a reversible vector ratchet. We examine vector ratchets for ac drives applied parallel or perpendicular to the substrate asymmetry direction, and show that reverse ratchet motion can be produced by collective effects. No reversals occur for an isolated skyrmion on an asymmetric substrate. Finally, since a vector ratchet can produce motion in any direction, it could represent a method for controlling skyrmion motion for spintronic applications.« less

Reversible vector ratchets for skyrmion systems

NASA Astrophysics Data System (ADS)

Ma, X.; Reichhardt, C. J. Olson; Reichhardt, C.

2017-03-01

We show that ac driven skyrmions interacting with an asymmetric substrate provide a realization of a class of ratchet system which we call a vector ratchet that arises due to the effect of the Magnus term on the skyrmion dynamics. In a vector ratchet, the dc motion induced by the ac drive can be described as a vector that can be rotated clockwise or counterclockwise relative to the substrate asymmetry direction. Up to a full 360∘ rotation is possible for varied ac amplitudes or skyrmion densities. In contrast to overdamped systems, in which ratchet motion is always parallel to the substrate asymmetry direction, vector ratchets allow the ratchet motion to be in any direction relative to the substrate asymmetry. It is also possible to obtain a reversal in the direction of rotation of the vector ratchet, permitting the creation of a reversible vector ratchet. We examine vector ratchets for ac drives applied parallel or perpendicular to the substrate asymmetry direction, and show that reverse ratchet motion can be produced by collective effects. No reversals occur for an isolated skyrmion on an asymmetric substrate. Since a vector ratchet can produce motion in any direction, it could represent a method for controlling skyrmion motion for spintronic applications.

Reversible vector ratchets for skyrmion systems

DOE PAGES

Ma, Xiu; Reichhardt, Cynthia Jane Olson; Reichhardt, Charles

2017-03-03

In this paper, we show that ac driven skyrmions interacting with an asymmetric substrate provide a realization of a class of ratchet system which we call a vector ratchet that arises due to the effect of the Magnus term on the skyrmion dynamics. In a vector ratchet, the dc motion induced by the ac drive can be described as a vector that can be rotated clockwise or counterclockwise relative to the substrate asymmetry direction. Up to a full 360° rotation is possible for varied ac amplitudes or skyrmion densities. In contrast to overdamped systems, in which ratchet motion is alwaysmore » parallel to the substrate asymmetry direction, vector ratchets allow the ratchet motion to be in any direction relative to the substrate asymmetry. It is also possible to obtain a reversal in the direction of rotation of the vector ratchet, permitting the creation of a reversible vector ratchet. We examine vector ratchets for ac drives applied parallel or perpendicular to the substrate asymmetry direction, and show that reverse ratchet motion can be produced by collective effects. No reversals occur for an isolated skyrmion on an asymmetric substrate. Finally, since a vector ratchet can produce motion in any direction, it could represent a method for controlling skyrmion motion for spintronic applications.« less

Evolution of the Magnetic Field during Chondrule Formation in Planetary Bow Shocks

NASA Astrophysics Data System (ADS)

Mai, Chuhong; Desch, Steven; Boley, Aaron C.

2016-10-01

Recent laboratory efforts (Fu et al., 2014, 2015) have constrained the remanent magnetizations of chondrules and the magnetic field strengths they were exposed to as they cooled below their Curie points. An outstanding question is whether these fields represent the background magnetic field of the solar nebula or were unique to the chondrule-forming environment. We investigate the amplification of the magnetic field above background values in a planetary bow shock, which is one proposed mechanism for chondrule formation. We use a hydrodynamic code to model the temperature and pressure around a 3000 km-radius planetary embryo as it moves supersonically through the nebula gas. We calculate the ionization of hot, shocked gas considering thermionic emission of electrons and ions from grains and thermal ionization of potassium. We calculate the magnetic diffusion rate, including Ohmic dissipation and ambipolar diffusion (assuming a magnetic field strength comparable to 0.5 G). We compute the steady-state magnetic field around in the bow shock and find that behind the planet the field is amplified, but everywhere else it quickly diffuses out of the shocked region and recovers the background value. We consider the trajectories taken by chondrules behind the shock and present likely values of the magnetic field amplification experienced by chondrules as they cool after melting in the shock.

A Laminar Model for the Magnetic Field Structure in Bow-Shock Pulsar Wind Nebulae

NASA Astrophysics Data System (ADS)

Bucciantini, N.

2018-05-01

Bow Shock Pulsar Wind Nebulae are a class of non-thermal sources, that form when the wind of a pulsar moving at supersonic speed interacts with the ambient medium, either the ISM or in a few cases the cold ejecta of the parent supernova. These systems have attracted attention in recent years, because they allow us to investigate the properties of the pulsar wind in a different environment from that of canonical Pulsar Wind Nebulae in Supernova Remnants. However, due to the complexity of the interaction, a full-fledged multidimensional analysis is still laking. We present here a simplified approach, based on Lagrangian tracers, to model the magnetic field structure in these systems, and use it to compute the magnetic field geometry, for various configurations in terms of relative orientation of the magnetic axis, pulsar speed and observer direction. Based on our solutions we have computed a set of radio emission maps, including polarization, to investigate the variety of possible appearances, and how the observed emission pattern can be used to constrain the orientation of the system, and the possible presence of turbulence.

Optical hydrogen absorption consistent with a bow shock around the hot Jupiter HD 189733 b

NASA Astrophysics Data System (ADS)

Cauley, P. Wilson; Redfield, Seth; Jensen, Adam G.; Barman, Travis; Endl, Michael; Cochran, William D.

Hot Jupiters, i.e., Jupiter-mass planets with orbital semi major axes of <10 stellar radii, can interact strongly with their host stars. If the planet is moving supersonically through the stellar wind, a bow shock will form ahead of the planet where the planetary magnetosphere slams into the the stellar wind or where the planetary outflow and stellar wind meet. Here we present high resolution spectra of the hydrogen Balmer lines for a single transit of the hot Jupiter HD 189733 b. Transmission spectra of the Balmer lines show strong absorption ~70 minutes before the predicted optical transit, implying a significant column density of excited hydrogen orbiting ahead of the planet. We show that a simple geometric bow shock model is able to reproduce the important features of the absorption time series while simultaneously matching the line profile morphology. Our model suggests a large planetary magnetic field strength of ~28 G. Follow-up observations are needed to confirm the pre-transit signal and investigate any variability in the measurement.

Note: Formation of the nematic splay-bend in two-dimensional systems of bow-shaped particles

NASA Astrophysics Data System (ADS)

Karbowniczek, Paweł

2018-04-01

Recently, Tavarone et al. (J. Chem. Phys. 143, 114505 (2015)) discussed phase behavior of zig-zag and bow-shaped particles composed of three needles. The authors presented very interesting results of extensive Monte Carlo simulations with periodic boundary conditions in the constant-NVT and the constant-NPT ensembles. In addition to isotropic, nematic, and smectic phases, they identified a modulated nematic, which is actually the nematic splay-bend phase ($N_{SB}$), long-anticipated for bent-core systems (Europhys. Lett. 56, 247 (2001)). They also described isotropic-nematic and nematic-smectic transitions using Density Functional Theory in mean-field approximation. The authors, however, did not provided a theoretical description of the $N_{SB}$. Here, we present a simple theory of a phase transition to the $N_{SB}$ phase to fill the gap. In our study, we use Onsager-type Density Functional Theory with perfect order approximation and Meyer parametrization of modulated structures. We present results for arbitrary ratios of the length of central and side segments and opening angles of bow-shaped particles.

Transitional paleointensities from Kauai, Hawaii, and geomagnetic reversal models

USGS Publications Warehouse

Bogue, Scott W.; Coe, Robert S.

1984-01-01

Previously presented paleointensity results from an R-N transition zone in Kauai, Hawaii, show that field intensity dropped from 0. 431 Oe to 0. 101 Oe while the field remained within 30 degree of the reversed axial dipole direction. A recovery in intensity and the main directional change followed this presumably short period of low field strength. As the reversal neared completion, the field has an intensity of 0. 217 Oe while still 40 degree from the final direction. The relationship of paleointensity to field direction during the early part of the reversal thus differs from that toward the end, a feature that only some reversal models are consistent with. For example, a model in which a standing nondipole component persists through the dipole reversal predicts only symmetric intensity patterns. In contrast, zonal flooding models generate suitably complex field behavior if multiple flooding schemes operate during a single reversal or if the flooding process is itself asymmetric.

An Ultrasonic Scanning Technique for In-Situ `Bowing' Measurement of Prototype Fast Breeder Reactor Fuel Sub-Assembly

NASA Astrophysics Data System (ADS)

Swaminathan, K.; Asokane, C.; Sylvia, J. I.; Kalyanasundaram, P.; Swaminathan, P.

2012-02-01

An ultrasonic under-sodium scanner has been developed for deployment in Prototype Fast Breeder Reactor (PFBR) which is in advanced stage of construction at Kalpakkam, India. Its purpose is to scan the above-core plenum for detection, if any, of displacement of sub-assemblies. During its burn-up in the reactor, the head of a Fuel Sub-Assembly (FSA) may undergo a lateral shift from its original position (called `bowing') due to the fast neutron induced damage on its structural material. A simple scanning technique has been developed for measuring the extent of bowing in-situ. This paper describes a PC-controlled mock-up of the scanner used to implement the scanning technique and the results obtained of scanning a mock-up FSA head under water. The details of the liquid-sodium proof transducer developed for use in the PFBR scanner and its performance are also discussed.

REINTERPRETATION OF SLOWDOWN OF SOLAR WIND MEAN VELOCITY IN NONLINEAR STRUCTURES OBSERVED UPSTREAM OF EARTH'S BOW SHOCK

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

Parks, G. K.; Lin, N.; Lee, E.

2013-07-10

Two of the many features associated with nonlinear upstream structures are (1) the solar wind (SW) mean flow slows down and deviates substantially and (2) the temperature of the plasma increases in the structure. In this Letter, we show that the SW beam can be present throughout the entire upstream event maintaining a nearly constant beam velocity and temperature. The decrease of the velocity is due to the appearance of new particles moving in the opposite direction that act against the SW beam and reduce the mean velocity as computed via moments. The new population, which occupies a larger velocitymore » space, also contributes to the second moment, increasing the temperature. The new particles include the reflected SW beam at the bow shock and another population of lower energies, accelerated nearby at the shock or at the boundary of the nonlinear structures.« less

A lower-limb training program to improve balance in healthy elderly women using the T-bow device.

PubMed

Chulvi-Medrano, Iván; Colado, Juan C; Pablos, Carlos; Naclerio, Fernando; García-Massó, Xavier

2009-06-01

Ageing impairs balance, which increases the risk of falls. Fall-related injuries are a serious health problem associated with dependency and disability in the elderly and results in high costs to public health systems. This study aims to determine the effects of a training program to develop balance using a new device called the T-Bow. A total of 28 women > 65 years were randomly assigned to an experimental group (EG) (n = 18; 69.50 [0.99] years), or a control group (CG) (n = 10; 70.70 [2.18] years). A program for lower limbs was applied for 8 weeks using 5 exercises on the T-Bow: squat, lateral and frontal swings, lunges, and plantarflexions. The intensity of the exercises was controlled by time of exposure, support base, and ratings of perceived exertion. Clinical tests were used to evaluate variables of balance. Static balance was measured by a 1-leg balance test (unipedal stance test), dynamic balance was measured by the 8-foot-up-and-go test, and overall balance was measured using the Tinetti test. Results for the EG showed an increase of 35.2% in static balance (P < 0.005), 12.7% in dynamic balance (P < 0.005), and 5.9% in overall balance (P > 0.05). Results for the CG showed a decline of 5.79% in static balance (P > 0.05) but no change in the other balance variables. Thus the data suggest that implementing a training program using the T-Bow could improve balance in healthy older women.

Direct observation of dynamical magnetization reversal process governed by shape anisotropy in single NiFe2O4 nanowire.

PubMed

Zhang, Junli; Zhu, Shimeng; Li, Hongli; Zhu, Liu; Hu, Yang; Xia, Weixing; Zhang, Xixiang; Peng, Yong; Fu, Jiecai

2018-05-31

Discovering how the magnetization reversal process is governed by the magnetic anisotropy in magnetic nanomaterials is essential and significant to understand the magnetic behaviour of micro-magnetics and to facilitate the design of magnetic nanostructures for diverse technological applications. In this study, we present a direct observation of a dynamical magnetization reversal process in single NiFe2O4 nanowire, thus clearly revealing the domination of shape anisotropy on its magnetic behaviour. Individual nanoparticles on the NiFe2O4 nanowire appear as single domain states in the remanence state, which is maintained until the magnetic field reaches 200 Oe. The magnetization reversal mechanism of the nanowire is observed to be a curling rotation mode. These observations are further verified by micromagnetic computational simulations. Our findings show that the modulation of shape anisotropy is an efficient way to tune the magnetic behaviours of cubic spinel nano-ferrites.

Broadband millimeter-wave GaAs transmitters and receivers using planar bow-tie antennas

NASA Technical Reports Server (NTRS)

Konishi, Y.; Kamegawa, M.; Case, M.; Yu, R.; Rodwell, M. J. W.; York, R. A.; Rutledge, D. B.

1992-01-01

We report broadband monolithic transmitters and receivers IC's for mm-wave electromagnetic measurements. The IC's use nonlinear transmission lines (NLTL) and sampling circuits as picosecond pulse generators and detectors. The pulses are radiated and received by planar monolithic bow-tie antennas, collimated with silicon substrate lenses and off-axis parabolic reflectors. Through Fourier transformation of the received pulse, 30-250 GHz free space gain-frequency measurements are demonstrated with an accuracy approximately = 0.17 dB, RMS.

Relativistic Electrons Produced by Foreshock Disturbances Observed Upstream of Earth's Bow Shock.

PubMed

Wilson, L B; Sibeck, D G; Turner, D L; Osmane, A; Caprioli, D; Angelopoulos, V

2016-11-18

Charged particles can be reflected and accelerated by strong (i.e., high Mach number) astrophysical collisionless shock waves, streaming away to form a foreshock region in communication with the shock. Foreshocks are primarily populated by suprathermal ions that can generate foreshock disturbances-large-scale (i.e., tens to thousands of thermal ion Larmor radii), transient (∼5-10  per day) structures. They have recently been found to accelerate ions to energies of several keV. Although electrons in Saturn's high Mach number (M>40) bow shock can be accelerated to relativistic energies (nearly 1000 keV), it has hitherto been thought impossible to accelerate electrons beyond a few tens of keV at Earth's low Mach number (1≤M<20) bow shock. Here we report observations of electrons energized by foreshock disturbances to energies up to at least ∼300  keV. Although such energetic electrons have been previously observed, their presence has been attributed to escaping magnetospheric particles or solar events. These relativistic electrons are not associated with any solar or magnetospheric activity. Further, due to their relatively small Larmor radii (compared to magnetic gradient scale lengths) and large thermal speeds (compared to shock speeds), no known shock acceleration mechanism can energize thermal electrons up to relativistic energies. The discovery of relativistic electrons associated with foreshock structures commonly generated in astrophysical shocks could provide a new paradigm for electron injections and acceleration in collisionless plasmas.

Electron Scattering by High-frequency Whistler Waves at Earth’s Bow Shock

NASA Astrophysics Data System (ADS)

Oka, M.; Wilson, L. B., III; Phan, T. D.; Hull, A. J.; Amano, T.; Hoshino, M.; Argall, M. R.; Le Contel, O.; Agapitov, O.; Gershman, D. J.; Khotyaintsev, Y. V.; Burch, J. L.; Torbert, R. B.; Pollock, C.; Dorelli, J. C.; Giles, B. L.; Moore, T. E.; Saito, Y.; Avanov, L. A.; Paterson, W.; Ergun, R. E.; Strangeway, R. J.; Russell, C. T.; Lindqvist, P. A.

2017-06-01

Electrons are accelerated to non-thermal energies at shocks in space and astrophysical environments. While different mechanisms of electron acceleration have been proposed, it remains unclear how non-thermal electrons are produced out of the thermal plasma pool. Here, we report in situ evidence of pitch-angle scattering of non-thermal electrons by whistler waves at Earth’s bow shock. On 2015 November 4, the Magnetospheric Multiscale (MMS) mission crossed the bow shock with an Alfvén Mach number ˜11 and a shock angle ˜84°. In the ramp and overshoot regions, MMS revealed bursty enhancements of non-thermal (0.5-2 keV) electron flux, correlated with high-frequency (0.2-0.4 {{{Ω }}}{ce}, where {{{Ω }}}{ce} is the cyclotron frequency) parallel-propagating whistler waves. The electron velocity distribution (measured at 30 ms cadence) showed an enhanced gradient of phase-space density at and around the region where the electron velocity component parallel to the magnetic field matched the resonant energy inferred from the wave frequency range. The flux of 0.5 keV electrons (measured at 1 ms cadence) showed fluctuations with the same frequency. These features indicate that non-thermal electrons were pitch-angle scattered by cyclotron resonance with the high-frequency whistler waves. However, the precise role of the pitch-angle scattering by the higher-frequency whistler waves and possible nonlinear effects in the electron acceleration process remains unclear.

Relativistic Electrons Produced by Foreshock Disturbances Observed Upstream of Earth's Bow Shock

NASA Technical Reports Server (NTRS)

Wilson, L. B., III; Sibeck, D. G.; Turner, D. L.; Osmane, A.; Caprioli, D.; Angelopoulos, V.

2016-01-01

Charged particles can be reflected and accelerated by strong (i.e., high Mach number) astrophysical collisionless shock waves, streaming away to form a foreshock region in communication with the shock. Foreshocks are primarily populated by suprathermal ions that can generate foreshock disturbances-largescale (i.e., tens to thousands of thermal ion Larmor radii), transient (approximately 5-10 per day) structures. They have recently been found to accelerate ions to energies of several keV. Although electrons in Saturn's high Mach number (M > 40) bow shock can be accelerated to relativistic energies (nearly 1000 keV), it has hitherto been thought impossible to accelerate electrons beyond a few tens of keV at Earth's low Mach number (1 =M <20) bow shock. Here we report observations of electrons energized by foreshock disturbances to energies up to at least approximately 300 keV. Although such energetic electrons have been previously observed, their presence has been attributed to escaping magnetospheric particles or solar events. These relativistic electrons are not associated with any solar or magnetospheric activity. Further, due to their relatively small Larmor radii (compared to magnetic gradient scale lengths) and large thermal speeds (compared to shock speeds), no known shock acceleration mechanism can energize thermal electrons up to relativistic energies. The discovery of relativistic electrons associated with foreshock structures commonly generated in astrophysical shocks could provide a new paradigm for electron injections and acceleration in collisionless plasmas.

Maskless direct laser writing with visible light: Breaking through the optical resolving limit with cooperative manipulations of nonlinear reverse saturation absorption and thermal diffusion

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

Wei, Jingsong, E-mail: weijingsong@siom.ac.cn; Wang, Rui; University of Chinese Academy of Sciences, Beijing 100049

In this work, the resolving limit of maskless direct laser writing is overcome by cooperative manipulation from nonlinear reverse saturation absorption and thermal diffusion, where the nonlinear reverse saturation absorption can induce the formation of below diffraction-limited energy absorption spot, and the thermal diffusion manipulation can make the heat quantity at the central region of energy absorption spot propagate along the thin film thickness direction. The temperature at the central region of energy absorption spot transiently reaches up to melting point and realizes nanolithography. The sample “glass substrate/AgInSbTe” is prepared, where AgInSbTe is taken as nonlinear reverse saturation absorption thinmore » film. The below diffraction-limited energy absorption spot is simulated theoretically and verified experimentally by near-field spot scanning method. The “glass substrate/Al/AgInSbTe” sample is prepared, where the Al is used as thermal conductive layer to manipulate the thermal diffusion channel because the thermal diffusivity coefficient of Al is much larger than that of AgInSbTe. The direct laser writing is conducted by a setup with a laser wavelength of 650 nm and a converging lens of NA=0.85, the lithographic marks with a size of about 100 nm are obtained, and the size is only about 1/10 the incident focused spot. The experimental results indicate that the cooperative manipulation from nonlinear reverse saturation absorption and thermal diffusion is a good method to realize nanolithography in maskless direct laser writing with visible light.« less

Time-reversed, flow-reversed ballistics simulations

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

Zernow, L.; Chapyak, E. J.; Scheffler, D. R.

2001-01-01

Two-dimensional simulations of planar sheet jet formation are studied to examine the hydrodynamic issues involved when simulations are carried out in the inverse direction, that is, with reversed time and flow. Both a realistic copper equation of state and a shockless equation of state were used. These studies are an initial step in evaluating this technique as a ballistics design tool.

Remote radio observations of solar wind parameters upstream of planetary bow shocks

NASA Technical Reports Server (NTRS)

Macdowall, R. J.; Stone, R. G.; Gaffey, J. D., Jr.

1992-01-01

Radio emission is frequently produced at twice the electron plasma frequency 2fp in the foreshock region upstream of the terrestrial bow shock. Observations of this emission provide a remote diagnostic of solar wind parameters in the foreshock. Using ISEE-3 radio data, we present the first evidence that the radio intensity is proportional to the kinetic energy flux and to other parameters correlated with solar wind density. We provide a qualitative explanation of this intensity behavior and predict the detection of similar emission at Jupiter by the Ulysses spacecraft.

Beams of protons and alpha particles greater than approximately 30 keV/charge from the earth's bow shock

NASA Technical Reports Server (NTRS)

Scholer, M.; Ipavich, F. M.; Gloeckler, G.

1981-01-01

Two beamlike particle events (30 keV/charge to 160 keV/charge) upstream of the earth's bow shock have been investigated with the Max-Planck-Institut/University of Maryland ultralow energy and charge analyzer on ISEE 1. These beams consist of protons as well as of alpha particles, and the spectra are generally steep and are decreasing with increasing energy. During one event the spectra of both protons and alpha particles have a maximum at approximately 65 keV/charge. During these events, the interplanetary magnetic field through the satellite position was almost tangent to the bow shock, and application of the theory of acceleration predicts acceleration of a solar wind particle up to 60 keV/nucleon in a single reflection. The observation of reflected protons as well as alpha particles has implications for the physical reflection process usually not discussed in acceleration theories.

Kinetic theory for the ion humps at the foot of the Earth's bow shock

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

Jovanovic, D.; Krasnoselskikh, V. V.

2009-10-15

The nonlinear kinetic theory is presented for the ion acoustic perturbations at the foot of the Earth's quasiperpendicular bow shock, that is characterized by weakly magnetized electrons and unmagnetized ions. The streaming ions, due to the reflection of the solar wind ions from the shock, provide the free energy source for the linear instability of the acoustic wave. In the fully nonlinear regime, a coherent localized solution is found in the form of a stationary ion hump, which is traveling with the velocity close to the phase velocity of the linear mode. The structure is supported by the nonlinearities comingmore » from the increased population of the resonant beam ions, trapped in the self-consistent potential. As their size in the direction perpendicular to the local magnetic field is somewhat smaller that the electron Larmor radius and much larger that the Debye length, their spatial properties are determined by the effects of the magnetic field on weakly magnetized electrons. These coherent structures provide a theoretical explanation for the bipolar electric pulses, observed upstream of the shock by Polar and Cluster satellite missions.« less

Particle injection and acceleration at earth's bow shock - Comparison of upstream and downstream events

NASA Technical Reports Server (NTRS)

Ellison, Donald C.; Moebius, Eberhard; Paschmann, Goetz

1990-01-01

The injection and acceleration of thermal solar wind ions at the quasi-parallel earth's bow shock during radial interplanetary magnetic field conditions is investigated. Active Magnetospheric Particle Tracer Explorers/Ion Release Module satellite observations of complete proton spectra, and of heavy ion spectra above 10 keV/Q, made on September 12, 1984 near the nose of the shock, are presented and compared to the predictions of a Monte Carlo shock simulation which includes diffusive shock acceleration. It is found that the spectral observations are in good agreement with the predictions of the simulation when it is assumed that all accelerated ions originate in the solar wind and are injected into the acceleration mechanism by thermal leakage from the downstream plasma. The efficiency, which is determined directly from the downstream observations, is high, with at least 15 percent of the solar wind energy flux going into accelerated particles. The comparisons allow constraints to be placed on the rigidity dependence of the scattering mean free path and suggest that the upstream solar wind must be slowed substantially by backstreaming accelerated ions prior to undergoing a sharp transition in the viscous subshock.

Parametric interaction and spatial collapse of beam-driven Langmuir waves in the solar wind. [upstream of Jupiter bow shock

NASA Technical Reports Server (NTRS)

Gurnett, D. A.; Maggs, J. E.; Gallagher, D. L.; Kurth, W. S.; Scarf, F. L.

1981-01-01

Observations are presented of the parametric decay and spatial collapse of Langmuir waves driven by an electron beam streaming into the solar wind from the Jovian bow shock. Long wavelength Langmuir waves upstream of the bow shock are effectively converted into short wavelength waves no longer in resonance with the beam. The conversion is shown to be the result of a nonlinear interaction involving the beam-driven pump, a sideband emission, and a low level of ion-acoustic turbulence. The beam-driven Langmuir wave emission breaks up into a complex sideband structure with both positive and negative Doppler shifts. In some cases, the sideband emission consists of isolated wave packets with very short duration bursts, which are very intense and are thought to consist of envelope solitons which have collapsed to spatial scales of only a few Debye lengths.

Geophysics: A reversal of geomagnetic polarity

USGS Publications Warehouse

Mankinen, Edward A.

1986-01-01

The detailed behaviour of the geomagnetic field during reversals is documented by palaeomagnetists to constrain models of the geomagnetic dynamo. Reversals are studied by measuring the magnetic remanence preserved in rocks to obtain both the direction and intensity of the ancient magnetic field.

The Interaction of Solar wind Discontinuities with the Earth's Bow Shock

NASA Technical Reports Server (NTRS)

Sibeck, David G.

2000-01-01

Funding from NASA Grant No. NAG54679 was received in three installments. The first year's installment amounted to only one month of salary support and was used to prepare survey plots. The second year's installment allowed us to complete two research papers concerning the interaction of solar wind discontinuities with the Earth's bow shock. In the first (published) paper, we reported that the discontinuities launch slow mode waves into the magnetosheath and the slow mode waves always propagate antisunward through the flank magnetosheath. Because the sunward/antisunward sense of the magnetosheath magnetic field reverses across local noon, so does the (north/south or east/west) sense of the velocity fluctuations associated with the waves. Wind, Geotail, and IMP-8 observations were used for this study. In the second study, we used Wind and Interball-1 observations to demonstrate that pressure pulses in the magnetosheath occur in pairs and that they bound pressure cavities and/or brief intervals of outward magnetopause motion. This paper is now in press. Funding from the third year's installment has been used to investigate the two aspects of the foreshock. Two manuscripts are now in preparation for submission to the Journal of Geophysical Research. The first reports that waves within the foreshock account for many instances of poor correlations between two solar wind monitors. Remaining cases of poor correlation occur during intervals of nearly constant IMF orientations and magnetic field strengths. While the former category pose a significant difficulty for space weather forecasts, the latter do not. The second study surveys IMP-8 observations of the foreshock. We find that diamagnetic cavities are common, particularly during periods of high solar wind velocity and low solar wind density. Plasma densities, temperatures, and magnetic field strengths fall during intervals of enhanced energetic particle fluxes. The cavities are bounded by regions of decelerated solar

Ionospheric Bow Waves and Perturbations Induced by the 21 August 2017 Solar Eclipse

NASA Astrophysics Data System (ADS)

Zhang, Shun-Rong; Erickson, Philip J.; Goncharenko, Larisa P.; Coster, Anthea J.; Rideout, William; Vierinen, Juha

2017-12-01

During solar eclipses, the Moon's shadow causes a large reduction in atmospheric energy input, including not only the stratosphere but also the thermosphere and ionosphere. The eclipse shadow has a supersonic motion which is theoretically expected to generate atmospheric bow waves, similar to a fast-moving river boat, with waves starting in the lower atmosphere and propagating into the ionosphere. However, previous geographically limited observations have had difficulty detecting these weak waves within the natural background atmospheric variability, and the existence of eclipse-induced ionospheric waves and their evolution in a complex coupling system remain controversial. During the 21 August 2017 eclipse, high fidelity and wide coverage ionospheric observations provided for the first time an oversampled set of eclipse data, using a dense network of Global Navigation Satellite System receivers at ˜2,000 sites in North America. We show the first unambiguous evidence of ionospheric bow waves as electron content disturbances over central/eastern United States, with ˜1 h duration, 300-400 km wavelength and 280 m/s phase speed emanating from and tailing the totality region. We also identify large ionospheric perturbations moving at the supersonic speed of the maximum solar obscuration which are too fast to be associated with known gravity wave or large-scale traveling ionospheric disturbance processes. This study reveals complex interconnections between the Sun, Moon, and Earth's neutral atmosphere and ionosphere and demonstrates persistent coupling processes between different components of the Earth's atmosphere, a topic of significant community interest.

Sex Reversal in Birds.

PubMed

Major, Andrew T; Smith, Craig A

2016-01-01

Sexual differentiation in birds is controlled genetically as in mammals, although the sex chromosomes are different. Males have a ZZ sex chromosome constitution, while females are ZW. Gene(s) on the sex chromosomes must initiate gonadal sex differentiation during embryonic life, inducing paired testes in ZZ individuals and unilateral ovaries in ZW individuals. The traditional view of avian sexual differentiation aligns with that expounded for other vertebrates; upon sexual differentiation, the gonads secrete sex steroid hormones that masculinise or feminise the rest of the body. However, recent studies on naturally occurring or experimentally induced avian sex reversal suggest a significant role for direct genetic factors, in addition to sex hormones, in regulating sexual differentiation of the soma in birds. This review will provide an overview of sex determination in birds and both naturally and experimentally induced sex reversal, with emphasis on the key role of oestrogen. We then consider how recent studies on sex reversal and gynandromorphic birds (half male:half female) are shaping our understanding of sexual differentiation in avians and in vertebrates more broadly. Current evidence shows that sexual differentiation in birds is a mix of direct genetic and hormonal mechanisms. Perturbation of either of these components may lead to sex reversal. © 2016 S. Karger AG, Basel.

Near real time determination of the magnetopause and bow shock shape and position

NASA Astrophysics Data System (ADS)

Kartalev, M. D.; Keremidarska, V. I.; Grigorov, K. G.; Romanov, D. K.

2002-03-01

We present a web based near real time (once in 90 minutes) automated running of our 3D magnetosheath gasdynamic numerical model. (http://geospace.nat.bg). The determination of the shape and position of the bow shock and the magnetopause is a part of the solution. This approach of the model is utilizing the realistic semi-empirical Tsyganenko magnetosphere model T96-01 for ensuring the pressure balance at the magnetopause. In this realization, we use a real time ACE data, averaged over a 6 minutes time interval.

Delineating functional principles of the bow tie structure of a kinase-phosphatase network in the budding yeast.

PubMed

Abd-Rabbo, Diala; Michnick, Stephen W

2017-03-16

Kinases and phosphatases (KP) form complex self-regulating networks essential for cellular signal processing. In spite of having a wealth of data about interactions among KPs and their substrates, we have very limited models of the structures of the directed networks they form and consequently our ability to formulate hypotheses about how their structure determines the flow of information in these networks is restricted. We assembled and studied the largest bona fide kinase-phosphatase network (KP-Net) known to date for the yeast Saccharomyces cerevisiae. Application of the vertex sort (VS) algorithm on the KP-Net allowed us to elucidate its hierarchical structure in which nodes are sorted into top, core and bottom layers, forming a bow tie structure with a strongly connected core layer. Surprisingly, phosphatases tend to sort into the top layer, implying they are less regulated by phosphorylation than kinases. Superposition of the widest range of KP biological properties over the KP-Net hierarchy shows that core layer KPs: (i), receive the largest number of inputs; (ii), form bottlenecks implicated in multiple pathways and in decision-making; (iii), and are among the most regulated KPs both temporally and spatially. Moreover, top layer KPs are more abundant and less noisy than those in the bottom layer. Finally, we showed that the VS algorithm depends on node degrees without biasing the biological results of the sorted network. The VS algorithm is available as an R package ( https://cran.r-project.org/web/packages/VertexSort/index.html ). The KP-Net model we propose possesses a bow tie hierarchical structure in which the top layer appears to ensure highest fidelity and the core layer appears to mediate signal integration and cell state-dependent signal interpretation. Our model of the yeast KP-Net provides both functional insight into its organization as we understand today and a framework for future investigation of information processing in yeast and eukaryotes

Dynamics of bow-tie shaped bursting: Forced pendulum with dynamic feedback.

PubMed

Hongray, Thotreithem; Balakrishnan, Janaki

2016-12-01

A detailed study is performed on the parameter space of the mechanical system of a driven pendulum with damping and constant torque under feedback control. We report an interesting bow-tie shaped bursting oscillatory behaviour, which is exhibited for small driving frequencies, in a certain parameter regime, which has not been reported earlier in this forced system with dynamic feedback. We show that the bursting oscillations are caused because of a transition of the quiescent state to the spiking state by a saddle-focus bifurcation, and because of another saddle-focus bifurcation, which leads to cessation of spiking, bringing the system back to the quiescent state. The resting period between two successive bursts (T rest ) is estimated analytically.

Band-gap bowing and p-type doping of (Zn, Mg, Be)O wide-gap semiconductor alloys: a first-principles study

NASA Astrophysics Data System (ADS)

Shi, H.-L.; Duan, Y.

2008-12-01

Using a first-principles band-structure method and a special quasirandom structure (SQS) approach, we systematically calculate the band gap bowing parameters and p-type doping properties of (Zn, Mg, Be)O related random ternary and quaternary alloys. We show that the bowing parameters for ZnBeO and MgBeO alloys are large and dependent on composition. This is due to the size difference and chemical mismatch between Be and Zn(Mg) atoms. We also demonstrate that adding a small amount of Be into MgO reduces the band gap indicating that the bowing parameter is larger than the band-gap difference. We select an ideal N atom with lower p atomic energy level as dopant to perform p-type doping of ZnBeO and ZnMgBeO alloys. For N doped in ZnBeO alloy, we show that the acceptor transition energies become shallower as the number of the nearest neighbor Be atoms increases. This is thought to be because of the reduction of p- d repulsion. The NO acceptor transition energies are deep in the ZnMgBeO quaternary alloy lattice-matched to GaN substrate due to the lower valence band maximum. These decrease slightly as there are more nearest neighbor Mg atoms surrounding the N dopant. The important natural valence band alignment between ZnO, MgO, BeO, ZnBeO, and ZnMgBeO quaternary alloy is also investigated.

Structure of a quasi-parallel, quasi-laminar bow shock

NASA Technical Reports Server (NTRS)

Greenstadt, E. W.; Russell, C. T.; Formisano, V.; Hedgecock, P. C.; Scarf, F. L.; Neugebauer, M.; Holzer, R. E.

1976-01-01

A thick, quasi-parallel bow shock structure was observed with field and particle detectors of both HEOS 1 and OGO 5. The typical magnetic pulsation structure was at least 1 to 2 earth radii thick radially and was accompanied by irregular but distinct plasma distributions characteristic of neither the solar wind nor the magnetosheath. Waves constituting the large pulsations were polarized principally in the plane of the nominal shock, therefore also in the plane perpendicular to the average interplanetary field. A separate interpulsation regime detected between bursts of large amplitude oscillations was similar to the upstream wave region magnetically, but was characterized by disturbed plasma flux and enhanced noise around the ion plasma frequency. The shock structure appeared to be largely of an oblique, whistler type, probably complicated by counterstreaming high energy protons. Evidence for firehose instability-based structure was weak at best and probably negative.

Static Holes in Geometrically Frustrated Bow Tie Ladder

NASA Astrophysics Data System (ADS)

Martins, George; Brenig, Wolfram

2007-03-01

Doping of the geometrically frustrated bow-tie spin ladder with static holes is investigated by a complementary approach using exact diagonalization and hard-core quantum dimers. Results for the thermodynamics in the undoped case, the singlet density of states, the hole-binding energy, and the spin correlations will be presented. We find that the static holes polarize their vicinity by a localization of singlets in order to reduce the frustration. As a consequence the singlet polarization cloud induces short range repulsive forces between the holes with oscillatory longer range behavior. For those systems we have studied, most results for the quantum dimer approach are found to be qualitatively if not quantitatively in agreement with exact diagonalization. The ground state of the undoped system is non-degenerate with translationally invariant nearest-neighbor spin correlations up to a few unit cells, which is consistent with a spin liquid state or a valence bond crystal with very large unit cell. C. Waldtmann, A. Kreutzmann, U. Schollwock, K. Maisinger, and H.-U. Everts, Phys. Rev. B 62, 9472 (2000).

Magnetohydrodynamic and gasdynamic theories for planetary bow waves

NASA Technical Reports Server (NTRS)

Spreiter, J. R.; Stahara, S. S.

1984-01-01

The observed properties of bow waves and the associated plasma flows are outlined, along with those features identified that can be described by a continuum magnetohydrodynamic flow theory as opposed to a more detailed multicomponent particle and field plasma theory. The primary objectives are to provide an account of the fundamental concepts and current status of the magnetohydrodynamic and gas dynamic theories for solar wind flow past planetary bodies. This includes a critical examination of: (1) the fundamental assumptions of the theories; (2) the various simplifying approximations introduced to obtain tractable mathematical problems; (3) the limitations they impose on the results; and (4) the relationship between the results of the simpler gas dynamic-frozen field theory and the more accurate but less completely worked out magnetohydrodynamic theory. Representative results of the various theories are presented and compared. A number of deficiencies, ambiguities, and suggestions for improvements are discussed, and several significant extensions of the theory required to provide comparable results for all planets, their satellites, and comets are noted.

Magnetic field analysis of the bow and terminal shock of the SS 433 jet

NASA Astrophysics Data System (ADS)

Sakemi, Haruka; Machida, Mami; Akahori, Takuya; Nakanishi, Hiroyuki; Akamatsu, Hiroki; Kurahara, Kohei; Farnes, Jamie

2018-03-01

We report a polarization analysis of the eastern region of W 50, observed with the Australia Telescope Compact Array (ATCA) at 1.4-3.0 GHz. In order to study the physical structures in the region where the SS 433 jet and W 50 interact, we obtain an intrinsic magnetic field vector map of that region. We find that the orientation of the intrinsic magnetic field vectors are aligned along the total intensity structures, and that there are characteristic, separate structures related to the jet, the bow shock, and the terminal shock. The Faraday rotation measures (RMs), and the results of Faraday tomography suggest that a high-intensity, filamentary structure in the north-south direction of the eastern-edge region can be separated into at least two parts to the north and south. The results of Faraday tomography also show that there are multiple components along the line of sight and/or within the beam area. In addition, we analyze the X-ray ring-like structure observed with XMM-Newton. While the possibility still remains that this X-ray ring is "real", it seems that the structure is not ring-like at radio wavelengths. Finally, we suggest that the structure is a part of the helical structure that coils the eastern ear of W 50.

Numerical Study of a Three Dimensional Interaction between two bow Shock Waves and the Aerodynamic Heating on a Wedge Shaped Nose Cone

NASA Astrophysics Data System (ADS)

Wu, N.; Wang, J. H.; Shen, L.

2017-03-01

This paper presents a numerical investigation on the three-dimensional interaction between two bow shock waves in two environments, i.e. ground high-enthalpy wind tunnel test and real space flight, using Fluent 15.0. The first bow shock wave, also called induced shock wave, which is generated by the leading edge of a hypersonic vehicle. The other bow shock wave can be deemed objective shock wave, which is generated by the cowl clip of hypersonic inlet, and in this paper the inlet is represented by a wedge shaped nose cone. The interaction performances including flow field structures, aerodynamic pressure and heating are analyzed and compared between the ground test and the real space flight. Through the analysis and comparison, we can find the following important phenomena: 1) Three-dimensional complicated flow structures appear in both cases, but only in the real space flight condition, a local two-dimensional type IV interaction appears; 2) The heat flux and pressure in the interaction region are much larger than those in the no-interaction region in both cases, but the peak values of the heat flux and pressure in real space flight are smaller than those in ground test. 3) The interaction region on the objective surface are different in the two cases, and there is a peak value displacement of 3 mm along the stagnation line.

Risk analysis using AS/NZS 4360:2004, Bow-Tie diagram and ALARP on construction projects of Banyumanik Hospital

NASA Astrophysics Data System (ADS)

Sari, Diana Puspita; Pujotomo, Darminto; Wardani, Nadira Kusuma

2017-11-01

The Determination of risk is an uncertain event. Risks can have negative or positive impacts on project objectives. A project was defined as a series of activities and tasks that have a purpose, specifications, and limits of cost. Banyumanik Hospital Development Project is one of the construction projects in Semarang which have experienced some problems. The first problem is project delays on building stake. The second problem is delay of material supply. Finally, the problem that occurs is less management attention to health safety as evidenced by the unavailability of PPE for the workers. These problems will pose a risk to be a very important risk management performed by contractors at the Banyumanik Hospital Development Project to reduce the impact that would be caused by the risk borne by the provider of construction services. This research aim to risk identification, risk assessment and risk mitigation. Project risk management begins with the identification of risks based on the project life cycle. The risk assessment carried out by AS I NZS 4360: 2004 to the impacts of cost, time and quality. The results obtained from the method of AS I NZS 4360: 2004 is the risk that requires the handling of mitigation. Mitigated risk is the risk that had significant and high level. There are four risks that require risk mitigation with Bow-Tie diagrams which is work accidents, contract delays, material delays and design changes. Bow-Tie diagram method is a method for identifying causal and preventive action and recovery of a risk. Results obtained from Bow-Tie diagram method is a preventive action and recovery. This action is used as input to the ALARP method. ALARP method is used to determine the priority of the strategy proposed in the category broadly acceptable, tolerable, and unacceptable.

Is "Bow" for an Arrow or for Hair? A Classroom Demonstration on Gender Differences in Interpreting Ambiguous Information

ERIC Educational Resources Information Center

Fa-Kaji, Naomi; Nguyen, Linda; Hebl, Mikki; Skorinko, Jeanine

2016-01-01

This article details a classroom demonstration of how gender differences in cognitive schemas can result in men and women differentially interpreting the same information. Students heard a series of six homonyms (e.g., bow and nail) spoken aloud and wrote down the first word with which they free-associated each homonym. When hearing the words…

Temperature and field direction dependences of first-order reversal curve (FORC) diagrams of hot-deformed Nd-Fe-B magnets

NASA Astrophysics Data System (ADS)

Yomogita, Takahiro; Okamoto, Satoshi; Kikuchi, Nobuaki; Kitakami, Osamu; Sepehri-Amin, Hossein; Ohkubo, Tadakatsu; Hono, Kazuhiro; Akiya, Takahiro; Hioki, Keiko; Hattori, Atsushi

2018-02-01

First-order reversal curve (FORC) diagram has been previously adopted for the analyses of magnetization reversal process and/or quantitative evaluation of coercivity and interaction field dispersions in various magnetic samples. Although these kinds of information are valuable for permanent magnets, previously reported FORC diagrams of sintered Nd-Fe-B magnets exhibit very complicated patterns. In this paper, we have studied the FORC diagrams of hot-deformed Nd-Fe-B magnets under various conditions. Contrary to the previous reports on sintered Nd-Fe-B magnets, the FORC diagram of the hot-deformed Nd-Fe-B magnet exhibits a very simple pattern consisting of a strong spot and a weak line. From this FORC diagram pattern, it is revealed that the coercivity dispersion of the hot-deformed Nd-Fe-B magnets is surprisingly small. Moreover, this feature of the FORC diagram pattern is very robust and unaffected by changes in various conditions such as grain boundary diffusion process, temperature, and field direction, whereas these conditions significantly change the coercivity and the shape of magnetization curve. This fact indicates that the magnetization reversal process of the hot-deformed Nd-Fe-B magnets is almost unchanged against these conditions.

The topology of intrasector reversals of the interplanetary magnetic field

NASA Astrophysics Data System (ADS)

Kahler, S. W.; Crooker, N. U.; Gosling, J. T.

1996-11-01

A technique has been developed recently to determine the polarities of interplanetary magnetic fields relative to their origins at the Sun by comparing energetic electron flow directions with local magnetic field directions. Here we use heat flux electrons from the Los Alamos National Laboratory (LANL) plasma detector on the ISEE 3 spacecraft to determine the field polarities. We examine periods within well-defined magnetic sectors when the field directions appear to be reversed from the normal spiral direction of the sector. About half of these intrasector field reversals (IFRs) are cases in which the polarities match those of the surrounding sectors, indicating that those fields have been folded back toward the Sun. The more interesting cases are those with polarity reversals. We find no clear cases of isolated reverse polarity fields, which suggests that islands of reverse polarity in the solar source dipole field probably do not exist. The IFRs with polarity reversals are strongly associated with periods of bidirectional electron flows, suggesting that those fields occur only in conjunction with closed fields. We propose that both those IFRs and the bidirectional flows are signatures of coronal mass ejections (CMEs). In that case, many interplanetary CMEs are larger and more complex than previously thought, consisting of both open and closed field components.

A Multi-wavelength Study of an Isolated MSP Bow Shock

NASA Astrophysics Data System (ADS)

Romani, Roger W.; Slane, Patrick; Green, Andrew

2017-08-01

PSR J2124-3358 is the only single MSP known to sport an Halpha bow shock. This shock, now also seen in the UV, encloses an unusual X-ray pulsar wind nebula (PWN) with a long off-axis trail. Combining the X-ray and UV images with AAT/KOALA integral field spectroscopy of the Halpha emission, we have an unusually complete picture of the pulsar's (101 km/s transverse) motion and the latitudinal distribution of its wind flux. These images reveal the 3-D orientation of a hard-spectrum PWN jet and a softer equatorial outflow. Within the context of a thin shock model, we can constrain the total energy output of the pulsar and the neutron star moment of inertia. The IFU spectra show extreme Balmer dominance, which also constrains the nature of the UV shock emission.

[Direct determination of purine bases in tea by reversed-phase high performance liquid chromatography].

PubMed

Ding, M; Yang, H; Xiao, S; Chen, P

1999-09-01

A reversed-phase high performance liquid chromatographic(RP-HPLC) method for the direct determination of three purine bases(theobromin, theophyllin and caffeine) in tea was developed. An ODS column with Zorbax SB-C18(4.6 mm i.d. x 250 mm, 5 microns) was employed. The aqueous solution of methanol containing 0.05% of acetic acid and 0.25% of N,N-dimethylformamide(DMF) was used as eluent with a flow rate of 0.8 mL/min. In this method, the aqueous extract of tea can be injected into HPLC directly, but in current HPLC methods for purine bases the coexisted tea polyphenols must be pre-separated. The three purine bases in tea were separated without any interference from the coexisted tea polyphenols. This method is simple (without any special sample pretreatment) and sensitive with detection limits (S/N = 3) of 0.7, 0.9 and 1.8 mg/L for theobromin, theophyllin and caffeine respectively. The linear range of the calibration curve of peak area for the three purine bases were from 6 mg/L to 1,000 mg/L with a correlation coefficient (r) of 0.998-0.999.

Modified technique for correction of isolated radial head dislocation without apparent ulnar bowing: a retrospective case study

PubMed Central

Tan, Lei; Li, Yan-Hui; Sun, Da-Hui; Zhu, Dong; Ning, Shu-Yan

2015-01-01

Objective: There is currently no general consensus on the optimal treatment of chronic radial head dislocation. Material and Methods: Considering that the annular ligament is important in maintaining elbow stability, we developed a modified method for annular ligament reconstruction in pediatric cases of radial head dislocation without ulnar bowing. We retrospectively investigated the therapeutic outcomes of this technique in a series of cases. We used our modified technique for the treatment of five patients between January 2006 and January 2012. The average age of the patients at the time of injury was 9 years (range, 6-14 years), and the patients were followed up for 1 to 3 years. Results: The perioperative and follow-up data of the patients were examined. All five surgical procedures were completed uneventfully and had been tolerated well by the patients, with minimal complications. Remarkable improvement was noted in all the cases at the end of the follow-up period. Conclusions: Our modified technique for annular ligament reconstruction was effective in achieving good reduction of the radial head dislocation with minimal complications in pediatric cases of isolated radial head dislocation without apparent ulnar bowing. PMID:26770420

How Uganda Reversed Its HIV Epidemic

PubMed Central

Okware, Sam; Naamara, Warren; Sutherland, Don; Flanagan, Donna; Carael, Michel; Blas, Erik; Delay, Paul; Tarantola, Daniel

2006-01-01

Uganda is one of only two countries in the world that has successfully reversed the course of its HIV epidemic. There remains much controversy about how Uganda's HIV prevalence declined in the 1990s. This article describes the prevention programs and activities that were implemented in Uganda during critical years in its HIV epidemic, 1987 to 1994. Multiple resources were aggregated to fuel HV prevention campaigns at multiple levels to a far greater degree than in neighboring countries. We conclude that the reversed direction of the HIV epidemic in Uganda was the direct result of these interventions and that other countries in the developing world could similarly prevent or reverse the escalation of HIV epidemics with greater availability of HIV prevention resources, and well designed programs that take efforts to a critical breadth and depth of effort. PMID:16858635

Tranexamic Acid Failed to Reverse the Anticoagulant Effect and Bleeding by an Oral Direct Factor Xa Inhibitor Edoxaban.

PubMed

Honda, Yuko; Furugohri, Taketoshi; Morishima, Yoshiyuki

2018-01-01

Agents to reverse the anticoagulant effect of edoxaban, an oral direct factor Xa inhibitor, would be desirable in emergency situations. The aim of this study is to determine the effect of tranexamic acid, an antifibrinolytic agent, on the anticoagulant activity and bleeding by edoxaban in rats. A supratherapeutic dose of edoxaban (3 mg/kg) was intravenously administered to rats. Three minutes after dosing, tranexamic acid (100 mg/kg) was given intravenously. Bleeding was induced by making an incision with a blade on the planta 8 min after edoxaban injection and bleeding time was measured. Prothrombin time (PT) and clot lysis were examined. A supratherapeutic dose of edoxaban significantly prolonged PT and bleeding time. Tranexamic acid did not affect PT or bleeding time prolonged by edoxaban, although tranexamic acid significantly inhibited clot lysis in rat plasma. An antifibrinolytic agent tranexamic acid failed to reverse the anticoagulant effect and bleeding by edoxaban in rats. © 2017 S. Karger AG, Basel.

Numerical investigation of the bowed stator effects in a transonic fan at low Reynolds number

NASA Astrophysics Data System (ADS)

Huang, Enliang; Zhao, Shengfeng; Gong, Jianbo; Lu, Xingen; Zhu, Junqiang

2017-02-01

The performance of fan stage in a small turbofan engines is significantly affected at high-altitude low Reynolds number. In order to examine the effect of low Reynolds number on the fan stage, 3D numerical simulation method was employed to analyse the performance variations and the underlying flow structure in the fan stage. For the sake of decreasing the influence of low Reynolds number, the different bowed stator airfoils were redesigned and the effect of the modified design was evaluated.

Four Years of Venus Express Magnetic Field Observations: Variable Bow Shock Location and Other Features

NASA Astrophysics Data System (ADS)

Zhang, Tielong; Baumjohann, Wolfgang; Russell, C. T.

Since the Venus Express insertion into a highly elliptical polar orbit with a period of 24 h around the planet Venus, the magnetometer has operated continuously for about 4 years and obtained a wealth of data in the solar minimum at rather low altitude, which was not reached by earlier missions. In this paper, we review the magnetic field observations by Venus Express emphasizing on the variable bow shock location and other space environment features such as the magnetic barrier and the magnetotail.

X-RAY OBSERVATIONS OF BOW SHOCKS AROUND RUNAWAY O STARS. THE CASE OF ζ OPH AND BD+43°3654

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

Toalá, J. A.; Guerrero, M. A.; Oskinova, L. M.

2016-04-20

Non-thermal radiation has been predicted within bow shocks around runaway stars by recent theoretical works. We present X-ray observations toward the runaway stars ζ Oph by Chandra and Suzaku and of BD+43°3654 by XMM-Newton to search for the presence of non-thermal X-ray emission. We found no evidence of non-thermal emission spatially coincident with the bow shocks; nonetheless, diffuse emission was detected in the vicinity of ζ Oph. After a careful analysis of its spectral characteristics, we conclude that this emission has a thermal nature with a plasma temperature of T ≈ 2 × 10{sup 6} K. The cometary shape ofmore » this emission seems to be in line with recent predictions of radiation-hydrodynamic models of runaway stars. The case of BD+43°3654 is puzzling, as non-thermal emission has been reported in a previous work for this source.« less

Similarities and Differences between the Termination Foreshock/ Bow Shock and Planetary Bow Shocks

NASA Astrophysics Data System (ADS)

Krimigis, S. M.; Decker, R. B.; Roelof, E. C.; Hill, M. E.

2006-05-01

It is now evident that Voyager 1 (V1) entered the termination foreshock (TFS) at ~~85 AU in mid-2002, exited this region in early 2003 and re-entered in the late 2003-early 2004 time frame, before finally crossing the termination shock (TS) at ~~94 AU on December 16, 2004. The TFS region is characterized by large intensities of tangentially outward-moving beams of energetic ions E > 40 keV, and generally isotropic electron intensity increases E > 350 keV (Krimigis et al, 2003; Decker et al, 2005). Elevated magnetic field intensities were observed throughout these periods (Burlaga et al, 2003, 2005) and comparison with particle pressures showed this region to be a high-beta plasma (Krimigis et al, 2004, 2005). Proximity of the TS was also evident from occasional electron plasma oscillations seen as early as 91 AU (Gurnett and Kurth, 2005). In this paper we examine the extent to which the TFS and TS exhibit properties seen in planetary bow shocks using data from Voyager?s flyby of the outer planets and Cassini data in the vicinity of Saturn. Magnetic field distributions in these high-beta regions appear to be Gaussian. A possible source for the TSF particles is the supertherma1 population residing in the heliosheath, similar to upstream ions observed leaking from planetary magnetospheres. Krimigis, S.M. et al, Nature, 426, pg 45-48, 2003. Decker, R. B. et al, Science, 309, 2020- 2024, 2005. Burlaga et al, Geophys. Res. Lett., 30, NO. 20, 2072, doi:10.1029/2003GL018291, 2003. Burlaga, L. F, et al, Science, 309, 2027-2029, 2005 Krimigis S. M., et al, V. Florinski, N. V. Pogorelov, and G. P. Zank (eds) CP719, American Institute of Physics, 0-7354-0199-3/04, 133-138, 2004. Krimigis, S. M., et al, Proceedings of the Solar Wind 11 / SOHO 16 Conference,12-17 June 2005, Whistler, Canada, , B. Fleck & T.H. Zurbuchen (eds), (ESA SP-592, September 2005) Gurnett, D. A., and W. S. Kurth, Science, 309, 2025- 2027, 2005

Reverse alignment "mirror image" visualization as a laparoscopic training tool improves task performance.

PubMed

Dunnican, Ward J; Singh, T Paul; Ata, Ashar; Bendana, Emma E; Conlee, Thomas D; Dolce, Charles J; Ramakrishnan, Rakesh

2010-06-01

Reverse alignment (mirror image) visualization is a disconcerting situation occasionally faced during laparoscopic operations. This occurs when the camera faces back at the surgeon in the opposite direction from which the surgeon's body and instruments are facing. Most surgeons will attempt to optimize trocar and camera placement to avoid this situation. The authors' objective was to determine whether the intentional use of reverse alignment visualization during laparoscopic training would improve performance. A standard box trainer was configured for reverse alignment, and 34 medical students and junior surgical residents were randomized to train with either forward alignment (DIRECT) or reverse alignment (MIRROR) visualization. Enrollees were tested on both modalities before and after a 4-week structured training program specific to their modality. Student's t test was used to determine differences in task performance between the 2 groups. Twenty-one participants completed the study (10 DIRECT, 11 MIRROR). There were no significant differences in performance time between DIRECT or MIRROR participants during forward or reverse alignment initial testing. At final testing, DIRECT participants had improved times only in forward alignment performance; they demonstrated no significant improvement in reverse alignment performance. MIRROR participants had significant time improvement in both forward and reverse alignment performance at final testing. Reverse alignment imaging for laparoscopic training improves task performance for both reverse alignment and forward alignment tasks. This may be translated into improved performance in the operating room when faced with reverse alignment situations. Minimal lab training can account for drastic adaptation to this environment.

Reversible logic gates on Physarum Polycephalum

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

Schumann, Andrew

2015-03-10

In this paper, we consider possibilities how to implement asynchronous sequential logic gates and quantum-style reversible logic gates on Physarum polycephalum motions. We show that in asynchronous sequential logic gates we can erase information because of uncertainty in the direction of plasmodium propagation. Therefore quantum-style reversible logic gates are more preferable for designing logic circuits on Physarum polycephalum.

Measurement of the potential drop across the earth's collisionless bow shock

NASA Technical Reports Server (NTRS)

Formisano, V.

1982-01-01

The normal component of the dc electric field measured on ISEE-1 ordinarily exhibits an enhancement of a few mV/m over both upstream and downstream values at the earth's bow shock. Using the measured relative velocity between the shock and the spacecraft (from the ISEE-1/2 time delay in the magnetometer data), it is possible to transform the observed E enhancement to a potential drop (delta phi). For a subcritical shock the potential drop is found to be very close to the measured change of particle kinetic energy (delta phi, approximately 280 V on day 330, 1977), whereas for a supercritical shock the potential drop is only a fraction of the measured change of kinetic energy (delta phi, approximately 140 V on day 324, 1977).

FEASIBILITY OF WIND TO SERVE UPPER SKAGIT'S BOW HILL TRIBAL LANDS AND FEASIBILITY UPDATE FOR RESIDENTIAL RENEWABLE ENERGY.

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

RICH, LAUREN

2013-09-30

A two year wind resource assessment was conducted to determine the feasibility of developing a community scale wind generation system for the Upper Skagit Indian Tribe's Bow Hill land base, and the project researched residential wind resource technologies to determine the feasibility of contributing renewable wind resource to the mix of energy options for our single and multi-family residential units.

Electron Bulk Acceleration and Thermalization at Earth's Quasiperpendicular Bow Shock.

PubMed

Chen, L-J; Wang, S; Wilson, L B; Schwartz, S; Bessho, N; Moore, T; Gershman, D; Giles, B; Malaspina, D; Wilder, F D; Ergun, R E; Hesse, M; Lai, H; Russell, C; Strangeway, R; Torbert, R B; F-Vinas, A; Burch, J; Lee, S; Pollock, C; Dorelli, J; Paterson, W; Ahmadi, N; Goodrich, K; Lavraud, B; Le Contel, O; Khotyaintsev, Yu V; Lindqvist, P-A; Boardsen, S; Wei, H; Le, A; Avanov, L

2018-06-01

Electron heating at Earth's quasiperpendicular bow shock has been surmised to be due to the combined effects of a quasistatic electric potential and scattering through wave-particle interaction. Here we report the observation of electron distribution functions indicating a new electron heating process occurring at the leading edge of the shock front. Incident solar wind electrons are accelerated parallel to the magnetic field toward downstream, reaching an electron-ion relative drift speed exceeding the electron thermal speed. The bulk acceleration is associated with an electric field pulse embedded in a whistler-mode wave. The high electron-ion relative drift is relaxed primarily through a nonlinear current-driven instability. The relaxed distributions contain a beam traveling toward the shock as a remnant of the accelerated electrons. Similar distribution functions prevail throughout the shock transition layer, suggesting that the observed acceleration and thermalization is essential to the cross-shock electron heating.

Electron Bulk Acceleration and Thermalization at Earth's Quasiperpendicular Bow Shock

NASA Astrophysics Data System (ADS)

Chen, L.-J.; Wang, S.; Wilson, L. B.; Schwartz, S.; Bessho, N.; Moore, T.; Gershman, D.; Giles, B.; Malaspina, D.; Wilder, F. D.; Ergun, R. E.; Hesse, M.; Lai, H.; Russell, C.; Strangeway, R.; Torbert, R. B.; F.-Vinas, A.; Burch, J.; Lee, S.; Pollock, C.; Dorelli, J.; Paterson, W.; Ahmadi, N.; Goodrich, K.; Lavraud, B.; Le Contel, O.; Khotyaintsev, Yu. V.; Lindqvist, P.-A.; Boardsen, S.; Wei, H.; Le, A.; Avanov, L.

2018-06-01

Electron heating at Earth's quasiperpendicular bow shock has been surmised to be due to the combined effects of a quasistatic electric potential and scattering through wave-particle interaction. Here we report the observation of electron distribution functions indicating a new electron heating process occurring at the leading edge of the shock front. Incident solar wind electrons are accelerated parallel to the magnetic field toward downstream, reaching an electron-ion relative drift speed exceeding the electron thermal speed. The bulk acceleration is associated with an electric field pulse embedded in a whistler-mode wave. The high electron-ion relative drift is relaxed primarily through a nonlinear current-driven instability. The relaxed distributions contain a beam traveling toward the shock as a remnant of the accelerated electrons. Similar distribution functions prevail throughout the shock transition layer, suggesting that the observed acceleration and thermalization is essential to the cross-shock electron heating.

Short stature/short limb skeletal dysplasia with severe combined immunodeficiency and bowing of the femora: report of two patients and review.

PubMed Central

MacDermot, K D; Winter, R M; Wigglesworth, J S; Strobel, S

1991-01-01

We report two patients with severe combined immunodeficiency and short stature/short limb skeletal dysplasia. Case 1 presented at birth with rhizomelic shortening of the extremities and bowing of the femora. She developed clinical signs of severe combined immunodeficiency at 13 months and died at 21 months. Case 2 had severe prenatal shortening and bowing of the extremities and a small, malformed chest. Symptoms of severe combined immunodeficiency and severe failure to thrive developed soon after birth and she died at 5 months. The diagnosis of severe combined immunodeficiency in our patients was based on their clinical course and necropsy findings, supported in case 1 by the results of immune function tests. The results of investigation of immune function (immunoglobulins, lymphocyte subpopulations, lymphocyte function) are very variable in this syndrome as in other variants of severe combined immunodeficiency. Bone histopathology in both patients showed grossly irregular costochondral junctions, but normal transition of proliferating to hypertrophic chondrocytes. These cases belong to early lethal type 1 short limb skeletal dysplasia with severe combined immunodeficiency. Review of previously published cases with severe combined immunodeficiency and well documented skeletal findings show eight patients with prenatal onset of bowing and shortening of the extremities and metaphyseal abnormalities. These include two sib pairs concordant for the skeletal changes. In these cases, adenosine deaminase levels were not reported. An additional four published cases with associated adenosine deaminase deficiency had only mild metaphyseal abnormalities, but subsequently showed no linear growth.(ABSTRACT TRUNCATED AT 250 WORDS) Images PMID:1999827

Interaction of a finite-length ion beam with a background plasma - Reflected ions at the quasi-parallel bow shock

NASA Technical Reports Server (NTRS)

Onsager, T. G.; Winske, D.; Thomsen, M. F.

1991-01-01

The coupling of a finite-length, field-aligned, ion beam with a uniform background plasma is investigated using one-dimensional hybrid computer simulations. The finite-length beam is used to study the interaction between the incident solar wind and ions reflected from the earth's quasi-parallel bow shock, where the reflection process may vary with time. The coupling between the reflected ions and the solar wind is relevant to ion heating at the bow shock and possibly to the formation of hot, flow anomalies and re-formation of the shock itself. Consistent with linear theory, the waves which dominate the interaction are the electromagnetic right-hand polarized resonant and nonresonant modes. However, in addition to the instability growth rates, the length of time that the waves are in contact with the beam is also an important factor in determining which wave mode will dominate the interaction. It is found that interaction will result in strong coupling, where a significant fraction of the available free energy is converted into thermal energy in a short time, provided the beam is sufficiently dense or sufficiently long.

COMPUTING THE DUST DISTRIBUTION IN THE BOW SHOCK OF A FAST-MOVING, EVOLVED STAR

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

Van Marle, A. J.; Meliani, Z.; Keppens, R.

2011-06-20

We study the hydrodynamical behavior occurring in the turbulent interaction zone of a fast-moving red supergiant star, where the circumstellar and interstellar material collide. In this wind-interstellar-medium collision, the familiar bow shock, contact discontinuity, and wind termination shock morphology form, with localized instability development. Our model includes a detailed treatment of dust grains in the stellar wind and takes into account the drag forces between dust and gas. The dust is treated as pressureless gas components binned per grain size, for which we use 10 representative grain size bins. Our simulations allow us to deduce how dust grains of varyingmore » sizes become distributed throughout the circumstellar medium. We show that smaller dust grains (radius <0.045 {mu}m) tend to be strongly bound to the gas and therefore follow the gas density distribution closely, with intricate fine structure due to essentially hydrodynamical instabilities at the wind-related contact discontinuity. Larger grains which are more resistant to drag forces are shown to have their own unique dust distribution, with progressive deviations from the gas morphology. Specifically, small dust grains stay entirely within the zone bound by shocked wind material. The large grains are capable of leaving the shocked wind layer and can penetrate into the shocked or even unshocked interstellar medium. Depending on how the number of dust grains varies with grain size, this should leave a clear imprint in infrared observations of bow shocks of red supergiants and other evolved stars.« less

The Uranian bow shock - Voyager 2 inbound observations of a high Mach number shock

NASA Technical Reports Server (NTRS)

Bagenal, Fran; Belcher, John W.; Sittler, Edward C., Jr.; Lepping, Ronald P.

1987-01-01

The Voyager 2 magnetometer and plasma detector measured a high Mach number, high beta bow shock on the dayside of the Uranian magnetosphere. Although the average conditions on either side of the shock are consistent with the Rankine-Hugoniot (MHD) relations for a stationary, quasi-perpendicular shock, the data revealed both detailed structure in the transition region as well as considerable variability in the downstream magnetosheath plasma. The bulk plasma parameters and the magnetic field exhibited some of the characteristics of a supercritical shock: an overshoot followed by damped oscillations downstream, consistent with recent theoretical models of high Mach number quasi-perpendicular shocks.

Direct Oral Anticoagulant- or Warfarin-Related Major Bleeding: Characteristics, Reversal Strategies, and Outcomes From a Multicenter Observational Study.

PubMed

Xu, Yan; Schulman, Sam; Dowlatshahi, Dar; Holbrook, Anne M; Simpson, Christopher S; Shepherd, Lois E; Wells, Philip S; Giulivi, Antonio; Gomes, Tara; Mamdani, Muhammad; Khuu, Wayne; Frymire, Eliot; Johnson, Ana P

2017-07-01

Direct oral anticoagulants (DOACs) have expanded the armamentarium for antithrombotic therapy. Although DOAC-related major bleeding was associated with favorable outcomes compared with warfarin in clinical trials, warfarin effects were reversed in < 40% of cases, raising concerns about the generalizability of this finding. Consecutive patients ≥ 66 years presented to five tertiary care hospitals across three cities in Ontario, Canada from October 2010 to March 2015 with diagnoses that included hemorrhage. Charts were screened for association with DOAC or warfarin use; eligible cases were abstracted and linked to administrative databases. Among 19,061 records screened, 2,002 (460 receiving DOAC, 1,542 receiving warfarin) were eligible. Reversal agents (72.9% vitamin K, 40.7% prothrombin complex concentrates) were frequently used in warfarin bleeding events. Red blood cell transfusions occurred more often in DOAC bleeding events than in warfarin events (52.0% vs 39.5%; adjusted relative risk [aRR], 1.32; 95% CI, 1.19-2.47). However, units of blood products transfused were not different between the two groups. Thirty-four DOAC cases (7.4%) received activated prothrombin complex concentrates or recombinant factor VIIa. In-hospital mortality was lower following DOAC bleeding events (9.8% vs 15.2%; aRR, 0.66; 95% CI, 0.49-0.89), although differences in 30-day mortality did not reach statistical significance (12.6% vs 16.3%; aRR, 0.79; 95% CI, 0.61-1.03). In this unselected cohort of patients with oral anticoagulant-related hemorrhage with high rates of warfarin reversal, in-hospital mortality was lower among DOAC-associated bleeding events. These findings support the safety of DOACs in routine care and present useful baseline measures for evaluations of DOAC-specific reversal agents. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Route Repetition and Route Reversal: Effects of Age and Encoding Method

PubMed Central

Allison, Samantha; Head, Denise

2017-01-01

Previous research indicates age-related impairments in learning routes from a start location to a target destination. There is less research on age effects on the ability to reverse a learned path. The method used to learn routes may also influence performance. This study examined how encoding methods influence the ability of younger and older adults to recreate a route in a virtual reality environment in forward and reverse directions. Younger (n=50) and older (n=50) adults learned a route by either self-navigation through the virtual environment or through studying a map. At test, participants recreated the route in the forward and reverse directions. Older adults in the map study condition had greater difficulty learning the route in the forward direction compared to younger adults. Older adults who learned the route by self-navigation were less accurate in traversing the route in the reverse compared to forward direction after a delay. In contrast, for older adults who learned via map study there were no significant differences between forward and reverse directions. Results suggest that older adults may not as readily develop and retain a sufficiently flexible representation of the environment during self-navigation to support accurate route reversal. Thus, initially learning a route from a map may be more difficult for older adults, but may ultimately be beneficial in terms of better supporting the ability to return to a start location. PMID:28504535

Nowcasting and forecasting of the magnetopause and bow shock—A status update

NASA Astrophysics Data System (ADS)

Petrinec, S. M.; Redmon, R. J.; Rastaetter, L.

2017-01-01

There has long been interest in knowing the shape and location of the Earth's magnetopause and of the standing fast-mode bow shock upstream of the Earth's magnetosphere. This quest for knowledge spans both the research and operations arenas. Pertinent to the latter, nowcasting and near-term forecasting are important for determining the extent to which the magnetosphere is compressed or expanded due to the influence of the solar wind bulk plasma and fields and the coupling to other magnetosphere-ionosphere processes with possible effects on assets. This article provides an update to a previous article on the same topic published 15 years earlier, with focus on studies that have been conducted, the current status of nowcasting and forecasting of geophysical boundaries, and future endeavors.

Towards an MHD Theory for the Standoff Distance of Earth's Bow Shock

NASA Technical Reports Server (NTRS)

Carins, Iver H.; Grabbe, Crockett L.

1994-01-01

A magnetohydrodynamic (MHD) theory is developed for the standoff distance a(s) of the bow shock and the thickness Delta(ms) of the magnetosheath, using the empirical Spreiter et al. relation Delta(ms) = kX and the MHD density ratio X across the shock. The theory includes as special cases the well-known gasdynamic theory and associated phenomenological MHD-like models for Delta(ms) and As. In general, however, MHD effects produce major differences from previous models, especially at low Alfev (Ma) and Sonic (Ms) Mach numbers. The magnetic field orientation Ma, Ms and the ratio of specific heats gamma are all important variables of the theory. In contrast, the fast mode Mach number need play no direct role. Three principle conclusions are reached. First the gasdynamic and phenomenological models miss important dependences of field orientation and Ms generally provide poor approximations to the MHD results. Second, changes in field orientation and Ms are predicted to cause factor of approximately 4 changes in Delta(ms) at low Ma. These effects should be important when predicting the shock's location or calculating gramma from observations. Third, using Spreiter et al.'s value for k in the MHD theory leads to maxima a(s) values at low Ma and nominal Ms that are much smaller than observations and MHD simulations require. Resolving this problem requires either the modified Spreiter-like relation and larger k found in recent MHD simulations and/or a breakdown in the Spreiter-like relation at very low Ma.

Confirming Time-reversal Symmetry of a Directed Percolation Phase Transition in a Model of Neutral Evolutionary Dynamics

NASA Astrophysics Data System (ADS)

Ordway, Stephen; King, Dawn; Bahar, Sonya

Reaction-diffusion processes, such as branching-coalescing random walks, can be used to describe the underlying dynamics of nonequilibrium phase transitions. In an agent-based, neutral model of evolutionary dynamics, we have previously shown that our system undergoes a continuous, nonequilibrium phase transition, from extinction to survival, as various system parameters were tuned. This model was shown to belong to the directed percolation (DP) universality class, by measuring the critical exponents corresponding to correlation length ξ⊥, correlation time ξ| |, and particle density β. The fourth critical exponent that defines the DP universality class is β', which measures the survival probability of growth from a single seed organism. Since DP universality is theorized to have time-reversal symmetry, it is assumed that β = β '. In order to confirm the existence of time-reversal symmetry in our model, we evaluate the system growth from a single asexually reproducing organism. Importantly, the critical exponent β' could be useful for comparison to experimental studies of phase transitions in biological systems, since observing growth of microbial populations is significantly easier than observing death. This research was supported by funding from the James S. McDonnell Foundation.

Electroosmotic Flow Reversal Outside Glass Nanopores

PubMed Central

2015-01-01

We report observations of a striking reversal in the direction of electroosmotic flow (EOF) outside a conical glass nanopore as a function of salt concentration. At high ionic strengths (>100 mM), we observe EOF in the expected direction as predicted by classical electrokinetic theory, while at low salt concentrations (<1 mM) the direction of the flow is reversed. The critical crossover salt concentration depends on the pore diameter. Finite-element simulations indicate a competition between the EOF generated from the inner and outer walls of the pore, which drives flows in opposite directions. We have developed a simple analytical model which reveals that, as the salt concentration is reduced, the flow rates inside the pore are geometrically constrained, whereas there is no such limit for flows outside the pore. This model captures all of the essential physics of the system and explains the observed data, highlighting the key role the external environment plays in determining the overall electroosmotic behavior. PMID:25490120

THE BALMER-DOMINATED BOW SHOCK AND WIND NEBULA STRUCTURE OF {gamma}-RAY PULSAR PSR J1741-2054

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

Romani, Roger W.; Shaw, Michael S.; Camilo, Fernando

2010-12-01

We have detected an H{alpha} bow shock nebula around PSR J1741-2054, a pulsar discovered through its GeV {gamma}-ray pulsations. The pulsar is only {approx}1.''5 behind the leading edge of the shock. Optical spectroscopy shows that the nebula is non-radiative, dominated by Balmer emission. The H{alpha} images and spectra suggest that the pulsar wind momentum is equatorially concentrated and implies a pulsar space velocity {approx}150 km s{sup -1}, directed 15{sup 0} {+-} 10{sup 0} out of the plane of the sky. The complex H{alpha} profile indicates that different portions of the post-shock flow dominate line emission as gas moves along themore » nebula and provide an opportunity to study the structure of this unusual slow non-radiative shock under a variety of conditions. CXO ACIS observations reveal an X-ray pulsar wind nebula within this nebula, with a compact {approx}2.''5 equatorial structure and a trail extending several arcminutes behind. Together these data support a close ({<=}0.5 kpc) distance, a spin geometry viewed edge-on, and highly efficient {gamma}-ray production for this unusual, energetic pulsar.« less

A specific antidote for reversal of anticoagulation by direct and indirect inhibitors of coagulation factor Xa.

PubMed

Lu, Genmin; DeGuzman, Francis R; Hollenbach, Stanley J; Karbarz, Mark J; Abe, Keith; Lee, Gail; Luan, Peng; Hutchaleelaha, Athiwat; Inagaki, Mayuko; Conley, Pamela B; Phillips, David R; Sinha, Uma

2013-04-01

Inhibitors of coagulation factor Xa (fXa) have emerged as a new class of antithrombotics but lack effective antidotes for patients experiencing serious bleeding. We designed and expressed a modified form of fXa as an antidote for fXa inhibitors. This recombinant protein (r-Antidote, PRT064445) is catalytically inactive and lacks the membrane-binding γ-carboxyglutamic acid domain of native fXa but retains the ability of native fXa to bind direct fXa inhibitors as well as low molecular weight heparin-activated antithrombin III (ATIII). r-Antidote dose-dependently reversed the inhibition of fXa by direct fXa inhibitors and corrected the prolongation of ex vivo clotting times by such inhibitors. In rabbits treated with the direct fXa inhibitor rivaroxaban, r-Antidote restored hemostasis in a liver laceration model. The effect of r-Antidote was mediated by reducing plasma anti-fXa activity and the non-protein bound fraction of the fXa inhibitor in plasma. In rats, r-Antidote administration dose-dependently and completely corrected increases in blood loss resulting from ATIII-dependent anticoagulation by enoxaparin or fondaparinux. r-Antidote has the potential to be used as a universal antidote for a broad range of fXa inhibitors.

Logistics Management: New trends in the Reverse Logistics

NASA Astrophysics Data System (ADS)

Antonyová, A.; Antony, P.; Soewito, B.

2016-04-01

Present level and quality of the environment are directly dependent on our access to natural resources, as well as their sustainability. In particular production activities and phenomena associated with it have a direct impact on the future of our planet. Recycling process, which in large enterprises often becomes an important and integral part of the production program, is usually in small and medium-sized enterprises problematic. We can specify a few factors, which have direct impact on the development and successful application of the effective reverse logistics system. Find the ways to economically acceptable model of reverse logistics, focusing on converting waste materials for renewable energy, is the task in progress.

O+ pickup ions outside of Venus' bow shock: Venus Express observations

NASA Astrophysics Data System (ADS)

Wei, Yong; Fraenz, Markus; Dubinin, Eduard; Zhang, Tielong; Jarvinen, Riku; Wan, Weixing; Kallio, Esa; Collinson, Glyn; Barabash, Stars; Norbert, Krupp; Woch, Joachim; Lundin, Rickard; delva, Magda

2013-04-01

Pickup ions are ions of planetary origin that become assimilated into the solar wind flow through their interaction with the solar wind magnetic and electric field. The speed of pickup ions varies between zero and twice the underlying plasma flow component perpendicular to magnetic field vector. For the unmagnetized planet Venus and Mars, oxygen (O+) pickup ions are known to be important because they can modify the global configuration of planetary plasma environment and significantly contribute to the atmospheric O+ loss [1]. Since the kinetic energy of an O+ pickup ion can reach 64 times that of a co-moving proton, an instrument must be able to measure O+ ions with energy of at least tens of keV to investigate the O+ pickup ion distribution from planetary ionosphere to solar wind. The in-situ observations and simulations at Mars have shown that the energy of O+ pickup ions can be 55-72 keV outside of the bow shock [2]. For Venus case, the plasma analyzer (OPA) onboard Pioneer Venus Orbiter (PVO), which was designed for solar wind monitoring, has an 8 keV energy limit for O+ detection and the limited sampling and data rate [3]. Therefore, OPA can only measure the O+ pickup ions in the sheath flow or inside the induced magnetosphere where the speed of ambient plasma flow is significantly lower than that of the unshocked solar wind outside of the bow shock. In addition, Galileo also did not capture O+ outside bowshock during its 1-hour Venus flyby though its plasma instrument had ability to cover the energy band of O+ pickup ions [4]. The Ion Mass Analyzer (IMA), included in the Analyzer of Space Plasma and Energetic Atoms (ASPERA-4) package on board Venus Express (VEX), determines the composition, energy, and angular distribution of ions in the energy range ~10 eV/q to 30 keV/q. Note that an O+ ion moving at the typical solar wind speed 400 km/s has kinetic energy 13.4 keV. Therefore, IMA has ability to measure the O+ pickup ions outside of Venus' bow shock. We

Illusory motion reversal is caused by rivalry, not by perceptual snapshots of the visual field.

PubMed

Kline, Keith; Holcombe, Alex O; Eagleman, David M

2004-10-01

In stroboscopic conditions--such as motion pictures--rotating objects may appear to rotate in the reverse direction due to under-sampling (aliasing). A seemingly similar phenomenon occurs in constant sunlight, which has been taken as evidence that the visual system processes discrete "snapshots" of the outside world. But if snapshots are indeed taken of the visual field, then when a rotating drum appears to transiently reverse direction, its mirror image should always appeared to reverse direction simultaneously. Contrary to this hypothesis, we found that when observers watched a rotating drum and its mirror image, almost all illusory motion reversals occurred for only one image at a time. This result indicates that the motion reversal illusion cannot be explained by snapshots of the visual field. The same result is found when the two images are presented within one visual hemifield, further ruling out the possibility that discrete sampling of the visual field occurs separately in each hemisphere. The frequency distribution of illusory reversal durations approximates a gamma distribution, suggesting perceptual rivalry as a better explanation for illusory motion reversal. After adaptation of motion detectors coding for the correct direction, the activity of motion-sensitive neurons coding for motion in the reverse direction may intermittently become dominant and drive the perception of motion.

Using Collaborative Modeling to Inform Policy Decisions in the Bow River Basin

NASA Astrophysics Data System (ADS)

Sheer, A. S.; Sheer, D. P.; Hill, D.

2011-12-01

The Bow River in Alberta, Canada serves a wide range of municipal, agricultural, recreational, and industrial purposes in the province. In 2006, the basin was deemed over-allocation and closed to new licenses. The Calgary region, however, continues to expand. In the next 60 to 70 years, population levels are expected to reach 2.8 million (more than double the current 1.2 million) with 800,000 new jobs. This increasing pressure led several stakeholders to work together in the development of a new management model to improve the management of the system as an integrated watershed. The major previous model of the system allowed only limited flexibility in management, focusing instead on strict license based operations. Over a 6 month period, with numerous multi-party meetings, the group developed the Bow River Operations Model (BROM). Based in OASIS software, this model integrated input from the major water users in the region to emulate the real-life decisions that are actually made on a daily bases, even when technically in violation of the strict license agreements (e.x. junior licensees receiving water despite senior priority due to exceedingly low volume requirements). Using historical records as forecasts, and performance measures developed with the best available science through expert opinion, participants jointly developed a new reservoir operation strategy. Even with such a short timeframe, the BROM exercise showed that there was substantial room for improvement. Utilizing a "Water Bank" of purchased storage, downstream flows could be significantly improved without affecting quality. Additional benefits included fishery improvement, new recreation opportunities, dissolved oxygen improvement during critical periods, and the ability to accommodate long-term demand forecasts for surrounding municipalities. This strategy has been presented to, and favorably received by, the Alberta Minister of Environment for guidance during negotiations with the local

Stable, polymer-directed and SPION-nucleated magnetic amphiphilic block copolymer nanoprecipitates with readily reversible assembly in magnetic fields

NASA Astrophysics Data System (ADS)

Giardiello, Marco; Hatton, Fiona L.; Slater, Rebecca A.; Chambon, Pierre; North, Jocelyn; Peacock, Anita K.; He, Tao; McDonald, Tom O.; Owen, Andrew; Rannard, Steve P.

2016-03-01

The formation of inorganic-organic magnetic nanocomposites using reactive chemistry often leads to a loss of super-paramagnetisim when conducted in the presence of iron oxide nanoparticles. We present here a low energy and chemically-mild process of co-nanoprecipitation using SPIONs and homopolymers or amphiphilic block copolymers, of varying architecture and hydrophilic/hydrophobic balance, which efficiently generates near monodisperse SPION-containing polymer nanoparticles with complete retention of magnetism, and highly reversible aggregation and redispersion behaviour. When linear and branched block copolymers with inherent water-solubility are used, a SPION-directed nanoprecipitation mechanism appears to dominate the nanoparticle formation presenting new opportunities for tailoring and scaling highly functional systems for a range of applications.The formation of inorganic-organic magnetic nanocomposites using reactive chemistry often leads to a loss of super-paramagnetisim when conducted in the presence of iron oxide nanoparticles. We present here a low energy and chemically-mild process of co-nanoprecipitation using SPIONs and homopolymers or amphiphilic block copolymers, of varying architecture and hydrophilic/hydrophobic balance, which efficiently generates near monodisperse SPION-containing polymer nanoparticles with complete retention of magnetism, and highly reversible aggregation and redispersion behaviour. When linear and branched block copolymers with inherent water-solubility are used, a SPION-directed nanoprecipitation mechanism appears to dominate the nanoparticle formation presenting new opportunities for tailoring and scaling highly functional systems for a range of applications. Electronic supplementary information (ESI) available: Additional experimental details, NMR spectra, GPC chromatograms, kinetics experiments, graphs of nanopreciptate aggregation and cycling studies and SPION characterisation. See DOI: 10.1039/c6nr00788k

Intermittent nature of solar wind turbulence near the Earth's bow shock: phase coherence and non-Gaussianity.

PubMed

Koga, D; Chian, A C-L; Miranda, R A; Rempel, E L

2007-04-01

The link between phase coherence and non-Gaussian statistics is investigated using magnetic field data observed in the solar wind turbulence near the Earth's bow shock. The phase coherence index Cphi, which characterizes the degree of phase correlation (i.e., nonlinear wave-wave interactions) among scales, displays a behavior similar to kurtosis and reflects a departure from Gaussianity in the probability density functions of magnetic field fluctuations. This demonstrates that nonlinear interactions among scales are the origin of intermittency in the magnetic field turbulence.

Pigment dispersion syndrome and pigmentary glaucoma--a major review.

PubMed

Niyadurupola, Nuwan; Broadway, David C

2008-12-01

Pigment dispersion syndrome (PDS) is an interesting condition that can lead to secondary open angle glaucoma. Pigmentary glaucoma is primarily a disease of young people, myopes and men. PDS is characterized by the presence of Krukenberg spindles, iris trans-illumination defects, trabecular meshwork pigmentation and backward bowing of the iris. Posterior bowing of the iris causes rubbing of the pigmented iris epithelium against lens structures, liberation of pigment and trabecular meshwork changes that result in reduced aqueous outflow with the risk of glaucoma. Peripheral laser iridotomy can reverse backward bowing of the iris and may prevent progression of pigmentary glaucoma.

On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

NASA Astrophysics Data System (ADS)

Lobzin, V. V.; Krasnoselskikh, V. V.; Musatenko, K.; Dudok de Wit, T.

2008-09-01

A new method for remote sensing of the quasiperpendicular part of the bow shock surface is presented. The method is based on analysis of high frequency electric field fluctuations corresponding to Langmuir, upshifted, and downshifted oscillations in the electron foreshock. Langmuir waves usually have maximum intensity at the upstream boundary of this region. All these waves are generated by energetic electrons accelerated by quasiperpendicular zone of the shock front. Nonstationary behavior of the shock, in particular due to rippling, should result in modulation of energetic electron fluxes, thereby giving rise to variations of Langmuir waves intensity. For upshifted and downshifted oscillations, the variations of both intensity and central frequency can be observed. For the present study, WHISPER measurements of electric field spectra obtained aboard Cluster spacecraft are used to choose 48 crossings of the electron foreshock boundary with dominating Langmuir waves and to perform for the first time a statistical analysis of nonstationary behavior of quasiperpendicular zone of the Earth's bow shock. Analysis of hidden periodicities in plasma wave energy reveals shock front nonstationarity in the frequency range 0.33 fBi

Active magnetic force microscopy of Sr-ferrite magnet by stimulating magnetization under an AC magnetic field: Direct observation of reversible and irreversible magnetization processes

NASA Astrophysics Data System (ADS)

Cao, Yongze; Kumar, Pawan; Zhao, Yue; Yoshimura, Satoru; Saito, Hitoshi

2018-05-01

Understanding the dynamic magnetization process of magnetic materials is crucial to improving their fundamental properties and technological applications. Here, we propose active magnetic force microscopy for observing reversible and irreversible magnetization processes by stimulating magnetization with an AC magnetic field based on alternating magnetic force microscopy with a sensitive superparamagnetic tip. This approach simultaneously measures sample's DC and AC magnetic fields. We used this microscopy approach to an anisotropic Sr-ferrite (SrF) sintered magnet. This is a single domain type magnet where magnetization mainly changes via magnetic rotation. The proposed method can directly observe the reversible and irreversible magnetization processes of SrF and clearly reveal magnetic domain evolution of SrF (without stimulating magnetization—stimulating reversible magnetization—stimulating irreversible magnetization switching) by slowly increasing the amplitude of the external AC magnetic field. This microscopy approach can evaluate magnetic inhomogeneity and explain the local magnetic process within the permanent magnet.

Electron bulk acceleration and thermalization at Earth's quasi-perpendicular bow shock

NASA Astrophysics Data System (ADS)

Chen, L.-J.; Wang, S.; Wilson, L. B., III; Schwartz, S. J.; Bessho, N.; Moore, T. E.; Gershman, D. J.; Giles, B. L.; Malaspina, D. M.; Wilder, F. D.; Ergun, R. E.; Hesse, M.; Lai, H.; Russell, C. T.; Strangeway, R. J.; Torbert, R. B.; Vinas, A. F.-; Burch, J. L.; Lee, S.; Pollock, C.; Dorelli, J.; Paterson, W. R.; Ahmadi, N.; Goodrich, K. A.; Lavraud, B.; Le Contel, O.; Khotyaintsev, Yu. V.; Lindqvist, P.-A.; Boardsen, S.; Wei, H.; Le, A.; Avanov, L. A.

2018-05-01

Electron heating at Earth's quasiperpendicular bow shock has been surmised to be due to the combined effects of a quasistatic electric potential and scattering through wave-particle interaction. Here we report the observation of electron distribution functions indicating a new electron heating process occurring at the leading edge of the shock front. Incident solar wind electrons are accelerated parallel to the magnetic field toward downstream, reaching an electron-ion relative drift speed exceeding the electron thermal speed. The bulk acceleration is associated with an electric field pulse embedded in a whistler-mode wave. The high electron-ion relative drift is relaxed primarily through a nonlinear current-driven instability. The relaxed distributions contain a beam traveling toward the shock as a remnant of the accelerated electrons. Similar distribution functions prevail throughout the shock transition layer, suggesting that the observed acceleration and thermalization is essential to the cross-shock electron heating.

Time-reversed wave mixing in nonlinear optics

PubMed Central

Zheng, Yuanlin; Ren, Huaijin; Wan, Wenjie; Chen, Xianfeng

2013-01-01

Time-reversal symmetry is important to optics. Optical processes can run in a forward or backward direction through time when such symmetry is preserved. In linear optics, a time-reversed process of laser emission can enable total absorption of coherent light fields inside an optical cavity of loss by time-reversing the original gain medium. Nonlinearity, however, can often destroy such symmetry in nonlinear optics, making it difficult to study time-reversal symmetry with nonlinear optical wave mixings. Here we demonstrate time-reversed wave mixings for optical second harmonic generation (SHG) and optical parametric amplification (OPA) by exploring this well-known but underappreciated symmetry in nonlinear optics. This allows us to observe the annihilation of coherent beams. Our study offers new avenues for flexible control in nonlinear optics and has potential applications in efficient wavelength conversion, all-optical computing. PMID:24247906

Comparison of picked-up protons and water group ions upstream of Comet Halley's bow shock

NASA Technical Reports Server (NTRS)

Neugebauer, M.; Coates, A. J.; Neubauer, F. M.

1990-01-01

The similarities and differences between the picked-up cometary protons and water-group (WG) ions upstream of the bow shock of Comet Halley are examined using measurements obtained by the ion mass spectrometer and plasma analyzer experiments on board Giotto. It was found that the dependencies of the pitch angle and the energy diffusion rates of the cometary protons and WG ions on the ion densities and on the angle alpha between the interplanetary field and the solar wind velocity vector were very different. This finding could not be explained in terms of presently available theories and models.

Human Promoters Are Intrinsically Directional

PubMed Central

Duttke, Sascha H.C.; Lacadie, Scott A.; Ibrahim, Mahmoud M.; Glass, Christopher K.; Corcoran, David L.; Benner, Christopher; Heinz, Sven; Kadonaga, James T.; Ohler, Uwe

2015-01-01

Divergent transcription, in which reverse-oriented transcripts occur upstream of eukaryotic promoters in regions devoid of annotated genes, has been suggested to be a general property of active promoters. Here we show that the human basal RNA polymerase II transcriptional machinery and core promoter are inherently unidirectional, and that reverse-oriented transcripts originate from their own cognate reverse-directed core promoters. In vitro transcription analysis and mapping of nascent transcripts in cells revealed that sequences at reverse start sites are similar to those of their forward counterparts. The use of DNase I accessibility to define proximal promoter borders revealed that up to half of promoters are unidirectional and that unidirectional promoters are depleted at their upstream edges of reverse core promoter sequences and their associated chromatin features. Divergent transcription is thus not an inherent property of the transcription process, but rather the consequence of the presence of both forward- and reverse-directed core promoters. PMID:25639469

Numerical Simulation of Bow Waves and Transom-Stern Flows

NASA Astrophysics Data System (ADS)

Dommermuth, Douglas G.; Schlageter, Eric A.; Talcott, John C.; Wyatt, Donald C.; Novikov, Evgeny A.

1997-11-01

A stratified-flow formulation is used to model the breaking bow wave and the separated transom-stern flow that are generated by a ship moving with forward speed. The interface of the air with the water is identified as the zero level-set of a three-dimensional function. The ship is modeled using a body-force technique on a cartesian grid. The three-dimensional body-force is generated using a surface panelization of the entire ship, including the above-water geometry up to and including the deck. The effects of surface tension are modeled as a source term that is concentrated at the air-water interface. The effects of gravity are modeled as a volumetric force. The three-dimensional, unsteady, Navier-Stokes equations are expressed in primitive-variable form. A LES formulation with a Smagorinsky sub-grid-scale model is used to model turbulence. Numerical convergence is demonstrated using 128x64x65, 256x128x129, and 512x256x257 grid points. The numerical results compare well to whisker-probe measurements of the free-surface elevation generated by a naval combatant.

Tubulin Dimer Reversible Dissociation

PubMed Central

Schuck, Peter; Sackett, Dan L.

2016-01-01

Tubulins are evolutionarily conserved proteins that reversibly polymerize and direct intracellular traffic. Of the tubulin family only αβ-tubulin forms stable dimers. We investigated the monomer-dimer equilibrium of rat brain αβ-tubulin using analytical ultracentrifugation and fluorescence anisotropy, observing tubulin in virtually fully monomeric and dimeric states. Monomeric tubulin was stable for a few hours and exchanged into preformed dimers, demonstrating reversibility of dimer dissociation. Global analysis combining sedimentation velocity and fluorescence anisotropy yielded Kd = 84 (54–123) nm. Dimer dissociation kinetics were measured by analyzing the shape of the sedimentation boundary and by the relaxation of fluorescence anisotropy following rapid dilution of labeled tubulin, yielding koff in the range 10−3–10−2 s−1. Thus, tubulin dimers reversibly dissociate with moderately fast kinetics. Monomer-monomer association is much less sensitive than dimer-dimer association to solution changes (GTP/GDP, urea, and trimethylamine oxide). PMID:26934918

Reversal bending fatigue testing

DOEpatents

Wang, Jy-An John; Wang, Hong; Tan, Ting

2014-10-21

Embodiments for apparatuses for testing reversal bending fatigue in an elongated beam are disclosed. Embodiments are configured to be coupled to first and second end portions of the beam and to apply a bending moment to the beam and create a pure bending condition in an intermediate portion of the beam. Embodiments are further configured to cyclically alternate the direction of the bending moment applied to the beam such that the intermediate portion of the beam cyclically bends in opposite directions in a pure bending condition.

Low-cost coding of directivity information for the recording of musical instruments

NASA Astrophysics Data System (ADS)

Braasch, Jonas; Martens, William L.; Woszczyk, Wieslaw

2004-05-01

Most musical instruments radiate sound according to characteristic spatial directivity patterns. These patterns are usually not only strongly frequency dependent, but also time-variant functions of various parameters of the instrument, such as pitch and the playing technique applied (e.g., plucking versus bowing of string instruments). To capture the directivity information when recording an instrument, Warusfel and Misdariis (2001) proposed to record an instrument using four channels, one for the monopole and the others for three orthogonal dipole parts. In the new recording setup presented here, it is proposed to store one channel at a high sampling frequency, along with directivity information that is updated only every few milliseconds. Taking the binaural sluggishness of the human auditory system into account in this way provides a low-cost coding scheme for subsequent reproduction of time-variant directivity patterns.

Plasma and wave properties downstream of Martian bow shock: Hybrid simulations and MAVEN observations

NASA Astrophysics Data System (ADS)

Dong, Chuanfei; Winske, Dan; Cowee, Misa; Bougher, Stephen W.; Andersson, Laila; Connerney, Jack; Epley, Jared; Ergun, Robert; McFadden, James P.; Ma, Yingjuan; Toth, Gabor; Curry, Shannon; Nagy, Andrew; Jakosky, Bruce

2015-04-01

Two-dimensional hybrid simulation codes are employed to investigate the kinetic properties of plasmas and waves downstream of the Martian bow shock. The simulations are two-dimensional in space but three dimensional in field and velocity components. Simulations show that ion cyclotron waves are generated by temperature anisotropy resulting from the reflected protons around the Martian bow shock. These proton cyclotron waves could propagate downward into the Martian ionosphere and are expected to heat the O+ layer peaked from 250 to 300 km due to the wave-particle interaction. The proton cyclotron wave heating is anticipated to be a significant source of energy into the thermosphere, which impacts atmospheric escape rates. The simulation results show that the specific dayside heating altitude depends on the Martian crustal field orientations, solar cycles and seasonal variations since both the cyclotron resonance condition and the non/sub-resonant stochastic heating threshold depend on the ambient magnetic field strength. The dayside magnetic field profiles for different crustal field orientation, solar cycle and seasonal variations are adopted from the BATS-R-US Mars multi-fluid MHD model. The simulation results, however, show that the heating of O+ via proton cyclotron wave resonant interaction is not likely in the relatively weak crustal field region, based on our simplified model. This indicates that either the drift motion resulted from the transport of ionospheric O+, or the non/sub-resonant stochastic heating mechanism are important to explain the heating of Martian O+ layer. We will investigate this further by comparing the simulation results with the available MAVEN data. These simulated ion cyclotron waves are important to explain the heating of Martian O+ layer and have significant implications for future observations.

Unusual locations of Earth's bow shock on September 24 - 25, 1987: Mach number effects

NASA Technical Reports Server (NTRS)

Cairns, Iver H.; Fairfield, Donald H.; Anderson, Oger R.; Carlton, Victoria E. H.; Paularena, Karolen I.; Lazarus, Alan J.

1995-01-01

International Sun Earth Explorer 1 (ISEE 1) and Interplanetary Monitoring Platform 8 (IMP 8) data are used to identify 19 crossings of Earth's bow shock during a 30-hour period following 0000 UT on September 24, 1987. Apparent standoff distances for the shock are calculated for each crossing using two methods and the spacecraft location; one method assumes the average shock shape, while the other assumes a ram pressure-dependent shock shape. The shock's apparent standoff distance, normally approximately 14 R(sub E), is shown to increase from near 10 R(sub E) initially to near 19 R(sub E) during an 8-hour period, followed by an excursion to near 35 R(sub E) (where two IMP 8 shock crossings occur) and an eventual return to values smaller than 19 R(sub E). The Alfven M(sub A) and fast magnetosonic M(sub ms). Mach numbers remain above 2 and the number density above 4/cu cm for almost the entire period. Ram pressure effects produce the initial near-Earth shock location, whereas expansions and contractions of the bow shock due to low Mach number effects account, qualitatively and semiquantitatively, for the timing and existence of almost all the remaining ISEE crossings and both IMP 8 crossings. Significant quantitative differences exist between the apparent standoff distances for the shock crossings and those predicted using the observed plasma parameters and the standard model based on Spreiter et al.'s (1966) gasdynamic equation. These differences can be explained in terms of either a different dependence of the standoff distance on Mach number at low M(sub A) and M(sub ms), or variations in shock shape with M(sub A) and M(sub ms) (becoming increasingly "puffed up" with decreasing M(sub A) and M(sub ms), as expected theoretically), or by a combination of both effects.

Band gap bowing in NixMg1−xO

PubMed Central

Niedermeier, Christian A.; Råsander, Mikael; Rhode, Sneha; Kachkanov, Vyacheslav; Zou, Bin; Alford, Neil; Moram, Michelle A.

2016-01-01

Epitaxial transparent oxide NixMg1−xO (0 ≤ x ≤ 1) thin films were grown on MgO(100) substrates by pulsed laser deposition. High-resolution synchrotron X-ray diffraction and high-resolution transmission electron microscopy analysis indicate that the thin films are compositionally and structurally homogeneous, forming a completely miscible solid solution. Nevertheless, the composition dependence of the NixMg1−xO optical band gap shows a strong non-parabolic bowing with a discontinuity at dilute NiO concentrations of x < 0.037. Density functional calculations of the NixMg1−xO band structure and the density of states demonstrate that deep Ni 3d levels are introduced into the MgO band gap, which significantly reduce the fundamental gap as confirmed by optical absorption spectra. These states broaden into a Ni 3d-derived conduction band for x > 0.074 and account for the anomalously large band gap narrowing in the NixMg1−xO solid solution system. PMID:27503808

Reverse logistics in the construction industry.

PubMed

Hosseini, M Reza; Rameezdeen, Raufdeen; Chileshe, Nicholas; Lehmann, Steffen

2015-06-01

Reverse logistics in construction refers to the movement of products and materials from salvaged buildings to a new construction site. While there is a plethora of studies looking at various aspects of the reverse logistics chain, there is no systematic review of literature on this important subject as applied to the construction industry. Therefore, the objective of this study is to integrate the fragmented body of knowledge on reverse logistics in construction, with the aim of promoting the concept among industry stakeholders and the wider construction community. Through a qualitative meta-analysis, the study synthesises the findings of previous studies and presents some actions needed by industry stakeholders to promote this concept within the real-life context. First, the trend of research and terminology related with reverse logistics is introduced. Second, it unearths the main advantages and barriers of reverse logistics in construction while providing some suggestions to harness the advantages and mitigate these barriers. Finally, it provides a future research direction based on the review. © The Author(s) 2015.

How the geomagnetic field vector reverses polarity

USGS Publications Warehouse

Prevot, M.; Mankinen, E.A.; Gromme, C.S.; Coe, R.S.

1985-01-01

A highly detailed record of both the direction and intensity of the Earth's magnetic field as it reverses has been obtained from a Miocene volcanic sequence. The transitional field is low in intensity and is typically non-axisymmetric. Geomagnetic impulses corresponding to astonishingly high rates of change of the field sometimes occur, suggesting that liquid velocity within the Earth's core increases during geomagnetic reversals. ?? 1985 Nature Publishing Group.

Features in the Behavior of the Solar Wind behind the Bow Shock Front near the Boundary of the Earth's Magnetosphere

NASA Astrophysics Data System (ADS)

Grib, S. A.; Leora, S. N.

2017-12-01

Macroscopic discontinuous structures observed in the solar wind are considered in the framework of magnetic hydrodynamics. The interaction of strong discontinuities is studied based on the solution of the generalized Riemann-Kochin problem. The appearance of discontinuities inside the magnetosheath after the collision of the solar wind shock wave with the bow shock front is taken into account. The propagation of secondary waves appearing in the magnetosheath is considered in the approximation of one-dimensional ideal magnetohydrodynamics. The appearance of a compression wave reflected from the magnetopause is indicated. The wave can nonlinearly break with the formation of a backward shock wave and cause the motion of the bow shock towards the Sun. The interaction between shock waves is considered with the well-known trial calculation method. It is assumed that the velocity of discontinuities in the magnetosheath in the first approximation is constant on the average. All reasonings and calculations correspond to consideration of a flow region with a velocity less than the magnetosonic speed near the Earth-Sun line. It is indicated that the results agree with the data from observations carried out on the WIND and Cluster spacecrafts.

Drill-hole data, drill-site geology, and geochemical data from the study of Precambrian uraniferous conglomerates of the Medicine Bow Mountains and Sierra Madre of southeastern Wyoming

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

Karlstrom, K.E.; Houston, R.S.; Schmidt, T.G.

1981-02-01

This volume is presented as a companion to Volume 1: The Geology and Uranium Potential of Precambrian Conglomerates in the Medicine Bow Mountains and Sierra Madre of Southeastern Wyoming; and to Volume 3: Uranium Assessment for Precambrian Pebble Conglomerates in Southeastern Wyoming. Volume 1 summarized the geologic setting and geologic and geochemical characteristics of uranium-bearing conglomerates in Precambrian metasedimentary rocks of southeastern Wyoming. Volume 3 is a geostatistical resource estimate of U and Th in quartz-pebble conglomerates. This volume contains supporting geochemical data, lithologic logs from 48 drill holes in Precambrian rocks of the Medicine Bow Mountains and Sierra Madre,more » and drill site geologic maps and cross-sections from most of the holes.« less

Nuclear reactor removable radial shielding assembly having a self-bowing feature

DOEpatents

Pennell, William E.; Kalinowski, Joseph E.; Waldby, Robert N.; Rylatt, John A.; Swenson, Daniel V.

1978-01-01

A removable radial shielding assembly for use in the periphery of the core of a liquid-metal-cooled fast-breeder reactor, for closing interassembly gaps in the reactor core assembly load plane prior to reactor criticality and power operation to prevent positive reactivity insertion. The assembly has a lower nozzle portion for inserting into the core support and a flexible heat-sensitive bimetallic central spine surrounded by blocks of shielding material. At refueling temperature and below the spine is relaxed and in a vertical position so that the tolerances permitted by the interassembly gaps allow removal and replacement of the various reactor core assemblies. During an increase in reactor temperature from refueling to hot standby, the bimetallic spine expands, bowing the assembly toward the core center line, exerting a radially inward gap-closing-force on the above core load plane of the reactor core assembly, closing load plane interassembly gaps throughout the core prior to startup and preventing positive reactivity insertion.

On the local time dependence of the bow shock wave structure

NASA Technical Reports Server (NTRS)

Olson, J. V.; Holzer, R. E.

1974-01-01

In the first 6 months after its launch, Ogo 3 crossed the earth's bow shock over 500 times. From this group, a set of 494 shock crossings were chosen for analysis. These crossings, as they were recorded by the UCLA/JPL search coil magnetometer, were scanned and classified according to the nature of the plasma waves detected near the shock. More than 85% of the shocks detected fell into a single category showing the predominance of two independent wave trains near the shock, the higher frequency appearing upstream and the lower downstream. The other 15%, which constitute an upper limit, appear to be composed of shocks dominated by a single wave pattern and of chaotic shocks showing no orderly progression of wave frequencies as the shock was penetrated. This division of wave pattern was found to occur at all local times, that is, in all regions where the satellite penetrated the shock.

Stagnation point reverse flow combustor

NASA Technical Reports Server (NTRS)

Zinn, Ben T. (Inventor); Neumeier, Yedidia (Inventor); Seitzman, Jerry M. (Inventor); Jagoda, Jechiel (Inventor); Weksler, Yoav (Inventor)

2008-01-01

A method for combusting a combustible fuel includes providing a vessel having an opening near a proximate end and a closed distal end defining a combustion chamber. A combustible reactants mixture is presented into the combustion chamber. The combustible reactants mixture is ignited creating a flame and combustion products. The closed end of the combustion chamber is utilized for directing combustion products toward the opening of the combustion chamber creating a reverse flow of combustion products within the combustion chamber. The reverse flow of combustion products is intermixed with combustible reactants mixture to maintain the flame.

The CHESS survey of the L1157-B1 bow-shock: Dissecting the water content

NASA Astrophysics Data System (ADS)

Busquet, Gemma; Lefloch, Bertrand; Benedettini, Milena; Ceccarelli, Cecilia; Codella, Claudio; Cabrit, Sylvie; Nisini, Brunella; Viti, Serena; Gómez-Ruiz, Arturo; Gusdorf, Antoine; Di Giorgio, Anna Maria; Wiesenfeld, Laurent

2013-07-01

Molecular outflows powered by young protostars strongly affect the kinematics and chemistry of the natal molecular cloud through strong shocks, resulting in an increase of the abundance of several species. In particular, water is a powerful tracer of shocked material due to its sensitivity to both physical conditions and chemical processes. The observations of the "Chemical Herschel Survey of Star forming regions" (CHESS) key program towards the shock region L1157-B1 offered a unique and comprehensive view of the water emission in a typical protostellar bow shock across the submillimeter and far-infrared window. A grand total of 13 water lines have been detected with the PACS and HIFI instruments, probing a wide range of excitation conditions and providing us with a detailed picture on both the kinematics and the spatial distribution of water emission. Several gas components have been identified coexisting in the L1157-B1 shock region. Large Velocity Gradient (LVG) analysis reveals that these components have different excitation conditions: i) a warm (T~250 K) and dense (n(H2)~10^6 cm-3) gas component seen also with the CO lines and associated with the partly dissociative shock produced by the impact of the protostellar jet against the bow shock; ii) a compact (size~5''), hot (T~700 K), and less dense (n(H2)~10^4 cm-3) gas component, and iii) an extended component associated with the B1 outflow cavity. These three components present clear differences in terms of water enrichment. Finally, we confront the physical and chemical properties of the H2O emission to the predictions of current shock models.

Chemical reactions in reverse micelle systems

DOEpatents

Matson, Dean W.; Fulton, John L.; Smith, Richard D.; Consani, Keith A.

1993-08-24

This invention is directed to conducting chemical reactions in reverse micelle or microemulsion systems comprising a substantially discontinuous phase including a polar fluid, typically an aqueous fluid, and a microemulsion promoter, typically a surfactant, for facilitating the formation of reverse micelles in the system. The system further includes a substantially continuous phase including a non-polar or low-polarity fluid material which is a gas under standard temperature and pressure and has a critical density, and which is generally a water-insoluble fluid in a near critical or supercritical state. Thus, the microemulsion system is maintained at a pressure and temperature such that the density of the non-polar or low-polarity fluid exceeds the critical density thereof. The method of carrying out chemical reactions generally comprises forming a first reverse micelle system including an aqueous fluid including reverse micelles in a water-insoluble fluid in the supercritical state. Then, a first reactant is introduced into the first reverse micelle system, and a chemical reaction is carried out with the first reactant to form a reaction product. In general, the first reactant can be incorporated into, and the product formed in, the reverse micelles. A second reactant can also be incorporated in the first reverse micelle system which is capable of reacting with the first reactant to form a product.

Quantified Energy Dissipation Rates in the Terrestrial Bow Shock. 2; Waves and Dissipation

NASA Technical Reports Server (NTRS)

Wilson, L. B., III; Sibeck, D. G.; Breneman, A. W.; Le Contel, O.; Cully, C.; Turner, D. L.; Angelopoulos, V.; Malaspina, D. M.

2014-01-01

We present the first quantified measure of the energy dissipation rates, due to wave-particle interactions, in the transition region of the Earth's collision-less bow shock using data from the Time History of Events and Macro-Scale Interactions during Sub-Storms spacecraft. Our results show that wave-particle interactions can regulate the global structure and dominate the energy dissipation of collision-less shocks. In every bow shock crossing examined, we observed both low-frequency (less than 10 hertz) and high-frequency (approximately or greater than10 hertz) electromagnetic waves throughout the entire transition region and into the magnetosheath. The low-frequency waves were consistent with magnetosonic-whistler waves. The high-frequency waves were combinations of ion-acoustic waves, electron cyclotron drift instability driven waves, electrostatic solitary waves, and whistler mode waves. The high-frequency waves had the following: (1) peak amplitudes exceeding delta B approximately equal to 10 nanoteslas and delta E approximately equal to 300 millivolts per meter, though more typical values were delta B approximately equal to 0.1-1.0 nanoteslas and delta E approximately equal to 10-50 millivolts per meter (2) Poynting fluxes in excess of 2000 microWm(sup -2) (micro-waves per square meter) (typical values were approximately 1-10 microWm(sup -2) (micro-waves per square meter); (3) resistivities greater than 9000 omega meters; and (4) associated energy dissipation rates greater than 10 microWm(sup -3) (micro-waves per cubic meter). The dissipation rates due to wave-particle interactions exceeded rates necessary to explain the increase in entropy across the shock ramps for approximately 90 percent of the wave burst durations. For approximately 22 percent of these times, the wave-particle interactions needed to only be less than or equal to 0.1 percent efficient to balance the nonlinear wave steepening that produced the shock waves. These results show that wave

Iris Positioning Using a Grid Attached to a Spring Bow for a Custom Ocular Prosthesis.

PubMed

Chamaria, Ankita; Aras, Meena Ajay; Chitre, Vidya; Costa, Godwin Clovis Da

2017-03-01

Eyes are among the first features of the face to be noticed. Loss of an eye due to congenital, traumatic or pathologic aetiologies causes disfigurement and loss of sensory feedback. It leaves a psychological impact on the patient, thus prosthesis should be provided at the earliest to raise the spirits of the afflicted. Iris positioning is one of the important steps in fabricating customized ocular prosthesis. In facial asymmetry cases, comparison of both irises together can be a major disadvantage. This case report illustrates the use of a unique customized frame spring bow assembly to position the iris disk using the established parallelism between inter pupillary line to the horizontal plane.

A study on dynamic heat assisted magnetization reversal mechanisms under insufficient reversal field conditions

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

Chen, Y. J.; Yang, H. Z.; Leong, S. H.

2014-10-20

We report an experimental study on the dynamic thermomagnetic (TM) reversal mechanisms at around Curie temperature (Tc) for isolated 60 nm pitch single-domain [Co/Pd] islands heated by a 1.5 μm spot size laser pulse under an applied magnetic reversal field (Hr). Magnetic force microscopy (MFM) observations with high resolution MFM tips clearly showed randomly trapped non-switched islands within the laser irradiated spot after dynamic TM reversal process with insufficient Hr strength. This observation provides direct experimental evidence by MFM of a large magnetization switching variation due to increased thermal fluctuation/agitation over magnetization energy at the elevated temperature of around Tc. The averagemore » percentage of non-switched islands/magnetization was further found to be inversely proportional to the applied reversal field Hr for incomplete magnetization reversal when Hr is less than 13% of the island coercivity (Hc), showing an increased switching field distribution (SFD) at elevated temperature of around Tc (where main contributions to SFD broadening are from Tc distribution and stronger thermal fluctuations). Our experimental study and results provide better understanding and insight on practical heat assisted magnetic recording (HAMR) process and recording performance, including HAMR writing magnetization dynamics induced SFD as well as associated DC saturation noise that limits areal density, as were previously observed and investigated by theoretical simulations.« less

Reverse spontaneous laser line sweeping in ytterbium fiber laser

NASA Astrophysics Data System (ADS)

Navratil, P.; Peterka, P.; Honzatko, P.; Kubecek, V.

2017-03-01

Self-induced laser line sweeping of various regimes of sweep direction is reported for an experimental ytterbium fiber laser. The regimes involve sweeping from shorter to longer wavelengths (1076~\\text{nm}\\to 1083 nm)—so-called normal self-sweeping; from longer to shorter wavelengths (1079~\\text{nm}\\to 1073 nm)—so-called reverse self-sweeping; and a mixed regime in which a precarious balance of the normal and reverse sweeping exists and the sweep direction can change between consecutive sweeps. The regimes of sweeping were selected by changing the pump wavelength only. A detailed explanation of this sweep direction dynamics is presented based on a semi-empirical model. This model also provides a way to predict the sweep direction of fiber lasers based on other rare-earth-doped laser media.

Dependence of the duration of geomagnetic polarity reversals on site latitude.

PubMed

Clement, Bradford M

2004-04-08

An important constraint on the processes governing the geodynamo--the flow in the outer core responsible for generating Earth's magnetic field--is the duration of geomagnetic polarity reversals; that is, how long it takes for Earth's magnetic field to reverse. It is generally accepted that Earth's magnetic field strength drops to low levels during polarity reversals, and the field direction progresses through a 180 degrees change while the field is weak. The time it takes for this process to happen, however, remains uncertain, with estimates ranging from a few thousand up to 28,000 years. Here I present an analysis of the available sediment records of the four most recent polarity reversals. These records yield an average estimate of about 7,000 years for the time it takes for the directional change to occur. The variation about this mean duration is not random, but instead varies with site latitude, with shorter durations observed at low-latitude sites, and longer durations observed at mid- to high-latitude sites. Such variation of duration with site latitude is predicted by simple geometrical reversal models, in which non-dipole fields are allowed to persist while the axial dipole decays through zero and then builds in the opposite direction, and provides a constraint on numerical dynamo models.

Reverse distal femoral locking compression plate a salvage option in nonunion of proximal femoral fractures.

PubMed

Dumbre Patil, Sampat S; Karkamkar, Sachin S; Patil, Vaishali S Dumbre; Patil, Shailesh S; Ranaware, Abhijeet S

2016-01-01

When primary fixation of proximal femoral fractures with implants fails, revision osteosynthesis may be challenging. Tracts of previous implants and remaining insufficient bone stock in the proximal femur pose unique problems for the treatment. Intramedullary implants like proximal femoral nail (PFN) or surface implants like Dynamic Condylar Screw (DCS) are few of the described implants for revision surgery. There is no evidence in the literature to choose one implant over the other. We used the reverse distal femur locking compression plate (LCP) of the contralateral side in such cases undergoing revision surgery. This implant has multiple options of fixation in proximal femur and its curvature along the length matches the anterior bow of the femur. We aimed to evaluate the efficacy of this implant in salvage situations. Twenty patients of failed primary proximal femoral fractures who underwent revision surgery with reverse distal femoral locking plate from February 2009 to November 2012 were included in this retrospective study. There were 18 subtrochanteric fractures and two ipsilateral femoral neck and shaft fractures, which exhibited delayed union or nonunion. The study included 14 males and six females. The mean patient age was 43.6 years (range 22-65 years) and mean followup period was 52.1 months (range 27-72 months). Delayed union was considered when clinical and radiological signs of union failed to progress at the end of four months from initial surgery. All fractures exhibited union without any complications. Union was assessed clinically and radiologically. One case of ipsilateral femoral neck and shaft fracture required bone grafting at the second stage for delayed union of the femoral shaft fracture. Reverse distal femoral LCP of the contralateral side can be used as a salvage option for failed fixation of proximal femoral fractures exhibiting nonunion.

Reverse genetics of Newcastle disease virus

USDA-ARS?s Scientific Manuscript database

Reverse genetics allows the generation of recombinant viruses or vectors used in functional studies, vaccine development, and gene therapy. This technique allows genetic manipulation and cloning of viral genomes, mutation through site-directed mutagenesis, and gene insertion or deletion, among othe...

Reversible colour change in Arthropoda.

PubMed

Umbers, Kate D L; Fabricant, Scott A; Gawryszewski, Felipe M; Seago, Ainsley E; Herberstein, Marie E

2014-11-01

The mechanisms and functions of reversible colour change in arthropods are highly diverse despite, or perhaps due to, the presence of an exoskeleton. Physiological colour changes, which have been recorded in 90 arthropod species, are rapid and are the result of changes in the positioning of microstructures or pigments, or in the refractive index of layers in the integument. By contrast, morphological colour changes, documented in 31 species, involve the anabolism or catabolism of components (e.g. pigments) directly related to the observable colour. In this review we highlight the diversity of mechanisms by which reversible colour change occurs and the evolutionary context and diversity of arthropod taxa in which it has been observed. Further, we discuss the functions of reversible colour change so far proposed, review the limited behavioural and ecological data, and argue that the field requires phylogenetically controlled approaches to understanding the evolution of reversible colour change. Finally, we encourage biologists to explore new model systems for colour change and to engage scientists from other disciplines; continued cross-disciplinary collaboration is the most promising approach to this nexus of biology, physics, and chemistry. © 2014 The Authors. Biological Reviews © 2014 Cambridge Philosophical Society.

Cessations and reversals of the large-scale circulation in turbulent thermal convection.

PubMed

Xi, Heng-Dong; Xia, Ke-Qing

2007-06-01

We present an experimental study of cessations and reversals of the large-scale circulation (LSC) in turbulent thermal convection in a cylindrical cell of aspect ratio (Gamma) 1/2 . It is found that cessations and reversals of the LSC occur in Gamma = 1/2 geometry an order-of-magnitude more frequently than they do in Gamma=1 cells, and that after a cessation the LSC is most likely to restart in the opposite direction, i.e., reversals of the LSC are the most probable cessation events. This contrasts sharply to the finding in Gamma=1 geometry and implies that cessations in the two geometries are governed by different dynamics. It is found that the occurrence of reversals is a Poisson process and that a stronger rebound of the flow strength after a reversal or cessation leads to a longer period of stability of the LSC. Several properties of reversals and cessations in this system are found to be statistically similar to those of geomagnetic reversals. A direct measurement of the velocity field reveals that a cessation corresponds to a momentary decoherence of the LSC.

Rattleback dynamics and its reversal time of rotation

NASA Astrophysics Data System (ADS)

Kondo, Yoichiro; Nakanishi, Hiizu

2017-06-01

A rattleback is a rigid, semielliptic toy which exhibits unintuitive behavior; when it is spun in one direction, it soon begins pitching and stops spinning, then it starts to spin in the opposite direction, but in the other direction, it seems to spin just steadily. This puzzling behavior results from the slight misalignment between the principal axes for the inertia and those for the curvature; the misalignment couples the spinning with the pitching and the rolling oscillations. It has been shown that under the no-slip condition and without dissipation the spin can reverse in both directions, and Garcia and Hubbard obtained the formula for the time required for the spin reversal tr [Proc. R. Soc. Lond. A 418, 165 (1988), 10.1098/rspa.1988.0078]. In this work, we reformulate the rattleback dynamics in a physically transparent way and reduce it to a three-variable dynamics for spinning, pitching, and rolling. We obtain an expression of the Garcia-Hubbard formula for tr by a simple product of four factors: (1) the misalignment angle, (2) the difference in the inverses of inertia moment for the two oscillations, (3) that in the radii for the two principal curvatures, and (4) the squared frequency of the oscillation. We perform extensive numerical simulations to examine validity and limitation of the formula, and find that (1) the Garcia-Hubbard formula is good for both spinning directions in the small spin and small oscillation regime, but (2) in the fast spin regime especially for the steady direction, the rattleback may not reverse and shows a rich variety of dynamics including steady spinning, spin wobbling, and chaotic behavior reminiscent of chaos in a dissipative system.

Iris Positioning Using a Grid Attached to a Spring Bow for a Custom Ocular Prosthesis

PubMed Central

Aras, Meena Ajay; Chitre, Vidya; Costa, Godwin Clovis Da

2017-01-01

Eyes are among the first features of the face to be noticed. Loss of an eye due to congenital, traumatic or pathologic aetiologies causes disfigurement and loss of sensory feedback. It leaves a psychological impact on the patient, thus prosthesis should be provided at the earliest to raise the spirits of the afflicted. Iris positioning is one of the important steps in fabricating customized ocular prosthesis. In facial asymmetry cases, comparison of both irises together can be a major disadvantage. This case report illustrates the use of a unique customized frame spring bow assembly to position the iris disk using the established parallelism between inter pupillary line to the horizontal plane. PMID:28511522

Reversal electron attachment ionizer for detection of trace species

NASA Technical Reports Server (NTRS)

Bernius, Mark T. (Inventor); Chutjian, Ara (Inventor)

1990-01-01

An in-line reversal electron, high-current ionizer capable of focusing a beam of electrons to a reversal region and executing a reversal of said electrons, such that the electrons possess zero kinetic energy at the point of reversal, may be used to produce both negative and positive ions. A sample gas is introduced at the point of electron reversal for low energy electron-(sample gas) molecule attachment with high efficiency. The attachment process produces negative ions from the sample gas, which includes species present in trace (minute) amounts. These ions are extracted efficiently and directed to a mass analyzer where they may be detected and identified. The generation and detection of positive ions is accomplished in a similar fashion with minimal adjustment to potentials applied to the apparatus.

Reversal electron attachment ionizer for detection of trace species

NASA Technical Reports Server (NTRS)

Bernius, Mark T. (Inventor); Chutjian, Ara (Inventor)

1989-01-01

An in-line reversal electron, high-current ionizer capable of focusing a beam of electrons to a reversal region and executing a reversal of the electrons, such that the electrons possess zero kinetic energy at the point of reversal, may be used to produce both negative and positive ions. A sample gas is introduced at the point of electron reversal for low energy electron-(sample gas) molecule attachment with high efficiency. The attachment process produces negative ions from the sample gas, which includes species present in trace (minute) amounts. These ions are extracted efficiently and directed to a mass analyzer where they may be detected and identified. The generation and detection of positive ions is accomplished in a similar fashion with minimal adjustment to potentials applied to the apparatus.

Anomalous flow deflection at earth's low-Alfvén-Mach-Number bow shock.

PubMed

Nishino, Masaki N; Fujimoto, Masaki; Phan, Tai-Duc; Mukai, Toshifumi; Saito, Yoshifumi; Kuznetsova, Masha M; Rastätter, Lutz

2008-08-08

Earth's magnetosphere is an obstacle to the supersonic solar wind and the bow shock is formed in the front side of it. In ordinary hydrodynamics, the flow decelerated at the shock is diverted around the obstacle symmetrically about the Earth-Sun line, which is indeed observed in the magnetosheath most of the time. Here we show a case under a very low-density solar wind in which duskward flow was observed in the dawnside magnetosheath. A Rankine-Hugoniot test shows that the magnetic effect is crucial for this "wrong flow" to appear. A full three-dimensional magnetohydrodynamics (MHD) simulation of the situation confirming this interpretation and earlier simulations is also performed. It is illustrated that in addition to the "wrong flow" feature, various peculiar characteristics appear in the global picture of the MHD flow interaction with the obstacle.

Domino model for geomagnetic field reversals.

PubMed

Mori, N; Schmitt, D; Wicht, J; Ferriz-Mas, A; Mouri, H; Nakamichi, A; Morikawa, M

2013-01-01

We solve the equations of motion of a one-dimensional planar Heisenberg (or Vaks-Larkin) model consisting of a system of interacting macrospins aligned along a ring. Each spin has unit length and is described by its angle with respect to the rotational axis. The orientation of the spins can vary in time due to spin-spin interaction and random forcing. We statistically describe the behavior of the sum of all spins for different parameters. The term "domino model" in the title refers to the interaction among the spins. We compare the model results with geomagnetic field reversals and dynamo simulations and find strikingly similar behavior. The aggregate of all spins keeps the same direction for a long time and, once in a while, begins flipping to change the orientation by almost 180 degrees (mimicking a geomagnetic reversal) or to move back to the original direction (mimicking an excursion). Most of the time the spins are aligned or antialigned and deviate only slightly with respect to the rotational axis (mimicking the secular variation of the geomagnetic pole with respect to the geographic pole). Reversals are fast compared to the times in between and they occur at random times, both in the model and in the case of the Earth's magnetic field.

Occurrence of high-beta superthermal plasma events in the close environment of Jupiter's bow shock as observed by Ulysses

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

Marhavilas, P. K.; Sarris, E. T.; Anagnostopoulos, G. C.

2011-01-04

The ratio of the plasma pressure to the magnetic field pressure (or of their energy densities) which is known as the plasma parameter 'beta'({beta}) has important implications to the propagation of energetic particles and the interaction of the solar wind with planetary magnetospheres. Although in the scientific literature the contribution of the superthermal particles to the plasma pressure is generally assumed negligible, we deduced, by analyzing energetic particles and magnetic field measurements recorded by the Ulysses spacecraft, that in a series of events, the energy density contained in the superthermal tail of the particle distribution is comparable to or evenmore » higher than the energy density of the magnetic field, creating conditions of high-beta plasma. More explicitly, in this paper we analyze Ulysses/HI-SCALE measurements of the energy density ratio (parameter {beta}{sub ep}) of the energetic ions'(20 keV to {approx}5 MeV) to the magnetic field's in order to find occurrences of high-beta ({beta}{sub ep}>1) superthermal plasma conditions in the environment of the Jovian magnetosphere, which is an interesting plasma laboratory and an important source of emissions in our solar system. In particular, we examine high-beta ion events close to Jupiter's bow shock, which are produced by two processes: (a) bow shock ion acceleration and (b) ion leakage from the magnetosphere.« less

The enigmatic nature of the circumstellar envelope and bow shock surrounding Betelgeuse as revealed by Herschel. I. Evidence of clumps, multiple arcs, and a linear bar-like structure

NASA Astrophysics Data System (ADS)

Decin, L.; Cox, N. L. J.; Royer, P.; Van Marle, A. J.; Vandenbussche, B.; Ladjal, D.; Kerschbaum, F.; Ottensamer, R.; Barlow, M. J.; Blommaert, J. A. D. L.; Gomez, H. L.; Groenewegen, M. A. T.; Lim, T.; Swinyard, B. M.; Waelkens, C.; Tielens, A. G. G. M.

2012-12-01

Context. The interaction between stellar winds and the interstellar medium (ISM) can create complex bow shocks. The photometers on board the Herschel Space Observatory are ideally suited to studying the morphologies of these bow shocks. Aims: We aim to study the circumstellar environment and wind-ISM interaction of the nearest red supergiant, Betelgeuse. Methods.Herschel PACS images at 70, 100, and 160 μm and SPIRE images at 250, 350, and 500 μm were obtained by scanning the region around Betelgeuse. These data were complemented with ultraviolet GALEX data, near-infrared WISE data, and radio 21 cm GALFA-HI data. The observational properties of the bow shock structure were deduced from the data and compared with hydrodynamical simulations. Results: The infrared Herschel images of the environment around Betelgeuse are spectacular, showing the occurrence of multiple arcs at ~6-7' from the central target and the presence of a linear bar at ~9'. Remarkably, no large-scale instabilities are seen in the outer arcs and linear bar. The dust temperature in the outer arcs varies between 40 and 140 K, with the linear bar having the same colour temperature as the arcs. The inner envelope shows clear evidence of a non-homogeneous clumpy structure (beyond 15''), probably related to the giant convection cells of the outer atmosphere. The non-homogeneous distribution of the material even persists until the collision with the ISM. A strong variation in brightness of the inner clumps at a radius of ~2' suggests a drastic change in mean gas and dust density ~32 000 yr ago. Using hydrodynamical simulations, we try to explain the observed morphology of the bow shock around Betelgeuse. Conclusions: Different hypotheses, based on observational and theoretical constraints, are formulated to explain the origin of the multiple arcs and the linear bar and the fact that no large-scale instabilities are visible in the bow shock region. We infer that the two main ingredients for explaining

Short term memory bowing effect is consistent with presentation rate dependent decay.

PubMed

Tarnow, Eugen

2010-12-01

I reanalyze the free recall data of Murdock, J Exp Psychol 64(5):482-488 (1962) and Murdock and Okada, J Verbal Learn and Verbal Behav 86:263-267 (1970) which show the famous bowing effect in which initial and recent items are recalled better than intermediate items (primacy and recency effects). Recent item recall probabilities follow a logarithmic decay with time of recall consistent with the tagging/retagging theory. The slope of the decay increases with increasing presentation rate. The initial items, with an effectively low presentation rate, decay with the slowest logarithmic slope, explaining the primacy effect. The finding that presentation rate limits the duration of short term memory suggests a basis for memory loss in busy adults, for the importance of slow music practice, for long term memory deficiencies for people with attention deficits who may be artificially increasing the presentation rates of their surroundings. A well-defined, quantitative measure of the primacy effect is introduced.

Evidence for specularly reflected ions upstream from the quasi-parallel bow shock

NASA Technical Reports Server (NTRS)

Gosling, J. T.; Thomsen, M. F.; Bame, S. J.; Feldman, W. C.; Paschmann, G.; Sckopke, N.

1982-01-01

Ion velocity distributions in the form of bunches of gyrating particles traveling along helical paths have been observed moving sunward immediately upstream from quasi-parallel parts of the earth's bow shock using Los Alamos/Garching instruments on ISEE-1 and -2. These distributions have characteristics which indicate that they are produced by the nearly specular reflection at the shock of a portion of the incident solar wind ions. In particular, the guiding center motion and the gyrospeeds of the gyrating ions are quantitatively consistent with simple geometrical considerations for specular reflection. These considerations reveal that specularly reflected ions can escape upstream when the angle between the upstream magnetic field and the local shock normal is less than 45 deg but not when the angle is greater than 45 deg. These upstream gyrating ions are an important signature of one of the processes by which solar wind streaming energy is dissipated into other forms of energy at the shock.

Laser iridotomy to treat uveitis-glaucoma-hyphema syndrome secondary to reverse pupillary block in sulcus-placed intraocular lenses: Case series.

PubMed

Singh, Harmanjit; Modabber, Milad; Safran, Steven G; Ahmed, Iqbal Ike K

2015-10-01

To present cases of uveitis-glaucoma-hyphema (UGH) syndrome due to reverse pupillary block in sulcus-placed posterior chamber intraocular lenses (PC IOLs) that were managed with laser peripheral iridotomy (LPI). Community-based subspecialty clinics. Retrospective interventional case series. A chart review of patients with a sulcus-placed PC IOLs presenting with UGH syndrome and reverse pupillary block with posterior iris bowing as diagnosed by gonioscopy and anterior segment optical coherence tomography was carried out. Laser peripheral iridotomy was performed in the eyes included in the study. The main outcome measure was clinical resolution of UGH syndrome. The study included 6 eyes of 6 patients with a mean age of 59.8 years (range 43.0 to 66.0 years) who presented with unilateral UGH syndrome a mean of 28.7 months (range 0.3 to 84.0 months) after PC IOL implantation. All patients were previously myopic, with 5 (83.3%) having a history of vitrectomy. The mean axial length was 27.0 mm ± 1.4 (SD). An LPI was used to treat the reverse pupillary block with resultant improvement in iris profile and resolution of UGH syndrome in all eyes. The mean intraocular pressure decreased from 30.5 ± 10.0 mm Hg on 0.5 ± 0.8 glaucoma medications to 15.5 ± 3.2 mm Hg postoperatively on 0.7 ± 1.2 medications. The UGH syndrome due to reverse pupillary block occurred after sulcus-placed PC IOLs in susceptible patients, those with axial myopia, and post-vitrectomized eyes. The cases were managed with LPIs. Dr. Ahmed is a consultant to Alcon Laboratories, Inc. and Abbott Medical Optics, Inc. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Mapping the magnetosheath field between the magnetopause and the bow shock - Implications for magnetospheric particle leakage

NASA Technical Reports Server (NTRS)

Luhmann, J. G.; Walker, R. J.; Russell, C. T.; Spreiter, J. R.; Stahara, S. S.; Williams, D. J.

1984-01-01

An approximate picture of the volumes occupied by particles that originate in the vicinity of the magnetopause is obtained by mapping magnetosheath magnetic field lines which drape over the magnetopause through the bow shock. Subsets of these field lines that connect to potential sites of magnetic merging on the magnetopause are also traced in the event that the particle leakage occurs preferentially where normal components of the field are present across that boundary. The results of this modeling exercise suggest that energetic magnetospheric particles which are not scattered by magnetosheath magnetic fluctuations are likely to exit the magnetosheath in the region of the quasi-parallel shock.

Time in Science: Reversibility vs. Irreversibility

NASA Astrophysics Data System (ADS)

Pomeau, Yves

To discuss properly the question of irreversibility one needs to make a careful distinction between reversibility of the equations of motion and the choice of the initial conditions. This is also relevant for the rather confuse philosophy of the wave packet reduction in quantum mechanics. The explanation of this reduction requires also to make precise assumptions on what initial data are accessible in our world. Finally I discuss how a given (and long) time record can be shown in an objective way to record an irreversible or reversible process. Or: can a direction of time be derived from its analysis? This leads quite naturally to examine if there is a possible spontaneous breaking of the time reversal symmetry in many body systems, a symmetry breaking that would be put in evidence objectively by looking at certain specific time correlations.

Reverse Algols

NASA Technical Reports Server (NTRS)

Leung, K. C.

1989-01-01

Reverse Algols, binary systems with a semidetached configuration in which the more massive component is in contact with the critical equipotential surface, are examined. Observational evidence for reverse Algols is presented and the parameters of seven reverse Algols are listed. The evolution of Algols and reverse Algols is discussed. It is suggested that, because reverse Algols represent the premass-reversal semidetached phase of close binary evolution, the evolutionary time scale between regular and reverse Algols is the ratio of the number of confirmed systems of these two Algol types.

Direct CRISPR spacer acquisition from RNA by a natural reverse-transcriptase-Cas1 fusion protein

PubMed Central

Sidote, David J.; Markham, Laura M.; Sanchez-Amat, Antonio; Bhaya, Devaki; Lambowitz, Alan M.; Fire, Andrew Z.

2016-01-01

CRISPR (Clustered Regularly Interspaced Short Palindromic Repeat) systems mediate adaptive immunity in diverse prokaryotes. CRISPR-associated Cas1 and Cas2 proteins have been shown to enable adaptation to new threats in Type I and II CRISPR systems by the acquisition of short segments of DNA (“spacers”) from invasive elements. In several Type III CRISPR systems, Cas1 is naturally fused to a reverse transcriptase (RT). In the marine bacterium Marinomonas mediterranea (MMB-1), we show that an RT-Cas1 fusion enables the acquisition of RNA spacers in vivo in an RT-dependent manner. In vitro, the MMB-1 RT-Cas1 and Cas2 proteins catalyze ligation of RNA segments into the CRISPR array, followed by reverse transcription. These observations outline a host-mediated mechanism for reverse information flow from RNA to DNA. PMID:26917774

HuR interacts with human immunodeficiency virus type 1 reverse transcriptase, and modulates reverse transcription in infected cells

PubMed Central

Lemay, Julie; Maidou-Peindara, Priscilla; Bader, Thomas; Ennifar, Eric; Rain, Jean-Christophe; Benarous, Richard; Liu, Lang Xia

2008-01-01

Reverse transcription of the genetic material of human immunodeficiency virus type 1 (HIV-1) is a critical step in the replication cycle of this virus. This process, catalyzed by reverse transcriptase (RT), is well characterized at the biochemical level. However, in infected cells, reverse transcription occurs in a multiprotein complex – the reverse transcription complex (RTC) – consisting of viral genomic RNA associated with viral proteins (including RT) and, presumably, as yet uncharacterized cellular proteins. Very little is known about the cellular proteins interacting with the RTC, and with reverse transcriptase in particular. We report here that HIV-1 reverse transcription is affected by the levels of a nucleocytoplasmic shuttling protein – the RNA-binding protein HuR. A direct protein-protein interaction between RT and HuR was observed in a yeast two-hybrid screen and confirmed in vitro by homogenous time-resolved fluorescence (HTRF). We mapped the domain interacting with HuR to the RNAse H domain of RT, and the binding domain for RT to the C-terminus of HuR, partially overlapping the third RRM RNA-binding domain of HuR. HuR silencing with specific siRNAs greatly impaired early and late steps of reverse transcription, significantly inhibiting HIV-1 infection. Moreover, by mutagenesis and immunoprecipitation studies, we could not detect the binding of HuR to the viral RNA. These results suggest that HuR may be involved in and may modulate the reverse transcription reaction of HIV-1, by an as yet unknown mechanism involving a protein-protein interaction with HIV-1 RT. PMID:18544151

An Archean Geomagnetic Reversal in the Kaap Valley Pluton, South Africa

PubMed

Layer; Kroner; McWilliams

1996-08-16

The Kaap Valley pluton in South Africa is a tonalite intrusion associated with the Archean Barberton Greenstone Belt. Antipodal paleomagnetic directions determined from the central and marginal parts of the pluton record a geomagnetic reversal that occurred as the pluton cooled. The age of the reversal is constrained by an 40Ar/39Ar plateau age from hornblende at 3214 +/- 4 million years, making it the oldest known reversal. The data presented here suggest that Earth has had a reversing, perhaps dipolar, magnetic field since at least 3.2 billion years ago.

Study on multi-satellite, multi-measurement of the structure of the earth's bow shock

NASA Technical Reports Server (NTRS)

1972-01-01

The pulsation model of the earth's bow shock proposed a nonuniform shock having both perpendicular (abrupt, monotonic) and oblique (oscillatory, multigradient) properties simultaneously, depending on local orientation of the shock surface to the interplanetary field B sub sw in parallel planes defined by B sub sw and solar wind velocity. Multiple, concurrent, satellite observations of the shock and solar wind conditions were used. Twenty-six potentially useful intervals of concurrent Explorer 33 and 35 data acquisition were examined, of which six were selected for closer study. In addition, two years of OGO-5 and HEOS 1 magnetometer data were examined for possible conjunctions to these spacecraft having applicable data. One case of clear nonuniformity and several of field-dependent structure were documented. A computational aid, called pulsation index, was developed.

High time resolution characteristics of intermediate ion distributions upstream of the earth's bow shock

NASA Technical Reports Server (NTRS)

Potter, D. W.

1985-01-01

High time resolution particle data upstream of the bow shock during time intervals that have been identified as having intermediate ion distributions often show high amplitude oscillations in the ion fluxes of energy 2 and 6 keV. These ion oscillations, observed with the particle instruments of the University of California, Berkeley, on the ISEE 1 and 2 spacecraft, are at the same frequency (about 0.04 Hz) as the magnetic field oscillations. Typically, the 6-keV ion flux increases then the 2-keV flux increases followed by a decrease in the 2-keV flux and then the 6-keV flux decreases. This process repeats many times. Although there is no entirely satisfactory explanation, the presence of these ion flux oscillations suggests that distributions often are misidentified as intermediate ion distributions.

Site-directed mutagenesis of α-L-rhamnosidase from Alternaria sp. L1 to enhance synthesis yield of reverse hydrolysis based on rational design.

PubMed

Xu, Li; Liu, Xiaohong; Yin, Zhenhao; Liu, Qian; Lu, Lili; Xiao, Min

2016-12-01

The α-L-rhamnosidase catalyzes the hydrolytic release of rhamnose from polysaccharides and glycosides and is widely used due to its applications in a variety of industrial processes. Our previous work reported that a wild-type α-L-rhamnosidase (RhaL1) from Alternaria sp. L1 could synthesize rhamnose-containing chemicals (RCCs) though reverse hydrolysis reaction with inexpensive rhamnose as glycosyl donor. To enhance the yield of reverse hydrolysis reaction and to determine the amino acid residues essential for the catalytic activity of RhaL1, site-directed mutagenesis of 11 residues was performed in this study. Through rationally designed mutations, the critical amino acid residues which may form direct or solvent-mediated hydrogen bonds with donor rhamnose (Asp 252 , Asp 257 , Asp 264 , Glu 530 , Arg 548 , His 553 , and Trp 555 ) and may form the hydrophobic pocket in stabilizing donor (Trp 261 , Tyr 302 , Tyr 316 , and Trp 369 ) in active-site of RhaL1 were analyzed, and three positive mutants (W261Y, Y302F, and Y316F) with improved product yield stood out. From the three positive variants, mutant W261Y accelerated the reverse hydrolysis with a prominent increase (43.7 %) in relative yield compared to the wild-type enzyme. Based on the 3D structural modeling, we supposed that the improved yield of mutant W261Y is due to the adjustment of the spatial position of the putative catalytic acid residue Asp 257 . Mutant W261Y also exhibited a shift in the pH-activity profile in hydrolysis reaction, indicating that introducing of a polar residue in the active site cavity may affect the catalysis behavior of the enzyme.

Assessing the potential for rainbow trout reproduction in tributaries of the Mountain Fork River below Broken Bow Dam, southeastern Oklahoma

Treesearch

James M. Long; Trevor A. Starks; Tyler Farling; Robert Bastarache

2016-01-01

Stocked trout (Salmonidae) in reservoir tailwater systems in the Southern United States have been shown to use tributary streams for spawning and rearing. The lower Mountain Fork of the Little River below Broken Bow Dam is one of two year-round tailwater trout fisheries in Oklahoma, and the only one with evidence of reproduction by stocked rainbow trout (Oncorhynchus...

Findings suggest possible link between geomagnetic reversals and field intensity

NASA Astrophysics Data System (ADS)

Hoffman, Kenneth A.

For the past 2000 years the Earth's magnetic field has been weakening. At the going rate of decay, the field's dipole—generated within the convecting metallic fluid of the outer core—would totally vanish, perhaps passing through zero and reversing polarity, in the coming millennia. This scenario of a coming attempt by Earth's dynamo to reverse its polarity is suggested by direct observation of the field since the 19th century and laboratory investigation of historic lavas and other fired materials that record the ambient field while cooling.The ongoing weakening of the field does not insure that a reversal will occur. After all, the north-south axial dipole changes to the opposite direction only on occasion; it currently reverses a few times each million years. How the dynamo actually approaches an attempted change of polarity and, moreover, the degree to which such a process can be predicted, are unclear. Nonetheless, a major step toward such an understanding may have been made through recently reported paleomagnetic findings obtained from the long, quasi-continuous records derived from Ocean Drilling Project (ODP) marine sediment cores.

Rattleback dynamics and its reversal time of rotation.

PubMed

Kondo, Yoichiro; Nakanishi, Hiizu

2017-06-01

A rattleback is a rigid, semielliptic toy which exhibits unintuitive behavior; when it is spun in one direction, it soon begins pitching and stops spinning, then it starts to spin in the opposite direction, but in the other direction, it seems to spin just steadily. This puzzling behavior results from the slight misalignment between the principal axes for the inertia and those for the curvature; the misalignment couples the spinning with the pitching and the rolling oscillations. It has been shown that under the no-slip condition and without dissipation the spin can reverse in both directions, and Garcia and Hubbard obtained the formula for the time required for the spin reversal t_{r} [Proc. R. Soc. Lond. A 418, 165 (1988)1364-502110.1098/rspa.1988.0078]. In this work, we reformulate the rattleback dynamics in a physically transparent way and reduce it to a three-variable dynamics for spinning, pitching, and rolling. We obtain an expression of the Garcia-Hubbard formula for t_{r} by a simple product of four factors: (1) the misalignment angle, (2) the difference in the inverses of inertia moment for the two oscillations, (3) that in the radii for the two principal curvatures, and (4) the squared frequency of the oscillation. We perform extensive numerical simulations to examine validity and limitation of the formula, and find that (1) the Garcia-Hubbard formula is good for both spinning directions in the small spin and small oscillation regime, but (2) in the fast spin regime especially for the steady direction, the rattleback may not reverse and shows a rich variety of dynamics including steady spinning, spin wobbling, and chaotic behavior reminiscent of chaos in a dissipative system.

Reversible unidirectional reflection and absorption of PT-symmetry structure under electro-optical modulation

NASA Astrophysics Data System (ADS)

Fang, Yun-tuan; Zhang, Yi-chi; Xia, Jing

2018-06-01

In order to obtain tunable unidirectional device, we assumed an ideal periodic layered Parity-Time (PT) symmetry structure inserted by doped LiNbO3 (LN) interlayers. LN is a typical electro-optical material of which the refractive index depends on the external electric field. In our work, we theoretically investigate the modulation effect of the external electric field on the transmittance and reflectance of the structure through numerical method. Through selected structural parameters, the one-way enhanced reflection and high absorption (above 0.9) behaviors are found. Within a special frequency band (not a single frequency), our theoretical model performs enhanced reflection in one incidence direction and high absorption in the other direction. Furthermore, the directions of enhanced reflection and absorption can be reversed through reversing the direction of applied electric field. Such structure with reversible properties has the potential in designing new optical devices.

Forward and reverse control system for induction motors

DOEpatents

Wright, J.T.

1987-09-15

A control system for controlling the direction of rotation of a rotor of an induction motor includes an array of five triacs with one of the triacs applying a current of fixed phase to the windings of the rotor and four of the triacs being switchable to apply either hot ac current or return ac current to the stator windings so as to reverse the phase of current in the stator relative to that of the rotor and thereby reverse the direction of rotation of the rotor. Switching current phase in the stator is accomplished by operating the gates of pairs of the triacs so as to connect either hot ac current or return ac current to the input winding of the stator. 1 fig.

Effect of q-profile structure on intrinsic torque reversals

NASA Astrophysics Data System (ADS)

Lu, Zhixin

2014-10-01

Intrinsic toroidal rotation plays an important role in mitigating macroinstability and regulating turbulent transport in ITER, where neutral beams are not sufficient to provide the requisite torque. Recent experiments on C-Mod with LHCD observed rotation reversal related to a change in the q profile. In this work, we focus on understanding the physics of intrinsic rotation reversals in LHCD plasmas, using nonlinear, global gyro-kinetic simulations and analysis of mode structure and spectrum symmetry breaking. The sensitive dependence of turbulent residual stress on magnetic shear is identified and characterized. The basic residual stress is non-vanishing when the k-parallel spectrum symmetry is broken, e.g., by E × B shear induced radial shift, non-uniformity in turbulence intensity, etc.. It is found that at low magnetic shear, the poloidal harmonics can shift strongly in the radial direction, as a feature of non-local effects, due to radial propagation and amplitude variation of the mode. This new symmetry breaking mechanism leads to a change in the sign of spectrum averaged parallel wave vector and thus the direction of intrinsic torque. Theoretical study shows that the competition between magnetic drift and ion kinetic effects determines the non-local effects and the structure of the asymmetry. Specifically, it is found that the direction of the intrinsic torque changes from counter- to co-current in the core, when magnetic shear decreases through a critical value. A critical shear ŝR = 0 . 2 ~ 0 . 5 for reversal of CTEM-induced intrinsic torque found by simulation is consistent with that from the LHCD C-Mod reversal experiments. In addition, simulations indicate ŝR = 1 ~ 2 for the reversal of ITG-induced torque, a prediction which can be tested by experiments. This work is supported by CER and CMTFO, UCSD and U.S. DOE-PPPL Contract DE-AC02-09CH11466.

Towards reversible basic linear algebra subprograms: A performance study

DOE PAGES

Perumalla, Kalyan S.; Yoginath, Srikanth B.

2014-12-06

Problems such as fault tolerance and scalable synchronization can be efficiently solved using reversibility of applications. Making applications reversible by relying on computation rather than on memory is ideal for large scale parallel computing, especially for the next generation of supercomputers in which memory is expensive in terms of latency, energy, and price. In this direction, a case study is presented here in reversing a computational core, namely, Basic Linear Algebra Subprograms, which is widely used in scientific applications. A new Reversible BLAS (RBLAS) library interface has been designed, and a prototype has been implemented with two modes: (1) amore » memory-mode in which reversibility is obtained by checkpointing to memory in forward and restoring from memory in reverse, and (2) a computational-mode in which nothing is saved in the forward, but restoration is done entirely via inverse computation in reverse. The article is focused on detailed performance benchmarking to evaluate the runtime dynamics and performance effects, comparing reversible computation with checkpointing on both traditional CPU platforms and recent GPU accelerator platforms. For BLAS Level-1 subprograms, data indicates over an order of magnitude better speed of reversible computation compared to checkpointing. For BLAS Level-2 and Level-3, a more complex tradeoff is observed between reversible computation and checkpointing, depending on computational and memory complexities of the subprograms.« less

A Statistical Study of the Magnetic Structure of Magnetic Clouds Downstream of the Earth's Bow Shock

NASA Astrophysics Data System (ADS)

Turc, L.; Fontaine, D.; Kilpua, E.; Escoubet, C. P.

2015-12-01

Magnetic clouds (MCs) are large-scale solar wind transients characterized primarily by an enhanced and smoothly-rotating magnetic field over periods of the order of one day. They are the drivers of the most intense geomagnetic storms, therefore understanding their interaction with the Earth's environment is of major interest for space weather forecasting. The first steps of this complex chain of processes are their interaction with the terrestrial bow shock and the ensuing propagation in the magnetosheath. Recent studies have shown that under certain conditions the distinctive magnetic structure of MCs can be significantly altered downstream of the bow shock. In such case, the magnetic field impinging on the magnetosphere strongly differs from that in the upstream solar wind and could lead to a reconnection pattern very different from that expected from the solar wind observations. The aim of the present work is to substantiate and generalize these results, obtained from a few MC events, in performing a statistical study. For this purpose, a comprehensive database of MC events, covering about 15 years of data, from 2000 to 2014, has been compiled. It lists presently 151 MCs observed in L1 by either Wind or ACE. Using the events during which spacecraft observations in the magnetosheath are simultaneously available, we investigate the evolution of the magnetic structure of MCs from the solar wind to the magnetosheath. The influence of the upstream solar wind parameters, such as the plasma beta, the Alfven Mach number or the magnetic field strength, is examined. Using a semi-analytical model, we estimate the local shock properties encountered upon entering the magnetosheath and find that the alteration of the magnetic structure of MCs strongly depend on the shock geometry. The large dataset allows us to assess the limitations of the magnetosheath model. The consequences of our results in terms of the geoeffectivity of MCs are discussed.

Hubble Space Telescope Images of the HH 34 Jet and Bow Shock: Structure and Proper Motions

NASA Astrophysics Data System (ADS)

Reipurth, Bo; Heathcote, Steve; Morse, Jon; Hartigan, Pat; Bally, John

2002-01-01

We present new, deep Hα and [S II] images of the HH 34 jet and bow shock obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope (HST), which reveal the structure of this fine HH flow with unprecedented detail. Many of the knots in the jet appear to form small working surfaces with bright [S II] cores and thin Hα filaments where the mini-bow shocks extend into the surrounding medium. In combination with earlier, short-exposure HST images we have determined very precise proper-motion vectors for the various shock structures in the outflow. The jet becomes visible within about an arcsecond of the source, where a new knot has emerged between our two epoch images; it has a space velocity of at least 300 km s-1, as derived from the proper motions and correcting for the 30° angle of the flow to the line of sight. The jet rapidly slows down to a mean space velocity of about 220 km s-1, with a standard deviation of 20 km s-1 among the jet knots. Such low internal velocities lead to weak shocks, consistent with the high [S II]/Hα ratio along the jet body and in accordance with the internal working surface model for jets. The jet motion appears to be ballistic, with no evidence for a turbulent boundary layer. The jet is well resolved and steadily expands with a half-opening angle of 0.4d. The large HH 34 working surface shows a multitude of knots, all of which are enveloped by a series of very thin, limb-brightened Hα-emitting filaments immediately behind the shock front where the flow faces into the preshock medium. One of these filaments developed four regularly spaced tiny knots between the two epochs, possibly due to a Rayleigh-Taylor instability along the filament or caused by the presence of small, dense clumps in the ambient medium. Proper motions of the HH 34 working surface show an obvious expansion due to material being squirted sideways. In addition to the large-scale S-shaped symmetry of the giant HH 34 flow, the jet shows a

Idarucizumab for Reversing Dabigatran-Induced Anticoagulation: A Systematic Review.

PubMed

Thibault, Nathan; Morrill, Amanda M; Willett, Kristine C

The approval of the oral direct thrombin inhibitor, dabigatran etexilate, gave patients an alternative to oral anticoagulation with warfarin. Like all anticoagulants, the primary adverse event (AE) associated with dabigatran is bleeding. Until the FDA approval of idarucizumab, there had been no reversal agent for dabigatran-induced anticoagulation in patients with life-threatening or uncontrollable bleeding, or those requiring emergent procedures. The primary purpose of this review is to summarize the safety and efficacy of idarucizumab, a monoclonal antibody fragment, and its use as a reversal agent for dabigatran. A literature search was conducted through MEDLINE (1946 to November week 1 2015) and Embase (1980-2015 week 46) using the search term idarucizumab. Clinicaltrials.gov was consulted for a comprehensive list of ongoing and completed studies. Additional studies were identified through bibliographical citations. Clinical trials in animals and humans published in English evaluating the safety and efficacy of idarucizumab for reversal of anticoagulant treatment with dabigatran were included for review. Idarucizumab has been shown to significantly reverse the anticoagulant effects of dabigatran in both healthy volunteers and patients requiring a reversal agent because of either overt bleeding or an emergency surgery or invasive procedure. The most common AEs were headache, nasopharyngitis, back pain, skin irritation, hypokalemia, delirium, constipation, pyrexia, and pneumonia. Deaths reported in idarucizumab studies were attributed to either the index event or a preexisting comorbidity. Most adverse effects were minor, but 21 serious AEs have been reported in the published data including thrombotic events. Given the increased use of direct oral anticoagulants, such as dabigatran, a need for specific reversal agents exists. Idarucizumab has been shown to be safe and effective in the reversal of dabigatran-induced anticoagulation in patients requiring emergent

Direct integration of MEMS, dielectric pumping and cell manipulation with reversibly bonded gecko adhesive microfluidics

NASA Astrophysics Data System (ADS)

Warnat, S.; King, H.; Wasay, A.; Sameoto, D.; Hubbard, T.

2016-09-01

We present an approach to form a microfluidic environment on top of MEMS dies using reversibly bonded microfluidics. The reversible polymeric microfluidics moulds bond to the MEMS die using a gecko-inspired gasket architecture. In this study the formed microchannels are demonstrated in conjunction with a MEMS mechanical single cell testing environment for BioMEMS applications. A reversible microfluidics placement technique with an x-y and rotational accuracy of  ±2 µm and 1° respectively on a MEMS die was developed. No leaks were observed during pneumatic pumping of common cell media (PBS, sorbitol, water, seawater) through the fluidic channels. Thermal chevron actuators were successful operated inside this fluidic environment and a performance deviation of ~15% was measured compared to an open MEMS configuration. Latex micro-spheres were pumped using traveling wave di-electrophoresis and compared to an open (no-microfluidics) configuration with velocities of 24 µm s-1 and 20 µm s-1.

Point-of-Care Coagulation Tests Monitoring of Direct Oral Anticoagulants and Their Reversal Therapy: State of the Art.

PubMed

Iapichino, Giacomo E; Bianchi, Paolo; Ranucci, Marco; Baryshnikova, Ekaterina

2017-06-01

Direct oral anticoagulants (DOACs) exert similar anticoagulant effects to vitamin K antagonists and are increasingly used worldwide. Nevertheless, an evidence-based approach to patients receiving DOACs when any unplanned urgent surgery or bleeding (either spontaneous or traumatic) occurs is still missing. In this review, we investigate the role of point-of-care coagulation tests when other, more specific tests are not available. Indeed, thromboelastography and activated clotting time can detect dabigatran-induced coagulopathy, while their accuracy is limited for apixaban and rivaroxaban, mostly in cases of low drug plasma concentrations. These tests can also be used to guide the reversal of DOAC-induced coagulopathy providing a quick, before-and-after picture in case of therapeutic use of hemostatic compounds. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Study of Ni-Mo electrodeposition in direct and pulse-reverse current

NASA Astrophysics Data System (ADS)

Stryuchkova, Yu M.; Rybin, N. B.; Suvorov, D. V.; Gololobov, G. P.; Tolstoguzov, A. B.; Tarabrin, D. Yu; Serpova, M. A.; Korotchenko, V. A.; Slivkin, E. V.

2017-05-01

Process of electrochemical deposition of the coating based on a binary nickel-molybdenum alloy onto a nickel substrate under pulse mode with current reverse within the range of current density change from 2 to 9 A/dm2 has been researched. Coating structure and its surface morphology have been studied. Method of X-ray energy dispersive spectroscopy has determined a percentage ratio of alloy components in the coating. Mode to obtain the densest and smoothest deposits has been identified under considered terms.

Infrared line scanner that digitally corrects for bow-tie distortions

NASA Astrophysics Data System (ADS)

Silva, Raymond J.; Shaw, William; Nordhaus, Kurt

1996-06-01

This paper describes the infrared line scanner (IRLS) developed by Loral Infrared & Imaging Systems for the Advanced Tactical Air Reconnaissance System (ATARS). Features include very wide fields of view, up to 140 degrees in wide mode; high resolution in the 8 - 14 micrometer band; and the ability to collect contiguous ground imagery at velocity to height (V/H) ratios of up to 5 rad per second. In real terms, a V/H ratio of five equates to an aircraft altitude of 200 feet at speeds approaching Mach 1. The ATARS IRLS is an evolution of the AN/AAD-5 and D-500 line scanners that provides several key improvements over its predecessors. Imagery is exported in digital format allowing for real time imagery exploitation. Additionally, by using some novel system approaches that combined the elements of receiver optics, detector geometry, and electronic signal processing, output data rates were held at tolerable levels. The combination of these techniques results in a system that is optimized for best ground area coverage with a minimum number of detector channels. As a consequence the bow-tie effect at the edges of the field of view has been virtually eliminated while simultaneously reducing data storage requirements.

Geological and geochemical investigations of uranium occurrences in the Arrastre Lake area of the Medicine Bow Mountains, Wyoming

USGS Publications Warehouse

Miller, W. Roger; Houston, R.S.; Karlstrom, K.E.; Hopkins, D.M.; Ficklin, W.H.

1977-01-01

Metasedimentary rocks of Precambrian X age in and near the Snowy Range wilderness study area of southeastern Wyoming are lithologically and chronologically similar to those on the north shore of Lake Huron in Canada. The rocks in Canada contain major deposits of uranium in quartz-pebble conglomerates near the base of the metasedimentary sequence. Similar conglomerates in the Deep Lake Formation in the Medicine Bow Mountains of southeastern Wyoming are slightly radioactive and may contain deposits of uranium and other valuable heavy metals. During the summer of 1976, a geological and geochemical pilot study was conducted in the vicinity of Arrastre Lake in the Medicine Bow Mountains to determine the most effective exploration methods for evaluating the uranium potential of the Snowy Range wilderness study area. The area around Arrastre Lake was selected because of the presence of a radioactive lens within a quartz-pebble conglomerate of the Deep Lake Formation. The results of the survey indicate possible uranium mineralization in the subsurface rocks of this formation. The radon content of the dilute waters of the area is much higher than can be accounted for by the uranium content of the surface rocks. Two sources for the high content of the radon are possible. In either case, the high values of radon obtained in this study are a positive indication of uranium mineralization in the subsurface rocks. The determination of the radon content of water samples is the recommended geochemical technique for uranium exploration in the area. The determination of uranium in water and in organic-rich bog material is also recommended.

MiR-424-5p reversed epithelial-mesenchymal transition of anchorage-independent HCC cells by directly targeting ICAT and suppressed HCC progression

PubMed Central

Zhang, Ying; Li, Tao; Guo, Pengbo; Kang, Jia; Wei, Qing; Jia, Xiaoqing; Zhao, Wei; Huai, Wanwan; Qiu, Yumin; Sun, Lei; Han, Lihui

2014-01-01

Resistance to anoikis and Epithelial-mesenchymal transition (EMT) are two processes critically involved in cancer metastasis. In this study, we demonstrated that after anchorage deprival, hepatocellular carcinoma (HCC) cells not only resisted anoikis, but also exhibited EMT process. Microarray expression profiling revealed that expression of miR-424-5p was significantly decreased in anoikis-resistant HCC cells. Ectopic overexpression of miR-424-5p was sufficient to reverse resistance to anoikis, block EMT process and inhibit malignant behaviors of HCC cells. Target analysis showed that a potent β-catenin inhibitor, ICAT/CTNNBIP1 was a direct target of miR-424-5p. Further study demonstrated that miR-424-5p reversed resistance to anoikis and EMT of HCCs by directly targeting ICAT and further maintaining the E-cadherin/β-catanin complex on the cellular membrance. In vivo study further demonstrated that miR-424-5p significantly inhibited the tumorigenicity of HCC cells in nude mice. Clinical investigation demonstrated that miR-424-5p was significantly downregulated in HCC tissues compared with that of the non-cancerous liver tissues, and this decreased expression of miR-424-5p was significantly correlated with higher pathological grades and more advanced TNM stages. Therefore, aberrant expression of miR-424-5p is critically involved in resistance to anoikis and EMT during the metastatic process of HCC, and its downregulation significantly contributes to liver cancer progression. PMID:25175916

The Tympanic Membrane Motion in Forward and Reverse Middle-Ear Sound Transmission

NASA Astrophysics Data System (ADS)

Cheng, Jeffrey Tao; Harrington, Ellery; Horwitz, Rachelle; Furlong, Cosme; Rosowski, John J.

2011-11-01

Sound-induced displacement of the tympanic membrane (TM) is the first stage in the forward transformation of environmental sound to sound within the inner ear, while displacement of the TM induced by mechanical motions of the ossicular chain is the last stage in the reverse transformation of sound generated within the inner ear to clinically valuable otoacoustic emissions (OAEs). In this study, we use stroboscopic holographic interferometry to study motions of the human cadaveric TM evoked by both forward and reverse stimuli. During forward acoustic stimulation, pure tones from 500 to 10000 Hz are used to stimulate the TM, while reverse stimulation is produced by direct mechanical stimulation of the ossicular chain. The TM surface motions in response to both forward and reverse stimuli show differences and similarities, including the modal motion patterns at specific frequencies as well as the presence and directions of traveling waves on the TM surface.

Multi-dimensional dynamics of stimulated Brillouin scattering in a laser speckle: Ion acoustic wave bowing, breakup, and laser-seeded two-ion-wave decay

DOE PAGES

Albright, B. J.; Yin, L.; Bowers, K. J.; ...

2016-03-04

Two- and three-dimensional particle-in-cell simulations of stimulated Brillouin scattering(SBS) in laser speckle geometry have been analyzed to evaluate the relative importance of competing nonlinear processes in the evolution and saturation of SBS. It is found that ion-trapping-induced wavefront bowing and breakup of ion acoustic waves(IAW) and the associated side-loss of trapped ions dominate electron-trapping-induced IAW wavefront bowing and breakup, as well as the two-ion-wave decay instability over a range of ZT e/T i conditions and incident laser intensities. In the simulations, the latter instability does not govern the nonlinear saturation of SBS; however, evidence of two-ion-wave decay is seen, appearingmore » as a modulation of the ion acoustic wavefronts. This modulation is periodic in the laser polarization plane, anti-symmetric across the speckle axis, and of a wavenumber matching that of the incident laser pulse. Furthermore, a simple analytic model is provided for how spatial “imprinting” from a high frequency inhomogeneity (in this case, the density modulation from the laser) in an unstable system with continuum eigenmodes can selectively amplify modes with wavenumbers that match that of the inhomogeneity.« less

Spurious behavior in volcanic records of geomagnetic field reversals

NASA Astrophysics Data System (ADS)

Carlut, Julie; Vella, Jerome; Valet, Jean-Pierre; Soler, Vicente; Legoff, Maxime

2016-04-01

Very large directional variations of magnetization have been reported in several lava flows recording a geomagnetic reversal. Such behavior could reflect real geomagnetic changes or be caused by artifacts due to post-emplacement alteration and/or non-ideal magnetic behavior. More recently, a high resolution paleomagnetic record from sediments pleads also for an extremely rapid reversal process during the last reversal. Assuming that the geomagnetic field would have moved by tens of degrees during cooling of moderate thickness lava flows implies brief episodes of rapid changes by a few degrees per day that are difficult to reconcile with the rate of liquid motions at the core surface. Systematical mineralogical bias is a most likely explanation to promote such behavior as recently reconsidered by Coe et al., 2014 for the rapid field changes recorded at Steens Mountain. We resampled three lava flows at La Palma island (Canarias) that are sandwiched between reverse polarity and normal polarity flows associated with the last reversal. The results show an evolution of the magnetization direction from top to bottom. Thermal demagnetization experiments were conducted using different heating and cooling rates. Similarly, continuous demagnetization and measurements. In both cases, we did not notice any remagnetization associated with mineralogical transformations during the experiments. Magnetic grain sizes do not show any correlation with the amplitude of the deviations. Microscopic observations indicate poor exsolution, which could suggests post-cooling thermochemical remagnetization processes.

Directional climate change and potential reversal of desertification in arid and semiarid ecosystems

USDA-ARS?s Scientific Manuscript database

Our objective was to determine if long-term increases in precipitation can maintain grasslands susceptible to desertification, and initiate a reversal of historic regime shifts on desertified shrublands. Long-term trends in desertification were documented using vegetation maps beginning in 1858. The...

Detection of singly ionized energetic lunar pick-up ions upstream of earth's bow shock

NASA Technical Reports Server (NTRS)

Hilchenbach, M.; Hovestadt, D.; Klecker, B.; Moebius, E.

1992-01-01

Singly ionized suprathermal ions upstream of the earth's bow shock have been detected by using the time-of-flight spectrometer SULEICA on the AMPTE/IRM satellite. The data were collected between August and December 1985. The flux of the ions in the mass range between 23 and 37 amu is highly anisotropic towards the earth. The ions are observed with a period of about 29 days around new moon (+/- 3 days). The correlation of the energy of the ions with the solar wind speed and the interplanetary magnetic field orientation indicates the relation to the pick-up process. We conclude that the source of these pick-up ions is the moon. We argue that due to the impinging solar wind, atoms are sputtered off the lunar surface, ionized in the sputtering process or by ensuing photoionization and picked up by the solar wind.

Remagnetization of lava flows spanning the last geomagnetic reversal

NASA Astrophysics Data System (ADS)

Vella, Jérôme; Carlut, Julie; Valet, Jean-Pierre; Goff, Maxime Le; Soler, Vicente; Lopes, Fernando

2017-08-01

Large directional changes of remanent magnetization within lava flows that cooled during geomagnetic reversals have been reported in several studies. A geomagnetic scenario implies extremely rapid geomagnetic changes of several degrees per day, thus difficult to reconcile with the rate of the earth's core liquid motions. So far, no complete rock magnetic model provides a clear explanation. We revisited lava flows sandwiched between an underlying reverse and an overlying normal polarity flow marking the last reversal in three distinct volcanic sequences of the La Palma Island (Canary archipelago, Spain) that are characterized by a gradual evolution of the direction of their remanent magnetization from bottom to top. Cleaning efficiency of thermal demagnetization was not improved by very rapid heating and cooling rates as well as by continuous demagnetization using a Triaxe magnetometer. We did not observe partial self-reversals and minor changes in magnetic grain sizes are not related to the within-flow directional changes. Microscopic observations indicate poor exsolution, which suggests post-cooling thermochemical remagnetization processes. This scenario is strongly reinforced by laboratory experiments that show large resistance to thermal demagnetization when thermoremanence was acquired over a long time period. We speculate that in the present situation exsolution was reactivated during in field reheating and yielded formation of new magnetite, yet magnetic domain state rearrangements could also play a role. Initial reheating when the overlying flow took place, albeit moderate (less than 200-300 °C), was enough to produce overlying components with significantly higher unblocking temperatures.

A TATA binding protein mutant with increased affinity for DNA directs transcription from a reversed TATA sequence in vivo.

PubMed

Spencer, J Vaughn; Arndt, Karen M

2002-12-01

The TATA-binding protein (TBP) nucleates the assembly and determines the position of the preinitiation complex at RNA polymerase II-transcribed genes. We investigated the importance of two conserved residues on the DNA binding surface of Saccharomyces cerevisiae TBP to DNA binding and sequence discrimination. Because they define a significant break in the twofold symmetry of the TBP-TATA interface, Ala100 and Pro191 have been proposed to be key determinants of TBP binding orientation and transcription directionality. In contrast to previous predictions, we found that substitution of an alanine for Pro191 did not allow recognition of a reversed TATA box in vivo; however, the reciprocal change, Ala100 to proline, resulted in efficient utilization of this and other variant TATA sequences. In vitro assays demonstrated that TBP mutants with the A100P and P191A substitutions have increased and decreased affinity for DNA, respectively. The TATA binding defect of TBP with the P191A mutation could be intragenically suppressed by the A100P substitution. Our results suggest that Ala100 and Pro191 are important for DNA binding and sequence recognition by TBP, that the naturally occurring asymmetry of Ala100 and Pro191 is not essential for function, and that a single amino acid change in TBP can lead to elevated DNA binding affinity and recognition of a reversed TATA sequence.

Magnetic field evolution and reversals in spiral galaxies

NASA Astrophysics Data System (ADS)

Dobbs, C. L.; Price, D. J.; Pettitt, A. R.; Bate, M. R.; Tricco, T. S.

2016-10-01

We study the evolution of galactic magnetic fields using 3D smoothed particle magnetohydrodynamics (SPMHD) simulations of galaxies with an imposed spiral potential. We consider the appearance of reversals of the field, and amplification of the field. We find that magnetic field reversals occur when the velocity jump across the spiral shock is above ≈20 km s-1, occurring where the velocity change is highest, typically at the inner Lindblad resonance in our models. Reversals also occur at corotation, where the direction of the velocity field reverses in the corotating frame of a spiral arm. They occur earlier with a stronger amplitude spiral potential, and later or not at all with weaker or no spiral arms. The presence of a reversal at radii of around 4-6 kpc in our fiducial model is consistent with a reversal identified in the Milky Way, though we caution that alternative Galaxy models could give a similar reversal. We find that relatively high resolution, a few million particles in SPMHD, is required to produce consistent behaviour of the magnetic field. Amplification of the magnetic field occurs in the models, and while some may be genuinely attributable to differential rotation or spiral arms, some may be a numerical artefact. We check our results using ATHENA, finding reversals but less amplification of the field, suggesting that some of the amplification of the field with SPMHD is numerical.

Light-dependent reversion gravitropism of the moss Pohlia nutans

NASA Astrophysics Data System (ADS)

Khorkavtsiv, O.

Plants have evolved highly sensitive mechanisms adapting their growth to the environmental conditions. Light and gravity are critical importance factors, which exerts an essential and specific influence on the determination of the growth direction and regulation of the early stages of plants ontogeny, sometimes effects of these factors being independent. The negative gravitropic resp onse of moss protonemata causes their spatial orientation towards light, which in its turn is the source of photosynthetic efficiency and phototropism. The gravitropism system does not function independently of other sensory response systems in plants. The competence of protonemata to gravity might be altered and the gravitropic response be reversed from negative to positive by light. It has been shown that response of apical cells to light depend on wavelenght: red light (max = 660 nm) represses the gravitropism and blue ( = 450 nm) inverts the protonemal gravitropism. Light, has also been shown for seed plants to modulate gravitropism of roots and stems through the action of phy B in red/far-red reversible way and by phy A in a non-reversible, very - low-fluence response (Hangarter, 1997). In P. nutans blue light reversed the gravitropism protonemal filaments. The mean angle after 24 h blue irradiation was 83 0, like that of negative gravitropic protonemata in darkness. We compared the effect of blue light on gravitropism of chloronemal filaments of Funaria hygrometrica having very low sensitivity to gravity. After action of blue light, however, the positive gravitropism of F. hygrometrica chloronemata was fairly high - 370 . Among blue light spectrum the highest reversion effectiveness in P. nutans had the UV light ( = 350 nm) initiated bends in 90% of protonemata. If a far-red pulse (5 min per h) was added to the blue/UV the gravitropic growth of protonemata resembled that in the dark control. Phytochrome has maxima of absorption in blue and red spectrum region and in our

PageRank and rank-reversal dependence on the damping factor

NASA Astrophysics Data System (ADS)

Son, S.-W.; Christensen, C.; Grassberger, P.; Paczuski, M.

2012-12-01

PageRank (PR) is an algorithm originally developed by Google to evaluate the importance of web pages. Considering how deeply rooted Google's PR algorithm is to gathering relevant information or to the success of modern businesses, the question of rank stability and choice of the damping factor (a parameter in the algorithm) is clearly important. We investigate PR as a function of the damping factor d on a network obtained from a domain of the World Wide Web, finding that rank reversal happens frequently over a broad range of PR (and of d). We use three different correlation measures, Pearson, Spearman, and Kendall, to study rank reversal as d changes, and we show that the correlation of PR vectors drops rapidly as d changes from its frequently cited value, d0=0.85. Rank reversal is also observed by measuring the Spearman and Kendall rank correlation, which evaluate relative ranks rather than absolute PR. Rank reversal happens not only in directed networks containing rank sinks but also in a single strongly connected component, which by definition does not contain any sinks. We relate rank reversals to rank pockets and bottlenecks in the directed network structure. For the network studied, the relative rank is more stable by our measures around d=0.65 than at d=d0.

Reverse-Tangent Injection in a Centrifugal Compressor

NASA Technical Reports Server (NTRS)

Skoch, Gary J.

2007-01-01

Injection of working fluid into a centrifugal compressor in the reverse tangent direction has been invented as a way of preventing flow instabilities (stall and surge) or restoring stability when stall or surge has already commenced. The invention applies, in particular, to a centrifugal compressor, the diffuser of which contains vanes that divide the flow into channels oriented partly radially and partly tangentially. In reverse-tangent injection, a stream or jet of the working fluid (the fluid that is compressed) is injected into the vaneless annular region between the blades of the impeller and the vanes of the diffuser. As used here, "reverse" signifies that the injected flow opposes (and thereby reduces) the tangential component of the velocity of the impeller discharge. At the same time, the injected jet acts to increase the radial component of the velocity of the impeller discharge.

Reverse surface-polariton cherenkov radiation

PubMed Central

Tao, Jin; Wang, Qi Jie; Zhang, Jingjing; Luo, Yu

2016-01-01

The existence of reverse Cherenkov radiation for surface plasmons is demonstrated analytically. It is shown that in a metal-insulator-metal (MIM) waveguide, surface plasmon polaritons (SPPs) excited by an electron moving at a speed higher than the phase velocity of SPPs can generate Cherenkov radiation, which can be switched from forward to reverse direction by tuning the core thickness of the waveguide. Calculations are performed in both frequency and time domains, demonstrating that a radiation pattern with a backward-pointing radiation cone can be achieved at small waveguide core widths, with energy flow opposite to the wave vector of SPPs. Our study suggests the feasibility of generating and steering electron radiation in simple plasmonic systems, opening the gate for various applications such as velocity-selective particle detections. PMID:27477061

Paleomagnetic Study of a Reversal of the Earth's Magnetic Field.

PubMed

Dunn, J R; Fuller, M; Ito, H; Schmidt, V A

1971-05-21

A detailed record of a field reversal has been obtained from the natural remanent magnetization of the Tatoosh intrusion in Mount Rainier National Park, Washington. The reversal took place at 14.7 +/- 1 million years and is interpreted to be from reverse to normal. A decrease in the intensity of the field of about an order of magnitude occurs immediately before the reversal, while its orientation remains substantially unchanged. The onset of the reversal is marked by abrupt swinging of the virtual geomagnetic pole along an arc of a great circle. During the reversal the pole traces a path across the Pacific. In the last stage of the process recorded in the sections, the succession of virtual geomagnetic poles is very similar to those generated by secular variation in the recent past. Although the cooling rate of the intrusion is not sufficiently well known to permit a useful calculation of the duration of the reversal process, an estimate based on the length of the supposed secular variation cycles gives 1 to 4 x 103 years for the reversal of field direction and approximately 1 x 104 years for the time scale of the intensity changes.

The criterion for time symmetry of probabilistic theories and the reversibility of quantum mechanics

NASA Astrophysics Data System (ADS)

Holster, A. T.

2003-10-01

Physicists routinely claim that the fundamental laws of physics are 'time symmetric' or 'time reversal invariant' or 'reversible'. In particular, it is claimed that the theory of quantum mechanics is time symmetric. But it is shown in this paper that the orthodox analysis suffers from a fatal conceptual error, because the logical criterion for judging the time symmetry of probabilistic theories has been incorrectly formulated. The correct criterion requires symmetry between future-directed laws and past-directed laws. This criterion is formulated and proved in detail. The orthodox claim that quantum mechanics is reversible is re-evaluated. The property demonstrated in the orthodox analysis is shown to be quite distinct from time reversal invariance. The view of Satosi Watanabe that quantum mechanics is time asymmetric is verified, as well as his view that this feature does not merely show a de facto or 'contingent' asymmetry, as commonly supposed, but implies a genuine failure of time reversal invariance of the laws of quantum mechanics. The laws of quantum mechanics would be incompatible with a time-reversed version of our universe.

Reverse Ecology: from systems to environments and back.

PubMed

Levy, Roie; Borenstein, Elhanan

2012-01-01

The structure of complex biological systems reflects not only their function but also the environments in which they evolved and are adapted to. Reverse Ecology-an emerging new frontier in Evolutionary Systems Biology-aims to extract this information and to obtain novel insights into an organism's ecology. The Reverse Ecology framework facilitates the translation of high-throughput genomic data into large-scale ecological data, and has the potential to transform ecology into a high-throughput field. In this chapter, we describe some of the pioneering work in Reverse Ecology, demonstrating how system-level analysis of complex biological networks can be used to predict the natural habitats of poorly characterized microbial species, their interactions with other species, and universal patterns governing the adaptation of organisms to their environments. We further present several studies that applied Reverse Ecology to elucidate various aspects of microbial ecology, and lay out exciting future directions and potential future applications in biotechnology, biomedicine, and ecological engineering.

The psycholegal factors for juvenile transfer and reverse transfer evaluations.

PubMed

King, Christopher M

2018-01-01

It remains unclear whether forensic mental health assessments for juvenile reverse transfer (to juvenile court) are distinct from those for juvenile transfer (to adult court). This survey consisted of an updated review of transfer and reverse transfer laws (in jurisdictions that have both mechanisms) in light of the generally accepted three-factor model of functional legal capacities involved in transfer evaluations (i.e., risk, sophistication-maturity, and treatment amenability). Results indicated that a majority of states' reverse transfer statutes refer explicitly or implicitly to the same three psycholegal constructs identified as central for transfer. Given the legal similarity between transfer and reverse transfer, potential practice implications and directions for future research are discussed. Copyright © 2017 John Wiley & Sons, Ltd.

Cold pulse and rotation reversals with turbulence spreading and residual stress

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

Hariri, F.; Naulin, V.; Juul Rasmussen, J.

2016-05-15

Transport modeling based on inclusion of turbulence spreading and residual stresses shows internal rotation reversals and polarity reversal of cold pulses, with a clear indication of nonlocal transport effects due to fast spreading in the turbulence intensity field. The effects of turbulence spreading and residual stress are calculated from the gradient of the turbulence intensity. In the model presented in this paper, the flux is carried by the turbulence intensity field, which in itself is subject to radial transport effects. The pulse polarity inversion and the rotation profile reversal positions are close to the radial location of the stable/unstable transition.more » Both effects have no direct explanation within the framework of classical transport modeling, where the fluxes are related directly to the linear growth rates, the turbulence intensity profile is not considered and the corresponding residual stress is absent. Our simulations are in qualitative agreement with measurements from ohmically heated plasmas. Rotation reversal at a finite radius is found in situations not displaying saturated confinement, which we identify as situations where the plasma is nearly everywhere unstable. As an additional and new effect, the model predicts a perturbation of the velocity profile following a cold pulse from the edge. This allows direct experimental confirmation of both the existence of residual stress caused by turbulence intensity profiles and fundamental ideas of transport modeling presented here.« less

Directed Energy HPM, PP, & PPS Efforts: Magnetized Target Fusion - Field Reversed Configuration

DTIC Science & Technology

2006-08-04

interior. 15. SUBJECT TERMS Magnetized Target Fusion (MTF), Field-Reversed Configuration (FRC), Alternative Confinement Concepts, Fusion Energy 16...research, the Department of Energy’s Office of Fusion Energy Studies (DOE OFES). Sections 2 through 4, which follow, describe in detail SAIC’s, FabTek’s...the plasma physics areas (FRCs and fusion energy ) in which we are working. The conference paper was submitted at this time, as well, and will

Waves in the Magnetic Field and Solar Wind Flow Outside the Bow Shock at Comet Halley

NASA Astrophysics Data System (ADS)

Johnstone, A. D.; Glassmeier, K.H.; Acuna, M.; Borg, H.; Byrant, D.; Coates, A.J.; Formisano, V.; Health, J.W.; Mariani, S.; Musmann, G.; Neubauer, F.M.; Thomsen, M.; Wilken, B.; Winningham, J.

1986-12-01

An investigation of the low frequency waves, upstream from the bow shock, has been carried out using data from the JPA and MAG instruments on Giotto. The former obtains a snapshot of the solar wind distribution every two spins of the spacecraft, i.e. 8 s. From this data the components of the flow velocity, density and temperature of both protons and alpha particles can be obtained. To compare with these data the magnetic field components, obtained at a rate of 28 values-per-second, have been averaged over the same period of 8 secs. The two data sets can be used to study frequencies up to 60 milliherz, well above the H2O+ gyrofrequency at 6 milliherz, but below the proton gyrofrequency of 100 milliherz.

Influence of atomic kinetics in the simulation of plasma microscopic properties and thermal instabilities for radiative bow shock experiments.

PubMed

Espinosa, G; Rodríguez, R; Gil, J M; Suzuki-Vidal, F; Lebedev, S V; Ciardi, A; Rubiano, J G; Martel, P

2017-03-01

Numerical simulations of laboratory astrophysics experiments on plasma flows require plasma microscopic properties that are obtained by means of an atomic kinetic model. This fact implies a careful choice of the most suitable model for the experiment under analysis. Otherwise, the calculations could lead to inaccurate results and inappropriate conclusions. First, a study of the validity of the local thermodynamic equilibrium in the calculation of the average ionization, mean radiative properties, and cooling times of argon plasmas in a range of plasma conditions of interest in laboratory astrophysics experiments on radiative shocks is performed in this work. In the second part, we have made an analysis of the influence of the atomic kinetic model used to calculate plasma microscopic properties of experiments carried out on magpie on radiative bow shocks propagating in argon. The models considered were developed assuming both local and nonlocal thermodynamic equilibrium and, for the latter situation, we have considered in the kinetic model different effects such as external radiation field and plasma mixture. The microscopic properties studied were the average ionization, the charge state distributions, the monochromatic opacities and emissivities, the Planck mean opacity, and the radiative power loss. The microscopic study was made as a postprocess of a radiative-hydrodynamic simulation of the experiment. We have also performed a theoretical analysis of the influence of these atomic kinetic models in the criteria for the onset possibility of thermal instabilities due to radiative cooling in those experiments in which small structures were experimentally observed in the bow shock that could be due to this kind of instability.

Influence of atomic kinetics in the simulation of plasma microscopic properties and thermal instabilities for radiative bow shock experiments

NASA Astrophysics Data System (ADS)

Espinosa, G.; Rodríguez, R.; Gil, J. M.; Suzuki-Vidal, F.; Lebedev, S. V.; Ciardi, A.; Rubiano, J. G.; Martel, P.

2017-03-01

Numerical simulations of laboratory astrophysics experiments on plasma flows require plasma microscopic properties that are obtained by means of an atomic kinetic model. This fact implies a careful choice of the most suitable model for the experiment under analysis. Otherwise, the calculations could lead to inaccurate results and inappropriate conclusions. First, a study of the validity of the local thermodynamic equilibrium in the calculation of the average ionization, mean radiative properties, and cooling times of argon plasmas in a range of plasma conditions of interest in laboratory astrophysics experiments on radiative shocks is performed in this work. In the second part, we have made an analysis of the influence of the atomic kinetic model used to calculate plasma microscopic properties of experiments carried out on magpie on radiative bow shocks propagating in argon. The models considered were developed assuming both local and nonlocal thermodynamic equilibrium and, for the latter situation, we have considered in the kinetic model different effects such as external radiation field and plasma mixture. The microscopic properties studied were the average ionization, the charge state distributions, the monochromatic opacities and emissivities, the Planck mean opacity, and the radiative power loss. The microscopic study was made as a postprocess of a radiative-hydrodynamic simulation of the experiment. We have also performed a theoretical analysis of the influence of these atomic kinetic models in the criteria for the onset possibility of thermal instabilities due to radiative cooling in those experiments in which small structures were experimentally observed in the bow shock that could be due to this kind of instability.

Monoamines stimulate sex reversal in the saddleback wrasse.

PubMed

Larson, Earl T; Norris, David O; Gordon Grau, E; Summers, Cliff H

2003-02-15

Monoamine neurotransmitters (norepinephrine, dopamine, and serotonin) play an important role in reproduction and sexual behavior throughout the vertebrates. They are the first endogenous chemical signals in the regulation of the hypothalamo-pituitary-gonadal (HPG) axis. In teleosts with behavioral sex determination, much is known about behavioral cues that induce sex reversal. The cues are social, processed via the visual system and depend on the ratio of females to males in the population. The mechanisms by which these external behavioral cues are converted to an internal chemical regulatory process are largely unknown. The protogynous Hawaiian saddleback wrasse, Thalassoma duperrey, was used to investigate the biological pathway mediating the conversion of a social cue into neuroendocrine events regulating sex reversal. Because monoamines play an important role in the regulation of the HPG axis, they were selected as likely candidates for such a conversion. To determine if monoamines could affect sex reversal, drugs affecting monoamines were used in an attempt to either induce sex reversal under non-permissive conditions, or prevent sex reversal under permissive conditions. Increasing norepinephrine or blocking dopamine or serotonin lead to sex reversal in experimental animals under non-permissive conditions. Increasing serotonin blocked sex reversal under permissive conditions, while blocking dopamine or norepinephrine retarded the process. The results presented here demonstrate that monoamines contribute significantly to the control sex reversal. Norepinephrine stimulates initiation and completion of gonadal sex of reversal as well as color change perhaps directly via its effects on the HPG axis. Dopamine exercises inhibitory action on the initiation of sex reversal while 5-HT inhibits both initiation and completion of sex reversal. The serotonergic system appears to be an integral part of the pathway mediating the conversion of a social cue into a

Reverse radiance: a fast accurate method for determining luminance

NASA Astrophysics Data System (ADS)

Moore, Kenneth E.; Rykowski, Ronald F.; Gangadhara, Sanjay

2012-10-01

Reverse ray tracing from a region of interest backward to the source has long been proposed as an efficient method of determining luminous flux. The idea is to trace rays only from where the final flux needs to be known back to the source, rather than tracing in the forward direction from the source outward to see where the light goes. Once the reverse ray reaches the source, the radiance the equivalent forward ray would have represented is determined and the resulting flux computed. Although reverse ray tracing is conceptually simple, the method critically depends upon an accurate source model in both the near and far field. An overly simplified source model, such as an ideal Lambertian surface substantially detracts from the accuracy and thus benefit of the method. This paper will introduce an improved method of reverse ray tracing that we call Reverse Radiance that avoids assumptions about the source properties. The new method uses measured data from a Source Imaging Goniometer (SIG) that simultaneously measures near and far field luminous data. Incorporating this data into a fast reverse ray tracing integration method yields fast, accurate data for a wide variety of illumination problems.

ARAMIS project: a more explicit demonstration of risk control through the use of bow-tie diagrams and the evaluation of safety barrier performance.

PubMed

de Dianous, Valérie; Fiévez, Cécile

2006-03-31

Over the last two decades a growing interest for risk analysis has been noted in the industries. The ARAMIS project has defined a methodology for risk assessment. This methodology has been built to help the industrialist to demonstrate that they have a sufficient risk control on their site. Risk analysis consists first in the identification of all the major accidents, assuming that safety functions in place are inefficient. This step of identification of the major accidents uses bow-tie diagrams. Secondly, the safety barriers really implemented on the site are taken into account. The barriers are identified on the bow-ties. An evaluation of their performance (response time, efficiency, and level of confidence) is performed to validate that they are relevant for the expected safety function. At last, the evaluation of their probability of failure enables to assess the frequency of occurrence of the accident. The demonstration of the risk control based on a couple gravity/frequency of occurrence is also possible for all the accident scenarios. During the risk analysis, a practical tool called risk graph is used to assess if the number and the reliability of the safety functions for a given cause are sufficient to reach a good risk control.

Reversible near-infrared light directed reflection in a self-organized helical superstructure loaded with upconversion nanoparticles.

PubMed

Wang, Ling; Dong, Hao; Li, Yannian; Xue, Chenming; Sun, Ling-Dong; Yan, Chun-Hua; Li, Quan

2014-03-26

Adding external, dynamic control to self-organized superstructures with desired functionalities is an important leap necessary in leveraging the fascinating molecular systems for applications. Here, the new light-driven chiral molecular switch and upconversion nanoparticles, doped in a liquid crystal media, were able to self-organize into an optically tunable helical superstructure. The resulting nanoparticle impregnated helical superstructure was found to exhibit unprecedented reversible near-infrared (NIR) light-guided tunable behavior only by modulating the excitation power density of a continuous-wave NIR laser (980 nm). Upon irradiation by the NIR laser at the high power density, the reflection wavelength of the photonic superstructure red-shifted, whereas its reverse process occurred upon irradiation by the same laser but with the lower power density. Furthermore, reversible dynamic NIR-light-driven red, green, and blue reflections in a single thin film, achieved only by varying the power density of the NIR light, were for the first time demonstrated.

Directional change during a Miocene R-N geomagnetic polarity reversal recorded by mafic lava flows, Sheep Creek Range, north central Nevada, USA

NASA Astrophysics Data System (ADS)

Bogue, S. W.; Glen, J. M. G.; Jarboe, N. A.

2017-09-01

Recurring transitional field directions during three Miocene geomagnetic reversals provide evidence that lateral inhomogeneity of the lower mantle affects flow in the outer core. We compare new paleomagnetic results from a composite sequence of 15.2 Ma lava flows in north central Nevada (Sheep Creek Range; 40.7°N, 243.2°E), erupted during a polarity reversal, to published data from Steens Mountain (250 km to the northwest in Oregon) and the Newberry Mountains (650 km to the south in California) that document reversals occurring millions of years and many polarity switches earlier. Alternating field demagnetization, followed by thermal demagnetization in half the samples, clearly isolated the primary thermoremanent magnetization of Sheep Creek Range flows. We correlated results from our three sampled sections to produce a composite record that begins with a single virtual geomagnetic pole (VGP) at low latitude in the Atlantic, followed by two VGPs situated near latitude 30°N in NE Africa. After jumping to 83°N (one VGP), the pole moves to equatorial South America (one VGP), back to NE Africa (three VGPs), to high southern latitudes (two VGPs), back to equatorial South America (three VGPs), and finally to high northern latitudes (nine VGPs). The repeated visits of the transitional VGP to positions in South America and near NE Africa, as well as the similar behavior recorded at Steens Mountain and the Newberry Mountains, suggest that lower mantle or core-mantle boundary features localize core flow structures, thereby imparting a discernible regional structure on the transitional geomagnetic field that persists for millions of years.

Flow reversal power limit for the HFBR

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

Cheng, L.Y.; Tichler, P.R.

The High Flux Beam Reactor (HFBR) is a pressurized heavy water moderated and cooled research reactor that began operation at 40 MW. The reactor was subsequently upgraded to 60 MW and operated at that level for several years. The reactor undergoes a buoyancy-driven reversal of flow in the reactor core following certain postulated accidents. Questions which were raised about the afterheat removal capability during the flow reversal transition led to a reactor shutdown and subsequent resumption of operation at a reduced power of 30 MW. An experimental and analytical program to address these questions is described in this report. Themore » experiments were single channel flow reversal tests under a range of conditions. The analytical phase involved simulations of the tests to benchmark the physical models and development of a criterion for dryout. The criterion is then used in simulations of reactor accidents to determine a safe operating power level. It is concluded that the limit on the HFBR operating power with respect to the issue of flow reversal is in excess of 60 MW. Direct use of the experimental results and an understanding of the governing phenomenology supports this conclusion.« less

Visually induced self-motion sensation adapts rapidly to left-right reversal of vision

NASA Technical Reports Server (NTRS)

Oman, C. M.; Bock, O. L.

1981-01-01

Three experiments were conducted using 15 adult volunteers with no overt oculomotor or vestibular disorders. In all experiments, left-right vision reversal was achieved using prism goggles, which permitted a binocular field of vision subtending approximately 45 deg horizontally and 28 deg vertically. In all experiments, circularvection (CV) was tested before and immediately after a period of exposure to reversed vision. After one to three hours of active movement while wearing vision-reversing goggles, 10 of 15 (stationary) human subjects viewing a moving stripe display experienced a self-rotation illusion in the same direction as seen stripe motion, rather than in the opposite (normal) direction, demonstrating that the central neural pathways that process visual self-rotation cues can undergo rapid adaptive modification.

Sampling properties of directed networks

NASA Astrophysics Data System (ADS)

Son, S.-W.; Christensen, C.; Bizhani, G.; Foster, D. V.; Grassberger, P.; Paczuski, M.

2012-10-01

For many real-world networks only a small “sampled” version of the original network may be investigated; those results are then used to draw conclusions about the actual system. Variants of breadth-first search (BFS) sampling, which are based on epidemic processes, are widely used. Although it is well established that BFS sampling fails, in most cases, to capture the IN component(s) of directed networks, a description of the effects of BFS sampling on other topological properties is all but absent from the literature. To systematically study the effects of sampling biases on directed networks, we compare BFS sampling to random sampling on complete large-scale directed networks. We present new results and a thorough analysis of the topological properties of seven complete directed networks (prior to sampling), including three versions of Wikipedia, three different sources of sampled World Wide Web data, and an Internet-based social network. We detail the differences that sampling method and coverage can make to the structural properties of sampled versions of these seven networks. Most notably, we find that sampling method and coverage affect both the bow-tie structure and the number and structure of strongly connected components in sampled networks. In addition, at a low sampling coverage (i.e., less than 40%), the values of average degree, variance of out-degree, degree autocorrelation, and link reciprocity are overestimated by 30% or more in BFS-sampled networks and only attain values within 10% of the corresponding values in the complete networks when sampling coverage is in excess of 65%. These results may cause us to rethink what we know about the structure, function, and evolution of real-world directed networks.

Effects of Edge Directions on the Structural Controllability of Complex Networks.

PubMed

Xiao, Yandong; Lao, Songyang; Hou, Lvlin; Small, Michael; Bai, Liang

2015-01-01

Recent advances indicate that assigning or reversing edge direction can significantly improve the structural controllability of complex networks. For directed networks, approaching the optimal structural controllability can be achieved by detecting and reversing certain "inappropriate" edge directions. However, the existence of multiple sets of "inappropriate" edge directions suggests that different edges have different effects on optimal controllability-that is, different combinations of edges can be reversed to achieve the same structural controllability. Therefore, we classify edges into three categories based on their direction: critical, redundant and intermittent. We then investigate the effects of changing these edge directions on network controllability, and demonstrate that the existence of more critical edge directions implies not only a lower cost of modifying inappropriate edges but also better controllability. Motivated by this finding, we present a simple edge orientation method aimed at producing more critical edge directions-utilizing only local information-which achieves near optimal controllability. Furthermore, we explore the effects of edge direction on the controllability of several real networks.

Reverse engineering of integrated circuits

DOEpatents

Chisholm, Gregory H.; Eckmann, Steven T.; Lain, Christopher M.; Veroff, Robert L.

2003-01-01

Software and a method therein to analyze circuits. The software comprises several tools, each of which perform particular functions in the Reverse Engineering process. The analyst, through a standard interface, directs each tool to the portion of the task to which it is most well suited, rendering previously intractable problems solvable. The tools are generally used iteratively to produce a successively more abstract picture of a circuit, about which incomplete a priori knowledge exists.

Community College Reverse Transfer Students: A Field Study of a Nontraditional Student Group.

ERIC Educational Resources Information Center

Winter, Paul A.; Harris, Michael R.

1999-01-01

Data from a survey directed at reverse transfer students in the University of Kentucky Community College System was analyzed based upon the responses from two groups: 734 completers (those who had completed a baccalaureate) and 148 noncompleters. Profiles of reverse transfer students are compiled. Contains 28 references. (TGO)

Magnetic field induced flow pattern reversal in a ferrofluidic Taylor-Couette system

PubMed Central

Altmeyer, Sebastian; Do, Younghae; Lai, Ying-Cheng

2015-01-01

We investigate the dynamics of ferrofluidic wavy vortex flows in the counter-rotating Taylor-Couette system, with a focus on wavy flows with a mixture of the dominant azimuthal modes. Without external magnetic field flows are stable and pro-grade with respect to the rotation of the inner cylinder. More complex behaviors can arise when an axial or a transverse magnetic field is applied. Depending on the direction and strength of the field, multi-stable wavy states and bifurcations can occur. We uncover the phenomenon of flow pattern reversal as the strength of the magnetic field is increased through a critical value. In between the regimes of pro-grade and retrograde flow rotations, standing waves with zero angular velocities can emerge. A striking finding is that, under a transverse magnetic field, a second reversal in the flow pattern direction can occur, where the flow pattern evolves into pro-grade rotation again from a retrograde state. Flow reversal is relevant to intriguing phenomena in nature such as geomagnetic reversal. Our results suggest that, in ferrofluids, flow pattern reversal can be induced by varying a magnetic field in a controlled manner, which can be realized in laboratory experiments with potential applications in the development of modern fluid devices. PMID:26687638

Magnetic field induced flow pattern reversal in a ferrofluidic Taylor-Couette system.

PubMed

Altmeyer, Sebastian; Do, Younghae; Lai, Ying-Cheng

2015-12-21

We investigate the dynamics of ferrofluidic wavy vortex flows in the counter-rotating Taylor-Couette system, with a focus on wavy flows with a mixture of the dominant azimuthal modes. Without external magnetic field flows are stable and pro-grade with respect to the rotation of the inner cylinder. More complex behaviors can arise when an axial or a transverse magnetic field is applied. Depending on the direction and strength of the field, multi-stable wavy states and bifurcations can occur. We uncover the phenomenon of flow pattern reversal as the strength of the magnetic field is increased through a critical value. In between the regimes of pro-grade and retrograde flow rotations, standing waves with zero angular velocities can emerge. A striking finding is that, under a transverse magnetic field, a second reversal in the flow pattern direction can occur, where the flow pattern evolves into pro-grade rotation again from a retrograde state. Flow reversal is relevant to intriguing phenomena in nature such as geomagnetic reversal. Our results suggest that, in ferrofluids, flow pattern reversal can be induced by varying a magnetic field in a controlled manner, which can be realized in laboratory experiments with potential applications in the development of modern fluid devices.

Reversible Thermoset Adhesives

NASA Technical Reports Server (NTRS)

Mac Murray, Benjamin C. (Inventor); Tong, Tat H. (Inventor); Hreha, Richard D. (Inventor)

2016-01-01

Embodiments of a reversible thermoset adhesive formed by incorporating thermally-reversible cross-linking units and a method for making the reversible thermoset adhesive are provided. One approach to formulating reversible thermoset adhesives includes incorporating dienes, such as furans, and dienophiles, such as maleimides, into a polymer network as reversible covalent cross-links using Diels Alder cross-link formation between the diene and dienophile. The chemical components may be selected based on their compatibility with adhesive chemistry as well as their ability to undergo controlled, reversible cross-linking chemistry.

The Parametric Study and Fine-Tuning of Bow-Tie Slot Antenna with Loaded Stub

PubMed Central

2017-01-01

A printed Bow-Tie slot antenna with loaded stub is proposed and the effects of changing the dimensions of the slot area, the stub and load sizes are considered in this paper. These parameters have a considerable effect on the antenna characteristics as well as its performance. An in-depth parametric study of these dimensions is presented. This paper proposes the necessary conditions for initial approximation of dimensions needed to design this antenna. In order to achieve the desired performance of the antenna fine tuning of all sizes of these parameters is required. The parametric studies used in this paper provide proper trends for initiation and tuning the design. A prototype of the antenna for 1.7GHz to 2.6GHz band is fabricated. Measurements conducted verify that the designed antenna has wideband characteristics with 50% bandwidth around the center frequency of 2.1GHz. Conducted measurements for reflection coefficient (S11) and radiation pattern also validate our simulation results. PMID:28114354

The Parametric Study and Fine-Tuning of Bow-Tie Slot Antenna with Loaded Stub.

PubMed

Shafiei, M M; Moghavvemi, Mahmoud; Wan Mahadi, Wan Nor Liza

2017-01-01

A printed Bow-Tie slot antenna with loaded stub is proposed and the effects of changing the dimensions of the slot area, the stub and load sizes are considered in this paper. These parameters have a considerable effect on the antenna characteristics as well as its performance. An in-depth parametric study of these dimensions is presented. This paper proposes the necessary conditions for initial approximation of dimensions needed to design this antenna. In order to achieve the desired performance of the antenna fine tuning of all sizes of these parameters is required. The parametric studies used in this paper provide proper trends for initiation and tuning the design. A prototype of the antenna for 1.7GHz to 2.6GHz band is fabricated. Measurements conducted verify that the designed antenna has wideband characteristics with 50% bandwidth around the center frequency of 2.1GHz. Conducted measurements for reflection coefficient (S11) and radiation pattern also validate our simulation results.

Operational formulation of time reversal in quantum theory

NASA Astrophysics Data System (ADS)

Oreshkov, Ognyan; Cerf, Nicolas J.

2015-10-01

The symmetry of quantum theory under time reversal has long been a subject of controversy because the transition probabilities given by Born’s rule do not apply backward in time. Here, we resolve this problem within a rigorous operational probabilistic framework. We argue that reconciling time reversal with the probabilistic rules of the theory requires a notion of operation that permits realizations through both pre- and post-selection. We develop the generalized formulation of quantum theory that stems from this approach and give a precise definition of time-reversal symmetry, emphasizing a previously overlooked distinction between states and effects. We prove an analogue of Wigner’s theorem, which characterizes all allowed symmetry transformations in this operationally time-symmetric quantum theory. Remarkably, we find larger classes of symmetry transformations than previously assumed, suggesting a possible direction in the search for extensions of known physics.

Influence of Voltage Rise Time for Oxidation Treatment of NO in Simulated Exhausted Gas by Polarity-Reversed Pulse Discharge

NASA Astrophysics Data System (ADS)

Shinmoto, Kazuya; Kadowaki, Kazunori; Nishimoto, Sakae; Kitani, Isamu

This paper describes experimental study on NO removal from a simulated exhausted-gas using repetitive surface discharge on a glass barrier subjected to polarity-reversed voltage pulses. The very fast polarity-reversal with a rise time of 20ns is caused by direct grounding of a charged coaxial cable of 10m in length. Influence of voltage rise time on energy efficiency for NO removal is studied. Results of NO removal using a barrier-type plasma reactor with screw-plane electrode system indicates that the energy efficiency for the very fast polarity reversal caused by direct grounding becomes higher than that for the slower polarity reversal caused by grounding through an inductor at the cable end. The energy efficiency for the direct grounding is about 80g/kWh for 50% NO removal ratio and is about 60g/kWh for 100% NO removal ratio. Very intense discharge light is observed at the initial time of 10ns for the fast polarity reversal, whereas the intensity in the initial discharge light for the slower polarity reversal is relatively small. To confirm the effectiveness of the polarity-reversed pulse application, comparison of the energy efficiency between the polarity-reversed voltage pulse and ac 60Hz voltage will be presented.

Zero field reversal probability in thermally assisted magnetization reversal

NASA Astrophysics Data System (ADS)

Prasetya, E. B.; Utari; Purnama, B.

2017-11-01

This paper discussed about zero field reversal probability in thermally assisted magnetization reversal (TAMR). Appearance of reversal probability in zero field investigated through micromagnetic simulation by solving stochastic Landau-Lifshitz-Gibert (LLG). The perpendicularly anisotropy magnetic dot of 50×50×20 nm3 is considered as single cell magnetic storage of magnetic random acces memory (MRAM). Thermally assisted magnetization reversal was performed by cooling writing process from near/almost Curie point to room temperature on 20 times runs for different randomly magnetized state. The results show that the probability reversal under zero magnetic field decreased with the increase of the energy barrier. The zero-field probability switching of 55% attained for energy barrier of 60 k B T and the reversal probability become zero noted at energy barrier of 2348 k B T. The higest zero-field switching probability of 55% attained for energy barrier of 60 k B T which corespond to magnetif field of 150 Oe for switching.

Dual capacity compressor with reversible motor and controls arrangement therefor

DOEpatents

Sisk, Francis J.

1980-12-02

A hermetic reciprocating compressor such as may be used in heat pump applications is provided for dual capacity operation by providing the crankpin of the crankshaft with an eccentric ring rotatably mounted thereon, and with the end of the connecting rod opposite the piston encompassing the outer circumference of the eccentric ring, with means limiting the rotation of the eccentric ring upon the crankpin between one end point and an opposite angularly displaced end point to provide different values of eccentricity depending upon which end point the eccentric ring is rotated to upon the crankpin, and a reversible motor in the hermetic shell of the compressor for rotating the crankshaft, the motor operating in one direction effecting the angular displacement of the eccentric ring relative to the crankpin to the one end point, and in the opposite direction effecting the angular displacement of the eccentric ring relative to the crankpin to the opposite end point, this arrangement automatically giving different stroke lengths depending upon the direction of motor rotation. The mechanical structure of the arrangement may take various forms including at least one in which any impact of reversal is reduced by utilizing lubricant passages and chambers at the interface area of the crankpin and eccentric ring to provide a dashpot effect. In the main intended application of the arrangement according to the invention, that is, in a refrigerating or air conditioning system, it is desirable to insure a delay during reversal of the direction of compressor operation. A control arrangement is provided in which the control system controls the direction of motor operation in accordance with temperature conditions, the system including control means for effecting operation in a low capacity direction or alternatively in a high capacity direction in response to one set, and another set, respectively, of temperature conditions and with timer means delaying a restart of the compressor

Large Scale Earth's Bow Shock with Northern IMF as Simulated by PIC Code in Parallel with MHD Model

NASA Astrophysics Data System (ADS)

Baraka, Suleiman

2016-06-01

In this paper, we propose a 3D kinetic model (particle-in-cell, PIC) for the description of the large scale Earth's bow shock. The proposed version is stable and does not require huge or extensive computer resources. Because PIC simulations work with scaled plasma and field parameters, we also propose to validate our code by comparing its results with the available MHD simulations under same scaled solar wind (SW) and (IMF) conditions. We report new results from the two models. In both codes the Earth's bow shock position is found to be ≈14.8 R E along the Sun-Earth line, and ≈29 R E on the dusk side. Those findings are consistent with past in situ observations. Both simulations reproduce the theoretical jump conditions at the shock. However, the PIC code density and temperature distributions are inflated and slightly shifted sunward when compared to the MHD results. Kinetic electron motions and reflected ions upstream may cause this sunward shift. Species distributions in the foreshock region are depicted within the transition of the shock (measured ≈2 c/ ω pi for Θ Bn = 90° and M MS = 4.7) and in the downstream. The size of the foot jump in the magnetic field at the shock is measured to be (1.7 c/ ω pi ). In the foreshocked region, the thermal velocity is found equal to 213 km s-1 at 15 R E and is equal to 63 km s -1 at 12 R E (magnetosheath region). Despite the large cell size of the current version of the PIC code, it is powerful to retain macrostructure of planets magnetospheres in very short time, thus it can be used for pedagogical test purposes. It is also likely complementary with MHD to deepen our understanding of the large scale magnetosphere.

Which Bow Shock Theory, Gasdynamic or Magnetohydrodynamic, Better Explains CME Stand-off Distance Ratios from LASCO-C2 Observations ?

NASA Astrophysics Data System (ADS)

Lee, Jae-Ok; Moon, Y.-J.; Lee, Jin-Yi; Kim, R.-S.; Cho, K.-S.

2017-03-01

It is generally believed that fast coronal mass ejections (CMEs) can generate their associated shocks, which are characterized by faint structures ahead of CMEs in white-light coronagraph images. In this study, we examine whether the observational stand-off distance ratio, defined as the CME stand-off distance divided by its radius, can be explained by bow shock theories. Of 535 SOHO/LASCO CMEs (from 1996 to 2015) with speeds greater than 1000 km s-1 and angular widths wider than 60°, we select 18 limb CMEs with the following conditions: (1) their Alfvénic Mach numbers are greater than one under Mann’s magnetic field and Saito’s density distributions; and (2) the shock structures ahead of the CMEs are well identified. We determine observational CME stand-off distance ratios by using brightness profiles from LASCO-C2 observations. We compare our estimates with theoretical stand-off distance ratios from gasdynamic (GD) and magnetohydrodynamic (MHD) theories. The main results are as follows. Under the GD theory, 39% (7/18) of the CMEs are explained in the acceptable ranges of adiabatic gamma (γ) and CME geometry. Under the MHD theory, all the events are well explained when we consider quasi-parallel MHD shocks with γ = 5/3. When we use polarized brightness (pB) measurements for coronal density distributions, we also find similar results: 8% (1/12) under GD theory and 100% (12/12) under MHD theory. Our results demonstrate that the bow shock relationships based on MHD theory are more suitable than those based on GD theory for analyzing CME-driven shock signatures.

Which Bow Shock Theory, Gasdynamic or Magnetohydrodynamic, Better Explains CME Stand-off Distance Ratios from LASCO-C2 Observations ?

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

Lee, Jae-Ok; Moon, Y.-J.; Lee, Jin-Yi

It is generally believed that fast coronal mass ejections (CMEs) can generate their associated shocks, which are characterized by faint structures ahead of CMEs in white-light coronagraph images. In this study, we examine whether the observational stand-off distance ratio, defined as the CME stand-off distance divided by its radius, can be explained by bow shock theories. Of 535 SOHO /LASCO CMEs (from 1996 to 2015) with speeds greater than 1000 km s{sup −1} and angular widths wider than 60°, we select 18 limb CMEs with the following conditions: (1) their Alfvénic Mach numbers are greater than one under Mann’s magneticmore » field and Saito’s density distributions; and (2) the shock structures ahead of the CMEs are well identified. We determine observational CME stand-off distance ratios by using brightness profiles from LASCO-C2 observations. We compare our estimates with theoretical stand-off distance ratios from gasdynamic (GD) and magnetohydrodynamic (MHD) theories. The main results are as follows. Under the GD theory, 39% (7/18) of the CMEs are explained in the acceptable ranges of adiabatic gamma ( γ ) and CME geometry. Under the MHD theory, all the events are well explained when we consider quasi-parallel MHD shocks with γ = 5/3. When we use polarized brightness (pB) measurements for coronal density distributions, we also find similar results: 8% (1/12) under GD theory and 100% (12/12) under MHD theory. Our results demonstrate that the bow shock relationships based on MHD theory are more suitable than those based on GD theory for analyzing CME-driven shock signatures.« less

Reversible S-nitrosylation in an engineered azurin

DOE PAGES

Tian, Shiliang; Liu, Jing; Cowley, Ryan E.; ...

2016-04-25

Here, S-Nitrosothiols are known as reagents for NO storage and transportation and as regulators in many physiological processes. Although the S-nitrosylation catalysed by haem proteins is well known, no direct evidence of S-nitrosylation in copper proteins has been reported. Here, we report reversible insertion of NO into a copper–thiolate bond in an engineered copper centre in Pseudomonas aeruginosa azurin by rational design of the primary coordination sphere and tuning its reduction potential by deleting a hydrogen bond in the secondary coordination sphere. The results not only provide the first direct evidence of S-nitrosylation of Cu(II)-bound cysteine in metalloproteins, but alsomore » shed light on the reaction mechanism and structural features responsible for stabilizing the elusive Cu(I)–S(Cys)NO species. The fast, efficient and reversible S-nitrosylation reaction is used to demonstrate its ability to prevent NO inhibition of cytochrome bo 3 oxidase activity by competing for NO binding with the native enzyme under physiologically relevant conditions.« less

Double-temperature ratchet model and current reversal of coupled Brownian motors

NASA Astrophysics Data System (ADS)

Li, Chen-Pu; Chen, Hong-Bin; Zheng, Zhi-Gang

2017-12-01

On the basis of the transport features and experimental phenomena observed in studies of molecular motors, we propose a double-temperature ratchet model of coupled motors to reveal the dynamical mechanism of cooperative transport of motors with two heads, where the interactions and asynchrony between two motor heads are taken into account. We investigate the collective unidirectional transport of coupled system and find that the direction of motion can be reversed under certain conditions. Reverse motion can be achieved by modulating the coupling strength, coupling free length, and asymmetric coefficient of the periodic potential, which is understood in terms of the effective potential theory. The dependence of the directed current on various parameters is studied systematically. Directed transport of coupled Brownian motors can be manipulated and optimized by adjusting the pulsation period or the phase shift of the pulsation temperature.

Do high school chemistry examinations inhibit deeper level understanding of dynamic reversible chemical reactions?

NASA Astrophysics Data System (ADS)

Wheeldon, R.; Atkinson, R.; Dawes, A.; Levinson, R.

2012-07-01

Background and purpose : Chemistry examinations can favour the deployment of algorithmic procedures like Le Chatelier's Principle (LCP) rather than reasoning using chemical principles. This study investigated the explanatory resources which high school students use to answer equilibrium problems and whether the marks given for examination answers require students to use approaches beyond direct application of LCP. Sample : The questionnaire was administered to 162 students studying their first year of advanced chemistry (age 16/17) in three high achieving London high schools. Design and methods : The students' explanations of reversible chemical systems were inductively coded to identify the explanatory approaches used and interviews with 13 students were used to check for consistency. AS level examination questions on reversible reactions were analysed to identify the types of explanations sought and the students' performance in these examinations was compared to questionnaire answers. Results : 19% of students used a holistic explanatory approach: when the rates of forward and reverse reactions are correctly described, recognising their simultaneous and mutually dependent nature. 36% used a mirrored reactions approach when the connected nature of the forward and reverse reactions is identified, but not their mutual dependency. 42% failed to recognize the interdependence of forward and reverse reactions (reactions not connected approach). Only 4% of marks for AS examination questions on reversible chemical systems asked for responses which went beyond either direct application of LCP or recall of equilibrium knowledge. 37% of students attained an A grade in their AS national examinations. Conclusions : Examinations favour the application of LCP making it possible to obtain the highest grade with little understanding of reversible chemical systems beyond a direct application of this algorithm. Therefore students' understanding may be attenuated so that they are

Distance-Dependent Sign Reversal in the Casimir-Lifshitz Torque

NASA Astrophysics Data System (ADS)

Thiyam, Priyadarshini; Parashar, Prachi; Shajesh, K. V.; Malyi, Oleksandr I.; Boström, Mathias; Milton, Kimball A.; Brevik, Iver; Persson, Clas

2018-03-01

The Casimir-Lifshitz torque between two biaxially polarizable anisotropic planar slabs is shown to exhibit a nontrivial sign reversal in its rotational sense. The critical distance ac between the slabs that marks this reversal is characterized by the frequency ωc˜c /2 ac at which the in-planar polarizabilities along the two principal axes are equal. The two materials seek to align their principal axes of polarizabilities in one direction below ac, while above ac their axes try to align rotated perpendicular relative to their previous minimum energy orientation. The sign reversal disappears in the nonretarded limit. Our perturbative result, derived for the case when the differences in the relative polarizabilities are small, matches excellently with the exact theory for uniaxial materials. We illustrate our results for black phosphorus and phosphorene.

Reverse osmosis desalination: water sources, technology, and today's challenges.

PubMed

Greenlee, Lauren F; Lawler, Desmond F; Freeman, Benny D; Marrot, Benoit; Moulin, Philippe

2009-05-01

Reverse osmosis membrane technology has developed over the past 40 years to a 44% share in world desalting production capacity, and an 80% share in the total number of desalination plants installed worldwide. The use of membrane desalination has increased as materials have improved and costs have decreased. Today, reverse osmosis membranes are the leading technology for new desalination installations, and they are applied to a variety of salt water resources using tailored pretreatment and membrane system design. Two distinct branches of reverse osmosis desalination have emerged: seawater reverse osmosis and brackish water reverse osmosis. Differences between the two water sources, including foulants, salinity, waste brine (concentrate) disposal options, and plant location, have created significant differences in process development, implementation, and key technical problems. Pretreatment options are similar for both types of reverse osmosis and depend on the specific components of the water source. Both brackish water and seawater reverse osmosis (RO) will continue to be used worldwide; new technology in energy recovery and renewable energy, as well as innovative plant design, will allow greater use of desalination for inland and rural communities, while providing more affordable water for large coastal cities. A wide variety of research and general information on RO desalination is available; however, a direct comparison of seawater and brackish water RO systems is necessary to highlight similarities and differences in process development. This article brings to light key parameters of an RO process and process modifications due to feed water characteristics.

Magnetization reversal dynamics in Co nanowires with competing magnetic anisotropies

NASA Astrophysics Data System (ADS)

Pal, Semanti; Saha, Susmita; Polley, Debanjan; Barman, Anjan

2011-12-01

We present the magnetization reversal dynamics of Co nanowires with competing magnetic anisotropies. The aspect ratio ( R) of the nanowires is varied between 2.5 and 60, and we observe a cross-over of the directions of the magnetic easy and hard axes at R=6.8. Micromagnetic simulations qualitatively reproduce the observed cross-over and give detailed insight into the reversal mechanisms associated with the cross-over. The reversal mechanism for a field applied along the long axis of the nanowire exhibits a quasi-coherent rotation mode and a corkscrew-like mode, respectively, above and below the cross-over, with the formation of a Bloch domain near the cross-over region. For a field applied along the short axis, the reversal occurs by nucleation and propagation of reversed domains from the two ends of the nanowires for very high values of the aspect ratio down to the cross-over region, but it transforms into quasi-coherent rotation mode for smaller aspect ratios (below the cross-over region).

A novel dynamic mechanical testing technique for reverse shoulder replacements.

PubMed

Dabirrahmani, Danè; Bokor, Desmond; Appleyard, Richard

2014-04-01

In vitro mechanical testing of orthopedic implants provides information regarding their mechanical performance under simulated biomechanical conditions. Current in vitro component stability testing methods for reverse shoulder implants are based on anatomical shoulder designs, which do not capture the dynamic nature of these loads. With glenoid component loosening as one of the most prevalent modes of failure in reverse shoulder replacements, it is important to establish a testing protocol with a more realistic loading regime. This paper introduces a novel method of mechanically testing reverse shoulder implants, using more realistic load magnitudes and vectors, than is currently practiced. Using a custom made jig setup within an Instron mechanical testing system, it is possible to simulate the change in magnitude and direction of the joint load during arm abduction. This method is a step towards a more realistic testing protocol for measuring reverse shoulder implant stability.

Influence of Additive and Multiplicative Structure and Direction of Comparison on the Reversal Error

ERIC Educational Resources Information Center

González-Calero, José Antonio; Arnau, David; Laserna-Belenguer, Belén

2015-01-01

An empirical study has been carried out to evaluate the potential of word order matching and static comparison as explanatory models of reversal error. Data was collected from 214 undergraduate students who translated a set of additive and multiplicative comparisons expressed in Spanish into algebraic language. In these multiplicative comparisons…

Direct observation of λ-DNA molecule reversal movement within microfluidic channels under electric field with single molecule imaging technique

NASA Astrophysics Data System (ADS)

Fengyun, Yang; Kaige, Wang; Dan, Sun; Wei, Zhao; Hai-qing, Wang; Xin, He; Gui-ren, Wang; Jin-tao, Bai

2016-07-01

The electrodynamic characteristics of single DNA molecules moving within micro-/nano-fluidic channels are important in the design of biomedical chips and bimolecular sensors. In this study, the dynamic properties of λ-DNA molecules transferring along the microchannels driven by the external electrickinetic force were systemically investigated with the single molecule fluorescence imaging technique. The experimental results indicated that the velocity of DNA molecules was strictly dependent on the value of the applied electric field and the diameter of the channel. The larger the external electric field, the larger the velocity, and the more significant deformation of DNA molecules. More meaningfully, it was found that the moving directions of DNA molecules had two completely different directions: (i) along the direction of the external electric field, when the electric field intensity was smaller than a certain threshold value; (ii) opposite to the direction of the external electric field, when the electric field intensity was greater than the threshold electric field intensity. The reversal movement of DNA molecules was mainly determined by the competition between the electrophoresis force and the influence of electro-osmosis flow. These new findings will theoretically guide the practical application of fluidic channel sensors and lab-on-chips for precisely manipulating single DNA molecules. Project supported by the National Natural Science Foundation of China (Grant No. 61378083), the International Cooperation Foundation of the National Science and Technology Major Project of the Ministry of Science and Technology of China (Grant No. 2011DFA12220), the Major Research Plan of National Natural Science Foundation of China (Grant No. 91123030), and the Natural Science Foundation of Shaanxi Province of China (Grant Nos. 2010JS110 and 2013SZS03-Z01).

Reversible and non-reversible changes in nanostructured Si in humid atmosphere

NASA Astrophysics Data System (ADS)

Zhigalov, V.; Pyatilova, O.; Timoshenkov, S.; Gavrilov, S.

2014-12-01

Atmosphere water influence in the nanostructured silicon (NSS) was investigated by IR-spectroscopy and electron work function measurement. Long-term non-reversible dynamics of IR-spectra was found as a result of 100% humidity influence on the nanostructured silicon. It was indicated that air humidity affects on the work function. Dynamics of the electron work function consists of reversible and non-reversible components. Reversible component appears as strong anti-correlation between work function and humidity. Work function change of NSS is about 0.4 eV while the humidity changes between 0% and 100%. Reversible component can be explained by physical sorption of water molecules on the surface. Non-reversible component manifests as long-term decreasing trend of work function in humid atmosphere. Transition curve during abruptly humidity changes alters its shape. Non-reversible component can be explained by chemisorption of water.

Generalised Sandpile Dynamics on Artificial and Real-World Directed Networks

PubMed Central

Zachariou, Nicky; Expert, Paul; Takayasu, Misako; Christensen, Kim

2015-01-01

The main finding of this paper is a novel avalanche-size exponent τ ≈ 1.87 when the generalised sandpile dynamics evolves on the real-world Japanese inter-firm network. The topology of this network is non-layered and directed, displaying the typical bow tie structure found in real-world directed networks, with cycles and triangles. We show that one can move from a strictly layered regular lattice to a more fluid structure of the inter-firm network in a few simple steps. Relaxing the regular lattice structure by introducing an interlayer distribution for the interactions, forces the scaling exponent of the avalanche-size probability density function τ out of the two-dimensional directed sandpile universality class τ = 4/3, into the mean field universality class τ = 3/2. Numerical investigation shows that these two classes are the only that exist on the directed sandpile, regardless of the underlying topology, as long as it is strictly layered. Randomly adding a small proportion of links connecting non adjacent layers in an otherwise layered network takes the system out of the mean field regime to produce non-trivial avalanche-size probability density function. Although these do not display proper scaling, they closely reproduce the behaviour observed on the Japanese inter-firm network. PMID:26606143

Generalised Sandpile Dynamics on Artificial and Real-World Directed Networks.

PubMed

Zachariou, Nicky; Expert, Paul; Takayasu, Misako; Christensen, Kim

2015-01-01

The main finding of this paper is a novel avalanche-size exponent τ ≈ 1.87 when the generalised sandpile dynamics evolves on the real-world Japanese inter-firm network. The topology of this network is non-layered and directed, displaying the typical bow tie structure found in real-world directed networks, with cycles and triangles. We show that one can move from a strictly layered regular lattice to a more fluid structure of the inter-firm network in a few simple steps. Relaxing the regular lattice structure by introducing an interlayer distribution for the interactions, forces the scaling exponent of the avalanche-size probability density function τ out of the two-dimensional directed sandpile universality class τ = 4/3, into the mean field universality class τ = 3/2. Numerical investigation shows that these two classes are the only that exist on the directed sandpile, regardless of the underlying topology, as long as it is strictly layered. Randomly adding a small proportion of links connecting non adjacent layers in an otherwise layered network takes the system out of the mean field regime to produce non-trivial avalanche-size probability density function. Although these do not display proper scaling, they closely reproduce the behaviour observed on the Japanese inter-firm network.

Effects of Edge Directions on the Structural Controllability of Complex Networks

PubMed Central

Xiao, Yandong; Lao, Songyang; Hou, Lvlin; Small, Michael; Bai, Liang

2015-01-01

Recent advances indicate that assigning or reversing edge direction can significantly improve the structural controllability of complex networks. For directed networks, approaching the optimal structural controllability can be achieved by detecting and reversing certain “inappropriate” edge directions. However, the existence of multiple sets of “inappropriate” edge directions suggests that different edges have different effects on optimal controllability—that is, different combinations of edges can be reversed to achieve the same structural controllability. Therefore, we classify edges into three categories based on their direction: critical, redundant and intermittent. We then investigate the effects of changing these edge directions on network controllability, and demonstrate that the existence of more critical edge directions implies not only a lower cost of modifying inappropriate edges but also better controllability. Motivated by this finding, we present a simple edge orientation method aimed at producing more critical edge directions—utilizing only local information—which achieves near optimal controllability. Furthermore, we explore the effects of edge direction on the controllability of several real networks. PMID:26281042

Site-directed mutagenesis of the conserved Asp-443 and Asp-498 carboxy-terminal residues of HIV-1 reverse transcriptase.

PubMed Central

Mizrahi, V; Usdin, M T; Harington, A; Dudding, L R

1990-01-01

Substitution of the conserved Asp-443 residue of HIV-1 reverse transcriptase by asparagine specifically suppressed the ribonuclease H activity of the enzyme without affecting the reverse transcriptase activity, suggesting involvement of this ionizable residue at the ribonuclease H active site. An analogous asparagine substitution of the Asp-498 residue yielded an unstable enzyme that was difficult to enzymatically characterize. However, the instability caused by the Asn-498 mutation was relieved by the introduction of a second distal Asn-443 substitution, yielding an enzyme with wild type reverse transcriptase activity, but lacking ribonuclease H activity. Images PMID:1699202

Mine safety assessment using gray relational analysis and bow tie model

PubMed Central

2018-01-01

Mine safety assessment is a precondition for ensuring orderly and safety in production. The main purpose of this study was to prevent mine accidents more effectively by proposing a composite risk analysis model. First, the weights of the assessment indicators were determined by the revised integrated weight method, in which the objective weights were determined by a variation coefficient method and the subjective weights determined by the Delphi method. A new formula was then adopted to calculate the integrated weights based on the subjective and objective weights. Second, after the assessment indicator weights were determined, gray relational analysis was used to evaluate the safety of mine enterprises. Mine enterprise safety was ranked according to the gray relational degree, and weak links of mine safety practices identified based on gray relational analysis. Third, to validate the revised integrated weight method adopted in the process of gray relational analysis, the fuzzy evaluation method was used to the safety assessment of mine enterprises. Fourth, for first time, bow tie model was adopted to identify the causes and consequences of weak links and allow corresponding safety measures to be taken to guarantee the mine’s safe production. A case study of mine safety assessment was presented to demonstrate the effectiveness and rationality of the proposed composite risk analysis model, which can be applied to other related industries for safety evaluation. PMID:29561875

Sand transportation and reverse patterns over leeward face of sand dune

NASA Astrophysics Data System (ADS)

Jiang, Hong; Dun, Hongchao; Tong, Ding; Huang, Ning

2017-04-01

Sand saltation has complex interactions with turbulent flow and dune form. Most models of wind-blown sand consider ideal circumstances such as steady wind velocity and a flat surface, and the bulk of data on wind flow and sand transport over an individual dune has focused mostly on the influence of dune shape or inter-dune space on the wind flow, neglecting the effect of morphology on sand saltation, particularly airflow and sand transportation over the leeward slope. Wind flow structures over the leeward slope of sand dunes have a fundamental influence on the organization of sand dunes. In order to understand sand dune dynamics, lee face airflow and sediment transportation should be paid more attention. Previous field observations could not measure turbulent flow structure well because of the limited observation points and the influence of experiment structure on wind field. In addition, the reverse sand particles over leeward face could not be collected by sand trap in field. Numerous field observations could not measure turbulent flow structure because of the limited observation points and the influence of experimental structures on the wind field. In addition, the reverse transport of sand particles over leeward face could not be collected by sand traps in field. Therefore, this paper aims to investigate the turbulent flow structure and sand transport pattern over the leeward slope. A numerical model of sand saltation over slope terrain is constructed, which also considers the coupling effects between air flow and sand particles. The large eddy simulation method is used to model turbulent flow. Sand transport is simulated by tracking the trajectory of each sand particle. The results show that terrain significantly alters the turbulent air flow structure and wind-blown sand movement, especially over the leeward slope. Here, mass flux increases initially and then decreases with height in the reversed flow region in the direction of wind flow, and the mass flux

Paleomagnetic full vector record of four consecutive Mid Miocene geomagnetic reversals

NASA Astrophysics Data System (ADS)

Linder, J.; Leonhardt, R.

2009-11-01

Seventy Mid Miocene lava flows from flood basalt piles near Neskaupstadur (East Iceland) were sampled, which provide a quasi-continuous record of geomagnetic field variations. Samples were collected along the profile B of Watkins and Walker [Watkins, N., Walker, G.P.L., 1977. Magnetostratigraphy of eastern Iceland. Am. J. Sci. 277, 513-584], which was extended about 250 m farther down in a neighboring stream bed. Published radiometric age determinations [Harrison, C., McDougall, I., Watkins, N., 1979. A geomagnetic field reversal time scale back to 13.0 million years before present. Earth Planet. Sci. Lett. 42, 143-152] range from 12.2 to 12.8 Ma for the sampled sequence. Four reversals were recorded in this profile, with 18 transitional lavas found within or between 17 normal and 30 reversed polarity flows. The large amount of transitional lavas and the large virtual geomagnetic pole dispersion for stable field directions are noteworthy as such features are commonly observed in Icelandic lavas and manifest in a far-sidedness of the average VGP. The reason for this characteristic, which could be related to an anomaly beneath Iceland, a global field phenomenon, local tectonics, and/or non-horizontal flow emplacement, is scrutinized. Non-horizontal flow emplacement is likely in volcanic environments particularly if the sampled lavas are located on the paleoslopes of a central volcano. From the difference of the observed paleomagnetic mean directions to the expected directions assuming a geocentric axial dipole (GAD), a paleoslope which would explain the observed difference was calculated numerically. The obtained dip and dip direction point consistently to a possible volcanic extrusion center of the lavas. The determined paleodip, however, proved to be significantly too high compared to the usual slope of a central volcano, suggesting further reasons for deviations from the GAD. Other datasets of this age from Europe also show enhanced VGP dispersion, suggesting

The effect of left-right reversal on film: Watching Kurosawa reversed