Science.gov

Sample records for strings small-scale structure

  1. Small scale structure on cosmic strings

    NASA Technical Reports Server (NTRS)

    Albrecht, Andreas

    1989-01-01

    The current understanding of cosmic string evolution is discussed, and the focus placed on the question of small scale structure on strings, where most of the disagreements lie. A physical picture designed to put the role of the small scale structure into more intuitive terms is presented. In this picture it can be seen how the small scale structure can feed back in a major way on the overall scaling solution. It is also argued that it is easy for small scale numerical errors to feed back in just such a way. The intuitive discussion presented here may form the basis for an analytic treatment of the small scale structure, which argued in any case would be extremely valuable in filling the gaps in the present understanding of cosmic string evolution.

  2. Small scale structure on cosmic strings

    SciTech Connect

    Albrecht, A.

    1989-10-30

    I discuss our current understanding of cosmic string evolution, and focus on the question of small scale structure on strings, where most of the disagreements lie. I present a physical picture designed to put the role of the small scale structure into more intuitive terms. In this picture one can see how the small scale structure can feed back in a major way on the overall scaling solution. I also argue that it is easy for small scale numerical errors to feed back in just such a way. The intuitive discussion presented here may form the basis for an analytic treatment of the small structure, which I argue in any case would be extremely valuable in filling the gaps in our resent understanding of cosmic string evolution. 24 refs., 8 figs.

  3. Kinks and small-scale structure on cosmic strings

    SciTech Connect

    Copeland, E. J.; Kibble, T. W. B.

    2009-12-15

    We discuss some hitherto puzzling features of the small-scale structure of cosmic strings. We argue that kinks play a key role, and that an important quantity to study is their sharpness distribution. In particular we suggest that for very small scales the two-point correlation function of the string tangent vector varies linearly with the separation and not as a fractional power, as proposed by Polchinski and Rocha [Phys. Rev. D 74, 083504 (2006)]. However, our results are consistent with theirs, because the range of scales to which this linearity applies shrinks as evolution proceeds.

  4. Electron Precipitation Associated with Small-Scale Auroral Structures

    NASA Astrophysics Data System (ADS)

    Michell, R.; Samara, M.; Grubbs, G. A., II; Hampton, D. L.; Bonnell, J. W.; Ogasawara, K.

    2014-12-01

    We present results from the Ground-to-Rocket Electrons Electrodynamics Correlative Experiment (GREECE) sounding rocket mission, where we combined high-resolution ground-based auroral imaging with high time-resolution precipitating electron measurements. The GREECE payload successfully launched from Poker Flat, Alaska on 03 March 2014 and reached an apogee of approximately 335 km. The narrow field-of-view auroral imaging was taken from Venetie, AK, which is directly under apogee. This enabled the small-scale auroral features at the magnetic footpoint of the rocket payload to be imaged in detail. The electron precipitation was measured with the Acute Precipitating Electron Spectrometer (APES) onboard the payload. Features in the electron data are matched up with their corresponding auroral structures and boundaries, enabling measurement of the exact electron distributions responsible for the specific small-scale auroral features. These electron distributions will then be used to infer what the potential electron acceleration processes were.

  5. Does small scale structure significantly affect cosmological dynamics?

    PubMed

    Adamek, Julian; Clarkson, Chris; Durrer, Ruth; Kunz, Martin

    2015-02-01

    The large-scale homogeneity and isotropy of the Universe is generally thought to imply a well-defined background cosmological model. It may not. Smoothing over structure adds in an extra contribution, transferring power from small scales up to large. Second-order perturbation theory implies that the effect is small, but suggests that formally the perturbation series may not converge. The amplitude of the effect is actually determined by the ratio of the Hubble scales at matter-radiation equality and today-which are entirely unrelated. This implies that a universe with significantly lower temperature today could have significant backreaction from more power on small scales, and so provides the ideal testing ground for understanding backreaction. We investigate this using two different N-body numerical simulations-a 3D Newtonian and a 1D simulation which includes all relevant relativistic effects. We show that while perturbation theory predicts an increasing backreaction as more initial small-scale power is added, in fact the virialization of structure saturates the backreaction effect at the same level independently of the equality scale. This implies that backreaction is a small effect independently of initial conditions. Nevertheless, it may still contribute at the percent level to certain cosmological observables and therefore it cannot be neglected in precision cosmology. PMID:25699430

  6. Does Small Scale Structure Significantly Affect Cosmological Dynamics?

    NASA Astrophysics Data System (ADS)

    Adamek, Julian; Clarkson, Chris; Durrer, Ruth; Kunz, Martin

    2015-02-01

    The large-scale homogeneity and isotropy of the Universe is generally thought to imply a well-defined background cosmological model. It may not. Smoothing over structure adds in an extra contribution, transferring power from small scales up to large. Second-order perturbation theory implies that the effect is small, but suggests that formally the perturbation series may not converge. The amplitude of the effect is actually determined by the ratio of the Hubble scales at matter-radiation equality and today—which are entirely unrelated. This implies that a universe with significantly lower temperature today could have significant backreaction from more power on small scales, and so provides the ideal testing ground for understanding backreaction. We investigate this using two different N -body numerical simulations—a 3D Newtonian and a 1D simulation which includes all relevant relativistic effects. We show that while perturbation theory predicts an increasing backreaction as more initial small-scale power is added, in fact the virialization of structure saturates the backreaction effect at the same level independently of the equality scale. This implies that backreaction is a small effect independently of initial conditions. Nevertheless, it may still contribute at the percent level to certain cosmological observables and therefore it cannot be neglected in precision cosmology.

  7. Cosmic string structure at the gravitational radiation scale

    SciTech Connect

    Polchinski, Joseph; Rocha, Jorge V.

    2007-06-15

    We use our model of the small scale structure on cosmic strings to develop further the result of Siemens, Olum, and Vilenkin that the gravitational radiation length scale on cosmic strings is smaller than the previously assumed {gamma}G{mu}t. We discuss some of the properties of cosmic string loops at this cutoff scale, and we argue that recent network simulations point to two populations of cosmic string loops, one near the horizon scale and one near the gravitational radiation cutoff.

  8. Cosmic strings as the source of small-scale microwave background anisotropy

    SciTech Connect

    Pogosian, Levon; Tye, S.-H. Henry; Wasserman, Ira; Wyman, Mark E-mail: tye@lepp.cornell.edu E-mail: mwyman@perimeterinstitute.ca

    2009-02-15

    Cosmic string networks generate cosmological perturbations actively throughout the history of the universe. Thus, the string sourced anisotropy of the cosmic microwave background is not affected by Silk damping as much as the anisotropy seeded by inflation. The spectrum of perturbations generated by strings does not match the observed CMB spectrum on large angular scales (l < 1000) and is bounded to contribute no more than 10% of the total power on those scales. However, when this bound is marginally saturated, the anisotropy created by cosmic strings on small angular scales l {approx}> 2000 will dominate over that created by the primary inflationary perturbations. This range of angular scales in the CMB is presently being measured by a number of experiments; their results will test this prediction of cosmic string networks soon.

  9. Small Scale Reconnection : Structure and Electron Jet Emission

    NASA Astrophysics Data System (ADS)

    Roth, I.

    2012-04-01

    The effects of small scale processes on the formation and evolution of macroscopic inhomogeneous magnetic configurations and the resulting super-Alfvenic jets have been investigated in space and lab over many years. Various satellite measurements at the magneto-sheath crossings observe features with small spatial scale of the order of electron skin depth, indicating the importance of processes dominated by electron dynamics. The data show structures which are (a) spatially non-symmetric with densities and magnetic field differing substantially on both sides of the region, while (b) the inhomogeneous magnetic and electric field structures consist of narrow, three-dimensional electron diffusion regions, with (c) bifurcated current over electron skin depth or below and (d) ejection of energetic, super-Alfvenic, non-Gaussian electrons perpendicularly to the magnetic field, away from the X-line. At small scales the main Alfven mode which describes the MHD regime is replaced by a helicon/whistler. The eMHD model, which includes the full dynamics of the electrons and stationary ions, with density gradients and asymptotically different values of the magnetic field is implemented for the experimentally observed configurations. Over the small scales the electron fluid follows the lines of the generalized vorticity (GV) as it decouples from the magnetic field. The regions of a significant deviation of the GV from the magnetic field become the potential sites for non-adiabatic electron acceleration. Effects of geometry, compressibility and thermal effects on this deviation will be discussed. The non-thermal jet distribution is conjectured to form when the standard diffusion is replaced by a non Markovian with large jumps random walk process, describing its evolution through the fractional diffusion equation and resulting in a non-Gaussian distribution.

  10. Cosmic string parameter constraints and model analysis using small scale Cosmic Microwave Background data

    SciTech Connect

    Urrestilla, Jon; Bevis, Neil; Hindmarsh, Mark; Kunz, Martin E-mail: n.bevis@imperial.ac.uk E-mail: martin.kunz@physics.unige.ch

    2011-12-01

    We present a significant update of the constraints on the Abelian Higgs cosmic string tension by cosmic microwave background (CMB) data, enabled both by the use of new high-resolution CMB data from suborbital experiments as well as the latest results of the WMAP satellite, and by improved predictions for the impact of Abelian Higgs cosmic strings on the CMB power spectra. The new cosmic string spectra [1] were improved especially for small angular scales, through the use of larger Abelian Higgs string simulations and careful extrapolation. If Abelian Higgs strings are present then we find improved bounds on their contribution to the CMB anisotropies, fd{sup AH} < 0.095, and on their tension, Gμ{sub AH} < 0.57 × 10{sup −6}, both at 95% confidence level using WMAP7 data; and fd{sup AH} < 0.048 and Gμ{sub AH} < 0.42 × 10{sup −6} using all the CMB data. We also find that using all the CMB data, a scale invariant initial perturbation spectrum, n{sub s} = 1, is now disfavoured at 2.4σ even if strings are present. A Bayesian model selection analysis no longer indicates a preference for strings.

  11. Minimal length and small scale structure of spacetime

    NASA Astrophysics Data System (ADS)

    Kothawala, Dawood

    2013-11-01

    Many generic arguments support the existence of a minimum spacetime interval L0. Such a “zero-point” length can be naturally introduced in a locally Lorentz invariant manner via Synge’s world function biscalar Ω(p,P) which measures squared geodesic interval between spacetime events p and P. I show that there exists a nonlocal deformation of spacetime geometry given by a disformal coupling of metric to the biscalar Ω(p,P), which yields a geodesic interval of L0 in the limit p→P. Locality is recovered when Ω(p,P)≫L02/2. I discuss several conceptual implications of the resultant small-scale structure of spacetime for QFT propagators as well as spacetime singularities.

  12. Structures and Intermittency in Small Scales Solar Wind Turbulence

    SciTech Connect

    Sahraoui, Fouad; Goldstein, Melvyn

    2010-03-25

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

  13. Small-Scale Fabrication of Biomimetic Structures for Periodontal Regeneration.

    PubMed

    Green, David W; Lee, Jung-Seok; Jung, Han-Sung

    2016-01-01

    The periodontium is the supporting tissues for the tooth organ and is vulnerable to destruction, arising from overpopulating pathogenic bacteria and spirochaetes. The presence of microbes together with host responses can destroy large parts of the periodontium sometimes leading tooth loss. Permanent tissue replacements are made possible with tissue engineering techniques. However, existing periodontal biomaterials cannot promote proper tissue architectures, necessary tissue volumes within the periodontal pocket and a "water-tight" barrier, to become clinically acceptable. New kinds of small-scale engineered biomaterials, with increasing biological complexity are needed to guide proper biomimetic regeneration of periodontal tissues. So the ability to make compound structures with small modules, filled with tissue components, is a promising design strategy for simulating the anatomical complexity of the periodotium attachment complexes along the tooth root and the abutment with the tooth collar. Anatomical structures such as, intima, adventitia, and special compartments such as the epithelial cell rests of Malassez or a stellate reticulum niche need to be engineered from the start of regeneration to produce proper periodontium replacement. It is our contention that the positioning of tissue components at the origin is also necessary to promote self-organizing cell-cell connections, cell-matrix connections. This leads to accelerated, synchronized and well-formed tissue architectures and anatomies. This strategy is a highly effective preparation for tackling periodontitis, periodontium tissue resorption, and to ultimately prevent tooth loss. Furthermore, such biomimetic tissue replacements will tackle problems associated with dental implant support and perimimplantitis. PMID:26903872

  14. Small-Scale Fabrication of Biomimetic Structures for Periodontal Regeneration

    PubMed Central

    Green, David W.; Lee, Jung-Seok; Jung, Han-Sung

    2016-01-01

    The periodontium is the supporting tissues for the tooth organ and is vulnerable to destruction, arising from overpopulating pathogenic bacteria and spirochaetes. The presence of microbes together with host responses can destroy large parts of the periodontium sometimes leading tooth loss. Permanent tissue replacements are made possible with tissue engineering techniques. However, existing periodontal biomaterials cannot promote proper tissue architectures, necessary tissue volumes within the periodontal pocket and a “water-tight” barrier, to become clinically acceptable. New kinds of small-scale engineered biomaterials, with increasing biological complexity are needed to guide proper biomimetic regeneration of periodontal tissues. So the ability to make compound structures with small modules, filled with tissue components, is a promising design strategy for simulating the anatomical complexity of the periodotium attachment complexes along the tooth root and the abutment with the tooth collar. Anatomical structures such as, intima, adventitia, and special compartments such as the epithelial cell rests of Malassez or a stellate reticulum niche need to be engineered from the start of regeneration to produce proper periodontium replacement. It is our contention that the positioning of tissue components at the origin is also necessary to promote self-organizing cell–cell connections, cell–matrix connections. This leads to accelerated, synchronized and well-formed tissue architectures and anatomies. This strategy is a highly effective preparation for tackling periodontitis, periodontium tissue resorption, and to ultimately prevent tooth loss. Furthermore, such biomimetic tissue replacements will tackle problems associated with dental implant support and perimimplantitis. PMID:26903872

  15. Small Scale Structure of the ISM Toward NGC 2264

    NASA Astrophysics Data System (ADS)

    Friedman, S. D.; Sonnentrucker, P.; Murphy, E. M.

    2001-12-01

    The spatial structure of the Galactic interstellar medium (ISM) is affected by many processes including bulk turbulence, winds from massive stars, and supernovae. But it has only been in the last few years that structure on scales ~1 parsec and less have been recognized. Most studies have been done by observing spatial or temporal changes in optical and radio spectra. For example, ground-based time series observations of Na I toward δ Ori A spanning several decades (Price, Crawford, & Barlow 2000, MNRAS 312, L43) as well as observations of Na I toward stars in globular cluster M92 (Andrews, Meyer, & Lauroesch, 2001, ApJ 552, L73) reveal structure on scales of 102 to 104 AU, respectively. Frail et al. (1991, ApJ 382, 168) inferred variation in the H I column density over tens of AU from 21 cm observations of a pulsar moving through the ISM. We report on observations of four stars in the open cluster NGC 2264, covering 910-1187Å, using the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. These are among the first UV studies of the small scale structure of the ISM. All target stars are classified as B2V or B3V, and have similar reddening characteristics, 0.05 <= EB-V <= 0.08. At a cluster distance of 750 pc the star-to-star separations range from 1.4 to 3.6 pc. We discuss variations in column densities of several species along these sight lines, including H2 and Fe II. This work is supported by NASA contract NAS5-32985 to the Johns Hopkins University.

  16. MeV Dark Matter and Small Scale Structure

    SciTech Connect

    Hooper, Dan; Kaplinghat, Manoj; Strigari, Louis E.; Zurek, Kathryn M.; /Wisconsin U., Madison

    2007-04-01

    WIMPs with electroweak scale masses (neutralinos, etc.) remain in kinetic equilibrium with other particle species until temperatures approximately in the range of 10 MeV to 1 GeV, leading to the formation of dark matter substructure with masses as small as 10{sup -4} M{sub {circle_dot}} to 10{sup -12} M{sub {circle_dot}}. However, if dark matter consists of particles with MeV scale masses, as motivated by the observation of 511 keV emission from the Galactic Bulge, such particles are naturally expected to remain in kinetic equilibrium with the cosmic neutrino background until considerably later times. This would lead to a strong suppression of small scale structure with masses below about 10{sup 7}M{sub {circle_dot}} to 10{sup 4} M{sub {circle_dot}}. This cutoff scale has important implications for present and future searches for faint Local Group satellite galaxies and for the missing satellites problem.

  17. Detecting small scale CO2 emission structures using OCO-2

    NASA Astrophysics Data System (ADS)

    Schwandner, Florian M.; Eldering, Annmarie; Verhulst, Kristal R.; Miller, Charles E.; Nguyen, Hai M.; Oda, Tomohiro; O'Dell, Christopher; Rao, Preeti; Kahn, Brian; Crisp, David; Gunson, Michael R.; Sanchez, Robert M.; Ashok, Manasa; Pieri, David; Linick, Justin P.; Yuen, Karen

    2016-04-01

    Localized carbon dioxide (CO2) emission structures cover spatial domains of less than 50 km diameter and include cities and transportation networks, as well as fossil fuel production, upgrading and distribution infra-structure. Anthropogenic sources increasingly upset the natural balance between natural carbon sources and sinks. Mitigation of resulting climate change impacts requires management of emissions, and emissions management requires monitoring, reporting and verification. Space-borne measurements provide a unique opportunity to detect, quantify, and analyze small scale and point source emissions on a global scale. NASA's first satellite dedicated to atmospheric CO2 observation, the July 2014 launched Orbiting Carbon Observatory (OCO-2), now leads the afternoon constellation of satellites (A-Train). Its continuous swath of 2 to 10 km in width and eight footprints across can slice through coincident emission plumes and may provide momentary cross sections. First OCO-2 results demonstrate that we can detect localized source signals in the form of urban total column averaged CO2 enhancements of ~2 ppm against suburban and rural backgrounds. OCO-2's multi-sounding swath observing geometry reveals intra-urban spatial structures reflected in XCO2 data, previously unobserved from space. The transition from single-shot GOSAT soundings detecting urban/rural differences (Kort et al., 2012) to hundreds of soundings per OCO-2 swath opens up the path to future capabilities enabling urban tomography of greenhouse gases. For singular point sources like coal fired power plants, we have developed proxy detections of plumes using bands of imaging spectrometers with sensitivity to SO2 in the thermal infrared (ASTER). This approach provides a means to automate plume detection with subsequent matching and mining of OCO-2 data for enhanced detection efficiency and validation. © California Institute of Technology

  18. The Physical Character of Small-Scale Interstellar Structures

    NASA Technical Reports Server (NTRS)

    Lauroesch, James T.

    2005-01-01

    The primary objective of this program was to obtain FUSE observations of the multiple interstellar absorption lines of H2 toward the members of 3 resolvable binary/multiple star systems to explore the physical conditions in known interstellar small-scale structures. Each of the selected systems was meant to address a different aspect of the models for the origin of these structures: 1) The stars HD 32039/40 were meant to probe a temporally varying component which probed a cloud with an inferred size of tens to a few hundreds of AU. The goal was to see if there was any significant H2 associated with this component; 2) The star HD 36408B and its companion HD 36408A (observed as part of FUSE GTO program P119) show significant spatial and temporal (proper motion induced) Na I column variations in a strong, relatively isolated component, as well as a relatively simple component structure. The key goal here was to identify any differences in H2 or C I excitation between the sightlines, and to measure the physical conditions (primarily density and temperature) in the temporally varying component; 3) The stars HD 206267C and HD 206267D are highly reddened sightlines which showed significant variations in K I and molecular absorption lines in multiple velocity components. Coupled with FUSE GTO observations of HD 206267A (program P116), the goal was to study the variations in H2 along sightlines which are significantly more distant, with larger separations, and with greater extinctions than the other selected binary systems.

  19. The Structure and Climate of Size: Small Scale Schooling in an Urban District

    ERIC Educational Resources Information Center

    LeChasseur, Kimberly

    2009-01-01

    This study explores mechanisms involved in small scale schooling and student engagement. Specifically, this study questions the validity of arguments for small scale schooling reforms that confound the promised effects of small scale schooling "structures" (such as smaller enrollments, schools-within-schools, and smaller class sizes) with the…

  20. Visualization of small scale structures on high resolution DEMs

    NASA Astrophysics Data System (ADS)

    Kokalj, Žiga; Zakšek, Klemen; Pehani, Peter; Čotar, Klemen; Oštir, Krištof

    2015-04-01

    Knowledge on the terrain morphology is very important for observation of numerous processes and events and digital elevation models are therefore one of the most important datasets in geographic analyses. Furthermore, recognition of natural and anthropogenic microrelief structures, which can be observed on detailed terrain models derived from aerial laser scanning (lidar) or structure-from-motion photogrammetry, is of paramount importance in many applications. In this paper we thus examine and evaluate methods of raster lidar data visualization for the determination (recognition) of microrelief features and present a series of strategies to assist selecting the preferred visualization of choice for structures of various shapes and sizes, set in varied landscapes. Often the answer is not definite and more frequently a combination of techniques has to be used to map a very diverse landscape. Researchers can only very recently benefit from free software for calculation of advanced visualization techniques. These tools are often difficult to understand, have numerous options that confuse the user, or require and produce non-standard data formats, because they were written for specific purposes. We therefore designed the Relief Visualization Toolbox (RVT) as a free, easy-to-use, standalone application to create visualisations from high-resolution digital elevation data. It is tailored for the very beginners in relief interpretation, but it can also be used by more advanced users in data processing and geographic information systems. It offers a range of techniques, such as simple hillshading and its derivatives, slope gradient, trend removal, positive and negative openness, sky-view factor, and anisotropic sky-view factor. All included methods have been proven to be effective for detection of small scale features and the default settings are optimised to accomplish this task. However, the usability of the tool goes beyond computation for visualization purposes, as sky

  1. Small-scale structures in the far-infrared background

    NASA Astrophysics Data System (ADS)

    Herbstmeier, Uwe; Abraham, Peter; Lemke, Dietrich; Laureijs, R. J.; Klaas, Ulrich; Mattila, Kalevi; Leinert, Christoph; Surace, Christian; Kunkel, Michael

    1998-04-01

    Four fields with areas ranging from 80 to 2000 arcmin(2) have been mapped with the photometer on board of the Infrared Space Observatory (ISO) at 90 and around 180mu m in regions of bright and faint cirrus. We examined the spatial characteristics of the infrared background emission with high spatial resolution and found that the fluctuations in the background emission limit the detection sensitivity of ISOPHOT for most of our observations. At 90mu m the power law relation between the power in the fluctuations and the spatial frequencies established from IRAS data could be extended to twice as high spatial frequencies. At 180mu m the small-scale fluctuations were studied for the first time by a cold space telescope with arcminute-resolution. A similar power law and spectral index down to spatial scales of 3arcmin as for the 90mu m component is found. For cirrus clouds the spatial frequency spectrum in the far-infrared has a similar shape as that derived from 21cm line observations of the interstellar neutral hydrogen. In faint regions the fluctuations are caused presumably by randomly distributed extragalactic sources. Future 3m class space telescopes surveying the sky around 200mu m will not be hampered by cirrus over most of the sphere. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA

  2. The structure of cosmic string wakes

    SciTech Connect

    Sornborger, A.; Brandenberger, R.; Fryxell, B.; Olson, K.

    1997-06-01

    The clustering of baryons and cold dark matter induced by a single moving string is analyzed numerically, making use of the new three-dimensional Eulerian cosmological hydrocode of Sornborger {ital et al.}, which uses the piecewise parabolic method to track the baryons and the particle-in-cell method to evolve the dark matter particles. A long straight string moving with a speed comparable to c induces a planar overdensity (a {open_quotes}wake{close_quotes}). Since the initial perturbation is a velocity kick toward the plane behind the string and there is no initial Newtonian gravitational line source, the baryons are trapped in the center of the wake, leading to an enhanced baryon to dark matter ratio. The cold coherent flow leads to very low postshock temperatures of the baryonic fluid. In contrast, long strings with small-scale structure (which can be described by adding a Newtonian gravitational line source) move slowly and form filamentary objects. The large central pressure due to the gravitational potential causes the baryons to be expelled from the central regions and leads to a relative deficit in the baryon to dark matter ratio. In this case, the velocity of the baryons is larger, leading to high postshock temperatures. {copyright} {ital 1997} {ital The American Astronomical Society}

  3. Modelling of Dust Extinction through Dark Clouds: Small Scale Structure

    NASA Astrophysics Data System (ADS)

    Clemens, D.; Lada, C.

    1993-12-01

    In order to understand some curious effects discovered in analyzing our deep JHK near-infrared survey of the background stars probing the IC 5146 dark cloud complex (Lada, Lada, Clemens, & Bally 1993), we have constructed a simple model of the dust extinction through a molecular cloud. The effect noticed involved a correlation between the dispersion of the E(H-K) based estimate of A_V, when the stellar estimates of E(H-K) were binned into arcmin sized bins, with the mean A_V computed for those bins. The sense of the correlation is that the dispersion of the extinction rises with the extinction in a nearly linear fashion. Further, the dispersion of the dispersion also rises with extinction. Our model was constructed to try to understand the origin of this unexpected behavior. The model consists of a Poisson generator to populate a bin with stars and various extinction generating functions to add extinction to each star. Additionally, measurement noise and varying amounts of foreground star contamination are added to simulate the actual observations. Remarkably, this simple model is able to rule out several cloud structure models, including uniform extinction across an arcmin sized bin and the case of dense clumplets (rocks) embedded in a low extinction medium. We show that a power law parameterization of the extinction variation with position across a bin is able to fully reproduce the observations for a fairly robust set of power law indices. We also show that foreground star contamination plus any simple extinction model cannot reproduce the observations, while foreground star contamination does not appreciably affect the power law extinction model for foreground stellar fractions less than 30 - 50% of the total stellar content.

  4. Fabrication of small-scale structures with non-planar features

    SciTech Connect

    Burckel, David B.; Ten Eyck, Gregory A.

    2015-11-19

    The fabrication of small-scale structures is disclosed. A unit-cell of a small-scale structure with non-planar features is fabricated by forming a membrane on a suitable material. A pattern is formed in the membrane and a portion of the substrate underneath the membrane is removed to form a cavity. Resonators are then directionally deposited on the wall or sides of the cavity. The cavity may be rotated during deposition to form closed-loop resonators. The resonators may be non-planar. The unit-cells can be formed in a layer that includes an array of unit-cells.

  5. Formation of the small-scale structure of auroral electron precipitations

    NASA Astrophysics Data System (ADS)

    Kropotkin, A. P.

    2016-10-01

    This paper is aimed at physical causes of the small-scale transverse structure in the flows of auroral electrons, generating the corresponding small-scale structure of discrete auroras. The parallel electric field existing in the lower part of the auroral magnetosphere, in the auroral cavity region, in the presence of a strong upward field-aligned current, accelerates magnetospheric electrons to energies of ∼ 1 - 10 keV. The flow of these particles while maintaining the high density of the field-aligned current, produces a current-driven instability, which generates Alfvénic turbulence at short perpendicular wavelengths ≤ 1 km. These short-wavelength inertial Alfvén disturbances possess a nonzero parallell electric field, which modulates the electron flow velocity. The modulation occurring at high altitudes ≥104 km leads to a nonlinear effect of formation of strong density peaks at low altitudes of electron precipitation. The transverse, horizontal scales of the corresponding electron flow structure coincide with the small scales of the Alfvénic turbulence; and this structuring leads to non-uniformities in the auroral luminosity on the same scales, i.e., to small-scale structure of discrete auroras.

  6. Transient small-scale structure in the main auroral emission at Jupiter

    NASA Astrophysics Data System (ADS)

    Palmaerts, B.; Radioti, A.; Grodent, D.; Chané, E.; Bonfond, B.

    2014-12-01

    The main auroral emission at Jupiter results from the ionosphere-magnetosphere coupling current system associated with the corotation breakdown of iogenic plasma in the current sheet. The morphology and brightness of the main auroral emission are generally suggested to be stable during time intervals of the order of an hour. Here we reveal a transient small-scale structure in the main emission that is characterized by a localized brightness enhancement close to noon local time. The evolution of this small-scale structure is investigated in both hemispheres on the basis of far UV images obtained with the Hubble Space Telescope between 1997 and 2007. Our observations indicate that the transient feature vary within a few tens of minutes. As one plausible explanation based on Galileo observations, we suggest that the localized enhancement of the field-aligned currents associated with the transient structure is due to the shear induced by intermittent inward plasma flow near noon in the equatorial plane.

  7. Small-Scale Heterogeneity in Deep-Sea Nematode Communities around Biogenic Structures

    PubMed Central

    Hasemann, Christiane; Soltwedel, Thomas

    2011-01-01

    The unexpected high species richness of deep-sea sediments gives rise to the questions, which processes produce and maintain diversity in the deep sea, and at what spatial scales do these processes operate? The idea of a small-scale habitat structure at the deep-sea floor provides the background for this study. At small scales biogenic structures create a heterogeneous environment that influences the structure of the surrounding communities and the dynamics of the meiobenthic populations. As an example for biogenic structures, small deep-sea sponges (Tentorium semisuberites Schmidt 1870) and their sedimentary environment were investigated for small-scale distribution patterns of benthic deep-sea nematodes. Sampling was carried out with the remotely operated vehicle Victor 6000 at the Arctic deep-sea observatory HAUSGARTEN. In order to investigate nematode community patterns sediment cores around three small sponges and corresponding control cores were analysed. A total of approx. 5800 nematodes were identified. The comparison of the nematode communities from sponge and control samples indicated an influence of the biogenic structure “sponge” on diversity patterns and habitat heterogeneity. The increased number of nematode species and functional groups found in the sediments around the sponges suggest that on a small scale the sponge acts as a gradient and creates a more divers habitat structure. The nematode community from the sponge sediments shows a greater taxonomic variance and species richness together with lower relative abundances of the species compared to those from control sediments. Obviously, the more homogeneous habitat conditions of the control sediments offer less micro-habitats than the sediments around the sponges. This seems to reduce the number of functional groups and species coexisting in the control sediments. PMID:22216193

  8. Transverse structure of the QCD string

    SciTech Connect

    Meyer, Harvey B.

    2010-11-15

    The characterization of the transverse structure of the QCD string is discussed. We formulate a conjecture as to how the stress-energy tensor of the underlying gauge theory couples to the string degrees of freedom. A consequence of the conjecture is that the energy density and the longitudinal-stress operators measure the distribution of the transverse position of the string, to leading order in the string fluctuations, whereas the transverse-stress operator does not. We interpret recent numerical measurements of the transverse size of the confining string and show that the difference of the energy and longitudinal-stress operators is a particularly natural probe at next-to-leading order. Second, we derive the constraints imposed by open-closed string duality on the transverse structure of the string. We show that a total of three independent ''gravitational'' form factors characterize the transverse profile of the closed string, and obtain the interpretation of recent effective string theory calculations: the square radius of a closed string of length {beta} defined from the slope of its gravitational form factor, is given by (d-1/2{pi}{sigma})log({beta}/4r{sub 0}) in d space dimensions. This is to be compared with the well-known result that the width of the open string at midpoint grows as (d-1/2{pi}{sigma})log(r/r{sub 0}). We also obtain predictions for transition form factors among closed-string states.

  9. The effect of small-scale structure on normal mode frequencies and global inversions

    NASA Astrophysics Data System (ADS)

    Snieder, Roel; Beckers, Jos; Neele, Filip

    1991-01-01

    A model of all the subduction zones and spreading ridges of the earth's upper mantle is used for the purpose of computing normal-mode frequency shifts for an earth model that contains significant small-scale structure. The model is detailed, and a short outline of the employed scattering theory is given. The normal-mode frequency shifts are shown, and inversions for a global earth model using the synthetic normal-mode frequency shifts are presented. The earth model in this inversion is presented as a truncated series of spherical harmonics, and a comparison is made with the true projection of structure on the same low-order spherical harmonics.

  10. THE OPACITY OF THE INTERGALACTIC MEDIUM DURING REIONIZATION: RESOLVING SMALL-SCALE STRUCTURE

    SciTech Connect

    Emberson, J. D.; Thomas, Rajat M.; Alvarez, Marcelo A.

    2013-02-15

    Early in the reionization process, the intergalactic medium (IGM) would have been quite inhomogeneous on small scales, due to the low Jeans mass in the neutral IGM and the hierarchical growth of structure in a cold dark matter universe. This small-scale structure acted as an important sink during the epoch of reionization, impeding the progress of the ionization fronts that swept out from the first sources of ionizing radiation. Here we present results of high-resolution cosmological hydrodynamics simulations that resolve the cosmological Jeans mass of the neutral IGM in representative volumes several Mpc across. The adiabatic hydrodynamics we follow are appropriate in an unheated IGM, before the gas has had a chance to respond to the photoionization heating. Our focus is determination of the resolution required in cosmological simulations in order to sufficiently sample and resolve small-scale structure regulating the opacity of an unheated IGM. We find that a dark matter particle mass of m {sub dm} {approx}< 50 M {sub Sun} and box size of L {approx}> 1 Mpc are required. With our converged results we show how the mean free path of ionizing radiation and clumping factor of ionized hydrogen depend on the ultraviolet background flux and redshift. We find, for example at z = 10, clumping factors typically of 10-20 for an ionization rate of {Gamma} {approx} (0.3-3) Multiplication-Sign 10{sup -12} s{sup -1}, with corresponding mean free paths of {approx}3-15 Mpc, extending previous work on the evolving mean free path to considerably smaller scales and earlier times.

  11. Infrared astronomical satellite (IRAS) catalogs and atlases. Volume 7: The small scale structure catalog

    NASA Technical Reports Server (NTRS)

    Helou, George (Editor); Walker, D. W. (Editor)

    1988-01-01

    The Infrared Astronomical Satellite (IRAS) was launched January 26, 1983. During its 300-day mission, it surveyed over 96 pct of the celestial sphere at four infrared wavelengths, centered approximately at 12, 25, 60, and 100 microns. Volume 1 describes the instrument, the mission, and the data reduction process. Volumes 2 through 6 present the observations of the approximately 245,000 individual point sources detected by IRAS; each volume gives sources within a specified range of declination. Volume 7 gives the observations of the approximately 16,000 sources spatially resolved by IRAS and smaller than 8'. This is Volume 7, The Small Scale Structure Catalog.

  12. Investigation of the small-scale structure and dynamics of Uranus' atmosphere

    NASA Technical Reports Server (NTRS)

    Eshleman, Von R.; Hinson, David P.

    1991-01-01

    This document constitutes the final technical report of the Uranus Analysis Program. Papers and/or abstracts resulting from this research are presented. The following topics are covered: (1) past and future of radio occultation studies of planetary atmospheres; (2) equatorial waves in the stratosphere of Uranus; (3) the atmosphere of Uranus- results of radio occultation measurements with Voyager 2; (4) Uranus' atmospheric dynamics and circulation; (5) small-scale structure and dynamics in the atmosphere of Uranus; (6) evidence for inertia-gravity waves in the stratosphere of Uranus derived from Voyager 2 radio occultation data; and (7) planetary waves in the equatorial stratosphere of Uranus.

  13. A Statistical Test of the Relationship between Galactic HI Structure and Small-scale Structure in the Cosmic Microwave Background

    NASA Astrophysics Data System (ADS)

    Verschuur, Gerrit L.

    2014-06-01

    The archive of IRIS, PLANCK and WMAP data available at the IRSA website of IPAC allows the apparent associations between galactic neutral hydrogen (HI) features and small-scale structure in WMAP and PLANCK data to be closely examined. In addition, HI new observations made with the Green Bank Telescope are used to perform a statistical test of putative associations. It is concluded that attention should be paid to the possibility that some of the small-scale structure found in WMAP and PLANCK data harbors the signature of a previously unrecognized source of high-frequency continuum emission in the Galaxy.

  14. Small-scale-structure of the interstellar medium probed through diffuse band observations.

    PubMed

    Cordiner, Martin A; Fossey, Stephen J; Smith, Arfon M; Sarre, Peter J

    2006-01-01

    The carriers of the diffuse interstellar band spectrum represent an important baryonic component of the interstellar medium (ISM) and it is expected that their identification will contribute significantly to the understanding of the chemistry and physics of interstellar clouds. It is widely held that the carriers are linked to the presence of dust grains on account of the good correlation of their strengths with interstellar reddening, so they offer an important potential route to improving our understanding of the composition and chemistry of grains and grain surfaces. In addition to the challenge of making the spectral assignments, an important current question concerns the spatial distribution and physical state of interstellar material, with recent observational atomic and molecular line absorption studies suggesting that diffuse clouds are more 'clumpy' than previously thought. We describe here high signal-to-noise optical observations made at the Anglo-Australian Telescope using UCLES that were undertaken to investigate the spatial distribution of diffuse band carriers. We describe the first detection of 'small-scale-structure' in the diffuse band carrier distribution in the ISM, and comment on the possibilities that these data hold for contributing to the solution of the diffuse band problem and our understanding of the nature of small-scale-structure in the diffuse ISM.

  15. Radio Brightness Temperatures and Angular Dimensions of Recently Predicted Vl-Bi Small-Scale Structures

    NASA Astrophysics Data System (ADS)

    Opher, R.

    1990-11-01

    RESUMEN. Muestro que analisis recientes publicados de fuentes de radio galacticas y extragalacticas predicen estructuras en pequera escala en fuentes de radio extendidas, remanentes de supernova, vientos protoestelares, nubes moleculares, distorsiones del fondo de 3 K, enanas blancas magnetizadas, estrellas de tipo tardio y el Sol. Discuto las temperatu- ras de brillo de radio de estas estructuras y sus ditnensiones. Muestro que estas estructuras son detectables con las sensibilidades actuales de VLBI (o en el futuro cercano). ABSTRACT. I show that recently published analysis of galactic and extragalactic radio sources make predictions of small-scale structures in extended radio sources, supernovae remnants, protostellar winds, molecu- lar clouds, distortions of the 3 K background, magnetized white dwarf binaries, late-type stars and the sun. I discuss the radio brightness temperatures of these structures and their dimensions. I show that these structures are detectable with present (or near future) VLBI sensitivities. : RADIO SOURCES-EXTENDED

  16. Challenges During Microstructural Analysis and Mechanical Testing of Small-Scale Pseudoelastic NiTi Structures

    NASA Astrophysics Data System (ADS)

    Hahn, S.; Wagner, M. F.-X.

    2016-06-01

    Most investigations on NiTi-based shape memory alloys involve large-scale bulk material; knowledge about the martensitic transformation in small-scale NiTi structures is still limited. In this paper, we study the microstructures of thin NiTi layers and their mechanical properties, and we discuss typical challenges that arise when experiments are performed on small samples. A physical vapor deposition (PVD) process was used to deposit thin NiTi wires with a cross section of 15 × 15 μm2 and dogbone-shaped samples 5 × 500 μm2. Microstructural properties were characterized by X-ray diffraction, electron backscatter diffraction, and scanning electron microscopy. Moreover, tensile tests were performed using optical strain measurements in order to observe martensite band formation during cyclic loading. The surfaces of the crystalline wires reflect the columnar growth of NiTi during deposition. The wires exhibit pseudoelastic material behavior during tensile testing. Fracture typically occurs along the columns because the column growth direction is perpendicular to the straining direction. Electropolishing removes these local stress raisers and hence increases fracture strains. Our results demonstrate that the pseudoelastic properties of the PVD-processed materials agree well with those of conventional NiTi, and that they provide new opportunities to study the fundamentals of martensitic transformation in small-scale model systems.

  17. SMALL-SCALE STRUCTURE OF THE INTERSTELLAR MEDIUM TOWARD {rho} Oph STARS: DIFFUSE BAND OBSERVATIONS

    SciTech Connect

    Cordiner, M. A.; Smith, A. M.; Sarre, P. J.; Fossey, S. J.

    2013-02-10

    We present an investigation of small-scale structure in the distribution of large molecules/dust in the interstellar medium through observations of diffuse interstellar bands (DIBs). High signal-to-noise optical spectra were recorded toward the stars {rho} Oph A, B, C, and DE using the University College London Echelle Spectrograph on the Anglo-Australian Telescope. The strengths of some of the DIBs are found to differ by about 5%-9% between the close binary stars {rho} Oph A and B, which are separated by a projected distance on the sky of only c. 344 AU. This is the first star system in which such small-scale DIB strength variations have been reported. The observed variations are attributed to differences between a combination of carrier abundance and the physical conditions present along each sightline. The sightline toward {rho} Oph C contains relatively dense, molecule-rich material and has the strongest {lambda}{lambda}5850 and 4726 DIBs. The gas toward DE is more diffuse and is found to exhibit weak ''C{sub 2}'' (blue) DIBs and strong yellow/red DIBs. The differences in diffuse band strengths between lines of sight are, in some cases, significantly greater in magnitude than the corresponding variations among atomic and diatomic species, indicating that the DIBs can be sensitive tracers of interstellar cloud conditions.

  18. Small-scale structure and turbulence observed in MAP/WINE)

    NASA Technical Reports Server (NTRS)

    Blix, T. A.

    1989-01-01

    During MAP/WINE small scale structure and turbulence in the mesosphere and lower thermosphere was studied in situ by rocket-borne instruments as well as from the ground by remote sensing techniques. The eight salvoes launched during the campaign resulted in a wealth of information on the dynamical structure of these regions. The experimental results are reviewed and their interpretation is discussed in terms of gravity waves and turbulence. It is shown that eddy diffusion coefficients and turbulent energy dissipation rates may be derived from the in situ measurements in a consistent manner. The observations are also shown to be consistent with the hypothesis that turbulence can be created by a process of gravity wave saturation.

  19. Diffuse Interstellar Bands as Probes of Small-Scale Interstellar Structure

    NASA Astrophysics Data System (ADS)

    Smith, K. T.; Cordiner, M. A.; Sarre, P. J.

    2014-02-01

    We present observations which probe the small-scale structure of the interstellar medium using diffuse interstellar bands (DIBs). Towards HD 168075/6 in the Eagle Nebula, significant differences in DIB absorption are found between the two lines of sight, which are separated by 0.25 pc, and λ 5797 exhibits a velocity shift. Similar data are presented for four stars in the μ Sgr system. We also present a search for variations in DIB absorption towards κ Vel, where the atomic lines are known to vary on scales of ~ 10 AU. Observations separated by ~ 9 yr yielded no evidence for changes in DIB absorption strength over this scale, but do reveal an unusual DIB spectrum.

  20. Solving the small-scale structure puzzles with dissipative dark matter

    NASA Astrophysics Data System (ADS)

    Foot, Robert; Vagnozzi, Sunny

    2016-07-01

    Small-scale structure is studied in the context of dissipative dark matter, arising for instance in models with a hidden unbroken Abelian sector, so that dark matter couples to a massless dark photon. The dark sector interacts with ordinary matter via gravity and photon-dark photon kinetic mixing. Mirror dark matter is a theoretically constrained special case where all parameters are fixed except for the kinetic mixing strength, epsilon. In these models, the dark matter halo around spiral and irregular galaxies takes the form of a dissipative plasma which evolves in response to various heating and cooling processes. It has been argued previously that such dynamics can account for the inferred cored density profiles of galaxies and other related structural features. Here we focus on the apparent deficit of nearby small galaxies (``missing satellite problem"), which these dissipative models have the potential to address through small-scale power suppression by acoustic and diffusion damping. Using a variant of the extended Press-Schechter formalism, we evaluate the halo mass function for the special case of mirror dark matter. Considering a simplified model where Mbaryons propto Mhalo, we relate the halo mass function to more directly observable quantities, and find that for epsilon ≈ 2 × 10-10 such a simplified description is compatible with the measured galaxy luminosity and velocity functions. On scales Mhalo lesssim 108 Msolar, diffusion damping exponentially suppresses the halo mass function, suggesting a nonprimordial origin for dwarf spheroidal satellite galaxies, which we speculate were formed via a top-down fragmentation process as the result of nonlinear dissipative collapse of larger density perturbations. This could explain the planar orientation of satellite galaxies around Andromeda and the Milky Way.

  1. Solving the small-scale structure puzzles with dissipative dark matter

    NASA Astrophysics Data System (ADS)

    Foot, Robert; Vagnozzi, Sunny

    2016-07-01

    Small-scale structure is studied in the context of dissipative dark matter, arising for instance in models with a hidden unbroken Abelian sector, so that dark matter couples to a massless dark photon. The dark sector interacts with ordinary matter via gravity and photon-dark photon kinetic mixing. Mirror dark matter is a theoretically constrained special case where all parameters are fixed except for the kinetic mixing strength, epsilon. In these models, the dark matter halo around spiral and irregular galaxies takes the form of a dissipative plasma which evolves in response to various heating and cooling processes. It has been argued previously that such dynamics can account for the inferred cored density profiles of galaxies and other related structural features. Here we focus on the apparent deficit of nearby small galaxies (``missing satellite problem"), which these dissipative models have the potential to address through small-scale power suppression by acoustic and diffusion damping. Using a variant of the extended Press-Schechter formalism, we evaluate the halo mass function for the special case of mirror dark matter. Considering a simplified model where Mbaryons propto Mhalo, we relate the halo mass function to more directly observable quantities, and find that for epsilon ≈ 2 × 10‑10 such a simplified description is compatible with the measured galaxy luminosity and velocity functions. On scales Mhalo lesssim 108 Msolar, diffusion damping exponentially suppresses the halo mass function, suggesting a nonprimordial origin for dwarf spheroidal satellite galaxies, which we speculate were formed via a top-down fragmentation process as the result of nonlinear dissipative collapse of larger density perturbations. This could explain the planar orientation of satellite galaxies around Andromeda and the Milky Way.

  2. Small-scale spatial structuring of interstitial invertebrates on three embayed beaches, Sydney, Australia

    NASA Astrophysics Data System (ADS)

    Cooke, Belinda C.; Goodwin, Ian D.; Bishop, Melanie J.

    2014-10-01

    An understanding of ecological processes hinges upon an understanding of the spatial structuring of their key biotic components. Interstitial invertebrates are a ubiquitous and ecologically important component of sandy beach ecosystems. As many sandy beach taxa have limited dispersal, it may be expected that their populations exhibit a high degree of spatial structuring, yet the spatial scales across which they display baseline variability remain largely unknown. To assess (1) whether interstitial invertebrates display patchiness on embayed sandy beaches, (2) whether the size of patches they form is consistent across three geographically proximal beaches, (3) the key environmental correlates of this variation and (4) its taxonomic dependence, samples were collected at regular (0.5 m) intervals along 15 m long geomorphically similar stretches of three proximal intermediate beaches and analyses of spatial autocorrelation were conducted. On each of the three beaches, interstitial invertebrate communities formed patches of 2-4.5 m in diameter. Spatial structuring of invertebrate communities was driven by harpacticoid copepods and gastrotrichs, and corresponded to spatial structuring of sediments. Sediments, however, explained only 33% of spatial variation in faunal communities, indicating the importance of other abiotic and/or biotic factors. Our study highlights that even on seemingly homogeneous sandy beaches, faunal communities may display considerable small-scale spatial structuring. Examination of spatial structure may lead to a greater understanding of the ecological processes in this system.

  3. A study of large, medium and small scale structures in the topside ionosphere

    NASA Technical Reports Server (NTRS)

    Gross, Stanley H.; Kuo, Spencer P.; Shmoys, Jerry

    1986-01-01

    Alouette and ISIS data were studied for large, medium, and small scale structures in the ionosphere. Correlation was also sought with measurements by other satellites, such as the Atmosphere Explorer C and E and the Dynamic Explorer 2 satellites, of both neutrals and ionization, and with measurements by ground facilities, such as the incoherent scatter radars. Large scale coherent wavelike structures were found from ISIS 2 electron density contours from above the F peak to nearly the satellite altitude. Such structures were also found to correlate with the observation by AE-C below the F peak during a conjunction of the two satellites. Vertical wavefronts found in the upper F region suggest the dominance of diffusion along field lines as well. Also discovered were multiple, evenly spaced field-aligned ducts in the F region that, at low latitudes, extended to the other hemisphere and were in the form of field-aligned sheets in the east-west direction. Low latitude heating events were discovered that could serve as sources for waves in the ionosphere.

  4. Analysis of small scale turbulent structures and the effect of spatial scales on gas transfer

    NASA Astrophysics Data System (ADS)

    Schnieders, Jana; Garbe, Christoph

    2014-05-01

    The exchange of gases through the air-sea interface strongly depends on environmental conditions such as wind stress and waves which in turn generate near surface turbulence. Near surface turbulence is a main driver of surface divergence which has been shown to cause highly variable transfer rates on relatively small spatial scales. Due to the cool skin of the ocean, heat can be used as a tracer to detect areas of surface convergence and thus gather information about size and intensity of a turbulent process. We use infrared imagery to visualize near surface aqueous turbulence and determine the impact of turbulent scales on exchange rates. Through the high temporal and spatial resolution of these types of measurements spatial scales as well as surface dynamics can be captured. The surface heat pattern is formed by distinct structures on two scales - small-scale short lived structures termed fish scales and larger scale cold streaks that are consistent with the footprints of Langmuir Circulations. There are two key characteristics of the observed surface heat patterns: 1. The surface heat patterns show characteristic features of scales. 2. The structure of these patterns change with increasing wind stress and surface conditions. In [2] turbulent cell sizes have been shown to systematically decrease with increasing wind speed until a saturation at u* = 0.7 cm/s is reached. Results suggest a saturation in the tangential stress. Similar behaviour has been observed by [1] for gas transfer measurements at higher wind speeds. In this contribution a new model to estimate the heat flux is applied which is based on the measured turbulent cell size und surface velocities. This approach allows the direct comparison of the net effect on heat flux of eddies of different sizes and a comparison to gas transfer measurements. Linking transport models with thermographic measurements, transfer velocities can be computed. In this contribution, we will quantify the effect of small scale

  5. Skewness-induced asymmetric modulation of small-scale turbulence by large-scale structures

    NASA Astrophysics Data System (ADS)

    Agostini, Lionel; Leschziner, Michael; Gaitonde, Datta

    2016-01-01

    Several recent studies discuss of role of skewness of the turbulent velocity fluctuations in near-wall shear layers, in the context of quantifying the correlation between large-scale motions and amplitude variations of small-scale fluctuations—referred to as "modulation." The present study is based on the premise that the skewness of the small-scale fluctuations should be accounted for explicitly in the process of defining their envelope, which characterizes their amplitude variations. This leads to the notion of two envelopes, one for positive and the other for negative small-scale fluctuations, and hence also to two corresponding correlation coefficients. Justification for this concept is provided first by an examination of a high-frequency synthetic signal subjected to realistic skewness-inducing modulation. A new formalism is provided for deriving the two envelopes, and its fidelity is demonstrated for the synthetic test case. The method is then applied to a channel flow at a friction Reynolds number of 4200, for which direct numerical simulation (DNS) data are available. The large-scale and small-scale fields are separated by the empirical mode decomposition method, and the modulation of the small-scale fluctuations by the large scales is examined. Separate maps of the correlation coefficient and of two-point correlations, the latter linking the large-scale motions and the envelopes of the small-scale motions, are derived for the two envelopes pertaining to positive and negative small-scale fluctuations, and these demonstrate a significant sensitivity to the envelope-definition process, especially close to the wall where the skewness of the small-scale fluctuations is the dominant contributor to the total value.

  6. Study of Structure and Small-Scale Fragmentation in TMC-1

    NASA Technical Reports Server (NTRS)

    Langer, W. D.; Velusamy, T.; Kuiper, T. B.; Levin, S.; Olsen, E.; Migenes, V.

    1995-01-01

    Large-scale C(sup 18)O maps show that the Taurus molecular cloud 1 (TMC-1) has numerous cores located along a ridge which extends about 12 minutes by at least 35 minutes. The cores traced by C(sup 18)O are about a few arcminutes (0.1-0.2 pc) in extent, typically contain about 0.5-3 solar mass, and are probably gravitationally bound. We present a detailed study of the small-scale fragmentary structure of one of these cores, called core D, within TMC-1 using very high spectral and spatial resolution maps of CCS and CS. The CCS lines are excellent tracers for investigating the density, temperature, and velocity structure in dense cores. The high spectral resolution, 0.008 km /s, data consist mainly of single-dish, Nyquist-sampled maps of CCS at 22 GHz with 45 sec spatial resolution taken with NASA's 70 m DSN antenna at Goldstone. The high spatial resolution spectral line maps were made with the Very Large Array (9 sec resolution) at 22 GHz and with the OVRO millimeter array in CCS and CS at 93 GHz and 98 GHz, respectively, with 6 sec resolution. These maps are supplemented with single-dish observations of CCS and CC(sup 34)S spectra at 33 GHz using a NASA 34 m DSN antenna, CCS 93 GHz, C(sup 34)S (2-1), and C(sup 18)O (1-0) single-dish observations made with the AT&T Bell Laboratories 7 m antenna. Our high spectral and spatial CCS and CS maps show that core D is highly fragmented. The single-dish CCS observations map out several clumps which range in size from approx. 45 sec to 90 sec (0.03-0.06 pc). These clumps have very narrow intrinsic line widths, 0.11-0.25 km/s, slightly larger than the thermal line width for CCS at 10 K, and masses about 0.03-0.2 solar mass. Interferometer observations of some of these clumps show that they have considerable additional internal structure, consisting of several condensations ranging in size from approx. 10 sec- 30 sec (0.007-0.021 pc), also with narrow line widths. The mass of these smallest fragments is of order 0.01 solar mass

  7. Early structure formation from cosmic string loops

    SciTech Connect

    Shlaer, Benjamin; Vilenkin, Alexander; Loeb, Abraham E-mail: vilenkin@cosmos.phy.tufts.edu

    2012-05-01

    We examine the effects of cosmic strings on structure formation and on the ionization history of the universe. While Gaussian perturbations from inflation are known to provide the dominant contribution to the large scale structure of the universe, density perturbations due to strings are highly non-Gaussian and can produce nonlinear structures at very early times. This could lead to early star formation and reionization of the universe. We improve on earlier studies of these effects by accounting for high loop velocities and for the filamentary shape of the resulting halos. We find that for string energy scales Gμ∼>10{sup −7}, the effect of strings on the CMB temperature and polarization power spectra can be significant and is likely to be detectable by the Planck satellite. We mention shortcomings of the standard cosmological model of galaxy formation which may be remedied with the addition of cosmic strings, and comment on other possible observational implications of early structure formation by strings.

  8. Small-scale transport structures in the Arctic winter 2009/2010

    NASA Astrophysics Data System (ADS)

    Kalicinsky, C.; Grooß, J.-U.; Günther, G.; Ungermann, J.; Blank, J.; Höfer, S.; Hoffmann, L.; Knieling, P.; Olschewski, F.; Spang, R.; Stroh, F.; Riese, M.

    2013-04-01

    The CRISTA-NF (Cryogenic Infrared Spectrometers and Telescope for the Atmosphere - New Frontiers) instrument is an airborne infrared limb sounder operated aboard the Russian research aircraft M55-Geophysica. The instrument successfully participated in a large Arctic aircraft campaign within the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions) project from January to March 2010 in Kiruna, Sweden. This paper concentrates on the measurements during one flight of the campaign, which took place on 2 March in the vicinity of the polar vortex. We present two-dimensional cross-sections of volume mixing ratios for the trace gases CFC-11, O3, and ClONO2 with an unprecedented vertical resolution of about 500 to 600 m for a large part of the observed altitude range and a dense horizontal sampling along flight direction of ≈ 15 km. The trace gas distributions show several structures like the polar vortex and filaments composed of air masses of different origin. The situation during the analysed flight is simulated by the chemistry and transport model CLaMS (Chemical Lagrangian Model of the Stratosphere) and compared with the measurements to assess the performance of the model with respect to advection, mixing, and the chemistry in the polar vortex. These comparisons confirm the capability of CLaMS to reproduce even very small-scale structures in the atmosphere. Based on the good agreement between simulation and observation, we use a model concept utilising artificial tracers to further analyse the CRISTA-NF observations in terms of air mass origin. A characteristic of the Arctic winter 2009/10 was a sudden stratospheric warming in early December that led to a split of the polar vortex. The vortex re-established at the end of December. Our passive tracer simulations suggest that large parts of the re-established vortex consisted to about 45% of high- and mid-latitude air.

  9. Space-borne detection of small scale CO2 emission structures with OCO-2

    NASA Astrophysics Data System (ADS)

    Schwandner, F. M.; Eldering, A.; Verhulst, K. R.; Miller, C. E.; Nguyen, H.; Oda, T.; O'Dell, C.; Rao, P.; Kahn, B. H.; Crisp, D.; Gunson, M. R.; Sanchez, R. M.; Ashok, M.; Birman, L.; Pieri, D. C.; Linick, J. P.; Xing, Z.; Yuen, K.

    2015-12-01

    Localized carbon dioxide (CO2) emission structures covering spatial domains of less than 50km diameter include cities, transportation infrastructure, fossil fuel production, upgrading and consumption sites. Anthropogenic sources upset the natural balance between carbon sources and sinks. Mitigation of resulting climate change impacts requires management of emissions, and emissions management requires monitoring, reporting and verification. Space-borne measurements provide a unique opportunity to detect, quantify, and analyze small scale and point source emissions on a global scale. In 2014, NASA launched its first satellite dedicated to atmospheric CO2 observation, the Orbiting Carbon Observatory (OCO-2). Its observation strategy differs from sparse point-wise measurements from the Japanese Greenhouse gas Observation SATellite (GOSAT) instrument. At the expense of GOSAT's fast time series capability (3-day repeat cycle, vs. 16 for OCO-2), its 8-footprint continuous swath of 2 to 10 km in width can slice through emission plumes and possibly provide momentary cross sections. While GOSAT measured approximately circular ~10.5 km diameter single-shot footprints, OCO-2 can provide hundreds more soundings per area at single kilometer scale footprint resolution. First OCO-2 results demonstrate that we can detect localized source signals in the form of urban XCO2 enhancements of ~2 ppmv against suburban and rural backgrounds. OCO-2's multi-sounding swath observing geometry reveals intra-urban emission spatial structures previously unobserved from space. The transition from single-shot GOSAT soundings detecting urban/rural differences (Kort et al., 2012) to hundreds of soundings per OCO-2 swath opens up the path to future capabilities enabling urban greenhouse gas tomography. © California Institute of Technology

  10. Small-Scale Interstellar Structure Toward the Open Cluster CHI Persei-Fuse II

    NASA Technical Reports Server (NTRS)

    Sonneborn, George (Technical Monitor); Friedman, Scott

    2003-01-01

    The purpose of this study was to measure the physical conditions of gas along sight lines toward 6 stars in the core Chi Persei open cluster. These sight lines traverse gas in both the Orion and Perseus spiral arms of the Galaxy, at distances of 500 and 2000 pc, respectively. The stars have angular separations ranging from 45 to 280 arcsec; 60 arcsec corresponds to linear distances of 0.15 and 0.6 pc in the two arms. Thus, abundance variations in these observations would constitute evidence for small-scale variations in the properties of the interstellar medium. Ground-based Na I observations at high resolution (approx. 15 km/sec) toward 172 stars (including the 6 in this study) in the double open cluster h and Chi Persei have revealed complex spatial variation. These variations are especially evident in the gas at velocities of -40 and -55 km/sec, corresponding to the Perseus spiral arm. 21 cm observations of HI emission using the Low Resolution DRAO Survey, with a 12-arcmin beam, also show variations. Averaging the Na I apparent optical depth profiles of neighboring sight lines in order to mimic such a beam size reduces the variation, as compared to the individual Na I measurements, but still show variations larger than seen in the 21 cm profiles. Na I is not the dominant ionization state of Na in the interstellar medium. Thus, it is possible that the variations seen really trace physical structures in the interstellar medium, or they may simply result from variations in the radiation field seen by the gas, or be due to some other environmental circumstance. To distinguish among these possibilities in the present study we obtained FUSE spectra toward the 6 targets in order to measure the molecular hydrogen absorption profiles along these sight lines. The higher J states of H2 are populated by the ambient W radiation field, and thus can provide insight into the environment affecting the gas. If both the high and low J states reveal absorption line profiles with

  11. Small-Scale Dust Structures in Halley's Coma: Evidence from the Vega-2 Electric Field Records

    NASA Astrophysics Data System (ADS)

    Oberc, P.

    1999-07-01

    Owing to simultaneous dust and plasma wave observations onboard the Vega mission to Comet Halley, previous studies have found that the two double probe antennas, short (of APV-N experiment) and long (APV-V), (i) responded to plasma clouds induced by impacts of relatively large particles, (ii) the target area was comparable to the whole spacecraft projection, and (iii) the mass thresholds depended on the ambient plasma conditions. Subsequently, the response mechanisms have been identified, and it was shown that if impacts became continuous, the sensitivity of the antennas to individual plasma clouds was reduced or even cancelled. In the present paper, about 30 short-time events of continuous impact (CIEs), recognized in the Vega-2 records from the two experiments mostly near the closest approach to (at ∼104 km from) the nucleus, are investigated. The high-resolution APV-N waveforms reveal that the respective dust formations were structured. A few types of structure, all belonging to one family, have been distinguished. The basic structure, as seen along the Vega-2 pass, is a sequence of particle clouds. CIEs have time scales shorter than or comparable to the time resolution of the dust experiments (spatial scale less than 200 km) and do not correlate with the SP-1 observations (m≤10-10 g) nor with the published SP-2 fluxes (m≤5.8×10-8 g). But, these dust data, combined with an integral criterion for continuous impact, provide a constraint which implies that the particles responsible were bigger than 10-9-10-8 g. The data from the DUCMA V-detector confirm positively this inference for about 1/3 (∼10) of CIEs and indicate that particles (much) bigger than 10-7 g were decisive in generating several other events. Using an argument from the dusty gas dynamics, it is shown that the small-scale dust structures were not jets but have originated from the disintegration of particle aggregates. An estimate of the total mass contained within a dust structure leads to

  12. Small-Scale Screening to Large-Scale Over-Expression of Human Membrane Proteins for Structural Studies.

    PubMed

    Chaudhary, Sarika; Saha, Sukanya; Thamminana, Sobrahani; Stroud, Robert M

    2016-01-01

    Membrane protein structural studies are frequently hampered by poor expression. The low natural abundance of these proteins implies a need for utilizing different heterologous expression systems. E. coli and yeast are commonly used expression systems due to rapid cell growth at high cell density, economical production, and ease of manipulation. Here we report a simplified, systematically developed robust strategy from small-scale screening to large-scale over-expression of human integral membrane proteins in the mammalian expression system for structural studies. This methodology streamlines small-scale screening of several different constructs utilizing fluorescence size-exclusion chromatography (FSEC) towards optimization of buffer, additives, and detergents for achieving stability and homogeneity. This is followed by the generation of stable clonal cell lines expressing desired constructs, and lastly large-scale expression for crystallization. These techniques are designed to rapidly advance the structural studies of eukaryotic integral membrane proteins including that of human membrane proteins. PMID:27485338

  13. SMALL-SCALE STRUCTURING OF ELLERMAN BOMBS AT THE SOLAR LIMB

    SciTech Connect

    Nelson, C. J.; Doyle, J. G.; Scullion, E. M.; Freij, N.; Erdélyi, R.

    2015-01-01

    Ellerman bombs (EBs) have been widely studied in recent years due to their dynamic, explosive nature and apparent links to the underlying photospheric magnetic field implying that they may be formed by magnetic reconnection in the photosphere. Despite a plethora of researches discussing the morphologies of EBs, there has been a limited investigation of how these events appear at the limb, specifically, whether they manifest as vertical extensions away from the disk. In this article, we make use of high-resolution, high-cadence observations of an Active Region at the solar limb, collected by the CRisp Imaging SpectroPolarimeter (CRISP) instrument, to identify EBs and infer their physical properties. The upper atmosphere is also probed using the Solar Dynamic Observatory's Atmospheric Imaging Assembly (SDO/AIA). We analyze 22 EB events evident within these data, finding that 20 appear to follow a parabolic path away from the solar surface at an average speed of 9 km s{sup –1}, extending away from their source by 580 km, before retreating back at a similar speed. These results show strong evidence of vertical motions associated with EBs, possibly explaining the dynamical ''flaring'' (changing in area and intensity) observed in on-disk events. Two in-depth case studies are also presented that highlight the unique dynamical nature of EBs within the lower solar atmosphere. The viewing angle of these observations allows for a direct linkage between these EBs and other small-scale events in the Hα line wings, including a potential flux emergence scenario. The findings presented here suggest that EBs could have a wider-reaching influence on the solar atmosphere than previously thought, as we reveal a direct linkage between EBs and an emerging small-scale loop, and other near-by small-scale explosive events. However, as previous research found, these extensions do not appear to impact upon the Hα line core, and are not observed by the SDO/AIA EUV filters.

  14. High overtone quasinormal modes of analog black holes and the small scale structure of the background fluid

    NASA Astrophysics Data System (ADS)

    Daghigh, Ramin G.; Green, Michael D.

    2015-05-01

    The goal of this paper is to build a foundation for, and explore the possibility of, using high overtone quasinormal modes (QNMs) of analog black holes to probe the small scale (microscopic) structure of a background fluid in which an analog black hole is formed. This may provide a tool to study the small scale structure of some interesting quantum systems such as Bose-Einstein condensates (BECs). In order to build this foundation, we first look into the hydrodynamic case where we calculate the high overtone QNM frequencies of a 3+1 dimensional canonical non-rotating acoustic black hole. The leading order calculations have been done earlier in the literature. Here, we obtain the first order correction. We then analyze the high overtone QNMs of acoustic black holes in a BEC using the linearized Gross-Pitaevskii equation. We point out that at the high overtone QNM limit, the only term that is important in the linearized Gross-Pitaevskii equation is the quantum potential term, which is a small scale effect.

  15. Small-scale structures in common-volume meteor wind measurements

    NASA Astrophysics Data System (ADS)

    Fraser, G. J.; Marsh, S. H.; Baggaley, W. J.; Bennett, R. G. T.; Lawrence, B. N.; McDonald, A. J.; Plank, G. E.

    2006-02-01

    Observational differences occur when different techniques are used for measuring mesospheric winds because the different instruments observe different physical quantities to infer the wind velocity, and have differing time and space resolution. The AMOR meteor wind radar near Christchurch, New Zealand [Marsh et al., 2000. Journal of Atmospheric and Solar-Terrestrial Physics 62,1129 1133.] has good resolution in time (˜0.1 s) and height (˜1 km) and a narrow beam centred in the geographic N S meridian. The meteor echoes randomly sample the atmosphere in a region extending over several hundred kilometres to the South of the radar. The volume of data obtained from the one instrument has made it possible to use correlations between measurements made from individual meteor trails to identify the contribution of atmospheric variability to the observational differences. Measurements of the meridional wind component made from May July 1997 inclusive show that a large part (20 30 m/s r.m.s.) of the atmospheric variation is due to inhomogeneities with small scales, of the order of 10 km and 1 h. There is also a component which has a random time phase over the observation interval but a spatial scale which is coherent over several hundred kilometres, consistent with the behaviour of gravity waves.

  16. The statistical analysis of energy release in small-scale coronal structures

    NASA Astrophysics Data System (ADS)

    Ulyanov, Artyom; Kuzin, Sergey; Bogachev, Sergey

    We present the results of statistical analysis of impulsive flare-like brightenings, which numerously occur in the quiet regions of solar corona. For our study, we utilized high-cadence observations performed with two EUV-telescopes - TESIS/Coronas-Photon and AIA/SDO. In total, we processed 6 sequences of images, registered throughout the period between 2009 and 2013, covering the rising phase of the 24th solar cycle. Based on high-speed DEM estimation method, we developed a new technique to evaluate the main parameters of detected events (geometrical sizes, duration, temperature and thermal energy). We then obtained the statistical distributions of these parameters and examined their variations depending on the level of solar activity. The results imply that near the minimum of the solar cycle the energy release in quiet corona is mainly provided by small-scale events (nanoflares), whereas larger events (microflares) prevail on the peak of activity. Furthermore, we investigated the coronal conditions that had specified the formation and triggering of registered flares. By means of photospheric magnetograms obtained with MDI/SoHO and HMI/SDO instruments, we examined the topology of local magnetic fields at different stages: the pre-flare phase, the peak of intensity and the ending phase. To do so, we introduced a number of topological parameters including the total magnetic flux, the distance between magnetic sources and their mutual arrangement. The found correlation between the change of these parameters and the formation of flares may offer an important tool for application of flare forecasting.

  17. Small-Scale Habitat Structure Modulates the Effects of No-Take Marine Reserves for Coral Reef Macroinvertebrates

    PubMed Central

    Dumas, Pascal; Jimenez, Haizea; Peignon, Christophe; Wantiez, Laurent; Adjeroud, Mehdi

    2013-01-01

    No-take marine reserves are one of the oldest and most versatile tools used across the Pacific for the conservation of reef resources, in particular for invertebrates traditionally targeted by local fishers. Assessing their actual efficiency is still a challenge in complex ecosystems such as coral reefs, where reserve effects are likely to be obscured by high levels of environmental variability. The goal of this study was to investigate the potential interference of small-scale habitat structure on the efficiency of reserves. The spatial distribution of widely harvested macroinvertebrates was surveyed in a large set of protected vs. unprotected stations from eleven reefs located in New Caledonia. Abundance, density and individual size data were collected along random, small-scale (20×1 m) transects. Fine habitat typology was derived with a quantitative photographic method using 17 local habitat variables. Marine reserves substantially augmented the local density, size structure and biomass of the target species. Density of Trochus niloticus and Tridacna maxima doubled globally inside the reserve network; average size was greater by 10 to 20% for T. niloticus. We demonstrated that the apparent success of protection could be obscured by marked variations in population structure occurring over short distances, resulting from small-scale heterogeneity in the reef habitat. The efficiency of reserves appeared to be modulated by the availability of suitable habitats at the decimetric scale (“microhabitats”) for the considered sessile/low-mobile macroinvertebrate species. Incorporating microhabitat distribution could significantly enhance the efficiency of habitat surrogacy, a valuable approach in the case of conservation targets focusing on endangered or emblematic macroinvertebrate or relatively sedentary fish species PMID:23554965

  18. Small-scale habitat structure modulates the effects of no-take marine reserves for coral reef macroinvertebrates.

    PubMed

    Dumas, Pascal; Jimenez, Haizea; Peignon, Christophe; Wantiez, Laurent; Adjeroud, Mehdi

    2013-01-01

    No-take marine reserves are one of the oldest and most versatile tools used across the Pacific for the conservation of reef resources, in particular for invertebrates traditionally targeted by local fishers. Assessing their actual efficiency is still a challenge in complex ecosystems such as coral reefs, where reserve effects are likely to be obscured by high levels of environmental variability. The goal of this study was to investigate the potential interference of small-scale habitat structure on the efficiency of reserves. The spatial distribution of widely harvested macroinvertebrates was surveyed in a large set of protected vs. unprotected stations from eleven reefs located in New Caledonia. Abundance, density and individual size data were collected along random, small-scale (20×1 m) transects. Fine habitat typology was derived with a quantitative photographic method using 17 local habitat variables. Marine reserves substantially augmented the local density, size structure and biomass of the target species. Density of Trochus niloticus and Tridacna maxima doubled globally inside the reserve network; average size was greater by 10 to 20% for T. niloticus. We demonstrated that the apparent success of protection could be obscured by marked variations in population structure occurring over short distances, resulting from small-scale heterogeneity in the reef habitat. The efficiency of reserves appeared to be modulated by the availability of suitable habitats at the decimetric scale ("microhabitats") for the considered sessile/low-mobile macroinvertebrate species. Incorporating microhabitat distribution could significantly enhance the efficiency of habitat surrogacy, a valuable approach in the case of conservation targets focusing on endangered or emblematic macroinvertebrate or relatively sedentary fish species.

  19. Discovery of small-scale-structure in the large molecule/dust distribution in the diffuse ISM

    NASA Astrophysics Data System (ADS)

    Cordiner, Martin A.; Fossey, Stephen J.; Sarre, Peter J.

    There is mounting evidence that far from being homogeneously distributed, interstellar matter can have a clumpy or filamentary structure on the scale of 10s to a few 1000s of AU and which is commonly described as small scale structure (SSS). Initially confined to VLBI HI observations and HI observations of high-velocity pulsars, evidence for SSS has also come indirectly from molecular radio studies of e.g. HCO+ and infrared absorption by H3+. Much of the recent data on SSS has been obtained through optical/UV detection of atomic and diatomic molecular lines. Is there small scale structure in the large molecule/dust distribution? While this question could in principle be explored by measuring differences in the interstellar extinction towards the components of binary stars, in practice this would be difficult. Rather we chose to investigate this by recording very high signal-to-noise spectra of diffuse interstellar absorption bands. Although the carriers remain unidentified, the diffuse bands are generally considered to be tracers of the large molecule/dust distribution and scale well with reddening. Using the Anglo-Australian Telescope we have made UCLES observations of pairs of stars with separations ranging between 500 and 30000 AU. The signal-to-noise achieved was up to 2000, thus allowing variations in central depth of less than a few tenths of a percent to be discernible. Striking differences in diffuse band strengths for closely spaced lines of sight are found showing clearly that there exists small-scale-structure in the large molecule/dust distribution. For example, in the Ophiuchus star-formation region the central depths for the λ6614 diffuse band towards the ρ Oph stars A, B, C and D/E all differ and range between 0.966 and 0.930. Further interesting behaviour is found when comparing the relative strengths of diffuse bands between closely parallel lines of sight. Taking again the ρ Oph group, for λ5797 the strengths follow the order DE > B > C > A

  20. Small Scale Organic Techniques

    ERIC Educational Resources Information Center

    Horak, V.; Crist, DeLanson R.

    1975-01-01

    Discusses the advantages of using small scale experimentation in the undergraduate organic chemistry laboratory. Describes small scale filtration techniques as an example of a semi-micro method applied to small quantities of material. (MLH)

  1. On the size, structure, and strength of the small-scale solar magnetic field

    NASA Technical Reports Server (NTRS)

    Ramsey, H. E.; Schoolman, S. A.; Title, A. M.

    1977-01-01

    High-resolution magnetograms place an upper limit of 0.33 arcsec on the smallest magnetic-field structures. These magnetograms show that the active-region field is organized into roughly cellular patterns 2-3 arcsec in diameter and that the field structures occur in the centers of 'abnormal' granules. Comparison of these data and other magnetograms with high signal-to-noise ratio indicates that there exists another component of the field that is diffuse on the scale of an arc second and has a maximum strength of less than 500 gauss.

  2. Characteristics of the behavior of the small-scale turbulence structure in the boundary layer

    SciTech Connect

    Dobrocheev, O.V.; Wojciechowski, J.

    1995-12-01

    Results of theoretical and experimental studies of the structure of turbulence in the boundary layer are presented. It is shown that the spectral density of turbulence energy deviates systematically from Kolmogorov-Obukhov`s law and a theoretical explanation of this deviation is given.

  3. DETECTION OF SMALL-SCALE GRANULAR STRUCTURES IN THE QUIET SUN WITH THE NEW SOLAR TELESCOPE

    SciTech Connect

    Abramenko, V. I.; Yurchyshyn, V. B.; Goode, P. R.; Kitiashvili, I. N.; Kosovichev, A. G.

    2012-09-10

    Results of a statistical analysis of solar granulation are presented. A data set of 36 images of a quiet-Sun area on the solar disk center was used. The data were obtained with the 1.6 m clear aperture New Solar Telescope at Big Bear Solar Observatory and with a broadband filter centered at the TiO (705.7 nm) spectral line. The very high spatial resolution of the data (diffraction limit of 77 km and pixel scale of 0.''0375) augmented by the very high image contrast (15.5% {+-} 0.6%) allowed us to detect for the first time a distinct subpopulation of mini-granular structures. These structures are dominant on spatial scales below 600 km. Their size is distributed as a power law with an index of -1.8 (which is close to the Kolmogorov's -5/3 law) and no predominant scale. The regular granules display a Gaussian (normal) size distribution with a mean diameter of 1050 km. Mini-granular structures contribute significantly to the total granular area. They are predominantly confined to the wide dark lanes between regular granules and often form chains and clusters, but different from magnetic bright points. A multi-fractality test reveals that the structures smaller than 600 km represent a multi-fractal, whereas on larger scales the granulation pattern shows no multi-fractality and can be considered as a Gaussian random field. The origin, properties, and role of the population of mini-granular structures in the solar magnetoconvection are yet to be explored.

  4. Adjoint-tomography Inversion of the Small-scale Surface Sedimentary Structures: Key Methodological Aspects

    NASA Astrophysics Data System (ADS)

    Kubina, Filip; Moczo, Peter; Kristek, Jozef; Michlik, Filip

    2016-04-01

    Adjoint tomography has proven an irreplaceable useful tool in exploring Earth's structure in the regional and global scales. It has not been widely applied for improving models of local surface sedimentary structures (LSSS) in numerical predictions of earthquake ground motion (EGM). Anomalous earthquake motions and corresponding damage in earthquakes are often due to site effects in local surface sedimentary basins. Because majority of world population is located atop surface sedimentary basins, it is important to predict EGM at these sites during future earthquakes. A major lesson learned from dedicated international tests focused on numerical prediction of EGM in LSSS is that it is hard to reach better agreement between data and synthetics without an improved structural model. If earthquake records are available for sites atop a LSSS it is natural to consider them for improving the structural model. Computationally efficient adjoint tomography might be a proper tool. A seismic wavefield in LSSS is relatively very complex due to diffractions, conversions, interference and often also resonant phenomena. In shallow basins, the first arrivals are not suitable for inversion due to almost vertical incidence and thus insufficient vertical resolution. Later wavefield consists mostly of local surface waves often without separated wave groups. Consequently, computed kernels are complicated and not suitable for inversion without pre-processing. The spatial complexity of a kernel can be dramatic in a typical situation with relatively low number of sources (local earthquakes) and surface receivers. This complexity can be simplified by directionally-dependent smoothing and spatially-dependent normalization that condition reasonable convergence. A multiscale approach seems necessary given the usual difference between the available and true models. Interestingly, only a successive inversion of μ and λ elastic moduli, and different scale sequences lead to good results.

  5. Mariner 9 photographs of small-scale volcanic structures on Mars

    NASA Technical Reports Server (NTRS)

    Greeley, R.

    1972-01-01

    Surface features on the flanks of Martian shield volcanoes photographed by Mariner 9 are identified as lava flow channels, rift zones, and partly collapsed lava tubes by comparisons with similar structures on the flanks of Mauna Loa shield volcano, Hawaii. From these identifications, the composition of the Martian lava flows is interpreted to be basaltic, with viscosities ranging from those of fluid pahoehoe to more viscous aa.

  6. On the Properties of Slow MHD Sausage Waves within Small-scale Photospheric Magnetic Structures

    NASA Astrophysics Data System (ADS)

    Freij, N.; Dorotovič, I.; Morton, R. J.; Ruderman, M. S.; Karlovský, V.; Erdélyi, R.

    2016-01-01

    The presence of magnetoacoustic waves in magnetic structures in the solar atmosphere is well-documented. Applying the technique of solar magneto-seismology (SMS) allows us to infer the background properties of these structures. Here, we aim to identify properties of the observed magnetoacoustic waves and study the background properties of magnetic structures within the lower solar atmosphere. Using the Dutch Open Telescope and Rapid Oscillations in the Solar Atmosphere instruments, we captured two series of high-resolution intensity images with short cadences of two isolated magnetic pores. Combining wavelet analysis and empirical mode decomposition (EMD), we determined characteristic periods within the cross-sectional (i.e., area) and intensity time series. Then, by applying the theory of linear magnetohydrodynamics (MHD), we identified the mode of these oscillations within the MHD framework. Several oscillations have been detected within these two magnetic pores. Their periods range from 3 to 20 minutes. Combining wavelet analysis and EMD enables us to confidently find the phase difference between the area and intensity oscillations. From these observed features, we concluded that the detected oscillations can be classified as slow sausage MHD waves. Furthermore, we determined several key properties of these oscillations such as the radial velocity perturbation, the magnetic field perturbation, and the vertical wavenumber using SMS. The estimated range of the related wavenumbers reveals that these oscillations are trapped within these magnetic structures. Our results suggest that the detected oscillations are standing harmonics, and this allows us to estimate the expansion factor of the waveguides by employing SMS. The calculated expansion factor ranges from 4 to 12.

  7. Characterizing the small scale structures in the earliest stages of low-mass star formation

    NASA Astrophysics Data System (ADS)

    Vilhelm Persson, Magnus; van Dishoeck, Ewine; Tobin, John; Harsono, Daniel; Jørgensen, Jes K.

    2015-08-01

    In deeply-embedded low-mass protostars, the density and temperature distribution in the inner few hundred AU’s are poorly constrained. In sources where the envelope is less massive, i.e. the Class I stage, disks with Keplerian rotation have been inferred using C18O lines. However, constraining the various disk characteristics turns out to be difficult even in this case. Continuum and molecular line observations of optically thin tracers at very high sensitivity and resolution are needed to constrain the density, temperature and kinematics. Ultimately the assumed structure affects the determination of molecular abundances.We are attempting to model high-resolution dust continuum radio-interferometric observations of a few deeply-embedded low-mass protostars with a power-law disk model embedded in a spherical envelope.We model the interferometric visibilities taken with either the Plateau de Bure Interferometer or the ALMA telescope, probing scales down to a few tens of AU in some cases. Given the assumptions, the study shows disk sizes in the deeply-embedded phase that could be slightly larger than typical found in the more evolved Class I sources. The fitting also highlights that models for the physical structure of the inner envelope, on 500-2000 AU scales, needs to be improved. With future high sensitivity observations, we could potentially also be able to constrain any vertical density and temperature structure. In this poster I will present the

  8. Single Cell Spectroscopy: Noninvasive Measures of Small-Scale Structure and Function

    PubMed Central

    Mousoulis, Charilaos; Xu, Xin; Reiter, David A.; Neu, Corey P.

    2013-01-01

    The advancement of spectroscopy methods attained through increases in sensitivity, and often with the coupling of complementary techniques, has enabled real-time structure and function measurements of single cells. The purpose of this review is to illustrate, in light of advances, the strengths and the weaknesses of these methods. Included also is an assessment of the impact of the experimental setup and conditions of each method on cellular function and integrity. A particular emphasis is placed on noninvasive and nondestructive techniques for achieving single cell detection, including nuclear magnetic resonance, in addition to physical, optical, and vibrational methods. PMID:23886910

  9. A COMPACT HIGH VELOCITY CLOUD NEAR THE MAGELLANIC STREAM: METALLICITY AND SMALL-SCALE STRUCTURE

    SciTech Connect

    Kumari, Nimisha; Fox, Andrew J.; Tumlinson, Jason; Thom, Christopher; Ely, Justin; Westmeier, Tobias

    2015-02-10

    The Magellanic Stream (MS) is a well-resolved gaseous tail originating from the Magellanic Clouds. Studies of its physical properties and chemical composition are needed to understand its role in Galactic evolution. We investigate the properties of a compact HVC (CHVC 224.0-83.4-197) lying close on the sky to the MS to determine whether it is physically connected to the Stream and to examine its internal structure. Our study is based on analysis of HST/COS spectra of three QSOs (Ton S210, B0120-28, and B0117-2837) all of which pass through this single cloud at small angular separation (≲0.°72), allowing us to compare physical conditions on small spatial scales. No significant variation is detected in the ionization structure from one part of the cloud to the other. Using Cloudy photoionization models, toward Ton S210 we derive elemental abundances of [C/H] = –1.21 ± 0.11, [Si/H] = –1.16 ± 0.11, [Al/H] = –1.19 ± 0.17, and [O/H] = –1.12 ± 0.22, which agree within 0.09 dex. The CHVC abundances match the 0.1 solar abundances measured along the main body of the Stream. This suggests that the CHVC (and by extension the extended network of filaments to which it belongs) has an origin in the MS. It may represent a fragment that has been removed from the Stream as it interacts with the gaseous Galactic halo.

  10. Reconstruction of the inner structure of small scale mining waste dumps by combining GPR and ERTdata.

    NASA Astrophysics Data System (ADS)

    Kniess, Rudolf; Martin, Tina

    2015-04-01

    Two abandoned small waste dumps in the west of the Harz mountains (Germany) were analysed using ground penetrating radar (GPR) and electrical resistivity tomography (ERT). Aim of the project (ROBEHA, funded by the German Federal Ministry of Education and Research (033R105)) is the assessment of the recycling potential of the mining residues taking into account environmental risks of reworking the dump site. One task of the geophysical prospection is the investigation of the inner structure of the mining dump. This is important for the estimation of the approximate volume of potentially reusable mining deposits within the waste dump. The two investigated dump sites are different in age and therefore differ in their structure. The older residues (< 1930) consist of ore processing waste from density separation (stamp mill sand). The younger dump site descends from comprises slag dump waste. The layer of fine grained residues at the first dump site is less than 6 m thick and the slag layer is less than 2 m thick. Both sites are partially overlain by forest or grassland vegetation and characterized by topographical irregularities. Due to the inhomogeneity of the sites we applied electrical resistivity tomography (ERT) and ground penetrating radar (GPR) for detailed investigation. Using ERT we could distinguish various layers within the mining dumps. The resistivities of the dumped material differ from the bedrock resistivities at both sites. The GPR measurements show near surface layer boundaries down to 3 - 4 m. In consecutive campaigns 100 MHz and 200 MHz antennas were used. The GPR results (layer boundaries) were included into the ERT inversion algorithm to enable more precise and stable resistivity models. This needs some special preprocessing steps. The 3D-Position of every electrode from ERT measurement and the GPR antenna position on the surface require an accuracy of less than 1cm. At some points, the layer boundaries and radar wave velocities can be calibrated

  11. The Area Coverage of Small-scale Solar Magnetic Structures in a Quiet Region

    NASA Astrophysics Data System (ADS)

    Wiehr, E.; Bovelet, B.

    Inter-granular structures, IgS, are segmented with the `multiple-level tracking' pattern recognition algorithm, MLT 4 in a 149 '' x 117 '' G-band image taken at disc centre of the non-active Sun. From the total of 7593 IgS, the non-magnetic ones are identified in the scatterplot of continuum and G-band brightness which is known to show a magnetic and a non-magnetic branch. The overlap regime of both is largely disentangled applying an intrinsic Ca II H contrast criterion. For the thus obtained 2995 magnetic IgS, the MIgS, we obtain a number density of 0.32 MIgS/Mm^2. Their sizes, provided by MLT 4 in pixel counts independent of the shape, yield a total area contribution of 2.0%. Superimposing the MIgS to the simultaneously observed Hα image, we find a preferred location at the foot points of the dark fibrils, which are known to mark the network boundaries. A substantial amount of the MIgS is, however, located in the fibril voids, and thus in the inter-network.

  12. Infrasonic ray tracing applied to small-scale atmospheric structures: thermal plumes and updrafts/downdrafts.

    PubMed

    Jones, R Michael; Bedard, Alfred J

    2015-02-01

    A ray-tracing program is used to estimate the refraction of infrasound by the vertical structure of the atmosphere in thermal plumes, showing only weak effects, as well as in updrafts and downdrafts, which can act as vertical wave guides. Thermal plumes are ubiquitous features of the daytime atmospheric boundary layer. The effects of thermal plumes on lower frequency sound propagation are minor with the exception of major events, such as volcanoes, forest fires, or industrial explosions where quite strong temperature gradients are involved. On the other hand, when strong, organized vertical flows occur (e.g., in mature thunderstorms and microbursts), there are significant effects. For example, a downdraft surrounded by an updraft focuses sound as it travels upward, and defocuses sound as it travels downward. Such propagation asymmetry may help explain observations that balloonists can hear people on the ground; but conversely, people on the ground cannot hear balloonists aloft. These results are pertinent for those making surface measurements from acoustic sources aloft, as well as for measurements of surface sound sources using elevated receivers. PMID:25697997

  13. Infrasonic ray tracing applied to small-scale atmospheric structures: thermal plumes and updrafts/downdrafts.

    PubMed

    Jones, R Michael; Bedard, Alfred J

    2015-02-01

    A ray-tracing program is used to estimate the refraction of infrasound by the vertical structure of the atmosphere in thermal plumes, showing only weak effects, as well as in updrafts and downdrafts, which can act as vertical wave guides. Thermal plumes are ubiquitous features of the daytime atmospheric boundary layer. The effects of thermal plumes on lower frequency sound propagation are minor with the exception of major events, such as volcanoes, forest fires, or industrial explosions where quite strong temperature gradients are involved. On the other hand, when strong, organized vertical flows occur (e.g., in mature thunderstorms and microbursts), there are significant effects. For example, a downdraft surrounded by an updraft focuses sound as it travels upward, and defocuses sound as it travels downward. Such propagation asymmetry may help explain observations that balloonists can hear people on the ground; but conversely, people on the ground cannot hear balloonists aloft. These results are pertinent for those making surface measurements from acoustic sources aloft, as well as for measurements of surface sound sources using elevated receivers.

  14. Small scale flux emergence, small flares, and the unresolved fine structure: modeling and observations

    NASA Astrophysics Data System (ADS)

    Haraldson Hansteen, Viggo H.

    2016-05-01

    The emergence of flux through the photosphere and into the outer solar atmosphere is known to produce dynamic events in the chromosphere and corona. In this talk we will describe three-dimensional (3d) magnetohydrodynamic simulations of magnetic flux emergence in a model that spans the convection zone and into the outer solar atmosphere with the Bifrost code. We will contrast this with models in which no flux emergence occurs. These are a ``realistic'' model, in the sense that the parameters and physical effects that control the atmosphere can be used to produce diagnostics that can be directly compared with observations. Thus we will also contrast the model predictions with with SST and IRIS observations of an emerging flux region. We discuss the evolution of the model and several synthetic observables. We discuss the model's possible relevance to the so called 'unresolved fine structure' observed in the solar transition region. Finally, we will report on developments to merge `deeper' models constructed from MURaM simulations with Bifrost models of the chromosphere and corona in flare relevant simulations.

  15. Large and small-scale structures and the dust energy balance problem in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Saftly, W.; Baes, M.; De Geyter, G.; Camps, P.; Renaud, F.; Guedes, J.; De Looze, I.

    2015-04-01

    The interstellar dust content in galaxies can be traced in extinction at optical wavelengths, or in emission in the far-infrared. Several studies have found that radiative transfer models that successfully explain the optical extinction in edge-on spiral galaxies generally underestimate the observed FIR/submm fluxes by a factor of about three. In order to investigate this so-called dust energy balance problem, we use two Milky Way-like galaxies produced by high-resolution hydrodynamical simulations. We create mock optical edge-on views of these simulated galaxies (using the radiative transfer code SKIRT), and we then fit the parameters of a basic spiral galaxy model to these images (using the fitting code FitSKIRT). The basic model includes smooth axisymmetric distributions along a Sérsic bulge and exponential disc for the stars, and a second exponential disc for the dust. We find that the dust mass recovered by the fitted models is about three times smaller than the known dust mass of the hydrodynamical input models. This factor is in agreement with previous energy balance studies of real edge-on spiral galaxies. On the other hand, fitting the same basic model to less complex input models (e.g. a smooth exponential disc with a spiral perturbation or with random clumps), does recover the dust mass of the input model almost perfectly. Thus it seems that the complex asymmetries and the inhomogeneous structure of real and hydrodynamically simulated galaxies are a lot more efficient at hiding dust than the rather contrived geometries in typical quasi-analytical models. This effect may help explain the discrepancy between the dust emission predicted by radiative transfer models and the observed emission in energy balance studies for edge-on spiral galaxies.

  16. The Small-Scale Structure of High-Velocity Na I Absorption Toward M81

    NASA Astrophysics Data System (ADS)

    Roth, K. C.; Meyer, D. M.; Lauroesch, J. T.

    2000-12-01

    We present high-resolution (R=20,000) integral field spectra of the Na I absorption toward the nucleus of the nearby spiral galaxy M81 (NGC 3031) obtained in April 2000 with the WIYN 3.5-m telescope and the DensePak fiber optic bundle. Our DensePak map covers the central 27 x 43 arcsec of M81 at a spatial resolution of 4 arcsec which corresponds to a projected length scale of 63 pc at the distance of the galaxy (3.25 Mpc). These data were intended to explore the spatial extent of high-velocity (v = 110-130 km/s) gas seen in Na I, Mg I and Mg II absorption toward SN 1993J by Bowen et al. (1994), which they proposed is due to tidal material associated with interactions between M81 and nearby M82 (Yun, Ho & Lo 1993). No H I gas at these velocities has been detected in 21 cm interferometry maps near the position of SN 1993J (2.6 arcmin SW of the M81 nucleus). Our Na I map of the M81 core shows no evidence of the strong absorption seen at v = 110-130 km/s toward SN 1993J. However, our map does reveal a strong Na I component at v = 220 km/s in several fibers that appears to trace a filamentary structure running from the SW to the NE across the M81 nuclear region. The origin and distance of this filament are unknown. No H I gas at v = 220 km/s has previously been detected in 21 cm studies of the core. At the location of SN 1993J, Bowen et al. measured weak Mg II absorption at this velocity but found no evidence of corresponding Na I absorption. The only known H I gas that corresponds to this velocity in the M81 group are the H I streamers found around M82 by Yun, Ho, & Lo that they interpreted as tidally disrupted M82 disk material.

  17. Knotted Strings and Leptonic Flavor Structure

    NASA Astrophysics Data System (ADS)

    Kephart, T. W.; Leser, P.; Päs, H.

    2012-12-01

    We propose a third idea for the explanation of the leptonic flavor structure in addition to the prominent approaches based on flavor symmetry and anarchy. Typical flavor patterns can be modeled by using mass spectra obtained from the discrete lengths spectrum of tight knots and links. We assume that a string theory model exists in which this idea can be incorporated via the Majorana mass structure of a type I seesaw model. It is shown by a scan over the parameter space that such a model is able to provide an excellent fit to current neutrino data and that it predicts a normal neutrino mass hierarchy as well as a small mixing angle θ13. Startlingly, such scenarios could be related to the dimensionality of spacetime via an anthropic argument.

  18. An improved method to characterise the modulation of small-scale turbulent by large-scale structures

    NASA Astrophysics Data System (ADS)

    Agostini, Lionel; Leschziner, Michael; Gaitonde, Datta

    2015-11-01

    A key aspect of turbulent boundary layer dynamics is ``modulation,'' which refers to degree to which the intensity of coherent large-scale structures (LS) cause an amplification or attenuation of the intensity of the small-scale structures (SS) through large-scale-linkage. In order to identify the variation of the amplitude of the SS motion, the envelope of the fluctuations needs to be determined. Mathis et al. (2009) proposed to define this latter by low-pass filtering the modulus of the analytic signal built from the Hilbert transform of SS. The validity of this definition, as a basis for quantifying the modulated SS signal, is re-examined on the basis of DNS data for a channel flow. The analysis shows that the modulus of the analytic signal is very sensitive to the skewness of its PDF, which is dependent, in turn, on the sign of the LS fluctuation and thus of whether these fluctuations are associated with sweeps or ejections. The conclusion is that generating an envelope by use of a low-pass filtering step leads to an important loss of information associated with the effects of the local skewness of the PDF of the SS on the modulation process. An improved Hilbert-transform-based method is proposed to characterize the modulation of SS turbulence by LS structures

  19. The dominating impact of small-scale streambed structural heterogeneity on hyporheic exchange and biogeochemical hotspots in lowland rivers

    NASA Astrophysics Data System (ADS)

    Krause, S.; Gomez, J. D.; Blume, T.; Weatherill, J.; Angermann, L.; Munz, M.; Tecklenburg, C.; Cassidy, N. J.; Wilson, J. L.

    2013-12-01

    Exchange fluxes and residence times of groundwater and surface water at aquifer-river interfaces are driven by hydrodynamic and hydrostatic forcing. While previous research, with a predominantly surface water perspective, has mainly focussed on the impact of bedform controlled advective pumping on hyporheic zone extent and residence times, little attention has been paid to the impact of streambed structural controls on groundwater up-welling patterns and its implications for hyporheic exchange. Following a combined experimental and model-based approach, this paper highlights the impact of small-scale streambed structural variability on spatial patterns of hyporheic exchange flow, residence time distribution and the development of hotspots of biogeochemical cycling in the hyporheic zone of a lowland river. Combining Fibre-optic DTS and active Heat Pulse Sensing, this study identified distinct low conductivities peat and clay structures in the streambed to determine patterns, quantity and temporal dynamics of groundwater up-welling. Model simulations confirmed that streambed structure controlled patterns of groundwater up-welling exceeded the impact of bedform driven fluxes on aquifer-river exchange flow patterns. In addition, enhanced residence times of up-welling groundwater in and around these organic rich structures lead to an increase in dissolved oxygen consumption and the development of anaerobic denitrification hotspots. The resulting increases in streambed nitrate attenuation as well as enhanced production of CO2, CH4 and N2O as respiration end products highlight the importance of biogeochemical hotspots at aquifer-river interfaces under the dominant impact of streambed structural heterogeneity. Conceptual model of streambed hydrofacies controlling groundwater up-welling in a typical lowland river including their effect on heat transport at the aquifer-river interface (the star indicates the temperature of the surface water). B: core logs of exemplary

  20. Cosmic strings and the large-scale structure

    NASA Technical Reports Server (NTRS)

    Stebbins, Albert

    1988-01-01

    A possible problem for cosmic string models of galaxy formation is presented. If very large voids are common and if loop fragmentation is not much more efficient than presently believed, then it may be impossible for string scenarios to produce the observed large-scale structure with Omega sub 0 = 1 and without strong environmental biasing.

  1. SMALL-SCALE PRESSURE-BALANCED STRUCTURES DRIVEN BY MIRROR-MODE WAVES IN THE SOLAR WIND

    SciTech Connect

    Yao, Shuo; He, J.-S.; Tu, C.-Y.; Wang, L.-H.; Marsch, E.

    2013-10-20

    Recently, small-scale pressure-balanced structures (PBSs) have been studied with regard to their dependence on the direction of the local mean magnetic field B{sub 0} . The present work continues these studies by investigating the compressive wave mode forming small PBSs, here for B{sub 0} quasi-perpendicular to the x-axis of Geocentric Solar Ecliptic coordinates (GSE-x). All the data used were measured by WIND in the quiet solar wind. From the distribution of PBSs on the plane determined by the temporal scale and angle θ{sub xB} between the GSE-x and B{sub 0} , we notice that at θ{sub xB} = 115° the PBSs appear at temporal scales ranging from 700 s to 60 s. In the corresponding temporal segment, the correlations between the plasma thermal pressure P{sub th} and the magnetic pressure P{sub B}, as well as that between the proton density N{sub p} and the magnetic field strength B, are investigated. In addition, we use the proton velocity distribution functions to calculate the proton temperatures T and T{sub ∥}. Minimum Variance Analysis is applied to find the magnetic field minimum variance vector B{sub N} . We also study the time variation of the cross-helicity σ{sub c} and the compressibility C{sub p} and compare these with values from numerical predictions for the mirror mode. In this way, we finally identify a short segment that has T > T{sub ∥}, proton β ≅ 1, both pairs of P{sub th}-P{sub B} and N{sub p}-B showing anti-correlation, and σ{sub c} ≈ 0 with C{sub p} > 0. Although the examination of σ{sub c} and C{sub p} is not conclusive, it provides helpful additional information for the wave mode identification. Additionally, B{sub N} is found to be highly oblique to B{sub 0} . Thus, this work suggests that a candidate mechanism for forming small-scale PBSs in the quiet solar wind is due to mirror-mode waves.

  2. Shape fluctuations of large unilamellar lipid vesicles observed by laser light scattering: influence of the small-scale structure.

    PubMed

    Brocca, Paola; Cantù, Laura; Corti, Mario; Del Favero, Elena; Motta, Simona

    2004-03-16

    In the present paper, we apply the dynamic laser light scattering technique to investigate the dependence of the characteristic times of thermally induced shape fluctuation of large unilamellar vesicles (LUVs) on bilayer composition. After addressing single-component LUVs made of two common phospholipids, dimyristoylphosphatidylcholine (DMPC) and dipalmitoylphosphatidylcholine (DPPC), we investigate the changes in vesicle shape fluctuation times due to the presence of cholesterol and gangliosides (GM1), added in small amounts. The experimental results show that the addition of a second component, even in small amount, to DMPC vesicles induces a change in membrane fluctuation times. Moreover, in the case of ganglioside addition, also the disposition of GM1 within the bilayer is of importance. Quite unexpectedly, the symmetric or asymmetric disposition of GM1 has opposite effects on bilayer dynamics, the first resulting in a "hardening" and the second in a "softening" of the membrane. Those results support that the small-scale structure of the bilayer is important in determining the overall dynamics of the vesicle. They also suggest that the physiological disposition of GM1 in the outer leaflet of real cells has a significative result in mechanical terms, positively affecting the dynamics of the membrane.

  3. Associations between Small-scale Structure in Local Galactic Neutral Hydrogen and in the Cosmic Microwave Background Observed by PLANCK

    NASA Astrophysics Data System (ADS)

    Verschuur, Gerrit L.

    2015-11-01

    High-resolution galactic neutral hydrogen (HI) data obtained with the Green Bank Telescope (GBT) over 56 square degrees of sky around l = 132°, b = 25° are compared with small-scale structure in the Cosmic Microwave Background observed by PLANCK, specifically at 143 and 857 GHz, as well as with 100 μm observations from the IRIS survey. The analysis uses data in 13 2° × 2° sub-areas found in the IRSA database at IPAC. The results confirm what has been reported previously; nearby galactic HI features and high-frequency continuum sources believed to be cosmological are in fact clearly associated. While several attempts strongly suggest that the associations are statistically significant, the key to understanding the phenomenon lies in the fact that in any given area HI is associated with cirrus dust at certain HI velocities and with 143 GHz features at different velocities. At the same time, for the 13 sub-areas studied, there is very little overlap between the dust and 143 GHz features. The data do not imply that the HI itself gives rise to the high-frequency continuum emission. Rather, they appear to indicate undiagnosed brightness enhancements indirectly associated with the HI. If low density interstellar electrons concentrated into clumps, or observed in directions where their integrated line-of-sight column densities are greater than the background in a manner similar to the phenomena that give rise to structure in diffuse HI structure, they will profoundly affect attempts to create a foreground electron mask used for processing PLANCK as well as WMAP data.

  4. ASSOCIATIONS BETWEEN SMALL-SCALE STRUCTURE IN LOCAL GALACTIC NEUTRAL HYDROGEN AND IN THE COSMIC MICROWAVE BACKGROUND OBSERVED BY PLANCK

    SciTech Connect

    Verschuur, Gerrit L.

    2015-11-01

    High-resolution galactic neutral hydrogen (HI) data obtained with the Green Bank Telescope (GBT) over 56 square degrees of sky around l = 132°, b = 25° are compared with small-scale structure in the Cosmic Microwave Background observed by PLANCK, specifically at 143 and 857 GHz, as well as with 100 μm observations from the IRIS survey. The analysis uses data in 13 2° × 2° sub-areas found in the IRSA database at IPAC. The results confirm what has been reported previously; nearby galactic HI features and high-frequency continuum sources believed to be cosmological are in fact clearly associated. While several attempts strongly suggest that the associations are statistically significant, the key to understanding the phenomenon lies in the fact that in any given area HI is associated with cirrus dust at certain HI velocities and with 143 GHz features at different velocities. At the same time, for the 13 sub-areas studied, there is very little overlap between the dust and 143 GHz features. The data do not imply that the HI itself gives rise to the high-frequency continuum emission. Rather, they appear to indicate undiagnosed brightness enhancements indirectly associated with the HI. If low density interstellar electrons concentrated into clumps, or observed in directions where their integrated line-of-sight column densities are greater than the background in a manner similar to the phenomena that give rise to structure in diffuse HI structure, they will profoundly affect attempts to create a foreground electron mask used for processing PLANCK as well as WMAP data.

  5. Large- and small-scale structure of the intermediate- and high-velocity clouds towards the LMC and SMC

    NASA Astrophysics Data System (ADS)

    Smoker, J. V.; Fox, A. J.; Keenan, F. P.

    2015-08-01

    We employ Ca II K and Na I D interstellar absorption-line spectroscopy of early-type stars in the Large and Small Magellanic Clouds (LMC, SMC) to investigate the large- and small-scale structure in foreground intermediate- and high-velocity clouds (I/HVCs). Data include FLAMES-GIRAFFE Ca II K observations of 403 stars in four open clusters, plus FEROS or UVES spectra of 156 stars in the LMC and SMC. The FLAMES observations are amongst the most extensive probes to date of Ca II structures on ˜20 arcsec scales in Magellanic I/HVCs. From the FLAMES data within a 0.5° field of view, the Ca II K equivalent width in the I/HVC components towards three clusters varies by factors of ≥10. There are no detections of molecular gas in absorption at intermediate or high velocities, although molecular absorption is present at LMC and Galactic velocities towards some sightlines. The FEROS/UVES data show Ca II K I/HVC absorption in ˜60 per cent of sightlines. The range in the Ca II/Na I ratio in I/HVCs is from -0.45 to +1.5 dex, similar to previous measurements for I/HVCs. In 10 sightlines we find Ca II/O I ratios in I/HVC gas ranging from 0.2 to 1.5 dex below the solar value, indicating either dust or ionization effects. In nine sightlines I/HVC gas is detected in both H I and Ca II at similar velocities, implying that the two elements form part of the same structure.

  6. ncRNA consensus secondary structure derivation using grammar strings.

    PubMed

    Achawanantakun, Rujira; Sun, Yanni; Takyar, Seyedeh Shohreh

    2011-04-01

    Many noncoding RNAs (ncRNAs) function through both their sequences and secondary structures. Thus, secondary structure derivation is an important issue in today's RNA research. The state-of-the-art structure annotation tools are based on comparative analysis, which derives consensus structure of homologous ncRNAs. Despite promising results from existing ncRNA aligning and consensus structure derivation tools, there is a need for more efficient and accurate ncRNA secondary structure modeling and alignment methods. In this work, we introduce a consensus structure derivation approach based on grammar string, a novel ncRNA secondary structure representation that encodes an ncRNA's sequence and secondary structure in the parameter space of a context-free grammar (CFG) and a full RNA grammar including pseudoknots. Being a string defined on a special alphabet constructed from a grammar, grammar string converts ncRNA alignment into sequence alignment. We derive consensus secondary structures from hundreds of ncRNA families from BraliBase 2.1 and 25 families containing pseudoknots using grammar string alignment. Our experiments have shown that grammar string-based structure derivation competes favorably in consensus structure quality with Murlet and RNASampler. Source code and experimental data are available at http://www.cse.msu.edu/~yannisun/grammar-string. PMID:21523935

  7. ncRNA consensus secondary structure derivation using grammar strings.

    PubMed

    Achawanantakun, Rujira; Sun, Yanni; Takyar, Seyedeh Shohreh

    2011-04-01

    Many noncoding RNAs (ncRNAs) function through both their sequences and secondary structures. Thus, secondary structure derivation is an important issue in today's RNA research. The state-of-the-art structure annotation tools are based on comparative analysis, which derives consensus structure of homologous ncRNAs. Despite promising results from existing ncRNA aligning and consensus structure derivation tools, there is a need for more efficient and accurate ncRNA secondary structure modeling and alignment methods. In this work, we introduce a consensus structure derivation approach based on grammar string, a novel ncRNA secondary structure representation that encodes an ncRNA's sequence and secondary structure in the parameter space of a context-free grammar (CFG) and a full RNA grammar including pseudoknots. Being a string defined on a special alphabet constructed from a grammar, grammar string converts ncRNA alignment into sequence alignment. We derive consensus secondary structures from hundreds of ncRNA families from BraliBase 2.1 and 25 families containing pseudoknots using grammar string alignment. Our experiments have shown that grammar string-based structure derivation competes favorably in consensus structure quality with Murlet and RNASampler. Source code and experimental data are available at http://www.cse.msu.edu/~yannisun/grammar-string.

  8. Gravitational radiation by cosmic strings in a junction

    SciTech Connect

    Brandenberger, R.; Karouby, J.; Firouzjahi, H.; Khosravi, S.

    2009-01-15

    The formalism for computing the gravitational power radiation from excitations on cosmic strings forming a junction is presented and applied to the simple case of co-planar strings at a junction when the excitations are generated along one string leg. The effects of polarization of the excitations and of the back-reaction of the gravitational radiation on the small scale structure of the strings are studied.

  9. Structure of small-scale field-aligned currents at middle and low latitudes having lower atmospheric origin

    NASA Astrophysics Data System (ADS)

    Nakanishi, K.; Iyemori, T.; Luhr, H.; Aoyama, T.

    2014-12-01

    The CHAMP magnetic data indicate that small amplitude (1-5 nT) magnetic fluctuations with period around a few tens of seconds along the orbit exist globally and almost all the time. Characteristics of the magnetic fluctuations including seasonal dependence having geographical characteristics strongly suggest that they are the small-scale spatial structure of field-aligned currents with lower atmospheric origin (Nakanishi et al., 2014). We suppose that gravity waves generated by lower atmospheric disturbances propagate to the ionosphere and drive the E-layer dynamo. The currents in the ionosphere divert along the magnetic field into the other hemisphere and make a closed circuit. To confirm the above scenario and to find the scale of the current circuit in longitudinal direction, we use the magnetic data observed by the SWARM satellites. By analysis of the magnetic data observed by the SWARM satellites, the magnetic fluctuations as recorded earlier by CHAMP are confirmed to have the same characteristics i.e., the magnetic fluctuation is perpendicular to the geomagnetic field; the amplitude on the dayside is much larger than that on the nightside; towards the dip equator the period tends to get longer. Because the three Swarm satellites have various spatial relations in 3-D space between their orbits, we could easily confirm that the objective magnetic fluctuations are not temporal but spatial structures. The longitudinal scale seems to be of the order of 100 km. We shall show the above results and some other characteristics of the current circuit and discuss whether or not our suggested model fits the observed characteristics.

  10. Small scale seismic measurement bench to assess imaging methods - application to Full Waveform Inversion of a shallow structure

    NASA Astrophysics Data System (ADS)

    Leparoux, D.; Bretaudeau, F.; Brossier, R.; Operto, S.; Virieux, J.

    2011-12-01

    Seismic imaging of subsurface is useful for civil engineering and landscape management topics. The usual methods use surface waves phase velocities or first arrival times of body waves. However, for complex structures, such methods can be inefficient and Full Waveform Inversion (FWI) promises relevant performances because all the signal is taken into account. FWI has been originally developed for deep explorations (Pratt et al. 1999). Heterogeneities and strong attenuation in the near surface make difficult the adaptation of the FWI to shallower media (Bretaudeau et al. 2009). For this reason, we have developed a physical modeling measurement bench that performs small scale seismic recording in well controlled contexts (Bretaudeau et al. 2011). In this paper we assess the capacity of the FWI method (Brossier 2010) for imaging a subsurface structure including a low velocity layer and a lateral variation of interfaces. The analog model is a 180mm long and 50mm thick layered epoxy resin block (fig. 1). Seismic data generated with a punctual piezoelectric source emitting a 120KHz Ricker wavelet at the medium surface were collected by an heterodyne laser interferometer. The laser allows recording the absolute normal particle displacement without contact, avoiding disturbances caused by coupling. The laser interferometer and the piezoelectric source were attached to automated arms that could be moved over the model surface to a precision of 0.01mm (fig. 1). The acquisition survey includes 241 receiver and 37 source positions respectively spaced at 1 and 5 mm. Figure 2 shows 2D maps of the Vs parameter after inversion of data sequentially processed with 13 frequencies. The geometry of the sloped interface is recovered. A low velocity zone is imaged but with a thickness thinner than expected. Moreover, artifacts appear in the near surface. Experimental modeling results showed the capacity of the FWI in this case and provided key issues for further works about inversion by

  11. Cosmic string scaling in flat space

    SciTech Connect

    Vanchurin, Vitaly; Olum, Ken; Vilenkin, Alexander

    2005-09-15

    We investigate the evolution of infinite strings as a part of a complete cosmic string network in flat space. We perform a simulation of the network which uses functional forms for the string position and thus is exact to the limits of computer arithmetic. Our results confirm that the wiggles on the strings obey a scaling law described by universal power spectrum. The average distance between long strings also scales accurately with the time. These results suggest that small-scale structure will also scale in an expanding universe, even in the absence of gravitational damping.

  12. Bosonic structure of realistic SO(10) supersymmetric cosmic strings

    NASA Astrophysics Data System (ADS)

    Allys, Erwan

    2016-05-01

    We study the bosonic structure of F -term Nambu-Goto cosmic strings forming in a realistic SO(10) implementation, assuming standard hybrid inflation. We describe the supersymmetric grand unified theory, and its spontaneous symmetry breaking scheme in parallel with the inflationary process. We also write the explicit tensor formulation of its scalar sector, focusing on the subrepresentations singlet under the standard model, which is sufficient to describe the string structure. We then introduce an ansatz for Abelian cosmic strings, discussing in details the hypothesis, and write down the field equations and boundary conditions. Finally, after doing a perturbative study of the model, we present and discuss the results obtained with numerical solutions of the string structure.

  13. Analysis of very-high-resolution Galileo images of Europa: Implications for small-scale structure and surface evolution

    NASA Astrophysics Data System (ADS)

    Leonard, E. J.; Pappalardo, R. T.; Yin, A.; Prockter, L. M.; Patthoff, D. A.

    2014-12-01

    The Galileo Solid State Imager (SSI) recorded nine very high-resolution frames (8 at 12 m/pixel and 1 at 6 m/pixel) during the E12 flyby of Europa in Dec. 1997. To understand the implications for the small-scale structure and evolution of Europa, we mosaicked these frames (observations 12ESMOTTLE01 and 02, incidence ≈18°, emission ≈77°) into their regional context (part of observation 11ESREGMAP01, 220 m/pixel, incidence ≈74°, emission ≈23°), despite their very different viewing and lighting conditions. We created a map of geological units based on morphology, structure, and albedo along with stereoscopic images where the frames overlapped. The highly diverse units range from: high albedo sub-parallel ridge and grooved terrain; to variegated-albedo hummocky terrain; to low albedo and relatively smooth terrain. We classified and analyzed the diverse units solely based on the high-resolution image mosaic, prior to comparison to the context image, to obtain an in-depth look at possible surface evolution and underlying formational processes. We infer that some of these units represent different stages and forms of resurfacing, including cryovolcanic and tectonic resurfacing. However, significant morphological variation among units in the region indicates that there are different degrees of resurfacing at work. We have created candidate morphological sequences that provide insight into the conversion of ridged plains to chaotic terrain—generally, a process of subduing formerly sharp features through tectonic modification and/or cryovolcanism. When the map of the high-resolution area is compared to the regional context, features that appear to be one unit at regional resolution are comprised of several distinct units at high resolution, and features that appear to be smooth in the context image are found to show distinct textures. Moreover, in the context image, transitions from ridged units to disrupted units appear to be gradual; however the high

  14. Global structure of Gott's two-string spacetime

    NASA Astrophysics Data System (ADS)

    Cutler, Curt

    1992-01-01

    Gott has recently obtained exact solutions to Einstein's equation representing two infinitely long, straight cosmic strings that gravitationally scatter off each other. A remarkable feature of these solutions is that they contain closed timelike curves when the relative velocity of the strings is sufficiently high. In this paper we elucidate the global structure of Gott's two-string spacetime. In particular, we prove that the closed timelike curves are confined to a certain region of the spacetime, and that the spacetime contains complete spacelike, edgeless, achronal hypersurfaces, from which the causality-violating regions may be said to evolve. We then explicitly determine the boundary of the region containing closed timelike curves.

  15. Wavelet transform analysis of the small-scale X-ray structure of the cluster Abell 1367

    NASA Technical Reports Server (NTRS)

    Grebeney, S. A.; Forman, W.; Jones, C.; Murray, S.

    1995-01-01

    We have developed a new technique based on a wavelet transform analysis to quantify the small-scale (less than a few arcminutes) X-ray structure of clusters of galaxies. We apply this technique to the ROSAT position sensitive proportional counter (PSPC) and Einstein high-resolution imager (HRI) images of the central region of the cluster Abell 1367 to detect sources embedded within the diffuse intracluster medium. In addition to detecting sources and determining their fluxes and positions, we show that the wavelet analysis allows a characterization of the sources extents. In particular, the wavelet scale at which a given source achieves a maximum signal-to-noise ratio in the wavelet images provides an estimate of the angular extent of the source. To account for the widely varying point response of the ROSAT PSPC as a function of off-axis angle requires a quantitative measurement of the source size and a comparison to a calibration derived from the analysis of a Deep Survey image. Therefore, we assume that each source could be described as an isotropic two-dimensional Gaussian and used the wavelet amplitudes, at different scales, to determine the equivalent Gaussian Full Width Half-Maximum (FWHM) (and its uncertainty) appropriate for each source. In our analysis of the ROSAT PSPC image, we detect 31 X-ray sources above the diffuse cluster emission (within a radius of 24 min), 16 of which are apparently associated with cluster galaxies and two with serendipitous, background quasars. We find that the angular extents of 11 sources exceed the nominal width of the PSPC point-spread function. Four of these extended sources were previously detected by Bechtold et al. (1983) as 1 sec scale features using the Einstein HRI. The same wavelet analysis technique was applied to the Einstein HRI image. We detect 28 sources in the HRI image, of which nine are extended. Eight of the extended sources correspond to sources previously detected by Bechtold et al. Overall, using both the

  16. Enhanced Monopropellant Fuel Decomposition by High Aspect Ratio, Catalytic CNT Structures for Propulsion of Small Scale Underwater Vehicles

    NASA Astrophysics Data System (ADS)

    Marr, Kevin; Claussen, Jonathan; Iverson, Brian

    2014-11-01

    Both maneuverability and efficiency for reagent-based propulsion systems of small-scale exploratory devices, such as autonomous underwater vehicles (AUVs), is largely dependent on their maximum fuel decomposition rate. Reagent-based systems, however, require large catalyst surface area to fuel volume ratios in order to achieve the fuel decomposition rates necessary for locomotion. This work demonstrates the utility of platinum-coated, carbon nanotube (CNT) scaffolds as high surface area catalysts for decomposition of hydrogen peroxide (H2O2) in a flowing environment. Usage of these functionalized microchannels ensures that both the maximum distance between fuel and catalyst is only half the microchannel diameter, and that the fuel concentration gradient increases due to boundary-layer thinning. These conditions facilitate intimate contact between fuel and catalyst and, therefore, faster decomposition rates. Electrochemical testing revealed that electroactive surface area to volume ratios of approximately 61.4 cm-1 can be achieved for samples fabricated using a static Pt deposition scheme. Thrust measurements were taken using a small-scale submersible which indicated a maximum thrust of 0.114 N using 50 weight percent H2O2 exposed to eight inline 2.867 cm2 Pt-CNT scaffolds.

  17. A novel method for the identification of conserved structural patterns in RNA: From small scale to high-throughput applications

    PubMed Central

    Pietrosanto, Marco; Mattei, Eugenio; Helmer-Citterich, Manuela; Ferrè, Fabrizio

    2016-01-01

    Functional RNA regions are often related to recurrent secondary structure patterns (or motifs), which can exert their role in several different ways, particularly in dictating the interaction with RNA-binding proteins, and acting in the regulation of a large number of cellular processes. Among the available motif-finding tools, the majority focuses on sequence patterns, sometimes including secondary structure as additional constraints to improve their performance. Nonetheless, secondary structures motifs may be concurrent to their sequence counterparts or even encode a stronger functional signal. Current methods for searching structural motifs generally require long pipelines and/or high computational efforts or previously aligned sequences. Here, we present BEAM (BEAr Motif finder), a novel method for structural motif discovery from a set of unaligned RNAs, taking advantage of a recently developed encoding for RNA secondary structure named BEAR (Brand nEw Alphabet for RNAs) and of evolutionary substitution rates of secondary structure elements. Tested in a varied set of scenarios, from small- to large-scale, BEAM is successful in retrieving structural motifs even in highly noisy data sets, such as those that can arise in CLIP-Seq or other high-throughput experiments. PMID:27580722

  18. Small Scale High Speed Turbomachinery

    NASA Technical Reports Server (NTRS)

    London, Adam P. (Inventor); Droppers, Lloyd J. (Inventor); Lehman, Matthew K. (Inventor); Mehra, Amitav (Inventor)

    2015-01-01

    A small scale, high speed turbomachine is described, as well as a process for manufacturing the turbomachine. The turbomachine is manufactured by diffusion bonding stacked sheets of metal foil, each of which has been pre-formed to correspond to a cross section of the turbomachine structure. The turbomachines include rotating elements as well as static structures. Using this process, turbomachines may be manufactured with rotating elements that have outer diameters of less than four inches in size, and/or blading heights of less than 0.1 inches. The rotating elements of the turbomachines are capable of rotating at speeds in excess of 150 feet per second. In addition, cooling features may be added internally to blading to facilitate cooling in high temperature operations.

  19. Small-scale gravity modeling of upper crustal structures in the Araba Valley along the Dead Sea Transform

    NASA Astrophysics Data System (ADS)

    TašáRová, Z.; GöTze, H.-J.; El-Kelani, R.; Ebbing, J.; Hassouneh, M.

    2006-09-01

    A detailed three-dimensional (3-D) gravity model of upper crustal structures was created for the Dead Sea Transform in the Araba/Arava Valley, located some 80 km south of the Dead Sea Basin. The density model covers an area of ˜30 × 30 km and incorporates results from several recent geophysical experiments performed in this region. The model presented is a local density model that focuses on the uppermost crustal layers to a depth of ˜5 km. Therefore, in order to separate the effect of regional structures (such as the crust-mantle boundary) from that of local structures within the crust, a residual anomaly was computed from a newly compiled Bouguer gravity anomaly database. In contrast to the Bouguer anomaly, which is negative across the entire study area, the residual gravity field contains both positive and negative values. The 3-D structural image of the upper crust reveals that the basement east and west of the Dead Sea Transform is vertically offset by 1.5 to 2.8 km. Considering the 105 km of sinistral displacement of the Dead Sea Transform, this result confirms the findings of other geophysical measurements that show an abrupt change in the physical parameters and geometry of the two lithological blocks that are juxtaposed along the Dead Sea Transform. Additionally, analysis of the calculated gravity gradients suggests that the Dead Sea Transform and the neighboring Zofar fault could be offset at depth with respect to the present-day traces at the surface.

  20. Small-scale variations in the galactic magnetic field - The rotation measure structure function and birefringence in interstellar scintillations

    NASA Technical Reports Server (NTRS)

    Simonetti, J. H.; Cordes, J. M.; Spangler, S. R.

    1984-01-01

    The structure function of rotation measures of extragalactic sources and birefringence in interstellar scintillations are used to investigate variations in the interstellar magnetic field on length scales of about 0.01-100 pc and 10 to the 11th cm, respectively. Model structure functions are derived for the case of a power-law power spectrum of irregularities in the quantity (n(e)B), and an estimate for the structure function is computed for several regions of the sky using data on extragalactic sources. The results indicate an outer angular scale for rotation measure (RM) variations of not less than about 5 deg (a linear scale of about 9-90 pc at a distance of 0.1-1 kpc). There is also evidence for RM variations on angular scales as small as 1 arcmin, but it cannot be determined whether these are intrinsic to the source or caused by the interstellar medium. The effect of a random, Faraday-active medium on the diffraction of radio waves is derived, and an upper limit to the variations in n(e)B on a length scale of 10 to the 11th cm is obtained from available observations.

  1. MICA sounding rocket observations of conductivity-gradient-generated auroral ionospheric responses: Small-scale structure with large-scale drivers

    NASA Astrophysics Data System (ADS)

    Lynch, K. A.; Hampton, D. L.; Zettergren, M.; Bekkeng, T. A.; Conde, M.; Fernandes, P. A.; Horak, P.; Lessard, M.; Miceli, R.; Michell, R.; Moen, J.; Nicolls, M.; Powell, S. P.; Samara, M.

    2015-11-01

    A detailed, in situ study of field-aligned current (FAC) structure in a transient, substorm expansion phase auroral arc is conducted using electric field, magnetometer, and electron density measurements from the Magnetosphere-Ionosphere Coupling in the Alfvén Resonator (MICA) sounding rocket, launched from Poker Flat, AK. These data are supplemented with larger-scale, contextual measurements from a heterogeneous collection of ground-based instruments including the Poker Flat incoherent scatter radar and nearby scanning doppler imagers and filtered all-sky cameras. An electrostatic ionospheric modeling case study of this event is also constructed by using available data (neutral winds, electron precipitation, and electric fields) to constrain model initial and boundary conditions. MICA magnetometer data are converted into FAC measurements using a sheet current approximation and show an up-down current pair, with small-scale current density and Poynting flux structures in the downward current channel. Model results are able to roughly recreate only the large-scale features of the field-aligned currents, suggesting that observed small-scale structures may be due to ionospheric feedback processes not encapsulated by the electrostatic model. The model is also used to assess the contributions of various processes to total FAC and suggests that both conductance gradients and neutral dynamos may contribute significantly to FACs in a narrow region where the current transitions from upward to downward. Comparison of Poker Flat Incoherent Scatter Radar versus in situ electric field estimates illustrates the high sensitivity of FAC estimates to measurement resolution.

  2. In situ ionospheric observations of severe weather-related gravity waves and associated small-scale plasma structure

    NASA Astrophysics Data System (ADS)

    Kelley, Michael C.

    1997-01-01

    On July 27, 1988, two sounding rockets were launched over a small thunderstorm cell which constituted the remnants of a large frontal event which had lasted for several hours over the eastern seaboard. One of the rockets was instrumented for detection of the electromagnetic impulse from lightning strikes and its subsequent interaction with the ionospheric plasma [Kelley et al., 1990]. The second had on board an absolute electron density probe, the results from which we report here. We present evidence that a gravity wave was spawned by the front and propagated nearly to the F peak in the ionosphere, where it steepened and created structure in the medium at scales much less than the vertical wavenumber of the major disturbance. The fluctuation spectrum along the rocket path was elevated for scales from 25 km down to less than 10 m. At scales between 10 km and just under 100 m, characterization of the spectrum by a power law yields a spectral index less than that displayed by such well-studied processes as bottomside spread F and barium cloud striations. Similar results have been reported for gravity wave induced intermediate scale structures at midlatitudes [Wernik et al., 1986]. The mixing theory described by Fridman [1990] may be relevant to these observations.

  3. Retrieving backbone string neighbors provides insights into structural modeling of membrane proteins.

    PubMed

    Sun, Jiang-Ming; Li, Tong-Hua; Cong, Pei-Sheng; Tang, Sheng-Nan; Xiong, Wen-Wei

    2012-07-01

    Identification of protein structural neighbors to a query is fundamental in structure and function prediction. Here we present BS-align, a systematic method to retrieve backbone string neighbors from primary sequences as templates for protein modeling. The backbone conformation of a protein is represented by the backbone string, as defined in Ramachandran space. The backbone string of a query can be accurately predicted by two innovative technologies: a knowledge-driven sequence alignment and encoding of a backbone string element profile. Then, the predicted backbone string is employed to align against a backbone string database and retrieve a set of backbone string neighbors. The backbone string neighbors were shown to be close to native structures of query proteins. BS-align was successfully employed to predict models of 10 membrane proteins with lengths ranging between 229 and 595 residues, and whose high-resolution structural determinations were difficult to elucidate both by experiment and prediction. The obtained TM-scores and root mean square deviations of the models confirmed that the models based on the backbone string neighbors retrieved by the BS-align were very close to the native membrane structures although the query and the neighbor shared a very low sequence identity. The backbone string system represents a new road for the prediction of protein structure from sequence, and suggests that the similarity of the backbone string would be more informative than describing a protein as belonging to a fold.

  4. Higher-order derivative correlations and the alignment of small-scale structures in isotropic numerical turbulence

    NASA Technical Reports Server (NTRS)

    Kerr, R. A.

    1983-01-01

    In a three dimensional simulation higher order derivative correlations, including skewness and flatness factors, are calculated for velocity and passive scalar fields and are compared with structures in the flow. The equations are forced to maintain steady state turbulence and collect statistics. It is found that the scalar derivative flatness increases much faster with Reynolds number than the velocity derivative flatness, and the velocity and mixed derivative skewness do not increase with Reynolds number. Separate exponents are found for the various fourth order velocity derivative correlations, with the vorticity flatness exponent the largest. Three dimensional graphics show strong alignment between the vorticity, rate of strain, and scalar-gradient fields. The vorticity is concentrated in tubes with the scalar gradient and the largest principal rate of strain aligned perpendicular to the tubes. Velocity spectra, in Kolmogorov variables, collapse to a single curve and a short minus 5/3 spectral regime is observed.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  6. Results from a high-speed imaging system for the observation of transient features in OH-Airglow with focus on small-scale structures

    NASA Astrophysics Data System (ADS)

    Hannawald, Patrick; Kazlova, Aliaksandra; Schmidt, Carsten; Wüst, Sabine; Bittner, Michael

    2016-04-01

    The OH-airglow layer in about 87 km altitude is suited to investigate atmospheric dynamics in a unique way, allowing continuous observations of the night-sky throughout the year. Especially, atmospheric gravity waves are prominent features in the data of airglow imaging systems. In the year 2014 the imaging system FAIM (Fast Airglow IMager) for the study of small-scale features (both in space and time) was operational at the NDMC (Network for the detection of mesospheric change) station Oberpfaffenhofen. The instrument covers many of the brightest OH vibrational bands between 1.0 μm and 1.7 μm and acquires images with a temporal resolution of 2 frames per second. It measures the night sky with an aperture angle of about 20° and a zenith angle of 45° oriented to the Southern Germany Alpine region. Hence, the field of view (FOV) is about 50 km times 60 km in the height of the mesopause (87 km) with a mean spatial resolution of about 200 m. With this resolution, the focus of the instrument is on small-scale wave structures ranging from about 1 km to 30 km and instability structures like so-called ripples or Kelvin-Helmholtz-Instabilities. Case studies will be presented showing dissipating gravity waves and the results of spectral analyses will give an overview of the prominent directions of propagation and the horizontal wavelengths within the year 2014. This work is funded by the Bavarian State Ministry of the Environment and Consumer Protection by grant no. TUS01UFS-67093. The project aims to analyse the influence of the Alpine region on the generation of atmospheric waves.

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

    NASA Astrophysics Data System (ADS)

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

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

  8. THE SMALL-SCALE PHYSICAL STRUCTURE AND FRAGMENTATION DIFFERENCE OF TWO EMBEDDED INTERMEDIATE-MASS PROTOSTARS IN ORION

    SciTech Connect

    Van Kempen, T. A.; Longmore, S. N.; Johnstone, D.; Pillai, T.; Fuente, A.

    2012-06-01

    Intermediate-mass (IM) protostars, the bridge between the very common solar-like protostars and the more massive, but rarer, O and B stars, can only be studied at high physical spatial resolutions in a handful of clouds. In this paper, we present and analyze the continuum results from an observing campaign at the Submillimeter Array (SMA) targeting two well-studied IM protostars in Orion, NGC 2071 and L1641 S3 MMS 1. The extended SMA (eSMA) probes structure at angular resolutions up to 0.''2, revealing protostellar disks on scales of {approx}200 AU. Continuum flux measurements on these scales indicate that a significant amount of mass, a few tens of M{sub Sun }, is present. Envelope, stellar, and disk masses are derived using compact, extended, and eSMA configurations and compared against spectral energy distribution fitting models. We hypothesize that fragmentation into three components occurred within NGC 2071 at an early time, when the envelopes were less than 10% of their current masses, e.g., <0.5 M{sub Sun }. No fragmentation occurred for L1641 S3 MMS 1. For NGC 2071, evidence is given that the bulk of the envelope material currently around each source was accreted after the initial fragmentation. In addition, about 30% of the total core mass is not yet associated to one of the three sources. A global accretion model is favored and a potential accretion history of NGC 2071 is presented. It is shown that the relatively low level of fragmentation in NGC 2071 was stifled compared to the expected fragmentation from a Jeans argument. Similarly, the lack of fragmentation in L1641 S3 MMS 1 is likely due to similar arguments.

  9. The Phenomenology of Small-Scale Turbulence

    NASA Astrophysics Data System (ADS)

    Sreenivasan, K. R.; Antonia, R. A.

    I have sometimes thought that what makes a man's work classic is often just this multiplicity [of interpretations], which invites and at the same time resists our craving for a clear understanding. Wright (1982, p. 34), on Wittgenstein's philosophy Small-scale turbulence has been an area of especially active research in the recent past, and several useful research directions have been pursued. Here, we selectively review this work. The emphasis is on scaling phenomenology and kinematics of small-scale structure. After providing a brief introduction to the classical notions of universality due to Kolmogorov and others, we survey the existing work on intermittency, refined similarity hypotheses, anomalous scaling exponents, derivative statistics, intermittency models, and the structure and kinematics of small-scale structure - the latter aspect coming largely from the direct numerical simulation of homogeneous turbulence in a periodic box.

  10. Bounds on cosmic strings from WMAP and SDSS

    SciTech Connect

    Wyman, Mark; Wasserman, Ira; Pogosian, Levon

    2005-07-15

    We find the constraints from Wilkinson microwave anisotropy probe (WMAP) and Sloan digital sky survey (SDSS) data on the fraction of cosmological fluctuations sourced by local cosmic strings using a Markov Chain Monte Carlo (MCMC) analysis. In addition to varying the usual 6 cosmological parameters and the string tension ({mu}), we also varied the amount of small-scale structure on the strings. Our results indicate that cosmic strings can account for up to 7 (14)% of the total power of the microwave anisotropy at 68 (95)% confidence level. The corresponding bound on the string mass per unit length, within our string model, is G{mu}<3.4(5)x10{sup -7} at 68 (95)% C.L. We also calculate the B-type polarization spectra sourced by cosmic strings and discuss the prospects of their detection.

  11. Composite strings in (2+1)-dimensional anisotropic weakly coupled Yang-Mills theory

    SciTech Connect

    Orland, Peter

    2008-01-15

    The small-scale structure of a string connecting a pair of static sources is explored for the weakly coupled anisotropic SU(2) Yang-Mills theory in (2+1) dimensions. A crucial ingredient in the formulation of the string Hamiltonian is the phenomenon of color smearing of the string constituents. The quark-antiquark potential is determined. We close with some discussion of the standard, fully Lorentz-invariant Yang-Mills theory.

  12. Geologic utility of small-scale airphotos

    NASA Technical Reports Server (NTRS)

    Clark, M. M.

    1969-01-01

    The geologic value of small scale airphotos is emphasized by describing the application of high altitude oblique and 1:120,000 to 1:145,000 scale vertical airphotos to several geologic problems in California. These examples show that small-scale airphotos can be of use to geologists in the following ways: (1) high altitude, high oblique airphotos show vast areas in one view; and (2) vertical airphotos offer the most efficient method of discovering the major topographic features and structural and lithologic characteristics of terrain.

  13. A geostatistical analysis of small-scale spatial variability in bacterial abundance and community structure in salt marsh creek bank sediments

    NASA Technical Reports Server (NTRS)

    Franklin, Rima B.; Blum, Linda K.; McComb, Alison C.; Mills, Aaron L.

    2002-01-01

    Small-scale variations in bacterial abundance and community structure were examined in salt marsh sediments from Virginia's eastern shore. Samples were collected at 5 cm intervals (horizontally) along a 50 cm elevation gradient, over a 215 cm horizontal transect. For each sample, bacterial abundance was determined using acridine orange direct counts and community structure was analyzed using randomly amplified polymorphic DNA fingerprinting of whole-community DNA extracts. A geostatistical analysis was used to determine the degree of spatial autocorrelation among the samples, for each variable and each direction (horizontal and vertical). The proportion of variance in bacterial abundance that could be accounted for by the spatial model was quite high (vertical: 60%, horizontal: 73%); significant autocorrelation was found among samples separated by 25 cm in the vertical direction and up to 115 cm horizontally. In contrast, most of the variability in community structure was not accounted for by simply considering the spatial separation of samples (vertical: 11%, horizontal: 22%), and must reflect variability from other parameters (e.g., variation at other spatial scales, experimental error, or environmental heterogeneity). Microbial community patch size based upon overall similarity in community structure varied between 17 cm (vertical) and 35 cm (horizontal). Overall, variability due to horizontal position (distance from the creek bank) was much smaller than that due to vertical position (elevation) for both community properties assayed. This suggests that processes more correlated with elevation (e.g., drainage and redox potential) vary at a smaller scale (therefore producing smaller patch sizes) than processes controlled by distance from the creek bank. c2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

  14. ETHOS - an effective theory of structure formation: dark matter physics as a possible explanation of the small-scale CDM problems

    NASA Astrophysics Data System (ADS)

    Vogelsberger, Mark; Zavala, Jesús; Cyr-Racine, Francis-Yan; Pfrommer, Christoph; Bringmann, Torsten; Sigurdson, Kris

    2016-08-01

    We present the first simulations within an effective theory of structure formation (ETHOS), which includes the effect of interactions between dark matter and dark radiation on the linear initial power spectrum and dark matter self-interactions during non-linear structure formation. We simulate a Milky Way-like halo in four different dark matter models and the cold dark matter case. Our highest resolution simulation has a particle mass of 2.8 × 104 M⊙ and a softening length of 72.4 pc. We demonstrate that all alternative models have only a negligible impact on large-scale structure formation. On galactic scales, however, the models significantly affect the structure and abundance of subhaloes due to the combined effects of small-scale primordial damping in the power spectrum and late-time self-interactions. We derive an analytic mapping from the primordial damping scale in the power spectrum to the cutoff scale in the halo mass function and the kinetic decoupling temperature. We demonstrate that certain models within this extended effective framework that can alleviate the too-big-to-fail and missing satellite problems simultaneously, and possibly the core-cusp problem. The primordial power spectrum cutoff of our models naturally creates a diversity in the circular velocity profiles, which is larger than that found for cold dark matter simulations. We show that the parameter space of models can be constrained by contrasting model predictions to astrophysical observations. For example, some models may be challenged by the missing satellite problem if baryonic processes were to be included and even oversolve the too-big-to-fail problem; thus ruling them out.

  15. Electrical phosphenes: on the influence of conductivity inhomogeneities and small-scale structures of the orbita on the current density threshold of excitation.

    PubMed

    Lindenblatt, G; Silny, J

    2002-05-01

    Electrical and magnetic phosphenes, perceptions of light as a result of non-adequate stimulation of the eye by electrical current or magnetic induction, respectively, are one of the cornerstones to justify limit values for extreme low-frequency fields specified by statutory regulations. However, the mechanism and place of action, as well as the excitation threshold, remain unknown until now. We suggest that the origin of phosphene excitation is the synaptic layer of the eye. The current density threshold value for electrical phosphene excitation was numerically quantified for this area on the basis of a detailed geometrical model in original submillimetre resolution and specifically measured conductivities in the LF range. The threshold values found were 1.8 A m-2 at 60 Hz and 0.3 A m-2 at 25 Hz. These values are comparable with values of other excitable tissues. It has been shown that the current density threshold for phosphene generation depends on small-scale structures not taken into account by previous models. PMID:12195984

  16. The Hydrodynamic Feedback of Cosmic Reionization on Small-scale Structures and Its Impact on Photon Consumption During the Epoch of Reionization

    NASA Astrophysics Data System (ADS)

    Park(박 현배, Hyunbae; Shapiro, Paul R.; Choi, Jun-hwan; Yoshida, Naoki; Hirano, Shingo; Ahn, Kyungjin

    2016-11-01

    Density inhomogeneity in the intergalactic medium (IGM) can boost the recombination rate of ionized gas substantially, affecting the growth of H ii regions during reionization. Previous attempts to quantify this effect typically failed to resolve down to the Jeans scale in the preionization IGM, which is important in establishing this effect, along with the hydrodynamical back-reaction of reionization on it. Toward that end, we perform a set of fully coupled, radiation-hydrodynamics simulations from cosmological initial conditions, extending the mass resolution of previous work to the scale of minihalos. Pre-reionization structure is evolved until a redshift z i at which the ionizing radiation from external sources arrives to sweep an R-type ionization front supersonically across the volume in a few million years, until it is trapped on the surfaces of minihalos and converted to D-type, after which the minihalo gas is removed by photoevaporative winds. Small-scale density structures during this time lead to a high (>10) clumping factor for ionized gas, which hugely boosts the recombination rate until the structures are disrupted by the hydrodynamic feedback after ∼10–100 Myr. For incoming stellar radiation with intensity J 21 in a 200 h ‑1 kpc box with the mean density contrast \\bar{δ }, the number of extra recombinations per H atom, on top of what is expected from homogeneously distributed gas, is given by 0.32{[{J}21]}0.12{[(1+{z}i)/11]}-1.7{[1+\\bar{δ }]}2.5. In models in which most of the volume is ionized toward the end of reionization, this can add more than one recombination per H atom to the ionizing photon budget to achieve reionization.

  17. APEX/SABOCA observations of small-scale structure of infrared-dark clouds . I. Early evolutionary stages of star-forming cores

    NASA Astrophysics Data System (ADS)

    Ragan, Sarah E.; Henning, Thomas; Beuther, Henrik

    2013-11-01

    Infrared-dark clouds (IRDCs) harbor the early phases of cluster and high-mass star formation and are comprised of cold (~20 K), dense (n > 104 cm-3) gas. The spectral energy distribution (SED) of IRDCs is dominated by the far-infrared and millimeter wavelength regime, and our initial Herschel study examined IRDCs at the peak of the SED with high angular resolution. Here we present a follow-up study using the SABOCA instrument on APEX which delivers 7.8″ angular resolution at 350 μm, matching the resolution we achieved with Herschel/PACS, and allowing us to characterize substructure on ~0.1 pc scales. Our sample of 11 nearby IRDCs are a mix of filamentary and clumpy morphologies, and the filamentary clouds show significant hierarchical structure, while the clumpy IRDCs exhibit little hierarchical structure. All IRDCs, regardless of morphology, have about 14% of their total mass in small scale core-like structures which roughly follow a trend of constant volume density over all size scales. Out of the 89 protostellar cores we identified in this sample with Herschel, we recover 40 of the brightest and re-fit their SEDs and find their properties agree fairly well with our previous estimates (⟨ T ⟩ ~ 19 K). We detect a new population of "cold cores" which have no 70 μm counterpart, but are 100 and 160 μm-bright, with colder temperatures (⟨ T ⟩ ~ 16 K). This latter population, along with SABOCA-only detections, are predominantly low-mass objects, but their evolutionary diagnostics are consistent with the earliest starless or prestellar phase of cores in IRDCs. Based on observations carried out with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between Max Planck Institut für Radioastronomie (MPIfR), Onsala Space Observatory (OSO), and the European Southern Observatory (ESO).Appendices are available in electronic form at http://www.aanda.org

  18. Cosmic string wakes and large-scale structure

    NASA Technical Reports Server (NTRS)

    Charlton, Jane C.

    1988-01-01

    The formation of structure from infinite cosmic string wakes is modeled for a universe dominated by cold dark matter (CDM). Cross-sectional slices through the wake distribution tend to outline empty regions with diameters which are not inconsistent with the range of sizes of the voids in the CfA slice of the universe. The topology of the wake distribution is found to be spongy rather than cell-like. Correlations between CDM wakes do not extend much beyond a horizon length, so it is unlikely that CDM wakes are responsible for the correlations between clusters of galaxies. An estimate of the fraction of matter to accrete onto CDM wakes indicates that wakes could be more important in galaxy formation than previously anticipated.

  19. Text string detection from natural scenes by structure-based partition and grouping.

    PubMed

    Yi, Chucai; Tian, YingLi

    2011-09-01

    Text information in natural scene images serves as important clues for many image-based applications such as scene understanding, content-based image retrieval, assistive navigation, and automatic geocoding. However, locating text from a complex background with multiple colors is a challenging task. In this paper, we explore a new framework to detect text strings with arbitrary orientations in complex natural scene images. Our proposed framework of text string detection consists of two steps: 1) image partition to find text character candidates based on local gradient features and color uniformity of character components and 2) character candidate grouping to detect text strings based on joint structural features of text characters in each text string such as character size differences, distances between neighboring characters, and character alignment. By assuming that a text string has at least three characters, we propose two algorithms of text string detection: 1) adjacent character grouping method and 2) text line grouping method. The adjacent character grouping method calculates the sibling groups of each character candidate as string segments and then merges the intersecting sibling groups into text string. The text line grouping method performs Hough transform to fit text line among the centroids of text candidates. Each fitted text line describes the orientation of a potential text string. The detected text string is presented by a rectangle region covering all characters whose centroids are cascaded in its text line. To improve efficiency and accuracy, our algorithms are carried out in multi-scales. The proposed methods outperform the state-of-the-art results on the public Robust Reading Dataset, which contains text only in horizontal orientation. Furthermore, the effectiveness of our methods to detect text strings with arbitrary orientations is evaluated on the Oriented Scene Text Dataset collected by ourselves containing text strings in nonhorizontal

  20. Cosmic strings and superconducting cosmic strings

    NASA Technical Reports Server (NTRS)

    Copeland, Edmund

    1988-01-01

    The possible consequences of forming cosmic strings and superconducting cosmic strings in the early universe are discussed. Lecture 1 describes the group theoretic reasons for and the field theoretic reasons why cosmic strings can form in spontaneously broken gauge theories. Lecture 2 discusses the accretion of matter onto string loops, emphasizing the scenario with a cold dark matter dominated universe. In lecture 3 superconducting cosmic strings are discussed, as is a mechanism which leads to the formation of structure from such strings.

  1. Simulation of large scale motions and small scale structures in planetary atmospheres and oceans: From laboratory to space experiments on ISS

    NASA Astrophysics Data System (ADS)

    Egbers, Christoph; Futterer, Birgit; Zaussinger, Florian; Harlander, Uwe

    2014-05-01

    Baroclinic waves are responsible for the transport of heat and momentum in the oceans, in the Earth's atmosphere as well as in other planetary atmospheres. The talk will give an overview on possibilities to simulate such large scale as well as co-existing small scale structures with the help of well defined laboratory experiments like the baroclinic wave tank (annulus experiment). The analogy between the Earth's atmosphere and the rotating cylindrical annulus experiment only driven by rotation and differential heating between polar and equatorial regions is obvious. From the Gulf stream single vortices seperate from time to time. The same dynamics and the co-existence of small and large scale structures and their separation can be also observed in laboratory experiments as in the rotating cylindrical annulus experiment. This experiment represents the mid latitude dynamics quite well and is part as a central reference experiment in the German-wide DFG priority research programme ("METSTRÖM", SPP 1276) yielding as a benchmark for lot of different numerical methods. On the other hand, those laboratory experiments in cylindrical geometry are limited due to the fact, that the surface and real interaction between polar and equatorial region and their different dynamics can not be really studied. Therefore, I demonstrate how to use the very successful Geoflow I and Geoflow II space experiment hardware on ISS with future modifications for simulations of small and large scale planetary atmospheric motion in spherical geometry with differential heating between inner and outer spheres as well as between the polar and equatorial regions. References: Harlander, U., Wenzel, J., Wang, Y., Alexandrov, K. & Egbers, Ch., 2012, Simultaneous PIV- and thermography measurements of partially blocked flow in a heated rotating annulus, Exp. in Fluids, 52 (4), 1077-1087 Futterer, B., Krebs, A., Plesa, A.-C., Zaussinger, F., Hollerbach, R., Breuer, D. & Egbers, Ch., 2013, Sheet-like and

  2. On Ramachandran angles, closed strings and knots in protein structure

    NASA Astrophysics Data System (ADS)

    Chen, Si; Niemi, Antti J.

    2016-08-01

    The Ramachandran angles (φ,\\psi ) of a protein backbone form the vertices of a piecewise geodesic curve on the surface of a torus. When the ends of the curve are connected to each other similarly, by a geodesic, the result is a closed string that in general wraps around the torus a number of times both in the meridional and the longitudinal directions. The two wrapping numbers are global characteristics of the protein structure. A statistical analysis of the wrapping numbers in terms of crystallographic x-ray structures in the protein data bank (PDB) reveals that proteins have no net chirality in the ϕ direction but in the ψ direction, proteins prefer to display chirality. A comparison between the wrapping numbers and the concept of folding index discloses a non-linearity in their relationship. Thus these three integer valued invariants can be used in tandem, to scrutinize and classify the global loop structure of individual PDB proteins, in terms of the overall fold topology.

  3. String mediated phase transitions

    NASA Technical Reports Server (NTRS)

    Copeland, ED; Haws, D.; Rivers, R.; Holbraad, S.

    1988-01-01

    It is demonstrated from first principles how the existence of string-like structures can cause a system to undergo a phase transition. In particular, the role of topologically stable cosmic string in the restoration of spontaneously broken symmetries is emphasized. How the thermodynamic properties of strings alter when stiffness and nearest neighbor string-string interactions are included is discussed.

  4. Spider silk violin strings with a unique packing structure generate a soft and profound timbre.

    PubMed

    Osaki, Shigeyoshi

    2012-04-13

    We overcome the difficulties in pulling long draglines from spiders, twist bundles of dragline filaments, and succeed in preparing violin strings. The twisting is found to change the cross section shapes of filaments from circular to polygonal and to optimize the packing structure with no openings among filaments providing mechanically strong and elastic strings. The spider string signal peaks of overtones for the violin are relatively large at high frequencies, generating a soft and profound timbre. Such a preferable timbre is considered to be due to the unique polygonal packing structure which provides valuable knowledge for developing new types of materials. PMID:22587257

  5. Spider Silk Violin Strings with a Unique Packing Structure Generate a Soft and Profound Timbre

    NASA Astrophysics Data System (ADS)

    Osaki, Shigeyoshi

    2012-04-01

    We overcome the difficulties in pulling long draglines from spiders, twist bundles of dragline filaments, and succeed in preparing violin strings. The twisting is found to change the cross section shapes of filaments from circular to polygonal and to optimize the packing structure with no openings among filaments providing mechanically strong and elastic strings. The spider string signal peaks of overtones for the violin are relatively large at high frequencies, generating a soft and profound timbre. Such a preferable timbre is considered to be due to the unique polygonal packing structure which provides valuable knowledge for developing new types of materials.

  6. Spider silk violin strings with a unique packing structure generate a soft and profound timbre.

    PubMed

    Osaki, Shigeyoshi

    2012-04-13

    We overcome the difficulties in pulling long draglines from spiders, twist bundles of dragline filaments, and succeed in preparing violin strings. The twisting is found to change the cross section shapes of filaments from circular to polygonal and to optimize the packing structure with no openings among filaments providing mechanically strong and elastic strings. The spider string signal peaks of overtones for the violin are relatively large at high frequencies, generating a soft and profound timbre. Such a preferable timbre is considered to be due to the unique polygonal packing structure which provides valuable knowledge for developing new types of materials.

  7. Annotating the structure and components of a nanoparticle formulation using computable string expressions.

    PubMed

    Thomas, Dennis G; Chikkagoudar, Satish; Chappell, Alan R; Baker, Nathan A

    2012-12-31

    Nanoparticle formulations that are being developed and tested for various medical applications are typically multi-component systems that vary in their structure, chemical composition, and function. It is difficult to compare and understand the differences between the structural and chemical descriptions of hundreds and thousands of nanoparticle formulations found in text documents. We have developed a string nomenclature to create computable string expressions that identify and enumerate the different high-level types of material parts of a nanoparticle formulation and represent the spatial order of their connectivity to each other. The string expressions are intended to be used as IDs, along with terms that describe a nanoparticle formulation and its material parts, in data sharing documents and nanomaterial research databases. The strings can be parsed and represented as a directed acyclic graph. The nodes of the graph can be used to display the string ID, name and other text descriptions of the nanoparticle formulation or its material part, while the edges represent the connectivity between the material parts with respect to the whole nanoparticle formulation. The different patterns in the string expressions can be searched for and used to compare the structure and chemical components of different nanoparticle formulations. The proposed string nomenclature is extensible and can be applied along with ontology terms to annotate the complete description of nanoparticles formulations.

  8. The large- and small-scale Ca II K structure of the Milky Way from observations of Galactic and Magellanic sightlines⋆

    NASA Astrophysics Data System (ADS)

    Smoker, J. V.; Keenan, F. P.; Fox, A. J.

    2015-10-01

    Aims: The large and small-scale (pc) structure of the Galactic interstellar medium can be investigated by utilising spectra of early-type stellar probes of known distances in the same region of the sky. This paper determines the variation in line strength of Ca ii at 3933.661 Å as a function of probe separation for a large sample of stars, including a number of sightlines in the Magellanic Clouds. Methods: FLAMES-GIRAFFE data taken with the Very Large Telescope towards early-type stars in 3 Galactic and 4 Magellanic open clusters in Ca ii are used to obtain the velocity, equivalent width, column density, and line width of interstellar Galactic calcium for a total of 657 stars, of which 443 are Magellanic Cloud sightlines. In each cluster there are between 43 and 111 stars observed. Additionally, FEROS and UVES Ca ii K and Na i D spectra of 21 Galactic and 154 Magellanic early-type stars are presented and combined with data from the literature to study the calcium column density - parallax relationship. Results: For the four Magellanic clusters studied with FLAMES, the strength of the Galactic interstellar Ca ii K equivalent width on transverse scales from ~0.05-9 pc is found to vary by factors of ~1.8-3.0, corresponding to column density variations of ~0.3-0.5 dex in the optically-thin approximation. Using FLAMES, FEROS, and UVES archive spectra, the minimum and maximum reduced equivalent widths for Milky Way gas are found to lie in the range ~35-125 mÅ and ~30-160 mÅ for Ca ii K and Na i D, respectively. The range is consistent with a previously published simple model of the interstellar medium consisting of spherical cloudlets of filling factor ~0.3, although other geometries are not ruled out. Finally, the derived functional form for parallax (π) and Ca ii column density (NCaII) is found to be π(mas) = 1 / (2.39 × 10-13 × NCaII (cm-2) + 0.11). Our derived parallax is ~25 per cent lower than predicted by Megier et al. (2009, A&A, 507, 833) at a distance of

  9. The structural dynamics of the American five-string banjo.

    PubMed

    Dickey, Joe

    2003-11-01

    The American five-string banjo is unique among musical instruments in that many significant parameters that effect tone are easily adjusted. This is probably why so many banjo players fiddle with their banjo. The instrument is a combination of canonical vibrating systems (strings, and a circular membrane) and therefore more amenable to analysis and modeling than most other musical instruments (e.g., the violin). Such an analysis is presented here. The model is a harmonically driven string which excites the other strings and a membrane under tension, causing the membrane to radiate sound. Three figures-of-merit, FOMs, are assumed. They are loudness, brightness, and decay of the sound. The effects of a number of parameters on the proposed FOMs are investigated. Among these are the loss factor and tension of the membrane, the mass of the bridge, and the location on the string of the excitation. It is noted that the calculated effects of the changes agree with generally accepted setup practices. PMID:14650029

  10. Note on structure formation from cosmic string wakes

    SciTech Connect

    Duplessis, Francis; Brandenberger, Robert E-mail: rhb@physics.mcgill.ca

    2013-04-01

    The search for cosmic strings has been of renewed interest with the advent of precision cosmology. In this note we give a quantitative description of the nonlinear matter density fluctuations that can form from a scaling network of cosmic string wakes. Specifically, we compute the distribution of dark matter halos. These halos would possess strong correlations in position space that should have survived until today. We also discuss the challenges involved in their detection due to their small size and the complex dynamics of their formation.

  11. Small scale folding observed in the NEEM ice core

    NASA Astrophysics Data System (ADS)

    Jansen, Daniela; Llorens, Maria-Gema; Westhoff, Julien; Steinbach, Florian; Bons, Paul D.; Kipfstuhl, Sepp; Griera, Albert; Weikusat, Ilka

    2015-04-01

    Disturbances on the centimeter scale in the layering of the NEEM ice core (North Greenland) can be mapped by means of visual stratigraphy as long as the ice does have a visual layering, such as, for example, cloudy bands. Different focal depths of the visual stratigraphy method allow, to a certain extent, a three dimensional view of the structures. In this study we present a structural analysis of the visible folds, discuss characteristics and frequency and present examples of typical fold structures. With this study we aim to quantify the potential impact of small scale folding on the integrity of climate proxy data. We also analyze the structures with regard to the stress environment under which they formed. The structures evolve from gentle waves at about 1700 m to overturned z-folds with increasing depth. Occasionally, the folding causes significant thickening of layers. Their shape indicates that they are passive features and are probably not initiated by rheology differences between layers. Layering is heavily disturbed and tracing of single layers is no longer possible below a depth of 2160 m. Lattice orientation distributions for the corresponding core sections were analyzed where available in addition to visual stratigraphy. The data show axial-plane parallel strings of grains with c.axis orientations that deviate from that of the matrix, which has more or less a single-maximum fabric at the depth where the folding occurs. We conclude from these data that folding is a consequence of deformation along localized shear planes and kink bands. The findings are compared with results from other deep ice cores. The observations presented are supplemented by microstructural modeling using a crystal plasticity code that reproduces deformation, applying a Fast Fourier Transform (FFT), coupled with ELLE to include dynamic recrystallization processes. The model results reproduce the development of bands of grains with a tilted orientation relative to the single maximum

  12. Philippines: Small-scale renewable energy update

    SciTech Connect

    1997-12-01

    This paper gives an overview of the application of small scale renewable energy sources in the Philippines. Sources looked at include solar, biomass, micro-hydroelectric, mini-hydroelectric, wind, mini-geothermal, and hybrid. A small power utilities group is being spun off the major utility, to provide a structure for developing rural electrification programs. In some instances, private companies have stepped forward, avoiding what is perceived as overwhelming beaurocracy, and installed systems with private financing. The paper provides information on survey work which has been done on resources, and the status of cooperative programs to develop renewable systems in the nation.

  13. On the large-scale structures formed by wakes of open cosmic strings

    NASA Technical Reports Server (NTRS)

    Hara, Tetsuya; Morioka, Shoji; Miyoshi, Shigeru

    1990-01-01

    Large-scale structures of the universe have been variously described as sheetlike, filamentary, cellular, bubbles or spongelike. Recently cosmic strings became one of viable candidates for a galaxy formation scenario, and some of the large-scale structures seem to be simply explained by the open cosmic strings. According to this scenario, sheets are wakes which are traces of moving open cosmic strings where dark matter and baryonic matter have accumulated. Filaments are intersections of such wakes and high density regions are places where three wakes intersect almost orthogonally. The wakes formed at t sub eq become the largest surface density among all wakes, where t sub eq is the epoch when matter density equals to radiation density. If we assume that there is one open cosmic string per each horizon, then it can be explained that the typical distances among wakes, filaments and clusters are also approx. 10(exp 2) Mpc. This model does not exclude a much more large scale structure. Open cosmic string may move even now and accumulate cold dark matter after its traces. However, the surface density is much smaller than the ones formed at t sub eq. From this model, it is expected that the typical high density region will have extended features such as six filaments and three sheets and be surrounded by eight empty regions (voids). Here, the authors are mainly concerned with such structures and have made numerical simulations for the formation of such large scale structures.

  14. ``Short'' spinning strings and structure of quantum AdS5×S5 spectrum

    NASA Astrophysics Data System (ADS)

    Beccaria, M.; Giombi, S.; Macorini, G.; Roiban, R.; Tseytlin, A. A.

    2012-09-01

    Using information from the marginality conditions of vertex operators for the AdS5×S5 superstring, we determine the structure of the dependence of the energy of quantum string states on their conserved charges and the string tension ˜λ. We consider states on the leading Regge trajectory in the flat space limit which carry one or two (equal) spins in AdS5 or S5 and an orbital momentum in S5, with Konishi multiplet states being particular cases. We argue that the coefficients in the energy may be found by using a semiclassical expansion. By analyzing the examples of folded spinning strings in AdS5 and S5, as well as three cases of circular two-spin strings, we demonstrate the universality of transcendental (zeta-function) parts of few leading coefficients. We also show the consistency with target space supersymmetry with different states belonging to the same multiplet having the same nontrivial part of the energy. We suggest, in particular, that a rational coefficient (found by Basso for the folded string using Bethe Ansatz considerations and which, in general, is yet to be determined by a direct two-loop string calculation) should, in fact, be universal.

  15. Effects of cosmic strings on free streaming

    SciTech Connect

    Takahashi, Tomo; Yamaguchi, Masahide

    2006-09-15

    We study the effect of free streaming in a universe with cosmic strings with time-varying tension as well as with constant tension. Although current cosmological observations suggest that fluctuation seeded by cosmic strings cannot be the primary source of cosmic density fluctuation, some contributions from them are still allowed. Since cosmic strings actively produce isocurvature fluctuation, the damping of small scale structure via free streaming by dark matter particles with large velocity dispersion at the epoch of radiation-matter equality is less efficient than that in models with conventional adiabatic fluctuation. We discuss its implications to the constraints on the properties of particles such as massive neutrinos and warm dark matter.

  16. Structure formation in a string-inspired modification of the cold dark matter model

    SciTech Connect

    Gubser, Steven S.; Peebles, P.J.E.

    2004-12-15

    Motivated in part by string theory, we consider the idea that the standard {lambda}CDM cosmological model might be modified by the effect of a long-range scalar dark matter interaction. The variant of this widely-discussed notion considered here is suggested by the Brandenberger-Vafa [R. H. Brandenberger and C. Vafa, Nucl. Phys. B316, 391 (1989).] picture for why we perceive three spatial dimensions. In this picture there may be at least two species of dark matter particles, with scalar charges such that the scalar interaction attracts particles with like sign and repels unlike signs. The net charge vanishes. Under this condition the evolution of the mass distribution in linear perturbation theory is the same as in the {lambda}CDM cosmology, and both models therefore can equally well pass the available cosmological tests. The physics can be very different on small scales, however: if the scalar interaction has the strength suggested by simple versions of the string scenario, nonlinear mass concentrations are unstable against separation into charged halos with properties unlike the standard model prediction and possibly of observational interest.

  17. Structure formation in a string-inspired modification of the cold dark matter model

    NASA Astrophysics Data System (ADS)

    Gubser, Steven S.; Peebles, P. J. E.

    2004-12-01

    Motivated in part by string theory, we consider the idea that the standard ΛCDM cosmological model might be modified by the effect of a long-range scalar dark matter interaction. The variant of this widely-discussed notion considered here is suggested by the Brandenberger-Vafa [R. H. BrandenbergerC. Vafa, Nucl. Phys.B3161989391] picture for why we perceive three spatial dimensions. In this picture there may be at least two species of dark matter particles, with scalar charges such that the scalar interaction attracts particles with like sign and repels unlike signs. The net charge vanishes. Under this condition the evolution of the mass distribution in linear perturbation theory is the same as in the ΛCDM cosmology, and both models therefore can equally well pass the available cosmological tests. The physics can be very different on small scales, however: if the scalar interaction has the strength suggested by simple versions of the string scenario, nonlinear mass concentrations are unstable against separation into charged halos with properties unlike the standard model prediction and possibly of observational interest.

  18. A small-scale turbulence model

    NASA Technical Reports Server (NTRS)

    Lundgren, T. S.

    1992-01-01

    A model for the small-scale structure of turbulence is reformulated in such a way that it may be conveniently computed. The model is an ensemble of randomly oriented structured two dimensional vortices stretched by an axially symmetric strain flow. The energy spectrum of the resulting flow may be expressed as a time integral involving only the enstrophy spectrum of the time evolving two-dimensional cross section flow, which may be obtained numerically. Examples are given in which a k(exp -5/3) spectrum is obtained by this method without using large wave number asymptotic analysis. The k(exp -5/3) inertial range spectrum is shown to be related to the existence of a self-similar enstrophy preserving range in the two-dimensional enstrophy spectrum. The results are insensitive to time dependence of the strain-rate, including even intermittent on-or-off strains.

  19. Axions, neutrinos and strings - The formation of structure in an SO(10) universe

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    1986-01-01

    In a class of grand unified theories containing SO(10), cosmologically significant axion and neutrino energy densities are obtainable naturally. To obtain large scale structure, both components of dark matter are considered to exist with comparable energy densities. To obtain large scale structure, inflationary and non-inflationary scenarios are considered, as well as scenarios with and without vacuum strings. It is shown that inflation may be compatible with recent observations of the mass density within galaxy clusters and superclusters, especially if strings are present.

  20. Axions, neutrinos and strings: The formation of structure in an SO(10) universe

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    1984-01-01

    In a class of grand unified theories containing SO(10), cosmologically significant axion and neutrino energy densities are obtainable naturally. To obtain large scale structure, both components of dark matter are considered to exist with comparable energy densities. To obtain large scale structure, inflationary and non-inflationary scenarios are considered, as well as scenarios with and without vacuum strings. It is shown that inflation may be compatible with recent observations of the mass density within galaxy clusters and superclusters, especially if strings are present.

  1. A High-Resolution X-Ray and Optical Study of SN1006: Asymmetric Expansion and Small-Scale Structure in a Type Ia Supernova Remnant

    NASA Technical Reports Server (NTRS)

    Winkler, P. Frank; Williams, Brian J.; Reynolds, Stephen P.; Petre, Robert; Long, Knox S.; Katsuda, Satoru; Hwang, Una

    2014-01-01

    We introduce a deep (670 ks) X-ray survey of the entire SN 1006 remnant from the Chandra X-Ray Observatory, together with a deep Ha image of SN 1006 from the 4 m Blanco telescope at CTIO. Comparison with Chandra images from 2003 gives the first measurement of the X-ray proper motions around the entire periphery, carried out over a 9 yr baseline. We find that the expansion velocity varies significantly with azimuth. The highest velocity of approx.7400 km/s (almost 2.5 times that in the northwest (NW)) is found along the southeast (SE) periphery, where both the kinematics and the spectra indicate that most of the X-ray emission stems from ejecta that have been decelerated little, if at all. Asymmetries in the distribution of ejecta are seen on a variety of spatial scales. Si-rich ejecta are especially prominent in the SE quadrant, while O and Mg are more uniformly distributed, indicating large-scale asymmetries arising from the explosion itself. Neon emission is strongest in a sharp filament just behind the primary shock along the NWrim, where the pre-shock density is highest. Here the Ne is likely interstellar, while Ne within the shell may include a contribution from ejecta. Within the interior of the projected shell we find a few isolated "bullets" of what appear to be supernova ejecta that are immediately preceded by bowshocks seen in Ha, features that we interpret as ejecta knots that have reached relatively dense regions of the surrounding interstellar medium, but that appear in the interior in projection. Recent three-dimensional hydrodynamic models for Type Ia supernovae display small-scale features that strongly resemble the ones seen in X-rays in SN 1006; an origin in the explosion itself or from subsequent hydrodynamic instabilities both remain viable options. We have expanded the search for precursor X-ray emission ahead of a synchrotron-dominated shock front, as expected from diffusive shock acceleration theory, to numerous regions along both the

  2. APOGEE strings: A fossil record of the gas kinematic structure

    NASA Astrophysics Data System (ADS)

    Hacar, A.; Alves, J.; Forbrich, J.; Meingast, S.; Kubiak, K.; Großschedl, J.

    2016-05-01

    We compare APOGEE radial velocities (RVs) of young stars in the Orion A cloud with CO line gas emission and find a correlation between the two at large scales in agreement with previous studies. However, at smaller scales we find evidence for the presence of a substructure in the stellar velocity field. Using a friends-of-friends approach we identify 37 stellar groups with almost identical RVs. These groups are not randomly distributed, but form elongated chains or strings of stars with five or more members with low velocity dispersion across lengths of 1-1.5 pc. The similarity between the kinematic properties of the APOGEE strings and the internal velocity field of the chains of dense cores and fibers recently identified in the dense interstellar medium is striking and suggests that for most of the Orion A cloud, young stars keep memory of the parental gas substructure where they originated. Full Table 2 is only available 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/589/A80

  3. Investigating dark matter substructure with pulsar timing - II. Improved limits on small-scale cosmology

    NASA Astrophysics Data System (ADS)

    Clark, Hamish A.; Lewis, Geraint F.; Scott, Pat

    2016-02-01

    Ultracompact minihaloes (UCMHs) have been proposed as a type of dark matter substructure seeded by large-amplitude primordial perturbations and topological defects. UCMHs are expected to survive to the present era, allowing constraints to be placed on their cosmic abundance using observations within our own Galaxy. Constraints on their number density can be linked to conditions in the early Universe that impact structure formation, such as increased primordial power on small scales, generic weak non-Gaussianity, and the presence of cosmic strings. We use new constraints on the abundance of UCMHs from pulsar timing to place generalized limits on the parameters of each of these cosmological scenarios. At some scales, the limits are the strongest to date, exceeding those from dark matter annihilation. Our new limits have the added advantage of being independent of the particle nature of dark matter, as they are based only on gravitational effects.

  4. Practical small-scale explosive seam welding

    NASA Technical Reports Server (NTRS)

    Bement, L. J.

    1983-01-01

    A small-scale explosive seam welding process has been developed that can significantly contribute to remote metal joining operations under hazardous or inaccessible conditions, such as nuclear reactor repair and assembly of structure in space. This paper describes this explosive seam welding process in terms of joining principles, variables, types of joints created, capabilities, and applications. Very small quantities of explosive in a ribbon configuration are used to create narrow (less than 0.5 inch), long-length, uniform, hermetically sealed joints that exhibit parent metal properties in a wide variety of metals, alloys, and combinations. The practicality of this process has been demonstrated by its current acceptance, as well as its capabilities that are superior in many applications to the universally accepted joining processes, such as mechanical fasteners, fusion and resistance welding, and adhesives.

  5. Supersymmetric structure of the bosonic string theory in the Beltrami parametrization

    NASA Astrophysics Data System (ADS)

    de Oliveira, M. Werneck; Schweda, M.; Sorella, S. P.

    1993-09-01

    We show that the bosonic string theory quantized in the Beltrami parametrization possesses a supersymmetric structure like the vector-supersymmetry already observed in topological field theories. Supported in part by the ``Fonds zur Förderung der Wissenschaftlichen Forschung'', M008-Lise Meitner Fellowship.

  6. Cold dark matter: Controversies on small scales

    PubMed Central

    Weinberg, David H.; Bullock, James S.; Governato, Fabio; Kuzio de Naray, Rachel; Peter, Annika H. G.

    2015-01-01

    The cold dark matter (CDM) cosmological model has been remarkably successful in explaining cosmic structure over an enormous span of redshift, but it has faced persistent challenges from observations that probe the innermost regions of dark matter halos and the properties of the Milky Way’s dwarf galaxy satellites. We review the current observational and theoretical status of these “small-scale controversies.” Cosmological simulations that incorporate only gravity and collisionless CDM predict halos with abundant substructure and central densities that are too high to match constraints from galaxy dynamics. The solution could lie in baryonic physics: Recent numerical simulations and analytical models suggest that gravitational potential fluctuations tied to efficient supernova feedback can flatten the central cusps of halos in massive galaxies, and a combination of feedback and low star formation efficiency could explain why most of the dark matter subhalos orbiting the Milky Way do not host visible galaxies. However, it is not clear that this solution can work in the lowest mass galaxies, where discrepancies are observed. Alternatively, the small-scale conflicts could be evidence of more complex physics in the dark sector itself. For example, elastic scattering from strong dark matter self-interactions can alter predicted halo mass profiles, leading to good agreement with observations across a wide range of galaxy mass. Gravitational lensing and dynamical perturbations of tidal streams in the stellar halo provide evidence for an abundant population of low-mass subhalos in accord with CDM predictions. These observational approaches will get more powerful over the next few years. PMID:25646464

  7. Cold dark matter: Controversies on small scales.

    PubMed

    Weinberg, David H; Bullock, James S; Governato, Fabio; Kuzio de Naray, Rachel; Peter, Annika H G

    2015-10-01

    The cold dark matter (CDM) cosmological model has been remarkably successful in explaining cosmic structure over an enormous span of redshift, but it has faced persistent challenges from observations that probe the innermost regions of dark matter halos and the properties of the Milky Way's dwarf galaxy satellites. We review the current observational and theoretical status of these "small-scale controversies." Cosmological simulations that incorporate only gravity and collisionless CDM predict halos with abundant substructure and central densities that are too high to match constraints from galaxy dynamics. The solution could lie in baryonic physics: Recent numerical simulations and analytical models suggest that gravitational potential fluctuations tied to efficient supernova feedback can flatten the central cusps of halos in massive galaxies, and a combination of feedback and low star formation efficiency could explain why most of the dark matter subhalos orbiting the Milky Way do not host visible galaxies. However, it is not clear that this solution can work in the lowest mass galaxies, where discrepancies are observed. Alternatively, the small-scale conflicts could be evidence of more complex physics in the dark sector itself. For example, elastic scattering from strong dark matter self-interactions can alter predicted halo mass profiles, leading to good agreement with observations across a wide range of galaxy mass. Gravitational lensing and dynamical perturbations of tidal streams in the stellar halo provide evidence for an abundant population of low-mass subhalos in accord with CDM predictions. These observational approaches will get more powerful over the next few years.

  8. Cold dark matter: Controversies on small scales

    NASA Astrophysics Data System (ADS)

    Weinberg, David H.; Bullock, James S.; Governato, Fabio; Kuzio de Naray, Rachel; Peter, Annika H. G.

    2015-10-01

    The cold dark matter (CDM) cosmological model has been remarkably successful in explaining cosmic structure over an enormous span of redshift, but it has faced persistent challenges from observations that probe the innermost regions of dark matter halos and the properties of the Milky Way's dwarf galaxy satellites. We review the current observational and theoretical status of these "small-scale controversies." Cosmological simulations that incorporate only gravity and collisionless CDM predict halos with abundant substructure and central densities that are too high to match constraints from galaxy dynamics. The solution could lie in baryonic physics: Recent numerical simulations and analytical models suggest that gravitational potential fluctuations tied to efficient supernova feedback can flatten the central cusps of halos in massive galaxies, and a combination of feedback and low star formation efficiency could explain why most of the dark matter subhalos orbiting the Milky Way do not host visible galaxies. However, it is not clear that this solution can work in the lowest mass galaxies, where discrepancies are observed. Alternatively, the small-scale conflicts could be evidence of more complex physics in the dark sector itself. For example, elastic scattering from strong dark matter self-interactions can alter predicted halo mass profiles, leading to good agreement with observations across a wide range of galaxy mass. Gravitational lensing and dynamical perturbations of tidal streams in the stellar halo provide evidence for an abundant population of low-mass subhalos in accord with CDM predictions. These observational approaches will get more powerful over the next few years.

  9. Cold dark matter: Controversies on small scales.

    PubMed

    Weinberg, David H; Bullock, James S; Governato, Fabio; Kuzio de Naray, Rachel; Peter, Annika H G

    2015-10-01

    The cold dark matter (CDM) cosmological model has been remarkably successful in explaining cosmic structure over an enormous span of redshift, but it has faced persistent challenges from observations that probe the innermost regions of dark matter halos and the properties of the Milky Way's dwarf galaxy satellites. We review the current observational and theoretical status of these "small-scale controversies." Cosmological simulations that incorporate only gravity and collisionless CDM predict halos with abundant substructure and central densities that are too high to match constraints from galaxy dynamics. The solution could lie in baryonic physics: Recent numerical simulations and analytical models suggest that gravitational potential fluctuations tied to efficient supernova feedback can flatten the central cusps of halos in massive galaxies, and a combination of feedback and low star formation efficiency could explain why most of the dark matter subhalos orbiting the Milky Way do not host visible galaxies. However, it is not clear that this solution can work in the lowest mass galaxies, where discrepancies are observed. Alternatively, the small-scale conflicts could be evidence of more complex physics in the dark sector itself. For example, elastic scattering from strong dark matter self-interactions can alter predicted halo mass profiles, leading to good agreement with observations across a wide range of galaxy mass. Gravitational lensing and dynamical perturbations of tidal streams in the stellar halo provide evidence for an abundant population of low-mass subhalos in accord with CDM predictions. These observational approaches will get more powerful over the next few years. PMID:25646464

  10. Small-scale sedimentary structures and their implications in recognizing large-scale ancient tidal bedforms. Example from Dur At Talah outcrop, Late Eocene, Sirt Basin, Libya

    NASA Astrophysics Data System (ADS)

    Abouessa, Ashour; Duringer, Philippe; Schuster, Mathieu; Pelletier, Jonathan; Rubino, Jean-Loup

    2014-12-01

    The Dur At Talah escarpment (150 m thick and 150 km long) is exposed at the southern side of the Sirt Basin, central Libya. This outcrop exposes an Upper Eocene succession, composed by highly bioturbated fine grained sandstones to claystones at the base (New Idam Unit; 80-100 m thick), overlain by medium grained to microconglomeratic sandstones at the top (Sarir Unit; 60 m thick). The latter is split into two subunits of nearly equal thickness: the lower Sarir subunit, composed of medium to coarse cross-bedded sandstones; and the upper Sarir subunit, composed of very coarse to microconglomeratic sandstones. The whole succession evolves from shallow marine estuarine (the New Idam Unit) to fluvial deposits (the upper Sarir subunit). The sandstone of the lower Sarir subunit, which is the focus of this article, is previously misinterpreted as being deposited in a purely fluvial environment. However, close observations revealed that the depositional environment is largely tide-influenced. It is notably marked by conspicuous subaqueous dune cross-stratifications that bear a variety of discrete, multi-scale, sedimentary structures evidencing their deposition in tidal rather than fluvial setting. Mud drapes, tidal bundles, and perpendicularly draining and oppositely climbing ripples are largely developed. Among these structures, the most diagnostic are of millimetric to centimetric scale. As a prime aim of this article, all these sedimentary structures are described, interpreted, and discussed for the first time from this outcrop. Their style of association and the quality of their preservation provide an outstanding ancient example of tide-dominated siliciclastic systems. Such structures are rarely found together in one outcrop as they are in Dur At Talah, and they provide a significant indicators in identifying ancient bedforms of tidal origin. Evidences of subtidal and intertidal depositional environments are afforded by these structures. Criteria indicative of

  11. Three-dimensional simulations of near-surface convection in main-sequence stars. III. The structure of small-scale magnetic flux concentrations

    NASA Astrophysics Data System (ADS)

    Beeck, B.; Schüssler, M.; Cameron, R. H.; Reiners, A.

    2015-09-01

    Context. The convective envelopes of cool main-sequence stars harbour magnetic fields with a complex global and local structure. These fields affect the near-surface convection and the outer stellar atmospheres in many ways and are responsible for the observable magnetic activity of stars. Aims: Our aim is to understand the local structure in unipolar regions with moderate average magnetic flux density. These correspond to plage regions covering a substantial fraction of the surface of the Sun (and likely also the surface of other Sun-like stars) during periods of high magnetic activity. Methods: We analyse the results of 18 local-box magnetohydrodynamics simulations covering the upper layers of the convection zones and the photospheres of cool main-sequence stars of spectral types F to early M. The average vertical field in these simulations ranges from 20 to 500 G. Results: We find a substantial variation of the properties of the surface magnetoconvection between main-sequence stars of different spectral types. As a consequence of a reduced efficiency of the convective collapse of flux tubes, M dwarfs lack bright magnetic structures in unipolar regions of moderate field strength. The spatial correlation between velocity and the magnetic field as well as the lifetime of magnetic structures and their sizes relative to the granules vary significantly along the model sequence of stellar types. Movies associated to Fig. A.1 are available in electronic form at http://www.aanda.org

  12. Method and system for small scale pumping

    DOEpatents

    Insepov, Zeke; Hassanein, Ahmed

    2010-01-26

    The present invention relates generally to the field of small scale pumping and, more specifically, to a method and system for very small scale pumping media through microtubes. One preferred embodiment of the invention generally comprises: method for small scale pumping, comprising the following steps: providing one or more media; providing one or more microtubes, the one or more tubes having a first end and a second end, wherein said first end of one or more tubes is in contact with the media; and creating surface waves on the tubes, wherein at least a portion of the media is pumped through the tube.

  13. Small scale bipolar nickel-hydrogen testing

    NASA Technical Reports Server (NTRS)

    Manzo, Michelle A.

    1988-01-01

    Bipolar nickel-hydrogen batteries, ranging in capacity from 6 to 40 A-hr, have been tested at the NASA Lewis Research Center over the past six years. Small scale tests of 1 A-hr nickel-hydrogen stacks have been initiated as a means of screening design and component variations for bipolar nickel-hydrogen cells and batteries. Four small-scale batteries have been built and tested. Characterization and limited cycle testing were performed to establish the validity of test results in the scaled down hardware. The results show characterization test results to be valid. LEO test results in the small scale hardware have limited value.

  14. Fabricating small-scale, curved, polymeric structures for biological applications using a combination of photocurable/thermocurable polydimethylsiloxane and phase interactions

    NASA Astrophysics Data System (ADS)

    Chang, Ting-Ya; Sung, Chun-Yen; Hashimoto, Michinao; Cheng, Chao-Min

    2016-09-01

    This paper describes an easy-to-handle technique for creating curved, millimetrically scaled polymeric structures in order to develop in vitro cell culture devices for biologically relevant applications. For the master mold in this study, the authors used UV-activated photocurable polydimethylsiloxane (PDMS). This product can readily be used to create millimetrically scaled pattern molds by controlling droplet contact angles during deposition onto a flexible paper-based substrate that has been prepatterned with ink/wax. Resultant desired patterns can be transferred onto thermocurable PDMS as arrays of wells for biological applications. By combining photocurable and thermocurable PDMS manufacturing processes, this approach endows PDMS-based structures with unique controllability in terms of size, pattern, and curvature. Providing such features enhances the biocompatibility and practicality of devices so manufactured in that they mimic the natural topography of the extracellular matrix. Additionally, three-dimensional cell culturing and immunofluorescent staining can be demonstrated on this biomimetic platform. This manufacturing method takes only several minutes to complete and does not require complicated facilities in order to fabricate PDMS-based biomedical devices. We believe that this method would be very useful for rapid, economical fabrication of cell-focused assay platforms, which would be particularly useful in resource-limited settings.

  15. Outmigration of landlocked Atlantic salmon (Salmo salar) smolts and effectiveness of an angled trash rack/fish bypass structure at a small scale hydroelectric facility. [Salmo salar

    SciTech Connect

    Nettles, D.C.; Gloss, S.P.

    1985-01-01

    Modes of downstream passage (penstock, spillway, diversion chute) by Atlantic salmon (Salmo salar) smolts were monitored using radio telemetry to assess the effectiveness of an angled trash rack/fish bypass structure at a small hydroelectric dam on the Boquet River, New York. Telemetry of 170 Atlantic salmon smolts and visual observations of stocked smolts were used to determine aspects of Atlantic salmon outmigration behavior. Smolts initiated mass migrations after river temperatures reached or exceeded 10/sup 0/C. Many radio-tagged smolts interrupted movements upon reaching ponded waters and/or the dam. River flow did not (P > .05) affect the frequency of migratory movements, passages, or rate of movement. Migrations were of approximately 30 days duration. Passages at the dam occurred primarily at night (61%) with diurnal passages (17%) and crepuscular passages (17%) of secondary importance. Timing of 5% of the passages was undetermined. All passages which occurred when angled trash racks were in place were through the bypass or over the spillway. Six (6) passages occurred when trash racks perpendicular to the penstock were in place: 3 of these were penstock passages. The angled trash rack and bypass structure served to reduce entrainment.

  16. Associations between small-scale structure in the GALFA survey data of HI in the galactic disk and similar features in the Cosmic Microwave Background observed by PLANCK

    NASA Astrophysics Data System (ADS)

    Verschuur, Gerrit L.

    2016-01-01

    High-resolution HI data obtained as part of the Arecibo GALFA survey have been compared with PLANCK data at 143 GHz and 857 GHz. The analysis confirms what has been reported previously, that sources of high-frequency continuum radiation exist in the galactic interstellar medium that produce structure that has been incorrectly interpreted as being cosmological in origin. The mechanism appears to be free-free emission from electron concentrations in regions where the dust and HI are similarly clumped or otherwise enhanced due to geometric effects. By comparing model calculations with the data it is concluded that the source of the radiation is relatively close to the sun, or order 25 to 50 pc distant. The required ionization fraction relative to HI is of order 0.05 - 0.08 for the areas tested.

  17. Small-scale explosive welding of aluminum

    NASA Technical Reports Server (NTRS)

    Bement, L. J.

    1972-01-01

    Welding technique uses very small quantities of explosive ribbon to accomplish small-scale lap-welding of aluminum plates. Technique can perform small controlled welding with no length limitations and requires minimal protective shielding.

  18. Large and small scale structural evolution of salt controlled minibasin in a fold and thrust belt setting: the case of the Sivas Basin, Turkey.

    NASA Astrophysics Data System (ADS)

    Kergaravat, Charlie; Ribes, Charlotte; Legeay, Etienne; Callot, Jean-Paul; Aubourg, Charles; Ringenbach, Jean-Claude

    2016-04-01

    The Sivas Basin in the Central Anatolian Plateau (Turkey) is a foreland fold-and-thrust belt, showing a core composed by a typical wall and basin structure (WABS), where the quality of reservoir rocks is governed primarily by the fracture and matrix damage, in relation to the macroscopic structure. Based on extensive fieldwork including detailed mapping of minibasins contacts, along with interpretation of a 2D regional seismic line, provide evidence for the development of a canopy separating two generations of MBs. The quality of reservoir rocks in these minibasins framed by evaporites is studied through (1) the characterization of the fracture network in two mini-basins, where 40 sites have been acquired, and (2) the magnetic fabric of 135 samples from sandstones to siltstones rocks from both Emirhan and Karayun mini-basins. The Late Eocene-early Oligocene evaporite level was remobilized during the northward migration of the sedimentary load during propagation of the foreland FTB. Evaporites occur at the base of several MBs, overlain by formations younger than those filling the initial generation of MBs. This support a second generation of MBs developped over an allochthonous evaporite level. The wavelength of tectonic structures increases away from the WABS domain and suggests a deepening of the decollement level. The polygonal pattern of the WABS influences the growing FTB system during the late stage of secondary MBs development, acting as a transfer zone between a forelandward thrust sheet propagating to the west and a triangular zone with hinterlandward thrusts to the east. The shortening is accommodated within the WABS by squeezed walls and diapirs, and by the translation/rotation of MBs, recorded by strike-slip fault zones. Considering the reservoir scale damage, both mini-basins display similar fracture network of pre-tilt fractures. In both mini-basins, we observed an early N-S fracture network, bed-perpendicular and parallel to the shortening. It is

  19. Slip Dynamics in Small Scale Crystals

    NASA Astrophysics Data System (ADS)

    Maass, Robert; Derlet, Peter; Greer, Julia; Volkert, Cynthia

    2015-03-01

    Classical work showed that dislocation velocities are strongly dependent on applied stress. Numerous experiments have validated this for individual or groups of dislocations in macroscopic crystals by using imaging techniques combined with either mechanical data or time resolved topological data. Developments in small scale mechanical testing allow to correlate the intermittency of collective dislocation motion with the mechanical response. Discrete forward surges in displacement can be related to dislocation avalanches, which are triggered by the evolving dislocation sub-structure. We study the spatiotemporal characteristics of intermittent plastic flow in quasi-statically sheared single crystalline Au crystals with diameters between 300 nm and 10000 nm, whose displacement bursts were recorded at several kHz (Scripta Mater. 2013, 69, 586; Small, available online). Both the crystallographic slip magnitude, as well as the velocity of the slip events are exhibiting power-law scaling as. The obtained slip velocity distribution has a cubic decay at high values, and a saturated flat shoulder at lower velocities. No correlation between the slip velocity and the applied stress or plastic strain is found. Further, we present DD-simulations that are supportive of our experimental findings. The simulations suggest that the dynamics of the internal stress fields dominate the evolving dislocation structure leading to velocities that are insensitive to the applied stress - a regime indicative of microplasticity.

  20. Interfacial structure of multi-layered thin-films produced by pulsed laser deposition for use in small-scale ceramic capacitors

    NASA Astrophysics Data System (ADS)

    Araki, Takao; Hino, Takanori; Ohara, Masahiro

    2014-08-01

    The aim of this study was to develop thin film capacitors with superior properties that could provide an alternative to materials currently used in conventional multi-layer ceramic capacitors fabricated by sintering. To this end, an artificial dielectric super lattice technique, incorporating pulsed laser deposition, was applied to improving the dielectric properties of thin film capacitors. This method permits the A-site atoms of a perovskite ABO3 structure to be selected layer by layer at a nanoscopic scale; consequently, multi-layer BaTiO3- SrTiO3 thin films were produced on Pt(111)/Ti/SiO2/Si(100) and SrTiO3(111) substrates. Hetero-epitaxial grain growth was observed between BaTiO3 and SrTiO3, with the lattice mismatch between them introducing a compressive residual strain at the interface. The dielectric properties of these multi-layer thin-film capacitors were found to be superior to those of conventional solid-solution thin films once the thickness of the layers and the ratio of the two oxides were optimized.

  1. X-ray computed tomography investigation of structures in Opalinus Clay from large-scale to small-scale after mechanical testing

    NASA Astrophysics Data System (ADS)

    Kaufhold, Annette; Halisch, Matthias; Zacher, Gerhard; Kaufhold, Stephan

    2016-08-01

    In the past years X-ray computed tomography (CT) has became more and more common for geoscientific applications and is used from the µm-scale (e.g. for investigations of microfossils or pore-scale structures) up to the dm-scale (full drill cores or soil columns). In this paper we present results from CT imaging and mineralogical investigations of an Opalinus Clay core on different scales and different regions of interest, emphasizing especially the 3-D evaluation and distribution of cracks and their impact on mechanical testing of such material. Enhanced knowledge of the testing behaviour of the Opalinus Clay is of great interest, especially since this material is considered for a long-term radioactive waste disposal and storage facility in Switzerland. Hence, results are compared regarding the mineral (i.e. phase) contrast resolution, the spatial resolution, and the overall scanning speed.With this extensive interdisciplinary scale-down approach it has been possible to characterize the general fracture propagation in comparison to mineralogical and textural features of the Opalinus Clay. Additionally, and as far as we know, a so-called mylonitic zone, located at an intersect of two main fractures, has been observed for the first time for an experimentally deformed Opalinus sample. The multi-scale results are in good accordance to data from naturally deformed Opalinus Clay samples, which enables us to perform systematical research under controlled laboratory conditions. Accompanying 3-D imaging greatly enhances the capability of data interpretation and assessment of such a material.

  2. Hidden founder effects: small-scale spatial genetic structure in recently established populations of the grassland specialist plant Anthyllis vulneraria.

    PubMed

    Helsen, Kenny; Jacquemyn, Hans; Honnay, Olivier

    2015-06-01

    The long-term establishment success of founder plant populations has been commonly assessed based on the measures of population genetic diversity and among population genetic differentiation, with founder populations expected to carry sufficient genetic diversity when population establishment is the result of many colonists from multiple source populations (the 'migrant pool' colonization model). Theory, however, predicts that, after initial colonization, rapid population expansion may result in a fast increase in the extent of spatial genetic structure (SGS), independent of extant genetic diversity. This SGS can reduce long-term population viability by increasing inbreeding. Using 12 microsatellite markers, we inferred colonization patterns in four recent populations of the grassland specialist plant Anthyllis vulneraria and compared the extent of SGS between recently established and old populations. Assignment analyses of the individuals of recent population based on the genetic composition of nine adjacent putative source populations suggested the occurrence of the 'migrant pool' colonization model, further confirmed by high genetic diversity within and low genetic differentiation among recent populations. Population establishment, however, resulted in the build-up of strong SGS, most likely as a result of spatially restricted recruitment of the progeny of initial colonists. Although reduced, significant SGS was nonetheless observed to persist in old populations. The presence of SGS was in all populations associated with elevated inbreeding coefficients, potentially affecting the long-term viability of these populations. In conclusion, this study illustrates the importance of studying SGS next to population genetic diversity and differentiation to adequately infer colonization patterns and long-term establishment success of plant species.

  3. SMALL-SCALE ANISOTROPIES OF COSMIC RAYS FROM RELATIVE DIFFUSION

    SciTech Connect

    Ahlers, Markus; Mertsch, Philipp

    2015-12-10

    The arrival directions of multi-TeV cosmic rays show significant anisotropies at small angular scales. It has been argued that this small-scale structure can naturally arise from cosmic ray scattering in local turbulent magnetic fields that distort a global dipole anisotropy set by diffusion. We study this effect in terms of the power spectrum of cosmic ray arrival directions and show that the strength of small-scale anisotropies is related to properties of relative diffusion. We provide a formalism for how these power spectra can be inferred from simulations and motivate a simple analytic extension of the ensemble-averaged diffusion equation that can account for the effect.

  4. Large-scale structure from cosmic-string loops in a baryon-dominated universe

    NASA Technical Reports Server (NTRS)

    Melott, Adrian L.; Scherrer, Robert J.

    1988-01-01

    The results are presented of a numerical simulation of the formation of large-scale structure in a universe with Omega(0) = 0.2 and h = 0.5 dominated by baryons in which cosmic strings provide the initial density perturbations. The numerical model yields a power spectrum. Nonlinear evolution confirms that the model can account for 700 km/s bulk flows and a strong cluster-cluster correlation, but does rather poorly on smaller scales. There is no visual 'filamentary' structure, and the two-point correlation has too steep a logarithmic slope. The value of G mu = 4 x 10 to the -6th is significantly lower than previous estimates for the value of G mu in baryon-dominated cosmic string models.

  5. Formation of large-scale structure from cosmic-string loops and cold dark matter

    NASA Technical Reports Server (NTRS)

    Melott, Adrian L.; Scherrer, Robert J.

    1987-01-01

    Some results from a numerical simulation of the formation of large-scale structure from cosmic-string loops are presented. It is found that even though G x mu is required to be lower than 2 x 10 to the -6th (where mu is the mass per unit length of the string) to give a low enough autocorrelation amplitude, there is excessive power on smaller scales, so that galaxies would be more dense than observed. The large-scale structure does not include a filamentary or connected appearance and shares with more conventional models based on Gaussian perturbations the lack of cluster-cluster correlation at the mean cluster separation scale as well as excessively small bulk velocities at these scales.

  6. Reconnection rates, small scale structures and simulations

    NASA Technical Reports Server (NTRS)

    Matthaeus, W. H.

    1983-01-01

    The study of reconnection in the context of one fluid, two dimensional magnetohydrodynamics (MHD), with spatially uniform constant density, viscosity and resistivity is though to retain most of the physics important in reconnection. Much of the existing reconnection literature makes use of this approach. This discussion focuses on attempts to determine the properties of reconnection solutions to MHD as precisely as possible without regard to the intrinsic limitations of the model.

  7. Formation of large-scale structure from cosmic strings and massive neutrinos

    NASA Technical Reports Server (NTRS)

    Scherrer, Robert J.; Melott, Adrian L.; Bertschinger, Edmund

    1989-01-01

    Numerical simulations of large-scale structure formation from cosmic strings and massive neutrinos are described. The linear power spectrum in this model resembles the cold-dark-matter power spectrum. Galaxy formation begins early, and the final distribution consists of isolated density peaks embedded in a smooth background, leading to a natural bias in the distribution of luminous matter. The distribution of clustered matter has a filamentary appearance with large voids.

  8. Discovery of Small-Scale Spiral Structures in the Disk of SAO 206462 (HD 135344B): Implications for the Physical State of the Disk from Spiral Density Wave Theory

    NASA Technical Reports Server (NTRS)

    Grady, C. A.; Currie, T.

    2012-01-01

    We present high-resolution, H-band, imaging observations, collected with Subaru/HiCIAO, of the scattered light from the transitional disk around SAO 206462 (HD 135344B). Although previous sub-mm imagery suggested the existence of the dust-depleted cavity at r approximates 46 AU, our observations reveal the presence of scattered light components as close as 0".2 (approx 28 AU) from the star. Moreover, we have discovered two small-scale spiral structures lying within 0".5 (approx 70 AU). We present models for the spiral structures using the spiral density wave theory, and derive a disk aspect ratio of h approx 0.1, which is consistent with previous sub-mm observations. This model can potentially give estimates of the temperature and rotation profiles of the disk based on dynamical processes, independently from sub-mm observations. It also predicts the evolution of the spiral structures, which can be observable on timescales of 10-20 years, providing conclusive tests of the model. While we cannot uniquely identify the origin of these spirals, planets embedded in the disk may be capable of exciting the observed morphology. Assuming that this is the case, we can make predictions on the locations and, possibly, the masses of the unseen planets. Such planets may be detected by future multi-wavelengths observations.

  9. Discovery of Small-Scale Spiral Structures in the Disk of SAO 206462 (HD 135344B)(exp 1): Implications for the Physical State of the Disk from Spiral Density Wave Theory

    NASA Technical Reports Server (NTRS)

    Muto, T.; Grady, C. A.; Hashimoto, J.; Fukagawa, M.; Hornbeck, J. B.; Sitko, M.; Russell, R.; Werren, C.; Cure, M; Currie, T.; Ohashi, N.; Okamoto, Y.; Momose, M.; Honda, M.; Inutsuka, S.; Takeuchi, T.; Dong, R.; Abe, L.; Brandner, W.; Brandt, T.; Carson, J.; Egner, S.; Feldt, M.; Fukue, T.; Goto, M.

    2012-01-01

    We present high-resolution, H-band, imaging observations, collected with Subaru /HiCIAO, of the scattered light from the transitional disk around SAO 206462 (HD 1353448). Although previous sub-mm imagery suggested the existence of the dust-depleted cavity at r <= 46 AU, our observations reveal the presence of scattered light components as close as O".2 (approx 28 AU) from the star. Moreover , we have discovered two small-scale spiral structures lying within 0".5 (approx 70 AU). We present models for the spiral structures using the spiral density wave theory, and derive a disk aspect ratio of h approx. 0.1, which is consistent with previous sub-mm observations. This model can potentially give estimates of the temperature and rotation profiles of the disk based on dynamical processes. independently from sub-nun observations. It also predicts the evolution of the spiral structures, which can be observable on timescales of 10-20 years, providing conclusive tests of the model. While we cannot uniquely identify the origin of these spirals, planets embedded in the disk may be capable of exciting the observed morphology. Assuming that this is the case, we can make predictions on the locations and, possibly, the masses of the unseen planets. Such planets may be detected by future multi-wavelengths observations,

  10. DISCOVERY OF SMALL-SCALE SPIRAL STRUCTURES IN THE DISK OF SAO 206462 (HD 135344B): IMPLICATIONS FOR THE PHYSICAL STATE OF THE DISK FROM SPIRAL DENSITY WAVE THEORY

    SciTech Connect

    Muto, T.; Takeuchi, T.; Grady, C. A.; Hashimoto, J.; Fukagawa, M.; Hornbeck, J. B.; Sitko, M.; Russell, R.; Werren, C.; Cure, M.; Currie, T.; Ohashi, N.; Okamoto, Y.; Momose, M.; Honda, M.; Inutsuka, S.; Dong, R.; Brandt, T.; Abe, L.; Brandner, W.; and others

    2012-04-01

    We present high-resolution, H-band imaging observations, collected with Subaru/HiCIAO, of the scattered light from the transitional disk around SAO 206462 (HD 135344B). Although previous sub-mm imagery suggested the existence of a dust-depleted cavity at r {<=} 46 AU, our observations reveal the presence of scattered light components as close as 0.''2 ({approx} 28 AU) from the star. Moreover, we have discovered two small-scale spiral structures lying within 0.''5 ({approx} 70 AU). We present models for the spiral structures using the spiral density wave theory, and derive a disk aspect ratio of h {approx} 0.1, which is consistent with previous sub-mm observations. This model can potentially give estimates of the temperature and rotation profiles of the disk based on dynamical processes, independently from sub-mm observations. It also predicts the evolution of the spiral structures, which can be observable on timescales of 10-20 years, providing conclusive tests of the model. While we cannot uniquely identify the origin of these spirals, planets embedded in the disk may be capable of exciting the observed morphology. Assuming that this is the case, we can make predictions on the locations and, possibly, the masses of the unseen planets. Such planets may be detected by future multi-wavelength observations.

  11. Small-scale models of multiring basins

    NASA Astrophysics Data System (ADS)

    Allemand, Pascal; Thomas, Pierre

    1999-07-01

    Small-scale sand-silicone simulations of multiring impact structures have been undertaken in order to understand the effects of the rheology of the lithosphere on the variability of natural multiring structures. For low sand-silicone thickness ratio (1:3), brittle strain is accommodated by spiral strike-slip faults. For higher sand-silicone ratios (1:1 or 2:1), an inner concentric ring affected by strike-slip faults is relayed by an external ring affected by concentric normal faults. The diameter of the inner ring decreases with the increase of the sand-silicone thickness ratio. It is suggested that the flexure of the brittle layer due to the silicone flow is responsible for the brittle strain field which is enhanced by the channel flow of the lower crust. The characteristic geometry of the intersection of conjugated strike-slip faults can be observed around large multiring basins on silicate crust such as Orientale on the Moon and on icy crust, such as Valhalla on Callisto and Gilgamesh on Ganymede. The strain field around these large craters is discussed in terms of mechanical properties of the lithospheres. On the Moon, large craters without relaxation faults, such as Imbrium are located on thin crust regions. The crust was too thin to have a ductile lower layer at the time of impact. Gilgamesh on Ganymede is surrounded mainly by strike-slip faults. Asgard on Callisto has the same diameter as Gilgamesh but is surrounded by concentric normal faults. The brittle-ductile thickness ratio is thus higher on Callisto than on Ganymede.

  12. Small-scale physics of the ocean

    NASA Technical Reports Server (NTRS)

    Caldwell, D. R.

    1983-01-01

    Progress in research on the small-scale physics of the ocean is reviewed. The contribution of such research to the understanding of the large scales is addressed and compared for various depth ranges of the ocean. The traditional framework for discussing small-scale measurements and turbulence is outlined, and recent research in the area is reviewed, citing references. Evidence for the existence of salt fingering in oceanic mixing is discussed. Factors that might inhibit the growth of salt fingers are assessed, and the influence of differences between laboratory tank and ocean in studying the fingers is discussed. The role of salt fingers in creating intrusions is examined. Instruments and methods used to measure the smallest scales at which there is appreciable variation and the stability of the patch of ocean in which the small-scale motions take place are considered.

  13. Thick strings, the liquid crystal blue phase, and cosmological large-scale structure

    NASA Technical Reports Server (NTRS)

    Luo, Xiaochun; Schramm, David N.

    1992-01-01

    A phenomenological model based on the liquid crystal blue phase is proposed as a model for a late-time cosmological phase transition. Topological defects, in particular thick strings and/or domain walls, are presented as seeds for structure formation. It is shown that the observed large-scale structure, including quasi-periodic wall structure, can be well fitted in the model without violating the microwave background isotropy bound or the limits from induced gravitational waves and the millisecond pulsar timing. Furthermore, such late-time transitions can produce objects such as quasars at high redshifts. The model appears to work with either cold or hot dark matter.

  14. Resurrecting hot dark matter - Large-scale structure from cosmic strings and massive neutrinos

    NASA Technical Reports Server (NTRS)

    Scherrer, Robert J.

    1988-01-01

    These are the results of a numerical simulation of the formation of large-scale structure from cosmic-string loops in a universe dominated by massive neutrinos (hot dark matter). This model has several desirable features. The final matter distribution contains isolated density peaks embedded in a smooth background, producing a natural bias in the distribution of luminous matter. Because baryons can accrete onto the cosmic strings before the neutrinos, the galaxies will have baryon cores and dark neutrino halos. Galaxy formation in this model begins much earlier than in random-phase models. On large scales the distribution of clustered matter visually resembles the CfA survey, with large voids and filaments.

  15. Pearl-necklace-like structures of microparticle strings observed in a dc complex plasma

    NASA Astrophysics Data System (ADS)

    Fink, M. A.; Zhdanov, S. K.; Thoma, M. H.; Höfner, H.; Morfill, G. E.

    2012-12-01

    The observation of a well-developed treelike string structure supported by a gas flow in a three-dimensional dc complex plasma is presented. The dynamically stable strings, comprising 10-20 particles, were up to 5 mm long. The experiments were performed using neon gas at a pressure of 100 Pa and melamine-formaldehyde particles with a diameter of 3.43 μm. Inside the discharge glass tube a nozzle had been built in to supply the controllable gas (plasma) flux intensity distribution along the tube. The walls of the nozzle were transparent for the laser light illuminating the particles. That gave the opportunity to closely study the particle dynamics deep inside the nozzle.

  16. Structural Transitions of Ion Strings in Quantum Potentials

    NASA Astrophysics Data System (ADS)

    Cormick, Cecilia; Morigi, Giovanna

    2012-08-01

    We analyze the stability and dynamics of an ion chain confined inside a high-finesse optical resonator. When the dipolar transition of the ions strongly couples to one cavity mode, the mechanical effects of light modify the chain properties close to a structural transition. We focus on the linear chain close to the zigzag instability and show that linear and zigzag arrays are bistable for certain strengths of the laser pumping the cavity. For these regimes the chain is cooled into one of the configurations by cavity-enhanced photon scattering. The excitations of these structures mix photonic and vibrational fluctuations, which can be entangled at steady state. These features are signaled by Fano-like resonances in the spectrum of light at the cavity output.

  17. Small-scale dynamo action in primordial halos

    NASA Astrophysics Data System (ADS)

    Schober, Jennifer; Schleicher, Dominik R. G.; Klessen, Ralf S.; Federrath, Christoph; Bovino, Stefano; Glover, Simon; Banerjee, Robi

    2013-07-01

    The first galaxies form due to gravitational collapse of primordial halos. During this collapse, weak magnetic seed fields get amplified exponentially by the small-scale dynamo - a process converting kinetic energy from turbulence into magnetic energy. We use the Kazantsev theory, which describes the small-scale dynamo analytically, to study magnetic field amplification for different turbulent velocity correlation functions. For incompressible turbulence (Kolmogorov turbulence), we find that the growth rate is proportional to the square root of the hydrodynamic Reynolds number, Re1/2. In the case of highly compressible turbulence (Burgers turbulence) the growth rate increases proportional to Re1/3. With a detailed chemical network we are able to follow the chemical evolution and determine the kinetic and magnetic viscosities (due to Ohmic and ambipolar diffusion) during the collapse of the halo. This way, we can calculate the growth rate of the small-scale dynamo quantitatively and predict the evolution of the small-scale magnetic field. As the magnetic energy is transported to larger scales on the local eddy-timescale, we obtain an estimate for the magnetic field on the Jeans scale. Even there, we find that equipartition with the kinetic energy is reached on small timescales. Dynamically relevant field structures can thus be expected already during the formation of the first objects in the Universe.

  18. IAPSA 2 small-scale system specification

    NASA Technical Reports Server (NTRS)

    Cohen, Gerald C.; Torkelson, Thomas C.

    1990-01-01

    The details of a hardware implementation of a representative small scale flight critical system is described using Advanced Information Processing System (AIPS) building block components and simulated sensor/actuator interfaces. The system was used to study application performance and reliability issues during both normal and faulted operation.

  19. SMALL SCALE BIOMASS FUELED GAS TURBINE ENGINE

    EPA Science Inventory

    A new generation of small scale (less than 20 MWe) biomass fueled, power plants are being developed based on a gas turbine (Brayton cycle) prime mover. These power plants are expected to increase the efficiency and lower the cost of generating power from fuels such as wood. The n...

  20. TS-AMIR: a topology string alignment method for intensive rapid protein structure comparison

    PubMed Central

    2012-01-01

    Background In structural biology, similarity analysis of protein structure is a crucial step in studying the relationship between proteins. Despite the considerable number of techniques that have been explored within the past two decades, the development of new alternative methods is still an active research area due to the need for high performance tools. Results In this paper, we present TS-AMIR, a Topology String Alignment Method for Intensive Rapid comparison of protein structures. The proposed method works in two stages: In the first stage, the method generates a topology string based on the geometric details of secondary structure elements, and then, utilizes an n-gram modelling technique over entropy concept to capture similarities in these strings. This initial correspondence map between secondary structure elements is submitted to the second stage in order to obtain the alignment at the residue level. Applying the Kabsch method, a heuristic step-by-step algorithm is adopted in the second stage to align the residues, resulting in an optimal rotation matrix and minimized RMSD. The performance of the method was assessed in different information retrieval tests and the results were compared with those of CE and TM-align, representing two geometrical tools, and YAKUSA, 3D-BLAST and SARST as three representatives of linear encoding schemes. It is shown that the method obtains a high running speed similar to that of the linear encoding schemes. In addition, the method runs about 800 and 7200 times faster than TM-align and CE respectively, while maintaining a competitive accuracy with TM-align and CE. Conclusions The experimental results demonstrate that linear encoding techniques are capable of reaching the same high degree of accuracy as that achieved by geometrical methods, while generally running hundreds of times faster than conventional programs. PMID:22336468

  1. A novel mechanism of generating extracellular vesicles during apoptosis via a beads-on-a-string membrane structure.

    PubMed

    Atkin-Smith, Georgia K; Tixeira, Rochelle; Paone, Stephanie; Mathivanan, Suresh; Collins, Christine; Liem, Michael; Goodall, Katharine J; Ravichandran, Kodi S; Hulett, Mark D; Poon, Ivan K H

    2015-06-15

    Disassembly of apoptotic cells into smaller fragments (a form of extracellular vesicle called apoptotic bodies) can facilitate removal of apoptotic debris and intercellular communication. However, the mechanism underpinning this process is unclear. While observing monocytes undergoing apoptosis by time-lapse microscopy, we discovered a new type of membrane protrusion that resembles a 'beads-on-a-string' structure. Strikingly, the 'beads' are frequently sheared off the 'string' to form apoptotic bodies. Generation of apoptotic bodies via this mechanism can facilitate a sorting process and results in the exclusion of nuclear contents from apoptotic bodies. Mechanistically, generation of 'beads-on-a-string' protrusion is controlled by the level of actomyosin contraction and apoptopodia formation. Furthermore, in an unbiased drug screen, we identified the ability of sertraline (an antidepressant) to block the formation of 'beads-on-a-string' protrusions and apoptotic bodies. These data uncover a new mechanism of apoptotic body formation in monocytes and also compounds that can modulate this process.

  2. The stochastic string model as a unifying theory of the term structure of interest rates

    NASA Astrophysics Data System (ADS)

    Bueno-Guerrero, Alberto; Moreno, Manuel; Navas, Javier F.

    2016-11-01

    We present the stochastic string model of Santa-Clara and Sornette (2001), as reformulated by Bueno-Guerrero et al. (2015), as a unifying theory of the continuous-time modeling of the term structure of interest rates. We provide several new results, such as: (a) an orthogonality condition for the volatilities in the Heath, Jarrow, and Morton (1992) (HJM) model, (b) the interpretation of multi-factor HJM models as approximations to a full infinite-dimensional model, (c) a result of consistency based on Hilbert spaces, and (d) a theorem for option valuation.

  3. DOE small scale fuel alcohol plant design

    SciTech Connect

    LaRue, D.M.; Richardson, J.G.

    1980-01-01

    The Department of Energy, in an effort to facilitate the deployment of rural-based ethanol production capability, has undertaken this effort to develop a basic small-scale plant design capable of producing anhydrous ethanol. The design, when completed, will contain all necessary specifications and diagrams sufficient for the construction of a plant. The design concept is modular; that is, sections of the plant can stand alone or be integrated into other designs with comparable throughput rates. The plant design will be easily scaled up or down from the designed flow rate of 25 gallons of ethanol per hour. Conversion factors will be provided with the final design package to explain scale-up and scale-down procedures. The intent of this program is to provide potential small-scale producers with sound information about the size, engineering requirements, costs and level of effort in building such a system.

  4. Dislocation dynamics simulations of plasticity at small scales

    SciTech Connect

    Zhou, Caizhi

    2010-01-01

    As metallic structures and devices are being created on a dimension comparable to the length scales of the underlying dislocation microstructures, the mechanical properties of them change drastically. Since such small structures are increasingly common in modern technologies, there is an emergent need to understand the critical roles of elasticity, plasticity, and fracture in small structures. Dislocation dynamics (DD) simulations, in which the dislocations are the simulated entities, offer a way to extend length scales beyond those of atomistic simulations and the results from DD simulations can be directly compared with the micromechanical tests. The primary objective of this research is to use 3-D DD simulations to study the plastic deformation of nano- and micro-scale materials and understand the correlation between dislocation motion, interactions and the mechanical response. Specifically, to identify what critical events (i.e., dislocation multiplication, cross-slip, storage, nucleation, junction and dipole formation, pinning etc.) determine the deformation response and how these change from bulk behavior as the system decreases in size and correlate and improve our current knowledge of bulk plasticity with the knowledge gained from the direct observations of small-scale plasticity. Our simulation results on single crystal micropillars and polycrystalline thin films can march the experiment results well and capture the essential features in small-scale plasticity. Furthermore, several simple and accurate models have been developed following our simulation results and can reasonably predict the plastic behavior of small scale materials.

  5. String test

    MedlinePlus

    Duodenal parasites test; Giardia - string test ... To have this test, you swallow a string with a weighted gelatin capsule on the end. The string is pulled out 4 hours later. Any bile , blood, or mucus attached to ...

  6. A Portrait of Cold Gas in Galaxies at 60 pc Resolution and a Simple Method to Test Hypotheses That Link Small-scale ISM Structure to Galaxy-scale Processes

    NASA Astrophysics Data System (ADS)

    Leroy, Adam K.; Hughes, Annie; Schruba, Andreas; Rosolowsky, Erik; Blanc, Guillermo A.; Bolatto, Alberto D.; Colombo, Dario; Escala, Andres; Kramer, Carsten; Kruijssen, J. M. Diederik; Meidt, Sharon; Pety, Jerome; Querejeta, Miguel; Sandstrom, Karin; Schinnerer, Eva; Sliwa, Kazimierz; Usero, Antonio

    2016-11-01

    The cloud-scale density, velocity dispersion, and gravitational boundedness of the interstellar medium (ISM) vary within and among galaxies. In turbulent models, these properties play key roles in the ability of gas to form stars. New high-fidelity, high-resolution surveys offer the prospect to measure these quantities across galaxies. We present a simple approach to make such measurements and to test hypotheses that link small-scale gas structure to star formation and galactic environment. Our calculations capture the key physics of the Larson scaling relations, and we show good correspondence between our approach and a traditional “cloud properties” treatment. However, we argue that our method is preferable in many cases because of its simple, reproducible characterization of all emission. Using, low-J 12CO data from recent surveys, we characterize the molecular ISM at 60 pc resolution in the Antennae, the Large Magellanic Cloud (LMC), M31, M33, M51, and M74. We report the distributions of surface density, velocity dispersion, and gravitational boundedness at 60 pc scales and show galaxy-to-galaxy and intragalaxy variations in each. The distribution of flux as a function of surface density appears roughly lognormal with a 1σ width of ∼0.3 dex, though the center of this distribution varies from galaxy to galaxy. The 60 pc resolution line width and molecular gas surface density correlate well, which is a fundamental behavior expected for virialized or free-falling gas. Varying the measurement scale for the LMC and M31, we show that the molecular ISM has higher surface densities, lower line widths, and more self-gravity at smaller scales.

  7. Optical measuring technique for small scale water surface waves

    NASA Astrophysics Data System (ADS)

    Jahne, Bernd; Waas, Stefan

    1989-10-01

    This paper describes two optical measuring techniques for determining the spatial and temporal structure of small-scale surface waves: (1) the imaging slope gage (ISG) and (2) the reflective stereo slope gage (RSSG). The ISG is based on light refraction at the water surface; it records image sequences of the wave slope at a maximum area of 1 sq m. The RSSG technique involves illumination of the water surface from above by a monochromatic light source; its two CCD camera take stereo images of sequences of the specular reflexes returned by the water surface. Both instruments were successfully used in wind/wave facility investigations. The results show that they permit a much more detailed investigation of the physics of small scale waves than those made using conventional equipment, such as point measuring devices or laser slope gages.

  8. Small-Scale Hydroelectric Power Demonstration Project

    SciTech Connect

    Gleeson, L.

    1991-12-01

    The US Department of Energy Field Office, Idaho, Small-Scale Hydroelectric Power Program was initiated in conjunction with the restoration of three power generating plants in Idaho Falls, Idaho, following damage caused by the Teton Dam failure on June 5, 1976. There were many parties interested in this project, including the state and environmental groups, with different concerns. This report was prepared by the developer and describes the design alternatives the applicant provided in an attempt to secure the Federal Energy Regulatory Commission license. Also included are correspondence between the related parties concerning the project, major design alternatives/project plan diagrams, the license, and energy and project economics.

  9. Small-scale physics of the ocean

    NASA Technical Reports Server (NTRS)

    Caldwell, Douglas R.

    1987-01-01

    Observations and theoretical models of small-scale phenomena in the oceans are reviewed, with a focus on progress during the period 1983-1986. Topics examined include surface layers, equatorial turbulence, off-equator mixed layers, the scaling of mixing, turbulence concepts, laboratory results, internal waves and mixing, rings, the nature of the bottom layer, double diffusion and intrusions, salt fingers, and biological interactions. Also discussed are developments in instrumentation (fast sampling profilers with upward-profiling capability, deep profilers, ship-motion correction, horizontal samplers, small submersibles, submarines, towed packages, conductivity sensors, dissolved-oxygen sensors, and acoustic Doppler current profilers) and goals for future research.

  10. Developing JSequitur to Study the Hierarchical Structure of Biological Sequences in a Grammatical Inference Framework of String Compression Algorithms.

    PubMed

    Galbadrakh, Bulgan; Lee, Kyung-Eun; Park, Hyun-Seok

    2012-12-01

    Grammatical inference methods are expected to find grammatical structures hidden in biological sequences. One hopes that studies of grammar serve as an appropriate tool for theory formation. Thus, we have developed JSequitur for automatically generating the grammatical structure of biological sequences in an inference framework of string compression algorithms. Our original motivation was to find any grammatical traits of several cancer genes that can be detected by string compression algorithms. Through this research, we could not find any meaningful unique traits of the cancer genes yet, but we could observe some interesting traits in regards to the relationship among gene length, similarity of sequences, the patterns of the generated grammar, and compression rate.

  11. Cosmic strings and galaxy formation

    NASA Technical Reports Server (NTRS)

    Bertschinger, Edmund

    1989-01-01

    The cosmogonical model proposed by Zel'dovich and Vilenkin (1981), in which superconducting cosmic strings act as seeds for the origin of structure in the universe, is discussed, summarizing the results of recent theoretical investigations. Consideration is given to the formation of cosmic strings, the microscopic structure of strings, gravitational effects, cosmic string evolution, and the formation of galaxies and large-scale structure. Simulation results are presented in graphs, and several outstanding issues are listed and briefly characterized.

  12. On the Dynamics of Small-Scale Solar Magnetic Elements

    NASA Technical Reports Server (NTRS)

    Berger, T. E.; Title, A. M.

    1996-01-01

    We report on the dynamics of the small-scale solar magnetic field, based on analysis of very high resolution images of the solar photosphere obtained at the Swedish Vacuum Solar Telescope. The data sets are movies from 1 to 4 hr in length, taken in several wavelength bands with a typical time between frames of 20 s. The primary method of tracking small-scale magnetic elements is with very high contrast images of photospheric bright points, taken through a 12 A bandpass filter centered at 4305 A in the Fraunhofer 'G band.' Previous studies have established that such bright points are unambiguously associated with sites of small-scale magnetic flux in the photosphere, although the details of the mechanism responsible for the brightening of the flux elements remain uncertain. The G band bright points move in the intergranular lanes at speeds from 0.5 to 5 km/s. The motions appear to be constrained to the intergranular lanes and are primarily driven by the evolution of the local granular convection flow field. Continual fragmentation and merging of flux is the fundamental evolutionary mode of small-scale magnetic structures in the solar photosphere. Rotation and folding of chains or groups of bright points are also observed. The timescale for magnetic flux evolution in active region plage is on the order of the correlation time of granulation (typically 6-8 minutes), but significant morphological changes can occur on timescales as short as 100 S. Smaller fragments are occasionally seen to fade beyond observable contrast. The concept of a stable, isolated subarcsecond magnetic 'flux tube' in the solar photosphere is inconsistent with the observations presented here.

  13. A new spatially scanning 2.7 µm laser hygrometer and new small-scale wind tunnel for direct analysis of the H2O boundary layer structure at single plant leaves

    NASA Astrophysics Data System (ADS)

    Wunderle, K.; Rascher, U.; Pieruschka, R.; Schurr, U.; Ebert, V.

    2015-01-01

    A new spatially scanning TDLAS in situ hygrometer based on a 2.7-µm DFB diode laser was constructed and used to analyse the water vapour concentration boundary layer structure at the surface of a single plant leaf. Using an absorption length of only 5.4 cm, the TDLAS hygrometer permits a H2O vapour concentration resolution of 31 ppmv. This corresponds to a normalized precision of 1.7 ppm m. In order to preserve and control the H2O boundary layer on an individual leaf and to study the boundary layer dependence on the wind speed to which the leaf might be exposed in nature, we also constructed a new, application specific, small-scale, wind tunnel for individual plant leaves. The rectangular, closed-loop tunnel has overall dimensions of 1.2 × 0.6 m and a measurement chamber dimension of 40 × 54 mm (H × W). It allows to generate a laminar flow with a precisely controlled wind speed at the plant leaf surface. Combining honeycombs and a miniaturized compression orifice, we could generate and control stable wind speeds from 0.1 to 0.9 m/s, and a highly laminar and homogeneous flow with an excellent relative spatial homogeneity of 0.969 ± 0.03. Combining the spectrometer and the wind tunnel, we analysed (for the first time) non-invasively the wind speed-dependent vertical structure of the H2O vapour distribution within the boundary layer of a single plant leaf. Using our time-lag-free data acquisition procedure for phase locked signal averaging, we achieved a temporal resolution of 0.2 s for an individual spatial point, while a complete vertical spatial scan at a spatial resolution of 0.18 mm took 77 s. The boundary layer thickness was found to decrease from 6.7 to 3.6 mm at increasing wind speeds of 0.1-0.9 m/s. According to our knowledge, this is the first experimental quantification of wind speed-dependent H2O vapour boundary layer concentration profiles of single plant leaves.

  14. Stringlike structures in Kerr-Schild geometry: The N=2 string, twistors, and the Calabi-Yau twofold

    NASA Astrophysics Data System (ADS)

    Burinskii, A. Ya.

    2013-11-01

    The four-dimensional Kerr-Schild geometry contains two stringy structures. The first is the closed string formed by the Kerr singular ring, and the second is an open complex string obtained in the complex structure of the Kerr-Schild geometry. The real and complex Kerr strings together form a membrane source of the over-rotating Kerr-Newman solution without a horizon, a = J/m ≫ m. It was also recently found that the principal null congruence of the Kerr geometry is determined by the Kerr theorem as a quartic in the projective twistor space, which corresponds to an embedding of the Calabi-Yau twofold into the bulk of the Kerr geometry. We describe this embedding in detail and show that the four sheets of the twistorial K3 surface represent an analytic extension of the Kerr congruence created by antipodal involution.

  15. Large- and small-scale constraints on power spectra in Omega = 1 universes

    NASA Technical Reports Server (NTRS)

    Gelb, James M.; Gradwohl, Ben-Ami; Frieman, Joshua A.

    1993-01-01

    The CDM model of structure formation, normalized on large scales, leads to excessive pairwise velocity dispersions on small scales. In an attempt to circumvent this problem, we study three scenarios (all with Omega = 1) with more large-scale and less small-scale power than the standard CDM model: (1) cold dark matter with significantly reduced small-scale power (inspired by models with an admixture of cold and hot dark matter); (2) cold dark matter with a non-scale-invariant power spectrum; and (3) cold dark matter with coupling of dark matter to a long-range vector field. When normalized to COBE on large scales, such models do lead to reduced velocities on small scales and they produce fewer halos compared with CDM. However, models with sufficiently low small-scale velocities apparently fail to produce an adequate number of halos.

  16. Biaxial shear of confined colloidal hard spheres: the structure and rheology of the vorticity-aligned string phase.

    PubMed

    Lin, Neil Y C; Cheng, Xiang; Cohen, Itai

    2014-03-28

    Using a novel biaxial confocal rheoscope, we investigate the flow of the shear induced vorticity aligned string phase [X. Cheng et al., Proc. Natl. Acad. Sci. U. S. A., 2011, 109, 63], which has a highly anisotropic microstructure. Using biaxial shear protocols we show that we have excellent control of the string phase anisotropic morphology. We choose a shear protocol that drives the system into the string phase. Subsequently, a biaxial force measurement device is used to determine the suspension rheology along both the flow and vorticity directions. We find no measurable dependence of the suspension stress response along the shear and vorticity directions due to the hydrodynamically induced string morphology. In particular, we find that the suspension's high frequency stress response is nearly identical along the two orthogonal directions. While we do observe an anisotropic stress response at lower shear frequencies associated with shear thinning, we show that this anisotropy is independent of the shear induced string structure. These results suggest that for the range of flows explored, Brownian and hydrodynamic contributions to the stress arising from the anisotropic suspension microstructure are sufficiently weak that they do not significantly contribute to the rheology. Collectively, this study presents a general and powerful approach for using biaxial confocal rheometry to elucidate the relationship between microstructure and rheology in complex fluids driven far-from-equilibrium.

  17. Nucleation in small scale multicrystalline silicon ingots

    NASA Astrophysics Data System (ADS)

    Brynjulfsen, I.; Arnberg, L.; Autruffe, A.

    2012-12-01

    Small scale solidification experiments were performed in order to study nucleation mechanisms of solar cell silicon. Ingots were grown in a Bridgman furnace; with a high rate (5 cm/min), inducing dendrite-like grains; and at a slow rate (0.2 mm/min), simulating the common slow crystal growth process. Two types of silicon were used, polysilicon and compensated material. The results showed that for the early stages of silicon solidification, the compensated material behaves similar to the polysilicon. A high undercooling of 11±3 K was obtained for one of the fast cooled experiments. This suggests that Si3N4-coating is not the important factor for nucleation, but Si3N4-precipitates in the melt could contribute as inoculants. Grains with similar orientation were observed for both the solidification rates, which indicates that the most important issue for grain growth selection in PV silicon is control of the vertical growth, rather than nucleation substrates.

  18. Models of Small-Scale Patchiness

    NASA Technical Reports Server (NTRS)

    McGillicuddy Dennis J., Jr.

    2001-01-01

    Patchiness is perhaps the most salient characteristic of plankton populations in the ocean. The scale of this heterogeneity spans many orders of magnitude in its spatial extent, ranging from planetary down to microscale. It has been argued that patchiness plays a fundamental role in the functioning of marine ecosystems, insofar as the mean conditions may not reflect the environment to which organisms are adapted. For example, the fact that some abundant predators cannot thrive on the mean concentration of their prey in the ocean implies that they are somehow capable of exploiting small-scale patches of prey whose concentrations are much larger than the mean. Understanding the nature of this patchiness is thus one of the major challenges of oceanographic ecology. Additional information is contained in the original extended abstract.

  19. Small-scale Features in Pulsating Aurora

    NASA Astrophysics Data System (ADS)

    Jones, S.; Jaynes, A. N.; Knudsen, D. J.; Trondsen, T.; Lessard, M.

    2011-12-01

    A field study was conducted from March 12-16, 2002 using a narrow-field intensified CCD camera installed at Churchill, Manitoba. The camera was oriented along the local magnetic zenith where small-scale black auroral forms are often visible. This analysis focuses on such forms occurring within a region of pulsating aurora. The observations show black forms with irregular shape and nonuniform drift with respect to the relatively stationary pulsating patches. The pulsating patches occur within a diffuse auroral background as a modulation of the auroral brightness in a localized region. The images analyzed show a decrease in the brightness of the diffuse background in the region of the pulsating patch at the beginning of the 'off' phase of the modulation. Throughout the off phase the brightness of the diffuse aurora gradually increases back to the average intensity. The time constant for this increase is measured as the first step toward determining the physical process.

  20. Role of string-like collective atomic motion on diffusion and structural relaxation in glass forming Cu-Zr alloys.

    PubMed

    Zhang, Hao; Zhong, Cheng; Douglas, Jack F; Wang, Xiaodong; Cao, Qingping; Zhang, Dongxian; Jiang, Jian-Zhong

    2015-04-28

    We investigate Cu-Zr liquid alloys using molecular dynamics simulation and well-accepted embedded atom method potentials over a wide range of chemical composition and temperature as model metallic glass-forming (GF) liquids. As with other types of GF materials, the dynamics of these complex liquids are characterized by "dynamic heterogeneity" in the form of transient polymeric clusters of highly mobile atoms that are composed in turn of atomic clusters exhibiting string-like cooperative motion. In accordance with the string model of relaxation, an extension of the Adam-Gibbs (AG) model, changes in the activation free energy ΔGa with temperature of both the Cu and Zr diffusion coefficients D, and the alpha structural relaxation time τα can be described to a good approximation by changes in the average string length, L. In particular, we confirm that the strings are a concrete realization of the abstract "cooperatively rearranging regions" of AG. We also find coexisting clusters of relatively "immobile" atoms that exhibit predominantly icosahedral local packing rather than the low symmetry packing of "mobile" atoms. These two distinct types of dynamic heterogeneity are then associated with different fluid structural states. Glass-forming liquids are thus analogous to polycrystalline materials where the icosahedrally packed regions correspond to crystal grains, and the strings reside in the relatively disordered grain boundary-like regions exterior to these locally well-ordered regions. A dynamic equilibrium between localized ("immobile") and wandering ("mobile") particles exists in the liquid so that the dynamic heterogeneity can be considered to be type of self-assembly process. We also characterize changes in the local atomic free volume in the course of string-like atomic motion to better understand the initiation and propagation of these fluid excitations. PMID:25933773

  1. Role of string-like collective atomic motion on diffusion and structural relaxation in glass forming Cu-Zr alloys

    SciTech Connect

    Zhang, Hao; Zhong, Cheng; Wang, Xiaodong; Cao, Qingping; Jiang, Jian-Zhong E-mail: jack.douglas@nist.gov; Douglas, Jack F. E-mail: jack.douglas@nist.gov; Zhang, Dongxian

    2015-04-28

    We investigate Cu-Zr liquid alloys using molecular dynamics simulation and well-accepted embedded atom method potentials over a wide range of chemical composition and temperature as model metallic glass-forming (GF) liquids. As with other types of GF materials, the dynamics of these complex liquids are characterized by “dynamic heterogeneity” in the form of transient polymeric clusters of highly mobile atoms that are composed in turn of atomic clusters exhibiting string-like cooperative motion. In accordance with the string model of relaxation, an extension of the Adam-Gibbs (AG) model, changes in the activation free energy ΔG{sub a} with temperature of both the Cu and Zr diffusion coefficients D, and the alpha structural relaxation time τ{sub α} can be described to a good approximation by changes in the average string length, L. In particular, we confirm that the strings are a concrete realization of the abstract “cooperatively rearranging regions” of AG. We also find coexisting clusters of relatively “immobile” atoms that exhibit predominantly icosahedral local packing rather than the low symmetry packing of “mobile” atoms. These two distinct types of dynamic heterogeneity are then associated with different fluid structural states. Glass-forming liquids are thus analogous to polycrystalline materials where the icosahedrally packed regions correspond to crystal grains, and the strings reside in the relatively disordered grain boundary-like regions exterior to these locally well-ordered regions. A dynamic equilibrium between localized (“immobile”) and wandering (“mobile”) particles exists in the liquid so that the dynamic heterogeneity can be considered to be type of self-assembly process. We also characterize changes in the local atomic free volume in the course of string-like atomic motion to better understand the initiation and propagation of these fluid excitations.

  2. Role of string-like collective atomic motion on diffusion and structural relaxation in glass forming Cu-Zr alloys.

    PubMed

    Zhang, Hao; Zhong, Cheng; Douglas, Jack F; Wang, Xiaodong; Cao, Qingping; Zhang, Dongxian; Jiang, Jian-Zhong

    2015-04-28

    We investigate Cu-Zr liquid alloys using molecular dynamics simulation and well-accepted embedded atom method potentials over a wide range of chemical composition and temperature as model metallic glass-forming (GF) liquids. As with other types of GF materials, the dynamics of these complex liquids are characterized by "dynamic heterogeneity" in the form of transient polymeric clusters of highly mobile atoms that are composed in turn of atomic clusters exhibiting string-like cooperative motion. In accordance with the string model of relaxation, an extension of the Adam-Gibbs (AG) model, changes in the activation free energy ΔGa with temperature of both the Cu and Zr diffusion coefficients D, and the alpha structural relaxation time τα can be described to a good approximation by changes in the average string length, L. In particular, we confirm that the strings are a concrete realization of the abstract "cooperatively rearranging regions" of AG. We also find coexisting clusters of relatively "immobile" atoms that exhibit predominantly icosahedral local packing rather than the low symmetry packing of "mobile" atoms. These two distinct types of dynamic heterogeneity are then associated with different fluid structural states. Glass-forming liquids are thus analogous to polycrystalline materials where the icosahedrally packed regions correspond to crystal grains, and the strings reside in the relatively disordered grain boundary-like regions exterior to these locally well-ordered regions. A dynamic equilibrium between localized ("immobile") and wandering ("mobile") particles exists in the liquid so that the dynamic heterogeneity can be considered to be type of self-assembly process. We also characterize changes in the local atomic free volume in the course of string-like atomic motion to better understand the initiation and propagation of these fluid excitations.

  3. Overview of the Testing of a Small-Scale Proprotor

    NASA Technical Reports Server (NTRS)

    Young, Larry A.; Yamauchi, Gloria K.; Booth, Earl R., Jr.; Botha, Gavin; Dawson, Seth

    1999-01-01

    This paper presents an overview of results from the wind tunnel test of a 1/4-scale V-22 proprotor in the Duits-Nederlandse Windtunnel (DNW) in The Netherlands. The small-scale proprotor was tested on the isolated rotor configuration of the Tilt Rotor Aeroacoustic Model (TRAM). The test was conducted by a joint team from NASA Ames, NASA Langley, U.S. Army Aeroflightdynamics Directorate, and The Boeing Company. The objective of the test was to acquire a benchmark database for validating aeroacoustic analyses. Representative examples of airloads, acoustics, structural loads, and performance data are provided and discussed.

  4. Bead-on-string structure printed by electrohydrodynamic jet under alternating current electric field

    NASA Astrophysics Data System (ADS)

    Liu, Juan; Lin, Yihuang; Jiang, Jiaxin; Liu, Haiyan; Zhao, Yang; Zheng, Gaofeng

    2016-09-01

    Electrohydrodynamic printing (EHDP) under alternating current (AC) electric field provides a novel way for the precise micro-/nano-droplet printing. The AC electric field induces the free charge to reciprocate along the EHDP jet and changes the electric field force on the jet periodically. The stability of jet can be enhanced by increasing the voltage frequency, and the regular bead-on-string structure is direct-written along the trajectory of collector. The deposition frequency of bead structure increases with the increasing of voltage frequency, due to the short period of AC electric field. As the voltage frequency is increased from 10 to 60 Hz, the diameter of bead structure decreases from 200 to 110 µm. As the duty ration increased from 10 to 60 %, the diameter of bead structure increased from 100 to 140 µm. This work would accelerate the development and the application of micro-/nano-printing technology in the fields of flexible electronic and micro-/nano-system.

  5. The social structure of experimental'' strings at Fermilab; a physics and detector driven model

    SciTech Connect

    Bodnarczuk, M.

    1990-12-12

    Physicists in HEP have been forced to organize large scientific projects without a well defined organizational or sociological model to guide them. In the absence of such models, what structures do experimentalists use to develop social structures in HEP In this paper, I claim that physicists organize around what they know best, the physics problems they study and the detectors and devices they study them with. After describing the advent of management'' in HEP, I use a case study of 4 Fermilab experiments as the base upon which to propose a physics and detector driven model of social structure for experiments. In addition, I show how this model can be extended to describe strings'' of experiments, where continuities of physics interests, spectrometer design, and a core group of physicists become a definable sociological unit that can exist for over 15 years. A dominate theme that emerges from my analysis is the conscious attempt on the part of experimenters to remove the uncertainties that are part of the practice of HEP.

  6. Galaxy alignment on large and small scales

    NASA Astrophysics Data System (ADS)

    Kang, X.; Lin, W. P.; Dong, X.; Wang, Y. O.; Dutton, A.; Macciò, A.

    2016-10-01

    Galaxies are not randomly distributed across the universe but showing different kinds of alignment on different scales. On small scales satellite galaxies have a tendency to distribute along the major axis of the central galaxy, with dependence on galaxy properties that both red satellites and centrals have stronger alignment than their blue counterparts. On large scales, it is found that the major axes of Luminous Red Galaxies (LRGs) have correlation up to 30Mpc/h. Using hydro-dynamical simulation with star formation, we investigate the origin of galaxy alignment on different scales. It is found that most red satellite galaxies stay in the inner region of dark matter halo inside which the shape of central galaxy is well aligned with the dark matter distribution. Red centrals have stronger alignment than blue ones as they live in massive haloes and the central galaxy-halo alignment increases with halo mass. On large scales, the alignment of LRGs is also from the galaxy-halo shape correlation, but with some extent of mis-alignment. The massive haloes have stronger alignment than haloes in filament which connect massive haloes. This is contrary to the naive expectation that cosmic filament is the cause of halo alignment.

  7. Small-scale accelerated pavement testing

    SciTech Connect

    Kim, S.M.; Hugo, F.; Roesset, J.M.

    1998-03-01

    This paper presents the results of a study conducted to explore the use of small-scale models of accelerated pavement testing (APT) devices to evaluate the performance of pavements in conjunction with full-scale tests. The motivation for the study was the availability of a model mobile load simulator (MMLS), which had been built originally to illustrate the operation of the full-scale mobile load simulator (MLS) under design at the time. The scaling requirements will be different depending on whether dynamic (inertia), viscous, or gravity effects are important. One must thus decide which one of these effects controls the behavior to try to reproduce it exactly. In the preliminary tests conducted with the MMLS, emphasis had been placed in reproducing accurately the viscoelastic behavior of the asphalt layer. The possibility of obtaining valid results, even if similitude is not maintained in relation to inertia forces, is explored in this paper. The effects of load frequency or velocity and the effects of layer thicknesses are studied. The total thickness of the model pavement, which must be finite, and its effects on displacements and strains are also considered. It is concluded that even when full similitude is not satisfied it is possible to obtain valid results that can be extrapolated to predict prototype performance if one were interested primarily in the behavior of the asphalt layer. Preliminary analyses should be conducted, however, to guide on the selection of the model dimensions.

  8. Hoopa Valley Small Scale Hydroelectric Feasibility Project

    SciTech Connect

    Curtis Miller

    2009-03-22

    This study considered assessing the feasibility of developing small scale hydro-electric power from seven major tributaries within the Hoopa Valley Indian Reservation of Northern California (http://www.hoopa-nsn.gov/). This study pursued the assessment of seven major tributaries of the Reservation that flow into the Trinity River. The feasibility of hydropower on the Hoopa Valley Indian Reservation has real potential for development and many alternative options for project locations, designs, operations and financing. In order to realize this opportunity further will require at least 2-3 years of intense data collection focusing on stream flow measurements at multiple locations in order to quantify real power potential. This also includes on the ground stream gradient surveys, road access planning and grid connectivity to PG&E for sale of electricity. Imperative to this effort is the need for negotiations between the Hoopa Tribal Council and PG&E to take place in order to finalize the power rate the Tribe will receive through any wholesale agreement that utilizes the alternative energy generated on the Reservation.

  9. Cosmic string with a light massive neutrino

    NASA Technical Reports Server (NTRS)

    Albrecht, Andreas; Stebbins, Albert

    1992-01-01

    We have estimated the power spectra of density fluctuations produced by cosmic strings with neutrino hot dark matter (HDM). Normalizing at 8/h Mpc, we find that the spectrum has more power on small scales than HDM + inflation, less than cold dark matter (CDM) + inflation, and significantly less the CDM + strings. With HDM, large wakes give significant contribution to the power on the galaxy scale and may give rise to large sheets of galaxies.

  10. TURBULENT SMALL-SCALE DYNAMO ACTION IN SOLAR SURFACE SIMULATIONS

    SciTech Connect

    Graham, Jonathan Pietarila; Cameron, Robert; Schuessler, Manfred

    2010-05-10

    We demonstrate that a magneto-convection simulation incorporating essential physical processes governing solar surface convection exhibits turbulent small-scale dynamo action. By presenting a derivation of the energy balance equation and transfer functions for compressible magnetohydrodynamics, we quantify the source of magnetic energy on a scale-by-scale basis. We rule out the two alternative mechanisms for the generation of the small-scale magnetic field in the simulations: the tangling of magnetic field lines associated with the turbulent cascade and Alfvenization of small-scale velocity fluctuations ('turbulent induction'). Instead, we find that the dominant source of small-scale magnetic energy is stretching by inertial-range fluid motions of small-scale magnetic field lines against the magnetic tension force to produce (against Ohmic dissipation) more small-scale magnetic field. The scales involved become smaller with increasing Reynolds number, which identifies the dynamo as a small-scale turbulent dynamo.

  11. String Things.

    ERIC Educational Resources Information Center

    Mesa Public Schools, AZ.

    Designed for music educators instructing grades 4 through 8 in string instruments, this Mesa (Arizona) public schools guide presents information on the string curriculum, orchestras, and practicing. The goals and objectives for string instruments delineate grade levels and how student skills will be verified. Following 17 curriculum goal tests,…

  12. Hammered Strings

    NASA Astrophysics Data System (ADS)

    Rossing, Thomas D.

    In the next three chapters we consider the science of hammered string instruments. In this chapter, we present a brief discussion of vibrating strings excited by a hard or soft hammer. Chapter 20 discusses the most important hammered string instrument, the piano - probably the most versatile and popular of all musical instruments. Chapter 21 discusses hammered dulcimers, especially the American folk dulcimer.

  13. Implications of cosmic strings with time-varying tension on the CMB and large scale structure

    SciTech Connect

    Ichikawa, Kazuhide; Takahashi, Tomo; Yamaguchi, Masahide

    2006-09-15

    We investigate cosmological evolution and implications of cosmic strings with time-dependent tension. We derive basic equations of time development of the correlation length and the velocity of such strings, based on the one-scale model. Then, we find that, in the case where the tension depends on some power of the cosmic time, cosmic strings with time-dependent tension goes into the scaling solution if the power is lower than a critical value. We also discuss cosmic microwave background anisotropy and matter power spectra produced by these strings. The constraints on their tensions from the Wilkinson microwave anisotropy probe (WMAP) 3 yr data and Sloan digital sky survey (SDSS) data are also given.

  14. Experimental, theoretical, and numerical studies of small scale combustion

    NASA Astrophysics Data System (ADS)

    Xu, Bo

    Recently, the demand increased for the development of microdevices such as microsatellites, microaerial vehicles, micro reactors, and micro power generators. To meet those demands the biggest challenge is obtaining stable and complete combustion at relatively small scale. To gain a fundamental understanding of small scale combustion in this thesis, thermal and kinetic coupling between the gas phase and the structure at meso and micro scales were theoretically, experimentally, and numerically studied; new stabilization and instability phenomena were identified; and new theories for the dynamic mechanisms of small scale combustion were developed. The reduction of thermal inertia at small scale significantly reduces the response time of the wall and leads to a strong flame-wall coupling and extension of burning limits. Mesoscale flame propagation and extinction in small quartz tubes were theoretically, experimentally and numerically studied. It was found that wall-flame interaction in mesoscale combustion led to two different flame regimes, a heat-loss dominant fast flame regime and a wall-flame coupling slow flame regime. The nonlinear transition between the two flame regimes was strongly dependent on the channel width and flow velocity. It is concluded that the existence of multiple flame regimes is an inherent phenomenon in mesoscale combustion. In addition, all practical combustors have variable channel width in the direction of flame propagation. Quasi-steady and unsteady propagations of methane and propane-air premixed flames in a mesoscale divergent channel were investigated experimentally and theoretically. The emphasis was the impact of variable cross-section area and the flame-wall coupling on the flame transition between different regimes and the onset of flame instability. For the first time, spinning flames were experimentally observed for both lean and rich methane and propane-air mixtures in a broad range of equivalence ratios. An effective Lewis number

  15. Elastocapillarity can control the formation and the morphology of beads-on-string structures in solid fibers

    NASA Astrophysics Data System (ADS)

    Taffetani, M.; Ciarletta, P.

    2015-03-01

    Beads-on-string patterns have been experimentally observed in solid cylinders for a wide range of material properties and structural lengths, from millimetric soft gels to nanometric hard fibers. In this work, we combine theoretical analysis and numerical tools to investigate the formation and nonlinear dynamics of such beaded structures. We show that this morphological transition is driven by elastocapillarity, i.e., a complex interplay between the effects of surface tension and bulk elasticity. Unlike buckling or wrinkling, the presence of an axial elongation is found here to favor the onset of fiber beading, in agreement with existing experimental results on electrospun fibers, hydrogels, and nerves. Our results also prove that the applied stretch can be used in fabrication techniques to control the morphology of the emerging beads-on-string patterns. Such quantitative predictions open the way for several applications, from tissue engineering to the design of stretchable electronics and the microfabrication of functionalized surfaces.

  16. Perturbations from cosmic strings in cold dark matter

    NASA Technical Reports Server (NTRS)

    Albrecht, Andreas; Stebbins, Albert

    1992-01-01

    A systematic linear analysis of the perturbations induced by cosmic strings in cold dark matter is presented. The power spectrum is calculated and it is found that the strings produce a great deal of power on small scales. It is shown that the perturbations on interesting scales are the result of many uncorrelated string motions, which indicates a much more Gaussian distribution than was previously supposed.

  17. Perturbations from cosmic strings in cold dark matter

    NASA Technical Reports Server (NTRS)

    Albrecht, Andreas; Stebbins, Albert

    1991-01-01

    A systematic linear analysis of the perturbations induced by cosmic strings in cold dark matter is presented. The power spectrum is calculated and it is found that the strings produce a great deal of power on small scales. It is shown that the perturbations on interesting scales are the result of many uncorrelated string motions, which indicates a much more Gaussian distribution than was previously supposed.

  18. Evolution of cosmic string networks

    NASA Technical Reports Server (NTRS)

    Albrecht, Andreas; Turok, Neil

    1989-01-01

    A discussion of the evolution and observable consequences of a network of cosmic strings is given. A simple model for the evolution of the string network is presented, and related to the statistical mechanics of string networks. The model predicts the long string density throughout the history of the universe from a single parameter, which researchers calculate in radiation era simulations. The statistical mechanics arguments indicate a particular thermal form for the spectrum of loops chopped off the network. Detailed numerical simulations of string networks in expanding backgrounds are performed to test the model. Consequences for large scale structure, the microwave and gravity wave backgrounds, nucleosynthesis and gravitational lensing are calculated.

  19. Bowed Strings

    NASA Astrophysics Data System (ADS)

    Rossing, Thomas D.; Hanson, Roger J.

    In the next eight chapters, we consider some aspects of the science of bowed string instruments, old and new. In this chapter, we present a brief discussion of bowed strings, a subject that will be developed much more thoroughly in Chap. 16. Chapters 13-15 discuss the violin, the cello, and the double bass. Chapter 17 discusses viols and other historic string instruments, and Chap. 18 discusses the Hutchins-Schelleng violin octet.

  20. Small scale tests on the progressive retreat of soil slopes

    NASA Astrophysics Data System (ADS)

    Voulgari, Chrysoula; Utili, Stefano; Castellanza, Riccardo

    2015-04-01

    In this paper, the influence due to the presence of cracks on the morphologic evolution of natural cliffs subject to progressive retreat induced by weathering is investigated through small scale laboratory tests. Weathering turns hard rocks into soft rocks that maintain the structure of the intact rocks, but are characterised by higher void ratios and reduced bond strengths; soft rocks are transformed into granular soils generally called residual soils. A number of landslides develop in slopes due to weathering which results in the progressive retrogression of the slope face and the further degradation within the weathering zone. Cracks, that are widely present, can be a result of weathering and they can cause a significant decrease in their stability, as they provide preferential flow channels which increase the soil permeability and decrease the soil strength. The geological models employed until now are mainly empirical. Several researchers have tried to study the stability of slopes through experimental procedures. Centrifuge modelling is widely used to investigate the failure of slopes. Small scale tests are also an important approach, in order to study the behaviour of a slope under certain conditions, such as the existence of water, as they allow the observation of the infiltration processes, the movement of the weathering front, deformation and failure. However, the deformation response of a slope subject to weathering is not yet thoroughly clarified. In this work, a set of experiments were conducted to investigate weathering induced successive landslides. Weathering was applied to the slope model by wetting the slope crest through a rainfall simulator device. The moisture content of the soil during the tests was monitored by soil moisture sensors that were buried inside the slope model. High resolution cameras were recording the behaviour of the slope model. GeoPIV was used to analyse the frames and obtain the deformations of the slope model during the

  1. Small-scale upper mantle extension beneath a destroyed craton

    NASA Astrophysics Data System (ADS)

    Zhao, L.; Zheng, T.; Chen, L.; Ai, Y.; He, Y.; Xu, X.

    2014-12-01

    The North China Craton (NCC), as an unusual craton with part of its thick lithosphere destructed, records the geodynamic processes associated with the convergence of Eurasia and the Pacific and Philippine plates lasting from the Mesozoic to the Cenozoic. How the cratonic lithosphere deformed in response to the extensional tectonics caused by the oceanic plate subduction, however, remains debated. In order to investigate the mantle deformation of the NCC, we present new shear wave splitting measurements and updated tomographic models beneath a 900-km long profile across the north NCC. Compared to our other observations in the NCC, this profile is shorter but also crosses a region that experienced strong lithospheric destruction, therefore provides a good opportunity to improve our understanding of upper mantle deformation during the craton destruction. The upper mantle deformation is studied using SKS data from 60 broadband stations with average spacing of 15 km. For the data from events occurring at distances of 85º-115º, fast polarization directions and delay times (fδt) are retrieved by a routine method, while for the events at distances < 85º, waveform modeling are applied to obtain (fδt) after separating the effects of S and SKS. The measured splitting parameters show small-scale variations from east to west: the major fast directions, trending NE-SW or NW-SE in contrast, distribute intermittently along the profile. We plot the splitting parameters overlapping on the geological map and the tomography image for a depth range of 120-300 km. Comparison shows good consistency of the splitting pattern and structural features both at shallow and deep depths: NW-SE trending fast directions are observed at stations located within the basins or extensional zones like metamorphic core complexes, with the fast direction parallel to the extensional or stretching directions; the fast directions and the shear-wave velocity anomalies within the upper mantle

  2. Small-Scale Farming: A Portrait from Polk County, Oregon.

    ERIC Educational Resources Information Center

    Young, John A.; Caday, Peter

    A study of small-scale farmers in Polk County, Oregon, examined characteristics of, and variations among, small-scale farmers and developed some guidelines for assistance programs targeted for such a group. During the months of May, June, and July of 1978 an average of 4 days a week was spent locating and interviewing 44 small farm operators in…

  3. Higher order intercommutations in cosmic string collisions.

    PubMed

    Achúcarro, A; Verbiest, G J

    2010-07-01

    We report the first observation of multiple intercommutation (more than two successive reconnections) of Abelian Higgs cosmic strings at ultrahigh collision speeds, and the formation of "kink trains" with up to four closely spaced left- or right-moving kinks, in the deep type-II regime 16 ≤ β ≤ 64 (where β=m(scalar)2/m(gauge)2). The minimum critical speed for double reconnection goes down from ∼0.98c at β = 1 to ∼0.86c for β = 64. The process leading to the second intercommutation changes with β: it involves an expanding loop if β ≥ 16, but only a radiation blob if 1 < β ≤ 8. Triple reconnections are generic in the loop-mediated regime for collision parameters on the boundary between single and double reconnection. For β = 16 we observe quadruple events. We comment on the effect of strongly repulsive core interactions on the small scale structure on the strings and their gravitational wave emission. PMID:20867697

  4. Higher Order Intercommutations in Cosmic String Collisions

    SciTech Connect

    Achucarro, A.; Verbiest, G. J.

    2010-07-09

    We report the first observation of multiple intercommutation (more than two successive reconnections) of Abelian Higgs cosmic strings at ultrahigh collision speeds, and the formation of ''kink trains'' with up to four closely spaced left- or right-moving kinks, in the deep type-II regime 16{<=}{beta}{<=}64 (where {beta}=m{sub scalar}{sup 2}/m{sub gauge}{sup 2}). The minimum critical speed for double reconnection goes down from {approx}0.98c at {beta}=1 to {approx}0.86c for {beta}=64. The process leading to the second intercommutation changes with {beta}: it involves an expanding loop if {beta}{>=}16, but only a radiation blob if 1<{beta}{<=}8. Triple reconnections are generic in the loop-mediated regime for collision parameters on the boundary between single and double reconnection. For {beta}=16 we observe quadruple events. We comment on the effect of strongly repulsive core interactions on the small scale structure on the strings and their gravitational wave emission.

  5. Small-scale Materials Behavior from X-ray Microdiffraction and Imaging

    SciTech Connect

    Barabash, Rozaliya; Ice, Gene E

    2010-01-01

    This commentary introduces a JOM topic that highlights novel applications of x-ray microdiffraction and imaging to study structural properties of materials at a small scale. The development of ultra-brilliant synchrotron x-ray sources provides important new opportunities for the analysis of local and near-surface material structures. This topic includes manuscripts that describe how different versions of polychromatic and monochromatic microdiffraction can be used to study small scale plasticity in a range of materials. A variety of ingenious methods are described as developed in laboratories around the world.

  6. Risk of Resource Failure and Toolkit Variation in Small-Scale Farmers and Herders

    PubMed Central

    Collard, Mark; Ruttle, April; Buchanan, Briggs; O’Brien, Michael J.

    2012-01-01

    Recent work suggests that global variation in toolkit structure among hunter-gatherers is driven by risk of resource failure such that as risk of resource failure increases, toolkits become more diverse and complex. Here we report a study in which we investigated whether the toolkits of small-scale farmers and herders are influenced by risk of resource failure in the same way. In the study, we applied simple linear and multiple regression analysis to data from 45 small-scale food-producing groups to test the risk hypothesis. Our results were not consistent with the hypothesis; none of the risk variables we examined had a significant impact on toolkit diversity or on toolkit complexity. It appears, therefore, that the drivers of toolkit structure differ between hunter-gatherers and small-scale food-producers. PMID:22844421

  7. Small-scale plasma irregularities in the nightside Venus ionosphere

    NASA Technical Reports Server (NTRS)

    Grebowsky, J. M.; Curtis, S. A.; Brace, L. H.

    1991-01-01

    The individual volt-ampere curves from the Pioneer Venus Orbiter electron temperature probe showed evidence for small-scale density irregularities, or short-period plasma waves, in regions of the nightside ionosphere where the Orbiter electric field detector observed waves in its 100-Hz channel. A survey of the nightside volt-ampere curves has revealed several hundred examples of such irregularities. The I-V structures correspond to plasma density structure with spatial scale sizes in the range of about 100-2000 m, or alternatively they could be viewed as waves having frequencies extending toward 100 Hz. They are often seen as isolated events, with spatial extent along the orbit frequently less than 80 km. The density irregularities or waves occur in or near prominent gradients in the ambient plasma concentrations both at low altitudes where molecular ions are dominant and at higher altitudes in regions of reduced plasma density where O(+) is the major ion. Electric field 100-Hz bursts occur simultaneously, with the majority of the structured I-V curves providing demonstrative evidence that at least some of the E field signals are produced within the ionosphere.

  8. Practical small-scale explosive seam welding

    NASA Technical Reports Server (NTRS)

    Bement, L. J.

    1983-01-01

    Joining principles and variables, types of joints, capabilities, and current and potential applications are described for an explosive seam welding process developed at NASA Langley Research Center. Variable small quantities of RDX explosive in a ribbon configuration are used to create narrow (less than 0.5 inch), long length, uniform, hermetrically sealed joints that exhibit parent metal properties in a wide variety of metals, alloys, and combinations. The first major all application of the process is the repair of four nuclear reactors in Canada. Potential applications include pipelines, sealing of vessels, and assembly of large space structures.

  9. Postmodern string theory: Stochastic formulation

    NASA Astrophysics Data System (ADS)

    Aurilia, A.; Spallucci, E.; Vanzetta, I.

    1994-11-01

    In this paper we study the dynamics of a statistical ensemble of strings, building on a recently proposed gauge theory of the string geodesic field. We show that this stochastic approach is equivalent to the Carathéodory formulation of the Nambu-Goto action, supplemented by an averaging procedure over the family of classical string world sheets which are solutions of the equation of motion. In this new framework, the string geodesic field is reinterpreted as the Gibbs current density associated with the string statistical ensemble. Next, we show that the classical field equations derived from the string gauge action can be obtained as the semiclassical limit of the string functional wave equation. For closed strings, the wave equation itself is completely analogous to the Wheeler-DeWitt equation used in quantum cosmology. Thus, in the string case, the wave function has support on the space of all possible spatial loop configurations. Finally, we show that the string distribution induces a multiphase, or cellular structure on the spacetime manifold characterized by domains with a purely Riemannian geometry separated by domain walls over which there exists a predominantly Weyl geometry.

  10. Small scale thematic mapping - A case for radar imagery

    NASA Technical Reports Server (NTRS)

    Henderson, F. M.

    1974-01-01

    Small scale thematic maps (1:250,000 and smaller) of physical and cultural phenomena manifested on the landscape are a major concern to scientists and investigators in diverse disciplines. A strip of K-band radar imagery consisting of a traverse from eastern Minnesota to northern Utah was employed to evaluate the potential of radar imagery for small scale land use mapping. In the course of this investigation, it was discovered that certain borders derived from radar imagery were compatible with borders found on the nonland use thematic maps used for comparison. Specifically, numerous borders and regions of small scale maps of landforms, soils, vegetation, and geology are found to be similar to the radar land use regions. Although far from conclusive it appears that radar imagery can be employed in the small scale mapping of landforms and possibly for mapping physiognomic or economic vegetation.

  11. Dynamic properties of small-scale solar wind plasma fluctuations.

    PubMed

    Riazantseva, M O; Budaev, V P; Zelenyi, L M; Zastenker, G N; Pavlos, G P; Safrankova, J; Nemecek, Z; Prech, L; Nemec, F

    2015-05-13

    The paper presents the latest results of the studies of small-scale fluctuations in a turbulent flow of solar wind (SW) using measurements with extremely high temporal resolution (up to 0.03 s) of the bright monitor of SW (BMSW) plasma spectrometer operating on astrophysical SPECTR-R spacecraft at distances up to 350,000 km from the Earth. The spectra of SW ion flux fluctuations in the range of scales between 0.03 and 100 s are systematically analysed. The difference of slopes in low- and high-frequency parts of spectra and the frequency of the break point between these two characteristic slopes was analysed for different conditions in the SW. The statistical properties of the SW ion flux fluctuations were thoroughly analysed on scales less than 10 s. A high level of intermittency is demonstrated. The extended self-similarity of SW ion flux turbulent flow is constantly observed. The approximation of non-Gaussian probability distribution function of ion flux fluctuations by the Tsallis statistics shows the non-extensive character of SW fluctuations. Statistical characteristics of ion flux fluctuations are compared with the predictions of a log-Poisson model. The log-Poisson parametrization of the structure function scaling has shown that well-defined filament-like plasma structures are, as a rule, observed in the turbulent SW flows. PMID:25848078

  12. Dynamic properties of small-scale solar wind plasma fluctuations.

    PubMed

    Riazantseva, M O; Budaev, V P; Zelenyi, L M; Zastenker, G N; Pavlos, G P; Safrankova, J; Nemecek, Z; Prech, L; Nemec, F

    2015-05-13

    The paper presents the latest results of the studies of small-scale fluctuations in a turbulent flow of solar wind (SW) using measurements with extremely high temporal resolution (up to 0.03 s) of the bright monitor of SW (BMSW) plasma spectrometer operating on astrophysical SPECTR-R spacecraft at distances up to 350,000 km from the Earth. The spectra of SW ion flux fluctuations in the range of scales between 0.03 and 100 s are systematically analysed. The difference of slopes in low- and high-frequency parts of spectra and the frequency of the break point between these two characteristic slopes was analysed for different conditions in the SW. The statistical properties of the SW ion flux fluctuations were thoroughly analysed on scales less than 10 s. A high level of intermittency is demonstrated. The extended self-similarity of SW ion flux turbulent flow is constantly observed. The approximation of non-Gaussian probability distribution function of ion flux fluctuations by the Tsallis statistics shows the non-extensive character of SW fluctuations. Statistical characteristics of ion flux fluctuations are compared with the predictions of a log-Poisson model. The log-Poisson parametrization of the structure function scaling has shown that well-defined filament-like plasma structures are, as a rule, observed in the turbulent SW flows.

  13. Dynamic properties of small-scale solar wind plasma fluctuations

    PubMed Central

    Riazantseva, M. O.; Budaev, V. P.; Zelenyi, L. M.; Zastenker, G. N.; Pavlos, G. P.; Safrankova, J.; Nemecek, Z.; Prech, L.; Nemec, F.

    2015-01-01

    The paper presents the latest results of the studies of small-scale fluctuations in a turbulent flow of solar wind (SW) using measurements with extremely high temporal resolution (up to 0.03 s) of the bright monitor of SW (BMSW) plasma spectrometer operating on astrophysical SPECTR-R spacecraft at distances up to 350 000 km from the Earth. The spectra of SW ion flux fluctuations in the range of scales between 0.03 and 100 s are systematically analysed. The difference of slopes in low- and high-frequency parts of spectra and the frequency of the break point between these two characteristic slopes was analysed for different conditions in the SW. The statistical properties of the SW ion flux fluctuations were thoroughly analysed on scales less than 10 s. A high level of intermittency is demonstrated. The extended self-similarity of SW ion flux turbulent flow is constantly observed. The approximation of non-Gaussian probability distribution function of ion flux fluctuations by the Tsallis statistics shows the non-extensive character of SW fluctuations. Statistical characteristics of ion flux fluctuations are compared with the predictions of a log-Poisson model. The log-Poisson parametrization of the structure function scaling has shown that well-defined filament-like plasma structures are, as a rule, observed in the turbulent SW flows. PMID:25848078

  14. Cosmic strings

    NASA Technical Reports Server (NTRS)

    Bennett, David P.

    1988-01-01

    Cosmic strings are linear topological defects which are predicted by some grand unified theories to form during a spontaneous symmetry breaking phase transition in the early universe. They are the basis for the only theories of galaxy formation aside from quantum fluctuations from inflation based on fundamental physics. In contrast to inflation, they can also be observed directly through gravitational lensing and their characterisitc microwave background anisotropy. It was recently discovered that details of cosmic string evolution are very differnt from the so-called standard model that was assumed in most of the string-induced galaxy formation calculations. Therefore, the details of galaxy formation in the cosmic string models are currently very uncertain.

  15. Cosmic strings

    SciTech Connect

    Bennett, D.P.

    1988-07-01

    Cosmic strings are linear topological defects that are predicted by some grand unified theories to form during a spontaneous symmetry breaking phase transition in the early universe. They are the basis for the only theories of galaxy formation aside from quantum fluctuations from inflation that are based on fundamental physics. In contrast to inflation, they can also be observed directly through gravitational lensing and their characteristic microwave background anistropy. It has recently been discovered by F. Bouchet and myself that details of cosmic string evolution are very different from the so-called ''standard model'' that has been assumed in most of the string induced galaxy formation calculations. Therefore, the details of galaxy formation in the cosmic string models are currently very uncertain. 29 refs., 9 figs.

  16. Dark strings

    SciTech Connect

    Vachaspati, Tanmay

    2009-09-15

    Recent astrophysical observations have motivated novel theoretical models of the dark matter sector. A class of such models predicts the existence of GeV scale cosmic strings that communicate with the standard model sector by Aharonov-Bohm interactions with electrically charged particles. We discuss the cosmology of these 'dark strings' and investigate possible observational signatures. More elaborate dark sector models are argued to contain hybrid topological defects that may also have observational signatures.

  17. Small-scale field-aligned currents observed by the AKEBONO (EXOS-D) satellite

    SciTech Connect

    Fukunishi, H.; Oya, H. ); Kokubun, S. ); Tohyama, F. ); Mukai, T.; Fujii, R.

    1991-02-01

    The EXOS-D fluxgate magnetometer data obtained at 3,000-10,000 km altitude have shown that small-scale field-aligned currents always exist in large-scale region 1, region 2, cusp and polar cap current systems. Assuming that these small-scale field-aligned currents have current sheet structure, the width of current sheet is estimated to be 5-20 km at ionospheric altitude. By comparing the magnetometer data with charged particle and high frequency plasma wave data simultaneously obtained from EXOS-D, it is found that small-scale currents have one-to-one correspondence with localized electron precipitation events characterized by flux enhancement over a wide energy range from 10 eV to several keV and broadband electrostatic bursts occasionally extending above local plasma frequencies or electron cyclotron frequencies.

  18. Cosmic String Global Superconducting Dirac Born Infeld

    NASA Astrophysics Data System (ADS)

    Ikrima, Ika; Ramadhan, Handhika S.; Mart, Terry

    2016-08-01

    Superconducting cosmic string possibly plays an important role in the formation of the universe structure. The physics of this phenomenon has been explored by studying the field theory in the string interior. Numerical solutions of superconducting strings with all relevant fields are presented in this paper. The field is constructed from a generalization of the usual field theory of superconducting global string, but the kinetic term consists of the Dirac Born Infeld (DBI). Some changes in the characteristic of the superconducting string DBI from the usual superconducting string case have been observed. The observation includes physical mechanism of all related fields.

  19. Efficiency of an unstable resonator with an active medium containing small-scale phase inhomogeneities

    SciTech Connect

    Lobachev, V V; Strakhov, S Yu

    2004-01-31

    Properties of an unstable resonator with small-scale periodic inhomogeneities of the refractive index in an active medium are considered. It is shown that the parameters of output radiation depend on the structure of a phase inhomogeneity. The methods for increasing the resonator efficiency are analysed. (resonators. interferometers)

  20. Two aspects of one loop structure: Unitarity delay in the Standard Model and modular invariance in string theory

    SciTech Connect

    Ahn, C.

    1989-08-01

    We study two aspects of one loop structures in quantum field theories which describe two different areas of particle physics: the one loop unitarity behavior of the Standard Model of electroweak interactions and modular invariance of string model theory. Loop expansion has its importance in that it contains quantum fluctuations due to all physical states in the theory. Therefore, by studying the various models to one loop, we can understand how the contents of the theory can contribute to physically measurable quantities and how the consistency at quantum level restricts the physical states of the theory, as well. In the first half of the thesis, we study one loop corrections to the process {ital e}{sup +}{ital e}{sup {minus}} {yields} {ital W}{sup +}{ital W}{sup {minus}}. In this process, there is a delicate unitarity-saving cancellation between s-channel and t-channel tree level Feynman diagrams. If the one loop contribution due to heavy particles corrects the channels asymmetrically, the cancellation, hence unitarity, will be delayed up to the mass scale of these heavy particles. We refer to this phenomena as the unitarity delay effect. Due to this effect, cross section below these mass scales can have significant radiative corrections which may provide an appropriate window through which we can see the high energy structure of the Standard Model from relatively low energy experiments. In the second half, we will show how quantum consistency can restrict the physical states in string theory. 53 refs., 13 figs.

  1. SCALING PROPERTIES OF SMALL-SCALE FLUCTUATIONS IN MAGNETOHYDRODYNAMIC TURBULENCE

    SciTech Connect

    Perez, Jean Carlos; Mason, Joanne; Boldyrev, Stanislav; Cattaneo, Fausto E-mail: j.mason@exeter.ac.uk E-mail: cattaneo@flash.uchicago.edu

    2014-09-20

    Magnetohydrodynamic (MHD) turbulence in the majority of natural systems, including the interstellar medium, the solar corona, and the solar wind, has Reynolds numbers far exceeding the Reynolds numbers achievable in numerical experiments. Much attention is therefore drawn to the universal scaling properties of small-scale fluctuations, which can be reliably measured in the simulations and then extrapolated to astrophysical scales. However, in contrast with hydrodynamic turbulence, where the universal structure of the inertial and dissipation intervals is described by the Kolmogorov self-similarity, the scaling for MHD turbulence cannot be established based solely on dimensional arguments due to the presence of an intrinsic velocity scale—the Alfvén velocity. In this Letter, we demonstrate that the Kolmogorov first self-similarity hypothesis cannot be formulated for MHD turbulence in the same way it is formulated for the hydrodynamic case. Besides profound consequences for the analytical consideration, this also imposes stringent conditions on numerical studies of MHD turbulence. In contrast with the hydrodynamic case, the discretization scale in numerical simulations of MHD turbulence should decrease faster than the dissipation scale, in order for the simulations to remain resolved as the Reynolds number increases.

  2. Arbuscular mycorrhizal fungal communities are phylogenetically clustered at small scales

    PubMed Central

    Horn, Sebastian; Caruso, Tancredi; Verbruggen, Erik; Rillig, Matthias C; Hempel, Stefan

    2014-01-01

    Next-generation sequencing technologies with markers covering the full Glomeromycota phylum were used to uncover phylogenetic community structure of arbuscular mycorrhizal fungi (AMF) associated with Festuca brevipila. The study system was a semi-arid grassland with high plant diversity and a steep environmental gradient in pH, C, N, P and soil water content. The AMF community in roots and rhizosphere soil were analyzed separately and consisted of 74 distinct operational taxonomic units (OTUs) in total. Community-level variance partitioning showed that the role of environmental factors in determining AM species composition was marginal when controlling for spatial autocorrelation at multiple scales. Instead, phylogenetic distance and spatial distance were major correlates of AMF communities: OTUs that were more closely related (and which therefore may have similar traits) were more likely to co-occur. This pattern was insensitive to phylogenetic sampling breadth. Given the minor effects of the environment, we propose that at small scales closely related AMF positively associate through biotic factors such as plant-AMF filtering and interactions within the soil biota. PMID:24824667

  3. Arbuscular mycorrhizal fungal communities are phylogenetically clustered at small scales.

    PubMed

    Horn, Sebastian; Caruso, Tancredi; Verbruggen, Erik; Rillig, Matthias C; Hempel, Stefan

    2014-11-01

    Next-generation sequencing technologies with markers covering the full Glomeromycota phylum were used to uncover phylogenetic community structure of arbuscular mycorrhizal fungi (AMF) associated with Festuca brevipila. The study system was a semi-arid grassland with high plant diversity and a steep environmental gradient in pH, C, N, P and soil water content. The AMF community in roots and rhizosphere soil were analyzed separately and consisted of 74 distinct operational taxonomic units (OTUs) in total. Community-level variance partitioning showed that the role of environmental factors in determining AM species composition was marginal when controlling for spatial autocorrelation at multiple scales. Instead, phylogenetic distance and spatial distance were major correlates of AMF communities: OTUs that were more closely related (and which therefore may have similar traits) were more likely to co-occur. This pattern was insensitive to phylogenetic sampling breadth. Given the minor effects of the environment, we propose that at small scales closely related AMF positively associate through biotic factors such as plant-AMF filtering and interactions within the soil biota.

  4. Small-Scale Fisheries Bycatch Jeopardizes Endangered Pacific Loggerhead Turtles

    PubMed Central

    Peckham, S. Hoyt; Diaz, David Maldonado; Walli, Andreas; Ruiz, Georgita; Crowder, Larry B.; Nichols, Wallace J.

    2007-01-01

    Background Although bycatch of industrial-scale fisheries can cause declines in migratory megafauna including seabirds, marine mammals, and sea turtles, the impacts of small-scale fisheries have been largely overlooked. Small-scale fisheries occur in coastal waters worldwide, employing over 99% of the world's 51 million fishers. New telemetry data reveal that migratory megafauna frequent coastal habitats well within the range of small-scale fisheries, potentially producing high bycatch. These fisheries occur primarily in developing nations, and their documentation and management are limited or non-existent, precluding evaluation of their impacts on non-target megafauna. Principal Findings/Methodology 30 North Pacific loggerhead turtles that we satellite-tracked from 1996–2005 ranged oceanwide, but juveniles spent 70% of their time at a high use area coincident with small-scale fisheries in Baja California Sur, Mexico (BCS). We assessed loggerhead bycatch mortality in this area by partnering with local fishers to 1) observe two small-scale fleets that operated closest to the high use area and 2) through shoreline surveys for discarded carcasses. Minimum annual bycatch mortality in just these two fleets at the high use area exceeded 1000 loggerheads year−1, rivaling that of oceanwide industrial-scale fisheries, and threatening the persistence of this critically endangered population. As a result of fisher participation in this study and a bycatch awareness campaign, a consortium of local fishers and other citizens are working to eliminate their bycatch and to establish a national loggerhead refuge. Conclusions/Significance Because of the overlap of ubiquitous small-scale fisheries with newly documented high-use areas in coastal waters worldwide, our case study suggests that small-scale fisheries may be among the greatest current threats to non-target megafauna. Future research is urgently needed to quantify small-scale fisheries bycatch worldwide. Localizing

  5. Plucked Strings

    NASA Astrophysics Data System (ADS)

    Rossing, Thomas D.

    In the next ten chapters we will discuss the science of plucked string instruments. Acoustic guitars and lutes are discussed in Chap. 3. Portuguese guitars, used in fado music, are discussed in Chap. 4 and guitars in Chap. 5, while electric guitars are discussed in Chap. 22. Banjos are discussed in Chap. 5, while mandolins are the subject of Chap. 6. Zithers and psalteries, especially Baltic psalteries, are discussed in Chap. 7. Harpsichords are discussed in Chap. 8, while harps are discussed in Chap. 9 and 10. Finally, plucked string instruments from Asia, such as the kito, shamisen, biwa, gayageum, geomungo, ch'in, p'I-p'a, and sitar are discussed in Chap. 11. These instruments are very different in character and in their musical roles, but they all depend upon plucked strings vibrating and exciting one or more soundboards or radiating surfaces.

  6. Small Scale Equidistribution of Eigenfunctions on the Torus

    NASA Astrophysics Data System (ADS)

    Lester, Stephen; Rudnick, Zeév

    2016-08-01

    We study the small scale distribution of the L 2 mass of eigenfunctions of the Laplacian on the flat torus {{T}d} . Given an orthonormal basis of eigenfunctions, we show the existence of a density one subsequence whose L 2 mass equidistributes at small scales. In dimension two our result holds all the way down to the Planck scale. For dimensions d = 3, 4 we can restrict to individual eigenspaces and show small scale equidistribution in that context. We also study irregularities of quantum equidistribution: We construct eigenfunctions whose L 2 mass does not equidistribute at all scales above the Planck scale. Additionally, in dimension d = 4 we show the existence of eigenfunctions for which the proportion of L 2 mass in small balls blows up at certain scales.

  7. A unified large/small-scale dynamo in helical turbulence

    NASA Astrophysics Data System (ADS)

    Bhat, Pallavi; Subramanian, Kandaswamy; Brandenburg, Axel

    2016-09-01

    We use high resolution direct numerical simulations (DNS) to show that helical turbulence can generate significant large-scale fields even in the presence of strong small-scale dynamo action. During the kinematic stage, the unified large/small-scale dynamo grows fields with a shape-invariant eigenfunction, with most power peaked at small scales or large k, as in Subramanian & Brandenburg. Nevertheless, the large-scale field can be clearly detected as an excess power at small k in the negatively polarized component of the energy spectrum for a forcing with positively polarized waves. Its strength overline{B}, relative to the total rms field Brms, decreases with increasing magnetic Reynolds number, ReM. However, as the Lorentz force becomes important, the field generated by the unified dynamo orders itself by saturating on successively larger scales. The magnetic integral scale for the positively polarized waves, characterizing the small-scale field, increases significantly from the kinematic stage to saturation. This implies that the small-scale field becomes as coherent as possible for a given forcing scale, which averts the ReM-dependent quenching of overline{B}/B_rms. These results are obtained for 10243 DNS with magnetic Prandtl numbers of PrM = 0.1 and 10. For PrM = 0.1, overline{B}/B_rms grows from about 0.04 to about 0.4 at saturation, aided in the final stages by helicity dissipation. For PrM = 10, overline{B}/B_rms grows from much less than 0.01 to values of the order the 0.2. Our results confirm that there is a unified large/small-scale dynamo in helical turbulence.

  8. Fundamental economic issues in the development of small scale hydro

    SciTech Connect

    Not Available

    1980-05-01

    Some basic economic issues involved in the development of small-scale hydroelectric power are addressed. The discussion represents an economist's view of the investment process in this resource. Very little investment has been made in small-scale hydro development and an attempt is made to show that the reason for this may not be that the expected present worth of the returns of the project do not exceed the construction cost by a sufficient amount. Rather, a set of factors in combination impose costs on the project not normally incurred in small businesses. The discussion covers costs, supply, demand, and profitability.

  9. String Cosmology: A Review

    SciTech Connect

    McAllister, Liam P.; Silverstein, Eva

    2007-10-22

    We give an overview of the status of string cosmology. We explain the motivation for the subject, outline the main problems, and assess some of the proposed solutions. Our focus is on those aspects of cosmology that benefit from the structure of an ultraviolet-complete theory.

  10. Exotic nonrelativistic string

    SciTech Connect

    Casalbuoni, Roberto; Gomis, Joaquim; Longhi, Giorgio

    2007-12-15

    We construct a classical nonrelativistic string model in 3+1 dimensions. The model contains a spurion tensor field that is responsible for the noncommutative structure of the model. Under double-dimensional reduction the model reduces to the exotic nonrelativistic particle in 2+1 dimensions.

  11. Updated constraints on the cosmic string tension

    SciTech Connect

    Battye, Richard; Moss, Adam

    2010-07-15

    We reexamine the constraints on the cosmic string tension from cosmic microwave background (CMB) and matter power spectra, and also from limits on a stochastic background of gravitational waves provided by pulsar timing. We discuss the different approaches to modeling string evolution and radiation. In particular, we show that the unconnected segment model can describe CMB spectra expected from thin string (Nambu) and field theory (Abelian-Higgs) simulations using the computed values for the correlation length, rms string velocity and small-scale structure relevant to each variety of simulation. Applying the computed spectra in a fit to CMB and SDSS data we find that G{mu}/c{sup 2}<2.6x10{sup -7} (2{sigma}) if the Nambu simulations are correct and G{mu}/c{sup 2}<6.4x10{sup -7} in the Abelian-Higgs case. The degeneracy between G{mu}/c{sup 2} and the power spectrum slope n{sub S} is substantially reduced from previous work. Inclusion of constraints on the baryon density from big bang nucleosynthesis (BBN) imply that n{sub S}<1 at around the 4{sigma} level for both the Nambu and Abelian-Higgs cases. As a by-product of our results, we find there is ''moderate-to-strong'' Bayesian evidence that the Harrison-Zel'dovich spectrum is excluded (odds ratio of {approx}100 ratio 1) by the combination of CMB, SDSS, and BBN when compared to the standard 6 parameter fit. Using the contribution to the gravitational wave background from radiation era loops as a conservative lower bound on the signal for specific values of G{mu}/c{sup 2} and loop production size, {alpha}, we find that G{mu}/c{sup 2}<7x10{sup -7} for {alpha}c{sup 2}/({Gamma}G{mu})<<1 and G{mu}/c{sup 2}<5x10{sup -11}/{alpha} for {alpha}c{sup 2}/({Gamma}G{mu})>>1.

  12. Small Scale Waves on Venus at High Latitudes

    NASA Astrophysics Data System (ADS)

    Limaye, Sanjay; Markiewicz, W. J.; Moissl, R.; Titov, D.

    2008-09-01

    On many occasions, the Venus Monitoring Camera (VMC) on Venus Express has observed several small scale waves or wave trains in high northern latitudes ( 70 to 75°) of Venus for the first time. Such waves were not detected earlier due to a combination of spatial resolution, observed region and duration. Wave trains with different characteristics have been seen at all four wavelengths used by the VMC (centered at 365, 513. 935 and 1010nm with 40, 50, 70 and 20 nm) in and are consistently in the same area on multiple consecutive orbits. Many are similar in appearance to ripples with wavelengths 5 to10 km with extents of some tens of km while others appear as thin straight lines, similar to the Circum Equatorial Belts (CEB) seen previously from Mariner 10 and Pioneer Venus missions at low latitudes. These are distinct from the fine scale transverse waves on the spiral bands on Venus which have been observed by both the VMC and the Visible Infrared Thermal Imaging Spectrometer (VIRTIS). In appearance and perhaps origins, these wave trains appear to be similar to gravity waves observed on Earth, particularly in the airglow images. Their detection on Venus confirms the existence of an atmospheric layer with a very stable lapse rate seen in the thermal structure data at an altitude of 65 to 67 km. The triggering mechanism for these waves could be horizontal or vertical wind shear. The contribution of these waves to momentum transport is not known, but likely is insignificant. However, this could be an observational limitation due to the combination of the eccentric orbit of Venus Express and the camera capabilities. This work has been made possible from a NASA Participating Scientist Grant NNG06GC68G and with the support provided by the VMC Team.

  13. Large- and Small-Scale Ring Current Electrodynamic Coupling

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.

    2003-01-01

    In this talk we will address the two primary issues of ring current (RC) electrodynamic coupling: 1. RC self-consistent magnetosphere-ionosphere coupling that includes calculation of the magnetospheric electric field (large scale electrodynamic coupling); and 2. RC self-consistent coupling with electromagnetic ion cyclotron (EMIC) waves (small scale electrodynamic coupling). Our study will be based on two RC models that we have recently developed in our group. The first model by Khazanov et al. [2002] couples the system of two kinetic equations: one equation which describes the RC ion dynamics and another equation which describes the energy density evolution of EMIC waves. The second model by Khazanov et al. [2003] deals with large scale electrodynamic coupling processes and provides a self-consistent simulation of RC ions and the magnetospheric electric field. There is presently no model that addresses both of these issues simultaneously in a self-consistent calculation. However, the need exists for such a model, because these two processes directly influence each other, with the mesoscale coupling changing the drift paths of the thermal and energetic particle populations in the inner magnetosphere, thereby changing the wave interactions, and the microscale coupling altering the pitch angle distributions and ionospheric conductivities (through increased precipitation), thus changing the field-aligned currents and electric potential structure. The initial thrust of the work will be the development of a combined kinetic model of micro- and meso-scale RC electrodynamic coupling processes and to examine their interactions with each other on a global scale.

  14. Teaching Strings.

    ERIC Educational Resources Information Center

    New York State Education Dept., Albany. Bureau of Secondary Curriculum Development.

    Intended primarily for use by instrumental music teachers who do not have a major concentration in strings, this guide provides pertinent basic resources, materials, teaching--learning expectation, and a general overall guide to achievement levels at various stages of development. Discussions are presented of Choosing the Proper Method Book,…

  15. Nanoflares, Spicules, and Other Small-Scale Dynamic Phenomena on the Sun

    NASA Technical Reports Server (NTRS)

    Klimchuk, James

    2010-01-01

    There is abundant evidence of highly dynamic phenomena occurring on very small scales in the solar atmosphere. For example, the observed pr operties of many coronal loops can only be explained if the loops are bundles of unresolved strands that are heated impulsively by nanoflares. Type II spicules recently discovered by Hinode are an example of small-scale impulsive events occurring in the chromosphere. The exist ence of these and other small-scale phenomena is not surprising given the highly structured nature of the magnetic field that is revealed by photospheric observations. Dynamic phenomena also occur on much lar ger scales, including coronal jets, flares, and CMEs. It is tempting to suggest that these different phenomena are all closely related and represent a continuous distribution of sizes and energies. However, this is a dangerous over simplification in my opinion. While it is tru e that the phenomena all involve "magnetic reconnection" (the changin g of field line connectivity) in some form, how this occurs depends s trongly on the magnetic geometry. A nanoflare resulting from the interaction of tangled magnetic strands within a confined coronal loop is much different from a major flare occurring at the current sheet form ed when a CME rips open an active region. I will review the evidence for ubiquitous small-scale dynamic phenomena on the Sun and discuss wh y different phenomena are not all fundamentally the same.

  16. Seismic small-scale discontinuity sparsity-constraint inversion method using a penalty decomposition algorithm

    NASA Astrophysics Data System (ADS)

    Zhao, Jingtao; Peng, Suping; Du, Wenfeng

    2016-02-01

    We consider sparsity-constraint inversion method for detecting seismic small-scale discontinuities, such as edges, faults and cavities, which provide rich information about petroleum reservoirs. However, where there is karstification and interference caused by macro-scale fault systems, these seismic small-scale discontinuities are hard to identify when using currently available discontinuity-detection methods. In the subsurface, these small-scale discontinuities are separately and sparsely distributed and their seismic responses occupy a very small part of seismic image. Considering these sparsity and non-smooth features, we propose an effective L 2-L 0 norm model for improvement of their resolution. First, we apply a low-order plane-wave destruction method to eliminate macro-scale smooth events. Then, based the residual data, we use a nonlinear structure-enhancing filter to build a L 2-L 0 norm model. In searching for its solution, an efficient and fast convergent penalty decomposition method is employed. The proposed method can achieve a significant improvement in enhancing seismic small-scale discontinuities. Numerical experiment and field data application demonstrate the effectiveness and feasibility of the proposed method in studying the relevant geology of these reservoirs.

  17. Study of Some Properties of Cosmic Strings.

    NASA Astrophysics Data System (ADS)

    Aryal, Mukunda Mani

    This work deals with some of the properties of stringlike topological structures that can arise in reasonable models of grand unified theories. We study stringlike structures formed when a simply or multiply connected group breaks spontaneously to an unbroken subgroup. If the original group is simply connected then the unbroken subgroup has to have two or more disconnected components in order to produce strings. If the number of such components of the unbroken subgroup is n, we call the resulting string Zn strings. In this work I want to study some properties of Z2 and Z3 strings. In some cases the unbroken subgroup Z2 can be embedded in different U(1) subgroups of G, giving topologically equivalent but dynamically different strings. We obtain the string mass in terms of the Higg's field vacuum expectation value of various values of the gauge and quartic Higg's field coupling constants by numerical calculation. We find that in a wide range of realistic cases the lowest mass embedding gives strings which are gauge equivalent to antistrings, in which case solitons of Hindmarsh and Kibble do not occur. Statistical properties of Z2 and Z3 strings produced in a phase transition in the early universe are studied using a Monte Carlo simulation. For Z3 strings it is shown that the system is dominated by one infinite network of Brownian strings. We calculate the gravitational field of a global string and conclude that distinguishing a global string from a gauge string observationally appears difficult at best in case such strings actually exist in nature. Our calculation is in weak field approximation. We also calculate the gravitational field of a cosmic string passing through a Schwarzschild black hole. We consider the thermodynamics of such an object. It is shown that S = (1/4)A where S is the entropy and A is the horizon area. Finally we discuss some problems in string electrodynamics.

  18. Environmentally Sound Small-Scale Forestry Projects. Guidelines for Planning.

    ERIC Educational Resources Information Center

    Ffolliott, Peter F.; Thames, John L.

    This manual, the third in a series of publications that address community development possibilities in developing nations, provides guidelines for small-scale forestry projects that are integrative and conservation-oriented. Chapters focus on: (1) users and uses (specifying targeted audience and general objectives); (2) planning process (including…

  19. Small Scale Beekeeping. Appropriate Technologies for Development. Manual M-17.

    ERIC Educational Resources Information Center

    Gentry, Curtis

    This manual is designed to assist Peace Corps volunteers in the development and implementation of small-scale beekeeping programs as a tool for development. Addressed in the individual chapters are bees and humans; project planning; the types and habits of bees; the essence of beekeeping; bee space and beehives; intermediate technology beekeeping;…

  20. 2010 Thin Film & Small Scale Mechanical Behavior Gordon Research Conference

    SciTech Connect

    Dr. Thomas Balk

    2010-07-30

    Over the past decades, it has been well established that the mechanical behavior of materials changes when they are confined geometrically at least in one dimension to small scale. It is the aim of the 2010 Gordon Conference on 'Thin Film and Small Scale Mechanical Behavior' to discuss cutting-edge research on elastic, plastic and time-dependent deformation as well as degradation mechanisms like fracture, fatigue and wear at small scales. As in the past, the conference will benefit from contributions from fundamental studies of physical mechanisms linked to material science and engineering reaching towards application in modern applications ranging from optical and microelectronic devices and nano- or micro-electrical mechanical systems to devices for energy production and storage. The conference will feature entirely new testing methodologies and in situ measurements as well as recent progress in atomistic and micromechanical modeling. Particularly, emerging topics in the area of energy conversion and storage, such as material for batteries will be highlighted. The study of small-scale mechanical phenomena in systems related to energy production, conversion or storage offer an enticing opportunity to materials scientists, who can provide new insight and investigate these phenomena with methods that have not previously been exploited.

  1. Small Scale Marine Fisheries: An Extension Training Manual. TR-30.

    ERIC Educational Resources Information Center

    Martinson, Steven; And Others

    This manual is designed for use in a preservice training program for prospective volunteers whose Peace Corps service will be spent working with small-scale artisanal fishing communities in developing nations. The program consists of 8 weeks of intensive training to develop competencies in marine fisheries technology and fisheries extension work…

  2. Environmentally Sound Small-Scale Water Projects. Guidelines for Planning.

    ERIC Educational Resources Information Center

    Tillman, Gus

    This manual is the second volume in a series of publications on community development programs. Guidelines are suggested for small-scale water projects that would benefit segments of the world's urban or rural poor. Strategies in project planning, implementation and evaluation are presented that emphasize environmental conservation and promote…

  3. Small Scale Charcoal Making: A Manual for Trainers.

    ERIC Educational Resources Information Center

    Karch, Ed; And Others

    This training program offers skills training in all stages of the development of technologies related to small-scale charcoal production, including the design, construction, operation, maintenance, repair, and evaluation of prototype kilns. The kiln designs are selected to be as consistent as possible with the realities of rural areas in…

  4. Small-Scale Spatial Variability of Ozone in Boulder, Colorado

    NASA Astrophysics Data System (ADS)

    Deanes, L. N.; Sadighi, K.; Casey, J. G.; Collier, A. M.; Hannigan, M.

    2015-12-01

    Surface ozone (O3) can pose several health risks to humans, such as an increased number of and intensity of asthma attacks. Considering this, it is important that ozone levels are monitored. While municipal air quality monitors are present in cities like Boulder, Colorado, these monitors often only consider regional analysis, neglecting the variability of compounds, such as ozone or carbon monoxide, over smaller distances. Small-scale (approximately 1 kilometer) spatial variability in ozone is important because humans experience these small scales on a daily basis. Using low-cost, next-generation air quality monitors ("pods") developed at the University of Colorado-Boulder, we assessed small-scale spatial variability of surface ozone in Boulder, Colorado. This was done by placing clusters of 4-5 pods within approximately 1 kilometer of each other at specific sites in the city of Boulder. We collected data at two sites: one on the University of Colorado-Boulder campus (i.e., an urban site) and one outside of the city (i.e., a rural site). Pods were left in their positions for one to two weeks allowing for observation of ozone trends. As expected the typical diurnal trend was observed; however, further analysis revealed differences between these daily trends. Data collected by the pods allows for better understanding of small-scale spatial variability of surface ozone and how this may be driven by nearby sources.

  5. On the Small-Scale Morphology of Asthenospheric Flow

    NASA Astrophysics Data System (ADS)

    Vidal, V.; Davaille, A.; Crambes, C.

    2003-12-01

    We investigated the interaction of small-scale cold instabilities dripping from a cooling lithosphere with a shear flow confined in the asthenosphere, using analog experiments. Rayleigh numbers ranged between 104 and 108. The fluids were either polymer solutions (constant viscosity), sugar or corn syrups (viscosity depending on temperature), or wax (phase transition). When cooling away from the ridge, the thickening lithosphere becomes thermally unstable and develops small-scale convective instabilities at its bottom. For sufficiently fast asthenospheric flow, these instabilities are sheared and remain trapped in the asthenosphere, following a helicoidal path aligned with the direction of plate motion. A phase diagram and scaling laws for the flow characteristics were determined. The observed helicoidal pattern could explain some geophysical observables such as small wavelength lineations in the terrestrial gravity field, or seismic anisotropy anomalies under the Pacific plate. Moreover, the distance from the ridge at which the small-scale instabilities form depends on the underlying mantle temperature: for a hotter mantle, they are generated closer to the ridge. Therefore, in the case of a ridge-centered plume, the hot temperature anomaly due to the plume triggers small-scale instabilities almost at the ridge. The heat transfer out of the mantle is accelerated, and the thickening of the lithosphere away from the ridge is delayed. Therefore, a groove at the bottom of the lithosphere may be expected along the track of a ridge-centred hotspot.

  6. Shaping Component Leads for Small-Scale Production

    NASA Technical Reports Server (NTRS)

    Jan, Lawrence

    1987-01-01

    Simple tool makes it easy to bend leads of electronic components quickly and uniformly for assembly on circuit board. Useful in small-scale production of electronic circuits; saves labor but avoids cost of complicated machinery. Made in range of sizes to accommodate components in variety of dimensions.

  7. Environmentally Sound Small-Scale Energy Projects. Guidelines for Planning.

    ERIC Educational Resources Information Center

    Bassan, Elizabeth Ann; Wood, Timothy S., Ed.

    This manual is the fourth volume in a series of publications that provide information for the planning of environmentally sound small-scale projects. Programs that aim to protect the renewable natural resources that supply most of the energy used in developing nations are suggested. Considerations are made for physical environmental factors as…

  8. Geometry, topology, and string theory

    SciTech Connect

    Varadarajan, Uday

    2003-07-10

    A variety of scenarios are considered which shed light upon the uses and limitations of classical geometric and topological notions in string theory. The primary focus is on situations in which D-brane or string probes of a given classical space-time see the geometry quite differently than one might naively expect. In particular, situations in which extra dimensions, non-commutative geometries as well as other non-local structures emerge are explored in detail. Further, a preliminary exploration of such issues in Lorentzian space-times with non-trivial causal structures within string theory is initiated.

  9. Sampling problems: The small scale structure of precipitation

    NASA Technical Reports Server (NTRS)

    Crane, R. K.

    1981-01-01

    The quantitative measurement of precipitation characteristics for any area on the surface of the Earth is not an easy task. Precipitation is rather variable in both space and time, and the distribution of surface rainfall data given location typically is substantially skewed. There are a number of precipitation process at work in the atmosphere, and few of them are well understood. The formal theory on sampling and estimating precipitation appears considerably deficient. Little systematic attention is given to nonsampling errors that always arise in utilizing any measurement system. Although the precipitation measurement problem is an old one, it continues to be one that is in need of systematic and careful attention. A brief history of the presently competing measurement technologies should aid us in understanding the problem inherent in this measurement task.

  10. The Effects of Kinetic Instabilities on Small-scale Turbulence in Earth’s Magnetosheath

    NASA Astrophysics Data System (ADS)

    Breuillard, H.; Yordanova, E.; Vaivads, A.; Alexandrova, O.

    2016-09-01

    The Earth's magnetosheath is the region delimited by the bow shock and the magnetopause. It is characterized by highly turbulent fluctuations covering all scales from MHD down to kinetic scales. Turbulence is thought to play a fundamental role in key processes such as energy transport and dissipation in plasma. In addition to turbulence, different plasma instabilities are generated in the magnetosheath because of the large anisotropies in plasma temperature introduced by its boundaries. In this study we use high-quality magnetic field measurements from Cluster spacecraft to investigate the effects of such instabilities on the small-scale turbulence (from ion down to electron scales). We show that the steepening of the power spectrum of magnetic field fluctuations in the magnetosheath occurs at the largest characteristic ion scale. However, the spectrum can be modified by the presence of waves/structures at ion scales, shifting the onset of the small-scale turbulent cascade toward the smallest ion scale. This cascade is therefore highly dependent on the presence of kinetic instabilities, waves, and local plasma parameters. Here we show that in the absence of strong waves the small-scale turbulence is quasi-isotropic and has a spectral index α ≈ -2.8. When transverse or compressive waves are present, we observe an anisotropy in the magnetic field components and a decrease in the absolute value of α. Slab/2D turbulence also develops in the presence of transverse/compressive waves, resulting in gyrotropy/non-gyrotropy of small-scale fluctuations. The presence of both types of waves reduces the anisotropy in the amplitude of fluctuations in the small-scale range.

  11. The "Magic" String

    ERIC Educational Resources Information Center

    Hoover, Todd F.

    2010-01-01

    The "Magic" String is a discrepant event that includes a canister with what appears to be the end of two strings protruding from opposite sides of it. Due to the way the strings are attached inside the canister, it appears as if the strings can magically switch the way they are connected. When one string end is pulled, the observer's expectation…

  12. LLNL Small-Scale Friction sensitivity (BAM) Test

    SciTech Connect

    Simpson, L.R.; Foltz, M.F.

    1996-06-01

    Small-scale safety testing of explosives, propellants and other energetic materials, is done to determine their sensitivity to various stimuli including friction, static spark, and impact. Testing is done to discover potential handling problems for either newly synthesized materials of unknown behavior, or materials that have been stored for long periods of time. This report describes the existing {open_quotes}BAM{close_quotes} Small-Scale Friction Test, and the methods used to determine the friction sensitivity pertinent to handling energetic materials. The accumulated data for the materials tested is not listed here - that information is in a database. Included is, however, a short list of (1) materials that had an unusual response, and (2), a few {open_quotes}standard{close_quotes} materials representing the range of typical responses usually seen.

  13. Leadership solves collective action problems in small-scale societies.

    PubMed

    Glowacki, Luke; von Rueden, Chris

    2015-12-01

    Observation of leadership in small-scale societies offers unique insights into the evolution of human collective action and the origins of sociopolitical complexity. Using behavioural data from the Tsimane forager-horticulturalists of Bolivia and Nyangatom nomadic pastoralists of Ethiopia, we evaluate the traits of leaders and the contexts in which leadership becomes more institutional. We find that leaders tend to have more capital, in the form of age-related knowledge, body size or social connections. These attributes can reduce the costs leaders incur and increase the efficacy of leadership. Leadership becomes more institutional in domains of collective action, such as resolution of intragroup conflict, where collective action failure threatens group integrity. Together these data support the hypothesis that leadership is an important means by which collective action problems are overcome in small-scale societies.

  14. Radar for small-scale land-use mapping

    NASA Technical Reports Server (NTRS)

    Henderson, F. M.

    1975-01-01

    Small-scale (1:250,000 and smaller) land-use maps are a major concern not only to geographers but also to national and regional planners. Unfortunately, such maps are usually out of date by the time they are printed. An interpretation key consisting of five physical and cultural characteristics of the environment evident on radar imagery is used to create land-use regions. Regions and borders interpreted from radar are compared with those found on two existing land-use maps created by traditional methods. Radar imagery can be used to create a small-scale land-use map with regions comparable to those found on existing land-use maps. However, the radar regions depict something more than land use and should be termed rural landscape regions.

  15. Statistical Evaluation of Small-scale Explosives Testing

    NASA Astrophysics Data System (ADS)

    Guymon, Clint

    2013-06-01

    Small-scale explosives sensitivity testing is used to qualitatively and quantitatively evaluate risk. Both relative comparison and characterization of the transition from no reaction to reaction is used to estimate that risk. Statistical comparisons and use of statistically efficient methods are critical to accurately and efficiently make risk related decisions. Many public and private entities are not making accurate decisions based on the test data because of the lack of properly applying basic statistical principles. We present methods and examples showing how to use statistics to accurately and efficiently evaluate the risk for relative comparison and in-process risk evaluation. Some of the methods presented include the Significance Chart Method and adaptive step-size techniques like the Neyer D-Optimal method. These methods are compared to the more traditional approaches like Bruceton and Probit. Use of statistical methods can significantly improve the efficiency, accuracy, and applicability of small-scale explosives sensitivity testing.

  16. Financing of private small scale hydroelectric projects: a summary guide

    SciTech Connect

    Not Available

    1981-05-01

    Small-scale hydroelectric (SSH) projects are increasingly being supported financially by private developers. Increases in fossil fuel prices, difficulties in the siting of large power plants, streamlining of the federal licensing process, changes in the marketing of power, and the extension of tax credits-all contribute to expectations of profitability in SSH projects. This document provides an overview of private financing for SSH projects.

  17. Legal factors affecting the financing of small scale hydroelectric projects

    SciTech Connect

    Wilson, W.H.; Ringo, M.J.; Forgione, N.

    1983-09-01

    An introduction to the major business organizational options open to small-scale hydroelectric (SSH) projects is given. The major federal income tax treatments of these options are compared. Significant general federal income tax factors affecting SSH projects are reintroduced and explained. Some of the special federal income tax problem areas in SSH development are isolated. Tax benefit flow through or transfer mechanisms are discussed. Tax exempt financing opportunities for private SSH projects are reviewed. (MHR)

  18. Interaction of dynamic rupture with small-scale heterogeneities

    NASA Astrophysics Data System (ADS)

    Galis, Martin; Mai, P. Martin

    2014-05-01

    Broadband ground motion simulations, with frequencies up to 10Hz, are important for engineering purposes, in particular for seismic hazard assessment for critical facilities. One problem in such simulations is the generation of high frequency radiation emitted during the dynamic rupture process. Ad-hoc kinematic rupture characterizations can be tweaked through empirical models to radiate over the desired frequency range, but their physical consistency remains questionable. In contrast, for physically self-consistent dynamic rupture modeling, controlled by friction, material parameters and the adopted physical laws, the mechanism that may lead to appropriate high-frequency radiation require heterogeneity in friction, stress, or fault geometry (or even all three quantities) at unknown but small length scales. Dunham at al. (2011) studied dynamic rupture propagation on rough faults in 2D, and described how fault roughness excites high-frequency radiation. In our study, we focus on the interaction of the dynamic rupture with small-scale heterogeneities on planar faults in 3D. We study effects of the interaction of dynamic rupture with 1) small-scale heterogeneities in the medium (that is, randomized 3D wave speed and density variations), and 2) small-scale heterogeneities in the frictional parameters. Our numerical results show significant variations in rupture velocity or peak slip velocity if small-scale heterogeneities are present. This indicates that the dynamic rupture is sensitive to both types of spatial inhomogeneity. At the same time we observe that the resulting near-source seismic wave fields are not very sensitive to these rupture variations, indicating that wavefront healing effects may "simplify" the complex seismic radiation once the waves propagated several wave-lengths away from the fault.

  19. Extraction of Extended Small-Scale Objects in Digital Images

    NASA Astrophysics Data System (ADS)

    Volkov, V. Y.

    2015-05-01

    Detection and localization problem of extended small-scale objects with different shapes appears in radio observation systems which use SAR, infra-red, lidar and television camera. Intensive non-stationary background is the main difficulty for processing. Other challenge is low quality of images, blobs, blurred boundaries; in addition SAR images suffer from a serious intrinsic speckle noise. Statistics of background is not normal, it has evident skewness and heavy tails in probability density, so it is hard to identify it. The problem of extraction small-scale objects is solved here on the basis of directional filtering, adaptive thresholding and morthological analysis. New kind of masks is used which are open-ended at one side so it is possible to extract ends of line segments with unknown length. An advanced method of dynamical adaptive threshold setting is investigated which is based on isolated fragments extraction after thresholding. Hierarchy of isolated fragments on binary image is proposed for the analysis of segmentation results. It includes small-scale objects with different shape, size and orientation. The method uses extraction of isolated fragments in binary image and counting points in these fragments. Number of points in extracted fragments is normalized to the total number of points for given threshold and is used as effectiveness of extraction for these fragments. New method for adaptive threshold setting and control maximises effectiveness of extraction. It has optimality properties for objects extraction in normal noise field and shows effective results for real SAR images.

  20. Strings and their compactification from the particle viewpoint

    SciTech Connect

    Slansky, R.

    1986-01-01

    A series of four lectures is given which deals with the particle formulation of string theory. An introductory lecture is given on where the idea of strings comes from and what strings are. An introduction is given to simple Lie algebras and their representations. Compactified strings and the heterotic theories are discussed, showing how infinite-dimensional Kac-Moody affine algebras can be spectrum generating algebras in (open) string theories. The spectrum of excited states of the heterotic string is examined, and comments are made on representations of affine algebras. Some aspects are shown of the algebraic structure of compactified closed bosonic strings. (LEW)

  1. The current status of observational constraints on cosmic strings

    SciTech Connect

    Caldwell, R.R.

    1993-10-01

    The observational restrictions on the cosmic string scenario for the formation of large scale structure are evaluated. this restrictions are due to the spectrum of gravitational radiation emitted by oscillating string loops, anisotropies in the cosmic microwave background caused by the strings, and evaporating black holes formed from collapsed cosmic string loops. It is shown that the only free parameter of the scenario, the cosmic string mass-per-unit-length, {mu}, is severely restricted.

  2. Detecting cosmic strings in the CMB with the Canny algorithm

    SciTech Connect

    Amsel, Stephen; Brandenberger, Robert H; Berger, Joshua E-mail: jb454@cornell.edu

    2008-04-15

    Line discontinuities in cosmic microwave background anisotropy maps are a distinctive prediction of models with cosmic strings. These signatures are visible in anisotropy maps with good angular resolution and should be identifiable using edge-detection algorithms. One such algorithm is the Canny algorithm. We study the potential of this algorithm to pick out the line discontinuities generated by cosmic strings. By applying the algorithm to small-scale microwave anisotropy maps generated from theoretical models with and without cosmic strings, we find that, given an angular resolution of several minutes of arc, cosmic strings can be detected down to a limit of the mass per unit length of the string which is one order of magnitude lower than the current upper bounds.

  3. Prevalence of small-scale jets from the networks of the solar transition region and chromosphere.

    PubMed

    Tian, H; DeLuca, E E; Cranmer, S R; De Pontieu, B; Peter, H; Martínez-Sykora, J; Golub, L; McKillop, S; Reeves, K K; Miralles, M P; McCauley, P; Saar, S; Testa, P; Weber, M; Murphy, N; Lemen, J; Title, A; Boerner, P; Hurlburt, N; Tarbell, T D; Wuelser, J P; Kleint, L; Kankelborg, C; Jaeggli, S; Carlsson, M; Hansteen, V; McIntosh, S W

    2014-10-17

    As the interface between the Sun's photosphere and corona, the chromosphere and transition region play a key role in the formation and acceleration of the solar wind. Observations from the Interface Region Imaging Spectrograph reveal the prevalence of intermittent small-scale jets with speeds of 80 to 250 kilometers per second from the narrow bright network lanes of this interface region. These jets have lifetimes of 20 to 80 seconds and widths of ≤300 kilometers. They originate from small-scale bright regions, often preceded by footpoint brightenings and accompanied by transverse waves with amplitudes of ~20 kilometers per second. Many jets reach temperatures of at least ~10(5) kelvin and constitute an important element of the transition region structures. They are likely an intermittent but persistent source of mass and energy for the solar wind. PMID:25324395

  4. Detecting small scale heterogeneities in the crust from ambient noise cross-correlation

    NASA Astrophysics Data System (ADS)

    Sun, W.; Fu, L.

    2012-12-01

    Ambient noise cross-correlation is extensively applied to obtain the surface wave dispersion, and further to study the structures of the crust and the upper mantle. In recent years, many applications of the ambient noise tomography are reported in many locations, e.g., California, Europe, New Zealand, Tibet, and even in the Antarctica. The scale is regional or even continental. However, the applications of the method in detecting small scale heterogeneities are paid little attention. Small scale heterogeneities may be important to monitor/predict activities of volcano. This is concluded from the fact activities of volcano will result in stress variations. Correspondingly, the velocity distribution, i.e., heterogeneities, will change. Here, we will try to extend the ambient noise cross-correlation method to study small heterogeneities in the crust.

  5. Prevalence of small-scale jets from the networks of the solar transition region and chromosphere.

    PubMed

    Tian, H; DeLuca, E E; Cranmer, S R; De Pontieu, B; Peter, H; Martínez-Sykora, J; Golub, L; McKillop, S; Reeves, K K; Miralles, M P; McCauley, P; Saar, S; Testa, P; Weber, M; Murphy, N; Lemen, J; Title, A; Boerner, P; Hurlburt, N; Tarbell, T D; Wuelser, J P; Kleint, L; Kankelborg, C; Jaeggli, S; Carlsson, M; Hansteen, V; McIntosh, S W

    2014-10-17

    As the interface between the Sun's photosphere and corona, the chromosphere and transition region play a key role in the formation and acceleration of the solar wind. Observations from the Interface Region Imaging Spectrograph reveal the prevalence of intermittent small-scale jets with speeds of 80 to 250 kilometers per second from the narrow bright network lanes of this interface region. These jets have lifetimes of 20 to 80 seconds and widths of ≤300 kilometers. They originate from small-scale bright regions, often preceded by footpoint brightenings and accompanied by transverse waves with amplitudes of ~20 kilometers per second. Many jets reach temperatures of at least ~10(5) kelvin and constitute an important element of the transition region structures. They are likely an intermittent but persistent source of mass and energy for the solar wind.

  6. Modeling the Influence of Small-Scale Surface Roughness on the Lunar Exosphere

    NASA Astrophysics Data System (ADS)

    Prem, Parvathy; Goldstein, David B.; Varghese, Philip L.; Trafton, Laurence M.

    2016-10-01

    The Moon and other virtually airless bodies provide distinctive environments for the transport and sequestration of water and other volatiles delivered to their surfaces by various sources. In this work, we conduct Monte Carlo simulations of water vapor transport on the Moon to investigate the role of small-scale roughness (unresolved by orbital measurements) in the migration and cold-trapping of volatiles. Observations indicate that the roughness of the lunar surface, together with the insulating nature of lunar regolith and the absence of significant exospheric heat flow, can cause large variations in temperature over very small scales. Surface temperature is a critical parameter in determining the residence time of migrating water molecules on the lunar surface, which in turn affects the rate and magnitude of volatile transport to permanently shadowed craters (cold traps) near the lunar poles, as well as exospheric structure and the susceptibility of migrating molecules to photodestruction. Here, we develop a rough surface temperature model suitable for simulations of volatile transport on a global scale. We compare results of Monte Carlo simulations of volatile transport with and without the surface roughness model and find that including small-scale temperature variations and shadowing leads to an increased probability of polar cold-trapping, as well as increased thermal escape, compensated for by decreased photodestruction. Exospheric structure is altered only slightly, primarily at the dawn terminator. We also examine the sensitivity of our results to the temperature of small-scale shadows, and the energetics of water molecule desorption from the lunar regolith (two factors that remain to be definitively constrained by other methods) and find that both these factors affect the rate at which cold trap capture and photodissociation occur, as well as exospheric longevity and density.

  7. Small-scale fluctuations in barium drifts at high latitudes and associated Joule heating effects

    NASA Astrophysics Data System (ADS)

    Hurd, L. D.; Larsen, M. F.

    2016-01-01

    Most previous estimates of Joule heating rates, especially the contribution of small-scale structure in the high-latitude ionosphere, have been based on incoherent scatter or coherent scatter radar measurements. An alternative estimate can be found from the plasma drifts obtained from ionized barium clouds released from sounding rockets. We have used barium drift data from three experiments to estimate Joule heating rates in the high-latitude E region for different magnetic activity levels. In particular, we are interested in the contribution of small-scale plasma drift fluctuations, corresponding to equivalent electric field fluctuations, to the local Joule heating rate on scales smaller than those typically resolved by radar or other measurements. Since Joule heating is a Lagrangian quantity, the inherently Lagrangian estimates provided by the chemical tracer measurements are a full description of the effects of electric field variance and neutral winds on the heating, differing from the Eulerian estimates of the type provided by ground-based measurements. Results suggest that the small-scale contributions to the heating can be more than a factor of 2 greater than the mean field contribution regardless of geomagnetic conditions, and at times the small-scale contribution is even larger. The high-resolution barium drift measurements, moreover, show that the fine structure in the electric field can be more variable than previous studies have reported for similar conditions. The neutral winds also affect the heating, altering the height-integrated Joule heating rates by as much as 12%, for the cases studied here, and modifying the height distribution of the heating profile as well.

  8. DSP: a protein shape string and its profile prediction server.

    PubMed

    Sun, Jiangming; Tang, Shengnan; Xiong, Wenwei; Cong, Peisheng; Li, Tonghua

    2012-07-01

    Many studies have demonstrated that shape string is an extremely important structure representation, since it is more complete than the classical secondary structure. The shape string provides detailed information also in the regions denoted random coil. But few services are provided for systematic analysis of protein shape string. To fill this gap, we have developed an accurate shape string predictor based on two innovative technologies: a knowledge-driven sequence alignment and a sequence shape string profile method. The performance on blind test data demonstrates that the proposed method can be used for accurate prediction of protein shape string. The DSP server provides both predicted shape string and sequence shape string profile for each query sequence. Using this information, the users can compare protein structure or display protein evolution in shape string space. The DSP server is available at both http://cheminfo.tongji.edu.cn/dsp/ and its main mirror http://chemcenter.tongji.edu.cn/dsp/.

  9. Examples of backreaction of small-scale inhomogeneities in cosmology

    NASA Astrophysics Data System (ADS)

    Green, Stephen R.; Wald, Robert M.

    2013-06-01

    In previous work, we introduced a new framework to treat large-scale backreaction effects due to small-scale inhomogeneities in general relativity. We considered one-parameter families of spacetimes for which such backreaction effects can occur, and we proved that, provided the weak energy condition on matter is satisfied, the leading effect of small-scale inhomogeneities on large-scale dynamics is to produce a traceless effective stress-energy tensor that itself satisfies the weak energy condition. In this work, we illustrate the nature of our framework by providing two explicit examples of one-parameter families with backreaction. The first, based on previous work of Berger, is a family of polarized vacuum Gowdy spacetimes on a torus, which satisfies all of the assumptions of our framework. As the parameter approaches its limiting value, the metric uniformly approaches a smooth background metric, but spacetime derivatives of the deviation of the metric from the background metric do not converge uniformly to zero. The limiting metric has nontrivial backreaction from the small-scale inhomogeneities, with an effective stress energy that is traceless and satisfies the weak energy condition, in accord with our theorems. Our second one-parameter family consists of metrics which have a uniform Friedmann-Lemaître-Robertson-Walker limit. This family satisfies all of our assumptions with the exception of the weak energy condition for matter. In this case, the limiting metric has an effective stress-energy tensor which is not traceless. We emphasize the importance of imposing energy conditions on matter in studies of backreaction.

  10. Small-scale Conformity of the Virgo Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Lee, Hye-Ran; Lee, Joon Hyeop; Jeong, Hyunjin; Park, Byeong-Gon

    2016-06-01

    We investigate the small-scale conformity in color between bright galaxies and their faint companions in the Virgo Cluster. Cluster member galaxies are spectroscopically determined using the Extended Virgo Cluster Catalog and the Sloan Digital Sky Survey Data Release 12. We find that the luminosity-weighted mean color of faint galaxies depends on the color of adjacent bright galaxy as well as on the cluster-scale environment (gravitational potential index). From this result for the entire area of the Virgo Cluster, it is not distinguishable whether the small-scale conformity is genuine or if it is artificially produced due to cluster-scale variation of galaxy color. To disentangle this degeneracy, we divide the Virgo Cluster area into three sub-areas so that the cluster-scale environmental dependence is minimized: A1 (central), A2 (intermediate), and A3 (outermost). We find conformity in color between bright galaxies and their faint companions (color-color slope significance S ˜ 2.73σ and correlation coefficient {cc}˜ 0.50) in A2, where the cluster-scale environmental dependence is almost negligible. On the other hand, the conformity is not significant or very marginal (S ˜ 1.75σ and {cc}˜ 0.27) in A1. The conformity is not significant either in A3 (S ˜ 1.59σ and {cc}˜ 0.44), but the sample size is too small in this area. These results are consistent with a scenario in which the small-scale conformity in a cluster is a vestige of infallen groups and these groups lose conformity as they come closer to the cluster center.

  11. Small-scale Conformity of the Virgo Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Lee, Hye-Ran; Lee, Joon Hyeop; Jeong, Hyunjin; Park, Byeong-Gon

    2016-06-01

    We investigate the small-scale conformity in color between bright galaxies and their faint companions in the Virgo Cluster. Cluster member galaxies are spectroscopically determined using the Extended Virgo Cluster Catalog and the Sloan Digital Sky Survey Data Release 12. We find that the luminosity-weighted mean color of faint galaxies depends on the color of adjacent bright galaxy as well as on the cluster-scale environment (gravitational potential index). From this result for the entire area of the Virgo Cluster, it is not distinguishable whether the small-scale conformity is genuine or if it is artificially produced due to cluster-scale variation of galaxy color. To disentangle this degeneracy, we divide the Virgo Cluster area into three sub-areas so that the cluster-scale environmental dependence is minimized: A1 (central), A2 (intermediate), and A3 (outermost). We find conformity in color between bright galaxies and their faint companions (color–color slope significance S ˜ 2.73σ and correlation coefficient {cc}˜ 0.50) in A2, where the cluster-scale environmental dependence is almost negligible. On the other hand, the conformity is not significant or very marginal (S ˜ 1.75σ and {cc}˜ 0.27) in A1. The conformity is not significant either in A3 (S ˜ 1.59σ and {cc}˜ 0.44), but the sample size is too small in this area. These results are consistent with a scenario in which the small-scale conformity in a cluster is a vestige of infallen groups and these groups lose conformity as they come closer to the cluster center.

  12. Small-Scale Chamber Test for Internal Blast Performance

    NASA Astrophysics Data System (ADS)

    Lee, Richard; Felts, Joshua

    2013-06-01

    The data reported here provides a validation of the use of a small-scale internal-blast test to predict the energy release of explosives in larger scale. The small-scale arrangement consisted of a 2-g booster and 10-g sample mounted in a holder attached at one end of a closed chamber. The internal volume of the chamber was 89 liters not including the charge holder. The design of the charge holder served two purposes. One was to provide confinement around the charge to avoid degradation of performance from explosives with critical diameters larger than that of the sample. The second was to provide a separate space from that of the chamber that retained the fragments from the confinement to minimize the absorption of heat from the products. The energy release was determined from measurements of the peak quasi-static overpressure and the ideal gas law. The results from six different explosives were compared to larger scale tests involving a bombproof chamber (180,000 liters) with bare charges between 1 and 16 kg. The energy release between small and large scale compared favorably with regard to relative ranking of each explosive. The energy release measured in the small chamber was lower than the large chamber analogs, possibly due to heat losses to the holder. Despite these differences, the small-scale chamber test appears to provide a ranking of explosives based on their energy release that correlates with larger scale tests. Hence, this test is a viable tool for optimizing compositional variations for internal blast performance in target scenarios of similar form factor.

  13. Classification of wetlands vegetation using small scale color infrared imagery

    NASA Technical Reports Server (NTRS)

    Williamson, F. S. L.

    1975-01-01

    A classification system for Chesapeake Bay wetlands was derived from the correlation of film density classes and actual vegetation classes. The data processing programs used were developed by the Laboratory for the Applications of Remote Sensing. These programs were tested for their value in classifying natural vegetation, using digitized data from small scale aerial photography. Existing imagery and the vegetation map of Farm Creek Marsh were used to determine the optimal number of classes, and to aid in determining if the computer maps were a believable product.

  14. A small scale biomass fueled gas turbine engine

    SciTech Connect

    Craig, J.D.; Purvis, C.R.

    1999-01-01

    A new generation of small scale (less than 20 MWd) biomass fueled, power plants are being developed based on a gas turbine (Brayton cycle) prime mover. These power plants are expected to increase the efficiency and lower the cost of generating power from fuels such as wood. The new power plants are also expected to economically utilize annual plant growth materials (such as rice hulls, cotton gin trash, nut shells, and various straws, grasses, and animal manures) that are not normally considered as fuel for power plants. This paper summarizes the new power generation concept with emphasis on the engineering challenges presented by the gas turbine component.

  15. Beads-on-String Structured Nanofibers for Smart and Reversible Oil/Water Separation with Outstanding Antifouling Property.

    PubMed

    Wang, Yuanfeng; Lai, Chuilin; Wang, Xiaowen; Liu, Yang; Hu, Huawen; Guo, Yujuan; Ma, Kaikai; Fei, Bin; Xin, John H

    2016-09-28

    It is challenging to explore a unified solution for the treatment of oily wastewater from complex sources. Thus, membrane materials with flexible separation schemes are highly desired. Herein, we fabricated a smart membrane by electrospinning TiO2 doped polyvinylidene fluoride (PVDF) nanofibers. The as-formed beads-on-string structure and hierarchical roughness of the nanofibers contribute to its superwetting/resisting property to liquids, which is desirable in oil/water separation. Switched simply by UV (or sunlight) irradiation and heating treatment, the smart membrane can realize reversible separation of oil/water mixtures by selectively allowing water or oil to pass through alone. Most importantly, the as-prepared nanofiber membrane possesses outstanding antifouling and self-cleaning performance resulting from the photocatalytic property of TiO2, which has practical significance in saving solvents and recycling materials. This work provides a route for fabricating cost-effective, easily scaled up, and recyclable membranes for on-demand oil/water separation in versatile situations, which can be of great usage in the new green separation technology. PMID:27588341

  16. Beads-on-String Structured Nanofibers for Smart and Reversible Oil/Water Separation with Outstanding Antifouling Property.

    PubMed

    Wang, Yuanfeng; Lai, Chuilin; Wang, Xiaowen; Liu, Yang; Hu, Huawen; Guo, Yujuan; Ma, Kaikai; Fei, Bin; Xin, John H

    2016-09-28

    It is challenging to explore a unified solution for the treatment of oily wastewater from complex sources. Thus, membrane materials with flexible separation schemes are highly desired. Herein, we fabricated a smart membrane by electrospinning TiO2 doped polyvinylidene fluoride (PVDF) nanofibers. The as-formed beads-on-string structure and hierarchical roughness of the nanofibers contribute to its superwetting/resisting property to liquids, which is desirable in oil/water separation. Switched simply by UV (or sunlight) irradiation and heating treatment, the smart membrane can realize reversible separation of oil/water mixtures by selectively allowing water or oil to pass through alone. Most importantly, the as-prepared nanofiber membrane possesses outstanding antifouling and self-cleaning performance resulting from the photocatalytic property of TiO2, which has practical significance in saving solvents and recycling materials. This work provides a route for fabricating cost-effective, easily scaled up, and recyclable membranes for on-demand oil/water separation in versatile situations, which can be of great usage in the new green separation technology.

  17. Systematic Work Environment Management: experiences from implementation in Swedish small-scale enterprises.

    PubMed

    Gunnarsson, Kristina; Andersson, Ing-Marie; Rosén, Gunnar

    2010-01-01

    Small-scale enterprises face difficulties in fulfilling the regulations for organising Systematic Work Environment Management. This study compared three groups of small-scale manufacturing enterprises with and without support for implementing the provision. Two implementation methods, supervised and network method, were used. The third group worked according to their own ideas. Twenty-three enterprises participated. The effects of the implementation were evaluated after one year by semi-structured dialogue with the manager and safety representative. Each enterprise was classified on compliance with ten demands concerning the provision. The work environment was estimated by the WEST-method. Impact of the implementation on daily work was also studied. At the follow-up, the enterprises in the supervised method reported slightly more improvements in the fulfilment of the demands in the provision than the enterprises in the network method and the enterprises working on their own did. The effect of the project reached the employees faster in the enterprises with the supervised method. In general, the work environment improved to some extent in all enterprises. Extensive support to small-scale enterprises in terms of advise and networking aimed to fulfil the regulations of Systematic Work Environment Management had limited effect - especially considering the cost of applying these methods.

  18. 2012 THIN FILM AND SMALL SCALE MECHANICAL BEHAVIOR GRS/GRC, JULY 21-27, 2012

    SciTech Connect

    Balk, Thomas

    2012-07-27

    The mechanical behavior of materials with small dimension(s) is of both fundamental scientific interest and technological relevance. The size effects and novel properties that arise from changes in deformation mechanism have important implications for modern technologies such as thin films for microelectronics and MEMS devices, thermal and tribological coatings, materials for energy production and advanced batteries, etc. The overarching goal of the 2012 Gordon Research Conference on "Thin Film and Small Scale Mechanical Behavior" is to discuss recent studies and future opportunities regarding elastic, plastic and time-dependent deformation, as well as degradation and failure mechanisms such as fatigue, fracture and wear. Specific topics of interest include, but are not limited to: fundamental studies of physical mechanisms governing small-scale mechanical behavior; advances in test techniques for materials at small length scales, such as nanotribology and high-temperature nanoindentation; in-situ mechanical testing and characterization; nanomechanics of battery materials, such as swelling-induced phenomena and chemomechanical behavior; flexible electronics; mechanical properties of graphene and carbon-based materials; mechanical behavior of small-scale biological structures and biomimetic materials. Both experimental and computational work will be included in the oral and poster presentations at this Conference.

  19. Atmospheric dispersion modelling over complex terrain at small scale

    NASA Astrophysics Data System (ADS)

    Nosek, S.; Janour, Z.; Kukacka, L.; Jurcakova, K.; Kellnerova, R.; Gulikova, E.

    2014-03-01

    Previous study concerned of qualitative modelling neutrally stratified flow over open-cut coal mine and important surrounding topography at meso-scale (1:9000) revealed an important area for quantitative modelling of atmospheric dispersion at small-scale (1:3300). The selected area includes a necessary part of the coal mine topography with respect to its future expansion and surrounding populated areas. At this small-scale simultaneous measurement of velocity components and concentrations in specified points of vertical and horizontal planes were performed by two-dimensional Laser Doppler Anemometry (LDA) and Fast-Response Flame Ionization Detector (FFID), respectively. The impact of the complex terrain on passive pollutant dispersion with respect to the prevailing wind direction was observed and the prediction of the air quality at populated areas is discussed. The measured data will be used for comparison with another model taking into account the future coal mine transformation. Thus, the impact of coal mine transformation on pollutant dispersion can be observed.

  20. Preliminary Scaling Estimate for Select Small Scale Mixing Demonstration Tests

    SciTech Connect

    Wells, Beric E.; Fort, James A.; Gauglitz, Phillip A.; Rector, David R.; Schonewill, Philip P.

    2013-09-12

    The Hanford Site double-shell tank (DST) system provides the staging location for waste that will be transferred to the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Specific WTP acceptance criteria for waste feed delivery describe the physical and chemical characteristics of the waste that must be met before the waste is transferred from the DSTs to the WTP. One of the more challenging requirements relates to the sampling and characterization of the undissolved solids (UDS) in a waste feed DST because the waste contains solid particles that settle and their concentration and relative proportion can change during the transfer of the waste in individual batches. A key uncertainty in the waste feed delivery system is the potential variation in UDS transferred in individual batches in comparison to an initial sample used for evaluating the acceptance criteria. To address this uncertainty, a number of small-scale mixing tests have been conducted as part of Washington River Protection Solutions’ Small Scale Mixing Demonstration (SSMD) project to determine the performance of the DST mixing and sampling systems.

  1. Interpreting chemical compositions of small scale basaltic systems: A review

    NASA Astrophysics Data System (ADS)

    McGee, Lucy E.; Smith, Ian E. M.

    2016-10-01

    Small scale basaltic magmatic systems occur in all of the major tectonic environments of planet Earth and are characteristically expressed at the Earth's surface as fields of small monogenetic cones. The chemical compositions of the materials that make up these cones reflect processes of magma generation and differentiation that occur in their plumbing system. The volumes of magmas involved are very small and significantly their compositional ranges reveal remarkably complex processes which are overwhelmed or homogenized in larger scale systems. Commonly, compositions are basaltic, alkalic and enriched in light rare earth elements and large ion lithophile elements, although the spectrum extends from highly enriched nephelinites to subalkalic and tholeiitic basalts. Isotopic analyses of rocks from volcanic fields almost always display compositions which can only be explained by the interaction of two or more mantle sources. Ultimately their basaltic magmas originate by small scale melting of mantle sources. Compositional variety is testament to melting processes at different depths, a range of melting proportions, a heterogeneous source and fractionation, magma mixing and assimilation within the plumbing system that brings magmas to the surface. The fact that such a variety of compositions is preserved in a single field shows that isolation of individual melting events and their ascent is an important and possibly defining feature of monogenetic volcanism, as well as the window their chemical behavior provides into the complex process of melt generation and extraction in the Earth's upper mantle.

  2. Economic analysis of small-scale fuel alcohol plants

    SciTech Connect

    Schafer, J.J. Jr.

    1980-01-01

    To plan Department of Energy support programs, it is essential to understand the fundamental economics of both the large industrial size plants and the small on-farm size alcohol plants. EG and G Idaho, Inc., has designed a 25 gallon per hour anhydrous ethanol plant for the Department of Energy's Alcohol Fuels Office. This is a state-of-the-art reference plant, which will demonstrate the cost and performance of currently available equipment. The objective of this report is to examine the economics of the EG and G small-scale alcohol plant design and to determine the conditions under which a farm plant is a financially sound investment. The reference EG and G Small-Scale Plant is estimated to cost $400,000. Given the baseline conditions defined in this report, it is calculated that this plant will provide an annual after-tax of return on equity of 15%, with alcohol selling at $1.62 per gallon. It is concluded that this plant is an excellent investment in today's market, where 200 proof ethanol sells for between $1.80 and $2.00 per gallon. The baseline conditions which have a significant effect on the economics include plant design parameters, cost estimates, financial assumptions and economic forecasts. Uncertainty associated with operational variables will be eliminated when EG and G's reference plant begins operation in the fall of 1980. Plant operation will verify alcohol yield per bushel of corn, labor costs, maintenance costs, plant availability and by-product value.

  3. Small-scale variability of metal concentrations in soil leachates

    SciTech Connect

    Wilcke, W.

    2000-02-01

    Soil tests often use composite soil samples to assess metal bioavailability. Composite soil samples cannot address small-scale soil heterogeneity. In this study, the concentrations of Al, Cd, Cu, Mn, Ni, Pb, Zn, dissolved organic C (DOC), and pH in soil leachates were examined as an index of small-scale soil heterogeneity. Ten undisturbed soil cores from a 1-m{sup 2} area of a Lithic Haplumbrept and a Typic Hapludoll (pH 4.3) under forest canopy were equilibrated with deionized water. The soil cores were then leached with a mock soil solution. In the Haplumbrept, the pH of the first 50-mL fraction of the leachates was 4.2 to 7.4, DOC concentrations were 11.4 to 38.9 mg L{sup {minus}1}. Aluminum, Cd, Mn, and Ni concentrations were significantly correlated with pH; varied little in the first 50-mL fractions; Cr, Cu, and Pb concentrations were correlated with DOC concentrations. The variability in metal concentrations of the first 50-mL fractions was comparable in both soils and did not change with increasing leachate volume except for Zn in the Haplumbrept. In all leachate fractions, variability was markedly higher than those reported for salt extracts of composite soil samples. Thus, the analysis of composite samples may be insufficient to address metal bioavailability in soils.

  4. Suprathermal Charged Particle Acceleration by Small-scale Flux Ropes.

    NASA Astrophysics Data System (ADS)

    Zank, G. P.; le Roux, J. A.; Webb, G. M.

    2015-12-01

    We consider different limits of our recently developed kinetic transport theory to investigate the potential of super-Alvenic solar wind regions containing several small-scale flux ropes to explain the acceleration of suprathermal ions to power-law spectra as observations show. Particle acceleration is modeled in response to flux-rope activity involving contraction, merging (reconnection), and collisions in the limit where the particle gyoradius is smaller than the characteristic flux-rope scale length. The emphasis is mainly on the statistical variance in the electric fields induced by flux-rope dynamics rather than on the mean electric field induced by multiple flux ropes whose acceleration effects are discussed elsewhere. Our steady-state analytical solutions suggest that particle drift acceleration by flux ropes, irrespective of whether displaying incompressible or compressible behavior, can yield power laws asymptotically at higher energies whereas an exponential spectral rollover results asymptotically when field-aligned guiding center motion acceleration occur by reconnection electric fields from merging flux ropes. This implies that at sufficiently high particle energies, drift acceleration might dominate. We also expect compressive flux ropes to yield harder power-law spectra than incompressible flux ropes. Preliminary results will be discussed to illustrate how particle acceleration might be affected when both diffusive shock and small-scale flux acceleration occur simultaneously at interplanetary shocks.

  5. Small-Scale Smart Grid Construction and Analysis

    NASA Astrophysics Data System (ADS)

    Surface, Nicholas James

    The smart grid (SG) is a commonly used catch-phrase in the energy industry yet there is no universally accepted definition. The objectives and most useful concepts have been investigated extensively in economic, environmental and engineering research by applying statistical knowledge and established theories to develop simulations without constructing physical models. In this study, a small-scale version (SSSG) is constructed to physically represent these ideas so they can be evaluated. Results of construction show data acquisition three times more expensive than the grid itself although mainly due to the incapability to downsize 70% of data acquisition costs to small-scale. Experimentation on the fully assembled grid exposes the limitations of low cost modified sine wave power, significant enough to recommend pure sine wave investment in future SSSG iterations. Findings can be projected to full-size SG at a ratio of 1:10, based on the appliance representing average US household peak daily load. However this exposes disproportionalities in the SSSG compared with previous SG investigations and recommended changes for future iterations are established to remedy this issue. Also discussed are other ideas investigated in the literature and their suitability for SSSG incorporation. It is highly recommended to develop a user-friendly bidirectional charger to more accurately represent vehicle-to-grid (V2G) infrastructure. Smart homes, BEV swap stations and pumped hydroelectric storage can also be researched on future iterations of the SSSG.

  6. MODELING THE VERY SMALL SCALE CLUSTERING OF LUMINOUS RED GALAXIES

    SciTech Connect

    Watson, Douglas F.; Berlind, Andreas A.; McBride, Cameron K.; Masjedi, Morad

    2010-01-20

    We model the small-scale clustering of luminous red galaxies (LRGs) in the Sloan Digital Sky Survey. Specifically, we use the halo occupation distribution formalism to model the projected two-point correlation function of LRGs on scales well within the sizes of their host halos (0.016 h {sup -1} Mpc <= r <= 0.42 h {sup -1} Mpc). We start by varying P(N|M), the probability distribution that a dark matter halo of mass M contains N LRGs, and assuming that the radial distribution of satellite LRGs within halos traces the Navarro-Frenk-White (NFW) dark matter density profile. We find that varying P(N|M) alone is not sufficient to match the small-scale data. We next allow the concentration of satellite LRG galaxies to differ from that of dark matter and find that this is also not sufficient. Finally, we relax the assumption of an NFW profile and allow the inner slope of the density profile to vary. We find that this model provides a good fit to the data and the resulting value of the slope is -2.17 +- 0.12. The radial density profile of satellite LRGs within halos is thus not compatible with that of the underlying dark matter, but rather is closer to an isothermal distribution.

  7. Constraint Reasoning Over Strings

    NASA Technical Reports Server (NTRS)

    Koga, Dennis (Technical Monitor); Golden, Keith; Pang, Wanlin

    2003-01-01

    This paper discusses an approach to representing and reasoning about constraints over strings. We discuss how many string domains can often be concisely represented using regular languages, and how constraints over strings, and domain operations on sets of strings, can be carried out using this representation.

  8. Evidence for string substructure

    SciTech Connect

    Bergman, O.

    1996-06-01

    The author argues that the behavior of string theory at high temperature and high longitudinal boosts, combined with the emergence of p-branes as necessary ingredients in various string dualities, point to a possible reformulation of strings, as well as p-branes, as composites of bits. He reviews the string-bit models, and suggests generalizations to incorporate p-branes.

  9. String driven inflation

    SciTech Connect

    Turok, N.

    1987-11-01

    It is argued that, in fundamental string theories, as one traces the universe back in time a point is reached when the expansion rate is so fast that the rate of string creation due to quantum effects balances the dilution of the string density due to the expansion. One is therefore led into a phase of constant string density and an exponentially expanding universe. Fundamental strings therefore seem to lead naturally to inflation. 17 refs., 1 fig.

  10. String-driven inflation

    NASA Technical Reports Server (NTRS)

    Turok, Neil

    1988-01-01

    It is argued that, in fundamental string theories, as one traces the universe back in time a point is reached when the expansion rate is so fast that the rate of string creation due to quantum effects balances the dilution of the string density due to the expansion. One is therefore led into a phase of constant string density and an exponentially expanding universe. Fundamental strings therefore seem to lead naturally to inflation.

  11. Small-scale nonlinear dynamics of K-mouflage theories

    NASA Astrophysics Data System (ADS)

    Brax, Philippe; Valageas, Patrick

    2014-12-01

    We investigate the small-scale static configurations of K-mouflage models defined by a general function K (χ ) of the kinetic terms. The fifth force is screened by the nonlinear K-mouflage mechanism if K'(χ ) grows sufficiently fast for large negative χ . In the general nonspherically symmetric case, the fifth force is not aligned with the Newtonian force. For spherically symmetric static matter density profiles, we show that the results depend on the potential function W-(y )=y K'(-y2/2 ) ; i.e., W-(y ) must be monotonically increasing to +∞ for y ≥0 to guarantee the existence of a single solution throughout space for any matter density profile. Small radial perturbations around these static profiles propagate as travelling waves with a velocity greater than the speed of light. Starting from vanishing initial conditions for the scalar field and for a time-dependent matter density corresponding to the formation of an overdensity, we numerically check that the scalar field converges to the static solution. If W- is bounded, for high-density objects there are no static solutions throughout space, but one can still define a static solution restricted to large radii. Our dynamical study shows that the scalar field relaxes to this static solution at large radii, whereas spatial gradients keep growing with time at smaller radii. If W- is not bounded but nonmonotonic, there is an infinite number of discontinuous static solutions. However, the Klein-Gordon equation is no longer a well-defined hyperbolic equation, which leads to complex characteristic speeds and exponential instabilities. Therefore, these discontinuous static solutions are not physical, and these models are not theoretically sound. Such K-mouflage scenarios provide an example of theories that can appear viable at the cosmological level, for the cosmological background and perturbative analysis, while being meaningless at a nonlinear level for small-scale configurations. This shows the importance of

  12. Small-scale Rainfall Challenges Tested with Semi-distributed and Distributed Hydrological Models

    NASA Astrophysics Data System (ADS)

    Ichiba, Abdellah; Tchiguirinskaia, Ioulia; Gires, Auguste; Schertzer, Daniel; Bompard, Philippe

    2016-04-01

    -France C-band radar data at 1km pixel scale and (3) ENPC X-band dual polarization radar data at 250m pixel scale. Results show that considering bigger number of smaller sub-catchments improve the response of CANOE model to small-scale rainfall. However, the fully distributed approach demonstrates much higher sensitivity than the semi-distributed one, suggesting that this approach is more appropriate to integrate the rainfall structures measured at small scales. Finally, we compare these results with those obtained earlier in the framework of the RainGain project (www.raingain.eu), which helps to re-interpret some of our former conclusions.

  13. Cosmic strings with twisted magnetic flux lines and wound-strings in extra dimensions

    SciTech Connect

    Lake, Matthew; Yokoyama, Jun'ichi E-mail: yokoyama@resceu.s.u-tokyo.ac.jp

    2012-09-01

    We consider a generalization of the Nielsen-Olesen ansatz, in the abelian-Higgs model, which describes strings with twisted magnetic flux lines in the vortex core. The solution does not possess cylindrical symmetry, which leads to the existence of components of conserved momentum, both around the core-axis and along the length of the string. In addition, we consider a model of F-strings with rotating, geodesic windings in the compact space of the Klebanov-Strassler geometry and determine matching conditions which ensure energy and momentum conservation when loops chop off from the long-string network. We find that the expressions for the constants of motion, which determine the macroscopic string dynamics, can be made to coincide with those for the twisted flux line string, suggesting that extra-dimensional effects for F-strings may be mimicked by field-theoretic structure in topological defects.

  14. Observational Evidence for Small Scale Distributed Energy Release and Acceleration

    NASA Astrophysics Data System (ADS)

    Vilmer, Nicole

    Particle acceleration in solar flares is a challenging issue. Not only, is it necessary to convert a large fraction of the free magnetic energy to supra-thermal particles on relatively short time scales, but it is also required to produce in some flares ultra-relativistic particles on timescales of a few tens of seconds. Several approaches have been considered in the solar physics literature for acceleration models: either the acceleration takes place in large scale features (shocks or current sheets) or it occurs in small scale distributed energy release sites. I shall review here some of the observations which support the scenario of spatially distributed energy release and acceleration sites: existence of narrow-band millisecond bursts in the radio range and spatial distributions of these emissions, distribution of time scales of energy release, statistical properties of flares and HXR pulses, waiting time distributions in flares,. . .

  15. Robust attitude tracking control of small-scale unmanned helicopter

    NASA Astrophysics Data System (ADS)

    Wang, Xiafu; Chen, You; Lu, Geng; Zhong, Yisheng

    2015-06-01

    Robust attitude control problem for small-scale unmanned helicopters is investigated to improve attitude control performances of roll and pitch channels under both small and large amplitude manoeuvre flight conditions. The model of the roll or pitch angular dynamics is regarded as a nominal single-input single-output linear system with equivalent disturbances which contain nonlinear uncertainties, coupling-effects, parameter perturbations, and external disturbances. Based on the signal compensation method, a robust controller is designed with two parts: a proportional-derivative controller and a robust compensator. The designed controller is linear and time-invariant, so it can be easily realised. The robust properties of the closed-loop system are proven. According to the ADS-33E-PRF military rotorcraft standard, the controller can achieve top control performances. Experimental results demonstrate the effectiveness of the proposed control strategy.

  16. Identifying T Tauri Stars using Small Scale Optical Telescopes

    NASA Astrophysics Data System (ADS)

    Spuck, Timothy; Saathoff, I.; Rebull, L.

    2010-05-01

    The Spuck-Butchart Optical Survey Method (SBOS) is a simplified method of identifying T Tauri stars using small scale optical telescopes. However, to date the method has only been used in an attempt to distinguish T Tauri stars from standard stars. AGN and active M dwarf stars emit excess in both infrared and H-alpha, similar to T Tauri stars, making it possible that these types of objects will contaminate T Tauri selection. This study uses observations from the Kitt Peak National Observatory 0.9 Meter Telescope to further investigate the SBOS method and its true efficiency. The results of this study indicate that the initial efficiency of 70% is incorrect. Due to potential contamination by active M dwarf stars, the true efficiency is closer to 35%. The study demonstrates that while identification efficiency is much lower than initially thought, the SBOS method shows great promise for both professional and amateur research of young stellar objects.

  17. Technology Overview and Assessment for Small-Scale EDL Systems

    NASA Technical Reports Server (NTRS)

    Heidrich, Casey R.; Smith, Brandon P.; Braun, Robert D.

    2016-01-01

    Motivated by missions to land large rovers and humans at Mars and other bodies, high-mass EDL technologies are a prevalent trend in the research community. In contrast, EDL systems for low-mass payloads have attracted less attention. Significant potential in science and discovery exists in small-scale EDL systems. Payloads acting secondary to a flagship mission are a currently under-utilzed resource. Before taking advantage of these opportunities, further developed of scaled EDL technologies is required. The key limitations identified in this study are compact decelerators and deformable impact systems. Current technologies may enable rough landing of small payloads, with moderate restrictions in packaging volume. Utilization of passive descent and landing stages will greatly increase the applicability of small systems, allowing for vehicles robust to entry environment uncertainties. These architectures will provide an efficient means of achieving science and support objectives while reducing cost and risk margins of a parent mission.

  18. Formation control for a network of small-scale robots.

    PubMed

    Kim, Yoonsoo

    2014-10-01

    In this paper, a network of small-scale robots (typically centimeter-scale robots) equipped with artificial actuators such as electric motors is considered. The purpose of this network is to have the robots keep a certain formation shape (or change to another formation shape) during maneuvers. The network has a fixed communication topology in the sense that robots have a fixed group of neighbors to communicate during maneuvers. Assuming that each robot and its actuator can be modeled as a linear system, a decentralized control law (such that each robot activates its actuator based on the information from its neighbors only) is introduced to achieve the purpose of formation keeping or change. A linear matrix inequality (LMI) for deriving the upper bound on the actuator's time constant is also presented. Simulation results are shown to demonstrate the merit of the introduced control law.

  19. Small-Scale Geothermal Power Plant Field Verification Projects: Preprint

    SciTech Connect

    Kutscher, C.

    2001-07-03

    In the spring of 2000, the National Renewable Energy Laboratory issued a Request for Proposal for the construction of small-scale (300 kilowatt [kW] to 1 megawatt [MW]) geothermal power plants in the western United States. Five projects were selected for funding. Of these five, subcontracts have been completed for three, and preliminary design work is being conducted. The three projects currently under contract represent a variety of concepts and locations: a 1-MW evaporatively enhanced, air-cooled binary-cycle plant in Nevada; a 1-MW water-cooled Kalina-cycle plant in New Mexico; and a 750-kW low-temperature flash plant in Utah. All three also incorporate direct heating: onion dehydration, heating for a fish hatchery, and greenhouse heating, respectively. These projects are expected to begin operation between April 2002 and September 2003. In each case, detailed data on performance and costs will be taken over a 3-year period.

  20. Small-Scale Performance Testing for Studying New Explosives

    SciTech Connect

    Gagliardi, F J; Chambers, R D; Tran, T D

    2005-04-29

    The development of new high-explosive (HE) formulations involves characterizing their safety and performance. Small-scale experiments requiring only a small amount of explosives are of interest because they can facilitate development while minimizing hazards and reducing cost. A detonation-spreading, dent test, called the Floret test, was designed to obtain performance data for new explosives. It utilizes the detonation of about a 1.0 g sample of HE, initiated by an accelerated aluminum flyer. Upon impact, the HE sample detonates and a copper witness plate absorbs the ensuing shock wave. The dent of the plate is then measured and correlated to the energetic output of the HE. Additionally, the dent measurement can be used to compare the performance of different explosives. The Floret test is beneficial because it quickly returns important performance information, while requiring only a small explosive sample. This work will explain the Floret test and discuss some exemplary results.

  1. Net energy of seven small-scale hydroelectric power plants

    NASA Astrophysics Data System (ADS)

    Gilliland, M. W.; Klopatek, J. M.; Hildebrand, S. G.

    1981-07-01

    The net energy results are expressed as the ratio of energy output to energy input. Two ratios were developed. In the first (R1), the energy output, expressed as electrically, was divided by the energy subsidy; in the second (R2), the energy output, expressed as the fossil fuel equivalent of electricity, was divided by the energy input. The results indicate that the energy output from the seven plants is 8.6 to 32.9 times greater than the energy input for the R1 case, and 26.3 to 101.4 times greater than the energy input for the R2 case. On the net energy criterion, the small scale plants are better than conventional peak load hydroelectric plants and similar to conventional base load hydroelectric plants.

  2. CAMUI Type Hybrid Rocket as Small Scale Ballistic Flight Testbed

    NASA Astrophysics Data System (ADS)

    Nagata, Harunori; Uematsu, Tsutomu; Ito, Kenichi

    The authors have been developing CAMUI (Cascaded Multistage Impinging-jet) type hybrid rockets, explosive-flee small rocket motors. This is to downsize the scale of suborbital flight experiments on space related technology development. A key idea is a new fuel grain design to increase gasification rates of a solid fuels. By the new fuel grain design, the combustion gas repeatedly impinges on fuel surfaces to hasten the heat transfer to the fuel. Suborbital flight experiments by sounding rockets provide variety of test beds to accumulate basic technologies common to the next step of space development in Japan. By using hybrid rockets one can take the cost advantage of small-scale rocket experiments. This cost advantage improves robustness of space technology development projects by dispersion of risk.

  3. Dustiness, silicosis & tuberculosis in small scale pottery workers.

    PubMed

    Saiyed, H N; Ghodasara, N B; Sathwara, N G; Patel, G C; Parikh, D J; Kashyap, S K

    1995-09-01

    Studies were carried out in eight small scale potteries to find out the airborne dust concentrations and the prevalence of dust related diseases like silicosis and tuberculosis in 292 workers. Chest radiography revealed that 44 (15.1%) pottery workers were suffering from silicosis and an equal number showed radiological evidence of tuberculosis. The environmental study showed that the concentrations of airborne dust, containing free silica, in the work environment of all departments (except packing department) of potteries were higher than threshold limit values (TLVs). The prevalence of silicosis and tuberculosis correlated with the levels of airborne dust. The prevalence of tuberculosis increased with radiological severity of silicosis. Dust control measures combined with pre-employment and periodical medical examinations are recommended for the control of silicosis and tuberculosis in the pottery industry.

  4. Small-scale volcanoes on Mars: distribution and types

    NASA Astrophysics Data System (ADS)

    Broz, Petr; Hauber, Ernst

    2015-04-01

    Volcanoes differ in sizes, as does the amount of magma which ascends to a planetary surface. On Earth, the size of volcanoes is anti-correlated with their frequency, i.e. small volcanoes are much more numerous than large ones. The most common terrestrial volcanoes are scoria cones (small-scale volcanoes were not intensely studied for a long time due to a lack of high-resolution data enabling their proper identification; however their existence and basic characteristics were predicted on theoretical grounds. Streams of new high-resolution images now enable discovering and studying kilometer-size volcanoes with various shapes in unprecedented detail. Several types of small-scale volcanoes in various regions on Mars were recently described. Scoria cones provide a record of magmatic volatile content and have been identified in Tharsis (Ulysses Colles), on flanks of large volcanoes (e.g., Pavonis Mons), in the caldera of Ulysses Patera, in chaotic terrains or other large depressions (Hydraotes Colles, Coprates Chasma) and in the northern lowlands. Tuff rings and tuff cones, formed as a result of water-magma interaction, seem to be relatively rare on Mars and were only tentatively identified in three locations (Nepenthes/Amenthes region, Arena Colles and inside Lederberg crater), and alternative interpretations (mud volcanoes) seem possible. Other relatively rare volcanoes seem to be lava domes, reported only from two regions (Acracida Planitia and Terra Sirenum). On the other hand, small shields and rootless cones (which are not primary volcanic landforms) represent widely spread phenomena recognized in Tharsis and Elysium. Based on these new observations, the distribution of small volcanoes on Mars seems to be much more widespread than anticipated a decade

  5. Remote plunger removal device for small-scale incremental pressing

    SciTech Connect

    Burnside, N.J.; Son, S.F.; Asay, B.W.

    1997-09-01

    Small-scale pressing of high explosives (HE) at Los Alamos National Laboratory (LANL) and elsewhere is routinely performed using pneumatic presses. Blast shields provide protection to the operator during the pressing procedure, but safety of the operator is a concern during removal of the plunger, which is currently performed manually. To minimize this risk, very high tolerances between the plunger and the die are required. These tolerances are often very costly, especially in the case of long, relatively narrow dies. The safety issue is an even greater concern with incremental pressing in which cleaning the die between increments is difficult or impossible. To better protect press operators, a device has been designed and constructed to allow remote plunger removal in a standard HE press. In this report the authors describe this modified press that allows remote removal of the plunger.

  6. Small-Scale Shock Reactivity and Internal Blast Test

    NASA Astrophysics Data System (ADS)

    Granholm, R. H.; Sandusky, H. W.

    2006-07-01

    Explosives react from a strong shock, even in quantities too small for detonation. The potential for a new material to be an explosive can be evaluated from this shock reactivity. The recently developed small-scale shock reactivity test (SSRT) uses very high confinement to allow prompt reactions to occur in less than half-gram samples well below critical diameter. Early and late-time reactions are simultaneously measured from a single sample subjected to the output from an RP-80 detonator. Prompt reactions are quantified by a dent in a soft aluminum witness block, while later reactions, such as from fuel/air combustion, are measured by recording blast pressure. Internal blast quasi-static pressure is obtained by confining the sample apparatus within a three-liter chamber. Late-time reaction effects of plastics, and results from HMX, HMX/Aluminum, and a plastic-bonded explosive (PBX) are reported.

  7. Small-scale anisotropy in turbulent shearless mixing.

    PubMed

    Tordella, Daniela; Iovieno, Michele

    2011-11-01

    The generation of small-scale anisotropy in turbulent shearless mixing is numerically investigated. Data from direct numerical simulations at Taylor Reynolds' numbers between 45 and 150 show not only that there is a significant departure of the longitudinal velocity derivative moments from the values found in homogeneous and isotropic turbulence but that the variation of skewness has an opposite sign for the components across the mixing layer and parallel to it. The anisotropy induced by the presence of a kinetic energy gradient has a very different pattern from the one generated by an homogeneous shear. The transversal derivative moments in the mixing are in fact found to be very small, which highlights that smallness of the transversal moments is not a sufficient condition for isotropy.

  8. Small-Scale Variability of Large Cloud Drops

    NASA Technical Reports Server (NTRS)

    Marshak, Alexander; Knyazikhin, Y.; Wiscombe, Warren

    2004-01-01

    Cloud droplet size distribution is one of the most fundamental subjects in cloud physics. Understanding of spatial distribution and small-scale fluctuations of cloud droplets is essential for both cloud physics and atmospheric radiation. For cloud physics, it relates to the coalescence growth of raindrops while for radiation, it has a strong impact on a cloud's radiative properties. Most of the existing cloud radiation and precipitation formation models assume that the mean number of drops with a given radius varies proportionally to volume. The analysis of microphysical data on liquid water drop sizes shows that, for sufficiently small volumes, the number is proportional to the drop size dependent power of the volume. For abundant small drops present, the exponent is 1 as assumed in the conventional approach. However, for rarer large drops, the exponents fall below unity. At small scales, therefore, the mean number of large drops decreases with volume at a slower rate than the conventional approach assumes, suggesting more large drops at these scales than conventional models account for; their impact is consequently underestimated. Size dependent models of spatial distribution of cloud drops that simulate the observed power laws show strong drop clustering, the more so the larger the drops. The degree of clustering is determined by the observed exponents. The strong clustering of large drops arises naturally from the observed power-law statistics. Current theories of photon-cloud interaction and warm rain formation will need radical revision in order to produce these statistics; their underlying equations are unable to yield the observed power law.

  9. String axiverse

    SciTech Connect

    Arvanitaki, Asimina; Dimopoulos, Savas; Dubovsky, Sergei; Kaloper, Nemanja; March-Russell, John

    2010-06-15

    String theory suggests the simultaneous presence of many ultralight axions, possibly populating each decade of mass down to the Hubble scale 10{sup -33} eV. Conversely the presence of such a plenitude of axions (an axiverse) would be evidence for string theory, since it arises due to the topological complexity of the extra-dimensional manifold and is ad hoc in a theory with just the four familiar dimensions. We investigate how several upcoming astrophysical experiments will be observationally exploring the possible existence of such axions over a vast mass range from 10{sup -33} eV to 10{sup -10} eV. Axions with masses between 10{sup -33} eV to 10{sup -28} eV can cause a rotation of the cosmic microwave background polarization that is constant throughout the sky. The predicted rotation angle is independent of the scale of inflation and the axion decay constant, and is of order {alpha}{approx}1/137-within reach of the just launched Planck satellite. Axions in the mass range 10{sup -28} eV to 10{sup -18} eV give rise to multiple steps in the matter power spectrum, providing us with a snapshot of the axiverse that will be probed by galaxy surveys-such as BOSS, and 21 cm line tomography. Axions in the mass range 10{sup -22} eV to 10{sup -10} eV can affect the dynamics and gravitational wave emission of rapidly rotating astrophysical black holes through the Penrose superradiance process. When the axion Compton wavelength is of order of the black hole size, the axions develop superradiant atomic bound states around the black hole nucleus. Their occupation number grows exponentially by extracting rotational energy and angular momentum from the ergosphere, culminating in a rotating Bose-Einstein axion condensate emitting gravitational waves. For black holes lighter than {approx}10{sup 7} solar masses accretion cannot replenish the spin of the black hole, creating mass gaps in the spectrum of rapidly rotating black holes that diagnose the presence of destabilizing axions

  10. Education, Training and Employment in Small-Scale Enterprises: Three Industries in Sao Paulo, Brazil. IIEP Research Report No. 63.

    ERIC Educational Resources Information Center

    Leite, Elenice M.; Caillods, Francoise

    Despite the prophecies forecasting their probable disappearance or annihilation, small-scale enterprises have persisted in the Brazilian industrial structure since 1950. To account for the survival of small firms in Brazil, specifically in the state of Sao Paulo, a study examined 100 small firms in three industrial sectors: clothing, mechanical…

  11. Small-scale properties of a stochastic cubic-autocatalytic reaction-diffusion model

    NASA Astrophysics Data System (ADS)

    Gagnon, Jean-Sébastien; Hochberg, David; Pérez-Mercader, Juan

    2015-10-01

    We investigate the small-scale properties of a stochastic cubic-autocatalytic reaction-diffusion (CARD) model using renormalization techniques. We renormalize noise-induced ultraviolet divergences and obtain β functions for the decay rate and coupling at one loop. Assuming colored (power-law) noise, our results show that the behavior of both decay rate and coupling with scale depends crucially on the noise exponent. Interpreting the CARD model as a proxy for a (very simple) living system, our results suggest that power-law correlations in environmental fluctuations can both decrease or increase the growth of structures at smaller scales.

  12. A small-scale plasmoid formed during the May 13, 1985, AMPTE magnetotail barium release

    NASA Technical Reports Server (NTRS)

    Baker, D. N.; Fritz, T. A.; Bernhardt, P. A.

    1989-01-01

    Plasmoids are closed magnetic-loop structures with entrained hot plasma which are inferred to occur on large spatial scales in space plasma systems. A model is proposed here to explain the brightening and rapid tailward movement of the barium cloud released by the AMPTE IRM spacecraft on May 13, 1985. The model suggests that a small-scale plasmoid was formed due to a predicted development of heavy-ion-induced tearing in the thinned near-tail plasma sheet. Thus, a plasmoid may actually have been imaged due to the emissions of the entrained plasma ions within the plasma bubble.

  13. Small-scale properties of a stochastic cubic-autocatalytic reaction-diffusion model.

    PubMed

    Gagnon, Jean-Sébastien; Hochberg, David; Pérez-Mercader, Juan

    2015-10-01

    We investigate the small-scale properties of a stochastic cubic-autocatalytic reaction-diffusion (CARD) model using renormalization techniques. We renormalize noise-induced ultraviolet divergences and obtain β functions for the decay rate and coupling at one loop. Assuming colored (power-law) noise, our results show that the behavior of both decay rate and coupling with scale depends crucially on the noise exponent. Interpreting the CARD model as a proxy for a (very simple) living system, our results suggest that power-law correlations in environmental fluctuations can both decrease or increase the growth of structures at smaller scales.

  14. On bulk singularity structures and all order α‧ contact terms of BPS string amplitudes

    NASA Astrophysics Data System (ADS)

    Hatefi, Ehsan

    2016-10-01

    The entire form of the amplitude of three SYM (involving two transverse scalar fields, a gauge field) and a potential Cn-1 Ramond-Ramond (RR) form field is found out. We first derive and then start constructing an infinite number of t , s channel bulk singularity structures by means of all order α‧ corrections to pull-back of brane in an Effective Field Theory (EFT). Due to presence of the complete form of S-matrix, several new contact interactions as well as new couplings are explored. It is also shown that these couplings can be verified at the level of EFT by either the combinations of Myers terms, pull-back, Taylor expanded of scalar fields or the mixed combination of the couplings of this paper as well as employed Bianchi identities. For the first time, we also derive the algebraic and the complete form of the integrations for some arbitrary combinations of Mandelstam variables and for the most general case ∫d2 z | 1 - z|a | z|b(z - z bar) c(z + z bar) 3 on upper half plane as well.

  15. Small-Scale Hydroelectric Power in the Pacific Northwest: New Impetus for an Old Energy Source

    NASA Astrophysics Data System (ADS)

    1980-07-01

    The small scale hydroelectric power policy projects of the national conference of state legislators (NCSL) was designed to assist state legislators in looking at the benefits of one alternative, small scale hydro. Because of the need for state legislative support in the development of small scale hydroelectric, NCSL, as part of its contract with the Department of Energy, conducted the following conference on small scale hydro in the Pacific Northwest. State obstacles to development and options for change available to policymakers were explored.

  16. Small-scale wind disturbances observed by the MU radar during the passage of typhoon Kelly

    SciTech Connect

    Sato, Kaoru )

    1993-02-14

    This paper describes small-scale wind disturbances associated with Typhoon Kelly (October 1987) that were observed by the MU radar, one of the MST (mesosphere, stratosphere, and troposphere) radars, for about 60 hours with fine time and height resolution. To elucidate the background of small-scale disturbances, synoptic-scale variation in atmospheric stability related to the typhoon structure during the observation is examined. When the typhoon passed near the MU radar site, the structure was no longer axisymmetric. There is deep convection only in north-northeast side of the typhoon while convection behind it is suppressed by a synoptic-scale cold air mass moving eastward to the west of the typhoon. A change in atmospheric stability over the radar site as indicated by echo power profiles is likely due to the passage of the sharp transition zone of convection. Strong small-scale wind disturbances were observed around the typhoon passage. The statistical characteristics are different before (BT) and after (AT) the typhoon passage, especially in frequency spectra of vertical wind fluctuations. The spectra for BT are unique compared with earlier studies of vertical winds observed by VHF radars. Another difference is dominance of a horizontal wind component with a vertical wavelength of about 3 km, observed only in AT. Further analyses are made of characteristics and vertical momentum fluxes for dominant disturbances. Some disturbances are generated to remove the momentum of cyclonic wind rotation of the typhoon. Deep convection, topographic effects in strong winds, and strong vertical shear of horizontal winds around an inversion layer are possible sources of the disturbances. Two monochromatic disturbances lasting for more than 10 h in the lower stratosphere observed in BT and AT are identified as inertio-gravity waves, by obtaining wave parameters consistent with all observed quantities. Both of the inertio-gravity waves propagate energy away from the typhoon.

  17. CMB ISW-lensing bispectrum from cosmic strings

    SciTech Connect

    Yamauchi, Daisuke; Sendouda, Yuuiti; Takahashi, Keitaro E-mail: sendouda@cc.hirosaki-u.ac.jp

    2014-02-01

    We study the effect of weak lensing by cosmic (super-)strings on the higher-order statistics of the cosmic microwave background (CMB). A cosmic string segment is expected to cause weak lensing as well as an integrated Sachs-Wolfe (ISW) effect, the so-called Gott-Kaiser-Stebbins (GKS) effect, to the CMB temperature fluctuation, which are thus naturally cross-correlated. We point out that, in the presence of such a correlation, yet another kind of the post-recombination CMB temperature bispectra, the ISW-lensing bispectra, will arise in the form of products of the auto- and cross-power spectra. We first present an analytic method to calculate the autocorrelation of the temperature fluctuations induced by the strings, and the cross-correlation between the temperature fluctuation and the lensing potential both due to the string network. In our formulation, the evolution of the string network is assumed to be characterized by the simple analytic model, the velocity-dependent one scale model, and the intercommutation probability is properly incorporated in order to characterize the possible superstringy nature. Furthermore, the obtained power spectra are dominated by the Poisson-distributed string segments, whose correlations are assumed to satisfy the simple relations. We then estimate the signal-to-noise ratios of the string-induced ISW-lensing bispectra and discuss the detectability of such CMB signals from the cosmic string network. It is found that in the case of the smaller string tension, Gμ << 10{sup -7}, the ISW-lensing bispectrum induced by a cosmic string network can constrain the string-model parameters even more tightly than the purely GKS-induced bispectrum in the ongoing and future CMB observations on small scales.

  18. Small-Scale Spray Releases: Additional Aerosol Test Results

    SciTech Connect

    Schonewill, Philip P.; Gauglitz, Phillip A.; Kimura, Marcia L.; Brown, G. N.; Mahoney, Lenna A.; Tran, Diana N.; Burns, Carolyn A.; Kurath, Dean E.

    2013-08-01

    One of the events postulated in the hazard analysis at the Waste Treatment and Immobilization Plant (WTP) and other U.S. Department of Energy (DOE) nuclear facilities is a breach in process piping that produces aerosols with droplet sizes in the respirable range. The current approach for predicting the size and concentration of aerosols produced in a spray leak involves extrapolating from correlations reported in the literature. These correlations are based on results obtained from small engineered spray nozzles using pure liquids with Newtonian fluid behavior. The narrow ranges of physical properties on which the correlations are based do not cover the wide range of slurries and viscous materials that will be processed in the WTP and across processing facilities in the DOE complex. To expand the data set upon which the WTP accident and safety analyses were based, an aerosol spray leak testing program was conducted by Pacific Northwest National Laboratory (PNNL). PNNL’s test program addressed two key technical areas to improve the WTP methodology (Larson and Allen 2010). The first technical area was to quantify the role of slurry particles in small breaches where slurry particles may plug the hole and prevent high-pressure sprays. The results from an effort to address this first technical area can be found in Mahoney et al. (2012a). The second technical area was to determine aerosol droplet size distribution and total droplet volume from prototypic breaches and fluids, including sprays from larger breaches and sprays of slurries for which literature data are largely absent. To address the second technical area, the testing program collected aerosol generation data at two scales, commonly referred to as small-scale and large-scale. The small-scale testing and resultant data are described in Mahoney et al. (2012b) and the large-scale testing and resultant data are presented in Schonewill et al. (2012). In tests at both scales, simulants were used to mimic the

  19. Spontaneous knotting of an agitated string.

    PubMed

    Raymer, Dorian M; Smith, Douglas E

    2007-10-16

    It is well known that a jostled string tends to become knotted; yet the factors governing the "spontaneous" formation of various knots are unclear. We performed experiments in which a string was tumbled inside a box and found that complex knots often form within seconds. We used mathematical knot theory to analyze the knots. Above a critical string length, the probability P of knotting at first increased sharply with length but then saturated below 100%. This behavior differs from that of mathematical self-avoiding random walks, where P has been proven to approach 100%. Finite agitation time and jamming of the string due to its stiffness result in lower probability, but P approaches 100% with long, flexible strings. We analyzed the knots by calculating their Jones polynomials via computer analysis of digital photos of the string. Remarkably, almost all were identified as prime knots: 120 different types, having minimum crossing numbers up to 11, were observed in 3,415 trials. All prime knots with up to seven crossings were observed. The relative probability of forming a knot decreased exponentially with minimum crossing number and Möbius energy, mathematical measures of knot complexity. Based on the observation that long, stiff strings tend to form a coiled structure when confined, we propose a simple model to describe the knot formation based on random "braid moves" of the string end. Our model can qualitatively account for the observed distribution of knots and dependence on agitation time and string length.

  20. Small-Scale Thermal Violence Cook Off Test

    NASA Astrophysics Data System (ADS)

    Cook, Malcolm; Curtis, John; Stennett, Christopher

    2015-06-01

    The Small-Scale thermal Violence Test (SSVT) is designed to quantify the violence (explosiveness) of test materials by means of observing the velocity history of a metal burst disk that forms one end of a strong thick-walled cylindrical test vehicle. A copper heating block is placed to the rear of, but in contact with, the sample and provides sealing. The difference in thermal conductivity between copper and steel is sufficient that thermal runaway is induced near to the explosive / copper interface in an unlagged test. A series of experiments has been made, in which explosive specimens were confined and heated to explosion. A high-accuracy velocity measurement system was used to record the motion of the bursting disk. These experiments have shown that the early-time motion of the bursting disk corresponds qualitatively to the onset of thermal explosion and growth of reaction within the explosive specimens. However, the velocity history traces are more complex than had been anticipated. In particular, unexplained shoulders were observed in the Phase-Doppler Velocimeter (PDV) data. Some preliminary modelling studies have been carried out in order to shed light on the complex shapes of the projectile velocity histories.

  1. Small Scale Evaporation Kinetics of a Binary Fluid Mixture

    NASA Astrophysics Data System (ADS)

    Basdeo, Carl; Ye, Dezhuang; Kalonia, Devendra; Fan, Tai-Hsi; Mechanical Engineering Team; Pharmaceutical Sciences Collaboration

    2013-03-01

    Evaporation induces a concentrating effect in liquid mixtures. The transient process has significant influence on the dynamic behaviors of a complex fluid. To simultaneously investigate the fluid properties and small-scale evaporation kinetics during the transient process, the quartz crystal microbalance is applied to a binary mixture droplet of light alcohols including both a single volatile component (a fast evaporation followed by a slow evaporation) and a mixture of two volatile components with comparable evaporation rates. The density and viscosity stratification are evaluated by the shear wave, and the evaporation kinetics is measured by the resonant signature of the acoustic p-wave. The evaporation flux can be precisely determined by the resonant frequency spikes and the complex impedance. To predict the concentration field, the moving interface, and the precision evaporation kinetics of the mixture, a multiphase model is developed to interpret the complex impedance signals based on the underlying mass and momentum transport phenomena. The experimental method and theoretical model are developed for better characterizing and understanding of the drying process involving liquid mixtures of protein pharmaceuticals.

  2. Some features of the small-scale solar wind fluctuations

    NASA Technical Reports Server (NTRS)

    Zastenker, G.; Eiges, P.; Avanov, L.; Astafyeva, N.; Zurbuchen, Th.; Bochsler, P.

    1995-01-01

    We have investigated small-scale variations of the solar wind ion flux measured with Faraday cups onboard the Prognoz-8 satellite. These measurements have a high time resolution of 1.24 seconds for intervals with a duration of several hours and as high as 0.02 seconds for some periods of about 1 hour duration. The main goal of this work is the determination of the quantitative features of fast ion flux fluctuations using mainly spectral analysis but also other methods. We also identify their association with interplanetary plasma parameters. Particularly, it is shown that the slope of the power spectra in the frequency range from 1E-4 to 6E-2 Hz is close to the classical Kolmogorov (-5/3) law. We also discuss some intervals with a very high level of the relative amplitude of flux fluctuations (10-20 percent) which were observed near the Earth's bow shock in the foreshock region. The use of the wavelet method for the long time series allows us to study the temporal evolution of power spectra.

  3. Small-scale electric generators for arctic applications

    NASA Astrophysics Data System (ADS)

    Lamp, Thomas R.

    1995-01-01

    Forest fires that have endangered remote US Air Force sites equipped with radioisotope thermoelectric generators (RTGs) has prompted the assessment of power generating systems as substitutes for RTGs in small scale (10-120 watt) applications. A team of scientists and engineers of the US Air Forces' Wright Laboratory conductd an assessment of electrical power technologies for use by the Air Force in remote, harsh environments. The surprisingly high logistics costs of operating fossil fuel generators resulted in the extension of the assessment to non-RTG sites. The candidate power sources must operate unattended for long periods at a high level of operational reliability. Selection of the optimum power generation technology is complicated and heavily driven by the severe operating environment and compounded by the remoteness of the location. It is these site-related characteristics, more than any other, that drive the selection of a safe and economical power source for Arctic applications. A number of proven power generation technologies were evaluated. The assessment concluded that RGTs are clearly the safest, most reliable, and most economical approach to supplying electrical power for remote, difficult to assess locations. The assessment also indicated that the logistics costs associated with combustion driven generator systems could be substantially reduced through the use of conversion technologies which have been previously developed for space power applications.

  4. Some features of the small-scale solar wind fluctuations

    NASA Astrophysics Data System (ADS)

    Zastenker, G.; Eiges, P.; Avanov, L.; Astafyeva, N.; Zurbuchen, Th.; Bochsler, P.

    1995-06-01

    We have investigated small-scale variations of the solar wind ion flux measured with Faraday cups onboard the Prognoz-8 satellite. These measurements have a high time resolution of 1.24 seconds for intervals with a duration of several hours and as high as 0.02 seconds for some periods of about 1 hour duration. The main goal of this work is the determination of the quantitative features of fast ion flux fluctuations using mainly spectral analysis but also other methods. We also identify their association with interplanetary plasma parameters. Particularly, it is shown that the slope of the power spectra in the frequency range from 1E-4 to 6E-2 Hz is close to the classical Kolmogorov (-5/3) law. We also discuss some intervals with a very high level of the relative amplitude of flux fluctuations (10-20 percent) which were observed near the Earth's bow shock in the foreshock region. The use of the wavelet method for the long time series allows us to study the temporal evolution of power spectra.

  5. Shaping mobile belts by small-scale convection.

    PubMed

    Faccenna, Claudio; Becker, Thorsten W

    2010-06-01

    Mobile belts are long-lived deformation zones composed of an ensemble of crustal fragments, distributed over hundreds of kilometres inside continental convergent margins. The Mediterranean represents a remarkable example of this tectonic setting: the region hosts a diffuse boundary between the Nubia and Eurasia plates comprised of a mosaic of microplates that move and deform independently from the overall plate convergence. Surface expressions of Mediterranean tectonics include deep, subsiding backarc basins, intraplate plateaux and uplifting orogenic belts. Although the kinematics of the area are now fairly well defined, the dynamical origins of many of these active features are controversial and usually attributed to crustal and lithospheric interactions. However, the effects of mantle convection, well established for continental interiors, should be particularly relevant in a mobile belt, and modelling may constrain important parameters such as slab coherence and lithospheric strength. Here we compute global mantle flow on the basis of recent, high-resolution seismic tomography to investigate the role of buoyancy-driven and plate-motion-induced mantle circulation for the Mediterranean. We show that mantle flow provides an explanation for much of the observed dynamic topography and microplate motion in the region. More generally, vigorous small-scale convection in the uppermost mantle may also underpin other complex mobile belts such as the North American Cordillera or the Himalayan-Tibetan collision zone. PMID:20520711

  6. Small scale clustering of late forming dark matter

    NASA Astrophysics Data System (ADS)

    Agarwal, S.; Corasaniti, P.-S.; Das, S.; Rasera, Y.

    2015-09-01

    We perform a study of the nonlinear clustering of matter in the late-forming dark matter (LFDM) scenario in which dark matter results from the transition of a nonminimally coupled scalar field from radiation to collisionless matter. A distinct feature of this model is the presence of a damped oscillatory cutoff in the linear matter power spectrum at small scales. We use a suite of high-resolution N-body simulations to study the imprints of LFDM on the nonlinear matter power spectrum, the halo mass and velocity functions and the halo density profiles. The model largely satisfies high-redshift matter power spectrum constraints from Lyman-α forest measurements, while it predicts suppressed abundance of low-mass halos (˜109- 1010 h-1 M⊙ ) at all redshifts compared to a vanilla Λ CDM model. The analysis of the LFDM halo velocity function shows a better agreement than the Λ CDM prediction with the observed abundance of low-velocity galaxies in the local volume. Halos with mass M ≳1011 h-1 M⊙ show minor departures of the density profiles from Λ CDM expectations, while smaller-mass halos are less dense, consistent with the fact that they form later than their Λ CDM counterparts.

  7. The small-scale turbulent dynamo in smoothed particle magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Tricco, T. S.; Price, D. J.; Federrath, C.

    2016-05-01

    Supersonic turbulence is believed to be at the heart of star formation. We have performed smoothed particle magnetohydrodynamics (SPMHD) simulations of the small- scale dynamo amplification of magnetic fields in supersonic turbulence. The calculations use isothermal gas driven at rms velocity of Mach 10 so that conditions are representative of starforming molecular clouds in the Milky Way. The growth of magnetic energy is followed for 10 orders in magnitude until it reaches saturation, a few percent of the kinetic energy. The results of our dynamo calculations are compared with results from grid-based methods, finding excellent agreement on their statistics and their qualitative behaviour. The simulations utilise the latest algorithmic developments we have developed, in particular, a new divergence cleaning approach to maintain the solenoidal constraint on the magnetic field and a method to reduce the numerical dissipation of the magnetic shock capturing scheme. We demonstrate that our divergence cleaning method may be used to achieve ∇ • B = 0 to machine precision, albeit at significant computational expense.

  8. Performance of small-scale tidal power plants

    NASA Astrophysics Data System (ADS)

    Fay, J. A.; Smachlo, M. A.

    1983-12-01

    Small-scale tidal power plants - having electric power between 1 and 100 MW, approximately - possess several attractive economic and environmental benefits. The dynamical behavior of such systems is calculated in terms of dimensionless variables and parameters, so that the size of the system is inconsequential (except for one parameter related to the slope of the walls of the tidal basin). Two measures of system performance are defined: capacity factor (ratio of average to rated power) and effectiveness (ratio of average to ideal tidal power). It was found that improving both parameters is mutually incompatible so that an economic analysis will determine the optimum values of the system design and performance parameters. The effects of variation of tidal range and basin shape were determined. Using typical variable flow properties of low-head hydroturbines, a favorable design head could be determined from the analysis. It was found that the change in the area of the intertidal zone relative to the surface area of the tidal pond is greater for small, as compared to large, systems, possibly leading to proportionately greater environmental effects. A comparison of the performance of several tidal power plant designs with the methodology of this paper showed generally good agreement with the dimensionless performance parameters and only a modest difference among them over several orders of magnitude in size of power plant.

  9. Small Scale Turbopump Manufacturing Technology and Material Processes

    NASA Technical Reports Server (NTRS)

    Alvarez, Erika; Morgan, Kristin; Wells, Doug; Zimmerman, Frank

    2011-01-01

    As part of an internal research and development project, NASA Marshall Space Flight Center (MSFC) has been developing a high specific impulse 9,000-lbf LOX/LH2 pump-fed engine testbed with the capability to throttle 10:1. A Fuel Turbopump (FTP) with the ability to operate across a speed range of 30,000-rpm to 100,000-rpm was developed and analyzed. This small size and flight-like Fuel Turbopump has completed the design and analysis phase and is currently in the manufacturing phase. This paper highlights the manufacturing and processes efforts to fabricate an approximately 20-lb turbopump with small flow passages, intricately bladed components and approximately 3-in diameter impellers. As a result of the small scale and tight tolerances of the hardware on this turbopump, several unique manufacturing and material challenges were encountered. Some of the technologies highlighted in this paper include the use of powder metallurgy technology to manufacture small impellers, electron beam welding of a turbine blisk shroud, and casting challenges. The use of risk reduction efforts such as non-destructive testing (NDT) and evaluation (NDE), fractography, material testing, and component spin testing are also discussed in this paper.

  10. Social and Ecological Dynamics of Small-Scale Fisheries

    NASA Astrophysics Data System (ADS)

    Stevens, K.; Kramer, D.; Frank, K.

    2012-12-01

    Globalization's reach is rapidly extending to touch some of the most remote communities of the world, but we have yet to understand its scale and impact. On Nicaragua's previously remote Miskitu Coast, the introduction of new markets and global demand for seafood has resulted in changes in fishermen's harvest behavior manifested within the local fishery. Small-scale fisheries are a significant component in sustaining global fish trade, ensuring food security, and alleviating poverty, but because the fishermen are disperse, numerous and located in remote areas, the social and ecological dynamics of the system are poorly understood. Previous work has indicated a decline in fish abundance as a result of connection to markets, yet fishermen's response to this decline and the resulting shift in harvest strategy requires further examination. I identify the ecological and social factors that explain changes in fishermen behavior and use an innovative application of social network analysis to understand these changes. I also use interviews with fishermen and fishery-dependent surveys to measure catch and release behavior and seasonal gear use. Results demonstrate multiple cliques within a community that mitigate the response of fishermen to changes in the fishery. This research applies techniques in social science to address challenges in sustainable management of fisheries. As fisheries managers consider implementing new regulations, such as seasonal restrictions on gear, it is essential to understand not just how this might impact fish abundance, but how and why human systems respond as they do.

  11. Small scale flow processes in aqueous heterogeneous porous media

    SciTech Connect

    Rashidi, M.; Dickenson, E.

    1996-04-01

    Small scale flow processes in aqueous heterogeneous porous systems have been studied experimentally via novel nonintrusive fluorescence imaging techniques. The techniques involve 3D visualization and quantification of flow fields within a refractive index-matched transparent porous column. The refractive index-matching yields a transparent porous medium, free from any scattering and refraction at the solid-liquid interfaces, as a result allowing direct optical probing at any point within the porous system. By illuminating the porous regions within the column with a planar sheet of laser beam, flow processes through the porous medium can be observed microscopically, and qualitative and quantitative in-pore transport information can be obtained at a good resolution and a good accuracy. A CCD camera is used to record the fluorescent images at every vertical plane location while sweeping back and forth across the column. These digitized flow images are then analyzed and accumulated over a 3D volume within the column. Series of flow experiments in aqueous, refractive index-matched, porous systems packed with natural mineral particles have been performed successfully in these laboratories.

  12. Advanced conversion technologies for small-scale remote power systems

    SciTech Connect

    Lamp, T.R.

    1996-12-31

    Forest fires that endangered remote US Air Force sites equipped with radioisotope thermoelectric generators (RTGs) prompted the assessment of power generating systems that could be substituted for RTGs in small scale (10--120 watt) applications. Other non-RTG sites were also studied during the assessment. The power system assessment was conducted by the US Air Forces` Wright Laboratory and included the evaluation of engine-driven generators, solar, wind generators, propane thermoelectric generators (TEGs), batteries, fuel cells, and power systems based on advanced conversion technologies; such as, thermionics, free piston Stirling Engines (FPSE), alkali metal thermoelectric conversion (AMTEC), and thermophotovoltaics (TPV). The assessment team concluded that continued use of the RTGs is clearly the safest, most reliable, and most economical approach to supplying electrical power for remote, difficult to access locations. If political considerations force the replacement of the RTGs, the likely replacement is a hybrid system consisting of solar-PV with a propane-TEG for off-solar times. The transport of combustible fuels in Arctic environments is extremely expensive. It is this high logistics cost that signaled the need to consider the option of more efficient and cost effective power sources for the remote, Arctic applications. This paper summarizes the assessment of some of the more attractive power systems that are based on the advanced conversion technologies of AMTEC, TPV and FPSE.

  13. Development of a small scale BIGGT power plant

    SciTech Connect

    Craig, J.D.

    1994-12-31

    Cratech, Inc. is progressing on a 3-phase plan to develop a one ton per hour (tph) biomass-fueled integrated-gasifier gas turbine (BIGGT) power plant. The goal is to develop economical, small scale (1-20 MWe) power plants for entities worldwide that desire to use a variety of biomass resources for fuel including those with high ash content and that are prone to slagging. Phase 1 has been successfully completed. Phase 1 included design, fabrication and operation of a 0.5 tph air-blown pressurized fluidized bed gasification unit complete with a hot gas cleanup system. The unit was fueled with cotton gin trash (CGT), a biomass resource that is high in ash and very prone to slagging. The system demonstrated production of a gas from CGT that can be maintained at a minimum chemical heating value of 130 BTU/SCF, at an outlet temperature of 1265 {+-} 15{degrees}F with a maximum particle content of 6.4 ppmw of 2.8 um maximum particle size.

  14. A Small-Scale Safety Test for Initiation Components

    SciTech Connect

    Cutting, J; Chow, C; Chau, H; Hodgin, R; Lee, R

    2002-04-22

    We have developed a small-scale safety test for initiation train components. A low-cost test was needed to assess the response of initiation components to an abnormal shock environment and to detect changes in the sensitivity of initiation components as they age. The test uses a disk of Detasheet to transmit a shock through a PMMA barrier into a the test article. A schematic drawing of the fixture is shown. The 10-cm-diameter disk of 3-mm-thick Detasheet, initiated at its center by a RISI, RP detonator, produces a shock wave that is attenuated by a variable-thickness PMMA spacer (gap). Layers of metal and plastic above the test article and the material surrounding the test article may be chosen to mock up the environment of the test article at its location in a warhead. A metal plate at the bottom serves as a witness plate to record whether or not the test article detonated. For articles containing a small amount of explosive, it can be difficult to determine whether or not a detonation has occurred. In such cases, one can use a pressure transducer or laser velocimeter to detect the shock wave from the detonation of the article. The assembly is contained in a 10-cm-ID section of PVC pipe and fired in a containment vessel rated at 100 g. Test results are given for a hemispherical, exploding-bridgewire (EBW) detonator.

  15. Cosmic-Ray Small-scale Anisotropies and Local Turbulent Magnetic Fields

    NASA Astrophysics Data System (ADS)

    López-Barquero, V.; Farber, R.; Xu, S.; Desiati, P.; Lazarian, A.

    2016-10-01

    Cosmic-ray anisotropy has been observed in a wide energy range and at different angular scales by a variety of experiments over the past decade. However, no comprehensive or satisfactory explanation has been put forth to date. The arrival distribution of cosmic rays at Earth is the convolution of the distribution of their sources and of the effects of geometry and properties of the magnetic field through which particles propagate. It is generally believed that the anisotropy topology at the largest angular scale is adiabatically shaped by diffusion in the structured interstellar magnetic field. On the contrary, the medium- and small-scale angular structure could be an effect of nondiffusive propagation of cosmic rays in perturbed magnetic fields. In particular, a possible explanation for the observed small-scale anisotropy observed at the TeV energy scale may be the effect of particle propagation in turbulent magnetized plasmas. We perform numerical integration of test particle trajectories in low-β compressible magnetohydrodynamic turbulence to study how the cosmic rays’ arrival direction distribution is perturbed when they stream along the local turbulent magnetic field. We utilize Liouville’s theorem for obtaining the anisotropy at Earth and provide the theoretical framework for the application of the theorem in the specific case of cosmic-ray arrival distribution. In this work, we discuss the effects on the anisotropy arising from propagation in this inhomogeneous and turbulent interstellar magnetic field.

  16. String resistance detector

    NASA Technical Reports Server (NTRS)

    Hall, A. Daniel (Inventor); Davies, Francis J. (Inventor)

    2007-01-01

    Method and system are disclosed for determining individual string resistance in a network of strings when the current through a parallel connected string is unknown and when the voltage across a series connected string is unknown. The method/system of the invention involves connecting one or more frequency-varying impedance components with known electrical characteristics to each string and applying a frequency-varying input signal to the network of strings. The frequency-varying impedance components may be one or more capacitors, inductors, or both, and are selected so that each string is uniquely identifiable in the output signal resulting from the frequency-varying input signal. Numerical methods, such as non-linear regression, may then be used to resolve the resistance associated with each string.

  17. Sorting Symbol Strings

    ERIC Educational Resources Information Center

    Novak, Jodie D.; Jacobs, Judith E.

    2005-01-01

    This article describes a variety of activities that ask students to identify, describe, compare, and classify symbol strings (algebraic expressions and equations). The activities use a collection of twelve symbol strings on cards. (Contains 2 figures.)

  18. Light from cosmic strings

    SciTech Connect

    Steer, Daniele A.; Vachaspati, Tanmay

    2011-02-15

    The time-dependent metric of a cosmic string leads to an effective interaction between the string and photons--the ''gravitational Aharonov-Bohm'' effect--and causes cosmic strings to emit light. We evaluate the radiation of pairs of photons from cosmic strings and find that the emission from cusps, kinks and kink-kink collisions occurs with a flat spectrum at all frequencies up to the string scale. Further, cusps emit a beam of photons, kinks emit along a curve, and the emission at a kink-kink collision is in all directions. The emission of light from cosmic strings could provide an important new observational signature of cosmic strings that is within reach of current experiments for a range of string tensions.

  19. Coronal hole boundaries evolution at small scales. II. XRT view. Can small-scale outflows at CHBs be a source of the slow solar wind

    NASA Astrophysics Data System (ADS)

    Subramanian, S.; Madjarska, M. S.; Doyle, J. G.

    2010-06-01

    Aims: We aim to further explore the small-scale evolution of coronal hole boundaries using X-ray high-resolution and high-cadence images. We intend to determine the fine structure and dynamics of the events causing changes of coronal hole boundaries and to explore the possibility that these events are the source of the slow solar wind. Methods: We developed an automated procedure for the identification of transient brightenings in images from the X-ray telescope on-board Hinode taken with an Al Poly filter in the equatorial coronal holes, polar coronal holes, and the quiet Sun with and without transient coronal holes. Results: We found that in comparison to the quiet Sun, the boundaries of coronal holes are abundant with brightening events including areas inside the coronal holes where closed magnetic field structures are present. The visual analysis of these brightenings revealed that around 70% of them in equatorial, polar and transient coronal holes and their boundaries show expanding loop structures and/or collimated outflows. In the quiet Sun only 30% of the brightenings show flows with most of them appearing to be contained in the solar corona by closed magnetic field lines. This strongly suggests that magnetic reconnection of co-spatial open and closed magnetic field lines creates the necessary conditions for plasma outflows to large distances. The ejected plasma always originates from pre-existing or newly emerging (at X-ray temperatures) bright points. Conclusions: The present study confirms our findings that the evolution of loop structures known as coronal bright points is associated with the small-scale changes of coronal hole boundaries. The loop structures show an expansion and eruption with the trapped plasma consequently escaping along the “quasi” open magnetic field lines. These ejections appear to be triggered by magnetic reconnection, e.g. the so-called interchange reconnection between the closed magnetic field lines (BPs) and the open

  20. [The string of Einthoven's string galvanometer].

    PubMed

    Wyers, P J

    1996-01-01

    The Dutch physiologist Willem Einthoven (1860-1927) published in 1901 his construction of a string galvanometer. With this apparatus he opened the era for electrocardiography. As the quality of his instrument largely depended on the string of the string galvanometer it is surprising to note that in his publications Einthoven never mentioned the exact way of producing the string. However, Einthoven's hand written laboratory notes are preserved at the Museum Boerhaave in Leiden. From these notes it comes clear what problems Einthoven had with the string. To get a very thin thread of quarts he first used the method of shooting the thread as was described by Boys (1887), later the blowing method of Nichols (1894). The silvering of the thread was done first chemically, later by cathode spray. In all cases premature breaking of the thread was a nuisance. Because of these failures Einthoven might have decided not to publish any details.

  1. [The string of Einthoven's string galvanometer].

    PubMed

    Wyers, P J

    1996-01-01

    The Dutch physiologist Willem Einthoven (1860-1927) published in 1901 his construction of a string galvanometer. With this apparatus he opened the era for electrocardiography. As the quality of his instrument largely depended on the string of the string galvanometer it is surprising to note that in his publications Einthoven never mentioned the exact way of producing the string. However, Einthoven's hand written laboratory notes are preserved at the Museum Boerhaave in Leiden. From these notes it comes clear what problems Einthoven had with the string. To get a very thin thread of quarts he first used the method of shooting the thread as was described by Boys (1887), later the blowing method of Nichols (1894). The silvering of the thread was done first chemically, later by cathode spray. In all cases premature breaking of the thread was a nuisance. Because of these failures Einthoven might have decided not to publish any details. PMID:11624925

  2. Drill string enclosure

    DOEpatents

    Jorgensen, Douglas K.; Kuhns, Douglass J.; Wiersholm, Otto; Miller, Timothy A.

    1993-01-01

    The drill string enclosure consists of six component parts, including; a top bracket, an upper acrylic cylinder, an acrylic drill casing guide, a lower acrylic cylinder, a bottom bracket, and three flexible ducts. The upper acrylic cylinder is optional based upon the drill string length. The drill string enclosure allows for an efficient drill and sight operation at a hazardous waste site.

  3. Drill string enclosure

    DOEpatents

    Jorgensen, D.K.; Kuhns, D.J.; Wiersholm, O.; Miller, T.A.

    1993-03-02

    The drill string enclosure consists of six component parts, including; a top bracket, an upper acrylic cylinder, an acrylic drill casing guide, a lower acrylic cylinder, a bottom bracket, and three flexible ducts. The upper acrylic cylinder is optional based upon the drill string length. The drill string enclosure allows for an efficient drill and sight operation at a hazardous waste site.

  4. Heavy cosmic strings

    SciTech Connect

    Donaire, M.; Rajantie, A.

    2006-03-15

    We argue that cosmic strings with high winding numbers generally form in first-order gauge symmetry breaking phase transitions, and we demonstrate this using computer simulations. These strings are heavier than single-winding strings and therefore more easily observable. Their cosmological evolution may also be very different.

  5. Dynamics of Carroll strings

    NASA Astrophysics Data System (ADS)

    Cardona, Biel; Gomis, Joaquim; Pons, Josep M.

    2016-07-01

    We construct the canonical action of a Carroll string doing the Carroll limit of a canonical relativistic string. We also study the Killing symmetries of the Carroll string, which close under an infinite dimensional algebra. The tensionless limit and the Carroll p-brane action are also discussed.

  6. A novel 3D structure composed of strings of hierarchical TiO{sub 2} spheres formed on TiO{sub 2} nanobelts with high photocatalytic properties

    SciTech Connect

    Jiang, Yongjian; Li, Meicheng; Song, Dandan; Li, Xiaodan; Yu, Yue

    2014-03-15

    A novel hierarchical titanium dioxide (TiO{sub 2}) composite nanostructure with strings of anatase TiO{sub 2} hierarchical micro-spheres and rutile nanobelts framework (TiO{sub 2} HSN) is successfully synthesized via a one-step hydrothermal method. Particularly, the strings of hierarchical spheres are assembled by very thin TiO{sub 2} nanosheets, which are composed of highly crystallized anatase nanocrystals. Meanwhile, the HSN has a large surface area of 191 m{sup 2}/g, which is about 3 times larger than Degussa P25. More importantly, the photocatalytic activity of HSN and P25 were evaluated by the photocatalytic oxidation decomposition of methyl orange (MO) under UV light illumination, and the TiO{sub 2} HSN shows enhanced photocatalytic activity compared with Degussa P25, as result of its continuous hierarchical structures, special conductive channel and large specific surface area. With these features, the hierarchical TiO{sub 2} may have more potential applications in the fields of dye-sensitized solar cells and lithium ion batteries. -- Graphical abstract: Novel TiO{sub 2} with anatase micro-spheres and rutile nanobelts is synthesized. Enhanced photocatalysis is attributed to hierarchical structures (3D spheres), conductive channel (1D nanobelts) and large specific surface area (2D nanosheet). Highlights: • The novel TiO{sub 2} nanostructure (HSN) is fabricated for the first time. • HSN is composed of strings of anatase hierarchical spheres and rutile nanobelt. • HSN presents a larger S{sub BET} of 191 m{sup 2}/g, 3 times larger than the Degussa P25 (59 m{sup 2}/g). • HSN owns three kinds of dimensional TiO{sub 2} (1D, 2D and 3D) simultaneously. • HSN exhibits better photocatalytic performance compared with Degussa P25.

  7. Small-Scale Spray Releases: Orifice Plugging Test Results

    SciTech Connect

    Mahoney, Lenna A.; Gauglitz, Phillip A.; Blanchard, Jeremy; Kimura, Marcia L.; Kurath, Dean E.

    2012-09-01

    included round holes and rectangular slots. Much of the testing was conducted at pressures of 200 and 380 psi, but some tests were conducted at 100 psi. Testing the largest postulated breaches was deemed impractical because of the large size of some of the WTP equipment. The purpose of the study described in this report is to provide experimental data for the first key technical area, potential plugging of small breaches, by performing small-scale tests with a range of orifice sizes and orientations representative of the WTP conditions. The simulants used were chosen to represent the range of process stream properties in the WTP. Testing conducted after the plugging tests in the small- and large-scale test stands addresses the second key technical area, aerosol generation. The results of the small-scale aerosol generation tests are included in Mahoney et al. 2012. The area of spray generation from large breaches is covered by large-scale testing in Schonewill et al. 2012.

  8. Small-scale thermal studies of volatile homemade explosives

    DOE PAGES

    Sandstrom, Mary M.; Brown, Geoffrey W.; Warner, Kirsten F.; Sorensen, Daniel N.; Phillips, Jason J.; Shelley, Timothy J.; Reyes, Jose A.; Hsu, Peter C.; Reynolds, John G.

    2016-01-26

    Several homemade or improvised explosive mixtures that either contained volatile components or produced volatile products were examined using standard small-scale safety and thermal (SSST) testing that employed differential scanning calorimetry (DSC) techniques (constant heating rate and standard sample holders). KClO3 and KClO4 mixtures with dodecane exhibited different enthalpy behavior when using a vented sample holder in contrast to a sealed sample holder. The standard configuration produced profiles that exhibited only endothermic transitions. The sealed system produced profiles that exhibited additional exothermic transitions absent in the standard configuration produced profiles. When H2O2/fuel mixtures were examined, the volatilization of the peroxide (endothermic)more » dominated the profiles. When a sealed sample holder was used, the energetic releases of the mixture could be clearly observed. For AN and AN mixtures, the high temperature decomposition appears as an intense endothermic event. Using a nominally sealed sample holder also did not adequately contain the system. Only when a high-pressure rated sample holder was used the high temperature decomposition of the AN could be detected as an exothermic release. The testing was conducted during a proficiency (or round-robin type) test that included three U.S. Department of Energy and two U.S. Department of Defense laboratories. In the course of this proficiency test, certain HMEs exhibited thermal behavior that was not adequately accounted for by standard techniques. Further examination of this atypical behavior highlighted issues that may have not been recognized previously because some of these materials are not routinely tested. More importantly, if not recognized, the SSST testing results could lead to inaccurate safety assessments. Furthermore, this study provides examples, where standard techniques can be applied, and results can be obtained, but these results may be misleading in establishing

  9. Propulsion engineering study for small-scale Mars missions

    SciTech Connect

    Whitehead, J.

    1995-09-12

    Rocket propulsion options for small-scale Mars missions are presented and compared, particularly for the terminal landing maneuver and for sample return. Mars landing has a low propulsive {Delta}v requirement on a {approximately}1-minute time scale, but at a high acceleration. High thrust/weight liquid rocket technologies, or advanced pulse-capable solids, developed during the past decade for missile defense, are therefore more appropriate for small Mars landers than are conventional space propulsion technologies. The advanced liquid systems are characterize by compact lightweight thrusters having high chamber pressures and short lifetimes. Blowdown or regulated pressure-fed operation can satisfy the Mars landing requirement, but hardware mass can be reduced by using pumps. Aggressive terminal landing propulsion designs can enable post-landing hop maneuvers for some surface mobility. The Mars sample return mission requires a small high performance launcher having either solid motors or miniature pump-fed engines. Terminal propulsion for 100 kg Mars landers is within the realm of flight-proven thruster designs, but custom tankage is desirable. Landers on a 10 kg scale also are feasible, using technology that has been demonstrated but not previously flown in space. The number of sources and the selection of components are extremely limited on this smallest scale, so some customized hardware is required. A key characteristic of kilogram-scale propulsion is that gas jets are much lighter than liquid thrusters for reaction control. The mass and volume of tanks for inert gas can be eliminated by systems which generate gas as needed from a liquid or a solid, but these have virtually no space flight history. Mars return propulsion is a major engineering challenge; earth launch is the only previously-solved propulsion problem requiring similar or greater performance.

  10. Potential small-scale development of western oil shale

    SciTech Connect

    Smith, V.; Renk, R.; Nordin, J.; Chatwin, T.; Harnsberger, M.; Fahy, L.J.; Cha, C.Y.; Smith, E.; Robertson, R.

    1989-10-01

    Several studies have been undertaken in an effort to determine ways to enhance development of western oil shale under current market conditions for energy resources. This study includes a review of the commercial potential of western oil shale products and byproducts, a review of retorting processes, an economic evaluation of a small-scale commercial operation, and a description of the environmental requirements of such an operation. Shale oil used as a blend in conventional asphalt appears to have the most potential for entering today's market. Based on present prices for conventional petroleum, other products from oil shale do not appear competitive at this time or will require considerable marketing to establish a position in the marketplace. Other uses for oil shale and spent shale, such as for sulfur sorbtion, power generation, cement, aggregate, and soil stabilization, are limited economically by transportation costs. The three-state area area consisting of Colorado, Utah, and Wyoming seems reasonable for the entry of shale oil-blended asphalt into the commercial market. From a review of retorting technologies and the product characteristics from various retorting processes it was determined that the direct heating Paraho and inclined fluidized-bed processes produce a high proportion of heavy material with a high nitrogen content. The two processes are complementary in that they are each best suited to processing different size ranges of materials. An economic evaluation of a 2000-b/d shale oil facility shows that the operation is potentially viable, if the price obtained for the shale oil residue is in the top range of prices projected for this product. Environmental requirements for building and operating an oil shale processing facility are concerned with permitting, control of emissions and discharges, and monitoring. 62 refs., 6 figs., 10 tabs.

  11. Small Scale Cold Traps on Airless Planetary Bodies

    NASA Astrophysics Data System (ADS)

    Hayne, Paul O.; Aharonson, O.; Williams, J.; Siegler, M. A.; Greenhagen, B. T.; Bandfield, J.; Vasavada, A. R.; Paige, D. A.; Diviner Lunar Radiometer Science Team

    2013-10-01

    Lacking an atmosphere to transport heat, temperatures on airless bodies are primarily controlled by latitude and local time. However, local topography strongly affects temperatures at the surface and in the subsurface by changing the intensity and timing of insolation. In the case of low-obliquity bodies such as Mercury and the Earth’s moon, topography near the poles casts perennial shadows where volatiles such as water ice may be cold-trapped for billions of years. Prior studies have focused primarily on large contiguous cold traps > 1 km resolvable by instruments in lunar orbit. In this investigation, we used infrared measurements of the Moon, thermal models, and a statistical rough surface model to show that such cold traps may exist on a vast range of scales, from the largest impact craters, down to the skin depth of the diurnal temperature oscillation. The extremely insulating nature of planetary regolith leads to extreme temperature gradients and shallow diurnal skin depths. For example, the lunar 29-day diurnal temperature oscillation is damped to ~1% at a depth of 0.5 m. Therefore, at latitudes > 60° where perennial shadow exists, cold traps as small as a few tens of centimeters could exist. As two test cases, we calculated the fractional surface areas on the Moon (obliquity = 1.6°) and Ceres (3-5°) where temperatures remain < 110 K all year round, such that water ice is thermally stable at the surface for billions of years. We also calculated fractional areas where subsurface temperatures are < 145 K, such that subsurface ice deposits are stable on similar timescales. Finally, we will discuss the implications of these proposed small-scale cold traps for other airless bodies, including asteroids and giant planet satellites.

  12. Cosmic Strings in the Universe: Achievements and prospects of research

    SciTech Connect

    Sazhina, O. S. Sazhin, M. V.

    2011-11-15

    Cosmic strings are linear structures of cosmological scales whose search has been actively conducted in recent years. Progress in constructing theoretical models and investigating the properties of cosmic strings and a significant growth of observational resources provide extensive possibilities for the search of such objects by several independent observational methods. These methods include searching for the events of gravitational lensing of distant background sources by strings and searching for the distinctive cosmic micro-wave background anisotropy structures induced by strings. We discuss these techniques and propose the methods of searching for strings oriented toward the latest spacecraft, including the Planck project.

  13. SMALL-SCALE HEATING EVENTS IN THE SOLAR ATMOSPHERE. I. IDENTIFICATION, SELECTION, AND IMPLICATIONS FOR CORONAL HEATING

    SciTech Connect

    Guerreiro, N.; Haberreiter, M.; Schmutz, W.; Hansteen, V.

    2015-11-01

    We present a comprehensive method to analyze small-scale heating events in detail in a 3D magnetohydrodynamics simulation for quiet-Sun conditions. The method determines the number, volume, and some general geometric properties of the small-scale heating events at different instants in a simulation with a volume of 16 × 8 × 16 Mm{sup 3}, spanning from the top of the convection zone to the corona. We found that there are about 10{sup 4} small-scale heating events at any instant above the simulated area of 128 Mm{sup 2}. They occur mainly at heights between 1.5 and 3.0 Mm. We determine the average value of their projected vertical extent, which ranges from 375 to 519 km over time, and we show that height, volume, and energy distribution of the events at any instant resemble power laws. Finally, we demonstrate that larger heating structures are a combination of much smaller heating events and that small-scale heating events dissipate enough energy to maintain the coronal energetic balance at any instant.

  14. Environmental Health and Safety Hazards of Indigenous Small-Scale Gold Mining Using Cyanidation in the Philippines

    PubMed Central

    Leung, Ana Marie R.; Lu, Jinky Leilanie DP.

    2016-01-01

    OBJECTIVES This cross-sectional study aimed at the environmental health hazards at work and cyanide exposure of small-scale gold miners engaged in gold extraction from ores in a mining area in the Philippines. METHODS Methods consisted of structured questionnaire-guided interviews, work process observation tools, physical health assessment by medical doctors, and laboratory examination and blood cyanide determination in the blood samples of 34 indigenous small-scale gold miners from Benguet, Philippines. RESULTS The small-scale gold miners worked for a mean of 10.3 years, had a mean age of 36 years, with mean lifetime mining work hours of 18,564. All were involved in tunneling work (100%) while a considerable number were involved in mixing cyanide with the ore (44%). A considerable number were injured (35%) during the mining activity, and an alarming number (35%) had elevated blood cyanide level. The most prevalent hazard was exposure to chemicals, particularly to cyanide and nitric acid, which were usually handled with bare hands. CONCLUSION The small-scale gold miners were exposed to occupational and environmental hazards at work. PMID:27547035

  15. Modeling the Sun’s Small-scale Global Photospheric Magnetic Field

    NASA Astrophysics Data System (ADS)

    Meyer, K. A.; Mackay, D. H.

    2016-10-01

    We present a new model for the Sun’s global photospheric magnetic field during a deep minimum of activity, in which no active regions emerge. The emergence and subsequent evolution of small-scale magnetic features across the full solar surface is simulated, subject to the influence of a global supergranular flow pattern. Visually, the resulting simulated magnetograms reproduce the typical structure and scale observed in quiet Sun magnetograms. Quantitatively, the simulation quickly reaches a steady state, resulting in a mean field and flux distribution that are in good agreement with those determined from observations. A potential coronal magnetic field is extrapolated from the simulated full Sun magnetograms to consider the implications of such a quiet photospheric magnetic field on the corona and inner heliosphere. The bulk of the coronal magnetic field closes very low down, in short connections between small-scale features in the simulated magnetic network. Just 0.1% of the photospheric magnetic flux is found to be open at 2.5 R ⊙, around 10–100 times less than that determined for typical Helioseismic and Magnetic Imager synoptic map observations. If such conditions were to exist on the Sun, this would lead to a significantly weaker interplanetary magnetic field than is currently observed, and hence a much higher cosmic ray flux at Earth.

  16. Formation of Small-Scale Vortex Rings from Vortex Pairs Close to the Ground

    NASA Astrophysics Data System (ADS)

    Asselin, Daniel; Williamson, Charles

    2013-11-01

    In this research, we examine the effect of a solid boundary on the dynamics and instabilities of a pair of counter-rotating vortices. An isolated vortex pair is subject to a short-wave elliptic instability and a long-wave Crow (1970) instability. Near a wall, the boundary layer between the primary vortices and the wall can separate, leading to the generation of secondary vorticity. These secondary vortices can be subject to small-scale instabilities (Harris & Williamson, 2012) as they come under the influence of the primary vortices. In contrast, in the present study we are interested in the long-wave Crow instability interrupted by interaction with a wall. This can cause significant axial flow, resulting in a periodic concentration of fluid containing vorticity at the peaks of each wavy vortex tube and a corresponding evacuation of fluid containing vorticity from the troughs. It appears that this axial flow is driven at least in part by the formation of vortex ring-like structures in the secondary vortex as it is deformed by the primary vortex. Furthermore, additional small scale-vortex rings evolve from the secondary vorticity and from the concentrated vortical regions in the primary vorticity. In both cases, these rings cause vorticity to rebound away from the ground.

  17. AN AUTOMATIC DETECTION METHOD FOR EXTREME-ULTRAVIOLET DIMMINGS ASSOCIATED WITH SMALL-SCALE ERUPTION

    SciTech Connect

    Alipour, N.; Safari, H.; Innes, D. E.

    2012-02-10

    Small-scale extreme-ultraviolet (EUV) dimming often surrounds sites of energy release in the quiet Sun. This paper describes a method for the automatic detection of these small-scale EUV dimmings using a feature-based classifier. The method is demonstrated using sequences of 171 Angstrom-Sign images taken by the STEREO/Extreme UltraViolet Imager (EUVI) on 2007 June 13 and by Solar Dynamics Observatory/Atmospheric Imaging Assembly on 2010 August 27. The feature identification relies on recognizing structure in sequences of space-time 171 Angstrom-Sign images using the Zernike moments of the images. The Zernike moments space-time slices with events and non-events are distinctive enough to be separated using a support vector machine (SVM) classifier. The SVM is trained using 150 events and 700 non-event space-time slices. We find a total of 1217 events in the EUVI images and 2064 events in the AIA images on the days studied. Most of the events are found between latitudes -35 Degree-Sign and +35 Degree-Sign . The sizes and expansion speeds of central dimming regions are extracted using a region grow algorithm. The histograms of the sizes in both EUVI and AIA follow a steep power law with slope of about -5. The AIA slope extends to smaller sizes before turning over. The mean velocity of 1325 dimming regions seen by AIA is found to be about 14 km s{sup -1}.

  18. Dilatonic global strings

    NASA Astrophysics Data System (ADS)

    Dando, Owen; Gregory, Ruth

    1998-07-01

    We examine the field equations of a self-gravitating global string in low energy superstring gravity, allowing for an arbitrary coupling of the global string to the dilaton. Massive and massless dilatons are considered. For the massive dilaton the spacetime is similar to the recently discovered non-singular time-dependent Einstein self-gravitating global string, but the massless dilaton generically gives a singular spacetime, even allowing for time dependence. We also demonstrate a time-dependent non-singular string-antistring configuration, in which the string pair causes a compactification of two of the spatial dimensions, albeit on a very large scale.

  19. Anomalies of E8 Gauge Theory on String Manifolds

    NASA Astrophysics Data System (ADS)

    Sati, Hisham

    In this paper we revisit the subject of anomaly cancelation in string theory and M-theory on manifolds with string structure and give three observations. First, that on string manifolds there is no E8 × E8 global anomaly in heterotic string theory. Second, that the description of the anomaly in the phase of the M-theory partition function of Diaconescu-Moore-Witten extends from the spin case to the string case. Third, that the cubic refinement law of Diaconescu-Freed-Moore for the phase of the M-theory partition function extends to string manifolds. The analysis relies on extending from invariants which depend on the spin structure to invariants which instead depend on the string structure. Along the way, the one-loop term is refined via the Witten genus.

  20. Semilocal cosmic string networks

    SciTech Connect

    Achucarro, Ana; Salmi, Petja; Urrestilla, Jon

    2007-06-15

    We report on a large-scale numerical study of networks of semilocal cosmic strings in flat space in the parameter regime in which they are perturbatively stable. We find a population of segments with an exponential length distribution and indications of a scaling network without significant loop formation. Very deep in the stability regime strings of superhorizon size grow rapidly and ''percolate'' through the box. We believe these should lead at late times to a population of infinite strings similar to topologically stable strings. However, the strings are very light; scalar gradients dominate the energy density, and the network has thus a global texturelike signature. As a result, the observational constraints, at least from the temperature power spectrum of the cosmic microwave background, on models predicting semilocal strings should be closer to those on global textures or monopoles, rather than on topologically stable gauged cosmic strings.

  1. Small-scale Geothermal Power Plants Using Hot Spring Water

    NASA Astrophysics Data System (ADS)

    Tosha, T.; Osato, K.; Kiuchi, T.; Miida, H.; Okumura, T.; Nakashima, H.

    2013-12-01

    The installed capacity of the geothermal power plants has been summed up to be about 515MW in Japan. However, the electricity generated by the geothermal resources only contributes to 0.2% of the whole electricity supply. After the catastrophic earthquake and tsunami devastated the Pacific coast of north-eastern Japan on Friday, March 11, 2011, the Japanese government is encouraging the increase of the renewable energy supply including the geothermal. It needs, however, more than 10 years to construct the geothermal power plant with more than 10MW capacity since the commencement of the development. Adding the problem of the long lead time, high temperature fluid is mainly observed in the national parks and the high quality of the geothermal resources is limited. On the other hand hot springs are often found. The utilisation of the low temperature hot water becomes worthy of notice. The low temperature hot water is traditionally used for bathing and there are many hot springs in Japan. Some of the springs have enough temperature and enthalpy to turn the geothermal turbine but a new technology of the binary power generation makes the lower temp fluid to generate electricity. Large power generators with the binary technology are already installed in many geothermal fields in the world. In the recent days small-scale geothermal binary generators with several tens to hundreds kW capacity are developed, which are originally used by the waste heat energy in an iron factory and so on. The newly developed binary unit is compact suitable for the installation in a Japanese inn but there are the restrictions for the temperature of the hot water and the working fluid. The binary power unit using alternatives for chlorofluorocarbon as the working fluid is relatively free from the restriction. KOBELCO, a company of the Kobe Steel Group, designed and developed the binary power unit with an alternative for chlorofluorocarbon. The unit has a 70 MW class electric generator. Three

  2. Experiments for comparison of small scale rainfall simulators

    NASA Astrophysics Data System (ADS)

    Iserloh, T.; Ries, J. B.

    2012-04-01

    Small scale portable rainfall simulators are an essential tool in research of recent process dynamics of soil erosion. Such rainfall simulators differ in design, rainfall intensities, rain spectra etc., impeding comparison of the results. Due to different research questions a standardisation of rainfall simulation is not in sight. Nevertheless, the data become progressively important for soil erosion modelling and therefore the basis for decision-makers in application-oriented erosion protection. The project aims at providing a criteria catalogue for estimation of the different simulators as well as the comparability of the results and a uniform calibration procedure for generated rainfall. Within the project "Comparability of simulation results of different rainfall simulators as input data for soil erosion modelling (Deutsche Forschungsgemeinschaft - DFG, Project No. Ri 835/6-1)" many rainfall simulators used by European research groups were compared. The artificially generated rainfall of the rainfall simulators at the Universities Basel, La Rioja, Malaga, Trier, Tübingen, Valencia, Wageningen, Zaragoza and at different Spanish CSIC-institutes (Almeria, Cordoba, Granada, Murcia, Zaragoza) were measured with the same methods (Laser Precipitation Monitor for drop spectra and rain collectors for spatial distribution). The data are very beneficial for improvements of simulators and comparison of simulators and results. Furthermore, they can be used for comparative studies with natural rainfall spectra. A broad range of rainfall data was measured (e.g. intensity: 30 - 149 mmh-1, Christiansen Coefficient for spatial rainfall distribution 61 - 98 %, mean drop diameter 0.375 - 5.0 mm, mean kinetic energy expenditure 25 - 1322 J m-2 h-1, mean kinetic energy per unit area and unit depth of rainfall 4 - 14 J m-2 mm-1). Similarities among the simulators could be found e.g. concerning drop size distributions (maximum drop numbers are reached within the two smallest drop

  3. Beads + String = Atoms You Can See.

    ERIC Educational Resources Information Center

    Hermann, Christine K. F.

    1998-01-01

    Presents hands-on activities that give students a head start in learning the vocabulary and basic theory involved in understanding atomic structure. Uses beads to represent protons, neutrons, and electrons and string to represent orbitals. (DDR)

  4. String Mining in Bioinformatics

    NASA Astrophysics Data System (ADS)

    Abouelhoda, Mohamed; Ghanem, Moustafa

    Sequence analysis is a major area in bioinformatics encompassing the methods and techniques for studying the biological sequences, DNA, RNA, and proteins, on the linear structure level. The focus of this area is generally on the identification of intra- and inter-molecular similarities. Identifying intra-molecular similarities boils down to detecting repeated segments within a given sequence, while identifying inter-molecular similarities amounts to spotting common segments among two or multiple sequences. From a data mining point of view, sequence analysis is nothing but string- or pattern mining specific to biological strings. For a long time, this point of view, however, has not been explicitly embraced neither in the data mining nor in the sequence analysis text books, which may be attributed to the co-evolution of the two apparently independent fields. In other words, although the word “data-mining” is almost missing in the sequence analysis literature, its basic concepts have been implicitly applied. Interestingly, recent research in biological sequence analysis introduced efficient solutions to many problems in data mining, such as querying and analyzing time series [49,53], extracting information from web pages [20], fighting spam mails [50], detecting plagiarism [22], and spotting duplications in software systems [14].

  5. String Mining in Bioinformatics

    NASA Astrophysics Data System (ADS)

    Abouelhoda, Mohamed; Ghanem, Moustafa

    Sequence analysis is a major area in bioinformatics encompassing the methods and techniques for studying the biological sequences, DNA, RNA, and proteins, on the linear structure level. The focus of this area is generally on the identification of intra- and inter-molecular similarities. Identifying intra-molecular similarities boils down to detecting repeated segments within a given sequence, while identifying inter-molecular similarities amounts to spotting common segments among two or multiple sequences. From a data mining point of view, sequence analysis is nothing but string- or pattern mining specific to biological strings. For a long time, this point of view, however, has not been explicitly embraced neither in the data mining nor in the sequence analysis text books, which may be attributed to the co-evolution of the two apparently independent fields. In other words, although the word "data-mining" is almost missing in the sequence analysis literature, its basic concepts have been implicitly applied. Interestingly, recent research in biological sequence analysis introduced efficient solutions to many problems in data mining, such as querying and analyzing time series [49,53], extracting information from web pages [20], fighting spam mails [50], detecting plagiarism [22], and spotting duplications in software systems [14].

  6. Cosmic string wakes

    NASA Technical Reports Server (NTRS)

    Stebbins, Albert; Veeraraghavan, Shoba; Silk, Joseph; Brandenberger, Robert; Turok, Neil

    1987-01-01

    Accretion of matter onto wakes left behind by horizon-sized pieces of cosmic string is investigated, and the effects of wakes on the large-scale structure of the universe are determined. Accretion of cold matter onto wakes, the effects of a long string on fluids with finite velocity dispersion or sound speeds, the interactions between loops and wakes, and the conditions for wakes to survive disruption by loops are discussed. It is concluded that the most important wakes are those which were formed at the time of equal matter and radiation density. This leads to sheetlike overdense regions of galaxies with a mean separation in agreement with the scale of the bubbles of de Lapparent, Geller, and Huchra (1986). However, for the value of G(mu) favored from galaxy formation considerations in a universe with cold dark matter, a wake accretes matter from a distance of only about 1.5 Mpc, which is much less than the distance between the wakes.

  7. Structure-Property Relationships in Hydroxide-Exchange Membranes with Cation Strings and High Ion-Exchange Capacity.

    PubMed

    Wang, Junhua; Gu, Shuang; Xiong, Ruichang; Zhang, Bingzi; Xu, Bingjun; Yan, Yushan

    2015-12-21

    A series of poly(2,4-dimethyl-1,4-phenylene oxide) hydroxide-exchange membranes (HEMs) with cation strings containing a well-defined number of cations (CS-n) and similar, high ion-exchange capacities are synthesized to investigate the effect of cation distribution on key HEM properties. As the number of cations on each string grows, the size of the ionic clusters increases from 10 to 55 nm. Well-connected ion pathways and a hydrophobic framework are observed for n≥4. The enhanced phase segregation increases the hydroxide conductivity from CS-1 to CS-6 (30 to 65 mS cm(-1) ) and suppresses the water uptake (from 143 % to 62 %). Moreover, molar hydroxide conductivities for CS-n membranes show two distinctive stages as n increases: ∼23 S cm(2)  mol(-1) for n≤3; and ∼34 cm(2)  mol(-1) for n≥4.

  8. Small-Scale Spray Releases: Initial Aerosol Test Results

    SciTech Connect

    Mahoney, Lenna A.; Gauglitz, Phillip A.; Kimura, Marcia L.; Brown, Garrett N.; Kurath, Dean E.; Buchmiller, William C.; Smith, Dennese M.; Blanchard, Jeremy; Song, Chen; Daniel, Richard C.; Wells, Beric E.; Tran, Diana N.; Burns, Carolyn A.

    2012-11-01

    rectangular slots. The round holes ranged in size from 0.2 to 4.46 mm. The slots ranged from (width × length) 0.3 × 5 to 2.74 × 76.2 mm. Most slots were oriented longitudinally along the pipe, but some were oriented circumferentially. In addition, a limited number of multi-hole test pieces were tested in an attempt to assess the impact of a more complex breach. Much of the testing was conducted at pressures of 200 and 380 psi, but some tests were conducted at 100 psi. Testing the largest postulated breaches was deemed impractical because of the large size of some of the WTP equipment. This report presents the experimental results and analyses for the aerosol measurements obtained in the small-scale test stand. It includes a description of the simulants used and their properties, equipment and operations, data analysis methodologies, and test results. The results of tests investigating the role of slurry particles in plugging small breaches are reported in Mahoney et al. (2012). The results of the aerosol measurements in the large-scale test stand are reported in Schonewill et al. (2012) along with an analysis of the combined results from both test scales.

  9. Small-Scale Spray Releases: Initial Aerosol Test Results

    SciTech Connect

    Mahoney, Lenna A.; Gauglitz, Phillip A.; Kimura, Marcia L.; Brown, Garrett N.; Kurath, Dean E.; Buchmiller, William C.; Smith, Dennese M.; Blanchard, Jeremy; Song, Chen; Daniel, Richard C.; Wells, Beric E.; Tran, Diana N.; Burns, Carolyn A.

    2013-05-29

    rectangular slots. For the combination of both test stands, the round holes ranged in size from 0.2 to 4.46 mm. The slots ranged from (width × length) 0.3 × 5 to 2.74 × 76.2 mm. Most slots were oriented longitudinally along the pipe, but some were oriented circumferentially. In addition, a limited number of multi-hole test pieces were tested in an attempt to assess the impact of a more complex breach. Much of the testing was conducted at pressures of 200 and 380 psi, but some tests were conducted at 100 psi. Testing the largest postulated breaches was deemed impractical because of the much larger flow rates and equipment that would be required. This report presents the experimental results and analyses for the aerosol measurements obtained in the small-scale test stand. It includes a description of the simulants used and their properties, equipment and operations, data analysis methodologies, and test results. The results of tests investigating the role of slurry particles in plugging small breaches are reported in Mahoney et al. (2012). The results of the aerosol measurements in the large-scale test stand are reported in Schonewill et al. (2012) along with an analysis of the combined results from both test scales.

  10. Small-scale expression of proteins in E. coli.

    PubMed

    Zerbs, Sarah; Giuliani, Sarah; Collart, Frank

    2014-01-01

    . Despite these advantages, many targets are unsuitable for expression in E. coli, and attempts will not yield protein that can be utilized in downstream applications. A thorough understanding of the protein target, the requirements of the final application, and available tools are all essential for planning a successful expression experiment. This protocol is designed to optimize expression and solubility using an E. coli host and expression vector with an IPTG-inducible T7 promoter. The general features of the method are easily extended to other organisms and expression systems. Small-scale expression cultures are used to identify the optimum expression parameters for a given target. Thorough analysis of the total cell content and soluble fraction is used to screen out failed targets and those unlikely to succeed in large-scale purification cultures. The protocol listed here can be used in individual tubes for a small number of targets or adapted for use in 48-well plates for high throughput applications (Abdullah et al., 2009). Using the same culture for initial expression analysis and solubility analysis reduces variability between expression trials and saves the time required to produce separate cultures.

  11. Small-scale geodiversity and dirt road management, Ede (NL)

    NASA Astrophysics Data System (ADS)

    van den Ancker, Hanneke; Jungerius, Pieter Dirk

    2016-04-01

    develop into potholes; - Although in general the natural infiltration of the terrains surrounding the roads is sufficient, in some road sections water from adjacent sloping terrain brings extra water on the road; - A thin cover of leaves on the footpaths and road sections with low car traffic improves the infiltration in the road, and reduces the run-off to other the road sections to nearly zero. Leaves along the roadside also help to retard and reduce the run-off over the roads. However leaves on or along the road are not tolerated by most inhabitants, the roads need to be 'clean'. Our conclusion: Each dirt road is unique, but also within one dirt road there are important geological differences that have consequences for its maintenance. Knowledge of geodiversity of the terrain and study of small-scale erosion processes can help to improve the management of dirt roads. References Gemeente Ede, Nota Zandwegen, 2009.

  12. Small-scale expression of proteins in E. coli.

    PubMed

    Zerbs, Sarah; Giuliani, Sarah; Collart, Frank

    2014-01-01

    . Despite these advantages, many targets are unsuitable for expression in E. coli, and attempts will not yield protein that can be utilized in downstream applications. A thorough understanding of the protein target, the requirements of the final application, and available tools are all essential for planning a successful expression experiment. This protocol is designed to optimize expression and solubility using an E. coli host and expression vector with an IPTG-inducible T7 promoter. The general features of the method are easily extended to other organisms and expression systems. Small-scale expression cultures are used to identify the optimum expression parameters for a given target. Thorough analysis of the total cell content and soluble fraction is used to screen out failed targets and those unlikely to succeed in large-scale purification cultures. The protocol listed here can be used in individual tubes for a small number of targets or adapted for use in 48-well plates for high throughput applications (Abdullah et al., 2009). Using the same culture for initial expression analysis and solubility analysis reduces variability between expression trials and saves the time required to produce separate cultures. PMID:24423272

  13. Small-scale explosive seam welding. [using ribbon explosive encased in lead sheath

    NASA Technical Reports Server (NTRS)

    Bement, L. J.

    1972-01-01

    A unique small scale explosive seam welding technique is reported that has successfully joined a variety of aluminum alloys and alloy combinations in thicknesses to 0.125 inch, as well as titanium in thicknesses to 0.056 inch. The explosively welded joints are less than one-half inch in width and apparently have no long length limitation. The ribbon explosive developed in this study contains very small quantities of explosive encased in a flexible thin lead sheath. The evaluation and demonstration of this welding technique was accomplished in three phases: evaluation and optimization of ten major explosive welding variables, the development of four weld joints, and an applicational analysis which included photomicrographs, pressure integrity tests, vacuum effects, and fabrication of some potentially useful structures in aluminum and titanium.

  14. Investigation Of Small Scale Hydrodynamic Processes Using High Resolution SAR Imagery And ADCP Data

    NASA Astrophysics Data System (ADS)

    Lavrova, Olga; Serebryany, Andrey; Bocharova, Tatiana

    2013-12-01

    Results of experimental work obtained in September- October 2011 and June and September 2012 on the northeastern Black Sea shelf are presented. Transects from the coast to the shelf edge were conducted using acoustic Doppler current profiler (ADCP) in conjunction with radar imaging of the region of experiment from satellites Envisat, Radarsat-2 and TerraSAR-X and optical imaging by Envisat MERIS and Terra/Aqua MODIS. A large number of anticyclonic and cyclonic small-scale eddies are detected and their characteristics assessed. Special focus is on coastal current reversal events in association with anticyclonic eddies. Cases of short-period internal waves induced by intense anticyclonic coastal eddies detected based on the ADCP data are discussed. A heavy rainfall accompanied by massive turbid freshwater outflow into the sea made suspended matter concentration charts compiled from Envisat MERIS data highly informative on the coastal water dynamics, eddy structures in particular.

  15. Numerical simulation of small-scale thermal convection in the atmosphere

    NASA Technical Reports Server (NTRS)

    Somerville, R. C. J.

    1973-01-01

    A Boussinesq system is integrated numerically in three dimensions and time in a study of nonhydrostatic convection in the atmosphere. Simulation of cloud convection is achieved by the inclusion of parametrized effects of latent heat and small-scale turbulence. The results are compared with the cell structure observed in Rayleigh-Benard laboratory conversion experiments in air. At a Rayleigh number of 4000, the numerical model adequately simulates the experimentally observed evolution, including some prominent transients of a flow from a randomly perturbed initial conductive state into the final state of steady large-amplitude two-dimensional rolls. At Rayleigh number 9000, the model reproduces the experimentally observed unsteady equilibrium of vertically coherent oscillatory waves superimposed on rolls.

  16. A new method to measure torsion moments on small-scaled specimens.

    PubMed

    Walter, M; Kraft, O

    2011-03-01

    As a result of a continuous evolution in the field of small-scaled components, an increasing need exists for mechanical characterization of single structures and materials in micrometer dimensions. Moreover, for a detailed analysis of the deformation and failure behavior, it is often necessary to perform investigations under multiaxial loading in addition to uniaxial loading. A simple possibility to create defined multiaxial stress-strain fields is offered by a torsion experiment. In the frame of this work, a new method is presented, which allows determining torsion moments applied to wires as thin as 10 μm in monotonic as well as cyclic manner. Besides a detailed description of the measuring principle, the experimental setup and the first results will be presented. In particular, investigations on gold wires with diameters ranging from 10 to 60 μm, applying torsion moments in the nNm regime, are shown.

  17. A new method to measure torsion moments on small-scaled specimens

    SciTech Connect

    Walter, M.; Kraft, O.

    2011-03-15

    As a result of a continuous evolution in the field of small-scaled components, an increasing need exists for mechanical characterization of single structures and materials in micrometer dimensions. Moreover, for a detailed analysis of the deformation and failure behavior, it is often necessary to perform investigations under multiaxial loading in addition to uniaxial loading. A simple possibility to create defined multiaxial stress-strain fields is offered by a torsion experiment. In the frame of this work, a new method is presented, which allows determining torsion moments applied to wires as thin as 10 {mu}m in monotonic as well as cyclic manner. Besides a detailed description of the measuring principle, the experimental setup and the first results will be presented. In particular, investigations on gold wires with diameters ranging from 10 to 60 {mu}m, applying torsion moments in the nNm regime, are shown.

  18. Effects of overlapping strings in pp collisions

    DOE PAGES

    Bierlich, Christian; Gustafson, Gösta; Lönnblad, Leif; Tarasov, Andrey

    2015-03-26

    In models for hadron collisions based on string hadronization, the strings are usually treated as independent, allowing no interaction between the confined colour fields. In studies of nucleus collisions it has been suggested that strings close in space can fuse to form "colour ropes." Such ropes are expected to give more strange particles and baryons, which also has been suggested as a signal for plasma formation. Overlapping strings can also be expected in pp collisions, where usually no phase transition is expected. In particular at the high LHC energies the expected density of strings is quite high. To investigate possiblemore » effects of rope formation, we present a model in which strings are allowed to combine into higher multiplets, giving rise to increased production of baryons and strangeness, or recombine into singlet structures and vanish. Also a crude model for strings recombining into junction structures is considered, again giving rise to increased baryon production. The models are implemented in the DIPSY MC event generator, using PYTHIA8 for hadronization, and comparison to pp minimum bias data, reveals improvement in the description of identified particle spectra.« less

  19. Effects of overlapping strings in pp collisions

    SciTech Connect

    Bierlich, Christian; Gustafson, Gösta; Lönnblad, Leif; Tarasov, Andrey

    2015-03-26

    In models for hadron collisions based on string hadronization, the strings are usually treated as independent, allowing no interaction between the confined colour fields. In studies of nucleus collisions it has been suggested that strings close in space can fuse to form "colour ropes." Such ropes are expected to give more strange particles and baryons, which also has been suggested as a signal for plasma formation. Overlapping strings can also be expected in pp collisions, where usually no phase transition is expected. In particular at the high LHC energies the expected density of strings is quite high. To investigate possible effects of rope formation, we present a model in which strings are allowed to combine into higher multiplets, giving rise to increased production of baryons and strangeness, or recombine into singlet structures and vanish. Also a crude model for strings recombining into junction structures is considered, again giving rise to increased baryon production. The models are implemented in the DIPSY MC event generator, using PYTHIA8 for hadronization, and comparison to pp minimum bias data, reveals improvement in the description of identified particle spectra.

  20. On the validity of the quasi-steady-turbulence hypothesis in representing the effects of large scales on small scales in boundary layers

    NASA Astrophysics Data System (ADS)

    Agostini, Lionel; Leschziner, Michael

    2016-04-01

    The "quasi-steady hypothesis," as understood in the context of large-scale/small-scale interactions in near-wall turbulence, rests on the assumption that the small scales near the wall react within very short time scales to changes imposed on them by energetic large scales whose length scales differ by at least one order of magnitude and whose energy reaches a maximum in the middle to the outer portion of the log-law layer. A key statistical manifestation of this assumption is that scaling the small-scale motions with the large-scale wall-friction-velocity footprints renders the small-scale statistics universal. This hypothesis is examined here by reference to direct numerical simulation (DNS) data for channel flow at Reτ ≈ 4200, subjected to a large-scale/small-scale separation by the empirical mode decomposition method. Flow properties examined include the mean velocity, second moments, joint probability density functions, and skewness. It is shown that the validity of the hypothesis depends on the particular property being considered and on the range of length scales of structures included within the large-scale spectrum. The quasi-steady hypothesis is found to be well justified for the mean velocity and streamwise energy of the small scales up to y + ˜ O ( 80 ) , but only up to y + ˜ O ( 30 ) for other properties.

  1. Which String Breaks? Revisited

    NASA Astrophysics Data System (ADS)

    Frye, Christopher

    2011-03-01

    Many have seen the common introductory physics demonstration in which a heavy ball hangs from a string, with another identical string hanging freely from the ball. When the instructor pulls the bottom string slowly, the top string breaks. However, when the instructor pulls the bottom string very rapidly, the bottom string breaks. This simple experiment is used to demonstrate inertia and Newton's laws. In The Physics Teacher of November 1996, there is an article in which the authors create a model of this problem in an attempt to explain the outcomes quantitatively. However, their analysis gave strange results. Using an improved model, I will show that the results of this demonstration can be obtained using only simple calculations. This work was funded by a RAMP grant from the University of Central Florida.

  2. N = 2 string amplitudes

    SciTech Connect

    Ooguri, H.

    1995-08-01

    In physics, solvable models have played very important roles. Understanding a simple model in detail teaches us a lot about more complicated models in generic situations. Five years ago, C. Vafa and I found that the closed N = 2 string theory, that is a string theory with the N = 2 local supersymmetry on the worldsheet, is classically equivalent to the self-dual Einstein gravity in four spacetime dimensions. Thus this string theory is solvable at the classical level. More recently, we have examined the N = 2 string partition function for spacial compactifications, and computed it to all order in the string perturbation expansion. The fact that such computation is possible at all suggests that the N = 2 string theory is solvable even quantum mechanically.

  3. Analysis of handling noises on wound strings.

    PubMed

    Pakarinen, J; Penttinen, H; Bank, B

    2007-12-01

    This study analyzes the handling noises that occur when a finger is slid along a wound string. The resulting noise has a harmonic structure due to the periodic texture of the wound string. The frequency of the harmonics and the root-mean-square amplitude of the noise were found to be linearly proportional to the sliding speed. In addition, the sliding excites the longitudinal modes of the string, thus resulting in a set of static harmonics in the noise spectrum. The sliding excites different longitudinal modes depending on the sliding location. PMID:18247641

  4. Coupled currents in cosmic strings

    SciTech Connect

    Lilley, Marc; Peter, Patrick; Martin, Xavier

    2009-05-15

    We examine the structure of a cosmic string endowed with two Abelian neutral currents, associated with two global U(1) symmetries. We first resolve the microstructure and show that it depends on two state parameters, namely, the squares of the phase gradients of the current carriers. We then provide a macroscopic description for such a string and show that it depends on an additional Lorentz-invariant state parameter that relates the two currents. We find that in most of the parameter space, the two-current string is essentially equivalent to the single-current-carrying string; i.e., only one field condenses onto the defect. In the regions where two currents are present, we find that as far as stability is concerned, one can approximate the dynamics with good accuracy using an analytic model based on either a logarithmic (on the electric side, i.e., for timelike currents) or a rational (on the magnetic side, i.e., for spacelike currents) world sheet Lagrangian. We end up by generalizing to the N current case.

  5. Tilted string cosmologies

    NASA Astrophysics Data System (ADS)

    Clancy, Dominic; Feinstein, Alexander; Lidsey, James E.; Tavakol, Reza

    1999-04-01

    Global symmetries of the string effective action are employed to generate tilted, homogeneous Bianchi type VIh string cosmologies from a previously known stiff perfect fluid solution to Einstein gravity. The dilaton field is not constant on the surfaces of homogeneity. The future asymptotic state of the models is interpreted as a plane wave and is itself an exact solution to the string equations of motion to all orders in the inverse string tension. An inhomogeneous generalization of the Bianchi type III model is also found.

  6. Heterotic cosmic strings

    SciTech Connect

    Becker, Katrin; Becker, Melanie; Krause, Axel

    2006-08-15

    We show that all three conditions for the cosmological relevance of heterotic cosmic strings, the right tension, stability and a production mechanism at the end of inflation, can be met in the strongly coupled M-theory regime. Whereas cosmic strings generated from weakly coupled heterotic strings have the well-known problems posed by Witten in 1985, we show that strings arising from M5-branes wrapped around 4-cycles (divisors) of a Calabi-Yau in heterotic M-theory compactifications solve these problems in an elegant fashion.

  7. Wormholes in string theory

    SciTech Connect

    Lyons, A. ); Hawking, S.W. )

    1991-12-15

    We discuss the wormhole effective interactions in string theory, thought of as a sum over two-dimensional field theories on different world sheets. The effective interactions are calculated in the dilute wormhole approximation,'' initially by considering the Green's functions on higher-genus Riemann surfaces, and then by calculating the effect of a complete basis of wave functions on scattering amplitudes for a surface with a boundary. The sum over wormholes is equivalent to having a world sheet of trivial topology and summing over different space-time and matter-field backgrounds. To leading order these consist of the massless fluctuations, since the tachyon cancels out when a sum is done over different spin structures going through the wormhole. In this way we recover quantized general relativity as an effective theory, from a sum over field theories on higher-genus Riemann surfaces.

  8. What Is the Effect of Small-Scale Schooling on Student Achievement? ERIC Digest.

    ERIC Educational Resources Information Center

    Howley, Craig B.

    This digest reviews recent evidence of the positive effects of small-scale schooling on student achievement. Historically, larger school size has been viewed as an important educational reform producing cost-effectiveness and educational efficiency. Today, small-scale schooling is found primarily in rural areas and small towns. A 1964 study…

  9. Environmentally Sound Small-Scale Livestock Projects. Guidelines for Planning Series Number 5.

    ERIC Educational Resources Information Center

    Jacobs, Linda

    This document was developed in response to the need for simplified technical information for planning environmentally sound small-scale projects in third world countries. It is aimed specifically at those who are planning or managing small-scale livestock projects in less-developed areas of the tropics and sub-tropics. The guidelines included in…

  10. Effect of small scale motions on dynamo actions generated by the Beltrami-like flows

    NASA Astrophysics Data System (ADS)

    Xu, Mingtian

    2016-08-01

    The geodynamo and solar dynamo are driven by the turbulent flows which involve motions of various scales. Of particular interest is what role is played by the small scale motions in these dynamos. In this paper, the integral equation approach is employed to investigate the effect of the small scale motions on dynamo actions driven by multiscale Beltrami-like flows in a cylindrical vessel. The result shows that some small scale motions can trigger a transition of a dynamo from a steady to an unsteady state. Our results also show that when the poloidal components of the small and large scale flows share the same direction in the equatorial plane, the small scale flows have more positive or less detrimental effect on the onsets of the dynamo actions in comparison with the case that the poloidal components have different directions. These findings shed light on the effect of the small scale turbulence on dynamo actions.

  11. Introduction to string field theory

    SciTech Connect

    Lykken, J.; Raby, S.

    1986-01-01

    An action is proposed for an interacting closed bosonic string. Our formalism relies heavily on ideas discussed by Witten for the open bosonic string. The gauge fixed quantum action for the fully interacting open bosonic string is obtained.

  12. Rainwater harvesting for small-scale irrigation of maize in the Central Rift Valley, Ethiopia

    NASA Astrophysics Data System (ADS)

    Keesstra, Saskia; Hartog, Maaike; Muluneh, Alemayehu; Stroosnijder, Leo

    2013-04-01

    In the Central Rift Valley of Ethiopia, small scale farmers mostly rely on rainfall for crop production. The erratic nature of rainfall causes frequent crop failures and makes the region structurally dependent on food aid. Rainwater Harvesting (RWH) is a technique to collect and store runoff that could provide water for livestock, domestic use or small scale irrigation. Usually, such irrigation is promoted for high value crops, but in the light of regional food security it may become interesting to invest in irrigation of maize. In this research, two cemented RWH cisterns were investigated to determine their economic and social potential for supplemental irrigation of maize using drip irrigation. For this, data from test fields with irrigated maize and monitoring of water levels of the cisterns were used, as well as a survey under 30 farmers living close to the experimental site. The results show that catchment size and management should be in balance with the designed RWH system, to prevent too little runoff or flooding. An analysis with Cropwat 8.0 was used to investigate the possibility of irrigating maize with the observed amounts of water in the RWH cisterns. This would suffice for 0.3-0.8 ha of maize. For a RWH cistern with a drip irrigation system to be economically viable, the production on this acreage should become 3-4 ton/ha; 2.5 times higher than the current yield. But the biggest challenge would be to change the perception of respondents, who don't find it logical to spend precious water on a common crop like maize. Therefore, if the Ethiopian government considers the irrigation of maize to be important for regional food security, it is recommended to either subsidize the construction of RWH cisterns or provide credit on favourable terms.

  13. Small-scale features of temperature and salinity surface fields in the Coral Sea

    NASA Astrophysics Data System (ADS)

    Maes, Christophe; Dewitte, Boris; Sudre, Joël.; Garçon, Véronique; Varillon, David

    2013-10-01

    The small-scale features in sea surface temperature and salinity fields (SST and SSS) of the Coral Sea are examined using high horizontal spatial and short-term temporal in situ measurements. These features are extracted from thermosalinographs (TSGs) gathered onboard commercial and research vessels and at one long-term fixed station. The analyses are performed along the vessel tracks and the structures of small-scale features are extracted by high-pass spatial filtering the original TSG data. For SSS, it is shown that the features at the scale of mesoscale eddies (˜100 km) vary from about -1.1 to +0.6 psu in the Coral Sea region. Processes sustaining such range include rainfall events, stirring by mesoscale eddies, and the latitudinal displacement of the sharp front associated with the edge of the Western Pacific Warm Pool at the seasonal time scales. The TSG data have revealed the presence of a sharp front (0.4-0.6 psu) between the subtropical and equatorial waters instead of a smooth gradient in the standard SSS climatologies. Within the context of recent remotely sensed observations of salinity, this could represent an important limitation for the validation and calibration of satellite products. In addition to these spatial considerations, temporal variations at one long-term station near Vanuatu show that the coupled air-sea responses to intraseasonal tropical variability, such as the Madden-Julian Oscillation, may have a signature in both SST and SSS fields. However, this response is found to be complex and not necessarily in phase. In the Coral Sea region, our results suggest that MJO-induced variability on SST and SSS exhibit little coherency at the seasonal time scales.

  14. Small-scale magnetic islands near the heliospheric current sheet and their role in particle acceleration

    NASA Astrophysics Data System (ADS)

    Khabarova, Olga; Zank, Gary; Li, Gang; le Roux, Jakobus A.; Webb, Gary M.; Dosch, Alexander; Malandraki, Olga E.; Zharkova, Valentina V.

    2015-04-01

    Increases of ion fluxes in the keV-MeV range are sometimes observed near the heliospheric current sheet (HCS) during periods when other sources are absent. These resemble solar energetic particle (SEP) events, but the events are weaker and apparently local. Conventional explanations based on either shock acceleration of charged particles or particle acceleration due to magnetic reconnection at interplanetary current sheets are not persuasive. We suggest instead that recurrent magnetic reconnection occurs at the HCS and smaller current sheets in the solar wind (Zharkova & Khabarova, ApJ, 2012), of which a consequence is particle energization by the dynamically evolving secondary current sheets and magnetic islands (Zank et al., ApJ, 2014; Drake et al., JRL, 2006). The effectiveness of the trapping and acceleration process associated with magnetic islands depends in part on the topology of the HCS. We show that the HCS possesses ripples superimposed on the large-scale flat or wavy structure. We conjecture that the ripples can efficiently confine plasma and provide tokamak-like conditions that are favorable for the appearance of small-scale magnetic islands that merge and/or contract. Particles trapped in the vicinity of merging islands and experiencing multiple small-scale reconnection events are accelerated by the induced electric field, and experience first-order Fermi acceleration in contracting magnetic islands (Zank et al., ApJ, 2014). We present multi-spacecraft observations of magnetic island merging and particle energization in the absence of other sources, providing support for theory and simulations that show particle energization by reconnection related processes of magnetic island merging and contraction.

  15. Nonthermal dark matter from cosmic strings

    SciTech Connect

    Cui Yanou; Morrissey, David E.

    2009-04-15

    Cosmic strings can be created in the early universe during symmetry-breaking phase transitions, such as might arise if the gauge structure of the standard model is extended by additional U(1) factors at high energies. Cosmic strings presented in the early universe form a network of long horizon-length segments, as well as a population of closed string loops. The closed loops are unstable against decay, and can be a source of nonthermal particle production. In this work we compute the density of weakly-interacting massive particle dark matter formed by the decay of gauge theory cosmic string loops derived from a network of long strings in the scaling regime or under the influence of frictional forces. We find that for symmetry-breaking scales larger than 10{sup 10} GeV, this mechanism has the potential to account for the observed relic density of dark matter. For symmetry-breaking scales lower than this, the density of dark matter created by loop decays from a scaling string network lies below the observed value. In particular, the cosmic strings originating from a U(1) gauge symmetry broken near the electroweak scale, that could lead to a massive Z{sup '} gauge boson observable at the LHC, produces a negligibly small dark matter relic density by this mechanism.

  16. Covariant Closed String Coherent States

    SciTech Connect

    Hindmarsh, Mark; Skliros, Dimitri

    2011-02-25

    We give the first construction of covariant coherent closed string states, which may be identified with fundamental cosmic strings. We outline the requirements for a string state to describe a cosmic string, and provide an explicit and simple map that relates three different descriptions: classical strings, light cone gauge quantum states, and covariant vertex operators. The resulting coherent state vertex operators have a classical interpretation and are in one-to-one correspondence with arbitrary classical closed string loops.

  17. Covariant closed string coherent states.

    PubMed

    Hindmarsh, Mark; Skliros, Dimitri

    2011-02-25

    We give the first construction of covariant coherent closed string states, which may be identified with fundamental cosmic strings. We outline the requirements for a string state to describe a cosmic string, and provide an explicit and simple map that relates three different descriptions: classical strings, light cone gauge quantum states, and covariant vertex operators. The resulting coherent state vertex operators have a classical interpretation and are in one-to-one correspondence with arbitrary classical closed string loops. PMID:21405564

  18. Cosmic strings with curvature corrections

    NASA Astrophysics Data System (ADS)

    Boisseau, Bruno; Letelier, Patricio S.

    1992-08-01

    A generic model of string described by a Lagrangian density that depends on the extrinsic curvature of the string worldsheet is studied. Using a system of coordinates adapted to the string world sheet the equation of motion and the energy-momentum tensor are derived for strings evolving in curved spacetime. We find that the curvature corrections may change the relation between the string energy density and the tension. It can also introduce heat propagation along the string. We also find for the Polyakov as well as Nambu strings with a topological term that the open string end points can travel with a speed less than the velocity of light.

  19. Constraints on cosmic strings due to black holes formed from collapsed cosmic string loops

    NASA Technical Reports Server (NTRS)

    Caldwell, R. R.; Gates, Evalyn

    1993-01-01

    The cosmological features of primordial black holes formed from collapsed cosmic string loops are studied. Observational restrictions on a population of primordial black holes are used to restrict f, the fraction of cosmic string loops which collapse to form black holes, and mu, the cosmic string mass-per-unit length. Using a realistic model of cosmic strings, we find the strongest restriction on the parameters f and mu is due to the energy density in 100MeV photons radiated by the black holes. We also find that inert black hole remnants cannot serve as the dark matter. If earlier, crude estimates of f are reliable, our results severely restrict mu, and therefore limit the viability of the cosmic string large-scale structure scenario.

  20. k-strings as fundamental strings

    NASA Astrophysics Data System (ADS)

    Giataganas, Dimitrios

    2015-05-01

    It has been noticed that the k-string observables can be expressed in terms of the fundamental string ones. We identify a sufficient condition for a generic gravity dual background which when satisfied the mapping can be done. The condition is naturally related to a preserved quantity under the T-dualities acting on the Dp-brane describing the high representation Wilson loops. We also find the explicit relation between the observables of the heavy k-quark and the single quark states. As an application to our generic study and motivated by the fact that the anisotropic theories satisfy our condition, we compute the width of the k-string in these theories to find that the logarithmic broadening is still present, but the total result is affected by the anisotropy of the space.

  1. Progress in string theory

    NASA Astrophysics Data System (ADS)

    Maldacena, Juan Martín

    D-Branes on Calabi-Yau manifolds / Paul S. Aspinwall -- Lectures on AdS/CFT / Juan M. Maldacena -- Tachyon dynamics in open string theory / Ashoke Sen -- TASI/PITP/ISS lectures on moduli and microphysics / Eva Silverstein -- The duality cascade / Matthew J. Strassler -- Perturbative computations in string field theory / Washington Taylor -- Student seminars -- Student participants -- Lecturers, directors, and local organizing committee.

  2. Small-scale behavior of Hall magnetohydrodynamic turbulence.

    PubMed

    Stawarz, Julia E; Pouquet, Annick

    2015-12-01

    Decaying Hall magnetohydrodynamic (HMHD) turbulence is studied using three-dimensional (3D) direct numerical simulations with grids up to 768(3) points and two different types of initial conditions. Results are compared to analogous magnetohydrodynamic (MHD) runs and both Laplacian and Laplacian-squared dissipative operators are examined. At scales below the ion inertial length, the ratio of magnetic to kinetic energy as a function of wave number transitions to a magnetically dominated state. The transition in behavior is associated with the advection term in the momentum equation becoming subdominant to dissipation. Examination of autocorrelation functions reveals that, while current and vorticity structures are similarly sized in MHD, HMHD current structures are narrower and vorticity structures are wider. The electric field autocorrelation function is significantly narrower in HMHD than in MHD and is similar to the HMHD current autocorrelation function at small separations. HMHD current structures are found to be significantly more intense than in MHD and appear to have an enhanced association with strong alignment between the current and magnetic field, which may be important in collisionless plasmas where field-aligned currents can be unstable. When hyperdiffusivity is used, a longer region consistent with a k(-7/3) scaling is present for right-polarized fluctuations when compared to Laplacian dissipation runs.

  3. Small-scale behavior of Hall magnetohydrodynamic turbulence.

    PubMed

    Stawarz, Julia E; Pouquet, Annick

    2015-12-01

    Decaying Hall magnetohydrodynamic (HMHD) turbulence is studied using three-dimensional (3D) direct numerical simulations with grids up to 768(3) points and two different types of initial conditions. Results are compared to analogous magnetohydrodynamic (MHD) runs and both Laplacian and Laplacian-squared dissipative operators are examined. At scales below the ion inertial length, the ratio of magnetic to kinetic energy as a function of wave number transitions to a magnetically dominated state. The transition in behavior is associated with the advection term in the momentum equation becoming subdominant to dissipation. Examination of autocorrelation functions reveals that, while current and vorticity structures are similarly sized in MHD, HMHD current structures are narrower and vorticity structures are wider. The electric field autocorrelation function is significantly narrower in HMHD than in MHD and is similar to the HMHD current autocorrelation function at small separations. HMHD current structures are found to be significantly more intense than in MHD and appear to have an enhanced association with strong alignment between the current and magnetic field, which may be important in collisionless plasmas where field-aligned currents can be unstable. When hyperdiffusivity is used, a longer region consistent with a k(-7/3) scaling is present for right-polarized fluctuations when compared to Laplacian dissipation runs. PMID:26764833

  4. The formation of small scale granularities in latex particles

    NASA Technical Reports Server (NTRS)

    Zukoski, C. F.; Saville, D. A.

    1985-01-01

    A series of latices were synthesized using emulsifier-free emulsion copolymerization of styrene and sodium styrene sulfonic acid. The final latex particles display an internal granular structure which can be ascribed to the primary particles present in the early stages of particle growth. In these systems, the primary particles appear to have maintained their integrity during the swelling and growth stage.

  5. Stable Charged Cosmic Strings

    SciTech Connect

    Weigel, H.; Quandt, M.; Graham, N.

    2011-03-11

    We study the quantum stabilization of a cosmic string by a heavy fermion doublet in a reduced version of the standard model. We show that charged strings, obtained by populating fermionic bound state levels, become stable if the electroweak bosons are coupled to a fermion that is less than twice as heavy as the top quark. This result suggests that extraordinarily large fermion masses or unrealistic couplings are not required to bind a cosmic string in the standard model. Numerically we find the most favorable string profile to be a simple trough in the Higgs vacuum expectation value of radius {approx_equal}10{sup -18} m. The vacuum remains stable in our model, because neutral strings are not energetically favored.

  6. Stable charged cosmic strings.

    PubMed

    Weigel, H; Quandt, M; Graham, N

    2011-03-11

    We study the quantum stabilization of a cosmic string by a heavy fermion doublet in a reduced version of the standard model. We show that charged strings, obtained by populating fermionic bound state levels, become stable if the electroweak bosons are coupled to a fermion that is less than twice as heavy as the top quark. This result suggests that extraordinarily large fermion masses or unrealistic couplings are not required to bind a cosmic string in the standard model. Numerically we find the most favorable string profile to be a simple trough in the Higgs vacuum expectation value of radius ≈10(-18)  m. The vacuum remains stable in our model, because neutral strings are not energetically favored. PMID:21469786

  7. Small-scale hydroelectric power in the southeast: new impetus for an old energy source

    SciTech Connect

    Not Available

    1980-06-01

    The Southeastern conference, Small-Scale Hydroelectric Power: New Impetus for an Old Energy Source, was convened to provide a forum for state legislators and other interested persons to discuss the problems facing small-scale hydro developers, and to recommend appropriate solutions to resolve those problems. During the two-day meeting state legislators and their staffs, along with dam developers, utility and industry representatives, environmentalists and federal/state officials examined and discussed the problems impeding small-scale hydro development at the state level. Based upon the problem-oriented discussions, alternative policy options were recommended for consideration by the US Department of Energy, state legislatures and the staff of the National Conference of State Legislatures (NCSL). Emphasis was placed on the legal, institutional, environmental and economic barriers at the state level, as well as the federal delays associated with licensing small-scale hydro projects. Whereas other previously held conferences have emphasized the identification and technology of small-scale hydro as an alternative energy source, this conference stressed legislative resolution of the problems and delays in small-scale hydro licensing and development. Panel discussions and workshops are summarized. Papers on the environmental, economic, and legal aspects of small-scale hydropower development are presented. (LCL)

  8. Middle atmosphere measurements of small-scale electron density irregularities and ion properties during the MAC/Epsilon campaign

    NASA Technical Reports Server (NTRS)

    Blood, S. P.; Mitchell, J. D.; Croskey, C. L.

    1989-01-01

    Rocket payloads designed to measure small scale electron density irregularities and ion properties in the middle atmosphere were flown with each of the three main salvos of the MAC/Epsilon campaign conducted at the Andoya Rocket Range, Norway, during October to November 1987. Fixed bias, hemispheric nose tip probes measured small scale electron density irregularities, indicative of neutral air turbulence, during the rocket's ascent; and subsequently, parachute-borne Gerdien condensers measured the region's polar electrical conductivity, ion mobility and density. One rocket was launched during daylight (October 15, 1052:20 UT), and the other two launches occurred at night (October 21, 2134 UT: November 12, 0021:40 UT) under moderately disturbed conditions which enhanced the detection and measurement of turbulence structures. A preliminary analysis of the real time data displays indicates the presence of small scale electron density irregularities in the altitude range of 60 to 90 km. Ongoing data reduction will determine turbulence parameters and also the region's electrical properties below 90 km.

  9. Responses of seabirds, in particular prions ( Pachyptila sp.), to small-scale processes in the Antarctic Polar Front

    NASA Astrophysics Data System (ADS)

    van Franeker, Jan A.; van den Brink, Nico W.; Bathmann, Ulrich V.; Pollard, Raymond T.; de Baar, Hein J. W.; Wolff, Wim J.

    Small-scale distribution patterns of seabirds in the Antarctic Polar Front (APF) were investigated in relation to other biological, physical, and chemical features during the ANT-XIII/2 research cruise of R.V. Polarstern from December 1995 to January 1996. The APF is characterized by steep gradients in sea-surface temperature and salinity. Within the APF, gradient zones were closely associated with elevated levels of primary production, chlorophyll- a (chl- a) concentrations, and zooplankton densities. Even broad-billed prions (' Pachyptila vittata-group'), which dominated the seabird community by 83% in carbon requirements, showed small-scale distributional patterns that were positively related to primary production, chl- a, and total zooplankton densities. The findings demonstrate a close, direct link between fine-scale physical processes in the APF and biological activity through several food web levels up to that of zooplankton-eating seabirds. Broad-billed prions appeared to forage on very small copepods ( Oithona spp.) in close association with the front. Fish- and squid-eating predators showed poor correlations with small-scale spatial structures of the APF. However, in a wider band around the APF, most top predators did occur in elevated densities, showing gradual spatio-temporal diffusion of the impact of the APF on higher trophic levels.

  10. String Theory, Unification and Quantum Gravity

    NASA Astrophysics Data System (ADS)

    Stelle, K. S.

    An overview is given of the way in which the unification program of particle physics has evolved into the proposal of superstring theory as a prime candidate for unifying quantum gravity with the other forces and particles of nature. A key concern with quantum gravity has been the problem of ultraviolet divergences, which is naturally solved in string theory by replacing particles with spatially extended states as the fundamental excitations. String theory turns out, however, to contain many more extended-object states than just strings. Combining all this into an integrated picture, called M-theory, requires recognition of the rôle played by a web of nonperturbative duality symmetries suggested by the nonlinear structures of the field-theoretic supergravity limits of string theory.

  11. EMERGENCE OF THE KENNICUTT-SCHMIDT RELATION FROM THE SMALL-SCALE SFR-DENSITY RELATION

    SciTech Connect

    Gnedin, Nickolay Y.; Tasker, Elizabeth J.; Fujimoto, Yusuke

    2014-05-20

    We use simulations of isolated galaxies with a few parsec resolution to explore the connection between the small-scale star formation rate (SFR)-gas density relation and the induced large-scale correlation between the SFR surface density and the surface density of the molecular gas (the Kennicutt-Schmidt relation). We find that, in the simulations, a power-law small-scale ''star formation law'' directly translates into an identical power-law Kennicutt-Schmidt relation. If this conclusion holds in the reality as well, it implies that the observed approximately linear Kennicutt-Schmidt relation must reflect the approximately linear small-scale ''star formation law''.

  12. Small-Scale Hydroelectric Power in the Southwest: New Impetus for an old Energy Source

    NASA Astrophysics Data System (ADS)

    1980-06-01

    A forum was provided for state legislators and other interested persons to discuss the problems facing small scale hydro developers, and to recommend appropriate solutions to resolve those problems. Alternative policy options were recommended for consideration by both state and federal agencies. Emphasis was placed on the legal, institutional, environmental and economic barriers at the state level, as well as the federal delays associated with licensing small scale hydro projects. Legislative resolution of the problems and delays in small scale hydro licensing and development were also stressed.

  13. Workshop 3 (synthesis): innovative processes in small scale agricultural production using water more effectively.

    PubMed

    Bras, R; Gordon, L

    2001-01-01

    The workshop discussed the possibilities of innovative technologies to increase food production. Most of the concepts discussed are based on rainfall management, conservation and recycling. Simple technologies, adopted to local circumstances, can increase farm yields in small-scale agriculture. Small-scale rainfed agriculture is viable with intelligent utilisation of harvested rainfall. These small-scale technologies need however to be complemented with educational programs, incentives and trade to be broadly adopted and effective. The need for better documentation of results was also raised in the discussion. PMID:11379208

  14. Direct Numerical Simulations of Small-Scale Gravity Wave Instability Dynamics in Variable Stratification and Shear

    NASA Astrophysics Data System (ADS)

    Mixa, T.; Fritts, D. C.; Laughman, B.; Wang, L.; Kantha, L. H.

    2015-12-01

    Multiple observations provide compelling evidence that gravity wave dissipation events often occur in multi-scale environments having highly-structured wind and stability profiles extending from the stable boundary layer into the mesosphere and lower thermosphere. Such events tend to be highly localized and thus yield local energy and momentum deposition and efficient secondary gravity wave generation expected to have strong influences at higher altitudes [e.g., Fritts et al., 2013; Baumgarten and Fritts, 2014]. Lidars, radars, and airglow imagers typically cannot achieve the spatial resolution needed to fully quantify these small-scale instability dynamics. Hence, we employ high-resolution modeling to explore these dynamics in representative environments. Specifically, we describe numerical studies of gravity wave packets impinging on a sheet of high stratification and shear and the resulting instabilities and impacts on the gravity wave amplitude and momentum flux for various flow and gravity wave parameters. References: Baumgarten, Gerd, and David C. Fritts (2014). Quantifying Kelvin-Helmholtz instability dynamics observed in noctilucent clouds: 1. Methods and observations. Journal of Geophysical Research: Atmospheres, 119.15, 9324-9337. Fritts, D. C., Wang, L., & Werne, J. A. (2013). Gravity wave-fine structure interactions. Part I: Influences of fine structure form and orientation on flow evolution and instability. Journal of the Atmospheric Sciences, 70(12), 3710-3734.

  15. Small-scale lacustrine drifts in Lake Champlain, Vermont

    USGS Publications Warehouse

    Manley, Patricia L.; Manley, T.O.; Hayo, Kathryn; Cronin, Thomas

    2012-01-01

    High resolution CHIRP (Compressed High Intensity Radar Pulse) seismic profiles reveal the presence of two lacustrine sediment drifts located in Lake Champlain's Juniper Deep. Both drifts are positive features composed of highly laminated sediments. Drift B sits on a basement high while Drift A is built on a trough-filling acoustically-transparent sediment unit inferred to be a mass-transport event. These drifts are oriented approximately north–south and are parallel to a steep ridge along the eastern shore of the basin. Drift A, located at the bottom of a structural trough, is classified as a confined, elongate drift that transitions northward to become a system of upslope asymmetric mudwaves. Drift B is perched atop a structural high to the west of Drift A and is classified as a detached elongate drift. Bottom current depositional control was investigated using Acoustic Doppler Current Profilers (ADCPs) located across Drift A. Sediment cores were taken at the crest and at the edges of the Drift A and were dated. Drift source, deposition, and evolution show that these drifts are formed by a water column shear with the highest deposition occurring along its crest and western flank and began developing circa 8700–8800 year BP.

  16. Unified treatment of cosmological perturbations from superhorizon to small scales

    SciTech Connect

    Carbone, Carmelita; Matarrese, Sabino

    2005-02-15

    We study the evolution of cosmological perturbations, using a hybrid approximation scheme which upgrades the weak-field limit of Einstein's field equations to account for post-Newtonian scalar and vector metric perturbations and for leading-order source terms of gravitational waves, while including also the first- and second-order perturbative approximations. Our equations, which are derived in the Poisson gauge, provide a unified description of matter inhomogeneities in a Universe filled with a pressureless and irrotational fluid and a cosmological constant, ranging from the linear to the highly nonlinear regime. The derived expressions for scalar, vector and tensor modes may have a wide range of cosmological applications, including secondary CMB anisotropy and polarization effects, cosmographic relations in a inhomogeneous Universe, gravitational lensing and the stochastic gravitational-wave backgrounds generated by nonlinear cosmic structures.

  17. Experiments With Small-scale Debris Flow Breakers

    NASA Astrophysics Data System (ADS)

    Hübl, J.; Steinwendtner, H.

    In Austria debris flow breakers are a common countermeasure against debris flows since several decades. Although a lot of practical experience exists, there is a gap on general design criteria for this kind of measure. To close this gap some flume experi- ments were carried out. The model tests are designed to analyse interactions of debris flows with structures under controlled conditions. The tests were performed to inves- tigate maximal possible dynamic loads by the impact of viscous and granular debris flows as well as to optimise the design of debris flow breakers. The experimental de- sign consists of a 4,0 m long and 0,3 m wide channel with variable slope and different check dam models. Ultrasonic sensors are used for the measurement of flow velocity and flow depth. Impact forces are recorded using strain gauges. Debris flow matrix consists of Xanthan, a thickener in food technology, and loam and water, respectively. As rigid phase PVC granulars and natural debris with different grain size distribution is used. To check the different interactions the mixtures (matrix and rigid phase) are varied in sediment concentration and grain size distribution. To determine flow be- haviour and rheological parameters a conveyor channel was used. This special exper- imental design enables to study the behaviour of debris flow material with maximum grain diameter up to 20mm. The results show that the main criteria for the deposition of debris flows is the width of the opening between the panels. The structural design of the waterfront plays a minor role in the stopping process.

  18. Universality and string theory

    NASA Astrophysics Data System (ADS)

    Bachlechner, Thomas Christian

    The first run at the Large Hadron Collider has deeply challenged conventional notions of naturalness, and CMB polarization experiments are about to open a new window to early universe cosmology. As a compelling candidate for the ultraviolet completion of the standard model, string theory provides a prime opportunity to study both early universe cosmology and particle physics. However, relating low energy observations to ultraviolet physics requires knowledge of the metastable states of string theory through the study of vacua. While it is difficult to directly obtain infrared data from explicit string theory constructions, string theory imposes constraints on low energy physics. The study of ensembles of low energy theories consistent with ultra-violet constraints provides insight on generic features we might expect to occur in string compactifications. In this thesis we present a statistical treatment of vacuum stability and vacuum properties in the context of random supergravity theories motivated by string theory. Early universe cosmology provides another avenue to high energy physics. From the low energy perspective large field inflation is typically considered highly unnatural: the scale relevant for the diameter of flat regions in moduli space is sub-Planckian in regions of perturbative control. To approach this problem, we consider generic Calabi-Yau compactifications of string theory and find that super-Planckian diameters of axion fundamental domains in fact arise generically. We further demonstrate that such super-Planckian flat regions are plausibly consistent with theWeak Gravity Conjecture.

  19. Supersymmetry and String Theory

    NASA Astrophysics Data System (ADS)

    Dine, Michael

    2016-01-01

    Preface to the first edition; Preface to the second edition; A note on choice of metric; Text website; Part I. Effective Field Theory: The Standard Model, Supersymmetry, Unification: 1. Before the Standard Model; 2. The Standard Model; 3. Phenomenology of the Standard Model; 4. The Standard Model as an effective field theory; 5. Anomalies, instantons and the strong CP problem; 6. Grand unification; 7. Magnetic monopoles and solitons; 8. Technicolor: a first attempt to explain hierarchies; Part II. Supersymmetry: 9. Supersymmetry; 10. A first look at supersymmetry breaking; 11. The Minimal Supersymmetric Standard Model; 12. Supersymmetric grand unification; 13. Supersymmetric dynamics; 14. Dynamical supersymmetry breaking; 15. Theories with more than four conserved supercharges; 16. More supersymmetric dynamics; 17. An introduction to general relativity; 18. Cosmology; 19. Astroparticle physics and inflation; Part III. String Theory: 20. Introduction; 21. The bosonic string; 22. The superstring; 23. The heterotic string; 24. Effective actions in ten dimensions; 25. Compactification of string theory I. Tori and orbifolds; 26. Compactification of string theory II. Calabi–Yau compactifications; 27. Dynamics of string theory at weak coupling; 28. Beyond weak coupling: non-perturbative string theory; 29. Large and warped extra dimensions; 30. The landscape: a challenge to the naturalness principle; 31. Coda: where are we headed?; Part IV. The Appendices: Appendix A. Two-component spinors; Appendix B. Goldstone's theorem and the pi mesons; Appendix C. Some practice with the path integral in field theory; Appendix D. The beta function in supersymmetric Yang–Mills theory; References; Index.

  20. Strings without supersymmetry

    NASA Astrophysics Data System (ADS)

    Adams, Allan Wilfred

    This dissertation examines the condensation of closed string tachyons in nonsupersymmetric spacetimes. Closed string tachyons signal instabilities of the spacetime background which make perturbation theory around the chosen vacuum inconsistent. Non-perturbative techniques developed in studying supersymmetric geometries provide a powerful set of tools with which to re-examine the classic problem of closed string tachyons. Such approaches allow remarkably controlled and complete descriptions of the condensation of closed string tachyons in a broad class of non-supersymmetric theories. The text begins with a discussion of closed string tachyons in non-supersymmetric orbifolds of AdS5 x S 5, using the orbifolded dual CFT to study non-perturbative features of the tachyonic instabilities in the orbifolded spacetime. We then discuss localized closed string tachyons in orbifolds of flat space which break spacetime supersymmetry only at isolated curvature singularities. Using worldsheet and D-probe techniques to follow these systems beyond perturbation theory, we show that these localized tachyons resolve the spacetime as they condense, leading generically to smooth and asymptotically supersymmetric spacetimes. Finally, we discuss a proposal for removing these instabilities from the perturbative string which is motivated by our results on non-supersymmetric orbifolds of the AdS/CFT correspondence.

  1. Small-scale hydroelectric power in the Pacific Northwest: new impetus for an old energy source

    SciTech Connect

    Not Available

    1980-07-01

    Energy supply is one of the most important issues facing Northwestern legislators today. To meet the challenge, state legislatures must address the development of alternative energy sources. The Small-Scale Hydroelectric Power Policy Project of the National Conference of State Legislators (NCSL) was designed to assist state legislators in looking at the benefits of one alternative, small-scale hydro. Because of the need for state legislative support in the development of small-scale hydroelectric, NCSL, as part of its contract with the Department of Energy, conducted the following conference on small-scale hydro in the Pacific Northwest. The conference was designed to identify state obstacles to development and to explore options for change available to policymakers. A summary of the conference proceedings is presented.

  2. Small scale hydroelectric power potential in Nevada: a preliminary reconnaissance survey

    SciTech Connect

    Cochran, G.F.; Fordham, J.W.; Richard, K.; Loux, R.

    1981-04-01

    This preliminary reconnaissance survey is intended to: develop a first estimate as to the potential number, location and characteristics of small-scale (50 kW to 15 MW) hydroelectric sites in Nevada; provide a compilation of various Federal and state laws and regulations, including tax and financing regulations, that affect small-scale hydroelectric development and provide information on sources of small-scale hydroelectric generation hardware and consultants/ contractors who do small scale hydroelectric work. The entire survey has been conducted in the office working with various available data bases. The site survey and site evaluation methods used are described, and data are tabulated on the flow, power potential, predicted capital expenditures required, etc. for 61 potential sites with measured flows and for 77 sites with derived flows. A map showing potential site locations is included. (LCL)

  3. Nonlinear Generation of shear flows and large scale magnetic fields by small scale

    NASA Astrophysics Data System (ADS)

    Aburjania, G.

    2009-04-01

    EGU2009-233 Nonlinear Generation of shear flows and large scale magnetic fields by small scale turbulence in the ionosphere by G. Aburjania Contact: George Aburjania, g.aburjania@gmail.com,aburj@mymail.ge

  4. Dominant Wavelength of Small-Scale Folds Between Enceladus' South Polar Tiger Stripes

    NASA Astrophysics Data System (ADS)

    Preuss, L. J.; Barr, A. C.

    2010-03-01

    High-resolution images of Enceladus' south polar terrain reveal regions of small-scale folds between Damascus and Baghdad sulci. We will present the results of a systematic study of the folding wavelength using Fourier transform methods.

  5. Impact of small-scale inhomogeneities on observations of standard candles

    NASA Astrophysics Data System (ADS)

    Iwata, Kengo; Yoo, Chul-Moon

    2015-02-01

    We investigate the effect of small-scale inhomogeneities on standard candle observations, such as type-Ia supernovae (SNe) observations. The existence of the small-scale inhomogeneities may cause a tension between SNe observations and other observations with larger-diameter sources, such as the cosmic microwave background (CMB) observation. To clarify the impact of the small-scale inhomogeneities, we use the Dyer-Roeder approach. We determined the smoothness parameter α(z) as a function of the redshift z so as to compensate the deviation of cosmological parameters for SNe from those for CMB. The range of the deviation which can be compensated by the smoothness parameter α(z) satisfying 0≤α(z)≤1 is reported. Our result suggests that the tension may give us the information of the small-scale inhomogeneities through the smoothness parameter.

  6. Getting It Right: Design Principles for Starting a Small-Scale School/College Collaboration.

    ERIC Educational Resources Information Center

    Leo-Nyquist, David; Rich, Bill

    1998-01-01

    Describes a small-scale school/college partnership first from the teacher's lens and then from the teacher educator's lens. Discusses 13 critical issues that have emerged from two years of working together. (SR)

  7. Free-Hand Small-Scale Maps: Activities for Cognitive Mapping.

    ERIC Educational Resources Information Center

    Saveland, Robert N.

    1978-01-01

    Suggests that small-scale mapping activities can be used in geography courses to help students understand geographic concepts such as latitude, longitude, situation, relative location, and national boundaries. (Author/DB)

  8. Autonomous Guidance of Agile Small-scale Rotorcraft

    NASA Technical Reports Server (NTRS)

    Mettler, Bernard; Feron, Eric

    2004-01-01

    This report describes a guidance system for agile vehicles based on a hybrid closed-loop model of the vehicle dynamics. The hybrid model represents the vehicle dynamics through a combination of linear-time-invariant control modes and pre-programmed, finite-duration maneuvers. This particular hybrid structure can be realized through a control system that combines trim controllers and a maneuvering control logic. The former enable precise trajectory tracking, and the latter enables trajectories at the edge of the vehicle capabilities. The closed-loop model is much simpler than the full vehicle equations of motion, yet it can capture a broad range of dynamic behaviors. It also supports a consistent link between the physical layer and the decision-making layer. The trajectory generation was formulated as an optimization problem using mixed-integer-linear-programming. The optimization is solved in a receding horizon fashion. Several techniques to improve the computational tractability were investigate. Simulation experiments using NASA Ames 'R-50 model show that this approach fully exploits the vehicle's agility.

  9. Cosmological cosmic strings

    NASA Technical Reports Server (NTRS)

    Gregory, Ruth

    1988-01-01

    The effect of an infinite cosmic string on a cosmological background is investigated. It is found that the metric is approximately a scaled version of the empty space string metric, i.e., conical in nature. Results are used to place bounds on the amount of cylindrical gravitational radiation currently emitted by such a string. The gravitational radiation equations are then analyzed explicitly and it is shown that even initially large disturbances are rapidly damped as the expansion proceeds. The implications of the gravitational radiation background and the limitations of the quadrupole formula are discussed.

  10. Final Report: "Strings 2014"

    SciTech Connect

    Witten, Edward

    2015-10-21

    The Strings 2014 meeting was held at Princeton University June 23-27, 2014, co-sponsored by Princeton University and the Institute for Advanced Study. The goal of the meeting was to provide a stimulating and up-to-date overview of research in string theory and its relations to other areas of physics and mathematics, ranging from geometry to quantum field theory, condensed matter physics, and more. This brief report lists committee members and speakers but contains no scientific information. Note that the talks at Strings 2014 were videotaped and are available on the conference website: http://physics.princeton.edustrings2014/Talk_titles.shtml.

  11. Supermassive cosmic string compactifications

    SciTech Connect

    Blanco-Pillado, Jose J.; Reina, Borja; Sousa, Kepa; Urrestilla, Jon E-mail: borja.reina@ehu.es E-mail: jon.urrestilla@ehu.es

    2014-06-01

    The space-time dimensions transverse to a static straight cosmic string with a sufficiently large tension (supermassive cosmic strings) are compact and typically have a singularity at a finite distance form the core. In this paper, we discuss how the presence of multiple supermassive cosmic strings in the 4d Abelian-Higgs model can induce the spontaneous compactification of the transverse space and explicitly construct solutions where the gravitational background becomes regular everywhere. We discuss the embedding of this model in N = 1 supergravity and show that some of these solutions are half-BPS, in the sense that they leave unbroken half of the supersymmetries of the model.

  12. Conspecific and Heterospecific Plant Densities at Small-Scale Can Drive Plant-Pollinator Interactions

    PubMed Central

    Janovský, Zdeněk; Mikát, Michael; Hadrava, Jiří; Horčičková, Eva; Kmecová, Kateřina; Požárová, Doubravka; Smyčka, Jan; Herben, Tomáš

    2013-01-01

    Generalist pollinators are important in many habitats, but little research has been done on small-scale spatial variation in interactions between them and the plants that they visit. Here, using a spatially explicit approach, we examined whether multiple species of flowering plants occurring within a single meadow showed spatial structure in their generalist pollinator assemblages. We report the results for eight plant species for which at least 200 individual visits were recorded. We found that for all of these species, the proportions of their general pollinator assemblages accounted for by particular functional groups showed spatial heterogeneity at the scale of tens of metres. This heterogeneity was connected either with no or only subtle changes of vegetation and flowering species composition. In five of these species, differences in conspecific plant density influenced the pollinator communities (with greater dominance of main pollinators at low-conspecific plant densities). The density of heterospecific plant individuals influenced the pollinator spectrum in one case. Our results indicate that the picture of plant-pollinator interactions provided by averaging data within large plots may be misleading and that within-site spatial heterogeneity should be accounted for in terms of sampling effort allocation and analysis. Moreover, spatially structured plant-pollinator interactions may have important ecological and evolutionary consequences, especially for plant population biology. PMID:24204818

  13. Flux Ropes and Small-Scale Interplanetary Transients - New Revelations from STEREO/SECCHI

    NASA Astrophysics Data System (ADS)

    Howard, T. A.; DeForest, C. E.; Reinard, A. A.; Tappin, S. J.

    2011-12-01

    We present scientific results using a new processing pipeline from the SECCHI instrument suite on STEREO-A. This pipeline reduces stellar and F coronal noise to an unprecedented level to where very small and faint solar wind transients can be observed and tracked. This allows the accomplishment of new revelations about small-scale transients and about the anatomy of coronal mass ejections (CMEs) en-route through the inner heliosphere. Our results are from the time period corresponding to the lowest part of the deep minimum of Solar Cycle 23-24 (December 2009 - January 2009) and find a dynamic solar wind even when at its quietest. We identify solar wind puffs and blobs, likely disconnection events, and a number of CMEs, and we track them through the SECCHI suite to distances out to and beyond 1 AU. We are therefore able to unambiguously identify each of their signatures upon their arrival at in-situ spacecraft. For the CMEs we track magnetic flux ropes (called magnetic clouds) back to their coronagraph origins and identify them as the cavity component of the so-called classic three-part CME structure. Finally we track the evolution of the structure of the flux ropes through the heliosphere, and find significant distortion.

  14. Small-scale behavior in distorted turbulent boundary layers at low Reynolds number

    NASA Technical Reports Server (NTRS)

    Saddoughi, Seyed G.

    1994-01-01

    During the last three years we have conducted high- and low-Reynolds-number experiments, including hot-wire measurements of the velocity fluctuations, in the test-section-ceiling boundary layer of the 80- by 120-foot Full-Scale Aerodynamics Facility at NASA Ames Research Center, to test the local-isotropy predictions of Kolmogorov's universal equilibrium theory. This hypothesis, which states that at sufficiently high Reynolds numbers the small-scale structures of turbulent motions are independent of large-scale structures and mean deformations, has been used in theoretical studies of turbulence and computational methods such as large-eddy simulation; however, its range of validity in shear flows has been a subject of controversy. The present experiments were planned to enhance our understanding of the local-isotropy hypothesis. Our experiments were divided into two sets. First, measurements were taken at different Reynolds numbers in a plane boundary layer, which is a 'simple' shear flow. Second, experiments were designed to address this question: will our criteria for the existence of local isotropy hold for 'complex' nonequilibrium flows in which extra rates of mean strain are added to the basic mean shear?

  15. Small-scale genetic connectivity of bicolor damselfish ( Stegastes partitus) recruits in Mexican Caribbean reefs

    NASA Astrophysics Data System (ADS)

    Villegas-Sánchez, C. A.; Rivera-Madrid, R.; Arias-González, J. E.

    2010-12-01

    The analysis of genetic similarities among marine populations is a key method for use in connectivity studies intended to provide information for management strategies. The present study aimed at assessing the connectivity levels of subpopulations of bicolor damselfish ( Stegastes partitus) recruits at a small scale (~200 km) among four reefs in the Mexican Caribbean. Samples were collected from 13 sites nested in two Marine Parks (Cozumel and Xcalak), one Biosphere Reserve (Chinchorro Bank) and one unprotected area (Mahahual). A total of 713 samples were genetically characterized by means of seven microsatellite DNA markers and were analyzed on a hierarchical basis. A strong genetic structure was detected among sites with a weak but significant genetic structure among reefs, the combination of which has not been reported in previous studies. These results appear to be related to a “sweepstake-chance effect” combined with oceanographic factors. An isolation by distance test, in addition to a hierarchical Bayesian method, revealed that neither distance among sites and reefs nor any of 10 environmental factors tested could be used to explain the genetic differences observed. The results suggest that conservation strategies for S. partitus based on local scales are likely to be effective.

  16. Small scale rotational disorder observed in epitaxial graphene on SiC(0001)

    NASA Astrophysics Data System (ADS)

    Walter, Andrew L.; Bostwick, Aaron; Speck, Florian; Ostler, Markus; Kim, Keun Su; Chang, Young Jun; Moreschini, Luca; Innocenti, Davide; Seyller, Thomas; Horn, Karsten; Rotenberg, Eli

    2013-02-01

    Interest in the use of graphene in electronic devices has motivated an explosion in the study of this remarkable material. The simple, linear, Dirac cone band structure offers a unique possibility to investigate its finer details by angle-resolved photoelectron spectroscopy (ARPES). Indeed, ARPES has been performed on graphene grown on metal substrates but electronic applications require an insulating substrate. Epitaxial graphene grown by the thermal decomposition of silicon carbide (SiC) is an ideal candidate for this due to the large scale, uniform, graphene layers produced. The experimental spectral function of epitaxial graphene on SiC has been extensively studied. However, until now the cause of an anisotropy in the spectral width of the Fermi surface has not been determined. In the current work we show, by comparison of the spectral function to a semi-empirical model, that the anisotropy is due to small scale rotational disorder (˜± 0.15°) of graphene domains in graphene grown on SiC(0001) samples. The complicated shape described by the line-width is accurately reproduced by the semi-empirical model only when rotational disorder is included. While spectra from rare regions of the sample containing only one or two rotational domains is also presented. In addition to the direct benefit in the understanding of graphene's electronic structure this work suggests a mechanism to explain similar variations in related ARPES data.

  17. Small-scale behavior in distorted turbulent boundary layers at low Reynolds number

    NASA Astrophysics Data System (ADS)

    Saddoughi, Seyed G.

    1994-12-01

    During the last three years we have conducted high- and low-Reynolds-number experiments, including hot-wire measurements of the velocity fluctuations, in the test-section-ceiling boundary layer of the 80- by 120-foot Full-Scale Aerodynamics Facility at NASA Ames Research Center, to test the local-isotropy predictions of Kolmogorov's universal equilibrium theory. This hypothesis, which states that at sufficiently high Reynolds numbers the small-scale structures of turbulent motions are independent of large-scale structures and mean deformations, has been used in theoretical studies of turbulence and computational methods such as large-eddy simulation; however, its range of validity in shear flows has been a subject of controversy. The present experiments were planned to enhance our understanding of the local-isotropy hypothesis. Our experiments were divided into two sets. First, measurements were taken at different Reynolds numbers in a plane boundary layer, which is a 'simple' shear flow. Second, experiments were designed to address this question: will our criteria for the existence of local isotropy hold for 'complex' nonequilibrium flows in which extra rates of mean strain are added to the basic mean shear?

  18. Improved energy output levels from small-scale Microbial Fuel Cells.

    PubMed

    Ieropoulos, I; Greenman, J; Melhuish, C

    2010-04-01

    This study reports on the findings from the investigation into small-scale (6.25 mL) MFCs, connected together as a network of multiple units. The MFCs contained unmodified (no catalyst) carbon fibre electrodes and for initial and later experiments, a standard ion-exchange membrane for the proton transfer from the anode to the cathode. The anode microbial culture was of the type commonly found in domestic wastewater fed with 5 mM acetate as the carbon-energy (C/E) source. The cultures were mature and acclimatised in the MFC environment for approximately 2 months before being re-inoculated in the experimental MFC units. The cathode was of the O(2) diffusion open-to-air type, but for the purposes of the polarization experiments, the cathodic electrodes were moistened with ferricyanide. The main aim of this study was to investigate the effects of connecting multiples of MFC units together as a method of scale up by using stacks and comparison of the effects of different PEM and MFC structural materials on the performance. Impedance matching (maximum-power-transfer) was achieved through calculation of total internal impedance. Three different PEM materials were compared in otherwise identical MFCs in sets of three. For individual isolated MFCs, Hyflon E87-03 was shown to produce twice, whilst E87-10 produced approximately 1.5 times the power output of the control (standard) PEM. However, when MFCs containing the E87-03 and E87-10 membranes were connected in a stack, the system suffered from severe instability and cell reversal. To study the effects of the various polymeric MFC structural materials, four small-scale units were manufactured from three different types of RP material; acrylo-butadiene-styrene coated (ABS), ABS coated (ABS-MEK) and polycarbonate (polyC). The stack of four (4) units prototyped out of polyC produced the highest power density values in polarisation experiments (80 mW/m(2)).

  19. Small scale variability of snow properties on Antarctic sea ice

    NASA Astrophysics Data System (ADS)

    Wever, Nander; Leonard, Katherine; Paul, Stephan; Jacobi, Hans-Werner; Proksch, Martin; Lehning, Michael

    2016-04-01

    Snow on sea ice plays an important role in air-ice-sea interactions, as snow accumulation may for example increase the albedo. Snow is also able to smooth the ice surface, thereby reducing the surface roughness, while at the same time it may generate new roughness elements by interactions with the wind. Snow density is a key property in many processes, for example by influencing the thermal conductivity of the snow layer, radiative transfer inside the snow as well as the effects of aerodynamic forcing on the snowpack. By comparing snow density and grain size from snow pits and snow micro penetrometer (SMP) measurements, highly resolved density and grain size profiles were acquired during two subsequent cruises of the RV Polarstern in the Weddell Sea, Antarctica, between June and October 2013. During the first cruise, SMP measurements were done along two approximately 40 m transects with a horizontal resolution of approximately 30 cm. During the second cruise, one transect was made with approximately 7.5 m resolution over a distance of 500 m. Average snow densities are about 300 kg/m3, but the analysis also reveals a high spatial variability in snow density on sea ice in both horizontal and vertical direction, ranging from roughly 180 to 360 kg/m3. This variability is expressed by coherent snow structures over several meters. On the first cruise, the measurements were accompanied by terrestrial laser scanning (TLS) on an area of 50x50 m2. The comparison with the TLS data indicates that the spatial variability is exhibiting similar spatial patterns as deviations in surface topology. This suggests a strong influence from surface processes, for example wind, on the temporal development of density or grain size profiles. The fundamental relationship between variations in snow properties, surface roughness and changes therein as investigated in this study is interpreted with respect to large-scale ice movement and the mass balance.

  20. Small scale shear zone in calcite: AMS and microstructure

    NASA Astrophysics Data System (ADS)

    Roxerová, Zuzana; Machek, Matěj; Kusbach, Vladimír; Racek, Martin; Silva, Pedro F.

    2016-04-01

    Two structural profiles across thin shear zone in calcite from quarry in Estremoz (Portugal) were studied to find a relationship between AMS and strain in natural rocks. The mesoscopic fabric is characterized by the change from the subhorizontal coarse-grained foliation towards the ~2cm-wide shear zone center with subvertical fine-grained foliation. In microstructure, the shear zone records dynamic recrystallization of calcite aggregate which resulted in development of porphyroclastic microstructure with increasing proportion of fine-grained recrystallized matrix towards the shear zone center. Two distinct crystallographic preferred orientations of calcite were recorded. One related with porphyroclasts, characterized by subvertical orientation of calcite axes and another associated with recrystallized matrix showing subhorizontal calcite axes orientation. The magnetic susceptibility ranges from -8e-6SI to 9e-6SI, with the average -4e-6SI. The majority of the rock mass is diamagnetic, corresponding well with the thermomagnetic curves, with local paramagnetic accumulations in form of thin bands. The AMS of the both profiles exhibits stable subvertical foliation bearing vertical lineation which is locally alternated by the medium-angle foliation. We interpret the AMS fabric pattern which is perpendicular to the mineral one as a type of inverse AMS fabric, due to high iron content in major part of calcite grains The magnetic and microstructural description of the shear zone is accompanied by numerical modeling of AMS based on CPO and different proportion of porphyroclasts, matrix and mica for purposes of deciphering the influence of present microstructural features on AMS.

  1. Failed eruptions of two intertwining small-scale filaments

    NASA Astrophysics Data System (ADS)

    Xue, Zhike; Yan, Xiaoli; Zhao, Li; Xiang, Yongyuan; Yang, Liheng; Guo, Yang

    2016-02-01

    Using multi-wavelength observations of the New Vacuum Solar Telescope (NVST), the Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO), we study the topology and evolutions of two filaments observed in NOAA active region (AR) 12031 on 2014 April 7. Before their eruptions, the two filaments (F1 and F2) were sinistral filaments, and the left part of F1 (LP) was located above F2, the right part of F1 (RP) under F2. They show an overall intertwining structure. LP erupted first and rotated clockwise. The total rotation angle was about 470° (≈2.61π). With its rotation, most of the plasma fell back, and thus it was a failed eruption. Meanwhile, when LP erupted to a higher altitude, the overlying magnetic loops were partially pushed from the northeast to the southwest with projected speeds from 36 to 105 km s-1. Next, F2 began to erupt and, when reaching a certain height, the plasma of F2 started to fall down to their footpoints. Using the potential-field source-surface (PFSS) model, the decay indexes at five positions along the polarity inversion line of AR 12031 were calculated to be from 1.03 to 1.25 with an average value of 1.20 that was lower than the critical value for torus instability. These results imply that the kink instability was the main triggering mechanism for the eruption of F1, and the eruption of F2 was due to the decreasing of overlying magnetic loops caused by the eruption of F1. The eruptions of two filaments were confined by the large-scale overlying magnetic loops.

  2. The Use of Small Scale Aerial Photography in a Regional Agricultural Survey

    NASA Technical Reports Server (NTRS)

    Draeger, W. C.

    1971-01-01

    The feasibility of performing inventories of agricultural resources using very small scale aerial or space photography has been investigated. Results to date are encouraging on two counts: (1) the questions posed initially are being answered, and (2) it would seem that a fully operational agricultural inventory using very small scale photography is not beyond the scope of present technology. The biggest problems to be faced in establishing a functional inventory system are those concerning logistics and data handling.

  3. Health and Safety Management for Small-scale Methane Fermentation Facilities

    NASA Astrophysics Data System (ADS)

    Yamaoka, Masaru; Yuyama, Yoshito; Nakamura, Masato; Oritate, Fumiko

    In this study, we considered health and safety management for small-scale methane fermentation facilities that treat 2-5 ton of biomass daily based on several years operation experience with an approximate capacity of 5 t·d-1. We also took account of existing knowledge, related laws and regulations. There are no qualifications or licenses required for management and operation of small-scale methane fermentation facilities, even though rural sewerage facilities with a relative similar function are required to obtain a legitimate license. Therefore, there are wide variations in health and safety consciousness of the operators of small-scale methane fermentation facilities. The industrial safety and health laws are not applied to the operation of small-scale methane fermentation facilities. However, in order to safely operate a small-scale methane fermentation facility, the occupational safety and health management system that the law recommends should be applied. The aims of this paper are to clarify the risk factors in small-scale methane fermentation facilities and encourage planning, design and operation of facilities based on health and safety management.

  4. Ethnographic Approaches to Understanding Social Sustainability in Small-scale Water Systems

    NASA Astrophysics Data System (ADS)

    Wutich, A.

    2011-12-01

    Social sustainability is an important, but often neglected, aspect of determining the success of small-scale water systems. This paper reviews ethnographic approaches for understanding how indigenous knowledge enhances social sustainability of small-scale water systems, particularly in small-scale water systems threatened by water scarcity. After reviewing the literature on common-pool and traditional resource management strategies, the paper will focus on the case of a community-managed small-scale water system in Cochabamba, Bolivia. This study uses ethnographic evidence to demonstrate how indigenous institutions can be used to manage a small-scale urban water system sustainably. Several factors were crucial to the institution's success. First, indigenous residents had previous experience with common management of rural irrigation systems which they were able to adapt for use in an urban environment. Second, institutional rules were designed to prioritize the conservation of the water source. Third, indigenous Andean social values of uniformity, regularity, and transparency ensured that community members perceived the system as legitimate and complied with community rules. Fourth, self-governance enabled community members to quickly adapt to changing environmental conditions, such as seasonal scarcity and groundwater overdraft. The paper concludes with a discussion of the promise and limitations of ethnographic approaches and indigenous knowledge for understanding social sustainability in small-scale water systems.

  5. Conformational changes of a single magnetic particle string within gels.

    PubMed

    An, Hai-Ning; Groenewold, Jan; Picken, S J; Mendes, Eduardo

    2014-02-21

    Magnetorheological (MR) gels consist of micron sized magnetic particles inside a gel matrix. Before physical cross-linking, the suspension is subjected to a small magnetic field which creates a particle string structure. After cross-linking, the string is kept within the gel at room temperature. Under an external homogeneous magnetic field and mechanical deformation, the soft swollen gel matrix allows the string to largely rearrange at microscopic scales. With the help of two homemade magneto cells mounted on an optical microscope, we were able to follow the conformational change and instabilities of a single magnetic particle string under the combined influence of shear (or stretch) and the magnetic field. In the absence of mechanical deformation, an external magnetic field, applied in the perpendicular direction to the string, breaks it into small pieces generating periodic structures like sawteeth. When an external magnetic field is applied parallel to the pre-aligned string, it exhibits a length contraction. However, under shear strain perpendicular to the original pre-structured string (and magnetic field), the string breaks and short string segments tilt, making an angle with the original direction that is smaller than that of the applied shear (non-affine). The difference in tilt angle scales with the inverse length of the small segments L-1 and the magnetic flux density B, reflecting the ability of the gel matrix to expel solvents under local stress.

  6. Stability of Liquid Films on Strings

    NASA Astrophysics Data System (ADS)

    Nair, Vineet; Sharma, Ishan; Shankar, Viswanathan

    2015-11-01

    The dynamics and stability of liquid films on rigid substrates is a well studied problem with recent studies extending the analysis to flexible substrates. Here, we study the stability of a liquid film on a string. The string is a one-dimensional continuum and we consider it to be linear elastic, isotropic, homogeneous, and flexible. It is assumed that the slope made by the string is small and that the motion is planar and the displacements are in transverse direction. The liquid film is a two-dimensional continuum and we consider it to be a Newtonian fluid with uniform density, viscosity, and surface tension. We consider the cases where the string has an initial horizontal configuration and inclined configuration, including both the finite and infinite cases. We use the lubrication approximation to simplify the governing equations and boundary conditions. The fluid-solid coupling results in a set of two coupled nonlinear partial differential equations in film thickness and string displacement. Subsequently, a linear stability analysis will be carried out and the equations will be solved numerically. The ultimate objective of this study is to understand the behavior of liquid film flow over translating structures such as strings and beams that may or may not be of finite extent.

  7. Strings at finite temperature

    SciTech Connect

    Arago C. de; Bazeia, D.; Eboli, O.J.P.; Marques, G.C.

    1985-12-15

    We obtain a semiclassical evaluation of the temperature for which the free energy of the strings of spontaneously broken scalar electrodynamics vanishes. We argue that, above this temperature, these objects should play a significant physical role.

  8. Universality in string interactions

    NASA Astrophysics Data System (ADS)

    Huang, Yu-tin; Schlotterer, Oliver; Wen, Congkao

    2016-09-01

    In this note, we provide evidence for universality in the low-energy expansion of tree-level string interactions. More precisely, in the α'-expansion of tree-level scattering amplitudes, we conjecture that the leading transcendental coefficient at each order in α' is universal for all perturbative string theories. We have checked this universality up to seven points and trace its origin to the ability to restructure the disk integrals of open bosonic string into those of the superstring. The accompanying kinematic functions have the same low-energy limit and do not introduce any transcendental numbers in their α'-corrections. Universality in the closed-string sector then follows from KLT-relations.

  9. Subsurface drill string

    DOEpatents

    Casper, William L.; Clark, Don T.; Grover, Blair K.; Mathewson, Rodney O.; Seymour, Craig A.

    2008-10-07

    A drill string comprises a first drill string member having a male end; and a second drill string member having a female end configured to be joined to the male end of the first drill string member, the male end having a threaded portion including generally square threads, the male end having a non-threaded extension portion coaxial with the threaded portion, and the male end further having a bearing surface, the female end having a female threaded portion having corresponding female threads, the female end having a non-threaded extension portion coaxial with the female threaded portion, and the female end having a bearing surface. Installation methods, including methods of installing instrumented probes are also provided.

  10. Instantons in string theory

    SciTech Connect

    Ahlén, Olof

    2015-12-17

    These proceedings from the second Caesar Lattes meeting in Rio de Janeiro 2015 are a brief introduction to how automorphic forms appear in the low energy effective action of maximally supersymmetric string theory. The explicit example of the R{sup 4}-interaction of type IIB string theory in ten dimensions is discussed. Its Fourier expansion is interpreted in terms of perturbative and non-perturbative contributions to the four graviton amplitude.

  11. Injury Profiles Associated with Artisanal and Small-Scale Gold Mining in Tarkwa, Ghana.

    PubMed

    Calys-Tagoe, Benedict N L; Ovadje, Lauretta; Clarke, Edith; Basu, Niladri; Robins, Thomas

    2015-07-10

    Artisanal and small-scale gold mining (ASGM) is inherently risky, but little is known about mining-associated hazards and injuries despite the tremendous growth worldwide of ASGM and the benefits it offers. The current study aimed to characterize the physical injuries associated with ASGM in Ghana to guide policy formulation. A cross-sectional survey was carried out in the Tarkwa mining district of the Western Region of Ghana in 2014. A total of 404 small-scale miners were recruited and interviewed regarding their occupational injury experiences over the preceding 10 years using a paper-based structured questionnaire. Nearly one-quarter (23.5%) of the miners interviewed reported getting injured over the previous 10 years, and the overall injury rate was calculated to be 5.39 per 100 person years. The rate was significantly higher for women (11.93 per 100 person years) and those with little mining experience (e.g., 25.31 per 100 person years for those with less than one year of work experience). The most injury-prone mining activities were excavation (58.7%) and crushing (23.1%), and over 70% of the injuries were reported to be due to miners being hit by an object. The majority of the injuries (57%) were lacerations, and nearly 70% of the injuries were to the upper or lower limbs. Approximately one-third (34.7%) of the injuries resulted in miners missing more than two weeks of work. One-quarter of the injured workers believed that abnormal work pressure played a role in their injuries, and nearly two-fifths believed that their injuries could have been prevented, with many citing personal protective equipment as a solution. About one-quarter of the employees reported that their employers never seemed to be interested in the welfare or safety of their employees. These findings greatly advance our understanding of occupational hazards and injuries amongst ASGM workers and help identify several intervention points.

  12. Injury Profiles Associated with Artisanal and Small-Scale Gold Mining in Tarkwa, Ghana

    PubMed Central

    Calys-Tagoe, Benedict N. L.; Ovadje, Lauretta; Clarke, Edith; Basu, Niladri; Robins, Thomas

    2015-01-01

    Artisanal and small-scale gold mining (ASGM) is inherently risky, but little is known about mining-associated hazards and injuries despite the tremendous growth worldwide of ASGM and the benefits it offers. The current study aimed to characterize the physical injuries associated with ASGM in Ghana to guide policy formulation. A cross-sectional survey was carried out in the Tarkwa mining district of the Western Region of Ghana in 2014. A total of 404 small-scale miners were recruited and interviewed regarding their occupational injury experiences over the preceding 10 years using a paper-based structured questionnaire. Nearly one-quarter (23.5%) of the miners interviewed reported getting injured over the previous 10 years, and the overall injury rate was calculated to be 5.39 per 100 person years. The rate was significantly higher for women (11.93 per 100 person years) and those with little mining experience (e.g., 25.31 per 100 person years for those with less than one year of work experience). The most injury-prone mining activities were excavation (58.7%) and crushing (23.1%), and over 70% of the injuries were reported to be due to miners being hit by an object. The majority of the injuries (57%) were lacerations, and nearly 70% of the injuries were to the upper or lower limbs. Approximately one-third (34.7%) of the injuries resulted in miners missing more than two weeks of work. One-quarter of the injured workers believed that abnormal work pressure played a role in their injuries, and nearly two-fifths believed that their injuries could have been prevented, with many citing personal protective equipment as a solution. About one-quarter of the employees reported that their employers never seemed to be interested in the welfare or safety of their employees. These findings greatly advance our understanding of occupational hazards and injuries amongst ASGM workers and help identify several intervention points. PMID:26184264

  13. Simulation of Erosion and Runoff on Forest Roads Using a Small Scale Rainfall Simulator

    NASA Astrophysics Data System (ADS)

    Zemke, Julian

    2014-05-01

    The study examines the influence of unpaved forest roads and skid trails on sediment delivery and runoff generation in a forested catchment area. A small scale rainfall simulator with a plot size of 0,64 m2 was used to measure sediment- and runoff-delivery for rainfall events with an intensity of 45 mm h-1, a kinetic energy of 4,60 J m-2 mm-1 and a duration of 90 min. Both sediment yield and runoff were collected with a temporal resolution of one minute. Therefore, it was possible to generate precise datasets of erodibility and hydrological characteristics of the surfaces over a rainfall event. The results show that even semi-persistent skid trails tend to a much earlier generation of runoff than nearby undisturbed forest topsoils. This effect is even more distinct on unpaved road surfaces. The relative sum of infiltrated rainfall underlines these results, while forest topsoils infiltrate rainfall up to 99,1%, skid trails only infiltrate Ø 53,6% and unpaved roads Ø 16,2%. The sediment delivery shows, that in contrast to the divergent hydrological characteristics, skid trails have an erodibility more comparable to undisturbed topsoils than to unpaved roads. While skid trails yielded Ø 10,8 g in 90 min, undisturbed topsoils produced a total of Ø 1,3 g. Unpaved roads on the other hand yielded Ø 181,3 g. Latter equates to a sediment delivery of 188,9 g m-2 min-1 with simultaneously higher sediment concentrations in the overland flow of about 6,4 g l-1 or 9,9 g mm-1 respectively. These findings lead to the conclusion, that compacted surfaces of forest roads not only affect the hydrological response of small scale catchments, but also generate an increase of sediment delivery and soil erosion. Besides the direct consequences of structural damage to the road surface, serious ecological off-site damage can derive from the yielded sediment when it reaches adjacent stream systems.

  14. Instabilities of twisted strings

    NASA Astrophysics Data System (ADS)

    Forgács, Péter; Lukács, Árpád

    2009-12-01

    A linear stability analysis of twisted flux-tubes (strings) in an SU(2) semilocal theory — an Abelian-Higgs model with two charged scalar fields with a global SU(2) symmetry — is carried out. Here the twist refers to a relative phase between the two complex scalars (with linear dependence on, say, the z coordinate), and importantly it leads to a global current flowing along the the string. Such twisted strings bifurcate with the Abrikosov-Nielsen-Olesen (ANO) solution embedded in the semilocal theory. Our numerical investigations of the small fluctuation spectrum confirm previous results that twisted strings exhibit instabilities whose amplitudes grow exponentially in time. More precisely twisted strings with a single magnetic flux quantum admit a continuous family of unstable eigenmodes with harmonic z dependence, indexed by a wavenumber kin[-km, km]. Carrying out a perturbative semi-analytic analysis of the bifurcation, it is found that the purely numerical results are very well reproduced. This way one obtains not only a good qualitative description of the twisted solutions themselves as well as of their instabilities, but also a quantitative description of the numerical results. Our semi-analytic results indicate that in close analogy to the known instability of the embedded ANO vortex a twisted string is also likely to expand in size caused by the spreading out of its magnetic flux.

  15. Twisted superconducting semilocal strings

    NASA Astrophysics Data System (ADS)

    Forgács, Péter; Reuillon, Sébastien; Volkov, Mikhail S.

    2006-09-01

    A new class of twisted, current carrying, stationary, straight string solutions having finite energy per unit length is constructed numerically in an extended Abelian Higgs model with global SU(2) symmetry. The new solutions correspond to deformations of the embedded Abrikosov Nielsen Olesen (ANO) vortices by a twist—a relative coordinate dependent phase between the two Higgs fields. The twist induces a global current flowing through the string, and the deformed solutions bifurcate with the ANO vortices in the limit of vanishing current. For each value of the winding number n=1,2,… (determining the magnetic flux through the plane orthogonal to the string) there are n distinct, two-parametric families of solutions. One of the continuously varying parameters is the twist, or the corresponding current, the other one can be chosen to be the momentum of the string. For fixed values of the momentum and twist, the n distinct solutions have different energies and can be viewed as a lowest energy “fundamental” string and its n-1 “excitations” characterized by different values of their “polarization”. The latter is defined as the ratio of the angular momentum of the vortex and its momentum. In their rest frame the twisted vortices have lower energy than the embedded ANO vortices and could be of considerable importance in various physical systems (from condensed matter to cosmic strings).

  16. Hydroball string sensing system

    DOEpatents

    Hurwitz, Michael J.; Ekeroth, Douglas E.; Squarer, David

    1991-01-01

    A hydroball string sensing system for a nuclear reactor that includes stainless tubes positioned to guide hydroball strings into and out of the nuclear reactor core. A sensor such as an ultrasonic transducer transmitter and receiver is positioned outside of the nuclear reactor core and adjacent to the tube. The presence of an object such a bullet member positioned at an end a hydroball string, or any one of the hydroballs interrupts the transmission of ultrasound from the transmitter to the receiver. Alternatively, if the bullet member and hydroballs include a ferritic material, either a Hall effect sensor or other magnetic field sensors such as a magnetic field rate of change sensor can be used to detect the location and position of a hydroball string. Placing two sensors along the tube with a known distance between the sensors enables the velocity of a hydroball string to be determined. This determined velocity can be used to control the flow rate of a fluid within the tube so as to control the velocity of the hydroball string.

  17. Cosmic D- and DF-strings from D3D3: Black strings and BPS limit

    SciTech Connect

    Kim, Taekyung; Kim, Yoonbai; Kyae, Bumseok; Lee, Jungjai

    2008-03-15

    We study D- and DF-strings in a D3D3 system by using Dirac-Born-Infeld type action. In the presence of an electric flux from the transverse direction, we discuss gravitating thick D-string solutions of a spatial manifold, S{sup 2}xR{sup 1}, in which straight D-strings stretched along the R{sup 1} direction are attached to the south and north poles of the two-sphere. There is a horizon along its equator, which means the structure of black strings is formed. We also discuss the BPS limit for thin parallel D- and DF-strings in both flat and curved spacetime. We obtain the BPS sum rule for an arbitrarily-separated multistring configuration with a Gaussian type tachyon potential. At the site of each thin BPS D(F)-string, the pressure takes a finite value. We find that there exists a maximum deficit angle {pi} in the conical geometry induced by thin BPS D- and DF-strings.

  18. Distinct soil bacterial communities along a small-scale elevational gradient in alpine tundra

    PubMed Central

    Shen, Congcong; Ni, Yingying; Liang, Wenju; Wang, Jianjun; Chu, Haiyan

    2015-01-01

    The elevational diversity pattern for microorganisms has received great attention recently but is still understudied, and phylogenetic relatedness is rarely studied for microbial elevational distributions. Using a bar-coded pyrosequencing technique, we examined the biodiversity patterns for soil bacterial communities of tundra ecosystem along 2000–2500 m elevations on Changbai Mountain in China. Bacterial taxonomic richness displayed a linear decreasing trend with increasing elevation. Phylogenetic diversity and mean nearest taxon distance (MNTD) exhibited a unimodal pattern with elevation. Bacterial communities were more phylogenetically clustered than expected by chance at all elevations based on the standardized effect size of MNTD metric. The bacterial communities differed dramatically among elevations, and the community composition was significantly correlated with soil total carbon (TC), total nitrogen, C:N ratio, and dissolved organic carbon. Multiple ordinary least squares regression analysis showed that the observed biodiversity patterns strongly correlated with soil TC and C:N ratio. Taken together, this is the first time that a significant bacterial diversity pattern has been observed across a small-scale elevational gradient. Our results indicated that soil carbon and nitrogen contents were the critical environmental factors affecting bacterial elevational distribution in Changbai Mountain tundra. This suggested that ecological niche-based environmental filtering processes related to soil carbon and nitrogen contents could play a dominant role in structuring bacterial communities along the elevational gradient. PMID:26217308

  19. Irreversible Wash Aid Additive for Cesium Mitigation. Small-Scale Demonstration and Lessons Learned

    SciTech Connect

    Kaminski, Michael

    2015-01-01

    The Irreversible Wash Aid Additive process has been under development by the U.S. Environmental Protection Agency (EPA) and Argonne National Laboratory (Argonne). This process for radioactive cesium mitigation consists of a solution to wash down contaminated structures, roadways, and vehicles and a sequestering agent to bind the radionuclides from the wash water and render them environmentally immobile. The purpose of this process is to restore functionality to basic services and immediately reduce the consequences of a radiologically-contaminated urban environment. Research and development have resulted in a down-selection of technologies for integration and demonstration at the pilot-scale level as part of the Wide Area Recovery and Resiliency Program (WARRP) under the Department of Homeland Security and the Denver Urban Area Security Initiative. As part of developing the methods for performing a pilot-scale demonstration at the WARRP conference in Denver in 2012, Argonne conducted small-scale field experiments at Separmatic Systems. The main purpose of these experiments was to refine the wash water collection and separations systems and demonstrate key unit operations to help in planning for the large scale demonstration in Denver. Since the purpose of these tests was to demonstrate the operations of the system, we used no radioactive materials. After a brief set of experiments with the LAKOS unit to familiarize ourselves with its operation, two experiments were completed on two separate dates with the Separmatic systems.

  20. Small-scale grassland assembly patterns differ above and below the soil surface.

    PubMed

    Price, Jodi N; Hiiesalu, Inga; Gerhold, Pille; Pärtel, Meelis

    2012-06-01

    The existence of deterministic assembly rules for plant communities remains an important and unresolved topic in ecology. Most studies examining community assembly have sampled aboveground species diversity and composition. However, plants also coexist belowground, and many coexistence theories invoke belowground competition as an explanation for aboveground patterns. We used next-generation sequencing that enables the identification of roots and rhizomes from mixed-species samples to measure coexisting species at small scales in temperate grasslands. We used comparable data from above (conventional methods) and below (molecular techniques) the soil surface (0.1 x 0.1 x 0.1 m volume). To detect evidence for nonrandom patterns in the direction of biotic or abiotic assembly processes, we used three assembly rules tests (richness variance, guild proportionality, and species co-occurrence indices) as well as pairwise association tests. We found support for biotic assembly rules aboveground, with lower variance in species richness than expected and more negative species associations. Belowground plant communities were structured more by abiotic processes, with greater variability in richness and guild proportionality than expected. Belowground assembly is largely driven by abiotic processes, with little evidence for competition-driven assembly, and this has implications for plant coexistence theories that are based on competition for soil resources.

  1. Distinct soil bacterial communities along a small-scale elevational gradient in alpine tundra.

    PubMed

    Shen, Congcong; Ni, Yingying; Liang, Wenju; Wang, Jianjun; Chu, Haiyan

    2015-01-01

    The elevational diversity pattern for microorganisms has received great attention recently but is still understudied, and phylogenetic relatedness is rarely studied for microbial elevational distributions. Using a bar-coded pyrosequencing technique, we examined the biodiversity patterns for soil bacterial communities of tundra ecosystem along 2000-2500 m elevations on Changbai Mountain in China. Bacterial taxonomic richness displayed a linear decreasing trend with increasing elevation. Phylogenetic diversity and mean nearest taxon distance (MNTD) exhibited a unimodal pattern with elevation. Bacterial communities were more phylogenetically clustered than expected by chance at all elevations based on the standardized effect size of MNTD metric. The bacterial communities differed dramatically among elevations, and the community composition was significantly correlated with soil total carbon (TC), total nitrogen, C:N ratio, and dissolved organic carbon. Multiple ordinary least squares regression analysis showed that the observed biodiversity patterns strongly correlated with soil TC and C:N ratio. Taken together, this is the first time that a significant bacterial diversity pattern has been observed across a small-scale elevational gradient. Our results indicated that soil carbon and nitrogen contents were the critical environmental factors affecting bacterial elevational distribution in Changbai Mountain tundra. This suggested that ecological niche-based environmental filtering processes related to soil carbon and nitrogen contents could play a dominant role in structuring bacterial communities along the elevational gradient.

  2. Ground and Flight Evaluation of a Small-Scale Inflatable-Winged Aircraft

    NASA Technical Reports Server (NTRS)

    Murray, James E.; Pahle, Joseph W.; Thornton, Stephen V.; Vogus, Shannon; Frackowiak, Tony; Mello, Joe; Norton, Brook; Bauer, Jeff (Technical Monitor)

    2002-01-01

    A small-scale, instrumented research aircraft was flown to investigate the night characteristics of innersole wings. Ground tests measured the static structural characteristics of the wing at different inflation pressures, and these results compared favorably with analytical predictions. A research-quality instrumentation system was assembled, largely from commercial off-the-shelf components, and installed in the aircraft. Initial flight operations were conducted with a conventional rigid wing having the same dimensions as the inflatable wing. Subsequent flights were conducted with the inflatable wing. Research maneuvers were executed to identify the trim, aerodynamic performance, and longitudinal stability and control characteristics of the vehicle in its different wing configurations. For the angle-of-attack range spanned in this flight program, measured flight data demonstrated that the rigid wing was an effective simulator of the lift-generating capability of the inflatable wing. In-flight inflation of the wing was demonstrated in three flight operations, and measured flight data illustrated the dynamic characteristics during wing inflation and transition to controlled lifting flight. Wing inflation was rapid and the vehicle dynamics during inflation and transition were benign. The resulting angles of attack and of sideslip ere small, and the dynamic response was limited to roll and heave motions.

  3. Small-scale variability of the current in the Strait of Bonifacio

    NASA Astrophysics Data System (ADS)

    Gérigny, Olivia; Coudray, Sylvain; Lapucci, Chiara; Tomasino, Corinne; Bisgambiglia, Paul-Antoine; Galgani, François

    2015-08-01

    Current dynamics in the Strait of Bonifacio (south Corsica) were investigated at a small scale during the STELLAMARE1 multidisciplinary cruise in summer 2012, using in situ measurements and modeling data. The Strait of Bonifacio is a particularly sensitive marine area in which specific conservation measures have been taken to preserve the natural environment and wild species. Good knowledge of the hydrodynamics in this area is essential to optimize the Marine Protected Area's management rules. Therefore, we used a high-resolution model (400 m) based on the MARS3D code to investigate the main flux exchanges and to formulate certain hypotheses about the formation of possible eddy structures. The aim of the present paper is first to synthetize the results obtained by combining Acoustic Doppler Current Profiler data, hydrological parameters, Lagrangian drifter data, and satellite observations such as MODIS OC5 chlorophyll a data or Metop-A AVHRR Sea Surface Temperature (SST) data. These elements are then used to validate the presence of the mesoscale eddies simulated by the model and their recurrence outside the cruise period. To complete the analysis, the response of the 3D hydrodynamical model was evaluated under two opposing wind systems and certain biases were detected. Strong velocities up to 1 m s-1 were recorded in the east part due to the Venturi effect; a complementary system of vortices governed by Coriolis effect and west wind was observed in the west part, and horizontal stratification in the central part has been identified under typical wind condition.

  4. Summary of Large-and Small-Scale Unreinforced Masonry Test Program

    SciTech Connect

    Fricke, K.E.

    2002-06-28

    A five-year, large- and small-scale, static and dynamic experimental research program, in which more than 700 tests were conducted, has demonstrated that unreinforced masonry infills are more ductile and resist lateral loads more effectively than anticipated by conventional code procedures. The tests were conducted both in the laboratory and on existing structures at the Department of Energy's Y-12 National Security Complex. The experimental data indicate that the combination of a steel frame and infill material efficiently resists lateral loads--the infilling provides significant lateral stiffness while the surrounding frame adds ductility and confinement to the overall system. The results from approximately 25 moderate- and full-scale tests on infills showed that with simulated seismic loads, the frames confined the masonry, and the load-carrying capacity of the infill was considerably above the load that caused initial cracking. This finding was a significant departure from classical code approaches that assumed first cracking to be failure of an unreinforced masonry wall. The experimental program, performed for the US Department of Energy, consisted of the following large-scale tests on infills: in situ airbag pressure testing, shake-table tests, and the application of quasi-static in-plane and out-of-plane drift loads. This paper provides a summary of the overall experimental methodology and results.

  5. Sediment depositions upstream of open check dams: new elements from small scale models

    NASA Astrophysics Data System (ADS)

    Piton, Guillaume; Le Guern, Jules; Carbonari, Costanza; Recking, Alain

    2015-04-01

    numbers that the flows tend to adopt? New small scale model experiments have been undertaken focusing on depositions processes and their related hydraulics. Accurate photogrammetric measurements allowed us to better describe the deposition processes3. Large Scale Particle Image Velocimetry (LS-PIV) was performed to determine surface velocity fields in highly active channels with low grain submersion4. We will present preliminary results of our experiments showing the new elements we observed in massive deposit dynamics. REFERENCES 1.Armanini, A., Dellagiacoma, F. & Ferrari, L. From the check dam to the development of functional check dams. Fluvial Hydraulics of Mountain Regions 37, 331-344 (1991). 2.Piton, G. & Recking, A. Design of sediment traps with open check dams: a review, part I: hydraulic and deposition processes. (Accepted by the) Journal of Hydraulic Engineering 1-23 (2015). 3.Le Guern, J. Ms Thesis: Modélisation physique des plages de depot : analyse de la dynamique de remplissage.(2014) . 4.Carbonari, C. Ms Thesis: Small scale experiments of deposition processes occuring in sediment traps, LS-PIV measurments and geomorphological descriptions. (in preparation).

  6. Partnerships between utilities and small-scale providers: Delegated management in Kisumu, Kenya

    NASA Astrophysics Data System (ADS)

    Schwartz, Klaas; Sanga, Anthony

    Increasingly, partnerships between small-scale providers and formal utilities are being promoted as an alternative model of infrastructure development and service provision. This paper analyzes the potential of such a model for bridging the gap in service provision in peri-urban areas. The model, which this article focuses on, is the delegated management model, which has been implemented in Kisumu, Kenya. In this model a formal utility entered into contracts with multiple small-scale providers to distribute water to an informal settlement. In this arrangement, the water utility sells bulk water to the small-scale providers and these then distribute the water to an area covering about 120 connections for each provider. The research finds that the arrangement in Kisumu has met with mixed results. On the one hand, the arrangement led to considerable service expansion and to service improvements for those not connected to the network. Also, the formal utility benefited from the fact that they generated additional revenue by selling bulk water to the small-scale providers. The arrangement has also generated employment for those working for the small-scale providers. On the other hand, experiences so far, show that some challenges need to be addressed before the partnership arrangement becomes truly sustainable. For some providers corruption seems to be a problem as funds have been misappropriated. Also, the utility has not upheld the agreement to transfer all ‘old connections’ to the small-scale providers. A particularly worrying feature is that in low-income areas of Nyalenda, the customers of kiosks run by the small-scale providers pay three times more for their water than households who have an in-house connection.

  7. Peculiarities of the optimisation of optical resonators with regular small-scale inhomogeneities of an active medium

    SciTech Connect

    Lobachev, V V; Strakhov, S Yu

    2005-10-31

    The peculiarities of parametric optimisation of resonators containing small-scale inhomogeneities are considered. The two most important practical cases are studied in detail: an unstable resonator with small-scale phase inhomogeneities in the active medium and a stable resonator with small-scale amplitude modulations caused by the use of a perforated output mirror. (resonators)

  8. Architecture of small-scale fault zones in the context of the Leinetalgraben Fault System

    NASA Astrophysics Data System (ADS)

    Reyer, Dorothea; Philipp, Sonja L.

    2010-05-01

    local stress field so that it stops many joints. Well developed fracture networks are therefore in most cases limited to single layers. From the data we finally determined the structural indices of the fault zones, that is, the ratios of damage zone and fault zone widths. By their nature structural indices can obtain values from 0 to 1; the values having implications for fault zone permeability. An ideal value of 0 would mean that a fault damage zone is absent. Such fault zones generally have low permeabilities as long as the faults are not active (slipping). A structural index of 1, however, would imply that there is practically no fault core and the fault zone permeability is entirely controlled by the fractures within the damage zone. Our measurements show that the damage zones of normal faults in the Muschelkalk limestone are relatively thick so that their structural indices are relatively high. In contrast to normal faults, reverse and strike-slip faults have smaller indices because of well developed brecciated fault cores. In addition we found that small-scale fault zones with parallel orientations to the major Leinetalgraben fault zones are more likely to have well developed damage zones than those with conjugate or perpendicular orientation. Our field data lead to the hypothesis that fault systems in the North German Basin may generally be surrounded by small-scale fault zones which have high permeabilities if orientated parallel to the major fault and lower permeabilities if conjugate or perpendicularly orientated. However, further studies of fault systems in different geological settings are needed to support or reject this hypothesis. Such studies help to improve the general understanding of fault zones and fault systems and thereby minimise the risk in matters of the exploitation of fault-related geothermal reservoirs.

  9. Label-free imaging of the dynamics of cell-to-cell string-like structure bridging in the free-space by low-coherent quantitative phase microscopy

    NASA Astrophysics Data System (ADS)

    Yamauchi, Toyohiko; Iwai, Hidenao; Yamashita, Yutaka

    2013-03-01

    We succeeded in utilizing our low-coherent quantitative phase microscopy (LC-QPM) to achieve label-free and three-dimensional imaging of string-like structures bridging the free-space between live cells. In past studies, three dimensional morphology of the string-like structures between cells had been investigated by electron microscopies and fluorescence microscopies and these structures were called "membrane nanotubes" or "tunneling nanotubes." However, use of electron microscopy inevitably kills these cells and fluorescence microscopy is itself a potentially invasive method. To achieve noninvasive imaging of live cells, we applied our LC-QPM which is a reflection-type, phase resolved and full-field interference microscope employing a low-coherent light source. LC-QPM is able to visualize the three-dimensional morphology of live cells without labeling by means of low-coherence interferometry. The lateral (diffraction limit) and longitudinal (coherence-length) spatial resolution of LC-QPM were respectively 0.49 and 0.93 micrometers and the repeatability of the phase measurement was 0.02 radians (1.0 nm). We successfully obtained three-dimensional morphology of live cultured epithelial cells (cell type: HeLa, derived from cervix cancer) and were able to clearly observe the individual string-like structures interconnecting the cells. When we performed volumetric imaging, a 80 micrometer by 60 micrometer by 6.5 micrometer volume was scanned every 5.67 seconds and 70 frames of a three-dimensional movie were recorded for a duration of 397 seconds. Moreover, the optical phase images gave us detailed information about the three-dimensional morphology of the string-like structure at sub-wavelength resolution. We believe that our LC-QPM will be a useful tool for the study of three-dimensional morphology of live cells.

  10. Small-scale plasma, magnetic, and neutral density fluctuations in the nightside Venus ionosphere

    SciTech Connect

    Hoegy, W.R.; Brace, L.H.; Kasprazak, W.T. ); Russell, C.T. )

    1990-04-01

    Pioneer Venus orbiter measurements have shown that coherent small-scale waves exist in the electron density, the electron temperature, and the magnetic field in the lower ionosphere of Venus just downstream of the solar terminator (Brace et al., 1983). The waves become less regular and less coherent at larger solar zenith angles, and Brace et al. suggested that these structures may have evolved from the terminator waves as they are convected into the nightside ionosphere, driven by the day-to-night plasma pressure gradient. In this paper the authors describe the changes in wave characteristics with solar zenith angle and show that the neutral gas also has related wave characteristics, probably because of atmospheric gravity waves. The plasma pressure exceeds the magnetic pressure in the nightside ionosphere at these altitudes, and thus the magnetic field is carried along and controlled by the turbulent motion of the plasma, but the wavelike nature of the thermosphere may also be coupled to the plasma and magnetic structure. They show that there is a significant coherence between the ionosphere, thermosphere, and magnetic parameters at altitudes below about 185 km, a coherence which weakens in the antisolar region. The electron temperature and density are approximately 180{degree} out of phase and consistently exhibit the highest correlation of any pair of variables. Waves in the electron and neutral densities are moderately correlated on most orbits, but with a phase difference that varies within each orbit. The average electron temperature is higher when the average magnetic field is more horizontal; however, the correlation between temperature and dip angle does not extend to individual wave structures observed within a satellite pass, particularly in the antisolar region.

  11. Living close, doing differently: small-scale asynchrony in demography of two species of seabirds.

    PubMed

    Tavecchia, Giacomo; Minguez, Eduardo; De León, Ana; Louzao, Maite; Oro, Daniel

    2008-01-01

    Studies on spatiotemporal pattern of population abundance predict that close populations should exhibit a high level of synchrony, reflected in a parallel time variation of at least one demographic parameter. We tested this prediction for two threatened species of Procellariiformes sharing similar life history traits: the European Storm Petrel (Hydrobates pelagicus) and the Balearic Shearwater (Puffinus mauretanicus). Within each species, we compared adult survival, proportion of transients (breeders that do not settle), and average productivity at two neighboring colonies. Physical and environmental features (e.g., food availability) of the breeding sites were similar. However, while Balearic Shearwater colonies were free of predators, aerial predators occurred especially in one colony of the European Storm Petrel. Despite this difference, we found similar results for the two species. A high proportion of transient birds was detected in only one colony of each species, ranging between 0.00-0.38 and 0.10-0.63 for the petrels and shearwaters, respectively. This seems to be an emergent feature of spatially structured populations of seabirds, unrelated to colony size or predator pressure, that can have important demographic consequences for local population dynamics and their synchrony. Local survival of resident birds was different at each colony, an unexpected result, especially for predator-free colonies of Balearic Shearwater. Productivity varied between the two colonies of European Storm Petrels, but not between the two colonies of Balearic Shearwaters. We demonstrated that within each species, several demographic parameters were colony specific and sufficiently different to generate short-term asynchronous dynamics. Our findings suggest that, in spatially structured populations, local factors, such as predation or small-scale habitat features, or population factors, such as individual quality or age structure, can generate unexpected asynchrony between

  12. A study of the relationship between permeability distributions and small scale sedimentary features in a fluvial formation

    SciTech Connect

    Gotkowitz, M.

    1993-10-01

    This study focuses on styles of small-scale heterogeneity found in fluvial sand and soil bodies. Over 1,700 in situ measurements of air permeability were taken in an outcrop-based study which joins observations of sedimentary features with their associated permeability distributions. The relationship between sedimentology and hydrologic parameters provides a geologic framework to assess geostatistical hypotheses. The soils in the study area are found to have a significantly lower permeability than the channel sand deposits. The soil deposits showed a significant lack of observable small scale sedimentary structures, which is reflected in the experimental variograms. The permeability distribution in these study sites appears to be adequately represented by a continuous gaussian random field model. The presence of calcium carbonate nodules in the soils is related to the permeability distribution. Correlation lengths in the channel sands perpendicular to stratigraphy are significantly shorter than those observed parallel to stratigraphy. A sedimentological, bounding surfaces model is evaluated with regard to permeability distributions. In deposits of little sedimentary structure, the mean and variance may adequately characterize the permeability distribution. Where significant sedimentary structure exists, the bounding surfaces model can be used to determine the scales of variability present in the permeability distribution and may also be used to infer an appropriate choice of random field model.

  13. Combine Effects of Plate Motions and Small-Scale Convection on Mantle Stirring Efficiency

    NASA Astrophysics Data System (ADS)

    King, S.; Samuel, H.

    2012-04-01

    Convection in Earth's mantle generates large scale, vigorous motions often thought to be the primary mechanism of mantle stirring. However additional thermal instabilities may progressively develop below lithospheric plates, leading to smaller scale convective motions. While there is growing evidence supporting the presence of small-scale convection in Earth's mantle, little is known of its contribution to the mixing of mantle heterogeneities. We have thus investigated the influence of small-scale convection on mantle stirring efficiency using 2D numerical modeling of infinite Prandtl number convection with imposed surface plate motion and temperature and pressure dependent rheology. We measure stirring efficiency using Finite Time Lyapunov Exponents (FTLE) and we vary systematically the Peclet number, Pe, defined as the ratio of the advection time scale based on surface plate velocity to a characteristic diffusion time. Our computational domain has an aspect ratio of 1:3. For moderate Pe, small-scale convection is well developed, leading to efficient stirring. However large Pe numbers do not allow the development of small-scale convection and result in significantly lower stirring efficiency, although plate motions are faster. This indicates that (i) small-scale convection contributes significantly to mantle stirring efficiency, (ii) mantle stirring efficiency many spatially vary significantly due to the local magnitude of plate velocity and (iii) the relationship between mantle stirring efficiency and large-scale convective motions may be more complex than previously thought.

  14. A small-scale study of magneto-rheological track vibration isolation system

    NASA Astrophysics Data System (ADS)

    Li, Rui; Mu, Wenjun; Zhang, Luyang; Wang, Xiaojie

    2016-04-01

    A magneto-rheological bearing (MRB) is proposed to improve the vibration isolation performance of a floating slab track system. However, it's difficult to carry out the test for the full-scale track vibration isolation system in the laboratory. In this paper, the research is based on scale analysis of the floating slab track system, from the point view of the dimensionless of the dynamic characteristics of physical quantity, to establish a small scale test bench system for the MRBs. A small scale MRB with squeeze mode using magneto-rheological grease is designed and its performance is tested. The major parameters of a small scale test bench are obtained according to the similarity theory. The force transmissibility ratio and the relative acceleration transmissibility ratio are selected as evaluation index of system similarity. Dynamics of these two similarity systems are calculated by MATLAB experiment. Simulation results show that the dynamics of the prototype and scale models have good similarity. Further, a test bench is built according to the small-scale model parameter analysis. The experiment shows that the bench testing results are consistency with that of theoretical model in evaluating the vibration force and acceleration. Therefore, the small-scale study of magneto-rheological track vibration isolation system based on similarity theory reveals the isolation performance of a real slab track prototype system.

  15. Experimental evidence for convergent evolution of maternal care heuristics in industrialized and small-scale populations.

    PubMed

    Kushnick, Geoff; Hanowell, Ben; Kim, Jun-Hong; Langstieh, Banrida; Magnano, Vittorio; Oláh, Katalin

    2015-06-01

    Maternal care decision rules should evolve responsiveness to factors impinging on the fitness pay-offs of care. Because the caretaking environments common in industrialized and small-scale societies vary in predictable ways, we hypothesize that heuristics guiding maternal behaviour will also differ between these two types of populations. We used a factorial vignette experiment to elicit third-party judgements about likely caretaking decisions of a hypothetical mother and her child when various fitness-relevant factors (maternal age and access to resources, and offspring age, sex and quality) were varied systematically in seven populations-three industrialized and four small-scale. Despite considerable variation in responses, we found that three of five main effects, and the two severity effects, exhibited statistically significant industrialized/ small-scale population differences. All differences could be explained as adaptive solutions to industrialized versus small-scale caretaking environments. Further, we found gradients in the relationship between the population-specific estimates and national-level socio-economic indicators, further implicating important aspects of the variation in industrialized and small-scale caretaking environments in shaping heuristics. Although there is mounting evidence for a genetic component to human maternal behaviour, there is no current evidence for interpopulation variation in candidate genes. We nonetheless suggest that heuristics guiding maternal behaviour in diverse societies emerge via convergent evolution in response to similar selective pressures. PMID:26543577

  16. Small scale effects on the mechanical behaviors of protein microtubules based on the nonlocal elasticity theory

    SciTech Connect

    Gao, Yuanwen; Lei, Fang-Ming

    2009-09-25

    Based on the nonlocal elastic theory, small scale effects are considered in the investigation of the mechanical properties of protein microtubules. A new prediction formula for the persistence lengths of microtubules with the consideration of the small scale effect is presented. Subsequently, the buckling of microtubules is studied based on a nonlocal elastic beam model. The predicted results of our model indicate that the length-dependence of persistence length is related not only to the shear terms, but also to the small scale effect. The Eular beam model, which is always considered unable to explain the length-dependence of microtubules, can capture the length-dependence of the persistence length of microtubules with the consideration of the small scale effect. The elastic buckling behaviors of microtubules in viscoelastic surrounding cytoplasm are also considered using the nonlocal Timoshenko beam model in this paper, and the results indicate that the small scale effect of microtubules also plays an important role in the buckling of microtubules.

  17. Properties of small-scale interfacial turbulence from a novel thermography based approach

    NASA Astrophysics Data System (ADS)

    Schnieders, Jana; Garbe, Christoph

    2013-04-01

    Oceans cover nearly two thirds of the earth's surface and exchange processes between the Atmosphere and the Ocean are of fundamental environmental importance. At the air-sea interface, complex interaction processes take place on a multitude of scales. Turbulence plays a key role in the coupling of momentum, heat and mass transfer [2]. Here we use high resolution infrared imagery to visualize near surface aqueous turbulence. Thermographic data is analized from a range of laboratory facilities and experimental conditions with wind speeds ranging from 1ms-1 to 7ms-1 and various surface conditions. The surface heat pattern is formed by distinct structures on two scales - small-scale short lived structures termed fish scales and larger scale cold streaks that are consistent with the footprints of Langmuir Circulations. There are two key characteristics of the observed surface heat patterns: (1) The surface heat patterns show characteristic features of scales. (2) The structure of these patterns change with increasing wind stress and surface conditions. We present a new image processing based approach to the analysis of the spacing of cold streaks based on a machine learning approach [4, 1] to classify the thermal footprints of near surface turbulence. Our random forest classifier is based on classical features in image processing such as gray value gradients and edge detecting features. The result is a pixel-wise classification of the surface heat pattern with a subsequent analysis of the streak spacing. This approach has been presented in [3] and can be applied to a wide range of experimental data. In spite of entirely different boundary conditions, the spacing of turbulent cells near the air-water interface seems to match the expected turbulent cell size for flow near a no-slip wall. The analysis of the spacing of cold streaks shows consistent behavior in a range of laboratory facilities when expressed as a function of water sided friction velocity, u*. The scales

  18. An asset-based approach to vulnerability: the case of small-scale fishing areas in Cameroon and Nigeria.

    PubMed

    Chiwaula, Levison S; Witt, Rudolf; Waibel, Hermann

    2011-01-01

    This paper analyses vulnerability to poverty of rural small-scale fishing communities using cross-section data from 295 households in Cameroon and 267 in Nigeria. We propose a vulnerability measure that incorporates the idea of asset poverty into the concept of expected poverty, which allows decomposing expected poverty into expected structural-chronic, structural-transient, and stochastic-transient poverty. The findings show that most households in our study areas are expected to be structurally-chronic and structurally-transient poor. This underlines the importance of asset formation for long-term poverty reduction strategies. Further refinements are possible with longitudinal data and information about future states of nature. PMID:21506304

  19. M-Strings

    NASA Astrophysics Data System (ADS)

    Haghighat, Babak; Iqbal, Amer; Kozçaz, Can; Lockhart, Guglielmo; Vafa, Cumrun

    2015-03-01

    M2 branes suspended between adjacent parallel M5 branes lead to light strings, the `M-strings'. In this paper we compute the elliptic genus of M-strings, twisted by maximally allowed symmetries that preserve 2 d (2, 0) supersymmetry. In a codimension one subspace of parameters this reduces to the elliptic genus of the (4, 4) supersymmetric A n-1 quiver theory in 2 d. We contrast the elliptic genus of N M-strings with the (4, 4) sigma model on the N-fold symmetric product of . For N = 1 they are the same, but for N > 1 they are close, but not identical. Instead the elliptic genus of (4, 4) N M-strings is the same as the elliptic genus of (4, 0) sigma models on the N-fold symmetric product of , but where the right-moving fermions couple to a modification of the tangent bundle. This construction arises from a dual A n-1 quiver 6 d gauge theory with U(1) gauge groups. Moreover, we compute the elliptic genus of domain walls which separate different numbers of M2 branes on the two sides of the wall.

  20. PT-symmetric strings

    SciTech Connect

    Amore, Paolo; Fernández, Francisco M.; Garcia, Javier; Gutierrez, German

    2014-04-15

    We study both analytically and numerically the spectrum of inhomogeneous strings with PT-symmetric density. We discuss an exactly solvable model of PT-symmetric string which is isospectral to the uniform string; for more general strings, we calculate exactly the sum rules Z(p)≡∑{sub n=1}{sup ∞}1/E{sub n}{sup p}, with p=1,2,… and find explicit expressions which can be used to obtain bounds on the lowest eigenvalue. A detailed numerical calculation is carried out for two non-solvable models depending on a parameter, obtaining precise estimates of the critical values where pair of real eigenvalues become complex. -- Highlights: •PT-symmetric Hamiltonians exhibit real eigenvalues when PT symmetry is unbroken. •We study PT-symmetric strings with complex density. •They exhibit regions of unbroken PT symmetry. •We calculate the critical parameters at the boundaries of those regions. •There are exact real sum rules for some particular complex densities.