7,662 research outputs found
Energy Loss from a Moving Vortex in Superfluid Helium
We present measurements on both energy loss and pinning for a vortex
terminating on the curved surface of a cylindrical container. We vary surface
roughness, cell diameter, fluid velocity, and temperature. Although energy loss
and pinning both arise from interactions between the vortex and the surface,
their dependences on the experimental parameters differ, suggesting that
different mechanisms govern the two effects. We propose that the energy loss
stems from reconnections with a mesh of microscopic vortices that covers the
cell wall, while pinning is dominated by other influences such as the local
fluid velocity.Comment: 8 pages, 6 figure
Pre-Merger Localization of Gravitational-Wave Standard Sirens With LISA I: Harmonic Mode Decomposition
The continuous improvement in localization errors (sky position and distance)
in real time as LISA observes the gradual inspiral of a supermassive black hole
(SMBH) binary can be of great help in identifying any prompt electromagnetic
counterpart associated with the merger. We develop a new method, based on a
Fourier decomposition of the time-dependent, LISA-modulated gravitational-wave
signal, to study this intricate problem. The method is faster than standard
Monte Carlo simulations by orders of magnitude. By surveying the parameter
space of potential LISA sources, we find that counterparts to SMBH binary
mergers with total mass M~10^5-10^7 M_Sun and redshifts z<~3 can be localized
to within the field of view of astronomical instruments (~deg^2) typically
hours to weeks prior to coalescence. This will allow targeted searches for
variable electromagnetic counterparts as the merger proceeds, as well as
monitoring of the most energetic coalescence phase. A rich set of astrophysical
and cosmological applications would emerge from the identification of
electromagnetic counterparts to these gravitational-wave standard sirens.Comment: 29 pages, 12 figures, version accepted by Phys Rev
Analysis and correction of the magnetic field effects in the Hybrid Photo-Detectors of the RICH2 Ring Imaging Cherenkov detector of LHCb
The Ring Imaging Cherenkov detectors of the LHCb experiment at the Large
Hadron Collider at CERN are equipped with Hybrid Photo-Detectors. These vacuum
photo-detectors are affected by the stray magnetic field of the LHCb magnet,
which degrades their imaging properties. This effect increases the error on the
Cherenkov angle measurement and would reduce the particle identification
capabilities of LHCb. A system has been developed for the RICH2 Ring Imaging
Cherenkov detector to perform a detailed characterisation of the magnetic
distortion effects. It is described, along with the methods implemented to
correct for these effects, restoring the optimal resolution.Comment: 16 pages, 11 figure
Comparison of BacT/ALERT 3D, Lowenstein-Jensen medium and Middlebrook 7H10/7H11 biplate for recovering mycobacteria from clinical specimens
Can Virialization Shocks be Detected Around Galaxy Clusters Through the Sunyaev-Zel'dovich Effect?
In cosmological structure formation models, massive non-linear objects in the
process of formation, such as galaxy clusters, are surrounded by large-scale
shocks at or around the expected virial radius. Direct observational evidence
for such virial shocks is currently lacking, but we show here that their
presence can be inferred from future, high resolution, high-sensitivity
observations of the Sunyaev-Zel'dovich (SZ) effect in galaxy clusters. We study
the detectability of virial shocks in mock SZ maps, using simple models of
cluster structure (gas density and temperature distributions) and noise
(background and foreground galaxy clusters projected along the line of sight,
as well as the cosmic microwave background anisotropies). We find that at an
angular resolution of 2'' and sensitivity of 10 micro K, expected to be reached
at ~ 100 GHz frequencies in a ~ 20 hr integration with the forthcoming ALMA
instrument, virial shocks associated with massive M ~ 10^15 M_Sun clusters will
stand out from the noise, and can be detected at high significance. More
generally, our results imply that the projected SZ surface brightness profile
in future, high-resolution experiments will provide sensitive constraints on
the density profile of cluster gas.Comment: 15 pages, submitted to Ap
Vinogradov's three primes theorem with primes having given primitive roots
The first purpose of our paper is to show how Hooley's celebrated method leading to his conditional proof of the Artin conjecture on primitive roots can be combined with the Hardy-Littlewood circle method. We do so by studying the number of representations of an odd integer as a sum of three primes, all of which have prescribed primitive roots. The second purpose is to analyse the singular series. In particular, using results of Lenstra, Stevenhagen and Moree, we provide a partial factorisation as an Euler product and prove that this does not extend to a complete factorisation
Element/Ca, C and O isotope ratios in modern brachiopods: Species-specific signals of biomineralization
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Fossil brachiopods are of major importance for the reconstruction of palaeoenvironmental conditions, particularly of the Paleozoic. In order to better understand signals of ancient shell materials, modern analogue studies have to be conducted.
Here we present C and O isotope data in conjunction with Mg/Ca, Sr/Ca, Mn/Ca and Fe/Ca data for nine modern rhynchonellid and terebratulid brachiopod species from tropical to intermediate latitudes and shallow to very deep marine settings. C and O isotope signals of most species suggest formation of secondary shell layers near or in isotopic equilibrium with ambient seawater. Some species – especially in the suborder Terebratellidina – show partly distinct disequilibrium signals, suggesting some degree of phylogenetic control on the expression of vital effects.
Mn/Ca and Fe/Ca ratios measured in the modern species form a baseline to assess fossil preservation, but also yield environmental information. Mg/Ca and Sr/Ca ratios follow previously observed patterns, with all studied brachiopod species comprising low-Mg calcite. Strong covariation of Sr/Ca ratios with Mg/Ca ratios is only observed in rhynchonellids and possibly one terebratulid species, potentially linking the incorporation behaviour of alkaline earth metals to phylogeny.
Sr/Ca show a strong negative correlation with δ13C values in terebratellidinid species which exhibit major isotopic disequilibrium and also combined data from three localities for which two species were studied indicate such a negative relation. The observed covariation of Sr/Ca ratios with δ13C values may therefore become a useful tool to detect δ13C disequilibrium and to robustly estimate δ13C values of ambient DIC in deep time.The authors acknowledge comments from two anonymous reviewers and Alberto Pérez-Huerta as well as the editor Michael E. Boettcher which helped to improve the quality and clarity of the manuscript. The authors thank the Museum für Naturkunde Berlin for providing brachiopod specimens of the species F. sanguinolenta (ZMB Bra 1934), M. venosa (ZMB Bra 2028), N. nigricans (ZMB Bra 2441), S. crosnieri (ZMB Bra 2442), C. inconspicua (ZMB Bra 2443), C. racovitzae (ZMB Bra 2444) and L. neozelanica (ZMB Bra 2445) and Andy Gale for providing specimens of T. transversa and Terebratulina sp. The authors are indebted to the crews of RV SONNE during the cruises SO 168 ZEALANDIA and SO 233 WALVIS 2 and their respective shipboard scientific parties. Financial support by the German Ministry of Education and Research (BMBF) within the project SO 168 ZEALANDIA (FKZ: 03G0168) and SO 233 WALVIS 2 (FKZ: 03G0233A) to CL is gratefully acknowledged. CVU acknowledges funding from the Leopoldina – German National Academy of Sciences (grant no. LPDS 2014-08)
GLADE: A galaxy catalogue for multimessenger searches in the advanced gravitational-wave detector era
We introduce a value-added full-sky catalogue of galaxies, named as Galaxy List for the Advanced Detector Era, or GLADE. The purpose of this catalogue is to (i) help identifications of host candidates for gravitational-wave events, (ii) support target selections for electromagnetic follow-up observations of gravitational-wave candidates, (iii) provide input data on the matter distribution of the local Universe for astrophysical or cosmological simulations, and (iv) help identifications of host candidates for poorly localized electromagnetic transients, such as gamma-ray bursts observed with the InterPlanetary Network. Both being potential hosts of astrophysical sources of gravitational waves, GLADE includes inactive and active galaxies as well. GLADE was constructed by cross-matching and combining data from five separate (but not independent) astronomical catalogues: GWGC, 2MPZ, 2MASS XSC, HyperLEDA, and SDSS-DR12Q. GLADE is complete up to
dL=37+3−4Mpc in terms of the cumulative B-band luminosity of galaxies within luminosity distance dL, and contains all of the brightest galaxies giving half of the total B-band luminosity up to dL=91Mpc. As B-band luminosity is expected to be a tracer of binary neutron star mergers (currently the prime targets of joint GW+EM detections), our completeness measures can be used as estimations of completeness for containing all binary neutron star merger hosts in the local Universe
Rendering Non-Euclidean Space in Real-Time Using Spherical and Hyperbolic Trigonometry
We introduce a method of calculating and rendering shapes in a non-Euclidean 2D space in real-time using hyperbolic and spherical trigonometry. We record the objects’ parameters in a polar coordinate system and use azimuthal equidistant projection to render the space onto the screen. We discuss the complexity of this method, renderings produced, limitations and possible applications of the created software as well as potential future developments
Fracturas de implantes de tibia. Consecuencias para los ensayos de los implantes
El objetivo de este trabajo es estudiar los modelos de fracturas de prótesis de tibia descritos en la literatura
y, sobre la base de dichos conocimientos, desarrollar un ensayo para implantes en la cual se logren simular
condiciones fisiológicas. El caso descrito con mayor frecuencia en la literatura es la migración de la parte
medial de la prótesis, fenómeno que, a menudo, antecede a la fractura de la prótesis. La posición defectuosa
resultante de dicha migración modifica el eje mecánico y provoca una sobrecarga en la parte medial de la
prótesis. Se ha desarrollado un ensayo de implantes que simula el modelo de fallo in-vivo. Dos bases de
material sintético de diferente dureza simulan la diferente densidad ósea medial y lateral, para permitir una
migración del lado medial del platillo. En el ensayo dinámico el platillo tibial es sometido a una carga de un
solo lado y el vástago de la prótesis se apuntala con un contrasoporte. Para simular el entorno fisiológico, todo
el dispositivo se encuentra sumergido en una solución de Ringer a 37°. El implante de tibia es expuesto durante
10 millones de ciclos a una carga que corresponde al quíntuple del peso del cuerpo (4.000 N). El punto de
aplicación de la fuerza fue tomado de datos de análisis del caminar (marcha en superficie plana, ascendente
y descendente, subir escaleras). Con esta carga fisiológica se efectuaron los primeros ensayos. En éstas quedó
demostrado que productos clínicamente exitosos podían superar el ensayo. Por el contrario, los productos con
modelos de fracturas conocidos no la superaron. Los primeros resultados con estos productos demostraron
también que el ensayo generaba muestras de fractura semejantes a las que se producen in vivo. Debido a la
configuración fisiológica del dispositivo se somete el sistema completo es decir el platillo, el vástago de la
prótesis y la unión - generalmente modular - entre ambos a ensayo. El "ensayo fisiológico de tibia " descrito
ayuda a evaluar los diseños de tibia antes de que se autorice su venta. Nuevos implantes y modificaciones de
diseño en implantes ya existentes son puestos a la venta después de cumplir con las exigencias del ensayo.Peer Reviewe
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