3,477 research outputs found
On BPS bounds in D=4 N=2 gauged supergravity II: general matter couplings and black hole masses
We continue the analysis of BPS bounds started in arXiv:1110.2688, extending
it to the full class of N=2 gauged supergravity theories with arbitrary vector
and hypermultiplets. We derive the general form of the asymptotic charges for
asymptotically flat (M_4), anti-de Sitter (AdS_4), and magnetic anti-de Sitter
(mAdS_4) spacetimes. Some particular examples from black hole physics are given
to explicitly demonstrate how AdS and mAdS masses differ when solutions with
non-trivial scalar profiles are considered.Comment: 21 pages; v2 added reference, published version; v3 minor correction
Vibration grinding - An approach for secondary use of refuse metallic aluminium
An investigation for recycling of refuse metallic aluminum grade AE having more than 99.5 % Al content has been studied by means of vibration attrition, The refuse meta-llic aluminum is produced by the cable manufacturing sector. The factors responsible for rendering the meta- llic aluminum into powder one, have been studied under normal batch lab-scale conditions. The following factors have been under consideration: quantity of the material to be ground; grinding media type; influence of surfactant addition etc. The conditions influencing the obtaining of aluminum powder with different particle shape have been established
The Herschel-SPIRE instrument and its in-flight performance
The Spectral and Photometric Imaging REceiver (SPIRE), is the Herschel Space Observatory`s submillimetre camera and spectrometer. It contains a three-band imaging photometer operating at 250, 350 and 500 Îźm, and an imaging Fourier-transform spectrometer (FTS) which covers simultaneously its whole operating range of 194â671 Îźm (447â1550 GHz). The SPIRE detectors are arrays of feedhorn-coupled bolometers cooled to 0.3 K. The photometer has a field of view of 4´à 8´, observed simultaneously in the three spectral bands. Its main operating mode is scan-mapping, whereby the field of view is scanned across the sky to achieve full spatial sampling and to cover large areas if desired. The spectrometer has an approximately circular field of view with a diameter of 2.6´. The spectral resolution can be adjusted between 1.2 and 25 GHz by changing the stroke length of the FTS scan mirror. Its main operating mode involves a fixed telescope pointing with multiple scans of the FTS mirror to acquire spectral data. For extended source measurements, multiple position offsets are implemented by means of an internal beam steering mirror to achieve the desired spatial sampling and by rastering of the telescope pointing to map areas larger than the field of view. The SPIRE instrument consists of a cold focal plane unit located inside the Herschel cryostat and warm electronics units, located on the spacecraft Service Module, for instrument control and data handling. Science data are transmitted to Earth with no on-board data compression, and processed by automatic pipelines to produce calibrated science products. The in-flight performance of the instrument matches or exceeds predictions based on pre-launch testing and modelling: the photometer sensitivity is comparable to or slightly better than estimated pre-launch, and the spectrometer sensitivity is also better by a factor of 1.5â2
Radiation Characteristics of 3D Resonant Cavity Antenna with Grid-Oscillator Integrated Inside
A three-dimensional (3D) rectangular cavity antenna with an aperture size of 80 mm Ă 80 mm and a length of 16 mm, integrated with a four-MESFET transistor grid-oscillator, is designed and studied experimentally. It is found that the use of 3D antenna resonant cavity in case of small or medium gain microwave active cavity antenna leads to effective and stable power combining and radiation. The lack of lateral cavity diffraction and radiation helps in producing a directive gain of about 17 dB and radiation aperture efficiency bigger than 75% at a resonance frequency of 8.62 GHz. Good DC to RF oscillator efficiency of 26%, effective isotropic radiated power (EIRP) of 5.2 W, and SSB spectral power density of â82 dBc/Hz are found from the measured data. The 3D antenna cavity serves also as a strong metal container for the solid-state oscillator circuitry
Rotating BPS black holes in matter-coupled AdS(4) supergravity
Using the general recipe given in arXiv:0804.0009, where all timelike
supersymmetric solutions of N=2, D=4 gauged supergravity coupled to abelian
vector multiplets were classified, we construct genuine rotating supersymmetric
black holes in AdS(4) with nonconstant scalar fields. This is done for the
SU(1,1)/U(1) model with prepotential F=-iX^0X^1. In the static case, the black
holes are uplifted to eleven dimensions, and generalize the solution found in
hep-th/0105250 corresponding to membranes wrapping holomorphic curves in a
Calabi-Yau five-fold. The constructed rotating black holes preserve one quarter
of the supersymmetry, whereas their near-horizon geometry is one half BPS.
Moreover, for constant scalars, we generalize (a supersymmetric subclass of)
the Plebanski-Demianski solution of cosmological Einstein-Maxwell theory to an
arbitrary number of vector multiplets. Remarkably, the latter turns out to be
related to the dimensionally reduced gravitational Chern-Simons action.Comment: 23 pages, uses JHEP3.cl
A meta-analysis of methane mitigation potential of feed additives evaluated in vitro
A systematic literature review of in vitro studies was performed to identify methane (CH4) mitigation interventions with a potential to reduce CH4 emission in vivo. Data from 277 peer-reviewed studies published between 1979 and 2018 were reviewed. Individual CH4 mitigation interventions were classified into 14 categories of feed additives based on their type, chemical composition, and mode of action. Response variables evaluated were absolute CH4 emission (number of treatment means comparisons = 1,325); total volatile fatty acids (VFA; n = 1,007), acetate (n = 783), propionate (n = 792), and butyrate (n = 776) concentrations; acetate to propionate ratio (A:P; n = 675); digestibility of dry matter (DM; n = 489), organic matter (OM; n = 277), and neutral detergent fiber (NDF; n = 177). Total gas production was used as an explanatory variable in the model for CH4 production. Relative mean difference between treatment and control means reported in the studies were calculated and used for statistical analysis. Robust variance estimation method was used to analyze the effects of CH4 mitigation interventions. In vitro CH4 production was decreased by antibodies (â38.9%), chemical inhibitors (â29.2%), electron sinks (â18.9%), essential oils (â18.2%), plant extracts (â14.5%), plants inclusion (â11.7%), saponins (â14.8%), and tannins (â14.5%). Overall effects of direct fed microbials, enzymes, macroalgae, and organic acids supplementation did not affect CH4 production in the current meta-analysis. When considering the effects of individual mitigation interventions containing a minimum number of 4 degrees of freedom within feed additives categories, Enterococcus spp. (i.e., direct fed microbial), nitrophenol (i.e., electron sink), and Leucaena spp. (i.e., tannins) decreased CH4 production by 20.3, 27.1, and 23.5%, respectively, without extensively, or only slightly, affecting ruminal fermentation and digestibility of nutrients. It should be noted, however, that although the total number of publications (n = 277) and treatment means comparisons (n = 1,325 for CH4 production) in the current analysis were high, data for most mitigation interventions were obtained from less than 5 observations (e.g., maximum number of observations was 4, 7, and 22 for nitrophenol, Enterococcus spp., and Leucaena spp., respectively), because of limited data available in the literature. These should be further evaluated in vitro and in vivo to determine their true potential to decrease enteric CH4 production, yield, and intensity. Some mitigation interventions (e.g., magnesium, Heracleum spp., nitroglycerin, β-cyclodextrin, Leptospermum pattersoni, Fructulus Ligustri, Salix caprea, and Sesbania grandiflora) decreased in vitro CH4 production by over 50% but did not have enough observations in the database. These should be more extensively investigated in vitro, and the dose effect must be considered before adoption of mitigation interventions in vivo
A Millimeter-wave Galactic Plane Survey with the BICEP Polarimeter
In order to study inflationary cosmology and the Milky Way Galaxy's composition and magnetic field structure, Stokes I, Q, and U maps of the Galactic plane covering the Galactic longitude range 260° < â < 340° in three atmospheric transmission windows centered on 100, 150, and 220 GHz are presented. The maps sample an optical depth 1 âž AV âž 30, and are consistent with previous characterizations of the Galactic millimeter-wave frequency spectrum and the large-scale magnetic field structure permeating the interstellar medium. The polarization angles in all three bands are generally perpendicular to those measured by starlight polarimetry as expected and show changes in the structure of the Galactic magnetic field on the scale of 60°. The frequency spectrum of degree-scale Galactic emission is plotted between 23 and 220 GHz (including WMAP data) and is fit to a two-component (synchrotron and dust) model showing that the higher frequency BICEP data are necessary to tightly constrain the amplitude and spectral index of Galactic dust. Polarized emission is detected over the entire region within two degrees of the Galactic plane, indicating the large-scale magnetic field is oriented parallel to the plane of the Galaxy. A trend of decreasing polarization fraction with increasing total intensity is observed, ruling out the simplest model of a constant Galactic magnetic field orientation along the line of sight in the Galactic plane. A generally increasing trend of polarization fraction with electromagnetic frequency is found, varying from 0.5%-1.5% at frequencies below 50 GHz to 2.5%-3.5% above 90 GHz. The effort to extend the capabilities of BICEP by installing 220 GHz band hardware is described along with analysis of the new band
Radiation Characteristics of 3D Resonant Cavity Antenna with Grid-Oscillator Integrated Inside
A three-dimensional (3D) rectangular cavity antenna with an aperture size of 80âmm Ă 80âmm and a length of 16âmm, integrated with a four-MESFET transistor grid-oscillator, is designed and studied experimentally. It is found that the use of 3D antenna resonant cavity in case of small or medium gain microwave active cavity antenna leads to effective and stable power combining and radiation. The lack of lateral cavity diffraction and radiation helps in producing a directive gain of about 17âdB and radiation aperture efficiency bigger than 75% at a resonance frequency of 8.62âGHz. Good DC to RF oscillator efficiency of 26%, effective isotropic radiated power (EIRP) of 5.2âW, and SSB spectral power density of â82âdBc/Hz are found from the measured data. The 3D antenna cavity serves also as a strong metal container for the solid-state oscillator circuitry
The Cosmic Infrared Background Experiment (CIBER): Instrumentation and First Results
Ultraviolet emission from the first generation of stars in the Universe ionized the intergalactic medium in a process which was completed by z similar to 6; the wavelength of these photons has been redshifted by (1 + z) into the near infrared today and can be measured using instruments situated above the Earth's atmosphere. First flying in February 2009, the Cosmic Infrared Background ExpeRiment (CIBER) comprises four instruments housed in a single reusable sounding rocket borne payload. CIBER will measure spatial anisotropies in the extragalactic IR background caused by cosmological structure from the epoch of reionization using two broadband imaging instruments, make a detailed characterization of the spectral shape of the IR background using a low resolution spectrometer, and measure the absolute brightness of the Zodiacal light foreground with a high resolution spectrometer in each of our six science fields. The scientific motivation for CIBER and details of its first and second flight instrumentation will be discussed. First flight results on the color of the zodiacal light around 1 mu m and plans for the future will also be presented
Observations of the Near-infrared Spectrum of the Zodiacal Light with CIBER
Interplanetary dust (IPD) scatters solar radiation which results in the zodiacal light that dominates the celestial diffuse brightness at optical and near-infrared wavelengths. Both asteroid collisions and cometary ejections produce the IPD, but the relative contribution from these two sources is still unknown. The low resolution spectrometer (LRS) onboard the Cosmic Infrared Background ExpeRiment (CIBER) observed the astrophysical sky spectrum between 0.75 and 2.1 Îźm over a wide range of ecliptic latitude. The resulting zodiacal light spectrum is redder than the solar spectrum, and shows a broad absorption feature, previously unreported, at approximately 0.9 Îźm, suggesting the existence of silicates in the IPD material. The spectral shape of the zodiacal light is isotropic at all ecliptic latitudes within the measurement error. The zodiacal light spectrum, including the extended wavelength range to 2.5 Îźm using Infrared Telescope in Space (IRTS) data, is qualitatively similar to the reflectance of S-type asteroids. This result can be explained by the proximity of S-type asteroidal dust to Earth's orbit, and the relatively high albedo of asteroidal dust compared with cometary dust
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