The dipole anisotropy of AllWISE galaxies Rameez, M; Mohayaee, R; Sarkar, S ...
Monthly notices of the Royal Astronomical Society,
06/2018, Letnik:
477, Številka:
2
Journal Article
Recenzirano
Abstract
We determine the dipole in the WISE (Wide Infrared Satellite Explorer) galaxy catalogue. After reducing star contamination to $<\!0.1\hbox{ per cent}$ by rejecting sources with high apparent ...motion and those close to the Galactic plane, we eliminate low redshift sources to suppress the non-kinematic, clustering dipole. We remove sources within ±5° of the supergalactic plane, as well as those within 1ʺ of 2MRS sources at redshift z < 0.03. We enforce cuts on the source angular extent to preferentially select distant ones. As we progress along these steps, the dipole converges in direction to within 5° of the Cosmic Microwave Background (CMB) dipole and its magnitude also progressively reduces but stabilizes at ∼0.012, corresponding to a velocity >1000 km s−1 if it is solely of kinematic origin. However, previous studies have shown that only ${\sim }70\hbox{ per cent}$ of the velocity of the Local Group as inferred from the CMB dipole is due to sources at z < 0.03. We examine the Dark Sky simulations to quantify the prevalence of such environments and find that <2.1 per cent of Milky Way-like observers in a ΛCDM universe should observe the bulk flow (>240 km s−1 extending to z > 0.03) that we do. We construct mock catalogues in the neighbourhood of such peculiar observers in order to mimic our final galaxy selection and quantify the residual clustering dipole. After subtracting this, the remaining dipole is 0.0048 ± 0.0022, corresponding to a velocity of 420 ± 213 km s−1, which is consistent with the CMB. However, the sources (at z > 0.03) of such a large clustering dipole remain to be identified.
The GRAPES-3 extensive air shower (EAS) array has been designed to study cosmic rays from 10
13
–10
16
eV. It employs 400 scintillator detectors spread across 25,000 m
2
, mainly of cone-type and ...fiber-type, each covering a 1 m
2
area. These detectors record EAS particle densities and arrival times, which are crucial for determining primary particle energy and direction. A decade (2013–2022) of EAS data is analyzed to investigate the dependence of particle densities on ambient temperature and atmospheric pressure. Notably, ambient temperature exhibits a delayed response, with a more pronounced delay in fiber-type detectors, while cone-type detectors exhibit a higher observed temperature coefficient. In contrast, atmospheric pressure instantly and uniformly affects both detector types, with Monte Carlo simulations backing the observed pressure coefficient. These findings established a reliable pressure coefficient for EAS within this distinctive energy range and contributed to the refinement of correction algorithms, ultimately improving particle density precision for more accurate shower parameter estimates.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The study was carried out to understand the effect of silver–silica nanocomposite (Ag–SiO2NC) on the cell wall integrity, metabolism and genetic stability of Pseudomonas aeruginosa, a multiple ...drug‐resistant bacterium. Bacterial sensitivity towards antibiotics and Ag–SiO2NC was studied using standard disc diffusion and death rate assay, respectively. The effect of Ag–SiO2NC on cell wall integrity was monitored using SDS assay and fatty acid profile analysis, while the effect on metabolism and genetic stability was assayed microscopically, using CTC viability staining and comet assay, respectively. Pseudomonas aeruginosa was found to be resistant to β‐lactamase, glycopeptidase, sulfonamide, quinolones, nitrofurantoin and macrolides classes of antibiotics. Complete mortality of the bacterium was achieved with 80 μg ml−1 concentration of Ag–SiO2NC. The cell wall integrity reduced with increasing time and reached a plateau of 70% in 110 min. Changes were also noticed in the proportion of fatty acids after the treatment. Inside the cytoplasm, a complete inhibition of electron transport system was achieved with 100 μg ml−1 Ag–SiO2NC, followed by DNA breakage. The study thus demonstrates that Ag–SiO2NC invades the cytoplasm of the multiple drug‐resistant P. aeruginosa by impinging upon the cell wall integrity and kills the cells by interfering with electron transport chain and the genetic stability.
Significance and Impact of Study
Although the synthesis, structural characteristics and biofunction of silver nanoparticles are well understood, their application in antimicrobial therapy is still at its infancy as only a small number of microorganisms are tested to be sensitive to nanoparticles. A thorough knowledge of the mode of interaction of nanoparticles with bacteria at subcellular level is mandatory for any clinical application. The present study deals with the interactions of Ag–SiO2NC with the cell wall integrity, metabolism and genetic stability of Pseudomonas aeruginosa, which would contribute substantially in strengthening the therapeutic applications of silver nanoparticles.
Significance and Impact of Study: Although the synthesis, structural characteristics and biofunction of silver nanoparticles are well understood, their application in antimicrobial therapy is still at its infancy as only a small number of microorganisms are tested to be sensitive to nanoparticles. A thorough knowledge of the mode of interaction of nanoparticles with bacteria at subcellular level is mandatory for any clinical application. The present study deals with the interactions of Ag–SiO2NC with the cell wall integrity, metabolism and genetic stability of Pseudomonas aeruginosa, which would contribute substantially in strengthening the therapeutic applications of silver nanoparticles.
We present the measurement of the cosmic ray proton spectrum from 50 TeV to 1.3 PeV using 7.81×10^{6} extensive air shower events recorded by the ground-based GRAPES-3 experiment between 1 January ...2014 and 26 October 2015 with a live time of 460 day. Our measurements provide an overlap with direct observations by satellite and balloon-based experiments. The electromagnetic and muon components in the shower were measured by a dense array of plastic scintillator detectors and a tracking muon telescope, respectively. The relative composition of the proton primary from the air shower data containing all primary particles was extracted using the multiplicity distribution of muons which is a sensitive observable for mass composition. The observed proton spectrum suggests a spectral hardening at ∼166 TeV and disfavors a single power law description of the spectrum up to the Knee energy (∼3 PeV).
Abstract
GRAPES-3 is a mid-altitude (2200 m) and near-equatorial (11.°4N) air shower array, overlapping in its field of view for cosmic-ray observations with experiments that are located in the ...Northern and Southern Hemispheres. We analyze a sample of 3.7 × 10
9
cosmic-ray events collected by the GRAPES-3 experiment between 2013 January 1 and 2016 December 31 with a median energy of ∼16 TeV for study of small-scale (<60°) angular-scale anisotropies. We observed two structures, labeled A and B, that deviate from the expected isotropic distribution of cosmic rays in a statistically significant manner. Structure A spans 50°–80° in R.A. and from −15° to 30° in decl. The relative excess observed in structure A is at the level of (6.5 ± 1.3) × 10
−4
with a statistical significance of 6.8 standard deviations. Structure B is observed in the R.A. range 110°–140° and at decl. from −10° to 30°. The relative excess observed in this region is at the level of (4.9 ± 1.4) × 10
−4
with a statistical significance of 4.7 standard deviations. These structures are consistent with those reported by Milagro, ARGO-YBJ, and HAWC. These observations could provide a better understanding of the sources of cosmic rays, their propagation, and the magnetic structures in our Galaxy.
The ability to non-invasively measure metabolic oxygen flux is a very important tool for physiologists interested in a variety of questions ranging from basic metabolism, growth/development, and ...stress adaptation. Technologies for measuring oxygen concentration near the surface of cells/tissues include electrochemical and optical techniques. A wealth of knowledge was gained using these tools for quantifying real-time physiology. Fiber-optic microprobes (optrodes) have recently been developed for measuring oxygen in a variety of biomedical and environmental applications. We have adopted the use of these optical microsensors for plant physiology applications, and used the microsensors in an advanced sensing modality known as self-referencing. Self-referencing is a non-invasive microsensor technique used for measuring real-time flux of analytes. This paper demonstrates the use of optical microsensors for non-invasively measuring rhizosphere oxygen flux associated with respiration in plant roots, as well as boundary layer oxygen flux in phytoplankton mats. Highly sensitive/selective optrodes had little to no hysteresis/calibration drift during experimentation, and an extremely high signal-to-noise ratio. We have used this new tool to compare various aspects of rhizosphere oxygen flux for roots of Glycine max, Zea mays, and Phaseolus vulgaris, and also mapped developmentally relevant profiles and distinct temporal patterns. We also characterized real-time respiratory patterns during inhibition of cytochrome and alternative oxidase pathways via pharmacology. Boundary layer oxygen flux was also measured for a phytoplankton mat during dark:light cycling and exposure to pharamacological inhibitors. This highly sensitive technology enables non-invasive study of oxygen transport in plant systems under physiologically relevant conditions.
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•The CPs based CEs and their current trends are reviewed upto date for DSSCs.•The desired properties of CE are briefly explained.•Photovoltaic performance of various CPs as CEs for ...DSSC are tabulated.•The various evaluation techniques for CE are also discussed.
Conducting polymers (CPs) have been widely investigated and applied in various applications such as sensors, supercapacitors, energy storage devices, dye-sensitized solar cells (DSSCs) and others. They are pseudo-capacitive materials and can undergo fast redox reactions. Counter electrode (CE) is an important component in DSSCs. The counter electrode function as an electron transfer agent as well as the regenerator of redox couple. So far various methods and materials are used to prepare different counter electrodes. This paper reviews the conducting polymers and their composites as counter electrodes which offer a valuable insight to find out the appropriate alternative to costly platinum (Pt) counter electrode for DSSCs. Furthermore, it also outlines the desirable properties for good counter electrode materials and their evaluation methods such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Tafel polarization and chronoamperometry with photovoltaic performance studies for DSSCs.
The focal-plane cameras of γ-ray telescopes frequently use light concentrators in front of the light sensors. The purpose of these concentrators is to increase the effective area of the camera as ...well as to reduce the stray light coming at large incident angles. These light concentrators are usually based on the Winston cone design. In this contribution we present the design of a hexagonal hollow light concentrator with a lateral profile optimized using a cubic Bézier function to achieve a higher collection efficiency in the angular region of interest. The design presented here is optimized for a Davies–Cotton telescope with a primary mirror of about 4m in diameter and a focal length of 5.6m. The described concentrators are part of an innovative camera made up of silicon-photomultiplier sensors, although a similar approach can be used for other sizes of single-mirror telescopes with different camera sensors, including photomultipliers. The challenge of our approach is to achieve a cost-effective design suitable for standard industrial production of both the plastic concentrator substrate and the reflective coating. At the same time we maximize the optical performance. In this paper we also describe the optical set-up to measure the absolute collection efficiency of the light concentrators and demonstrate our good understanding of the measured data using a professional ray-tracing simulation.
Previous studies have found our velocity in the rest frame of radio galaxies at high redshift to be much larger than that inferred from the dipole anisotropy of the cosmic microwave background. We ...construct a full sky catalogue, NVSUMSS, by merging the NRAO VLA Sky Survey and the Sydney University Molonglo Sky Survey catalogues and removing local sources by various means including cross-correlating with the 2MASS Redshift Survey catalogue. We take into account both aberration and Doppler boost to deduce our velocity from the hemispheric number count asymmetry, as well as via a three-dimensional linear estimator. Both its magnitude and direction depend on cuts made to the catalogue, e.g. on the lowest source flux; however these effects are small. From the hemispheric number count asymmetry we obtain a velocity of 1729 ± 187 km s^−1, i.e. about four times larger than that obtained from the cosmic microwave background dipole, but close in direction, towards RA=149° ± 2°, Dec. = −17° ± 12°. With the three-dimensional estimator, the derived velocity is 1355 ± 174 km s^−1 towards RA = 141° ± 11°, Dec. = −9° ± 10°. We assess the statistical significance of these results by comparison with catalogues of random distributions, finding it to be 2.81σ (99.75 per cent confidence).
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