6,349 research outputs found
Constraining the Dark Matter decay lifetime with very deep observations of the Perseus cluster with the MAGIC telescopes
We present preliminary results on Dark Matter searches from observations of
the Perseus galaxy cluster with the MAGIC Telescopes. MAGIC is a system of two
Imaging Atmospheric Cherenkov Telescopes located in the Canary island of La
Palma, Spain. Galaxy clusters are the largest known gravitationally bound
structures in the Universe, with masses of ~10^15 Solar masses. There is strong
evidence that galaxy clusters are Dark Matter dominated objects, and therefore
promising targets for Dark Matter searches, particularly for decay signals.
MAGIC has taken almost 300 hours of data on the Perseus Cluster between 2009
and 2015, the deepest observational campaign on any galaxy cluster performed so
far in the very high energy range of the electromagnetic spectrum. We analyze
here a small sample of this data and search for signs of dark matter in the
mass range between 100 GeV and 20 TeV. We apply a likelihood analysis optimized
for the spectral and morphological features expected in the dark matter decay
signals. This is the first time that a dedicated Dark Matter optimization is
applied in a MAGIC analysis, taking into account the inferred Dark Matter
distribution of the source. The results with the full dataset analysis will be
published soon by the MAGIC Collaboration
Ionizing Radiation, an Instrument in Chemical Evolution Studies: Scope and Perspectives
The study of synthesis and stability of molecules in different environments itâs been part of chemistry evolution and origin of life studies for more than 70 years. Various kinds of ionizing radiation have been analyzed as possible sources of energy for the transformations undergone by the first organic molecules. Now experimental and computational simulation approaches continue with different groups of organic molecules, in search for more information that help us to understand and reconstruct somehow the mechanisms that toke place on early Earth and space. In that line, this paper presents first approach of keto acids stability to ionizing radiation, an interesting group of molecules involved in the Krebs cycle and glycolysis. Preliminary results obtained by HPLC/UV analysis of irradiating aqueous solutions of 5 keto acids ranging from 3 to 6 carbons with a 60Co gamma ray source, using doses up to 53 kGy, show different stabilities and a general tendency of shifting the keto-enol equilibrium to the enol tautomer before decomposition
Using a Floating-Gate MOS Transistor as a Transducer in a MEMS Gas Sensing System
Floating-gate MOS transistors have been widely used in diverse analog and digital applications. One of these is as a charge sensitive device in sensors for pH measurement in solutions or using gates with metals like Pd or Pt for hydrogen sensing. Efforts are being made to monolithically integrate sensors together with controlling and signal processing electronics using standard technologies. This can be achieved with the demonstrated compatibility between available CMOS technology and MEMS technology. In this paper an in-depth analysis is done regarding the reliability of floating-gate MOS transistors when charge produced by a chemical reaction between metallic oxide thin films with either reducing or oxidizing gases is present. These chemical reactions need temperatures around 200 °C or higher to take place, so thermal insulation of the sensing area must be assured for appropriate operation of the electronics at room temperature. The operation principle of the proposal here presented is confirmed by connecting the gate of a conventional MOS transistor in series with a Fe2O3 layer. It is shown that an electrochemical potential is present on the ferrite layer when reacting with propane
Factorial and Economic Evaluation of an Aqueous Two-Phase Partitioning Pilot Plant for Invertase Recovery From Spent Brewery Yeast
Aqueous two-phase systems (ATPS) have been reported as an attractive biocompatible extraction system for recovery and purification of biological products. In this work, the implementation, characterization, and optimization (operational and economic) of invertase extraction from spent brewery yeast in a semi-automatized pilot plant using ATPS is reported. Gentian violet was used as tracer for the selection of phase composition through phase entrainment minimization. Yeast suspension was chosen as a complex cell matrix model for the recovery of the industrial relevant enzyme invertase. Flow rates of phases did not have an effect, given that a bottom continuous phase is given, while load of sample and number of agitators improved the recovery of the enzyme. The best combination of factors reached a recovery of 129.35 Âą 2.76% and a purification factor of 4.98 Âą 1.10 in the bottom phase of a PEG-Phosphate system, also resulting in the removal of inhibitor molecules increasing invertase activity as reported by several other authors. Then, an economic analysis was performed to study the production cost of invertase analyzing only the significant parameters for production. Results indicate that the parameters being analyzed only affect the production cost per enzymatic unit, while variations in the cost per batch are not significant. Moreover, only the sample load is significant, which, combined with operational optimization results, gives the same optimal result for operation, maximizing recovery yield (15% of sample load and 1 static mixer). Overall res ults of these case studies show continuous pilot-scale ATPS as a viable and reproducible extraction/purification system for high added-value biological compounds
A search for spectral hysteresis and energy-dependent time lags from X-ray and TeV gamma-ray observations of Mrk 421
Blazars are variable emitters across all wavelengths over a wide range of
timescales, from months down to minutes. It is therefore essential to observe
blazars simultaneously at different wavelengths, especially in the X-ray and
gamma-ray bands, where the broadband spectral energy distributions usually
peak.
In this work, we report on three "target-of-opportunity" (ToO) observations
of Mrk 421, one of the brightest TeV blazars, triggered by a strong flaring
event at TeV energies in 2014. These observations feature long, continuous, and
simultaneous exposures with XMM-Newton (covering X-ray and optical/ultraviolet
bands) and VERITAS (covering TeV gamma-ray band), along with contemporaneous
observations from other gamma-ray facilities (MAGIC and Fermi-LAT) and a number
of radio and optical facilities. Although neither rapid flares nor significant
X-ray/TeV correlation are detected, these observations reveal subtle changes in
the X-ray spectrum of the source over the course of a few days. We search the
simultaneous X-ray and TeV data for spectral hysteresis patterns and time
delays, which could provide insight into the emission mechanisms and the source
properties (e.g. the radius of the emitting region, the strength of the
magnetic field, and related timescales). The observed broadband spectra are
consistent with a one-zone synchrotron self-Compton model. We find that the
power spectral density distribution at Hz from the
X-ray data can be described by a power-law model with an index value between
1.2 and 1.8, and do not find evidence for a steepening of the power spectral
index (often associated with a characteristic length scale) compared to the
previously reported values at lower frequencies.Comment: 45 pages, 15 figure
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
Search for anomalous t t-bar production in the highly-boosted all-hadronic final state
A search is presented for a massive particle, generically referred to as a
Z', decaying into a t t-bar pair. The search focuses on Z' resonances that are
sufficiently massive to produce highly Lorentz-boosted top quarks, which yield
collimated decay products that are partially or fully merged into single jets.
The analysis uses new methods to analyze jet substructure, providing
suppression of the non-top multijet backgrounds. The analysis is based on a
data sample of proton-proton collisions at a center-of-mass energy of 7 TeV,
corresponding to an integrated luminosity of 5 inverse femtobarns. Upper limits
in the range of 1 pb are set on the product of the production cross section and
branching fraction for a topcolor Z' modeled for several widths, as well as for
a Randall--Sundrum Kaluza--Klein gluon. In addition, the results constrain any
enhancement in t t-bar production beyond expectations of the standard model for
t t-bar invariant masses larger than 1 TeV.Comment: Submitted to the Journal of High Energy Physics; this version
includes a minor typo correction that will be submitted as an erratu
Combined search for the quarks of a sequential fourth generation
Results are presented from a search for a fourth generation of quarks
produced singly or in pairs in a data set corresponding to an integrated
luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in
2011. A novel strategy has been developed for a combined search for quarks of
the up and down type in decay channels with at least one isolated muon or
electron. Limits on the mass of the fourth-generation quarks and the relevant
Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a
simple extension of the standard model with a sequential fourth generation of
fermions. The existence of mass-degenerate fourth-generation quarks with masses
below 685 GeV is excluded at 95% confidence level for minimal off-diagonal
mixing between the third- and the fourth-generation quarks. With a mass
difference of 25 GeV between the quark masses, the obtained limit on the masses
of the fourth-generation quarks shifts by about +/- 20 GeV. These results
significantly reduce the allowed parameter space for a fourth generation of
fermions.Comment: Replaced with published version. Added journal reference and DO
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