9,462 research outputs found
Simulation of a Cross Section and Mass Measurement of a SM Higgs Boson in the H->WW->lvlv Channel at the LHC
The potential to discover a Standard-Model-like Higgs boson at the LHC in the
mass range from 150-180 GeV, decaying into a pair of W bosons with subsequent
leptonic decays, has been established during the last 10 years. Assuming that
such a signal will eventually be observed, the analysis described in this paper
investigates how accurate the signal cross section can be measured and how the
observable lepton pt spectra can be used to constrain the mass of the Higgs
boson. Combining the signal cross section with the analysis of the lepton pt
spectra and assuming the SM Higgs cross section is known with an accuracy of
+-5%, our study indicates that an integrated luminosity of about 10 fb-1 allows
to measure the mass of a SM Higgs boson with an accuracy between 2 and 2.5 GeV.Comment: 19 pages, 11 Figure
Lepton flavor violating Higgs decays and unparticle physics
We predict the branching ratios of the lepton flavor violating Higgs decays
H^0->e^{\pm} \mu^{\pm}, H^0-> e^{\pm} \tau^{\pm} and H^0->\mu^{\pm} \tau^{\pm}
in the case that the lepton flavor violation is carried by the scalar
unparticle mediation. We observe that their branching ratios are strongly
sensitive to the unparticle scaling dimension and they can reach to the values
of the order of , for the heavy lepton flavor case and for the small
values of the scaling dimension.Comment: 12 pages, 7 Figures, 1 Table
Noise of the SR-6 propeller model at 2 deg and 4 deg angles of attack
The noise generated by supersonic-tip-speed propellers creates a cabin noise problem for future airplanes powered by these propellers. Noise of a number of propeller models were measured in the NASA Lewis 8- by 6-Foot Wind Tunnel with flow parallel to the propeller axis. In flight, as a result of the induced upwash from the airplane wing, the propeller is at an angle of attack with respect to the incoming flow. Therefore, the 10-blade SR-6 propeller was operated at angle of attack to determine its noise behavior. Higher blade passage tones were observed for the propeller operating at angle of attack in a 0.6 axial Mach number flow. The noise increase was not symmetrical, with one wall of the wind tunnel showing a larger noise increase than the other wall. No noise increase was observed at angle of attack in a 0.8 axial Mach number flow. For this propeller the dominance of thickness noise, which does not increase with angle of attack, explains the lack of noise increase at the higher 0.8 Mach number
The effect of swirl recovery vanes on the cruise noise of an advanced propeller
The SR-7A propeller was acoustically tested with and without downstream swirl recovery vanes to determine if any extra noise was caused by the interaction of the propeller wakes and vortices with these vanes. No additional noise was observed at the cruise condition over the angular range tested. The presence of the swirl recovery vanes did unload the propeller and some small peak noise reductions were observed from lower propeller loading noise. The propeller was also tested alone to investigate the behavior of the peak propeller noise with helical tip Mach number. As observed before on other propellers, the peak noise first rose with helical tip Mach number and then leveled off or decreased at higher helical tip Mach numbers. Detailed pressure-time histories indicate that a portion of the primary pressure pulse is progressively cancelled by a secondary pulse as the helical tip Mach number is increased. This cancellation appears to be responsible for the peak noise behavior at high helical tip Mach numbers
Detailed noise measurements on the SR-7A propeller: Tone behavior with helical tip Mach number
Detailed noise measurements were taken on the SR-7A propeller to investigate the behavior of the noise with helical tip Mach number and then to level off as Mach number was increased further. This behavior was further investigated by obtaining detailed pressure-time histories of data. The pressure-time histories indicate that a portion of the primary pressure pulse is progressively cancelled by a secondary pulse which results in the noise leveling off as the helical tip Mach number is increased. This second pulse appears to originate on the same blade as the primary pulse and is in some way connected to the blade itself. This leaves open the possibility of redesigning the blade to improve the cancellation; thereby, the propeller noise is reduced
A preliminary comparison between the SR-6 propeller noise in flight and in a wind tunnel
High speed turboprops offer an attractive candidate for aircraft because of their high propulsive efficiency. However, one of the possible problems associated with these propellers is their high noise level at cruise condition that may create a cabin environment problem. Models of these propellers were tested for acoustics in the 8 by 6-foot wind tunnel and on the Jet Star airplane. Comparisons between the airplane and wind tunnel data for the SR-6 propeller are shown. The comparison of maximum blade passing tone variation with helical tip Mach number between the tunnel and flight data was good when corrected to the same test conditions. Directivity comparisons also showed fairly good agreement. These good comparisons indicate that the wind tunnel is a viable location for measuring the blade passage tone noise of these propellers
Noise of fan designed to reduce stator lift fluctuations
An existing fan stage was redesigned to reduce stator lift fluctuations and was acoustically tested at three nozzle sizes for reduced noise generation. The lift fluctuations on the stator were reduced by increasing the stator cord, adjusting incidence angles, and adjusting the rotor velocity diagrams. Broadband noise levels were signficantly reduced in the middle to high frequencies. Blade passage tone sound power was not lessened, but decreases in the harmonics were observed. Aerodynamic improvements in both performance and efficiency were obtained
Noise of the 10-bladed 60 deg swept SR-5 propeller in a wind tunnel
Noise generated by supersonic helical tip speed propellers is a possible cabin environment problem for future airplanes powered by these propellers. Noise characteristics of one of these propellers, designated SR-5, are presented. A matrix of tests was conducted to provide as much acoustic information as possible. During aerodynamic testing it was discovered that the propeller had an aeroelastic instability which prevented testing the propeller at its design advance ratio of 4.08 at axial Mach numbers over 0.7. Plots of the variation of the maximum blade passage tone with helical tip Mach number indicate that, at higher helical tip Mach numbers, the propeller operated on sharply increasing portion of the noise curve; therefore, extrapolations to the design condition would not be accurate. A possible extrapolation indicated that SR-5 at its design point should be quieter than SR-3 at its design point. Directivity plots at the higher helical tip Mach numbers indicate a lobed directivity pattern as was observed previously on the SR-3 propeller
SILAC for biomarker discovery
Stable isotope labeling in cell culture (SILAC) has been employed in mass spectrometry-based proteomics for nearly a decade. This method is based on cells in culture metabolically incorporating isotope-coded essential amino acids and allows the quantification of global protein populations to identify characteristic changes. Variations of this technique developed over the years allow the application of SILAC not only to cell culture-derived samples but also to tissues and human specimens, making this powerful technique amenable to clinically relevant samples. In this review we provide an overview of different SILAC-derived methods and their use in the identification and development of biomarkers
Tissue specific labeling in proteomics
Mass spectrometry-based proteomics is a powerful tool for identifying and quantifying proteins in biological samples. While it is routinely used for the characterization of simple cell line systems, the analysis of the cell specific proteome in multicellular organisms and tissues poses a significant challenge. Isolating a subset of cells from tissues requires mechanical and biochemical separation or sorting, a process which can alter cellular signaling, and thus, the composition of the proteome. Recently, several approaches for cell selective labeling of proteins, that include bioorthogonal amino acids, biotinylating enzymes, and genetic tools, have been developed. These tools facilitate the selective labeling of proteins, their interactome, or of specific cell types within a tissue or an organism, while avoiding the difficult and contamination-prone biochemical separation of cells from the tissue. In this review, we give an overview of existing techniques and their application in cell culture models and whole animals
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