8,766 research outputs found
Analytical screening of low emissions, high performance duct burners for supersonic cruise aircraft engines
An analytical screening study was conducted to identify duct burner concepts capable of providing low emissions and high performance in advanced supersonic engines. Duct burner configurations ranging from current augmenter technology to advanced concepts such as premix-prevaporized burners were defined. Aerothermal and mechanical design studies provided the basis for screening these configurations using the criteria of emissions, performance, engine compatibility, cost, weight and relative risk. Technology levels derived from recently defined experimental low emissions main burners are required to achieve both low emissions and high performance goals. A configuration based on the Vorbix (Vortex burning and mixing) combustor concept was analytically determined to meet the performance goals and is consistent with the fan duct envelope of a variable cycle engine. The duct burner configuration has a moderate risk level compatible with the schedule of anticipated experimental programs
Measurement of the Higgs Boson Mass with a Linear e+e- Collider
The potential of a linear e+e- collider operated at a centre-of-mass energy
of 350 GeV is studied for the measurement of the Higgs boson mass. An
integrated luminosity of 500 fb-1 is assumed. For Higgs boson masses of 120,
150 and 180 GeV the uncertainty on the Higgs boson mass measurement is
estimated to be 40, 65 and 70 MeV, respectively. The effects of beam related
systematics, namely a bias in the beam energy measurement, the beam energy
spread and the luminosity spectrum due to beamstrahlung, on the precision of
the Higgs boson mass measurement are investigated. In order to keep the
systematic uncertainty on the Higgs boson mass well below the level of the
statistical error, the beam energy measurement must be controlled with a
relative precision better than 10-4.Comment: 19 pages, 10 Figure
Identification problems of muon and electron events in the Super-Kamiokande detector
In the measurement of atmospheric nu_e and nu_mu fluxes, the calculations of
the Super Kamiokande group for the distinction between muon-like and
electronlike events observed in the water Cerenkov detector have initially
assumed a misidentification probability of less than 1 % and later 2 % for the
sub-GeV range. In the multi-GeV range, they compared only the observed
behaviors of ring patterns of muon and electron events, and claimed a 3 %
mis-identification. However, the expressions and the calculation method do not
include the fluctuation properties due to the stochastic nature of the
processes which determine the expected number of photoelectrons (p.e.) produced
by muons and electrons. Our full Monte Carlo (MC) simulations including the
fluctuations of photoelectron production show that the total mis-identification
rate for electrons and muons should be larger than or equal to 20 % for sub-GeV
region. Even in the multi-GeV region we expect a mis-identification rate of
several % based on our MC simulations taking into account the ring patterns.
The mis-identified events are mostly of muonic origin.Comment: 17 pages, 12 figure
Paleoelevation estimates for the northern and central protoâBasin and Range from carbonate clumped isotope thermometry
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99057/1/tect20016.pd
Antimatter and Matter Production in Heavy Ion Collisions at CERN (The NEWMASS Experiment NA52)
Besides the dedicated search for strangelets NA52 measures light
(anti)particle and (anti)nuclei production over a wide range of rapidity.
Compared to previous runs the statistics has been increased in the 1998 run by
more than one order of magnitude for negatively charged objects at different
spectrometer rigidities. Together with previous data taking at a rigidity of
-20 GeV/c we obtained 10^6 antiprotons 10^3 antideuterons and two antihelium3
without centrality requirements. We measured nuclei and antinuclei
(p,d,antiprotons, antideuterons) near midrapidity covering an impact parameter
range of b=2-12 fm. Our results strongly indicate that nuclei and antinuclei
are mainly produced via the coalescence mechanism. However the centrality
dependence of the antibaryon to baryon ratios show that antibaryons are
diminished due to annihilation and breakup reactions in the hadron dense
environment. The volume of the particle source extracted from coalescence
models agrees with results from pion interferometry for an expanding source.
The chemical and thermal freeze-out of nuclei and antinuclei appear to coincide
with each other and with the thermal freeze-out of hadrons.Comment: 12 pages, 8 figures, to appear in the proceedings of the conference
on 'Fundamental Issues in Elementary Matter' Bad Honnef, Germany, Sept.
25-29, 200
3',5'-Cyclic Adenosine Monophosphate- and Ca2+-Calmodulin-Dependent Endogenous Protein Phosphorylation Activity in Membranes of the Bovine Chromaffin Secretory Vesicles: Identification of Two Phosphorylated Components as Tyrosine Hydroxylase and Protein Kinase Regulatory Subunit Type II
Abstract: Membranes of the secretory vesicles from bovine adrenal medulla were investigated for the presence of the endogenous protein phosphorylation activity. Seven phosphoprotein bands in the molecular weight range of 250,000 to 30,000 were observed by means of the sodium dodecyl sulphate electrophoresis and autoradiography. On the basis of the criteria of molecular weight, selective stimulation of the phosphorylation by cyclic AMP (as compared with cyclic GMP) and immunoprecipitation by specific antibodies, band 5 (molecular weight 60,300) was found to represent the phosphorylated form of the secretory vesicle-bound tyrosine hydroxylase. The electrophoretic mobility, the stimulatory and inhibitory effects of cyclic AMP in presence of Mg2+ and Zn,2+ respectively, and immunoreactivity toward antibodies showed band 6 to contain two forms of the regulatory subunits of the type II cyclic AMP-dependent protein kinase, distinguishable by their molecular weights (56,000 and 52,000, respectively). Phosphorylation of band 7 (molecular weight 29,800) was stimulated about 2 to 3 times by Ca2+ and calmodulin in the concentration range of both agents believed to occur in the secretory tissues under physiological conditions
Orbital order in the low-dimensional quantum spin system TiOCl probed by ESR
We present electron spin resonance data of Ti (3) ions in single
crystals of the novel layered quantum spin magnet TiOCl. The analysis of the g
tensor yields direct evidence that the d_{xy} orbital from the t_{2g} set is
predominantly occupied and owing to the occurrence of orbital order a linear
spin chain forms along the crystallographic b axis. This result corroborates
recent theoretical LDA+U calculations of the band structure. The temperature
dependence of the parameters of the resonance signal suggests a strong coupling
between spin and lattice degrees of freedom and gives evidence for a transition
to a nonmagnetic ground state at 67 K.Comment: revised version, accepted for publication in Phys. Rev. B, Rapid Com
Total aerosol effect: forcing or radiative flux perturbation
Uncertainties in aerosol radiative forcings, especially those associated with clouds, contribute to a large extent to uncertainties in the total anthropogenic forcing. The interaction of aerosols with clouds and radiation introduces feedbacks which can affect the rate of precipitation formation. In former assessments of aerosol radiative forcings, these effects have not been quantified. Also, with global aerosol-climate models simulating interactively aerosols and cloud microphysical properties, a quantification of the aerosol forcings in the traditional way is difficult to define properly. Here we argue that fast feedbacks should be included because they act quickly compared with the time scale of global warming. We show that for different forcing agents (aerosols and greenhouse gases) the radiative forcings as traditionally defined agree rather well with estimates from a method, here referred to as radiative flux perturbations (RFP), that takes these fast feedbacks and interactions into account. Based on our results, we recommend RFP as a valid option to compare different forcing agents, and to compare the effects of particular forcing agents in different models
Tunable nano Peltier cooling device from geometric effects using a single graphene nanoribbon
Based on the phenomenon of curvature-induced doping in graphene we propose a
class of Peltier cooling devices, produced by geometrical effects, without
gating. We show how a graphene nanorib- bon laid on an array of curved nano
cylinders can be used to create a targeted and tunable cooling device. Using
two different approaches, the Nonequlibrium Green's Function (NEGF) method and
experimental inputs, we predict that the cooling power of such a device can
approach the order of kW/cm2, on par with the best known techniques using
standard superlattice structures. The struc- ture proposed here helps pave the
way toward designing graphene electronics which use geometry rather than gating
to control devices.Comment: 12 pages, 5 figure
Anthropogenic aerosol forcing - insights from multiple estimates from aerosol-climate models with reduced complexity
This study assesses the change in anthropogenic aerosol forcing from the mid-1970s to the mid-2000s. Both decades had similar global-mean anthropogenic aerosol optical depths but substantially different global distributions. For both years, we quantify (i) the forcing spread due to model-internal variability and (ii) the forcing spread among models. Our assessment is based on new ensembles of atmosphere-only simulations with five state-of-the-art Earth system models. Four of these models will be used in the sixth Coupled Model Intercomparison Project (CMIP6; Eyring et al., 2016). Here, the complexity of the anthropogenic aerosol has been reduced in the participating models. In all our simulations, we prescribe the same patterns of the anthropogenic aerosol optical properties and associated effects on the cloud droplet number concentration. We calculate the instantaneous radiative forcing (RF) and the effective radiative forcing (ERF). Their difference defines the net contribution from rapid adjustments. Our simulations show a model spread in ERF from -0.4 to -0.9 W m(-2). The standard deviation in annual ERF is 0.3 W m(-2), based on 180 individual estimates from each participating model. This result implies that identifying the model spread in ERF due to systematic differences requires averaging over a sufficiently large number of years. Moreover, we find almost identical ERFs for the mid-1970s and mid-2000s for individual models, although there are major model differences in natural aerosols and clouds. The model-ensemble mean ERF is -0.54 W m(-2) for the pre-industrial era to the mid-1970s and -0.59 W m(-2) for the pre-industrial era to the mid-2000s. Our result suggests that comparing ERF changes between two observable periods rather than absolute magnitudes relative to a poorly constrained pre-industrial state might provide a better test for a model's ability to represent transient climate changes.Peer reviewe
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