2,685 research outputs found
Molecular dynamics simulations for hydrogen adsorption in low energy collisions with carbon and boron-nitride nanotubes
Rotational and vibrational effects on the energy loss of hydrogen colliding on glycine at low irradiation energies
Theoretical study of the formation of C<sub>18</sub>H and C<sub>18</sub>H<sub>2</sub> molecules by low energy irradiation with atomic and molecular hydrogen
Joint multifractal analysis of air temperature, relative humidity and reference evapotranspiration in the middle zone of the Guadalquivir river valley
Previous works have analysed the relationship existing between reference
evapotranspiration (ET0) and other climatic variables under a one-at-a-time
perturbation condition. However, due to the physical relationships between
these climatic variables is advisable to study their joint influence on ET0.
The box-counting joint multifractal algorithm describes the relations between
variables using relevant information extracted from the data singularities.
This work investigated the use of this algorithm to describe the simultaneous
behaviour of ET0, calculated by means of Penman-Monteith (PM) equation, and
relative humidity (RH) and air temperature (T), influencing on it in the middle
zone of the Guadalquivir river valley, Andalusia, southern Spain. The studied
cases were grouped according to the fractal dimension values, which were
related to their probability of occurrence. The most likely cases were linked
to smooth behaviour and weak dependence between variables, both circumstances
were detected in the local multifractal analysis. For these cases, the rest of
Penman Monteith (PM) equation variables, neither the T nor the RH, seemed to
influence on ET0 determination, especially when low T values were involved. By
contrast, the least frequent cases were those with variables showing high
fluctuations and strong relationship between them. In these situations, when T
is low, the ET0 is affected by the rest of PM equation variables. This fact
confirmed T as main driver of ET0 because the higher T values the lesser
influence of other climate variables on ET0. Joint multifractal analysis shows
some limitations when it is applied to large number of variables, the results
reported are promising and suggest the convenience of exploring the
relationships between ET0 and other climatic variables not considered here with
this framework such as wind speed and net radiation.Comment: 40 pages, 10 figure
Superplasticity and Joining of Zirconia-Based Ceramics
Steady-state creep and joining of alumina/zirconia composites containing alumina volume fractions of 20, 60, and 85% have been investigated between 1,250 and 1,350 C. Superplasticity of these compounds is controlled by grain-boundary sliding and the creep rate is a function of alumina volume fraction, not grain size. Using the principles of superplasticity, pieces of the composite have been joined by applying the stress required to achieve 5 to 10% strain to form a strong interface at temperatures as low as 1,200 C
Measurement of the B0_s semileptonic branching ratio to an orbitally excited D_s** state, Br(B0_s -> Ds1(2536) mu nu)
In a data sample of approximately 1.3 fb-1 collected with the D0 detector
between 2002 and 2006, the orbitally excited charm state D_s1(2536) has been
observed with a measured mass of 2535.7 +/- 0.6 (stat) +/- 0.5 (syst) MeV via
the decay mode B0_s -> D_s1(2536) mu nu X. A first measurement is made of the
branching ratio product Br(b(bar) -> D_s1(2536) mu nu X).Br(D_s1(2536)->D*
K0_S). Assuming that D_s1(2536) production in semileptonic decay is entirely
from B0_s, an extraction of the semileptonic branching ratio Br(B0_s ->
D_s1(2536) mu nu X) is made.Comment: 7 pages, 2 figures, LaTeX, version with minor changes as accepted by
Phys. Rev. Let
Simultaneous measurement of the ratio B(t->Wb)/B(t->Wq) and the top quark pair production cross section with the D0 detector at sqrt(s)=1.96 TeV
We present the first simultaneous measurement of the ratio of branching
fractions, R=B(t->Wb)/B(t->Wq), with q being a d, s, or b quark, and the top
quark pair production cross section sigma_ttbar in the lepton plus jets channel
using 0.9 fb-1 of ppbar collision data at sqrt(s)=1.96 TeV collected with the
D0 detector. We extract R and sigma_ttbar by analyzing samples of events with
0, 1 and >= 2 identified b jets. We measure R = 0.97 +0.09-0.08 (stat+syst) and
sigma_ttbar = 8.18 +0.90-0.84 (stat+syst)} +/-0.50 (lumi) pb, in agreement with
the standard model prediction.Comment: submitted to Phys.Rev.Letter
Search for charged Higgs bosons decaying to top and bottom quarks in ppbar collisions
We describe a search for production of a charged Higgs boson, q \bar{q'} ->
H^+, reconstructed in the t\bar{b} final state in the mass range 180 <= M_{H^+}
<= 300 GeV. The search was undertaken at the Fermilab Tevatron collider with a
center-of-mass energy sqrt{s} = 1.96 TeV and uses 0.9 fb^{-1} of data collected
with the D0 detector. We find no evidence for charged Higgs boson production
and set upper limits on the production cross section in the Types I, II and III
two-Higgs-doublet models (2HDMs). An excluded region in the (M_{H^+},tan\beta)
plane for Type I 2HDM is presented.Comment: Submitted to Phys. Rev. Letter
Journal Staff
We present the first measurements of the differential cross section d sigma/dp(T)(gamma) for the production of an isolated photon in association with at least two b-quark jets. The measurements consider photons with rapidities vertical bar y(gamma)vertical bar < 1.0 and transverse momenta 30 < p(T)(gamma) < 200 GeV. The b-quark jets are required to have p(T)(jet) > 15 GeVand vertical bar y(jet)vertical bar < 1.5. The ratio of differential production cross sections for gamma + 2 b-jets to gamma + b-jet as a function of p(T)(gamma) is also presented. The results are based on the proton-antiproton collision data at root s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. The measured cross sections and their ratios are compared to the next- to- leading order perturbative QCD calculations as well as predictions based on the k(T)- factorization approach and those from the sherpa and pythia Monte Carlo event generators
- …