726 research outputs found
Livestock policy in the Brazilian Amazonia colonization
The objective of this chapter is to present, based on a diachronic analysis, the main steps of livestock farming in the Brazilian Amazonia and the policies that have been associated with it
Universal light quark mass dependence and heavy-light meson spectroscopy
Clean predictions are presented for all the spin-averaged heavy-light meson
spectroscopies. A new symmetry is identified wherein the energy eigenstates
have a universal dependence on both the light and heavy quark masses. This
universality is used in an efficient analysis of these mesons within the QCD
string/flux tube picture. Unique predictions for all the D, D_s, B, and B_s
type mesons in terms of just four measured quantities.Comment: REVTeX4, 6 pages, 9 eps figure
Protective Mechanical Ventilation during General Anesthesia for Open Abdominal Surgery Improves Postoperative Pulmonary Function
BACKGROUND:: The impact of intraoperative ventilation on postoperative pulmonary complications is not defined. The authors aimed at determining the effectiveness of protective mechanical ventilation during open abdominal surgery on a modified Clinical Pulmonary Infection Score as primary outcome and postoperative pulmonary function. METHODS:: Prospective randomized, open-label, clinical trial performed in 56 patients scheduled to undergo elective open abdominal surgery lasting more than 2 h. Patients were assigned by envelopes to mechanical ventilation with tidal volume of 9 ml/kg ideal body weight and zero-positive end-expiratory pressure (standard ventilation strategy) or tidal volumes of 7 ml/kg ideal body weight, 10 cm H2O positive end-expiratory pressure, and recruitment maneuvers (protective ventilation strategy). Modified Clinical Pulmonary Infection Score, gas exchange, and pulmonary functional tests were measured preoperatively, as well as at days 1, 3, and 5 after surgery. RESULTS:: Patients ventilated protectively showed better pulmonary functional tests up to day 5, fewer alterations on chest x-ray up to day 3 and higher arterial oxygenation in air at days 1, 3, and 5 (mmHg; mean \ub1 SD): 77.1 \ub1 13.0 versus 64.9 \ub1 11.3 (P = 0.0006), 80.5 \ub1 10.1 versus 69.7 \ub1 9.3 (P = 0.0002), and 82.1 \ub1 10.7 versus 78.5 \ub1 21.7 (P = 0.44) respectively. The modified Clinical Pulmonary Infection Score was lower in the protective ventilation strategy at days 1 and 3. The percentage of patients in hospital at day 28 after surgery was not different between groups (7 vs. 15% respectively, P = 0.42). CONCLUSION:: A protective ventilation strategy during abdominal surgery lasting more than 2 h improved respiratory function and reduced the modified Clinical Pulmonary Infection Score without affecting length of hospital stay
Dirac-like Monopoles in Three Dimensions and Their Possible Influences on the Dynamics of Particles
Dirac-like monopoles are studied in three-dimensional Abelian Maxwell and
Maxwell-Chern-Simons models. Their scalar nature is highlighted and discussed
through a dimensional reduction of four-dimensional electrodynamics with
electric and magnetic sources. Some general properties and similarities of them
when are considered in Minkowski or Euclidian space are mentioned. However, by
virtue of the structure of the space-time in which they are considered a number
of differences among them take place. Furthermore, we pay attention to some
consequences of these objects when acting upon usual particles. Among other
subjects, special attention is given to the study of a Lorentz-violating
non-minimal coupling between neutral fermions and the field generated by a
monopole alone. In addition, an analogue of the Aharonov-Casher effect is
discussed in this framework.Comment: 20 pages. Latex format. No figures. Accepted for publication in Phys.
Rev.
On the bounds for the curvature and higher derivatives of the Isgur-Wise function
We discuss constraints imposed on the zero-recoil curvature and higher
derivatives of the Isgur-Wise function by a general quark model. These
constraints are expressed as bounds for a given slope parameter, and compared
with those based upon analyticity properties of QCD spectral functions. Our
results also indicate that in the analysis of the experimental data for
semileptonic B\rar D^{(*)} decays it may be important to include at least the
third term in the form factor expansion about the zero recoil point.Comment: 14 pages, latex, uses epsf macro, 5 postscript figures include
New hadrons as ultra-high energy cosmic rays
Ultra-high energy cosmic ray (UHECR) protons produced by uniformly
distributed astrophysical sources contradict the energy spectrum measured by
both the AGASA and HiRes experiments, assuming the small scale clustering of
UHECR observed by AGASA is caused by point-like sources. In that case, the
small number of sources leads to a sharp exponential cutoff at the energy
E<10^{20} eV in the UHECR spectrum. New hadrons with mass 1.5-3 GeV can solve
this cutoff problem. For the first time we discuss the production of such
hadrons in proton collisions with infrared/optical photons in astrophysical
sources. This production mechanism, in contrast to proton-proton collisions,
requires the acceleration of protons only to energies E<10^{21} eV. The diffuse
gamma-ray and neutrino fluxes in this model obey all existing experimental
limits. We predict large UHE neutrino fluxes well above the sensitivity of the
next generation of high-energy neutrino experiments. As an example we study
hadrons containing a light bottom squark. These models can be tested by
accelerator experiments, UHECR observatories and neutrino telescopes.Comment: 17 pages, revtex style; v2: shortened, as to appear in PR
Search for R-parity Violating Decays of Supersymmetric Particles in e+e- Collisions at LEP
A search, in e^+e^- collisions, for chargino, neutralino, scalar lepton and
scalar quark pair-production is performed, without assuming R-parity
conservation in decays, in the case that only one of the coupling constants
lambda_ijk or lambda''_ijk is non-negligible. No signal is found in data up to
a centre-of-mass energy of 208GeV. Limits on the production cross sections and
on the masses of supersymmetric particles are derived
Measurement of the Charged Multiplicities in b, c and Light Quark Events from Z0 Decays
Average charged multiplicities have been measured separately in , and
light quark () events from decays measured in the SLD experiment.
Impact parameters of charged tracks were used to select enriched samples of
and light quark events, and reconstructed charmed mesons were used to select
quark events. We measured the charged multiplicities:
,
, from
which we derived the differences between the total average charged
multiplicities of or quark events and light quark events: and . We compared
these measurements with those at lower center-of-mass energies and with
perturbative QCD predictions. These combined results are in agreement with the
QCD expectations and disfavor the hypothesis of flavor-independent
fragmentation.Comment: 19 pages LaTex, 4 EPS figures, to appear in Physics Letters
Measurement of Bose-Einstein Correlations in e+e- -> W+W- at root(s)=189GeV
We investigate Bose-Einstein correlations (BEC) in W-pair production at
root(s)=189GeV using the L3 detector at LEP. We observe BEC between particles
from a single W decay in good agreement with those from a light-quark Z decay
sample. We investigate their possible existence between particles coming from
different W's. No evidence for such inter-W BEC is found
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