1,060 research outputs found
Avaliação acústica das chapas de partículas produzidas com bagaço de cana-de-açúcar e folha caulinar de bambu
O escopo dessa pesquisa é aproveitar o bagaço da cana-de-açúcar proveniente do processo
industrial de beneficiamento do açúcar e do álcool das usinas do estado de São Paulo-Brasil, cujo
tema é a gestão de resíduos agroindustriais, utilizando-se desse resíduo em conjunto com as
folhas caulinares do bambu na fabricação de chapas de partículas. Essas chapas podem ser
empregadas em forros e revestimentos de paredes e móveis como alternativa à utilização da
madeira, pois o bagaço tem em sua composição a celulose e a hemicelulose, que estão presentes
em cerca de 70% da composição dos resíduos agrícolas, podendo assim, substituir a madeira em
alguns casos, como por exemplo, nas chapas de aglomerado. Confeccionados em forma de
blocos (ou tijolos) nos traços 100%, 75%, 50%, 40%, 25% e 0% de cana, estes tiveram seu
desempenho acústico avaliado por meio do ensaio de condutividade acústica, que consiste em
medir o isolamento sonoro que os blocos absorvem.The scope of this research is centered in the reuse of the sugarcane bagasse produced from the
industrial processing of sugar and ethanol from the mills in Sao Paulo state, Brazil. It is analyzed
the use of this abundant industrial residue, mixed with bamboo leaves steam in the manufacturing
of particleboards. These plates can be eventually used in ceilings and wall coverings, or in
furniture, as an alternative to the use of wood. The sugarcane bagasse residue has in its
composition cellulose and hemicelluloses. In fact, these components represent 70% of the
agricultural residues composition. In many applications, the studied product may be able to replace
the wood, for instance, in the particleboards. Acoustic conductivity tests were made in the prisms
produced with 100%, 75%, 50%, 40%, 25% and 0% of sugar cane incorporation. The results, in
terms of noise insulation are compared with reference values for other materials
Bounds on the mass of the b' quark, revisited
Recent results from the DELPHI collaboration led us to review the present
bounds on the b' quark mass. We use all available experimental data for m_b' >
96 GeV to constrain the b' quark mass as a function of the
Cabibbo-Kobayashi-Maskawa elements in a sequential four generations model. We
find that there is still room for a b' with a mass larger than 96 GeV.Comment: 9 pages and 7 figures. REVTEX
Search for the Rare Decay KL --> pi0 ee
The KTeV/E799 experiment at Fermilab has searched for the rare kaon decay
KL--> pi0ee. This mode is expected to have a significant CP violating
component. The measurement of its branching ratio could support the Standard
Model or could indicate the existence of new physics. This letter reports new
results from the 1999-2000 data set. One event is observed with an expected
background at 0.99 +/- 0.35 events. We set a limit on the branching ratio of
3.5 x 10^(-10) at the 90% confidence level. Combining the results with the
dataset taken in 1997 yields the final KTeV result: BR(KL --> pi0 ee) < 2.8 x
10^(-10) at 90% CL.Comment: 4 pages, three figure
Improving clinical diagnosis of early-stage cutaneous melanoma based on Raman spectroscopy
Dermatology-oncolog
Marine megafauna niche coexistence and hotspot areas in a temperate ecosystem
Versión del editor2,08
f(R,L_m) gravity
We generalize the type gravity models by assuming that the
gravitational Lagrangian is given by an arbitrary function of the Ricci scalar
and of the matter Lagrangian . We obtain the gravitational field
equations in the metric formalism, as well as the equations of motion for test
particles, which follow from the covariant divergence of the energy-momentum
tensor. The equations of motion for test particles can also be derived from a
variational principle in the particular case in which the Lagrangian density of
the matter is an arbitrary function of the energy-density of the matter only.
Generally, the motion is non-geodesic, and takes place in the presence of an
extra force orthogonal to the four-velocity. The Newtonian limit of the
equation of motion is also considered, and a procedure for obtaining the
energy-momentum tensor of the matter is presented. The gravitational field
equations and the equations of motion for a particular model in which the
action of the gravitational field has an exponential dependence on the standard
general relativistic Hilbert--Einstein Lagrange density are also derived.Comment: 6 pages, no figures; minor modifications, references added; accepted
for publication in EPJ
The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets
This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term near-Sun comets to encompass all objects that pass sunward of the perihelion distance of planet Mercury (0.307 AU). Sunskirters are defined as objects that pass within 33 solar radii of the Sun’s centre, equal to half of Mercury’s perihelion distance, and the commonly-used phrase sungrazers to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed sundivers. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and tails are described, including dust, neutral and ionised gases, their chemical reactions, and their contributions to the near-Sun environment. Comet-solar wind interactions are discussed, including the use of comets as probes of solar wind and coronal conditions in their vicinities. We address the relevance of work on comets near the Sun to similar objects orbiting other stars, and conclude with a discussion of future directions for the field and the planned ground- and space-based facilities that will allow us to address those science topics
Search for Higgs bosons decaying to tautau pairs in ppbar collisions at sqrt(s) = 1.96 TeV
We present a search for the production of neutral Higgs bosons decaying into
tautau pairs in ppbar collisions at a center-of-mass energy of 1.96 TeV. The
data, corresponding to an integrated luminosity of 5.4 fb-1, were collected by
the D0 experiment at the Fermilab Tevatron Collider. We set upper limits at the
95% C.L. on the product of production cross section and branching ratio for a
scalar resonance decaying into tautau pairs, and we then interpret these limits
as limits on the production of Higgs bosons in the minimal supersymmetric
standard model (MSSM) and as constraints in the MSSM parameter space.Comment: 7 pages, 5 figures, submitted to PL
Search for pair production of the scalar top quark in muon+tau final states
We present a search for the pair production of scalar top quarks
(), the lightest supersymmetric partners of the top quarks, in
collisions at a center-of-mass energy of 1.96 TeV, using data
corresponding to an integrated luminosity of {7.3 } collected with the
\dzero experiment at the Fermilab Tevatron Collider. Each scalar top quark is
assumed to decay into a quark, a charged lepton, and a scalar neutrino
(). We investigate final states arising from and
. With no significant excess of events observed above the
background expected from the standard model, we set exclusion limits on this
production process in the (,) plane.Comment: Submitted to Phys. Lett.
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