604 research outputs found
Testing the interaction of dark energy to dark matter through the analysis of virial relaxation of clusters Abell Clusters A586 and A1689 using realistic density profiles
Interaction between dark energy and dark matter is probed through deviation
from the virial equilibrium for two relaxed clusters: A586 and A1689. The
evaluation of the virial equilibrium is performed using realistic density
profiles. The virial ratios found for the more realistic density profiles are
consistent with the absence of interaction.Comment: 16pp 1 fig; accepted by GeR
Lack of evidence for superantigen activity of Toxoplasma gondii towards human T cells
Toxoplasma gondii is an obligatory intracellular parasite whose life cycle may include man as an intermediate host. More than 500 million people are infected with this parasite worldwide. It has been previously reported that T. gondii contains a superantigen activity. The purpose of the present study was to determine if the putative superantigen activity of T. gondii would manifest towards human T cells. Peripheral blood mononuclear cells (PBMC) from individuals with no previous contact with the parasite were evaluated for proliferation as well as specific Vß expansion after exposure to Toxoplasma antigens. Likewise, PBMC from individuals with the congenital infection were evaluated for putative Vß family deletions in their T cell repertoire. We also evaluated, over a period of one year, the PBMC proliferation pattern in response to Toxoplasma antigens in patients with recently acquired infection. Some degree of proliferation in response to T. gondii was observed in the PBMC from individuals never exposed to the parasite, accompanied by specific Vß expansion, suggesting a superantigen effect. However, we found no specific deletion of Vß (or Valpha) families in the blood of congenitally infected individuals. Furthermore, PBMC from recently infected individuals followed up over a period of one year did not present a reduction of the Vß families that were originally expanded in response to the parasite antigens. Taken together, our data suggest that T. gondii does not have a strong superantigen activity on human T cells.Universidade de São Paulo Faculdade de Medicina Instituto de Ciências BiomédicasUniversidade de São Paulo Faculdade de Medicina Divisão de OftalmologiaUniversidade de São Paulo Faculdade de Medicina Divisão de Alergia e Imunologia ClínicaUniversidade Federal de São Paulo (UNIFESP) Departamento de OftalmologiaFundação E.J. ZerbiniUNIFESP, Depto. de OftalmologiaSciEL
Cosmological Constraints on an Invisibly Decaying Higgs Boson
Working in the context of a proposal for collisional dark matter, we derive
bounds on the Higgs boson coupling to a stable light scalar
particle, which we refer to as phion (), required to solve problems with
small scale structure formation which arise in collisionless dark matter
models. We discuss the behaviour of the phion in the early universe for
different ranges of its mass. We find that a phion in the mass range of 100 MeV
is excluded and that a phion in the mass range of 1 GeV requires a large
coupling constant, g^{\prime} \gsim 2, and m_h \lsim 130 GeV in order to
avoid overabundance, in which case the invisible decay mode of the Higgs boson
would be dominant.Comment: 5 pages, 2 figures, Revtex style, changed conten
Supersymmetric economical 3-3-1 model
The supersymmetric extension of the economical 3-3-1 model is presented. The
constraint equations and the gauge boson identification establish a relation
between the vacuum expectation values (VEVs) at the top and bottom elements of
the Higgs triplet and its supersymmetric counterpart .
Because of this relation, the exact diagonalization of neutral gauge boson
sector has been performed. The gauge bosons and their associated Goldstone ones
mix in the same way as in non-supersymmetric version. This is also correct in
the case of gauginos. The eigenvalues and eigenstates in the Higgs sector are
derived. The model contains a heavy neutral Higgs boson with mass equal to
those of the neutral non-Hermitian gauge boson and a charged scalar with
mass equal to those of the boson in the standard model, i. e. . This result is in good agreement with the present
estimation: GeV, CL= 95 %. We also show that the boson
sector and the fermion sector gain masses in the same way as in the
non-supersymmetric case.Comment: 33 page
Corrigendum to “Golden carbon of Sargassum forests revealed as an opportunity for climate change mitigation” [Sci. Total Environ., 729 (2020) Start page – End page/ 138745]
info:eu-repo/semantics/publishedVersio
Linear and non-linear perturbations in dark energy models
I review the linear and second-order perturbation theory in dark energy
models with explicit interaction to matter in view of applications to N-body
simulations and non-linear phenomena. Several new or generalized results are
obtained: the general equations for the linear perturbation growth; an
analytical expression for the bias induced by a species-dependent interaction;
the Yukawa correction to the gravitational potential due to dark energy
interaction; the second-order perturbation equations in coupled dark energy and
their Newtonian limit. I also show that a density-dependent effective dark
energy mass arises if the dark energy coupling is varying.Comment: 12 pages, submitted to Phys. Rev; v2: added a ref. and corrected a
typ
Antihydrogen formation dynamics in a multipolar neutral anti-atom trap
Antihydrogen production in a neutral atom trap formed by an octupole-based
magnetic field minimum is demonstrated using field-ionization of weakly bound
anti-atoms. Using our unique annihilation imaging detector, we correlate
antihydrogen detection by imaging and by field-ionization for the first time.
We further establish how field-ionization causes radial redistribution of the
antiprotons during antihydrogen formation and use this effect for the first
simultaneous measurements of strongly and weakly bound antihydrogen atoms.
Distinguishing between these provides critical information needed in the
process of optimizing for trappable antihydrogen. These observations are of
crucial importance to the ultimate goal of performing CPT tests involving
antihydrogen, which likely depends upon trapping the anti-atom
Egg parasitoid wasps as natural enemies of the neotropical stink bug Dichelops melacanthus
O objetivo deste trabalho foi determinar o potencial de cinco espécies de vespas Scelionidae – Telenomus podisi, Trissolcus basalis, Trissolcus urichi, Trissolcus teretis e Trissolcus brochymenae –, como inimigos naturais do percevejo neotropical Dichelops melacanthus, e determinar se a presença de ovos de outras espécies de percevejo tem influência sobre o parasitismo e o desenvolvimento dos parasitoides. Foram realizados dois tipos de experimentos em laboratório: sem escolha de hospedeiros (ovos de D. melacanthus) e com escolha (ovos de D. melacanthus e de Euschistus heros). Foram registrados parâmetros biológicos que incluíram: proporção de parasitismo, sobrevivência de imaturos, razão sexual da progênie, tempo de desenvolvimento dos estágios imaturos e preferência de hospedeiro. Todas as espécies de parasitóides avaliadas podem parasitar e desenvolver-se em ovos de D. melacanthus. A escolha inicial de ovos não influenciou a proporção de ovos de D. melacanthus parasitados por Tr. basalis, Tr. teretis ou Tr. brochymenae. Entretanto, para Te. podisi e Tr. urichi, a escolha inicial por ovos de D. melacanthus aumentou em 9 e 14 vezes, respectivamente, a chance de parasitismo nesta espécie. Aspectos comportamentais e ecológicos dos inimigos naturais devem ser considerados antes de sua utilização em programas de controle biológico.The objective of this work was to determine the potential of five species of Scelionidae wasps – Telenomus podisi, Trissolcus basalis, Trissolcus urichi, Trissolcus teretis and Trissolcus brochymenae – as natural enemies of the neotropical stink bug Dichelops melacanthus, and to determine if the presence of eggs of other stink bug species influences the parasitism and development of the parasitoids. Two kinds of experiments were done in laboratory: without choice of hosts (eggs of D. melacanthus) and with choice (eggs of D. melacanthus and of Euschistus heros). Biological parameters, including proportion of parasitism, immature survivorship, progeny sex ratio, immature stage development period, and host preference were recorded. All the evaluated parasitoids can parasitize and develop on D. melacanthus eggs. The first choice of eggs did not influence the proportion of D. melacanthus eggs parasitized by Tr. basalis, Tr. teretis or Tr. brochymenae. However, D. melacanthus eggs as the first choice of Te. podisi and Tr. urichi increased, respectively, 9 and 14 times the chance for parasitism on eggs of this species. Behavioral and ecological aspects of parasitoids should be considered prior to their use in biological control programs
Search For Trapped Antihydrogen
We present the results of an experiment to search for trapped antihydrogen
atoms with the ALPHA antihydrogen trap at the CERN Antiproton Decelerator.
Sensitive diagnostics of the temperatures, sizes, and densities of the trapped
antiproton and positron plasmas have been developed, which in turn permitted
development of techniques to precisely and reproducibly control the initial
experimental parameters. The use of a position-sensitive annihilation vertex
detector, together with the capability of controllably quenching the
superconducting magnetic minimum trap, enabled us to carry out a
high-sensitivity and low-background search for trapped synthesised antihydrogen
atoms. We aim to identify the annihilations of antihydrogen atoms held for at
least 130 ms in the trap before being released over ~30 ms. After a three-week
experimental run in 2009 involving mixing of 10^7 antiprotons with 1.3 10^9
positrons to produce 6 10^5 antihydrogen atoms, we have identified six
antiproton annihilation events that are consistent with the release of trapped
antihydrogen. The cosmic ray background, estimated to contribute 0.14 counts,
is incompatible with this observation at a significance of 5.6 sigma. Extensive
simulations predict that an alternative source of annihilations, the escape of
mirror-trapped antiprotons, is highly unlikely, though this possibility has not
yet been ruled out experimentally.Comment: 12 pages, 7 figure
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