943 research outputs found
Metastable states, the adiabatic theorem and parity violating geometric phases II
We discuss and calculate parity conserving (PC) and parity violating (PV)
geometric phases for the metastable 2S states of hydrogen and deuterium. The
atoms are supposed to be subjected to slowly varying electric and magnetic
fields which act as external parameters for the atoms. Geometric flux density
fields are introduced which allow for an easy overview how to choose the paths
in parameter space in order to obtain only PC or only PV geometric phases. The
PV phases are calculated in the Standard Model of particle physics. Even if
numerically they come out small they have interest of principle as a new
manifestation of parity violation in atomic physics.Comment: 63 pages, 8 figures, 10 table
Sistema simplificado para melhoria da qualidade da água consumida nas comunidades rurais do semi-árido do Brasil.
Além da quantidade, a qualidade da água também é uma questão que preocupa. A má qualidade da água consumida é a maior responsável pelas doenças endêmicas nos países em desenvolvimento, como por exemplo, hepatite, cólera, febre tifóide, entre outras. Falta de acesso à água de boa qualidade e ao saneamento resulta em centenas de milhões de casos de doenças de veiculação hídrica. No Brasil, de acordo com pesquisa do Censo 2000, 5,9% dos domicílios brasileiros lançam seus esgotos em valas, rios, lagos ou no mar. Dessa proporção, a maior parte ocorre nas áreas rurais (10%) do que nas urbanas (5%). Já os domicílios que não possuem instalações sanitárias chegam a 8,3% do total do país, sendo mais freqüentes nas regiões rurais (35,3%). Essa situação torna-se gritante na área rural da Região Nordeste (60,5%), num contraste brutal com as áreas rurais da Região Sul (7,4%) (IBGE, 2002). Na região do Semi-Árido do Brasil, a população de algumas comunidades rurais, devido à escassez é obrigada a percorrer grandes distâncias para a obtenção de água, na maioria das vezes de péssima qualidade e de turbidez muito elevada. Entre os objetivos deste trabalho, estão a proposição de sistemas simplificados, econômicos, práticos e viáveis para a melhoria da qualidade da água consumida nas comunidades rurais do semi-áridodo Brasil; a comprovação da viabilidade de aplicação desses sistemas; e a apresentação dos resultados obtidos a partir da aplicação desses sistemas.bitstream/CNPMA/7457/1/documentos_53.pd
Zircon Geochronology and Petrology of Plutonic Rocks in Rhode Island
Guidebook to geologic field studies in Rhode Island and adjacent areas: The 73rd annual meeting of the New England Intercollegiate Geological Conference, October 16-18, 1981: Trip C-
Discovery of an ultramassive pulsating white dwarf
We announce the discovery of the most massive pulsating hydrogen-atmosphere
(DA) white dwarf (WD) ever discovered, GD 518. Model atmosphere fits to the
optical spectrum of this star show it is a 12,030 +/- 210 K WD with a log(g) =
9.08 +/- 0.06, which corresponds to a mass of 1.20 +/- 0.03 Msun. Stellar
evolution models indicate that the progenitor of such a high-mass WD endured a
stable carbon-burning phase, producing an oxygen-neon-core WD. The discovery of
pulsations in GD 518 thus offers the first opportunity to probe the interior of
a WD with a possible oxygen-neon core. Such a massive WD should also be
significantly crystallized at this temperature. The star exhibits
multi-periodic luminosity variations at timescales ranging from roughly 425-595
s and amplitudes up to 0.7%, consistent in period and amplitude with the
observed variability of typical ZZ Ceti stars, which exhibit non-radial g-mode
pulsations driven by a hydrogen partial ionization zone. Successfully
unraveling both the total mass and core composition of GD 518 provides a unique
opportunity to investigate intermediate-mass stellar evolution, and can
possibly place an upper limit to the mass of a carbon-oxygen-core WD, which in
turn constrains SNe Ia progenitor systems.Comment: 5 pages, 3 figures, Astrophysical Journal Letters, 771, L2 (2013
Contact Relationships of the Late Paleozoic Narragansett Pier Granite and Country Rock
Guidebook to geologic field studies in Rhode Island and adjacent areas: The 73rd annual meeting of the New England Intercollegiate Geological Conference, October 16-18, 1981: Trip B-
Local moments and symmetry breaking in metallic PrMnSbO
We report a combined experimental and theoretical investigation of the
layered antimonide PrMnSbO which is isostructural to the parent phase of the
iron pnictide superconductors. We find linear resistivity near room temperature
and Fermi liquid-like T^{2} behaviour below 150 K. Neutron powder diffraction
shows that unfrustrated C-type Mn magnetic order develops below \sim 230 K,
followed by a spin-flop coupled to induced Pr order. At T \sim 35 K, we find a
tetragonal to orthorhombic (T-O) transition. First principles calculations show
that the large magnetic moments observed in this metallic compound are of local
origin. Our results are thus inconsistent with either the itinerant or
frustrated models proposed for symmetry breaking in the iron pnictides. We show
that PrMnSbO is instead a rare example of a metal where structural distortions
are driven by f-electron degrees of freedom
General Structural Setting of Rhode Island and Tectonic History of Southeastern New England
Guidebook to geologic field studies in Rhode Island and adjacent areas: The 73rd annual meeting of the New England Intercollegiate Geological Conference, October 16-18, 1981: title pages, table of contents, foreword, essa
Guidebook to geologic field studies in Rhode Island and adjacent areas: The 73rd annual meeting of the New England Intercollegiate Geological Conference, October 16-18, 1981
22 trips including emphasis on a variety of geologic problems that range from surficial to bedrock studie
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