798 research outputs found
Toward a test of angular momentum coherence in a twin-atom interferometer
We present a scheme well-suited to investigate quantitatively the angular
momentum coherence of molecular fragments. Assuming that the dissociated
molecule has a null total angular momentum, we investigate the propagation of
the corresponding atomic fragments in the apparatus. We show that the
envisioned interferometer enables one to distinguish unambiguously a
spin-coherent from a spin-incoherent dissociation, as well as to estimate the
purity of the angular momentum density matrix associated with the fragments.
This setup, which may be seen as an atomic analogue of a twin-photon
interferometer, can be used to investigate the suitability of molecule
dissociation processes -- such as the metastable hydrogen atoms H()-H() dissociation - for coherent twin-atom optics.Comment: 6 pages, 3 Figures. Final version accepted for publication in
Europhysics Letter
Descritores morfo agronĂŽmicos e fenolĂłgicos de linhagens de arroz (Oryza sativa L.) de vĂĄrzeas e de terras altas.
O presente trabalho teve por objetivo apresentar os descritores morfo agronĂŽmicos e fenolĂłgicos de linhagens de arroz irrigado e de terras altas com possibilidades de serem recomendadas como novas cultivares comerciais.bitstream/CNPAF-2009-09/27599/1/doc_219.pd
Ionisation and dissociation of cometary gaseous organic molecules by solar wind particles I: Formic Acid
In order to simulate the effects of energetic charged particles present in
the solar wind colliding with the cometary gaseous formic acid molecule
(HCOOH), laboratory experiments have been performed. The absolute ionisation
and dissociation cross sections for this molecule interacting with solar wind
particles were measured employing fast electrons in the energy range of 0.5 to
2 keV and energetic protons with energies varying from 0.128 to 2 MeV. Despite
the fact that both projectiles lead to a very similar fragmentation pattern,
differences in the relative intensities of the fragments were observed. Formic
acid survives about 4-5 times more to the proton beam than to the energetic
electron collision.The minimum momentum transfer in the electron impact case
was estimated to be 3-38% larger than the minimum momentum transfer observed
with the equivelocity protons. The UV photodissociation rates and half-lives
for HCOOH are roughly closer to the values obtained with energetic electrons.
It is consequently important to take electron impact data into account when
developing chemical models to simulate the interplanetary conditions.Comment: 11 pages, 7 figures, 5 tables, Accepted to be published in MNRA
Relativistic treatment of harmonics from impurity systems in quantum wires
Within a one particle approximation of the Dirac equation we investigate a
defect system in a quantum wire. We demonstrate that by minimally coupling a
laser field of frequency omega to such an impurity system, one may generate
harmonics of multiples of the driving frequency. In a multiple defect system
one may employ the distance between the defects in order to tune the cut-off
frequency.Comment: 9 pages Latex, 8 eps figures, section added, numerics improve
Metric versus observable operator representation, higher spin models
We elaborate further on the metric representation that is obtained by transferring the time-dependence from a Hermitian Hamiltonian to the metric operator in a related non-Hermitian system. We provide further insight into the procedure on how to employ the time-dependent Dyson relation and the quasi-Hermiticity relation to solve time-dependent Hermitian Hamiltonian systems. By solving both equations separately we argue here that it is in general easier to solve the former. We solve the mutually related time-dependent Schrödinger equation for a Hermitian and non-Hermitian spin 1/2, 1 and 3/2 model with time-independent and time-dependent metric, respectively. In all models the overdetermined coupled system of equations for the Dyson map can be decoupled algebraic manipulations and reduces to simple linear differential equations and an equation that can be converted into the non-linear Ermakov-Pinney equation
AgrotĂłxicos e saĂșde: realidade e desafios para mudança de prĂĄticas na agricultura.
Este artigo apresenta os resultados de uma pesquisa que teve como objetivo principal caracterizar o contexto e as prĂĄticas relacionadas ao uso de agrotĂłxicos entre agricultores residentes na Serrinha do Mendanha, comunidade agrĂcola situada em Campo Grande, municĂpio do Rio de Janeiro. A proposta metodolĂłgica teve uma abordagem qualitativa, sendo a principal fonte de dados a aplicação de questionĂĄrio semiestruturado. Participaram da pesquisa 38 agricultores familiares. O perfil socioeconĂŽmico mostra uma realidade de idosos no trabalho agrĂcola, percentuais expressivos de analfabetismo e baixa renda. O uso de agrotĂłxicos Ă© uma rotina para essas famĂlias. Apesar de existir uma naturalização do uso, a maioria dos informantes acredita que agrotĂłxicos podem afetar sua saĂșde, apresenta preocupação com o consumidor e gostaria de conhecer formas alternativas de cultivo. Tais achados apontam para a possibilidade de busca de mudança de prĂĄticas. NĂŁo se trata de repasse de conhecimento, pois este tipo de informação de alguma forma eles jĂĄ possuem. Trataâse de desenvolver estratĂ©gias objetivando a minimização dos riscos ou mesmo o desuso de agrotĂłxicos na lavoura
Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC
The uncertainty on the calorimeter energy response to jets of particles is
derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the
calorimeter response to single isolated charged hadrons is measured and
compared to the Monte Carlo simulation using proton-proton collisions at
centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009
and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter
response to specific types of particles (positively and negatively charged
pions, protons, and anti-protons) is measured and compared to the Monte Carlo
predictions. Finally, the jet energy scale uncertainty is determined by
propagating the response uncertainty for single charged and neutral particles
to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3%
for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table,
submitted to European Physical Journal
SARS-CoV-2 antibody dynamics in blood donors and COVID-19 epidemiology in eight Brazilian state capitals: A serial cross-sectional study
BACKGROUND: The COVID-19 situation in Brazil is complex due to large differences in the shape and size of regional epidemics. Understanding these patterns is crucial to understand future outbreaks of SARS-CoV-2 or other respiratory pathogens in the country. METHODS: We tested 97,950 blood donation samples for IgG antibodies from March 2020 to March 2021 in 8 of Brazil's most populous cities. Residential postal codes were used to obtain representative samples. Weekly age- and sex-specific seroprevalence were estimated by correcting the crude seroprevalence by test sensitivity, specificity, and antibody waning. RESULTS: The inferred attack rate of SARS-CoV-2 in December 2020, before the Gamma variant of concern (VOC) was dominant, ranged from 19.3% (95% credible interval [CrI] 17.5-21.2%) in Curitiba to 75.0% (95% CrI 70.8-80.3%) in Manaus. Seroprevalence was consistently smaller in women and donors older than 55 years. The age-specific infection fatality rate (IFR) differed between cities and consistently increased with age. The infection hospitalisation rate increased significantly during the Gamma-dominated second wave in Manaus, suggesting increased morbidity of the Gamma VOC compared to previous variants circulating in Manaus. The higher disease penetrance associated with the health system's collapse increased the overall IFR by a minimum factor of 2.91 (95% CrI 2.43-3.53). CONCLUSIONS: These results highlight the utility of blood donor serosurveillance to track epidemic maturity and demonstrate demographic and spatial heterogeneity in SARS-CoV-2 spread. FUNDING: This work was supported by ItaĂș Unibanco 'Todos pela Saude' program; FAPESP (grants 18/14389-0, 2019/21585-0); Wellcome Trust and Royal Society Sir Henry Dale Fellowship 204311/Z/16/Z; the Gates Foundation (INV- 034540 and INV-034652); REDS-IV-P (grant HHSN268201100007I); the UK Medical Research Council (MR/S0195/1, MR/V038109/1); CAPES; CNPq (304714/2018-6); Fundação Faculdade de Medicina; Programa Inova Fiocruz-CE/Funcap - Edital 01/2020 Number: FIO-0167-00065.01.00/20 SPU N°06531047/2020; JBS - Fazer o bem faz bem
- âŠ