599 research outputs found
Ácidos orgânicos de folhas de três variedades de cana-de-açúcar (Saccharum spp) em quatro estádios de maturidade
Leaves of sugarcane (Saccharum spp) from three different varieties (NA-56-79, RB 73-5275 and IAC 58-480) at four maturity stages (11, 12, 13 and 14 months) were analysed for organic acids and potassium content. Trans-aconitic acid represented about 60% of total organic acids followed by malic, glutaric, succinic, alpha-ketoglutaric, malonic and fumaric acids. There were significant differences among varieties and maturity stages for all acids studied. There were no significant correlations between potassium and organic acids content.Folhas de cana-de-açúcar (Saccharum spp) de três variedades (NA 56-79, IAC 58-480 e RB 73-5275)em quatro estádios de maturidade (11, 12, 13 e 14 meses) foram analisadas para a determinação de ácidos orgânicos e potássio. O ácido trans-aconítico constituiu cerca de 60% do total de ácidos orgânicos seguido pelos ácidos málico, glutárico, succinics, alfa cetoglutárico, malônico e fumárico. Foram observadas diferenças significativas entre as variedades e entre os estádios de maturidade para todos os ácidos orgânicos identificados. Não foram observados coeficientes de correlação significativos entre os teores de potássio e de ácidos orgânicos
Stochastic background of gravitational waves
A continuous stochastic background of gravitational waves (GWs) for burst
sources is produced if the mean time interval between the occurrence of bursts
is smaller than the average time duration of a single burst at the emission,
i.e., the so called duty cycle must be greater than one. To evaluate the
background of GWs produced by an ensemble of sources, during their formation,
for example, one needs to know the average energy flux emitted during the
formation of a single object and the formation rate of such objects as well. In
many cases the energy flux emitted during an event of production of GWs is not
known in detail, only characteristic values for the dimensionless amplitude and
frequencies are known. Here we present a shortcut to calculate stochastic
backgrounds of GWs produced from cosmological sources. For this approach it is
not necessary to know in detail the energy flux emitted at each frequency.
Knowing the characteristic values for the ``lumped'' dimensionless amplitude
and frequency we show that it is possible to calculate the stochastic
background of GWs produced by an ensemble of sources.Comment: 6 pages, 4 eps figures, (Revtex) Latex. Physical Review D (in press
Ácidos orgânicos de caldo de três variedades de cana-de-açúcar (Saccharum spp) em quatro estádios de maturidade
Levels of trans-aconitic, malic, malonic and succinic acids were measured in sugarcane juice from three varieties in four maturity stages. Trans-aconitic acid represented about 84% of the total organic acids analysed in sugarcane juice followed by malic acid with 14%. Oxalic, glutaric, alpha-ketoglutaric and citric acids were found in levels lower than 1% of total organic acids. The content of trans-aconitic, malic and succinic acids decreased with the stage of maturity while malonic acid increased. No significant differences were observed among the varieties studied in relation to trans-aconitic acid content.Os teores dos ácidos trans-aconítico, málico, malônico e succínico foram determinados no caldo de cana das variedades IAC 58-480, RB 73-5275 e NA 56-79, em quatro estádios de maturidade (11, 12, 13 e 14 meses). O ácido trans-aconítico constituiu cerca de 84% do total dos ácidos orgânicos seguido pelo ácido málico com 14%. Os ácidos oxálico, glutárico, alfa-cetoglutárico e cítrico foram encontrados em níveis inferiores a 1%. Os níveis dos ácidos succínico, málico e trans-aconítico diminuíram com a maturidade da planta enquanto os de malônico aumentaram. Não foram encontradas diferenças significativas entre as variedades estudadas em relação aos teores de ácido trans-aconítico
Recent trends and potential drivers of non-invasive cardiovascular imaging use in the United States of America and England
Background: Non-invasive Cardiovascular imaging (NICI), including cardiovascular magnetic resonance (CMR) imaging provides important information to guide the management of patients with cardiovascular conditions. Current rates of NICI use and potential policy determinants in the United States of America (US) and England remain unexplored. Methods: We compared NICI activity in the US (Medicare fee-for-service, 2011–2015) and England (National Health Service, 2012–2016). We reviewed recommendations related to CMR from Clinical Practice Guidelines, Appropriate Use Criteria (AUC), and Choosing Wisely. We then categorized recommendations according to whether CMR was the only recommended NICI technique (substitutable indications). Reimbursement policies in both settings were systematically collated and reviewed using publicly available information. Results: The 2015 rate of NICI activity in the US was 3.1 times higher than in England (31,055 vs. 9,916 per 100,000 beneficiaries). The proportion of CMR of all NICI was small in both jurisdictions, but nuclear cardiac imaging was more frequent in the US in absolute and relative terms. American and European CPGs were similar, both in terms of number of recommendations and proportions of indications where CMR was not the only recommended NICI technique (substitutable indications). Reimbursement schemes for NICI activity differed for physicians and hospitals between the two settings. Conclusions: Fee-for-service physician compensation in the US for NICI may contribute to higher NICI activity compared to England where physicians are salaried. Reimbursement arrangements for the performance of the test may contribute to the higher proportion of nuclear cardiac imaging out of the total NICI activity. Differences in CPG recommendations appear not to explain the variation in NICI activity between the US and England
Efeito da aplicação da vinhaça como fertilizante sobre os teores de ácido trans-aconítico de caldo de cana-de-açúcar (Saccharum spp)
Sugarcane juice from NA 56-79 variety at four maturity stages (4, 6, 8 and 12 months) fertilized with vinasse was analysed for potassium and trans-aconitic acid content. With vinasse fertilization there was a significant reduction in total reducing sugars and an increase in potassium and trans-aconitic acid content of sugarcane juice. A significant positive correlation was observed between trans-aconitic acid production and potassium content. Trans-aconitic acid content was inversely related to the plant maturity.Caldo de cana da variedade NA 56-79, em quatro estádios de maturidade (4, 6, 8 e 12 meses) fertilizada com vinhaça foi analisada para a determinação dos teores de potássio e ácido trans-aconítico. A fertilização com vinhaça provocou redução significativa nos teores de açúcares redutores totais e aumento nos teores de potássio e de ácido trans-aconítico. Uma correlação positiva significativa foi encontrada entre a produção de ácido trans-aconítico e o teor de potássio. O teor de ácido trans-aconítico foi reduzido com a maturidade das plantas
Probing Rock Type, Fe Redox State, and Transition Metal Contents with Six-Window VNIR Spectroscopy Under Venus Conditions
VEM-window data are shown to distinguish among key rock types on Venus, and evaluate redox state and transition metal contents of Venus surface rocks
Electron neutrino tagging through tertiary lepton detection
We discuss an experimental technique aimed at tagging electron neutrinos in
multi-GeV artificial sources on an event-by-event basis. It exploits in a novel
manner calorimetric and tracking technologies developed in the framework of the
LHC experiments and of rare kaon decay searches. The setup is suited for
slow-extraction, moderate power beams and it is based on an instrumented decay
tunnel equipped with tagging units that intercept secondary and tertiary
leptons from the bulk of undecayed \pi^+ and protons. We show that the taggers
are able to reduce the \nue contamination originating from K_e3 decays by about
one order of magnitude. Only a limited suppression (~60%) is achieved for \nue
produced by the decay-in-flight of muons; for low beam powers, similar
performance as for K_e3 can be reached supplementing the tagging system with an
instrumented beam dump.Comment: 19 pages, 7 figures; minor changes, version to appear in EPJ
Lattice Pseudospin Model for Quantum Hall Bilayers
We present a new theoretical approach to the study of quantum Hall
bilayer that is based on a systematic mapping of the microscopic Hamiltonian to
an anisotropic SU(4) spin model on a lattice. To study the properties of this
model we generalize the Heisenberg model Schwinger boson mean field theory
(SBMFT) of Arovas and Auerbach to spin models with anisotropy. We calculate the
temperature dependence of experimentally observable quantities, including the
spin magnetization, and the differential interlayer capacitance. Our theory
represents a substantial improvement over the conventional Hartree-Fock picture
which neglects quantum and thermal fluctuations, and has advantages over
long-wavelength effective models that fail to capture important microscopic
physics at all realistic layer separations. The formalism we develop can be
generalized to treat quantum Hall bilayers at filling factor .Comment: 26 pages, 10 figures. The final version, to appear in PR
NMR and NQR Fluctuation Effects in Layered Superconductors
We study the effect of thermal fluctuations of the s-wave order parameter of
a quasi two dimensional superconductor on the nuclear spin relaxation rate near
the transition temperature Tc. We consider both the effects of the amplitude
fluctuations and the Berezinskii-Kosterlitz-Thouless (BKT) phase fluctuations
in weakly coupled layered superconductors. In the treatment of the amplitude
fluctuations we employ the Gaussian approximation and evaluate the longitudinal
relaxation rate 1/T1 for a clean s-wave superconductor, with and without pair
breaking effects, using the static pair fluctuation propagator D. The increase
in 1/T1 due to pair breaking in D is overcompensated by the decrease arising
from the single particle Green's functions. The result is a strong effect on
1/T1 for even a small amount of pair breaking. The phase fluctuations are
described in terms of dynamical BKT excitations in the form of pancake
vortex-antivortex (VA) pairs. We calculate the effect of the magnetic field
fluctuations caused by the translational motion of VA excitations on 1/T1 and
on the transverse relaxation rate 1/T2 on both sides of the BKT transitation
temperature T(BKT)<Tc. The results for the NQR relaxation rates depend strongly
on the diffusion constant that governs the motion of free and bound vortices as
well as the annihilation of VA pairs. We discuss the relaxation rates for real
multilayer systems where the diffusion constant can be small and thus increase
the lifetime of a VA pair, leading to an enhancement of the rates. We also
discuss in some detail the experimental feasibility of observing the effects of
amplitude fluctuations in layered s-wave superconductors such as the
dichalcogenides and the effects of phase fluctuations in s- or d-wave
superconductors such as the layered cuprates.Comment: 38 pages, 12 figure
Gravitational radiation from gamma-ray bursts as observational opportunities for LIGO and VIRGO
Gamma-ray bursts are believed to originate in core-collapse of massive stars.
This produces an active nucleus containing a rapidly rotating Kerr black hole
surrounded by a uniformly magnetized torus represented by two counter-oriented
current rings. We quantify black hole spin-interactions with the torus and
charged particles along open magnetic flux-tubes subtended by the event
horizon. A major output of Egw=4e53 erg is radiated in gravitational waves of
frequency fgw=500 Hz by a quadrupole mass-moment in the torus. Consistent with
GRB-SNe, we find (i) Ts=90s (tens of s, Kouveliotou et al. 1993), (ii)
aspherical SNe of kinetic energy Esn=2e51 erg (2e51 erg in SN1998bw, Hoeflich
et al. 1999) and (iii) GRB-energies Egamma=2e50 erg (3e50erg in Frail et al.
2001). GRB-SNe occur perhaps about once a year within D=100Mpc. Correlating
LIGO/Virgo detectors enables searches for nearby events and their spectral
closure density 6e-9 around 250Hz in the stochastic background radiation in
gravitational waves. At current sensitivity, LIGO-Hanford may place an upper
bound around 150MSolar in GRB030329. Detection of Egw thus provides a method
for identifying Kerr black holes by calorimetry.Comment: to appear in PRD, 49
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