3,112 research outputs found
Distillation methods affect the chemical composition of Varronia curassavica Jacq, essential oil?
The objective of this work was to evaluate the chemical composition of essential oil from Varronia curassavica Jacq. obtained by microwave (MI) and hydrodistillation (HD) extraction methods. The MI method tested three powers (500, 600, and 700W), three distillation times (20, 30, and 40 min.), and three water volumes (0, 25, and 50 mL per sample). The HD method tested three distillation times (100, 120, and 140 min.) and three water volumes (1.0, 1.5, and 2.0 L per 3-liter flask). The essential oils were analyzed by GC/MS-FID. The optimal condition for the essential oil extraction by the MI method was 700W for 40 min. (3.28%), regardless of the volume of water. In its turn, the best condition for essential oil extraction by the HD method was 120 min. with 1.0 L of water per flask (3.34%). The most abundant compounds for MI (700 W for 40 min. without water) were shyobunol (26.53%) and bicyclogermacrene (4.96%); and the most abundant compounds for HD (120 min. with 1.0 L of water/flask) were shyobunol (24.00%) and germacrene D-4-ol (10.23%). Methyl farnesoate (2E, 6E) and farnesyl acetate (2Z, 6E) were not detected in the essential oil extracted by HD; however, they were identified by the MI method. By increasing the distillation time and/or volume of water in HD, a reduction was observed for the content of the chemical compounds -elemene (from 1.23 to 0.97%), Ecaryophyllene (from 5.49 to 4.35%), -humulene (from 1.80 to 1.43%), alloaromadendrene (from 1.78 to 1.44%), bicyclogermacrene (from 5.63 to 4.55%), and germacrene D-4-ol (from 11.40 to 9.86%). Power, extraction time, and their interactions influenced the content of essential oil obtained by microwave extraction (MI). Within each power, the highest essential oil content was extracted at the longest distillation time (40 min.), except for 600W, where no significant difference was detected between 30 and 40 min. The optimal essential oil contents for both extraction methods were statically similar by the t-test for dependent samples. However, the MI method presents advantages, such as shorter distillation time and less energy and water consumption
Chaotic Cascades with Kolmogorov 1941 Scaling
We define a (chaotic) deterministic variant of random multiplicative cascade
models of turbulence. It preserves the hierarchical tree structure, thanks to
the addition of infinitesimal noise. The zero-noise limit can be handled by
Perron-Frobenius theory, just as the zero-diffusivity limit for the fast dynamo
problem. Random multiplicative models do not possess Kolmogorov 1941 (K41)
scaling because of a large-deviations effect. Our numerical studies indicate
that deterministic multiplicative models can be chaotic and still have exact
K41 scaling. A mechanism is suggested for avoiding large deviations, which is
present in maps with a neutrally unstable fixed point.Comment: 14 pages, plain LaTex, 6 figures available upon request as hard copy
(no local report #
First observation of 54Zn and its decay by two-proton emission
The nucleus 54Zn has been observed for the first time in an experiment at the
SISSI/LISE3 facility of GANIL in the quasi-fragmentation of a 58Ni beam at 74.5
MeV/nucleon in a natNi target. The fragments were analysed by means of the
ALPHA-LISE3 separator and implanted in a silicon-strip detector where
correlations in space and time between implantation and subsequent decay events
allowed us to generate almost background free decay spectra for about 25
different nuclei at the same time. Eight 54Zn implantation events were
observed. From the correlated decay events, the half-life of 54Zn is determined
to be 3.2 +1.8/-0.8 ms. Seven of the eight implantations are followed by
two-proton emission with a decay energy of 1.48(2) MeV. The decay energy and
the partial half-life are compared to model predictions and allow for a test of
these two-proton decay models.Comment: 4 pages, 4 figures, accepted for publication in PR
The beta-decay of 22Al
In an experiment performed at the LISE3 facility of GANIL, we studied the
decay of 22Al produced by the fragmentation of a 36Ar primary beam. A
beta-decay half-life of 91.1 +- 0.5 ms was measured. The beta-delayed one- and
two-proton emission as well as beta-alpha and beta-delayed gamma decays were
measured and allowed us to establish a partial decay scheme for this nucleus.
New levels were determined in the daughter nucleus 22Mg. The comparison with
model calculations strongly favours a spin-parity of 4+ for the ground state of
22Al
Non-perturbative flow equations from continuous unitary transformations
We use a novel parameterization of the flowing Hamiltonian to show that the
flow equations based on continuous unitary transformations, as proposed by
Wegner, can be implemented through a nonlinear partial differential equation
involving one flow parameter and two system specific auxiliary variables. The
implementation is non-perturbative as the partial differential equation
involves a systematic expansion in fluctuations, controlled by the size of the
system, rather than the coupling constant. The method is applied to the Lipkin
model to construct a mapping which maps the non-interacting spectrum onto the
interacting spectrum to a very high accuracy. This function is universal in the
sense that the full spectrum for any (large) number of particles can be
obtained from it. In a similar way expectation values for a large class of
operators can be obtained, which also makes it possible to probe the stucture
of the eigenstates.Comment: 24 pages, 13 figure
Integración in vivo de secuencias provirales del virus linfotrópico humano tipo i (htlv-1) y expresión de genes virales en células del epitelio oral en individuos seropositivos
Determinar la integración in vivo de secuencias provirales en células del epitelio bucal de individuos seropositivos para el HTLV-I
Integración in vivo de secuencias provirales del virus linfotrópico humano tipo i (htlv-1) y expresión de genes virales en células del epitelio oral en individuos seropositivos
Determinar la integración in vivo de secuencias provirales en células del epitelio bucal de individuos seropositivos para el HTLV-I
Magnetic strip waveguides
We analyze the spectrum of the "local" Iwatsuka model, i.e. a two-dimensional
charged particle interacting with a magnetic field which is homogeneous outside
a finite strip and translationally invariant along it. We derive two new
sufficient conditions for absolute continuity of the spectrum. We also show
that in most cases the number of open spectral gaps of the model is finite. To
illustrate these results we investigate numerically the situation when the
field is zero in the strip being screened, e.g. by a superconducting mask.Comment: 22 pages, a LaTeX source file with three eps figure
Absence of Normalizable Time-periodic Solutions for The Dirac Equation in Kerr-Newman-dS Black Hole Background
We consider the Dirac equation on the background of a Kerr-Newman-de Sitter
black hole. By performing variable separation, we show that there exists no
time-periodic and normalizable solution of the Dirac equation. This conclusion
holds true even in the extremal case. With respect to previously considered
cases, the novelty is represented by the presence, together with a black hole
event horizon, of a cosmological (non degenerate) event horizon, which is at
the root of the possibility to draw a conclusion on the aforementioned topic in
a straightforward way even in the extremal case.Comment: 12 pages. AMS styl
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