2,432 research outputs found
Bilinear and quadratic Hamiltonians in two-mode cavity quantum electrodynamics
In this work we show how to engineer bilinear and quadratic Hamiltonians in
cavity quantum electrodynamics (QED) through the interaction of a single driven
two-level atom with cavity modes. The validity of the engineered Hamiltonians
is numerically analyzed even considering the effects of both dissipative
mechanisms, the cavity field and the atom. The present scheme can be used, in
both optical and microwave regimes, for quantum state preparation, the
implementation of quantum logical operations, and fundamental tests of quantum
theory.Comment: 11 pages, 3 figure
Nonadiabatic coherent evolution of two-level systems under spontaneous decay
In this paper we extend current perspectives in engineering reservoirs by
producing a time-dependent master equation leading to a nonstationary
superposition equilibrium state that can be nonadiabatically controlled by the
system-reservoir parameters. Working with an ion trapped inside a nonindeal
cavity we first engineer effective Hamiltonians that couple the electronic
states of the ion with the cavity mode. Subsequently, two classes of
decoherence-free evolution of the superposition of the ground and decaying
excited levels are achieved: those with time-dependent azimuthal or polar
angle. As an application, we generalise the purpose of an earlier study [Phys.
Rev. Lett. 96, 150403 (2006)], showing how to observe the geometric phases
acquired by the protected nonstationary states even under a nonadiabatic
evolution.Comment: 5 pages, no figure
A Study of Single- and Double-Averaged Second-Order Models to Evaluate Third-Body Perturbation Considering Elliptic Orbits for the Perturbing Body
The equations for the variations of the Keplerian elements of the orbit of a spacecraft perturbed by a third body are developed using a single average over the motion of the spacecraft, considering an elliptic orbit for the disturbing body. A comparison is made between this approach and the more used double averaged technique, as well as with the full elliptic restricted three-body problem. the disturbing function is expanded in Legendre polynomials up to the second order in both cases. the equations of motion are obtained from the planetary equations, and several numerical simulations are made to show the evolution of the orbit of the spacecraft. Some characteristics known from the circular perturbing body are studied: circular, elliptic equatorial, and frozen orbits. Different initial eccentricities for the perturbed body are considered, since the effect of this variable is one of the goals of the present study. the results show the impact of this parameter as well as the differences between both models compared to the full elliptic restricted three-body problem. Regions below, near, and above the critical angle of the third-body perturbation are considered, as well as different altitudes for the orbit of the spacecraft.Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de NÃvel Superior (CAPES)Inst Nacl Pesquisas Espaciais, BR-12227010 Sao Jose Dos Campos, SP, BrazilUniversidade Federal de São Paulo UNIFESP, BR-12231280 Sao Jose Dos Campos, SP, BrazilUniversidade Federal de São Paulo UNIFESP, BR-12231280 Sao Jose Dos Campos, SP, BrazilCNPq: 150195/2012-5CNPq: 304700/2009-6FAPESP: 2011/09310-7FAPESP: 2011/08171-3Web of Scienc
Using low Lift-to-Drag spacecraft to perform upper atmospheric Aero-Gravity Assisted Maneuvers
The Gravity Assisted Maneuver has been applied in lots of space missions, to
change the spacecraft heliocentric velocity vector and the geometry of the
orbit, after the close approach to a celestial body, saving propellant
consumption. It is possible to take advantage of additional forces to improve
the maneuver, like the forces generated by the spacecraft-atmosphere
interaction and/or propulsion systems; reducing the time of flight and the need
for multiple passages around secondary bodies. However, these applications
require improvements in critical subsystems, which are necessary to accomplish
the mission. In this paper, a few combinations of the Gravity-Assist were
classified, including maneuvers with thrust and aerodynamic forces; presenting
the advantages and limitations of these variations. There are analyzed the
effects of implementing low Lift-to-Drag ratios at high altitudes for
Aero-gravity Assist maneuvers, with and without propulsion. The maneuvers were
simulated for Venus and Mars, due to their relevance in interplanetary
missions, the interest in exploration, and the knowledge about their
atmospheres. The Aero-gravity Assist maneuver with low Lift-to-Drag ratios at
high altitudes shows an increase of more than 10{\deg} in the turn angle for
Venus and 2.5{\deg} for Mars. The maneuvers increase the energy gains by more
than 15% when compared to the Gravity-Assist. From the Technology Readiness
Levels, it was observed that the current level of development of the space
technology makes feasible the application of Aero-gravity Assisted Maneuvers at
high altitudes in short term
Superscars in the LiNC=LiCN isomerization reaction
We demonstrate the existence of superscarring in the LiNC=LiCN isomerization
reaction described by a realistic potential interaction in the range of readily
attainable experimental energies. This phenomenon arises as the effect of two
periodic orbits appearing "out of the blue"in a saddle--node bifurcation taking
place in the dynamics of the system. Potential practical consequences of this
superlocalization in the corresponding wave functions are also considered.Comment: 6 pages, 5 figures. to appear in EP
Applying the perturbative integral in aeromaneuvers around Mars to calculate the cost
The perturbative integral method was applied to quantify the contribution of
external forces during a specific interval of time in trajectories of
spacecraft around asteroids and under the Luni-solar influence. However, this
method has not been used to quantify the contributions of drag in aerocapture
and aerobraking. For this reason, the planet Mars is selected to apply this
method during an aerogravity-assisted maneuver. Several trajectories are
analyzed, making use of a drag device with area to mass ratios varying from 0.0
to 20.0 m2/kg, simulating solar sails or de-orbit devices. The mathematical
model is based in the restricted three-body problem. The use of this maneuver
makes it possible to obtain the variations of energy in the trajectory,
replacing expensive maneuvers based on fuel consumption. To observe the effects
of the maneuvers, different values of pericenter velocity and altitude were
selected for prograde and retrograde orbits. The innovation of this research is
the application of an integral method to quantify the delta-V of the aero
gravity maneuver, comparing the cost of the maneuver with the traditional
methods of space propulsion. The results allow the identification of orbits
with conditions to capture, and the perturbative maps show the velocity
variations
Protein extract and activity antioxidant of corn (Zea mays) and sorghum (Sorghum bicolor L. Moench) grains
Brazil is a major producer of grains, such as sorgh
um and corn, which are used for export. Sorghum
and corn grains have in its composition 9.5% and 9.
8 protein, respectively. Proteins are the most
abundant and most diverse functions in living syste
ms molecules. Currently, food proteins are
increasingly recognized as a source of beneficial b
ioactive peptides, and they are physiologically
released during digestion. The aim of the work was
to evaluate the protein extraction (four methods)
and antioxidant activity of sorghum and corn grains
. The proximal composition of grains was
evaluated in relation to moisture, protein, lipids
and ash contents, furthermore were quantified
proteins concentration and antioxidant activity by
FRAP method in the four extracts. The corn and
sorghum grains were ground, homogenized (60 mesh) a
nd stored at 5°C until analysis. The protein
extraction utilized were: 1) dichloromethane/methan
ol; 2) NH
4
HCO
3
(5mM, pH 8.0)/heat treatment;
3) water/ethanol/heat treatment; and 4) alkaline ex
traction and precipitation. The corn and sorghum
presented, protein 6.62% and 9.87%, lipids 4.45% an
d 4.32%, moisture 8.87% and 8.23%, ash
0.96% and 1.15%, carbohydrates 79.01% and 76.41%, t
otalizing a caloric value of 382.9 and 384.1
Kcal g
-1
, respectively. The 2 and 3 methods in corn grain p
resented highest protein content 133.16
and 142.24 μ g g
-1
, respectively. In sorghum grain, methods 1, 2 and
3 presented protein content
between 173.59 – 223.63 μg g
-1
. The antioxidant activity of protein extracts was
between 0.90 –
9.73μM of ferrous sulphate for corn and between 4.4
1 – 15.04μ M of ferrous sulphate for sorghum.
The best results in the extraction using the method
3 for both grains could be due to the structure of
proteins (zein and kafirins) which are soluble in a
lcoholic solutions and insoluble in water. In
conclusion, method 3 - water/ethanol/heat treatment
(corn: 142.24 μg g
-1
and sorghum: 223.63 μg g
-
1
) and method 3 (corn: 9.73 μM and sorghum: 15.04 μ M
) showed the best results for extracting
protein and antioxidant activity, respectively. The
protein extracts obtainedhave great potential as
natural antioxidant
Protein extraction of the sunflower grains and bran
[Excerpt] Sunflower grains have a high protein content (24%) with high quality amino acid profile and are
used to extraction of vegetable oil. The sunflower brain is produced during the processing of vegetal
oil. The sunflower grains and by-product (bran) can be used with raw materials for obtaining
peptides with bioactivity for protein hydrolysis after extraction, since they have great amount of
essential amino acids, typically nonpolar, soluble and insoluble alcoholic solutions in water. The
aim of this work was to evaluate protein extraction (three methods) of sunflower grains and bran. (...
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