141 research outputs found
Separation of n-hexane - ethyl acetate mixture by azeotropic batch distillation with heterogeneous entrainers
In this article, a systematic study of the separation of the n-hexane - ethyl acetate mixture with an entrainer by heterogeneous azeotropic batch distillation is performed. Based upon the thermodynamic behaviour of the ternary mixtures, potential entrainers partially miscible with one or two original azeotropic components are chosen. In all cases, the entrainer adds a heterogeneous binary or ternary azeotrope that is the lowest boiling point in the ternary diagram. Therefore, it leaves the column by the overhead stream which is subcooled to get two liquid phases in the decanter. The phase with the highest amount of the original component is removed as distillate product whereas the entrainer – rich phase is continuously refluxed to the column. Considering methanol, acetonitrile, water and nitromethane as heterogeneous entrainers, screening was performed based on the composition of the unstable heteroazeotropic mixture, the ratio of both liquid phases in the condensed top vapour and the purity of the distillate product determined by the liquid – liquid envelope at the decanter temperature. The process feasibility analysis is validated by using rigorous simulation with the batch process simulator ProSimBatch. Simulation results are then corroborated in a bench experimental column for the selected entrainer, showing several advantages of heterogeneous batch distillation compared to homogeneous systems
Boson-conserving one-nucleon transfer operator in the interacting boson model
The boson-conserving one-nucleon transfer operator in the interacting boson
model (IBA) is reanalyzed. Extra terms are added to the usual form used for
that operator. These new terms change generalized seniority by one unit, as the
ones considered up to now. The results obtained using the new form for the
transfer operator are compared with those obtained with the traditional form in
a simple case involving the pseudo-spin Bose-Fermi symmetry in its limit. Sizeable differences are
found. These results are of relevance in the study of transfer reactions to
check nuclear supersymmetry and in the description of (\beta)-decay within IBA.Comment: 13 pages, 1 table, 0 figures. To be published in Phys. Rev.
In situ neutron diffraction measurement of residual stress relaxation in a welded steel pipe during heat treatment
Cute Balloons with Thickness
Based on the fnite element method, we present a simple volume-preserved thin shell deformation algorithm to simulate the process of inflating a balloon. Diff erent from other thin shells, the material of balloons has special features: large stretch, small bend and shear, and incompressibility. Previous deformation methods often focus on typical three-dimensional models or thin plate models such as cloth model. The rest thin shell methods are complex or ignore the special features of thin shells especially balloons. We modify the triangle element to simple three-prism element, ignore bending and shearing deformation, and use volume preservation algorithm to match the incompressibility of balloons. Simple gas model is used, which interacts with shells to make the balloons inflated. Di different balloon examples have been tested in our experiments and the results are compared with those of other methods. The experiments show that our algorithm is simple and effective
Gamow-Teller Strength in the Region of Sn
New calculations are presented for Gamow-Teller beta decay of nuclei near
Sn. Essentially all of the Sn Gamow-Teller decay strength is
predicted to go to a single state at an excitation energy of 1.8 MeV in
In. The first calculations are presented for the decays of neighboring
odd-even and odd-odd nuclei which show, in contrast to Sn, surprisingly
complex and broad Gamow-Teller strength distributions. The results are compared
to existing experimental data and the resulting hindrance factors are
discussed.Comment: 12 pages (latex) and 2 figures available on reques
Overconstrained estimates of neutrinoless double beta decay within the QRPA
Estimates of nuclear matrix elements for neutrinoless double beta decay
(0nu2beta) based on the quasiparticle random phase approximations (QRPA) are
affected by theoretical uncertainties, which can be substantially reduced by
fixing the unknown strength parameter g_pp of the residual particle-particle
interaction through one experimental constraint - most notably through the
two-neutrino double beta decay (2nu2beta) lifetime. However, it has been noted
that the g_pp adjustment via 2\nu2\beta data may bring QRPA models in
disagreement with independent data on electron capture (EC) and single beta
decay (beta^-) lifetimes. Actually, in two nuclei of interest for 0nu2beta
decay (Mo-100 and Cd-116), for which all such data are available, we show that
the disagreement vanishes, provided that the axial vector coupling g_A is
treated as a free parameter, with allowance for g_A<1 (``strong quenching'').
Three independent lifetime data (2nu2beta, EC, \beta^-) are then accurately
reproduced by means of two free parameters (g_pp, g_A), resulting in an
overconstrained parameter space. In addition, the sign of the 2nu2beta matrix
element M^2nu is unambiguously selected (M^2nu>0) by the combination of all
data. We discuss quantitatively, in each of the two nuclei, these
phenomenological constraints and their consequences for QRPA estimates of the
0nu2beta matrix elements and of their uncertainties.Comment: Revised version (27 pages, including 10 figures), focussed on Mo-100
and Cd-116. To appear in J. Phys. G: Nucl. Phys. (2008
Neutrinoless Double Beta Decay in Gauge Theories
Neutrinoless double beta decay is a very important process both from the
particle and nuclear physics point of view. Its observation will severely
constrain the existing models and signal that the neutrinos are massive
Majorana particles. From the elementary particle point of view it pops up in
almost every model. In addition to the traditional mechanisms, like the
neutrino mass, the admixture of right handed currents etc, it may occur due to
the R-parity violating supersymmetric (SUSY) interactions. From the nuclear
physics point of view it is challenging, because: 1) The relevant nuclei have
complicated nuclear structure. 2) The energetically allowed transitions are
exhaust a small part of all the strength. 3) One must cope with the short
distance behavior of the transition operators, especially when the intermediate
particles are heavy (eg in SUSY models). Thus novel effects, like the double
beta decay of pions in flight between nucleons, have to be considered. 4) The
intermediate momenta involved are about 100 MeV. Thus one has to take into
account possible momentum dependent terms in the nucleon current. We find that,
for the mass mechanism, such modifications of the nucleon current for light
neutrinos reduce the nuclear matrix elements by about 25 per cent, almost
regardless of the nuclear model. In the case of heavy neutrinos the effect is
much larger and model dependent.
Taking the above effects into account, the available nuclear matrix elements
for the experimentally interesting nuclei A = 76, 82, 96, 100, 116, 128, 130,
136 and 150 and the experimental limits on the life times we have extracted new
stringent limits on the average neutrino mass and on the R-parity violating
coupling for various SUSY models.Comment: Latex, 24 pages, 1 postscript figure, uses iopconf.st
Kynurenine monooxygenase regulates inflammation during critical illness and recovery in experimental acute pancreatitis
Structural and mechanistic basis of differentiated inhibitors of the acute pancreatitis target kynurenine-3-monooxygenase
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