363 research outputs found
Structure and activity relationships for amine-based CO2 absorbents-II
A study to determine the structure and activity relationships of various amine-based CO2 absorbents was performed, in which the absorption of pure CO2 at atmospheric pressure was measured to assess the total absorption rates and capacities. Steric hindrance effect was noticed when side chain with alkyl group was present at the α-carbon to the amine group in the absorbent structure. An increase in the number of amine groups in absorbent structure, results in a higher capacity of upto 3.03 moles CO2/moles amine. Aromatic amines substituted with alkyl groups at the 2nd and 5th position show an increase in both absorption rate and capacity. © 2008 The Institution of Chemical Engineers
Influence of the pressure on the product distribution in the oxidative dehydrogenation of propane over a Ga2O3/MoO3 catalystInfluence of the pressure on the product distribution in the oxidative dehydrogenation of propane over a Ga2O3/MoO3 catalyst
Thermodynamics of Black Holes in Schroedinger Space
A black hole and a black hyperboloid solutions in the space with the
Schroedinger isometries are presented and their thermodynamics is examined. The
on-shell action is obtained by the difference between the extremal and
non-extremal ones with the unusual matching of the boundary metrics. This
regularization method is first applied to the black brane solution in the space
of the Schroedinger symmetry and shown to correctly reproduce the known
thermodynamics. The actions of the black solutions all turn out to be the same
as the AdS counterparts. The phase diagram of the black hole system is obtained
in the parameter space of the temperature and chemical potential and the
diagram contains the Hawking-Page phase transition and instability lines.Comment: 20 page
Fluorescence spectroscopy for identification of atherosclerotic tissue
Objective: Vessel perforation and limited steerability of the laser light are the major limitations of laser angioplasty. To improve steerability fluoresence spectroscopy has been proposed for identification of atherosclerotic plaques. The aim was to investigate this. Methods: Fluorescence spectroscopy with three different excitation wavelengths (325 nm, 380 nm, 450 nm) was tested in an emission range of 400 nm to 600 nm. Intensity ratios at 480/420 nm were determined in different types of blood vessels. Necropsy material from 40 patients (punch biopsies of 4 mm diameter from the coronary and carotid artery as well as from the ascending and descending aorta) was studied spectroscopically. Histological alterations of the vessel wall were assessed by a semiquantitative score (0 to 10 points): (a) normal tissue, 0 to 2 points (mean=0.25; n=38); (b) mild atherosclerotic lesions, 3 to 5 points (mean=3.35; n=39); (c) severe atherosclerotic lesions, ≥ 6 points (mean=6.75; n=43). Results: Best spectroscopic results were obtained with an excitation wavelength of 325 nm. In samples with severe atherosclerotic lesions the fluoresence spectra showed a significant reduction of the emitted wavelength intensities when compared to normal tissue. There was a clear separation of the fluorescence spectra between normal and mild as well as between normal and severe atherosclerotic lesions; normal tissue showed an increased intensity in the range from 420 nm to 540 nm, whereas atherosclerotic lesions had no or only a small peak at 480 nm. There was a significant correlation between the semiquantitative score (n=120) and the fluorescence ratio at 480/420 nm (excitation wavelength 325 nm) with a correlation coefficient of 0.87. The spectroscopic results showed no differences between the samples taken from different types of vessels. Conclusions: Fluorescence spectroscopy allows a reliable identification of normal and atherosclerotic lesions. The close correlation between the emitted light intensity ratio at 480/420 nm and the histological alterations of the vessel wall suggests a relationship between vessel wall fluorescence and the atherosclerotic alterations of the wal
Galilean Conformal and Superconformal Symmetries
Firstly we discuss briefly three different algebras named as nonrelativistic
(NR) conformal: Schroedinger, Galilean conformal and infinite algebra of local
NR conformal isometries. Further we shall consider in some detail Galilean
conformal algebra (GCA) obtained in the limit c equal to infinity from
relativistic conformal algebra O(d+1,2) (d - number of space dimensions). Two
different contraction limits providing GCA and some recently considered
realizations will be briefly discussed. Finally by considering NR contraction
of D=4 superconformal algebra the Galilei conformal superalgebra (GCSA) is
obtained, in the formulation using complex Weyl supercharges.Comment: 16 pages, LateX; talk presented at XIV International Conference
"Symmetry Methods in Physics", Tsakhkadzor, Armenia, August 16-22, 201
Ageing without detailed balance: local scale invariance applied to two exactly solvable models
I consider ageing behaviour in two exactly solvable reaction-diffusion
systems. Ageing exponents and scaling functions are determined. I discuss in
particular a case in which the equality of two critical exponents, known from
systems with detailed balance, does not hold any more. Secondly it is shown
that the form of the scaling functions can be understood by symmetry
considerations.Comment: 6 pages, contribution to the summer school "Ageing and the Glass
Transition" held in Luxemburg in September 05. Published versio
The non-linear Schr\"odinger equation and the conformal properties of non-relativistic space-time
The cubic non-linear Schr\"odinger equation where the coefficient of the
nonlinear term is a function only passes the Painlev\'e test of Weiss,
Tabor, and Carnevale only for , where and are constants.
This is explained by transforming the time-dependent system into the
constant-coefficient NLS by means of a time-dependent non-linear
transformation, related to the conformal properties of non-relativistic
space-time. A similar argument explains the integrability of the NLS in a
uniform force field or in an oscillator background.Comment: Thoroughly revised version, in the light of new interest in
non-relativistic conformal tranformation, with a new reference list. 8 pages,
LaTex, no figures. To be published in Int. J. Theor. Phy
Exact results on the dynamics of multi-component Bose-Einstein condensate
We study the time-evolution of the two dimensional multi-component
Bose-Einstein condensate in an external harmonic trap with arbitrary
time-dependent frequency. We show analytically that the time-evolution of the
total mean-square radius of the wave-packet is determined in terms of the same
solvable equation as in the case of a single-component condensate. The dynamics
of the total mean-square radius is also the same for the rotating as well as
the non-rotating multi-component condensate. We determine the criteria for the
collapse of the condensate at a finite time. Generalizing our previous work on
a single-component condensate, we show explosion-implosion duality in the
multi-component condensate.Comment: Two-column 6 pages, RevTeX, no figures(v1); Added an important
reference, version to appear in Physical Review A (v2
Kinetics of phase-separation in the critical spherical model and local scale-invariance
The scaling forms of the space- and time-dependent two-time correlation and
response functions are calculated for the kinetic spherical model with a
conserved order-parameter and quenched to its critical point from a completely
disordered initial state. The stochastic Langevin equation can be split into a
noise part and into a deterministic part which has local scale-transformations
with a dynamical exponent z=4 as a dynamical symmetry. An exact reduction
formula allows to express any physical average in terms of averages calculable
from the deterministic part alone. The exact spherical model results are shown
to agree with these predictions of local scale-invariance. The results also
include kinetic growth with mass conservation as described by the
Mullins-Herring equation.Comment: Latex2e with IOP macros, 28 pp, 2 figures, final for
Invariant vector fields and the prolongation method for supersymmetric quantum systems
The kinematical and dynamical symmetries of equations describing the time
evolution of quantum systems like the supersymmetric harmonic oscillator in one
space dimension and the interaction of a non-relativistic spin one-half
particle in a constant magnetic field are reviewed from the point of view of
the vector field prolongation method. Generators of supersymmetries are then
introduced so that we get Lie superalgebras of symmetries and supersymmetries.
This approach does not require the introduction of Grassmann valued
differential equations but a specific matrix realization and the concept of
dynamical symmetry. The Jaynes-Cummings model and supersymmetric
generalizations are then studied. We show how it is closely related to the
preceding models. Lie algebras of symmetries and supersymmetries are also
obtained.Comment: 37 pages, 7 table
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