5,169 research outputs found
Microencapsulation of clove essential oil with gelatin and alginate
Content:
Essential oils are of commercial interest primarily because of their potential antimicrobial, antifungal and antioxidant properties and for being of natural origin, which generally represents lower risk to the
environment and human health. Clove essential oil not only contains many kinds of biological active compositions but also has highly effective and comprehensive antibacterial functions. Remarkably, clove
has strong antimicrobial activities against a wide range of pathogenic microorganisms. To prevent chemical changes the oil is microencapsulated. The aim of this study is to develop essential oil
microcapsules with gelatin and alginate. Various solutions were prepared for the capsule wall material at different concentrations. The encapsulation efficiency (%) was accessed and the microcapsules were
characterized by oil content (%), oil charge (%), morphology, functional groups present, thermogravimetric analysis and by Fourier transform - infrared spectral analysis. FT-IR spectra of the clove oil shows some special peaks at 1148,01 and 1033,33 cm-1. The spectra of the capsule showed peaks 1148.34 and 1033.29 cm -1, the same peaks present in clove oil, showing that the encapsulation did not alter the
structure of the oil's main assets. In case of the gelatin and alginate microcapsules containing clove oil, most of the characteristic peaks of clove oil remained unchanged, indicating the successful incorporation
of clove oil into the microcapsules and the chemical stability of the clove oil after encapsulation. In otherwords, there was no significant chemical interaction between the oil and the wall of the microcapsule.
Take-Away:
The clove oil was microencapsulated according the FTIR spectra
Three-point correlations for quantum star graphs
We compute the three point correlation function for the eigenvalues of the
Laplacian on quantum star graphs in the limit where the number of edges tends
to infinity. This extends a work by Berkolaiko and Keating, where they get the
2-point correlation function and show that it follows neither Poisson, nor
random matrix statistics. It makes use of the trace formula and combinatorial
analysis.Comment: 10 pages, 2 figure
Giant mass and anomalous mobility of particles in fermionic systems
We calculate the mobility of a heavy particle coupled to a Fermi sea within a
non-perturbative approach valid at all temperatures. The interplay of particle
recoil and of strong coupling effects, leading to the orthogonality catastrophe
for an infinitely heavy particle, is carefully taken into account. We find two
novel types of strong coupling effects: a new low energy scale and
a giant mass renormalization in the case of either near-resonant scattering or
a large transport cross section . The mobility is shown to obey two
different power laws below and above . For ,
where is the Fermi wave length, an exponentially large effective
mass suppresses the mobility.Comment: 4 pages, 4 figure
A diagrammatic treatment of neutrino oscillations
We present a covariant wave-packet approach to neutrino flavor transitions in
vacuum. The approach is based on the technique of macroscopic Feynman diagrams
describing the lepton number violating processes of production and absorption
of virtual massive neutrinos at the macroscopically separated space-time
regions ("source" and "detector"). Accordingly, the flavor transitions are a
result of interference of the diagrams with neutrinos of different masses in
the intermediate states. The statistically averaged probability of the process
is representable as a multidimensional integral of the product of the factors
which describe the differential flux density of massless neutrinos from the
source, differential cross section of the neutrino interaction with the
detector and a dimensionless factor responsible for the flavor transition. The
conditions are analyzed under which the last factor can be treated as the
flavor transition probability in the usual quantum-mechanical sense.Comment: 27 pages,7 figures, iopart class. Includes minor corrections made in
proofs. References update
Separate Universes Do Not Constrain Primordial Black Hole Formation
Carr and Hawking showed that the proper size of a spherical overdense region
surrounded by a flat FRW universe cannot be arbitrarily large as otherwise the
region would close up on itself and become a separate universe. From this
result they derived a condition connecting size and density of the overdense
region ensuring that it is part of our universe. Carr used this condition to
obtain an upper bound for the density fluctuation amplitude with the property
that for smaller amplitudes the formation of a primordial black hole is
possible, while larger ones indicate a separate universe. In contrast, we find
that the appearance of a maximum is not a consequence of avoiding separate
universes but arises naturally from the geometry of the chosen slicing. Using
instead of density a volume fluctuation variable reveals that a fluctuation is
a separate universe iff this variable diverges on superhorizon scales. Hence
Carr's and Hawking's condition does not pose a physical constraint on density
fluctuations. The dynamics of primordial black hole formation with an initial
curvature fluctuation amplitude larger than the one corresponding to the
maximum density fluctuation amplitude was previously not considered in detail
and so we compare it to the well-known case where the amplitude is smaller by
presenting embedding and conformal diagrams of both types in dust spacetimes.Comment: Updated version corresponds to the published version
10.1103/PhysRevD.83.124025, 22 pages, 22 figure
Coherent Matter Wave Transport in Speckle Potentials
This article studies multiple scattering of matter waves by a disordered
optical potential in two and in three dimensions. We calculate fundamental
transport quantities such as the scattering mean free path , the
Boltzmann transport mean free path \elltrb, and the Boltzmann diffusion
constant , using a diagrammatic Green functions approach. Coherent
multiple scattering induces interference corrections known as weak localization
which entail a reduced diffusion constant. We derive the corresponding
expressions for matter wave transport in an correlated speckle potential and
provide the relevant parameter values for a possible experimental study of this
coherent transport regime, including the critical crossover to the regime of
strong or Anderson localization.Comment: 33 pages, minor corrections, published versio
Non-relativistic effective theory of dark matter direct detection
Dark matter direct detection searches for signals coming from dark matter
scattering against nuclei at a very low recoil energy scale ~ 10 keV. In this
paper, a simple non-relativistic effective theory is constructed to describe
interactions between dark matter and nuclei without referring to any underlying
high energy models. It contains the minimal set of operators that will be
tested by direct detection. The effective theory approach highlights the set of
distinguishable recoil spectra that could arise from different theoretical
models. If dark matter is discovered in the near future in direct detection
experiments, a measurement of the shape of the recoil spectrum will provide
valuable information on the underlying dynamics. We bound the coefficients of
the operators in our non-relativistic effective theory by the null results of
current dark matter direct detection experiments. We also discuss the mapping
between the non-relativistic effective theory and field theory models or
operators, including aspects of the matching of quark and gluon operators to
nuclear form factors.Comment: 35 pages, 3 figures, Appendix C.3 revised, acknowledgments and
references adde
Signatures of photon localization
Signatures of photon localization are observed in a constellation of
transport phenomena which reflect the transition from diffusive to localized
waves. The dimensionless conductance, g, and the ratio of the typical spectral
width and spacing of quasimodes, \delta, are key indicators of electronic and
classical wave localization when inelastic processes are absent. However, these
can no longer serve as localization parameters in absorbing samples since the
affect of absorption depends upon the length of the trajectories of partial
waves traversing the sample, which are superposed to create the scattered
field. A robust determination of localization in the presence of absorption is
found, however, in steady-state measurements of the statistics of radiation
transmitted through random samples. This is captured in a single parameter, the
variance of the total transmission normalized to its ensemble average value,
which is equal to the degree of intensity correlation of the transmitted wave,
\kappa. The intertwined effects of localization and absorption can also be
disentangled in the time domain since all waves emerging from the sample at a
fixed time delay from an exciting pulse, t, are suppressed equally by
absorption. As a result, the relative weights of partial waves emerging from
the sample, and hence the statistics of intensity fluctuations and correlation,
and the suppression of propagation by weak localization are not changed by
absorption, and manifest the growing impact of weak localization with t.Comment: RevTex 16 pages, 12 figures; to appear in special issue of J. Phys. A
on quantum chaotic scatterin
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