1,683 research outputs found
Comparison of stabilization by Vitamin E and 2,6-di-tert-butylphenols during polyethylene radio-thermal-oxidation
This paper reports a compilation of data for PE+Vitamin E and 2,6-di-tert-butylphenols oxidation in radio-thermal ageing. Data unambiguously show that Vitamin E reacts with P° and POO° whereas 2,6-di-tert-butyl phenols only react with POO°. Kinetic parameters of the stabilization reactions for both kinds of antioxidants were tentatively extracted from phenol depletion curves, and discussed regarding the structure of the stabilizer. They were also used for completing an existing kinetic model used for predicting the stabilization by antioxidants. This one permits to compare the efficiency of stabilizer with dose rate or sample thickness
The phase-separation mechanism of a binary mixture in a ring trimer
We show that, depending on the ratio between the inter- and the intra-species
interactions, a binary mixture trapped in a three-well potential with periodic
boundary conditions exhibits three macroscopic ground-state configurations
which differ in the degree of mixing. Accordingly, the corresponding quantum
states feature either delocalization or a Schr\"odinger cat-like structure. The
two-step phase separation occurring in the system, which is smoothed by the
activation of tunnelling processes, is confirmed by the analysis of the energy
spectrum that collapses and rearranges at the two critical points. In such
points, we show that also Entanglement Entropy, a quantity borrowed from
quantum-information theory, features singularities, thus demonstrating its
ability to witness the double mixining-demixing phase transition. The developed
analysis, which is of interest to both the experimental and theoretical
communities, opens the door to the study of the demixing mechanism in complex
lattice geometries.Comment: 14 pages, 9 figure
Pathway toward the formation of supermixed states in ultracold boson mixtures loaded in ring lattices
We investigate the mechanism of formation of supermixed soliton-like states
in bosonic binary mixtures loaded in ring lattices. We evidence the presence of
a common pathway which, irrespective of the number of lattice sites and upon
variation of the interspecies attraction, leads the system from a mixed and
delocalized phase to a supermixed and localized one, passing through an
intermediate phase where the supermixed soliton progressively emerges. The
degrees of mixing, localization and quantum correlation of the two condensed
species, quantified by means of suitable indicators commonly used in
Statistical Thermodynamics and Quantum Information Theory, allow one to
reconstruct a bi-dimensional mixing-supermixing phase diagram featuring two
characteristic critical lines. Our analysis is developed both within a
semiclassical approach capable of capturing the essential features of the
two-step mixing-demixing transition and with a fully-quantum approach.Comment: 12 pages, 8 figure
Phase separation can be stronger than chaos
We investigate several dynamical regimes characterizing a bosonic binary
mixture loaded in a ring trimer, with particular reference to the persistence
of demixing. The degree of phase separation is evaluated by means of the
"Entropy of mixing", an indicator borrowed from Statistical Thermodynamics.
Three classes of demixed stationary configurations are identified and their
energetic and linear stability carefully analyzed. An extended set of
trajectories originating in the vicinity of fixed points are explicitly
simulated and chaos is shown to arise according to three different mechanisms.
In many dynamical regimes, we show that chaos is not able to disrupt the order
imposed by phase separation, i.e. boson populations, despite evolving in a
chaotic fashion, do not mix. This circumstance can be explained either with
energetic considerations or in terms of dynamical restrictions.Comment: 21 pages, 9 figure
Two-species boson mixture on a ring: A group theoretic approach to the quantum dynamics of low-energy excitations
We investigate the weak excitations of a system made up of two condensates
trapped in a Bose-Hubbard ring and coupled by an interspecies repulsive
interaction. Our approach, based on the Bogoliubov approximation scheme, shows
that one can reduce the problem Hamiltonian to the sum of sub-Hamiltonians
, each one associated to momentum modes . Each is
then recognized to be an element of a dynamical algebra. This uncommon and
remarkable property allows us to present a straightforward diagonalization
scheme, to find constants of motion, to highlight the significant microscopic
processes, and to compute their time evolution. The proposed solution scheme is
applied to a simple but still very interesting closed circuit, the trimer. The
dynamics of low-energy excitations, corresponding to weakly-populated vortices,
is investigated considering different choices of the initial conditions, and
the angular-momentum transfer between the two condensates is evidenced.
Finally, the condition for which the spectral collapse and dynamical
instability are observed is derived analytically.Comment: 11 pages, 7 figure
Summability of solutions of the heat equation with inhomogeneous thermal conductivity in two variables
We investigate Gevrey order and 1-summability properties of the formal
solution of a general heat equation in two variables. In particular, we give
necessary and sufficient conditions for the 1-summability of the solution in a
given direction. When restricted to the case of constants coefficients, these
conditions coincide with those given by D.A. Lutz, M. Miyake, R. Schaefke in a
1999 article, and we thus provide a new proof of their result.Comment: 16 page
A Review Study of Psychometric Functioning of a Picture Scale to Assess Joy in Childhood
The early emergence of emotional understanding by means of facial expressions allows the assessmentof basic emotions from young ages through pictures or photographs of human faces. Thisevaluation strategy allows children, with limited language to reveal feelings that neither investigatorsnor clinicians would be able to obtain verbally. The present work presents a non-verbal activityaimed at testing children?s joy. It is based on a visual analogue scale integrated by sevenpictures of infant facial expressions. This scale has the advantage of presenting an animated design,more friendly and appealing than simplified face scales. Its psychometric functioning, revisedfrom different studies, demonstrates that it is a reliable and valid alternative to analyze the experienceof joy in small children.Fil: Oros, Laura Beatriz. Universidad de la Cuenca del Plata. Secretaria de Politicas del Conocimiento. Instituto de Investigaciones Científicas (sede Posadas); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Richaud, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Centro Interdisciplinario de Investigaciones en Psicología Matemática y Experimental Dr. Horacio J. A. Rimoldi; Argentin
A statistical theory of polymer network degradation
A statistical theory was proposed for the degradation (random scission of chains) of a network having f-functional nodes in the case where all chains contain equireactive groups and a chain scission event does not create new groups or suppress more than one group. Closedform relations were established between the conversion ratio of the degradation process and the crosslink density. Emphasis was put on the value of the conversion ratio for which the gel disappears. Some limited cases already considered in the literature were recovered, but a general solution was proposed for networks having any number of reactive groups per chain, be it uniform or not, and for conversion ratios up to the degelation point. The results were applied successfully to recent experiments regarding the hydrolysis of a polyester
Residual entropy and critical behavior of two interacting boson species in a double well
Motivated by the importance of entanglement and correlation indicators in the
analysis of quantum systems, we study the equilibrium and the bipartite
residual entropy in a two-species Bose Hubbard dimer when the spatial phase
separation of the two species takes place. We consider both the zero and
non-zero-temperature regime. We present different kinds of residual entropies
(each one associated to a different way of partitioning the system), and we
show that they strictly depend on the specific quantum phase characterizing the
two species (supermixed, mixed or demixed) even at finite temperature. To
provide a deeper physical insight into the zero-temperature scenario, we apply
the fully-analytical variational approach based on su(2) coherent states and
provide a considerably good approximation of the entanglement entropy. Finally,
we show that the effectiveness of bipartite residual entropy as a critical
indicator at non-zero temperature is unchanged when considering a restricted
combination of energy eigenstates.Comment: 18 pages, 9 figure
Human leukocyte antigen class I, class II, and tumor necrosis factor-alpha polymorphisms in a healthy elder Mexican Mestizo population
BACKGROUND: There is strong evidence that an individual's genetic background is an important predisposing factor to longevity. In the present study we analysed the frequency of HLA class I, class II, as well as the TNF-α -308 polymorphism that may be related to an increased life span in Mexican Mestizo healthy elders. RESULTS: HLA typing was performed by polymerase chain reaction sequence specific oligonucleotide (PCR SSO) reverse dot blot. The TNF-α -308 polymorphism was assessed by PCR restriction fragment length polymorphism. A significant increased frequency of HLA-DRB1*11 was found in elderly women whereas this allele was not present in elderly males. The TNF2 allele was also increased in the elder group when compared to young controls. The frequencies of the remaining alleles tested were not statistically different among groups. CONCLUSION: These data suggest an ethnicity independent tendency of HLA-DRB1*11 in elder females to increase life span and a possible role of the TNF2 allele with the successful remodelling of senescent immune system
- …