132 research outputs found
Preparation and Physicochemical characterisation of caprylocapryl macrogol -8- glycerides microemulsion for oral drug delivery
Se evaluó el rendimiento de los macrogol -8- glicéridos de caprilocaproilo en el desarrollo de una microemulsión
autoemulsionante, estable y aceptable desde el punto de vista farmacológico. Se evaluó la idoneidad de la concentración
de surfactante en relación con la fase oleosa a través de la medición de la tensión interfacial. Se elaboró un
sistema de microemulsiones pseudoternario con macrogol -8- glicéridos de caprilocaproilo/poligliceril 6-dioleato/
triglicéridos de cadena media y agua. La microemulsión modelo se caracterizó en relación con su comportamiento
electroconductivo y la medición del tamaño de las gotitas tras su dilución en agua y fluido gástrico simulado, y se
realizaron estudios de carga de superficie, estabilidad centrífuga, viscosidad y estabilidad. Se aplicó la teoría de la
transición de percolación al sistema, lo que hizo posible la determinación del umbral de percolación y la identificación
de las estructuras bicontinuas. Los cambios de tensión interfacial asociados a la formación de las microemulsiones
mostraron valores muy bajos, hasta un 30% de aceite en una proporción 4:1 de surfactante/cosurfactante. Además,
el tamaño de las partículas investigadas tras la dilución en agua abundante y en fluido gástrico simulado demostraron
la eficacia del sistema de microemulsiones como un posible sistema de transporte para la administración oral de fármacos.The performance of caprylocapryl macrogol -8- glycerides in the development of pharmaceutically acceptable, stable, selfemulsifying
microemulsion was assessed. The suitability of the concentration of surfactant with respect to the oil phase
was assessed by interfacial tension measurement. A pseudoternary microemulsion system was constructed using caprylocapryl
macrogol -8- glycerides / polyglyceryl 6-dioleate / medium chain triglycerides and water. The model microemulsion was
characterised with regard to its electroconductive behaviour and droplet size measurement after dilution with water as
well as with simulated gastric fluid, surface charge, centrifugal stability, viscosity and stability studies. The percolation
transition theory, which makes it possible to determine the percolation threshold and to identify the bicontinuous
structures, was applied to the system. The interfacial tension changes associated with the microemulsion formation shows
ultra low values upto 30% oil at a surfactant / cosurfactant ratio 4:1. Moreover, the investigated particle size after dilution
with excess of water as well as with simulated gastric fluid proved the efficiency of the microemulsion system as a potential
carrier for oral drug delivery.La financiación de este proyecto se ha realizado a través del Consejo de Investigación Científica e Industrial (Council of Scientific and Industrial Research, CSIR) de Nueva Delhi, India
Hamiltonian Theory of the Composite Fermion Wigner Crystal
Experimental results indicating the existence of the high magnetic field
Wigner Crystal have been available for a number of years. While variational
wavefunctions have demonstrated the instability of the Laughlin liquid to a
Wigner Crystal at sufficiently small filling, calculations of the excitation
gaps have been hampered by the strong correlations. Recently a new Hamiltonian
formulation of the fractional quantum Hall problem has been developed. In this
work we extend the Hamiltonian approach to include states of nonuniform
density, and use it to compute the excitation gaps of the Wigner Crystal
states. We find that the Wigner Crystal states near are
quantitatively well described as crystals of Composite Fermions with four
vortices attached. Predictions for gaps and the shear modulus of the crystal
are presented, and found to be in reasonable agreement with experiments.Comment: 41 page, 6 figures, 3 table
A novel realization of the Calogero-Moser scattering states as coherent states
A novel realization is provided for the scattering states of the -particle
Calogero-Moser Hamiltonian. They are explicitly shown to be the coherent states
of the singular oscillators of the Calogero-Sutherland model. Our algebraic
treatment is straightforwardly extendable to a large number of few and
many-body interacting systems in one and higher dimensions.Comment: 9 pages, REVTe
An explicit realization of fractional statistics in one dimension
An explicit realization of anyons is provided, using the three-body Calogero
model. The fact that in the coupling domain, , the angular spectrum
can have a band structure, leads to the manifestation of the desired phase in
the wave function, under the exchange of the paticles. Concurrently, the
momentum corresponding to the angular variable is quantized, exactly akin to
the relative angular momentum quantization in two dimensional anyonic systemComment: 12 page
Competition between quantum-liquid and electron-solid phases in intermediate Landau levels
On the basis of energy calculations we investigate the competition between
quantum-liquid and electron-solid phases in the Landau levels n=1,2, and 3 as a
function of their partial filling factor. Whereas the quantum-liquid phases are
stable only in the vicinity of quantized values 1/(2s+1) of the partial filling
factor, an electron solid in the form of a triangular lattice of clusters with
a few number of electrons (bubble phase) is energetically favorable between
these fillings. This alternation of electron-solid phases, which are insulating
because they are pinned by the residual impurities in the sample, and quantum
liquids displaying the fractional quantum Hall effect explains a recently
observed reentrance of the integral quantum Hall effect in the Landau levels
n=1 and 2. Around half-filling of the last Landau level, a uni-directional
charge density wave (stripe phase) has a lower energy than the bubble phase.Comment: 12 pages, 9 figures; calculation of exact exchange potential for
n=1,2,3 included, energies of electron-solid phases now calculated with the
help of the exact potential, and discussion of approximation include
Equivalence of the Calogero-Sutherland Model to Free Harmonic Oscillators
A similarity transformation is constructed through which a system of
particles interacting with inverse-square two-body and harmonic potentials in
one dimension, can be mapped identically, to a set of free harmonic
oscillators. This equivalence provides a straightforward method to find the
complete set of eigenfunctions, the exact constants of motion and a linear
algebra associated with this model. It is also demonstrated that
a large class of models with long-range interactions, both in one and higher
dimensions can be made equivalent to decoupled oscillators.Comment: 9 pages, REVTeX, Completely revised, few new equations and references
are adde
Hamiltonian Description of Composite Fermions: Magnetoexciton Dispersions
A microscopic Hamiltonian theory of the FQHE, developed by Shankar and myself
based on the fermionic Chern-Simons approach, has recently been quite
successful in calculating gaps in Fractional Quantum Hall states, and in
predicting approximate scaling relations between the gaps of different
fractions. I now apply this formalism towards computing magnetoexciton
dispersions (including spin-flip dispersions) in the , 2/5, and 3/7
gapped fractions, and find approximate agreement with numerical results. I also
analyse the evolution of these dispersions with increasing sample thickness,
modelled by a potential soft at high momenta. New results are obtained for
instabilities as a function of thickness for 2/5 and 3/7, and it is shown that
the spin-polarized 2/5 state, in contrast to the spin-polarized 1/3 state,
cannot be described as a simple quantum ferromagnet.Comment: 18 pages, 18 encapsulated ps figure
Vision-based portuguese sign language recognition system
Vision-based hand gesture recognition is an area of active current research in computer vision and machine learning. Being a natural way of human interaction, it is an area where many researchers are working on, with the goal of making human computer interaction (HCI) easier and natural, without the need for any extra devices. So, the primary goal of gesture recognition research is to create systems, which can identify specific human gestures and use them, for example, to convey information. For that, vision-based hand gesture interfaces require fast and extremely robust hand detection, and gesture recognition in real time. Hand gestures are a powerful human communication modality with lots of potential applications and in this context we have sign language recognition, the communication method of deaf people. Sign lan- guages are not standard and universal and the grammars differ from country to coun- try. In this paper, a real-time system able to interpret the Portuguese Sign Language is presented and described. Experiments showed that the system was able to reliably recognize the vowels in real-time, with an accuracy of 99.4% with one dataset of fea- tures and an accuracy of 99.6% with a second dataset of features. Although the im- plemented solution was only trained to recognize the vowels, it is easily extended to recognize the rest of the alphabet, being a solid foundation for the development of any vision-based sign language recognition user interface system
A Unified Algebraic Approach to Few and Many-Body Correlated Systems
The present article is an extended version of the paper {\it Phys. Rev.} {\bf
B 59}, R2490 (1999), where, we have established the equivalence of the
Calogero-Sutherland model to decoupled oscillators. Here, we first employ the
same approach for finding the eigenstates of a large class of Hamiltonians,
dealing with correlated systems. A number of few and many-body interacting
models are studied and the relationship between their respective Hilbert
spaces, with that of oscillators, is found. This connection is then used to
obtain the spectrum generating algebras for these systems and make an algebraic
statement about correlated systems. The procedure to generate new solvable
interacting models is outlined. We then point out the inadequacies of the
present technique and make use of a novel method for solving linear
differential equations to diagonalize the Sutherland model and establish a
precise connection between this correlated system's wave functions, with those
of the free particles on a circle. In the process, we obtain a new expression
for the Jack polynomials. In two dimensions, we analyze the Hamiltonian having
Laughlin wave function as the ground-state and point out the natural emergence
of the underlying linear symmetry in this approach.Comment: 18 pages, Revtex format, To appear in Physical Review
SIRT1-NOX4 Signaling Axis Regulates Cancer Cachexia
Approximately one third of cancer patients die due to complexities related to cachexia. However, the mechanisms of cachexia and the potential therapeutic interventions remain poorly studied. We observed a significant positive correlation between SIRT1 expression and muscle fiber cross-sectional area in pancreatic cancer patients. Rescuing Sirt1 expression by exogenous expression or pharmacological agents reverted cancer cell-induced myotube wasting in culture conditions and mouse models. RNA-seq and follow-up analyses showed cancer cell-mediated SIRT1 loss induced NF-κB signaling in cachectic muscles that enhanced the expression of FOXO transcription factors and NADPH oxidase 4 (Nox4), a key regulator of reactive oxygen species production. Additionally, we observed a negative correlation between NOX4 expression and skeletal muscle fiber cross-sectional area in pancreatic cancer patients. Knocking out Nox4 in skeletal muscles or pharmacological blockade of Nox4 activity abrogated tumor-induced cachexia in mice. Thus, we conclude that targeting the Sirt1-Nox4 axis in muscles is an effective therapeutic intervention for mitigating pancreatic cancer-induced cachexia
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