944 research outputs found
Efecto quinioprofilactico de nanocapsulas cardagas con albendazol sobre Echinococcus Granulosus
Development of triamcionolone based lipid nanocapsules as platforms for ocular drug delivery
Purpose
Triamcinolone acetonide (TAA) is considered a first-line drug by itself or as a combined treatment of several intraocular diseases such as macular edema, retinal vein thrombosis, uveitis and age-related macular degeneration. The development of TAA dosage forms is limited due to its poor solubility in water and physiologically acceptable solvents. Lipid nanocapsules (LNCs) are biocompatible systems that allow loading both hydrophobic and hydrophilic drugs. LNCs present a versatile composition and application suitable for different routes of administration. The aim of this work was to develop and characterize a novel lipid LNCs formulation containing TAA as drug delivery system.
Methods
LNCs were prepared in triplicate using an optimized phase inversion-based method described by Heurtault et al., 2002. Due to the poor solubility of TAA in the oily phase of the original formulation, two co-surfactants (captex® 500p -Glyceryl triacetate and oleic acid) in three proportions (20, 30 and 50%) were tested. The average particle size (APS), polydispersity index (PI), zeta potential (ZP) and entrapment efficacy (EE) were measured.
Results
Acceptable results were obtained with a 20% of both co-surfactants. LNCs with captex® 500p leads to about (40±1) nm size nanoparticles with a narrow size distribution (PI less than 0.2), a negative ZP (-1.2±0.7) mV and EE (85.8±0.8) % while LNCs with oleic acid showed an APS of (35.9± 0.6) nm and a PI below 0.1 with a negative ZP (-3.6±0.6) mV and EE (87±2) %. Moreover, both systems were stable for two months.
Conclusions
LNCs allow encapsulation of TAA and their properties remain constant over long periods of time. Thus, LNCs are promising systems than may be a potential strategy to improve efficacy and decrease side effects of this drug so used in the treatment of intraocular diseases
Gauge Coupling Variation in Brane Models
We consider the space-time variation of gauge couplings in brane-world models
induced by the coupling to a bulk scalar field. A variation is generated by the
running of the gauge couplings with energy and a conformal anomaly while going
from the Jordan to the Einstein frame. We indicate that the one-loop
corrections cancel implying that one obtains a variation of the fine structure
constant by either directly coupling the gauge fields to the bulk scalar field
or having bulk scalar field dependent Yukawa couplings. Taking into account the
cosmological dynamics of the bulk scalar field, we constrain the strength of
the gauge coupling dependence on the bulk scalar field and relate it to
modifications of gravity at low energy.Comment: 4 pages, 1 figur
Features of heavy physics in the CMB power spectrum
The computation of the primordial power spectrum in multi-field inflation
models requires us to correctly account for all relevant interactions between
adiabatic and non-adiabatic modes around and after horizon crossing. One
specific complication arises from derivative interactions induced by the
curvilinear trajectory of the inflaton in a multi-dimensional field space. In
this work we compute the power spectrum in general multi-field models and show
that certain inflaton trajectories may lead to observationally significant
imprints of `heavy' physics in the primordial power spectrum if the inflaton
trajectory turns, that is, traverses a bend, sufficiently fast (without
interrupting slow roll), even in cases where the normal modes have masses
approaching the cutoff of our theory. We emphasise that turning is defined with
respect to the geodesics of the sigma model metric, irrespective of whether
this is canonical or non-trivial. The imprints generically take the form of
damped superimposed oscillations on the power spectrum. In the particular case
of two-field models, if one of the fields is sufficiently massive compared to
the scale of inflation, we are able to compute an effective low energy theory
for the adiabatic mode encapsulating certain relevant operators of the full
multi-field dynamics. As expected, a particular characteristic of this
effective theory is a modified speed of sound for the adiabatic mode which is a
functional of the background inflaton trajectory and the turns traversed during
inflation. Hence in addition, we expect non-Gaussian signatures directly
related to the features imprinted in the power spectrum.Comment: 41 pages, 6 figures, references updated, minor modifications. Version
to appear in JCAP. v4: Equations (4.28) and (4.30) and Figures 5 and 6
correcte
Quantum computing with mixed states
We discuss a model for quantum computing with initially mixed states.
Although such a computer is known to be less powerful than a quantum computer
operating with pure (entangled) states, it may efficiently solve some problems
for which no efficient classical algorithms are known. We suggest a new
implementation of quantum computation with initially mixed states in which an
algorithm realization is achieved by means of optimal basis independent
transformations of qubits.Comment: 2 figures, 52 reference
Theory of Decoherence-Free Fault-Tolerant Universal Quantum Computation
Universal quantum computation on decoherence-free subspaces and subsystems
(DFSs) is examined with particular emphasis on using only physically relevant
interactions. A necessary and sufficient condition for the existence of
decoherence-free (noiseless) subsystems in the Markovian regime is derived here
for the first time. A stabilizer formalism for DFSs is then developed which
allows for the explicit understanding of these in their dual role as quantum
error correcting codes. Conditions for the existence of Hamiltonians whose
induced evolution always preserves a DFS are derived within this stabilizer
formalism. Two possible collective decoherence mechanisms arising from
permutation symmetries of the system-bath coupling are examined within this
framework. It is shown that in both cases universal quantum computation which
always preserves the DFS (*natural fault-tolerant computation*) can be
performed using only two-body interactions. This is in marked contrast to
standard error correcting codes, where all known constructions using one or
two-body interactions must leave the codespace during the on-time of the
fault-tolerant gates. A further consequence of our universality construction is
that a single exchange Hamiltonian can be used to perform universal quantum
computation on an encoded space whose asymptotic coding efficiency is unity.
The exchange Hamiltonian, which is naturally present in many quantum systems,
is thus *asymptotically universal*.Comment: 40 pages (body: 30, appendices: 3, figures: 5, references: 2). Fixed
problem with non-printing figures. New references added, minor typos
correcte
Encoded Recoupling and Decoupling: An Alternative to Quantum Error Correcting Codes, Applied to Trapped Ion Quantum Computation
A recently developed theory for eliminating decoherence and design
constraints in quantum computers, ``encoded recoupling and decoupling'', is
shown to be fully compatible with a promising proposal for an architecture
enabling scalable ion-trap quantum computation [D. Kielpinski et al., Nature
417, 709 (2002)]. Logical qubits are encoded into pairs of ions. Logic gates
are implemented using the Sorensen-Molmer (SM) scheme applied to pairs of ions
at a time. The encoding offers continuous protection against collective
dephasing. Decoupling pulses, that are also implemented using the SM scheme
directly to the encoded qubits, are capable of further reducing various other
sources of qubit decoherence, such as due to differential dephasing and due to
decohered vibrational modes. The feasibility of using the relatively slow SM
pulses in a decoupling scheme quenching the latter source of decoherence
follows from the observed 1/f spectrum of the vibrational bath.Comment: 12 pages, no figure
Constraints on Dark Matter Annihilation in Clusters of Galaxies with the Fermi Large Area Telescope
Nearby clusters and groups of galaxies are potentially bright sources of
high-energy gamma-ray emission resulting from the pair-annihilation of dark
matter particles. However, no significant gamma-ray emission has been detected
so far from clusters in the first 11 months of observations with the Fermi
Large Area Telescope. We interpret this non-detection in terms of constraints
on dark matter particle properties. In particular for leptonic annihilation
final states and particle masses greater than ~200 GeV, gamma-ray emission from
inverse Compton scattering of CMB photons is expected to dominate the dark
matter annihilation signal from clusters, and our gamma-ray limits exclude
large regions of the parameter space that would give a good fit to the recent
anomalous Pamela and Fermi-LAT electron-positron measurements. We also present
constraints on the annihilation of more standard dark matter candidates, such
as the lightest neutralino of supersymmetric models. The constraints are
particularly strong when including the fact that clusters are known to contain
substructure at least on galaxy scales, increasing the expected gamma-ray flux
by a factor of ~5 over a smooth-halo assumption. We also explore the effect of
uncertainties in cluster dark matter density profiles, finding a systematic
uncertainty in the constraints of roughly a factor of two, but similar overall
conclusions. In this work, we focus on deriving limits on dark matter models; a
more general consideration of the Fermi-LAT data on clusters and clusters as
gamma-ray sources is forthcoming.Comment: accepted to JCAP, Corresponding authors: T.E. Jeltema and S. Profumo,
minor revisions to be consistent with accepted versio
Effect of a single nutritional intervention previous to a critical period of fat gain in university students with overweight and obesity: A randomized controlled trial
Indexación: ScopusBackground: the present study aimed to investigate the effects of a single nutritional preventive session previous to a critical period linked to fat gain in university students with overweightness and obesity, emulating a nutritional session of a public health system. Methods: In this single-blind randomized controlled trial, 23 students met all the criteria to be included (20.91 ± 2.52-year-old; 52.2% women) who were divided into two groups: intervention group (IG) and control group (CG). Fat mass (FM) by dual-energy X-ray absorptiometry (DXA), physical activity by accelerometry, feeding evaluation through three questionnaires, and a set of healthy lifestyle recommendations were evaluated before and after the national holidays (NH). Results: Our findings showed that FM increased significantly in the CG, but not in the IG (CG = 428.1g; IG = 321.9g; ∆ = 106.2g; p = 0.654 [95% CI = −379.57, 591.92]). However, no differences were found during the NH between them (Hedges’ g effect size = 0.19; p = 0.654). In addition, no statistical differences were observed between groups in feeding evaluations, the set of recommendations performed, and physical activity. Conclusion: a single preventive session before a critical period, using a similar counselling approach as used in the public health system, might not be enough to promote changes in eating and physical activity patterns and preventing fat gain in overweight/obese university students. Long-term interventions are a must. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.https://www.mdpi.com/1660-4601/17/14/514
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