4,830 research outputs found
Clock spectroscopy of interacting bosons in deep optical lattices
We report on high-resolution optical spectroscopy of interacting bosonic
Yb atoms in deep optical lattices with negligible tunneling. We prepare
Mott insulator phases with singly- and doubly-occupied isolated sites and probe
the atoms using an ultra-narrow "clock" transition. Atoms in singly-occupied
sites undergo long-lived Rabi oscillations. Atoms in doubly-occupied sites are
strongly affected by interatomic interactions, and we measure their inelastic
decay rates and energy shifts. We deduce from these measurements all relevant
collisional parameters involving both clock states, in particular the intra-
and inter-state scattering lengths
Non-linear Relaxation of Interacting Bosons Coherently Driven on a Narrow Optical Transition
We study the dynamics of a two-component Bose-Einstein condensate (BEC) of
Yb atoms coherently driven on a narrow optical transition. The
excitation transfers the BEC to a superposition of states with different
internal and momentum quantum numbers. We observe a crossover with decreasing
driving strength between a regime of damped oscillations, where coherent
driving prevails, and an incoherent regime, where relaxation takes over.
Several relaxation mechanisms are involved: inelastic losses involving two
excited atoms, leading to a non-exponential decay of populations; Doppler
broadening due to the finite momentum width of the BEC and inhomogeneous
elastic interactions, both leading to dephasing and to damping of the
oscillations. We compare our observations to a two-component Gross-Pitaevskii
(GP) model that fully includes these effects. For small or moderate densities,
the damping of the oscillations is mostly due to Doppler broadening. In this
regime, we find excellent agreement between the model and the experimental
results. For higher densities, the role of interactions increases and so does
the damping rate of the oscillations. The damping in the GP model is less
pronounced than in the experiment, possibly a hint for many-body effects not
captured by the mean-field description.Comment: 7 pages, 4 figures; supplementary material available as ancillary
fil
Low-cost technology for the integration of micro- and nanochips into fluidic systems on printed circuit board: fabrication challenges
Nowadays, micro- and nanochips are usually\ud
fabricated with Silicon and/or glass. A simple, low-cost and\ud
reliable integration packaging method that provides flexibility\ud
to the incorporation of electronic and fluidic devices into a\ud
system has not been fully developed yet. The use of Printed\ud
Circuit Board material as substrate to create dry film resist\ud
microfluidic channels is the core technology to provide such an\ud
integration method. The feasibility and potential of the\ud
proposed packaging method is demonstrated in this wor
Spin-one color superconductivity in compact stars?- an analysis within NJL-type models
We present results of a microscopic calculation using NJL-type model of
possible spin-one pairings in two flavor quark matter for applications in
compact star phenomenology. We focus on the color-spin locking phase (CSL) in
which all quarks pair in a symmetric way, in which color and spin states are
locked. The CSL condensate is particularly interesting for compact star
applications since it is flavor symmetric and could easily satisfy charge
neutrality. Moreover, the fact that in this phase all quarks are gapped might
help to suppress the direct Urca process, consistent with cooling models. The
order of magnitude of these small gaps (~1 MeV) will not influence the EoS, but
their also small critical temperatures (T_c ~800 keV) could be relevant in the
late stages neutron star evolution, when the temperature falls below this value
and a CSL quark core could form.Comment: 7 pages, 7 figures, revised version, accepted for the Conference
Proceedings of "Isolated Neutron Stars: from the Interior to the Surface",
London, 24-28. April 200
Simultaneous Optical Model Analyses of Elastic Scattering, Breakup, and Fusion Cross Section Data for the He + Bi System at Near-Coulomb-Barrier Energies
Based on an approach recently proposed by us, simultaneous
-analyses are performed for elastic scattering, direct reaction (DR)
and fusion cross sections data for the He+Bi system at
near-Coulomb-barrier energies to determine the parameters of the polarization
potential consisting of DR and fusion parts. We show that the data are well
reproduced by the resultant potential, which also satisfies the proper
dispersion relation. A discussion is given of the nature of the threshold
anomaly seen in the potential
Synthesis of Tannic Acid nanoparticles
Motivation: Tannic Acid (TA) is a polyphenolic compound with a huge variety of biological activities. Most interestingly, it has anticancer activity through a variety of mechanisms, especially in those cancers that overexpress the epidermal growth factor receptor (EGFR). It has been demonstrated that TA is able to interact with EGFR/Jak2/STAT pathway and inhibit cellular proliferation induced by EGF, triggering apoptosis [1]. The aim of this work is to optimize TA polymeric nanoparticles previously developed by our group [2], with especial focus on diminishing their hydrodynamic diameter. This characteristic is extremely important, so that once the nanoparticle enters the circulatory system, it should be able to cross the vascular walls to reach the target tissue and then release the payload.Methods and results: In this work it has been optimize the size of TA nanoparticles. The new nanoparticles obtained have been characterized by Infrared Spectroscopy, UV-Visible, Raman Spectroscopy, Tyndall Effect, Scanning Electron Microscopy (SEM) and Dynamic Light Scattering (DLS).We have been able to diminish by a four-factor the hydrodynamic diameter. In this way, our nanoparticles have a hydrodynamic diameter of just 160nm and a zeta potential of -28mV. In addition, the entrapment efficiency is very high (92.2%), and we have simplified the synthesis procedure by reducing the number of steps and the amount of coating polymer of the nanoparticles.Conclusions: We have optimized the size of TA nanoparticles. These nanoparticles have a suitable size for intravenous administration and extremely high entrapment efficiency. In addition, our synthesis does not require the use of organic solvents and the polymers used to construct the nanoparticle are classified as Generally Recognized As Safe (or GRAS) by the Food and Drug Administration
Synthesis of Tannic acid and Gallic acid nanostructures with biomedical applications
Motivation: Tannic acid (TA) and Gallic acid (GA) are natural polyphenolic compounds belonging to the family of tannins, a subset of secondary metabolites that stands out due to their biological activity, including anticancer, antioxidant, antimicrobial and antiviral activities [1,2]. Our group has developed TA nanoparticles with antitumor activity that can be selectively targeted to tumors, thereby reducing the undesirable side effects associated with chemotherapy [3].In this work we have broadened the scope of these promising nanoparticles by introducing GA in their formulation. Additionally, we have tackled the synthesis of metal-organic frameworks (MOFs) based on TA and GA. Methods and Results: The obtained nanostructures have been characterized by physicochemical techniques: Scanning Electron Microscopy (SEM), Raman Spectroscopy, Tyndall Effect, Dynamic Light Scattering (DLS), UV-Visible and Infrared Spectroscopy.Our TA/GA nanoparticles have a hydrodynamic diameter of just 202 nm and a zeta potential of -34 mV. This is an improvement over the previously described TA nanoparticles. Their entrapment efficiency is very high (92.4 %). Moreover, we have simplified the synthesis by reducing the amount of coating polymer.In a different approach we have also synthesized MOFs using TA and GA as ligand and different metal cations (Fe2+, Fe3+ or Ni2+). They have different hydrodynamic diameters and shapes, and their crystallinity is being studied by X-Ray Diffraction.Conclusions: TA/GA nanoparticles have been obtained by using polymers Generally Recognized As Safe (or GRAS) by the Food and Drug Administration. Their size has been optimized, so they are suitable for intravenous administration. With respect to the MOFs structures synthesized, their potential applications are more diverse (including, for example, catalytic processes) depending on their size, porosity and crystallinity
Ellagic acid: Biological properties and biotechnological development for production processes
Ellagic acid, 2,3,7,8-tetrahydroxy-chromeno[5,4,3-cde]chromene-5,10-dione, is a powerful bioactive compound with many potential pharmacological and industrial applications. In this review, the chemical aspects, biological properties and diverse potential applications of ellagic acid for different industries were described. This review also discussed the advance in ellagitannin biodegradation, focusing on the process of isolation of microorganisms and strain selection, medium and culture optimization, as well as fermentation systems for commercially viable industrial scale production. The performances of various fermentation techniques that have been applied for the production of ellagic acid from residual by-products were compared, while the advantages and disadvantages of each plant source were also discussed.Key words: Ellagic acid, ellagitannin, biodegradation, fungal physiology, solid-state fermentation, submerged fermentation
A basis for variational calculations in d dimensions
In this paper we derive expressions for matrix elements (\phi_i,H\phi_j) for
the Hamiltonian H=-\Delta+\sum_q a(q)r^q in d > 1 dimensions.
The basis functions in each angular momentum subspace are of the form
phi_i(r)=r^{i+1+(t-d)/2}e^{-r^p/2}, i >= 0, p > 0, t > 0. The matrix elements
are given in terms of the Gamma function for all d. The significance of the
parameters t and p and scale s are discussed. Applications to a variety of
potentials are presented, including potentials with singular repulsive terms of
the form b/r^a, a,b > 0, perturbed Coulomb potentials -D/r + B r + Ar^2, and
potentials with weak repulsive terms, such as -g r^2 + r^4, g > 0.Comment: 22 page
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