1,509 research outputs found
Controlling quantum critical dynamics of isolated systems
Controlling the non adiabatic dynamics of isolated quantum systems driven
through a critical point is of interest in a variety of fields ranging from
quantum simulation to finite-time thermodynamics. We briefly review the
different methods for designing protocols which minimize excitation (defect)
production in a closed quantum critical system driven out of equilibrium. We
chart out the role of specific driving schemes for this procedure, point out
their experimental relevance, and discuss their implementation in the context
of ultracold atom and spin systems.Comment: Second version of invited review article submitted to EPJ-ST.
References added, typos corrected. 3 figures, 14 p
Exclusive light particle measurements for the system F + C at 96 MeV
Decay sequence of hot {31}^P nucleus has been investigated through
exclusive light charged particle measurements in coincidence with individual
evaporation residues using the reaction {19}^F (96 MeV) + {12}^C.
Information on the sequential decay chain have been extracted by confronting
the data with the predictions of the statistical model. It is observed from the
present analysis that such exclusive light charged particle data may be used as
a powerful tool to probe the decay sequence of the hot light compound systems.Comment: 13 pages, 8 figures, Physical Review C (in press
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Thiol-Methylsulfone Based Hydrogels: Enhanced Control on Gelation Kinetics for 3D Cell Encapsulation
Hydrogels are useful temporal matrices for cell culture technologies. The successful mixing and encapsulation of cells within the gel requires the selection of efficient and cytocompatible gelation reactions occurring in the minute timescale under physiological conditions. The thiol-methylsulfonyl (MS) chemical reaction is introduced here as a novel chemistry to encapsulate cells in polymeric matrices. Thiol-MS crosslinking does not require a light activation step and can occur within the seconds-to-minutes timescale by adjusting the pH in the physiological range 8.0-6.6. This reaction is cytocompatible and the reaction product is hydrolytically stable in cell culture media up to 4 weeks. Cell encapsulation protocols enabling comfortable handling and yielding homogenous distribution of the embedded cells are described. All these features are relevant for the application of this crosslinking reaction to biomedical scenarios. Finally, this manuscript also compares the performance of thiol-MS hydrogels with the established thiol-maleimide and thiol-vinylsulfone hydrogels. The benefit of thiol-MS crosslinking in terms of control over hydrogelation kinetics is demonstrated
Shortcuts to adiabaticity in a time-dependent box
A method is proposed to drive an ultrafast non-adiabatic dynamics of an
ultracold gas trapped in a box potential. The resulting state is free from
spurious excitations associated with the breakdown of adiabaticity, and
preserves the quantum correlations of the initial state up to a scaling factor.
The process relies on the existence of an adiabatic invariant and the inversion
of the dynamical self-similar scaling law dictated by it. Its physical
implementation generally requires the use of an auxiliary expulsive potential
analogous to those used in soliton control. The method is extended to a broad
family of many-body systems. As illustrative examples we consider the ultrafast
expansion of a Tonks-Girardeau gas and of Bose-Einstein condensates in
different dimensions, where the method exhibits an excellent robustness against
different regimes of interactions and the features of an experimentally
realizable box potential.Comment: 6 pp, 4 figures, typo in Eq. (6) fixe
Elastomeric Optical Waveguides by Extrusion Printing
Advances in optogenetics and the increasing use of implantable devices for therapies and health monitoring are driving demand for compliant, biocompatible optical waveguides and scalable methods for their manufacture. Molding, thermal drawing, and dip-coating are the most prevalent approaches in recent literature. Here the authors demonstrate that extrusion printing at room temperature can be used for continuous fabrication of compliant optical waveguides with polydimethylsiloxane (PDMS) core and crosslinked Pluronic F127-diacrylate (Pluronic-DA) cladding. The optical fibers are printed from fluid precursor inks and stabilized by physical interactions and photoinitiated crosslinking in the Pluronic-DA. The printed fibers show optical loss values of 0.13–0.34 dB cm–1 in air and tissue within the wavelength range of 405–520 nm. The fibers have a Young's Modulus (Pluronic cladding) of 150 kPa and can be stretched to more than 5 times their length. The optical loss of the fibers shows little variation with extension. This work demonstrates how printing can simplify the fabrication of compliant and stretchable devices from materials approved for clinical use. These can be of interest for optogenetic or photopharmacology applications in extensible tissues, like muscles or heart
Intermediate inflation in Gauss-Bonnet braneworld
In this article we study an intermediate inflationary universe models using
the Gauss-Bonnet brane. General conditions required for these models to be
realizable are derived and discussed. We use recent astronomical observations
to constraint the parameters appearing in the model.Comment: 16 pages, 2 figures, accepted for publication in European Physical
Journal
Quantum cosmology of a classically constrained nonsingular Universe
The quantum cosmological version of a nonsingular Universe presented by
Mukhanov and Brandenberger in the early nineties has been developed and the
Hamilton Jacobi equation has been found under semiclassical (WKB)
approximation. It has been pointed out that, parameterization of classical
trajectories with semiclassical time parameter, for such a classically
constrained system, is a nontrivial task and requires Lagrangian formulation
rather than the Hamiltonian formalism.Comment: 15 page
Emission of intermediate mass fragments from hot Ba formed in low-energy Ni+Ni reaction
The complex fragments (or intermediate mass fragments) observed in the
low-energy Ni+NiBa reaction, are studied within
the dynamical cluster decay model for s-wave with the use of the
temperature-dependent liquid drop, Coulomb and proximity energies. The
important result is that, due to the temperature effects in liquid drop energy,
the explicit preference for -like fragments is washed out, though the
C (or the complementary Sn) decay is still predicted to be one
of the most probable -nucleus decay for this reaction. The production
rates for non- like intermediate mass fragments (IMFs) are now higher
and the light particle production is shown to accompany the IMFs at all
incident energies, without involving any statistical evaporation process in the
model. The comparisons between the experimental data and the (s-wave)
calculations for IMFs production cross sections are rather satisfactory and the
contributions from other -waves need to be added for a further
improvement of these comparisons and for calculations of the total kinetic
energies of fragments.Comment: 22 pages, 15 figure
Accelerated closed universes in scalar-tensor theories
We describe an accelerating universe model in the context of a scalar-tensor
theory. This model is intrinsically closed, and is filled with
quintessence-like scalar field components, in addition to the Cold Dark Matter
component. With a background geometry specified by the
Friedman-Robertson-Walker metric, we establish conditions under which this
closed cosmological model, described in a scalar-tensor theory, may look flat
in a genuine Jordan-Brans-Dicke theory. Both models become indistinguishable at
low enough redshift.Comment: 8 pages, 4 figures, in press (CQG
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Development of bioactive catechol functionalized nanoparticles applicable for 3D bioprinting
Efficient wound treatments to target specific events in the healing process of chronic wounds constitute a significant aim in regenerative medicine. In this sense, nanomedicine can offer new opportunities to improve the effectiveness of existing wound therapies. The aim of this study was to develop catechol bearing polymeric nanoparticles (NPs) and to evaluate their potential in the field of wound healing. Thus, NPs wound healing promoting activities, potential for drug encapsulation and controlled release, and further incorporation in a hydrogel bioink formulation to fabricate cell-laden 3D scaffolds are studied. NPs with 2 and 29 M % catechol contents (named NP2 and NP29) were obtained by nanoprecipitation and presented hydrodynamic diameters of 100 and 75 nm respectively. These nanocarriers encapsulated the hydrophobic compound coumarin-6 with 70% encapsulation efficiency values. In cell culture studies, the NPs had a protective effect in RAW 264.7 macrophages against oxidative stress damage induced by radical oxygen species (ROS). They also presented a regulatory effect on the inflammatory response of stimulated macrophages and promoted upregulation of the vascular endothelial growth factor (VEGF) in fibroblasts and endothelial cells. In particular, NP29 were used in a hydrogel bioink formulation using carboxymethyl chitosan and hyaluronic acid as polymeric matrices. Using a reactive mixing bioprinting approach, NP-loaded hydrogel scaffolds with good structural integrity, shape fidelity and homogeneous NPs dispersion, were obtained. The in vitro catechol NPs release profile of the printed scaffolds revealed a sustained delivery. The bioprinted scaffolds supported viability and proliferation of encapsulated L929 fibroblasts over 14 days. We envision that the catechol functionalized NPs and resulting bioactive bioink presented in this work offer promising advantages for wound healing applications, as they: 1) support controlled release of bioactive catechol NPs to the wound site; 2) can incorporate additional therapeutic functions by co-encapsulating drugs; 3) can be printed into 3D scaffolds with tailored geometries based on patient requirements
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