1,356 research outputs found
Effective band-structure in the insulating phase versus strong dynamical correlations in metallic VO2
Using a general analytical continuation scheme for cluster dynamical mean
field calculations, we analyze real-frequency self-energies, momentum-resolved
spectral functions, and one-particle excitations of the metallic and insulating
phases of VO2. While for the former dynamical correlations and lifetime effects
prevent a description in terms of quasi-particles, the excitations of the
latter allow for an effective band-structure. We construct an
orbital-dependent, but static one-particle potential that reproduces the full
many-body spectrum. Yet, the ground state is well beyond a static one-particle
description. The emerging picture gives a non-trivial answer to the decade-old
question of the nature of the insulator, which we characterize as a ``many-body
Peierls'' state.Comment: 5 pages, 4 color figure
A novel copper precursor for electron beam induced deposition
A fluorine free copper precursor, Cu(tbaoac)2 with the chemical sum formula CuC16O6H26 is introduced for focused electron beam induced deposition (FEBID). FEBID with 15 keV and 7 nA results in deposits with an atomic composition of Cu:O:C of approximately 1:1:2. Transmission electron microscopy proved that pure copper nanocrystals with sizes of up to around 15 nm were dispersed inside the carbonaceous matrix. Raman investigations revealed a high degree of amorphization of the carbonaceous matrix and showed hints for partial copper oxidation taking place selectively on the surfaces of the deposits. Optical transmission/reflection measurements of deposited pads showed a dielectric behavior of the material in the optical spectral range. The general behavior of the permittivity could be described by applying the MaxwellâGarnett mixing model to amorphous carbon and copper. The dielectric function measured from deposited pads was used to simulate the optical response of tip arrays fabricated out of the same precursor and showed good agreement with measurements. This paves the way for future plasmonic applications with copper-FEBID
Kansas Early Childhood Transition Task Force Tour: Preliminary Results from Community Engagement Tour
Kansas Executive Order 23-01 established the Early Childhood Transition Task Force (ECTTF) and tasked the group with holding a series of meetings across the state to generate public feedback and responses to Kansasâ current early childhood system. To better understand the current situation of early childhood efforts in the State of Kansas, the Kansas ECTTF conducted a statewide tour with virtual and in-person opportunities for participants to reflect on Kansasâ early childhood system.
The participantsâ responses were prompted by questions in three different categories: Needs and Barriers, Bright Spots, and Stateâs Efficiency in Early Child Care and Education. Participants were also asked to rate how hopeful they are that Kansas is going in the right direction in early childhood. The average hope score was high, which conveys trust and confidence from those in attendance.
Based on these findings, the Task Force developed recommendations to improve Kansasâ current early childhood system and the stateâs role in it
Analogue model of a FRW universe in Bose-Einstein condensates: Application of the classical field method
Analogue models of gravity have been motivated by the possibility of
investigating phenomena not readily accessible in their cosmological
counterparts. In this paper, we investigate the analogue of cosmological
particle creation in a Friedmann-Robertson-Walker universe by numerically
simulating a Bose-Einstein condensate with a time-dependent scattering length.
In particular, we focus on a two-dimensional homogeneous condensate using the
classical field method via the truncated Wigner approximation. We show that for
various forms of the scaling function the particle production is consistent
with the underlying theory in the long wavelength limit. In this context, we
further discuss the implications of modified dispersion relations that arise
from the microscopic theory of a weakly interacting Bose gas.Comment: 26 pages, 8 figure
Low-frequency vibrations of soft colloidal glasses
We conduct experiments on two-dimensional packings of colloidal
thermosensitive hydrogel particles whose packing fraction can be tuned above
the jamming transition by varying the temperature. By measuring displacement
correlations between particles, we extract the vibrational properties of a
corresponding "shadow" system with the same configuration and interactions, but
for which the dynamics of the particles are undamped. The vibrational spectrum
and the nature of the modes are very similar to those predicted for
zero-temperature idealized sphere models and found in atomic and molecular
glasses; there is a boson peak at low frequency that shifts to higher frequency
as the system is compressed above the jamming transition.Comment: 4 figure
Trans-Planckian physics and signature change events in Bose gas hydrodynamics
We present an example of emergent spacetime as the hydrodynamic limit of a
more fundamental microscopic theory. The low-energy, long-wavelength limit in
our model is dominated by collective variables that generate an effective
Lorentzian metric. This system naturally exhibits a microscopic mechanism
allowing us to perform controlled signature change between Lorentzian and
Riemannian geometries. We calculate the number of particles produced from a
finite-duration Euclidean-signature event, where we take the position that to a
good approximation the dynamics is dominated by the evolution of the linearized
perturbations, as suggested by Calzetta and Hu [Phys. Rev. A 68 (2003) 043625].
We adapt the ideas presented by Dray et al. [Gen. Rel. Grav. 23 (1991) 967],
such that the field and its canonical momentum are continuous at the
signature-change event.
We investigate the interplay between the underlying microscopic structure and
the emergent gravitational field, focussing on its impact on particle
production in the ultraviolet regime. In general, this can be thought of as the
combination of trans-Planckian physics and signature-change physics. Further we
investigate the possibility of using the proposed signature change event as an
amplifier for analogue "cosmological particle production" in condensed matter
experiments.Comment: 18 pages, revtex
Human serum albumin nanoparticles loaded with phthalocyanine dyes for potential use in photodynamic therapy of atherosclerotic plaques
Diseases caused by obstruction or rupture of vulnerable plaques in the arterial walls such as cardiovascular infarction or stroke are the leading cause of death in the world. In the present work, we developed human serum albuminnanoparticles loaded by physisorption with zinc phthalocyanine, TT1, mainly used for industrial application as near-infrared photosensitizer and compared these to HSA NPsloaded with the well-known silicone phthalocyanine (Pc4). The use of NIR light allows for better tissue penetration, while the use of nanoparticles permitshigh local concentrations. The particles were characterized and tested for toxicity and stability as well as for their potential use as a contrast agent and NIR photosensitizer for photodynamic therapy in cardiovascular disease. We focused on the distribution of the nanoparticles in RAW264.7macrophage cells and atherosclerotic mice. The nanoparticles had an average size of 120 nm according todynamic light scattering, good loading capacity for zinc phthalocyanine,and satisfying stability in 50% (v/v) fetal bovine serum for 8 hours and in an aqueous environment at 4°C for 4â6 weeks. Under light irradiation we found a high production of singlet oxygen and the products showed no dark toxicity in vitro with macrophages(the target cells in vulnerable plaques),but at a low ÎŒg/mL nanoparticleconcentration killed efficiently the macrophagesupon LED illumination. Injection of the contrast agentin atherosclerotic mice led to a visible fluorescence signal of zinc phthalocyaninein the atherosclerotic plaque at 30 minutes and in the lungs with afast clearance of the nanoparticles. Zinc phthalocyanine loaded human serum albumin nanoparticles present an interesting candidate for the visualization and potentially photodynamictreatment of macrophages in atherosclerotic plaquesThe research leading to these results has received funding from FP7-NMP CosmoPHOS-Nano under grant agreement No. 310337. Additional funding was received by the Spanish groups from MINECO (CTQ2017-85393-P) and ERA-NET/MINECO EuroNanoMed2017-191 / PCIN-2017-04
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