2,429 research outputs found
Noise Correlations in Three-Terminal Diffusive Superconductor-Normal Metal-Superconductor Nanostructures
We present measurements of current noise and cross-correlations in
three-terminal Superconductor-Normal metal-Superconductor (S-N-S)
nanostructures that are potential solid-state entanglers thanks to Andreev
reflections at the N-S interfaces. The noise correlation measurements spanned
from the regime where electron-electron interactions are relevant to the regime
of Incoherent Multiple Andreev Reflection (IMAR). In the latter regime,
negative cross-correlations are observed in samples with closely-spaced
junctions.Comment: Include Supplemental Materia
Resistive transport in a mesoscopic proximity superconductor
We review transport measurements in a normal metal (N) in contact with one or
two superconducting (S) islands. From the experiment, we distinguish the
Josephson coupling, the mesoscopic fluctuations and the proximity effect. In a
loop-shaped N conductor, we observe large h/2e-periodic magnetoresistance
oscillations that decay with temperature T with a 1/T power-law. This behaviour
is the signature of the long-range coherence of the low-energy electron pairs
induced by the Andreev reflection at the S interface. At temperature and
voltage below the Thouless energy , we observe the re-entrance
of the metallic resistance. Experimental results agree with the linearized
quasiclassical theory.Comment: 8 pages, 6 included epsf figures, Invited paper at the LT21
Conference, Praha, August 1996. To appear in Czech. J. of Phys. 46, Part S6
(1996
The effects of aggregation and protein corona on the cellular internalization of iron oxide nanoparticles
Engineered inorganic nanoparticles are essential components in the
development of nanotechnologies. For applications in nanomedicine, particles
need to be functionalized to ensure a good dispersibility in biological fluids.
In many cases however, functionalization is not sufficient : the particles
become either coated by a corona of serum proteins or precipitate out of the
solvent. In the present paper, we show that by changing the coating of iron
oxide nanoparticles from a low-molecular weight ligand (citrate ions) to small
carboxylated polymers (poly(acrylic acid)), the colloidal stability of the
dispersion is improved and the adsorption/internalization of iron towards
living mammalian cells is profoundly affected. Citrate-coated particles are
shown to destabilize in all fetal-calf-serum based physiological conditions
tested, whereas the polymer coated particles exhibit an outstanding
dispersibility as well as a structure devoid of protein corona. The
interactions between nanoparticles and human lymphoblastoid cells are
investigated by transmission electron microscopy and flow cytometry. Two types
of nanoparticle/cell interactions are underlined. Iron oxides are found either
adsorbed on the cellular membranes, or internalized into membrane-bound
endocytosis compartments. For the precipitating citrate-coated particles, the
kinetics of interactions reveal a massive and rapid adsorption of iron oxide on
the cell surfaces. The quantification of the partition between adsorbed and
internalized iron was performed from the cytometry data. The results highlight
the importance of resilient adsorbed nanomaterials at the cytoplasmic membrane.Comment: 21 pages, 11 figures, accepted at Biomaterials (2011
Use of psychoactive substances in persons with spinal cord injury: A literature review
AbstractObjectiveTo undertake a critical review of literature on use of legal and illegal psychoactive substances (PAS) in persons with spinal cord injury (SCI) before and after trauma.Material and methodsHundred and five articles published between 1980 and 2014 on alcohol and drug use in persons with SCI before and after trauma were retrieved from the PubMed and PsycInfo search engines.ResultsBefore injury, 25% to 96% of people with SCI reported using alcohol, while 32% to 35% had used illegal drugs. At the time of injury, 31% to 50% of individuals with SCI were intoxicated with alcohol, 16% to 33% with drugs and 26% with a combination of drugs and alcohol. Among those reporting PAS use before injury, up to 50% stated that they had reduced their use during active rehabilitation, during which time only 6% consumed psychoactive substances for the first time. A variety of risk factors are associated with consumption subsequent to spinal cord injury: personality alteration (impulsiveness, aggressiveness), posttraumatic depression, poor coping skills, lack of social support and pain. PAS use can affect the process of rehabilitation, diminish the effectiveness of medication and result in various medical complications.Discussion/conclusionsFew studies have explored the use of alcohol, drugs and psychoactive medications before SCI and during active rehabilitation. To our knowledge, no study has analyzed the evolution of PAS use after hospital discharge, even though return home is associated with new stressors that may trigger risky behaviors. It should be a priority, as early as possible during rehabilitation, to detect persons at risk of developing PAS abuse
Circuit approach to photonic heat transport
We discuss the heat transfer by photons between two metals coupled by a
linear element with a reactive impedance. Using a simple circuit approach, we
calculate the spectral power transmitted from one resistor to the other and
find that it is determined by the photon transmission coefficient, which
depends on the impedances of the metals and the coupling element. We study the
total photonic power flow for different coupling impedances, both in the linear
regime, where the temperature difference between the metals is small, and in
the non-linear regime of large temperature differences.Comment: 6 pages, 6 figure
Poly(acrylic acid)-coated iron oxide nanoparticles : quantitative evaluation of the coating properties and applications for the removal of a pollutant dye
In this work, 6 to 12 nm iron oxide nanoparticles were synthesized and coated
with poly(acrylic acid) chains of molecular weight 2100 g/mol. Based on a
quantitative evaluation of the dispersions, the bare and coated particles were
thoroughly characterized. The number densities of polymers adsorbed at the
particle surface and of available chargeable groups were found to be 1.9 +/-
0.3 nm-2 and 26 +/- 4 nm-2, respectively. Occurring via a multi-site binding
mechanism, the electrostatic coupling leads to a solid and resilient anchoring
of the chains. To assess the efficacy of the particles for pollutant
remediation, the adsorption isotherm of methylene blue molecules, a model of
pollutant, was determined. The excellent agreement between the predicted and
measured amounts of adsorbed dyes suggests that most carboxylates participate
to the complexation and adsorption mechanisms. An adsorption of 830 mg/g was
obtained. This quantity compares well with the highest values available for
this dye.Comment: 14 pages 5 figures, accepted 06-Dec-2012; Journal of Colloid and
Interface Science (2013
The Josephson critical current in a long mesoscopic S-N-S junction
We carry out an extensive experimental and theoretical study of the Josephson
effect in S-N-S junctions made of a diffusive normal metal (N) embedded between
two superconducting electrodes (S). Our experiments are performed on Nb-Cu-Nb
junctions with highly-transparent interfaces. We give the predictions of the
quasiclassical theory in various regimes on a precise and quantitative level.
We describe the crossover between the short and the long junction regimes and
provide the temperature dependence of the critical current using dimensionless
units and where
is the Thouless energy. Experimental and theoretical results are in excellent
quantitative agreement.Comment: 5 pages, 4 figures, slighly modified version, publishe
Calorimetric readout of a superconducting proximity-effect thermometer
A proximity-effect thermometer measures the temperature dependent critical
supercurrent in a long superconductor - normal metal - superconductor (SNS)
Josephson junction. Typically, the transition from the superconducting to the
normal state is detected by monitoring the appearance of a voltage across the
junction. We describe a new approach to detect the transition based on the
temperature increase in the resistive state due to Joule heating. Our method
increases the sensitivity and is especially applicable for temperatures below
about 300 mK.Comment: 10 pages, 5 figures. To appear in the proceedings of the Conference
on Micro- and Nanocryogenics (LT25 satellite) organized in Espoo, Finland
(2008
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