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 $\hbar D / L^2$, 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 $eR_{N}I_{c}/\epsilon_{c}$ and $k_{B}T/\epsilon_{c}$ where $\epsilon_{c}$ 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