The main hurdle preventing the widespread useof single-walled carbon nanotubes remains the lack ofmethods with which to produce formulations of pristine,unshortened, unfunctionalized, individualized single-walledcarbon nanotubes, thus preserving their extraordinary properties.In particular, sonication leads to shortening, which isdetrimental to percolation properties (electrical, thermal,mechanical, etc.). Using reductive dissolution and transfer intodegassed water, open-ended, water-filled nanotubes can bedispersed as individualized nanotubes in water−dimethylsulfoxide mixtures, avoiding the use of sonication andsurfactant. Closed nanotubes, however, aggregate immediately upon contact with water. Photoluminescence andabsorption spectroscopy both point out a very high degree of individualization while retaining lengths of several microns.The resulting transparent conducting films are 1 order of magnitude more conductive than surfactant-based blanks atequal transmittance.

The study of open quantum systems often relies on approximate master equations derived under the assumptions of weak coupling to the environment. However when the system is made of several interacting subsystems such a derivation is in many cases very hard. An alternative method, employed especially in the modeling of transport in mesoscopic systems, consists in using local master equations (LMEs) containing Lindblad operators acting locally only on the corresponding subsystem. It has been shown that this approach however generates inconsistencies with the laws of thermodynamics. In this paper we demonstrate that using a microscopic model of LMEs based on repeated collisions all thermodynamic inconsistencies can be resolved by correctly taking into account the breaking of global detailed balance related to the work cost of maintaining the collisions. We provide examples based on a chain of quantum harmonic oscillators whose ends are connected to thermal reservoirs at different temperatures. We prove that this system behaves precisely as a quantum heat engine or refrigerator, with properties that are fully consistent with basic thermodynamics.

The addition of nanoparticles to a polymermatrix is a well-known process to improve the mechanicalproperties of polymers. Many studies of mechanical reinforcementin polymer nanocomposites (PNCs) focus on rubberymatrices; however, much less effort concentrates on thefactors controlling the mechanical performance of thetechnologically important glassy PNCs. This paper presentsa study of the effect of the polymer molecular weight (MW)on the overall mechanical properties of glassy PNCs withattractive interaction by using Brillouin light scattering. Wefound that the mechanical moduli (bulk and shear) have anonmonotonic dependence on MW that cannot be predictedby simple rule of mixtures. The moduli increase with increasing MW up to 100 kg/mol followed by a drop at higher MW. Wedemonstrate that the change in the mechanical properties of PNCs can be associated with the properties of the interfacialpolymer layer. The latter depend on the interfacial chain packing and stretching, as well as polymer bridging,which vary differently with the MW of the polymer. These competing contributions lead to the observed nonmonotonicvariations of the glassy PNC moduli with MW. Our work provides a simple, cost-effective, and efficient way to control themechanical properties of glassy PNCs by tuning the polymer chain length. Our finding can be beneficial for the rational designof PNCs with desired mechanical performance.

We investigate the dynamics of thin sheets freely expanding in air. The sheets are produced by impacting a drop onto a small solid target or onto a cushion of liquid nitrogen, in order to suppress any dissipation process. To disentangle the role of capillary, viscous and elastic forces in the dynamics of the sheets several materials are used, whose rheological characteristics are tuned over several orders of magnitude: viscous liquids, viscoelastic Maxwell fluids and ultrasoft solids. In this talk, I will present our approaches to rationalize the spreading of sheets for viscous, viscoelastic and elastic materials by taking into account surface tension, elastic deformation and shear and biaxial viscous dissipations.

We apply an integral transformation to solutions of a partial differential equa-tion for the five-point correlation functions in Liouville theory on a sphere withone degenerate field $V_{ − 1/(2b)}$ . By repeating this transformation, we can reach a whole lattice of values for the conformal dimensions of the four other operators. Factorizing out the degenerate field leads to integral representations of the corresponding four-point conformal blocks. We illustrate this procedure on the elliptic conformal blocks discovered in a previous publication.

We propose a computational method to measure the configurational entropy in generic polydisperse glass-formers. In particular, our method resolves issues related to the diverging mixing entropy term due to a continuous polydispersity. The configurational entropy is measured as the difference between the well-defined fluid entropy and a more problematic glass entropy. We show that the glass entropy can be computed by a simple generalisation of the Frenkel-Ladd thermodynamic integration method, which includes permutations of the particle diameters. This approach automatically provides a physically meaningful mixing entropy, and includes contributions that are not purely vibrational. The proposed configurational entropy is thus devoid of conceptual and technical difficulties due to continuous polydispersity, while being conceptually closer and technically simpler than alternative free energy approaches.

We report the first experimental study of low-frequency noise in reverse biased P-InAsSbP/n-InAs infrared photodiodes at 300 K and 77 K. At room temperature, the current noise spectral density, SI, depends on frequency as 1/f over the entire current range and tends to the Nyquist noise when the frequency increases. At small reverse currents Irb ≤ 3.10-5 A, SI is proportional to Irb^2 ; at higher currents this dependence changes to SI~ Irb^4 . With temperature decrease down to 77 K, SI becomes proportional to Irb^0.5 , while the reverse current decreasesand the differential resistance grows by 4 orders of magnitude. The noise was also studied in the photovoltaic mode at 100 K, where SI is proportional to 2rb I . We conclude that at 100 K, the Nyquist noise is dominant and can be used for estimations of the specific detectivity of PInAsSbP/n-InAs diodes.