Crumpling a Thin Sheet

Crumpled sheets have a surprisingly large resistance to further compression. We have studied the crumpling of thin sheets of Mylar under different loading conditions. When placed under a fixed compressive force, the size of a crumpled material decreases logarithmically in time for periods up to three weeks. We also find hysteretic behavior when measuring the compression as a function of applied force. By using a pre-treating protocol, we control this hysteresis and find reproducible scaling behavior for the size of the crumpled material as a function of the applied force.Comment: revtex 4 pages, 6 eps figures submitted to Phys Rev. let

Fabrication and mechanical testing of a new sandwich structure with carbon fiber network core

The aim is the fabrication and mechanical testing of sandwich structures including a new core material known as fiber network sandwich materials. As fabrication norms for such a material do not exist as such, so the primary goal is to reproduce successfully fiber network sandwich specimens. Enhanced vibration testing diagnoses the quality of the fabrication process. These sandwich materials possess low structural strength as proved by the static tests (compression, bending), but the vibration test results give high damping values, making the material suitable for vibro-acoustic applications where structural strength is of secondary importance e.g., internal panelling of a helicopter

Asymmetric Organocatalysis in Deep Eutectic Solvents

The recent advances in asymmetric organocatalysis using eutectic mixtures as a reaction medium are revised in this mini‐review. In addition, the first enantioselective transformations using chiral eutectic solvents, which play the role of a green medium and organocatalyst, are described. In this mini‐review we intend to deepen not only in the synthetic aspects of asymmetric organocatalysis in eutectic mixtures, but also in the fundamental issues that seem to be essential for a successful development of this promising, and at the same time challenging, methodology.This work was supported by the Spanish Ministerio de Ciencia, Innovación y Universidades (MICINN, PGC2018-096616-B-I00), the University of Alicante (VIGROB-173 and VIGROB-316FI), and the University of Pisa (PRA_2018_36)

Non-linear elastic behavior of light fibrous materials

PACS. 62.20.-x Mechanical properties of solids[:AND:]62.20.Dc Elasticity, elastic constants,

Des canaux d’irrigation aux canaux de distribution d’eau brute ? Regarder le passé pour comprendre le présent et préparer l’avenir

National audienceNous faisons l’hypothèse que l’« eau agricole », autrefois « eau des moulins », est en train de changer de statut. Elle devient ce que nous qualifierons d’ » eau environnementale ». Cette nouvelle qualification induit le fait que le regard porté par les sociétés contemporaines sur sa vocation productive se transforme. Maintenant, on prend en compte non seulement les retombées bénéfiques pour les cultures agricoles et les revenus des agriculteurs, mais aussi et de manière grandissante, les effets connexes des aménagements qui ont présidé à sa vocation économique (barrages, canaux, forages, dérivations, pompages, terrasses…

Glucose detection at single gold nanowires

Compared to traditional macroelectrodes, nanoscale electrodes have tremendous potential as electrochemical sensors exhibiting enhanced performance. As critical dimensions of the electrodes enter the nano regime, 3D analyte diffusion profiles to the electrode dominate with a corresponding increase in mass transport, higher current densities giving rise to an increase in the ratio of faradaic to charging current, higher signal to noise ratios, steadystate sigmoidal voltammograms, low depletion of target molecules, low supporting electrolyte concentration requirements and shorter RC time constant 1, 2 . A variety of different fabrication approaches of nanoelectrodes have been reported to date. However challenges arising from difficultly in fabrication pathways, lack of reproducibility and small electrochemical currents (<100 pA), are still prevalent. Recently 1-dimensional nanostructures based on bands and wires are being explored as nanoelectrodes to provide practical solutions. 1-dimensional nanoelectrodes, such as nanowires, benefit from nanoscale critical dimensions (width) ensuring enhanced mass transport, while the high aspect ratio permits higher measurable currents in the ≥1 nA regime and with uniform current densities. In the work, we report the fabrication and in-depth electrochemical analysis of discrete gold nanowire electrodes for use in electrochemical applications. The single nanowire electrodes and nanowire electrode arrays were fabricated using a hybrid E-beam / photolithography approach, providing electrodes with well-defined and reproducible dimensions. Finite element diffusion domain simulation studies were employed to explore mass transport to nanowire electrodes. Simulation results suggested that radial diffusion to nanowires should be present at fast scan rates. This behavior was confirmed experimentally where CVs obtained in FcCOOH, were observed to be steady-state, with high currents (nA) and sigmoidal up to 5000 mV s -1 . The electrochemical responses of nanowires, in model redox mediators, were excellently described by Butler-Volmer kinetics. The nanowire electrodes are applied to reproducible determination of heterogeneous electron transfer-rate constants, k 0 , for three key model redox analytes, FcCOOH, Fe(II)(CN) 6 4-, and Ru(NH 3 ) 6 3+ . 3-6 We explore the application of single on-chip gold nanowires for use as electrochemical sensors employing glucose as target molecule. For glucose sensing, ferrocene monocarboxylic acid was employed as a redox mediator, while also amplifying the electrochemical signal. The nanowire-based devices demonstrated rapid glucose detection across the linear concentration range of 10 M to 1 mM with a theoretical limit of detection of 3 M (S/N = 3) Reference