The ALICE experiment at the CERN LHC

ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 161626 m3 with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008

Tetrabutylammonium-modified clay film electrodes: Characterization and application to the detection of metal ions

International audienceThis work describes the preparation and characterization of smectite clay partially exchanged with tetrabutylammonium ions (TBA(+)) and its subsequent deposition onto glassy carbon electrode (GCE) for application to the preconcentration electroanalysis of metal ions (Cd, Pb, and Cu). Such partial exchange of TBA(+) induces the expansion of the interlayer region between the clay sheets (as ascertained by XRD) while maintaining its ion exchange capacity, which resulted in enhanced mass transport rates (as pointed out by electrochemical monitoring of permeability properties of these thin (organo)clay films on GCE). This principle was applied here to the anodic stripping square wave voltammetric analysis of metal ions after accumulation at open circuit. Among others, detection limits as low as 3.6 x 10(-8) M for copper and 7.2 x 10(-8) M for cadmium have been achieved

Chiral enhancement via surface-confined supramolecular self-assembly at the electrified liquid/solid interface

A new simple and convenient strategy for boosting the enantioselectivity of cyclodextrins (CDs) as highly available homochiral macrocyclic hosts using the co-assembly of physisorbed propranolol (PRNL) enantiomers on gold nanoparticles (AuNPs) and different CDs was reported, exploiting the gainful effects of surface-confined supramolecular associations. All the experiments were conducted both in bulk enantiomer solution (unrestricted, homogenous system) and on the antipodes physisorbed at the gold-liquid interface (surface confined, heterogenous system), employing various electroanalytical techniques (differential pulse voltammetry, cyclic voltammetry and electrochemical impedance spectroscopy), isothermal titration calorimetry and computational modeling. In the unrestricted system, where the freedom of movement of PRNL molecules is not hampered, unassailable enantioselectivity may not be allocated to either of the tested CDs. However, by limiting the degrees of freedom of PRNL antipodes upon their adsorption to a non-chiral surface of electrochemically-generated AuNPs, a particular amplification of the conformational differences between the resulting supramolecular complexes with native CDs may arise. Molecular dynamics simulations of the supramolecular interactions on both homogenous and heterogenous system revealed important differences compared to the previously reported quantum chemical calculations performed in vacuo. Besides the advances of fundamental knowledge, this proof-of-concept data may offer an alternative strategy for the fast chiral probing of various analytes by interfacial supramolecular electrochemistry