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

Chemoselective recognition with phosphonate cavitands: the ephedrine over pseudoephedrine case

Complete discrimination of ephedrine and pseudoephedrine, both in solution and in the solid state, was achieved with a phosphonate cavitand receptor. The molecular origin of the epimer discrimination was revealed by the crystal structure of the respective complexes

Organic guests inclusion by tungsten-calix[4]arene hosts

The binding mode of a series of lower rim tungsten-calix[4]arenes toward different neutral organic guests has been investigated in the solid state and through ab initio computational studies. From the structure of the inclusion compounds examined it emerges that the metal can be employed as a control element to confer different cone shapes to the calixarene cavity and to act as an additional binding site

CH/pi interaction between benzene and model neutral organic molecules bearing acid CH groups

To explore the binding properties of benzene towards small molecules bearing C H groups with different acidities, we have undertaken ab initio quantum-chemical calculations, including correlation effects through Density Functional Theory methods, on the benzene CH3X (X = F, Cl, Br, I, CN, NO2) adducts. Benzene acts as a Lewis base and the CH3X molecule as a Lewis acid. The partial charge transferred from benzene to the Lewis acid is mainly confined on the X group and increases with the electron withdrawing character of X. The calculations performed on the various systems predict that two different stable structures for each adduct exist: one with C-3v and the other with C-s symmetry, the latter being the most stable one. A simple HOMO-LUMO model suggests that the charge is transferred from the benzene HOMO to the CH3X LUMO and that this process is easier in the systems with C-s symmetry due to the better overlap between the frontier orbitals

SYNTHESIS OF NEW CALIX[4]ARENE-BASED IONOPHORES

A synthesis of new calix[4]arene-based ionophores is reported. These ligands are characterized by the presence of two types of coordination sites on their lower rim: one crowning unit of different length, linking two proximal calix[4]arene phenolic oxygens, and two esters or amide groups acting as additional hard binding sites. The choice of the proper reaction conditions, such as the base counterion and the solvent polarity, during the functionalization of the macrocycle lower rim, allows to modulate the stereochemistry of the final ligands. In this way the ligands in cone and 1,2-alternate conformations were obtained in good yields. Complexation properties of these new compounds towards alkali and alkaline-earth cations were studied by means of liquid-liquid extraction experiments. The X-ray solid state structure of the p-tert-butylcalix[4]arene-N,N-diethylacetamide-crown-5 (6a) complex with strontium picrate shows the effective cooperativity among the two type of coordination site in the binding event

CALIX[6]ARENE-BASED PSEUDOROTAXANES: A SOLID STATE STRUCTURAL INVESTIGATION

Triphenylureido-calix[6] arene derivatives act as a heteroditopic and asymmetrical wheel. They are able to form pseudorotaxanes with dialkylviologen salts. These supramolecular complexes are stabilised by several noncovalent interactions whose nature and role has been evidenced through single crystal X-ray diffraction and computational methods

Self-assembly of heteroditopic calix[4]arene capsules through ion-pair recognition.

The chemical information stored in a rigid heteroditopic calix[4]arene receptor allows the formation in the solid state of an extended 1D superstructure of self-assembled capsules through ion-pair recognition processes of N-methylpyridinium chloride

Monotopic and heteroditopic calix[4]arene receptors as hosts for pyridinium and viologen ion pairs: a solution and solid-state study

The binding efficiency of a series of monotopic (1–2) and heteroditopic (3–4) calix[4]arene-based receptors has been evaluated in chloroform solution toward N-methylpyridinium ion pairs using NMR and UV/vis spectroscopic techniques. These experiments provided evidence that, due to a positive cooperative effect, the presence of a phenylurea H-bond donor group on the upper rim of the calix[4]arene macrocycle increases the recognition abilities of the heteroditopic receptors by up to two orders of magnitude with respect to the monotopic receptors. The heteroditopic receptors are also able to form 2:1 host–guest inclusion complexes with dimethylviologen salts both in low polarity solvents and in the solid state. These complexes are stabilized through the cooperation of weak (CH–π and cation–π) and strong (hydrogen bonding) intramolecular interactions between the binding domains of the calix[4]arene host and the two ions of the guest ion pair