Observation of antihydrogen production in flight at CERN

The observation of the production of antihydrogen atoms \overlineH ⁰\equiv\barpe⁺, the simplest atomic bound state of antimatter, is presented. A method has been used by the PS210 collaboration at LEAR which assumes that the production of \overlineH⁰ is predominantly mediated by the e⁺e^--pair creation via the two-photon mechanism in the antiproton--nucleus interaction. Neutral \overlineH⁰ atoms are indentified by a unique sequence of characteristics. In principle \overlineH⁰ is well suited for investigations of fundamental CPT violation studies under different forces, however, in our investigations we concentrate on the production of this antimatter object, since so far it had not been observed. The production of eleven antihydrogen atoms is reported including possibly 2± 1 background signals, the observed yield agrees with theoretical predictions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of the TiO2 content as support with carbon toward methanol electro-oxidation in alkaline media using platinum nanoparticles as electrocatalysts

Platinum nanoparticles supported on physical mixtures of Vulcan carbon and TiO₂ (Pt/(C?+?TiO₂)) were prepared by the borohydride method and tested for methanol electro-oxidation in alkaline media. X-ray diffraction (XRD) analyses showed peaks characteristic of Pt face-centered cubic (fcc) structure and peaks associated with TiO₂ and carbon. Transmission electron microscopy (TEM) images showed the Pt nanoparticles distributed preferentially over the TiO₂ support with average particle sizes between 5 and 6 nm. Cyclic voltammograms showed a decrease of Pt surface area with increasing TiO₂ load while linear sweep in the presence of methanol showed Pt/(C?+?TiO₂) (60:40) with the highest current density in accordance with chronoamperometry. The results were attributed to Pt-based nanoparticles on TiO₂ which show enhanced catalytic activities for methanol oxidation due to a metal-support interaction. Furthermore, TiO₂ is a semiconductor with low conductivity when compared to carbon. Thus, it is expected that an intermediate proportion of carbon and TiO₂ as substrate could improve the activity of Pt nanoparticles without substantial loss of conductivity, resulting in a synergic effect.     

Polyfluorinated amino acids for sensitive 19F NMR-based screening and kinetic measurements

Two novel series of polyfluorinated amino acids (PFAs) were designed and synthesized according to a very short and scalable synthetic sequence. The advantages and limitations of these moieties for screening purposes are presented and discussed. The potential applications of these PFAs were tested with their incorporation into small arginine-containing peptides that represent suitable substrates for the enzyme trypsin. The enzymatic reactions were monitored by 19F NMR spectroscopy, using the 3-FABS (three fluorine atoms for biochemical screening) technique. The high sensitivity achieved with these PFAs permits a reduction in substrate concentration required for 3-FABS. This is relevant in the utilization of 3-FABS in fragment-based screening for identification of small scaffolds that bind weakly to the receptor of interest. The large dispersion of 19F isotropic chemical shifts allows the simultaneous measurement of the efficiency of the different substrates, thus identifying the best substrate for screening purposes. Furthermore, the knowledge of KM and Kcat for the different substrates allows the identification of the structural motifs responsible for the binding affinity to the receptor and those affecting the chemical steps in enzymatic catalysis. This enables the construction of suitable pharmacophores that can be used for designing nonpeptidic inhibitors with high affinity for the enzyme or molecules that mimic the transition state. The novel PFAs can also find useful application in the FAXS (fluorine chemical shift anisotropy and exchange for screening) experiment, a 19F-based competition binding assay for the detection of molecules that inhibit the interaction between two proteins.     

Interference study of the chi c0(13P0) in the reaction -pp-->pi0pi0

Fermilab experiment E835 has observed (-)pp annihilation production of the charmonium state chi(c0) and its subsequent decay into pi(0)pi(0). Although the resonant amplitude is an order of magnitude smaller than that of the nonresonant continuum production of pi(0)pi(0), an enhanced interference signal is evident. A partial wave expansion is used to extract physics parameters. The amplitudes J=0 and 2, of comparable strength, dominate the expansion. Both are accessed by L=1 in the entrance (-)pp channel. The product of the input and output branching fractions is determined to be B((-)pp-->chi(c0))xB(chi(c0)-->pi(0)pi(0))=(5.09+/-0.81+/-0.25)x10(-7).