Double prompt photon production at high transverse momentum byπ − on protons at 280 GeV/c

A search for pairs of highp _T prompt photons produced in hydrogen by a 280 GeV/c incidentπ ^- beam has been carried out using a fine-grained electromagnetic calorimeter and the Omega spectrometer at the CERN SPS. Clear evidence for the existence of such events is found with a six standard deviation signal forp _T >3.0 GeV/c. The cross-sections are consistent with beyond leading order QCD calculations. A discussion on the determination of α _s is also presented.     

The structure of events triggered by direct photons in π− p, π+ p andpp collisions at 280 GeV/c

The structure of events associated with the production of direct photons in π^? p, π⁺ p andpp reactions of 280 GeV/c has been studied using data from the WA 70 experiment at the CERN SPS. Results are presented on the distributions of the fractional momenta of the colliding partons and on the fragmentation of the recoil jet and a comparison is made with predictions using the structure functions of Duke and Owens in the Lund Monte Carlo with string fragmentation.     

Copper and iron interactions with angiotensin-converting enzyme inhibitors. A study by fast-atom bombardment tandem mass spectrometry

Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.     

ESI‐MS/MS of expanded porphyrins: a look into their structure and aromaticity

Electrospray mass spectrometry/mass spectrometry was used to investigate the gas‐phase properties of protonated expanded porphyrins, in order to correlate those with their structure and conformation. We have selected five expanded meso‐pentafluorophenyl porphyrins, respectively, a pair of oxidized/reduced fused pentaphyrins (22 and 24 π electrons), a pair of oxidized/reduced regular hexaphyrins (26 and 28 π electrons) and a regular doubly N‐fused hexaphyrin (28 π electrons). The gas‐phase behavior of the protonated species of oxidized and reduced expanded porphyrins is different. The oxidized species (aromatic Hückel systems) fragment more extensively, mainly by the loss of two HF molecules. The reduced species (Möbius aromatic or Möbius‐like aromatic systems) fragment less than their oxidized counterparts because of their increased flexibility. The protonated regular doubly fused hexaphyrin (non‐aromatic Hückel system) shows the least fragmentation even at higher collision energies. In general, cyclization through losses of HF molecules decreases from the aromatic Hückel systems to Möbius aromatic or Möbius‐like aromatic systems to non‐aromatic Hückel systems and is related to an increase in conformational distortion. Copyright © 2016 John Wiley & Sons, Ltd.     

High transverse momentumη production in π− p, π+ p,andpp interactions at 280 GeV/c

The inclusive cross sections for η production by the interactions of 280 GeV/c momentum π^?, π⁺, and proton beams in hydrogen have been measured. The kinematical range covered is ?0.45<x _F <0.45, and 4.0<P _T <7.0 GeV/c for Feynmanx _F and transverse momentum respectively. The η to π⁰ cross section ratios are given for the three reactions. The ratio of π^? p to π⁺ p cross sections for η production in the above kinematic ranges is 1.22±0.08±0.11.     

Trialkyltin Compounds as Neutral Carriers for Anions in PVC Liquid Membranes and Complex Formation with Oxoanions

Under the influence of an electric field, trialkyltin compounds of the type R₃SnX behave as electrically neutral carriers for anions in poly(vinyl chloride) liquid membranes. The interaction of tinorganic compounds with oxoanions was studied in organic phase by means of ¹¹⁹Sn-NMR-monitored titrations. In the case of tributyltin chloride, no appreciable amount of complex was formed with hydrogensulfate, whereas dihydrogenphosphate gave rise to a new species. Dioctyltin dichloride and dioctyltin dioctyltin diacetate formed a 1:2 (salt/ligand) complex with hydrogenphosphate.     

Search for exotic mesons produced by baryon exchange in the reaction π+p → Λ + x++ at 12 GeV/c

A search for exotic mesons has been carried out at the CERN Omega spectrometer. The baryon-exchange reaction π⁺p → Λ + x⁺⁺ was studied at 12 GeV/c incident beam momentum. No evidence was found for the existence of doubly-charged strange mesons. The upper limit (95% confidence level) for this reaction is 60 nb for exotic mesons with squared masses from 1 to 7 (GeV/c²)² and 150 nb for 7 to 13 (GeV/c²)². These limits are of the same order of magnitude as the exotic cross-sections expected from two-component duality arguments.     

Test of the Zweig rule in π−p interactions at 19 GeV/c

We have observed φ production in π^?p interactions at 19 GeV/c with (44±10) events in the final state φπ⁺π^?π^?p and (45±9) events in φK⁺K^?π^?p. The production ratios φπ⁺π^?π^?p/ωπ⁺π^?π^?p ≈ 0.005 and φK⁺K^?π^?p/?°K⁺K^?π^?p ≈ 0.45 agree with Zweig-rule expectations.     

A two-electrode configuration for simplified amperometric detection in a microfabricated electrophoretic separation device

The simplified amperometric detection scheme demonstrated is based on the amperometric working and electrophoretic ground electrodes only. The latter serves as counter and pseudo-reference as well. It is shown via the successful determination of neurotransmitters, ascorbic acid and phenols on gold or platinum working electrodes that this approach is feasible for detection on a channel based electrophoretic separation device. Also presented is the detection of carbohydrates and amino acids with copper electrodes. The results were found to be similar to those obtained with conventional capillary systems with amperometric detection, albeit at much reduced analysis times.