Cyclodextrin-MEEKC for the analysis of oxybutynin and its impurities

The development of a cyclodextrin-MEEKC method for the analysis of oxybutynin and five related impurities is described. Experimental design strategies were applied in order to reach baseline separation of the compounds in a short analysis time. Mixture design made it possible to find the best composition for the microemulsion acting as pseudostationary phase, which was constituted by 89.1% 10 mM borate buffer pH 9.2, 1.7% n-heptane, 9.2% SDS/n-butanol in 1:2 ratio. The addition of (2-hydroxypropyl)-β-cyclodextrin to the background electrolyte was found to improve analysis performance. A Doehlert design, for the factors cyclodextrin concentration and voltage, was carried out and Derringer desirability function led to the identification of 18 mM and 29 kV as the optimal values. Applying the optimum conditions, separation of all the compounds, including the enantiomers of impurity 1, was obtained in less than 12 min. The method was validated according to ICH guidelines for drug assay and determination of impurities and was applied to oxybutynin tablet analysis.     

Compensating for parasitic phase shift in microwave digitally controlled attenuators

Design issues of digitally controlled attenuators are considered: the parasitic phase shift effect, occurring with every change in the attenuator cell state, is highlighted, investigated and corrected. The technique adopted consists of inserting an appropriately sized capacitor in the attenuator cell topology, compensating for the above-mentioned parasitic phase shift. A design equation is inferred and an X-band MMIC 5-bit constant phase digital attenuator is designed as a test vehicle for the proposed approach.     

Meson exchange interactions at low and intermediate energies: colour screening effects

We consider the colour screening effects of constituent quarks and the exchange of effective gluons in the interaction of hadrons. To this end we propose two different processes derived from fundamental properties of the underlying microscopic theory (QCD). Sum rules for diagrams providing colour screening are also given.     

Measurement of the local latch-up sensitivity by means of computer-controller scanning electron microscopy

The scanning electron microscopy (SEM) technique for the study of the local sensitivity to latch-up of CMOS integrated circuits is discussed. The technique is independent of a particular electric firing mechanism of latchup and does not require in-depth electrical characterization of the IC before the analysis. The electron beam in the SEM is adopted as a localized current injector, and the injected carriers are used to induce the latch-up state rather than to visualize its paths. A minicomputer-based system drives the beam position and automatically blanks the beam if the scan path has to cross areas which should be protected from charge injection. An example of application is described.<>     

Complex particles produced from graphite powder by acoustic cavitation in water

Spaghetti-like structures made of fibers whose diameter are of about 1-2 microns, straight structures from about 10-20 microns and optically semitransparent particles, with linear dimension up to about 0.3 mm, were obtained from fine graphite powder in water subjected for 20 h to acoustic cavitation at a frequency of 19.5 kHz. A picture of spaghetti-like structures obtained by scanning electron microscopy is reported. From X-ray diffraction pattern, it was found that the semitransparent precipitates have an amorphous nature.     

Mass and lifetime limits on new long-lived particles in 300 GeV/c π− interactions

A sensitive search has been done for the production of new long-lived and penetrating particles by 300 GeV/c negative pions. No new state —decaying into at least two charged known particles —has been detected with mass above 1 GeV/c² and lifetime in the range 5·10^?11 s to 5·10^?7s. We give upper limits on production cross sections, and consequences on the existence of heavy “axion-like” particles, heavy neutrinos and supersymmetric particles. In particular, this experiment excludes the existence of light gluinos with lifetime in the range 5·10^?11 to 10^?8s: this closes the last “window of opportunity” for gluinos withM<2 GeV/c² and lifetime measurable in particle physics experiments.     

Spectroscopy of pentaquark states

We construct a complete classification of pentaquark states in terms of the spin-flavour SU(6) representations. We find that only some definite SU(3) representations are allowed, that is singlets, octects, decuplets, anti-decuplets, 27-plets and 35-plets. The latter three contain exotic states, which cannot be constructed from three quarks only. This complete classification is general and model independent and is useful both for model builders and experimentalists. The mass spectrum is obtained from a Gürsey-Radicati type mass formula, whose coefficients have been determined previously by a study of qqq-baryons. The ground-state pentaquark, which is identified with the recently observed state, is predicted to be an isosinglet anti-decuplet state. Its parity depends on the interplay between the spin-flavour and orbital contributions to the mass operator.PACS: 14.20.-c Baryons (including antiparticles) - 12.39.-x Phenomenological quark models - 02.20.-a Group theory     

Inclusive highP T π0 production from π± and protons at 200 GeV/c

We have measured the inclusive cross-section for π⁰ production at large transverse momentum by 200 GeV/c positive and negative hadron beams on Carbon targets (2.9<P _T <6 GeV/c; ?0.4<y ^*<1.2). We used the NA3 spectrometer at the CERNSPS.