Lifetimes of charged and neutralD mesons

We have measured the lifetimes of hadronically produced charged and neutralD mesons using silicon microstrip detectors and an active silicon target in the NA32 spectrometer at the CERN SPS. We obtainτ _D± = (10.9± _1.5 ^1.9 )·10^?13s andτ _D ^(?)10 = (4.2±0.5)·10^?13s based on 59 and 90 fully reconstructed decays respectively, giving a ratioτ _D±/τ _D ^(?)10 of 2.6 ±0.5.     

Fragmentations and reactions of the organophosphate insecticide Diazinon and its oxygen analog Diazoxon studied by electrospray ionization ion trap mass spectrometry

The fragmentations and reactions of Diazinon and related compounds have been studied by electrospray ionization ion trap mass spectrometry. Several novel fragmentation and rearrangements have been observed, including an intramolecular thiono-thiolo rearrangement. The stability, in the gas-phase, of the protomers of 2-isopropyl-4-methyl-6-pyrimidinol has been demonstrated. The complexity of the gas phase ion processes observed suggest that, at present, caution should be exercised in using this approach for the analysis of environmental and other samples until our understanding of these processes increases considerably.     

Joint production of ϕ mesons andπ ±,π 0,p,\bar p,K s 0 andK ± in hadronic interactions

The joint production of ? mesons andπ ^±,π ⁰,p, \(\bar p\) ,K _s ⁰ andK ^± is investigated using a sample of 600,000 inclusive ? meson events obtained in hadron Be interactions with incidentπ ^±,p, \(\bar p\) andK ^± beams. Evidence is presented for the joint production of ? mesons and strange particles produced with non-strange incident beams. With incidentK ^± beam the number of additional strange particles is suppressed. The results are found to be in agreement with the qualitative predictions of a parton fusion model. The comparison with the Lund model for lowp _T processes is fair.     

The polarizability of a pair of hydrogen atoms at long range

The coefficients of R^?6 and R^?9 in the long-range expansion of the parallel and perpendicular components of the polarizability of a pair of hydrogen atoms at a separation R have been calculated. The results are A⁽⁶⁾₆ = 2558.59. A⁽⁶⁾_⊥ = 1268.25, A⁽⁸⁾₆ = 90639.5 and A⁽⁸⁾_⊥ = 22010.3 au. The values of A⁽⁶⁾₆ and A⁽⁶⁾₆ and A⁽⁶⁾_| are somewhat larger than previous theoretical estimates and much larger than the classical values of 729 and 182.25 au. The terms in R^?8 arise from distortion associated with the dispersion forces and from the field of the quadrupole moment induced by the field-gradient at each atom.     

Precursor-directed biosynthesis of epothilone in Escherichia coli

Engineered biosynthetic pathways provide a powerful method for generating complex molecules. Precursor-directed biosynthesis, which combines chemical synthesis and enzymatic transformations, allows non-native starting materials to be incorporated into biosynthetic pathways. Using this approach, we achieved the production of the anticancer agent epothilone C in Escherichia coli. An E. coli strain was engineered to express the last three modules of the epothilone biosynthetic pathway (epoD-M6, epoE, and epoF) and the substrate required to complement the biosynthetic enzymes was obtained by chemical synthesis. Under high-density cell culture conditions, the E. coli strain processed exogenously fed synthetic substrate into epothilone C at levels comparable to the native host (1 mg/L) and at higher levels than other heterologous hosts. Importantly, this precursor-directed approach will allow chemical modifications to be introduced into the polyketide backbone and may ultimately provide access to epothilone analogues with improved pharmacological properties in quantities sufficient for clinical development.     

Analysis of the OH bend and stretch region in the vibrational spectrum of water

A method for calculating the infrared absorption spectrum of water in a range of different physical environments is described. Calculations are based on Monte Carlo simulations together with local-mode analyses of the H₂O vibrations. Results for liquid water and amorphous ice show clearly that the major features of the OH stretching motions are reproduced with good accuracy.