Bacterial reduction of N-oxides of tobacco- specific nitrosamines (TSNA)

1 Contrary to established metabolic pattern, a recent investigation of NNK metabolism produced in rat urine higher levels of 4-(methylnitrosamino)-1-(3-pyridyl)-1- butanone (NNK) and 4-(methylnitrosamino)-1-(3-pyri dyl)-1-butanol (NNAL) than their N-oxides, suggesting that reconversion of N-oxides could occur after urine formation. 2 To verify the possible role of bacteria in the reduction of NNK-N-oxide and NNAL-N-oxide to their respective parent compounds, NNK and NNAL, in smokers with urinary tract infection (UTI), the N-oxides were isolated from the urine of rats treated with 5-3HNNK and individually incubated at 37°C with ten bacterial species in sterile human urine under different pH regimens. After incubation with the bacteria, aliquots of culture media were analyzed by high pressure liquid chromatography (HPLC) with radiochemical detection. 3 Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae and Proteus mirabilis possessed varying capacity to regenerate NNK and NNAL from their N- oxides while others showed no detectable reductive capability within 24 h. 4 This result constitutes the first experimental evidence that in tobacco users with concomitant UTI, bacterial regeneration of the procarcinogenic NNK and NNAL from their N-oxides could occur in the bladder leading to increased carcinogen burden in these individuals

Recent star formation in high-redshift early-type galaxies: insights from the rest-frame UV

We combine deep UBVRIzJK photometry from the MUSYC survey with redshifts from the COMBO-17 survey to study the rest-frame ultraviolet (UV) properties of 674 high-redshift (0.5<z<1) early-type galaxies, drawn from the Extended Chandra Deep Field South (E-CDFS). Galaxy morphologies are determined through visual inspection of Hubble Space Telescope (HST) images taken from the GEMS survey. We harness the sensitivity of the UV to young (<1 Gyrs old) stars to quantify the recent star formation history of the early-type population. We find compelling evidence that early-types of all luminosities form stars over the lifetime of the Universe, although the bulk of their star formation is already complete at high redshift. Luminous (-23<M(V)<-20.5) early-types form 10-15 percent of their mass after z=1, while their less luminous (M(V)>-20.5) counterparts form 30-60 percent of their mass in the same redshift range.Comment: To appear in the proceedings of the IAU 245, eds. M. Bureau, E. Athanassoula, and B. Barbu

``Fermi Liquid'' Shell Model Approach to Composite Fermion Excitation Spectra in Fractional Quantum Hall States

Numerical results for the energy spectra of $N$ electrons on a spherical surface are used as input data to determine the quasiparticle energies and the pairwise ``Fermi liquid'' interactions of composite Fermion (CF) excitations in fractional quantum Hall systems. The quasiparticle energies and their interactions are then used to determine the energy spectra, $E$ vs total angular momentum $L$, of states containing more than two quasiparticles. The qualitative agreement with the numerical results gives a remarkable new confirmation of the CF picture.Comment: LaTex, 4 pages, including 4 .eps-figures, to be appear in pr

Phased arrays of buried-ridge InP/InGaAsP diode lasers

Phase-locked arrays of buried-ridge InP/InGaAsP lasers, emitting at 1.3 µm, were grown by liquid phase epitaxy. The arrays consist of index-guided, buried-ridge lasers which are coupled via their evanescent optical fields. This index-guided structure makes it possible to avoid the occurrence of lower gain in the interchannel regions. As a result, the buried-ridge arrays oscillate mainly in the fundamental supermode, which yields single lobed, narrow far-field patterns. Single lobed beams less than 4° in width were obtained from buried-ridge InP/InGaAsP phased arrays up to more than twice the threshold current

Phase-locking characteristics of coupled ridge-waveguide InP/InGaAsP diode lasers

The phase-locking characteristics of two coupled, ridge waveguide InP/InGaAsP diode lasers emitting at 1.2 µm were investigated experimentally. The phase locking of the lasers was verified by the observation of phase-locked modes (supermodes) in the spectrally resolved near fields and distinct diffraction patterns in the far field. By independent control of the laser currents it was possible to vary continuously the mutual phase shift between the two phase-locked lasers and thus steer the far-field diffraction lobes. In addition, the separate current control could be utilized to obtain single longitudinal mode oscillation of the phase-locked lasers. Variation in one of the laser currents resulted then in tuning of the wavelength of this single mode over a range of 90 Å

Probing dipolar effects with condensate shape oscillation

We discuss the low energy shape oscillations of a magnetic trapped atomic condensate including the spin dipole interaction. When the nominal isotropic s-wave interaction strength becomes tunable through a Feshbach resonance (e.g. as for $^{85}$Rb atoms), anisotropic dipolar effects are shown to be detectable under current experimental conditions [E. A. Donley {\it et al.}, Nature {\bf 412}, 295 (2001)].Comment: revised version, submitte

Cd diffused mesa-substrate buried heterostructure InGaAsP/InP laser

A new type of buried heterostructure InGaAsP/InP lasers grown by a single-step liquid phase epitaxy on Cd diffused mesa substrate is described. These lasers exhibit excellent current and optical confinement. Threshold currents as low as 15 mA are achieved for a laser with a 2-µm-wide active region