Q value of the superallowed decay of 46V and its influence on Vud and the unitarity of the Cabibbo-Kobayashi-Maskawa matrix

The masses of the radioactive nuclei (46)V and its decay daughter (46)Ti have been measured with the Canadian Penning Trap on-line Penning trap mass spectrometer to a precision of 1 x 10(-8). A Q(EC) value of 7052.90(40) keV for the superallowed beta decay of (46)V is obtained from the difference of these two masses. With this precise Q value, the Ft value for this decay is determined with improved precision. An investigation of an earlier Q-value measurement for (46)V uncovers a set of 7 measurements that cannot be reconciled with modern data and affects previous evaluations of V(ud) from superallowed Fermi decays. A new evaluation, adding our new data and removing the discredited subset, yields new values for G(V) and V(ud). When combined with recent results for V(us), this yields modified constraints for the unitarity of the Cabibbo-Kobayashi-Maskawa matrix and other extensions of the standard model.     

Avenues into the synthesis of illusive poly(m-phenylene-alt-squaraine)s: polycondensation of m-phenylenediamines with squaric acid intercepted by intermediate semisquaraines of exceptionally low reactivity

The synthesis and properties of a novel class of ortho-dialkylamino-substituted semisquaraines are described. The exceptionally low reactivity of the investigated compounds is caused by an intramolecular hydrogen bond as evidenced by experimental and computational studies. Although this constitutes the reason for our failed attempts to prepare poly(m-phenylene-alt-squaraine)s, the discovered influence of hydrogen bonding on the photophysical properties of these semisquaraines provides a promising new motif for sensor design.     

Gamow-teller strengths of the inverse beta transition 176Yb-->176Lu for spectroscopy of proton-proton and other sub-MeV solar neutrinos

Discrete Gamow-Teller (GT) transitions 176Yb-->176Lu at low excitation energies have been measured via the ( 3He,t) reaction at 450 MeV and at 0 degrees. For 176Yb, two low-lying states are observed, setting low thresholds Q(nu) = 301 and 445 keV for neutrino ( nu) capture. Capture rates estimated from the measured GT strengths, the simple two-state excitation structure, and the low Q(nu) in Yb-Lu indicate that Yb-based nu detectors are well suited for a direct measurement of the sub-MeV solar electron-neutrino ( nu(e)) spectrum including pp neutrinos.     

Gas-temperature imaging in a low-pressure flame reactor for nano-particle synthesis with multi-line NO-LIF thermometry

Multi-line NO-LIF temperature imaging was applied to measure two-dimensional gas-temperature fields in a low-pressure, premixed flat-flame nano-particle generator during nano-particles synthesis. It was the first time that this calibration-free technique was applied in a low-pressure combustion system. The laser fluence was limited to 4 kW/cm² in order to avoid saturation of the LIF signal, which influences the temperature results. While minimizing the elastically scattered light, the efficiency of the LIF detection system improved. This enables measurements with low tracer concentrations that do not influence the nano-particle generation process or the flame chemistry. An optimized scan range for excitation spectra was applied to measure flame temperatures between 600 and 1500 K in a 175×50 mm² field with an accuracy of ±2%. It was found that the TiO₂ nano-particle generation process does not influence the flame temperature under typical operating conditions. Pressure effects on the temperature distribution were investigated. The data is required for the simulation of nano-particle formation based on kinetic modeling. PACS 07.20.Dt; 42.62.Fi; 61.46.Df     

Scars of the Wigner Function

We propose a picture of Wigner function scars as a sequence of concentric rings along a two-dimensional surface inside a periodic orbit. This is verified for a two-dimensional plane that contains a classical hyperbolic orbit of a Hamiltonian system with 2 degrees of freedom. The stationary wave functions are the familiar mixture of scarred and random waves, but the spectral average of the Wigner functions in part of the plane is nearly that of a harmonic oscillator and individual states are also remarkably regular. These results are interpreted in terms of the semiclassical picture of chords and centers.     

Total synthesis of deamido bleomycin a(2), the major catabolite of the antitumor agent bleomycin

Metabolic inactivation of the antitumor antibiotic bleomycin is believed to be mediated exclusively via the action of bleomycin hydrolase, a cysteine proteinase that is widely distributed in nature. While the spectrum of antitumor activity exhibited by the bleomycins is believed to reflect the anatomical distribution of bleomycin hydrolase within the host, little has been done to characterize the product of the putative inactivation at a chemical or biochemical level. The present report describes the synthesis of deamidobleomycin demethyl A(2) (3) and deamido bleomycin A(2) (4), as well as the respective aglycones. These compounds were all accessible via the key intermediate N(alpha)-Boc-N(beta)-[1-amino-3(S)-(4-amino-6-carboxy-5-methylpyrimidin-2-yl)propion-3-yl]-(S)-beta-aminoalanine tert-butyl ester (16). Synthetic deamido bleomycin A(2) was shown to be identical to the product formed by treatment of bleomycin A(2) with human bleomycin hydrolase, as judged by reversed-phase HPLC analysis and (1)H NMR spectroscopy. Deamido bleomycin A(2) was found to retain significant DNA cleavage activity in DNA plasmid relaxation assays and had the same sequence selectivity of DNA cleavage as bleomycin A(2). The most significant alteration of function noted in this study was a reduction in the ability of deamido bleomycin A(2) to mediate double-strand DNA cleavage, relative to that produced by BLM A(2).