Evaluation of TA10 broth for recovery of heat- and freeze-injured Salmonella from beef

The Bacteriological Analytical Manual (BAM) Salmonella pre-enrichment broth [lactose (LAC) broth], buffered peptone water, and universal pre-enrichment (UP) broth were compared with TA10 broth, developed in our laboratory, for recovery of heat- and freeze-injured Salmonella (55 degrees C for 2-20 min and -20 degrees C for 2 months, respectively) from beef. Beef samples were contaminated with single Salmonella serovars, and contamination levels of 0.44 to <0.001 most probable number (MPN)/g and 0.74 to 0.14 MPN/g were used for heat- and freezing-induced injury studies, respectively. Twenty test portions (25 g) of the contaminated beef were pre-enriched in each broth, and the BAM Salmonella culture method was used thereafter. There was a significant difference (chi2 = 7.73) in recovery of heat-injured Salmonella between TA10 broth and LAC broth, 189 (67.5%) versus 156 (55.7%) positive samples, respectively, determined by plating onto selective agars and identification by biochemical tests. For the recovery of freeze-injured Salmonella, there was a significant difference (chi2 = 24.7) between TA10 and LAC broth, 189 (72.7%) versus 133 (51.2%) positive samples, respectively. TA10 broth was more effective than LAC broth and UP broth for recovery of freeze-injured Salmonella. The results indicate that TA10 broth should be used instead of LAC broth for testing of beef that may be contaminated with heat- and freeze-injured Salmonella spp.     

Langmuir monolayers of a cholesterol-armed cyclen complex that can control enantioselectivity of amino acid recognition by surface pressure

The cholesterol-armed cyclen Na(+) complex formed stable Langmuir monolayers at the air-water interface. The π-A isotherm displayed a reasonable limiting molecular area of ～1.57 nm(2) and the areas expanded when amino acids were dissolved in water, indicating the efficient accommodation in the monolayers. Brewster angle microscopy (BAM) images exhibited almost no defects of the compressed Langmuir monolayers regardless of the presence of amino acids. Based on the idea that the increase in the limiting molecular areas corresponds to the amount of the adsorbed amino acid, the binding constants of three enantiomeric amino acids, namely valine (Val), leucine (Leu), and phenylalanine (Phe), were calculated at different surface pressures. Remarkably, a surface pressure dependent enantioselectivity of amino acid recognition was observed. Upon compression of the monolayers, the binding constants of amino acids increased accompanying an inversion of chiral selectivity from the D- to L-form in the case of Val and, conversely, from L- to D-form in the case of Phe.     

Particle pairs in the cranked Hartree-Fock-Bogoliubov approximation and the interacting boson model

The number projected HFB wave function is analyzed in terms of particle pairs. It is found that the S(J = 0) and D(J = 2) pairs have dominant probabilities in this wave function before the occurrence of backbending, which is clarified from the behaviour of the O(J = 12) and M(J = 10) pairs arising from the $\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$ level. After backbending the wave function can be described mainly in terms of the O and M pairs plus the core made of S and D pairs.     

Pyrolysis of amines: Infrared spectrum of methyleneimine

Methyleneimine was detected in the gas phase by a moderately high resolution infrared spectrometer as one of the intermediate species produced by a pyrolysis of amines. Observed vibrational frequencies of some isotopic derivatives have been combined with the ab initio values to reach a most reliable force constants set. Some other spectroscopic parameters, involving geometrical parameters and dipole moment derivatives, have also been calculated ab initio and compared with the observation. Its half-life in our experimental apparatus was about 10 min, which is much longer than the previously reported values, 0.1 or 10 sec.     

10 GHz, 2.4 ps pulse generation using a single-stage dual-drive Mach-Zehnder modulator

This Letter reports on picosecond pulse generation at a repetition of 10 GHz by using a single-stage electro-optic LiNbO(3) Mach-Zehnder modulator, stressing the simplicity of its setup. It is analytically and experimentally proved that dual-arm modulation with in-phase sinusoidal signals having slightly different amplitudes generated a highly coherent optical comb with a great spectral flatness and a parabolic phase relationship in its spectrum. The generated comb was Fourier synthesized and shaped into an ultrashort pulse train with an optical bandpass filter and a dispersive fiber. The pulse source was highly stable, exhibiting an ultralow timing jitter of less than 130 fs.