Reduction of strained polycycles: how much strain can a pyrene anion take?

The reduction of a series of [n](2,7)pyrenophanes (n = 7-10) with lithium or potassium metal shows that the strain in the system, controlled by the length of the tether, determines the nature of the reduction products. The reduction of [7](2,7)pyrenophane (2) and [2]metacyclo[2](2,7)pyrenophane (3) leads to reductive dimerization followed by novel intramolecular sigma-bond formation as a means of escaping strained anti-aromaticity. [8](2,7)Pyrenophane (4) affords only reductive dimerization, and no two-electron reduction is observed. The reduction of [9](2,7) pyrenophane (5) and [10](2,7)pyrenophane (6) leads to reductive dimerization, followed by the formation of a dianionic anti-aromatic species, which eventually cleaves the solvent, THF-d(8). The similarity between the reduction of the latter systems and the reduction of pyrene (1) is discussed.     

Characterization of a second-order nonlinear layer profile in thermally poled optical fibers with second-harmonic microscopy

Second-harmonic microscopy has been successfully applied to characterize the second-order nonlinear layer in optical fibers thermally poled at 280 degrees C and 3.5 kV for 30 min. The nonlinear layer was found to be approximately 5.1 microm deep under the anode and was not always centered about the closest point between the electrodes.     

Lifting polarization degeneracy of modes by fiber design: a platform for polarization-insensitive microbend fiber gratings

Polarization dependence in microbend gratings is an inherent problem, even in perfectly circular fibers, since antisymmetric modes are almost degenerate linear combinations of four distinct, polarization-sensitive modes. We demonstrate a novel fiber design that lifts polarization degeneracies of the antisymmetric modes to solve this problem. By intentionally exacerbating the polarization splittings, we achieve coupling to only the polarization-insensitive doublet, over wavelength ranges exceeding 100 nm, thus demonstrating a device with practical usable bandwidths. This allows all previous applications envisaged with UV-induced long-period gratings to be realized with the significantly lower-cost microbend technology platform.     

"The great escape" from antiaromaticity: reduction of strained pyrenes

The two-electron reduction of strained pyrenes ([7](2,7)pyrenophanes) with lithium metal leads to the formation of a new sigma-bond as a means to "escape" strained antiaromaticity.     

Use of double-depleted 13C and 15N culture media for analysis of whole cell bacteria by MALDI time-of-flight and Fourier transform mass spectrometry

In the present paper, results demonstrating the significant advantages of matrix-assisted laser desorption/ionization (MALDI) analysis of whole cell samples of bacteria grown on double isotopically-depleted (13C and 15N) media are presented. It is shown that several advantages accrue for MALDI with a 9.4 T Fourier transform mass spectrometer (FTMS). Of particular note, for analysis of whole cells, sample preparation is simple and chemical interference is reduced. Moreover, ion coalescence problems are minimized, and data-base identification of proteins facilitated. Furthermore, high resolution mass spectra obtained from such whole cells show significant improvement in apparent mass resolving power and mass measurement accuracy, whether time-of-flight or FTMS MALDI is used. As a consequence, it becomes possible to detect subtle details in the chemistry of the organism, such as the presence of both post-translationally modified and unmodified versions of the same proteins. This approach is also adaptable to direct assay of over-expressed proteins from Escherichia coli cultures and should facilitate studies aimed at the detection of medically important cellular biomarker proteins.     

The reaction of phenyldimethylsilyllithium with N-phenylpyrrolidone

Phenyldimethylsilyllithium reacts with N-phenylpyrrolidone 5 to give the known tetracyclic amines [2,3,3a,3b,4,5,6,11b-octahydro-3aalpha,3balpha, 11balpha-1-phenyl-1H-dipyrrolo(1,2a:3',2'c)quinoline and its 3bbeta isomer] 6 and 7.     

High-quality-factor Bragg onion resonators with omnidirectional reflector cladding

We propose to approximate a spherically symmetric Bragg resonator in an onionlike geometry. We develop a transfer-matrix theory for calculation of the quality factors and analyze the effect of the onion stem on cavity Q factors. We find that it is possible to achieve significant inhibition of spontaneous emission in an onion resonator with omnidirectional cladding layers.     

Search for the lepton family number violating process nu(mu)e(-) --> mu(-)nu(e)

The NuTeV experiment at Fermilab has used a sign-selected neutrino beam to perform a search for the lepton number violating process nu(mu)e(-)-->mu(-)nu(e), and to measure the cross section of the standard model inverse muon decay process nu(mu)e(-)-->mu(-)nu(e). NuTeV measures the inverse muon decay asymptotic cross-section slope sigma/E to be (13.8 +/- 1.2 +/- 1.4) x 10(-42) cm(2)/GeV. The experiment also observes no evidence for lepton number violation and places one of the most restrictive limits on the cross-section ratio sigma(nu(mu)e(-)-->mu(-)nu(e))/sigma(nu(mu)e(-)-->mu(-)nu(e)) < or = 1.7% at 90% C.L. for V-A couplings and < or = 0.6% for scalar couplings.     

Why ALC μSR is superior for gas‐phase radical spectroscopy

ALC μSR spectra of the muonated ethyl and cyclohexadienyl radicals in the gas phase are reported. They have surprisingly narrow lines for a magnetic resonance type technique under conditions near ambient temperature and near 1 atmosphere pressure. The main reason for this behaviour is the dramatic reduction of electron spin relaxation in high magnetic fields. This revised version was published online in August 2006 with corrections to the Cover Date.