The Pure Rotational Spectra of AuCl and AuBr.

The pure rotational spectra of AuCl and AuBr have been measured in the v = 0 and 1 (also for v = 2 for Au(35)Cl) vibrational states in the 5-22 GHz spectral region using a cavity pulsed-jet Fourier transform microwave spectrometer. The molecules were prepared by ablating Au metal in the presence of Cl(2) or Br(2) entrained in the Ar or Ne backing gas of the jet. The equilibrium internuclear distances r(e) have been determined along with estimates of the harmonic vibration frequencies and the dissociation energies. The ionic characters of the AuCl and AuBr bonds have been estimated from the halogen nuclear quadrupole-coupling constants to be i(c) approximately 38%. The gold nuclear quadrupole coupling constants change appreciably from AuF to AuCl to AuBr (including a sign change), indicating substantial differences in their electronic structures at Au; these variations could not be accounted for with a simple Townes-Dailey calculation. Copyright 2000 Academic Press.

Acoustic emission monitoring of high speed grinding of silicon nitride

Acoustic emission (AE) monitoring of a machining process offers real-time sensory input which could provide tool condition and part quality information that is critical to effective process control. However, the choice of sensor, its placement, and how to process the data and extract useful information are challenging application-specific questions which researchers must consider. Here we report an effort to resolve these questions for the case of high speed grinding of silicon nitride using an electroplated single-layered diamond wheel. A grinding experiment was conducted at a wheel speed of 149 m s-1 and continued until the end of the useful wheel life. AE signal data were then collected for each complete pass at given grinding times throughout the useful wheel life. We found that the amplitude of the AE signal monotonically increases with wheel wear, as do grinding forces and energy. Furthermore, the signal power contained in the AE signal proportionally increases with the associated grinding power, which suggests that the AE signal could provide quantitative information of wheel wear in high-speed grinding, and could also be used to determine when the grinding wheel needs replacement.

The Hyperfine Structures of ScCl and ScF.

The Fourier transform microwave spectra of gaseous ScF and ScCl have been measured in their (1)Sigma(+) ground electronic states. Transitions have been observed for ScF (J = 1-0) and for both Sc(35)Cl and Sc(37)Cl (J = 1-0 and J = 2-1) in the ground vibrational state, and for Sc(35)Cl (J = 1-0 and J = 2-1) in the first excited vibrational state. The nuclear quadrupole coupling constants of Sc and of both isotopes of Cl, the spin-rotation constants for all the nuclei and the nuclear spin-nuclear spin constants for both molecules, have been determined. From these hyperfine constants, the electronic structures of ScF and ScCl have been investigated and comparisons have been made to similar molecules. ScCl has been found to be highly ionic. For Sc(35)Cl, the equilibrium bond length has been reevaluated and the vibration frequency and dissociation energy have been estimated. A simple approach to account for the Sc quadrupole coupling constants has been shown to be flawed. Copyright 2000 Academic Press.

Hyperfine Structure in the Rotational Spectrum of GaF: A Comparison of Experimental and Calculated Spin-Rotation and Electric Field Gradient Tensors.

The high-resolution pure rotational spectrum of GaF has been measured using a Balle-Flygare-type Fourier transform spectrometer. Improved nuclear quadrupolar coupling constants and rotational constants have been obtained along with the first reported fluorine spin-rotation constant for gallium fluoride, C(I) ((69)Ga(19)F, v = 0) = +32.0(21) kHz. Accurate spin-rotation tensors from microwave or molecular beam spectroscopy are particularly important to NMR spectroscopists and theoreticians because these data provide information about anisotropic nuclear magnetic shielding in the absence of intermolecular effects. For quadrupolar nuclei such as gallium, the quadrupolar interaction is sufficiently large that it is very difficult to characterize shielding tensors directly via NMR spectroscopy. The experimentally determined nuclear quadrupolar coupling constants and spin-rotation constants for GaF are compared with the results of a series of high-level ab initio calculations carried out at various levels of theory with a range of basis sets. Further calculations on BF and AlF, supplemented with available experimental data for InF and TlF, allow for the investigation of trends in nuclear magnetic shielding, spin-rotation, and electric field gradient tensors in the group-13 fluorides. Calculations at the MP2/6-311++G** and MP2/6-311G(2df, 2pd) levels provide the most consistently satisfactory results in comparison with the experimental data. Copyright 2000 Academic Press.

The High-Resolution FTIR Far-Infrared Spectrum of Vinylamine.

The infrared spectrum of vinylamine, generated by pyrolysis of cyclobutylamine, has been investigated at low and high resolution. The rovibrational structure of the far infrared spectrum (0.002 cm(-1)) has been analyzed, and effective rotational and centrifugal distortion constants have been derived for eight vibration-rotation bands in the region 250-750 cm(-1). The rovibrational structure of two further bands has been assigned using combination differences, and some conclusions have been drawn about the vibrational energy levels involved. With the large amount of new data it is possible to achieve a vibrational analysis of the far infrared region, but not to totally exclude an alternative assignment. Copyright 1999 Academic Press.

Vascular surgical society of great britain and ireland: symptoms of varicose veins

BACKGROUND: The relationships between varicose veins (VVs) and leg symptoms have not been studied. The aim of this study was to define the relationships between age, sex, leg symptoms and VVs. METHODS: An age-stratified sample of 699 men and 867 women aged 18-64 years, selected randomly from 12 general practices distributed socioeconomically throughout the city, completed a questionnaire regarding leg symptoms (heaviness/tension, swelling, aching, restless legs, cramps, itching, tingling) and underwent a clinical examination. RESULTS: In men, swelling and cramps (both P

The High-Resolution FTIR Far-Infrared Spectrum of Formamide.

The far-infrared spectrum of formamide (HCONH2) has been recorded at high resolution and over 9000 vibration-rotation lines assigned. Molecular parameters from the rovibrational analyses of the unperturbed 12(1)0 out-of-plane vibration band have been obtained for the ground state and the excited state. An analysis of the complicated resonance system between the 9(1)0, 11(1)0, and 12(2)0 bands has also been carried out. The mid-infrared spectrum of formamide has been recorded at low resolution and assignments for the fundamental, combination, and overtone bands in this region are given. The Large Amplitude Motion (LAM) of the out-of-plane mode has been reanalyzed using the new parameter set. Copyright 1999 Academic Press.

High-Resolution Fourier Transform Infrared Spectroscopy of Nitrosyl Fluoride

The high-resolution FTIR spectrum of FNO has been recorded and the rovibrational structure of the essentially unperturbed nu3, 2nu3, and nu1 + nu3 cold bands and the 2nu3 <-- nu3, nu2 + nu3 <-- nu3, and nu1 + nu2 + nu3 <-- nu3 hot bands has been analyzed. The perturbed bands nu1 and nu1 + nu2 have been assigned and the data analyzed by fitting the transitions with the dark states nu2 + 2nu3 and 2nu2 + 2nu3. Parameters for both light and dark states together with Coriolis coupling parameters have been determined. Copyright 1998 Academic Press. Copyright 1998Academic Press