The microwave spectrum and structure of chloryl fluoride

The microwave spectra of three isotopic species of chloryl fluoride, FClO₂, in its ground vibrational state, have been measured in the frequency region 8–37 GHz. The spectra have yielded values for the rotational constants, centrifugal distortion constants, and chlorine nuclear quadrupole coupling constants, as well as the molecular dipole moment, 1.722 ± 0.03 D. The molecule has been shown to have C_s symmetry, and a pyramidal configuration, with the chlorine atom at the apex of the pyramid. The following internuclear parameters were obtained:r(Cl?F)1.697±0.003 A r(Cl?F)=1.418±0.002AThe structural parameters, quadrupole coupling constants, dipole moment and force field are explained in terms of a bonding scheme in which a fluorine 2p atomic orbital overlaps with the highest occupied orbital of ClO₂; there is considerable evidence for withdrawal of electron density from this singly occupied antibonding orbital of ClO₂ toward the fluorine atom.     

A virtually nondestructive EPR technique accounting for diagnostic X-rays

We have implemented the method proposed by Aldrich and Pass (Aldrich, J.E., Pass, B., 1988. Determining radiation exposure from nuclear accidents and atomic tests using dental enamel. Health Phys. 54, 469–471.) to measure both the interior and exterior portions of a tooth in order to determine the diagnostic X-ray component of the total dose in the teeth. This was done using a modified nondestructive approach of Haskell et al. (Haskell, E.H., Hayes, R.B., Romanyukha, A.A., Kenner, G.H., 2000. Preliminary report on the development of a virtually non-destructive additive dose technique for EPR dosimetry Appl. Radiat Isot. 52, 1065–1070.) given in Hayes et al. ( Hayes, R.B., Haskell, E.H., Barrus, J.K., Kenner, G.H., Romanyukha, A.A., 2000. Accurate EPR radiosensitivity calibration using small sample masses. Nucl. Instr. Meth. A. 441, 535–550). Here only 5% of the total tooth enamel sample from an enamel crown was used for individual sample sensitivity calibration. A cavity response correction for the low mass samples was also used ( Hayes et al., 2000). The teeth were American wisdom teeth having unknown doses applied by the IAEA in the range of 0 to 1 Gy as part of the second international intercomparison ( Wieser, A., Mehta, K., Amira, S., Aragno, S., Bercea, S., Brik, A., Bugai, A., Callens, F., Chumak, V., Ciesielski, B., Debuyst, R., Dubovsky, S., Duliu, O., Fattibene, P., Haskell, E., Hayes, R., Ignatiev, E., Ivannikov, A., Kirillov, V., Kleschenko, E., Nakamura, N., Nathe, M., Nowak, J., Onori, S., Pass, B., Pivovarov, S., Romanyukha, A., Scherbina, O., Shames, A., Sholom, S., Skvortsov, V., Stepanenko, V., Tikounov, D., Toyoda, S., 2000. The 2nd international intercomparison on EPR tooth dosimetry. Radiat. Meas. in press). Final dose reconstruction estimates of the IAEA applied values showed a very high correlation (R=0.996). The approximate excess dose measured on the outside of the teeth relative to the inside was 49±35 mGy which is attributed to the diagnostic X-ray exposure given to the America wisdom teeth prior to extraction. The method used showed only a small dependence on the accelerating voltage of the X-ray source.     

Predictive Current Control for Multilevel Active Rectifiers With Reduced Switching Frequency

In this paper, a new low-frequency predictive current control is proposed for a single-phase cascaded H-bridge multilevel rectifier. The control method has been fully investigated with theoretical analysis, simulation, and experiments on a laboratory prototype with five series-connected H-bridges. However, the analysis and technique are valid for any general level structure. The simulations and experimental results presented demonstrate the excellent performance of the predictive control in terms of AC current waveform quality, power factor, and reduced switching frequency of each bridge, in comparison to traditional control schemes.     

A facile and general route to 4-substituted-2 butenolides

Grignard reagents react with 7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride and produce in high yields the corresponding substituted bicyclo-γ-butanolides. These lactones produce the title compounds by retro Diels-Alder reaction during distillation.     

Cobinamide chemistries for photometric cyanide determination. A merging zone liquid core waveguide cyanide analyzer using cyanoaquacobinamide

Diaquacobinamide (H₂O)₂Cbi²⁺ or its conjugate base hydroxyaquacobinamide (OH(H₂O)Cbi⁺)) can bind up to two cyanide ions, making dicyanocobinamide. This transition is accompanied by a significant change in color, previously exploited for cyanide determination. The reagent OH(H₂O)Cbi⁺ is used in excess; when trace amounts of cyanide are added, CN(H₂O)Cbi⁺ should be formed. But the spectral absorption of CN(H₂O)Cbi⁺ is virtually the same as that of OH(H₂O)Cbi⁺. It has been inexplicable how trace amounts of cyanide are sensitively measured by this reaction. It is shown here that even with excess OH(H₂O)Cbi⁺, (CN)₂Cbi is formed first due to kinetic reasons; this only slowly forms CN(H₂O)Cbi⁺. This understanding implies that CN(H₂O)Cbi⁺ will itself be a better reagent.     

Time-dependent invariants and generalized coherent states

We construct time-dependent invariants of the hamiltonian operators preserving displacement operator-type coherent states under time evolution. We consider the usual oscillator coherent states and those associated with the dynamical group SU(1,1).     

The high-resolution infrared spectrum of the 201 band of carbonyl fluoride: Determination of the far infrared laser frequencies

The first high-resolution (0.0024 cm^?1) spectrum of the 2₀¹ band of COF₂ at 963 cm^?1 is reported. Nearly 4000 rotational transitions have been observed and assigned in the band between 936 and 990 cm^?1. The line positions are estimated to be accurate to 0.0001 cm^?1 (relative). The spectrum was calibrated using two adjacent bands of OCS. Approximately 1560 infrared transitions have been fitted simultaneously with the previously reported microwave data. The wave numbers of far infrared laser lines recently observed by Tobin and by Temps and Wagner have been calculated from the 2¹ energy levels, with estimated uncertainties of between 10^?5 and 10^?6 cm^?1.     

The microwave spectrum,harmonic force field,and structure of carbonyl chlorofluoride,OCCIF

Rotational spectra of three isotopic species of carbonyl chlorofluoride, OCCIF, have been extensively measured, and have been analyzed for rotational constants, quartic centrifugal distortion constants, and chlorine nuclear quadrupole coupling constants. Ab initio calculations of the harmonic force field have been made using several different sets of basis functions, and their relative cost efficiency has been assessed. The measured distortion constants have been combined with vibrational wavenumbers (both from the literature and from the present work) and with the ab initio force constants to refine the force field. Ground state effective (r₀) and average (r_z) structures have been evaluated for the molecule.     

Design of Wearable Radio Frequency Identification Antenna

This paper focuses on the development of a wearable radio frequency identification (RFID) antenna to be embedded on shirt collars or cuffs. Wearable RFID tags tend to be conformal, and are required to reasonably meet design specifications even when under deformation. A simple circular dipole structure was selected as the base design for the antenna. Operating in the ultra-high frequency band at 866 MHz and over an operating range of around 5 m, the antenna is versatile enough to be used for a number of applications such as the tagging of patients in a hospital or for workers on dangerous construction sites. The designs presented account for the complex input impedance generally observed in RFID systems and the final design employs an intricate spiral structure to accommodate longer wavelengths. This resulted in a compact portable antenna able to meet device specifications.