Continuous-Wave Operation of a 460-GHz Second Harmonic Gyrotron Oscillator

We report the regulated continuous-wave (CW) operation of a second harmonic gyrotron oscillator at output power levels of over 8 W (12.4 kV and 135 mA beam voltage and current) in the TE(0,6,1) mode near 460 GHz. The gyrotron also operates in the second harmonic TE(2,6,1) mode at 456 GHz and in the TE(2,3,1) fundamental mode at 233 GHz. CW operation was demonstrated for a one-hour period in the TE(0,6,1) mode with better than 1% power stability, where the power was regulated using feedback control. Nonlinear simulations of the gyrotron operation agree with the experimentally measured output power and radio-frequency (RF) efficiency when cavity ohmic losses are included in the analysis. The output radiation pattern was measured using a pyroelectric camera and is highly Gaussian, with an ellipticity of 4%. The 460-GHz gyrotron will serve as a millimeter-wave source for sensitivity-enhanced nuclear magnetic resonance (dynamic nuclear polarization) experiments at a magnetic field of 16.4 T.     

Geometric optimization andD P -completeness

In this paper we show a number of natural geometric optimization problems in the plane to becomplete for a classD ^P . The classD ^p contains both NP and Co-NP and is contained in ₂ ^P =P ^NP. Completeness inD ^p is exhibited under many-one and positive reductions. Further anOptP(O(logn)) result is also obtained for some of these optimization problems.Work on this paper by the first author was supported in part by NSF Grant No. MIP 85-21356 and ARO Contract No. DAAG29-85-C-0018 under Cornell/MSI. Work by the second author was supported in part by NSF Grant No. DCR 86-06366 at Ohio State and ONR Grant No. N00014-k-0045 at Harvard.On leave from Ohio State University.     

The structure of malabricol

A single crystal X-ray analysis has confirmed the constitution and established the stereochemistry of the triterpene, malabaricol.     

Topochemical models for anti-HIV activity of 1-alkoxy-5-alkyl-6-(arylthio)uracils

Relationship between topochemical indices and anti-HIV-1 (HTLV-III) inhibitory activity of 1-alkoxy-5-alkyl-6-(arylthio)uracils has been studied. Superadjacency, an adjacency-cum-distance-based, topochemical index and Wiener’s, a distance-based, topochemical index were calculated for a set of 36 1-alkoxy-5-alkyl-6-(arylthio)uracils. Resulting data were analyzed and suitable models were developed after identification of the active ranges. Subsequently, a biological activity was assigned to each of the compounds using these models and compared with the reported anti-HIV-1 activity. High accuracy of prediction was observed using these models. Statistical analysis revealed significance of the proposed models as well as a lack of correlation between the topochemical indices employed for the chosen data set.     

The stereochemistry of guggulsterol-1

The steroechemistry of guggulsterol-1, a component of the exudate of $\text{Commiphora}$$\text{mukul}$, is shown to be 20(R), 22(R)($\text{3}$).     

A sensitive colorimetric determination of 2,2′-dihydroxybiphenyl

Summary A colorimetric method for the determination of 2,2-dihydroxy-biphenyl in rat urine is described. The ether extract is subjected to thin-layer chromatography on silica gel-G plates in the solvent system benzene-methanol (8020) and spots corresponding to 2,2-dihydroxybiphenyl and its glucuronide derivative are eluted with ethanol. The glucuronide is hydrolysed with HCl and the 2,2-di-hydroxybiphenyl content is determined after colour development with sodium cobaltinitrite, the absorbance being read at 410 nm. The method is sensitive and reproducible. It obeys the Lambert-Beer law in the concentration range 0.7–8.9g/ml.

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Eine empfindliche kolorimetrische Methode zur Bestimmung von 2,2 -Dihydroxybiphenyl

Zusammenfassung Eine kolorimetrische Methode zur Bestimmung von 2,2-Dihydroxy-biphenyl in Rattenharn wurde beschrieben. Der ätherische Extrakt wird auf Silikagel-G-Platten dünnschicht-chromatographisch mit dem Lösungsmittelsystem Benzol-Methanol (8020) getrennt. Die dem genannten Stoff und seinem Glucuronid entsprechenden Flecken werden mit äthanol eluiert. Das Glucuronid wird mit Salzsäure hydrolysiert und der Gehalt an 2,2-Di-hydroxybiphenyl nach Ausführung der Farbreaktion mit Natriumkobalti-nitrit und Messung bei 410 nm bestimmt. Das Verfahren ist empfindlich und gut reproduzierbar. Es entspricht dem Lambert-Beerschen Gesetz zwischen 0,7 und 8,9g/ml.

     

Insertion reactions of organochlorosilanes with cyclic ethers

Phenyl glycidyl ether and allyl glycidyl ether (3-phenoxy- and 3-allyloxy-1,2-epoxypropane) cause fission of the silicon---chlorine bonds in a number of alkylchlorosilanes to form chloro-substituted alkoxysilanes. Relative reactivities of cyclic ethers with chlorosilanes have been discussed. Structures of the adducts are suggested on the basis of their IR and proton magnetic resonance spectra.