New FIR laser lines and frequency measurements for optically pumped CD3OH

Twenty new cw FIR laser lines in CD₃OH, optically pumped by a CO₂ laser, are reported. The frequencies of 39 of the stronger laser lines were measured relative to stabilized CO₂ lasers with a fractional uncertainty, as determined by the reproducibility of the FIR frequency itself, of 2 parts in 10⁷.Contribution of the U.S. Government, not subject to copyright.     

Tangential chow forms — rank 1 hypersurfaces in a Grassmannian

Let X ⁿ P ^N be an n-dimensional projective variety, and N–n–1kN–1. The closure in the Grassmannian G(k+1, N+1) of the set of k-planes meeting the smooth locus of X nontransversally is a tangential Chow form (TCF) of X.TCF's are generally hypersurfaces. We show that a hypersurface is a TCF iff its conormal form has rank 1, and that a TCF is a hypersurface iff some quadric in the second fundamental form of X has rank n+k+1–N.     

Simulation of the electronic and vibrational structure of hydrogenated amorphous silicon using cluster models

A set of simple models of hydrogenated amorphous silicon (a-Si:H) consisting of hypothetical silane molecules with diamond or similar lattices was studied by the semiempirical AM1 method. Densities of states and infrared spectra were calculated for the silane molecules and similar molecules with dangling bonds disorder, and with boron or phosphorus substitution to simulate doping. Some examples are presented, and a comparison is made with experimental properties of a-Si:H. It is proposed to use these models in a study of the Staebler–Wronski photodegradation of a-Si:H and other aspects of amorphous silicon technology. © John Wiley & Sons, Inc.     

Collisional activation spectra at improved resolving power obtained by the use of a collision chamber and a linked scan of the electric and magnetic sector field strengths

A method for obtaining collisional activation spectra at much higher resolving power than before by use of a collision chamber and a B/E linked scan, is described.     

Titrimetric study of the reaction of chloramine-T with ammonia

A titrimetric study of the reaction between chloramine-T (CAT) and ammonia is described. The effects of the presence of bromide, the ratio of CAT to ammonia concentrations, the time for reaction and the pH of the reaction media are all significant in the quantitativeness of the reaction that occurs.     

Solution kinetics of the degradation of the chemiluminescent reagent bis(2,4-dinitrophenyl) oxalate in water/acetonitrile

Simultaenous ultraviolet absorbance measurements at 240 and 260 nm are used to quantify DNPO and its principle degradation product 2,4-dinitrophenol. The stability of DNPO was determined in various water acetonitrile mixtures (23±0.5°C). The decomposition follows (pseudo)- first-order kinetics in each system, and is third order in water concentration. An Arrhenius plot was used to obtain estimates for the activation energy, activation enthalphy, and activation entropy.     

The use of ion-molecule reactions in the mass spectrometric location of double bonds

A method for the location of the positions of carbon-carbon double bonds using high pressure mass spectrometry is proposed. A known olefinic molecular ion reacts with a second, unknown olefin to form a four-centre complex, which fragments with retention of the structural identity of methylene and substituted methylene groups to eliminate a new olefin molecule and to form an unsaturated ion from which the position of the double bond in the unknown olefin can be inferred. Vinyl methyl ether proved to be a convenient reagent gas and its molecular ion undergoes the required reaction with several classes of olefinic compound. Conjugated dienes and unsaturated compounds containing electronegative groups do not undergo this reaction.     

Automation of pesticide residue analysis

Summary The routine analysis of pesticide residue levels in biological tissue by gas-liquid chromatography is greatly facilitated by the use of computers to reduce computation time. Modern systems can be readily adapted to small computers. The nature of gas chromatographic signals permits the insertion of digitizers between the gas chromatograph and the computer. The resulting system permits completely automatic retrieval of data; thus time is saved and operating efficiency of the analytical laboratory is increased.

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Die Automatisierung der Analyse von Pestizid-Rückständen

Zusammenfassung Die Routineanalyse des Gehalts an Pestizid-Rückständen in biologischem Gewebe durch Gas-Flüssig-Chromatographie wird durch den Einsatz von Computern zur Einsparung von Rechenzeit wesentlich erleichtert. Modeme Systeme können leicht an kleine Computer angepaßt werden. Die Art der gas-chromatographischen Signale gestattet die Einfügung von Digitalisierungs-Gliedern zwischen Gas-Chromatographen und Computer. Mit dem entstandenen System läßt sich die Datensuche vollständig automatisieren; auf diese Weise wird Zeit gespart, und die Leistungsfähigkeit des analytischen Labors wird erhöht.

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Automatisation de l'analyse des résidus de pesticides

Sommaire La determination de routine des teneurs en résidus de pesticides dans des tissues biologiques par chromatographie gaz-liquide est notablement facilitée par l'emploi d'ordinateurs; ceci réduit la durée du calcul. Des systèmes modernes sont faciles à adapter à de petits ordinateurs. La nature des signaux émis en chromatographie en phase gazeuse permet l'insertion de membres de digitalisation entre le chromatographe en phase gazeuse et l'ordinateur. Le système ainsi obtenu permet la recherche tout à fait automatique des données; ainsi on gagne du temps, et l'efficacité du laboratoire analytique est augmentée.