Synthesis of 2-substituted-5-rnethylthiazolo[ 3,2-b ] -1,2,4-lriazoles and acylatcd 3-amino-2-imino-4-methyl-2-thiazolines

3-Amino-2-imino-4-mcthyl-2-thiazoline, 1, underwent ring closure with ethyl formate, cyanogen bromide and carbon disulfide, giving moderate yields of 2-substituted-5-methylthiazolo[ 3,2-b ]-1,2,4-triazoles, II. Reaction of I-HCl with acid anhydrides (acetic, propionie, trifluoroacetic) resulted in the formation of the corresponding II compounds, whereas other anhydrides (benzoic, perfluoropropionic, perfluorobutyric) gave high yields of 3-aeylamido-2-acylimido-4-melhyl-2-thiazolines. With acid chlorides and I-HCl, in the presence of trielhylamine, mixtures of 2-acyl-irnino-3-aniino-4-methyl-2-thiazolines and 2-aeylimino-3-(diacylamido)-4-methyl-2-thiazolines are formed. Spectral characteristics are reported.     

Characteristics of the dropping mercury electrode below the limiting current: Part II. Drop time and scan rate effects

A mathematical model of the dropping mercury electrode that includes the effects of electrochemical kinetics, ohmic potential drop, and mass transfer is used to examine the influence of scan rate and drop time on the shape of the polarographic wave. The system behavior is described in terms of three characteristic dimensionless parameters. For certain parameter values, the half-wave potential predicted for a metal deposition reaction is dependent on the drop time and scan rate used to obtain the polarogram.     

The paper chromatographic separation of ammonium chloride,hydrazine, hydroxylamine,phenylhydrazine and phenylhydroxylamine

The paper chromatographie separation of ammonium chloride, hydrazine, hydroxylamme, phenylhydrazine and phenylhydroxylamine is accomplished using the solvent system; 50 parts by volume diethyl ether, 30 parts methyl alcohol, 15 parts water and 4 parts concentrated bydrochloric acid. A double-spot phenomenon is described which depends upon the distance of the starting line from the solvent level.     

Limit theorems for empirical processes

Summary The empirical measure P _n for iid sampling on a distribution P is formed by placing mass n ^–1 at each of the first n observations. Generalizations of the classical Glivenko-Cantelli theorem for empirical measures have been proved by Vapnik and ervonenkis using combinatorial methods. They found simple conditions on a class C to ensure that sup {|P _n (C) – P(C)|: C C} converges in probability to zero. They used a randomization device that reduced the problem to finding exponential bounds on the tails of a hypergeometric distribution. In this paper an alternative randomization is proposed. The role of the hypergeometric distribution is thereby taken over by the binomial distribution, for which the elementary Bernstein inequalities provide exponential boundson the tails. This leads to easier proofs of both the basic results of Vapnik-ervonenkis and the extensions due to Steele. A similar simplification is made in the proof of Dudley's central limit theorem forn ^1/2(P P _n –P)— a result that generalizes Donsker's functional central limit theorem for empirical distribution functions.This research was supported in part by the Air Force Office of Scientific Research, Contract No. F49620-79-C-0164     

A comparative study of standards for determinations of trace wear metals in jet engine oils

The feasibility of using acid-treated metal powder standards for the determination of trace wear metals in spent jet engine oils is evaluated. The addition of 2:3:3 (v/v/v) HF—HCl—HNO₃ mixture to used lubricating oils did not cause any statistically reliable differences from results obtained with organometallic standards. Two sets of six correlation samples, one set being acid-treated, were analyzed for Cu, Cr, Mg, Fe, Mo and V by flame atomic absorption and flame atomic fluorescence spectrometry against each set of standards.     

INDUCED REPAIR IN ESCHERICHIA COLI: INDUCTION BY ULTRAVIOLET LIGHT AT-79°C

Two of the phenomena associated with induced (S.O.S.) repair, namely induced inhibition of post radiation DNA degradation and induced radioresistance have been shown to be elicited by 245 nm radiation applied to E. coli cells in the frozen state at -79°C. The effect of radiation in this condition is considerably less photoreactivable than similar effects produced by exposure in the wet state. Since protein-DNA crosslinks are believed to be formed under these conditions, such consequences of UV radiation appear to be a potent inducer of induced repair.     

Counterion-dependent excitonic spectra of tetra(p-carboxyphenyl)porphyrin aggregates in acidic aqueous solution

Aggregates of the diacid form of tetra(p-carboxyphenyl)porphyrin (TCPP) are found to be stabilized in aqueous solution at low pH in the presence of poly(vinyl alcohol). At pH values in the range from about 1 to 4, a split Soret band is observed which is independent of counterion and tentatively assigned to a dimer species. As the pH is made lower than 1, the spectra evolve to reveal the presence of porphyrin aggregates. As in the case of the well-known aggregates of the related tetra(p-sulfonatophenyl)porphyrin (TSPP) diacid, the concentration of spectroscopically distinguishable aggregates increases with increasing ionic strength or decreasing pH. Unlike aggregates of TSPP, however, TCPP aggregates below pH 1 have visible absorption spectra which depend on the counterion, which is Cl(-) or NO(3)(-) in this study. In this work, we present visible absorption, light-scattering, and resonance Raman spectra of TCPP diacid in its monomer, dimer, and aggregated forms and attempt to understand the structural basis for counterion-dependent structure and excitonic coupling in the aggregates. Evidence is presented for intercalation of inorganic counterions between porphyrin molecules in the aggregate, an effect which to our knowledge has not been previously reported.     

Peroxycarbenium-mediated C-C bond formation: applications to the synthesis of hydroperoxides and peroxides

The Lewis acid-mediated reaction of alkene nucleophiles with peroxyacetals provides an effective route for the synthesis of homologated peroxides and hydroperoxides. In the presence of Lewis acids such as TiCl(4), SnCl(4), and trimethylsilyl triflate, peroxyacetals and peroxyketals undergo reaction with allyltrimethylsilane, silyl enol ethers, and silyl ketene acetals to afford homoallyl peroxides, 3-peroxyketones, and 3-peroxyalkanoates, respectively. Reactions of peroxyacetals are Lewis acid dependent; TiCl(4) promotes formation of ethers while SnCl(4) and trimethylsilyl triflate promote formation of peroxides. Lewis acid-promoted reactions of silylated hydroperoxyacetals furnish silylated hydroperoxides, which can be deprotected to homologated hydroperoxides. Hydroperoxyketals undergo Lewis acid-mediated allylation to furnish 1,2-dioxolanes via attack of hydroperoxide on the intermediate carbocation. Lewis acid-mediated cyclization of unsaturated peroxyacetals furnishes 1,2-dioxanes, 1,2-dioxepanes, and 1,2-dioxacanes through 6-endo/exo, 7-endo/endo, and 8-endo/endo pathways. The corresponding reactions involving 6-endo/endo and 5-endo/exo pathways were unsuccessful.     

General chi-square goodness-of-fit tests with data-dependent cells

Summary The goodness-of-fit of a parametric model for non-categorical data can be tested using the x ² statistic calculated after grouping the data into a finite number of disjoint cells. Work of Watson, ebyev, Moore and others shows that the classical limit distributions still hold even for certain methods of grouping that depend on the data themselves. These results are generalised to cover a much wider class of methods of grouping; the parameters can be estimated from either the grouped or the ungrouped data. The proofs use a Central Limit Theorem for Empirical Measures due to Dudley. The grouping cells are allowed to come from any Donsker class for the underlying sampling distribution.Dedicated to Leopold Schmetterer, on his sixtieth birthdayMost of the work for this paper was carried out with the support of a fellowship of the Alexander von Humboldt Foundation at the Ruhr-Universität Bochum