1,2-fused pyrimidines. V. Synthesis of 1-alkyl or phenyl-2H-dipyrido-[1,2-a:2′,3′-d]pyrimidine-2,5(1H)-diones

The reaction of 2-[(N-acyl, N-alkyl or phenyl)amino]-4H-pyrido[1,2-a]pyrimidin-4-ones 8a-g with the N,N-dimethylformamide/phosphorus oxychloride Vilsmeier reagent 1 (95°, 90 minutes) afforded 1-alkyl or phenyl-2H-dipyrido[1,2-a:2′,3′-d]pyrimidine-2,5(1H)^?diones, 3-alkyl substituted or not, 10a-g . The starting compounds 8 were prepared by treating 2-amino-4H-pyrido[1,2-a]pyrimidin-4-ones N-alkyl substituted 7a,b or N-phenyl substituted 4 with excess anhydrides (130°, 7 hours) when the 2-(alkylamino) derivatives 7 were used in the reaction, compounds 8 were obtained along with very small amounts of 3-acyl-2-(alkylamino)-4H-pyrido[1,2-a]pyrimidin-4-ones 9 .     

IRRADIATION OF CIRCULAR DNA WITH 254 nm RADIATION OR SENSITIZATION IN THE PRESENCE OF Ag+ EVIDENCE FOR UNWINDING BY PHOTOPRODUCTS OTHER THAN PYRIMIDINE DIMERS

Abstract— Structural alterations of DNA irradiated with UV light were analyzed by the agarose gel technique. Relaxed, circular pAT 153 DNA molecules were sensitized by broad band radiation with a maximum at 313 nm in the presence of silver ions or irradiated with 254 nm light in buffer only. In both cases the electrophoretic mobility of DNA topoisomers was altered as a linear function of UV exposure. For DNA irradiated in the sensitized reaction the unwinding angle per site sensitive to Micrococcus luteus pyrimidine dimer endonuclease was found tobe–11.4°. This value is significantly smaller thanthe–14.3° already known for DNA topoisomers irradiated with 254 nm light. The irradiated DNAs were a very good substrate for the Escherichia coli photoreactivating enzyme (PRE). However, the photoenzymic removal of all sites sensitive to the endonuclease specific for pyrimidine dimers was not coupled to a full restoration of the original electrophoretic mobility. Thirty and 23% of the unwinding were still present in the photoreactivated topoisomers and the unwinding angles per pyrimidine dimer were then recalculatedas–10.1°and–8.7° for DNAs irradiated with 254 nm and sensitized, respectively. The limited difference between these two values could result from the different base composition of the pyrimidine dimers generated in the conditions of irradiation used. These results show that the tertiary structure of DNA is measureably altered by UV photodamages other than pyrimidine dimers.     

Un teorema di unicità per una equazione iperbolica,non lineare

We prove the uniqueness of weak solutions of initial boundary value problems Each functiona _i is required to be sufficiently smooth and must satisfy the following conditions: \(e) \sum\limits_1^n {ij} \partial _{\eta _j \eta _h }^2 a_i (x, \ldots , \eta 1, \ldots , \eta _n )\xi _i \xi _j \leqslant 0, h = 1, \ldots , n,\) for some positive constantsK ₀, α, some non negative constantsK _i , some positive functionsH(t)∈L ¹(0,T) and for all ξ≡(ξ _i ), η≡(η _i )∈R ⁿ      

Positive\partial \bar \partial - closed currents and non-Kähler geometrycurrents and non-Kähler geometry

In this paper some new results on positive \(\partial \bar \partial - closed\) currents are applied to modifications \(f:\bar M \to M\) . The main result in this topic is that every smooth proper modification of a compact Kähler manifoldM is balanced. Moreover, under suitable hypotheses on the map, the Kähler degrees of \(\bar M\) corresponds to homological properties of the exceptional set of the modification. More examples ofp-Kähler manifolds are discussed in the last section of the paper.     

X-ray spectroscopic characterization of Cu2+-phenanthroline complexes intercalated in α-zirconium phosphate

X-ray photoelectron spectroscopy provides evidence that when [Cu(phen)₂]²⁺(phen = 1,10-phenanthroline) is diffused between the layers of -zirconium phosphate, the complex species does not remain intact after intercalation, but some Cu-N bonds are broken, replaced with Cu-O bonds and the released nitrogen atoms can now interact with the PO₃-OH groups of the host. XPS also provides evidence for coordination of the Cu²⁺ ions when they are diffused by ion exchange in the phenanthroline--zirconium phosphate intercalation compound. Although Cu²⁺ and phen are in a 1 : 1 molar ratio in the interlayer region of the host, so that a 1 : 1 coordination could be expected between the two species, the characteristic peaks of the uncoordinated phenanthroline, even though at a low intensity, are still present. The differences between the two Cu(II)-intercalation compounds are discussed.     

The Chemistry of Coumarin Derivatives. Part 5. Unusual course of the reaction of 4-hydroxycoumarin and aliphatic aldehydes

The reaction of 4-hydroxycoumarin and certain aliphatic aldehydes affords 1:1 or complex 2:2 adducts besides (or in place) of the expected 2:1 bis(coumarin) adducts. Reaction with heptanal, cyclohexanecarbaldehyde, and pivalaldehyde are reported as representative. The structure of the reaction products was established by spectroscopical techniques, including X-ray analysis, and their formation was mechanistically rationalized. Some of the 1:1 adducts are synthetically useful for the preparation of 3-alkyl-4-hydroxycoumarins.     

Determination of chlorite in drinking water by differential pulse voltammetry on graphite

The chlorite ion is an unavoidable by-product of the disinfection of drinking water by means of chlorine dioxide. The maximum concentration values of chlorite accepted in many countries regulations range from 0.2 to 1.0 mg L^–1. A simple, inexpensive and quickly set up voltammetric procedure for the on-site determination of chlorite in drinking water networks is described. This procedure is suitable for the whole range of applications in drinking water plants. A useful cell for on-field analysis has been developed. Surface morphology and behaviour of carbon-based working electrodes have been investigated by voltammetry and atomic force microscopy (AFM). Actual samples of different types of water networks have been analysed for chlorite concentration.     

Alignment of molecules in pulsed resonant laser fields

We investigate by numerical simulations the dynamics of alignment of linear molecules in resonant pulsed laser fields and its dependence on pulse length, field strength, and molecular parameters. We propose an analytical short-time approximation for the time-dependent wave packets. We provide a theoretical basis for the occurrence of saturation in the rotational pumping. We present a formula to predict the time at which the maximum alignment occurs. We discuss the magnitude of the laser-induced alignment and we relate it to a theoretical upper limit.     

Liquid—liquid extraction and determination of uranium(IV) with 2,6-diacetylpyridine bis(benzoylhydrazone)

2,6-Diacetylpyridine bis(benzoylhydrazone) (H₂DPBH) is proposed as a ligand for the extraction of uranium(VI). Complete extraction from aqueous solutions into dichloromethane is achieved with a ligand/metal mole ratio of < for 10^?5?10^?4 M uranyl ion. Potentiometric measurements indicate that the extracted species is UO₂ (DPBH). Uranium can be determined in the extract by spectrophotometric measurements at 420 nm and by differentail pulse polarography (E_p = ?0.67 V) with tetraethylammonium bromide as supporting electrolyte. For both methods, the detection limit is about 2 × 10^?6 M in the extract.     

First order linear partial differential equations with discontinuous coefficients

Summary Si dà un teorema di esistenza e di unicità di soluzione generalizzata per il problema di Cauchy relativo all'equazione . Le ipotesi fatte sui coefficienti a_i(t, x) permettono discontinuità di tipo molto generale, purchè sia soddisfatta una certa «condizione di trasversalità» tra le caratteristiche dell'equazione e le discontinuità del campo di vettori che le definisce.