Microscopic calculations of signals of double beta decay in a Ge detector and first application to the Heidelberg–Moscow experiment

The identification of signals of neutrinoless double beta decay is a question of extreme interest. Starting from the Monte Carlo calculated time history and spatial energy distribution of neutrinoless double beta events, for the first time the expected pulse shapes to be observed in a big ⁷⁶Ge detector have been calculated ‘microscopically  ’, by using the Poisson Superfish code for determination of the field distribution in the detector. It is shown, that for the majority of 0νββ$0\nu \beta \beta$ events it is not possible to differentiate between the contributions of different particle physics parameters entering into the 0νββ$0\nu \beta \beta$ decay process—in the mass mechanism the effective neutrino mass and the right-handed weak current parameters 〈λ〉$〈\lambda 〉$, 〈η〉$〈\eta 〉$. It is shown, that on the other hand it is possible in a ⁷⁶Ge double beta decay experiment to reject a background of larger sizes (high multiplicity) gamma events by selecting low size (low multiplicity) events. First application of the theoretical ββ   pulses to events from the line observed at Q_ββ$Q_{\beta \beta }$ [H.V. Klapdor-Kleingrothaus, I.V. Krivosheina, A. Dietz, et al., Phys. Lett. B 586 (2004) 198; H.V. Klapdor-Kleingrothaus, A. Dietz, I.V. Krivosheina, et al., Nucl. Instrum. Methods A 522 (2004) 371] shows very good agreement. It is shown further, and confirmed by measurements with a collimated source, that a rather good radial position determination of ββ events in the detector is possible. By the same type of calculation it is shown that use of the pulse shapes of the 1592 keV double escape line of the 2614 keV γ-transition from ²²⁸Th for calibrating a neuronal net for search of events of neutrinoless double beta decay can be helpful.     

Critical concentrations of polymers in solutions according to measurements of the viscosity and specific surface area of aerogels resulting after sublimation of the solvent

Summary Critical concentrations of polystyrene and cyclolinear polyphenylsiloxane solutions corresponding to rising of structural networks have been determined by viscosity measurements and by measurements of specific surface of aerogels obtained by solvent sublimation. Theoretical and experimental values of critical concentrations coincide. Conditions for preparation of aerogels with developed surface by sublimation drying have been determined. Dependence of aerogel specific surface on polymer concentration in solutions shows distinct maximum at critical concentration found by viscosimetric method.

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Zusammenfassung Mit Viskositätsmessungen und mittels Bestimmung der spezifischen Oberfläche an Aerogelen, erhalten durch Sublimation des Lösungsmittels aus Lösungen Polymerer, wurde die Existenz einer kritischen Konzentration für Polystyrol und zyklisches lineares Polyphenylsiloxan festgestellt, hervorgerufen durch Aufbau struktureller Netzwerke.Theoretisch vorausgesagte und experimentell gefundene Werte für die kritischen Konzentrationen stimmen überein. Bedingungen für die Präparation von definierten Aerogelen mit durch Sublimationstrocknung erzielter Oberfläche wurden festgelegt. Die Abhängigkeit der spezifischen Oberflächen von Aerogel von der Polymerkonzentration in Lösung zeigt ein ausgeprägtes Maximum bei der kritischen Konzentration, die man aus den Viskositätsmessungen findet.

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With 19 figures and 3 tables     

Protonation of 1, 5-naphthyridine derivatives

The direction of protonation (1-N or 5-N) or 2-, 2,3-, and 2,6-substituted derivatives of 1,5-naphthyridine was determined on the basis of the basicity constants.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 965–968, July, 1977.     

1,5-naphthyridines and their N-oxides

The N-oxidation reactions of 2-hydroxy- and 2-amino-1,5-naphthyridines were investigated. 2-Hydroxy-1,5-naphthyridine 5-oxide and 2-hydroxy-, 2-amino-, and 2-acetamido-1,5-naphthyridine 1,5-dioxides were obtained. The structures of the compounds obtained were proved by means of IR and PMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1237–1240, September, 1972.     

Solution properties of poly(methacrylamide)

Poly(methacrylamide) samples obtained by radical polymerization were fractionated by isothermal precipitation (formamide-methanol). Molecular weights were determined by light scattering and the Archibald approach-to-equilibrium method (in 0.4 M aqueous magnesium perchlorate), and the [η] M correlation was constructed. The characteristic ratio (C₁ = 6.1). Its temperature coefficient (dln C₁ dT ? 0) and the interaction parameters of the polymer in aqueous solutions of urea (2–8 M) and magnesium perchlorate (0.4–1.2 M) at 10–50°C were determined using analysis of the viscometric data ([η], dln [η]/dT). The data thus obtained are used to discuss the behaviour of the polymer in water.     

Structure and flow behavior of crosslinked ethyl acrylate–methacrylic acid copolymer dispersion particles

 Changes in viscosity, pH and static light scattering behavior on alkali addition of model dispersions of statistical copolymers of ethyl acrylate with 15 and 50 wt% of methacrylic acid prepared by semicontinuous emuslion copolymerization and crosslinked with various amount of N,N′-methylenebisacrylamide were investigated. It was found that about 1% of crosslinking agent was sufficient to prevent unpredictable disintegration of dispersion particles and gauranteed reproducible flow behavior of alkalinized dispersions. The viscosity of alkalinized dispersions of crosslinked particles at low concentration is controlled by the effective hydrodynamic volume of swelled particles which decreases with the crosslinking degree of copolymer. On the other hand, at higher particle concentration close to critical concentration at which the space is filled up by swelled particles the influence of particle interaction prevails and due to lower deformability of crosslinked particles viscosity increases with a crosslinking degree. In comparison with similar dispersions prepared without a crosslinking agent these results indicated much uniform structure of dispersion particles and suppression of influence of random crosslinking due to chain transfer reactions. The study shows that dispersions of crosslinked copolymers of this type could be considered as thickners of latex binders with stable and reproducible thickening properties. Received: 23 February 1998 Accepted: 11 June 1998     

Peculiarities of flow and viscoelastic properties of solutions of polymers with a narrow molecular-weight distribution

The concepts developed for flexible-chain linear high-molecular-weight polymers of narrow molecular weight distribution, according to which transition from the fluid to the highelastic state at increased shear rates is accompanied by loss of fluidity, have been extended to concentrated solutions of these polymers. The change of principal viscoelastic characteristics, in a concentration range which can be associated with the effect of formation of an entanglement network in polymer solution, is considered. On the basis of the parameters characterizing the viscous properties of dilute polymer solutions (the intrinsic viscosity and the Martin constant), a generalized representation of the dependence of the initial viscosity of polybutadiene solutions on concentration over the entire range up to bulk polymer has been derived.     

Synthesis and properties of 4-substituted 1,5-naphthyridines and their N-oxides

4-Substituted 1,5-naphthyridines and their N-oxides were synthesized, and their structures and properties were studied. The IR and UV spectra of 4-hydroxy- and 4-methoxy-1,5-naphthyridines and their 1-oxides and 1-ethyl-4-oxo-1,4-dihydro-1,5-naphthyridine were examined. It is shown that 4-hydroxy-1,5-naphthyridine and its 1-oxide exist in the crystalline state in the lactam form. A quantitative estimate of the position of the tautomeric equilibrium of 4-hydroxy-1,5-naphthyridine as a function of the polarity of the solvent is given, and the tautomeric equilibrium constants and the percentages of the lactim form are calculated. The basicity constants of 4-chloro-, 4-methoxy-, 4-hydrazino-, 4-methylthio-, 4-acetamido-, and 4-amino-1,5-naphthyridines were measured. A comparison of the calculated and experimental pK_a data provides evidence in favor of the fact that the compounds are protonated at the N₁ atom. A correlation of the basicity constants with the substituent constants is examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 792–799, June, 1981.     

Critical concentrations of polymers in solutions according to measurements of the viscosity and specific surface area of aerogels resulting after sublimation of the solvent

Conclusion Measurement of the viscosities of polystyrene and cyclolinear polyphenylsiloxane depending on their concentrations has revealed critical concentrations of these polymers to exist corresponding to the formation of a fluctuating continuous supermolecular network in the solutions. It has been shown on the example of polystyrene solutions that changing from a good to a poor solvent has little effect on the value of the critical concentration. Calculation of the critical concentration with the use of the parameters employed in the free volume theory after the Pezzin method shows good agreement with the critical concentrations determined from the shape of the viscosity vs. concentration dependences of polystyrene solutions.A method is described for producing polymer aerogels by sublimation of the frozen solvent from polymer solutions. It is shown that to obtain aerogels with very high specific surface areas from crystallized solutions is necessary to fulfil at least two conditions: 1. to freeze them quickly; 2. to sublimate the solvent in vacuo at a sufficiently low temperature. Special attention is drawn to the fact that the effectivity of sublimation drying should be estimated by the specific surface area of the preparations obtained as a result of drying.Mesurement of the specific surface areas of aerogels obtained under appropriate conditions from polymer solutions of different concentrations shows that with a poor solvent the aerogels have specific surface areas one decimal order lower. Hence it is concluded that solutions of polymers in poor solvents should yield stronger and less permeable polymeric systems. In all the cases studied the dependence of the specific surface area of the aerogel on the concentration of the polymer in the solution has a distinct maximum which corresponds to the critical concentration determined viscometrically. This is evidence of the correspondence between the structure of the aerogels and the structure of the initial solutions, at least, at concentrations in the region of their critical and above-critical values. Sublimation of the solvent from frozen polymer solutions results in contraction of the samples, which is the most considerable at polymer concentrations below critical. This is also connected with the relatively low specific surface areas of aerogels obtained from solutions of low concentrations.