Scrollar invariants and resolutions of certaind-gonal curves

In this note we compute the scrollar invariants of certaind-gonal curves (e.g. Castelnuovo curves and bielliptic curves) by using appropriate plane models. Ford=4 andg(C)≥10, we show that those invariants discriminate bielliptic curves among tetragonal ones.

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Sunto In questa nota si determinano gli invarianti scrollari per alcuni tipi di curved-gonaliC (ad esempio curve di Castelnuovo, curve biellittiche) tramite appropriati modelli piani. Perd=4 eg(C)≥10, si mostra che tali invarianti individuano le curve biellittiche fra le tetragonali.

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An erratum to this article is available at .     

Scrollar invariants and resolutions of certaind-gonal curves

The online version of the original article can be found at     

Spectrofluorimetric determination of stoichiometry and association constants of the complexes of harmane and harmine with beta-cyclodextrin and chemically modified beta-cyclodextrins

The association characteristics of the inclusion complexes of the beta-carboline alkaloids harmane and harmine with beta-cyclodextrin (beta-CD) and chemically modified beta-cyclodextrins such as hydroxypropyl-beta-cyclodextrin (HPbeta-CD), 2,3-di-O-methyl-beta-cyclodextrin (DMbeta-CD) and 2,3,6-tri-O-methyl-beta-cyclodextrin (TMbeta-CD) are described. The association constants vary from 112 for harmine/DMbeta-CD to 418 for harmane/HPbeta-CD. The magnitude of the interactions between the host and the guest molecules depends on the chemical and geometrical characteristics of the guest molecules and therefore the association constants vary for the different cyclodextrin complexes. The steric hindrance is higher in the case of harmine due to the presence of methoxy group on the beta-carboline ring. The association obtained for the harmane complexes is stronger than the one observed for harmine complexes except in the case of harmine/TMbeta-CD. Important differences in the association constants were observed depending on the experimental variable used in the calculations (absolute value of fluorescence intensity or the ratio between the fluorescence intensities corresponding to the neutral and cationic forms). When fluorescence intensity values were considered, the association constants were higher than when the ratio of the emission intensity for the cationic and neutral species was used. These differences are a consequence of the co-existence of acid-base equilibria in the ground and in excited states together with the complexation equilibria. The existence of a proton transfer reaction in the excited states of harmane or harmine implies the need for the experimental dialysis procedure for separation of the complexes from free harmane or harmine. Such methodology allows quantitative results for stoichiometry determinations to be obtained, which show the existence of both 1:1 and 1:2 beta-carboline alkaloid:CD complexes with different solubility properties.     

The effect ofpH on thermal stability of globular proteins

In this study we try to re-analyze thepH dependence of thermal stability of small globular proteins. From the thermodynamic point of view a long series of calorimetric and spectroscopic investigations has shown that the decreased stability in very acidic conditions can be ascribed to entropic effects. The same conclusion is reached, from a microscopic point of view, by assuming that a binding of protons on equal and noninteracting sites takes place as a consequence of unfolding process. By linking the conformational unfolding equilibrium to the proton binding equilibrium, a model is developed that is able to describe the dependence on thepH of the thermal denaturation processes of small globular protiens. The application of the model to hen lysozyme and T4 lysozyme correctly accounts for the experimental results.     

Forced volume magnetostriction in (rare earth) ni2 cubic intermetallic compounds

The forced volume magnetostriction has been measured for the RENi₂ intermetallic compounds (RE = Ce, Pr, Sm, Gd, Tb and Dy). In GdNi₂ both spontaneous and forced magnetostriction originate from pure exchange and it is necessary to invoke short-range spin correlations to explain the peculiar temperature dependence. In PrNi₂, SmNi₂, TbNi₂ and DyNi₂ the magnetostriction is contributed to by strains from both crystalline electric field and exchange, the temperature dependence in TbNi₂ and SmNi₂ being also peculiar. Magnetoelastic coupling parameters for both types of contribution have been determined. At low temperatures a cooperative Jahn-Teller distortion has been identified in PrNi₂ by measuring thermal expansion. The volume magnetostriction of CeNi₂ appears to be anomalous, probably as a consequence of Ce being in an intermediate valence state.     

Synthesis of 2,8-disubstituted 1,2,4-triazolo[5,1-i]purines

This paper describes the preparation of 2-aryl-8-fluorobenzyl-1,2,4-triazolo[5,1-i]purines 2 , starting from 2-aryl-7,8-diamino-1,2,4-triazolo[1,5-c]pyrimidines 9 . Our synthetic procedure represents the first example of a feasible approach for the synthesis of 2,8-disubstituted triazolo[5,1-i]purines. New syntheses of 5-amino-3-arylpyrimido[5,4-e]1,2,4-triazines 12 and 8-fluorobenzyl-6-hydrazinopurines 15 are also reported.     

Second-order expression of born probabilities by partitioning and laplace transform methods

The formalism and first- and second-order approximations for a perturbation-theoretical treatment of the time-dependent solutions of the Schrödinger equation are discussed in the context of possible applications to hydrogen-bonded systems. Equations are proposed that can help to model the essential features of such systems.     

Search for narrow resonances in the mass region 1.45–1.92 GeV,in e+e− annihilation into hadrons

We have searched for possible narrow resonances produced in the reaction e⁺e^? → hadrons, at Adone, in the mass interval. 1.45–1.92 GeV. Within the present statistics, no evidence has been found. We obtain an upper limit on the energy integrated resonant cross section of about 6% of the corresponding J/ψ(3.1) value.