Influence of pH and Salt on the Photocrosslinking in Polyelectrolyte Thymine‐Containing Films

Photocrosslinking of thymine‐based water‐soluble polymer films was investigated at varying preparation conditions. Adding salt or decreasing the pH of the solution from which the films were cast resulted in the decreased efficiency of photoimmobilization, while increasing the pH was found to increase the photoimmobilization efficiency. A mechanistic rationale for the observed effects is proposed.     

Neutron activation analysis of Ca, Cl, Mg, Na, and P content in human bone affected by osteomyelitis or osteogenic sarcoma

The Ca, Cl, Mg, Na, and P content and Ca/P, Ca/Mg, Ca/Na, Cl/Ca, and Cl/Na ratios in samples of intact cortical bone, inflamed bone and osteogenic sarcoma tissue were investigated by neutron activation analysis with high resolution spectrometry of short-lived radionuclides. In osteogenic sarcoma tissue the mass fractions of Cl and Na are higher and the mass fraction of Ca is lower than that of both normal and inflamed bone tissues. It was shown that the differences between the Cl/Ca ratio can be used as an additional test for differential diagnosis between normal or inflamed bone and osteogenic sarcoma.     

Lanthanide borohydrido complexes for MMA polymerization: syndio‐ vs iso‐ stereocontrol

This paper presents an extensive study of the polymerization of MMA with borohydrido lanthanide complexes for the first time. Catalytic systems are made from a lanthanide derivative bearing zero one, or two bulky ligands: substituted cyclopentadienyl (Cp^*′ = C₅Me₄nPr, Cp⁴ⁱ = C₅HiPr₄, Cp^Ph3 = H₂C₅Ph₃‐1,2,4), and/or diketiminate ([(p‐tol)NN] = [(p‐CH₃C₆H₄)N(CH₃)C]₂CH), in the presence of variable quantities of alkylating agent. With BuLi in apolar medium, highly isotactic polymer (up to 95.6%) is formed. In THF, syndiotactic‐rich PMMA is obtained whatever the nature of the co‐catalyst (BuLi or MgⁿBu₂). The presence of an electron‐withdrawing ligand such as Cp^Ph3 allows high syndioregularity, up to 81.8% at 0 °C, together with the highest conversion. There is quite good concordance between calculated and experimental molecular data in THF. Divalent Cp^*′₂Sm^II(THF) and (Cp^Ph3)₂Sm^II(THF) are active as single‐component initiators; the former affords PMMA 88% syndiotactic at 0 °C. Copyright © 2005 John Wiley & Sons, Ltd.     

Comparison of carbon-silicon hyperconjugation at the 2- and 4-positions of the N-methylpyridinium cation

[structure: see text] N-Methyl-2-trialkylsilylmethylpyridinium cations 6a-c and 4-trialkylsilylmethylpyridinium cations 5a-c were prepared and investigated using (29)Si and (13)C NMR and single-crystal X-ray crystallography. Systematic differences in the (29)Si chemical shifts and (29)Si-(13)C one-bond coupling constants for these cations suggested that the Si-CH(2) bond interacts more strongly at the 2-position of the electron-deficient pyridinium ring than at the 4-position. This result is supported by the X-ray structures of the pyridinium cations 5b and 6b.     

Dynamic synthesis of a macrocycle containing a porphyrin and an electron donor

New macrocycles incorporating a porphyrin and a [small pi] electron-rich aromatic were prepared from a dynamic disulfide library. The outcome could be influenced by use of templates.     

Analysis of (6Li,d) and (d, 6Li) reactions in the nickel and tin regions

The (⁶Li, d) and (d, ⁶Li) L = 0 transitions in the mass regions $\text{A ? 60}\text{and}\text{A ? 116}$ are analyzed utilizing microscopic form factors. The cross sections follow the pattern given by the two-proton and two-neutron transfer cross sections.     

Su un procedimento per il calcolo degli autovalori di problemi al contorno per equazioni differenziali di ordine 2n

Sunto Si espone un metodo per la determinazione degli autovalori per difetto e se ne dà un'applicazione al calcolo delle frequenze di una piastra. A Mauro Picone nel suo 70^mo compleanno. Lavoro eseguito nell'Istituto Nazionale per le Appliczaioni del Calcolo.