Gamma irradiation of protein-based textiles for historical collections decontamination

In order to investigate the effect of gamma rays on cultural heritage materials, samples of silk and wool fabrics were subjected to accelerated ageing testing and then irradiated with different gamma-ray doses: 10 and 25 kGy. In the data analysis, combining thermal analysis (TG and DTG), infrared spectroscopy (FTIR-ATR) and mechanical tests allowed us to explore the changes in physical and chemical features for silk and wool, in relationship to the radiation doses. This analytical protocol offers a way to examine the behaviour of the textiles made of wool and silk within museum collections and their response to gamma-rays irradiation treatment. An exposure to a dose of 10 kGy did not cause significant changes in the tested properties; however, higher doses initiated irreversible loss in the physical and chemical stability of protein-based fabrics. Increasing the irradiation dose above 10 kGy has drastic effects in the loss of elasticity and the mechanical resistance of the tested yarns.     

Chitosan Based Diamond Paste Stochastic Microsensors Modified with Gold Nanoparticles Detect Hepatitis C Virus Core Antigen

Three types of chitosan (chitosan I (n=371–744), chitosan II (n=682–930), and chitosan III (n=868–1365)) as well as gold nanoparticles (10 nm diameter) were used to modify diamond paste for the design of new stochastic microsensors. Hepatitis C virus core antigen was used as model analyte to prove the stochastic behavior of the proposed microsensors. The microsensors cover a linear range of concentration between 40 fg/mL and 4 ng/mL. The highest sensitivity (1.38×10⁵ s^?1/mg/mL) and the lower limit of determination (40 fg/mL) were obtained for chitosan III based microsensor. The hepatitis C virus core antigen was assayed from whole blood samples with recoveries higher than 98.00 %.     

Irreducibility Results for Compositions of Polynomials with Integer Coefficients

We obtain explicit upper bounds for the number of irreducible factors for a class of polynomials of the form f ○ g, where f,g are polynomials with integer coefficients, in terms of the prime factorization of the leading coefficients of f and g, the degrees of f and g, and the size of coefficients of f. In particular, some irreducibility results are given for this class of compositions of polynomials.     

Polydimethylsiloxane/silica/titania composites prepared by solvent-free sol–gel technique

Composites based on polydimethylsiloxane incorporating silica and titania were prepared by mixing polydimethylsiloxane with proper oxides precursors, tetraethyl-orthosilicate and tetrabutyl-orthotitanate. In the presence of environmental humidity and in acid catalysis, hydrolysis/condensation processes take place with formation of oxides and concomitantly polymer crosslinking. Partial replacement of SiO₂ in a polydimethylsiloxane/silica composite with titania (both generated in situ by sol–gel process) affects surface hydrophilicity (evaluated by dynamic contact angle), water vapor sorption ability (determined by dynamic vapor sorption) and thermal stability. The dielectric properties are also controlled by composition.     

Asymmetric Michael Additions of α-Nitrocyclohexanone to Aryl Nitroalkenes Catalyzed by Natural Amino Acid-Derived Bifunctional Thioureas

A series of new thiourea catalysts prepared from natural amino acids have been applied in organocatalytic asymmetric Michael additions of α-nitrocyclohexanone to nitroalkenes. The resulting addition products are formed with excellent enantioselectivities (up to an er of 98:2) in good yields (up to 90%).     

Catalytic asymmetric addition of aldehydes to oxocarbenium ions: a dual catalytic system for the synthesis of chromenes

A synergistic catalytic system for the first asymmetric addition of aldehydes to in situ generated prochiral oxocarbenium ions has been developed. The dual catalytic protocol allows the simultaneous activation of both electrophile and nucleophile and provides access to a variety of valuable chiral 2H-chromenes with excellent enantioselectivities.     

Determination of phase transitions in binary systems of mesogenic compounds by optical absorption spectroscopy

The use is described of absorption spectroscopy for determining phase transitions in the mesogenic compound cholesteryl myristate (CM) and in binary mixtures of terephthalbis-butyl-aniline (TBBA) and cholesteryl myristate. The temperature dependence of the optical densities in the visible region at phase transitions is reported. The transition temperatures obtained with this method are in good agreement with the results obtained with other methods.     

Evidence for an isomer in 76 Ni

In the experiment performed at the LISE2000 spectrometer at GANIL neutron-rich nickel isotopes were studied by microsecond isomer spectroscopy. Evidence for an isomer in ⁷⁶Ni is found, consistently with the shell model prediction of an 8 ⁺ state of structure.Received: 24 October 2002, Published online: 17 February 2004PACS: 23.20.Lv transitions and level energies - 27.50. + e