Changes in chemical composition and collagen structure of dentine tissue after erbium laser irradiation

Erbium laser radiation has a great affinity for the water molecule, which is present in quantity in biological hard tissues. The objective of this work is to identify chemical changes by infrared spectroscopy of irradiated dentine by an Er:YAG-2.94 microm laser. The irradiation was performed with fluences between 0.365 and 1.94 J/cm2. For the infrared analysis a Fourier transform infrared spectrometer was used. After the irradiation were observed: loss of water, alteration of the structure and composition of the collagen, and increase of the OH- radical. These alterations can be identified by a decrease in intensity of the water band between 2800-3800 cm(-1), OH- band at 3575 cm(-1) and bands ascribed to organic matrix between 2800-3400 cm(-1) and 1100-1400 cm(-1).     

Sorption-desorption behavior of bispyrazolato-copper(II) 1D coordination polymers

A new polycrystalline vapochromic polymorph of the one-dimensional copper bispyrazolate polymer reversibly and selectively absorbs a number of small molecules; the crystal structures of the anhydrous and fully hydrated species, determined by powder diffraction methods, are markedly different despite their simple, fast, and reversible interconversion.     

Barkas effect for antiproton stopping in H2

We report the stopping power of molecular hydrogen for antiprotons of kinetic energy above the maximum (approximately 100 keV) with the purpose of comparing with the proton one. Our result is consistent with a positive difference in antiproton-proton stopping powers above approximately 250 keV and with a maximum difference between the stopping powers of 21%+/-3% at around 600 keV.     

New relativistic effects in the dynamics of nonlinear hydrodynamical waves

In Newtonian and relativistic hydrodynamics the Riemann problem determines the evolution of a fluid which is initially characterized by two states having different rest-mass density, pressure, and velocity. When the fluid is allowed to relax, one of three possible wave patterns is produced, corresponding to the propagation in opposite directions of two nonlinear hydrodynamical waves. New effects emerge in a relativistic Riemann problem when velocities tangential to the initial discontinuity are present. A smooth transition from one wave pattern to another can be produced by varying the initial tangential velocities while maintaining the initial states unmodified. These special relativistic effects are produced by the Lorentz factors and do not have a Newtonian counterpart.     

Chromatographic and electrophoretic behaviour of primary aromatic amines on anion-exchange thin layers

The use of polystyrene-based anion exchangers with aqueous eluents for the separation of primary aromatic amines has been investigated, and extended with satisfactory results to microcrystalline cellulose, cellulose-based anion-exchangers and sodium CM-cellulose layers.Interesting separations of the amines have also been effected electrophoretically on AG 1-X4 layers.The use of water-organic solvent mixtures on polystyrene-based cation exchangers is discussed.     

Brominaed β-carbolines from the marine hydroid linnaeus

Three new brotminated β-carbolines (1–3) have been isolated from the lipophylic extract of the marine hydroid Linnaeus and their structures determined on the basis of spectral data including two dimensional proton-carbon shift correlation (direct and long range) NMR spectroscopy. The syntheses of compounds 1–3, starting from the appropriate brominated tryptophan derivatives, are also described.     

Apparent molar volumes of alkaline earth hexacyanocobaltates (III) in aqueous solution at 25°C

The apparent molar volumes of Mg, Ca, Sr, and Ba hexacyanocobaltates (III) have been determined from 1×10⁴ to 0.2M (mol-dm^–3), using both vibrating tube densimeter and dilatometric methods. The semiempirical Pitzer equation has been used to reproduce the experimental data. Positive deviations from the Debye-Hueckel limiting law (DHLL) have been observed at C<0.01M and are compared with the predictions of two other electrostatic approaches, the DHLL+B₂ approximation of the Mayer theory and the numerical integration of the exponential Poisson-Boltzmann equation. A least squares procedure has been used to obtain the best fit parameters, including the apparent molar volume at infinite dilution.     

Synthesis,Reactivity Studies,and X-ray Crystal Structure of (11R)-25-O-Deacetyl-11-deoxo-11-hydroxy-21,23-O-isopropylidenerifamycin S

The protected intermediate (11R)-25-O-deacetyl-11-deoxo-11-hydroxy-21,23-O-isopropylidenerifamycin S ( 7 ) has been synthesized starting from rifamicin S ( 2 ; Scheme 2), the former being a potential substrate for the preparation of new types of rifamicin-S derivatives modified at C(11) and/or C(25). The reactivity of 7 toward acylations has been studied under both base- and acid-catalyzed conditions. The compound either did not react or nr underwent unexpected reactions, and no acylation products could be isolated. The X-ray crystal structure of 7 reveals that both OH groups at C(11) and C(25) are hindered, and this is probably the reason, why other take place faster than acylation.