Solubility of Solid Hexane and Cyclohexane in Liquid Argon at 87.3 K

The solubilities of solid hexane and cyclohexane in liquid argon at 87.3 K have been measured by the filtration method. The hexane and cyclohexane content in solution was determined using gas chromatography. The solubilities of the C₆ hydrocarbons in liquid argon at 87.3 K are (0.56 ± 0.11) × 10^-7 mole fraction for hexane and (1.04 ± 0.30) × 10^-7 mole fraction for cyclohexane. The Preston–Prausnitz method was used for calculation of the solubilities of solid hexane and cyclohexane in liquid argon in the temperature range 84–110 K. The values of the solvent–solute interaction constant l₁₂ were also calculated.     

Degradation of Engineering Materials – Implications to Regenerative Medicine

Summary: Materials in general, to some degree are susceptible to environmental degradation. The degradation of biomaterials is one of the most relevant issues in the field of regenerative medicine. In industrial practice, the degradation is always a negative phenomenon. In bioengineering, the degradation may be undesirable (e.g. corrosion of metallic implants, wear of artificial joint implant) or desirable (biodegradable devices and tissue engineering). In both cases, the knowledge of the kinetics of degradation is crucial for safe use of biocomponents. The methods for predicting remaining life commonly used in industrial practice will be presented in the context of biomaterials. Non destructive techniques for monitoring degradation will be discussed and some ideas about their application to bio-environments proposed.     

New BCS and renormalized QRPA formalism with application to double beta decay

A new analysis of the renormalized proton–neutron quasiparticle random phase approximation based on simultaneous recalculation of the one-body density matrix and the pairing tensor has been used to study the double beta decay. We demonstrated that inclusion of the quasiparticle correlations at the BCS level reduces ground state correlations in the particle–particle channel of the proton–neutron interaction. We also simplified the RQRPA equations significantly obtaining a low-dimensioned set of linear equations for the quasiparticle densities. The formalism was applied to the double beta decay of ⁷⁶Ge. Received: 4 January 1999 / Revised version: 29 March 1999     

Determination of the proton and neutron densities at the nuclear periphery with antiprotonic X-rays and \overline p -nucleus reactions

The nucleon density at the nuclear periphery has been investigated with two different methods. The first one is the measurement of the energy shift and the width of antiprotonic X-ray lines. Besides various other nuclides the X-rays from the isotopes ¹⁷²Yb and ¹⁷⁶Yb have been measured very extensively. From these data the absorption widths of six antiprotonic levels and the shifts of the lowest visible transitions could be determined. The comparison of the experimental intensities of the transitions with results from calculations of the antiprotonic cascade showed a good agreement. The second method is the determination of the yield of the annihilation products from the reaction of the antiprotons with nuclei. From this the neutron-to-proton density ratio at a distance of about 3 fm outside the half-density radius can be determined. This method was extended to short-lived residual nuclei with a half-life down to 5 s. The experiment confirmed the previously found negative correlation between the size of the neutron skin and the binding energy of the last neutron. The results have been compared with calculations. For many nuclei a good agreement was found between experiment and calculation, however for some nuclei measured and calculated values are at variance. This revised version was published online in August 2006 with corrections to the Cover Date.     

Sensitive adsorptive stripping voltammetric procedure of Imatinib determination in spiked urine samples using solid lead microelectrode

This article reports for the first time the application of solid lead microelectrode for organic compound determination. The proposed sensor was used for anticancer drug Imatinib quantification by adsorptive stripping voltammetry. Procedure of Imatinib determination was developed utilizing advantages ensured by solid lead microelectrode: reusability and durability for a long period of time and its ecological character as compared to film electrodes. The detection limit of Imatinib determination was calculated to be 1.9 × 10⁻¹⁰ mol L⁻¹. The analytical usability of the developed procedure was confirmed by acceptable recoveries of Imatinib determination in spiked urine samples.     

Bispalladium(II) Complexes of di-p-Pyrirubyrin Derivatives as Promising Near-Infrared Photoacoustic Dyes

The insertion of palladium(II) into di-p-pyrirubyrin results in mutually convertible bimetallic complexes. Post-synthetic functionalization of one of them yielded bispalladium(II) dioxo-di-p-pyrirubyrin and, after demetallation, dioxo-di-p-pyrirubyrin, introducing for the first time the α,β′-pyridin-2-one unit into the macrocyclic frame. Bispalladium(II) di-p-pyrirubyrin 6 , bispalladium(II) dioxo-di-p-pyrirubyrin 9 , and dioxo-di-p-pyrirubyrin 10 absorb and emit light around 1000 nm and are characterized by high photostability. Thus, they are promising candidates for near-infrared photoacoustic dyes, ideally targeting ( 9 ) the wavelength of Yb-based fiber lasers. The incorporation of an α,β′-pyridine moiety into expanded porphyrins opens a highly interesting area of research due to the attractive optical and coordination properties of the resulting molecules.     

Loading of Amino Acids onto RNA in a Putative RNA-Peptide World

RNA is a molecule that can both store genetic information and perform catalytic reactions. This observed dualism places RNA into the limelight of concepts about the origin of life. The RNA world concept argues that life started from self-replicating RNA molecules, which evolved toward increasingly complex structures. Recently, we demonstrated that RNA, with the help of conserved non-canonical nucleosides, which are also putative relics of an early RNA world, had the ability to grow peptides covalently connected to RNA nucleobases, creating RNA-peptide chimeras. It is conceivable that such molecules, which combined the information-coding properties of RNA with the catalytic potential of amino acid side chains, were once the structures from which life emerged. Herein, we report prebiotic chemistry that enabled the loading of both nucleosides and RNAs with amino acids as the first step toward RNA-based peptide synthesis in a putative RNA-peptide world.     

Application of Double Deposition and Stripping Steps System for Minimization of Interferences of Peaks’ Overlapping in Anodic Stripping Voltammetry

An anodic stripping voltammetric procedure for the determination of bismuth in the presence of excess of Cu²⁺ ions at two ex situ plated gold film electrodes was described. The procedure is based on utilization of two deposition and two stripping steps system. The presented procedure ensures increasing the sensitivity of Bi³⁺ determination and minimization of interferences related to peaks’ overlapping. The calibration graph for bismuth determination was linear from 2.5×10⁻⁹ to 2×10⁻⁸ mol L⁻¹ for deposition time of 300 s at both working electrodes while detection limit was 7.7×10⁻¹⁰ mol L⁻¹.