Total syntheses of (±)-β-irone

The conversion of the product of the ene reaction of PhSOCl with geranyl acetate into racemic -irone has been accomplished in seven steps, using highpressure techniques for the olefination of -methylcyclocitral.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2607–2610, November, 1989.     

Characterization of the distribution of the sintering activator boron in powder metallurgical steels with SIMS

Powder metallurgy is a well-established method for manufacturing ferrous precision parts. A very important step is sintering, which can be strongly enhanced by the formation of a liquid phase during the sintering process. Boron activates this process by forming such a liquid phase at about 1200 °C. In this work, the sintering of Fe–B was performed under the protective atmospheres of hydrogen, argon or nitrogen. Using different grain sizes of the added ferroboron leads to different formations of pores and to the formation of secondary pores. The effect of boron was investigated by means of Secondary Ion Mass Spectrometry (SIMS) supported by Scanning Electron Microscopy (SEM) and Light Microscopy (LM). To verify the influence of the process parameters on the mechanical properties, the microstructure (pore shape) was examined and impact energy measurements were performed.The concentrations of B in different samples were varied from 0.03–0.6 weight percent (wt%). Higher boron concentrations are detectable by EPMA, whereas the distributions of boron in the samples with interesting overall concentration in the low wt% range are only detectable by means of SIMS.This work shows that the distribution of boron strongly depends on its concentration and the sintering atmosphere used. At low concentration (up to 0.1 wt%) there are boride precipitations; at higher concentration there is a eutectic iron–boron grain boundary network. There is a decrease of the impact energy observed that correlates with the amount of eutectic phase.     

Is the low-l microwave background cosmic?

The large-angle (low-l) correlations of the cosmic microwave background exhibit several statistically significant anomalies compared to the standard inflationary cosmology. We show that the quadrupole plane and the three octopole planes are far more aligned than previously thought (99.9% C.L.). Three of these planes are orthogonal to the ecliptic at 99.1% C.L., and the normals to these planes are aligned at 99.6% C.L. with the direction of the cosmological dipole and with the equinoxes. The remaining octopole plane is orthogonal to the supergalactic plane at 99.6% C.L.     

Development and validation of an HPLC method for the determination of verapamil residues in supports of cleaning procedure

Analytical method validation, determining the recovery rate from the equipment surface, and stability of a potential contaminant are important steps of a cleaning validation process. An HPLC method for the determination of the verapamil residues on stainless steel surfaces of the equipment employed in drug manufacture is described. The cleaning validation sample impurities as well as excipients of the commercial sample did not interfere in the analysis which proved the selectivity of the method. The validation of the method demonstrated acceptable levels of the linearity, precision and accuracy. Cotton swabs, moistened with methanol were used to remove any residues of drugs from stainless steel surfaces, and give recoveries of above 78.59% for three diferent concentration levels. The precision of the results, reported as the relative standard deviation (RSD, %), were below 1.58%. Low quantities of the drug residues were determined by HPLC using a Hypersil ODS column (125 × 4.0 mm, 5 μm) at 25°C with the mobile phase metanol-water-triethylamine (70: 30: 0.2, v/v/v) at a flow rate of 0.6 mL/min, injection volume of 50 μL and detection at 278 nm.     

Solution behavior of progressively quaternized poly(dimethylaminoethyl methacrylate) as a function of charge density

Hydrodynamic behavior of progressively quaternized poly(dimethylaminoethyl methacrylate) (PDMAEM) in dilute and semi-dilute salt–free aqueous solutions as a function of molar mass and charge density, which varied from 5 up to 100 mol%, was studied. The role of long range electrostatic interactions on the viscosity and on the position and value of the reduced viscosity corresponding to the peak, η_red,p, as a function of the charge density of polycation has been evaluated. The overlap concentration of polyelectrolytes, c^∗, has been evaluated as the inverse of the intrinsic viscosity determined by fitting the viscometric results on Rao equation. The values of c^∗ have been discussed as a function of polyion molar mass and charge density. The c^∗ values calculated in the frame of Odijk model for polyelectrolytes having quaternization degree ?50 were lower but comparable with those determined by viscometry, for the same molar mass.     

The influence of oxygen on radiation crosslinking and degradation of polymers at low irradiation doses

The influence of oxygen on radiation cross-linking and scission at low doses has been followed in order to explain anomalous drop of molecular weight found in polyethylene at low irradiation doses. The G - values and yields of crosslinking and scission estimated on the basis of molecular weight measurements (by GPC) are much higher than those obtained through gel content determinations at higher doses. The possible explanations of such a peculiar behavior are suggested and discussed. The influence of oxygen, even when present in the form of air absorbed in the sample, was found to be an important factor of scission process in irradiated polymer.     

The weak and strong asymptotic equivalence relations and the generalized inverse<Superscript>*</Superscript>

We discuss the relationship between the weak and strong asymptotic equivalence relations and the generalized inverse in the class A \mathcal {A} of all nondecreasing unbounded positive functions on a half-axis [a,+∞) (a > 0). As a main result, we prove a proper characterization of the functional class R _∞ ∩ A \mathcal {A} , where R _∞ is the class of all rapidly varying functions. Also, we prove a characterization of the functional class PI ^* ∩ A \mathcal {A} .     

Development and Evaluation of a Kinetic‐Spectrophotometric Method for Determination of Arginine

A kinetic method for the determination of micro quantities of amino acid arginine (Arg) is described in this paper. The catalytic activity of cobalt in the reaction of oxidation of purpurin (1,2,4‐trihydroxy‐antraquinone, PP) by hydrogen peroxide in alkaline buffer solution decreases in the presence of micro quantities of arginine, because of the formation of the complex. Operating conditions for the successful determination of arginine were optimized. The optimized conditions yielded a theoretical detection limit of 1.45 μg mL^?1. Kinetic equations are proposed for the investigated process. The interference effects of certain foreign ions and amino acids upon the reaction rate were studied and removed in order to assess the selectivity of the method. The developed procedure was successfully applied to the determination of arginine in various pharmaceutical samples. The typical feature of this procedure is that determination can be carried out at room temperature and in a short analysis time. The newly developed method is simple, inexpensive and efficient for use in the analysis of a large number of samples.