A characterization of {\square(\kappa^{+})} in extender models

We prove that, in any fine structural extender model with Jensen’s λ-indexing, there is a ${\square(\kappa^{+})}$ -sequence if and only if there is a pair of stationary subsets of ${\kappa^{+} \cap {\rm {cof}}( < \kappa)}$ without common reflection point of cofinality ${ < \kappa}$ which, in turn, is equivalent to the existence of a family of size ${ < \kappa}$ of stationary subsets of ${\kappa^{+} \cap {\rm {cof}}( < \kappa)}$ without common reflection point of cofinality ${ < \kappa}$ . By a result of Burke/Jensen, ${\square_\kappa}$ fails whenever ${\kappa}$ is a subcompact cardinal. Our result shows that in extender models, it is still possible to construct a canonical ${\square(\kappa^{+})}$ -sequence where ${\kappa}$ is the first subcompact.     

Influence of internal parametric and kinematic excitation on nonlinear gearbox vibration

This paper deals with mathematical modelling of nonlinear vibration of large rotating shaft systems with gears and rollingelement bearings. Gearing and bearing couplings bring into the system nonlinear phenomena like impact motions due to the possibility of the mesh interruption. The motion of the system is influenced by the internal kinematic excitation in gearing and by the parametric excitation caused by periodic change of number of teeth in gear meshing. The influence of simultaneous internal kinematic and parametric excitation is investigated in dependence on revolutions of the driving shaft of a test-gearbox. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Notes on the use of the vacuum stability test in the study of initiation reactivity of attractive cyclic nitramines in the C4 matrix

The zero-order reaction rates (specific rate constants) for isothermal decomposition at 120 °C of plastic bonded explosives (PBXs) were measured by means of the Czech vacuum stability test, STABIL. The PBXs are based on 1,3,5-trinitro-1,3,5-triazinane (RDX), β-1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX), cis-1,3,4,6-tetranitro-octahydroimidazo-[4,5-d] imidazole (BCHMX), and ε-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (ε-HNIW, ε-CL-20) with 9 wt.% of the C4 type matrix, i.e., a matrix containing 25 wt.% of polyisobutylene, 59 wt.% of dioctyl sebacate and 16 wt.% of the oil HM46. Dependencies were found between the specific rate constants mentioned and the detonation velocities of the PBXs, and consequently between these constants and the impact of pure explosive fillers, i.e., RDX, β-HMX, ε-HNIW, RS-ε-HNIW, and BCHMX and, at the same time, the corresponding PBXs. The results obtained are compared with those from a recent analogous study of PBXs using an SBR (Formex P1) binder which could increase the PBXs’ reactivity in comparison with C4 matrix. These results also help to dispel a widely held view about HNIW being a relatively sensitive explosive.     

Block Conjugate Gradient Iteration for Fourier-Galerkin Homogenization of Periodic Media

The Fourier-Galerkin method is considered here for the solution of the unit cell problem that describes the homogenized properties of periodic materials in the scalar elliptic setting. The method is based on a Galerkin approximation with trigonometric polynomials and leads to linear systems suitable for iterative solvers. In [1], Zeman et al show the effectiveness of Conjugate gradients (CG) which is compared here with its block version (BCG). We show that the latter version outperforms the CG especially for anisotropic materials with non-symmetric distribution of material properties. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Automated radioanalytical determination of lead and beryllium

The automated modification of the radioanalytical determination of lead and beryllium using AutoAnalyzer modules has been developed. The method for lead determination is based on a two-phase isotope exchange of lead between the sample solution labelled with²¹²Pb and the standard lead diethyldithiocarbamate solution in carbon tetrachloride. For the determination of beryllium a substoichiometric isotope dilution method using⁷Be as tracer and acetylacetone in chloroform as extractant was used. As little as 0.02 μg/ml of lead and 2 μg/ml of beryllium can be determined by the methods above. The flow diagrams of the automated procedures are presented.     

QSPR approach to the calculation of rate constants of homolysis of nitro compounds in different states of aggregation

A method for the theoretical estimation and prediction of rate constants of homolysis of nitro compounds of different chemical classes in the gas phase is proposed on the basis of the QSPR approach.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1653–1656, September, 1995.The authors express gratitude to B. A. Lur'e (D. I. Mendelev Moscow Academy of Chemical Technology) for fruitful advice during discussion of the results.     

Evaluation of STIR imaging as a complement to spin-echo MR and CT of the porta hepatis/hepatoduodenal ligament

Short TI inversion-recovery (STIR) imaging provides specific advantages over standard spin-echo (SE) MR sequences by producing additive effects of T1 and T2 brightening of pathology and suppression of the signal from surrounding fat. We retrospectively evaluated 12 patients with abnormalities, primarily neoplastic, of the porta hepatis/hepatoduodenal ligament (PH/HdL) with CT and MR imaging, including SE and STIR imaging. Masses on CT were of slightly decreased density compared to liver and seen in contrast to surrounding fat in the PH/HdL region. On MR, T1-weighted images provided comparable anatomic detail to CT, with masses clearly distinguished from surrounding fat due to the low signal intensity of masses as compared to fat. T2-weighted images clearly depicted intrahepatic lesions because of their high signal intensity relative to liver. Increased signal in extrahepatic lesions made them less distinctly seen from surrounding fat. STIR images best demonstrated tumor relative to fat. In six cases, CT was equivalent in demonstrating pathology to the best MR sequence. At least one MR sequence demonstrated pathology better than CT in 6 of 12 cases. In five of these six cases, the STIR sequence was better than CT. Thus, MR, particularly STIR imaging, provides a useful technique in imaging of PH/HdL pathology.     

Analyse synthetischer Schmier?le auf Esterbasis durch Gas-Chromatographie-CI(NH3)-Massenspektrometrie

Zusammenfassung Zur Produktkontrolle und QualitÄtsbeurteilung von Esterölen werden leistungsfÄhige Analysenverfahren benötigt. Dies gilt besonders für die Beurteilung von gebrauchten ölen. Es wird am Beispiel der Neopentylpolyolesteröle gezeigt, da\ die Capillar-Gas-Chromatographie in Kombination mit der CI(NH₃)-Massenspektrometrie einen erheblichen Fortschritt bei der Charakterisierung von komplexen Esterölen und ihren Additivsystemen darstellt.

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Analysis of synthetic lubricating oils based on esters by gas chromatography-CI(NH₃)-mass spectrometry

Summary For product control and quality assessment of ester oils efficient analytical methods are needed. This is especially true for the assessment of used oils. It is shown with neopentylpolyol ester oils that capillary gas chromatography in combination with chemical ionization (NH₃)-mass spectrometry presents a considerable progress in the characterisation of complex ester oils and their additive systems.