Sz Values Research Articles

Testing of Mechanical-Physical Properties of Aggregates, Used for Producing Asphalt Mixtures, and Statistical Analysis of Test Results

In Lithuania, since 2007 the suitability of aggregates, used for producing asphalt mixtures, has been tested in accordance with the requirements of TRA MIN 07:2007 The List of Technical Requirements for the Mineral Materials of Roads. When analysing mechanical-physical properties of aggregates the tests of different type of aggregates of different manufacturers were carried out to determine the resistance of aggregates to freezing and thawing (F value), resistance to fragmentation by the Los Angeles Test (LA value) and the Impact Test (SZ value), the polished stone value PSV, resistance to wear MDE and dry particle density ρrd value. Taking into consideration mineral materials, available in Lithuania and used in road building, the suitability tests were carried out and the requirements for their properties were described. When testing mineral materials, used in road building, the suitability of each test method was assessed for Lithuanian climatic conditions. Having made statistical estimations the hypotheses were tested on the correspondence of the same (mechanical-physical) quality indices of different type crushed rock (granite, dolomite and gravel). Having analysed the results of statistical estimations correlation dependencies were determined between the values of mechanical-physical properties F, LA, SZ and ρrd quality indices of aggregates of the same origin. Based on the histograms of frequencies of the impact test values and dry particle density values the hypotheses were tested whether the test data of these quality indices are distributed by normal distribution. It was determined that in Lithuania mechanical-physical properties of crushed gravel, used for producing asphalt mixtures, have not been sufficiently tested, therefore, it is necessary to carry out more comprehensive tests and analysis of crushed gravel of various fractions. The mechanical strength of mixture is simulated and experimentally validated by various techniques developed for sandy soils, namely: strength and deformation properties.

Improving upon the accuracy for doubly excited states within the coupled cluster singles and doubles theory

An alternative strategy of computations for double character excited states has been examined. The basic idea is to employ the reference function specific to the excited state of interest, as opposed to the traditionally used reference function, usually corresponding to the ground state, specific to the entire spectrum of a molecule. The procedure is used within the framework of the coupled cluster singles and doubles (CCSD) method. The conventional spin-conserving CC approach as well as its spin-flip (SF) extension has been analyzed. For the latter, two variants are considered, changing the S(z) value of the reference function by one [equation-of-motion (EOM)-SF] and two (EOM-2SF). The accuracy of the methods is benchmarked for the C(2) and C(4) molecules and referred to the full configuration interaction (FCI) or CC singles, doubles, and triples results. The vertical and adiabatic excitation energies, equilibrium geometries, and harmonic frequencies are studied. A significant improvement is demonstrated for the excitation energies of doubly excited states. Comparing these values with the FCI method, the errors of the conventional EOM CCSD method of about 1.7-2.2 eV are reduced to about 0.0-0.4 eV for the SF method. An improvement is also shown for the equilibrium geometries and harmonic frequencies.

Can transventricular intracardiac impedance measurement discriminate haemodynamically unstable ventricular arrhythmias in human?

To measure changes in transventricular impedance during arrhythmias. Patients were studied during electrophysiological studies. A quadrapolar catheter was positioned at the right ventricular apex (RVA) and a decapolar catheter within the coronary sinus (CS). Transventricular impedance was measured by injecting a subthreshold biphasic rectangular pulse of 600 micro A between poles 1 of the CS catheter and pole 1 of the RVA catheter and the voltage measured between CS pole 10 and RVA catheter pole 4. Stroke impedance (SZ), surface ECG, intracardiac electrogram (IEGM), and invasive femoral artery blood pressure (FAP) were recorded. Twenty-eight patients were analysed, 5 with inducible, haemodynamically unstable ventricular tachycardia (VT) (HUSVT), 5 with stable VT (HSVT). During HUSVT, the SZ value reduced to 22% (range 0.15-0.32 P < 0.001) in comparison with sinus rhythm. For HSVT, the SZ value reduced to 58% (range 0.33-0.88) P < 0.01, significantly different from HUSVT (P < 0.01). There was a good correlation between reduction of SZ and arterial pulse pressure (PP) during arrhythmias (r = 0.95). Changes in SZ strongly correlated with PP amplitude. Transventricular impedance fell significantly during unstable arrhythmias and may be useful as a sensor capable of haemodynamic discrimination.

Exchange interaction in core excitation of diatomic systems

Abstract The core hole localization, multiplets in the singly core-excited state, and their Auger-like two-electron de-excitation are discussed in some diatomic systems from the viewpoint of the exchange interaction. The exchange repulsion arising from the core–core overlap is proved very small, indicating that the core electron is essentially localized on a specified atom, even in homonuclear systems. Relatively large core–valence exchange interaction between the adjacent atoms results in observable 1sσg–σu splittings in N2 and C2H2. The 1s→π* excitation of a doublet radical NO gives three different electronic states. The 2 Σ − state energy relative to the 2 Δ and 2 Σ + states is dependent on the exchange integral between the core and π* electrons. The two dipole-allowed 2 Π 1 s → σ * excited states of NO are characterized by singlet and triplet couplings between two of the three open-shell electrons. In the N 1s excitation, the σ* and π* electrons are strongly coupled with the triplet and singlet spins. In the O 1s, the core and π* electrons are weakly coupled; then, the singlet-coupled is lower in energy and weaker in intensity than the triplet. Triplet radicals O2, S2, and Se2 have two dipole-allowed 3 Σ u − 1s→σ* excited states with four open shells, which are characterized by doublet and quartet couplings among three of the four electrons. In the S and Se 1s excitations, the σ* and two π* electrons are relatively strongly coupled with the quartet and doublet spins. In the O 1s, the core and two π* electrons are weakly coupled; then, the doublet-coupled is lower in energy and weaker in intensity than the quartet. In the resonant photoionization via the 1s→π* and 1s→σ* excited states in NO and O2, the two-electron de-excitation selection and propensity rules are discussed in terms of state symmetry, spin multiplet and Sz value. In the case that the two electrons taking part in the de-excitation have the same spins, additional exchange-type interaction reduces the transition probability.