The Ordered K-Theory of C/*-Algebras¶Associated with Substitution Tilings

We consider the C ^*-algebra, A _T , constructed from a substitution tiling system which is primitive, aperiodic and satisfies the finite pattern condition. Such a C ^*-algebra has a unique trace. We show that this trace completely determines the order structure on the group K ₀(A _T ); a non-zero element in K ₀(A _T ) is positive if and only if its image under the map induced from the trace is positive. Received: 12 August 1999 / Accepted: 2 May 2000     

TDDFT Study on the Electronic Excitations and First Hyperpolarizabilities of Mixed-metal Carbonyl Clusters W2Ir2（μ-L）（CO）8（η^5-C5H4Me）2（L = dppe/dppf）

Mixed-metal carbonyl clusters of W2Ir2（CO）10（η^5-C5H4Me）2 1 and W2Ir2（μ-L）（CO）8（η^5-C5H4Me）2 （L = dppe 2, dppf 3） have been studied by TDDFT method focusing on their electronic and nonlinear optical properties. These three clusters exhibit the first static hyperpolarizabilities of medium magnitude （βtot-10×10^-30 esu）. The origin of β is discussed by the new proposed orbital-pair decomposition scheme by Barandes et al. The result suggests that the β values of the two clusters are mainly originated from d-d electron transition within the metal skeleton, and d-p （π＊） electron transition from metals to carbonyls and phenyl. The additional coordination by the electron donor group, ferrocene, makes cluster 3 own much larger β values, and the relatively longer range charge transfer from d orbitals of ferrocene to d orbirals of Ir and W is responsible for the enhanced β values.     

Characterizing the Memory Effect on the amylose tris(3,5-dimethylphenyl) carbamate stationary phase

Acid/base modifiers are sometimes used as additives in normal phase elution on columns packed with CHIRALPAK^® AD^®. They affect enantioseparations in ways that are not understood for the lack of systematic studies, which makes the scale-up of preparative separations difficult to predict. Once a column has been exposed to these modifiers, the selectivity of certain pairs of enantiomers may change, for the better or the worse. Numerous molecules that are affected by this phenomenon are listed in the literature. We selected five of them, the selectivity of which changes as more acidic or basic solutions are percolated through the column. The selectivity of ketoprofen, 4-chlorophenylalanine methyl and ethyl esters improves as a solution of Ethanesulfonic Acid is percolated through the column. The selectivity of Propranolol HCl and Tröger’s base increases as a solution of diisopropylamine is percolated through the column. Each one of these five compounds is inversely affected by the percolation of the opposite acid/base solution. We used trans-Stilbene Oxide (tso) as a “standard” to determine the columns stability because no Memory Effect is observed for it (its retention, enantioselectivity, and resolution remain constant). Karl Fisher titrations showed that only slight changes in the water content of the mobile phase occurred, and that a unique water to polymer moiety ratio is important. Analytical studies of the stationary phase suggest that slow protonation/deprotonation of water attached to the carbamate moiety may be responsible for the acid/base Memory Effect. Finally, we showed that the Memory Effect can be minimized by percolating through the column a sufficiently concentrated solution of the appropriate acid or base. Thus, columns that were unreliable for method development, due to the Memory Effect, can now be used. As a result, the need to store several CHIRALPAK AD columns, specific for each condition of the Memory Effect, is eliminated.     

Charge fluctuations in Au+Au collisions at RHIC energy

A hadron and string cascade model, JPCIAE, together with the corresponding Monte Carlo event generator, has been employed in this paper to investigate further the charge fluctuations in Au+Au collisions at Snn = 130 GeV. The default JPCIAE calculations are in good agreement with PHENIX and STAR data. We found that the thermal predictions for the π gas, the resonance π gas and quark matter deviate, respectively, from the corresponding dynamical simulations from the JPCIAE model. The discrepancies were also found between the π charge fluctuations and the charge fluctuations of all species of hadrons. However the charge fluctuations for "π from ρ and ω decay" and for all the hadrons from resonance decay are close to each other, indicating the correlation between positively and negatively charged hadrons is not sensitive to the species of hadrons. This work shows further that it is questionable to use the charge fluctuations as a signature of QGP.     

Breathing modes and induced resonant melting of the double helix

Breathing modes are found in double helical DNA which can induce melting by excessive stretching of H-bonds. Energy for such melting may be supplied by splitting of nucleoside triphosphate bonds.