Hilbert’s early career: Encounters with allies and rivals

It seems to me that the mathematicians of today understand each other far too little and that they do not take an intense enough interest in one another. They also seem to know—so far as I can judge—too little of our classical authors (Klassiker); many, moreover, spend much effort working on dead ends. “ David Hilbert to Felix Klein, 24 July 1890     

Large boson number IBM calculations and their relationship to the Bohr model

Recently, the SO(5) Clebsch-Gordan (CG) coefficients up to the seniority v _max = 40 were computed in floating point arithmetic (T.A. Welsh, unpublished (2008)); and, in exact arithmetic, as square roots of rational numbers (M.A. Caprio et al., to be published in Comput. Phys. Commun.). It is shown in this paper that extending the QQQ model calculations set up in the work by D.J. Rowe and G. Thiamova (Nucl. Phys. A 760, 59 (2005)) to N = v _max = 40 is sufficient to obtain the IBM results converged to its Bohr contraction limit. This will be done by comparing some important matrix elements in both models, by looking at the seniority decomposition of low-lying states and at the behavior of the energy and B(E2) transition strengths ratios with increasing seniority.     

Quantum hysteresis loops in microscopic system: The loop area as a dynamical parameter

The area enclosed by hysteresis loops in a periodically forced bistable microscopic system at zero-temperature is examined by using the time dependent Hellmann-Feynman theorem and the Fourier grid Hamiltonian recipe for solving time-dependent Schrödinger equation. Effects of non-zero temperatures are explored with reference to a symmetric double well potential. The barrier crossing or, relaxation rates are shown to correlate systematically with the area of the loop. The possible use of hysteresis loop area in designing field parameters for optimal control is suggested.     

Synthesis and Microtubule‐Destabilizing Activity of N‐Cyclopropyl‐4‐((3,4‐dihydroquinolin‐1(2H)‐yl)sulfonyl)benzamide and its Analogs

While clinically useful, microtubule‐targeting agents are limited by factors that include their susceptibility to multidrug resistance. A series of aryl sulfonamides, terminally substituted with an amide or carboxylic acid, was synthesized and assayed for biological activity in two human cancer cell lines. The resulting antiproliferative activity data demonstrated that an amide was superior to a carboxylic acid in the para position. The most potent compound ( 3 ) had an IC₅₀ for growth inhibition in the low micromolar range, caused cells to accumulate in G₂M of the cell cycle, and led to depolymerization of microtubules. It was also not susceptible to the P‐glycoprotein drug efflux pump that underpins the resistance of cells to long‐term drug treatment schedules.     

Mesomorphic 2,2'-bipyridine diesters and their related metal complexes

Esterification of 2.2'-bipyridine-5,5'- and 4,4'-dicarboxylic acids with 4-alkoxyphenols leads to new mesomorphic bipyridine esters which are subsequently complexed with various metals. The synthesis and properties of these compounds are discussed.     

Quasidynamical symmetry in an interacting boson model phase transition

The apparent persistence of symmetry in the face of strong symmetry-breaking interactions is examined in a many-boson model. The model exhibits a transition between two phases associated with U(5) and O(6) symmetries, respectively, as the value of a control parameter progresses from 0 to 1. The remarkable fact is that, in spite of strong mixing of the symmetries for intermediate values of the control parameter, the model continues to exhibit the characteristics of its closest symmetry limit for all but a relatively narrow transition region that becomes progressively narrower as the boson number increases. This phenomenon is explained in terms of quasidynamical symmetry.     

The reaction of anthracene with OH radicals: an experimental study of the kinetics between 58 and 470 K

The first direct measurement of the reaction rate constant of a polycyclic aromatic hydrocarbon in the gas phase in the temperature range 58-470 K is reported. The reaction is OH+ anthracene and the experiment has been performed in a continuous flow Cinetique de Reaction en Ecoulement Supersonique Uniforme apparatus, which had to be modified for this purpose. Pulsed laser photolysis of H(2)O(2) has been used to generate OH radicals and laser-induced fluorescence to observe the kinetic decay of the radicals and hence determine the rate coefficients. The reaction is found to be fast, and the rate constant increases monotonically as the temperature is lowered. The rate coefficients match the expression k(cm(3) molecules(-1) s(-1))=1.12 x 10(-10)(T/300)(-0.46).