Parametric multiple sequence alignment and phylogeny construction

Bounds are given on the size of the parameter-space decomposition induced by multiple sequence alignment problems where phylogenetic information may be given or inferred. It is shown that many of the usual formulations of these problems fall within the same integer parametric framework, implying that the number of distinct optima obtained as the parameters are varied across their ranges is polynomially bounded in the length and number of sequences.     

Gas phase unimolecular decomposition and chemiluminescence of tetramethyldioxetane initiated by a tea CO2 laser

Time resolved chemiluminescence spectra of pure tetramethyldioxetane are obtained for the first time using pulsed infrared laser excitation. The only major product, acetone, is shown to be formed by at least two pathways: a unimolecular, collision free, decomposition and a collision induced mechanism. Spectral and temporal behaviour indicate that neither singlet nor triplet acetone are the primary products. Other possibilities are discussed.     

A new method for absolute absorption cross-section measurements: rhodamine-6G excited singlet-singlet absorption spectrum

A novel method is suggested to measure the absolute excited single-singlet absorption spectrum of rhodamine by bleaching completely the solution. The molar decadic extinction coefficient of the excited state (? = 4.8 × 10⁴ liter mole^?1 cm^?1 at 440 nm) is estimated directly from the plateau-like absorption signal at very high excitation intensities.     

Selective fluorination of bile acids using elemental fluorine

Specific direct mono fluorinations on various sites of the steroidal skeleton of bile acids were achieved by introduction of electronegative groups at selected points.     

Thermal and physical properties of ZrO2–AlO(OH) nanopowders synthesised by microwave hydrothermal method

Journal of Thermal Analysis and Calorimetry - Industrially relevant nanopowder was synthesised by microwave hydrothermal synthesis to obtain well-controlled composition (ZrO2–AlO(OH) system)...     

A theory of PWD-structures

A general study is undertaken of product-wedge-diagonal (=PWD) structures on a space. In part this concept may be viewed as arising from G.W. Whitehead's fat-wedge characterization of Lusternik-Schnirelmann category. From another viewpoint PWD-structures occupy a distinguished position among those structures that provide data allowing Hopf invariants to be defined. Indeed the Hopf invariant associated with a PWD-structure is a crucial component of the structure. Our overall theme addresses the basic question of existence of compatible structures on X and Y with regard to a map X→Y. A principal result of the paper uses Hopf invariants to formulate a Berstein-Hilton type result when the space involved is a double mapping cylinder (or homotopy pushout). A decomposition formula for the Hopf invariant (extending previous work of Marcum) is provided in case the space is a topological join U*V that has PWD-structure defined canonically via the join structure in terms of diagonal maps on U and V.     

Silicon tetrafluoride visible luminescence induced by high-power CO2 laser irradiation

The visible luminescence induced by a high-power CO₂ laser in SiF₄ occurs within the laser pulse even at pressures as low as 10^?2 Torr. The unirnolecular nature of the process is also supported by pressure-dependence studies of the luminescence intensity and the incubation period. A possible assignment of the transition involving inverse electronic relaxation is discussed.     

A duality theory for bilattices

Recent studies of the algebraic properties of bilattices have provided insight into their internal strucutres, and have led to practical results, especially in reducing the computational complexity of bilattice-based multi-valued logic programs. In this paper the representation theorem for interlaced bilattices without negation found in [19] and extended to arbitrary interlaced bilattices without negation in [2] is presented. A natural equivalence is then established between the category of interlaced bilattices and the cartesian square of the category of bounded lattices. As a consequence a dual natural equivalence is obtained between the category of distributive bilattices and the coproduct of the category of bounded Priestley spaces with itself. Some applications of these equivalences are given. The subdirectly irreducible interlaced bilattices are characterized in terms of subdirectly irreducible lattices. A known characterization of the join-irreducible elements of the "knowledge" lattice of an interlaced bilattice is used to establish a natural equivalence between the category of finite, distributive bilattices and the category of posets of the form . Received February 2, 1998; accepted in final form September 2, 1999.     

From Propagation to Structure: The Experimental Technique of Bombardment as a Contributing Factor to the Emerging Quantum Physics

I observe that quantum physics emerged at the turn of the last century when physics had shifted its concern from propagation phenomena to questions of structure. This transition materialized with the development of a new experimental technique, the bombardment method. The transition is well exemplified by the move from the experimental studies of Heinrich Hertz to those of Ernest Rutherford, and from those of Heinrich Hertz and Philipp Lenard to those of James Franck and Gustav Hertz. I trace the history of Rutherford's experimental bombardment method as it emerged from nineteenth-century propagation studies. I then demonstrate the use of the bombardment method in another experimental context, namely, in the celebrated experiment of Franck and Hertz. I locate the root of this experiment in Lenard's experimental studies and analyze Franck and Hertz's flawed interpretation of it. I conclude by underlining the crucial role that Bohr's quantum theory of the atom played in helping to establish these bombardment experiments as milestones of modern physics.     

Ranking participants in generalized tournaments

Consider the problem of ranking social alternatives based on the number of voters that prefer one alternative to the other. Or consider the problem of ranking chess players by their past performance. A wide variety of ranking methods have been proposed to deal with these problems. Using six independent axioms, we characterize the fair-bets ranking method proposed by Daniels [4] and Moon and Pullman [14].Received: January 2005