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.     

Outcomes matter: estimating pre-transplant survival rates of kidney-transplant patients using simulator-based propensity scores

The current kidney allocation system in the United States fails to match donors and recipients well. In an effort to improve the allocation system, the United Network of Organ Sharing (UNOS) defined factors that should determine a new allocation policy, and particularly patients’ potential remaining lifetime without a transplant (pre-transplant survival rates). Estimating pre-transplant survival rates is challenging because the data available on candidates and organ recipients is already “contaminated” by the current allocation policy. In particular, the selection of patients who are offered (and decide to accept) a kidney is not random. We therefore expect differences in mortality-related characteristics of organ recipients and of candidates who have not received transplant. Such differences introduce bias into survival models. Existing approaches for tackling this selection bias either ignore the difference between candidates and recipients or assume that selection to transplant is based solely on patients’ pre-transplant information, irrespective of the potential allocation outcome. We argue that in practice the allocation is dependent on the anticipated allocation outcome, which is a major factor in selection to transplant. Moreover, we show that ignoring the anticipated outcome increases model bias rather than decreases it. In this paper, we propose a novel simulator-based approach (SimBa) that adjusts for the selection bias by taking into account both pre-transplant and anticipated outcome information using simulation. We then fit survival models to kidney transplant waitlist data and compare the different adjustment methods. We find that SimBa not only fits the data best, but also captures a key aspect of the current allocation policy, namely, that the probability of kidney allocation increases in the expected pre-transplant life years.     

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.     

The number of visits of vector walks to bounded regions

The main result of this note states that if the expected number of visits of a vector random walk to a bounded region is finite than all the moments of the number of visits are finite.     

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)...     

On generating multivariate Poisson data in management science applications

Generating multivariate Poisson random variables is essential in many applications, such as multi echelon supply chain systems, multi‐item/multi‐period pricing models, accident monitoring systems, etc. Current simulation methods suffer from limitations ranging from computational complexity to restrictions on the structure of the correlation matrix, and therefore are rarely used in management science. Instead, multivariate Poisson data are commonly approximated by either univariate Poisson or multivariate Normal data. However, these approximations are often not adequate in practice. In this paper, we propose a conceptually appealing correction for NORTA (NORmal To Anything) for generating multivariate Poisson data with a flexible correlation structure and rates. NORTA is based on simulating data from a multivariate Normal distribution and converting it into an arbitrary continuous distribution with a specific correlation matrix. We show that our method is both highly accurate and computationally efficient. We also show the managerial advantages of generating multivariate Poisson data over univariate Poisson or multivariate Normal data. Copyright © 2011 John Wiley & Sons, Ltd.     

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.