Elastic pion-deuteron scattering near the 3-3 resonance

The elastic scattering of positive pions by deuterium has been studied at seven energies between 82 MeV and 292 MeV laboratory kinetic energy in the angular range between 30° and 130° (lab). The results are compared to recent relativistic three-body calculations.     

Elastic scattering of positive pions by O between 80 and 340 MeV

Angular distributions of cross sections for π⁺ elastic scattering by ¹⁶O have been measured between 14° and 138° at five energies (79, 114, 163, 240 and 343 MeV). They are compared to calculations using a first-order static model and an isobar doorway model. Phase-shift analyses have been done using the theoretical inputs as guidelines. The validity of these models is discussed.     

The pyrolytic identification of organic molecules: III. A mechanistic approach

The results are presented of a study of the pyrolytic behavior of methanol, ethanol, n-propanol, and isopropanol. Samples were pyrolysed in an atmosphere of helium over a temperature range of 300–1200 °C, and the volatile products were determined by gas chromatographic techniques. Mechanisms have been derived for the thermal degradation of the alcohols as an aid in the determination of their atomic constitution and their molecular structure.     

Scaling of matrices to achieve specified row and column sums

IfA is ann ×n matrix with strictly positive elements, then according to a theorem ofSinkhorn, there exist diagonal matricesD ₁ andD ₂ with strictly positive diagonal elements such thatD ₁ A D ₂ is doubly stochastic. This note offers an alternative proof of a generalization due toBrualdi, Parter andScheider, and independently toSinkhorn andKnopp, who show that A need not be strictly positive, but only fully indecomposable. In addition, we show that the same scaling is possible (withD ₁ =D ₂) whenA is strictly copositive, and also discuss related scaling for rectangular matrices. The proofs given show thatD ₁ andD ₂ can be obtained as the solution of an appropriate extremal problem.The scaled matrixD ₁ A D ₂ is of interest in connection with the problem of estimating the transition matrix of a Markov chain which is known to be doubly stochastic. The scaling may also be of interest as an aid in numerical computations.Research sponsored in part by the Boeing Scientific Research Laboratories.     

What variable-pressure variable-temperature measurements are telling us about ion transport in glass

Variable-pressure, variable-temperature (VPVT) measurements of ionic conductivity in typical inorganic (sodium aluminoborate and lithium-sodium phosphate) glasses provide information concerning two independent activation parameters: the activation energy (E(A) = - R d ln sigma T/d(1/T)) and the activation volume (V(A) = - RT d ln sigma/dP). In single-cation glasses there is no simple link between E(A) and V(A). The strong increase in E(A) seen with decreasing alkali content is not paralleled by an increase in V(A). However, in mixed cation glasses, maxima are observed in both E(A) and V(A). To account for these observations, a new model is being developed where ion transport is limited by a shortage of available volume. In this model, the measured V(A) values represent the volumes of opened up 'target sites', the larger values observed in mixed-cation glasses providing evidence for the coupled motion of unlike ions. The extent of this pairwise coupling increases with increasing temperature.     

Synthesis,Morphological Structures,and Material Characterization of Electrospun PLA:PCL/Magnetic Nanoparticle Composites for Drug Delivery

The effects of pure and impure magnetic nanoparticles (MPs) with three different concentrations (0.01, 0.1, and 1 wt %/v) on the morphological structure, crystallinity level, thermal properties and constituent interactions of electrospun poly(lactic acid) (PLA): poly(ε‐caprolactone) (PCL)‐based composites were investigated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), and drug release tests using UV–vis spectrophotometry. Tetracycline hydrochloride (TCH), as a typical therapeutic compound, was loaded into these composite fibrous structures to study their application for drug delivery. The infrared spectra of composite nanofibers confirm the successful embedding of MPs into the fibrous networks. The addition of pure MPs increased the solution viscosity and thus promoted the MP dispersion inside the electrospun composite fiber mats. Impure MPs led to considerably lower average fiber diameters, and could generate unique cell structures that were reported for the first time in this study. The accelerated release of TCH was found by adding pure MPs to PLA:PCL blends. This characteristic was reflected in the parameters of Ritger‐Peppas and Zeng models, which were well fitted to our experimental drug release data. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1607–1617     

The development of a Cartesian cut cell method for incompressible viscous flows

This paper describes the extension of the Cartesian cut cell method to applications involving unsteady incompressible viscous fluid flow. The underlying scheme is based on the solution of the full Navier–Stokes equations for a variable density fluid system using the artificial compressibility technique together with a Jameson‐type dual time iteration. The computational domain encompasses two fluid regions and the interface between them is treated as a contact discontinuity in the density field, thereby eliminating the need for special free surface tracking procedures. The Cartesian cut cell technique is used for fitting the complex geometry of solid boundaries across a stationary background Cartesian grid which is located inside the computational domain. A time accurate solution is achieved by using an implicit dual‐time iteration technique based on a slope‐limited, high‐order, Godunov‐type scheme for the inviscid fluxes, while the viscous fluxes are estimated using central differencing. Validation of the new technique is by modelling the unsteady Couette flow and the Rayleigh–Taylor instability problems. Finally, a test case for wave run‐up and overtopping over an impermeable sea dike is performed. Copyright © 2006 John Wiley & Sons, Ltd.