Exceptional convergent evolution in a virus

Replicate lineages of the bacteriophage phiX 174 adapted to growth at high temperature on either of two hosts exhibited high rates of identical, independent substitutions. Typically, a dozen or more substitutions accumulated in the 5.4-kilobase genome during propagation. Across the entire data set of nine lineages, 119 independent substitutions occurred at 68 nucleotide sites. Over half of these substitutions, accounting for one third of the sites, were identical with substitutions in other lineages. Some convergent substitutions were specific to the host used for phage propagation, but others occurred across both hosts. Continued adaptation of an evolved phage at high temperature, but on the other host, led to additional changes that included reversions of previous substitutions. Phylogenetic reconstruction using the complete genome sequence not only failed to recover the correct evolutionary history because of these convergent changes, but the true history was rejected as being a significantly inferior fit to the data. Replicate lineages subjected to similar environmental challenges showed similar rates of substitution and similar rates of fitness improvement across corresponding times of adaptation. Substitution rates and fitness improvements were higher during the initial period of adaptation than during a later period, except when the host was changed.     

A comprehensive approach to the solution of direct-coupledmultislice model of skewed rotor induction motors using time-steppingeddy-current finite element method

Normally a complicated three-dimensional (3-D) approach is needed to study the field pattern of induction machines with skewed rotor bars. In this paper, a time-stepping two-dimensional (2-D) eddy-current finite element method, based on multislice technique, is described to study the steady-state operation and the starting process of skewed rotor induction machines. The fields of the multislices are being solved en bloc simultaneously, and thus, the effects of the eddy current and saturation can be taken into account directly. New forms of the governing equations for the multislice model are derived, which allow the meshes of multislices to be taken as one 2-D mesh so that the algorithm is very similar to that of general 2-D problems. Special techniques required for the mesh generation in the multislice model and the salient structures of the software are also described. The results obtained by using the program being developed have very good correlation with test data     

Extraction of halide quaternary salts in an organic solvent/water system: Hydrodynamics and mass transfer

The hydrodynamic characteristics and mass transfers of halide quaternary salts between two immiscible phases in a stirred membrane permeation cell were investigated. The concentration of quaternary salt, temperature, solvent and the four kinds of halide quaternary salts were evaluated to achieve the extractive optimum condition. The diffusivity, overall mass‐transfer coefficients and individual mass‐transfer coefficients were determined and correlated in terms of the conventional Sh‐Re‐Sc relationship. The transfer time of quaternary salts across the membrane and the thickness of the hydrodynamic diffusion boundary layer were determined as well, so as to characterize the extractive phenomenon of quaternary salts between the two phases that is useful in phase‐transfer catalysis.     

Preparation of core–shell type nanoparticles of diblock copolymers of poly(L‐lactide)/poly(ethylene glycol) and their characterization in vitro

Core–shell type nanoparticles of poly(L ‐lactide)/poly(ethylene glycol) (LE) diblock copolymer were prepared by a dialysis technique. Their size was confirmed as 40–70 nm using photon correlation spectroscopy. The ¹H‐NMR analysis confirmed the formation of core–shell type nanoparticles and drug loading. The particle size, drug loading, and drug release rate of the LE nanoparticles were slightly changed by the initial solvents that were used. The drug release behavior of LE core–shell type nanoparticles showed an initial burst during the first 12 h and then a sustained release until 100 h. The degradation behavior of LE block copolymer nanoparticles was divided into three phases: the initial rapid degradation phase, the stationary phase, and the rapid degradation phase until complete degradation. It was suggested that lidocaine release kinetics were predominantly governed by the diffusion mechanism in the initial burst phase and after that by both of the diffusion and degradation mechanisms. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2625–2634, 2002     

Contact areas in the thumb carpometacarpal joint

The thumb carpometacarpal joint is a common site of osteoarthritis. It has been hypothesized that peaks of localized stress on the dorsoradial or volar-ulnar regions, or both, of the articular surfaces of the trapezium and metacarpal lead to erosion of cartilage and may be responsible for the progression of the disease. The objective of this study was to determine the contact areas in this joint under the functional position of lateral (key) pinch and in the extremes of range of motion of the joint. These contact areas were assessed relative to the observed sites of cartilage thinning. Eight hands from cadavers of women and five from cadavers of men were tested in vitro with the thumb under a 25 N load in the lateral pinch position, and under small muscle loads (0-5 N) with the thumb in flexion, extension, abduction, adduction, and neutral positions. Contact areas of articular surfaces of the thumb carpometacarpal joint were determined for these positions using a stereophotogrammetric technique. The lateral pinch position produced contact areas predominantly on the central, volar, and volar-ulnar regions of the trapezium and the metacarpal. In three specimens, contact areas were distinctly separated between the dorsoradial and volar-ulnar regions, and in one specimen, from a man, contact occurred exclusively on the dorsoradial region of the trapezium. Using stereophotogrammetry, maps of cartilage thickness also were determined for a subset of nine specimens. The volar-ulnar, ulnar, and dorsoradial regions of the trapezium were the most common sites of thin cartilage, and these may be sites of cartilage wear.(ABSTRACT TRUNCATED AT 250 WORDS)     

Capacity and power control for CDMA microcells

Capacity and power control issues are considered for urban CDMA microcells that operate on channels characterized by log-normal shadowing and Nakagami fading. The effects of fading on the desired and interfering signals, variations in the shadow standard deviation, imperfect power control, and the requiredE _b /N _o for satisfactory link operation are investigated. It is shown that the reverse channel is relatively insensitive, and the forward channel very sensitive, to shadow and fading variations. Power control error is shown to significantly degrade reverse channel capacity. Twobiased forward channel power control strategies are introduced to enhance existing unbiasedbalancing forward channel power control algorithms.This research has been supported by BNR Inc.     

Microscopic Origin of Casimir-Polder Forces

We establish a general relation between dispersion forces. First, based on QED in causal media, leading-order perturbation theory is used to express both the single-atom Casimir-Polder and the two-atom van der Waals potentials in terms of the atomic polarizabilities and the Green tensor for the body-assisted electromagnetic field. Endowed with this geometry-independent framework, we then employ the Born expansion of the Green tensor together with the Clausius-Mosotti relation to prove that the macroscopic Casimir-Polder potential of an atom in the presence of dielectric bodies is due to an infinite sum of its microscopic many-atom van der Waals interactions with the atoms comprising the bodies. This theorem holds for inhomogeneous, dispersing, and absorbing bodies of arbitrary shapes and arbitrary atomic composition on an arbitrary background of additional magnetodielectric bodies.     

Alcoholism at the time of injury among trauma center patients: Vehicular crash victims compared with other patients

A structured in-depth interview employing standardized criteria was used to determine the prevalence of lifetime and current alcohol dependence (alcoholism) in unselected consecutive patients admitted to a regional Level I trauma center. Of 629 patients, 157 (25.0%) were current alcoholics at the time of injury. An additional 87 (13.8%) were diagnosed as lifetime non-current alcoholics. There was no significant difference in the rates of current alcohol dependence among patients injured in vehicular crashes (23.5%), other unintentional trauma victims (29.3%), and those injured as a result of violence (24.6%). Of BAC + (blood alcohol concentration positive) patients, 54.5% were current alcoholics. However, 14.4% of alcohol-negative patients were also diagnosed as alcohol dependent.