Approximate Theoretical Calculation of Continuum Opacities

An approxhnate procedure is described for the theoretical calculation of the spectral absorption coefficient produced by bound-free and free-free transitions in plasmas containing polyelectronic atoms and ions. Our method of calculation is based on the assumption that only two ionized species make important contributions to the opacity and that these two ionic constituents are present in equal concentrations. The approximate formulas are shown to yield results that are in good accord with estimates based on detailed numerical computations for nitrogen

Contribution à l'étude de la validité de différents modèles, utilisés lors de l'adsorption de solutés sur charbon actif

Les résultats de l'adsorption sur charbon actif en poudre de solutions aqueuses de différents composés organiques: phénol, aniline, nitrobenzène, acide salicylique, nitro-4 phénol, méthyl-2 dinitro-4,6 phénol, phénylalanine et tyrosine ont été traités à l'aide des équations de Langmuir, Elovich, Freundlich, Temkin, Fowler-Guggenheim, Hill et De Boer, Kiselev afin de déterminer divers paramètres d'équilibre: la capacité maximum d'adsorption, l'énergie d'adsorption, l'énergie d'interaction, les constantes d'équilibre adsorbat-adsorbant et les interactions (éventuelles) entre les molécules adsorbées.La relation de Temkin (3=RTt~Q In KoC permet de déterminer la variation de l'énergie d'adsorption ~Q et la constante Ko de l'équilibre (~3 est le degré de re- couvrement du charbon par le soluté, et C la concentration à l'équilibre). L'équa- tion de Fowler-Guggenheim KC=~3/(1~3) Exp (2 ~ W/RT) conduit à la déter- mination de l'énergie d'interaction W entre molécules adsorbées et à une constante d'équilibre K. Par contre, dans l'équation de Hill et de De Boer KlC=~/(1~)) Exp [~/(1~) - K2~/RTI, K2 représente une constante d'énergie d'interaction entre molécules adsorbées et, dans celle de Kiselev KIC=~3/[(1+ ~) (1 + Kn~3)]~ Kn est une constante de formation de complexe éventuel entre molécules adsorbées. On vérifie que l'application de la relation de Temkin est satisfaisante pour tous les composés étudiés et permet de les classer selon leur affinité sur le charbon mais les résultats obtenus en utilisant les équations suivantes (Fowler ...) montrent qu'il n'y aurait pas de formation de complexe ou d'interaction entre molécules adsorbées.Analysis of the results of adsorption from aqueous liquid media onto activated carbon can be carried out by different models based on thermodynamic principles. Classically the Langmuir (eq. 1), Freundlich or Elovich (eq. 4) isotherms are used, which lead to the determination of an experimental maximum capacity, qm, and a constant K, characteristic of the adsorbate-adsorbent interactions. The following equations (Table I) have been transposed from the vapour phase to the liquid phase. With the Temkin relation: [Theta]=RT/[Delta]QlnK[inf]0C (eq. 6), it is possible to determine the variation of adsorption energy, [Delta]Q, between the adsorbed molecules and the solid phase, and the equilibrium constant K[inf]0 ([Theta] is the degree of surface covering of the solid phase [Theta]=q/qm, q is the adsorption capacity). The Fowler-Guggenheim equation: KC=[[Theta]/(1-[Theta])] Exp (2[Theta]W/RT) (eq. 7) gives the interaction energy, W, between the adsorbed molecules and an equilibrium constant, K. The Hill and De Boer relation: K[inf]1C=[Theta]/(1-[Theta])] Exp [[Theta]/(1-[Theta]) -K[inf]2[Theta]/RT] (eq. 8) yields an energetic interaction constant K[inf]2 (J.mol-¹) characteristic of the interactions between the adsorbate molecules and an equilibrium constant, K[inf]1. In the Kiselev relation: K[inf]1C=([Theta]/[(1-[Theta]) (1 + K[inf]n[Theta]] (eq. 9), K[inf]n is a complex formation constant between adsorbed molecules and K[inf]1 is a constant relative to the adsorbate-adsorbent interaction. Linearization of the equations of Langmuir, and Elovich leads to qm and K values. For the Freundlich relation, if the experiments are made at constant Co and variable concentrations of adsorbent, the Freundlich relation can be transformed as relation (5): q=qm (C/Co)[sup]1/n). The value of qm and K are reported in the Table II. When the values obtained by the Elovich equation are very different from the Langmuir relation, they are not in concordance with the experimental adsorption isotherm as shown on the Figures 4, 5 and 6.A value of qm is necessary to calculate the ([Theta](=q/qm) of the Temkin, Hill-De Boer, Fowler- Guggenheim and Kiselev equations; [Theta] is calculated with the Langmuir value of qm: the linearized relations were tested for the following compounds: phenol, aniline, nitrobenzene, salicylic acid, 4-nitro phenol, 2-methyl-4,6 dinitro phenol, phenylalanine and tyrosine, studied at micromolar concentration. The results are shown in Table II. The Temkin linearization is of good quality for all the compounds; an example is given on the Figure 1. For the others (Figs. 2, 3), the linearization is not always verified (Hill-De Boer for phenylalanine: Fig. 3a) and the results are framed two times in the Table II.With the obtention of the two parameters [Delta][Theta], K K, W; K[inf]1, K[inf]2 and K[inf]1, K[inf]n, the isotherm can be recalculated. The results for some solutes are on Figures 4, 5, 6, 7, 8. Relatively poor results are obtained for Fowler-Guggenheim, Kiselev or Hill-De Boer models, where no association is present between the adsorbed molecules.The evolution of the variation of the adsorption energy ([Delta][Theta]) is reported on the Figure 9 for the different compounds. The greatest values are obtained for nitrobenzene and 4-nitro-phenol (+ 80, + 40 kJ.mol-¹ probably due to the presence of the nitro group). All the values are positive (exothermic reaction ( [Delta][Theta]=-[Delta]H)) showing the affinity of molecules for the activated carbon

Emergence and Breaking of Duality Symmetry in Thermodynamic Behavior: Repeated Measurements and Macroscopic Limit

Thermodynamic laws are limiting behavior of the statistics of repeated measurements of an arbitrary system with a priori probability distribution. A duality symmetry arises, between Massieu-Guggenheim entropy and Gibbs entropy, in the limit of large number of measurements. This yields the fundamental thermodynamic relation and Hill-Gibbs-Duhem (HGD) equation as a dual pair. We show if the system itself has a second macroscopic limit that satisfies Callen's postulate that entropy being an Eulerian homogeneous function of all extensive variables, the symmetry is lost: the HGD equation reduces to the Gibbs-Duhem equation. This theory provides better logic to textbook thermodynamics, a clarification on nanothermodynamics, as well as novel ideas for a thermodynamic-like framework for single-cell biology.Comment: 4 page

Boston University Symphony Orchestra

This is the concert program of the Boston University Symphony Orchestra performance on Tuesday, December 9, 1997 at 8:00 p.m., at the Tsai Performance Center, 685 Commonwealth Avenue. Works performed were Elegy by Samuel Headrick, Symphonic Metamorphosis on Themes of Carl Maria von Weber by Paul Hindemith, Kommos B (Lament) by Theodore Antoniou, and Orchestral Excerpts from "Parsifal" (compiled by Lukas Foss) by Richard Wagner. Digitization for Boston University Concert Programs was supported by the Boston University Humanities Library Endowed Fund

Polymicrobial oral biofilm models: simplifying the complex

Over the past century, numerous studies have used oral biofilm models to investigate growth kinetics, biofilm formation, structure and composition, antimicrobial susceptibility and host–pathogen interactions. In vivo animal models provide useful models of some oral diseases; however, these are expensive and carry vast ethical implications. Oral biofilms grown or maintained in vitro offer a useful platform for certain studies and have the advantages of being inexpensive to establish and easy to reproduce and manipulate. In addition, a wide range of variables can be monitored and adjusted to mimic the dynamic environmental changes at different sites in the oral cavity, such as pH, temperature, salivary and gingival crevicular fluid flow rates, or microbial composition. This review provides a detailed insight for early-career oral science researchers into how the biofilm models used in oral research have progressed and improved over the years, their advantages and disadvantages, and how such systems have contributed to our current understanding of oral disease pathogenesis and aetiology

Dipole Moment of Indene

The dipole moment of indene is determined in three non-polar solventscyclohexane, CCl4 and CS2 covering a dielectric constant range of about 2.0 to 2.6. The experimental observations are treated in the manner of Guggenheim for obtaining the dipole moment values. The high value of about 0.85 D obtained for the moment of the compound is suggested as probably arising out of the resonance of the molecule between various structures as in the ease of the related compounds cyclopentadiene and fluorene

Effect of interaction and mobility on fixed-bed reactor performance

The roles of interaction and mobility in determining surface rates and hence reactor performance, as reflected in the space time values required for achieving a desired conversion or selectivity, are demonstrated. It is shown that localized adsorption models predict larger space times in comparison to the mobile models. Further, repulsive forces lead to higher space times in comparison to attractive forces, and the divergence between models is most marked for localized adsorption

Substrate specificity of amine oxidase

The tyramine oxidase activity of liver extracts found by Hare (1), the aliphatic amine oxidase activity of brain, kidney, and liver extracts observed by Pugh and Quastel (2), and the adrenalin oxidase activity of similar extracts noted by Blaschko, Richter, and Schlossman (3) were brought under a common enzyme view-point by the latter authors. They were able to show (4) that extracts of brain, instestine, kindey, and liver from a number of mammals or representatives of the birds, reptiles, amphibians, and fishes all acted to absorb oxygen in the presence of several amine substrates. Hare (1) had shown that tyramine and phenethylamine form ammonia in the course of such oxidations, and Richter (5) showed that an ethylamino and a dimethylamino compound, as well as a number of methylamino and amino compounds, all yield the corresponding alkyl-amines or ammonia in the enzymic oxidation. The conslusion that the demonstrated variey of such enzymic activity can be acribed to the presence of a single type pf amine oxidase was dependent in large part on observations that the relative activities of a preparation from one source on a series of substrates bear some relation to the relative activities exhibited by a preparation from another source. Further evidence depended on the action of certain amines as inihibitors and apparent competition between substrates when two oxidizable substrates are present in the system. The degree to which relative activities of different enzyme preparations were constant in a series of substrates was not good in the data reported, and the fact that Hare (1) had not been able to note activity of the liver preparations she used upon adrenalin as the substrate appeared to require special explanations

Potential of shock waves to remove calculus and biofilm

Effective calculus and biofilm removal is essential to treat periodontitis. Sonic and ultrasonic technologies are used in several scaler applications. This was the first feasibility study to assess the potential of a shock wave device to remove calculus and biofilms and to kill bacteria. Ten extracted teeth with visible subgingival calculus were treated with either shock waves for 1min at an energy output of 0.4mJ/mm2 at 3Hz or a magnetostrictive ultrasonic scaler at medium power setting for 1min, which served as a control. Calculus was determined before and after treatment planimetrically using a custom-made software using a grey scale threshold. In a second experiment, multispecies biofilms were formed on saliva-preconditioned bovine enamel discs during 64.5h. They were subsequently treated with shock waves or the ultrasonic scaler (N = 6/group) using identical settings. Biofilm detachment and bactericidal effects were then assessed. Limited efficiency of the shock wave therapy in terms of calculus removal was observed: only 5% of the calculus was removed as compared to 100% when ultrasound was used (P ≤ 0.0001). However, shock waves were able to significantly reduce adherent bacteria by three orders of magnitude (P ≤ 0.0001). The extent of biofilm removal by the ultrasonic device was statistically similar. Only limited bactericidal effects were observed using both methods. Within the limitations of this preliminary study, the shock wave device was not able to reliably remove calculus but had the potential to remove biofilms by three log steps. To increase the efficacy, technical improvements are still required. This novel noninvasive intervention, however, merits further investigatio