Criticality in multicomponent spherical models : results and cautions

To enable the study of criticality in multicomponent fluids, the standard spherical model is generalized to describe an \ns-species hard core lattice gas. On introducing \ns spherical constraints, the free energy may be expressed generally in terms of an \ns\times\ns matrix describing the species interactions. For binary systems, thermodynamic properties have simple expressions, while all the pair correlation functions are combinations of just two eigenmodes. When only hard-core and short-range overall attractive interactions are present, a choice of variables relates the behavior to that of one-component systems. Criticality occurs on a locus terminating a coexistence surface; however, except at some special points, an unexpected ``demagnetization effect'' suppresses the normal divergence of susceptibilities at criticality and distorts two-phase coexistence. This effect, unphysical for fluids, arises from a general lack of symmetry and from the vectorial and multicomponent character of the spherical model. Its origin can be understood via a mean-field treatment of an XY spin system below criticality.Comment: 4 figure

Criticality in Charge-asymmetric Hard-sphere Ionic Fluids

Phase separation and criticality are analyzed in $z$:1 charge-asymmetric ionic fluids of equisized hard spheres by generalizing the Debye-H\"{u}ckel approach combined with ionic association, cluster solvation by charged ions, and hard-core interactions, following lines developed by Fisher and Levin (1993, 1996) for the 1:1 case (i.e., the restricted primitive model). Explicit analytical calculations for 2:1 and 3:1 systems account for ionic association into dimers, trimers, and tetramers and subsequent multipolar cluster solvation. The reduced critical temperatures, $T_c^*$ (normalized by $z$), \textit{decrease} with charge asymmetry, while the critical densities \textit{increase} rapidly with $z$. The results compare favorably with simulations and represent a distinct improvement over all current theories such as the MSA, SPB, etc. For $z$$\ne$1, the interphase Galvani (or absolute electrostatic) potential difference, $\Delta \phi(T)$, between coexisting liquid and vapor phases is calculated and found to vanish as $|T-T_c|^\beta$ when $T\to T_c-$ with, since our approximations are classical, $\beta={1/2}$. Above $T_c$, the compressibility maxima and so-called $k$-inflection loci (which aid the fast and accurate determination of the critical parameters) are found to exhibit a strong $z$-dependence.Comment: 25 pages, 14 figures; last update with typos corrected and some added reference

Rhapsodically Speaking

Like timid pizzicatos riding a sustained legato, the cricket sounds outside my window are cradling themselves in the fused night noises. Rising in gentle crescendos above them are waves of wind; now they waken the leaves; soft bits of breeze sift through screen and curtain to move a curl across my cheek - shyly, like a child fearfully touching a dog; and shyly too, retire till the now tremulous vibrato of the crickets plays the nocturnal solo once more. The wind mounts again. It throbs against these brick walls; rudely musses my hair, disturbing my thoughts; the sleeper on the bed behind me moves in unconscious annoyance

Evolution of a Hospital Labor System: Technology, Coercion, and Conflict

The paper investigates the labor process at a private, nonprofit hospital, Children\u27s Charity Hospital of Hudson, between 1947 and 1978. The author explains changes in the labor system that hospital management made, such as adding to the number and variety of intermediate outputs, increasing mechanization, stratifying and specializing skills and authority, and replacing an informal, personalized organization by bureaucratic structures. The author contends that management\u27s choise of labor process characteristics depended not only on market and technical constraints but also on management\u27s desire to maintain and increase worker\u27s pace and accuracy and to secure its authority over their production activities. Put another way, considerations of power and of potential for conflict, not just of technically optimal input combinations, determined the characteristics of the hospital labor process

An appraisal of certain student personnel services in the Boston University College of Music.

Thesis (Ed.M.)--Boston Universit

What is the best way to identify patients with white-coat hypertension?

Ambulatory blood pressure monitoring is currently the gold standard for detecting patients with white-coat hypertension. Women and all patients with lower office systolic blood pressures, stage I hypertension, and no target organ damage are more likely to have white-coat hypertension (strength of recommendation [SOR]: B, based on prospective cohort studies). Self or home blood pressure monitoring has also been used to detect patients with white-coat hypertension. However, it has a low sensitivity (61%-68%) and low positive predictive value (PV+) (33%-48%) (SOR: B, short-term prospective cohort studies)

Formation of forearc basins by collision between seamounts and accretionary wedges : an example from the New Hebrides subduction zone

L'interprétation des données bathymétriques Seabeam obtenues le long de la fosse des Nouvelles-Hébrides permet de proposer un modèle en deux stades pour la formation de bassins avant-arc sub-insulaires. Ces bassins résultent de l'indentation du bas de la marge lors de la collision entre un mont sous-marin et l'arc ainsi que de la reconstruction du bas de la pente par accrétion de sédiments de la plaque plongeante et piégeage de sédiments provenant de l'arc. (Résumé d'auteur