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Fundamental Measure Theory (FMT) is a successful and versatile approach for describing the properties of the hard-sphere fluid and hard-sphere mixtures within the framework of classical density functional theory (DFT). Lutsko [Phys. Rev. E 102, 062137 (2020)] introduced a version of FMT containing two free parameters, to be fixed by additional physical constraints. Whereas Lutsko focused on the stability of crystalline phases, we introduce and employ two statistical mechanical sum rules pertinent for the fluid phase, that are not automatically satisfied by FMT. By minimizing the relative deviation between different routes to calculate the excess chemical potential and the isothermal compressibility we determine the two free parameters of the theory. Our results indicate that requiring consistency with these sum rules can improve the quality of predictions of FMT for properties of the hard-sphere fluid phase. We suggest that employing these (test particle) sum rules, which apply for any interparticle pair-potential, might provide a means of testing the performance and accuracy of general DFT approximations.

We use supervised machine learning together with the concepts of classical density functional theory to investigate the effects of interparticle attraction on the pair structure, thermodynamics, bulk liquid-gas coexistence, and associated interfacial phenomena in many-body systems. Local learning of the one-body direct correlation functional is based on Monte Carlo simulations of inhomogeneous systems with randomized thermodynamic conditions, randomized planar shapes of the external potential, and randomized box sizes. Focusing on the prototypical Lennard-Jones system, we test predictions of the resulting neural attractive density functional across a broad spectrum of physical behaviour associated with liquid-gas phase coexistence in bulk and at interfaces. We analyse the bulk radial distribution function $g(r)$ obtained from automatic differentiation and the Ornstein-Zernike route and determine i) the Fisher-Widom line, i.e.\ the crossover of the asymptotic (large distance) decay of $g(r)$ from monotonic to oscillatory, ii) the (Widom) line of maximal correlation length, iii) the line of maximal isothermal compressibility and iv) the spinodal by calculating the poles of the structure factor in the complex plane. The bulk binodal and the density profile of the free liquid-gas interface are obtained from density functional minimization and the corresponding surface tension from functional line integration. We also show that the neural functional describes accurately the phenomena of drying at a hard wall and of capillary evaporation for a liquid confined in a slit pore. Our neural framework yields results that improve significantly upon standard mean-field treatments of interparticle attraction. Comparison with independent simulation results demonstrates a consistent picture of phase separation even when restricting the training to supercritical states only., Comment: 21 pages, 9 figures

Measurements of local density fluctuations are crucial to characterizing the interfacial properties of equilibrium fluids. A specific case that has been well-explored involves the heightened compressibility of water near hydrophobic entities. Commonly, a spatial profile of local fluctuation strength is constructed from measurements of the mean and variance of solvent particle number fluctuations in a set of contiguous sub-volumes of the system adjacent to the solvo/hydrophobe. An alternative measure proposed by Evans and Stewart (J. Phys.: Condens. Matter 27, 194111 (2015)) defines a local compressibility profile in terms of the chemical potential derivative of the spatial number density profile. Using Grand Canonical Monte Carlo simulation, we compare and contrast the efficacy of these two approaches for a Lennard-Jones solvent at spherical and planar solvophobic interfaces, and SPC/E water at a hydrophobic spherical solute. Our principal findings are that: (i) the local compressibility profile $\chi({\bf r})$ of Evans and Stewart is considerably more sensitive to variations in the strength of local density fluctuations than the spatial fluctuation profile $F({\bf r})$ and can resolve much more detailed structure; (ii) while the local compressibility profile is essentially independent of the choice of spatial discretization used to construct the profile, the spatial fluctuation profile exhibits strong systematic dependence on the size of the subvolumes on which the profile is defined. We clarify the origin and nature of this finite-size effect., Comment: 12 pages, 6 figures

Let $A/\mathbb{Q}$ be a Jacobian variety and let $F$ be a totally real, tamely ramified, abelian number field. Given a character $\psi$ of $F/\mathbb{Q}$, Deligne's Period Conjecture asserts the algebraicity of the suitably normalised value $\mathcal{L}(A,\psi,1)$ at $z=1$ of the Hasse-Weil-Artin $L$-function of the $\psi$-twist of $A$. We formulate a conjecture regarding the integrality properties of the family of normalised $L$-values $(\mathcal{L}(A,\psi,1))_{\psi}$, and its relation to the Tate-Shafarevich group of $A$ over $F$. We numerically investigate our conjecture through $p$-adic congruence relations between these values., Comment: 24 pages

Simulations of water near extended hydrophobic spherical solutes have revealed the presence of a region of depleted density and accompanying enhanced density fluctuations.The physical origin of both phenomena has remained somewhat obscure. We investigate these effects employing a mesoscopic binding potential analysis, classical density functional theory (DFT) calculations for a simple Lennard-Jones (LJ) solvent and Grand Canonical Monte Carlo (GCMC) simulations of a monatomic water (mw) model. We argue that the density depletion and enhanced fluctuations are near-critical phenomena. Specifically, we show that they can be viewed as remnants of the critical drying surface phase transition that occurs at bulk liquid-vapor coexistence in the macroscopic planar limit, i.e.~as the solute radius $R_s\to\infty$. Focusing on the radial density profile $\rho(r)$ and a sensitive spatial measure of fluctuations, the local compressibility profile $\chi(r)$, our binding potential analysis provides explicit predictions for the manner in which the key features of $\rho(r)$ and $\chi(r)$ scale with $R_s$, the strength of solute-water attraction $\varepsilon_{sf}$, and the deviation from liquid-vapor coexistence of the chemical potential, $\delta\mu$. These scaling predictions are confirmed by our DFT calculations and GCMC simulations. As such our theory provides a firm basis for understanding the physics of hydrophobic solvation., Comment: 18 pages

We investigate density fluctuations in a liquid close to a solvophobic substrate at which a surface critical drying transition occurs. Using classical density functional theory, we determine three measures of the spatial extent and strength of the fluctuations, i.e., the local compressibility $\chi_{\mu}(z)$, the local thermal susceptibility $\chi_T(z)$ and the reduced density $\chi_*(z)$; $z$ is the distance from the substrate. Whilst the first measure is frequently used, the second and third were introduced very recently by Eckert et.al., Phys. Rev. Lett. 125, 268004 (2020). For state points in the critical drying regime, all three measures, each scaled by its bulk value, exhibit very similar forms and the ratio of $\chi_T(z)$ to $\chi_{\mu}(z)$, for fixed $z$ in the vapour-liquid transition region, is constant. Using a scaling treatment of surface thermodynamics we show that such behaviour is to be expected on general grounds., Comment: 7 pages, 3 figures. Accepted by Physical Review E

We investigate the origin of the density depletion and enhanced density fluctuations that occur in water in the vicinity of an extended hydrophobic solute. We argue that both phenomena are remnants of the critical drying surface phase transition that occurs at liquid-vapor coexistence in the macroscopic planar limit, ie. as the solute radius $R_s\to\infty$. Focusing on the density profile $\rho(r)$ and a sensitive spatial measure of fluctuations, the local compressibility profile $\chi(r)$, we develop a scaling theory which expresses the extent of the density depletion and enhancement in compressibility in terms of $R_s$, the strength of solute-water attraction $\varepsilon_s$, and the deviation from liquid-vapor coexistence $\delta\mu$. Testing the predictions against results of classical density functional theory for a simple solvent and Grand Canonical Monte Carlo simulations of a popular water model, we find that the theory provides a firm physical basis for understanding how water behaves at a hydrophobe., Comment: 5 pages, 4 figures. To appear in Phys. Rev. Lett

Density functional calculations can fail for want of an accurate exchange-correlation approximation. The energy can instead be extracted from a sequence of density functional calculations of conditional probabilities (CP-DFT). Simple CP approximations yield usefully accurate results for two-electron ions, the hydrogen dimer, and the uniform gas at all temperatures. CP-DFT has no self-interaction error for one electron, and correctly dissociates H2, both major challenges. For warm dense matter, classical CP-DFT calculations can overcome the convergence problems of Kohn-Sham DFT., Comment: 6 pages, 3 figures, 2 tables

Clarifying the factors that control the contact angle of a liquid on a solid substrate is a long-standing scientific problem pertinent across physics, chemistry and materials science. Progress has been hampered by the lack of a comprehensive and unified understanding of the physics of wetting and drying phase transitions. Using various theoretical and simulational techniques applied to realistic fluid models, we elucidate how the character of these transitions depends sensitively on both the range of fluid-fluid and substrate-fluid interactions and the temperature. Our calculations uncover previously unrecognised classes of surface phase diagram which differ from that established for simple lattice models and often assumed to be universal. The differences relate both to the topology of the phase diagram and to the nature of the transitions, with a remarkable feature being a difference between drying and wetting transitions which persists even in the approach to the bulk critical point. Most experimental and simulational studies of liquids at a substrate belong to one of these previously unrecognised classes. We predict that while there appears to be nothing particularly special about water with regard to its wetting and drying behavior, superhydrophobic behavior should be more readily observable in experiments conducted at high temperatures than at room temperature., Comment: 10 pages plus SI

We re-visit the competition between attractive and repulsive interparticle forces in simple fluids and how this governs and connects the macroscopic phase behavior and structural properties as manifest in pair correlation functions. We focus on the asymptotic decay of the total correlation function $h(r)$ which is, in turn, controlled by the form of the pair direct correlation function $c(r)$. The decay of $r h(r)$ to zero can be either exponential (monotonic) if attraction dominates repulsion and exponentially damped oscillatory otherwise. The Fisher-Widom (FW) line separates the phase diagram into two regions characterized by the two different types of asymptotic decay. We show that there is a new and physically intuitive thermodynamic criterion which approximates well the actual FW line. This new criterion defines a line where the isothermal compressibility takes its ideal gas value $\chi_T=\chi_T^\text{id}$. We test our hypothesis by considering four commonly used models for simple fluids. In all cases the new criterion yields a line in the phase diagram that is close to the actual FW line for the thermodynamic state points that are most relevant. We also investigate (Widom) lines of maximal correlation length, emphasizing the importance of distinguishing between the true and Ornstein-Zernike correlation lengths

This is an investigation into the possible existence and consequences of a Birch-Swinnerton-Dyer-type formula for L-functions of elliptic curves twisted by Artin representations. We translate expected properties of L-functions into purely arithmetic predictions for elliptic curves, and show that these force some peculiar properties of the Tate-Shafarevich group, which do not appear to be tractable by traditional Selmer group techniques. In particular we exhibit settings where the different p-primary components of the Tate-Shafarevich group do not behave independently of one another. We also give examples of "arithmetically identical" settings for elliptic curves twisted by Artin representations, where the associated L-values can nonetheless differ, in contrast to the classical Birch-Swinnerton-Dyer conjecture., Comment: 27 pages, new version

Understanding the phase behaviour of mixtures continues to pose challenges, even for systems that might be considered "simple". Here we consider a very simple mixture of two colloidal and one non-adsorbing polymer species which can be simplified even further to a size-asymmetrical binary mixture, in which the effective colloid-colloid interactions depend on the polymer concentration. We show that this basic system exhibits surprisingly rich phase behaviour. In particular, we enquire whether such a system features only a liquid-vapor phase separation (as in one-component colloid-polymer mixtures) or whether, additionally, liquid-liquid demixing of two colloidal phases can occur. Particle-resolved experiments show demixing-like behaviour, but when combined with bespoke Monte Carlo simulations, this proves illusory, and we reveal that only a single liquid-vapor transition occurs. Progressive migration of the small particles to the liquid phase as the polymer concentration increases gives rise to composition inversion - a maximum in the large particle concentration in the liquid phase. Near criticality the density fluctuations are found to be dominated by the larger colloids., Comment: submitted to J. Chem. Phys

We describe and then elaborate the model of trading zones first presented in Collins et al 2007, Trading Zones and Interactional Expertise. We believe this expanded version of the model includes some very important but previously overlooked ways for separate language communities to communicate. We illustrate the argument with examples., Comment: 9 pages, 1 Figure

In classical density functional theory (DFT) the part of the Helmholtz free energy functional arising from attractive inter-particle interactions is often treated in a mean-field or van der Waals approximation. On the face of it, this is a somewhat crude treatment as the resulting functional generates the simple random phase approximation (RPA) for the bulk fluid pair direct correlation function. We explain why using standard mean-field DFT to describe inhomogeneous fluid structure and thermodynamics is more accurate than one might expect based on this observation. By considering the pair correlation function $g(x)$ and structure factor $S(k)$ of a one-dimensional model fluid, for which exact results are available, we show that the mean-field DFT, employed within the test-particle procedure, yields results much superior to those from the RPA closure of the bulk Ornstein-Zernike equation. We argue that one should not judge the quality of a DFT based solely on the approximation it generates for the bulk pair direct correlation function., Comment: 9 pages, 3 figures

We report a theoretical and simulation study of the drying and wetting phase transitions of a truncated Lennard-Jones fluid at a flat structureless wall. Binding potential calculations predict that the nature of these transitions depends on whether the wall-fluid attraction has a long ranged (LR) power law decay, or is instead truncated, rendering it short ranged (SR). Using grand canonical Monte Carlo simulation and classical density functional theory we examine both cases in detail. We find that for the LR case wetting is first order, while drying is continuous (critical) and occurs exactly at zero attractive wall strength, ie. in the limit of a hard wall. In the SR case, drying is also critical but the order of the wetting transition depends on the truncation range of the wall-fluid potential. We characterize the approach to critical drying and wetting in terms of the density and local compressibility profiles and via the finite-size scaling properties of the probability distribution of the overall density. For the LR case, where the drying point is known exactly, this analysis allows us to estimate the exponent $\nu_\parallel$ which controls the parallel correlation length, i.e. the extent of vapor bubbles at the wall. Surprisingly, the value we obtain is over twice that predicted by mean field and renormalization group calculations, despite the fact that our three dimensional system is at the upper critical dimension where mean field theory for critical exponents is expected to hold. We suggest reasons for this discrepancy., Comment: 22 pages, 19 figures

Using classical density functional theory (DFT) we calculate the density profile $\rho({\mathbf r})$ and local compressibility $\chi({\mathbf r})$ of a simple liquid solvent in which a pair of blocks with (microscopic) rectangular cross-section are immersed. We consider blocks that are solvophobic, solvophilic and also ones that have both solvophobic and solvophilic patches. Large values of $\chi({\mathbf r})$ correspond to regions in space where the liquid density is fluctuating most strongly. We seek to elucidate how enhanced density fluctuations correlate with the solvent mediated force between the blocks, as the distance between the blocks and the chemical potential of the liquid reservoir vary. For sufficiently solvophobic blocks, at small block separations and small deviations from bulk gas-liquid coexistence, we observe a strongly attractive (near constant) force, stemming from capillary evaporation to form a low density gas-like intrusion between the blocks. The accompanying $\chi({\mathbf r})$ exhibits structure which reflects the incipient gas-liquid interfaces that develop. We argue that our model system provides a means to understanding the basic physics of solvent mediated interactions between nanostructures, and between objects such as proteins in water, that possess hydrophobic and hydrophilic patches., Comment: 19 pages, 21 figures

The notion of interactional expertise is explained starting with its origins and discussing its many applications. Interactional expertise is the ability to understand a technical area purely be deeply immersed in its 'practice-language' without actually practising. One of its many applications is to explain how large sciences are managed., Comment: 39 pages, one table

We report a detailed simulation and classical density functional theory study of the drying transition in a realistic model fluid at a smooth substrate. This transition (in which the contact angle $\theta\to 180^\circ$) is shown to be critical for both short ranged and long-ranged substrate-fluid interaction potentials. In the latter case critical drying occurs at exactly zero attractive substrate strength. This observation permits the accurate elucidation of the character of the transition via a finite-size scaling analysis of the density probability function. We find that the critical exponent $\nu_\parallel$ that controls the parallel correlation length, i.e. the extent of vapor bubbles at the wall, is over twice as large as predicted by mean field and renormalization group calculations. We suggest a reason for the discrepancy. Our findings shed new light on fluctuation phenomena in fluids near hydrophobic and solvophobic interfaces., Comment: 5 pages plus supplementary information. To appear in Physical Review Letters

For binary fluid mixtures of spherical particles in which the two species are sufficiently different in size, the dominant wavelength of oscillations of the pair correlation functions is predicted to change from roughly the diameter of the large species to that of the small species along a sharp crossover line in the phase diagram [C. Grodon, M. Dijkstra, R. Evans & R. Roth, J.Chem.Phys. 121, 7869 (2004)]. Using particle-resolved colloid experiments in 3d we demonstrate that crossover exists and that its location in the phase diagram is in quantitative agreement with the results of both theory and our Monte-Carlo simulations. In contrast with previous work [J. Baumgartl, R. Dullens, M. Dijkstra, R. Roth & C. Bechinger, Phys.Rev.Lett. 98, 198303 (2007)], where a correspondence was drawn between crossover and percolation of both species, in our 3d study we find that structural crossover is unrelated to percolation.

Employing smart Monte Carlo sampling techniques within the grand canonical ensemble, we investigate the properties of water at a model hydrophobic substrate. By reducing the strength of substrate-water attraction we find that fluctuations in the local number density, quantified by a rigorous definition of the local compressibility $\chi(z)$, increase rapidly for distances $z$ within $1$ or $2$ molecular diameters from the substrate as the degree of hydrophobicity, measured by the macroscopic contact angle $\theta$, increases. Our simulations provide evidence for a continuous (critical) drying transition as the substrate-water interaction becomes very weak: $\cos(\theta)\to -1$. We speculate that the existence of such a transition might account for earlier simulation observations of strongly enhanced density fluctuations.

We investigate the suitability of the local compressibility chi(z) as a measure of the solvophobicity or hydrophobicity of a substrate. Defining the local compressibility as the derivative of the local one-body density w.r.t. the chemical potential at fixed temperature, we use density functional theory (DFT) to calculate chi(z) for a model fluid, close to bulk liquid-gas coexistence, at various planar substrates. These range from a `neutral' substrate with a contact angle of approximately 90 degrees, which favours neither the liquid nor the gas phase, to a very solvophobic, purely repulsive substrate which exhibits complete drying (i.e. contact angle 180 degrees). We find that the maximum in the local compressibility, which occurs within one-two molecular diameters of the substrate, and the integrated quantity chi_ex (the surface excess compressibility, defined below) both increase rapidly as the contact angle increases and the substrate becomes more solvophobic. The local compressibility provides a more pronounced indicator of solvophobicity than the density depletion in the vicinity of the surface which increases only weakly with increasing contact angle. When the fluid is confined in a parallel slit with two identical solvophobic walls, or with competing solvophobic and solvophilic walls, chi(z) close to the solvophobic wall is altered little from that at the single substrate. We connect our results with simulation studies of water near to hydrophobic surfaces exploring the relationship between chi(z) and fluctuations in the local density and between chi_ex and the mean-square fluctuation in the number of adsorbed molecules., Comment: 23 pages, 9 figures, submitted to Journal of Physics: Condensed Matter as a Special Issue Article

We consider a simple fluid confined between two parallel walls (substrates), separated by a distance L. The walls exert competing surface fields so that one wall is attractive and may be completely wet by liquid (it is solvophilic) while the other is solvophobic. Such asymmetric confinement is sometimes termed a `Janus Interface'. The second wall is: (i) purely repulsive and therefore completely dry (contact angle 180 degrees) or (ii) weakly attractive and partially dry (the contact angle is typically in the range 160-170 degrees). At low temperatures, but above the bulk triple point, we find using classical density functional theory (DFT) that the fluid is highly structured in the liquid part of the density profile. In case (i) a sequence of layering transitions occurs: as L is increased at fixed chemical potential (mu) close to bulk gas--liquid coexistence, new layers of liquid-like density develop discontinuously. In contrast to confinement between identical walls, the solvation force is repulsive for all wall separations and jumps discontinuously at each layering transition and the excess grand potential exhibits many metastable minima as a function of the adsorption. For a fixed temperature T=0.56Tc, where Tc is the bulk critical temperature, we determine the transition lines in the L, mu plane. In case (ii) we do not find layering transitions and the solvation force oscillates about zero. We discuss how our mean-field DFT results might be altered by including effects of fluctuations and comment on how the phenomenology we have revealed might be relevant for experimental and simulation studies of water confined between hydrophilic and hydrophobic substrates, emphasizing it is important to distinguish between cases (i) and (ii)., Comment: 16 pages, 13 figures

From experimental studies it is well-known that colloidal particles suspended in a near-critical binary solvent exhibit interesting aggregation phenomena, often associated with colloidal phase transitions, and assumed to be driven by long-ranged solvent mediated (SM) interactions (critical Casimir forces), set by the (diverging) correlation length of the solvent. We present the first simulation and theoretical study of an explicit model of a ternary mixture that mimics this situation. Both the effective SM pair interactions and the full ternary phase diagram are determined for Brownian discs suspended in an explicit two-dimensional supercritical binary liquid mixture. Gas-liquid and fluid-solid transitions are observed in a region that extends well-away from criticality of the solvent reservoir. We discuss to what extent an effective pair-potential description can account for the phase behavior we observe. Our study provides a fresh perspective on how critical fluctuations of the solvent might influence colloidal self-assembly., Comment: 4 pages, 4 figures

This chapter examines three different classroom teacher perspectives when using ASSIST-ME project formative assessment methods as described in the introductory chapter. The first 'teacher perspective' is about changes in teacher self-efficacies while using formative assessment methods as monitored by a pre- and post-teacher questionnaire. Teachers who tried the unfamiliar formative methods of assessment (see introductory book chapter for these methods) as well as their colleagues who did not were surveyed. The second 'teacher perspective' examines changes in teachers' subjective theories while trying project-specific formative assessment methods in Czech Republic. Analyses are done through case studies and interviews. The final part of the chapter looks at teacher perspectives while using an Internet-based application to facilitate formative assessment. The teacher use of the application and their feedback about its utility are discussed. [For the complete volume, "Transforming Assessment: Through an Interplay between Practice, Research and Policy. Contributions from Science Education Research. Volume 4," see ED611936.]

This chapter surveys the status of educational systems and assessment practices across eight European countries that are part of the ASSIST-ME project. First, variations in the country's educational systems are examined to identify possible connections between systems and educational practices. Such associations are useful both for understanding different existing assessment conditions as well as for providing possible pathways for change. Next, the chapter takes a closer look at teacher practices in these educational systems in order to identify the actual assessment practices of teachers in each country. With these understandings of the systems and current uses of assessment, it is possible to identify affordances and challenges for improving assessment practices. [For the complete volume, "Transforming Assessment: Through an Interplay between Practice, Research and Policy. Contributions from Science Education Research. Volume 4," see ED611936.]

The curricular statements of most European countries contain goals for scientific literacies and process competencies. However, we argue that direct targeting by teachers of these goals, or active achievement of them by students, may not actually occur. We report our experience of implementing a teacher development initiative aimed at supporting teachers to target these goals more directly through drawing on the natural relationship between scientific literacy and inquiry-based activities, while also focusing on the support potential of self-efficacy. In workshops, science teachers used concept networks of their national scientific literacy statements to help identify literacy-related objectives and then transformed existing lessons towards these objectives using inquiry in order to achieve the goals. We collected open-ended answers to standard questions concerning the strengths and weaknesses of the workshops, along with quantitative assessments of participant self-efficacy taken two or three times during each trial. We found that the use of concept networks of national scientific literacy statements helped science teachers readily identify objectives and then match inquiry-based lessons to achieve them. Also, societally relevant goals, when taught using engaging IBST/L methods, can be used to actively increase self-efficacy for the teaching and learning of science and hence provide substantial motivation for teachers and students. [For the complete volume, "Professional Development for Inquiry-Based Science Teaching and Learning. Contributions from Science Education Research. Volume 5," see ED613991.]

We investigate the response to temperature of a well-known colloid-polymer mixture. At room temperature, the critical value of the second virial coefficient of the effective interaction for the Asakura-Oosawa model predicts the onset of gelation with remarkable accuracy. Upon cooling the system, the effective attractions between colloids induced by polymer depletion are reduced, because the polymer radius of gyration is decreases as the theta-temperature is approached. Paradoxically, this raises the effective temperature, leading to "melting" of colloidal gels. We find the Asakura-Oosawa model of effective colloid interactions with a simple description of the polymer temperature response provides a quantitative description of the fluid-gel transition. Further we present evidence for enhancement of crystallisation rates near the metastable critical point., Comment: 13 pages

We report a detailed study, using state-of-the-art simulation and theoretical methods, of the depletion potential between a pair of big hard spheres immersed in a reservoir of much smaller hard spheres, the size disparity being measured by the ratio of diameters q=\sigma_s/\sigma_b. Small particles are treated grand canonically, their influence being parameterized in terms of their packing fraction in the reservoir, \eta_s^r. Two specialized Monte Carlo simulation schemes --the geometrical cluster algorithm, and staged particle insertion-- are deployed to obtain accurate depletion potentials for a number of combinations of q\leq 0.1 and \eta_s^r. After applying corrections for simulation finite-size effects, the depletion potentials are compared with the prediction of new density functional theory (DFT) calculations based on the insertion trick using the Rosenfeld functional and several subsequent modifications. While agreement between the DFT and simulation is generally good, significant discrepancies are evident at the largest reservoir packing fraction accessible to our simulation methods, namely \eta_s^r=0.35. These discrepancies are, however, small compared to those between simulation and the much poorer predictions of the Derjaguin approximation at this \eta_s^r. The recently proposed morphometric approximation performs better than Derjaguin but is somewhat poorer than DFT for the size ratios and small sphere packing fractions that we consider. The effective potentials from simulation, DFT and the morphometric approximation were used to compute the second virial coefficient B_2 as a function of \eta_s^r. Comparison of the results enables an assessment of the extent to which DFT can be expected to correctly predict the propensity towards fluid fluid phase separation in additive binary hard sphere mixtures with q\leq 0.1., Comment: 16 pages, 9 figures, revised treatment of morphometric approximation and reordered some material

We determine the solvent mediated contribution to the effective potentials for model colloidal or nano- particles dispersed in a binary solvent that exhibits fluid-fluid phase separation. Using a simple density functional theory we calculate the density profiles of both solvent species in the presence of the `colloids', which are treated as external potentials, and determine the solvent mediated (SM) potentials. Specifically, we calculate SM potentials between (i) two colloids, (ii) a colloid and a planar fluid-fluid interface, and (iii) a colloid and a planar wall with an adsorbed wetting film. We consider three different types of colloidal particles: colloid A which prefers the bulk solvent phase rich in species 2, colloid C which prefers the solvent phase rich in species 1, and `neutral' colloid B which has no strong preference for either phase, i.e. the free energies to insert the colloid into either of the coexisting bulk phases are almost equal. When a colloid which has a preference for one of the two solvent phases is inserted into the disfavored phase at statepoints close to coexistence a thick adsorbed `wetting' film of the preferred phase may form around the colloids. The presence of the adsorbed film has a profound influence on the form of the SM potentials., Comment: 17 Pages, 13 Figures. Accepted for publication in Journal of Chemical Physics

We investigate the interfacial phase behavior of a binary fluid mixture composed of repulsive point Yukawa particles. Using a simple approximation for the Helmholtz free energy functional, which yields the random phase approximation (RPA) for the pair direct correlation functions, we calculate the equilibrium fluid density profiles of the two species of particles adsorbed at a planar wall. We show that for a particular choice (repulsive exponential) of the wall potentials and the fluid pair-potential parameters, the Euler-Lagrange equations for the equilibrium fluid density profiles may be transformed into a single ordinary differential equation and the profiles obtained by a simple quadrature. For certain other choices of the fluid pair-potential parameters fluid-fluid phase separation of the bulk fluid is observed. We find that when such a mixture is exposed to a planar hard-wall, the fluid exhibits complete wetting on the species 2 poor side of the binodal, i.e. we observe a thick film of fluid rich in species 2 adsorbed at the hard-wall. The thickness of the wetting film grows logarithmically with the concentration difference between the fluid state-point and the binodal and is proportional to the bulk correlation length of the intruding (wetting) fluid phase. However, for state points on the binodal that are further from the critical point, we find there is no thick wetting film. We determine the accompanying line of first-order (pre-wetting) surface phase transitions which separate a thin and thick adsorbed film. We show that for some other choices of repulsive wall potentials the pre-wetting line is still present, but its location and extent in the phase diagram is strongly dependent on the wall-fluid interaction parameters., Comment: 11 pages, 7 figures. Accepted for publication in Journal of Chemical Physics

We comment on a recent theory of dynamic wetting, that is based directly upon a model for interface formation, introduced by Shikhmurzaev. We argue that the treatment of surface tension and its relaxation, inherent in the original model, is physically flawed., Comment: comment submitted to Journal of Colloid and Interface Science

With some notable exceptions, the school critics in the first and second "waves" of restructuring have largely neglected problems of resistance in implementation of reform. The primary task of managing change is not technical, but motivational. Building commitment to innovation among those who must implement it requires a focus on readiness. Implementation depends on four change dimensions that often impede restructuring efforts: (1) substance (the content of reform); (2) staff (the faculty's willingness and capacity for change); (3) setting (the strength of a school as an organization); and (4) leadership. Problems encountered in the first three dimensions place an exceptional burden on the fourth. Authentic leadership is needed to overcome these obstacles; leaders must no longer aim at manipulating subordinates, but at motivating followers who invest themselves actively and become self-managing, engaged participants. Five biases for innovative leadership action include clarity, participation, communication, recognition, and confrontation (versus avoidance). All these artful endeavors are effective when rooted in authenticity. Authentic leaders demonstrate a clear commitment to new goals while inspiring, pushing, modeling, advocating, and confronting. At the same time, they show a strong investment in teachers by acknowledging, encouraging, rewarding, respecting, and listening. (Contains 20 references.) (MLH)

The Cincinnati (Ohio) Public School System was evaluated for the eighth year on progress on ongoing issues resulting from the Bronson Settlement, a court ordered equal education program. This year's evaluation focused on staff racial balance, the Coalition of Innovative Schools, student discipline, and continuation of Bronson initiatives. The district was released from continued court involvement in staff racial balance when the teaching staffs of each district school were brought within the established guidelines in September, 1991. The Coalition for Innovative Schools was modified in 1991, and the success experienced in the first years of the program was documented once again. The district addressed student discipline, focusing on the disproportionate number of suspensions of black students through court-instigated recommendations, increases in the in-school suspension classes, involving many of the staff and students in disciples-related training programs, and work done by the Discipline and Truancy Improvement Team. Review of the district and its board's past support for Bronson initiatives suggests a firm, ongoing commitment to equal education in Cincinnati. Appendixes contain supporting documents and include the court decision on staff racial balance, an evaluation report, a study of racial disparities in student discipline, a Discipline and Truancy Improvement Team final report, a summary of suspensions, minutes of the Community Wide Task Force meeting, and a report on Taeuber Index values. (JB)

A study was conducted to determine whether existing work tests affected the timing and quality of jobs found after a period during which a person both received welfare benefits and had to register with the Employment Service (ES) in connection with their receipt. Six measurable aspects of a work test applicable to individuals were identified: Individuals could be (1) called into the ES office, (2) called in frequently, (3) questioned about job search activities, (4) asked for proof of job search activities, (5) referred to a job, and/or (6) pressured to accept a job. Based on a survey of 1966 Food Stamp (FS) and Aid to Families with Dependent Children (AFDC) and Aid to Families with Dependent Children of Unemployed Fathers (AFDC-UF), the study was conducted in five cities using a questionnaire designed to capture employment experience following a stretch of unemployment or part-time employment during which respondents received FS or AFDC/AFDC-UF benefits. Three principal concerns were (1) how the application of the work tests varied by city and within cities by type of individual; (2) how the different work tests influenced job search patterns; and (3) how they influenced employment behavior. The overall conclusion is that results of the study provide a pessimistic picture of the usefulness of existing work tests in encouraging registrants to return to work. This report organizes the findings and conclusions under each of the three principle concerns and presents general conclusions and recommendations in the form of policy alternatives. (JT)

One objective of this study was to discover whether education of students on the 45-15 plan differed from that provided on the traditional schedule. Another objective was to assess the attitudes of the educators, parents, students, and business people of Prince William County toward the two plans. The educational evaluation compared, across calendars, indicators of student achievement and quality of education such as test scores, grades, failure rates, attendance, extracurricular activities, course offerings, pursuit of further education by high school graduates, and summer school attendance. Results showed that education afforded by the two plans did not differ, but attitudes about them were considerably polarized. Negative aspects of the 45-15 plan included potential problems involving student use of time outside of school, vacations and time spent with the family, and opportunities for part-time jobs. (Author/LD)

A look at the case method of studying higher education ministries begins with an essay on the use of the method and is followed by three case studies. In the introductory essay, Robert A. Evans discusses the advantages of the method: that it represents slices of real life and not imagined illustrations of issues, that it can focus on specific issues that require examination, and that it can facilitate progress toward three goals of instruction: wisdom, maturity, and discernment. Hints for teaching and learning the case are given including the instructor role, preparation for discussion, and teaching tools. The first case study presented, by Douglas H. Gregg, examines the campus ministry's role in helping a new and controversial faculty member deal with a difficult academic issue. The second case study, described by Alice Frazer Evans, looks at the role of a woman pastor in dealing with the problems of Iranian students on the campus shortly after the 1979 taking of American hostages in Iran. The final case study, also by Alice Frazer Evans, focuses on the issue of student desire for opportunities for worship at a state college. In each case study, ideas are presented for the uses of the case and areas for possible discussion. (MSE)

While the prediction of college grade point average (GPA) has been extensively investigated, research results seem inconclusive. Recent developments in the realm of intelligence have emphasized word knowledge and world knowledge. These two components were investigated relative to college GPA in a group of elementary and secondary student teachers (N=137) and in a group of college freshmen (N=36). Subjects were administered the Nelson-Denny Reading Test to measure reading rate and reading comprehension, the Peabody Individual Achievement Test (PIAT) to measure general world knowledge, and the Peabody Picture Vocabulary Test Revised (PPVT-R) to measure word knowledge. Further information was gathered to provide values for the subjects' high school and college GPA's. Data analysis from both groups provided similar findings: high school GPA and the score from the PPVT-R were the best predictors of college GPA with high school GPA being the best single predictor. These findings suggest that past behavior is a good predictor of future behavior. Since the addition of scores from the PPVT-R provided an even better prediction model, word knowledge may be a significant factor in predicting college GPA. The fact that both the PPVT-R and the PIAT, tests designed for high school students, proved difficult for some subjects may raise other issues of concern to educators and researchers alike. (NRB)

The factors which discourage prospective teachers from pursuing teaching careers are examined in this study. College freshmen from a medium-sized engineering university in the Midwest were selected to participate in the investigation. Based on responses to a questionnaire, these students were grouped as "teaching oriented" and "non-teaching oriented." Reasons for not teaching given by the "teaching oriented" students (N=20) included, in order of priority: (1) low salary; (2) not wanting to do the typical things that teachers do each day; (3) concern for job security; (4) low maximum salaries after years of work; and (5) poor job availability. The findings of this study confirm concerns about the level of teaching salaries as a major deterrent to prospective teachers. It was also stated that increased guidance counselor encouragement might add to the number of "teacher oriented" students who would pursue teaching careers. Appendices contain the survey forms used in the study. (ML)

This analysis originally prepared for the Japan Study Meeting, held November 1985, compares high school graduates in the United States and Japan who will not attend college, and includes directions of vocational training in both countries. Vocational training in the United States involves five areas: secondary schools, post-secondary schools, proprietary schools, formal apprenticeships, and employee training programs. Course areas divide into types of institutions, race, and sex. Females are represented most in office and health occupations. Males are over-represented in agriculture, technical trades, and industrial occupation training programs. Transition to the full-time labor force is discussed. Information on Japanese youth cites fewer public vocational opportunities and similar sex ratios in curriculum choices, but finds the employees to be the main source of vocational education rather than post-secondary training institutions, and mentions greater use of employment services to secure post-school employment. The report finds there is not a close relationship between types of training received and the occupation in which an individual is engaged. The report concludes with 19 tables of data and four pages of references. (CC)

This is a critical review of the analytical models developed by the U.S. Army to predict training device effectiveness. The Simulation Systems Technical Area of the U.S. Army Research Institute for the Behavioral and Social Sciences performed the research. Special consideration is given to a family of models known collectively as TRAINVICE. These four models differ in several important ways, although they are all intended to provide an index of transfer potential. The variables considered in the calculation of the indices are assigned different degrees of emphasis in each model. In selected cases a variable is completely ignored: e.g., the instructional features of a training device. The preparatory analyses employed to estimate the values of each variable change from model to model. The combinatorial procedures used to calculate an index of effectiveness from the variable values are different in each model. The principal points of difference among the various predictive models are presented to facilitate a comparative assessment of their merit. Results of the analysis and subsequent validation will provide a basis for the selection and refinement of one or more of the models for incorporation into a defined set of procedures for specifying training device effectiveness. (Author/DWH)

Because resistance is inevitable, the primary task of managing change is motivational, not technical. Implementation depends on five change dimensions: reform content, faculty willingness and capacity for change, the school's organizational strength, support and training, and leadership. Innovation is fostered by clarity and focus, participation, communication, recognition, and confrontation. (Contains 18 references.) (MLH)