Droplet shapes on structured substrates and conformal invariance

We consider the finite-size scaling of equilibrium droplet shapes for fluid adsorption (at bulk two-phase co-existence) on heterogeneous substrates and also in wedge geometries in which only a finite domain $\Lambda_{A}$ of the substrate is completely wet. For three-dimensional systems with short-ranged forces we use renormalization group ideas to establish that both the shape of the droplet height and the height-height correlations can be understood from the conformal invariance of an appropriate operator. This allows us to predict the explicit scaling form of the droplet height for a number of different domain shapes. For systems with long-ranged forces, conformal invariance is not obeyed but the droplet shape is still shown to exhibit strong scaling behaviour. We argue that droplet formation in heterogeneous wedge geometries also shows a number of different scaling regimes depending on the range of the forces. The conformal invariance of the wedge droplet shape for short-ranged forces is shown explicitly.Comment: 20 pages, 7 figures. (Submitted to J.Phys.:Cond.Mat.

Slave Hounds and Abolition in the Americas

The lash and shackles remain two primary symbols of material degradation fixed in the historical memory of slavery in the Americas. Yet as recounted by states, abolitionists, travellers, and most importantly slaves themselves, perhaps the most terrifying and effective tool for disciplining black bodies and dominating their space was the dog. This article draws upon archival research and the published materials of former slaves, novelists, slave owners, abolitionists, Atlantic travelers, and police reports to link the systems of slave hunting in Cuba, Jamaica, Haiti, and the US South throughout the eighteenth and nineteenth centuries. Slave hounds were skillfully honed biopower predicated upon scenting, hearing, sighting, outrunning, outlasting, signaling, attacking, and sometimes terminating, black runaways. These animals permeated slave societies throughout the Americas and bolstered European ambitions for colonial expansion, indigenous extirpation, economic extraction, and social domination in slave societies. as dogs were bred to track and hunt enslaved runaways, slave communities utilized resources from the natural environment to obfuscate the animal\u27s heightened senses, which produced successful escapes on multiple occasions. This insistence of slaves\u27 humanity, and the intensity of dog attacks against black resistance in the Caribbean and US South, both served as proof of slavery\u27s inhumanity to abolitionists. Examining racialized canine attacks also contextualizes representations of anti-blackness and interspecies ideas of race. An Atlantic network of breeding, training and sales facilitated the use of slave hounds in each major American slave society to subdue human property, actualize legal categories of subjugation, and build efficient economic and state regimes. This integral process is often overlooked in histories of slavery, the African Diaspora, and colonialism. By violently enforcing slavery’s regimes of racism and profit, exposing the humanity of the enslaved and depravity of enslavers, and enraging transnational abolitionists, hounds were central to the rise and fall of slavery in the Americas

Local functional models of critical correlations in thin-films

Recent work on local functional theories of critical inhomogeneous fluids and Ising-like magnets has shown them to be a potentially exact, or near exact, description of universal finite-size effects associated with the excess free-energy and scaling of one-point functions in critical thin films. This approach is extended to predict the two-point correlation function G in critical thin-films with symmetric surface fields in arbitrary dimension d. In d=2 we show there is exact agreement with the predictions of conformal invariance for the complete spectrum of correlation lengths as well as the detailed position dependence of the asymptotic decay of G. In d=3 and d>=4 we present new numerical predictions for the universal finite-size correlation length and scaling functions determining the structure of G across the thin-film. Highly accurate analytical closed form expressions for these universal properties are derived in arbitrary dimension.Comment: 4 pages, 1 postscript figure. Submitted to Phys Rev Let

Growth studies on Si0.8Ge0.2 channel two-dimensional hole gases

We report a study of the influences of MBE conditions on the low-temperature mobilities of Si/Si0.8Ge0.2 2DHG structures. A significant dependence of 2DHG mobility on growth temperature is observed with the maximum mobility of 3640 cm2 V−1 s−1 at 5.4 K being achieved at the relatively high-growth temperature of 640 °C. This dependence is associated with a reduction in interface charge density. Studies on lower mobility samples show that Cu contamination can be reduced both by growth interruptions and by modifications to the Ge source; this reduction produces improvements in the low-temperature mobilities. We suggest that interface charge deriving from residual metal contamination is currently limiting the 4-K mobility

Lateral Pile Response from Model Tests in a Large Centrifuge

Lateral loading tests on instrumented model piles in saturated sand in a centrifuge are described. Piles were tested in isolation and in groups of two, three and six piles. Data were obtained on deflections and bending moments in single piles and on interaction factors between piles. Response of single piles compared favourably with data from Mustang Island field tests. Experimental interaction factors generally differed from those commonly used which are derived from elastic theory. The difference depends on pile spacing

Uniform generation in trace monoids

We consider the problem of random uniform generation of traces (the elements of a free partially commutative monoid) in light of the uniform measure on the boundary at infinity of the associated monoid. We obtain a product decomposition of the uniform measure at infinity if the trace monoid has several irreducible components-a case where other notions such as Parry measures, are not defined. Random generation algorithms are then examined.Comment: Full version of the paper in MFCS 2015 with the same titl

Coordinate-free Solutions for Cosmological Superspace

Hamilton-Jacobi theory for general relativity provides an elegant covariant formulation of the gravitational field. A general `coordinate-free' method of integrating the functional Hamilton-Jacobi equation for gravity and matter is described. This series approximation method represents a large generalization of the spatial gradient expansion that had been employed earlier. Additional solutions may be constructed using a nonlinear superposition principle. This formalism may be applied to problems in cosmology.Comment: 11 pages, self-unpacking, uuencoded tex file, to be published in Physical Review D (1997

The 190 kDa centrosome-associated protein of Drosophila melanogaster contains four zinc finger motifs and binds to specific sites on polytene chromosomes

Microinjection of a bacterially expressed, TRITC labelled fragment of the centrosome-associated protein CP190 of Drosophila melanogaster, into syncytial Drosophila embryos, shows it to associate with the centrosomes during mitosis, and to relocate to chromatin during interphase. Indirect immunofluorescence staining of salivary gland chromosomes of third instar Drosophila larvae, with antibodies specific to CP190, indicate that the protein is associated with a large number of loci on these interphase polytene chromosomes. The 190 kDa CP190 protein is encoded by a 4.1 kb transcript with a single, long open reading frame specifying a polypeptide of 1,096 amino acids, with a molecular mass of 120 kDa, and an isoelectric point of 4.5. The central region of the predicted amino acid sequence of the CP190 protein contains four CysX₂CysX₁₂HisX₄His zinc-finger motifs which are similar to those described for several well characterised DNA binding proteins. The data suggest that the function of CP190 involves cell cycle dependent associations with both the centrosome, and with specific chromosomal loci