Wetting of soap bubbles on hydrophilic, hydrophobic and superhydrophobic surfaces

Wetting of sessile bubbles on solid and liquid surfaces has been studied. A model is presented for the contact angle of a sessile bubble based on a modified Young equation - the experimental results agree with the model. A hydrophilic surface results in a bubble contact angle of 90 deg whereas on a superhydrophobic surface one observes 134 deg. For hydrophilic surfaces, the bubble angle diminishes with bubble radius - whereas on a superhydrophobic surface, the bubble angle increases. The size of the Plateau borders governs the bubble contact angle - depending on the wetting of the surface

Electrowetting of a soap bubble

A proof-of-concept demonstration of the electrowetting-on-dielectric of a sessile soap bubble is reported here. The bubbles are generated using a commercial soap bubble mixture - the surfaces are composed of highly doped, commercial silicon wafers covered with nanometre thick films of Teflon. Voltages less than 40V are sufficient to observe the modification of the bubble shape and the apparent bubble contact angle. Such observations open the way to inter alia the possibility of bubble-transport, as opposed to droplet-transport, in fluidic microsystems (e.g. laboratory-on-a-chip) - the potential gains in terms of volume, speed and surface/volume ratio are non-negligible

Modern life subjects in British painting 1840-60

A small number of paintings with modern settings and figures in modern dress can be identified in the exhibitions of the 1840s. During the 1850s such pictures became far more common, particularly in the wake of the success of William Powell Frith's outdoor crowd scene, Ramsgate Sands, exhibited at the Royal Academy of 1854, and distributed as an Art Union engraving in 1859. This thesis locates those modern life scenes in the broader context of mid-nineteenth century genre painting. Examining the critical debates of the 1840s, it is possible to identify anxieties concerning the appeal and value of genre painting, as an aspect of the political and ideological construction of the bourgeoisie. The expansion of the art-buying and art-viewing public generated critical concern over the status and powers of discrimination of middle-class patrons. Genre painting was thought to present a special danger because it offered viewers sensory stimulation, in the form of visual excitement, untempered by the moral and intellectual qualities of high art. Rather than proceding by compiling a catalogue of modern life paintings this thesis examines in depth a number of pictures produced in the 1850s. It considers, as case studies, two pictures exhibited in 1854: Ramsgate Sands by Frith, and The Awakening Conscience by William Holman Hunt. As a third example a picture by William Maw Egley, Omnibus Life In London, is investigated. This was exhibited at the British Institution, and engraved for the Illustrated London News, in 1859. These case studies develop new frameworks for the analysis of Victorianpaintings. Social and political history is not presented as background, but as integral to the construction and deployment of meaning in the pictures. The analysis draws on psychoanalytic writing and on structuralist theory. It argues that the choice of modern subjects posed particular problems for both artists and audiences. Whether the representations were of private morality and immorality, or of public situations where sexual propriety became an issue, there was an engagement by the paintings with questions of sexuality and its regulation. At the same time the viewing of these genre paintings was, in terms of contemporary critical theory, already a sexualised activity. The thesis looks at the interface between sexuality and vision in the pictures. Developments in portraiture are mapped on to changing attitudes to genre subjects in a discussion of the relationship between realism and the narrative qualities of painting in the mid-nineteenth century

Explosive than any Terrorist’s time Bomb: the RCSW, Then and Now

I was on a panel with two presenters who addressed the RCSW’s recommendations on childcare. The commentator, Alexandra Dobrowolsky used my paper to contextualize the other papers. Members of the audience remarked that my paper presented information that was not familiar to them and that they would like to be able to refer students to this material. The implication of these comments and the activity poses a challenge to present my research in a form that makes it accessible to a new generation of students and other readers, including younger instructors, who do not have ready access to readily digestible information about the RCSW. In revising the book mss from which the material has been drawn, I will keep this prospective audience in the front of my mind.The Report of the RCSW has been a landmark public document, ‘the public face of liberal feminism,’ a foundational document in the inception of Women’s Studies and the progenitor for the emergence of Women and Politics as a subfield in the study of Canadian politics. Scholarship about the RCSW has relied heavily over the past 40 years on the reflections of two participants, the Chairman and the Executive Secretary, for accounts of what happened and why. This excessively narrow interpretive frame has entirely disregards all but 10% of the submissions, the Minutes of the meetings of the Commission that were supposed to have been destroyed, audiotapes of the public hearings available since 1995, surveillance by the Security Intelligence branch of the RCMP of some organizations that prepared briefs, and almost all of the materials deposited by the Commission with the Library and Archives of Canada. This paper draws on these primary sources, elaborated in “Primed and Ticking, the Royal Commission on the Status of Women, 1970” (University of Toronto Press, forthcoming 2010) to provide a more complete and nuanced account of this formative contribution to the development of women’s equality in Canada. Based on those findings the paper looks ahead to areas requiring further work in order to realize more of the explosive power of gender analysis in the next half century

Vacuum Structure of Two-Dimensional ϕ4\phi^4 Theory on the Orbifold S1/Z2S^{1}/Z_{2}

We consider the vacuum structure of two-dimensional $\phi^4$ theory on $S^{1}/Z_{2}$ both in the bosonic and the supersymmetric cases. When the size of the orbifold is varied, a phase transition occurs at $L_{c}=2\pi/m$, where $m$ is the mass of $\phi$. For $L<L_{c}$, there is a unique vacuum, while for $L>L_{c}$, there are two degenerate vacua. We also obtain the 1-loop quantum corrections around these vacuum solutions, exactly in the case of $L<L_{c}$ and perturbatively for $L$ greater than but close to $L_{c}$. Including the fermions we find that the "chiral" zero modes around the fixed points are different for $LL_{c}$. As for the quantum corrections, the fermionic contributions cancel the singular part of the bosonic contributions at L=0. Then the total quantum correction has a minimum at the critical length $L_{c}$.Comment: Revtex, 15 pages, 3 eps figure

On giant piezoresistance effects in silicon nanowires and microwires

The giant piezoresistance (PZR) previously reported in silicon nanowires is experimentally investigated in a large number of surface depleted silicon nano- and micro-structures. The resistance is shown to vary strongly with time due to electron and hole trapping at the sample surfaces. Importantly, this time varying resistance manifests itself as an apparent giant PZR identical to that reported elsewhere. By modulating the applied stress in time, the true PZR of the structures is found to be comparable with that of bulk silicon

"Actuation at a distance" of microelectromechanical systems using photoelectrowetting: proof-of-concept

We demonstrate here a proof-of-concept experiment that microelectromechanical systems (MEMS) can be actuated using photoelectrowetting. In order to demonstrate this, a 30 \mu m thick aluminum cantilever is actuated using an ordinary white light source. A deflection of 56 \mu m is observed using a light irradiance equal to \approx 1000 W m-2 at a bias of 7 V. The deflection of the cantilever relies on the recently observed photoelectrowetting effect [Sci. Rep.1, 184 (2011)]. Such "actuation at a distance" could be useful for optical addressing and control of autonomous wireless sensors, MEMS and microsystems

Effect of the Pauli principle on photoelectron spin transport in p+p^+ GaAs

In p+ GaAs thin films, the effect of photoelectron degeneracy on spin transport is investigated theoretically and experimentally by imaging the spin polarization profile as a function of distance from a tightly-focussed light excitation spot. Under degeneracy of the electron gas (high concentration, low temperature), a dip at the center of the polarization profile appears with a polarization maximum at a distance of about $2 \; \mu m$ from the center. This counterintuitive result reveals that photoelectron diffusion depends on spin, as a direct consequence of the Pauli principle. This causes a concentration dependence of the spin stiffness while the spin dependence of the mobility is found to be weak in doped material. The various effects which can modify spin transport in a degenerate electron gas under local laser excitation are considered. A comparison of the data with a numerical solution of the coupled diffusion equations reveals that ambipolar coupling with holes increases the steady-state photo-electron density at the excitation spot and therefore the amplitude of the degeneracy-induced polarization dip. Thermoelectric currrents are predicted to depend on spin under degeneracy (spin Soret currents), but these currents are negligible except at very high excitation power where they play a relatively small role. Coulomb spin drag and bandgap renormalization are negligible due to electrostatic screening by the hole gas