Wetting and contact-line effects for spherical and cylindrical droplets on graphene layers: A comparative molecular-dynamics investigation

In Molecular Dynamics (MD) simulations, interactions between water molecules and graphitic surfaces are often modeled as a simple Lennard-Jones potential between oxygen and carbon atoms. A possible method for tuning this parameter consists of simulating a water nanodroplet on a flat graphitic surface, measuring the equilibrium contact angle, extrapolating it to the limit of a macroscopic droplet and finally matching this quantity to experimental results. Considering recent evidence demonstrating that the contact angle of water on a graphitic plane is much higher than what was previously reported, we estimate the oxygen-carbon interaction for the recent SPC/Fwwater model. Results indicate a value of about 0.2 kJ/mol, much lower than previous estimations. We then perform simulations of cylindrical water filaments on graphitic surfaces, in order to compare and correlate contact angles resulting from these two different systems. Results suggest that modified Young's equation does not describe the relation between contact angle and drop size in the case of extremely small systems and that contributions different from the one deriving from contact line tension should be taken into account.Comment: To be published on Physical Review E (http://pre.aps.org/

Mechanism of Molybdenum-Mediated Carbon Monoxide Deoxygenation and Coupling: Mono- and Dicarbyne Complexes Precede C–O Bond Cleavage and C–C Bond Formation

Deoxygenative coupling of CO to value-added C_(≥2) products is challenging and mechanistically poorly understood. Herein, we report a mechanistic investigation into the reductive coupling of CO, which provides new fundamental insights into a multielectron bond-breaking and bond-making transformation. In our studies, the formation of a bis(siloxycarbyne) complex precedes C–O bond cleavage. At −78 °C, over days, C–C coupling occurs without C–O cleavage. However, upon warming to 0 °C, C–O cleavage is observed from this bis(siloxycarbyne) complex. A siloxycarbyne/CO species undergoes C–O bond cleavage at lower temperatures, indicating that monosilylation, and a more electron-rich Mo center, favors deoxygenative pathways. From the bis(siloxycarbyne), isotopic labeling experiments and kinetics are consistent with a mechanism involving unimolecular silyl loss or C–O cleavage as rate-determining steps toward carbide formation. Reduction of Mo(IV) CO adducts of carbide and silylcarbyne species allowed for the spectroscopic detection of reduced silylcarbyne/CO and mixed silylcarbyne/siloxycarbyne complexes, respectively. Upon warming, both of these silylcarbynes undergo C–C bond formation, releasing silylated C_2O_1 fragments and demonstrating that the multiple bonded terminal Mo≡C moiety is an intermediate on the path to deoxygenated, C–C coupled products. The electronic structures of Mo carbide and carbyne species were investigated quantum mechanically. Overall, the present studies establish the elementary reactions steps by which CO is cleaved and coupled at a single metal site

The Open Access Advantage Revisited

This paper is a revision of one that appeared in 2008, incorporating the many developments and changes that have happened since then.published_or_final_versio

The Open Access Advantage

Hong Kong Open Access Committeepublished_or_final_versio

The Early Optical Afterglow of GRB 030418 and Progenitor Mass Loss

The ROTSE-IIIa telescope and the SSO 40 inch (1.0 m) telescope, both located at Siding Spring Observatory, imaged the early-time afterglow of GRB 030418. In this report, we present observations of the early afterglow, first detected by the ROTSE-IIIa telescope 211 s after the start of the burst and only 76 s after the end of the gamma-ray activity. We detect optical emission that rises for ∼600 s, slowly varies around R = 17.3 mag for ∼1400 s, and then fades as a power law of index α = -1.36. Additionally, the ROTSE-IIIb telescope, located at McDonald Observatory, imaged the early-time afterglow of GRB 030723. The behavior of this light curve was qualitatively similar to that of GRB 030418, but 2 mag dimmer. These two afterglows are dissimilar to other afterglows such as GRB 990123 and GRB 021211. We investigate whether or not the early afterglow can be attributed to a synchrotron break in a cooling synchrotron spectrum as it passes through the optical band, but we find that this model is unable to accurately describe the early light curve. We present a simple model for gamma-ray burst emission emerging from a wind medium surrounding a massive progenitor star. This model provides an effective description of the data and suggests that the rise of the afterglow can be ascribed to extinction in the local circumburst environment. In this interpretation, these events provide further evidence of the connection between gamma-ray bursts and the collapse of massive stars.This work has been supported by NASA grants NAG5- 5281 and F006794, NSF grants AST 01-19685 and 01-05221, the Australian Research Council, the University of New South Wales, and the University of Michigan. Work performed at LANL is supported by NASA SR&T through Department of Energy (DOE) contract W-7405-ENG-36 and through internal LDRD funding

The colonial ascidian Didemnum sp. A: Current distribution, basic biology and potential threat to marine communities of the northeast and west coasts of North America

Author Posting. © The Author(s), 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Experimental Marine Biology and Ecology 342 (2007): 99-108, doi:10.1016/j.jembe.2006.10.020.Didemnum sp. A is a colonial ascidian with rapidly expanding populations on the east and west coasts of North America. The origin of Didemum sp. A is unknown. Populations were first observed on the northeast coast of the U.S. in the late 1980s and on the west coast during the 1990s. It is currently undergoing a massive population explosion and is now a dominant member of many subtidal communities on both coasts. To determine Didemnum sp. A’s current distribution, we conducted surveys from Maine to Virginia on the east coast and from British Columbia to southern California on the west coast of the U.S. between 1998 and 2005. In nearshore locations Didemnum sp. A currently ranges from Eastport, Maine to Shinnecock Bay, New York on the east coast. On the west coast it has been recorded from Humboldt Bay to Port San Luis in California, several sites in Puget Sound, Washington, including a heavily fouled mussel culture facility, and several sites in southwestern British Columbia on and adjacent to oyster and mussel farms. The species also occurs at deeper subtidal sites (up to 81 m) off New England, including Georges, Stellwagen and Tillies Banks. On Georges Bank numerous sites within a 147 km2 area are 50-90% covered by Didemnum sp. A; large colonies cement the pebble gravel into nearly solid mats that may smother infaunal organisms. These observations suggest that Didemnum sp. A has the potential to alter marine communities and affect economically important activities such as fishing and aquaculture.Funding for this project was provided by EPA (STAR) grant GZ1910464 to R.B. Whitlatch, NSF-DGE 0114432 to J. Byrnes, NSF-OCE 0117839 to R. Etter and R.J. Miller, MIT Sea Grant NA86RG0074 and USEPA Grant GX83055701-0 to J. Pederson. RI Sea Grant NA07R90363 to J.S. Collie. Funding for A.N. Cohen and G. Lambert was provided by Mass. Sea Grant, U.S. EPA, Smithsonian Envl. Research Center Invasions Lab, Natl. Geographic Soc., San Francisco Bay-Delta Science Consortium and CALFED Science Program, Calif. Coastal Conservancy and the Rose Foundation. Additional funding and support was provided by the Stellwagen Bank National Marine Sanctuary

Are Patient Self-Reported Outcome Measures Sensitive Enough to Be Used as End Points in Clinical Trials?: Evidence from the United Kingdom Glaucoma Treatment Study

Purpose The United Kingdom Glaucoma Treatment Study (UKGTS) demonstrated the effectiveness of an intraocular pressure-lowering drug in patients with glaucoma using visual field progression as a primary outcome. The present study tested the hypothesis that responses on patient-reported outcome measures (PROMs; secondary outcome measure) differ between patients receiving a topical prostaglandin analog (latanoprost) or placebo eye drops in UKGTS. Design Multicenter, randomized, triple-masked, placebo-controlled trial. Participants Newly diagnosed glaucoma patients in the UKGTS with baseline and exit PROMs (n = 182 and n = 168 patients from the treatment and placebo groups, respectively). Methods In the UKGTS (trial registration number, ISRCTN96423140), patients with open-angle glaucoma were allocated to receive latanoprost (treatment) or placebo; the observation period was 24 months. Patients completed general health PROMs (European Quality of Life in 5 Dimensions [EQ-5D] and 36-item Short Form [SF-36]) and PROMs specific to glaucoma (15-item Glaucoma Quality of Life [GQL-15] and 9-item Glaucoma Activity Limitation [GAL-9]) at baseline and exit from the trial. Percentage changes between measurement on PROMs were calculated for each patient and compared between treatment arms. In addition, differences between stable patients (n = 272) and those with glaucomatous progression (n = 78), as determined by visual field change (primary outcome), were assessed. Main Outcome Measure PROMs on health-related and vision-related quality of life. Results Average percentage change on PROMs was similar for patients in both arms of the trial, with no statistically significant differences between treatment and placebo groups (EQ-5D, P = 0.98; EQ-5D visual analog scale, P = 0.88; SF-36, P = 0.94, GQL-15, P = 0.66; GAL-9, P = 0.87). There were statistically significant differences between stable and progressing patients on glaucoma-specific PROMs (GQL-15, P = 0.02; GAL-9, P = 0.02), but not on general health PROMs (EQ-5D, P = 0.62; EQ-5D visual analog scale, P = 0.23; SF-36, P = 0.65). Conclusions Average change in PROMs on health-related and vision-related quality of life was similar for the treatment and placebo groups in the UKGTS. The PROMs used may not be sensitive enough to function as primary end points in clinical trials when participants have newly diagnosed early-stage glaucoma

Feminisation of success or successful femininities? Disentangling ‘new femininities’ under neoliberal conditions

This article critically examines what might be titled the feminisation of success that is ascribed to optimistic characterisations of new constructions of femininity for young women in the UK, particularly in relation to classed positions. In order to do this it is necessary to understand the complex relationship between feminism, post-feminism, neoliberalism and femininities, especially since the millennium. Young women have been positioned as the beneficiaries of successful social and political change which, together with ideas of individualism and reflexive constructions of identity, almost mandate young women to embody success. The article seeks to examine and assess the discursive constructions of ‘successful femininities’ in relation to their normative limitations and asks in particular whether the putative existence of ‘new femininities’ is attainable for all young women. With the impact of over a decade of neoliberal policies and austerity measures being felt by many, it is argued that the discourses of ‘successful femininities’ work to obscure the recalibrated inequalities that have been forged by neoliberal conditions