GPS-aided gravimetry at 30 km altitude from a balloon-borne platform

A balloon-borne experiment, flown at 30 km altitude over New Mexico, was used to test dynamic differential Global Positioning System (GPS) tracking in support of gravimetry at high-altitudes. The experiment package contained a gravimeter (Vibrating String Accelerometer), a full complement of inertial instruments, a TI-4100 GPS receiver and a radar transponder. The flight was supported by two GPS receivers on the ground near the flight path. From the 8 hour flight, about a forty minute period was selected for analysis. Differential GPS phase measurements were used to estimate changes in position over the sample time interval, or average velocity. In addition to average velocity, differential positions and numerical averages of acceleration were obtained in three components. Gravitational acceleration was estimated by correcting for accelerations due to translational motion, ignoring all rotational effects

Solvent mediated interactions between model colloids and interfaces: A microscopic approach

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 Physic

Latent entrepreneurship across nations

The paper studies latent entrepreneurship across nations. There are three main findings. First, large numbers of people in the industrial countries say they would prefer to be self-employed. Top of the international ranking of entrepreneurial spirit come Poland (with 80% saying so), Portugal and the USA; bottom of the table come Norway (with 27% saying so), Denmark and Russia. Second, for individuals the probability of preferring to be self-employed is strongly decreasing with age, while the probability of being self-employed is strongly increasing with age. Third, we show that self-employed individuals have noticeably higher job satisfaction than the employed, so people's expressed wish to run their business cannot easily be written off as mistaken. We speculate on why so much entrepreneurial spirit lies dormant

Latent entrepreneurship across nations

The paper studies latent entrepreneurship across nations. There are three main findings. First, large numbers of people in the industrial countries say they would prefer to be self-employed. Top of the international ranking of entrepreneurial spirit come Poland (with 80% saying so), Portugal and the USA; bottom of the table come Norway (with 27% saying so), Denmark and Russia. Second, for individuals the probability of preferring to be self-employed is strongly decreasing with age, while the probability of being self-employed is strongly increasing with age. Third, we show that self-employed individuals have noticeably higher job satisfaction than the employed, so people's expressed wish to run their business cannot easily be written off as mistaken. We speculate on why so much entrepreneurial spirit lies dormant

Generated randomly and selected functionally? The nature of enterovirus recombination

FA was supported by a PhD studentship from the Ministry of Education, Government of Saudi Arabia and KB was supported by Biological Sciences Research Council award BB/M009343/1to D.J.E and an ISSF award from The Wellcome Trust to the BSRC, University of St Andrews.Genetic recombination in RNA viruses is an important evolutionary mechanism. It con-tributes to population diversity, host/tissue adaptation and compromises vaccine efficacy. Both the molecular mechanism and initial products of recombination are relatively poorly understood. We used an established poliovirus-based in vitro recombination assay to investigate the roles of se-quence identity and RNA structure, both implicated or inferred from analysis of circulating recom-binant viruses, in the process. In addition, we used next generation sequencing to investigate the early products of recombination after cellular co-infection with different poliovirus serotypes. In independent studies we find no evidence for a role for RNA identity or structure in determining recombination junctions location. Instead, genome function and fitness are of greater importance in determining the identity of recombinant progeny. These studies provide further insights into this important evolutionary mechanism and emphasise the critical nature of the selection process on a mixed virus population.Publisher PDFPeer reviewe

Light emission from Er at the As-terminated Si(111) surface

Erbium atoms at an arsenic-terminated Si(111) surface can be made to emit light at the 1.55 mu m wavelength associated with an internal transition in the Er3+ ion. The As-terminated surface prepared under ultrahigh vacuum conditions has a surface recombination velocity of 50 cm s(-1) and partially suppresses competing nonradiative recombination mechanisms. Following the deposition of Er, its characteristic light emission is observed only after oxygen reacts with the surface. The intensity of the light emitted by Er increases significantly upon cooling from 310 to 215 K. No light emission was observed from Er atoms deposited on 7x7 or H-terminated surfaces.Physic

Dynamical density functional theory for interacting Brownian particles: stochastic or deterministic?

We aim to clarify confusions in the literature as to whether or not dynamical density functional theories for the one-body density of a classical Brownian fluid should contain a stochastic noise term. We point out that a stochastic as well as a deterministic equation of motion for the density distribution can be justified, depending on how the fluid one-body density is defined -- i.e. whether it is an ensemble averaged density distribution or a spatially and/or temporally coarse grained density distribution.Comment: 10 pages, 1 figure, to be submitted to Journal of Physics A: Mathematical and Genera

Oxidation of tertiary amine-derivatized surfaces to control protein adhesion

Selective oxidation of omega-tertiary amine self-assembled thiol monolayers to tertiary amine N-oxides is shown to transform the adhesion of model proteins lysozyme and fibrinogen upon them. Efficient preparation of both secondary and tertiary linker amides as judged by X-ray photoelectron spectroscopy (XPS) and water droplet contact angle was achieved with an improved amide bond formation on gold quartz crystal microbalance (QCM) sensors using 2-(1H-7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyl hexafluorophosphate methanaminium uronium (HATU). Oxidation with hydrogen peroxide was similarly assessed, and adhesion of lysozyme and fibrinogen from phosphate buffered saline was then assayed by QCM and imaged by AFM. Tertiary amine-functionalized sensors adsorbed multilayers of aggregated lysozyme, whereas tertiary amine N-oxides and triethylene glycol-terminated monolayers are consistent with small protein aggregates. The surface containing a dimethylamine N-oxide headgroup and ethyl secondary amide linker showed the largest difference in adsorption of both proteins. Oxidation of tertiary amine decorated surfaces therefore holds the potential for selective deposition of proteins and cells through masking and other patterning techniques