Freeform Extrusion Fabrication of Titanium Fiber Reinforced Bioactive Glass Scaffolds

Although implants made with bioactive glass have shown promising results for bone repair, their application in repairing load-bearing long bones is limited due to their low fracture toughness and fairly fast degradation response in vivo. In this paper, we describe our investigation of freeform extrusion fabrication of silicate based 13-93 bioactive glass scaffolds reinforced with titanium fibers. A composite paste was prepared with 13-93 bioactive glass filled with titanium fibers (~16 µm in diameter and aspect ratio of ~250) having a volume fraction of 0.4 vol. %. This paste was then extruded to fabricate scaffolds with an extrudate diameter of about ~0.8 mm. The sintered scaffolds, with and without titanium fibers, had measured pore sizes ranging from 400 to 800 µm and a porosity of ~50%. Scaffolds produced with 0.4 vol. % titanium fibers were measured to have a fracture toughness of ~0.8 MPa•m1/2 and a flexural strength of ~15 MPa. Bioactive glass scaffolds without titanium fibers had a toughness of ~ 0.5 MPa•m1/2 and strength of ~10 MPa. The addition of titanium fibers increased the fracture toughness of the scaffolds by ~70% and flexural strength by ~40%. The scaffolds’ biocompatibility and their degradation in mechanical properties, in vitro were assessed by immersing the scaffolds in a simulated body fluid over a period of one to four weeks.Mechanical Engineerin

Thermomechanical deformation behavior and mechanisms in transition metal carbides

Mechanical testing over 2000oC is arduous because of the required heating, compliance in components, and potential specimen reactions to name a few. In this talk, the use of a non-contact means of thermomechanical loading, initially demonstrated by Gangireddy and Halloran, is applied to TaC and HfC. By passing a current through the carbide, it is resistively heated and, in the presence of a magnetic field, the specimen bends under the Lorentz force. Using a variety of loads and temperatures up to 3000oC, the thermomechanical behavior is quantified for a series of tantalum and hafnium carbides. Findings include more deflection in TaC than HfC at equivalent load/temperatures which is contributed to TaC’s ease of {111} slip. At failure, TaC exhibited abnormal grain growth with multiple slip band formations on the fractured surface. In contrast, HfC exhibited minimal grain growth and substantially less slip band formations. Additional studies determining the relationship between load at failure as a function of temperature were determined. The collective results will be discussed in terms of TEM and DFT analysis of slip mechanisms in transition metal carbides

High Value Manufacturing in the UK: A Study of its Challenges, Opportunities and Emerging Technologies

The High Value Manufacturing (HVM) Catapult is a collection of manufacturing research centres designed by the UK government to help foster and develop manufacturing in the UK. The Landscape project will inform the manufacturing strategy adopted by the UK Government and its HVM Catapult. The intention is for these results to continue to inform strategy and public policy development in the UK. The Landscape project endeavoured to explore current and future environments by identifying the trends, drivers and challenges in UK manufacturing and the technologies and their related capabilities that could be at the leading edge of manufacturing in 2025. This paper outlines the process that was undertaken to develop the current and future global 'landscape' of manufacturing. The project identified dozens of capabilities that UK firms could develop to be competitive in manufacturing, given the challenges and emerging technologies facing the industry. It also identified national competencies that could be developed to foster the growth of industrial commons in the UK. This paper will present the project's major outcomes, highlighting the opportunities in UK manufacturin

Measurement of the binding energy of ultracold 87Rb133Cs molecules using an offset-free optical frequency comb

We report the binding energy of Rb87Cs133 molecules in their rovibrational ground state measured using an offset-free optical frequency comb based on difference frequency generation technology. We create molecules in the absolute ground state using stimulated Raman adiabatic passage (STIRAP) with a transfer efficiency of 88%. By measuring the absolute frequencies of our STIRAP lasers, we find the energy-level difference from an initial weakly bound Feshbach state to the rovibrational ground state with a resolution of ∼5 kHz over an energy-level difference of more than 114THz; this lets us discern the hyperfine splitting of the ground state. Combined with theoretical models of the Feshbach-state binding energies and ground-state hyperfine structure, we determine a zero-field binding energy of h×114268135.24(4)(3)MHz. To our knowledge, this is the most accurate determination to date of the dissociation energy of a molecule

The eta' meson from lattice QCD

We study the flavour singlet pseudoscalar mesons from first principles using lattice QCD. With N_f=2 flavours of light quark, this is the so-called eta_2 meson and we discuss the phenomenological status of this. Using maximally twisted-mass lattice QCD, we extract the mass of the eta_2 meson at two values of the lattice spacing for lighter quarks than previously discussed in the literature. We are able to estimate the mass value in the limit of light quarks with their physical masses.Comment: 16 pages: version accepted for publicatio

New black holes in the brane-world?

It is known that the Einstein field equations in five dimensions admit more general spherically symmetric black holes on the brane than four-dimensional general relativity. We propose two families of analytic solutions (with g_tt\not=-1/g_rr), parameterized by the ADM mass and the PPN parameter beta, which reduce to Schwarzschild for beta=1. Agreement with observations requires |\beta-1| |\eta|<<1. The sign of eta plays a key role in the global causal structure, separating metrics which behave like Schwarzschild (eta<0) from those similar to Reissner-Nordstroem (eta>0). In the latter case, we find a family of black hole space-times completely regular.Comment: 4 pages, RevTeX, 3 eps figures, final version to appear in Phys. Rev.

Astronaut ophthalmic syndrome

During and after missions on the International Space Station, some astronauts experience ophthalmic changes, including choroidal folds, optic disc edema, cotton-wool spots, globe flattening, and refraction changes. Astronauts with ophthalmic issues had significantly higher plasma concentrations of metabolites that are associated with the 1-carbon metabolic pathway than those without ophthalmic issues. We hypothesized that genetic differences might explain the metabolite differences. Indeed, genetics and B vitamin status were significant predictors of ophthalmic issues. We now have developed a hypothesis regarding the mechanisms that link 1-carbon pathway genetics and the condition that we suggest calling, “astronaut ophthalmic syndrome.” We maintain that this condition is genetically predisposed and is associated with endothelial dysfunction that is induced by oxidative stress. Subsequent edema can hinder cerebrospinal fluid efflux and can lead to locally increased pressures in the subarachnoid space within the orbit, which impinges on the optic nerve and/or eye in affected individuals. Confirming this hypothesis will help characterize the genetics of 1-carbon pathway metabolism, homocysteine, oxidative stress, endothelial dysfunction, and cardiovascular and potentially other diseases

Angular Correlations in Top Quark Pair Production and Decay at Hadron Colliders

We show how to observe sizable angular correlations between the decay products of the top quark and those of the anti-top quark in top quark pair production and decay at hadron colliders. These correlations result from the large asymmetry in the rate for producing like-spin versus unlike-spin top quark pairs provided the appropriate spin axes are used. The effects of new physics at production or decay on these correlations are briefly discussed.Comment: 34 pages, revtex, including 12 uuencoded postscript figure

Immune pathways and defence mechanisms in honey bees Apis mellifera

Social insects are able to mount both group-level and individual defences against pathogens. Here we focus on individual defences, by presenting a genome-wide analysis of immunity in a social insect, the honey bee Apis mellifera. We present honey bee models for each of four signalling pathways associated with immunity, identifying plausible orthologues for nearly all predicted pathway members. When compared to the sequenced Drosophila and Anopheles genomes, honey bees possess roughly one-third as many genes in 17 gene families implicated in insect immunity. We suggest that an implied reduction in immune flexibility in bees reflects either the strength of social barriers to disease, or a tendency for bees to be attacked by a limited set of highly coevolved pathogens

Orbital resonances in discs around braneworld Kerr black holes

Rotating black holes in the brany universe of the Randall-Sundrum type are described by the Kerr geometry with a tidal charge b representing the interaction of the brany black hole and the bulk spacetime. For b<0 rotating black holes with dimensionless spin a>1 are allowed. We investigate the role of the tidal charge b in the orbital resonance model of QPOs in black hole systems. The orbital Keplerian, the radial and vertical epicyclic frequencies of the equatorial, quasicircular geodetical motion are given and their radial profiles are discussed. The resonant conditions are given in three astrophysically relevant situations: for direct (parametric) resonances, for the relativistic precession model, and for some trapped oscillations of the warped discs, with resonant combinational frequencies. It is shown, how b could influence matching of the observational data indicating the 3:2 frequency ratio observed in GRS 1915+105 microquasar with prediction of the orbital resonance model; limits on allowed range of the black hole parameters a and b are established. The "magic" dimensionless black hole spin enabling presence of strong resonant phenomena at the radius where \nu_K:\nu_{\theta}:\nu_r=3:2:1 is determined in dependence on b. Such strong resonances could be relevant even in sources with highly scattered resonant frequencies, as those expected in Sgr A*. The specific values of a and b are given also for existence of specific radius where \nu_K:\nu_{\theta}:\nu_r=s:t:u with 5>=s>t>u being small natural numbers. It is shown that for some ratios such situation is impossible in the field of black holes. We can conclude that analysing the microquasars high-frequency QPOs in the framework of orbital resonance models, we can put relevant limits on the tidal charge of brany Kerr black holes.Comment: 31 pages, 19 figures, to appear in General Relativity and Gravitatio