2D linear friction weld modelling of a Ti-6Al-4V T-joint

Most examples of linear friction weld process models have focused on joining two identically shaped workpieces. This article reports on the development of a 2D model, using the DEFORM finite element package, to investigate the joining of a rectangular Ti-6Al-4V workpiece to a plate of the same material. The work focuses on how this geometry affects the material flow, thermal fields and interface contaminant removal. The results showed that the material flow and thermal fields were not even across the two workpieces. This resulted in more material expulsion being required to remove the interface contaminants from the weld line when compared to joining two identically shaped workpieces. The model also showed that the flash curves away from the weld due to the rectangular upstand "burrowing" into the base plate.Understanding these critical relationships between the geometry and process outputs is crucial for further industrial implementation of the LFW process.EPSRC, The Welding Institut

Primary goals, information-giving and men\u27s understanding: A qualitative study of Australian and UK doctors\u27 varied communication about PSA screening

Objectives: (1) To characterise variation in general practitioners’ (GPs’) accounts of communicating with men about prostate cancer screening using the prostate-specific antigen (PSA) test, (2) to characterise GPs’ reasons for communicating as they do and (3) to explain why and under what conditions GP communication approaches vary. Study design and setting: A grounded theory study. We interviewed 69 GPs consulting in primary care practices in Australia (n=40) and the UK (n=29). Results: GPs explained their communication practices in relation to their primary goals. In Australia, three different communication goals were reported: to encourage asymptomatic men to either have a PSA test, or not test, or alternatively, to support men to make their own decision. As well as having different primary goals, GPs aimed to provide different information (from comprehensive to strongly filtered) and to support men to develop different kinds of understanding, from population-level to ‘gist’ understanding. Taking into account these three dimensions (goals, information, understanding) and building on Entwistle et al’s Consider an Offer framework, we derived four overarching approaches to communication: Be screened, Do not be screened, Analyse and choose, and As you wish. We also describe ways in which situational and relational factors influenced GPs’ preferred communication approach. Conclusion: GPs’ reported approach to communicating about prostate cancer screening varies according to three dimensions—their primary goal, information provision preference and understanding sought—and in response to specific practice situations. If GP communication about PSA screening is to become more standardized in Australia, it is likely that each of these dimensions will require attention in policy and practice support interventions

Genotype-specific interactions and the trade-off between host and parasite fitness

<p>Abstract</p> <p>Background</p> <p>Evolution of parasite traits is inextricably linked to their hosts. For instance one common definition of parasite virulence is the reduction in host fitness due to infection. Thus, traits of infection must be viewed in both protagonists and may be under shared genetic and physiological control. We investigated these questions on the oomycete <it>Hyaloperonospora arabidopsis </it>(= <it>parasitica</it>), a natural pathogen of the Brassicaceae <it>Arabidopsis thaliana</it>.</p> <p>Results</p> <p>We performed a controlled cross inoculation experiment confronting six lines of the host plant with seven strains of the parasite in order to evaluate genetic variation for phenotypic traits of infection among hosts, parasites, and distinct combinations. Parasite infection intensity and transmission were highly variable among parasite strains and host lines but depended also on the interaction between particular genotypes of the protagonists, and genetic variation for the infection phenotype of parasites from natural populations was found even at a small spatial scale within population. Furthermore, increased parasite fitness led to a significant decrease in host fitness only on a single host line (Gb), although a trade-off between these two traits was expected because host and parasite share the same resource pool for their respective reproduction. We propose that different levels of compatibility dependent on genotype by genotype interactions might lead to different amounts of resources available for host and parasite reproduction. This variation in compatibility could thus mask the expected negative relationship between host and parasite fitness, as the total resource pool would not be constant.</p> <p>Conclusion</p> <p>These results highlight the importance of host variation in the determination of parasite fitness traits. This kind of interaction may in turn decouple the relationship between parasite transmission and its negative effect on host fitness, altering theoretical predictions of parasite evolution.</p

Visibility bound caused by a distinguishable noise particle

We investigate how distinguishability of a "noise" particle degrades interference of the "signal" particle. The signal, represented by an equatorial state of a photonic qubit, is mixed with noise, represented by another photonic qubit, via linear coupling on the beam splitter. We report on the degradation of the "signal" photon interference depending on the degree of indistinguishability between "signal" and "noise" photon. When the photons are principally completely distinguishable but technically indistinguishable the visibility drops to the value 1/sqrt(2). As the photons become more indistinguishable the maximal visibility increases and reaches the unit value for completely indistinguishable photons. We have examined this effect experimentally using setup with fiber optics two-photon Mach-Zehnder interferometer.Comment: 5 pages, 3 figures, Accepted to Phys. Rev.

Optical implementation of the encoding of two qubits to a single qutrit

We have devised an optical scheme for the recently proposed protocol for encoding two qubits into one qutrit. In this protocol, Alice encodes an arbitrary pure product state of two qubits into a state of one qutrit. Bob can then restore error-free any of the two encoded qubit states but not both of them simultaneously. We have successfully realized this scheme experimentally using spatial-mode encoding. Each qubit (qutrit) was represented by a single photon that could propagate through two (three) separate fibers. We theoretically propose two generalizations of the original protocol. We have found a probabilistic operation that enables to retrieve both qubits simultaneously with the average fidelity above 90% and we have proposed extension of the original encoding transformation to encode N qubits into one (N+1)-dimensional system.Comment: 6 pages, 3 figures, RevTeX

Tissue Engineering

There is little doubt that tissue engineering is a revolutionary addition to the therapeutic armamentarium of medicine. The dilemma of adequately repairing either failing or traumatized organs has been looming larger as patients either become older or are in dire need of grafts. Compounding some of the intrinsic problems of transplantation is the chronic shortage of tissues and organs. Tissue engineering allows the hope of a regular creation of spare parts for the human body. This is a most significant approach to reconstruct, replace, or repair organs in a way that could not be foreseen 25 years ago. Reconstructive medicine is, in a way, not a very recent concept. If one stays away from punctilious definitions, one of its forms, reconstructive surgery, has been practiced for quite some time, with a surge of development after the Second World War. In 1970s, the development of microsurgery allowed distant tissue transfer and reimplantation.[1-5] Since then, the introduction of various biomaterials has allowed vast and diversified types of reconstruction of the human body. Vascular grafts and prosthetic articulation are two prominent examples.[6] However, tissue engineering does open a radically new chapter in reconstructive medicine, for it is now deemed possible to reconstruct in the laboratory human living tissues and organs for either in-vivo, ex-vivo, and even invitro applications.[7-3] This new domain of biotechnology is remarkably multidisciplinary, bringing together cell and molecular biologists, biochemists, engineers, pharmacologists, physicians, and others. When the aim of tissue engineers is to obtain grafts for in-vivo applications, then the biological and mechanical functions are of utmost importance. In some subdivisions of the field, one can essentially choose between a biological function, as in cell therapy, and a principally mechanical function, as in the use of tissue templates[14] (Fig. 1). Tissue-engineered substitutes are three-dimensional reconstructions that can be implanted into the human body, leading to rapid host integration and acceptance. These substitutes must have at least minimal biological and mechanical functions for such a reparative role