2,159 research outputs found
Beta lives - some statistical perspectives on the capital asset pricing model
This note summarizes some technical issues relevant to the use of the idea of excess return in empirical modelling. We cover the case where the aim is to construct a measure of expected return on an asset and a model of the CAPM type is used. We review some of the problems and show examples where the basic CAPM may be used to develop other results which relate the expected returns on assets both to the expected return on the market and other factors
Focused Crossed Andreev Reflection
We consider non-local transport in a system with one superconducting and two
normal metal terminals. Electron focusing by weak perpendicular magnetic fields
is shown to tune the ratio between crossed Andreev reflection (CAR) and
electron transfer (ET) in the non-local current response. Additionally,
electron focusing facilitates non-local signals between normal metal contacts
where the separation is as large as the mean free path rather than being
limited by the coherence length of the superconductor. CAR and ET can be
selectively enhanced by modulating the magnetic field
Intracellular Penetration and Accumulation of Radiographic Contrast Media in the Rat Kidney
Radiographic iodine-containing contrast media (meglumine calcium metrizoate, iohexol and meglumine sodium ioxaglate) were injected intravenously in rats. At various intervals after exposure, in situ cryofixation of kidneys was performed. Thin, freeze-dried cryosections were examined by electron microscopy and X-ray microanalysis. In endothelial cells, erythrocytes and tubular cells high dry weight concentrations of iodine were found. Twenty-four hours after iohexol was injected, no trace of iodine was found in the plasma, microvilli or the nuclei of the tubular cells. Small organelle-like compartments in the cytoplasm of the proximal tubular cells contained high concentrations of iodine, whereas no iodine was found in the surrounding cytoplasm. Since no metabolism of contrast medium has been demonstrated, the iodine signals must be emitted from contrast medium molecules. Other elements were also measured, with the concentrations being always within the ranges found in tubular cells of control animals. The detection of intracellular contrast thus does not seem to be an artifact due to cell injury, but rather represents a physiological event in healthy cells in the rat kidney. Our results are in contradiction to the prevailing opinion that contrast media do not enter healthy cells. However, previous conclusions have been based on the use of conventional preparation methods, and the highly water soluble contrast molecules may have been lost during the different steps of fixation and processing
Simvastatin coating of TiO2 scaffold induces osteogenic differentiation of human adipose tissue-derived mesenchymal stem cells
AbstractBone tissue engineering requires an osteoconductive scaffold, multipotent cells with regenerative capacity and bioactive molecules. In this study we investigated the osteogenic differentiation of human adipose tissue-derived mesenchymal stem cells (hAD-MSCs) on titanium dioxide (TiO2) scaffold coated with alginate hydrogel containing various concentrations of simvastatin (SIM). The mRNA expression of osteoblast-related genes such as collagen type I alpha 1 (COL1A1), alkaline phosphatase (ALPL), osteopontin (SPP1), osteocalcin (BGLAP) and vascular endothelial growth factor A (VEGFA) was enhanced in hAD-MSCs cultured on scaffolds with SIM in comparison to scaffolds without SIM. Furthermore, the secretion of osteoprotegerin (OPG), vascular endothelial growth factor A (VEGFA), osteopontin (OPN) and osteocalcin (OC) to the cell culture medium was higher from hAD-MSCs cultured on scaffolds with SIM compared to scaffolds without SIM. The TiO2 scaffold coated with alginate hydrogel containing SIM promote osteogenic differentiation of hAD-MSCs in vitro, and demonstrate feasibility as scaffold for hAD-MSC based bone tissue engineering
The spirit of sport: the case for criminalisation of doping in the UK
This article examines public perceptions of doping in sport, critically evaluates the effectiveness of current anti-doping sanctions and proposes the criminalisation of doping in sport in the UK as part of a growing global movement towards such criminalisation at national level. Criminalising doping is advanced on two main grounds: as a stigmatic deterrent and as a form of retributive punishment enforced through the criminal justice system. The âspirit of sportâ defined by the World Anti-Doping Agency (WADA) as being based on the values of ethics, health and fair-play is identified as being undermined by the ineffectiveness of existing anti-doping policy in the current climate of doping revelations, and is assessed as relevant to public perceptions and the future of sport as a whole. The harm-reductionist approach permitting the use of certain performance enhancing drugs (PEDs) is considered as an alternative to anti-doping, taking into account athlete psychology, the problems encountered in containing doping in sport through anti-doping measures and the effect of these difficulties on the âspirit of sportâ. This approach is dismissed in favour of criminalising doping in sport based on the offence of fraud. It will be argued that the criminalisation of doping could act as a greater deterrent than existing sanctions imposed by International Federations, and, when used in conjunction with those sanctions, will raise the overall âpriceâ of doping. The revelations of corruption within the existing system of self-governance within sport have contributed to a disbelieving public and it will be argued that the criminalisation of doping in sport could assist in satisfying the public that justice is being done and in turn achieve greater belief in the truth of athletic performances
Two-stage dissipation in a superconducting microbridge: Experiment and modeling
Using fluorescent microthermal imaging we have investigated the origin of
"two-step" behavior in I-V curves for a current-carrying YBa_2Cu_3O_x
superconducting bridge. High resolution temperature maps reveal that as the
applied current increases the first step in the voltage corresponds to local
dissipation (hot spot), whereas the second step is associated with onset of
global dissipation throughout the entire bridge. A quantitative explanation of
the experimental results is provided by a simple model for an inhomogeneous
superconductor, assuming that the hot spot nucleates at a location with
slightly depressed superconducting properties.Comment: 4 pages, 4 figure
The onset of a small-scale turbulent dynamo at low magnetic Prandtl numbers
We study numerically the dependence of the critical magnetic Reynolds number
Rmc for the turbulent small-scale dynamo on the hydrodynamic Reynolds number
Re. The turbulence is statistically homogeneous, isotropic, and
mirror--symmetric. We are interested in the regime of low magnetic Prandtl
number Pm=Rm/Re<1, which is relevant for stellar convective zones, protostellar
disks, and laboratory liquid-metal experiments. The two asymptotic
possibilities are Rmc->const as Re->infinity (a small-scale dynamo exists at
low Pm) or Rmc/Re=Pmc->const as Re->infinity (no small-scale dynamo exists at
low Pm). Results obtained in two independent sets of simulations of MHD
turbulence using grid and spectral codes are brought together and found to be
in quantitative agreement. We find that at currently accessible resolutions,
Rmc grows with Re with no sign of approaching a constant limit. We reach the
maximum values of Rmc~500 for Re~3000. By comparing simulations with Laplacian
viscosity, fourth-, sixth-, and eighth-order hyperviscosity and Smagorinsky
large-eddy viscosity, we find that Rmc is not sensitive to the particular form
of the viscous cutoff. This work represents a significant extension of the
studies previously published by Schekochihin et al. 2004, PRL 92, 054502 and
Haugen et al. 2004, PRE, 70, 016308 and the first detailed scan of the
numerically accessible part of the stability curve Rmc(Re).Comment: 4 pages, emulateapj aastex, 2 figures; final version as published in
ApJL (but with colour figures
Beginning Counselor Educatorsâ Experiences of Teaching Mentorship
Mentoring can positively impact counselor educatorsâ teaching in terms of self-efficacy and growth in skills. Yet, counselor educators have reported a desire for more mentoring in the development of their teaching. Utilizing consensual qualitative research methodology, we explored the teaching-specific mentorship of beginning counselor educatorsâ (N = 13) within their first two to four years as faculty. Emergent themes included mentoring structure such as mentorsâ methods of providing mentorship, mentoring relationship dynamics such as relational supports and frustrations, and the positive and negative impacts of mentoring relationships. In addition to building rapport and strengthening menteesâ self-efficacy, mentors and mentees can develop intentional mentoring relationships with a comprehensive focus emphasizing the development of teaching knowledge and skills through practices such as teaching observation and feedback. Additionally, discussing the needs, goals, and expectations of both parties and the inherent power differential of the relationships can help focus the mentoring experiences
Funding models in palliative care: lessons from international experience
Background:Funding models influence provision and development of palliative care services. As palliative care integrates into mainstream health care provision, opportunities to develop funding mechanisms arise. However, little has been reported on what funding models exist or how we can learn from them.Aim:To assess national models and methods for financing and reimbursing palliative care.Design:Initial literature scoping yielded limited evidence on the subject as national policy documents are difficult to identify, access and interpret. We undertook expert consultations to appraise national models of palliative care financing in England, Germany, Hungary, Republic of Ireland, New Zealand, The Netherlands, Norway, Poland, Spain, Sweden, Switzerland, the United States and Wales. These represent different levels of service development and a variety of funding mechanisms.Results:Funding mechanisms reflect country-specific context and local variations in care provision. Patterns emerging include the following:Provider payment is rarely linked to population need and often perpetuates existing inequitable patterns in service provision.Funding is frequently characterised as a mixed system of charitable, public and private payers.The basis on which providers are paid for services rarely reflects individual care input or patient needs.Conclusion:Funding mechanisms need to be well understood and used with caution to ensure best practice and minimise perverse incentives. Before we can conduct cross-national comparisons of costs and impact of palliative care, we need to understand the funding and policy context for palliative care in each country of interest
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