68 research outputs found
The Sick Person and Science: The Role of Religion in Medicine and Modernity
The secularization thesis predicts that science will eventually render religion useless due to inherent incompatibilities. Modern discourses have created a similar conflict between scientific competence and more humanistic aspects of medicine. I will use the secularization thesis to analyze the unusual role of medicine as both a scientific discipline and a venture into the moral realm. Religion affects the way humans understand nature, which impacts the possibility of the scientific method as well as the role of the sick person in society. Though individuals have always been healers, institutionalizing healthcare through the creation of hospitals indicates a profound shift of values. The Greeks did not share these convictions, and thus did not have a mechanistic view of science nor a community responsibility towards healing.
I will argue that non-scientific modes of competence are ancient. Christianity has contributed to these values by building upon the contributions of the ancient Greeks, bringing forward shifts in both realms—scientific and moral—that have created the paradigm in which modern medicine exists. The persisting religious values and assumptions in medicine provide a practical example of the secularization thesis applied and overcome; they illustrate how a “scientific” discipline is inextricably bound to religion, both historically and in contemporary expectations. These foundations have never gone away; religious assumptions remain crucial for the scientific and moral capacities of the modern doctor. Medicine provides a lens to evaluate the role of religion in today’s pluralistic and secular society
3D-printed coded apertures for x-ray backscatter radiography
Copyright 2017 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.Many different mask patterns can be used for X-ray backscatter imaging using coded apertures, which can find application in the medical, industrial and security sectors. While some of these patterns may be considered to have a self-supporting structure, this is not the case for some of the most frequently used patterns such as uniformly redundant arrays or any pattern with a high open fraction. This makes mask construction difficult and usually requires a compromise in its design by drilling holes or adopting a no two holes touching version of the original pattern. In this study, this compromise was avoided by 3D printing a support structure that was then filled with a radiopaque material to create the completed mask. The coded masks were manufactured using two different methods, hot cast and cold cast. Hot casting involved casting a bismuth alloy at 80°C into the 3D printed acrylonitrile butadiene styrene mould which produced an absorber with density of 8.6 g cm-3. Cold casting was undertaken at room temperature, when a tungsten/epoxy composite was cast into a 3D printed polylactic acid mould. The cold cast procedure offered a greater density of around 9.6 to 10 g cm-3 and consequently greater X-ray attenuation. It was also found to be much easier to manufacture and more cost effective. A critical review of the manufacturing procedure is presented along with some typical images. In both cases the 3D printing process allowed square apertures to be created avoiding their approximation by circular holes when conventional drilling is used
Density of states in SF bilayers with arbitrary strength of magnetic scattering
We developed the self-consistent method for the calculation of the density of
states in the SF bilayers. It based on the quasi-classical Usadel
equations and takes into account the suppression of superconductivity in the S
layer due to the proximity effect with the F metal, as well as existing
mechanisms of the spin dependent electron scattering. We demonstrate that the
increase of the spin orbit or spin flip electron scattering rates results in
completely different transformations of at the free F layer
interface. The developed formalism has been applied for the interpretation of
the available experimental data.Comment: 5 pages, 8 figure
X-ray backscatter radiography with lower open fraction coded masks
Copyright 2017 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.Single sided radiographic imaging would find great utility for medical, aerospace and security applications. While coded apertures can be used to form such an image from backscattered X-rays they suffer from near field limitations that introduce noise. Several theoretical studies have indicated that for an extended source the images signal to noise ratio may be optimised by using a low open fraction (<0.5) mask. However, few experimental results have been published for such low open fraction patterns and details of their formulation are often unavailable or are ambiguous. In this paper we address this process for two types of low open fraction mask, the dilute URA and the Singer set array. For the dilute URA the procedure for producing multiple 2D array patterns from given 1D binary sequences (Barker codes) is explained. Their point spread functions are calculated and their imaging properties are critically reviewed. These results are then compared to those from the Singer set and experimental exposures are presented for both type of pattern; their prospects for near field imaging are discussed
Proximity effect gaps in S/N/FI structures
We study the proximity effect in hybrid structures consisting of
superconductor and ferromagnetic insulator separated by a normal diffusive
metal (S/N/FI structures). These stuctures were proposed to realize the
absolute spin-valve effect. We pay special attention to the gaps in the density
of states of the normal part. We show that the effect of the ferromagnet is
twofold: It not only shifts the density of states but also provides suppression
of the gap. The mechanism of this suppression is remarkably similar to that due
to magnetic impurities. Our results are obtained from the solution of
one-dimensional Usadel equation supplemented with boundary conditions for
matrix current at both interfaces.Comment: Published in The European Physical Journal
Josephson currents through spin-active interfaces
The Josephson coupling of two isotropic s-wave superconductors through a
small, magnetically active junction is studied. This is done as a function of
junction transparency and of the degree of spin-mixing occurring in the
barrier. In the tunneling limit, the critical current shows an anomalous 1/T
temperature dependence at low temperatures and for certain magnetic
realizations of the junction. The behavior of the Josephson current is governed
by Andreev bound states appearing within the superconducting gap and the
position of these states in energy is tunable with the magnetic properties of
the barrier. This study is done using the equilibrium part of the
quasiclassical Zaitsev-Millis-Rainer-Sauls boundary condition for spin-active
interfaces and a general solution of the boundary condition is found. This
solution is a generalization of the one recently presented by Eschrig [M.
Eschrig, Phys. Rev B 61, 9061 (2000)] for spin-conserving interfaces and allows
an effective treatment of the problem of a superconductor in proximity to a
magnetically active material.Comment: 8 pages + 3 eps figure
Quasiparticle energy spectrum in ferromagnetic Josephson weak links
The quasiparticles energy spectrum in clean ferromagnetic weak links between
conventional superconductors is calculated. Large peaks in DOS, due to a
special case of Andreev reflection at the ferromagnetic barrier, correspond to
spin-splitt bound states. Their energies are obtained as a function of the
barrier thickness, exchange field strength, and of the macroscopic phase
difference at the link, related to the Josephson current. In the ground
state, can be 0 or , depending on the ferromagnetic barrier
influence. Conditions for the appearence of the zero-energy bound states (ZES)
and for the spin polarized ground state (SPGS) are obtained analytically. It is
shown that ZES appear only outside the weak link ground state.Comment: 11 pages, 6 figure
Andreev Reflection In Ferromagnet-Superconductor Junctions
The transport properties of a ferromagnet-superconductor (FS) junction are
studied in a scattering formulation. Andreev reflection at the FS interface is
strongly affected by the exchange interaction in the ferromagnet. The
conductance G_FS of a ballistic point contact between F and S can be both
larger or smaller than the value G_FN with the superconductor in the normal
state, depending on the ratio of the exchange and Fermi energies. If the
ferromagnet contains a tunnel barrier (I), the conductance G_FIFS exhibits
resonances which do not vanish in linear response -- in contrast to the Tomasch
oscillations for non-ferromagnetic materials.Comment: 8 pages, RevTeX v3.0, including 3 encapsulated postscript figures;
[2017: figures included in text
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