17,603 research outputs found
Creating citizen-consumers? Public service reform and (un)willing selves
About the book: Postmodern theories heralded the "death of the subject", and thereby deeply contested our intuition that we are free and willing selves. In recent times, the (free) will has come under attack yet again. Findings from the neuro- and cognitive sciences claim the concept of will to be scientifically untenable, specifying that it is our brain rather than our 'self' which decides what we want to do. In spite of these challenges however, the willing self has come to take centre stage in our society: juridical and moral practices ascribing guilt, or the organization of everyday life attributing responsibilities, for instance, can hardly be understood without taking recourse to the willing subject.
In this vein, the authors address topics such as the genealogy of the concept of willing selves, the discourse on agency in neuroscience and sociology, the political debate on volition within neoliberal and neoconservative regimes, approaches toward novel forms of relational responsibility as well as moral evaluations in conceptualizing autonomy
Boltzmann Equations for Spin and Charge Relaxations in Superconductors
In a superconductor coupled with a ferromagnetic metal, spin and charge
imbalances can be induced by injecting spin-polarized electron current from the
ferromagnetic metal. We theoretically study a nonequilibrium distribution of
quasiparticles in the presence of spin and charge imbalances. We show that four
distribution functions are needed to characterize such a nonequilibrium
situation, and derive a set of linearized Boltzmann equations for them by
extending the argument by Schmid and Sch\"{o}n based on the quasiclassical
Green's function method. Using the Boltzmann equations, we analyze the spin
imbalance in a thin superconducting wire weakly coupled with a ferromagnetic
electrode. The spin imbalance induces a shift () of
the chemical potential for up-spin (down-spin) quasiparticles. We discuss how
is relaxed by spin-orbit impurity scattering.Comment: 16 pages, 2 figure
Strongly enhanced photon collection from diamond defect centres under micro-fabricated integrated solid immersion lenses
The efficiency of collecting photons from optically active defect centres in
bulk diamond is greatly reduced by refraction and reflection at the diamond-air
interface. We report on the fabrication and measurement of a geometrical
solution to the problem; integrated solid immersion lenses (SILs) etched
directly into the surface of diamond. An increase of a factor of 10 was
observed in the saturated count-rate from a single negatively charged
nitrogen-vacancy (NV-) within a 5um diameter SIL compared with NV-s under a
planar surface in the same crystal. A factor of 3 reduction in background
emission was also observed due to the reduced excitation volume with a SIL
present. Such a system is potentially scalable and easily adaptable to other
defect centres in bulk diamond.Comment: 5 Pages, 5 figures (4 subfigures) - corrected typ
Multiscale Kinetic Monte-Carlo for Simulating Epitaxial Growth
We present a fast Monte-Carlo algorithm for simulating epitaxial surface
growth, based on the continuous-time Monte-Carlo algorithm of Bortz, Kalos and
Lebowitz. When simulating realistic growth regimes, much computational time is
consumed by the relatively fast dynamics of the adatoms. Continuum and
continuum-discrete hybrid methods have been developed to approach this issue;
however in many situations, the density of adatoms is too low to efficiently
and accurately simulate as a continuum. To solve the problem of fast adatom
dynamics, we allow adatoms to take larger steps, effectively reducing the
number of transitions required. We achieve nearly a factor of ten speed up, for
growth at moderate temperatures and large D/F.Comment: 7 pages, 6 figures; revised text, accepted by PR
The Birth of High Mass Stars: Accretion and/or Mergers?
The observational consequences of the merger scenario for massive star
formation are explored and contrasted with the gradual accumulation of mass by
accretion. Protostellar mergers may produce high luminosity infrared flares
lasting years to centuries followed by a luminosity decline on the
Kelvin-Helmholtz time-scale of the merger product. Mergers may be surrounded by
thick tori of expanding debris, impulsive wide-angle outflows, and shock
induced maser and radio continuum emission. Collision products are expected to
have fast stellar rotation and a large multiplicity fraction. Close encounters
or mergers will produce circumstellar debris disks with an orientation that
differs form that of a pre-existing disk. The extremely rare merger of two
stars close to the upper-mass end of the IMF may be a possible pathway to
hypernova generated gamma-ray bursters. While accretional growth can lead to
the formation of massive stars in isolation or in loose clusters, mergers can
only occur in high-density cluster environments. It is proposed that the
outflow emerging from the OMC1 core in the Orion molecular cloud was produced
by a protostellar merger that released between to ergs less
than a thousand years ago
Temperature dependence of the interlayer magnetoresistance of quasi-one-dimensional Fermi liquids at the magic angles
The interlayer magnetoresistance of a quasi-one-dimensional Fermi liquid is
considered for the case of a magnetic field that is rotated within the plane
perpendicular to the most-conducting direction. Within semi-classical transport
theory dips in the magnetoresistance occur at integer amgic angles only when
the electronic dispersion parallel to the chains is nonlinear. If the field
direction is fixed at one of the magic angles and the temperature is varied the
resulting variation of the scattering rate can lead to a non-monotonic
variation of the interlayer magnetoresistance with temperature. Although the
model considered here gives a good description of some of the properties of the
Bechgaard salts, (TMTSF)2PF6 for pressures less than 8kbar and (TMTSF)2ClO4 it
gives a poor description of their properties when the field is parallel to the
layers and of the intralayer transport.Comment: 10pages, RevTeX + epsf, 3 figure
The spectrum and outcome of paediatric traumatic brain injury in KwaZulu-Natal Province, South Africa has not changed over the last two decades
Objectives. This retrospective review of a prospectively entered and maintained hybrid electronic trauma registry was intended to develop a comprehensive overview of traumatic brain injury (TBI) in children and adolescents and to compare it with previous audits from our local environment and from other developing world centres. All TBI patients admitted to hospital were included in this study. We reviewed the age, gender, outcomes, radiological findings and treatment of the patients.Methods. All patients aged ≤18 years old who were admitted by the Pietermaritzburg Metropolitan Trauma Service (PMTS) with TBI between December 2012 and December 2016 were included in this audit. Results. During the 4-year period under review, a total of 563 children and adolescents were treated for TBI by the PMTS. The median age was 6.4 years and 29% (n=165) were females. The mechanism of TBI was blunt trauma in 96% (n=544) of cases, with 4% (n=19) suffering penetrating trauma. The penetrating mechanisms included impalement by a cow horn and miscellaneous injuries due to saws, axes, barbed wire, spades, stones and knives. The blunt mechanisms included falls (n=102), assaults (n=108), collapse of a building (n=28), bicycle-related injury (n=14), falling off a moving vehicle (n=280), motor vehicle accident (MVA; n=59), pedestrian vehicle accident (PVA; n=183) and animal-related injuries (n=8). There were 454 (80%) mild, 67 (12%) moderate and 42 (7%) severe cases of TBI. A total of 48 patients were admitted to the intensive care unit and 23 were admitted to the high care unit. Nine patients died. All the deaths were in the MVA and PVA group. The spectrum of TBI as diagnosed on computed tomography scans was nonspecific cerebral contusion (n=92), depressed skull fracture (n=70), sub-arachnoid haemorrhage (n=60), extradural haemorrhage (n=41), intracerebral haemorrhage (n=19), free air (n=19), subdural haemorrhage (n=13), intraventricular haemorrhage (n=9). A total of 62 (11%) patients required surgery.Conclusion. There is a significant burden of paediatric TBI in Pietermaritzburg. The majority of TBI was related to blunt trauma and assaults were very common. Although the short-term outcomes are good, the long-term consequences are poorly understood. Injury prevention programmes are needed to help reduce this burden of disease and a nationwide trauma registry is long overdue.
Heated Cooling Flows
In conventional models of galactic and cluster cooling flows widespread
cooling (mass dropout) is assumed to avoid accumulation of unacceptably large
central masses. However, recent XMM observations have failed to find spectral
evidence for locally cooling gas. This has revived the notion that cooling
flows are heated by some process such as an intermittent, low-level AGN
involving supermassive black holes in the central galaxy. To explore this
hypothesis, we consider the gasdynamical consequences of galactic cooling flows
heated by many different scenarios without specifying the detailed physics of
the heating process. We are unable to find a single acceptable heated flow in
reasonable agreement with well observed hot gas temperature and density
profiles, even using finely tuned parameters. Idealized flows in which
radiative cooling is perfectly balanced by global heating are grossly
incompatible with observations. Flows heated by episodic central feedback
generate quasi-cyclic changes in the hot gas density profile which are not
supported by current observations. Paradoxically, centrally heated (or
pressurized) cooling flows experience spontaneous non-linear compressions that
result in spatially widespread cooling instabilities. Therefore, spectral
evidence for cooling gas is difficult to avoid by central heating.Comment: 17 pages (emulateapj5) with 12 figures and Appendix; accepted by The
Astrophysical Journa
First Results from the Cryogenic Dark Matter Search in the Soudan Underground Lab
We report the first results from a search for weakly interacting massive
particles (WIMPs) in the Cryogenic Dark Matter Search (CDMS) experiment at the
Soudan Underground Laboratory. Four Ge and two Si detectors were operated for
52.6 live days, providing 19.4 kg-d of Ge net exposure after cuts for recoil
energies between 10--100 keV. A blind analysis was performed using only
calibration data to define the energy threshold and selection criteria for
nuclear-recoil candidates. Using the standard dark-matter halo and
nuclear-physics WIMP model, these data set the world's lowest exclusion limits
on the coherent WIMP-nucleon scalar cross-section for all WIMP masses above 15
GeV, ruling out a significant range of neutralino supersymmetric models. The
minimum of this limit curve at the 90% C.L. is 4 x 10^{-43} cm^2 at a WIMP mass
of 60 GeV.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Lett; minor
clarifications in response to referee's comment
Superconductivity Induced by Bond Breaking in the Triangular Lattice of IrTe2
IrTe2, a layered compound with a triangular iridium lattice, exhibits a
structural phase transition at approximately 250 K. This transition is
characterized by the formation of Ir-Ir bonds along the b-axis. We found that
the breaking of Ir-Ir bonds that occurs in Ir1-xPtxTe2 results in the
appearance of a structural critical point in the T = 0 limit at xc = 0.035.
Although both IrTe2 and PtTe2 are paramagnetic metals, superconductivity at Tc
= 3.1 K is induced by the bond breaking in a narrow range of x > xc in
Ir1-xPtxTe2. This result indicates that structural fluctuations can be involved
in the emergence of superconductivity.Comment: 10 pages, 4 figure
- …