42,785 research outputs found
Handmaidens and pioneers: Three female anaesthetists and their contribution to anaesthesia in South Africa
The period during and after World War II saw enormous changes in the practice and status of anaesthesia, as well as in female participation. This article offers an account of three South African (SA) women who trained in anaesthetics before and during the War and participated in these changes. By the mid-1960s, they presided over the three independent anaesthetic departments at Johannesburg’s three main teaching hospitals, teaching generations of junior doctors. The first woman to register as a specialist anaesthetist in SA, Miriam (Mollie) Barlow, broke the glass ceiling in her own career by lobbying for the professional rights of medical women, although working within the constraints of the medical and political establishment. She also contributed to important SA research on malignant hyperthermia. Hilde Ginsberg collaborated with Barlow in the 1950s, reducing intraoperative and perioperative mortality at Coronation Hospital, and fought for key interventions in anaesthetic practice and policy through the South African Society of Anaesthetists (SASA), becoming its most long-serving and honoured female member. Kathleen Barbara Vetten’s exemplary career in academic medicine, including pioneering animal research (developing anaesthetic techniques for open-heart surgery in dogs and protocols for liver transplantation in primates) and a successful operation to separate craniopagus twins, shows both the achievement of and limits to female achievement at the end of this period. This article also offers a short account of factors that hindered black women from entering anaesthesia training, contributing to this history before the 1990s
Damping of gravitational waves by matter
We develop a unified description, via the Boltzmann equation, of damping of
gravitational waves by matter, incorporating collisions. We identify two
physically distinct damping mechanisms -- collisional and Landau damping. We
first consider damping in flat spacetime, and then generalize the results to
allow for cosmological expansion. In the first regime, maximal collisional
damping of a gravitational wave, independent of the details of the collisions
in the matter is, as we show, significant only when its wavelength is
comparable to the size of the horizon. Thus damping by intergalactic or
interstellar matter for all but primordial gravitational radiation can be
neglected. Although collisions in matter lead to a shear viscosity, they also
act to erase anisotropic stresses, thus suppressing the damping of
gravitational waves. Damping of primordial gravitational waves remains
possible. We generalize Weinberg's calculation of gravitational wave damping,
now including collisions and particles of finite mass, and interpret the
collisionless limit in terms of Landau damping. While Landau damping of
gravitational waves cannot occur in flat spacetime, the expansion of the
universe allows such damping by spreading the frequency of a gravitational wave
of given wavevector.Comment: 9 pages (10 pages in journal), published versio
Quantum-mechanical communication theory
Optimum signal reception using quantum-mechanical communication theor
Wrong drug administration errors amongst anaesthetists in a South African teaching hospital
A confidential, self-reporting survey was sent out to all 65 anaesthetists (25 specialists and 40 registrars) in the Department of Anaesthesia at the University of Cape Town with the aim of determining the incidence and possible causes of “wrong drug” administrations. The response rate was 95%. 93.5 % of respondents admitted to having administered the wrong drug at some stage of their anaesthetic career. 19/62 (30.6%) have injected the wrong drug or the correct drug into the wrong site on at least three occasions. 56.9 % of incidents involved muscle relaxants with suxamethonium chloride administered instead of fentanyl accounting for nearly a third of cases. 17.6 % of reported incidents were classified as being dangerous, with the potential to cause either severe haemodynamic instability and/or neurological damage or seizures
Landau critical velocity in weakly interacting Bose gases
The flow of a uniform Bose gas at speeds greater than the Landau critical
velocity, v_c, does not necessarily destroy superfluidity, but rather need only
lead to a decrease of the superfluid mass density, {\rho}_s. Analyzing a weakly
interacting Bose gas with a finite range interparticle interaction that leads
to a Landau critical velocity at non-zero quasiparticle momentum, we explicitly
construct the (non-uniform) condensate for fluid flow faster than v_c and
calculate the accompanying decrease in {\rho}_s. We briefly comment on the
relation of the physics to other problems in superfluids, e.g., solitons, and
vortices in Bose-Einstein condensates, and critical currents in
superconductors.Comment: 5 pages, 1 figur
Transverse-Longitudinal Coupling by Space Charge in Cyclotrons
A method is presented that enables to compute the parameters of matched beams
with space charge in cyclotrons with emphasis on the effect of the
transverse-longitudinal coupling. Equations describing the
transverse-longitudinal coupling and corresponding tune-shifts in first order
are derived for the model of an azimuthally symmetric cyclotron. The
eigenellipsoid of the beam is calculated and the transfer matrix is transformed
into block-diagonal form. The influence of the slope of the phase curve on the
transverse-longitudinal coupling is accounted for. The results are generalized
and numerical procedures for the case of an AVF cyclotron are presented. The
algorithm is applied to the PSI Injector II and Ring cyclotron and the results
are compared to TRANSPORT.Comment: 8 pages, 2 figure
Possible High-Redshift, Low-Luminosity AGN Activity in the Hubble Deep Field
In the Hubble Deep Field (HDF), twelve candidate sources of high-redshift (z
> 3.5) AGN activity have been identified. The color selection criteria were
established by passing spectra of selected quasars and Seyfert galaxies
(appropriately redshifted and modified for "Lyman forest" absorption), as well
as stars, observed normal and starburst galaxies, and galaxy models for various
redshifts through the filters used for the HDF observations. The actual
identification of AGN candidates also involved convolving a
Laplacian-of-Gaussian filter with the HDF images, thereby removing relatively
flat galactic backgrounds and leaving only the point-like components in the
centers. Along with positions and colors, estimated redshifts and absolute
magnitudes are reported, with the candidates falling toward the faint end of
the AGN luminosity function. One candidate has been previously observed
spectroscopically, with a measured redshift of 4.02. The number of sources
reported here is consistent with a simple extrapolation of the observed quasar
luminosity function to magnitude 30 in B_Johnson. Implications for ionization
of the intergalactic medium and for gravitational lensing are discussed.Comment: 10 pages LaTex plus 2 separate files (Table 1 which is a two-page
landscape LaTex file; and Figure 6 which is a large (0.7 MB) non-encapsulated
postscript file). Accepted for publication in the Astronomical Journa
Contamination in complex healthcare trials:the falls in care homes (FinCH) study experience
BACKGROUND: Trials are at risk of contamination bias which can occur when participants in the control group are inadvertently exposed to the intervention. This is a particular risk in rehabilitation studies where it is easy for trial interventions to be either intentionally or inadvertently adopted in control settings. The Falls in Care Homes (FinCH) trial is used in this paper as an example of a large randomised controlled trial of a complex intervention to explore the potential risks of contamination bias. We outline the FinCH trial design, present the potential risks from contamination bias, and the strategies used in the design of the trial to minimise or mitigate against this. The FinCH trial was a multi-centre randomised controlled trial, with embedded process evaluation, which evaluated whether systematic training in the use of the Guide to Action Tool for Care Homes reduced falls in care home residents. Data were collected from a number of sources to explore contamination in the FinCH trial. Where specific procedures were adopted to reduce risk of, or mitigate against, contamination, this was recorded. Data were collected from study e-mails, meetings with clinicians, research assistant and clinician network communications, and an embedded process evaluation in six intervention care homes. During the FinCH trial, there were six new falls prevention initiatives implemented outside the study which could have contaminated our intervention and findings. Methods used to minimise contamination were: cluster randomisation at the level of care home; engagement with the clinical community to highlight the risks of early adoption; establishing local collaborators in each site familiar with the local context; signing agreements with NHS falls specialists that they would maintain confidentiality regarding details of the intervention; opening additional research sites; and by raising awareness about the importance of contamination in research among participants. CONCLUSION: Complex rehabilitation trials are at risk of contamination bias. The potential for contamination bias in studies can be minimized by strengthening collaboration and dialogue with the clinical community. Researchers should recognise that clinicians may contaminate a study through lack of research expertise
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