83,400 research outputs found
The effect of wall compliance on the Goertler vortex instability
The stability of the flow of a viscous incompressible fluid over a curved compliant wall to longitudinal Goertler vortices is investigated. The compliant wall is modeled by a particularly simple equation relating the induced wall displacement to the pressure in the overlying fluid. Attention is restricted to the large Goertler number regime; this regime being appropriate to the most unstable Goertler mode. The effect of wall compliance on this most unstable mode is investigated
Roles, service knowledge and priorities in the provision of palliative care: a postal survey of London GPs
Objectives: To explore general practitioners' (GPs) current involvement in and attitudes towards the provision of palliative care in primary care. Methods: Postal survey of 356 London-based GPs, assessing attitudes towards palliative care provision, district nursing and specialist palliative care services, and priorities for future service development. Results: Currently, 65% of GPs were providing palliative care to patients on their list; 72% agreed or strongly agreed palliative care was a central part of their role; and 27% wanted to hand care over to specialists. Most GPs (66%) disagreed with the statement that 'palliative care is mainly district nursing (DN) work'. Many were unaware of out-of-hours DN and specialist palliative care services. Multi-variable analysis found four GP characteristics - larger practice size, more years experience as a GP, receipt of palliative care education, and current provision of palliative care - were associated with agreement that palliative care was central to a GP's role. Conclusion: A minority of NHS GPs in London would rather have no involvement in palliative care in primary care. Knowledge of current services for palliative care is generally poor among GPs. These findings highlight potential gaps in services, particularly in small practices. Specialists will need to consider these factors in working with GPs to develop primary palliative care and to enable greater access to specialist palliative care
EISCAT observations during MAC/SINE and MAC/Epsilon
The EISCAT incoherent scatter radar facility in Tromsoe, Norway was operated during the MAC/SINE campaign for 78 hours in the period 10 June to 17 July 1987, and during the MAC/Epsilon campaign for 90 hours in the period 15 October to 5 November 1987. The VHF (224 MHz) radar operations during MAC/SINE yielded most interesting observations of strong coherent echoes from the mesopause region. Characteristic data of these polar mesospheric summer echoes are presented. The UHF (933 MHz) radar operations during MAC/Epsilon were done with 18 deg off zenith beam and allows the deduction of meridonal and horizontal wind components as well as radial velocity spectra in addition to the usual electron density profiles in the D and lower E regions. Some results from the VHF and UHF radars indicating the presence of gravity waves are examined
Polynuclear ruthenium and osmium complexes, and related electron-dense staining reagents
Imperial Users onl
Discovery of hydroxyl and water masers in R Aquarii and H1-36 Arae
We present the first results from an all-sky maser-line survey of symbiotic
Miras. Interferometric spectral-line observations of R Aqr and H1-36 Arae have
revealed a 22-GHz water maser in the former and 1612-MHz hydroxyl and weak
22-GHz water maser emission from the latter. H1-36 has thus become the first
known symbiotic OH/IR star. We have also detected weak OH line emission from
the vicinity of R Aqr, but we note that there are small discrepencies between
the OH- and H2O-line velocities and positions. These detections demonstrate
unequivocally that dust can shield some circumstellar hydroxyl and water
molecules from dissociation, even in systems which possess intense local
sources of UV. Finally, we discuss some of the implications of these
observations. The narrow profile of the water maser in R Aqr means that there
may finally be an opportunity to determine the system's orbital parameters. We
also point out that high resolution synthesis observations may trace the
distribution of dust in H1-36 and R Aqr, possibly throwing light on the
mass-loss process in symbiotic Miras and placing constraints on the amount of
collimation experienced by UV radiation from their hot, compact companions.Comment: 7 pages; no figures attached; LaTex (MN style); postscript figures
via anonymous ftp in /users/ers on astro.caltech.edu; University of Toronto
pre-print; ERSRJI
A Bohmian approach to quantum fractals
A quantum fractal is a wavefunction with a real and an imaginary part
continuous everywhere, but differentiable nowhere. This lack of
differentiability has been used as an argument to deny the general validity of
Bohmian mechanics (and other trajectory--based approaches) in providing a
complete interpretation of quantum mechanics. Here, this assertion is overcome
by means of a formal extension of Bohmian mechanics based on a limiting
approach. Within this novel formulation, the particle dynamics is always
satisfactorily described by a well defined equation of motion. In particular,
in the case of guidance under quantum fractals, the corresponding trajectories
will also be fractal.Comment: 19 pages, 3 figures (revised version
Statistical Understanding of Quark and Lepton Masses in Gaussian Landscapes
The fundamental theory of nature may allow a large landscape of vacua. Even
if the theory contains a unified gauge symmetry, the 22 flavor parameters of
the Standard Model, including neutrino masses, may be largely determined by the
statistics of this landscape, and not by any symmetry. Then the measured values
of the flavor parameters do not lead to any fundamental symmetries, but are
statistical accidents; their precise values do not provide any insights into
the fundamental theory, rather the overall pattern of flavor reflects the
underlying landscape. We investigate whether random selection from the
statistics of a simple landscape can explain the broad patterns of quark,
charged lepton, and neutrino masses and mixings. We propose Gaussian landscapes
as simplified models of landscapes where Yukawa couplings result from overlap
integrals of zero-mode wavefunctions in higher-dimensional supersymmetric gauge
theories. In terms of just five free parameters, such landscapes can account
for all gross features of flavor, including: the hierarchy of quark and charged
lepton masses; small quark mixing angles, with 13 mixing less than 12 and 23
mixing; very light Majorana neutrino masses, with the solar to atmospheric
neutrino mass ratio consistent with data; distributions for leptonic 12 and 23
mixings that are peaked at large values, while the distribution for 13 mixing
is peaked at low values; and order unity CP violating phases in both the quark
and lepton sectors. While the statistical distributions for flavor parameters
are broad, the distributions are robust to changes in the geometry of the extra
dimensions. Constraining the distributions by loose cuts about observed values
leads to narrower distributions for neutrino measurements of 13 mixing, CP
violation, and neutrinoless double beta decay.Comment: 86 pages, 26 figures, 2 tables, and table of content
Quark and Lepton Masses from Gaussian Landscapes
The flavor structure of the standard model (SM) might arise from random selection on a landscape. We propose a class of simple models, “Gaussian landscapes,” where Yukawa couplings derive from overlap integrals of Gaussian wave functions on extra-dimensions. Statistics of vacua are generated by scanning the peak positions of these zero-modes, giving probability distributions for all flavor observables. Gaussian landscapes can account for all observed flavor patterns with few free parameters. Although they give broad probability distributions, the predictions are correlated and accounting for measured parameters sharpens the distributions of future neutrino measurements
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