1,445 research outputs found
"Roll back the years": A study of grandparent special guardians' experiences and implications for social work policy and practice in England
Growing numbers of grandparent special guardians (GSGs) are assuming responsibility for increasing numbers of children in the care system in England. Special guardianship arrangements are increasingly used as a permanency option as they allow children to remain in their kinship networks, rather than in local authority care or be adopted; yet there is a scarcity of research on GSG carers’ experiences. This article reports a small qualitative research study where ten sets of grandparents were interviewed to explore their journey to becoming GSGs and to theorise their subsequent experiences. Two themes emerge. Firstly, experiences of the assessment process are elaborated, decisions often being made at a time of family crisis, impacting on GSGs: financial, employment, relational. Secondly, GSGs’ experiences of managing often-challenging relationships and contact arrangements between the grandchildren and the parents reveal three main relationship management approaches emerging: containing-flexible; containing-controlled and; uncontained/defeated approaches. Anthropological concepts of affinity help theorise the GSGs’ ambivalent responses to becoming carers in later life, enabling reconfigured kinship relationships in new family forms. Family policy and social work practice is critiqued as GSGs appear often left alone to ‘roll back the years’, to heal previous harms done to the grandchildren who end-up in their care
Re-localisation of microscopic lesions in their macroscopic context for surgical instrument guidance
Optical biopsies interrogate microscopic structure in vivo with a 2mm diameter miniprobe
placed in contact with the tissue for detection of lesions and assessment of disease
progression. After detection, instruments are guided to the lesion location for a new optical
interrogation, or for treatment, or for tissue excision during the same or a future examination.
As the optical measurement can be considered as a point source of information at the surface
of the tissue of interest, accurate guidance can be difficult. A method for re-localisation of the
sampling point is, therefore, needed.
The method presented in this thesis has been developed for biopsy site re-localisation
during a surveillance examination of Barrett’s Oesophagus. The biopsy site, invisible
macroscopically during conventional endoscopy, is re-localised in the target endoscopic
image using epipolar lines derived from its locations given by the tip of the miniprobe visible
in a series of reference endoscopic images. A confidence region can be drawn around the relocalised
biopsy site from its uncertainty that is derived analytically. This thesis also presents
a method to improve the accuracy of the epipolar lines derived for the biopsy site relocalisation
using an electromagnetic tracking system.
Simulations and tests on patient data identified the cases when the analytical
uncertainty is a good approximation of the confidence region and showed that biopsy sites
can be re-localised with accuracies better than 1mm. Studies on phantom and on porcine
excised tissue demonstrated that an electromagnetic tracking system contributes to more
accurate epipolar lines and re-localised biopsy sites for an endoscope displacement greater
than 5mm. The re-localisation method can be applied to images acquired during different
endoscopic examinations. It may also be useful for pulmonary applications. Finally, it can be
combined with a Magnetic Resonance scanner which can steer cells to the biopsy site for
tissue treatment
Microscopic nanomechanical dissipation in gallium arsenide resonators
We report on a systematic study of nanomechanical dissipation in
high-frequency (approximatively 300 MHz) gallium arsenide optomechanical disk
resonators, in conditions where clamping and fluidic losses are negligible.
Phonon-phonon interactions are shown to contribute with a loss background
fading away at cryogenic temperatures (3 K). Atomic layer deposition of alumina
at the surface modifies the quality factor of resonators, pointing towards the
importance of surface dissipation. The temperature evolution is accurately
fitted by two-level systems models, showing that nanomechanical dissipation in
gallium arsenide resonators directly connects to their microscopic properties.
Two-level systems, notably at surfaces, appear to rule the damping and
fluctuations of such high-quality crystalline nanomechanical devices, at all
temperatures from 3 to 300K
Elastic Scattering by Deterministic and Random Fractals: Self-Affinity of the Diffraction Spectrum
The diffraction spectrum of coherent waves scattered from fractal supports is
calculated exactly. The fractals considered are of the class generated
iteratively by successive dilations and translations, and include
generalizations of the Cantor set and Sierpinski carpet as special cases. Also
randomized versions of these fractals are treated. The general result is that
the diffraction intensities obey a strict recursion relation, and become
self-affine in the limit of large iteration number, with a self-affinity
exponent related directly to the fractal dimension of the scattering object.
Applications include neutron scattering, x-rays, optical diffraction, magnetic
resonance imaging, electron diffraction, and He scattering, which all display
the same universal scaling.Comment: 20 pages, 11 figures. Phys. Rev. E, in press. More info available at
http://www.fh.huji.ac.il/~dani
Early SPI/INTEGRAL contraints on the morphology of the 511 keV line emission in the 4th galactic quadrant
We provide first constraints on the morphology of the 511 keV line emission
from the galactic centre region on basis of data taken with the spectrometer
SPI on the INTEGRAL gamma-ray observatory. The data suggest an azimuthally
symmetric galactic bulge component with FWHM of ~9 deg with a 2 sigma
uncertainty range covering 6-18 deg. The 511 keV line flux in the bulge
component amounts to (9.9+4.7-2.1) 10e-4 ph cm-2 s-1. No evidence for a
galactic disk component has been found so far; upper 2 sigma flux limits in the
range (1.4-3.4) 10e-3 ph cm-2 s-1 have been obtained that depend on the assumed
disk morphology. These limits correspond to lower limits on the bulge-to-disk
ratio of 0.3-0.6.Comment: 5 pages, 3 figures, accepted for publication in A&
Fission of a multiphase membrane tube
A common mechanism for intracellular transport is the use of controlled
deformations of the membrane to create spherical or tubular buds. While the
basic physical properties of homogeneous membranes are relatively well-known,
the effects of inhomogeneities within membranes are very much an active field
of study. Membrane domains enriched in certain lipids in particular are
attracting much attention, and in this Letter we investigate the effect of such
domains on the shape and fate of membrane tubes. Recent experiments have
demonstrated that forced lipid phase separation can trigger tube fission, and
we demonstrate how this can be understood purely from the difference in elastic
constants between the domains. Moreover, the proposed model predicts timescales
for fission that agree well with experimental findings
The [CII] 158 um Line Deficit in Ultraluminous Infrared Galaxies Revisited
We present a study of the [CII] 157.74 um fine-structure line in a sample of
15 ultraluminous infrared (IR) galaxies (L_IR>10^12 Lsun; ULIRGs) using the
Long Wavelength Spectrometer (LWS) on the Infrared Space Observatory (ISO). We
confirm the observed order of magnitude deficit (compared to normal and
starburst galaxies) in the strength of the [CII] line relative to the far-IR
dust continuum emission found in our initial report (Luhman et al. 1998), but
here with a sample that is twice as large. This result suggests that the
deficit is a general phenomenon affecting 4/5 ULIRGs. We present an analysis
using observations of generally acknowledged photodissociation region (PDR)
tracers ([CII], [OI] 63 and 145 um, and FIR continuum emission), which suggests
that a high UV flux G_o incident on a moderate density n PDR could explain the
deficit. However, comparisons with other ULIRG observations, including CO
(1-0), [CI] (1-0), and 6.2 um polycyclic aromatic hydrocarbon (PAH) emission,
suggest that high G_o/n PDRs alone cannot produce a self-consistent solution
that is compatible with all of the observations. We propose that non-PDR
contributions to the FIR continuum can explain the apparent [CII] deficiency.
Here, unusually high G_o and/or n physical conditions in ULIRGs as compared to
those in normal and starburst galaxies are not required to explain the [CII]
deficit. Dust-bounded photoionization regions, which generate much of the FIR
emission but do not contribute significant [CII] emission, offer one possible
physical origin for this additional non-PDR component. Such environments may
also contribute to the observed suppression of FIR fine-structure emission from
ionized gas and PAHs, as well as the warmer FIR colors found in ULIRGs. The
implications for observations at higher redshifts are also revisited.Comment: to be published in The Astrophysical Journal, 58 page
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