13,992 research outputs found
The high-energy gamma-ray light curve of PSR B1259 -63
The high-energy gamma-ray light curve of the binary system PSR B1259 -63, is
computed using the approach that successfully predicted the spectrum at
periastron. The simultaneous INTEGRAL and H.E.S.S. spectra taken 16 days after
periastron currently permit both a model with dominant radiative losses, high
pulsar wind Lorentz factor and modest efficiency as well as one with dominant
adiabatic losses, a slower wind and higher efficiency. In this paper we shown
how the long-term light curve may help to lift this degeneracy.Comment: 4 pages, to appear in proceedings of: Astrophysical Sources of High
Energy Particles and Radiation, Torun (2005
Supporting children and young people to assume responsibility from their parents for the self-management of their long-term condition: An integrative review
© 2019 John Wiley & Sons Ltd Background: Children and young people with long-term conditions (LTCs) are usually dependent on, or share management with, their families and are expected to develop self-management skills as they mature. However, during adolescence, young people can find it challenging to follow prescribed treatment regimens resulting in poor clinical outcomes. Though reviews have looked at children's and parents' experiences of self-management, none have explicitly examined the parent-to-child transfer of self-management responsibility. Methods: An integrative review was conducted with the aim of exploring the parent-to-child transfer of LTC self-management responsibility, through addressing two questions: (a) How do children assume responsibility from their parents for self-management of their LTC? (b) What influences the parent-to-child transfer of this responsibility? Eight databases were searched for papers published from 1995 to 2017. Methodological quality was assessed; included papers were synthesized to identify themes. Results: Twenty-nine papers were identified. Most papers used qualitative designs and focused on children with diabetes. Participants were predominantly children and/or parents; only two studies included health professionals. Assuming self-management responsibility was viewed as part of normal development but was rarely explored within the context of the child gaining independence in other areas of their life. Children and parents adopted strategies to help the transfer, but there was limited evidence around health professionals' roles and ambivalence around what was helpful. There was a lack of clarity over whether children and parents were aiming for shared management, or self-management, and whether this was a realistic or desired goal for families. Multiple factors such as the child, family, social networks, health professional, and LTC influenced how a child assumed responsibility. Conclusions: Evidence suggests that the parent-to-child transfer of self-management responsibility is a complex, individualized process. Further research across childhood LTCs is needed to explore children's, parents', and professionals' views on this process and what support families require as responsibilities change
Failure of non-vacuum steam sterilization processes for dental handpieces
Background:
Dental handpieces are used in critical and semi-critical operative interventions. Although a number of dental professional bodies recommend that dental handpieces are sterilized between patient use there is a lack of clarity and understanding of the effectiveness of different steam sterilization processes. The internal mechanisms of dental handpieces contain narrow lumens (0·8-2·3mm) which can impede the removal of air and ingress of saturated steam required to achieve sterilization conditions.
Aim:
To identify the extent of sterilization failure in dental handpieces using a non-vacuum process.
Methods:
In-vitro and in-vivo investigations were conducted on commonly used UK benchtop steam sterilizers and three different types of dental handpieces. The sterilization process was monitored inside the lumens of dental handpieces using thermometric (TM) methods (dataloggers), chemical indicators (CI) and biological indicators (BI).
Findings:
All three methods of assessing achievement of sterility within dental handpieces that had been exposed to non-vacuum sterilization conditions demonstrated a significant number of failures (CI=8/3,024(fails/n tests); BI=15/3,024; TM=56/56) compared to vacuum sterilization conditions (CI=2/1,944; BI=0/1,944; TM=0/36). The dental handpiece most likely to fail sterilization in the non-vacuum process was the surgical handpiece. Non-vacuum sterilizers located in general dental practice had a higher rate of sterilization failure (CI=25/1,620; BI=32/1,620; TM=56/56) with no failures in vacuum process.
Conclusion:
Non-vacuum downward/gravity displacement, type-N steam sterilizers are an unreliable method for sterilization of dental handpieces in general dental practice. The handpiece most likely to fail sterilization is the type most frequently used for surgical interventions
Investigating steam penetration using thermometric methods in dental handpieces with narrow internal lumens during sterilizing processes with non-vacuum or vacuum processes
Background:
Dental handpieces are required to be sterilized between patient use. Vacuum steam sterilization processes with fractionated pre/post-vacuum phases or unique cycles for specified medical devices, are required for hollow instruments with internal lumens to assure successful air removal. Entrapped air will compromise achievement of required sterilization conditions. Many countries and professional organisations still advocate non-vacuum sterilization processes for these devices.
Aim:
To investigate non-vacuum downward/gravity displacement, type-N steam sterilization of dental handpieces, using thermometric methods to measure time to achieve sterilization temperature at different handpiece locations.
Methods:
Measurements at different positions within air turbines were undertaken with thermocouples and dataloggers. Two examples of commonly used UK benchtop steam sterilizers were tested; a non-vacuum benchtop sterilizer (Little Sister 3, Eschmann, UK) and a vacuum benchtop sterilizer (Lisa, W&H, Austria). Each sterilizer cycle was completed with three handpieces and each cycle in triplicate.
Findings:
A total of 140 measurements inside dental handpiece lumens were recorded. We demonstrate that the non-vacuum process fails (time range 0-150 seconds) to reliably achieve sterilization temperatures within the time limit specified by the International standard (15 seconds equilibration time). The measurement point at the base of the handpiece failed in all test runs (n=9) to meet the standard. No failures were detected with the vacuum steam sterilization type B process with fractionated pre-vacuum and post-vacuum phases.
Conclusion:
Non-vacuum downward/gravity displacement, type-N steam sterilization processes are unreliable in achieving sterilization conditions inside dental handpieces and the base of the handpiece is the site most likely to fail
Complex X-ray spectral variability in Mkn 421 observed with XMM-Newton
The bright blazar Mkn 421 has been observed four times for uninterrupted
durations of ~ 9 - 13 hr during the performance verification and calibration
phases of the XMM-Newton mission. The source was strongly variable in all
epochs, with variability amplitudes that generally increased to higher energy
bands. Although the detailed relationship between soft (0.1 - 0.75 keV) and
hard (2 - 10 keV) band differed from one epoch to the next, in no case was
there any evidence for a measurable interband lag, with robust upper limits of
hr in the best-correlated light curves. This is in conflict
with previous claims of both hard and soft lags of ~1 hr in this and other
blazars. However, previous observations suffered a repeated 1.6 hr feature
induced by the low-Earth orbital period, a feature that is not present in the
uninterrupted XMM-Newton data. The new upper limit on leads to a lower
limit on the magnetic field strength and Doppler factor of B \delta^{1/3} \gs
4.7 G, mildly out of line with the predictions from a variety of homogeneous
synchrotron self-Compton emission models in the literature of G. Time-dependent spectral fitting was performed on all epochs,
and no detectable spectral hysteresis was seen. We note however that the source
exhibited significantly different spectral evolutionary behavior from one epoch
to the next, with the strongest correlations in the first and last and an
actual divergance between soft and hard X-ray bands in the third. This
indicates that the range of spectral variability behavior in Mkn 421 is not
fully described in these short snippets; significantly longer uninterrupted
light curves are required, and can be obtained with XMM-Newton.Comment: 21 pages, 4 figures, accepted for ApJ, scheduled for August 1, 200
Electrical current distribution across a metal-insulator-metal structure during bistable switching
Combining scanning electron microscopy (SEM) and electron-beam-induced
current (EBIC) imaging with transport measurements, it is shown that the
current flowing across a two-terminal oxide-based capacitor-like structure is
preferentially confined in areas localized at defects. As the thin-film device
switches between two different resistance states, the distribution and
intensity of the current paths, appearing as bright spots, change. This implies
that switching and memory effects are mainly determined by the conducting
properties along such paths. A model based on the storage and release of charge
carriers within the insulator seems adequate to explain the observed memory
effect.Comment: 8 pages, 7 figures, submitted to J. Appl. Phy
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Longitudinal Effects of Supplemental Forage on the Honey Bee (Apis mellifera) Microbiota and Inter- and Intra-Colony Variability
Direct observation of size scaling and elastic interaction between nano-scale defects in collision cascades
Using in-situ transmission electron microscopy, we have directly observed
nano-scale defects formed in ultra-high purity tungsten by low-dose high energy
self-ion irradiation at 30K. At cryogenic temperature lattice defects have
reduced mobility, so these microscope observations offer a window on the
initial, primary damage caused by individual collision cascade events. Electron
microscope images provide direct evidence for a power-law size distribution of
nano-scale defects formed in high-energy cascades, with an upper size limit
independent of the incident ion energy, as predicted by Sand et al. [Eur. Phys.
Lett., 103:46003, (2013)]. Furthermore, the analysis of pair distribution
functions of defects observed in the micrographs shows significant
intra-cascade spatial correlations consistent with strong elastic interaction
between the defects
X-Ray Spectral Variability of PKS 2005-489 During the Spectacular November 1998 Flare
We report on monitoring of the BL Lac object PKS 2005-489 by the Rossi X-ray
Timing Explorer (RXTE) in October-December 1998. During these months, the
source underwent a spectacular flare; at its peak on November 10, its 2-10 keV
flux was , over 30 times
brighter than in quiescence. During the rising phase, the X-ray spectrum of PKS
2005-489 hardened considerably, reaching near maximum. During the declining phase, the X-ray spectrum
steepened rapidly, reaching , then became somewhat harder
towards the end of December (). While such behavior has been
seen before, the simplicity, magnitude and duration of this flare allowed us to
study it in great detail. We argue that this flare was caused by either the
injection of particles into the jet or {\it in situ} particle acceleration, and
that the spectral steepening which followed the flare maximum was the result of
synchrotron cooling. Contrary to other recently observed blazar flares (e.g.,
Mkn 501, 3C 279, PKS 2155-304), our results do not imply a major shift in the
location of the synchrotron peak during this flare.Comment: ApJ Letters in press, 6 pages, 2 figures Corrected reference
Gamma-rays from PSR B1259 -63
The high-energy gamma-ray emission discovered using the H.E.S.S. telescopes
from the binary system PSR B1259 -63, is modelled using an extension of the
approach that successfully predicted it. We find that the simultaneous INTEGRAL
and H.E.S.S. data permit both a model with dominant radiative losses, high
pulsar wind Lorentz factor and modest efficiency as well as one with dominant
adiabatic losses, a slower wind and higher efficiency. Additional,
simultaneous, X-ray and TeV data sets are needed to lift this degeneracy.Comment: 4 pages, to appear in: Proceedings of the 29th International Cosmic
Ray Conference, Pune (2005
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