570 research outputs found
Online peer support for students
While many UK higher education institutions have websites offering information and advice on common student problems, interactive online support is less common. This article describes a project developing internet-based mutual support for students experiencing psychological problems at University College London
Evidence of a Plasmoid-Looptop Interaction and Magnetic Inflows During a Solar Flare/CME Eruptive Event
Observational evidence is presented for the merging of a downward-propagating
plasmoid with a looptop kernel during an occulted limb event on 2007 January
25. RHESSI lightcurves in the 9-18 keV energy range, as well as that of the 245
MHz channel of the Learmonth Solar Observatory, show enhanced nonthermal
emission in the corona at the time of the merging suggesting that additional
particle acceleration took place. This was attributed to a secondary episode of
reconnection in the current sheet that formed between the two merging sources.
RHESSI images were used to establish a mean downward velocity of the plasmoid
of 12 km/s. Complementary observations from the SECCHI suite of instruments
onboard STEREO-Behind showed that this process occurred during the acceleration
phase of the associated CME. From wavelet-enhanced EUVI, images evidence of
inflowing magnetic field lines prior to the CME eruption is also presented. The
derived inflow velocity was found to be 1.5 km/s. This combination of
observations supports a recent numerical simulation of plasmoid formation,
propagation and subsequent particle acceleration due to the tearing mode
instability during current sheet formation.Comment: 8 pages, 9 figures, ApJ (Accepted
Examining the role of Scotland’s telephone advice service (NHS 24) for managing health in the community : analysis of routinely collected NHS 24 data
Date of Acceptance: 15/06/2015 Funding This work was supported by the Chief Scientist Office, ScottishExecutive (grant no. CZH/4/692). Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.Peer reviewedPublisher PD
Retention and growth of urinary stones: insights from imaging
Recent work in nephrolithiasis has benefited from 2 special kinds of imaging: endoscopic study of patient kidneys with high-quality instruments, and examination of stones with microscopic computed tomography (micro CT). The combination of these has provided new evidence that there is more than 1 mechanism by which stones are retained in the kidney until they achieve sizes to be clinically relevant. This review describes what is known about the formation of stones on Randall's plaque, the formation of stones on ductal plugs and the ways in which stones may grow in free solution within the calyceal or pelvic spaces. Studies of urolithiasis need to recognize that any group of "stone formers" likely includes patients who differ fundamentally regarding which mechanism of stone formation is the primary route for their stones. Separation of patients on the basis of which mechanism (or combination of mechanisms) underlies their disease will be important for advancing research in the area of urolithiasis
Effective Techniques in Healthy Eating and Physical Activity Interventions: A Meta-Regression
This article may not exactly replicate the final version published in the APA journal. It is not the copy of record(c) 2012 APA, all rights reservedOBJECTIVE:
Meta-analyses of behavior change (BC) interventions typically find large heterogeneity in effectiveness and small effects. This study aimed to assess the effectiveness of active BC interventions designed to promote physical activity and healthy eating and investigate whether theoretically specified BC techniques improve outcome.
DESIGN:
Interventions, evaluated in experimental or quasi-experimental studies, using behavioral and/or cognitive techniques to increase physical activity and healthy eating in adults, were systematically reviewed. Intervention content was reliably classified into 26 BC techniques and the effects of individual techniques, and of a theoretically derived combination of self-regulation techniques, were assessed using meta-regression.
MAIN OUTCOME MEASURES:
Valid outcomes of physical activity and healthy eating.
RESULTS:
The 122 evaluations (N = 44,747) produced an overall pooled effect size of 0.31 (95% confidence interval = 0.26 to 0.36, I(2) = 69%). The technique, "self-monitoring," explained the greatest amount of among-study heterogeneity (13%). Interventions that combined self-monitoring with at least one other technique derived from control theory were significantly more effective than the other interventions (0.42 vs. 0.26).
CONCLUSION:
Classifying interventions according to component techniques and theoretically derived technique combinations and conducting meta-regression enabled identification of effective components of interventions designed to increase physical activity and healthy eating
Effect of the body wall on lithotripter shock waves
PURPOSE:
Determine the influence of passage through the body wall on the properties of lithotripter shock waves (SWs) and the characteristics of the acoustic field of an electromagnetic lithotripter.
METHODS:
Full-thickness ex vivo segments of pig abdominal wall were secured against the acoustic window of a test tank coupled to the lithotripter. A fiber-optic probe hydrophone was used to measure SW pressures, determine shock rise time, and map the acoustic field in the focal plane.
RESULTS:
Peak positive pressure on axis was attenuated roughly proportional to tissue thickness-approximately 6% per cm. Irregularities in the tissue path affected the symmetry of SW focusing, shifting the maximum peak positive pressure laterally by as much as ∼2 mm. Within the time resolution of the hydrophone (7-15 ns), shock rise time was unchanged, measuring ∼17-21 ns with and without tissue present. Mapping of the field showed no effect of the body wall on focal width, regardless of thickness of the body wall.
CONCLUSIONS:
Passage through the body wall has minimal effect on the characteristics of lithotripter SWs. Other than reducing pulse amplitude and having the potential to affect the symmetry of the focused wave, the body wall has little influence on the acoustic field. These findings help to validate laboratory assessment of lithotripter acoustic field and suggest that the properties of SWs in the body are much the same as have been measured in vitro
Mechanical haemolysis in shock wave lithotripsy (SWL): II. In vitro cell lysis due to shear
In this work we report injury to isolated red blood cells (RBCs) due to focused shock waves in a cavitation-free environment. The lithotripter-generated shock wave was refocused by a parabolic reflector. This refocused wave field had a tighter focus (smaller beam width and a higher amplitude) than the lithotripter wave field, as characterized by a membrane hydrophone.
Cavitation was eliminated by applying overpressure to the fluid. A novel passive cavitation detector (HP-PCD) operating at high overpressure (up to 7 MPa) was used to measure acoustic emission due to bubble activity. The typical 'double-bang' emission measured in the lithotripter free-field was replaced by a continuum of weak signals when the fluid was enclosed in a pressure chamber. No acoustic emissions were measured above an overpressure of 5.5 MPa. Aluminium foils were used to study shock wave damage and had distinct deformation features corresponding to exposure conditions, i.e. pitting and denting accompanied by wrinkling. Pitting was eliminated by high overpressure and so was due to cavitation bubble collapse, whereas denting and wrinkling were caused by the reflected shock wave refocused by the parabolic reflector.
RBCs suspended in phosphate-buffered saline (PBS) were exposed to the reflected wave field from a parabolic reflector and also from a flat reflector. Exposure to the wave field from the parabolic reflector increased haemolysis four-fold compared with untreated controls and was twice that of cell lysis with the flat reflector. Recently we analysed deformation and rupture of RBCs when subjected to a flow field set up by a focused shock. The cell lysis results presented here are in qualitative agreement with our theoretical prediction that haemolysis is directly related to the gradient of shock strength and validates shearing as a cell lysis mechanism in SWL
Multiresolution analysis of active region magnetic structure and its correlation with the Mt. Wilson classification and flaring activity
Two different multi-resolution analyses are used to decompose the structure
of active region magnetic flux into concentrations of different size scales.
Lines separating these opposite polarity regions of flux at each size scale are
found. These lines are used as a mask on a map of the magnetic field gradient
to sample the local gradient between opposite polarity regions of given scale
sizes. It is shown that the maximum, average and standard deviation of the
magnetic flux gradient for alpha, beta, beta-gamma and beta-gamma-delta active
regions increase in the order listed, and that the order is maintained over all
length-scales. This study demonstrates that, on average, the Mt. Wilson
classification encodes the notion of activity over all length-scales in the
active region, and not just those length-scales at which the strongest flux
gradients are found. Further, it is also shown that the average gradients in
the field, and the average length-scale at which they occur, also increase in
the same order. Finally, there are significant differences in the gradient
distribution, between flaring and non-flaring active regions, which are
maintained over all length-scales. It is also shown that the average gradient
content of active regions that have large flares (GOES class 'M' and above) is
larger than that for active regions containing flares of all flare sizes; this
difference is also maintained at all length-scales.Comment: Accepted for publication in Solar Physic
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