A Novel Method of Solution for the Fluid Loaded Plate

We study the Cauchy problem associated with the equations governing a fluid loaded plate formulated on either the line or the half-line. We show that in both cases the problem can be solved by employing the unified approach to boundary value problems introduced by on of the authors in the late 1990s. The problem on the full line was analysed by Crighton et. al. using a combination of Laplace and Fourier transforms. The new approach avoids the technical difficulty of the a priori assumption that the amplitude of the plate is in $L^1_{dt}(R^+)$ and furthermore yields a simpler solution representation which immediately implies the problem is well-posed. For the problem on the half-line, a similar analysis yields a solution representation, but this formula involves two unknown functions. The main difficulty with the half-line problem is the characterisation of these two functions. By employing the so-called global relation, we show that the two functions can be obtained via the solution of a complex valued integral equation of the convolution type. This equation can be solved in closed form using the Laplace transform. By prescribing the initial data $\eta_0$ to be in $H^3(R^+)$, we show that the solution depends continuously on the initial data, and hence, the problem is well-posed.Comment: 17 pages, 3 figures. Minor adjustments made to the introductio

Plasma REST: A novel candidate biomarker of Alzheimer\u27s disease is modified by psychological intervention in an at-risk population

The repressor element 1-silencing transcription (REST) factor is a key regulator of the aging brain’s stress response. It is reduced in conditions of stress and Alzheimer’s disease (AD), which suggests that increasing REST may be neuroprotective. REST can be measured peripherally in blood plasma. Our study aimed to (1) examine plasma REST levels in relation to clinical and biological markers of neurodegeneration and (2) alter plasma REST levels through a stress-reduction intervention—mindfulness training. In study 1, REST levels were compared across the following four well-characterized groups: healthy elderly (n=65), mild cognitive impairment who remained stable (stable MCI, n=36), MCI who later converted to dementia (converter MCI, n=29) and AD (n=65) from the AddNeuroMed cohort. REST levels declined with increasing severity of risk and impairment (healthy elderly>stable MCI>converter MCI>AD, F=6.35, P<0.001). REST levels were also positively associated with magnetic resonance imaging-based hippocampal and entorhinal atrophy and other putative blood-based biomarkers of AD (Ps<0.05). In study 2, REST was measured in 81 older adults with psychiatric risk factors for AD before and after a mindfulness-based stress reduction intervention or an education-based placebo intervention. Mindfulness-based training caused an increase in REST compared with the placebo intervention (F=8.57, P=0.006), and increased REST was associated with a reduction in psychiatric symptoms associated with stress and AD risk (Ps<0.02). Our data confirm plasma REST associations with clinical severity and neurodegeneration, and originally, that REST is modifiable by a psychological intervention with clinical benefit

XMM-Newton observations of the Seyfert 1 AGN H0557-385

We present XMM-Newton observations of the Seyfert 1 AGN H0557-385. We have conducted a study into the warm absorber present in this source, and using high-resolution RGS data we find that the absorption can be characterised by two phases: a phase with log ionisation parameter xi of 0.50 (where xi is in units of ergs cm/s) and a column of 0.2e21 cm^-2, and a phase with log xi of 1.62 and a column of 1.3e22 cm^-2. An iron K alpha line is detected. Neutral absorption is also present in the source, and we discuss possible origins for this. On the assumption that the ionised absorbers originate as an outflow from the inner edge of the torus, we use a new method for finding the volume filling factor. Both phases of H0557-385 have small volume filling factors (< 1%). We also derive the volume filling factors for a sample of 23 AGN using this assumption and for the absorbers with log xi > 0.7 we find reasonable agreement with the filling factors obtained through the alternative method of equating the momentum flow of the absorbers to the momentum loss of the radiation field. By comparing the filling factors obtained by the two methods, we infer that some absorbers with log xi < 0.7 occur at significantly larger distances from the nucleus than the inner edge of the torus.Comment: Accepted for publication in MNRA

Plasma REST: a novel candidate biomarker of Alzheimer's disease is modified by psychological intervention in an at-risk population.

The repressor element 1-silencing transcription (REST) factor is a key regulator of the aging brain's stress response. It is reduced in conditions of stress and Alzheimer's disease (AD), which suggests that increasing REST may be neuroprotective. REST can be measured peripherally in blood plasma. Our study aimed to (1) examine plasma REST levels in relation to clinical and biological markers of neurodegeneration and (2) alter plasma REST levels through a stress-reduction intervention-mindfulness training. In study 1, REST levels were compared across the following four well-characterized groups: healthy elderly (n=65), mild cognitive impairment who remained stable (stable MCI, n=36), MCI who later converted to dementia (converter MCI, n=29) and AD (n=65) from the AddNeuroMed cohort. REST levels declined with increasing severity of risk and impairment (healthy elderly&gt;stable MCI&gt;converter MCI&gt;AD, F=6.35, P&lt;0.001). REST levels were also positively associated with magnetic resonance imaging-based hippocampal and entorhinal atrophy and other putative blood-based biomarkers of AD (Ps&lt;0.05). In study 2, REST was measured in 81 older adults with psychiatric risk factors for AD before and after a mindfulness-based stress reduction intervention or an education-based placebo intervention. Mindfulness-based training caused an increase in REST compared with the placebo intervention (F=8.57, P=0.006), and increased REST was associated with a reduction in psychiatric symptoms associated with stress and AD risk (Ps&lt;0.02). Our data confirm plasma REST associations with clinical severity and neurodegeneration, and originally, that REST is modifiable by a psychological intervention with clinical benefit

Development of virtual ophthalmic surgical skills training

Background: This study aims to assess whether ophthalmic surgical skills can be taught successfully online to a diverse international and interprofessional student group. Methods: Mixed methods study involving 20 students and 5 instructors. Each student completed a pre-session and post-session questionnaire to assess their perceptions regarding online instruction. Changes in questionnaire responses were analysed using Wilcoxon signed rank (SPSS 25). Semi-structured interviews were conducted to assess instructor perceptions towards virtual surgical skills teaching. Thematic analysis was undertaken using NVivo 12.0 software. Results: There was a 100% completion rate of pre- and post-session questionnaires. Prior to the session, lack of instructor supervision and inability to provide constructive feedback were emergent themes from students. Pre-session concerns regarding online delivery: 40% of students thought their view of skills demonstration would be negatively impacted, 60% their level of supervision and 55% their interaction with instructors. Following the session 10%, 15% and 5% held this view respectively. All students were ‘satisfied’ or ‘very satisfied’ regarding the ‘Surgeon’s View’ camera angle as well as the use of breakout rooms. 75% perceived an improvement in their confidence in instrument handling, 80% in cable knot tying and 70% in suture tying. Overall student rating for the virtual surgical skills session was 8.85 (±1.19) out of 10 (10 being most satisfied). Conclusions: We demonstrate that successful delivery of a virtual ophthalmic surgical skills course is feasible. We were able to widen accessibility and participation through virtual delivery, which has future implications for ophthalmic surgical teaching and its reach