Quantum dot clusters as single-molecules: deciphering collective fluorescence and energy transfer signatures

2016 Fall.Includes bibliographical references.Applications of quantum dot nanocrystals span from the individual single-molecule use to large, densely-packed bulk solids. Already, the fluorescence behavior of individual particles is complex and nuanced, particularly involving the blinking phenomenon. When particles are combined into higher-order structures where interaction may occur, a complete description becomes intractable. However, clusters---between two and ten particles---can be effective model systems to explore the local behaviors that occur in larger networks. A benefit of small clusters is the viability of using single-molecule spectroscopic techniques, which are often more informative than bulk measurements. In this work we combine fluorescence microscopy with structure-probing electron microscopy to elucidate the fluorescence dynamics clusters of semiconductor nanocrystals. The spectral characteristics of clusters are explored in the context of an energy transfer model showing low-intensity emission is blue-shifted, corresponding to the weaker emission from donor particles with a larger band gap. Because energy transfer depends intimately on the specific topographical structure of the cluster, the inter-particle spacing, and relative alignment, characterization of specific cluster behavior is better informed by correlated measurements. Next, we present the mapping results from super-resolution microscopy where the spatial distributions of fluorescence in the sub-10 nanometer realm is clearly correlated with scanning electron microscopy imaging of the same clusters. Stochastic blinking events enable such observations. The enhanced blinking associated with energy transfer has practical implications for donor and acceptor roles in clusters. Finally, the dynamic evolution of the emission dipole orientation for single nanocrystals and nanocrystal clusters is measured. The orientation signature suggests coupling strengths and constitutes a first-step towards determining corrections to Förster resonant energy transfer theory involving nanocrystals

Should one measure balance or gait to best predict falls among people with Parkinson disease?

Introduction. We aimed to determine whether gait velocity is as useful as a balance test, a self-report measure of freezing of gait (FOG), and/or a measure of motor symptom severity for predicting falls among people with Parkinson Disease (PD). Methods. Fifty-six individuals with idiopathic PD completed a baseline assessment consisting of these measures: (1) MDS-UPDRS III, (2) Mini-BESTest, (3) gait velocity (forward, backward, dual task, and fast), and (4) FOGQ. Retrospective fall history was collected at baseline and six months later. Participants were considered fallers if they had two or more falls in the surveillance period. Ability of the tests to discriminate between fallers and nonfallers was determined using ROC curves followed by pairwise statistical noninferiority comparisons (P=.05) of the area under the ROC curve (AUC) for each test. Results. At six months, 22% (n=21) of the sample were fallers. Fallers differed significantly from nonfallers on the MDS-UPDRS III, Mini-BESTest, backward gait velocity, and FOGQ. The Mini-BESTest had the highest AUC and was superior to all gait velocity measures at identifying fallers. Conclusion. A single measure of gait velocity, even in a challenging condition, may not be as effective as the Mini-BESTest in identifying fallers among people with PD

Counsellors in the National Health Service: A mixed‐method study of efficacy and satisfaction from the counsellor perspective

Background: It is difficult to know how many counsellors work in the UK’s National Health Service (NHS). At a time when the British Government is pledging an expansion of the mental health workforce it is important to understand both the opportunities and barriers for counsellors to work in the NHS. Aim: To understand counsellors’ job roles, pay, perceptions of services, workplace stress, and reasons for leaving the NHS.Method: An online survey was advertised to members of the British Association for Counselling and Psychotherapy (BACP); just under 2,000 counsellors responded. The sample was majority female, white and had completed training. Mixed methods were utilised to analyse the data which incorporated use of thematic analysis. Findings: The data suggest that, as a workforce, counsellors are prone to being ‘squeezed’ out of the NHS workforce, that they are comparatively ‘underpaid’, are ‘pressurised’ by high level of work demand and are consequently experiencing concerning levels of workplace stress, and that they perceive themselves to be, in multiple ways, ‘under-valued’. Despite this, members reported high adequacy of therapist qualifications and supervision quality within NHS services. Conclusions: Counsellors have expressed a desire to undertake more work in the NHS and are a potentially cost-effective mental health workforce in comparison with other types of professionals. However, this study has evidenced significant structural, cultural and pay and promotion-related barriers that are pushing counsellors out of the NHS. Of particular concern is what appears to be a broad under-valuing of counsellors as a professional group

Physical therapy and deep brain stimulation in Parkinson’s Disease: Protocol for a pilot randomized controlled trial

Abstract Background Subthalamic nucleus deep brain stimulation (STN-DBS) reduces tremor, muscle stiffness, and bradykinesia in people with Parkinson’s Disease (PD). Walking speed, known to be reduced in PD, typically improves after surgery; however, other important aspects of gait may not improve. Furthermore, balance may worsen and falls may increase after STN-DBS. Thus, interventions to improve balance and gait could reduce morbidity and improve quality of life following STN-DBS. Physical therapy (PT) effectively improves balance and gait in people with PD, but studies on the effects of PT have not been extended to those treated with STN-DBS. As such, the efficacy, safety, and feasibility of PT in this population remain to be determined. The purpose of this pilot study is to address these unmet needs. We hypothesize that PT designed to target balance and gait impairment will be effective, safe, and feasible in this population. Methods/design Participants with PD treated with STN-DBS will be randomly assigned to either a PT or control group. Participants assigned to PT will complete an 8-week, twice-weekly PT program consisting of exercises designed to improve balance and gait. Control group participants will receive the current standard of care following STN-DBS, which does not include prescription of PT. The primary aim is to assess preliminary efficacy of PT on balance (Balance Evaluation Systems Test). A secondary aim is to assess efficacy of PT on gait (GAITRite instrumented walkway). Participants will be assessed OFF medication/OFF stimulation and ON medication/ON stimulation at baseline and at 8 and 12 weeks after baseline. Adverse events will be measured over the duration of the study, and adherence to PT will be measured to determine feasibility. Discussion To our knowledge, this will be the first study to explore the preliminary efficacy, safety, and feasibility of PT for individuals with PD with STN-DBS. If the study suggests potential efficacy, then this would justify larger trials to test effectiveness and safety of PT for those with PD with STN-DBS. Trial registration NCT03181282 (clinicaltrials.gov). Registered on 7 June 2017