Thermal effects in exciton harvesting in biased one-dimensional systems

The study of energy harvesting in chain-like structures is important due to its relevance to a variety of interesting physical systems. Harvesting is understood as the combination of exciton transport through intra-band exciton relaxation (via scattering on phonon modes) and subsequent quenching by a trap. Previously, we have shown that in the low temperature limit different harvesting scenarios as a function of the applied bias strength (slope of the energy gradient towards the trap) are possible \cite{Vlaming07}. This paper generalizes the results for both homogeneous and disordered chains to nonzero temperatures. We show that thermal effects are appreciable only for low bias strengths, particularly so in disordered systems, and lead to faster harvesting.Comment: 8 pages, 2 fugures, to appear in Journal of Luminescenc

Correlation functions quantify super-resolution images and estimate apparent clustering due to over-counting

We present an analytical method to quantify clustering in super-resolution localization images of static surfaces in two dimensions. The method also describes how over-counting of labeled molecules contributes to apparent self-clustering and how the effective lateral resolution of an image can be determined. This treatment applies to clustering of proteins and lipids in membranes, where there is significant interest in using super-resolution localization techniques to probe membrane heterogeneity. When images are quantified using pair correlation functions, the magnitude of apparent clustering due to over-counting will vary inversely with the surface density of labeled molecules and does not depend on the number of times an average molecule is counted. Over-counting does not yield apparent co-clustering in double label experiments when pair cross-correlation functions are measured. We apply our analytical method to quantify the distribution of the IgE receptor (Fc{\epsilon}RI) on the plasma membranes of chemically fixed RBL-2H3 mast cells from images acquired using stochastic optical reconstruction microscopy (STORM) and scanning electron microscopy (SEM). We find that apparent clustering of labeled IgE bound to Fc{\epsilon}RI detected with both methods arises from over-counting of individual complexes. Thus our results indicate that these receptors are randomly distributed within the resolution and sensitivity limits of these experiments.Comment: 22 pages, 5 figure

Conversation Therapy with People with Aphasia and Conversation Partners using Video Feedback: A Group and Case Series Investigation of Changes in Interaction

Conversation therapies employing video for feedback and to facilitate outcome measurement are increasingly used with people with post-stroke aphasia and their conversation partners; however the evidence base for change in everyday interaction remains limited. We investigated the effect of Better Conversations with Aphasia (BCA), an intervention that is freely available online at https://extend.ucl.ac.uk/. Eight people with chronic agrammatic aphasia, and their regular conversation partners participated in the tailored 8 week program involving significant video feedback. We explored changes in: (i) conversation facilitators (such as multi-modal turns by people with aphasia); and (ii) conversation barriers (such as use of test questions by conversation partners). The outcome of intervention was evaluated directly by measuring change in video-recorded everyday conversations. The study employed a pre-post design with multiple 5 minute samples of conversation before and after intervention, scored by trained raters blind to the point of data collection. Group level analysis showed no significant increase in conversation facilitators. There was, however, a significant reduction in the number of conversation barriers. The case series data revealed variability in conversation behaviors across occasions for the same dyad and between different dyads. Specifically, post-intervention there was a significant increase in facilitator behaviors for two dyads, a decrease for one and no significant change for five dyads. There was a significant decrease in barrier behaviors for five dyads and no significant change for three dyads. The reduction in barrier behaviors was considerable; on average change from over eight to fewer than three barrier behaviors in 5 minutes of conversation. The pre-post design has the limitation of no comparison group. However, change occurs in targeted conversational behaviors and in people with chronic aphasia and their partners. The findings suggest change can occur after eight therapy sessions and have implications for clinical practice. A reduction in barrier behaviors may be easier to obtain, although the controlled case series results demonstrate a significant increase in conversation facilitators is also possible. The rehabilitation tool is available online and video technology was central to delivering intervention and evaluating change

Simple method for sub-diffraction resolution imaging of cellular structures on standard confocal microscopes by three-photon absorption of quantum dots

This study describes a simple technique that improves a recently developed 3D sub-diffraction imaging method based on three-photon absorption of commercially available quantum dots. The method combines imaging of biological samples via tri-exciton generation in quantum dots with deconvolution and spectral multiplexing, resulting in a novel approach for multi-color imaging of even thick biological samples at a 1.4 to 1.9-fold better spatial resolution. This approach is realized on a conventional confocal microscope equipped with standard continuous-wave lasers. We demonstrate the potential of multi-color tri-exciton imaging of quantum dots combined with deconvolution on viral vesicles in lentivirally transduced cells as well as intermediate filaments in three-dimensional clusters of mouse-derived neural stem cells (neurospheres) and dense microtubuli arrays in myotubes formed by stacks of differentiated C2C12 myoblasts

Reporting on novel complex intervention development for adults with social communication impairments after acquired brain injury

Purpose: Interventions are often poorly described in published controlled trials, with relatively little information regarding intervention development, content and fidelity. This makes it difficult to conduct replication studies, interpret and compare findings across studies and for therapists to deliver the intervention in clinical practice. Complete reporting of interventions (including fidelity) is now recommended for treatment studies, and this standardised approach is achieved using the Template for Intervention Description and Replication (TIDieR). The aim of this paper is to describe the multi-phase process of developing a novel intervention for adults with acquired brain injury (ABI), and report on the findings from involving practicing therapists in this process. Methods: Phase 1 involved a review of relevant literature and specifying the intervention as a prototype intervention manual. Phase 2 comprised a focus group with eight practicing therapists exploring their experiences and perceptions of the intervention, potential active components, and essential elements; it also included review of the prototype manual. Data from the focus group discussion was transcribed and analysed thematically. Phase 3 investigated actual fidelity of the intervention undertaken, achieved by observers viewing videoed sessions and appraising against the fidelity checklist, which was then analysed using Cohen’s kappa. Results: Project-based intervention was defined as having six essential elements: a project or tangible end product focus; group-based intervention; individualised communication-based goals; communication partner involvement; acknowledgement and support of participants’ cognitive ability; and consideration and plan to address impaired awareness. Analysis of focus group data revealed four themes of essential elements; group context; therapeutic skills; and manual core components and informed the development of a fidelity checklist with 13 essential and 6 desirable criteria. Fidelity assessed using percent agreement was acceptable for almost all rater pairs; where significant, Kappa coefficients had values ranging from poor to excellent (k=0.34 – 1.0) depending on rater pair and session. Discussion: The TIDieR framework provided a clear systematic approach for the complete description and reporting of a complex communication intervention for people with ABI. This paper comprehensively described the development and manualisation of an intervention in collaboration with practicing therapists which can be used for future testing. In addition, the process undertaken has the potential to inform rehabilitation researchers in other fields on the development of complex interventions

Three-Dimensional, Tomographic Super-Resolution Fluorescence Imaging of Serially Sectioned Thick Samples

Three-dimensional fluorescence imaging of thick tissue samples with near-molecular resolution remains a fundamental challenge in the life sciences. To tackle this, we developed tomoSTORM, an approach combining single-molecule localization-based super-resolution microscopy with array tomography of structurally intact brain tissue. Consecutive sections organized in a ribbon were serially imaged with a lateral resolution of 28 nm and an axial resolution of 40 nm in tissue volumes of up to 50 µm×50 µm×2.5 µm. Using targeted expression of membrane bound (m)GFP and immunohistochemistry at the calyx of Held, a model synapse for central glutamatergic neurotransmission, we delineated the course of the membrane and fine-structure of mitochondria. This method allows multiplexed super-resolution imaging in large tissue volumes with a resolution three orders of magnitude better than confocal microscopy

Enabling Better Conversations Between a Man With Aphasia and His Conversation Partner: Incorporating Writing Into Turn Taking

This article reports an intervention in the conversations between a man with chronic aphasia, Barry, and his wife, Louise (both names are pseudonyms). Preintervention analysis revealed the potential of writing as a resource for turn construction. Intervention consisted of enabling Barry to use writing to produce more complete turns at talk, thereby increasing the likelihood of mutual understanding, and encouraging Louise to modify her responses to Barry’s turns and thus enhance his interactional potential. Quantitative analysis revealed that Barry significantly increased his use of writing after intervention, but there was no change in other trained strategies. Louise eradicated correct production sequences (designed to elicit the correct production of a word despite her knowing the target) but did not implement trained strategies. In conclusion, individually tailored input underpinned by Conversation Analysis principles can alter the conversational behavior of a person with aphasia. It appears easier for a conversation partner to reduce unhelpful behaviors than to adopt facilitatory strategies. Data are in British English

Virtual-'light-sheet' single-molecule localisation microscopy enables quantitative optical sectioning for super-resolution imaging.

Single-molecule super-resolution microscopy allows imaging of fluorescently-tagged proteins in live cells with a precision well below that of the diffraction limit. Here, we demonstrate 3D sectioning with single-molecule super-resolution microscopy by making use of the fitting information that is usually discarded to reject fluorophores that emit from above or below a virtual-'light-sheet', a thin volume centred on the focal plane of the microscope. We describe an easy-to-use routine (implemented as an open-source ImageJ plug-in) to quickly analyse a calibration sample to define and use such a virtual light-sheet. In addition, the plug-in is easily usable on almost any existing 2D super-resolution instrumentation. This optical sectioning of super-resolution images is achieved by applying well-characterised width and amplitude thresholds to diffraction-limited spots that can be used to tune the thickness of the virtual light-sheet. This allows qualitative and quantitative imaging improvements: by rejecting out-of-focus fluorophores, the super-resolution image gains contrast and local features may be revealed; by retaining only fluorophores close to the focal plane, virtual-'light-sheet' single-molecule localisation microscopy improves the probability that all emitting fluorophores will be detected, fitted and quantitatively evaluated.We thank the Wellcome Trust for the PhD studentship of MP (093756/B/10/Z), and the Royal Society for the University Research Fellowship of SFL (UF120277). The work by SB and DL was also funded by the Wellcome Trust (082010/Z/07/Z). UE and MH acknowledge funding by the German Science Foundation (grants EXC 115 and SFB 902). SB is funded by a BBSRC grant (BB/K013726/1). AMC acknowledges ERC Award 268788-SMI-DDR. We also thank the European Commision for support through the 4DCellFate project (EC FP7 CP 277899).This is the final version of the article. It first appeared from PLOS via http://dx.doi.org/10.1371/journal.pone.012543

Quantification of DNA-associated proteins inside eukaryotic cells using single-molecule localization microscopy

Development of single-molecule localization microscopy techniques has allowed nanometre scale localization accuracy inside cells, permitting the resolution of ultra-fine cell structure and the elucidation of crucial molecular mechanisms. Application of these methodologies to understanding processes underlying DNA replication and repair has been limited to defined in vitro biochemical analysis and prokaryotic cells. In order to expand these techniques to eukaryotic systems, we have further developed a photo-activated localization microscopy-based method to directly visualize DNA-associated proteins in unfixed eukaryotic cells. We demonstrate that motion blurring of fluorescence due to protein diffusivity can be used to selectively image the DNA-bound population of proteins. We designed and tested a simple methodology and show that it can be used to detect changes in DNA binding of a replicative helicase subunit, Mcm4, and the replication sliding clamp, PCNA, between different stages of the cell cycle and between distinct genetic backgrounds

Conversation focused aphasia therapy: investigating the adoption of strategies by people with agrammatism.

Background: A recent review of interaction (or conversation)-focused therapy highlighted the potential of programmes targeting the person with aphasia (PWA) directly. However, it noted the key limitations of current work in this field to be a reliance on single case analyses and qualitative evidence of change, a situation that is not unusual when a complex behavioural intervention is in the early stages of development and evaluation. Aims: This article aims to evaluate an intervention that targeted a PWA and their conversation partner (CP), a dyad, as equals in a novel conversation therapy for agrammatic aphasia, using both quantitative and qualitative evidence of change. The intervention aimed to increase the insight of a dyad into facilitator and barrier conversation behaviours, to increase the understanding of the effect of agrammatism on communication, and to support each speaker to choose three strategies to work on in therapy to increase mutual understanding and enhance conversation. Methods & Procedures: Quantitative and qualitative methods are used to analyse multiple pre-therapy and follow up assessments of conversation for two dyads. Outcomes & Results: Results show that one person with severe and chronic agrammatic aphasia was able to select and practise strategies that led to qualitative and quantitative changes in his post-therapy conversations. The other PWA showed a numerical increase in one of his three strategies post therapy, but no significant quantitative change. Although both CPs significantly reduced barrier behaviours in their post-therapy conversations, neither showed a significant increase in the strategies they chose to work on. For one CP, there was qualitative evidence of the use of different turn types. Conclusions: Individually tailored input from a speech and language therapist can assist some people with chronic agrammatism to develop conversational strategies that enhance communication. Outcomes are influenced by the severity and extent of language deficits affecting, for example, single word writing. In terms of behaviour change for CPs, it appears that it may be easier to reduce barrier behaviours rather than to increase the use of facilitatory strategies. The results have implications for collaborative goal setting with clients undergoing conversation therapy