Balltracking: an highly efficient method for tracking flow fields

We present a method for tracking solar photospheric flows that is highly efficient, and demonstrate it using high resolution MDI continuum images. The method involves making a surface from the photospheric granulation data, and allowing many small floating tracers or balls to be moved around by the evolving granulation pattern. The results are tested against synthesised granulation with known flow fields and compared to the results produced by Local Correlation tracking (LCT). The results from this new method have similar accuracy to those produced by LCT. We also investigate the maximum spatial and temporal resolution of the velocity field that it is possible to extract, based on the statistical properties of the granulation data. We conclude that both methods produce results that are close to the maximum resolution possible from granulation data. The code runs very significantly faster than our similarly optimised LCT code, making real time applications on large data sets possible. The tracking method is not limited to photospheric flows, and will also work on any velocity field where there are visible moving features of known scale length

Estimating the p-mode frequencies of the solar twin 18 Sco

Solar twins have been a focus of attention for more than a decade, because their structure is extremely close to that of the Sun. Today, thanks to high-precision spectrometers, it is possible to use asteroseismology to probe their interiors. Our goal is to use time series obtained from the HARPS spectrometer to extract the oscillation frequencies of 18 Sco, the brightest solar twin. We used the tools of spectral analysis to estimate these quantities. We estimate 52 frequencies using an MCMC algorithm. After examination of their probability densities and comparison with results from direct MAP optimization, we obtain a minimal set of 21 reliable modes. The identification of each pulsation mode is straightforwardly accomplished by comparing to the well-established solar pulsation modes. We also derived some basic seismic indicators using these values. These results offer a good basis to start a detailed seismic analysis of 18 Sco using stellar models.Comment: 12 pages, 6 figures, to be published in A&

Remembering verbally-presented items as pictures:brain activity underlying visual mental images in schizophrenia patients with visual hallucinations

Background: Previous research suggests that visual hallucinations in schizophrenia consist of mental images mistaken for percepts due to failure of the reality-monitoring processes. However, the neural substrates that underpin such dysfunction are currently unknown. We conducted a brain imaging study to investigate the role of visual mental imagery in visual hallucinations. Method: Twenty-three patients with schizophrenia and 26 healthy participants were administered a reality-monitoring task whilst undergoing an fMRI protocol. At the encoding phase, a mixture of pictures of common items and labels designating common items were presented. On the memory test, participants were requested to remember whether a picture of the item had been presented or merely its label. Results: Visual hallucination scores were associated with a liberal response bias reflecting propensity to erroneously remember pictures of the items that had in fact been presented as words. At encoding, patients with visual hallucinations differentially activated the right fusiform gyrus when processing the words they later remembered as pictures, which suggests the formation of visual mental images. On the memory test, the whole patient group activated the anterior cingulate and medial superior frontal gyrus when falsely remembering pictures. However, no differential activation was observed in patients with visual hallucinations, whereas in the healthy sample, the production of visual mental images at encoding led to greater activation of a fronto-parietal decisional network on the memory test. Conclusions: Visual hallucinations are associated with enhanced visual imagery and possibly with a failure of the reality-monitoring processes that enable discrimination between imagined and perceived events

The International Natural Product Sciences Taskforce (INPST) and the power of Twitter networking exemplified through #INPST hashtag analysis

Background: The development of digital technologies and the evolution of open innovation approaches have enabled the creation of diverse virtual organizations and enterprises coordinating their activities primarily online. The open innovation platform titled "International Natural Product Sciences Taskforce" (INPST) was established in 2018, to bring together in collaborative environment individuals and organizations interested in natural product scientific research, and to empower their interactions by using digital communication tools. Methods: In this work, we present a general overview of INPST activities and showcase the specific use of Twitter as a powerful networking tool that was used to host a one-week "2021 INPST Twitter Networking Event" (spanning from 31st May 2021 to 6th June 2021) based on the application of the Twitter hashtag #INPST. Results and Conclusion: The use of this hashtag during the networking event period was analyzed with Symplur Signals (https://www.symplur.com/), revealing a total of 6,036 tweets, shared by 686 users, which generated a total of 65,004,773 impressions (views of the respective tweets). This networking event's achieved high visibility and participation rate showcases a convincing example of how this social media platform can be used as a highly effective tool to host virtual Twitter-based international biomedical research events

Mapping neurotransmitter systems to the structural and functional organization of the human neocortex

Neurotransmitter receptors support the propagation of signals in the human brain. How receptor systems are situated within macro-scale neuroanatomy and how they shape emergent function remain poorly understood, and there exists no comprehensive atlas of receptors. Here we collate positron emission tomography data from more than 1,200 healthy individuals to construct a whole-brain three-dimensional normative atlas of 19 receptors and transporters across nine different neurotransmitter systems. We found that receptor profiles align with structural connectivity and mediate function, including neurophysiological oscillatory dynamics and resting-state hemodynamic functional connectivity. Using the Neurosynth cognitive atlas, we uncovered a topographic gradient of overlapping receptor distributions that separates extrinsic and intrinsic psychological processes. Finally, we found both expected and novel associations between receptor distributions and cortical abnormality patterns across 13 disorders. We replicated all findings in an independently collected autoradiography dataset. This work demonstrates how chemoarchitecture shapes brain structure and function, providing a new direction for studying multi-scale brain organization.</p

Computational modelling of the degradation of poly-L-lactide for a bioresorbable polymeric stent

The interest in biodegradable polymers for the design of bioresorbable stents, temporary vascular scaffolds designed to restore patency to obstructed vessels, has witnessed a dramatic growth over the last ten to fifteen years. While bioresorbable polymeric stents (BPS) offer possibilities to help address the long-term complications (e.g. in-stent restenosis, stent thrombosis) associated with permanent devices, in-vivo degradation behaviours are not yet fully understood. The application of computational modelling, for example finite element analysis (FEA), to predict and analyse BPS degradation behaviour provides a means to investigate in-vivo performance and further enhance BPS design. Current computational modelling techniques for the degradation of BPS predominately focus on the phenomenological aspects of degradation, with little emphasis given to the inherent microstructure changes (bulk degradation, crystallisation) which occur in the degrading polymer. This research aims to advance the computational modelling techniques for examination of BPS degradation behaviours, though development of co-simulation techniques which are applied to evaluate the physio-chemical degradation of BPS and assess the impacts of material, design and degradation product boundary condition on the physio-chemical degradation, and on the subsequent mechanical performance and scaffolding ability of the device. Physio-chemical degradation of BPS geometries and materials is simulated through adaptation of the heat equation in FE. Model predictions reveal a significant dependency of degradation on the imposed degradation product boundary conditions. Predictions indicate that BPS design does not have a significant impact on molecular weight reduction rates; however, material crystallinity and heterogeneities in crystallinity emerge as key contributors to device performance. Consideration of the device mechanical boundary conditions shows a reliance of the scaffolding ability of degrading BPS on the imposed initial loading. This research proposes considerations for the modelling requirements surrounding BPS regulatory approval. In conclusion, the work performed in this thesis has led to an enhanced understanding of the in-vivo degradation behaviours and mechanical performance of BPS. This work has generated new insight into the expected clinical performance of BPS and presents a solid framework for the development of further design and analysis techniques for BPS.2021-05-0

Computational modelling of the degradation of poly-L-lactide for a bioresorbable polymeric stent

The interest in biodegradable polymers for the design of bioresorbable stents, temporary vascular scaffolds designed to restore patency to obstructed vessels, has witnessed a dramatic growth over the last ten to fifteen years. While bioresorbable polymeric stents (BPS) offer possibilities to help address the long-term complications (e.g. in-stent restenosis, stent thrombosis) associated with permanent devices, in-vivo degradation behaviours are not yet fully understood. The application of computational modelling, for example finite element analysis (FEA), to predict and analyse BPS degradation behaviour provides a means to investigate in-vivo performance and further enhance BPS design. Current computational modelling techniques for the degradation of BPS predominately focus on the phenomenological aspects of degradation, with little emphasis given to the inherent microstructure changes (bulk degradation, crystallisation) which occur in the degrading polymer. This research aims to advance the computational modelling techniques for examination of BPS degradation behaviours, though development of co-simulation techniques which are applied to evaluate the physio-chemical degradation of BPS and assess the impacts of material, design and degradation product boundary condition on the physio-chemical degradation, and on the subsequent mechanical performance and scaffolding ability of the device. Physio-chemical degradation of BPS geometries and materials is simulated through adaptation of the heat equation in FE. Model predictions reveal a significant dependency of degradation on the imposed degradation product boundary conditions. Predictions indicate that BPS design does not have a significant impact on molecular weight reduction rates; however, material crystallinity and heterogeneities in crystallinity emerge as key contributors to device performance. Consideration of the device mechanical boundary conditions shows a reliance of the scaffolding ability of degrading BPS on the imposed initial loading. This research proposes considerations for the modelling requirements surrounding BPS regulatory approval. In conclusion, the work performed in this thesis has led to an enhanced understanding of the in-vivo degradation behaviours and mechanical performance of BPS. This work has generated new insight into the expected clinical performance of BPS and presents a solid framework for the development of further design and analysis techniques for BPS.2021-05-0