Retinal blood vessels extraction using probabilistic modelling

© 2014 Kaba et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.This article has been made available through the Brunel Open Access Publishing Fund.The analysis of retinal blood vessels plays an important role in detecting and treating retinal diseases. In this review, we present an automated method to segment blood vessels of fundus retinal image. The proposed method could be used to support a non-intrusive diagnosis in modern ophthalmology for early detection of retinal diseases, treatment evaluation or clinical study. This study combines the bias correction and an adaptive histogram equalisation to enhance the appearance of the blood vessels. Then the blood vessels are extracted using probabilistic modelling that is optimised by the expectation maximisation algorithm. The method is evaluated on fundus retinal images of STARE and DRIVE datasets. The experimental results are compared with some recently published methods of retinal blood vessels segmentation. The experimental results show that our method achieved the best overall performance and it is comparable to the performance of human experts.The Department of Information Systems, Computing and Mathematics, Brunel University

Electrophysiological dynamics of Chinese phonology during visual word recognition in Chinese-English bilinguals

Silent word reading leads to the activation of orthographic (spelling), meaning, as well as phonological (sound) information. For bilinguals, native language information can also be activated automatically when they read words in their second language. For example, when Chinese-English bilinguals read words in their second language (English), the phonology of the Chinese translations is automatically activated. Chinese phonology, however, consists of consonants and vowels (segmental) and tonal information. To what extent these two aspects of Chinese phonology are activated is yet unclear. Here, we used behavioural measures, event-related potentials and oscillatory EEG to investigate Chinese segmental and tonal activation during word recognition. Evidence of Chinese segmental activation was found when bilinguals read English words (faster responses, reduced N400, gamma-band power reduction) and when they read Chinese words (increased LPC, gamma-band power reduction). In contrast, evidence for Chinese tonal activation was only found when bilinguals read Chinese words (gamma-band power increase). Together, our converging behavioural and electrophysiological evidence indicates that Chinese segmental information is activated during English word reading, whereas both segmental and tonal information are activated during Chinese word reading. Importantly, gamma-band oscillations are modulated differently by tonal and segmental activation, suggesting independent processing of Chinese tones and segments

Combining two-photon photoemission and transient absorption spectroscopy to resolve hot carrier cooling in 2D perovskite single crystals: the effect of surface layer

We investigate hot carrier (HC) cooling in two-dimensional (2D) perovskite single crystals by applying two complementary ultrafast spectroscopy techniques – transient absorption (TA) and time-resolved two-photon photoemission (TR-2PPE) spectroscopies. TR-2PPE directly maps the hot electron distribution and its dynamics in the conduction band to the detected photoelectron distribution. While TR-2PPE selectively probes the upper layer of the material, TA provides information on the whole bulk. Two cooling regimes are resolved in both techniques. The fast timescale of 100–200 fs is related to the electron scattering by longitudinal optical (LO) phonons and the slow timescale of 3–4 ps corresponds to the LO phonon relaxation. The HC cooling dynamic of TA measurement has faster initial stage and higher starting temperature for the slower stage than in TR-2PPE measurements. Conclusions about spatial sensitivity of the cooling dynamics across the 2D perovskite single crystals constitute valuable information that can guide the future development of HC solar cells and thermoelectric applications based on 2D perovskites

DIA-datasnooping and identifiability

In this contribution, we present and analyze datasnooping in the context of the DIA method. As the DIA method for the detection, identification and adaptation of mismodelling errors is concerned with estimation and testing, it is the combination of both that needs to be considered. This combination is rigorously captured by the DIA estimator. We discuss and analyze the DIA-datasnooping decision probabilities and the construction of the corresponding partitioning of misclosure space. We also investigate the circumstances under which two or more hypotheses are nonseparable in the identification step. By means of a theorem on the equivalence between the nonseparability of hypotheses and the inestimability of parameters, we demonstrate that one can forget about adapting the parameter vector for hypotheses that are nonseparable. However, as this concerns the complete vector and not necessarily functions of it, we also show that parameter functions may exist for which adaptation is still possible. It is shown how this adaptation looks like and how it changes the structure of the DIA estimator. To demonstrate the performance of the various elements of DIA-datasnooping, we apply the theory to some selected examples. We analyze how geometry changes in the measurement setup affect the testing procedure, by studying their partitioning of misclosure space, the decision probabilities and the minimal detectable and identifiable biases. The difference between these two minimal biases is highlighted by showing the difference between their corresponding contributing factors. We also show that if two alternative hypotheses, say (Formula presented.) and (Formula presented.), are nonseparable, the testing procedure may have different levels of sensitivity to (Formula presented.)-biases compared to the same (Formula presented.)-biases

Inner Speech during Silent Reading Reflects the Reader's Regional Accent

While reading silently, we often have the subjective experience of inner speech. However, there is currently little evidence regarding whether this inner voice resembles our own voice while we are speaking out loud. To investigate this issue, we compared reading behaviour of Northern and Southern English participants who have differing pronunciations for words like ‘glass’, in which the vowel duration is short in a Northern accent and long in a Southern accent. Participants' eye movements were monitored while they silently read limericks in which the end words of the first two lines (e.g., glass/class) would be pronounced differently by Northern and Southern participants. The final word of the limerick (e.g., mass/sparse) then either did or did not rhyme, depending on the reader's accent. Results showed disruption to eye movement behaviour when the final word did not rhyme, determined by the reader's accent, suggesting that inner speech resembles our own voice

Differential effects of glucagon-like peptide-1 receptor agonists on heart rate

Abstract While glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are known to increase heart rate (HR), it is insufficiently recognized that the extent varies greatly between the various agonists and is affected by the assessment methods employed. Here we review published data from 24-h time-averaged HR monitoring in healthy individuals and subjects with type 2 diabetes mellitus (T2DM) treated with either short-acting GLP-1 RAs, lixisenatide or exenatide, or long-acting GLP-1 RAs, exenatide LAR, liraglutide, albiglutide, or dulaglutide (N\ua0=\ua01112; active-treatment arms). HR effects observed in two independent head-to-head trials of lixisenatide and liraglutide (N\ua0=\ua0202; active-treatment arms) are also reviewed. Short-acting GLP-1 RAs, exenatide and lixisenatide, are associated with a transient (1\u201312\ua0h) mean placebo- and baseline-adjusted 24-h HR increase of 1\u20133\ua0beats per minute (bpm). Conversely, long-acting GLP-1 RAs are associated with more pronounced increases in mean 24-h HR; the highest seen with liraglutide and albiglutide at 6\u201310\ua0bpm compared with dulaglutide and exenatide LAR at 3\u20134\ua0bpm. For both liraglutide and dulaglutide, HR increases were recorded during both the day and at night. In two head-to-head comparisons, a small, transient mean increase in HR from baseline was observed with lixisenatide; liraglutide induced a substantially greater increase that remained significantly elevated over 24\ua0h. The underlying mechanism for increased HR remains to be elucidated; however, it could be related to a direct effect at the sinus node and/or stimulation of the sympathetic nervous system, with this effect related to the duration of action of the respective GLP-1 RAs. In conclusion, this review indicates that the effects on HR differ within the class of GLP-1 RAs: short-acting GLP-1 RAs are associated with a modest and transient HR increase before returning to baseline levels, while some long-acting GLP-1 RAs are associated with a more pronounced and sustained increase during the day and night. Findings from recently completed trials indicate that a GLP-1 RA-induced increase in HR, regardless of magnitude, does not present an increased cardiovascular risk for subjects with T2DM, although a pronounced increase in HR may be associated with adverse clinical outcomes in those with advanced heart failure

Fast Retinal Vessel Detection and Measurement Using Wavelets and Edge Location Refinement

The relationship between changes in retinal vessel morphology and the onset and progression of diseases such as diabetes, hypertension and retinopathy of prematurity (ROP) has been the subject of several large scale clinical studies. However, the difficulty of quantifying changes in retinal vessels in a sufficiently fast, accurate and repeatable manner has restricted the application of the insights gleaned from these studies to clinical practice. This paper presents a novel algorithm for the efficient detection and measurement of retinal vessels, which is general enough that it can be applied to both low and high resolution fundus photographs and fluorescein angiograms upon the adjustment of only a few intuitive parameters. Firstly, we describe the simple vessel segmentation strategy, formulated in the language of wavelets, that is used for fast vessel detection. When validated using a publicly available database of retinal images, this segmentation achieves a true positive rate of 70.27%, false positive rate of 2.83%, and accuracy score of 0.9371. Vessel edges are then more precisely localised using image profiles computed perpendicularly across a spline fit of each detected vessel centreline, so that both local and global changes in vessel diameter can be readily quantified. Using a second image database, we show that the diameters output by our algorithm display good agreement with the manual measurements made by three independent observers. We conclude that the improved speed and generality offered by our algorithm are achieved without sacrificing accuracy. The algorithm is implemented in MATLAB along with a graphical user interface, and we have made the source code freely available

SUBTLEX-CH: Chinese Word and Character Frequencies Based on Film Subtitles

Background: Word frequency is the most important variable in language research. However, despite the growing interest in the Chinese language, there are only a few sources of word frequency measures available to researchers, and the quality is less than what researchers in other languages are used to. Methodology: Following recent work by New, Brysbaert, and colleagues in English, French and Dutch, we assembled a database of word and character frequencies based on a corpus of film and television subtitles (46.8 million characters, 33.5 million words). In line with what has been found in the other languages, the new word and character frequencies explain significantly more of the variance in Chinese word naming and lexical decision performance than measures based on written texts. Conclusions: Our results confirm that word frequencies based on subtitles are a good estimate of daily language exposure and capture much of the variance in word processing efficiency. In addition, our database is the first to include information about the contextual diversity of the words and to provide good frequency estimates for multi-character words and the different syntactic roles in which the words are used. The word frequencies are freely available for research purposes