Techniques and errors in measuring cross- correlation and cross-spectral density functions

Techniques and errors in measuring cross spectral density and cross correlation functions of stationary dynamic pressure dat

Clip and snare lifting technique to assist cannulation of a papilla hidden behind a mucosal fold

No abstract availabl

Adaptive spectral tracking for coherence estimation: the z-tracker

Objective: A major challenge in non-stationary signal analysis is reliable estimation of correlation. Neurophysiological recordings can be many minutes in duration with data that exhibits correlation which changes over different time scales. Local smoothing can be used to estimate time-dependency, however, an effective framework needs to adjust levels of smoothing in response to changes in correlation. Approach: Here we present a novel data-adaptive algorithm, the z-tracker, for estimating local correlation in segmented data. The algorithm constructs single segment coherence estimates using multi-taper windows. These are subject to adaptive Kalman filtering/smoothing in the z-domain to construct a local coherence estimate for each segment. The error residual for each segment determines the levels of process noise, allowing the filter to adapt rapidly to sudden changes in correlation while applying greater smoothing to data where the correlation is consistent across segments. The method is compared to wavelet coherence, calculated using orthogonal Morse wavelets. Main results: The performance of the z-tracker is quantified against Morse wavelet coherence using a mean square deviation (MSD) metric. The z-tracker has significantly lower MSD than the wavelet estimate for time-varying coherence over long time scales (∼10–20 s), whereas the wavelet has lower MSD for coherence varying over short time scales (∼1–2 s). The z-tracker also has a lower MSD for slowly varying coherence with occasional step changes. The method is applied to detect changes in coherence in paired LFP recordings from rat prefrontal cortex and amygdala in response to a pharmacological challenge. Significance: The z-tracker provides an effective and efficient method to estimate time varying correlation in multivariate data, leading to better characterisation of neurophysiology signals where correlation is subject to slow modulation over time. A number of suggestions are included for future refinements

Pathways to understanding the genomic aetiology of osteoarthritis

Osteoarthritis is a common, complex disease with no curative therapy. In this review, we summarize current knowledge on disease aetiopathogenesis and outline genetics and genomics approaches that are helping catalyse a much-needed improved understanding of the biological underpinning of disease development and progression

Patterns in German /ʃC/-cluster acquisition

This study reports on the developmental patterns of /ʃC/ clusters in 145 normally developing monolingual German-speaking children between 2;00 and 2;11. All children completed a picture naming task to allow a systematic qualitative analysis of the production patterns. Children’s reductions of target /ʃC/clusters are examined and are evaluated with respect to two models, ‘factorial typology’ and ‘headedness’, to account for them. The results reveal expected patterns of C2 retention for ‘/ʃ/+[−continuant]’ (e.g. ‘/ʃ/+stop’ and ‘/ʃ/+nasal’) targets, and a rather indeterminate pattern for /ʃl/ and /ʃʁ/. The results for /ʃv/, a clear-cut preference of C2 retention, were rather unexpected, as the C2 is a [+continuant]. The explanation offered for the retention of /v/ is related to a place constraint. The study also examines the data from children who reached an advanced stage of cluster formation with differential targets. More specifically, in several children, one target, /ʃv/, is found to have stayed behind in the reduction phase while all others have advanced to the ‘cluster stage’. Neither the type nor the token frequencies seem satisfactory in accounting for the specific behaviour of /ʃv/. The explanation offered for the uniqueness of this target may be its non-abidence to the Sonority Sequencing Principle (SSP) because of its flat sonority and the Obligatory Contour Principle (OCP) [continuant], because of the unchanging ‘continuance’ which is demanded by the OCP. Theoretical and clinical implications are discussed

Collecting Psycholinguistic Response Time Data Using Amazon Mechanical Turk

Researchers in linguistics and related fields have recently begun exploiting online crowd-sourcing tools, like Amazon Mechanical Turk (AMT), to gather behavioral data. While this method has been successfully validated for various offline measures--grammaticality judgment or other forced-choice tasks--its use for mainstream psycholinguistic research remains limited. This is because psycholinguistic effects are often dependent on relatively small differences in response times, and there remains some doubt as to whether precise timing measurements can be gathered over the web. Here we show that three classic psycholinguistic effects can in fact be replicated using AMT in combination with open-source software for gathering response times client-side. Specifically, we find reliable effects of subject definiteness, filler-gap dependency processing, and agreement attraction in self-paced reading tasks using approximately the same numbers of participants and/or trials as similar laboratory studies. Our results suggest that psycholinguists can and should be taking advantage of AMT and similar online crowd-sourcing marketplaces as a fast, low-resource alternative to traditional laboratory research

Healing Cartilage - aspects on regenerative methods

Articular cartilage has poor intrinsic capacity to heal and defects can cause severe pain for the patient. If the healing process is not assisted the damage might deteriorate and lead to the onset of osteoarthritis. Autologous chondrocyte implantation is a successful method in treating focal cartilage defects, with good clinical outcome. Low cellularity of the tissue and low proliferative capacity of the chondrocytes are limitations to the treatment. The aim of the present thesis was to improve assisted articular cartilage healing and to evaluate how an eventual osteoarthritis progression could be halted. In particular, we investigated how anabolic chondrogenic processes in chondrocytes and chondrocyte derived induced pluripotent stem cells can be improved, thereby optimising the use of autologous cells in articular cartilage regenerative therapies and methods. Further, we studied if the application of plasma-mediated ablation can induce an anabolic response in the chondrocytes. Finally, we investigated how GDF5 signalling, a pathway implemented in the development of osteoarthritis, affects cartilage homeostasis. The results indicated that plasma-mediated ablation induces an anabolic response in chondrocytes. ECM production by the chondrocytes was improved by optimizing the standard chondrogenic medium through the use of factorial design of experiments. We were able to demonstrate that GDF5 can contribute to the redifferentiation process, and has potential in inhibiting degenerative processes in the cells. Finally, the reprogramming of chondrocytes into induced pluripotent stem cells showed that these cells could be useful tools in the determination of cell signalling pathways in tissue regeneration and disease. In conclusion, the methods investigated in this thesis can be used to improve the regenerative capacity of the articular chondrocytes and the thesis sheds further light on the intricate problems of healing cartilage