Time-frequency analysis based on split spectrum applied to audio and ultrasonic signals

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonSignal processing is a large subject with applications integral to a number of technological fields such as communication, audio, Voice over IP (VoIP), pattern recognition, sonar, radar, ultrasound and medical imaging. Techniques exist for the analysis, modelling, extraction, recognition and synthesis of signals of interest. The focus of this thesis is signal processing for acoustics (both sonic and ultrasonic). In the applications examined, signals of interest are usually incomplete, distorted and/or noisy. Therefore, reconstructing the signal, noise reduction and removal of any distortion/interference are the main goals of the signal processing techniques presented. The primary aim is to study and develop an advanced time-frequency signal processing technique for acoustic applications to enhance the quality of the signals. In the first part of the thesis, a technique is presented that models and maintains the correlation between temporal and spectral parameters of audio signals. A novel Packet Loss Concealment (PLC) method is developed with applications to VoIP, audio broadcasting, and streaming. The problem of modelling the time-varying frequency spectrum in the context of PLC is addressed, and a novel solution is proposed for tracking and using the temporal motion of spectral flow to reconstruct the signal. The proposed method utilises a Time-Frequency Motion (TFM) matrix representation of the audio signal, where each frequency is tagged with a motion vector estimate that is assessed by cross-correlation of the movement of spectral energy within sub-bands across time frames. The missing packets are estimated using extrapolation or interpolation algorithms using a TFM matrix and then inverse transformed to the time-domain for reconstruction of the signal. The proposed method is compared with conventional approaches using objective Performance Evaluation of Speech Quality (PESQ), and subjective Mean Opinion Scores (MOS) in a range of packet loss from 5% to 20%. The evaluation results demonstrate that the proposed algorithm substantially improves performance by an average of 2.85% and 5.9% in terms of PESQ and MOS respectively. In the second part of the thesis, the proposed method is extended and modified to address challenges of excessive coherent noise arising from ultrasonic signals gathered during Guided Wave Testing (GWT). It is an advanced Non-destructive testing technique which is used over several branches of industry to inspect large structures for defects where the structural integrity is of concern. In such systems, signal interpretation can often be challenging due to the multi-modal and dispersive propagation of Ultrasonic Guided Waves (UGWs). The multi-modal and dispersive nature of the received signals hampers the ability to detect defects in a given structure. The Split-Spectrum Processing (SSP) method with application for such signal has been studied and reviewed quantitatively to measure the enhancement in terms of Signal-to-Noise Ratio (SNR) and spatial resolution. In this thesis, the influence of SSP filter bank parameters on these signals is studied and optimised to improve SNR and spatial resolution considerably. The proposed method is compared analytically and experimentally with conventional approaches. The proposed SSP algorithm substantially improves SNR by an average of 30dB. The conclusions reached in this thesis will contribute to the progression of the GWT technique through considerable improvement in defect detection capability.Centre for Electronic Systems Research (CESR) of Brunel University London, The National Structural Integrity Research Centre (NSIRC) and TWI Ltd

Tooth Discoloration Resulting from a Nano Zinc Oxide-Eugenol Sealer

Introduction: A desirable quality of any endodontic sealer is its ability to be tooth color friendly. Therefore the aim of the present study was to evaluate the tooth discoloration potential of a nano zinc oxide-eugenol (NZOE) sealer. Methods and Materials: In order to evaluate tooth discoloration, the pulp chamber of 60 human maxillary central and lateral incisors were filled with one of the sealers, naming AH-26 (resin-based sealer), Pulpdent sealer (ZOE-based) and a NZOE experimental sealer. Color measurements was assessed at the baseline (before placement of sealers) (T0), 24 h (T1) and 72 h (T2) h, 1-week (T3), and 1-month (T4) after the placement of sealers using the Easy Shade spectrophotometer. Data were analyzed in SPSS software using one-way ANOVA, and repeated measured ANOVA. Results: No significant differences were observed when the paired comparison test was performed (P>0.05). Conclusion: The tested nZOE sealer had similar tooth discoloration potential in comparison with AH-26 and ZOE sealer.Keywords: Nano Particle; Root Canal Sealer; Tooth Discoloration; Spectrophotometry; Zinc-Oxide Eugenol

Study of antioxidant activity and free radical scavenging power of Physalis alkekengi flower extract

According to the undesirable effects of many chemical preservatives in food products such as oilseed extraction industry, the possibility of substituting these materials with effective compounds of herbal plants have been considered by the researchers. In this study, at first, the Physalis Alkekengi flower extract was extracted by using maceration method with methanol. The Phenolic compounds and the amount of free radical scavenging activity of the flower extract were investigated in different concentrations (200, 400, 600, 800 and 1000 ppm), respectively by Folin–Ciocalteu method and DPPH test and were compared with the synthetic antioxidant activity (BHT) at 200 ppm. The results showed a significant difference between different concentrations of Physalis Alkekengi flower extract, in terms of the rate of Phenolic compounds and free radical scavenging activity of flower extract (p < 0.05). In general, the results of this study showed that the methanol extract of Physalis Alkekengi flower, as a source of cheap and available natural antioxidant, after conducting supplementary experiments can be used in food industry.Keywords: Physalis Alkekengi flower, Free radical scavenging power, Natural antioxidants,Phenolic compounds

Understanding and promoting racial diversity in healthcare settings to address disparities in pandemic crisis management

Background: Health disparities have become apparent since the beginning of the COVID-19 pandemic. When observing racial discrimination in healthcare, self-reported incidences, and perceptions among minority groups in the United States suggest that, the most socioeconomically underrepresented groups will suffer disproportionately in COVID-19 due to synergistic mechanisms. This study reports racially-stratified data regarding the experiences and impacts of different groups availing the healthcare system to identify disparities in outcomes of minority and majority groups in the United States.Methods: Studies were identified utilizing PubMed, Embase, CINAHL Plus, and PsycINFO search engines without date and language restrictions. The following keywords were used: Healthcare, raci*, ethnic*, discriminant, hosti*, harass*, insur*, education, income, psychiat*, COVID-19, incidence, mortality, mechanical ventilation. Statistical analysis was conducted in Review Manager (RevMan V.5.4). Unadjusted Odds Ratios, P-values, and 95% confidence intervals were presented.Results: Discrimination in the United States is evident among racial groups regarding medical care portraying mental risk behaviors as having serious outcomes in the health of minority groups. The perceived health inequity had a low association to the majority group as compared to the minority group (OR = 0.41; 95% CI = 0.22 to 0.78; P = .007), and the association of mental health problems to the Caucasian-American majority group was low (OR = 0.51; 95% CI = 0.45 to 0.58; P \u3c .001).Conclusion: As the pandemic continues into its next stage, efforts should be taken to address the gaps in clinical training and education, and medical practice to avoid the recurring patterns of racial health disparities that become especially prominent in community health emergencies. A standardized tool to assess racial discrimination and inequity will potentially improve pandemic healthcare delivery