Acoustic emission monitoring and quantitative evaluation of damage in reinforced concrete members and bridges

A considerable proportion of highway bridges in the US, are made of reinforced concrete. The vulnerability of these structures during their long service life is a cause of major concern for civil engineers. Since there is a need to detect and recuperate the condition of the bridge structures numerous innovative non-destructive testing (NDT) techniques have come into the forefront. Of the many available technologies, acoustic emission (AE) monitoring has been the most popular non-destructive technique used on highway bridges. Acoustic emission is a passive monitoring technique. Thus, it can be appropriately used for field bridge monitoring applications. Usually AE monitoring is used to obtain qualitative results by observing the trends of the conventional AE parameters recorded by the data acquisition system. The extent of damage is then determined using other NDT techniques. The current study aims at applying the intensity analysis technique of damage quantification to conventional AE parameters generated from reinforced concrete members. A few reinforced concrete beams are subjected to varied cyclic load patterns in the laboratory to study the trends that may be observed in the intensity chart during damage propagation. The results thus obtained are then compared to other prevalent damage assessment techniques as well. Additionally, AE data collected from two field bridge tests are also subjected to intensity analysis technique of damage quantification to evaluate the practical viability of the technique in assessing the severity of the damage in the monitored structures

Damage detection and identification in fiber reinforced plastic structural members and field bridges using acoustic emission technique

With the increased use of fiber reinforced polymer (FRP) based structural systems for rehabilitation of existing and construction of new bridges there is a requirement for identification of critical components of these structural systems and the determination of critical damage thresholds in them. Of the many available non-destructive techniques (NDT), acoustic emission (AE) monitoring had been identified as one of the most popular techniques applicable for damage discrimination in composites. The current study aimed at using patterns in AE data for the identification of damage modes exhibited by composite structural systems. The extensive experimental program involved testing of two structural systems: (i) Reinforced concrete specimens with CFRP retrofit to study debonding failure mechanism and (ii) GFRP laminates coupon specimens tested under varied load conditions to study critical failure modes such as fiber breakage, matrix cracking, delamination and debonding. Real-time AE monitoring was also conducted for a newly installed FRP deck field bridge subjected to live load tests. The AE data collected from the bridge revealed the overall structural performance of the new bridge and helped establish baseline AE activity for future condition evaluation. The AE data acquired from all the experimental tests conducted in this research were subjected two methods of analysis. The first analysis technique involved subjecting the data to the traditional signal processing techniques and identifying various AE sources by visual observations of trends in correlation plots. Meanwhile the same dataset was analyzed using neural networks to perform pattern recognition. In this work, a methodology based on the use of an unsupervised k-means clustering to generate the learning dataset for the training of the multi-layer perceptron (MLP) classifier was developed. The method adopted here showed good results for the clustering and classification of AE signals from different sources for the specimens studied in this research. But, clustering does not always lead to a unique solution and some failure mode characteristics were more easily identifiable than others. Thus further study for enriching of the training dataset is warranted. The high performance efficiency achieved by the developed neural network model for damage identification in full scale specimens further confirms the potential of the developed methodology in being feasible for damage identification in full-scale structures

Moderators and predictors of response to cognitive behaviour therapy for pediatric obsessive-compulsive disorder: A systematic review

We report a systematic review of moderators of CBT efficacy for pediatric OCD relative to other treatments. CENTRAL, MEDLINE, EMBASE, CINAHL, and PsycINFO were searched for RCTs reporting on effect moderation for CBT outcomes. Five studies (N = 365) examined 17 variables with three significant moderators identified. Compared to pill-placebo, CBT monotherapy was not effective for children with a family history of OCD but was for those without a family history. For children with a family history, CBT plus sertraline efficacy was attenuated but remained significant. For children with tics, CBT but not sertraline remained superior to pill-placebo. For non-responders to initial treatment with CBT, continuing CBT was inferior to commencing sertraline for those with tics but was not different for those without tics. A supplementary review identified older age, symptom and impairment severity, co-morbidity and family accommodation as consistent predictors of a poorer outcome to CBT. Current evidence for moderation effects is post-hoc, from single RCTs, has small Ns and requires replication. The review identifies family history of OCD and the presence of tics as factors requiring further examination in properly conducted trials and about which clinicians need to show care in their treatment recommendations

NANODISCS: A NEW EPOCH IN THE STUDY OF MEMBRANE PROTEINS AND AS AN EMERGING DRUG DELIVERY SYSTEM

Nano discs recently evolved as a novel tool for studying the membrane associated proteins and serve as an effective drug delivery system. Nano discs constitute disc shaped nano particles and can be defined as a membrane system which is synthetic in nature and aids in the study of membrane proteins. It is mainly made of phospholipid bilayer and the water repelling edge is isolated by amphipathic proteins called membrane scaffolding proteins [MSP]. Micelles present in the nano disc mimics the property of the biological membrane proteins. It is a powerful technology that competently delivers the drug components in to the right cells in the right tissues. Membrane scaffold proteins are primarily expressed, purified and characterized and self-assembled to form Nano discs by the process of dialysis using biobeads. Nano discs are proven to be effective in the study of membrane proteins because they can fluidize and counterbalance and also help in reclusion, refinement, biophysical and biochemical studies of them. It also presents a more genuine environment than liposomes, bicelles, amphipols and detergent micelles. Major technological advantages of nano discs include the higher stability and carrier capacity and also the increased feasibility of incorporating both hydrophilic and hydrophobic substances of drug carrier. Thus nano discs serves as an excellent system in its ability to precisely control its composition and provide a nano scale membrane surface for investigating molecular recognition events. This article reviews the emphasis of nanodiscs in studying membrane proteins as well as its effectivity in transforming into a major drug delivery system. An overview of published literatures between 1996 and 2017 was conducted to write the review

High-speed Beveled Tip Versus Standard Tip Vitrectomy Probe: A Prospective Randomized Clinical Trial

Purpose: To compare the efficiency of the advanced ultravit beveled vitrector probe (10,000 cuts per minute) to the current standard ultravit highspeed (7500 cuts per minute) vitrector probe. Methods: A prospective, randomized controlled trial was conducted on patients undergoing routine vitrectomy surgery for epiretinal membrane, full-thickness macular hole, and vitreous opacities. Patients were randomly assigned to undergo PPV with the ultravit highspeed probe (Probe 1) or the advanced ultravit beveled probe (Probe 2). The main outcome measure was time to completion of core vitrectomy and vitreous base shave. Results: Forty patients were enrolled in this study, 20 in each cohort. The average time to completion of core vitrectomy was 10.4 +/- 1.8 min in the Probe 1 cohort compared to 9.7 +/- 2 min in the Probe 2 cohort (P = 0.21). The average time to completion of vitreous base shave was 9.6 +/- 2.7 min in the Probe 1 cohort compared to 9.4 +/- 1.8 min in the Probe 2 cohort (P = 0.39). Conclusion: In the current study, the advanced ultravit beveled probe was noninferior to the ultravit highspeed vitrectomy probe when looking at the time to completion of core vitrectomy and vitreous base shave. The increased cut rate did not affect the efficiency of vitreous removal

Molecular-receptor-specific, non-toxic, near-infrared-emitting Au cluster-protein nanoconjugates for targeted cancer imaging

Molecular-receptor-targeted imaging of folate receptor positive oral carcinoma cells using folic-acid-conjugated fluorescent Au25 nanoclusters (Au NCs) is reported. Highly fluorescent Au25 clusters were synthesized by controlled reduction of Au+ ions, stabilized in bovine serum albumin (BSA), using a green-chemical reducing agent, ascorbic acid (vitamin-C). For targeted-imaging-based detection of cancer cells, the clusters were conjugated with folic acid (FA) through amide linkage with the BSA shell. The bioconjugated clusters show excellent stability over a wide range of pH from 4 to 14 and fluorescence efficiency of ~5.7% at pH 7.4 in phosphate buffer saline (PBS), indicating effective protection of nanoclusters by serum albumin during the bioconjugation reaction and cell-cluster interaction. The nanoclusters were characterized for their physico-chemical properties, toxicity and cancer targeting efficacy in vitro. X-ray photoelectron spectroscopy (XPS) suggests binding energies correlating to metal Au 4f7/2˜83.97 eV and Au 4f5/2~87.768 eV. Transmission electron microscopy and atomic force microscopy revealed the formation of individual nanoclusters of size ~1 nm and protein cluster aggregates of size ~8 nm. Photoluminescence studies show bright fluorescence with peak maximum at ~674 nm with the spectral profile covering the near-infrared (NIR) region, making it possible to image clusters at the 700-800 nm emission window where the tissue absorption of light is minimum. The cell viability and reactive oxygen toxicity studies indicate the non-toxic nature of the Au clusters up to relatively higher concentrations of 500 µg ml-1. Receptor-targeted cancer detection using Au clusters is demonstrated on FR+ve oral squamous cell carcinoma (KB) and breast adenocarcinoma cell MCF-7, where the FA-conjugated Au25 clusters were found internalized in significantly higher concentrations compared to the negative control cell lines. This study demonstrates the potential of using non-toxic fluorescent Au nanoclusters for the targeted imaging of cancer

RECOGNITION AND TRACKING MOVING OBJECTS USING MOVING CAMERA IN COMPLEX SCENES

ABSTRAC