Efficacy of rectal indomethacin in prevention of post-operative hyperamylasemia following pancreatoduodenectomy: a randomized controlled trial.

BACKGROUND: Post-operative hyperamylasemia (POH) following pancreatoduodenectomy (PD) may play a key role in pathogenesis of post-operative pancreatic fistula (POPF). Aim of the current study was to evaluate efficacy of perioperative administration of indomethacin in preventing POH. METHODS: Single-center, double-blind, randomized controlled trial (RCT) conducted on consecutive patients undergoing PD. Patients received either 100 mg of indomethacin per-rectally at induction of anesthesia or standard care. Primary endpoint was incidence of POH in the two arms. POH was defined as postoperative day (POD) 1 serum amylase (S. amylase) levels greater than the upper limit of normal. RESULTS: After exclusion 44 patients were randomized. The two arms were comparable for preoperative and intraoperative parameters. POH was noted in 20/44 (45.5%) with significantly lower incidence of POH (60.9% vs. 28.6%, p = 0.032) in intervention arm (IA). Median S. amylase, POD 1, 3, and 5 drain amylase, and incidence of clinically relevant POPF (CR-POPF) were lower in IA but failed to reach statistical significance (30.4% vs. 14.3%, p = 0.18). The severity of delayed gastric emptying (DGE) was significantly lower in the IA (grade B/C DGE 23.8% vs. 47.8%, p = 0.023). Evaluation of risk factors for POH showed IA to confer an independent protective effect and increased risk with soft pancreas. CONCLUSION: Perioperative per-rectal indomethacin administration is effective in decreasing the incidence of POH following pancreatoduodenectomy.

Live donor liver transplantation for pediatric acute liver failure: challenges and outcomes.

OBJECTIVE: This study aimed at studying the challenges and outcomes of live-donor liver transplantation (LDLT) for pediatric acute liver failure (PALF). STUDY DESIGN: A total of 315 patients with PALF were treated over a period of 11 years. 42 underwent LT (41 LDLT and one DDLT), constituting 38% (41/110) of all pediatric transplants during this duration. The outcomes of LDLT for PALF were analyzed. RESULTS: All the 41 children who underwent LT met the Kings College criteria (KCC). The etiology was indeterminate in 46.3% (n = 19) children. 75.6% (n = 31) were on mechanical ventilation for grade 3/4 hepatic encephalopathy. There was presence of cerebral edema on a computed tomography scan of the brain in 50% of the children. One-third of our children required hemodynamic support with vasopressors. Systemic inflammatory response syndrome and sepsis were observed in 46.3% and 41.4% of patients, respectively. Post-LDLT 1- and 5-yr patient and graft survival were 75.6% and 70.9%, respectively. The survival in children satisfying KCC but did not undergo LT was 24% (38/161). Vascular and biliary complication rates were 2.4% and 4.8%, respectively. No graft loss occurred because of acute rejection. In multivariate analysis, pre-LT culture positivity and cerebral edema, persistence of brain edema after transplantation, and resultant pulmonary complications were significantly associated with post-LT death. Thirteen (32%) children who underwent plasmapheresis prior to LT had better post-LT neurological recovery, as evidenced by early extubation. CONCLUSION: LDLT for PALF is lifesaving and provides a unique opportunity to time transplantation. Good long-term survival can be achieved, despite the majority of patients presenting late for transplantation. Early referral and better selection can save more lives through timely transplantation.

Spontaneous Generation of Aryl Carbocations from Phenols in Aqueous Microdroplets: Aromatic SN1 Reactions at the Air-Water Interface.

Although phenol is stable in bulk water, we report an exceptional phenomenon in which phenol is spontaneously transformed into a phenyl carbocation (Ph+) in water microdroplets. The high electric field at the air-water interface is proposed to break the phenolic Csp2-OH bond, forming Ph+, which remains in equilibrium with phenol as deciphered by mass spectrometry. We detected up to 70% conversion of phenol to Ph+ in aqueous microdroplets, although catalyst-free activation of the phenolic Csp2-OH bond is challenging. This transformation is well tolerated by a wide range of electron-donating and -withdrawing substituents in phenolic compounds. The Ph+ in water microdroplets could be reacted with various nucleophiles (amine, pyridine, azide, thiol, carboxylic acid, alcohol, and 18O-water), yielding the ipso-substitution products of phenol through an aromatic SN1 mechanism. Despite the fleeting life of Ph+ in the bulk, this study demonstrates its unusual stability at the aqueous microdroplet surface, enabling its detection and transformation.

Mass Spectrometry Imaging of Lumpectomy Specimens Deciphers Diacylglycerols as Potent Biomarkers for the Diagnosis of Breast Cancer.

Detecting breast tumor markers with a fast turnaround time from frozen sections should foster intraoperative histopathology in breast-conserving surgery, reducing the need for a second operation. Hence, rapid label-free discrimination of the spatially resolved molecular makeup between cancer and adjacent normal breast tissue is of growing importance. We performed desorption electrospray ionization mass spectrometry imaging (DESI-MSI) of fresh-frozen excision specimens, including cancer and paired adjacent normal sections, obtained from the lumpectomy of 73 breast cancer patients. The results demonstrate that breast cancer tissue posits sharp metabolic upregulation of diacylglycerol, a lipid second messenger that activates protein kinase C for promoting tumor growth. We identified four specific sn-1,2-diacylglycerols that outperformed all other lipids simultaneously mapped by the positive ion mode DESI-MSI for distinguishing cancers from adjacent normal specimens. This result contrasts with several previous DESI-MSI studies that probed metabolic dysregulation of glycerophospholipids, sphingolipids, and free fatty acids for cancer diagnoses. A random forest-based supervised machine learning considering all detected ion signals also deciphered the highest diagnostic potential of these four diacylglycerols with the top four importance scores. This led us to construct a classifier with 100% overall prediction accuracy of breast cancer by using the parsimonious set of four diacylglycerol biomarkers only. The metabolic pathway analysis suggested that increased catabolism of phosphatidylcholine in breast cancer contributes to diacylglycerol overexpression. These results open up opportunities for mapping diacylglycerol signaling in breast cancer in the context of novel therapeutic and diagnostic developments, including the intraoperative assessment of breast cancer margin status.

Hepatic artery-related complications after live donor liver transplantation.

BACKGROUND: Hepatic artery-related complications (HARC) after live donor liver transplantation (LDLT) is associated with high morbidity and mortality rate. METHODS: Prospectively maintained data from July 2011 to September 2020 was analyzed for etiology, detection, management, and outcome of HARC. RESULTS: Six hundred fifty-seven LDLT (adult 572/pediatrics 85) were performed during the study period. Twenty-one (3.2%) patient developed HARC; 16 (2.4%) hepatic artery thrombosis (HAT) and 5 (0.76%) non-thrombotic hepatic artery complication (NTHAC). Ninety percent (19/21) HARC were asymptomatic and detected on protocol Doppler. Median time to detection was day 4 (range - 1 to 35), which included 18 early (within 7 days) vs 3 late incidents. Only one pediatric patient had HAT. Seven patients underwent surgical revascularization, 11 had endovascular intervention and 3 with attenuated flow required only systemic anticoagulation. All NTHAC survived without any sequelae. Revascularization was successful in 81% (13/16) with HAT. Biliary complications were seen in 5 (23.8%); four were managed successfully. Overall mortality was 14.8% (3/21). The 1-year and 5-year survival were similar to those who did not develop HARC (80.9% vs 84.2%, p = 0.27 and 71.4% vs 75.19%, p = 0.36 respectively) but biliary complications were significantly higher (23.8% vs 14.2%, p = 0.03). On multivariate analysis, clockwise technique of arterial reconstruction was associated with decreased risk of HAT (1.7% vs 4.1% (p value - 0.003)). CONCLUSION: Technical refinement, early detection, and revascularization can achieve good outcome in patients with HARC after LDLT.

Rapid Molecular Evaluation of Human Kidney Tissue Sections by In Situ Mass Spectrometry and Machine Learning to Classify the Nephrotic Syndrome.

Nephrotic syndrome (NS) is classified based on morphological changes of glomeruli in biopsied kidney tissues evaluated by time-consuming microscopy methods. In contrast, we employed desorption electrospray ionization mass spectrometry (DESI-MS) directly on renal biopsy specimens obtained from 37 NS patients to rapidly differentiate lipid profiles of three prevalent forms of NS: IgA nephropathy (n = 9), membranous glomerulonephritis (n = 7), and lupus nephritis (n = 8), along with other types of glomerular diseases (n = 13). As we noted molecular heterogeneity in regularly spaced renal tissue regions, multiple sections from each biopsy specimen were collected, providing a total of 973 samples for investigation. Using multivariate analysis, we report differential expressions of glycerophospholipids, sphingolipids, and glycerolipids among the above four classes of NS kidneys, which were otherwise overlooked in several past studies correlating lipid abnormalities with glomerular diseases. We developed machine learning (ML) models with the top 100 features using the support vector machine, which enabled us to discriminate the concerned glomerular diseases with 100% overall accuracy in the training, validation, and holdout test set. This DESI-MS/ML-based tissue analysis can be completed in a few minutes, in sharp contrast to a daylong procedure followed in the conventional histopathology of NS.

A proteomic study to unveil lead toxicity-induced memory impairments invoked by synaptic dysregulation.

Lead (Pb2+), a ubiquitously present heavy metal toxin, has various detrimental effects on memory and cognition. However, the molecular processes affected by Pb2+ causing structural and functional anomalies are still unclear. To explore this, we employed behavioral and proteomic approaches using rat pups exposed to lead acetate through maternal lactation from postnatal day 0 (P0) until weaning. Behavioral results from three-month-old rats clearly emphasized the early life Pb2+ exposure induced impairments in spatial cognition. Further, proteomic analysis of synaptosomal fractions revealed differential alteration of 289 proteins, which shows functional significance in elucidating Pb2+ induced physiological changes. Focusing on the association of Small Ubiquitin-like MOdifier (SUMO), a post-translational modification, with Pb2+ induced cognitive abnormalities, we identified 45 key SUMO target proteins. The significant downregulation of SUMO target proteins such as metabotropic glutamate receptor 3 (GRM3), glutamate receptor isoforms 2 and 3 (GRIA 2 and GRIA3) and flotilin-1 (FLOT1) indicates SUMOylation at the synapses could contribute to and drive Pb2+ induced physiological imbalance. These findings identify SUMOylation as a vital protein modifier with potential roles in hippocampal memory consolidation and regulation of cognition. Data availbility: The mass spectrometry proteomics data have been deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the dataset identifier PXD034212".

Capturing Reactive Carbanions by Microdroplets.

Carbanions appear in many organic or biological reactions as fleeting intermediates, prohibiting direct observation or spectroscopic measurement. An aqueous environment is known to rapidly annihilate a carbanion species, reducing its lifetime to as short as picoseconds. We report that aqueous microdroplets can capture and stabilize reactive carbanion intermediates isolated from four classic organic reactions, aldol and Knoevenagel condensations, alkyne alkylation, and the Reimer-Tiemann reaction, enabling the detection of their carbanion intermediates by desorption electrospray ionization mass spectrometry. This is accomplished in real time of the reaction, allowing new insights into reaction mechanisms to be obtained. The efficacy of microdroplets in capturing such elusive species was examined by varying the solvent and the microdroplet negative charge density. We observed that microdroplets composed of water-methanol outperform other solvents, such as pure water, in capturing carbanions, which is in contrast to the earlier report that presented the highest performance of pure water microdroplets in capturing carbocations. We offer some mechanistic insights to explain the discriminatory behavior of these two oppositely charged species in microdroplets.

Destabilized Carbocations Caged in Water Microdroplets: Isolation and Real-Time Detection of α-Carbonyl Cation Intermediates.

Over the last 50 years, proposals of α-carbonyl cation intermediates have been driven by chemical intuition and indirect evidence. Recently, wide interest in α-carbonyl cation chemistry has opened new gates to prepare α-functionalized carbonyl compounds. Though these intrinsically unstable carbocations are formed under forcing conditions (e.g., in a strong acid medium), their fleeting existence prohibits direct observation or spectroscopic measurement. We report that high-speed aqueous microdroplets can directly capture α-carbonyl cation intermediates from various reactions (Friedel-Crafts arylation, deoxygenation, and azidation) upon bombarding with the corresponding reaction aliquots. The α-carbonyl cations caged in water droplets are then desorbed to the gas phase, allowing their successful measurement by mass spectrometry. This has also enabled us to simultaneously monitor the relative abundance of the associated precursor, α-carbonyl cation intermediate, and product during the progress of the reaction.

Cystic artery pseudoaneurysm-a rare complication of acute cholecystitis: review of literature.

OBJECTIVE: To acquaint with the presentation and management of the cystic artery aneurysm by enriching the reviewed literature with our own experience. BACKGROUND: Cystic artery pseudoaneurysm is an uncommon entity with varied clinical presentation. Inflammation and trauma are associated with most of the cases. Limited experience with the condition challenges the management of individual cases. MATERIALS AND METHODS: We retrieved all the reported cases of cystic artery pseudoaneurysm, published up to December 2019, from the PubMed database and excluded those arising as postoperative complications. A total of 59 cases were analyzed, and we also included our experience of managing a case of cystic artery pseudoaneurysm. RESULTS: Abdominal pain (77.9%) was the most common presentation followed by upper GI bleed (64.4%), while 19 patients (32.2%) had presented with classic Quincke's Triad. Most of the cases were diagnosed following the rupture of the pseudoaneurysm (n = 49, 83.05%). Fifteen patients presented with shock. Hyperbilirubinemia (59.3%) and anemia (55.9%) were the commonest laboratory findings. Although CT angiogram remains the investigation of choice, a conventional angiogram is the gold standard and sufficed as the definitive management in 20 cases. Cholecystectomy formed the definitive management in the rest of the cases. We successfully managed a middle-aged female patient of cystic artery aneurysm with xanthogranulomatous cholecystitis by open cholecystectomy. CONCLUSION: Cystic artery pseudoaneurysms are amenable to successful management with careful evaluation and timely cholecystectomy or angioembolization or a combination of both.

Mass Spectrometry Imaging Deciphers Dysregulated Lipid Metabolism in the Human Hippocampus Affected by Temporal Lobe Epilepsy.

Temporal lobe epilepsy (TLE) is the most prevalent form of human epilepsy, often accompanied by neurodegeneration in the hippocampus. Like other neurological diseases, TLE is expected to disrupt lipid homeostasis. However, the lipid architecture of the human TLE brain is relatively understudied, and the molecular mechanism of epileptogenesis is poorly understood. We performed desorption electrospray ionization mass spectrometry imaging of 39 fresh frozen surgical specimens of the human hippocampus to investigate lipid profiles in TLE with hippocampal sclerosis (n = 14) and control (non-TLE; n = 25) groups. In contrast to several previous studies on animal models of epilepsy, we report reduced expression of various important lipids, notably phosphatidylcholine (PC) and phosphatidylethanolamine (PE), in the human TLE hippocampus. In addition, metabolic pathway analysis suggested the possible dysregulation of the Kennedy pathway in TLE, resulting in striking reductions of PC and PE levels. This revelation opens up opportunities to further investigate the associated molecular mechanisms and possible therapeutic targets for TLE.

A Novel Defect Estimation Approach in Wind Turbine Blades Based on Phase Velocity Variation of Ultrasonic Guided Waves.

The reliability of the wind turbine blade (WTB) evaluation using a new criterion is presented in the work. Variation of the ultrasonic guided waves (UGW) phase velocity is proposed to be used as a new criterion for defect detection. Based on an intermediate value between the maximum and minimum values, the calculation of the phase velocity threshold is used for defect detection, location and sizing. The operation of the proposed technique is verified using simulation and experimental studies. The artificially milled defect having a diameter of 81 mm on the segment of WTB is used for verification of the proposed technique. After the application of the proposed evaluation technique for analysis of the simulated B-scan image, the coordinates of defect edges have been estimated with relative errors of 3.7% and 3%, respectively. The size of the defect was estimated with a relative error of 2.7%. In the case of an experimentally measured B-scan image, the coordinates of defect edges have been estimated with relative errors of 12.5% and 3.9%, respectively. The size of the defect was estimated with a relative error of 10%. The comparative results obtained by modelling and experiment show the suitability of the proposed new criterion to be used for the defect detection tasks solving.

Aqueous Microdroplets Capture Elusive Carbocations.

Carbocations are short-lived reactive intermediates in many organic and biological reactions that are difficult to observe. This field sprung to life with the discovery by Olah that a superacidic solution allowed the successful capture and nuclear magnetic resonance characterization of transient carbocations. We report here that water microdroplets can directly capture the fleeting carbocation from a reaction aliquot followed by its desorption to the gas phase for mass spectrometric detection. This was accomplished by employing desorption electrospray ionization mass spectrometry to detect a variety of short-lived carbocations (average lifetime ranges from nanoseconds to picoseconds) obtained from different reactions (e.g., elimination, substitution, and oxidation). Solvent-dependent studies revealed that aqueous microdroplets outperform organic microdroplets in the capture of carbocations. We provide a mechanistic insight demonstrating the survival of the reactive carbocation in a positively charged aqueous microdroplet and its subsequent ejection to the gas phase for mass spectrometric analysis.

Diagnostics of Melanocytic Skin Tumours by a Combination of Ultrasonic, Dermatoscopic and Spectrophotometric Image Parameters.

Dermatoscopy, high-frequency ultrasonography (HFUS) and spectrophotometry are promising quantitative imaging techniques for the investigation and diagnostics of cutaneous melanocytic tumors. In this paper, we propose the hybrid technique and automatic prognostic models by combining the quantitative image parameters of ultrasonic B-scan images, dermatoscopic and spectrophotometric images (melanin, blood and collagen) to increase accuracy in the diagnostics of cutaneous melanoma. The extracted sets of various quantitative parameters and features of dermatoscopic, ultrasonic and spectrometric images were used to develop the four different classification models: logistic regression (LR), linear discriminant analysis (LDA), support vector machine (SVM) and Naive Bayes. The results were compared to the combination of only two techniques out of three. The reliable differentiation between melanocytic naevus and melanoma were achieved by the proposed technique. The accuracy of more than 90% was estimated in the case of LR, LDA and SVM by the proposed method.

Analysis of Wave Patterns Under the Region of Macro-Fiber Composite Transducer to Improve the Analytical Modelling for Directivity Calculation in Isotropic Medium.

Analytical modelling is an efficient approach to estimate the directivity of a transducer generating guided waves in the research field of ultrasonic non-destructive testing of the large and complex structures due to its short processing time as compared to the numerical modelling and experimental techniques. The wave patterns or the amplitude variations along the region of ultrasonic transducer itself depend on its behavior, excitation frequency, and the type of propagating wave mode. Depending on the wave-pattern of a propagating wave mode, the appropriate value of the amplitude correction factor must be multiplied to the amplitudes of the excitation signal for the accurate evaluation of directivity pattern of the ultrasonic transducers generating guided waves in analytical modelling. The objective of this work is to analyse the wave patterns under the region of macro-fiber composite (MFC) transducer to improve the accuracy of a previously developed analytical model for the prediction of directivity patterns. Firstly, the amplitude correction factor based on the wave patterns under the region of P1-type MFC (MFC-2814) transducer at two different frequencies (80 kHz, 3 periods and 220 kHz, 3 period) glued on 2 mm Al alloy plate has been estimated analytically in the case of an asymmetric (A0) guided Lamb wave. The validation of analytically estimated amplitude correction factor is performed by a proposed experimental method that allows analyzing the behaviour of MFC transducer under its region by gluing MFC on bottom surface and scanning the receiver on the top surface of the sample. Later on, the estimated amplitude correction factor is included in the previously developed 2D analytical model for the improvement in the directivity patterns of the A0 mode. The modified analytical model shows a significant improvement in the directivity pattern of the A0 wave mode in comparison to the results obtained by the previous model without considering the proper wave patterns. The results reveal that errors between the directivity estimated by the present modified 2D analytical model and experimental investigation are reduced by more than 58% in comparison to the previously developed analytical model.

Mechanistic insights of Cu(ii)-mediated ortho-C-H amination of arenes by capturing fleeting intermediates and theoretical calculations.

The capture of reactive intermediates empowers chemists to conjecture the detail of a chemical transformation. Here we explore the mechanism of a C-H amination by intercepting short-lived intermediates in real time using online mass spectrometry. Computational study unravels the favorable pathway of the proposed dual mechanism of the reaction.

Identification and Characterization of Defects in Glass Fiber Reinforced Plastic by Refining the Guided Lamb Waves.

In this paper, the disbond-type defect presented on glass fiber reinforced plastic material is analyzed by refining the guided Lamb wave signals. A segment of wind turbine blade is considered as a test sample. The low-frequency ultrasonic measurement system is used for the non-destructive testing of the test sample using guided waves. The P-1 type macro-fiber composite transducer as a transmitter and contact-type piezoceramic transducer as a receiver are used for the testing of a sample. The disbond type defect having a diameter of 81 mm is detected from the experimental results. To improve the accuracy in locating and sizing the defects and estimation of the time of flight and phase velocity of ultrasonic guided waves in defective region, signal processing algorithm is developed by utilizing the promising properties of various ultrasonic signal processing techniques such as wavelet transform, amplitude detection, two-dimensional Fast-Fourier transform, Hilbert transform and variational mode decomposition. The discrete wavelet transform is used to denoise the guided wave signals and then, the size and location of defects are estimated by amplitude detection. The reflected wave signals from the opposite edge of the sample are removed by applying the two-dimensional Fast-Fourier transform to the experimental B-scan signal. Afterwards, variational mode decomposition and Hilbert transform are used for the phase velocity and time-delay estimation by comparing the instantaneous amplitudes of the defective and defect-free signal. The validation and the demonstration of reproducibility of the algorithm is performed by extracting the features of a 51 mm defect from another experimental B-scan.

A comparison of APACHE II, BISAP, Ranson's score and modified CTSI in predicting the severity of acute pancreatitis based on the 2012 revised Atlanta Classification.

OBJECTIVE: Our aim was to prospectively compare the Accuracy of Acute Physiology and Chronic Health Evaluation (APACHE) II, Bedside Index of Severity in Acute Pancreatitis (BISAP), Ranson's score and modified Computed Tomography Severity Index (CTSI) in predicting the severity of acute pancreatitis based on Atlanta 2012 definitions in a tertiary care hospital in northern India. METHODS: Fifty patients with acute pancreatitis admitted to our hospital during the period of March 2015 to September 2016 were included in the study. APACHE II, BISAP and Ranson's score were calculated for all the cases. Modified CTSI was also determined based on a pancreatic protocol contrast enhanced computerized tomography (CT). Optimal cut-offs for these scoring systems and the area under the curve (AUC) were evaluated based on the receiver operating characteristics (ROC) curve and these scoring systems were compared prospectively. RESULTS: Of the 50 cases, 14 were graded as severe acute pancreatitis. Pancreatic necrosis was present in 15 patients, while 14 developed persistent organ failure and 14 needed intensive care unit (ICU) admission. The AUC for modified CTSI was consistently the highest for predicting severe acute pancreatitis (0.919), pancreatic necrosis (0.993), organ failure (0.893) and ICU admission (0.993). APACHE II was the second most accurate in predicting severe acute pancreatitis (AUC 0.834) and organ failure (0.831). APACHE II had a high sensitivity for predicting pancreatic necrosis (93.33%), organ failure (92.86%) and ICU admission (92.31%), and also had a high negative predictive value for predicting pancreatic necrosis (96.15%), organ failure (96.15%) and ICU admission (95.83%). CONCLUSION: APACHE II is a useful prognostic scoring system for predicting the severity of acute pancreatitis and can be a crucial aid in determining the group of patients that have a high chance of need for tertiary care during the course of their illness and therefore need early resuscitation and prompt referral, especially in resource-limited developing countries.

2D Analytical Model for the Directivity Prediction of Ultrasonic Contact Type Transducers in the Generation of Guided Waves.

In this paper, a novel 2D analytical model based on the Huygens's principle of wave propagation is proposed in order to predict the directivity patterns of contact type ultrasonic transducers in the generation of guided waves (GWs). The developed model is able to estimate the directivity patterns at any distance, at any excitation frequency and for any configuration and shape of the transducers with prior information of phase dispersive characteristics of the guided wave modes and the behavior of transducer. This, in turn, facilitates to choose the appropriate transducer or arrays of transducers, suitable guided wave modes and excitation frequency for the nondestructive testing (NDT) and structural health monitoring (SHM) applications. The model is demonstrated for P1-type macro-fiber composite (MFC) transducer glued on a 2 mm thick aluminum (Al) alloy plate. The directivity patterns of MFC transducer in the generation of fundamental guided Lamb modes (the S0 and A0) and shear horizontal mode (the SH0) are successfully obtained at 80 kHz, 5-period excitation signal. The results are verified using 3D finite element (FE) modelling and experimental investigation. The results obtained using the proposed model shows the good agreement with those obtained using numerical simulations and experimental analysis. The calculation time using the analytical model was significantly shorter as compared to the time spent in experimental analysis and FE numerical modelling.

Hybrid Signal Processing Technique to Improve the Defect Estimation in Ultrasonic Non-Destructive Testing of Composite Structures.

This work proposes a novel hybrid signal processing technique to extract information on disbond-type defects from a single B-scan in the process of non-destructive testing (NDT) of glass fiber reinforced plastic (GFRP) material using ultrasonic guided waves (GW). The selected GFRP sample has been a segment of wind turbine blade, which possessed an aerodynamic shape. Two disbond type defects having diameters of 15 mm and 25 mm were artificially constructed on its trailing edge. The experiment has been performed using the low-frequency ultrasonic system developed at the Ultrasound Institute of Kaunas University of Technology and only one side of the sample was accessed. A special configuration of the transmitting and receiving transducers fixed on a movable panel with a separation distance of 50 mm was proposed for recording the ultrasonic guided wave signals at each one-millimeter step along the scanning distance up to 500 mm. Finally, the hybrid signal processing technique comprising the valuable features of the three most promising signal processing techniques: cross-correlation, wavelet transform, and Hilbert-Huang transform has been applied to the received signals for the extraction of defects information from a single B-scan image. The wavelet transform and cross-correlation techniques have been combined in order to extract the approximated size and location of the defects and measurements of time delays. Thereafter, Hilbert-Huang transform has been applied to the wavelet transformed signal to compare the variation of instantaneous frequencies and instantaneous amplitudes of the defect-free and defective signals.