Guided-wave structural health monitoring

Guided-wave (GW) approaches have shown potential in various initial laboratory demonstrations as a solution to structural health monitoring (SHM) for damage prognosis. This thesis starts with an introduction to and a detailed survey of this field. Some critical areas where further research was required and those that were chosen to be addressed herein are highlighted. Those were modeling, design guidelines, signal processing and effects of elevated temperature. Three-dimensional elasticity-based models for GW excitation and sensing by finite dimensional surface-bonded piezoelectric wafer transducers and anisotropic piezocomposites are developed for various configurations in isotropic structures. The validity of these models is extensively examined in numerical simulations and experiments. These models and other ideas are then exploited to furnish a set of design guidelines for the excitation signal and transducers in GW SHM systems. A novel signal processing algorithm based on chirplet matching pursuits and mode identification for pulse-echo GW SHM is proposed. The potential of the algorithm to automatically resolve and identify overlapping, multimodal reflections is discussed and explored with numerical simulations and experiments. Next, the effects of elevated temperature as expected in internal spacecraft structures on GW transduction and propagation are explored based on data from the literature incorporated into the developed models. Results from the model are compared with experiments. The feasibility of damage characterization at elevated temperatures is also investigated. An extension of the modeling effort for GW excitation by finite-dimensional piezoelectric wafer transducers to composite plates is also proposed and verified by numerical simulations. At the end, future directions for research to make this technology more easily deployable in field applications are suggested.Ph.D.Aerospace EngineeringUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/77498/1/Raghavan_PhD_thesis_GWSHM.pd

3-D Elasticity-based Modeling of Anisotropic Piezocomposite Transducers for Guided Wave Structural Health Monitoring

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77350/1/AIAA-2006-1793-887.pd

SARS-CoV-2 vaccination induced cerebral venous sinus thrombosis: Do megakaryocytes, platelets and lipid mediators make up the orchestra?

The COVID-19 vaccines comprised of adenoviral vectors encoding the Spike (S) glycoprotein of SARS-CoV-2 are highly effective but associated with rare thrombotic complications. The adenovirus vector infects epithelial cells expressing the coxsackievirus and adenovirus receptor (CAR). The S glycoprotein expressed locally stimulates neutralizing antibody and cellular immune responses. These vaccines have been associated with thromboembolic events including cerebral venous sinus thrombosis (CVST). S glycoprotein stimulates the expression of cyclooxygenase-2 (COX-2) and leads to massive generation of thromboxane A2 in COVID-19. Megakaryocytes express CAR and we postulate that S glycoprotein stimulated generation of thromboxane A2 leads to megakaryocyte activation, biogenesis of activated platelets and thereby increased thrombogenicity. Cerebral vein sinuses express podoplanin, a natural ligand for CLEC2 receptors on platelets. Platelets traversing through the cerebral vein sinuses could be further activated by thromboxane A2-dependent podoplanin-CLEC2 signaling, leading to CVST. A prothrombotic hormonal milieu, and increased generation of thromboxane A2 and platelet activation in healthy females compared to males is consistent with increased risk for CVST observed in women. We propose that antiplatelet agents targeting thromboxane A2 receptor signaling such as low-dose aspirin merit consideration for chemoprophylaxis when administering the adenovirus based COVID-19 vaccines to young adults at risk of thrombosis provided there are no contraindications

Modeling of Wedge-Shaped Anisotropic Piezocomposite Transducer for Guided Wave-based Structural Health Monitoring

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77008/1/AIAA-2007-1723-966.pd

Sposobnost hvatanja slobodnih radikala biljke Saussarea costus

Saussurea costus (Falc.) Lipschitz belonging to the family Asteraceae is an important medicinal drug, roots of which are widely used as a folk medicine. The antioxidant activity of the plant has been studied using its ability to scavenge DPPH, nitric oxide, superoxide radicals along with the ability to inhibit lipid peroxidation and GSH oxidation. The 1 mg mL-1 extract had antioxidant activity with 85.2% reduction of DPPH and a 72.7% decrease in lipid peroxidation. It showed the maximum inhibition of superoxide radical of 66,0%, and 58.4% inhibition of the nitric oxide formation. The concentration of chlorogenic acid was found to be 0.027% in the extract of S. costus. Thus therapeutic activity of the plant may be due to its antioxidant activity, which may be as a result of chlorogenic acid presence.Saussurea costus (Falc.) Lipschitz (Asteraceae) važna je ljekovita biljka čiji se korijen upotrebljava u narodnoj medicini. U ovom radu proučavano je antioksidativno djelovanje te biljke. Praćena je sposobnost vezanja DPPH, oksida dušika, superoksidnih radikala i inhibicije peroksidacije lipida i oksidacije GSH. 1 mg mL-1 ekstrakta reducira 85,2% DPPH i za 72,7% smanjuje peroksidaciju lipida. Maksimalna inhibicija superoksidnih radikala bila je 66%, a inhibicija stvaranja oksida dušika 58,4%. Koncentracija klorogenske kiseline u ekstraktu S. costus je 0,027%. Smatra se da je upravo prisutnost te kiseline presudno za antioksidativno djelovanje

High-Resolution Health Monitoring of Track and Rail Systems with Fiber Optic Sensors and High-Frequency Multiplexed Readouts

Health monitoring of railway systems is critical for detecting incipient faults or degradation. In order to reliably do so, an effective monitoring system must be deployed to provide railroad operators with the highest level of operational awareness and safety. In this study, we explore the use of Fiber Bragg Gratings (FBGs) and a highresolution, low-cost optical readout developed at PARC to interrogate the acoustic emissions generated by a train-rail system. The proposed sensing configuration can allow for a scalable, low-cost, field-deployable solution that could enable near real-time monitoring of tracks and wheels. A proof-of-concept was demonstrated with a G-scale train-rail system with FBGs embedded within the ballast layer. Using PARC’s wavelength shift detector, the acoustic emission signal was resolved in both the time and frequency domain. The findings of this work show promise that this could be a viable solution to deploy an optically-based health monitoring system for railroads

Nutritional, Medicinal and Industrial Uses of Sesame (Sesamum indicum L.) Seeds - An Overview

Sesame (Sesamum indicum L.) seeds have been grown in tropical regions throughout the world since prehistoric times. Sesame seed, a rich source of protein, is one of the first crops processed for oil production. Its non-culinary application includes its use as an ingredient in soap, cosmetics, lubricants and medicines. Sesame seeds also contain two unique substances: sesamin and sesamolin known to have a cholesterol lowering effect in humans and to prevent high blood pressure. Both of these were also reported to increase the hepatic mitochondrial and the peroxisomal fatty acid oxidation rate in experimental animals. Cephalin, a phospholipid from sesame seed has been reported to possess hemostatic activity. The oil has wide medical and pharmaceutical applications. It is mildly laxative, emollient and demulcent. The seeds and fresh leaves may be used as a poultice. Th e antibacterial activity of seeds against Staphylococcus and Streptococcus as well as common skin fungi, such as athlete’s foot fungus has also been well recognized. The oil is also known to maintain high density lipoprotein cholesterol (HDL) and lower low density lipoprotein cholesterol (LDL). Refined sesame oil is rich with antioxidant components like lignans allowing for greater shelf-life of foods plus improving their flavor and taste. In addition to its use as an antioxidant, sesame oil contains a large amount of linoleate in triglyceride form that selectively inhibit malignant melanoma growth. Off -late, the work has also been oriented towards the production of biodiesel from sesame seed oil as a viable alternative to the diesel fuel. The ethno-botanical and medicinal uses of this commercially important, nutritionally rich oilseed need to be explored for better utilization

Sposobnost hvatanja slobodnih radikala biljke Saussarea costus

Saussurea costus (Falc.) Lipschitz belonging to the family Asteraceae is an important medicinal drug, roots of which are widely used as a folk medicine. The antioxidant activity of the plant has been studied using its ability to scavenge DPPH, nitric oxide, superoxide radicals along with the ability to inhibit lipid peroxidation and GSH oxidation. The 1 mg mL-1 extract had antioxidant activity with 85.2% reduction of DPPH and a 72.7% decrease in lipid peroxidation. It showed the maximum inhibition of superoxide radical of 66,0%, and 58.4% inhibition of the nitric oxide formation. The concentration of chlorogenic acid was found to be 0.027% in the extract of S. costus. Thus therapeutic activity of the plant may be due to its antioxidant activity, which may be as a result of chlorogenic acid presence.Saussurea costus (Falc.) Lipschitz (Asteraceae) važna je ljekovita biljka čiji se korijen upotrebljava u narodnoj medicini. U ovom radu proučavano je antioksidativno djelovanje te biljke. Praćena je sposobnost vezanja DPPH, oksida dušika, superoksidnih radikala i inhibicije peroksidacije lipida i oksidacije GSH. 1 mg mL-1 ekstrakta reducira 85,2% DPPH i za 72,7% smanjuje peroksidaciju lipida. Maksimalna inhibicija superoksidnih radikala bila je 66%, a inhibicija stvaranja oksida dušika 58,4%. Koncentracija klorogenske kiseline u ekstraktu S. costus je 0,027%. Smatra se da je upravo prisutnost te kiseline presudno za antioksidativno djelovanje