Effect of Fatigue Crack Growth Rate on Varied Percentage of Martensite for Welded DP Steel

The objective of this investigation is to study the fatigue behaviour of Dual phase(DP)steel with varying percentage of martensite. The study is conducted on samples of welded Dual phase steel prepared by intercritical annealing process with temperature varying from 7300C to 8100C. In this process both coarse and fine ferrite-martensite structures are produced with volume fraction of martensite varying from 48 to 69%. It has been observed from the investigation that the fatigue crack propagation rates were found to decrease and threshold values of stress intensity factor increase with the increase in martensite content upto 69% for the intercritically annealed structures

Dry Sliding wear behaviour of Ferrite-Martensite Dual Phase Steels

In the present investigation, High Strength Low Alloy Steel (HSLA) was subjected to Intermediate Quench (IQ) heat treatment process at four different intercritical temperatures to obtain Dual Phase(DP) steels of varying percentages of ferrite-martensite microstructure The intercritical holding temperatures were 730oC, 750oC, 780oC and 810oC. The corresponding martensite volume fraction obtained were48%,56%,63%and 69%. Specimens for the wear test were prepared as per the ASTM recommended procedures and were tested for the dry sliding wear behaviour at different loading conditions ranging from 19.62N to 49.05N and at constant sliding velocity of 1.257ms-1, on a Pin-on-Disc wear testing machine. The investigation reveals that amount of martensite volume fraction in the dual phase microstructure increases with increase in intercritical temperature and the wear resistance of the Dual Phase steel increases with increase in percentage volume fraction of martensite in the dual phase ferrite-martensite microstructure

Analysis of MEMS Piezoelectric Hydrophone at High Sensitivity for underwater application

Micro-electromechanical systems (MEMS), is a technology that is used to design small integrated devices that combines both electrical (voltage, resistance) and mechanical components (stress, displacement). These devices are assembled using integrated circuit batch processing methods and their size can vary from Micrometers (μm) to Millimeters (mm). MEMS devices have the capability to sense and control the environment. These devices are fabricated using System Integrated chip technology and micro-level segments are manufactured using silicon. To remove the selective parts of silicon i.e. extra silicon parts, Processes such as back etching, high-aspect-ratio micromachining are used to remove selective parts of silicon or to add the extra layers to form the electromechanical components. The study is concerned to design a T- Shape vector Hydrophone using MEMS Technology and to analyses mechanical properties like induced stresses, deformation and to analyses the piezoelectric hydrophone characteristics like frequency response, sensitivity and Voltage to achieve improved sensitivity. MEMS Directional Hydrophone PZT is simulated. Both the structure resembles the fish lateral line and auditory cilia system which converts acoustic pressure into voltage. © 2017 Elsevier Ltd

Identification of a human TFPI-2 splice variant that is upregulated in human tumor tissues

BACKGROUND: Previous studies have shown that the expression of tissue factor pathway inhibitor-2 (TFPI-2), a matrix-associated Kunitz-type serine proteinase inhibitor, is markedly down-regulated in several tumor cells through hypermethylation of the TFPI-2 gene promoter. In the present study, RT-PCR analysis of total RNA from both human normal and tumor cells revealed a novel 289 nucleotide splice variant of the TFPI-2 transcript designated as aberrantly-spliced TFPI-2 (asTFPI-2). RESULTS: Nucleotide sequence analyses indicated that asTFPI-2 consists of complete exons II and V, fused with several nucleotides derived from exons III and IV, as well as six nucleotides derived from intron C. 5'- and 3'-RACE analyses of total RNA amplified exclusively the wild-type TFPI-2 transcript, indicating that asTFPI-2 lacks either a 5'-untranslated region (UTR) or a 3'-poly (A)(+ )tail. Quantitative real-time RT-PCR analyses revealed that several human tumor cells contain 4 to 50-fold more copies of asTFPI-2 in comparison to normal cells. In spite of the absence of a 5'-UTR or poly (A)(+ )tail, the asTFPI-2 variant exhibited a half-life of ~16 h in tumor cells. CONCLUSION: Our studies reveal the existence of a novel, aberrantly-spliced TFPI-2 transcript predominantly expressed in tumor cells and provides suggestive evidence for an additional mechanism for tumor cells to down-regulate TFPI-2 protein expression enhancing their ability to degrade the extracellular matrix

Synthesis of some novel benzimidazole derivatives and it's biological evaluation

A series of new benzimidazole derivatives have been synthesized by simple condensation reaction between benzimidazole derivatives and phenyl sulphonyl chloride derivatives. All these compounds were characterized by FT-IR, 1H NMR, MS and elemental analysis. These compounds were screened for antibacterial and antioxidant activities, respectively. The antibacterial activities were compared with the standard drug such as chlorophenicol and antioxidant activities were compared with the ascorbic acid

Synergistic pH effect for reversible shuttling aptamer-based biosensors between graphene oxide and target molecules

DNA aptamers are known to desorb from graphene oxide (GO) surface in the presence of target molecules. We demonstrate herein that the binding equilibrium can be shifted by simply tuning the solution pH. At lower pH, the aptamer/GO binding is enhanced while aptamer/target binding is weakened, making this system a regenerable biosensor without covalent conjugation.University of Waterloo || Natural Sciences and Engineering Research Council |

Dielectric studies of Liquid Crystal Nanocomposites and Nanomaterial systems.

Liquid crystals (LCs) have revolutionized the display and communication technologies. Doping of LCs with inorganic nanoparticles such as carbon nanotubes, gold nanoparticles and ferroelectric nanoparticles have garnered the interest of research community as they aid in improving the electro-optic performance. In this thesis, we examine a hybrid nanocomposite comprising of 5CB liquid crystal and block copolymer functionalized barium titanate ferroelectric nanoparticles. This hybrid system exhibits a giant soft-memory effect. Here, spontaneous polarization of ferroelectric nanoparticles couples synergistically with the radially aligned BCP chains to create nanoscopic domains that can be rotated electromechanically and locked in space even after the removal of the applied electric field. The resulting non-volatile memory is several times larger than the non-functionalized sample and provides an insight into the role of non-covalent polymer functionalization. We also present the latest results from the dielectric and spectroscopic study of field assisted alignment of gold nanorods

Risk factors for post-partum hemorrhage in patients who underwent operative vaginal delivery in a tertiary care center

Background: Operative vaginal delivery is a timely intervention to cut short second stage labor when imminent delivery is in the interests of mother, fetus, or both. It reduces second stage cesarean section morbidity and uterine scar and its influence on future obstetric career. The possible structural neonatal adverse outcomes due to operative vaginal delivery are well quantified. However, its effects on maternal outcome need to be understood better. In this paper, we study the effect of operative vaginal delivery on maternal post-partum hemorrhage (PPH) and the associated risk factors.Methods: It was a retrospective study carried out for the period July 2016 to July 2020 at Ramaiah Medical College, Bengaluru. Total number of vaginal deliveries in this period were 6318. Out of these, 1020 patients underwent assisted vaginal delivery using vacuum/ forceps/ sequential use of instrument. Blood loss greater than 500 ml is considered PPH for the purpose of this study. 15% of the study population was noted to have PPH. We employ a multivariate logistic regression to identify statistically significant risk factors for PPH in women undergoing operative vaginal delivery.Results: The logistic regression model identifies multiparity, maternal age, neonatal birth weight more than 3.5 kg, application of forceps in women with hypertensive disorders, III-degree tear, cervical tear to significantly increase the risk of PPH in our study population.Conclusions: Certain factors seem to increase the risk of PPH in operative vaginal delivery. The risks and benefits must be weighed properly before use of instruments

Electromechanical Coupling of Graphene With Cells

Nanomaterials have been studied extensively in the last decade in the context of many applications such as polymer composites, energy harvesting systems, sensors, ‘transparent’-like materials, field-effect transistors (FETs), spintronic devices, gas sensors and biomedical applications. Graphene, a recently discovered two-dimensional form of carbon has captured the interest of material scientists, and physicists alike due to its excellent electrical, mechanical and thermal properties. Graphene has also kindled a tremendous interest among chemists and cell biologists to create cellular-electronic interface in the context of bio-electronic devices as it can enable fabricating devices with enhanced potential as compared to conventional bio-electronics. Graphene’s unique electronic properties and sizes comparable with biological structures involved in cellular communication makes it a promising nanostructure for establishing active interfaces with biological systems. In the recent past Field effect transistors (FETs) have been successfully fabricated using carbon nanotubes (CNTs) and nanowires (NWs) and electrical characterization of these FETs were done by interfacing them with various cell cultures, tissues and muscle cells. In these cases, exceptionally high surface area to thickness ratio of FETs provides high percentage of collectible signals and the cells that are used for the study are typically placed on the FET. In this thesis, we examine a different approach towards forming bio-electronic interfaces by covering the graphene oxide (reduced) sheets on the yeast cells. Graphene oxide and reduced graphene oxide sheets as two-dimensional electronic materials have very high charge carrier mobility, extremely high surface area to thickness ratio, mechanical modulus and elasticity. We report the synthesis of graphene oxide using wet chemistry method, reduction of graphene oxide using different reducing agents and electrical characterization of graphene oxide’s conductivity. Micro-meter sized graphene sheets are used to encapsulate the yeast cells with the aid of calcium and gold nanoparticle chains. We also demonstrate that graphene sheets form electrically conductive layers on the yeast cells and developing an electromechanical coupling with the cell. The mechanical and electrical characteristics of graphene sheets are highly dependent on the cell volume and structure which are in turn related to the environment around the cell. Furthermore, using the same principle of electromechanical coupling we study the dynamics of cell surface stresses and cell volume modification, which are of importance in processes such as cell growth, division, and response to physiological factors such as osmotic stresses