Laser Processing of Metals and Polymers

A laser offers a unique set of opportunities for precise delivery of high quality coherent energy. This energy can be tailored to alter the properties of material allowing a very flexible adjustment of the interaction that can lead to melting, vaporization, or just surface modification. Nowadays laser systems can be found in nearly all branches of research and industry for numerous applications. Sufficient evidence exists in the literature to suggest that further advancements in the field of laser material processing will rely significantly on the development of new process schemes. As a result they can be applied in various applications starting from fundamental research on systems, materials and processes performed on a scientific and technical basis for the industrial needs. The interaction of intense laser radiation with solid surfaces has extensively been studied for many years, in part, for development of possible applications. In this thesis, I present several applications of laser processing of metals and polymers including polishing niobium surface, producing a superconducting phase niobium nitride and depositing thin films of niobium nitride and organic material (cyclic olefin copolymer). The treated materials were examined by scanning electron microscopy (SEM), electron probe microanalysis (EPMA), atomic force microscopy (AFM), high resolution optical microscopy, surface profilometry. Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD). Power spectral density (PSD) spectra computed from AFM data gives further insight into the effect of laser melting on the topography of the treated niobium

Diseases and Medicine referred to in Tamil Epics

Birth is a rare opportunity given by nature to all living beings that appear in the world.  It is our duty to maintain health and protect the body from diseases. Diseases have arisen since the time of man's birth. Diseases are a source of pain for our body. It is customary to wish us to live without disease when others greet us. To live without disease is great wealth. The epics contain information about the definition of the disease, the causes of the onset of the disease, and the types of diseases

The Potential to Build Collective Capacity for Organisational Learning in the Context of Teachers’ Use of Digital Technology for School Improvement

This article considers how digital spaces focused on whole school improvement combined with supportive leadership may be mobilised towards building collective capacity for evidence-informed practice and organisational learning. This topic originated from a qualitative, multi-method design-based research (DBR) project that studied practitioners’ use of an online resource for primary school practitioners called Pathways for school improvement, designed by Oxford University Press (OUP). Semi-structured interviews, participant observations and a documentary analysis were conducted with teachers and senior leaders in five primary schools across England between 2014 and 2016. Connections were made with the dynamic approach to school improvement (DASI) that encourages practitioners to systematically engage with a variety of evidence in their reflections and efforts to design school and classroom improvement strategies. Pathways’ four-step system and series of systematised tasks under each step seemed to provide opportunities for practitioners to explore elements of theory and practice in conjunction with empirical and pupil performance data, and potentially guide them through how to collaborate with others in developing specific whole school approaches to improvement. Opportunities and challenges in developing collective capacity for improvement are also explored

Privacy in wireless sensor networks using ring signature

AbstractThe veracity of a message from a sensor node must be verified in order to avoid a false reaction by the sink. This verification requires the authentication of the source node. The authentication process must also preserve the privacy such that the node and the sensed object are not endangered. In this work, a ring signature was proposed to authenticate the source node while preserving its spatial privacy. However, other nodes as signers and their numbers must be chosen to preclude the possibility of a traffic analysis attack by an adversary. The spatial uncertainty increases with the number of signers but requires larger memory size and communication overhead. This requirement can breach the privacy of the sensed object. To determine the effectiveness of the proposed scheme, the location estimate of a sensor node by an adversary and enhancement in the location uncertainty with a ring signature was evaluated. Using simulation studies, the ring signature was estimated to require approximately four members from the same neighbor region of the source node to sustain the privacy of the node. Furthermore, the ring signature was also determined to have a small overhead and not to adversely affect the performance of the sensor network

Substrate Integrated Waveguide fed Wideband Circularly Polarised Antenna with Parasitic Patches

In this study, a wideband circularly polarised (CP) antenna is developed and demonstrated. The antenna comprises of two-layered substrates, the top layer holds a driven patch and eight surrounding parasitic patches of similar dimensions, and substrate integrated waveguide (SIW) based feeding topology is designed at the bottom layer. The driven patch is excited through coupling mechanism using a cross-slot carved on the upper clad of the SIW. The corners of the driven patch are curtailed and arms of the coupling slot made unequal, which constructively generates the CP wave. Moreover, the proposed antenna is prototyped, and experimentally verified. The antenna shows measured impedance and axial-ratio (AR) bandwidths of 1.29 GHz (21 per cent) and 460 MHz (7.35 per cent), respectively, while maintaining the high gain of ~8 dBic over the operating CP region. This design aids the favorable characteristics such as light weight, wide impedance and (AR) bandwidths, high-gain as well as lenience of production, and integration

Thorough QT/QTc (TQT) study

With a number of drugs entering the market, cardiac safety remains a cause of major concern for the regulatory authorities, before approval. The incidence of drug induced arrhythmia with non-cardiovascular drugs is low, however the result is fatal, hence much focus is being given to assess the pro-arrhythmic potential of a drug. The arrhythmogenic risk of the drug is higher if the patient is on polypharmacy or has other risk factors such as an electrolyte imbalance or an underlying structural heart disease. QT prolongation can be either due to congenital causes such as Long QT syndromes (LQTS) which include Romano-Ward syndrome, Jervell and Lange-Nielson syndrome or can be acquired, which is mainly due to drugs. Several drugs such as terfenadine, astemizole, cisapride and grepafloxacin have been withdrawn from the market due to QT prolongation and development of a fatal ventricular arrythmia - torsades de pointes (TdP). This has led to implementation of guidelines to assess cardiac safety. The pro-arrhythmic risk can be assessed using thorough QT/QTc studies or exposure response modelling of intensive ECGs. This article will give an overall view of the use of QT/QTc interval as a biomarker for cardiac safety and the current guidelines for thorough QT/QTc studies which are mainly done to assess the pro-arrhythmic potential of a non-anti-arrhythmic drug

Prospecting for scarabid specific Bacillus thuringiensis crystal toxin cry8 gene in sugarcane ecosystem of Tamil Nadu, India

In the present study, we report the occurrence of cry8 positive isolates of Bacillus thuringiensis (Bt) in selected white grub, Holotrichia serrata F. (Coleoptera: Scarabaeidae), endemic soils of sugarcane ecosystem and other places in Tamil Nadu. Out of the 66 soil samples collected and screened for white grub specific Bt, 74 isolates of the bacterium, all containing only spherical crystal toxin, were identified. PCR screening of these isolates with cry8 gene universal primer revealed six isolates to be positive. Further, the amplicon of a 370 bp band, amplified with another set of degenerate primer designed based on the conserved sequence of cry8 genes, was sequenced from four isolates. Multiple sequence alignment revealed the gene sequences to be the same for all the isolates. The present report of the availability of cry8 positive Bt isolates opens the avenue for controlling white grubs through transgenic research

CYTOMORPHOMETRIC ANALYSIS OF BUCCAL CELLS IN BUILDING WORKERS EXPOSED TO POLYCYCLIC AROMATIC HYDROCARBON IN AND AROUND COIMBATORE DISTRICT

Objective: Building workers are exposed to a mixture of chemicals and polycyclic aromatic hydrocarbons at the time exposure by inhalation which is suspected to cause genetic damage. The aim of the study was to assess the level of genetic damage in south Indian building workers are exposed to PAHs.Methods: 30 Building workers and standardized control groups are examined for frequencies of micronuclei in buccal epithelial cells.Results: The genetic damage observed in the buccal cells of building workers was significantly higher than in controls. Chewing also related to genetic damage since the observed in PAHs exposed groups with chewers was significantly higher than non-chewing workers.Conclusion: Occupational exposure of PAHs from building workplaces has been associated with increased genetic damage and chewers represent an additional risk factor. Exposure to PAHs may be related to increased risk of cancer in building workers

Magnetic Properties of Gadolinium-Doped ZnO Films and Nanostructures

The magnetic properties of Gd-doped ZnO films and nanostructures are important to the development of next-generation spintronic devices. Here, we elucidate the significant role played by Gd-oxygen-deficiency defects in mediating/inducing ferromagnetic coupling in in situ Gd-doped ZnO thin films deposited at low oxygen pressure by pulsed laser deposition (PLD). Samples deposited at higher oxygen pressures exhibited diamagnetic responses. Vacuum annealing was used on these diamagnetic samples (grown at a relatively high oxygen pressures) to create oxygen-deficiency defects with the aim of demonstrating reproducibility of room-temperature ferromagnetism (RTFM). Samples annealed at oxygen environment exhibited superparamagnetism and blocking-temperature effects. The samples possessed secondary phases; Gd segregation led to superparamagnetism. Theoretical studies showed a shift of the 4f level of Gd to the conduction band minimum (CBM) in Gd-doped ZnO nanowires, which led to an overlap with the Fermi level, resulting in strong exchange coupling and consequently RTFM