EFFECTS OF SURFACE STATES, DEFECTS AND DOPANTS ON THE OPTICAL AND MAGNETIC PROPERTIES OF LOW-DIMENSIONAL MATERIALS

Nanomaterials have attracted the attention of researchers from various fields due to their unique features (that are otherwise absent in the bulk) such as quantum confinement, high surface to volume ratio, ability for surface modification etc. Since the discovery of fullerenes and carbon nanotubes, several synthesis techniques have been developed for nanomaterial growth. However, different control parameters in different synthesis techniques often result in nanostructures with varying defects that may alter their fundamental behavior. Such defects or disorder in the crystal lattice can lead to the disruption of lattice symmetry. The defect-induced symmetry lowering (or breaking) effects play a vital role in the determination of fundamental material characteristics. Thus, it is very important to characterize the defects in order to understand their effects on the nanomaterial properties. This thesis describes the effects of defects in low dimesional systems such as ZnO nanowires, graphene and carbon nanotubes are studied. Firstly, it describes the synthesis and characterization of ZnO nanostructures and discusses the effects of surface states, defects and dopants on their optical and magnetic properties. An unexpected presence of ferromagnetic (FM) ordering in nanostructured nonmagnetic metal oxides has been reported previously. Though this property was attributed to the presence of defects, systematic experimental and theoretical studies to pinpoint its origin and mechanism were lacking. While it is widely believed that oxygen vacancies are responsible for FM ordering, surprisingly annealing as-prepared samples at low temperature (high temperature) in flowing oxygen actually enhances (diminishes) the FM ordering. For these reasons, we have prepared, annealed in different environments, and measured the ensuing magnetization in micrometer and nanoscale ZnO with varying crystallinity. We further find from our magnetization measurements and ab-initio calculations that a range of magnetic properties in ZnO can result, depending on the sample preparation and annealing conditions. For example, within the same ZnO sample we have observed ferro- to para- and diamagnetic responses depending on the annealing conditions. We also explored the effects of surface states on the magnetic behavior of nanoscale ZnO through detailed calculations. In the case of grapheme, we have observed new combination modes in the range from 1650 to 2300 cm−1 in single-(SLG), bi-, few-layer and incommensurate bilayer graphene (IBLG) on silicon dioxide substrates. A peak at 1860 cm−1 (iTALO−) is observed due to a combination of the in-plane transverse acoustic (iTA) and the longitudinal optical (LO) phonons. The intensity of this peak decreases with increasing number of layers and this peak is absent for bulk graphite. The overtone of the out-of-plane transverse optical (oTO) phonon at 1750 cm−1, also called the M band, is suppressed for both SLG and IBLG. In addition, two previously unidentified modes at 2200 and 1880 cm−1 are observed in SLG. The 2220 cm−1 (1880 cm−1) mode is tentatively assigned to the combination mode of in-plane transverse optical (iTO) and TA phonons (oTO+LO phonons) around the K point in the graphene Brillouin zone. Finally, the peak frequency of the 1880 (2220) cm−1 mode is observed to increase (decrease) linearly with increasing graphene layers. Finally, we find that the high curvature in sub-nm SWCNTs leads to (i) an unusual S-like dispersion of the G-band frequency due to perturbations caused by the strong electron-phonon coupling, (ii) an activation of diameter-selective intermediate frequency modes that are as intense as the radial breathing modes (RBMs), and (iii) a clear observation of the IR modes

Animating Predator and Prey Fish Interactions

Schooling behavior is one of the most salient social and group activities among fish. They form schools for social reasons like foraging, mating and escaping from predators. Animating a school of fish is difficult because they are large in number, often swim in distinctive patterns that is they take the shape of long thin lines, squares, ovals or amoeboid and exhibit complex coordinated patterns especially when they are attacked by a predator. Previous work in computer graphics has not provided satisfactory models to simulate the many distinctive interactions between a school of prey fish and their predator, how does a predator pick its target? and how does a school of fish react to such attacks? This dissertation presents a method to simulate interactions between prey fish and predator fish in the 3D world based on the biological research findings. Firstly, a model is described by representing a school of fish as a complex network information flow with structural properties. Using this model, a predator fish targeting isolated peripheral fish is simulated. Secondly, the escape behavior state machine model and escape maneuvers exhibited by fish schools are described. The escape maneuvers include compact, avoid, fast avoid, skitter, fountain, flash, ball, split, join, herd, vacuole, and hourglass are identified in the biological studies. This proposed escape behavior animation model can free an animator from dealing with the low-level animations but instead, control the fish behavior on a higher level by modifying a state machine and a small set of system parameters. With the state machine and relatively few system parameters, the proposed system is stable, predictable, and easy to tune, which represent important properties for animators to control the outcome. This system is developed in Unity (3D). In addition, a plug-in is also developed for full-fledged graphics tool Blender software to simulate escape maneuvers. The animator has to simply select escape maneuvers, adjust parameters and work on animating predator using keyframe method. It does not deal with the state machine model. The proposed model is useful not only in generating group behaviors but also in scientific visualization tool for studying fish behavior

Retrieval of Nano-Size Particles from a Solid Substrate

The retrieval of nano-size particles from suspects and crime scenes can significantly enhance surveillance and crime investigation. The Thesis deals with extensive study of free surface energy coupled with Hertzian contact energy under different conditions between a nano-sized particle and a substrate and the various methods of dislodging the particle. Using the Johnson-Kendall-Roberts (JKR) theory, a physical spring-mass-damper model is defined. Mathematical equations are formulated and solved with non-linear equations simulating the real world situation. Using Newmark’s β method, the system is solved for response of free and forced vibrations taking moisture to be responsible for damping. Key assumptions such as the particle and substrate are perfectly elastic and damping force is linear have been applied. Then a parameter study is conducted on two types of particles. The results have been summarized along with suggestions for future work

Pharmacovigilance programme of India from the perspective of nursing students

Background: Lack of knowledge and awareness of reporting adverse drug reactions is common among the nursing staff. As the nursing staffs are more close to the patients, this study was undertaken to evaluate their knowledge, attitude and perception about pharmacovigilance and ADR reporting. The objective of this study was to assess the knowledge, attitude and perception of nursing staff about pharmacovigilance programme and finding out the ways of improving the ADR reporting rate.Methods: Across-sectional, anonymous, questionnaire based study was conducted at the Government hospital, Nizamabad among the nursing staff. A predesigned, pretested and validated questionnaire consisting of 15 questions and 8 statements on knowledge, attitude and practice aspects of Pharmacovigilance programme in India. All the nursing staffs were explained about the purpose of the study and the questionnaire was distributed. Adequate time was given to fill them. Data spread on the excel sheet and the results were analysed using Microsoft office 2007 version.Results: Out of 65 students, 74.1% were aware of the term pharmacovigilance, 44.4% of the pharmacovigilance programme in India and 70.4% of the pharmacovigilance cell in their institute. 22.2%stated that known reactions, 14.8% unknown and 63% that all ADRs are to be reported.63% stated herbal drugs are safe, 44.4% that over the counter drugs are safe. Reporting system stated was by making call/by e-mail (25.9), written form (29.6%). Underreporting was due to lack of awareness (51.9%), lack of time (22.2%), feeling of creating negative impression on heath personnel (11.1%), or due to the feeling of waste of time (14.8%).Conclusions: Lack of facilities and clinical knowledge about ADR discourages them from reporting. Educational interventions and improvement of facilities were also suggested to enhance reporting rate in the hospital

Data Governance in Data Mesh Infrastructures: The Saxo Bank Case Study

Data governance (DG) is the management of data in a manner that the value of data is maximised and data related risks are minimised. Three aspects of DG are data catalogue, data quality, and data ownership and these aim to provide transparency, foster trust, and manage access and control the data. DG solution involves change management and alignment of incentives and mere technology is not enough to address this. In this paper we aim to provide a holistic view of data governance that is a synthesis of academic and practitioner viewpoints, and conclude by giving an example of a pilot case study (Saxo Bank) where authors worked on tech and cultural interventions to address the data governance challenges

Evaluation of anti-nociceptive effect of venlafaxine in experimental animal model of mice

Background: Pain is an unpleasant sensation with varying subjective experience. Its management is always challenging for physicians particularly in case of chronic pain. Chronic pain and depression usually co-exist due to poor quality of life and increase in health care costs posing an individual to suffer from depression. Anti-depressants for pain management are being used successfully using since years. In this study venlafaxine, a newer anti-depressant drug was evaluated for anti-nociceptive activity, tail immersion test an analgesic animal model of albino mice.Methods: Randomly selected albino mice of either sex with reaction time of <6 seconds were included in the study and divided into 7 groups with 6 mice in each group. Grouping was done based on the drug received i.e., venlafaxine 15, 30 and 60 mg/kg, tramadol 10 and 20 mg/kg, control group (normal saline) and combination group venlafaxine 15 mg/kg+tramadol 10 mg/kg. Drugs were administered by intra-peritoneal route.Results: Venlafaxine (30 and 60 mg/kg), tramadol (20 mg/kg) and combination group venlafaxine (15 mg/kg+tramadol 10 mg/kg) has shown significant (p<0.001) increase in tail withdrawal latency compared to control group (normal saline) by tail immersion test. Venlafaxine potentiated anti-nociceptive activity of tramadol on concomitant administration with tramadol. Venlafaxine at 60 mg/kg has comparable anti-nociceptive effect to tramadol at 20 mg/kg.Conclusions: Venlafaxine at doses of 30 and 60 mg/kg is having anti-nociceptive effect, but less potent than tramadol

Ultrasensitive Immunosensing Platform Based on Analyte Induced Disruption of Luminescence Quenching (AIDLuQ)

In this study, we design an extremely fast and sensitive immunosensing platform using graphene as the sensing platform. A solution containing a mixture of graphene nanoplatelets and gold nanoparticles was coated on to a copier paper using a spray gun to form a uniform coating. Fluorescent quantum dots (QDs) functionalized with antibodies (Ab) were drop casted on to this platform, whose fluorescence was quenched by the graphene on the graphene/gold paper. With the addition of the antigen to this graphene/gold-QD-Ab complex, a disruption of quenching was observed, and the fluorescence intensity increased with increasing concentration of the antigen. A detection limit of as low as 10 fM was obtained for the detection of human Immunoglobulin G (IgG)

Plants having modified reproductive capacity

This invention relates to plants having modified reproductive capacity. In particular, it relates to a plant reproductive tissue specific promoter, the PrAGl promoter isolated from Pinus radiata, and its use in promoting transcription/ expression of associated sequences in plant reproductive tissue, including for the purpose of producing plants which have diminished reproductive capacity or which are sterile.https://digitalcommons.mtu.edu/patents/1048/thumbnail.jp