Magnetic Domains and Domain Wall Oscillations in Planar and 3D Curved Membranes

This dissertation presents a substantial contribution to a new field of material science, the investigation of the magnetic properties of 3D curved surfaces, achieved by using a self-assembled geometrical transformation of an initially planar membrane. Essential magnetic properties of thin films can be modified by the process of transforming them from a 2D planar film to a 3D curved surface. By investigating and controlling the reasons that influence the properties, it is possible to improve the functionality of existing devices in addition to laying the foundation for the future development of microelectronic devices based on curved magnetic structures. To accomplish this, it is necessary both to fabricate high-quality 3D curved objects and to establish reliable characterization methods based on commonly available technology. The primary objective of this dissertation is to develop techniques for characterizing the static and dynamic magnetic properties of self-assembled rolled 3D geometries. The second objective is to examine the origin of shape-, size- and strain/curvature-induced effects. The developed approach based on anisotropic magnetoresistance (AMR) measurement can quantitatively define the rolling-induced static magnetic changes, namely the induced magnetoelastic anisotropy, thus eliminating the need for microscopic imaging to characterize the structures. The interpretation of the AMR signal obtained on curved stripes is enabled by simultaneous visualization of the domain patterns and micromagnetic simulations. The developed approach is used to examine the effect of sign and magnitude of curvature on the induced anisotropies by altering the rolling direction and diameter of the 'Swiss-roll'. Furthermore, a time-averaged imaging technique based on conventional microscopies (magnetic force microscopy and Kerr microscopy) offers a novel strategy for investigating nanoscale periodic domain wall oscillations and hence dynamic magnetic characteristics of flat and curved structures. This method exploits the benefit of a position-dependent dwell time of periodically oscillating DWs and can determine the trajectory and amplitude of DW oscillation with sub-100 nm resolution. The uniqueness of this technique resides in the ease of the imaging procedure, unlike other DW dynamics imaging methods. The combined understanding of rolling-induced anisotropy and imaging DW oscillation is utilized to examine the dependence of DW dynamics on external stimuli and the structure's physical properties, such as lateral size, film thickness, and curvature-induced anisotropy. The presented methods and fundamental studies help to comprehend the rapidly expanding field of 3-dimensional nanomagnetism and advance high-performance magneto-electronic devices based on self-assembly rolling

Characterization of Zinc oxide & Aluminum Ferrite and Simulation studies of M-H plots of Cobalt/Cobaltoxide

Zinc oxide and Aluminum Ferrite were prepared Chemical route. The samples were characterized by XRD and VSM. Simulation of M-H plots of Co/CoO thin films were performed. Effect of parameters was observed on saturation magnetization.Comment: Working paper (11 pages, 8 figures

Correlation coefficient analysis in twelve gladiolus (Gladiolus hybrids Hort.) genotypes

Study was undertaken to analyses the correlation co-efficient for twenty seven characters in twelve genotypes of gladiolus (Gladiolus hybridusHort.) grown atthe Instructional Farm, Department of Floriculture & Landscaping, College of Horticulture & Forestry, Jhalarapatan, Jhalawar. Spike length had highly positive association with rachis length (rg:0.92, rp:0.88), floret diameter (rg:0.94, rp:0.0.74), spike diameter (rg:0.66, rp:0.50), duration of flowering (rg:0.71, rp:0.42), number of florets per spike (rg:0.89, rp:0.84), number of cormels per plant (rg:0.69, rp:0.65), diameter of corm (rg:0.48, rp:0.41), weight of corm (rg:0.44, rp:0.40), weight of cormels per plant (rg:0.20, rp:0.19), size index of corms (rg:0.41, rp:0.38), florets remaining open at a time in vase (rg:0.56, rp:0.33). At both genotypic and phenotypic levels it had negative correlation with number of spikes per plot (rg:-0.56, rp:-0.48), number of corms per plant (rg:-0.72, rp:-0.50), number of corms per plot (rg:-0.60, rp:-0.54) and florets remaining unopened (rg:-0.39, rp:-0.37). It was observed that for most of the characters genotypic correlation coefficients were higher than phenotypic correlation coefficients

Selection Criterion Based on Trait Linkages in African and Asian Pearl Millet [Pennisetum glaucum (L.) R. Br.] Populations to Enhance Productivity

Pearl millet [Pennisetum glaucum (L.) R. Br.] is commonly grown in the arid and semi-arid regions of Africa and Asia. It serves as staple food for the people living in relatively dry tracts of the India and Sub-Sahelian Africa and an important source of fodder/ feed for livestock and poultry. It can be cultivated even in the poor infertile soils and drought prone environments, where no other cereal crop can survive. In India, currently pearl milletis cultivated on ~7.5 m ha area with grain production of 9.7 Mt with an average productivity of 1,305 kg ha-1(www.indiastat.com). The ultimate aim in most plant breeding programs is the improvement in the productivity of grains as measured in terms of the yield per unit area. The possibilities of achieving this goal through genetic improvement have been elucidated by evolving high yielding hybrids and varieties of pearl millet in Asia and West Africa

Implementation of drone based delivery of medical supplies in North-East India: experiences, challenges and adopted strategies

Timely delivery of medical supplies is essential in the healthcare sector, which is hampered by factors such as poor transportation network, traffic and adverse environmental conditions. Alternatively, drone operations can leapfrog the last mile logistic solutions in hard-to-reach terrains. The present paper elucidates the implementation process of drone-based delivery of medical supplies, operational challenges and innovations adopted by scientists in Manipur and Nagaland. Three districts, Bishnupur, Imphal West and Churachandpur from Manipur and two districts, Mokokchung and Tuensang from Nagaland, were selected for the study. Regulatory and ethical approvals and coordination with state health and administrative authorities were accorded. Implementation and operational challenges faced by the research team were recorded elaborately in the field diaries and assessed qualitatively. The experiences encountered by the team for case-to-case based permission and coordination with the central and state aviation authorities, district administration and health authorities were observed. The drone-related technical and logistic challenges were identified as the deployment of suitable drones, payload capacity, time management for operations, and transportation of drones. The officials adopted mitigation strategies to overcome field-based challenges. Drone-based deliveries of medical supplies are proving to be time efficient, however, overcoming operational challenges could provide an effective long-term deployment strategy

Acute electrocardiographic changes during smoking: An observational study

Objective To study the temporal relationship of smoking with electrophysiological changes. Design Prospective observational study. Setting Tertiary cardiac center. Participants Male smokers with atypical chest pain were screened with a treadmill exercise test (TMT). A total of 31 such patients aged 49.8±10.5 years, in whom TMT was either negative or mildly positive were included. Heart rate variability (HRV) parameters of smokers were compared to those of 15 healthy non-smoking participants. Interventions All patients underwent a 24 h Holter monitoring to assess ECG changes during smoking periods. Results Heart rate increased acutely during smoking. Mean heart rate increased from 83.8±13.7 bpm 10 min before smoking, to 90.5±16.4 bpm during smoking, (p <0.0001) and returned to baseline after 30 min. Smoking was also associated with increased ectopic beats (mean of 5.3/h prior to smoking to 9.8/h during smoking to 11.3/h during the hour after smoking; p <0.001). Three patients (9.7%) had significant ST–T changes after smoking. HRV index significantly decreased in smokers (15.2±5.3) as compared to non-smoking controls participants (19.4±3.6; p=0.02), but the other spectral HRV parameters were comparable. Conclusions Heart rate and ectopic beats increase acutely following smoking. Ischaemic ST–T changes were also detected during smoking. Spectral parameters of HRV analysis of smokers remained in normal limits, but more importantly geometrical parameter—HRV index—showed significant abnormality

Recovery of Nickel from Waste Printed Circuit Boards of Personal Computers

Present study reports, the application-oriented process for the recovery of nickel from printed circuit boards (PCBs) of scrap personal computers. The PCBs were initially depopulated, crushed, pulverized, and beneficiated to get the metallic concentrate. The concentrate was further processed by hydrometallurgical leaching and solvent extraction processes to extract nickel and copper. At first, leaching studies were carried out in sulphuric acid at different process parameters such as acid concentration, reaction time, temperature, etc., to dissolve the metals. Results show that 99% of Ni and Cu was leached in 20% H SO at 75°C for 2 h maintaining the pulp density of 100 g/L in the presence of 20% H O . The obtained leach liquor was further processed by solvent extraction technique to separate the Cu and Ni. It was found that 99% Cu and Ni were selectively extracted with LIX-984 N at pH: ±2.5 and ±4.5, respectively. Electrolysis, evaporation and crystallization processes could be used to obtain the pure metal and its salt from the pure metallic solutions

Direct imaging of nanoscale field-driven domain wall oscillations in Landau structures

Linear oscillatory motion of domain walls (DWs) in the kHz and MHz regime is crucial when realizing precise magnetic field sensors such as giant magnetoimpedance devices. Numerous magnetically active defects lead to pinning of the DWs during their motion, affecting the overall behavior. Thus, the direct monitoring of the domain wall's oscillatory behavior is an important step to comprehend the underlying micromagnetic processes and to improve the magnetoresistive performance of these devices. Here, we report an imaging approach to investigate such DW dynamics with nanoscale spatial resolution employing conventional table-top microscopy techniques. Time-averaged magnetic force microscopy and Kerr imaging methods are applied to quantify the DW oscillations in Ni81Fe19 rectangular structures with Landau domain configuration and are complemented by numeric micromagnetic simulations. We study the oscillation amplitude as a function of external magnetic field strength, frequency, magnetic structure size, thickness and anisotropy and understand the excited DW behavior as a forced damped harmonic oscillator with restoring force being influenced by the geometry, thickness, and anisotropy of the Ni81Fe19 structure. This approach offers new possibilities for the analysis of DW motion at elevated frequencies and at a spatial resolution of well below 100 nm in various branches of nanomagnetism

Novel Nanostructured Organosilicate Nanoparticle Coatings for Chem-Bio Sensing [abstract]

Plenary speakerWe present novel nanostructured organosilicate particulate based films and demonstrate that these materials have a great potential for chemical-biological sensor development. With unprecedented high surface areas (> 1400 m2/g) and optical transparency together with its easy surface functionalization, these materials can be readily interfaced with existing immunoassays for the rapid and trace detection of both chemical and biological warfare agents. The ultra high surface area associated with these films stems from its unique nanostructure consisting of nanoparticles (2-5nm) in a “raspberry” structure in combination with interconnected nanopores (3-10nm). This unique nanostructure has been exploited to immobilize high areal density of sensor probes to improve the sensing performance. Two orders of magnitude increase in binding density was achieved when fluorescently tagged protein A molecules were immobilized upon these surfaces compared to flat substrates (glass and Silicon). Our on-going work applies these materials to develop platforms for multiplexed sensitive detection of biological and chemical agents at point of care for both army and civilian use

Self-assembly as a tool to study microscale curvature and strain-dependent magnetic properties

The extension of 2D ferromagnetic structures into 3D curved geometry enables to tune its magnetic properties such as uniaxial magnetic anisotropy. Tuning the anisotropy with strain and curvature has become a promising ingredient in modern electronics, such as flexible and stretchable magnetoelectronic devices, impedance-based field sensors, and strain gauges, however, has been limited to extended thin films and to only moderate bending. By applying a self-assembly rolling technique using a polymeric platform, we provide a template that allows homogeneous and controlled bending of a functional layer adhered to it, irrespective of its shape and size. This is an intriguing possibility to tailor the sign and magnitude of the surface strain of integrated, micron-sized devices. In this article, the impact of strain and curvature on the magnetic ground state and anisotropy is quantified for thin-film Permalloy micro-scale structures, fabricated on the surface of the tubular architectures, using solely electrical measurements