Study of magnetic interlayer coupling in synthetic antiferromagnets for use in MRAM devices

In recent years, there has been an ever increasing level of effort focused on creating novel technologies based on spintronics. One of the most exciting of these technologies is spin transfer torque random access memory (STT-MRAM), which is a solid state non-volatile memory technology that is orders of magnitude better than flash memory in terms of speed and write endurance. One critical component of an STT-MRAM memory cell is the so-called fixed magnetic layer. The direction of magnetization of this layer must remain fixed so that it can act as a reference for the reading and writing of information to the cell. This layer is ideally composed of a synthetic antiferromagnet (SAF) with zero net magnetization because it can offer thermal stability, have its magnetization be less effected by external magnetic fields, and have reduced stray fields. One challenge with integrating a SAF into an STT-MRAM memory cell is that they are typically not thermally robust. Creating an STT-MRAM device generally requires at least one annealing step at temperatures between 200 and 300C. During this annealing process, the antiferromagnetic coupling (AFC) within the SAF changes dramatically and usually becomes ferromagnetic, thereby eliminating the SAF and all of its advantages. The work in this thesis centers around understanding exactly how and why this magnetic coupling changes during the annealing process, and how to prevent it so that a SAF fixed magnetic layer can be used in STT-MRAM devices. We start by depositing thin films containing two FeCoB layers coupled across several different non-magnetic spacer layers of varying thicknesses. We determine the magnitude and direction of the magnetic coupling between the two FeCoB layers both before and after annealing my analyzing ferromagnetic resonance (FMR) and magnetostatic measurements. Next, we study the role that boron has on the magnetic coupling by co-depositing it into the Ru spacer layer of samples with the structure NiFe/Ru/FeCo. From this, we conclude that the presence of boron within the FeCoB layer leads to increased diffusion of magnetic atoms into the non-magnetic spacer layer during the annealing process, which is responsible for the change in coupling seen in SAF structures. In order to prevent this, we insert diffusion barriers next to the FeCoB layers within a SAF. We find that with the diffusion barriers, we are able to create a thermally robust SAF structure that maintains AFC coupling even after annealing at temperatures of up to 350C

Academic integrity and oral examination: an Arabian Gulf perspective

Academic dishonesty is a major challenge facing educational institutions worldwide. Within the context of undergraduate education in the Arabian Gulf, oral assessment can help validate the originality of student work, whilst simultaneously facilitating assessment in a mode highly resonant with the region\u27s own educational traditions and collectivist cultural norms. The present study aims to examine student perceptions of a group-based oral examination. This was introduced as an alternative to written examinations, and as an adjunctive assessment of a course essay. Three undergraduate sections (N = 75) of an introductory psychology course at Zayed University in the United Arab Emirates sat the oral examination. Participants were later surveyed about their experience immediately after the exam (prior to knowing their grade). The dominant themes to emerge from the analysis were relief, satisfaction with the process and ecological relevance. Another theme was a perception of fairness and promotion of academic integrity. The group oral exam appears to provide a well-tolerated, culturally resonant means of assessment, which also promotes academic integrity within the present Arabian Gulf context. © 2013 Taylor & Francis

Von Willebrand factor glycans : modifiers of function & proteolysis

Imperial Users onl

Combustion of PTFE: The effects of gravity on ultrafine particle generation

The objective of this project is to obtain an understanding of the effect of gravity on the toxicity of ultrafine particle and gas phase materials produced when fluorocarbon polymers are thermally degraded or burned. The motivation for the project is to provide a basic technical foundation on which policies for spacecraft health and safety with regard to fire and polymers can be formulated

Thermal degradation of polytetrafluoroethylene in tube reactors

We have studied the thermal degradation of polytetrafluoroethylene (PTFE) in wet air, dry air and nitrogen gas at temperatures ranging from 310 to 520 C. The principal gas product was tetrafluoroethylene (TFE). The nitrogen experiments yielded only TFE, but experiments in dry and wet air also produced several other minor gas products. The dry air experiments produced the most smoke and the least gas products, with the nitrogen experiments giving no smoke and the highest amounts of gas products. Wet air experiments gave intermediate results for smoke and gas formation. The rate of degradation in wet air showed an apparent activation energy of 103 kca/mol. We also performed FTIR analyses of the smoke particulate, determining that the particulate formed in dry air is different than that formed in wet air

Fine-Water-Mist Multiple-Orientation-Discharge Fire Extinguisher

A fine-water-mist fire-suppression device has been designed so that it can be discharged uniformly in any orientation via a high-pressure gas propellant. Standard fire extinguishers used while slightly tilted or on their side will not discharge all of their contents. Thanks to the new design, this extinguisher can be used in multiple environments such as aboard low-gravity spacecraft, airplanes, and aboard vehicles that may become overturned prior to or during a fire emergency. Research in recent years has shown that fine water mist can be an effective alternative to Halons now banned from manufacture. Currently, NASA uses carbon dioxide for fire suppression on the International Space Station (ISS) and Halon chemical extinguishers on the space shuttle. While each of these agents is effective, they have drawbacks. The toxicity of carbon dioxide requires that the crew don breathing apparatus when the extinguishers are deployed on the ISS, and Halon use in future spacecraft has been eliminated because of international protocols on substances that destroy atmospheric ozone. A major advantage to the new system on occupied spacecraft is that the discharged system is locally rechargeable. Since the only fluids used are water and nitrogen, the system can be recharged from stores of both carried aboard the ISS or spacecraft. The only support requirement would be a pump to fill the water and a compressor to pressurize the nitrogen propellant gas. This system uses a gaseous agent to pressurize the storage container as well as to assist in the generation of the fine water mist. The portable fire extinguisher hardware works like a standard fire extinguisher with a single storage container for the agents (water and nitrogen), a control valve assembly for manual actuation, and a discharge nozzle. The design implemented in the proof-of-concept experiment successfully extinguished both open fires and fires in baffled enclosures

Achirality in the low temperature structure and lattice modes of tris(acetylacetonate)iron(iii)

Tris(acetylacteonate) iron(III) is a relatively ubiquitous mononuclear inorganic coordination complex. The bidentate nature of the three acetylacteonate ligands coordinating around a single centre inevitably leads to structural isomeric forms, however whether or not this relates to chirality in the solid state has been questioned in the literature. Variable temperature neutron diffraction data down to T = 3 K, highlights the dynamic nature of the ligand environment, including the motions of the hydrogen atoms. The Fourier transform of the molecular dynamics simulation based on the experimentally determined structure was shown to closely reproduce the low temperature vibrational density of states obtained using inelastic neutron scattering

Rice bran arabinoxylan compound and quality of life of cancer patients (RBAC-QoL): Study protocol for a randomized pilot feasibility trial

© 2020 Introduction: Rice bran arabinoxylan compound (RBAC) is a nutraceutical for enhancing a depleted immune system during and after cancer treatment. This pilot feasibility trial aims to evaluate the effects of RBAC on cancer patients\u27 quality of life during active treatment, compared to placebo, using a validated questionnaire. Other outcome measures include changes in inflammatory and nutritional status, cytokine profile, and gut microbiota. Methods/Design: The study will recruit 50 participants from a regional cancer center in Australia. Patients aged 18–70, diagnosed with solid organ cancers stage II and above, and currently undergoing active systemic therapies, are eligible. Random allocation of participants into two groups is stratified based on metastatic status and treatment type. The dosage is either 3 g/day of RBAC or placebo in identical packaging. The participants, study coordinator, and treating oncologists are blinded to the interventions. Data collections are at baseline and at four follow-up sessions, which are six weeks apart (24 weeks). Statistical analysis will involve a protected p-value with multiple dependent values and analyzed by ANOVA with repeated measures on the occasion of testing and with both a full Bonferroni or Sidak corrections applied to protect against Type I errors. Any observed significance warrants further analysis with pairwise comparisons. Analysis of covariance will also be performed to assess any influence of the demographic data, cancer diagnosis, as well as changes in physical activity, dietary habits, and complementary medicine usage. Comparisons of gut microbiota will be based on the analysis of the fecal microbiome using 16S ribosomal ribonucleic acid amplicon sequencing. The proposed research timeline is from October 2018 to May 2022. Trial registration: ANZCTR. Reg No: ACTRN12619000562178p