Next generation high density three-dimensional magnetic recording systems

This work is the first work using patterned soft underlayers in multilevel three-dimensional vertical magnetic data storage systems. The motivation stems from an exponentially growing information stockpile, and a corresponding need for more efficient storage devices with higher density. The world information stockpile currently exceeds 150EB (ExaByte=1x1018Bytes); most of which is in analog form. Among the storage technologies (semiconductor, optical and magnetic), magnetic hard disk drives are posed to occupy a big role in personal, network as well as corporate storage. However; this mode suffers from a limit known as the Superparamagnetic limit; which limits achievable areal density due to fundamental quantum mechanical stability requirements. There are many viable techniques considered to defer superparamagnetism into the 100's of Gbit/in2 such as: patterned media, Heat-Assisted Magnetic Recording (HAMR), Self Organized Magnetic Arrays (SOMA), antiferromagnetically coupled structures (AFC), and perpendicular magnetic recording. Nonetheless, these techniques utilize a single magnetic layer; and can thusly be viewed as two-dimensional in nature. In this work a novel three-dimensional vertical magnetic recording approach is proposed. This approach utilizes the entire thickness of a magnetic multilayer structure to store information; with potential areal density well into the Tbit/in2 regime. ^ There are several possible implementations for 3D magnetic recording; each presenting its own set of requirements, merits and challenges. The issues and considerations pertaining to the development of such systems will be examined, and analyzed using empirical and numerical analysis techniques. Two novel key approaches are proposed and developed: (1) Patterned soft underlayer (SUL) which allows for enhanced recording of thicker media, (2) A combinatorial approach for 3D media development that facilitates concurrent investigation of various film parameters on a predefined performance metric. A case study is presented using combinatorial overcoats of Tantalum and Zirconium Oxides for corrosion protection in magnetic media. ^ Feasibility of 3D recording is demonstrated, and an emphasis on 3D media development is emphasized as a key prerequisite. Patterned SUL shows significant enhancement over conventional "un-patterned" SUL, and shows that geometry can be used as a design tool to achieve favorable field distribution where magnetic storage and magnetic phenomena are involved. ^

Antibacterial Activity of Extracellular Products from Cyanobacteria.

Cyanobacteria are photosynthetic prokaryotes that can be found in freshwater and marine environments as well as in soil. These organisms produce a variety of different biologically active compounds exhibiting anti-bacterial, anti-fungal and anti-cancer properties among others. In this study, cyanobacterial isolates were screened for their ability to produce extracellular antibacterial products. Cyanobacteria were isolated from fresh water and soil samples collected in the Pembroke Pines, FL area. Twenty- seven strains of cyanobacteria were isolated belonging to the following genera: Limnothrix, Nostoc, Fischerella, Anabaena, Pseudoanabaena, Lyngbya, Leptolyngbya, Tychonema, and Calothrix. Individual strains were grown in liquid culture in laboratory conditions. Following 14-day cultivation, the culture liquid was filtered and tested for activity against the following bacteria: Escherichia coli, Bacillus megatarium, Staphylococcus aureus, and Micrococcus luteus. Among all genera of cyanobacterial strains tested, Fischerella exhibited the greatest inhibitory activity. An attempt was made to isolate the active compound from the culture liquid of the active strains. Lipophilic extracts from culture liquid were obtained from three selected Fischerella strains. The extracts proved to have varying levels of activity against the tested bacteria. Inhibitory activity from all three Fischerella strains was detected against B. megatarium and M luteus. The only strain that was active against S. aureus was Fischerella sp. 114-12 while none of the extracts showed activity against E. coli. This kind of screening has potential pharmaceutical and agricultural benefits, including possible discovery of novel antibiotics.

Stripe domains formation and their affect on three-dimensional and perpendicular magnetic recording

In this study, the formation of stripe domains in permalloy (NisoFe20) thin films was investigated mainly utilizing magnetic force microscopy. Stripe domains are a known phenomenon, which reduces the "softness" of magnetic material and introduces a significant source of noise when used in perpendicular magnetic media. For the particular setup mentioned in this report, a critical thickness for stripe domains initiation depended on the sputtering rate, the substrate temperature, and the film thickness. Beyond the stripe domain formation, an increase in the periodicity of highly ordered stripe domains was evident with increasing film thickness. Above a particular thickness, stripe domains periodicity decreased along with magnetic domain randomization. The results led to the inference that the perpendicular anisotropy responsible for the formation of stripe domains originated mainly from magnetostriction.

Determination of Extracellular Molecules Produced by Vibrio Harveyi Using MS/MS

Quorum sensing (QS) is a process that allows bacteria to sense the population density of cells around them by communicating with each other via autoinducer molecules. This cross-communication is crucial in the regulation of bacterial processes such as bioluminescence, virulence, and biofilm formation. Previous research by Milburn and Makemson on Vibrio harveyi suggested that in addition of the known biosynthesis of three well-characterized autoinducers, dozens of unknown molecules are also produced and released to the environment by V. harveyi. This study was performed using electrospray tandem mass spectrometry with the purpose of detection and characterization of the extracellular molecules produced by V. harveyi, and assessment of their relationship to QS. A total of 11 molecules were characterized, from which three could be related to QS. These findings provide a glimpse of the nature of novel secondary metabolites produced by V. harveyi and provide the groundwork for further research.