Design of a manufacturable discrete track recording medium

The potential benefits of patterning discrete tracks onto a disk for magnetic data storage have long been investigated. A practical process for manufacturing a cost-effective discrete track recording (DTR) medium has prevented such a disk from being introduced into a product. In this paper, a process utilizing nano-imprint lithography techniques to create a land and groove structure on the surface of a disk substrate will be described. Design considerations for the geometry of the structure, as well as of the magnetic write and read widths of the head, are discussed. Data showing the magnetic characteristics and recording performance of a DTR medium are also presented.     

Temperature dependence of the magnetic properties of amorphous Co-Gd-Mo thin films

RF sputter deposited amorphous Co-Gd-Mo thin films have previously been shown to be potential materials for bubble device applications. However, the operation of a bubble device over a realistic temperature range requires materials with magnetic properties which are relatively temperature insensitive. An assessment of the temperature dependence of the magnetic properties of amorphous Co-Gd-Mo films is reported. The results of a mean field analysis of the magnetization data of Co-Gd-Mo thin films over wide composition and temperature ranges allowed optimization of the film composition for obtaining most suitable temperature dependences of magnetic properties. It has been found that even with the optimum compositions, the degree of temperature insensitivity improves with decreasing bubble diameters and is satisfactory only for sub-half-micron bubble materials. These results and analysis suggest that similar qualitative behavior may also be expected for other transition metal-rare earth alloys.     

Dynamics of droplet breakup through a grid spacer in a rod bundle

The dynamics of droplet breakup associated with the flow of a dispersed two-phase mixture through a rod bundle grid spacer during a reflood transient in a pressurized water reactor is studied theoretically. By considering the conservation of liquid mass and the kinetic as well as the surface energies of the droplets, an expression is derived for the ratio of the Sauter mean diameters of the droplets downstream and upstream of the grid. It is found that the Sauter mean diameter could decrease appreciably as a result of the shattering of the droplets when flowing through the grid spacer, thus increasing the interfacial heat transfer surface area. The decrease in the droplet size is dependent upon the Weber number of the incoming droplets, the blockage ratio of the grid spacer, and the fraction of the kinetic energy of the incoming droplets required to convert to the surface energy of the newly generated droplets during the breakup process. Comparisons of the theoretical results are made with the experimental data obtained at the rod bundle heat transfer test facility as well as with other relevant data in the literature and found to be good.     

Proteasome Channel Opening as a Rate-Limiting Step in the Ubiquitin-Proteasome System

The 26S proteasome eliminates multiubiquitinated proteins in cytosol and nucleus, and from the secretory pathway by a mechanism known as ER-associated degradation (ERAD). Access to the proteasomal 20S catalytic core particle is hindered by conserved N-terminal tails of α-subunits that form a gated pore into the central channel. Hence, the isolated 20S core particle possesses slower peptide hydrolysis rates and cannot degrade multiubiquitinated proteins. Purified catalytic particles from an α3α7ΔN open channel double mutant, in which the N-terminal tails of α-subunits from opposite sites of the α ring are deleted, showed significantly enhanced peptidase activity and proteolytic properties. Here we show that also in vivo the access of substrates to the proteasomal catalytic chamber partially limits the overall rate of protein elimination. This regulation applies to unstable cytosolic proteins of the N-end rule and ubiquitin fusion degradation (UFD) pathways, as well as to ERAD substrates that must dislocate from the ER back to the cytosol in order to become ubiquitinated and degraded by the proteasome. Hence, even for a complicated multistep process such as ERAD, traffic through the proteasome itself is partially rate limiting for the entire proteolytic process. However, proteasome gating can be added to a growing list of phenomena that distinguish membrane ERAD substrates from lumenal ones because while gating hinders access of lumenal substrates, it is less effective in controlling the entry of membrane substrates. The open channel mutant is a new class of proteasome mutant, which is unrelated to the catalytic protease active sites or to the “classical” regulatory particle mutants. Its improved performance at high temperatures is in stark contrast to the behavior of the “classical” mutants, suggesting that the α3α7ΔN mutant adapts better to mild stress conditions.     

Novel,N-ethyl-2-styrylquinolinum iodides as fluorophores for monitoring of polymerization process,Part I

A series of of p-substituted 2-styrylquinolinium iodides were prepared by the condensation of N-ethyl-2-methylquinolinium salts with p-substituted benzaldehydes. The spectroscopic properties of the styryl quinolinium dyes are characterized in organic solvents of varying polarities. The electronic absorption and fluorescence emission spectra of the dyes demonstrate their high sensitivity to the nature of substituents introduced into the aromatic ring. The dyes were investigated as fluorescent probes for monitoring the progress of the photochemically initiated free-radical polymerization of a mixture of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol triacrylate and 1-methyl-2-pyrrolidinone. During the course of the polymerization an increase in the fluorescence intensity of the dyes by at least one order of magnitude was recorded; a feature which renders the dyes as good fluorescent probes for such polymerization reactions. The term “probe sensitivity” has been defined and appears in the range from 0.08 to 11 for the styryl dyes.     

Tuning Physical Properties of NiFe2O4 and NiFe2O4@SiO2 Nanoferrites by Thermal Treatment

Metallurgical and Materials Transactions A - The comparison between NiFe2O4 (co-precipitation) and NiFe2O4@SiO2 (co-precipitation and microemulsion) ferrite nanoparticles in their as-received and...     

Admittance and impedance matrices of multiconductor power cables: Application of Poynting's theorem

A mathematical model suitable for the analysis of multiconductor cable admittance and impedance matrices is presented. The model is derived from Poynting's theorem and, therefore, it can be treated as the general formulation of cable transient characteristics. Using general formulation, the analytic function method for the admittance matrix and the two limit method for the impedance matrix are developed.