Bilayer Media Research Articles

Recording properties of multilayered thin film media

The recording properties of layered film media, including the bit error rate, have been measured for comparison with the results found on single layer film media. This investigation centered on the ability of magnetostatic coupling between layers to affect the magnetic performance in ways other than noise reduction. Multilayered magnetic films were fabricated with interlayer thickness from 25 to 330 AA and with one to six magnetic layers using a CoPtCr alloy on a Cr underlayer. In most tests the single layer media perform better than the multilayer media, but the differences are small and do not appear to influence the error rate significantly. The largest distinguishing feature. is the improvement in the signal-to-noise ratio which comes from two thin layers that are coupled magnetostatically. This leads to an improvement of up to four orders of magnitude in the bit error rate for the bilayer media. Increasing the number of layers gives additional improvement. >

Potato Protoplast‐derived Callus Tissue Challenged with Erwinia carotovora subsp. carotovora: Survival, Growth and Identification of Resistant Callus Lines*

Abstract Potato (cv. Crystal) protoplast‐derived callus tissue was evaluated for survival and growth when exposed to Erwinia carotovora subsp. carotovora (strain Ecc71). Calli were either directly exposed to the pathogen by inoculation or to metabolites produced by the pathogen via a bilayer medium. Individual calli were inoculated with 0.5 μl of bacterial suspensions at 104, 105, 106, 107, 108 and 109 cfu/ml. The bilayer consistedof 10 ml of callus proliferation medium supplemented with pectin (2 g/l) and contained bacteria at 102, 103, 104, 105 and 106 cfu/ml. This medium was overlaid with 10 ml of bacteria free callus induction medium. Mean callus diameter of the inoculated treatments increased for 24 h, then declined. Over 90% of the inoculated calli were killed within 5 days but some survived as long as 14 days. Calli grown on the bilayer medium containing 106, 105 and 104 cfu/ml also decreased in size. Most were killed within 9 days but some survived 20 days. Calli exposed to 103 and 102 cfu/ml experienced limited growth with 20% and 7%, respectively, surviving after 27 days. Reactions to the pathogen varied considerably within the callus populations and individual calli with extended survival were identified in both experiments.

Thermodynamic and kinetic studies on the association of melittin with a phospholipid bilayer

Association of the amphiphilic peptide melittin with unilamellar vesicles of dioleoylphosphatidylcholine has been experimentally investigated by means of circular dichroism, fluorescence energy transfer and stopped-flow experiments. Circular dichroism changes upon titration of the peptide with vesicles (at low salt concentration) were analyzed to yield thermodynamic association isotherms. These isotherms are quantitatively interpreted in terms of a monomer-monomer partitioning of melittin between the aqueous and bilayer media. The data can be very well fitted by theoretical curves based on a Gouy-Chapman surface potential. Energy transfer involving chemically modified tryptophan confirms a lack of aggregation of the associated peptide. According to the kinetic measurements the association proceeds in practice as a one-step process, which is rather fast but not fully diffusion-controlled. We propose a simple mechanism where the inherent conformational transition determines the overall rate.

Transmission electron microscopy for optical storage material analysis

Transmission electron microscopy is the most natural tool for investigating in detail the physical and metallurgical changes produced in optical storage media by laser writing. Examples of laser writing in bilayer media with low melting points such as Te/Se and Te/C are compared with laser-written spots in metal silicide bilayers formed by the deposition of amorphous silicon onto tellurium, rhodium or gold. Particulate gold films with and without carbon coatings are investigated as potential storage media. Simulated life tests performed by annealing are presented for some of the media.

Rotational relaxation of the “microviscosity” probe diphenylhexatriene in paraffin oil and egg lecithin vesicles.

The rotational relaxation of the widely used "microviscosity" probe, 1,6-diphenyl-1,3,5-hexatriene, was examined by the technique of nanosecond time-resolved fluorescence depolarization. The decays of the emission anisotropy were determined at five temperatures in the range 3-31 degrees both in a reference paraffin oil and in sonicated egg lecithin vesicles. These decays were complex in both media. Marked qualitative as well as quantitative differences were observed in the rotational behavior of the probe in the complex bilayer medium as opposed to the homogeneous reference solvent. The results are discussed in relation to the structure of the hydrophobic bilayer membrane interior and the concept of its "microviscosity".