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To reduce the loss of the dynamic range M/# of medium, we have proposed and demonstrated a high-pass filtering method for coaxial holographic data storage. Total exposure power decreased to 1/2 by removing the DC components of the Fourier-transformed signal and reference beams with a high-pass filter. Our proposed method can reduce the wasted dynamic range of medium. We evaluated the bit error rate of a high-pass-filtered signal beam to be 5.0×10-4 and that of an unfiltered signal beam to be 1.3×10-3. Thus, we confirmed that the quality of the signal beams without the DC component is comparable to that with the DC component. Next, we successfully recorded and reconstructed the filtered signal beam with the coaxial holographic configuration. The bit error rate of the retrieved signal beam was 1.4×10-3, showing the absence of degradation without the DC component of the retrieved signal beam. We also evaluated the shift selectivity improved from 5 to 2 µm by high-pass filtering.

We have proposed and demonstrated a new holographic medium that can act as a write once read many (WORM) polarization-recordable medium. The new medium, composed of azobenzene-containing polymer and photocurable liquid crystal, exhibited birefringence when irradiated by polarized light. Additionally, the diffraction efficiency and the birefringence of this recorded complex increased to several times those of the simple rewritable azopolymer. This occurred because the orientation of photocurable liquid crystals was as good as that of the azopolymer because of the interaction with the mesogens. By measuring the birefringence, we confirmed that unlike the azopolymer, the orientation of the liquid crystal polymer was maintained even after circularly polarized beam irradiation. In this medium, only the photocurable liquid crystals were cured and became polymers with fixed orientation. Therefore, we propose that the new medium, which is polarization-recordable, WORM and highly sensitive, is very promising and practical for digital holographic storage.

The texture of food is considered related to its rheological behavior when confined within thin films between two shearing or squeezing surfaces. Such thin-film tribological properties may represent foods undergoing massive grinding and deformation during mastication. The thin-film tribological properties rather than the bulk rheological properties correlated with the composition (oil droplets, etc.) and texture of mayonnaise samples. Using the Surface Forces Apparatus (SFA) technique and optical interferometry using fringes of equal chromatic order, we characterized the thin-film morphology and measured tribological and other interfacial properties of mayonnaise emulsions. Results revealed new properties that help differentiate between full fat, light and fat free mayonnaises. This provides an important approach to determine properties of such foods in thin films which cannot be deduced from bulk properties.

Interaction forces were measured between surfactant-coated mica surfaces in tetradecane containing polyethylene−propylene. Two molecular weights, Mw = 5800 and 33 000 g/mol, were studied on two different surfactant layers at 15, 25, and 35 °C. At low polymer concentration, the force curves exhibited two maxima and two minima. On approach, a very weak repulsion at a separation of D = 6−10Rg was followed by an attractive regime down to a minimum at D ≈ Rg, where Rg is the radius of gyration. At smaller separations we found a second repulsive maximum, followed by a second attractive minimum at a separation of a few polymer segment widths. At the overlap concentration, a similar force profile, but with an additional depletion attraction, was measured under partial adsorption conditions, while equilibrium adsorption gave a monotonic steric repulsion for both Mw. Only monotonic repulsion was measured in tetradecane containing a polyethylene−propylene with an amino end group, which appeared to have bound to the ...

Adhesion and friction forces between deposited monolayers of poly({gamma}-methyl L-glutamate){sub x} co-({gamma}-n-octadecyl L-glutamate){sub y}--a hairy rod polymer having a rigid main chain rod and alkyl side chains containing either 1 or 18 C atoms--were measured using the surface forces apparatus technique. By performing dynamic (time-dependent) adhesion energy and friction experiments as a function of temperature T, the authors obtained the energy loss spectra for these quasi two-dimensional films. The measured adhesion energy losses or hysteresis as a function of temperature are shown to be related to the interdigitation of the octadecyl side chains, caused by different molecular motions that have been previously shown to be active at different temperatures. Friction experiments probed the energy dissipation processes arising from lateral motion. Assuming that the molecular dissipation processes are the same in both types of measurements (adhesion and friction), they used a previously derived simple formula to relate quantitatively the adhesion energy hysteresis and friction forces.

The Surface Forces Apparatus technique was used to measure the normal (perpendicular) and lateral forces between variously prepared surfaces under both dry and lubricated conditions. 'Normal' forces include the force vs distance functions, F(D), for surfaces separated by thin liquid films as well as the adhesion forces and energies, γ, for two surfaces in adhesional contact. 'Lateral' forces include the static and kinetic friction forces F of the surfaces as they slide past each other at a given separation, D. The results show that very thin liquid films confined between two solid surfaces can sustain both normal and shear forces or stresses. The results further indicate that the normal force, F(D) or γ, may be directly related to the static friction force, Fs, and simple equations are proposed that relate these forces (by 'static' friction force is meant the lateral force that must be applied to initiate motion, but not necessarily to maintain this motion). In contrast, the kinetic friction force, Fk, wh...

The friction and rheological properties of molecularly thin films of hexadecane between two shearing mica surfaces were measured under different conditions of load or applied pressure, film thickness, sliding velocity, temperature, and time or previous history. The aim was to investigate the tribological and rheological properties of ultrathin liquid films composed of chain molecules and to compare these properties with those of spherical molecules. The differences were found to be more quantitative than qualitative, and the results therefore provide insights into the general properties of liquids in thin films. The results show that during steady-state sliding between two solid crystalline surfaces, a liquid film may be considered to be in a one-phase or two-phase dynamic regime. In the two-phase regime, the film undergoes periodic [open quotes]stick-slip[close quotes] transitions between a solidlike and a liquidlike state. However, especially in the case of chain molecules such as hexadecane, the liquidlike state is very different from the bulk liquid. The frequency of transitions between the two dynamic states determines the static and dynamic friction forces and other dynamic properties of a shearing film. The effects produced by changing the load, temperature, sliding velocity, stopping time, etc., were found to be highly correlated. 49more » refs., 21 figs., 3 tabs.« less

We have studied both the equilibrium and the hydrodynamic lubrication forces that act in the normal direction between mica surfaces in toluene when bearing polystyrene chains anchored to each surface by a zwitterionic group at one end. The quasistatic force-distance profiles reveal the long-ranged repulsion characteristic of steric interactions between the extended brush-like layers in the good solvent and provide a measure of the brush thickness L in close agreement with earlier studies of such brushes

In order to investigate the mechanism of boundary friction, adhesion and friction experiments were carried out with a variety of surfactant-monolayer-coated surfaces using the surface forces apparatus. The friction forces were measured as a function of monolayer coverage and phase state, load, temperature, shear rate and relative humidity. We report on two important findings. (i) Stick-slip motion can occur not only between a “static” and a “kinetic” state but also between a static or kinetic state and some “superkinetic” state that exhibits ultralow friction. (ii) The friction coefficient is not directly correlated with adhesion but rather with the adhesion hysteresis, which is a measure of the energy dissipated during an irreversible adhesion ( e.g. loading-unloading) cycle. We also conclude that chain interdigitation is the most important molecular mechanism that gives rise to “boundary” friction and adhesion hysteresis of monolayer-coated surfaces.

Stick-slip, or interrupted, motion rather than smooth uninterrupted motion occurs in many different phenomena such as friction, fluid flow, material fracture and wear, sound generation, and sensory "texture." During stick-slip, a system is believed to undergo transitions between a static (solid-like) state and a kinetic (liquid-like) state. The stick-slip motion between various types of pretreated surfaces was measured, and a second, much more kinetic state that exhibits ultra-low friction was found. Transitions to and from this super-kinetic state also give rise to stick-slip motion but are fundamentally different from conventional static-kinetic transitions. The results here suggest practical conditions for the control of unwanted stick-slip and the attainment of ultra-low friction.

The effects of residual acetyl group rates of poly (vinyl alcohol) s (PVA) on the stability of pyrithion zinc particle (Zpt) dispersion were examined. With decrease in the residual acetyl group rate of PVA, Zpt dispersion became less stable in sodium dodecyl sulfate (SDS) solution. However, in NaCl solution, the residual acetyl group rate of PVA had no effect on Zpt stability.The amount of SDS adsorbed on PVA and that of PVA on Zpt were determined. When the residual acetyl group rate of PVA decreased, the amount of SDS adsorbed on PVA was noted to decrease and that of PVA on Zpt to increase.The PVA-SDS complex was prepared for use as a dispersing agent. The stability of Zpt dispersed by this complex in NaCl solution was studied and found to depend on the quantity of the PVA-SDS complex present. These results indicate that PVA may be concluded to form complexes with SDS at acetyl groups by which Zpt dispersion is stabilized.

We could optimize the crystallinity of azopolymers for sensitive and stable holographic recordings by controlling the ratio of crystalline unit of the main chain of azopolymers. In this study, we synthesized several azopolymers with the different ratios of crystalline and amorphous moieties of the main chain. Those polymers clearly had different crystallinity depending on the ratios. We measured their photo induced birefringence, which contributes to the formation of a hologram, and evaluated their photosensitivity defined as the growth speed of the birefringence. We also examined the relaxation properties of the induced birefringence after the recording. As a result, we found that the azopolymer of which the main chain consisted of 90% crystalline moieties and 10% amorphous moieties represented the best sensitivity performance. After irradiation, the birefringence relaxation for it was suppressed to one eighth of that for a 100% amorphous azopolymer. Furthermore, TEM image revealed that several microcrystals less than 20 nm in diameter, which caused negligible light scattering, existed in this 90% crystalline azopolymer. The microcrystal domains seemed to help the azobenzene moieties maintain the orientation, which resulted in the stabilization of the recorded birefringence. Therefore, it could be said that the microphaseseparation is the key for achieving optical recordings.

We propose a new recording method in which essential Fourier spectrum components for recovering digital data are abstracted. This method can reduce the noise of reconstructed data and the wasted dynamic range of media

To fabricate commercially available hologram cards, we show what kind of layers and properties are required to record and readout faithfully Fourier transform holograms on plastic cards, mainly focusing on protective and reflective layers

It is found that, in the case of polymers that attach densely from solution onto a surface via a given functional group at one end, shorter chains may displace longer ones from the substrate, in contrast to the behavior of adsorbed homopolymers. Within the range of the experimental parameters, this displacement is found to be complete and rapid

A technique of recovering the data pages from Fourier holograms recorded without the dc components is demonstrated theoretically and experimentally by use of a coaxial holographic storage system. A reconstructed image is obtained by adding a phase-modulated dc component of the signal beam on reading. The bit error rate of the reconstructed image is comparable with that for the hologram recorded with the dc component as well. Since high intensities of the dc components are not recorded in this technique, the dynamic range of the recording media can be saved, which potentially contributes to increasing the number of multiplexed holograms.

A technique for reconstructing positive and negative images from an identical intensity-modulated hologram is demonstrated theoretically and experimentally by use of a coaxial holographic storage system. Negative images are obtained by adding a phase-modulated dc component of signal beam on reading. By comparing positive and negative images, the bit error rate (BER) is improved by two orders of magnitude. This technique can reduce optical noise of reconstructed images to attain low BERs.

We have measured the normal and shear forces for a symmetric polystyrene-polyisoprene (PS-PI) diblock copolymer liquid in toluene, a good solvent for both blocks, between two mica surfaces. The aim was to investigate the structure of the macromolecular liquid when confined between surfaces separated by molecular-sized distances. The surface forces apparatus was used for these studies, and the microstructure was manipulated by varying the fraction of diblock in solution. Measurements of the equilibrium normal force profiles (intermolecular force versus separation distance between the confining surfaces) were made. All of these normal force profiles exhibited monotonic repulsive behavior. We found that in the disordered regime, as the fraction of diblock was increased, the intermolecular forces became much longer-ranged. As the fraction of diblock was further increased to concentrations near the bulk order-disorder transition (ODT), the ranges of the force profiles unexpectedly collapsed to shorter distances. In a series of dynamic surface forces experiments, the frictional force required to slide steadily one surface past the other with the macromolecular liquid intervening was measured as a function of shear rate. The shearing results reflected the same pattern of behavior exhibited in the normal force experiments. We determined that the frictional force of the most concentrated liquid was distinctly lower than that of the disordered samples at all shear rates and attribute both the equilibrium and dynamic results to be reflective to the inherent structure of the liquid. We believe that the reduction in the range of the normal force profiles and the reduction in frictional forces at the highest concentrations reflect pretransitional ordering in the confined sample. Our results are discussed in terms of surface-induced ordering and composition fluctuations, which are not accounted for in the mean-field description of polymer phase behavior.