Dimensional memories

There are three types of cross-linking one is chemical and two physical. Physical cross-linking results from formation of crystalline regions within polymer structures and from chain entanglement. Cross-linked materials have good dimensional memory. Chemically cross-linked materials do not dissolve and do not melt. 

In this chapter a theory of encounter between pairs of particles has been develojjed and applied to a wide range of problems, which illustrates the utility and ease of application of the theory. The theoretical foundations of the model require further work—in particular an appropriate one-dimensional memory kernel should be develojjed that gives a kinematically weighted friction... 

The photoreactivity of DTE derivatives in the crystalline state is of special interest because of their potential usefulness for holographic and three-dimensional memories. In crystals, molecules are regularly oriented and packed in fixed conformations. In many cases, free rotation is inhibited. Therefore, the photoreactivity in the crystalline phase is dependent on the space for free rotation of the thienyl rings and the conformation formed in the crystal lattice. Several reports on the synthesis of metal complexes of photochromic diarylethenes and their photo-reactivity in the single-crystalline phase or the photoswitching of the coordination structure have been reported. These studies demonstrate that complexation to metal ions does not prohibit the photochromic reactions of the diarylethene units in the single-crystalline phase. 

Ribcage, a trademark of Staktek Corporation for a three-dimensional memory module design. Also see Uniframe Stakpack Module. 

Turing machines, invented by Alan Turing in 1936, are extremely simple computers that consist of a finite-state compute head that can move back and forth on an infinite one-dimensional memory tape. Turing showed that these machines are universal in the sense that they can perform any computation that can be performed by any other mechanical device—there is no fundamental need to use a more complicated kind of computer ... 

Vigo Intelligent fibrous substrates with thermal and dimensional memories were studied. 33... 

Vigo T L, Intelligent fiber substrates with thermal and dimensional memories , Polym. Adv. Technol., 1997, 8(5), 281-8. 

Dirge, R.R. (1994) Protein-based three-dimensional memory. American Scientist 82, 348-355. 

BR-based memory devices are primarily based on M-state or O-state photochemistry. Holographic devices are based on the blue-shifted M state, although a Q-state-based holography will be discussed. In three-dimensional memories, the write process is particularly dependent on O-state photochemistry. 

Note in Figure 135.4 the presence of the branched photocycle intermediates P and Q. These intermediates will be discussed in more detail later in this section, but it should be pointed out that this branching reaction provides a potential dead end for the protein. Any protein that enters this branched photocycle will become unable to pump protons and is therefore considered functionally silent. As will be discussed in the section on BR-based three-dimensional memories, regeneration of the bR state from the Q state is possible and is responsible for resetting the memo bit. In the salt marsh, the P and Q states may serve as a photochemical sunscreen. " ... 

This was accomplished in the Val-49 and Leu-93 mutants, shown in Figure 135.3(B), Group 3. However, these mutants are not optimal for use in BR-based three-dimensional memories, because the O —> P transition requires all-trans to 9-cis photochemistry.Thus, mutants that inhibit chromophore isomerization to all-tra s wiU decrease the probability of entry into the branched photocycle. 

Shown in Figure 135.4 are the branched photocycle intermediates P and Q. The O state absorbs maximally at 640 nm protein molecules that are in the O-state intermediate and absorb a photon enter the P state. The P state is actually a pair of distinct intermediates that will spontaneously form Q. The P —> Q transition is a hydrolysis reaction that results in detachment of the chromophore from the protein. Removal of water from the sample results in trapping of the P intermediate. The bR state can be regenerated from Q upon illumination with UV light. This bistable system is the basis for BR-based three-dimensional memories. 

Three-dimensional memory devices using BR as a substrate were demonstrated. A schematic diagram of the optical system used to write, read, and erase information within a cuvette containing the protein is shown in Figure 135.7. The resting state (bR) is assigned to bit 0, and P and Q are assigned to bit 1 (bit 0 should not be confused with the O state) ... 

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