Mechanism, nature

Tunnelling is a phenomenon that involves particles moving from one state to another tlnough an energy barrier. It occurs as a consequence of the quantum mechanical nature of particles such as electrons and has no explanation in classical physical tenns. Tuimelling has been experimentally observed in many physical systems, including both semiconductors [10] and superconductors [11],... 

Kresge C T, Leonowicz M E, Roth W J, Vartuli J C and Beck J S 1992 Ordered mesoporous molecular sieves synthesized by a liquid-crystal template mechanism Nature 359 710-12... 

Resist Printing. In resist printing, print pastes are used that can inhibit the development or fixation of different dyes that are apphed to the textile prior to or after printing. These resists can be of a chemical or mechanical nature, or combine both methods. For example, fiber-reactive dyes, which require alkaU for their fixation, can be made resistant by printing a nonvolatile organic acid, such as tartaric acid, on the textile. Colored resists are obtained by printing pigments with a nonvolatile acid. 

Mechanisms of Failure. The causes of connector contact failute can be of a thermal, chemical, or mechanical nature, in addition to misapphcation and physical abuse. 

Individual fins may be preformed and inserted over the tube, after which the mechanical bond may be obtained by either shrink fitting the fins onto the tube or by expanding the tube radially outward to make pressure contact with the fin material. The means to expand the tube may be hydraulic by pressurizing the tube beyond its yield point or it may be of a mechanical nature, in which an oversized ball or rod is pushed through the length of the tube, forcing the tube material outward against the fin. 

Because the hazard is still present, there is always a danger that its potential impacts could be realized by some unanticipated route or mechanism. Nature may be more creative in inventing ways by which a hazardous event can occur than experts are in identifying them. Accidents can occur by mechanisms that were unanticipated or poorly understood. 

In 1968, after many years experience in plant operations, I was appointed safety adviser to the heavy organic chemicals division (later the petrochemicals division) of Imperial Chemical Industries. My appointment followed a number of serious fires in the 1960s, and therefore I was mainly concerned with process hazards rather than those of a mechanical nature. 

Estimate acceptable air leakages resulting from leakage around static and rotary seals, valves, access ports, and other items of mechanical nature required for process operation from the following equations and the specific leak rates 0 indicated in Table 6-8, which is based on w < 10 lb/hr. 

Plastics have a unique contribution to make in exploring new environments. Their applications in space vehicles are well known and are generally of a mechanical nature. Plastics are used extensively in equipment for exploring under the sea. One unique application for plastics used in the sea environment and which is important in other areas that range from packaging to space is in filtering... 

Mechanical Fuze. Any fuze which depends for its arming and functioning on events primarily of a mechanical nature. Fuzes may consist of a combination of mechanical and electronic features. Proximity fuzes may contain a mechanical delayed arming device mechanical fuzes may be functioned by electrical energy from a piezoelectric element. The classification is dependent upon which features are predominant... 

Mitchell, P. (1961). Coupling of phosphorylation to electron and hydrogen transfer by a chemiosmotic type of mechanism. Nature 191, 144-148. 

Kokufuta, E Jinbo, E, A Hydrogel Capable of Facilitating Polymer Diffusion through the Gel Porosity and Its Application in Enzyme Immobilization, Macromolecules 25, 3549, 1992. Kresge, CT Leonowicz, ME Roth, WJ Vartuli, JC Beck, JS, Ordered Mesoporous Molecular Sieves Synthesized by a Liquid-Crystal Template Mechanism, Nature 359, 710, 1992. 

His wife, Marie-Anne, studied drawing with the great painter Jacques-Louis David in order to transcribe her husband s laboratory notes and illustrate them. David s ravishing portrait of the Lavoisiers hangs in the Metropolitan Museum of Art in New York. The son of Marie-Anne s longtime lover founded the E. I. Du Pont de Nemours Corporation in Delaware. Marie-Anne later married the American physicist, Benjamin Thomson. Later ennobled as the Count of Rumford, Thomson demonstrated the mechanical nature of heat. Marie-Anne had an excellent eye for scientific talent. 

This inequality of interactions leads to a phenomenon whose quantum-mechanical nature will be addressed later (Chapter 7), and whose practical appearance is given here simply by description. Let us first make the distinction between half-integer... 

Most of the AIMD simulations described in the literature have assumed that Newtonian dynamics was sufficient for the nuclei. While this is often justified, there are important cases where the quantum mechanical nature of the nuclei is crucial for even a qualitative understanding. For example, tunneling is intrinsically quantum mechanical and can be important in chemistry involving proton transfer. A second area where nuclei must be described quantum mechanically is when the BOA breaks down, as is always the case when multiple coupled electronic states participate in chemistry. In particular, photochemical processes are often dominated by conical intersections [14,15], where two electronic states are exactly degenerate and the BOA fails. In this chapter, we discuss our recent development of the ab initio multiple spawning (AIMS) method which solves the elecronic and nuclear Schrodinger equations simultaneously this makes AIMD approaches applicable for problems where quantum mechanical effects of both electrons and nuclei are important. We present an overview of what has been achieved, and make a special effort to point out areas where further improvements can be made. Theoretical aspects of the AIMS method are... 

Strictly speaking, all steps in the model (72) have a quantum mechanical nature. The measured rate is determined by the relative values of the kinetic parameters and a number of situations can be envisaged. The rate limiting step for the forward direction, defined from left to the right in Eq.(72), may be located at any level depending of course on the nature of the species. There is, however, a necessary and sufficient condition for the process to occur. This is related to the relaxation time of ASC into quantum states of P1-P2. This relaxation time must be finite. 

We turn now to a review and analysis of the shared epistemological values and problems that have spurred the efforts of the philosophical and theoretical chemists. We ask in conclusion whether the achievements of theoretical chemistry by the mid-twentieth century led its practitioners to identify their discipline with the aims of mechanical natural philosophy and modern physics. 

Expression (9.15) gives the total electrostatic energy and not the cohesive energy of a molecular crystal. It ignores the quantum-mechanical nature of the charge distribution an electron cannot interact with itself, but just such a self-energy is included in the expression. 

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