Proximity fuse

Beam-rider guidance with semi-active homing is employed to direct the missile against a target designated by the ship s tactical data system. Terrier is launched by a solid fuel rocket booster and propelled by a solid fuel sustainer. The normal warhead is of the HE type with direct action or proximity fuse, but one version of.the Terrier (RIM-2D) has been produced with a... 

Special tests. We observed several special tests the army carried out. One was the use a proximity fuse, only recendy developed, to detonate a nitrogen dioxide bomb over a barge floating offshore. The pilot s aim was perfect, as was the fuse and the red cloud enveloped the barge. 

Chemistry was supplanted during World War II by physics, which brought forth treasures radar, proximity fuses, electronic computers, and finally the atom bomb. More recently, the elite armies of the world have turned to the fruits of computer science and electronic engineering. They fight wars by remote control, with video cameras aboard pilotless aircraft and bombs that home in precisely on geographic coordinates delivered by orbiting satellites. 

Another polymer that came into use dnring World War II was polyte-traflnoroethylene (PTFE), which received the trademark Teflon. Dr. Roy J. Plnnkett and his assistant Jack Rebock at Dn Pont discovered PTFE accidentally on April 6, 1938. They had been conducting research on alternate refrigeration methods when they discovered the polymerization of tetraflnoroethylene. Plunkett received a patent for PTFE in 1941. It was fonnd that the material was resistant to corrosion by all the solvents, acids, and bases that were available for testing at that time. This led to the U.S. military s interest in PTFE, and its subseqnent use as a cover for proximity fuses on the nose cones of artillery shells. It was not until the material was declassified in 1946 that the public learned of the material Du Pont had named Teflon two years earlier. Teflon has since become a household name its best-known nse being its contribution to nonstick surfaces on pots and pans. 

For example, I was permitted to develop a new heind grenade — not really permitted. I used money from proximity fuses and developed a new hand grenade because our then current hand grenades were terrible weapons. I don t mean terrible for the enemy it wets terrible for us. If you should happen to drop it, it exploded in three seconds, give or take two seconds. This incidentally, technically is a very important point. When you... 

The proximity fuse was a miniature radar unit shaped to replace the ballistic nose of anti-aircraft shells. It sensed its proximity to a target— an enemy plane— and exploded the shell it rode at a preset range, often turning a miss into a kill. Its development was another of Bush s responsibilities and it was one of science s most important contributions to the war. Merle Tuve, Richard Roberts and most of the physics team at the Department of Terrestrial Magnetism of the Carnegie Institution had turned from fission research in August 1940 to develop it. 

The excellent properties of PTFE led to its adoption for military uses during World War II, The first use was as a nose cone covering Che proximity fuses on artillery shells. 

Any region where two surfaces are loosely joined or come into close proximity qualifies as a crevice site as long as water may enter. Partially exfoliated coatings may produce crevices. Surfaces may be metallic or nonmetallic. Usually, however, at least one surface is metallic. Crevices commonly are present at gaskets, flanges, washers, bolt holes, rolled tube ends, incompletely fused welds, contact points in plate-and-... 

The hydroxylation reaction, whose stereochemical course is controlled by the strong inherent preference for the formation of a cis-fused 5,5 ring system, creates a molecule which would appear to be well suited for an intramolecular etherification reaction to give ring E of ginkgolide B (1). Indeed, when a solution of 11 in methylene chloride is exposed to camphorsulfonic acid (CSA), a smooth cycli-zation reaction takes place to give intermediate 10 in an overall yield of 75% from 12. The action of CSA on 11 produces a transient oxonium ion at C-12 which is intercepted intramolecularly by the proximal hydroxyl group at C 4. 

In one of the above-mentioned cases [86], a significant improvement of reaction rates was observed when compared to the reactions carried out by uncoupled biocatalysts. This fact suggests that owing to the close proximity of the enzymes the local concentration of the intermediate is higher around the fused biocatalyst. 

In this exercise we shall estimate the influence of transport limitations when testing an ammonia catalyst such as that described in Exercise 5.1 by estimating the effectiveness factor e. We are aware that the radius of the catalyst particles is essential so the fused and reduced catalyst is crushed into small particles. A fraction with a narrow distribution of = 0.2 mm is used for the experiment. We shall assume that the particles are ideally spherical. The effective diffusion constant is not easily accessible but we assume that it is approximately a factor of 100 lower than the free diffusion, which is in the proximity of 0.4 cm s . A test is then made with a stoichiometric mixture of N2/H2 at 4 bar under the assumption that the process is far from equilibrium and first order in nitrogen. The reaction is planned to run at 600 K, and from fundamental studies on a single crystal the TOP is roughly 0.05 per iron atom in the surface. From Exercise 5.1 we utilize that 1 g of reduced catalyst has a volume of 0.2 cm g , that the pore volume constitutes 0.1 cm g and that the total surface area, which we will assume is the pore area, is 29 m g , and that of this is the 18 m g- is the pure iron Fe(lOO) surface. Note that there is some dispute as to which are the active sites on iron (a dispute that we disregard here). 

It has been assumed that formation of the cis-fused product 2-771 in the domino reaction of aldehyde 2-769 is due to a strongly favored exo-Z-syn transition state 2-770. The endo-E-syn structure is prohibited by the rigidity of the acetonide existing in 2-769, whereas the proximity of the same moiety to the benzyloxymethyl substituent at the double bond disfavors the exo-E-anti transition state, which would be responsible for the formation of the trans-fused diastereomer. 

The results summarized above were obtained by using fluorescence based assays employing phospholipid vesicles and fluorescent labeled lipopeptides. Recently, surface plasmon resonance (SPR) was developed as new a technique for the study of membrane association of lipidated peptides. Thus, artificial membranes on the surface of biosensors offered new tools for the study of lipopeptides. In SPR (surface plasmon resonance) systemsI713bl changes of the refractive index (RI) in the proximity of the sensor layer are monitored. In a commercial BIAcore system1341 the resonance signal is proportional to the mass of macromolecules bound to the membrane and allows analysis with a time resolution of seconds. Vesicles of defined size distribution were prepared from mixtures of lipids and biotinylated lipopeptides by extruder technique and fused with a alkane thiol surface of a hydrophobic SPR sensor. 

Both the physics and the chemistry of proximity to a surface can alter the excited-state lifetime and rotational motion of a fluorescent molecule. An extrinsic label attached to BSA has been found to reduce its fluorescence lifetime upon BSA adsorption to fused silica.(95) The decrease is too large to arise from the physical near-field proximity effects discussed in Section 7.3 ... 

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