Electron radiation

Polymers. The molecular weights of polymers used in high energy electron radiation-curable coating systems are ca 1,000—25,000 and the polymers usually contain acryUc, methacrylic, or fumaric vinyl unsaturation along or attached to the polymer backbone (4,48). Aromatic or aUphatic diisocyanates react with glycols or alcohol-terrninated polyether or polyester to form either isocyanate or hydroxyl functional polyurethane intermediates. The isocyanate functional polyurethane intermediates react with hydroxyl functional polyurethane and with acryUc or methacrylic acids to form reactive p olyurethanes. 

Hot air, steam, and hot water vulcanisation is widely used in the latex industry, and fluid-bed heat transfer and electronic microwave curing has also been used. Cross-linking by electron radiation has been experimentally used, but has not yet been developed commercially. 

The British Pharmacopoeia (1993) recognizes five methods for the sterilization of pharmaceutical products. These are (i) dry heat (ii) heating in an autoclave (steam sterilization) (iii) filtration (iv) ethylene oxide gas and (v) gamma or electron radiation. In addition, other approaches involving steam and formaldehyde and ultraviolet (UV) light have evolved for use in certain situations. For each method, the possible permutations of exposure conditions are numerous, but experience and product stability... 

What is the nature of the defects seen in the EPR spectra For alkali and alkali earth halogenides it is well known that irradiation with X-ray, neutrons, gamma-radiation, or electrons produce paramagnetic color centers (F-center) [109-111]. If these centers are created in large amounts, they can be stabilized by the formation of metal clusters as observed for MgCl2 films after prolonged electron radiation [106]. From the temperature dependence... 

Auger electron spectroscopy is preferred over XPS where high spatial resolution is required, although the samples need to be conducting and tolerant to damage from the electron beam. Many oxides readily decompose under electron radiation, and this may give rise to difficulty in spectral interpretation, and this has restricted the application of AES in the field of catalysis. 

Mankind + Extra-organism space (a) Wires (b) All space Sound Electrons Radiation As above + 1(L10 1(L10... 

The electron itself is frequently used as a primary source of radiation, various kinds of accelerators being available for that purpose. Particularly important are pulsed electron sources, such as the nanosecond and picosecond pulse radiolysis machines, which allow very fast radiation-induced reactions to be studied (Tabata et al, 1991). Note that secondary electron radiation always constitutes a significant part of energy transferred by heavy charged particles. For these reasons, the electron occupies a central role in radiation chemistry. 

Corbett, J.W. (1966). Electron Radiation Damage in Semiconductors and Metals, Academic press, N.Y. 

In the early years of Theosophy during Blavatsky s lifetime, the modem science that most occupied the movement was, without doubt, the theory of evolution rather than Victorian discoveries in physics and chemistry.4 While Blavatksy in Isis Unveiled and Secret Doctrine grappled in a limited way with modem physics and chemistry, she engaged much more fully with the work of alchemists, especially that of Paracelsus. Her defense of alchemical transmutation was based not upon contemporary science—though she asked of transmutation, Is the idea so absurd as to be totally unworthy of consideration in this age of chemical discovery (Isis 1 503)—but rather upon the exalted reputation of medieval and early modem scientists and alchemists who claimed to have witnessed transmutation (1 503-504). Moreover, the major events that launched modem particle physics—the discoveries of X-rays, the electron, radiation, radium, and radioactive decay—all occurred after Blavatsky died in 1891. 

Experimental results are presented that show that high doses of electron radiation combined with thermal cycling can significantly change the mechanical and physical properties of graphite fiber-reinforced polymer-matrix composites. Polymeric materials examined have included 121 °C and 177°C cure epoxies, polyimide, amorphous thermoplastic, and semicrystalline thermoplastics. Composite panels fabricated and tested included four-ply unidirectional, four-ply [0,90, 90,0] and eight-ply quasi-isotropic [0/ 45/90]s. Test specimens with fiber orientations of [10] and [45] were cut from the unidirectional panels to determine shear properties. Mechanical and physical property tests were conducted at cold (-157°C), room (24°C) and elevated (121°C) temperatures. 

Figure 5. Effect of electron radiation fluence on the Tg damping peak width (at half height). (Reproduced from reference 8.)...

Figure 21. Effects of 1 MeV electron radiation (6 x 109 rads fluence) on the relative damping of [0/ 45/90]s T300/5208 graphite/epoxy composite. (Reproduced from reference 18.)...

Later chapters will deal with a more complete description of the diffraction process, but we now have enough to discuss the selection of radiations and techniques. If the structure factor and scattering strength of the radiation are high, the penetration is low and the rocking curve is broad. This is the case with electron radiation. For X-rays and even more for neutrons, the structure and absorption factors are small, penetration is high and rocking curves are narrow. These factors have three main consequences for X-rays and also for neutrons ... 

The IRT method was applied initially to the kinetics of isolated spurs. Such calculations were used to test the model and the validity of the independent pairs approximation upon which the technique is based. When applied to real radiation chemical systems, isolated spur calculations were found to predict physically unrealistic radii for the spurs, demonstrating that the concept of a distribution of isolated spurs is physically inappropriate [59]. Application of the IRT methodology to realistic electron radiation track structures has now been reported by several research groups [60-64], and the excellent agreement found between experimental data for scavenger and time-dependent yields and the predictions of IRT simulation shows that the important input parameter in determining the chemical kinetics is the initial configuration of the reactants, i.e., the use of a realistic radiation track structure. 

ICRU (1992). International Commission on Radiation Units and Meeisure-ments. Measurement of Dose Equivalents from External Photon and Electron Radiations, ICRU Report No. 47 (International Commission on Radiation Units and Measurements, Bethesda, Maryland). 

Burns, F., Albert, R.E. and Heimback, R.D. (1968). RBE for skin tumors and hair follicle damage in the rat following irradiation with alpha particles and electrons, Radiat. Res. 36,225. 

Further insight into radiation mechanisms can be obtained by comparing different types of radiation, in particular alpha radiation, gamma (or fast electron) radiation, and ultraviolet light. Their effects are also important in such varied fields as space materials and radiological protection. 

Alpha radiation differs from gamma or electron radiation primarily in the much denser distribution of reactive entities along the alpha particle track with ultraviolet light at 254m often requiring the presence of a sensitizer, one is dealing primarily with excitation and not ionization. 

A dose of r rads of gamma or electron radiation achieves a random hit density of 0.625 X 1012 Grp per cc. (G hits per 100 e.v., density of material p— 1). A target volume v cc. therefore receives an average number of hits ... 

The purpose of the present work was to determine if the temporary effect of radiation on the creep rate of polymers could be confirmed using high intensity electron radiation, and if so, to attempt to elucidate the basic cause of the effect. 

Figure 3. Effect of 2-m.e.v. electron radiation on shear stability of Poltjox solution. 5% aqueous solutions prepared from dry irradiated polymer...

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