Irradiation procedure

Irradiation Procedure. Reaction mixtures were prepared at room temperature by transferring desired quantities of reactants from their storage bulbs to the reaction vessel, a 500-cc. spherical borosilicate glass flask attached to the vacuum line by a section of glass capillary tubing and a 4-mm. bore threaded glass valve with a Teflon plug (Fischer and Porter 795-609). Prior to each experiment this vessel was baked under vacuum at 500°C. for 12 or more hours. 

Both the pre-irradiation and simultaneous irradiation procedures have been utilised for this purpose, however the latter technique is the more flexible and more extensively investigated. In the simultaneous procedure, the monomer, usually in the presence of solvent, is simultaneously irradiated in contact with the backbone polymer. The predominant variables which influence the grafting yield include radiation dose and dose-rate, concentration of monomer in solvent and the structures of both monomer and backbone polymer. 

Materials and Irradiation Procedure. The materials examined are shown in Table I. 

Likewise, the only synthesis of 3,7-phenanthroline is that due to Perkampus and Kassebeer.12 Irradiation of a benzene solution of trans-l-(2-pyridyl)-2-(3-pyridyl)ethylene for 10 hours gave a 15% yield of 3,7-phenanthroline. If air was drawn through the system the hydrated product, l-(2-pyridyl)-2-(3-pyridyl)ethan-2-ol (20%) predominated, along with 3,7-phenanthroline (6%) and 1,7-phenanthroline ( 1%). The irradiation procedure was used subsequently.15... 

Knowledge of the volatile components of irradiated and nonir-radiated beef is reviewed. Concurrent and nonconcurrent irradiation procedures produce the same compounds but in different relative quantities. Storage of irradiated beef decreases irradiation flavor and the quantity of volatile constituents. Methional, 1-nonanal, and phenylacetaldehyde are of primary importance in beef irradiation off-flavor produced under the conditions described. 

A problem associated with beef sterilized by irradiation at approximately room temperature is the production of an unpleasant flavor and aroma. This paper summarizes knowledge of the volatile components of enzyme-inactivated irradiated and nonirradiated beef, reviews the effects of concurrent and nonconcurrent irradiation procedures and of storage on these components, and presents evidence that methional (3-methylmercaptopropion-aldehyde), 1-nonanal, and phenylacetaldehyde are of primary importance to irradiation off-odor in beef thus processed. 

The data of Table IV seem to indicate slightly less damage to amino acids with 7-irradiation than with 24 m.e.v. electrons. The marked stability of these amino acids in beef to 7-irradiation has also recently been observed by Rhodes and Southern (39) and is somewhat in contrast to the earlier report of Tsien and Johnson (50). The rather extensive losses of glutamate reported in the earlier work may have been caused by incomplete recoveries from the analytical columns or by differences in irradiation procedure. Our samples were irradiated from a cobalt-60 source, while the earlier samples were irradiated from spent fuel rods. It has recently been reported (15) that 7-ray irradiation of glutamic acid yields the corresponding a-keto acid, the amount obtained depending on irradiation conditions. 

Irradiation procedures. Mesophase solutions and neat solid samples of BN were prepared and sealed under N2 or vacuum in Kimax capillary tubes. Isotropic samples were either degassed (freeze-pump-thaw techniques) and sealed in pyrex tubes or saturated with N2 in pyrex tubes. Nitrogen was bubbled through the latter solutions during irradiation periods. When ther-mostatted, samples were placed in a temperature controlled ( 1°) water bath. All samples were irradiated with a 450 W Hanovia medium pressure Hg arc and were stored at -30°C until their futher use. Usually, a "dark sample was prepared and treated in an identical fashion to the irradiated samples except that it was shielded from the light. JSN from each tube was recovered by either column chromatography (silica or alumina and pentane eluant) at 4°C followed by solvent removal at 0°C and reduced pressure or by hplc (tr-hexane) at room temperature followed by solvent removal at 0°C and reduced pressure. Neat solid samples were dissolved in one of either benzene, tetrahydrofuran or toluene and were frozen until analyzed. 

In order to test the reliability of the chemical and irradiation procedure, detection, and data reduction described in reference (15), each irradiation batch had several sets of chemical standards. In Table 1, "in" represents the amounts in nanograms, ng, of Sb and Ba standards deposited on swabs, the mean of 12 determinations each is in the "found" column and the standard deviation, "std. dev.", is given as a percentage of the "found" value. The average value in terms of CPM (counts per minute) per ng calculated from the three concentrations (5,10 and 20ng) yielded 98 CPM 27% for Ba and was used as a basis to calculate "found" values. 

Irradiation Procedure. 30% w/w solutions of poloxamer were prepared in distilled water by the cold process and saturated with nitrous oxide. This agent is a known scavenger of hydrated electrons and is known to enhance crosslinking of poly(oxyethylene) chains (9). Vials containing these solutions were irradiated at ambient temperature in a 2000 Ci ° Co source at a dose rate of 0.5 Mrad h- Physicochemical measurements were performed on solutions prepared by dilution of these irradiated samples. 

The methods of preparation of glassware are indicated in Chapter 8, and if sterilisation is monitored as described the glassware should not be a source of contamination. Likewise plasticware is obtained from the manufacturer in a sterile condition. Usually sterilisation of plastic is achieved using ethylene oxide or irradiation procedures and vessels are supplied wrapped in cellophane. 

Irradiation procedure. The LDPE samples (size 40 mm x 20 mm, thickness 37 pm) were purified in an ultrasonic bath (10 minutes, 30 °C) using a mixture of acetone/water and then dried in vacuo (20 mbar, 1 hour at 40 °C). The samples were positioned in the reaction chamber, which was then purged with a mixture of SO2 and synthetic air (1 1, volume) for about 10 minutes for conditioning. Subsequently, the polyethylene samples were irradiated with the Hg lamp for different periods of time (1 to 5 minutes) maintaining the gas flow. Finally the chamber was purged... 

In our view, one of the difficulties to understand the surface structuring mechanism is due to the fact that, up to this moment, there is no well established standard methodology concerning the UV irradiation procedure. For example, usually in the papers it is not specified if the polymeric film UV irradiation is done in the presence or in the absence of natural visible light, in the presence or in the absence of neon tube light etc. All these additional visible light sources influence in a strong manner the cis-trans relaxation process and implicitly the isomerisation equilibrium. 

NOTE These values are not elemental concentrations. Measured with INAA with a 10-min irradiation procedure. Washed with 5% HC1. cn.a. means not available. 

With the neutron activation procedure, the measurement of P is reliable only when there is very little Al (<20 ppm), or when an epithermal irradiation (Cd-covered) is used to correct for the direct activation of 28Al from the Al. For badly contaminated samples, the X-ray fluorescence data are more suitable for the P determination. The sequential irradiation procedures (with and without cadmium) showed that many of the mummy samples were contaminated to some extent and contained more than 20 ppm of Al. 

Organo-Mercury Associations. Experimentally, the mercury measurements in seawater have been divided into two fractions— reactive and total mercury. The reactive fraction represents the amount of mercury measured in pre-acidified raw seawater samples at approximately pH 1. The total mercury measurement is carried out on aliquots of the preacidified seawater samples in which the organic matter has been destroyed by ultraviolet photooxidation (31). This irradiation procedure is as effective as the persulfate oxidation method (32) commonly used to destroy organic matter in seawater. A complete discussion of our photooxidation methodology can be found in Fitzgerald (33). The amount of mercury determined as the difference between the reactive and total mercury measurements represents a very stable organo-mercury association. 

The filters were reweighed after 24 hours of exposure, indicating a weight gain of c. 15. A distinct odour was noticed during the irradiation procedure. 

Fig. 20 Two-step irradiation of a cross-linked PVP layer with an electron beam, (a) Principal sketch of the irradiation procedure, (b) Three lines of 0.4 pm and one line of 14 pm were written into a PVP square of about 60 pm width. The degree of swelling Q of the pre-irradiated PVP was 10 and of the double irradiated 2 = 6. For details see Burkert et al. (2007b)...

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