Incomplete fusion

In the course of the fusion of the projectile and target nuclei, it is possible that one of the partners will emit a single nucleon or a nucleonic cluster prior to the formation of a completely fused system. Such processes are referred to as preequilibrium emission (in the case of nucleon emission) or incomplete fusion (in the case of cluster emission). As the projectile energy increases, these emission processes become more important and they generally dominate over fusion at projectile energies 

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For pipelines in service in chemical plants, it is not usually convenient to place a radiation source inside the pipe and position it to irradiate each welded joint. The radioisotope source container maybe placed on the outer surface of the pipe. The radiation beams then pass through two pipe wall thicknesses to expose films placed diametrically opposite the radiation source, also on the outside of the pipe wall. Other methods, such as magnetic particle inspection of welds in steel pipe, or ultrasonic inspection of welds in pipes of all materials, supplement x-rays in many critical appHcations. The ultrasonic tests can often detect the thin, laminar discontinuities parallel to the pipe surface or the incomplete fusion discontinuities along the weld... 

General description. In incomplete fusion, complete melting and fusion between the base metal and the weld metal or between individual weld beads does not occur (Fig. 15.8). Incomplete fusion that produces crevices or notches at surfaces can combine with environmental factors to induce corrosion fatigue (Chap. 10), stress-corrosion cracking (Chap. 9), or crevice corrosion (Chap. 2). See Fig. 15.9. 

Location. Incomplete fusion may occur in any welded joint. 

Critical factors. The basic cause of incomplete fusion is failure to elevate the temperature of the base metal, or of the previously deposited weld metal, to the melting point. In addition, failure to flux metal oxides or other foreign substances adhering to metal surfaces properly may interfere with proper fusion. 

Identification. Incomplete fusion generally results in discontinuities along the side walls of a joint. When these discontinuities emerge at surfaces, they can be observed visually if accessible (Figs. 15.10 and 15.11). Defects of this type may also be detected by ultrasonics, radiography, magnetic particle inspection, and eddy-current testing. 

Figure 15.9 Cross section of stainless steel weld showing crevice corrosion along a site of incomplete fusion. (Magnification 15x.)...

In lOOmM NaCl, the amount of CF released is dependent on the concentration of Mg2+ present (see Figure 5A). The release is correlated with incomplete fusion of the vesicles (50) where the extent of release is related to the relative increase in size. Ca2+-induced CF release, however, proceeds until complete release occurs, which is expected since Ca2+-induced fusion eventually results in the formation of cochleate lipid cylinders with no internal aqueous space (15,27)... 

Mouse (ICR) once Gd 10 (GW) 8 (incomplete fusion of sternebrae) 12 (cleft palate decreased fetal weight) Fuyuta et al. 1979 MMC... 

Methylmercuric chloride administered via gavage to pregnant rats at 8 mg Hg/kg on Gd 10 resulted in increased skeletal variations (incomplete fusion of the stemebrae) (Fuyuta et al. 1979). At higher doses, decreased fetal weight and increased malformations (cleft palate) were observed. Administration of lower doses of methylmercury (4 mg Hg/kg/day) for a longer duration of gestation (Gd 7-9 or 6-14)... 

Pancreas divisum is the most common congenital anomaly of the pancreatic duct system. It arises from an incomplete fusion of the dorsal and ventral pancreatic ducts. The incidence of pancreas divisum at autopsy ranges between 4.7% and 11%, but in patients with unexplained pancreatitis the incidence can be as high as 25.6%. Multiple attacks of pancre-... 

Figure 6.20 The wall of a PVC pipe after exposure to methylene chloride for 10 min. The white areas are where there is incomplete fusion of the particles (Courtesy Dr. J. Marshall).

Definition Bicornuate uterus is the result of incomplete fusion of the cranial parts of the miillerian ducts [21,28] (Fig. 4.5). 

A longitudinal vaginal septum (Fig. 12.9) occurs as a consequence of incomplete fusion of the miille-rian ducts or resorption failure of the vaginal septum. This anomaly is also typically associated with other malformations of the mullerian ducts [septate uterus, bicornuate uterus, uterus didelphys (Fig. 12.9), cervical duplication] [2j. 

Granular structure n. Non-uniform appearance of finished plastic material due to retention of, or incomplete fusion of, particles of compound either within the mass or on the surface or to the presence of coarse filler particles. 

Inelastic scattering Few nucleon transfer Damped collisions (DC) Incomplete fusion (ICF) Complete fusion (CF) —... 

In some heavy-ion reactions a small fraction of the projectile mass may escape capture and proceed forward with the beam momentum. These reactions are called incomplete fusion (ICF) or massive transfer. The result of such incomplete fusion is, aside from the uncaptured fragment, an excited nucleus that is fully internally equilibrated and thus its decay is suitably treated by statistical models of compound nucleus decay, the subject dealt with in the next major section. 

Incomplete fusion of the distal segments of the two mullerian ducts results in various degrees of bifidity of the uterus and/or vagina (Jarcho 1946) (Fig. 7.6). Disorders of the lateral fusion are rare in the general population and, in the absence of obstruction, are asymptomatic during childhood or at puberty. However, these anomalies are more frequently encoun-... 

The process of incomplete-fusion reactions, also called transfer reactions , encompasses a variety of mechanisms that are defined by the extent of the interaction between the colliding reaction participants and the dmation of time in which the reactant nuclei are in contact [108]. In Coulomb fission there is no exchange of nucleons between the reacting nuclei, but there is enough overlap of the nuclear and Coulomb potentials at closest approach that a heavy-element target nucleus can be induced to fission [461]. Quasi-elastic transfer reactions involve the direct exchange of nucleons between the participants, whose nuclear potentials overlap... 

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