Fused Twins

Fig. 4 (a-c) HRTEM images showing the nanowires and fused ZnSe dots. These are observed at different regions on the TEM grid. HRTEM image of a (d) single and (e,f) fused twin and triple ZnSe dots, respectively. Inset of panel d shows an atomic model of a single ZB dot, and that of panel f presents the selected area EFT pattern. Reproduced from ref. 47 with permission from the American Chemical Society. 

In fused twins the two mesogenic moieties are linked rigidly. Four-fold substituted ring systems (e.g. 17 [216]) can belong to this class. Induced in the research in this area are... 

Several workers have introduced polymerizable groups into twin-tailed amphiphiles and formed vesicles by sonication. They then link the amphi-philes by initiating polymerization, either chemically or photochemically. The polymerized vesicles which are so generated show little tendency to fuse, and are much more stable than the vesicles formed by sonication or vaporization. They therefore have considerable potential for compartmentalizing reagents, although as with normal vesicles there is always the... 

The next step of condensation is reached when chains are fused together. There exist a number of different structure types based on the characteristic building unit of the twin chain, e.g. in R6X7C2, R7X10C2, SC7CI10 and GdjIjC. With the exception of SC7Q10 the presence of interstitial atoms is well established in all of these structures. 

Four materials have been certified for thermal expansion SRM 731, borosili-cate glass (80 to 680 K) SRM 736, copper (20 to 800 K) SRM 737, tungsten (80 to 1800 K) and SRM 739, fused silica (80 to 1000 K) (see Fig. 2). The temperature range over which the tungsten is certified is expected to be extended to 2800 K. The thermal expansion of these materials at temperatures below 1000 K was determined with a Fizeau interferometer [ ]. At the higher temperatures, a twin-telemicroscope technique [ ] was used. All these SRMs are in the form of rods, 6 mm in diameter, and are provided in various lengths. 

A different interpretation of alite has been given by Fundal (1982), who stated that alite crystals are twinned individuals of a lower symmetry which imitate a higher symmetry (a mimetic relationship). The monoclinic form of alite was said to have an index of refraction of 1.72 and a birefringence of approximately 0.0050. Tri clinic alite was reported to be polysynthetically twinned in a fused clinker and have a birefringence of 0.0020. Alite birefringence, however, exhibits two average val ues in Fundal s Table 1 (1982) 0.0043 (monoclinic) and... 

According to very nearly everything you will read, human embryogenic chimeras are exquisitely rare. This is quite compatible with chimerism being thought to arise from the fusion of placental circulations of independent dichorionic dizygotic twin fetuses. It does not happen that way. Anastomosis of placental circulation has been found to have happened only a handful of times in examination of several thousand fused dichorionic dizygotic placentas (Foschini et al., 2003). 

A non-fused spur may only feed one single or one twin socket outlet. 

There are two main considerations particular to PVC extrusion. First, in most cases, the feedstock will be dryblend, and there is a need to remove air and volatile components as the material fuses. To accomplish this, a vented barrel was developed in the early 1960s. The screw had two compression areas, one before the vent to start the fusion and the other after the vent to finish the melting and push the melt through the die. Both single- and twin-screw extruders today for PVC dry blend have a vent connected to a vacuum for gas removal. 

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