Comb Structure

Expansions of the forms of Eqs. (6.1) and (6.6) hold also for branched polymers, though the numerical values of the coefficients are different, and depend on the type of branching. The coefficient al has been obtained (25) for regular star and symmetrical comb structures it is found that for these at is greater than the value 134/105 for linear polymers. This implies that as the temperature is increased above T= , branched molecules expand more rapidly than linear ones, so that for T> 0, g> g0. For molecules having many short branches on a long backbone, as the number of branches increases at approaches a limit ... 

Figure 1. Anthraxolite-bearing nodule in slate, seen on cleavage surface. ExplodedV anthraxolite fragments are engulfed in matrix of quartz and calcite intergroum in comb structure which parallels the tectonic z-lineation of the slate. Darker bands are distorted carbonaceous primary laminae. (Compare with Figure 3.)...

The z transform of the parallel comb structure is given by [Jot and Chaigne, 1991] ... 

Because NL(t) has the same periodicity as A(t) the comb structure of the spectrum, as derived in section 3, is not affected. In an optical fiber self-phase modulation can be quite efficient even though the nonlinear coefficient in fused silica is comparatively small. This is because the fiber core carries a high intensity over an extended length. 

The liver tissue has a characteristic honey-comb structure (Figure 2.3b). The individual hexagons of the honeycomb are referred to as lobuli. The portal vein and liver artery branehes spread along the boundaries of the lobuli. The blood that leaves them is filtered through the tissue towards the eenter of the lobulus, where it reaches the central vein. The eentral veins then siphon the blood toward the systemic circulation. 

Figure 5. Photomicrograph of mammillary calcite in cross-polarized light. Note the closely packed comb structure of the crystals with the teeth (T) of the comb meeting the back (B) of the comb at an acute angle. White arrow indicates direction to the substrate.

In some instances, the macromonomers synthesized by CCT can be copolymerized with acrylics to form comb copolymers. While /1-scission predominates in copolymerizations with methacrylates, acrylates and styrene give both incorporation to yield comb copolymers and /1-scission.492 Products of this type have been thoroughly characterized by a variety of spectroscopic techniques. When high levels of CCT macromonomers are employed, it is possible to go beyond the comb structure and obtain more highly branched polymers.493... 

The ceramic catalyst is a homogeneous mixture of all components. After mixing with binders, plastifiers, and glass fiber the mass is extruded to honey-comb-structured elements, which are dried and calcined (Fig. 10.1). 

This is one of the most widely distributed plants cultivated to obtain cashew nut. The phenolic lipid is only a by-product known as cashew nut shell liquid (CNSL). The nut, attached to the base of the cashew nut apple consists of an ivory-colored kernel covered by a thin brown membrane (testa) and enclosed by an outer porous shell, the mesocarp which is about 3 mm thick with a honey-comb structure where the reddish brown liquid (CNSL) is stored [91]. The major components of CNSL are a phenolic acid, anacardic acid, a dihydric phenol, cardol with traces of mono hydric phenol, cardanol, and 2-methyl cardol [92-95]. 

Figure 9. Comb structure of EDA zinc-chloride electrodes. (Courtesy of EDA, Gulf + Western Company, Dr. Peter Carr.)...

Starting from the analytical description, we can create a first rough design of the sensor system, including the resonant frequencies for drive and detection and the sizes of the sensing element, the electrostatic comb structures, and the detecting capacitors. While this work is done, the physical properties of the technology already have to be considered. 

The epi-polysilicon functional layer is patterned and then etched by the trench etch process described in Section 5.3.4.2. The trench etching forms cantilever beams that act as comb fingers in the acceleration sensor, as well as the insulating trench required for electrical separation of the epipolysilicon wiring and bond pad structures (Fig. 5.3.11 e). Straight, unnotched sidewalls are strictly required, especially for all design elements that form springs or capacitive comb structures. 

The stress gradient within the thin films. High stress gradients lead to extreme curvatures of the released structures, thereby modifying the functionality of, for example, comb-structure acceleration sensors produced by Bosch or Analog Devices. 

Fig. 5.10.1 Schematic drawing of a rotational disc gyro. The rotor (in blue) is oscillating around the z axis, driven by fixed comb structures. A yaw rate around the y axis generates a Coriolis force in the z direction. The resulting seesaw-like out-of-plane motion of the rotor is detected by measuring the difference in capacities between the rotor and detecting electrodes beneath it...

Complementary structures exhibit substantially lower offset and reduced susceptibility to errors by using two nominally equal sense elements that change in opposite direction. This can be achieved for example by adding a second fixed electrode above the movable plate [3], Most planar processes have no provision for stacking a third electrode above the movable structure. In this case, complementary parallel-plate sensing can still be achieved with the planar comb structure shown schematically in Fig. 6.1.4. The sense capacitance consists of many individual capacitances between movable fingers and fixed electrodes connected in parallel to detect in-plane displacements. 

The mechanical resonance frequency is mainly determined by the masses and the coupling stiffness between the masses, here 6 kHz. For the detection an acceleration sensor is placed on each of the two masses, arranged in a comb structure by surface micromachining. The drive works electrodynamically. A permanent magnet causes a magnetic field vertical to the surface of the sensor element. Conductors on the masses, stimulated by an electrical current, experience a Lorentz force, which drives the masses. 

Fig. 7.2.14 Principle of the micromachined rotational yaw-rate sensor 1, comb structure for drive and drive detection 2, rotating mass 3, sensitive direction Fc, Coriolis force ...

Monolith Honey comb structure of cordierite containing 64- square channels per square centimeter from Corning Glass GmbH, Wiesbaden-Biebrich, West Germany. 

Commercial catalyst Honey comb structure made by Degussa AG., West Germany, and obtained from Volvo AB, Gothenburg, Sweden. 

A particularly interesting example of graft copolymers produced via active ester synthesis is that of the comb structure (25, Fig. 19) with a hydrophobic backbone and hydrophilic grafts. A series of these amphiphilic graft copolymers have been produced by partial displacement of the trichlorophenoxyl groups... 

Essential details of four graft copolymer samples (25a-25d) thus obtained are given in Table 11. The samples have been briefly examined by sedimentation equilibrium analysis. The molecular weights (M ) obtained by this method are consistent with, but lower than, the expected values recorded in Table 11. Another series of amphiphilic graft copolymers with a double comb structure has also been synthesized (26, in Fig. 19) [47]. Similarly, type 27 graft copolymers have been prepared by the reaction of the activated copolymer with hydroxy-terminated polyurethanes, but these have not so far been characterized. 

Egelhaaf et al. found SCLC behaviour for 5T on Au comb structures even for voltages as low as 100 mV, whereas on Pt comb structures, no SCLC could be detected up to 100 V [38]. This is in line with results from Vaterlein et al. [242] which do not find any evidence of SCLC in their a6T thin films on Pt comb structures measured in high vacuum. 

Silicone polyethers are non-ionic in nature, and have both a hydrophilic part (low molecular weight polymer of ethylene oxide or propylene oxide or both) and a hydrophobic part (the methylated siloxane moiety). The polyether groups are either ethylene oxide or propylene oxide, and are attached to a side chain of the siloxane backbone through a hydrosilylation or condensation process. They can form a rake-like, comb structure, or linear structure. Silicone polyethers are stable up to 160-180 degrees Celsius. There is a great degree of flexibility in designing these types of polymers. A very wide variety of co-polymers is possible when the two chemistries are combined. 

Fig. 6.3 Sketch of a comb structure with a nearest neighbor distance a and secondary branches of length /. The symbols A, A, A",... denote sites on the lattice (see text)...

---