Cylindrical dumbbells

Cylindrical dumbbells were also prepared at high temperatures (220 to 260°C) utilizing a CSl Mini-max small injection molder to determine baseline as well as in-vitro (pH=7.27, 37 C) physical properties. For example, the poly[bis-1,6(p-carboxyphenoxy) hexane anhydride], 1,6 PA, was processed at 220°C. 1,6 PA processed at 220°C, was still soluble (i.e., no gelation), and had no observable changes in chemical structure as determined by NMR (Figure 4). 

The mechanical properties as well as in-vitro testing of cylindrical dumbbells were also studied (Tables 4-6 and 8-14). As can be seen from the tables, the yield strength and modulus of the aromatic poly(anhydride)s developed by the methods described herein are similar to or greater than poly(p-dioxanone), an absorbable polyester used extensively for medical devices, and poly(anhydride)s described by other researchers. This is another indication that the aromatic poly(anhydride)s have the high molecular weights (I.V. > 1.0 dl/g), and consequently, the high strengths required in wound closure devices. 

Like the 1,6 PA, poly[l,4-bis(p-carboxyphenoxy)butane anhydride] (1,4 PA) was also molded into cylindrical dumbbells, and baseline as well in-vitro physical properties were determined (Tables 5, 6 and 8-10). As can be seen from these tables, the yield strength and modulus is greater than that of 1,6 PA. This is as expected, since the 1,4 PA contains two less methylene groups per repeat unit. This leads to a polymeric chain, which is slightly stiffer and, therefore, causes a corresponding increase in yield strength and modulus. 

The cylindrical dumbbells were prepared by utilizing a CSI Mini-max injection molder equipped with a dry nitrogen atmospheric chamber at temperatures ranging from 220°C to 260°C with a residence time of 3 minutes. 

Baseline and in-vitro mechanical properties of the cylindrical dumbbells of the poly(anhydride) polymers so produced were performed on an Instron model 1122 at a crosshead rate of 0.35 in/min. Specimen gauge length was 0.35 in., with a width of 0.06 in. Results are an average of 8 to 12 dumbbell specimens. 

In-vitro studies were determined in a buffer solution (pH=7.27) at a temperature of 37°C for periods of 1, 3, 6, and 9 weeks. Eight to ten cylindrical dumbbells (2.4 to 3.0 grams) were placed in 100 ml of buffer solution. The buffer solution was replaced on a weekly basis. Sterilization of the dumbbells was conducted by Cobalt-60 irradiation at a dosage of 2.5 Mrad. 

Eqs. (6.4) and (6.5) lead to the cylindrical symmetry of the final photofragment angular distribution W(0f, pf) in the form of a dumbbell and a toroid, which are symmetrical with respect to the E-vector (the 2-axis). The distribution W(0f,ipf) is proportional to a differential photodissociation cross-section in the laboratory frame, f(0f,(fif) = daph/dO. For a proper description of its symmetry properties it is usually [376, 402] expanded in a set of spherical harmonics Ykq The cylindric symmetry in this case means that only spherical functions Too and Y20 appear with non-zero coefficients, and then... 

The most reasonable explanation for the increase in apparent hydrodynamic diameter measured by DLS is the enhanced micelle-micelle interactions as the boundary of a two-phase system is approached (i.e., the pressure is lowered). Figure 4 illustrates this concept of micelle-micelle interactions, which is manifested as aggregation (or clustering) of the reverse micelle or microemulsion droplets. Since the solvent environment is essentially unchanged by this "macromolecular aggregation" (Ui) we exclude the possibility of (other than transitory) micelle-micelle coalescence to form stable, larger micelles. The micelles may coalesce briefly to form transitional species (which might be a "dumbbell" or more cylindrical structures), in which the water cores collide and intermix. 

In belladonna plants deuteration had a drastic effect on flower development (25). The number of calyx lobes, corolla lobes, and stamens, while invariably 5 in control flowers, increased to as many as 9 or 10 in plants grown in 70 percent D2O medium. Abnormally shaped berries formed in plants grown in heavy water. The extent of malformation depended,on the D2O content of the medium and how late in the life cycle of the plant that the berry formed. The shapes ranged from pear-shaped to dumbbell-shaped to cylindrical. The misshapened berries resulted from the tenacity with which the corolla remained attached to the ripening berry in deuterated plants. As the berry enlarged, a constriction developed where the corolla was attached to the berry. The size and number of seeds were severely reduced in deuterated berries with only a few rudimentary seeds apparent in the 70 percent berries. 

Fig. 30 Schematic phase morphologies of binary cylindrical bottle brushes Janus cylinder (left), Janus dumbbell (middle) and lamellar-like (right) morphologies. The red and blue domains are filled by the A and B monomers interfacial regions are green. From [99]...

Figure 13 A graphic representation of the two models proposed to describe the mechanism of spheronization. The model proposed by Baert et al. (38) describes a transition from initial cylindrical particles (lA) into a bent rope (IB), dumbbell (IQ, two spherical particles with a hollow cavity (ID), and spheres (lE).The model proposed by Rowe (25) describes a transition from cylindrical particles (2A) into cylindrical particles with rounded edges (2B), dumbbells (2Q, ellipsoids (2D), and spheres (2E). (From Refs. 35,49.)...

Chilcott and Rallison (1988) simulated the zero Reynolds number flow of a dumbbell model with finite extensibility across a cylinder. In particular, they performed time-dependent calculations and reported the regions of high deformations near stagnation points, especially downstream from stagnation points. Likewise, Ambari et al. (1984) have considered the underlying phenomena of coil-stretch transition of macromolecules in laminar flow about cylindrical obstacles. 

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