Melt blending of a variety of conventional isotropic polymers (both crystalline and amorphous) has shown that considerable reinforcement is obtained from the inclusion of thermotropic liquid crystalline polymers (LCP). When the LCP is a minor component it forms highly elongated domains parallel to the flow direction. The intrinsically high strength and stiffness of the LCP improve the mechanical properties of the resulting blend. This approach is distinguished from the common practice of filling polymers with chopped glass and carbon fibers by the fact that the reinforcing component comes into existence during processing (molding or extrusion). Many of the problems associated with fibrous fillers are avoided. For example, viscosity of the “in situ composite” is actually lower than that of the base polymer and wear on the compounding and processing equipment is reduced.

SynopsisRheological studies were carried out on concentrated m-cresol solutions of two helical synthetic polypeptides; poly-y-benzyl-1.-glutamate (PRLG; molecular weight, 150,000) and poly-6-carbobenzyloxy-L-lysine (PCHZL; molecular weight, 200,000). Steady shear measurements were made over a range of0.01-16,000 sec-' to obtain steady shear viscosity and first normal stress difference. I)ynamic viscosity and dynamic storage modulus were measured both by oscillatory shear between cone and plate and also by a n eccentric rotat.ing disk device over frequency ranges of 0.1-400 and 0. I -4 4 r d s e c , respectively. The concentration ranges were such that both liquid crystalline and isotropic solutions were investigated. The previously reported observations of an apparent negative I'irst normal stress difference within a defined range of shear rate for liquid crystalline solutions were u)nl'irmed 1i)r the PHI,(; and PCRZL solutions. At high shear rates the peaks in plots of steady shear viscosity against concentration were profoundly suppressed but peaks in first normal stress difference VCI'SUS cwncentratioii were not. The observation of liquid crystalline order in PCBZL/m -cresol solutions ;it room temperature constitutes evidence that the inverse coil-helix transition temperature is lower in concentrated solutions than in dilute solutions. The critical concentration for formation 01' the liquid crystalline phase was higher for PCHZI, than for PRI,G, despite a higher axial ratio. due to helix Ilexil)ilitv.

The 2014 Ebola Virus Disease (EVD) outbreak in West Africa was the largest and longest ever reported since the first identification of this disease. We propose a compartmental model for EVD dynamics, including virus transmission in the community, at hospitals, and at funerals. Using time-dependent parameters, we incorporate the increasing intensity of intervention efforts. Fitting the system to the early phase of the 2014 West Africa Ebola outbreak, we estimate the basic reproduction number as 1.44. We derive a final size relation which allows us to forecast the total number of cases during the outbreak when effective interventions are in place. Our model predictions show that, as long as cases are reported in any country, intervention strategies cannot be dismissed. Since the main driver in the current slowdown of the epidemic is not the depletion of susceptibles, future waves of infection might be possible, if control measures or population behavior are relaxed.

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The shear dependence of structures of liquid crystalline solutions of Poly-y-benzyl-L-glutamate PBLG in m-cresol was examined in a polarizing microscope using a specially constructed shearing stage and stroboscopic illumination. Three different textures were observed depending on shear rate. The shear rates at which the texture changes occurred correlated well with the changes in sign of the first normal stress difference reported earlier.'~* The region of negative first normal stress difference corresponded to a texture consisting of striations perpendicular to shear.The transverse striations were also observed to develop over a period of seconds or minutes after cessation of shear at rates within the first positive region of N , . These striations could be fixed in a dried film by using a volatile helicogenic solvent (1,4-droxane).A speculative model is proposed to account for the rheologicdl observations in Refs.'.' and the rheo-optical observations reported herein.

Steady shear viscosity, dynamic viscosity, dynamic modulus, and normal force were measured via rotational rheometry for concentrated solutions of racemic mixtures of poly(benzyl‐L‐glutamate) and poly(benzyl‐D‐glutamate) in m‐cresol. A transition from the isotropic state to liquid–crystalline order with increase in concentration was indicated by optical anisotropy and maxima in all four material functions. This occurred at a critical concentration higher than the Flory prediction. Over a well‐defined range of concentrations and shear stresses, some of the liquid–crystalline solutions exhibited negative first normal‐stress differences that were not due to inertial effects.

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