Studies on compatibilization of blends of polypropylene and a thermotropic liquid crystalline polymer

Thermotropic liquid crystalline polymers, LCPs, are frequently blended with thermoplastics to achieve an in situ composite structure. Significant mechanical reinforcement is obtained for the matrix polymer in the direction of the LCP fibers, but the transversal properties are often inferior because of the incompatibility of the components. Blends of LCP with polypropylene, and with three related matrix polymers, and PP/LCP blends with added potential compatibilizers were prepared and studied for their mechanical properties and morphology. A notable improvement in impact strength was achieved when a small amount of ethylene-based terpolymer was added as compatibilizer. © 1993 John Wiley & Sons, Inc.     

Influence of molecular tilt angle on the SHG response of pyroelectric liquid crystal polymers

Second harmonic generation in novel pyroelectric liquid crystal polymers (PLCP) made from a series binary mixtures, was studied using 1100 nm as the fundamental wavelength. The PLCPs were prepared by photo-polymerization of binary mixtures of two monomers which exhibit a smectic C^* phase, A2c (4″-(R)-(−)-2-[(10-acrylo-yloxy)decyl]oxy-3-nitrophenyl 4-{4′-[(11-acryloyloxy)-undecyloxy]phenyl}benzoate) and Alb (4″-((R)-(+)-2-octyloxy)-3″-nitrophenyl 4-(4′-(11-acryloyloxy)undecyloxy)-phenyl)-benzoate). The highest d₁₆ and d₂₃ coefficients were found to be in the range 0.65–0.8 pm/V, and differed depending on the detailed preparation of the sample. All cases of polymers formed from the chiral smectic C* phase showed an SHG-signal with no external field present, indicating that polar order became fixed. The SHG-signal was found to increase with the tilt angle of the FLC molecules.     

Lung density for assessment of hydration status in hemodialysis patients using the computed tomographic densitometry technique

The density of the lung reflects the total mass of fluid, air, and dry lung tissue per unit volume of the lung. Lung density can be measured by evaluation of attenuation of an electron beam with computed tomography (CT). This technique has been shown to be sufficiently reliable and sensitive to distinguish normal from abnormal lung water. The aim of this study was to find out whether lung density properly reflects the hydration status in hemodialysis patients in comparison with other standard methods. Fourteen hemodialysis patients, with an ultrafiltration ranging from 0.3 to 4.5 liters per session, underwent CT measurements of lung density, ultrasonographic measurements of the diameter of the inferior vena cava after quiet expiration (IVCe) and quiet inspiration (IVCi), and measurements of the hematocrit and plasma levels of the biochemical hydration markers cyclic guanosine monophosphate (cGMP) and atrial natriuretic peptide (ANP). These measurements were performed before and 3.5 to 4 hours after termination of dialysis. Quantitative estimates of lung density were obtained within pixels with CT numbers ranging between -1000 and -100 Hounsfield Units (HU), and compared with normal data from 18 normal controls. In normal controls, the lung density ranged from -800 to -730 HU. In hemodialysis patients, lung density was significantly higher than normal before dialysis (-678 +/- 96 HU, P < 0.01) and significantly decreased after dialysis (-706 +/- 92 HU, P < 0.05), indicating a decrease in fluid content of the lung. The density was normalized in 5 patients. A significant correlation was found between lung density and IVCe both before and after dialysis (r = 0.8, P < 0.01 for both). Change in density was significantly correlated to amount of ultrafiltration (r = 0.67, P < 0.01) and percent change in blood volume (r = 0.63, P < 0.05), indicating that lung density is greatly affected by changes in the extracellular fluid volume, mainly the intravascular volume. In conclusion, lung water reflects the hydration status in hemodialysis patients and can be monitored by measuring the lung density by CT. Accordingly, normalization of lung density can help to achieve a proper dry weight in these patients.     

24-GHz modulation bandwidth and passive alignment of flip-chip mounted DFB laser diodes

High-frequency lasers have been flip-chip mounted on silicon motherboards. Small-signal modulation bandwidths around 24 GHz were obtained. It was shown that the bandwidth was not limited by extrinsic parasitics associated with the mounting scheme. Lasers were passively aligned to single mode fibers in V-grooves with the self-aligning solder bump technique. By passive alignment 50% of maximum coupling efficiency obtained by active alignment was achieved.     

What Is Perseverated in Schizophrenia? Evidence of Abnormal Response Plasticity in the Saccadic System.

Although perseveration is sometimes attributed to defective set switching, the authors have recently shown that set-switching is normal in schizophrenia. In this article, the authors tested for persistent states of the saccadic response system, rather than set perseveration. Schizophrenic and healthy subjects performed antisaccades and prosaccades. The authors analyzed for 3 carry-over effects. First, whereas the latency of the current saccade correlated with that of the prior saccade in both groups, the correlations under mixed-task conditions declined in healthy but not in schizophrenic subjects. Second, antisaccades in penultimate trials delayed upcoming saccades in schizophrenic but not in healthy subjects. Third, schizophrenic subjects were more likely to erroneously perseverate the direction of a prior antisaccade but not a prior prosaccade. The authors concluded that, in schizophrenia, the effects of correct antisaccades are persistent not weak. Saccades in schizophrenia are characterized by perseveration of antisaccade-induced changes in the saccadic response system rather than failures to switch task set. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of viscosity ratio and processing conditions on the morphology of blends of liquid crystalline polymer and polypropylene

The effect of viscosity ratio and processing conditions on LCP/PP blend morphology was studied. The viscosity ratio (η_LCP/η_PP) was varied from 0.1 to 3.6 by using five different polypropylene grades as the matrix and two LCPs as the dispersed phase (20 wt %). The most spontaneous fiber formation was achieved when the viscosity ratio was between 0.5 and 1. In addition to shear forces, elongational forces are important in achieving a highly fibrillar structure and significant mechanical reinforcement. The lubricating effect induced by the low viscosity of LCP was most pronounced for the blends exhibiting a fibrillar morphology. The morphologies of blends produced by different mixing equipment differed only slightly. The greatest variation in the mixing efficiency was found for blends whose components had totally dissimilar melt viscosities. The slight differences in morphology due to melt blending in dissimilar equipment were decreased after injection molding, whereas the differences in morphology due to dissimilar viscosity ratios were still evident in the injection molded blends. Thus, the viscosity ratio at processing in the actual processing conditions is of great importance. © 1994 John Wiley & Sons, Inc.     

Long-term tests of reinforced concrete beams loaded by temperature gradient or settlement of a support

The creep of concrete has a considerable influence on the relaxation of the restraint effects and restraint stresses; particularly if the temperature of the concrete is higher than normal. The risk of cracking, for example, caused by the settlement of supports, is also diminished owing to creep; particularly if the rate of restrained displacement (settlement of a support) is slower than the rate of creep. It is difficult to consider the effect of relaxation from a calculational point of view, because the time dependences of several factors cannot be reliably modelled.In this research the relaxation of the restraint effects, due to both sudden and slow settlement of a support, was examined as a function of time; the relaxation of the restraint effect due to a thermal gradient was also investigated. In particular, was observed that the relaxation was fairly rapid in a heated beam. The relaxation of restraint effects caused by the settlement of supports was also considerable.     

Open systems interconnection — the teletex-based session protocol: Part 1

Two draft proposals for an international standard for the teletex-based session protocol have now been considered by the ISO. The ECMA 75 protocol has been found to be relatively complex as a result of ECMA having to sort out some weak points within the protocol. S.62, proposed by the CCITT, is quite suitable for the kernel of the session service, but not for the entire service. The paper suggests possible developments towards an international standard, and discusses the specification of the BAS subset. It then examines the services available, and how they operate. A proposal for a standard for service conventions is presented, along with a summary of the parameters of the service elements.     

Lipid and lipoprotein measurements in a normal adult American population

From a parent population of 774, a subpopulation of 160 normal adults ages 27-66 was randomly selected, 20 from each decade and sex. A detailed comparison was made by analytic ultracentrifugation and complete agarose gel electrophoresis on serum and the 1.006 g/ml top and bottom preparative ultracentrifuge lipoprotein fractions. The latter was internally standardized by total lipid and plasma total cholesterol and triglyceride determinations giving normal reference lipoprotein values. The reading procedure allowed the identification and quantification of floating beta and sinking pre-beta. In the subpopulation, there were two of the former and 13 of the latter. For large scale clinical application of such quantitative lipoprotein electrophoresis full automation of the microdensitometry and calculations will be required.