Influence of corticotropin-releasing factor on pancreatic and islet blood flow in different regions of the rat pancreas

Corticotropin-releasing factor (CRF) has previously been shown to selectively dilate the mesenteric vascular bed, without affecting other vascular beds. Pancreatic blood flow and islet blood flow were therefore measured separately with a microsphere technique in the two regions of the rat pancreas perfused by the superior mesenteric artery (SMA) or celiac artery (CA) respectively. Intravenous infusion of CRF (0.25 microgram/kg b.w./min) caused an increase in both whole pancreatic blood flow and islet blood flow in the region of the pancreas perfused by the SMA. The fraction of whole pancreatic blood flow diverted through the islets in this part of the pancreas was, however, unaffected by CRF infusion (approximately 10%). CRF did not change either pancreatic or islet blood flow in the CA-perfused part of the pancreas, and did not affect the release of insulin.     

Variations in fundamental frequency peak position in Japanese macaque (Macaca fuscata) coo calls.

Japanese macaques (Macaca fuscata) produce coo calls whose use in various contexts is correlated with differences in the relative temporal position of the peak value of a call's fundamental frequency (S. Green, 1975). Studies have produced conflicting results about both the location of the category boundary between smooth early high and smooth late high coo subtypes and macaques' perceptual sensitivity to variations in peak position. In this study, fundamental frequency peak positions were measured in 578 coos produced by 8 captive adult female Japanese macaques in order to test whether calls with peak positions close to either of 2 hypothesized boundaries occurred at low rates. Overall, such calls were found to occur at rates equal to or higher than predicted by chance. Peak position varied more consistently between animals than by behavioral context. The results may indicate that peak position in coos does not form 2 distinct categories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluation of Serum Volume Losses During Long-Term Storage

Aliquots of serum collected in a large case-control study of cervical cancer were stored at −70°C for up to 4 years during implementation of the study. When 500 μL serum aliquots were thawed in preparation for carotenoid and vitamin A assays, volumes were noticeably variable and fell below 500 μL in the majority of the samples. We were concerned about evaporation/sublimation during storage of the samples because loss of water would concentrate the analytes of interest. We evaluated the use of density and sodium ion concentration measurements to confirm its occurrence. We found that serum density was an unreliable indicator of extent of volume loss since the anticipated increases in density due to evaporation were of the same magnitude as inter-individual variation in serum density. In contrast, Na⁺ concentration is tightly regulated and would rise if water had been lost from the samples. In a representative sample of serum aliquots from the case-control study, 24 of 25 vials contained less than 500 μL of serum. The mean sodium ion concentration (138.1 ± 3.6 mmol/L) was within the normal range for human serum of 136–145 mmol/L, and no correlation was observed between serum volume and Na⁺ concentration. These results strongly suggest that the observed low volumes were not due to evaporative losses. Instead, the variably low volumes of serum aliquots were probably due to pipetting errors in the initial aliquotting resulting from the use of air-displacement pipettes.     

The effect of cooling rate on the impact performance and dynamic mechanical properties of rotationally molded metallocene catalyzed linear low density polyethylene

This article examines changes to the morphology of rotationally molded metallocene catalyzed linear low density polyethylene brought about by varying the cooling rate during processing. These changes in morphology lead to variations in the impact performance, which is reflected in the dynamic mechanical characteristics of the materials. Various analytical techniques are used in an attempt to explain the differences in impact behavior. Slow cooling is shown to result in high crystallinity, and in the formation of large spherulites, which in turn is detrimental to the impact performance of the material, particularly at low temperatures. The high crystallinity corresponds with a shift in the β transition of the material to a higher temperature, and is shown to result in a higher brittle–ductile transition. A case study was also carried out on samples from a finished part provided by an industrial molder, one section of which failed in a brittle manner when impact tested while the other failed in a ductile manner. Microscopy results showed that the brittle material had large spherulites at the inside surface, while the ductile material showed incipient degradation at this surface, which has previously been shown to be of benefit to impact strength in rotationally molded parts. Dynamic mechanical studies again showed a β transition at a higher temperature in the brittle samples. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1963–1971, 2006     

An anomaly in the necking behavior of polyethylene

Tensile creep measurements at constant load on nonoriented polyethylene have shown a marked transition at a certain stress level from a neck formation followed by instantaneous fracture to the formation of a neck which resists fracture for a considerable time. The transition, which shifts towards shorter time and higher nominal stress with increasing molecular weight, has been studied for 16 polyethylenes of different molecular weights, degrees of branching and crystalline structures. The marked. transition has only been observed for high density polyethylene of high molecular weight. Deformation measurements show a more distinct necking for the high density than for the medium density polyethylenes. This is consistent with current molecular deformation theories. A hypothesis for the transition is proposed based on the distinctness of the neck process in the high density polyethylene and the large difference in strength between the spherulitic structure and the fibrillar structure. The dependence of the transition on molecular weight is expected since the number of tic chains incrcrtses with increasing molecular weight.     

Quasi three-dimensional, n-bit optical memory based on the ellipsometric principle: model calculations

Model calculations on the ellipsometric memory are presented. The ellipsometric memory is an n-bit optical memory whose information is extracted by use of the ellipsometric principle. The memory cells of the device consist of thin-film multilayer structures, and the information of each memory cell is contained in the optical properties of the thin films. Several thin-film multilayer structures were examined in order to find out how different choices of layer materials and other system parameters such as layer thicknesses and wavelength affect resolutions and limitations of the ellipsometric memory. Such calculations are also useful for optimizing the readout resolution. It was found that it is possible to use memory cells having up to at least eight layers, which would permit 8-bit words to be stored at each location. It was also found that, in principle, several types of materials can be used as layer materials, and various aspects of different choices of materials are discussed.     

On Forward–Backward MODE for Array Signal Processing

We apply the MODE (method of direction estimation) principle to the forward–backward (FB) covariance of the output vector of a sensor array to obtain what we call the FB-MODE procedure. The derivation of FB-MODE is an interesting exercise in matrix analysis, the outcome of which was somewhat unexpected: FB-MODE simply consists of applying the standard MODE approach to the eigenelements of the FB sample covariance matrix. By using an asymptotic expansion technique we also establish the surprising result that FB-MODE is outperformed, from a statistical standpoint, by the standard MODE applied to the forward-only sample covariance (F-MODE). We believe this to be an important result that shows that the FB approach, which proved quite useful for improving the performance of many suboptimal array processing methods, shouldnotbe used with a statistically optimal method such as F-MODE.