Exchange reactions as a basis of thermopiastic behaviour in crosslinked polymers

An attempt has been made to achieve thermoplastic behaviour in a chemically crosslinked elastomer by arranging that the crosslinks should undergo rapid exchange at high temperatures. Natural rubber was chemically modified to give pendent hydroxyl groups which were then used as crosslinking sites to form β-keto-ester or malonate crosslinks. The resultant vulcanisates showed high stress relaxation rates in the temperature range 120 to 160°C and some degree of remouldability at 180°C. The incursion of permanent crosslinking prevented quantitative correlation between stress relaxation rates and chemical exchange rates of the crosslinking systems.     

Perceptual sharpening in the developing rat.

Studied the development of perceptual sharpening in 4 experiments with 514 Sprague-Dawley rats using the heart rate orienting response ([HROR] marked cardiac deceleration to novel stimuli) as the dependent measure. Preweanling Ss either 16–17 or 19–20 days of age were habituated to a 1,600-Hz tone over 15 trials. On Trial 16, the stimulus frequency was changed to 1 of 7 tones distributed on either side of the habituated stimulus. Analysis of the HROR showed that 16–27 day old Ss failed to respond to any of the new frequencies, which indicated generalization of habituation to the auditory stimuli within the frequency range studied. In marked contrast, 19–20 day old Ss displayed an HROR proportional to the difference between the habituated and the test stimuli. These age-related differences were not due to differences in sensitivity to the test stimuli, effector fatigue, or inability to discriminate between the test stimuli. Results indicate that perceptual sharpening develops relatively rapidly in rats and that perceptual sharpening, stimulus detection, and stimulus discrimination follow separate ontogenetic time courses. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A model of anisotropic Alnico magnets for field computation

The modeling of an anistropic Alnico magnet for the purpose of field computation involves assigning a value for the material's permeability in the transverse direction. This is generally based upon the preferred direction properties, being all that are easily available. By analyzing the rotation of intrinsic magnetization due to the self-demagnetizing field, it is shown that the common assumptions relating the transverse to the preferred direction are not accurate. Transverse magnetization characteristics are needed, and these are given for Alnico 5, 5-7, and 8 magnets, yielding appropriate permeability values.     

Characterization of thin films on metals using proton- induced X-rays

The measurement of characteristic X-rays produced by proton bombardment of a solid surface is being used to provide quantitative compositional analyses of surface layers of metals. An integral X-ray yield equation was developed that quantitatively relates the experimentally measured X-ray yield to the thickness of thin films ranging from less than a monolayer to several thousand ångströms. The use of the equation is demonstrated for the growth of thin films through either vacuum evaporation or oxidation processes. The sensitivity of proton-induced X- ray emission (PIXE) for the measurement of very thin film growth kinetics is demonstrated from studies of the effect of fractional monolayer coverages of sulfur on the initial oxidation kinetics of iron. By combining PIXE with inert gas ion sputtering, quantitative composition-depth profiles of surface layers were obtained. Examples are presented for the profiling of iron samples implanted with 25 keV nickel ions and for a molten salt electrodeposited platinum coating on an Fe-5% Cr substrate.     

Variation in ovarian morphology in four species of New World moles with a peniform clitoris

Female moles of the Old World genus Talpa display a curious suite of reproductive features that include a peniform clitoris and ovaries with a discrete interstitial gland or testis-like region (so-called 'ovotestes'). The masculinization of the female external genitalia in Talpa has accordingly been linked with secretion of androgens from the interstitial gland region of the fetal gonad. Although their ovarian morphology has received less attention, some species of New World moles also have ovaries with a pronounced interstitial gland (for example star-nosed mole, Condylura cristata), whereas females of other species do not (for example eastern mole, Scalopus aquaticus). Although it is difficult to determine the sex of both Old and New World moles, published accounts describing the external genitalia of female moles are available only for Talpa. The hypothesis that masculinization of the female external genitalia in moles is associated with the presence of an ovarian interstitial gland (OIG) was tested in the present study by using a comparative approach to determine whether these features are ever found in isolation of one another. Three genera of North American moles (Scapanus, Condylura and Neurotrichus) were studied and a peniform clitoris was found in all three species, but OIG were found in only two of three genera. The ovaries of S. latimanus and S. orarius were unremarkable, with no evidence of a discrete interstitial gland or testis-like region. Mapping these results onto recent talpid phylogenies indicates that loss of the bipolar ovarian morphology is a derived trait in Scapanus, and conclusively demonstrates that masculinization of the external genitalia in female moles can develop in the presence or absence of 'ovotestes'.     

A Review of the U.S. Department of Energy's Inertial Fusion Energy Program

This is the final report of a panel set up by the U.S. Department of Energy (DOE) Fusion Energy Sciences Advisory Committee (FESAC) in response to a charge letter from Dr. Ray Orbach (Appendix A). In that letter, Dr. Orbach asked FESAC for an assessment of the present status of inertial fusion energy (IFE) research carried out in contributing programs. These programs include the heavy ion (HI) beam, the high average power laser (HAPL), and Z-Pinch drivers and associated technologies, including fast ignition (FI). This report, presented to FESAC on March 29, 2004, and subsequently approved by them (Appendix B), presents FESAC's response to that charge.     

System for the design, manufacture, and testing of custom lenses with known amounts of high-order aberrations

Now that excimer laser systems can be programmed to correct complex aberrations of the eye on the basis of wave-front measurements, a method is needed to test the accuracy of the system from measurement through treatment. A closed-loop test method was developed to ensure that treatment plans generated by a wavefront measuring system were accurately transferred to and executed by the excimer laser. A surface was analytically defined, and a Shack-Hartmann-based wave-front system was used to formulate a treatment plan, which was downloaded to an excimer laser system. A plastic lens was ablated by the laser and then returned to the wave-front device, where it was measured and compared with the analytically defined wave-front surface. The two surfaces agreed up to 6th-order Zernike terms, validating the accuracy of the system.     

Unrealistic optimism in internet events

This study assessed the tendency for individuals to be unrealistically optimistic about internet related activities. Ninety-seven participants estimated their chances of experiencing 31 positive and negative internet events compared to the average student at their school. The data indicated that students believed positive internet events were more likely to happen to them and negative events were less likely to happen to them compared to the average student. Heavy internet users reported more optimistic responses than did light users. Perceptions of event characteristics (controllability, desirability, and personal experience) were also significantly correlated with optimistic bias.