Crystallization and melting studies of branched isotactic polypropylenes

Crystallization, melting and structural studies were conducted on iostactic polypropylenes treated with varying dosages of electron beam radiation and an untreated iPP. Through FTIR methods, all specimens were found to be greater than 99% isotactic. Crystallization and melting studies were performed using light depolarizing microscopy (LDM) and other melting experiments were conducted using differential scanning calorimetry (DSC). Structural studies were conducted by use of a wide-angle x-ray diffractometer (WAXD). Through isothermal crystallization studies it was found that at the highest supercoolings all specimens had approximately the same half-time of crystallization values, t½, attributed to increased nucleation by increased supercooling. At higher temperatures of crystallization, Tc, it was observed that t½ varied for the specimens. This was attributed to the effects of branching on primary nucleation and to the size of the spherulites. All specimens were observed to nucleate in the heterogeneous mode, meaning that nuclei density stayed constant throughout the isothermal crystallization process. Average spherulite growth geometry (Avrami) exponent, n, values were in the range of 2.2 and 2.5. These low values were a consequence of the amount of branching and stereoregularity of the polymer chains and secondary crystallization. The spherulite growth rates, k, for all the samples decreased with decreasing supercooling, resulting from the decrease in the number of nuclei forming into spherulites. Through x-ray studies the predominant crystal form was found to be of the α modification, with some β and γ modifications observed. No structural changes at the crystal lattice level were detected. The degree of crystallization was seen to decrease as a result of increased branching in the treated specimens and attributed to thermal degradation in the untreated one. From the DSC endotherms small melting peaks in the range of 140 °C to approximately 145 °C was noticed in some of the specimens and attributed to the β modification as a consequence of nucleating agent(s) and stresses induced during sample film preparations. The equilibrium melting points taken from the highest peak and the return to baseline of the endothermic curves showed that the treated samples had lower points than the untreated one. This was due to branching and degradation from the irradiation process. The melting ranges of the treated specimens were shifted to lower values as compared to the untreated specimen, as a consequence of branching and degradation The temperature ranges for the irradiated specimens were broader than the melt range of the untreated sample The α peak also showed broadening as a result of branching

Difficulties in early ice detection with the Small Ice Detector 2 HIAPER (SID-2H) in maritime cumuli

© Copyright 2014 American Meteorological Society (AMS).The Small Ice Detector 2 HIAPER (SID-2H) was used to attempt to detect small ice particles in the early stages of ice formation in the high liquid water environment of tropical maritime cumulus clouds sampled during the Ice in Clouds Experiment - Tropical (ICE-T) field campaign. Its performance in comparison to other probes, and the development of new corrections applied to the data, are presented. The SID-2H detected small ice crystals among larger particles. It correctly identified water drops, and discriminated between round and irregular particle shapes in water-dominated clouds with errors less than 5%. Remaining uncertainties in the sensing volume, and the volume over which coincidence of particles occurred, result in the data being used here in a qualitative manner to identify the presence of ice, its habits and sizes.Peer reviewe

Design of a horizontal neutron reflectometer for the European Spallation Source

A design study of a horizontal neutron reflectometer adapted to the general baseline of the long pulse European Spallation Source (ESS) is presented. The instrument layout comprises solutions for the neutron guide, high-resolution pulse shaping and beam bending onto a sample surface being so far unique in the field of reflectometry. The length of this instrument is roughly 55 m, enabling $\delta \lambda / \lambda$ resolutions from 0.5% to 10%. The incident beam is focussed in horizontal plane to boost measurements of sample sizes of 1*1 cm{^2} and smaller with potential beam deflection in both downward and upward direction. The range of neutron wavelengths untilized by the instrument is 2 to 7.1 (12.2, ...) {\AA}, if every (second, ...) neutron source ulse is used. Angles of incidence can be set between 0{\deg} and 9{\deg} with a total accessible q-range from 4*10^{-3} {\AA}^{-1} up to 1 {\AA}^{-1}. The instrument operates both in {\theta}/{\theta} (free liquid surfaces) and {\theta}/2{\theta} (solid/liquid, air/solid interfaces) geometry. The experimental setup will in particular enable direct studies on ultrathin films (d ~ 10 {\AA}) and buried monolayers to multilayered structures of up to 3000 {\AA} total thickness. The horizontal reflectometer will further foster investigations of hierarchical systems from nanometer to micrometer length scale, as well as their kinetics and dynamical properties, in particular under load (shear, pressure, external fields). Polarization and polarization analysis as well as the GISANS option are designed as potential modules to be implemented separately in the generic instrument layout. The instrument is highly flexible and offers a variety of different measurement modes. With respect to its mechanical components the instrument is exclusively based on current technology. Risks of failure for the chosen setup are minimum.Comment: Matched to the version submitted to Nuclear Instruments and Methods

An Investigation into the Prevalence, Quantification, and Survival of Escherichia coli in Stormwater Basin Sediment of Withers Swash, Myrtle Beach, SC

2012 S.C. Water Resources Conference - Exploring Opportunities for Collaborative Water Research, Policy and Managemen

Reconstructing 3D x-ray CT images of polymer gel dosimeters using the zero-scan method

In this study x-ray CT has been used to produce a 3D image of an irradiated PAGAT gel sample, with noise-reduction achieved using the ‘zero-scan’ method. The gel was repeatedly CT scanned and a linear fit to the varying Hounsfield unit of each pixel in the 3D volume was evaluated across the repeated scans, allowing a zero-scan extrapolation of the image to be obtained. To minimise heating of the CT scanner’s x-ray tube, this study used a large slice thickness (1 cm), to provide image slices across the irradiated region of the gel, and a relatively small number of CT scans (63), to extrapolate the zero-scan image. The resulting set of transverse images shows reduced noise compared to images from the initial CT scan of the gel, without being degraded by the additional radiation dose delivered to the gel during the repeated scanning. The full, 3D image of the gel has a low spatial resolution in the longitudinal direction, due to the selected scan parameters. Nonetheless, important features of the dose distribution are apparent in the 3D x-ray CT scan of the gel. The results of this study demonstrate that the zero-scan extrapolation method can be applied to the reconstruction of multiple x-ray CT slices, to provide useful 2D and 3D images of irradiated dosimetry gels

Quantitative evaluation of polymer gel dosimeters by broadband ultrasound attenuation

Ultrasound has been examined previously as an alternative readout method for irradiated polymer gel dosimeters, with authors reporting varying dose response to ultrasound transmission measurements. In this current work we extend previous work to measure the broadband ultrasound attenuation (BUA) response of irradiated PAGAT gel dosimeters, using a novel ultrasound computed tomography system

Pregnancy Diagnosis in the Ewe

A total 378 ewe lambs were evaluated for signs of pregnancy by five operators using five methods of detection. The methods used were breeding mark, rectal-abdominal palpation, an intrarectal Doppler instrument and two ultrasonic devices, the Scanoprobe and Scanopreg (Model 738) for sheep. Accuracies of pregnancy diagnosis by grease mark were 65.7% in 1976 and 75.5% in 1977 (P\u3c.05) based on lambing results. Accuracy of daignosis for ewe lambs called pregnany or nonpregnany using the recetal-abdominal palpation technique was 62.7%. The overall accuracy on the same ewes using the intrarectal Doppler device was 72.7%. The ewes were examined when they were from 60 to 96 days of gestation using the two rectal probes. Seven ewes died from peritonitis and six aborted following pregnancy detection using the rectal instruments. Accuracy using the Scanoprobe device was 89.1% for ewe lambs which ranged from 69 to 103 days pregnant. The accuracy achieved when the same ewes were evaluated at 78 to 112 days of gestation using the Scanopreg device 94.8%. No injuries occurred following pregnancy detection using the two ultrasonic devices. Ewes called open with the Scanopreg were retested the following day with a 98.8% accuracy rate