Seven-pinhole tomography of the thyroid

In this paper we introduce a new application of the sevenpinhole (7P) collimator: tomographic imaging of the thyroid. The collimator design has been reoptimized for this particular application by diminishing the distance from the collimator plate to the crystal and by choosing a smaller pinhole diameter. To reconstruct thyroid images from the two-dimensional projection data we use a method which we developed for 7P tomographic imaging of the heart [1]. Phantom experiments and patient studies demonstrate that this new device is capable of producing tomographic images of good quality and high resolution. Therefore, it seems to offer a promising alternative to conventional planar imaging of the thyroid (using a single-pinhole collimator).     

Time-coded aperture tomography: experimental results

In this paper, we discuss the applicability of a time-coded aperture system especially designed for thyroid tomography on the basis of phantom experiments. Our studies show that 1) the quality of the reconstructions is high (e.g., a cold spot of 6 mm diameter in a thyroid phantom can easily be detected), and 2) the reconstruction can be carried out in less than 11 min on a standard 16 bit minicomputer (HP1000). It is therefore concluded that the clinical potentiality of the device is good.     

Characterizing steel tube for hydroforming applications

With the increased use of tubular steel products, especially for hydroforming applications, it is important to be able to predict the performance of tube from sheet tensile tests. In the present study, two aluminum killed draw quality (AKDQ) steels and one high strength low alloy (HSLA) steel were evaluated. Tensile properties and plastic strain ratios were measured on sheet material in the longitudinal and transverse directions. Axial tensile tests were performed on material extracted from production tubes. Material from quasi tubes, which are strip material bent to the same curvature as the tubes but not welded or sized, was also tested. Residual stresses in the production and quasi tube were determined by displacement methods. A hydraulic burst test was performed on the production tubes to simulate a hydroforming operation. Effective strains resulting from tubemaking are calculated for two discrete operations: bending and sizing. For the production tubes, a linear relationship was found between a load factor (strength times thickness) and effective sizing strain. The relationship between load factor and residual stress was also linear. Predictions of the maximum pressure and the strain at instability during a hydraulic burst test are shown to compare favorably with experimental values, based on flat sheet properties and tubemaking strains. The prediction of the yield strength in the tube based on flat sheet properties is shown to be fairly accurate when the effective sizing strain is small compared to the effective bending strain.     

High resolution STEM/EDX spectral imaging to resolve metal distributions within ∼100 nm combustion generated ash particles

Ultrafine ash particles play an important role in establishing a sticky inner deposit layer on heat transfer surface for power plants, but it is still unclear whether a thin surface alkali coating on these ultrafine particles might control this deposition behavior. In this research, we used a high resolution FE-TEM/STEM equipped with twin SDD EDX detectors for high X-ray detection efficiency, to determine the presence and absence of surface enrichment of alkali metals on ultrafine solid fuel ash samples that had low bulk alkali compositions but high deposition rates. Results from two types of combustion generated nano-sized ash particles are presented. One was from the oxy-combustion of pulverized bituminous coal, the other from oxy-combustion of pulverized rice husks, both being burned in a 100?kW rated down-flow laboratory combustor. Elemental mapping results from STEM/EDX uncovered some surface enrichment of alkali metals in ultrafine ash particles, where it existed, as it did for combustion of rice husks. However, it was not able to discern similar alkali metal surface enrichment for the bituminous coal ultrafines that had resulted in even higher deposition rates. Since deposition rates from both of these cases lie on the same correlation with PM₁, one can conclude that although surface enrichment of alkali metals is present for some ～100?nm particles, it is not a prerequisite to achieve high inner surface deposition rates. This is in contrast to prevailing theories that point to alkali metals as “bad actors” as far as the sticky inner deposition rate is concerned.

Copyright © 2019 American Association for Aerosol Research     

Effect of iridoid glycoside content on oviposition host plant choice and parasitism in a specialist herbivore

The Glanville fritillary butterfly Melitaea cinxia feeds upon two host plant species in Å land, Finland, Plantago lanceolataand Veronica spicata, both of which produce iridoid glycosides. Iridoids are known to deter feeding or decrease the growth rate of many generalist insect herbivores, but they often act as oviposition cues to specialist butterflies and are feeding stimulants to their larvae. In this study, two iridoid glycosides (aucubin and catalpol) were analyzed by micellar electrokinetic capillary chromatography. We measured the spatial and temporal variation of iridoid glycosides in natural populations of the host plants of M. cinxia. We also analyzed the aucubin and catalpol content in plants in relation to their use by ovipositing females, and in relation to the incidence of parasitism of M. cinxia larvae in natural populations. The mean concentrations of aucubin and catalpol were higher in P. lanceolata than in V. spicata, and catalpol concentrations were higher than aucubin concentrations in both host species. Plantago lanceolata individuals that were used for oviposition by M. cinxia had higher aucubin concentrations than random plants and neighboring plants. Additionally, oviposition and random plants had higher catalpol concentrations than neighboring plants, indicating that ovipositing females select for high iridoid glycoside plants or that oviposition induces iridoid glycoside production in P. lanceolata. Parasitism by the specialist parasitoid wasp Cotesia melitaearum occurred most frequently in larval groups that were feeding on plants with low concentrations of catalpol, irrespective of year, population, and host plant species. Therefore, parasitoids appear to avoid or perform poorly in host larvae with high catalpol content.     

On the Predominant Electron-Donicity of Polar Solid Surfaces

The reasons for the predominant electron-donicity of almost all solid polar surfaces and its implications are discussed in this paper. By contact angle or interfacial tension measurements, the electron-accepting as well as the electron-donating properties of polar liquids can be ascertained, through the interplay between their energies of adhesion and cohesion. For the solid-liquid interface, direct interfacial tension measurements are not possible, but indirectly, solid/liquid interfacial tensions of polar systems can be obtained by contact angle measurement. However, as the energy of cohesion of a solid does not influence the contact angle formed by a liquid drop placed upon its surface, one can only measure the solid surface'ks residual polar property, manifested by the energy of adhesion between solid and liquid. This residual polar property is of necessity the dominant component; in most cases this turns out to be its electron donicity. When, by means of contact angle measurements with polar liquids, both electron-accepting and electron-donating potentials are found on a polar solid, it is most likely still partly covered with a polar liquid: usually water. The amount of residual water of hydration of a polar solid follows from its polar (Lewis acid-base) surface tension component (γ^AB). The degree of orientation of the residual water of hydration on a polar solid can be expressed by the ratio of the electron-donating to electron-accepting potentials (γ^⊖/γ^⊕), measured on the hydrated surface.     

Effects of bile salts on rat hepatic acyl CoA:Cholesterol acyltransferase

Acyl CoA:cholesterol acyltransferase (EC2.3.1.26, ACAT), responsible for intracellular esterification of cholesterol, may play an important role in cholesterol trafficking within the cell, and thus, in maintenance of cellular cholesterol homeostasis. Bile acids are potential regulators of cholesterol trafficking in the liver. Therefore, the effect of bile salts on hepatic ACAT activity was studied in the perfused rat liver. ACAT activity was increased after liver perfusion with either taurocholate or taurochenodeoxycholate. However, addition of these bile salts at physiological concentrationsin vitro had little effect on microsomal ACAT activity. The increase in hepatic ACAT activity due to perfusion with bile salts was accompanied by reduced accumulation of very low density lipoprotein cholesterol in the perfusate, but there was no effect on 3-hydroxy-3-methylglutaryl-CoA reductase activity. Hepatic ACAT activity was decreased after bile diversion for four hours in the intact animal. This treatment had no statistically significant effect on 3-hydroxy-3-methylglutaryl-CoA reductase activity. These data suggest that bile salts induce changes in hepatic compartmentation and traffic of cholesterol within the hepatocyte accompanied by response of ACAT activity to maintain cellular cholesterol homeostasis.     

Reaction kinetics modeling and thermal properties of epoxy–amines as measured by modulated‐temperature DSC. II. Network‐forming DGEBA + MDA

Reaction‐induced vitrification takes place in the network‐forming epoxy–amine system diglycidyl ether of bisphenol A (DGEBA) + methylenedianiline (MDA) when the glass‐transition temperature (T_g) rises above the cure temperature (T_cure). This chemorheological transition results in diffusion‐controlled reaction and can be followed simultaneously with the reaction rate in modulated‐temperature DSC (MTDSC). To predict the effect of T_cure and the NH/epoxy molar mixing ratio (r) on the reaction rate in chemically controlled conditions, a mechanistic approach was used based on the nonreversing heat flow and heat capacity MTDSC signals, in which the reaction steps of primary (E_1OH = 44 kJ mol^?1) and secondary amine (E_2OH = 48 kJ mol^?1) with the epoxy–hydroxyl complex predominating. The diffusion factor DF as defined by the Rabinowitch approach expresses whether the chemical reaction rate or the diffusion rate determines the overall reaction rate. A model based on the free volume theory together with an Arrhenius temperature dependency was used to calculate the diffusion rate constant in DF as a function of conversion (x) and T_cure. The relation between x, r, and T_g, needed in this model, can be predicted with the Couchman equation. An experimental approximation for DF is the mobility factor DF* obtained from the heat capacity signal at a modulation frequency of 1/60 Hz, normalized for the effect of the reaction heat capacity in the liquid state and the change in C_p in the glassy region with x and T_cure. In this way, an optimized set of diffusion parameters was obtained that, together with the optimized kinetic parameters set, can predict the reaction rate for different cure schedules and for stoichiometric and off‐stoichiometric mixtures. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2814–2833, 2004     

Non-isothermal laminar pipe flow — II. Experimental

In a previous article [1] theoretical predictions of velocity distributions, pressure drops and mean Nusselt-numbers are given for non-isothermal pipe flow of power-law fluids having a temperature dependent consistency-index. In the present investigation these solutions are checked for Newtonian fluids with extensive experimental data.A flow visualization technique was used for measuring the non-isothermal, laminar velocity profiles of glycerol in a round tube. Furthermore, accurate pressure drop measurements were carried out for non-isothermal tube flow of a viscous. Newtonian liquid. Finally logarithmic mean heat transfer coefficients were measured in laminar flow heat transfer.The experimental velocity profiles, pressure drops and heat transfer coefficients show a good agreement with those predicted theoretically.     

Softening and melting mechanisms of polyamides interfering with sliding stability under adhesive conditions

The thermal stability of polymers is a main issue when used as friction elements under dry sliding. Cast polyamide grades processed with either natrium or magnesium catalysors are slid on a small-scale and a large-scale test configuration to reveal the effect of softening or degradation on the sliding stability and to investigate possibilities for extrapolation of friction and wear rates between both testing scales. The combination of softening and afterwards transition into the glassy state is detrimental for the sliding stability of natrium catalysed polyamides, characterised by heavy noise during sliding. A transfer film formed under continuous softening also provides high friction. Melting during initial sliding is necessary for stabilisation in both friction and wear, and eventual softening of a molten film near the end of the test then not deteriorates the sliding stability. Softening of magnesium catalysed polyamides is favourable for the formation of a coherent transfer film resulting in more stable sliding than natrium catalysed polyamides. The differences in softening mechanisms of both polyamide grades is correlated to structural changes investigated by thermal analysis and Raman spectroscopy: the γ crystalline structure prevails in magnesium catalysed samples and the α crystalline structure is predominant in natrium catalysed samples. For internal oil lubricated polyamides, a time dependent degradation of the polyamide bulk deteriorates the supply of internal oil lubricant to the sliding interface, resulting in high friction and wear under overload conditions. As the degradation mechanisms during sliding are strongly correlated to the test set-up, extrapolation is only possible for friction in a limited application range, while wear rates cannot be extrapolated.