Quantitative X-ray microanalysis of hydrogen peroxide within plant cells

Using quantitative X-ray microanalysis in combination with CeCl3-based cytochemical staining of hydrogen peroxide (H2O2) we have developed a new solution for quantification of H2O2 at the subcellular level. Quantitative X-ray microanalysis of plastic-embedded leaves of Populus euphratica Oliv. showed that the obtained cerium precipitates by CeCl3 staining were the mixture of cerium perhydroxides and cerium phosphate, in which the fractions of CePO4 were: (1) 52-74% in cell walls of fresh leaf segments, and (2) 34-70% in the cytoplasm in 10 mM H2O2-treated leaf segments that were previously freeze-dried. Taking the concentration of cerium phosphate as staining background, we reached the cellular concentration of cerium perhydroxides and the corresponding concentration of H2O2. Results showed that H2O2 was present in the cytoplasm of rehydrated leaf segments (29-58 mM), but in fresh leaves, H2O2 was observed in the walls of all measured cell types (17-74 mM).     

Eine Untersuchung zum Einfluss voll verfilterter Messstellen auf die Grundwasserbeschaffenheit

Advantages and disadvantages of fully screened and depth-orientated observation wells in porous aquifers are diversely evaluated in hydrogeological practice. Although guidelines refer to the risk of groundwater mixing downstream of fully screened wells, installation of fully screened wells continues. This paper includes an overview of guidelines for selection of suitable observation wells as well as results from an investigation on the impact of fully screened wells in two observation well installations. These results indicate that, after filling the fully screened wells, the measured groundwater quality changed drastically. The mean nitrate concentrations in the upper layer of the aquifer decreased from 90 to 14 mg/L within six weeks. Building new fully screened wells in porous aquifers is discouraged if vertical flow in the wells cannot be excluded.     

Design and implementation of dynamic near-infrared optical tomographic imaging instrumentation for simultaneous dual-breast measurements

Dynamic near-infrared optical tomographic measurement instrumentation capable of simultaneous bilateral breast imaging, having a capability of four source wavelengths and 32 source-detector fibers for each breast, is described. The system records dynamic optical data simultaneously from both breasts, while verifying proper optical fiber contact with the tissue through implementation of automatic schemes for evaluating data integrity. Factors influencing system complexity and performance are discussed, and experimental measurements are provided to demonstrate the repeatability of the instrumentation. Considerations in experimental design are presented, as well as techniques for avoiding undesirable measurement artifacts, given the high sensitivity and dynamic range (1:10(9)) of the system. We present exemplary clinical results comparing the measured physiologic response of a healthy individual and of a subject with breast cancer to a Valsalva maneuver.     

Investigation on adhesion, interphases, and failure behaviour of cyclic butylene terephthalate (CBT)/glass fiber composites

Interphases exist in hybrid materials and significantly influence their mechanical performance. To find a bridge between the microscopic and macroscopic mechanical properties, this work investigates the microscopic nature of glass fiber surfaces and glass/CBT interphases in terms of topography, fractography, and adhesion properties. The variations in glass fiber surface properties result from the different sizings. Using the single fiber pull-out test, AFM, and ζ potential tests, it is shown that the interfacial bond strengths in CBT resin composites can vary depending on the kind of sizing formulation and properties. The greatest adhesion strength is achieved by aminosilane sizings with epoxy resin film former. The surface roughness of the fibers can be varied by sizings with different content and ζ potential values, which has no significant contribution to interphase adhesion strength from ‘mechanical interlocking’. For the systems with film formers, cohesive failure occurs and similar values of both interfacial adhesion strength, τ_d, and fracture energy release rate, G_ic, are obtained, in which τ_d approaches the shear yield strength of CBT matrix. A further enhancement of interfacial adhesion is limited by the mechanical properties and the non-homogeneous microstructure of CBT resin due to the less-than-perfect CBT polymerization.     

A multimedia speech learning system for the hearing impaired

The lack (or limited amount) of audio feedback for many persons with hearing disabilities greatly reduces the quality of speech development and use. Current methodologies for the teaching speech techniques are relatively primitive, and generally require the active participation of a therapist. This makes essential practice difficult, time consuming, and expensive for the student. However, using multimedia technology, it is possible to amplify the efforts of the teachers and students for improving the quality of speech. This paper presents a multimedia visualization system that augments the limited hearing capabilities of hearing impaired persons using visual and tactile feedback approaches and provides alternate representations of sound for increasing speech capabilities and reduced learning time. The proposed system has the capability of not only decreasing the learning time for many persons, but can also be adopted for teaching young children correct speech patterns through the use of speech learning games based on the system.     

A comparison of the biological properties of of androst-5-en-3β-ol,a series of (20R)-n-alkylpregn-5-en-3β-ols and 21-isopentylcholesterol with those of cholesterol

The Δ⁵-sterol, androst-5-en-3β-ol, which has no side chain at C-17, did not permit molting of the insectHeliothis zea, growth of either the protozoanTetrahymena pyriformis, or the yeastSaccharomyces cerevisiae adapted to anaerobic conditions, nor was the sterol esterified by a mammalian microsomal ACAT preparation. However, the sterol did form a liposome with egg lecithin and, when fed to mice, did inhibit hepatic cholesterol synthesis. 21-Isopentylcholesterol also formed a liposome but neither supported the growth of the yeast nor was metabolized by the protozoan. When sterols, 20(R)-n-alkylpregn-5-en-3β-ols, with side chains of varying lengths were added to the medium of the protozoan, maximal esterification with fatty acids occurred with the 20(R)-n-pentyl derivative, and maximal inhibition of tetrahymanol formation occurred with then-butyl,n-pentyl andn-hexyl derivatives. In all of the assays, cholesterol showed a positive response, either permitting molting or growth, being metabolized, inhibiting sterol or tetrahymanol synthesis, or forming a liposome.