Mechanisms of Hydroquinone-Induced Growth Reduction in Leafy Spurge

Field observations indicate leafy spurge (Euphorbia esula) is inhibited by the presence of Antennaria microphylla. Hydroquinone (HQ), one of several compounds isolated from A. microphylla has been shown to inhibit leafy spurge seed germination, root elongation, and callus culture growth. The present study was designed to analyze the effects of HQ on water relations and photosynthesis of leafy spurge. Plants grown in 0.25 mM HQ had consistently higher leaf diffusive resistance and lower transpiration rates than control plants (P < 0.05). Chlorophyll fluorescence was significantly lower than controls (P < 0.05) towards the end of the treatment period. At the end of the treatment, tissue from 0.25 mM HQ plants had higher levels of ¹³C, indicating there had been a sustained interference with stomatal function. These data suggest that a disruption of the plant water balance is one mechanism of leafy spurge inhibition by A. microphylla.     

The fatty acids and glycerides of babassu oil

Summary The fatty acids of babassu oil were determined quantitatively by the ester fractionation procedure. The values found in molar percentages were: caproic 0.3, caprylic 7.1, capric 8.3, lauric 47.3, myristic 14.5, palmitic 7.1, stearic 2.0, arachidic 0.1, oleic 12.2, and linoleic acid 1.1. Confirmatory evidence for the presence of linoleic acid was obtained by the isolation of one of its characteristic derivatives, tetrabromostearic acid, m.p. 115°C. A similarity in fatty acid composition was shown between babassu oil and seed fats of other members of the Palmae family. The molar proportion of trisaturated glycerides found in babassu oil (67.3%) was close to the proportion calculated (65.2%) on the assumption that all of the acids in babassu oil were distributed at random. Likewise, the determined fatty acid analysis of the trisaturated glycerides was a first approximation of the analysis calculated on the basis of complete random distribution of the component acids of the whole fat. This work was accomplished as part of a research program supported by a grant from the Buhl Foundation. A sample of babassu oil was furnished by the National Products Company, Harrison, New Jersey, through the courtesy of Mr. Roland Kapp.     

Mechanical/physical characteristics of polymer mortar recycled from rapid-chilled steel slag

In order to recycle rapid-chilled steel slag, 20 different specimens in total were prepared using varied replacement ratio of steel slag and the added quantity of polymer-binder. The performance of these specimens were then examined by compressive strength test, flexural strength test, absorption test, hot water resistance test, measurement of pore distribution and observation of micro-structures using scanning electron microscope (SEM). Results showed that compressive strength and flexural strength increased significantly while absorption ratio significantly decreased as more polymer-binder and steel slag were added. Hot water resistance test showed significant decrease in compressive strength and flexural strength but significant increase in pore volume and porosity. SEM observation of structure before hot water resistance test revealed very compact infusion of structure but decomposition or thermal degradation appeared in polymer-binder when observed after the hot water resistance test.     

Experimental study on the plastic rotation capacity of reinforced high strength concrete beams

This paper describes an experimental study on the plastic rotation capacity of reinforced high strength concrete beams. Thirty-six beams with various compressive strengths of concrete, tensile reinforcement ratios, compressive reinforcement ratios, and patterns of loading (1 point loading and 2-point loading) were tested to evaluate the plastic rotation capacity, extreme fiber concrete compressive strain and equivalent plastic hinge length, etc. The same quantities were also obtained from numerical analysis and compared with experimental data. According to the results, the yield curvatures obtained from experiments turned out to be quite close to those obtained from theoretical approach. However, the experimental results for ultimate curvatures were significantly larger than those of theoretical prediction based on the assumption of ε_cu=0.003. Based on these observations, a new formula for ultimate strain is proposed for high strength concrete beams. Also the test results for plastic rotation capacity were found to be closer to those obtained using moment-curvature relationship considering tension stiffening of concrete and shear effect than those obtained using equivalent plastic hinge length. This substantiates that for accurate evaluation of plastic rotation capacity the consideration of tension stiffening of concrete and shear effect is most important.     

Search for a wetting layer in thin film growth of para-hexaphenyl on KCl(001)

The non-existence of a strongly bound wetting layer for the system para-hexaphenyl (6P)-KCl(001) was verified by thermal desorption spectroscopy (TDS) and X-ray photoelectron spectroscopy (XPS). The 6P films were grown by physical vapour deposition under ultrahigh vacuum conditions at 400 K. TDS showed just a single desorption peak even down to a coverage of 0.1 nm mean film thickness. The heat of evaporation for 6P was determined to 2.3 eV. From the change of the XPS K2p substrate signal as a function of the mean film thickness one can conclude that a strong de-wetting exists at the very beginning of the 6P layer growth at 400 K. Additional investigations with atomic force microscopy reveal that at this initial stage the film grows in a form of needle like islands with a high aspect ratio and subsequently terraced mounds of 6P are formed. No dissociation of 6P on KCl was observed.     

Compact integrated diversity antenna for wireless communications

We introduce a compact integrated antenna that has two feed ports with more than 20 dB isolation between them. The significance of the design is that it can be utilized in compact wireless communication handsets to provide diversity signals or act as a duplexer allowing the receive and transmit signals to be well isolated. The antenna design is based on merging two patch antennas together in combination with capacitive loading so that a compact design can be obtained. Justification for the design is provided by considering the mutual coupling using the reaction principle and finite-dimensional time-domain (FDTD) simulations. Experimental results are also presented for a design that operates in the 2100-2200 MHz band for possible application in forthcoming third-generation wireless systems. Results include radiation patterns, S-parameters, and signal correlations between ports so that the diversity performance and isolation characteristics of the antenna can be demonstrated. These show that in typical wireless environments envelope cross correlations of less than 0.1 between the ports are obtained     

Dependence of thermo-mechanical and mechanical properties of novel fluorophosphate glass on various rare earth dopants

The dependence of thermo-mechanical, and mechanical properties on various rare earth dopants (RE) including Nd₂O₃, Er₂O₃, and Yb₂O₃ in 0.4MgF₂-0.4BaF₂-0.1Ba(PO₃)₂-0.1Al(PO₃)₃ glasses (MBBA system) is systematically investigated. MBBA system doped with RE dopants presented the potential application in the field of communication and high power layer system in the previous reports. In this work, it is found that the density of the doped glass increases with an increasing of RE concentration, which could be understood in terms of cationic field strength (CFS) effect. The Knoop hardness is found to decrease with the loading time and dopant concentration due to the indentation size effect (ISE) effect. The observed decrease of thermal expansion coefficient and the increase of glass transition temperature T _g with increasing dopant concentration are elucidated in terms of the increasing number of strong covalent bonds with increasing RE dopant concentration. Those results will be of paramount importance before designing optical devices.