Structure and properties of the Al/SiC composite material

Structure has been studied and the distribution of the filler in the samples of the metal-matrix Al/SiC composite containing 50% SiC has been analyzed. The sizes and shapes of the particles of the filler have been determined; the cohesion of the metallic matrix with the filler has been investigated. The analysis of the mechanism of fracture after tensile tests at 350°C and uniaxial compression of the samples of composite at 300 and 600°C has been carried out.     

Determination of glycerin content of fibre of the impregnation bath

Conclusions A procedure has been developed for determining glycerin in impregnation baths containing from 30 to 40% glycerin by wt., and also for determining glycerin in finished fibre containing from 105 to 125% glycerin based on dry fibre.Translated from Khimicheskie Volokna, No. 4, pp. 57–59, July–August, 1989.     

Ultrasonic and Viscoelastic Properties of Small-Volume Mesogen Samples at the Phase Transition

The ultrasonic method is very informative for research of viscoelastic properties of mesogens at changing thermodynamic parameters of state. At phase transitions, anomalies of the velocity of propagation and coefficient of absorption of ultrasound waves as well as of viscoelastic properties are observed. These anomalies for liquid crystals are most pronounced at frequencies lower that 1 MHz. Up to now acoustic resonators with volumes of about 5 cm³ have been used, which considerably prevents the application of this method for science-based newly synthesized mesogenic compounds. This article presents experimental results obtained by means of a new resonator method with samples with volumes of 0.06 cm³ to 0.15 cm³. The velocity and coefficient of absorption of ultrasound were measured at frequencies from 0.68 MHz to 1.63 MHz for four mesogens: esters of alkyloxyphenylcyclo-hexane-2-carbonic acid and n-amylphenol. It has been shown that temperature dependencies of ultrasonic parameters obtained in small-volume cells correspond to those established previously by traditional methods using measuring cells with larger volumes. It is also shown that the temperature dependencies of the bulk viscosity and the bulk elasticity modulus derived from our ultrasonic measurements, in general features, duplicate the corresponding dependencies obtained by standard methods. It confirms that the proposed acoustic method is suitable for routine investigations of viscoelastic properties of small-volume samples of mesogenic compounds.     

Determination of the Concentration of Polymers in Spinning Solutions for Production of Aromatic Polyamide Fibres

A method was developed for finding the concentration of fibre-forming polymers in spinning solutions based on extraction and subsequent titrimetric determination of the solvent. It was found that the solvent is totally extracted from the spinning solution in most cases only during titration. When an extractant is added to the solution, two related equilibria are established between polymer and solvent and between solvent and extractant. The acid-base interaction between solvent and titrant shifts the equilibrium toward extraction of the solvent from the polymer solution.     

Emission of Volatile Compounds from Apple Plants Infested with <Emphasis Type="Italic">Pandemis heparana</Emphasis> Larvae,Antennal Response of Conspecific Adults,and Preliminary Field Trial

This study investigated the volatile emission from apple (Malus x domestica Borkh., cv. Golden Delicious) foliage that was either intact, mechanically-damaged, or exposed to larval feeding by Pandemis heparana (Denis and Schiffermüller) (Lepidoptera: Tortricidae). Volatiles were collected by closed-loop-stripping-analysis and characterized by gas chromatography-mass spectrometry in three time periods: after 1 h and again 24 and 48 h later. Volatiles for all treatments also were monitored continuously over a 72-h period by the use of proton transfer reaction – time of flight-mass spectrometry (PTR-ToF-MS). In addition, the volatile samples were analyzed by gas chromatography-electroantennographic detection (GC-EAD) using male and female antennae of P. heparana. Twelve compounds were detected from intact foliage compared with 23 from mechanically-damaged, and 30 from P. heparana-infested foliage. Interestingly, six compounds were released only by P. heparana-infested foliage. The emission dynamics of many compounds measured by PTR-ToF-MS showed striking differences according to the timing of herbivory and the circadian cycle. For example, the emission of green leaf volatiles began shortly after the start of herbivory, and increased over time independently from the light-dark cycle. Conversely, the emission of terpenes and aromatic compounds showed a several-hour delay in response to herbivory, and followed a diurnal rhythm. Methanol was the only identified volatile showing a nocturnal rhythm. Consistent GC-EAD responses were found for sixteen compounds, including five aromatic ones. A field trial in Sweden demonstrated that benzyl alcohol, 2-phenylethanol, phenylacetonitrile, and indole lures placed in traps were not attractive to Pandemis spp. adults, but 2-phenylethanol and phenylacetonitrile when used in combination with acetic acid were attractive to both sexes.     

Operation of Centrifugal Compressor as Annular Array of Blading

We demonstrate that the polytropic efficiency of modern centrifugal compressors can be raised to the level reached by axial-flow compressors. We consider systems of circulation flows around the impeller, the flows past the blading of axial and centrifugal compressors. And we make recommendations for the compressor blade design.     

A Breach in Plant Defences: Pseudomonas syringae pv. actinidiae Targets Ethylene Signalling to Overcome Actinidia chinensis Pathogen Responses

Ethylene interacts with other plant hormones to modulate many aspects of plant metabolism, including defence and stomata regulation. Therefore, its manipulation may allow plant pathogens to overcome the host’s immune responses. This work investigates the role of ethylene as a virulence factor for Pseudomonas syringae pv. actinidiae (Psa), the aetiological agent of the bacterial canker of kiwifruit. The pandemic, highly virulent biovar of this pathogen produces ethylene, whereas the biovars isolated in Japan and Korea do not. Ethylene production is modulated in planta by light/dark cycle. Exogenous ethylene application stimulates bacterial virulence, and restricts or increases host colonisation if performed before or after inoculation, respectively. The deletion of a gene, unrelated to known bacterial biosynthetic pathways and putatively encoding for an oxidoreductase, abolishes ethylene production and reduces the pathogen growth rate in planta. Ethylene production by Psa may be a recently and independently evolved virulence trait in the arms race against the host. Plant- and pathogen-derived ethylene may concur in the activation/suppression of immune responses, in the chemotaxis toward a suitable entry point, or in the endophytic colonisation.     

Enantioselective Gas Chromatography in Search of the Origin of Biomolecular Asymmetry in Outer Space

Since the pioneering work of Emanuel Gil-Av and his associates at the Weizmann Institute of Science the direct gas chromatographic resolution of enantiomers has found its application in different fields of natural sciences, even expanding to space research and astrobiology. In these domains the resolution of chiral molecules of prebiotic relevance is of particular interest, since the determination of ratios between l - and d -enantiomers within non-terrestrial samples is assumed to shed light on the origin of biomolecular homochirality and the beginnings of life itself. According to an astrophysical scenario, the first molecular symmetry breaking event occurred upon irradiation of chiral organic molecules with circularly polarized light present in the interstellar medium. To examine this hypothesis, among others, chiral gas chromatographic stationary phases have been widely used to provide the differentiation of enantiomers in extracts of meteorites, samples of simulated interstellar ices and Mars soil analogues. Moreover several chiral capillary columns have been selected for in situ analyses of extraterrestrial organic matter by Mars missions and the cometary Rosetta mission. This review will highlight current advances of enantioselective gas chromatography applied to space science.