Strain Patterns Across the Root-Stem Transition Zone in Urban Trees

Trees are subjected to mechanical loading during their life span or face premature mortality. The strain resulting from loads intercepted by the canopy and transferred throughout the tree is of significant importance, not only for the survival of the tree, but for the safety and well-being of the human population found in close proximity. To test the function of tree orientation to an applied load, static load tests were conducted on 15 mature pin oak trees (Quercus palustris Muenchh.). We applied the static load tests to tilt the trees 0.1° from natural position. We used a digital image correlation system to map strain in the leeward, windward, and tangential roots in the root-stem transition zone. Results indicate that mean maximum strain magnitudes are similar in the leeward and windward orientations and lower on the tangential orientation. The leeward orientation experienced compressive strain, the windward orientation experienced tensile strain, and the tangential orientation had both tensile and compressive strain. This information provides the arboricultural and plant science sectors with a better understanding of how loading force moves through trees and will further enhance tree risk assessment and root zone management protocols.

Research of Operational Characterizations of Cutting Discs with Oriented Abrasive Grains

Efficiency of the polishing process is determined by the properties of abrasive grains, including its form parameter and orientation in the body of the grinding tool. It is possible to improve the operational characterizations of the grinding instruments, in particular – cutting discs, by ordering of the grain geometry, selection of the rational form and orientation of abrasive grains for specific processing conditions and parameters of the power load. For the solution of such problem the developed and patented method for production of grinding tools with the orientated abrasive grains is offered [1]. According to the specified method the cutting discs with radial and tangential orientation of abrasive grains are made. As a comparative standard, discs without orientation of abrasive grains are made also. Comparative tests by cutting according to the scheme of pressing of workpiece to a disc with a constant effort are carried out. It is established that orientation of abrasive grains significantly influences the operational characterizations of cutting discs. So, the cutting ability of cutting discs with radial orientation of abrasive grains is 15-17% higher during processing of various materials, than at standard tools. The grinding coefficient of cutting discs with tangential orientation of abrasive grains is 25-29% higher, than at usual discs with non-oriented grains. Results of an assessment of effective power of cutting in addition confirm that discs with the radial orientation of grains are working with the greatest intensity and at the same time with biggest wear. Further, on decrease, cutting discs with non-oriented grains follow. Instruments with tangential orientation of abrasive grains are characterized by the smallest cutting ability and the smallest wear. Such effect is caused by that the radial focused abrasive grains possess the greatest sizes of forward corners, and tangential focused grains possess the smallest sizes. It is established also that application of cutting discs with radial orientation of abrasive grains in comparison with ordinary tools allows to reduce temperature in a cutting zone by 20-30 °C and to reduce the size of zones of thermal influence.

Influence of chemical treatments on moisture-induced dimensional change and elastic modulus of earlywood and latewood

To better understand the performance of bonded, coated, and modified wood, knowledge of how these processes alter the dimensional change and mechanical properties of wood at a given moisture content (MC) are important. These localized influences on earlywood (EW) and latewood (LW) properties are not well understood. In the present study, the influence of chemical treatments by hydroxymethylated resorcinol (HMR) and acetylation on moisture-induced dimensional change and longitudinal modulus of elasticity (MOE) of isolated EW and LW specimens of Loblolly pine (Pinus taeda L.) was evaluated. The dimensional change was not altered by the HMR treatment, whereas acetylation lowered it by ∼50% in EW and LW in both radial and tangential directions. The MOE was not influenced by the two chemical treatments tested. Based on results of swelling, shrinkage, and MOE it can be concluded that chemical treatment does not modify EW selectively compared with LW neither in radial nor in tangential orientation.

Perithecium growth and expansion in Chaetomium globosum

The development of the perithecium of Chaetomium globosum has been studied by light and transmission electron microscopy. During all developmental stages the growth and expansion seem to be caused by the growth and enlargement of actively growing hyphae in an apical growth region. This growth region, at a later stage, also gives rise to the ostiole. The perithecial cavity is formed by the autolysis of hyphae in the inner growth region and in the hymenium. The possibility that the perithecial expansion is caused by volume increase of the hyphae in the lower parts of the growth region is discussed. The ostiole seems to be opened by the action of an inner pressure caused by the hymenial growth. The tangential orientation of the inner peridial cells and the cells lining the centrum is caused by displacement of cells from the growth axis and by perithecial unfolding.

Freezing of Water Drops

Investigations were made of the ice structures, air-bubble size distributions, and heat exchanges of water drops frozen freely-floating in the purified air of a vertical wind tunnel. Drop diameters varied from 1 to 8 mm, air temperature from −1 to −18.5°C; the ice phase was initiated artificially. It was found that the mass of ice in a freezing drop increases linearly with time. Both mean air bubble and crystal sizes decrease in a regular fashion as the air temperature decreases, whereas the bubble concentration increases. Histograms show a preferred tangential orientation of the projections into the plane of observation of the crystallographic hexagonal axis (c′-axes), a preference which weakens as the temperature decreases.