Convex Ends Research Articles

Changes of plasmolysis form in epidermal cells of Hordeum vulgare infected by Erysiphe graminis: evidence for increased membrane–wall adhesion

When coleoptile epidermal tissues of Hordeum vulgare were plasmolyzed with α-methylglucose or mannitol, 24–72 h after inoculation with Erysiphe graminis f. sp. hordei, host protoplasts tended to pull away from one or more sites on longitudinal host cell walls producing a concave pocket at each site. This contrasted with the usual convex form of plasmolysis in uninfected tissue in which protoplasts pulled from the short transversal end walls of host cells forming protoplasts with convex ends. The tendency for concave plasmolysis encompassed entire inoculated areas at 5 colonies/mm2 and above. The concave response occurred in coleoptiles inoculated 7–12 days after planting, but not in ones inoculated at 5 days. It occurred in four of five barley lines tested at 48 h postinoculation. Treatment before plasmolysis with 10 mM Ca2+ promoted the disease-induced concavities; treatment with 15 mM K+ partially inhibited them. The concave form in plasmolyzed infected tissue was changed to the convex form by addition of 250 μM octylguanidine to the plasmolyticum or by replacement of α-methylglucose with isosmolar urea or methyl urea solutions. The results suggest that Erysiphe graminis infection increased adhesion of the host plasmalemma to the cell wall, probably as a consequence of change in membrane structure and bridging by Ca2+ ions.

A Buried Pipe System for Controlling Erosion and Sediment Loss on Irrigated Land

AbstractA new system comprised of a buried pipe, with riser inlets from the surface at intervals, along the lower end of furrow‐irrigated fields was designed, installed, and evaluated on 21 fields to determine its effectiveness as an erosion and sediment loss control system for irrigated land. The system utilizes small sediment collection ponds with the riser inlets from the buried pipe serving as overflow outlets for the ponds. This system corrects convex‐shaped field ends caused by erosion and solves an energy related erosion problem common on furrow‐irrigated land. During the first season, these system removed from 80 to 95% of the sediment from runoff water and collected from 4.1 to 40.5 Mg ha−1 from 12 fields on irrigated land where detailed data were collected. All systems performed without problems and all convex end problems except one were corrected the first season. After the convex ends are corrected, the system continues to reduce sediment loss. This new system eliminates the tailwater ditch, puts more land into crop production, reduces weed problems, and prevents the usual problems associated with a wet tail‐water ditch. The buried pipe erosion and sediment loss control system is a major advance in the control of erosion and sediment loss on irrigated land.

Investigation of internal friction in fused quartz, steel, plexiglass, and westerly granite from 0.01 to 1.00 Hertz at 10−8 to 10−7 strain amplitude

A detailed evaluation on the method of internal friction measurement by the stress‐strain hysteresis loop method from 0.01 to 1 Hz at 10−8 to 10−7 strain amplitude and 23.9°C is presented. Significant systematic errors in relative phase measurement can result from convex end surfaces of the sample and stress sensor and from end surface irregularities such as nicks and asperities. Preparation of concave end surfaces polished to optical smoothness having a radius of curvature >3.6×104 cm reduces the systematic error in relative phase measurements to <(5.5±2.2)×10−4 radians. The values of QE−1 (internal friction under uniaxial compression) determined from the relative phase measurements are |QE−1–Qs−1|< 2.8×10−3 for the tool steel sample and |QE−1–Qs−1|< 2.2×10−3 for the Westerly granite sample, where Qs−1 is the internal friction of the fused quartz stress sensor under uniaxial compression. These values are consistent with those inferred from the relative modulus dispersion data also presented in this paper. The polymethyl methacrylate (PMM, trade name Plexiglass) sample shows high values of internal friction (QE−1 ≅5×10−2) with strong frequency dependence and with a maximum in QE−1 at ≅0.4 Hz.

The shape of smooth objects and the way contours end.

It is shown, by elementary mathematical reasoning, that visual contours can only be concave at their endpoints. This simple natural fact is contrasted with general mannerisms of draftsmen: in the great majority of cases contours are drawn to have convex ends. It is argued that this results from our general concept of solid shapes: a general shape is conceived of as a conglomerate of convex (‘ovoid’) elementary shapes, these shapes act as ‘figure’ and the way they are glued together is treated as the—relatively unimportant—‘ground’. The hypothesis is supported through citations from academic-art literature. An attempt is made to give a geometrical specification of just what draftsmen draw if they disregard the contour.

Heterodera Solanacearum N. Sp., a Parasite of Solanaceous Plants 1)

Heterodera solanacearum n. sp. in the Piedmont region of Virginia is described as a parasite of solanaceous plants. It is distinguished in the female by the angle (d) between the stylet and the anterior face of the dorsal knob of approximately 108° ; by the fenestra which is barrel-shaped with convex ends; and an average Granek's ratio of 2.2. The breadth of the grooves of the posterior cyst wall is highly variable with the greatest breadth equal to or usually greater than breadth of adjacent ridge. The color of young cysts formed from the yellow females is equivalent to Munsell's 2.5 yellow-red hue and a 6/12 light strength/chroma notation.

Al Wusail. Mesolitiske Flintpladser i Qatar

Al Wusail. Mesolitiske Flintpladser i Qatar