On the distribution of tree growth stresses

Summary A plane strain pure bending model is used to predict stress states in a transversely isotropic cylinder due to asymmetric strain distributions continuously induced at the periphery. A general solution for the stress states related to each component of the strain distribution expanded in a Fourier series is given. An expression for the change of curvature due to each new growth increment is derived.This work was supported in part by NSF Grant ENG 74-02428.     

Application of the SB distribution to the prediction of concomitant wood properties

Summary It is frequently the case that multiple strength properties of structural wood members are simultaneously needed in design or research. A method has been developed to predict the probability distribution of concomitant material properties of wood from a knowledge of some correlated, nondestructive material property. The method developed in this study is based on properties of the univariate S_B distribution and the bivariate S_BB distribution. The technique involves a priori knowledge of the correlation relationship between a nondestructive parameter and the strength parameter for the two concomitant properties in question. A relationship is developed between the two nondestructive parameters and a simulation procedure is presented to predict either concomitant property from a single nondestructive measurement. The results showed that when a single parameter was predicted directly from a correlated variable, the simulated and experimental distributions were very similar (average error 3–4%). This result confirms previous findings. For the prediction of the concomitant property from an indirect relationship with another parameter, the absolute value of the average error was about 13%.     

Alley cropping Sesbania sesban (L) Merill with food crops in the highland region of Rwanda

Food production in the densely populated Rwandan highlands is impeded by soil erosion and loss in fertility. Alley cropping leguminous shrubs with food crops on contours is purported to minimize the problem and to provide wood and forage. This study reports the effect of Sesbania prunings plus moderate levels of N and P on bean (Phaseolus sp) and maize (Zea mays) yields in alley cropping. Experimental design was a randomized complete block with split-split plots. Main plots were alley width: 2, 4, 6 and 8 m. Phosphorus (P) at 0, 30 and 60 kg P₂O₅/ha occupied the subplot and nitrogen (N) at 0, 30 and 60 kg/ha were assigned at the sub-sub plot level. No P was applied to maize during the second cropping season. Crop yield in kg/ha included the land space taken by hedgerows. Bean yield in 6 m alleys (1100 kg/ha) was about twice that in 2 m alleys (500 kg/ha). Bean responded to N and P. Optimum alley width and N for bean yield were 6 m and 30 kg/ha, respectively. Cuttings from alley hedgerows provided stakes for climbing beans. Maize responded to N but not to residual P. The highest maize yield came from 8 m alleys with 40 kg/ha, but yields from 8 and 6 m alleys with the same N treatment were not significantly different. Maize plants in middle rows were significantly taller than plants in rows adjacent to hedgerows. Maize rust development showed significant alley width and row position effect. There were significantly fewer uredinia in the Sebania alleys relative to the control plots without shrub hedgerows. Rust development on maize in middle rows was significantly greater than development in border rows.     

Manna

Zusammenfassung Es wird ein Überblick sowohl über die Geschichte der Manna-Kunde als auch über den neuesten Stand der Erkenntnisse über die Erzeugung und Verwendung von Manna gegeben. Manna sind süße Ausscheidungen von Insekten (Blattläuse, Schildläuse, Blattflöhe, Käfer) und bestimmte Süßstoffe aus Pflanzen (Pilze, Flechten, Bäume). Das im 2. Buch Moses genannte Brot vom Himmel in der Wüste Sinai ist ein Schildlaus-Manna, vor allem vonTrabutina mannipara Ehr. an Tamariske (Tamarix nilotica) gewesen. Die größte Bedeutung als Nahrung oder Medizin für den Menschen hat Aphiden-Manna.

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Manna

A view is given as well of the former understanding about manna as of the newest knowledge of production an utilization of manna. This term stands for sweet exsudations coming from insects (Aphidida, Coccida, Psyllida, Coleoptera) or from plants (fungi, lichens, trees). The bread dropped from the sky in the Sinai desert as described in the Bible has been a manna produced by coccids particularTrabutina mannipara Ehr. on tamarisk (Tamarix nilotica). Most important as food or medicine for men is the aphid manna.

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