Mechano-sorptive creep in wood fibres

In order to investigate the way in which fibre properties affect the mechano-sorptive creep phenomenon in paper, single wood fibres were exposed to tensile stresses at a constant humidity of 80% relative humidity (RH) and in a cyclic humidity environment varying between 80 and 30% RH. Contrary to earlier claims, it was demonstrated that single wood fibres exposed to a cyclic RH show a considerably higher creep than that corresponding to the highest RH experienced in the cycle, i.e., a mechano-sorptive behaviour. The creep strain rate at cyclic humidity was shown to be a function of the creep rate at constant climate, and to be an apparent linear function of the applied stress.     

Deformation of wet wood under combined shear and compression

During refining of mechanical pulp, a process occurring at high speed at temperatures of 140–160°C, the flexibility and bonding ability of wood fibres are increased. To understand the mechanical behaviour of the fibres in this operation, deformations at low speed of wet wood specimens at 50°C were studied under two different combinations of shear and compression loadings. The results were compared with the behaviour of wet wood in pure compression. Some features of the deformation that occurred in earlywood were analysed using an image analysis procedure. During pure compression the cell walls bend independently of the shape of the fibre cells and their cell wall thickness. Under combined shear and compression, however, mainly the corners of the fibre cells get deformed. In a second deformation performed in compression, the fibre cells follow the same deformation pattern as given by the first deformation type whether in compression or in combined shear and compression. The interpretation was that permanent defects in the cells themselves were introduced already in the first load cycle of the wood samples. The load combination with lower shear gave the same permanent strain as the case of pure compression but using less energy.     

Effect of Broken Corn Levels on Water Absorption and Steepwater Characteristics

Broken corn created by grounding sound corn kernels was added back at levels of 0, 4, 8, 12, or 16%, by weight, to whole kernels of three corresponding hybrids: FR27 × FRMo17 (a soft endosperm corn), FR618 × FR600 (amedium‐hard endosperm corn), and FR618 × LH123 (a hard endosperm corn). The samples had been dried from 28% moisture content to 15% moisture content either by using ambient air at ≈25°C or at 110°C. Samples were steeped for 36 hr at 52°C in 0.15% sulfur dioxide and 0.5% lactic acid steeping solution. The steepwater characteristics, such as water absorption, solids and protein content in the steepwater, and steepwater pH, were measured by periodic sampling and analyzed. Broken corn level has a significant effect on the amount of solids released during steeping and steepwater protein content for all samples. Both steepwater solids and protein content increased linearly as broken corn content increased. Corn drying temperature, kernel hardness, and interactions between drying temperature and kernel hardness has a significant effect on steepwater solids and protein content and steepwater pH in both broken and unbroken corn. Corn dried at low temperature released more soluble solids and protein into the steepwater than corn dried at high temperature. Soft endosperm and medium‐hard endosperm corn released more soluble solids and protein into the steepwater than hard endosperm corn. Soft endosperm corn resulted in a higher steepwater pH than medium‐hard and hard endosperm corn. No significant effect of broken corn content on final moisture content of steeped corn and steepwater pH was observed.     

Effect of Various Acids and Sulfites in Steep Solution on Yields and Composition of Corn Fiber and Corn Fiber Oil

The addition of six acids (organic and inorganic) and four sulfite compounds (including gaseous SO₂) during the conventional corn wet‐milling steeping process of two yellow dent corn hybrids were evaluated for the effect on corn fiber yield, corn fiber oil yield, and the composition of three phytosterol compounds (ferulate phytosterol esters [FPE], free phytosterols [St], and phytosterol fatty acyl esters [St:E]) in the corn fiber oil. No significant effect of different sulfite compounds and acids were observed on corn fiber yields. However, a significant effect was observed on corn fiber oil yield and the composition of corn fiber oil for phytosterol compounds. Three of the sulfite compounds (including gaseous SO₂) caused very little effect on the levels of phytosterol compounds compared with the control sample (corn steeped with sodium metabisulfite and lactic acid). However, for one hybrid, ammonium sulfite gave a significantly higher yield of FPE and St:E and had no effect on the yield of St. For the other hybrid, it gave a significantly higher yield of FPE and had no effect on the yield of St and St:E compared with the control sample. This indicates that the effect of these sulfite compounds on yields of these phytosterol compounds in corn fiber oil is probably hybrid‐dependent. No significant effect of acids was observed on corn fiber yields, but significant effects were observed on corn fiber oil yields and yields of phytosterol compounds in the corn fiber oil. The effect also seems to be hybrid‐dependent because different acids affected the two hybrids differently. Overall, it seems that weak acids have a positive effect on increasing the individual phytosterol compounds in the corn fiber. When comparing the effect of experimental acids and sulfites on the two hybrids, acids have a more positive effect than sulfites in increasing the yield of phytosterol compounds in corn fiber oil.     

Wet-Milling Characteristics of Selected Yellow Dent Corn Hybrids as Influenced by Storage Conditions

Three yellow dent corn hybrids (FR1064×LH59, FR600×FR1087, and FR618×LH123HT) from the 1994 crop, one hybrid (FR1064×LH59) from the 1995 crop, and two hybrids (FR1064×LH59 and FR618×LH123HT) from the 1996 crop were used to study the effect of storage time and storage temperature on starch yields. Samples of all of the corn hybrids were stored under one of two conditions: in a 4°C cold room or under a shed exposed to ambient conditions. The hybrids from the 1994, 1995, and 1996 crops were stored for up to 24, 12, and 3 months, respectively. No significant differences were found between starch yields of the hybrids with respect to storage time. However, there was a significant difference in hybrids from the 1994 samples. Starch yields of two of the three corn hybrids (from the 1994 crop) stored in the 4°C cold room were higher when compared to the starch yields of the same hybrids stored at ambient conditions.     

Effect of biobed composition, moisture, and temperature on the degradation of pesticides

Biobeds retain and degrade pesticides through the presence of a biobed mixture consisting of straw, peat, and soil. The effects of biobed composition, moisture content, and temperature on pesticide degradation were investigated in laboratory studies. Straw produced the main microbial activity in the biobed mixtures as strong positive correlations were observed between straw, respiration, and phenoloxidase content. Most pesticides investigated were dissipated by cometabolic processes, and their dissipation was correlated with respiration and/ or phenoloxidase content. More pesticides were more dissipated at biobed moisture levels of 60% water holding capacity (WHC) than at 30% and 90% WHC, while 20 degrees C gave higher dissipation rates than 2 and 10 degrees C. A straw:peat:soil ratio of 50:25:25% v/v is recommended in field biobeds since this produces high microbial activity and low pH, favorable for lignin-degrading fungi and phenoloxidase activity.     

Effect of Steeping with Sulfite Salts and Adjunct Acids on Corn Wet‐Milling Yields and Starch Properties

Two corn hybrids (3394 and 33R87) were steeped with three sulfite salts and five acids to test the effect of sulfur dioxide (SO₂) source and acid sources on wet‐milling yields and starch properties. Milling yields from each treatment were compared with a control sample that was steeped with 2,000 ppm of SO₂ (using sodium metabisulfite) and 0.55% lactic acid. Sulfur dioxide sources were potassium sulfite, sodium sulfite, and ammonium sulfite; acids were acetic, hydrochloric, oxalic, phosphoric, and sulfuric. Starch yields were affected by the SO₂ source and steep acids but the effects were hybrid‐dependent. Different steep acids gave different starch yields when wet milled at the same pH. Among the acids tested, weak acids (lactic and acetic) tended to give higher starch yields compared with strong acids (hydrochloric, sulfuric, phosphoric, and oxalic). Some differences were observed with different sulfite salts and acids on starch pasting properties; however, there were no clear trends.     

Glycoalkaloids of Solanum commersonii Dun. ex Poir

Five glycoalkaloids were identified from the aerial parts of wild Solanum commersonii Dun. ex Poir growing in Uruguay and their structures elucidated mainly by chemical and spectroscopic methods. In addition to the already known commersonine, demissine, tomatine and dehydrocommersonine, a new glycoalkaloid, identified as δ₅-demissine, solanid -5-en-3-O- {β-D-Glcp-(1→2)-[β-D-Xylp-(1→3) ]β-D-Glcp-(1→4)-β-D-Galp } was found. Tomatine and dehydrocommersonine have not been reported earlier as components of this plant. The glycoalkaloid composition found in the wild plants studied differ significatively from those described earlier, and have some implications in taxonomy and its use in potato breeding. This revised version was published online in July 2006 with corrections to the Cover Date.     

Tree communities and structural dynamics in miombo (Brachystegia–Julbernardia) woodland, Tanzania

Tree vegetation and size structure was sampled in a miombo woodland area in E Tanzania and related to environmental factors, particularly soil and disturbance history. A total of 86 tree species was found. Four plant communities were distinguished through multivariate classification. Community 1 was dominated by Brachystegia boehmii, Brachystegia bussei and Julbernardia globiflora, and community 2 by B. boehmii and Brachystegia spiciformis. Community 1 was found on grey, eroded soil and community 2 on red, residual soil, a fact that opens up possibilities to use soil signals of satellite data for vegetation mapping. Community 3 is heavily disturbed miombo woodland near villages and community 4 was found on more clayey soil where miombo woodland is not expected.

At our 42 sampled sites, density ranged from 74 to 1041 individuals ha⁻¹ and basal area from 3.9 to 16.7 m² ha⁻¹. Regeneration is generally good but large sized trees are less prominent in communities 3 and 4 due to harvesting. With reduced disturbance miombo species may rapidly resume dominance in community 3. A higher than expected representation by the size class 30–40 (−50) cm dbh in community 2 is probably related to disturbance history. Prevalence of certain species (Pseudolachnostylis maprouneifolia, Pterocarpus angolensis and Diplorhynchos condylocarpon) may be related to frequent fires. Selective logging will soon cause extinction of Dalbergia melanoxylon, whereas Pterocarpus angolensis still has good regeneration, possibly because individuals below logging size have a good seed set.

A way to get an easy overview of size classes in all species in an area using PCA is discussed.     

Potential leaching of elements in three Danish Spruce forest soils

On three localities in Denmark, all with 40 to 50 yr old Norway spruce plantations, but different soil chemistry, ion balance studies have been implemented in 1983. The annual variations in soil water concentrations of cations and anions are described and the potential annual leaching fluxes are determined by means of zero-tension percolation lysimeters at 2 depths (A- and B-horizon). Leaching of A1 and and heavy metals was much more severe on the acidic sites, whereas especially Ca was leached from the nutrient rich site. In parallel with the high concentrations of Al and heavy metals, great needle loss was observed on the two acidic sites. The maximum leaching from the A-horizon was obtained either in the late summer, associated with the effluent of organic material, or in the winter due to large amounts of percolation water. Apart from low Ca and kin levels of one of the sites, the findings from the two acidic localities were comparable to similar studies in Sweden.