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  • Springer  (61,397)
  • American Association for the Advancement of Science (AAAS)  (2,572)
  • American Chemical Society (ACS)
  • Springer Science + Business Media
  • 1995-1999
  • 1990-1994  (63,969)
  • 1991  (63,969)
Collection
Keywords
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  • 1995-1999
  • 1990-1994  (63,969)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Confocal laser scanning microscopy of fluorescently stained wood cells: a new method for three-dimensional imaging of xylem elements (1991)
    Springer
    Trees 5 (1991), S. 1-4 
    Details
    ISSN: 1432-2285
    Keywords: Confocal laser scanning microscopy ; Wood cell structure ; Three-dimensional imaging ; Lignification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Xylem cells were fluorescently stained with periodic acid — Schiff reaction or with Schiffs reagent alone and studied by confocal laser scanning microscopy. Single images with extremely low depth of focus, series of optical sections, computed stereo scopic images and “shadow casting” images as well as x-z images are obtained. In contrast to scanning electron microscopy, not only are the surfaces imaged, but elements concealed by other structures can be visualized by this system. Quantitative data on cell depth are provided and differences in lignification are detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225328
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  • 2
    Electronic Resource
    Electronic Resource
    Impairment of gas exchange and structure in birch leaves (Betula pendula) caused by low ozone concentrations (1991)
    Springer
    Trees 5 (1991), S. 5-13 
    Details
    ISSN: 1432-2285
    Keywords: Ozone ; Betula pendula ; Leaf gas exchange ; Leaf structure ; Senescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Injury caused by low O3 concentrations (0, 0.05, 0.075, 0.1 μl 1-1) was analyzed in the epidermis and mesophyll of fully developed birch leaves by gas exchange experiments and low-temperature SEM: (I) after leaf formation in O3-free and ozonated air, and (II) after transferring control plants into ozonated air. In control leaves, autumnal senescence also was studied in O3-free air (III). As O3 concentration increased, leaves of (I) stayed reduced in size, but showed increased specific weight and stomatal density. The declining photosynthetic capacity, quantum yield and carboxylation efficiency lowered the light saturation of CO2 uptake and the water-use efficiency (WUE). Carbon gain was less limited by the reduced stomatal conductance than by the declining ability of CO2 fixation in the mesophyll. The changes in gas exchange were related to the O3 dose and were mediated by narrowed stomatal pores (overriding the increase in stomatal density) and by progressive collapse of mesophyll cells. The air space in the mesophyll increased, preceded by exudate formation on cell walls. Ozonated leaves, which had developed in O3-free air (II), displayed a similar but more rapid decline than the leaves from (I). In senescent leaves (III), CO2 uptake showed a similar decrease as in leaves with O3 injury but no changes in mesophyll structure and WUE. The nitrogen concentration declined only in senescent leaves in parallel with the rate of CO2 uptake. A thorough understanding of O3 injury and natural senescence requires combined structural and functional analyses of leaves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225329
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  • 3
    Electronic Resource
    Electronic Resource
    Ammonium and nitrate uptake rates and rhizosphere pH in non-mycorrhizal roots of Norway spruce [Picea abies (L.) Karst.] (1991)
    Springer
    Trees 5 (1991), S. 14-21 
    Details
    ISSN: 1432-2285
    Keywords: Ammonium ; Calcium ; Nitrate ; Picea abies ; Rhizosphere pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Relationships between root zone temperature, concentrations and uptake rates of NH 4 + and NO 3 − were studied in non-mycorrhizal roots of 4-year-old Norway spruce under controlled environmental conditions. Additionally, in a forest stand NH 4 + and NO 3 − uptake rates along the root axis and changes in the rhizosphere pH were measured. In the concentration (Cmin) range of 100–150 μM uptake rates of NH 4 + were 3–4 times higher than those of NO 3 − The preference for NH 4 + uptake was also reflected in the minimum concentration (Cmin) values. Supplying NH4NO3, the rate of NO 3 − uptake was very low until the NH 4 + concentrations had fallen below about 100 μM. The shift from NH 4 + to NO 3 − uptake was correlated with a corresponding shift from net H+ production to net H+ consumption in the external solution. The uptake rates of NH 4 + were correlated with equimolar net production of H+. With NO 3 − nutrition net consumption of H+ was approximately twice as high as uptake rates of NO 3 − In the forest stand the NO 3 − concentration in the soil solution was more than 10 times higher than the NH 4 + concentration (〈100 μM), and the rhizosphere pH of non-mycorrhizal roots considerably higher than the bulk soil pH. The rhizosphere pH increase was particularly evident in apical root zones where the rates of water and NO 3 − uptake and nitrate reductase activity were also higher. The results are summarized in a model of water and nutrient transport to, and uptake by, non-mycorrhizal roots of Norway spruce in a forest stand. Model calculations indicate that delivery to the roots by mass flow may meet most of the plant demand of nitrogen and calcium, and that non-mycorrhizal root tips have the potential to take up most of the delivered nitrate and calcium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225330
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of stand density effects on canopy structure: a conceptual approach (1991)
    Springer
    Trees 5 (1991), S. 44-49 
    Details
    ISSN: 1432-2285
    Keywords: Crown dimensions ; Canopy structure ; Stand density ; Stand structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A few assumptions were used to generate a series of specific, quantitative predictions for the relationships between stand density and various dimensional measures of canopy structure. The predictions, each indicating an increase in mean crown size as density decreased, appeared to be reasonable and intuitive. Predictions were compared to data for two conifer species with different crown forms, Pinus contorta var. latifolia and Abies lasiocarpa. Results of these comparisons were mixed — the linear, directly measured dimensions were consistent with predicted relationships, but dimensions calculated from the linear measures were not. Re-examination of the original assumptions indicated that the model should account for crown shyness (engagement/disengagement) to adequately reflect the influence of stand density on canopy structure. The results also indicated a strong association between stand height and measures of mean crown size. Mean crown size of lodgepole pine was altered much more by density than was mean crown size of subalpine fir, due primarily to the different relative shade tolerances of the two species. Some of the observed differences between species may also reflect the range of densities examined and uneven spacing in the unmanaged natural stands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225334
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  • 5
    Electronic Resource
    Electronic Resource
    Regulation of photoassimilate allocation in Pinus sylvestris seedlings by the nutritional status of the mycorrhizal fungus Suillus variegatus (1991)
    Springer
    Trees 5 (1991), S. 36-43 
    Details
    ISSN: 1432-2285
    Keywords: Microautoradiography ; Mycorrhiza ; Pinus sylvestris ; Suillus variegatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Seedlings of Pinus sylvestris L. were grown on defined nutrient solutions on carbon filters, either sterile or infected with the basidiomycete Suillus variegatus O. Kuntze. After mycorrhizas were established, the shoot of the seedling was subjected to 14CO2 photosynthesis. 14C-labelled photoassimilates were translocated to both mycorrhizas and non-infected root tips. Microautoradiographs of mycorrhizas indicated that omission of external sugars did not affect the formation of mycorrhizas; 14C-photoassimilates were supplied to cortex, Hartig net and the mantle of hyphae surrounding the rootlet. Nutrient solution containing sugars (malt extract, glucose) enhanced the growth of the fungus. As a consequence, 14C-photoassimilates from the seedling were accumulated in the mantle, but defence mechanisms of the host cannot be excluded. When soluble nitrogen was omitted from the nutrient solution and replaced by chitin precipitated on the filter-bearing mycorrhizas, the fungus appeared strongly labelled in the mantle, where the fungal chitinase provided soluble nitrogen compounds, necessary for the growth of the seedling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225333
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  • 6
    Electronic Resource
    Electronic Resource
    Proliferated seed cones and pollen cones in young black spruce (1991)
    Springer
    Trees 5 (1991), S. 65-74 
    Details
    ISSN: 1432-2285
    Keywords: Developmental plasticity ; Seed-cone proliferation ; Pollen-cone proliferation ; Morphological diversity ; Proliferated cone production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The number of proliferated seed cones (PSc) and proliferated pollen cones (PPc) borne by young plantation-grown Picea mariana (Mill.) B.S.P. was established for trees aged 9–17 years from seed. A description and composition of a range of morphological forms of proliferations were produced. Through paired-comparison analyses, compositions of PSc and PPc were compared to those of nearby non-proliferated cones or to vegetative shoots. Between 41% and 88% of trees of different ages that bore seed cones also bore some PSc; 17–58% with pollen cones also had PPc. The total number of PSc represented 2.3–20% of total numbers of seed cones and PSc at each tree age; PPc represented 1.5–5.8% of the total. Proliferated seed cones were greatly diversified in forms ranging from only a few distal needle-like bracts to mainly needles with a few needle-like bracts. A similar range of diversity existed for PPc. Proliferations involving production of distal needles went on to produce a terminal bud. The diversity of morphological forms and their variable occurrence encountered in this study indicate that the developmental pathway of an apical meristem, although defined somewhat by differentiation, has a degree of flexibility. Manifestation of this developmental flexibility throughout a wild population indicates that this phenomenon may be a normal event in P. mariana.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227487
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  • 7
    Electronic Resource
    Electronic Resource
    Fluoride effects on leaf cell ultrastructure of olive trees growing in the vicinity of the Aluminium Factory of Greece (1991)
    Springer
    Trees 5 (1991), S. 83-89 
    Details
    ISSN: 1432-2285
    Keywords: Air pollutants ; Chloroplasts ; Fluoride ; Olive tree leaves ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Leaves of olive trees growing in the vicinity of the Aluminium Factory of Greece were ultrastructurally investigated in order to determine any malformations caused by environmental air pollutants, especially hydrogen fluoride, in comparison with control samples and normal seasonal senescence. Estimation of some elements accumulated by these leaves showed that they contained high amounts of F and Al attributable to the operation of the nearby factory. The most seriously effected cell components were found to be the mesophyll chloroplasts that show a dilation of the intrathylakoid space, increase of the number of plastoglobuli, discoloration of plastoglobuli, accumulation of large starch grains and an overall disorganized appearance of the organelle. The nuclear crystalloid inclusions have unusual shapes, while the vacuoles contain a fibrillar/granular material that increases their electron density. It is concluded that the ultrastructural malformations are caused by a combination of environmental stresses and air pollutants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227489
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  • 8
    Electronic Resource
    Electronic Resource
    Quantitative and localized element analysis in cross-sections of spruce [Picea abies (L.) Karst.] needles with different degrees of damage (1991)
    Springer
    Trees 5 (1991), S. 95-100 
    Details
    ISSN: 1432-2285
    Keywords: Element content ; Element distribution ; Forest decline ; Micro-PIXE ; Picea abies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Proton-induced X-ray microanalysis (micro-PIXE) permits the simultaneous determination of the content and the distribution of elements with atomic numbers higher than Z = 13 in biological samples. This method was used to investigate element content and localization in cross-sections of 6-month-old spruce needles. It was possible to detect the elements silicon, phosphorus, sulphur, chlorine, potassium, calcium, manganese, iron and zinc in semithin (10 μm) sections of the needles. The localization of the cationic elements like potassium, calcium and manganese was determined in the one-dimensional line scan mode and in the two-dimensional raster scan mode. To demonstrate the usefulness of this method for forest decline research, element content and localization were compared in needles from two trees, which differed in their degree of damage. We were able to detect differences in the amount of cations and in their distribution inside the needles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227491
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  • 9
    Electronic Resource
    Electronic Resource
    Changes in hydraulic conductivity upon freezing of the xylem of Populus x canadensis Moench “robusta” (1991)
    Springer
    Trees 5 (1991), S. 117-121 
    Details
    ISSN: 1432-2285
    Keywords: Freezing stress ; Hydraulic conductivity ; Populus ; Vessels ; Water conduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The impact of freezing stress on the hydraulic conductivity was studied in 4- to 6-year-old branches of Populus x canadensis Moench “robusta” under gravity flow conditions. In fresh branch segments, the hydraulic conductivity was approximately 3–6×10-2 1 h-1kPa-1m and the specific conductivity approximately 22 1 h-1kPa-1m-1. Depending on the gas content of the solutions fed to the xylem of the segments, their hydraulic conductivity was lowered by a freezing-thawing cycle by 20–50%. However, full recovery of hydraulic conductivity was found after about 2 days. Degassed solutions in contrast showed no impediment to flow after the same treatment. The results give evidence, firstly, that the harmful effect of freezing on functioning of water conducting elements is due to the formation of bubbles in xylem sap containing gas in solution, and secondly, that recovery from this impediment is possible in microporous vessels within a period of about 2 days.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227494
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  • 10
    Electronic Resource
    Electronic Resource
    Preformed and neoformed extension of shoots and sylleptic branching in relation to shoot length in Tsuga canadensis (1991)
    Springer
    Trees 5 (1991), S. 107-116 
    Details
    ISSN: 1432-2285
    Keywords: Architectural model ; Eastern hemlock ; Leaf distribution ; Patterns of vigour ; Shoot development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Shoot systems developed over 3 successive years were investigated on 55 understorey Tsuga canadensis (L.) Carr. trees. Paired comparisons of preformed-leaf content of terminal buds and numbers of leaves produced on new shoots showed that neoformed leaves were produced in large numbers. Parent-shoot character was not useful in predicting numbers of preformed leaves, was better related to total leaves produced, but left the majority of the variation unexplained. This reflected the capacity of any terminal bud to produce a shoot with more or less neoformation, depending on conditions for growth. All shoots over 6 cm long produced sylleptic shoots that bore from two to many leaves and were arranged in a mesitonic pattern along the parent. Some of the longer sylleptic shoots produced lateral buds or second-order sylleptic shoots. Monopodial second-year extensions of sylleptic-shoot axes followed an acrotonic pattern, as did proleptic shoots from the few lateral buds borne on the parent shoots. Such lateral buds were more frequent on shorter parent shoots: they typically occurred near the proximal and distal ends. Duration of shoot extension was positively correlated with shoot length: terminal buds became evident as shoot extension neared cessation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227493
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  • 11
    Electronic Resource
    Electronic Resource
    Function of spiral grain in trees (1991)
    Springer
    Trees 5 (1991), S. 125-135 
    Details
    ISSN: 1432-2285
    Keywords: Transport ; Strength ; Fiber deviations ; Cambial growth ; Reorientation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Through spiral grain, conduits for sap lead from each root to all branches. This uniform distribution of sap is indicated by the paths of vessels and tracheids, and has been proven experimentally by means of dyed sap injected into the base of stems or taken up by roots. Trees receiving water only from roots at one side of the root collar nevertheless stay green and continue growing. Spiral grain in bark distributes food from each branch to other flanks of the stem and to most roots. Experimental interruptions of the sap and food conduits caused the cambial zone to reorient new conduit cells in new directions, bypassing the interruption. In particular, spiral grooves cut into the stem surface caused spiral grain. The new cells reorient through division and growth. Although spiral grain is largely under genetic control, trees appear to have a spiral grain especially where needed for distribution of water when root spheres are dry at one side. Compared with straight-grained trees, spiral-grained stems and branches bend and twist more when exposed to strong wind, in this way offering less wind resistance and being less likely to break. Through the bending and twisting, snow slides down from branches rather than breaking them, but the main function of spiral grain is the uniform distribution of supplies from each root to all branches, and from each branch to many roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204333
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  • 12
    Electronic Resource
    Electronic Resource
    Occurrence of unidentified bodies that resemble “plastid initials” in poplar cells after breaking of dormancy in midwinter (1991)
    Springer
    Trees 5 (1991), S. 143-148 
    Details
    ISSN: 1432-2285
    Keywords: Amyloplast ; Dormancy ; Plastid initial ; Plastid proliferation ; Poplar cortical cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Electron-microscopic studies of plastids in cortical cells of poplar (Populus euramericana cv. gelrica) were carried out to examine whether any structural changes were initiated after breaking of dormancy in midwinter under non-growing conditions. After the breaking of dormancy, ultrastructural changes became evident and the profiles of plastids became heterogeneous. Organelles resembling the “plastid initials” proposed by Mühlenthaler and Frey-Wyssling in 1965 were frequently observed concomitant with changes in the plastid envelope. The formation of “plastid initials” appeared to be initiated by the formation of septa in pre-existing plastids. After this stage, narrow connections appeared between the “initials” and the parent plastids. Approximately 50 days after the breaking of dormancy in late March, further heterogeneity in the profiles of plastids was observed. At this stage, young plastids (plastids without starch granules) were frequently observed and the formation of “plastid initials” was hardly ever observed. These observations suggest that the “plastid initials” may be present for only a limited period in the cortical cells of the poplar and may be the precursors of the proplastids. Similar ultrastructural profiles were found in cortical cells of mulberry and in leaf buds of apple trees, suggesting that such changes in the ultrastructure of plastids are a general feature of perennials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204335
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  • 13
    Electronic Resource
    Electronic Resource
    Crown profile of foliage area characterized with the Weibull distribution in a hinoki (Chamaecyparis obtusa) stand (1991)
    Springer
    Trees 5 (1991), S. 149-152 
    Details
    ISSN: 1432-2285
    Keywords: Foliage area profile ; Chamaecyparis obtusa (Sieb, et Zucc.) Endl ; Weibull distribution ; Shape parameter ; Scale parameter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Thirten sample trees of various sizes in a 29-year-old hinoki [Chamaecyparis obtusa (Sieb, et Zucc.) Endl.] plantation were felled and subjected to the stratified clip technique. Crown profile of foliage area fitted well with the Weibull distribution. The crown profile tended to be more skewed toward the top of crowns in smaller trees than in larger trees. This tendency was reflected in the value of the shape parameter of the Weibull distribution. The shape parameter ranged from 1.73 to 3.23 and gradually increased up to an asymptotic value with an increase of stem diameter at breast height. The scale parameter of the distribution ranged from 1.0 to 4.2 and tended to increase in proportion to stem diameter at breast height. Foliage area of a tree correlated well with stem diameter at breast height through an ordinary allometric equation. Tree height could be approximated fairly well by a generalized allometric equation as a function of stem diameter at breast height. On the basis of the census of stem diameter at breast height, canopy profile could be constructed synthesizing crown profiles of foliage area for individual trees in the stand. Leaf area index was estimated to be 6.6 ha ha−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204336
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  • 14
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    A survey of seasonal bark proteins in eight temperate hardwoods (1991)
    Springer
    Trees 5 (1991), S. 153-157 
    Details
    ISSN: 1432-2285
    Keywords: Bark proteins ; Nitrogen storage ; Hardwoods ; Overwintering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Bark proteins of eight temperate hardwoods were analyzed by SDS-PAGE at monthly intervals to determine whether an accumulation of specific proteins, potential storage proteins, occurred in the fall at the time of leaf senescence. Storage proteins were identified as proteins that accumulated during the fall and were present in reduced amounts in the summer. Total protein levels were higher in the winter than in the summer in Fagus sylvatica, Fraxinus americana, Tilia americana, Alnus glulinosa, Betula papyrifera and Querus rubra, but not in Gleditsia triacanthos or Robinia pseudoacacia. Betula contained the most abundant storage protein, although in all species minor bands, which fluctuated seasonally, could be identified. With the exception of Alnus and Betula, results generally correlated with previous microscopy studies of these tree species, which showed varying amounts of protein storage vacuoles present in phloem parenchyma cells during the winter, but not during the summer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204337
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  • 15
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    Tree vigor and height growth in Black Spruce (1991)
    Springer
    Trees 5 (1991), S. 158-163 
    Details
    ISSN: 1432-2285
    Keywords: Specific volume increment ; Waring vigor estimates ; Site quality ; Sapwood respiration ; Photosynthate availability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The relationship between tree height and tree vigor was examined in order to test the hypothesis that increased height results in a reduction in photosynthate availability for growth due to an increase in respiratory load of the sapwood. Various vigor indices were measured on black spruce [Picea mariana (Mill.) B. S. P.] trees on a wide range of sites and ages. The relationship between these vigor indices and tree height and site quality were then evaluated through correlation and regression analyses. Vigor indices based on meristematic activity such as specific volume increment and height growth rate were generally more strongly correlated than foliage based indices (i.e. Waring vigor estimates). Both tree height and site index were found to have a significant effect on specific volume increment and height growth rate. However the height effect decreased with a decrease in site quality, and became insignificant (P 〈0.05) on the poorer sites. The full regression model, allowing the height effect to vary between different site quality groups, explained 82% and 72% of the variability in specific volume increment and height growth rate, respectively. The results support the hypothesis that increases in the ratio of respiration to photosynthesis in trees as they increase in size is largely a function of tree height. Possible explanations for the decreased height effect on poor sites are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204338
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  • 16
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    Experiments on the water budget of densely and sparsely needled spruces [Picea abies (L.) Karst.] in a declining stand (1991)
    Springer
    Trees 5 (1991), S. 164-170 
    Details
    ISSN: 1432-2285
    Keywords: Forest decline ; Osmotic potential ; Picea abies ; Water content ; Water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The osmotic potentials of needles were compared from numerous trees that had been classified according to needle loss along an altitude profile. With the increasing degree of damage of the trees, the maximum and minimum values deviated more strongly above and below the common mean of all samples. The level of water content of the needles unequivocally reflected the vitality of the trees. Experiments covering a whole vegetation period were performed on a tree pair selected from a natural stand. They were designed to demonstrate differences in water balance between the “healthy” and “damaged” state of the trees. For the “damaged” tree, measurements of the water potentials of single needles showed a greater reduction of potential during the course of the day compared to the “healthy” tree. Recovery in the evenings was slower and often incomplete. The osmotic potentials of “damaged” and “healthy” shoots measured in individual needles also differed both predawn and especially after transpiration stress. Depending on weather and soil desiccation, the differences were more or less pronounced. In the “damaged” tree, the rises in potential after saturation of the twigs fell far short of the “healthy” tree. Reduction of water potential, osmotic potential and relative water content under comparable stress conditions suggest a reduced tolerance of drought by damaged trees. In the context of earlier experiments this result was ascribed to a lack of stomatal control, and long-term pollution effects were thus explained as a specific disturbance of hydroregulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204339
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  • 17
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    Root responses of flood-tolerant and flood-sensitive tree species to soil redox conditions (1991)
    Springer
    Trees 5 (1991), S. 180-186 
    Details
    ISSN: 1432-2285
    Keywords: Flood-stress ; Root elongation ; Quercus falcata ; Quercus lyrata ; Taxodium distichum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Under controlled rhizotron conditions, roots of Taxodium distichum L., Quercus lyrata Walt, and Q. falcata var. pagodaefolia Ell. were subjected to low soil redox potentials. Root elongation was inhibited at low soil redox potentials. In T. distichum, redox potentials below +200 mV resulted in a significant inhibition of root elongation. In Q. falcata var. pagodaefolia and Q. lyrata, redox potentials below +350 mV resulted in complete cessation of root growth. Studies on root anatomy indicated that low soil redox potenials resulted in a changed cellular structure in the cortex of T. distichum. However, little change was noted in stress roots of oak species. Alcohol dehydrogenase activity in T. distichum roots was approximately doubled compared to control plants, indicating stimulated alcoholic fermentation. In T. distichum, alcoholic fermentation and anatomical changes contribute to flood tolerance but oak species lack these characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204341
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  • 18
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    The effect of two growth forms of Norway spruce on stand development and radiation interception: a model analysis (1991)
    Springer
    Trees 5 (1991), S. 171-179 
    Details
    ISSN: 1432-2285
    Keywords: Biomass ; Computer simulation ; Picea abies ; Stand dynamics ; Tree architecture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Development of tree and canopy structure, and interception of photosynthetically active radiation (PAR) were studied in two model stands of Norway spruce consisting of trees with rapid versus slow site capture. The tree models were derived using Burger's (1953) sample tree material, from which two subpopulations of dominant trees were selected using the rate of horizontal site capture of the tree crowns as the criterion of division. The development of stand structure and interception of PAR were simulated in the two model canopies. The simulation period covered the period from tree age 15–80 years. The average development of the trees in the two subpopulations proved to be very different. The rapidly expanding trees were characterized by low mean within-crown needle area density and a long crown. The slowly expanding trees were smaller but had a higher mean within-crown needle area density. Up to approximately 40 years of age the stand of rapidly expanding trees contained more leaf area and intercepted more radiation than the stand of slowly expanding trees, when canopy cover was held constant. After 40 years of age this relationship was reversed due to the subsequent decline of leaf area in the stand of rapidly expanding trees and the increase in leaf area in the stand of slowly expanding trees. The biological relevancy and silvicultural implications of the simulated patterns of tree and stand development are discussed.
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    URL: http://dx.doi.org/10.1007/BF00204340
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    Food reserves of Scots pine (Pinus sylvestris L.) (1991)
    Springer
    Trees 5 (1991), S. 187-195 
    Details
    ISSN: 1432-2285
    Keywords: Food reserves ; Pinus sylvestris ; Starch ; Sugars ; Triacylglycerol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The amounts of starch, soluble sugars, triacylglycerols, diacylglycerols and free fatty acids were studied in Scots pine (Pinus sylvestris L.) during an annual cycle in current-year needles and in 1-, 2- and 3-year-old needles collected shortly after bud break. Determination of the compounds was performed using specific enzymatic assays, capillary gas chromatography and thin layer chromatography. Newly emerging needles contained relatively large amounts of starch, but only trace amounts of fat. During autumn and winter, fat content rose, while starch content decreased; amounts of both these reserve materials were very high the next spring shortly before bud break and decreased again during shoot elongation. Concentration of intermediates in triacylglycerol biosynthesis (diacylglycerols and free fatty acids), were low in summer and high in winter. The same pattern was observed for fructose and glucose (the predominant soluble sugars), galactose/arabinose and raffinose/melibiose. In contrast, sucrose concentrations were highest in spring and in autumn. Mature needles of different ages collected in May showed significant differences only in their triacylglycerol and starch content. Concentration changes of reserve materials are discussed in relation to season, mobilization and translocation processes, dormancy, frost resistance and the possibility of carbohydrate-fat interconversions.
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    URL: http://dx.doi.org/10.1007/BF00227524
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    Protein-storing vacuoles in inner bark and leaves of softwoods (1991)
    Springer
    Trees 5 (1991), S. 196-202 
    Details
    ISSN: 1432-2285
    Keywords: Protein-storage vacuole ; Protein body ; Softwoods ; Nitrogen storage ; Overwintering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The seasonal occurrence of protein-storage vacuoles in parenchyma cells of the inner bark and leaf tissues of seven softwood species was examined. Previously published results showed that these organelles often fill the phloem parenchyma cells of the inner bark tissues in overwintering hardwoods, whereas they are absent from this tissue during the summer. We hypothesize that the organelles are involved in the storage of reduced nitrogen during wintering, in a manner analogous to protein bodies of seeds. A survey of the phloem and cambial parenchyma tissues in six evergreen softwood species (Pinus strobus, P. sylvestris, Picea abies, P. glauca, Abies balsamea, and Thuja occidentalis) and in one deciduous softwood species (Larix decidua) was conducted. There was a large variation in the degree and timing of protein-storage vacuole formation between the individual genera and species. The organelles were not seen in summer samples of inner bark tissues of any of the genera or species examined. Protein-storage vacuoles were common in the bark tissues of Pinus, Abies and Thuja, occasionally seen in Picea, and rarely found in Larix during the winter. One-year-old leaves were also examined, since in all but Larix they are overwintering structures and can act as potential sites of nitrogen storage. Protein-storage vacuoles were present in Pinus and Thuja leaf tissue in both summer and winter, in Abies during winter only, and were absent from Picea leaf tissue at all times. These results indicate that the formation of protein-storage vacuoles prior to overwintering is not a ubiquitous phenomenon in softwoods.
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    URL: http://dx.doi.org/10.1007/BF00227525
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    Formation of heartwood substances in the stem of Robinia pseudoacacia L. (1991)
    Springer
    Trees 5 (1991), S. 203-207 
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    ISSN: 1432-2285
    Keywords: Chalcone synthase ; Heartwood extractives ; Phenylalanine ammonia-lyase ; Robinia pseudoacacia L. ; Sapwood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The activities of two key enzymes in flavonoid biosynthesis, phenylalanine ammonia-lyase (PAL, E.C. 4.3.1.5) and chalcone synthase (CHS, E.C. 2.3.1.74) were determined in the trunkwood of Robinia pseudoacacia L. The trees under investigation were cut at different times of the year (September, November, January and April). At all times PAL is active, both in the youngest wood layer (the outermost growth ring) and at the sapwood heartwood boundary. On the other hand, CHS is active exclusively in the vicinity of the heartwood boundary. The results indicate that PAL is involved both in the formation of lignin (outermost annual ring), and in flavonoid biosynthesis (heartwood boundary). Highest activity of both PAL and CHS could be measured at the sapwood heartwood boundary in the tree felled in November, indicating that heartwood formation was occurring mainly at that time. The flavonoids accumulated in the heartwood are obviously formed in situ and seem to be transported only to a minor extent — if at all — via the phloem and the ray cells to the heartwood.
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    URL: http://dx.doi.org/10.1007/BF00227526
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    Growth patterns and bending mechanics of branches (1991)
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    Trees 5 (1991), S. 232-238 
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    ISSN: 1432-2285
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227530
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    Influence of needle loss, yellowing and mineral content on monoterpenes in the needles of Picea abies (L.) Karst. (1991)
    Springer
    Trees 5 (1991), S. 208-214 
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    ISSN: 1432-2285
    Keywords: Bavaria ; Disease ; Needle ; (Mono)terpenes ; Picea abies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Monoterpenes in needles of Picea abies (L.) Karst. were studied to reveal whether or not the symptoms of forest decline observed in three mountain regions of South Germany (Bavaria) — needle loss and needle yellowing — are related to changes in the amounts of all or individual terpenes. The nutrient supply of the needles was examined in addition to the terpene concentrations, since the disease symptom montane yellowing is often associated with mineral deficiency. At two of the eight locations, trees exhibited Mg-deficiency, at one location K-deficiency was observed, and at another location the S-content of the needles indicated SO2-pollution. Using various statistical methods of analysis, no correlation was observed between the mineral element content of the needles, the percentage of needle loss and either the absolute or percentile terpene amounts stored within the needles. This finding is independent of needle age, date of sampling and terpene pattern. Concerning needle yellowing, the data show a tendency towards a reduction of the terpene concentrations in needles originating from branches with partly yellow needles compared to needles from exclusively green-needled branches. In spite of the fact that only 2-year-old and older needles show the disease symptom of yellowing, the terpene level is reduced even in still green, juvenile and 1-year-old needles. No terpene was found to be an indicator for early recognition of injury.
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    URL: http://dx.doi.org/10.1007/BF00227527
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    Nitrate levels affect the development of the black locust-Rhizobium symbiosis (1991)
    Springer
    Trees 5 (1991), S. 227-231 
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    ISSN: 1432-2285
    Keywords: Robinia pseudoacacia L. ; Nitrate ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Experiments with black locust (Robinia pseudoacacia L.) seedlings grown under strictly controlled laboratory conditions indicated that the availability of nitrate has a marked impact on nitrogen fixation. When nitrate concentrations were very low, both nodulation and seedling growth were impaired, whereas nitrate concentrations high enough to promote plant growth strongly inhibited symbiotic nitrogen fixation. When nitrate was added to the growth medium after infection, nodulation and nitrogen fixation of the seedlings decreased. This effect was even more marked when nitrate was applied before infection with rhizobia. Higher nitrogen concentrations also reduced nodule number and nodule mass when applied simultaneously with the infecting bacteria. The contribution of symbiotic nitrogen fixation to black locust shoot mass by far exceeded its effects on shoot length and root mass. When nitrate availability was very low, specific nitrogen fixation (i. e. nitrogenase activity per nodule wet weight) was improved with increasing nitrogen supply, but rapidly decreased with higher nitrogen concentrations.
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    URL: http://dx.doi.org/10.1007/BF00227529
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    Nitrate reductase in needles, roots and trunk wood of spruce trees [Picea abies (L.) Karst.] (1991)
    Springer
    Trees 5 (1991), S. 215-226 
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    ISSN: 1432-2285
    Keywords: Picea abies ; Nitrate reductase ; Xylem sap ; Fumigation ; Fertilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrate reductase (EC 1.6.6.2) activity (NRA), as measured by an in vivo assay, is present in needle leaves and mycorrhizal fine root tips of adult Norway spruce [Picea abies (L.) Karst.] in at least equal amounts on a fresh weight basis, in both adult and 5-year-old trees. NRA could also be demonstrated in trunk wood of deroted trees after fertilization with 5 mM $${\text{NO}}_{{\text{3}}^{\text{ - }} }$$ , exhibiting a longitudinal profile in the trunk. Inducibility in needles can more efficiently be achieved by NO2 (100 μg·m-3) than by 5 mM nitrate, which is effective only in root-amputated trees. A remarkably high level of needle-NRA in unfertilized trees, which are characterized by a very low level of nitrate in the xylem sap, suggests that NRA in spruce needles may in part be constitutive. Organic-N is a major nitrogen source for the needles even in root-amputated trees, indicating pronounced exchange processes between ray parenchyma and trunk xylem, which in turn are modified by the nitrogen source fed to the trunk stump. Intact trees exhibit a very similar amino acid composition of the xylem sap, regardless of whether $${\text{NO}}_{{\text{3}}^{\text{ - }} }$$ or $${\text{NH}}_{{\text{4}}^{\text{ + }} }$$ has been fed. The amino acid pattern of the needles is not thrown out of balance by “flooding” with $${\text{NO}}_{{\text{3}}^{\text{ - }} }$$ and $${\text{NH}}_{{\text{4}}^{\text{ + }} }$$ , which occurs in fertilized derooted trees. This indicates a distinct potential for homoeostasis of nitrogen entrance-metabolism (i.e. NRA and glutamine synthetase activity) in the needles. In the ectomycorrhiza/fine root-system (EMC), marked differences in NRA were observed depending on root-tip diameter and along the longitudinal profile of the fine roots. EMC-nitrate reductase is strongly enhanced by $${\text{NO}}_{{\text{3}}^{\text{ - }} }$$ . Needle-NRA exhibits a circannual rhythm. An early summer maximum is followed by a December minimum. This activity pattern matches well the transitory increase of soluble nitrogen in spring and the total protein maximum in winter. In an indirect way assimilatory NRA may well contribute to nitrogen overfertilization (by consumption of NOX) as one possible cause of the contemporary decline of spruce populations.
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    URL: http://dx.doi.org/10.1007/BF00227528
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    Small fruit problem in Citrus trees (1991)
    Springer
    Trees 5 (1991), S. 239-243 
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    ISSN: 1432-2285
    Keywords: Citrus sinensis ; Fruit ; Photosynthesis ; Respiration ; Transpiration ; Water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Physiological causes of the small fruit problem which occurs in certain trees of orange [Citrus sinensis (L.) Osbeck cv. Valencia] were investigated in terms of water relations and gas exchange of fruits during early fruit development as well as tree carbohydrate reserves. These data from cv. Valencia trees with and without a small fruit potential were compared with those of the large fruited cv. Navel. Neither fruit water potential nor fruit transpiration nor tree carbohydrate reserves appeared to be a cause of the small fruit. Yield records showed the small fruit to be assocaited with a large number of fruit per tree. However, fruits from cv. Valencia trees with a small fruit potential respired faster than either fruits of the same cultivar and size from trees without the physiological disorder or fruits of the same size of cv. Navel and also exceeded the dark respiration of the respective leaves. Hence, the small fruit problem in cv. Valencia was partly attributed to inefficient fruit photosynthesis, causing excessive respiration of each of a larger number of fruits compared to fruits of a tree of the same cultivar but without the physiological disorder. Fruits of cv. Valencia respired more in their 2 months longer lifetime on the tree relative to those of cv. Navel. It is concluded that orchard management methods will have to be investigated to balance the fruit load of the cv. Valencia tree utilizing the carbon available for fruit growth and to minimise stress during the early fruit development.
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    URL: http://dx.doi.org/10.1007/BF00227531
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    Dormancy in peach (Prunus persica L.) flower buds (1991)
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    Trees 5 (1991), S. 244-246 
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    ISSN: 1432-2285
    Keywords: Peach ; Floral buds ; Vegetative buds ; Morphology ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Peach buds (floral and vegetative) were periodically collected from midsummer until the spring flowering and sprouted under continuous light, 100% relative humidity and 20–25°C. Treatments with 200 ppm gibberellin A3 (GA3) or chilling (2–4°C for 30 days before planting) were applied. Vegetative buds showed well-defined phenological stages: pre-dormancy, “true dormancy”, and end of dormancy. Both GA3 and chilling treatments shortened the sprouting times of vegetative dormant buds close to those in predormancy. Isolated floral buds were irresponsive under all conditions and did not sprout even with the GA3 or chilling treatments. In a comparative study with buds immediately after collection anatomical analysis demonstrated that vegetative buds were almost completely developed by midsummer/early automn and remained in a resting state until the end of winter. Floral buds developed continuously over the same period. Both types of verticils began to differentiate in midsummer. Sepals and petals developed mainly in late summer, androecious floral parts developed throughout the resting period, while gynoecious floral parts showed differentiation in late winter. The flower was completely formed a few days prior to blossoming. Thus, in isolated peach buds fertile verticils are not sufficiently developed during the resting time to allow sprouting.
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    URL: http://dx.doi.org/10.1007/BF00227532
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    Drawing human hair using the Wisp model (1991)
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    The visual computer 7 (1991), S. 97-103 
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    ISSN: 1432-2315
    Keywords: Anisotropic shading ; Surface modeling ; Hair ; z-Buffer ; Real-time rendering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper presents a new powerful method for hair-image generation. A simplified computer graphics (CG) model of human hair is presented to describe and render various kinds of hair images with a small number of parameters. Practical methods for handling hair styles and for generating realistic images are presented. A notable feature of the proposed method is that it is run on the conventional z-buffer algorithm. Experiments have proven that the proposed algorithm is very useful for generating various human-hair images.
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    URL: http://dx.doi.org/10.1007/BF01901180
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    Reliability of computer graphic images for visual assessment (1991)
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    The visual computer 7 (1991), S. 138-148 
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    ISSN: 1432-2315
    Keywords: Reliability ; Montage image ; Assessment ; Architectural simulation ; Computer graphics system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper analyzes the use of computer graphics images as an architectural assessment tool. The characteristics of such images as an architectural simulation tool are discussed and their reliability as an assessment tool is evaluated and compared with that of traditional hand-generated perspective drawings. A specimen application, architectural simulation of a city renewal plan, is presented.
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    URL: http://dx.doi.org/10.1007/BF01901184
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    A flexible quantitative method for NC machining verification using a space-division based solid model (1991)
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    The visual computer 7 (1991), S. 149-157 
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    ISSN: 1432-2315
    Keywords: Numerical control machining ; NC-Geometric simulation ; Solid modeling ; Oct-tree ; Space division ; Z-buffer ; CSG ; Interference detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A geometric-modeling method called Graftree and a system design of an NC (numerical control) machining verifier based on Graftree are proposed. Graftree is constructed by combining Oct-tree and constructive solid geometry (CSG) so as to simulate machining processes precisely in three-dimensional space. Using Graftree, the Boolean operation produces no risk of yielding topological conflicts, which often cause the simulation to stop abnormally. Based on the properties of Graftree, an NC machining verifier is designed to consist of three individual subsystems: data-input operations, geometric simulation, and interactive verification, i.e., visuluatzation of machining scenes and evaluation of the machined product using models of the measuring instruments. This design lets the users watch selectively only the machining steps they want to check precisely, and verify the machining according to dimensional tolerance.
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    Events (1991)
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    The visual computer 7 (1991), S. 230-230 
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    ISSN: 1432-2315
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
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    URL: http://dx.doi.org/10.1007/BF01900840
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    Editorial (1991)
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    The visual computer 7 (1991), S. 231-231 
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    ISSN: 1432-2315
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
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    URL: http://dx.doi.org/10.1007/BF01905688
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    A scanline algorithm for displaying trimmed surfaces by using Bézier clipping (1991)
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    The visual computer 7 (1991), S. 269-279 
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    ISSN: 1432-2315
    Keywords: Bézier surfaces ; Scanline algorithm ; Robustness ; High-quality rendering ; Surface trimming ; Silhouette detection ; Shadowing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Displaying objects with high accuracy is necessary for CAGD (computer-aided geometric design) and for the synthesis of photo-realistic images. Traditionally, polygonal approximation methods have been employed to display free-form surfaces. They bring on low accuracy of display not only in shape, but also in intensity of objects. In this paper, a scanline algorithm to directly display parametric surface patches, expressed by trimmed Bézier surfaces, without polygonal approximation is proposed. In the method proposed here, curved surfaces are subdivided into subpatches with curved edges intersecting with a scanline, and the intersections of every subpatch and the scanline are calculated. This method is extremely robust for calculating the intersections, which can be obtained with only a few iterations; the Bézier clipping method is used for the iteration. Anti-aliased images with shadows and texture mapping are given to show the effectiveness of the method proposed.
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    URL: http://dx.doi.org/10.1007/BF01905692
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    Boolean operations for solids with free-form surfaces through polyhedral approximation (1991)
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    The visual computer 7 (1991), S. 87-96 
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    ISSN: 1432-2315
    Keywords: Free-form surface ; Polyhedral approximation ; Boolean operation ; Repatching ; Gregory patch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper describes a new implementation method for Boolean operations between solids with free-form surfaces. Boolean operations consist of two processes-topological modification and geometric modification-which are performed separately in our method. This separation makes the Boolean operation process simple and robust. Surfaces contained in the final solid are interpolated by the repatching facility using Gregory patches.
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    URL: http://dx.doi.org/10.1007/BF01901179
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    Lignin distribution across tracheid cell walls of poorly lignified wood from deformed copper deficient Pinus radiata (D. Don) (1991)
    Springer
    Wood science and technology 25 (1991), S. 7-14 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Lignin topochemistry of tracheid walls from a deformed, copper deficient Pinus radiata (D. Don) tree was examined by linescan and point analyses using a Scanning Electron Microscope and Energy Dispersive Spectrometry. Both opposite and compression wood had abnormal lignin distributions compared to those observed in normal wood from a straight tree. Lignin contents in the compound middle lamella were lower than lignin contents in the secondary wall in both opposite and compression wood tracheids.
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    Knot dinteraction in wood poles (1991)
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    Wood science and technology 25 (1991), S. 47-56 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Superposition of the longitudinal stress distributions associated with neighboring knots was used to determine the interaction distances between different knot sizes. The interaction between two knots was considered significant when the superposition of the stress distribution caused an increase in the longitudinal stress level of ten percent or more. Out of 4,374 knots measured in 44 Douglas-fir poles only 55 knots showed significant interactions with adjacent knots. However, in more than half of the poles at least one interacting knot pairs existed. Therefore, it has been concluded that stress interaction between knots could play a major role in controlling the failure of poles in bending.
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    Modelling elastic and shrinkage properties of wood based on cell structure (1991)
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    Wood science and technology 25 (1991), S. 25-32 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary In a previous article of the authors a model was developed for estimating elastic and shrinkage properties of a softwood cell-wall. In the present article this model is enlarged to simulate the elastic properties of defect-free softwoods. The wood model consists of earlywood, latewood and ray cells, each of which have a different cell-wall structure. In the model the ratio of earlywood to latewood is defined by a given wood density. The calculated elastic properties are in good agreement with test results.
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    Book reviews (1991)
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    Wood science and technology 25 (1991), S. 83-84 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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    URL: http://dx.doi.org/10.1007/BF00195559
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    Degradation of pine kraft lignin by Coriolopsis gallica growing on a fibre-glass support (1991)
    Springer
    Wood science and technology 25 (1991), S. 91-97 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Coriolopsis gallica was grown in static liquid cultures on an inert support consisting of fibre-glass impregnated with Indulin AT (pine kraft lignin). The fungus developed well in such conditions enabling the study with the SEM of the morphology and penetration of the fungus. The method also pemits the recovery of degraded lignin, the characteristics of which was monitored by direct analysis of its elementary composition, methoxyls groups, and by spectroscopic techniques and gel permeation. Degraded lignin differed from sound lignin by its higher percentages of oxygen, and lower percentages of C, H, and OCH3 was richer in oxygen. The IR and vis-UV spectra as well as the fractionation by gel filtration showed that the structure of the lignin incubated in the presence of the fungus had been modified.
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    URL: http://dx.doi.org/10.1007/BF00226809
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    On the basic equation of sorption and the isosteric heat (1991)
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    Wood science and technology 25 (1991), S. 99-111 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Precise derivations are given for the basic equation of sorption, -RT ln r = Δh -T Δs. and for the isosteric heat. The prefix Δ indicates the change from sorbed liquid to free liquid. The above basic equation is interpreted as an equilibrium moisture constant (emc) equation. It is shown how Δs/R varies with temperature under the assumption that Δh/l is a function of moisture content only. The above ratios are the obvious non-dimensional expressions for Δh and Δs and these are evaluated for wood as typified by klinki pine (Araucaria klinkii Lauterb.).
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    URL: http://dx.doi.org/10.1007/BF00226810
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    Nonlinear superposition model for the behavior of bolted joints (1991)
    Springer
    Wood science and technology 25 (1991), S. 113-123 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary A previously developed model to predict the load-slip relationship for mechanical joints using one bolt subjected to lateral loading (Part 1) was extended to incorporate the rotational resistance of joints containing two bolts. The rotation is about the long axis direction of the bolts, and considers the wood members oriented at arbitrary angles to the grain. The model utilizes nonlinear translational springs to represent the parallel and perpendicular to grain components of the reaction force present on each bolt resisting the applied moment. A series of experiments were conducted to determine the spring constants of bolted joints in axial loading and to verify the predictions of the mathematical model. Bolted joints subjected to a pure rotation were tested using combinations of steel plates and wood side members experiencing bolt reaction forces at various angles of load to grain. The results indicated an excellent agreement between theoretical predictions and experimentally obtained data.
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    URL: http://dx.doi.org/10.1007/BF00226811
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    Fiber swelling favoured by lignin softening (1991)
    Springer
    Wood science and technology 25 (1991), S. 135-144 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The effect of temperature on the uptake of water by various pulps has been studied at temperatures from 20 to 95°C. In the case of lignin-containing pulps, i.e. pulps which have been chlorite-delignified to various degrees, the swelling increases rapidly above a temperature of 60 to 75°C. For a CTMP where the softening temperature of the lignin has been lowered, a maximum in swelling is obtained at 50 to 60°C. When no lignin is present, as in cotton linters and holocellulose, the temperature has no effect on the swelling but the level of swelling in the holocellulose pulp is very high. It is suggested that the increase in swelling above 60 to 75°C is due to the softening of the lignin, the flow of which makes swelling possible. Below its softening temperature, the stiff lignin restricts the swelling which is primarily promoted by water uptake in the hemicelluloses. Some implications for pulping processes are discussed.
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    URL: http://dx.doi.org/10.1007/BF00226813
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    Chemical characterization of Chilean hardwoods (1991)
    Springer
    Wood science and technology 25 (1991), S. 145-149 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Six Chilean native hardwoods (Nothofagus obliqua, Nothofagus glauca, Lithraea caustica, Quillaja saponaria, Cryptocarya alba, and Acacia caven) and four introduced species (Pinus radiata, Acacia melanoxylon, Acacia dealbata and Eucalyptus globulus) were chemically characterized in their lignin, cellulose, hollocellulose, extractives and ash content. Seven metallic ions and phosphorous were analyzed in ashes. Basic density and calorific value were also determined. No correlations were found between calcium content and basic density.
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    URL: http://dx.doi.org/10.1007/BF00226814
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    Aging and fossilization of wood and its components (1991)
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    Wood science and technology 25 (1991), S. 153-177 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Aging of wood begins with the cutting of a tree. The subsequent changes of the wood substance proceed very slowly and depend on environmental conditions. In a hot, dry desert climate wooden objects and cellulose textiles are preserved for several millenia, whereas their degradation is accelerated by conditions which favor the attack of microorganisms. Two conditions under which aging processes take place can be distinguished: a) aerobic conditions as prevailing in wooden buildings, sculptures etc.; b) anaerobic conditions valid for wooden items buried in the ground or submerged in water such as foundation pillars, ships etc. Submersion and underground embedding initiate the very slow process of fossilization in which the cell wall substance is transformed into highly condensed compounds (coalification) or is substituted by minerals (silicification). The various wood components are subjected to different kinds of degradation and conversion. The polysaccharides disappear with aging and seem to be more sensitive than lignin. Although more resistant, the lignin is converted chemically and its structure differs increasingly from its original state. Even extractives may survive millions of years.
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    Heterogeneity in formation of lignin (1991)
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    Wood science and technology 25 (1991), S. 371-381 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The formation of lignin in the cell wall of compression wood of Pinus thunbergii was examined by selective radio-labeling of specific structural units in the lignin and visualization of the label in the different morphological regions by microautoradiography. Deposition of lignin in the tracheid cell wall of compression wood occurred in the order: p-hydroxyphenyl, guaiacyl and syringyl lignin, which is the same order as observed in normal wood. However, the period of lignification in the compression wood was quite different from those of normal and opposite woods. The p-hydroxyphenyl units were deposited mainly in the early stage of cell wall formation in compound middle lamella in normal and opposite woods, while in compression wood, they were formed in both the compound middle lamella and the secondary wall. The most intensive lignification was observed during the formation of the S2 layer, proceeding from the outer to inner S2 layers for a long period in compression wood. In the normal or opposite woods, in contrast, the lignification became active after formation of S3 had begun, then proceeded uniformly in the secondary wall and ended after a short period.
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    URL: http://dx.doi.org/10.1007/BF00226177
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    Creep in chipboard (1991)
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    Wood science and technology 25 (1991), S. 225-238 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Deflection under 4-point bending of a range of board types was measured for up to six months. Results were obtained under steady-state conditions of stress level (30%, 45%, 60%, 67.5% and 75% of the short term breaking stress), relative humidity (30%, 65% and 90% rh) and temperature (10°C, 20°C and 30°C). These results are presented in terms of relative creep and creep modulus. The relative creep for all board types increased with increasing stress level, increasing relative humidity and increasing temperature. An analysis of variance investigating variations between materials showed significant differences in relative creep. When the relative creep of all materials was compared over all conditions and all stress levels, plywood and waferboard had consistently low relative creep values. High alkaline cured PF chipboard and non-British Standard UF chipboard had consistently high relative creep values. The creep modulus of MUF bonded chipboard decreased with increasing log10 (time) under all conditions. Creep modulus also decreased with increasing stress level.
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    Image analysis to measure strain in wood and paper (1991)
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    Wood science and technology 25 (1991), S. 251-262 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary A fast and accurate strain measurement method was developed to quantify microscopic deformation in wood and paper using video images. Two or more video images, one of which was undeformed and the others of which were deformed, were digitized and compared using the image correlation technique. This digital computer pattern recognition technique permitted the displacement of any point in the image to be measured. Then, strain between any two points in this observation field could be calculated and, hence, normal, shearing strains and Poisson's ratio could be measured directly. Independent strain measurements showed that the method using video images provided accurate strain measurements and could be applied to complex materials like wood and wood products. The strain measurements using the image analysis produced not only normal strains but strain profiles of the normal strains. From the strain profiles, it was possible to detect local areas of strain concentration which might be beyond the elastic range. As it measures displacements and strains from a set of video images using the image correlation technique, the method is non-contact and the observation field can be adjusted easily by changing magnifying power of the optical devices. Thus, the method can be applied to mechanical testing of wood and wood products from the cellular level to full size lumber and will no longer be limited by the fragile nature of the material being tested, industry standards, or equipment restrictions.
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    URL: http://dx.doi.org/10.1007/BF00225465
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    Moisture content—water potential relationship of wood from saturated to dry conditions (1991)
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    Wood science and technology 25 (1991), S. 263-280 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The water potential concept as applied to wood-water relations is presented. The gradient in water potential can be used as the driving force of moisture in wood in a model of drying in isothermal conditions provided the moisture content — water potential relationship is known. This relationship is established for aspen sapwood in desorption from saturated to dry conditions at 20, 35 and 50 °C for two specimen orientations. The tension plate, pressure plate and pressure membrane methods were used at high moisture contents and equilibration over saturated salt solutions was used at low moisture contents. The results obtained demonstrate that these methods can be used in combination in order to establish the relationship within the whole range of moisture contents. The equilibrium moisture contents obtained by the tension plate, the pressure plate and the pressure membrane methods for tangential desorption were slightly higher than those measured for radial desorption. The water potential increased with temperature at a given moisture content. This effect cannot be solely explained by the variation of surface tension of water with temperature.
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    Book reviews (1991)
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    Wood science and technology 25 (1991), S. 319-320 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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    URL: http://dx.doi.org/10.1007/BF00225471
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    Dynamic behavior of wood strip over elastic underlayment composite flooring subjected to light impact loads (1991)
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    Wood science and technology 25 (1991), S. 309-318 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The dynamic behavior of composites consisting of wood flooring strips placed over rubber sheeting was investigated. A light impact load was applied to the center of the strips and impact force, contact duration and contact area were measured. The energy transfer from the impacting mass to the composite was estimated by measuring the restitution coefficient. Frequency analysis was conducted in order to examine the vibration characteristics of the composites.
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    Erratum (1991)
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    Wood science and technology 25 (1991), S. 474-474 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225241
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    Modelling the process of absorption and desorption of water in two dimensions (transverse) in a square wood beam (1991)
    Springer
    Wood science and technology 26 (1991), S. 23-37 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The process of absorption and desorption of water by two-dimensional transport in wood was studied at a moisture content beyond the fiber saturation point. The transverse directions through a square wood beam were considered. A numerical model capable of describing the process was constructed and successfully tested. It can predict by calculation the kinetics of absorption when wood is immersed into water and the kinetics of desorption when it is exposed to air. The model gives a fuller insight into the process with the profiles of moisture content developed through the cross-section of the wood at any time.
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    URL: http://dx.doi.org/10.1007/BF00225689
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    Creep in chipboard (1991)
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    Wood science and technology 26 (1991), S. 39-51 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Ten samples from each of ten brands of commercial chipboard, covering a range of UF, MUF and PF resins, were stressed over a 5-year period at 30% of their short term ultimate bending strength, under protected external conditions. No relationship could be established for the term of the experiment between fluctuations in creep deflection and changes in environmental conditions. Exceptionally, for two short periods of time, relationships were established and these were in line with current views on mechano-sorptive behaviour. Differences in relative creep between the ten brands were significantly greater than those occurring between samples of any one brand. Although there were significant differences in relative creep among the six brands of MUF bonded boards, the relative creep of all these boards was significantly lower than those brands made with UF and high-alkaline cured PF resins. While most of the MUF bonded samples survived the duration of the experiment, all UF and PF samples failed before the end of the 5-year period. For the first 6 months of the experiment, the mean relative creep under protected external conditions was equal to, or slightly less than, that obtained in matched samples tested under a constant environment of 20°C 90% rh.
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    Comparing two measures of flake alignment (1991)
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    Wood science and technology 26 (1991), S. 53-61 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Alignment of particles in structural composites is desirable to increase the strength and stiffness of the panel in one direction. The magnitude of resulting orthotropic panel properties are influenced by the degree of alignment. Quantification of the degree of alignment in the literature has primarily been attained by a parameter known as percent alignment. Measures of flake alignment in probability distribution form have received some, though more limited attention. However, use of statistical distributions to describes particle orientation, such as that provided by the von Mises distribution are needed for simulations of composite panel properties. It is shown that percent flake alignment is a linear transformation of the first moment (arithmetic mean) of the absolute value of angles in the range ±90 degrees. Assuming the von Mises distributional form accurately measures flake alignment, this implies that percent flake alignment is a measure of both the variability in flake direction and the mean flake angle. The numerical relationship of percent alignment with mean angle and variability is presented with a look-up table provided for converting between the two systems of measure. The relation will permit verification of models which employ the von Mises distribution to describe flake alignment using information in the literature based on percent flake alignment. A computer program is available from the author which will calculate percent alignment and distribution parameters for an experimentally obtained samples of angles.
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    Improvement of physical and biological properties of particleboards by impregnation with phenolic resin (1991)
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    Wood science and technology 26 (1991), S. 63-70 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Particleboards were treated with a low molecular-weight phenol-formaldehyde resin and their properties were evaluated. Particles were dipped into aqueous solutions of resin or sprayed with resin solutions before spraying the conventional phenol-formaldehyde resin adhesive, or sprayed with a mixture of low molecular-weight resin and the adhesive resin in a single step. Though mechanical properties and dimensional stability of the phenolic-resin-treated boards were affected considerably by the incorporated resin loading (IRL), the methods of treatment did not produce significantly different results. After boiling for 2-hours, the boards treated at 10% IRL retained 80% of their strength values in the dry condition. The internal bond strength increased with increasing IRL values, and the boards with 20% IRL showed twice the value of untreated controls at the same level of board density. Treated particleboards showed a dramatic reduction in the rate of swelling even at low resin loading. Results obtained from accelerated laboratory tests of biodegradation suggested that incorporated resin-solids worked well to enhance decay and termite resistance of particleboards. For a brown-rot fungus, the weight loss was substantially reduced at 15% IRL, whereas attack was suppressed almost entirely even at low resin loadings for the white-rot fungus.
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    Properties of protein constituents of black locust bark (1991)
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    Wood science and technology 25 (1991), S. 1-6 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The total protein content of black locust bark increased in December, remained at an elevated level throughout the winter and spring, and decreased in June. Hemagglutinating activity of lectin in the bark did not follow this pattern but increased to a maximum in February and decreased in March. Lectin may be involved in protein storage as others have suggested, but the role of its ability to bind carbohydrates is not evident. A role for lectin as a protective compound could not be assigned because lectin extracts did not inhibit bacterial or fungal growth even though they affected fungal growth characteristics. Chitinase activity, however, was present in black locust inner bark at a concentration which inhibited fungal growth in vitro.
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    URL: http://dx.doi.org/10.1007/BF00195551
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    Seasonal changes in lignin distribution during tracheid development in Pinus radiata D. Don (1991)
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    Wood science and technology 25 (1991), S. 15-24 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Lignin distribution in developing tracheids of Pinus radiata was studied throughout the growth' season using quantitative interference microscopy. The pattern of lignification remained constant although the number of lignifying cells varied reaching a maximum in summer. Lignification of the secondary wall of latewood tracheids was incomplete at the onset of winter. Each stage of lignification was preceded by deposition of carbohydrates with lignification of the middle lamella starting after S1 formation and lignification of the secondary wall starting after S3 formation. Lignification of the middle lamella was completed before the start of lignin deposition in the secondary wall. In one of the trees examined, the secondary wall lignified concurrently with the middle lamella and this was associated with a low lignin concentration in the middle lamella of mature cells. The secondary wall reached a mature lignin concentration of 21–22% v/v except in one specimen containing severe compression wood which reached 28% v/v. The cell corner middle lamella reached a mature lignin concentration of 74–87% v/v.
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    Nonlinear superposition model for the behavior of bolted joints (1991)
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    Wood science and technology 25 (1991), S. 33-45 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary A nonlinear superposition model was developed to assess the load-slip behavior of bolted joints consisting of a single bolt subjected to lateral loading at angles of load to grain. This model characterizes the bolted joint as a pair of orthogonal nonlinear springs aligned parallel and perpendicular to the grain of the wood members. The spring stiffnesses are quantified by a logarithmic or exponential function depending upon whether the connection softens or stiffens with increasing slip. The spring deformations are superimposed to determine the movement of each component of the connection. Deformations of connected members are added vectorially to determine their relative displacement. Spring constant were determined experimentally using metal-to-wood connections. Thick steel side plates were employed to limit the system deformation to the wood component. Wood members were evaluated at angles of load to grain ranging from zero to ninety degrees. Once the spring constants had been determined, the model was executed to predict the load-slip behavior of wood-to-wood connections. These predictions were compared to experimentally obtained load-slip values. The results indicate that the nonlinear superposition concept is a valid approach to predict joint deformation at angles of load to grain.
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    Fundamentals of flakeboard manufacture: wood-moisture relationships (1991)
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    Wood science and technology 25 (1991), S. 57-71 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary A procedure is presented to estimate the relative vapor pressure, equilibrium moisture content, average flake temperature, and average flake moisture content in a flakeboard mat during hot-pressing. This method is based on measurements of temperature and total gas pressure in the mat during hot-pressing. A heat and mass transfer model was adapted from the literature to predict the temperature and moisture content inside an individual flake. Significant moisture gradients are predicted to develop within flakes. Convective heat transfer appears to control the change of moisture content within a flake. Thermodynamic equilibrium between the gas phase and the wood component is not achieved during hot-pressing.
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    Thickness swelling and density variation in aspen flakeboards (1991)
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    Wood science and technology 25 (1991), S. 73-82 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary This paper reports the relationship between thickness swelling and density in labmade aspen flakeboards. The boards were manufactured with several levels of initial mat moisture content and urea resin content. Weight increase and thickness swelling at 12 locations on each board were recorded under specified environmental conditions over a period of 71 days. Each board was then cut into 12 specimens, each containing one of the 12 locations at its center, and density was calculated. No definite relationship was found between thickness swelling and density among the 12 specimens of each board. Our results suggest that high initial moisture content and high resin content can decrease thickness swelling. Variations in mat pressure and core temperature during the press cycle and weight increase at 80 percent relative humidity are discussed.
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    Heartwood development and its relationship to growth in Pinus radiata (1991)
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    Wood science and technology 25 (1991), S. 85-90 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The rate of heartwood development was examined at four heights in stems of Pinus radiata D. Don from 18 mature stands in south-eastern Australia. While the diameter of heartwood tended to be greatest at stump and breast heights, formation commenced earlier (i.e. with fewer sapwood rings) and/or progressed more rapidly 10–20 m above ground level. Appreciable variation in heartwood development was detected between trees in the same and different stands, with both environmental and genetic factors apparently important. Regression analyses involving three parameters of heartwood development (number of rings, diameter and percentage area) and stem characteristics including height, diameter and ring width suggested that heartwood formation is affected little by tree vigour in the post-juvenile growth phase. Rather it seems that the rate at which annual increments are included in heartwood is largely fixed for any particular height level and stem. Thus the amount (but not necessarily the percentage) or heartwood in a stem is substantially dependent on diameter growth early in tree life.
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    Simultaneous evaluation of bending and shear moduli of wood and the influence of knots on these parameters (1991)
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    Wood science and technology 25 (1991), S. 125-134 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary This paper presents a method of simultaneous evaluation of bending and shear moduli of wooden beams. The method, which is based upon the measurement of two natural frequencies of a beam, is simple to perform. Existing techniques for determining shear moduli of wood based materials are either too cumbersome to carry out or prone to measurement errors. Using this method tests were conducted on matched groups of clear and knotty specimens. It was found that for clear specimens a value of 20 can be assumed for the E to G ratio. For specimens which contain knots the variation was so large that no corresponding figure can be suggested with confidence. But the ratio for knotty materials is though to be higher than 20.
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    Book reviews (1991)
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    Wood science and technology 25 (1991), S. 151-152 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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    URL: http://dx.doi.org/10.1007/BF00226815
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    The thermodynamics of sorption with reference to klinki pine (1991)
    Springer
    Wood science and technology 25 (1991), S. 179-192 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary An investigation into the bonding energy relationships for water in wood indicates that as the temperature increases at constant total moisture content, water moves from within the chemical structure to the adsorption surface. The analysis is evaluated for the wood Araucaria klinkii Lauterb and it is indicated that at 25 °C, less water is held in the chemical structure during adsorption than during desorption.
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    Heats of transfer and activation energy for bound water diffusion in wood (1991)
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    Wood science and technology 25 (1991), S. 193-202 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Concepts of nonequilibrium thermodynamics are used to discuss two molar heats of transfer associated with diffusion of water in wood. These different heats of transfer originate from energy flows that are referenced to enthalpies of water vapor and bound water. They represent heat that must be absorbed by the vapor or sorbed water phases, respectively, to maintain constant local temperatures and pressures during the process of steady-state diffusion. In addition, equations for bound water flux and moisture conductivity are used to show that the heat of transfer for adsorbed water exceeds the activation energy for bound water diffusion. The distinction between these quantities remains unclear, but may be related to diffusing molecules which carry energy in excess of the minimum required for participation in diffusion.
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    URL: http://dx.doi.org/10.1007/BF00223470
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    Durability evaluation of particleboards by accelerated aging tests (1991)
    Springer
    Wood science and technology 25 (1991), S. 239-249 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Specimens of four commercially produced particleboards were exposed to various accelerated aging treatments: 1) 6-cycle ASTM D-1037 exposure, 2) 6-cycle WCAMA exposure, 3) BS 5669 test, 4) cyclic soak-dry test, and 5) cyclic boil-dry test. Thickness swelling (TS) and internal bond strength (IB) were measured after each step of each cycle. Phenol and phenol (face)/isocyanate (core)bonded boards are more durable than urea and melamine urea bonded boards. The effect of treatment 1) is most severe on TS and IB retention, followed in order by treatments 2), 5), 4) and 3). When the value of springback reached about 35%, IB became equal to zero.
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    Polymer distribution in the cell wall of a wood-polyethylenimine composite (1991)
    Springer
    Wood science and technology 25 (1991), S. 215-224 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary A light microscopic (LM) visual technique to determine the polyethylenimine (PEI) distribution in a wood-PEI composite was studied by the adsorption of acid red or the circulation of Cu(II) ion with PEI in the composite. The amount of the adsorbed dye or Cu(II) on the composite increased linearly with an increase in the PEI content of the wood-PEI. The dyed composites were observed with LM under monochromatic light, corresponding to their absorption maxima at 560 nm for acid red and at 640 nm for copper chelate. The microscopic image was photographically recorded and the negative was subjected to densitometric analysis. At a polymer content lower than 4% in the composite, about 70% of total polymer was located in the middle lamella region, leaving only 30% in the secondary wall. With increasing PEI content of the composite, the concentration in the secondary wall increased, and about 80% of the polymer was located in the secondary wall at a PEI content of 27%. There were no noticeable differences between the amount of polymer detected by dyeing with acid red and by chelating with Cu(II). From the results of the line analysis of the intensity of the characteristic X-ray of uranium, the distribution of the PEI in the cell wall agreed closely with that determined by the LM method. It was concluded that the LM visual technique to determine the PEI location in the wood-PEI composite by dyeing with acid red or by chelating with Cu(II) is a simple and reliable method.
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    Active enzymes in wood chips and their action on lignin during outside storage (1991)
    Springer
    Wood science and technology 25 (1991), S. 281-287 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Wood storage has a great influence on the efficiency of a pulpmill. Great problems arise when using outside chip storage, especially in processing hardwoods, in that hardwood chips discolorate after a few days, which is not the case with spruce chips. The causes of such a different behavior of beech and spruce were investigated. It could be shown that a sufficient amount of active peroxidase, malate dehydrogenase and oxygen are prerequisites for the formation of phenoxy radicals within the beech lignin. This causes formation of new chromophores that discolorize the wood. Sufficient amounts of such enzymes are present in beech wood after harvesting.
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    Gas flow in hardwoods (1991)
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    Wood science and technology 25 (1991), S. 289-299 
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary A model was developed for describing the axial gas flow through hardwood samples, and gas permeability variations with increasing specimen length. To that effect, the mean vessel length of the wood species (λ) was taken into account, and the intervessel junction was modelled as a perforated plate. Mass and momentum conservation equations were then used to describe the fluid evolution through it. Outside the junction, wood was assumed to be a permeable material of Darcian behaviour. Thus, by combining Darcy's equations with the one derived for the junction zone, a system of equations was obtained modelling the overall fluid flow through the sample. The model was experimentally tested on ceibo (Erythrina crista-galli L.) samples of different lengths. Their gas permeabilities were measured, and the permeability of a zero-length sample (equivalent to that of an ideal specimen of infinitely long vessels) was calculated by means of an existing model. By introducing this last parameter into the above mentioned equation system, a theoretical value for the gas permeability was obtained. A fair agreement was observed between the model and experimental values, the differences between them being attributable to a number of simplifying assumptions that were made in order to render the system mathematically tractable.
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    Determination of the fibre saturation point in whole wood using differential scanning calorimetry (1991)
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    Wood science and technology 25 (1991), S. 301-308 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary A new method for determining the fibre saturation point (FSP) of whole never-dried wood is described. Enthalpy of melting values from differential scanning calorimetry (DSC) experiments are used to calculate the proportion of non-freezing water. Two methods for calculating the FSP from the enthalpy data are described. FSP determinations were carried out on the commercially important West Australian eucalypt species, Eucalyptus marginata and Eucalyptus diversicolor and a plantation softwood, Pinus radiata. Results are reproducible and are corroborated by the traditional volumetric shrinkage method for determining the FSP. On all samples below 10 mg a low temperature endothermic peak is observed as a shoulder on the main peak. It is postulated that this is due to an intermediate layer of water between the freezing and non-freezing water.
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    Test of an equation for nonisothermal moisture transport in wood (1991)
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    Wood science and technology 25 (1991), S. 321-325 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Reported moisture and temperature distributions in wood exposed to a temperature gradient under conditions of zero flow were used to compute changes in moisture content per change in Kelvin temperature, dm/dT. Corresponding theoretical values were calculated from a model based on nonequilibrium thermodynamics. Comparison of the measured and theoretical values supports the notion that moisture transport in wood can be modeled successfully with thermodynamic methods.
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    Medical CAT-scanning: X-ray absorption coefficients, CT-numbers and their relation to wood density (1991)
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    Wood science and technology 25 (1991), S. 341-349 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary This paper describes how X-ray absorption coefficients and CT-number in medical CAT-scanning can be calculated for dry and wet wood. A comparison with earlier recorded data for dry wood showed that the deviation between calculated and measured CT-numbers was not significant. Linear regression showed that wood density could be measured with an accuracy of ±4 kg/m3. Wood having the same green density but containing different amounts of water have different absorption coefficients and CT-numbers. A linear relationship between CT-numbers and density of wood containing water was developed. Wood density could be measured with an accuracy of ±13.4 kg/m3.
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    Elasticity of wood and wood polymer composites in tension compression and bending (1991)
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    Wood science and technology 25 (1991), S. 361-364 
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The ratio of tensile to compressive modulus of elasticity for untreated basswood was approx. 1.9 and for untreated sugar maple approx. 1.3. It approached 1.1 with high polymer loadings. The method of transformed sections gave good estimates of along the grain, tensile, compressive and bending elastic values for maple wood and maple wood polymer composite.
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    Friction coefficient as a guide to optimum rake angle in wood machining (1991)
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    Wood science and technology 25 (1991), S. 397-401 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary In spite of the obviously important role of friction in the wood cutting process, there has been little application in wood machining practice of “true” friction coefficients obtained from rubbing tests. Friction coefficients were measured during slow rubbing of incense-cedar blocks at two moisture contents on surfaces of saw steel, high speed steel and tungsten carbide. The coefficients were used in an orthogonal model of cutting to estimate the optimum rake angle for the planing of incense-cedar, and some evaluation of the estimate was made using data from cutting experiments reported elsewhere.
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    Form and treatment effects on conical roundwood tested in bending (1991)
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    Wood science and technology 25 (1991), S. 203-214 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary This article presents the results and the comments of a sampling of 80 spruce conical roundwoods (tree trunks with the bark removed) of structural sizes tested in bending. Pressure impregnated samples were prepared with and without heart holes and paired with the untreated samples. Treatment effects have been studied in order to investigate their influences on the mechanical behavior. With a non-destructive evaluation by ultrasound, the mechanical results have been compared with an equivalent sawn timber series to analyze the effect of the form. The results show a negative influence of about 10% for the pressure-impregnated treatment on the mechanical properties only and up to 20% for the samples which were associated with pinholes for the heart treatment. On the other hand, the form effect increases the mechanical characteristics by 30% when compared to the square cross section. These results can be explained by a semi-ductile phase observed before failure. This conical roundwood form contributes to optimize the mechanical behavior linked to the anisotropic conditions where the grain is continuous and has a zero angle value with the longitudinal axis.
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    Laser-excited fluorescence spectra of eastern SPF wood species. An optical technique for identification and separation of wood species? (1991)
    Springer
    Wood science and technology 25 (1991), S. 405-413 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Use of UV-laser excitation to produce fluorescence spectra for heartwood and sapwood from jack pine (Pinus banksiana), white spruce (Picea glauca) and balsam fir (Abies balsamea) was examined. Spectra were fairly broad without sharp spectral features and overlap of spectra between species was common. Sample to sample and in-sample variation of the recorded fluorescence spectra was observed. The fluorescence spectra obtained from heartwood samples of jack pine showed evidence of photochemical bleaching as a result of the multiple laser pulses needed to produce a complete spectrum. Bleaching may have obscured differences between species. For the mix of species examined no sapwood nor heartwood samples were distinguishable by this technique with the detector used. Use of an optical multichannel analyzer (OMA) could reduce the number of laser pulses needed to obtain an entire spectrum. Under these conditions it would be possible to determine whether the minor differences in spectral features observed for the different species are more pronounced in the first few laser pulses and if they are characteristic of species. Certain aspects of the data suggest that with improved analytical equipment UV-fluorescence might prove to be a useful technique for the identification of certain species.
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    The accuracy of medical CAT-scan images for non-destructive density measurements in small volume elements within solid wood (1991)
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    Wood science and technology 25 (1991), S. 425-432 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary A comparison between identically sampled CAT-scan images of five wooden test pieces (Pinus sylvestris) showed that the CT-number in each pixel varied with a standard deviation of ±3.9–11.1 CT numbers. This inaccuracy in CT-numbers is called “noise”. As long as the direction of rotation can be controlled the noise in CAT-scan images of wood can be assumed to be approx. ±4 CT-numbers in each pixel. A calculation showed the average CT-number must differ ±1 unit to distinguish average CT-numbers in 2 × 2 × 1.5 mm volumes within solid wood. It has previously been shown that a change of ±1 CT-number corresponds approx. to a change in density of ±1 kg/m3. On the other hand, there is a difference in X-ray absorption coefficients between wood and water. Thereby dry wood densities in corresponding volumes must differ approx. ±2 kg/m3 to significantly be distinguished. The corresponding figure is approx. ±6 kg/m3 for wet wood densities with moisture content levels ranging from 6–100%.
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    Sapwood, heartwood and bark thickness of silviculturally treated Eucalyptus grandis (1991)
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    Wood science and technology 25 (1991), S. 415-423 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The effects of a number of silvicultural treatments on the quantity of heartwood, sapwood and bark of 9.5 year old plantation grown Eucalyptus grandis were examined at three heights (butt 10–25 cm, 25% and 50% of total tree height). Treatments were: control (C); pre-ploughing & thinning (P); insecticide & P (I); weeding & P (W); fertilizer & P (F); and fertilizer, weeding, insecticide & P (A). Compared to controls, all silvicultural treatments produced wider sapwood (up to 134% in W at the 25% height), a greater area of sapwood (up to 160% in A at all heights), a greater area of heartwood (up to 315% in A at the butt height) a greater area of bark (up to 171% in W at the 25% height), a higher proportion of heartwood (up to 131% in A at the butt height) and increased rates of growth (up to 237% in A at the butt height). The percentage of bark was lower in treatment A. Increases in heartwood area in treatments I, F, W and A were proportionally greater at the butt height. Sapwood width and area decreased above butt height. Overall, the percentage of sapwood was correlated negatively with rate of growth and positively with height in the stem.
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    Fractionation of lignocellulose materials with phenol and dilute HCl (1991)
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    Wood science and technology 25 (1991), S. 459-466 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary We describe a way of fragmenting the lignocellulose material in furze (Ulex europæus) stems by chemical means. The process separates the three principal components in the stem: cellulose, hemicelluloses and lignin, by the joint action of a mixture of dilute hydrochloric acid to hydrolyse the hemicelluloses, and phenol, to dissolve the lignin. The effects of the process variables on the yield have been studied. The fractions obtained have been characterized and methods for their use are proposed.
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    Variation of tensile strength along the length of lumber (1991)
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    Wood science and technology 25 (1991), S. 351-359 
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The within member variation of tensile strength parallel to grain in nominal 38×89 mm No. 2 Spruce-Pine-Fir lumber has been experimentally evaluated. Window analyses yielded the within member tensile strength cumulative probability distributions of lumber segments with various lengths. Semivariogram and regression analyses have been performed to characterize the spatial correlation of the tensile strength of lumber. The results indicate that the tensile strength values within a piece of lumber separated by a distance greater than 1.83 m can be considered statistically independent.
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    Modeling the process of absorption and desorption of water above and below the fiber saturation point (1991)
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    Wood science and technology 25 (1991), S. 327-339 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The process of absorption of water along the tangential direction of the wood is studied by immersing the sample in water. The transport of water is then obtained below the fiber saturation point at the beginning of the absorption and above this fiber saturation point during the process. The potential which drives the transport of the bound-water and free-water through the wood has been considered by testing a diffusional transport model. The transient diffusion with a constant diffusivity has been found to describe not only the process of absorption but also the process of desorption with diffusion of water through the solid and evaporation from the surface. Analytical solutions have been successfully used to describe the stage of absorption during a time of four hours at the end of which an equilibrium of absorption is attained, as well as the following stage of desorption. A model based on a numerical method with finite differences has been found to describe the process of absorption and desorption in various cases, and especially when the equilibrium of absorption has not been attained.
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    Analysis of beech wood fatty acids by supercritical acetone extraction (1991)
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    Wood science and technology 25 (1991), S. 365-370 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Soxhlet and supercritical fluid extracts of freshly cut oriental beech (Fagus orientalis) have been obtained using acetone. While the yield of the Soxhlet extract was 2.54% the yield of the supercritical acetone extract obtained at 240°C and 6.0–6.5 MPa was 9.55% (dry wood basis). The fatty acids present in the extracts were separated by chemical and Chromatographic methods and analysed by combined gas chromatography and mass spectrometry. Linoleic acid was the major fatty acid in both extracts.
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    Book reviews (1991)
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    Wood science and technology 25 (1991), S. 402-403 
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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    Creep in chipboard (1991)
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    Wood science and technology 25 (1991), S. 383-396 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Samples of five chipboards, one waferboard, one plywood, one fibre building board and redwood timber (Pinus sylvestris) were loaded in 4-point bending under four stress levels: 30, 45, 67.5 and 75% of the short term ultimate, thereby extending earlier work at 60% stress level. Five environmental conditions were used at each stress level: 10°C 62% relative humidity (rh); 20°C 30% rh; 20 °C 65% rh; 20°C 90% rh and 30°C 68% rh. Deflections were recorded at least on a daily basis for a period of 6 months, unless failure of the sample occurred earlier. Values for the elastic, viscoelastic and viscous components of creep deflection were calculated for two time periods using the 4-element rheological model developed in an earlier paper: comparisons were made on the basis of the percentage contribution of each component. The relative proportions of the elastic, viscoelastic and viscous components making up total deflection were found to vary considerably with time, temperature, relative humidity, stress level and material. The relationships were complex with strong interactions occurring among environmental condition, stress level and material. Thus, for example, the effect of high temperature, or high relative humidity, in determining the magnitude of the viscous component was much greater at higher levels of stressing: waferboard appeared to be less sensitive to high humidity and solid timber more sensitive to high temperature than the other materials. T-tests further confirmed the complexity of the relationships. It is concluded that much of the variability in creep deflection recorded in Part 8 of this series is primarily due to changes in the percentage contribution of the viscous component.
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    Bending strength adjustments for moisture content for structural lumber (1991)
    Springer
    Wood science and technology 25 (1991), S. 433-447 
    Details
    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Effects of moisture content on bending strength and section capacity have been studied assuming that strength properties are linearly related to moisture content below the fiber saturation point. The models developed using the linear strength vs. moisture content relationships are compared with quadratic models developed earlier. The linear representation of strength variation with moisture content leads to predicted member bending capacity relationships which show that increases in member bending strength with moisture content will compensate for section property decreases at all bending strength property levels. Comparisons of bending strength and bending capacity models show that the two modelling approaches lead to similar predicted member performance. Simplified procedures are provided for adjusting member bending strength for moisture content which are suitable for materials properties codes or standards.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225236
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    Book reviews (1991)
    Springer
    Wood science and technology 25 (1991), S. 473-473 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225240
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  • 87
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    Variation of tensile strength along the length of lumber (1991)
    Springer
    Wood science and technology 25 (1991), S. 449-458 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary A model has been developed for the within member variation of tensile strengths parallel to grain in nominal 38 × 89 mm No. 2 Spruce-Pine-Fir lumber. Tensile strength data from two modulus of elasticity matched groups were considered. Model parameters obtained from data group 1 were used to generate tensile strength profiles of lumber 6.10 m long. Within member tensile strength cumulative probability distributions of the simulated data were evaluated by window analyses. The spatial correlation of the simulated data were evaluated by semivariogram and regression analyses. Good agreement was obtained between model predictions and test results of both groups.
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    URL: http://dx.doi.org/10.1007/BF00225237
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  • 88
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    Variation of the phenolic hydroxyl group content in wood lignins (1991)
    Springer
    Wood science and technology 25 (1991), S. 467-472 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The phenolic hydroxyl group content of wood lignin has been determined in situ by a periodate oxidation method for four softwood and six hardwood species. Hardwood lignins, in contrast to softwood lignins, showed a significant variation among different species in this functional group content which decreased with an increase in the proportion of syringyl units in the wood lignin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225239
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  • 89
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    Dependence of the water vapor diffusion coefficient of aspen (Populus spec.) on moisture content (1991)
    Springer
    Wood science and technology 26 (1991), S. 9-21 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The dependence of the diffusion coefficient of water in aspen (Populus sp.) on moisture content over the range of 0 to 18 percent moisture content at 43 °C was determined. The method requires a series of adsorption experiments and application of a numerical method for solving the diffusion equation with a moisture-content-dependent diffusion coefficient. The diffusion coefficient was found to increase exponentially with moisture content. The numerical method includes variable boundary conditions, as defined by the surface emission coefficient, so that the effect of surface equilibrium moisture content can be examined. The experimental moisture content-time curves can be predicted by the numerical method and showed an average deviation of 0.2 percent moisture content with the largest deviation being 0.7 percent moisture content. Practical implications and uses of the information derived from the numerical method are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225688
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  • 90
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    Early detection of brown-rot decay in southern yellow pine using immunodiagnostic procedures (1991)
    Springer
    Wood science and technology 26 (1991), S. 1-8 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Immunodiagnostic procedures have been used to detect incipient decay of southern yellow pine by six common brown-rot fungi. Rabbit polyclonal antibodies were raised to liquid culture fractions of the six fungi. The antibodies, after preadsorption to sawdust, were tested in particle agglutination assays, immuno-dot blot, and enzyme-linked immunosorbent assay (ELISA) for their ability to detect the decay organisms when they were grown in southern yellow pine. Results were correlated to wood-block weight loss. Each method specifically detected five of the six test organisms at very low wood-block weight loss. Agglutination assays were the least effective and lacked the sensitivity of the other assays, even though the latex particles were more sensitive and reproducible than charcoal particles. Cross-reactivity was noted only for one of the control organisms and only in the charcoal agglutination assay. Both dot blot and ELISA were sensitive test methods, but ELISA had the advantage of quantification. We feel that two of these assays, latex for presumptive results and ELISA for definitive results, could effectively detect incipient decay of common brown-rot fungi.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225687
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  • 91
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    Book reviews (1991)
    Springer
    Wood science and technology 26 (1991), S. 71-72 
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    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225693
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  • 92
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    The ultrastructure of the posterior gut and caecum inAlona affinis (Crustacea, Cladocera) (1991)
    Springer
    Zoomorphology 110 (1991), S. 139-144 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The posterior midgut, the anterior hindgut and the caecum ofAlona affinis were studied by transmission electron microscopy. The caecum arises from the junction of the entodermal midgut and the ectodermal hindgut. It consists of gastrodermis and epidermis. Because of the ultrastructural similarity of the caecum with the posterior midgut and the anterior hindgut it is concluded that the caecum is a functional supplement of the latter gut parts. But the functional significance of these gut parts is poorly understood. Some ultrastructural features suggest that they contribute in excretion and salt regulation.
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    URL: http://dx.doi.org/10.1007/BF01632870
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    Formation, properties and degradation of the peritrophic membranes of larval and adult fleshflies,Parasarcophaga argyrostoma (Insecta, Diptera) (1991)
    Springer
    Zoomorphology 111 (1991), S. 103-111 
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    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Parasarcophaga argyrostoma larvae continuously secrete a single, tube-like peritrophic membrane (PM), which has an electron-dense layer on the lumen side and a thicker chitin-containing electron-lucent part on the epithelium side. In the adult fleshfly, the secretion of PMs starts immediately after emergence. The initial part of the PMs is twisted and tight. The formation zone is folded with two separate secretory pads in which two tube-like PMs are formed continuously. The PMs are different, morphologically and with respect to their peripheral carbohydrate residues. The latter could be demonstrated with lectin gold conjugates. PM 1 consists of an electron-dense, chitin-free layer on the lumen side and a thicker part which contains chitin microfibrils in the matrix. PM 2 appears fluffy and has chitin microfibrils in its matrix, too. Chitin could be localized with WGA gold. Incubation of isolated PM 1 with lectin gold resulted in a peculiar pattern of bound lectins and gaps on the electron dense layer which otherwise appeared to be homogenous. Degradation of peritrophic membranes takes place in the hindgut. The cuticle of the anterior hindgut is studded with small teeth, which seem to be responsible for mechanical degradation of the peritrophic membranes into frayed pieces. This may be completed by the teeth on the rectal pads. From the appearance of the remnants of the peritrophic membranes it can be inferred that chemical degradation takes place in the hindgut.
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    URL: http://dx.doi.org/10.1007/BF01632876
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    Construction of the avian skull, as demonstrated by direct magnifying microfocal radiography (Aves) (1991)
    Springer
    Zoomorphology 111 (1991), S. 119-124 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The new microfocus X-ray technique works with X-ray sources smaller than 10 Μm in diameter. Thus, in contrast to conventional X-ray systems, it is possible to obtain direct magnifications with high spatial resolution, i.e., well-focused radiographs with better contrast and “depth of focus”. In this connection, specific construction principles of the avian skull are elucidated, comparing several bird groups. The typical pneumatization effects are demonstrated, as are other biologically important anatomical features, in particular those of the bills/beaks as related to mechanical demands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01632878
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    Cytoskeletal modifications of the sensorimotor interneurons ofHydra vulgaris (Cnidaria, Hydrozoa), indicating a sensory function similar to chordotonal receptors of insects (1991)
    Springer
    Zoomorphology 111 (1991), S. 113-118 
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    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The battery mother cell complexes in the tentacles ofHydra vulgaris contain a neuronal cell known as sensorimotor interneuron that is characterized by a modified cilium lying parallel to the mesoglea. The cilium is surrounded by up to three rings of microvilli. Microvilli and cilium arise in an unusual antiparallel orientation from the opposite poles of a central cellular cavity. The lumen of this cavity communicates with the extracellular environment by way of a straight channel-like opening that is encircled by the microvillar rings. The modified cilium extends into the channel and terminates outside in the intercellular space. The wall of the cavity and the channel are stabilized by bundles of microtubules. A prominent glycocalyx interconnects all microvilli and links the innermost microvillar ring to the cilium. Within this contact region approximately 0.7 Μm in length the ciliary axoneme is specifically modified: all nine microtubule doublets and up to six additional microtubules are embedded in electron-dense material. The microtubule doublets are connected to the ciliary membrane by ledges of Y-shaped cross-bridging elements. These axonemal modifications resemble those known from the hydrozoan cnidocil complex or from the outer segments of insect mechanoreceptor cells. Distribution and orientation of the sensorimotor interneuron within the tentacles indicate a mechanosensory function of the cell similar to that of chordotonal receptors of insects.
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    URL: http://dx.doi.org/10.1007/BF01632877
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    Identification of human genes involved in repair and tolerance of DNA damage (1991)
    Springer
    Radiation and environmental biophysics 30 (1991), S. 1-19 
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    ISSN: 1432-2099
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Summary An overview is presented on strategies of cloning mammalian DNA repair genes. Complementation of human and rodent repair defects and mutagen hypersensitivities by chromosome and DNA mediated gene transfer and mRNA microinjection is described, and the features of the cloned human DNA repair genes are summarized. It is shown that transfection of repair deficient cell lines with cloned bacterial and human genes may give rise to protection from the genotoxic effects of mutagens.
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    URL: http://dx.doi.org/10.1007/BF01595570
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    After X-irradiation a transient arrest of L929 cells inG 2-phase coincides with a rapid elevation of the level of O6-alkylguanine-DNA alkyltransferase (1991)
    Springer
    Radiation and environmental biophysics 30 (1991), S. 21-31 
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    ISSN: 1432-2099
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Summary Following X-irradiation of exponentially growing L929 cells two major phenomena have been observed. First, there was a delay in cell division which can be ascribed to the arrest of cells in theG 2-phase (G 2-block), and, second, the cellular content of the O6-alkylguanine-DNA alkyltransferase (AGT) was markedly increased. Flow cytometrical DNA-measurements revealed that cells began to accumulate in theG 2-phase 4 h after irradiation (p.r.) irrespective of the X-ray dose, while both the fraction of cells blocked inG 2 and the time period the cells persisted inG 2 increased with the radiation dose. About 24 h past release from theG 2-block the distribution of cells in the cell cycle was similar to that of untreated control cells. In comparison with control cells the AGT content in irradiated cells (4 Gy) was highest at about 48 h p.r. (3.4-fold increase). The highest ratio of increase in AGT was, however, observed to occur between about 4 and 13 h p.r. (2.6-fold increase). As shown by flow cytometrical measurements using a BrdUrd/DNA double labeling technique, this rapid primary increase in AGT coincides very well with the entrance of cells into theG 2-phase. This indicates that the cellular AGT content in X-irradiated (parental) cells started to exceed the basal level at the beginning of theG 2-phase, but not before or during theS-phase. Once the AGT level was elevated it continued to increase for 2 to 3 cell doubling times.
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    URL: http://dx.doi.org/10.1007/BF01595571
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    Ionizing radiation-induced structural modification of human red blood cells (1991)
    Springer
    Radiation and environmental biophysics 30 (1991), S. 45-52 
    Details
    ISSN: 1432-2099
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Summary The effect of gamma radiation on red blood cells have been examined using a spin labeling method. For this purpose two spin labels were used to monitor membrane fluidity: methyl 5-doxylpalmitate (Met 5-DP) and methyl 12-doxylstearate (Met 12-DS). The irradiation of red cells with the doses of 200 and 500 Gy caused decrease of microviscosity in certain regions of lipid bilayer (as indicated by Met 5-DP and Met 12-DS spectra) but did not affect lipid order parameter. The behavior of two other spin labels, maleimide(4-malei-mido-2,2,6,6-tetramethylpiperidine-1-oxyl) and TEMPONE (4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl) indicated:1) conformational changes of membrane proteins,2) modification of cell internal peptides and proteins,3) decreased internal viscosity of red blood cells.
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    URL: http://dx.doi.org/10.1007/BF01595573
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    Mössbauer effect study of gamma-irradiated human oxyhemoglobin (1991)
    Springer
    Radiation and environmental biophysics 30 (1991), S. 33-44 
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    ISSN: 1432-2099
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Summary Preliminary results of the Mössbauer effect study of human adult oxyhemoglobin in erythrocytes exposed to gamma-irradiation with doses of ∼ 100, ∼ 300 and ∼ 600 kGy are presented. Mössbauer spectra measured at 87 K have been analyzed in two ways. At first, to fit these spectra we used the four components oxyhemoglobin, deoxyhemoglobin, hemochromes and nonheme Fe(III) compound which had been obtained earlier from Mössbauer spectra of X-irradiated oxyhemoglobin by Chevalier et al. (1983). However, this approximation was not satisfactory. Then a new model of spectral fitting with five components was used. These were oxyhemoglobin, deoxyhemoglobin and components marked1, 2 and3. Using Mössbauer hyperfine parameters of each component the valence/spin states of iron ions were determined and possible complexes were considered. The most probable compounds for components1, 2 and3 were hematin and/orµ-oxodimers, methemoglobin hydroxide and/or hemichromes, and the high spin Fe(III) complex, respectively. Changes of the relative areas of Mössbauer subspectra of all components (its content in samples) versus doses were evaluated and the presence of the high and low spin aquomethemoglobin was indicated.
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    URL: http://dx.doi.org/10.1007/BF01595572
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  • 100
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    Cross sections for single and double strand breaks in SV-40 virus in EO buffer after heavy ion irradiation: Experiment and theory (1991)
    Springer
    Radiation and environmental biophysics 30 (1991), S. 81-85 
    Details
    ISSN: 1432-2099
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Summary Measured cross sections after heavy ion bombardment, for both single and double strand breaks of SV-40 virus in EO buffer (which emphasizes indirect effects), are consistent with the theory of Butts and Katz for 1-hit detectors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01219342
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