Dimensional changes of cell wall and cell lumens upon water sorption revisited. Literature review and mathematical considerations based on the cylindrical model

Holzforschung ◽  
2018 ◽  
Vol 72 (5) ◽  
pp. 413-419
Author(s):  
Takato Nakano
Keyword(s):  
Cell Wall ◽  
Wood Species ◽  
Water Sorption ◽  
Point Of View ◽  
Thickness Variation ◽  
Swelling Ratio ◽  
Cylindrical Model ◽  
Dimensional Changes ◽  
Wall Thickness Variation ◽  
S2 Layer

AbstractThe dimensional changes of the cell wall and cell lumens are revisited based on literature data and on the mathematical cylindrical model. The external swelling ratio in the cross-section of the wood cell is considered as a function of the moisture content (MC)mfrom the point of view of the swelling ratio of the cell wall, the swelling parameterk, which is defined as the ratio of the outer variation to the cell wall thickness variation, and the cell wall densityds. The swelling behavior of the cell lumen is evaluated based on the parameterkcalculated from experimental observations, which accounts for both the swelling direction and variation degree of the lumen: the lumen radius (i) decreases atk<1, (ii) remains fixed atk=1, and (iii) increases atk>1. The derived equation was applied to 176 wood species from the literature, and it was found that 0.4<k<1.4, while in most cases 0.8<k<1.0. In other words, the lumen radius in most wood species is decreasing with water sorption. As expected, the S2 layer swelling is differently restricted in the circumferencial direction by the S1 and S3 layers with their different cell wall architecture.

Analysis of cell wall swelling on the basis of a cylindrical model

Holzforschung ◽  
2008 ◽  
Vol 62 (3) ◽  
Author(s):  
Takato Nakano
Keyword(s):  
Cell Wall ◽  
Moisture Content ◽  
Wall Thickness ◽  
Water Adsorption ◽  
Cell Wall Thickness ◽  
Swelling Ratio ◽  
Cylindrical Model ◽  
Number Of Factors ◽  
The Relationship

Abstract The relationship between inward and outward swelling of cell wall surfaces was examined. A formula was derived based on a cylindrical model of a wood cell. The equation clarifies that the slope of the swelling ratio of the whole wood versus moisture content is governed by a number of factors. This equation allows the examination of how the swelling direction of cell wall surfaces is determined during water adsorption. The swelling direction is given by the parameter Δh/Δr, where Δh is the increase of cell wall thickness as a result of inward and outward swelling and Δr is the outward increase.

Mechanics of Conventional Spinning

1963 ◽  
Vol 85 (4) ◽  
pp. 346-350 ◽  
Author(s):  
H. C. Sortais ◽  
S. Kobayashi ◽  
E. G. Thomsen
Keyword(s):  
Wall Thickness ◽  
Pure Aluminum ◽  
Tangential Force ◽  
Deformation Energy ◽  
Thickness Variation ◽  
Force Component ◽  
Commercially Pure ◽  
Conventional Spinning ◽  
Wall Thickness Variation ◽  
Experimental Values

In conventional spinning of cones, the cone-wall thickness variation was studied using blanks of 1100-0 commercially pure aluminum sheet of 0.050-in. thickness. The results revealed that the radial stress induced in the unspun flange is the major cause of nonuniform wall thickness of spun cones. The theoretical tangential force component was derived by use of the deformation energy method. Qualitative agreement was found between the theoretical and the experimental values of tangential force component in the underspinning conditions.

scholarly journals Alterações dimensionais em pastas de óxido de zinco/eugenol: um novo método para sua mensuração

2021 ◽  
pp. 39-55
Author(s):  
Léo Werner Süffert ◽  
Ennio Pessôa
Keyword(s):  
Standard Deviation ◽  
Personal Information ◽  
High Variability ◽  
Point Of View ◽  
New Method ◽  
Extensive Review ◽  
Review Of The Literature ◽  
Dimensional Changes ◽  
Impression Materials ◽  
Clinical Point

After an extensive review of the literature, regarding zinc.oxide/eugenol impression pastes, we selected 20 of the most representatives as our references. Trough personal information of several of the investigators it was discovered that dimensional changes of theese materials is one of the most difficult properties to be measured. A new method was developed to measure dimensional changes ot 4 (four) of the most widely used zinc.oxide/eugenol impression materials in Brazil. The results, presented through several graphs and tables showed that dimensional changes varied from 0,003%, values which may probably be considered negligible from a clinical point of view. We noticed, however, high values for standard deviation and variance which indicate the high variability within the experiments. Those values were not found when we used the same method with mercaptan and silicone impression materials, in which the measurement of dimensional changes was highly reproducible. One hypothesis (which we intend to investigate in a later research) is that, during storage, a sedimentation could occur, of the components of greater density! Consequently ther might result a change in composition, independent of the method used to establishe the proportion of the two pastes, be it by wheight or measurement of lenght, which could be the cause of variability of the composition of each mixture!

Cell Wall Pore Structures of Bamboo as Relation to Species and Tissue Types

2021 ◽  
Author(s):  
Mengdan Cao ◽  
Wenting Ren ◽  
Jiawei Zhu ◽  
Hankun Wang ◽  
Juan Guo ◽  
...  
Keyword(s):  
Cell Wall ◽  
Wood Species ◽  
Distinct Species ◽  
Bamboo Species ◽  
Compact Structure ◽  
Pore Structures ◽  
Mesopore Structure ◽  
Parenchyma Cells ◽  
Bamboo Fibers ◽  
Cell Wall Porosity

Abstract Efficient convention of bamboo biomass into biofuel and biomaterials, as well as chemical treatment are both highly related to the porosity of cell wall. The present work characterizes the micropore and mesopore structure in cell walls of six different bamboo species and tissue types using CO2 and N2 adsorption. Two plantation wood species were also tested for comparison. Bamboo species normally showed lower cell wall porosity (2.64%-3.75%) than wood species (3.98%-5.06%), indicating a more compact structure for bamboo than wood. A distinct species dependence of cell wall pore structures and porosity was also observed. Furthermore, the cell wall pore structure and porosity are shown to be tissue-specific, as the parenchyma cells exhibit higher pore volume and porosity compared to bamboo fibers. The obtained results give new explanations on the known facts that both bamboo and bamboo fibers exhibit higher biomass recalcitrance as compared to wood and bamboo parenchyma cells, constructing the base of pretreatment optimization and subsequent processing for bamboo-derived biofuels and biomaterials.

Fließpressen hohler Wellen mit Wanddickenvariation/Cold forging of hollow shafts with wall thickness variation – Numerical investigation of a hollow forward extrusion process with adjustable deformation zone

2020 ◽  
Vol 110 (10) ◽  
pp. 684-688
Author(s):  
Alexander Weiß ◽  
Mathias Liewald
Keyword(s):  
Numerical Investigation ◽  
Metal Forming ◽  
Extrusion Process ◽  
Cold Forging ◽  
Thickness Variation ◽  
Part Geometry ◽  
Forming Technology ◽  
Wall Thickness Variation ◽  
The University ◽  
Hollow Shafts

Die Fertigung von Hohlwellen mit komplexer Innengeometrie bedingte bisher meist aufwendige Prozessrouten. Ein am Institut für Umformtechnik der Universität Stuttgart entwickeltes Kaltfließpressverfahren soll nun die wirtschaftliche und flexible Fertigung von Hohlwellen mit Wanddickenvariation ermöglichen. In diesem Beitrag werden das Verfahren beschrieben und die Ergebnisse der numerischen Untersuchung des Einflusses der Werkzeugkinematik auf die erzielbare Pressteilgeometrie dargelegt. &nbsp; Usually, the production of hollow shafts with complex internal geometry by cold forging requires extensive process routes. A novel cold forging process developed at the Institute for Metal Forming Technology at the University of Stuttgart allows for an economical and flexible production of hollow shafts. This article describes the manufacturing process and presents the results of a numerical investigation for determining the influence of tool kinematics on the achievable part geometry.

scholarly journals Comparison of the Decay Behavior of Two White-Rot Fungi in Relation to Wood Type and Exposure Conditions

2020 ◽  
Vol 8 (12) ◽  
pp. 1931
Author(s):  
Ehsan Bari ◽  
Geoffrey Daniel ◽  
Nural Yilgor ◽  
Jong Sik Kim ◽  
Mohammad Ali Tajick-Ghanbary ◽  
...  
Keyword(s):  
Cell Wall ◽  
Moisture Content ◽  
Wood Species ◽  
White Rot Fungi ◽  
White Rot ◽  
High Mass ◽  
Type I ◽  
Oak Wood ◽  
Mass Losses ◽  
Decay Behavior

Fungal wood decay strategies are influenced by several factors, such as wood species, moisture content, and temperature. This study aims to evaluate wood degradation characteristics of spruce, beech, and oak after exposure to the white-rot fungi Pleurotusostreatus and Trametesversicolor. Both fungi caused high mass losses in beech wood, while spruce and oak wood were more resistant to decay. The moisture content values of the decayed wood correlated with the mass losses for all three wood species and incubation periods. Combined microscopic and chemical studies indicated that the two fungi differed in their decay behavior. While T. versicolor produced a decay pattern (cell wall erosion) typical of white-rot fungi in all wood species, P. ostreatus caused cell wall erosion in spruce and beech and soft-rot type I (cavity formation) decay in oak wood. These observations suggest that P. ostreatus may have the capacity to produce a wider range of enzymes/radicals triggered by the chemical composition of wood cell walls and/or local compositional variability within the cell wall.

Scanning UV microspectrophotometry as a tool to study the changes of lignin in hydrothermally modified wood

Holzforschung ◽  
2016 ◽  
Vol 70 (3) ◽  
pp. 215-221 ◽  
Author(s):  
Bruno Andersons ◽  
Guna Noldt ◽  
Gerald Koch ◽  
Ingeborga Andersone ◽  
Anete Meija-Feldmane ◽  
...  
Keyword(s):  
Cell Wall ◽  
Degradation Products ◽  
Middle Lamella ◽  
Temperature Range ◽  
Wood Protection ◽  
Lower Temperature Range ◽  
Lower Temperature ◽  
The One ◽  
S2 Layer ◽  
Uv Microspectrophotometry

Abstract Thermal modification (TM) of wood has occupied a relatively narrow but stable niche as an alternative for chemical wood protection. There are different technological solutions for TM and not all details of their effects on wood tissue have been understood. The one-stage hydrothermal modification (HTM) at elevated vapour pressure essentially changes the wood’s composition and structure. In the present paper, the changes in three hardwood lignins (alder, aspen, and birch) were observed within the cell wall by means of cellular UV microspectrophotometry. The lignin absorbances in the compound middle lamella (CML) of unmodified wood are 1.7- to 2.0-fold higher than those in the fibre S2 layer. The woods were modified in the temperature range from 140 to 180°C, while in the lower temperature range (140°C/1 h), the UV absorbances are little affected. Essential changes occur in the range of 160–180°C and the UV data reflect these by absorbtion changes, while the absorbances at 278 nm rise with factors around 2 more in the S2 layer than in the CML. The absorbance increments are interpreted as polycondensation reactions with furfural and other degradation products of hemicelluloses with the lignin moiety of the cell wall.

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