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Sorghum stems comprise different tissue components, i.e., rind, pith, and vascular bundles in the rind and pith regions, of different cell morphologies and cell wall characteristics. The overall responses of stems to mechanical loadings depend on the responses of these tissues themselves. Investigating how each tissue deforms to various loading conditions will inform us of the failure mechanisms in sorghum stems when exposed to wind loadings, which can guide the development of lodging-resistant variants. To this end, numerical analyses were implemented to investigate the effects of cell morphologies and cell wall properties on the overall mechanical responses of the above four tissues under tension and compression. Microstructures of different tissues were constructed from microscopic images of the tissues using computer-aided design (CAD), which were then used for finite element (FE) analyses. Shell finite elements were used to model the cell walls, and the classical lamination model was used to determine the overall mechanical responses of cell walls having different fiber composite arrangements. The results from the numerical analyses helped explain how the loading (boundary) conditions, the cell microstructures, the mechanical properties of cell walls of different tissues, the cell wall thickness, the microfibril angle (MFA) of fiber composites of the cell walls, and the turgor pressure affected the overall mechanical responses of the tissues. Tissue stiffening or softening behaviors were attributed to different microstructural deformations, i.e., local or global buckling of cell walls, cell collapse, densifications of cells, or reorientation and rearrangement of cells. The mechanical properties and thickness of cell walls only affected the stiffness and load-bearing ability of the tissues. The turgor pressure affected the compressive responses but its effect on tensile responses was negligible. The MFA had a significant influence on the stiffness and load-bearing ability when the tissues were loaded along their longitudinal axis, but it had an insignificant effect on loading in the transverse direction. Tissues with smaller cell sizes and denser cells were stronger and stiffer than those with larger cell sizes. The numerical simulations also revealed that rind and rind vascular bundles were stiffer and had higher load-bearing ability than pith and pith vascular bundles. [ABSTRACT FROM AUTHOR]

An investigation was carried out in the years 2006-2008 in order to compare the chemical composition of sweet sorghum stems. Two varieties of sweet sorghum: Sucrosorgo G-1990 (photoperiodically sensitive -- headless) and Sucrosorgo 506 (photoperiodically insensitive -- headed) were tested. Samples of large and small diameter stems were collected from both types of sorghum, from different parts of stem (lower, medium and top internodes). Each internode was fractionated into three stem part: leaves, the outer (rind) and the inner part (pith). The effect of the part of a stem and the place from which internodes were collected on the chemical composition was determined. The content of crude fibre and its fractions: neutral detergent fibre (NDF), acid detergent fibre (ADF), hemicellulose, crude proteins, carbohydrates: total carbohydrates, sucrose, reducing sugars and macroelements was determined in the plant material. The largest diversity in proportions of the chemical compounds was observed in the pith. Amounts of the NDF fraction in the rind depended on a stem's diameter. The site from where an internode sample was collected had the greatest effect on the chemical composition, mostly the concentrations of macroelements (N, P -- in all three stem parts, K and Mg -- in the pith, Ca -- in leaves and the rind, Na -- in leaves). The diameter of a stem had a negative effect on the chemical composition and deteriorated the technological value of sorghum, since the content of crude fibre and its fraction increased. [ABSTRACT FROM AUTHOR]

The incorporation of natural fibres in earth construction elements is a common practice that is found both in traditional and in contemporary building systems. The positive effect that such materials have on the mechanical properties of the clay mixtures has been established in previous research. However, their effect on the hydric and thermal properties is less well understood and these properties are important for thermal mass and passive humidity control in buildings, aspects linked to occupant health and reductions in energy use. The present paper includes the first in-depth study of the thermal conductivity and diffusivity, as well as the water vapour permeability and moisture buffering of compressed earth blocks and plasters incorporating natural fibres. Two different vegetable materials, barley straw and corn pith, were mixed to the clay materials in two different percentages (1% and 2%). The results show that the vegetable materials have a great impact on the thermal properties and the apparent density of the mixtures, but a limited effect on the hydric properties. The greatest improvement of the moisture behaviour was shown by the specimens incorporating 2% of corn pith. This improvement is greater for short time exposure than long time exposure. After 3 h, these mixtures adsorbed 15.5 g of moisture more than the plain samples, but after 8 h the difference was reduced to 8.0 g. This indicates that such mixtures might be more appropriate in environments with short and intense moisture loads, such as bathrooms. Previous research has demonstrated that earth provides the highest moisture buffering capacity of common building materials, and this research demonstrates how these properties can be enhanced for specific applications. [ABSTRACT FROM AUTHOR]

The sorption of two dyes, namely, Basic Red 22 and Acid Red 114 ontopith has been studied in terms of pseudo-second-order, pseudo-first-order sorption and intraparticle diffusion processes thus comparing chemical sorption and diffusion sorption processes. The pseudo-second-order model, based on the assumption of a pseudo-second-order mechanism, has been developed to predict the rate constant of sorption, the equilibrium capacity and initial sorption rate as a function of the effect of initial dye concentration, pith particle size, pith dose andtemperature. [ABSTRACT FROM AUTHOR]