Wood density and wood shrinkage in relation to initial spacing and tree growth in black spruce (Picea mariana)

This study has quantified basic wood density and various types of wood shrinkage in relation to initial spacing (or initial planting density) and tree growth based on a 48-year-old black spruce (Picea mariana) spacing trial in eastern Canada. A total of 139 sample trees were collected from four initial spacings (3086, 2500, 2066, 1372 trees/ha) for this study. Analyses of variance (ANOVA) show that initial spacing is the most important parameter affecting wood density significantly, followed by tree diameter at breast height (DBH) class. With increasing spacing, wood density, radial and volumetric shrinkage tend to decrease, whereas longitudinal shrinkage tends to increase gradually. The largest spacing has the lowest wood density, the smallest transverse shrinkage and the largest longitudinal shrinkage. Path analysis indicates that wood density is the most important parameter affecting transverse shrinkage, followed by the distance from the pith. Furthermore, much of the variation of the transverse shrinkage with wood density may be due to the initial spacing and tree DBH class. Path analysis also reveals that longitudinal shrinkage is mainly related to log height and tree DBH class. With increasing log height, longitudinal shrinkage tends to increase, and transverse shrinkage tends to decrease. With increasing DBH class, the trees tend to have an increasing longitudinal shrinkage and a decreasing transverse shrinkage. Overall, this study suggests that a large increase in the initial spacing (e.g., 1372 trees/ha) might lead to a significant reduction in both wood density and transverse shrinkage, and a significant increase in longitudinal shrinkage in black spruce.

Muscle, Ageing and Temperature Influence the Changes in Texture, Cooking Loss and Shrinkage of Cooked Beef

This study aimed to quantify the effect of muscle, ageing and cooking temperature on the texture, cooking loss and shrinkage of cooked beef. Cuboids from unaged (1 day post mortem) and aged (14 days post mortem) semitendinosus, biceps femoris and psoas major muscles, from both sides of five beef carcasses, were cooked at four different cooking temperatures (50, 60, 70 and 80 °C) for 30 min. and their Warner–Bratzler shear force (WBSF), cooking loss and shrinkage (longitudinal and transverse) were quantified. The WBSF was reduced by ageing in the muscles at the specific cooking temperatures: psoas major (cooked at 50, 60 and 80 °C), semitendinosus (70 and 80 °C) and biceps femoris (80 °C). The cooking loss was 3% greater in aged compared to unaged muscles. The longitudinal shrinkage was greatest in psoas major at 80 °C amongst the muscle types and it was reduced by ageing in psoas major (70 and 80 °C) and biceps femoris (80 °C). The transverse shrinkage was reduced by ageing only in biceps femoris, across all temperatures; and the diameter of homogenized fibre fragments from semitendinosus and biceps femoris was reduced more by cooking at 50 °C in unaged compared to aged condition. WBSF was related to transverse shrinkage, and cooking loss was related to longitudinal shrinkage. The effect of muscle type on the physical changes occurring during cooking of beef is dependent on ageing and cooking temperature.

Some physical properties of the date palm stem

The main objective of this study was to test some technological performances of date palm stem (Phoenix dactylifera L.) from the region of Marrakech in Morocco with a view to its use in housing construction in southern Moroccan regions. Physical characteristics were determined according to French AFNOR standards. The samples used were respectively 20 mm × 20 mm × 20 mm in the longitudinal, radial and tangential directions. All the results obtained were the average of the measurements on 50 samples. The results obtained showed that the moisture content has an average value of 15 % at the center of stem and 18 % at the periphery and the infradensity has a value of 0.18 g / cm3 in the center and 0.42 g / cm3 in the periphery. For samples from the center, the tangential, radial and longitudinal shrinkage were respectively 2.02 %, 1.77 %, and 0.42 %, while on the periphery of the stem the tangential, radial and longitudinal shrinkage were respectively 3.41 %, 2.98 % and 0.34 %. These results showed that the stem center has better dimensional stability compared to the peripheral region of the stem.

The effect of using synthetic fibers on some properties of modified juss

This paper examines the mechanical properties of a composite material made of modified Iraqi gypsum (juss) reinforced with polypropylene fibers. The modified juss was prepared by adding two percentages of cement (5, 10) %. Two percentages of polypropylene fibers were used, to reinforce the modified juss (1, 2) %. The water/dry compound ratio used was equal to 0.53%. The composite was evaluated based on compressive strength, flexural strengths, absorption percentage, density, acoustic impedance, ultra - pulse velocity, longitudinal shrinkage and setting time tests. The results indicated that the inclusion of cement on to juss increases the compressive strength, absorption percentage, density, acoustic impedance, ultra - pulse velocity, longitudinal shrinkage and a reduction in flexural strength and setting time were observed by adding the cement. In addition, the inclusion of polypropylene fiber was significant in improving mechanical performance of the composite material, it shows a great improvement in longitudinal shrinkage, modulus of rupture and absorption percentages.

Longitudinal shrinkage of compression wood in dependence on water content and cell wall structure

Compression wood from branches of <i>Pinus silvestris</i> L. was examined. Wide differences were noted in longitudinal shrinkage of the wood when dried from water saturated state. A relation was found between shrinkage and cell wall thickness, particularly of layer S₂, and the degree of callose accumulation in the wall. No dependence could be revealed between the shrinkage and the fibril angle in S₂.

Modelling of tangential, radial, and longitudinal shrinkage after drying in jack pine and white spruce

The purpose of this study was to develop an understanding of the pattern of variation in longitudinal, radial, and tangential shrinkage in two commercially important Canadian wood species using multivariate nonlinear mixed-effects models. Shrinkage data were measured in each growth ring at different heights on trees harvested from a mixed-species Nelder tree-spacing plot located in New Brunswick, Canada. Live crown base was reconstructed based on stem analysis. Cambial age, sampling height, crown characteristics (crown length, crown ratio, and distance to live crown base), and ring width at time of wood formation were used as prediction variables. The results indicated that shrinkage magnitude and pattern were closely related to crown dimensions and stem position at time of wood formation. Trees from wider tree spacings with larger crown lengths and ratios tended to have smaller tangential and radial shrinkage. Longitudinal shrinkage decreased nonlinearly from pith outwards with slower rate changes near the bottom of the trees. The model fixed effects accounted for more variation in jack pine (Pinus banksiana Lamb.) than in white spruce (Picea glauca (Moench) Voss) for shrinkage in the same anatomical direction. After further validation, the model developed can be used to provide shrinkage predictions for lumber distortion models within the framework of an individual tree growth model.

Evidence that release of internal stress contributes to drying strains of wood

Wood shrinks during drying, with the departure of bond water. Along the fibre direction, the magnitude of this shrinkage is mainly governed by the orientation of cellulose microfibrils (MF) in the cell wall. However, tension wood has an unexpectedly high longitudinal shrinkage considering the fact that MFs are oriented nearly parallel to the cell direction. This effect is thought to be caused by the gel collapse of the G-layer; however, some species producing a tension wood without a G-layer also exhibit a higher longitudinal shrinkage than normal wood. The aim of this study is to analyse the contribution of maturation stresses to drying shrinkage. Longitudinal and tangential drying shrinkage of tension wood and normal wood were measured on two sets of matched chestnut wood samples. The first set was directly oven-dried, whereas on the second set, a hygrothermal treatment released the maturation stress before oven-drying. The analysis of the strains during each step of the procedure revealed that part of the drying shrinkage is caused by the release of internal stresses during the desorption process. Finally, a tentative schematic model is proposed, taking into account the cumulative contributions to longitudinal drying shrinkage.