Your search resulted in 88 documents. Displaying 25 entries per page.
Radial flow of Bornmullerian fir (Abies bornmulleriana Mattf.) as affected by wood tapering and the condition of end wall structure of uniseriate ray parenchyma cells
2008 - IRG/WP 08-40441
Amenability to radial permeability of Bornmullerian fir (Abies bornmulleriana Mattf.) was studied on the base of the effects of wood tapering and the structure of end walls of uniseriate ray parenchyma cells. The results showed that the most remarkable culprits of the greatest fluid uptake (as the percentage of void volume filled by the fluid in the radial flow direction, RVVF%) are the lesser wood tapering and a slight inclination of the end walls. It was also noticed that the thinner end walls having the larger apertures of the simple pits influence to RVVF%. It could be therefore stated that both wood tapering and the situation of the end walls of uniseriate ray parenchyma cells were the most important factors for regulating radial flow for Bornmullerian fir.
I Usta, S Aslan
The dry rot fungus Serpula lacrymans. Examples of attack and remedial treatment
1988 - IRG/WP 1347
The film deals with several aspects of dry rot attack and eradication in buildings. The detailed biology and morphological charasteristics of the fungus are portrayed. The various forms of mycelial growth, the role of the strands in the nourishment and spread of the fungus, as well as the many types of fruitbody formation are outlined. Environmental and nutritional requirements of the fungus as well as the potential infection danger posed by the basidiospores are discussed. The second part of the film, outlining the main reasons for dry-rot attack and spread in building together with the significant damage caused, shows the full extent of the problem to expert and lay-person alike. The necessity of correct survey and inspection of decayed areas to determine the full range of attack is stressed. Examples of various remedial treatments and the present technological state of eradication techniques, e.g. pressure injection, in Germany are discussed.
G Buchwald, B M Hegarty, W Metzner, R Pospischil, H Siegmund, P Grabow
Ultra-structural observations on the degradation of wood surfaces during weathering
1987 - IRG/WP 2280
Radiata pine (Pinus radiata D. Don) sapwood was converted into blocks with a transverse face about 5 mm square and measuring 8 mm longitudinally. Transverse (T.S.), Radial (R.L.S.) and Tangential (T.L.S.) surfaces were prepared and specimens exposed to the weather inclined at 45° facing equatorially for periods of between 20-60 days. After 30 days exposure erosion of the middle lamella was observed followed after 40 days exposure by extensive separation of individual fibres at the interface of the middle lamella and secondary wall. Degradation of the S2 layer of the cell wall revealed corrugations orientated parallel to the fibre axis suggesting preferential removal of cell wall components. Further degradation proceeded by progressive delamination and checking of the S2 and erosion of the S3 cell wall layer. In addition to the above changes preferential degradation of the rays was observed in radial (R.L.S.) and tangential (T.L.S.) longitudinal surfaces.
P D Evans, S Thein
Resistance of Alstonia scholaris vestures to degradation by tunnelling bacteria
1992 - IRG/WP 92-1547
Electron microscopic examination of vessels and fibre-tracheids in the wood of Alstonia scholaris exposed to tunnelling bacteria (TB) in a liquid culture showed degradation of all areas of the secondary wall. The highly lignified middle lamella was also degraded in advanced stages of TB attack. However, vestured pit membranes and vestures appeared to be resistant to degradation by TB even when other wall areas in Alstonia scholaris wood cells were severely degraded. The size comparison indicated vestures to be considerably smaller than TB, and we suspect that this may primarily be the reason why vestures in Alstonia scholaris wood were found to be resistant to degradation by TB.
A P Singh, T Nilsson, G F Daniel
Water-based water repellents for treatment of wood
1987 - IRG/WP 3446
The water uptake by wood can be reduced by treatment with a water repellent. The water repellents most commonly used are solvent based. In the present work a new type of water repellent that is water-based has been investigated. Two different treatments have shown an effect of the same order as a commercial solvent based product. The cellular distribution of the water repellents has been investigated and for one of the formulations a more uniform distribution can be seen at the impregnated surface. Use of water as a solvent would be advantageous due to lower cost and non-toxicity.
I G Svensson, G Hägglund, I Johansson, W B Banks
Ultrastructural observations on wood-degrading erosion bacteria
1986 - IRG/WP 1283
G F Daniel, T Nilsson
End grain sealants for wood preservation studies
1985 - IRG/WP 3341
The results of tests with possible end grain sealants for wood preservation studies are reported. The epoxy resins used gave satisfactory performance on wet or dry Sitka spruce and have been used with success for diffusion treatment studies.
R J Murphy, N A Summers
The influence of formulation on the behaviour of LOSP's during industrial impregnation of spruce
1986 - IRG/WP 3387
Evidence is presented that the comparative behaviour of two LOSP formulations during impregnation treatment of spruce cannot be predicted purely on the basis of their physical characteristics (viscosity, surface tension and contact angle) nor on the extent of their 'passive' penetration into pine sapwood.
L D A Saunders, D M Zuvencko
A new model for wetting and drying of wood end-grain – with implications for durability and service-life
2011 - IRG/WP 11-20477
New experimental data for wetting and drying of wood end-grain, Sandberg (2009), imply that traditional models for moisture transport are not at all applicable. A new model is developed to consider the phenomenological behaviour of water transport in and out of end-grain, using the pore water pressure and sorption scanning properties. Modelling results are compared to experimental results and the consequences for durability are discussed.
L-O Nilsson, K Sandberg
Laboratory and field evaluation of Plasmite Reticulation System using bifenthrin as a chemical barrier within wall cavities against subterranean termites.
2005 - IRG/WP 05-20307
Laboratory and field bioassays undertaken to demonstrate Plasmite Reticulation system effectively delivers the termiticide (bifenthrin) within a simulated wall cavity at the required concentration. The chemical assay indicated that the amount of bifenthrin sampled at 5, 10, 15, 20, and 25m along the simulated reticulation system tested (30m) exceeded the manufacturer’s minimum recommendation of 0.0044%m/m. Results of the laboratory bioassay, using Coptotermes acinaciformis, indicated that the concentrations of bifenthrin present in the soil core samples at 5, 10, 15, 20, and 25m were extremely toxic and prevented termite penetration of bifenthrin treated soil in laboratory bioassays immediately after field soil treatment. No penetration of any soil core samples was observed in the field test against Coptotermes lacteus.
J R J French, B M Ahmed, J Thorpe, A Anderson
Degradation of the normal fibre walls of rubberwood (Hevea brasiliensis) by the tropical blue-stain fungus Botryodiplodia theobromae
1998 - IRG/WP 98-10286
Rubberwood was examined by light microscopy and transmission electron microscopy (TEM) after exposure to the common tropical sapstain fungus Botryodiplodia theobromae for four weeks to study hyphal colonisation of wood cells and to determine if this fungus also degraded lignified normal fibre cell walls in addition to the walls of non-lignified elements. Light microscopy revealed relatively large diameter hyphae to be abundantly present in parenchyma cells. The hyphae were also present in other types of wood cells, including fibres. TEM provided evidence of fibre wall degradation in the normal rubberwood in the form of lumen wall erosion (type-2 soft rot decay). These observations suggest that the ability of B. theobromae to degrade lignified wood cells walls should be viewed with concern when utilising rubberwood which has been severely sapstained, particularly after prolonged exposure to this fungus.
A A H Wong, A P Singh
Ultrastructural aspects of bacterial attacks on an archaeological wood
1993 - IRG/WP 93-10007
Transmission electron microscopy of wood from a Chinese ship submerged in the mud for over 900 years showed bacteria to be the main factor for its deterioration. The micromorphology of degraded wood cell walls was similar to that observed during the attacks of wood by erosion bacteria. Other bacterial forms, previously considered lo be scavenging bacteria, were also abundant in degraded areas of the wall. The observations on the breakdown of the waterlogged archaeological wood are discussed in context with the available information on bacterial degradation of wood under near-anaerobic conditions.
Yoon Soo Kim, A P Singh
The Relationship of Fiber Cell Wall Ultrastructure to Soft Rot Decay in Kempas (Koompassia malaccensis) Heartwoo
2004 - IRG/WP 04-10541
The ultrastructure of fiber walls in kempas (koompassia malaccensis) heartwood was examined in relation to soft rot cavity formation. The fibers consisted of middle lamella and thick secondary wall. The secondary wall was differentiated in to a S1 layer, and a unique multi-lamellar S2 layer. Two distinct forms of lamellae were recognisable, one type being considerably thicker than the other. They also differed in their electron density, the thin lamellae being much denser than the thick lamellae. It was not possible to determine whether a S3 layer also existed, because of the presence of a dense material coating the lumen wall, which obscured the definition of this region of the fiber wall. The resistance to soft rot varied with different regions of the fiber wall, middle lamella being completely resistant and the thick S2 lamellae least resistant. The observed relationship between the ultrastructure of these fiber wall regions and the degree of their resistance/susceptibility to soft rot cavity formation is discussed.
A P Singh, A H H Wong, Yoon Soo Kim, Seung-Gon Wi
Estimation of effective diffusion path lengths in wood by swelling studies
1989 - IRG/WP 3524
The effective average distance that a solute must diffuse to penetrate the cell wall matrix following pressure treatment is estimated from the rate of swelling of wood, vacuum treated with water. It is assumed that the diffusion paths are similar for water and a solute such as a wood preservative component. Since bound water diffusion coefficients for water in wood have been estimated by others, the effective path lengths (Le) can be estimated. Effective average path lengths are estimated for red pine (Pinus resinosa), Southern yellow pine (Pinus sp), trembling aspen (Populus tremuloides) and soft maple (Acer rubra) sapwood and red oak (Quercus rubra) heartwood samples. The estimated path lengths are shortest for the softwoods, and longest for the ring porous oak. The results reflect the different patterns of cell penetration and different densities of the wood species.
P A Cooper, R Churma
The attack of naturally durable and creosote treated timbers by Limnoria tripunctata Menzies
1995 - IRG/WP 95-10132
Limnoria tripunctata was found tunnelling in creosote treated Douglas fir (Pseudotsuga menziesii) pilings and naturally durable greenheart (Ocotea rodiaei) gate seals at two sites on the south coast of the United Kingdom. Examination of thc creosote-treated wood showed that Limnoria tunnels were concentrated at a depth of 2-3 cm from the timber surface, where creosote loading was lower. Fewer tunnels occured in the heavily creosoted outer zone. Sections through Limnoria tunnels in wood fixed on site were examined using the scanning electron microscope (SEM). These studies showed that S2 layers of wood cell walls adjacent to Limnoria tunnels were decayed by tunnelling bacteria in many cases. Examination of greenheart seals showed that Limnoria tunnelled to a depth of 1.5 cm, in the soft-rot decay zone. The heads of the Limnoria tunnels also penetrated "sound" wood to a depth of 2 cm. Examination of sections through Limnoria tunnels showed that wood cells adjacent to tunnels were decayed by both soft-rot fungi and tunnelling bacteria. In addition, a range of prokaryotes and protoctists were attached to tunnel walls in this instance. The size of bitemarks along the tunnel walls suggested Limnoria would ingest a range of these micro-organisms along with the wood substrate. Gut contents of Limnoria fixed at both sites were screened for microorganisms using the SEM. This study failed to show micro-organisms on the surface of wood particles during gut transit, which suggested that ingested microbes were digested by Limnoria.
A J Pitman, G S Sawyer, G F Daniel
Role of cell wall structure in soft rot decay of bamboo
1995 - IRG/WP 95-10133
Models of soft rot hyphal penetration of bamboo cell walls are proposed. Soft rot hyphae show an interesting capability of penetrating the bamboo cell wall in different forms; typical longitudinal penetrating hyphae and tangentially orientated penetrating hyphae. The second form of penetration was found to be different from that normally associated with wood cell walls. The differences can be attributed to the cell wall structure of bamboo. Soft rot hyphae normally follow the microfibrillar orientation in either the broad lamellae or the narrow lamellae in bamboo cell walls. Hyphae that grow in the broad lamellae normally penetrate in the longitudinal direction and follow the orientation of the microfibrils of this layer of the cell wall. This produces a 'typical' longitudinal penetrating hyphae and cavity. Soft rot hyphae are also found penetrating in the tangential direction. These arise from radially orientated hyphae trying to penetrate across the lamellated cell wall neighbouring cells. When a radially orientated hyphae encounters the narrow lamellae, the hyphae can reorientate in the direction of the microfibrils in this lamellae. Thus, the hyphae penetrate in a tangential direction in the cell wall. These types of penetrations are not seen in wood cell walls.
O Sulaiman, R J Murphy
Ultrastructure of degraded, CCA-treated Pinus radiata wood from a marine pile
1990 - IRG/WP 1461
During an inspection of marine piles, 12 years after installation, severe degradation was noted on one of them in the vicinity of a corroded eye-bolt. The wood was dark brown in colour and tended to crumble easily. Wood fragments were examined by light microscopy and scanning and transmission electron microscopy and were also analysed for carbohydrates and lignin. Light microscopy showed numerous cracks in tracheid walls resulting in delamination at middle lamella - S1 and S1 - S2 junctures and also in fractures across the tracheid wall. Chemical analysis showed extensive losses in hemicelluloses and also losses in cellulose. Observations with polarised light microscopy supported the data from chemical analysis on cellulose degradation. Although presence of microbial flora in the lumen of wood cells was revealed by scanning electron microscopy, transmission electron microscopy showed only occasional soft rot decay zones in the S2 layer. We suggest that the degradation of Pinus radiata wood cell wall is primarily due to chemical attack, fungal decay playing a minor role.
A P Singh, M E Hedley
Degradation of the gelatinous-layer in aspen and rubber wood by the blue stain fungus Lasiodiplodia theobromae
1996 - IRG/WP 96-10168
Studies on the degradative ability of the blue stain fungus Lasiodiplodia theobromae Pat. have shown several strains to cause significant weight losses (i.e. ca 20%) in the temperate and tropical wood species, aspen (Populus tremula) and rubber wood (Hevea brasiliensis). In addition to the consumption of soluble carbohydrates and extractives, major changes in the ultrastructure of fibre cell walls was apparent with rapid attack of the gelatinous layer noted. In both wood species following G layer degradation, early wood fibres showed true cell wall degradation with pronounced erosion attack suggesting that prior destruction of the G layer afforded greater accessibility and ease of attack of the outer secondary cell layers.
O Encinas, G F Daniel
EELS (Electron Energy Loss Spectroscopy) - a technique for quantification of nitrogen and other light elements in the cell wall
1999 - IRG/WP 99-20163
A literature survey was performed to find progress in techniques for monitoring penetration of synthetic resins in wood cell walls. Electron energy loss spectroscopy (EELS) in combination with transmission electron microscopy (TEM) was successfully applied for the high resolution examination of the distribution of a partly methylated hydroxymethyl melamine resin in Norway spruce (Picea abies Karst.) earlywood cell walls. The nitrogen of the resin was found as clearly detectable signals in all layers of the lignified cell wall, thus allowing the quantification of resin which had penetrated into the different layers.
A O Rapp, H Bestgen, W Adam, R-D Peek
Evidence for wood cell wall degradation by the blue stain fungus Botryodiplodia theobromae Pat
1994 - IRG/WP 94-10077
Botryodiplodia theobromae Pat., a world wide ubiquitous polyfagus sapstain fungus, was found able to destroy the cell walls of birch fibres (Betula verrucosa Ehrh.) but not Caribbean (Pinus caribaea var. hondurensis Barr. and Golf.) and Scots pine (Pinus sylvestris L.) tracheids. The fungus caused characteristic erosion of fibre cell walls similar to soft rot type 2; destruction of the S1 - S2 interface and delamination and degradation of the S2 layer. No attack of middle lamellar regions or birch vessel walls was noted.
O Encinas, G F Daniel
Butt-end incising to improve penetration and retention of creosote in Eucalyptus saligna power transmission poles in Kenya. Preliminary results
2002 - IRG/WP 02-40249
Incising as a possible technique to improve penetration and retention of creosote in the butt end of Eucalyptus saligna power transmission poles in Kenya was investigated. Debarked, butt-end samples from whole poles were seasoned (15% MC), incised using four patterns of incisions, sealed at the top or small diameter end, and pressure treated with a mixture of creosote-furnace oil (60/40 mix) at a commercial plant using a full cell process. They were then conditioned in the open for 3 months to allow evaporation, migration, and bleeding. The samples were subsequently leached in running tap water for 21 days, air-dried for 8 weeks under cover and retentions calculated on a weight-gain basis and compared. Discs were removed from the middle (450mm) of the samples, and radial penetration assessed visually and measured. Compared to un-incised samples, both penetration and retention were substantially improved in samples with closer incisions of 20 mm x 20 mm, by 58.6% or 89.8 mm and 87.0% or 146.4 Kg/m3 respectively. Wider incisions 0f 40 mm x 40 mm achieved lower improvements, 17.3% or 66.4 mm for penetration and 19.8% or 93.8 Kg/M3 for retention. The 4 incising patterns achieved consistently higher penetration and retention of creosote compared to un-incised control samples, which achieved lower average penetrations (56.6mm) and retentions (78.3Kg/M3). Butt-end, or incising the ground-contact sections of transmission poles may be a feasible technique for improving both penetration and retention in the more vulnerable portions of poles, and thus substantially increase service lives of eucalyptus poles in the country. Further investigations are necessary to establish patterns of incision and appropriate treatment schedules.
Étude in vitro de la colonisation et de la dégradation structurale du bois d'aubier de Pin sylvestre par la Mérule: Serpula lacrymans Schum. ex Fr. S. F. Gray
1979 - IRG/WP 198
The degradation of Scots pine sapwood cell walls by Serpula lacrymans, a brown rot fungus, is observed after various periods of exposure from two weeks to twelve weeks. The observation by microscopy shows that the hyphae of Serpula rapidly invade the wood tissues as cell wall degradation starts. That deterioration is not gradual, it is observed to be very irregular as well within the whole of the tissues as within one single tracheid considered alone. The enzymatic action occurs at a distance from the secreting hyphae, causing an irregular desintegration of the various layers of the wall. The degradation of the wall is observed and analysed by scanning electron microscopy.
Formation of soft rot cavities in relation to concentric layers in wood fibre walls
1983 - IRG/WP 1185
A large number of timber species attacked by soft rot have been examined using light microscopy. The S2 layers in a large number of the timbers exhibited special structural features in the form of thin concentric layers. Several observations indicate that these layers may be characterised as "weak" zones by being more easily degradable than the surrounding wall layers. The chemical structure of the concentric layers is not known although some suggestions regarding their composition are given. It was observed that soft rot cavities regularly formed in the thin concentric layers. A hypothesis is put forward suggesting that T-branching occurs as a response to a chemical stimulus, possibly by sugars released by penetrating hyphae when they transverse the thin concentric layers.
T Nilsson, G F Daniel
Changes in pore structure and cell wall volume in wood decayed by brown- and white-rot fungi
1991 - IRG/WP 1501
Sweetgum (Liquidambar styraciflua L.) wood blocks were decayed by Postia (=Poria) placenta or Phanerochaete chrysosporium in soil-block cultures. Decay was terminated at various weight losses, and the pore volumes available to probes of various molecular weight and diameter were determined by the solute exclusion technique (Stone, J.E. and A.M. Scallan. 1968. Cellulose Chem. Technol. 2, 343-358.). The volume in sound (undecayed) wood that was accessible to the probes varied from 1.0 ml g-1 for the largest to 1.35 ml g-1 for water. Thus, the volume in sound wood attributable to cell wall was 0.35 ml g-1. In brown-rotted samples, the volume of pores in the cell wall increased steadily to 0.7 ml g-1at 35% weight loss. New cell wall volume was accessible to low molecular weight probes but not to molecules of Mr ³ 6,000. Within experimental error, no pores of > 20Å were observed in sound wood or >38Å in brown-rotted wood. Most of the new cell wall volume create by rermoval of components during decay was in the pore size range of 12Å to 38Å. Our results are consistent with the hypothesis that the initial depolymerization of cellulose, characteristic of brown rot, is caused by a diffusible agent. The molecular diameter of the agent is apparently in the range 12Å to 38Å and it causes erosion and thus enlargement of the pores to which it has access. In the white-rotted wood, cell wall volume increased to 0.6 ml g-1 at 40% weight loss and maximum pore diameter increased to 50Å. Most of the cell wall volume increase resulted from the creation of pore of 20-50Å diameter. Analysis of loss of major wood components as a function of weight loss revealed that lignin, cellulose, and hemicellulose were removed at approximately equal rates. Under our experimental conditions, ligninolytic enzymes have access to only a small portion of the new cell wall volume, even after extensive decay.
D S Flournoy
Butt-end incising to improve penetration and retention of CCA in Eucalyptus saligna telegraph poles in Kenya: Preliminary results
2002 - IRG/WP 02-40243
Incising to improve penetration and retention of Copper Chrome Arsenate (CCA) in the butt end of Eucalyptus saligna telegraph poles was investigated. Debarked, seasoned (15% MC) butt-end samples from full size telegraph poles were incised using four patterns of incisions, sealed at the top or small diameter end, and pressure treated, together with un-incised samples, with CCA-C (3.0% oxide type) at a commercial pole treatment plant, using a full cell process. After conditioning under cover for 6 weeks to allow fixation and air-drying to 15% MC, samples were leached in running tap water for 12 days, re-dried to 15% MC, retentions calculated on a weight gain basis and compared. Discs were removed from the middle 50mm sections of samples, sprayed with Chrome-azurol S, and average radial penetration computed. In comparison to un-incised samples, both penetration and retention were substantially improved in samples with closer incisions of 20 mm x 20 mm, by 59.9 %, or 79.3 mm and 59.0%, or 28.3 Kg/m3 respectively. For the wider incisions of 40 mm x 40 mm, improvements were lower, 13.1%, or 56.1 mm for penetration and 19.7%, or 21.3 Kg/m3 for retention. Un-incised samples achieved consistently lower average penetrations of 49.6 mm and retentions of 17.8 Kg/M3. Butt-end incising maybe a feasible technique for improving the otherwise unacceptable short service lives of eucalyptus telegraph poles in the country. Intensity, depth, and method of incising, together with appropriate treatment schedules, need to be investigated further.