Your search resulted in 46 documents. Displaying 25 entries per page.
Towards a colour assay of wood degradation
1982 - IRG/WP 2180
A colour assay for the enzyme catalase is described. Since the activity of this enzyme has previously been shown to be correlated with degree of wood degradation as determined by other methods, this assay may provide a rapid quantitative indicator of superficial and internal wood decay.
M A Line
Safer alternative reagents for colour differentiation of heartwood and sapwood
1994 - IRG/WP 94-20028
Benzidine and dimethyl yellow reagents have been used for distinguishing heartwood from sapwood in the Pinaceae and Araucariacae families, and in Eucalypt species. Both have been classified as carcinogenic by European and United States authoritites, yet the need for effective heartwood/sapwood differentiation remains, not only in the laboratory but also out in the timber processing chain. Safer alternative reagents have been proposed over the past twenty years, but some of these have since been linked with health problems, and most of the rest lack the specificity and general usefulness of those traditionally used. Recent research has investigated various azo, diazo, and other nitrated reagents. Safe but useful alternative methods of sapwood/heartwood differentiation are being established, and recommendations are made for several timber species.
A Zosars, M J Kennedy
Evaluating the natural durability of a number of lesser known species of Ghanaian hardwoods using a short term laboratory assay
2004 - IRG/WP 04-10540
Resistance of a number of Ghanaian hardwoods to attack by the crustacean Limnoria quadripunctata was assessed by measuring the production of faecal pellets under forced feeding conditions over a two week period. Small sticks of commercially available, lesser known timber species, were leached in seawater for one week then placed in a cell culture chamber with one animal and 4 ml of seawater. At intervals, the number of faecal pellets per chamber was counted. The number of pellets produced by animals feeding on Scots pine sapwood, which is non-durable, and on greeheart or ekki, timbers with a reputation for resistance to marine borer attack, were used as a basis for comparison. Mortality rates were also compared. Lower pellet production rates and higher mortality rates were taken as measures of natural durability. Feeding on ekki (Lophira alata), kusia (Nauclea trillesii) and ananta (Cynometra ananta) was about one tenth of that on Scots pine. Mortality of animals with wonton (Morus mesozygia) was 90%, but high mortality did not occur with any of the other species.
J R Williams, S M Cragg, L M S Borges, B Shayler
Preliminary screening of diffusion formulations for the control of soft rot
1978 - IRG/WP 2104
We have an urgent need in Australia to develop in situ remedial treatments for the present population of in-service transmission poles. For various reasons we have opted for formulations which can be applied as bandage treatments and thus we are primarily concerned with assaying diffusable toxicants. Two basic approaches have been made: an assay of the formulation's toxicity; and a combination assay of the formulation's diffusibility and toxicity. Of the direct assay methods the filter-paper technique is the more rapid although with highly soluble formulations some leaching of toxicants will occur during the preparatory stages and probably during incubation also. Furthermore, filter papers are not strictly comparable to wood, and a modification we have considered is to use 'papers' prepared from mechanically beaten pulps rather than chemically degraded pulps. An additional modification would be to substitute veneers for filter papers, although this may give rise to surface concentration effects since the veneers could prove difficult to impregnate homogeneously. By far the most valuable technique for our own screening programme of potential toxicants to control soft rot in standing poles is the Petri dish/wood slab technique. While agar diffusion systems are rapid and provide valuable 'short list' data, the information obtained on diffusion rates cannot easily be applied to solid wood. Da Costa's slab technique is obviously advantageous in this respect. Furthermore, it can be so tailored that successive inocula can be sequentially assessed, thereby providing added information on component diffusion as well as total formulation movement. However, care must be taken in interpreting the data since it is not possible to distinguish directly which chemicals in a mult-component formulation have diffused first and hence which are the toxic ones. Similarly, it could be necessary to impose a time restriction on the test with certain types of formulations.
A rapid colorimetric assay for mold spore germination using XTT tetrazolium salt
2011 - IRG/WP 11-20462
A rapid colorimetric assay was developed to quantitate metabolic activity in mold spores during germination using 2,3-Bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[9phenyl-amino)carbonyl]-2H-tetrazolium hydroxide (XTT). The assay was used to demonstrate inhibition of spore germination following exposure to different biocides and variability in the inhibition of spore germination of different mold species to the same biocide.
C A Clausen, V W Yang
A behavioral assay for measuring feeding deterrency of a slow-acting biocide, A-9248, against the Formosan subterranean termite (Isoptera: Rhinotermitidae)
1988 - IRG/WP 1366
Concentration-dependent feeding deterrency of a slow-acting compound, A-9248 (diiodomethyl para-tolyl sulfone) was studied in a choice test against the Formosan subterranean termite, Coptotermes formosanus Shiraki. A-9248 was a feeding deterrent at concentrations ³8,000 ppm. Initially, Coptotermes formosanus fed on wood treated with 1,000-6,000 ppm A-9248 but learned to avoid the treatment as a result of ingesting sublethal doses of A-9248. Only those groups exposed to wood treated with <1,000 ppm continued feeding on the treated substrates, and ingestion of these concentrations resulted in 85-100% mortality at the end of the 4-week experiment.
N-Y Su, R H Scheffrahn
Correlation between changes in colour and chemical composition during photo-degradation of wood surfaces
2005 - IRG/WP 05-40301
Changes in colour of wood (yellowing) during photo degradation or weathering reflect chemical changes in wood. Therefore, the relationship between changes in chemical composition and CIELAB colour parameters is very important to characterize photodegradation of lignocellulosic surfaces. In this study, the changes in chemical composition and yellowing due to photo-degradation was studied by exposing wood surfaces of Pinus roxburghii (chir pine) to a xenon source. Changes in chemical composition were monitored by measuring IR and fluorescence spectra and were correlated with colour changes. A linear correlation between degradation of lignin and total colour change (E) was observed.
K K Pandey
ATP assay for the determination of mould activity on wood at different moisture conditions
1992 - IRG/WP 92-2397
To determine fungal responses to fungicides and environmental conditions and for detection of microbial activity in wood, sensitive and objective methods are needed. We have developed a suitable assay based on analysis of adenosine triphosphate (ATP) by using the luciferin-luciferase reaction. With the aid of this assay the activity of Penicillium brevicompactum on wood at different RH levels was studied. The ATP content in a two week old culture responded quite rapidly to changes in humidity. The ATP content in the colony moved to 70% or lower RH for one week was 10 times lower than the ATP content in the colony kept at 100% relative humidity for the same time period. Increasing the humidity level to 100% RH one week before the ATP determination from a period at lower humidities did not result in a significant increase in the ATP content. This probably indicates that the mycelia of the fungus did not survive the low humidity treatment.
An appraisal of methods for environmental testing of leachates from salt-treated wood; part 1
1998 - IRG/WP 98-50115
The magnitude and diversity of leaching tests with salt-treated wood, performed by institutes as well as industry, strongly appeal for harmonisation towards one single method. That procedure should be well-defined, cost- and time-effective and moreover be extended with a clear detection and interpretation scheme. The paper(s) presented here tend to evaluate 2 existing leaching methods, the ENV 1250.2 and the EN 84, for their potential use as an environmental standard in high hazard class wood preservation. The leachates obtained are chemically examined for their patterns and levels of metal emission and are biologically screened for their releavance towards in service biomonitored samples. Upon strengthening the objectives and characteristics of the EN 84 ageing test, the results reported here justify the support and upgrading of this procedure as an early stage leaching method within the standard efficacy testing of new or renewed wood preservatives.
G M F Van Eetvelde, M Stevens, F Mahieu, H-W Wegen, A Platen
Oxalic acid quantification, oxaloacetase assay and ESI localization of P, C, and Fe from the brown rot fungus Postia placenta
1994 - IRG/WP 94-10063
The mechanism by which brown-rot fungi initiate depolymerization of holocellulose in wood remains unknown. Recently, oxalic acid (OA) has received considerable attention in cellulose breakdown by brown-rot fungi. The OA could serve as a proton donor for hydrolytic or an electron donor for oxidative (Fenton's reaction-H2O2/Fe2+) cleavages of cellulose. The acid may originate via oxaloacetase's action upon oxaloacetate. We report electron microscopic imaging (ESI) to localize Fe and HPLC/oxalic kit colorimetry to purify/quantify OA from hyphae upon agar, southern pine wood blocks (WBs) or in liquid culture. Comparative ESI at 25, 59, 110, 222, and 710 ev of hyphae grown upon agar or WBs demonstrated hyphal Fe (710 ev). Although Fe was not visualized in cell walls of uninoculated WBs, it was in certain wood cell walls of inoculated WBs. The Fe distribution differed from C and P. Oxaloacetase activity was not observed in either Amicon YM10 filter-retained intra-or extracellular fractions of liquid cultured hyphae or in homogenates from decayed WBs. In contrast, HPLC detected OA in both Postia placenta liquid cultures and decayed WBs. The less sensitive oxalic kit (mg vs. ug) did not detect OA in liquid cultures. These results constitute additional evidence for an OA Fe2+/H2O2-Fenton's mechanism for brown rot-induced cellulose degradation. However, OA's origin was not established.
C R Jordan, W V Dashek, T L Highley
Early detection of brown-rot decay in southern yellow pine using immunodiagnostic procedures
1990 - IRG/WP 2356
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 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 only noted 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.
C A Clausen, F Green III, T L Highley
Comparing the resistance of a number of lesser known species of tropical hardwoods to the marine borer Limnoria using a short term laboratory assay
2003 - IRG/WP 03-10500
Naturally durable species of timber are used as an alternative to preservative treated timber for marine structures, but many species have not been evaluated for their potential for use in this environment. EN 275 specifies a 5-year test period - too long a period for screening tests to be economically viable. In this study, durability was assessed by measuring the production of faecal pellets by the crustacean Limnoria quadripunctata under forced feeding conditions over a number of days. Small sticks of a wide range of wood species, mainly of South American origin, were leached in seawater for one week then placed in a cell culture chamber with one animal and 4 ml of seawater. At intervals, the number of faecal pellets per chamber was counted, and the dimensions of the faecal pellets were measured. The number of pellets produced by animals feeding on Scots pine sapwood, which is non-durable, was used as a basis for comparison. Mortality rates were also compared. Lower pellet production rates and higher mortality rates were taken as measures of natural durability. Some lesser known species performed as well or better than species with a reputation for durability in the marine environment.
L M S Borges, S M Cragg, J R Williams
The biological effectiveness of wood modified with heptadecenylsuccinic anhydride against two brown rot fungi: Coniophora puteana and Gloeophyllum trabeum
1992 - IRG/WP 92-3705
A modified soil block test was carried out using wood samples reacted with heptadecenylsuccinic anhydride (ASA). This modification gave good resistance to decay brought about by the brown rot fungi Coniophora puteana and Gloeophyllum trabeum during the twelve week exposure period. Results indicated that there was a good correlation between increased loading of modifying reagent and an increase in effectiveness paralleled by a marked reduction in wood moisture content. The effective resistance threshold level was calculated to be about 30% weight gain of ASA. Further discussions regarding the mode of action are included.
C Codd, W B Banks, J A Cornfield, G R Williams
Preliminary evaluations of a small wafer assay for screening potential biological control agents
1989 - IRG/WP 2332
Screening potential biological agents for controlling wood decay fungi poses a dilemma. The ideal test would eliminate as many variables as possible. Most tests utilize pure cultures of the test organism on an artificial media which in no way resembles wood. The use of sawdust improves this approach, but the sawdust increases fungal access to the lignocellulose matrix, potentially inflating the importance of fungi which might not compete in the normal wood system. This report describes a simple wafer sandwich assay in which small test wafers colonized by the potential biocontrol agent and a Basidiomycete are placed above and below a sterile test wafer on moist soil in a glass petri dish. Weight loss of the middle wafer is used as a measure of biocontrol potential. Preliminary trials indicate that several previously identified biocontrol agents performed well in this test, inhibiting wood weight losses by both white and brown rot fungi. Because the wood structure is not disturbed, this method could also be used to screen wood treatments which might enhance colonization by the biological control agent.
C M Freitag, J J Morrell
Improved preservative penetration of spruce after pre-treatment with selected fungi. I. Fungal pre-treatment of pole sections
1998 - IRG/WP 98-40117
European spruce logs were pre-treated with either Phanaerochete chrysosporium, Dichomitus squalens, Trichoderma viride and Trichoderma aureoviride for incubation periods of between 1-4 weeks prior to pressure treatment with creosote in a commercial treatment plant and analysed for strength and creosote uptake (see part II Tucker et al.). A method to pre-treat logs was optimised. The pole sections were surface sterilised, inoculated with a spore suspension or blended fungal mycelium and supplemented with a nutrient solution. The colonisation of the logs was investigated by light microscopy, SEM and by an ergosterol method, quantifying the fungal biomass in the wood. The assays indicated a rapid and even colonisation of the wood down to the heartwood within a period of approximately 1 week. Dichomilus squalens was also seen to colonise the heartwood. The microscopic and quantitative assays correlated well and reflected the depth of penetration of creosote on subsequent treatment. SEM observations showed that the increased permeability is due to an enzymatic opening of the pit membranes rather than physical penetration of the pits by fungal hyphae.
B Rosner, K Messner, E J B Tucker, A Bruce
Comparison of two laboratory methods for screening potential anti-sapstain chemicals
1993 - IRG/WP 93-10036
Two methods were used to screen a number of potential anti-sapstain chemicals in the laboratory. In one method miniature boards of freshly felled Scots pine sapwood were dip treated with the candidate chemical, sprayed with a suspension of stainers or moulds and incubated for five weeks. In the other method antibiotic assay discs were treated with precise quantities of chemical, plated out on malt extract agar, inoculated with a spore suspension of one of four stainers and moulds and incubated for a few days. This was repeated for each of the four fungi. The results obtained from the two methods provided information on different aspects of the chemicals but the overall conclusions on efficacy were the same.
S M Gray, D J Dickinson
Some practical implications from recent research on the fixation of CCA preservatives
1975 - IRG/WP 358
The mechanism of fixation of CCA preservatives is briefly described. If the temperature is increased during the primary fixation period, the formation of intermediate fixation compounds is less extensive. The length of the primary fixation period is of practical interest. It is determined by preservative composition and concentration, temperature and wood species. Diagrams are given for Pinus sylvestris. Light exposure and drying during the primary fixation period cause variability in colour intensity of CCA treated wood. Disproportionation of preservative elements with penetration depth is explained by the fixation mechanism. Conversion of intermediate fixation compounds into stable ones occurs even below the fibre saturation point, as long as the moisture ratio is sufficiently high to allow ion transport. Conversion reactions are very slow. A correlation was found between the final pH of treated timber and leachability in fresh water of copper and arsenic. The final pH depends on preservative composition and concentration, wood species and to some degree of drying and storage conditions. An electrolyte such as sodium sulfate does not affect the leachability. In saline waters leachability is increased by complex formation of Cu(II) and Cr(III) with chloride and hydroxide and the salt effect on activity coefficients. The leaching of arsenic is delayed.
Preference of swarming termites for various colored lights
1984 - IRG/WP 1238
The ability of the alates of the drywood termite Bifiditermes beesoni (Gardner) to discriminate ten different colored lights was studied. When an alternative choice of any of two colors was offered, the light-blue was preferred to all other tested colors by 97.7% of the alates. A lower degree of attractivity was found for some other colors and certain other colors were indistinguishable. Furthermore, the effects of light intensity and preconditioning to certain colors have been studied and finally the response of swarming alates from natural colonies is compared to that of the individuals from laboratory colonies.
The potential application of rapid gas-chromatographic assay of microbial respiration to the monitoring of wood decay in field trial situations
1983 - IRG/WP 2196
Gas chromatographic detection of microbial activity (C02 production) within stakes in a field trial situation would appear to provide a sensitive, non-destructive and relatively rapid method for the quantitative assessment of preservative treatments. Most consistent results were obtained when stakes were removed from the soil, washed, saturated with water and incubated in sealed PVC tubes at 25°C for 24 h prior to assay of gas samples from the tubes. Each assay took 1.6 min to perform and stakes were returned to the field within 48 h. Microbial activity was readily detected in untreated Eucalyptus regnans stakes after 18 days field exposure. Stakes pressure impregnated with CCA, busan-30 or creosote displayed consistently low levels of activity to the present time (3 months after insertion).
M A Line
Degradation of polycyclic aromatic hydrocarbons by laccase
1998 - IRG/WP 98-10267
The degradation of polycyclic aromatic hydrocarbons (PAH) by laccase was investigated. Laccase catalyzed oxidation of phenanthrene, solubilized in the surfactant Tween 20, exhibited an absolute requirement for the mediator compound 1-hydroxybenzotriazole. When Tween 80 was used as the solubilizing agent, the oxidation rates were more than six times higher as compared to Tween 20. Using the thiobarbituric acid (TBA) assay, it was shown that the laccase-HBT couple peroxidized linoleic acid. The results suggest that unsaturated fatty acids present in Tween 80 are responsible for the enhanced degradation of phenanthrene by laccase-HBT. The system comprising laccase, HBT, and Tween 80 was applied to the sixteen EPA priority PAH with the result that all of the PAH were extensively degraded.
S Böhmer, E Srebotnik, K Messner
Effect of fungal degradation on the chemical composition of acetylated beech wood
2003 - IRG/WP 03-40267
This study investigated the impact of fungal attack on the chemical composition of acetylated wood. Beech wood acetylated to different degrees was exposed to decay by the white-rot fungus Trametes versicolor under solid-state fermentation conditions. Laboratory soil-bed assays were also conducted to study the degradation of acetylated wood by soft rot fungi and other soil-inhabiting microorganisms. Changes in the chemical composition of untreated wood and acetylated wood following exposure to fungal attack were examined by wet chemical analysis, as well as FT-IR and CP/MAS 13C-NMR spectral methods.
H Militz, Dong-won Son, L Gómez-Hernández, R Sierra-Alvarez
Heat treatment of less-valuable Nigerian-grown Ceiba pentandra wood for improved properties
2006 - IRG/WP 06-40332
The hardwood Ceiba pentandra locally known as “ araba “ in Nigeria is rarely used for structural and construction works due to its high dimensional instability, low strength and durability values. Samples (10 x 10 x 150mm) were removed from four green boards (25 x 200 x 3000mm) of this species originating from a natural forest stand in Nigeria and subjected to 2-hour heat treatment at 160°C and 220°C. Heat treatment reduced swelling, hygroscopicity and swelling intensity of Ceiba pentandra wood with the reductions being generally higher in the 220°C treatment than the 160°C treatment. The reductions constitute improvements in these properties. These improvement in properties have the potential to increase the market value of this species through wider acceptability for various purposes hitherto considered impossible. This however is subject to further investigations on the effects on durability and strength properties which are other key features in the choice of wood for various purposes.
The Effect of Flavonoids on Colour and Spectral Changes of the Wood Surface Caused by Heat Treatment or Ultra-violet Irradiation
2006 - IRG/WP 06-40341
Both heat treatment and UV irradiation can cause discolouration and change in the spectral properties of wood surface. Some of the characteristic flavonols have significant role on colour and spectral changes, despite of their relative small quantities in wood. Colour changes and spectral properties of natural and extracted black locust (Robinia pseudoacacia L.) and poplar (Populus nigra L.) were investigated by CIELAB colour measurement system, FTIR and UV/Vis spectrophotometry. Spectral properties of representative flavonols, impregnated on inert silica gel thin layer, were studied in addition to the two types of wood samples. Chemical structure of flavonols was established to have both influence on the colour and spectral changes of woods and close connection with their thermal and photo stability. A slow but continuous decrease of lightness was observed in the case of quercetin and its homologous compounds. Chemical reaction of robinetin was detected by thermal analysis and differential scanning calorimetry under 200 °C and both oxidative and inert conditions. The colour changes of quercetin homolog compounds, kaempferol and fisetin, which contain one and two hydroxyl group on their “B” ring, are similar to quercetin; while myricetin with three hydroxyl groups on its “B” ring shows “robinetin-type” changes. The colour changes of the hardwoods are depended on the time and temperature of heating, as well as on the time of light irradiation. The character of spectral changes of black locust can be classified on the type of robinetin, in contrast with the “quercetin-type” of poplar.
R Csonka-Rákosa, L Molnár-Hamvas, E Börcsök, J Molnár, K Németh
A method and apparatus for rapid assessment of termite barriers.
2007 - IRG/WP 07-20366
This paper describes an apparatus for rapid assessment of barriers to subterranean termite foraging. The method and apparatus arose from the development of a novel physical termite barrier. The barrier had to be flexible, resilient, able to be applied as a liquid and be neither toxic nor repellent. This posed a special problem as existing laboratory assessment techniques did not offer a sufficient incentive for termites to challenge the test samples. Previously developed laboratory methods of exposing a candidate barrier material provided either (i) only chance and incidental contact with the termites with termite damage restricted to the edges or (ii) an unnatural situation where termites were attempting escape. A method was required that would reliably provide sustained contact and challenge the termites to penetrate the test sample. Observation of termite attack on structures provided a means to use the termites’ own foraging strategy to situate the barrier sample in a location of maximum termite activity. A high density of termites in a restricted space has feeding activity focussed so as to ensure sustained contact and challenge for the material under test. The focus of termite attention is achieved by providing the termites with a minimally sized timber dowel as a food source. The dowel is hollow which leads the termites to concentrate their feeding activity within its confines. The test sample is held at the distal end of the dowel, in a separate container.
D McG Ewart
Photo-degradation of modified and non-modified wood, coated with water borne acrylic coatings during artificial light exposure
2007 - IRG/WP 07-30416
A series of experiments were carried out to investigate photo-degradation of thermally modified (at 210oC and – 0.9 bars for two hours) and non-modified spruce wood (Picea abies L (Karst)), coated with transparent and semitransparent (with 3% pigment content) acrylic coatings during artificial UV light irradiation for 200 hours. Photo-degradation was evaluated in terms of colour changes throughout the irradiation period at an interval of 50 hours, along with IR and EPR spectroscopic study. One set of modified and non-modified woods was painted with coatings, while the other set was covered with free films made of coatings, just to simulate coated wood. The average thickness of paint-coats and dried free films at 25oC and 50% RH was 144.8?m and 143.4?m for transparent and semitransparent coating, respectively. The colour changes for both modified and non-modified wood samples without paint-coat and free film cover were comparable to that of wood samples with paint-coat and free film cover for transparent coat type, which indicated its ineffectiveness to prevent photo-degradation of wood underneath. However, the colour changes for both modified and non-modified wood samples with paint-coat and free film cover were much more lower than that of samples without paint-coat and free film cover for semitransparent coat type, which might be due to hindrance of transmission of light energy through pigment to reach the underlying wood surface. On the other hand, whole substrate-coating systems showed better photo-stability, when thermally modified wood was used as substrate. It might be due to increase in lignin stability by condensation during thermal modification process of wood substrate. However, the colour changes of coat-painted and free-film covered samples for both modified and non modified woods might be due to due colour changes of wood specimen underneath, because free films of both the coat types showed negligible colour change during UV irradiation.
M Deka, M Tomažic, M Petric