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Moisture distribution in glulam beams with natural cracks observed with CT Scanning before and after rain
2013 - IRG/WP 13-20534
The way cracks in outdoor wooden constructions affect durability is an interesting topic, since a certain amount of cracks can always be found naturally in wood and glued laminated wood. The question in this was, can cracks lead water into the wood and thereby increase the risk for decay and reduce strength and service life. Moisture balance, i.e., water absorption and water distribution were studied in two 2-meter-long glulam beams after exposure to rain. For the experiment, computer tomography and image processing were used. The beams were X-ray scanned on four occasions during one year: August (CT1), September (CT2), June (CT3) and the following August (CT4). One red-painted spruce beam 215 x 315 mm and one oiled pressure-treated pine beam 140 x 315 mm were studied. The study shows that water can enter a crack for many millimeters by capillary forces, but that this does not necessarily occur. How and to what extent water enters into a crack or delamination depends on material, surface treatment, position and size of the crack or delamination and the quantity of rain and wind. The sizes of the cracks depend on the climate, that is, moisture and temperature variation over time. Some of the cracks become invisible during this movement, and the variation can be as much as 2.5 mm over a 36-hour period. Under certain conditions, small cracks disappear as the woods swells.
K Sandberg

CT scanning of decay in creosoted poles for overhead lines
2013 - IRG/WP 13-30634
Creosote-treated poles have been examined by means of CT scanning in order to investigate the nature of soft spots that have been found more frequently during the last five years in Sweden. CT scanning provides a very good picture of the interior of the poles and decay can easily be detected. It was concluded that the soft spots in most cases were caused by decay which in turn had to do with extremely poor treatment of the poles. Both high temperature kiln dried and open air dried poles were studied, but the drying method had no significance. Based on the findings a new procedure for inspection of poles is suggested.
C-J Johansson, A Clang, I Johansson, G Berggren

Non-destructive monitoring of structure and moisture dynamics of plywood exposed outdoors to improve service life prediction and fit-for-purpose design
2015 - IRG/WP 15-20570
Plywood is an important construction material yet prone to water uptake, which can decrease strength and increase decay risk. To predict service life and improve fit-for-purpose design, it is crucial to understand the moisture behavior and structural changes of plywood. In this research, several plywood specimens were exposed outdoors for approximately one year. During this period, the moisture distribution in different layers of the exposed plywood specimens was monitored continuously and detailed field weather information was collected simultaneously. The internal structure of the specimens was also investigated by periodically scanning using 3D X-ray CT. The moisture distribution throughout the different plies is not always homogeneous. The second layer can accumulate a significant amount of water in outdoor weathering conditions, giving rise to high Time of Wetness (TOW) and long rainfall events can keep wetting the inner layers of plywood. TOW, moisture dynamics and wood species used are the main factors causing structural changes of the plywood veneers in service mainly occurring as cracks. Most internal structural changes were found in the second veneers of plywood specimens. The glue line between veneers can hardly be ruptured after exposing outdoors for one year. Plywood with veneers showing a slow water sorption and fast water desorption could effectively avoid internal moisture accumulation and cracks in service. Based on the knowledge of the relationship among weathering data, internal moisture behavior and structural changes in service, the dedicated plywood could be designed by optimizing the characteristics, i.e. veneer wood species, veneer thickness, glue type and such. The above knowledge could also contribute to the service life prediction of plywood.
W Li, J Van den Bulcke, I De Windt, M Dierick, J Van Acker

Confocal laser scanning microscopy of a novel decay in preservative treated radiata pine in wet acidic soils
1997 - IRG/WP 97-10215
Light microscopy of radiata pine (Pinus radiata D. Don) field test stakes (20x20x500mm3) exposed in wet acidic (pH 3-4) soil for 12 - 24 months showed predominance of an unusual type of decay characte-rised by tunnelling attack of wood cell walls. After two years decay was moderate to severe in wood treated to ground contact CCA specifications and also equivalent retentions of creosote, and a number of new generation preservatives. Relative to other New Zealand temperate test sites and also an Australian tropical site, the New Zealand acidic soil test site was very aggressive. Correlative scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were used to elucidate the micromorphology of this attack. Tunnels of diameter 0.2-5 µm were present throughout all layers of the cell wall, and their orientation was not related to cellulose microfibril orientation. They also showed no preference for particular cell wall layers, indicating a lignin degrading capability. CLSM images showed that living, connecting fungal hyphae were present in the cell lumina and tunnels. This type of attack was predominant in wood that was highly saturated with water whereas wood that was less moist was predominantly attacked by classical white rot. Ongoing isolation and incubation studies in conjunction with further microscopy should enable identification of the fungal species involved.
R N Wakeling, Ying Xiao, A P Singh

Collaborative soft rot tests: PRL tests of Cu/Cr/As preservative using method of Document No: IRG/WP/208
1973 - IRG/WP 223
These tests were undertaken as a preliminary to the next series of collaborative soft rot tests. An interim report has already been presented at Berlin in 1972 as Document No: IRG/WP/211
J K Carey, J G Savory

Collaborative soft rot tests: Proposals for a standardized soil burial test
1971 - IRG/WP 201
A F Bravery

Collaborative soft rot tests: Interim report on PRL tests of Cu/Cr/As preservative using method of Document No: IRG/WP/208
1972 - IRG/WP 211
Preservative: Tanalith CT.106 - Results obtained with beech are given in the table and indicate a toxic limit of 16.7-19.2 kg/m³ - The initial soil moisture content was adjusted to 27.8% (the water holding capacity). Noticeable drying out has occurred in some of the test bottles.
J G Savory

SEM of wood dust particles
1997 - IRG/WP 97-50084
Dust particles from beech and oak trees have been classified in Germany as being "working materials which are definitely carcinogenic to humans". All other wood dusts, including those from softwoods, are classified as being materials "with reasonable suspicion of carcinogenic potential". The carcinogenic principle of action continues to remain unclear. The mechanical irritation is one of a number of possible triggering principles. In this connection the morphology of the dust particles is of decisive importance. With the aid of a scanning electron microscope this study characterises the dust from spruce, Scots pine, beech and oak. With regard to shape and size the dust particles of all sample collections were divided into 5 groups with principle structural similarity. Therefore a different particle morphology with correspondingly different mechanical irritation in the nose can not be the main principle of action. When compared to asbestos fibers, the small amount of fibrous dust particles as one of the five groups could be clearly distinguished by their structure and dimensions. Mechanical irritation as the main principle of action in the formation of malignant nasal tumors is also contradicted by the findings of different working groups which have established a strong association between hardwood dust and adenocarcinomas of the nasal cavity and paranasal sinuses, and a connection between softwood dust and other types of nasal carcinoma.
U Schmitt, R-D Peek, A O Rapp

The use of immunofluorescence labelling for detecting Ophiostoma piceae in radiata pine
1998 - IRG/WP 98-10268
The primary objective of the current investigation is to understand fungal interactions of dominant sapstaining fungi in radiata pine using confocal laser scanning microscopy (CLSM). In the current paper, an immunofluorescence labelling technique was developed for detection of Ophiostoma piceae using a monoclonal antibody. The primary antibody was labelled with Oregon green 514 Goat anti-mouse IgG fluorescent dye before examining with CLSM. The study showed that immunofluoresence labelling was achieved satisfactorily for detecting fungal hyphae of Ophiostoma piceae but not for some other important sapstaining fungi that occur in radiata pine.
Ying Xiao, B Kreber, C Breuil

Termite and fungal resistance of in situ polymerized tributyltin acrylate and acetylated Indonesian and USA wood
2000 - IRG/WP 00-30219
Wood [Indonesian pine (IP), Indonesian Jabon (IJ) and USA southern yellow pine (USP)] was either in situ polymerized with tributyltin acrylate (TBTA) or acetylated and then exposed to termite and fungal degradation both in laboratory tests and field exposure. The TBTA woods had an average weight percent gain (WPG) of 11% for IP, 12% for IJ, and 10% for USP. The acetylated woods had a WPG of 15-27% for IP, 16% for IJ, and 12-21% for USP. All levels of TBTA and acetylation treatments were effective against the brown-rot fungus Tyromyces palustris and the white-rot fungus Coriolus versicolor in laboratory testing. Resistance to subterranean termites [Coptotermes gestroi (Wasmann)] and dry wood termites [Cryptotermes cynocephalus (Light)] was shown in laboratory tests with all treatments. After one year of field testing in Indonesia (AWPA Standard E7-93), TBTA treated specimens gave a grade number of 8 for all 3 woods compared to 0 for the untreated controls (based on a 10 - point scale.) The acetylated specimens gave a grade number of 4 for IP, 8 for IJ, and 6 for USP. Scanning electron microscopy (SEM) showed polymer located in the lumen of the earlywood and latewood of selected TBTA treated specimens, but at low overall polymer weight gain the lumens were not evenly filled. Termite field testing continues on all treated wood specimens.
R E Ibach, Y S Hadi, D Nandika, S Yusuf, Y Indrayani

Studies of the ray parenchyma cell ends on the radial flow of Sitka spruce (Picea sitchensis)
2000 - IRG/WP 00-40164
It is widely accepted that either ray tracheids or ray parenchyma cells offer the major flow pathways radially for the impregnation of softwood with preservative chemicals. It is now generally recognised that, if radial flow does occur through ray parenchyma cells, the cross-field pits play a dominating role for the liquid movement in the radial direction. In this case, the radial flow of fluid is through the ray parenchyma cells to the longitudinal tracheids across cross-field pit apertures and then back again to the other ray parenchyma cells. It is in this context that cross-field pits which favours flow in the radial direction via a longitudinal route, and thus gives a long path length for radial flow. However, the presence of small channels (i.e. simple pits) between the two ray parenchyma cells may also have a recognisable influence on the radial flow, and exceed the continuous pathway for liquid movement. In this study, therefore, the anatomical structure (the end platform angle, the number of the simple pits per ray parenchyma cell end, their dimensions and the changes in dimensions across growth rings) of the ray parenchyma cell ends have been examined by scanning electron microscope (and microscopic images were then analysed by image analyser) to explain the differences in radial permeability between the extremes in the radial treatment data.
I Usta

Confocal Laser Scanning Microscopy (CLSM) of decayed wood
1998 - IRG/WP 98-10273
Confocal laser scanning microscopy (CLSM) is currently being used to examine biodegraded wood and is proving to be a useful new technique in this area of work. Non-invasive optical sectioning within a thick specimen (20 - 50 µm), coupled with post image processing techniques allows manipulation of images and 3-D reconstruction from serial sections. Glutaraldehyde can cause cell autofluorescence, and since wood cell components do not react with it, a relatively simple technique for localising fungal hyphae, using glutaraldehyde as a fixative, was developed. Subsequent use of probes specific for chitin provided superior images of fungal hyphae in wood. High resolution, sequential, 2-D images can be produced to determine the mode of fungal attack within a thick wood specimen in a dynamic way. Voxel 3-D reconstruction of a series of image stacks enabled stereo viewing of objects.
Ying Xiao, R N Wakeling, A P Singh

Effect of test site, preservative and wood species on decay type Glenbervie pastoral and radiata pine forest sites
2000 - IRG/WP 00-30248
Pinus radiata stakes were treated with 0.8, 1.2, 1.8, 2.7 and 4.1 kg/m3 of CCA and Fagus sylvatica with 2.7, 4.1 and 6.1 kg/m3 of CCA. Both wood species were also treated with equivalent retentions of a copper plus triazole preservative (CT) (0.89, 1.3, 2 and 3 kg/m3 of copper for pine & 2.5 and 4 for beech) and chlorothalonil plus chlorpyriphos in oil (CC) (1.4, 2.1, 3.2 and 4.8 kg/m3 of chlorothalonil for pine and 3.2 and 7.2 for beech). Furthermore, P. radiata was treated with ammoniacal copper plus a quaternary ammmonium compound (ACQ) (0.8, 1.1, 1.7 and 2.6 kg/m3 copper) and a 60/40 mixture of high temperature creosote plus oil (C) (18, 27, 41 and 61 kg/m3). Treated and untreated stakes were exposed in the ground at 13 sites in New Zealand and Australia for between 4 and 6 years. This paper reports the significance of site, timber species, preservative and its concentration and time of exposure, on extent and type of decay, at two sites in Northland, New Zealand. The two sites were adjacent (200 metres), appeared to have essentially similar clay loam soil and climate but one was pastoral and the other was situated within a radiata pine forest. Most types of decay reported in the literature, were observed in this study but other undescribed or only partially characterised types were also found. The decay types found differed between test sites, preservative and timber species. The significance of tunnelling hyphae, which often caused severe decay of wood treated with the higher retentions of various preservatives, appears much greater than the prior literature would suggest. For pine the highest retentions of CC, CT and ACQ gave at least equivalent performance to the reference standards creosote and CCA, after approximately 5 years, at both test sites. For beech CC and CT both gave superior protection to CCA, at both sites. All the preservatives tested exhibited some weaknesses in terms of resistance to the various decay types observed.
R N Wakeling

Addendum to paper for discussion in Working II
1970 - IRG/WP II 5B
In view of the limited time that will be available for discussions in Nancy, this addendum has been prepared. Arising from the previous collaborative work and Mr Bravery’s visit to most of the co-operating Institutes, a scheme of work entailing tests carried out 1) by a technique chosen by individual Institutes; 2) by an agreed standardised technique would appear to be the best approach. A complete programme of work would embrace a) agar tests; b) soil tests -in sterile soil -in unsterile soil. Clearly allocation of priorities eg to concentrate in the first place on tests in unsterile soil, will be needed. To facilitate discussion on a standardised technique, possible methods for conduct of both agar and soil tests are included in appendix I and II respectively. Full details of practical procedures and methods of computing results have not been included.
J G Savory, A F Bravery

Visualising Bacteria in Wood Using Confocal Laser Scanning Microscopy (CLSM)
1998 - IRG/WP 98-10272
A fluorescent phospholipid probe was used in conjunction with confocal laser scanning microscopy (CLSM), to visualise bacteria which inhabit in radiata pine wood and degrade pit membranes. CLSM has the ability to collect fluorescent images through different emission filters at the same time, so it is possible to distinguish gram-positive and gram-negative bacteria in infected wood by counterstaining wood sections with specific fluorescent stains. Images obtained using CLSM were compared with those acquired using light microscopy (LM) and scanning electron microscopy (SEM). Strong fluorescence of the phospholipid probe made it possible to visualise bacteria in wood even when present in numbers too small to detect by LM or SEM.
Ying Xiao, A P Singh, R N Wakeling

Investigation of extracellular mucilaginous material in some wood decay fungi
1996 - IRG/WP 96-10188
The external morphology of the extracellular mucilagenous material (ECM) produced by Coriolus versicolor and Coniophora puteana during colonization of Scots pine and beech was studies using SEM. Specimens were examined in the frozen hydrated, freeze-dried and critical point dried state. All technics produced artefacts but the ECM was best preserved when examined the frozen hydated state. Critical point drying damaged the ECM extensively but was useful in partly explaining its nature. ECM was found to line much of the lumen and coated aerial fungal mycelium. Some morphological patterns in which the ECM and fungal hyphae were involved are also descibed.
A R Abu, D J Dickinson, R J Murphy

Immuno-scanning electron microscopic localization of extracellular polysaccharidases within the fibrillar sheath of the brown rot fungus Postia placenta
1991 - IRG/WP 1497
Extracellular polysaccharidases of the brown-rot fungus Postia placenta were localized using colloidal gold labeled monoclonal antibodies to the B-1,4-xylanase (32-36kDa) fraction of Postia placenta. Postia placenta was grown from agar onto glass coverslips, immunolabeled with or without prior fixation, and examined by SEM. Enzymes were localized on the hyphal surface and on the clumped fibrillar elements (mycofibrils) of the hyphal sheath following fixation with enzymes. If fixation was omitted, labeling was diffuse and not localized on individual or clumped mycofibrils. We conclude that extracellular decay enzymes are weakly bound (non-covalently), but not identical to, the linear mycofibrillar elements of the hyphal sheath. Enzymes appear to dissociate into the water soluble glucan matrix of the sheath during incubation in physiological buffers when fixation is omitted.
F Green III, C A Clausen, M J Larsen, T L Highley

Preliminary Studies on ZiBOC- A Potential Eco-friendly Wood Preservative
2005 - IRG/WP 05-30372
Over the past decade, the wood processing industry has been increasingly involved in strategies to minimize the environmental impacts of treated wood. One sign of this is the dramatic increase in the use of preservatives based on inorganic metal oxides, which fix in wood. Among such preservatives the most common is chromated-copper-arsenate. In Ascu chromium and arsenic both are carcinogenic thus in the present study a new and fixed composition of three chemicals (Copper sulphate, Zinc chloride and Sodium borate) has been used to develop an environment friendly preservative. The formulation is amorphous and water insoluble and dissolved with the help of co-solvents. Fixation study of ZiBOC in Chir and Poplar exhibited only 23.6, 13.1 and 12.1 % leachability of Copper, Zinc and Boron in Chir and 53.5, 6.5 and 5 % leachability of respective metals in Poplar. Efficient fixation of Zinc, Boron in both the species and Copper in Chir was achieved. Efficacy against Polyporous versicolar (PV) and Poria monticola (PM) a white and brown rot fungus respectively showed that 0.50% concentration of salt (3.13 kg/m3) protected Poplar completely against both the fungus as compared to control whereas PV caused 18% and PM caused 52.1% weight loss in control samples. In Chir, 0.2%(1.39 kg/m3) and 0.1% (0.68 kg/m3) concentration of salt protected blocks completely against PM and PV respectively as compared to control (54 and 11.4% weight loss caused by PM and PV). Accelerated field test after three months of installation reveals full protection of both the species against termite & fungus. Scanning electron micrograph revealed the difference of parent individual salts with the derived product. Thus, study is directed to develop synergistic biocidal compositions that combine a copper salt and inorganic biocide, removing arsenic and chromium, giving fourth generation of preservatives.
S Tripathi, J K Bagga, V K Jain

Hole delimination inside round timber via ultrasonic techniques
1990 - IRG/WP 2358
A fast and economic circular scanning method to localize and evaluate holes inside round timber is presented. This method consists in measuring transit times of the ultrasonic wave by fixing the transmitter probe in the perimeter of the sample, then moving the receiver probe every ten degrees until completion of the circle. The scanning is done with a cheap and light instrument. Tests are made with clear wood samples. First, each sample is scanned by this method. Second, the process is repeated after drilling different holes in the samples. Results show that the method allows to quantify holes size and position in a fast and reliable way.
G Prieto, A Fernández Cancio

Micro-Distribution of Metals in Wood Treated with a Nano-Copper Wood Preservative
2007 - IRG/WP 07-40360
The microdistribution of copper in southern pine treated with a newly-developed nano-copper wood preservative was examined to determine if it differed from that reported for wood treated with conventional copper-based wood preservatives. Field Emission Scanning Electron Microscopy (FE-SEM) in combination with x-ray microanalysis (EDX) revealed the presence of nano-sized copper and iron particles in treated wood. These particles ranged in size from 10 to 700 nm and were abundantly present in pit chambers and on tertiary wall layers adjacent to the lumens of tracheids and ray parenchyma cells. FE-SEM and EDX clarified that copper and iron was mainly present as separate particles. Copper was also found in wood cell walls where its concentration was slightly higher in the middle lamella than in the secondary wall layer. In this respect the microdistribution of copper in wood treated with nano-copper resembles that observed in wood treated with conventional copper-based wood preservatives. However, the presence of numerous particulate deposits of copper in voids within the wood creates a different microdistribution pattern for copper in wood treated with the nano-copper preservative compared to that observed in wood treated with current copper-based wood preservatives.
H Matsunaga, M Kiguchi, P Evans

Micro-Distribution of Micronized Copper in Southern Pine
2008 - IRG/WP 08-30479
For copper-based preservatives to be used in ground contact, penetration of copper into the cell wall is believed to be important to protect the wood from soft rot fungi. Preservatives containing soluble copper are known to do this. It is not known whether preservatives containing particulate copper will also migrate into the cell wall in sufficient quantities to control soft rot decay. An AWPA standard E11 leaching test found that leachate from southern pine blocks treated with a preservative containing particulate copper (Micronized copper quat) contained copper ions, suggesting that copper-containing particles in the treated wood slowly release mobile copper. Southern pine sapwood samples treated with wood preservatives containing soluble (ACQ-D) and particulate copper (Micronized copper quat), as well as untreated southern pine sapwood, were analyzed by Environmental Scanning Electron Microscopy (ESEM) and Energy Dispersive X-Ray Spectrometry (EDS). Copper was detected in the lumens of wood treated with both preservatives, and not in the untreated control. Moreover, the presence of small amounts of copper in the cell walls of samples treated with Micronized copper quat and ACQ-D was indicated by ESEM and EDS. This was further supported by the results of a fungal cellar test and a field stake test which demonstrated that wood treated with Micronized copper quat is resistant to soft rot attack. Future work will investigate copper mobility from particles lodged in the lumens.
R Stirling, J Drummond, Jun Zhang, R J Ziobro

Re-Distribution of Copper in the Cell Walls of Wood Treated with Micronized Copper Quat
2009 - IRG/WP 09-30506
Wood treated with copper-based preservatives to be used in ground contact may fail to inhibit soft rot fungi if penetration of copper into the cell wall is insufficient. Preservatives containing soluble copper are known to penetrate the cell wall; however, it is not known whether preservatives containing particulate copper will also migrate into the cell wall in sufficient quantities to control soft rot decay. A method was developed to accelerate and detect re-distribution of copper into the cell wall. Copper was found to re-distribute into the cell wall, presumably from cell lumen deposits, in both ACQ- and micronized copper quat-treated samples after exposure to high temperature and relative humidity. In a non-accelerated test, copper was not found to re-distribute into the cell wall in either ACQ- or micronized copper quat-treated samples after exposure in soil at 15°C for eight weeks.
R Stirling, J Drummond

The invasion channels of damage fungi in bamboo lumber
2010 - IRG/WP 10-10712
The micro-agents on bamboo lumber damage are mould, stain, and decay fungi. This research is about invasion channels of bamboo lumber damage fungi by scanning electron microscope (SEM). The results showed that the conidia of mould were only accumulated on the surface of bamboo and no hyphae detected in bamboo vascular bundle, and hyphae of stain penetrated into bamboo and grew in metaxylem vessel, then expanded from cell to cell through the pits. The brown-rot hyphae extended in cell to cell of bamboo via pits of cell wall, like stain fungi. But branches of brown-rot hyphae were gradually increased and thicker. Hyphae formed nicks (bore holes) on lumen wall contact and then rapidly penetrated. The bore holes later enlarged uniformly. Vertical section showed that bamboo decay firstly on metaxylem vessel wall, then parenchyma cells, finally fibre.
Xingxia Ma, Mingliang Jiang, Daochun Qin

Analyzing hyphal growth of the bio incising fungus Physisporinus vitreus with light-, confocal laser scanning- and, Synchrotron X-ray tomographic microscopy
2010 - IRG/WP 10-20438
Norway spruce wood is an important building material for the forest and wood industry. To improve wood permeability and uptake of wood modification substances Physisporinus vitreus is employed as a bioincising agent. In this study wood specimens were incubated with P. vitreus to assess hyphal colonisation and structural alterations of Norway spruce wood. After different incubation periods, semi-thin sections were prepared and analysed with light-, confocal laser scanning- and Synchrotron X-ray tomographic microscopy. Each method revealed valuable information on hyphal growth in wood and enhances knowledge about underlying processes of fungus – wood interactions.
C Stührk, M Fuhr, M Schubert, F W M R Schwarze

Copper nanoparticles in southern pine wood treated with a micronised preservative: Can nanoparticles penetrate the cell walls of tracheids and ray parenchyma?
2010 - IRG/WP 10-30547
This study tests the hypothesis that copper nanoparticles can penetrate the cell walls of southern pine wood treated with a micronised preservative. We examined the nanodistribution of particles in tracheid and ray parenchyma cell walls using state-of-the-art HR (High Resolution)-TEM and HR-STEM (Scanning Transmission Electron Microscope)-EDX. These devices are capable of atomic-scale resolution. FIB (Focused Ion Beam) processing was used to make ultra-thin sections for electron microscopy. Our results show that FIB sectioning in combination with HR-TEM and HR-STEM is a powerful tool for observing the penetration of wood cell walls by nanoparticles or clusters of metal atoms. HR-STEM with a Cs corrector revealed that copper carbonate nanoparticles could not penetrate the cell walls of tracheids. Copper, however, is present in cell walls of tracheids as atoms or ions. In contrast, small copper nanoparticles (2.5 nm in diameter) were able to penetrate ray parenchyma cell walls. These particles were identified as copper carbonate by HR-TEM lattice image analysis. We conclude that the cell walls of unlignified ray parenchyma tissue in southern pine are accessible to copper nanoparticles whereas nanoparticles are excluded from lignified tracheid walls.
H Matsunaga, Y Kataoka, M Kiguchi, P Evans

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