Oak Samples Research Articles

Complex resistivity measurements on oak

In this paper complex electrical resistivity measurements on oak samples are described. They were performed to study the effect of anisotropy, moisture content and fungi-infection. The laboratory results indicate that anisotropy of wood affects not only the electrical resistivity but also the phase shift. The results can be explained by the macro- and microstructure of wood. The moisture experiment showed that resistivity and phase behave differently. As expected, resistivity decreases with increasing moisture. In contrast, phase and the imaginary part of conductivity first increase with rising moisture content but then start to decrease again at higher moisture level.

Antioxidant Activity of Oak (Quercus) Leaves Infusions against Free Radicals and their Cardioprotective Potential

The aim of present study was to evaluate antioxidant capacity and cardioprotective potential of leaves infusions and partially purified fractions of Quercus sideroxyla and Q. eduardii (red oaks) and Q. resinosa (white oak). Consumption of polyphenol-rich beverages derived from plants, such as oak may represent a beneficial diet in terms of cardiovascular protection. Infusions from Oak leaves were obtained and probed for total phenolics by Folin-Ciocalteu, DPPH and hydroxyl radicals scavenging by DPPH test and Deoxy-D-ribose method, the antioxidant capacity was evaluated by FRAP and ORAC tests, inhibitions of Low Density Lipoproteins (LDL) oxidation and Angiotensin Converting Enzyme (ACE) activity were measured. A HPLC analysis was performed by HPLC-MS. Bioactive polyphenols such as gallic and ellagic acids, catechin, quercetin and derivatives: naringenin and naringin were detected in Quercus infusions. A distinctive HPLC profile was observed among the red and white oak samples. Q. resinosa infusions have exhibited the highest antioxidant activity in comparison with the other species, although in the inhibition of LDL oxidation no differences were observed. In the inhibition of the ACE, Q. resinosa was more effective (IC50, 18 ppm) than Q. sideroxyla, showing same effect as the control Captopril. From the results it is possible to postulate that not only chelating activity is important in these infusions, especially in Q. resinosa.

High-Precision Radiocarbon Dating of the Construction Phase of Oakbank Crannog, Loch Tay, Perthshire

Many of the Loch Tay crannogs were built in the Early Iron Age and so calibration of the radiocarbon ages produces very broad calendar age ranges due to the well-documented Hallstatt plateau in the calibration curve. However, the large oak timbers that were used in the construction of some of the crannogs potentially provide a means of improving the precision of the dating through subdividing them into decadal or subdecadal increments, dating them to high precision and wiggle-matching the resulting data to the master 14C calibration curve. We obtained a sample from 1 oak timber from Oakbank Crannog comprising 70 rings (Sample OB06 WMS 1, T103) including sapwood that was complete to the bark edge. The timber is situated on the northeast edge of the main living area of the crannog and as a large and strong oak pile would have been a useful support in more than 1 phase of occupation and may be related to the earliest construction phase of the site. This was sectioned into 5-yr increments and dated to a precision of approximately ±8–16 14C yr (1 σ). The wiggle-match predicts that the last ring dated was formed around 500 BC (maximum range of 520–465 BC) and should be taken as indicative of the likely time of construction of Oakbank Crannog. This is a considerable improvement on the estimates based on single 14C ages made on oak samples, which typically encompassed the period from around 800–400 BC.

14C Calibration in the 2nd and 1st Millennia BC—Eastern Mediterranean Radiocarbon Comparison Project (EMRCP)

We have measured additional known-age German oak samples in 4 intervals in the 2nd and 1st millennia BC to add to (and to replicate) parts of the international Northern Hemisphere radiocarbon calibration data set. In the 17th, 16th, and 12th centuries BC, our results agree well with IntCal04. In the 14th and 13th centuries BC, however, we observe a significant offset, with our results on average 27 yr older than IntCal04. The previously reported 14C offset between Anatolian juniper trees and central European oaks in the 9th and 8th centuries BC is smaller now, on the basis of our new measurements of German oak, but still evident. In the 17th and 16th centuries BC, the 14C ages from the Anatolian chronology agree well with IntCal04 and our new German oak data.

Ectomycorrhizal fungal communities of pedunculate and sessile oak seedlings from bare-root forest nurseries

In this study, we present the detailed molecular investigation of the ectomycorrhizal (ECM) community of Quercus petraea and Quercus robur seedlings grown in bare-root forest nurseries. In all tested oak samples, mycorrhizal colonization was nearly 100%. Morphological observation and molecular investigations (sequencing of fungal ITS rDNA) revealed a total of 23 mycorrhizal taxa. The most frequent and abundant fungal taxa were Hebeloma sacchariolens, Tuber sp., and Peziza sp.; from the detected fungal taxa, 20 were noted for Q. petraea and 23 for Q. robur. Depending on the nursery, the species richness of identified ECM fungal taxa for both oak species ranged from six to 11 taxa. The mean species richness for all nurseries was 5.36 and 5.82 taxa per Q. petraea and Q. robur sample, respectively. According to the analysis of similarity, ECM fungal communities were similar for Q. petraea and Q. robur (R = 0.019; p = 0.151). On the other hand, detected fungal communities were significantly different between nurseries (R = 0.927; p < 0.0001). Using the Spearman rank correlation, it was determined that the ectomycorrhizal diversity (in terms of richness, the Shannon diversity, evenness, and Simpson dominance indices) is significantly related to the soil parameters of each nursery. We conclude that individual nursery may be considered as separate ecological niches that strongly discriminate diversity of ECM fungi.

Progress in Constructing a Long Oak Chronology from the Central United States

We describe methods and progress in developing the American Long Oak Chronology (ALOC), an effort to construct an oak tree-ring chronology from the Central US that spans the Holocene. Since 2000, we have collected and measured ring widths on over 550 pieces of subfossil oak (Quercus) wood. Over 330 oak samples have been radiocarbon dated, with ages ranging up to 14,000 cal yr B.P. A 1,093-year-long tree-ring record has been constructed from live and subfossil bur oaks (Q. macrocarpa Michx.) and swamp white oaks (Q. bicolor Willd.) growing along and buried in sediments of streams that flow through northern Missouri and southern Iowa, USA. Here we describe the ALOC for the period A.D. 912–2004 to demonstrate its dendrochronological value, display the material quality, and emphasize the importance of chronology construction. We also report on progress in developing older floating chronologies. The development of more long, multi-millennium chronologies will be an important contribution to dendroclimatology. These chronologies will be particularly useful to the Central US, a region with a continental climate and limited temporal depth of annually resolved paleo-records. Perhaps more critical is its location in the middle of one of the most important agricultural regions in the world.

Relation between chemical composition of oak wood used in cooperage and sensory perception of model extracts

AbstractBACKGROUND: Oak extractive substances modify the aroma and taste of ‘oaked’ wines, with an increased intensity of sensory descriptors such as ‘oaky’, ‘spicy’, ‘vanilla’, ‘smoky’, etc. arising during barrel maturation. In this study the relationship between the chemical composition of untoasted oak wood and the sensory assessment of oak extract was investigated. Oak wood samples (140) were analysed both chemically (using gas chromatography/mass spectrometry after extraction with dichloromethane) and using sensory descriptive analysis of oak‐extracted model wine solutions.RESULTS: Oak samples from the USA, France and Eastern Europe had different chemical compositions in terms of principal odour‐active extractives, and this was reflected by perceived sensory differences.CONCLUSION: The major sensory differences were associated with cis‐whisky‐lactone concentrations of the wood extracts and were related to sensory descriptors such as coconut, caramel and milk. Other compounds studied (trans‐whisky‐lactone, eugenol and vanillin) were found to have a minor impact on sensory differences between samples in spite of their odour activity. This fact could be explained by the natural differences between samples not being sufficiently large to be perceived. The effects of aroma amplification and/or masking linked to the presence of other odorous chemicals could also explain these observations. Copyright © 2009 Society of Chemical Industry

Investigating the Interhemispheric 14C Offset in the 1st Millennium AD and Assessment of Laboratory Bias and Calibration Errors

Past measurements of the radiocarbon interhemispheric offset have been restricted to relatively young samples because of a lack of older dendrochronologically secure Southern Hemisphere tree-ring chronologies. The Southern Hemisphere calibration data set SHCal04 earlier than AD 950 utilizes a variable interhemispheric offset derived from measured 2nd millennium AD Southern Hemisphere/Northern Hemisphere sample pairs with the assumption of stable Holocene ocean/atmosphere interactions. This study extends the range of measured interhemispheric offset values with 20 decadal New Zealand kauri and Irish oak sample pairs from 3 selected time intervals in the 1st millennium AD and is part of a larger program to obtain high-precision Southern Hemisphere 14C data continuously back to 200 BC. We found an average interhemispheric offset of 35 ± 6 yr, which although consistent with previously published 2nd millennium AD measurements, is lower than the offset of 55–58 yr utilized in SHCal04. We concur with McCormac et al. (2008) that the IntCal04 measurement for AD 775 may indeed be slightly too old but also suggest the McCormac results appear excessively young for the interval AD 755–785. In addition, we raise the issue of laboratory bias and calibration errors, and encourage all laboratories to check their consistency with appropriate calibration curves and invest more effort into improving the accuracy of those curves.

The effects of pilot hole, screw types and layer thickness on the withdrawal strength of screws in laminated veneer lumber

The objective of this study was to evaluate the effects of screw type, pilot hole and layer thickness on the withdrawal strength of some screws in laminated veneer lumbers (LVL). For this purpose, three, four and five layered laminated samples were produced in different veneer thickness (4, 5 and 7 mm) of Uludag fir ( Abies bornmülleriana Mattf.) and oak ( Quercus petraea spp.) woods. And melamine-formaldehyde (MF) and phenol-formaldehyde (PF) adhesives were also used for laminated veneer lumber manufacturing. Withdrawal strength test was applied on the test samples. According to the test results, it was found that the highest withdrawal strength was obtained in oak samples having 4 mm veneer thickness bonded with PF for 3.5 × 16 screw as 23.14 MPa, the lowest was obtained for Uludag fir having 5 mm veneer thickness bonded with MF adhesive with 4.0 × 50 screw as 7.61 MPa. The use of proper size of pilot holes is advised in order to avoid splitting of the face during insertion of screws as well as to obtain maximum withdrawal strength.

Quercus suber and Betula pendula outer barks as renewable sources of oleochemicals: A comparative study

A comparative study on the chemical composition of oak cork ( Quercus suber L.) and corresponding industrial residues and birch ( Betula pendula L.) outer bark is reported. Cork oak samples have lower extractives contents (6–9%) and higher contents of carbohydrates and lignin (23–27 and 33–38%, respectively) than those found for birch outer bark (40, 6 and 9%, respectively); suberin contents accounted for around 30% of cork, 11% of industrial cork powder and 45% of birch outer bark. Analysis of the suberin monomeric composition revealed that C18 and C22 ω-hydroxyfatty acids (including mid-chain epoxy- and dihydroxy-derivatives), followed by α,ω-dicarboxylic acids, are the main components in both suberins, with 9,10-epoxy-18-hydroxyoctadecanoic, 18-hydroxyoctadec-9-enoic, 9,10,18-trihydroxyoctadecanoic and octadec-9-enoic acids as the major components. The differences in the relative amounts of these acids in the suberin samples and the impact on the potential exploitation of the different industrial by-products are discussed.

Sugarcane spirit extracts of oak and Brazilian woods: antioxidant capacity and activity

Sugarcane spirit extracts of six different Brazilian woods for potential use in manufacturing aging casks were compared with similar extracts of five oak samples from different geographic origin and heat treatment regarding: (1) content of phenolics and copper; (2) radical reducing capacity and reactivity toward 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·); and (3) effect on the rate of oxygen depletion rate in a peroxidating lipid model system. Total phenolic contents of the Brazilian wood extracts ranged from 0.65 (canela-sassafras) to 6.4 (jatoba) mmolGAE L−1 and from 1.39 to 2.87 mmolGAE L−1 for oak extracts. Flavonoids ranged from 1.54 × 10−4 (ipe) to 6.5 × 10−2 (oak) mmolrutin L−1, and tannins from below the detection limit to 0.22 (jatoba) mmoltannic acid L−1. Correlation was observed for the antioxidant capacity versus phenolics/flavonoids/tannins content, where oak extracts exhibit the highest radical scavenging capacity compared to Brazilian woods. Rate constant for radical scavenging by the extracts ranged from 4.9 × 103 M−1 s−1 (canela-sassafras) to 9.7 × 104 M−1 s−1 (oak). The oxygen consumption index showed the Brazilian woods amendoim and jatoba to be more efficient inhibitors than the oak extracts for lipid autoxidation initiated by metmyoglobin, despite that the oak extracts seem to be more efficient to scavenge DPPH·. No simple correlation with phenolics or copper content could be established, and a prooxidative tendency was observed for the extracts of canela-sassafras, castanheira, and louro-canela.

The shrinkage of oak predicted from its anatomical pattern: validation of a cognitive model

This paper deals with the ability of a scientific strategy to compute the shrinkage behaviour of any oak sample, regardless of its origin, density, growth ring, etc. This approach uses the description of the actual oak structure at the annual ring level (i.e. the spatial organisation of the radial ray-cells, fibre, parenchyma areas and large vessels), to evaluate its shrinkage/swelling and elastic properties in the transverse directions. For the shrinkage properties, computed results were compared with experimental values measured on a set of samples depicting a very large diversity of anatomical patterns. The accuracy of our prediction is about 5% in the tangential direction and 20% in the radial direction, which is much better than statistical models over a wide range of variables. These results are discussed and a few microscopic observations with ESEM allow explanation of anomaly points of behaviour to be formulated. Such good results could allow this approach to be used to study the influence of growing conditions or of global changes upon physical wood properties.

Medieval oak chronology from the Vilnius Lower Castle

The paper describes the results of a dendrochronological investigation on historical oak (Q uercus robur L.) timbers from the Vilnius Lower Castle excavations. In Lithuania, oak was used only in specific cases during the Middle Ages. Therefore, historical material for tree ring chronology building is lacking. However, the construction of a local oak chronology is of great importance as it can help to determine the provenance of many imported timbers that are part of wooden cultural heritage in Western Europe. Oak samples make 9.2% of the analysed timbers excavated in the Vilnius Lower Castle territory – the largest present-day collection of historical timbers in Lithuania. The main material for Vilnius oak chronology was obtained from the ‘bridge foundation (BF)’ construction found close to the Royal Palace gate at a depth of 4–5 m. Ring-width series of the oak beams of the ‘BF’, together with other excavated oak logs were cross-dated and a mean chronology of 217-year length was constructed. The chronology was dated to AD 1202–1418 against the Baltic reference chronologies BALTIC1 ( t = 7.57 ), BALTIC2 ( t = 4.52 ) and WINCHCOL ( t = 5.74 ) (authors J. Hilliam, I. Tyers, D. Mills). The average date of the hardwood – sapwood boundary on the ‘bridge’ samples that have partially preserved sapwood is between 1406 and 1407. As the average number of oak sapwood rings is considered to be 16, the most probable felling date of trees used for the ‘BF’ is situated around 1423.

Influence of Geographical Origin and Botanical Species on the Content of Extractives in American, French, and East European Oak Woods

The chemical composition of East European (Republic of Moldova, Ukraine, and Romania) oaks was investigated profoundly for the first time in the present study and compared with American and French counterparts. Taking into account the high natural variability of oak extractives contents, the wide-ranging sampling was performed for all oak origins: 276 French oaks, 102 East European oaks of both species (Quercus robur L. and Quercus petraea Liebl.), and 56 American oaks (Quercus alba). These oaks were compared with great attention paid to the extractives, which are most important for sensorial impact in wine or spirit maturation, such as ellagitannins and principal odorant substances (aromatic aldehydes, lactones and phenols). The substances in question were studied by application of HPLC and GC-MS techniques. The pattern of all studied extractive contents allowed adequate separation of oak samples according to their geographical origin or botanical species. The highest separation rate was for American and French oaks, whereas East European samples could be partially misclassified in two sets mentioned above. The most important variables for species discrimination were whiskey lactone related variables and ellagitannins, whereas the most important features for distinguishing the origin were eugenol, 2-phenylethanol, vanillin, and syringaldehyde. These substances allowed the distinction of French and East European woods of the same species. With regard to chemical composition, East European wood held the intermediary place between American and French oaks according to their ellagitannin and whiskey lactone levels; nevertheless, it was characterized by specific high values of eugenol, aromatic aldehydes, and 2-phenylethanol.

Bond strength and durabilty behavior of polyurethane‐based Desmodur‐VTKA adhesives used for building materials after being exposed to water‐resistance test

AbstractPolyurethane adhesives are being used increasingly in the construction of furniture frames and buildings. Yet, there is little information available concerning the durability behavior of polyurethane adhesives on various wood species, after being exposed to water‐resistance test. For this purpose, oriental beech (Fagus orientalis L.), oak (Qercus petraea spp.), and scotch pine (Pinus sylvestris lipsky) woods were chosen as test materials and bonded with Desmodur‐VTKA polymarine, according to the procedure of BS EN 204 standards. The shear strength test was applied to the samples, according to the procedure of BS EN 205 standards, before and after immersion in cold water and in hot water, and afterward boiled and boiled recurrently. At the end of the shear test, it was found that Desmodur‐VTKA polymarine had lost its durability. The highest shear strength (10.723 N/mm2) was obtained in oak samples not exposed to water‐resistance test. Owing to dissimilar swelling of Desmodur‐VTKA polymarine and oak, resulting from moisture sorption, oak samples lost 85.6% of its strength after being boiled and boiled recurrently, and gave the lowest shear strength as 1.540 N/mm2. As a result, if Desmodur‐VTKA is used as an adhesive material in the long‐term humidity condition, it cannot be recommended for bonding of wood materials with high density. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3943–3947, 2006

Investigation of the Relationships between Anatomical Pattern, Density and Local Swelling of Oak Wood

We coupled a digital X-ray imaging system with a humid air conditioner. This new configuration allows the shrinkage behaviour of thin samples to be measured. In order to control both the temperature and the relative humidity in the chamber, an air generator was developed which ensures very stable conditions even over several months. The X-ray beam passes through the chamber to the 2D detector. Twelve samples can be placed on a rotating sample holder. The strain field due to the moisture content variations is determined by an image correlation algorithm, which compares X-ray images collected at different moisture conditions. Moreover, inspection by X-ray simultaneously produces complementary data: the local density and the spatial organisation of the tissues within the anatomical pattern. Twelve oak samples, chosen for their wide variability of the anatomical pattern, were characterised using this device. Some models available in the literature are used to predict the swelling. fThe comparison between measurements and prediction is rather poor. The variable anatomical structure of the annual rings permits some explanations for this decrepancy and leads to the conclusion that the complete spatial organisation of the tissues has to be quantified to understand and to predict the behaviour of oak wood.

The Effect of Some Factors on Surface Roughness of Sanded Wood Material

In this study, the effect of section direction and kind of sand paper on surface roughness of sanded wood samples was investigated. For this purpose, radial and tangential parts were taken from acacia (Robinia pseudoacacia L.), pear (Pirus communis L.), chestnut (Castanea sativa Mill.), oak (Quercus petraea Lieble) and cedar (Cedrus libani A. Rich), which are commonly grown, trees in Turkey. Samples were prepared by processing the sanding machine for 80 and 120 numbers. Surface roughness were tested by using method of ISO 4287. The results of this study suggest that the highest value for surface roughness value was found on the oak samples while the lowest value was obtained from the pear samples. Furthermore, according to radial and tangential direction, the sanding paper of 80 numbered has given worst surface roughness in comparisons with using the sanding paper of 120 numbered.

The effects of size, temperature and air contact on the outcome of heating oak fragments

The concentrations of the important oak aroma volatiles guaiacol, 4-methylguaiacol cis- and trans-oak lactone and vanillin in extracts of French and American oak heated under various conditions were measured using stable isotope dilution analyses coupled with gas chromatography-mass spectrometry. Heating resulted in marked increases in the concentrations of guaiacol, 4-methylguaiacol and vanillin, with more formed at higher temperature. Approximately twice as much guaiacol and 4-methylguaiacol and two to five times as much vanillin were formed by heating in the presence of air compared to heating under argon. Oak lactone concentration was less affected by heating. The effects of heating different sized oak pieces were investigated for French and American oak samples. Compared to heating larger oak pieces, heating smaller fragments of oak generated up to twice as much guaiacol and 4-methylguaiacol and two to four times as much vanillin at 235oC for both French and American oak. This effect is ascribed to the exposure of a greater surface area of oak to air when smaller fragments are heated. Variable effects were observed for cis- and trans-oak lactone. Variation in chip size, as well as heating time and temperature, is clearly one way of obtaining different aroma profiles from oak products.

Effects of ammonium hydroxide treatment on the in vitro dry matter digestibility and gas production of wheat straw, sugarcane bagasse medium and konara oak rotted by edible basidiomycetes

ABSTRACTWheat straw, sugarcane bagasse medium and konara oak logs used to cultivate edible basidiomycetes were treated with ammonium hydroxide to investigate the relationship between the degree of rotting and the effect of ammonium hydroxide treatment on digestibility. Wheat straw was sampled before inoculation and on days 67 and 97 after inoculation with Pleurotus salmoneostramineus. Similarly, bagasse media were sampled before inoculation and on days 47 and 96 after inoculation with Pleurotus abalonus. Konara oak logs were sampled before inoculation and at 2 and 4 years after inoculation with Lentinula edodes. Aliquots of the samples were treated with ammonium hydroxide (NH4‐N, 3% dry matter) at 45°C for 10 days. Ammonium hydroxide treatment increased the in vitro dry matter digestibility (IVDMD) and gas production (IVGP) of all the samples, except the konara oak samples collected before inoculation. The degree of increased digestibility was largest for the samples collected after short cultivation periods, followed by those collected after long cultivation periods and those collected before inoculation. However, the IVDMD and IVGP values after short cultivation periods were lower than those after long cultivation periods. Ammonium hydroxide treatment is effective at improving the digestibility of white‐rotted materials, although the effect is lessened as rotting proceeds.

Use of X-ray computed microtomography for non-invasive determination of wood anatomical characteristics

Quantitative analysis of wood anatomical characteristics is usually performed using classical microtomy yielding optical micrographs of stained thin sections. It is time-consuming to obtain high quality cross-sections from microtomy, and sections can be damaged. This approach, therefore, is often impractical for those who need quick acquisition of quantitative data on vessel characteristics in wood. This paper reports results of a novel approach using X-ray computed microtomography (microCT) for non-invasive determination of wood anatomy. As a case study, stem wood samples of a 2-year-old beech ( Fagus sylvatica L.) and a 3-year-old oak ( Quercus robur L.) tree were investigated with this technique, beech being a diffuse-porous and oak a ring-porous tree species. MicroCT allowed non-invasive mapping of 2-D transverse cross-sections of both wood samples with micrometer resolution. Self-developed software `μCTanalysis' was used for image processing of the 2-D cross-sections in order to automatically determine the inner vessel diameters, the transverse cross-sectional surface area of the vessels, the vessel density and the porosity with computer assistance. Performance of this new software was compared with manual analysis of the same micrographs. The automatically obtained results showed no significant statistical differences compared to the manual measurements. Visual inspection of the microCT slices revealed very good correspondence with the optical micrographs. Statistical analysis confirmed this observation in a more quantitative way, and it was, therefore, argued that anatomical analysis of optical micrographs can be readily substituted by automated use of microCT, and this without loss of accuracy. Furthermore, as an additional application of microCT, the 3-D renderings of the internal microstructure of the xylem vessels for both the beech and the oak sample could be reconstructed, clearly showing the complex nature of vessel networks. It can be concluded that the use of microCT in wood science offers an interesting potential for all those who need quantitative data of wood anatomical characteristics in either the 2-D or the 3-D space.