bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular Modeling of Lignin β-O-4 Model Compounds. Comparative Study of the Computed and Experimental Conformational Properties for a Guaiacyl β-O-4 Dimer
Authors: Besombes S. , Robert D. , Utille J.-P. , Taravel F. R. , Mazeau K. 
Published: September 2004

SummaryThe conformational preferences of thethreoanderythrodiastereomeric forms of a guaiacyl β-O-4 dimer have been investigated by molecular modeling using the CHARMM force field. Many low energy conformations have been identified for each diastereomer, showing that β-O-4 dimers can adopt a large variety of shapes. A consistent structural model has emerged that indicates different conformational behavior for thethreoanderythroforms, corresponding to a preferential extended overall shape for thethreoform. All the low energy conformers are stabilized by intramolecular H-bonds. In particular, the highly directional H-bond between the α or γ hydroxyl hydrogen and the aromatic methoxy oxygen governs the B aromatic ring orientation. However, it has appeared that the conformational preferences are predominantly governed by local steric interactions rather than by differences in the H-bonding pattern. From the satisfactory agreement between computed data (geometries and the Boltzmann distribution of the low energy conformers) and the experimental data reported in the literature (X-ray crystal structures and3JHαHβNMR coupling constant), the CHARMM force field has been validated for the study of β-O-4 structures. Clearly, the molecular modeling calculations have led to an improved rationalization of the conformational data collected by experimental techniques.
Kraft Green Liquor Pretreatment of Softwood Chips. Part III: Lignin Chemical Modifications
Authors: Ban W. , Singh J. , Lucia L. A. 
Published: September 2004

Summary
Quantitative 31P NMR analysis of residual lignin structures isolated from pulps pretreated by
green liquor (GL) as a function of various operating parameters are discussed. Uncondensed phenolics
and condensed hydroxyl groups decreased as the GL charge increased, but increased with
increasing pretreatment temperature. During the cooking of pulps employing variable sulfidities
and the addition of anthraquinone (AQ) or polysulfide (PS), various hydroxyl groups exhibited no
obvious differences in the case of AQ addition, but dramatic changes were observed at variable
sulfidities when the PS was used. The results implied that PS can exert a stronger catalytic effect
under a higher sulfidity and result in more cleavage of the lignin macrostructure. The results also
demonstrated a correlation between the nature of residual lignin and the efficiency of oxygen
delignification based on the finding that the residual lignin in GL modified pulp exhibited a higher
reactivity toward oxygen delignification.
The Role of Ferulic Acid Removal during Bleaching of Wheat Straw Mechanical Pulp with Peroxygen Reagents
Authors: Pan G. X. , Thomson C. I. , Leary G. J. 
Published: September 2004

Summary
The present paper reports our investigation into the use of two peroxygen reagents, peroxymonosulfate
(PMS) and dimethyldioxirane (DMD), in bleaching sequences with peroxide to bleach
wheat straw mechanical pulp, their reactivity with ferulic acid model compounds, and the likely relation
between the two aspects. It was observed that combinations of PMS or DMD with peroxide
offered a synergy leading to substantially improved brightness development in bleaching of wheat
straw pulp. At the same time, these oxidizing reagents, especially DMD, were shown to be highly
reactive with ferulic acid derivatives and increased the removal of ferulic acid from wheat straw
pulp in bleaching. The results would suggest that the presence of non-lignin, peroxide-resistant
chromophoric components, such as ferulic acid derivatives, might be an important factor limiting
the brightness development of wheat straw mechanical pulp by conventional peroxide bleaching.
Evaluation of the Microclimate in a Stored Softwood Chip Pile for Biopulping
Authors: Wolfaardt F. , Rabie C. 
Published: September 2004

Summary
Storage of wood chips is preferred to storage of round wood, however, chip deterioration causes
considerable problems in chip piles. Factors contributing to deterioration have, therefore, been
studied to manage chip storage. The requirements of biopulping processes have renewed interest
in the microclimate in these piles. The aim of this study was to assess the suitability of a 3000 ton
softwood chip pile for colonization by a biopulping fungus. This study evaluated conditions such as
temperature, moisture and CO2 that developed over a 3-week period in the chip pile. Zones that
formed within the pile varied in temperature, CO2 concentration and moisture content. The high
temperatures that developed in some areas in the chip pile could make a large volume (29%) of
the chip pile unsuitable for colonization by mesophilic white-rot fungi. The moisture content in
24% of the chip pile reached 55%, but is not expected to have a large impact on biopulping. The
areas of high temperature and high moisture also overlapped. Special management practices
would, therefore, be required to produce a suitable environment in the chip pile for uniform colonization
by biopulping fungi. High levels of CO2 (12.7%) accumulated for a short period in some
areas, but biopulping could still be effective at these levels.
The Relationship between Longitudinal Growth Strain, Tree Form and Tension Wood at the Stem Periphery of Ten- to Eleven-Year-Old Eucalyptus globulus Labill.
Authors: Washusen R. , Ilic J. , Waugh G. 
Published: September 2004

Summary
The potential for growth strain measurements for detection of tension wood was assessed in trees
from two plantations of 10- to 11-year-old Eucalyptus globulus. Tension wood had commonly developed
at or near the stem periphery of straight, vertical and dominant trees. At a localized level
growth strain was found to be a good indicator of tension wood. However, in some cases moderate
to low growth strain was also detected in some trees where tension wood had been overgrown with
small amounts of normal wood. On a whole tree basis the relationship was not as clear. In this case
growth strain values determined from multiple measurements appear to be influenced primarily
by tissue close to the site of measurements and not by wood at relatively remote locations. In some
cases low growth strain values were found in trees with significant tension wood and in others high
growth strain values where little tension wood had developed.
Topochemical Characterisation of Phenolic Extractives in Discoloured Beechwood (Fagus sylvatica L.)
Authors: Koch G. , Puls J. , Bauch J. 
Published: September 2004

Summary
The topochemical distribution of phenolic extractives in steamed and kiln-dried beechwood with
discolourations was investigated on a cellular level by using scanning UV microspectrophotometry
(UMSP). For the chemical characterisation of accessory compounds, acetone and methanol
extracts of the discoloured beechwood were separated by accelerated solvent extraction (ASE)
and analysed with high performance liquid chromatography (HPLC). The UV microscopic investigations
reveal that the accessory compounds responsible for the discolouration of beechwood
are mainly restricted to the longitudinal and ray parenchyma cells and the lumen of vessels. The
detected extractives are characterised by high UV absorbance values and an absorbance maximum
in a wavelength range between 280 and 290 nm. The separation of the acetone and methanol
extracts of discoloured beechwood shows the presence of different low molecular phenols such as
catechin and 2,6-dimethoxybenzochinon, which are transformed into high condensation compounds
during steaming and kiln-drying.
Phenolic and Lipophilic Extractives in Scots Pine Knots and Stemwood
Authors: Willför S. , Hemming J. , Reunanen M. , Holmbom B. 
Published: September 2004

Summary
The phenolic and lipophilic extractives in the heartwood of knots from seven Scots pine trees were
analysed by GC, GC-MS and HPSEC. The knots contained large amounts of phenolic stilbenes,
1–7% (w/w), and lignans, 0.4–3% (w/w), while the stemwood contained around 1% (w/w) of stilbenes
and no detectable lignans. In young trees without stem heartwood the stilbene content in the
knots was up to 200 times that in the stem. Some in-tree and between-tree variation was seen in the
content of phenolic compounds in the knots. The ratio of pinosylvin monomethyl ether to
pinosylvin was higher in the knots than in the stemwood. The most abundant lignan was nortrachelogenin,
but also matairesinol, secoisolariciresinol and liovil were present in small amounts in the
knots. The knots also contained a complex mixture of lignan-like compounds, here called oligolignans.
The flavonoid pinocembrin was present in both stemwood and knots in amounts below
0.02% (w/w). The stilbene concentration in the radial direction, from the pith to the outer branch,
decreased or was on the same level inside the stem, while it decreased markedly in the outer
branch. The lignan concentration was on the same level or decreased slightly inside the stem, while
it decreased markedly in the branches and became almost non-existent within 10 cm out in the
branches. The knots contained large amounts (4.5–32% (w/w)) of lipophilic extractives, mainly
resin acids. Some in-tree and between-tree variation was seen for the resin acids. The abietane-type
resin acids dominated over the pimarane-type acids and abietic acid was the most abundant
resin acid in the knots and in stem heartwood. The amount of resin acids in the radial direction decreased
or was on the same level inside the stem, while a clear decrease was detected in the branches.
The profile of the distribution of resin acids and phenolic compounds was similar. The knots
also contained up to 0.5% (w/w) of diterpenyl aldehydes.
Measuring Relative Fibre Length in Scots Pine by Non-Destructive Wood Sampling
Authors: Fries A. , Ericsson T. , Mörling T. 
Published: September 2004

SummaryWood fibre length of Scots pine (Pinus sylvestrisL.) was measured in wood sticks and 5-mm increment cores. The aim was to evaluate whether fibre length estimates from such small-diameter cores could be used to calculate genetic parameters, in spite of the increased amount of cut fibres produced at boring. The correlation between mean fibre lengths obtained from cores and sticks, with substantially fewer cut fibres, was high (r= 0.87,n= 53) and of the same magnitude as the correlation between samples from varied positions in the same tree (r= 0.87,n= 46). As regards evaluation of genetic tests and ranking for selection purposes, values from non-destructively sampled 5-mm cores from 0.5 m tree height appear to serve well. Fibre length development along annual ring classes started to differentiate between trees at annual rings 13–15, and after ring 16 there was a slight tendency towards stabilisation which may be interpreted as a reasonably advanced transition from juvenile wood to mature wood.
Modelling Log-End Cracks Due to Growth Stresses: Calculation of the Elastic Energy Release Rate
Authors: Jullien D. , Laghdir A. , Gril J. 
Published: September 2004

Summary
The occurrence of log-end cracks, due to the release of growth stress pre-existing in the standing
tree, causes severe damage at the early stage of wood transformation. A mechanical model based
on Griffith's theory for elastic-fragile materials has been developed to explain the observed patterns:
a crack can only progress when the elastic energy release rate (G) exceeds the toughness
(Gc) of the material for the given fracture mode and orientation. At each stage of the crack propagation,
G was calculated using the finite-element method. The influence of various parameters related
to the rigidity components, the initial growth stress field or the crack geometry has been investigated,
based on a set of experimental data gathered on a population of Eucalyptus. In all cases
the high G values just after crack initiation are followed by a marked decrease until the periphery
has been reached. Their order of magnitude for a typical log is similar to Gc values measured independently
on similar material, thus supporting the validity of the approach.
A Theoretical Analysis of Timber Drying in Oscillating Climates
Authors: Salin J.-G. 
Published: September 2004

Summary
In this study the influence of oscillating climates on the drying of timber is investigated theoretically.
First, the effect of oscillations superimposed on an ordinary drying schedule is examined by
solving the corresponding partial differential equations. It is shown that the average drying rate is
not affected by the oscillations. Second, properly selected oscillation amplitudes and frequencies
can result in enhanced mechano-sorptive creep in the board surface layer, which enables increased
external driving forces with an unchanged risk of checking. This method is analysed by using a drying
simulation model. It is shown that substantial reductions in the drying time can be obtained in
theory. From a practical point of view the benefit is probably rather marginal.
Wood-Derived Porous Ceramics via Infiltration of SiO2-Sol and Carbothermal Reduction
Authors: Klingner R. , Sell J. , Zimmermann T. , Herzog A. , Vogt U. , Graule T. , Thurner P. , Beckmann F. , Müller B. 
Published: September 2004

Summary
The use of wood as a structure-giving material may be the key to producing temperature-resistant
ceramics featuring high and directed porosity combined with necessary strength. The objective of
this study was to develop a simple process to convert the evolutionarily optimized material wood
into highly porous ceramics. Beech and pine, known to be relatively permeable, were pyrolyzed in
a nitrogen atmosphere. The carbon-templates formed were infiltrated with various kinds of silica
sol (SiO2). The resulting SiO2/C composite was transformed into a SiC-ceramic (silicon carbide)
via carbothermal reduction. Through the described process the macroscopic pore-structure of
wood was transformed exactly into SiC. The SiC-ceramic produced proved to be thermo-resistant.
It remained stable in oxygen atmosphere at 1200°C, after a SiO2 coating around the SiC had been
formed. This study focused on the alteration of the cell wall microstructure during the conversion
of wood into SiC. Furthermore, the optimization of the individual process steps, pyrolysis, infiltration
and ceramization along the most efficient route was pursued.
Manufacture of Fiberboard from Wood Fibers Activated with Fentons Reagent (H2O2/FeSO4)
Authors: Widsten P. , Qvintus-Leino P. , Tuominen S. , Laine J. E. 
Published: September 2004

Summary
Fiberboard was manufactured without synthetic resins from spruce and beech fibers activated by
treatment with Fenton's reagent (H2O2/FeSO4) and the formation of radicals in the fibers by the
action of Fenton's reagent was studied. The treatment resulted in a strong improvement of board
strength and a large increase in fiber free radical content. The improved adhesion is probably
largely due to interfiber bonds formed by reactions of radicals or other reactive groups generated
in the fibers by Fenton's reagent. The reactivity of spruce fibers in terms of radical formation increased
as defibration temperature increased. The thickness swell of the boards depended more
on the amount of sizing agent or other additive than on the defibration temperature or fiber reactivity
toward Fenton's reagent.
Formation of β-O-4 Lignin Models -A Theoretical Study
Authors: Durbeej B. , Eriksson L. A. 
Published: September 2004

Summary
The formation of two different β-O-4 lignin models is investigated by means of density functional
calculations. It is found that the coupling of two coniferyl alcohol radicals forming a quinone methide
proceeds by an energy barrier of ~2–5 kcal/mol, and that the associated reaction energy is
negative by more than 20 kcal/mol. On the basis of the corresponding results obtained for the coupling
of a coniferyl alcohol radical to a coniferyl alcohol, it is argued that the resulting radical, albeit
being formed in an energetically less favourable process, might play an important role in lignin
polymerisation. Finally, two different reaction mechanisms for the conversion of a quinone methide
into a guaiacylglycerol-β-coniferyl ether dilignol through the addition of water are explored.
Alkaline Chemi-Mechanical Pulp from Poplar. Relationship between Chemical State, Swelling and Papermaking Properties
Authors: Zanuttini M. , Marzocchi V. 
Published: September 2004

Summary
In order to analyse the fundamentals of alkaline chemi-mechanical pulping of hardwoods, the
chemical state of the wood was related to both the swelling level of fibres and the papermaking
properties of pulp. Wafers of poplar wood were alkali treated following a factorial experimental
design for two variables: temperature and alkali concentration. Treated wafers were hot defibrated
in a 300-mm disk mill at 15% consistency, and then refined in PFI mill at 20% consistency. Results
show how fibre swelling gradually increases as alkaline action is increased. The significant improvement
in tensile and tear strength of the pulp can, in great part, be ascribed to the development
of fibre bonding capacity. A limited effect of ion content on cell wall swelling was found.
Swelling correlates well with deacetylation level, and is a major factor in determining the tensile
strength and scattering ability of the pulp.
Analysis of Pinus radiata D. Don Bark by Near Infrared Spectroscopy
Authors: Schimleck L. R. , Yazaki Y. 
Published: September 2004

Summary
The estimation of a range of Pinus radiata D. Don bark properties by calibrated near infrared
(NIR) spectroscopy is reported. A series of P. radiata samples were characterised in terms of hot
water extractives, NaOH extractives and Stiasny value. NIR spectra were obtained from the milled
bark of each sample and used to develop calibrations for each parameter. Coefficients of determination
(R2) ranged from 0.84 (NaOH extractives) to 0.94 (Stiasny value). Standard errors of calibration
ranged from 0.96 (NaOH extractives) to 2.47 (Stiasny value). When applied to a separate
test set, the hot water extractives and Stiasny value calibrations performed well, while the NaOH
calibration was disappointing. The calibration developed for Stiasny value could be of considerable
practical importance as the method used to determine Stiasny value is particularly time consuming.
Effect of High Temperature on the Change in Color, Dimensional Stability and Mechanical Properties of Spruce Wood
Authors: Bekhta P. , Niemz P. 
Published: September 2004

Summary
In this study the effect of high temperature on mechanical properties, dimensional stability and
color of spruce was investigated. Wood specimens conditioned at different relative humidities (50,
65, 80 and 95%) were subjected to heat treatment at 200°C for 2, 4, 8, 10 and 24 h and at 100, 150
and 200°C for 24 h. Color changes were measured in the Minolta Croma-Meter CR-300 color system.
Bending strength and modulus of elasticity were determined according to DIN 52186. The results
show that heat treatment mainly resulted in a darkening of wood tissues, improvement of the
dimensional stability of wood and reduction of its mechanical properties. The darkening accelerated
generally when treatment temperature exceeded approximately 200°C. Most of the darkening
occurred within the first 4 h of exposure. For the specimens heated to high temperatures, the average
decrease in bending strength was about 44–50%, while modulus of elasticity was reduced by
only 4–9%. We found that treatment time and temperature were more important than relative humidity
regarding the color responses. Strong correlations between total color difference and both
modulus of elasticity and bending strength were found. Thus, the color parameters can be estimated
quantitatively and used as a prediction of wood strength.
Effects of Clonal Selection by Microfibril Angle on the Genetic Improvement of Stiffness in Cryptomeria japonica D. Don
Authors: Nakada R. , Fujisawa Y. , Hirakawa Y. 
Published: September 2004

Summary
The microfibril angle (MFA) of latewood tracheids and its radial variation at breast height in
Cryptomeria japonica D. Don (sugi) were investigated with twelve clones collected from three
sites in the Kyushu region, Japan. Large variations both between clones and between sites were observed.
The MFAs were well correlated to the stiffness of the logs collected from the sample trees.
A simulation of clonal selection according to the ranking of the clones in MFA demonstrated that
the log stiffness of the selected population was much improved even when the selection relied on
MFAs in the second ring from the pith. The improvement in log stiffness by MFA selection was not
different from the selection by log stiffness itself. The results indicate that early selection by MFA
is very effective in improving log stiffness in this species.
Prevalence of Palatal and Alveolar Cysts in Babies with Cleft Lip and Palate
Authors: Alves Karina Mirela Ribeiro Pinto , Peixoto Virginia , Gomide Márcia Ribeiro , Carrara Cleide Felíciode Carvalho , Costa Beatriz 
Published: September 2004

Objective To evaluate the prevalence of palatal and alveolar cysts in babies with cleft lip and/or palate. Design Cross-sectional. Setting Hospital for Rehabilitation of Craniofacial Anomalies, University of São Paulo (HRAC-USP), Bauru, São Paulo, Brazil. Participants Two hundred ninety-one Caucasian babies divided into four groups according to the type of cleft: cleft lip with or without cleft alveolus (70), complete unilateral cleft lip and palate (112), complete bilateral cleft lip and palate (56), and cleft palate (53). Results A low prevalence of palatal and alveolar cysts was observed among patients with the four different types of clefts, with no statistically significant difference between genders. The maxilla and the anterior area of the mouth were more affected than the mandible and the posterior area. Conclusions The low prevalence of palatal and alveolar cysts in the four groups of babies with clefts included in this study may have been due to the high mean age of the sample.
Dentoalveolar Growth of Patients with Complete Unilateral Cleft Lip and Palate by Early Two-Stage Furlow and Push-Back Method: Preliminary Results
Authors: Kitagawa Taiji , Kohara Hiroshi , Sohmura Taiji , Takahashi Junzo , Tachimura Takashi , Wada Takeshi , Kogo Mikihiko 
Published: September 2004

Objective This study examined dentoalveolar growth changes prior to the time of palatoplasty up to 3 years of age by the early two-stage Furlow and push-back methods. Subjects Thirty-four Japanese patients with complete unilateral cleft lip and palate (UCLP) treated with either a two-stage Furlow procedure (Furlow group: seven boys, eight girls) from 1998 to 2002 or a push-back procedure (push-back group; 12 boys, 7 girls) from 1993 to 1997. Method Consecutive plaster models were measured by three-dimensional laser scanner, before primary palatoplasty, before hard palate closure (Furlow group only), and at 3 years of age. Bite measures were taken at 3 years of age. Results In the Furlow group, arch length, canine width, first and second deciduous molar width and cross-sectional area, and depth and volume at midpoint showed greater growth than in the push-back group. In the Furlow group, the crossbite score was also better than in the push-back group at 3 years of age. In comparison with the push-back group, inhibition of growth impediment in the anterior region was observed in the horizontal direction in the Furlow group. In the midregion, it was observed in the horizontal and vertical directions, and in the posterior region it was observed in the horizontal direction. Conclusion The results demonstrate that the early two-stage Furlow method showed progressive alveolar growth. Therefore, the early two-stage Furlow method is a more beneficial procedure than the push-back method.