The evolutionary relationships of woodrats (Neotoma) were elulcidated through phylogenetic analyses of mitochondrial DNA restriction site and allozyme data. DNA samples from eleven nominal species from the genus Neotoma and two outgroup taxa, Ototylomys phyttotis and Xenomys nelsoni, were cleaved using a suite of 17 Type II restriction endonucleases. Mitochondrial DNA restriction profiles were visualized following electrophoresis of restriction digests via methods of Southern transfer and hybridization with 32P- and digoxigenin-labeled mtDNA probes. Restriction mapping resulted in the identification of 37 unique mtDNA haplotypes among the woodrat taxa examined. Proteins representing 24 presumptive structural gene loci were examined through starch gel electrophoresis. Binary-coded allozyme data and allozyme frequency data were analyzed using PAUP and FREQPARS, respectively. Phylogenetic analyses of the mtDNA restriction site data incorporated three different character type assumptions: unordered binary characters, Dollo characters, and differentially weighted unordered characters employing the STEPMATRIX option of PAUP. Proposed phylogenies for Neotoma are based on majority-rule consensus trees produced using bootstrap procedures. Phylogenetic analyses of the woodrat data sets revealed a distinct dichotomy among populations of white-throated woodrats (N. albigula) suggesting the presence of cryptic species within that taxon. MtDNA and allozyme data support the specific status of N. devia as distinct from N. lepida, and additionally reveal the presence of a third cryptic species referable to N. intermedia among the desert woodrats. Phylogenetic analyses of the genetic data also suggest subgeneric status for the desert woodrats, which is in agreement with evidence from morphology. The genetic data revealed a sister group relationship between N. stephensi and samples of N. mexicana, suggesting the placement of N. stephensi into the N. mexicana species-group. Neotoma fuscipes and N. cinerea formed a monophyletic lineage basal to the remaining members of the subgenus Neotoma which supports the assignment of N. fuscipes to the subgenus Teonoma with N. cinerea. Although stringent, Dollo parsimony methods produced the best supported phylogenies among the species of Neotoma. The STEPMATRIX approach was unable to resolve species relationships within species-groups but clearly delineated the higher taxonomic levels between species-groups and subgenera.

No description available.

The longitudinal air permeabilities of the wood of 1116 specimens from 279 trees, two sapwood and two heartwood replicates, representing two varieties of lodgepole pine (Pinus contorta, vars. latifolia and murrayana) were measured with a steady state apparatus. It was found that the mean ratio of sapwood to heartwood permeability was ca. 10:1 for both varieties. The mean ratio of var. latifolia to murrayana was 1.5:5 and 1.75:5 for sapwood and heartwood, respectively. The most important source of variation following the difference between heartwood and sapwood was that among trees. Geographical locations, such as latitude and elevation did not significantly influence permeability. Tree size did, but only because the small trees (3 inch diameter) showed higher heartwood permeability and lower sapwood permeability than normal. Ca. 20 specimens of latifolia heartwood showed extremely high permeabilities. They were also deeply brown in color, which probably was caused by fungal or bacterial infestation. Pit pore size and number per cm² were determined for sapwood by making four permeability measurements, each at a different average pressure on each specimen. A mean pit pore radius of 1.5 µm and 1.3 µm for sapwood of var. latifolia and var. murrayana was calculated. The median values between 1200-1300 pit pores per cm² indicate an average rate of tracheid connection of 1.2-1.3%. Of the tested wood parameters including moisture content and specific gravity average ringwidth, only the permeability of var. latifolia was significantly correlated with moisture content for both heartwood and sapwood, with a negative correlation coefficient. Water retention measurements were carried out to relate the measured gas permeability of an individual specimen to its ability to absorb water. For both varieties the retention was significantly and quadratically correlated with sapwood permeability (R² = 0.286 and 0.224) and was linearly correlated with heartwood permeability (R² = 0.488 and 0.5775). The correlation factors for the regression between retention and the logarithm of permeability were 0.239 and 0.227 for sapwood and 0.447 and 0.420 for heartwood. / M.S.

The quality of whole-tree wood chips has been the focus of much attention during the past few years because of the increased use of lower grade wood über in pulp production. The need to up-grade the quality has resulted in the use of some form of screening system to separate acceptable wood chips from unwanted material at most pulp mills. In order to upgrade the chip quality, a study was conducted to determine the effect of selected parameters of a separation system with an inclined, vibrating screen on screening efficiency. The parameters studied included screen aperture size and frequency of oscillation. Two screen sizes (3/8 and 1/4 inch apertures) and four different frequencies (1.25, 1.50, 1.75, and 2.00 Hertz) were considered. All other shaker unit parameters were held constant. Statistical analysis revealed that the lowest frequency resulted in the highest screening efficiencies for both the pin chips and fines categories. Screening efficiencies were higher with 3/8 inch screen as opposed to 1/4 inch screen, for all frequencies considered, but at 1.25 Hertz, the screening efficiency of fines was only 6 percent better with 3/8 inch screen. This analysis revealed that the lowest acceleration vectors produced the best screening efficiencies. Velocity and acceleration vectors were directly related to frequency of oscillation since all other parameters were held constant for this study. A Programmer’s Hierarchical Interactive Graphics System (PHIGS) program was developed to graphically simulate the screen motion and to analyze the maximum velocity and acceleration vectors of the upper swing arm (input link). By interactively changing the shaker unit parameters, the screen motion was animated and viewed, with the calculated vectors used in the statistical analysis. / Master of Science

The project begins with the elaboration of a single wooden joinery detail for a temple pavilion. A singular joint study became the basis for an interrelated series of elaborated joints forming a structural whole. A detailed model of a single structural bay was produced. The purpose of this model was to investigate the subtleties of its overall formal expression. Attention was given to both the hidden internal complexity of individual parts and the interconnections between parts. Knowledge of stereotomy was an important consideration ensuring precision in the marking and cutting of the poplar wood. Photographs, sketches and drawings accompany the making of the model as way to further its realization. / Master of Architecture

This project addresses two main subjects of moisture-cure polyurethane (PUR) wood adhesives: wood/PUR interactions and structure-property behavior emphasizing on weather durability. For these purposes, one simplified model PUR (MPUR) and three more commercially significant PURs (CPURs) with different hard segment contents were prepared. Separately, an early side project involved the synthesis of a 13C and 15N double-labeled polymeric methylenebis(phenylisocyanate) (pMDI) resin; this was used for the solid-state NMR characterization of isocyanate cure chemistry in wood bondline. MPUR and a CPUR were employed to investigate whether wood/adhesive interactions influence PUR properties. Wood interactions significantly altered PUR hard/soft domain size distribution (atomic force microscopy, AFM), thermal transition temperatures (dynamic mechanical analyses, DMA), and urethane/urea hydrogen bonds (Fourier transform infrared spectroscopy, FTIR). The effects of hard segment content on properties of PUR prepolymers, and cured PURs (films and wood composites) were studied. Hard segment content largely influenced the PURs’ molecular weights, viscosity, penetration, thermal transitions, and hard segment hydrogen bonds, but only slightly altered the dry (unweathered) bondline toughness. Three accelerated weathering procedures were developed to evaluate CPUR bondline weather durability through mode-I fracture testing. Both hard segment content and weathering conditions were found to significantly influence the bondline weather durability. Among these weathering procedures, only one (VPSS) was able to effectively distinguish weather durability of PUR adhesives, and therefore it was selected for detailed structure-weather durability studies. PUR weather durability was found to correlate with its moisture sensitivity and hard segment softening temperature; both were provided by water-submersion DMA. Much attention was directed to the investigation of weather-induced PUR molecular changes. FTIR studies provided evidences of post-cure, hydrolytic degradation, and variation of urethane/urea hydrogen bonds. DMA presented weathering effects on PUR thermal properties. Special efforts have been made to correlate these analytical results with PUR weather durability. A 13C and 15N double-labeled pMDI resin was synthesized and used for solid-state NMR characterization of isocyanate cure chemistry in wood bondline, particularly to detect the evidence of urethane formation. Rotational echo double resonance (REDOR) NMR clearly revealed the formation of urethane linkages, but largely overestimated their content. / Ph. D.

Rational design of wood pallets requires estimates of average flexural properties of pallet lumber of many species and visual grades. The objective of this study was to develop procedures for estimating these design values for use in a first-order second-moment design format. Preliminary studies were performed to assess the effects of increased loading rates on in-grade flexural data, size effects between deckboard and stringer properties, and the effectiveness of the ASTM strength ratio concept as applied to pallet shook. An increased load rate (ten times the ASTM rate) resulted in an 8.0% increase in average MOR and a 4.7% increase in average MOE. No definite conclusions could be reached concerning the relative strength of deckboards vs. stringers. Several factors, other than a statistical size effect, may influence their relative strength. Estimated strength ratios (ESR) generally underpredicted the experimentally determined actual strength ratios (ASR). As knot size increased, the ESR increasingly underpredicted the ASR. Two approaches were used to values. The best is full-size commercial material. However, derive pallet shook design in-grade testing of only yellow-poplar and eastern oak species have currently been evaluated in this manner. For all other species, a modified procedure based largely on the methods of ASTM D 2555 and D 245 was recommended. This procedure yields conservative estimates of strength for grades allowing large knots. / M.S.

The primary objective of this study was to improve residue chip quality at high production southern pine Sawmills. A general economic analysis suggested that improving sawmill residue chip quality could be beneficial to both pulp and sawmills. Studies were conducted at several sawmills to determine methods of improving residue chip quality. The first study examined the composition of material entering a residue chipper. Trim ends and oversize chips contributed the most pieces, but only 10% of the residue weight. Two-foot trim blocks accounted for the remaining material, 90% by weight. A number of these pieces resulted from slashing entire boards or cutting longer trim lengths into 2-foot pieces to clear them from the mill. Two studies were conducted to examine the possibility of leaving trim in longer lengths to improve piece orientation and stability. Both studies found significant improvements in chip quality, the over-thick chips decreased while the percentage of acceptable chips increased. Chip quality improved with each incremental increase in trim length, but increasing trim length to four feet alone accounted for 50% of the overall improvements. Four-foot trim lengths would generate an additional 4-5 tons of acceptable chips per day for the sawmill. Feed conveyor loading was found to affect chip quality. Highest chip quality was achieved when the feed conveyor was half-full, with two or three pieces entering simultaneously. An overloaded conveyor produced higher percentages of large chips, whereas chipping single pieces increased the percentage of smaller chips. The effect of seasonal temperatures on pin chip and fine production at southern pine and hardwood chip mills was examined as a secondary objective. The pin chip and fine content at the hardwood mills increased as temperatures decreased, but variability in species and inventory obscured the relationship. Southern pine chip mills experienced 4-5% increases in the pin chip and fine content during the winter months. Pin chips and fines increased 1% for every 10°F drop in temperature. / Master of Science

The purpose of this study is to determine the characteristic wood-carving designs of England, France, Italy, Germany, and China. It attempts to present the findings in a form which will be of assistance to both college and public school teachers of wood-carving and to aid in classification of typical types of furniture.

Thesis (PhD (Forest and Wood Science))--Stellenbosch University, 2007. / ENGLISH ABSTRACT: There has been a reported reduction in the durability of creosote treated, wooden utility poles in South Africa in recent years. Several factors could have been responsible for this. In this study, Eucalyptus grandis pole drying schedules currently used, methods of measurement of moisture content (MC) after drying and drying defects were investigated. Relationships involving drying defects and MC gradient before treatment which may help in the development of simple nondestructive methods of assessing defects such as surface checking, honeycomb and collapse, and MC gradient were also explored. The long term goal of this study was to increase the durability of treated poles by avoiding unacceptable drying defects and MC values before treatment. The results of this investigation are presented in the following chapters: an introduction motivating the aims of the investigations (Chapter 1); a review of literature relevant to MC and drying defects in sawn or round wood (Chapter 2); ready for press manuscripts on MC and drying defects in kiln-dried E. grandis poles (Chapters 3 to 7) and a general conclusion that links up chapters 3 to 7, and recommendations (Chapter 8). The auger drill method gave reliable MC values when samples in increments of 25 mm depths into the pole were taken. However, when single samples of 50 mm and 75 mm depths were considered, the auger drill MC measurements were unreliable. It was concluded that SABS SM 983 (2000), which specifies taking single radial auger drill samples of depth 70±5 mm at pole mid length, is not a reliable method of measuring MC in a kiln-dried E. grandis pole. Correlation results indicated that tree growth factors such as sapwood depth, green MC and heartwood percentage were related to final drying defects and may be used as criteria for pole sorting before kiln drying. Also, the number of valleys per unit length (VPUL) of the circumference at the theoretical ground line (TGL) was positively correlated with honeycomb and closed surface checks, implying that VPUL as a parameter of the pole circumference profile can be used to assess invisible, internal defects. The dry bulb temperature (Tdb) of 80oC, used to dry poles in industry, was too high and resulted into unacceptable levels of drying defects in kiln dried E. grandis poles. In addition, the drying period of 8 days was too short to attain an acceptable MC gradient in poles. It is, therefore, recommended that: To use the auger drill method to reliably determine the moisture content of a pole, samples in increments of 25 mm should be taken. MC measurements should be made at the most critical zones of a pole such as the TGL and not higher up since there is normally considerable MC variation in the longitudinal direction. It is also important to consider sampling more than one position on the pole circumference to cater for the MC variation in the tangential direction. For poles with large sapwood depths i.e. >15mm, mild drying conditions at the beginning of a drying run should be used, since such poles may be more susceptible to surface checking. Poles with large heartwood percentages should also be dried with suitable kiln schedules, i.e. with low Tdb to minimise honeycomb and collapse. In general, Tdb lower than 80oC should be considered in order to reduce the defects to acceptable levels. Poles should be dried for longer than 8 days even at Tdb as high as 80oC to reduce the MC to acceptable values and gradients. Since only three schedules were tested, more drying schedules should be investigated to make reliable conclusions about the effect of schedule on drying defects. In addition, more poles per schedule should be considered in order to obtain statistically reliable results. The relationship of pole diameter and drying defects also requires further investigation. Since a limited sample was used to test for the effect of source of poles and drying schedules on defect correlations, further studies should be done on sufficient samples to come up with more reliable conclusions. It is also necessary to further investigate the possible variation in correlation of VPUL and internal defects on a large sample of poles from specific sources and drying schedules. / AFRIKAANSE OPSOMMING: Die afgelope paar jaar is waargeneem dat kreosootbehandelde transmissiepale 'n afname in duursaamheid toon. Verskeie faktore kan hiervoor verantwoordelik wees. In hierdie studie is huidige Eucalyptus grandis oonddrogingskedules en voggehalte- (VG) bepalingsmetodes vóór en na droging asook drogingsdefekte ondersoek. Verwantskappe tussen drogingsdefekte en VG-gradiënt vóór behandeling wat kan meehelp om nie-destruktiewe metodes te ontwikkel om defekte soos oppervlaktekrake, interne barste en instorting en VG-gradiënt te bepaal, is ook bestudeer. Die langtermyn doelwit van hierdie studie is om die duursaamheid van behandelde pale te verbeter deur onaanvaarbare drogingsdefekte en voggehaltes vóór behandeling te vermy. Die resultate van hierdie ondersoek word in die volgende hoofstukke bespreek: 'n inleiding waarin die doelwitte van die onderskeie ondersoeke motiveer word (Hoofstuk 1); 'n oorsig van die literatuur relevant tot VG en drogingsdefekte in gesaagde en rondehout (Hoofstuk 2); persklaar manuskripte oor VG en drogingsdefekte in oondgedroogde E. grandis pale (Hoofstukke 3 tot 7) en 'n algemene gevolgtrekking wat bevindings uit hoofstukke 3 tot 7 saamvat gevolg deur aanbevelings (Hoofstuk 8). Die augerboor-metode kon betroubare VG-waardes lewer indien monsters van 25mm diepteinkremente in die paal geneem is. Augerboor-voggehaltemetings met enkel 50mm en 75mm monsters was egter onbetroubaar. Daar is bevind dat SABS SM 983 (2000), wat 'n enkel radiale augerboormonster tot op 'n diepte van 70±5 mm in die middel van die lengte van die paal spesifiseer, nie 'n betroubare VG-bepalingsmetode vir oondgedroogde E. grandis pale is nie. Die resultate het aangetoon dat boomgroeifaktore soos spinthoutdiepte, groen voggehalte en die persentasie kernhout aan drogingsdefekte verwant is en as basis vir sortering van pale vóór oonddroging gebruik kan word. Ook kon die aantal valleie per eenheidslengte (e. VPUL) van die omtrek by die teoretiese grondlyn (TGL) positief met interne barste en geslote oppervlaktekrake korreleer word wat impliseer dat VPUL as parameter van die omtrekprofiel van die paal gebruik kan word om onsigbare, interne defekte mee vas te stel. Die droëbaltemperatuur (Tdb) van 80oC wat in die industrie gebruik word, was te hoog omdat dit onaanvaarbare vlakke van drogingsdefekte in oondgedroogde E. grandis veroorsaak het. Daarbenewens was die drogingsperiode van 8 dae by 'n Tdb van 80oC te kort om 'n aanvaarbare VG-gradiënt te lewer. Die volgende word derhalwe aanbeveel: Om betroubare VG-resultate d.m.v. die augerboormetode te verkry, behoort monsters in inkremente van 25mm geneem te word. VG-metings behoort in die mees kritiese dele van 'n paal gedoen te word byv. by TGL en nie hoër nie omdat daar normaalweg beduidende VG-variasie in die longitudinale rigting is. Dis ook belangrik om op meer as een posisie op die omtrek te meet om vir die variasie in die tangensiale rigting voorsiening te maak. Ligte drogingstoestande behoort aan die begin van die drogingsproses by pale met groot spinthoutdieptes, bv. > 15mm, gebruik te word omdat sulke pale meer geneigd tot oppervlaktekrake is. Pale met hoë kernhoutpersentasies moet ook met geskikte drogingskedules, bv. met lae Tdb, gedroog word om interne barste en ineenstorting te verminder. Oor die algemeen behoort Tdb laer as 80oC oorweeg te word om die omvang van defekte by aanvaarbare vlakke te hou. Selfs by Tdb so hoog as 80oC behoort pale langer as 8 dae te droog om die VG tot by aanvaarbare waardes en 'n gradiënt te bring. Omdat slegs drie skedules evalueer is, behoort meer skedules ondersoek word om betroubare gevolgtrekkings oor die effek van skedule op drogingsdefekte te verskaf. Addisioneel behoort meer pale per skedule oorweeg word om statisties betroubare resultate te verkry. Die verwantskap tussen paaldeursnee en drogingsdefekte benodig ook verdere ondersoek. Aangesien 'n beperkte aantal pale gebruik is om die herkoms en drogingskedule met defekte te korreleer, behoort verdere studie op genoeg pale gedoen te word om meer betroubare gevolgtrekkings te kry. Dit is ook noodsaaklik om die moontlike variasie in die korrelasie tussen VPUL en interne defekte op 'n groot aantal pale van spesifieke herkoms en drogingskedules vas te stel.