bluuebunny/crossref_metadata_2025 huggingface dataset:
Atomic-Level Models of the Bacterial Carboxysome Shell
Authors: Tanaka Shiho , Kerfeld Cheryl A. , Sawaya Michael R. , Cai Fei , Heinhorst Sabine , Cannon Gordon C. , Yeates Todd O.
Published: February 2008

The carboxysome is a bacterial microcompartment that functions as a simple organelle by sequestering enzymes involved in carbon fixation. The carboxysome shell is roughly 800 to 1400 angstroms in diameter and is assembled from several thousand protein subunits. Previous studies have revealed the three-dimensional structures of hexameric carboxysome shell proteins, which self-assemble into molecular layers that most likely constitute the facets of the polyhedral shell. Here, we report the three-dimensional structures of two proteins of previously unknown function, CcmL and OrfA (or CsoS4A), from the two known classes of carboxysomes, at resolutions of 2.4 and 2.15 angstroms. Both proteins assemble to form pentameric structures whose size and shape are compatible with formation of vertices in an icosahedral shell. Combining these pentamers with the hexamers previously elucidated gives two plausible, preliminary atomic models for the carboxysome shell.
Finding Freedom Through Complexity
Authors: Ganson Todd Stuart
Published: February 2008

Did My Neurons Make Me Do It?
. Philosophical and Neurobiological Perspectives on Moral Responsibility and Free Will.
By Nancey Murphy and Warren S. Brown
. Oxford University Press, Oxford, 2007. 352 pp. $65, £40. ISBN 9780199215393.

Murphy and Brown present a case for a "nonreductive version of physicalism whereby humans are (sometimes) the authors of their own thoughts and actions."
Role of Protein Tyrosine Kinase and Erk1/2 Activities in the Toll-Like Receptor 2-Induced Cellular Activation of Murine B Cells by Neisserial Porin
Authors: MacLeod Heather , Bhasin Navneet , Wetzler Lee M.
Published: February 2008

Neisserial porins are potent immune adjuvants and have been demonstrated to stimulate and induce the activation of human and murine B lymphocytes. Their immunopotentiating ability is due largely to the upregulation of the surface expression of the costimulatory ligand CD86 (B7-2) on B cells and other antigen-presenting cells. Porin-induced activation is dependent on the innate immune pattern recognition receptor Toll-like receptor 2 (TLR2). These data have led us to investigate the signal transduction events induced by PorB fromNeisseria meningitidisand then, using inhibitors of these pathways, to establish the mechanism by which this bacterial major outer membrane protein induces CD86 upregulation and the proliferation of murine B cells. PorB was able to induce (i) protein tyrosine kinase (PTK) activity, (ii) the phosphorylation of Erk1 and Erk2, and (iii) IκB-α phosphorylation, leading to NF-κB nuclear translocation in B cells in a TLR2-dependent manner. PorB-induced NF-κB nuclear translocation was not dependent on either PTK or Erk1/2 activities. However, B-cell proliferation and the induction of increased surface expression of CD86 by PorB were dependent on PTK activity and not Erk1/2 activation. In conclusion, PorB acts through TLR2 as a B-cell mitogen, triggering tyrosine phosphorylation of various cellular proteins that are involved in proliferation and CD86 expression, as well as the phosphorylation of Erk1/2, which is not necessary for CD86 upregulation or the proliferation of B cells.
Performance of the Cobas AmpliPrep/Cobas TaqMan Real-Time PCR Assay for Hepatitis B Virus DNA Quantification
Authors: Chevaliez Stéphane , Bouvier-Alias Magali , Laperche Syria , Pawlotsky Jean-Michel
Published: February 2008

Hepatitis B virus (HBV) DNA quantification is used to establish the prognosis of chronic HBV-related liver disease, to identify those patients who need to be treated, and to monitor the virologic response and resistance to antiviral therapies. Real-time PCR-based assays are gradually replacing other technologies for routine quantification of HBV DNA in clinical practice. The goal of this study was to evaluate the intrinsic characteristics and clinical performance of the real-time PCR Cobas AmpliPrep/Cobas TaqMan (CAP/CTM) platform for HBV DNA quantification. Specificity was satisfactory (95% confidence interval, 98.1 to 100%). Intra-assay coefficients of variation ranged from 0.22% to 2.68%, and interassay coefficients of variation ranged from 1.31% to 4.13%. Quantification was linear over the full dynamic range of quantification of the assay (1.7 to 8.0 log
10
IU/ml) and was not affected by dilution. The assay was accurate regardless of the HBV genotype. Samples containing HBV DNA levels above 4.5 log
10
IU/ml were slightly underestimated relative to another accurate assay based on branched-DNA technology, but this is unlikely to have noteworthy clinical implications. Thus, the CAP/CTM HBV DNA assay is sensitive, specific, and reproducible, and it accurately quantifies HBV DNA levels in patients chronically infected by HBV genotypes A to F. Samples with HBV DNA concentrations above the upper limit of quantification need to be diluted and then retested. Broad use of fully automated real-time PCR assays should improve the management of patients with chronic HBV infection.
Relationship between
Mycobacterium tuberculosis
Genotype and the Clinical Phenotype of Pulmonary and Meningeal Tuberculosis
Authors: Thwaites Guy , Caws Maxine , Chau Tran Thi Hong , D'Sa Anthony , Lan Nguyen Thi Ngoc , Huyen Mai Nguyet Thu , Gagneux Sebastien , Anh Phan Thi Hoang , Tho Dau Quang , Torok Estee , Nhu Nguyen Thi Quynh , Duyen Nguyen Thi Hong , Duy Phan Minh , Richenberg Jonathan , Simmons Cameron , Hien Tran Tinh , Farrar Jeremy
Published: February 2008

We used large sequence polymorphisms to determine the genotypes of 397 isolates of
Mycobacterium tuberculosis
from human immunodeficiency virus-uninfected Vietnamese adults with pulmonary (
n
= 235) or meningeal (
n
= 162) tuberculosis. We compared the pretreatment radiographic appearances of pulmonary tuberculosis and the presentation, response to treatment, and outcome of tuberculous meningitis between the genotypes. Multivariate analysis identified variables independently associated with genotype and outcome. A higher proportion of adults with pulmonary tuberculosis caused by the Euro-American genotype had consolidation on chest X-ray than was the case with disease caused by other genotypes (
P
= 0.006). Multivariate analysis revealed that meningitis caused by the East Asian/Beijing genotype was independently associated with a shorter duration of illness before presentation and fewer cerebrospinal fluid (CSF) leukocytes. Older age, fewer CSF leukocytes, and the presence of hemiplegia (but not strain lineage) were independently associated with death or severe disability, although the East Asian/Beijing genotype was strongly associated with drug-resistant tuberculosis. The genotype of
M. tuberculosis
influenced the presenting features of pulmonary and meningeal tuberculosis. The association between the East Asian/Beijing lineage and disease progression and CSF leukocyte count suggests the lineage may alter the presentation of meningitis by influencing the intracerebral inflammatory response. In addition, increased drug resistance among bacteria of the East Asian/Beijing lineage might influence the response to treatment. This study suggests the genetic diversity of
M. tuberculosis
has important clinical consequences.
NF-κB-Mediated Activation of the Chemokine CCL22 by the Product of the Human Cytomegalovirus Gene UL144 Escapes Regulation by Viral IE86
Authors: Poole Emma , Atkins Elizabeth , Nakayama Takashi , Yoshie Osamu , Groves Ian , Alcami Antonio , Sinclair John
Published: February 2008

The product of the human cytomegalovirus (HCMV) gene UL144, expressed at early times postinfection, is located in the UL/b′ region of the viral genome and is related to members of the tumor necrosis factor receptor superfamily, but it does not bind tumor necrosis factor superfamily ligands. However, UL144 does activate NF-κB, resulting in NF-κB-mediated activation of the cellular chemokine CCL22. Consistent with this finding, isolates of HCMV lacking the UL/b′ region show no such activation of CCL22. Recently, it has been suggested that activation of NF-κB is repressed by the product of the viral gene IE86: IE86 appears to block NF-κB binding to DNA but not nuclear translocation of NF-κB. Intriguingly, IE86 is detectable throughout an infection with the virus, so how UL144 is able to activate NF-κB in the presence of continued IE86 expression is unclear. Here we show that although IE86 does repress the UL144-mediated activation of a synthetic NF-κB promoter, it is unable to block UL144-mediated activation of the CCL22 promoter, and this lack of responsiveness to IE86 appears to be regulated by binding of the CREB transcription factor.
Cytokine Responses in Porcine Respiratory Coronavirus-Infected Pigs Treated with Corticosteroids as a Model for Severe Acute Respiratory Syndrome
Authors: Zhang Xinsheng , Alekseev Konstantin , Jung Kwonil , Vlasova Anastasia , Hadya Nagesh , Saif Linda J.
Published: February 2008

The effectiveness and potential immunosuppressive effects of anti-inflammatory glucocorticoids in the lungs of severe acute respiratory syndrome (SARS) patients are undefined. We treated porcine respiratory coronavirus (PRCV)-infected conventional pigs with the corticosteroid dexamethasone (DEX) as a model for SARS. Innate and Th1 cytokines in bronchoalveolar lavage (BAL) and serum were elevated in PRCV-infected pigs compared to controls, but were decreased after DEX treatment in the PRCV-infected, DEX-treated (PRCV/DEX) pigs. Although decreased in BAL, Th2 cytokine levels were higher in serum after DEX treatment. Levels of the proinflammatory cytokine interleukin-6 in BAL and serum were decreased in PRCV/DEX pigs early but increased later compared to those in phosphate-buffered saline-treated, PRCV-infected pigs, corresponding to a similar trend for lung lesions. PRCV infection increased T-cell frequencies in BAL, but DEX treatment of PRCV-infected pigs reduced frequencies of T cells; interestingly B and SWC3a+(monocytes/macrophages/granulocytes) cell frequencies were increased. DEX reduced numbers of PRCV-stimulated Th1 gamma interferon-secreting cells in spleen, tracheobroncheolar lymph nodes, and blood. Our findings suggest that future glucocorticoid treatment of SARS patients should be reconsidered in the context of potential local immunosuppression of immune responses in lung and systemic Th1 cytokine-biased suppression.
Calibration of Multiple Poliovirus Molecular Clocks Covering an Extended Evolutionary Range
Authors: Jorba Jaume , Campagnoli Ray , De Lina , Kew Olen
Published: February 2008

We have calibrated five different molecular clocks for circulating poliovirus based upon the rates of fixation of total substitutions (Kt), synonymous substitutions (Ks), synonymous transitions (As), synonymous transversions (Bs), and nonsynonymous substitutions (Ka) into the P1/capsid region (2,643 nucleotides). Rates were determined over a 10-year period by analysis of sequences of 31 wild poliovirus type 1 isolates representing a well-defined phylogeny derived from a common imported ancestor. Similar rates were obtained by linear regression, the maximum likelihood/single-rate dated-tip method, and Bayesian inference. The very rapidKt[(1.03 ± 0.10) × 10−2substitutions/site/year] andKs[(1.00 ± 0.08) × 10−2] clocks were driven primarily by theAsclock [(0.96 ± 0.09) × 10−2], theBsclock was ∼10-fold slower [(0.10 ± 0.03) × 10−2], and the more stochasticKaclock was ∼30-fold slower [(0.03 ± 0.01) × 10−2]. Nonsynonymous substitutions at all P1/capsid sites, including the neutralizing antigenic sites, appeared to be constrained by purifying selection. Simulation of the evolution of third-codon positions suggested that saturation of synonymous transitions would be evident at 10 years and complete at ∼65 years of independent transmission. Saturation of synonymous transversions was predicted to be minimal at 20 years and incomplete at 100 years. The rapid evolution of theKt,Ks, andAsclocks can be used to estimate the dates of divergence of closely related viruses, whereas the slowerBsandKaclocks may be used to explore deeper evolutionary relationships within and across poliovirus genotypes.
Cell Surface Expression of the Vaccinia Virus Complement Control Protein Is Mediated by Interaction with the Viral A56 Protein and Protects Infected Cells from Complement Attack
Authors: Girgis Natasha M. , DeHaven Brian C. , Fan Xin , Viner Kendra M. , Shamim Mohammad , Isaacs Stuart N.
Published: February 2008

The vaccinia virus (VACV) complement control protein (VCP) is the major protein secreted from VACV-infected cells. It has been reported that VCP binds to the surfaces of uninfected cells by interacting with heparan sulfate proteoglycans (HSPGs). In this study, we show that VCP is also expressed on the surfaces of infected cells and demonstrate that surface localization occurs independently of HSPGs. Since VCP does not contain a transmembrane domain, we hypothesized that VCP interacts with a membrane protein that localizes to the infected-cell surface. We show that the VACV A56 membrane protein is necessary for the cell surface expression of VCP and demonstrate that VCP and A56 interact in VACV-infected cells. Since the surface expression of VCP was abrogated by reducing agents, we examined the contribution of an unpaired cysteine residue on VCP to VCP surface expression and VCP's interaction with A56. To do this, we mutated the unpaired cysteine in VCP and generated a recombinant virus expressing the altered form of VCP. Following the infection of cells with the mutant virus, VCP was neither expressed on the cell surface nor able to interact with A56. Importantly, the cell surface expression of VCP was found to protect infected cells from complement-mediated lysis. Our findings suggest a new function for VCP that may be important for poxvirus pathogenesis and impact immune responses to VACV-based vaccines.
Deletion of Epstein-Barr Virus BFLF2 Leads to Impaired Viral DNA Packaging and Primary Egress as Well as to the Production of Defective Viral Particles
Authors: Granato Marisa , Feederle Regina , Farina Antonella , Gonnella Roberta , Santarelli Roberta , Hub Birgit , Faggioni Alberto , Delecluse Henri-Jacques
Published: February 2008

Previous genetic and biochemical studies performed with several members of the
Alphaherpesvirus
subfamily have shown that the UL31 and UL34 proteins are essential components of the molecular machinery that mediates the primary egress of newly assembled capsids across the nuclear membrane. Further, there is substantial evidence that BFLF2 and BFRF1, the respective positional homologs of UL31 and UL34 in the Epstein-Barr virus (EBV) genome, are also their functional homologs, i.e., that the UL31/UL34 pathway is common to distant herpesviruses. However, the low degree of protein sequence identity between UL31 and BFLF2 would argue against such a hypothesis. To further clarify this issue, we have constructed a recombinant EBV strain devoid of BFLF2 (ΔBFLF2) and show that BFLF2 is crucial for efficient virus production but not for lytic DNA replication or B-cell transformation. This defective phenotype could be efficiently restored by
trans
complementation with a BFLF2 expression plasmid. Detailed analysis of replicating cells by electron microscopy revealed that, as expected, ΔBFLF2 viruses not only failed to egress from the nucleus but also showed defective DNA packaging. Nonfunctional primary egress did not, however, impair the production and extracellular release of enveloped but empty viral particles that comprised L particles containing tegument-like structures and a few virus-like particles carrying empty capsids. The ΔBFLF2 and ΔUL31 phenotypes therefore only partly overlap, from which we infer that BFLF2 and UL31 have substantially diverged during evolution to fulfil related but distinct functions.
Primer Binding Site-Dependent Restriction of Murine Leukemia Virus Requires HP1 Binding by TRIM28
Authors: Wolf Daniel , Cammas Florence , Losson Régine , Goff Stephen P.
Published: February 2008

TRIM28 is a transcriptional corepressor which is required for primer binding site (PBS)-dependent restriction of murine leukemia virus (MLV) replication in embryonic stem and embryonic carcinoma (EC) cells. PBS-dependent restriction of MLV leads to transcriptional silencing of the integrated provirus and has been shown to correlate with TRIM28-mediated recruitment of HP1 to the silenced loci. Here we show, using a cell line with a point mutation in the HP1 binding domain of TRIM28, that interaction with HP1 is absolutely required for the PBS-dependent restriction of MLV in the F9 EC cell line.
Spectrofluorimetric Study on Inclusion Complexation of 2-Amino-6-fluorobenzothiazole with β-Cyclodextrin
Authors: Rajamohan Rajaram , Kothai Nayaki Sundarajulu , Swaminathan Meenakshisundaram
Published: February 2008

The interaction between 2-amino-6-fluorobenzothiazole (AFBT) and β-cyclodextrin (β-CDx) has been investigated in aqueous solution and in the solid state. The stoichiometry and binding constant of the complex between AFBT and β-CDx in solution were determined by steady-state and time-resolved fluorescence spectroscopy. The FT-IR spectral data and SEM images of the solid complex confirmed the formation of inclusion complex. The proton transfer behaviour of AFBT has been investigated in aqueous and β-CDx solutions.
Contribution à l'étude du Bayoud, fosariose du palmier-dattier. I. Étude du cultivar sensible Deglet-Nour
Authors: Mathéron Béatrice , Benbadis Abdellatif
Published: February 2008

Date palm seedlings were inoculated at the two-leaf stage with Fusarium oxysporum f. sp. albedinis, the causal agent of Bayoud. Following spore germination, hyphae bore a bole through the walls of the root epidermis and penetrated into the cortical parenchyma. The fungus then grows inter- or intra-cellularly towards the central cylinder and enters the xylem vessels. There, it continues to grow towards the leaves. The progression from vessel to vessel is achieved through bordered pits. The cultivar Deglet-Nour, known for its susceptibility to this wilt disease, exhibited no early reaction to the presence of the parasite in its tissues. Key words: date palm, Fusarium oxysporum f. sp. albedinis, scanning electron microscopy.
A taxonomic simplification of Medicago italica
Authors: Small Ernest , Brookes Brenda
Published: February 2008

Various taxonomies have been proposed by previous students of Medicago italica (Miller) Fiori, considered by some to be the most polymorphic species of the large genus Medicago. However, this study ascribes most of the polymorphism to introgression from another species, and accordingly proposes a simple taxonomy based on this interpretation. Hybridization with the allied species M. littoralis Rohde ex Lois.-Deslong. is extensive, and because the latter is far more abundant, the predominant result is introgression of M. littoralis characteristics into M. italica. A numerical taxonomic analysis was conducted on 158 collections supplied as Medicago italica, grown under standard conditions, and 42 collections of M. littoralis grown under comparable conditions. Israeli M. italica are the most geographically isolated plants of the natural range of this species; these proved to be morphologically separable from the remaining plants. Little introgression seems to have occurred into the Israeli plants studied, compared with more pronounced introgression into a majority of the remaining plants of M. italica examined. Variation is continuous between apparently "pure" plants of M. italica, such as the Israeli plants studied, and apparently strongly introgressed plants, some of whose character states approach those of M. littoralis. As a result of procedures adopted, the spectrum of variants initially identified as M. italica was split into two: the group that included the Israeli plants was identified as M. italica, and the group tending towards M. littoralis was identified as M. italica × M. littoralis. As defined here, M. italica is most easily discriminated from M. italica × M. littoralis by having less than 3.5 coils in the coiled fruit, whereas the latter has more than 3.5.
Differential tolerances among soft-water macrophyte species to acidification
Authors: Arts G. H. P. , Roelofs J. G. M. , Lyon M. J. H. De
Published: February 2008

Twenty-six macrophyte species were studied for their degree of tolerance to extremely acid conditions. They are characteristic of soft water on sandy soils in The Netherlands. These species were divided into two groups based on their recent distribution by pH and alkalinity. The first group consists of the species that can (at least temporarily) survive under extremely acid conditions (pH < 5); the second group contains species that are limited by a distinct minimum pH of the water (pH 5–6). This sharp distinction between groups on.the basis of pH can be used for reconstruction of the development of acidification in waters using historical data on the macrophytes involved. The two groups of species can be used to discriminate between two types of soft water in The Netherlands. Key words: soft-water macrophytes, ecological groups of macrophytes, autecology, acidification, indicator species.
Morphological, electrophoretic, and ecological analysis of Quercus macrocarpa populations in the Black Hills of South Dakota and Wyoming
Authors: Chechowitz Naomi , Chappell Dorothy M. , Guttman Sheldon I. , Weigt Lee A.
Published: February 2008

Morphological data support the hypothesis that oak populations in the Black Hills of South Dakota and Wyoming reflect the effect of introgressive hybridization between Quercus macrocarpa and Q. gambelii; these populations cannot be electro-phoretically differentiated from Q. macrocarpa. Thirteen populations of oaks were sampled in the Black Hills of South Dakota and Wyoming, and a single population each of Q. macrocarpa and Q. gambelii were sampled outside of the Black Hills. Morphological data suggest significant similarities of populations located in northwestern Black Hills with Q. gambelii and populations located in the eastern Black Hills with Q. macrocarpa. Disparity between morphological and electrophoretic data suggests that natural selection is operating differently on the morphological and isozymic characters.
Predicting long-term patterns of mass loss, nitrogen dynamics, and soil organic matter formation from initial fine litter chemistry in temperate forest ecosystems
Authors: Aber John D. , Melillo Jerry M. , McClaugherty Charles A.
Published: February 2008

Long-term decomposition data are presented for several types of foliar and fine root litter in different stands in Wisconsin and Massachusetts, U.S.A. Changes in mass remaining as well as nitrogen and carbon fraction (extractives, cellulose, lignin) concentration are reported. Three models were developed for describing change in mass remaining with time: a litter-specific exponential decay function (statistical fit of data for each litter type), a generalized exponential decay function (k predicted from initial litter chemistry), and a carbon fraction model that calculates the weight loss of each carbon fraction individually as a function of current carbon chemistry regardless of litter type. The exponential decay function fits all litter data well for the portion of decomposition described here, but would not be appropriate for modeling longer term decomposition. Both the generalized and carbon fraction models predicted weight loss accurately. All litter types had similar carbon fraction chemistries at the end of the first phase of decomposition described here and also exhibited a narrow range of changes in nitrogen concentration per unit weight loss. It is concluded that the length of time required to convert litter into soil organic matter and the chemistry of the material produced by this process can be predicted from initial litter chemistry and (or) relatively short-term litter decay data. Key words: immobilization, mineralization, humus, lignin, cellulose, extractives.
Mean characteristics of asymmetric flows: application to flow below ice jams
Authors: Gogus Mustafa , Tatinclaux Jean-Claude
Published: February 2008

Results are presented of a laboratory study on the effect of the introduction of a floating cover at the surface of a channel on the mean flow velocity distribution in the then “closed conduit” flow, and on the bed friction factor. It is pointed out that, contrary to common assumption, the location of the maximum velocity is not a point of zero shear stress when the bed and the cover have different roughness characteristics. Semi-empirical and graphical relationships between bed and cover friction factors, relative location of maximum velocity, and bed and cover roughness sizes are presented which are sufficient to estimate the mean flow characteristics below the cover for a given flow discharge and flow depth below the cover. The results may be of importance in the calculation of the characteristics of river ice jams in their initial stage of formation when their roughness is significantly greater than that of the river bed.
Optimization of laterally unsupported unstiffened steel I-beams
Authors: Azad Abul Kalam
Published: February 2008

A procedure to find the optimum proportioning of laterally unsupported homogeneous I-beams following the limit state design method of CSA S16.1-1974 specification is presented. Both bending moment and shear force is considered in the optimization procedure. The web is unstiffened and the proportioning is restricted to Class 1, 2, and 3 type sections. Some design charts covering a large range of values of unsupported lengths of compression flange and design moments are provided.
Reliability indices for road geometric design
Authors: Navin Francis P. D.
Published: February 2008

Highway engineers, when asked to state the safety of a particular design, are usually at a loss to give a single meaningful measure as is possible in structural or geotechnical engineering. This paper outlines a method to estimate the margin of safety and reliability index for isolated highway components. The stopping sight distance is used to demonstrate the method. The method uses the basic highway design equations. On the assumption that the variables are random, the expected value of the mean and the variance are estimated; and from these the margin of safety and the reliability index are calculated. The most likely combination of variables for the existing design condition may also be estimated. The variables included represent the characteristics of the driver, the vehicle, and the road surface.A method is proposed to specify the design parameter's value representing a road's strategic importance, the users, the vehicles, the drivers, the environment, the terrain, and the standard of design and construction. The apparent advantage of the proposed reliability-based method is that the designer must explicitly specify the importance of the modifying factors and may also more closely investigate the behaviour of the variables in the design parameters in the critical region near noncompliance. Key words: limit states design, stopping sight distance, safety, highway design, reliability.
Rationalizing spacing requirements for nailed wood connections by induced wood splitting
Authors: Lau Peter W. C.
Published: February 2008

Nails of five different types and sizes were driven through test specimens cut from 35 × 85 mm Douglas-fir and eastern spruce (spruce-pine-fir) dimension lumber, preconditioned to 12% moisture content. Each specimen received either a single nail or two identical nails, spaced at 10 times the nail diameter for common and spiral nails, or at 25 mm for glulam rivets. Nail-induced crack size was evaluated using digital imaging techniques. These crack data were analysed together with the data on single-nail specimens obtained in a parallel study. This permitted the development of a model predicting mean crack length on the basis of spacing between nails. This model was used to generate the spacing requirements based on a criterion on critical stress for fracture, and on crack length. Key words: nailing, wood connections, cracking, nail spacing.
Développement et usage d'un système expert pour le choix des évacuateurs de crues
Authors: Robert Benoît , Taleb Mohamed , Marche Claude
Published: February 2008

Expert systems are computer tools allowing the management of nonnumerical, qualitative knowledge. In that way, they depart from the numerical tools used for solving complex equation systems in computer assisted design. The integration of both types of tools is therefore desirable. Typically, the design of spillways involves long and tedious calculations, dependant on the type and nature of the structure. An expert system was developed to assist the design engineer in the initial and crucial task of choosing the baseline conditions. This expert system is based solely on technical criterion and integrates the knowledge of several experts in the field. A management tool for this multiple-source knowledge was therefore developed and integrated to the many design criterions. The system, currently being developed and implemented in an industry, was tested against approximately 40 worldwide existing structures. The responses, very promising, are presented with the system structure and its technical content. Key words: expert system, design, spillway, hydraulics.
Probability analysis of historical ice jam flood data for a complex reach: a case study
Authors: Stanley S. J. , Gerard R.
Published: February 2008

Two obstacles are encountered in the probability analysis of ice jam floods: the first is the general lack of long-term hydrometric records in cold regions; the second, which compounds the first, is that the few records that are available for ice jam floods are difficult to transpose to even nearby sites. This means there must be heavy reliance placed on local historical data.A good illustration of the effort required and the rewards obtained in collecting and analyzing such data is provided by the situation at Hay River, N.W.T. The flood population at this site is completely dominated by ice jam floods for which there is no standard hydrometric data.This paper describes the approach used in the collection and analysis of the historical data at this site to define the flood probability distribution. A comparison of the resulting probability distribution with the previously designated flood zone, which was defined simply on the basis of the historical high water level, reveals the risk involved in designation based on the latter approach and demonstrates that even in the complex and apparently data-limited situation at Hay River, the systematic collection, collation, and probability analysis of historical data is well worthwhile. Key words: ice jams, historical flood analysis, probability analysis, hydrology, river floods, river ice.
Decrease of CO2 exchange in Scots pine after naturally occurring or artificial low temperatures
Authors: Pelkonen Paavo , Hari Pertti , Luukkanen Olavi
Published: February 2008

A decrease in the net photosynthetic rate was recorded using an infrared gas analyzer after subjecting pine seedlings to naturally occurring or artificial low temperature pulses in field and laboratory experiments. Mathematical models were developed to quantify the depression in CO2 exchange observed when autumn measurements taken in the field were analyzed. A model which included a mathematically determined additional parameter gave values more closely correlated with CO2 exchange at the end of the measuring period better than one which included only temperature and light as independent variables. This modelling approach was similar to one used earlier to quantify the effect of water stress on photosynthesis. The same kind of effect was found in a laboratory experiment after artificial low temperatures, as shown in this paper.
The whole-bole system: a conditioned dual-equation system for precise prediction of tree profiles
Authors: Demaerschalk J. P. , Kozak A.
Published: February 2008

A review is presented of the shortcomings of most existing taper equations which predict diameter along the stem as a function of tree height and diameter at breast height. A new computerized system is developed that has many desirable features for tree profile prediction. This new system consists of two mathematical functions, one describing the upper bole and the other describing the lower bole. The two functions are linked together at the inflection point and are continuous at that point. Tests of this model on 32 species age and locality groupings of British Columbia species show that although there is still a slight bias near ground level, the prediction of diameter inside bark is almost perfect over most of the length of the trees.
A new technique for measuring oscillatory and diurnal changes in leaf thickness
Authors: Tyree M. T. , Cameron S. I.
Published: February 2008

A new technique is described for measuring oscillatory and diurnal changes in leaf thickness. Mature leaves of Populusdeltoides × nigra undergo diurnal or oscillatory changes in thickness of up to 20 μm in amplitude; thickness changes were measured to ±0.2 μm and appear to correlate with expected levels of leaf water stress.
Income and price elasticities of demand for sawn wood and wood-based panels: a pooled cross-section and time-series analysis
Authors: Buongiorno Joseph
Published: February 2008

Income and price elasticities of demand for coniferous and nonconiferous sawn wood, plywood, particle board, and fibreboard were estimated using yearly data from 43 countries, over the period 1963–1973. A static and a dynamic model were estimated by analysis of covariance and generalized least squares. The simpler technique, analysis of covariance, gave satisfactory estimates for both models. Demand for all products was found to be price inelastic, with long-term elasticities ranging from −0.1 for particle board to −0.2 for coniferous sawn wood. Price elasticities for plywood and nonconiferous sawn wood were not significantly different from zero but this result might only reflect price-data inadequacies. Long-term income elasticities were +0.7 and +0.5 for coniferous and nonconiferous sawn wood, respectively. Demand for all wood-based panels was income elastic, with long-term elasticities of +1.0 for plywood and fibreboard, and of +2.3 for particle board. The results indicated that in discussing elasticities of demand for forest products, the length of the time period should be specified. Full adjustment of demand to changing prices and income was shown to always take more than 1 year. Demand for fibreboard appeared to adjust most rapidly to changes in economic conditions; the demand for nonconiferous sawnwood adjusted most slowly.
Temperature and time affect the release and quality of seed from cones of lodgepole pine from Alberta
Authors: Hellum A. K. , Pelchat M.
Published: February 2008

The purpose of this study was to determine how optimum seed release, with minimum resultant loss of seed viability, could be obtained in nursery extraction of lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) seed from Alberta. Temperatures between 60.0 and 82.2 °C were used and cones were kept in kilns for 4, 6, and 8 h. The cones were soaked in 50 °C water for 5 min before being placed in the kilns. As the temperatures were raised from 60.0 to 82.2 °C, seed release from cones increased from 20% to full seed release. Full seed release was defined as maximum seed yield under the given test conditions, realizing that a small but undetermined amount of seed was not released. Average germination dropped from about 85 to less than 40% over this same temperature range. The best average seed release and average germination, called seed value, approached 80% when cones were exposed to 69 °C for 8 h in the kiln. It is suggested that temperatures slightly lower than 69 °C be used and that kiln times be increased to about 12 h. This might yield seed values approaching 90%.
Effects of plant water stress on photosynthesis and survival of four conifers
Authors: Brix H.
Published: February 2008

Seedlings of four coniferous species, Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), western hemlock (Tsugaheterophylla (Raf.) Sarg.), white spruce (Piceaglauca (Moench) Voss), and lodgepole pine (Pinuscontorta Dougl.), were grown for 4 months from germination and then exposed to soil drying. Rates of photosynthesis were measured for all species and rates of dark respiration and transpiration were measured for Douglas-fir and hemlock. In a study of survival, seedlings were exposed to various durations of soil drying and the plant water potential was determined before the plants were rewatered; seedling survival was subsequently recorded.Rates of photosynthesis declined for Douglas-fir, hemlock, spruce, and pine when the plant water potential decreased from −10.0, −10.7, −12.4, and −6.6 bars (1 bar = 100 kPa), respectively, and became zero with potentials of −53.9, −39.7, −28.6, and −22.4 bars. When grown together in the same pot and exposed to soil drought, hemlock had a consistently lower potential than Douglas-fir, and spruce had a lower potential than pine. Hemlock could survive potentials of −40 to −60 bars, whereas seedlings of the other species survived potentials to −110 bars.
Vesicular–arbuscular mycorrhiza influence growth but not mineral concentrations in seedlings of eight sweetgum families
Authors: Schultz R. C. , Kormanik P. P. , Bryan W. C. , Brister G. H.
Published: February 2008

Seedlings of eight half-sib sweetgum (Liquidambarstyraciflua L.) families were grown for 6 months in a fumigated soil mixture, with or without inoculum from a mixture of Glomusmosseae and Glomusetunicatus fungi, at levels of 140, 280, 560, and 1120 kg/ha of 10–10–10 fertilizer. All seedlings received three additions of 187 kg/ha of N during the growing season. Inoculated seedlings had significantly greater biomass, height, and stem diameters at each fertilizer level than nonmycorrhizal control seedlings. Significant differences in growth occurred between families in mycorrhizal plants. However, fertilizer did not significantly affect growth or nutrient uptake of the seedlings. Inoculation with VA mycorrhizal fungi did not increase N, P, K, or Mg concentrations in the leaves, stems, or roots. Leaves of VA mycorrhizal seedlings had higher concentrations of calcium but stems and roots had lower concentrations of this element than the nonmycorrhizal seedlings. Seedlings with endomycorrhizae contained higher absolute quantities of each nutrient simply because of their greater biomass. The results suggest that the role of VA mycorrhizal fungi in the initial growth of sweetgum seedlings may be the result of physiological stimuli other than increased nutrient uptake.
The effect of genotype on biomass and nutrient content in 11-year-old loblolly pine plantations
Authors: Pope P. E.
Published: February 2008

Dry weights and nutrient contents of all aboveground biomass components were estimated for four seed sources of 11-year-old loblolly pine (Pinustaeda L.) grown in plantations of the same spacing on an old-field site of high quality in the hilly region of north-central Arkansas, U.S.A. Soil nutrient content was estimated to a depth of 0.61 m. Stand data averaged over all seeds sources are in agreement with published reports for dry weight and nutrient accumulation for loblolly pine if differences associated with seasonal variation are considered. Seed source significantly affected total dry matter and nutrient accumulations. Estimated total aboveground mean annual accumulation of biomass for the four seed sources ranged from 5.99 × 103 to 11.17 × 103 kg/ha per year. Elemental accumulation (kilograms per hectare per year) ranged from 14.06 to 23.66 for N, 1.54 to 3.45 for P, and 6.96 to 18.43 for K. On the average, trees comprise 84% of the aboveground plant biomass and contain 76% of the N, 77% of the P, and 90%, of the K associated with plant tissue. The significant influence of seed source on these stand values can affect the potential impact of short rotation, total tree harvesting on long-term site productivity. The elemental content of the tree biomass ranged from 7 to 11% of the total N, 20 to 35% of the P, and 14 to 30% of the K in the soil–litter–plant system.
Fungal and arboreal biomass in a western Oregon Douglas-fir ecosystem: distribution patterns and turnover
Authors: Fogel Robert , Hunt Gary
Published: February 2008

The allocation of biomass and the turnover time of various components were measured from August 1976 to August 1977 in a young, second-growth Douglas-fir stand in the Oregon Coast Range. Allocation of biomass among the tree components was 14 732 kg foliage ha−1, 30 455 kg branches ha−1, 212 941 kg boles ha−1, 49 289 kg nonmycorrhizal roots ha−1, and 15 015 kg host portion of mycorrhizae ha−1. Biomass allocation of fungal components was 10 009 kg mycorrhizal mantles ha−1, 2785 kg Cenococcumgeophilum sclerotia ha−1, 65 kg sporocarps ha−1, 369 kg litter hyphae ha−1, and 6666 kg soil hyphae ha−1. The forest floor was composed of 6970 kg fine (<2 mm) litter ha−1, 6564 kg coarse (2–25 mm) litter ha−1, and 5500 kg log (>25 mm) litter ha−1. Soil organic matter (<0.494 mm) was 87 600 kg ha−1. Total annual stand throughput was 30 324 kg ha−1, excluding soil organic matter throughput. Of this total, 50.5% was accounted for by fungal throughput, 39.5% by tree throughput, and 10.0% by forest floor throughput.
Red pine cones: distribution within trees and methods for sampling
Authors: Mattson Jr. William John
Published: February 2008

Numbers of Pinusresinosa cones (1-month-old pistillate strobili) per branch increased with branch length and exposure. South branches invariably had significantly more cones than other branches. Cones per branch decreased from top to bottom of the crown and with increasing stand density. Highest cone yields will probably occur at densities of 80 to 100 stems/acre (181 to 277 stems/ha). Cone abundance per acre (1 acre = 0.404 685 6 ha) can be efficiently estimated [Formula: see text] by sampling three branches from both upper and middle crown thirds of only 12 trees per stand.
Hypoxylon canker incidence on pruned and unpruned aspen
Authors: Ostry Michael E. , Anderson Gerald W.
Published: February 2008

This study was designed to measure the relation between the incidence of Hypoxylon canker, Hypoxylonmammatum Wahl. Mill., and the presence of branches on an aspen stem. Two test areas were established in sprout aspen stands in Minnesota and Wisconsin where paired sprouts were chosen for study. Limbs were pruned from the lower two-thirds of the stem of one member of each pair; the other was left unpruned. Pruning was continued during the study period to keep the lower two-thirds of the stem 'branch-free.' Pruned trees had less lower stem infection and more upper stem infection than unpruned trees. Results indicate that initial infection occurs on branches and the fungus then grows down the branch and into the stem.
Biomass, density, and nutrient content of plant arthropods in the taiga of Alaska
Authors: Werner Richard A.
Published: February 2008

Arthropod composition was similar in six vegetation types in a taiga ecosystem of Alaska. Four taxonomic classes representing 94 arthropod families were found at the herb, shrub, and tree levels of aspen (Populustremuloides Michx.), paper birch (Betulapapyrifera Marsh.), balsam poplar (Populusbalsamifera L.), white spruce (Piceaglauca (Moench) Voss), and black spruce (Piceamariana (Mill.) B.S.P.) vegetation types. Of all vegetation types, ground herbs contained the highest density of arthropods. Black spruce types had the highest arthropod densities at the tree level but the lowest diversity of species. Populations of arthropods were highest during June and July in hardwood types and during July and August in spruce types. Concentrations of sodium and magnesium increased as trophic levels increased; highest concentrations were in arthropod predators. Concentrations of potassium and calcium increased from the herbivore to the saprovore level. Annual element budgets for sodium, magnesium, potassium, and calcium are discussed.
Dusting roots of Abiesconcolor and other conifers with Pisolithustinctorius spores at outplanting time proves ineffective
Authors: Alvarez Isabel F. , Trappe James M.
Published: February 2008

Dusting roots of white fir (Abiesconcolor (Gord. & Glend.) Lindl.), shasta red fir (Abiesmagnifica var. shastensis Lemm.), Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), and ponderosa pine (Pinusponderosa Dougl. ex Laws.) with Pisolithustinctorius (Pers.) Coker & Couch (Pt) spores when outplanted produced no Pt mycorrhizae at the end of the first growing season. In the 3rd year occasional Pt mycorrhizae had formed on white fir. Inoculations reduced seedling survival in some cases. High rate of spore application may have desiccated roots of the true firs; levels of spore application need careful attention. Soil scarification and ripping significantly promoted growth of white fir seedlings compared with scarification alone.
Trend surface analysis of a Douglas-fir provenance–progeny transfer test
Authors: Thomson A. J. , El-Kassaby Y. A.
Published: February 2008

Spatial variability in heights of 8-year-old Douglas-fir in a IUFRO provenance–progeny transfer test was analyzed using trend surface analysis to differentiate genetic and environmental effects on tree height. The test installation was located in the University of British Columbia Research Forest, and was a randomized incomplete block design with three replications. Only the 25 provenances that were replicated in each block and had a balanced data set (eight families, five trees per family) were used. Trends were fitted to the average height of each replicate of each provenance, and also to the average size of the largest and smallest families per replicate. Interpretation was based on the assumption that the effects of microsite (mainly grass invasion of one block) were defined by the trend surface, while genetic effects were represented by the residuals from the trend. The data had previously been analyzed by ANOVA methods and these results were contrasted with the results using trend surface analysis. Trend surface analysis generally gave results similar to ANOVA, but in some cases resulted in different conclusions. Additional insights into the interaction of genotype and environment were obtained. Trend surface analysis is proposed as a useful supplement to analysis of variance in provenance transfer studies. Potential problems in using the method are discussed.
Thirty-six years of tree population change in an old-growth Pseudotsuga–Tsuga forest
Authors: Franklin Jerry F. , DeBell Dean S.
Published: February 2008

Tree populations exhibited considerable individual plant mortality and replacement over a 36-year period in a 500-year-old Pseudotsugamenziesii (Mirb.) Franco var. menziesii (Douglas-fir)–Tsugaheterophylla (Raf.). Sarg. (western hemlock) forest in the Cascade Range of southern Washington, U.S.A. Nearly 22% (113/ha) of the original stems died at an annual rate of 0.75%. This was balanced by recruitment (117/ha) of Tsuga, Abiesamabilis Dougl. ex Forbes (Pacific silver fir), and Taxusbrevifolia Nutt. (Pacific yew) saplings. Diameter distributions and relative species composition were nearly identical at the beginning and end of the 36 years. Compositional changes were slow despite the high turnover; extinction of Pseudotsuga is predicted in 755 years at its current mortality rate. Mortality was generally caused by wind (45.5%) or suppression and unknown causes (39.4%). Additional long-term studies of old-growth forests are needed to understand the direction and rate of successional change.