Processing conditions analysis of Eucalyptus globulus plywood bonded with resol-tannin adhesives

Phenol-formaldehyde resol containing mimosa tannin extract was employed to produce plywood panels with two plies from Eucalyptus globulus veneers. The effect of processing conditions and tannin content on the gelation time of the adhesive in the glue line was evaluated by dynamic-mechanical analysis (DMA). These results were related with shear strength and wood failure of glue line in the final panels. Hazardous petrochemical phenol could be partially substituted in resols in industrial applications by addition of mimosa tannin extracts.     

Characterising the structure of photosynthetic biofilms using fluid dynamic gauging

A new configuration of the fluid dynamic gauging technique for measuring soft layers on surfaces was used to monitor the growth of a cyanobacterium, Synechococcus sp. WH 5701, on stainless steel (SS), glass and an indium tin oxide (ITO) on a polyethylene terephthalate (PET) substratum. The biofilm thickness increased steadily over 4 weeks and exhibited noticeable changes in microstructure and strength. The biofilms all exhibited a two-layer structure, with a compact layer next to the substratum and a loose layer above. Biofilms on ITO or SS exhibited cohesive failure when removed by fluid shear whereas those on glass exhibited adhesive failure. The technique is able to elucidate various aspects of biofilm behaviour, as illustrated by the action of a biocide (NaOCl) on a mature biofilm.     

Characterising the structure of photosynthetic biofilms using fluid dynamic gauging

A new configuration of the fluid dynamic gauging technique for measuring soft layers on surfaces was used to monitor the growth of a cyanobacterium, Synechococcus sp. WH 5701, on stainless steel (SS), glass and an indium tinoxide (ITO) on a polyethylene terephthalate (PET) substratum. The biofilm thickness increased steadily over 4weeks and exhibited noticeable changes in microstructure and strength. The biofilms all exhibited a two-layer structure, with a compact layer next to the substratum and a loose layer above. Biofilms on ITO or SS exhibited cohesive failure when removed by fluid shear whereas those on glass exhibited adhesive failure. The technique is able to elucidate various aspects of biofilm behaviour, as illustrated by the action of a biocide (NaOCl) on a mature biofilm.     

Compression wood in rooted cuttings of Douglas-fir

Rooted cuttings of three clones of Douglas-fir [ Pseudotsuga menziesii (Mirb.) Franco] were growing plagiotropically two seasons after propagation. The oblique growth habit of cuttings was due, in part, to dorsoconvex curvature of the wood of the original 12-cm cuttings after rooting. In cross sections taken 1.5–2.0 cm from the bases of cutting stems, the total widths of xylem and compression wood were significantly greater on the morphologically upper (convex) than on the lower sides of the stems. This was due to an asymmetry in the growth ring produced the season following rooting. In nearly every cross section examined, 80–90% of the width of the upper side of this growth ring was compression wood. Examination of cross sections taken 1.5–2.0 cm from the distal ends of the wood of original cuttings revealed a shift in the position of compression wood formation during the second season. As the distal portions of their stems were displaced from the vertical by curvature, cuttings of two clones produced compression wood on their lower sides in this region. Cuttings from the third clone, which showed the least basal curvature, continued forming compression wood on their upper sides in the distal portions of the original cuttings.     

Predatory and nesting behaviour of Cocalus gibbosus,a spartaeine jumping spider (Araneae: Salticidae) from Queensland

Abstract

Cocalus gibbosus was studied in the field in Queensland and in the laboratory. This is the first behavioural study of a species from the spartaeine genus Cocalus. C. gibbosus often omitted elements which are usually present in the predatory sequences of typical salticids and tended to lunge at prey from close range rather than leap from afar. Experiments showed that C. gibbosus prefers moths to other prey. In nature, C. gibbosus moulted and oviposited on silk sheets spun against tree trunks, and in the laboratory on sides of cages or blocks of wood, but this species never built an enclosing nest like typical salticids nor a large prey-catching web like some other spartaeines. C. gibbosus stalked across alien webs to catch spiders and insects, but it did not make vibratory signals. It did not stick to cribellate or ecribellate glue on alien webs. The behaviour of C. gibbosus is compared to that of other spartaeine salticids.     

Mycelial wastes of penicillin fermentation as glue components]

A new trend in the rational use of micelial wastes after antibiotics fermentation was elaborated. The modification of P. chrysogenum micelium by means of acid and alkaline solutions allows to use it as bone glue component. As a result physico-mechanical characteristics of the mixture increase, while the ratio cost-price decreases. The obtained glue composition can be used in the production of glue paper tape, for paper and wood glue.     

Responses of two semiarid conifer tree species to reduced precipitation and warming reveal new perspectives for stomatal regulation

Relatively anisohydric species are predicted to be more predisposed to hydraulic failure than relatively isohydric species, as they operate with narrower hydraulic safety margins. We subjected co‐occurring anisohydric Juniperus monosperma and isohydric Pinus edulis trees to warming, reduced precipitation, or both, and measured their gas exchange and hydraulic responses. We found that reductions in stomatal conductance and assimilation by heat and drought were more frequent during relatively moist periods, but these effects were not exacerbated in the combined heat and drought treatment. Counter to expectations, both species exhibited similar g_s temporal dynamics in response to drought. Further, whereas P. edulis exhibited chronic embolism, J. monosperma showed very little embolism due to its conservative stomatal regulation and maintenance of xylem water potential above the embolism entry point. This tight stomatal control and low levels of embolism experienced by juniper refuted the notion that very low water potentials during drought are associated with loose stomatal control and with the hypothesis that anisohydric species are more prone to hydraulic failure than isohydric species. Because direct association of stomatal behaviour with embolism resistance can be misleading, we advocate consideration of stomatal behaviour relative to embolism resistance for classifying species drought response strategies.     

Conformational change of 23S RNA in 50S ribosome is responsible for translocation in protein synthesis

Since the recognition of the ‘translocation’ phenomenon during protein synthesis several theories have been proposed, without much success, to explain the translocation of peptidyl tRNA from the aminoacyl site to the peptidyl site. The involvement of L7/L12 proteins and therefore the L7/L12 stalk region of 50S ribosomes in the translocation process has been widely accepted. The mobility of the stalk region, as recognised by many workers, must be of physiological significance. It has recently been shown in this laboratory that 50S ribosomes derived from tight and loose couple 70S ribosomes differ markedly in quite a few physical and biological properties and it appears that these differences are due to the different conformations of 23S RNAs. It has also been possible to interconvert tight and loose couple 50S ribosomes with the help of the agents, elongation factor -G, GTP (and its analogues) which are responsible for translocation. Thus loose couple 70S ribosomes so long thought to be inactive ribosomes are actually products of translocation. Further, the conformational change of 23S RNA appears to be responsible for the interconversion of tight and loose couple 50S ribosomes and thus the process of translocation. A model has been proposed for translocation on the basis of the direct experimental evidences obtained in this laboratory.     

Unusual adhesive production system in the barnacle Lepas anatifera: An ultrastructural and histochemical investigation

Adhesives that are naturally produced by marine organisms are potential sources of inspiration in the search for medical adhesives. Investigations of barnacle adhesives are at an early stage but it is becoming obvious that barnacles utilize a unique adhesive system compared to other marine organisms. The current study examined the fine structure and chemistry of the glandular system that produces the adhesive of the barnacle Lepas anatifera. All components for the glue originated from large single‐cell glands (70–180 μm). Staining (including immunostaining) showed that L ‐3,4‐dihydroxyphenylalanine and phosphoserine were not present in the glue producing tissues, demonstrating that the molecular adhesion of barnacles differs from all other permanently gluing marine animals studied to date. The glandular tissue and adhesive secretion primarily consisted of slightly acidic proteins but also included some carbohydrate. Adhesive proteins were stored in cytoplasmic granules adjacent to an intracellular drainage canal (ICC); observations implicated both merocrine and apocrine mechanisms in the transport of the secretion from the cell cytoplasm to the ICC. Inside the ICC, the secretion was no longer contained within granules but was a flocculent material which became “clumped” as it traveled through the canal network. Hemocytes were not seen within the adhesive “apparatus” (comprising of the glue producing cells and drainage canals), nor was there any structural mechanism by which additions such as hemocytes could be made to the secretion. The unicellular adhesive gland in barnacles is distinct from multicellular adhesive systems observed in marine animals such as mussels and tubeworms. Because the various components are not physically separated in the apparatus, the barnacle adhesive system appears to utilize completely different and unknown mechanisms for maintaining the liquid state of the glue within the body, as well as unidentified mechanisms for the conversion of extruded glue into hard cement. J. Morphol., 2012. © 2012 Wiley Periodicals, Inc.     

Clonal consistency of wood technological properties in canker-resistant <Emphasis Type="Italic">Cupressus sempervirens</Emphasis> clones at two contrasting sites

Cupressus sempervirens L. (Mediterranean cypress) has been traditionally used as a multipurpose tree. In the past, its wood was extensively used as a highly durable raw material in the Mediterranean, but nowadays, production of cypress wood is constrained by the lack of exploitable woods and plantations and by the spread of bark canker. In this study, the wood properties of canker-resistant clones specifically meant for timber production were assessed in two different locations. The aim was to evaluate the effect of genotype and environment on physical and mechanical properties of wood and its bonding quality. Four ramets of each of 10 clones were sampled in both sites, wood density, shrinkage, hardness, and the bonding strengths when glued together with two different adhesives were determined, and clonal repeatabilities and genetic correlations were also estimated. Clonal consistency for wood traits was moderate to high within and across environments, far higher than for growth- and morphological traits. Indications are that selection based exclusively on tree height would result in a lower wood density and hardness. Bonding strength reflected the combination of the material properties and the selected adhesive: For adhesive M (polyvinyl acetate dispersion), it was negatively correlated with density, whilst for adhesive E (emulsion polymerization isocyanate), it was not as influenced. Thus, even favouring higher-density wood (and therefore not only hardness but also higher shrinkages), adhesive E would give excellent bonding.     

Structural dynamics of bacterial ribosomes: IV. Classification of ribosomes by subunit interaction

Previous studies in this series (M. Noll et al., 1973a,b; Noll & Noll, 1974) have established that in Escherichia coli the ability of subunits to form vacant 70 S ribosome couples at 10 mm-Mg²⁺ is a stringent condition for activity in the translation of natural messenger (R17 RNA). The present study examines the structural basis of subunit interaction. It is found that vacant ribosome couples prepared by various methods fall into two classes, “tight” couples and “loose” couples, that differ in the affinity of their subunits for each other. Detection and separation of the two particle species is possible by ultracentrifugation. When analyzed on sucrose gradients at 6 mm-Mg²⁺ and moderate speed (30,000 revs/min), tight couples sediment as undissociated 70 S ribosomes, whereas loose couples are completely dissociated and sediment as 30 S and 50 S subunits. At 15 mm-Mg²⁺ in the gradient, both species sediment as a 70S peak. At 10 mm-Mg²⁺ and 60,000 revs/min, two peaks (63 S and 55 S) are seen because the high hydrostatic pressure causes more pronounced dissociation of the loose than of the tight couples.Association is dependent on the state of each subunit. Removal of Mg²⁺ produces 30 S b-particles that are unable to associate with 50 S subunits unless reconverted to the 30 S a-form by thermal activation according to Zamir et al. (1971). In the dissociated state, 50 S subunits tend to change irreversibly to a 50 S b-modification that produces loose couples upon association with 30 S a-subunits. The 50 S a → 50 S b transition could not be related to breaks in 23 S RNA detectable by sedimentation analysis. However, mild treatment of 50 S a-subunits with RNase produces particles that associate with 30 S a-subunits to couples that are less stable than the loose couples resulting from a dissociation/association step.Fresh S-30 extracts contain only tight couples (approx. 80%) and subunits (approx. 20%). Our results suggest that loose couples are artefacts derived from tight couples by a structural or conformational modification.Interaction-free subunits that previously were found to form a primitive initiation complex with poly(U) and tRNA_Phe (Schreier & Noll, 1970,1971), and to be active in phenylalanine polymerization, are shown to consist of the b-form of each subunit.It is likely that conflicting results obtained in the study of the mechanism of initiation and other aspects of ribosome function are due to the lack of structural criteria required for standardizing the ribosome preparation used by different investigators. This study provides simple methods and criteria to classify and separate physically all ribosome and ribosome subunits that have been observed into well-defined classes of predictable activity.     

Investigation of chitosan-phenolics systems as wood adhesives

Chitosan-phenolics systems were investigated as wood adhesives. Adhesion between two pieces of wood veneer developed only when all three components-chitosan, a phenolic compound, and laccase-were present. For the adhesive systems containing a phenolic compound with only one phenolic hydroxyl group, adhesive strengths were highly dependent upon the chemical structures of phenolic compounds used in the system and the relative oxidation rates of the phenolic compounds by laccase. The adhesive strengths were also directly related to the viscosity of the adhesive systems. However, for the adhesive systems containing a phenolic compound with two or three phenolic hydroxyl groups adjacent to each other, no correlations among adhesive strengths, relative oxidation rates of the phenolic compounds by laccase, and viscosities were observed. The adhesion mechanisms of these chitosan-phenolics systems were proposed to be similar to those of mussel adhesive proteins.     

Conformational change of L7/L12 stalk in the different functional states of 50S ribosomes

Conformational change of 50S ribosomes takes place during protein synthesis. The primary change is most likely in the secondary or tertiary structure of rRNA in the L7/L12 stalk region. In order to throw further light on this conformational change, the change in fluorescence of tight couple 50S ribosomes on conversion to loose couple 50S ribosomes containing 5-(iodoacetamido ethyl)-aminonaphthalene-l-sulphonic acid-labelled L7/L12, following the treatment with elongation factor-G and 5′-guanylyl methylene diphosphate was measured. It was enhanced in agreement with the results reported earlier. Further, the quenching of fluorescence of 50S ribosomes containing 5-(iodoacetamido ethyl)-aminonaphthalene-1-sulphonic acid-labelled L7/L12 by acrylamide was studied. The quenching is more in case of loose couples. On conversion of loose couple 50S ribosomes to tight couple ones the quenching becomes less whereas the reverse happens on conversion of tight couple 70S ribosomes to loose couples. These results indicate the conformational change of L7/L12 stalk in the different functional states of 50S ribosomes.     

Direct litter interference and indirect soil competitive effects of two contrasting phenotypes of a spiny legume shrub drive the forb composition of an oromediterranean community

Contrasting phenotypes of foundation species are known to differentially affect understorey plants. However, there is little knowledge on both the mechanisms of competition (resource competition versus interference) of stress‐tolerant phenotypes and the importance of indirect interactions. In an oromediterranean community from Mount Lebanon we assessed the effects on understorey forbs of two contrasting phenotypes, a tight competitive from stressful habitat and a loose facilitative from more benign habitat. In a dry south and a wet north exposure we assessed short‐term resource effects removing shrub canopy and long‐term soil effects (including litter interference) with the comparison of forb performances in adjacent naturally open areas vs no shrub. Indirect effects were quantified through the removal of grasses. Abundance, richness and biomass of forbs were measured in all treatments after one year of experiment, together with litter depth and soil moisture. We found strong direct negative soil effects of the tight phenotype on all forb performances and in particular in south exposure. These effects were due to litter interference on water availability, but not to resource competition. They were likely explained by the high hydrophobicity of organic matter accumulating in the stressful habitat of the tight phenotype. We also found an indirect competition of the loose phenotype for forb richness, due to its direct positive soil effect on competitive grasses, and in particular in south exposure. Our results improve our knowledge on the importance of litter interference in dry nutrient‐poor habitats and the role of indirect interactions in phenotypic effects on understorey species.     

Moisture dynamics and fungal susceptibility of plywood

Engineered wood products are widely used in construction and transportation. Plywood has one of the best physical and mechanical properties for application under moist conditions in use class 3, i.e. exterior exposure without ground contact. Yet a profound knowledge of their moisture dynamics and fungal susceptibility is a prerequisite for proper use. In this paper the results of more than two years of continuous recording of the moisture content of different plywood types in exterior exposure is presented. Clear differences concerning moisture dynamics are apparent regarding wood species, glue type, and veneer thickness. X-ray tomography scans literally offer insight into the weathering state of the veneer layers and glue lines. Fungal susceptibility of the samples relates primarily to wood species and glue type. Furthermore, edge-sealing for fungal testing is necessary to represent in-service situations and yields distinct differences compared to non-sealed test results. There seems to be a relationship between the accumulated moisture content and layered structure of the plywood, but an unequivocal link with fungal decay is not straightforward.     

Old and sticky-adhesive mechanisms in the living fossil Nautilus pompilius (Mollusca, Cephalopoda)

Nautiloidea is the oldest group within the cephalopoda, and modern Nautilus differs much in its outer morphology from all other recent species; its external shell and pinhole camera eye are the most prominent distinguishing characters. A further unique feature of Nautilus within the cephalopods is the lack of suckers or hooks on the tentacles. Instead, the animals use adhesive structures present on the digital tentacles. Earlier studies focused on the general tentacle morphology and put little attention on the adhesive gland system. Our results show that the epithelial parts on the oral adhesive ridge contain three secretory cell types (columnar, goblet, and cell type 1) that differ in shape and granule size. In the non-adhesive aboral epithelium, two glandular cell types (cell types 2 and 3) are present; these were not mentioned in any earlier study and differ from the cells in the adhesive area. The secretory material of all glandular cell types consists mainly of neutral mucopolysaccharide units, whereas one cell type in the non-adhesive epithelium also reacts positive for acidic mucopolysaccharides. The present data indicate that the glue in Nautilus consists mainly of neutral mucopolysaccharides. The glue seems to be a viscous carbohydrate gel, as known from another cephalopod species. De-attachment is apparently effectuated mechanically, i.e., by muscle contraction of the adhesive ridges and tentacle retraction.     

Solid residues from<Emphasis Type="Italic"> Ruminococcus</Emphasis> cellulose fermentations as components of wood adhesive formulations

Residues from the fermentation of cellulose by the anaerobic bacteria Ruminococcus albus (strain 7) or Ruminococcus flavefaciens (strains FD-1 or B34b) containing residual cellulose, bacterial cells and their associated adhesins, were examined for their ability to serve as components of adhesives for plywood fabrication. The residues contained differing amounts of protein (0.4–4.2% of dry weight), but the ratios of monosaccharides recovered following two-stage treatment of the residue with detergent (pH 7) and TFA were similar for all three strains (0.71 glucose:0.18 xylose:0.08 mannose:0.02 galactose), suggesting similarities in exopolysaccharide composition. Three-ply aspen panels prepared with fermentation residues (FR) displayed better shear strength and wood failure under dry conditions than following a vacuum/pressure/soak/dry treatment, but adhesive properties were inferior to those prepared with conventional phenol-formaldehyde (PF) adhesives. However, panels prepared by incorporating the R. albus 7 FR into PF formulation, at 73% by weight of the total adhesive, exhibited shear strength and wood failure similar to that obtained with PF adhesive alone. Use of residues from fermentations by these bacteria as components of adhesives may add value to biomass fermentations aimed primarily at producing ethanol and other chemical products.Mention of specific products is for informational purposes only and does not imply an endorsement or warranty by the United States Department of Agriculture, over similar products that may also be suitable.     

Early postoperative efficacy of fibrin glue in face lifts: a prospective randomized trial

Fibrin glue is increasingly finding use in plastic surgery at the clinical and basic science level. The authors conducted a prospective, nonblinded, randomized, controlled trial in 30 patients undergoing face lifts to examine the efficacy of fibrin glue in reducing postoperative wound drainage, hematomas, and, in particular, the degree of ecchymosis and edema at 24 hours and at 8 days. Patients were their own controls and were randomized to have the glue on one side of their face only to compare the glued and unglued sides. The patients ranged in age from 42 to 72 years (mean age, 60 years). There was one major hematoma requiring surgical evacuation. In the remaining 29 patients, the mean drainage on the glued side was 26 ml, compared with 33.5 ml on the control, unglued side. This difference was statistically significant numerically (p = 0.037) but was not thought to be surgically significant. Comparing scores among grades of hematomas, ecchymosis, and edema, there were minimal differences between the glued and unglued sides. This study suggests that fibrin glue may not be as beneficial as previously thought in reducing ecchymosis and edema in the early postoperative period after face lifts, and its future role is discussed.     

Structure of a loose dimer: an intermediate in nitric oxide synthase assembly

Cooperativity among ligand binding, subunit association, and protein folding has implications for enzyme regulation as well as protein aggregation events associated with disease. The binding of substrate l-arginine or cofactor tetrahydrobiopterin converts nitric oxide synthases (NOSs) from a "loose dimer", with an exposed active center and higher sensitivity to proteolysis, to a "tight dimer" competent for catalysis. The crystallographic structure of the Bacillus subtilis NOS loose dimer shows an altered association state with severely destabilized subdomains. Ligand binding or heme reduction converts loose dimers to tight dimers in solution and crystals. Mutations at key positions in the dimer interface that distinguish prokaryotic from eukaryotic NOSs affect the propensity to form loose dimers. The loose dimer structure indicates that non-native interactions can mediate subunit association in NOS.     

Thermodynamic studies of a series of homologous HIV-1 TAR RNA ligands reveal that loose binders are stronger Tat competitors than tight ones

RNA is a major drug target, but the design of small molecules that modulate RNA function remains a great challenge. In this context, a series of structurally homologous ‘polyamide amino acids’ (PAA) was studied as HIV-1 trans-activating response (TAR) RNA ligands. An extensive thermodynamic study revealed the occurence of an enthalpy–entropy compensation phenomenon resulting in very close TAR affinities for all PAA. However, their binding modes and their ability to compete with the Tat fragment strongly differ according to their structure. Surprisingly, PAA that form loose complexes with TAR were shown to be stronger Tat competitors than those forming tight ones, and thermal denaturation studies demonstrated that loose complexes are more stable than tight ones. This could be correlated to the fact that loose and tight ligands induce distinct RNA conformational changes as revealed by circular dichroism experiments, although nuclear magnetic resonance (NMR) experiments showed that the TAR binding site is the same in all cases. Finally, some loose PAA also display promising inhibitory activities on HIV-infected cells. Altogether, these results lead to a better understanding of RNA interaction modes that could be very useful for devising new ligands of relevant RNA targets.