Decay and termite resistance of medium density fiberboard (MDF) made from different wood species

Medium density fiberboard (MDF) production worldwide is increasing due to the development of new manufacturing technologies. As a result, MDF products are increasingly utilized in traditional wood applications that require fungal and insect resistance. This study evaluated the ability of white and brown rot fungi and termites to decompose MDF consisting of different wood species by measuring weight loss. Furnish in the boards was prepared from heart and sapwood portions of pine (Pinus nigra Arnold var. pallasiana), beech (Fagus orientalis Lipsky), and European oak (Quercus robur L.) species. Fungal decay resistance tests were performed according to ASTM D 2017-81 standard method using two brown-rot fungi, Gloeophyllum trabeum (Pers. ex Fr.) Murr. (Mad 617), Postia placenta (Fries) M. Larsen et Lombard (Mad 698), and one white-rot fungus, Trametes versicolor (L. ex Ft.) Pilat (Mad 697). MDF and wood specimens were also bioassayed against the eastern subterranean termite, Reticulitermes flavipes (Kollar) in order to determine termite resistance of the specimens. MDF specimens containing oak and mixed furnish demonstrated increased durability against decay fungi. Only pine, oak, and mixed MDF specimens met the 25% or less weight loss limit to be classified resistant according to ASTM D 2017-81 standard method. Overall, MDF specimens made from oak showed better performance than oak solid wood specimens. Accelerated aging according to ASTM D 1037-96a standard method before fungal bioassay decreased fungal resistance of the specimens. In contrast to the fungal bioassay, MDF specimens made from beech and mixed furnish showed decreased weight losses from termite attack after 4 weeks. However, none of the MDF specimens were resistant to termite attack. In severe conditions, the MDFs may require the incorporation of chemical biocides prior to board production for increasing the resistance of MDF to termite attack.     

Mechanical and water soaking properties of medium density fiberboard with wood fiber and soybean protein adhesive

Soybean protein is a renewable and abundant material that offers an alternative to formaldehyde-based resins. In this study, soybean protein was modified with sodium dodecyl sulfate (SDS) as an adhesive for wood fiber medium density fiberboard (MDF) preparation. Second-order response surface regression models were used to study the effects and interactions of initial moisture content (IMC) of coated wood fiber, press time (PT) and temperature on mechanical and water soaking properties of MDF. Results showed that IMC of coated fiber was the dominant influencing factor. Mechanical and soaking properties improved as IMC increased and reached their highest point at an IMC of 35%. Press time and temperature also had a significant effect on mechanical and water soaking properties of MDF. Second-order regression results showed that there were strong relationships between mechanical and soaking properties of MDF and processing parameters. Properties of MDF made using soybean protein adhesive are similar to those of commercial board.     

Properties of medium density fiberboards made from renewable biomass

The goal of this study was to determine the comparative properties of dry-formed medium density fiberboards (MDF) made from renewable biomass (wheat and soybean straw) and those from conventional soft wood fiber. The MDF properties evaluated were modulus of elasticity, modulus of rupture, internal bond strength, thickness swell, and screw holding capacity. The results show that MDF made from wheat straw fiber and soy straw fiber have weaker mechanical and water resistance properties than those made from softwood fiber. Soybean straw is comparable to wheat straw in terms of both mechanical and water resistance properties to make MDF. Water resistance of MDF decreased drastically with increasing straw fiber composition. Wheat straw fiber and soybean straw fiber should be physically or chemically treated to increase their water resistance property for MDF production.     

Identification of aerobic mesophilic bacilli isolated from board and paper products containing recycled fibres

AIMS: To identify aerobic mesophilic bacteria isolated from coreboard, kitchen roll paper and food packaging boards containing recycled fibres and to create a rapid fingerprint-based database for their identification. METHODS AND RESULTS: A total of 197 isolates and 20 relevant type strains were characterized by automated ribotyping and as far as possible identified by the similarities of their riboprints to the relevant type strains. One strain from each unidentified ribotype, a total of 87 strains, was subjected to partial 16S rDNA sequencing and in most cases also to fatty acid analysis and physiological tests. From the isolates 113 and seven different ribotypes were generated belonging to the genera Bacillus and Paenibacillus, respectively. The dominating species, or closest related to them, were B. simplex (22.8% of isolates), B. licheniformis (18.3%) and B. amyloliquefaciens (12.7%); 5.1% of the isolates were identified as B. cereus, a potential food-borne pathogen. In particular, this species was present in one food packaging board (26.3% of isolates). Based on these results, 40.1% of the isolates and 45.0% of ribotypes were so different from the relevant type strains that they may represent novel species. CONCLUSIONS: All isolates were aerobic spore-formers, indicating that all non-spore-formers were eliminated during the drying stage of the processes. Although many isolates could be affiliated to described species of Bacillus or Paenibacillus, a significant proportion of the isolates could not be identified unambiguously as members of a described species. SIGNIFICANCE AND IMPACT OF THE STUDY: A RiboPrint identification database, composed of 120 composite patters, was established for bacteria originating from the pulp and paper industry. Considering the discrimination power of ribotyping, this database will be extremely useful in future for the reliable and rapid identification of bacteria isolated from pulp and paper industrial sources.     

Some properties of IgG against diphtheria toxin synthesized in Xenopus oocytes containing mRNA from hybridoma

When a mixture of mRNA from hybridoma producing IgG, anti-diphtheria toxin antibody, and mRNA from rat liver was injected into Xenopus oocytes, most of the IgG synthesized in the oocytes was not secreted into the medium and remained in the rough endoplasmic reticulum fraction. In contrast, rat serum albumin was rapidly secreted. The glycosylation of IgG in the oocytes was of a high-mannose type, while that of IgG secreted very slowly into the medium was of a complex type. The IgG in the membrane fraction and in the medium could both bind to diphtheria toxin.     

Occurrence and characterization of actinobacteria and thermoactinomycetes isolated from pulp and board samples containing recycled fibres

The aim of this study was to characterize the actinobacterial population present in pulps and boards containing recycled fibres. A total of 107 isolates was identified on the basis of their pigmentation, morphological properties, fatty acid profiles and growth temperature. Of the wet pulp and water sample isolates (n=87), 74.7% belonged to the genus Streptomyces, 17.2% to Nocardiopsis and 8.0% to thermoactinomycetes, whereas all the board sample isolates (n=20) were thermoactinomycetes. The identification of 53 isolates was continued by molecular methods. Partial 16S rDNA sequencing and automated ribotyping divided the Streptomyces isolates (n=31) into 14 different taxa. The most common streptomycetes were the mesophilic S. albidoflavus and moderately thermophilic S. thermocarboxydus. The Nocardiopsis isolates (n=11) belonged to six different taxa, whereas the thermoactinomycetes were mainly members of the species Laceyella sacchari (formerly Thermoactinomyces sacchari). The results indicated the probable presence of one or more new species within each of these genera. Obviously, the drying stage used in the board making processes had eliminated all members of the species Streptomyces and Nocardiopsis present in the wet recycled fibre pulp samples. Only the thermotolerant endospores of L. sacchari were still present in the final products. The potential of automated ribotyping for identifying actinobacteria was indicated, as soon as comprehensive identification libraries became available.     

Mechanical and thermal properties of particle boards made from farm residues

Five farm residues were used for the manufacture of low-density particle boards in a hot platter press using urea formaldehyde as the binding material. Mechanical and thermal properties of the boards were evaluated. The maize-cob board was superior to other boards in mechanical and screw/nail holding strength, suggesting its use for interior applications, while paddy-straw board and coconut-pith board were found to be suitable for insulation purposes.     

Growth of insect cells in recycled medium and the use of various serum supplements

Summary Medium that had supported the growth of insect cells was depleted in components of both the basal medium and foetal calf serum. In addition, a non-dialysable growth-inhibiting factor(s) appeared to exist. The pH had risen to a sub-optimal level and simply readjusting this to pH 6.6 partially restored its capacity to support cell growth. The most promising alternative serum supplement tested was new-born calf serum.     

Comparative genotoxicity studies of the flame retardant tris(2,3-dibromopropyl)phosphate and possible metabolites

Tris(2,3-dibromopropyl)phosphate (Tris-BP) was activated to mutagens in the Salmonella/microsome quantitative test system. Liver microsomes from rats pretreated with phenobarbital (PB) increased the mutagenicity of 0.05 mM Tris-BP to 186% of the activity obtained with liver microsomes from untreated rats. The addition of 0.02 mM Tris-BP to V79 Chinese hamster cells co-incubated with liver microsomes from PB-pretreated rats increased the number of mutants by a factor of 9.7. Tris-BP also caused genotoxic and cytotoxic responses in primary monolayers of rat hepatocytes. The relative increase in unscheduled DNA synthesis after treatment with 0.05 mM Tris-BP was 2.3-fold as measured by scintillation counting of radiolabelled thymidine incorporated into DNA of isolated nuclei. The use of hepatocytes isolated from PB-pretreated rats reduced the increases in DNA repair synthesis relatively to that in control cells. Monolayers of hepatocytes from untreated rats co-cultured with Salmonella typhimurium TA100 activated Tris-BP to mutagenic intermediates which were released into the culture medium. The studies with the V79 and liver-cell systems indicate that the reactive intermediates formed from Tris-BP are sufficiently stable and lipophilic to traverse the various membranes from the site of generation to the respective cellular targets. The relative degree of genotoxic responses of bis(2,3-dibromopropyl)phosphate, 2,3-dibromopropylphosphate, tris(2,3-bromopropyl)phosphate, tris(2-bromopropyl)phosphate and 2,3-dibromopropanol in the systems studied did not indicate that these compounds were proximate or ultimate reactive metabolites of Tris-BP in liver-derived activation systems.     

Some observations on the dielectric properties of hemoglobin's suspending medium inside human erythrocytes.

Dielectric permittivity and conductivity data for human erythrocytes exhibit two consecutive dispersions with frequency in the range from 0.1 to 250 MHz. The dispersion observed above 50 MHz yields a circle in the complex impedance plane with its center on the real axis, suggesting a Debye relaxation, for the erythrocyte interior medium, centered in the microwave frequency range as for bulk water. Moreover, the Maxwell mixture equation, indicates that this "free" water forms most of the suspending medium of hemoglobin macromolecules. These results extend to lower frequencies (earlier results obtained by Schwan) with biological tissues such as muscles, skin, or liver at microwaves frequencies.     

Some properties of the protease from Aspergillus terricola

A tumor like case of Cryptococcosis with a rare location in the abdomen of a young healthy woman is commented. It gave the opportunity to refer to the pathogeny of the disease, making in that way a brief review of the cases known in Venezuela and some not still published from which we got information. That review showed that generally doctors found more frequently organic lesions within the fields they are specially working for. It is obvious that mycosis must be considered in the diagnosis of nearly every patient in many countries and that laboratories must get appropriate equipment and personnel to help in that diagnosis.     

Some properties of the point processes generated by integral density modulation of renewal processes

Integral density modulation of point processes is defined, and the properties of the modulated point processes are described. When a homogeneous renewal process is modulated by a step random signal, the mathematical expressions are derived of the probability density functions of the sums of r-successive inter point intervals, the intensity functions and the first order correlation coefficient of intervals. These quantities are calculated and illustrated for several parameter values. Modulated point sequences are generated by computer simulation method. The interval histograms and the serial correlation coefficients of counts and of intervals of the sequences are obtained. The results are compared with the theoretical results on the point processes modulated by the step random signal.Abbreviations IDM Integral density modulation - SRS Step random signal - PP Point process - PS Point sequence - PDF Probability density function - CPDF Conditional probability density function - JCPDF Joint conditional probability density function - SED Special Earlangian distribution - SCC Serial correlation coefficients - SIC Serial intensity coefficients     

Structure and mechanical properties of wet-spun fibers made from natural cellulose nanofibers

Cellulose nanofibers were prepared by TEMPO-mediated oxidation of wood pulp and tunicate cellulose. The cellulose nanofiber suspension in water was spun into an acetone coagulation bath. The spinning rate was varied from 0.1 to 100 m/min to align the nanofibers to the spun fibers. The fibers spun from the wood nanofibers had a hollow structure at spinning rates of >10 m/min, whereas the fibers spun from tunicate nanofibers were porous. Wide-angle X-ray diffraction analysis revealed that the wood and tunicate nanofibers were aligned to the fiber direction of the spun fibers at higher spinning rates. The wood spun fibers at 100 m/min had a Young's modulus of 23.6 GPa, tensile strength of 321 MPa, and elongation at break of 2.2%. The Young's modulus of the wood spun fibers increased with an increase in the spinning rate because of the nanofiber orientation effect.     

Some properties of the lipoxygenase from rabbit reticulocytes.

A lipoxygenase was enriched from the stoma-free supernatant of rabbit reticulocytes. The enzyme causes drastic deterioration of mitochondrial membranes. The release of matrix enzymes is paralleled by formation of products of lipid peroxidation. The enzyme reacts with isolated phospholipds and free cis-unsaturated fatty acids. Some properties were determined: molecular weight, isoelectric point, temperature and pH-dependence and Km value for linoleic acid. The enzyme is inhibited by reaction products and a variety of inhibitors, especially antioxidants and chelating agents.     

Effects of flame retardants on the properties of particle boards prepared from cottonseed hulls

The effects of fire retardants on the properties of particle boards made from cottonseed hulls were studied. The boards were treated with (1) 70% borax + 30% boric acid (FR(1)); (2) 60% borax + 25% boric acid + 15% ammonium dihydrogen orthophosphate (FR(2)) and were evaluated for duration of flaming, after-glow, charred area, charred length and per cent loss in weight, along with physico-mechanical properties. Fire retardant properties, water resistance and per cent thickness swelling improved, and bending strength decreased, with increase in concentration of fire retardants. Treatment (2) was found to be the better fire retardants since it served the dual purposes of flame and glow retardation.     

Purification and properties of colony-stimulating factor from mouse lung-conditioned medium.

Colony-stimulating factor, which specifically stimulates mouse bone marrow cells to proliferate in vitro and generate colonies of granulocytes, or macrophages, or both, was purified 3500-fold from mouse lung-conditioned medium. Analysis by discontinuous polyacrylamide gel electrophoresis in the presence and absence of sodium dodecyl sulfate indicated that there was a single protein component. All of the colony-stimulating activity was coincident with the protein band. The molecular weight of colony-stimulating factor estimated by gel filtration was approximately 29,000 and by electrophoresis approximately 23,000. The specific activity of purified colony-stimulating factor from mouse lung-conditioned medium bound to concanavalin A-Sapharose, indicating that it is a glycoprotein. The small percentage of colony-stimulating factor in mouse lung-conditioned medium which did not bind to concanavalin A-Sepharose appeared to represent molecules which lacked the carbohydrate moieties required for binding to this lectin. It was necessary to include low concentrations (less than 0.01%, v/v) of polymers such as gelatin and polyethylene glycol, or nonionic detergents such as Triton X-100, in all of the buffers used throughout the purification scheme, otherwise colony-stimulating factor was lost from solution. At high concentrations (greater than 20 mug/ml) the factor stimulated the formation of granulocytic, macrophage, and mixed colonies from C57BL mouse bone marrow cells. As the concentration of purified colony-stimulating factor was decreased, the frequency of colonies containing granulocytes also decreased. At low concentrations of colony-stimulating factor (less than 70 pg/ml) only macrophage colonies were stimulated.     

Some observations on the use of cylinders made from different materials in the cylinder plate method

Summary Aluminium has been reported as material for test cylinders. Our observations indicate that certain qualities of commercial aluminium tubes exert a pronounced inhibitive effect on a Staph. aureus culture.