A Note on Cell Wall and Wood Substance Densities

The differences in reported values of material densities for wood are discussed and analyzed with respect to cell-wall voids. A model is proposed to account for the reported differences and for general use in calculating relationships between wood volume and density

Photo sensor array technology development

The development of an improved capability photo sensor array imager for use in a Viking '75 type facsimile camera is presented. This imager consists of silicon photodiodes and lead sulfide detectors to cover a spectral range from 0.4 to 2.7 microns. An optical design specifying filter configurations and convergence angles is described. Three electronics design approaches: AC-chopped light, DC-dual detector, and DC-single detector, are investigated. Experimental and calculated results are compared whenever possible using breadboard testing and tolerance analysis techniques. Results show that any design used must be forgiving of the relative instability of lead sulfide detectors. A final design using lead sulfide detectors and associated electronics is implemented by fabrication of a hybrid prototype device. Test results of this device show a good agreement with calculated values

Polymerization of Methyl Methacrylate by Heat-Catalyst and Gamma-Irradiation Methods

Methyl methacrylate (MMA) was bulk-polymerized with 0 to 4% crosslinker (ethylene glycol dimethacrylate, EGDM, and trimethylol propane trimethacrylate, TMPTM), initiated with 0.05 to 5% catalyst (Vazo) at 65-75 C or 0.1 to 1 Mrad/hr gamma radiation at 20 C. Heat-catalyzed MMA conversion to polymer vs. time was obtained directly from polymer mass, which indicated that about 90% conversion had occurred at the exothermic peak temperature. The time to the exothermic peak temperature was used to determine sample polymerization time. The over-all polymerization rate varied with the half-power of initiator concentration. An Arrhenius plot of the initiator-time data gave an activation energy of 18 kcal/mole. A log-log relationship was found between crosslinker concentration and polymerization time over the 65-75 C temperature and 0.1-0.4% initiator range. The crosslinkers were found equally efficient in reducing polymerization time. Peak exothermie temperature varied directly with time, irrespective of the initiator and crosslinker concentrations or bath temperature except as they affected time. In the irradiation tests, the crosslinkers exhibited different data fits: log-log with EGDM and semilog for TMPTM. The time-dose rate equation for uncrosslinked MMA was analogous to that for heat-catalyzed polymerization. Molecular weight of uncrosslinked PMMA was determined as a function of temperature and catalyst concentration, and dose rate. Similar molecular weights were obtained for heat-catalyzed polymerization at 65 C and gamma irradiation at 20 C for numerically the same initiator concentration (%) and does rate (Mrad/hr)

Longitudinal Diffusion and Permeability of Nonpolar Gases in Eastern Hemlock

Longitudinal ethane diffusion and nitrogen permeability were measured in oven-dry eastern hemlock sapwood. Samples were selected from 2 trees, 3 heights, and 4 quadrants, and either air- or solvent-dried for aspirated or unaspirated conditions. An IR method was used to detect ethane concentration in nitrogen at 25 C from which diffusion coefficients were calculated. The mean diffusion coefficient of the solvent-dried samples was 40% of free diffusion; the air-dried coefficient was about 16% of the free diffusion coefficient. No significant differences were found between position in the tree or oven-dry density and the diffusion coefficients. Diffusion coefficients were used to determine tortuosity differences in air- and solvent-dried wood. Effective pore openings obtained from permeability measurements, the Klinkenberg equation, and the temperature coefficient of diffusion confirmed that diffusion was occurring in the Kundsen end of the slip-flow region. A linear relationship was found between the permeability constant and diffusion coefficient. Diffusion and permeability measurements produce separate and complementary data that can be used to determine the mode of conductivity of gases in wood

Dynamic Mechanical Behavior of Black Cherry (Prunus Serotina EHRH.)

The dynamic mechanical properties of black cherry (Prunus serotina Ehrh.) have been investigated as a function of temperature at audio frequencies. Relaxation processes are evident near 200, 360, and 510 K. The process near 200 K was investigated as a function of initial moisture content (based on mass measurements prior to testing). At moisture contents greater than about 20%, the damping peak is centered near 185 K. This relaxation shifts with moisture content, and at moisture contents below 6%, the peak is centered near 225 K. The relaxation in the 360 K region is also associated with initial moisture content. For oven-dry black cherry specimens, the dynamic mechanical properties in the 360 K region are nearly temperature-independent. The relaxation near 510 K is believed to be associated with thermal degradation of wood constituents that are known to degrade in that temperature region

Trends in International Compulsory Licensing of Pharmaceuticals Since the Institution of the Trade-Related Aspects of Intellectual Property Protection (TRIPS) Agreement

The Trade-related Aspects of Intellectual Property Rights (TRIPS) Agreement went into effect for World Trade Organization (WTO) members in 1995. The agreement defines minimum standards of patent protection that must eventually be observed by all signatories. TRIPS includes compulsory licensing , a policy that allows for states under certain conditions to permit the use of a patented innovation without the consent of the patent holder. This paper considers instances of compulsory licenses (CLs) aimed to increase access to pharmaceuticals during urgent public health scenarios. The WTO maintains no registry of CLs; therefore, this research is an effort to catalog as many CL case studies as possible since the policy\u27s institution and analyze them as a whole. Findings include 24 case studies involving 43 CLs in 18 nations. Results show that most CLs are issued by middle income nations such as Brazil and Thailand. Possible structural and institutional explanations are explored. The paper concludes that the policy is commonly practiced for purposes beyond its original design and that suboptimal outcomes are likely to result

Drouth rations for Oklahoma livestock

The Oklahoma Cooperative Extension Service periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311

Thermogravimetric Evaluation of Fungal Degradation of Wood

Yellow birch (Betula alleghaniensis Brit.) was degraded by a white rot fungus (Polyporus versicolor L. ex Fr.; now Coriolus versicolor (L.) Quél.) and a brown rot fungus (Poria monticola Murr.; now Poria placenta (Fr.) Cke.) under controlled conditions. Samples of known weight loss from fungi were milled to pass a 40-mesh screen, oven-dried, and then measured for rate of mass loss over selected temperature ranges. Rates of mass loss of nominal 4-mg samples were obtained isothermally in flowing oxygen using a thermo-gravimetric (TG) system containing a Cahn electrobalance. Activation energy (E) was found using zero-order kinetics for the initial mass loss. White-rotted birch (to 60% weight loss) had an E of 35 to 43 kcal/mole over the range of approximately 190 to 210 C. On the basis of TG data, the weight loss from fungal attack could be predicted within about 5%. Brown-rotted birch had more variation in E (30 to 44 kcal/mole), over a temperature range of 170 to 195 C. The rate of mass loss of brown-rotted birch (to 52% weight loss) was more sensitive to temperature because of the known nonlinear decrease in cellulose DP during fungal attack. Dynamic thermogravimetry, a much simpler method, indicated a similar degree of instability from fungal attack as did the isothermal tests. TG appears to be a viable research method to evaluate fungal attack of wood

Some Physical Properties of Birch Carbonized in A Nitrogen Atmosphere

The dynamic mechanical properties, mass loss, and shrinkage data of birch carbonized in a nitrogen atmosphere to different temperatures from 473 to 973 K have been investigated. The dynamic elastic modulus data decreased as the heat treatment temperatures approached 673 K. Major mass loss and shrinkage accompanied the decrease in the modulus data. Treatments at higher temperatures (> 673 K) produced substantially less additional mass loss and shrinkage but produced increased rigidity in the char. The internal friction behavior of the char was complex