A comparison of regression methods for estimating soil-atmosphere diffusion gas fluxes by a closed-chamber technique

Continuous changes in methane (CH₄) and carbon dioxide (CO₂) concentrations inside a closed chamber were measured on the forest floor at three sites: a deciduous forest and a coniferous forest in Hokkaido, Japan, and a birch forest in West Siberia, Russian Federation. Flux estimations by three types of regression methods, exponential, nonlinear, and linear, were examined using field-collected concentration data. The pattern of change with time of the gas concentration in the headspace differed, mainly according to site but also, to a lesser extent, according to the gas. This was a function of both the chamber height and surface soil property relating to soil gas diffusion and the gas concentration profile. Flux estimations did not differ statistically between the exponential and nonlinear methods for either gas at any site, because both of those regression methods were based on diffusion theory. However, the flux values estimated by linear regression were significantly different from those estimated by the other two methods for both CH₄ and CO₂ at the deciduous forest site and for CO₂ at the coniferous forest site. Shortening the chamber deployment period improved the linearity of the curve, but did not completely eliminate the error. Our results suggest that linear regression is not a good model of the change in headspace concentration with time.     

Incorporation of 15N into various nitrogenous compounds in intact soybean nodules after exposure to 15N2 gas

The intact nodules attached to the upper part of soybean roots were exposed to ¹⁵N₂ and the incorporation of ¹⁵N into various soluble nitrogen constituents was investigated. Results indicated that ammonia, a primary product of N₂ fixation, was located in more than two compartments. Ammonia reduced from N₂ gas seemed to be incorporated firstly into glutamine especially amido-group nitrogen. Newly fixed nitrogen was secondly incorporated into glutamic acid and alanine in this sequence. These results suggested that fixed ammonia was assimilated by glutamine synthetase/glutamate synthase pathway. Turn-over rate of allantoin plus allantoic acid and serine was relatively high, although apparently these compounds were not primary products of newly fixed ammonia. ¹⁵N content of allantoin was always higher than that of allantoic acid. ¹⁵N incorporation to aspartic acid and asparagine was relatively slow, especially in early period. In bacteroid fraction there is much amount of ammonia comparing with other compounds, while allantoin and asparagine were presented exclusively in cytosol. ¹⁵N was incorporated into nitrate within a few minutes especially in bacteroids.     

Changes in net ecosystem production associated with forest fire in taiga ecosystems,near Yakutsk,Russia

Abstract

The effect of sucrose on the growth of rice plants under gnotobiotic conditions was studied at test tube scale in vinyl isolators under weak or strong light. Under weak light (500 lux) the growth of rice plants on agar medium containing only inorganic nutrients during the 20 days after transplanting stopped at 3rd leaf stage, whereas plants on agar medium containing inorganic nutrient plus 2% sucrose grew to 5th or 6th leaf stage. Under strong light (1.5 × 10⁴ lux) the stage of tillering was promoted by supplying sucrose. The growth of rice plants in pot-hydroculture under weak light had the same tendency as that obtained in test tube culture under weak light.

Considering the concentration of inorganic elements in rice shoots, it seems most likely that the uptake of inorganic elements. especially phosphorus and potassium, was enhanced by the supplements of 2% sucrose under weak light. An increase of calcium and manganese uptake was observed in plants grown in medium containing 2% sucrose compared with that of plants grown in inorganic medium alone under strong light. The uptake of inorganic elements from medium containing inorganic nutrients plus 2% sucrose depended chiefly on light energy under strong light in the phytotron used.     

Analysis of intracellular distribution of Borna disease virus glycoprotein fused with fluorescent markers in living cells

Borna disease virus (BDV) is a non-segmented, negative-strand RNA virus that is characterized by nuclear replication and persistent infection. A unique feature of BDV is that it releases only a small number of infectious particles from infected cells. Although these characteristics might make it difficult to obtain a large amount of recombinant viruses in a reverse genetics system, the mechanism underlying the budding or assembly of BDV particle has remained largely unknown. In this study, as a first step toward understanding the virion formation of BDV, we investigated the intracellular distribution and mobility of the fluorescent marker fusion envelope glycoprotein (G) of BDV in living cells. Expression analysis revealed that fusion proteins seem to cleave into functional subunits and localize in the endoplasmic reticulum (ER)/Golgi apparatus, as well as the authentic BDV G. Furthermore, we demonstrated using fluorescence recovery after photobleaching analysis that BDV G fluorescence shows rapid recovery in both the ER/Golgi and plasma membrane regions, indicating that BDV G fusion protein may be a useful tool to investigate not only the maturation of BDV G but also the budding and assembly of BDV particles in living cells.     

Distribution of mecA-harboring staphylococci in healthy mares

The prevalence of staphylococci that harbor the mecA gene responsible for methicillin resistance was examined in healthy breeding mares. Staphylococci often cause diseases of horses such as metritis, keratitis, and abscess. Methicillin-resistant staphylococci would make antibiotic treatments ineffective, so it may be significant to know the distribution of mecA-harboring staphylococci in mares. Isolation of mecA-harboring staphylococci was achieved from nares and pasterns of 100 mares in Hokkaido, Japan. From 13% of the mares, mecA-harboring staphylococci, including 15 isolates of Staphylococcus sciuri and 3 of Staphylococcus lentus, were isolated. Isolates of S. sciuri were found to be genetically polyclonal by pulsed-field gel electrophoresis. These isolates produced no PCase and showed low or no resistance to beta-lactam and other classes of antibiotics. Distribution of staphylococcal species and levels of antibiotic resistance were found to be different between isolates from the present mares and those previously reported from riding-horses. Antibiotic pressure may lead to these differences. In addition, it appears that mecA-harboring S. sciuri may be native to horses.     

Dimensional stability and strength properties of particleboard produced by a closed-press system

The purpose of this study was to reveal the effects of various levels of mat-moisture content (m.m.c.) and the closed-press system for making single- or three-layer particleboard on the density profile, thickness swelling, specific moduli of elasticity (MOE) and rupture (MOR) and internal bond strength. Internal gas pressure was measured in an enclosed frame; and the larger the m.m.c., the higher the internal gas pressure became. When rising water vapor (steam) struck particles, it plasticized them and cured the adhesive, resulting in improved interparticle contact. The vertical density gradient in the three-layer board was larger than that in the single-layer board. As for thickness swelling by cold-water soaking, the single-layer boards were less affected than the three-layer boards and showed good dimensional stability with increased m.m.c. The open-system boards swelled more than the closed-system boards. The closed-system single-layer board made at high m.m.c. returned nearly to the prime thickness by air-drying after cold-water soaking. Specific MOE and MOR were larger at 15% or 10% m.m.c. than those at other m.m.c. Considerable reductions of specific MOR and MOE of the closed-system three-layer board were observed at 20% or 25% m.m.c.Part of this report was presented at the 45th annual meeting of the Japan Wood Research Society, Tokyo, April 1995 and at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998