Migration of methylene bis thiocyanate in wood and its effect on a wood degrading fungus

The mobility and concentrations of methylene bis thiocyanate (MBT) at different depths of wood billets (200 mm long, 40 mm in diameter) of Pinus radiata were determined using NMR spectroscopy and ICP-ASE. Results were then correlated with the effect of wood MBT concentrations on growth of O. floccosum in a bioassay using stereomicroscopy and confocal laser scanning microscopy (CLSM). The ¹³C NMR spectra showed the presence or the absence of MBT in wood but it was unable to detect small concentrations. ICP-ASE, however produced quantitative data across the depth (40 mm) of the wood billets tested. Within 7 days of storage, MBT penetrated from surface to pith but showed significantly higher concentrations of MBT in surface wood compared to pith wood. Present study highlighted the benefit of using CLSM for fungal detection in wood. The information obtained from ICP-ASE and CLSM analysis suggested to inhibit growth of O. floccosum, the MBT concentration needs to be >55 μg/g of dry wood. Due to its high detection capacity, ICP-ASE is identified as an excellent tool for MBT detection and quantification in wood.     

基于DLA模型模拟植物生长系统的设计与实现

概述了分形理论的产生和DLA扩散有限凝聚模型,提出了基于DLA模型在计算机上进行植物生长模拟的实现方法。并在此基础上,设计了一个基于Visual Basic平台的分形生长模拟系统,并对模拟的结果进行了讨论,同时给出了模拟效果图。     

Dry-jet wet spinning of polyhydroxyamide fibers

A high molecular weight polyhydroxyamide (PHA) solution in N, N-dimethyl acetamide (DMAc) was prepared from 3,3′-dihydroxybenzidine and isophthalic chloride (IPC), which was used for spinning PHA fiber. Before spinning, the diffusion property of DMAc into various coagulants was examined. The fiber was well formed in coagulants such as water/ethanol with a composition of 5/5, ethanol, and ethanol/isopropanol with a composition of 7/3 and 5/5. However, the PHA fiber spun in the water/ethanol mixture contained voids. After the fiber spun in ethanol was annealed at over 350°C, the ultimate stress and initial modulus of the fiber increased from 75.5 MPa and 3.22 GPa to 369 MPa and 29.5 GPa, respectively. These properties of the PHA fiber spun by the dry spinning method were also enhanced, attaining 154 MPa and 5.56 Gpa, respectively.     

Development and testing of a model for predicting tillage effects on nitrate leaching from cracked clay soils

Both water movement and nitrate leaching in structured soils are strongly influenced by the nature of the macro-porosity. That macro-porosity can however also be manipulated by choice of tillage operations. In order to investigate the potential impacts of tillage on rates of nitrate leaching from structured soils, a model specific to these soils, CRACK-NP was developed. The model, its application and validation for an experimental site on a heavy clay soil (Verti-Eutric Gleysoil) at Brimstone Farm, Oxfordshire, UK, is described. The model considers the soil as a series of aggregates whose size is also the spacing of the macro-porosity. Water and solutes move in the macro-pores, but within the peds they move only by diffusion, internal infiltration and root uptake (evaporation). The model reflects the influence of diffusion limitation in the release of solutes to by-passing water. The model was then used to investigate the influence of variable ped spacings which were created by variations in tillage practices. The results both from the model and from the field data demonstrated that finer soil structures, which have larger surface contact areas and shorter diffusion path lengths, present greater opportunities for interaction between peds and the water moving around them, and so release more nitrates through the drainage waters.     

Cultivar differences in gaseous 1-methylcyclopropene accumulation in whole and fresh-cut apple fruit

A number of studies have shown that responses of apple fruit to 1-methylcyclopropene (1-MCP) vary considerably among cultivars. This study was designed to determine if cultivars show differences in accumulation of gaseous 1-MCP. Apple fruit were placed in 1.76 L jars that were sealed and injected with 20 μL L⁻¹ 1-MCP. After 12 h, samples of intercellular atmosphere were removed and analyzed for 1-MCP concentration. Accumulation of internal gaseous 1-MCP varied markedly among cultivars, ranging from 0.14 ± 0.06, 0.22 ± 0.03, and 0.77 ± 0.30 in ‘Redcort’, ‘McIntosh’, and ‘Empire’, respectively, to 2.10 ± 0.28, 3.33 ± 0.13, and 6.93 ± 0.35 μL L⁻¹ in ‘Gala’, ‘Cameo’, and ‘Honeycrisp’, respectively. Accumulation of gaseous 1-MCP was reduced an average of 51% in fruit treated with Sta-Fresh 8711 fruit wax. The role of the epidermis in modulating 1-MCP ingress was determined by measuring gaseous 1-MCP accumulation in fresh-cut tissue. Fresh-cut cortical tissue rapidly depleted headspace 1-MCP (>95%) over a 1-h exposure yet accumulated negligible quantities of internal gaseous 1-MCP. By contrast, cortical tissue treated with ascorbic acid or hypotaurine, or aged for several hours prior to exposure to 1-MCP, showed reduced consumption of headspace 1-MCP and high accumulation of internal gaseous 1-MCP. Levels of internal 1-MCP in cortical tissue from the cultivars generally paralleled those for intact fruit, ranging from 0.23 ± 0.07, 0.37 ± 0.18 and 1.09 ± 0.14 μL L⁻¹ in ‘Empire’, ‘McIntosh’ and ‘Redcort’, respectively, to 2.40 ± 0.71, 4.55 ± 0.15, and 6.24 ± 0.85 in Gala’, ‘Cameo’, and ‘Honeycrisp’, respectively. Although commercial fruit wax influences gaseous 1-MCP accumulation, the comparable accumulation patterns in unwaxed whole and fresh-cut apple fruit suggest that epidermal tissue/native waxes alone do not account for cultivar differences.     

Detection of mast cell degranulation by fluorescent molecular diffusion dynamic measurement

AIM：To establish a rapid in vitro method for mast cell degranulation tracing by raster image correlation spectroscopy (RICS). METHODS：RBL-2H3, a basophilic granulocyte mast cell line transfected with CD63-GFP plasmid, was used for evaluating the methods, including β-hexosaminidase (HEX) colorimetric assay, scanning electron microscopy (SEM) and RICS in the detection of mast cell degranulation. The sensibilities of these methods were compared. RESULTS：The sensitivities of β-HEX colorimetric assay and SEM were 5 mg/L and 3.9×10-2 mg/L, respectively. RICS detection showed obvious decrease in the diffusion coefficient at dose of 3.9×10-2 mg/L. CONCLUSION：Fluorescent molecular diffusion dynamic measurement can be used for rapid tracing of allergic substances in vitro. According to the results, RICS can achieve nearly the same extent of sensitivity as the SEM does and is far more sensitive than β-HEX colorimetric assay. Compared with SEM, RICS has several advantages: it is faster, simpler and cheaper; it can be used in living cells; it is more suitable for rapid in vitro allergenic compounds tracing. Therefore, RICS is applicable in clinic allergic antigen screening and may also be used in pharmaceutical quality control.     

Mass transport studies of model migrants within dry foodstuffs

Cereals are widely consumed foodstuffs and it is therefore important to take them into account when estimating consumer exposure to packaging-related chemicals. The mass transport of three model migrants (diphenylbutadiene, triclosan and BHT) from low-density polyethylene (LDPE) within dry foodstuffs of different particle size (rice and wheat flour) was studied because of the relationship between consumer exposure and possible harmful effects on human health. The conditions that most affect the mass transport of substances within dry foods are evaluated and discussed. The diffusion coefficients (D_F) for diphenylbutadiene (DPBD) and triclosan in the studied foodstuffs were estimated. The D_F values for DPBD and triclosan in wheat flour at 25 °C were 7.1 × 10⁻⁸ cm²/s and 3.3 × 10⁻⁸ cm²/s, respectively. The D_F values for DPBD and triclosan in rice at 25 °C were 4.7 × 10⁻⁸ and 4.3 × 10⁻⁸ cm²/s, respectively. BHT displayed different behaviour and other tests were therefore carried out to elucidate the associated mass transport process.     

拟Shannon区间小波的构造及其在数值逼近中的应用

为克服拟Shannon小波变换边界效应明显，导致计算精度下降的缺点，根据插值小波的概念构造了拟Shannon区间小波，给出了在对连续函数进行数值逼近时，配置点参数j=4，5时的数值计算结果。随着j的增大x=0处的误差越来越突出，且逼近精度越来越高，而边界处的逼近误差并不大，即使j=4时，边界处也没有明显的震荡现象。与拟Shannon小波相比，拟Shannon区间小波不仅精确度更高，而且能有效消除边界效应。     

The potential of microdialysis to monitor organic and inorganic nitrogen compounds in soil

Plant nitrogen (N) acquisition is strongly controlled by the concentration of available inorganic and organic N in the soil solution and by biogeochemical processes in the rhizosphere. However, until now it was hardly possible to reliably estimate plant-available N in soil microsites. Here, a novel microdialysis approach based on passive diffusion sampling is presented and compared qualitatively and quantitatively with lysimeter and soil extraction techniques when analyzing two contrasting boreal soils. Further, preliminary dialysis membrane calibration issues for sampling plant-available N compounds are discussed. Due to its miniaturized design microdialysis was shown to be a suitable tool for continuous sampling of ammonium, nitrate and free amino acids from the soil solution with only minimal disturbance of the soil structure. Microdialysis proved to be outstanding regarding the possible spatial (<0.5 mm) and temporal (<30 min) resolution of soil solution N chemistry. The different methods for soil N sampling resulted in significantly different results. In lysimeter and soil extraction samples, nitrate and ammonium were found at the highest concentrations, while results from microdialysis revealed that the pool of plant-available amino acids was contributing most to the total N pool tested. Application of a standard N solution to the tested soils led to an immediate peak of recovery via the microdialysis probes followed by a rapid decrease due to the formation of a depletion zone at the probe surfaces. Therefore, this relatively new technique will not only provide essential data on diffusion rates of a variety of N compounds in the soil but might be used for monitoring quantitative and qualitative changes in plant-available N in soil microsites such as the rhizosphere.