对草鱼、鲢、鳙、团头鲂鱼种阶段的RNA／DNA的初步研究

本文对草鱼、鲢、鳙、团头鲂4种养殖鱼类在鱼苗期、1龄期、2龄期的RNA和DNA含量进行测定．结果指出RNA／DNA的变化规律与鱼类的生长情况一致，因此，RNA／DNA可以怍为评定这4种养殖鱼类在鱼种阶段生长的指标。     

淡水养殖鱼类死后生化变化及其对鲜度质量的影响

本文采用不同致死方法研究究死前不同生理状态对死后ATP及其相关物质的生化变化，并结合编、鲢、草鱼的部分K值测定结果，考察了鱼体在僵硬前期与全僵期的鲜度质量变化。测定结果表明：（1）活杀、挣扎死和半死的精，死后最初ATP和乳酸含量与达到全僵的时间直接相关，死前肌肉ATP和糖原消耗的有无和程度是决定其死后达到全僵时间长短与活杀效果大小的根本因素，因而对改进保鲜技术具有重要指导意义。（2）编死后达到全僵的时间与IMP达到最高值的时间一致，随后IMP缓慢下降，HxR及K值缓慢上升，达到解僵前的IMP仍保持在较高的水平。（3）不同季节的镛、鲢和草鱼死后达到全僵时的K值均基本保持在20％以内的高鲜度范围，但达到解僵时的K值，仅在解僵时间短的夏季和春季可能保持在20％以内，对在解僵时间长的秋季和冬季，均超过20％，甚至接近40％．表明鲜度质量逐渐下降。     

Silver thiosulphate: An experimental tool in plant science

The anti-ethylene properties of silver thiosulphate (STS) are reviewed. Because of the specificity of the silver ion in STS, ethylene sensitive and non-sensitive components can be distinguished in studies on the effects of ethylene on plant growth and development. The ability of STS to prevent wilting in cut flowers and petal drop in potted flowering plants, and to induce sex transformations in female plants, together with its relative ease of application and low cost per plant, are arguments in favour of using STS in commercial horticulture.     

Controlled release of avermectin from porous hollow silica nanoparticles

Porous hollow silica nanoparticles (PHSNs) with a diameter of ca 100 nm and a pore size of ca 4.5 nm were synthesized via a sol-gel route using inorganic calcium carbonate nanoparticles as templates. The synthesized PHSNs were subsequently employed as pesticide carriers to study the controlled release behaviour of avermectin. The avermectin-loaded PHSN (Av-PHSN) samples were characterized by BET, thermogravimetric analysis and IR, showing that the amount of avermectin encapsulated in the PHSN carrier could reach 58.3% w/w by a simple immersion loading method, and that most of the adsorption of avermectin on the Av-PHSN carrier might be physical. Avermectin may be loaded on the external surface, the pore channels in the wall and the inner core of the PHSN carriers, thus leading to a multi-stage sustained-release pattern from the Av-PHSN samples. Increasing pH or temperature intensified the avermectin release.     

C_(18)键合磁珠固相萃取-液质联用检测蜂王浆中磺胺二甲嘧啶残留

[目的]建立一种应用C18键合磁珠固相萃取-液质联用检测蜂王浆中磺胺二甲嘧啶残留的方法。[方法]MCX固相萃取小柱联合C18磁珠对蜂王浆进行前处理,用HPLC-串联质谱仪对净化后样本进行检测。[结果]该方法的线性范围是5～80μg/kg,相关系数0.993 1。添加水平为5、10、20μg/kg时各种化合物的平均回收率范围为93%～104%,RSD值均不大于11.3%。[结论]该方法简单、快速,结合自动化设备,可实现蜂王浆样品中磺胺二甲嘧啶测定前处理的自动化。     

Influence of felling season,drying method and within-tree location on the brinell hardness and equilibrium moisture content of wood from 27–35-year-old Betula pendula

The Brinell hardness and equilibrium moisture content (EMC) were measured from thinning-aged silver birch wood. Wood material both from the trees harvested in the first commercial thinning and from trees remaining on site after the thinning was included. The average Brinell hardness was 19.40 MPa. It correlated significantly with the basic density of wood. With respect to the distance from the pith, the Brinell hardness of air-dried wood was higher than that of artificially dried wood. The average EMC of the conditioned (20°C, 65% relative humidity) wood was 12.0%. The EMC of the wood also varied, with the EMC being higher for air-dried wood than for kiln-dried wood. EMC was the highest at a distance of 30–40 mm from the pith, decreasing towards both pith and log surface. Seasonal variation in both the Brinell hardness and the EMC of the wood was found. It was presumed to be a consequence of season-dependent physiological changes in trees.     

Current growth differences of Norway spruce (Picea abies), Scots pine (Pinus sylvestris) and birch (Betula pendula and Betula pubescens) in different regions in Sweden

Abstract

The choice of species in forestry is important, and a real issue as large areas of wind-damaged forest land in southern Sweden need to be regenerated. To compare the growth potential between the most common tree species in Sweden, ratios between site quality derived from site index values determined with site properties were used. A regression function to determine site index for birch from site properties was used to complement the known relationships between site properties and site index for spruce and pine. In large regions of Sweden the distribution of site quality classes was calculated to compare the special characteristics and demands of the three species. On average, the growth difference for pine compared to spruce was about 60% in southern Sweden and 95% in northern Sweden. Corresponding figures between birch and spruce were 40% and 60%. Birch was expected to produce around 60% of pine in northern Sweden and about 70% in southern Sweden. However, it must be stressed that the comparison is based on survey data encompassing mainly naturally regenerated birch, whereas spruce and pine are mainly planted.     

Browsing by large herbivores on Scots pine (Pinus sylvestris) seedlings in mixture with ash (Fraxinus excelsior) or silver birch (Betula pendula)

Abstract

Food selection by large herbivores occurs at a hierarchy of scales, for example landscape, patch or plant. Several hypotheses regarding food plant selection on patch or plant level have been developed. In this cafeteria-type design field experiment, conducted during one winter immediately after planting, we tested the effect of species mixture on browsing by large herbivores (mainly roe deer) on Scots pine seedlings in mixture with seedlings of ash (highly preferred) or silver birch (less preferred). Browsing on Scots pine was not affected by species mixture, neither in terms of the number of browsed pines nor browsing intensity. Instead, browsed biomass was positively and significantly correlated to the total biomass available for browsing. Also, there were differences due to species, with ash being most browsed (44.6%), followed by Scots pine (18.9%) and silver birch (11.6%). Browsed biomass per browsed seedling, however, was largest for Scots pine. In addition, browsed seedlings were initially taller compared to unbrowsed seedlings for all species. The main management implication in this study is that the species mixture did not influence large herbivore browsing on Scots pine seedlings. Hence, removing or discouraging more (or less) attractive browse species in early stages of pine regeneration activities seems unnecessary from the point of large herbivore browsing.     

C18-磁性纳米颗粒萃取虾肉中氯霉素残留

建立了一种用C18键合磁珠固相萃取虾肉中氯霉素残留的方法。在Fe3O4超顺磁性纳米颗粒的表面键合C18基团,制备双功能反相萃取颗粒。用该颗粒对样品中的氯霉素残留进行固相萃取,对结合时间、温度、磁珠用量等因素进行了优化,建立磁珠法兽药残留固相萃取方法。用标准方法(SN/T 1864-2007)对萃取所得产物进行检测。经过优化,C18键合磁珠的最佳萃取条件为50℃结合5 min,用1 mL甲醇洗脱3次。检测结果显示该方法具有良好的精密度和回收率。在0.1～10μg/kg之间具有良好的线性关系,相关系数为0.9941,检出限为0.1μg/kg。该方法灵敏度高、重现性好、准确度高,可满足虾肉中氯霉素残留检测的需要。