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。     

利用产黄青霉培养液的上清液生物合成纳米银影响因素的研究

[目的]对利用产黄青霉培养液的上清液生物合成纳米银的影响因素进行研究。[方法]利用紫外-可见光谱和投射电镜研究硝酸银起始浓度、pH值、光照和微波辐照等条件对合成反应速率及合成纳米银粒径的影响。[结果]硝酸银的最佳起始浓度为2 mmol/L;随着反应体系pH值的升高,反应速率随之加快,合成纳米银粒子的粒径变小;光照和微波辐照均能有效促进纳米银的合成。[结论]该研究为实现纳米银的可控合成提供了试验基础。     

长丰鲢生长性状相关微卫星标记的初步筛选

为了筛选出与长丰鲢生长性状相关的分子标记,以指导其种质鉴定和选择育种工作,实验利用15个多态微卫星标记,对6、17和36月龄长丰鲢进行了遗传多样性和生长性状关联分析.结果 显示,各月龄长丰鲢的观测杂合度(Ho)和期望杂合度(Hc)均高于0.5,PIC均值分别为0.555、0.445和0.490,表明各月龄长丰鲢群体均具...     

Long-term dynamics of leaf and root decomposition and nitrogen release in a grey alder (Alnus incana (L.) Moench) and silver birch (Betula pendula Roth.) stands

The decomposition of the leaf litter, fine roots (d?<?2?mm) and coarser roots (2?≤?d?<?5?mm) of grey alder and silver birch, as well as of α-cellulose sheets using the litterbag method was studied in two experimental stands on Podzoluvisol soils in Southern Estonia. For both tree species, the coarser roots decomposed faster than the fine roots, (p?<?.05), tree species did not affect the decomposition rate of the roots (p?>?.5). The nitrogen (N) input to soil from aboveground litter was multiple times higher than the N flux from roots. The remaining relative ash-free mass of the leaves of grey alder and silver birch after three and a half years was similar. After 11 years the remaining relative ash-free mass of the fine and coarser roots of grey alder still accounted for around 10% of the initial value. For silver birch the remaining value was around 20% after 9 years. The litterbag method to underestimates in fertile soils the decomposition of organic matter and thus did not reflect the actual dynamics of decomposition.