微波消解塞曼石墨炉原子吸收法测定大米中微量镍

利用微波消解技术处理样品,用塞曼石墨炉原子吸收法测定了大米中的镍,该方法具有简便、快速、结果准确可靠的优点。测定结果表明:镍的浓度在0~25μg/L范围线性良好,相关系数0.9991,镍的加标回收率为97.3%~104.2%;测定结果的相对标准偏差为1.9%,检出限为0.152μg/L。     

球磨仪-微波消解石墨炉原子吸收法测定土壤中的铅元素

采用行星式球磨仪制样、微波消解、石墨炉原子吸收法测定了土壤样品中的铅含量,球磨仪制样颗粒超细且均匀,干净卫生,不存在扬尘污染;微波消解仪操作简便快速,消耗试剂少,密闭消解,酸污染少。结果表明:测定土壤标准样品GSS-22的相对误差为1%,GSS-26相对误差为1.2%,测定实际试样相对标准偏差均值为1.6%,均满足试验要求。     

原子吸收石墨炉法测定固体废物中钡

采用醋酸缓冲溶液对固体废物样品进行了浸提,经微波消解后,用原子吸收石墨炉法测定了消解液中的钡。此方法检出限为4．15μg／L ,测定下限为16．6μg／L。相对标准偏差为2．93％,实际样品加标回收率在87．5％～107．0％之间,具有检出限低、灵敏度高、精确度和准确度高等优点,适用于固体废物中钡浸出毒性的测定。     

石墨炉原子吸收标准加入校正法测定土壤中痕量镉

选用硝酸-氢氟酸-高氯酸、硝酸-盐酸-氢氟酸-高氯酸2种消解体系,建立了石墨炉原子吸收标准加入校正法测定土壤中镉的方法,能够实现对土壤镉的准确测定.以硝酸钯为基体改进剂,优化灰化温度为550℃,原子化温度为1600℃.分别取土壤标准样品GBW07452、GBW07388经微波消解或全自动消解后,定量加入到标准溶液系列中...     

石墨炉原子吸收光谱法测定2,3,4,4'-四羟基二苯甲酮中痕量铁

建立了用石墨炉原子吸收光谱法测定2,3,4,4′-四羟基二苯甲酮中痕量铁的方法,用Zeeman/200型原子吸收分光光度计,在干燥温度120℃、灰化温度700℃、原子化温度2400℃、空心阴极灯电流3mA时,测定其铁的含量.铁质量浓度在2.5～10.0μg/L范围内与吸光度呈良好的线性关系,重复性(RSD)为1.99%,测定方法的回收率为94.2%,本方法精密度好,重现性好,可满足2,3,4,4′-四羟基二苯甲酮中痕量铁的原子吸收测定要求.     

不同品种核桃仁中钙、铁、锌微量元素的检测分析

以云南、陕西、山西等6个核桃主产区40个核桃仁试样为原料,采用微波消解-火焰/石墨炉原子吸收光谱仪测定样中铁、锌和钙。结果表明,核桃仁中Fe含量在0.010-0.193mg/g之间,平均含量0.072mg/g;Zn含量在0.005-0.070mg/g之间,平均含量0.036mg/g;Ca含量在0.255-0.660mg/g之间,平均含量0.491mg/g。所测试样中铁元素含量差异较大,其次是钙元素,锌元素含量差异较小。     

桑叶茶元素分析及其保健功能分析

用微波消解技术对样品进行消解,用火焰原子吸收法测定了浙江桐乡桑叶茶中8种矿物元素的含量,结果表明,桑叶茶中的矿物元素含量较高,其中含量最高的是K、Ca、Mg,比茶叶高出3 ～ 6倍,且其比例有利于人体吸收,有较高的营养保健价值,适合各类人群饮用.     

石墨炉原子吸收光谱法测定2,3,4,4'-四羟基二苯甲酮中痕量铁

建立了用石墨炉原子吸收光谱法测定2,3,4,4′-四羟基二苯甲酮中痕量铁的方法,用Zeeman/200型原子吸收分光光度计,在干燥温度120℃、灰化温度700℃、原子化温度2400℃、空心阴极灯电流3mA时,测定其铁的含量。铁质量浓度在2.5~10.0μg/L范围内与吸光度呈良好的线性关系,重复性(RSD)为1.99%,测定方法的回收率为94.2%,本方法精密度好,重现性好,可满足2,3,4,4′-四羟基二苯甲酮中痕量铁的原子吸收测定要求。     

正交试验在石墨炉原子吸收法测定食用菌中铅的应用

通过正交试验优选出了较满意的测定食用菌中铅的石墨炉原子吸收法检测条件,并采用该方法测定了34个食用菌样品中的Pb含量。结果表明:Pb含量测定的最适条件为磷酸二氢铵+硝酸镁混合基体改进剂,加入量10μL,灰化温度600℃,原子化温度1900℃;铅的检出限为0.24ng/mL,回收率为95.5%～100.3%;34个食用菌样品中97%的食用菌铅含量小于2.0mg/kg。     

石墨炉原子吸收法测定核桃仁中重金属铅的含量

采用石墨炉原子吸收光谱法测定核桃仁中的重金属铅的含量,通过对GB5009.12-2010食品安全国家标准食品中铅的测定第一法中提供的前处理方法和条件的研究,确定了较佳的核桃仁消解方法为干灰化法,条件为灰化温度500℃,灰化时间6h。同时,对标准中使用的机体改进剂和其他机体改进剂进行比较,结果表明,添加200mg/L磷酸氢二铵机体改进剂效果较好。本文旨在为合理检测核桃仁中铅含量提供一定科学依据。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。