基质固相分散-离子色谱法测定卷烟样品中的糖和多元醇

[目的]研究用基质固相分散法提取净化,离子色谱法测定卷烟中的糖和多元醇。[方法]将样品与石墨化碳黑球（w／w,1：4）充分研磨后装柱,用热水洗脱,洗脱液中的糖用离子色谱测定。以CarboPacMAl（4×250mm,5μm）阴离子交换柱为固定相,0．5mol／LNaOH溶液为流动相分离,脉冲安培检测器检测。[结果]一次进样可实现卷烟样品中甘油、丙二醇、木糖醇、山梨醇、葡萄糖、果糖、蔗糖、麦芽糖和半乳糖9种成分的同时测定。方法加标回收率在94．6％～105．7％,相对标准偏差小于3．0％,检测限均小于50μg/L.[结论]该方法重现性好,准确可靠,回收率较好,可用于实际烟草样品中糖和多元醇的测定。     

手术致奶牛真胃左方变位对其瘤胃、真胃和血液相关指标的影响

[目的]建立奶牛左方真胃变位模型,为深入探讨该病的发病机理和早期诊断方法提供理论依据。[方法]选取经产荷斯坦奶牛6头,随即分为2组,利用手术法制作奶牛左方真胃变位模型,并于手术前后采样测定。[结果]奶牛真胃人工变位后,瘤胃液和真胃液中的K＋和Cl-浓度升高（P〈0.05）,Na＋浓度降低（P〈0.05）;而血清中Na＋浓度升高,K＋,Cl-和Ca2＋的浓度降低。瘤胃液中pH值和乙酸浓度降低（P〈0.05）,丙酸和丁酸的含量上升;真胃液中乙酸、丙酸的含量上升,丁酸和pH值含量下降。[结论]真胃人工变位可导致奶牛瘤胃和真胃内环境发生改变,酸度增加,发酵类型改变,进而影响奶牛的生理功能。     

离子束注人技术在食用菌育种上的应用进展

离子束是一束具有能量的带电粒子．注入细胞内可引发染色体变异。离子注入诱变育种以变异率高、变异谱宽、变异稳定快、技术稳定可靠、简便易行的优点被广泛地应用于植物、微生物育种和外源DNA大分子转导。在食用茵诱变育种方面选育了耐高温的杏鲍菇、阿魏菇,优质生物转化率高的白金针、鸡腿菇、姬松茸,经济高效的灵芝漆酶茵株,多糖含量显著提高的香菇、猴头菇、阿魏菇等优质菌株,与茵丝体生长速度和生物转达化率呈正相关。     

Incidence of swallowing during exercise in horses with dorsal displacement of the soft palate

Reasons for performing study: The relationship between dorsal displacement of the soft palate (DDSP) and swallowing is unclear. Objective: To quantify the relationship between DDSP and swallowing in horses at exercise. Hypotheses: The frequency of swallowing increases immediately prior to DDSP in horses at exercise. Methods: Videoendoscopic and upper airway pressure data were collated from horses with a definitive diagnosis of DDSP at exercise. Horses with no upper airway abnormalities were matched by age, breed and sex and used as controls. Sixty‐nine horses were identified with a definitive diagnosis of DDSP during the study interval. Airway pressure data were available for 42 horses. Results: The majority of horses displaced at high exercising speeds while accelerating; a smaller number displaced during deceleration after peak speed had been reached. Horses swallowed significantly more frequently in the 1 min immediately preceding DDSP than in the control horses at equivalent speeds. DDSP at exercise results in a significant increase in tracheal expiratory pressure, a significant decrease in pharyngeal expiratory pressure and a significantly less negative pharyngeal inspiratory pressure compared to matched controls and compared to the pressures during the 1 min interval prior to DDSP. There was no significant difference between any measure of airway pressure before or after a swallow when examined at each time interval in the DDSP population. Conclusions: The frequency of swallowing decreases with increasing speed in normal horses. In contrast, the frequency of swallowing increases immediately prior to onset of DDSP. This is not a result of pharyngeal and tracheal pressure changes. Potential relevance: The increased frequency of swallowing observed prior to DDSP may be related to the aetiology of the disease.     

Tree morphology responds to neighbourhood competition and slope in species-rich forests of subtropical China

Trees are able to respond to their local biotic and abiotic environment with morphological adjustments which improve resource acquisition and, thus, growth. In forests, light is broadly recognised as one of the major factors determining growth, and morphological responses comprise changes in crown architecture and stem stature. On sloping terrain, the interplay of phototropism and gravitropism may further affect morphological growth characteristics. However, different tree species are expected to show species-specific responses. In this study, we analysed three growth characteristics of tree individuals belonging to four species of two functional groups (evergreen: Schima superba, Castanopsis eyrei, deciduous: Quercus serrata var. brevipetiolata, Castanea henryi) in a species-rich Chinese subtropical forest. Crown projection area, relative crown displacement and stem inclination were related to biotic (local species richness, functional richness, competition, stand age) and abiotic (slope aspect and inclination, soil depth) variables in the local neighbourhood of the tree individuals. We hypothesised that (i) there are species-specific differences in the morphological response of crown architecture and stem stature and (ii) that crown size and asymmetry as well as stem inclination are influenced by both, biotic and abiotic factors. In contrast to our expectations we were unable to reveal any species-specific differences in any of the three growth characteristics. The results of mixed effects models showed that crown area was mainly affected by the target tree's dbh and biotic variables related to neighbours (competition, functional diversity), whereas stem inclination was mainly influenced by slope. Relative crown displacement was influenced by both, biotic and abiotic variables. We conclude that growth responses resulting in crown displacement and stem inclination seem to be an important mechanism to ameliorate foraging for light in our study area, but that these responses appear to be species-independent. The interplay of stem inclination and crown displacement allows for a plastic response of tree individuals in biotically and abiotically heterogeneous environments. Our results indicate that forest management in this region should focus on functionally diverse stands which are promoting crown area positively resulting in increased growth rates of individual trees.     

Displacement of US‐1 clonal lineage by a new lineage of Phytophthora infestans on potato in Kenya and Uganda

Phytophthora infestans, the pathogen responsible for causing late blight in potato and tomato, is a rapidly evolving and highly adaptable pathogen. Following the appearance of a new clonal genotype in Kenya (KE‐1 lineage) in 2007, there was a need to document possible displacement of the US‐1 genotype by the newer lineage. Samples from Kenya (260) collected on potato and from Uganda collected on potato (134) and tomato (32) were genotyped with simple sequence repeat (SSR) and mitochondrial DNA haplotype (mtDNA) markers. Results show that, four years after its discovery, the KE‐1 lineage has completely displaced the US‐1 lineage on potato in Kenya. The KE‐1 lineage has also migrated into Uganda through the eastern part of the country that borders western Kenya. All potato samples from eastern Uganda were of the KE‐1 lineage. Moreover, samples from eight fields in western Uganda were also of the KE‐1 lineage, which is in agreement with an ongoing westward displacement. However, the new lineage has not displaced the old lineage on tomato, as all samples from tomato were US‐1. Principal coordinate analysis (PCA) scatter plots revealed clustering that indicated separation between the lineages and also between the subpopulations of the US‐1 lineage on potato and tomato.     

适用于梯级泵站压力管道的传感器优化布置方法

为解决梯级泵站压力管道传感器优化布置问题,提出一种基于有效独立-总位移法的传感器优化布置方法。该方法针对有效独立法所选测点能量较小的缺陷,将测点的总位移以权重的方式加入传感器优化过程中,并保留有效独立法的优点,最终得到独立性较好且满足能量要求的测点。以景泰压力管道为例,运用该方法进行传感器优化布置,并与传统有效独立法比较,通过模态置信准则、Fisher信息矩阵值、最大奇异值比以及总位移等指标评价2种方法的优劣。结果表明,有效独立-总位移法得到的测点在满足独立性的前提下,增加了测点信息量,可观性更好。优化前后实测数据的比较分析,表明该方案对实际结构检测具有较好的适用性,是一种实用有效的传感器优化布置方法。     

基于双向流固耦合的贯流式水轮机动力特性分析

为了深入研究流固耦合作用对贯流式水轮机转轮动力特性及内部流场的影响,文中采用商业软件CFX和ANSYS APDL对贯流式水轮机流体域和固体域进行耦合求解,分析了耦合作用对结构应力及应变的影响,并将耦合数值计算得到的转轮外特性与实测值进行了对比。结果表明:考虑耦合作用后,转轮的效率、水头与耦合前相比都有不同程度的下降,最大值分别为0.6%、0.21 m。同时在靠近叶片出水边轮缘附近,耦合后压力面与吸力面压力差有所下降,说明耦合作用会降低转轮的水力性能。2种耦合计算方法求解得到的叶片的等效应力分布基本一致,应力集中都出现在转轮叶片与枢轴法兰联接处,同时双向耦合下最大等效应力的主频与单向耦合相比有明显下降的趋势,由于双向耦合考虑了结构在运动过程中周围水体与结构的相互影响。该研究为实际工程中准确地进行转轮的水力性能预估和叶片结构在水中瞬态响应计算提供了参考。     

Anionic Exchange Membranes as a Soil Test for Nitrogen Availability

Abstract

A better understanding of nitrogen (N) availability to crops remains an essential key for a productive and safe production system. The main objective of this study was to evaluate the potential of anionic exchange membranes (AEMs) as part of a soil‐testing procedure to predict in situ soil NO₃‐N availability for forage and corn produced in eastern Canada. The AEMs were buried in the surface horizon (0–15 cm) at four experimental sites for forage and at one site for corn. Treatments consisted of five NH₄NO₃ rates (0, 60, 120, 180, and 240 kg N ha^?1) in forage and of six anhydrous ammonia (0, 50, 100, 150, 200, and 250 kg N ha^?1) in corn production. In all sites, NO₃ ^? adsorbed on AEMs (NO_3AEMs) increased significantly with N fertilizer rates, indicating the ability of the AEMs to detect differences between N fertilizer treatments and to predict the soil N availability to crops. The NO_3AEMs fluxes were significantly related to soil NO₃‐N concentration as extracted by water or KCl (0.66≤R²≤0.95). Significant relationships between crop N uptake and NO_3AEMs were obtained (0.52≤R²≤0.94), suggesting that AEMs can be used as an index of soil N availability. Results indicated that AEMs provide a reasonably accurate evaluation of N availability to forage and corn. Because of their low cost, simplicity, and consistency over years, soils, and crops, AEMs could be efficiently used in soil N availability analysis.     

Analysis of cationic elements in liquid samples by x‐ray

Abstract

Plant analyses methods have expanded immensely to document plant mineral element deficiency and toxicity disorders and to note mineral element interactions. Experiments were conducted to determine the feasibility of using cation exchange papers for the extraction of cationic elements from solutions to be analyzed by x‐ray fluorescence. The cationic elements Al, Fe, Mn, Zn, and Cu were effectively extracted from solutions by one exchange resin paper disk if solutions were passed several times through the exchange resin paper. Calcium and Mg were extracted from solutions if two or three separate exchange papers were used, and K was not extracted from solutions with the use of up to five separate exchange papers. The relatively high concentrations of K in solutions and the relatively low exchange capacity of ion exchange resin papers apparently prevented the effective removal of K from solution. The detectability limits on the exchange resin disks by this technique were <2.8 μg Al, 0.5 μg Fe, 0.10 μg Mn, 0.10 μg Zn, and 0.08 μg Cu. Extraction of cationic elements from solutions for x‐ray analysis appeared practical and relatively rapid for Al, Fe, Mn, Zn, and Cu, less practical for Ca and Mg, and impractical for K.