食糜在矛尾复鰕虎鱼消化道排空速度及其营养含量的变化

选择规格一致、健康无病、初始体质量(43.42±0.75)g的矛尾复鳙虎鱼240尾,随机分到20个水族箱内,每箱12尾.饱食量投喂鲜杂鱼.然后不同时间取样,测定胃、前肠、中肠、后肠内容物的质量及其粗蛋白、脂肪和水分含量,探讨食糜在矛尾复鰕虎鱼消化道排空速度及其营养含量的变化.试验结果表明,矛尾复鰕虎鱼在刚摄食后胃内容物达到最大值,并随着时间的延长减少,至22 h排空为0.线性回归模型能较好地用来模拟食糜在胃中的变化;食糜在前肠、中肠和后肠出现的时间分别为摄食后1、3 h和4 h.达到最大值的时间分别为摄食后12、9 h和10 h.试验结束时(投喂后26 h)前肠、中肠和后肠仍有剩余食糜.食糜中粗蛋白和脂肪含量在胃、前肠、中肠、后肠逐渐降低,但胃中粗脂肪含量高于食糜中的含量,而粗蛋白含量低于食糜中含量.     

Nitrate leaching in a silage maize field under different irrigation and nitrogen fertilizer rates

Quantification of the interactive effects of nitrogen (N) and water on nitrate (NO₃) loss provides an important insight for more effective N and water management. The goal of this study was to evaluate the effect of different irrigation and nitrogen fertilizer levels on nitrate-nitrogen (NO₃-N) leaching in a silage maize field. The experiment included four irrigation levels (0.7, 0.85, 1.0, and 1.13 of soil moisture depletion, SMD) and three N fertilization levels (0, 142, and 189 kg N ha⁻¹), with three replications. Ceramic suction cups were used to extract soil solution at 30 and 60 cm soil depths for all 36 experimental plots. Soil NO₃-N content of 0-30 and 30-60-cm layers were evaluated at planting and harvest maturity. Total N uptake (NU) by the crop was also determined. Maximum NO₃-N leaching out of the 60-cm soil layer was 8.43 kg N ha⁻¹, for the 142 kg N ha⁻¹ and over irrigation (1.13 SMD) treatment. The minimum and maximum seasonal average NO₃ concentration at the 60 cm depth was 46 and 138 mg l⁻¹, respectively. Based on our findings, it is possible to control NO₃ leaching out of the root zone during the growing season with a proper combination of irrigation and fertilizer management.     

泰山赤鳞鱼异地饲养试验

从泰山引进５０尾赤鳞鱼鱼苗，在淄博室内水泥池进行异地饲养试验，经过合理投饵，调控水质，加强管理，试养１０个月，体重增长３５３％，体长增长１７３％，成活率９４％，打破“离开泰山之水，赤鳞鱼不能生存”的古有说法，证明异地饲养可行的，对泰山赤鳞鱼的食性，生长及所适水温，溶氧，ｐＨ值，水肥度，光照等进行了研究。     

Wheat Seed Presoaking for Improved Germination

Seed presoaking improves wheat germination under marginal moisture conditions. The duration of seed presoaking was studied at The University of Arid Agriculture, Rawalpindi, using 10 wheat varieties. Seed presoaking beyond 12 h does not improve germination further, and beyond 21 h, germination rate is drastically reduced.     

预处理对SFE提取月见草种子、被孢霉菌丝体油脂的影响

以月见草种子、被孢霉菌丝体为超临界流体萃取(SFE)的试验材料,研究了不同预处理条件(水分、粉碎度、粉碎方式)在不同萃取压力下对超临界流体萃取油脂得率的影响;确定粉碎度、粉碎方式、水分与油脂萃取之间的关系。     

Early-maturing dual-purpose sorghums: Agronomic trait variation and covariation among landraces

Landrace cultivars represent potentially valuable source material for breeding dual-purpose (grain and stover) sorghums. To characterize the genetic variation and interrelationships for major agronomic traits among potential dual-purpose sorghum landraces, 74 accessions, primarily from Southern Africa, the Sudan, and India, were evaluated in five environments at Patancheru, India. These environments, at 17°N with 520-540 mm rainfall during the growing season, are representative of the major sorghum-growing areas in India and the Sudanian Zone of Western and Central Africa. Significant genetic variation and high heritabilities (P = 0.01, h²= 0.63-0.92) were observed for seedling vigour, grain and stover yields, growth rate and harvest index. Time to flower was correlated with stover yield (r = 0.48, P = 0.01) and an index (I_ev) of total economic value (r = 0.44, P = 0.01) but not with grain yield (r = 0.22, P = 0.05). Grain and stover yields varied independently (r = 0.22, P = 0.05) and were similarly related to I_ev, values (r = 0.79 and r = 0.77 (P = 0.01), respectively). The 13 landraces with the highest I_ev values (adjusted for maturity) had above-average growth rates and harvest indices that ranged from 20 to 38%. Landraces from Botswana and India were more highly represented in the high I_ev set than in the full set of accessions.     

Preharvest and postharvest factors related to off-odours of fresh-cut iceberg lettuce

The influence of different preharvest and postharvest factors affecting off-odour development of fresh-cut iceberg lettuce in low-O₂ modified atmospheres (MA) was investigated. Fresh-cut iceberg lettuce developed undesirable off-odours under low O₂ and elevated CO₂ atmospheres. A strong relationship between CO₂ concentration and off-odour development was observed. Significant differences in off-odour development existed among different cultivars in two harvests in consecutive years. The influence of maturity stage was evaluated, comparing fresh-cut product from immature and over-mature heads with commercial ones. Higher CO₂ concentrations and higher accumulation of ethanol and acetaldehyde were detected in the headspace of MA-packed lettuce from immature heads. Differences in respiration rate of the fresh-cut product from heads cultivated during the winter–spring seasons were around 30%. Respiration rate of fresh-cut iceberg lettuce increased when medium temperature during cultivation increased. Changes in the product weight generated different CO₂ levels which correlated with the production of ethanol and acetaldehyde and other off-odour metabolites related with the lipoxygenase (LOX) pathway such as hexanal, 1-hexanol, and cis-3-hexen-1-ol. Volatile compounds such as cis-3-hexen-1-ol, β-elemene, ethyl acetate and dimethyl sulphide increased their content more than 10 times compared with other volatiles. Moreover, differences in the initial flushed gas-mixture with or without CO₂ showed higher CO₂ concentrations and the development of stronger off-odours when samples were flushed with an enriched CO₂ gas-mixture. In summary, visual quality of fresh-cut iceberg lettuce is important but so are odour and flavour. MAP currently used for fresh-cut lettuce may need some modification to inhibit off-odours and achieve better aroma and flavour qualities for preserving “freshness” of the cut product. Screening for cultivars with low browning potential and fermentation, harvested at optimum maturity stage and with an adequate package design are recommended.     

利用塑料大棚延长对虾交尾期的研究

为提高对虾交尾率，１９９３，１９９４年进行了塑料大棚延长对虾交尾期试验，通过大棚控制交尾水温，采取合理安排雌雄比，调节水质，投喂沙蚕，防治疾病等综合技术措施，２年共出棚交尾虾１２３５２尾，未交尾虾５９２２尾，雄虾５２５２尾，平均交尾率６７．５９％，雌雄虾成活率分别为８７．５４％，６３．００％，共获产值６２６１００元，纯利４４２６００元，平均每尾入棚雌虾净协效益２１．２３元，专家鉴定认为，本研究达国     

水力旋流器在多泥沙河流中应用的研究

利用水力旋流器，对水力机械的润滑、轴封用水进行净化，降低泥沙含量，使之达到技术供水标准。本文研究和分析了水力旋流器的结构、各部构件尺寸与净化泥沙性能的关系；指明了水经过旋流器的压力降的确定，使之既满足泥沙沉降的要求，又要保证供水系统的所需的压力值。     

企业负债经营初探

本文在阐述负债经营为企业带来诸多经济利益的同时，也阐述了它给企业带来的财务风险。控制财务风险的关键在于把握负债经营的适度性。为此，着重论述企业如何通过财务管理手段，并运用一系列财务指标的计算、预测和分析，确定负债经营的最佳度，尽可能地降低负债经营的财务风险