Polyphosphorylated L-ascorbic Acid: A Stable Form of Vitamin C for Aquaculture Feeds

A protected form of vitamin C, L-ascorbyl-2-poly phosphate (APP), was tested for safety and efficacy in fishes. Phosphorylation of the 2-hydroxyl group protected the 2,3-enediol of L-ascorbic acid against oxidation. When APP was added to feed, about 15% of its vitamin C activity was lost during milling and storing 5–7 d at ambient temperature. Stability of APP in pelleted feeds at 25 or 40 C was up to 83 times or 45 times greater than that of ascorbic acid (AA), respectively. In later tests, trout feed mash, steam-pelleted in triplicate, frozen, and shipped on dry ice before analysis, had 46% loss of AA and no apparent loss of APP. With 16% milling loss (highest detected in trout feeds assayed in initial tests) and 22% storage loss after 90 d, conservative APP mix rates were estimated. Mixing 153 g L-ascorbate-equivalent as APP per metric ton of airdry ingredients (153 ppm) would give 128 ppm in the finished feed after steam-pelleting and 100 ppm after 60–90 d storage at 40 C. Low-temperature extrusion of Oregon-Moist salmon feed reduced AA slightly. Ascorbic acid oxidized in frozen storage and while thawing and, after 12 h at room temperature, only trace amounts remained. Ascorbyl-2-polyphosphate at 0.05 to 0.2 times that of equimolar AA in casein-base or practical feeds supported long-term growth and development in rainbow trout and other fishes. Trout feeding trials with practical feeds in actual production regimens documented APP activity at growth rates approaching the maximum for trout farming. Corrected for greater stability, APP antiscorbutic activity appeared to be comparable to that of AA on a molar-equivalent basis. Similarly, apparent equimolar activity was inferred from estimated equilibrium levels of liver, kidney, and whole-body AA and L-ascorbyl-2-sulfate (AS) after prolonged APP use in trout feeds. Fathead minnow growth and reproduction in egg-to-egg life-cycle tests also confirmed APP safety and efficacy as a stabilized source of vitamin C for feeds. None of the typical lesions of scoliosis, malformed gill lamellae, and crenulated opercles, nor conditions of poor health, anorexia, and eventual torpor seen in vitamin C-deficient controls occurred in trout fed APP. No liver pathology was evident in trout fed APP for 252 d at 1.7 to 3.3 times the National Research Council's recommended vitamin C (equivalent) rates.     

农户参与森林保险意愿的实证分析——以江西为例

对农户参与森林保险意愿进行实证分析,利用Logistic模型对影响农户参与森林保险的各个因素进行回归.结果表明:显著的变量有户主的年龄、家庭收入的主要来源、林业灾害带来的经济损失程度、农户的森林是否经历过灾害、农户对林业保险的了解程度、农户对森林保险的需求态度、森林保险的索赔额度、农户对森林保费的态度、国家补贴保费下的参保态度.     

浅析外来生物入侵与林业外来有害生物防控

本文通过对外来生物入侵的危害、机制和途径的论述,从江西主要林业外来生物入侵现状分析入手,并结合森林健康理论,提出了林业对外来有害生物防控的对策.     

岭峰自然保护区被子植物区系研究

根据野外标本采集并结合相关文献鉴定,对黑龙江省大兴安岭岭峰自然保护区被子植物区系进行了初步研究,结果表明:岭峰自然保护区自然分布的被子植物有577种,隶属74科270属。     

香根草复合农林技术的应用探讨

分析了利用香根草独特的生物学特性,结合农林果业技术在龙胜县山区坡地、荒废地复合种植香根草绿篱、果树,建设灌溉系统,以扶助山区少数民族农民发展经济,减少水土流失,保护生态环境。探讨了香根草叶片手工艺品编织技术。     

应用多元统计分析玉米农艺性状

在作物遗传育种研究中,产量及其相关性状多属于数量性状范畴,这类性状由多基因控制,易受环境影响使其遗传极为复杂,并且性状间常存在复杂相关关系.产量及其相关性状间的复杂关系使得育种中对以产量为目标的选择极为困难.多元统计分析是研究客观事物中多个变量之间相互依赖的统计规律性综合分析方法.合理利用多元统计分析可以加深对性状间相互关系的遗传规律及各相关性状对产量影响的主次和依存关系认识,为新品种选育和改良提供理论依据.对35个玉米品种(组合)的20个农艺性状应用GGE双标图、因子分析和聚类分析研究,结果表明,平均日产量、千粒重、穗长与产量呈显著正相关;20个农艺性状可综合为6个公因子;以6个公因子为综合指标对35个品种(组合)聚类结果聚成17个类群,其中G8、G14、G12、G10和G17为综合性状优良品种(组合).     

两收敛且等值的无界函数广义积分变量代换的存在性与唯一性

本文讨论两个收敛且等值的无界函数广义积分变量代换的存在与唯一性，文中提出并证明了在一定的条件下，这个代换是存在的，也是唯一的。     

带式同步机构中传动滚筒的有限元分析

通过对移栽机中带式同步机构中的传动滚筒进行结构分析,将Pro/E中建立的传动滚筒三维实体模型导入有限元分析软件ANSYS APDL中,建立有限元模型,并施加约束与载荷,进行有限元数值分析,得出传动滚筒的综合应力分布和位移分布,从而掌握传动滚筒在工作过程中的受力和变形情况。同时,与实际的参数要求进行校核与对比,确定危险区域和结构设计缺陷,为后续传动滚筒的设计和优化提供科学依据。     

基于高光谱的油茶籽内部品质检测最优预测模型研究

以油茶籽中油酸、亚油酸、棕榈酸为研究对象,寻求一种油茶籽脂肪酸成分含量的最佳预测模型。首先,利用高光谱成像系统以线扫描方式获取其反射光谱图像,选择感兴趣区域(ROI);然后,对原始光谱进行平滑与多元散射校正(MSC),通过相关性分析和逐步回归分析,得到能反映油酸、亚油酸、棕榈酸含量变化的最佳优化波段;进而对最优波段采用偏最小二乘回归(PLS)方法、主成分回归(PCR)方法及径向基神经网络(RBF)方法组建预测模型。比较这3种方法的建模效果,经外部验证表明:径向基神经网络建立的预测模型效果最好,其油酸、亚油酸、棕榈酸的交叉验证相关系数R分别为0.940 3、0.893 5、0.912 2;校正均方根误差和预测均方根误差分别为0.441、0.174 9、0.066 4和0.351 8、0.184、0.162。     

棉花介电常数单因素实验研究

棉花含水率是收购和加工环节的一个重要参数,电容法是检测棉花含水率的有效手段。为了给棉花含水率的在线检测仪器开发提供基础数据,利用单因素试验研究的方法,研究得到了不同的测试频率、测量电压、容积密度、含水率对机采籽棉、手摘籽棉、皮棉的介电常数的影响规律及影响显著性。分析表明:所有试验因素对介电常数的影响均高度显著,并得到了在特定条件下含水率与介电常数的线性回归方程。研究可为开发在线的高精度籽棉含水率检测仪器提供理论基础。