两种不同镁盐在牛粪堆肥高温期的保氮效果研究

利用恒温培养箱模拟堆肥高温期,添加硫酸镁、磷酸二氢钾和含镁废渣,研究磷酸铵镁(MAP)反应中各成分的保氮效果以及含镁废渣作为堆肥过程中氮素固定剂的可行性。结果表明:添加镁盐固定剂显著降低了堆体中的pH值,减少了氮素损失。同时添加硫酸镁和磷酸二氢钾的保氮效果最佳,添加相同比例的含镁废渣和硫酸镁的保氮效果无显著差别。含镁废渣添加量的保氮效果与其添加量成正相关,添加质量比为2%、4%、8%的含镁废渣的保氮率分别为6.15%、10.13%、19.51%。添加镁盐会提高堆体中的EC值,降低GI值,各处理均可达到腐熟。说明可以利用镁盐作为堆肥保氮固定剂,而含镁废渣因其价格低廉,更具应用前景。     

Dietary mannitol increased the absorption of calcium and magnesium in rats

The effect of mannitol on bone‐related mineral absorption and retention and the mechanism was investigated in this study. Fourteen 8‐week‐old male Wistar rats in experiment 1 and same number and age cecectomized Wistar male rats in experiment 2 were divided into two subgroups of seven animals, respectively, fed diets containing 0 or 4% mannitol for 28 days. Mineral balance tests were determined twice during days 8–12 and days 22–26, and the rats were slaughtered on day 28 both in experiment 1 and experiment 2. The whole caecum and colon were collected with the content to analyse tissue weight, content weight, content's pH and moisture, organic acids' concentration and mineral levels. In experiment 1, Ca absorption and retention and Mg absorption were significantly increased by mannitol feeding during days 8–12. Caecal total weight, tissue weight and content weight were increased, the pH of caecum and colon was reduced, and the concentrations of caecal short‐chain fatty acids (SCFAs) were modified by mannitol feeding. In experiment 2, during days 8–12 and days 22–26, Ca absorption and retention were significantly lowered by mannitol feeding in cecectomized rats; however, mannitol feeding decreased Mg absorption during days 8–12, but did not impact Mg retention. Colonic total weight, tissue weight and content weight were significantly increased, and colonic pH was reduced by mannitol feeding. In conclusion, dietary mannitol increased the absorption of Ca and Mg and the caecum markedly contributed to this promoting effect of mannitol.     

A free-choice intake of mineral blocks in beef cows during the grazing season and in winter

A herd of 25 beef cows were offered four types of mineral blocks (A, B, C, D) with a different Ca to P ratio (A 0.6:1, B 0.8:1, C 2:1 and D 3.6:1). The Mg content was identical in all blocks whereas the Na content was equal in B, C and D, while the Na content in A block was double. The mineral block intake was monitored for 1 year, which was broken down to the grazing period (Pa) and the winter period (Wi). The intake of pasture grass and winter forage was assessed and the feed chemical composition was analysed; based on the obtained values, a macroelement balance (for Ca, P, Mg, Na and K) was calculated.The results showed the forage diet met requirements for all the observed macroelements (except in Na). The macroelement intake from forage was considerably higher than from mineral blocks. There were significant seasonal (Pa versus Wi) differences in B and C blocks intake. The consumption of D block was relatively invariable all year round; block A was refused in both seasons though it contained the highest amount of highly deficient Na.It can be concluded that mineral content in forage meets beef cattle requirements for Ca, Mg and K, P content is just satisfactory, and Na content is insufficient. It appears that cows control, to some extent, the Ca to P ratio in their diet by choosing the appropriate type of mineral block. However, the preference or refusal of some types of mineral blocks regardless of the season suggests the influence of other factors affecting mineral block intake which were not the subject of our observation.     

羧甲基壳聚糖对Mg~(2+)的吸附性能研究

研究羧甲基壳聚糖对Mg2+的吸附作用,探讨了溶液的pH、吸附时间、温度等因素对吸附率的影响。实验表明,在pH值为4~5时,羧甲基壳聚糖对Mg2+的吸附性能很好,其饱和吸附容量为106mg/g,方法的相对标准偏差为9.6%。     

Mg2Si单轴应变的结构和电子性能

基于密度泛函理论的第一性原理计算方法研究了Mg2 Si半导体沿[001]方向单轴应变下的结构、力学性质以及电子性质.计算结果表明：无应变时晶格参数和弹性常数与其他理论及实验值吻合的很好.施加应变后,其与应变方向垂直的晶格常数随应变值呈近似线性变化.通过应力-应变曲线和Born力学稳定性判据,确定了Mg2Si化合物在拉伸、压缩过程中的稳定范围和理想强度.Mg2Si的电子布居和电子态密度分析,表明Si-Mg之间的显示离子键特性,并给出了在拉伸压缩过程中Mg和Si原子轨道电子对总的态密度影响.     

基于卤水的养殖用水中Ca2+/Mg2+对凡纳滨对虾生长及体内SOD和AKP的影响

淡水稀释取自盐场的卤水,调节Ca2 、Mg2 的质量浓度和比例,设置系列梯度,进行凡纳滨对虾的养殖试验,测定生长比速及超氧化物歧化酶(SOD)和碱性磷酸酶(AKP)的酶活性。试验表明,过高或过低的Ca2 质量浓度都会影响凡纳滨对虾的存活和生长,在Ca2 质量浓度为320 mg/L,Ca2 /Mg2 为1∶2.5时,其存活与生长最佳;同时SOD和AKP酶活性也最高。酶活性可以指示凡纳滨对虾的生长状况。     

水体中Ca2+、Mg2+、K+对南美白对虾淡化苗生存的影响

通过南美白对虾淡化苗在放养水体不同Ca^2 、Mg^2 、K^ 浓度下成活率的试验，初步阐明了水质因子对淡化苗成活率的影响，提出了淡化苗在投放淡水养殖中水质调配的要求，以保证放苗的成活率。     

交联碱木质素--聚乙烯醇基钾镁缓释膜肥对钾、镁的缓释性能

为了提高工业碱木质素的利用率和扩大其应用范围,以工业碱木质素和聚乙烯醇(PVA)为原料、甲醛作为交 联剂、添加硫酸钾和硫酸镁制备交联碱木质素-聚乙烯醇基钾镁缓释膜肥。采用FTIR-ATR 方法测定缓释膜肥的化 学结构,并用淋溶实验检验缓释膜肥对钾、镁的缓释作用。结果表明:1)缓释膜肥在3 260 cm-1 左右的峰变小变宽, 1 332.57 cm-1 处吸收峰消失,1 145.51 ~983.52 cm-1 范围内吸收峰变大,说明碱木质素、聚乙烯醇经甲醛交联有化 学反应发生。2)与纯PVA 交联薄膜相比,碱木质素的加入不利于钾的缓释,而适量的碱木质素有利于镁的缓释, 碱木质素加入量可达20%。随着甲醛加入量的增大,钾累积释放率减小;适量甲醛有利于镁的缓释,但随着甲醛加 入量的增大,缓释膜肥对镁的缓释性能降低。对镁的缓释,甲醛的合适加入量为3.59%。缓释膜肥对钾的缓释主 要是分子结构的物理阻挡作用,而镁缓释除了物理阻挡作用还有木质素的螯合作用。3)对缓释膜肥的动力学试验 数据进行拟合,钾缓释的4 种模型拟合程度都很高,其中Higuchi 模型拟合程度最高,决定系数为0.994 1,说明钾缓 释行为遵循Fick 扩散。镁缓释模型中Ritger-Peppas 模型的拟合程度最高,决定系数为0.974 2,其缓释指数(0.5 n1.0)表明镁缓释行为是扩散和溶蚀综合作用的结果。      

内蒙古锡林浩特地区土壤-牧草-家畜系统中Cu、Fe、Zn、Mn、Mg、Se六种元素含量的分析

对内蒙古锡林浩特地区土壤，牧草，家畜（羊）被毛中6种元素含量进行了测定。结果表明：土壤硒含量于缺乏的临界水平；尖草，羊草及针草中锌含量低于羊正常生长对锌的需求数量，兔毛草及羊草中的硒的含量很低，不能满足其正常生长需要，被毛中硒含量低于临界值，提示羊群缺硒。