初始碱酸阶段摩尔比对脲醛树脂结构的影响

分别运用传统工艺及低起始甲醛与尿素的摩尔比( F/U)工艺,并进一步分别在酸性阶段降低反应的F/U摩尔比,进行脲醛树脂的合成。借助13 C￣NMR技术,对不同工艺条件下合成的脲醛树脂的最终结构进行了定量分析,并讨论了各反应阶段的F/U摩尔比对脲醛树脂( UF)最终结构的影响。结果表明：降低碱性阶段起始的F/U摩尔比,可有效地降低最终树脂结构中醚键的含量,其中,对直链型醚键的差异较小, Uron环含量的差异较大。通过在酸性阶段加入尿素,由于尿素中的游离氨基可与体系内的羟甲基发生反应,生成大量的亚甲基桥键,因此,在酸性阶段降低F/U摩尔比可以提高树脂最终结构中亚甲基桥键含量。     

螯合剂对不同磷源的释磷效应研究

了解螯合剂等肥料增效物质对不同磷源磷素释放效果的影响,可为全面认识螯合剂对磷素释放后在液相中的赋存形态提供依据。选取两种不同类型的土壤(酸性红壤和石灰性土壤)和五种磷酸盐矿物[磷酸氢二钙(DCP)、磷酸八钙(OCP)、羟基磷灰石(FA)、铝磷(Al-P)、铁磷(Fe-P)]作为磷源,通过实验室化学浸提试验,研究了螯合剂(EDTA-2Na)对不同磷源的磷素释放率和释放形态的影响。结果表明:(1)螯合剂对不同磷源磷素的释放均具有促进作用,且不同磷源的磷素释放率均随螯合剂浓度的增加而显著增加;(2)随着螯合剂浓度的增加,酸性红壤和石灰性土壤浸提液中钼酸盐非反应磷占总磷的比值均显著下降,DCP、OCP、FA浸提液中钼酸盐非反应磷占总磷的比例则显著增加,而Al-P和Fe-P浸提液中钼酸盐非反应磷占总磷的比例变化不大;(3)浸提液中的磷只有极少量以游离态磷酸根的形态存在,3.00 g·L~(-1)的DETA-2Na处理下,DCP、Al-P和Fe-P浸提液中游离态的磷酸根占总磷含量的比例分别仅为0.43%、1.12%、0.63%;(4)螯合剂对不同磷源磷素释放后,溶液中总磷与相应金属离子的摩尔比基本不变。     

饲粮植酸与锌摩尔比作为评定鸡饲料锌利用方法的研究

试验观察饲粮植酸与锌摩尔比对肉仔鸡（１１－２５日龄）锌利用的影响。以植酸水溶液取代半纯合饲粮（５０ｐｐｍ）锌中的蔗糖，其植酸与锌摩尔分别为８：１（对照）、１６：１、２５：１、３７：１及５１：１。试验结果表明，植酸与锌摩尔比对肉仔鸡的锌利用有着明显的影响效应。当该比值从１６：１增至５１：１香，中脚趾和胫骨灰分中锌含量分别降低１２．４－１９．６％（Ｐ＜０．０１）和４．４－１０．９％（Ｐ＜０．０５），二     

橡胶树整体叶片衰老的几项生理变化

测定了橡胶树幼苗不同物候期叶片的丙二醛、透性、过氧化物酶、过氧化氢酶、NAD—苹果酸去氢酶、水溶性蛋白质、干重及抗氧化能力。结果表明:叶片“膜系统”受损伤,透性增加是橡胶树叶片衰老的一方面原因,另一方面是叶片的代谢失调。叶片代谢失调表现为参与多种代谢反应的苹果酸脱氢酶活性下降,生活的基本物质——水溶性蛋白质含量下降。在叶片的衰老进程中,代谢失调发生在“膜”严重受损伤以前。     

海水亚硝酸盐和硝酸盐测定方法的优化

从精简方法流程提高工作效率角度,对国标《海洋监测规范(海水分析)》GB17378.4-2007中,海水亚硝酸盐和硝酸盐的测定方法进行了实验室系列条件优化。将磺胺和盐酸萘乙二胺配制成一定比例的混合溶液一次性加入待测样品中显色10min测定,比国标法减少了一步操作,共节省时间10min,提高工作效率30%以上。     

植物在高温胁迫下的生理研究进展

(石河子大学农学院,新疆石河子832003)     

Spontaneous Gingivitis Related to Hair Penetration in Rats

Maxillary gingivae from male and female Crl:CD(SD) rats at 12, 16, 21, and 34 weeks of age were examined histologically. The incidence of gingivitis was approximately 40%, with no age or sex predilection, and was most frequent between the first and second molar. Lesions were characterized by acute focal neutrophilic infiltration into the gingival mucosa, occasionally with inflammatory exudate. In severe cases, inflammation extended to the periodontal ligament with abscess formation, and adjacent alveolar bone destruction/resorption. The most characteristic finding was the presence of hair shafts associated with the lesion, which was observed in approximately 80% of the rats with gingivitis. These findings suggest that molar gingivitis occurs in rats from an early age and persists thereafter, and that the main cause of gingivitis in rats is hair penetration into the gingiva. It would be prudent to keep these background lesions in mind as potential modifiers in toxicity studies.     

Prevalence of dental and mandibular disorders in culled sheep in Spain

At the slaughterhouse, 1465 culled sheep heads were studied in order to identify disorders of the mandibular cheek teeth. Of these, 227 (15.5%) had evidence of osteomyelitis. The lesional profile showed that the mandible was affected in a similar proportion on both sides (46.7% on the right side vs 50.7% on the left side), mainly in the middle region (55.3%) and with most of the lesions closed without fistulisation (89.4%). In addition, swelling was palpable, with an increase in thickness in the area of the affected body (2.65 ± 0.065 cm vs 1.74 ± 0.030 cm). In 78.6% of the animals, the regional lymph nodes were enlarged. Concerning the mandibular cheek teeth, more than half of the animals lacked at least one tooth (57.0%), with the first premolar being the most frequently missing tooth (34.8%) and the third molar the least (8.2%). The impaction of food around the teeth was very common with the posterior molars being more frequently affected. In the knowledge of the authors, this is the first study that analyses the prevalence of mandibular molar and premolar disorders in sheep, and these are revealed as an important condition affecting culled sheep.     

A molar pregnancy in an embryo donor cow

A 6-year-old Hereford embryo donor cow was referred to Auburn University College of Veterinary Medicine for a mass in the tip of her left uterine horn. The cow had recently undergone an embryo collection which yielded unfertilized, degenerated ova. Transrectal palpation and ultrasound revealed a multi-locular mass enveloped by two separate compartments that resembled an amniotic and allantoic cavity within the uterus. Tissue was collected via a uterine flush and submitted for histopathology. The tissue was determined to be placenta, confirming the diagnosis of a molar pregnancy. Following treatment, the cow was able to produce numerous viable embryos. Molar pregnancies are rare and characterized by abnormal growth of trophoblastic cells leading to formation of intrauterine cystic masses. It is important to routinely perform an ultrasonographic examination of the cow's reproductive tract approximately 30 days following non-surgical in vivo embryo collections to detect and treat unwanted conditions such as pregnancy and cystic conditions.     

恒电荷土壤胶体的电导特性

采用电导滴定法研究了恒电荷土壤胶体表面的电导特性 ,提出了几个特征参数 :表观碱量电导率、表观碱量电导贡献率 ,这些参数是氢铝离子与胶体亲和力、碱金属阳离子在土壤胶体表面解离度及离子自身导电能力的综合表征。电导滴定法测定的阳离子代换量 (CEC)与滴定体系有关