N,N′-双{双[4-(二甲氨基)苯基]甲基}尿素合成的反应机理

由对二甲氨基苯甲醛(A)和N,N′-二甲基苯胺(B)在盐酸存在下与尿素反应,合成题示化合物。研究了它的反应机理。结果表明,在强酸存在下,该反应是分两步进行的。首先是A和B缩合形成米氏醇(4,4′-二甲氨基二苯甲醇)中间物,然后再与尿素作用得到尿素衍生物。同时证明,该类取代苯甲醛与取代芳胺,在强酸介质中与尿素作用合成相应的尿素衍生物,都是按上述两步机理进行的。     

An early cretaceous<Emphasis Type="Italic">Ginkgo</Emphasis> ovule-bearing organ fossil from Liaoning,Northeast China and its evolutionary implications

Ginkgo is a very important gymnospermous genus that has only one surviving species, Ginkgo biloba L. As a so-called “living fossil“, wild Ginkgo was found only in China, but it once flourished well and had a world-wide distribution in the Mesozoic. The earliest Ginkgo has been known from the Middle Jurassic, based on ovule-bearin gorgans. In the Jurassic and Early Cretaceous, Ginkgo was one of the dominant gymnosperms in floras and possibly one of the coal-forming plants in North China. During the Early Tertiary, it reduced to a circumpolar distribution in the North Hemisphere; only a few reported from the South Hemisphere. From the Pliocene onwards, the Ginkgoales has been represented by the extant monotypic “living fossil“ Ginkgo biloba.     

福建绿竹地理种源的生长适应性

以不同的选择指标,在不同的试验点选择与当地环境相适宜的优良种源,结果表明：种源问的差异随着造林时间的延长逐渐增强;标准枝的叶片数各处理间的差异显性较其它性状大。试验期间永安试验点各种源笋产量较稳定,福安和永安种源在永安地区生长良好,而适宜在龙海大力推广的是漳州和永安种源。     

Study of β—amyloid adsorption and aggregation on graphite by STM and AFM

The scanning tunneling microscopy(STM) and the atomic force microscopy(AMF) have been applied to the direct study of the adsorption and aggregation of β-amyloid(1-42)(Aβ42)on the hydrophobic graphite surface.It was found that Aβ42 were preferentially adsorbed on graphite defects such as the edges.Aβ42 peptides self-assembled into intermediate protofibrils,which in turn self-associated to form fibrils.Usually,two or more fibrils intertwined to form the helical structure.These results will provide an important clue to studying the aggregation process of β-amyloid.     

蒙脱土催化下N,N一二甲基氨基芳基甲烷和结晶紫的合成新方法

摘要：本文研究了用蒙脱土作催化荆，合成MicNer＇shydride（5），无色结晶紫（4）和结晶紫（5）的新方法。在蒙脱土催化下，3由N,N一二甲基苯胺（1）和多聚甲醛反应制得，收率达到98％；再以它和1作原料合成4，收率为58％-64％；结晶紫用1，NaCI，CuCl2作原料来制备，收率95％。     

杂交油菜冷害原因及预防

油菜是河南省第三大油料作物.油菜作为秋冬播作物,由于收获较小麦、豌豆早,所以,对下茬夏播作物的早播、高产提供了有利条件.然而,近些年来,由于诸多原因,河南省油菜常受冷害侵袭,造成减产.     

Boundedness for commutators of fractional Hardy operators on Herz spaces

Some boundedness results are established for commutators generated by classical fractional Hardy operators and one-sided CMO functions on the homogeneous Herz spaces, which extends some known results.     

P?un’s systems as models of economic systems

In the paper a concept for modeling the economic systems by the formalism of P?un’s systems is proposed. The main idea is to represent economic systems as homomorphic images of Petri nets corresponding to the (super) cells of P?un’s systems.     

三华李优质丰产栽培技术

三华李为李类优良晶种之一，对气候适应性较强，易种易管，生长快，结果早，一般定植3年就能结果，由于栽培三华李投资少、收效快、植经济效益好，因而很受生产者欢迎：现将其优质丰产栽培技术介绍如下：