The human tumour-associated epithelial mucins are coded by an expressed hypervariable gene locus PUM

A single highly-polymorphic autosomal gene locus PUM codes for a family of mucin-type glycoproteins, separable by SDS-gel electrophoresis, which we first identified in human urine. The locus also codes for glycoproteins which are abundant in several other normal epithelial tissues and body fluids, including milk, and in tumours of epithelial origin. These mucin-type glycoproteins seem to be very immunogenic in rodents and, in a search for epithelial specific or tumour-associated antigens, a large number of related antibodies have been isolated which bind to the PUM-coded mucins. Many of the antibodies show a pronounced tumour specificity on immunohistology and are being used widely in cancer diagnosis in vitro and in vivo and even in cancer therapy. To investigate the expression of these antigens in normal and malignant cells complementary DNA coding for the mammary mucin has been isolated. Here we present evidence obtained using this cDNA that the PUM locus is a hypervariable 'minisatellite' region of human DNA similar to those described by several groups, but which is novel in that it is transcribed and translated, and that the same polymorphism is demonstrable in the expressed gene product.     

热处理作用下碳钢氢腐蚀裂纹愈合规律

对含氢腐蚀裂纹的碳钢进行再热处理后,SEM观察表明,氢蚀裂发生了不同程度的愈合,实验结果表明：长度约为10μm的碳钢氢蚀裂纹完全愈合的热处理条件下是从室温到1000℃热循环5次,共10h,氢蚀裂纹的愈合机制是热扩散,发生氢蚀裂纹愈合的动力是氢蚀气泡或裂纹长大导致的塑性变 能E8。在铁、碳和氢原子扩散都足够快的情况下,氢蚀裂纹愈合的条件是E8大于裂纹愈合所必须克服的表面张力能。     

Pressure-induced crystallization of a spin liquid

Liquids are expected to crystallize at low temperature. The only exception is helium, which can remain liquid at 0 K, owing to quantum fluctuations. Similarly, the atomic magnetic moments (spins) in a magnet are expected to order at a temperature scale set by the Curie-Weiss temperature theta(CW) (ref. 3). Geometrically frustrated magnets represent an exception. In these systems, the pairwise spin interactions cannot be simultaneously minimized because of the lattice symmetry. This can stabilize a liquid-like state of short-range-ordered fluctuating moments well below theta(CW) (refs 5-7). Here we use neutron scattering to observe the spin liquid state in a geometrically frustrated system, Tb(2)Ti(2)O(7), under conditions of high pressure (approximately 9 GPa) and low temperature (approximately 1 K). This compound is a three-dimensional magnet with theta(CW) = -19 K, where the negative value indicates antiferromagnetic interactions. At ambient pressure Tb(2)Ti(2)O(7) remains in a spin liquid state down to at least 70 mK (ref. 8). But we find that, under high pressure, the spins start to order or 'crystallize' below 2.1 K, with antiferromagnetic order coexisting with liquid-like fluctuations. These results indicate that a spin liquid/solid mixture can be induced by pressure in geometrically frustrated systems.     

流化床燃烧工况下N_2O生成机理的试验研究

在一个小型固定床反应器上对流化床煤燃烧温度下Ｎ＿２Ｏ均相和多相生成机理进行了试验研究。研究表明，ＮＨ＿３氧化形成的Ｎ＿２Ｏ量很少，其主要产物是ＮＯ，当增加Ｏ＿２浓度时，Ｎ＿２Ｏ略有增加，在９５０℃左右时，Ｎ＿２Ｏ量最大，而在８８０℃时，ＮＯ量最大。焦炭直接燃烧能形成一定量的Ｎ＿２Ｏ，ＮＯ能在焦炭表面还原成Ｎ＿２Ｏ，氧化性气氛下，焦炭的还原能力降低。最后，对煤焦生成Ｎ＿２Ｏ的多相反应机理进行了讨论。