Observation of random-phase lattice solitons

The coherence of waves in periodic systems (lattices) is crucial to their dynamics, as interference effects, such as Bragg reflections, largely determine their propagation. Whereas linear systems allow superposition, nonlinearity introduces a non-trivial interplay between localization effects, coupling between lattice sites, and incoherence. Until recently, all research on solitary waves (solitons) in nonlinear lattices has involved only coherent waves. In such cases, linear dispersion or diffraction of wave packets can be balanced by nonlinear effects, resulting in coherent lattice (or 'discrete') solitons; these have been studied in many branches of science. However, in most natural systems, waves with only partial coherence are more common, because fluctuations (thermal, quantum or some other) can reduce the correlation length to a distance comparable to the lattice spacing. Such systems should support random-phase lattice solitons displaying distinct features. Here we report the experimental observation of random-phase lattice solitons, demonstrating their self-trapping and local periodicity in real space, in addition to their multi-peaked power spectrum in momentum space. We discuss the relevance of such solitons to other nonlinear periodic systems in which fluctuating waves propagate, such as atomic systems, plasmas and molecular chains.     

Localization of gene for human p53 tumour antigen to band 17p13

Recently the gene for the cellular tumour antigen p53, a phosphoprotein found in increased concentration in a variety of human cells, had been mapped to region 17q22 by in situ hybridization techniques and has been shown to translocate to the chromosome carrying the translocation [t(15; 17)] associated with acute promyelocytic leukaemia (APL). Based on this finding it has been postulated that this gene has a role in the pathogenesis of APL. Here we present evidence that the gene for p53 is not located on the long arm of chromosome 17, but maps to band 17p13. We therefore suggest that this gene is not directly involved in the chromosome translocation observed in APL.     

一株产木聚糖酶菌固体发酵条件的优化

采用单因素试验设计对黑曲霉发酵产木聚糖酶的条件进行了研究,并探讨了黑曲霉发酵的产酶模式.以麸皮和玉米芯质量比7:3混合后作为碳源,含0.15%的硫酸铵为无机氮源,物料与水分的比为1:1.5,培养温度28～30℃,培养基起始pH值为4.8,接种量为4%(107个/mL),外加吐温-20±0.05%,发酵时间为72h,用10倍培养基的自来水,40℃摇床浸提1h,木聚糖酶活可达650.45U,为木聚糖酶固体发酵的工业化生产和应用提供参考.