环境生物工程技术的发展前景展望

环境生物技术是一门利用微生物介质为人类提供服务的技术科学,其核心思想是依据各类微生物的生态活动规律,从中寻找最有效的能解决目前一些环境问题的途径,如稀释污染物、截留废物中的可循环利用资源等．在过去15年里,分子生物技术的广泛使用,为逐步掌握微生物生态活动规律提供了可能,如：它们是如何自组织繁衍的,不同类体之间是如何相互影响的;同时,一些新的数学模型方法和新材料的尝试使用,也极大地拓宽了学科研究的手段．目前,有两种力量正在推动该学科的进行,一是其他学科领域的发展所带来的“推力”,二是社会的环境安全需求所产生的“拉力”．为了利用这种大好的发展时机,未来学科的研究耍注意以下4个方面：①把解决水和能源可持续发展问题放在首要位置;②开发和采用更有效的分子技术工具去揭示微生物的生态活动规律;③综合利用分子技术工具、模型分析工具和采用新材料去努力解决实际环境问题;④耍注重生物膜技术的研究．还提供了几个案例说明了如何把这4个方面的思想贯彻到实际研究之中。     

Dynamics of fat cell turnover in humans

Obesity is increasing in an epidemic manner in most countries and constitutes a public health problem by enhancing the risk for cardiovascular disease and metabolic disorders such as type 2 diabetes. Owing to the increase in obesity, life expectancy may start to decrease in developed countries for the first time in recent history. The factors determining fat mass in adult humans are not fully understood, but increased lipid storage in already developed fat cells (adipocytes) is thought to be most important. Here we show that adipocyte number is a major determinant for the fat mass in adults. However, the number of fat cells stays constant in adulthood in lean and obese individuals, even after marked weight loss, indicating that the number of adipocytes is set during childhood and adolescence. To establish the dynamics within the stable population of adipocytes in adults, we have measured adipocyte turnover by analysing the integration of 14C derived from nuclear bomb tests in genomic DNA. Approximately 10% of fat cells are renewed annually at all adult ages and levels of body mass index. Neither adipocyte death nor generation rate is altered in early onset obesity, suggesting a tight regulation of fat cell number in this condition during adulthood. The high turnover of adipocytes establishes a new therapeutic target for pharmacological intervention in obesity.     

The information in the term structure: A non-parametric investigation

This paper proposes a non-linear term structure model that nests the discrete and continuous time models as special cases. I estimate the model non-parametrically using nearest-neighbours regression. In sample, the non-linear model matches the standard theories, but out of sample, it offers substantial improvement. Linear models fail to track future interest rates: a random walk dominates the forward rate as a predictor for 3-month Treasury bills. A non-linear forecast based on the spread is shown statistically to be the best forecast.     

Ancestry and pharmacogenomics of relapse in acute lymphoblastic leukemia

Although five-year survival rates for childhood acute lymphoblastic leukemia (ALL) are now over 80% in most industrialized countries, not all children have benefited equally from this progress. Ethnic differences in survival after childhood ALL have been reported in many clinical studies, with poorer survival observed among African Americans or those with Hispanic ethnicity when compared with European Americans or Asians. The causes of ethnic differences remain uncertain, although both genetic and non-genetic factors are likely important. Interrogating genome-wide germline SNP genotypes in an unselected large cohort of children with ALL, we observed that the component of genomic variation that co-segregated with Native American ancestry was associated with risk of relapse (P = 0.0029) even after adjusting for known prognostic factors (P = 0.017). Ancestry-related differences in relapse risk were abrogated by the addition of a single extra phase of chemotherapy, indicating that modifications to therapy can mitigate the ancestry-related risk of relapse.     

Planting depth of 'Hobble Creek' mountain big sagebrush seed

We conducted a greenhouse study in which 'Hobble Creek' mountain big sagebrush ( Artemisia tridentata ssp. vaseyana ) seeds were planted at various depths in soil to determine the optimal planting depth. Results showed that the optimal planting depth is 5 mm or less.     

First North American record of Cichlasoma managuense (Pisces: Cichlidae)

An established population of a neotropical cichlid fish, Cichlasoma managuense , was found in a spring pool in the Virgin River basin, Utah. Presence of this predatory species poses an additional threat to the native fish fauna of the Virgin River, which already has suffered multiple impacts of water development and introduced fishes.