南水北调中线总干渠藻类的生态调度

南水北调中线总干渠无在线调蓄水库,对藻类生态调度过程中出现的问题开展生态调度实现策略和实施方式研究。主要实现策略包括:划定自身的调蓄区,隔离生态调度对下游的影响;采用高效的渠池运行方式,减少生态调度时蓄量的反复调整;综合考虑安全、快速、平稳等需求,设定生态调度实施进程和方式。具体实施方式包括:将总干渠划分为流速调控区、调蓄区和正常运行区,分别实施等体积、控制蓄量和闸前常水位方式运行;将生态调度过程划分为充水阶段和泄水阶段,基于流速调控目标值、持续时长和水位降幅约束条件,确定各阶段时长和各分区的闸门群调控方案等。基于2018年3月输水工况,采用明渠一维非恒定流模型,仿真总干渠上游15个渠池的藻类生态调度过程。结果表明,生态调度可在3.5 d内完成,各渠池的平均流速由0.48 m/s增至0.93 m/s,持续时间超过2 h。在整个生态调度过程中,水位变化平稳,水位变幅符合安全阈值要求,下游渠道的正常运行未受生态调度明显影响。     

Optimized Biocatalytic Synthesis of 2-Selenopyrimidine Nucleosides by Transglycosylation**

Selenium-modified nucleosides are powerful tools to study the structure and function of nucleic acids and their protein interactions. The widespread application of 2-selenopyrimidine nucleosides is currently limited by low yields in established synthetic routes. Herein, we describe the optimization of the synthesis of 2-Se-uridine and 2-Se-thymidine derivatives by thermostable nucleoside phosphorylases in transglycosylation reactions using natural uridine or thymidine as sugar donors. Reactions were performed at 60 or 80 °C and at pH 9 under hypoxic conditions to improve the solubility and stability of the 2-Se-nucleobases in aqueous media. To optimize the conversion, the reaction equilibria in analytical transglycosylation reactions were studied. The equilibrium constants of phosphorolysis of the 2-Se-pyrimidines were between 5 and 10, and therefore differ by an order of magnitude from the equilibrium constants of any other known case. Hence, the thermodynamic properties of the target nucleosides are inherently unfavorable, and this complicates their synthesis significantly. A tenfold excess of sugar donor was needed to achieve 40−48 % conversion to the target nucleoside. Scale-up of the optimized conditions provided four Se-containing nucleosides in 6–40 % isolated yield, which compares favorably to established chemical routes.     

Genome-Wide Analyses of the Temperature-Responsive Genetic Loci of the Pectinolytic Plant Pathogenic Pectobacterium atrosepticum

Temperature is one of the critical factors affecting gene expression in bacteria. Despite the general interest in the link between bacterial phenotypes and environmental temperature, little is known about temperature-dependent gene expression in plant pathogenic Pectobacterium atrosepticum, a causative agent of potato blackleg and tuber soft rot worldwide. In this study, twenty-nine P. atrosepticum SCRI1043 thermoregulated genes were identified using Tn5-based transposon mutagenesis coupled with an inducible promotorless gusA gene as a reporter. From the pool of 29 genes, 14 were up-regulated at 18 °C, whereas 15 other genes were up-regulated at 28 °C. Among the thermoregulated loci, genes involved in primary bacterial metabolism, membrane-related proteins, fitness-corresponding factors, and several hypothetical proteins were found. The Tn5 mutants were tested for their pathogenicity in planta and for features that are likely to remain important for the pathogen to succeed in the (plant) environment. Five Tn5 mutants expressed visible phenotypes differentiating these mutants from the phenotype of the SCRI1043 wild-type strain. The gene disruptions in the Tn5 transposon mutants caused alterations in bacterial generation time, ability to form a biofilm, production of lipopolysaccharides, and virulence on potato tuber slices. The consequences of environmental temperature on the ability of P. atrosepticum to cause disease symptoms in potato are discussed.     

The challenges of regulating water and sanitation tariffs under a three-level shared-authority federalism model: The case of Brazil

Water and sanitation regulation in Brazil shall be addressed as part of a major problem that involves institutional disputes and legal uncertainty. The paper investigates the hypothesis that the complex institutional framework plays a central role in explaining country's poor performance in the sector. Methodology is mainly qualitative, presenting an analysis that shows how political, institutional and legal hurdles play a major role in explaining the government's inability to secure a financially self-sustainable structure to the sector. The paper suggests that empowering the National Water Agency to issue general guidelines may help reducing transaction costs and fostering sector's development.     

应用变频器技术实现SO2风机节能改造

铜目前,硫酸车间制酸一系列共有三台SO2风机,这三台风机均采用液力耦合器的调速方式,这种方式可以实现无极调速,但是存在着传动效率低,耗能大的缺点,并且这三台风机均已使用20年以上,处于设备的中晚期,工作效率已大大降低。目前行业内,均采用先进的变频调速方式。使用变频器来控制风机的转速,可以极大的节省电能,尤其是在低负荷情况下,可以实现低转速运转,大大提高硫酸系统的综合能耗指标。     

All the players in the game: driving home the global commitment for legitimate drugs

Substandard, falsified, and counterfeit medications are a concern for the industry and for the public’s health. Data collection and research on these illegitimate drugs must continue to be a priority and common recommendations must be implemented immediately. The health of the public continues to be at risk, and as such global consensus and collaboration must be swift. Process improvements and policy decisions can support expert recommendations while technology and research continue to drive home change. Addressing counterfeit and substandard drugs is cost effective, feasible, and the right thing to do.     

Economic effects of regulating the seismic strengthening of older buildings

The marked increase in the awareness of earthquake risk following the Canterbury earthquakes in New Zealand offered a unique opportunity to investigate the economic effect of disaster-mitigation regulations on the commercial building stock. A difference-in-differences (DD) framework was used to determine whether earthquake risk has been capitalized into the property prices of buildings constructed prior to 1976, as a response to the national policy requiring assessment and strengthening (or demolition) of the existing earthquake-prone building stock. A negative externality is found in the policy announcement on affected (pre-1970s) office and retail buildings which caused office buildings to suffer a 12.5% stigma discount. However, retail properties were less impacted suffering a 2.3% stigma loss. The value of the commercial building stock has been affected by the policy. These findings provide policy-makers with timely evidence as to the economic effects of New Zealand’s earthquake-prone buildings policy. Facing losses in property value and financial responsibility for retrofitting their assets, building owners will be looking for a workable set of regulatory and non-regulatory incentives to encourage disaster risk management and protect the built environment.