Optimization of Time-Varying Parking Charges and Parking Supply in Networks with Multiple User Classes and Multiple Parking Facilities

The optimization of parking charges and parking supply over the time of a day is an important problem in the design of transportation networks. This paper presents a bilevel model to determine the opti-mal time-varying parking charges and parking supply in road networks with multiple user classes and different types of parking facilities. The upper level of the model aims to maximize the network net benefit in response to the parking charges and parking supply, whereas the lower level is a time-dependent network equilibrium problem with elastic demand. A descent-gradient-based solution algorithm is adapted to solve the model. The numerical results show that the implementation of time-varying parking charges and parking supply is useful to effectively cater to the time-varying demand with different parking needs. The model provides a powerful tool for strategically designing parking locations and evaluating various parking policies.     

Programmed cell death, mitochondria and the plant hypersensitive response.

The plant response to attempted infection by microbial pathogens is often accompanied by rapid cell death in and around the initial infection site, a reaction known as the hypersensitive response. This response is associated with restricted pathogen growth and represents a form of programmed cell death (PCD). Recent pharmacological and molecular studies have provided functional evidence for the conservation of some of the basic regulatory mechanisms underlying the response to pathogens and the activation of PCD in animal and plant systems. In animals, the mitochondrion integrates diverse cellular stress signals and initiates the death execution pathway, and studies indicate a similar involvement for mitochondria in regulating PCD in plants. But many of the cell-death regulators that have been characterized in humans, worms and flies are absent from the Arabidopsis genome, indicating that plants probably use other regulators to control this process.     

太湖梅梁湾沉积物和水生生物中有机氯农药分布特征及风险评估

根据太湖梅梁湾有机氯农药(OCPs)污染情况,采用GC/ECD分析了梅梁湾沉积物,并对4种鱼及螺狮为代表的水生生物中有机氯农药的残留现状进行了风险评估.结果表明:沉积物(干重)中OCPs浓度范围在8.45~48.54 ng/g之间,生物样品(湿重)中的浓度范围在2.68~31.34 ng/g之间.人类食用OCPs污染的水产品的潜在健康风险评估显示,从非致癌风险角度滴滴涕(DDTs)、六氯苯(HCB)、氯丹(CHL)和七氯环氧的危险商RHQ均小于1;从致癌风险角度,除CHL外,DDTs、HCB、六六六(HCHs)、七氯环氧的危险比RHR均大于1,长期癌症风险不容忽视.根据淡水沉积物质量导则标准估算,太湖梅梁湾沉积物中OCPs残留对水生生态系统的影响较小.