Induction of host specificity in larvae of Manduca sexta: chemical dependence controlling host recognition and developmental rate

Summary. The tobacco hornworm, Manduca sexta L. (Lepidoptera: Sphingidae) is a specialist on Solanaceae. This host specificity is induced as the larva feeds on solanaceous foliage, so that solanaceous-reared larvae will refuse to feed on other plants. Experiments were designed to determine the role of dietary constituents on the induction of host specificity and the effects of these on development of M. sexta. Choice assays using leaf discs of cowpea, Vigna sinensis (Fabaceae), were used to monitor the isolation of relevant chemical cues from foliage of potato. An aqueous extract of potato foliage strongly stimulated feeding. This extract was partitioned with n-butanol under alkaline conditions to obtain a highly active butanol extract. Reversed phase flash chromatography with a water-methanol gradient gave an active fraction that was used as a supplement for wheat germ-based artificial diet. Larvae reared on this s-diet became dependent on potato allelochemicals for initiation and continuation of feeding activity. These larvae also developed faster than larvae reared on the control p-diet, but no effect on adult mass was detected. Further flash chromatography of the active fraction under alkaline conditions provided a highly active sub-fraction, and semi-preparative HPLC using gradients of water and acetonitrile resulted in the isolation of a single compound. Bioassays indicated that this compound alone can account for host recognition by solanaceous-reared larvae. The results suggest that the mechanism of induced host specificity in M. sexta involves development of dependence on this compound. Received 21 December 1999; accepted 14 March 2000     

农村联户沼气工程可行性研究及经验——以浙江省江山市淤头镇为例

以浙江省江山市淤头镇联户沼气工程为例,从经济、技术及社会可行性三方面进行具体分析,指出联户沼气相比户用沼气具有规模经济效益显著、资金支持渠道多、管理便利、农户满意度高、技术和市场创新空间大等突出优势,可为联户沼气工程推广提供经验借鉴。     

体验经济时代下体验旅游产品开发策略

随着人们生活水平的提高,体验经济时代的来临,人们正进入体验消费时代,游客期望的是通过自身参与而得到难忘的整体旅游体验。结合体验旅游产品的涵义及其开发中存在的问题,分析了体验旅游产品的开发原则,从个性化、文化性、绿色产品等方面探讨体验旅游产品的开发策略具有重要的意义。     

民族村寨游客的旅游体验质量研究——以西双版纳傣族园为例

目前国内对旅游体验和体验旅游的研究大多停留在理论研究层面。针对这一情况,以西双版纳傣族园游客为对象进行了实地问卷调查,采用社会统计学基本原理探索性地对游客的旅游体验质量进行了定量评价。结果表明,加强民族村寨的个性化体验旅游产品开发和民族文化旅游资源保护对少数民族地区旅游业的可持续发展具有重要的现实意义。     

国外农村生活污水分散治理管理经验的启示

总结了在农村生活污水处理上日本的成功经验和新西兰的探索实践,提出我国今后推广农村生活污水治理要确定治理范围,制定相应的技术标准,明确强制性责任,建立专业化服务体系和信息平台。     

基于Internet的大气分布式实时在线可控监测网的应用

主要论述了分布式实时在线可控大气监测网的总体设计、技术要点及解决途径。通过软件的设计策略和数据流图阐明了当前大气监测控制技术向网络化、分布性和互操作性方向发展的特点，结合开发的实例介绍了网络监测技术的应用效果。     

重大活动空气质量保障预报会商机制及经验探讨

重大活动空气质量保障预报会商已经成为保障过程中的重要环节,旨在以精细化空气质量预报为环境管理部门制定高效可行的区域大气污染管控措施提供关键技术依据。预报会商机制可有效规范区域联动预报会商的开展,在多个重大活动空气质量保障中,预报会商机制已日益完善,尤其是在强化立体化监测网、开展多技术组协同作业、建立多维预报会商流程、提升多种重点污染物预报能力等方面积累了大量宝贵的实践经验。该文首次系统性探讨国内空气质量保障预报会商机制和经验,以期为今后承办重大活动的地区开展空气质量保障预报会商提供借鉴。     

When mobility makes sense: A qualitative and longitudinal study of the daily mobility of the elderly

A majority of North Americans hopes to grow old in the suburbs. This aspiration depends upon their ability to drive and their access to a car. Because it is essential for everyday travel, car-mobility in the suburbs is becoming a symbolic goal. The meanings of mobility for elderly will evolve over time, notably as a result of changes in autonomy. However, the mobility of older adults is mainly understood in terms of daily trips. Little research has considered the temporal dimension of aging as an evolving process. This study aimed at understanding with a qualitative and longitudinal perspective how older people stay (auto-)mobile in their house and their neighborhood against the need to adapt to reduced autonomy and mobility over time. A group of 22 suburbanites aged from 62 to 89 was interviewed in 1999 and in 2006. The results show that even if older people succeed in increasing their mobility, they are headed for inevitable immobility. Among the environmental adaptation strategies that were observed, the constructed behaviors, the dependencies demanding additional supports as well as the social life modulate different evolving experiences of the city: the shrinking city, the fragmented city, and the city by proxy. The built environment is at the heart of a complex process in which the adaptation of mobility contributes to the emergence of new residential experiences.     

氧化沟在汽车工业小区污水处理上的应用

根据汽车城工业污水水质特点,采用水解酸化氧化沟处理工艺,出水水质确保达到二级排放标准,设计上尽量按一级排放标准考虑。该文主要阐述氧化沟工艺的特点以及污水厂设计参数选择和一些体会。     

露天煤矿待复垦土地生产潜力评价方法研究

露天煤矿待复垦土地生产潜力评价是编制土地复垦规划的一个重要内容。本文从露天煤矿待复垦土地生产潜力评价的必要性和特殊性出发,分别对评价因子指标定量或定性易量化和定性不易量化等不同类问题进行了评价方法及评价过程的研究,并根据安太堡露天煤矿复垦10年的经验进行了验证。同时,验证的结果应用于生态条件相似的将要开采的安家岭露天煤矿。