Comparative Analysis of Headspace Volatiles from Different Caterpillar-Infested or Uninfested Food Plants of Pieris Species

Plants that are infested by herbivores emit volatile cues that can be used by the natural enemies of the herbivores in their search for hosts. Based on results from behavioral studies, we investigated to what extent intact and herbivore-infested plant species and varieties from the food plant range of Pieris herbivore species differ in the composition of the volatile blends. Parasitoids of Pieris species, Cotesia glomerata and C. rubecula, show differential responses towards various herbivore-infested food plants, whereas differences in responses to plants infested by other herbivore species were less clear. Chemical analysis of the headspace samples of red cabbage, white cabbage, and nasturtium plants that were infested by P. brassicae or P. rapae larvae, or that were intact, yielded 88 compounds including alcohols, ketones, aldehydes, esters, nitriles, terpenoids, sulfides, (iso)thiocyanates, carboxylic acids, and others. The analysis revealed that herbivore-infested plants emit the largest number of compounds in the highest amounts. The plant species affected the volatile blend more than did the herbivore species, and differences between plant varieties were less pronounced than differences between plant species. Differences in headspace composition between plants infested by P. brassicae or P. rapae were mainly of a quantitative nature. Herbivore-infested nasturtium differed considerably from the cabbage varieties in a qualitative way. Headspace compositions of red and white cabbage varieties were comparable to that of the food plant Brussels sprouts (Brassica oleracea gemmifera cv. Titurel) as determined in earlier studies in our laboratory. With respect to plant response to herbivory, nasturtium differed considerably from the cabbage varieties analyzed so far and shows resemblance with Lima bean, cucumber, and corn. These plant species produce a greater quantity and variety of volatiles under herbivore attack than intact plants. The results of this study are discussed in relation to behavioral observations on C. glomerata and C. rubecula.     

Attraction of Colorado Potato Beetle to Herbivore-Damaged Plants During Herbivory and After Its Termination

Large, undamaged potato plants (>60 cm, 5–6 weeks old) attract the Colorado potato beetle (Leptinotarsa decemlineata), but small potato plants (15–25 cm high, 2–3 weeks old) do not. However, small plants become attractive to CPB when they are damaged. Mechanical damage inflicted with scissors results in short-term (lasting less than 15 min) attraction, while more severe damage with carborundum powder results in a longer lasting attraction (at least 1 hr). CPB adults are also attracted to small plants infested with CPB and Spodoptera exigua larvae. After the larvae had been removed for 50 min following a short duration (30 min) of feeding, CPB adults were no longer attracted to the plants. However, when CPB larvae had been removed after they had fed for 60–90 min, the plants were somewhat attractive to the beetles, although significantly less than they had been when the larvae were feeding. Attraction increased with time after feeding ceased. Furthermore, beetles were strongly attracted to plants 50 min after larvae were removed when the plants had been fed upon by larvae for 18–24 hr. Thus it appears that there are two stages of attraction, first, to volatiles released directly from the wound site, and second, to volatiles that are induced in response to herbivory. Chemical analyses of the headspace of infested potato plants show that infestation results in the emission of a mixture of chemicals that is qualitatively quite similar to that emitted by undamaged plants. The major components of the mixture are that emitted by undamaged plants. The major components of the mixture are terpenoids and fatty acid derivatives such as aldehydes and alcohols. The emission rate of some of these chemicals declines after removal of the beetles, while the emission rate of other chemicals increases with the duration of beetle feeding and remains at a high level even after removal of the beetles. Thus, the composition of the mixture changes temporally during and after herbivore feeding, which may explain the recorded behavior of the beetles.     

FDTs for ODP

This paper discusses the use and integration of formal techniques into the Open Distributed Processing (ODP) standardization initiative.

The ODP reference model is a natural progression from OSI. Multiple viewpoints are used to specify complex ODP systems. Formal methods are playing an increasing role within ODP.

We provide an overview of the ODP reference model, before discussing the ODP requirements on FDTs, and the role such techniques play. Finally, we discuss the use of formalisms in the central problem of maintaining cross viewpoint consistency.     

Investigating patterns of interaction in networked learning and computer-supported collaborative learning: A role for Social Network Analysis

The focus of this study is to explore the advances that Social Network Analysis (SNA) can bring, in combination with other methods, when studying Networked Learning/Computer-Supported Collaborative Learning (NL/CSCL). We present a general overview of how SNA is applied in NL/CSCL research; we then go on to illustrate how this research method can be integrated with existing studies on NL/CSCL, using an example from our own data, as a way to synthesize and extend our understanding of teaching and learning processes in NLCs. The example study reports empirical work using content analysis (CA), critical event recall (CER) and social network analysis (SNA). The aim is to use these methods to study the nature of the interaction patterns within a networked learning community (NLC), and the way its members share and construct knowledge. The paper also examines some of the current findings of SNA analysis work elsewhere in the literature, and discusses future prospects for SNA. This paper is part of a continuing international study that is investigating NL/CSCL among a community of learners engaged in a master’s program in e-learning.     

Identification of Volatile Potato Sesquiterpenoids and Their Olfactory Detection by the Two-spotted Stinkbug Perillus bioculatus

The predaceous stinkbug Perillus bioculatus is attracted towards volatiles emitted by damaged potato plants. Whereas mechanically damaged plants lost attractiveness 1 h after damage was inflicted, attraction was long-lasting when the plants were damaged by Colorado potato beetles Leptinotarsa decemlineata, a prey of P. bioculatus. A range of sesquiterpenoids was previously shown to be induced upon beetle damage. In order to evaluate the potential role of sesquiterpenoids in the attraction response, volatiles from damaged potato plants were collected and analyzed with GC-MS and GC-EAG. The antennae of P. bioculatus responded to -caryophyllene, -humulene, (E)--farnesene, (–)-germacrene D, and germacrene D-4-ol. Two sesquiterpenes that coeluted, -zingiberene and bicyclogermacrene, together also elicited olfactory responses of P. bioculatus, whereas the individual compounds did not. The response of P. bioculatus to a variety of sesquiterpenes at low dosages suggests a role for these compounds in prey detection of this stinkbug.     

建筑乌托邦比利时年轻事务所的从业实践策略

文章介绍了比利时年轻建筑师事务所的运作状况．通过对B612、V 、Label、MDMA等事务所的建筑理念与实践的分析．作者试图阐明这些事务所的建筑之路往往始于建筑之外。     

Electronic excitations of a single molecule contacted in a three-terminal configuration

Low-temperature three-terminal transport measurements through a thiol end-capped pi-conjugated molecule have been carried out. Electronic excitations, including zero and finite-bias Kondo-effects, have been observed and studied as a function of magnetic field. Using a simplified two-orbital model, we have accounted for the spin and the electronic configuration of the first four charge states of the molecule. The charge-dependent couplings to gate, source, and drain electrodes suggest a scenario in which charges and spins are localized at the ends of the molecule, close to the electrodes.     

Single quantum dot nanowire LEDs

We report reproducible fabrication of InP-InAsP nanowire light-emitting diodes in which electron-hole recombination is restricted to a quantum-dot-sized InAsP section. The nanowire geometry naturally self-aligns the quantum dot with the n-InP and p-InP ends of the wire, making these devices promising candidates for electrically driven quantum optics experiments. We have investigated the operation of these nanoLEDs with a consistent series of experiments at room temperature and at 10 K, demonstrating the potential of this system for single photon applications.