Herbivore benefits from vectoring plant virus through reduction of period of vulnerability to predation

Herbivores can profit from vectoring plant pathogens because the induced defence of plants against pathogens sometimes interferes with the induced defence of plants against herbivores. Plants can also defend themselves indirectly by the action of the natural enemies of the herbivores. It is unknown whether the defence against pathogens induced in the plant also interferes with the indirect defence against herbivores mediated via the third trophic level. We previously showed that infection of plants with Tomato spotted wilt virus (TSWV) increased the developmental rate of and juvenile survival of its vector, the thrips Frankliniella occidentalis. Here, we present the results of a study on the effects of TSWV infections of plants on the effectiveness of three species of natural enemies of F. occidentalis: the predatory mites Neoseiulus cucumeris and Iphiseius degenerans, and the predatory bug Orius laevigatus. The growth rate of thrips larvae was positively affected by the presence of virus in the host plant. Because large larvae are invulnerable to predation by the two species of predatory mites, this resulted in a shorter period of vulnerability to predation for thrips that developed on plants with virus than thrips developing on uninfected plants (4.4 vs. 7.9 days, respectively). Because large thrips larvae are not invulnerable to predation by the predatory bug Orius laevigatus, infection of the plant did not affect the predation risk of thrips larvae from this predator. This is the first demonstration of a negative effect of a plant pathogen on the predation risk of its vector

Qualitative Migration Research: Viable Goals, Open-Ended Questions, and Multidimensional Answers

Following a brief review of the epistemological premises informing qualitative methodologies, I identify the key features of qualitative research undertaken in the verstehende or interpretative social-science tradition, which render it particularly well suited to capturing the inherent dynamics of the lived experience of human beings in general and, in our case, of immigrants: its multi-dimensionality; its ability to accommodate ambiguity and outright contradictions; its emphasis on the temporality and fluidity of social phenomena; and its insistence on the contextual and situational nature of human perceptions and agency. Next, I argue that the research goals appropriate for qualitative investigations as proposed by Charles Ragin (Constructing social research. Pine Forge Press, Thousand Oaks, 1994) – exploring diversity, giving voice, testing/refining theories or guiding concepts, and generating new research questions – can be realized by asking questions and gathering answers related to these issues in the context of (im)migrants’ experience. These claims are illustrated with questions asked and answers obtained through three standard methods of qualitative research: interviewing, observation, and document analysis. The examples draw from the current and emerging problem agendas in migration studies. I also discuss the strengths and limitations of research questions probing the complexity and un(der)determinacy of (im)migrants’ lives and the answers they generate

We took a bath with the chickens: memories of childhood visits to the homeland by second-generation Greek and Greek Cypriot returnees

Drawing on a wider study of 90 second-generation Greeks and Greek Cypriots who have relocated to their ancestral homeland, in this article we focus on the significance of childhood visits to the homeland. Freedom – how children were allowed to roam free and stay up late – is the key trope of such memories, in contrast with the strict spatio-temporal parenting they received in the host country. Different, sometimes less pleasant memories, however, emerge when the visits took place during later, teenage years. We explore the connections between childhood visits and adult relocation. Adult returnees find that settlement in the homeland produces a new set of challenges and reactions that differ markedly from childhood experiences and memories. They engage a second narrative trope, nostalgia, reflecting on the loss of the ‘authentic’ nature of the homeland and its customs and values. Instead, they highlight the materialism and xenophobia of Greek and Cypriot society nowadays. However, they see the ‘homeland’ as a safer place in which to raise their own children

Consumption in a varied or in a monotonous condition : women vs men

International audienc

Tales of satisfaction and disillusionment: second-generation ‘return’ migration to Greece and Cyprus

We examine the comparative “return” experiences of second-generation Greek-Americans and British-born Greek Cypriots who have relocated to their respective parental homelands of Greece and Cyprus. Sixty individuals, born in the United States or the United Kingdom yet now living in Greece or Cyprus, were interviewed and detailed life narratives recorded. We find both similarities and differences between the two groups. While the broad narrative themes “explaining” their returns are similar—a search for a “place to belong” in the ancestral homeland linked to what is, or was, perceived to be a more relaxed and genuine way of life—the post-return outcomes vary. In Greece there is disappointment, even profound disillusionment, whereas in Cyprus the return is generally viewed with satisfaction. For Greek-Americans, negative experiences include difficulty in accessing employment, frustration with bureaucracy and a culture of corruption, struggles with the chaos and stress of life in Athens, and pessimism about the future for their children in Greece. As a result, some Greek-Americans contemplate a second return, back to the United States. For the returnee British Cypriots, these problems are far less evident; they generally rationalize their relocation to Cyprus as the “right decision,” both for themselves and for their children. Greek-Americans tend to withdraw into a social circle of their own kind, whereas British-born returnee Cypriots adopt a more cosmopolitan or “third-space” cultural identity related, arguably, to the small scale and intimate spaces of social [End Page 262] Second-Generation “Return” Migration to Greece and Cyprus exchange in an island setting, and to the colonial and postcolonial history of Cyprus and its diaspora

Effect of progress variable definition on the mass burning rate of premixed laminar flames predicted by the Flamelet Generated Manifold method

This paper investigates how the choice of progress variable in tabulated chemistry affects the mass burning rates of premixed laminar flames. Simulations are carried out using finite rate, detailed chemistry (DC) and Flamelet Generated Manifolds (FGM). Through comparison of detailed chemistry and FGM (using different progress variable definitions), it is found that for FGM the mass burning rate depends on the choice of progress variable and thus results in a different mass burning rate than detailed chemistry. Since the mass burning rate is influenced by stretch and transport phenomena, the effects of these on mass burning rates are analysed. While FGM qualitatively predicts the effect of stretch on the mass burning rate compared to detailed chemistry, there are quantitative differences. It is shown that this is mainly caused by a lack of projection in usual FGM applications. When the projection of the source term and the diffusion term are included in the table, FGM becomes independent of the choice of progress variable and the effects of stretch are better represented by FGM similar to detailed chemistry

Use of heat exchanger for passive control of combustion instabilities

One of the major concerns in the operability of power generation systems is their susceptibility to combustion instabilities. In this work, we aim to examine the effective use of heat exchangers, an integral component in any power generation system, to passively control combustion instability. The combustor is modelled as a quarter-wave resonator (1-D, open at one end, closed at the other) with a compact heat source within, which follows time lag law for heat release. The heat exchanger (hex) is modelled as an array of tubes with bias flow and is placed near the closed end of the resonator, causing it to behave like a cavity-backed slit plate: an effective acoustic absorber. For simplicity and ease of analysis, we treat the physical processes of heat transfer and acoustic scattering occurring at the hex as two individual processes separated by an infinitesimal distance. The aeroacoustic response of the tube array is modelled using a quasi-steady approach and the heat transfer across the hex is modelled by assuming it to be a heat sink. Unsteady numerical simulations were carried out to obtain the heat exchanger transfer function (HTF), which is the response of the heat transfer at hex to upstream velocity perturbations. Combining the aeroacoustic response and the HTF, in the limit of the infinitesimal distance between these processes tending to zero, gives the net influence of the hex. Other parameters of interest are the heat source location and the cavity length (the distance between the tube array and the closed end). We then construct stability maps for the first resonant mode of the aforementioned combustor configuration, for various parameter combinations. Preliminary observations show that stability can be achieved for a wide range of parameters

Passive control of instabilities in combustion systems with heat exchanger

One of the major concerns in the operability of power generation systems is their susceptibility to combustion instabilities. In this work, we explore whether a heat exchanger, an integral component of a domestic boiler, can be made to act as a passive controller that suppresses combustion instabilities. The combustor is modelled as a quarter-wave resonator (1-D, open at one end, closed at the other) with a compact heat source inside, which is modelled by a time-lag law. The heat exchanger is modelled as an array of tubes with bias flow and is placed near the closed end of the resonator, causing it to behave like a cavity-backed slit plate: an effective acoustic absorber. For simplicity and ease of analysis, we treat the physical processes of heat transfer and acoustic scattering occurring at the heat exchanger as two individual processes separated by an infinitesimal distance. The aeroacoustic response of the tube array is modelled using a quasi-steady approach and the heat transfer across the heat exchanger is modelled by assuming it to be a heat sink. Unsteady numerical simulations were carried out to obtain the heat exchanger transfer function, which is the response of the heat transfer at heat exchanger to upstream velocity perturbations. Combining the aeroacoustic response and the heat exchanger transfer function, in the limit of the distance between these processes tending to zero, gives the net influence of the heat exchanger. Other parameters of interest are the heat source location and the cavity length (the distance between the tube array and the closed end). We then construct stability maps for the first resonant mode of the aforementioned combustor configuration, for various parameter combinations. Our model predicts that stability can be achieved for a wide range of parameters