Invader-invader interactions in relation to environmental heterogeneity leads to zonation of two invasive amphipods, Dikerogammarus villosus (Sowinsky) and Gammarus tigrinus Sexton: amphipod pilot species project (AMPIS) report 6

As biological invasions continue, interactions occur not only between invaders and natives, but increasingly new invaders come into contact with previous invaders. Whilst this can lead to species replacements, co-existence may occur, but we lack knowledge of processes driving such patterns. Since environmental heterogeneity can determine species richness and co-existence, the present study examines habitat use and its mediation of the predatory interaction between invasive aquatic amphipods, the Ponto-Caspian Dikerogammarus villosus and the N. American Gammarus tigrinus. In the Dutch Lake IJsselmeer, we found broad segregation of D. villosus and G. tigrinus by habitat type, the former predominating in the boulder zone and the latter in the soft sediment. However, the two species co-exist in the boulder zone, both on the short and longer terms. We used an experimental simulation of habitat heterogeneity and show that both species utilize crevices, different sized holes in a plastic grid, non-randomly. These amphipods appear to optimise the use of holes with respect to their 'C-shape' body size. When placed together, D. villosus adults preyed on G. tigrinus adults and juveniles, while G. tigrinus adults preyed on D. villosus juveniles. Juveniles were also predators and both species were cannibalistic. However, the impact on G. tigrinus of the superior intraguild predator, D. villosus, was significantly reduced where experimental grids were present as compared to absent. This mitigation of intraguild predation between the two species in complex habitats may explain the co-existence of these two invasive species.

Adolescent men's attitudes in relation to pregnancy and pregnancy outcomes: A systematic review of the literature from 1980-2009

This review article reveals a long-standing gender bias in academic and policy research on adolescent pregnancy, which has led to the neglect of adolescent men's perspectives. The review summarizes the available literature on adolescent men's attitudes in relation to pregnancy occurrence and pregnancy outcomes in the context of addressing three questions: (1) What are adolescent men's attitudes to an adolescent pregnancy? (2) What are adolescent men's attitudes in relation to pregnancy outcomes? (3) What explanations are offered for the identified attitudes to adolescent pregnancy and resolution? The review establishes a foundation for future quantitative and qualitative research on adolescent men's perspectives. It emphasizes that a greater understanding of adolescent men's perspectives could lead to a re-framing of adolescent pregnancy away from being seen solely as a woman's issue. Furthermore, it is argued that the inclusion of adolescent men would lead to more effective adolescent pregnancy prevention and counseling programmes.

Investigation on drop penetration and wetting characteristics of powder-liquid systems in relation to the mixing of acrylic bone cement

This study investigated methyl methacrylate – polymethyl methacrylate powder bed interactions through droplet analyses, using model fluids and commercially available bone cement. The effects of storage temperature of liquid monomer and powder packing configuration on drop penetration time were investigated. Methyl methacrylate showed much more rapid imbibition than caprolactone due to decrease in both contact angle and fluid viscosity. Drop penetration of caprolactone through polymethyl methacrylate increased with decrease in bed macro-voids and increase in bulk density as predicted by the modified constant drawing area penetration model and confirmed by drop penetration images. Linear relationships were found between droplet mass and drawing area with imbibition time. Further experiments showed gravimetric analysis of the polymerised methyl methacrylate – polymethyl methacrylate matrix under various storage temperatures correlated with Reynolds number and Washburn analyses. These observations have direct implications for the design of mixing and delivery systems for acrylic bone cements used in orthopaedic surgery.

Holocene deposits from Neptune’s Cave, Nordland, Norway: Environmental interpretation and relation to the deglacial and emergence history of the Velfjord–Tosenfjord area

Neptune’s Cave in the Velfjord–Tosenfjord area of Nordland, Norway is described, together with its various organic deposits. Samples of attached barnacles, loose marine molluscs, animal bones and organic sediments were dated, with radiocarbon ages of 9840+/-90 and 9570+/-80 yr BP being derived for the barnacles and molluscs, based on the superseded but locally used marine reservoir age of 440 years. A growth temperature of c. 7.51C in undiluted seawater is deduced from the d13C and d18O values of both types of marine shell, which is consistent with their early Holocene age. From the dates, and an assessment of local Holocene uplift and Weichselian deglaciation, a scenario is constructed that could explain the situation and condition of the various deposits. The analysis uses assumed local isobases and sea-level curve to give results: that are consistent with previous data, that equate the demise of the barnacles to the collapse of a tidewater glacier in Tosenfjord, and that constrain the minimum extent of local Holocene uplift. An elk fell into the cave in the mid-Holocene at 510070 yr BP, after which a much later single ‘bog-burst’ event at 178070 yr BP could explain the transport of the various loose deposits further into the cave.

Is low self-esteem an inevitable consequence of stigma? An example from women with chronic mental health problems

It is often assumed that membership in a stigmatized group has negative consequences for the self-concept. However, this relationship is neither straightforward nor inevitable, and there is evidence suggesting that negative consequences may not necessarily occur (Psychol. Rev. 96(4) (1989) 608). This paper argues that the relationship has not been sufficiently theorized, and that a more detailed analysis is called for in order to understand the relationship between stigma and the self. The paper presents a critical examination of modified labeling theory (Am. Sociol. Rev. 52 (1987) 96), with examples from a study examining perceptions of stigma and their relationship to self-evaluation in women with chronic mental health problems. Open-ended interviews and qualitative analyses were used in preference to global measures of self-esteem. It was found that although the women were aware of society's unfavorable representations of mental illness, and the effects this had on their lives, they did not accept these representations as valid and therefore rejected them as applicable to the self. The participants did not deny their mental health problems, but their acceptance of labels was critical and pragmatic. Labels were rejected when they were perceived as carrying an unrealistic and negative stereotype, or when the women felt that their symptoms did not fit with the diagnostic criteria. The research illustrates the importance of considering people's subjective understandings of stigmatized conditions and societal reactions in order to understand the relation between stigma and the self. (C) 2002 Elsevier Science Ltd. All rights reserved.

Quantitative genetics of preference and performance on chickpeas in the noctuid moth, Helicoverpa armigera

If a novel, resistant host-plant genotype arises in the environment, insect populations utilising that host must be able to overcome that resistance in order that they can maintain their ability to feed on that host. The ability to evolve resistance to host-plant defences depends upon additive genetic variation in larval performance and adult host-choice preference. To investigate the potential of a generalist herbivore to respond to a novel resistant host, we estimated the heritability of larval performance in the noctuid moth, Helicoverpa armigera, on a resistant and a susceptible variety of the chickpea, Cicer arietinum, at two different life stages. Heritability estimates were higher for neonates than for third-instar larvae, suggesting that their ability to establish on plants could be key to the evolution of resistance in this species; however, further information regarding the nature of selection in the field would be required to confirm this prediction. There was no genetic correlation between larval performance and oviposition preference, indicating that female moths do not choose the most suitable plant for their offspring. We also found significant genotype by environment interactions for neonates (but not third-instar larvae), suggesting that the larval response to different plant genotypes is stage-specific in this species.

Learning design contingent valuation (LDCV): NOAA guidelines, preference learning and coherent arbitrariness

We extend the contingent valuation (CV) method to test three differing conceptions of individuals' preferences as either (i) a-priori well-formed or readily divined and revealed through a single dichotomous choice question (as per the NOAA CV guidelines [K. Arrow, R. Solow, P.R. Portney, E.E. Learner, R. Radner, H. Schuman, Report of the NOAA panel on contingent valuation, Fed. Reg. 58 (1993) 4601-4614]); (ii) learned or 'discovered' through a process of repetition and experience [J.A. List, Does market experience eliminate market anomalies? Q. J. Econ. (2003) 41-72; C.R. Plott, Rational individual behaviour in markets and social choice processes: the discovered preference hypothesis, in: K. Arrow, E. Colombatto, M. Perleman, C. Schmidt (Eds.), Rational Foundations of Economic Behaviour, Macmillan, London, St. Martin's, New York, 1996, pp. 225-250]; (iii) internally coherent but strongly influenced by some initial arbitrary anchor [D. Ariely, G. Loewenstein, D. Prelec, 'Coherent arbitrariness': stable demand curves without stable preferences, Q. J. Econ. 118(l) (2003) 73-105]. Findings reject both the first and last of these conceptions in favour of a model in which preferences converge towards standard expectations through a process of repetition and learning. In doing so, we show that such a 'learning design CV method overturns the 'stylised facts' of bias and anchoring within the double bound dichotomous choice elicitation format. (C) 2007 Elsevier Inc. All rights reserved.