Size-assortative pairing in Gammarus pulex (Crustacea : Amphipoda): a test of the timing hypothesis

We present the first empirical test of the timing hypothesis regarding the generation of size-assortative pairing in amphipods. The timing hypothesis proposes that, since large males are better able to afford the costs of mate guarding than small males, the former can take larger females into precopula earlier in the female moult cycle than is feasible for the latter. This leaves small males to form pairs with smaller females closer to moult, thus generating size assortment. We presented male Gammarus pulex, collected both in precopula and as singletons, with females that were (1) previously guarded and therefore near to copulatory moult and (2) previously unguarded and therefore far from copulatory moult. This comparison tested the prediction of the timing hypothesis, that size assortment should break down when the opportunity for time-based male decisions is removed, but that size assortment should occur where timing is not disrupted. Counter to the hypothesis, we found that size assortment did not break down upon removal of the time factor. Large males tended to initiate mate guarding earlier than small males in both female moult groups. However, only in the previously unguarded group did large males guard for longer than small males. This result suggests that, although size assortment occurred in all groups, the causative mechanisms that generated this pattern may differ between these groups. We therefore consider the possible importance of mechanisms such as aggression, simultaneous manipulation of females and female resistance in producing size assortment where males encounter numerous females that are close to moult. We also observed that prior recent guarding experience by males had no effect on latency to guard or size-assortative pairing. (C) 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.

Implicit and explicit processes in a hypothesis testing task

We present the results of two experiments investigating the factors that determine responding on the pseudo-diagnosticity task. In Expt I we manipulated people's beliefs about the degree to which an initial piece of evidence supported a focal hypothesis and found decreased pseudo-diagnostic (PD) responding when the evidence offered low support for the focal hypothesis. In Expt 2 we manipulated the instructions given to participants. We found that instructions to select evidence to help decide between the focal and the complementary hypotheses produced fewer PD responses than both instructions to decide whether the focal hypothesis was the case and instructions to decide whether its complement was the case. The results are interpreted within the framework of recent dual process theories of reasoning.

Nebular and auroral emission lines of [Cl III] in the optical spectra of planetary nebulae

Electron impact excitation rates in Cl III, recently determined with the R-matrix code, are used to calculate electron temperature (T-e) and density (N-e) emission line ratios involving both the nebular (5517.7, 5537.9 Angstrom) and auroral (8433.9, 8480.9, 8500.0 Angstrom) transitions. A comparison of these results with observational data for a sample of planetary nebulae, obtained with the Hamilton Echelle Spectrograph on the 3-m Shane Telescope, reveals that the R-1 = /(5518 Angstrom)/I(5538 Angstrom) intensity ratio provides estimates of N-e in excellent agreement with the values derived from other line ratios in the echelle spectra. This agreement indicates that R-1 is a reliable density diagnostic for planetary nebulae, and it also provides observational support for the accuracy of the atomic data adopted in the line ratio calculations. However the [Cl III] 8433.9 Angstrom line is found to be frequently blended with a weak telluric emission feature, although in those instances when the [Cl III] intensity may be reliably measured, it provides accurate determinations of T-e when ratioed against the sum of the 5518 and 5538 Angstrom line fluxes. Similarly, the 8500.0 Angstrom line, previously believed to be free of contamination by the Earth's atmosphere, is also shown to be generally blended with a weak telluric emission feature. The [CI III] transition at 8480.9 Angstrom is found to be blended with the He I 8480.7 Angstrom line, except in planetary nebulae that show a relatively weak He I spectrum, where it also provides reliable estimates of T-e when ratioed against the nebular lines. Finally, the diagnostic potential of the near-UV [Cl III] lines at 3344 and 3354 Angstrom is briefly discussed.

Nebular and Auroral Emission Lines of [Ar IV] in the Optical Spectra of Planetary Nebulae

Recent R-matrix calculations of electron impact excitation rates in Ar IV are used to calculate the emission-line ratio: ratio diagrams (R₁, R₂), (R_1, R₃), and (R_1, R₄), where K₁ = I(4711 Å)/I(4740 Å), R₂ = I(7238 Å)/I(4711 + 4740 Å), R₃ = I(7263 Å)/I(4711 + 4740 Å), and R₄ = I(7171 Å)/I(4711 + 4740 Å), for a range of electron temperatures (T_e = 5000-20,000 K) and electron densities (N_e = 10-10⁶ cm^-3) appropriate to gaseous nebulae. These diagrams should, in principle, allow the simultaneous determination of T_e and N_e from measurements of the [Ar IV] lines in a spectrum. Plasma parameters deduced for a sample of planetary nebulae from (R_1, R₃) and (R_1, R₄), using observational date obtained with the Hamilton echelle spectrograph on the 3 m Shane Telescope at the Lick Observatory, are found to show excellent internal consistency and to be in generally good agreement with the values of T_e and N_e estimated from other line ratios in the echelle spectra. These results provide observational support for the accuracy of the theoretical ratios and, hence, the atomic data adopted in their derivation. In addition, they imply that the 7171 Å line is not as seriously affected by telluric absorption as previously thought. However, the observed values of R₂ are mostly larger than the theoretical high-temperature and density limit, which is due to blending of the Ar IV 7237.54 Å line with the strong C II transition at 7236 Å. 

Congruence between nuclear and mitochondrial genes in Demospongiae: A new hypothesis for relationships within the G4 clade (Porifera: Demospongiae)

The current morphological classification of the Demospongiae G4 clade was tested using large subunit ribosomal RNA (LSU rRNA) sequences from 119 taxa. Fifty-three mitochondrial cytochrome oxidase 1 (CO1) barcoding sequences were also analysed to test whether the 28S phylogeny could be recovered using an independent gene. This is the largest and most comprehensive study of the Demospongiae G4 clade. The 28S and CO1 genetrees result in congruent clades but conflict with the current morphological classification. The results confirm the polyphyly of Halichondrida, Hadromerida, Dictyonellidae, Axinellidae and Poecilosclerida and show that several of the characters used in morphological classifications are homoplasious. Robust clades are clearly shown and a new hypothesis for relationships of taxa allocated to G4 is proposed. (C) 2011 Elsevier Inc. All rights reserved.

What now for the contact hypothesis? Towards a new research agenda

This article begins with a review of recent research on the Contact Hypothesis. It will be shown that the literature in this area has become essentially closed and self-referential where the core political and theoretical premises that underpin the Hypothesis have been taken for granted and the debates have therefore become restricted simply to how best to measure the influence of inter-group contact. One of the key reasons for this is the lack of critical engagement with the Contact Hypothesis from those of a more structuralist and/or ‘radical’ perspective. This may be because the individualistic focus of the Hypothesis is seen from such a perspective as largely irrelevant to addressing racial and ethnic divisions and/or because it may be felt that to engage with the concept is to give it undue legitimacy. It will be argued in this article, however, that the wholesale dismissal of the Contact Hypothesis is a little premature. Just as recent research on racial and ethnic divisions has drawn attention to the way in which such divisions exist at a number of layers within the social formation – from the structural, political and ideological through to the sub-cultural, interactional and biographical – so must any initiatives aimed at addressing these divisions be similarly ‘multi-layered’ in their approach. However, it will be argued that for research to help inform specific strategies at the interactional level, there needs to be a significant change in the way that inter-group contact, and the Contact Hypothesis more generally, is studied. The article will ‘model out’ one potentially fruitful way in which such research can develop through the use of an ethnographic case study involving a cross-community scheme arranged for Protestant and Catholic children in Northern Ireland.

A test of the extended intergroup contact hypothesis: The mediating role of intergroup anxiety, perceived ingroup and outgroup norms, and inclusion of the outgroup in the self

S. C. Wright, A. Aron, T. McLaughlin-Volpe, and S. A. Ropp (1997) proposed that the benefits associated with cross-group friendship might also stem from vicarious experiences of friendship. Extended contact was proposed to reduce prejudice by reducing intergroup anxiety, by generating perceptions of positive ingroup and outgroup norms regarding the other group, and through inclusion of the outgroup in the self. This article documents the first test of Wright et al.'s model, which used structural equation modeling among two independent samples in the context of South Asian-White relations in the United Kingdom. Supporting the model, all four variables mediated the relationship between extended contact and outgroup attitude, controlling for the effect of direct contact. A number of alternative models were ruled out, indicating that the four mediators operate concurrently rather than predicting one another.

The renin-angiotensin system and antihypertensive drugs in Alzheimer's disease:current standing of the angiotensin hypothesis?

There is an urgent need to improve upon Alzheimer's disease (AD) treatments. Limitations of existing drugs are that they target specific downstream neurochemical abnormalities while the upstream underlying pathology continues unchecked. Preferable treatments would be those that can target a number of the broad range of molecular and cellular abnormalities that occur in AD such as amyloid-ß (Aß) and hyperphosphorylated tau-mediated damage, inflammation, and mitochondrial dysfunction, as well more systemic abnormalities such as brain atrophy, impaired cerebral blood flow (CBF), and cerebrovascular disease. Recent pre-clinical, epidemiological, and a limited number of clinical investigations have shown that prevention of the signaling of the multifunctional and potent vasoconstrictor angiotensin II (Ang II) may offer broad benefits in AD. In addition to helping to ameliorate co-morbid hypertension, these drugs also likely improve diminished CBF which is common in AD and can contribute to focal Aß pathology. These drugs, angiotensin converting enzyme (ACE) inhibitors, or angiotensin receptor antagonists (ARAs) may also help deteriorating cognitive function by preventing Ang II-mediated inhibition of acetylcholine release as well as interrupt the upregulation of deleterious inflammatory pathways that are widely recognized in AD. Given the current urgency to find better treatments for AD and the relatively immediate availability of drugs that are already widely prescribed for the treatment of hypertension, one of the largest modifiable risk factors for AD, this article reviews current knowledge as to the eligibility of ACE-inhibitors and ARAs for consideration in future clinical trials in AD.

Testing the Prebish-Singer hypothesis using second-generation panel data stationarity tests with a break

In this paper, we test the Prebish-Singer (PS) hypothesis, which states that real commodity prices decline in the long run, using two recent powerful panel data stationarity tests accounting for cross-sectional dependence and a structural break. We find that the hypothesis cannot be rejected for most commodities other than oil.

Late industrialization and the increased merit selection hypothesis - Ireland as a test case

The Irish case provides a particularly appropriate test of the increasing merit selection hypothesis deriving from the liberal theory of industrialization. This is so not only because the lateness and speed of economic change allows us to capture such change through a set of national surveys conducted in the past three decades, but also because such change was based on a sustained policy of increased openness to international competitive forces. The functional requirements of the economy and a rapid increase in the supply of those with higher educational qualifications provided an ideal context in which to observe the movement from ascription to achievement predicted by the liberal theory. However, while changes in the class structure and a rapid expansion of educational opportunity had significant consequences in terms of absolute mobility, there was no evidence of a significant shift towards meritocratic principles. At the same time as the service class increased their advantage over other classes in the pursuit of educational qualifications, the impact of educational qualifications on class destination diminished. Controlling for education, we find that the impact of class origin effects is substantial and shows little sign of diminishing over time. In our conclusion we discuss the implications of our findings in the context of the recent debate on meritocracy.

THE ROLE OF SENSE OF CONTROL AND SOCIAL SUPPORT IN MEDIATING THE IMPACT OF PSYCHOLOGICAL DISTRESS - A TEST OF THE HYPOTHESIS OF FUNCTIONAL SUBSTITUTION

The purpose of this paper is to examine the manner in which beliefs relating to sense of control and perceived social support mediate the impact of objective circumstances on psychological distress. In particular it focuses on the nature of the interaction between such variables. The results provide no evidence favouring the displacement hypothesis whereby the benefits of social support involve costs in terms of independence. Consistent support, however, is found for the functional substitution hypothesis. The conclusion is unaffected by the introduction of distinctions relating to types of support and types of power.

Nebular emission-line profiles of Type Ib/c supernovae - Probing the ejecta asphericity

In order to assess qualitatively the ejecta geometry of stripped-envelope core-collapse supernovae (SNe), we investigate 98 late-time spectra of 39 objects, many of them previously unpublished. We perform a Gauss-fitting of the [O ] ??6300, 6364 feature in all spectra, with the position, full width at half maximum and intensity of the ?6300 Gaussian as free parameters, and the ?6364 Gaussian added appropriately to account for the doublet nature of the [O ] feature. On the basis of the best-fitting parameters, the objects are organized into morphological classes, and we conclude that at least half of all Type Ib/c SNe must be aspherical. Bipolar jet models do not seem to be universally applicable, as we find too few symmetric double-peaked [O ] profiles. In some objects, the [O ] line exhibits a variety of shifted secondary peaks or shoulders, interpreted as blobs of matter ejected at high velocity and possibly accompanied by neutron-star kicks to assure momentum conservation. At phases earlier than ~200 d, a systematic blueshift of the [O ] ??6300, 6364 line centroids can be discerned. Residual opacity provides the most convincing explanation of this phenomenon, photons emitted on the rear side of the SN being scattered or absorbed on their way through the ejecta. Once modified to account for the doublet nature of the oxygen feature, the profile of Mg i] ?4571 at sufficiently late phases generally resembles that of [O ] ??6300, 6364, suggesting negligible contamination from other lines and confirming that O and Mg are similarly distributed within the ejecta. © 2009 RAS.