Sex allocation and the emergence of helping in cooperatively breeding species.

In cooperative breeding systems individuals invest in the reproductive success of others. In this paper, we study the emergence of cooperative breeding systems in which reproductively active breeders receive investment from reproductively non-active helpers. Our goal is to understand how the division of an investment between male and female components of breeder fitness (i.e. the helper sex-allocation strategy) influences the emergence of cooperative breeding itself. Using mathematical models, we arrive at expressions for the inclusive-fitness advantage of helpful behaviour that generalize previous work. These expressions assume an ecologically stable environment, and that breeders make evolutionarily stable sex-allocation decisions. We find that, when breeders are extremely resource limited, the sex-allocation strategy used by a helper can be a key determinant in the success of helpful alleles. This finding, however, is restricted to cases in which helpers have access to intermediate levels of resources. Surprisingly, when helpers can make only a small investment in a recipient the division of the investment matters only very little to advantage of help. By contrast when resources are extremely abundant, we obtain the unsurprising result that the manner in which resources are allocated has little influence on the emergence of help. When breeders have access to intermediate levels of resources we find increasing relatedness can, in certain cases, inhibit the emergence of help. We also find that increasing the amount of resources available to a breeder can impede help as well. Both of these counter-intuitive results are mediated by evolutionary responses in breeder sex allocation

Simulated Swaption Delta-Hedging in the Lognormal Forward Libor Model

Alternative approaches to hedging swaptions are explored and tested by simulation. Hedging methods implied by the Balck swaption formula are compared with a lognormal forward LIBOR model approach encompassing all the relevant forward rates. The simulation is undertaken within the LIBOR model framework for a range of swaptions and volatility structures. Despite incompatibilities with the model assumptions, the Black method performs equally well as the LIBOR method, yielding very similar distributions for the hedging profit and loss - even at high rehedging frequencies. This result demonstrates the robustness of the Black hedging technique and implies that - being simpler and generally better understood by financial practitioners - it would be the preferred method in practice.term structure of interest rates; hedging; simulation; lognormal forward LIBOR model

Impact ionisation electroluminescence in planar GaAs-based heterostructure Gunn diodes:Spatial distribution and impact of doping nonuniformities

When biased in the negative differential resistance regime, electroluminescence (EL) is emitted from planar GaAs heterostructure Gunn diodes. This EL is due to the recombination of electrons in the device channel with holes that are generated by impact ionisation when the Gunn domains reach the anode edge. The EL forms non-uniform patterns whose intensity shows short-range intensity variations in the direction parallel to the contacts and decreases along the device channel towards the cathode. This paper employs Monte Carlo models, in conjunction with the experimental data, to analyse these non-uniform EL patterns and to study the carrier dynamics responsible for them. It is found that the short-range lateral (i.e., parallel to the device contacts) EL patterns are probably due to non-uniformities in the doping of the anode contact, illustrating the usefulness of EL analysis on the detection of such inhomogeneities. The overall decreasing EL intensity towards the anode is also discussed in terms of the interaction of holes with the time-dependent electric field due to the transit of the Gunn domains. Due to their lower relative mobility and the low electric field outside of the Gunn domain, freshly generated holes remain close to the anode until the arrival of a new domain accelerates them towards the cathode. When the average over the transit of several Gunn domains is considered, this results in a higher hole density, and hence a higher EL intensity, next to the anode

Vulnerability to bullying in children with a history of specific speech and language difficulties

This is an electronic version of an article published in Lindsay, Geoff and Dockrell, Julie and Mackie, Clare (2008) Vulnerability to bullying in children with a history of specific speech and language difficulties. European Journal of Special Needs Education, 23 (1). pp. 1-16. European Journal of Special Needs Education is available online at: http://www.informaworld.com/10.1080/0885625070179120

An electrical equivalent circuit to simulate the output power of an AlGaAs/GaAs planar Gunn diode

The planar Gunn diode offers the potential of microwave, milli-metric and THz based oscillator which can be fabricated as part of a microwave monolithic integrated circuit (mmic). To-date the RF output power has been too low for many applications. This paper looks at a simple electrical equivalent circuit model representation of an aluminium gallium arsenide (AlGaAs) based planar Gunn diode with an active channel length of approximately 4μm and width of 120μm. The model indicated a maximum RF output power of +5dBm compared with published experimental results of –19dBm for similar diodes

An electrical equivalent circuit to simulate the output power of an AlGaAs/GaAs planar Gunn diode

The planar Gunn diode offers the potential of microwave, milli-metric and THz based oscillator which can be fabricated as part of a microwave monolithic integrated circuit (mmic). To-date the RF output power has been too low for many applications. This paper looks at a simple electrical equivalent circuit model representation of an aluminium gallium arsenide (AlGaAs) based planar Gunn diode with an active channel length of approximately 4μm and width of 120μm. The model indicated a maximum RF output power of +5dBm compared with published experimental results of –19dBm for similar diodes

Does age acquired immunity confer selective protection to common serotypes of Campylobacter jejuni?

BACKGROUND: Campylobacter infection is a major cause of bacterial gastrointestinal disease. Exposure to Campylobacter is known to produce an immune response in humans that can prevent future symptomatic infections. Further, studies of the general population have shown that seroprevalence to Campylobacter increases with age. METHODS: A large collection of serotyped Campylobacter isolates, obtained from human clinical faecal samples, were analysed by comparing the ratio of uncommon to common serotypes by different age groups, using χ(2 )tests. RESULTS: We have identified that older age groups, as well as having generally lower incidence, are significantly less likely to be infected by the more common serotypes. CONCLUSION: These results are indicative of acquired immunity, however, further studies are needed to rule out the confounding effects of the variations in exposure pathways experienced by different age groups

Identifying a typology of men who use Anabolic Androgenic Steroids (AAS)

Abstract: Background: Despite recognition that the Anabolic Androgenic Steroid (AAS) using population is diverse, empirical studies to develop theories to conceptualise this variance in use have been limited. Methods: In this study, using cluster analysis and multinomial logistic regression, we identify typologies of people who use AAS and examine variations in motivations for AAS use across types in a sample of 611 men who use AAS. Results: The cluster analysis identified four groups in the data with different risk profiles. These groups largely reflect the ideal types of people who use AAS proposed by Christiansen and colleagues (2016): Cluster 1 (You Only Live Once (YOLO) type, n=68, 11.1%) were younger and motivated by fat loss; Cluster 2 (Well-being type, n=236, 38.6%) were concerned with getting fit; Cluster 3 (Athlete type, n=155, 25.4%) were motivated by muscle and strength gains; Cluster 4 (Expert type, n=152, 24.9%) were focused on specific goals (i.e. not 'getting fit'). Conclusion: The results of this study demonstrate the need to make information about AAS accessible to the general population and to inform health service providers about variations in motivations and associated risk behaviours. Attention should also be given to ensuring existing harm minimisation services are equipped to disseminate information about safe intra-muscular injecting and ensuring needle disposal sites are accessible to the different types

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

On the interpretation of removable interactions: A survey of the field 33 years after Loftus

In a classic 1978 Memory &Cognition article, Geoff Loftus explained why noncrossover interactions are removable. These removable interactions are tied to the scale of measurement for the dependent variable and therefore do not allow unambiguous conclusions about latent psychological processes. In the present article, we present concrete examples of how this insight helps prevent experimental psychologists from drawing incorrect conclusions about the effects of forgetting and aging. In addition, we extend the Loftus classification scheme for interactions to include those on the cusp between removable and nonremovable. Finally, we use various methods (i.e., a study of citation histories, a questionnaire for psychology students and faculty members, an analysis of statistical textbooks, and a review of articles published in the 2008 issue of Psychology andAging) to show that experimental psychologists have remained generally unaware of the concept of removable interactions. We conclude that there is more to interactions in a 2 × 2 design than meets the eye