Liquid drop stability for protein crystal growth in microgravity

It is possible to grow protein crystals for biomedical research in microgravity by deploying a protein-rich solution from a syringe, forming a drop in which crystallization can occur with the proper degree of supersaturation. Drop stability is critical to the success of this research, due to the large drop sizes which can be achieved in space. In order to determine the type of syringe tips most suitable to support these large drops, tests were performed during brief periods of weightlessness onboard the NASA KC-135 low-gravity simulation aircraft. The drops were analyzed using three simple models in which the samples were approximated by modified pendulum and spring systems. It was concluded that the higher frequency systems were the most stable, indicating that of the syringes utilized, a disk-shaped configuration provided the most stable environment of low-gravity protein crystal growth

Kleptoparasitic melees--modelling food stealing featuring contests with multiple individuals

Kleptoparasitism is the stealing of food by one animal from another. This has been modelled in various ways before, but all previous models have only allowed contests between two individuals. We investigate a model of kleptoparasitism where individuals are allowed to fight in groups of more than two, as often occurs in real populations. We find the equilibrium distribution of the population amongst various behavioural states, conditional upon the strategies played and environmental parameters, and then find evolutionarily stable challenging strategies. We find that there is always at least one ESS, but sometimes there are two or more, and discuss the circumstances when particular ESSs occur, and when there are likely to be multiple ESSs

Signal verification can promote reliable signalling.

The central question in communication theory is whether communication is reliable, and if so, which mechanisms select for reliability. The primary approach in the past has been to attribute reliability to strategic costs associated with signalling as predicted by the handicap principle. Yet, reliability can arise through other mechanisms, such as signal verification; but the theoretical understanding of such mechanisms has received relatively little attention. Here, we model whether verification can lead to reliability in repeated interactions that typically characterize mutualisms. Specifically, we model whether fruit consumers that discriminate among poor- and good-quality fruits within a population can select for reliable fruit signals. In our model, plants either signal or they do not; costs associated with signalling are fixed and independent of plant quality. We find parameter combinations where discriminating fruit consumers can select for signal reliability by abandoning unprofitable plants more quickly. This self-serving behaviour imposes costs upon plants as a by-product, rendering it unprofitable for unrewarding plants to signal. Thus, strategic costs to signalling are not a prerequisite for reliable communication. We expect verification to more generally explain signal reliability in repeated consumer-resource interactions that typify mutualisms but also in antagonistic interactions such as mimicry and aposematism

Evolutionary Dynamics on Small-Order Graphs

Abstract. We study the stochastic birth-death model for structured finite populations popularized by Lieberman et al. [Lieberman, E., Hauert, C., Nowak, M.A., 2005. Evolutionary dynamics on graphs. Nature 433, 312-316]. We consider all possible connected undirected graphs of orders three through eight. For each graph, using the Monte Carlo Markov Chain simulations, we determine the fixation probability of a mutant introduced at every possible vertex. We show that the fixation probability depends on the vertex and on the graph. A randomly placed mutant has the highest chances of fixation in a star graph, closely followed by star-like graphs. The fixation probability was lowest for regular and almost regular graphs. We also find that within a fixed graph, the fixation probability of a mutant has a negative correlation with the degree of the starting vertex. 1

Characteristics of women who practice yoga in different locations during pregnancy

Objectives: Yoga practice during pregnancy is gaining increasing popularity. This study examined the characteristics of pregnant women who practiced yoga in regard to the different locations (at home, in yoga classes, or both). Design: The study sample was drawn from the Australian Longitudinal Study on Women's Health (ALSWH), a national longitudinal study of women to investigate multiple factors affecting health and wellbeing of women over a 20-year period. Setting: Postal survey. Participants: Women born between 1973 and 1978, who were randomly selected from the national Medicare database and identified as being pregnant or having recently given birth (n=2316). Outcome measures: Relationships between yoga use (attending yoga classes and/or practising yoga at home) and women's characteristics (demographic measures, pregnancy-related health concerns, health service utilisation, attitudes to complementary and alternative medicine). Results: Practising yoga both at home and in classes was associated with perceiving complementary and alternative medicine (CAM) as preventative (odds ratio (OR)=1.62); perceiving CAM as affording health control (OR=1.50); experiencing sadness (OR=1.72); preparing for labour (OR=2.31); birthing in a birth centre (OR=7.97); and experiencing less vomiting (OR=0.38). Practising at home only was associated with perceiving CAM as affording health control (OR=1.76); perceiving CAM as promoting a holistic health approach (OR=1.65); and birthing in a birth centre (OR=3.54). Practising in classes only was associated with experiencing stress (OR=1.97); and birthing in a birth centre (OR=4.85) (all p<0.05). Conclusions: The findings suggest that the location in which a woman practices yoga is associated with attitudinal, health-related and birth environmental factors

The effect of fight cost structure on fighting behaviour

A common feature of animal populations is the stealing by animals of resources such as food from other animals. This has previously been the subject of a range of modelling approaches, one of which is the so called "producer-scrounger" model. In this model a producer finds a resource that takes some time to be consumed, and some time later a (generally) conspecific scrounger discovers the producer with its resource and potentially attempts to steal it. In this paper we consider a variant of this scenario where each individual can choose to invest an amount of energy into this contest, and the level of investment of each individual determines the probability of it winning the contest, but also the additional cost it has to bear. We analyse the model for a specific set of cost functions and maximum investment levels and show how the evolutionarily stable behaviour depends upon them. In particular we see that for high levels of maximum investment, the producer keeps the resource without a fight for concave cost functions, but for convex functions the scrounger obtains the resource (albeit at some cost)

The effect of fight cost structure on fighting behaviour involving simultaneous decisions and variable investment levels

In the “producer–scrounger” model, a producer discovers a resource and is in turn discovered by a second individual, the scrounger, who attempts to steal it. This resource can be food or a territory, and in some situations, potentially divisible. In a previous paper we considered a producer and scrounger competing for an indivisible resource, where each individual could choose the level of energy that they would invest in the contest. The higher the investment, the higher the probability of success, but also the higher the costs incurred in the contest. In that paper decisions were sequential with the scrounger choosing their strategy before the producer. In this paper we consider a version of the game where decisions are made simultaneously. For the same cost functions as before, we analyse this case in detail, and then make comparisons between the two cases. Finally we discuss some real examples with potentially variable and asymmetric energetic investments, including intraspecific contests amongst spiders and amongst parasitoid wasps. In the case of the spiders, detailed estimates of energetic expenditure are available which demonstrate the asymmetric values assumed in our models. For the wasps the value of the resource can affect the probabilities of success of the defender and attacker, and differential energetic investment can be inferred. In general for real populations energy usage varies markedly depending upon crucial parameters extrinsic to the individual such as resource value and intrinsic ones such as age, and is thus an important factor to consider when modelling

"It doesn't exist…": negotiating palliative care from a culturally and linguistically diverse patient and caregiver perspective.

BACKGROUND: The end of life represents a therapeutic context that acutely raises cultural and linguistic specificities, yet there is very little evidence illustrating the importance of such dynamics in shaping choices, trajectories and care practices. Culture and language interplay to offer considerable potential challenges to both patient and provider, with further work needed to explore patient and caregiver perspectives across cultures and linguistic groups, and provider perspectives. The objective of this study was to develop a critical, evidence-based understanding of the experiences of people from Culturally and Linguistically Diverse (CALD) backgrounds, and their caregivers, in a palliative care setting. METHODS: A qualitative study, using semi-structured interviews to explore key experiences and perspectives of CALD patients and caregivers currently undergoing treatment under oncology or palliative care specialists in two Australian hospitals. Interviews were digitally audio recorded and transcribed in full. A thematic analysis was conducted utilising the framework approach. RESULTS: Sixteen patients and fourteen caregivers from a range of CALD backgrounds participated in semi-structured interviews. The research identified four prevalent themes among participants: (1) Terminology in the transition to palliative care; (2) Communication, culture and pain management; (3) (Not) Talking about death and dying; and, (4) Religious faith as a coping strategy: challenging the terminal diagnosis. CONCLUSIONS: CALD patients and caregivers' experiences are multifaceted, particularly in negotiating linguistic difficulties, beliefs about treatment, and issues related to death and dying. Greater attention is needed to develop effective communication skills, recognise CALD patients' particular cultural, linguistic and spiritual values and needs, and acknowledge the unique nature of each doctor-patient interaction

New genera and species of dicynodont reptiles

p. [441]-457 : ill. ; 24 cm