抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

In 1974 an article appeared in Science magazine with the dry-sounding title “Judgment Under Uncertainty: Heuristics and Biases” by a pair of psychologists who were not well known outside their discipline of decision theory. In it Amos Tversky and Daniel Kahneman introduced the world to Prospect Theory, which mapped out how humans actually behave when faced with decisions about gains and losses, in contrast to how economists assumed that people behave. Prospect Theory turned Economics on its head by demonstrating through a series of ingenious experiments that people are much more concerned with losses than they are with gains, and that framing a choice from one perspective or the other will result in decisions that are exactly the opposite of each other, even if the outcomes are monetarily the same. Prospect Theory led cognitive psychology in a new direction that began to uncover other human biases in thinking that are probably not learned but are part of our brain’s wiring.

Thinking fast and slow.

Doing Qualitative Research

© 2016 John Wiley & Sons LtdBitter personal experience and meta-analysis converge on the conclusion that people do not always do the things that they intend to do. This paper synthesizes research on intention–behavior relations to address questions such as: How big is the intention–behavior gap? When are intentions more or less likely to get translated into action? What kinds of problems prevent people from realizing their intentions? And what strategies show promise in closing the intention–behavior gap and helping people do the things that they intend to do?.

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The Intention–Behavior Gap

Delis‐Kaplan Executive Function System

Physically active lifestyles contribute to better executive function. However, it is unclear whether high levels of executive function lead people to be more active. This study uses a large sample and multi-wave data to identify whether a reciprocal association exists between physical activity and executive function. Participants were 4555 older adults tracked across four waves of the English Longitudinal Study of Aging. In each wave executive function was assessed using a verbal fluency test and a letter cancelation task and participants reported their physical activity levels. Fixed effects regressions showed that changes in executive function corresponded with changes in physical activity. In longitudinal multilevel models low levels of physical activity led to subsequent declines in executive function. Importantly, poor executive function predicted reductions in physical activity over time. This association was found to be over 50% larger in magnitude than the contribution of physical activity to changes in executive function. This is the first study to identify evidence for a robust bidirectional link between executive function and physical activity in a large sample of older adults tracked over time.

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A bidirectional relationship between physical activity and executive function in older adults

Objective: To test the dimensionality of Type-D personality, using taxometric procedures, to assess if Type-D personality is taxonic or dimensional. Type-D personality is treated as a categorical variable and caseness has been shown to be a risk factor for poor prognosis in coronary heart disease. However, at present, there is no direct evidence to support the assumption that Type D is categorical and able to differentiate true cases from noncases. Methods: In total, 1012 healthy young adults from across the United Kingdom and Ireland completed the DS14, the standard index of Type D, and scores were submitted to two taxometric procedures MAMBAC and MAXCOV. Results: Graphical representations (comparing actual with simulated data) and fit indices indicated that Type D is more accurately represented as a dimensional rather than categorical construct. Conclusion: Type D is better represented as a dimensional construct. Implications for theory development and clinical practice with respect to Type D are examined as well as the wider use of taxometrics within psychosomatic medicine (e.g., to investigate if there are medically unexplained syndrome taxons, such as a Gulf War Syndrome taxon).

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A taxometric analysis of type-D personality.

Physically active lifestyles and other health-enhancing behaviors play an important role in preserving executive function into old age. Conversely, emerging research suggests that executive functions facilitate participation in a broad range of healthy behaviors including physical activity and reduced fatty food, tobacco and alcohol consumption. They do this by supporting the volition, planning, performance monitoring, and inhibition necessary to enact intentions and override urges to engage in health damaging behavior. Here, we focus firstly on evidence suggesting that health-enhancing behaviors can induce improvements in executive function. We then switch our focus to findings linking executive function to the consistent performance of health-promoting behaviors and the avoidance of health risk behaviors. We suggest that executive function, health behavior, and disease processes are interdependent. In particular, we argue that a positive feedback loop may exist whereby health behavior-induced changes in executive function foster subsequent health-enhancing behaviors, which in turn help sustain efficient executive functions and good health. We conclude by outlining the implications of this reciprocal relationship for intervention strategies, the design of research studies, and the study of healthy ageing.

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A bidirectional relationship between executive function and health behavior : evidence, implications, and future directions

Failing to achieve healthy intentions can have a direct impact on subsequent health. The extent of this impact is partially determined by the size of the discrepancy between intentions and behaviour, that is, on whether an unachieved behavioural target is missed by an inch or a mile. Over two studies, measures of 'executive control' ability were used to predict the size of the intention-behaviour gap for two dietary behaviours - eating fruits and vegetables and snacking. In Study 1, participants (n=50) reported intended dietary intake, completed objective and self-report measures of executive control ability and recorded actual dietary intake over 3 days with computerised diaries. Using multiple regression, general executive control ability was found to account for 16-23% of the variance in the size of intention-behaviour gap for both the dietary behaviours. In Study 2 (n=52), deviation from intentions about snacking was significantly related to individual differences in prepotent response inhibition. Overall, individuals with weak executive control ate less fruits and vegetables and more snacks than intended. Intention-behaviour 'failures' are not homogenous, but instead vary predictably with the availability of executive control resources. This suggests that individuals with large intention-behaviour shortfalls may benefit from interventions designed to reduce the demands on executive control.

Missed by an inch or a mile? Predicting the size of intention-behaviour gap from measures of executive control.

Theories of action control emphasise the importance of planning, but plans are not universally beneficial. The present study investigates whether the effectiveness of plans depends upon the skill of the planner. Study 1 prospectively predicted changes in unhealthy snacking behaviour over 1 week from intentions, action planning and performance on a standardised cognitive test of planning skill (n = 72). Study 2 experimentally randomised skilled and poor planners to receive (or not) a planning intervention before completing an online food diary (n = 144) Spontaneously generated action plans about snacking explained significantly more variance in subsequent snacking if produced by a skilled rather than a poor planner. The planning intervention (implementation intention) significantly improved goal attainment but only in poor planners. Plans are only as good as the people who make them. Poor planners’ plans do not help achieve goals. Planning interventions can compensate for a lack of planning skill.

Julia L. Allan

Papers

A bidirectional relationship between physical activity and executive function in older adults

A taxometric analysis of type-D personality.

A bidirectional relationship between executive function and health behavior : evidence, implications, and future directions

Missed by an inch or a mile? Predicting the size of intention-behaviour gap from measures of executive control.

The Best Laid Plans : Planning Skill Determines the Effectiveness of Action Plans and Implementation Intentions