323 research outputs found

    Maladaptation and the paradox of robustness in evolution

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    Background. Organisms use a variety of mechanisms to protect themselves against perturbations. For example, repair mechanisms fix damage, feedback loops keep homeostatic systems at their setpoints, and biochemical filters distinguish signal from noise. Such buffering mechanisms are often discussed in terms of robustness, which may be measured by reduced sensitivity of performance to perturbations. Methodology/Principal Findings. I use a mathematical model to analyze the evolutionary dynamics of robustness in order to understand aspects of organismal design by natural selection. I focus on two characters: one character performs an adaptive task; the other character buffers the performance of the first character against perturbations. Increased perturbations favor enhanced buffering and robustness, which in turn decreases sensitivity and reduces the intensity of natural selection on the adaptive character. Reduced selective pressure on the adaptive character often leads to a less costly, lower performance trait. Conclusions/Significance. The paradox of robustness arises from evolutionary dynamics: enhanced robustness causes an evolutionary reduction in the adaptive performance of the target character, leading to a degree of maladaptation compared to what could be achieved by natural selection in the absence of robustness mechanisms. Over evolutionary time, buffering traits may become layered on top of each other, while the underlying adaptive traits become replaced by cheaper, lower performance components. The paradox of robustness has widespread implications for understanding organismal design

    'They're told all the time they're different': how educators understand development of sense of self for autistic pupils

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    School is a site of critical importance in the development of self yet little is known about the ways in which school affects how autistic pupils come to describe and evaluate themselves. Educators are centrally positioned to support autistic pupils with development of an empowered sense of self. This article reports on a study which captured how staff in four English schools understood development of sense of self for autistic pupils. We found that educators perceived autistic pupils as being affected by both a particular biology and their social encounters with others. Our participants identified the school environment as a significant influencer on sense of self development but seemed uncertain how to make this more enabling. We suggest that one response could be to develop a framework of activism engagement in schools that might enable autistic pupils to work collectively with other autistic people towards a positive sense of self

    The Wide Brown Dwarf Binary Oph 1622-2405 and Discovery of A Wide, Low Mass Binary in Ophiuchus (Oph 1623-2402): A New Class of Young Evaporating Wide Binaries?

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    We imaged five objects near the star forming clouds of Ophiuchus with the Keck Laser Guide Star AO system. We resolved Allers et al. (2006)'s #11 (Oph 16222-2405) and #16 (Oph 16233-2402) into binary systems. The #11 object is resolved into a 243 AU binary, the widest known for a very low mass (VLM) binary. The binary nature of #11 was discovered first by Allers (2005) and independently here during which we obtained the first spatially resolved R~2000 near-infrared (J & K) spectra, mid-IR photometry, and orbital motion estimates. We estimate for 11A and 11B gravities (log(g)>3.75), ages (5+/-2 Myr), luminosities (log(L/Lsun)=-2.77+/-0.10 and -2.96+/-0.10), and temperatures (Teff=2375+/-175 and 2175+/-175 K). We find self-consistent DUSTY evolutionary model (Chabrier et al. 2000) masses of 17+4-5 MJup and 14+6-5 MJup, for 11A and 11B respectively. Our masses are higher than those previously reported (13-15 MJup and 7-8 MJup) by Jayawardhana & Ivanov (2006b). Hence, we find the system is unlikely a ``planetary mass binary'', (in agreement with Luhman et al. 2007) but it has the second lowest mass and lowest binding energy of any known binary. Oph #11 and Oph #16 belong to a newly recognized population of wide (>100 AU), young (<10 Myr), roughly equal mass, VLM stellar and brown dwarf binaries. We deduce that ~6+/-3% of young (<10 Myr) VLM objects are in such wide systems. However, only 0.3+/-0.1% of old field VLM objects are found in such wide systems. Thus, young, wide, VLM binary populations may be evaporating, due to stellar encounters in their natal clusters, leading to a field population depleted in wide VLM systems.Comment: Accepted version V2. Now 13 pages longer (45 total) due to a new discussion of the stability of the wide brown dwarf binary population, new summary Figure 17 now included, Astrophysical Journal 2007 in pres

    Mental health resilience in the adolescent offspring of parents with depression:a prospective longitudinal study

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    Background Young people whose parents have depression have a greatly increased risk of developing a psychiatric disorder, but poor outcomes are not inevitable. Identification of the contributors to mental health resilience in young people at high familial risk is an internationally recognised priority. Our objectives were to identify protective factors that predict sustained good mental health in adolescents with a parent with depression and to test whether these contribute beyond what is explained by parent illness severity. Methods The Early Prediction of Adolescent Depression study (EPAD) is a prospective longitudinal study of offspring of parents with recurrent depression. Parents with recurrent major depressive disorder, co-parents, and offspring (aged 9–17 years at baseline) were assessed three times over 4 years in a community setting. Offspring outcomes were operationalised as absence of mental health disorder, subthreshold symptoms, or suicidality on all three study occasions (sustained good mental health); and better than expected mental health (mood and behavioural symptoms at follow-up lower than predicted given severity of parental depression). Family, social, cognitive, and health behaviour predictor variables were assessed using interview and questionnaire measures. Findings Between February and June, 2007, we screened 337 families at baseline, of which 331 were eligible. Of these, 262 completed the three assessments and were included in the data for sustained mental health. Adolescent mental health problems were common, but 53 (20%) of the 262 adolescents showed sustained good mental health. Index parent positive expressed emotion (odds ratio 1·91 [95% CI 1·31–2·79]; p=0·001), co-parent support (1·90 [1·38–2·62]; p<0·0001), good-quality social relationships (2·07 [1·35–3·18]; p=0·001), self-efficacy (1·49 [1·05–2·11]; p=0·03), and frequent exercise (2·96 [1·26–6·92]; p=0·01) were associated with sustained good mental health. Analyses accounting for parent depression severity were consistent, but frequent exercise only predicted better than expected mood-related mental health (β=–0·22; p=0·0004) not behavioural mental health, whereas index parents' expression of positive emotions predicted better than expected behavioural mental health (β=–0·16; p=0·01) not mood-related mental health. Multiple protective factors were required for offspring to be free of mental health problems (zero or one protective factor, 4% sustained good mental health; two protective factors, 10%; three protective factors, 13%, four protective factors, 38%; five protective factors, 48%). Interpretation Adolescent mental health problems are common, but not inevitable, even when parental depression is severe and recurrent. These findings suggest that prevention programmes will need to enhance multiple protective factors across different domains of functioning

    Instrumentation for open ocean aquaculture monitoring

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    The Woods Hole Oceanographic Institution is assisting the University of New Hampshire by instrumenting a fish cage and mooring as part of their Open Ocean Aquaculture demonstration program in the Gulf of Maine. To understand these systems, the wave and current forcing and the response of the mooring and fish cage needs to be measured. A UNH mooring with an ADCP measured the current forcing. Tension in the mooring lines was measured by load cells deployed with the mooring during servicing in August 2000. Load cells were placed in each anchor line, and, in the NE corner, also in the two grid lines and the riser line to the fish cage. Low power recording systems were deployed on the load cell mounting bars by divers on 22 October 2000, recorded good data through January 2001, when they were turned around and redeployed. Three single load cell recorders were recovered in July 2001 and recorded though 23 June when their data storage filled. The four load cell system was recovered in March after a large winter storm, and had failed in early March. The wave forcing was measured with a wave rider buoy with a 3-axis accelerometer measuring its motion. The acceleration was integrated twice to obtain wave displacement. The system mooring contained a compliant elastic. The wave rider was deployed on 4 January 2001 and recovered on 17 March 2001 after a major Northeast storm. It recorded data throughout its deployment. The motion of the moored fish cage was measured by a motion package constructed around a 6-axis Motion-Pak and a PC-104 data system. The motion package was deployed on the fish cage from Jan into March 2001 and recorded motions thoughout without difficuly. It observed a major storm in early March where the counter weight was lost from the fish cage, and its increase in motion thereafter.Fudning was provided by National Oceanic and Atmospheric Adminstration for the Open Ocean Aquaculture Project under Contract No. NA86RG0016 to the University of New Hampshire and under Subcontracts 00-394 and 01-442 to the Woods Hole Oceanographic Institution

    Real-world word learning: exploring children's developing semantic representations of a science term

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    Assessments of lexical acquisition are often limited to pre-school children on forced choice comprehension measures. This study assessed the understandings 30 school-age children (mean age = 6;7) acquired about the science term, eclipse following a naturalistic exposure to a solar eclipse. The knowledge children acquired about eclipses and a control term, comet was assessed at three points in time (baseline-test, two-week post-test and five-month post-test) using a range of assessment tasks (multiple-choice comprehension, picture-naming, drawing and a model of a solar system task). Children's knowledge was compared to 15 adult controls during the baseline-test and two-week post-test. Children acquired extensive knowledge about eclipses, but not comets; at the two-week post-test and five-month post-test, the majority of children named and drew eclipses and „made? an eclipse using models of the sun, moon and earth. Also, children's eclipse knowledge more closely approximated adult-level understandings at the two-week post-test than at the baseline-test. Implications for the study of lexical acquisition in later development are discussed

    Evaluating high-cost technologies - no need to throw the baby out with the bathwater

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    INTRODUCTION: Evidence generation for the health technology assessment (HTA) of a new technology is a long and expensive process with no guarantees that the health technology will be adopted and implemented into a health-care system. This would suggest that there is a greater risk of failure for a company developing a high-cost technology and therefore incentives (such as increasing the funding available for research or additional market exclusivity) may be needed to encourage development of such technologies as has been seen with many high-cost orphan drugs. AREAS COVERED: This paper discusses some of the key issues relating to the evaluation of high-cost technologies through the use of existing HTA processes and what the challenges will be going forward. EXPERT OPINION: We propose that while the current HTA process is robust, its evolution into accommodating the incorporation of real-world data and evidence alongside a life-cycle HTA approach should better enable developers to produce the evidence required on effectiveness and cost-effectiveness. This should lead to reduced decision uncertainty for HTA agencies to make adoption decisions in a more timely and efficient manner. Furthermore, budget impact analysis remains important in understanding the actual financial impact on health-care systems and budgets outside of the cost-effectiveness framework used to aid decision-making
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