2,834 research outputs found
Reticulation, Data Combination, and Inferring Evolutionary History: An Example from Danthonioideae (Poaceae)
We explore the potential impact of conflicting gene trees on inferences of evolutionary history above the species level. When conflict between gene trees is discovered, it is common practice either to analyze the data separately or to combine the data having excluded the conflicting taxa or data partitions for those taxa (which are then recoded as missing). We demonstrate an alternative approach, which involves duplicating conflicting taxa in the matrix, such that each duplicate is represented by one partition only. This allows the combination of all available data in standard phylogenetic analyses, despite reticulations. We show how interpretation of contradictory gene trees can lead to conflicting inferences of both morphological evolution and biogeographic history, using the example of the pampas grasses, Cortaderia. The characteristic morphological syndrome of Cortaderia can be inferred as having arisen multiple times (chloroplast DNA [cpDNA]) or just once (nuclear ribosomal DNA [nrDNA]). The distributions of species of Cortaderia and related genera in Australia/New Guinea, New Zealand, and South America can be explained by few (nrDNA) or several (cpDNA) dispersals between the southern continents. These contradictions can be explained by past hybridization events, which have linked gains of complex morphologies with unrelated chloroplast lineages and have erased evidence of dispersals from the nuclear genome. Given the discrepancies between inferences based on the gene trees individually, we urge the use of approaches such as ours that take multiple gene trees into accoun
The neural correlates of emotion regulation by implementation intentions
Several studies have investigated the neural basis of effortful emotion regulation (ER) but the neural basis of automatic ER has been less comprehensively explored. The present study investigated the neural basis of automatic ER supported by ‘implementation intentions’. 40 healthy participants underwent fMRI while viewing emotion-eliciting images and used either a previously-taught effortful ER strategy, in the form of a goal intention (e.g., try to take a detached perspective), or a more automatic ER strategy, in the form of an implementation intention (e.g., “If I see something disgusting, then I will think these are just pixels on the screen!”), to regulate their emotional response. Whereas goal intention ER strategies were associated with activation of brain areas previously reported to be involved in effortful ER (including dorsolateral prefrontal cortex), ER strategies based on an implementation intention strategy were associated with activation of right inferior frontal gyrus and ventro-parietal cortex, which may reflect the attentional control processes automatically captured by the cue for action contained within the implementation intention. Goal intentions were also associated with less effective modulation of left amygdala, supporting the increased efficacy of ER under implementation intention instructions, which showed coupling of orbitofrontal cortex and amygdala. The findings support previous behavioural studies in suggesting that forming an implementation intention enables people to enact goal-directed responses with less effort and more efficiency
Performance of Hamamatsu 64-anode photomultipliers for use with wavelength--shifting optical fibres
Hamamatsu R5900-00-M64 and R7600-00-M64 photomultiplier tubes will be used
with wavelength--shifting optical fibres to read out scintillator strips in the
MINOS near detector. We report on measurements of the gain, efficiency,
linearity, crosstalk, and dark noise of 232 of these PMTs, of which 219 met
MINOS requirements.Comment: 15 pages, 12 figures. Accepted by Nucl. Inst. Meth.
A Total Evidence Approach to Understanding Phylogenetic Relationships and Ecological Diversity in Selanginella subg. Tetragonostachys
• Premise of the Study: Several members of Selaginella are renowned for their ability to survive extreme drought and “resurrect”
when conditions improve. Many of these belong to subgenus Tetragonostachys , a group of ~45 species primarily found in
North and Central America, with substantial diversity in the Sonoran and Chihuahuan Deserts. We evaluated the monophyly
and the age of subgenus Tetragonostachys and assess how drought tolerance contributed to the evolution of this clade.
• Methods: Our study included most Tetragonostachys species, using plastid and nuclear sequences, fossil and herbarium records,
and climate variables to describe the species diversity, phylogenetic relationships, divergence times, and climatic niche
evolution in the subgenus.
• Key Results: We found that subgenus Tetragonostachys forms a monophyletic group sister to Selaginella lepidophylla and may
have diverged from other Selaginella because of a Gondwanan–Laurasian vicariance event ca. 240 mya. The North American
radiation of Tetragonostachys appears to be much more recent and to have occurred during the Early Cretaceous–late Paleocene
interval. We identifi ed two signifi cant and nested ecological niche shifts during the evolution of Tetragonostachys associated
with extreme drought tolerance and a more recent shift to cold climates. Our analyses suggest that drought tolerance
evolved in the warm deserts of southwest North America and may have been advantageous for colonization of cold and dry
boreal climates.
• Conclusions: Our investigation provides a foundation for future research addressing the genomics of ecological niche evolution
and the potential role of reticulate evolution in Selaginella subgenus Tetragonostachys .The authors thank P. Korall for sharing data. S. Buerki, N. Alvarez, and
B. Marazzi provided technical assistance and valuable comments on the manuscript. N.A. was funded by the Swiss National Science Foundation (grant no. PBNEP3-132747). C.L.A. was funded by the Swedish Research Council
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Why does early childhood deprivation increase the risk for depression and anxiety in adulthood? A developmental cascade model
Abstract Background: Using data from the English & Romanian Adoptees (ERA) study we recently reported that early time-lmited exposure to severe institutional deprivation is
associated with early onset and persistent neurodevelopmental problems and later
onset emotional problems. Here we examine possible reasons for the late
emergence of emotional problems in this cohort. Our main focus is on testing a
developmental cascade mediated via the functional impact of early-appearing
neurodevelopmental problems on late adolescent functioning. We also explore a
second putative pathway via sensitization to stress. Methods: The ERA study includes 165 Romanian individuals who spent their early lives in grossly depriving institutions and were subsequently adopted into UK
families, along with 52 UK adoptees with no history of deprivation. Age six years
symptoms of neurodevelopmental problems and age 15 anxiety/depression
symptoms were assessed via parental reports. Young adult symptoms of depression
and anxiety were assessed by both parent and self-reports; young adults also
completed measures of stress reactivity , exposure to adverse life events and
functioning in work and interpersonal relationships. Results: The path between early institutional deprivation and adult emotional problems was mediated via the impact of early neurodevelopmental problems on
unemployment and poor friendship functioning during the transition to adulthood.
The findings with regard to early deprivation, later life stress reactivity and emotional
problems were inconclusive.
Conclusions: Our analysis suggests that the risk for adult depression and anxiety following extreme institutional deprivation is explained through the effects of early neurodevelopmental problems on later social and vocational functioning. Future research should more fully examine the role of stress susceptibility in this model
Prototype finline-coupled TES bolometers for CLOVER
CLOVER is an experiment which aims to detect the signature of gravitational
waves from inflation by measuring the B-mode polarization of the cosmic
microwave background. CLOVER consists of three telescopes operating at 97, 150,
and 220 GHz. The 97-GHz telescope has 160 feedhorns in its focal plane while
the 150 and 220-GHz telescopes have 256 horns each. The horns are arranged in a
hexagonal array and feed a polarimeter which uses finline-coupled TES
bolometers as detectors. To detect the two polarizations the 97-GHz telescope
has 320 detectors while the 150 and 220-GHz telescopes have 512 detectors each.
To achieve the target NEPs (1.5, 2.5, and 4.5x10^-17 W/rtHz) the detectors are
cooled to 100 mK for the 97 and 150-GHz polarimeters and 230 mK for the 220-GHz
polarimeter. Each detector is fabricated as a single chip to ensure a 100%
operational focal plane. The detectors are contained in linear modules made of
copper which form split-block waveguides. The detector modules contain 16 or 20
detectors each for compatibility with the hexagonal arrays of horns in the
telescopes' focal planes. Each detector module contains a time-division SQUID
multiplexer to read out the detectors. Further amplification of the multiplexed
signals is provided by SQUID series arrays. The first prototype detectors for
CLOVER operate with a bath temperature of 230 mK and are used to validate the
detector design as well as the polarimeter technology. We describe the design
of the CLOVER detectors, detector blocks, and readout, and present preliminary
measurements of the prototype detectors performance.Comment: 4 pages, 6 figures; to appear in the Proceedings of the 17th
International Symposium on Space Terahertz Technology, held 10-12 May 2006 in
Pari
Forensic Investigation of Failed Mast Arms of Traffic Signal Supported Structures
In Missouri, 11 traffic signal mast arms fractured at the arm-post weld connection in 7 years. To reduce this fatigue failure, the Missouri Department of Transportation developed a fatigue-resistant weld profile that increases the weld leg and reduces the slope of the weld at the toe. This study investigated causes of the failed arms, compared performance of new and old weld profiles, and suggested retrofitting measures for further investigation. The scope included a metallurgical investigation of one failed field mast arm, laboratory fatigue testing of five prototype mast arms (two new and three old profiles), and laboratory failure analysis of one arm tested to cracking. Metallographic and fractographic analyses indicated that the fatigue crack in the failed mast arm initiates near the weld toe of the arm due to undercutting, creating a sharp local toe angle. Location of undercutting at the heat-affected zone of the base material, where the material is softest, further contributed to early fatigue failure. Tests showed that the new weld profile does not consistently increase fatigue strength. Premature fracture surfaces of one tested arm indicated that the fatigue cracks initiate in an area at the weld toe as observed in the failed mast arm. Therefore, changing the weld profile alone is unlikely to increase mast arm fatigue life. Pinning the weldment surface at the weld toe of mast arms is suggested to increase the life of mast arms
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