1,564 research outputs found
Conserved carotenoid pigmentation in reproductive organs of Charophyceae
No full textSexual reproduction in Charophyceae abounds in complex traits. Their gametangia develop as intricate structures, with oogonia spirally surrounded by envelope cells and richly pigmented antheridia. The red—probably protectant—pigmentation of antheridia is conserved across Charophyceae. Chara tomentosa is, however, unique in exhibiting this pigmentation and also in vegetative tissue. Here, we investigated the two sympatric species, C. tomentosa and Chara baltica , and compared their molecular chassis for pigmentation. Using reversed phase C 30 high performance liquid chromatography (RP-C 30 -HPLC), we uncover that the major pigments are β-carotene, δ-carotene and γ-carotene; using headspace solid-phase microextraction coupled to gas chromatography equipped with a mass spectrometer (HS-SPME-GC-MS), we pinpoint that the unusually large carotenoid pool in C. tomentosa gives rise to diverse volatile apocarotenoids, including abundant 6-methyl-5-hepten-2-one. Based on transcriptome analyses, we uncover signatures of the unique biology of Charophycaee and genes for pigment production, including monocyclized carotenoids. The rich carotenoid pool probably serves as a substrate for diverse carotenoid-derived metabolites, signified not only by (i) the volatile apocarotenoids we detected but (ii) the high expression of a gene coding for a cytochrome P450 enzyme related to land plant proteins involved in the biosynthesis of carotenoid-derived hormones. Overall, our data shed light on a key protection strategy of sexual reproduction in the widespread group of macroalgae. The genetic underpinnings of this are shared across hundreds of millions of years of plant and algal evolution. This article is part of the theme issue ‘The evolution of plant metabolism’.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659H2020 European Research Council http://dx.doi.org/10.13039/10001066
Evaluating Citebase, an open access Web-based citation-ranked search and impact discovery service
No full textCitebase is a new citation-ranked search and impact discovery service that measures citations of scholarly research papers which are openly accessible on the Web, i.e. papers that are assessable continuously online. Other services, such as ResearchIndex, have emerged in recent years to offer citation indexing of Web research papers. In the first detailed user evaluation of an open access Web citation indexing service, Citebase has been evaluated by nearly 200 users from different backgrounds. The paper details the procedures used in the evaluation, and analyses the results of this study, which took place between June and October 2002. It was found that within the scope of its primary components, the search interface and services available from its rich bibliographic records, Citebase can be used simply and reliably for the purpose intended, and that it compares favourably with other bibliographic services. It is shown tasks can be accomplished efficiently with Citebase regardless of the background of the user. More data need to be collected and the process refined before it is as reliable for measuring citation impact of indexed papers. Better explanations and guidance are required for first-time users. Coverage is seen as a limiting factor, even though Citebase indexes over 200,000 papers from arXiv. Non-physicists were frustrated at the lack of papers from other sciences. The principle of citation searching of open access archives has thus been demonstrated and need not be restricted to current users. Since the evaluation, Citebase has become a featured service of the ArXiv physics eprint archives
Divergent responses in desiccation experiments in two ecophysiologically different Zygnematophyceae
No full textAbstract Water scarcity can be considered a major stressor on land, with desiccation being its most extreme form. Land plants have found two different solutions to this challenge: avoidance and tolerance. The closest algal relatives to land plants, the Zygnematophyceae, use the latter, and how this is realized is of great interest for our understanding of the conquest of land. Here, we worked with two representatives of the Zygnematophyceae, Zygnema circumcarinatum SAG 698‐1b and Mesotaenium endlicherianum SAG 12.97, who differ in habitats and drought resilience. We challenged both algal species with severe desiccation in a laboratory setup until photosynthesis ceased, followed by a recovery period. We assessed their morphological, photophysiological, and transcriptomic responses. Our data pinpoint global differential gene expression patterns that speak of conserved responses, from calcium‐mediated signaling to the adjustment of plastid biology, cell envelopes, and amino acid pathways, between Zygnematophyceae and land plants despite their strong ecophysiological divergence. The main difference between the two species appears to rest in a readjustment of the photobiology of Zygnema , while Mesotaenium experiences stress beyond a tipping point.Deutsche Forschungsgemeinschaft https://doi.org/10.13039/501100001659European Research Council https://doi.org/10.13039/10001066
Environmental gradients reveal stress hubs pre-dating plant terrestrialization
No full textPlant terrestrialization brought forth the land plants (embryophytes). Embryophytes account for most of the biomass on land and evolved from streptophyte algae in a singular event. Recent advances have unravelled the first full genomes of the closest algal relatives of land plants; among the first such species was Mesotaenium endlicherianum . Here we used fine-combed RNA sequencing in tandem with a photophysiological assessment on Mesotaenium exposed to a continuous range of temperature and light cues. Our data establish a grid of 42 different conditions, resulting in 128 transcriptomes and ~1.5 Tbp (~9.9 billion reads) of data to study the combinatory effects of stress response using clustering along gradients. Mesotaenium shares with land plants major hubs in genetic networks underpinning stress response and acclimation. Our data suggest that lipid droplet formation and plastid and cell wall-derived signals have denominated molecular programmes since more than 600 million years of streptophyte evolution—before plants made their first steps on land.Deutsche Forschungsgemeinschaft https://doi.org/10.13039/501100001659EC | Horizon 2020 Framework Programme https://doi.org/10.13039/100010661Ministry of Education - Singapore https://doi.org/10.13039/50110000145
Author Talk
No full textUniversity president, Jim Schmotter, introduces Tim O'Brien at the author talk in Ives Auditorium, October 26, 2010.</p
Who Belongs? Immigrants, Refugees, Migrants, and Actions Towards Justice: A Conversation With Tim Wise
No full textTim Wise is an antiracist activist, essayist and author of seven books on racism, inequality and white privilege. He is among the most prominent anti-racist writers and educators in the United States. Over the past 25 years he has engaged audiences in all 50 states, at over 1000 college and high school campuses, at hundreds of professional and academic conferences, and to community groups across the country. While visiting Iowa State University Tim Wise interviewed with us to discuss Who Belongs? by providing a brief historical perspective of immigration, the current political climate, and the role of activism.</p
Accepting Optimally in Automated Negotiation with Incomplete Information (abstract)
No full textIntelligent SystemsElectrical Engineering, Mathematics and Computer Scienc
Whose Voice? Tim Crouch’s The Author and Active Listening on the Contemporary Stage
No full textThe essay discusses Tim Crouch’s recent play The Author (2009) in the context of active listening, audience participation, response and responsibility in contemporary theatre. It provides a critical engagement with the spectatorial experience of the piece so as to problematize the multiple uses of the physical medium of voice and speech in a contemporary play that delivers a fresh angle to narrativity and metatheatricality. At the same time, the essay probes the varied range of possibilities but also realistic extent of audience involvement in the play, tracing its deep textual contingencies to produce an overall understanding of the equally rewarding and precarious interrelationship between performance piece and audience.</p
UTSim2 validation
No full textThe Center for NDE (CNDE) at Iowa State University has a long history of developing physics models for NDE and packaging these models into simulation tools which make the modeling capabilities accessible to CNDEs industrial sponsors. Recent work at CNDE has led to the development of a new ultrasonic simulation package, UTSim2, which aims to continue this tradition of supporting industrial application of CNDE models. In order to meet this goal, UTSim2 has been designed as an extensible software package which can support previously-developed physics models as well as future models yet to be developed. Initial work has focused on the implementation of a Gauss-Hermite beam model, a paraxial approximation, which is implemented as part of the Thompson-Gray measurement model. This paper will present recent validation results and include comparisons against both previously-validated model output and newly-performed experiments.This proceeding may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This proceeding appeared in Grandin, Robert, and Tim Gray. "UTSim2 validation." AIP Conference Proceedings, 1806, no. 1 (2017): 150007, and may be found at DOI: 10.1063/1.4974731. Posted with permission.</p
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