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1,294 results on '"Hutchins, David A."'

4. Capacitive imaging using fused amplitude and phase information for improved defect detection

Author

Amato, Silvio, Hutchins, David, Yin, Xiaokang, Ricci, Marco, and Laureti, Stefano

Subjects
Electrical Engineering and Systems Science - Signal Processing
Abstract

This paper introduces an improved image processing method usable in capacitive imaging applications. Standard capacitive imaging tends to prefer amplitude-based images over the use of phase due to better signal-to-noise ratios. The new approach exploits the best features of both types of information by combining them to form clearer images, hence improving both defect detection and characterization in non-destructive evaluation. The methodology is demonstrated and optimized using a benchmark sample. Additional experiments on glass fibre composite sample illustrate the advantages of the technique.

Published
2021
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8. Trapped air metamaterials for ultrasonic sub-wavelength imaging in water

Author

Laureti, Stefano, Hutchins, David A., Astolfi, Lorenzo, Watson, Richard L., Thomas, Peter J., Burrascano, Pietro, Nie, Luzhen, Freear, Steven, Askari, Meisam, Clare, Adam T., and Ricci, Marco

Subjects
Physics - Applied Physics, Physics - Instrumentation and Detectors
Abstract

Acoustic metamaterials constructed from conventional base materials can exhibit exotic phenomena such as negative refractive index, extraordinary transmission-absorption and sub-wavelength imaging. These are typically achieved by combining geometrical and resonance effects. Holey-structured acoustic metamaterials have already shown potential for sub-wavelength acoustic imaging in air, where it is relatively simple to achieve the required difference in acoustic impedance needed to create resonances within the holes. However, the use of polymers for metamaterial operation in water is difficult, due to the much lower difference in acoustic impedance between water and the many polymers used, for example, in additive manufacturing. Hence, metals are commonly used. Here we show that this can be overcome by trapping air layers so that they surround each water-filled channel, making sub-wavelength imaging in water possible. The operation of such a Trapped air design is confirmed at 200-300 kHz ultrasonic frequencies via both finite element modelling and experimental measurements in a water tank. It is also shown quantitatively that the trapped air design outperforms its metal counterpart. The results indicate a way forward for exploiting additive-manufacturing for realising acoustic metamaterials in water at ultrasonic frequencies., Comment: 29 pages, 14 figures

Published
2020
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12. The biogeochemical balance of oceanic nickel cycling

Author

John, Seth G., Kelly, Rachel L., Bian, Xiaopeng, Fu, Feixue, Smith, M. Isabel, Lanning, Nathan T., Liang, Hengdi, Pasquier, Benoît, Seelen, Emily A., Holzer, Mark, Wasylenki, Laura, Conway, Tim M., Fitzsimmons, Jessica N., Hutchins, David A., and Yang, Shun-Chung

Published
2022
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13. Scientists’ warning to humanity: microorganisms and climate change

Author

Cavicchioli, Ricardo, Ripple, William J, Timmis, Kenneth N, Azam, Farooq, Bakken, Lars R, Baylis, Matthew, Behrenfeld, Michael J, Boetius, Antje, Boyd, Philip W, Classen, Aimée T, Crowther, Thomas W, Danovaro, Roberto, Foreman, Christine M, Huisman, Jef, Hutchins, David A, Jansson, Janet K, Karl, David M, Koskella, Britt, Mark Welch, David B, Martiny, Jennifer BH, Moran, Mary Ann, Orphan, Victoria J, Reay, David S, Remais, Justin V, Rich, Virginia I, Singh, Brajesh K, Stein, Lisa Y, Stewart, Frank J, Sullivan, Matthew B, van Oppen, Madeleine JH, Weaver, Scott C, Webb, Eric A, and Webster, Nicole S

Subjects
Microbiology, Biological Sciences, Climate Action, Climate Change, Ecosystem, Greenhouse Gases, Human Activities, Humans, Microbial Viability, Medical Microbiology
Abstract

In the Anthropocene, in which we now live, climate change is impacting most life on Earth. Microorganisms support the existence of all higher trophic life forms. To understand how humans and other life forms on Earth (including those we are yet to discover) can withstand anthropogenic climate change, it is vital to incorporate knowledge of the microbial 'unseen majority'. We must learn not just how microorganisms affect climate change (including production and consumption of greenhouse gases) but also how they will be affected by climate change and other human activities. This Consensus Statement documents the central role and global importance of microorganisms in climate change biology. It also puts humanity on notice that the impact of climate change will depend heavily on responses of microorganisms, which are essential for achieving an environmentally sustainable future.

Published
2019

21. Biosynthesis of the neurotoxin domoic acid in a bloom-forming diatom

Author

Brunson, John K, McKinnie, Shaun MK, Chekan, Jonathan R, McCrow, John P, Miles, Zachary D, Bertrand, Erin M, Bielinski, Vincent A, Luhavaya, Hanna, Oborník, Miroslav, Smith, G Jason, Hutchins, David A, Allen, Andrew E, and Moore, Bradley S

Subjects
Rare Diseases, Biotechnology, Genetics, Diatoms, Eutrophication, Kainic Acid, Multigene Family, Neurotoxins, Recombinant Proteins, General Science & Technology
Abstract

Oceanic harmful algal blooms of Pseudo-nitzschia diatoms produce the potent mammalian neurotoxin domoic acid (DA). Despite decades of research, the molecular basis for its biosynthesis is not known. By using growth conditions known to induce DA production in Pseudo-nitzschia multiseries, we implemented transcriptome sequencing in order to identify DA biosynthesis genes that colocalize in a genomic four-gene cluster. We biochemically investigated the recombinant DA biosynthetic enzymes and linked their mechanisms to the construction of DA's diagnostic pyrrolidine skeleton, establishing a model for DA biosynthesis. Knowledge of the genetic basis for toxin production provides an orthogonal approach to bloom monitoring and enables study of environmental factors that drive oceanic DA production.

Published
2018

28. Additive manufacturing of metamaterials: A review

Author

Askari, Meisam, Hutchins, David A., Thomas, Peter J., Astolfi, Lorenzo, Watson, Richard L., Abdi, Meisam, Ricci, Marco, Laureti, Stefano, Nie, Luzhen, Freear, Steven, Wildman, Ricky, Tuck, Christopher, Clarke, Matt, Woods, Emma, and Clare, Adam T.

Published
2020
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35. Dual thermal ecotypes coexist within a nearly genetically identical population of the unicellular marine cyanobacteriumSynechococcus

Author

Kling, Joshua D., primary, Lee, Michael D., additional, Walworth, Nathan G., additional, Webb, Eric A., additional, Coelho, Jordan T., additional, Wilburn, Paul, additional, Anderson, Stephanie I., additional, Zhou, Qianqian, additional, Wang, Chunguang, additional, Phan, Megan D., additional, Fu, Feixue, additional, Kremer, Colin T., additional, Litchman, Elena, additional, Rynearson, Tatiana A., additional, and Hutchins, David A., additional

Published
2023
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36. Microbial Catalysis for CO2Sequestration: A Geobiological Approach

Author

Van Den Berghe, Martin, primary, Walworth, Nathan G., additional, Dalvie, Neil C., additional, Dupont, Chris L., additional, Springer, Michael, additional, Andrews, M. Grace, additional, Romaniello, Stephen J., additional, Hutchins, David A., additional, Montserrat, Francesc, additional, Silver, Pamela A., additional, and Nealson, Kenneth H., additional

Published
2023
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45. Trichodesmium genome maintains abundant, widespread noncoding DNA in situ, despite oligotrophic lifestyle

Author

Walworth, Nathan, Pfreundt, Ulrike, Nelson, William C, Mincer, Tracy, Heidelberg, John F, Fu, Feixue, Waterbury, John B, del Rio, Tijana Glavina, Goodwin, Lynne, Kyrpides, Nikos C, Land, Miriam L, Woyke, Tanja, Hutchins, David A, Hess, Wolfgang R, and Webb, Eric A

Subjects
Biological Sciences, Bioinformatics and Computational Biology, Ecology, Genetics, Microbiology, Human Genome, 1.1 Normal biological development and functioning, Generic health relevance, Bacterial Proteins, Carbon, Computational Biology, Cyanobacteria, DNA, Bacterial, DNA, Intergenic, Ecosystem, Gene Expression Regulation, Bacterial, Genes, Bacterial, Genome, Genomics, Molecular Sequence Data, Nitrogen, Nitrogen Fixation, Nucleic Acid Conformation, Oceans and Seas, Prochlorococcus, RNA, Signal Transduction, Synechococcus, Transposases, marine microbiology, oligotrophic, evolution genomics, nitrogen fixation
Abstract

Understanding the evolution of the free-living, cyanobacterial, diazotroph Trichodesmium is of great importance because of its critical role in oceanic biogeochemistry and primary production. Unlike the other >150 available genomes of free-living cyanobacteria, only 63.8% of the Trichodesmium erythraeum (strain IMS101) genome is predicted to encode protein, which is 20-25% less than the average for other cyanobacteria and nonpathogenic, free-living bacteria. We use distinctive isolates and metagenomic data to show that low coding density observed in IMS101 is a common feature of the Trichodesmium genus, both in culture and in situ. Transcriptome analysis indicates that 86% of the noncoding space is expressed, although the function of these transcripts is unclear. The density of noncoding, possible regulatory elements predicted in Trichodesmium, when normalized per intergenic kilobase, was comparable and twofold higher than that found in the gene-dense genomes of the sympatric cyanobacterial genera Synechococcus and Prochlorococcus, respectively. Conserved Trichodesmium noncoding RNA secondary structures were predicted between most culture and metagenomic sequences, lending support to the structural conservation. Conservation of these intergenic regions in spatiotemporally separated Trichodesmium populations suggests possible genus-wide selection for their maintenance. These large intergenic spacers may have developed during intervals of strong genetic drift caused by periodic blooms of a subset of genotypes, which may have reduced effective population size. Our data suggest that transposition of selfish DNA, low effective population size, and high-fidelity replication allowed the unusual "inflation" of noncoding sequence observed in Trichodesmium despite its oligotrophic lifestyle.

Published
2015

49. Natural ocean iron fertilization and climate variability over geological periods.

Author

Jiang, Hai‐Bo, Hutchins, David A., Ma, Wentao, Zhang, Rui‐Feng, Wells, Mark, Jiao, Nianzhi, Wang, Yuntao, and Chai, Fei

Subjects
*SNOWBALL Earth (Geology), *GREAT Oxidation Event, *CARBON sequestration, *ATMOSPHERIC carbon dioxide, *LAST Glacial Maximum, *IRON, *CARBON cycle, *ATMOSPHERE
Abstract

Marine primary producers are largely dependent on and shape the Earth's climate, although their relationship with climate varies over space and time. The growth of phytoplankton and associated marine primary productivity in most of the modern global ocean is limited by the supply of nutrients, including the micronutrient iron. The addition of iron via episodic and frequent events drives the biological carbon pump and promotes the sequestration of atmospheric carbon dioxide (CO2) into the ocean. However, the dependence between iron and marine primary producers adaptively changes over different geological periods due to the variation in global climate and environment. In this review, we examined the role and importance of iron in modulating marine primary production during some specific geological periods, that is, the Great Oxidation Event (GOE) during the Huronian glaciation, the Snowball Earth Event during the Cryogenian, the glacial–interglacial cycles during the Pleistocene, and the period from the last glacial maximum to the late Holocene. Only the change trend of iron bioavailability and climate in the glacial–interglacial cycles is consistent with the Iron Hypothesis. During the GOE and the Snowball Earth periods, although the bioavailability of iron in the ocean and the climate changed dramatically, the changing trend of many factors contradicted the Iron Hypothesis. By detangling the relationship among marine primary productivity, iron availability and oceanic environments in different geological periods, this review can offer some new insights for evaluating the impact of ocean iron fertilization on removing CO2 from the atmosphere and regulating the climate. [ABSTRACT FROM AUTHOR]

Published
2023
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