Search

Your search keyword '"Harrison, Richard J."' showing total 686 results
Start Over Author "Harrison, Richard J."
686 results on '"Harrison, Richard J."'

4. Group theoretical analysis of structural instability, vacancy ordering and magnetic transitions in the system troilite (FeS) - pyrrhotite (Fe$_{1-x}$S)

Author

Haines, Charles Robert Sebastian, Howard, Christopher J., Harrison, Richard J., and Carpenter, Michael A.

Subjects
Condensed Matter - Materials Science
Abstract

A group-theoretical framework to describe vacancy ordering and magnetism in the Fe$_{1-x}$S system is developed. This framework is used to determine the sequence of crystal structures consistent with the observed magnetic structures of troilite (FeS), and to determine the crystallographic nature of the low-temperature Besnus transition in Fe$_{0.875}$S. We conclude that the Besnus transition is a magnetically driven transition characterised by the rotation of the moments out of the ac-plane, accompanied by small atomic displacements that lower the symmetry to triclinic at low temperatures. Based on our phase diagram, we predict related magnetically driven phase transitions at low temperatures in all the commensurate superstructures of pyrrhotite. The exact nature of the transition is determined by the symmetry of the vacancy ordered state Based on this we predict spin-flop transitions in 3C and 5C pyrrhotite and a transition akin to the Besnus transition in 6C pyrrhotite. Furthermore, we clarify that 3C and 4C pyrrhotite carry a ferrimagnetic moment whereas 5C and 6C are antiferromagnetic., Comment: 65 pages including Supplementary Material

Published
2019
Full Text
View/download PDF

7. Genetic dissection of the tissue‐specific roles of type III effectors and phytotoxins in the pathogenicity of Pseudomonas syringae pv. syringae to cherry

Author

Vadillo‐Dieguez, Andrea, primary, Zeng, Ziyue, additional, Mansfield, John W., additional, Grinberg, Nastasiya F., additional, Lynn, Samantha C., additional, Gregg, Adam, additional, Connell, John, additional, Harrison, Richard J., additional, Jackson, Robert W., additional, and Hulin, Michelle T., additional

Published
2024
Full Text
View/download PDF

9. Field Response of Magnetic Vortices in Dusty Olivine From the Semarkona Chondrite

Author

Nichols, Claire IO, Einsle, Joshua F, Im, Mi‐Young, Kasama, Takeshi, Saghi, Zineb, Midgley, Paul A, and Harrison, Richard J

Subjects
Physical Sciences, Earth Sciences, Geochemistry & Geophysics
Abstract

Recent paleomagnetic studies have constrained the strength and longevity of the magnetic field generated by the solar nebula, which has broad implications for the early evolution of the solar system. Paleomagnetic evidence was recorded by nanoscale iron inclusions in olivine crystals in the Semarkona LL 3.0 chondrite. These dusty olivines have been shown to be credible carriers of ancient magnetic remanence. The small scale of the iron inclusions presents several challenges for defining their fundamental magnetic properties. Here we present the first correlative study of the response of these magnetic structures under applied laboratory fields. Results show that the majority of particles are in a single-vortex state and exhibit stable magnetic behavior in applied fields up to 200 mT. Experimental observations using Lorentz microscopy and magnetic transmission X-ray microscopy are shown to compare well with the results of finite-element micromagnetic simulations derived from 3-D models of the particles obtained using electron tomography. This correlative approach may be used to characterize the fundamental magnetic behavior of many terrestrial and extraterrestrial paleomagnetic carriers in the single-vortex to multivortex size range, which represent the vast majority of stable magnetic carriers in rocks and meteorites.

Published
2019

11. Genetic dissection of the tissue-specific roles of type III effectors and phytotoxins in the pathogenicity ofPseudomonas syringaepv.syringaeto cherry

Author

Vadillo-Dieguez, Andrea, primary, Zeng, Ziyue, additional, Mansfield, John W., additional, Grinberg, Nastasiya F., additional, Lynn, Samantha C., additional, Gregg, Adam, additional, Connell, John, additional, Harrison, Richard J., additional, Jackson, Robert W., additional, and Hulin, Michelle T., additional

Published
2024
Full Text
View/download PDF

12. Evaluating the paleomagnetic potential of single zircon crystals using the Bishop Tuff

Author

Fu, Roger R., Weiss, Benjamin P., Lima, Eduardo A., Kehayias, Pauli, Araujo, Jefferson F. D. F., Glenn, David R., Gelb, Jeff, Einsle, Joshua F., Bauer, Ann M., Harrison, Richard J., Ali, Guleed A. H., and Walsworth, Ronald L.

Subjects
Physics - Geophysics
Abstract

Zircon crystals offer a unique combination of suitability for high-precision radiometric dating and high resistance to alteration. Paleomagnetic experiments on ancient zircons may potentially constrain the earliest geodynamo, which holds broad implications for the early Earth interior and atmosphere. However, the ability of zircons to record accurately the geomagnetic field has not been fully demonstrated. Here we conduct thermal and room temperature alternating field (AF) paleointensity experiments on 767.1 thousand year old (ka) zircons from the Bishop Tuff, California. The rapid emplacement of these zircons in a well-characterized magnetic field provides a high-fidelity test of the zircons intrinsic paleomagnetic recording accuracy. Successful dual heating experiments on nine zircons measured using a superconducting quantum interference device (SQUID) microscope yield a mean paleointensity of 46.2 +/- 18.8 microtesla (1sigma), which agrees closely with high-precision results from Bishop Tuff whole rock (43.0 +/- 3.2 microtesla). High-resolution quantum diamond magnetic mapping, electron microscopy, and X-ray tomography indicate that the bulk of the remanent magnetization in Bishop Tuff zircons is carried by Fe oxides associated with apatite inclusions, which would be susceptible to destruction via metamorphism and aqueous alteration in older zircons. As such, while zircons can reliably record the geomagnetic field, robust zircon-derived paleomagnetic results require careful characterization of the ferromagnetic carrier and demonstration of their occurrence in primary inclusions. We further conclude that a combination of quantum diamond magnetometry and high-resolution imaging can provide detailed, direct characterization of the ferromagnetic mineralogy of geological samples., Comment: In review in Earth and Planetary Science Letters

Published
2016
Full Text
View/download PDF

13. Foundational and Translational Research Opportunities to Improve Plant Health.

Author

Michelmore, Richard, Coaker, Gitta, Bart, Rebecca, Beattie, Gwyn, Bent, Andrew, Bruce, Toby, Cameron, Duncan, Dangl, Jeffery, Dinesh-Kumar, Savithramma, Edwards, Rob, Eves-van den Akker, Sebastian, Gassmann, Walter, Greenberg, Jean T, Hanley-Bowdoin, Linda, Harrison, Richard J, Harvey, Jagger, He, Ping, Huffaker, Alisa, Hulbert, Scot, Innes, Roger, Jones, Jonathan DG, Kaloshian, Isgouhi, Kamoun, Sophien, Katagiri, Fumiaki, Leach, Jan, Ma, Wenbo, McDowell, John, Medford, June, Meyers, Blake, Nelson, Rebecca, Oliver, Richard, Qi, Yiping, Saunders, Diane, Shaw, Michael, Smart, Christine, Subudhi, Prasanta, Torrance, Lesley, Tyler, Bret, Valent, Barbara, and Walsh, John

Subjects
Microbiology, Plant Biology, Biological Sciences, Genetics, Zero Hunger, Agriculture, Biotechnology, Climate Change, Crops, Agricultural, Food Supply, Humans, Plant Diseases, Translational Research, Biomedical, Plant Biology & Botany, Plant biology
Abstract

Reader Comments | Submit a Comment The white paper reports the deliberations of a workshop focused on biotic challenges to plant health held in Washington, D.C. in September 2016. Ensuring health of food plants is critical to maintaining the quality and productivity of crops and for sustenance of the rapidly growing human population. There is a close linkage between food security and societal stability; however, global food security is threatened by the vulnerability of our agricultural systems to numerous pests, pathogens, weeds, and environmental stresses. These threats are aggravated by climate change, the globalization of agriculture, and an over-reliance on nonsustainable inputs. New analytical and computational technologies are providing unprecedented resolution at a variety of molecular, cellular, organismal, and population scales for crop plants as well as pathogens, pests, beneficial microbes, and weeds. It is now possible to both characterize useful or deleterious variation as well as precisely manipulate it. Data-driven, informed decisions based on knowledge of the variation of biotic challenges and of natural and synthetic variation in crop plants will enable deployment of durable interventions throughout the world. These should be integral, dynamic components of agricultural strategies for sustainable agriculture.

Published
2017

19. Chromosome-scale genome sequence assemblies of the ‘Autumn Bliss’ and ‘Malling Jewel’ cultivars of the highly heterozygous red raspberry (Rubus idaeus L.) derived from long-read Oxford Nanopore sequence data

Author

Price, R. Jordan, primary, Davik, Jahn, additional, Fernandéz Fernandéz, Felicidad, additional, Bates, Helen J., additional, Lynn, Samantha, additional, Nellist, Charlotte F., additional, Buti, Matteo, additional, Røen, Dag, additional, Šurbanovski, Nada, additional, Alsheikh, Muath, additional, Harrison, Richard J., additional, and Sargent, Daniel James, additional

Published
2023
Full Text
View/download PDF

23. The Winchcombe meteorite, a unique and pristine witness from the outer solar system

Author

King, Ashley J, Daly, Luke, Rowe, James, Joy, Katherine H, Greenwood, Richard C, Devillepoix, Hadrien AR, Suttle, Martin D, Chan, Queenie HS, Russell, Sara S, Bates, Helena C, Bryson, James FJ, Clay, Patricia L, Vida, Denis, Lee, Martin R, O'Brien, Áine, Hallis, Lydia J, Stephen, Natasha R, Tartèse, Romain, Sansom, Eleanor K, Towner, Martin C, Cupak, Martin, Shober, Patrick M, Bland, Phil A, Findlay, Ross, Franchi, Ian A, Verchovsky, Alexander B, Abernethy, Feargus AJ, Grady, Monica M, Floyd, Cameron J, Van Ginneken, Matthias, Bridges, John, Hicks, Leon J, Jones, Rhian H, Mitchell, Jennifer T, Genge, Matthew J, Jenkins, Laura, Martin, Pierre-Etienne, Sephton, Mark A, Watson, Jonathan S, Salge, Tobias, Shirley, Katherine A, Curtis, Rowan J, Warren, Tristram J, Bowles, Neil E, Stuart, Finlay M, Di Nicola, Luigia, Györe, Domokos, Boyce, Adrian J, Shaw, Kathryn MM, Elliott, Tim, Steele, Robert CJ, Povinec, Pavel, Laubenstein, Matthias, Sanderson, David, Cresswell, Alan, Jull, Anthony JT, Sýkora, Ivan, Sridhar, Sanjana, Harrison, Richard J, Willcocks, Francesca M, Harrison, Catherine S, Hallatt, Daniel, Wozniakiewicz, Penny J, Burchell, Mark J, Alesbrook, Luke S, Dignam, Aishling, Almeida, Natasha V, Smith, Caroline L, Clark, Brett, Humphreys-Williams, Emma R, Schofield, Paul F, Cornwell, Luke T, Spathis, Vassilia, Morgan, Geraint H, Perkins, Mark J, Kacerek, Richard, Campbell-Burns, Peter, Colas, Francois, Zanda, Brigitte, Vernazza, Pierre, Bouley, Sylvain, Jeanne, Simon, Hankey, Mike, Collins, Gareth S, Young, John S, Shaw, Clive, Horak, Jana, Jones, Dave, James, Nick, Bosley, Steve, Shuttleworth, Alan, Dickinson, Paul, McMullan, Ian, Robson, Derek, Smedley, Andrew RD, Stanley, Ben, Bassom, Richard, McIntyre, Mark, Suttle, Adam A, Fleet, Richard, Bastiaens, Luc, Ihász, Míra B, McMullan, Sarah, Boazman, Sarah J, Dickeson, Zach I, Grindrod, Peter M, Pickersgill, Annemarie E, Weir, Colin J, Suttle, Fiona M, Farrelly, Sarah, Spencer, Ieun, Naqvi, Sheeraz, Mayne, Ben, Skilton, Dan, Kirk, Dan, Mounsey, Ann, Mounsey, Sally E, Mounsey, Sarah, Godfrey, Pamela, Bond, Lachlan, Bond, Victoria, Wilcock, Cathryn, Wilcock, Hannah, Wilcock, Rob, King, Ashley J [0000-0001-6113-5417], Daly, Luke [0000-0002-7150-4092], Joy, Katherine H [0000-0003-4992-8750], Greenwood, Richard C [0000-0002-5544-8027], Devillepoix, Hadrien AR [0000-0001-9226-1870], Suttle, Martin D [0000-0001-7165-2215], Chan, Queenie HS [0000-0001-7205-8699], Russell, Sara S [0000-0001-5531-7847], Bates, Helena C [0000-0002-0469-9483], Bryson, James FJ [0000-0002-5675-8545], Vida, Denis [0000-0003-4166-8704], Lee, Martin R [0000-0002-6004-3622], O'Brien, Áine [0000-0002-2591-7902], Hallis, Lydia J [0000-0001-6455-8415], Stephen, Natasha R [0000-0003-3952-922X], Tartèse, Romain [0000-0002-3490-9875], Sansom, Eleanor K [0000-0003-2702-673X], Towner, Martin C [0000-0002-8240-4150], Cupak, Martin [0000-0003-2193-0867], Shober, Patrick M [0000-0003-4766-2098], Bland, Phil A [0000-0002-4681-7898], Findlay, Ross [0000-0001-7794-1819], Franchi, Ian A [0000-0003-4151-0480], Verchovsky, Alexander B [0000-0002-3532-5003], Abernethy, Feargus AJ [0000-0001-7210-3058], Grady, Monica M [0000-0002-4055-533X], Floyd, Cameron J [0000-0001-5986-491X], Van Ginneken, Matthias [0000-0002-2508-7021], Bridges, John [0000-0002-9579-5779], Hicks, Leon J [0000-0002-2464-0948], Jones, Rhian H [0000-0001-8238-9379], Mitchell, Jennifer T [0000-0002-5922-2463], Genge, Matthew J [0000-0002-9528-5971], Jenkins, Laura [0000-0003-0886-8667], Martin, Pierre-Etienne [0000-0003-1848-9695], Sephton, Mark A [0000-0002-2190-5402], Watson, Jonathan S [0000-0003-0354-1729], Salge, Tobias [0000-0002-4414-4917], Shirley, Katherine A [0000-0003-0669-7497], Curtis, Rowan J [0000-0002-9554-3053], Warren, Tristram J [0000-0003-3877-0046], Bowles, Neil E [0000-0001-5400-1461], Stuart, Finlay M [0000-0002-6395-7868], Di Nicola, Luigia [0000-0002-7596-474X], Györe, Domokos [0000-0003-4438-8361], Boyce, Adrian J [0000-0002-9680-0787], Shaw, Kathryn MM [0000-0002-3847-9382], Elliott, Tim [0000-0002-0984-0191], Steele, Robert CJ [0000-0003-1406-6855], Povinec, Pavel [0000-0003-0275-794X], Laubenstein, Matthias [0000-0001-5390-4343], Sanderson, David [0000-0002-9615-4412], Cresswell, Alan [0000-0002-5100-8075], Jull, Anthony JT [0000-0002-4079-4947], Sýkora, Ivan [0000-0003-3447-5621], Sridhar, Sanjana [0000-0003-1179-2093], Harrison, Richard J [0000-0003-3469-762X], Willcocks, Francesca M [0000-0002-3726-0258], Hallatt, Daniel [0000-0002-4426-9891], Wozniakiewicz, Penny J [0000-0002-1441-4883], Burchell, Mark J [0000-0002-2680-8943], Alesbrook, Luke S [0000-0001-9892-281X], Dignam, Aishling [0000-0001-5408-9061], Almeida, Natasha V [0000-0003-4871-8225], Smith, Caroline L [0000-0001-7005-6470], Humphreys-Williams, Emma R [0000-0002-1397-5785], Schofield, Paul F [0000-0003-0902-0588], Cornwell, Luke T [0000-0003-1428-2160], Spathis, Vassilia [0000-0002-5745-4383], Morgan, Geraint H [0000-0002-7580-6880], Campbell-Burns, Peter [0000-0001-8544-728X], Zanda, Brigitte [0000-0002-4210-7151], Vernazza, Pierre [0000-0002-2564-6743], Bouley, Sylvain [0000-0003-0377-5517], Collins, Gareth S [0000-0002-6087-6149], Young, John S [0000-0001-6583-7643], Horak, Jana [0000-0002-0492-2235], Jones, Dave [0000-0002-7215-0521], Bosley, Steve [0000-0002-9478-8518], Dickinson, Paul [0000-0003-0078-0919], McMullan, Ian [0000-0002-5579-8115], Robson, Derek [0000-0001-7807-9853], Smedley, Andrew RD [0000-0001-7137-6628], McIntyre, Mark [0000-0002-5769-4280], Suttle, Adam A [0000-0002-6075-976X], Fleet, Richard [0000-0002-8366-7673], McMullan, Sarah [0000-0002-7194-6317], Boazman, Sarah J [0000-0003-4694-0818], Dickeson, Zach I [0000-0001-9116-2571], Grindrod, Peter M [0000-0002-0934-5131], Pickersgill, Annemarie E [0000-0001-5452-2849], Suttle, Fiona M [0000-0003-1970-0034], Wilcock, Cathryn [0000-0001-7731-2860], Wilcock, Hannah [0000-0002-1043-2267], Wilcock, Rob [0000-0001-8977-7956], Apollo - University of Cambridge Repository, Science and Technology Facilities Council (STFC), and University of St Andrews. School of Earth & Environmental Sciences

Subjects
MCC, QC Physics, Multidisciplinary, 5101 Astronomical Sciences, NDAS, QB Astronomy, 37 Earth Sciences, 3705 Geology, 5109 Space Sciences, 51 Physical Sciences, QC, QB
Abstract

Funding: This study was supported by urgency funding from the U.K.’s Science and Technology Facilities Council (STFC) as part of the project “Curation and Preliminary Examination of the Winchcombe Carbonaceous Chondrite Fall.” Additional work was funded by STFC through grants ST/N000846/1, ST/T002328/1, ST/T506096/1, and ST/W001128/1 (to L.D., M.R.L., and L.J.Ha.); ST/V000675/1 (to K.H.J. and R.H.J.); ST/P005225/1 (to R.T.); ST/S000348/1 (to M.V.G., P.J.W., and M.J.B.); ST/R00143X/1 (to J.B. and L.J.Hi.); ST/S000615/1 (to G.S.C.); ST/V000799/1 (to P.G.); and ST/V000888/1 (to T.E.). A.J.K. and H.C.B. acknowledge funding support from UK Research and Innovation (UKRI) grant MR/T020261/1. P.L.C. acknowledges funding support from UKRI grant MR/S03465X/1. K.H.J. acknowledges funding support from the Royal Society, grant URF\R\201009. L.J.Ha. and M.R.L. acknowledge funding from Natural Environment Research Council (NERC) National Environmental Isotope Facility (NEIF) grant no. 2406.0321. L.D., M.R.L., and L.J.Ha. acknowledge COVID-19 funding support from the University of Glasgow, UK. D.V. was supported in part by NASA cooperative agreement 80NSSC21M0073. P.P. and I.Sy. acknowledge funding from the VEGA agency, project no.1/0421/20. A.J.T.J. acknowledges support from the European Union and the State of Hungary, cofinanced by the European Regional Development Fund in the project of GINOP-2.3.2-15-2016-00009 “ICER.” P.M.S. acknowledges support from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 945298. FRIPON was initiated by funding from ANR (grant N.13-BS05-0009-03), carried out by the Paris Observatory, Muséum National d’Histoire Naturelle, Paris-Saclay University, and Institut Pythéas (LAM-CEREGE). FRIPON data are hosted and processed at Institut Pythéas SIP (Service Informatique Pythéas). The Desert Fireball Network team and Global Fireball Observatory are funded by the Australian Research Council (DP200102073). Direct links between carbonaceous chondrites and their parent bodies in the solar system are rare. The Winchcombe meteorite is the most accurately recorded carbonaceous chondrite fall. Its pre-atmospheric orbit and cosmic-ray exposure age confirm that it arrived on Earth shortly after ejection from a primitive asteroid. Recovered only hours after falling, the composition of the Winchcombe meteorite is largely unmodified by the terrestrial environment. It contains abundant hydrated silicates formed during fluid-rock reactions, and carbon- and nitrogen-bearing organic matter including soluble protein amino acids. The near-pristine hydrogen isotopic composition of the Winchcombe meteorite is comparable to the terrestrial hydrosphere, providing further evidence that volatile-rich carbonaceous asteroids played an important role in the origin of Earth's water. Publisher PDF

Published
2022

25. Direct age constraints on the magnetism of Jack Hills zircon

Author

Taylor, Richard J. M., primary, Reddy, Steven M., additional, Saxey, David W., additional, Rickard, William D. A., additional, Tang, Fengzai, additional, Borlina, Cauê S., additional, Fu, Roger R., additional, Weiss, Benjamin P., additional, Bagot, Paul, additional, Williams, Helen M., additional, and Harrison, Richard J., additional

Published
2023
Full Text
View/download PDF

27. Comparative Genomic Analysis of 31 Phytophthora Genomes Reveals Genome Plasticity and Horizontal Gene Transfer

Author

Kronmiller, Brent A., primary, Feau, Nicolas, additional, Shen, Danyu, additional, Tabima, Javier F., additional, Ali, Shahin S., additional, Armitage, Andrew D., additional, Arredondo, Felipe, additional, Bailey, Bryan A., additional, Bollmann, Stephanie R., additional, Dale, Angela, additional, Harrison, Richard J., additional, Hrywkiw, Kelly, additional, Kasuga, Takao, additional, McDougal, Rebecca, additional, Nellist, Charlotte F., additional, Panda, Preeti, additional, Tripathy, Sucheta, additional, Williams, Nari M., additional, Ye, Wenwu, additional, Wang, Yuanchao, additional, Hamelin, Richard C., additional, and Grünwald, Niklaus J., additional

Published
2023
Full Text
View/download PDF

35. Managing Data in Breeding, Selection and in Practice: A Hundred Year Problem That Requires a Rapid Solution

Author

Harrison, Richard J. and Caccamo, Mario

Subjects
Life Science
Abstract

Following the rediscovery of Mendelian genetics, food supply pressures and the rapid expansion of crop varieties with defined performance characteristics, international systems were set up throughout the 20 C to regulate the trade of seed, the protection of intellectual property and the sale of productive varieties of key agricultural crops. These systems are a highly connected but largely linear set of processes. System changes are slow to be adopted due to the cascade of effects that structural alteration would have globally. Multi-omic technologies and the subsequent proliferation of data types used within modern breeding, offer the possibility to gain deeper insights into the performance characteristics of varieties. Current integration of data, standards and ownership structures limit their applications for wider purposes, both private and public. We explore how data within and between breeding programmes and the varietal approval and monitoring processes could be made FAIR. We examine what role expanded or aligned programmes of data collection and expanded trait evaluation at the point of varietal registration and evaluation, as well as on farm could have in ensuring the best linkage of public and private data to address some of the challenges society faces over the next 30 years with the required, rapid transition to sustainable agricultural systems.

Published
2022

36. Solar nebula magnetic fields recorded in the Semarkona meteorite

Author

Fu, Roger R., Weiss, Benjamin P., Lima, Eduardo A., Harrison, Richard J., Bai, Xue-Ning, Desch, Steven J., Ebel, Denton S., Suavet, Clément, Wang, Huapei, Glenn, David, Le Sage, David, Kasama, Takeshi, Walsworth, Ronald L., and Kuan, Aaron T.

Published
2014

45. Additional file 1 of Identification of novel genetic regions associated with resistance to European canker in apple

Author

Karlström, Amanda, Gómez-Cortecero, Antonio, Nellist, Charlotte F., Ordidge, Matthew, Dunwell, Jim M., and Harrison, Richard J.

Abstract

Additional file 1: Supplementary Fig. 1A-1H. Phenotypic distributions for each European canker phenotype by family. Supplementary Fig. 2. Best Linear Unbiased Estimates (BLUEs) of parents and standard varieties. Supplementary Fig. 3. Scree plot from the principal component analysis of European canker phenotypes. Supplementary Fig. 4. Phenotypic distributions for progeny of ‘Golden Delicious’ x ‘M9’.

Published
2022
Full Text
View/download PDF

46. Micromagnetic Tomography for Paleomagnetism and Rock-Magnetism

Author

de Groot, Lennart V., Fabian, Karl, Béguin, Annemarieke, Kosters, Martha E., Cortés-Ortuño, David, Fu, Roger R., Jansen, Chloë M.L., Harrison, Richard J., van Leeuwen, Tristan, Barnhoorn, Auke, Paleomagnetism, Sub Mathematical Modeling, Mathematical Modeling, Paleomagnetism, Sub Mathematical Modeling, Mathematical Modeling, de Groot, Lennart V [0000-0002-1151-5662], Fabian, Karl [0000-0002-3504-3292], Béguin, Annemarieke [0000-0002-6196-4247], Kosters, Martha E [0000-0001-5035-1034], Cortés-Ortuño, David [0000-0003-3799-3141], Fu, Roger R [0000-0003-3635-2676], Harrison, Richard J [0000-0003-3469-762X], van Leeuwen, Tristan [0000-0002-8794-6426], Barnhoorn, Auke [0000-0002-3074-5535], and Apollo - University of Cambridge Repository

Subjects
Paleomagnetism, Computational geophysics, microCT, 010504 meteorology & atmospheric sciences, Sample (material), Geophysics, rock‐magnetism, 010502 geochemistry & geophysics, scanning magnetometry, 01 natural sciences, Rock magnetism, Magnetic field, Physics::Geophysics, rock-magnetism, Potential field inversion, Magnetization, Earth's magnetic field, Geochemistry and Petrology, Space and Planetary Science, Earth and Planetary Sciences (miscellaneous), Tomography, micromagnetic tomography, 0105 earth and related environmental sciences
Abstract

Our understanding of the past behavior of the geomagnetic field arises from magnetic signals stored in geological materials, e.g., (volcanic) rocks. Bulk rock samples, however, often contain magnetic grains that differ in chemistry, size, and shape; some of them record the Earth's magnetic field well, others are unreliable. The presence of a small amount of adverse behaved magnetic grains in a sample may already obscure important information on the past state of the geomagnetic field. Recently it was shown that it is possible to determine magnetizations of individual grains in a sample by combining X-ray computed tomography and magnetic surface scanning measurements. Here we establish this new Micromagnetic Tomography (MMT) technique and make it suitable for use with different magnetic scanning techniques, and for both synthetic and natural samples. We acquired reliable magnetic directions by selecting subsets of grains in a synthetic sample, and we obtained rock-magnetic information of individual grains in a volcanic sample. This illustrates that MMT opens up entirely new venues of paleomagnetic and rock-magnetic research. MMT's unique ability to determine the magnetization of individual grains in a nondestructive way allows for a systematic analysis of how geological materials record and retain information on the past state of the Earth's magnetic field. Moreover, by interpreting only the contributions of known magnetically well-behaved grains in a sample, MMT has the potential to unlock paleomagnetic information from even the most complex, crucial, or valuable recorders that current methods are unable to recover.

Published
2021

47. Long-lived magnetism from solidification-driven convection on the pallasite parent body

Author

Bryson, James F.J., Nichols, Claire I.O., Herrero-Albillos, Julia, Kronast, Florian, Kasama, Takeshi, Alimadadi, Hossein, van der Laan, Gerrit, Nimmo, Francis, and Harrison, Richard J.

Subjects
Silicates -- Chemical properties, Solidification -- Analysis, Magnetism -- Analysis, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Palaeomagnetic measurements of meteorites (1-5) suggest that, shortly after the birth of the Solar System, the molten metallic cores of many small planetary bodies converted vigorously and were capable of generating magnetic fields (6). Convection on these bodies is currently thought to have been thermally driven (7, 8), implying that magnetic activity would have been short-lived (9). Here we report a time-series palaeomagnetic record derived from nano magnetic imaging (10) of the Imilac and Esquel pallasite meteorites, a group of meteorites consisting of centimetre-sized metallic and silicate phases. We find a history of long-lived magnetic activity on the pallasite parent body, capturing the decay and eventual shutdown of the magnetic field as core solidification completed. We demonstrate that magnetic activity driven by progressive solidification of an inner core (11-13) is consistent with our measured magnetic field characteristics and cooling rates (14). Solidification-driven convection was probably common among small body cores (15), and, in contrast to thermally driven convection, will have led to a relatively late (hundreds of millions of years after accretion), long-lasting, intense and widespread epoch of magnetic activity among these bodies in the early Solar System., The pallasites are slowly cooled (2-9 K per million years, Myr; ref. 14) meteorites consisting of olivine crystals embedded in an Fe-Ni matrix (16), which have been suggested to originate [...]

Published
2015

48. Genomic and functional analysis of phage‐mediated horizontal gene transfer in Pseudomonas syringae on the plant surface.

Author

Hulin, Michelle T., Rabiey, Mojgan, Zeng, Ziyue, Vadillo Dieguez, Andrea, Bellamy, Sophia, Swift, Phoebe, Mansfield, John W., Jackson, Robert W., and Harrison, Richard J.

Subjects
HORIZONTAL gene transfer, PLANT surfaces, GENOMICS, PSEUDOMONAS syringae, FUNCTIONAL analysis, KIWIFRUIT, GENETIC transformation, CHERRIES
Abstract

Summary: Many strains of Pseudomonas colonise plant surfaces, including the cherry canker pathogens, Pseudomonas syringae pathovars syringae and morsprunorum. We have examined the genomic diversity of P. syringae in the cherry phyllosphere and focused on the role of prophages in transfer of genes encoding Type 3 secreted effector (T3SE) proteins contributing to the evolution of virulence.Phylogenomic analysis was carried out on epiphytic pseudomonads in the UK orchards. Significant differences in epiphytic populations occurred between regions. Nonpathogenic strains were found to contain reservoirs of T3SE genes. Members of P. syringae phylogroups 4 and 10 were identified for the first time from Prunus.Using bioinformatics, we explored the presence of the gene encoding T3SE HopAR1 within related prophage sequences in diverse P. syringae strains including cherry epiphytes and pathogens. Results indicated that horizontal gene transfer (HGT) of this effector between phylogroups may have involved phage. Prophages containing hopAR1 were demonstrated to excise, circularise and transfer the gene on the leaf surface.The phyllosphere provides a dynamic environment for prophage‐mediated gene exchange and the potential for the emergence of new more virulent pathotypes. Our results suggest that genome‐based epidemiological surveillance of environmental populations will allow the timely application of control measures to prevent damaging diseases. [ABSTRACT FROM AUTHOR]

Published
2023
Full Text
View/download PDF

49. SIGMA: Spectral Interpretation Using Gaussian Mixtures and Autoencoder.

Author

Po-Yen Tung, Sheikh, Hassan A., Ball, Matthew, Nabiei, Farhang, and Harrison, Richard J.

Subjects
GRAPHICAL user interfaces, GAUSSIAN mixture models, MATRIX decomposition, NONNEGATIVE matrices, MACHINE learning, ELECTRON energy loss spectroscopy, SPECTRAL imaging, ELECTRON beams, MIXTURES
Abstract

Identification of unknown micro- and nano-sized mineral phases is commonly achieved by analyzing chemical maps generated from hyperspectral imaging data sets, particularly scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS). However, the accuracy and reliability of mineral identification are often limited by subjective human interpretation, non-ideal sample preparation, and the presence of mixed chemical signals generated within the electron-beam interaction volume. Machine learning has emerged as a powerful tool to overcome these problems. Here, we propose a machine-learning approach to identify unknown phases and unmix their overlapped chemical signals. This approach leverages the guidance of Gaussian mixture modeling clustering fitted on an informative latent space of pixel-wise elemental data points modeled using a neural network autoencoder, and unmixes the overlapped chemical signals of phases using non-negative matrix factorization. We evaluate the reliability and the accuracy of the new approach using two SEM-EDS data sets: a synthetic mixture sample and a real-world particulate matter sample. In the former, the proposed approach successfully identifies all major phases and extracts background-subtracted single-phase chemical signals. The unmixed chemical spectra show an average similarity of 83.0% with the ground truth spectra. In the second case, the approach demonstrates the ability to identify potentially magnetic Fe-bearing particles and their background-subtracted chemical signals. We demonstrate a flexible and adaptable approach that brings a significant improvement to mineralogical and chemical analysis in a fully automated manner. The proposed analysis process has been built into a user-friendly Python code with a graphical user interface for ease of use by general users. [ABSTRACT FROM AUTHOR]

Published
2023
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results