| 1. |
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| 2. |
- Heywood, I., et al.
(författare)
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Inflation of 430-parsec bipolar radio bubbles in the Galactic Centre by an energetic event
- 2019
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 573:7773, s. 235-237
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Tidskriftsartikel (refereegranskat)abstract
- The Galactic Centre contains a supermassive black hole with a mass of four million Suns1 within an environment that differs markedly from that of the Galactic disk. Although the black hole is essentially quiescent in the broader context of active galactic nuclei, X-ray observations have provided evidence for energetic outbursts from its surroundings2. Also, although the levels of star formation in the Galactic Centre have been approximately constant over the past few hundred million years, there is evidence of increased short-duration bursts3, strongly influenced by the interaction of the black hole with the enhanced gas density present within the ring-like central molecular zone4 at Galactic longitude |l| < 0.7 degrees and latitude |b| < 0.2 degrees. The inner 200-parsec region is characterized by large amounts of warm molecular gas5, a high cosmic-ray ionization rate6, unusual gas chemistry, enhanced synchrotron emission7,8, and a multitude of radio-emitting magnetized filaments9, the origin of which has not been established. Here we report radio imaging that reveals a bipolar bubble structure, with an overall span of 1 degree by 3 degrees (140 parsecs × 430 parsecs), extending above and below the Galactic plane and apparently associated with the Galactic Centre. The structure is edge-brightened and bounded, with symmetry implying creation by an energetic event in the Galactic Centre. We estimate the age of the bubbles to be a few million years, with a total energy of 7 × 1052 ergs. We postulate that the progenitor event was a major contributor to the increased cosmic-ray density in the Galactic Centre, and is in turn the principal source of the relativistic particles required to power the synchrotron emission of the radio filaments within and in the vicinity of the bubble cavities.
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| 3. |
- Camilo, F., et al.
(författare)
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Revival of the Magnetar PSR J1622-4950: Observations with MeerKAT, Parkes, XMM-Newton, Swift, Chandra, and NuSTAR
- 2018
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 856:2
-
Tidskriftsartikel (refereegranskat)abstract
- New radio (MeerKAT and Parkes) and X-ray (XMM-Newton, Swift, Chandra, and NuSTAR) observations of PSR J1622-4950 indicate that the magnetar, in a quiescent state since at least early 2015, reactivated between 2017 March 19 and April 5. The radio flux density, while variable, is approximately 100 larger than during its dormant state. The X-ray flux one month after reactivation was at least 800 larger than during quiescence, and has been decaying exponentially on a 111 19 day timescale. This high-flux state, together with a radio-derived rotational ephemeris, enabled for the first time the detection of X-ray pulsations for this magnetar. At 5%, the 0.3-6 keV pulsed fraction is comparable to the smallest observed for magnetars. The overall pulsar geometry inferred from polarized radio emission appears to be broadly consistent with that determined 6-8 years earlier. However, rotating vector model fits suggest that we are now seeing radio emission from a different location in the magnetosphere than previously. This indicates a novel way in which radio emission from magnetars can differ from that of ordinary pulsars. The torque on the neutron star is varying rapidly and unsteadily, as is common for magnetars following outburst, having changed by a factor of 7 within six months of reactivation.
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| 4. |
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| 5. |
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| 6. |
- Echelmeier, A., et al.
(författare)
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Segmented flow generator for serial crystallography at the European X-ray free electron laser
- 2020
-
Ingår i: Nature Communications. - : Nature Research. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Serial femtosecond crystallography (SFX) with X-ray free electron lasers (XFELs) allows structure determination of membrane proteins and time-resolved crystallography. Common liquid sample delivery continuously jets the protein crystal suspension into the path of the XFEL, wasting a vast amount of sample due to the pulsed nature of all current XFEL sources. The European XFEL (EuXFEL) delivers femtosecond (fs) X-ray pulses in trains spaced 100 ms apart whereas pulses within trains are currently separated by 889 ns. Therefore, continuous sample delivery via fast jets wastes >99% of sample. Here, we introduce a microfluidic device delivering crystal laden droplets segmented with an immiscible oil reducing sample waste and demonstrate droplet injection at the EuXFEL compatible with high pressure liquid delivery of an SFX experiment. While achieving ~60% reduction in sample waste, we determine the structure of the enzyme 3-deoxy-D-manno-octulosonate-8-phosphate synthase from microcrystals delivered in droplets revealing distinct structural features not previously reported.
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| 7. |
- Crous, P.W., et al.
(författare)
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Fungal Planet description sheets: 1112–1181
- 2020
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Ingår i: Persoonia. - : Naturalis Biodiversity Center. - 0031-5850. ; 45, s. 251-409
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Tidskriftsartikel (refereegranskat)abstract
- Novel species of fungi described in this study include those from various countries as follows: Australia, Austroboletus asper on soil, Cylindromonium alloxyli on leaves of Alloxylon pinnatum, Davidhawksworthia quintiniae on leaves of Quintinia sieberi, Exophiala prostantherae on leaves of Prostanthera sp., Lactifluus lactiglaucus on soil, Linteromyces quintiniae (incl. Linteromyces gen. nov.) on leaves of Quintinia sieberi, Lophotrichus medusoides from stem tissue of Citrus garrawayi, Mycena pulchra on soil, Neocalonectria tristaniopsidis (incl. Neocalonectria gen. nov.) and Xyladictyochaeta tristaniopsidis on leaves of Tristaniopsis collina, Parasarocladium tasmanniae on leaves of Tasmannia insipida, Phytophthora aquae-cooljarloo from pond water, Serendipita whamiae as endophyte from roots of Eriochilus cucullatus, Veloboletus limbatus (incl. Veloboletus gen. nov.) on soil. Austria, Cortinarius glaucoelotus on soil. Bulgaria, Suhomyces rilaensis from the gut of Bolitophagus interruptus found on a Polyporus sp. Canada, Cantharellus betularum among leaf litter of Betula, Penicillium saanichii from house dust. Chile, Circinella lampensis on soil, Exophiala embothrii from rhizosphere of Embothrium coccineum. China, Colletotrichum cycadis on leaves of Cycas revoluta. Croatia, Phialocephala melitaea on fallen branch of Pinus halepensis. Czech Republic, Geoglossum jirinae on soil, Pyrenochaetopsis rajhradensis from dead wood of Buxus sempervirens. Dominican Republic, Amanita domingensis on litter of deciduous wood, Melanoleuca dominicana on forest litter. France, Crin- ipellis nigrolamellata (Martinique) on leaves of Pisonia fragrans, Talaromyces pulveris from bore dust of Xestobium rufovillosum infesting floorboards. French Guiana, Hypoxylon hepaticolor on dead corticated branch. Great Britain, Inocybe ionolepis on soil. India, Cortinarius indopurpurascens among leaf litter of Quercus leucotrichophora. Iran, Pseudopyricularia javanii on infected leaves of Cyperus sp., Xenomonodictys iranica (incl. Xenomonodictys gen. nov.) on wood of Fagus orientalis. Italy, Penicillium vallebormidaense from compost. Namibia, Alternaria mira- bibensis on plant litter, Curvularia moringae and Moringomyces phantasmae (incl. Moringomyces gen. nov.) on leaves and flowers of Moringa ovalifolia, Gobabebomyces vachelliae (incl. Gobabebomyces gen. nov.) on leaves of Vachellia erioloba, Preussia procaviae on dung of Procavia capensis. Pakistan, Russula shawarensis from soil on forest floor. Russia, Cyberlindnera dauci from Daucus carota. South Africa, Acremonium behniae on leaves of Behnia reticulata, Dothiora aloidendri and Hantamomyces aloidendri (incl. Hantamomyces gen. nov.) on leaves of Aloidendron dichotomum, Endoconidioma euphorbiae on leaves of Euphorbia mauritanica, Eucasphaeria pro- teae on leaves of Protea neriifolia, Exophiala mali from inner fruit tissue of Malus sp., Graminopassalora geisso- rhizae on leaves of Geissorhiza splendidissima, Neocamarosporium leipoldtiae on leaves of Leipoldtia schultzii,Neocladosporium osteospermi on leaf spots of Osteospermum moniliferum, Neometulocladosporiella seifertii on leaves of Combretum caffrum, Paramyrothecium pituitipietianum on stems of Grielum humifusum, Phytopythium paucipapillatum from roots of Vitis sp., Stemphylium carpobroti and Verrucocladosporium carpobroti on leaves of Carpobrotus quadrifolius, Suttonomyces cephalophylli on leaves of Cephalophyllum pilansii. Sweden, Coprinopsis rubra on cow dung, Elaphomyces nemoreus from deciduous woodlands. Spain, Polyscytalum pini-canariensis on needles of Pinus canariensis, Pseudosubramaniomyces septatus from stream sediment, Tuber lusitanicum on soil under Quercus suber. Thailand, Tolypocladium flavonigrum on Elaphomyces sp. USA, Chaetothyrina spondiadis on fruits of Spondias mombin, Gymnascella minnisii from bat guano, Juncomyces patwiniorum on culms of Juncus effusus, Moelleriella puertoricoensis on scale insect, Neodothiora populina (incl. Neodothiora gen. nov.) on stem cankers of Populus tremuloides, Pseudogymnoascus palmeri from cave sediment. Vietnam, Cyphellophora viet- namensis on leaf litter, Tylopilus subotsuensis on soil in montane evergreen broadleaf forest. Morphological and culture characteristics are supported by DNA barcodes.
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| 8. |
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| 9. |
- Wang, J., et al.
(författare)
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Final report of the CCQM-K145 : Toxic and essential elements in bovine liver
- 2020
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Ingår i: Metrologia. - : IOP Publishing Ltd. - 0026-1394 .- 1681-7575. ; 57:1 A
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Tidskriftsartikel (refereegranskat)abstract
- Liver plays a major role in metabolism and acts as a source of energy for the body by storing glycogen. With the growing interest and investigation in the biological effects in recent years, it is important and necessary to develop accurate and comparable analytical methods for elements in bio-samples. It has, however, been 10 years since the tissue sample (bovine liver) of CCQM-K49 key comparison. The purpose of CCQM-K145 is to ensure the comparable and traceable measurement results for essential and toxic elements such as P, S, Zn, Mn, Ni, Mo, Sr, Cr, Co, Pb, As and Hg in bovine liver among NMIs and other designated measurement bodies worldwide. The comparison was agreed by IAWG as 6th IAWG Benchmarking Exercise with Zn and Ni as exemplary elements at the meeting in Korea in the early October 2016. The results of CCQM-K145 are expected to cover the measurement capability and support CMCs claiming for inorganic elements in the similar biological tissue materials and food samples. 30 NMIs and DIs registered in CCQM-K145. With respect to the methodology, a variety of techniques such as IDMS, ICP-OES, ICP-MS(non-ID), AAS and NAA were adopted by the participants. For Zn, Ni, Sr, Pb and Hg measurements, most participants chose ID-ICP-MS method, which showed the better performance in terms of consistency and reliability of the measurement results. In aspect of the traceability for the measurement results in CCQM-K145, most participants used their own (in house) CRMs or other NMI's CRMs to guarantee trace to SI unit. Most participants used similar matrix CRMs for quality control or method validation. Base on different statistic way to calculate the reference mass fraction values and associated uncertainties for each measurand, removal of the suspected extreme values, and discussion at the IAWG meetings, the median values are proposed as the KCRV for Zn, Ni, Mn, Mo, Cr, Pb and Hg; the arithmetic mean values are proposed as the KCRV for P, S, Sr, Co and As. In general, the performances of the majority of CCQM-K145 participants are very good, illustrating their measurement capabilities for Zn, Ni, P, S, Mn, Mo, Sr, Cr, As, Co, Pb and Hg in a complex biological tissue matrix. Bovine liver contains many kinds of nutrients and microelements, it can be regarded as a typical representative material of biological tissue and food. In CCQM-K145, the analytes involved alkali metals and transition elements, metalloids/semi-metals and non metals with a range of mass fraction from mg/g to μg/kg. CCQM-K145 also tested the ability of NMIs/DIs to determine elements that were easy to be lost and polluted, and interfered significantly. The chemical pretreatment methods of samples used in the comparison is suitable for general food and biological matrix samples. A variety of measurement methods used in the comparison represent the main instrumental technology for elemental analysis. Therefore, for supporting CMC claim, CCQM-K145 is readily applicable to measurement of more elements in a wide range of biological materials (including liquids and solids) and meat products. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
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| 10. |
- Wiedorn, Max O., et al.
(författare)
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Megahertz serial crystallography
- 2018
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- The new European X-ray Free-Electron Laser is the first X-ray free-electron laser capable of delivering X-ray pulses with a megahertz inter-pulse spacing, more than four orders of magnitude higher than previously possible. However, to date, it has been unclear whether it would indeed be possible to measure high-quality diffraction data at megahertz pulse repetition rates. Here, we show that high-quality structures can indeed be obtained using currently available operating conditions at the European XFEL. We present two complete data sets, one from the well-known model system lysozyme and the other from a so far unknown complex of a beta-lactamase from K. pneumoniae involved in antibiotic resistance. This result opens up megahertz serial femtosecond crystallography (SFX) as a tool for reliable structure determination, substrate screening and the efficient measurement of the evolution and dynamics of molecular structures using megahertz repetition rate pulses available at this new class of X-ray laser source.
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| 11. |
- Botha-le Roux, Shani, et al.
(författare)
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Cardiovascular Profile of South African Adults with Low-Level Viremia during Antiretroviral Therapy
- 2022
-
Ingår i: Journal of Clinical Medicine. - : MDPI AG. - 2077-0383. ; 11:10
-
Tidskriftsartikel (refereegranskat)abstract
- Chronic inflammation is an HIV infection feature, contributing to elevated risk of cardiovascular disease among people with HIV, which can be induced by viral replication. A proportion of antiretroviral therapy (ART) recipients fail to achieve viral suppression, despite not meeting criteria for treatment failure, so-called low-level viremia (LLV). We investigated the relationship between LLV and an array of cardiovascular measures and biomarkers. South Africans with LLV (viral load = 50–999 copies/mL) and virological suppression (viral load <50 copies/mL) were selected from the EndoAfrica study (all receiving efavirenz-based ART) for cross-sectional comparison of vascular structure and function measures, as well as 21 plasma biomarkers related to cardiovascular risk and inflammation. Associations were investigated with univariate, multivariate, and binomial logistic regression analyses (having outcome measures above (cases) or below (controls) the 75th percentile). Among 208 participants, 95 (46%) had LLV, and 113 (54%) had viral suppression. The median age was 44 years, 73% were women, and the median ART duration was 4.5 years. Cardiovascular measures and biomarker levels were similar between these two categories. Cardiovascular function and structure measures were not associated with viremia status and having LLV did not increase the odds of having outcome measures above the 75th percentile. In this study among South African ART recipients, LLV did not associate with cardiovascular risk.
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| 12. |
- Hartmann, S., et al.
(författare)
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Can single-cell and spatial omics unravel the pathophysiology of pre-eclampsia?
- 2023
-
Ingår i: Journal of Reproductive Immunology. - : Elsevier. - 0165-0378 .- 1872-7603. ; 159
-
Tidskriftsartikel (refereegranskat)abstract
- Pre-eclampsia is a leading cause of maternal and fetal morbidity and mortality. Characterised by the onset of hypertension and proteinuria in the second half of pregnancy, it can lead to maternal end-organ injury such as cerebral ischemia and oedema, pulmonary oedema and renal failure, and potentially fatal outcomes for both mother and fetus. The causes of the different maternal end-organ phenotypes of pre-eclampsia and why some women develop pre-eclampsia condition early in pregnancy have yet to be elucidated. Omics methods include proteomics, genomics, metabolomics, transcriptomics. These omics techniques, previously mostly used on bulk tissue and individually, are increasingly available at a single cellular level and can be combined with each other. Multi-omics techniques on a single-cell or spatial level provide us with a powerful tool to understand the pathophysiology of pre-eclampsia. This review will explore the status of omics methods and how they can and could contribute to understanding the pathophysiology of pre-eclampsia.
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| 13. |
- Ludick, D. J., et al.
(författare)
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Enhancing the Jacobi Method with the CBFM for array antenna analysis
- 2017
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Ingår i: IEEE Antennas and Propagation Society International Symposium. - 1522-3965. - 9781538632840 ; , s. 727-728
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Konferensbidrag (refereegranskat)abstract
- The analysis of sparse, disjoint finite antenna array structures is considered in this work. The Method-of-Moments (MoM) based CBFM-enhanced Jacobi technique is presented, and offers an improvement over the standard iterative Jacobi method in terms of convergence and accuracy. By applying the Characteristic Basis Function Method (CBFM) during each iteration the effect of mutual coupling between the array elements can be accounted for more accurately than in the standard Jacobi method. The convergence rate of the method is found to be better than that of the Jacobi technique.
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| 14. |
- Botha, Elise M., 1983-
(författare)
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A means to an end : Using political satire to go viral
- 2014
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Ingår i: Public Relations Review. - : Elsevier. - 0363-8111 .- 1873-4537. ; 40:2, s. 363-374
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Tidskriftsartikel (refereegranskat)abstract
- With the rise of video sharing giants like Youtube and Google Video, coupled with increased broadband connectivity and improved sharing functionality across social networking sites, the role of the viral video has been cemented in many IMC strategies. While most agree about the importance of better understanding viral marketing, there is less agreement about what makes content become viral. While some content gets viewed by millions of people, others struggle to gain viral traction. Content specific, intrapersonal and interpersonal reasons have been proposed for viral marketing success. This paper' focuses on the intrapersonal reasons for content going viral in the context of political satire. More specifically, the role of emotion in the spread of content online, is investigated. Political satire focuses on gaining entertainment from politics. Satire, and specifically political satire, forms part of using humour in advertising and has been influential in shifting public opinion since ancient Greece. This study compares success and unsuccessful viral campaigns that used political satire, by first analysing the online comments that viewers made about the video. Following these findings, an experiment is conducted and the influence of intensity, creativity, humour and utility on virality is modelled, controlling for valence and previous exposure. The findings suggest that, when using political satire in viral campaigns, creativity and the intensity of the emotions felt are key influencing factors in whether videos get "shared" or "liked". Therefore, while many authors contend that particular emotions or positive content has a greater likelihood to become viral, this paper shows that it is not the particular emotion, but the intensity with which that emotion was felt that drives viral success.
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| 15. |
- Botha, Elsie Margaretha, et al.
(författare)
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To share or not to share : The role of content and emotion in viral marketing
- 2013
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Ingår i: Journal of Public Affairs. - : Wiley. - 1472-3891 .- 1479-1854. ; 13:2, s. 160-171
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Tidskriftsartikel (refereegranskat)abstract
- One of the most recent influential trends in the global environment has been the rise of social media. Stakeholders have found a strong voice in social media, and messages are spread among social media users at an astounding speed across a global landscape. As a result of this phenomenon and in an effort to use this viral spread of messages across social media, companies are increasingly making use of viral marketing. Viral messages are playing an increasingly important role in influencing and shifting public opinion on corporate reputations, brands, and products as well as political parties and public personalities to name but a few. Very little is known about the motivations, attitudes, and behavior of the people who forward viral messages to their online networks. Through in-depth interviews with college-going Generation Y consumers, we explore this relationship between viral media and emotions. We look at two very specific components of online videos that have gone viral: first, the relevance of the video's content and, second, participants' emotional reaction to these videos to try and better explain the viral spread of online video messages. The paper concludes by proposing a decision tree that interusers might subconsciously experience when deciding whether to share a video with their friends or not. The article concludes with a discussion about future research avenues in the area of emotions and viral marketing.
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| 16. |
- Botha, J. D. M., et al.
(författare)
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Some noise predictions for small wind turbines
- 2016
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Ingår i: Proceedings of ISMA 2016 - International Conference on Noise and Vibration Engineering and USD2016 - International Conference on Uncertainty in Structural Dynamics. - : KU Leuven, Departement Werktuigkunde. - 9789073802940 ; , s. 4019-4032
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Konferensbidrag (refereegranskat)abstract
- In the FP7 SWIP project three small wind turbine designs have been considered. These include two Horizontal Axis machine with a rated power of 4 and 20 kW and a 2 kW Vertical axis configuration. These will be mounted at three pilot sites with supporting atmospheric modelling and measurements. This paper presents broadband aeroacoustic noise predictions. The prediction methods compare semi empirical predictions more usually used for large turbine applications) supported where appropriate by CFD flow calculations. In order to pursue mitigation measures for these scales of machines, the noise is analysed on a component basis and considered from the viewpoints of self noise and inflow noise. The vertical axis machine is shown to dominated by boundary layer noise whereas the horizontal axis machines are more susceptible to inflow noise. In this the modelling of the inflow turbulence spectrum is seen to be critical.
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| 17. |
- Botha, Matthys M, et al.
(författare)
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An improved quadrature error estimate for nearly-singular MoM integrals
- 2018
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Ingår i: 2018 IEEE Antennas and Propagation Society International Symposium and USNC/URSI National Radio Science Meeting, APSURSI 2018 - Proceedings. ; , s. 2431-2432
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Konferensbidrag (refereegranskat)abstract
- A well-known numerical integration scheme for weakly near-singular integrands on triangle domains, is the Radial-Angular-RI-Sqrt near-singularity cancellation transformation quadrature scheme. Such integrals feature routinely in the method of moments (MoM), for integral equation based numerical electromagnetic field calculations. Recently, a closed-form quadrature error estimate has been proposed for this scheme. In this paper, the estimate is further improved, such that its range of applicability is extended.
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| 18. |
- Botha, Matthys M, et al.
(författare)
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Analysis and estimation of quadrature errors in weakly singular source integrals of the method of moments
- 2018
-
Ingår i: International Journal of Numerical Modelling: Electronic Networks, Devices and Fields. - : Wiley. - 0894-3370 .- 1099-1204. ; 31:1
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Tidskriftsartikel (refereegranskat)abstract
- The method of moments (MoM) is used for the numerical solution of electromagnetic field integral equations. Weakly singular integrals over surfaces in 3 dimensions (3D) are routinely evaluated for the impedance matrix setup and for post-processing. Available numerical integration schemes range from direct application of Gauss-Legendre product-rule quadrature, to singularity and near-singularity cancellation, coordinate transformation schemes. This paper presents a general, explicit, pole-based, a priori procedure to estimate quadrature errors in the numerical evaluation of weakly singular and near-singular, 3D surface integrals in the MoM. It is based on an error theorem for linear Gaussian quadrature, which involves the analytic extension of the integrand into the complex plane. Errors are linked to poles in the complex plane. New closed-form estimates are presented for direct Gaussian product-rule integration, polar-coordinate integration, and the Radial-Angular-R 1 -Sqrt singularity cancellation scheme, for triangle integration domains. This work can serve as a foundation/template for further, 3D MoM-related work to identify appropriate quadrature schemes according to their error characteristics; for automatic selection of optimal schemes and quadrature orders in a computer implementation of the MoM; and for local and global estimation of MoM quadrature errors. This work can be specialized to the MoM for surfaces in 2D.
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| 19. |
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| 20. |
- Botha, Matthys M, et al.
(författare)
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Quadrature error estimation for MoM matrix entries
- 2017
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Ingår i: 19th International Conference on Electromagnetics in Advanced Applications, ICEAA 2017; Verona; Italy; 11 September 2017 through 15 September 2017. - 9781509044511 ; , s. 973-975
-
Konferensbidrag (refereegranskat)abstract
- This paper is concerned with the method of moments (MoM) for electric field integral equation (EFIE) based numerical electromagnetic analysis of conducting surface structures. Inner (source) and outer (testing) integrals are encountered, when evaluating matrix entries. The well-known Radial-Angular-R1-Sqrt (RA-R1-Sqrt) weak near singularity cancellation transformation quadrature scheme for the inner integrals and standard Gaussian numerical integration for the outer integrals, are considered. It is shown that the quadrature error in the matrix entries, due to inner integral evaluation, can be accurately estimated under certain circumstances. A closed-form quadrature error estimate for the RA-R1-Sqrt scheme is employed.
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| 21. |
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| 22. |
- Dommisse, William R., et al.
(författare)
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Macro Basis Functions for Efficient Analysis of Thick Wires in the MoM
- 2024
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- This article presents a macro basis function (MBF) formulation for efficient method of moments (MoM) modelling of conducting wires with appreciable thickness. General surface formulations are prohibitively inefficient for electrically thin wires, while the typical exact-kernel, rooftop-basis, thin-wire MoM becomes wholly inaccurate for electrically thick cylinders. The MBF formulation bridges the gap between thin-wire MoM, and general conducting surface MoM formulations, by introducing circumferential variations and components beyond the standard rooftop basis functions. The MBFs are constructed upon a full-order, divergence-conforming, triangle element MoM discretization. Comprehensive junction and end-cap treatment, and tapered wire support, are natural features of the formulation. As with thin-wire MoM, degrees of freedom (DoFs) are purely proportional to the electrical length of the wire. Results demonstrate that the intermediate range of “thick wires” is analyzed with practically the same accuracy as general surface MoM, with significantly reduced DoFs.
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| 23. |
- Du Plessis, Jacques T., et al.
(författare)
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Scattering Analysis of Thick Wires with the MoM using Macro Basis Functions
- 2022
-
Ingår i: 2022 International Conference on Electromagnetics in Advanced Applications, ICEAA 2022. ; , s. 340-342
-
Konferensbidrag (refereegranskat)abstract
- This work is concerned with the analysis of scattering by conducting wires connected to conducting structures, using the method of moments (MoM). Based on thin-wire assumptions, low numbers of degrees of freedom (DoFs) are required by typical exact-kernel thin-wire MoM solvers, for accurate analysis. However, the thin-wire assumptions break down when the wire diameter becomes appreciably large in terms of the wavelength. An approach based on macro basis functions (MBFs) for wire current representation is outlined, aimed at extending the wire thickness range of accurate analysis, while maintaining a low number of DoFs similar to that of thin-wire formulations. Preliminary results demonstrate the effectiveness of the MBF approach.
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| 24. |
- Engelbrecht, J. A. A., et al.
(författare)
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Comparison of experimental results with theoretical models for the temperature dependence of the band gap of AlxGa1-xN epilayers
- 2022
-
Ingår i: Journal of materials science. Materials in electronics. - : SPRINGER. - 0957-4522 .- 1573-482X. ; 33, s. 22492-22498
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Tidskriftsartikel (refereegranskat)abstract
- The band gap energies AlxGa1-xN epilayers prepared on two different substrates were assessed using Fourier Transform Infrared (FTIR) reflectance spectroscopy, photoluminescence (PL) and scanning electron microscopy electron dispersive spectroscopy (SEM-EDS). The results were compared to various theoretical formulae to calculate the band gap, and deviations elucidated.
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| 25. |
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| 26. |
- Galli, Lorenzo, et al.
(författare)
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Towards phasing using high X-ray intensity
- 2015
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Ingår i: IUCrJ. - 2052-2525. ; 2, s. 627-634
-
Tidskriftsartikel (refereegranskat)abstract
- X-ray free-electron lasers (XFELs) show great promise for macromolecular structure determination from sub-micrometre-sized crystals, using the emerging method of serial femtosecond crystallography. The extreme brightness of the XFEL radiation can multiply ionize most, if not all, atoms in a protein, causing their scattering factors to change during the pulse, with a preferential ‘bleaching’ of heavy atoms. This paper investigates the effects of electronic damage on experimental data collected from a Gd derivative of lysozyme microcrystals at different X-ray intensities, and the degree of ionization of Gd atoms is quantified from phased difference Fourier maps. A pattern sorting scheme is proposed to maximize the ionization contrast and the way in which the local electronic damage can be used for a new experimental phasing method is discussed.
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| 27. |
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| 28. |
- Larsson, Kristina A. E., et al.
(författare)
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Differential regulation of 3-aminomethylindole/N-methyl-3-aminomethylindole N-methyltransferase and gramine in barley by both biotic and abiotic stress conditions
- 2011
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Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 49:1, s. 96-102
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Tidskriftsartikel (refereegranskat)abstract
- The expression of NMT (3-aminomethylindole/N-methyl-3-aminomethylindole N-methyltransferase; EC 2.1.1.), involved in the biosynthesis of the indole alkaloid gramine, was investigated in aphid-infested barley (Hordeum vulgare L). NMT is induced by methyl jasmonate and it was hypothesized that the gene would be more strongly upregulated in aphid-resistant barley. We examined the effects of feeding by three aphid species; Russian wheat aphid (Diuraphis noxia Mordvilko), rose-grain aphid (Metopolophium dirhodum Walker) and bird cherry-oat aphid (Rhopalosiphum padi L.) on barley genotypes with varying resistance characteristics. The barley genotypes selected included the cultivar Libra, known to upregulate gramine after feeding by Schizaphis graminum. Infestation by R. padi and M. dirhodum resulted in higher NMT expression in the doubled haploid line 5172-28:4 (DH28:4), which has moderate resistance against R. padi, but not in other aphid barley combinations. None of the aphid plant combinations had however increased gramine, suggesting that aphid-induction of gramine is specific to S. graminum. The increased abundance of NMT transcript in aphid-infested DH28:4 did not lead to higher amounts of NMT protein or NMT enzyme activity, neither did 200 times upregulation of NMT transcript in cotyledons incubated with methyl jasmonate, illustrating that even large differences measured at transcript level may have no metabolic consequences. Drought stress or treatments with abscisic acid did lead to higher gramine concentrations in several barley cultivars, but without any concomitant increase of NMT transcripts. Thus, the regulation of the biosynthetic pathway to gramine at transcript and metabolite level diverges during two different stress conditions.
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| 29. |
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| 30. |
- Ludick, D. J., et al.
(författare)
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Accelerating the CBFM-enhanced jacobi method
- 2017
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Ingår i: 19th International Conference on Electromagnetics in Advanced Applications, ICEAA 2017; Verona; Italy; 11 September 2017 through 15 September 2017. - 9781509044511 ; , s. 346-349
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Konferensbidrag (refereegranskat)abstract
- The Characteristic Basis Function Method (CBFM)-enhanced Jacobi method has been introduced as an improvement to the standard iterative Jacobi method for finite array analysis. This technique is a domain decomposition approach based on the Method of Moments (MoM) formulation. In some cases, e.g. array environments with a low degree of mutual coupling, the runtime benefit of the CBFM-enhanced Jacobi method is not as significant when compared to that of the Jacobi technique. The reason for this is that additional computational overhead is introduced during each iteration, i.e. setting up and solving the CBFM reduced matrix equation. In this work the adaptive cross approximation (ACA) algorithm is used to accelerate this step in the CBFM-enhanced Jacobi method.
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| 31. |
- Ludick, D. J., et al.
(författare)
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Comparison of the iterative jacobi method and the iterative Domain Green'S Function Method for finite array analysis
- 2016
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Ingår i: 10th European Conference on Antennas and Propagation, EuCAP 2016, Davos, Switzerland, 10-15 April 2016. - 2164-3342. - 9788890701863
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Konferensbidrag (refereegranskat)abstract
- The purpose of this work is to compare two iterative techniques that may be used for the analysis of large, disjoint finite antenna arrays, viz. the iterative Jacobi method and the iterative Domain Green's Function Method. These methods are conceptually similar, in that they offer alternative ways to improve non-local current distributions during the iterative process. The error convergence of each method will be studied at the hand of an example.
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| 32. |
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| 33. |
- Nass, Karol, et al.
(författare)
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Indications of radiation damage in ferredoxin microcrystals using high-intensity X-FEL beams
- 2015
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Ingår i: Journal of Synchrotron Radiation. - 0909-0495 .- 1600-5775. ; 22:2, s. 225-238
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Tidskriftsartikel (refereegranskat)abstract
- Proteins that contain metal cofactors are expected to be highly radiation sensitive since the degree of X-ray absorption correlates with the presence of high-atomic-number elements and X-ray energy. To explore the effects of local damage in serial femtosecond crystallography (SFX), Clostridium ferredoxin was used as a model system. The protein contains two [4Fe–4S] clusters that serve as sensitive probes for radiation-induced electronic and structural changes. High-dose room-temperature SFX datasets were collected at the Linac Coherent Light Source of ferredoxin microcrystals. Difference electron density maps calculated from high-dose SFX and synchrotron data show peaks at the iron positions of the clusters, indicative of decrease of atomic scattering factors due to ionization. The electron density of the two [4Fe–4S] clusters differs in the FEL data, but not in the synchrotron data. Since the clusters differ in their detailed architecture, this observation is suggestive of an influence of the molecular bonding and geometry on the atomic displacement dynamics following initial photoionization. The experiments are complemented by plasma code calculations.
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| 34. |
- Rasam, Amin, et al.
(författare)
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Aerodynamic noise prediction for a wind turbine using numerical flow simulations and semi-empirical modelling approaches
- 2016
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Ingår i: 22nd AIAA/CEAS Aeroacoustics Conference. - Reston, Virginia : American Institute of Aeronautics and Astronautics.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, aerodynamic and aero-acoustic simulations are performed for a small horizontal axis wind turbine, suitable for the integration of wind energy in urban and peri-urban areas. Detached-eddy simulation (DES) of compressible flow is performed to compute the flow field over the wind turbine. The far-field noise is computed using the Ffowcs - Williams and Hawkings acoustic analogy. Furthermore, the blade element momentum theory is used with a semi-empirical acoustic modeling approach to predict the wind turbine noise. The acoustic modeling approach is based on a semi-empirical formulation for airfoil self noise and an analytic formulation for inflow noise.
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| 35. |
- Rylander, Thomas, 1972, et al.
(författare)
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Exact-Kernel Thin-Wire MoM with Geometric Representation by Bezier Curves
- 2022
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Ingår i: IEEE International Symposium on Electromagnetic Compatibility. - 1077-4076 .- 2158-1118. ; 2022-September, s. 389-393
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Konferensbidrag (refereegranskat)abstract
- Electromagnetic field simulation of wire structures is important to high-frequency electromagnetic engineering applications, including antenna design and electromagnetic compatibility studies. This paper exploits the electric field integral equation to solve for the induced current on a curved thin-wire, which is modelled as a perfect electric conductor (PEC). The singular part of the Green's function is integrated by means of the complete elliptic integral of the first kind. The geometry of the curved wire is described by Bezier-curve segments, where this approach is particularly useful for problems where a smooth wire-geometry requires better representation than the current at (typically) low frequencies. The formulation is tested on the scattering from a closed PEC ring shaped as a circle for three different frequencies. As the number of elements is increased, the induced currents tend toward the reference solution provided by FEKO.
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| 36. |
- Saheed, Sefiu A., et al.
(författare)
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Russian wheat aphid causes greater reduction in phloem transport apacity of barley leaves than bird cherry-oat aphid.
- 2010
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Ingår i: Acta Botanica Croatica. - 0365-0588 .- 1847-8476. ; 69:1, s. 7-18
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Tidskriftsartikel (refereegranskat)abstract
- The effects of feeding by the Russian wheat aphid (RWA). Dutraplu.s nom! ordvilko and the Bird cherry-oat aphid (BC A). Rhopaloppluan pad, L on he transport capacity of barley Holdeum vulgare L leaves were nvestigated and compated with a view to i-elan ng these effects to the isible symptoms shown by the respective infested plants RWA causes xtensive chlorosis and neciosis on an infested plant whereas I3CA auses no obseivable symptoms Our results using the xenobiotic. phloem obile Bum ophole. 5, 6 carboxyBurn escei n chacetate (5. 6-CFDA) evealed striking ch fletences in damage to the transpol t of ssimilates thiough the phloem by these two aphids The result clearly uggests that short-term feeding by RWA causes a reduction in tiansport f assimikites and a mole severe reduction oi pei haps even permanent essation of transport during long-term feed111,2. In contrast. feechntz y BCA does not lead to a !milked dect ease in transport do ring hort-term feeding period. howevei, a !eduction in the uanspoit was ecorded donne long-term feeding activities These iesults perhaps uggest that damage to ti ansport capacities of the barley leaves ppeals lobe partly responsible for the observed symptoms in WIA-infested plants and the lack of them during BCA in symptoms such as eduction ol cessation in transport of assionlates to growing tissues ay lead to such observable symptoms
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| 37. |
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| 38. |
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| 39. |
- Saheed, Sefiu, et al.
(författare)
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Stronger induction of callose deposition in barley by Russian wheat aphid than bird cherry-oat aphid is not associated with differences in callose synthase or beta-1,3-glucanase transcript abundance
- 2009
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 135:2, s. 150-161
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Tidskriftsartikel (refereegranskat)abstract
- The effects of infestation by the bird cherry-oat aphid (BCA), (Rhopalosiphum padi L) and the Russian wheat aphid (RWA) (Diuraphis noxia Mordvilko) on callose deposition and transcription of genes related to callose accumulation were investigated in barley (Hordeum vulgare L. cv. Clipper). The BCA, which gives no visible symptoms, induced very limited callose deposition, even after 14 days of infestation. In contrast, RWA, which causes chlorosis, white and yellow streaking and leaf rolling, induced callose accumulation already after 24 h in longitudinal leaf veins. The deposition was pronounced after 72 h, progressing during 7 and 14 days of infestation. In RWA-infested source leaves, callose was also induced in longitudinal veins basipetal to the aphid-infested tissue, whereas in sink leaves, more callose deposition was found above the feeding sites. Eight putative callose synthase genes were identified in a database search, of which seven were expressed in the leaves, but with similar transcript accumulation in control and aphid-infested tissue. Five out of 12 examined beta-1,3-glucanases were expressed in the leaves. All five were upregulated in RWA-infested tissue, but only two in BCA-infested tissue, and to a lesser extent than by RWA. The results suggest that callose accumulation may be partly responsible for the symptoms resulting from RWA infestation and that a callose-inducing signal may be transported in the phloem. Furthermore, it is concluded that the absence of callose deposition in BCA-infested leaves is not because of a stronger upregulation of callose-degrading beta-1,3-glucanases in this tissue, as compared to RWA-infested leaves.
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| 40. |
- Urgessa, Z. N., et al.
(författare)
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Low temperature near band edge recombination dynamics in ZnO nanorods
- 2014
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 116:12, s. 123506-
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Tidskriftsartikel (refereegranskat)abstract
- The recombination dynamics of neutral donor bound excitons ((DX)-X-o: I-4, I-6/6a) and near band edge defect-related emission in solution grown ZnO nanorods are investigated using steady state and time-resolved photoluminescence (PL) measurements. The effects of annealing are also studied. Low temperature steady state PL shows a systematic removal of the I-4 line after annealing at 450 degrees C and the subsequent domination of I-6a in these PL spectra. Additionally, the time decay of the I-4, I-6/6a, free exciton (FX), and basal plane stacking fault-related (BSF) PL transitions are studied as a function of annealing temperature. For the various annealing temperatures studied, the PL decay is described by a bi-exponential profile with a fast component (contribution from the surface) and slow component (related to bulk recombination). The fast component dominates in the case of as-grown and low temperature annealed samples (anneal temperatures up to 300 degrees C), suggesting the presence of surface adsorbed impurities. For samples annealed above 400 degrees C, the effects of the surface are reduced. The sample annealed at 850 degrees C produced an overall enhancement of the crystal quality. The underlying mechanisms for the observed PL characteristics are discussed based on near surface band bending caused by surface impurities.
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| 41. |
- Vogel, Jacob W., et al.
(författare)
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Connectome-based modelling of neurodegenerative diseases: towards precision medicine and mechanistic insight
- 2023
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Ingår i: Nature Reviews Neuroscience. - 1471-003X .- 1471-0048. ; 24:10, s. 620-639
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Tidskriftsartikel (refereegranskat)abstract
- Neurodegenerative diseases are the most common cause of dementia. Although their underlying molecular pathologies have been identified, there is substantial heterogeneity in the patterns of progressive brain alterations across and within these diseases. Recent advances in neuroimaging methods have revealed that pathological proteins accumulate along specific macroscale brain networks, implicating the network architecture of the brain in the system-level pathophysiology of neurodegenerative diseases. However, the extent to which 'network-based neurodegeneration' applies across the wide range of neurodegenerative disorders remains unclear. Here, we discuss the state-of-the-art of neuroimaging-based connectomics for the mapping and prediction of neurodegenerative processes. We review findings supporting brain networks as passive conduits through which pathological proteins spread. As an alternative view, we also discuss complementary work suggesting that network alterations actively modulate the spreading of pathological proteins between connected brain regions. We conclude this Perspective by proposing an integrative framework in which connectome-based models can be advanced along three dimensions of innovation: incorporating parameters that modulate propagation behaviour on the basis of measurable biological features; building patient-tailored models that use individual-level information and allowing model parameters to interact dynamically over time. We discuss promises and pitfalls of these strategies for improving disease insights and moving towards precision medicine. Neurodegenerative diseases show idiosyncratic spatial patterns of progressive protein malformations in the brain. In this Perspective, Vogel et al. discuss the role of inter-regional connectivity in constraining and modulating the spread of pathological proteins and provide a framework for patient-tailored prognostics.
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