| 1. |
- Tran, K. B., et al.
(författare)
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The global burden of cancer attributable to risk factors, 2010-19: a systematic analysis for the Global Burden of Disease Study 2019
- 2022
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Ingår i: Lancet. - 0140-6736. ; 400:10352, s. 563-591
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Tidskriftsartikel (refereegranskat)abstract
- Background Understanding the magnitude of cancer burden attributable to potentially modifiable risk factors is crucial for development of effective prevention and mitigation strategies. We analysed results from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 to inform cancer control planning efforts globally. Methods The GBD 2019 comparative risk assessment framework was used to estimate cancer burden attributable to behavioural, environmental and occupational, and metabolic risk factors. A total of 82 risk-outcome pairs were included on the basis of the World Cancer Research Fund criteria. Estimated cancer deaths and disability-adjusted life-years (DALYs) in 2019 and change in these measures between 2010 and 2019 are presented. Findings Globally, in 2019, the risk factors included in this analysis accounted for 4.45 million (95% uncertainty interval 4.01-4.94) deaths and 105 million (95.0-116) DALYs for both sexes combined, representing 44.4% (41.3-48.4) of all cancer deaths and 42.0% (39.1-45.6) of all DALYs. There were 2.88 million (2.60-3.18) risk-attributable cancer deaths in males (50.6% [47.8-54.1] of all male cancer deaths) and 1.58 million (1.36-1.84) risk-attributable cancer deaths in females (36.3% [32.5-41.3] of all female cancer deaths). The leading risk factors at the most detailed level globally for risk-attributable cancer deaths and DALYs in 2019 for both sexes combined were smoking, followed by alcohol use and high BMI. Risk-attributable cancer burden varied by world region and Socio-demographic Index (SDI), with smoking, unsafe sex, and alcohol use being the three leading risk factors for risk-attributable cancer DALYs in low SDI locations in 2019, whereas DALYs in high SDI locations mirrored the top three global risk factor rankings. From 2010 to 2019, global risk-attributable cancer deaths increased by 20.4% (12.6-28.4) and DALYs by 16.8% (8.8-25.0), with the greatest percentage increase in metabolic risks (34.7% [27.9-42.8] and 33.3% [25.8-42.0]). Interpretation The leading risk factors contributing to global cancer burden in 2019 were behavioural, whereas metabolic risk factors saw the largest increases between 2010 and 2019. Reducing exposure to these modifiable risk factors would decrease cancer mortality and DALY rates worldwide, and policies should be tailored appropriately to local cancer risk factor burden. Copyright (C) 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.
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| 2. |
- Ikuta, K. S., et al.
(författare)
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Global mortality associated with 33 bacterial pathogens in 2019: a systematic analysis for the Global Burden of Disease Study 2019
- 2022
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Ingår i: Lancet. - : Elsevier BV. - 0140-6736. ; 400:10369, s. 2221-2248
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Tidskriftsartikel (refereegranskat)abstract
- Background Reducing the burden of death due to infection is an urgent global public health priority. Previous studies have estimated the number of deaths associated with drug-resistant infections and sepsis and found that infections remain a leading cause of death globally. Understanding the global burden of common bacterial pathogens (both susceptible and resistant to antimicrobials) is essential to identify the greatest threats to public health. To our knowledge, this is the first study to present global comprehensive estimates of deaths associated with 33 bacterial pathogens across 11 major infectious syndromes. Methods We estimated deaths associated with 33 bacterial genera or species across 11 infectious syndromes in 2019 using methods from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019, in addition to a subset of the input data described in the Global Burden of Antimicrobial Resistance 2019 study. This study included 343 million individual records or isolates covering 11 361 study-location-years. We used three modelling steps to estimate the number of deaths associated with each pathogen: deaths in which infection had a role, the fraction of deaths due to infection that are attributable to a given infectious syndrome, and the fraction of deaths due to an infectious syndrome that are attributable to a given pathogen. Estimates were produced for all ages and for males and females across 204 countries and territories in 2019. 95% uncertainty intervals (UIs) were calculated for final estimates of deaths and infections associated with the 33 bacterial pathogens following standard GBD methods by taking the 2.5th and 97.5th percentiles across 1000 posterior draws for each quantity of interest. Findings From an estimated 13.7 million (95% UI 10.9-17.1) infection-related deaths in 2019, there were 7.7 million deaths (5.7-10.2) associated with the 33 bacterial pathogens (both resistant and susceptible to antimicrobials) across the 11 infectious syndromes estimated in this study. We estimated deaths associated with the 33 bacterial pathogens to comprise 13.6% (10.2-18.1) of all global deaths and 56.2% (52.1-60.1) of all sepsis-related deaths in 2019. Five leading pathogens-Staphylococcus aureus, Escherichia coli, Streptococcus pneumoniae, Klebsiella pneumoniae, and Pseudomonas aeruginosa-were responsible for 54.9% (52.9-56.9) of deaths among the investigated bacteria. The deadliest infectious syndromes and pathogens varied by location and age. The age-standardised mortality rate associated with these bacterial pathogens was highest in the sub-Saharan Africa super-region, with 230 deaths (185-285) per 100 000 population, and lowest in the high-income super-region, with 52.2 deaths (37.4-71.5) per 100 000 population. S aureus was the leading bacterial cause of death in 135 countries and was also associated with the most deaths in individuals older than 15 years, globally. Among children younger than 5 years, S pneumoniae was the pathogen associated with the most deaths. In 2019, more than 6 million deaths occurred as a result of three bacterial infectious syndromes, with lower respiratory infections and bloodstream infections each causing more than 2 million deaths and peritoneal and intra-abdominal infections causing more than 1 million deaths. Interpretation The 33 bacterial pathogens that we investigated in this study are a substantial source of health loss globally, with considerable variation in their distribution across infectious syndromes and locations. Compared with GBD Level 3 underlying causes of death, deaths associated with these bacteria would rank as the second leading cause of death globally in 2019; hence, they should be considered an urgent priority for intervention within the global health community. Strategies to address the burden of bacterial infections include infection prevention, optimised use of antibiotics, improved capacity for microbiological analysis, vaccine development, and improved and more pervasive use of available vaccines. These estimates can be used to help set priorities for vaccine need, demand, and development. Copyright (c) 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.
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| 10. |
- Klionsky, Daniel J., et al.
(författare)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 11. |
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| 12. |
- Bass, Gary Alan, 1979-, et al.
(författare)
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Techniques for mesoappendix transection and appendix resection: insights from the ESTES SnapAppy study
- 2023
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Ingår i: European Journal of Trauma and Emergency Surgery. - : Springer Science and Business Media LLC. - 1863-9933 .- 1615-3146 .- 1863-9941. ; 49, s. 17-32
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Surgically managed appendicitis exhibits great heterogeneity in techniques for mesoappendix transection and appendix amputation from its base. It is unclear whether a particular surgical technique provides outcome benefit or reduces complications. Material and methods: We undertook a pre-specified subgroup analysis of all patients who underwent laparoscopic appendectomy at index admission during SnapAppy (ClinicalTrials.gov Registration: NCT04365491). We collected routine, anonymized observational data regarding surgical technique, patient demographics and indices of disease severity, without change to clinical care pathway or usual surgeon preference. Outcome measures of interest were the incidence of complications, unplanned reoperation, readmission, admission to the ICU, death, hospital length of stay, and procedure duration. We used Poisson regression models with robust standard errors to calculate incident rate ratios (IRRs) and 95% confidence intervals (CIs). Results: Three-thousand seven hundred sixty-eight consecutive adult patients, included from 71 centers in 14 countries, were followed up from date of admission for 90days. The mesoappendix was divided hemostatically using electrocautery in 1564(69.4%) and an energy device in 688(30.5%). The appendix was amputated by division of its base between looped ligatures in 1379(37.0%), with a stapler in 1421(38.1%) and between clips in 929(24.9%). The technique for securely dividing the appendix at its base in acutely inflamed (AAST Grade 1) appendicitis was equally divided between division between looped ligatures, clips and stapled transection. However, the technique used differed in complicated appendicitis (AAST Grade 2 +) compared with uncomplicated (Grade 1), with a shift toward transection of the appendix base by stapler (58% vs. 38%; p < 0.001). While no statistical difference in outcomes could be detected between different techniques for division of appendix base, decreased risk of any [adjusted IRR (95% CI): 0.58 (0.41–0.82), p = 0.002] and severe [adjusted IRR (95% CI): 0.33 (0.11–0.96), p = 0.045] complications could be detected when using energy devices. Conclusions: Safe mesoappendix transection and appendix resection are accomplished using heterogeneous techniques. Technique selection for both mesoappendix transection and appendix resection correlates with AAST grade. Higher grade led to more ultrasonic tissue transection and stapled appendix resection. Higher AAST appendicitis grade also correlated with infection-related complication occurrence. Despite the overall well-tolerated heterogeneity of approaches to acute appendicitis, increasing disease acuity or complexity appears to encourage homogeneity of intraoperative surgical technique toward advanced adjuncts.
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| 13. |
- Forssten, Maximilian Peter, 1996-, et al.
(författare)
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Surgical management of acute appendicitis during the European COVID-19 second wave: safe and effective
- 2023
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Ingår i: European Journal of Trauma and Emergency Surgery. - : Springer Science and Business Media LLC. - 1863-9933 .- 1615-3146 .- 1863-9941. ; 49, s. 57-67
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: The COVID-19 (SARS-CoV-2) pandemic drove acute care surgeons to pivot from long established practice patterns. Early safety concerns regarding increased postoperative complication risk in those with active COVID infection promoted antibiotic-driven non-operative therapy for select conditions ahead of an evidence-base. Our study assesses whether active or recent SARS-CoV-2 positivity increases hospital length of stay (LOS) or postoperative complications following appendectomy. Methods: Data were derived from the prospective multi-institutional observational SnapAppy cohort study. This preplanned data analysis assessed consecutive patients aged ≥ 15years who underwent appendectomy for appendicitis (November 2020–May 2021). Patients were categorized based on SARS-CoV-2 seropositivity: no infection, active infection, and prior infection. Appendectomy method, LOS, and complications were abstracted. The association between SARS-CoV-2 seropositivity and complications was determined using Poisson regression, while the association with LOS was calculated using a quantile regression model. Results: Appendectomy for acute appendicitis was performed in 4047 patients during the second and third European COVID waves. The majority were SARS-CoV-2 uninfected (3861, 95.4%), while 70 (1.7%) were acutely SARS-CoV-2 positive, and 116 (2.8%) reported prior SARS-CoV-2 infection. After confounder adjustment, there was no statistically significant association between SARS-CoV-2 seropositivity and LOS, any complication, or severe complications. Conclusion: During sequential SARS-CoV-2 infection waves, neither active nor prior SARS-CoV-2 infection was associated with prolonged hospital LOS or postoperative complication. Despite early concerns regarding postoperative safety and outcome during active SARS-CoV-2 infection, no such association was noted for those with appendicitis who underwent operative management.
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| 14. |
- Sheykhifard, Z., et al.
(författare)
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Magnetic graphene/Ni-nano-crystal hybrid for small field magnetoresistive effect synthesized via electrochemical exfoliation/deposition technique
- 2018
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Ingår i: Journal of Materials Science-Materials in Electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 29:5, s. 4171-4178
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional heterostructures of graphene (Gr) and metal/semiconducting elements convey new direction in electronic devices. They can be useful for spintronics because of small spin orbit interaction of Gr as a non-magnetic metal host with promising electrochemical stability. In this paper, we demonstrate one-step fabrication of magnetic Ni-particles entrapped within Gr-flakes based on simultaneous electrochemical exfoliation/deposition procedure by two-electrode system using platinum as the cathode electrode and a graphite foil as the anode electrode. The final product is an air stable hybrid element including Gr flakes hosting magnetic Ni-nano-crystals showing superparamagnetic-like response and room temperature giant magnetoresistance (GMR) effect at small magnetic field range. The GMR effect is originated from spin scattering through ferromagnetic/non-magnetic nature of Ni/Gr heterostructure and interpreted based on a phenomenological spin transport model. Our work benefits from XRD, XPS, Raman, TEM, FTIR and VSM measurements We addressed that how our results can be used for rapid manufacturing of magnetic Gr for low field magneto resistive elements and potential printed spintronic devices.
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| 15. |
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| 16. |
- Ahmadi, K., et al.
(författare)
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Inducing Dzyaloshinskii-Moriya interaction in symmetrical multilayers using post annealing
- 2022
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- The interfacial Dzyaloshinskii-Moriya Interaction (iDMI) is an antisymmetric exchange interaction that is induced by the broken inversion symmetry at the interface of, e.g., a ferromagnet/heavy metal. Thus, the presence of iDMI is not expected in symmetrical multilayer stacks of such structures. Here, we use thermal annealing to induce the iDMI in a [Py/Pt](x10) symmetrical multilayer stack. Brillouin light scattering spectroscopy is used to directly evidence the iDMI induction in the annealed sample. Structural characterizations highlight the modified crystallinity as well as a higher surface roughness of the sample after annealing. First principles electronic structure calculations demonstrate a monotonic increase of the iDMI with the interfacial disorder due to the interdiffusion of atoms, depicting the possible origin of the induced iDMI. The presented method can be used to tune the iDMI strength in symmetric multilayers, which are the integral part of racetrack memories, magnonic devices as well as spin-orbitronic elements.
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| 17. |
- Polyakov, A., et al.
(författare)
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Instability of the topological surface state in Bi2Se3 upon deposition of gold
- 2017
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 95:18
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Tidskriftsartikel (refereegranskat)abstract
- Momentum-resolved photoemission spectroscopy indicates the instability of the Dirac surface state upon deposition of gold on the (0001) surface of the topological insulator Bi2Se3. Based on the structure model derived from extended x-ray absorption fine structure experiments showing that gold atoms substitute bismuth atoms, first-principles calculations provide evidence that a gap appears due to hybridization of the surface state with gold d states near the Fermi level. Our findings provide insights into the mechanisms affecting the stability of the surface state.
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| 18. |
- Polyakov, A., et al.
(författare)
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Reply to Comment on 'Instability of the topological surface state in Bi2Se3 upon deposition of gold'
- 2018
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 98:13
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Tidskriftsartikel (refereegranskat)abstract
- In the Comment on our publication [Phys. Rev. B 95, 180202(R) (2017)], R. A. Gordon claims that our main conclusion is not valid, namely that gold atoms deposited in situ on the (0001) surface of single-crystalline Bi2Se3 reside in substitutional sites, i.e., replacing bismuth atoms within the topmost quintuple layer (QL). Based on x-ray absorption near-edge (XANES) spectra and a re-evaluation of extended x-ray absorption fine structure (EXAFS) data above the Au L-III edge, R. A. Gordon concludes that Au resides in a twofold environment as a result of an interface reaction leading to an Au2S-type local structure, in which gold adopts an Au(I) state and is linearly coordinated by selenium atoms. In this Reply, we will confirm the results published in the original paper and their interpretation that Au atoms reside in the substitutional site.
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| 19. |
- Ahlberg, Martina, et al.
(författare)
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Freezing and thawing magnetic droplet solitons
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic droplets are a type of non-topological magnetic soliton, which are stabilised and sustained by spin-transfer torques for instance. Without this, they would collapse. Here Ahlberg et al show that by decreasing the applied magnetic field, droplets can be frozen, forming a static nanobubble Magnetic droplets are non-topological magnetodynamical solitons displaying a wide range of complex dynamic phenomena with potential for microwave signal generation. Bubbles, on the other hand, are internally static cylindrical magnetic domains, stabilized by external fields and magnetostatic interactions. In its original theory, the droplet was described as an imminently collapsing bubble stabilized by spin transfer torque and, in its zero-frequency limit, as equivalent to a bubble. Without nanoscale lateral confinement, pinning, or an external applied field, such a nanobubble is unstable, and should collapse. Here, we show that we can freeze dynamic droplets into static nanobubbles by decreasing the magnetic field. While the bubble has virtually the same resistance as the droplet, all signs of low-frequency microwave noise disappear. The transition is fully reversible and the bubble can be thawed back into a droplet if the magnetic field is increased under current. Whereas the droplet collapses without a sustaining current, the bubble is highly stable and remains intact for days without external drive. Electrical measurements are complemented by direct observation using scanning transmission x-ray microscopy, which corroborates the analysis and confirms that the bubble is stabilized by pinning.
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| 20. |
- Banuazizi, Seyed Amir Hossein, et al.
(författare)
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Order of magnitude improvement of nano-contact spin torque nano-oscillator performance
- 2017
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 9:5, s. 1896-1900
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Tidskriftsartikel (refereegranskat)abstract
- Spin torque nano-oscillators (STNO) represent a unique class of nano-scale microwave signal generators and offer a combination of intriguing properties, such as nano sized footprint, ultrafast modulation rates, and highly tunable microwave frequencies from 100 MHz to close to 100 GHz. However, their low output power and relatively high threshold current still limit their applicability and must be improved. In this study, we investigate the influence of the bottom Cu electrode thickness (t(Cu)) in nano-contact STNOs based on Co/Cu/NiFe GMR stacks and with nano-contact diameters ranging from 60 to 500 nm. Increasing t(Cu) from 10 to 70 nm results in a 40% reduction of the threshold current, an order of magnitude higher microwave output power, and close to two orders of magnitude better power conversion efficiency. Numerical simulations of the current distribution suggest that these dramatic improvements originate from a strongly reduced lateral current spread in the magneto-dynamically active region.
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| 21. |
- Burgos-Parra, E., et al.
(författare)
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Investigation of magnetic droplet solitons using x-ray holography with extended references
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- A dissipative magnetic soliton, or magnetic droplet, is a structure that has been predicted to exist within a thin magnetic layer when non-linearity is balanced by dispersion, and a driving force counteracts the inherent damping of the spin precession. Such a soliton can be formed beneath a nano-contact (NC) that delivers a large spin-polarized current density into a magnetic layer with perpendicular magnetic anisotropy. Although the existence of droplets has been confirmed from electrical measurements and by micromagnetic simulations, only a few attempts have been made to directly observe the magnetic landscape that sustains these structures, and then only for a restricted set of experimental parameter values. In this work we use and x-ray holography technique HERALDO, to image the magnetic structure of the [ Co/ Ni] x4 multilayer within a NC orthogonal pseudo spin-valve, for different range of magnetic fields and injected electric currents. The magnetic configuration imaged at -33 mA and 0.3 T for devices with 90 nm NC diameter reveals a structure that is within the range of current where the droplet soliton exist based on our electrical measurements and have it is consistent with the expected size of the droplet (similar to 100 nm diameter) and its spatial position within the sample. We also report the magnetisation configurations observed at lower DC currents in the presence of fields (0-50 mT), where it is expected to observe regimes of the unstable droplet formation.
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| 22. |
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| 23. |
- Mohseni, M., et al.
(författare)
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Chiral excitations of magnetic droplet solitons driven by their own inertia
- 2020
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 101:2
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Tidskriftsartikel (refereegranskat)abstract
- The inertial effects of magnetic solitons play a crucial role in their dynamics and stability. Yet governing their inertial effects is a challenge for their use in real devices. Here, we show how to control the inertial effects of magnetic droplet solitons. Magnetic droplets are more strongly nonlinear and localized autosolitons than can form in current-driven nanocontacts. Droplets can be considered as dynamical particles with an effective mass. We show that the dynamical droplet bears a second excitation under its own inertia. These excitations comprise a chiral profile, and appear when the droplet resists the force induced by the Oersted field of the current injected into the nanocontact. We reveal the role of the spin torque on the excitation of these chiral modes and we show how to control these modes using the current and the field.
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| 24. |
- Mohseni, Seyed Morteza, et al.
(författare)
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Magnetic droplet soliton nucleation in oblique fields
- 2018
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 97:18
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Tidskriftsartikel (refereegranskat)abstract
- We study the auto-oscillating magnetodynamics in orthogonal spin-torque nano-oscillators (STNOs) as a function of the out-of-plane (OOP) magnetic-field angle. In perpendicular fields and at OOP field angles down to approximately 50°, we observe the nucleation of a droplet. However, for field angles below 50°, experiments indicate that the droplet gives way to propagating spin waves, in agreement with our micromagnetic simulations. Theoretical calculations show that the physical mechanism behind these observations is the sign changing of spin-wave nonlinearity (SWN) by angle. In addition, we show that the presence of a strong perpendicular magnetic anisotropy free layer in the system reverses the angular dependence of the SWN and dynamics in STNOs with respect to the known behavior determined for the in-plane magnetic anisotropy free layer. Our results are of fundamental interest in understanding the rich dynamics of nanoscale solitons and spin-wave dynamics in STNOs.
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| 25. |
- Mohseni, S. M., et al.
(författare)
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Magnetostatically driven domain replication in Ni/Co based perpendicular pseudo-spin-valves
- 2016
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Ingår i: Journal of Physics D-Applied Physics. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 49:41
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Tidskriftsartikel (refereegranskat)abstract
- The effect of ferromagnetic layer thickness on the temperature-dependent stray-field-induced coupling mechanism is investigated in perpendicular pseudo-spin-valves based on [Ni/Co](5)/ Cu/Co-[Ni/Co](n) (n = 2, 3, 4, and 5). Experimental observations show that as n increases from 2 to 4, the difference in coercivity and anisotropy between the two ([Ni/Co](5) or bottom-layer, and [Ni/Co](n) or top-layer) layers increases and the room temperature coupling strength decreases. The coupling then increases for n = 5, as the coercivity difference shrinks and anisotropy decreases. At reduced temperature, the layers start to decouple at a temperature, which increases with n from 2 to 4 and decreases for n = 5 via a stray-field domain-replication mechanism. Our results are useful to control the coupling in pseudo-spin-valves for practical applications in magnetoresistive devices.
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| 26. |
- Moradi, M., et al.
(författare)
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Au/NiFe Magnetoplasmonics: Large Enhancement of Magneto-Optical Kerr Effect for Magnetic Field Sensors and Memories
- 2015
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Ingår i: Electronic Materials Letters. - : Springer Science and Business Media LLC. - 1738-8090 .- 2093-6788. ; 11:3, s. 440-446
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Tidskriftsartikel (refereegranskat)abstract
- Surface plasmon polariton resonance (SPPR) can be originated from the surface charge oscillation via light localization at the interface of a metal, for example, Au or Ag and a dielectric. Such localization can be implemented to increase the magneto-optical (MO) activity of a magnetic medium while SPPR is fulfilled, which is known as magnetoplasmonics. In this paper, a magnetoplasmonic bilayer of Au/NiFe (Py) sputter deposited on glass is demonstrated. Large enhancement in MO-Ken effedt (MOKE) response due to SPPR effect is observed at different light incident angles. By measuring and analyzing the MO signals from the sample with different thicknesses of Au and Py layers, the optimal thicknesses' range is obtained with the largest MOKE. The large MOKE intensity from ultra-soft magnetic Py layer with low coercivity and small saturation field suggests a weak magnetic field-sensitive MO-based element. Finally, different applications of such structures, for example, weak magnetic field sensors and magnetic multilevel memory elements are demonstrated.
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| 27. |
- Persson, Johan, et al.
(författare)
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Spin-Torque Oscillator in an Electromagnet Package
- 2012
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Ingår i: IEEE Transactions on Magnetics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9464 .- 1941-0069. ; 48:11, s. 4378-4381
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Tidskriftsartikel (refereegranskat)abstract
- Spin-torque oscillators (STO) hold promise for multi-octave frequency operation at very high frequencies and modulation speeds. STO operation is typically demonstrated using large electromagnets and probe stations, and has so far not been packaged with a portable form factor. For STOs to be utilized in real applications, a smaller packaging solution is needed. We integrate STOs with packages originally developed for YIG oscillators, modified to incorporate permanent magnets and to achieve a compact portable oscillator based on the STO.
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| 28. |
- Qejvanaj, Fatjon, et al.
(författare)
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Thick Double-Biased IrMn/NiFe/IrMn Planar Hall Effect Bridge Sensors
- 2014
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 50:11
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present a new material stack for planar Hall effect bridge (PHEB) sensors and a detailed investigation of the sensitivity and noise properties of PHEB sensors made from these. The sputter deposited material stack was based on a ferromagnetic (FM) NiFe sensing layer surrounded by two layers of anti-FM IrMn. This material stack enables implementation of a thick NiFe layer without loss of sensitivity. We present an improvement in detectivity in the PHEB by changing the shape and the materials of the corners between the sensors in a meander shape. A significant reduction of noise also comes from the thick NiFe layer, due to the reduced resistance of the sensor.
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| 29. |
- Roozmeh, S. E., et al.
(författare)
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Study of magnetoimpedance effect of Co-based amorphous ribbons after current annealing at various kinds of ambient pressure
- 2009
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Ingår i: Journal of Non-Crystalline Solids. - : Elsevier BV. - 0022-3093 .- 1873-4812. ; 355:52-54, s. 2653-2656
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Tidskriftsartikel (refereegranskat)abstract
- The physical properties of magnetic amorphous alloys can be improved by using different annealing processes. In this paper, for annealing purposes, different driving currents were flowed through Co-based magnetic amorphous ribbons at different ambient air pressures between 5 x 10(-5) mbar and 10(3) mbar. The magnetoimpedance effect in the annealed samples was studied at a frequency interval between 250 kHz and 10 MHz. Magnetic properties and microstructures of samples were investigated by means of alternative gradient force magnetometers and X-ray diffraction. Regarding the giant magnetoimpedance (GMI) effect, annealing at different ambient pressures with the same current can lead to various responses. For annealing at higher pressures such as in air, higher current is necessary for crystallization of samples which results in the development of greater transverse magnetic anisotropy.
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| 30. |
- Ah, Rebecka, et al.
(författare)
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Prognostic Value of P-POSSUM and Osteopenia for Predicting Mortality After Emergency Laparotomy in Geriatric Patients
- 2019
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Ingår i: Bulletin of emergency and trauma. - : Shiraz University of Medical Sciences. - 2322-2522 .- 2322-3960. ; 7:3, s. 223-231
-
Tidskriftsartikel (refereegranskat)abstract
- Objective: To evaluate the Portsmouth-Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (P-POSSUM) in comparison with other risk factors for mortality including osteopenia as an indicator for frailty in geriatric patients subjected to emergency laparotomy.Methods: All geriatric patients (≥65 years) undergoing emergency laparotomy at a single university hospital between 1/2015 and 12/2016 were included in this cohort study. Demographics and outcomes were retrospectively collected from medical records. Association between prognostic markers and 30-day mortality was assessed using Poisson and backward stepwise regression models. Prognostic value was assessed using receiver operating characteristic (ROC) curves.Results: =0.004) while osteopenia was not. P-POSSUM had poor prognostic value for 30-day mortality with an area under the ROC curve (AUC) of 0.59. The prognostic value of P-POSSUM improved significantly when adjusting for patient covariates (AUC=0.83).Conclusion: P-POSSUM and osteopenia alone hardly predict 30-day mortality in geriatric patients following emergency laparotomy. P-POSSUM adjusted for other patient covariates improves the prediction.
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| 31. |
- Banuazizi, Seyed Amir Hossein, et al.
(författare)
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Control of thermal budget in nanocontact spin-torque nano-oscillators
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We investigate the influence of the bottom Cu electrode thickness (tCu) in nanocontact spin-torque nano-oscillators (NC-STNOs) based on Si/SiO2/Pd(8)/Cu(tCu)/Co(8)/Cu(7)/NiFe(4.5)/Cu(3)/Pd(3) GMR stacks on the thermal budget of the magnetodynamically active region. Increasing tCu from 10 to 70 nm results in a ~50% reduction in Joule heating in both the Co and NiFe layers, which directly improves the microwave output stability and linewidth. Numerical simulations of the NC-STNO current distribution suggest that this improvement originates from a strongly reduced lateral current spread in the top ferromagnetic layer and a reduction in the device's resistance.
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| 32. |
- Bukur, M., et al.
(författare)
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Efficacy of beta-blockade after isolated blunt head injury : Does race matter? (vol 72, pg 1013, 2012)
- 2012
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Ingår i: Journal of Trauma and Acute Care Surgery. - : Lippincott Williams & Wilkins. - 2163-0755 .- 2163-0763. ; 72:6, s. 1725-1725
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Several retrospective clinical studies and recent prospective animal models demonstrate improved outcomes with beta-blocker administration after isolated blunt head injury. However, no investigations to date have examined the influence of race on the potential therapeutic effectiveness of these medications. Our hypothesis was that mortality benefits associated with beta-blocker exposure after isolated blunt head injury varies based on ethnicity.METHODS: The trauma registry and the surgical intensive care unit (ICU) databases of an academic Level I trauma center were used to identify all patients sustaining blunt head injury requiring ICU admission from July 1998 to December 2009. Patients sustaining major associated extracranial injuries (Abbreviated Injury Scale [AIS] score ≥3 in any body region) were excluded. Patient demographics, injury profile, Injury Severity Score, and beta-blocker exposure were abstracted. The primary outcome evaluated was in-hospital mortality stratified by ethnicity.RESULTS: During the 11-year study period, 3,750 patients were admitted to the Los Angeles County + University of Southern California Medical Center trauma ICU because of blunt trauma. Of these, 65% (n = 2,446) had an “isolated” head injury. When stratified by race, most patients were Hispanics (60%), followed by Whites (21%), Asians (11%), and African Americans (8%). After adjusting for confounding variables with multivariate regression, only those of Asian and Hispanic descent demonstrated significantly improved outcomes associated with beta-blocker administration.CONCLUSIONS: Our results indicate that beta-blockade after traumatic brain injury may not benefit all races equally. Further prospective research is necessary to assess this discrepancy in treatment benefit and explore other possible therapeutic interventions.LEVEL OF EVIDENCE: III, therapeutic study; II, prognostic study.
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| 33. |
- Chung, Sunjae, et al.
(författare)
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Magnetic droplet solitons in orthogonal spin valves
- 2015
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Ingår i: Fizika Nizkih Temperatur. - : American Institute of Physics (AIP). - 0132-6414 .- 1816-0328. ; 41:10, s. 833-837
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Tidskriftsartikel (refereegranskat)abstract
- We review the recent experimental advancements in the realization and understanding of magnetic droplet solitons generated by spin transfer torque in orthogonal nanocontact based spin torque nanooscillators (STNOs) fabricated on extended spin valves and spin valve nanowires. The magnetic droplets are detected and studied using the STNO microwave signal and its resistance, the latter both quasistatically and time-resolved. The droplet nucleation current is found to have a minimum at intermediate magnetic field strengths and the nature of the nucleation changes gradually from a single sharp step well above this field, mode-hopping around the minimum, and continuous at low fields. The mode-hopping and continuous transitions are ascribed to droplet drift instability and re-nucleation at different time scales, which is corroborated by time-resolved measurements. We argue that the use of tilted anisotropy fixed layers could reduce the nucleation current further, move the nucleation current minimum to lower fields, and potentially remove the need for an applied magnetic field altogether. Finally, evidence of an edge mode droplet in a nanowire is presented.
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| 34. |
- Chung, Sunjae, et al.
(författare)
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Spin transfer torque generated magnetic droplet solitons (invited)
- 2014
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 115:17
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Tidskriftsartikel (refereegranskat)abstract
- We present recent experimental and numerical advancements in the understanding of spin transfer torque generated magnetic droplet solitons. The experimental work focuses on nano-contact spin torque oscillators (NC-STOs) based on orthogonal (pseudo) spin valves where the Co fixed layer has an easy-plane anisotropy, and the [Co/Ni] free layer has a strong perpendicular magnetic anisotropy. The NC-STO resistance and microwave signal generation are measured simultaneously as a function of drive current and applied perpendicular magnetic field. Both exhibit dramatic transitions at a certain current dependent critical field value, where the microwave frequency drops 10 GHz, modulation sidebands appear, and the resistance exhibits a jump, while the magnetoresistance changes sign. We interpret these observations as the nucleation of a magnetic droplet soliton with a large fraction of its magnetization processing with an angle greater than 90 degrees, i.e., around a direction opposite that of the applied field. This interpretation is corroborated by numerical simulations. When the field is further increased, we find that the droplet eventually collapses under the pressure from the Zeeman energy. (C) 2014 AIP Publishing LLC.
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| 35. |
- Dhanasekara, Chathurika S., et al.
(författare)
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A comparison of outcomes including bile duct injury of subtotal cholecystectomy versus open total cholecystectomy as bailout procedures for severe cholecystitis : A multicenter real-world study
- 2024
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Ingår i: Surgery. - : Elsevier. - 0039-6060 .- 1532-7361.
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Dense inflammation obscuring the hepatocystic anatomy can hinder the ability to perform a safe standard laparoscopic cholecystectomy in severe cholecystitis, requiring use of a bailout procedure. We compared clinical outcomes of laparoscopic and open subtotal cholecystectomy against the traditional standard of open total cholecystectomy to identify the optimal bailout strategy for the difficult gallbladder.METHODS: A multicenter, multinational retrospective cohort study of patients who underwent bailout procedures for severe cholecystitis. Procedures were compared using one-way analysis of variance/Kruskal-Wallis tests and χ2 tests with multiple pairwise comparisons, maintaining a family-wise error rate at 0.05. Multiple multivariate linear/logistical regression models were created.RESULTS: In 11 centers, 727 bailout procedures were conducted: 317 laparoscopic subtotal cholecystectomies, 172 open subtotal cholecystectomies, and 238 open cholecystectomies. Baseline characteristics were similar among subgroups. Bile leak was common in laparoscopic and open fenestrating subtotal cholecystectomies, with increased intraoperative drain placements and postoperative endoscopic retrograde cholangiopancreatography(P < .05). In contrast, intraoperative bleeding (odds ratio = 3.71 [1.9, 7.22]), surgical site infection (odds ratio = 2.41 [1.09, 5.3]), intensive care unit admission (odds ratio = 2.65 [1.51, 4.63]), and length of stay (Δ = 2 days, P < .001) were higher in open procedures. Reoperation rates were higher for open reconstituting subtotal cholecystectomies (odds ratio = 3.43 [1.03, 11.44]) than other subtypes. The overall rate of bile duct injury was 1.1% and was not statistically different between groups. Laparoscopic subtotal cholecystectomy had a bile duct injury rate of 0.63%.CONCLUSION: Laparoscopic subtotal cholecystectomy is a feasible surgical bailout procedure in cases of severe cholecystitis where standard laparoscopic cholecystectomy may carry undue risk of bile duct injury. Open cholecystectomy remains a reasonable option.
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| 36. |
- Dumas, Randy K., et al.
(författare)
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Recent Advances in Nanocontact Spin-Torque Oscillators
- 2014
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Ingår i: Ieee Transactions on Magnetics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9464 .- 1941-0069. ; 50:6
-
Tidskriftsartikel (refereegranskat)abstract
- We present a comprehensive review of the most recent advances in nanocontact spin torque oscillators (NC-STOs). NC-STOs are highly tunable, with both applied magnetic field and dc, broadband microwave signal generators. As opposed to the nanopillar geometry, where the lateral cross section of the entire device has been confined to a typically <100 nm diameter, in NC-STOs, it is only the current injection site that has been laterally confined on top of an extended magnetic film stack. Three distinct material combinations will be discussed: 1) a Co/Cu/NiFe pseudospin valve (PSV) where both the Co and NiFe have a dominant in-plane anisotropy; 2) a Co/Cu/[Co/Ni](4) orthogonal PSV where the Co/Ni multilayer has a strong perpendicular anisotropy; and 3) a single NiFe layer with asymmetric non-magnetic Cu leads. We explore the rich and diverse magnetodynamic modes that can be generated in these three distinct sample geometries.
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| 37. |
- Dürrenfeld, Philipp, et al.
(författare)
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Low-current, narrow-linewidth microwave signal generation in NiMnSb based single-layer nanocontact spin-torque oscillators
- 2016
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 109:22
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Tidskriftsartikel (refereegranskat)abstract
- We report on the fabrication of nano-contact spin-torque oscillators based on single layers of the epitaxially grown half-metal NiMnSb with ultralow spin wave damping. We demonstrate magnetization auto-oscillations at microwave frequencies in the 1-3 GHz range in out-of-plane magnetic fields. Threshold current densities as low as 3 x 10(11) A m(-2) are observed as well as minimum oscillation linewidths of 200 kHz, both of which are much lower than the values achieved in conventional metallic spin-valve-based devices of comparable dimensions. These results enable the fabrication of spin transfer torque driven magnonic devices with low current density requirements, improved signal linewidths, and in a simplified single-layer geometry. Published by AIP Publishing.
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| 38. |
- Escobar, Roberto A., et al.
(författare)
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Monte Carlo Modeling of Mixed-Anisotropy [Co/Ni](2)/NiFe Multilayers
- 2016
-
Ingår i: IEEE Magnetics Letters. - : IEEE. - 1949-307X .- 1949-3088. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- The magnetic properties of a thin film consisting of an exchange-coupled [Co/Ni](2)/NiFe multilayer have been studied as a function of the NiFe thickness by using Monte Carlo modeling and compared with experimental results of [Co/Ni](4)/Co/NiFe multilayers. Both modeling and experiment showed that the NiFe thickness controls the effective anisotropy. The direction of the easy axis is determined by a competition between the perpendicular crystalline anisotropy of the Co/Ni and the shape anisotropy of the multilayer. As the thickness of the NiFe layer increases, the reversal mechanism of the thin film changes from the nucleation of reverse domains to vortex propagation. Therefore, our results reveal the magnetic configurations and the easy axis reorientation of mixed-anisotropy multilayers.
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| 39. |
- Fazlali, Masoumeh, et al.
(författare)
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Tuning exchange-dominated spin-waves using lateral current spread in nanocontact spin-torque nano-oscillators
- 2019
-
Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 492
-
Tidskriftsartikel (refereegranskat)abstract
- We present an efficient method to tailor propagating spin waves in quasi-confined systems. We use nanocontact spin-torque nano-oscillators based on NiFe/Cu/Co spin-valves and study the ferromagnetic and spin-wave resonances (FMR and SWR) of both layers. We employ homodyne-detected ferromagnetic resonance spectroscopy, resembling spin-torque FMR, to detect the magnetodynamics. The external field is applied in-plane, giving a parallel configuration of the magnetic layers, which do not provide any spin-transfer torque. Instead, the excitation is caused by the Oersted field. By varying the thickness of the bottom Cu electrode (t(Cu)) of the devices, we tune the current distribution in the samples, and thereby the Oersted field, which governs the spin wave characteristics. Both the average k-vector and the bandwidth of the SWR increases as t(Cu) increases.
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| 40. |
- Ghomi, Erfan Rezvani, et al.
(författare)
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A collection of the novel coronavirus (COVID-19) detection assays, issues, and challenges
- 2021
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Ingår i: Heliyon. - : Elsevier BV. - 2405-8440. ; 7:6
-
Forskningsöversikt (refereegranskat)abstract
- The global pandemic of COVID-19 has rapidly increased the number of infected cases as well as asymptomatic individuals in many, if not all the societies around the world. This issue increases the demand for accurate and rapid detection of SARS-CoV-2. While accurate and rapid detection is critical for diagnosing SARS-CoV-2, the appropriate course of treatment must be chosen to help patients and prevent its further spread. Testing platform accuracy with high sensitivity and specificity for SARS-CoV-2 is equally important for clinical, regional, and global arenas to mitigate secondary transmission rounds. The objective of this article is to compare the current detection technology and introduce the most accurate and rapid ones that are suitable for pandemic circumstances. Hence, the importance of rapid detection in societies is discussed initially. Following this, the current technology for rapid detection of SARS-CoV-2 is explained and classified into three different categories: nucleic acid-based, protein-based, and point of care (PoC) detection testing. Then, the current issues for diagnostic procedures in laboratories are discussed. Finally, the role of new technologies in countering COVID-19 is also introduced to assist researchers in the development of accurate and timely detection of coronaviruses. As coronavirus continues to affect human lives in a detrimental manner, the development of rapid and accurate virus detection methods could promote COVID-19 diagnosis accessible to both individuals and the mass population at patient care. In this regard, rRT-PCR and multiplex RT-PCR detection techniques hold promise.
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| 41. |
- Goncalves, Nadia P., et al.
(författare)
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Peripheral Nerve Regeneration Is Independent From Schwann Cell p75(NTR) Expression
- 2019
-
Ingår i: Frontiers in Cellular Neuroscience. - : FRONTIERS MEDIA SA. - 1662-5102. ; 13
-
Tidskriftsartikel (refereegranskat)abstract
- Schwann cell reprogramming and differentiation are crucial prerequisites for neuronal regeneration and re-myelination to occur following injury to peripheral nerves. The neurotrophin receptor p75(NTR) has been identified as a positive modulator for Schwann cell myelination during development and implicated in promoting nerve regeneration after injury. However, most studies base this conclusion on results obtained from complete p75(NTR) knockout mouse models and cannot dissect the specific role of p75(NTR) expressed by Schwann cells. In this present study, a conditional knockout model selectively deleting p75(NTR) expression in Schwann cells was generated, where p75(NTR) expression is replaced with that of an mCherry reporter. Silencing of Schwann cell p75(NTR) expression was confirmed in the sciatic nerve in vivo and in vitro, without altering axonal expression of p75(NTR). No difference in sciatic nerve myelination during development or following sciatic nerve crush injury was observed, as determined by quantification of both myelinated and unmyelinated nerve fiber densities, myelinated axonal diameter and myelin thickness. However, the absence of Schwann cell p75(NTR) reduced motor nerve conduction velocity after crush injury. Our data indicate that the absence of Schwann cell p75(NTR) expression in vivo is not critical for axonal regrowth or remyelination following sciatic nerve crush injury, but does play a key role in functional recovery. Overall, this represents the first step in redefining the role of p75(NTR) in the peripheral nervous system, suggesting that the Schwann cell-axon unit functions as a syncytium, with the previous published involvement of p75(NTR) in remyelination most likely depending on axonal/neuronal p75(NTR) and/or mutual glial-axonal interactions.
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| 42. |
- Iacocca, Ezio, 1986, et al.
(författare)
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Confined Dissipative Droplet Solitons in Spin-Valve Nanowires with Perpendicular Magnetic Anisotropy
- 2014
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 112:4
-
Tidskriftsartikel (refereegranskat)abstract
- Magnetic dissipative droplets are localized, strongly nonlinear dynamical modes excited in nanocontact spin valves with perpendicular magnetic anisotropy. These modes find potential application in nanoscale structures for magnetic storage and computation, but dissipative droplet studies have so far been limited to extended thin films. Here, numerical and asymptotic analyses are used to demonstrate the existence and properties of novel solitons in confined structures. As a nanowire's width is decreased with a nanocontact of fixed size at its center, the observed modes undergo transitions from a fully localized two-dimensional droplet into a two-dimensional droplet edge mode and then a pulsating one-dimensional droplet. These solitons are interpreted as dissipative versions of classical, conservative solitons, allowing for an analytical description of the modes and the mechanisms of bifurcation. The presented results open up new possibilities for the study of low-dimensional solitons and droplet applications in nanostructures.
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| 43. |
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| 44. |
- Keatley, P. S., et al.
(författare)
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Direct observation of magnetization dynamics generated by nanocontact spin-torque vortex oscillators
- 2016
-
Ingår i: Physical Review B - Condensed Matter and Materials Physics. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 94:6
-
Tidskriftsartikel (refereegranskat)abstract
- Time-resolved scanning Kerr microscopy has been used to directly image the magnetization dynamics of nanocontact (NC) spin-torque vortex oscillators (STVOs) when phase locked to an injected microwave (rf) current. The Kerr images reveal free-layer magnetization dynamics that extend outside the NC footprint, where they cannot be detected electrically, but which are crucial to phase-lock STVOs that share common magnetic layers. For a single NC, dynamics were observed not only when the STVO frequency was fully locked to that of the rf current, but also for a partially locked state characterized by periodic changes in the core trajectory at the rf frequency. For a pair of NCs, we explore the correlation between the spatial character of injection-locked dynamics and the free-running spectra. Insight gained from these images may improve understanding of the conditions required for mutual phase locking of multiple STVOs, and hence enhanced microwave power emission.
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| 45. |
- Keatley, P. S., et al.
(författare)
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Imaging magnetisation dynamics in nano-contact spin-torque vortex oscillators exhibiting gyrotropic mode splitting
- 2017
-
Ingår i: Journal of Physics D-Applied Physics. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 50:16
-
Tidskriftsartikel (refereegranskat)abstract
- Nano-contact spin-torque vortex oscillators (STVOs) are anticipated to find application as nanoscale sources of microwave emission in future technological applications. Presently the output power and phase stability of individual STVOs are not competitive with existing oscillator technologies. Synchronisation of multiple nano-contact STVOs via magnetisation dynamics has been proposed to enhance the microwave emission. The control of device-to-device variations, such as mode splitting of the microwave emission, is essential if multiple STVOs are to be successfully synchronised. In this work a combination of electrical measurements and time-resolved scanning Kerr microscopy (TRSKM) was used to demonstrate how mode splitting in the microwave emission of STVOs was related to the magnetisation dynamics that are generated. The free-running STVO response to a DC current only was used to identify devices and bias magnetic field configurations for which single and multiple modes of microwave emission were observed. Stroboscopic Kerr images were acquired by injecting a small amplitude RF current to phase lock the free-running STVO response. The images showed that the magnetisation dynamics of a multimode device with moderate splitting could be controlled by the injected RF current so that they exhibit similar spatial character to that of a single mode. Significant splitting was found to result from a complicated equilibrium magnetic state that was observed in Kerr images as irregular spatial characteristics of the magnetisation dynamics. Such dynamics were observed far from the nano-contact and so their presence cannot be detected in electrical measurements. This work demonstrates that TRSKM is a powerful tool for the direct observation of the magnetisation dynamics generated by STVOs that exhibit complicated microwave emission. Characterisation of such dynamics outside the nano-contact perimeter permits a deeper insight into the requirements for optimal phase-locking of multiple STVOs that share common magnetic layers.
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| 46. |
- Keatley, P. S., et al.
(författare)
-
Superharmonic injection locking of nanocontact spin-torque vortex oscillators
- 2016
-
Ingår i: Physical Review B. - : american physical society. - 2469-9950 .- 2469-9969. ; 94:9
-
Tidskriftsartikel (refereegranskat)abstract
- Superharmonic injection locking of single nanocontact (NC) spin-torque vortex oscillators (STVOs) subject to a small microwave current has been explored. Frequency locking was observed up to the fourth harmonic of the STVO fundamental frequency f(0) in microwave magnetoelectronic measurements. The large frequency tunability of the STVO with respect to f(0) allowed the device to be locked to multiple subharmonics of the microwave frequency f(RF), or to the same subharmonic over a wide range of fRF by tuning the dc current. In general, analysis of the locking range, linewidth, and amplitude showed that the locking efficiency decreased as the harmonic number increased, as expected for harmonic synchronization of a nonlinear oscillator. Time-resolved scanning Kerr microscopy (TRSKM) revealed significant differences in the spatial character of the magnetization dynamics of states locked to the fundamental and harmonic frequencies, suggesting significant differences in the vortex core trajectories within the same device. Superharmonic injection locking of a NC-STVO may open up possibilities for devices such as nanoscale frequency dividers, while differences in the core trajectory may allow mutual synchronization to be achieved in multioscillator networks by tuning the spatial character of the dynamics within shared magnetic layers.
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| 47. |
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| 48. |
- Larsson, M., et al.
(författare)
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Energy system analysis of the implications of hydrogen fuel cell vehicles in the Swedish road transport system
- 2014
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Ingår i: 20th World Hydrogen Energy Conference, WHEC 2014. - 9780000000002 ; , s. 2084-2091
-
Konferensbidrag (refereegranskat)abstract
- The focus on pathways to reduce the use of fossil fuels in the transport sector is intense in many countries worldwide. Considering that biofuels have a limited technical production potential and that battery electric vehicles suffer from technical limitations that put constraints on their general use in the transport sector, hydrogen-fuelled fuel cell vehicles may become a feasible alternative. Introduction of hydrogen in the transport sector will also transform the energy sector and create new interactions. The aim of this paper is to analyse the consequences and feasibility of such an integration in Sweden. Different pathways for hydrogen, electricity and methane to the transport sector are compared with regard to system energy efficiency. The efficiencies for hydrogen and electricity are used for estimating the energy resources needed for hydrogen production and electric vehicles for a future Swedish transport sector based on renewable fuels. The analysis reveal that the well to wheel system efficiencies for hydrogen fuel cell vehicles are comparable to those of methane gas vehicles, even when methane gas is the primary energy source. The results further indicate that an increased hydrogen demand may have a less than expected impact on the primary energy supply in Sweden.
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| 49. |
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| 50. |
- Mohseni, Fatemeh, 1984-, et al.
(författare)
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Distributed model predictive coverage control for decoupled mobile robots
- 2015
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Ingår i: Robotica (Cambridge. Print). - : Cambridge University Press. - 0263-5747 .- 1469-8668. ; 35:4, s. 922-941
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A distributed coverage control scheme based on the state space model predictive control, which is known as receding horizon control (RHC) for decoupled systems, is presented. An optimal control problem is formulated for a set of decoupled robotic systems where a cost function couples the dynamical behavior of the robots. The coupling is described through a connected graph using a Voronoi diagram, where each robot is a node and the cost and constraints of the optimization problem associated with each robot are a function of its state and of the states of its neighbors. The complexity of the problem is addressed by breaking a centralized receding horizon controller into distinct RHC controllers of smaller sizes. Each RHC controller is associated with a different node and it computes the local control inputs based only on the position of the robot and that of its neighbors. The stability of the distributed scheme is analyzed and its properties compared with the linear quadratic regulator (LQR) design which has been proposed in the literature. Moreover, the proposed coverage algorithm is also applied to deploy a group of mobile robots in a desired formation pattern. The simulation results are used to illustrate the good performance of the proposed coverage control scheme.
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