| 1. |
- Aad, G, et al.
(författare)
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- 2015
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swepub:Mat__t
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| 2. |
- Ademuyiwa, Adesoji O., et al.
(författare)
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Determinants of morbidity and mortality following emergency abdominal surgery in children in low-income and middle-income countries
- 2016
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Ingår i: BMJ Global Health. - : BMJ Publishing Group Ltd. - 2059-7908. ; 1:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Child health is a key priority on the global health agenda, yet the provision of essential and emergency surgery in children is patchy in resource-poor regions. This study was aimed to determine the mortality risk for emergency abdominal paediatric surgery in low-income countries globally.Methods: Multicentre, international, prospective, cohort study. Self-selected surgical units performing emergency abdominal surgery submitted prespecified data for consecutive children aged <16 years during a 2-week period between July and December 2014. The United Nation's Human Development Index (HDI) was used to stratify countries. The main outcome measure was 30-day postoperative mortality, analysed by multilevel logistic regression.Results: This study included 1409 patients from 253 centres in 43 countries; 282 children were under 2 years of age. Among them, 265 (18.8%) were from low-HDI, 450 (31.9%) from middle-HDI and 694 (49.3%) from high-HDI countries. The most common operations performed were appendectomy, small bowel resection, pyloromyotomy and correction of intussusception. After adjustment for patient and hospital risk factors, child mortality at 30 days was significantly higher in low-HDI (adjusted OR 7.14 (95% CI 2.52 to 20.23), p<0.001) and middle-HDI (4.42 (1.44 to 13.56), p=0.009) countries compared with high-HDI countries, translating to 40 excess deaths per 1000 procedures performed.Conclusions: Adjusted mortality in children following emergency abdominal surgery may be as high as 7 times greater in low-HDI and middle-HDI countries compared with high-HDI countries. Effective provision of emergency essential surgery should be a key priority for global child health agendas.
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| 3. |
- Grazian, A., et al.
(författare)
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Lyman continuum escape fraction of faint galaxies at z similar to 3.3 in the CANDELS/GOODS-North, EGS, and COSMOS fields with LBC
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 602
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Tidskriftsartikel (refereegranskat)abstract
- Context. The reionization of the Universe is one of the most important topics of present-day astrophysical research. The most plausible candidates for the reionization process are star-forming galaxies, which according to the predictions of the majority of the theoretical and semi-analytical models should dominate the H I ionizing background at z greater than or similar to 3. Aims. We measure the Lyman continuum escape fraction, which is one of the key parameters used to compute the contribution of star-forming galaxies to the UV background. It provides the ratio between the photons produced at lambda <= 912 angstrom rest-frame and those that are able to reach the inter-galactic medium, i.e. that are not absorbed by the neutral hydrogen or by the dust of the galaxy's inter-stellar medium. Methods. We used ultra-deep U-band imaging (U = 30.2 mag at 1 sigma) from Large Binocular Camera at the Large Binocular Telescope (LBC/LBT) in the CANDELS/GOODS-North field and deep imaging in the COSMOS and EGS fields in order to estimate the Lyman continuum escape fraction of 69 star-forming galaxies with secure spectroscopic redshifts at 3.27 <= z <= 3.40 to faint magnitude limits (L = 0.2L*, or equivalently M-1500 similar to -19). The narrow redshift range implies that the LBC U-band filter exclusively samples the lambda <= 912 angstrom rest-frame wavelengths. Results. We measured through stacks a stringent upper limit (<1.7% at 1 sigma) for the relative escape fraction of H I ionizing photons from bright galaxies (L > L*), while for the faint population (L = 0.2L*) the limit to the escape fraction is less than or similar to 10%. We computed the contribution of star-forming galaxies to the observed UV background at z similar to 3 and find that it is not sufficient to keep the Universe ionized at these redshifts unless their escape fraction increases significantly (>= 10%) at low luminosities (M-1500 >= -19). Conclusions. We compare our results on the Lyman continuum escape fraction of high-z galaxies with recent estimates in the literature, and discuss future prospects to shed light on the end of the Dark Ages. In the future, strong gravitational lensing will be fundamental in order to measure the Lyman continuum escape fraction down to faint magnitudes (M-1500 similar to -16) that are inaccessible with the present instrumentation on blank fields. These results will be important in order to quantify the role of faint galaxies to the reionization budget.
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| 4. |
- Carozzi, F. M., et al.
(författare)
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Effectiveness of HPV vaccination in women reaching screening age in Italy
- 2016
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Ingår i: Journal of Clinical Virology. - : Elsevier BV. - 1386-6532. ; 84, s. 74-81
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Tidskriftsartikel (refereegranskat)abstract
- Background and objectives A randomized trial was conducted in Tuscany, Italy, to evaluate the effectiveness of HPV vaccination for 25 year old (yo) women who attend at the first time cervical cancer screening. The trial also evaluated immune response after vaccination, reductions of cytological abnormalities and the impact of vaccination on screening activity. Study design During 2010–2011, all 25 yo women who were invited to the Florence cervical cancer screening programme were also asked to participate in the trial. Enrolled women were randomized into study and control groups. Those in the study group were offered HPV vaccination after the usual Pap test. The cytology distribution and prevalence for any high risk (hr) HPV type were compared at the subsequent screening round in an intention-to-treat analysis. The impact of HPV vaccination was evaluated per protocol comparing vaccinated women with the control group. Results Our results showed a reduction in HPV prevalence at recall for any hr-HPV type but it was not statistically significant, being 17.1% vs 21.4%, p = 0.20 in the study and control groups, respectively. If we restricted the analysis to vaccinated women, strong reductions of the HPV 16,18,31,33,45 and HPV 31,33,45 infections were observed, being 5.3% vs 12.8%, p < 0.01 and 2.1% vs 6.5%, p = 0.02, respectively. Significant reductions for any hr-HPV infection and for HPV 16 infection were also observed in women HPV 16/18 negative at enrolment, being 12% vs 21.4%, p < 0.01 and 0.6% vs 6.7%, p-value < 0.01, respectively. In women hr-HPV negative at enrolment no infections due to HPV 16 or HPV 18 were observed and there was a big reduction for any hr-HPV infection (7.1% vs 21.4% p < 0.01). A strong antibody response was observed not only for HPV 16 & 18 but also for their related types. Conclusions Our findings suggest that HPV vaccination at the age 25 is beneficial if it is offered to hr-HPV negative women. Our data will assist in developing a cost effectiveness model for choosing the best strategy to integrate screening and vaccination for the coming years. Clinical trial registration number is NCT02296255.
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| 5. |
- Araujo de Pina Cabral, DB, et al.
(författare)
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Prospective evaluation of glutamine and phospholipids levels in first degree relatives of patients with Type 1 Diabetes from a multiethnic population
- 2015
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Ingår i: Diabetology and Metabolic Syndrome. - : BioMed Central (BMC). - 1758-5996 .- 1758-5996. ; 7:52
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: A dysregulation in the metabolism of lipids may be an early marker of autoimmunity in Type 1 Diabetes (T1D). It would be of general importance to identify metabolic patterns that would predict the risk for T1D later in life. The aim of this study was to perform a prospective evaluation of glutamine and phospholipids levels in Brazilian first degree relatives (FDR) of patients with T1D in a mean interval of 5 years.FINDINGS: Brazilian FDR (n = 30) of patients with T1D were evaluated and blood was sampled to measure the levels of glutamine and phospholipids in the fasting serum by quantitative colorimetric method. The tests were repeated after a mean interval of 5 years and compared to a control group (n = 20). The FDR presented lower levels of phospholipids than controls (p = 0.028), but not of glutamine (p = 0.075). Phospholipids levels decreased over time (p = 0.028) in FDR and were associated with Glutamic acid decarboxylase autoantibody (GADA) titers (p = 0.045), autoantibody positivity (p = 0.008) and PTPN22 polymorphisms (p = 0.014).CONCLUSIONS: In this Brazilian multiethnic population, there was a significant decrease in phospholipids levels in FDR in patients with T1D during a 5-year prospective follow-up, as well as a significant association between these metabolite, GADA and PTPN22 polymorphisms. For Glutamine no difference was found. These findings suggest that a dysregulation in the metabolism of lipids may precede the onset of the autoimmunity in T1D.
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| 6. |
- 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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| 7. |
- 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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| 8. |
- Kanatsuna, N, et al.
(författare)
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Doubly reactive INS-IGF2 autoantibodies in children with newly diagnosed autoimmune (type 1) diabetes
- 2015
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Ingår i: Scandinavian Journal of Immunology. - : Wiley-Blackwell. - 0300-9475 .- 1365-3083. ; 82:4, s. 361-369
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Tidskriftsartikel (refereegranskat)abstract
- The splice variant INS-IGF2 entails the preproinsulin signal peptide, the insulin B-chain, eight amino acids of the C-peptide and 138 unique amino acids from an ORF in the IGF2 gene. The aim of this study was to determine whether levels of specific INS-IGF2 autoantibodies (INS-IGF2A) were related to age at diagnosis, islet autoantibodies, HLA-DQ or both, in patients and controls with newly diagnosed type 1 diabetes. Patients (n = 676), 0-18 years of age, diagnosed with type 1 diabetes in 1996-2005 and controls (n = 363) were analysed for specific INS-IGF2A after displacement with both cold insulin and INS-IGF2 to correct for non-specific binding and identify double reactive sera. GADA, IA-2A, IAA, ICA, ZnT8RA, ZnT8WA, ZnT8QA and HLA-DQ genotypes were also determined. The median level of specific INS-IGF2A was higher in patients than in controls (P < 0.001). Irrespective of age at diagnosis, 19% (126/676) of the patients had INS-IGF2A when the cut-off was the 95th percentile of the controls (P < 0.001). The risk of INS-IGF2A was increased among HLA-DQ2/8 (OR = 1.509; 95th CI 1.011, 2.252; P = 0.045) but not in 2/2, 2/X, 8/8, 8/X or X/X (X is neither 2 nor 8) patients. The association with HLA-DQ2/8 suggests that this autoantigen may be presented on HLA-DQ trans-heterodimers, rather than cis-heterodimers. Autoantibodies reactive with both insulin and INS-IGF2A at diagnosis support the notion that INS-IGF2 autoimmunity contributes to type 1 diabetes.
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| 9. |
- 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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| 10. |
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| 11. |
- Chilkoor, Govinda, et al.
(författare)
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Hexagonal Boron Nitride : The Thinnest Insulating Barrier to Microbial Corrosion
- 2018
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 12:3, s. 2242-2252
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Tidskriftsartikel (refereegranskat)abstract
- We report the use of a single layer of two-dimensional hexagonal boron nitride (SL-hBN) as the thinnest insulating barrier to microbial corrosion induced by the sulfate-reducing bacteria Desulfovibrio alaskensis G20. We used electrochemical methods to assess the corrosion resistance of SL-hBN on copper against the effects of both the planktonic and sessile forms of the sulfate-reducing bacteria. Cyclic voltammetry results show that SL-hBN-Cu is effective in suppressing corrosion effects of the planktonic cells at potentials as high as 0.2 V (vs Ag/AgCl). The peak anodic current for the SL-hBN coatings is ∼36 times lower than that of bare Cu. Linear polarization resistance tests confirm that the SL-hBN coatings serve as a barrier against corrosive effects of the G20 biofilm when compared to bare Cu. The SL-hBN serves as an impermeable barrier to aggressive metabolites and offers ∼91% corrosion inhibition efficiency, which is comparable to much thicker commercial coatings such as polyaniline. In addition to impermeability, the insulating nature of SL-hBN suppresses galvanic effects and improves its ability to combat microbial corrosion.
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| 12. |
- 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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| 13. |
- 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
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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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| 14. |
- 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
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 492
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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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| 15. |
- Keatley, P. S., et al.
(författare)
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Direct observation of magnetization dynamics generated by nanocontact spin-torque vortex oscillators
- 2016
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 94:6
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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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| 16. |
- 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
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Ingår i: Journal of Physics D-Applied Physics. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 50:16
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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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| 17. |
- Keatley, P. S., et al.
(författare)
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Superharmonic injection locking of nanocontact spin-torque vortex oscillators
- 2016
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Ingår i: Physical Review B. - : american physical society. - 2469-9950 .- 2469-9969. ; 94:9
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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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| 18. |
- Madami, M., et al.
(författare)
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Propagating spin waves excited by spin-transfer torque: A combined electrical and optical study
- 2015
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 2469-9950 .- 2469-9969 .- 1550-235X. ; 92:2
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Tidskriftsartikel (refereegranskat)abstract
- Nanocontact spin-torque oscillators are devices in which the generation of propagating spin waves can be sustained by spin transfer torque. In the present paper, we perform combined electrical and optical measurements in a single experimental setup to systematically investigate the excitation of spin waves by a nanocontact spin-torque oscillator and their propagation in a Ni80Fe20 extended layer. By using microfocused Brillouin light scattering we observe an anisotropic emission of spin waves, due to the broken symmetry imposed by the inhomogeneous Oersted field generated by the injected current. In particular, spin waves propagate on the side of the nanocontact where the Oersted field and the in-plane component of the applied magnetic field are antiparallel, while propagation is inhibited on the opposite side. Moreover, propagating spin waves are efficiently excited only in a limited frequency range corresponding to wavevectors inversely proportional to the size of the nanocontact. This frequency range obeys the dispersion relation for exchange-dominated spin waves in the far field, as confirmed by micromagnetic simulations of similar devices. The present results have direct consequences for spin wave based applications, such as synchronization, computation, and magnonics.
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| 19. |
- 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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| 20. |
- Sani, Negar
(författare)
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Addressability and GHz Operation in Flexible Electronics
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The discovery of conductive polymers in 1977 opened up a whole new path for flexible electronics. Conducting polymers and organic semiconductors are carbon rich compounds that are able to conduct charges while flexed and are compatible with low-cost and large-scale processes including printing and coating techniques. The conducting polymer has aided the rapidly expanding field of flexible electronics, leading to many new applications such as electronic skin, RFID tags, smart labels, flexible displays, implantable medical devices, and flexible sensors.However, there are several remaining challenges in the production and implementation of flexible electronic materials and devices. The conductivity of organic conductors and semiconductors is still orders of magnitude lower compared to their inorganic counterparts. In addition, non-flexible inorganic semiconductors still remain the materials of choice for high frequency applications; since the charge carrier mobility and thus operational speed of the organic materials are limited. Therefore, there remains a high demand to combine the high frequency operation of inorganic semiconductors with the flexible fabrication methods of organic systems for future electronics.In addition to the challenges in the choice of materials in flexible electronics, the upscaling of the flexible devices and implementing them in circuits can also be complicated. Lack of non-linearity is an issue that arises when flexible devices with linear behavior need to be incorporated in an array or matrix form. Non-linearity is important for applications such as displays and memory arrays, where the devices are arranged as matrix cells addressed by their row and column number. If the behavior of cells in the matrix is linear, addressing each cell affects the adjacent cells. Therefore, inducing non-linearity and, consequently, addressability in such linear devices is the first step before scaling up into matrix schemes.In this work, non-linear organic/inorganic hybrid devices are produced to overcome the limitations mentioned above and leverage the advantages of both organic and inorganic materials. Two novel methods are developed to incorporate non-flexible inorganic semiconductors into ultra-high frequency (UHF) flexible devices. In the first method, Si is ground into a powder with micrometer-sized particles and printed through standard screen printing. For the first time, allprinted flexible diodes operating in the GHz range are produced. The energy harvesting application of the printed diodes is demonstrated in a flexible circuit coupling an antenna and the display to the diode.A second and simpler room-temperature method based on lamination was later developed, which further improves device performance and operational frequency. For the first time, a flexible semiconducting composite film consisting of Si micro-particles, glycerol, and nano-fibrillated cellulose is produced and used as the semiconducting layer of the UHF diode.The diodes fabricated through both mentioned processes are demonstrated in energy harvesting applications in the GHz range; however, they can also serve as rectifiers or non-linear elements in any other flexible and UHF circuit.Furthermore, a new approach is developed to induce non-linearity and hence addressability in linear devices in order to make their implementation in flexible matrix form feasible. This is accomplished by depositing a ferroelectric layer on a device electrode and thus controlling charge transfer through the electrode. The electrode current becomes limited to the charge displacement current established in the ferroelectric layer during polarization. Thus, the current does not follow the voltage linearly and non-linearity is induced in the device. The polarization voltage is dictated by the thickness of the ferroelectric layer. Therefore, the switching voltage of the device can be tuned by adjusting the ferroelectric layer thickness. In this work, the organic ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) is used due to its distinctive properties such as stability, high polarizability and simple processability. The polarization of P(VDF-TrFE) through an electrolyte and an electrophoretic liquid is investigated. In addition, a simple model is presented in order to understand the field and potential distribution, and the ferroelectric polarization, in the P(VDF-TrFE)-electrolyte contact. The induction of non-linearity through P(VDF-TrFE) is successfully demonstrated in novel addressable and bistable devices and memory elements such as non-linear electrophoretic display cells, organic ferroelectrochromic displays (FeOECDs), and ferroelectrochemical organic transistors (FeOECTs).
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| 21. |
- Wakefield, J. R. H., et al.
(författare)
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Greater family identification—but not greater contact with family members—leads to better health : Evidence from a Spanish longitudinal study
- 2016
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Ingår i: European Journal of Social Psychology. - : John Wiley & Sons. - 0046-2772 .- 1099-0992. ; 46:4, s. 506-513
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the effect of family identification ( one's subjective sense of belonging to and commonality with the family) on self-reported ill-health in 206 Valencian undergraduates, with eight months between Time 1 ( T1) and Time 2 ( T2). While greater family identification T1 predicted lower ill-health T2, ill-health T1 did not predict family identification T2. Family contact T1 ( one's intensity of interaction with family) was unrelated to ill-health T2. This shows that family identification impacts positively on health over time ( rather than health impacting positively on family identification over time), and this is not reducible to effects exerted by family contact. These findings indicate that encouraging patients to engage in group activities might produce negligible health gains unless the patient identifies with the group in question.
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