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| 2. |
- Kim, Hyeong Seok, et al.
(författare)
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Development, validation, and comparison of a nomogram based on radiologic findings for predicting malignancy in intraductal papillary mucinous neoplasms of the pancreas : An international multicenter study
- 2021
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Ingår i: Journal of hepato-biliary-pancreatic sciences. - : Wiley-Blackwell. - 1868-6974 .- 1868-6982.
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Although we previously proposed a nomogram to predict malignancy in intraductal papillary mucinous neoplasms (IPMN) and validated it in an external cohort, its application is challenging without data on tumor markers. Moreover, existing nomograms have not been compared. This study aimed to develop a nomogram based on radiologic findings and to compare its performance with previously proposed American and Korean/Japanese nomograms.METHODS: We recruited 3708 patients who underwent surgical resection at 31 tertiary institutions in eight countries, and patients with main pancreatic duct >10 mm were excluded. To construct the nomogram, 2606 patients were randomly allocated 1:1 into training and internal validation sets, and area under the receiver operating characteristics curve (AUC) was calculated using 10-fold cross validation by exhaustive search. This nomogram was then validated and compared to the American and Korean/Japanese nomograms using 1102 patients.RESULTS: Among the 2606 patients, 90 had main-duct type, 900 had branch-duct type, and 1616 had mixed-type IPMN. Pathologic results revealed 1628 low-grade dysplasia, 476 high-grade dysplasia, and 502 invasive carcinoma. Location, cyst size, duct dilatation, and mural nodule were selected to construct the nomogram. AUC of this nomogram was higher than the American nomogram (0.691 vs 0.664, P = .014) and comparable with the Korean/Japanese nomogram (0.659 vs 0.653, P = .255).CONCLUSIONS: A novel nomogram based on radiologic findings of IPMN is competitive for predicting risk of malignancy. This nomogram would be clinically helpful in circumstances where tumor markers are not available. The nomogram is freely available at http://statgen.snu.ac.kr/software/nomogramIPMN.
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| 3. |
- Andersson, Mikael Svante, et al.
(författare)
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Ageing dynamics of a superspin glass
- 2014
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 108:1, s. 17004-
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Tidskriftsartikel (refereegranskat)abstract
- Magnetization dynamics of a model superspin glass system consisting of nearly monodispersed close-packed maghemite particles of diameter 8 nm is investigated. The observed non-equilibrium features of the dynamics are qualitatively similar to those of atomic spin glass systems. The intrinsic relaxation function, as observed in zero-field-cooled magnetization relaxation experiments, depends on the time the sample has been kept at constant temperature (ageing). Accompanying low-field experiments show that the archetypal spin glass characteristics -ageing, memory and rejuvenation- are reproduced in this dense system of dipolar-dipolar interacting superspins.
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| 4. |
- Andersson, Mikael Svante, et al.
(författare)
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Effects of the individual particle relaxation time on superspin glass dynamics
- 2016
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Ingår i: PHYSICAL REVIEW B. - 2469-9950. ; 93:5
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Tidskriftsartikel (refereegranskat)abstract
- The low temperature dynamic magnetic properties of two dense magnetic nanoparticle assemblies with similar superspin glass transition temperatures T-g similar to 140 K are compared. The two samples are made from batches of 6 and 8 nm monodisperse gamma-Fe2O3 nanoparticles, respectively. The properties of the individual particles are extracted from measurements on reference samples where the particles have been covered with a thick silica coating. The blocking temperatures of these dilute assemblies are found at 12.5 K for the 6 nm particles and at 35 K for the 8 nm particles, which implies different anisotropy energy barriers of the individual particles and vastly different temperature evolution of their relaxation times. The results of the measurements on the concentrated particle assemblies suggest a strong influence of the particle energy barrier on the details of the aging dynamics, memory behavior, and apparent superspin dimensionality of the particles.
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| 5. |
- Andersson, Mikael Svante, et al.
(författare)
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Magnetic properties of nanoparticle compacts with controlled broadening of the particle size distribution
- 2017
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Ingår i: Physical Review B. - 2469-9950 .- 2469-9969. ; 95:18
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Tidskriftsartikel (refereegranskat)abstract
- Binary random compacts with different proportions of small (volume V) and large (volume 2V) essentially bare maghemite nanoparticles are used to investigate the effect of controllably broadening the particle size distribution on the magnetic properties of magnetic nanoparticle assemblies with strong dipolar interaction. A series of eight random mixtures of highly uniform 9.0- and 11.5-nm-diameter maghemite particles prepared by thermal decomposition is studied. In spite of the severely broadened size distributions in the mixed samples, well-defined superspin glass transition temperatures are observed across the series, their values increasing linearly with the weight fraction of large particles.
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| 6. |
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| 7. |
- Andersson, Mikael Svante, et al.
(författare)
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Particle size-dependent superspin glass behavior in random compacts of monodisperse maghemite nanoparticles
- 2016
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Ingår i: Materials Research Express. - : IOP Publishing. - 2053-1591. ; 3:4
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Tidskriftsartikel (refereegranskat)abstract
- Dense random assemblies made from highly monodisperse gamma-Fe2O3 nanoparticles with sizes ranging from 6.2 to 11.5 nm have been investigated by DC and AC magnetometry. It is found that all assemblies undergo superspin glass phase transitions. The superspin glass phase transition temperature is strongly dependent on the particle size and the nature of the interparticle interaction. However the transition from superparamagnet to superspin glass, as evidenced by the shape of the ac-susceptibility curves and the dynamic critical exponents associated with the transition, is similar in all systems.
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| 8. |
- Andersson, Mikael Svante, et al.
(författare)
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Size-dependent surface effects in maghemite nanoparticles and its impact on interparticle interactions in dense assemblies
- 2015
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 26:47
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Tidskriftsartikel (refereegranskat)abstract
- The question of the dominant interparticle magnetic interaction type in random closely packed assemblies of different diameter (6.2-11.5 nm) bare maghemite nanoparticles (NPs) is addressed. Single-particle magnetic properties such as particle anisotropy and exchange bias field are first of all studied in dilute (reference) systems of these same NPs, where interparticle interactions are neglible. Substantial surface spin disorder is revealed in all particles except the smallest, viz. for diameters d = 8-11.5 nm but not for d = 6.2-6.3 nm. X-ray diffraction analysis points to a crystallographic origin of this effect. The study of closely packed assemblies of the d >= 8 nm particles observes collective (superspin) freezing that clearly appears to be governed by interparticle dipole interactions. However, the dense assemblies of the smallest particles exhibit freezing temperatures that are higher than expected from a simple (dipole) extrapolation of the corresponding temperatures found in the d >= 8 nm assemblies. It is suggested that the nature of the dominant interparticle interaction in these smaller particle assemblies is superexchange, whereby the lack of significant surface spin disorder allows this mechanism to become important at the level of interacting superspins.
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| 9. |
- De Toro, Jose A., et al.
(författare)
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Controlled Close-Packing of Ferrimagnetic Nanoparticles : An Assessment of the Role of Interparticle Superexchange Versus Dipolar Interactions
- 2013
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:19, s. 10213-10219
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Tidskriftsartikel (refereegranskat)abstract
- The fundamental question as to the relative importance of interparticle superexchange versus dipolar interaction between oxide magnetic particles in direct physical contact is addressed by examining the magnetic. properties of a series of compacted samples comprising identical maghemite particles (8 nm in diameter) coated by nonmagnetic shells (oleic acid or silica) of varying thickness that control the distance between the magnetic cores and hence the packing density (particle volume fraction). A remarkably narrow maghemite particle size distribution is established by electron microscopy and small-angle X-ray scattering. The series includes a sample made up of bare particles in a random-close-packed configuration (therefore in direct contact) that exhibits ideal superspin-glass behavior with a relatively high freezing transition temperature. It is shown that interparticle superexchange interactions between the nanoparticles in this sample play a minor role compared to classical dipolar interactions in establishing the collective, superspin-glass state. This follows from the freezing temperature of the most concentrated samples in the series (those with 0 <= shell thickness < 3 nm), which are found to vary in direct proportionality with the volume fraction of the maghemite cores and therefore with the strength of dipolar interactions.
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| 10. |
- De Toro, José A., et al.
(författare)
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Remanence Plots as a Probe of Spin Disorder in Magnetic Nanoparticles
- 2017
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Ingår i: Chemistry of Materials. - Washington, D.C., USA : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 29:19, s. 8258-8268
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Tidskriftsartikel (refereegranskat)abstract
- Remanence magnetization plots (e.g., Henkel or delta M plots) have been extensively used as a straightforward way to determine the presence and intensity of dipolar and exchange interactions in assemblies of magnetic nanoparticles or single domain grains. Their evaluation is particularly important in functional materials whose performance is strongly affected by the intensity of interparticle interactions, such as patterned recording media and nanostructured permanent magnets, as well as in applications such as hyperthermia and magnetic resonance imaging. Here, we demonstrate that delta M plots may be misleading when the nanoparticles do not have a homogeneous internal magnetic configuration. Substantial dips in the delta M plots of gamma-Fe2O3 nanoparticles isolated by thick SiO2 shells indicate the presence of demagnetizing interactions, usually identified as dipolar interactions. results, however, demonstrate that it is the inhomogeneous spin structure of the nanoparticles, as most clearly evidenced by Mossbauer measurements, that has a pronounced effect on the delta M plots, leading to features remarkably similar to those produced by dipolar interactions. X-ray diffraction results combined with magnetic characterization indicate that this inhomogeneity is due to the presence of surface structural (and spin) disorder. Monte Carlo simulations unambiguously corroborate the critical role of the internal magnetic structure in the delta M plots. Our findings constitute a cautionary tale on the widespread use of remanence plots to assess interparticle interactions as well as offer new perspectives in the use of Henkel and delta M plots to quantify the rather elusive inhomogeneous magnetization states in nanoparticles.
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| 11. |
- Muscas, Giuseppe, et al.
(författare)
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The interplay between single particle anisotropy and interparticle interactions in ensembles of magnetic nanoparticles
- 2018
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 20, s. 28634-28643
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Tidskriftsartikel (refereegranskat)abstract
- This paper aims to analyze the competition of single particle anisotropy and interparticle interactions in nanoparticle ensembles using a random anisotropy model. The model is first applied to ideal systems of non-interacting and strongly dipolar interacting ensembles of maghemite nanoparticles. The investigation is then extended to more complex systems of pure cobalt ferrite CoFe2O4 (CFO) and mixed cobalt-nickel ferrite (Co,Ni)Fe2O4 (CNFO) nanoparticles. Both samples were synthetized by the polyol process and exhibit the same particle size (D-TEM approximate to 5 nm), but with different interparticle interaction strengths and single particle anisotropy. The implementation of the random anisotropy model allows investigation of the influence of single particle anisotropy and interparticle interactions, and sheds light on their complex interplay as well as on their individual contribution. This analysis is of fundamental importance in order to understand the physics of these systems and to develop technological applications based on concentrated magnetic nanoparticles, where single and collective behaviors coexist.
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| 12. |
- Sánchez, Elena H., et al.
(författare)
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Crossover From Individual to Collective Magnetism in Dense Nanoparticle Systems: Local Anisotropy Versus Dipolar Interactions
- 2022
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 18:28
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Tidskriftsartikel (refereegranskat)abstract
- Dense systems of magnetic nanoparticles may exhibit dipolar collective behavior. However, two fundamental questions remain unsolved: i) whether the transition temperature may be affected by the particle anisotropy or it is essentially determined by the intensity of the interparticle dipolar interactions, and ii) what is the minimum ratio of dipole–dipole interaction (Edd) to nanoparticle anisotropy (KefV, anisotropy⋅volume) energies necessary to crossover from individual to collective behavior. A series of particle assemblies with similarly intense dipolar interactions but widely varying anisotropy is studied. The Kef is tuned through different degrees of cobalt-doping in maghemite nanoparticles, resulting in a variation of nearly an order of magnitude. All the bare particle compacts display collective behavior, except the one made with the highest anisotropy particles, which presents “marginal” features. Thus, a threshold of KefV/Edd ≈ 130 to suppress collective behavior is derived, in good agreement with Monte Carlo simulations. This translates into a crossover value of ≈1.7 for the easily accessible parameter TMAX(interacting)/TMAX(non-interacting) (ratio of the peak temperatures of the zero-field-cooled magnetization curves of interacting and dilute particle systems), which is successfully tested against the literature to predict the individual-like/collective behavior of any given interacting particle assembly comprising relatively uniform particles.
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| 13. |
- Sanchez, Elena H., et al.
(författare)
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Simultaneous Individual and Dipolar Collective Properties in Binary Assemblies of Magnetic Nanoparticles
- 2020
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 32:3, s. 969-981
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Tidskriftsartikel (refereegranskat)abstract
- Applications based on aggregates of magnetic nanoparticles are becoming increasingly widespread, ranging from hyperthermia to magnetic recording. However, although some uses require collective behavior, others need a more individual-like response, the conditions leading to either of these behaviors are still poorly understood. Here, we use nanoscale-uniform binary random dense mixtures with different proportions of oxide magnetic nanoparticles with low/high anisotropy as a valuable tool to explore the crossover from individual to collective behavior. Two different anisotropy scenarios have been studied in two series of binary compacts: M1, comprising maghemite (gamma-Fe2O3) nanoparticles of different sizes (9.0 nm/11.5 nm) with barely a factor of 2 between their anisotropy energies, and M2, mixing equally sized pure maghemite (low-anisotropy) and Co-doped maghemite (high-anisotropy) nanoparticles with a large difference in anisotropy energy (ratio > 8). Interestingly, while the M1 series exhibits collective behavior typical of strongly coupled dipolar systems, the M2 series presents a more complex scenario where different magnetic properties resemble either "individual-like" or "collective", crucially emphasizing that the collective character must be ascribed to specific properties and not to the system as a whole. The strong differences between the two series offer new insight (systematically ratified by simulations) into the subtle interplay between dipolar interactions, local anisotropy and sample heterogeneity to determine the behavior of dense assemblies of magnetic nanoparticles.
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| 14. |
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The Seventeenth Data Release of the Sloan Digital Sky Surveys : Complete Release of MaNGA, MaStar, and APOGEE-2 Data
- 2022
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Ingår i: Astrophysical Journal Supplement Series. - : Institute of Physics (IOP). - 0067-0049 .- 1538-4365. ; 259:2
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Tidskriftsartikel (refereegranskat)abstract
- This paper documents the seventeenth data release (DR17) from the Sloan Digital Sky Surveys; the fifth and final release from the fourth phase (SDSS-IV). DR17 contains the complete release of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, which reached its goal of surveying over 10,000 nearby galaxies. The complete release of the MaNGA Stellar Library accompanies this data, providing observations of almost 30,000 stars through the MaNGA instrument during bright time. DR17 also contains the complete release of the Apache Point Observatory Galactic Evolution Experiment 2 survey that publicly releases infrared spectra of over 650,000 stars. The main sample from the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), as well as the subsurvey Time Domain Spectroscopic Survey data were fully released in DR16. New single-fiber optical spectroscopy released in DR17 is from the SPectroscipic IDentification of ERosita Survey subsurvey and the eBOSS-RM program. Along with the primary data sets, DR17 includes 25 new or updated value-added catalogs. This paper concludes the release of SDSS-IV survey data. SDSS continues into its fifth phase with observations already underway for the Milky Way Mapper, Local Volume Mapper, and Black Hole Mapper surveys.
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