| 1. |
- Midtvedt, Daniel, et al.
(författare)
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Size and Refractive Index Determination of Subwavelength Particles and Air Bubbles by Holographic Nanoparticle Tracking Analysis
- 2020
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 92:2, s. 1908-1915
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Tidskriftsartikel (refereegranskat)abstract
- Determination of size and refractive index (RI) of dispersed unlabeled subwavelength particles is of growing interest in several fields, including biotechnology, wastewater monitoring, and nanobubble preparations. Conventionally, the size distribution of such samples is determined via the Brownian motion of the particles, but simultaneous determination of their R1 remains challenging. This work demonstrates nanoparticle tracking analysis (NTA) in an off-axis digital holographic microscope (DHM) enabling determination of both particle size and RI of individual subwavelength particles from the combined information about size and optical phase shift. The potential of the method to separate particle populations is demonstrated by analyzing a mixture of three types of dielectric particles within a narrow size range, where conventional NTA methods based on Brownian motion alone would fail. Using this approach, the phase shift allowed individual populations of dielectric beads overlapping in either size or RI to be clearly distinguished and quantified with respect to these properties. The method was furthermore applied for analysis of surfactant-stabilized micro- and nanobubbles, with RI lower than that of water. Since bubbles induce a phase shift of opposite sign to that of solid particles, they were easily distinguished from similarly sized solid particles made up of undissolved surfactant. Surprisingly, the dependence of the phase shift on bubble size indicates that only those with 0.15-0.20 mu m radius were individual bubbles, whereas larger bubbles were actually clusters of bubbles. This label-free means to quantify multiple parameters of suspended individual submicrometer particles offers a crucial complement to current characterization strategies, suggesting broad applicability for a wide range of nanoparticle systems.
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| 2. |
- Aleman, Alexandru, et al.
(författare)
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Fatou and brothers Riesz theorems in the infinite-dimensional polydisc
- 2019
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Ingår i: Journal d'Analyse Mathematique. - : Springer Science and Business Media LLC. - 0021-7670 .- 1565-8538. ; 137:1, s. 429-447
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Tidskriftsartikel (refereegranskat)abstract
- We study the boundary behavior of functions in the Hardy spaces on the infinite-dimensional polydisc. These spaces are intimately related to the Hardy spaces of Dirichlet series. We exhibit several Fatou and Marcinkiewicz- Zygmund type theorems for radial convergence of functions with Fourier spectrum supported on N0∞∪(−N0∞). As a consequence one obtains easy new proofs of the brothers F. and M. Riesz Theorems in infinite dimensions, as well as being able to extend a result of Rudin concerning which functions are equal to the modulus of an H 1 function almost everywhere to T ∞ . Finally, we provide counterexamples showing that the pointwise Fatou theorem is not true in infinite dimensions without restrictions to the mode of radial convergence even for bounded analytic functions.
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| 3. |
- Aleman, Alexandru, et al.
(författare)
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Fourier Multipliers for Hardy Spaces of Dirichlet Series
- 2014
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Ingår i: International Mathematics Research Notices. - : Oxford University Press (OUP). - 1073-7928 .- 1687-0247. ; :16, s. 4368-4378
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Tidskriftsartikel (refereegranskat)abstract
- We obtain new results on Fourier multipliers for Dirichlet-Hardy spaces. As a consequence, we establish a Littlewood-Paley inequality, and we give a simple proof that the Dirichlet monomials form a Schauder basis for p>1.
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| 4. |
- Antezana, Jorge, et al.
(författare)
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Gap probabilities for the cardinal sine
- 2012
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Ingår i: Journal of Mathematical Analysis and Applications. - : Elsevier BV. - 0022-247X. ; 396:2, s. 466-472
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Tidskriftsartikel (refereegranskat)abstract
- We study the zero sets of random analytic functions generated by a sum of the cardinal sine functions which form an orthonormal basis for the Paley-Wiener space. As a model case, we consider real-valued Gaussian coefficients. It is shown that the asymptotic probability that there is no zero in a bounded interval decays exponentially as a function of the length. (C) 2012 Elsevier Inc. All rights reserved.
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| 5. |
- Antezana, Jorge, et al.
(författare)
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Zeros of random functions generated with de branges kernels
- 2017
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Ingår i: International Mathematics Research Notices. - : Oxford University Press (OUP). - 1073-7928 .- 1687-0247. ; 2017:8, s. 2284-2299
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Tidskriftsartikel (refereegranskat)abstract
- We study the point process given by the set of real zeros of random series generated with orthonormal bases of reproducing kernels of de Branges spaces. We find an explicit formula for the intensity function in terms of the phase of the Hermite-Biehler function generating the de Branges space. We prove that the intensity of the point process completely characterizes the underlying de Branges space.
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| 6. |
- Bengmark, Samuel, 1965, et al.
(författare)
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Pragmatic Research on Educational Practice
- 2023
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Ingår i: Proceedings Chalmers Conference on Teaching and Learning 2023. - 9789188041548 ; , s. 56-59
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Konferensbidrag (refereegranskat)abstract
- During a round table discussion at a collegial conference on teaching and learning, a focus group with 12 teachers from a technical university discuss challenges with studying their own teaching practice. Furthermore, a concept called PREP – Pragmatic Research on Educational Practice, with the goal of engaging engineering educators in studying, documenting, and sharing their initiatives to improve teaching practices, is introduced and discussed. Among the main obstacles to researching their own teaching practice, the participants pointed to a lack of time, know-how, and motivation. They expressed that there is potential in the collegial part of PREP and the time efficiency of using what can be studied during a course. The role of PREP studies, in relation to regular educational research, is also discussed, and that PREP may be perceived as a devaluation of educational science was problematized. Some participants felt that it was very likely that they would participate in a PREP group next academic year if given the opportunity.
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| 7. |
- Bengmark, Samuel, 1965, et al.
(författare)
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PREP – en kollegial process för att forska på sin egen undervisning.
- 2023
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Ingår i: Bidrag från den 9:e utvecklingskonferensen för Sveriges ingenjörsutbildningar. - 9789174856200
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Många av oss ingenjörsutbildare prövar olika pedagogiska idéer i vår undervisning och försöker förstå om de fungerar bra. Dock är det oftast svårt att lyckas driva analysen hela vägen, inte sällan på grund av tidsbrist, osäkerhet om hur man skall gå till väga eller bristande motivation. Vi tror därför att det behövs en ny form av kollegialt samarbete med målet att stödja undersökningar av egen undervisningspraktik som hjälper lärare att överkomma dessa utmaningar. Vi föreslår därför en kollegial process, som vi kallar PREP, Pragmatic Research on Educational Practice, som innebär att en grupp kollegor, gärna från olika universitet, stöttar varandra att genomföra studier av sina undervisningsaktiviteter. Vårt syfte med denna workshop är att berätta lite om våra erfarenheter med PREP så långt, samt att du skall få smaka på PREP och se om denna process kan vara till hjälp för dig. Samtidigt önskar vi få ta del av dina åsikter om vad i denna process som är mest värdefullt och vad som kan förbättras.
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| 8. |
- Bergqvist, Linus, 1994-
(författare)
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Function spaces and rational inner functions on polydiscs
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis we consider problems related to rational inner functionsand several different Hilbert spaces on the unit polydisc. In the general introduction the functions and the function spaces we will be interested in are introduced, and in particular we point outproblems and phenomena that occur in higher dimensions and are notpresent for one variable functions. For example, we provide a detailed construction of a non-trivial shift-invariant subspace of Dirichlet-type spaces on the bidisc which is not fnitely generated. Furthermore, Clark-Aleksandrov measures are generalized to higher dimensions, and certain results about such measures are proved.Paper I concerns containment of rational inner functions in Dirichlet-type spaces on polydiscs. In particular a theorem relating H^p integrability of the partial derivatives of a rational inner function to containment of the function in certain Dirichlet-type spaces is proved. As a corollary, we see that every rational inner function on D^n belongs to the isotropic Dirichlet-type space with weight 1/n. In Paper II, Zhu's sub-Bergman spaces of one variable functions on the unit disc are generalized to weighted Bergman spaces on D^n. Unlike in one variable,we show that sub-Bergman spaces associated to a rational inner function are generally not contained in a weighted Bergman space of higher regularity. We also show how Clark measures on the n-torus can be used to study model spaces on D^n associated to rational inner functions.
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| 9. |
- Fjellstad, Andreas, et al.
(författare)
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IKT! and Łukasiewicz-models
- 2021
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Ingår i: Notre Dame Journal of Formal Logic. - : Duke University Press. - 0029-4527. ; 62:2, s. 247-256
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Tidskriftsartikel (refereegranskat)abstract
- In this note, we show that the first-order logic IK! is sound with regard to the models obtained from continuum-valued Łukasiewicz-models for first-order languages by treating the quantifiers as infinitary strong disjunction/conjunction rather than infinitary weak disjunction/conjunction. Moreover, we show that these models cannot be used to provide a new consistency proof for the theory of truth IKT! obtained by expanding IK! with transparent truth, because the models are inconsistent with transparent truth. Finally, we show that whether or not this inconsistency can be reproduced in the sequent calculus for IKT! depends on how vacuous quantification is treated.
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| 10. |
- Halvdansson, Simon, et al.
(författare)
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Existence of uncertainty minimizers for the continuous wavelet transform
- 2023
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Ingår i: Mathematische Nachrichten. - : Wiley. - 0025-584X .- 1522-2616. ; 296:3, s. 1156-1172
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Tidskriftsartikel (refereegranskat)abstract
- Continuous wavelet design is the endeavor to construct mother wavelets with desirable properties for the continuous wavelet transform (CWT). One class of methods for choosing a mother wavelet involves minimizing a functional, called the wavelet uncertainty functional. Recently, two new wavelet uncertainty functionals were derived from theoretical foundations. In both approaches, the uncertainty of a mother wavelet describes its concentration, or accuracy, as a time-scale probe. While an uncertainty minimizing mother wavelet can be proven to have desirable localization properties, the existence of such a minimizer was never studied. In this paper, we prove the existence of minimizers for the two uncertainty functionals.
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