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- Prencipe, Alessandro, et al.
(author)
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Tunable Ultranarrowband Grating Filters in Thin-Film Lithium Niobate
- 2021
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In: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 8:10, s. 2923-2930
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Journal article (peer-reviewed)abstract
- Several applications in modern photonics require compact on-chip optical filters with a tailored spectral response. However, achieving subnanometric bandwidths and high extinction ratios is particularly challenging, especially in low-footprint device formats. Phase-shifted Bragg gratings implemented by the sidewall modulation of photonic nanowire waveguides are a good solution for on-chip narrowband operation with reasonable requirements in fabrication and scalability. In this work we report on their implementation and optimization in thin film lithium niobate, a photonic platform that affords reconfigurability by exploiting electrooptic effects. The phase-shifted Bragg grating filters have a footprint smaller than 1 mu m x 1 mm and operate at telecom wavelengths, featuring extinction ratios up to 25 dB. We demonstrate transmission bandwidths as narrow as 14.4 pm (Q = 1.1 x 10(5)) and 8.8 pm (Q = 1.76 x 10(5)) in critically coupled structures and multiwavelength Fabry-Perot configurations, respectively, in full agreement with theoretical predictions. Moreover, by taking advantage of the strong electro-optic effect in lithium niobate, in combination with the tight light confinement of nanophotonic wires and the ultranarrow spectral resonances of optimized grating structures, we demonstrate an electric tunability in peak wavelength and transmission of 25.1 pm/V and 2.1 dB/V, respectively, and a 10.5 dB contrast at CMOS voltages. The results pave the way for reconfigurable narrowband photonic filters with a small footprint and low consumption, to be exploited toward on-chip quantum and nonlinear optics, as well as optical sensing and microwave photonics.
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- Skiles, Alexander
(author)
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There is no haecceitic Euthyphro problem
- 2019
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In: Analysis. - : Oxford University Press (OUP). - 0003-2638 .- 1467-8284. ; 79:3, s. 477-484
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Journal article (peer-reviewed)abstract
- Jason Bowers and Meg Wallace (‘The Haecceitic Euthyphro Problem’, Analysis, 2018) have recently argued that those who hold that every individual instantiates a ‘haecceity’ (or ‘individual essence’) are caught up in a Euthyphro-style dilemma when confronted with familiar cases of fission and fusion. Key to Bowers and Wallace’s dilemma are certain assumptions about the nature of metaphysical explanation and the explanatory commitments of belief in haecceities. However, I argue that the dilemma only arises due to a failure to distinguish between providing a metaphysical explanation of why a fact holds vs. a metaphysical explanation of what it is for a fact to hold. In the process, I also shed light on the explanatory commitments of belief in haecceities.
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- Skiljic, Dragana, 1985, et al.
(author)
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Effects of 17β-Estradiol on Activity, Gene and Protein Expression of Superoxide Dismutases in Primary Cultured Human Lens Epithelial Cells
- 2018
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In: Current Eye Research. - : Informa UK Limited. - 1460-2202 .- 0271-3683. ; 43:5, s. 639-646
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Journal article (peer-reviewed)abstract
- Purpose: Protective effects of estradiol against H 2 O 2 -induced oxidative stress have been demonstrated in lens epithelial cells. The purpose of this study was to investigate the effects of 17β-estradiol (E2) on the different superoxide dismutase (SOD) isoenzymes, SOD-1, SOD-2, and SOD-3, as well as estrogen receptors (ERs), ERα and ERβ, in primary cultured human lens epithelial cells (HLECs). Materia ls and methods: HLECs were exposed to 0.1 µM or 1 µM E2 for 1.5 h and 24 h after which the effects were studied. Protein expression and immunolocalization of SOD-1, SOD-2, ERα, and ERβ were studied with Western blot and immunocytochemistry. Total SOD activity was measured, and gene expression analyses were performed for SOD1, SOD2, and SOD3. Results: Increased SOD activity was seen after 1.5 h exposure to both 0.1 µM and 1 µM E2. There were no significant changes in protein or gene expression of the different SODs. Immunolabeling of SOD-1 was evident in the cytosol and nucleus; whereas, SOD-2 was localized in the mitochondria. Both ERα and ERβ were immunolocalized to the nucleus, and mitochondrial localization of ERβ was evident by colocalization with MitoTracker. Both ERα and ERβ showed altered protein expression levels after exposure to E2. Conclusions: The observed increase in SOD activity after exposure to E2 without accompanying increase in gene or protein expression supports a role for E2 in protection against oxidative stress mediated through non-genomic mechanisms.
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- Ghosh, Souvik, et al.
(author)
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Modal and non-modal linear stability of Poiseuille flow through a channel with a porous substrate
- 2019
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In: European journal of mechanics. B, Fluids. - : Elsevier. - 0997-7546 .- 1873-7390. ; 75, s. 29-43
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Journal article (peer-reviewed)abstract
- We present modal and non-modal linear stability analyses of Poiseuille flow through a plane channel with a porous substrate modeled using the Volume Averaged Navier-Stokes (VANS) equations. Modal stability analysis shows the destabilization of the flow with increasing porosity of the layer. The instability mode originates from the homogeneous fluid region of the channel for all the values of porosity considered but the governing mechanism changes. Perturbation kinetic energy analysis reveals the importance of viscous dissipation at low porosity values while dissipation in the porous substrate becomes significant at higher porosity. Scaling analysis highlights the invariance of the critical wavenumber with changing porosity. On the other hand, the critical Reynolds number remains invariant at low porosity and scales as Re-c similar to (H/delta)(1.4) at high porosity where delta is the typical thickness of the vorticity layer at the fluid-porous interface. This reveals the existence of a Tollmien-Schlichting-like viscous instability mechanism at low porosity values, and Rayleigh analysis shows the presence of an inviscid instability mechanism at high porosity. For the whole range of porosities considered, the non-modal analysis shows that the optimal mechanism responsible for transient energy amplification is the lift-up effect, giving rise to streaky structure as in single-phase plane Poiseuille flow. The present results strongly suggest that the transition to turbulence follows the same path as that of classical Poiseuille flow at low porosity values, while it is dictated by the modal instability for high porosity values. SAS. All rights reserved.
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- Skiljic, Dragana, 1985, et al.
(author)
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Ophthalmological findings in neuroborreliosis : a prospective study performed in western Sweden
- 2019
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In: Acta Ophthalmologica. - : John Wiley & Sons. - 1755-375X .- 1755-3768. ; 97:1, s. 44-52
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Journal article (peer-reviewed)abstract
- PURPOSE: To evaluate and follow-up ophthalmological findings in individuals diagnosed with neuroborreliosis, confirmed by cerebrospinal fluid (CSF) analysis.METHODS: Twenty-four individuals (13 males), mean age 43.5 ± 18.2 years, with strong clinical suspicion of neuroborreliosis, were referred to the Department of Ophthalmology by the Department of Infectious Diseases at Sahlgrenska University Hospital, Gothenburg, Sweden. All subjects underwent serological and CSF analysis. A structured history taking and a detailed ophthalmological examination were performed prospectively.RESULTS: Diagnosis for neuroborreliosis was confirmed as definite in 16, possible in two and negative in four individuals, while two had unknown diagnosis. The majority (n = 14/18) with definite and possible diagnoses had ophthalmological symptoms and/or findings either in history or at examination. The most common findings were visual disturbance, diplopia, red eyes, photophobia, facial palsy with palpebral diastasis, strabismus and sixth nerve palsy. The number of symptoms and findings was correlated with immunoglobulin G (IgG)/IgM in CSF (r = 0.6, p = 0.009/0.016; Spearman's correlation). All subjects improved, except one with initially fulminant papilloedema, who still suffered from optic disc atrophy and affected visual fields at the last follow-up.CONCLUSION: The majority of patients diagnosed with neuroborreliosis had ophthalmological symptoms and/or findings. Facial palsy with palpebral diastasis was a common finding. Onset of diplopia and/or sixth nerve affection may be a first sign of neuroborreliosis. Number of ophthalmological findings was correlated with the CSF antibody titre. Ticks are becoming more widespread and abundant, resulting in a higher incidence of neuroborreliosis. Hence, the knowledge of ophthalmological symptoms and findings is of great importance.
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