Nonlinear propagation and quasi self-confinement of light in plasmonic resonant media

We study nonlinear propagation of light in colloidal suspension of metallic nanoparticles, in the regime of particles surface plasmon resonance. We show that the propagation exhibits features typical for purely defocusing media and the observed spatial confinement is not a real self-trapping, as for solitons, but rather than is caused by the phase modulation of the beam via nonlocal defocusing nonlinearity. We also show that the light-induced refractive index change in the suspension leads to stabilization of structured light beams. In particular, we demonstrate a stable nonlinear propagation of bright ring beams with complex states of polarization, including practically important radial and azimuthal states.Qatar National Research Fund (grant # NPRP 9-020-1-006). Y.S-R. acknowledges support from CONACyT and Australian and Mexican Academies of Science for Ph.D. internship grant

The oxidized phospholipid PazePC modulates interactions between Bax and mitochondrial membranes

AbstractActivation of the pro-apoptotic protein Bax under intracellular oxidative stress is closely related to its association with the mitochondrial outer membrane (MOM) system, ultimately resulting in cell death. The precise mechanism by which this activation and the subsequent structural changes in the protein occur is currently unknown. In addition to triggering the onset of apoptosis, oxidative stress generates oxidized lipids whose impact on mitochondrial membrane integrity and the activity of membrane-associated Bax is unclear. We therefore devised a model system that mimics oxidative stress conditions by incorporating oxidized phospholipids (OxPls) into mitochondria-like liposomes, and studied the OxPls' impact on Bax-membrane interactions. Differential scanning calorimetry (DSC) was used to study membrane organization and protein stability, while conformational changes in the protein upon contact with lipid vesicles were monitored using far-UV circular dichroism (CD) spectroscopy. The thermograms for liposomes containing the OxPl 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PazePC) differed dramatically from those for unmodified liposomes. Moreover, Bax exhibited enhanced thermal stability in the presence of the modified liposomes, indicating that it interacted strongly with PazePC-containing membranes. The presence of PazePC also increased the α-helical character of Bax compared to the protein alone or with PazePC-free vesicles, at 10°C, 20°C, and 37°C. Presumably, the presence of PazePC-like OxPls a) increases the population of membrane-associated Bax and b) facilitates the protein's insertion into the membrane by distorting the bilayer's organization, as seen by solid-state high-resolution 1H and 31P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy

Interplay of Stimulated Emission and Fluorescence Resonance Energy Transfer in Electrospun Light-Emitting Fibers

Concomitant amplified spontaneous emission (ASE) and F\"orster resonance energy transfer (FRET) are investigated in electrospun light-emitting fibers. Upon dye-doping with a proper FRET couple system, free-standing fibrous mats exhibit tunable FRET efficiency and, more importantly, tailorable threshold conditions for stimulated emission. In addition, effective scattering of light is found in the fibrous material by measuring the transport mean free path of photons by coherent backscattering experiments. The interplay of ASE and FRET leads to high control in designing optical properties from electrospun fibers, including the occurrence of simultaneous stimulated emission from both donor and acceptor components. All tunable-optical properties are highly interesting in view of applying electrospun light-emitting materials in lightening, display, and sensing technologies.Comment: 32 pages, 13 figure

"Siihen se tarina loppuu" Osallisuuden tukeminen saduttamalla

Opinnäytetyö oli toiminnallinen opinnäytetyö, jonka tavoitteena oli osallisuuden tukeminen sadutusmenetelmää hyödyntäen ja työn tarkoituksena oli myös tuottaa satukirja lasten kertomista saduista. Opinnäytetyö toteutettiin yhteistyössä päiväkoti Touhula Kangasalan kanssa kevään 2018 aikana. Työn tietoperusta koostui sadutuksesta, osallisuudesta, lasten kuulluksi tulemisesta, sekä varhaiskasvatuksesta. Opinnäytetyön toiminnallisessa osuudessa yksilösadutettiin lapsia ja näistä saduista koottiin työn liitteissä oleva satukirja. Lapset saivat kuvittaa omat satunsa ja kuvat liitettiin osaksi satukirjaa. Toiminnallinen osuus toteutettiin huhtikuussa 2018 ja sen aikana sadutettiin seitsemää 4-5-vuotiasta lasta. Työn tilaaja sai opinnäytetyön aikana syntyneen satukirjan jaettavaksi toiminnalliseen osuuteen osallistuneille lapsille. Lapset saivat antaa palautetta valmiista satukirjasta ja palaute heiltä oli positiivista. Lisäksi työ auttoi tukemaan lasten osallisuutta saduttamisen yhteydessä sekä opinnäytetyö toivottavasti innosti päiväkodin henkilökuntaa käyttämään sadutusmenetelmää myös tulevaisuudessa.This Bachelor’s thesis was practice-based and the aim was to support inclusion in the daycare centre Touhula in Kangasala by using the storycrafting method. Another goal was to make a storybook from the stories the children told. The thesis was implemented in spring 2018. The theoretical background consists of the storycrafting method, inclusion, what being heard is and early childhood education. In the practice part of the thesis, seven children aged four to five attended individual storycrafting sessiona. The children drew pictures to their stories and the stories were collected into a storybook. This practice part was carried out in April 2018. The Touhula Kangasala daycare centre received the finished storybook in May 2018. The children who took part into the storycrafting, also received copies of the storybook. The children also gave feedback about the book. The feedback was positive and the main aim of the thesis, to support the inclusion in the group, was achieved. The thesis also hopefully inspired the personnel to use the storycrafting method in the future

Tailoring the Random Lasing Properties by Controlled Phase Separation Process in PMMA:PVK Dye-Doped Polymeric Blends

This article describes the random lasing (RL) phenomenon obtained in a dye-doped, polymeric double-phase system composed of PMMA and PVK polymers. It shows how relative concentrations between mentioned macromolecules can influence lasing parameters of the resulting blends, including obtained emission spectra and threshold conditions. We describe the influence of lasers’ composition on their morphologies and link them with particular RL properties. Our studies reveal that the disorder caused by phase separation can support the RL phenomenon both in the waveguiding and quasi-waveguiding regimes. Changing the relative concentration of polymers enables one to switch between both regimes, which significantly influences threshold conditions, spectral shift, number of lasing modes, and ability to support extended and/or localized modes. Finally, we show that a simple phase separation technique can be used to fabricate efficient materials for RL. Moreover, it enables the tailoring of lasing properties of materials in a relatively wide range at the stage of the laser material fabrication process in a simple way. Therefore, this technique can be seen as a fast, cheap, and easy to perform way of random lasers fabrication

Plasmonic Nanoparticles Driven Enhanced Light Amplification in a Local 2D and 3D Self-Assembly

We present fluorescence and a random lasing enhancement effect due to the interaction between gold nanoparticles (AuNPs) and Rhodamine 6G (Rh6G) dye. Non-covalently bounded dyes in the proximity of nanoparticles are studied in three systems of varying dimensionality: from (i) three-dimensional freely distributed suspensions, through (ii) quasi-two-dimensional multilamellar liposomes, to (iii) solid two-dimensional thin layers. Liposomes facilitate the formation of stable AuNPs/Rh6G composition showing enhanced fluorescence, while solid thin films exhibit plasmon-assisted random lasing

Anomalous interaction of spatial solitons in nematic liquid crystals

We study experimentally the interaction of mutually incoherent bright spatial solitons in dye-doped nematic liquid crystals (LCs). The dye-induced light absorption results in a complex nonlinear optical response of the LC having spatially nonlocal focusing and defocusing contributions. The competition between both nonlinearities leads to the separation-dependent soliton interaction with repulsion of distant and attraction of closely placed solitons.Qatar National Research Fund (QNRF) (NPRP 9-020-1-006); Polish Ministry of Higher Education (“Mobility Plus”); Narodowe Centrum Nauki (NCN) (2016/23/D/ ST5/00278)

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