Effect of wavelength dependence of nonlinearity, gain, and dispersion in photonic crystal fiber amplifiers

Photonic crystal fibers are used in fiber amplifiers and lasers because of the flexibility in the design of mode area and dispersion. However, these quantities depend strongly on the wavelength. The wavelength dependence of gain, nonlinearity and dispersion are investigated here by including the wavelength dependence explicitly in the nonlinear Schr\"odinger equation for photonic crystal fibers with varying periods and hole sizes. The effect of the wavelength dependence of each parameter is studied separately as well as combined. The wavelength dependence of the parameters is shown to create asymmetry to the spectrum and chirp, but to have a moderating effect on pulse broadening. The effect of including the wavelength dependence of nonlinearity in the simulations is demonstrated to be the most significant compared that of dispersion or gain

Conditions for waveguide decoupling in square-lattice photonic crystals

We study coupling and decoupling of parallel waveguides in two-dimensional square-lattice photonic crystals. We show that the waveguide coupling is prohibited at some wavelengths when there is an odd number of rows between the waveguides. In contrast, decoupling does not take place when there is even number of rows between the waveguides. Decoupling can be used to avoid cross talk between adjacent waveguides.Comment: 6 pages, 2 figure

Controlling cooling fans with Arduino Pulse Width Modulation controller

Abstract. In this thesis a fan controller was implemented using an Arduino to supply a pulse width modulation (PWM) control signal. The controller is used to control fans when there is no control signal and power available from a finished base transceiver station. This Bachelors thesis consists of the planning, sourcing, building, developing software and testing the implemented controller. The controller was built with an Arduino board and 48V power supply which are controlled via a PC. Two different types of software were used, a simpler one using Windows Remote Arduino Experience and a Python based software which enabled more precise control

Ekologinen näkökulma ihmiskasvojen elokuvalliseen valaisuun - pilottitutkimus

One key aspect of cinematographic lighting – and lighting in general – is its direction and how the lighting illumi-nates people and other objects of attention. In a natural set-ting, the light reaching the target usually has at least some level of directionality instead of being just ambient overall light. In cinematography directionality is used, among other things, to enhance the lit object’s three-dimensional-ity in an otherwise two-dimensional medium by bringing out its shape and texture and separating it from the back-ground. While lighting has typically been studied based on its physical qualities that render for quantitative measures, such as intensity or color spectrum, less is known about how cinematographic lighting gives rise to the spectator’s emotive-cognitive experiences. Overall, film lighting has been studied surprisingly little, although both practical and academic literature emphasize its important role in cinematic expression. This paper presents a pilot study that examines viewers’ emotional reactions to photographs of an expressionless human face under lighting from differ-ent directions. The initial results indicate that lighting that obscures, hides, or distorts facial features creates stronger emotional reactions in the viewer than lighting that reveals them, contributing to the scientific understanding of the audience’s reactions and the filmmaker’s creative decisions.Peer reviewe

Cuticular Needle Erosion and Winter Drought in Polluted Environments - A Model Analysis

A method is developed for analyzing the consequences of pollutant-imposed cuticular erosion for the tolerance of winter drought in coniferous trees. The erosion rate of cuticular wax is modeled in terms of the contact angle of water droplets, as a function of sulphur dioxide, air temperature and relative humidity. Whole tree transpiration during drought is considered, assuming that the state of erosion affects the cuticular resistance of each needle age class. A formula is derived to compare transpiration with the water available in foliage and stem storage. The derivations are applied to a numerical example concerning the transpiration during a warm spell in the spring. Under certain assumptions, increased cuticular transpiration may well give rise to increased winter drought damage. However, many of the parameters and processes still need to be more thoroughly investigated. The most critical open question appears to be the quantitative relationship between cuticular resistance and the state of erosion of the cuticle

Transport model for hot positrons in layered structures

The transport of hyperthermal, monoenergetic (≤10-eV) positrons injected in metal bilayer structures is investigated. The transport is modeled using the Boltzmann equation and the two-flux approximation. Analyzing reported experimental data in terms of the developed model enables us to separate the different scattering channels and to estimate the mean free paths for these events. Our study is the first quantitative treatment of hot positrons, and the extracted transport parameters agree with theoretical predictions.Peer reviewe

Happamien sulfaattimaanäytteiden analysointi kannettavilla pXRF- ja pLIBS-analysaattoreilla

Tiivistelmä. Happamien sulfaattimaiden analysointi ja tutkiminen on tärkeää ympäristön tilan arvioimiseksi ja mahdollisten ympäristöhaittojen tunnistamiseksi rannikkoalueilla. Viimeisen vuosituhannen alusta alkaen kannettavat analysaattorit, pXRF (kannettava röntgenfluoresenssi) ja pLIBS (kannettava laserindusoitu plasmaspektroskopia), ovat suosittuja analyysimenetelmiä alkuaineiden tunnistamiseksi. Tässä tutkielmassa selvitettiin, miten eri kannettavat analysaattorit sopivat happamien sulfaattimaiden tunnistamiseen ja määrittämiseen, sekä miten tarkkoja rikkipitoisuuksia saadaan selvitettyä, ja kuinka tulokset korreloivat laboratoriossa tehtyjen analyysien tulosten kanssa. Käytin työssäni kolmea eri pXRF-analysaattoria ja kahta eri pLIBS-analysaattoria. Analyysitestauksessa käytettiin jauhetuista sedimenttinäytteistä puristamalla tehtyjä näytenappeja. pXRF on analyysimenetelmä, joka perustuu röntgenfluoresenssi-ilmiöön. Se käyttää röntgenvaloa indusoimaan maanäytteessä olevia alkuaineita emittoimaan kullekin karakteristista röntgensäteilyä. Säteiden intensiteetin avulla voidaan tunnistaa ja kvantifioida eri alkuaineiden pitoisuudet näytteessä. pLIBS puolestaan käyttää laserin tuottamaa plasmasta emittoivaa valoa alkuainetunnistukseen. Laserimpulssin osuessa maanäytteeseen, se aiheuttaa plasman syntymisen, joka säteilee valoa. pLIBS-analysaattori havaitsee tämän säteilyn ja analysoi sen spektrin tunnistaakseen alkuaineita. pLIBS voi tunnistaa monia alkuaineita, ja jopa enemmän kuin pXRF-analyysimenetelmä. Työssä tutkittiin happamien sulfaattimaanäytteiden rikkipitoisuuksia sekä nikkeli-, kupari- ja kobolttipitoisuuksia kannettavilla analysaattoreilla. Sekä pXRF- että pLIBS-tulokset korreloivat hyvin laboratoriossa analysoitujen rikkipitoisuuksien kanssa. Näiden tulosten perusteella voidaan sanoa, että testatut analysaattorit soveltuvat hyvin rikkipitoisuuksien määrittämiseen ja sitä kautta happamien sulfaattimaiden tunnistamiseen. Nikkeli-, kupari- ja kobolttipitoisuuksien osalta kannettavien analysaattorien tuloksissa oli enemmän hajontaa. Tutkimus myös osoitti, että pXRF:n ja pLIBS:n käyttö happamien sulfaattimaiden analysoinnissa tarjoaa useita etuja perinteisiin laboratorioanalyysimenetelmiin verrattuna. Kannettavat analysaattorit mahdollistavat nopean ja reaaliaikaisen maaperän alkuainepitoisuuksien analyysin, mikä säästää aikaa ja kustannuksia. Yhden näytteen analysointiin kannettavalla analysaattorilla menee aikaa noin 5 minuuttia. Lisäksi pXRF:llä ja pLIBS:llä tehdyt rikkipitoisuuden määritykset mahdollistavat happamien sulfaattimaiden potentiaalin arvioinnin. Kannettavien analysaattorien käyttö kuitenkin edellyttää asianmukaista koulutusta ja kalibrointia varmistamaan luotettavat tulokset.Analyzing acid sulfate soil samples using portable pXRF and pLIBS analyzers. Abstract. The analysis and investigation of acid sulfate soils are important for assessing the environmental condition and identifying potential environmental hazards in coastal areas. Since the turn of the millennium, portable analyzers, pXRF (portable X-ray fluorescence) and pLIBS (portable laser-induced breakdown spectroscopy), have become popular methods for elemental identification. This study aimed to determine how different portable analyzers are suitable for identifying and quantifying acid sulfate soils, as well as the accuracy of sulfur measurements and their correlation with laboratory analysis results conducted by the Geological Survey of Finland (GTK). Three different pXRF analyzers and two different pLIBS analyzers were used in this study. The analysis was performed on powdered sediment samples, which were compressed into pellets for measurement. pXRF is an analysis method based on X-ray fluorescence. It uses X-ray light to induce emission of characteristic X-rays from the elements present in the soil sample. By measuring the intensity of these X-rays, it is possible to identify and quantify the concentrations of different elements in the sample. On the other hand, pLIBS utilizes the emission of light from plasma generated by laser pulses for elemental identification. When the laser pulse hits the soil sample, it creates plasma that emits light. The pLIBS analyzer detects and analyzes this emitted light spectrum to identify the elements. pLIBS can identify numerous elements, even more than the pXRF analysis method. The study investigated sulfur concentrations, as well as nickel, copper, and cobalt concentrations in acid sulfate soil samples using the portable analyzers. Both pXRF and pLIBS results correlated well with the sulfur concentrations analyzed in the laboratory. Based on these results, it can be concluded that the tested analyzers are suitable for determining sulfur concentrations and, consequently, for identifying acid sulfate soils. However, there was more variation in the results for nickel, copper, and cobalt concentrations obtained with the portable analyzers. The study also demonstrated several advantages of using pXRF and pLIBS for analyzing acid sulfate soils compared to traditional laboratory analysis methods. Portable analyzers enable fast and real-time analysis of soil elemental concentrations, saving time and costs. It takes approximately 5 minutes to analyze a single sample with a portable analyzer. Additionally, sulfur measurements conducted with pXRF and pLIBS allow for assessing the potential of acid sulfate soils. However, the use of portable analyzers requires proper training and calibration to ensure reliable results

Mechanisms of secretion and spreading of pathological tau protein

Accumulation of misfolded and aggregated forms of tau protein in the brain is a neuropathological hallmark of tauopathies, such as Alzheimer’s disease and frontotemporal lobar degeneration. Tau aggregates have the ability to transfer from one cell to another and to induce templated misfolding and aggregation of healthy tau molecules in previously healthy cells, thereby propagating tau pathology across different brain areas in a prion-like manner. The molecular mechanisms involved in cell-to-cell transfer of tau aggregates are diverse, not mutually exclusive and only partially understood. Intracellular accumulation of misfolded tau induces several mechanisms that aim to reduce the cellular burden of aggregated proteins and also promote secretion of tau aggregates. However, tau may also be released from cells physiologically unrelated to protein aggregation. Tau secretion involves multiple vesicular and non-vesicle-mediated pathways, including secretion directly through the plasma membrane. Consequently, extracellular tau can be found in various forms, both as a free protein and in vesicles, such as exosomes and ectosomes. Once in the extracellular space, tau aggregates can be internalized by neighboring cells, both neurons and glial cells, via endocytic, pinocytic and phagocytic mechanisms. Importantly, accumulating evidence suggests that prion-like propagation of misfolding protein pathology could provide a general mechanism for disease progression in tauopathies and other related neurodegenerative diseases. Here, we review the recent literature on cellular mechanisms involved in cell-to-cell transfer of tau, with a particular focus in tau secretion.Peer reviewe