Studying the growth and cloud activation of sodium decanoate and sodium chloride particles as surrogates of organic marine aerosols

Abstract. Aerosol particles transform into cloud condensation nuclei (CCN) above a critical value of the ambient water vapor supersaturation. Global climate models (GCMs) use parameterizations to estimate number concentrations of these CCN in clouds. Surfactants are organic compounds that can affect the droplet growth by e.g. decreasing surface tension of the droplet. Marine aerosols could contain an unaccounted amount of these kind of surfactants. Surfactant induced effects should be considered into calculation modules of droplet activation, droplet growth and droplet light extinction. In this thesis the cloud droplet activation of surfactant enriched aerosols is evaluated with the “simple” Köhler model (Köhler, 1936) and Köhler model combined with the monolayer model (Malila & Prisle, 2018) for surface thermodynamics. The main goal was the assessment of a modelling framework that accounts for complex surfactant effects on the droplet activation of sodium decanoate/sodium chloride particles as surrogates of marine aerosols. It is questioned that the estimations of the cloud forming potential of secondary marine aerosols with the conventional setting of the Köhler model could be misled by using the corrected water mole fraction as a measure of the water activity. The new composition-dependent parametrizations of water activity and density including micelles we used show a different perspective of the activation efficiency of surfactant-enriched aerosols. Even when these are surrogates of primary marine aerosols (enriched in NaCl not in SO4 as the secondary marine aerosols), the interaction organic/inorganic controlling the surfactant behavior are very similar. The study confirmed that the critical radius of particles values varies between 20 nm–150 nm in normal conditions but activated droplets can be as small as 10 nm–15 nm in radius. Our calculations agree with the results from previous studies as both models predict the minimum critical particle radius to be around 15 nm–70 nm. The more particles there are taking up water in the cloud the less likely it gets for an individual droplet to become a CCN. This would result in a decrease in precipitation. Our study gives insight to what is to be expected when using the conventional Köhler models for predicting aerosol-cloud inter-actions in marine environments. More precise and computationally efficient ways of property calculation are needed to understand the role of biogenic aerosols in the radiative forcing of marine clouds

Inhomogeneous Structures in Holographic Superfluids: II. Vortices

We study vortex solutions in a holographic model of Herzog, Hartnoll, and Horowitz, with a vanishing external magnetic field on the boundary, as is appropriate for vortices in a superfluid. We study relevant length scales related to the vortices and how the charge density inside the core of the vortex behaves as a function of temperature or chemical potential. We extract the critical superfluid velocity from the vortex solutions, study how it behaves as a function of the temperature, and compare it to earlier studies and to the Landau criterion. We also comment on the possibility of a Berezinskii-Kosterlitz-Thouless vortex confinement-deconfinement transition.Comment: 32 pages, 10 figures, typos corrected, references adde

Particle Number Fluctuations in Statistical Model with Exact Charge Conservation Laws

Even though the first momenta i.e. the ensemble average quantities in canonical ensemble (CE) give the grand canonical (GC) results in large multiplicity limit, the fluctuations involving second moments do not respect this asymptotic behaviour. Instead, the asymptotics are strikingly different, giving a new handle in study of statistical particle number fluctuations in relativistic nuclear reactions. Here we study the analytical large volume asymptotics to general case of multispecies hadron gas carrying fixed baryon number, strangeness and electric charge. By means of Monte Carlo simulations we have also studied the general multiplicity probability distributions taking into account the decay chains of resonance states.Comment: 4 pages, 2 figures. The report of the talk given in Strangeness in Quark Matter 2004, Cape Town. Submitted to J. Phys. G: Nucl. Part. Phy

Holographic pump probe spectroscopy

We study the non-linear response of a 2+1 dimensional holographic model with weak momentum relaxation and finite charge density to an oscillatory electric field pump pulse. Following the time evolution of one point functions after the pumping has ended, we find that deviations from thermality are well captured within the linear response theory. For electric pulses with a negligible zero frequency component the response approaches the instantaneously thermalizing form typical of holographic Vaidya models. We link this to the suppression of the amplitude of the quasinormal mode that governs the approach to equilibrium. In the large frequency limit, we are also able to show analytically that the holographic geometry takes the Vaidya form. A simple toy model captures these features of our holographic setup. Computing the out-of-equilibrium probe optical conductivity after the pump pulse, we similarly find that for high-frequency pulses the optical conductivity reaches its final equilibrium value effectively instantaneously. Pulses with significant DC components show exponential relaxation governed by twice the frequency of the vector quasinormal mode that governs the approach to equilibrium for the background solution. We explain this numerical factor in terms of a simple symmetry argument.Peer reviewe

Holography and thermalization in optical pump-probe spectroscopy

Using holography, we model experiments in which a 2 + 1D strange metal is pumped by a laser pulse into a highly excited state, after which the time evolution of the optical conductivity is probed. We consider a finite-density state with mildly broken translation invariance and excite it by oscillating electric field pulses. At zero density, the optical conductivity would assume its thermalized value immediately after the pumping has ended. At finite density, pulses with significant dc components give rise to slow exponential relaxation, governed by a vector quasinormal mode. In contrast, for high-frequency pulses the amplitude of the quasinormal mode is strongly suppressed, so that the optical conductivity assumes its thermalized value effectively instantaneously. This surprising prediction may provide a stimulus for taking up the challenge to realize these experiments in the laboratory. Such experiments would test a crucial open question faced by applied holography: are its predictions artifacts of the large N limit or do they enjoy sufficient UV independence to hold at least qualitatively in real-world systems?Peer reviewe

Ympäristökasvatus osana luokanopettajien kokemusta ja toimijuutta alakoulussa

Tiivistelmä. Ympäristökasvatukselle on suurempi tarve kuin koskaan aikaisemmin. Ympäristö muuttuu ihmisten toiminnan seurauksena kiihtyvällä tahdilla. Ympäristöahdistus ja huoli maapallon tilasta on lisääntynyt, mutta samaan aikaan ihmiset vieraantuvat luonnosta yhä enemmän. Jotta voidaan toimia ympäristön kannalta kestävällä tavalla, ihmisten täytyy löytää yhteys luontoon. Luokanopettajat ovat merkittävässä roolissa ympäristötiedon välittäjänä lapsille ja nuorille, mutta myös luontokokemusten tarjoajana. Luokanopettajan työtä ohjaa valtakunnallinen opetussuunnitelma. Tällä hetkellä voimassa oleva Perusopetuksen opetussuunnitelman perusteet 2014 painottaa ympäristö- ja kestävyysasioiden käsittelemistä opetuksessa ja kasvatuksessa erilaisissa ympäristöissä. Jo perusopetuksen arvoperusta linjaa, että koulujen tulee ottaa huomioon kestävän elämäntavan välttämättömyys sekä vastuullinen suhtautuminen ympäristöön. Tämän tutkimuksen tavoitteena oli selvittää luokanopettajien teoreettista ymmärrystä ympäristökasvatuksesta ja sen käytännön toteutusta heidän opetustyössään. Tutkimuksessa tarkasteltiin myös ympäristökasvatuksen järjestämiseen vaikuttavia tekijöitä, joiden nähtiin joko tukevan tai estävän opetus- ja kasvatustyötä. Tutkimus toteutettiin laadullisena tutkimuksena fenomenologisen lähestymistavan kautta. Tutkimuksen aineisto kerättiin sähköisellä kyselytutkimuksella, johon osallistuivat alakoulussa työskentelevät luokanopettajat. Aineisto analysoitiin teoriaohjaavan sisällönanalyysin vaiheiden kautta. Tutkimuksen tulosten mukaan luokanopettajien teoreettinen ymmärrys ympäristökasvatus-käsitteestä on monipuolinen ja yhteneväinen aikaisemman tutkimuksen kanssa. Käytäntöön liitettiin osittain samoja sisältöjä kuin teoriaan, mutta etenkään osallisuus ja toimijuus eivät toteutuneet koko opetusta ja muuta toimintaa läpäisevällä tavalla. Tutkimuksen tulokset osoittivat, että luokanopettajien ympäristökasvatustyötä tukevia tekijöitä ovat käytössä olevat resurssit, sisäinen motivaatio, vuorovaikutus työyhteisössä ja sen ulkopuolella, lait ja asetukset sekä eheyttävä opetus. Estäviä tekijöitä olivat riittämättömät resurssit, sosiaaliset haasteet, työkyky sekä aikataululliset haasteet

Continuous Mental Effort Evaluation during 3D Object Manipulation Tasks based on Brain and Physiological Signals

Designing 3D User Interfaces (UI) requires adequate evaluation tools to ensure good usability and user experience. While many evaluation tools are already available and widely used, existing approaches generally cannot provide continuous and objective measures of usa-bility qualities during interaction without interrupting the user. In this paper, we propose to use brain (with ElectroEncephaloGraphy) and physiological (ElectroCardioGraphy, Galvanic Skin Response) signals to continuously assess the mental effort made by the user to perform 3D object manipulation tasks. We first show how this mental effort (a.k.a., mental workload) can be estimated from such signals, and then measure it on 8 participants during an actual 3D object manipulation task with an input device known as the CubTile. Our results suggest that monitoring workload enables us to continuously assess the 3DUI and/or interaction technique ease-of-use. Overall, this suggests that this new measure could become a useful addition to the repertoire of available evaluation tools, enabling a finer grain assessment of the ergonomic qualities of a given 3D user interface.Comment: Published in INTERACT, Sep 2015, Bamberg, German

Words with the Maximum Number of Abelian Squares

An abelian square is the concatenation of two words that are anagrams of one another. A word of length $n$ can contain $\Theta(n^2)$ distinct factors that are abelian squares. We study infinite words such that the number of abelian square factors of length $n$ grows quadratically with $n$.Comment: To appear in the proceedings of WORDS 201