8,154 research outputs found
High-order harmonic generation from Rydberg states at fixed Keldysh parameter
Because the commonly adopted viewpoint that the Keldysh parameter
determines the dynamical regime in strong field physics has long been
demonstrated to be misleading, one can ask what happens as relevant physical
parameters, such as laser intensity and frequency, are varied while is
kept fixed. We present results from our one- and fully three-dimensional
quantum simulations of high-order harmonic generation (HHG) from various bound
states of hydrogen with up to 40, where the laser intensities and the
frequencies are scaled from those for in order to maintain a fixed
Keldysh parameter for all . We find that as we increase
while keeping fixed, the position of the cut-off scales in well
defined manner. Moreover, a secondary plateau forms with a new cut-off,
splitting the HHG plateau into two regions. First of these sub-plateaus is
composed of lower harmonics, and has a higher yield than the second one. The
latter extends up to the semiclassical cut-off. We find that this
structure is universal, and the HHG spectra look the same for all
when plotted as a function of the scaled harmonic order. We investigate the
-, - and momentum distributions to elucidate the physical mechanism
leading to this universal structure
Phase-dependent interference fringes in the wavelength scaling of harmonic efficiency
We describe phase-dependent wavelength scaling of high-order harmonic
generation efficiency driven by ultra-short laser fields in the mid-infrared.
We employ both numerical solution of the time-dependent Schr\"{o}dinger
equation and the Strong Field Approximation to analyze the fine-scale
oscillations in the harmonic yield in the context of channel-closing effects.
We show, by varying the carrier-envelope phase, that the amplitude of these
oscillations depend strongly on the number of returning electron trajectories.
Furthermore, the peak positions of the oscillations vary significantly as a
function of the carrier-envelope phase. Owing to its practical applications, we
also study the wavelength dependence of harmonic yield in the "single-cycle"
limit, and observe a smooth variation in the wavelength scaling originating
from the vanishing fine-scale oscillations.Comment: 5 pages, 4 figure
Anorexia Nervosa Ett Durkheimianskt perspektiv
I denna uppsats konstrueras en teoretisk modell över fenomenet sjĂ€lvsvĂ€lt/anorexia nervosa sett mot bakgrund av den teoretiska referensramen i Ămile Durkheims studie SjĂ€lvmordet. Den empiriska metoden baserar sig pĂ„ litteraturstudier och befintlig aktuell forskning om de bĂ„da fenomenen sjĂ€lvsvĂ€lt/anorexia nervosa och sjĂ€lvmord. Mitt syfte Ă€r att utröna huruvida de sociala orsaksfaktorer som förklarar variationen av sjĂ€lvmordsfrekvensen i olika typer av samhĂ€llen Ă€r de samma som ligger bakom fenomenet asketiskt religiöst fastande under medel-tiden och nutida anorektiskt beteende i icke-vĂ€sterlĂ€ndska och vĂ€sterlĂ€ndska samhĂ€llen.
Durkheim betonade att patologiska sociala fenomen kan orsakas bÄde av en alltför lÄngt dri-ven individualism och av dess motsats, en alltför stark reglering och integrering. Anorexia nervosa sÄsom sjukdomen yttrar sig i den sydasiatiska kulturen skulle kunna ses som symtom pÄ ett sociokulturellt system som genom sin struktur kan framkalla fenomen av fatalis-tisk/altruistisk art. I sina bakomliggande orsaker yttrar sig anorexia nervosa i denna kulturella kontext som en antites till de faktorer som förklarar fenomenet i vÀstvÀrlden dÀr samhÀlls-strukturen framkallar fenomen av egoistisk/anomisk art. PÄ var sin sida av den imaginÀra ska-la dÀr styrkan i samhÀllets integrering och reglering framtrÀder och fÀrgade av olika sociokulturella faktorer blir ÀndÄ konsekvensen samma sjukdomstillstÄnd
The ecological impact of artificial light at night in landscape architecture
Artificial light at night (ALAN) is an increasingly common form of light pollution that contributes to biodiversity loss, loss of dark habitats, disrupting populations both on an individual- and population level by invading biodiversity hot spots. Recent studies show that artificial light is increasing at a rate of approximately 6% annually over Earthâs surface, and 88% of Europe and 47% of the United States experience light pollution on a nightly basis. Although the primary function of artificial light is to enhance safety, security, aesthetics, and navigation, ecological disruption is often a resulting effect post-design. Despite its prevalence and ecological impact, there has been little research on avoiding light pollution in landscape architecture. This thesis presents precautionary methods and practices for landscape architects and other actors, to mitigate and avoid light pollution specifically integrating into areas and habitats where biodiversity is at risk.
In this thesis, various strategies and adaptations are used while utilising the Swedish legislation as a foundation and framework. In the context of the construction process (byggprocessen), landscape architects play a crucial role in the design department. However, they may face certain limitations when it comes to the construction of street lights. To create guidelines, it is important to identify and focus on the variables that landscape architects can take into consideration, manage, and design in relation to street lights. This thesis identified these variables as placement of street lights, type of light, colour, shielding, scheduling, appropriate light illuminance, and consideration of façade lighting.
By utilising strategies and guidelines, landscape architects and other professions can introduce a more informed and intentional design. The strategies and guidelines can help to reduce the negative impact of artificial light on biodiversity and local wildlife. This thesis offers important insights into the urgent need for effective solutions to address the growing problem of light pollution and provides guidance on how to achieve this in the context of landscape architecture.Artificiellt ljus pÄ natten (ALAN) Àr en allt vanligare form av ljusförorening som bidrar till förlust av biologisk mÄngfald, förlust av mörka habitat, störningar för populationer bÄde pÄ individ- och populationsnivÄ genom att invadera biologiska hotspots. Nya studier visar att artificiellt ljus ökar med circa 6% Ärligen över jordens yta, och att 88% av Europa och 47% av USA upplever ljusförorening varje natt. Trots att den primÀra funktionen av artificiellt ljus Àr att öka sÀkerhet, trygghet, estetik och navigering, sÄ Àr ekologiska störningar ofta resultatet efter designfasen. Trots dess utbredning och ekologiska pÄverkan har det varit lite forskning om att undvika ljusförorening i landskapsarkitektur. Denna uppsats presenterar försikitighetsÄtgÀrder och metoder för landskapsarkitekter och andra aktörer, för att minska och undvika ljusförorening speciellt i omrÄden och habitat dÀr biologisk mÄngfald Àr hotad.
I denna uppsats anvÀnds olika strategier och anpassningar med den Svenska lagstiftningen som grund och ram. I kontexten av byggprocessen spelar landskapsarkitekter en avgörande roll i designavdelningen. Dock kan de möta visa begrÀsningar nÀr det gÀller konstruktionen av gatubelysning. För att skapa riktlinjer Àr det viktigt att identifiera och fokusera pÄ variablerna som landskapsarkitekter kan ta hÀnsyn till, hantera och designa i relation till gatubelysning. Denna uppsats identifierade dessa variabler som placering av gatubelysning, typ av ljus, fÀrg, skÀrmning, schemalÀggning, lÀmplig belysningsstyrka och hÀnsyn till fasadbelysning.
Genom att anvÀnda strategier och riktlinjer kan landskapsarkitekter och andra aktörer introducera en mer informerad och medveten design. Strategierna och riktlinjerna kan hjÀlpa till att minska den negativa pÄverkan av artificiellt ljus pÄ biologisk mÄngfald och lokalt viltliv. Denna uppsats erbjuder viktiga insikter i den brÄdskande nödvÀndigheten av effektiva lösningar för att hantera det vÀxande problemet med ljusförorening och ger vÀgledning i hur man uppnÄr detta i kontexten av landskapsarkitektur
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Microbial Biodegradation of Lignocellulose for Ethanol Production
Bioethanol can be produced from a range of substrates and it is considered to be renewable. Lignocellulose is one of the substrates that can be used for bioethanol production. Genetic engineering of a microorganism that can completely convert all the sugars of cellulosic material into ethanol is one of the important steps for the production process.
This study has two parts that aim to produce bioethanol by using genetically modified microorganisms. The first part of the study deals with bioethanol production from lignocellulosic material by microbial fermentation in two steps. The first step is the degradation of the lignocellulosic material by Bacilli to produce cellobiose, and the second step is to convert cellobiose into glucose by a B-glucosidase expressing recombinant yeast strain. As lignocellulosic material, wood powder from industrial waste was used and the degradation of the wood powder into glucose was confirmed by following the growth curve of the microorganisms and through appropriate enzymatic assays.
The second part of the study utilizes two novel technologies, Yeast Artificial Chromosome (YAC) and Bridge-Induced Translocation (BIT) to introduce new, multi-factorial genetic traits into a yeast strain, a process that would otherwise take several time-consuming and labor-intensive rounds of genetic engineering. After cloning exogenous cellulases onto a YAC vector, this was transformed into a PEP4 mutant yeast upon which BIT technology was applied. This technology allowed the research to gain two advantages; one of them was to stabilize the YAC within the yeast genome and the other one was to have increased gene expression level consequent to the translocation event.
In conclusion, this work defines a successful microbial system that is able to efficiently utilize lignocellulosic material as a carbon source and a translocant yeast strain that has high level of cellulase activity
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