N-body Study of Anisotropic Membrane Inclusions: Membrane Mediated Interactions and Ordered Aggregation

We study the collective behavior of inclusions inducing local anisotropic curvatures in a flexible fluid membrane. The N-body interaction energy for general anisotropic inclusions is calculated explicitly, including multi-body interactions. Long-range attractive interactions between inclusions are found to be sufficiently strong to induce aggregation. Monte Carlo simulations show a transition from compact clusters to aggregation on lines or circles. These results might be relevant to proteins in biological membranes or colloidal particles bound to surfactant membranes.Comment: 4 pages, 3 figs, LaTe

Potential Utilization of Neutron Logging for Casing Cement Evaluation

Master's thesis in Petroleum engineeringVerification of casing cement integrity is crucial to ensure that the cement fulfills its purpose of zonal isolation, for optimal production and safety. This thesis introduces cement evaluation technology on the market today and highlights advantages and current limitations of each. The scope of this work was to assess neutron logging for the same purpose, and cases such as good cement, cement with channels, foamed cement and a through-tubing configuration has been modelled in a basic preliminary analysis. Results where compared to highlight relative differences in neutron attenuation. Other aspects of the neutron logging technology are assessed for a comprehensive review. This preliminary analysis has shown that neutrons have the potential to reach the cement-formation interface and be backscattered to the detector for all cases considered. Neutrons experience large attenuation in liquids present in or near the wellbore, while it is less attenuated for gas and foamed cement. For a single casing configuration, results indicate distinguishable results between good and channeled cement. For a through-tubing configuration it cannot be concluded the same as final energy were either too close to the good cement base case or undetectable. Assessment of other aspects has shown that adding tracer material to the cement can be beneficial in terms of increased absorption and neutron spectroscopy. While specific neutron sources have HSE concerns, there are available alternatives on the market. Neutron logging could present an increased cost which must be weighed against potential gains of applying this technology as a replacement or complimentary to existing cement evaluation methods. Based on the outcomes of this thesis, a paper to be published is drafted (Appendix C)

Dynamin recruitment by clathrin coats: a physical step?

Recent structural findings have shown that dynamin, a cytosol protein playing a key-role in clathrin-mediated endocytosis, inserts partly within the lipid bilayer and tends to self-assemble around lipid tubules. Taking into account these observations, we make the hypothesis that individual membrane inserted dynamins imprint a local cylindrical curvature to the membrane. This imprint may give rise to long-range mechanical forces mediated by the elasticity of the membrane. Calculating the resulting many-body interaction between a collection of inserted dynamins and a membrane bud, we find a regime in which the dynamins are elastically recruited by the bud to form a collar around its neck, which is reminiscent of the actual process preempting vesicle scission. This physical mechanism might therefore be implied in the recruitment of dynamins by clathrin coats.Comment: 11 pages, 6 figures, to appear in C.R.A.S. ser II

Indirect interactions of membrane-adsorbed cylinders

Biological and biomimetic membranes often contain aggregates of embedded or adsorbed macromolecules. In this article, the indirect interactions of cylindrical objects adhering to a planar membrane are considered theoretically. The adhesion of the cylinders causes a local perturbation of the equilibrium membrane shape, which leads to membrane-mediated interactions. For a planar membrane under lateral tension, the interaction is repulsive for a pair of cylinders adhering to the same side of the membrane, and attractive for cylinders adhering at opposite membrane sides. For a membrane in an external harmonic potential, the interaction of adsorbed cylinders is always attractive and increases if forces perpendicular to the membrane act on the cylinders.Comment: 9 pages, 8 figures; typos correcte

Satan’s romance with Romance: An analysis of satanic relationships and the projection of satanic wandering in Charlotte Dacre’s Zofloya, or the Moor (1806) and Matthew Lewis’s The Monk (1796)

Satan as a literary character is one of the most recurring characters throughout literature. The aim of this thesis is to explore a small fragment of the stories Satan has been a part of, and investigate the satanic impact on the characters that encounters and befriends the devil, in two literary works from the Romantic period. This pursuit will be conducted through an investigation of Satanic relations between the protagonists and Satan as represented in Charlotte Dacre’s Zofloya, or The Moor and Matthew Lewis’s The Monk. The Romantic period is significant in the history of Satan as a literary character, as a group of British artists and writers started to, think and create works about Satan, in a different manner than the writers that came before them. The fictional character Satan was no longer regarded as an arrogate driven by lust without means, but a sort of disturbed hero, that readers could sympathise with. As this thesis will argue, in Dacre’s – and Lewis’s works where we encounter Satan, romance is significant in the making of a Satanic character that is possible to be sympathetic towards, in these literary works Satan gains his sympathy by being portrayed as a victim of unrequited love. Dacre’s and Lewis’s works are particularly interesting in this instance since one is traditionally understood as being influenced by the other, even though the progression of the narrative and the end for the narrators have similarities, there are difference in their approach to the character of Satan when we consider the differences in the two ambiguous characters. Both authors are commonly regarded as conservatives of their time; as I will argue, and their approach in creation of these two at the time radical literary, and their commentary to gender, race and indulgence is ambiguous

Lipid Self-Spreading on Solid Substrates

This chapter is dedicated to wetting and fracturing processes involving molecular phospholipid films and high-energy solid surfaces. In these systems, wetting of planar surfaces occurs in an aqueous environment by means of self-spreading of phospholipid membranes from artificially generated lipid sources, which range from manually deposited single sources (multilamellar liposomes) to liposome suspensions of different particle sizes, which are directly pipetted onto the substrate. The most prominent of the molecular lipid films is the phospholipid bilayer, which constitutes the fundamental structure of the biological cell membrane. Lipid membranes have peculiar characteristics, are highly dynamic, feature two-dimensional fluidity, and can accommodate functional molecules. Understanding the interactions of lipid films with solid interfaces is of high importance in areas like cell biology, biomedical engineering, and drug delivery

«Å skrive seg et rom»

Artikkelen tar for seg aktørskap (‘agency’), et begrep som i økende grad blir brukt for å studere samspillet mellom sosiale og individuelle prosesser i andrespråkstilegnelse. I artikkelen undersøker jeg hvilket potensial begrepet har som analytisk verktøy for å studere andrespråksskriving. Gjennom å analysere fire tekster skrevet av en elev i grunnskoleopplæringen for minoritetsspråklig ungdom, utforsker jeg hvordan aktørskap kan operasjonaliseres og videreutvikles innenfor et dialogisk rammeverk. Formålet med artikkelen er dermed todelt og inkluderer både 1) å utforske hvordan aktørskap kan videreutvikles og operasjonaliseres i studier av andrespråksskriving og 2) diskutere hvordan aktørskap kan belyse og forklare viktige trekk ved andrespråksskriveres språk- og skriveutvikling. I artikkelen blir andrespråkstekstene analysert med tanke på hvordan de inngår i et dialogisk samspill med noen av de diskursive rammene som omgir skrivingen. Jeg argumenterer for at aktørskap kan forstås som evnen og muligheten til å skape et rom for seg selv i og gjennom teksten. Begrepet åpner derfor for en mulighet til å diskutere hvordan nye språkbrukere forhandler om medlemskap og konstruerer sine identiteter i en ny språkkultur, og kan bidra med interessante perspektiver på både andrespråksskriving spesielt og andrespråkslæring generelt

«Løslatelsens smerter» - En kvalitativ studie av utfordringene ved overgang fra fengsel til samfunn

Dette er en kvalitativ studie, med en kritisk, sosiologisk tilnærming til straffegjennomføring og tilbakeføring i Norge, sett i lys av den norske velferdsstaten og kriminalomsorgens rehabiliterende mandat. Gjennom intervjuer med 13 tidligere innsatte, utforsker studien følgende problemstilling: Hvilke utfordringer møter innsatte i deres tilbakeføringsprosesser fra fengsel til samfunn? For å besvare problemstillingen vil oppgaven også besvare følgende forskningsspørsmål: (1) Hvilke implikasjoner har disse utfordringene for tilbakeføringsprosessen? og (2) Hvilke tiltak kan redusere utfordringene innsatte møter på i tilbakeføringsprosessen? Studiens funn inviterer til en kritisk diskusjon av den norske velferdsstaten og norsk rehabiliteringspolitikk. Problemstillingen diskuteres i samspill med habitus, stigma og andre relevante sosiologiske teorier. Studien viser til at domfelte står ovenfor en rekke hindringer i deres tilbakeføringsprosesser, både under og etter soning. Totalt ni hindringer blir analysert og utgjør: «soningsmodus», økt risiko- og sikkerhetsfokus, innsatt-betjent-forholdet, manglende forberedelser til løslatelse, «overgangsjokket», et komplisert velferdssystem, «negativ» sosial kapital, «gaten» og fengselets «nærvær», og behovet for å jobbe langsiktig med tilpasning. Studien viser til at tilbakeføring kan utgjøre en lang og smertefull prosess, med tilbakeslag og tilbakefall til narkotikamisbruk og kriminalitet. En gjennomgående kritisk åre i studien er ideen om Kriminalomsorgens, men også den norske stats, «antistrukturelle» tilnærming til straff og tilbakeføring. Avslutningsvis drøftes sosiologien og strafferetten opp mot hverandre, der studien argumenterer for en bredere implementering av sosiologien i samfunnets forståelser av kriminalitet og tilbakeføring

Fluctuations of the Casimir-like force between two membrane inclusions

Although Casimir forces are inseparable from their fluctuations, little is known about these fluctuations in soft matter systems. We use the membrane stress tensor to study the fluctuations of the membrane-mediated Casimir-like force. This method enables us to recover the Casimir force between two inclusions and to calculate its variance. We show that the Casimir force is dominated by its fluctuations. Furthermore, when the distance d between the inclusions is decreased from infinity, the variance of the Casimir force decreases as -1/d^2. This distance dependence shares a common physical origin with the Casimir force itself.Comment: 5 pages, 3 figure