Lipid ion channels and the role of proteins

Synthetic lipid membranes in the absence of proteins can display quantized conduction events for ions that are virtually indistinguishable from those of protein channel. By indistinguishable we mean that one cannot decide based on the current trace alone whether conductance events originate from a membrane, which does or does not contain channel proteins. Additional evidence is required to distinguish between the two cases, and it is not always certain that such evidence can be provided. The phenomenological similarities are striking and span a wide range of phenomena: The typical conductances are of equal order and both lifetime distributions and current histograms are similar. One finds conduction bursts, flickering, and multistep-conductance. Lipid channels can be gated by voltage, and can be blocked by drugs. They respond to changes in lateral membrane tension and temperature. Thus, they behave like voltage-gated, temperature-gated and mechano-sensitive protein channels, or like receptors. Lipid channels are remarkably under-appreciated. However, the similarity between lipid and protein channels poses an eminent problem for the interpretation of protein channel data. For instance, the Hodgkin-Huxley theory for nerve pulse conduction requires a selective mechanism for the conduction of sodium and potassium ions. To this end, the lipid membrane must act both as a capacitor and as an insulator. Non-selective ion conductance by mechanisms other than the gated protein-channels challenges the proposed mechanism for pulse propagation. ... Some important questions arise: Are lipid and protein channels similar due a common mechanism, or are these similarities fortuitous? Is it possible that both phenomena are different aspects of the same phenomenon? Are lipid and protein channels different at all? ... (abbreviated)Comment: 10 pages, 10 figures - accepted by 'Accounts of Chemical Research

The Typology of Foreignness. A Case Study of Othering & Belonging amongst Refugees in Northern Norway

In this thesis I examine the relationship between social boundaries and processes of othering and belonging amongst refugees in a Northern Norwegian community. I find that organizing concepts such as 'integration', 'culture' and 'second generation immigrant' permeate everyday talk on, and definitions of refugees amongst my Norwegian majority informants. In this context, I argue that dynamics of micro-humiliation may arise as a consequence to widespread and largely self-evident cultural assumptions about belonging and non-belonging along the Norwegian/refugee divide which come together as a particular type of othering: 'A typology of foreignness'. To discuss how the typology of foreignness may transcend into experiences of micro-humiliation amongst societal newcomers, I develop the concept of 'total identification'. I argue that the use of labelling concepts such as 'immigrant' may translate into a problematic form of identity-based reductionism, overshadow individual constellations of personhood and routinely invite subject positions towards refugees with a taken-for-granted ontological quality of ethnic/cultural non-belonging. I then go on to examine social boundaries as they are experienced from the position of individuals with a refugee status. I discuss how certain markers of foreignness, such as religion, skin colour, language, gender and ideas of 'cultural difference' may be intersectionally linked and appear to be cumulative and mutually reinforcing. To describe this individual multidimensionality of micro-humiliation, and how the typology of foreignness may impact people in varying ways according to the broader situatedness of their identity, I develop the concept of 'negative symbolic capital'. I argue that what is often understood as dynamics of ethnic/residential segregation may be thought of as a feedback loop of foreignness. Thus, to emphasise one's minority status may be an emergency plan for establishing belonging; a way for some individuals to create a sense of social attachment, self-worth and dignity in a society where Norwegian ethnicity has become a highly salient marker for 'genuine' belonging within the nation

Solitary electromechanical pulses in Lobster neurons

Investigations of nerve activity have focused predominantly on electrical phenomena. Nerves, however, are thermodynamic systems, and changes in temperature and in the dimensions of the nerve can also be observed during the action potential. Measurements of heat changes during the action potential suggest that the nerve pulse shares many characteristics with an adiabatic pulse. First experiments in the 1980s suggested small changes in nerve thickness and length during the action potential. Such findings have led to the suggestion that the action potential may be related to electromechanical solitons traveling without dissipation. However, they have been no modern attempts to study mechanical phenomena in nerves. Here, we present ultrasensitive AFM recordings of mechanical changes on the order of 2 - 12 {\AA} in the giant axons of the lobster. We show that the nerve thickness changes in phase with voltage change. When stimulated at opposite ends of the same axon, colliding action potentials pass through one another and do not annihilate. These observations are consistent with a mechanical interpretation of the nervous impulse.Comment: 9 pages, 4 figure

A critical review of the role of repair cafés in a sustainable circular transition

Extending the useful life of consumer products is a critical element in the circular economy. Although commercial repair is an established part of the global economy, the repair is often conducted informally. This means that non-commercial repair ecosystems exist, including the international network of repair cafés, spreading worldwide to over 2000 repair cafés in 37 countries (April 2021). As the first review on this topic, this article investigates and gains more knowledge about repair cafés, and critically assesses their role as a sustainability initiative, i.e., how the concept may translate into a broader sustainability context. A systematic literature review (2010–2020) was conducted, including 44 articles in descriptive and content analyses. The bibliometric data revealed an increase in the number of publications on repair cafés, particularly over the last four years, indicating that repair cafés as a research topic have started to gain attention, and this is likely to grow in numbers. However, the significant number of different places of publication indicates that this is not (yet) a well-established field with defined research channels. The content analysis revealed that the concept has spread to a range of different contexts, beyond the original scope, influencing the mindset and acts of a broad field of practitioners. This indicates a wide range of possibilities for the expansion of the concept of repair cafés, bringing different expectations on calling into question the future role of repair cafés. However, the aims of the people involved in repair cafés span from the altruistic and strategic, over personal gains, to critical consumer, financial and educational aims. This may challenge repair cafés’ future role(s), i.e., ambitions set by the international organisation of repair cafés. Notably, the ambition for actors at the micro-level is to feed in data on repair and achieve ‘collaborative repair’, as the aims of the people involved are complex, and their expectations lack alignment, both vertically and horizontally

Lipid Membranes as Non-Linear Capacitors

Digitalitzat per Artypla