Nonionic Hydrophilic Surfaces: Adsorption and Interactions

An overview is given of recent studies of nonionic, hydrophilic surfaces formed by the adsorption of surfactants or surface active polymers. Hydrophobic surfaces can be easily hydrophilized by the adsorption of nonionic surfactants or block copolymers containing hydrophobic chain segments; the cooperative interaction between the hydrocarbon moieties contributes more to the free energy of adsorption than the interaction with the hydro- phobic surface. Hydrophilic layers are also readily formed on hydrophilic surfaces provided specific interaction between the hydrophilic end groups and the surface creates a sufficiently hydrophobic surface so that a second layer can be formed through cooperative interaction. The temperature dependence of the interaction forces between layers of surfactants can be closely correlated with their phase equilibria with water. In order to prevent protein adsorption the surface should be neither charged nor hydrophobic; it is shown that, accordingly, protein adsorption is extremely low on polyethylene oxide-covered surfaces

Gårdarnas Smaker

Historiskt sett har det varit svårt för småskaliga livsmedelsproducenter att få marknadstillträde. Dagligvaruhandeln har stor makt över vad som saluförs i butikerna och butikskedjorna har strävat mot ett fåtal leverantörer med hög effektivitet. För att överbrygga dessa problem har en grupp småskaliga livsmedelsproducenter i Västeråstrakten startat en ekonomisk förening vid namn Gårdarnas Smaker. Denna studie analyserar olika faktorer, som påverkar Gårdarnas Smakers utveckling. I problemanalysen identifieras fyra faktorer, som påverkar Gårdarnas Smakers grad av framgång. Dessa faktorer är konceptets utformning, kapitalanskaffning, gratispassagerarproblem samt associationsform och styrning. Jämförelser med två liknande koncept, Dalslandsmat och Sjuhäradsmat, vilka båda är ekonomiska föreningar görs. Även Bjäre Hembygd, som är ett aktiebolag, används som jämförelseobjekt. Den teoretiska bas, som använts för att analysera Gårdarnas Smaker, är agent- och äganderättsteorierna. Agentteorin innebär att agenten anlitas av huvudmannen för att göra något i den senares intresse. Förutsättningar för teorin är individuell nyttomaximering, begränsad rationalitet, och informationsasymmetri. Grundtanken i äganderättsteorin är att det man äger, det vårdar man. Äganderättsproblem kan delas in i problem med gemensam egendom, horisontproblem samt portföljproblem. Konceptets utformning och flexibilitet är av stor vikt, då efterfrågan på lokalproducerade livsmedel har ökat. Dessutom har lokalproducerade livsmedel under senaste tiden fått nya förutsättningar på marknaden. Det blir därmed viktigt att kunna anpassa verksamheten till omvärldsförändringar för att kunna kostnadsminimera, effektivisera samt bibehålla produktiviteten. Kapitalanskaffningen i Gårdarnas Smaker har i ett första skede skett genom en medlemsavgift på 2500 kr. Ytterligare kapital tillkommer genom en serviceavgift på fyra procent av försäljningsbeloppet. Detta föranleder en låg kapitalnivå som begränsar flexibiliteten vid en marknadsförändring, vilket medför sårbarhet. Olika former av gratispassagerarproblem dels i form av delaktighet i styrningen och graden av engagemang och dels i form av kapitalnivån förekommer i Gårdarna Smaker. Ett fåtal av medlemmarna visar mycket starkt engagemang och delaktighet i styrningen av Gårdarnas Smaker, medan de andra inte har lika stort engagemang. Valet av associationsform var i Gårdarnas Smakers fall tämligen naturligt. I en ekonomisk förening har alla medlemmar lika möjlighet att vara delaktiga i styrningen, och uppstartskostnaderna för en ekonomisk förening är låga. Styrningen av Gårdarnas Smaker blir komplex, då alla större beslut måste förankras i medlemskåren, där varje medlem har en röst.Historically it has been difficult for small-scale food-producers to gain market access. The three large chains dominating the Swedish retail market have great power over what is to be sold in the stores, and they strive for a small number of suppliers with high efficiency. To break these problems a group of small-scale food-producers in the Västeråsarea started a cooperative firm named Gårdarnas Smaker. This study analyses different factors that affect the development of Gårdarnas Smaker. Four such factors are identified in the problem analysis. These are; design of the concept, capital acquisition, freerider-problems and legal form along with control. Comparisons with similar projects like Dalslandsmat and Sjuhäradsmat, which both are co-operatives, are made. Bjäre Hembygd which is an investor owned firm is also used as comparison. The theories used to analyse Gårdarnas Smaker are the agency and property rights theories. The agency theory implies that an agent is engaged by the principal to do something in his interest. The presumptions of the theory are individual profit-maximisation, bounded rationality and asymmetric information. The cornerstone in the property rights theory is that what you own is something you take care of. Property rights problem can be divided into problems with joint resources, horizon problems and portfolio problems. The design of the concept and flexibility is of great importance when the demand for locallyproduced food has increased during the last period of time, and locally produced food has got new conditions on the market. Therefore it stresses to adapt the activities due to changes on the market, to be able to maintain efficiency and productivity. The capital acquisition in Gårdarnas Smaker takes place by a member-fee of 2500 SEK. Additional capital occurs by a service-fee of four percent. This leads to a low level of capital which restricts flexibility in a change on the market, which leads to vulnerability. Different types of freerider problems occur in Gårdarnas Smaker both in terms participation in the control and the degree of engagement and in terms of amount of capital within the cooperative. Some of the members show very strong engagement and participation in the control of Gårdarnas Smaker, while the others don’t have the same engagement. The selection of type of association in the Gårdarnas Smaker’s case was fairly simple. In a cooperative all members have the same possibility to take part in the control, and the start-upcosts in a co-operative are low. The control of Gårdarnas Smaker turns complex when all major decisions have to be approved by the membership, where each member has one vote

On modeling and measuring viscoelasticity with dynamic Atomic Force Microscopy

The interaction between a rapidly oscillating atomic force microscope tip and a soft material surface is described using both elastic and viscous forces with a moving surface model. We derive the simplest form of this model, motivating it as a way to capture the impact dynamics of the tip and sample with an interaction consisting of two components: interfacial or surface force, and bulk or volumetric force. Analytic solutions to the piece-wise linear model identify characteristic time constants, providing a physical explanation of the hysteresis observed in the measured dynamic force quadrature curves. Numerical simulation is used to fit the model to experimental data and excellent agreement is found with a variety of different samples. The model parameters form a dimensionless impact-rheology factor, giving a quantitative physical number to characterize a viscoelastic surface that does not depend on the tip shape or cantilever frequency.Comment: 13 pages, 7 figure

Microstructure of chemically modified wood using X-ray computed tomography in relation to wetting properties

X-ray computed tomography (XCT) was utilized to visualize and quantify the 2D and 3D microstructure of acetylated southern yellow pine (pine) and maple, as well as furfurylated pine samples. The total porosity and the porosity of different cell types, as well as cell wall thickness and maximum opening of tracheid lumens were evaluated. The wetting properties (swelling and capillary uptake) were related to these microstructural characteristics. The data show significant changes in the wood structure for furfurylated pine sapwood samples, including a change in tracheid shape and filling of tracheids by furan polymer. In contrast, no such changes were noted for the acetylated pine samples at the high resolution of 0.8 mu m. The XCT images obtained for the furfurylated maple samples demonstrated that all ray cells and some vessel elements were filled with furan polymer while the fibers largely remained unchanged. Furfurylation significantly decreased the total porosity of both the maple and pine samples. Furthermore, this was observed in both earlywood (EW) and latewood (LW) regions in the pine samples. In contrast, the total porosity of pine samples was hardly affected by acetylation. These findings are in line with wetting results demonstrating that furfurylation reduces both swelling and capillary uptake in contrast to acetylation which reduces mostly swelling. Furfurylation significantly increased the cell wall thickness of both the maple and pine samples, especially at higher levels of furfurylation

Effect of solvent quality and chain density on normal and frictional forces between electrostatically anchored thermoresponsive diblock copolymer layers

Equilibration in adsorbing polymer systems can be very slow, leading to different physical properties at a given condition depending on the pathway that was used to reach this state. Here we explore this phenomenon using a diblock copolymer consisting of a cationic anchor block and a thermoresponsive block of poly(2-isopropyl-2-oxazoline), PIPOZ. We find that at a given temperature different polymer chain densities at the silica surface are achieved depending on the previous temperature history. We explore how this affects surface and friction forces between such layers using the atomic force microscope colloidal probe technique. The surface forces are purely repulsive at temperaturesPeer reviewe

Expression of 5-lipoxygenase and 15-lipoxygenase in rheumatoid arthritis synovium and effects of intraarticular glucocorticoids

The past years have witnessed tremendous progress in the treatment of rheumatoid arthritis, a chronic debilitating autoimmune disease mainly characterized by joint inflammation with progressive tissue destruction and loss of function. This condition affects 0.5-1% of the population, is associated with important co-morbidities and represents a heavy economical burden. New strategies, employing early and aggressive therapies with classical drugs or new agents, have resulted in impressive improvements in controlling disease activity. In some cases they even lead to clinical remission. Despite potent and efficient biological agents that specifically modulate distinct pathological pathways a large proportion of patients remain unresponsive to these therapies; drug-free remission is also difficult to achieve since attempting discontinuation of treatment usually results in disease flare. In rheumatoid arthritis joints there is a constant activation of complex networks of cytokines and factors mediating immune interactions and inflammation, in which prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) are important players and contributors to pathogenesis. Our research aimed to investigate the synovial expression of enzymes controlling prostaglandin E2 synthesis and degradation – cyclooxygenase (COX) 1 and 2, microsomal prostaglandin E2 synthase 1 (MPGES1) and 15-prostaglandin dihydrogenase (15-PGDH) as well as enzymes involved in leukotriene synthesis, such as 5-lipoxygenase (LO) and 15-LO. In addition, we evaluated how traditional and new therapies influence these pathways, by analyzing enzyme expression before and after systemic treatment with tumor necrosis factor (TNF) antagonists, rituximab or methotrexate, as well as before and after intra-articular treatment with glucocorticoids. We also evaluated the in vitro effects of TNF antagonists and glucocorticoids on synovial fluid cells and that of methotrexate on synovial fibroblasts. We demonstrated that synovial tissue from RA patients displayed an important expression of enzymes involved in the metabolism of PGE2, as well as 5-LO and 15-LO. MPGES1 and COX-2, the inflammation-inducible enzymes co-localized mainly in fibroblasts and macrophage-like cells and accounted for the local PGE2 production. Intra-articular glucocorticoids significantly reduced all enzymes involved in the PGE2 cascade – COX-1 and COX-2, MPGES1 and 15-PGDH, but also 5-LO, responsible for leukotriene formation. However, they did not influence the expression of 15-LO, an enzyme involved in the formation of both pro-and anti-inflammatory lipid mediators. Regarding the effects of TNF blockers, rituximab or methotrexate, they did not alter the expression profile of enzymes involved in PGE2 metabolism despite showing clinical efficiency in improving disease activity. Although anti-TNF agents reduced the in vitro expression of MPGES1 and COX-2 in synovial fluid cells, the lack of effect ex vivo in biopsies emphasized once again the differences between synovial compartments and possibly the difficulty in mimicking the micro-environment at the site of inflammation in vitro. In conclusion, this thesis demonstrates that potent anti-rheumatic drugs currently used in the clinic with good efficiency also leave inflammatory pathways un-affected, which may account for subclinical ongoing disease activity. Blocking the PGE2 pathway by using MPGES1 inhibitors as combination therapy may show benefit in dampening ongoing local inflammation

Polymersomes at the solid-liquid interface:Dynamic morphological transformation and lubrication

Polymersomes are hollow spheres self-assembled from amphiphilic block copolymers of certain molecular architecture. Whilst they have been widely studied for biomedical applications, relatively few studies have reported their interfacial properties. In particular, lubrication by polymersomes has not been previously reported. Here, interfacial properties of polymersomes self-assembled from poly(butadiene)-poly(ethylene oxide) (PBD-PEO; molecular weight 10,400 g mol−1) have been studied at both hydrophilic and hydrophobic surfaces. Their morphology at silica and mica surfaces was imaged with quantitative nanomechanical property mapping atomic force microscopy (QNM AFM), and friction and surface forces they mediate under confinement between two surfaces were studied using colloidal probe AFM (CP-AFM). We find that the polymersomes remained intact but adopted flattened conformation once adsorbed to mica, with a relatively low coverage. However, on silica these polymersomes were unstable, rupturing to form donut shaped residues or patchy bilayers. On a silica surface hydrophobized with a 19 nm polystyrene (PS) film, the polymer vesicles formed a more stable layer with a higher surface coverage as compared to the hydrophilic surface, and the interfacial structure also evolved over time. Moreover, friction was greatly reduced on hydrophobized silica surfaces in the presence of polymersomes, suggesting their potential as effective aqueous lubricants.</p

Thermoresponsive Pentablock Copolymer on Silica : Temperature Effects on Adsorption, Surface Forces, and Friction

The adsorption of hydrophilic or amphiphilic multiblock copolymers provides a powerful means to produce well-defined "smart" surfaces, especially if one or several blocks are sensitive to external stimuli. We focus here on an A-B-A-B-A copolymer, where A is a cationic poly((3acrylamido-propyl)-trimethylammonium chloride) (PAMPTMA) block containing 15 (end blocks) or 30 (middle block) repeat units and B is a neutral thermosensitive water-soluble poly(2-isopropyl-2-oxazoline) (PIPOZ) block with 50 repeat units. X-ray reflectivity and quartz crystal microbalance with dissipation monitoring were employed to study the adsorption of PAMPTMA(15)-PAMPTMA(30)-PIPOZ(50)-PAMPTMA(15) on silica surfaces. The latter technique was employed at different temperatures up to 50 degrees C. Surface forces and friction between the two silica surfaces across aqueous pentablock copolymer solutions at different temperatures were determined with the atomic force microscopy colloidal probe force and friction measurements. The cationic pentablock copolymer was found to have a high affinity to the negatively charged silica surface, leading to a thin (2 nm) and rigid adsorbed layer. A steric force was encountered at a separation of around 3 nm from hard wall contact. A capillary condensation of a polymer-rich phase was observed at the cloud point of the solution. The friction forces were evaluated using Amontons' rule modified with an adhesion term.Peer reviewe