| 1. |
- Backlund, S, et al.
(author)
-
Partial phase behavior of ionic microemulsions stabilized by sodium dodecylsulfate and alcohol cosurfactants
- 1992
-
In: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 88, s. 36-41
-
Journal article (peer-reviewed)abstract
- Ionic microemulsions, stabilized by sodium dodecylsulfate and alcohol cosurfactants, have been characterized with respect to phase behavior, particularly the composition of the different phases in Winsor type I, II and III systems. The system containing brine, octane, sodium dodecylsulfate and 1-butanol shows a regular phase behavior, in conformity with the anticipated behavior, i.e., 2-3-2 phases. The phase transitions with increasing 1-butanol concentration are analogous to those occurring with increasing salinity, when compared with previous investigations. For the system containing brine, cyclohexane, sodium dodecylsulfate and benzyl alcohol, the behavior becomes more complex, even at low surfactant contents. The transitions are 2-3-2-3-2 phases over a wide composition range. The compositions of the phases at equilibrium are discussed in relation to structural considerations, as determined by conductivity and NMR self-diffusion measurements.
|
|
| 2. |
- Lundgren, Sarah M., et al.
(author)
-
Effects of unsaturation on film structure and friction of fatty acids in a model base oil
- 2008
-
In: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 326:2, s. 530-536
-
Journal article (peer-reviewed)abstract
- The normal and friction forces between layers of three fatty acids (stearic, oleic, and linoleic acid) and a rosin acid (dehydroabietic acid) have been measured in n-hexadecane with a surface forces apparatus. Stearic, oleic, and dehydroabietic acid form loose-packed monolayers on mica surfaces when adsorbed from dry n-hexadecane. Linoleic acid forms an additional dimer layer between monolayer-covered surfaces, where it is stabilized by interactions between the double-bond-rich regions of the molecules. The monolayers formed by linoleic and dehydroabietic acid are thinner than the ones formed by stearic and oleic acid, but are not as easily removed from between the mica surfaces when the load or pressure is increased. The friction force increased linearly with load in all systems, and the friction coefficient increased with increasing unsaturation. Linoleic acid showed two regimes of linear friction with increasing load, corresponding to two different film thicknesses. its friction was sensitive to sliding speed and adsorption time, and the thinner film observed at higher load had a lower friction coefficient. Such features were not observed for stearic and oleic acid, where the monolayers were removed and the friction coefficient changed to that of pure n-hexadecane at a pressure of 3.5 MPa.
|
|
| 3. |
- Ruths, M., et al.
(author)
-
Friction of fatty acids in nanometer-sized contacts of different adhesive strength
- 2008
-
In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 24:4, s. 1509-1516
-
Journal article (peer-reviewed)abstract
- The effects of adhesion, contact area, and pressure on the lubricating properties of self-assembled monolayers on steel have been investigated with friction force microscopy. The adsorbed molecules were fatty acids with varying degrees of unsaturation (0-2 double bonds; stearic, oleic, and linoleic acid) and a rosin acid (dehydroabietic acid), adsorbed from n-hexadecane solution. The friction of these loose-packed monolayers was studied in dry N-2 gas and in ethanol. Low adhesion (in ethanol) resulted in a linear increase in friction force at low loads, that is, F = mu L, whereas higher adhesion (in N-2 gas) gave an apparent area-dependence at low loads of the form F = S(c)A, where S-c is the critical shear stress. A recent model for the contact mechanics of a compliant elastic film confined between stiffer substrates was applied to the data obtained in dry N-2. Using this approach, we obtained interfacial energies of the compliant monolayers in good agreement with van der Waals-Lifshitz theory. With a low monolayer elastic modulus of E-1' = 0.2 GPa, we obtained a slightly higher value of S, for stearic acid than that established for more close-packed stearic acid monolayers. An increase of p and Sc was found with increasing degree of unsaturation of the fatty acid.
|
|
| 4. |
- Jin, R., et al.
(author)
-
Bioinspired Self-Assembled 3D Patterned Polymer Textures as Skin Coatings Models : Tribology and Tactile Behavior
- 2020
-
In: Biotribology. - : Elsevier Ltd. - 2352-5738. ; 24
-
Journal article (peer-reviewed)abstract
- It is well known that during evolution, specific surface patterns emerged (e.g., on lotus leaves and butterfly wings) endowed with many remarkable surface properties (superhydrophobicity, vibrant structural color, delicate textures, etc.). In order to obtain these natural effects in cosmetics, we look for ways to transfer topographic patterns in coatings and treatments. Textured polymer surfaces were studied to explore their friction properties on the microscale and possible correlations with human tactile friction on the macroscale. We have chosen self-assembling block and random copolymers as model systems to prepare reliable biomimetic films with different micrometer and nanometer scale randomly patterned and randomly rough surfaces. The surface texture of the films was characterized by atomic force microscopy (AFM), and their tribological (friction) properties were studied with a surface forces apparatus (SFA) at a low sliding speed of 3 μm/s and at a speed of 10 cm/s relevant to realistic applications. The results are evaluated in terms of polymer segment mobility, interpenetration, entanglement and relaxation at interfaces, surface texture as described by roughness parameters, and interlocking of asperities. A stiction spike (static friction) was commonly found for the randomly patterned glassy polymer films. Random roughness patterns made from semi-crystalline polymers above their Tg gave high friction at low speed, but their friction coefficients were reduced at high speed due to less time for local entanglement and relaxations. The friction response of one of them was also affected differently by humidity than that of glassy polymer films. Tactile friction measurements with a human finger sliding against the polymer films revealed that the textures also provided differences at the macroscale, although the dynamic changes possibly due to lipid transfer, occlusion of moisture and/or damage of the films makes it difficult to draw robust conclusions. Finally, as an example, it is shown that these textures can be transferred to a soft elastomeric skin mimic substrate. This study introduces the concept of surface patterning by self-assembly to deliver tactile sensorial properties in coatings.
|
|
| 5. |
- Meling, H. M., et al.
(author)
-
Level of education and sustainable return to work among long-term sick-listed workers with depression: a register-based cohort study (The Norwegian GP-DEP Study)
- 2023
-
In: Bmj Open. - 2044-6055. ; 13:7
-
Journal article (peer-reviewed)abstract
- ObjectivesSick-listed workers with depression are at higher risk of long-term, recurrent sickness absence and work disability, suggesting reduced likelihood of sustainable return to work (SRTW). Though likelihood of RTW has been associated with education level, less is known about the association over time, post-RTW. We aimed to investigate associations between educational level and SRTW among long-term sick-listed workers with depression. MethodsNationwide cohort study, based on linked data from Norwegian health and population registries, including all inhabitants of Norway aged 20-64 years on long-term sick leave with a depression diagnosis given in general practice between 1 January 2009 and 10 April 2011 (n=13.624, 63.7% women). Exposure was the highest attained education level (five groups). Three outcome measures for SRTW were used, with 0 days, & LE;30 days and & LE;90 days of accumulated sickness absence post-RTW during a 2-year follow-up. Associations between exposure and outcomes were estimated in gender-stratified generalised linear models, adjusting for sociodemographic factors and duration of sick leave. ResultsHigher-educated workers had a higher likelihood of SRTW 0, SRTW & LE;30 and SRTW & LE;90 than the lowest-educated groups in the crude models. Among men, this association was mainly explained when adjusting for occupation. Among women, the highest educated group had a higher likelihood of SRTW 0 (RR=1.45, 95% CI 1.23 to 1.71) and SRTW & LE;30 and SRTW & LE;90 in the fully adjusted models. ConclusionsAn educational gradient in SRTW was mainly explained by occupation among men but not among women. These findings suggest gendered differences in associations between education level and SRTW, which could inform interventions aiming to promote equal opportunities for SRTW.
|
|
| 6. |
|
|
| 7. |
- Ruths, M, et al.
(author)
-
Friction of fatty acids in nanometer-sized contacts of different adhesive strength
- 2008
-
In: Langmuir. - 0743-7463 .- 1520-5827. ; 24, s. 1509-1516
-
Journal article (peer-reviewed)abstract
- The effects of adhesion, contact area, and pressure on the lubricating properties of self-assembled monolayers on steel have been investigated with friction force microscopy. The adsorbed molecules were fatty acids with varying degrees of unsaturation (0-2 double bonds; stearic, oleic, and linoleic acid) and a rosin acid (dehydroabietic acid), adsorbed from n-hexadecane solution. The friction of these loose-packed monolayers was studied in dry N2 gas and in ethanol. Low adhesion (in ethanol) resulted in a linear increase in friction force at low loads, that is, F = L, whereas higher adhesion (in N2 gas) gave an apparent area-dependence at low loads of the form F = ScA, where Sc is the critical shear stress. A recent model for the contact mechanics of a compliant elastic film confined between stiffer substrates was applied to the data obtained in dry N2. Using this approach, we obtained interfacial energies of the compliant monolayers in good agreement with van der Waals-Lifshitz theory. With a low monolayer elastic modulus of = 0.2 GPa, we obtained a slightly higher value of Sc for stearic acid than that established for more close-packed stearic acid monolayers. An increase of and Sc was found with increasing degree of unsaturation of the fatty acid.
|
|
| 8. |
- Urbina, D. I., et al.
(author)
-
Limiting the impact of stealthy attacks on Industrial Control Systems
- 2016
-
In: CCS '16 Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security. - New York, NY, USA : ACM Digital Library. - 9781450341394 ; , s. 1092-1105
-
Conference paper (peer-reviewed)abstract
- While attacks on information systems have for most practical purposes binary outcomes (information was manipulated/eavesdropped, or not), attacks manipulating the sensor or control signals of Industrial Control Systems (ICS) can be tuned by the attacker to cause a continuous spectrum in damages. Attackers that want to remain undetected can attempt to hide their manipulation of the system by following closely the expected behavior of the system, while injecting just enough false information at each time step to achieve their goals. In this work, we study if physics-based attack detection can limit the impact of such stealthy attacks. We start with a comprehensive review of related work on attack detection schemes in the security and control systems community. We then show that many of these works use detection schemes that are not limiting the impact of stealthy attacks. We propose a new metric to measure the impact of stealthy attacks and how they relate to our selection on an upper bound on false alarms. We finally show that the impact of such attacks can be mitigated in several cases by the proper combination and configuration of detection schemes. We demonstrate the effectiveness of our algorithms through simulations and experiments using real ICS testbeds and real ICS systems.
|
|
