| 1. |
- Tonpheng, Bounphanh, 1959-, et al.
(författare)
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Tensile strength and young's modulus of polyisoprene/single-wall carbon nanotube composites increased by high pressure cross-linking
- 2010
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Ingår i: Macromolecules. - : American Chemical Society. - 0024-9297 .- 1520-5835. ; 43:18, s. 7680-7688
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Tidskriftsartikel (refereegranskat)abstract
- High-viscosity liquid cis-1,4 polyisoprene (PI), with up to 20 wt % single-wall carbon nanotubes (SWCNTs), has been cross-linked by high pressure and high temperature (HP&HT) treatment at 513 K and pressures in the range 0.5 to 1.5 GPa to yield densified network polymer composites. A composite with 5 wt % SWCNTs showed 2.2 times higher tensile strength σUTS (σUTS = 17 MPa), 2.3 times higher Young’s modulus E (E = 220 MPa) and longer extension at break than pure PI. The improvement is attributed to SWCNT reinforcement and improved SWCNT−PI interfacial contact as a result of the HP&HT cross-linking process, and reduced brittleness despite a higher measured cross-link density than that of pure PI. The latter may originate from an effect similar to crazing, i.e., bridging of microcracks by polymer fibrils. We surmise that the higher cross-link densities of the composites are due mainly to physical cross-links/constraints caused by the SWCNT−PI interaction, which also reflects the improved interfacial contact, and that the CNTs promote material flow by disrupting an otherwise chemically cross-linked network. We also deduce that the PI density increase at HP&HT cross-linking is augmented by the presence of CNTs.
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| 2. |
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| 3. |
- Andersson, Ove, et al.
(författare)
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Effect of pressure on thermal conductivity and pressure collapse of ice in a polymer-hydrogel and kinetic unfreezing at 1 GPa
- 2011
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 134:12, s. 124903-
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Tidskriftsartikel (refereegranskat)abstract
- We report a study of aqueous solutions of poly(vinylalcohol) and its hydrogel by thermal conductivity,κ, and specific heat measurements. In particular, we investigate (i) the changes in the solution and the hydrogel at 0.1 MPa observed in the 350-90 K range and of the frozen hydrogel at 130 K observed in the range from 0.1 MPa to 1.3 GPa, and (ii) the nature of the pressure collapse of ice in the frozen hydrogel and kinetic unfreezing on heating of its high density water at 1 GPa. The water component of the polymer solution on cooling either first phase separates and then freezes to hexagonal ice or freezes without phase separation and the dispersed polymer chains freeze-concentrate in nanoscopic and microscopic regions of the grain boundaries and grain junctions of the ice crystals in the frozen state of water in the hydrogel. The change in κ with temperature at 1 bar is reversible with some hysteresis, but not reversible with pressure after compression to 0.8 GPa at 130 K. At high pressures the crystallized state collapses showing features of. and specific heat characteristic of formation of high density amorphous solid water. The pressure of structural collapse is 0.08 GPa higher than that of ice at 130 K. The slowly formed collapsed state shows kinetic unfreezing or glass-liquid transition temperature at 140 K for a time scale of 1 s. Comparison with the change in the properties observed for ice shows that κ decreases when the polymer is added.
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| 4. |
- Andersson, Ove, et al.
(författare)
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Effects of pressure and temperature on the thermal conductivity of Sn2P2S6
- 2011
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 83:13
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity kappa of the ferroelectric, paraelectric, and incommensurate phases of polycrystalline Sn2P2S6 has been measured in the 0.1-0.7 GPa range. The thermal conductivity kappa of the ferroelectric phase decreases with increasing pressure p. This unusual behavior, which is found in only a few other phases, is attributed to a negative Gruneisen parameter. The temperature T dependence of kappa for the ferroelectric phase (kappa similar to T-1) is well described by the Debye model for kappa, with three-phonon Umklapp scattering serving as the dominant scattering mechanism near and above the Debye temperature (similar to 100 K) up to a few tenths of degrees below the ferro- to paraelectric phase transition, where kappa(T) gradually changes and becomes temperature independent upon further heating. The thermal conductivity of the paraelectric and incommensurate phases was temperature independent and indistinguishable. Possible causes for the unusually weak T dependence at high temperatures and implications of the p dependence of kappa are discussed.
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| 5. |
- Andersson, Ove
(författare)
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Glass-liquid transition of water at high pressure
- 2011
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 108:27, s. 11013-11016
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Tidskriftsartikel (refereegranskat)abstract
- The knowledge of the existence of liquid water under extreme conditions and its concomitant properties are important in many fields of science. Glassy water has previously been prepared by hyperquenching micron-sized droplets of liquid water and vapor deposition on a cold substrate (ASW), and its transformation to an ultraviscous liquid form has been reported on heating. A densified amorphous solid form of water, high-density amorphous ice (HDA), has also been made by collapsing the structure of ice at pressures above 1 GPa and temperatures below approximately 140 K, but a corresponding liquid phase has not been detected. Here we report results of heat capacity C(p) and thermal conductivity, in situ, measurements, which are consistent with a reversible transition from annealed HDA to ultraviscous high-density liquid water at 1 GPa and 140 K. On heating of HDA, the Cp increases abruptly by (3.4 ± 0.2) J mol-1 K-1 before crystallization starts at (153 ± 1) K. This is larger than the Cp rise at the glass to liquid transition of annealed ASW at 1 atm, which suggests the existence of liquid water under these extreme conditions.
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| 6. |
- Andersson, Ove, et al.
(författare)
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Glass Transitions in Pressure-Collapsed Ice Clathrates and Implications for Cold Water
- 2012
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Ingår i: Journal of Physical Chemistry Letters. - Washington : American Chemical Society (ACS). - 1948-7185 .- 1948-7185. ; 3:15, s. 1951-1955
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Tidskriftsartikel (refereegranskat)abstract
- Ice is known to collapse to amorphous ice upon pressurization at low temperatures and shows the unusual feature of multiple distinct solid amorphous water states, which have inspired models of liquid water’s structure and unusual properties.Here, we use heat capacity Cp measurements to show that similarly collapsed ice clathrates display identical glass behavior as amorphous ice but that crystallization above the glass transition temperature Tg of ∼140 K at 1 GPa is inhibited. This effect of the homogeneously distributed “guest molecules” in water reveals a relatively strong reversible Cp increase above Tg but no further transition before crystallization at ∼190 K.This is consistent with a glass−liquid transition of water at Tg, which suggests a new path to study an ultraviscous liquid water network and evaluate water models
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| 7. |
- Andersson, Ove, et al.
(författare)
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Phase coexistence and hysteresis effects in the pressure-temperature phase diagram of NH3BH3
- 2011
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 84:2, s. 024115-
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Tidskriftsartikel (refereegranskat)abstract
- The potential hydrogen storage compound NH3BH3 has three known structural phases in the temperature and pressure ranges 110–300 K and 0–1.5 GPa, respectively. We report here the boundaries between, and the ranges of stability of, these phases. The phase boundaries were located by in situ measurements of the thermal conductivity, while the actual structures in selected areas were identified by in situ Raman spectroscopy and x-ray diffraction. Below 0.6 GPa, reversible transitions involving only small hysteresis effects occur between the room-temperature tetragonal plastic crystal I4mm phase and the low-temperature orthorhombic Pmn21 phase. Transformations of the I4mm phase into the high-pressure orthorhombic Cmc21 phase, occurring above 0.8 GPa, are associated with very large hysteresis effects, such that the reverse transition may occur at up to 0.5 GPa lower pressures. Below 230 K, a fraction of the Cmc21 phase is metastable to atmospheric pressure, suggesting the possibility that dense structural phases of NH3BH3, stable at room temperature, could possibly be created and stabilized by alloying or by other methods. Mixed orthorhombic Pmn21/Cmc21 phases were observed in an intermediate pressure-temperature range, but a fourth structural phase predicted by Filinchuk et al. [ Phys. Rev. B 79 214111 (2009)] was not observed in the pressure-temperature ranges of this experiment. The thermal conductivity of the plastic crystal I4mm phase is about 0.6 W m−1 K−1 and only weakly dependent on temperature, while the ordered orthorhombic phases have higher thermal conductivities limited by phonon-phonon scattering.
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| 8. |
- Andersson, Sten-Ove, et al.
(författare)
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Interaction, Action, and Reflection : How Medics Learn Medical Care in the Swedish Armed Forces
- 2013
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Ingår i: Military medicine. - : Association of Military Surgeons of the U S. - 0026-4075 .- 1930-613X. ; 178:8, s. 861-866
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study is to examine how medics within the Swedish Armed Forces perceive their learning outcome following military prehospital training. A qualitative study with a phenomenographic approach was used to investigate how learning is perceived among military medics. At meta level, the results can be viewed as an interaction, i.e., being able to collaborate in the medical platoon, including the ability to interact within the group and being able to lead; an action, i.e., being able to assess and treat casualties, including the ability to communicate with the casualty, to prioritize, and to be able to act; and a reflection, i.e., having confidence in one's own ability in first aid, including being prepared and feeling confident. interaction during the period of education is important for learning. action, being able to act in the field, is based on a drill in which the subject progresses from simple to complex procedures. reflection, learning to help others, is important for confidence, which in turn creates preparedness, thereby making the knowledge meaningful.
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| 9. |
- Andersson, Swen-Olof, et al.
(författare)
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Managing localized prostate cancer by radical prostatectomy or watchful waiting: Cost analysis of a randomized trial (SPCG-4)
- 2011
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Ingår i: SCANDINAVIAN JOURNAL OF UROLOGY AND NEPHROLOGY. - : Informa Healthcare. - 0036-5599 .- 1651-2065. ; 45:3, s. 177-183
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Tidskriftsartikel (refereegranskat)abstract
- Objective. The cost of radical prostatectomy (RP) compared to watchful waiting (WW) has never been estimated in a randomized trial. The goal of this study was to estimate long-term total costs per patient associated with RP and WW arising from inpatient and outpatient hospital care. Material and methods. This investigation used the Scandinavian Prostate Cancer Group Study Number 4 (SPCG-4) trial, comparing RP to WW, and included data from 212 participants living in two counties in Sweden from 1989 to 1999 (105 randomized to WW and 107 to RP). All costs were included from randomization date until death or end of follow-up in July 2007. Resource use arising from inpatient and outpatient hospital costs was measured in physical units and multiplied by a unit cost to come up with a total cost per patient. Results. During a median follow-up of 12 years, the overall cost in the RP group was 34% higher (p andlt; 0.01) than in the WW group, corresponding to euroa,not sign6123 in Sweden. The difference was driven almost exclusively by the cost of the surgical procedure. The cost difference between RP and WW was two times higher among men with low (2--6) than among those with high (7--10) Gleason score. Conclusion. In this economic evaluation of RP versus WW of localized prostate cancer in a randomized study, RP was associated with 34% higher costs. This difference, attributed exclusively to the cost of the RP procedure, was not overcome during extended follow-up.
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| 10. |
- Axner, Ove, 1957-, et al.
(författare)
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Assessing bacterial adhesion on an individual adhesin and single pili level using optical tweezers
- 2011
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Ingår i: Bacterial adhesion. - Berlin : Springer Berlin/Heidelberg. ; , s. 301-313
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Bokkapitel (refereegranskat)abstract
- Optical tweezers (OT) are a technique that, by focused laser light, can both manipulate micrometer sized objects and measure minute forces (in the pN range) in biological systems. The technique is therefore suitable for assessment of bacterial adhesion on an individual adhesin-receptor and single attachment organelle (pili) level. This chapter summarizes the use of OT for assessment of adhesion mechanisms of both non-piliated and piliated bacteria. The latter include the important helix-like pili expressed by uropathogenic Escherichia coli (UPEC), which have shown to have unique and intricate biomechanical properties. It is conjectured that the large flexibility of this type of pili allows for a redistribution of an external shear force among several pili, thereby extending the adhesion lifetime of bacteria. Systems with helix-like adhesion organelles may therefore act as dynamic biomechanical machineries, enhancing the ability of bacteria to withstand high shear forces originating from rinsing flows such as in the urinary tract. This implies that pili constitute an important virulence factor and a possible target for future anti-microbial drugs.
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