| 311. |
- Ullakko, Kari, et al.
(författare)
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Isothermal Martensite Transformation of Fe-Ni-C Alloys as a Function of Hydrostatic Pressure
- 1990
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Ingår i: Materials Science Forum volumes 56-58. - Zürich : Trans Tech Publiations. ; , s. 197-200
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Konferensbidrag (refereegranskat)abstract
- Isothermal martensite transformation as a function of hydrostatic pressure was studied in Fe-Ni-C alloys. It was observed that the transformation was much the same as it happens as a function of time. Any noticeable differences in the morphology between isothermal and athermal martensite were not seen.
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| 312. |
- Ulyanov, A.N., et al.
(författare)
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Crystal symmetry and pressure effects on the properties of mixed-valence manganites
- 2003
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Ingår i: Journal of Magnetism and Magnetic Materials vol. 258-259, Special Issue SI. - Amsterdam : Elsevier B.V.. ; , s. 312-314
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Konferensbidrag (refereegranskat)abstract
- A lattice structure effect on the magnetic and magnetotransport properties of La0.7Ca(0.3-x)SrxMnO3 lanthanum manganites have been studied. The Curie temperature pressure coefficient increased almost linearly under an applied pressure as dTc/dP=14K/GPa and as dTc/dP=7.5K/GPa in the orthorhombic and rhombohedral structures,respectively. This is caused by the different pressure effect on the Mn–O bond distances and on the Mn–O–Mn bond angles in those phases. The anomalous low value of dTc/dP(=3.5K/GPa) for La0.7Ca0.15Sr0.15MnO3 composition and a jump of the magnetoresistance maximum value at the concentrational Pbnm2R%3c phase transition were observed and discussed.
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| 313. |
- Ulyanov, A.N., et al.
(författare)
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La0.7Ca0.3-xSrxMnO3 manganites: Effect of structure on the magnetic and transport properties.
- 2002
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Ingår i: Journal of the Physical Society of Japan. - : The Physical Society of Japan. - 0031-9015 .- 1347-4073. ; 71:3, s. 927-929
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Tidskriftsartikel (refereegranskat)abstract
- The effect of lattice structure on the magnetic and transport properties of La0.7Ca0.3-xSrxMnO3 (x= 0; 0.03; 0.06; ...; 0.3) lanthanum manganites have been studied. Curie temperature pressure coefficient, dTc/dP, showed the dependence on x value. Temperature Tc increased almost linearly under applied pressure as dTc/dP≈14 K/GPa and as dTc/dP≈7.5 K/GPa in the orthorhombic (Pbnm) and rhombohedral (R3c) phases, respectively. The value of dTc/dP(≈3.5 K/GPa) showed a minimum and a temperature of the resistance maximum, Tp(x), showed a change of slope at x=0.15, corresponding to the concentration structural phase transition. Differences between the values of dTc/dP and slopes of Tp versus x in Pbnm and R3c phases are explained by the different effect of external pressure on the Mn–O bond length and Mn–O–Mn bond angle, and by the different internal pressure effect in those phases, respectively
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| 314. |
- Ulyanov, A. N., et al.
(författare)
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Structure and pressure effects on the properties of La0.7Ca0.3-xSrxMnO3 manganites.
- 2002
-
Ingår i: Journal of Applied Physics vol. 91. - : American Institute of Physics. ; , s. 7739-7741
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Konferensbidrag (refereegranskat)abstract
- We report a study of the structure and pressure effects on magnetic and transport properties of a lanthanum manganite, La0.7Ca0.3–xSrxMnO3 (0<=x<=0.3, Deltax = 0.03). The pressure coefficient of the Curie temperature (Tc), dTc/dP, is shown to depend on x. The temperature Tc increases approximately linearly under applied pressure as dTc/dP[approximate]14 K/GPa in the orthorhombic (Pbnm) phase and as dTc/dP[approximate]7.5 K/GPa in the rhombohedral (R3-bar c). The value of dTc/dP shows a minimum ([approximate]3.5 K/GPa) and the temperature of the resistance maximum, Tp(x), shows a change of slope at x = 0.15, corresponding to a concentration structural phase transition. Differences between the values of dTc/dP and the slopes of Tp vs x in Pbnm and R3-bar c phases are explained by the different effect of external pressure on the Mn–O bond length and the Mn–O–Mn bond angle, and by the different internal pressure effect (depending on the value of x) in those phases, respectively.
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| 315. |
- Vilaythong, Thongloon, 1960-
(författare)
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The role of practical work in physics education in Lao PDR
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis is to get a better understanding of the role of practical work in physics education in the Lao People’s Democratic Republic (Lao PDR). The Lao PDR is one of least developed countries in the world with a weak base for science, and poor market opportunities for science graduates. The rapidly expanding educational system has many problems concerning quality of the infrastructure and staff competence. A combination of qualitative and quantitative methods was used in the study in order to assure reliability of the results. Data was collected through questionnaires, interviews, video-recordings, and my own ethnographic experiences of working in the Lao educational system for more than thirty years. The study was informed and results analysed with help of curriculum perspective and Cultural-Historical Activity Theory (CHAT). The findings show that Lao physics education curriculum at all levels is dominated by very traditional forms of teaching with an almost total absence of practical. Official curricular documents have statements prescribing teachers to do practical work in high school and university courses. However, few institutions have functioning equipment and skilled teachers for organising practical activities. Therefore, the majority of Lao students come to university and even can finish university without experience of practical work in physics. This shows the gap that exists between intended and implemented curricula. The majority of the students understand the importance of having practical activities in physics. However, after being exposed to laboratory experiments in an introductory physics course, they expressed criticism about the quality of instruction and the process of the practical work organisation. The laboratory group work analysis showed that discussions were mainly focused on understanding the experimental procedures, manipulating equipment, and collecting data for the report rather than on the physics content (object of activity, in CHAT terms). Based on the research results, it is possible to suggest that a systemic approach is needed to stimulate the development of a new practical work culture in schools and universities. This approach should include training and incentives for science teachers, development of assessment strategies including practical work, maintenance structures for physics equipment, and technical support for the organisation of demonstrations and laboratory exercises.
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| 316. |
- Wang, Lin, et al.
(författare)
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High-pressure studies of Nano/sub-micrometer C70 rods
- 2005
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Ingår i: High Energy Physics and Nuclear Physics B. - 0254-3052. ; 29:Supplement, s. 112-115
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Tidskriftsartikel (refereegranskat)abstract
- We have successfully synthesized C-70 rods in nano/sub-micrometers scale by evaporating solvent method. The diameter of the as grown C-70 rods is similar to 500 nm, and the length is similar to 10 mu m. The EDXD pattern and Raman spectroscopy for as -grown sample indicate that the as grown C-70 rod is in hcp structure. The pressure-induced structural phase transition has been studied by using DAC combined with EDXD and Raman spectroscopy methods under quasi-hydrostatic pressure up to 26.1GPa. It is found that hcp structure transforms into amorphous phase for C-70 rods in the pressure range from 23.3 to 26.1GPa, which is higher than the transformation pressure for bulk C-70 crystals. The phase transition is irreversible and it is induced by the collapse of C-70 cage.
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| 317. |
- Wang, Lin, et al.
(författare)
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Highly Enhanced Luminescence from Single-Crystalline C60·1m-xylene Nanorods
- 2006
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 18:17, s. 4190-4194
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Tidskriftsartikel (refereegranskat)abstract
- Single-crystalline C60â1m-xylene nanorods with a hexagonal structure were successfully synthesizedby evaporating a C60 solution in m-xylene at room temperature. The ratio of the length to the diameterof the nanorods can be controlled in the range of 10 to over 1000 for different applications. Thephotoluminescence (PL) intensity of the nanorods is about 2 orders of magnitude higher than that forpristine C60 crystals in air. Both UV and Raman results indicate that there is no charge transfer betweenC60 and m-xylene. It was found that the interaction between C60 and m-xylene molecules is of the vander Waals type. This interaction reduces the icosahedral symmetry of C60 molecule and induces strongPL from the solvate nanorods.
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| 318. |
- Wang, Lin, et al.
(författare)
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Synthesis and high pressure induced amorphization of C60 nanosheets
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:10, s. 103112-
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Tidskriftsartikel (refereegranskat)abstract
- C-60 nanosheets with thicknesses in the nanometer range were synthesized by a simple method. Compared to bulk C-60, the lattice of the nanosheets is expanded by about 0.4%. In situ Raman spectroscopy and energy-dispersive x-ray diffraction under high pressures have been employed to study the structure of the nanosheets. The studies indicate that the bulk modulus of the C-60 nanosheets is significantly larger than that of bulk C-60. The C-60 cages in nanosheets can persist at pressures over 30 GPa, 3 GPa higher than for bulk C-60. These results suggest that C-60 crystals in even small size will be a potential candidate of superhard materials.
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| 319. |
- Wang, Lin, et al.
(författare)
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Synthesis of thin, rectangular C60 nanorods using m-xylene as shape controller
- 2006
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Ingår i: Advanced Materials. - : Wiley Interscience. - 0935-9648 .- 1521-4095. ; 18:14, s. 1883-1888
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Tidskriftsartikel (refereegranskat)abstract
- Thin, rectangular C60 nanorods in face-centered cubic structure are synthesized by using m-xylene as a shape controller. These unusual nanorods can easily grow on various substrates. The smallest nanorods have widths smaller than 30 nm. The nanorods are highly crystalline in single phase. A significant expansion of the lattice constant is also found in the C60 nanorods when their widths decrease below about 80 nm.
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| 320. |
- Warme, Jonatan, et al.
(författare)
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Helicobacter pylori and Pro-Inflammatory Protein Biomarkers in Myocardial Infarction with and without Obstructive Coronary Artery Disease
- 2023
-
Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 44
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Tidskriftsartikel (refereegranskat)abstract
- Myocardial infarction (MI) with obstructive coronary artery disease (MI-CAD) and MI in the absence of obstructive coronary artery disease (MINOCA) affect different populations and may have separate pathophysiological mechanisms, with greater inflammatory activity in MINOCA compared to MI-CAD. Helicobacter pylori (Hp) can cause systemic inflammation and has been associated with cardiovascular disease (CVD). We aimed to investigate whether Hp infection is associated with concentrations of protein biomarkers of inflammation and CVD. In a case-control study, patients with MINOCA (n = 99) in Sweden were included, complemented by matched subjects with MI-CAD (n = 99) and controls (n = 100). Protein biomarkers were measured with a proximity extension assay in plasma samples collected 3 months after MI. The seroprevalence of Hp and cytotoxin-associated gene A (CagA) was determined using ELISA. The associations between protein levels and Hp status were studied with linear regression. The prevalence of Hp was 20.2%, 19.2%, and 16.0% for MINOCA, MI-CAD, and controls, respectively (p = 0.73). Seven proteins were associated with Hp in an adjusted model: tissue plasminogen activator (tPA), interleukin-6 (IL-6), myeloperoxidase (MPO), TNF-related activation-induced cytokine (TRANCE), pappalysin-1 (PAPPA), soluble urokinase plasminogen activator receptor (suPAR), and P-selectin glycoprotein ligand 1 (PSGL-1). Hp infection was present in one in five patients with MI, irrespective of the presence of obstructive CAD. Inflammatory proteins were elevated in Hp-positive subjects, thus not ruling out that Hp may promote an inflammatory response and potentially contribute to the development of CVD.
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