| 161. |
- Johari, G.P., et al.
(författare)
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Vibrational and relaxational properties of crystalline and amorphous ices
- 2007
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Ingår i: Thermochimica Acta 461, issue 1-2. - : Elsevier BV. ; , s. 14-43
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Konferensbidrag (refereegranskat)abstract
- Pure water forms 15 crystalline ices at different temperatures and pressures, and its solutions containing small molecules form three crystallographically distinct clathrates. Its vapours deposited on a substrate at T< 100K produce a porous amorphous solid and pure water vitrifies (T-g = 136 K) when hyperquenched in micron-size droplets. At a temperature below 140 K, hexagonal and cubic ice collapse when pressure exceeds similar to 1 GPa to a similar to 30% denser amorphous solid, which on heating at ambient pressure transforms to an amorphous solid with density similar to that of hexagonal ice. In this essay, we describe (i) the thermal conductivity of the ices and clathrates and the thermal conductivity and heat capacity of water's amorphous solids, their thermodynamic paths and their transformations, and (ii) the dielectric relaxation time of ultraviscous water formed on heating the amorphous solids. We also describe the characteristics of pressure collapse and subsequent amorphization of hexagonal and cubic ices that occurs over a period of several days according to a stretched exponential kinetics and a pressure-, and temperature-dependent rate constant. This process is attributed to the production of lattice faults during deformation of the ice and the consequent distribution of the Born instability pressures. This ultimately produces a kinetically unstable high-energy amorphs in the same manner as random deformation of crystals produces kinetically unstable high-energy amorphs, with density and properties depending upon their temperature-pressure-time history. On heating at 1 GPa pressure, the pressure-amorphized solid relaxes to a lower energy state, becoming ultraviscous water at 140 K. But on heating at ambient pressure, it irreversibly transforms slowly to a low-density amorph that differs from glassy water and vapour-deposited amorphous solid.
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| 162. |
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| 163. |
- Johari, Gyan P, et al.
(författare)
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Water's polyamorphic transitions and amorphization of ice under pressure
- 2004
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Ingår i: Journal of Chemical Physics. - : API. - 0021-9606 .- 1089-7690. ; 120:13, s. 6207-6213
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Tidskriftsartikel (refereegranskat)abstract
- Transformations of water’s high density amorph (HDA) to low density amorph (LDA) and of LDA’s to cubic ice (Ic) have been studied by in situ thermal conductivity κ measurements at high pressures. The HDA to LDA transformation is unobservable at p of 0.07 GPa, indicating that, for a fixed heating rate, an increase in pressure increases the temperature of HDA to LDA transformation and decreases that of LDA to ice Ic, causing thereby the two transformations to merge, and HDA appears to convert directly to ice Ic. Thus either LDA forms but converts extremely rapidly to ice Ic, or LDA does not form. At a fixed p and T, in the range of pressure amorphization of hexagonal ice, κ continues to decrease with time. Therefore, the amorphization of ice Ih is kinetically controlled. When HDA at 1 GPa was heated from 130 to 157 K and densified to very HDA, its κ increased by 3%. Our findings and a scrutiny of earlier reports show that a reversible transition between HDA and LDA does not occur at ∼135 K and ∼0.2 GPa. Since there is no unique HDA, it is difficult to justify the conjecture for a second critical point for water.
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| 164. |
- Jonsson, Ove, et al.
(författare)
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TIMFIE-provtagning för tidsintegrerad haltbestämning av växtskyddsmedel, PFAS, läkemedel och metaller i ytvatten : En pilotstudie
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- TIMFIE (Time Integrating, Micro Flow, In situ Extraction) är en enkel och billig tidsintegrerad provtagningsmetod som här användes för bestämning av ett stort antal organiska ämnen från vitt skilda substansgrupper. Tekniken bygger på kontinuerlig fastfasextraktion i fält under en till två veckor och den efterföljande bestämningen av organiska ämnen är kvantitativ och baseras på helvatten, dvs. med partikelbunden fraktion inkluderad.Förutom organiska ämnen som växtskyddsmedel, PFAS och läkemedel mättes i detta projekt även metallhalter och löst organiskt kol (DOC) i det uppsamlade, filtrerade vattnet. Merparten av de studerade metallerna och DOC påverkades dock negativt av fastfaskolonnerna som används för extraktion av de organiska ämnena. En separat TIMFIE utan kolonner ska därför användas vid bestämning av metaller. En fältstudie med veckovisa TIMFIE-provtagningar i tolv provpunkter fördelade på fem regioner utfördes i samarbete med länsstyrelserna i Gotland, Östergötland och Dalarna samt med en avfallsanläggning i Mälardalen. Totalt analyserades 47 TIMFIE-prover för drygt 200 organiska ämnen och 21 metaller, samt ytterligare 8 TIMFIE-prover endast för metaller.I framtiden kommer två olika TIMFIE-provtagare att användas i studier där både organiska och oorganiska ämnen bestäms. Fortsatt arbete med att även inkludera näringsämnen i det oorganiska analyspaketet pågår och möjligheten att göra dessa bestämningar på ett återskapat helvatten undersöks.
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| 165. |
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| 166. |
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| 167. |
- Julin, B., et al.
(författare)
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Dietary cadmium exposure and prostate cancer incidence : a population-based prospective cohort study
- 2012
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Ingår i: British Journal of Cancer. - London, United Kingdom : Nature Publishing Group. - 0007-0920 .- 1532-1827. ; 21:5, s. 895-900
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Tidskriftsartikel (refereegranskat)abstract
- Background: Experimental data convincingly propose the toxic metal cadmium as a prostate carcinogen. Cadmium is widely dispersed into the environment and, consequently, food is contaminated.Methods: A population-based cohort of 41 089 Swedish men aged 45-79 years was followed prospectively from 1998 through 2009 to assess the association between food frequency questionnaire-based estimates of dietary cadmium exposure (at baseline, 1998) and incidence of prostate cancer (3085 cases, of which 894 were localised and 794 advanced) and through 2008 for prostate cancer mortality (326 fatal cases).Results: Mean dietary cadmium exposure was 19 μg per day±s.d. 3.7. Multivariable-adjusted dietary cadmium exposure was positively associated with overall prostate cancer, comparing extreme tertiles; rate ratio (RR) 1.13 (95% confidence interval (CI): 1.03-1.24). For subtypes of prostate cancer, the RR was 1.29 (95% CI: 1.08-1.53) for localised, 1.05 (95% CI: 0.87-1.25) for advanced, and 1.14 (95% CI: 0.86-1.51) for fatal cases. No statistically significant difference was observed in the multivariable-adjusted risk estimates between tumour subtypes (P(heterogeneity)=0.27). For localised prostate cancer, RR was 1.55 (1.16-2.08) among men with a small waist circumference and RR 1.45 (1.15, 1.83) among ever smokers.Conclusion: Our findings provide support that dietary cadmium exposure may have a role in prostate cancer development.
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| 168. |
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| 169. |
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| 170. |
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