| 1. |
- Mattsson, Johan, 1969, et al.
(författare)
-
Effects of hydrogen bonding on supercooled liquid dynamics and the implications for supercooled water
- 2009
-
Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 79:17, s. 174205-
-
Tidskriftsartikel (refereegranskat)abstract
- The supercooled state of bulk water is largely hidden by unavoidable crystallization, which creates an experimentally inaccessible temperature regime - a "no man's land." We address this, and circumvent the crystallization problem by systematically studying the supercooled dynamics of hydrogen bonded oligomeric liquids (glycols), where water corresponds to the chain ends alone. This approach permits a "dilution of water" by altering the hydrogen bond concentration via variations in chain length. We observe a dynamic crossover in the temperature dependence of the structural relaxation time for all glycols, consistent with the common behavior of most supercooled liquids. We find that the crossover becomes more pronounced for increasing hydrogen bond concentrations, which leads to the prediction of a marked dynamic transition for water within "no man's land" at T similar to 220 K. Interestingly, the predicted transition thus takes place at a temperature where a so called "strong-fragile" transition has previously been suggested. Our results, however, imply that the dynamic transition of supercooled water is analogous to that commonly observed in supercooled liquids. Moreover, we find support also for the existence of a secondary relaxation of water with behavior analogous to that of the secondary relaxation observed for the glycols.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Berntsen, Peter, 1974, et al.
(författare)
-
Dielectric and calorimetric studies of hydrated purple membrane
- 2005
-
Ingår i: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 89:5, s. 3111-3128
-
Tidskriftsartikel (refereegranskat)abstract
- Purple membranes (PM) from halobacteria were hydrated to ∼0.4 and ∼0.2 g H 2 O/g of PM and studied by dielectric spectroscopy and differential scanning calorimetry between 120 and 300 K. The dielectric process, attributed to a local (β) relaxation of the confined supercooled water, shows an Arrhenius temperature behavior at low temperatures. In the case of the most hydrated PM a small deviation from the Arrhenius behavior occurs at 190-200 K together with a pronounced endothermic process and an increased activation energy. The observed crossover is accompanied by a reduction of the interlayer spacing due to the partial loss of the intermembrane water. All these effects at ∼200 K are consistent with a scenario where the local relaxation process merges with a nonobservable α-relaxation of the interlayer water, giving rise to a more liquid-like behavior of the interfacial water. For the less hydrated sample the effects are less pronounced and shift to a slightly higher temperature. © 2005 by the Biophysical Society.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
|
|
