| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Lammertsma, Emmy I., et al.
(författare)
-
Sensitivity of wetland hydrology to external climate forcing in central Florida
- 2015
-
Ingår i: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; 84:3, s. 287-300
-
Tidskriftsartikel (refereegranskat)abstract
- Available proxy records from the Florida peninsula give a varying view on hydrological changes during the late Holocene. Here we evaluate the consistency and sensitivity of local wetland records in relation to hydrological changes over the past ~ 5 ka based on pollen and diatom proxies from peat cores in Highlands Hammock State Park, central Florida. Around 5 cal ka BP, a dynamic floodplain environment is present. Subsequently, a wetland forest establishes, followed by a change to persistent wet conditions between ~ 2.5 and 2.0 ka. Long hydroperiods remain despite gradual succession and basin infilling with maximum wet conditions between ~ 1.3 and 1.0 ka. The wet phase and subsequent strong drying over the last millennium, as indicated by shifts in both pollen and diatom assemblages, can be linked to the early Medieval Warm Period and Little Ice Age, respectively, driven by regionally higher sea-surface temperatures and a temporary northward migration of the Intertropical Convergence Zone. Changes during the 20th century are the result of constructions intended to protect the Highlands Hammock State Park from wildfires. The multiple cores and proxies allow distinguishing local and regional hydrological changes. The peat records reflect relatively subtle climatic changes that are not evident from regional pollen records from lakes.
|
|
| 5. |
- Okur, Halil I., et al.
(författare)
-
The Jones-Ray Effect Is Not Caused by Surface-Active Impurities
- 2018
-
Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185 .- 1948-7185. ; 9:23, s. 6739-6743
-
Tidskriftsartikel (refereegranskat)abstract
- Pure aqueous electrolyte solutions display a minimum in surface tension at concentrations of 2 +/- 1 mM. This effect has been a source of controversy since it was first reported by Jones and Ray in the 1930s. The Jones Ray effect has frequently been dismissed as an artifact linked to the presence of surface-active impurities. Herein we systematically consider the effect of surface-active impurities by purposely adding nanomolar concentrations of surfactants to dilute electrolyte solutions. Trace amounts of surfactant are indeed found to decrease the surface tension and influence the surface chemistry. However, surfactants can be removed by repeated aspiration and stirring cycles, which eventually deplete the surfactant from solution, creating a pristine surface. Upon following this cleaning procedure, a reduction in the surface tension by millimolar concentrations of salt is still observed. Consequently, we demonstrate that the Jones Ray effect is not caused by surface-active impurities.
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Okur, Halil I., et al.
(författare)
-
Beyond the Hofmeister Series : Ion-Specific Effects on Proteins and Their Biological Functions
- 2017
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 121:9, s. 1997-2014
-
Forskningsöversikt (refereegranskat)abstract
- Ions differ in their ability to salt out proteins from solution as expressed in the lyotropic or Hofmeister series of cations and anions. Since its first formulation in 1888, this series has been invoked in a plethora of effects, going beyond the original salting out/salting in idea to include enzyme activities and the crystallization of proteins, as well as to processes not involving proteins like ion exchange, the surface tension of electrolytes, or bubble coalescence. Although it has been clear that the Hofmeister series is intimately connected to ion hydration in homogeneous and heterogeneous environments and to ion pairing, its molecular origin has not been fully understood. This situation could have been summarized as follows: Many chemists used the Hofmeister series as a mantra to put a label on ion-specific behavior in various environments, rather than to reach a molecular level understanding and, consequently, an ability to predict a particular effect of a given salt ion on proteins in solutions. In this Feature Article we show that the cationic and anionic Hofmeister series can now be rationalized primarily in terms of specific interactions of salt ions with the backbone and charged side chain groups at the protein surface in solution. At the same time, we demonstrate the limitations of separating Hofmeister effects into independent cationic and anionic contributions due to the electroneutrality condition, as well as specific ion pairing, leading to interactions of ions of opposite polarity. Finally, we outline the route beyond Hofmeister chemistry in the direction of understanding specific roles of ions in various biological functionalities, where generic Hofmeister-type interactions can be complemented or even overruled by particular steric arrangements in various ion binding sites. (Chemical Equation Presented).
|
|
