| 1. |
-
- 2019
-
Tidskriftsartikel (refereegranskat)
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Blösch, Günter, et al.
(författare)
-
Twenty-three unsolved problems in hydrology (UPH) - a community perspective
- 2019
-
Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 64:10, s. 1141-1158
-
Tidskriftsartikel (refereegranskat)abstract
- This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Jasechko, S., et al.
(författare)
-
Late-glacial to late-Holocene shifts in global precipitation delta O-18
- 2015
-
Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 11:10, s. 1375-1393
-
Tidskriftsartikel (refereegranskat)abstract
- Reconstructions of Quaternary climate are often based on the isotopic content of paleo-precipitation preserved in proxy records. While many paleo-precipitation isotope records are available, few studies have synthesized these dispersed records to explore spatial patterns of late-glacial precipitation delta O-18. Here we present a synthesis of 86 globally distributed groundwater (n = 59), cave calcite (n = 15) and ice core (n = 12) isotope records spanning the late-glacial (defined as similar to 50 000 to similar to 20 000 years ago) to the late-Holocene (within the past similar to 5000 years). We show that precipitation delta O-18 changes from the late-glacial to the late-Holocene range from -7.1% (delta O-18(late-Holocene) > delta O-18(late-glacial)) to + 1.7% (delta O-18(late-glacial) > delta O-18(late-Holocene)), with the majority (77 %) of records having lower late-glacial delta O-18 than late-Holocene delta O-18 values. High-magnitude, negative precipitation delta O-18 shifts are common at high latitudes, high altitudes and continental interiors (delta O-18(late-Holocene) > delta O-18(late-glacial) by more than 3 %). Conversely, low-magnitude, positive precipitation delta O-18 shifts are concentrated along tropical and subtropical coasts (delta O-18(late-glacial) > delta O-18(late-Holocene) by less than 2 %). Broad, global patterns of late-glacial to late-Holocene precipitation delta O-18 shifts suggest that stronger-than-modern isotopic distillation of air masses prevailed during the late-glacial, likely impacted by larger global temperature differences between the tropics and the poles. Further, to test how well general circulation models reproduce global precipitation delta O-18 shifts, we compiled simulated precipitation delta O-18 shifts from five isotope-enabled general circulation models simulated under recent and last glacial maximum climate states. Climate simulations generally show better intermodel and model-measurement agreement in temperate regions than in the tropics, highlighting a need for further research to better understand how inter-model spread in convective rainout, seawater delta O-18 and glacial topography parameterizations impact simulated precipitation delta O-18. Future research on paleo-precipitation delta O-18 records can use the global maps of measured and simulated late-glacial precipitation isotope compositions to target and prioritize field sites.
|
|
| 9. |
- Ross, A. J., et al.
(författare)
-
A first-principles based description of the Hf-Ni system supported by high-temperature synchrotron experiments
- 2018
-
Ingår i: Thermochimica Acta. - : Elsevier B.V.. - 0040-6031 .- 1872-762X. ; 668, s. 142-151
-
Tidskriftsartikel (refereegranskat)abstract
- Hf-Ni is an important binary system for high temperature alloys and shape memory alloys which has been investigated several times in the literature but often using samples of Hf contaminated by Zr. The thermodynamics of this system are remodeled in this work based on first-principles calculations and additional experiments using Hf with relatively low Zr contamination (0.25 wt. %). Diffusion couples in the Ni-rich portion of the Hf-Ni system heat treated at 1173, 1273 and 1373 K are used to measure phase stability and Hf solubility in the fcc phase. The solubility observed in fcc Ni from Ni/Ni50Hf50 (at.%) diffusion couples is larger than that observed in previous experiments. These results are the only source fit to during modeling of the fcc solubility to mitigate effects from Zr contamination. Data in the literature suggests that the high temperature crystal structure of the B33 NiHf phase is, in fact, the B2 structure. High temperature synchrotron measurements provide confirmation of this crystal structure. Modeling of the B2 phase was aided by first-principles calculations using special quasi-random structures (SQS). The present CALPHAD model will prove useful when designing shape memory alloys containing Hf and when modeling the Hf activity in Ni-base high temperature alloys.
|
|
