We present a selection of methodologies for using the palaeo-climate model component of the Coupled Model Intercomparison Project (Phase 5) (CMIP5) to attempt to constrain future climate projections ...using the same models. The constraints arise from measures of skill in hindcasting palaeo-climate changes from the present over three periods: the Last Glacial Maximum (LGM) (21 000 yr before present, ka), the mid-Holocene (MH) (6 ka) and the Last Millennium (LM) (850-1850 CE). The skill measures may be used to validate robust patterns of climate change across scenarios or to distinguish between models that have differing outcomes in future scenarios. We find that the multi-model ensemble of palaeo-simulations is adequate for addressing at least some of these issues. For example, selected benchmarks for the LGM and MH are correlated to the rank of future projections of precipitation/temperature or sea ice extent to indicate that models that produce the best agreement with palaeo-climate information give demonstrably different future results than the rest of the models. We also explore cases where comparisons are strongly dependent on uncertain forcing time series or show important non-stationarity, making direct inferences for the future problematic. Overall, we demonstrate that there is a strong potential for the palaeo-climate simulations to help inform the future projections and urge all the modelling groups to complete this subset of the CMIP5 runs.
NK-cell resistance to transduction is a major technical hurdle for developing NK-cell immunotherapy. By using Baboon envelope pseudotyped lentiviral vectors (BaEV-LVs) encoding eGFP, we obtained a ...transduction rate of 23.0 ± 6.6% (mean ± SD) in freshly-isolated human NK-cells (FI-NK) and 83.4 ± 10.1% (mean ± SD) in NK-cells obtained from the NK-cell Activation and Expansion System (NKAES), with a sustained transgene expression for at least 21 days. BaEV-LVs outperformed Vesicular Stomatitis Virus type-G (VSV-G)-, RD114- and Measles Virus (MV)- pseudotyped LVs (
< 0.0001). mRNA expression of both BaEV receptors, ASCT1 and ASCT2, was detected in FI-NK and NKAES, with higher expression in NKAES. Transduction with BaEV-LVs encoding for CAR-CD22 resulted in robust CAR-expression on 38.3 ± 23.8% (mean ± SD) of NKAES cells, leading to specific killing of NK-resistant pre-B-ALL-RS4;11 cell line. Using a larger vector encoding a dual CD19/CD22-CAR, we were able to transduce and re-expand dual-CAR-expressing NKAES, even with lower viral titer. These dual-CAR-NK efficiently killed both CD19
- and CD22
-RS4;11 cells. Our results suggest that BaEV-LVs may efficiently enable NK-cell biological studies and translation of NK-cell-based immunotherapy to the clinic.
Nitrogen fertilization is considered as an important source of atmospheric N₂O emission. A seven site-year on-farm field experiment was conducted at Ottawa and Guelph, ON and Saint-Valentin, QC, ...Canada to characterize the affect of the amount and timing of N fertilizer on N₂O emission in corn (Zea mays L.) production. Using the static chamber method, gas samples were collected for 28-days after preplant and 28-days after sidedress fertilization at the seven site-year, resulting in 14 monitoring periods. For both methods of fertilization, peak N₂O flux and cumulative emission increased with the amount of N applied, with rates ranging from 30 to 900 μg N m⁻² h⁻¹. Depending on N amount and time of application, cumulative emission varied from 0.05 to 2.42 kg N ha⁻¹, equivalent to 0.03% to 1.45% of the N fertilizer applied. Differences in N₂O emission peaks among fertilizer treatments were clearly separated in 13 out of 14 monitoring periods. Total N₂O emissions may have been underestimated compared with annual monitoring in 10 out of the 49 cases because the monitoring period ended before N₂O efflux returned to the baseline level. The flux of N₂O was negligible when soil mineral N in the 0-15 cm layer was < 20 mg N kg⁻¹. While rainfall stimulated emission, soil temperature > 15 °C was likely the driving force responsible for the higher levels of N₂O found for sidedress than preplant application methods. However, caution must be taken when interpreting these later results as preplant fertilization may have continuously stimulated N₂O emissions after the 28-days monitoring period, especially in situations where N₂O effluxes have not fallen back to their baseline levels. Increasing fertilizer rates from 90 to 150 kg N ha⁻¹ resulted in slight increases in yields, but doubled cumulative N₂O emissions.
Abstract
We present a spectroscopic survey of 248 white dwarf candidates within 40 pc of the Sun; of these 244 are in the Southern hemisphere. Observations were performed mostly with the Very Large ...Telescope (X-Shooter) and Southern Astrophysical Research Telescope. Almost all candidates were selected from Gaia Data Release 3 (DR3). We find a total of 246 confirmed white dwarfs, 209 of which had no previously published spectra, and two main-sequence star contaminants. Of these, 100 white dwarfs display hydrogen Balmer lines, 69 have featureless spectra, and two show only neutral helium lines. Additionally, 14 white dwarfs display traces of carbon, while 37 have traces of other elements that are heavier than helium. We observe 35 magnetic white dwarfs through the detection of Zeeman splitting of their hydrogen Balmer or metal spectral lines. High spectroscopic completeness (> 97 per cent) has now been reached, such that we have 1058 confirmed Gaia DR3 white dwarfs out of 1083 candidates within 40 pc of the Sun at all declinations.
We found a consistent distribution pattern for radiocarbon in dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and methane replicated across spatial and temporal scales in northern ...peatlands from Minnesota to Alaska. The 14C content of DOC is relatively modern throughout the peat column, to depths of 3 m. In sedge‐dominated peatlands, the 14C contents of the products of respiration, CH4 and DIC, are essentially the same and are similar to that of DOC. In Sphagnum‐ and woody plant–dominated peatlands with few sedges, however, the respiration products are similar but intermediate between the 14C contents of the solid phase peat and the DOC. Preliminary data indicates qualitative differences in the pore water DOC, depending on the extent of sedge cover, consistent with the hypothesis that the DOC in sedge‐dominated peatlands is more reactive than DOC in peatlands where Sphagnum or other vascular plants dominate. These data are supported by molecular level analysis of DOC by ultrahigh‐resolution mass spectrometry that suggests more dramatic changes with depth in the composition of DOC in the sedge‐dominated peatland pore waters relative to changes observed in DOC where Sphagnum dominates. The higher reactivity of DOC from sedge‐dominated peatlands may be a function of either different source materials or environmental factors that are related to the abundance of sedges in peatlands.
Ammonia (NH3) volatilization is one of the main pathways through which applied N enters the environment undesirably. A seven site-year on-farm field experiment was performed for 3 yr at Ottawa, ON, ...and 2 yr at Guelph, ON, and Saint-Valentin, QC, Canada. Our objectives were to (i) quantify the flux and the amount of NH3 volatilization as affected by the rate and time of N fertilizer; (ii) assess the impact of rainfall and soil temperatures on NH3 volatilization; and (iii) determine the threshold level of N fertilizer at which large NH3 volatilization losses occur. Using the static chamber method, NH3 volatilization was monitored after preplant or sidedress N application. Rate of NH3 volatilization peaked at 3 to 7 d and then dropped sharply within next 7 d before leveling off in the following weeks. The amount of NH3 volatilization increased with increasing N levels applied preplant or sidedress at all site-years. Peak NH3 volatilization ranged from 40 to 8000 g N ha–1 d–1 after preplant fertilization and from about 100 to 2100 g N ha–1 d–1 after sidedress, resulting in NH3 losses of 0.1 to 47 kg N ha–1 and 0.6 to 20 kg N ha–1, respectively, equivalent to 0.1 to 38% and 0.3 to 13% of fertilizer-induced emission (FIE) within 28 d after preplant or sidedress N fertilization. Our data clearly indicate that sidedress applications enable reduction in N fertilizer for economic crop yields, and may reduce losses simply due to lower total N rates.
Abstract
Satellite-derived sea ice drift maps and sea level pressure from reanalysis data are used to infer upper and lower bounds on the large-scale compressive strength of Arctic sea ice. To this ...end, the two datasets are searched for special situations in which the wind forcing and its orientation with respect to the coastline allowed the authors to deduce a mean sea ice compressive strength from simple theory. Many estimates of ice compressive strength were possible for the winter of 1992/93 when the Arctic high was confined to the western Arctic and deep penetration of the Icelandic low produced wind patterns that pushed the ice perpendicular to the coastline in the Beaufort and East Siberian Seas. The winter of 1996/97, on the other hand, was characterized by a well-established Arctic high, producing wind patterns that generally pushed ice along coastlines rather than against them. Results show lower and upper bounds on the sea ice compressive strength parameter of 30 and 40 kN m−2, and 35 and 45 kN m−2, for the winters of 1992/93 and 1996/97, respectively (with a potential bias low of about 10 kN m−2). A tensile strength for sea ice of about 25 kN m−2 is also found in the East Siberian Sea in the first few hundred kilometers from the land, presumably associated with land-fast ice. The proposed mean ice compressive strength estimate is higher than those derived by minimizing the cumulative error between simulated and observed buoy drift trajectories. It is noted that the uncertainties in the estimates derived from models are large (with an unbiased estimate of standard deviation of 8.75 kN m−2). The estimates of yield strength in isotropic compression presented herein are in good agreement with a previous estimate made during the Arctic Ice Dynamic Joint Experiment, and with in situ ice compressive stress measurements made in the Beaufort Sea.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
New numerical solvers are being considered in response to the rising computational cost of properly solving the sea ice momentum equation at high resolution. The Jacobian free version of Newton's ...method has allowed models to obtain the converged solution faster than other implicit solvers used previously. To further improve on this recent development, the analytical Jacobian of the 1D sea ice momentum equation is derived and used inside Newton's method. The results are promising in terms of computational efficiency. Although robustness remains an issue for some test cases, it is improved compared to the Jacobian free approach. In order to make use of the strong points of both the new and Jacobian free methods, a hybrid preconditioner using the Picard and Jacobian matrices to improve global and local convergence, respectively, is also introduced. This preconditioner combines the robustness and computational efficiency of the previously used preconditioning matrices when solving the sea ice momentum equation.
Observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) are analyzed to develop a consistent data set suitable for the validation of snow and sea ice components used in climate models. ...Since the snow depth is a crucial variable to properly determine the ice thickness evolution, several methods are tested to estimate the actual snow depth at the exact location of the measured internal temperatures. Snow and ice thickness gauge measurements show high spatial variability at small spatial scales. Consequently, individual measurements of snow/ice thickness are not representative of the thickness at the locations where temperature profiles were measured. Observed skin temperatures and snow internal temperature profiles suggest that the mean winter snow cover at the reference mass balance site was thicker by 11 cm when compared with gauge observations at a small distance from that reference site. The mean winter snow cover thickness measured at the SHEBA mass balance site, Pittsburgh, is larger by a factor of 2.3 when compared to the snow depth derived from precipitation measurements. Assuming continuity of heat fluxes at the snow‐ice interface, an effective snow thermal conductivity of 0.50 Wm−1 K−1 is calculated. This is significantly higher than values generally used in climate models (0.31 Wm−1 K−1) or derived from in situ measurements (0.14 Wm−1 K−1) at SHEBA. Ocean heat fluxes, inferred from ice thickness and internal temperature measurements at various sites, are very consistent and match reasonably well those derived from turbulence measurements and a bulk formulation. A heat budget of surface fluxes shows a mean annual net imbalance of 1.5 Wm−2, with a mean energy deficit of 3.5 Wm−2 during winter and a mean surplus of 6.4 Wm−2 during summer.
The 40 pc sample of white dwarfs from Gaia O’Brien, Mairi W; Tremblay, P-E; Klein, B L ...
Monthly notices of the Royal Astronomical Society,
11/2023, Letnik:
527, Številka:
3
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
We present a comprehensive overview of a volume-complete sample of white dwarfs located within 40 pc of the Sun, a significant proportion of which were detected in Gaia Data Release 3 (DR3). ...Our DR3 sample contains 1076 spectroscopically confirmed white dwarfs, with just five candidates within the volume remaining unconfirmed (> 99 per cent spectroscopic completeness). Additionally, 28 white dwarfs were not in our initial selection from Gaia DR3, most of which are in unresolved binaries. We use Gaia DR3 photometry and astrometry to determine a uniform set of white dwarf parameters, including mass, effective temperature, and cooling age. We assess the demographics of the 40 pc sample, specifically magnetic fields, binarity, space density, and mass distributions.
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