Developing daily precipitation scenarios for climate change impact studies in the Guadiana and the Tejo basins

International audienceHydrological models to evaluate the impacts of climate change in the water resources sector require spatially correlated daily precipitation scenarios as model inputs. This paper presents a practical procedure for developing such precipitation scenarios using multisite stochastic weather models or generators conditional on large-scale daily circulation patterns, based on GCM-simulated future mean sea level pressure (MSLP) fields. The procedure is demonstrated on the basis of HadCM3 and HadAM3H simulations with an example for two river basins in the Iberian Peninsula. Changes in daily precipitation scenarios for the region generated by stochastic models are consistent with large-scale precipitation scenarios from direct GCM outputs; however, more localised characteristics have to be found from downscaled precipitation scenarios rather than from direct GCM outputs. This may imply that possible changes in downscaled precipitation reflect the underlying physics in GCMs, so that downscaled daily precipitation scenarios may be more suitable for impact models than the coarse GCM outputs

Evaluation of the integrated Canadian crop yield forecaster (ICCYF) model for in-season prediction of crop yield across the Canadian agricultural landscape

Early warning information on crop yield and production are very crucial for both farmers and decision-makers. In this study, we assess the skill and the reliability of the Integrated Canadian Crop Yield Forecaster (ICCYF), a regional crop yield forecasting tool, at different temporal (i.e. 1–3 months before harvest) and spatial (i.e. census agricultural region – CAR, provincial and national) scales across Canada. A distinct feature of the ICCYF is that it generates in-season yield forecasts well before the end of the growing season and provides a probability distribution of the forecasted yields. The ICCYF integrates climate, remote sensing derived vegetation indices, soil and crop information through a physical process-based soil water budget model and statistical algorithms. The model was evaluated against yield survey data of spring wheat, barley and canola during the 1987–2012 period. Our results showed that the ICCYF performance exhibited a strong spatial pattern at both CAR and provincial scales. Model performance was better from regions with a good coverage of climate stations and a high percentage of cropped area. On average, the model coefficient of determination at CAR level was 66%, 51% and 67%, for spring wheat, barley and canola, respectively. Skilful forecasts (i.e. model efficiency index & gt; 0) were achieved in 70% of the CARs for spring wheat and canola, and 43% for barley (low values observed in CAR with small harvested area). At the provincial scale, the mean absolute percentage errors (MAPE) of the September forecasts ranged from 7% to 16%, 7% to 14%, and 6% to 14% for spring wheat, barley and canola, respectively. For forecasts at the national scale, MAPE values (i.e. 8%, 5% and 9% for the three respective crops) were considerably smaller than the corresponding historical coefficients of variation (i.e. 17%, 10% and 17% for the three crops). Overall, the ICCYF performed better for spring wheat than for canola and barley at all the three spatial scales. Skilful forecasts were achieved by mid-August, giving a lead time of about 1 month before harvest and about 3–4 months before the final release of official survey results. As such, the ICCYF could be used as a complementary tool for the traditional survey method, especially in areas where it is not practical to conduct such surveys

Polycomb CBX7 Directly Controls Trimethylation of Histone H3 at Lysine 9 at the p16 Locus

BACKGROUND: H3K9 trimethylation (H3K9me3) and binding of PcG repressor complex-1 (PRC1) may play crucial roles in the epigenetic silencing of the p16 gene. However, the mechanism of the initiation of this trimethylation is unknown. METHODOLOGY/PRINCIPAL FINDINGS: In the present study, we found that upregulating the expression of PRC1 component Cbx7 in gastric cancer cell lines MGC803 and BGC823 led to significantly suppress the expression of genes within the p16-Arf-p15 locus. H3K9me3 formation was observed at the p16 promoter and Regulatory Domain (RD). CBX7 and SUV39H2 binding to these regions were also detectable in the CBX7-stably upregulated cells. CBX7-SUV39H2 complexes were observed within nucleus in bimolecular fluorescence complementation assay (BiFC). Mutations of the chromodomain or deletion of Pc-box abolished the CBX7-binding and H3K9me3 formation, and thus partially repressed the function of CBX7. SiRNA-knockdown of Suv39h2 blocked the repressive effect of CBX7 on p16 transcription. Moreover, we found that expression of CBX7 in gastric carcinoma tissues with p16 methylation was significantly lower than that in their corresponding normal tissues, which showed a negative correlation with transcription of p16 in gastric mucosa. CONCLUSION/SIGNIFICANCE: These results demonstrated for the first time, to our knowledge, that CBX7 could initiate H3K9me3 formation at the p16 promoter

The chaos in calibrating crop models

Calibration, the estimation of model parameters based on fitting the model to experimental data, is among the first steps in many applications of system models and has an important impact on simulated values. Here we propose and illustrate a novel method of developing guidelines for calibration of system models. Our example is calibration of the phenology component of crop models. The approach is based on a multi-model study, where all teams are provided with the same data and asked to return simulations for the same conditions. All teams are asked to document in detail their calibration approach, including choices with respect to criteria for best parameters, choice of parameters to estimate and software. Based on an analysis of the advantages and disadvantages of the various choices, we propose calibration recommendations that cover a comprehensive list of decisions and that are based on actual practices.HighlightsWe propose a new approach to deriving calibration recommendations for system modelsApproach is based on analyzing calibration in multi-model simulation exercisesResulting recommendations are holistic and anchored in actual practiceWe apply the approach to calibration of crop models used to simulate phenologyRecommendations concern: objective function, parameters to estimate, software usedCompeting Interest StatementThe authors have declared no competing interest

Experimental and numerical investigation of laser assisted milling of silicon nitride ceramics

Doctor of PhilosophyDepartment of Industrial & Manufacturing Systems EngineeringShuting LeiThis study experimentally and numerically investigates laser assisted milling (LAMill) of silicon nitride ceramics. Experiments are conducted to study the machinability of Si3N4 under LAMill. The effects of temperature on cutting forces, tool wear, surface integrity, edge chipping and material removal mechanisms are investigated. It is shown that when temperature increases, cutting force and tool wear are significantly decreased, surface integrity is improved, chip size is increased and material removal demonstrates more plastic characteristics. The mechanisms of edge chipping at elevated temperature are investigated theoretically and experimentally. When temperature is above the softening point and below the brittle/ductile transition temperature, the mechanism is mainly through softening. When temperature is above the brittle/ductile transition temperature, toughening mechanism contributes significantly to the reduced edge chipping. The coupled effect of softening and toughening mechanisms shows that temperature range between 1200 to 1400°C has the most significant effect to reduce edge chipping. Distinct element method (DEM) is applied to simulate the micro-mechanical behavior of Si3N4. First, quantitative relationships between particle level parameters and macro-properties of the bonded particle specimens are obtained, which builds a foundation for simulation of Si3N4. Then, extensive DEM simulations are conducted to model the material removal of machining Si3N4. The simulation results demonstrate that DEM can reproduce the conceptual material removal model summarized from experimental observations, including the initiation and propagation of cracks, chip formation process and material removal mechanisms. It is shown that material removal is mainly realized by propagation of lateral cracks in machining of silicon nitride. At the elevated temperature under laser assisted machining, lateral cracks are easier to propagate to form larger machined chips, there are fewer and smaller median cracks therefore less surface/subsurface damage, and crushing-type material removal is reduced. The material removal at elevated temperature demonstrates more plastic characteristics. The numerical results agree very well with experimental observations. It shows that DEM is a promising method to model the micro-mechanical process of machining Si3N4

A Long-Term, 1-km Resolution Daily Meteorological Dataset for Modeling and Mapping Permafrost in Canada

Climate warming is causing permafrost thaw and there is an urgent need to understand the spatial distribution of permafrost and its potential changes with climate. This study developed a long-term (1901–2100), 1-km resolution daily meteorological dataset (Met1km) for modeling and mapping permafrost at high spatial resolutions in Canada. Met1km includes eight climate variables (daily minimum, maximum, and mean air temperatures, precipitation, vapor pressure, wind speed, solar radiation, and downward longwave radiation) and is suitable to drive process-based permafrost and other land-surface models. Met1km was developed based on four coarser gridded meteorological datasets for the historical period. Future values were developed using the output of a new Canadian regional climate model under medium-low and high emission scenarios. These datasets were downscaled to 1-km resolution using the re-baselining method based on the WorldClim2 dataset as spatial templates. We assessed Met1km by comparing it to climate station observations across Canada and a gridded monthly anomaly time-series dataset. The accuracy of Met1km is similar to or better than the four coarser gridded datasets. The errors in long-term averages and average seasonal patterns are small. The error occurs mainly in day-to-day fluctuations, thus the error decreases significantly when averaged over 5 to 10 days. Met1km, as a data generating system, is relatively small in data volume, flexible to use, and easy to update when new or improved source datasets are available. The method can also be used to generate similar datasets for other regions, even for the entire global landmass

Surgical treatment of carotid ⁃ ophthalmic aneurysm

Objective To explore the anatomical features of carotid ⁃ ophthalmic aneurysm and clinoid process and the surgical technique and outcome. Methods In this study there were 15 patients with carotid ⁃ ophthalmic aneurysm (12 patients ophthalmic aneurysm, 1 superior hypophsial aneurysm, 2 dorsal internal carotid aneurysm). Patients were treated by clipping procedure through pterional approach. During the procedure, intra⁃ and extra⁃cranial internal carotid arteries were temporarily occluded. Results Postoperative digital subtraction angiography (DSA) or CT angiography (CTA) examinations showed that the effect of clipping treatment was satisfactory in 13 patients, the blood flow was good in parent artery and distal artery. Visual acuity was improved in 2 cases with visual disturbance. After surgery only one case presented hemiparesis of contralateral limb. No severe operative ⁃ related complications occurred. All patients were followed up for 3-10 months (average 5 months) after surgery. The recovery was good. Conclusion Pterional approach combined with temporary blocking of intra ⁃ and extra ⁃ cranial internal carotid artery is an effective and safety surgical method for treating carotid⁃ophthalmic aneurysm. During operation, fluorescence imaging can immediately indicate whether there are residual aneurysm and narrow parent artery, so that it can help the physician to adjust the clipping procedure and achieve satisfactory effect. DOI：10.3969/j.issn.1672-6731.2011.02.01