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  1. Free, publicly-accessible full text available February 1, 2024
  2. null (Ed.)
  3. Survival relies on the ability to flexibly choose between different actions according to varying environmental circumstances. Many lines of evidence indicate that action selection involves signaling in corticostriatal circuits, including the orbitofrontal cortex (OFC) and dorsomedial striatum (DMS). While choice-specific responses have been found in individual neurons from both areas, it is unclear whether populations of OFC or DMS neurons are better at encoding an animal’s choice. To address this, we trained head-fixed mice to perform an auditory guided two-alternative choice task, which required moving a joystick forward or backward. We then used silicon microprobes to simultaneously measure the spiking activity of OFC and DMS ensembles, allowing us to directly compare population dynamics between these areas within the same animals. Consistent with previous literature, both areas contained neurons that were selective for specific stimulus-action associations. However, analysis of concurrently recorded ensemble activity revealed that the animal’s trial-by-trial behavior could be decoded more accurately from DMS dynamics. These results reveal substantial regional differences in encoding action selection, suggesting that DMS neural dynamics are more specialized than OFC at representing an animal’s choice of action. NEW & NOTEWORTHY While previous literature shows that both orbitofrontal cortex (OFC) and dorsomedial striatum (DMS) represent information relevant to selecting specific actions, few studies have directly compared neural signals between these areas. Here we compared OFC and DMS dynamics in mice performing a two-alternative choice task. We found that the animal’s choice could be decoded more accurately from DMS population activity. This work provides among the first evidence that OFC and DMS differentially represent information about an animal’s selected action. 
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  4. Abstract

    Using Pair Distribution Function (PDF) analysis of in situ total scattering data, we investigate the formation of tungsten and niobium oxides in a simple solvothermal synthesis. We use Pearson Correlation Coefficient (PCC) analysis of the time resolved PDFs to both map the structural changes taking place throughout the synthesis and identify structural models for precursor and product through PCC‐based structure mining. Our analysis first shows that ultra‐small tungsten and niobium oxide nanoparticles form instantaneously upon heating, with sizes between 1.5 and 2 nm. We show that the main structural motifs in the nanoparticles can be described with structures containing pentagonal columns, which is characteristic for many bulk tungsten and niobium oxides. We furthermore elucidate the structure of the precursor complex as clusters of octahedra with O‐ and Cl‐ligands. The PCC based methodology automates the structure characterization and proves useful for analysis of large datasets of for example, time resolved X‐ray scattering studies. The PCC is implemented in ‘PDF in the cloud’, a web platform for PDF analysis.

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  5. Abstract

    Mesoscale climate models provide indispensable tools to understand land‐atmosphere interactions over urban regions. However, uncertainties in urban canopy parameters (UCPs) and parameterization schemes lead to degraded representation of the drag effect in complex built terrains. In particular, for the widely applied single‐layer urban canopy model (SLUCM) coupled with the Weather Research and Forecasting (WRF) model, near‐surface horizontal wind speed is known to be overestimated systematically. In this study, idealized large eddy simulations (LES) and WRF‐SLUCM simulations are conducted to study the separate effect of UCPs and aerodynamic parameterization on atmospheric boundary layer processes and rainfall variabilities in Phoenix, Arizona. For LES that explicitly resolves surface geometry, significant differences between three‐dimensional (3D) versus two‐dimensional (2D) representation of urban morphology are found in the surface layer and above. When surface drag is parameterized following SLUCM, surface morphologies have little impacts on the mean momentum transfer. WRF‐SLUCM simulation results, incorporated with 3D urban morphology data, indicate that simply refining the frontal area index will reduce the surface drag, which further amplifies the systematic positive bias of SLUCM in predicting horizontal wind speed. Replacing the drag parameterization in SLUCM by LES‐based aerodynamic parameters has evident impacts on near‐surface wind speed. The impact of urban roughness representation becomes the most evident during rainfall periods, due to the important role of surface drag in dictating moisture convergence. Our study underlines that apart from intensive efforts in obtaining detailed UCPs, it is also critical to enhance the urban momentum exchange parameterization schemes.

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  6. Abstract. The impact of spatial and temporal variability of rainfall on hydrological response remains poorly understood, in particular in urban catchments due to their strong variability in land use, a high degree of imperviousness and the presence of stormwater infrastructure. In this study, we analyze the effect of storm scale, position and movement in relation to basin scale and flow-path network structure on urban hydrological response. A catalog of 279 peak events was extracted from a high-quality observational dataset covering 15 years of flow observations and radar rainfall data for five (semi)urbanized basins ranging from 7.0 to 111.1 km2 in size. Results showed that the largest peak flows in the event catalog were associated with storm core scales exceeding basin scale, for all except the largest basin. Spatial scale of flood-producing storm events in the smaller basins fell into two groups: storms of large spatial scales exceeding basin size or small, concentrated events, with storm core much smaller than basin size. For the majority of events, spatial rainfall variability was strongly smoothed by the flow-path network, increasingly so for larger basin size. Correlation analysis showed that position of the storm in relation to the flow-path network was significantly correlated with peak flow in the smallest and in the two more urbanized basins. Analysis of storm movement relative to the flow-path network showed that direction of storm movement, upstream or downstream relative to the flow-path network, had little influence on hydrological response. Slow-moving storms tend to be associated with higher peak flows and longer lag times. Unexpectedly, position of the storm relative to impervious cover within the basins had little effect on flow peaks. These findings show the importance of observation-based analysis in validating and improving our understanding of interactions between the spatial distribution of rainfall and catchment variability. 
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  7. Abstract

    Hydrometeorological impacts due to urbanization for cities close to complex terrain are poorly understood due to the complexities of terrain‐related circulation and urban perturbations of atmospheric flow. In this study, we examine urban impacts on extreme monsoon rainfall and the resultant flooding over central Arizona based on high‐resolution atmospheric and hydrological model simulations. Strong positive rainfall anomalies at the urban‐rural interface downwind of the city are mainly related to dynamic effects (increased surface roughness) on convective outflow boundaries. Urban‐related thermodynamic disturbances slightly increase rain rates over the downtown core of Phoenix. Contrasting rainfall anomalies for two consecutive storm episodes highlight the importance of flow regime analysis in understanding urban impacts on extreme rainfall in complex terrain. Urban‐induced rainfall anomalies result in amplification of flood peak magnitudes by as much as a factor of 2 for Phoenix watersheds. Our results highlight the urban impacts on regional flood hydrology through land‐atmosphere interactions.

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