Social network size can influence linguistic malleability and the propagation of linguistic change

We learn language from our social environment, but the more sources we have, the less informative each source is, and therefore, the less weight we ascribe its input. According to this principle, people with larger social networks should give less weight to new incoming information, and should therefore be less susceptible to the influence of new speakers. This paper tests this prediction, and shows that speakers with smaller social networks indeed have more malleable linguistic representations. In particular, they are more likely to adjust their lexical boundary following exposure to a new speaker. Experiment 2 uses computational simulations to test whether this greater malleability could lead people with smaller social networks to be important for the propagation of linguistic change despite the fact that they interact with fewer people. The results indicate that when innovators were connected with people with smaller rather than larger social networks, the population exhibited greater and faster diffusion. Together these experiments show that the properties of people’s social networks can influence individuals’ learning and use as well as linguistic phenomena at the community level

How are distractibility and hazard prediction in driving related? Role of driving experience as a moderating factor

Distraction constitute one of the ‘five fatal’ behaviours that contribute to road trauma, and some people may be more susceptible to it than others. It is also known that a greater ability to predict danger is related to a lower probability of suffering accidents. It could be hypothesised that drivers with a higher tendency to distraction are worse at predicting traffic hazards, but to what extent might driving experience serve to mitigate this tendency to distraction? The current study collected self-reported attentional errors from drivers by using the Attention-Related Driving Errors Scale (ARDES-Spain) in order to examine whether novice drivers suffered from inattention more than experienced drivers. The results demonstrated that novice drivers scored more highly on ARDES than experienced drivers. ARDES scores were then related to performance in a Hazard Prediction test, where participants had to report what hazard was about to happen in a series of video clips that occlude just as the hazard begins to develop. While experienced drivers were better at the Hazard Prediction test than novice drivers, those participants who reported fewer attention errors were also better able to detect the upcoming hazard following occlusion. In addition, our results demonstrate a relationship between self-reported attentional errors and the ability to predict upcoming hazards on the road, with driving experience having a moderating role. In the case of novice drivers, as their scores in the Manoeuvring Errors ARDES factor increase, their ability in Hazard Prediction diminishes, while for experienced drivers the increase is not significant. Guidance on how to improve training for drivers in order to mitigate the effects of inattention on driving safety can be addressed

River Hydro- and Morphodynamics: Restoration, Modeling, and Uncertainty

The study of fluvial geomorphology is one of the critical sciences in the 21st Century. The previous century witnessed a virtual disregard of the hydro and morphodynamic processes occurring in rivers when it came to design of transportation, flood control, and water resources infrastructure. This disregard, along with urbanization, industrialization, and other land uses has imperiled many waterways. New technologies including geospatially referenced data collection, laser-based measurement tools, and increasing computational powers by personal computers are significantly improving our ability to represent these complex and diverse systems. We can accomplish this through both the building of more sophisticated models and our ability to calibrate those models with more detailed data sets. The effort put forth in this dissertation is to first introduce the accomplishments and challenges in fluvial geomorphology and then to illustrate two specific efforts to add to the growing body of knowledge in this exciting field.First, we explore a dramatic phenomenon occurring in the Middle Rio Grande River. The San Marcial Reach of the Rio Grande River has experienced four events that completely filled the main channel with sediment over the past 20 years. This sediment plug has cost the nation millions of dollars in both costs to dredge and rebuild main channels and levees, along with detailed studies by engineering consultants. Previous efforts focused on empirical relations developed with historical data and very simple one dimensional representation of river hydrodynamics. This effort uses the state-of-the-art three-dimensional hydro and morphodynamic model Delft3D. We were able to use this model8to test those hypotheses put forth in previous empirical studies. We were also able to use this model to test theories associated with channel avulsion. Testing found that channel avulsions thresholds do exist and can be predicted based on channel bathymetric changes.The second effort included is a simple yet sophisticated model of river meander evolution. Prediction of river meandering planform evolution has proven to be one of the most difficult problems in all of geosciences. The limitations of using detailed three dimensional hydro and morphodynamic models is that the computational intensity precludes the modeling of large spatial or temporal scale phenomenon. Therefore, analytical solutions to the standard Navier-Stokes equations with simplifications made for hydrostatic pressure among others, along with sediment transport functions still have a place in our toolbox to understand and predict this phenomenon. One of the most widely used models of meander propagation is the Linear Bend Model that employs a bank erosion coefficient. Due to the various simplifications required to find analytical solutions to these sets of equations, efforts to build the stochasticity seen in nature into the models have proven useful and successful. This effort builds upon this commonly used meander propogation model by introducing stochasticity to the known variability in outer bank erodibility, resulting in a more realistic representation of model results

MODIS Inundation Estimate Assimilation into Soil Moisture Accounting Hydrologic Model: A Case Study in Southeast Asia

Flash Flood Guidance consists of indices that estimate the amount of rain of a certain duration that is needed over a given small basin in order to cause minor flooding. Backwater catchment inundation from swollen rivers or regional groundwater inputs are not significant over the spatial and temporal scales for the majority of upland flash flood prone basins, as such, these effects are not considered. However, some lowland areas and flat terrain near large rivers experience standing water long after local precipitation has ceased. NASA is producing an experimental product from the MODIS that detects standing water. These observations were assimilated into the hydrologic model in order to more accurately represent soil moisture conditions within basins, from sources of water from outside of the basin. Based on the upper soil water content, relations are used to derive an error estimate for the modeled soil saturation fraction; whereby, the soil saturation fraction model state can be updated given the availability of satellite observed inundation. Model error estimates were used in a Monte Carlo ensemble forecast of soil water and flash flood potential. Numerical experiments with six months of data (July 2011–December 2011) showed that MODIS inundation data, when assimilated to correct soil moisture estimates, increased the likelihood that bankfull flow would occur, over non-assimilated modeling, at catchment outlets for approximately 44% of basin-days during the study time period. While this is a much more realistic representation of conditions, no actual events occurred allowing for validation during the time period

MODIS Inundation Estimate Assimilation into Soil Moisture Accounting Hydrologic Model: A Case Study in Southeast Asia

Flash Flood Guidance consists of indices that estimate the amount of rain of a certain duration that is needed over a given small basin in order to cause minor flooding. Backwater catchment inundation from swollen rivers or regional groundwater inputs are not significant over the spatial and temporal scales for the majority of upland flash flood prone basins, as such, these effects are not considered. However, some lowland areas and flat terrain near large rivers experience standing water long after local precipitation has ceased. NASA is producing an experimental product from the MODIS that detects standing water. These observations were assimilated into the hydrologic model in order to more accurately represent soil moisture conditions within basins, from sources of water from outside of the basin. Based on the upper soil water content, relations are used to derive an error estimate for the modeled soil saturation fraction; whereby, the soil saturation fraction model state can be updated given the availability of satellite observed inundation. Model error estimates were used in a Monte Carlo ensemble forecast of soil water and flash flood potential. Numerical experiments with six months of data (July 2011–December 2011) showed that MODIS inundation data, when assimilated to correct soil moisture estimates, increased the likelihood that bankfull flow would occur, over non-assimilated modeling, at catchment outlets for approximately 44% of basin-days during the study time period. While this is a much more realistic representation of conditions, no actual events occurred allowing for validation during the time period

River meander modeling and confronting uncertainty.

This study examines the meandering phenomenon as it occurs in media throughout terrestrial, glacial, atmospheric, and aquatic environments. Analysis of the minimum energy principle, along with theories of Coriolis forces (and random walks to explain the meandering phenomenon) found that these theories apply at different temporal and spatial scales. Coriolis forces might induce topological changes resulting in meandering planforms. The minimum energy principle might explain how these forces combine to limit the sinuosity to depth and width ratios that are common throughout various media. The study then compares the first order analytical solutions for flow field by Ikeda, et al. (1981) and Johannesson and Parker (1989b). Ikeda's et al. linear bank erosion model was implemented to predict the rate of bank erosion in which the bank erosion coefficient is treated as a stochastic variable that varies with physical properties of the bank (e.g., cohesiveness, stratigraphy, or vegetation density). The developed model was used to predict the evolution of meandering planforms. Then, the modeling results were analyzed and compared to the observed data. Since the migration of a meandering channel consists of downstream translation, lateral expansion, and downstream or upstream rotations several measures are formulated in order to determine which of the resulting planforms is closest to the experimental measured one. Results from the deterministic model highly depend on the calibrated erosion coefficient. Since field measurements are always limited, the stochastic model yielded more realistic predictions of meandering planform evolutions. Due to the random nature of bank erosion coefficient, the meandering planform evolution is a stochastic process that can only be accurately predicted by a stochastic model

N–H Activation by Rh(I) via Metal–Ligand Cooperation

In continuation of our studies on bond activation and catalysis by pincer complexes, based on metal–ligand cooperation, we present here a rare example of amine N–H activation by Rh­(I) complexes. The novel dearomatized pincer complexes [(PNN*)­RhL′] (PNN = 2-(CH₂-P^<i>t</i>Bu₂)-6-(CH₂-NEt₂)­C₅H₃N, PNN* = deprotonated PNN, L′ = N₂ (<b>5</b>), C₂H₄ (<b>6</b>)) and [(^<i>i</i>PrPNP*)­RhL′] (^<i>i</i>PrPNP = 2,6-(CH₂-P^<i>i</i>Pr₂)₂C₅H₃N, ^<i>i</i>PrPNP* = deprotonated ^<i>i</i>PrPNP, L′ = C₂H₄ (<b>7</b>), cyclooctene (<b>9</b>)) were prepared and fully characterized by NMR and X-ray analysis. Complexes <b>5</b>–<b>7</b> and <b>9</b> undergo facile N–H activation of anilines involving aromatization of the pincer ligand without a change in the formal oxidation state of the metal center to form stable anilide complexes [(PNN)­Rh­(NHAr)] and [(^<i>i</i>PrPNP)­Rh­(NHAr)] (Ar = C₆H₅, <i>o</i>-Br-C₆H₄, <i>m</i>-Cl-<i>p</i>-Cl-C₆H₃, <i>p</i>-NO₂-C₆H₄). Anilines possessing electron-withdrawing groups accelerate the N–H activation and yield more stable anilide complexes. The pincer and the ancillary ligands also affect the activation rate, which supports an associative mechanism. Spin saturation transfer experiments show chemical exchange between the pyridylic arm of the pincer ligand and the NH– protons of anilines prior to and after the N–H activation. The reverse N–H formation by metal–ligand cooperation from the anilide complexes was observed to give free anilines and dearomatized Rh­(I) complexes upon addition of CO or PEt₃. Deprotonation of complexes [(PNL)­Rh­(<i>p</i>-NO₂-NH₂C₆H₄)] (<b>13</b>, P = P^<i>t</i>Bu₂, L = NEt₂; <b>15</b>, P = L = P^<i>i</i>Pr₂) yields the dearomatized anionic complexes [(PNL*)­Rh­(<i>p</i>-NO₂-NH₂C₆H₄)]. An associative mechanism, involving N–H activation of an apically coordinated aniline in a pentacoordinated Rh­(I) complex, is suggested

N–H Activation by Rh(I) via Metal–Ligand Cooperation

In continuation of our studies on bond activation and catalysis by pincer complexes, based on metal–ligand cooperation, we present here a rare example of amine N–H activation by Rh­(I) complexes. The novel dearomatized pincer complexes [(PNN*)­RhL′] (PNN = 2-(CH₂-P^<i>t</i>Bu₂)-6-(CH₂-NEt₂)­C₅H₃N, PNN* = deprotonated PNN, L′ = N₂ (<b>5</b>), C₂H₄ (<b>6</b>)) and [(^<i>i</i>PrPNP*)­RhL′] (^<i>i</i>PrPNP = 2,6-(CH₂-P^<i>i</i>Pr₂)₂C₅H₃N, ^<i>i</i>PrPNP* = deprotonated ^<i>i</i>PrPNP, L′ = C₂H₄ (<b>7</b>), cyclooctene (<b>9</b>)) were prepared and fully characterized by NMR and X-ray analysis. Complexes <b>5</b>–<b>7</b> and <b>9</b> undergo facile N–H activation of anilines involving aromatization of the pincer ligand without a change in the formal oxidation state of the metal center to form stable anilide complexes [(PNN)­Rh­(NHAr)] and [(^<i>i</i>PrPNP)­Rh­(NHAr)] (Ar = C₆H₅, <i>o</i>-Br-C₆H₄, <i>m</i>-Cl-<i>p</i>-Cl-C₆H₃, <i>p</i>-NO₂-C₆H₄). Anilines possessing electron-withdrawing groups accelerate the N–H activation and yield more stable anilide complexes. The pincer and the ancillary ligands also affect the activation rate, which supports an associative mechanism. Spin saturation transfer experiments show chemical exchange between the pyridylic arm of the pincer ligand and the NH– protons of anilines prior to and after the N–H activation. The reverse N–H formation by metal–ligand cooperation from the anilide complexes was observed to give free anilines and dearomatized Rh­(I) complexes upon addition of CO or PEt₃. Deprotonation of complexes [(PNL)­Rh­(<i>p</i>-NO₂-NH₂C₆H₄)] (<b>13</b>, P = P^<i>t</i>Bu₂, L = NEt₂; <b>15</b>, P = L = P^<i>i</i>Pr₂) yields the dearomatized anionic complexes [(PNL*)­Rh­(<i>p</i>-NO₂-NH₂C₆H₄)]. An associative mechanism, involving N–H activation of an apically coordinated aniline in a pentacoordinated Rh­(I) complex, is suggested