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We develop a physical and computational model for performing fully coupled, grain-resolved direct numerical simulations of cohesive sediment, based on the immersed boundary method. The model distributes the cohesive forces over a thin shell surrounding each particle, thereby allowing for the spatial and temporal resolution of the cohesive forces during particle–particle interactions. The influence of the cohesive forces is captured by a single dimensionless parameter in the form of a cohesion number, which represents the ratio of cohesive and gravitational forces acting on a particle. We test and validate the cohesive force model for binary particle interactions in the drafting–kissing–tumbling (DKT) configuration. Cohesive sediment grains can remain attached to each other during the tumbling phase following the initial collision, thereby giving rise to the formation of flocs. The DKT simulations demonstrate that cohesive particle pairs settle in a preferred orientation, with particles of very different sizes preferentially aligning themselves in the vertical direction, so that the smaller particle is drafted in the wake of the larger one. This preferred orientation of cohesive particle pairs is found to remain influential for systems of higher complexity. To this end, we perform large simulations of 1261 polydisperse settling particles starting from rest. These simulations reproduce several earlier experimental observations by other authors, such as the accelerated settling of sand and silt particles due to particle bonding, the stratification of cohesive sediment deposits, and the consolidation process of the deposit. They identify three characteristic phases of the polydisperse settling process, viz. (i) initial stir-up phase with limited flocculation, (ii) enhanced settling phase characterized by increased flocculation, and (iii) consolidation phase. The simulations demonstrate that cohesive forces accelerate the overall settling process primarily because smaller grains attach to larger ones and settle in their wakes. For the present cohesive number values, we observe that settling can be accelerated by up to 29 %. We propose physically based parametrization of classical hindered settling functions introduced by earlier authors, in order to account for cohesive forces. An investigation of the energy budget shows that, even though the work of the collision forces is much smaller than that of the hydrodynamic drag forces, it can substantially modify the relevant energy conversion processes.

Invasive Canadian waterweed Elodea canadensis and western waterweed E. nuttallii are a threat to native salmon Onchorhynchus spp. in Alaska. Early detection is important to stop or mitigate spread. We evaluated detection of environmental DNA (eDNA) as a tool for early detection of these invasive species in Alaska. First, we evaluated four quantitative real-time PCR assays, one for each species, and two targeting either species, using samples taken at known infestations in Chena Lakes and Potter Marsh, Alaska. We also deployed E. nuttallii in screened containers at the Small Arms Complex Pond, Fort Wainwright, Alaska (Test Pond), in 2018 and 2019 to evaluate the detection of eDNA as a function of distance from the containers. At the known infestations, we detected the eDNA of both species in water samples. However, in our Test Pond, we only detected Elodea eDNA in 2 of 126 samples collected in 2019. Both detections were from samples collected within 10 cm of the containers. There were no detections in 60 samples collected in 2018 at the Test Pond. While there are potential uses for the eDNA markers we developed (e.g., species identification), we found no evidence to support their use as an early-detection tool for Elodea in Alaska. [ABSTRACT FROM AUTHOR]

It has been shown that competing molecular interactions of atypical protein kinase C isoforms regulate neuronal polarity. For instance, silencing one particular isoform known as protein kinase M- ζ or overexpression of a second isoform known as protein kinase C- λ in hippocampal neurons alters neuronal polarity, resulting in neurons with extra axons. In contrast, the overexpression of protein kinase M- ζ prevents axon specification. These data suggest that antagonistic competition between PKC isoforms could contribute to the development of polarity and axon specification. Here, an excitatory and inhibitory non-linear network model is employed to describe neuronal polarity under different conditions. The model shifts the balance of excitation and inhibition to replicate a variety of scenarios during axon outgrowth, which are then compared with experimental results.

We develop a physical and computational model for performing fully coupled, grain-resolved direct numerical simulations of cohesive sediment, based on the immersed boundary method. The model distributes the cohesive forces over a thin shell surrounding each particle, thereby allowing for the spatial and temporal resolution of the cohesive forces during particle–particle interactions. The influence of the cohesive forces is captured by a single dimensionless parameter in the form of a cohesion number, which represents the ratio of cohesive and gravitational forces acting on a particle. We test and validate the cohesive force model for binary particle interactions in the drafting–kissing–tumbling (DKT) configuration. Cohesive sediment grains can remain attached to each other during the tumbling phase following the initial collision, thereby giving rise to the formation of flocs. The DKT simulations demonstrate that cohesive particle pairs settle in a preferred orientation, with particles of very different sizes preferentially aligning themselves in the vertical direction, so that the smaller particle is drafted in the wake of the larger one. This preferred orientation of cohesive particle pairs is found to remain influential for systems of higher complexity. To this end, we perform large simulations of 1261 polydisperse settling particles starting from rest. These simulations reproduce several earlier experimental observations by other authors, such as the accelerated settling of sand and silt particles due to particle bonding, the stratification of cohesive sediment deposits, and the consolidation process of the deposit. They identify three characteristic phases of the polydisperse settling process, viz. (i) initial stir-up phase with limited flocculation, (ii) enhanced settling phase characterized by increased flocculation, and (iii) consolidation phase. The simulations demonstrate that cohesive forces accelerate the overall settling process primarily because smaller grains attach to larger ones and settle in their wakes. For the present cohesive number values, we observe that settling can be accelerated by up to 29 %. We propose physically based parametrization of classical hindered settling functions introduced by earlier authors, in order to account for cohesive forces. An investigation of the energy budget shows that, even though the work of the collision forces is much smaller than that of the hydrodynamic drag forces, it can substantially modify the relevant energy conversion processes. [ABSTRACT FROM AUTHOR]

Purpose This study aims to explore the relationship between concussion-related sleep symptoms and affective symptoms in high school athlete. Methods A retrospective analysis of the Maine Concussion Management Initiative (MCMI) Immediate Post-concussion Assessment Tool ™ (ImPACT™) database was conducted to investigate the relationship between sleep and affective symptom scores in high school athletes (14-18 years) within 7 days of sustaining a concussion. The Post-Concussion Symptom Scale (PCSS) was completed by each athlete as part of their post-injury ImPACT™ testing battery. Sleep-related symptoms and affective/mood related symptoms from the PCSS were summed to create a sleep and affective symptom score, respectively. Results The final sample included 548 adolescents (M=15.94±1.06 years old; 50.4% female) were evaluated 3.16±1.85 days after injury. The results of a simple linear regression revealed a significant relationship between sleep and affective symptoms (F(1,546)=142.60, p<.001), and the model explained 20.7% of the total variance of affective symptom scores. Additionally, there was an association between gender and affective symptoms (Χ2(1)=6.39, p=.01), with females 1.6 times more likely to report at least one affective symptom. Females (M=3.62±4.33) had significantly higher affective symptom scores compared to their male (M=2.35±3.46) counterparts (t(546)=3.79, p<.001). Conclusions This study provides evidence of a significant relationship between sleep disturbance and affective symptoms in high school-aged athletes following concussion. Female athletes reported higher affective symptom scores. [ABSTRACT FROM AUTHOR]