Pathophysiological changes in the cortex, thalamus, and hippocampus have been implicated as contributors to motor and cognitive deficits in a number of animal models of traumatic brain injury (TBI). Indirect cerebellar injury may contribute to TBI pathophysiology because impairment of motor function and coordination are common consequences of TBI, but are also domains associated with cerebellar function. However, there is a lack of direct evidence to support this claim. Hence, in this study, a dose-response relationship of the cerebellum's susceptibility was determined at four grades of fluid percussion injury (1.5, 2.0, 2.5, and 3.0 atm) applied in the right lateral cerebral cortex of adult male Sprague-Dawley rats. Evidence suggests primary and secondary injury mechanisms resulting in selective cerebellar Purkinje neuron (PN) loss, whereas interneurons of the molecular layer were spared. The posterior region of the cerebellar vermis displayed significant PN loss (p = 0.001) at 1 day postinjury, whereas the gyrus of the horizontal fissure and gyrus of lobules III and IV exhibited delayed PN loss at higher levels of injury severity. Interestingly, neither terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) or cleaved caspase-3 colocalized with PNs at any time point or injury severity. Expression of calbindin-28k increased in regions of greatest PN loss, suggesting that the surviving PNs possess higher calcium-buffering capacities, which may account for their survival.

Demand for lithium for batteries is growing rapidly with the global push to decarbonize energy systems. The Salar de Atacama, Chile holds ∼42% of the planet's reserves in the form of brine hosted in massive evaporite aquifers. The mining of these brines and associated freshwater use has raised concerns over the environmental responsibility of lithium extraction, yet large uncertainties remain regarding fundamental aspects of governing hydrological processes in these environments. This incomplete understanding has led to the perpetuation of misconceptions about what constitutes sustainable or renewable water use and therefore what justifies responsible allocation. We present an integrated hydrological assessment using tritium and stable oxygen, and hydrogen isotopes paired with remotely sensed and terrestrial hydroclimate data to define unique sources of water distinguished by residence time, physical characteristics, and connectivity to modern climate. Our results describe the impacts of prolonged drought on surface and groundwaters and demonstrate that nearly all inflow to the basin is composed of water recharged >65 years ago. Still, modern precipitation is critical to sustaining important wetlands around the salar. Recent large rain events have increased surface water and vegetation extents and terrestrial water storage while mining‐related water withdrawals have continued. As we show, poor conceptualizations of these complex hydrological systems have perpetuated the misallocation of water and the misattribution of impacts. These fundamental issues apply to arid regions globally. Our new framework for hydrological assessment in these basins moves beyond calculating gross inputs‐outputs at a steady state to include all compartmentalized stores that constitute “modern” budgets.

The marginal environments of salar (e.g., salt flats) systems are unique ecological and hydrogeological regions of great importance in arid to hyper-arid climates (Pigati et al., 2014; Rosen, 1994; Warren, 2016). These distinctive places have become one of the most significant areas of concern in regions where groundwater and/or brine extraction are relied on for human use including resource development and fresh water sources used by communities (Houston et al., 2011; Tyler et al., 2006; Warren, 2010). As demand for water sources continues to increase (Gleeson et al., 2020; Wang et al., 2018; Zipper et al., 2020) it is critical to have a complete and scientifically based assessment of these transitional zone regions where freshwater discharges and evaporates above brackish and brine water in the subsurface. This process is what supports the formation of springs, wetlands or marshes (vegas), and lagoons (lagunas) that form important ecosystems on the margins of all salars on a global scale. However, the extent of development of these groundwater

Numerical simulations of density-dependent flow assess the risk of saline groundwater intrusion in coastal areas (Heiss & Michael, 2014;Meng et al., 2002;Trabelsi et al., 2013), and in arid and often endorheic basins where evaporation outpaces recharge and concentrates solutes in groundwater (Stein et al., 2019). The discrepancy in fluid density develops an interface where the denser brine underlies the less dense fluid to create a freshwater lens, which is commonly known as a brine-to-freshwater interface (Duffy & Hassan, 1988;

Despite the prevalence of density-driven flow systems in brine-rich aquifers of arid climates and coastal aquifers, the impact of realistic geologic conditions remains poorly constrained regarding interface geometry in arid regions and time-sensitive density-dependent dynamics in brine-bearing aquifers in general. Salar de Atacama provides an analog for exploring interface dynamics in arid regions. A site-specific 2D hydrostratigraphic interpretation is used to examine the dynamics of the brine-to-freshwater interface. With the same simulation framework and core data, a separate parametric series of hydraulic conductivity distributions with varying horizontal continuity provides a mechanistic explanation for observed dynamics. Comparing modeled interfaces and their sensitivity to perturbations in recharge in each realization yields insight into interface dynamics coupled with horizontal continuity in subsurface heterogeneity. Recharge fluctuation is introduced to each distribution following the interface reaching a dynamic steady state. Metrics for results evaluation include migration length, interface slope geometry, and response rate. Analyses suggest that the slope of the modeled interface shallows or decreases by 0.01 to 0.05 m $\cdot$ m\textsuperscript{-1} for every increase in continuity of highly permeable pathways by a factor. Increasing continuity also increases both the overall response times and the variability in response. Results indicate that accurate representations of transient dynamics in modeling density-driven brine-to-freshwater interface dynamics requires the consideration of heterogeneity, as saline intrusion in the highest continuity group extends over twice as far on average and the modeled interface takes over 43 percent more time on average to reach a new dynamic steady state when compared to their homogeneous counterparts.