The stratified inclined duct (SID) sustains an exchange flow in a long, gently sloping duct as a model for continuously forced density-stratified flows such as those found in estuaries. Experiments have shown that the emergence of interfacial waves and their transition to turbulence as the tilt angle is increased appears to be linked to a threshold in the exchange flow rate given by inviscid two-layer hydraulics. We uncover these hydraulic mechanisms by (i) using recent direct numerical simulations (DNS) providing full flow data in the key flow regimes (Zhu et al., J. Fluid Mech., vol. 969, 2023, A20), (ii) averaging these DNS into two layers, and (iii) using an inviscid two-layer shallow-water and instability theory to diagnose interfacial wave behaviour and provide physical insight. The laminar flow is subcritical and stable throughout the duct and hydraulically controlled at the ends of the duct. As the tilt is increased, the flow becomes supercritical everywhere and unstable to long waves. An internal jump featuring stationary waves first appears near the centre of the duct, then leads to larger-amplitude travelling waves, and to stronger jumps, wave breaking and intermittent turbulence at the largest tilt angle. Long waves described by the (nonlinear) shallow-water equation are interpreted locally as linear waves on a two-layer parallel base flow described by the Taylor–Goldstein equation. This link helps us to interpret long-wave instability and contrast it with short-wave (e.g. Kelvin–Helmholtz) instability. Our results suggest a transition to turbulence in SID through long-wave instability relying on vertical confinement by the top and bottom walls.

The stratified inclined duct (SID) experiment consists of a zero-net-volume exchange flow in a long tilted rectangular duct, which allows the study of realistic stratified shear flows with sustained internal forcing. We present the first three-dimensional direct numerical simulations (DNS) of SID to explore the transitions between increasingly turbulent flow regimes first described by Meyer & Linden (J. Fluid Mech., vol. 753, 2014, pp. 242–253). We develop a numerical set-up that faithfully reproduces the experiments and sustains the flow for arbitrarily long times at minimal computational cost. We recover the four qualitative flow regimes found experimentally in the same regions of parameter space: laminar flow, waves, intermittent turbulence and fully developed turbulence. We find good qualitative and quantitative agreement between DNS and experiments and highlight the added value of DNS to complement experimental diagnostics and increase our understanding of the transition to turbulence, both temporally (laminar/turbulent cycles) and parametrically (as the tilt angle of the duct and the Reynolds number are increased). These results demonstrate that numerical studies of SID – and deeper integration between simulations and experiments – have the potential to lead to a better understanding of stratified turbulence.

OBJECTIVES/GOALS: Glioblastomas (GBMs) are heterogeneous, treatment-resistant tumors that are driven by populations of cancer stem cells (CSCs). In this study, we perform an epigenetic-focused functional genomics screen in GBM organoids and identify WDR5 as an essential epigenetic regulator in the SOX2-enriched, therapy resistant cancer stem cell niche. METHODS/STUDY POPULATION: Despite their importance for tumor growth, few molecular mechanisms critical for CSC population maintenance have been exploited for therapeutic development. We developed a spatially resolved loss-of-function screen in GBM patient-derived organoids to identify essential epigenetic regulators in the SOX2-enriched, therapy resistant niche. Our niche-specific screens identified WDR5, an H3K4 histone methyltransferase responsible for activating specific gene expression, as indispensable for GBM CSC growth and survival. RESULTS/ANTICIPATED RESULTS: In GBM CSC models, WDR5 inhibitors blocked WRAD complex assembly and reduced H3K4 trimethylation and expression of genes involved in CSC-relevant oncogenic pathways. H3K4me3 peaks lost with WDR5 inhibitor treatment occurred disproportionally on POU transcription factor motifs, required for stem cell maintenance and including the POU5F1(OCT4)::SOX2 motif. We incorporated a SOX2/OCT4 motif driven GFP reporter system into our CSC cell models and found that WDR5 inhibitor treatment resulted in dose-dependent silencing of stem cell reporter activity. Further, WDR5 inhibitor treatment altered the stem cell state, disrupting CSC in vitro growth and self-renewal as well as in vivo tumor growth. DISCUSSION/SIGNIFICANCE: Our results unveiled the role of WDR5 in maintaining the CSC state in GBM and provide a rationale for therapeutic development of WDR5 inhibitors for GBM and other advanced cancers. This conceptual and experimental framework can be applied to many cancers, and can unmask unique microenvironmental biology and rationally designed combination therapies.

Field experiments were conducted at four locations in the Central Pacific region of Costa Rica between 1994 and 1996 to determine suitable tactics for integrated control of propanil-resistant junglerice in rain-fed rice. Stubble incorporation within 3 mo after rice harvest did not affect the density of junglerice that emerged with the crop at the beginning of the rainy season at any location. However, the elimination with glyphosate of the first junglerice seedling population emerging before rice planting consistently reduced the in-crop infestation of junglerice and resulted in increased grain yields. The positive effect of eliminating the first junglerice flush remained even after the in-crop treatments were applied and lasted after rice harvest. Substitution of the two customary applications of propanil (3.8 kg ha−1 each) with a single application of pendimethalin (0.75 to 1.5 kg ha−1), preemergence or early postemergence, also reduced junglerice infestation and improved grain yield. Both propanil, in mixture with the synergist piperophos, and quinclorac controlled propanil-resistant junglerice and increased grain yields. Control of the initial junglerice population and improved in-crop weed management can serve as the basis for integrated management of herbicide-resistant junglerice in rain-fed rice.

Rapid detection methods were developed for discriminating between resistant (R) and susceptible (S) biotypes of Echinochloa colona to either propanil or fenoxaprop-P at all growth stages. In the pregerminated seed assay for fenoxaprop-P, seeds were placed on 1.0% agar containing a range of concentrations of herbicides and kept under humid conditions. For propanil, pregerminated seeds were placed on moist filter paper in the lid of a petri dish and, when one leaf had developed, the lid was inverted for 1 min into propanil solutions at a range of concentrations. For the fenoxaprop-P and propanil test, seedling length and fresh weight were measured after 1 wk. For juvenile plants with four-leaf to one-tiller, shoots and roots were trimmed and placed in 20-ml glass tubes containing 0.2% (wt/v) agar and a range of concentrations of herbicides. Shoot extension and weight were recorded after 7 d. Larger plants with several small tillers were also assayed by this method. Tillers were removed from larger plants and were evaluated as described for juvenile plants. At later growth stages from ear emergence to flowering, excised stem node segments (8 cm) were soaked in water to stimulate rooting. Rooted nodes were placed in 30-ml glass bottles containing 0.2% agar with a range of concentrations of herbicides, and the test was conducted as described for juvenile plants but with the final assessment of new shoot extension and weight being recorded after 10 d. Discrimination between R and S biotypes was possible on the basis of GR50 values for shoot length and fresh weight in all testing methods. With few exceptions, GR50 values for the length of new shoot were very similar to those for the new shoot fresh weight. We concluded that all testing methods in our study provided reliable and quick discrimination between biotypes for both propanil and fenoxaprop-P susceptibility, covering various growth stages from seed to flowering stage. Trimming plants before herbicide treatment gives a rapid method of discrimination by measuring not only newly grown shoot fresh weight but also shoot length.

We use the underlying data of the IMPLAN Pro 3.0 regional economic simulation model to estimate the current economic contribution of Michigan's local food system and explore the chain of transactions giving rise to consumption of locally sourced goods from producer to processor to consumption. The proposed methodology includes both unprocessed and processed foods in the estimation of the local food system's economic value. The model also provides a replicable and consistent approach to estimating the value of local food systems within regional and state economies.