Convectively driven coastal currents in a rotating basin

Density driven coastal currents were produced in the laboratory by differentially heating and cooling the end walls of a rotating rectangular cavity. After turning on the heat flux, intrusions propagated along the side walls of the cavity under an inertial buoyancy balance, with a geostrophic cross-stream balance. These boundary currents were internally stratified in temperature, while the environment during the early stages of development of the flow was isothermal. Rotational instabilities developed on the edge of the currents and broke to form cyclone-anticyclone eddy pairs. Measurements were made of the intrusion velocity, the temporal development of the width of the boundary currents, their internal thermal structure, and the characteristics of the unstable waves, including their growth rates, wavelengths, and phase speeds. Comparisons are made with previous field observations of the Leeuwin Current off Western and Southern Australia

Simple mixing criteria for the growth of negatively buoyant phytoplankton

Phytoplankton population dynamics are controlled by the relative rather than absolute timescales of mixing, growth, and loss processes such as sedimentation, grazing, and so on. Here, the vertical distribution and biomass of phytoplankton populations are quantified by two timescale ratios: the Peclet number Pe the ratio of mixing and sedimentation timescales-and the growth number G the ratio of sedimentation and net growth timescales. Three mixing regimes are defined for phytoplankton and other particles. For Pe greater than or equal to 100, the population is translated linearly down the water column over time and will leave the surface mixing layer completely after sedimentation time 7, For 0.

Observations of diurnal coastal-trapped waves with a thermocline-intensified velocity field

Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(7), (2019): 1973-1994, doi: 10.1175/JPO-D-18-0194.1.Using 18 days of field observations, we investigate the diurnal (D1) frequency wave dynamics on the Tasmanian eastern continental shelf. At this latitude, the D1 frequency is subinertial and separable from the highly energetic near-inertial motion. We use a linear coastal-trapped wave (CTW) solution with the observed background current, stratification, and shelf bathymetry to determine the modal structure of the first three resonant CTWs. We associate the observed D1 velocity with a superimposed mode-zero and mode-one CTW, with mode one dominating mode zero. Both the observed and mode-one D1 velocity was intensified near the thermocline, with stronger velocities occurring when the thermocline stratification was stronger and/or the thermocline was deeper (up to the shelfbreak depth). The CTW modal structure and amplitude varied with the background stratification and alongshore current, with no spring–neap relationship evident for the observed 18 days. Within the surface and bottom Ekman layers on the shelf, the observed velocity phase changed in the cross-shelf and/or vertical directions, inconsistent with an alongshore propagating CTW. In the near-surface and near-bottom regions, the linear CTW solution also did not match the observed velocity, particularly within the bottom Ekman layer. Boundary layer processes were likely causing this observed inconsistency with linear CTW theory. As linear CTW solutions have an idealized representation of boundary dynamics, they should be cautiously applied on the shelf.An Australian Research Council Discovery Project (DP 140101322), and a UWA Research Collaboration Award funded this work. T. L. Schlosser acknowledges the support of an Australian Government Research Training Program (RTP) Scholarship. We thank the crew, volunteers and scientists who aided in the field data collection aboard the R/V Revelle, which was funded by the National Science Foundation (OCE-1129763). The continental slope moorings, T4 (M32) and T3 (M44), were also funded by the National Science Foundation (OCE-1129763) and were conceived, planned, and executed by Matthew Alford, Jennifer Mackinnon, Jonathan Nash, Harper Simmons, and Gunnar Voet. We also thank Harper Simmons for the combined R/V Revelle multibeam and Geoscience Australia bathymetry used in this study. We thank the two anonymous reviewers whose comments improved this work.2020-01-1

MicroRNA profiling of the pubertal mouse mammary gland identifies miR-184 as a candidate breast tumour suppressor gene

INTRODUCTION: The study of mammalian development has offered many insights into the molecular aetiology of cancer. We previously used analysis of mammary morphogenesis to discover a critical role for GATA-3 in mammary developmental and carcinogenesis. In recent years an important role for microRNAs (miRNAs) in a myriad of cellular processes in development and in oncogenesis has emerged. METHODS: microRNA profiling was conducted on stromal and epithelial cellular subsets microdissected from the pubertal mouse mammary gland. miR-184 was reactivated by transient or stable overexpression in breast cancer cell lines and examined using a series of in vitro (proliferation, tumour-sphere and protein synthesis) assays. Orthotopic xenografts of breast cancer cells were used to assess the effect of miR-184 on tumourigenesis as well as distant metastasis. Interactions between miR-184 and its putative targets were assessed by quantitative PCR, microarray, bioinformatics and 3' untranslated region Luciferase reporter assay. The methylation status of primary patient samples was determined by MBD-Cap sequencing. Lastly, the clinical prognostic significance of miR-184 putative targets was assessed using publicly available datasets. RESULTS: A large number of microRNA were restricted in their expression to specific tissue subsets. MicroRNA-184 (miR-184) was exclusively expressed in epithelial cells and markedly upregulated during differentiation of the proliferative, invasive cells of the pubertal terminal end bud (TEB) into ductal epithelial cells in vivo. miR-184 expression was silenced in mouse tumour models compared to non-transformed epithelium and in a majority of breast cancer cell line models. Ectopic reactivation of miR-184 inhibited the proliferation and self-renewal of triple negative breast cancer (TNBC) cell lines in vitro and delayed primary tumour formation and reduced metastatic burden in vivo. Gene expression studies uncovered multi-factorial regulation of genes in the AKT/mTORC1 pathway by miR-184. In clinical breast cancer tissues, expression of miR-184 is lost in primary TNBCs while the miR-184 promoter is methylated in a subset of lymph node metastases from TNBC patients. CONCLUSIONS: These studies elucidate a new layer of regulation in the PI3K/AKT/mTOR pathway with relevance to mammary development and tumour progression and identify miR-184 as a putative breast tumour suppressor

Investigation of Methods for Target State Estimation Using Vision Sensors,” AIAA guidance, navigation, and control conference

Identifying object location and orientation are important tasks in target tracking and obstacle avoidance. This paper proposes an algorithm for identifying target location, size, and orientation without any prior knowledge based on machine vision. The algorithm uses target measurements taken from a video camera to update estimates of the target. Two forms of the Kalman filter were compared as methods for estimating the targets ’ states. The first, the extended Kalman filter (EKF), uses a Taylor series expansion about the current state to estimate the nonlinear measurement update. The second, the square-root unscented Kalman filter (SRUKF), a form of the unscented Kalman filter (UKF), uses perturbed sigma points to estimate the mean and covariance of the measurement update. The algorithm was tested using periodic vehicle motion and random target location, orientation, and area. Both Kalman filter methods converged on the targets ’ 3-D position, orientation, and area but required an irregular trajectory to accurately estimate the orientation and area. The estimators were simulated using identical parameters to compare them based on equivalent conditions. This produced similar results from the EKF and SRUKF and therefore neither showed a significant improvement over the other

Experimental study on resonantly forced interfacial waves in a stratified circular cylindrical basin

International audienceLaboratory experiments have been performed on resonantly forced interfacial waves in a circular cylindrical basin containing a two-layer stratified fluid. The results of this shallow-water study exhibit a number of similarities to previous shallow-water studies performed in single-layer fluids, such as the generation of a large-amplitude response over a frequency bandwidth offset from the primary resonance, generation of a swirling mode at the observed resonant condition, and the significant contribution of higher harmonics. The two-layer experiments also produce results that are unique to stratified domains. In particular, the observed negative nonlinearity of the resonant condition at shallow water depth, mixing of the density interface resulting in detuning the forced response from the resonant condition, the enhanced role of viscous dissipation, and an alternative pathway for the nonlinear generation of higher-frequency waves when the layer depths are disparate. The results of this study are considered with regard to their implications for enclosed basins at the geophysical scale that are subject to near resonant forcing

Cylinder wakes in shallow oscillatory flow: the coastal island wake problem

International audienceTopographic complexity on continental shelves is the catalyst that transforms the barotropic tide into the secondary and residual circulations that dominate vertical and cross-shelf mixing processes. Island wakes are one such example that are observed to significantly influence the transport and distribution of biological and physical scalars. Despite the importance of island wakes, to date, no sufficient, mechanistic description of the physical processes governing their development exists for the general case of unsteady tidal forcing. Controlled laboratory experiments are necessary for the understanding of this complex flow phenomena. Three-dimensional velocity field measurements of cylinder wakes in shallow-water, oscillatory flow are conducted across a parameter space that is typical of tidal flow around shallow islands. Previous studies investigated the wake form dependance on $KC=U_0T/D$, where $KC$ is the Keulegan-Carpenter number, $D$ is the island diameter, $U_0$ the tidal velocity amplitude and $T$ the tidal period, and the stability parameter $S=c_fD/h$ where $h$ is the water depth and $c_f$ is the bottom boundary friction coefficient. In this study we demonstrate that when the influence of bottom friction is confined to a Stokes boundary layer the parameter $S=\delta^+/KC$ where $\delta^+=\delta/h$ and $\delta=2\pi\sqrt{2\nu/\omega}$ is the wavelength of the Stokes bottom boundary layer. Three classes of wake form are observed for decreasing wake stability: \emph{(1) Steady Bubble} for $S\gtrsim 0.1$; \emph{(2) Unsteady Bubble} for $0.06\lesssim S \lesssim 0.1$; and \emph{(3) Vortex Shedding} for $S\lesssim 0.06$. Transitions in wake form and wake stability are shown to depend on the magnitude and temporal evolution of the wake return flow. Scaling laws are developed to allow upscaling of the laboratory results to island wakes. Vertical and lateral transport depend on th..