Kinematics of an Ebb Plume Front in a Tidal Crossflow Honegger, D. A.; Ralston, D. K.; Jurisa, J. ...
Journal of geophysical research. Oceans,
June 2024, 2024-06-00, 20240601, Letnik:
129, Številka:
6
Journal Article
Recenzirano
X‐band marine radar observations and a hindcast simulation from a 3D hydrostatic model are used to provide an overview of Connecticut River (USA) ebb plume front expansion into the strong tidal ...crossflow of eastern Long Island Sound. The model performance is evaluated against in situ and remote sensing observations and demonstrates dominant control of the front by semidiurnal tides. The recurring frontal evolution is classified into three dynamical stages of arrest, propagation, and advection. A conceptual model that follows this progressing balance between outflow buoyancy and crossflow momentum qualitatively reproduces frontal evolution in both the radar observations and the hindcast. The majority of the residual, intertidal variability of front timing and geometry is explained by co‐varying tidal amplitude, freshwater discharge, and wind stress using a multi‐linear regression analysis of the radar observation record. Intrinsic front speeds in the modeled frontal propagation are compared with the analytical model of Benjamin (1968, https://doi.org/10.1017/s0022112068000133), with better agreement achieved after accounting for ambient near‐surface shear associated with wind forcing.
Plain Language Summary
The fresh buoyant water that exits the Connecticut River mouth (USA) during each ebb tide expands as a plume, and floats above the denser waters of Long Island Sound. Currents in the Sound flow back and forth along the coast each tide, pushing the plume along the shore first to the east and then to the west. The location of the plume boundary (front) goes through a similar cycle almost every tide, initially being held stationary by eastward tidal currents, then expanding freely around slack tide, and subsequently being aided as it moves to the west by the ambient flow. Small changes to the arrival time and shape of the front are linked to changes in river discharge, tidal strength, and winds. Realistic simulations using a type of numerical model that aids coastal decision making are able to reproduce the tidal progression of front movement that was observed in 6 weeks of marine radar images of the water surface. Front movement in the numerical model also fits a simple analytical theory to a degree not previously seen on such a large scale, despite the complicating effects of wind.
Key Points
Buoyant ebb plume front kinematics in a tidal cross‐flow are characterized by stages of arrest, propagation, and advection
Wind, tide, and discharge variations explain modifications to the dominant semidiurnal control of the Connecticut River plume front
Front propagation in a hydrostatic numerical model reproduces both radar remote sensing observations and gravity current theory
A high-precision polarimeter Hauger, M.; Honegger, A.; Jourdan, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2001, Letnik:
462, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We have built a polarimeter in order to measure the electron beam polarization in hall C at JLAB. Using a superconducting solenoid to drive the pure-iron target foil into saturation, and a ...symmetrical setup to detect the M
øller electrons in coincidence, we achieve an accuracy of <1%. This sets a new standard for M
øller polarimeters.
Cultured NIH 3T3 cells devoid of endogenous EGF receptors were transfected with cDNA constructs encoding either the human EGF receptor or an EGF receptor mutant in which Lys721, a key residue in the ...ATP binding site, was replaced with an alanine residue. The mutant receptor was properly processed, and it displayed both high- and low-affinity surface binding sites. Unlike the wild-type receptor, the mutant receptor did not possess intrinsic protein-tyrosine kinase activity. The initial rate of EGF internalization was similar for wild-type and mutant EGF receptors. Surprisingly, the mutant receptors were not down regulated, but appeared to recycle in transfected cells. These data suggest that degradation of normal EGF receptors after endocytosis is due to the kinase activity endogenous to this receptor. A single amino acid substitution rendered a "down-regulated" receptor into a receptor that can recycle from cytoplasmic compartment back to the cell surface.
Aerial image sequences of an ebbing river plume propagating into a tidal cross‐flow demonstrate the presence of along‐front instabilities at multiple scales, which appear to propagate along‐front in ...the direction of the shear flow. We hypothesize the instabilities are due to cross‐front shear in the along‐front velocity field. Image analysis quantifies the horizontal shear across the plume front as well as the length scales and propagation speeds of the instabilities. In situ measurements from cross‐front ship transects are also used to examine shear and the width of the shear layer. A non‐hydrostatic numerical simulation of an ebb plume in an idealized tidal cross‐flow was conducted using comparable flow parameters and confirms the presence of shear instabilities. An additional numerical simulation without a tidal‐cross flow demonstrates that shear instabilities are not present; rather, lobe‐and‐cleft structures on the nose of the gravity current emerge. According to the scaling of White and Helfrich (2013), utilizing both the observed and modeled parameters, it is shown that shear instabilities are likely in the observed and modeled cross‐flow scenario, and confirms that they are unlikely to emerge in the no cross‐flow model case.
Plain Language Summary
Where rivers discharge into the ocean, distinct fronts form between the fresher river and more saline ocean waters. Fluid instabilities often form along these fronts. The dynamics of these frontal structures can be complicated, and influence the river plume during its life cycle. Here, we present unique observations of horizontal instabilities that develop along an ebbing river plume, and propagate along the front of the plume like waves. We analyze these instabilities for their spatial and temporal characteristics, and use a model forced with similar flow properties to see if such instabilities can be simulated.
Key Points
Novel observations of frontal instabilities on an ebbing plume are presented and their speeds and length scales are quantified
Non‐hydrostatic modeling of a plume ebbing into a tidal cross‐flow demonstrates similar shear instabilities
Modeling also confirms instability vs. gravity current behavior using a non‐dimensional parameter characterization
Recombinant antibody fragments, most notably Fab and scFv, have become important tools in research, diagnostics and therapy. Since different recombinant antibody formats exist, it is crucial to ...understand the difference in their respective biophysical properties. We assessed the potential stability benefits of changing the scFv into the Fab format, the influence of the variable domains on the stability of the Fab fragment, and the influence of the interchain disulfide bond in the Fab fragment. To analyze domain interactions, the Fab fragment was broken down into its individual domains, several two-domain assemblies and one three-domain assembly. The equilibrium denaturation properties of these constructs were then compared to those of the Fab fragment. It was found that mutual stabilization occurred across the V
H/V
L and the C
H1/C
L interface, whereas the direct interaction between the V
L and the C
L domain had no influence on the stability of either domain. This observation can be explained by the different interfaces used for interaction. In contrast, the whole C
H1C
L and V
HV
L unit showed significant mutual stabilization, indicating a high degree of cooperation between the V
H/V
L and C
H1/C
L interface. The interchain disulfide bond in the Fab fragment plays an essential role in this stabilization. In addition to the effects of domain association on the thermodynamic (equilibrium) stability, Fab fragments differ from scFv fragments of similar equilibrium stability by having a very slow unfolding rate. This kinetic stabilization may increase significantly the resistance of Fab fragments against short time exposure to adverse conditions.
We have isolated cDNA clones and deduced the complete amino acid sequence of a large receptor-type protein tyrosine phosphatase containing 2307 amino acids. The human gene encoding this phosphatase, ...denoted RPTP beta (or PTP zeta), has been localized to chromosome 7q31-33. RPTP beta is composed of a large extracellular domain, a single transmembrane domain, and a cytoplasmic portion with two tandem catalytic domains. We have also cloned a variant of RPTP beta lacking 859 amino acids from the extracellular domain but with intact transmembrane and cytoplasmic domains. Interestingly, the amino-terminal region of the extracellular domain of RPTP beta contains a stretch of 266 amino acids with striking homology to the enzyme carbonic anhydrase. Immunoprecipitation experiments from a human neuroblastoma cell line indicate that the apparent molecular mass of the core and glycosylated forms of RPTP beta are approximately 250 and 300 kDa, respectively. Northern blot analysis shows that RPTP beta is strictly expressed in the central nervous system. In situ hybridization was used to further localize the expression to different regions of the adult brain including the Purkinje cell layer of the cerebellum, the dentate gyrus, and the subependymal layer of the anterior horn of the lateral ventricle. Hence, RPTP beta represents the first mammalian tyrosine phosphatase whose expression is restricted to the nervous system. The high level of expression of RPTP beta transcripts in the ventricular and subventricular zones of the embryonic mouse brain suggests the importance of this tyrosine phosphatase in the development of the central nervous system.
The time and space variability of wave transformation through a tidal inlet is investigated with radar remote sensing. The frequency of wave breaking and the net wave breaking dissipation at high ...spatial resolution is estimated using image sequences acquired with a land-based X-band marine radar. Using the radar intensity data, transformed to normalized radar cross section sigma super(0), the temporal and spatial distributions of wave breaking are identified using a threshold developed via the data probability density function. In addition, the inlet bathymetry is determined via depth inversion of the radar-derived frequencies and wavenumbers of the surface waves using a preexisting algorithm (cBathy). Wave height transformation is calculated through the 1D cross-shore energy flux equation incorporating the radar-estimated breaking distribution and bathymetry. The accuracy of the methodology is tested by comparison with in situ wave height observations over a 9-day period, obtaining correlation values R = 0.68 to 0.96, and root-mean-square errors from 0.05 to 0.19 m. Predicted wave forcing, computed as the along-inlet gradient of the cross-shore radiation stress was onshore during high-wave conditions, in good agreement (R = 0.95) with observations.
Tensor polarization observables ( t(20), t(21), and t(22)) have been measured in elastic electron-deuteron scattering for six values of momentum transfer between 0.66 and 1.7 (GeV/c)(2). The ...experiment was performed at the Jefferson Laboratory in Hall C using the electron High Momentum Spectrometer, a specially designed deuteron magnetic channel and the recoil deuteron polarimeter POLDER. The new data determine to much larger Q2 the deuteron charge form factors G(C) and G(Q). They are in good agreement with relativistic calculations and disagree with perturbative QCD predictions.
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