scholarly journals Upstream Internal Jumps in Stratified Sill Flow: Observations of Formation, Evolution, and Release

2010 ◽  
Vol 40 (6) ◽  
pp. 1419-1426 ◽  
Author(s):  
Patrick F. Cummins ◽  
Laurence Armi
Keyword(s):  
Hydraulic Jump ◽  
Early Stage ◽  
Gravity Current ◽  
Tidal Flow ◽  
Time Dependent ◽  
Upstream Region ◽  
Exchange Flow ◽  
Near Surface ◽  
Undular Bore ◽  
First Case

Abstract The time-dependent response of upstream undular bores and internal hydraulic jumps from initial formation to eventual release is documented. Two events, characterized by qualitatively different responses, are discussed. In the first case, an undular bore develops upstream of the sill crest. This disturbance remains upstream through the ebb tidal flow but is transformed to a hydraulic jump as its amplitude increases. Toward the end of ebb tide, it is released and subsequently disperses into a group of solitary-like waves. During the second event, an upstream jump also develops at an early stage of the tide. However, it is subsequently swept downstream by the tidal flow such that the upstream region then appears featureless. Approaching slack tide, as an exchange flow becomes established, a large bore or gravity current is emitted. The different responses seen in these two events are interpreted in terms of the Froude number associated with the near-surface stratification.

Upstream Internal Hydraulic Jumps

2006 ◽  
Vol 36 (5) ◽  
pp. 753-769 ◽  
Author(s):  
Patrick F. Cummins ◽  
Laurence Armi ◽  
Svein Vagle
Keyword(s):  
Froude Number ◽  
Gravity Current ◽  
Tidal Flow ◽  
Acoustic Backscatter ◽  
Velocity Data ◽  
Near Surface ◽  
Undular Bore ◽  
Weak Density ◽  
Internal Hydraulic Jump ◽  
Internal Bore

Abstract In stratified tidal flow over a sill, the character of the upstream response is determined by a Froude number Fs based on the stratification near the surface. This is distinguished from the Froude number governing the response in the neighborhood of the sill crest, which is based on the weak density step associated with a flow bifurcation. For moderate values of Fs, the upstream response consists of nonlinear waves or a weak undular bore. For larger values of Fs, a strong, quasi-stationary, internal hydraulic jump dominates the upstream response. At sufficiently large values of Fs, the upstream bore is swept downstream and lost. Acoustic backscatter and velocity data are presented for the case of a strong internal bore or gravity current in a tidally modulated sill flow. Numerical simulations with varying near-surface stratification are presented to illustrate the upstream responses at different values of Fs. The theory of two-layer hydraulic flows is invoked to account for the development of the upstream jump.

scholarly journals COVID-19 Response in Thailand and Its Implications on Future Preparedness

2021 ◽  
Vol 18 (3) ◽  
pp. 1089
Author(s):  
Wijitbusaba Marome ◽  
Rajib Shaw
Keyword(s):  
Early Stage ◽  
Health Resources ◽  
Holistic Approach ◽  
Disaster Risk ◽  
Community Level ◽  
Multilateral Cooperation ◽  
First Case ◽  
Multiple Dimensions ◽  
Economic And Social Impacts

Thailand has been affected by COVID-19, like other countries in the Asian region at an early stage, and the first case was reported as early as mid-January 2020. Thailand’s response to the COVID-19 pandemic has been guided by the “Integrated Plan for Multilateral Cooperation for Safety and Mitigation of COVID-19”. This paper analyses the health resources in the country and focuses on the response through community-level public health system and legislative measures. The paper draws some lessons on future preparedness, especially with respect to the four priorities of Sendai Framework for Disaster Risk Reduction. At the end, the paper puts some key learning for future preparedness. While Thailand’s response to COVID-19 has been effective in limiting the spread of the disease, it falls short at being able to address the multiple dimensions of the crisis such as the economic and social impacts. The socioeconomic sectors have been hardest hit, with significant impact on tourism sectors. Sociopolitical system also plays an important role in governance and decision-making for pandemic responses. The analysis suggests that one opportunity for enhancing resilience in Thailand is to strive for more multilevel governance that engages with various stakeholders and to support grassroots and community-level networks. The COVID-19 pandemic recovery is a chance to recover better while leaving no one behind. An inclusive long-term recovery plan for the various impacted countries needs to take a holistic approach to address existing gaps and work towards a sustainable society. Furthering the Health Emergency Disaster Risk Management (HEDRM) Framework may support a coordinated response across various linked sectors rather than straining one particular sector.

Histopathologic-Based Prognostic Factors of Colorectal Cancers Are Associated With the State of the Local Immune Reaction

2011 ◽  
Vol 29 (6) ◽  
pp. 610-618 ◽  
Author(s):  
Bernhard Mlecnik ◽  
Marie Tosolini ◽  
Amos Kirilovsky ◽  
Anne Berger ◽  
Gabriela Bindea ◽  
...  
Keyword(s):  
Predictive Accuracy ◽  
Early Stage ◽  
Univariate Analysis ◽  
Prognostic Significance ◽  
Tnm Staging ◽  
Time Dependent ◽  
Colorectal Cancers ◽  
Tumor Extension ◽  
T Stage ◽  
Immune Score

Purpose The prognosis of patients with colorectal cancer has sometimes proved uncertain; thus, the prognostic significance of immune criteria was compared with that of the tumor extension criteria using the American Joint Committee on Cancer/International Union Against Cancer–TNM (AJCC/UICC-TNM) staging system. Patients and Methods We studied the intratumoral immune infiltrates in the center of the tumor and in the invasive margin of 599 specimens of stage I to IV colorectal cancers from two independent cohorts. We analyzed these findings in relation to the degree of tumor extension and to the frequency of recurrence. Results Growth of the primary tumor and metastatic spread were associated with decreased intratumoral immune T-cell densities. Sixty percent of patients with high densities of CD8+ cytotoxic T-lymphocyte infiltrate presented with stage Tis/T1 tumor, whereas no patients with low densities presented with such early-stage tumor. In patients who did not relapse, the density of CD8 infiltrates was inversely correlated with T stage. In contrast, in patients whose tumor recurred, the number of CD8 cells was low regardless of the T stage of the tumor. Univariate analysis showed that the immune score was significantly associated with differences in disease-free, disease-specific, and overall survival (hazard ratio [HR], 0.64, 0.60, and 0.70, respectively; P < .005). Time-dependent receiver operating characteristic curve analysis illustrated the predictive accuracy of the immune parameters (c-index = 65.3%, time-dependent c-index [Cτ] = 66.5%). A final stepwise model for Cox multivariate analysis supports the advantage of the immune score (HR, 0.64; P < .001; Cτ = 67.9%) compared with histopathologic features in predicting recurrence as well as survival. Conclusion Assessment of CD8+ cytotoxic T lymphocytes in combined tumor regions provides an indicator of tumor recurrence beyond that predicted by AJCC/UICC-TNM staging.

A New Time-dependent Theory of Tropical Cyclone Intensification

2021 ◽  
Author(s):  
Yuqing Wang ◽  
Yuanlong Li ◽  
Jing Xu
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclone ◽  
Numerical Simulations ◽  
Strong Dependence ◽  
Surface Wind ◽  
Time Dependent ◽  
Quasi Equilibrium ◽  
Free Atmosphere ◽  
Near Surface ◽  
Tangential Wind

AbstractIn this study, the boundary-layer tangential wind budget equation following the radius of maximum wind, together with an assumed thermodynamical quasi-equilibrium boundary layer is used to derive a new equation for tropical cyclone (TC) intensification rate (IR). A TC is assumed to be axisymmetric in thermal wind balance with eyewall convection becoming in moist slantwise neutrality in the free atmosphere above the boundary layer as the storm intensifies as found recently based on idealized numerical simulations. An ad-hoc parameter is introduced to measure the degree of congruence of the absolute angular momentum and the entropy surfaces. The new IR equation is evaluated using results from idealized ensemble full-physics axisymmetric numerical simulations. Results show that the new IR equation can reproduce the time evolution of the simulated TC intensity. The new IR equation indicates a strong dependence of IR on both TC intensity and the corresponding maximum potential intensity (MPI). A new finding is the dependence of TC IR on the square of the MPI in terms of the near-surface wind speed for any given relative intensity. Results from some numerical integrations of the new IR equation also suggest the finite-amplitude nature of TC genesis. In addition, the new IR theory is also supported by some preliminary results based on best-track TC data over the North Atlantic and eastern and western North Pacific. Compared with the available time-dependent theories of TC intensification, the new IR equation can provide a realistic intensity-dependent IR during weak intensity stage as in observations.

A Risk-Adapted Strategy of Adjuvant Paclitaxel/Carboplatin in Early-Stage Ovarian Cancer: Time-Dependent Effect of 4 versus 6 Cycles on Outcome

Oncology ◽  
2011 ◽  
Vol 81 (5-6) ◽  
pp. 365-371 ◽  
Author(s):  
Aristotle Bamias ◽  
Christina Bamia ◽  
Alexandra Karadimou ◽  
Nikolaos Soupos ◽  
Flora Zagouri ◽  
...  
Keyword(s):  
Ovarian Cancer ◽  
Early Stage ◽  
Time Dependent ◽  
Dependent Effect ◽  
Time Dependent Effect ◽  
Early Stage Ovarian Cancer

scholarly journals Impact of Enzymatic Degradation on the Material Properties of Poly(Ethylene Terephthalate)

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3885
Author(s):  
Teresa Menzel ◽  
Sebastian Weigert ◽  
Andreas Gagsteiger ◽  
Yannik Eich ◽  
Sebastian Sittl ◽  
...  
Keyword(s):  
Material Properties ◽  
Enzymatic Degradation ◽  
Ethylene Terephthalate ◽  
Compact Tension ◽  
Time Dependent ◽  
Material Failure ◽  
Near Surface ◽  
Poly Ethylene Terephthalate ◽  
Poly Ethylene ◽  
The Impact

With macroscopic litter and its degradation into secondary microplastic as a major source of environmental pollution, one key challenge is understanding the pathways from macro- to microplastic by abiotic and biotic environmental impact. So far, little is known about the impact of biota on material properties. This study focuses on recycled, bottle-grade poly(ethylene terephthalate) (r-PET) and the degrading enzyme PETase from Ideonella sakaiensis. Compact tension (CT) specimens were incubated in an enzymatic solution and thermally and mechanically characterized. A time-dependent study up to 96 h revealed the formation of steadily growing colloidal structures. After 96 h incubation, high amounts of BHET dimer were found in a near-surface layer, affecting crack propagation and leading to faster material failure. The results of this pilot study show that enzymatic activity accelerates embrittlement and favors fragmentation. We conclude that PET-degrading enzymes must be viewed as a potentially relevant acceleration factor in macroplastic degradation.

Time-dependent changes in kidney histopathology in ethylene glycol poisoning

2018 ◽  
Vol 58 (4) ◽  
pp. 257-260 ◽  
Author(s):  
Janos Bokor ◽  
Krisztina Danics ◽  
Eva Keller ◽  
Zoltan Szollosi
Keyword(s):  
Epithelial Cells ◽  
Basement Membrane ◽  
Ethylene Glycol ◽  
Calcium Oxalate ◽  
Early Stage ◽  
Time Dependent ◽  
Calcium Oxalate Crystals ◽  
Oxalate Crystals ◽  
Cellular Debris ◽  
Tubular Lumen

Ethylene glycol (EG) may be acutely toxic following ingestion. In fatal cases, microscopic examination of urine and kidney specimens can establish a post-mortem diagnosis of EG poisoning. We describe the main renal histopathologic changes during different stages of EG poisoning, which might be helpful when dating the EG poisoning itself. A single-centre retrospective study conducted on all EG poisoning cases demonstrated that in an early stage of EG poisoning, fine dust-like crystals were deposited to the tubular cell basement membrane, followed by internalisation of calcium oxalate crystals into the epithelial cells. Later, the crystals formed larger aggregates within the epithelial cells. As the changes became advanced, pronounced tubular epithelial damage occurred, with detachment of epithelial cells from the basement membrane. In the final stage, coarse calcium oxalate crystals were recognised in the tubular lumen, with cellular debris from damaged epithelial cells. Our study shows that the time-dependent histological changes described follow the clinical stages of EG poisoning and may therefore provide a rough estimate of the time of EG ingestion before death.

A Consistent Approach for the Development of a Comprehensive Data Base of Time-Dependent Parameters for Concrete Engineered Barriers

2013 ◽  
Author(s):  
Suresh C. Seetharam ◽  
Dirk Mallants ◽  
Janez Perko ◽  
Diederik Jacques
Keyword(s):  
Data Base ◽  
Experimental Studies ◽  
Cementitious Materials ◽  
Time Dependent ◽  
Extensive Literature ◽  
Near Surface ◽  
Comprehensive Data ◽  
Engineered Barriers ◽  
Parameter Values ◽  
Consistent Approach

This paper presents a consistent approach for the development of a comprehensive data base of time-dependent hydraulic and transport parameters for concrete engineered barriers of the future Dessel near surface repository for low level waste. The parameter derivation is based on integration of selected data obtained through an extensive literature review, data from experimental studies on cementitious materials specific for the Dessel repository and numerical modelling using physically-based models of water and mass transport. Best estimate parameter values for assessment calculations are derived, together with source and expert range and their probability density function wherever the data was sufficient. We further discuss a numerical method for upscaling laboratory derived parameter values to the repository scale; the resulting large-scale effective parameters are commensurate with numerical grids used in models for radionuclide migration. To accommodate different levels of conservatism in the various assessment calculations defined by ONDRAF/NIRAS, several sets of parameter values have been derived based on assumptions that introduce different degrees of conservatism. For pertinent parameters, the time evolution of such properties due to the long-term concrete degradation is also addressed. The implementation of the consistent approach is demonstrated by considering the pore water diffusion coefficient as an example.

scholarly journals Tidal modulation of two-layer hydraulic exchange flows

Ocean Science ◽  
2007 ◽  
Vol 3 (2) ◽  
pp. 179-188 ◽  
Author(s):  
L. M. Frankcombe ◽  
A. McC. Hogg
Keyword(s):  
Time Dependent ◽  
Water Model ◽  
Exchange Flow ◽  
Shallow Water Model ◽  
Tidal Amplitude ◽  
Layer System ◽  
Tidal Period ◽  
Exchange Flows ◽  
The Relationship ◽  
Exchange Flux

Abstract. Time-dependent, two layer hydraulic exchange flow is studied using an idealised shallow water model. It is found that barotropic time-dependent perturbations, representing tidal forcing, increase the baroclinic exchange flux above the steady hydraulic limit, with flux increasing monotonically with tidal amplitude (measured either by height or flux amplitude over a tidal period). Exchange flux also depends on the non-dimensional tidal period, γ, which was introduced by by Helfrich (1995). When tidal amplitude is characterised by the barotropic flux amplitude, exchange flux is a monotonic function of γ as predicted by Helfrich (1995). However, the relationship between the (imposed) free surface amplitude and flux amplitude is complicated by reflections within the channel and by the baroclinic response of the two layer system, leading to a non-monotonic relationship between the height amplitude and γ.

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