Summary
Wound healing studies are intricate, mainly because of the multifaceted nature of the wound environment and the complexity of the healing process, which integrates a variety of cells and ...repair phases, including inflammation, proliferation, reepithelialization and remodelling. There are a variety of possible preclinical models, such as in mice, rabbits and pigs, which can be used to mimic acute or impaired for example, diabetic and nutrition‐related wounds. These can be induced by many different techniques, with excision or incision being the most common. After determining a suitable model for a study, investigators need to select appropriate and reproducible methods that will allow the monitoring of the wound progression over time. The assessment can be performed by non‐invasive protocols such as wound tracing, photographic documentation (including image analysis), biophysical techniques and/or by invasive protocols that will require wound biopsies. In this article, we provide an overview of some of the most often needed and used: (a) preclinical/animal models including incisional, excisional, burn and impaired wounds; (b) methods to evaluate the healing progression such as wound healing rate, wound analysis by image, biophysical assessment, histopathological, immunological and biochemical assays. The aim is to help researchers during the design and execution of their wound healing studies.
Western boundary currents (WBCs) are critical to Earth's climate. In the last decade, mesoscale air‐sea interactions emerged as an important factor of WBC dynamics. Recently, coupled models including ...the feedback of surface oceanic currents to the atmosphere confirmed the existence of a physical process called eddy killing, which may correct long‐lasting biases in the representation of WBCs by providing an unambiguous energy sink mechanism. Using ocean‐atmosphere coupled simulations of the Gulf Stream and the Agulhas Current, we show that eddy killing reduces the eddy‐mean flow interaction (both forward and inverse cascades) and leads to more realistic solutions. Model and data fluxes are in good agreement when the same coarse grid is used for their computation, although in this case they are underestimated. We conclude that the uncoupled approach is no longer suitable for continued ocean model improvement and discuss new formulations that should better account for air‐sea interactions.
Plain Language Summary
Western boundary currents (WBCs), such as the Gulf Stream and the Agulhas Current play a crucial role in global ocean circulation and in determining and stabilizing the Earth's climate. In the last decade, mesoscale air‐sea interactions emerged as important in WBC dynamics. Recently, coupled models including the feedback of surface oceanic currents to the atmosphere revealed a process called eddy killing, which potentially corrects long‐lasting biases in the representation of WBCs. In this study, using ocean‐atmosphere coupled simulations of the Gulf Stream and Agulhas Current, we show that eddy killing reduces the interactions between eddies and mean flow. The influence of the eddies on the mean flow can be measured by the cascade of energy, and, in particular, the inverse cascade of energy. The reduction of inverse energy flux by eddy killing leads to realistic solutions and, in particular, to the observed stabilization of WBCs. Model and data fluxes are in good agreement when the same coarse grid is used for their computation, although in this case they are underestimated. We conclude that uncoupled models are no longer suitable for continuing our model improvement of ocean dynamics and discuss new formulations that should better account for air‐sea interactions.
Key Points
The oceanic inverse energy cascade is weakened by eddy killing associated with current feedback during eddy‐wind interaction
Western boundary currents are subdued by eddy killing through weakened inverse energy cascade
The spectral energy flux is validated using satellite currents; these data underestimate eddy‐mean flow interaction due to coarse resolution
We address the problem of how particles are accelerated by solar flares can escape into the heliosphere on timescales of an hour or less. Impulsive solar energetic particle (SEP) bursts are generally ...observed in association with so-called eruptive flares consisting of a coronal mass ejection (CME) and a flare. These fast SEPs are believed to be accelerated directly by the flare, rather than by the CME shock. However, the precise mechanism by which the particles are accelerated remains controversial. Regardless of the origin of the acceleration, the particles should remain trapped in the closed magnetic fields of the coronal flare loops and the ejected flux rope, given the magnetic geometry of the standard eruptive-flare model. In this case, the particles would reach the Earth only after a delay of many hours to a few days (coincident with the bulk ejecta arriving at Earth). We propose that the external magnetic reconnection intrinsic to the breakout model for CME initiation can naturally account for the prompt escape of flare-accelerated energetic particles onto open interplanetary magnetic flux tubes. We present detailed 2.5-dimensional magnetohydrodynamic simulations of a breakout CME/flare event with a background isothermal solar wind. Our calculations demonstrate that if the event occurs sufficiently near a coronal-hole boundary, interchange reconnection between open and closed fields can occur. This process allows particles from deep inside the ejected flux rope to access solar wind field lines soon after eruption. We compare these results to standard observations of impulsive SEPs and discuss the implications of the model on further observations and calculations.
•Heat pipe temperature and response time are influenced by the hysteresis phenomenon.•Ascending heat flux crenel enables lower vapor temperature but more start up delay.•Heat pipe could be used as an ...efficient alternative solution for cooling electronic chips.•Hot air from fans crosses and heats the other electronic components.
In this study, a porous wick copper flat heat pipe is investigated in horizontal position. The hysteresis phenomenon shows that the heat flux increase enables lower vapor temperatures and more transient state delay 840 s at 5 W compared to the heat flux decrease. Working fluid filling ratios effects on the cooling performance were examined including temperatures distribution, heat pipe thermal resistances and effective thermal conductivity. The fill ratio of 25% is found to be the optimal charge, for which the maximum effective thermal conductivity was about 891 W/mK at 7 W input load. Experimental results and figure of limit factors show that n-pentane be the optimal working fluid comparing to the other studied fluids.
The application of the studied heat pipe in cooling a television box is investigated by comparing the conventional cooling solution using fans and a passive cooling configuration using the flat heat pipe. Experimental results show that heat pipe is an efficient alternative passive cooling device which enables cooling all electronic components of the television box.
Flare ribbons are commonly attributed to the low-altitude impact, along the footprints of separatrices or quasi-separatrix layers (QSLs), of particle beams accelerated through magnetic reconnection. ...If reconnection occurs at a three-dimensional coronal magnetic null point, the footprint of the dome-shaped fan surface would map a closed circular ribbon. This paper addresses the following issues: does the entire circular ribbon brighten simultaneously, as expected because all fan field lines pass through the null point? And since the spine separatrices are singular field lines, do spine-related ribbons look like compact kernels? What can we learn from these observations about current sheet formation and magnetic reconnection in a null-point topology? The present study addresses these questions by analyzing Transition Region and Coronal Explorer and Solar and Heliospheric Observatory/Michelson Doppler Imager observations of a confined flare presenting a circular ribbon. Using a potential field extrapolation, we linked the circular shape of the ribbon with the photospheric mapping of the fan field lines originating from a coronal null point. Observations show that the flare ribbon outlining the fan lines brightens sequentially along the counterclockwise direction and that the spine-related ribbons are elongated. Using the potential field extrapolation as initial condition, we conduct a low-beta resistive magnetohydrodynamics simulation of this observed event. We drive the coronal evolution by line-tied diverging boundary motions, so as to emulate the observed photospheric flow pattern associated with some magnetic flux emergence. The numerical analysis allows us to explain several observed features of the confined flare. The vorticity induced in the fan by the prescribed motions causes the spines to tear apart along the fan. This leads to formation of a thin current sheet and induces null-point reconnection. We also find that the null point and its associated topological structure is embedded within QSLs, already present in the asymmetric potential field configuration. We find that the QSL footprints correspond to the observed elongated spine ribbons. Finally, we observe that before and after reconnecting at the null point, all field lines undergo slipping and slip-running reconnection within the QSLs. Field lines, and therefore particle impacts, slip or slip-run according to their distance from the spine, in directions and over distances that are compatible with the observed dynamics of the ribbons.
The development of vascularized scaffolds remains one of the major challenges in tissue engineering, and co‐culturing with endothelial cells is known as one of the possible approaches for this ...purpose. In this approach, optimization of cell culture conditions, scaffolds, and fabrication techniques is needed to develop tissue equivalents that will enable in vitro formation of a capillary network. Prevascularized equivalents will be more physiologically comparable to the native tissues and potentially prevent insufficient vascularization after implantation. This study aimed to culture human umbilical vein endothelial cells (HUVECs), alone or in co‐culture with fibroblasts, on collagen scaffolds prepared by simple fabrication approaches for in vitro prevascularization. Different concentrations and ratios of HUVECs and fibroblasts seeded on collagen gel and sponge scaffolds under several culture conditions were examined. Cell viability, scaffolds morphology, and structure were analyzed. Collagen gel scaffolds showed good cell proliferation and viability, with higher proliferation rates for cells cultured in a 2:1 (fibroblasts: HUVECs) ratio and kept in endothelial cell growth medium. However, these matrices were unable to support endothelial cell sprouting. Collagen sponges were highly porous and showed good cell viability. However, they became fragile over time in culture, and they still lack signs of vascularization. Collagen scaffolds were a good platform for cell growth and viability. However, under the experimental conditions of this study, the HUVEC/fibroblast‐seeded scaffolds were not suitable platforms to generate in vitro prevascularized equivalents. Our findings will be a valuable starting point to optimize culture microenvironments and scaffolds during fabrication of prevascularized scaffolds.
Recipes for How to Force Oceanic Model Dynamics Renault, Lionel; Masson, S.; Arsouze, T. ...
Journal of advances in modeling earth systems,
February 2020, Letnik:
12, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The current feedback to the atmosphere (CFB) contributes to the oceanic circulation by damping eddies. In an ocean‐atmosphere coupled model, CFB can be correctly accounted for by using the wind ...relative to the oceanic current. However, its implementation in a forced oceanic model is less straightforward as CFB also enhances the 10‐m wind. Wind products based on observations have seen real currents that will not necessarily correspond to model currents, whereas meteorological reanalyses often neglect surface currents or use surface currents that, again, will differ from the surface currents of the forced oceanic simulation. In this study, we use a set of quasi‐global oceanic simulations, coupled or not with the atmosphere, to (i) quantify the error associated with the different existing strategies of forcing an oceanic model, (ii) test different parameterizations of the CFB, and (iii) propose the best strategy to account for CFB in forced oceanic simulation. We show that scatterometer wind or stress are not suitable to properly represent the CFB in forced oceanic simulation. We furthermore demonstrate that a parameterization of CFB based on a wind‐predicted coupling coefficient between the surface current and the stress allows us to reproduce the main characteristics of a coupled simulation. Such a parameterization can be used with any forcing set, including future coupled reanalyses, assuming that the associated oceanic surface currents are known. A further assessment of the thermal feedback of the surface wind in response to oceanic surface temperature gradients shows a weak forcing effect on oceanic currents.
Key Points
The Current FeedBack to the Atmosphere (CFB) can be parameterized in a forced oceanic model
A parameterization of the CFB based on a predicted coupling coefficient is the best parameterization
Scatterometers are not suitable to correctly represent the CFB in a forced oceanic model (unless coherent surface currents are known)
The new 3.6 version of the Louvain-la-Neuve sea ice model (LIM) is presented, as integrated in the most recent stable release of Nucleus for European Modelling of the Ocean (NEMO) (3.6). The release ...will be used for the next Climate Model Inter-comparison Project (CMIP6). Developments focussed around three axes: improvements of robustness, versatility and sophistication of the code, which involved numerous changes. Robustness was improved by enforcing exact conservation through the inspection of the different processes driving the air–ice–ocean exchanges of heat, mass and salt. Versatility was enhanced by implementing lateral boundary conditions for sea ice and more flexible ice thickness categories. The latter includes a more practical computation of category boundaries, parameterizations to use LIM3.6 with a single ice category and a flux redistributor for coupling with atmospheric models that cannot handle multiple sub-grid fluxes. Sophistication was upgraded by including the effect of ice and snow weight on the sea surface. We illustrate some of the new capabilities of the code in two standard simulations. One is an ORCA2-LIM3 global simulation at a nominal 2° resolution, forced by reference atmospheric climatologies. The other one is a regional simulation at 2 km resolution around the Svalbard Archipelago in the Arctic Ocean, with open boundaries and tides. We show that the LIM3.6 forms a solid and flexible base for future scientific studies and model developments.
Toll-like receptor 4 (TLR4) signaling induces tissue pro-inflammatory cytokine release and endoplasmic reticulum (ER) stress. We examined the role of TLR4 in autonomic dysfunction and the ...contribution of ER stress.
Our study included animals divided in 6 experimental groups: rats treated with saline (i.v., 0.9%), LPS (i.v., 10mg/kg), VIPER (i.v., 0.1 mg/kg), or 4-PBA (i.p., 10 mg/kg). Two other groups were pretreated either with VIPER (TLR4 viral inhibitory peptide) LPS + VIPER (i.v., 0.1 mg/kg) or 4-Phenyl butyric acid (4-PBA) LPS + PBA (i.p., 10 mg/kg). Arterial pressure (AP) and heart rate (HR) were measured in conscious Sprague-Dawley rats. AP, HR variability, as well as baroreflex sensitivity (BrS), was determined after LPS or saline treatment for 2 hours. Immunofluorescence staining for NeuN, Ib1a, TLR4 and GRP78 in the hypothalamic paraventricular nucleus (PVN) was performed. TNF-α, TLR4 and GRP78 protein expression in the PVN were evaluated by western blot. Plasma norepinephrine levels were determined by ELISA.
Acute LPS treatment increased HR and plasma norepinephrine concentration. It also decreased HR variability and high frequency (HF) components of HR variability, as well BrS. Acute LPS treatment increased TLR4 and TNF-α protein expression in the PVN. These hemodynamic and molecular effects were partially abrogated with TLR4 blocker or ER stress inhibitor pretreatment. In addition, immunofluorescence study showed that TLR4 is co-localized with GRP78in the neurons. Further inhibition of TLR4 or ER stress was able to attenuate the LPS-induced microglia activation.
TLR4 signaling promotes autonomic dysfunction, inflammation and microglia activation, through neuronal ER stress, in the PVN.
The densely populated Bay of Bengal (BoB) rim witnesses the deadliest tropical cyclones (TCs) globally, before and after the summer monsoon. Previous studies indicated that enhanced salinity and ...reduced thermal stratification reduce cooling under BoB TCs after the monsoon, suggesting that air‐sea coupling may favor stronger TCs during that season. Using observations and simulations from a one fourth degree regional ocean‐atmosphere model, we show that BoB TCs are stronger before the monsoon due to a more favorable large‐scale background state (less vertical wind shear and higher sea surface temperature). Air‐sea coupling however alleviates this background state influence, by reducing the number of premonsoon intense TCs, because of larger cooling and reduced upward enthalpy fluxes below TCs during that season. As the impact of air‐sea interactions on BoB TCs is largest for intense TCs, it should be further investigated for Category 3 and above TCs, which are not reproduced at one fourth degree resolution.
Plain language summary
Tropical cyclones that develop in the Bay of Bengal are amongst the most lethal globally, owing to the dense and vulnerable coastal population living along its rim. These cyclones mostly occur in April–May and October–December, that is, before and after the Indian summer monsoon. In this study, we show that there are more intense cyclones before than after the monsoon, because of more favorable large‐scale background conditions. We however also show that more intense interactions between the cyclone and the ocean tend to reduce risks for intense cyclones before the monsoon, hence opposing the effect of background conditions. Since air‐sea coupling clearly contributes to the Bay of Bengal cyclone intensity, in particular before the monsoon, it should be accounted for in operational forecasts.
Key Points
Bay of Bengal tropical cyclones are stronger before than after the monsoon, due to more favorable large‐scale background conditions
Air‐sea coupling alleviates the effect of large‐scale background conditions, by inhibiting premonsoon tropical cyclones
The air‐sea coupling negative feedback on tropical cyclones is weak after the monsoon, due to a fresher, less thermally stratified BoB
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