Experimental Model For Study Research Articles

Conceptual model of the process of formation of immobilization contractures

Contractures — limitation of passive movements in the joint — are a fairly frequent complication after immobilization or limitation of mobility and loading of the limb due to injuries, but the exact cause of their formation has not been clarified. Objective. Based on the meta-analysis of the results of experimental modeling and clinical studies of immobilization contractures, create a conceptual model of their formation. Methods. Literature sources from scientific bases were analyzed: Cochrane Library, Scopus, National Library of Medicine, ReLAB-HS Rehabilitation Resources Repository, Mendeley Reference Manager, The Physiological Society library, Google Scholar. Results. A conceptual model of the development of contractures was created. It is shown that immobilization of the joint of the injured limb blocks the execution of the signal of motor impulses. The lack of movement in the joint leads to a decrease in muscle strength and a slowdown in blood circulation. These processes are interrelated: hypotonia of the muscle is due to the restriction of nutrition through the blood supply, and the lack of contractile activity of the muscles leads to the rearrangement of the blood vessels. Articular cartilage is nourished through the subchondral bone and due to osmosis from the synovial fluid during movements. The lack of movement limits nutrition, protein synthesis is disrupted, the surface of the cartilage, synovial membrane and fluid begins to be rebuilt, the joint capsule, ligaments, and tendons thicken. At the same time, the structure of the muscles changes, they shorten and become denser. With long-term immobilization, degenerative processes in the tissues of the joint worsen its general condition, which can eventually lead to complete immobilization. Conclusions. The created conceptual model of the formation of immobilization contractures of joints takes into account the morphological changes of tissues as a result of immobilization. Immobilization affects all components of the joint and adjacent tissues from the first days, the changes progress over time. The use of the model will allow the development of a system of treatment measures to prevent the development of contractures.

Isomeric effects on the reactivity of branched alkenes: An experimental and kinetic modeling study of methylbutenes

A detailed experimental study of the low-to-intermediate temperature combustion of methylbutene isomers, i.e., branched C5 alkenes, has been undertaken with multiple experimental facilities. Ignition delay times were measured at equivalence ratios 0.5–2.0, 685–1020 K and up to 45 bar condition from two rapid compression machines and showed slight deviation from an Arrhenius behavior for all three isomers, while their reactivity order differs as temperature changes. Sampled intermediates formed during the oxidation process of mixtures at 900–1150 K and 0.82 bar from a flow reactor and at 730 K and 20 bar from a rapid compression machine were analyzed using gas chromatography techniques. Trends in the formation and consumption of sampled intermediates were modeled using a kinetic model developed in this work for all three isomers. Rate of production and sensitivity analyses emphasize the role of double bond-specific reactions governing the global reactivity of these fuels. Additional studies of the addition reactions of HO2 radicals to the double bond and to allylic radicals may improve the model performance.

The influence of methyl butyrate and n-butanol on the laminar burning characteristics of RP-3: An experimental and kinetic modeling study

An experimental study was conducted to investigate the oxidation of methyl butyrate (MB), n-butanol, RP-3 aviation kerosene, and their binary mixtures in laminar premixed flames. The experiments were carried out using the spherical flame method under conditions of P0 = 0.1/0.2/0.3 MPa, T0 = 470 K, φ = 0.8–1.4, and the volume mixing ratio is 20%, 50% and 80%. The effects of adding two potential C4 oxygenated fuels to RP-3 on the laminar burning velocity (SL) and flame instability were first evaluated. A new skeletal mechanism was proposed for this blended fuel system based on the CRECK mechanism, and the new experimental results were extensively used to validate this skeletal mechanism. The results showed that the addition of MB and n-butanol caused a slight decrease and increase, respectively, in the SL of RP-3. After adding 50 % MB and 50% n-butanol, the peak SL of RP-3 decreased by 3.5 cm/s and increased by 2.1 cm/s, respectively. Furthermore, the addition of esters was more favorable for reducing flame instability. Reaction path analysis and flame structure analysis revealed that the effects of adding MB and n-butanol on the oxidation pathway of RP-3 were mainly concentrated in primary oxidation reactions, and their effects on the SL were mainly attributed to changes in the concentrations of OH and H radicals.

An experimental and theoretical kinetic modeling study of the thermal decomposition of methyl-2-methyl butanoate behind shock waves

In order to investigate the combustion chemistry of a branched ester namely Methyl-2-methylbutanoate (M2MB), thermal decomposition of M2MB diluted in Argon was carried out behind reflected shock waves in the temperature range 959 -1392 K using a single pulse shock tube (SPST). The post shock mixtures were analyzed quantitatively as well as qualitatively using gas chromatography (GC) and gas chromatography coupled with mass spectrometry (GC–MS). Methane (CH4), Ethane (C2H6), Ethylene (C2H4), Methanol (CH3OH), Propene (C3H6) and Methyl acrylate (C4H6O2) were the major products observed during thermal decomposition. The various oxygenated compounds were found as minor products. The first order rate constant observed for the decomposition of M2MB is kexpt(959–1392 K) = (2.13 ± 0.457) × 109 exp [(19200 ± 561)/T] s−1 The temperature dependent kinetics of the CC and CO homolytic bond cleavages as well as of the H-migration for the unimolecular decomposition reactions were calculated using RRKM/ME over the temperature range of 959–1392 K. A reaction scheme involving 42 species and 61 elementary reactions, was proposed to simulate the reactant and product concentration over the studied temperature range. A comparison study of decomposition kinetics of branched chain ester and long chain ester is discussed in this work. The concentration profiles for reactant and all the products observed from simulations and experimental results were observed to be in very good agreement.

The emerging role of the endocannabinoidome-gut microbiome axis in eating disorders

Among the sources of chemical signals regulating food intake, energy metabolism and body weight, few have attracted recently as much attention as the expanded endocannabinoid system, or endocannabinoidome (eCBome), and the gut microbiome, the two systems on which this review article is focussed. Therefore, it is legitimate to expect that these two systems also play a major role in the etiopathology of eating disorders (EDs), in particular of anorexia nervosa, bulimia nervosa and binge-eating disorder. The major mechanisms through which, also via interactions with other endogenous signaling systems, the eCBome, with its several lipid mediators and receptors, and the gut microbiome, via its variety of microbial kingdoms, phyla and species, and armamentarium of metabolites, intervene in these disorders, are described here, based on several published studies in either experimental models or patients. Additionally, in view of the emerging multi-faceted cross-talk mechanisms between these two complex systems, we discuss the possibility that the eCBome-gut microbiome axis is also involved in EDs.

A New Preclinical Model of Retinitis Pigmentosa Due to Pde6g Deficiency

Retinitis pigmentosa (RP) is the most common cause of inherited blindness, with onset occurring as early as 4 years of age in certain rare but severe forms caused by mutations in the gamma subunit of phosphodiesterase 6 (PDE6). Studies in humans and mice have shown that RP pathology begins with progressive photoreceptor death, which then drives changes in downstream neurons, neighboring retinal pigment epithelium (RPE), and vasculature. Here, we present the first detailed analysis of RP disease progression in Pde6g-deficient mice. Experimental study of an RP mouse model. We studied Pde6g-/- and Pde6g+/- mice at the age of 7, 16, 30, 44, and 56 days with n=2 to 5 per group and time point. Photoreceptor degeneration and retinal remodeling were analyzed in retinal sections by immunofluorescence. Retinal blood vessel degradation was analyzed in flat-mounted retinas immunolabeled for isolectin GS-IB4. Protein expression was measured by immunoblot. Acellular capillaries were assessed in trypsin-digested and hematoxylin-eosin-stained retinas at postnatal day (P) 44. Retinal pigment epithelium cells were delineated in flat-mounted RPE-choroid-sclera by immunolabeling for the cell-adhesion protein β-catenin. Immunofluorescence and morphometry (quantitative analysis of outer nuclear layer, dendrite area, vessel area, acellular vessels, RPE cell size, number of nuclei per RPE cell, RPE cell eccentricity, and RPE cell solidity). This novel RP model exhibits early onset and rapid rod degeneration, with the vast majority gone by P16. This pathology leads to retinal remodeling, including changes of inner retinal neurons, early activation of glia cells, degradation of retinal vasculature, and structural abnormalities of the RPE. The pathology in our Pde6g-/- mouse model precisely mirrors human RP progression. The results demonstrate the significant role of the gamma subunit in maintaining phosphodiesterase activity and provide new insights into the disease progression due to Pde6g deficiency. Proprietary or commercial disclosure may be found after the references.

Experimental and kinetic modeling study of low-temperature oxidation of n-pentane

Attractiveness in advanced low-temperature combustion engines drives a constantly updated understanding of low-temperature oxidation chemistry. In this work, the low-temperature oxidation chemistry of n-pentane in two jet-stirred reactors at atmospheric pressure and in the temperature range of 500–825 K was investigated using combined analysis methods of synchrotron vacuum ultraviolet photoionization mass spectrometry, gas chromatography, and Fourier transform infrared spectroscopy. Furthermore, the gaseous mixture from JSR was collected in acetonitrile for subsequent product characterization using flow injection analysis, high-pressure and ultra-high-pressure liquid chromatography coupled to a Thermo Scientific™ Orbitrap® Q-Exactive high-resolution mass spectrometry. Numerous intermediate species were identified by these analytical methods, which contributed to unraveling the low-temperature oxidation reaction network of n-pentane. A detailed n-pentane model was tentatively developed to reduce deviations between experimental measurements and model predictions by updating the rate constants of C5 keto-hydroperoxide decomposition, C5 hydroperoxy cyclic ether decomposition, and Korcek reactions of C5 keto-hydroperoxide, and by introducing pressure-dependent rate constants for the reaction classes of Q˙OOH + O2, Q˙OOH decompositions, concerted HȮ2-elimination of RȮ2, C5 keto-hydroperoxide decomposition, C5 hydroperoxy cyclic ether decomposition, and Korcek reactions of C5 keto-hydroperoxide, and by adding more detailed sub-mechanisms for C5 cyclic ethers and C5 keto-hydroperoxides. This updated model was validated against a set of available experimental data, including jet-stirred reactor species data and ignition delay times. These exploratory updates of the kinetic model reveal the considerable influence of the rate constants of hydroperoxide decomposition and the pressure-dependent rate constants of key reaction classes on the kinetic model predictions, highlighting the future demands for high-precision quantum chemistry calculations of the pressure-dependent rate constants of the aforementioned reaction classes to reduce mechanism uncertainties and to develop accurate and robust chemical kinetic models.

Experimental and kinetic modelling studies on the gas hydrate inhibition effect of PVP K-90 in drilling fluids

The hydrate inhibitors play a very important role in preventing hydrate growth inside the drilling fluid systems, which is desirable for smooth drilling operation. It has been demonstrated in several scenarios that the water-soluble polymer such as polyvinyl pyrrolidone (PVP K-90) efficiently reduces hydrate formation rates. In this study, the influence of on hydrate inhibition in predesigned drilling fluids in presence of a mixture gas of methane, ethane and propane has been investigated. As the concentration of the PVP K-90 increase, the induction time continues to increase. The rheological studies of drilling fluids conducted at different temperature and pressure condition with varying concentration of indicates their better performance. The chemical structure of polymer is a single 5-membered lactam ring attached to a carbon backbone which is responsible for the inhibition effect of the drilling fluid samples. The large concentration range tested allows unprecedented visualization of the shifting of formation rate in compare to pure water. Hydrate formation rate appears to reduce as concentration of increases from 0.1 wt% to 0.7 wt%. The results suggest that increasing the concentration of the inhibitor up to 0.7 wt% may reach to a level that saturates all the growth sites and there are enough PVP K-90 molecules available to block the hydrate crystal growth, which significantly reduces the formation rate. The experimental investigation offers new understanding of the operational mechanics of kinetic hydrate inhibitor (KHI) in drilling operations.

Experimental and kinetic modeling study on propane enhancing the laminar flame speeds of ammonia

The laminar flame speeds of ammonia/propane in air were investigated in a constant volume combustion bomb at 1–5 atm, over 298–453 K, at the equivalence ratios of 0.7–1.6, with the propane in fuel varying from 0 to 90 vol%. The measured data were provided for the validity of the proposed M-NUIG model. The comparison showed that M-NUIG model could successfully predict the measured data of propane, ammonia and mixtures under wide conditions. The results showed that the addition of 20% propane can enhance the LBV of ammonia by a factor of 3 at 1 atm, 298 K. Based on kinetic analysis, NH2 is mainly consumed by the oxidation of N-contained species in NH3/air flame, and it is completely consumed through reacting with O, OH, H and HO2 in NH3/C3H8/air flame. As for the NH3/C3H8 interactions, NH can react with CH3, forming CH2NH which completely converts to HCN. HNO also reacts with CH3 to generate NO. Thus, the CN interactions are crucial to the formation of harmful emissions. Moreover, with 50% propane addition, the peak concentrations of OH and H radicals are much higher than in NH3/air flame which is the main reason for the higher LBV.

An experimental and kinetic modeling study on the low-temperature oxidation of oxymethylene ether-2 (OME-2) by means of stabilized cool flames

Oxymethylene ethers have received much attention in recent years as a high-potential alternative for fossil-based fuels. These alternative fuels produced via carbon capture and utilization technologies driven by renewable energy can contribute to the solution of environmental issues in the short term. In this study, the low-temperature oxidation chemistry of oxymethylene ether-2 was investigated by combining experimental and kinetic modeling work. New experimental data were acquired from stabilized, ozone-seeded oxymethylene ether-2/dimethyl ether/oxygen premixed cool flames in a heated stagnation plate burner. Two fuel-lean equivalence ratios were investigated, i.e., ϕ = 0.3 and ϕ = 0.5. The observed and quantified reaction products were methoxymethyl formate, methyl formate, methanol, formaldehyde, CO and CO2. A new detailed kinetic model based on first principles was constructed for the pyrolysis and oxidation of oxymethylene ether-2 with the in-house developed automatic kinetic model generation code Genesys. Compared to an earlier study by De Ras et al. (Combustion and Flame, 2022), additional species and reactions were added to describe the low-temperature oxidation chemistry with more detail, in addition to an update of several thermodynamic and kinetic parameters based on new quantum chemical calculations. The newly developed kinetic model is able to predict the experimental observations of the stabilized cool flames satisfactorily and can reproduce ignition delay times from the literature on average within the experimental uncertainty margin. Rate of production and sensitivity analyses were performed for different reaction conditions to unravel the important decomposition pathways during low-temperature oxidation. It is concluded that oxymethylene ether-2 is a highly reactive fuel, and this without fuel-specific chain branching reactions significantly contributing to the low-temperature oxidation chemistry.

Bioinspired design optimization for pseudo-ductility in platelet fibre laminates

Platelet designs inspired by nacre shell microstructure are a novel approach to confer pseudo-ductile deformation properties to brittle fibre reinforced polymer laminates while retaining high stiffness and strength. Here we present an experimental and finite element modelling study to investigate the effects of tiling pattern, overlapping length and interlaminar toughness of the ply platelets on the tensile properties, pseudo-ductility, and failure modes of platelet laminates inspired by nacre. The findings are then used to optimize the design for maximal pseudo-ductility for a given tensile strength. Experimental results show that unidirectional platelet laminates can possess tensile strengths in excess of 1 GPa while pseudo-ductile deformation accounts for more than ∼ 50% of the ultimate failure strain. Finite element modelling of platelet laminates reveals that the amount of pseudo-ductility can be tailored via the design optimization of the tiling pattern, overlap length, composite thickness and mode II interlaminar toughness of the platelets. The mechanisms controlling the pseudo-ductility effect in the bioinspired platelet laminates is described.

Experimental Study of Geysering in an Upstream Vertical Shaft

Transient flows in stormwater systems can lead to damaging and dangerous operational conditions, as exemplified by geysering events created by the uncontrolled release of entrapped air pockets. Extreme rain and associated rapid inflows may result in air pocket entrapment, which causes significant changes in flow conditions and potentially geysering. Stormwater geysers have been studied in different experimental and numerical modeling studies, as well as from limited data gathered within real systems. However, there is still no complete understanding of geysering events, as stormwater system geometries vary considerably. Most past studies involved releasing air from an intermediate shaft, in which a significant fraction of the entrapped air may bypass the release. This work advances the understanding of geysering by considering uncontrolled air release through an upstream shaft or manhole. In such cases, the entire air pocket is released upon reaching the shaft, worsening the occurrence of geysering. Pressure and water level measurements were performed for various combinations of initial water pressure, trapped air pocket volume, and vertical shaft geometries, indicating the higher severity of these geysering events. The results obtained also corroborate previous studies in that the measured pressure heads were lower than the grade elevation. Future studies should include larger-scale testing and the representation of this geometry using CFD.

A comprehensive experimental and kinetic modeling study of laminar flame propagation of ammonia blended with propene

Enhancement of ammonia reactivity is crucial for potential applications of ammonia as an engine and gas turbine fuel. A common strategy for improving ammonia's poor reactivity is blending it with more reactive fuels like hydrogen and methane. However, fundamental studies of ammonia combustion with higher hydrocarbons and key intermediate oxidation species of higher alkanes such as propene do not exist. Thus, this work presents an effort to study the laminar flame propagation of ammonia blended with propene. Laminar burning velocity (SL) of NH3/C3H6/air mixtures was measured at 298 K, pressures up to 5 bar, equivalence ratios of 0.7 to 1.3, and various propene to ammonia ratios (i.e.,% propene to ammonia mole fraction, xC3H6 = 10 to 50) in a high-pressure spherical propagating flame vessel. A kinetic model was developed based on our previous work to characterize the combustion behavior of NH3/C3H6/air mixture. The model reasonably agrees with the experimental data and follows the observed trends very well. The results showed that blending NH3 with C3H6 positively enhanced SL of NH3 by promoting the formation of key radicals e.g., O, OH, and H. Relative to a neat ammonia/air mixture, co-firing ammonia with propene leads to a reduced pressure dependence of the laminar burning velocity. However, the reaction H + O2(+M)=HO2(+M) leads to strong pressure dependency of lean NH3/C3H6 mixtures compared to rich mixtures. The model reveals that besides fuel-NO coming from NH3, prompt NO also actively contributes to NO formation. It is seen that N2O formation is significantly suppressed with increasing pressure or increasing C3H6 content in the fuel blend. In contrast to NO and N2O, NO2 concentration increases slightly with an increase in pressure. The reported experimental data and model will be useful in understanding the interaction between NH3 and alkenes.

Multiple system atrophy: at the crossroads of cellular, molecular and genetic mechanisms

Multiple system atrophy (MSA) is a rare oligodendroglial α-synucleinopathy characterized by neurodegeneration in striatonigral and olivopontocerebellar regions and autonomic brain centres. It causes complex cumulative motor and non-motor disability with fast progression and effective therapy is currentlylacking. The difficulties in the diagnosis and treatment of MSA are largely related to the incomplete understanding of the pathogenesis of the disease. The MSA pathogenic landscape is complex, and converging findings from geneticand neuropathological studiesas well as studies in experimental models of MSA have indicated the involvement ofgenetic and epigenetic changes; α-synuclein misfolding, aggregationand spreading; and α-synucleinstrain specificity. These studies also indicate the involvement of myelin and iron dyshomeostasis, neuroinflammation, mitochondrial dysfunction and other cell-specific aspects that are relevant to the fast progression of MSA. In this Review, we discuss these findings and emphasize the implications of the complexity of the multifactorial pathogenic cascade for future translational research and itsimpact on biomarker discovery and treatment target definitions.

The impact of membrane perforation and L-PRF for vertical ridge augmentation with a xenogeneic block graft: an experimental study in a canine model

ObjectivesThis study evaluated clinically and histologically the efficacy of modified perforated collagen membrane (PCM) and/or leukocyte- and platelet-rich fibrin (L-PRF) in combination with xenogeneic block bone graft in the vertical alveolar ridge augmentation.Materials and methodsSix adult mongrel dogs were enrolled in this randomized blinded study. After defect preparation, xenogeneic screw-fixed block graft was covered by an occlusive collagen membrane in group 1 that represented the control group (Block + CM). In group 2, L-PRF membrane was added first before top coverage by occlusive collagen membrane (Block + L-PRF + CM). Groups 3 (Block + PCM) and 4 (Block + L-PRF + PCM) were identical to the first two groups except that the occlusive collagen membrane was replaced by a perforated one. Following a healing period of 2 months, the dogs were submitted to the surgical reentry phase for clinical and histological evaluation.ResultsClinically, no significant differences were found among all groups regarding vertical and horizontal ridge dimensions (p = 0.155, 0.492, respectively). Histomorphometric analysis revealed that the percentage of the total bone area and mature bone was significantly higher in group 4 (69.36 ± 2.72, 33.11 ± 5.18) compared to the control group (59.17 ± 4.27, 21.94 ± 2.86) (p = 0. 027, p = 0.029).ConclusionThe use of xenogenic block grafts in combination with a double-layered perforated collagen L-PRF membrane in vertical ridge augmentation appeared to improve the inductive power of this challenging defect type.Clinical relevanceSize and number of perforations may affect the mechanical and handling properties of the membrane.

Effects of SDS surface-active agents on hydrodynamics and oxygen mass transfer in a square bubble column reactor: Experimental and CFD modeling study

This work examined experimentally and numerically the effects of sodium dodecyl sulfate (SDS) surfactant agent on mass transfer coefficients kLaL and kL in a high-aspect square bubble column reactor. To this end, SDS aqueous solutions at concentrations between 5 ppm and 30 ppm were prepared. Superficial gas velocity was varied from 0.74 cm.s−1 to 9.44 cm.s−1 covering all flow regimes to analyze the interaction between different phases and the effect of liquid surface tension on gas-liquid interfaces. Experimental data indicated that the presence of the SDS in the liquid phase augmented the overall gas holdup up to 25% at a constant gas velocity (Ug = 7.3 cm.s−1) in the transition regime, which is due to the role of SDS in bubble interactions. The impact of SDS addition on the mass transfer is twofold. Firstly, it reduced kL because the SDS molecules migrate towards the bubble-liquid interface thanks to the lower O2 diffusivity in water, thus hindering the O2 transfer from one phase to the other. Secondly, it increased aL owing to the inhibition of bubbles coalescence and, therefore, the lower mean bubble size. Among these two effects, the latter is prevailing, which led to an increase in kLaL in contaminated systems. In the second part of this work, a population balance model (PBM) was coupled with a computational fluid dynamics (CFD) model based on large-eddy simulation (LES) to analyze the effect of both tap water and SDS contaminated systems on the breakage phenomena, local flow pattern, and the resulting hydrodynamics and mass transfer features in the reactor. Ultimately, experiments and numerical simulations agreed well in terms of global gas holdup and kLaL coefficient. In particular, the transition points in the case of the SDS media (except for foam formation) provided the model with adequate PBM definitions for the dispersed phase.

An experimental and kinetic modeling study on the high-temperature ignition and pyrolysis characteristics of cyclohexylamine

Amine compounds are an important class of nitro-containing fuels and represent as promising renewable fuels. However, the structural effect from the alkyl group on the combustion characteristics of amines remains an urgent problem to promote their usage in practical engines. To probe and replenish the combustion properties of amine fuels, this work reported an experimental and kinetic modeling study on the high-temperature ignition and pyrolysis characteristics of cyclohexylamine over a wide range of conditions. Specifically, a high-pressure shock tube is used to measure the ignition delay times under the temperature range from 1100 K to 1700 K with pressure of 2 and 5 bar and the equivalence ratios of 0.5, 1.0 and 2.0. The pyrolysis characteristics is studied using a single-pulse shock tube at fuel concentration of 0.5% diluted by argon in the temperature range 950–1400 K at 5 and 10 bar with the residence time around 1.6 microsecond. A detailed kinetic mechanism is developed to simulate the experimental results. To improve the accuracy of the detailed mechanism, primary initial reactions of cyclohexylamine including the hydrogen abstraction reactions and the CN decomposition reaction are theoretically studied at G4//M06–2X/6–311++G(d, p) level of theory with transition state theory and RRKM/mater equation. The detailed kinetic mechanism shows good prediction accuracy of the ignition delay times and pyrolysis product distributions under different temperature, pressure and equivalence ratio conditions. Sensitivity analysis results indicate that the most sensitive reaction is O2 + H = O + OH with the most negative sensitivity coefficient and the abstraction reaction of vinylamine with OH radical, C2H3NH2 + OH = C2H3NH + H2O also exhibits large sensitivity coefficients. Reaction path analysis reveals that the abstraction reactions control the initial oxidation of cyclohexylamine and cyclohexen-1-amine, cyclohexen-2-amine, and cyclohexen-3-amine are also major intermediates during the oxidation of cyclohexylamine besides small pyrolysis products.

Experimental and modeling studies on dynamic barite sag and effects of particle size, shear rate, and fluid rheology

Barite is often utilized to control the weight of drilling muds. However, in inclined wellbores, barite particles settle out of the mud in a lateral direction and quickly reach the wellbore wall. Over time, deposited particles form unstable barite beds that slide intermittently downward, causing downhole pressure fluctuations. The observation is often referred to as barite sag, which occurs prominently when the system is in a dynamic state. Barite sag leads to density variation in the mud system, resulting in drilling issues such as stuck pipe, fluid loss and lost circulation, loss of well control, and wellbore instability. Various experimental studies have been conducted on barite sag, but limited mathematical modeling has been undertaken.This article presents the results of experimental and mathematical modeling studies on barite sag. First, particle size distribution tests were performed with API barite. Then, different oil-based muds (OBMs) were prepared using barite samples with various particle size distributions. Next, the apparent viscosities of the muds were measured with a rheometer. Then, the Viscometer Sag Shoe Test (VSST) method was used to study barite sag at 49 °C varying rotational speed and barite particle size distribution. Furthermore, the settling behavior of barite particles under dynamic conditions was simulated using a sedimentation-consolidation model. The model is solved numerically by applying a fully implicit finite difference method. The accuracy of the numerical solution is validated using simulation results presented in a previous study. The model has been improved to handle non-Newtonian fluids and simulate dynamic conditions.According to the apparent viscosity measurements, barite particle size has a minor effect on OBM rheology. The VSST results also show that barite sag increases with particle size and rotational speed. The improved model predicts VSST results fairly well. Additionally, a model-based parametric study indicates that barite sag decreases with increasing OBM rheological parameters (consistency index, yield stress, and fluid behavior index).

TRPV1 Channel in Pathogenesis of Inflammatory Bowel Disease

Abstract—Inflammatory Bowel Disease (IBD) including Ulcerative colitis (UC) and Crohn’s disease (CD) is a group of chronic immune-mediated diseases of the gastrointestinal tract (GIT) with complex pathophysiology and pathogenesis. Although the exact pathophysiological mechanisms are poorly understood, in recent years, studies have described the activation and alteration of nociceptor functions and their signaling pathways in the inflammation development in IBD and associated hyperalgesia, in particular, the key role of the transient receptor potential vanilloid channel 1 (TRPV1) has been demonstrated. The highest expression level of TRPV1 is specific for sensory neurons, however, it can also be expressed by other cell types, including epithelial cells of the intestine and bladder, immunoreactive cells such as lymphocytes, mast and dendritic cells, vascular endothelial cells, etc. An increasing number of studies in various experimental models, including humans, demonstrate that activation of the TRP superfamily channels, which includes TRPV1, can significantly enhance visceral hypersensitivity, mediate the development of inflammation and pain. In this review, we highlight the present knowledge on the structure, functions and potential role of TRPV1 in the pathogenesis of IBD. Much attention is paid to the discussion of the signaling pathways underlying TRPV1 modulation. We propose that further research in this area will contribute to a better understanding of the general mechanisms of inflammatory and pain response formation and may facilitate the development of new therapeutic targets for the treatment of IBD.

Editorial introductions.

Current Opinion in Anesthesiology was launched in 1988. It is one of a successful series of review journals whose unique format is designed to provide a systematic and critical assessment of the literature as presented in the many primary journals. The field of anesthesiology is divided into 16 sections that are reviewed once a year. Each section is assigned a Section Editor, a leading authority in the area, who identifies the most important topics at that time. Here we are pleased to introduce the Journal's Section Editors for this issue. SECTION EDITORS Catherine M. KuzaCatherine M. KuzaDr Catherine M. Kuza, MD, FASA is an Associate Professor of Anesthesiology in the Department of Anesthesiology, Division of Critical Care at the Keck School of Medicine of the University of Southern California (KSOM USC), Los Angeles, USA. She completed her anesthesiology residency training at the University of Massachusetts School of Medicine in Worcester, MA, USA and went on to complete a critical care fellowship at Brigham and Women's Hospital in Boston, MA, USA. She has been faculty at KSOM USC since 2016, where she served as the Director of Resident Research and Quality Improvement from 2017–2019, and in 2019 became the Director of Trauma Researcher. In 2021 she was appointed Associate Director of the Surgical Intensive Care Unit. Her areas of research include trauma anesthesiology, emergency preparedness and mass casualties, burns, critical care delirium, and post-intensive care unit syndrome. She enjoys teaching and has served as a mentor in research, anesthesiology, and critical care to numerous medical students, residents, and fellows. She has published a number of journal articles and book chapters related to trauma, burns, critical care, and emergency preparedness. She is an active member of numerous professional societies including the American Society of Anesthesiologists (ASA). While serving on the ASA Committee of Trauma and Emergency Preparedness, she has spearheaded several multicentre trauma studies. Edoardo De RobertisEdoardo De RobertisEdoardo De Robertis is Professor of Anaesthesiology at the University of Perugia, Italy, where he coordinates the Division of Anaesthesia, Analgesia, and Intensive Care. He is the Director of the clinical university department of Anaesthesia and Intensive Care and director of the Residency Program and School in Anaesthesia, Intensive Care and Pain. He is President of the European Society of Anaesthesia and Intensive Care (ESAIC) for the two years term 2022–23. Prof Edoardo De Robertis graduated with honour in Medicine and Surgery at the University of Napoli Federico II, Italy, where he completed his anaesthesiology residency. At the University of Lund, Sweden he received his PhD. Leader of a research group at the University Federico II, Italy, and more recently at the University of Perugia, Italy, Prof De Robertis has been involved in the planning, management and coordination of experimental studies in complex animal models and clinical studies on mechanical ventilation. An innovative system of ventilation aimed at the reduction of airway dead space (ASPIDS) was developed. Prof De Robertis has been actively involved in numerous collaboration and research projects with European partners and in the drafting of guidelines of the European Society of Anesthesiology (ESA/IC). He coordinated for Italy the ESA multicentric study PROVHILO and the ESICM consensus study WELPICUS. Prof De Robertis has focused his research activity on mechanical ventilation in critically ill patients and on the management of peri-operative massive bleeding, with particular attention to postpartum haemorrhage. He is also interested in the preoperative evaluation of the obstetric patient, and in the management of neuromuscular block in pelvic laparoscopic surgery.