Experimental Model For Study Research Articles

An experimental and kinetic modeling study of the ignition delay and heat release characteristics of a five component gasoline surrogate and its blends with iso‐butanol within a rapid compression machine

AbstractThis study investigates the performance of a five component gasoline surrogate (iso‐octane, toluene, n‐heptane, 1‐hexene, and ethanol) in representing the ignition delay time (IDT) behavior of gasoline (reference gasoline PR5801—research octane number 95.4, motor octane number 86.6), at conditions of 675–870 K, 20 bar, and Ф = 1 (stoichiometric) within a rapid compression machine (RCM). Experimentally, the surrogate produces a good representation of the ignition behavior of the gasoline at these conditions, displaying a similar IDT profile. The influence of blending with iso‐butanol on the surrogate's ignition delay behavior is also investigated, at blends from 5% to 70% of iso‐butanol by volume. The surrogate continues to produce a reasonable representation of the experimental IDTs of gasoline and iso‐butanol blends, except under a high degree of iso‐butanol blending (50% iso‐butanol), where the surrogate produced longer IDTs, particularly at temperatures below 740 K. Blends of 5% and 10% iso‐butanol produce IDTs shorter than that of any other blend, including the “neat” surrogate, at temperatures of 740–770 and 830 K, respectively. Kinetic modeling of RCM IDTs is performed using CHEMKIN‐PRO (Reaction Design: San Diego, CA, 2011) and a combined mechanism of the Sarathy et al. butanol isomers mechanism (Progress in Energy and Combustion Science 2014; 44: 40–102) and Lawrence Livermore National Laboratories “Gasoline Surrogate” mechanism (Proceedings of the Combustion Institute 2011; 33(1): 193–200). The model produces good IDT predictions below 740 K but overpredicts reactivity in the negative temperature coefficient region. Heat release rate analysis is conducted for experimental and modeling results to investigate low‐temperature heat release (LTHR) behavior. Simulations largely fail to accurately reproduce this behavior. This analysis, combined with local OH and brute force Δhf sensitivity analyses, indicates the significance of LTHR in the determination of IDTs and provides RCM heat release rates for future model validation.

COMPARATIVE ANALYSIS OF SUCCESS IN HIGHER EDUCATION IN UKRAINE AND THE USA

The article is devoted to the study of the success in the system of higher education in the USA and Ukraine. This concept in higher education has interested scholars in recent decades and has caused many debates about determining student progress. At the end of the twentieth century in the United States, student achievement was measured by quantitative indicators that demonstrated the effectiveness of higher education. But the gradual change in the higher education priorities, the characteristics of the students, the need to improve the educational process has led to a revision of the definition of this phenomenon and provoked a number of studies to expand this concept, creating models of success. The modern definition of student success in US higher education establishments involves academic success and the development of the necessary personality traits, skills and abilities for further self-realization. Ukrainian researchers consider success as a category of pedagogical psychology, as this concept concerns, first of all, the personal development of the student, the skills and abilities of useful interaction. At the same time, a number of studies made by Ukrainian educators are devoted to the issue of academic success, which is also considered as a qualitative development of the student`s personality. Unfortunately, compared to the United States, Ukraine does not have sufficient data on the quality of higher education, there are no experimental studies of success models for students. There is a lack of information on further self-realization of students, their employment. Thus comparing student success in the two countries, it can be concluded that there is a difference in understanding of this concept by American and Ukrainian scholars, the issue of retention, persistence and graduation is not sufficiently developed by Ukrainian educators. The problem to find the ways to improve higher education is common, but its development, as well as the creation of models for achieving success is not sufficiently represented in Ukrainian scientific discourses.

An experimental and kinetic modeling study on the laminar burning velocity of NH3+N2O+air flames

In the present work, the laminar burning velocities of the NH3+N2O+air flames were measured using the heat flux method at 1 atm and 298 K, with varied equivalence ratios and N2O mixing ratios. For the mixing ratio N2O/(N2O+air) = 0.5, a full range of equivalence ratios was covered. Moreover, at three equivalence ratios an extended range of mixing ratios was investigated. The laminar burning velocity has an approximately linear relationship against the fraction of nitrous oxide in the oxidizer mixture, regardless of the tested equivalence ratios. Several recently published NH3 mechanisms were compared with these new experimental data; among them the models of Nakamura et al. and Stagni et al. show the best performance for NH3+N2O+air flames over the entire range of the mixing ratios. The H/N/O kinetic mechanism of the authors was analyzed and updated focusing on the rate constants of reactions most sensitive in ammonia flame propagation and self-ignition of NH3+O2 and H2+N2O mixtures. The choice of the new rate constants is outlined, however, no modification (adjustment or tuning) of the rate parameters to accommodate experimental results was attempted. The updated mechanism demonstrates significantly improved agreement with all measurements used for the model development and with other experimental data from the literature for ammonia flames and self-ignition. A comparative reaction path analysis for NH3+N2O+air and NH3+air flames revealed that an almost linear increase of the laminar burning velocity with an increased fraction of N2O in the oxidizer originates from the rate controlling reaction N2O+H = N2+OH, which produces OH radicals dominating ammonia oxidation.

Biomechanical Comparison of Different Numbers and Configurations of Cross-Links in Long-Segment Spinal Fixation-An Experimental Study in a Porcine Model.

Biomechanical study. Cross-links are a type of common clinical spinal instrumentation. However, the effects of the position and number of cross-links have never been investigated in long-segment spinal fixation, and the variables have not been optimized. We conducted an in vitro biomechanical study by using a porcine long-segment spinal model with 5 different crosslink configurations to determine the optimal construct for clinical practice. Five modalities with paired segmental screws from T15-L5 were tested in 20 porcine spines. The spines without cross-links composed the control group, Group A; those with a single cross-link from L2-3 composed Group B; those with 2 cross-links from L1-2 and L3-4 composed Group C; those with 2 cross-links from T15-L1 and L4-5 composed Group D; and those with 3 cross-links from T15-L1, L2-3 and L4-5 composed Group E. Spinal stiffnesses in flexion, extension, lateral bending, and axial rotation were compared among 5 different cross-link configurations in 5-level porcine spinal units. Flexional, extensional and lateral bending stiffnesses did not significantly change with an increasing number of cross-links or positions in the construct. Axial stiffness was significantly increased with 2 cross-links compared to one (P < 0.05) and with placement more distant from the center of the long spinal fixation construct (P < 0.05). Two cross-links individually placed proximal and distal from the center of a construct is an optimal and efficient configuration to achieve biomechanical stability in non-rigid lumbar spines undergoing long-level fixation.

ELTD1 as a biomarker for multiple sclerosis: Pre-clinical molecular-targeted studies in a mouse experimental autoimmune encephalomyelitis model

Multiple sclerosis (MS) and glioblastoma (GBM) are two distinct diseases that affect the central nervous system (CNS). However, perturbation in CNS vasculature are hallmarks of both diseases. ELTD1 (epidermal growth factor, latrophilin, and 7 transmembrane domain containing protein 1 on chromosome 1) is associated with vascular development, and has been linked with tumor angiogenesis. In glioblastomas, we detected over-expression of ELTD1, and found that an antibody targeting ELTD1 could increase animal survival and decrease tumor volumes in a xenograft GBM model. RNA-seq analysis of the preclinical data in the model for GBM identified that some of the molecular pathways affected by the anti-ELTD1 antibody therapy are also found to be associated with MS. In this study, we used molecular-targeted (mt) MR imaging and immunohistochemistry to assess ELTD1 levels in experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. Specifically, we found that ELTD1 is readily detected in the brains of mice with EAE and is predominantly found in the corpus callosum. In addition, we found that the blood-brain barrier (BBB) was compromised in the brains of EAE mice using contrast-enhanced MRI (CE-MRI), as well as altered relative cerebral blood flow (rCBF) in the brains and cervical spinal cords of these mice using perfusion imaging, compared to controls. These findings indicate that ELTD1 may be a promising biomarker for CNS-inflammation in MS.

Importance of Non-pharmacological Approaches for Treating Irritable Bowel Syndrome: Mechanisms and Clinical Relevance.

Chronic visceral pain represents a major unmet clinical need with the severity of pain ranging from mild to so severe as to prevent individuals from participating in day-to-day activities and detrimentally affecting their quality of life. Although chronic visceral pain can be multifactorial with many different biological and psychological systems contributing to the onset and severity of symptoms, one of the major triggers for visceral pain is the exposure to emotional and physical stress. Chronic visceral pain that is worsened by stress is a hallmark feature of functional gastrointestinal disorders such as irritable bowel syndrome (IBS). Current pharmacological interventions for patients with chronic visceral pain generally lack efficacy and many are fraught with unwanted side effects. Cognitive behavioral therapy (CBT) has emerged as a psychotherapy that shows efficacy at ameliorating stress-induced chronic visceral pain; however, the molecular mechanisms underlying CBT remain incompletely understood. Preclinical studies in experimental models of stress-induced visceral pain employing environmental enrichment (EE) as an animal model surrogate for CBT are unraveling the mechanism by which environmental signals can lead to long-lasting changes in gene expression and behavior. Evidence suggests that EE signaling interacts with stress and nociceptive signaling. This review will (1) critically evaluate the behavioral and molecular changes that lead to chronic pain in IBS, (2) summarize the pharmacological and non-pharmacological approaches used to treat IBS patients, and (3) provide experimental evidence supporting the potential mechanisms by which CBT ameliorates stress-induced visceral pain.

Porosity changes due to analcime in a basaltic tuff from the Janggi Basin, Korea: experimental and geochemical modeling study of CO2–water–rock interactions

Porosity changes due to analcime in a basaltic tuff from the Janggi Basin, Korea: experimental and geochemical modeling study of CO2–water–rock interactions

Carboxypeptidase inhibition by NvCI suppresses airway hyperreactivity in a mouse asthma model

Carboxypeptidase inhibition by NvCI suppresses airway hyperreactivity in a mouse asthma model

An updated experimental and kinetic modeling study of n-pentane pyrolysis at atmospheric pressure in a flow reactor

In a flow reactor, the pyrolysis process of n-pentane in the 450–750 °C temperature range was investigated at 760 Torr. The pyrolysis products, particularly free radicals and isomers, were identified using synchrotron radiation vacuum ultraviolet photoionization mass spectrometry, and their mole fractions were determined. In this study, the existing n-pentane pyrolysis kinetic model was updated according to the C5-mechanism, and the new pyrolysis data were validated. The rate of production and sensitivity analyses were conducted to determine the significant reactions controlling the pyrolysis of fuel and their effects on the reactant concentration and product species profiles. The unimolecular decomposition reaction and free radical attack reaction via H attack dominate n-pentane pyrolysis at atmospheric pressure. Alkenes including 1-pentene, 1-butene, propene and ethylene are produced with higher concentrations than other product species in n-pentane pyrolysis.

Exploration of processes governing microbial reductive dechlorination in a heterogeneous aquifer flow cell

Although microbial reductive dechlorination (MRD) has proven to be an effective approach for in situ treatment of chlorinated ethenes, field implementation of this technology is complicated by many factors, including subsurface heterogeneity, electron donor availability, and distribution of microbial populations. This work presents a coupled experimental and mathematical modeling study designed to explore the influence of heterogeneity on MRD and to assess the suitability of microcosm-derived rate parameters for modeling complex heterogeneous systems. A Monod-based model is applied to simulate a bioremediation experiment conducted in a laboratory-scale aquifer cell packed with aquifer material from the Commerce Street Superfund site in Williston, VT. Results reveal that (uncalibrated) model application of microcosm-derived dechlorination and microbial growth rates for transformation of trichloroethene (TCE), cis-1,2-dichloroethene (cis-DCE), and vinyl chloride (VC) reproduced observed aquifer cell concentration levels and trends. Mean relative errors between predicted and measured effluent concentrations were quantified as 6.7%, 27.0%, 41.5%, 32.0% and 21.6% over time for TCE, cis-DCE, VC, ethene and total volatile fatty acids (fermentable electron donor substrate and carbon source), respectively. The time-averaged extent of MRD (i.e., ethene formation) was well-predicted (4% underprediction), with modeled MRD exhibiting increased deviation from measured values under electron donor limiting conditions (maximum discrepancy of 14%). In contrast, simulations employing a homogeneous (uniform flow) domain resulted in underprediction of MRD extent by an average of 13%, with a maximum discrepancy of 45%. Model sensitivity analysis suggested that trace amounts of natural dissolved organic carbon served as an important fermentable substrate, providing up to 69% of the reducing equivalents consumed for MRD under donor-limiting conditions. Aquifer cell port concentration data and model simulations revealed that ethene formation varied spatially within the domain and was associated with regions of longer residence times. These results demonstrate the strong influence of subsurface heterogeneity on the accuracy of MRD predictions, and highlight the importance of subsurface characterization and the incorporation of flow field uncertainty in model applications for successful design and assessment of in situ bioremediation.

Intraoperative Perfusion Assessment in Enhanced Reality Using Quantitative Optical Imaging: An Experimental Study in a Pancreatic Partial Ischemia Model.

To reduce the risk of pancreatic fistula after pancreatectomy, a satisfactory blood flow at the pancreatic stump is considered crucial. Our group has developed and validated a real-time computational imaging analysis of tissue perfusion, using fluorescence imaging, the fluorescence-based enhanced reality (FLER). Hyperspectral imaging (HSI) is another emerging technology, which provides tissue-specific spectral signatures, allowing for perfusion quantification. Both imaging modalities were employed to estimate perfusion in a porcine model of partial pancreatic ischemia. Perfusion quantification was assessed using the metrics of both imaging modalities (slope of the time to reach maximum fluorescence intensity and tissue oxygen saturation (StO2), for FLER and HSI, respectively). We found that the HSI-StO2 and the FLER slope were statistically correlated using the Spearman analysis (R = 0.697; p = 0.013). Local capillary lactate values were statistically correlated to the HSI-StO2 and to the FLER slope (R = −0.88; p < 0.001 and R = −0.608; p = 0.0074). HSI-based and FLER-based lactate prediction models had statistically similar predictive abilities (p = 0.112). Both modalities are promising to assess real-time pancreatic perfusion. Clinical translation in human pancreatic surgery is currently underway.

Nucleation pathways in barium silicate glasses

Nucleation is generally viewed as a structural fluctuation that passes a critical size to eventually become a stable emerging new phase. However, this concept leaves out many details, such as changes in cluster composition and competing pathways to the new phase. In this work, both experimental and computer modeling studies are used to understand the cluster composition and pathways. Monte Carlo and molecular dynamics approaches are used to analyze the thermodynamic and kinetic contributions to the nucleation landscape in barium silicate glasses. Experimental techniques examine the resulting polycrystals that form. Both the modeling and experimental data indicate that a silica rich core plays a dominant role in the nucleation process.

Experimental-Modeling Study of Phase Equilibria, Densities, and Viscosities for the Propanenitrile–Decane Mixture at Low Pressure

In this work, experimental data for vapor–liquid equilibria at 84.49 kPa, densities, and viscosities at 318.15 K are reported for the propanenitrile–decane mixture. To validate the methodology and ...

Experimental and kinetic modeling studies of 2-ethylfuran pyrolysis at low and atmospheric pressures

The pyrolysis of 2-ethylfuran (EF2) in a flow reactor was studied by using synchrotron vacuum ultraviolet photoionization mass spectrometry at 846 – 1319 K and at 30 and 760 Torr. Over 20 pyrolysis products were detected and measured. A detailed kinetic model was constructed by extending the reported comprehensive 2,5-dimethylfuran model to describe the pyrolysis of EF2 and validated against the current experimental results, including methyl, 2-furylmethyl, propargyl, acetylene , ethylene, propene , ketene, 2-vinylfuran, furan/vinylketene and benzene, etc. Rate of production analysis and sensitivity analysis indicate that the main reaction pathways of EF2 pyrolysis are H-abstraction reactions forming 1-(2-furyl)ethyl and 2-(2-furyl)ethyl, unimolecular decomposition reactions forming 2-furylmethyl, and H-addition reactions forming furan and vinylketene. The corresponding products, 2-vinylfuran, 2-furylmethyl and vinylketene, etc., are indicated to be the most key products in EF2 pyrolysis. Comparisons of the formation of aromatic hydrocarbons in the pyrolysis of EF2, 2-methylfuran and 2,5-dimethylfuran show that EF2 had a lower tendency to produce aromatic soot precursors.

Impact of sodium glucose cotransporter 2 (SGLT2) inhibitors on atherosclerosis: from pharmacology to pre-clinical and clinical therapeutics

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are new oral drugs for the therapy of patients with type 2 diabetes mellitus (T2DM). Research in the past decade has shown that drugs of the SGLT2i class, such as empagliflozin, canagliflozin, and dapagliflozin, have pleiotropic effects in preventing cardiovascular diseases beyond their favorable impact on hyperglycemia. Of clinical relevance, recent landmark cardiovascular outcome trials have demonstrated that SGLT2i reduce major adverse cardiovascular events, hospitalization for heart failure, and cardiovascular death in T2DM patients with/without cardiovascular diseases (including atherosclerotic cardiovascular diseases and various types of heart failure). The major pharmacological action of SGLT2i is through inhibiting glucose re-absorption in the kidney and thus promoting glucose excretion. Studies in experimental models of atherosclerosis have shown that SGLT2i ameliorate the progression of atherosclerosis by mechanisms including inhibition of vascular inflammation, reduction in oxidative stress, reversing endothelial dysfunction, reducing foam cell formation and preventing platelet activation. Here, we summarize the anti-atherosclerotic actions and mechanisms of action of SGLT2i, with an aim to emphasize the clinical utility of this class of agents in preventing the insidious cardiovascular complications accompanying diabetes.

Disruption of Endoplasmic Reticulum Proteostasis in Age-Related Nervous System Disorders.

Endoplasmic reticulum (ER) stress is a prominent cellular alteration of diseases impacting the nervous system that are associated to the accumulation of misfolded and aggregated protein species during aging. The unfolded protein response (UPR) is the main pathway mediating adaptation to ER stress, but it can also trigger deleterious cascades of inflammation and cell death leading to cell dysfunction and neurodegeneration. Genetic and pharmacological studies in experimental models shed light into molecular pathways possibly contributing to ER stress and the UPR activation in human neuropathies. Most of experimental models are, however, based on the overexpression of mutant proteins causing familial forms of these diseases or the administration of neurotoxins that induce pathology in young animals. Whether the mechanisms uncovered in these models are relevant for the etiology of the vast majority of age-related sporadic forms of neurodegenerative diseases is an open question. Here, we provide a systematic analysis of the current evidence linking ER stress to human pathology and the main mechanisms elucidated in experimental models. Furthermore, we highlight the recent association of metabolic syndrome to increased risk to undergo neurodegeneration, where ER stress arises as a common denominator in the pathogenic crosstalk between peripheral organs and the nervous system.

Alpha-Synuclein in the Blood of Mice in a Neurotoxic Model of Parkinson’s Disease

Abstract—One of the priorities of neuroscience is the fight against socially relevant neurodegenerative diseases, including Parkinson’s disease (PD). Given the limited possibilities of studying the pathogenesis of this disease, the creation and detailed study of appropriate experimental models is of great importance. Therefore, the purpose of this work was to continue the long-term study of the cellular and molecular mechanisms of the pathogenesis of Parkinson’s disease and their systemic manifestations in a model of this disease in mice which is based on the use of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Here, using Western blotting, it was shown that in the blood plasma of mice with MPTP-induced clinical stage of PD, the ratio of monomeric to oligomeric α-synuclein is almost halved, and there is a tendency toward a decrease in the ratio of total α-synuclein to α-synuclein phosphorylated at serine-129. According to several studies, these changes are typical in patients with PD. Unlike plasma, no change in the ratio of these proteins was found in lymphocytes. From the alignment of our data on the content of α-synuclein and its isoforms in the blood of Parkinsonian mice, and the literature data on the content of α-synuclein in PD patients, it follows that our PD model can be used for an in-depth assessment of the peripheral manifestations of this disease, as well as for improving the differential diagnosis of PD, analyzing the effectiveness therapy, and screening for new drugs.

Hyperuricemia and chronic kidney disease: to treat or not to treat.

Hyperuricemia is common in chronic kidney disease (CKD) and may be present in 50% of patients presenting for dialysis. Hyperuricemia can be secondary to impaired glomerular filtration rate (GFR) that occurs in CKD. However, hyperuricemia can also precede the development of kidney disease and predict incident CKD. Experimental studies of hyperuricemic models have found that both soluble and crystalline uric acid can cause significant kidney damage, characterized by ischemia, tubulointerstitial fibrosis, and inflammation. However, most Mendelian randomization studies failed to demonstrate a causal relationship between uric acid and CKD, and clinical trials have had variable results. Here we suggest potential explanations for the negative clinical and genetic findings, including the role of crystalline uric acid, intracellular uric acid, and xanthine oxidase activity in uric acid-mediated kidney injury. We propose future clinical trials as well as an algorithm for treatment of hyperuricemia in patients with CKD.

Stepped spillways with aerators: hydrodynamic pressures and air entrainment

ABSTRACT The possibility of damage due to the phenomenon of cavitation leads the design of stepped spillways considering maximum specific discharges of 15 to 30 m2/s, a limit considerably lower than that practiced on smooth chutes. Aerators promote the insertion of air in the flow, allowing for the increase of specific flow rates. This work analyzes the pressures on the vertical faces of the steps and the air entrainment coefficient in the flow, through an experimental study in a physical model with a stepped chute angle of 53.13o, considering the installation of aerators in different places of the channel. Comparing the tested conditions with the natural aeration, it is concluded that the installation of the aerator does not change the magnitude of the minimum extreme hydrodynamic pressures, but anticipates the beginning of the flow aeration. A new equation is proposed to estimate the air entrainment coefficient, as well as a methodology for forecasting extreme pressures on the vertical faces of the steps, both valid in the range 3.0 ≤ Fr ≤ 6.0.

Effects of natural extracts in the treatment of oral ulcers: A systematic review of evidence from experimental studies in animals.

BackgroundTo evaluate the clinical and histopathological effects of natural extracts in the treatment of oral ulcers induced in animal experimental models. Material and MethodsWe carried out a search in the Medline, Scopus, WoS and Embase databases from the start of the databases to December 2020, and also made a manual search of the references. The search and selection were carried out by two researchers independently. The inclusion criteria were: experimental studies in animal models, in english, which complied with the study object. ResultsA total of 705 articles were identified. After selection by title, abstract and full text, 19 articles were finally included. Natural extracts of Jasminum grandiflorum, Ficus deltoidea, curcumin and Bixina orellana provoked a significantly greater reduction in the size of the ulcer. Extracts of Salvatora persica, Musa acuminate, Ganoderma lucidum mycelia and Bixina Orellana, as well as preparations of Kouyanqing Granule and curcumin, were able to reduce levels of pro-inflammatory cytokines and increase the expression and serum levels of growth factors and anti-inflammatory cytokines. Extracts of Piper sarmentosus, Cannabis sativa and Bletilla striata provoked a reduction in the severity of the histological inflammation. No significant differences were observed compared to controls in the treatments with extracts of Cannabis sativa, Aloe barbadensus Miller and Malva sylvestris in reducing the area of the oral ulcers. ConclusionsMost of the natural extracts described in this review presented a positive clinical and histological effect on the cicatrisation of oral ulcers induced in animal models. Key words:Recurrent aphthous stomatitis, oral ulcer, plants, herbs, extracts, medicine, treatment.