Search

Objectives: To investigate the risk factors and biomechanical mechanisms of in-stent restenosis (ISR) in central venous occlusive disease (CVOD).Patients and methods: This retrospective study consecutively included 77 maintenance hemodialysis (MHD) patients with CVOD who received the first percutaneous transluminal angioplasty with stenting (PTS) due to symptomatic CVOD in a tertiary hospital. The mean age was 59.7 ± 14.0 years, and 51.9% of patients were male. The clinical characteristics, occurrence of ISR and patency rates were recorded. Finite element method was applied to assess the biomechanical properties of stents.Results: Among 77 patients with a mean CVS score of 8.0 ± 2.8, 20.8%, 62.3%, and 16.9% of patients had the main vein of CVOD in the subclavian vein, brachiocephalic vein, and superior vena cava, respectively. A total of 72 (93.5%) patients received successful PTS treatment, for which the stents implanted were mainly Fluency covered stent (48.6%) and SMART bare stent (31.9%). During 15 (10–24)-months of follow-up, ISR occurred in 36.1% of the 72 patients. The primary and assisted primary patency rates at 12, 18, and 24 months were 78%, 56%, 42% and 95%, 90%, 87%, respectively. A prolonged dialysis vintage was an independent risk factor for ISR, yet the stent type or the main vein location was not correlated with ISR. Among three laser-engraving stents, the SMART stent was the best in terms of flexibility, stress, and strain on stents but worst in stress or strain on vessels. The Luminexx stent was the best in radial force and worst in stress or strain on stents. The Vici stent was the best in stress and strain on vessels and worst in radial force and flexibility.Conclusions: An unsatisfactory comprehensive biomechanical performance from configurations rooted in existing stents may account for the high incidence of ISR in CVOD.

Based on machine learning models, an approach for the type recognition of oxygenated additives (ester isomers, i.e., methyl butyrate, methyl crotonate, ethyl acrylate, and ethyl acrylate) via optical diagnostics was proposed. By utilizing optical diagnostic methods flame features were extracted, and three models including random forest (RF), artificial neural network (ANN), and support vector machine (SVM), were employed to establish the relationship between flame images and oxygenated additives. Moreover, the impact of multiple factors on model performance, including image compression, dataset size, and feature number was also investigated. The images of flame obtained from inverse diffusion flame under four different oxygenated additives and various combustion conditions were used as examples to examine the effectiveness of the proposed approach. Results indicated that the accuracy of the recognition of ester isomers by the proposed approach exceeded 90%. Furthermore, it is observed that image compression had minimal impact on prediction accuracy but significantly reduced processing time. Different types of features contributed to predicting the type of ester isomers variously, and all models exhibited improved accuracy with an increased number of features. The number of samples significantly affected model accuracy. The investigation of feature missing and insufficient training samples suggested that ANN and RF models were more suitable for cases with many missing features, while SVM was more suitable for dealing with small samples.

In this paper, we consider the tensor absolute value equations (TAVEs), which is a newly introduced problem in the context of multilinear systems. Although the system of the TAVEs is an interesting generalization of matrix absolute value equations (AVEs), the well-developed theory and algorithms for the AVEs are not directly applicable to the TAVEs due to the nonlinearity (or multilinearity) of the problem under consideration. Therefore, we first study the solutions existence of some classes of the TAVEs with the help of degree theory, in addition to showing, by fixed point theory, that the system of the TAVEs has at least one solution under some checkable conditions. Then, we give a bound of solutions of the TAVEs for some special cases. To find a solution to the TAVEs, we employ the generalized Newton method and report some preliminary results.

Currently, the silicon thermal method is the main process to produce primary magnesium, which is controlled by chemical reaction kinetics and the heat transfer process in the retort. However, the unbelievably low thermal conductivity and point contact thermal resistance of the pellets greatly reduce the heat transfer efficiency, resulting in low magnesium production efficiency. To increase productivity, the enhanced heat transfer mechanism was studied in detail by experiments in this paper. The results show that temperature rise may not accurately reflect the enhanced heat transfer effect, thus a synthetical valuation method which took total heat transfer, effective heat transfer ratio and temperature rise into account is proposed. On this basis, a new recycling technique which uses high temperature silicon carbide particles to enhance the heat transfer in the retort is developed. Then a three-dimensional unsteady numerical model incorporating the chemical reaction kinetics and heat transfer was established and used to prove the superiority of this new technique in terms of heat transfer efficiency, magnesium production rate and production cycle. Numerical results show that when the initial temperature of silicon carbide is 1373 K, the instantaneous magnesium production rate can reach 13.2 kg/h within 30 min of heating, which is three times that of the traditional silicothermic process. The production cycle could also be shortened to 240 min, which is half of the original, and the production efficiency can be doubled. This new technique can significantly improve heat transfer efficiency, shorten the production cycle and reduce the production cost.

ABSTRACTMacroautophagy/autophagy is vital for neuronal homeostasis and functions. Accumulating evidence suggest that autophagy is impaired during cerebral ischemia, contributing to neuronal dysfunction and neurodegeneration. However, the outcomes after transient modification in autophagy machinery are not fully understood. This study investigated the effects of ischemic stress on autophagy and synaptic structures using a rat model of oxygen-glucose deprivation (OGD) in hippocampal neurons and a mouse model of middle cerebral artery occlusion (MCAO). Upon acute ischemia, an initial autophagy modification occurred in an upregulation manner. Following, the number of lysosomes increased, as well as lysosomal volume, indicating dysfunctional lysosomal storage. These changes were prevented by inhibiting autophagy via 3-methyladenine (3-MA) treatment or ATG7 (autophagy related 7) knockdown, or were mimicked by rapamycin (RAPA), a known activator of autophagy. This suggests that dysfunctional lysosomal storage is associated with the early burst of autophagy. Dysfunctional lysosomal storage contributed to autophagy dysfunction because the basal level of MTOR-dependent lysosomal biogenesis in the reperfusion was not sufficient to clear undegraded cargoes after transient autophagy upregulation. Further investigation revealed that impairment of synaptic ultra-structures, accompanied by dysfunctional lysosomal storage, may result from a failure in dynamic turnover of synaptic proteins. This indicates a vital role of autophagy-lysosomal machinery in the maintenance of synaptic structures. This study supports previous evidence that dysfunctional lysosomal storage may occur following the upregulation of autophagy in neurons. Appropriate autophagosome-lysosomal functioning is vital for maintenance of neuronal synaptic function and impacts more than the few known synaptic proteins.Abbreviations:3-MA: 3-methyladenine; ACTB: actin beta; AD: Alzheimer disease; ALR: autophagic lysosome reformation; ATG7: autophagy related 7; CTSB: cathepsin B; CTSD: cathepsin D; DAPI: 4ʹ,6-diamidino-2-phenylindole; DEGs: differentially expressed genes; DMEM: Dulbecco’s modified Eagle’s medium; DMSO: dimethyl sulfoxide; GO: Gene Ontology; HBSS: Hanks’ balanced salt solution; HPCA: hippocalcin; i.c.v: intracerebroventricular; KEGG: kyoto encyclopedia of genes and genomes; LAMP1: lysosomal-associated membrane protein 1; MAP1LC3B/LC3: microtubule-associated protein 1 light chain 3 beta; LSDs: lysosomal storage disorders; MAP2: microtubule-associated protein 2; MCAO: middle cerebral artery occlusion; mCTSB: mature CTSB; mCTSD: mature CTSD; MOI: multiplicity of infection; MTOR: mechanistic target of rapamycin kinase; OGD/R: oxygen-glucose deprivation/reoxygenation; PBS: phosphate-buffered saline; PRKAA/AMPKα: protein kinase AMP-activated catalytic subunit alpha; proCTSD: pro-cathepsin D; RAPA: rapamycin; RNA-seq: RNA sequencing; RPS6KB/p70S6K: ribosomal protein S6 kinase; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; SIM: Structured Illumination Microscopy; SNAP25: synaptosomal-associated protein 25; SQSTM1/p62: sequestosome 1; SYN1: synapsin I; SYT1: synaptotagmin I; TBST: tris-buffered saline Tween-20; TEM: transmission electron microscopy; TFEB: transcription factor EB; tMCAO: transient middle cerebral artery occlusion; TTC: 2,3,5-triphenyltetrazolium chloride; TUBB3: tubulin, beta 3 class III.

In this paper, a new measurement method based on flame emission spectrometry (FES) is applied to establish a functional model between Na concentration (CNa), the temperature (T), and the radiation intensity of Na (INa589), namely INa589= 1.2966·Ib(λ589,T)·CNa, in which the temperature and CNaare simultaneously measured by the radiation spectrum. A combustion experiment was carried out to study the influence of water-washing on the combustion characteristics and the CNaof Zhundong coal pellets (raw, 40 °C water-washed, and 80 °C water-washed) at the heating environment temperature of 1600 K. The results show that water-washing effectively reduces the maximum and the total amount of Na released both in the devolatilization phase and the char phase. Among them, the maximum CNavalues of the raw, 40 °C water-washed, and 80 °C water-washed coal were 3.48, 1.91, and 1.43 ppm during the devolatilization phase, and the maximum CNavalues were 11.01, 6.57, and 5.18 ppm during the char phase, respectively. Moreover, water-washing was found to shorten the ignition time, lengthen the duration of the devolatilization phase and the char phase, and reduce the maximum temperature of the devolatilization phase and the average temperature of the char phase.

This article presents a method for real-time simultaneous measurements of the temperature and soot volume fraction distribution of volatile matter flames, forming during combustion of biomass pellets. This method uses flame radiation spectra, captured by a spectrometer, and images, captured by a digital camera, as inputs during combustion of three different types of biomass pellets (pine wood, rice straw, and corn straw). The pellets were ignited and burned in the post-combustion zone of methane gas at 1300 K. The radiation spectrum of the flame in the 500–800 nm wavelength band was selected for spectral analysis, combined with a spectral emissivity model based on polynomial fitting. The flame emissivity was measured at the response wavelengths of a dual band-pass filter (centered at 615 and 517 nm) fitted on the camera, and the resulting emissivity ratio showed the degree of departure from the gray radiation model. The measured emissivity ratio approached unity as the combustion intensity increased. The emissivity ratio of the spectrometer measurement was used to correct the flame temperature measurement obtained by the image method. Upon correction, the maximum relative error of the image temperature measurement was determined to be 2.7% by comparison to thermocouple readings. The experimental results showed that the maximum flame temperatures of pine wood, rice straw, and corn straw pellets were remarkably similar at 1876 ± 2 K. Moreover, the flame burnout durations and the peak soot volume fractions were both positively correlated with the volatile content of biomass pellets; the value of the latter was 1.19 ± 3 ppm. The experimental results measured in this article can provide data for models of the soot generation mechanism of biomass pellet combustion in industrial furnaces.

Integration of membrane hydrogen separation and carbon dioxide capture with fuel steam reforming efficiently promoted hydrogen production and feedstock conversion. In this study, catalytic steam reforming of coke oven gas in a sorption-enhanced fluidized bed membrane reactor (MA-SE-SRCOG) was simulated using a reactive three-fluid model under the Euler framework. The numerical studies provided insights into details about interactions of multiscale subprocesses, including hydrogen permeation, carbon dioxide adsorption, catalytic reforming, and multiphase flow dynamics, during MA-SE-SRCOG. Concentration polarization caused by hydrogen separation was also examined. Meanwhile, impacts of several operating parameters, such as reaction pressure, steam concentration, membrane position, and reactor scale, on the performance of MA-SE-SRCOG were evaluated in terms of CH4conversion, CO selectivity, hydrogen recovery factor, and CO2fix factor. The simulation results demonstrated that membrane hydrogen separation and carbon dioxide adsorption promoted reforming kinetics and reactant conversions in the fast reaction zone, and also extended the reactive zone, thus efficiently improving the overall reforming efficiencies. Fast CO2adsorption kinetics showed more profound enhancements on reducing CO selectivity compared to membrane separation, which instead had greater potential to facilitate high CH4conversion when membrane effectiveness (a parameter representing impacts of membrane area, layer thickness and composite on permeation rates) was sufficiently large, particularly at high operation pressures. With membrane effectiveness increasing from 1 to 5, a CH4conversion of 91.3% was achieved by MA-SE-SRCOG at 0.33 MPa and 560 °C, while the H2permeation flux was augmented from 0.077 mol/(m2·s) to 0.192 mol/(m2·s). However, the increase of membrane effectiveness would cause more serious H2concentration polarization in FBMR, which inhibited the effective H2separation rates, so membrane effectiveness >10 has been observed to not remarkably benefit CH4conversion and H2production further. High S/C(>6) enhanced the occurrence of larger bubbles, and decreased the driving force (hydrogen partial pressure) for hydrogen permeation, both of which degraded the reforming performances and reduced yield of high purity H2. The more closely membrane units were installed to the fast reaction zone, the larger the enhancements of membrane expected to exert on COG-steam reforming reactions. With the given dimensions of the membrane tube, the decrease of reactor diameter helped to decrease concentration polarization, so higher CH4conversion and H2separation factors were achieved.

In this paper, a method for the simultaneous measurement of the flame temperature and emissivity using spectral thermometry and image thermometry was proposed; experiments were conducted using a laboratory furnace burning solid particle fuel derived from biomass. First, a non-gray emissivity model with a third-order polynomial function was established, and the accuracy of the temperature estimates obtained from the gray emissivity model, the non-gray emissivity model, and the Hottel and Broughton emissivity model was determined. The results showed that the proposed non-gray emissivity model had the highest accuracy and the maximum relative error compared to the thermocouple measurements was less than 1.5%. Second, the spectral emissivity obtained from the spectral thermometry was used to correct the image pyrometer data. The two-dimensional distributions of the flame temperature and emissivity are measured after correction using image pyrometry. It showed that the results of the spectral thermometry and image thermometry were highly consistent with the thermocouple measurements and the maximum relative errors were 1.5 and 3.2%, respectively. Finally, the effects of the equivalent ratio on the temperature and spectral emissivity were investigated. The results showed that the maximum temperature of the volatile combustion flame was 1000–1250 K and the maximum emissivity of the flame ranged from 0.05 to 0.25 in the equivalent ratio range of 0.91–0.71. The maximum temperature and emissivity decreased as the equivalent ratio decreased.

The presence of circulating flue gas in oxy-fuel combustion leads to mercury pollution. Acid–chlorine-modified biomass coke was used to prepare mercury adsorbents. The influence of individual flue gas components (HCl, NO, SO2, and H2O) and complex flue gas on the behavior of modified straw coke for mercury removal under an oxy-fuel combustion atmosphere was studied. The mechanism of the flue gas reaction with mercury was investigated using temperature-programmed desorption (TPD) characterization. The density functional theory (DFT) was employed to study the mechanism of mercury removal by the adsorbent. The results showed that H2O has a dual effect on mercury removal: the low concentrations of H2O promote mercury removal, while moderate to high concentrations of H2O inhibit it. HCl and NO exhibited promotional effects on mercury removal. SO2competed with Hg0for active adsorption sites or adsorbed on the surface of the adsorbent, consuming active oxygen species and chlorinated functional groups to inhibit the adsorption and oxidation of Hg0. Under the atmosphere of complex flue gas, H2O and SO2inhibited the generation of highly oxidizing intermediate products from HCl and NO. Additionally, the coexistence of H2O and SO2generated H2SO4, further blocking the surface pore structure and hindering the diffusion of Hg0on the adsorbent surface. The result of the electron localization function (ELF) indicated that the introduction of O and Cl atoms can form stable covalent compounds (C═O and C–Cl) through bonding with the carbonaceous surface, serving as favorable chemical adsorption sites. The high reactivity of Cl induces Hg0adsorption, and the presence of O atoms not only acts as a chemical adsorption site but also activates the reactivity of Cl atoms, promoting the efficiency of mercury removal. This study provided a theoretical basis for the application of mercury adsorbents in oxy-fuel combustion fuel gas.

High-purity hydrogen was produced by catalytic steam reforming of coke oven gas (COG) in a fluidized bed membrane reactor (FBMR), assisted by calcined dolomite and a tubular palladium membrane. This membrane-assisted and sorption-enhanced steam-COG reforming process was denoted as MA-SE-SRCOG. A novel bimetallic Ni–Fe/mayenite (Ca12Al14O33) catalyst was first tested in a fixed bed reactor and was then applied to steam reforming of COG in the pilot-scale FBMR. The Ni-0.1Fe/mayenite catalyst showed good sulfur tolerance during steam reforming of COG, and no carbon deposition was detected on the catalyst surface. Partial substitution of “free oxygens” in Ca12Al14O33by sulfur to form Ca12Al14O32S was observed by XRD characterization. With hydrogen being separated by palladium membrane and CO2being captured by calcined dolomite, a hydrogen recovery efficiency > 1.7 along with a CH4conversion of 0.93 and near-zero CO selectivity was achieved by steam reforming of COG at 560 °C, S/C = 4 in the FBMR. Initial CO and H2contents suppressed conversion of CH4during steam reforming of COG at specific operating temperature, and restrictions from initial CO were more serious than initial H2. MA-SE-SRCOG efficiently overcame the restrictions of initial CO and H2and was able to produce over 4.0-fold H2from COG. A hydrogen permeation flux of 2.14 × 10–2–3.34 × 10–2mol/m2·s having a purity of >99.9 vol % (with deletion of N2) was obtained at the permeation side. Excessive steam (S/C > 4) was observed to decrease CH4conversion, which could be ascribed to the decreased residence time of reactants and increased bypassing of reactants through large voids in the reactor at a high S/C ratio. Over high concentration of steam in the reactor side also inhibited permeation of H2. Strong attachment of filler particles on the Pd membrane surface was detected by EPMA analysis, but no metal contents from the catalyst/sorbent were found inside the Pd layer yet after 30 h serving in FBMR.

Zero-carbon alternative fuels such as hydrogen and ammonia are gaining popularity. Blending these fuels with hydrocarbons is an intermediate approach to mitigate soot and carbon dioxide production. Recent studies have concentrated their attention to the effects of ammonia and hydrogen on the soot production of hydrocarbon fuels. It is still necessary to completely comprehend how this influence is dependent on the type of fuel and flame configuration. In this work, the effect of hydrogen and ammonia addition on soot production in ethylene laminar inverse diffusion flames (IDF) was numerically examined for the first time. The thermal, chemical, and combined effects of hydrogen and ammonia were assessed by fictitious species. The experimental results from the literature were used to validate the temperature and soot volume fraction profiles. Results indicated that the flame temperature and the production of radicals are promoted chemically by hydrogen addition but inhibited under the thermal effect of ammonia. The principal source of the reduction in OH-represented flame height, soot volume fraction, average diameter, and primary particle number density in the IDF is the thermal effect of additives, and hydrogen addition performs better than ammonia. The major and intermediate species, the aromatic hydrocarbons, and the soot formation or oxidation reaction rates are decreased mainly by the hydrogen and ammonia thermal effect while increased moderately by the chemical effect. Therein, the reduction in soot generation is mainly due to the polycyclic aromatic hydrocarbon condensation rate being slowed down by additives. The inhibition is attributed to the thermal effect of additions, and hydrogen behaves better than ammonia.