► Fuel reactivity can be well controlled by adjusting the methanol fraction and SOI. ► Appropriate methanol fraction and SOI contribute to the reduction of emissions. ► Both increased methanol ...fraction and advanced SOI are beneficial to fuel economy. ► Methanol addition is an effective way to achieve the efficient and clean combustion. ► Compared to diesel PCCI, methanol/diesel RCCI shows outstanding advantages.
An improved multi-dimensional model coupled with detailed chemical kinetics mechanism was applied to investigate the combustion and emission characteristics of a methanol/diesel reactivity controlled compression ignition (RCCI) engine. The fuel was supplied separately by directly injecting diesel fuel into cylinder well before top dead center, while premixing methanol through the intake port in the tested methanol/diesel RCCI engine. The effects of mass fraction of premixed methanol, start of injection (SOI) of diesel and initial in-cylinder temperature at intake valve closing (IVC) on engine combustion and emission were investigated in detail. The results show that both methanol mass fraction and SOI have a significant impact on cetane number (CN) distribution, i.e. fuel reactivity distribution, which determines the ignition delay and peak of heat release rate (HRR). Due to larger area with high-temperature region and more homogeneous fuel distribution with increased methanol, and the oxygen atom contained by methanol molecule, all the emissions are reduced with moderate methanol addition. Advanced SOI with high combustion temperature is favorable to hydrocarbon (HC) and soot reduction, yet not to the decrease of nitrogen oxide (NOx) and carbon monoxide (CO) emissions. Both increasing methanol fraction and advancing the SOI are beneficial to improve fuel economy and avoid engine knock. Moreover, it was revealed that the initial temperature must be increased with increased methanol fraction to keep the 50% burn point (CA50) constant, which results in decrease of the equivalent indicated specific fuel consumption (EISFC) and all emissions, except for slight increase in NOx due to the higher burning temperature.
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A new skeletal mechanism for n-decane oxidation was developed based on a decoupling methodology with the special emphasis on the engine-relevant operating conditions from low to high temperature at ...high pressure. With the decoupling methodology, an extremely simplified model for C2–C10 was used to simulate the oxidation of heavy hydrocarbons for prediction of the ignition characteristics, while the mechanism of H2/CO/C1 was considered in details for providing accurate information of laminar flame speed and extinction strain rate. The new skeletal n-decane oxidation mechanism consists of 40 species and 141 reactions. Extensive validations of the present mechanism were performed by comparing with the experimental data available in the literature on n-decane oxidation, including ignition delay in shock tube and rapid compression machine, species concentrations in jet-stirred reactor and variable pressure flow reactor in wide ranges of temperature (550–1800K), pressure (1–80bar) and equivalence ratio (0.5–2). Moreover, the experimental data on the profiles of species concentration, laminar flame speed and extinction strain rate in premixed flame and counterflow flame was also being used in the validations. Finally, the skeletal n-decane mechanism was applied to predict the combustion and emissions of premixed charge compression ignition (PCCI) engines by using the multi-dimensional simulation. Overall, the current prediction from the present mechanism shows a good agreement with the experimental measurements, which indicates the potential of the decoupling methodology for the development of oxidation mechanism for heavy alkanes.
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The influence of fuel chemical properties on combustion characteristics of a RCCI (reactivity controlled compression ignition) engine was investigated using multi-dimensional simulations. The ...operating ranges of combustion phasing (CA50) for gasoline/diesel and methanol/diesel RCCI combustion were determined with respect to limited boundaries of fuel efficiency, RI (ringing intensity), and NOx (nitrogen oxide) emissions. The results indicated that a more retarded CA50 was necessary for methanol/diesel RCCI to avoid excessive RI due to its fast combustion rate. Because of the shortened combustion duration, reduced incomplete combustion, and lower heat transfer losses, improved fuel efficiency was achieved by methanol/diesel RCCI than gasoline/diesel RCCI. The trade-off relationship between RI and EISFC (equivalent indicated specific fuel consumption) could be defeated by increasing premixed fuel ratio (methanol or gasoline). For methanol/diesel RCCI, the more retarded CA50 was the primary reason for the higher sensitivity of CA50 to the variation of in–cylinder initial temperature (TIVC), which consequently could lead to higher cyclic variations. In addition, the weakened low temperature heat release of methanol/diesel also deteriorated the stability of CA50 with the variation of TIVC. Overall, with optimized premixed fuel ratio, RCCI combustion demonstrated more advantages in EISFC, RI, controllability, and stable operation over HCCI (homogeneous charge compression ignition) combustion for a wide load range.
•Fuel efficiency of methanol/diesel RCCI is better than that of gasoline/diesel.•More stable CA50 can be achieved with gasoline/diesel than with methanol/diesel.•High premixed ratio is beneficial to achieve good engine performance for RCCI.•Compared to HCCI combustion, RCCI can achieve stable operation more easily.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
By integrating an updated multi-dimensional model and the NSGA-II (non-dominated sorting genetic algorithm II), the combustion of a RCCI (reactivity controlled compression ignition) engine fueled ...with methanol/diesel was optimized. Based on the optimization results, parametric study was performed by varying energy fraction of methanol, EGR (exhaust gas recirculation rate, initial in-cylinder pressure at IVC (intake valve closing), initial in-cylinder temperature at IVC, and SOI (start of injection). Furthermore, the sensitivities of these five parameters on fuel efficiency, emissions, ignition timing and RI (ringing intensity) were analyzed. The results indicated that initial temperature and EGR rate exhibited the most significant effect on engine performance and emissions for their obvious effect on combustion temperature. By varying the local fuel-rich and high-temperature regions, methanol fraction and SOI could dramatically affect NOx (nitrogen oxide) emission. Overall, the RCCI combustion with high methanol fraction and advanced SOI exhibited higher fuel efficiency and lower emissions. Moreover, it was found that both decreasing EGR rate and increasing initial temperature led to the monotonously increased RI. While decreasing methanol fraction and increasing initial pressure demonstrated the negligible effect on RI at CA50 earlier than 4.3 degree CA ATDC, which was contributed to their obvious effect on fuel spatial distributions.
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•58 volatile compounds were identified in raw muscle of triploid rainbow trout by using the SPME-GC-MS analysis.•Based on the odor activity value (OAV ≥ 1), aldehydes, ketones, alcohols and furan may ...contribute to the overall odor.•Based on the PCA and cluster analysis, the overall odors of raw muscle might be similar in triploid rainbow trout with different marketable sizes.
The present study identified the volatile compounds profile in raw muscle of triploid rainbow trout with different marketable sizes (eviscerated weight: 2 kg, 3 kg and 4 kg, respectively). Six fish per each size treatment were sampled in a local commercial trout farm, then raw muscles of sampled fish were filleted to detect the volatile compounds by using the gas chromatography-mass spectrometry (GCMS) analysis coupled with automated solid-phase microextraction (SPME) system. Results showed that a total of 58 volatile compounds were identified in raw muscle of triploid rainbow trout, including aldehydes (20 species), ketones (6 species), alcohols (9 species), hydrocarbons (11 species), aromatics (6 species) and miscellaneous compounds groups (6 species). The subtotal estimated concentration of aldehydes group was significantly higher than those of the other volatile groups (P < 0.05). Based on the odor activity value (OAV ≥ 1), 21 odor-active compounds may contribute to the overall odor, including pentanal, hexanal, (Z)-4-heptenal, heptanal, (E)-2-heptenal, octanal, (E,E)-2,4-heptadienal, (E)-2-octenal, nonanal, (E,Z)-2,6-nonadienal, (E)-2-nonenal, decanal, (E,E)-2,4-nonadienal, (E)-2-decenal, undecanal, 2,3-pentanedione, 2,3-octanedione, 1-heptanol, 1-octen-3-ol, 2-ethyl-furan and 2-pentyl-funan. The marketable fish of 2 kg had the most numerous volatiles species and the highest total estimated concentration. The profile of 58 identified volatile compounds in 2 kg fish was different with it in 3 kg and 4 kg fish. However, there was no difference in the total odor activity value of all odor-active compounds among three size treatments (P > 0.05). Based on the principle component analysis and cluster analysis using the odor activity values of 21 odor-active compounds, the overall odors of raw muscle might be similar in triploid rainbow trout with different marketable sizes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A full-engine-cycle multidimensional model was applied to investigate the effect of late (intake valve closing) IVC on combustion and emission characteristics in a diesel (premixed charge compression ...ignition) PCCI engine in a wide speed and load range. The results indicate that the in-cylinder swirl ratio and turbulence kinetic energy are significantly enhanced with increased engine speed, while only swirl ratio is slightly affected by the variation in IVC timing. In PCCI combustion mode, ignition timing varies with engine load and speed, and late IVC strategy leads to a noticeable delay in ignition timing by decreasing the effective compression ratio over all the operating range. Late IVC is a very effective approach for reduction of (nitrogen oxides) NOx emissions in the whole operating range, but the benefit of soot reduction with late IVC only locates in the low-to-medium load range. Moreover, it is found that indicated specific fuel consumption is effectively decreased with the employment of late IVC strategy in the medium-to-high load and low-to-medium speed range. Overall, by delaying ignition phasing and decreasing combustion temperature from late IVC timing, the high NOx emissions at medium load, and low fuel efficiency at low speed can be avoided for PCCI combustion.
► Multidimensional model was applied to investigate the effect late IVC (intake valve closing) on PCCI (premixed charge compression ignition) combustion under wide speed and load. ► The in-cylinder flow characteristics were investigated under various IVC timings and engine speeds. ► The NOx (nitrogen oxides) and soot suppression mechanism with late IVC was deeply understood by using the equivalence ratio–temperature map. ► The operating range for PCCI combustion with late IVC was developed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Diffuse intrinsic pontine gliomas (DIPGs) are rare and fatal pediatric brainstem gliomas with no cure. Chimeric antigen receptor (CAR)-engineered natural killer (NK) cells have been proven effective ...in treating glioblastoma (GBM) in preclinical studies. However, there are no relevant studies on the CAR-NK treatment for DIPG. Our study is the first to evaluate the anti-tumor activity and safety of GD2-CAR NK-92 cells treatment for DIPG.
Five patient-derived DIPG cells and primary pontine neural progenitor cell (PPC) were used to access disialoganglioside GD2 expression. Cell killing activity of GD2-CAR NK-92 cells was analyzed by
cytotoxicity assays. Two DIPG patient-derived xenograft models were established to detect the anti-tumor efficacy of GD2-CAR NK-92 cells
.
Among the five patient-derived DIPG cells, four had high GD2 expression, and one had low GD2 expression. In
assays, GD2-CAR NK-92 cells could effectively kill DIPG cells with high GD2 expression while having limited activity against DIPG cells with low GD2 expression. In
assays, GD2-CAR NK-92 cells could inhibit tumor growth in TT150630 DIPG patient-derived xenograft mice (high GD2 expression) and prolong the overall survival of the mice. However, GD2-CAR NK-92 showed limited anti-tumor activity for TT190326DIPG patient-derived xenograft mice (low GD2 expression).
Our study demonstrates the potential and safety of GD2-CAR NK-92 cells for adoptive immunotherapy of DIPG. The safety and anti-tumor effect of this therapy need to be further demonstrated in future clinical trials.
This experiment simulated the hypoxic environment caused by actual production operations in fish farming (i.e., catching, gathering, transferring, and weighting) to study the effects of acute hypoxic ...conditions on the physiological and metabolic responses of triploid rainbow trout (
O. mykiss
). Two groups of fish weighting 590 g were sampled in the normoxia group (dissolved oxygen above 7 mg/L) and hypoxia group (dissolved oxygen ranged from 2 to 5 mg/L for 10 min). The results showed that 1) regarding stress response, hypoxia increased plasma levels of cortisol, heat shock protein 70 (HSP-70), lysozyme, alanine aminotransferase (ALT), aspartate aminotransferase (AST) and creatine phosphokinase (CPK); induced the expression of hepatic genes encoding nuclear factor erythroid 2 related factor 2 (
Nrf2
), interferon
γ
(
IFN-γ
) and interleukin-1β (
IL-1β
). 2) Regarding metabolism response, hypoxia increased plasma levels of globulin (GLOB), glucose (GLU), triglyceride (TG) and lactate dehydrogenase (LDH); upregulated the hepatic gene expression of phosphoenolpyruvate carboxykinase, (
PEPCK
), pyruvate dehydrogenase kinase (
PDK1
), acetyl-CoA carboxylase (
ACC
) and acetyl-CoA oxidase (
ACO
); downregulated the hepatic gene expression of carnitine palmitoyl transferase 1 (
CPT1
); and unchanged the expression of hepatic genes in glycolysis and autophagy. 3) In response to hypoxia-inducible factors (HIFs), the hepatic
HIF-2α
gene was activated in the hypoxia group, but
HIF-1α
gene expression remained unchanged. Thus, during acute hypoxic stress, triploid rainbow trout were in a defensive state, with an enhanced immune response and altered antioxidant status. Additionally, the hepatic mitochondrial oxidation of glucose- and lipid-derived carbon in trout was suppressed, and hepatic gluconeogenesis and lipid synthesis were activated, which might be regulated by the HIF-2α pathway.
Haematococcus pluvialis is an important source of natural astaxanthin, which plays a key role in the regulation of color, antioxidant capacity, and immunity in aquatic animals. However, it is unclear ...that the effects of long-term H. pluvialis astaxanthin feeding on the growth performance, coloration, and antioxidant capacity of commercial-sized rainbow trout Oncorhynchus mykiss. The commercial feed of O. mykiss was used as the basic feed, and 15, 30 mg/kg H. pluvialis astaxanthin were added to prepare isonitrogenous and isolipidic experimental diets, defined as HPA0, HPA15, and HPA30, respectively. Juvenile O. mykiss with an initial weight of 0.60 kg were fed with three experimental diets for 4 months, which was conducted to investigate the effects of long-term H. pluvialis astaxanthin feeding on the growth performance, coloration, antioxidant capacity, and biochemical composition. The results showed that the weight gain rate and specific growth rate of the HPA30 from 0 to 4 months were significantly higher than those of the other two diet groups. In the 4th month, the viscerosomatic index of O. mykiss significantly increased with increasing dietary astaxanthin levels. The redness (a*), DSM SalmoFan™ scores, and astaxanthin content of fillets significantly increased with increasing dietary astaxanthin levels during the whole feeding trial. The activities of total antioxidant capacity and glutathione peroxidase in the serum and liver, and serum immunoglobulin (IgM) content significantly increased with increasing dietary astaxanthin levels, while the levels of total antioxidant capacity, and malondialdehyde in the serum and liver showed a decreasing trend. The contents of total lipids in the fillet of O. mykiss increased significantly with increasing dietary astaxanthin levels, while the percentages of total saturated fatty acid (∑SFA), C18:3n3, and n-3/n-6 PUFA ratio showed a decreasing trend; the percentages of C18:2n6 and total n-6 polyunsaturated fatty acids (∑n-6PUFA) in the HPA15 and HPA30 were significantly higher than those of the HPA0. In conclusion, four months of feeding with 30 mg/kg H. pluvialis astaxanthin diet could improve the growth performance, fillet coloration, antioxidant capacity, and fillet total lipids content of commercial-sized O. mykiss.
•The Haematococcus pluvialis is used to be dietary natural astaxanthin resource of commercial-sized Oncorhynchus mykiss.•Dietary H. pluvialis improved the growth, coloration, antioxidant capacity and fillet total lipids content of O. mykiss.•Fillet visual color of O. mykiss met the requirement of market after two months 30 mg/kg of H. pluvialis astaxanthin feeding.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•This work investigated applying the directed message passing neural network (D-MPNN) deep learning framework for quantitative structure-property relation (QSPR) research of biofuel-relevant species ...and proposed graph edge attentions (GAE) which are incorporated in D-MPNN.•The proposed attention mechanism is shown to be able to boost D-MPNN model performance in predicting properties of biofuel-related species.•This work also discussed and tested machine learning methods, along with available public datasets, for biofuel QSPR from a general perspective.
Predictive models based on graph neural network (GNN) have attracted increasing interest in quantitative structure-property relation (QSPR) modeling of organic species including biofuel components in recent years. For the task of property prediction of biofuel-relevant species, the present work applies the Directed Message Passing Neural Network (D-MPNN) framework, an emerging type of GNN, and incorporates graph attention on the D-MPNN architecture to improve its capability. modeling using other common machine learning methods is also conducted, confirming the advantage of D-MPNN in comparison. Graph Edge Attention (GEA) is proposed for the D-MPNN layers and shows success in increasing model accuracy after implementation. A relatively sizable subset from the QM9 data and 4 other datasets forming a wide scope of target properties (e.g., thermodynamic properties, ignition properties, surface tension, etc.) are selected for the models. A breakdown analysis of the species distribution of these datasets is conducted for more informed modeling. As the data availability of biofuel species is often a main obstacle for related modeling tasks, this study shows that the performance of D-MPNN with the proposed GEA attention mechanism is most enhanced when using a medium data size of 2000∼5000. Some discussions are made regarding data issues and the use of machine learning methods and graph attention for the predictive modeling of biofuel properties, pointing out the need for more data with better species distribution that is representative of biofuels.
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