Interactions of graphene with oxidants in a mixed atmosphere: synergistic effects of O2/H2O and O2/CO2 on gasification reactivity and kinetics.

The gasification of carbon with O2, CO2, and H2O oxidants plays an important role in several energy-based applications. As most of the industrial gasification processes are conducted under mixed-atmosphere conditions, the oxidation of carbon in binary oxidant mixtures becomes crucially important. Using reactive force-field (ReaxFF) potentials, extensive MD simulations were carried out on the oxidation behavior of graphene in mixed O2/H2O and O2/CO2 environments for a range of gas compositions and temperatures. A graphene sheet with a line defect comprising of eight and four-membered rings was used as the starting carbon structure. In addition to enhanced carbon gasification with oxygen additions, MD simulations showed synergistic interactions between different oxidants and their net influence on the overall reactivities. The gasification levels achieved under the binary system were higher than the linear combination of contributions from individual oxidants. The addition of ∼40% O2 in the binary mix was identified as the region with the highest reactivity during the initial stages of gasification. The oxidation reactions with oxygen were found to start instantaneously in the presence of H2O or CO2 instead of the usual initial delay. A very fast reaction kinetics was also observed in the initial stages in the presence of oxygen. Our results show that the gasification reactions under H2O and CO2 started at lower temperatures than O2 thereby creating a partially oxidized structure. Due to the presence of a large number of activation sites, very high rates of gasification were achieved with oxygen. These findings could help identify optimal oxidant compositions towards maximizing carbon gasification and minimizing CO2 emissions.

The evolution of atomistic structure and mechanical property of coke in the gasification process with CO2 and H2O at different temperatures: A ReaxFF molecular dynamics study.

CONTEXT: An atomistic coke carbon model was constructed to simulate the structural evolution in the gasification and stretching process. The coke model was placed in a box with different CO2/H2O content to investigate the evolution of the atomistic structure of coke during the gasification. It was found that different atmospheric concentrations had different effects on the structure and reaction sites of the coke model. The CO2 molecules tended to dissolve on the surface of coke and disrupt its surface structure, while H2O molecules were more likely to enter the coke model to disrupt the internal structure. For tensile simulation, it was found that CO2 and H2O had different effects on the tensile resistance of the coke model. Controlling the composition content of the reaction gas can effectively influence the tensile strength of the coke model. By revealing the behavior of coke model at the micro scale, it provides a theoretical basis for the industrial coke application process. METHODS: Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) was used to conduct the molecular dynamics using the reactive force field (ReaxFF). The atomistic model of coke carbon was constructed using the well-known annealing and quenching method, and its composition is determined according to the element analysis of industrial coke. The structural evolution in the gasification with CO2/H2O and the stretching process were analyzed in detail. Molecular dynamics simulations with reactive force field (ReaxFF-MD) were used to simulate the coke dissolution reaction under CO2/H2O atmosphere and the coke stretching process. The atmosphere ratio was modified to investigate the changes in coke structure under different atmosphere conditions. The Packmol software was used to place gas and coke models into the same box. During the reaction process, the Ovito software was used to perform corresponding visualization analysis on the changes in the atomic structure of coke.

Enhanced Yield of Bioactive Compounds and Antioxidant Activities in Four Fermented Beans of Phellinus linteus Strains (Agaricomycetes) by Solid-State Fermentation.

Phellinus linteus is a famous medicinal mushroom which exhibits various biological activities. This study aimed to investigate the effects of solid-state fermentation by Ph. linteus on the yield of bioactive compounds and antioxidant activities of beans. Four bean substrates were prepared and inoculated with inoculum of three strains of Ph. linteus, respectively. During the cultivation, the harvested samples were dried, grounded, extracted, and determined the contents of bioactive compounds and antioxidant activities. The results indicated that the mung bean fermented by Ph. linteus 04 had the highest polysaccharide content (98.8 mg/g). The highest total phenolic and flavonoid contents were in fermented soybeans by Ph. linteus 03 (15.03 mg gallic acid equivalents/g and 63.24 mg rutin equivalents/g, respectively). The 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activities of hot water extracts were higher than those of ethanolic extracts for fermented beans by three Ph. linteus strains. However, the superoxide anion radical scavenging ability of ethanolic extracts was higher than those of hot water extracts in the fermented beans of the three strains. The ferrous ion (Fe2+)-chelating abilities of hot water extracts were higher than those of ethanolic extracts in fermented beans by Ph. linteus 03 and 04. In contrast, ethanolic extracts were higher than hot water extracts in fermented beans by Ph. linteus 06. Overall, these results indicate that the fermentation by Ph. linteus strains increased the bioactive compounds and antioxidant activities of four beans.

Effect of Different sp2 Bond Contents on the Reactivity and Mechanical Properties of Coke Carbon: A ReaxFF Molecular Dynamics Study.

In this study, ReaxFF-MD was used to construct a large-molecule model of coke containing 3000 atoms, and the sp2 bond content of the model was controlled by changing the heating and cooling rates. The increase of the sp2 bond content led to a significant difference in the reactivity of coke. The presence of the sp2 bond caused the carbon atoms inside the coke to change into a circular structure, making it more difficult for the gaseous atoms to adsorb on the surface of the coke. It significantly reduced the gasification reaction rate of coke in the CO2 and H2O atmospheres. In the tensile simulation experiment, it was found that the stretching process of coke was mainly divided into three stages: an elastic stretching stage, a plastic stretching stage, and a model fracture stage. During the stretching process, the carbon ring structure would undergo a C-C bond fracture while generating carbon chains to resist stress. The results indicated that the presence of sp2 bonds can effectively reduce the phenomenon of excessive local stress on coke to improve its tensile resistance. The method developed in this paper may provide further ideas and platforms for the research on coke performance.

The Adsorption Mechanism of Hydrogen on FeO Crystal Surfaces: A Density Functional Theory Study.

The hydrogen-based direct reduction of iron ores is a disruptive routine used to mitigate the large amount of CO2 emissions produced by the steel industry. The reduction of iron oxides by H2 involves a variety of physicochemical phenomena from macroscopic to atomistic scales. Particularly at the atomistic scale, the underlying mechanisms of the interaction of hydrogen and iron oxides is not yet fully understood. In this study, density functional theory (DFT) was employed to investigate the adsorption behavior of hydrogen atoms and H2 on different crystal FeO surfaces to gain a fundamental understanding of the associated interfacial adsorption mechanisms. It was found that H2 molecules tend to be physically adsorbed on the top site of Fe atoms, while Fe atoms on the FeO surface act as active sites to catalyze H2 dissociation. The dissociated H atoms were found to prefer to be chemically bonded with surface O atoms. These results provide a new insight into the catalytic effect of the studied FeO surfaces, by showing that both Fe (catalytic site) and O (binding site) atoms contribute to the interaction between H2 and FeO surfaces.

Enhanced electron transport and self-similarity in quasiperiodic borophene nanoribbons with line defects.

Recent experiments have revealed multiple borophene phases of distinct lattice structures, suggesting that the unit cells of ν1/6 and ν1/5 boron sheets, namely α and ß chains, serve as building blocks to assemble into novel borophene phases. Motivated by these experiments, we present a theoretical study of electron transport along two-terminal quasiperiodic borophene nanoribbons (BNRs), with the arrangement of the α and ß chains following the generalized Fibonacci sequence. Our results indicate that the energy spectrum of these quasiperiodic BNRs is multifractal and characterized by numerous transmission peaks. In contrast to the Fibonacci model that all the electronic states should be critical, both delocalized and critical states appear in the quasiperiodic BNRs, where the averaged resistance saturates at the inverse of one conductance quantum for the delocalized states in the large length limit and contrarily exhibits a power-law dependence on the nanoribbon length for the critical states. Besides, the self-similarity is observed from the transmission spectrum, where the conductance curves overlap at different energy regions of two quasiperiodic BNRs of different Fibonacci indices and the resistance curves are analogous to each other at different energy scales of a single quasiperiodic BNR. These results complement previous studies on quasiperiodic systems where the multifractal energy spectrum and the self-similarity are observed by generating quasiperiodic potential energies, suggesting that borophene may provide an intriguing platform for understanding the structure-property relationships and exploring the physical properties of quasiperiodic systems.

The Dynamic Nature of Graphene Active Sites in the H2O Gasification process: A ReaxFF and DFT Study.

CONTEXT: A steam-rich environment is a more promising application scenario for future coal-fired processes, while active sites are the key factor that determines the reactivity of carbonaceous fuels. The steam gasification process of carbon surfaces with different numbers of active sites (0, 12, 24, 36) was simulated using reactive molecular dynamics in the present study. The temperature for the decomposition of H2O and the gasification of carbon is determined using temperature-increasing simulation. The decomposition of H2O was influenced by two driving forces, thermodynamics and active sites on the carbon surface, which dominated the different reaction stages, leading to the observed segmentation phenomenon of the H2 production rate. The existence and number of initial active sites have a positive correlation with both two stages of the reaction, greatly reducing the activation energy. Residual OH groups play an important role in the gasification of carbon surfaces. The supply of OH groups through the cleavage of OH bonds in H2O is the rate-limiting step in the carbon gasification reaction. The adsorption preference at carbon defect sites was calculated using density functional theory. Two stable configurations (ether & semiquinone groups) can be formed with O atoms adsorbed on the carbon surface according to the number of active sites. This study will provide further insights into the tuning of active sites for advanced carbonaceous fuels or materials. METHODS: The large-scale atomic/molecule massively parallel simulator (LAMMPS) code combined with the reaction force-field method was used to carry out the ReaxFF molecular dynamics simulation, where the ReaxFF potentials were taken from Castro-Marcano, Weismiller and William. The initial configuration was built using Packmol, and the visualization of the calculation results was realized through Visual Molecular Dynamics (VMD). The timestep was set to 0.1 fs to detect the oxidation process with high precision. PWscf code in QUANTUM ESPRESSO (QE) package, was used to evaluate the relative stability of different possible intermediate configurations and the thermodynamic stability of gasification reactions. The projector augmented wave (PAW) and the generalized gradient approximation of Perdew-Burke-Ernzerhof (PBE-GGA) were adopted. Kinetic energy cutoffs of 50 Ry and 600 Ry, and a uniform mesh of 4 × 4 × 1 k-points were used.

A reactive molecular dynamics study of thermal pyrolysis behavior and mechanisms of lignin during the hydrothermal process: The function of the water molecules.

The lignin hydrothermal processing is an important option but a full understanding of the role played by the water molecules in the depolymerization of lignin is still lacking. In order to clarify the role of the water molecules in the depolymerization of lignin, the evolution of chemical bonds, microstructural changes, and possible mechanisms of product generation were compared during the pyrolysis process under vacuum and water conditions using Reactive Molecular Dynamics Simulation. Compared with vacuum conditions, the role of water changes with temperature, identifying three stages: promotion (1200-1800 K)-inhibition (2100-2400 K)-promotion (2700-3000 K). Also compared with vacuum conditions, hydrothermal processing can promote the cleavage of the ether bonds while inhibiting the destruction of carbocycles. Water molecules promote the depolymerization of lignin into more C4-molecules, thereby generating more combustible gas resources. Based on the research results, the pyrolysis conditions of lignin can be flexibly controlled to obtain solids, liquids or gases.

Evaluation of subjective scale in allergen nasal provocation test / 临床耳鼻咽喉头颈外科杂志

Objective:To compare the clinical value of visual analogue scale （VAS）, Lebel scale and total nasal symptom scores （TNSS） in evaluating nasal allergen provocation test （NAPT）. Methods:A total of 151 patients suspected of allergic rhinitis admitted to the Department of Otolaryngology-Head and Neck Surgery of our hospital from April 2020 to September 2020 were included, of which 76 were positive for house dust mites and 75 were negative for allergens. Nasal airway resistance（NAR） was measured by active anterior nasal manometry. Nasal symptoms were evaluated by VAS, Lebel and TNSS. House dust mite allergen was used for NAPT by spray method. An increase≥40% in NAR was used as the gold standard for objective evaluation of NAPT. ROC curves of VAS, Lebel and TNSS were drawn to compare the evaluation effectiveness of different subjective evaluation methods, and the optimal critical point of each ROC curve was obtained. Results:With NAR increased by ≥40% as the gold standard, the area under ROC curve of VAS was 0.884, and the sensitivity and specificity were 97.75% and 80.65%, respectively. The area under ROC curve of Lebel was 0.773, and the sensitivity and specificity were 68.54% and 75.81%, respectively. The area under ROC curve of TNSS was 0.792, and the sensitivity and specificity were 68.54% and 79.03%, respectively. There was no significant difference between Lebel and TNSS（P>0.05）. The VAS differed significantly from Lebel and TNSS（P<0.05）. The Kappa values of VAS, Lebel, TNSS and NAR were 0.803, 0.432 and 0.459, respectively. Conclusion:The VAS, Lebel, TNSS subjective scale and NAR are consistent in evaluating the efficacy of NAPT, with the VAS assessment showing highest consistency with NAR. As objective assessment instruments are not widely used in China, subjective assessment method could be adopted to evaluate the efficacy of NAPT in clinical practice, and VAS scale is recommended as a priority.

Intracranial activity of first-line immune checkpoint inhibitors combined with chemotherapy in advanced non-small cell lung cancer / 中华医学杂志(英文版)

BACKGROUND@#Immune checkpoint inhibitors (ICIs) are increasingly used as first-line therapy for patients with advanced non-small cell lung cancer (NSCLC) harboring no actionable mutations; however, data on their efficacy among patients presenting with intracranial lesions are limited. This study aimed to explore the efficacy and safety of ICIs combined with chemotherapy in advanced NSCLC patients with measurable brain metastasis at initial diagnosis.@*METHODS@#Our study retrospectively analyzed clinical data of a total of 211 patients diagnosed with driver gene mutation-negative advanced NSCLC with measurable, asymptomatic brain metastasis at baseline from Hunan Cancer Hospital between January 1, 2019 and September 30, 2021. The patients were stratified into two groups according to the first-line treatment regimen received: ICI combined with chemotherapy ( n = 102) or chemotherapy ( n = 109). Systemic and intracranial objective response rates (ORRs) and progression-free survival (PFS) were analyzed. Adverse events were also compared between the groups.@*RESULTS@#Compared with the chemotherapy-based regimen, the ICI-containing regimen was associated with a significantly higher intracranial (44.1% [45/102] vs . 28.4% [31/109], χ2 = 5.620, P = 0.013) and systemic (49.0% [50/102] vs . 33.9% [37/109], χ2 = 4.942, P = 0.019) ORRs and longer intracranial (11.0 months vs . 7.0 months, P <0.001) and systemic (9.0 months vs . 5.0 months, P <0.001) PFS. Multivariable analysis consistently revealed an independent association between receiving ICI plus platinum-based chemotherapy as a first-line regimen and prolonged intracranial PFS (hazard ratio [HR] = 0.52, 95% confidence interval [CI]: 0.37-0.73, P <0.001) and systemic PFS (HR = 0.48, 95% CI: 0.35-0.66, P <0.001). No unexpected serious adverse effects were observed.@*CONCLUSION@#Our study provides real-world clinical evidence that ICI combined with chemotherapy is a promising first-line treatment option for driver gene mutation-negative advanced NSCLC patients who present with brain metastasis at initial diagnosis.@*CLINICAL TRIAL REGISTRATION@#https://www.clinicaltrials.gov/ , OMESIA, NCT05129202.

Density Functional Studies on the Atomistic Structure and Properties of Iron Oxides: A Parametric Study.

With the aim to find the best simulation routine to accurately predict the ground-state structures and properties of iron oxides (hematite, magnetite, and wustite) using density functional theory (DFT) with Hubbard-U correction, a significant amount of DFT calculations were conducted to investigate the influence of various simulation parameters (energy cutoff, K-point, U value, magnetization setting, smearing value, etc.) and pseudopotentials on the structures and properties of iron oxides. With optimized simulation parameters, the obtained equation of state, lattice constant, bulk moduli, and band gap is much closer to the experimental values compared with previous studies. Due to the strong coupling between the 2p orbital of O and the 3d orbital of Fe, it was found that Hubbard-U correction obviously improved the results for all three kinds of iron oxides including magnetite which has not yet been tested with U correction before, but the U value should be different for different oxides (3 ev, 4 ev, 4 ev for hematite, magnetite, and wustite, respectively). Two kinds of spin magnetism settings for FeO are considered, which should be chosen according to different calculation purposes. The detailed relationship between the parameter settings and the atomic structures and properties were analyzed, and the general principles for future DFT calculation of iron oxides were provided.

Optimal Liquid Inoculum Conditions and Grain Medium Enhanced Hispidin Production by Species of Genus Phellinus (Agaricomycetes) in Solid-State Fermentation.

This study aimed 1) to screen a high hispidin production strain from 12 strains of genus Phellinus and 2) to evaluate the effects of liquid inoculum conditions and grain medium on this strain's hispidin production levels after solid-state fermentation. The results showed that Ph. linteus 04 led to the highest hispidin production; this strain was then selected to elucidate the optimal liquid inoculum conditions and grain medium for hispidin production. Various liquid inoculum conditions were evaluated, and the highest hispidin yield, specific productivity of hispidin, and total content of hispidin were found to be optimal at 1 week of liquid inoculum culture time, cultured with potato dextrose broth, and using a 10% inoculum rate, with each condition resulting in 0.350, 0.325, and 0.328 mg/g dry weight of mycelium, 0.352, 0.251, and 0.249 µg/mg of specific productivity per week, and 57.90, 60.23, and 61.77 mg/kg dry weight of brown rice medium, respectively. These liquid inoculum conditions were then used to determine the appropriate grain medium for hispidin production. The highest hispidin yield and total content of hispidin were observed in pearl barley (1.107 mg/g dry weight of mycelium and 199.76 mg/kg dry weight of pearl barley), which led to results that were 4.73-fold and 5.35-fold higher than those of the control (brown rice medium). Overall, this study shows that Ph. linteus hispidin production can be enhanced by solid-state fermentation using optimal liquid inoculum conditions and the appropriate grain medium.

A density functional theory study on the adsorption reaction mechanism of double CO2 on the surface of graphene defects.

Much research has been done on reactions of a single CO2 molecule with a graphene surface. In this paper, density functional theory calculations are used to investigate the adsorption and reaction of double CO2 on the surface of single vacancy (SV) and divacancy (DV) defect graphene. The study found that due to the mutual repulsion between CO2 and the size of the SV defect, it is difficult for two CO2 molecular to be adsorbed directly above the SV defect at the same time. Regardless of SV or DV, the adsorption of the first CO2 in the defect center will have a beneficial effect on the adsorption of the second CO2. In addition, the transition state calculation of the CO2 reaction on the DV plane was carried out, and the adsorption behavior was analyzed and studied. This in-depth study is helpful to the understanding of the reaction behavior of CO2 on graphene, and further exploration in the direction of the effective application of graphene to the reaction and adsorption of CO2. Our work explores the adsorption behavior of CO2 on graphene surfaces, the physical and chemical adsorption of double CO2 at the defect was studied and analyzed.

Calcined Oyster Shell Powder as a Natural Preservative for Maintaining Quality of White Shrimp (Litopenaeus vannamei).

Oyster shell waste has led to many problems, including displeasing odors, pollution of the seaside, and harm to the environment. Using calcined oyster shells as a natural preservative might solve the problem of oyster shell waste. We studied the use of calcined oyster shell powder (COSP) as a natural preservative for improving shrimp shelf-life over 12 days under refrigerated conditions. As compared with the control, COSP treatment effectively retarded pH change, reduced the formation of total volatile basic nitrogen, and inhibited bacterial growth during refrigerated storage. In addition, shrimp muscle lipid oxidation measured by peroxide value (PV) and thiobarbituric acid (TBA) was decreased during storage. The quality was preserved up to 12 days with 2.0-4.0% COSP treatment as compared with only 6 days for un-treated shrimp. The development of preservatives for aquatic products is expected to delay growth of and spoilage by microorganisms in the refrigerated state, thus providing more barrier protection for aquatic food safety.

Natural exosome-like nanovesicles from edible tea flowers suppress metastatic breast cancer via ROS generation and microbiota modulation

Although several artificial nanotherapeutics have been approved for practical treatment of metastatic breast cancer, their inefficient therapeutic outcomes, serious adverse effects, and high cost of mass production remain crucial challenges. Herein, we developed an alternative strategy to specifically trigger apoptosis of breast tumors and inhibit their lung metastasis by using natural nanovehicles from tea flowers (TFENs). These nanovehicles had desirable particle sizes (131 nm), exosome-like morphology, and negative zeta potentials. Furthermore, TFENs were found to contain large amounts of polyphenols, flavonoids, functional proteins, and lipids. Cell experiments revealed that TFENs showed strong cytotoxicities against cancer cells due to the stimulation of reactive oxygen species (ROS) amplification. The increased intracellular ROS amounts could not only trigger mitochondrial damage, but also arrest cell cycle, resulting in the in vitro anti-proliferation, anti-migration, and anti-invasion activities against breast cancer cells. Further mice investigations demonstrated that TFENs after intravenous (i.v.) injection or oral administration could accumulate in breast tumors and lung metastatic sites, inhibit the growth and metastasis of breast cancer, and modulate gut microbiota. This study brings new insights to the green production of natural exosome-like nanoplatform for the inhibition of breast cancer and its lung metastasis via i.v. and oral routes.

Research advancements of two-dimensional black phosphorus in dentistry / 中华口腔医学杂志

Two-dimensional black phosphorus (BP) has unique layered structure, excellent photothermal properties, good biocompatibility and high biodegradability. In recent years, it has been found that BP has stable drug loading and light controlled sustained-release drug functions, excellent antibacterial properties and the ability to promote vascular and nerve regeneration in the medicine field, which has a broad application prospect in dentistry. This review elaborates the biological properties of two-dimensional BP and its application progress in dentistry, so as to provide new ideas for the further research and application of two-dimensional BP.

An improved Vision Transformer model for the recognition of blood cells / 生物医学工程学杂志

Leukemia is a common, multiple and dangerous blood disease, whose early diagnosis and treatment are very important. At present, the diagnosis of leukemia heavily relies on morphological examination of blood cell images by pathologists, which is tedious and time-consuming. Meanwhile, the diagnostic results are highly subjective, which may lead to misdiagnosis and missed diagnosis. To address the gap above, we proposed an improved Vision Transformer model for blood cell recognition. First, a faster R-CNN network was used to locate and extract individual blood cell slices from original images. Then, we split the single-cell image into multiple image patches and put them into the encoder layer for feature extraction. Based on the self-attention mechanism of the Transformer, we proposed a sparse attention module which could focus on the discriminative parts of blood cell images and improve the fine-grained feature representation ability of the model. Finally, a contrastive loss function was adopted to further increase the inter-class difference and intra-class consistency of the extracted features. Experimental results showed that the proposed module outperformed the other approaches and significantly improved the accuracy to 91.96% on the Munich single-cell morphological dataset of leukocytes, which is expected to provide a reference for physicians' clinical diagnosis.

The incidence of psoriasis among smokers and/or former smokers inflammatory bowel diseases patients treated with tumor necrosis factor antagonist: A systematic review and meta-analysis.

BACKGROUND: Infliximab (IFX) and adalimumab (ADA) refer to the classic drugs to treat moderate-severe inflammatory bowel disease (IBD), which have been proven to be effective to control IBD. However, the side effects exerted by IFX and ADA should be monitored in therapies, especially the paradoxical reaction of the skin system (e.g., psoriasis). Psoriasis is recognized as the most common skin lesion, capable of significantly affecting the quality of patients' life. METHODS: This study searched literatures published in English language with the qualifications on PubMed, Embase, Web of Science, Google, and Geenmedical databases. Over 2 co-authors assessed the quality of the articles and extracted the data independently. The data acquired were statistically analyzed with the statistical software of Revman and Stata. RESULTS: The ADA Group achieved a higher incidence of psoriasis (odds ratio [OR] = 0.658, 95% confidence interval [CI] [0.471-0.919]); Females achieved a higher incidence of psoriasis than males (OR = 1.941, 95%CI [1.326-2.843], P < .05); Smoking up-regulated the incidence of psoriasis (OR = 1.679, 95%CI [1.237-2.279], P < .05); The interval of medication was over 1 year, and the interval of medication applying IFX was longer than that of the ADA Group; most cases could be relieved by using local hormone, phototherapy, or systemic hormone therapy under the strategy of biological agents. CONCLUSIONS: The frequency of reported in IBD exceeds those of other autoimmune diseases, and the ADA treatment for IBD is safer than IFX. Psoriasis is more common in females than in males. Smoking refers to one of risk factors of psoriasis.

Bioactive and Physicochemical Characteristics of Natural Food: Palmyra Palm (Borassus flabellifer Linn.) Syrup.

Palmyra palm syrup, produced from Borassus flabellifer flowers' sap, is rich in nutrients and minerals and has unique flavors. This study evaluated the in vitro antioxidant activity, physicochemical characteristics, and Maillard reaction products of palmyra palm syrup prepared by thermal and ultrafiltration processes. Palmyra palm syrup prepared by a thermal process had smaller L*, b* values, and larger a* values than that prepared by an ultrafiltration process. Palmyra palm syrup contained 10 vitamins, the most abundant being vitamin E. Overall, 38 volatile compounds were found and classified into six groups in the order of alcohols > acids > ketones > sulfurs > pyrazines > phenols and aldehyde. Volatile compounds depended on concentration, temperature, and ultrafiltration process. Protein content decreased because of participation in the Maillard reaction and increased 5-hydroxymethylfurfural (HMF) and total phenolic content. The HMF content was very low (0.02-14.95 mg/100 g). The radical scavenging activity of 2,2-diphenyl-1-1 picrylhydrazyl and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) in palmyra palm syrup with thermal process was higher than with ultrafiltration. This study established that ultrafiltration pretreatment of palmyra palm syrup generated a good appearance and reduced the HMF content, however, it negatively affected the volatile compounds and physicochemical characteristics.

Adsorption and reaction mechanisms of single and double H2O molecules on graphene surfaces with defects: a density functional theory study.

More attention needs to be drawn to the high application value of the gasification reaction between carbonaceous materials and water in industry. In this study, density functional theory is used to investigate the adsorption and reaction mechanism of water molecules on graphene surfaces with various kinds of defects. The desorption mechanism of the reaction product is also analyzed. The optimal and stable physical adsorption configuration of water molecules on the pristine graphene and various defects graphene surface has been determined. Chemisorption configurations of a single water molecule and double water molecules on the graphene surface with single vacancy defects are discussed and used as reaction precursors to explore the reaction path of water molecules in the process of desorbing hydrogen at active sites. The whole process of the reaction is largely exothermic and the thermodynamic advantages of double water molecules participating in the reaction are determined. The two reaction mechanisms of two-steps or co-adsorption and desorption of double water molecules are compared, and the lowest energy barrier advantage of the latter is determined.