Important Reactions Research Articles

A process-based geochemical framework for carbonate sediments during marine diagenesis

A significant proportion of marine calcium carbonate sediments are comprised of metastable minerals that are susceptible to diagenetic alterations during burial. These reactions can reset the geochemical signature of sediments and pore fluids and influence elemental cycling in the ocean. However, the timing and mechanisms by which these reactions take place are poorly constrained. This study uses cores drilled on the slope of the Great Bahama Bank to provide quantitative constraints on important diagenetic reactions; namely respiration-driven dissolution, authigenic carbonate mineral formation, and conversion of aragonite to low Mg calcite (LMC). We perform detailed mineralogical characterization using newly acquired, high resolution X-ray diffraction (XRD) data and over 1000 reanalyzed XRD scans, characterize sediments texturally and elementally using electron microprobe data, calculate pore fluid saturation state with respect to aragonite using a Pitzer ion interaction approach, and use pore fluid chemistry and experimental distribution coefficients to predict authigenic carbonate compositions. These data suggest that aerobic organic matter oxidation, enabled by the advection of oxygenated seawater throughout the upper ∼ 30 m interval of sediment, causes undersaturation and thus dissolution of biogenic high Mg calcite (HMC) and aragonite. Deeper, anaerobic organic matter oxidation takes over and causes supersaturation, promoting authigenic precipitation in the form of HMC, which in turn decreases pore fluid Mg/Ca and promotes aragonite conversion to LMC. One novel aspect of this study is the identification of three types of calcites using the newly acquired XRD and electron microprobe data. Based on their unique crystallographic characteristics and chemical compositions, these types of calcites are interpreted to represent pelagic biogenic LMC, bank-derived biogenic HMC, and authigenic HMC precipitated from pore fluids. Notably, the composition of the authigenic calcite matches that predicted to precipitate from pore fluids using an empirical Mg partition coefficient in calcite. Calcites that form authigenically and from aragonite via replacement are suggested to recrystallize with burial as evidenced by the decrease in Mg content and micro-strain. This process-based geochemical framework assigns diagenetic processes to a specific depth window within the sediment column and paves the way for a mechanistic understanding of carbonate diagenesis, one that is rooted in thermodynamic and kinetic bases.

A quantitative analysis on thermochemical sulfate reduction products of two model compounds: Implications for reaction mechanism and alteration process of hydrocarbons

Thermochemical sulfate reduction (TSR) is an important redox reaction that markedly alters hydrocarbons in deep reservoirs. Although the major achievements that involve reaction mechanism, process, and geochemical characteristics were attained in the last 50 years, a quantitative TSR model that includes major products was not built, which restricts the understanding of the reaction mechanism and the generation process of hydrocarbons in TSR. In this study, two series of thermal simulation experiments of the TSR involving n-octadecane (n-C18) and n-dodecylbenzene (C12B) with MgSO4 and H2O in a confined gold-tube system were conducted, and all the major products in different phases, particularly oxygen-containing compounds, were quantitatively analyzed. The results indicated that the high-molecular-weight (HMW) oxygenated compounds in heavy products were predominated by ketones, followed by alcohol and acids, and the low-molecular-weight (LMW) organic acids in water mainly comprised acetic acids, followed by formic acid and propionic acid. Both oxygen-containing compounds prompted the TSR process but in different ways. The accumulation of HMW oxygenated compounds in the non-autocatalytic stages was essential for initiating the catalyzed reaction of TSR. In addition, the oxygenated compounds of hydrocarbons enhance polarity, making hydrocarbons easier to contact with HSO4− or [MgSO4] CIP. The LMW organic acids possibly prompted the TSR process by acidifying the water and thus facilitating the formation of HSO4− and [MgSO4] CIP. The oxidation reaction during TSR possibly converted HMW oxygenated compounds to LMW organic acids and CO2. The quantitative analysis of products in TSR revealed that TSR destroyed the hydrocarbons more rapidly but in a different way from thermal cracking and that the generation process of hydrocarbon types in TSR was in the following order: heavy hydrocarbon, gaseous hydrocarbon/light hydrocarbon/solid bitumen, and gaseous hydrocarbon/solid bitumen. Compared with oil cracking, the TSR promoted the oil reservoir to rapidly progress to more mature stages. The hydrocarbon precursor and reaction extent affected the generation process and the character of all products in the TSR. These results can provide an improved understanding of the TSR mechanism and process and be useful in the evaluation of petroleum potential for TSR-altered oils.

Regulating the oxidation state of Pd to enhance the selective hydrogenation for 5-hydroxymethylfurfural

The highly selective hydrogenation of 5-hydroxymethylfurfural to 2,5-dihydroxymethylfuran is an important reaction in the field of biomass hydrogenation, because it is a bridge between biomass resources and chemical industry. Here, we precisely constructed carbon nitride supported Pd-based catalysts by a simple impregnation-reduction method. By changing the reduction temperature, catalysts with different oxidation state could be precisely constructed. Moreover, the important correlation between the ratio of Pd0/Pd2+ and catalytic activity is revealed during the selective hydrogenation of HMF. The Pd/g–C3N4–300 catalyst with a Pd0/Pd2+ ratio of 3/2 showed the highest catalytic activity, which could get 96.9% 5-hydroxymethylfurfural conversion and 90.3% 2,5-dihydroxymethylfuran selectivity. Further density functional theory calculation revealed that the synergistic effect between Pd0 and Pd2+ in Pd/g–C3N4–300 system could boost the adsorption of the substrate and the dissociation of hydrogen. In this work, we highlight the important correlation between metal oxidation state and catalytic activity, which provides valuable insights for the rational design of precious metal catalysts for hydrogenation reactions.

Hydroxyl-Bonded Co Single Atom Site on Boroncarbonitride Surface Realizes Nonsacrificial H2O2 Synthesis in the Near-Infrared Region.

Photocatalytic synthesis of hydrogen peroxide (H2O2) from O2 and H2O under near-infrared light is a sustainable renewable energy production strategy, but challenging reaction. The bottleneck of this reaction lies in the regulation of O2 reduction path by photocatalyst. Herein, the center of the one-step two-electron reduction (OSR) pathway of O2 for H2O2 evolution via the formation of the hydroxyl-bonded Co single-atom sites on boroncarbonitride surface (BCN-OH2/Co1) is constructed. The experimental and theoretical prediction results confirm that the hydroxyl group on the surface and the electronic band structure of BCN-OH2/Co1 are the key factor in regulating the O2 reduction pathway. In addition, the hydroxyl-bonded Co single-atom sites can further enrich O2 molecules with more electrons, which can avoid the one-electron reduction of O2 to •O2 -, thus promoting the direct two-electron activation hydrogenation of O2. Consequently, BCN-OH2/Co1 exhibits a high H2O2 evolution apparent quantum efficiency of 0.8% at 850nm, better than most of the previously reported photocatalysts. This study reveals an important reaction pathway for the generation of H2O2, emphasizing that precise control of the active site structure of the photocatalyst is essential for achieving efficient conversion of solar-to-chemical.

A review on chemical mechanisms of kraft pulping

Abstract Kraft pulping of wood is based on efficient depolymerization and solubilization of lignin, while cellulose is relatively undamaged. Non-cellulose cell wall polysaccharides are however in some cases heavily degraded, especially pectin and to a lesser degree also glucomannan while, xylan is relatively stable. In this mini-review, the most important reactions in lignin and polysaccharide degradation in kraft pulping are described, both the technically favorable and the problematic reactions, and the chemical background to discuss the advantages and drawbacks of the process. An attempt to put the different reactions in the perspective of the goals of the pulping process is made and a special focus is on the development of color in the pulp fiber during the kraft pulping.

Fostering a Holistic Understanding of the Full Volatility Spectrum of Organic Compounds from Benzene Series Precursors through Mechanistic Modeling.

A comprehensive understanding of the full volatility spectrum of organic oxidation products from the benzene series precursors is important to quantify the air quality and climate effects of secondary organic aerosol (SOA) and new particle formation (NPF). However, current models fail to capture the full volatility spectrum due to the absence of important reaction pathways. Here, we develop a novel unified model framework, the integrated two-dimensional volatility basis set (I2D-VBS), to simulate the full volatility spectrum of products from benzene series precursors by simultaneously representing first-generational oxidation, multigenerational aging, autoxidation, dimerization, nitrate formation, etc. The model successfully reproduces the volatility and O/C distributions of oxygenated organic molecules (OOMs) as well as the concentrations and the O/C of SOA over wide-ranging experimental conditions. In typical urban environments, autoxidation and multigenerational oxidation are the two main pathways for the formation of OOMs and SOA with similar contributions, but autoxidation contributes more to low-volatility products. NOx can reduce about two-thirds of OOMs and SOA, and most of the extremely low-volatility products compared to clean conditions, by suppressing dimerization and autoxidation. The I2D-VBS facilitates a holistic understanding of full volatility product formation, which helps fill the large gap in the predictions of organic NPF, particle growth, and SOA formation.

Surface engineered sustainable nanocatalyst with improved coke resistance for dry methane reforming to produce hydrogen

The ever-growing carbon-based economy has led to alarming increases in greenhouse gas (GHG) emissions, particularly methane (CH4) and carbon dioxide (CO2). These emissions accelerate global warming, pollution and environmental challenges. Methane Dry Reforming (DRM) offers a promising technology to address this issue by converting CH4 and CO2 into a valuable syngas (CO + H2) mixture, which is a valuable fuel and a building block for many important chemical reactions (Fischer-Tropsch process). However, finding affordable and environmentally friendly catalysts for large-scale applications remains a critical hurdle. This study delves into the development of stable nickel-zirconia catalysts prepared via impregnation method. The weight percentage of nickel and zirconia was varied to optimize the catalyst's activity by controlling deactivation phenomenon that is a major challenge at higher temperatures during DRM. Various characterization techniques (XRD, FT-IR, SEM-EDX, TGA, TEM and BET) were employed to evaluate synthesized catalysts physio-chemical properties. Additionally, catalytic performance was assessed at temperatures ranging from 550 to 750 °C and a gas hourly space velocity (GHSV) of 72,000 mL/h.gcat. Among tested catalysts, 15% Ni/ZrO2 displayed remarkable conversion values for both CH4 (62.9%) and CO2 (64.9%). Importantly, it exhibited significantly lower weight loss (ca. 15.42%) compared to other variants, indicating better resilience against coke deposition. This enhanced stability can be attributed to synergistic interplay between nickel and zirconia support, effectively suppressing carbon formation. These findings demonstrate potential of 15% Ni/ZrO2 as a promising catalyst for experimental DRM application. With the obvious high activity and stability, 15% Ni/ZrO2 candidate serves as an eco-friendly candidate for greenhouse gas conversion into green fuel energy, contributing to a sustainable economy and clean environment.

Placental alkaline phosphatase is a biocatalyst of metabolic dysfunctions of the placenta

The parameters of the enzyme involved in biologically important reactions occurring in an open thermodynamic system — the body of a pregnant woman during the gestational period — were studied. The role of an unfavorable premorbid back ground has been established: infectious diseases, repeated exacerbations of chronic inflammatory processes during prolongation of pregnancy, risk factors for perinatal complications, which causes certain morphofunctional changes in the placenta, form ing placental insufficiency. Pregnant women associated with diseases of the genitouri nary system are more often susceptible to infection. Ultrasound examinations made as part of screening the physiology of the system: mother — placenta — fetus, revealed changes in the structure of the placenta, which indicated a disruption in the relationship between the nascent embryo and the mother’s body, and ultimately manifested itself as violations of compensatory and adaptive mechanisms in the placenta, more pronounced in the sample, burdened by the presence of chronic foci of infection. The dependence of disturbances in the functional ability of the placenta on the level of the enzyme — thermostable alkaline phosphatase specific for it — was revealed. At the same time, a change in the activity of this enzyme was observed, which determined the compensatory capabilities of the provisional organ. In patients with an increased infectious index and placental dysfunction, unstable values of a specific placental enzyme are observed, as evidenced by an unfavorable course of pregnancy, accompanied by the threat of miscar riage and premature birth. These disorders occurred during prolongation of pregnancy and during the process of delivery. A significant decrease in the activity of placental alkaline phosphatase and a decrease in its relationship to alkaline phosphatase were es tablished. The worst indicators reflecting the intrauterine development of the fetus were observed in the sample with placental dysfunction and the risk of infectious complica tions, which was associated with delayed fetal development, and the birth of children with a combination of signs of intrauterine suf fering and hypoxia.

Density functional theory studies on dehydrogenation of methanol to formaldehyde on Pt(1 1 1) surface at different coverage

Platinum metal exhibits excellent catalytic activity and selectivity in many important chemical reactions. In this paper, density functional theory is used to study the adsorption configurations of oxygen in methanol on Pt(111) surface and dehydrogenation reaction (CH3OH → CH2O) at different coverage. It is found that methanol molecules prefer to adsorb at the top position of Pt(111) at various coverage levels. With the coverage increases, the adsorption capacity of methanol decreases rapidly, and then tends to flatten until the coverage reaches 1/6. The product of CH2O is formed by two-step dehydrogenation process. The energy barrier for both dehydrogenations increase first and then decreases with increasing coverage. The lowest energy barrier for both dehydrogenations occurs on the Pt(111) surface with coverage of 1/6 (Ea, OH = 0.66 eV, Ea, CH = 0.16 eV). Therefore, coverage of 1/6 is the optimal coverage for CH3OH generating CH2O on the Pt(111) surface.

Thymus vulgaris-assisted growth of nickel nanoparticles onto Luffa fibers: A robust and recyclable catalyst for the reduction of organic pollutants

A green and efficient synthetic pathway was developed to prepare nickel@Luffa nanocomposite. Thymus vulgaris extract was used to functionalize the surface of Luffa fibers with hydroxyl, carbonyl, and amide groups, which assisted in the adsorption of nickel ions. The scanning electron microscope images revealed that nickel nanoparticles grew as aggregates of semi-spherical particles and randomly dispersed on the Luffa fibers. The X-ray diffraction pattern of the nickel@Luffa nanocomposite showed the diffraction pattern of a face-centered cubic Ni crystal. XPS spectrum indicated the formation of metallic Ni at the Luffa surface. The prepared nickel@Luffa was used to catalyze the degradation of 4-nitrophenol, methyl orange, bromophenol blue and a mixture of both. The reaction rate constant for nickel@Luffa nanocomposite was calculated as 15.47 × 10−3 s−1 at pH = 10 and even after ten cycles its conversion was about 90%. The nickel nanoparticles could be recycled/reused for ten catalytic cycles with adequate catalytic activity. Such synthetic pathways encourage the application of renewable natural resources to fabricate separable/recyclable heterogeneous catalyst for many important reactions. The proposed nanocomposite is industrially applicable and environmentally-benign, fulfilling the requirements for the sustainable development.

Non-adiabatic excited-state time-dependent GW molecular dynamics (TDGW) satisfying extended Koopmans' theorem: An accurate description of methane photolysis.

There is a longstanding difficulty that time-dependent density functional theory relying on adiabatic local density approximation is not applicable to the electron dynamics, for example, for an initially excited state, such as in photochemical reactions. To overcome this, we develop non-adiabatic excited-state time-dependent GW molecular dynamics (TDGW) on the basis of the extended quasiparticle theory. Replacing Kohn-Sham orbitals/energies with correlated, interacting quasiparticle orbitals/energies allows the full correspondence to the excited-state surfaces and corresponding total energies, with satisfying extended Koopmans' theorem. We demonstrate the power of TDGW using methane photolysis, CH4→CH3•+H, an important initiation reaction for combustion/pyrolysis and hydrogen production of methane. We successfully explore several possible pathways and show how this reaction dynamics is captured accurately through simultaneously time-tracing all quasiparticle levels. TDGW scales as O(NB3-4), where NB is the number of basis functions, which is distinctly advantageous to performing dynamics using configuration interaction and coupled cluster methods.

Effect of Ag Addition to Au Catalysts for the Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Furandicarboxylic Acid

AbstractThe addition of Ag to Au nanocatalysts is known to improve several catalytic reduction and oxidation reactions. Until now, bimetallic AuAg catalysts have not been studied in detail in liquid phase oxidation reactions. We investigated the activity, selectivity, and stability of silica supported Au, Ag and AuAg catalysts in the oxidation of 5‐hydroxymethylfurfural (HMF) to 2,5‐furandicarboxylic acid (FDCA), an important reaction to produce bio‐based polymers. We demonstrate that addition of an optimum amount of inactive Ag to the active Au catalyst substantially increases the overall selectivity and yield of the desired FDCA. Interestingly, Ag addition decreased the conversion rate of the reactant HMF to the intermediate HMFCA, but improved (up to 10–20 % Ag addition) much the conversion of the intermediate product to the desired final product. This is probably due to tuning the electronic properties of the nanoparticles to achieve an optimum adsorption strength of the intermediate on the surface of AuAg catalysts. Moreover, particle growth was suppressed by the bimetallic AuAg catalyst, ultimately leading to superior stability compared to its monometallic counterparts.

Synthesis of InZrOx nanosheets and its application in CO2 hydrogenation to methanol

Synthesis of methanol via CO2 hydrogenation is a very important reaction. In recent years, the In2O3 based catalysts were proved to be a sort of promising catalysts to accelerate this reaction, which have aroused extensive attention. However, design of novel In2O3 based catalysts that can efficiently produce methanol from CO2 hydrogenation at low temperature is still in great need. Herein we fabricated the InZrOx nanosheets via a simple solvothermal method, which had peculiar surface structure and plenty of oxygen defects. The InZrOx nanosheets displayed excellent low temperature catalytic performance in a slurry reactor. The methanol selectivity (90 %) and activity (1.4 mmol gIn-1h−1) were achieved at 180 °C, which are 2.3 and 1.6 times than that of the counterpart nanoparticles, respectively. Water as a clean and cheap reaction solvent played a crucial role, which participated in the kinetic process of the catalysis. The particular catalyst structure and the solvent effect of water accounting for the outstanding reaction results.

Ferrochrome Production in a Submerged Electric Arc Furnace: Fundamental Analysis Based upon the FactSage‐Macro Program Approach

Around 80% of the FeCr produced worldwide is utilized in stainless steelmaking. Thus, the growth of the stainless‐steel industry is directly related to FeCr production. Although the FeCr production in submerged arc furnace (SAF) is fairly stabilized, new challenges have emerged in the furnace operation due to the depletion of lumpy ores, high SiO2 content, and lower Cr/Fe ratio in the low‐grade ores. In this regard, the addition of various fluxes such as quartz, magnesite, and bauxite are considered to improve the Cr recovery in SAF operation, particularly in the context of low‐grade ores. In this study, thermodynamic calculations are performed to discuss the effect of various additives (MgO in magnesite, Al2O3 as bauxite, and SiO2 in quartz form) on Cr recovery and slag formation temperature. In addition, a comprehensive thermodynamic‐based process model has been developed for FeCr operation that captures the most important thermochemical reactions. The modeling results are compared with the plant data, and suitable modifications in the slag compositions are made to maximize Cr recovery. Moreover, new plant trials are performed with modified slag composition, and its effect on Cr recovery is also discussed.

New insight into knockout reactions from the two-proton halo nucleus Ne17

The unexplained disagreement in the dependence of spectroscopic factors (C2Sexp) on the binding energy obtained by nucleon knockout using different targets is still a puzzle that needs to be addressed. To find an explanation of this riddle through exclusive measurements using different targets. The exclusive measurements were performed by using a Ne17 beam with an energy of 500 MeV/u incident on C and CH2 targets. Through the standard theoretical approach, C2Sexp were derived from the analysis of the experimental data on proton ejection from the proton halo in Ne17 as well as from its core O15. For the C target, proton ejection from the proton halo gave C2Sexp about 37% smaller than for the H target. But when protons are ejected from the core of Ne17, C2Sexp are identical within statistical uncertainties. An explanation for the difference in C2Sexp could be the removal of both halo protons, a more important reaction pathway for the C target. The C2Sexp values obtained by analyzing the proton ejection from the core indicate that it is not affected by the interaction with the halo protons.Published by the American Physical Society2024

An experimental and chemical kinetic modeling study of octane isomer oxidation. Part 1: 2,3,4-trimethyl pentane

2,3,4-trimethyl pentane (234-TMP) is an isomer of octane with the same number of methyl branching groups as 2,2,4-trimethyl pentane (iso-octane). However, there are very few studies of this fuel available in the literature. In this work, a detailed chemical kinetic model is developed to describe the oxidation of 234-TMP using NUIGMech1.3 as the core mechanism. The rate constants for some important reaction classes are updated following a review of literature rate constants. Additionally, the impact of each rate constant on simulated ignition delay times for 234-TMP compared to 2,2,3-trimethyl pentane and 2,2,4-trimethyl pentane (iso-octane) is discussed. The thermodynamic data of the alkanes (RH), alkyl (Ṙ), alkyl peroxy (RȮ2), hydroperoxy-alkyl Q˙OOH, and peroxy hydroperoxyalkyl (Ȯ2QOOH) radicals are newly estimated based on recently updated group values in the literature. Moreover, this study presents the first set of data available for the oxidation of 234-TMP at higher pressures (15 and 30 atm), in the temperature range 600–1600 K, and at fuel/‘air’ equivalence ratios (φ) of 0.5, 1.0 and 2.0. The chemical kinetic model shows general good agreement with the experimental measurements. In addition, flux and sensitivity analyses are conducted to identify the important pathways and reactions controlling fuel oxidation at different temperatures. Furthermore, the reactivity of 234-TMP is compared to that of iso-octane, indicating that 234-TMP is slower to react as it has more tertiary carbon sites compared to iso--octane.

Theoretical Study of the Temperature- and Pressure-Dependent Rate Constants for Nine Reactions between COn (n = 0-4), Om (m = 1-3), C2O, and C3O2 during the Radiolysis of Carbon Dioxide.

We investigate the reaction pathways of nine important CO2-related reactions using the revDSD-PBEP86-D3(BJ)/jun-cc-pV(T+d)Z level and simultaneously employ an accurate composite method (jun-Cheap) based on coupled-cluster (CC) theory. Subsequently, the Rice-Ramsperger-Kassel-Marcus/master equation (RRKM/ME) is solved to calculate the temperature- and pressure-dependent rate constants. This work investigates reactions involving transition states that have been overlooked in previous literature, including the dissociation of singlet-state C3O2, the triple channel formation of C2O + CO to form C3O2, and the formation of O3 + CO. The results show that CO3 is highly prone to dissociation at high temperatures. Finally, the kinetic data show that over a wide temperature range, our calculations are consistent with previous experimental measurements. The majority of the reaction rate constants studied exhibit significant pressure dependence, while the O3 + CO reaction is pressure-independent at low temperatures. These results are instrumental in the development of detailed kinetic models for the CO2 radiolysis reaction network.

Contrasting effects of increasing dissolved iron on photosynthesis and O2 availability in the gastric cavity of two Mediterranean corals.

Iron (Fe) plays a fundamental role in coral symbiosis, supporting photosynthesis, respiration, and many important enzymatic reactions. However, the extent to which corals are limited by Fe and their metabolic responses to inorganic Fe enrichment remains to be understood. We used respirometry, variable chlorophyll fluorescence, and O2 microsensors to investigate the impact of increasing Fe(III) concentrations (20, 50, and 100 nM) on the photosynthetic capacity of two Mediterranean coral species, Cladocora caespitosa and Oculina patagonica. While the bioavailability of inorganic Fe can rapidly decrease, we nevertheless observed significant physiological effects at all Fe concentrations. In C. caespitosa, exposure to 50 nM Fe(III) increased rates of respiration and photosynthesis, while the relative electron transport rate (rETR(II)) decreased at higher Fe(III) exposure (100 nM). In contrast, O. patagonica reduced respiration, photosynthesis rates, and maximum PSII quantum yield (Fv/Fm) across all iron enrichments. Both corals exhibited increased hypoxia (<50µmol O2 L-1) within their gastric cavity at night when exposed to 50 and 100 nM Fe(III), leading to increased polyp contraction time and reduced O2 exchange with the surrounding water. Our results indicate that C. caespitosa, but not O.patagonica, might be limited in Fe for achieving maximal photosynthetic efficiency. Understanding the multifaceted role of iron in corals' health and their response to environmental change is crucial for effective coral conservation.

Borane-Trimethylamine Complex: A Versatile Reagent in Organic Synthesis.

Borane-trimethylamine complex (Me3N·BH3; BTM) is the most stable of the amine-borane complexes that are commercially available, and it is cost-effective. It is a valuable reagent in organic chemistry with applications in the reduction of carbonyl groups and carbon-nitrogen double bond reduction, with considerable examples in the reduction of oximes, hydrazones and azines. The transfer hydrogenation of aromatic N-heterocycles and the selective N-monomethylation of primary anilines are further examples of recent applications, whereas the reduction of nitrobenzenes to anilines and the reductive deprotection of N-tritylamines are useful tools in the organic synthesis. Moreover, BTM is the main reagent in the regioselective cleavage of cyclic acetals, a reaction of great importance for carbohydrate chemistry. Recent innovative applications of BTM, such as CO2 utilization as feedstock and radical chemistry by photocatalysis, have extended their usefulness in new reactions. The present review is focused on the applications of borane-trimethylamine complex as a reagent in organic synthesis and has not been covered in previous reviews regarding amine-borane complexes.

GEHGAN[formula omitted] CircRNA–disease association prediction via graph embedding and heterogeneous graph attention network

There is growing proof suggested that circRNAs play a crucial function in diverse important biological reactions related to human diseases. Within the area of biochemistry, a massive range of wet experiments have been carried out to find out the connections of circRNA–disease in recent years. Since wet experiments are expensive and laborious, nowadays, calculation-based solutions have increasingly attracted the attention of researchers. However, the performance of these methods is restricted due to the inability to balance the distribution among various types of nodes. To remedy the problem, we present a novel computational method called GEHGAN to forecast the new relationships in this research, leveraging graph embedding and heterogeneous graph attention networks. Firstly, we calculate circRNA sequences similarity, circRNA RBP similarity, disease semantic similarity and corresponding GIP kernel similarity to construct heterogeneous graph. Secondly, a graph embedding method using random walks with jump and stay strategies is applied to obtain the preliminary embeddings of circRNAs and diseases, greatly improving the performance of the model. Thirdly, a multi-head graph attention network is employed to further update the embeddings, followed by the employment of the MLP as a predictor. As a result, the five-fold cross-validation indicates that GEHGAN achieves an outstanding AUC score of 0.9829 and an AUPR value of 0.9815 on the CircR2Diseasev2.0 database, and case studies on osteosarcoma, gastric and colorectal neoplasms further confirm the model’s efficacy at identifying circRNA–disease correlations.