Biochar derived from animal and plant facilitates synergistic transformation of heavy metals and phosphorus in sewage sludge composting.

This study investigated the influence of plant-derived biochar (PB) and animal-derived biochar (AB) on behavior of heavy metals and phosphorus fractions during sewage sludge composting. PB was highly effective in reducing the bioavailability of Zn and Cu by 39% and 50%, respectively, while AB decreased the bioavailability of Pb (30%) and Cd (12%). Both biochar increased available phosphorus by over 38%. Acid extractable and bioavailable Pb in AB, and water-soluble, oxidizable and total Zn, acid extractable and oxidizable Cu in PB were positively correlated with moderately resistant organic phosphorus (MROP). Besides, in AB, Cd had strong and positive correlation with highly resistant organic phosphorus (HROP). This suggested biochar facilitated the formation of stable organometallic complexes through binding metal ions to phosphorus fractions, with notable differences based on biochar source. FT-IR showed biochar promoted humification, with PB enhancing carboxyl and polysaccharide formation, while AB encouraged quinone and aryl ether structures. These surface functional groups on the biochar likely contributed to heavy metals and phosphorus binding through chelation, adsorption, and electron shuttling.

The influence of biochar from animal and plant on the transformation of phosphorus during paper mill sludge composting.

Biochar has effect on phosphorus adsorption, release, and transformation. This study compared the influence of biochar derived from animal (AB) and plant (PB) during paper mill sludge composting. Results indicated AB not only accelerated sludge decomposition but also had significantly higher levels of available phosphorus (AP) than PB and CK (no biochar), with AP contents in the order of AB > PB > CK. Compared to CK, AB was found to increase the relative abundance of thermophilic bacteria, and PB diversified the microbial community. Based on Pearson and RDA results, TOC/TN ratio (C/N) and organic matter (OM) explained above 50% of the variance in microbial community and phosphorus fractions. Thermophilic bacteria with high levels of OM and C/N promoted the conversion among labile and moderately labile organic phosphorus, moderately labile inorganic phosphorus, and AP. Biochar could enhance the AP conversion pathway, leading to increased levels of AP.

Phage lysate can regulate the humification process of composting.

Phages play a crucial role in orchestrating top-down control within microbial communities, influencing the dynamics of the composting process. Despite this, the impact of phage-induced thermophilic bacterial lysis on humification remains ambiguous. This study investigates the effects of phage lysate, derived explicitly from Geobacillus subterraneus, on simulated composting, employing ultrahigh-resolution mass spectrometry and 16S rRNA sequencing techniques. The results show the significant role of phage lysate in expediting humus formation over 40 days. Notably, the rapid transformation of protein-like precursors released from phage-induced lysis of the host bacterium resulted in a 14.8 % increase in the proportion of lignins/CRAM-like molecules. Furthermore, the phage lysate orchestrated a succession in bacterial communities, leading to the enrichment of core microbes, exemplified by the prevalence of Geobacillus. Through network analysis, it was revealed that these enriched microbes exhibit a capacity to convert protein and lignin into essential building blocks such as amino acids and phenols. Subsequently, these components were polymerized into humus, aligning with the phenol-protein theory. These findings enhance our understanding of the intricate microbial interactions during composting and provide a scientific foundation for developing engineering-ready composting humification regulation technologies.

Molecular design and theoretical study of oxadiazole-bifurazan derivatives.

CONTEXT: The design and synthesis of new high energy density materials is an important part of the research in the field of high energy materials. However, the synthesis of high-energy materials is very difficult and dangerous. Therefore, it is necessary to design the compounds in advance and evaluate the performance of the designed compounds, so as to screen the high-energy candidate compounds with excellent performance and provide reference for future synthesis and application. 1,2,5-oxadiazole (furazan) and 1,2,4-oxadiazole are five-membered nitrogen-oxygen heterocycles. Because their structures contain high-energy N-O, C=N bonds, they can effectively improve the energy density and oxygen balance of compounds, which has attracted widespread attention. In this paper, 42 kinds of oxadiazole-bifurazan energetic derivatives were designed by inserting different functional groups and changing the parent bridging groups with 1,2,4-oxadiazole and furazan as the basic structural units. Their electronic structures, aromaticity, heats of formation (HOFs), detonation properties, thermodynamic properties and electrostatic potential were systematically studied by density functional than theory (DFT). The results show that -C (NO2)3 has the greatest improvement effect on HOFs among all the substituent groups. The detonation performance of -N=N- bridged oxadiazole-bifurazan derivatives is better than that of -NH-NH- bridged derivatives. And -C(NO2)3 is the most effective group to improve the detonation performance and density of compounds. Compared with the parent compounds, when a -C(NO2)3 was introduced, the density increased by about 5.5%. A6 (D = 10.30 km·s-1, P = 48.86 GPa) and D6 (D = 9.57 km·s-1, P = 42.31 GPa) are the compounds with the best D and P among the designed compounds, which are higher than RDX and HMX, and are potential candidates for new high-energy materials. METHODS: With the help of Gaussian16 software and Multiwfn 3.8 package, the B3LYP method in density functional theory was selected. The 6-311G (d, p) basis set was used to optimize the structure of the 42 derivatives, and the high-precision def2-TZVPP basis set was used to calculate the energy.

Regulation of external electric field on sensitivity of ICM energetic materials.

CONTEXT: [2,2'-Bi(1,3,4-oxadiazole)]-5,5'-dinitramide (ICM-101), 2,4,6-triamino-5-nitropyrimidine-1,3-dioxide (ICM-102), and 6-nitro-7-azido-pyrazol[3,4-d][1,2,3]triazine-2-oxide (ICM-103) are excellent China-made explosives, but their performance under external electric fields (EEF) has never been explored, especially sensitivity. To study the induction effect of EEF on it, the chemical reactivity, electron localization function (ELF), spectrum, and other parameters were calculated by density functional theory. The results show that the increasing EEF can weaken the △EHOMO-LUMO (△EHOMO-LUMO = EHOMO-ELUMO) materials, making the stability worse and the sensitivity higher. The proportion of the positive electrostatic surface potential area is also smaller under the increasing EEF, indicating that ICM molecules are becoming more and more unstable. The ELF and localized orbital locator (LOL) decrease with the increase of EEF strength, which suggests that the trigger bond length increases, the EBDE decreases, and the molecular sensitivity increases. When the intensity of EEF increases, the absorption peak of the molecular spectrum gradually redshifts, and even a weak new absorption peak appears, indicating that the color of the material may change. Finally, EEF strength affects electron density, nitro charge, and chemical reactivity parameters. METHODS: Gaussian 16 software was used for calculation. The calculation levels are B3LYP/6-311G+ (d, p) and B3LYP/Def2-TZVPP. The optimized structure has a local true minimum energy on the potential energy surface and no imaginary frequency. Multiwfn 3.8 and VMD 1.9.3 were used in this work to analyze the ICM series of energetic material wave functions. The strength range of EEF is 0.000-0.016 a.u., and the increasing gradient is 0.002 a.u.

Regulation of external electric field on the high-energy polynitrogen compound 1,5-diaminotetrazole-4 N-oxide.

BACKGROUND: The external electric field (EEF) tends to have a significant impact on chemicals, especially energetic materials. METHODS: Molecular structure, electrostatic potential (ESP), electron density difference, density of states (DOS), and frontier molecular orbitals (FMOs) of 1,5-diaminotetrazole-4N-oxide (SYX-9) are calculated by density functional theory (DFT) at B3LYP/6-311G+(d, p) and M062X/def2-TZVP under external electric field. RESULTS: Calculated results reveal that EEF has definite influence on the trigger bond of SYX-9, especially in positive direction, and the shortening of the trigger bond caused by it can effectively reduce the sensitive of SYX-9. In addition, EEF has an effect on the electron density of SYX-9. The positive EEF can reduce the HOMO-LUMO gap. From the perspective of components of energy variation and the force on atoms, the factors of structural deformation are specifically investigated. The aromaticity of SYX-9 makes its structure stable under the influence of EEF, which is verified by the method of the iso-chemical shielding surface (ICSS).

Lactobacillus buchneri S-layer protein-coated liposomes loaded with ß-cyclodextrin-carvacrol inclusion complexes for the enhancement of antibacterial effect.

This article describes the development of a novel liposome nanocarrier system. Carvacrol (Car) is first embedded in ß-cyclodextrin (ß-CD) by the freeze-drying method to form the ß-cyclodextrin-carvacrol inclusion compound (ß-CD-Car), and then ß-CD-Car liposomes (ß-CD-Car-LPs) and ß-CD-Car liposomes coated with S-layer proteins (SLPs) from Lactobacillus buchneri 20023 (SLP/ß-CD-Car-LPs) were prepared. The liposomes were characterized, and their stabilities, in vitro release characteristics, and antibacterial activities were investigated. Results showed that the fabricated liposome SLP/ß-CD-Car-LPs was nanosized, oval and homogenous, with the particle size of 229.1 ± 6.81 nm, the polydispersity index of 0.139, and the zeta potential of 27.9 mV. Measurements based on Triton X-100 resistance indicated that the SLP-coated liposomes were more stable than naked liposomes. The in vitro release study results showed that the rate of release from SLP-coated liposomes was much lower than that from uncoated liposomes. The minimum inhibitory activity (MIC) of SLP/ß-CD-Car-LPs (0.05 mg/mL) was 6.4 times higher than that of the free carvacrol (0.32 mg/mL) and was twice that of ß-CD-Car-LPs (0.1 mg/mL). In general, the stability, antibacterial activity, and sustained release effect of ß-CD-Car-LPs modified with SLPs were improved. Findings suggested that SLP-coated liposomes could be developed as a favorable delivery system for potential applications in the food industry.

Structural transformation of methyl urotropine perchlorate under high pressure.

Based on the first-principles calculations of density functional theory (DFT), the crystal structure, molecular structure, electronic properties, and optical absorption properties of methyl urotropine perchlorate under hydrostatic compression in the range of 0 ~ 100 GPa were calculated. The results show that the crystal structure of methyl urotropine perchlorate undergoes two structural transformations under hydrostatic compression. The H1A-H1B bond breaks at 25 GPa, generating two new covalent bonds N3-H1A and O1-H1B. The covalent bonds of O2A-C1 and Cl1-H3A are formed at 85 GPa. The compression ratio of lattice constants (a, b, c) and unit cell volume change abruptly at 25 GPa and 85 GPa, respectively. The conclusion that new bonds are formed under high pressure is further demonstrated by analyzing the partial density of states (PDOS) of N3, H1A, O1, H1B, O2A, C1, Cl1, and H3A atoms. The absorption spectrum showed that the absorption peak of methyl urotropine perchlorate gradually enhanced with the increase of pressure and the highest absorption peak shifted to high frequency.

Effect of Autoinducer-2 Quorum Sensing Inhibitor on Interspecies Quorum Sensing.

Bacterial drug resistance caused by overuse and misuse of antibiotics is common, especially in clinical multispecies infections. It is of great significance to discover novel agents to treat clinical bacterial infections. Studies have demonstrated that autoinducer-2 (AI-2), a signal molecule in quorum sensing (QS), plays an important role in communication among multiple bacterial species and bacterial drug-resistance. Previously, 14 AI-2 inhibited compounds were selected through virtual screening by using the AI-2 receptor protein LuxP as a target. Here, we used Vibrio harveyi BB170 as a reporter strain for the preliminary screening of 14 inhibitors and compound Str7410 had higher AI-2 QS inhibition activity (IC50 = 0.3724 ± 0.1091 µM). Then, co-culture of Pseudomonas aeruginosa PAO1 with Staphylococcus aureus ATCC 25923 was used to evaluate the inhibitory effects of Str7410 on multispecies infection in vitro and in vivo. In vitro, Str7410 significantly inhibited the formation of mixed bacterial biofilms. Meanwhile, the combination of Str7410 with meropenem trihydrate (MEPM) significantly improved the susceptibility of mixed-species-biofilm cells to the antibiotic. In vivo, Str7410 significantly increased the survival rate of wild-type Caenorhabditis elegans N2 co-infected by P. aeruginosa PAO1 and S. aureus ATCC 25923. Real-time quantitative PCR analysis showed that Str7410 reduced virulence factor (pyocyanin and elastase) production and swarming motility of P. aeruginosa PAO1 by downregulating the expression of QS-related genes in strain PAO1 in co-culture with S. aureus ATCC 25923. Compound Str7410 is a candidate agent for treating drug-resistant multispecies infections. The work described here provides a strategy for discovering novel antibacterial drugs.

Effect of biochar on transformation of dissolved organic matter and DTPA-extractable Cu and Cd during sediment composting.

This study investigated the influence of biochar on temperature, pH, organic matter (OM), seed germination index (GI), the fluorescent components of dissolved organic matter (DOM), and bioavailability of DTPA-extractable Cu and Cd during composting and analyzed the relation between DTPA-extractable metals with pH, OM, and the fluorescent components of DOM. Results showed that the addition of biochar shortened the thermophilic phase, reduced the pH at maturation period, accelerated the decomposition of OM, and raised GI. Besides, it promoted the formation of components with benzene ring in FA and HyI and the degradation of protein-like organic-matters in FA and HA, which was mainly related with the decrease of DTPA-extractable Cd and the increase of DTPA-extractable Cu. After composting, DTPA-extractable Cd in pile A and pile B were decreased by 37.15% and 27.54%, respectively, while the bioavailability of Cu in pile A and pile B was increased by 65.71% and 68.70%, respectively. All these findings demonstrate positive and negative impact produced by biochar into various heavy metals and the necessary of optimization measures with biochar in sediment composting.

Strong adsorption properties and mechanism of action with regard to tetracycline adsorption of double-network polyvinyl alcohol-copper alginate gel beads.

In the present study, glutaraldehyde was used as a hydrophobic modifier to crosslink polyvinyl alcohol (PVA), and copper ion was immobilized by sodium alginate (SA). Polyvinyl alcohol-copper alginate (PVA-CA) gel beads were prepared by a one-step process, and were used to adsorb and remove tetracycline (TC) from an aqueous solution. The beads were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) measurement, X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR). The adsorption experiment showed that the optimal pH value of the beads was 5, and that their adsorption met pseudo-second-order kinetic and Langmuir isothermal models. The adsorption thermodynamics experiment showed that the adsorption process was spontaneous and endothermic. Under optimal adsorption conditions, the maximum adsorption capacity for TC of the beads was 231.431 mg/g, which was much higher than that of a single copper alginate matrix. After 5 adsorption-desorption cycles, the adsorption capacity remained high. FTIR and X-ray photoelectron spectroscopy (XPS) revealed that the cation bonding bridge reaction was the main driving force behind the adsorption mechanism. Compared with other reported adsorption materials, the PVA-CA gel beads have high adsorption capacity, a simple preparation process, and excellent recovery performance.

Microbial profiles associated improving bioelectricity generation from sludge fermentation liquid via microbial fuel cells with adding fruit waste extracts.

This first-attempt study illustrated the microbial cooperative interactions related to bioelectricity generation from the mixture of sludge fermentation liquid (SFL) and fruit waste extracts (FWEs) via microbial fuel cells (MFCs). The optimal output voltages of 0.65 V for SFL-MFCs, 0.51 V for FWEs-MFCs and 0.75 V for mixture-MFCs associated with bioelectricity conversion efficiencies of 1.061, 0.718 and 1.391 kWh/kg COD were reached, respectively. FWEs addition for substrates C/N ratio optimization contributed considerably to increase SFL-fed MFCs performance via triggering a higher microbial diversity, larger relatively abundance of functional genes and microbial synergistic interactions with genera enrichment of Clostridium, Alicycliphilus, Thermomonas, Geobacter, Paludibaculum, Pseudomonas, Taibaiella and Comamonas. Furthermore, a conceptual illustration of co-locating scenario of wastewater treatment plant(s), waste sludge in situ acidogenic fermentation, fruit waste collection/crushing station and MFC plant was proposed for the first time, which provided new thinking for future waste sludge treatment toward maximizing solid reduction and power recovery.

Neuroprotective Effects of 2-Substituted 1, 3-Selenazole Amide Derivatives on Amyloid-Beta-Induced Toxicity in a Transgenic Caenorhabditis Elegans Model of Alzheimer's Disease.

Alzheimer's disease is an age-related neurodegenerative disease, associated with the presence of extracellular amyloid-ß (Aß) plaques and neurofibrillary tangles. Although the pathogenesis of AD remains unclear, the characteristic feature of AD was reported to be the buildup of Aß plaques. In this study, we extensively investigated the neuroprotective effects of 2-substituted 1,3-selenazole amide derivatives (CHF11) on Aß1-42 transgenic Caenorhabditis elegans CL4176. Results showed that worms fed with CHF11 exhibited remarkably reduced paralysis, decreased levels of toxic Aß oligomers and Aß plaque deposition, as well as less ROS production in comparison with the untreated worms. The effective concentrations of CHF11 were arranged in the descending order of 100 µM > 10 µM > 1 µM. Real-time PCR analysis showed that there was no significant difference in Aß expression between CHF11-administered group and the blank control group, suggesting that CHF11-induced reduction in toxic protein deposition may be regulated at the post-transcriptional level. In the meantime, the gene expressions of hsf-1 and its downstream target hsp-12.6 were significantly increased, indicating that CHF11 against Aß toxicity may involve in HSF-1 signaling pathway in worms. In conclusion, CHF11 exhibits a significant protective effect against ß-amyloid-induced toxicity in CL4176 by reducing ß-amyloid aggregation and ROS production, which may involve in HSF-1 and downstream target HSP-12.6 pathway.

Interaction between tetracycline and microorganisms during wastewater treatment: A review.

Tetracycline (TC) is a commonly used human and veterinary antibiotic that is mostly discharged into wastewater in the form of the parent compounds. At present, wastewater treatment plants (WWTPs) use activated sludge processes that are not specifically designed to remove such pollutants. Considering the biological toxicity of TC in aquatic environment, the migration and fate of TC in the process of wastewater treatment deserve attention. This paper reviews the influence of TC on the functional bacteria in the sludge matrix and the development of tetracycline-resistant genes, and also discusses their adsorption removal rates, their adsorption kinetics and adsorption isotherm models, and infers their adsorption mechanism. In addition, the biodegradation of TC in the process of biological treatment is reviewed. Co-metabolism and the role of dominant bacteria in the degradation process are described, along with the formation of degradation byproducts and their toxicity. Furthermore, the current popular integrated coupling-system for TC degradation is also introduced. This paper systematically introduces the interaction between TC and activated sludge in WWTPs. The review concludes by providing directions to address research and knowledge gaps in TC removal from wastewater.

Long intergenic non­coding RNA LINC01232 contributes to esophageal squamous cell carcinoma progression by sequestering microRNA­654­3p and consequently promoting hepatoma­derived growth factor expression.

Long intergenic non­coding RNA 01232 (LINC01232) was identified as a critical regulator of the development of pancreatic adenocarcinoma. The present study investigated the expression and regulatory roles of LINC01232 in esophageal squamous cell carcinoma (ESCC). The main aim of the present study was to elucidate the underlying mechanisms through which LINC01232 affects the malignancy of ESCC. Initially, LINC01232 expression in ESCC was analyzed using the TCGA and GTEx databases and was confirmed using reverse transcription­quantitative polymerase chain reaction. ESCC cell proliferation, apoptosis and migration and invasion were assessed using the Cell Counting kit­8 assay, flow cytometric analysis, and migration and invasion assays, respectively. ESCC tumor growth in vivo was examined using a xenograft mouse model. As shown by the results, a high LINC01232 expression was detected in ESCC tissues and cell lines. LINC01232 downregulation suppressed the proliferation, migration and invasion of ESCC cells, and promoted cell apoptosis in vitro. In addition, LINC01232 depletion restricted tumor growth in vivo. Mechanistically, LINC01232 was shown to function as an microRNA­654­3p (miR­654­3p) sponge in ESCC cells, and hepatoma­derived growth factor (HDGF) was identified as a direct target of miR­654­3p. LINC01232 could bind competitively to miR­654­3p and decrease its expression in ESCC cells, thereby promoting HDGF expression. Rescue experiments reconfirmed that the effects of LINC01232 deficiency in ESCC cells were restored by increasing the output of the miR­654­3p/HDGF axis. On the whole, the present study demonstrates that LINC01232 plays a tumor­promoting role during the progression of ESCC by regulating the miR­654­3p/HDGF axis. The LINC01232/miR­654­3p/HDGF pathway may thus provide a novel theoretical basis for the management of ESCC.

Ambient Chemical Fixation of CO2 Using a Robust Ag27 Cluster-Based Two-Dimensional Metal-Organic Framework.

Unprecedented double S2- templated Ag27 clusters have been stabilized by 5,10,15,20-tetra(4-pyridyl)porphyrin (TPyP-H2 ) ligands to afford a robust 2D metal-organic framework (Ag27-MOF). This silver cluster-assembled material serves as a highly efficient heterogeneous catalyst for the cyclization of both terminal and internal propargylamines with CO2 under atmospheric pressure. Density functional theory (DFT) calculations illustrate that the high catalytic activity and broad substrate scope are attributable to the saddle-shaped metallic node in Ag27-MOF, which features an accessible platform with high-density silver atoms as π-Lewis acid sites for activating C≡C triple bonds. As a result, different sterically hindered alkyne substrates can be effectively activated through π-interactions with these cationic silver centers.

Design, synthesis, and biological evaluation of 3-amino-2-oxazolidinone derivatives as potent quorum-sensing inhibitors of Pseudomonas aeruginosa PAO1.

Due to the increasing resistance of Pseudomonas aeruginosa to most clinically relevant antimicrobials, it is challenging to treat bacterial infection with traditional antibiotics. Quorum sensing can regulate the production of biofilms and virulence factors which are closely related to bacterial resistance. Previously we synthesized a series of oxazolidinone compounds targeting the quorum-sensing transcriptional regulatory protein CviR and ZS-12 showed good activity against Chromobacterium violaceum CV026 quorum-sensing. In this study, eighteen 3-amino-2-oxazolidinone compounds were designed and synthesized using ZS-12 as the lead compound. We initially evaluated the inhibitory activities of novel oxazolidinone compounds against QS using C. violaceum CV026 as a reporter strain. Thirteen compounds showed good activities (IC50 range 3.69-63.58 µM) and YXL-13 inhibition was the most significant (IC50 = 3.686 ± 0.5790 µM) against biofilm formation and virulence factors determination of P. aeruginosa PAO1. In vitro, YXL-13 significantly inhibited the formation of PAO1 biofilm (range 42.98%-17.67%), the production of virulence factors (pyocyanin, elastase, rhamnolipid, and protease), and bacterial motility. Moreover, the combination of YXL-13 with an antibiotic (meropenem trihydrate) could significantly improve the antibiotic susceptibility of biofilm P. aeruginosa PAO1 cells. In vivo, YXL-13 significantly prolonged the lifespan of wildtype Caenorhabditis elegans N2 infected by P. aeruginosa PAO1. In conclusion, YXL-13 is a candidate agent for antibiotic-resistant P. aeruginosa PAO1and provides a method for finding new antibacterial drugs.

BNN-1,3-dipoles: isolation and intramolecular cycloaddition with unactivated arenes.

The mono-base-stabilized 1,2-diboranylidenehydrazine derivatives featuring a 1,3-dipolar BNN skeleton are obtained by dehydrobromination of [ArB(Br)NH]2 (Ar = 2,6-diphenylphenyl (Dpp), Ar = 2,6-bis(2,4,6-trimethylphenyl)phenyl (Dmp) or Ar = 2,4,6-tri-tert-butylphenyl (Mes*)) with N-heterocyclic carbenes (NHCs). Depending on the Ar substituents, such species can be isolated as a crystalline solid (Ar = Mes*) or generated as reactive intermediates undergoing spontaneous intramolecular aminoboration of the proximal arene rings via [3 + 2] cycloaddition (Ar = Dpp or Dmp). The latter reactions showcase the 1,3-dipolar reactivity toward unactivated arenes at ambient temperature. In addition, double cycloaddition of the isolable BNN species with two CO2 molecules affords a bicyclic species consisting of two fused five-membered BN2CO rings. The electronic structures of these BNN species and the mechanisms of these cascade reactions are interrogated through density functional theory (DFT) calculations.

Bifurcated Hydrogen-Bond-Stabilized Boron Analogues of Carboxylic Acids.

The reactivity of a bulky m-terphenylboronic acid, DmpB(OH)2 [1; Dmp = 2,6-bis(2,4,6-trimethylphenyl)phenyl], toward three different N-heterocyclic carbenes has been examined. The reaction of 1 with 1 equiv of bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) leads to the formation of a hydrogen-bonded carbene boronic acid adduct, 2, featuring strong O-H···C contacts. In contrast, more basic 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (IPr2Me2) and 1,3-di-tert-butylimidazol-2-ylidene (ItBu) deprotonate 1 smoothly to afford the rare anionic boranuidacarboxylic acids 3 and 4, respectively. Structural determination reveals that 3 and 4 bear unprecedented bifurcated hydrogen bonds with a BO- unit as a double hydrogen-bond acceptor, which contribute significantly to stabilization of the highly reactive B═O double bond. Quantum-mechanical calculations were conducted to disclose the unique electronic properties of the multiple bonds, as well as the important hydrogen bonds in these compounds.

A Learning-Based Framework for Error Compensation in 3D Printing.

As a typical cyber-physical system, 3D printing has developed very fast in recent years. There is a strong demand for mass customization, such as printing dental crowns. However, the accuracy of the 3D printed objects is low compared with traditional methods. The main reason is that the model to be printed is arbitrary and usually the quantity is small. The deformation is affected by the shape of the object and there is a lack of a universal method for the error compensation. It is neither easy nor economical to perform the compensation manually. In this paper, we present a framework for the automatic error compensation. We obtain the shape by technologies such as 3D scanning. And we use the "3D deep learning" method to train a deep neural network. For a specific task, such as dental crown printing, the network can learn the function of deformation when a large amount of data is used for training. To the best of our knowledge, this is the first application of the deep neural network to the error compensation in 3D printing. And we propose the "inverse function network" to compensate for the error. We use four types of deformations of the dental crowns to verify the performance of the neural network: 1) translation; 2) scaling up; 3) scaling down; and 4) rotation. The convolutional AutoEncoder structure is employed for the end-to-end learning. The experiments show that the network can predict and compensate for the error well. By introducing the new method, we can improve the accuracy with little need for increasing the hardware cost.