A carbon allotrope with twisted Dirac cones induced by grain boundaries composed of pentagons and octagons.

The grain boundaries (GBs) composed of pentagons and octagons (558 GBs) have been demonstrated to induce attractive transport properties such as Van Hove singularity (VHS) and quasi-one-dimensional metallic wires. Here, we propose a monolayer carbon allotrope which is formed from the introduction of periodic 558 GBs to decorate intact graphene, termed as PHO-graphene. The calculated electronic properties indicate that PHO-graphene not only inherits the previously superior characteristics such as Van Hove singularity and quasi-one-dimensional metallic wires, but also possesses two twisted Dirac cones near the Fermi level. Further calculation finds that the Berry phase is quantized to ± π at the two Dirac points, which is consistent with the distribution of the corresponding Berry curvature. The parity argument uncovers that PHO-graphene hosts a nontrivial band topology and the edge states connecting the two Dirac points are clearly visible. Our findings not only provide a reliable avenue to realize the abundant and extraordinary properties of carbon allotropes, but also offer an attractive approach for designing all carbon-based devices.

Epidemiological Investigation of Pediatric Fractures-A Retrospective Cohort Study of 1129 Patients.

Background and Objectives: Fractures are common in pediatric trauma, and they are caused by a broad spectrum of factors. Only a few studies have discussed the mechanisms of injury and their relationships to different types of fractures. The most frequent type of fractures in different age groups remains unclear. Therefore, we aim to summarize the epidemiological characteristics of pediatric fractures in a medical center in Zhuhai, China from 2006 to 2021 and analyze the causes of fractures with the highest frequency in different age groups. Materials and Methods: We extracted the information from the Zhuhai Center for Maternal and Child Health Care of those under 14 years old who had fractures from 2006 to 2021. Results: We reviewed the information of 1145 children. The number of patients increased during the 15 years (p < 0.0001). The number of patients was significantly different between genders after Y2 (p = 0.014). In addition, more than two-thirds of patients (71.3%) had upper limb fractures, and all types of falls were the most common cause of fractures (83.6%). The incidence demonstrated an insignificant difference in age groups except for the fractures of humerus and radius. Moreover, we discovered that the prevalence of fall-related injuries decreased with age, while that of sports-related injuries increased with age. Conclusions: Our study demonstrates that the prevalence of fall-related injuries decreases with age, and that of sports-related injuries increases with age. Most patients have upper limb fractures, and all types of falls are the most common cause of fractures. Fracture types with the highest frequency differ in each age group. These findings might supplement current epidemiological knowledge of childhood fracture and provide references for decision-making in children's health policies.

Bio-oxidation of Elemental Mercury into Mercury Sulfide and Humic Acid-Bound Mercury by Sulfate Reduction for Hg0 Removal in Flue Gas.

Bioconversion of elemental mercury (Hg0) into immobile, nontoxic, and less bioavailable species is of vital environmental significance. Here, we investigated bioconversion of Hg0 in a sulfate-reducing membrane biofilm reactor (MBfR). The MBfR achieved effective Hg0 removal by sulfate bioreduction. 16 S rDNA sequencing and metagenomic sequencing revealed that diverse groups of mercury-oxidizing/sulfate-reducing bacteria (Desulfobulbus, Desulfuromonas, Desulfomicrobium, etc.) utilized Hg0 as the initial electron donor and sulfate as the terminal electron acceptor to form the overall redox. These microorganisms coupled Hg0 bio-oxidation to sulfate bioreduction. Analysis on mercury speciation in biofilm by sequential extraction processes (SEPs) and inductively coupled mass spectrometry (ICP-MS) and by mercury temperature programmed desorption (Hg-TPD) showed that mercury sulfide (HgS) and humic acid-bound mercury (HA-Hg) were two major products of Hg0 bio-oxidation. With HgS and HA-Hg comprehensively characterized by X-ray diffraction (XRD), excitation-emission matrix spectra (EEM), scanning electron microscopy-energy disperse spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR), it was proposed that biologically oxidized mercury (Hg2+) further reacted with biogenic sulfides to form cubically crystallized metacinnabar (ß-HgS) extracellular particles. Hg2+ was also complexed with functional groups -SH, -OH, -NH-, and -COO- in humic acids from extracellular polymeric substances (EPS) to form HA-Hg. HA-Hg may further react with biogenic sulfides to form HgS. Bioconversion of Hg0 into HgS was therefore achieved and can be a feasible biotechnique for flue gas demercuration.

Simultaneous removal of elemental mercury and NO by mercury induced thermophilic community in membrane biofilm reactor.

Thermophilic membrane biofilm reactor (TMBR) for elemental mercury (Hg0) and NO removal in simulated flue gas was investigated at oxygen content of 6% and 60 °C. The performance, the microbial community structures, gene function and the mechanism for Hg0 and NO removal in the TMBR were evaluated. TMBR achieved effective simultaneous Hg0 and NO removal in 210 days of operation, Hg0 and NO removal efficiency were up to 88.9% and 85.3%, respectively. Mercury induced thermophilic community had been formed significantly. Comamonas, Pseudomonas, Desulfomicrobium, Burkholderia and Halomonas were thermophilic mercury resistant bacteria. Brucella, Paracoccus, Tepidiphilus, Proteobacteria, Pseudomonas and Symbiobacterium were nitrifying/denitrifying genera, and had functional genes of mercury and nitrogen metabolism, as shown by16S rDNA and metagenomic sequencing. The biofilm in TMBR was characterized by XPS, HPLC. XPS and HPLC spectra indicate the formation of a mercuric species (Hg2+) from mercury oxidation. TMBR used oxygen as electron acceptor, NO and Hg0 as electron donor in nitrification; O2, NO and NO3- could be used as electron acceptor and Hg0 as electron donor in denitrification.

Coupled catalytic-biodegradation of toluene over manganese oxide-coated catalytic membranes.

Volatile organic compounds (VOCs) harm human health and the ecological environment. This work demonstrated manganese oxide catalytic membrane coupled to biodegradation of toluene in a catalytic membrane biofilm rector (CMBfR). Toluene removal efficiency in CMBfR was up to 91% in a 200-day operation. Manganese oxide combined to membrane biofilm reactor could promote degradation of toluene. Manganese oxide catalysts were characterized by XRD, Raman, XPS, and FT-IR. Raman and XPS spectra verified the existence of Mn defects, adsorbed oxygen species, and the oxygen vacancy, which was catalytic of toluene on the Mn oxides coated membranes significantly. Pseudomonas, Hydrogenophaga, Flavobacterium, Bacillus, Clostridium and Prosthecobacter were the dominant bacteria of toluene degradation. Mn oxides catalysis could degrade toluene into intermediate products; these products were entered into the biological phase eventually metabolized to CO2 and H2O. These results show that the catalytic membrane biofilm reactor is achievable and opens new possibilities for applying the catalytic membrane biofilm reactor to VOCs treatment.

Dirac Fermions in the Boron Nitride Monolayer with a Tetragon.

Two-dimensional (2D) boron nitride (BN) is a promising candidate for aerospace materials due to its excellent mechanical and thermal stability properties. However, its unusually prominent band gap limits its application prospects. In this work, we report a gapless monolayer BN, t-BN, which has four anisotropic Dirac cones in the first Brillouin zone exactly at the Fermi level. To further confirm the semimetallic character, the nontrivial topological properties are proven through the topologically protected edge states and the invariant non-zero Z2. Additionally, the Young's modulus and Poisson ratio characterize the strong mechanical strength of t-BN. Our theoretical predictions provide more possibilities for exploring the Dirac cone in BN, which will enhance the 2D boron derivative materials.

Is Early Surgical Intervention Necessary for Acute Neonatal Humeral Epiphyseal Osteomyelitis: A Retrospective Study of 31 Patients.

Objective: To review the treatment experience of neonatal humeral epiphyseal osteomyelitis retrospectively. Study design: Retrospective cohort study of infants with neonatal humeral epiphyseal osteomyelitis. Patients were divided into conservative group and surgical group, and the surgical group was subdivided into early and delayed surgical group. Results: In total, there were 7 patients in the conservative group and 24 in the surgical group. The length of hospital stay and intravenous course of antibiotic therapy were both significantly shorter in the surgical group (p < 0.001). The full recovery rate was also higher in the surgical group (83.3%) than the conservative group (14.3%) (p < 0.001). Early surgery group (n = 14) had an insignificantly higher positive rate of pus/aspirate culture and full recovery rate than delayed surgery group (n = 10). Conclusion: Surgical treatment for neonatal humeral epiphyseal osteomyelitis demonstrated significantly higher rates of positive culture for the pathogen, a shorter course of intravenous oral antibiotics, and lower incidence of growth abnormality than conservative treatment. In our institution, most of culture outcome Gram-positive bacteria, and early surgical treatment was recommended with better outcome than delayed surgical group. Empirical antibiotics should be tailored to the epidemiological characteristics of local virulent bacteria.

The Dirac cone in two-dimensional tetragonal silicon carbides: a ring coupling mechanism.

The exploration of novel two-dimensional semimetallic materials is always an attractive topic. We propose a series of two-dimensional silicon carbides with a tetragonal lattice. The band structure of silicon carbides with tetragonal carbon rings and silicon rings exhibits Dirac cones. Interestingly, the Dirac cone of tetragonal SiC originates from a "ring coupling" mechanism. This mechanism refers to the mutual coupling between the four carbon atoms in the tetragonal C ring, and the same coupling in the tetragonal Si ring. Additionally, the "ring coupling" mechanism is applicable to other group IV binary compounds such as monolayer GeC and SnC. This work provides reliable evidence for the argument that two-dimensional tetragonal materials can produce Dirac cones.

Dirac Fermions in Graphene with Stacking Fault Induced Periodic Line Defects.

The exploration of carbon phases with intact massless Dirac fermions in the presence of defects is critical for practical applications to nanoelectronics. Here, we identify by first-principles calculations that the Dirac cones can exist in graphene with stacking fault (SF) induced periodic line defects. These structures are width (n)-dependent to graphene nanoribbon and are thus termed as (SF)n-graphene. The electronic properties reveal that the semimetallic features with Dirac cones occur in (SF)n-graphene with n = 3m + 1, where m is a positive integer, and then lead to a quasi-one-dimensional conducting channel. Importantly, it is found that the twisted Dirac cone in the (SF)4-graphene is tunable among type-I, type-II, and type-III through a small uniaxial strain. The further stability analysis shows that (SF)n-graphene is thermodynamic stable. Our findings provide an artificial avenue for exploring Dirac Ffermions in carbon-allotropic structures in the presence of defects.

Nitrification/denitrification shaped the mercury-oxidizing microbial community for simultaneous Hg0 and NO removal.

A denitrifying/nitrifying membrane biofilm reactor for simultaneous removal of Hg0 and NO was investigated. Hg0 and NO removal efficiency attained 94.5% and 86%, respectively. The mercury-oxidizing microbial community was significantly shaped by nitrification/denitrification after the supply of gaseous Hg0and NO continuously. Dominant genera Rhodanobacter and Nitrosomonas participated in Hg0 oxidation, nitrification and denitrification simultaneously. Hg0 oxidizing bacteria (Gallionella, Rhodanobacter, Ottowia, Nitrosomonas and etc.), nitrifying bacteria (Nitrosomonas, Rhodanobacter, Diaphorobacte and etc.) and denitrifying bacteria (Nitrosomonas, Rhodanobacter, Castellaniella and etc.) co-existed in the MBfR, as shown by metagenomic sequencing. X-ray photoelectron spectroscopy (XPS) and high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) confirmed the formation of a mercuric species (Hg2+) from mercury bio-oxidation. Mechanism of mercury oxidation can be described as the bacterial oxidation of Hg0 in which Hg0 serves as electron donor, NO serves as electron donor in nitrification and electron acceptor in denitrification, oxygen serves as electron acceptor.