Optimization of deposition process for a productive and cohesive bio-CaCO3 to repair concrete existing cracks.

Microbial-induced carbonate precipitation (MICP) is being investigated to repair concrete cracks because of its good durability and compatibility with cementitious matrix. However, during the in-situ application, the repairing often lasts weeks, even months. And the strength regain is quite low. The repairing time is largely determined by the CaCO3 yield, and the strength regain after the repair is closely related to the cohesion and bonding strength of CaCO3 itself. Thus, the purpose of this paper is to obtain an efficient precipitation of bio-CaCO3 with both high yield and good cohesion to improve the in-situ repairing efficiency. Firstly, the most influential factors on urease activity were screened and the precipitation kinetics were detailly investigated. The results show that the CaCO3 with the largest yield and cohesion was obtained when the bacterial concentration was 107 cells/mL and the concentration of urea and calcium was both 0.5 M at 20 °C. This weight loss of bio-CaCO3 was 9.24% under ultrasonic attack. Secondly, two models were established to quantify or semi-quantify the relationship between the most influential factors and the yield and cohesion of precipitates, respectively. The results showed the order of contribution for bio-CaCO3 precipitation was calcium ions concentration > bacterial concentration > urea concentration > temperature > initial pH. According to these models, the required yield and cohesion of CaCO3 by engineering could be obtained by adjusting affecting factors. Models were proposed for guiding the application of MICP in practical engineering. KEY POINTS: • Screened the most affecting factors on urease activity and investigated the precipitation kinetics. • Obtained optimal conditions of bio-CaCO. • Established two models in order to give some guidance for practical civil engineering.

Biomass-derived Fe-NC hybrid for hydrogenation with formic acid: control of Fe-based nanoparticle distribution.

A series of Fe-NC catalysts were synthesized by pyrolyzing an Fe complex and wheat flour at 500 °C. All of them were characterized and applied in the catalytic transfer hydrogenation of nitroarenes with formic acid. It was found that the catalytic activity was significantly affected by the size and distribution of Fe-based nanoparticles (NPs), which could be easily regulated by altering the Fe source. Meanwhile, more basic nitrogen sites were preserved on the catalyst so that the reaction ran smoothly without base additives. Among all catalysts, Fe-NC-FeCl2 exhibited the best catalytic performance due to smaller Fe3O4 NPs and greater N doping. Moreover, it showed excellent applicability for diverse nitroarenes. Obviously, this work demonstrates the importance of the metallic NPs' size and distribution, providing a new insight into the design of M-NC catalysts. The catalyst is economical and eco-friendly, and shows potential application value in industry.

Controllable Sulfur, Nitrogen Co-doped Porous Carbon for Ethylbenzene Oxidation: The Role of Nano-CaCO3.

Heteroatom-doped porous carbon materials have exhibited promising applications in various fields. In this work, sulfur, nitrogen co-doped carbon materials (SNCs) with abundant pore structure were prepared by pyrolysis of sulfur, nitrogen-containing porous organic polymers (POPs) mixed with nano-CaCO3 at high temperature. Among the resultant materials, SNC-Ca-850 possesses a relatively high level of doped heteroatoms and exhibits an excellent catalytic performance for the selective oxidation of benzylic C-H bonds. It is noteworthy that nano-CaCO3 increases the doped sulfur content in the synthesized carbon materials to a large extent and impacts the existence modes of sulfur. In addition, it enhances the porous structure and specific surface area of the resultant SNCs significantly. This work provides a viable strategy to promote the doping of sulfur into carbon materials during the pyrolysis process.

Cobalt Entrapped in N,S-Codoped Porous Carbon: Catalysts for Transfer Hydrogenation with Formic Acid.

Catalysts with Co nanoparticles (NPs) entrapped in N,S-codoped carbon shells were successfully fabricated by pyrolysis of porous organic polymers (POPs) with cobalt salts. The encapsulated structure consisting of Co NPs and N,S-codoped carbon layers was verified by TEM, XRD, and X-ray photoelectron spectroscopy. The catalysts displayed excellent activity and stability for the catalytic transfer hydrogenation (CTH) of nitrobenzene with formic acid under base-free conditions. Furthermore, the resultant catalysts allowed for highly efficient and selective transfer hydrogenation of various functionalized nitroarenes to the corresponding anilines. Through control experiments, the covered Co NPs were identified as active sites for CTH. The incorporation of S into the N-doped carbon lattice promoted the electron transfer from metallic cobalt NPs to their shells, which played a significant role in the acceleration of CTH. Moreover, the Co-NSPC-850 catalyst pyrolyzed at 850 °C showed excellent stability in the recycling experiments.

A Comparative Study on the Role of Xpert MTB/RIF in Testing Different Types of Spinal Tuberculosis Tissue Specimens.

AIMS: The aim of the present study was to compare the efficacy of the commercial Xpert Mycobacterium tuberculosis/rifampin (MTB/RIF) test for evaluating different types of spinal tuberculosis (TB) tissue specimens. METHODS: Pus, granulation tissue, and caseous necrotic tissue specimens from 223 patients who were diagnosed with spinal TB and who underwent curettage were collected for bacterial culture and the Xpert MTB/RIF assay to calculate the positive rate. Bacterial culture and phenotypic drug sensitivity testing (pDST) were adopted as the gold standards to calculate the sensitivity and specificity of the Xpert bacterial detection and drug resistance (DR) test. RESULTS: The positive rate (68.61% ± 7.35%) from the Xpert MTB/RIF assays of spinal TB patients' tissue specimens was higher compared with bacterial culture (44.39% ± 6.51%, Z = 5.1642, p < 0.01), and the positive rates from Xpert MTB/RIF assays on the three types of specimens were all higher than those of bacterial culture, with statistically significant results for pus and granulation tissue specimens. The positive rates for pus using the two bacteriological tests were higher than those for granulation tissue but were not statistically significant. However, the positive rates obtained from granulation tissue were statistically significantly higher than those obtained from caseous necrotic tissue. With bacterial culture and pDST as the gold standards, the sensitivity of Xpert MTB/RIF assays for MTB was 96.97%, while the sensitivity and specificity of the DR test also remained relatively high. CONCLUSION: For efficient and accurate diagnosis of spinal TB and DR and timely provision of effective treatment, multiple specimens, especially the pus of spinal TB patients, should be collected for Xpert MTB/RIF assays.

Study on the relationship between vitamin D deficiency and susceptibility to spinal tuberculosis.

OBJECTIVE: To investigate the effect of vitamin D deficiency on susceptibility to spinal tuberculosis and its pathological development. METHODS: A case-control design was used in this study. A total of 163 treatment-naïve patients with spinal tuberculosis admitted to this institute for an operation from June 2013 to May 2016 were included in the case group, and 170 subjects who received a health examination in the same hospital were included in the control group. Control group patients were frequency-matched with the case group by age, gender, and season. Serum 25-hydroxyvitamin D levels were detected using an enzyme linked immunosorbent assay (ELISA). Pathological classification of patients in the case group was conducted according to intraoperative findings, and definite diagnosis of spinal tuberculosis was confirmed after operation. RESULTS: The serum level of vitamin D [23.99 (20.55, 29.54) nmol/L] in the case group was lower than that in the control group [42.94 (35.68, 51.04) nmol/L], and the difference was statistically significant (Z = -9.048, P < 0.05). Out of the 163 patients with spinal tuberculosis who underwent pathological classification, 107 cases of caseous necrosis and 56 cases of hyperplasia were identified. Based on the vitamin D levels of the patients in the case group, these patients were further divided into a low-level group (<25 nmol/L) and a high-level group (≥25 nmol/L). The proportion of patients with caseous necrosis in the low-level group (79.17%) was higher than that in the high-level group (46.27%), with a statistically significant difference (χ2 = 18.937, P < 0.05). CONCLUSION: Vitamin D deficiency is associated with susceptibility to spinal tuberculosis and its pathological classification, and vitamin D deficiency affects the occurrence and development of spinal tuberculosis.

Pyreniporphyrins: Porphyrin Analogues That Incorporate a Polycyclic Aromatic Hydrocarbon Subunit within the Macrocyclic Framework.

The first examples of porphyrin analogues incorporating pyrene units are reported. Acid-catalyzed condensation of a pyrene dialdehyde with a tripyrrane, followed by oxidation with DDQ, afforded a polycyclic aromatic hydrocarbon (PAH)-porphyrin hybrid in 38% yield. Pyreniporphyrin proved to be devoid of global aromatic character, but upon protonation aromatic mono- and dicationic species were generated. In the proton NMR spectrum for the dication, the internal CH was shifted upfield to approximately +3 ppm. NICS calculations and ACID plots confirmed the diatropic nature of these structures. Pyreniporphyrin reacted with palladium(II) acetate to give excellent yields of a palladium(II) complex that showed weakly diatropic properties. Treatment of the pyrene dialdehyde with phenylmagnesium bromide generated a dicarbinol that reacted with excess pyrrole in the presence of boron trifluoride etherate to give a tripyrrane analogue. Lewis acid catalyzed ring closure with a thiophene dialcohol in 2% ethanol-dichloromethane afforded a tetraphenylthiapyreniporphyrin in 31% yield. This porphyrinoid was nonaromatic in the free-base form but showed significant diatropicity upon protonation. These results demonstrate that PAH-porphyrin hybrids are easily accessible, and this strategy may allow the incorporation of even larger aromatic subunits.