Comparison of Homo-Polyimide Films Derived from Two Isomeric Bis-Benzimidazole Diamines.

Heteroaromatic polyimides (PIs) containing benzimidazole have attracted tremendous attention due to their positive impact on the properties of PIs. Some research on PIs containing 4,4'-[5,5'-bi-1H-benzimidazole]-2,2'-diylbis-benzenamine (4-AB) has been reported. However, reports are lacking on homo-polyimides (homo-PIs) containing 3,3'-[5,5'-bi-1H-benzimidazole]-2,2'-diylbis-benzenamine (3-AB), which is one of the isomers of 4-AB. In this paper, the influence of amino groups' positions on the performance of homo-PIs was investigated. It was found that the net charge of the amine N group in 4-AB was lower than that of 3-AB, resulting in higher reactivity of 4-AB. Consequently, PIs containing 4-AB displayed better mechanical performance. Molecular simulation confirmed that 3-AB and its corresponding PI chain exhibited distorted conformation, leading to the PI films containing 3-AB having a lighter color. In addition, the 3-AB structure was calculated to have higher rotational energy compared to 4-AB, resulting in a higher glass transition temperature (Tg) in PIs prepared from 3-AB. On the other hand, PIs containing 4-AB exhibited a higher level of molecular linearity, leading to a lower coefficient of thermal expansion (CTE) compared to PIs prepared from 3-AB. Furthermore, all PIs showed higher thermal stability with a 5% weight loss temperature above 530 °C and Tg higher than 400 °C.

Developing Atomically Thin Li1.81H0.19Ti2O5·2H2O Nanosheets for Selective Photocatalytic CO2 Reduction to CO.

Solar-driven CO2 conversion to carbon-based fuels is an attractive approach to alleviate the worsening global climate change and increasing energy issues. However, exploring and designing efficient photocatalysts with excellent activity and stability still remain challenging. Herein, layered Li1.81H0.19Ti2O5·2H2O (LHTO) nanosheets were explored as the photocatalyst for photocatalytic CO2 reduction, and atomically thin LHTO nanosheets with one-unit-cell thickness were successfully constructed for photocatalytic CO2 reduction. The atomically thin LHTO nanosheets exhibited excellent performance for CO2 photoreduction to CO, with a yield rate of 4.0 µmol g-1 h-1, a selectivity of 93%, and over 25 h photostability, dramatically outperforming the bulk LHTO. The better performance of the atomically thin LHTO nanosheets was experimentally verified to benefit from more sites for CO2 adsorption, faster electron transfer rate, and a more negative conduction band edge compared with bulk LHTO. This work provided a methodological basis for designing more efficient photocatalytic CO2 reduction catalysts.

Identification of two aliphatic position isomers between α- and ß-ketoglutaric acid by using a Briggs-Rauscher oscillating system.

This paper reports a novel method for identification of two aliphatic position isomers between α-ketoglutaric acid (α-KA) and ß-ketoglutaric acid (ß-KA) by their different perturbation effects on a Briggs-Rauscher oscillating system, in which tetraaza-macrocyclic complex [NiL](ClO4)2 is used as the catalyst. The ligand L in the complex is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene. The experimental results have shown that addition of α-KA into the system does not affect the oscillating patterns, while the presence of ß-KA in a dynamic system influences the oscillatory amplitude. A more interesting feature is that, in the presence of a higher concentration of ß-KA, there are damped oscillations after the initial spike, followed by quenching (more exactly: very small oscillations) of the oscillations before the subsequent regeneration of oscillations. A qualitative approach was thus established by employing a Briggs-Rauscher system for identification of these two isomers. The concentrations of these two isomers that can be distinguished lie over the range between 5.0 × 10(-6) and 2.5 × 10(-3) mol/L. A reaction mechanism based on the FCA model has been proposed. An explanation is that ß-KA reacts with HOO(•) radicals to form acetone, whereas the α-KA does not.

Non-linear associations of cardiometabolic index with insulin resistance, impaired fasting glucose, and type 2 diabetes among US adults: a cross-sectional study.

Background: Cardiometabolic index (CMI) is a novel indicator for predicting the risk of obesity-related diseases. We aimed to determine the relationships of CMI with insulin resistance (IR), impaired fasting glucose (IFG), and type 2 diabetes mellitus (T2DM) using NHANES data from 1999 to 2020. Methods: After CMI values were estimated, weighted univariate and multivariate logistic regression analyses were used to ascertain whether CMI was an independent risk indicator for IR, IFG, and T2DM. Furthermore, stratified analyses and interaction analyses were carried out to investigate the heterogeneity of correlations across various subgroups. Subsequently, restricted cubic splines (RCS) were used to examine nonlinear relationships. Results: 21,304 US adults were enrolled in our study, of whom 5,326 (22.38%) had IR, 4,706 (20.17%) had IFG, and 3,724 (13.02%) had T2DM. In the studied population, a higher CMI index value was significantly associated with an elevated likelihood of IR, IFG, and T2DM. In the RCS regression model, the relationship between CMI and IR, IFG, and T2DM was identified as nonlinear. A nonlinear inverted U-shaped relationship was found between CMI and IFG, and an inverse L-shaped association was observed between CMI and IR, CMI and T2DM. The cut-off values of CMI were 1.35, 1.48, and 1.30 for IR, IFG, and T2DM, respectively. Conclusion: Our results indicate that CMI was positively correlated with an increase in IR, IFG, and T2DM in the studied population. CMI may be a simple and effective surrogate indicator of IR, IFG, and T2DM.

High-efficiency and durable V-Ti-Nb ternary catalyst prepared by a wet-solid mechanochemical method for sustainably producing acrylic acid via acetic acid-formaldehyde condensation.

Based on the precise phase control V species adjustment of vanadium phosphorus oxides (VPOs), a series of metal oxides (Nb2O5, MoO3, WO3, and Bi2O3) were selected as modification agents to further enhance the catalytic activity and retain the excellent durability of VPO-TiO2-based catalysts for the new procedure of producing acrylic acid via acetic acid-formaldehyde condensation. At an elevated liquid hourly space velocity (LHSV), the (AA + MA) selectivity reached 92.3% with a (MA + AA) formation rate of 63.8 µmol-1 gcat -1 min-1 over the Nb-decorated catalyst (catalyst VTi-Nb), and it maintained good durability for up to 100 h. The detailed characterization results of XRD, Raman, XPS, NH3-TPD, CO2-TPD, and H2-TPR, demonstrated that the addition of Nb2O5 could observably enhance the catalytic efficiency of the VPO-TiO2 catalyst. It not only improved the catalyst durability by enhancing prereduction of the V5+ species, but also enhanced the active site density to improve the catalytic activity.

Synthesis of Manganese Carbonate Templates with Different Morphologies and Their Application in Preparing Hollow MoS2 Micro/Nanostructures for Photocatalysis.

Spherical manganese carbonate (MnCO³) templates were successfully prepared by a facile chemical precipitation method. The size of the as-prepared samples was changed by adjusting the ratio of MnSO4·H2O and NaHCO3 (1:1, 1:5, 1:10 and 1:15). More interestingly, when adding Na2SO4 to the reaction solution, the morphology of MnCO³ further evolved from an irregular spheroid to a cube. Next, spherical and cubic MnCO³ particles with the most uniform size were selected as precursor templates to synthesize intermediate compounds (MnCO³/MnS/MoS2). Eventually, MoS2 microspheres and microcubes with a hollow structure were obtained by removing the MnCO³ and MnS with acid pickling. The structure, morphology and elemental composition of the products were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectrometry (EDS). The results of the photocatalytic experiments show that hollow MoS2 prepared with an MnCO³ template exhibited excellent photocatalytic performance. Therefore, the application of a template method to prepare hollow structure materials is worthy of further study in the photocatalysis field.

Novel Carbon-Based Magnetic Luminescent Nanocomposites for Multimodal Imaging.

Multifunctional nanocomposites can combine multiple functions into a single nanosystem and thus have attracted extensive interest in various fields. The combination of magnetic and upconversion luminescent nanoparticles into one single nanoplatform, which have a good application in biomedical fields such as bio-magnetic separation, magnetic resonance imaging (MRI), and optical imaging, is highly desirable. Here we reported multifunctional nanocomposites by using hollow carbon sphere to integrate magnetic Fe3O4 and upconversion nanoparticles (UCNPs) into one nanosystem. The as-prepared UCNPs/Fe3O4@h-C have near-infrared (NIR) luminescence under 980 nm excitation and superparamagnetism. In addition, since the carbon layer can absorb NIR light and transfer it into heat with high efficiency, the nanocomposites can realize photo thermal (PT), upconversion luminescence (UCL) and MRI tri-mode imaging. The UCNPs/Fe3O4@h-C might be further utilized as a potential theranostic agent, including its in-depth monitoring through luminescent imaging and MRI diagnosis, as well as its direct use in tumors as a photothermal therapy (PTT) agent.

Development of bovine-ovine interspecies cloned embryos and mitochondria segregation in blastomeres during preimplantation.

The objective of the study was to investigate interspecies somatic cell nuclear transfer (iSCNT) embryonic potential and mitochondrial DNA (mtDNA) segregation during preimplantation development. We generated bovine-ovine reconstructed embryos via iSCNT using bovine oocytes as recipient cytoplasm and ovine fetal fibroblast as donor cells. Chromosome composition, the total cell number of blastocyst and embryonic morphology were analyzed. In addition, mtDNA copy numbers both from donor cell and recipient cytoplasm were assessed by real-time PCR in individual blastocysts and blastomeres from 1- to 16-cell stage embryos. The results indicated the following: (1) cell nuclei of ovine fetal fibroblasts can dedifferentiate in enucleated bovine ooplasm, and the reconstructed embryos can develop to blastocysts. (2) 66% of iSCNT embryos had the same number of chromosome as that of donor cell, and the total cell number of iSCNT blastocysts was comparable to that of sheep parthenogenetic blastocysts. (3) RT-PCR analysis in individual blastomeres revealed that the ratio of donor cell mtDNA: recipient cytoplasm mtDNA remained constant (1%) from the one- to eight-cell stage. However, the ratio decreased from 0.6% at the 16-cell stage to 0.1% at the blastocyst stage. (4) Both donor cell- and recipient cytoplasm-derived mitochondria distributed unequally in blastomeres with progression of cell mitotic division. Considerable unequal mitochondrial segregation occurred between blastomeres from the same iSCNT embryos.

Culture, characteristics and chromosome complement of Siberian tiger fibroblasts for nuclear transfer.

Tiger (Panthera tigris Linnaeus, 1758) is a characteristic species of Asia, which is in severe danger. Siberian tiger (Panthera tigris altaica) is the largest one of the five existent tiger subspecies. It is extremely endangered. One new way for tiger protection and rescue is to study interspecies cloning. But there is few research data about Siberian tiger. In this study, we cultured Siberian tiger fibroblasts in vitro, analyzed their biological characteristics, chromosomes, and cell cycles, to provide not only nuclear donors with good morphology, normal biological characteristics, and chromosome quantity for tiger interspecies cloning, but also reliable data for further studying Siberian tiger. The results indicated that Siberian tiger ear fibroblasts can be successfully obtained by tissue culture either with or without overnight cold digestion, the cultured cells were typical fibroblasts with normal morphology, growth curve, and chromosome quantity; G0/G1 percentage increased and S percentage decreased with the confluence of cells. G0/G1 and S stage rate was significantly different between 40-50% and 80-90%, 95-100% confluence; there is no distinct difference between 80-90% and 95-100% confluence. The cells at the same density (80-90% confluence) were treated with or without 0.5% serum starving, GO/G1 rate of the former was higher than the latter, but the difference was not significant. GO/G1 proportion of 95-100% confluence was slightly higher than serum starving (80-90% confluence), but no significant difference. Therefore, the Siberian tiger fibroblasts we cultured in vitro can be used as donor cells, and the donor cells do not need to be treated with normal serum starvation during nuclear transfer; if we will just consider the rate of the G0/G1 stage cells, serum starvation can be replaced by confluence inhibition when cultured cells were more than 80-90% confluence.

[Study on the characteristic and significance of synchronous fluorescence spectrum of crude oil and nature gas samples].

Based on studying characteristic of constant-wavelength synchronous fluorescence spectrum of various kinds of crude oils and nature gases from the large fields of our nation, the similar peak and characteristic peak of various crude oils and nature gas were proposed. This approach has several advantages, including narrowing of spectral bands, simplification of conventional fluorescence spectra, contraction of the spectral range and so on. The technique can be used not only in judging oil and gas layers, types of crude oil, but also in providing the arms of petrolium exploration. In fact, the synchronous fluorescence spectrum and the three dimensional fluorescence spectra are the same in essence. The more achievement will be obtained by replacing the three dimensional fluorescence spectra analysis with the synchronous the fluorescence spectrum analysis.

Micro-nanopores fabricated by high-energy electron beam irradiation: suitable structure for controlling pesticide loss.

Pesticide sprayed onto crop leaves tends to be washed off by rainwater and discharge into the environment through leaching and runoff, resulting in severe pollution to both soil and water. Here, to control pesticide loss, we developed a loss-control pesticide (LCP) by adding modified natural nanoclay (diatomite) through high-energy electron beam (HEEB) to traditional pesticide. After HEEB treatment, the originally clogged pores in diatomite opened, resulting in plenty of micro-nanopores in diatomite, which are beneficial for the pesticide molecules to access and be adsorbed. This pesticide-diatomite complex tended to be retained by the rough surface of crop leaves, displaying a high adhesion performance onto the leaves, so that the pesticide loss reduced, sufficient pesticide for crops was supplied, and the pollution risk of the pesticide could be substantially lowered.