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Carbonate clumped isotope (Δ47) is a new and reliable geothermometer. Endogenic carbonates in lake sediments are good archives to reconstruct lake water temperature using clumped isotope thermometry. However, applications of carbonate clumped isotope thermometry to lacustrine carbonates are still scarce because the existed organic and/or sulfur contaminants in such samples interfere with clumped isotope analysis and cause notable temperature biases. Therefore, exploring an effective way to remove contamination is a prerequisite to widely applying carbonate clumped isotope thermometry to lake sediments. By pretreating fine-grained endogenic carbonates from Dali lake sediments with hydrogen peroxide of different concentrations for different lengths of time, we conducted a series of conditional experiments to seek the optimal pretreatment condition for clumped isotope analysis. Δ47, Δ48 offset and 49 parameter were obtained from clumped isotope measurements to assess the effect of contamination removal. Results showed that untreated samples (“0%-0”) had a very high 49 parameter. After the treatment with hydrogen peroxide, the 49 parameter was significantly reduced while the Δ48 offset evidently increased. The Δ47 , Δ48 offset and 49 parameter of samples pretreated under different conditions showed significant variability, even though the measured Δ47 temperatures changed within a relatively narrow range (i.e., from 17.0±1.3 to 22.8±1.6°C). Among various treated samples, the sample “3%-8” yielded a smaller Δ48 offset and 49 parameter, and lower Δ47 temperature of 17.0±1.3°C. Therefore, “reacting with 3% hydrogen peroxide for 8 h” was suggested to be the optimal condition for removing contaminants from lacustrine endogenic carbonates prior to clumped isotope analysis. At the time when the pretreatment condition was too intense (i.e., H2O2 concentration >3% and/or reaction time > 8 h), secondary contaminants might have been generated in the closed reaction system, whose ultimately transformed state may interfere with masses 47, 48. Using the optimal pretreatment procedure, we obtained reasonable Δ47 temperature changes during the last deglaciation and found a temperature decrease of about 6°C in Northern China during the Younger Dryas period. Our study demonstrates a great potential of applying carbonate clumped isotope thermometry to lacustrine carbonates for paleo-temperature and paleo-elevation reconstructions in the future.

High-dielectric-constant (high-k) polymer/conductor composites with low dielectric loss are desirable for energy storage. However, high leakage currents from interfacial regions with high charge density are difficult to handle. In this work, high permittivity and low dielectric loss were achieved in poly(vinyl alcohol) (PVA)/V2C MXene nanocomposite films fabricated by solution casting by taking advantage of the interfacial compatibility and moderate interfacial charge density of the nanocomposites. Water-soluble PVA was utilized as the polymer matrix. Delaminated V2C MXene nanosheets with appropriate conductivity were prepared and used as the filler. The mild interface polarization of the nanocomposites was responsible for achieving favourable permittivity values. The small gap between the work functions of PVA and V2C contributed to moderate interfacial charge density values and thus low dielectric loss values. A proportional correlation between the interfacial charge density and the conductivity of composites was also verified. The depth of charge injection from the MXene to PVA was found to be half of the interlamellar spacing of the delaminated MXene. The dependence of the electrical properties of the nanocomposites on the frequency and MXene content was also studied. The composite with 4 wt% MXene exhibited a permittivity of ~24 (16 times that of PVA) and a dielectric loss of ~0.14 (1.5 times that of PVA) at 1 kHz, as well as breakdown strength of ~31 MV m−1 (63% of PVA). This work might enable environmentally friendly fabrication of promising composite dielectrics.

Land snail fossils are abundantly distributed in geological deposits and their isotopic compositions provide a means to determine paleoclimatic changes. With the development of the clumped isotopes (Δ47) geothermometer, many efforts have been made in recent years to study clumped isotopes in land snail shell carbonate. Although there have been several recent attempts, there is, as yet, no empirical calibration function to convert land snail Δ47 to environmental temperature. Here, we systematically analyzed clumped isotopes (Δ47) of two common land snail species (Bradybaena and Cathaica) from China. Results showed that temperatures calculated using the Δ47 (T47) of both species did not correlate with the mean annual temperatures (MAT) at the study sites. However, the T47-MAT offset is negatively correlated to MAT, suggesting that land snails tend to add shell during the warmer months at colder sites or modulate their body temperature differently in colder regions. Meanwhile, clumped temperatures of Cathaica are 3.4 ± 1.5 °C higher than those of Bradybaena at 18 sites, indicating that a species-specific transfer function is needed to reconstruct paleotemperature using land snail clumped isotopes. After determining the proper duration of the growing season for land snails at different locations, we developed a Δ47-growth season temperature (GST) transfer function for the two species. The calibration function for Bradybaena land snails is expressed by a linear regression between 1/T2 and absolute Δ47 (R2 = 0.94): Δ47 = (0.0513 ± 0.0036) × 106/T2 + (0.0930 ± 0.0413), where Δ47 is expressed in ‰ and T in K. The calibration function for Cathaica is as follows (R2 = 0.80): Δ47 = (0.055 ± 0.011) × 106/T2 + (0.035 ± 0.129). The function for Cathaica was successfully applied to reconstruct mean summer (June-July-August) temperatures during the Last Glacial Maximum and modern times on the central Chinese Loess Plateau, based on Δ47 data of Cathaica sp. provided by Eagle et al (2013a). This testifies to the validity of the aforementioned constructed transfer function. In addition, the calculated δ18O of body water (δ18OBW) for Bradybaena showed a robust correlation with the δ18O of rainfall (δ18Op), particularly in northern China, which points to the potential to trace hydrological changes in the region. In contrast, Cathaica δ18OBW did not show a straightforward relation to δ18Op. This inter-species complexity warrants further study.

A contradiction between high permittivity and breakdown strength has long been problematic for obtaining high energy density in conductor/polymer composites. Recently, a gradient-sandwich strategy has been employed to achieve favorable dielectric and breakdown properties in metallic inorganic nanoparticles filled polymer nanocomposites. However, a desirable high breakdown strength cannot be retained once the filler concentration is further increased. In this work, metallic TaB2@semiconducting Ta2O5 nanoparticles were employed to prepare polyvinylidene fluoride (PVDF) nanocomposites with a gradient-sandwich construction to induce an interface barrier effect for depressing the growth of electric trees. Interface polarization (between Ta2O5 and PVDF) and interface barrier (between two adjacent sub-layers) effects contributed to an elevation of the permittivity and breakdown strength, respectively. The novelty lies in utilizing the Schottky barrier effect (between Ta2O5 and TaB2) to simultaneously improve the permittivity and breakdown strength of the composites based on the TaB2 electron-trap and induced electron–hole dipoles. A combination of triple effects (Schottky barrier, interface barrier and interface polarization effects) resulted in high permittivity and breakdown strength at the same time. Tri-effect cooperation from the core–shell filler, gradient sandwich structure and organic–inorganic blend was helpful to decrease the temperature-dependence of the electrical properties, increase the electric insulation at high applied field and elevate the dielectric tunability. The comprehensive electric performances of two composite systems filled with TaB2@Ta2O5 and TaB2 were compared. The superiority of the core–shell filler was confirmed. A high breakdown strength of ∼286 MV m−1 and permittivity of ∼126 @ 1 kHz were achieved. This work might open up a door to large-scale preparation of high-performance nanocomposite dielectrics.

Composite dielectrics with high permittivity, low dielectric loss and low conductivity are desired. Low loss and low conductivity are difficult to achieve due to the poor interfacial compatibility and high leakage conductance. In this work, polymer/ionic liquid (IL)/hexagonal boron nitride (h-BN) nanocomposites were fabricated. A synergy between IL and BN was found. The blocked conductive path and reduced dipole coupling contributed to reduced loss and conductivity. Polyvinylidene fluoride (PVDF) was used as the polymeric matrix. The 1-butyl-3-methylimidazolium hexafluorophosphate IL with a high interface compatibility onto PVDF was employed as an organic filler. The ultrahigh polarity of IL contributed to the improved permittivity. BN, with an ultrahigh insulation property, was utilized as an inorganic filler. The BN could block the conductive path and reduce the coupling between the ionic dipoles in the IL. Compared with PVDF/IL composites, the ternary composites showed improved overall electrical properties. The ternary composite with 1.5 wt % IL and 5.0 wt % BN had a high permittivity of ∼46, low loss of ∼0.23 and low conductivity of ∼2.49 × 10−7 S m-1 at 100 Hz. This work might offer the design ideas for the promising composite dielectrics.

Ervaoffine E (1), a new pseudoindoxyl alkaloid possessing a unique rearranged 1,4-diazacycloheptane skeleton, ervaoffine F (2), the first 5,6-seco-6-nor iboga-type alkaloid featuring ring C cleavage, and ervaoffine G (3), bearing an unusual contracted valerolactam ring, together with six known alkaloids were isolated from Ervatamia officinalis. Their structures and absolute configurations were determined by extensive spectroscopic analysis, single-crystal X-ray diffraction and quantum chemical ECD calculations. Plausible biogenetic pathways of these new alkaloids were also proposed and provided new insights into the structural plasticity of ring C in iboga-type alkaloids. Compound 3 exhibited a significant neuroprotective effect against oxygen-glucose deprivation (OGD)-induced damage of cultured cortical neurons, an in vitro model of ischemic stroke.

Bismuth ferrite (BiFeO3) acting as a significant multiferroic material exhibits unique magnetic and ferroelectric properties. Here we report the size-controlled synthesis of BiFeO3 nanoparticles via a facile and stable Pechini sol–gel method, in which uses tartaric acid as a complexing agent, ethylene glycol as a polymerizing agent. It is found that the nanoparticle size is sensitive to the gel-forming temperature. The nanoparticles with size as small as 30 nm have been obtained. A sequential reaction process and the mechanism of size controllable growth of BiFeO3 has been presented. The effects of size on optical and magnetic properties have been also investigated. The decreasing particles lead to blue shift in the band gap. BiFeO3 nanoparticles show weak ferromagnetic character due to a Fe3+ oxidation state, and the magnetization increases with decrease in the particle size.

It is known that CH3NH3PbI3 perovskite films with high crystallization and controlled morphology always show enhanced power conversion efficiency. Here we incorporate a small amount of polyvinylidene fluoride–trifluoroethylene polymer P(VDF-TrFE) into PbI2 solution to control the crystallinity and morphology of perovskite layer in a two-step deposition process. Our results show that the P(VDF-TrFE) bridges the grain boundaries and also enhances the crystallinity of the perovskite layer significantly. By adjusting P(VDF-TrFE) concentration, the fabricated perovskite solar cells show improved average power conversion efficiency from 9.57 ± 0.25% to 12.54 ± 0.40% under a standard illumination of 100 milliwatts per square centimeter, which increases by nearly 31%. Thus, we demonstrate a new strategy to control the crystallinity and morphology of perovskite films by incorporating polymer into PbI2 film in a two-step deposition process. In addition, this method has been proven as an effective way to prepare hig...

Five novel compounds, including four neoclerodane diterpenoids, named ajugacumbins KN (1-4) along with a phytoecdysterone, named ajugacetalsterone E (5), were isolated from the whole herbs of Ajuga decumbens (Labiatae). Their structures were elucidated on the basis of detailed spectroscopic analysis including IR, HRESIMS, CD, 1D and 2D NMR spectroscopic experiments. Compounds 1-5 were evaluated for their cytotoxic activities and the effects on superoxide anion generation and elastase release in FMLP/CB-induced human neutrophils.

Anstifolines A and B, two dimeric furoquinoline alkaloids with unique coupling patterns were isolated from the root bark of Dictamnus angustifolius. The biosynthetic pathway of anstifoline A was proposed. All of the isolates exhibited cytotoxicities and inhibition of superoxide anion generation and elastase release.

Two pairs of new enantiomeric benzofurans with unusual skeletons, (+)- and (−)-eupachinin A (1), as well as (+)- and (−)-eupachinin B (2), were isolated from the roots of Eupatorium chinense by chiral HPLC. Their structures with absolute configurations were elucidated on the basis of spectroscopic methods, X-ray diffraction analysis, and quantum chemical calculation. The plausible biogenetic pathway of 1 and 2 was also proposed.

Three novel limonoids, dictangustone G (1), dictangustone H (2), and dictangustone I (3) were isolated from the root bark of Dictamnus angustifolius. Their structures were elucidated on the basis of detailed spectroscopic analysis including UV, IR, HRESIMS, 1D and 2D NMR spectroscopic experiments. Compounds 1–3 were evaluated for their cytotoxic activities using Hela, A549, MCF7, and LN229 cell lines.

Anstifolines A (I) and B (II) are isolated together with two known compounds, dictamnine and robustine.

In this paper, the feasibility of preparing activated carbon from corncob furfural residue with ZnCl2 by microwave irradiation was studied. The effect of the ratio by weight of ZnCl2 to corncob furfural residue, ZnCl2 solution soaking time, microwave irradiation time and the pH value of ZnCl2 solution on the quality of activated carbon was investigated. On the condition that the microwave power is 800 W and ZnCl2 solution mass concentration is 50%, the best technological parameter on preparing activated carbon with ZnCl2 by microwave irradiation is obtained: at the ratio of 3.5:1 by weight of ZnCl2 to corncob furfural residue, microwave irradiation time is 20 min, ZnCl2 solution soaking time is 12 h, the pH value of ZnCl2 solution is 2, the activated carbon yield reached 33.1% and the decolorizing capacity for methylene blue is 202.5 mg/g, the product is used in treating Cr6+ solution(pH value 4.0, concentration 50 mg/L), its adsorption capacity of Cr6+ is 7.583 mg/g.

A new cycloartane-type triterpenoid, named 22-hydroxy-cyclolaudenol (1), together with two known cycloartane-type triterpenoids were isolated from the roots of Dianella ensifolia. Their structures were determined based on spectroscopic methods, including UV, IR, HR-ESI-MS, NMR and X-ray diffraction. Compound 1 displayed cytotoxic effects against cancer cell lines B16-F10, A549 and MDA-MB-231.

Ervahainine A ( 1 ), a new cyano-substituted oxindole alkaloid, was isolated from Ervatamia hainanensis . The structure was elucidated on the basis of spectroscopic methods and further confirmed by the single-crystal X-ray diffraction analysis. Ervahainine A exhibited potential inhibition against two human cancer cell lines.

Seven new iboga-type alkaloids, ervaoffines A–D (1–4), (7S)-3-oxoibogaine hydroxyindolenine (5), ibogaine-5,6-dione (6), and 19-epi-5-oxovoacristine (7), and 10 known alkaloids were isolated from Ervatamia officinalis. The absolute configurations of 1–7 were determined through X-ray diffraction and electronic circular dichroism (ECD) analyses. Ervaoffines A and B represent the first iboga-type pseudoindoxyl alkaloids in which the C-2 spiro carbon configuration is opposite to that of other members of this class, such as iboluteine (8). The relationship between the absolute configuration of the spiro carbons and the Cotton effect in the ECD spectrum is established for the first time for iboga-type pseudoindoxyl and oxindole alkaloids. Additionally, a plausible biogenetic pathway for these alkaloids is proposed.