Search

In this study, three new germacranolide sesquiterpenes (1-3), together with six related known analogues (4-9) were isolated from the whole plant of Carpesium cernuum. Their structures were established by a combination of extensive NMR spectroscopic analysis, HR-ESIMS data, and ECD calculations. The anti-leukemia activities of all compounds towards three cell lines (HEL, KG-1a, and K562) were evaluated in vitro. Compounds 1-3 exhibited moderate cytotoxicity with IC50 values ranging from 1.59 to 5.47 μmol·L-1. Mechanistic studies indicated that 2 induced apoptosis by decreasing anti-apoptotic protein Bcl-2 and activating the caspase family in K562 cells. These results suggest that compound 2 is a potential anti-leukemia agent.

Potato insurance plays an important role in transferring agricultural risks to promote the potato staple strategy. Understanding farmers' real preferences for potato insurance attributes is important to improve the potato insurance. In this study, a choice experiment was designed with attributes such as peril, minimum compensation ratio for production loss, types of crops covered by insurance, annual premium per mu after subsidy, and complexity of claims procedures. We constructed a mixed logit model based on a questionnaire survey of 362 potato farmers' choices of insurance attributes from 24 villages in Dingxi City of Gansu Province using random sampling. The results show that: (1) farmers prefer agricultural insurance with widely perils including output price drop and input cost risk; (2) farmers who have suffered plant disease and insect and pest damage are willing to pay a high premium for the insurance with a high compensation ratio and several types of crops covered; full-time farmers and large-scale farmers preferred insurance products with low complexity of claims procedures. Therefore, new potato insurance design could be considered specifically for different farmer groups such as those who had previous disaster experiences, and large- or small-scale farm operations.

Hydrogen abstraction reaction of hydrogen sulfide (H2S) by molecule oxygen (O2) forming hydroperoxyl radical (HO2) and hydrosulfide radical (SH) is very important for both atmospheric and combustion chemistry. This work reports a systematic theoretical study on this reaction using a combination of high-level quantum chemistry methods and chemical kinetic theory. Geometry optimizations for all species are performed at QCISD/cc-pVQZ level of theory. The energies for minima and transition state are computed using both single- and multi-reference ab initio methods. It is found that the transition state of this reaction exhibits significant multi-reference nature based on 〈S2〉 and T1 diagnostic during CCSD(T) calculations. The predicted reaction barrier from high-level multi-reference CASPT2(20e,13o)/aug-cc-pVTZ method is higher than those from CCSD(T) and W1BD methods by 6–7 kcal mol−1. Reaction energy barriers from a series of DFT methods also show large deviations compared with both single- and multi-reference methods. Thermal rate constants are calculated over a temperature range from 300 to 2500 K by employing canonical transition state theory with Eckart tunneling correction and the treatment of torsional mode. This work provides accurate rate constants for this reaction and fundamental benchmark results for H/O/S reaction systems, which is valuable for theoretical chemistry and kinetic modeling of sulfur chemistry.

Two new highly oxygenated germacranolides, Carpescernolides A (1) and B (2), were isolated from the whole plant of Carpesium cernuum. Their structures were established by extensive analysis of NMR spectra, as well as HRESIMS data. X-ray diffraction studies were used to confirm the absolute configurations of 1 and 2. Notably, compound 1, with an oxygen bridge unit (C-2–O-C-5) and a 4, 8-ketal system at C-8, resulted in a novel type of germacranolide compound. Compound 1 showed a moderate inhibition against SMMC-7721 cancer cells in vitro.

Stability is one of essential factors for evaluating the photoelectrochemical (PEC) water splitting performance on photocorroded semiconductors for practical applications. Cocatalyst decoration can only maintain the stability for several hours, and organic/inorganic hybrid photoelectrodes (e.g. polymer coated photoelectrodes) also has a limited durability. Therefore, it is challenging to develop a facile but effective approach for stabilizing the photoelectrodes. In this work, we induced a handful of cheap urea into the Ni,Fe-based hydroxides as robust and conformal OECs layers, deposited on the BiVO4 photoanodes by an one-step impregnation process. Urea, an assisted nitrogen/carbon source, played an active role on the uniform growth of ultrathin OEC layer, replacing the complex organic cocatalyst. The thickness of urea induced Ni,Fe-based OEC could be modified by tuning the amount of urea, thereby improving the carrier dynamics and protecting photoelectrodes from photocorrosion. The presence of urea facilitates to deposit a homogeneous cocatalyst layer with higher electron transfer than the absence of urea, resulting in a high electrocatalytic OER and PEC performance. The optimized urea-NiFeOOH/BiVO4 photoanode showed a photocurrent density of 4.8 mA cm−2 at 1.23 VRHE with impressive stability over 40 h at a potential of 0.8 VRHE, which is one of the best PEC stabilities using NiFe-based OECs on BiVO4. Benefiting from the strong coordination bond between the metal ions and urea, the C and N elements remained stable in the OEC layer before and after PEC test. This work presents a potential application using cheap, non-precious metal based electrocatalysts to overcome the bottle-necks limiting a long-term stability of PEC water splitting.

The added mass forces of three-dimensional (3D) flapping wings of some representative insects, and the accuracy of the often used simple two-dimensional (2D) method, are studied. The added mass force of a flapping wing is calculated by both 3D and 2D methods, and the total aerodynamic force of the wing is calculated by the CFD method. Our findings are as following. The added mass force has a significant contribution to the total aerodynamic force of the flapping wings during and near the stroke reversals, and the shorter the stroke amplitude is, the larger the added mass force becomes. Thus the added mass force could not be neglected when using the simple models to estimate the aerodynamics force, especially for insects with relatively small stroke amplitudes. The accuracy of the often used simple 2D method is reasonably good: when the aspect ratio of the wing is greater than about 3.3, error in the added mass force calculation due to the 2D assumption is less than 9%; even when the aspect ratio is 2.8 (approximately the smallest for an insect), the error is no more than 13%.

Engineering the interfacial structure of hybrid catalysts is crucial for enhanced electrocatalytic performances. Herein, a new strongly heterogeneous catalyst of Co/CoO/Co(OH)2 nanowires with proper interfacial structure was synthesized via a plasma etching approach. X-ray photoelectron spectroscopy and electron energy loss spectroscopy revealed that strong chemical couplings at the hybrid interface induced fast charge transfer, leading to considerable amounts of Co2+/Co sites present in the hybrid. The high conductivity from metal Co and one dimensional nanostructure favored the electron transfer and electrolyte access. The metallic Co was further oxidized to Co2+/Co3+ to address instability under applied potential during long-term testing. The resulting catalyst exhibited an excellent overpotential of 266 mV at 20 mA cm−2 and a Tafel slope of 85 mV dec−1 in alkaline medium. Importantly, the hybrid Co/CoO/Co(OH)2 demonstrated a super long-term durability over 200 h among the most ultra-long stability Co-based OEC catalysts. This catalyst was applied on light absorbing BiVO4 for solar-driven water splitting, exhibiting a significantly enhanced photoelectrochemical (PEC) activity, 5.32 mA cm−2 obtained at 1.23 VRHE, which represented one of the best performances achieved by Co-based OER cocatalysts.

Eleven triterpenoids were isolated from the fruits of Phellodendron chinense Schneid, and their structures were determined by spectroscopic analysis. The results show that four new tirucallane-type triterpenoids 1, 2, 5, and 6 and seven known compounds 3, 4, 7, 8, 9, 10, and 11 were isolated. Structurally, compound 6 was uncommon; it has a chlorine atom instead of a methyl group at the C-20 position. The cytotoxicities of the compounds was evaluated against the in vitro proliferation of four human tumor cell lines HEL, K562, MDA, and PC3 using adriamycin as the positive control. Compound 1 showed a similar cytotoxicity as the positive control; compounds 3 and 10 showed moderate cytotoxicities compared to the control (P

The growing interest in the use of bio-oils requires a detailed understanding of its combustion chemical kinetics. Bio-oils contain a large variety of oxygenated organic species, in which substituted phenolic compounds are among the most significant fractions. Hence, accurate assessment of key reaction rate constants and systematically investigated the structural effect on the reactivity are critical. This work reports a systematic theoretical study of the hydrogen abstraction reactions from phenol, anisole, o-guaiacol, m-guaiacol, and p-guaiacol, which are considered as reference components in bio-oil surrogates. The hydrogen abstraction reactions by five different radicals (H/CH3/O(3P)/OH/HO2) are investigated at ROCBS-QB3//M06-2X/cc-pVTZ level. The high-pressure limit rate constants are computed via transition state theory with Eckart tunnelling and the 1-D hindered rotor approximation. Comparisons of site-specific hydrogen abstractions from the studied species with other related species are performed to understand the effects of the aromatic ring and side-chain substituent on hydrogen abstractions.

Allele frequencies for 12 X STR loci (DXS8378, DXS10159, DXS10162, DXS10164, DXS981, DXS6789, DXS7424, DXS101, DXS7133, GATA165B12, GATA31E08 and DXS7423) were obtained from a sample of 518 unrelated individuals from Shaanxi, China. We observed a total of 108 alleles in the group with the allelic frequency values ranging from less than 0.0014 to 0.6768. Our statistic analysis indicates that the 12 X STR conform to the Hardy-Weinberg's equilibrium. Heterozygosity among the studied 12 X STR loci showed a distribution of 42.33-86.20%. This is first report on allele frequencies of DXS10162 from Han population. The results may provide useful information for forensic sciences and population genetics studies. The present findings indicate that the 12 X STR loci are highly genetically polymorphic in the Han population of Shaanxi.

The longitudinal dynamic flight stability of a model dragonfly at hovering flight is studied, using the method of computational fluid dynamics to compute the stability derivatives and the techniques of eigenvalue and eigenvector analysis for solving the equations of motion. Three natural modes of motion are identified for the hovering flight: one unstable oscillatory mode, one stable fast subsidence mode and one stable slow subsidence mode. The flight is dynamically unstable owing to the unstable oscillatory mode. The instability is caused by a pitch-moment derivative with respect to horizontal velocity. The damping force and moment derivatives (with respect to horizontal and vertical velocities and pitch-rotational velocity, respectively) weaken the instability considerably. The aerodynamic interaction between the forewing and the hindwing does not have significant effect on the stability properties. The dragonfly has similar stability derivatives, hence stability properties, to that of a one-wing-pair insect at normal hovering, but there are differences in how the derivatives are produced because of the highly inclined stroke plane of the dragonfly.

A proton exchange membrane's conductivity increases with increasing water content. However, water on the electrode surface inhibits the inlet of oxidant/fuel, resulting in lower performance of the proton exchange membrane fuel cell (PEMFC). Therefore, water management is a critical issue that needs to be addressed in low-temperature PEMFCs. Two strategies used to manage water are the embedding of hydrophobic materials in the electrode (catalyst or gas diffusion layer), and controlling the fuel/oxidant flow rate. In this study, ladder-structure flow fields were manufactured with hydrophobic PTFE materials coated on different ladders. These were used to investigate the effect of oxidant flow rate and oxidant humidity on PEMFC performance and dynamic variation. We have found that using a flow field with hydrophobic PTFE coated on the second ladder (from the GDL) results in the greatest improvement in performance and durability.

In this paper, we study the aerodynamic interactions between the contralateral wings and between the body and wings of a model insect, when the insect is hovering and has various translational and rotational motions, using the method numerically solving the Navier-Stokes equations over moving overset grids. The aerodynamic interactional effects are identified by comparing the results of a complete model insect, the corresponding wing pair, single wing and body without the wings. Horizontal, vertical and lateral translations and roll, pitch and yaw rotations at small speeds are considered. The results indicate that for the motions considered, both the interaction between the contralateral wings and the interaction between the body and wings are weak. The changes in the forces and moments of a wing due to the contralateral wing interaction, of the wings due to the presence of the body, and of the body due to the presence of the wings are generally less than 4.5%. Results show that aerodynamic forces of wings and body can be measured or computed separately in the analysis of flight stability and control of hovering insects.

Sporamin is a soluble protein in sweet potato, and falls into two distinct homology groups, subfamilies A and B. In this research, a sporamin B was purified and its amino acid sequences, trypsin inhibitor activity (Ti activity) were analyzed. This sporamin B was isolated from sweet potato tubers [Ipomoea batatas (L.) Lam cv. 55-2] through extraction of the water-soluble fraction, dialysis, ultrafiltration and ion-exchange chromatography. Homology determined by polyacrylamide gel electrophoresis showed that mainly one bond appeared in gel after being reduced by SDS (sodium dodecyl sulfate), or by SDS and 2-mercaptoethanol, or in native situation. By comparing the data of the polypeptide mass Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry with those of the mass of the theoretical amino acid sequences from NCBI protein database, it was revealed that it was Q40091|Q40091_IPOBA, sweet potato sporamin B – Ipomoea Batatas (sweet potato) (Batate). The sequence coverage was 70.6%. N-terminal sequence was SETPV (Ser-Glu-Thr-Pro-Val). There is a linear relationship between trypsin inhibitor activity (Ti activity) and amounts of this sporamin B (3-18 μg mL−1). The equation of linear regression was y = 2.5809x + 17.049 (r2 = 0.9966). There was a curvilinear relationship between Ti activity and amounts of this sporamin B (21–150 μg mL−1). The equation of curvilinear regression is y = 14.417ln(x) + 23.26 (r2 = 0.9924). The concentration of sporamin B with Ti activity after heating at 40°C may induce part denature of this sporamin B, and there was no statistic difference after heating at 40, 50, 60°C for 20 min. Heat treatment at more than 90°C leads to a dramatic decrease of trypsin inhibitor efficiency. The results suggested that Q40091|Q40091_IPOBA was the major sporamin B in sweet potato tubers [Ipomoea Batatas (L.) Lam cv. 55-2], which had strong Ti activity, and was stable to both thermal and DTT (DL-dithiothreitol) relatively.

Objective To investigate the characteristics of fat metabolism in rat skeletal muscle after hypobaric hypoxia acclimation.

An asymmetric synthesis of chiral intermediate 15 for (+)-gliocladin C has been accomplished from N-phthaloyl l -tryptophan methyl ester.

Oxidative stress, the result of cellular production of reactive oxygen species (ROS), has been implicated in a number of diseases of the eye. Exposure of eye tissues (e.g. the cornea and retina) to oxidative stress over time has been hypothesized to underlie the development of age-related macular degeneration (AMD) and maturity onset cataract formation. Light-induced free radicals can damage the eye, and alterations in the antioxidant defenses of the eye have been suggested to play a role in the etiology of glaucoma. Mitochondria are both a major endogenous source and target of ROS, and oxidative stress has been shown to induce apoptotic cell death by targeting the mitochondria directly. Mitochondrial-dependent apoptosis has been shown to require release of cytochrome c from mitochondria and subsequent activation of a specific class of cytoplasmic proteases known as caspases. Bcl-2, an anti-apoptotic protein localized to mitochondria, has been shown to inhibit cytochrome c release and protect against oxidative stress-induced apoptosis. Here we demonstrate that oxidative stress causes activation of mitochondrial matrix caspase-2 and -9 activity that is associated with Bcl-2-inhibitable acidification of mitochondrial pH (pH(m)). In conjunction with recent reports that caspase activation is maximal at acidic pH, these findings have led us to hypothesize that Bcl-2 may modulate cytochrome c release following oxidative stress by modifying the pH-dependent activation of mitochondrial caspase activity. These studies provide an increased understanding of the mechanism(s) by which oxidative stress damages tissues, and may have important therapeutic implications for treatment of opthamological diseases.

In this decade, the production of Penaeus monodon using the traditional open pond method decreased seriously due to disease that spread via seawater. In order to prevent the introduction of pathogenic micro-organisms from seawater, a recirculating system was constructed and tested in this study. This system includes culture tanks (CT), a lamella separator (LS), an aeration tank (AT), a submerged biofilter (BF) and an aeration reservoir (R). The prawns were cultured at three stocking densities (40, 80 and 160 prawn m−2, each density in triplicate) for 8 weeks. During the experiment, the water quality in CT was stable. The daily variations of temperature, pH, DO and ammonia were small. For prawns cultured at densities of 40, 80 and 160 prawn m−2, the average body weights (BW, g) increased from 7.8±0.1 to 23.3±0.6 g, 5.4±0.1 to 18.3±0.4 g and 5.7±0.1 to 15.1±0.5 g, respectively. The average growth rates (GR, g day−1) were 0.28±0.02, 0.23±0.00 and 0.17±0.02 g day−1, respectively. The survival rates (SR, %) were 89±6, 76±2 and 60±0%, respectively. These results show that the recirculating system could be used for P. monodon culture.

When packaged in a bacteriophage capsid, double-stranded DNA occupies a cavity whose volume is roughly twice the volume of the DNA double helix. The data thus far have not revealed whether the compactness of packaged bacteriophage DNA is achieved by folding of the DNA, undirectional winding of the DNA, or a combination of both folding and winding. To assist in discriminating among these possibilities, the present study uses electron microscopy, together with ultraviolet light-induced DNA-DNA cross-linking, to obtain the following information about the conformation of DNA packaged in the comparatively large bacteriophage, G: 1) At the periphery of some negatively stained particles of bacteriophage G, electron microscopy reveals standards of DNA that are both parallel to each other and parallel to the polyhedral bacteriophage G capsid. However, these strands are not visible toward the center of the zone of packaged DNA. 2) Within some positively stained particles, electron microscopy reveals DNA-associated stain in relatively high concentration at corners of the polyhedral bacteriophage G capsid. 3) When cross-linked DNA is expelled from its capsid during preparation for electron microscopy, some DNA molecules consist primarily of a compacted central region, surrounded by DNA strands that appear to be unravelling at multiple positions uniformly distributed around the compacted DNA region. The above results are explained by a previously presented model in which DNA is compacted by folding to form 12 icosahedrally arranged pear-shaped rings.

The fibrous network of those agarose gels typically used for electrophoresis is too fine to observe by light microscopy. In the present study, light microscopy, apparently for the first time, reveals the fibrous network of an agarose gel that has a micrometer-scale fibrous network. The agarose used is a derivatized, irradiated agarose previously shown by electron microscopy to have the following characteristic: When a 1.5% gel is cast at 30°C, but not at 10°C, fibrous bundles of agarose chains partition to form wider fibers that, in turn, form a network that has micrometer-sized and larger pores. When observed by phase-contrast light microscopy, gels cast at 30°C have a clearly defined fibrous network not present for gels cast at 0°C. The temperature-dependence of the network observed by light microscopy indicates that this network is the same as the micrometer-scale network observed by electron microscopy. For the network observed by light microscopy, the mean chord length varies inversely with the agarose concentration. The least concentrated gel observed had a concentration of 0.3%. Slight pressure on a 0.4% gel caused microfracture of the gel, thereby producing pores of a dimension between 5 and 50 μm. These pores, freely permeable to latex spheres, will be useful for determining the hydrodynamic damping of intrapore, single-particle motion by gel fibers.