13 research outputs found
Studies on the effect of Celastrus orbiculatus (Celastraceae) extract on chemosensitivity of liver cancer cells via Wnt/β-catenin pathway
Purpose: To examine the efficacy of Celastrus orbiculatus extract (COE) on the chemosensitivity of liver cancer (LC) cells and its mechanism of action.Methods: Hep G2/ADM cells in the logarithmic growth phase were assigned to a control group (no treatment for cell culture medium only) and a study group (120 μg/ml COE added to the culture medium). After 48 h of incubation, the biological responses were compared. The study group wasdivided into groups A and B, while control group was divided into groups C and D, with 1 μmol/L XAV939 added in groups A and C. Cell proliferation, cell invasion, cell apoptosis rate, and apoptosis protein in the four groups were evaluated.Results: The study group showed significantly lower values in terms of cell proliferation and cell invasiveness (p < 0.05) and a higher apoptotic rate than the control group (p < 0.05)). The study group also demonstrated an elevated pro-apoptotic protein Bax level and a declined anti-apoptotic protein Bcl-2 level. In contrast to group B, the proliferation and invasiveness of Hep G2/ADM cells in group A treated with the inhibitor, XAV939, were significantly lower (p < 0.05), while the apoptotic rate exhibited a significant increase (p < 0.05). There was a rise in the level of pro-apoptotic protein, Bax, and a fall in the anti-apoptotic protein Bcl-2 level in group A. Lower levels of β-catenin, c-Myc, and cyclin D1 protein were observed in the study group compared with the control group (p < 0.05). Compared with other groups, the multiplication capacity and invasiveness of cells in group A treated with COE and inhibitor XAV939 significantly declined, while the apoptotic rate increased (p < 0.05).Conclusion: COE reverses drug resistance in chemotherapy by inhibiting the expression of Wnt/β-catenin pathway in LC cells. Therefore, COE has potentials for use along with chemotherapeutic agents in the management of liver cancer
Investigation of cracks in GaN films grown by combined hydride and metal organic vapor-phase epitaxial method
Cracks appeared in GaN epitaxial layers which were grown by a novel method combining metal organic vapor-phase epitaxy (MOCVD) and hydride vapor-phase epitaxy (HVPE) in one chamber. The origin of cracks in a 22-μm thick GaN film was fully investigated by high-resolution X-ray diffraction (XRD), micro-Raman spectra, and scanning electron microscopy (SEM). Many cracks under the surface were first observed by SEM after etching for 10 min. By investigating the cross section of the sample with high-resolution micro-Raman spectra, the distribution of the stress along the depth was determined. From the interface of the film/substrate to the top surface of the film, several turnings were found. A large compressive stress existed at the interface. The stress went down as the detecting area was moved up from the interface to the overlayer, and it was maintained at a large value for a long depth area. Then it went down again, and it finally increased near the top surface. The cross-section of the film was observed after cleaving and etching for 2 min. It was found that the crystal quality of the healed part was nearly the same as the uncracked region. This indicated that cracking occurred in the growth, when the tensile stress accumulated and reached the critical value. Moreover, the cracks would heal because of high lateral growth rate
Study on the Influence of Different Factors on Pneumatic Conveying in Horizontal Pipe
Aiming at the problems of high energy consumption and particle breakage in the pneumatic conveying process of large-scale breeding enterprises, in this paper, based on the theoretical calculated value of particle suspension velocity, a computational fluid model and a discrete element model are established based on computational fluid dynamics (CFD) and discrete element method (DEM). Then, through the numerical simulation of gas-solid two-phase flow, the influence of four factors of conveying wind speed, particle mass flow rate, pipe diameter, and particle size on the velocity distribution of particles in a horizontal pipe, dynamic pressure change in the pipe, pressure drop in the pipe, and solid mass concentration are studied. The results show that the k-ε turbulence model can better simulate the movement of gas-solid two-phase flow, and through the analysis of the simulation, the influence of four different factors on the conveying characteristics is obtained, which provides a scientific basis for the construction of the conveying line
Characteristics of Soil Organic Carbon Fractions and Stability along a Chronosequence of Cryptomeria japonica var. sinensis Plantation in the Rainy Area of Western China
Soil organic carbon (SOC) is critical for carbon cycling and sequestration in forest ecosystems. However, how stand age affects SOC components and stability still remains poorly understood. Here, soil samples (0–20 cm) were collected from Cryptomeria japonica var. sinensis (L. f.) D. Don plantations of seven stand ages (6, 12, 23, 27, 32, 46, 52 a) in the rainy area of western China. SOC fractions, including soil particulate organic carbon (POC), easily oxidizable carbon (EOC), labile organic carbon (LOC), recalcitrant organic carbon (ROC), and light fraction organic carbon (LFOC), were determined to explore the nature of carbon components and stability across a chronosequence of C. japonica plantation. Soil carbon fractions first increased and then trended to be stable with an increase in stand age. SOC concentrations were the largest in mature forests (27 or 32 a), but the concentrations of other carbon components often peaked in early over-mature forests (46 a). The concentrations of all carbon fractions were the lowest in the young forests (6 a). The ratios of ROC/SOC increased and LOC/SOC decreased with increasing stand age. Almost all carbon fractions were positively correlated with soil bulk density and negatively correlated with soil moisture. The allometric exponent of ROC or HFOC and soil physicochemical properties was higher as compared to LOC and LFOC. The results noted in this study indicate that SOC components often accumulate fast over the first 20 years of afforestation and SOC stability increases with increasing stand age for C. japonica plantation in this specific region
Investigation of cracks in GaN films grown by combined hydride and metal organic vapor-phase epitaxial method
Abstract Cracks appeared in GaN epitaxial layers which were grown by a novel method combining metal organic vapor-phase epitaxy (MOCVD) and hydride vapor-phase epitaxy (HVPE) in one chamber. The origin of cracks in a 22-μm thick GaN film was fully investigated by high-resolution X-ray diffraction (XRD), micro-Raman spectra, and scanning electron microscopy (SEM). Many cracks under the surface were first observed by SEM after etching for 10 min. By investigating the cross section of the sample with high-resolution micro-Raman spectra, the distribution of the stress along the depth was determined. From the interface of the film/substrate to the top surface of the film, several turnings were found. A large compressive stress existed at the interface. The stress went down as the detecting area was moved up from the interface to the overlayer, and it was maintained at a large value for a long depth area. Then it went down again, and it finally increased near the top surface. The cross-section of the film was observed after cleaving and etching for 2 min. It was found that the crystal quality of the healed part was nearly the same as the uncracked region. This indicated that cracking occurred in the growth, when the tensile stress accumulated and reached the critical value. Moreover, the cracks would heal because of high lateral growth rate.</p
Highly Efficient and Exceptionally Durable CO<sub>2</sub> Photoreduction to Methanol over Freestanding Defective Single-Unit-Cell Bismuth Vanadate Layers
Unearthing
an ideal model for disclosing the role of defect sites
in solar CO<sub>2</sub> reduction remains a great challenge. Here,
freestanding gram-scale single-unit-cell <i>o</i>-BiVO<sub>4</sub> layers are successfully synthesized for the first time. Positron
annihilation spectrometry and X-ray fluorescence unveil their distinct
vanadium vacancy concentrations. Density functional calculations reveal
that the introduction of vanadium vacancies brings a new defect level
and higher hole concentration near Fermi level, resulting in increased
photoabsorption and superior electronic conductivity. The higher surface
photovoltage intensity of single-unit-cell <i>o</i>-BiVO<sub>4</sub> layers with rich vanadium vacancies ensures their higher
carriers separation efficiency, further confirmed by the increased
carriers lifetime from 74.5 to 143.6 ns revealed by time-resolved
fluorescence emission decay spectra. As a result, single-unit-cell <i>o</i>-BiVO<sub>4</sub> layers with rich vanadium vacancies exhibit
a high methanol formation rate up to 398.3 μmol g<sup>–1</sup> h<sup>–1</sup> and an apparent quantum efficiency of 5.96%
at 350 nm, much larger than that of single-unit-cell <i>o</i>-BiVO<sub>4</sub> layers with poor vanadium vacancies, and also the
former’s catalytic activity proceeds without deactivation even
after 96 h. This highly efficient and spectrally stable CO<sub>2</sub> photoconversion performances hold great promise for practical implementation
of solar fuel production
Defect-Mediated Electron–Hole Separation in One-Unit-Cell ZnIn<sub>2</sub>S<sub>4</sub> Layers for Boosted Solar-Driven CO<sub>2</sub> Reduction
The
effect of defects on electron–hole separation is not
always clear and is sometimes contradictory. Herein, we initially
built clear models of two-dimensional atomic layers with tunable defect
concentrations, and hence directly disclose the defect type and distribution
at atomic level. As a prototype, defective one-unit-cell ZnIn<sub>2</sub>S<sub>4</sub> atomic layers are successfully synthesized for
the first time. Aberration-corrected scanning transmission electron
microscopy directly manifests their distinct zinc vacancy concentrations,
confirmed by positron annihilation spectrometry and electron spin
resonance analysis. Density-functional calculations reveal that the
presence of zinc vacancies ensures higher charge density and efficient
carrier transport, verified by ultrafast photogenerated electron transfer
time of ∼15 ps from the conduction band of ZnIn<sub>2</sub>S<sub>4</sub> to the trap states. Ultrafast transient absorption
spectroscopy manifests the higher zinc vacancy concentration that
allows for ∼1.7-fold increase in average recovery lifetime,
confirmed by surface photovoltage spectroscopy and PL spectroscopy
analysis, which ensures promoted carrier separation rates. As a result,
the one-unit-cell ZnIn<sub>2</sub>S<sub>4</sub> layers with rich zinc
vacancies exhibit a carbon monoxide formation rate of 33.2 μmol
g<sup>–1</sup> h<sup>–1</sup>, roughly 3.6 times higher
than that of the one-unit-cell ZnIn<sub>2</sub>S<sub>4</sub> layers
with poor zinc vacancies, while the former’s photocatalytic
activity shows negligible loss after 24 h photocatalysis. This present
work uncovers the role of defects in affecting electron–hole
separation at atomic level, opening new opportunities for achieving
highly efficient solar CO<sub>2</sub> reduction performances