Linear fractal evolution characteristics of rock crack distributions during loading process.

To investigate the fractal characteristics of rock crack distributions during the loading process, discrete element method was used to make rock samples with joints and record the crack propagation. The Box-counting method was used to quantitatively analyze the fractal dimension of the crack distribution at each moment, and the relationship between the crack fractal dimension and strain ratio was established based on fractal theory. The results indicated that the relationship between the fractal dimension of the crack distribution and strain ratio showed a strong linear characteristic. By transforming this linear relationship into a linear function, the slope of the function was found to be linked to the failure patterns of the sample, and a refinement coefficient (damage-fracture reduction factor) was identified from the slope as an effective basis for determining the degree of sample damage and fracture. The damage-fracture reduction factor can be categorized: 0.25-0.5 (spilt and fracture), 0.5-0.9 (synergy between fracture and damage), 0.9-1 (microcrack asymptotic damage). Owing to the linear fractal characteristics, an expression for the damage variables influenced by failure patterns can be established from the geometric aspect. In addition, the linear fractal characteristics of the cracks were verified in other acoustic emission and crack extension experiments.

Structure characterization and protective effect against UVB irradiation of polysaccharides isolated from the plateau plant Gentiana dahurica Fisch.

Gentiana dahurica Fisch. (G. dahurica) is one of the legitimate sources of Qinjiao in Traditional Chinese Medicine (TCM) and grows on high-altitude plateaus. Plants develop unique biochemical accumulations to resist plateau conditions, especially the strong UV irradiation. Thus, this study aimed to investigate the polysaccharide of G. dahurica (GDP), its structure and its activity against UVB irradiation. Four GDPs were isolated and two of them were subjected to structural elucidation. The results suggested that GDP-1 has 53.5 % Ara and 30.8 % GalA as its main monosaccharides, with a molecular weight (Mw) of 23 kDa; the GDP-2 has 33.9 % Ara and 48.5 % GalA, with a Mw of 82 kDa. Methylation and NMR spectroscopy analysis revealed that GDP-1 contains →5)-α-Araf-(1 â†’ 5)-α-Araf-(1 â†’ 3,5)-α-Araf-(1 â†’ 3,4)-α-GalpA-(6-OMe)-(1→ as the main chain, the branches of GalA (with esterification), and the terminal Ara; the GDP-2 contains →4)-α-GalpA-(1 â†’ 4)-α-GalpA-(6-OMe)-(1 â†’ 5)-α-Araf-(1 â†’ 3,5)-α-Araf-(1→ as the main chain, the branches of →5)-α-Araf-(1-5)-α-Araf, and the terminal GalA. Both GDP-1 and GDP-2 exhibited concentration-dependent antioxidant activity against DPPH, ABTS and hydroxyl radicals. Moreover, GDPs significantly attenuated the decreases in viability and proliferation of HaCaT cells after UVB irradiation. They can scavenge reactive oxygen species (ROS) and improve the activities of endogenous antioxidant enzymes, including superoxide dismutase (SOD) and glutathione peroxidase (GSH). The potential mechanism explored by flow cytometry assays of cell apoptosis and cell cycle distribution suggested that GDPs exert protective effects against UVB irradiation by reducing ROS and attenuating S phase cell arrest. In brief, the GDP-1 and GDP-2 are α-1,3- and α-1,4- arabinogalacturonan, respectively. The high content of Ara could be attributed to biochemical accumulation in resisting to the plateau environment and to prevent UVB irradiation-related damage in cells. These findings provide insight into authentic medicinal herbs and the development of GDPs in the modern pharmaceutical and cosmetics industry.

High-efficiency and low-hazard artillery recoil reduction technology based on barrel gas reflection.

Reducing recoil as well as reducing muzzle hazards are important issues in artillery design. This paper presents a barrel gas reflection method for the artillery aiming for efficient recoil reduction while reducing muzzle hazards. The launching process is modeled by coupling the interior ballistic equations and the flow equations of the barrel gas reflection device. The fourth-order Runge-Kutta method was used to solve the model, and the LHS method as well as the Kriging model was used to establish a mapping relationship between the parameters and the effect. To validate the proposed model, shooting experiments are carried out on a 30 mm caliber artillery. The maximum error between the experiment and simulation results was 5.32%. The experiment has demonstrated that the barrel gas reflection method increases the recoil reduction efficiency of artillery by 44.54% and reduces the muzzle hazard by 52.18%. Finally, the barrel gas reflection method can produce effects with the muzzle device at the same time, and it has little effect on the velocity of the projectile muzzle velocity, and it provides a new way of thinking for the development of future artillery recoil reduction technology.

Headspace solid-phase microextraction comprehensive 2D gas chromatography-time of flight mass spectrometry (HS-SPME-GC × GC-TOFMS) for origin traceability of the genus Hymenaea resinites.

Differentiating the chemical compositions of resinite (amber, copal, and resin) is very crucial for determining the botanical origin and chemical compositions of the fossilised amber and copal. This differentiation also assists in understanding the ecological functions of resinite. Headspace solid-phase microextraction-comprehensive two-dimensional (2D) gas chromatography-time-of-flight mass-spectroscopy (HS-SPME-GC × GC-TOFMS) was firstly proposed and utilised in this research to investigate the chemical components (volatile and semi-volatile compositions) and structures of Dominican amber, Mexican amber, and Colombian copal for origin traceability, which were all produced by trees belonging to the genus Hymenaea. Principal component analysis (PCA) was used to analyse the relative abundances of each compound. Several informative variables were selected, such as caryophyllene oxide, which was only found in Dominican amber, and copaene, which was only found in Colombian copal. 1H-Indene, 2,3-dihydro-1,1,5,6-tetramethyl- and 1,1,4,5,6-pentamethyl-2,3-dihydro-1H-indene were abundantly present in Mexican amber, which were the critical fingerprints for the origin traceability of amber and copal produced by trees from the genus Hymenaea of various geological places. Meanwhile, some characteristic compounds were closely related to the invasion of fungi and insects; their links with ancient fungi and insect categories were also decoded in this study and these special compounds could be used to further study the plant-insect interactions.

Burnout among doctors in China through 2020: A systematic review and meta-analysis.

Objective: To analyze surveys measuring the prevalence of burnout among Chinese doctors and reveal the overall prevalence, characteristics, timeline, and factors related to burnout. Methods: A comprehensive search was conducted on China National Knowledge Infrastructure, WANFANG, PubMed, EMBASE, PsycINFO and Cochrane Library databases from their inception to 28 February 2021. Random-effects meta-analyses, meta-regression and planned subgroup analyses were performed, and the standardized mean difference was adopted for comparisons between subgroups. Egger's and Begg's tests were performed to evaluate publication bias. Heterogeneity across the studies was tested using the I2 statistic. The study protocol was registered on PROSPERO (CRD42018104249). Results: In total, 3,210 records were reviewed; 64 studies including 48,638 Chinese doctors were eligible for meta-analysis. The prevalence of burnout increased continuously from 2008 to 2017 and decreased significantly from 2018 to 2020, a little increase from 2020 to 2021. The overall prevalence of burnout was 75.48% (95% CI, 69.20 to 81.26; I2 = 99.23%, P < 0.001), and high burnout was 9.37% (95% CI, 4.91 to 15.05, I2 = 98.88%, P < 0.001). The prevalence of emotional exhaustion was 48.64% (95% CI, 38.73 to 58.59; I2 = 99.53%, P < 0.001), depersonalization was 54.67% (95% CI, 46.95 to 62.27; I2 = 99.20%, P < 0.001), and reduced personal accomplishment was 66.53% (95% CI, 58.13 to 74.44; I2 = 99.37%, P < 0.001). Gender, marriage, professional title and specialty all influenced burnout. Conclusions: The results showed that the total prevalence of doctor burnout in China is very high. The prevalence of burnout varies by location. Gender, marital status and professional title all affect burnout scores.

Nek2B accelerates the progression of hepatocellular carcinoma through regulating SFRP1 to activate the Wnt/ß-catenin pathway.

PURPOSE: The purpose of this study was to clarify the expression pattern of Nek2B in hepatocellular carcinoma (HCC) and its influence on malignant phenotypes of HCC through regulating SFRP1 and the Wnt/ß-catenin pathway. METHODS: Nek2B levels in 64 paired HCC tissues and adjacent normal ones were detected by quantitative real-time polymerase chain reaction (qRT-PCR). The correlation between Nek2B level and clinical parameters of HCC patients was analyzed. Regulatory effects of Nek2B and SFRP1 on clonality, proliferation and apoptosis of MHCC97H and Hep3B cells were determined through functional experiments. Western blot was conducted to detect protein levels of SFRP1, ß-catenin, c-myc, cyclinD1 and MMP7 in HCC cells with overexpression or knockdown of Nek2B. At last, rescue experiments were performed to clarify the role of Nek2B/SFRP1 regulatory loop in aggravating the progression of HCC. RESULTS: Nek2B was upregulated in HCC tissues and cells. HCC patients expressing a high level of Nek2B were in more advanced tumor stage and had worse prognosis. Overexpression of Nek2B in MHCC97H cells enhanced clonality, 5-Ethynyl-2'- deoxyuridine (EdU)-positive ratio and suppressed apoptosis. Besides, knockdown of Nek2B in Hep3B cells yielded the opposite results. SFRP1 was downregulated in HCC, and low level of SFRP1 predicted worse prognosis of HCC. Overexpression of Nek2B downregulated SFRP1, but upregulated ß-catenin, c-myc, cyclinD1 and MMP7 in HCC cells. Importantly, Nek2B/SFRP1 regulatory loop was identified to aggravate the progression of HCC. CONCLUSIONS: Nek2B is upregulated in HCC, and closely linked to tumor stage and poor prognosis in HCC patients. Through interaction with SFRP1, Nek2B aggravates the progression of HCC by activating the Wnt/ß-catenin pathway.

Efficacy and safety of Morinda officinalis oligosaccharide capsules for depressive disorder: a systematic review and meta-analysis

Objective: To evaluate the efficacy and safety of Morinda officinalis oligosaccharide (MOO) capsules for depressive disorder. Methods: Eight electronic databases were searched for relevant studies from inception to April 19, 2020. Randomized controlled trials comparing MOO capsules with antidepressants were included. Data analysis was conducted using Review Manager 5.3 software. The risk of bias was assessed using the Cochrane Risk of Bias Tool, and the quality of the studies was evaluated by two researchers using the Grading of Recommendation, Assessment, Development and Evaluations (GRADE) software. Results: Seven studies involving 1,384 participants were included in this study. The effect of MOO capsules for moderate depressive disorder was not different from that of antidepressants (risk ratio [RR] = 0.99, 95%CI 0.92-1.06). Regarding adverse events, no significant difference was found between MOO capsules and antidepressants (RR = 0.84, 95%CI 0.65-1.07). In addition, the quality of evidence related to these adverse events was rated as low. Conclusion: This systematic review suggests that the efficacy of MOO capsules in the treatment of mild to moderate depression is not inferior to that of conventional antidepressants, which may provide a new direction for clinical alternative selection of antidepressants. However, more high-quality research and detailed assessments are needed.

Efficacy and safety of Morinda officinalis oligosaccharide capsules for depressive disorder: a systematic review and meta-analysis.

OBJECTIVE: To evaluate the efficacy and safety of Morinda officinalis oligosaccharide (MOO) capsules for depressive disorder. METHODS: Eight electronic databases were searched for relevant studies from inception to April 19, 2020. Randomized controlled trials comparing MOO capsules with antidepressants were included. Data analysis was conducted using Review Manager 5.3 software. The risk of bias was assessed using the Cochrane Risk of Bias Tool, and the quality of the studies was evaluated by two researchers using the Grading of Recommendation, Assessment, Development and Evaluations (GRADE) software. RESULTS: Seven studies involving 1,384 participants were included in this study. The effect of MOO capsules for moderate depressive disorder was not different from that of antidepressants (risk ratio [RR] = 0.99, 95%CI 0.92-1.06). Regarding adverse events, no significant difference was found between MOO capsules and antidepressants (RR = 0.84, 95%CI 0.65-1.07). In addition, the quality of evidence related to these adverse events was rated as low. CONCLUSION: This systematic review suggests that the efficacy of MOO capsules in the treatment of mild to moderate depression is not inferior to that of conventional antidepressants, which may provide a new direction for clinical alternative selection of antidepressants. However, more high-quality research and detailed assessments are needed.

Burnout among doctors in China through 2018: A protocol of systematic review and meta-analysis.

BACKGROUND: Burnout negatively impacts the mental and physical health doctors. More seriously, it leads to poor patient care. In China, the situation is severe and more efforts are needed to reveal the epidemiological characteristics of doctor burnout to develop improved strategies of alleviating it. Due to the large number of heterogeneous and sample size-restricted surveys currently published, meta-analysis and systematic reviews are critical to a thorough understanding of burnout among Chinese doctors. METHODS: The Cochrane Collaboration criteria and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) will be followed to conduct and report the systematic review. We will conduct a comprehensive search on the data bases of China National Knowledge Infrastructure (CNKI), WanFang, PubMed, EMBASE, PsycINFO, and the Cochrane Library from their inception to December 2018. Prospective cohort and cross-sectional studies that described the prevalence of Chinese doctors' prevalence will be eligible for inclusion. The risk of bias and methodological quality of the included studies will be assessed using a risk of bias tool and the Cochrane guidelines for observational studies. A generalized linear mixed model framework with the Poisson likelihood and the log link function will be used to access the incidence rate ratio. Multivariate Poisson regression framework will be conducted to adjust modeling heterogeneity and confounders, like difference regions and time periods. The risk of bias, heterogeneity, and quality of evidence will be assessed in accordance with the aforementioned guidelines. RESULTS: The primary outcome will be the prevalence and distribution of 3 dimension of burnout in Chinese doctors, and the second will be the difference of prevalence between difference regions and time periods. DISCUSSION: This systematic review and meta-analysis will help us to reveal the prevalence, characteristics, timeline, and correlation between these factors in burnout; we expect our work may provide a scientific basis for further prevention and intervention of burnout in Chinese doctors, eventually to improve the quality of health care. PROSPERO REGISTRATION NUMBER: CRD42018104249.

Synthesis of polymer-functionalized nanoscale graphene oxide with different surface charge and its cellular uptake, biosafety and immune responses in Raw264.7 macrophages.

Polymer-functionalized graphene oxide (GO) has superior properties such as large surface area, extraordinary mechanical strength, high carrier mobility, good stability in physiological media and low cytotoxicity, making it an attractive material for drug and gene delivery. Herein, we successfully synthesized GO with an average size of 168.3 nm by a modified Hummers' method. Branched polyethylenimine (PEI) and 6-armed polyethylene glycol (PEG) functionalized GO complexes (GO-PEI and GO-PEG) with different zeta potentials of 47.2 mV and -43.0 mV, respectively, were successfully synthesized through amide linkages between the COOH groups of GO and the NH2 groups of PEI and PEG. Then, the interactions between GO-PEI and GO-PEG complexes and Raw264.7 mouse monocyte-macrophage cells were investigated. The GO-PEI and GO-PEG complexes could both be internalized by Raw264.7 cells. However, compared with the GO-PEG complex, the GO-PEI complex showed higher intracellular delivery efficiency in Raw264.7 cells. Moreover, it was found that the GO-PEI complex not only gathered in endosomes but also in the cytoplasm, whereas GO-PEG gathered in endosomes only. The MTT tests showed that both GO-PEI and GO-PEG complexes exhibited very low cytotoxicity towards Raw264.7 cells when at a low concentration. The cellular immune response test demonstrated the GO-PEG complex enhanced the secretion of IL-6, illustrating it was more stimulus towards macrophage cells. The above results indicated that the GO-PEI complex, with a positive surface charge, demonstrated better potential to be used in effective drug and gene delivery.

Interactions between rGO/TNT nanocomposites and cells: Regulation of cell morphology, uptake, cytotoxicity, adhesion and migration.

Reduced graphene oxide/titanium dioxide nanotube (rGO/TNT) composites have superior properties, such as a large surface area, extraordinary mechanical strength, high carrier mobility, etc. However, the biosafety and biocompatibility of these composites, such as their influences on cell viability and cell functions, which are of paramount importance, are still not fully addressed. In this study, rGO/TNT nanocomposites were successfully synthesized through a modified hydrothermal treatment method. Then, the interactions between the rGO/TNT nanocomposites and Raw264.7 mouse monocyte-macrophage cells were further investigated. The results show that the rGO/TNT nanocomposites could be internalized by Raw264.7 cells and mainly gathered inside the cytoplasm. No rGO/TNT nanocomposites were observed in the nucleus. Moreover, the rGO/TNT nanocomposites exhibited low cytotoxicity toward Raw264.7 cells at a lower dose, though they may exhibit cytotoxicity to some extent at very high concentrations. In addition, the uptake of the nanocomposites influenced the cell cytoskeleton organization, while the cell adhesion and migration abilities were also impaired.

Negative reflection from metal/graphene plasmonic gratings.

We propose a scheme of metal/graphene plasmonic gratings for negative reflection. The existence of graphene ribbons, introducing abrupt discontinuity on tangential components of magnetic fields for scattering waves across a graphene interface, substantially alters the dispersion of surface states on plasmonic gratings such that negative reflection that is robust against the incidence angle and can be tuned in a wide frequency range as a function of Fermi energy of graphene. Circularly polarized incidence waves are reflected and split along specular and negative directions, with respective to transverse magnetic and electric polarization. Our findings are potentially helpful for light steering in integrated optical circuits.

Highly efficient beam steering with a transparent metasurface.

We propose an ultra-thin planar metasurface with phase discontinuities for highly efficient beam steering. The effect benefits from the broadband transparency and flexible phase modulation of stacked metal/dielectric multi-layers that is perforated with coaxial annular apertures. Proof-of-principle experiments verify that an efficiency of 65% and a deflection angle of 18° at 10 GHz are achieved for the transmitted beam, which are also in good agreement with the finite-difference-method-in-time-domain (FDTD) simulations. The scheme shall be general for the design of beam-steering transmitters in all frequencies.

[Detection and functional analysis of CD-4+ CD-25+ regulatory T cells in the peripheral blood of patients with generalized aggressive periodontitis].

OBJECTIVE: To investigate the changes of proportion and suppression function of CD-4+ CD-25+ regulatory T cells in the peripheral blood of patients with aggressive periodontitis. METHODS: Flow cytometric analysis was used to detect the frequency of CD-4+ CD-25+ regulatory T cells in the peripheral blood of 16 patients with generalized aggressive periodontitis and 17 patients with chronic periodontitis, as well as 17 periodontal healthy controls. Furthermore, CD-4+ CD-25+ regulatory T cells and CD-4+ CD-25- T cells were separated from peripheral blood of each enrolling subject using magnetic cell sorting technology. The direct suppression effect of CD-4+ CD-25+ regulatory T cells on CD-4+ CD-25- T lymphocytes proliferation was performed by the mixed lymphocytes reaction and measured by 3H-thymidine radioactive assay. RESULTS: The patients with generalized aggressive periodontitis had a lower frequency of CD4+ CD-25+ regulatory T cells (9.71 +/- 4.01)% in the peripheral blood than periodontal healthy controls [(14.72 +/- 3.51)%] and chronic periodontitis patients [(17.01 +/- 5.16 )%], P < 0.05. A significant decrease was found in the suppression function of CD-4+ CD-25+ regulatory T cells from peripheral blood of patients with generalized aggressive periodontitis when co-cultured with CD-4+ CD-25- T lymphocytes in the proportion of 2 : 1, 1 : 1 and 1 : 2 as compared with chronic periodontitis patients and periodontal healthy controls (P < 0.05). CONCLUSIONS: Diminished numbers and decreased suppression function of CD-4+ CD-25+ regulatory T cells were found in patients with generalized aggressive periodontitis.

[Biologic effects of advanced oxidative protein products on the human gingival fibroblasts].

OBJECTIVE: To investigate the effects of advanced oxidative protein products (AOPP) on the proliferation, apoptosis and matrix metalloproteinase-1 (MMP-1) synthesis of the human gingival fibroblast (HGF). To explore the possible mechanism of the periodontal destruction acceleration in diabetes through AOPP-mediated oxidative stress. METHODS: HGF were isolated by both tissue explant cultivation technique and enzyme digestion method. The culture media with 5, 50, 100 mg/L AOPP-HAS were added into each experimental group, but the culture media in the control group didn't contain AOPP-HAS. MTT colorimetric assay and ELISA were used to measure the changes of HGF proliferation and the levels of MMP-1 protein from HGF at different time periods, respectively. Seventy-two hours after co-culture with 50 mg/L AOPP-HSA, cell apoptosis was detected by flow cytometry with Annexin V/PI staining. RESULTS: Compared to the control group, the growth inhibition rate of HGF in 5, 50, 100 mg/L AOPP-HSA group was significantly different (P < 0.05). The peak value appeared at 48 hours of co-culture [(19.01 +/- 6.28)%, (30.48 +/- 5.75)%, (39.75 +/- 4.60)%, respectively]. There was a dose-dependent relationship between the growth inhibition rate and AOPP-HSA. No significant difference was detected on the apoptotic level between experimental group and the control (P > 0.05). The MMP-1 synthesis in 0.5, 5, 50, 100 mg/L AOPP-HAS group [(55.61 +/- 1.06), (65.78 +/- 4.04), (79.24 +/- 3.09), (89.76 +/- 28.88) mg/L, respectively] was significantly higher than that in the control [(34.90 +/- 3.15) mg/L] after 72 hours co-culture (P < 0.05). There was a dose-dependent relationship between MMP-1 and AOPP-HSA. CONCLUSIONS: AOPP may inhibit the proliferation of HGF and such effect was not achieved through apoptosis. AOPP may increase collagen degradation by promoting MMP-1 synthesis and thus may accelerate periodontal destruction process in diabetes.