Diagonal root separation method for extracting impacted double-root mandibular third molars / 华西口腔医学杂志

Double-root mandibular third molars are the common types of mandibular third molars that are prone to impac-tion. Based on the summary of clinical cases and experience, the commonly used crown-root separation technique is improved as diagonal root separation technique that divides the roots by the line connecting the distal axis angle to the root furcation. This new method improves the efficiency of the operation and reduces surgical trauma. This paper details the surgical method, minimally invasive mechanics, and key points of this technique, compares the technique with the crown-root separation tech-nique, and discusses their joint applications.

Negative pressure promotes epidermal differentiation of bone marrow mesenchymal stem cells / 中国组织工程研究

BACKGROUND: As a physical factor, negative pressure can promote the osteogenic differentiation and endothelial differentiation of mesenchymal stem cells. If a negative pressure exerts effects on the epidermal differentiation of mesenchymal stem cells, it will be highly important for the combination use of negative pressure and mesenchymal stem cells in wound healing. OBJECTIVE: To explore the effect of negative pressure on the epidermal differentiation of bone marrow mesenchymal stem cells. METHODS: Bone marrow mesenchymal stem cells of New Zealand white rabbits were isolated and cultured. Then, the passage 3 cells were induced for epidermal differentiation under negative pressure (-16.625 kPA, twice a day, once for 4 hours) as experimental group. Another cells induced under no negative pressure were used as control group. After induction, cell growth curve was drawn in each group, and the expression of cytokeratin 5 and cytokeratin 10 mRNA was examined by real-time PCR at 2 weeks after induction. RESULTS AND CONCLUSION: The cell growth of the experimental group was inhibited, and the mRNA expression of cytokeratin 5 and cytokeratin 10 was significantly increased compared with the control group (P < 0.05). These findings indicate that under the condition of negative pressures, the epidermal differentiation ability of bone marrow mesenchymal stem cells is increased, and in contrary, the cell proliferation is inhibited.

[CoCuMnOx Photocatalyzed Oxidation of Multi-component VOCs and Kinetic Analysis].

Solar energy absorption coating CoCuMnOx was prepared by co-precipitation method and applied to photodegrade multi- component VOCs including toluene, ethyl acetate and acetone under visible light irradiation. The photocatalytic oxidation performance of toluene, ethyl acetate and acetone was analyzed and reaction kinetics of VOCs were investigated synchronously. The research indicated that removal rates of single-component toluene, ethyl acetate and acetone were 57%, 62% and 58% respectively under conditions of 400 mg · m⁻³ initial concentration, 120 mm illumination distance, 1 g/350 cm² dosage of CoCuMnOx and 6 h of irradiation time by 100 W tungsten halogen lamp. Due to the competition among different VOCs, removal efficiencies in three-component mixture were reduced by 5%-26% as compared with single VOC. Degradation processes of single-component VOC and three-component VOCs both fitted pseudo first order reaction kinetics, and kinetic constants of toluene, ethyl acetate and acetone were 0.002, 0.002 8 and 0.002 33 min⁻¹ respectively under single-component condition. Reaction rates of VOCs in three-component mixture were 0.49-0.88 times of single components.

[Microwave In-situ Regeneration of Cu-Mn-Ce/ZSM Catalyst Adsorbed Toluene and Distribution of Bed Temperature].

Microwave in-situ regeneration of Cu-Mn-Ce/ZSM catalyst adsorbed toluene, distribution of fixed bed temperature, adsorption breakthrough curves of the catalyst after several regenerations and characterizations of the catalyst by BET and SEM were investigated in this study. The research indicated that regeneration effect of the catalyst adsorbed was excellent under conditions of microwave power 117 W, air flow 0.5 m3 x h(-1) and catalyst dosage of 800 g. Toluene desorbed was oxidized onto the surface of the catalyst, and the adsorption capacity of the catalyst was recovered simultaneously. Under microwave irradiation, bed temperature decreased slowly from inside to outside in horizontal level, and increased gradually from down to up in vertical level so that the highest temperature reached 250-350 degrees C at the upper sites of the bed. Sintering and agglomeration occurred on the surface of the catalyst in the course of regeneration so that the special surface area and micropore volume of the catalyst were reduced and breakthrough time was shortened, which was verified by six adsorption breakthrough curves and related characteristics of the catalyst. However, the structure of the catalyst was steady after two regenerations, and adsorption breakthrough time was kept at 70 min. The result showed that the changes of surface morphology and pore structure were positively correlated with the distribution of bed temperature.

[Catalytic oxidation of two-component VOCs and kinetic analysis ].

Catalytic oxidations of two-component volatile organic compounds (VOCs) toluene and chlorobenzene were investigated under microwave heating and tube furnace heating, respectively, and reaction kinetics were analyzed in this paper. The research indicated that competitive adsorption between toluene and chlorobenzene reduced their removal efficiencies by 3% -12% as compared to single component. 'Hot spot effect' and 'non-thermal effect' under microwave irradiation obviously enhanced conversion efficiencies of VOCs, especially, the chlorobenzene removal was increased by 31% -38%. Moreover, reaction temperature and energy consumption were both reduced under microwave heating. The dynamic calculations showed that microwave heating decreased the activation energies by 2 146 J. mol-1 and 1 450 J mol-1 for toluene and chlorobenzene, respectively, as compared with tube furnace heating. Meanwhile, microwave heating enhanced the reaction rate constants of chlorobenzene and toluene to about 35 times and 6 times of that of tube furnace heating.

[Synergetic effects of silicon carbide and molecular sieve loaded catalyst on microwave assisted catalytic oxidation of toluene].

Molecular sieve loaded catalyst was prepared by impregnation method, microwave-absorbing material silicon carbide and the catalyst were investigated for catalytic oxidation of toluene by microwave irradiation. Research work examined effects of silicon carbide and molecular sieve loading Cu-V catalyst's mixture ratio as well as mixed approach changes on degradation of toluene, and characteristics of catalyst were measured through scanning electron microscope, specific surface area test and X-ray diffraction analysis. The result showed that the fixed bed reactor had advantages of both thermal storage property and low-temperature catalytic oxidation when 20% silicon carbide was filled at the bottom of the reactor, and this could effectively improve the utilization of microwave energy as well as catalytic oxidation efficiency of toluene. Under microwave power of 75 W and 47 W, complete-combustion temperatures of molecular sieve loaded Cu-V catalyst and Cu-V-Ce catalyst to toluene were 325 degrees C and 160 degrees C, respectively. Characteristics of the catalysts showed that mixture of rare-earth element Ce increased the dispersion of active components in the surface of catalyst, micropore structure of catalyst effectively guaranteed high adsorption capacity for toluene, while amorphous phase of Cu and V oxides increased the activity of catalyst greatly.

[Study on catalytic oxidation of benzene by microwave heating].

The performance in catalytic oxidation of benzene was investigated in two different heating modes, microwave heating and conventional electric furnace heating. The effects of copper (Cu)-manganese (Mn) mass ratio, doping dose of cerium (Ce) and calcination temperature on the catalytic activity of Cu-Mn-Ce/molecular sieve catalyst were also checked in catalytic oxidation of benzene with microwave heating, and the catalysts were subsequently characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). The results showed that the catalyst had better catalytic activity for the oxidation of benzene under microwave heating than electric furnace heating, and high oxidation efficiency for benzene was reached due to the "local hot spots" and dipole polarization effect of microwave and stable bed reaction temperature. Under the conditions of Cu, Mn and Ce mass ratio 1:1:0.33 and calcination temperature 500 degrees C, the catalyst had the optimal catalytic activity for benzene oxidation, and its light-off temperature and complete combustion temperature were 165 degrees C and 230 degrees C, respectively. It was indicated by characteristics of XRD and SEM that the presence of copper and manganese oxides and Cu1.5Mn1.5O4 with spinel crystal improved the catalytic activity of the catalyst, and the doping of Ce promoted the dispersion and regularization of active components. High calcination temperature led to the sintering of the catalyst surface and agglomeration of active components, which decreased the catalytic activity of the catalyst in the catalytic oxidation