China's low-carbon economic growth: an empirical analysis based on the combination of parametric and nonparametric methods.

As the world's most populous developing country and the world's largest carbon emitter, China has already completed its 2020 Intended National Determined Contribution set out in the Paris Agreement. It achieved this result by adopting a dual-goal strategy of economic growth and reducing carbon emission, that is, low-carbon economic growth. Based on both parametric and nonparametric methods, quantitative and qualitative conclusions about China's low-carbon economic growth are presented. It is found that since the beginning of this century, China has maintained an annual growth efficiency of 1% in low-carbon total factor productivity (TFP) and low-carbon technological progress rate. The Eastern region has leading advantages in low-carbon TFP, low-carbon technology advancement, low-carbon efficiency, and low-carbon technology revolution. It has the potential to be the first to reach its CO2 turning point. The inefficiency ratio of labor and CO2 is higher at the national level and in the Eastern region, with the two accounting for about seven tenths and eight to nine tenths, respectively. The difference is that at the national level, the input-output inefficiency is similar, and the inefficiency in the Eastern region is more from the input side, about eight tenths. At the present stage, China is still lenient in the implementation of low-carbon environmental regulations. In the future, the adjustment of low-carbon policy should pay attention to regional heterogeneity, focus on reducing labor and CO2 inefficiency, and be more stringent in policy implementation.

Synthesis and Characterization of ß-Tricalcium Phosphate Derived From Haliotis sp. Shells.

PURPOSE: To develop a methodology for the synthesis of ß-tricalcium phosphate (ß-TCP, Ca3(PO4)2) from the shell of Haliotis sp. (abalone shell) and to verify its characterization and biocompatibility. MATERIALS AND METHODS: Calcium oxide (CaO) was synthesized from abalone shell by sintering and was suspended in distilled water to prepare calcium hydroxide (Ca(OH)2). For the synthesis of calcium carbonate (CaCO3), carbon dioxide was used to infuse Ca(OH)2 at pH 7.4. CaCO3 was reacted with phosphoric acid at pH 6.0 to obtain dicalcium phosphate (CaHPO4). Subsequently, ß-TCP was synthesized by a chemical reaction between CaHPO4 and CaO at 950°C to 1100°C for 3 hours. Fourier transform infrared spectroscopy (FT-IR) and x-ray diffraction (XRD) was performed to verify the physiochemical characteristics of the composite synthesized from abalone shell. RESULTS: FT-IR and XRD results showed that ß-TCP was successfully synthesized from abalone shell. The synthesized ß-TCP did not affect cell viability of either normal human oral keratinocytes or osteoblastic MG-63 cells. These data indicate that ß-TCP synthesized from abalone shell is biologically safe. CONCLUSIONS: ß-TCP (Ca3(PO4)2) synthesized from abalone shell can be used as a potential source of bone grafting material.

Osteogenic evaluation of collagen membrane containing drug-loaded polymeric microparticles in a rat calvarial defect model.

The aim of this study was to develop a functional collagen membrane that is treated with poly (lactic-co-glycolic acid) (PLGA) nanoparticles loaded with dexamethasone (DEX) as a bioactive molecule for guided bone regeneration (GBR). The DEX-loaded PLGA microparticles prepared using water-in-oil standard emulsion method were precoated with positively charged polyethylenimine molecules and later immobilized onto the surface of the collagen membrane; the microparticles were physically immobilized using counter charges of positively charged PLGA microparticles and the negatively charged collagen membrane surface. The release profile of DEX over a 4-week immersion study indicated an initial burst release followed by a sustained release. The performance of this system was investigated using rats with calvarial bone defects. The in vivo evaluation of the defects filled with membrane containing DEX-loaded PLGA microparticles indicated enhanced volume and quality of new bone formation compared with defects that were either unfilled or filled with membrane alone. This innovative platform for bioactive molecule delivery more potently induced osteogenesis, which may be exploited in implantable membranes for stem cell therapy or improved in vivo performance. In conclusion, this newly developed collagen membrane treated with drug-loaded PLGA microparticles might be applicable as a promising bone graft substitute for GBR.

Enhanced attachment of human osteoblasts on NH3-treated poly(L-lactic acid) membranes for guided bone regeneration.

Barrier membranes for guided bone regeneration (GBR) were prepared by a solvent casting method using solutions of poly(L-lactic acid) (PLLA) and chitosan. PLLA and PLLA/chitosan membranes were treated with ammonia gas plasma. PLLA/chitosan membranes were successfully fabricated, and the surface of the PLLA/chitosan membrane was clearly modified by NH3 plasma treatment according to attenuated total reflectance (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analyses. Additionally, water contact angle testing indicated that the hydrophilicity of these membranes was significantly increased. MG-63 cells were cultured on each type of membrane, and cell viability was examined using an MTT assay. After one week of culturing, MG-63 cells were more abundant on PLLA/chitosan membranes than on PLLA membranes. The cell viability of PLLA/chitosan membranes with plasma treatment was significantly higher than that of PLLA membranes. These results suggest that this plasma-treated membrane is suitable for GBR and is a promising source of bioactive membrane material for bone regeneration.

A comparative study of bone formation following grafting with different ratios of particle dentin and tricalcium phosphate combinations.

This study aimed to evaluate the bone regeneration relative to tooth powder and tricalcium phosphate (TCP) mixing ratios using the rabbit cranium defect model. The tooth powder was mixed with TCP in 1:1, 3:1, and 1:3 ratios, and the different ratios were implanted in the rabbit cranium defect for 4 and 8 weeks. Powders crystal structure evaluated using scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and new bone formation (NBF) was analyzed using micro-computed tomography (CT) and histologic examination. NBF in the control group was restricted to the defect margins. More NBF was observed around the defect margins in the experimental groups compared with the control group. Specifically, active NBF was identified around the implant materials of the centrifugal part of the defect and defect margins in the 3:1 tooth powder: TCP group. Our results suggested that tooth powder and TCP may be useful in bone regeneration.

Development and structure of a novel barrier membrane composed of drug-loaded poly(lactic-co-glycolic acid) particles for guided bone regeneration.

A novel barrier membrane composed of poly(lactic-co-glycolic acid) particles loaded with dexamethasone (DEX) as a bioactive molecule was produced via a modified nanoprecipitation method without any mixing. The particle membranes had a bilayer structure: one side was smooth and had a compact surface that was connected to larger particles, while the opposite side was rough, porous and connected to smaller particles. Additionally, a cross-section of the particle membrane had a porous structure with nano and micro sized irregular pores. Process optimization revealed that NaCl concentration in the water phase, with acetone as solvent and water as a non-solvent, played critical roles in determining the properties of the particle membranes, such as DEX encapsulation efficiency, thickness and surface morphologies of the particle membranes. A novel barrier membrane containing DEX using polymer particle drug capture technology has been successfully developed.