Fabrication and characterization of biodegradable Zn scaffold by vacuum heating-press sintering for bone repair.

Bone repair materials with excellent mechanical properties are highly desirable, especially in load-bearing sits. However, the currently used ceramic- and polymer-based ones mainly show poor mechanical properties. Recently, biodegradable metals have attracted extensive attention due to their reliable mechanical strength and degradability. As biodegradable metals, zinc-based materials are promising due to their suitable degradation rate and good biocompatibility. Here, we fabricated biodegradable porous Zn scaffolds with relatively high mechanical properties by vacuum heating-press sintering using NaCl particles as space holders. The microstructure, actual porosity, compressive mechanical properties, in vitro degradation behavior and the vitality of osteoblasts of porous Zn scaffolds were tested and investigated. The results show the porosities of the prepared porous Zn scaffolds are ranging from 11.3 % to 63.3 %, and the pore sizes are similar to the size range of the screened NaCl particles (200-500 µm). Compressive yield strength of 14.2-73.7 MPa and compressive elastic modulus of 1.9-6.7 GPa are shown on porous Zn scaffolds, some of which approach to that of cancellous bone (2-12 MPa and 0.1-5 GPa). Compared to bulk Zn, although the porous structures cause a partial loss of strength, the reliable mechanical properties are still retained. In addition, the porous structures not only greatly increase the degradation rate, but also promote the proliferation of osteoblasts. Based on these results, biodegradable porous Zn scaffolds (porosity in the 40 %-50 %) fabricated by vacuum heating-press sintering method show high application potential for clinical bone repair.

Effects of tall fescue biochar on the adsorption and desorption of atrazine in different types of soil.

The excessive application of atrazine in agriculture has resulted in serious environmental contamination. The addition of biochar could reduce the bioavailability and mobility of atrazine in soil through adsorption-desorption processes. In this study, tall fescue biochar was prepared at 500 °C, and its effect on the adsorption-desorption behavior of atrazine in red soil, brown soil, and black soil was investigated. The tall fescue biochar with the pH value of 9.64 had a developed porous structure and large specific area that contained abundant surface functional groups. The element composition of the tall fescue biochar was C (50.46%), O (15.01%), N (4.54%), H (2.56%), and S (1.47%). The adsorption process of atrazine in the three soil types with and without biochar addition was divided into a fast stage, slow stage, and equilibrium stage. A pseudo second-order kinetic model was suitable for fitting the adsorption process of atrazine, and the determination coefficient (R2) ranged from 0.985 to 0.999. The adsorption-desorption processes of atrazine were described accurately by the Freundlich model (R2 of 0.967-0.999). The adsorption capacity of the three soil types for atrazine increased significantly with the addition of biochar, whereby the equilibrium adsorption amount increased from an initial range of 3.968 to 5.902 µg g-1 to a final range of 21.397 to 21.968 µg g-1. The desorption of atrazine was also inhibited as the hysteresis coefficient (HI) increased from an initial range of 0.451 to 0.586 to a final range of 0.916 to 0.941. The adsorption capacity of the red soil improved more than did the brown soil or black soil. Moreover, spontaneous adsorption of atrazine by the biochar-soil system occurred more easily at 35 °C than at 15 °C and 25 °C. Overall, tall fescue biochar was a prospective soil amendment material.

Rapid prediction of atrazine sorption in soil using visible near-infrared spectroscopy.

Sorption is an important process for determining the fate, effects, and ecological risks of pesticides in terrestrial and aquatic environments. Within a watershed, soil properties vary greatly because of landscape and management practices, leading to spatial variation of pesticide sorption coefficients (Kd). A method for the rapid determination of the sorption variability of atrazine in soils of the Baima river catchment using visible near-infrared (Vis-NIR) spectroscopy is studied in this work. Partial least square regression (PLS) was used to build calibration models. To achieve optimum models, several methods of spectral preprocessing and variable selection were investigated. The results show that the combination of standard normal variant transform (SNV) and Monte Carlo uninformative variable elimination (MC-UVE) can significantly improve the model. For validation samples, the correlation coefficient between the predicted value and the reference value determined by high-performance liquid chromatography (HPLC) analysis is 0.8090. Moreover, positive correlations are observed between the pesticide adsorption coefficient and the organic carbon (OC) and total nitrogen (TN) contents, respectively. Prediction models for OC and TN were built. The correlation coefficients of OC and TN between the predicted values and the reference values are 0.9285 and 0.6599, respectively. The results show that Vis-NIR can be used as a rapid and simple method to predict soil composition and pesticide sorption.

Spatio-temporal variation of land use and ecosystem service values and their impact factors in an urbanized agricultural basin since the reform and opening of China.

The provision capacity of ecosystem services is affected by land-use/land-cover (LULC) change and biophysical and socio-economic characteristics. Studies related to ecosystem service values (ESVs) and their impact factors can provide a good reference for natural capital management. In this paper, the temporal and spatial dynamics of LULC and ESVs in the Nansihu Lake basin, China, since the reform and opening of China were analyzed by a combined method of spatial analysis and correlation analysis, and the factors that influence ESV changes were discussed. The results indicated that the main LULC changes were the enormous loss of cultivated land and rapid urban land expansion since the policy of reformation and opening in 1978. The ESVs in the basin decreased by 1.64% (1.70 × 108 US$) from 1975 to 2015, and the main impact factors of this temporal change in ESVs were the changes in waterbodies and cultivated land. Spatial patterns of ESVs were significantly influenced by socio-economic factors in the basin, such as population density and intensity of land use. This research provides alternatives and robust information for policy-making processes for the Nansihu Lake basin, and similar work can be conducted in other parts of the country.

Spatiotemporal distributions of Cu, Zn, metribuzin, atrazine, and their transformation products in the surface water of a small plain stream in eastern China.

The intensive use of fertilizers and pesticides in agriculture has led to widespread nonpoint source pollution in surface waterbodies. In this work, the occurrence and distribution of nonpoint source metals (Cu and Zn) and herbicides (metribuzin; atrazine; and its degradates, including desethyl atrazine (DEA), desisoproylatrazine (DIA), and deethyldeisopropylatrazine (DEDIA)) in the surface water of the Baima River, which is located in a region noted for its intense agricultural activities, were investigated during a high water period in August and a low water period in October. The results showed that the heavy metals and herbicides investigated were detected frequently in the surface water of the river during the two periods. The average concentrations of Cu during the high water period and low water period were 9.3 (0-20.7) and 8.7 (0-15.55) µg/L, and the average concentrations of Zn during the two periods were 11.4 (6.65-22.15) and 10.6 (7.55-15.15) µg/L, respectively. The concentrations of atrazine were higher than those of metribuzin, which ranged from 0.07 to 1.12 µg/L during the high water period and 0.01-0.74 µg/L during the low water period. The total concentrations of atrazine and its transformation products in 60.00% of the samples during the high water period exceeded the maximum contaminant level (MCL) of 3 µg/L for the drinking water criteria in the USA, and 33.33% of the samples exceeded the MCL during the low water period. The spatial and temporal distributions of nonpoint source pollutants along the Baima River were influenced by land use and hydrogeomorphic settings. The ecotoxicological risk assessment indicated that atrazine and DIA have moderate risks to aquatic environment in Baima River.

Multilevel analysis of temperature dependent near-infrared spectra.

Quantitative spectra-temperature relationship (QSTR) between near-infrared (NIR) spectra and temperature has been used for quantitative determination of the compositions in mixtures. In this work, QSTR is studied using multilevel simultaneous component analysis (MSCA) and the spectral data of the samples with different concentrations measured at different temperatures. MSCA model contains a between-individual model describing the differences between the individuals and a within-individual model capturing the differences within the data of all the individuals. NIR spectra of five different compositions (water-ethanol-isopropanol) measured at seven temperatures were analyzed. A between-temperature model describing the effect of temperature and a within-temperature model describing the variation of concentration were obtained, from which QSTR model is established and quantitative analysis is achieved. Furthermore, the difference between the between-temperature or within-temperature models of different mixtures is used to study the composition of the solvent.

Optimizing the models for rapid determination of chlorogenic acid, scopoletin and rutin in plant samples by near-infrared diffuse reflectance spectroscopy.

Polyphenols in plant samples have been extensively studied because phenolic compounds are ubiquitous in plants and can be used as antioxidants in promoting human health. A method for rapid determination of three phenolic compounds (chlorogenic acid, scopoletin and rutin) in plant samples using near-infrared diffuse reflectance spectroscopy (NIRDRS) is studied in this work. Partial least squares (PLS) regression was used for building the calibration models, and the effects of spectral preprocessing and variable selection on the models are investigated for optimization of the models. The results show that individual spectral preprocessing and variable selection has no or slight influence on the models, but the combination of the techniques can significantly improve the models. The combination of continuous wavelet transform (CWT) for removing the variant background, multiplicative scatter correction (MSC) for correcting the scattering effect and randomization test (RT) for selecting the informative variables was found to be the best way for building the optimal models. For validation of the models, the polyphenol contents in an independent sample set were predicted. The correlation coefficients between the predicted values and the contents determined by high performance liquid chromatography (HPLC) analysis are as high as 0.964, 0.948 and 0.934 for chlorogenic acid, scopoletin and rutin, respectively.