Structure-property relationship and shape memory effect of polyurethane copolymer cross-linked with pentaerythritol

Polyurethane block copolymers chemically cross-linked by pentaerythritol, a four-way cross-linker, are tested for the shape memory effect. One of the copolymers shows higher shape recovery than any other shape memory copolymer synthesized by us so far. The copolymer maintains a surprising 94 % shape recovery after the third cyclic test. The four-way cross-linking by pentaerythritol and interaction between hard segments are mainly responsible for the very high shape recovery. Tensile mechanical properties also significantly improve by cross-linking. Glass transition temperature (T _g ) slightly increases with cross-linking content. Other characterization such molecular weight, IR, and X-ray diffraction is also carried out to understand the arrangement of copolymer chains.     

基于转录组测序信息的德国鸢尾MADS-box基因家族分析

为探究MADS-box基因家族对德国鸢尾多季花品种花期的影响,本研究基于德国鸢尾(Iris germanica)转录组数据,利用生物信息学方法对MADS-box家族基因进行筛选鉴定,并对其理化性质、功能域及亲/疏水性等方面进行预测分析,且构建德国鸢尾和模式植物拟南芥MADS-box蛋白家族的系统进化树。结果表明,在德国鸢尾中鉴定出39个MADS-box基因家族成员,其编码的氨基酸序列分子量在4704.58~30112.19 k D之间,理论等电点(pI)介于5.01~10.92之间,其中32个表现为碱性蛋白,7个表现为酸性蛋白。大多数MADS-box蛋白定位于细胞核和线粒体基质,少许分布在其他细胞器均不含有信号肽。α-螺旋和无规则卷曲为二级结构的主要原件,所有蛋白均表现为亲水性蛋白。进化树分析结果显示,德国鸢尾MADS-box蛋白可聚为5大类(MIKC,Mα,Mβ,Mγ,Mδ)。本研究可为今后进一步研究德国鸢尾MADS-box蛋白的生物学功能提供一定的参考依据。     

A new color index for vegetation segmentation and classification

Color vegetation indices enable various precision agriculture applications by transforming a 3D-color image into its 1D-grayscale counterpart, such that the color of vegetation pixels can be accentuated, while those of nonvegetation pixels are attenuated. The quality of the transformation is essential to the outcomes of computational analyses to follow. The objective of this article is to propose a new vegetation index, the Elliptical Color Index (ECI), which leverages the quadratic discriminant analysis of 3D-color images along a normalized red (r)—green (g) plane. The proposed index is defined as an ellipse function of r and g variables with a shape parameter. For comparison, the ECI’s performance was evaluated along with six other indices, by using 240 color images as a test sample captured from four vegetation species under different illumination and background conditions, together with the corresponding ground-truth patterns. For comparative analysis, the receiver operating characteristic (ROC) and the precision–recall (PR) curves helped quantify the overall performance of vegetation segmentation across all of the vegetation indices evaluated. For a practical appraisal of vegetation segmentation outcomes, this paper applied Gaussian filtering, and then the thresholding method of Otsu, to the grayscale images transformed by each of the indices. Overall, the test results confirmed that ECI outperforms the other indices, in terms of the area under the curves of ROC and PR, as well as other performance metrics, including total error, precision, and F-score.

     

Application of microbially induced calcite precipitation to prevent soil loss by rainfall: effect of particle size and organic matter content

Journal of Soils and Sediments - Soil loss by rainfall is a serious problem in civil and environmental engineering. In this study, microbially induced calcite precipitation (MICP) was applied to...     

Electrokinetic remediation of heavy metal-contaminated soils: performance comparison between one- and two-dimensional electrode configurations

Journal of Soils and Sediments - Electrokinetic (EK) soil remediation is significantly affected by the electrode configurations. Therefore, this study was conducted to compare the performance of...     

不同类型水稻土微生物群落结构特征及其影响因素

选取基于我国土壤地理发生分类的不同类型土壤发育的四种水稻土,利用¹⁵N₂气体示踪法测定生物固氮速率,采用实时荧光定量PCR（Real-time PCR）技术测定细菌丰度,通过16S rRNA基因高通量测序分析微生物群落组成和多样性。结果表明：变形菌门（Proteobacteria）、酸杆菌门（Acidobacteria）、绿弯菌门（Chloroflexi）和蓝藻门（Cyanobacteria）是水稻土中优势微生物类群。四种类型土壤发育的水稻土细菌群落结构差异显著（Stress<0.001）,群落结构分异（NMDS1）与土壤pH存在极显著正相关关系（P<0.01）。土壤有机碳和碱解氮含量显著影响水稻土中细菌丰度和群落多样性（P<0.01）。红壤发育的水稻土细菌16S rRNA基因拷贝数显著高于其他三种类型水稻土,但OTU数量、Chao1指数和PD指数均低于其他三种类型水稻土。土壤pH对水稻土生物固氮速率有显著影响（P<0.01）,紫色土发育的水稻土具有最高的生物固氮速率（3.2±0.7 mg×kg^-1×d^-1）,其中优势类群细鞘丝藻属（Leptolyngbya）可能是生物固氮的主要贡献者。研究结果丰富了对水稻土微生物多样性的认识,为通过调控土壤pH和微生物群落组成来提高稻田生物固氮潜力提供了理论依据。     

Fluorescence and NIR spectroscopic study on the water interaction in polycarbonate film

Water interactions in polycarbonate films have been studied using fluorescence and NIR Fourier transform spectroscopy. During water sorption process, the fluorescence emission spectra showed sensitive changes with the peak at 332 nm red shifted by 18 nm with water sorption. This red-shifted peak could be due to phenyl-2-phenoxybezoate, which is one of two major thermal degradation products in polycarbonate. In the spectra of phenyl-2-phenoxybenzoate in dimethyl formamide solution, a progressive red shift was also observed with the water addition. By using the NIR spectra, hydrogen-bonding interactions of the sorbed water with polycarbonate were investigated. It was found that water can be analyzed as free water S₀ or single hydrogen bonded water, S₁ while double hydrogen bonded water was negligible. During water immersion, most water species which are present as S₀ species decrease slightly, with a small increase in S₁ species. During desorption, S₀ species decrease sharply, while S1 species is reduced gradually. Two examples of S₁ structure in water-sorbed polycarbonate are proposed.     

Effect of glycerol cross-linking and PDI on the shape memory effect and mechanical properties of polyurethane

A series of shape memory polyurethane (PU) copolymers synthesized from 1,4-phenyldiisocyanate (PDI), poly(tetramethyleneglycol) (PTMG), 1,4-butanediol (BD) as a chain extender, and glycerol as a cross-linking agent were tested for the mechanical properties and the shape memory effect at the temperature 20 °C above melting temperature (T _m), and were compared with other PUs synthesized from 4,4′-methylene-bis-phenyldiisocyanate (MDI), PTMG, and BD. Mechanical properties and shape memory effect were improved substantially by adopting both PDI and glycerol. Interestingly, enthalpy of melting and T _m were not affected by the glycerol content. Vibration and shock absorption ability was investigated by measuring both loss tan δ and storage modulus with dynamic mechanical analyzer (DMA).     

肥料增效剂对脱毒马铃薯作用效果研究

2008年在马铃薯上进行了肥料增效剂一抗腐威试验,在传统秋施肥地块上,第二年播种时,施用常规肥料与仅施抗腐威进行试验对比.结果表明:抗腐威处理,平均产量:20616 kg/hm2.与常规施肥相比差异不显著,有效地提高了肥料利用率,节约肥料,可以在马铃薯上推广应用.     

Evaluation of water holding capacity and breadmaking properties for frozen dough containing ice structuring proteins from winter wheat

The effects of ice structuring proteins (ISPs) from white wheat and storage conditions on the water holding capacity (WHC) and breadmaking properties of frozen dough were investigated. The WHC of frozen dough was measured by centrifugation and the breadmaking properties were assessed as proofing time and bread specific volume. It was found that the prolonged frozen storage and freeze–thaw cycles decreased the WHC and breadmaking properties of dough. ISPs were highly effective in increasing the WHC of frozen dough and improving the breadmaking properties. There was a strong correlation between WHC and breadmaking properties (proofing time and bread specific volume) of frozen dough.