Synthesis of high molecular weight polylactic acid from aqueous lactic acid co-catalyzed by tin（Ⅱ）chloride dihydrate and succinic anhydride

Polylactic acid was synthesized from commercial available cheap aqueous lactic acid （85%-90% w/w） using succinic anhydride and SnCl2·2H2O as catalyst in the absence of organic solvents. As a result, polylactic acid with a molecular weight of 60000 was prepared in 10 h. The new procedure is much simple, cheap and outstanding in that the start material is aqueous lactic acid; the catalytic system is environmentally benign.     

Effect of Media on the in vitro Degradation of Biodegradable Ureteral Stent

The biodegradable ureteral stent should retain their supporting properties for defined period and then gradually degrade to small particles with the flow of urine. The mechanism and process of the stent’s degradation should be investigated and understood well due to its direct impact on the stents’ usage. An enhanced braidbased degradable ureteral stent composed of poly-glycolic acid(PGA) and the copolymer of lactic and glycolic acid(PGLA) was evaluated in vitro in this study with four kinds of degradable media:human urine(HU,pH = 7. 4),artificial urine(AU,pH = 5. 8),and phosphate buffer solutions( PBS,pH = 5. 8 and 7. 4) so as to compare the effects of media on the degradation of stents. The mechanical properties and morphology were observed at different degradaing time intervals of 0,7,14,21,28,and 35 d. The in vitro degradation behaviors of stents in four kinds of media were extremely different. The degradation rate of stents in HU was the highest. The impact of media’s pH to the degradation is not obvious while the components in the media contribute much to the difference.     

Synthesis of high molecular weight polylactic acid from aqueous lactic acid co-catalyzed by tin(II)chloride dihydrate and succinic anhydride

Poly(lactic acid) (PLA) is widely used as biodegradable plastic and biomedical materials due to its excellent me- chanical properties and biodegradable characterization. The price of poly(lactic acid) has gradually become com- petitive to the average alkene polymers since the method for the preparation of lactic acid from starch fermentation has been developed. With the decline of petroleum re- serves, much attention is devoted to polylactic acid due to its environmentally benignancy and its …     

Microwave absorbing properties of polyaniline/montmorillonite doped with dodecylbenzensulfonic acid nanocomposite

In this paper, we reported a new type of high performance microwave-absorbing material, polyaniline/montmorillonite doped with dodecylbenzensulfonic acid (PAni-DBSA/MMT) nanocomposite. The microwave-absorbing properties of this nanocomposite were investigated for the frist time. The nanocomposites were synthesized from emulsion polymerization using dodecylbenzensulfonic acid (DBSA) as dopant and emulsifier. The structure of the nanocomposite was analyzed by X-ray diffraction(XRD) and FT-IR, and its results denoted that PAni-DBSA/MMT is a typical intercalative polymer/layered silicate(PLS) nanocomposite, and the interaction between MMT layers and PAni chains enhances the delocalization of free electrons in PAni chains. The complex permittivity, permeability and reflection loss (R.L.) of microwave of a 2.00 mm thick samples containing 50% by weight of PAni-DBSA/MMT nanocomposite and PANI?DBSA were measured, respectively, in 2?18 GHz range. The results showed that the PANI-DBSA/MMT nanocomposite is capable of absorbing 2.0?18 GHz microwaves, and the reflection loss was less than -10 dB in the frequency range of 9.1?12.5 GHz, while the minimum reflection loss was -15.8 dB at 11 GHz. The microwave absorbing mechanism of nanocomposite is disscused.     

Effects of cultivation conditions on the optical purity of L（＋）-lactic acid produced from corncob hydrolysate by Rhizopus oryzae

The effect ofcultivation conditionson the opticalpurity ofL(+)-lactic acid produced by Rhizopusoryzae HZS6 from corncob hydrolysate was investigated. The isomeric composition of lactic acid was influenced by the supplementation of L(+)-lactic acid to fermentation medium. L(+)-Isomer increased with the dosage,no(-)-lactic acid was observed when the concentration of supplemented L(+)-lactic acid in matrix was≥1.5g l-1. However,the L(+)-lactic acid yield decreased with the dosage. Under suitable conditions,100...     

Mechanism of Cathode Process of B(Ⅲ) in LiF-NaF-KBF4 Melt by Electrochemical Titration Technique

The mechanism of cathode process of B(Ⅲ) at molybdenum and platinum electrodes in LiF-NaF-KBF₄ melt was studied and the transferred electron number of the reaction was calculated by means of cyclic voltammetry.The effect of adsorption of electroactive component on the electrochemical response (e.g., the voltammetric i─E curves) was analyzed and discussed. The "electrochemical spectra" for linear sweep voltammetry was used to elucidate the electrode reaction accompanied by a following transform process. The results show that the reduction of B(Ⅲ) to B(0) proceeds in reversible one step three-electron reaction and the cathode process of B(Ⅲ) is affected by product adsorbed strongly at the electrode surface. It is assumed that the reduction and deposition of B(Ⅲ) at molybdenum and platinum electrodes proceed in two kinds of mechanism: (1) B(Ⅲ)+ 3e = B_ads→ B (surface diffusion deposition mechanism) and (2) B(Ⅲ) + 3e = B (direct deposition mechanism).     

Preparation and characterization of poly（styrene／maleic anhydride）／kaolin nanocomposites

The direct exfoliation of in situ intercalative copolymerized styrene/maleic anhydride charge-transfer-complex (PSMA) into the inter lamellar spaces of modified kaolin (Kao-DMSO), which was intercalated and surface modified by dimethyl sulfoxide (DMSO), was reported. The nano structure of the composites was investigated by wide-angle X-ray diffraction (XRD) and transmission electron microscopy (TEM). The interaction between kaolin surface and PSMA chain was conformed by FTIR analysis.The XRD results showed that the intercalated polystyrene-maleic anhydride units were arranged in the flattened monolayer arrangements, and the 001 diffraction peak of the original kaolin disappeared. The TEM image showed that thekaolin was exfoliated into nanometer size and dispersed in the polymer matrix. Additionally the thermal stability of the nanocomposites was studied by thermo-gravimetric analysis(TGA), and the resulting thermogram indicated that the thermal stability of the nanocomposites was significantly increased.     

Photodegradation of N-nitrosodiethylamine in water with UV irradiation

The direct photolysis of N-nitrosodiethylamine(NDEA) in water with ultraviolet(UV) irradiation was investigated.Results showed that NDEA could be completely degraded under the direct UV irradiation.The effects of the experimental conditions,including the initial concentration of NDEA,humic acid and solution pH,were studied.The degradation products of NDEA were identified and quantified with gas chromatography-mass spectrometry(GC-MS) and high performance liquid chromatography(HPLC).It was confirmed that methylamine(MA),dimethylamine(DMA),ethylamine(EA),diethylamine(DEA),NO2-and NO3-were the main degradation products.The photolysis degradation mechanism of NDEA was also discussed.As a result of N-N bond fission,NDEA was degraded by direct UV irradiation.     

Effects of Foliage Boron-Spraying on Seed Yields and Fatty Acid Composition of Tree Peony(Paeonia ostii ‘Feng Dan')

The influence of the foliage boron(B)-spaying concentration on the yield and fatty acid composition of tree peony(Paeonia ostii ‘Feng Dan') was explored in the experiment of 2014-2015. In this research, a statistically significant correlation was found between the mass concentration of foliage boron-spraying and tree peony seed yield. Maximum yield increment of tree peony seeds was obtained when the boron-spraying concentration was 4 g/L. The composition of fatty acid was analyzed by gas chromatography-mass spectrometry(GC-MS), and the main components of the fatty acid composition were quantified by internal standard method. The increase in the oil extraction rate after foliage boron-spraying nutrition of different concentration was significant and ranged between 0.04% and 11.43%. Seed oil production and oil extraction rate were also increased due to the increase of seed yields. Furthermore, foliage boron-spraying had a significant effect on the content of linolenic acid and linoleic acid in seed oil.     

Review on aggregation of acid extractants in solvent extraction of metal ions: remark on the general model

The aggregation behavior of various acid extractants in the solvent extraction systems of metal ions is re-examined and explained according to knowledge obtained in recent work. The conclusions are as follows. (1) Complexes formed by the extractants and metal ions can form reversed micelles in organic diluents, depending on the microstructures of the complexes. The dimers of the acid extractant cannot percolate to the metal-extractant aggregates, and the acid-salt complexes are always formed in the aggregates. The reversed micelles or the W/O microemulsions formed by different species cannot be associated with each other to form a unified aggregate. (2) In solvent extraction systems, hydration of the extractants and metal ions can be considered as the driving force of forming reversed micelles. (3) Information of the first approach to the insight of the bicontinuous microemulsion of NaDEHP shows that various components in the aqueous phase behave confined and very similar to the typical AOT/n-heptane W/O microemulsions. (4) In the extraction of lanthanide ions by the W/O microemulsion of sodium naphthenate, the saponification is a process of forming reversed micelle or W/O microemulsion, while the extraction step is a process of destroying reversed micelles or W/O microemulsion droplets.     

直接缩聚法合成淀粉接枝可降解聚酯和聚酯酰胺及其表征

以可溶性淀粉、乳酸、乙醇酸和己内酰胺为原料在氯化亚锡催化下直接缩聚制备得到了淀粉接枝乳酸-乙醇酸共聚物及淀粉接枝乳酸-乙醇酸-己内酰胺共聚物。用核磁共振(NMR)、差热(DSC)及热重(TG)分析分别对产物的结构和热性能进行了表征。     

聚5-羧基吲哚-聚乙交酯可降解导电共聚物的合成与表征

以N,N'-二环己基碳化二亚胺(DCC)为脱水剂、4-二甲氨基吡啶(DMAP)为催化剂,通过低温缩聚法合成可生物降解并导电的聚5-羧基吲哚(PICA)与聚乙交酯(PGA)的共聚物.合成的产物采用红外光谱仪(FT- IR)、核磁共振氢谱仪(1H NMR)、质谱仪(MS)进行表征.结果表明:产物经25 d降解了41.7％,测得掺杂的共聚物电导率为9.1×10-4 S/cm.将乳仓鼠肾细胞(BHK21)黏附于合成的齐聚物膜上,细胞增殖生长效果明显.     

丙酮酸、乳酸对体外肌酸激酶活性的抑制作用

 应用酶活测定的方法分析了肌酸激酶在不同浓度的乳酸、丙酮酸中的活性变化.实验结果说明在失活过程中没有蛋白质的聚沉,失活与乳酸浓度、丙酮酸的浓度呈正相关.通过对比实验结果提示,丙酮酸离子、乳酸离子对肌酸激酶没有明显影响,丙酮酸、乳酸是通过其解离状态的H⁺改变了机体pH值而影响肌酸激酶活性的,作者就丙酮酸、乳酸对肌酸激酶影响及其意义进行探讨.     

聚酯类可吸收型医用缝合线的单体——乙交酯及丙交酯的合成

可吸收型医用缝合线是一种能经受生物组织反应,经降解后被人体吸收的高分子材料。本文以α-羟基酸为原料合成了聚酯类可吸收型缝合线的单体:乙交酯和丙交酯,测定了它们的IR,NMR,MS以及DSC图谱。利用中间产物的质谱讨论了交酯生成的反应途径。运用DSC图谱以及加热红外光谱讨论了α-乙交酯、β-乙交酯的稳定性,得到α-乙交酯较为稳定的结论。     

BaO催化纤维素转化制备乳酸的研究

通过探索水热条件下不同类型固体碱催化剂催化糖及纤维素等转化制乳酸的反应,优选出了直接由Ba（OH）₂焙烧制备的高效固体碱BaO催化剂,进而对反应温度、催化剂用量、底物浓度等实验条件进行了优化,结果表明,在220℃、0.6 MPa N₂压力的水热条件下,BaO（0.8 g）催化纤维素（0.25 g）分解得到的乳酸收率可达75%,反应时间仅7 h。通过傅里叶红外光谱分析及X射线衍射（XRD）表征确定了催化剂组成,进而明确了催化剂的活性组分。最后,对纤维素催化转化机制进行推导后认为：BaO及其水解产生的Ba²⁺作用于纤维素分子间及分子内氢键,促进其断裂,而BaO水合生成的Ba（OH）₂提供了纤维素单体间糖苷键断键、葡萄糖异构及果糖分子内C3-C4键断键所需的碱条件。     

双金属离子水热催化转化葡萄糖制备乳酸

选择不同的双金属阳离子作为催化剂,在碱性条件下用于水热转化葡萄糖制备乳酸,发现Sn2+和Cu2+具有一定的协同作用.研究了反应温度、时间、碱加入量和金属离子比例对乳酸产率的影响,获得最优工艺条件如下:0.025 g葡萄糖,2 mmol NaOH,n(Sn2+)∶n(Cu2+)=0.25∶0.75(共1mmol),20 ...     

重组大肠杆菌利用醋酸及乳酸为碳源合成PHB

以廉价的工业副产物醋酸及乳酸为碳源,对产PHB重组大肠杆菌进行培养,考察醋酸及乳酸的添加对重组大肠杆菌生长及PHB产量的影响。将来自Cupriavidusnecator的PHB合成操纵子phaCAB基因簇克隆至pBAD载体,得到产PHB菌株BL21＿pBAD＿phaCAB,以阿拉伯糖为诱导剂,在大肠杆菌中进行重组表达。分别使用LB及M9培养基,对重组菌株BL21＿pBAD＿phaCAB进行培养,研究其生长速度及PHB产量,探索产PHB重组大肠杆菌最适培养基。以添加0.04 g/L乳酸、1.2 g/L乳酸、0.02 g/L醋酸、0.6 g/L醋酸、0.04 g/L乳酸+0.02g/L醋酸、1.2g/L乳酸+0.4g/L醋酸的M9培养基(均含2 g/L葡萄糖)为实验组,以M9培养基(含2g/L葡萄糖)为对照组,考察醋酸及乳酸的添加对重组大肠杆菌生长及PHB产量的影响。分别取第6,12,24和36小时的培养液,分析其葡萄糖、醋酸及乳酸含量的变化。结果表明,低氮型M9培养基更适合产PHB重组大肠杆菌在低糖培养环境中生长。在葡萄糖消耗殆尽后,大肠杆菌能够以醋酸及乳酸为碳源进行代谢,因此在培养基中...     

血乳酸生物传感器在新冠肺炎诊疗中的应用探讨

新冠肺炎（COVID-19）疫情爆发已造成严重危害，对新冠肺炎进行快速诊断和实施精准治疗是目前面临的重大挑战。对近年来血乳酸指标在肺炎临床中的应用及血乳酸生物传感器方法学进行了回顾，提出血乳酸水平或血乳酸清除率是新冠肺炎病情分层、治疗效果评估和判断预后的重要指标。其中POCT(即时检验)血乳酸生物传感器快捷、经济、可靠，可实现临床患者或个人（家庭）血乳酸快速和连续的检测，有利于新冠肺炎病情严重度分层和治疗效果评估，也可使患者及时识别自身状况，解除心理顾虑，促进机体康复。     

聚乳酸-聚扁桃酸共聚物的合成与表征

合成乳酸OCA和扁桃酸OCA单体,用DMAP引发乳酸OCA和扁桃酸OCA开环共聚合成可生物降解的聚乳酸-聚扁桃酸共聚物,通过调节聚合共聚单体的比例,可得到分子量从3 620¹1 800 g/mol不等的共聚物,实现了分子量可控的目的.使用1H NMR、GPC、DSC、TEM、XRD等手段对共聚物进行了表征,所得共聚物的热力学性能、降解性能等均得到改善.并对轮状病毒进行负载制备成载药微球,对其降解行为进行研究,为药物控制释放提供一类新的载体材料.