小麦秸秆半纤维素丙酸法预处理降解动力学

研究了小麦秸秆丙酸法预处理过程中半纤维素的降解动力学。结果表明,半纤维素降解过程可分为0～60 min的快速降解和60～180 min的缓慢降解2个阶段。通过建立反应动力学方程,获得了小麦秸秆丙酸法预处理的化学反应速率常数和反应级数。当温度为60、70、80和90℃时,速率常数分别为1.98×10-4、1.67×10-3、1.79×10-2和4.42×10-2,反应级数分别为1.99、1.40、0.61和0.46。在一定温度和时间条件范围内的动力学研究表明,小麦秸秆的丙酸法预处理的平均反应活化能为180.16 kJ/mol,频率因子为5.27×1024L/(mol.min)。

纤维素制备乙酰丙酸乙酯的研究进展

从纤维素原料入手,总结了合成乙酰丙酸乙酯的多种技术路线。通过技术路线优缺点对比,优选了纤维素直接醇解法,并探究了纤维素直接醇解法下乙酰丙酸乙酯形成的关键反应机理。以催化剂为切入点,指出了制备乙酰丙酸乙酯催化剂的研究进展,讨论了该领域研究存在的3个问题,特别强调了适用生物质种类的选择,展望了催化剂进一步研究的发展方向。

用气相法测定丙酸盐酸盐中N-甲基正戊胺的含量

目的建立丙酸盐酸盐中可能含有的杂质—N-甲基正戊胺的气相检测方法。方法采用RTX-5毛细管色谱柱,测定N-甲基正戊胺的含量。结果:线性范围为0.0380～0.4755mg/ml;方法的检出限为2.5575μg/ml。平均回收率为100.63%。结论:N-甲基正戊胺在气相色谱中响应值良好,采用顶空法测定避免了样品热分解引起的杂质干扰,经过方法学的验证可以作为检测N-甲基正戊胺含量的简便有效的方法。

平台化合物乙酰丙酸酯的合成研究进展

生物质被认为是世界上最丰富的可再生资源,对其进行高值化利用有助于绿色能源发展。生物质可高效转化为生物质基平台化合物——乙酰丙酸酯,并进一步制备高附加值化学品。本文详细介绍了传统的乙酰丙酸酯化法及生物质直接催化醇解法、糠醇醇解法制备乙酰丙酸酯的最新研究进展,指出催化剂的性能、反应原料、反应物物质的量比、反应时间和温度等都是影响反应的重要参数。详细综述了液体酸催化剂、固体酸催化剂、混酸催化剂及金属盐催化剂等不同体系催化制备乙酰丙酸酯的最新研究进展。总结比较了3种制备方法的优势和不足,并根据现有转化方法中仍存在着的原料的选择和预处理、反应过程复杂且副产物难控制以及催化剂成本较高、催化效率低、腐蚀设备、难回收等问题,对未来研究方向提出展望。

Application of response surface methodology in medium optimization for pyruvic acid production of Torulopsis glabrata TP19 in batch fermentation

Response surface methodology (RSM) was used to optimize the fermentation medium for enhancing pyruvic acid production by Torulopsis glabrata TP19. In the first step of optimization, with Plackett-Burman design, ammonium sulfate, glucose and nicotinic acid were found to be the important factors affecting pyruvic acid production significantly. In the second step, a 23 full factorial central composite design and RSM were applied to determine the optimal concentration of each significant variable. A second-order polynomial was determined by the multiple regression analysis of the experimental data. The optimum values for the critical components were obtained as follows: ammonium sulfate 0.7498 (10.75 g/L), glucose 0.9383 (109.38 g/L) and nicotinic acid 0.3633 (7.86 mg/L) with a predicted value of maximum pyruvic acid production of 42.2 g/L. Under the optimal conditions, the practical pyruvic acid production was 42.4 g/L. The determination coefficient (R2) was 0.9483, which ensures adequate credibility of the model. By scaling up fermentation from flask to jar fermentor, we obtained promising results.

A new multifunctional polymer:Synthesis and characterization of mPEG-b-PAA-grafted chitosan copolymer

A new multifunctional mPEG-b-PAA-grafted chitosan copolymer possessing amino and carboxyl groups,mPEG-b-PAA-g-CHI(compound 6) ,was designed for a potential application in gene/drug delivery and synthesized by the methods of reversible addition-fragmentation chain transfer(RAFT) polymerization of acrylic acid(AA) and grafting reaction of a biodegradable chitosan(CHI) derivative.Completion of the reactions and characterization of the resulting compounds were demonstrated by 1 H NMR,FTIR and gel permeation chtomatography(GPC) studies.The results show that the molar ratio of amino groups to carboxyl groups in the copolymer(compound 6) is 0.41-0.59.

Preliminary Theoretical Studies on the Combination of Halogen Ions with Crown Tetraalanylpeptide

The density functional theory based hybrid-method B3LYP was used to investigate the interaction of the halogen ions with crown tetraalanylpeptide which was the coronary structures of homodetic cyclotetraalapeptide and was represented as the model basic. Many properties including combination energy, optimum geometry structures and population analysis were calculated. It was shown that there was scarcely any change in the coronary structure of C4-Ala after combination with X. The electrons moved from halogen ions to C4-Ala during the combining process. Combination of C4-Ala with F was obviously stronger than that of Cl^- and Br. When the energy of C4-Ala-X was at minimum, the distances between halogen ions and the center of C4-Ala were 0.084 nm, 0.210 nm and 0.200 nm, respectively.

YFa and analogs:Investigation of opioid receptors in smooth muscle contraction

AIM:To study the pharmacological profile and inhibition of smooth muscle contraction by YFa and its analogs in conjunction with their receptor selectivity. METHODS:The effects of YFa and its analogs (D-Ala2) YFa, Y (D-Ala2) GFMKKKFMRF amide and Des-Phe-YGGFMKKKFMR amide in guinea pig ileum (GPI) and mouse vas deferens (MVD) motility were studied using an isolated tissue organ bath system, and morphine and DynA (1-13) served as controls. Acetylcholine was used for muscle stimulation. The observations were validated by specific antagonist pretreatment experiments using naloxonazine, naltrindole and norbinaltor-phimine norBNI. RESULTS:YFa did not demonstrate significant inhibition of GPI muscle contraction as compared with mor-phine (15% vs 62%, P = 0.0002), but moderate inhibition of MVD muscle contraction, indicating the role of κ opioid receptors in the contraction. A moderate inhibition of GPI muscles by (Des-Phe) YFa revealed the role of anti-opiate receptors in the smooth muscle contraction. (D-Ala-2) YFa showed significant inhibition of smooth muscle contraction, indicating the involvement of mainly δ receptors in MVD contraction. These results were supported by specific antagonist pretreatment assays. CONCLUSION:YFa revealed its side-effect-free analgesic properties with regard to arrest of gastroin-testinal transit. The study provides evidences for the involvement of κ and anti-opioid receptors in smooth muscle contraction.

Comparison of photodynamic therapy for skin cancers and pre-cancers with δ-aminolevulinic acid

Objective:The aim of the study was to compare the effects of photodynamic therapy(PDT) with δ-aminolevulinic acid(ALA) for patients with different kinds of skin cancers and pre-cancers.Methods:The present study enrolled seventyfive cases,which included 17 cases of actinic keratosis(AK),9 cases of Bowen's disease,11 cases of superficial basal cell carcinomas(BCC),23 cases of nodule basal cell carcinomas and 15 cases of squamous cell carcinomas(SCC),and every patient had single lesion.All patients were treated with 20% ALA topically and He-Ne laser weekly for three times,and followed up 1-3 years.Results:After therapy,the rates of complete reaction(CR) were 100% in AK lesions,77.8% in Bowen's diseases,90.9% in superficial BCCs,47.8% in nodule BCCs,and 50.3% in SCCs,which had significant differences among these five kinds of lesions(H = 18.27,P < 0.05).The therapeutic effectiveness of ALA-PDT for AK was superior to that of Bowen's disease(Q = 4.364,P < 0.05),superficial BCC(Q = 5.55,P < 0.01),SCC(Q = 8.94,P < 0.01) and nodule BCC(Q = 17.91,P < 0.01);the effect of Bowen's disease was better than that of SCC(Q = 7.8,P < 0.01),nodule BCC(Q = 13.44,P < 0.01);the effect of superficial BCC was better than that of SCC(Q = 9.73,P < 0.01),nodule BCC(Q = 16.28,P < 0.01),but similar with Bowen's disease(Q = 0.96,P > 0.05);the effect of SCC was better than that of nodule BCC(Q = 17.74,P < 0.01).Conclusion:Our study shows that therapeutic effectiveness of ALA-PDT for AK is best in five diseases,and Bowen's disease and superficial BCC are secondary,while nodule BCC and SCC are at the bottom.

A new solid acid SO_4^(2-)/TiO_2 catalyst modified with tin to synthesize 1,6-hexanediol diacrylate

A new solid acid catalyst,SO4^2-/TiO2 modified with tin,was prepared using a sol-gel method and its physicochemical properties were revealed by nitrogen adsorption-desorption,X-ray powder diffraction,scanning electron microscopy,Fourier transform infrared spectroscopy,infrared spectroscopy of adsorbed pyridine,temperature-programmed desorption of ammonia and thermal gravimetric analysis.The structure,acidity and thermal stability of the SO4^2-/TiO2-SnO2 catalyst were studied.Incorporating tin enlarged the specific surface area and decreased crystallite size of the SO4^2-/TiO2 catalyst.The total acid sites of the modified catalyst increased and Bronsted acid strength remarkably increased with increasing tin content.The decomposition temperature of sulfate radical in the modified catalyst was 100 ℃ greater and its mass loss was more than twice that of the SO4^2-/TiO2 catalyst.The SO4^2-/TiO2-SnO2 catalyst was designed to synthesize 1,6-hexanediol diacrylate by esterification of 1,6-hexanediol with crylic acid.The yield of 1,6-hexanediol diacrylate exceeded 87% under the optimal reaction conditions：crylic acid to 1,6-hexanediol molar ratio = 3.5,catalyst loading = 7%,reaction temperature = 130 ℃ and reaction time = 3 h.The modified catalyst exhibited excellent reusability and after 10 cycles the conversion of 1,6-hexanediol was above 81%.

Synthesis of Novel Electron Donors and Their Application to Propylene Polymerization

A series of electron donors,including 1,1-cyclopentanecarboxylic acid diethyl ester (CPCADEE),1,1cyclopentanedimethanol acetic diester (CPDMAD),1,1-biethoxymethyl pentane (BEMP),2,2-diethyl diethylmalonate (DEDEM)and 2,2-diethyl-1,3-propanediol acetic diester (DEPDADE),were synthesized by diethyl malonate (DEM).The purities and structures of the above products were characterized by gas chromatography (GC) and gas chromatography-mass spectrometer (GC-MS),respectively.Furthermore,the possible optimal three-dimensional structures of these donors were simulated by means of Gaussian 03 and Chem 3D.Then these electron donors were coordinated with tetrachloro titanium (TiCl 4) and chloride magnesium (MgCl 2)to obtain the catalysts for the polymerization of propylene.The catalytic activities and properties of polypropylene are greatly improved by adding external donor(ED) when CPCADEE or DEPDADE is used as internal donor(ID).However,when BEMP was used as ID,the highest catalytic activity is obtained without adding ED,which can reduce production costs and simplify catalytic synthesis.The experiments indicate that BEMP has the shortest distance of oxygen atoms and the highest electronegativity.

Design and Synthesis of Novel Fluorine-containing Acrylates

A series of novel fluorine-containing acrylates 6a-6g were synthesized via the condensation of ethyl cyanoacetate and trifluoroacetic anhydride, followed by chloridization and the coupling reaction with amines. These new compounds exhibited some biological activity as preliminary bioassay indicated. A plausible reaction mechanism was outlined and discussed.

Prevalence of gastric varices and results of sclerotherapy with N-butyl 2 cyanoacrylate for controlling acute gastric variceal bleeding

AIM： To study the prevalence, predictors and control of bleeding following N-butyl 2 cyanoacrylate （NBC） sclerotherapy of gastric varix （GV）. METHODS： We analyzed case records of 1436 patients with portal hypertension, who underwent endoscopy during the past five years for variceal screening or upper gastrointestinal （GI） bleeding. Fifty patients with bleeding GV underwent sclerotherapy with a mean of 2 mL NBC for control of bleeding. Outcome parameters were primary hemostasis （bleeding control within the first 48 h）, recurrent bleeding （after 48 h of esophagogastro-duodenoscopy） and in-hospital mortality were analyzed. RESULTS： The prevalence of GV in patients with portal hypertension was 15% （220/1436） and the incidence of bleeding was 22.7% （50/220）. Out of the 50 bleeding GV patients, isolated gastric varices （IGV-Ⅰ） were seen in 22 （44%）, gastro-oesophageal varices （GOV） on lesser curvature （GOV-Ⅰ） in 16 （32%）, and GOV on greater curvature （GOV-Ⅱ） in 15 （30%）. IGV-Ⅰ was seen in 44% （22/50） patients who had bleeding as compared to 23% （39/170） who did not have bleeding （P 〈 0.003）. Primary hernostasis was achieved with NBC in all patients. Re-bleeding occurred in 7 （14%） patients after 48 h of initial sclerotherapy. Secondary hemostasis was achieved with repeat NBC sclerotherapy in 4/7 （57%）. Three patients died after repeat sclerotherapy, one during transjugular intrahepatic portosystemic stem shunt （TIPSS）, one during surgery and one due to uncontrolled bleeding. Treatment failure-related mortality rate was 6% （3/50）. CONCLUSION： GV can be seen in 15% of patients with portal hypertension and the incidence of bleeding is 22.7%. NBC is highly effective in controlling GV bleeding. In hospital mortality of patients with bleeding GV is 6%.

Grafting of 2-Hydroxyethyl Methacrylate onto Silk by Atom Transfer Radical Polymerization

Silk was grafted using 2-hydroxyethyl methacrylate(HEMA)by atom transfer radical polymerization(ATRP)method.The amino groups and hydroxyl groups on the side chains of the silk fibroin was reacted with 2-bromoisobutyryl bromide(BriB-Br)to obtain efficient macroinitiator for ATRP.And the macroinitiator was grafted with HEMA in water aqueous using CuBr/N,N,N',N",N"-pentamethyldiethylenetriamine(PMDETA)as catalyst system.The effects of monomer concentration,the proportion of CuBr and PMDETA,grafting temperature and time on the silk grafting were discussed,and the optimal grafting technology was obtained.FT-IR characterization of the grafted silk showed a peak corresponding to HEMA,which indicated that HEMA was grafted onto the surface of silk.ATRP method could be applied on the silk modification and this technique provided a new way for silk grafting.

Preparation of pH-responsive membranes with amphiphilic copolymers by surface segregation method

Novel pH-responsive membranes were prepared by blending pH-responsive amphiphilic copolymers with polyethersulfone(PES) via a nonsolvent-induced phase separation(NIPS) technique. The amphiphilic copolymers bearing Pluronic F127 and poly(methacrylic acid)(PMAA) segments, abbreviated as PMAA n–F127–PMAA n,were synthesized by free radical polymerization. The physical and chemical properties of the blend membranes were evaluated by scanning electron microscopy(SEM), Fourier transform infrared(FTIR) spectrum, water contact angle, Zeta potential and X-ray photoelectron spectroscopy(XPS). The enrichment of hydrophilic PMAA segments on the membrane surfaces was attributed to surface segregation during the membrane preparation process. The blend membranes had signi ficant p H-responsive properties due to the conformational changes of surface-segregated PMAA segments under different pH values of feed solutions. Fluxes of the blend membranes were larger at low p H values of feed solutions than that at high pH values. The pH-responsive ability of the membranes was enhanced with the increase of the degree of PMAA near-surface coverage.

Direct fabrication of carbon nanotube-graphene hybrid films by a blown bubble method

Hybridization of carbon nanotubes （CNT） with graphene provides a promising means of integrating the attributes of both materials, thereby enabling widespread application. Here, we present a method to directly assemble hybrid CNT- graphene films by a blown bubble method combined with selective substrate annealing. We use polymethylmethacrylate （PMMA） as the polymeric matrix to blow bubbles containing self-assembled multi-walled CNT arrays, and then transform the bubble film into a CNT-graphene hybrid film by thermal annealing on a Cu substrate; PMMA serves as the carbon source for growing single to few-layer graphene among the CNT network until a continuously hybridized structure is formed. Compared to the bare （non-hybridized） CNT networks, the hybrid films exhibit improved electrical conductivity and structural integrity. Our method also enables the fabrication of a multi-walled CNT-Si solar cell, which has high power conversion efficiency, through the assembly of hybrid CNT-graphene structures.

States of Water in Hydrogels Containing with Glyceryl Methacrylate

Hydrogel materials were prepared by thermopolymerization with different content of glyceryl methacrylate and hydroxyethyl methacrylate. The different states of water in swelling hydrogels were described and studied by differential scanning calorimetry(DSC). It was found that the hydrophilicity of GMA was stronger than HEMA,the water content and bound water of GMA hydrogel are higher than HEMA hydrogel.With the increase of GMA content, the content of free water in hydrogel increased. When GMA content was lower than 50%, the increase of GMA content also increased the content of bound water; but when GMA content was higher than 50%, the increase of GMA content decreased the content of bound water, which was caused by the chain hydrogen bond formed on the GMA chain with hydroxyl group each other.