聚乙烯醇水凝胶自修复性能

高浓度聚乙烯醇（PVA）水凝胶具有一定的修复功能,但其自修复机理及制备工艺参数对其修复性能的影响缺乏研究。本文采用冷冻-解冻法制备了高浓度自修复PVA水凝胶,通过调整PVA水凝胶制备工艺参数（PVA分子量、PVA浓度、冷冻时间、解冻时间、冷冻-解冻次数、修复时间、冷冻温度等）得到了最佳工艺条件,分析了水凝胶自修复机理,并研究了PVA水凝胶的多次自修复性能。研究结果表明：相对分子质量大的PVA制备的水凝胶自修复性能好;其中冷冻时间为2h,解冻时间为1h,一次冷冻-解冻循环制备得到的水凝胶自修复性能最好,最佳修复时间为12h,能较好地进行反复自修复。指出水凝胶自修复性能主要是由其内部可逆氢键的相互作用形成的,其主要影响源于冷冻-解冻处理后水凝胶内部羟基含量及PVA分子的流动性。     

聚乙烯醇/粘土复合凝胶的制备及性能

文章采用冷冻-解冻法和硼酸法完成了聚乙烯醇包埋粘土微球复合材料的制备,进行了复合凝胶的力学性能和溶胀特性的测试,研究比较了不同的制备方法对复合凝胶的影响。结果表明冷冻-解冻法制备的PVA凝胶比硼酸法制备的PVA凝胶承受的拉升强度更大可以达到3.29MPa,添加粘土后的复合凝胶的溶胀性能减弱到原来的一半。     

聚乙烯醇/膨润土杂化水凝胶的力学性能和溶胀行为

利用冷冻-解冻法制备了聚乙烯醇/膨润土杂化水凝胶. X射线衍射结果表明,膨润土以剥离形式分布在水凝胶基体中. 研究结果表明,与纯PVA5水凝胶相比,经过5个冷冻-解冻循环制备的含2%(w)膨润土的杂化水凝胶的拉伸模量、拉伸强度和断裂伸长率分别增加了44.0%, 74.2%和25.2%,而溶胀行为与5个循环的纯水凝胶相近. 含0.5%(w)膨润土的杂化水凝胶的拉伸模量和拉伸强度高于基体水凝胶,其在溶胀400 min时的溶胀度高于所有的样品.     

高强度多孔聚乙烯醇水凝胶的制备

为制备兼顾多孔性和高强度的水凝胶,本研究利用循环冷冻和冷冻干燥联用设计和制备了一系列聚乙烯醇水凝胶。从聚乙烯醇溶液的浓度、循环冷冻次数、单次冷冻时长三个方面对水凝胶的力学性能、内部微观形貌、含水量进行了研究。结果表明:以质量分数14%浓度的聚乙烯醇水溶液经过3次循环冷冻过程(16h冷冻,8h解冻)和液氮冷冻冰干后的支架,再经溶胀平衡后得到的PVA水凝胶具有最佳的力学性能,此时PVA水凝胶的拉伸强度为5.74MPa,断裂伸长率为347%;改变循环冷冻次数可有效地调节PVA水凝胶的含水量;水凝胶力学性能提高来源于体系结晶度的增大。     

具有各向异性结构的聚乙烯醇水凝胶的制备及性能表征

首先对聚乙烯醇（PVA）水溶液进行定向冷冻-解冻制备出具有各向异性结构的PVA水凝胶,然后采用⁶⁰Co-γ射线对其进行辐射交联以提高其热稳定性和力学性能。扫描电子显微镜（SEM）结果显示PVA水凝胶保持了各向异性的微观结构,在平行冷冻方向上具有相对规整的取向结构,在垂直冷冻方向上呈现均匀孔洞结构。热稳定性测试结果表明：辐射剂量在30~70 kGy范围内、定向冷冻次数为1次的PVA水凝胶在60℃热水浴中保持凝胶状态长达10 h以上。对辐射交联PVA水凝胶进行拉伸力学性能测试,凝胶具有各向异性的拉伸性能,且拉伸强度和弹性模量均有提高,辐射剂量为10 kGy、定向冷冻次数为3次的PVA水凝胶（DFT-RC-3-10）在垂直定向冷冻方向上的拉伸强度和弹性模量分别为0.86和0.10 MPa。     

羧化淀粉/PVA复合水凝胶的制备与性质研究

由顺丁烯二酸酐羧化的淀粉与聚乙烯醇按比例进行溶液混合,经冷冻-解冻形成物理交联复合水凝胶。采用WAXD和DSC分析了复合凝胶的结晶性和热性能,探讨了羧化淀粉的含量及其取代度对凝胶结构和溶胀性质的影响。结果表明,羧化改性增强了淀粉与PVA的相互作用,复合水凝胶的稳定性和溶胀性取决于羧化淀粉的质量分数及其取代度。     

中国专利

<正>一种用于光热水蒸气转化的聚乙烯醇碳纳米管凝胶材料本发明公开了一种用于光热水蒸气转化的聚乙烯醇碳纳米管凝胶材料,将聚乙烯醇颗粒加热溶解在去离子水中得A溶液,用去离子水稀释碳纳米管分散液,常温搅拌稀释得B溶液;依次混合戊二醛溶液、甲醇溶液、乙酸溶液、浓硫酸和去离子水,配置成C溶液;将A溶液、B溶液、C溶液和去离子水混合,常温搅拌待完全均匀混合后倒入模具承装;将用模具承装的溶液冷冻、解冻重复若干次;最后将冷冻的凝胶干燥处理完全,得到聚乙烯醇碳纳米管复合凝胶。本发明制备的聚乙烯醇/碳纳米管凝胶能够实现高效光热水蒸气转化。     

高浓度聚乙烯醇水凝胶性能研究

利用冷冻-解冻法制备了不同类型高浓度(30wt.%)聚乙烯醇(PVA)水凝胶,研究了PVA水凝胶的溶胀率、拉伸强度和流变特性。结果表明,高浓度PVA水凝胶的溶胀率受PVA的分子量和醇解度影响较大,PVA分子量越大,水凝胶的溶胀率越高;醇解度越高,溶胀率越低。随着冻融循环次数的增加,PVA水凝胶的强度增强;分子量越大,PVA水凝胶的强度反而越弱。在一定的频率范围内,PVA水凝胶的模量随着频率的增加而增加;随着冻融循环次数的增加,PVA水凝胶的储能模量增大。     

冷冻解冻法破除液体石蜡W/O乳状液

冷冻解冻法是一种新型的破除W/O乳状液的物理破乳方法.为了揭示冷冻解冻破乳作用机制,本文以稳定性好的液体石蜡W/O乳状液为研究对象,采用差热扫描量热仪（DSC）与显微镜,研究了高黏度连续相液体石蜡体系的W/O乳状液的冷冻解冻破乳过程.结果表明：该破乳过程是一个渐进过程.当乳珠粒径均匀细小,小于5.5 μm时,乳珠在冷冻解冻循环中逐渐长大,经多次冷冻解冻后完成破乳;然而当乳珠粒径较大时,如51 μm,乳状液体系仅需单次冷冻解冻循环就可破乳较完全,破乳率超过90%.此外,乳状液含水量的增加有利于提高破乳效率.乳状液水相的凝固点受乳珠尺度的影响,但受含水量的影响不显著.当乳珠粒径较大时,水相凝固点随乳珠粒径的减小而降低;但是当乳珠粒径降至5.5 μm时,乳珠粒径的改变对其影响已不明显.     

一种形状记忆水凝胶材料的制备及其应用

具有形状记忆功能的水凝胶材料在可穿戴电子设备方面的应用具有广阔的应用前景。如何利用更加简洁的方法制备出新型的环保型水凝胶材料目前仍然是一个大的挑战。研究通过采用冷冻—解冻的制备方法,得到了一种具有形状记忆功能的新型水凝胶材料。在该材料中,微纤化纤维素通过氢键与海藻酸钠结合,增强了水凝胶网络的机械性能,铁离子与海藻酸钠的羧基官能团配位,从而以共价键方式与水凝胶网络骨架稳定相连,进一步增强水凝胶网络骨架的力学性能。该材料可以用于识别五倍子酸。该类水凝胶材料的制备方法具有良好的应用前景。     

Eicosapentaenoic and arachidonic acid: Comparison of metabolism and activity in murine epidermal cells

The biological activity, including metabolism and modulation of ornithine decarboxylase activity and DNA synthesis, of arachidonic acid (AA) and eicosapentaenoic acid (EPA) were compared in epidermal cells from SENCAR mice. Radiolabelled AA and EPA were found to be similarly incorporated into and released from membrane phospholipids of unstimulated cultures. However, when cells were stimulated with the tumor promoter 12-0-tetradecanoylphorbol-13-acetate (TPA), the release of AA was significantly higher than the release of EPA. The extent of metabolism of AA and EPA to prostaglandins was determined in both freeze-thawed cell preparations and in viable cultured cells. In the freeze-thawed preparations, use of AA as a substrate resulted in significantly more PGF than when EPA was used as the substrate. However, more PGE₃ was formed than PGE₂. PGD levels were the same for either fatty acid precursor. Prostaglandin production was also determined in viable cultured cells since other influences such as phospholipase A₂ activity can modify prostaglandin production. Control cultures prelabelled with either AA or EPA produced similar amounts of the respective PGF, PGE, and PGD. However, TPA-stimulated cultures produced significantly higher amounts of each prostaglandin in cultures prelabelled with AA compared to cells prelabelled with EPA. HETE or HEPE production was the same both for cultured cells prelabelled with AA or EPA and for homogenates from uncultured cells incubated directly with the radiolabelled fatty acids. TPA-induced ornithine decarboxylase (ODC) was significantly higher in AA-treated cultures compared to EPA-treated cultures. AA supports DNA synthesis to a greater extent than EPA, either alone or in the presence of TPA. These findings suggest that AA and EPA do not have equivalent biological activity in mouse epidermal cells.     

MAGEA4 Coated Extracellular Vesicles Are Stable and Can Be Assembled In Vitro

Extracellular vesicles (EVs) are valued candidates for the development of new tools for medical applications. Vesicles carrying melanoma-associated antigen A (MAGEA) proteins, a subfamily of cancer-testis antigens, are particularly promising tools in the fight against cancer. Here, we have studied the biophysical and chemical properties of MAGEA4-EVs and show that they are stable under common storage conditions such as keeping at +4 °C and −80 °C for at least 3 weeks after purification. The MAGEA4-EVs can be freeze-thawed two times without losing MAGEA4 in detectable quantities. The attachment of MAGEA4 to the surface of EVs cannot be disrupted by high salt concentrations or chelators, but the vesicles are sensitive to high pH. The MAGEA4 protein can bind to the surface of EVs in vitro, using robust passive incubation. In addition, EVs can be loaded with recombinant proteins fused to the MAGEA4 open reading frame within the cells and also in vitro. The high stability of MAGEA4-EVs ensures their potential for the development of EV-based anti-cancer applications.     

Drying of Potato Tissue Pretreated by Ohmic Heating

The influence of the ohmic heating pretreatment on convective drying of potato tissue was investigated. The degree of material damage Z under the different modes of electrical treatment is studied and the electroporation phenomena is assumed to be the main reason of material disintegration. The relations between Z, electric field strength E, energy input W, and temperature of ohmic heating T are analyzed. Two different damage stages, short and long, are revealed in this study. It is shown that ohmic treatment at relatively low fields (E < 100 V/cm) results in incomplete damage of material, but allows to obtain material with high disintegration degree Z ≈ 0.7 at E > 70 V/cm. The electric field strength E and the total electric energy input W influence considerably the drying rate. The highest drying rates are always observed for more energy consuming freeze-thawed pretreatment, but the AC pretreatment seems to be promising for enhancing the air drying processes.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

Sapindaceae,cyanolipids, and bugs

Scentless plant bugs (Heteroptera: Rhopalidae) are so named because adults of the Serinethinae have vestigial metathoracic scent glands. Serinethines are seed predators of Sapindales, especially Sapindaceae that produce toxic cyanolipids. In two serinethine species whose ranges extend into the southern United States,Jadera haematoloma andJ. sanguinolenta, sequestration of host cyanolipids as glucosides renders these gregarious, aposematic insects unpalatable to a variety of predators. The blood glucoside profile and cyanogenesis ofJadera varies depending on the cyanolipid chemistry of hosts, and adults and larvae fed golden rain tree seeds (Koelreuteria paniculata) excrete the volatile lactone, 4-methyl-2(5H)-furanone, to which they are attracted.Jadera fed balloon vine seeds (Cardiospermum spp.) do not excrete the attractive lactone. Loss of the usual heteropteran defensive glands in serinethines may have coevolved with host specificity on toxic plants, and the orientation ofJadera to a volatile excretory product could be an adaptive response to save time.Mention of a commercial product does not consititute an endorsement by the USDA.     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.