Formation of mesoscopically organized phase structures in polymer mixtures

Mesomorphic phase structures in blends of sulfonic acid-terminated poly(ethylene glycol) (sPEG) and tertiary amino-terminated poly(2-ethylhexyl methacrylate) (aP2EHMA) were investigated by small angle X-ray scattering technique. SAXS results suggest the blends form lamellar morphology regardless of the blend composition between 30 and 70 wt% in sPEG. The blend containing 50 wt% of sPEG forms the highest ordered lamellar morphology and variation of the composition causes distortion of the ordered morphology. Due to the dissociating and reconstructing natures of the non-covalent bond between the sPEG and aP2EHMA, the lamellar morphology is maintained with the variation of the composition.     

Freeze-fracture studies on lipids and membranes

Freeze-fracture electron microscopy is especially useful for investigation of lipid structures by the advantageous fracture course within hydrophobic zones. Freezing is, on the other hand, a restriction because the structures of lamellar and non-lamellar phase states with disordered acyl chains (L(alpha), H(II,) cubic) are difficult to preserve. An important aspect of this method is therefore the lipid structure of phase states with ordered acyl chains (crystal, gel), and with a different degree of hydration. Freeze-fracture of pure lipid systems creates a valid representation of the structure of non-lamellar phases and of the general structure of the "lamellar" lipid bilayer, and lamellar phases with characteristic deformations (ripples, curvatures, plane sectors) can be identified. Fracture through the hydrophobic bilayer centre of biological membranes reveals characteristic protein components, the intramembraneous particles (IMPs). The lateral distribution of the IMPs is a helpful marker for fluid and rigid phase states, also without deformation of the lamella. The overall history and the present state of knowledge concerning the different structures revealed by the freeze-fracture and freeze-etch techniques in lipid systems, and to a limited extent in biological membranes, is reviewed, taking into account studies from our own laboratory.     

Pressure-induced phase changes of cubic monoolein - Cytochrome C mesophases

Incorporation of the protein cytochrome c (cyt c) into the hydrated bicontinuous Ia3d cubic mesophase of monoolein (MO) was investigated within a wide range of pressures by small-angle X-ray scattering (SAXS). We found that incorporation of cyt c into the cubic phase of MO has a drastic effect on the structure and pressure stability of the system: At high pressures, the lipid systems with less than 0.2 wt.% embedded protein undergo a transition to a fluid lamellar phase with smaller partial molar lipid volume. Incorporation of cyt c at levels above 0.2 wt.% promotes the formation of a new cubic phase, probably a cubic micellar phase of space group P4₃32 (Q²¹²) whose pressure stability rises with increasing protein content.     

电晕充电的聚丙烯无纺布空气过滤膜的电荷储存及稳定性

讨论了用作空气过滤材料的聚丙烯（polypropylene，PP）无纺布驻极体的电荷储存能力及 其稳定性. 研究了温度和环境湿度对电荷稳定性的影响，并从材料形貌特征和能阱结构方面 分析了电荷储存对湿度敏感效应的结构根源. 指出热处理工艺（包括常温充电后老化和高温 充电）对电荷稳定性的明显改善. 结果说明PP无纺布驻极体在常温常湿时呈现出很好的电荷 储存寿命，脱阱电荷的输运规律受慢再俘获效应控制. 关键词： 聚丙烯无纺布 驻极体 电荷稳定性 湿度和温度     

Long-range hydration effect of lipid membrane studied by terahertz time-domain spectroscopy

The hydration state of biomolecules is believed to affect their self-assembly. The hydration state of phospholipid bilayers is studied precisely by terahertz spectroscopy, by which water perturbed by a lipid membrane is detected sensitively from the observation of the relaxation dynamics of water molecules in the subpicosecond time scale. Combined with x-ray observation of the lamellar structure of the lipid, a long-range hydration effect on up to 4-5 layers of water is confirmed. Most water molecules in the lamellae fall into the hydration water, and condensation of them is also indicated.     

The combinational effect of PP electret and monoolein on transdermal delivery of cyclosporine A in vitro

In this study, single and combined enhancing effect of polypropylene (PP) electret and 10% monoolein (Mono) on cyclosporine A (CsA) transdermal delivery were studied using improved Franz diffusion cell and high performance liquid chromatography (HPLC) technique. Single use of each PP electret or 10% Mono could enhance the transdermal delivery of CsA. +500 V or ?500 V corona charged electret in combination with 10% Mono had the most significant enhancing effect. The PP electrets with the same corona voltage in absolute value had the similar enhancing effect on transdermal delivery of CsA when they were used in combination with Mono.     

Electret accelerometers: physics and dynamic characterization

Electret microphones are produced in numbers that significantly exceed those for all other microphone types. This is due to the fact that air-borne electret sensors are of simple and low-cost design but have very good acoustical properties. In contrast, most of the discrete structure-borne sound sensors (or accelerometers) are based on the piezoelectric effect. In the present work, capacitive accelerometers utilizing the electret principle were constructed, built, and characterized. These electret accelerometers comprise a metallic seismic mass, covered by an electret film, a ring of a soft cellular polymer supplying the restoring force, and a metallic backplate. These components replace membrane, spacer, and back electrode, respectively, of the electret microphone. An adjustable static pressure to the seismic mass is generated by two metal springs. The dynamic characterization of the accelerometers was carried out by using an electrodynamic shaker and an external charge or voltage amplifier. Sensors with various seismic masses, air gap distances, and electret voltages were investigated. Charge sensitivities from 10 to 40 pC/g, voltage sensitivities from 600 to 2000 mV/g, and resonance frequencies from 3 to 1.5 kHz were measured. A model describing both the charge and the voltage sensitivity is presented. Good agreement of experimental and calculated values is found. The experimental results show that sensitive, lightweight, and inexpensive electret accelerometers can be built.     

恒流电晕充电对聚四氟乙烯多孔薄膜驻极体驻极态的影响

利用常温下恒流和恒压电晕充电、充电后的等温表面电位衰减、热刺激放电和扫描电镜等实 验手段研究了恒流和恒压电晕充电技术对聚四氟乙烯多孔薄膜驻极体驻极态的影响.与恒压电晕充电相比较，恒流电晕充电时由于流过薄膜的电流恒定，增加了注入电荷在多孔结构厚度方向界面处的俘获概率，使沉积电荷密度上升，改善了驻极体的储电能力.然而，这些位于不同层深多孔界面处的俘获电荷在这类功能膜储存或使用过程中，经外激发从脱阱位置 以跳动（hopping）模式输运至背电极的路径相对缩短将导致脱阱电荷衰减较快. 关键词： 恒流电晕充电 聚四氟乙烯多孔膜 驻极体 电荷稳定性     

甘油对酪蛋白酸钠光谱性质的影响

酪蛋白酸钠(sodium caseinate, SC)所制的可食食品包装膜能有效延缓食品中水份的迁移和扩散以及阻止氧气的氧化等从而对食品起到很好地保鲜和保护作用,由于酪蛋白亲水性较强,使其所制膜阻水性和机械性能均较差, 甘油(glycerol, G)作为添加剂可以增强酪蛋白酸钠膜的韧性和阻水性,为进一步阐明G和SC之间的作用方式及对酪蛋白酸钠结构产生的影响,本实验利用荧光光谱、傅里叶红外光谱和紫外光谱特性对它们的作用方式进行了研究。结果表明：G的加入可以使SC的荧光强度降低,由荧光强度变化速率和甘油的浓度的双对数回归曲线得出了G和SC的结合常数为1.127×103 L·mol-1和结合位点数为1.161, 得出G和SC分子之间结合方式为弱化学键;虽然添加G前后SC的红外光谱的吸收峰几乎相同,但吸收强度存在较大差异,说明SC二级结构受到了影响,使得β折叠β-转角结构减少,α螺旋、无规则卷曲、结构显著增多,以及分子间氢键加强;分析紫外光谱得出,G的加入没有改变SC肽键的结构,而是与SC以非共价键的方式结合形成分子质量更大的聚合物并使吸收峰值强度下降。该研究从分子的角度揭示了G和SC分子间的作用方式。     

Thermally stimulated depolarization of human blood

Thermally stimulated current spectra of human blood preparations are investigated. The electret effect in blood is interpreted using the fundamental concepts of the electret state of matter and electrical polarization of biopolymers. It is speculated that the electret effect in blood is related to the biological cycles in the organism and associated biochemical processes. It is noted that the method of thermally stimulated current is appropriate for express diagnostics of biological objects.     

Microstructural evolution of SiC joints soldered using Zn–Al filler metals with the assistance of ultrasound

SiC ceramics were successfully soldered with the assistance of ultrasound. Two kinds of filler metals, namely non-eutectic Zn–5Al–3Cu and eutectic Zn–5Al alloys, were used. The effects of ultrasonic action on the microstructure and mechanical properties of the soldered joints were investigated. The results showed that ultrasound could promote the wetting and bonding between the SiC ceramic and filler metals within tens of seconds. For the Zn–5Al–3Cu solder, a fully grain-refined structure in the bond layer was obtained as the ultrasonic action time increased. This may lead to a substantial enhancement in the strength of the soldered joints. For the Zn–5Al solder, the shear strength of the soldered joints was only ∼102 MPa when the ultrasonic action time was shorter, and fractures occurred in the brittle lamellar eutectic phases in the center of the bond layer. With increasing ultrasonic action time, the lamellar eutectic phase in the bond layer of SiC joints could be completely transformed to a fine non-lamellar eutectic structure. Meanwhile, the grains in the bond layer were obviously refined. Those results led to the remarkable enhancement of the shear strength of the joints (∼138 MPa) using the Zn–5Al solder, which had approached that enhancement using the Zn–5Al–3Cu solder. The enhanced mechanical properties of the joints were attributed to the significant refinement of the grains and the change in the eutectic structure in the bond layer. Prolonged enhanced heterogeneous nucleation triggered by ultrasonic cavitation is the predominant refinement mechanism of the bond metals of the SiC joints.     

Realization, characterization and functionalization of lipidic wrapped carbon nanotubes

Mass-produced carbon nanotubes (CNTs) are strongly aggregated and highly hydrophobic, and processes to make them water soluble are required for biological applications. Both covalent and non-covalent strategies are pursued for obtaining stable, highly concentrated CNT aqueous dispersions. Covalent functionalization has the great disadvantage of producing an irreversible chemical modification of nanotubes, thus alterating their mechanical, chemical and electric properties. On the other hand, non-covalent functionalization is often obtained by employing surfactants that sensibly affect cell viability. Moreover, derivatization with biological moieties is often impossible through non-covalent CNT dispersion. This paper proposes a non-covalent dispersion of multi-wall CNT based on a lipidic mixture that can guarantee high concentration and high stability as well as high cytocompatibility. Moreover, CNTs wrapped with a lipid membrane are realized to demonstrate that the proposed CNTs can be functionalised with a dodecapeptide that specifically recognizes activated platelets without chemical modification of the nanotube itself.     

The comparative studies of charge storage stabilities among three PP/porous PTFE/PP electret

In this paper, PP/porous PTFE/PP electret, pressure sensitive adhesive PP/porous PTFE/PP electret and PP/porous PTFE/PP electret drug transdermal patch were prepared. By means of the surface potential decaying measurement and thermal discharge method, the charged storage stability was compared among them. The results indicated that (1) negative PP/porous PTFE/PP electret could still hold 93.4% of its initial surface potential when it was kept at RT for 16 days and exhibited better charge storage stability than positive electret. (2) The humidity almost had no influence in the charge storage stability of the electret. (3) The positive and negative PP/porous PTFE/PP adhesive electret could respectively hold 87.5% and 75.6% of their initial surface potential when being kept at room temperature for 13 days. The adhesive had a little influence in the charge storage stability of the electret. (4) Both the negative and positive PP/porous PTFE/PP electret drug transdermal patch had excellent charge storage stability.     

DITFB/4-OH-TEMPO体系中卤键作用的19F DNP研究

卤键与氢键相似,是实现分子与分子非共价键连接的作用之一,其广泛地应用于工程材料和生命化学等领域．有关卤键相互作用的动态核极化（DNP）研究还未见报道．本文利用连续波-电子顺磁共振（CW-EPR）谱仪及自主研制的DNP实验平台对存在卤键相互作用的体系——1,4-二碘四氟苯（DITFB）/4-羟基-2,2,6,6-四甲基吡啶-1-氧自由基（4-OH-TEMPO）进行¹⁹F DNP研究,并与无卤键作用对照组——六氟苯（PFB）/4-OH-TEMPO的¹⁹F DNP增强效果进行了比较．结果发现,DITFB/4-OH-TEMPO较PFB/4-OH-TEMPO具有更窄的EPR线宽和更大的¹⁹F DNP增强．这表明自由基与DITFB卤键作用削弱了自由基之间的电子自旋-自旋相互作用,从而使自由基横向弛豫时间（T_2e）增加、线宽变窄,导致DNP饱和因子和增强倍数变大．因此,可以通过卤键调控自由基电子自旋相互作用,以改善核的DNP增强效果．     

叠氮化钠对辣根过氧化物酶的荧光猝灭机制的研究

研究了辣根过氧化物酶 (HRP)和叠氮化钠 (NaN3 )作用前后的荧光光谱变化。探讨了HRP的荧光猝灭机制 ,首次运用了HRP的荧光猝灭行为确认了HRP和NaN3 之间生成了配合物。计算了HRP和NaN3 之间生成的配合物的形成常数为 7 9× 10 8L·mol-1,结合位点数为 1。研究还发现 ,NaN3 与HRP的结合 ,影响了分子构象 ,使酪氨酸和色氨酸残基的微环境受到不同程度的影响。     

Supramolecular polymorphism of DNA in non-cationic L<Subscript>α</Subscript> lipid phases

The structure of a complex between hydrated DNA and a non-cationic lipid is studied, including its phase diagram. The complex is spontaneously formed by adding DNA fragments (ca. 150 base pairs in length) to non-cationic lipids and water. The self-assembly process often leads to highly ordered structures. The structures were studied by combining X-ray scattering, fluorescence and polarized microscopy, as well as freeze-fracture experiments with transmission electron microscopy. We observe a significant increase of the smectic order as DNA is incorporated into the water layers of the lamellar host phase, and stabilization of single phase domains for large amounts of DNA. The effect of confinement on DNA ordering is investigated by varying the water content, following three dilution lines. A rich polymorphism is found, ranging from weakly correlated DNA-DNA in-plane organizations to highly ordered structures, where transmembrane correlations lead to the formation of columnar rectangular and columnar hexagonal superlattices of nucleotides embedded between lipid lamellae. From these observations, we suggest that addition of DNA to the lamellar phase significantly restricts membrane fluctuations above a certain concentration and helps the formation of the lipoplex. The alteration of membrane steric interactions, together with the appearance of interfacial interactions between membranes and DNA molecules may be a relevant mechanism for the emergence of highly ordered structures in the concentrated regime.     

退火与极化温度对尼龙11薄膜驻极体内陷阱能级分布的影响

用热释电技术研究了尼龙11薄膜驻极体制备过程中热处理与极化温度对驻极体陷阱能级分布的影响.结果显示，淬火驻极体的热释电流谱上存在四个空间电荷退陷阱电流峰，而在退火处理后则显示两个退陷阱电流峰.采用多点法对热释电流谱进行理论拟合可以将各个退陷阱电流峰分离并得到它们的陷阱深度参数.这些参数进一步表明，淬火尼龙11薄膜驻极体内存在四个空间电荷的陷阱能级，极化温度升高对它们的分布情况影响不大；退火处理后，陷阱能级减少为两个，且随着极化温度的升高，较浅的陷阱能级有明显向较深陷阱能级接近的趋势. 关键词： 尼龙11 薄膜驻极体 热释电 热处理     

毫米级栅型电场分布FEP薄膜驻极体的制备及其电荷存储性能研究

采用电晕注极和热注极技术, 在厚度为25 μm的氟化乙丙烯共聚物(FEP)表面制备了宽度为2 mm和3 mm的具有栅型电场分布的驻极体, 研究了注极温度和电极宽度对其电荷存储性能的影响. 样品注极后经150天的存储, 栅型电场分布变得清晰而有规律, 覆盖铝电极区电位已衰减至接近零, 未覆盖铝电极区仍保持高电位; 对电极宽度为2 mm和3 mm的样品, 覆盖铝电极区与未覆盖铝电极区的表面电位差分别为110 V和130 V(电场强度差分别为44 kV/cm和52 kV/cm). 表面电位跟踪测试结果表明: 电晕注极样品初始表面电位高于热注极样品; 在相同的注极方法下, 注极温度越高初始表面电位越高, 电极宽度越小初始表面电位越低. 依据电晕注极和热注极原理对实验结果的分析表明, FEP和金属铝在电荷存储性能上的差异是FEP表面蒸镀铝电极后能获得栅型电场分布的原因所在.     

白蛋白对单取代酞菁锌光谱性质和存在状态的影响

研究了单取代酞菁锌(1-[4-(2-羧基乙基)苯氧基]酞菁锌,即ZnPcC1)与白蛋白(人血清白蛋白HSA和牛血清白蛋白BSA)的共价和非共价结合作用,进而研究了结合方式对ZnPcC1的光谱性质和存住状态的影响.结果表明,ZnPcC1可以通过成酰胺键的方式与白蛋白构成共价结合物(摩尔组成比大约为7:1);ZnPc1与白...     

Structural properties of low-density liquid alkali metals

The static structure factors of liquid alkali metals have been modelled at temperatures close to their melting points and a few higher temperatures using the reverse Monte Carlo (RMC) method. The positions of 5000 atoms in a box, with full periodicity, were altered until the experimental diffraction data of the structure factor agrees with the associated model structure factor within the errors. The model generated is then analysed. The position of the first peak of the pair distribution function g(r) does not show any significant temperature dependence and the mean bond lengths can be approximated within an interval of 3.6–5.3 Å, 4.5–6.6 Å, 4.8–6.7 Å and 5.1–7.3 Å for Na, K, Rb and Cs respectively. The cosine bond distributions show similar trend with the flattening up of the first peak with increase in temperature. In addition, the coordination numbers of these liquid metals are high due to the presence of non-covalent bonding between them. On the average, we surmise that the coordination number decreases with increase in temperature