稠油降黏剂与树形大分子破乳剂的界面相互作用

利用界面膨胀流变仪和原子力显微镜(AFM)研究了2种稠油降黏剂OP 10和AES对树形大分子破乳剂SD 1的界面性质和聚集行为的影响,从界面膜角度分析2种降黏剂对稠油乳状液破乳的影响。结果表明,由于3种表面活性剂具有较高的表面活性,在界面层中具有较快的弛豫过程,因而界面弹性模量显示出明显的频率依赖性。在SD 1破乳体系中加入降黏剂OP 10后,因OP 10分子与界面聚集体之间存在快速交换过程,使界面弹性模量降低,促使脱水率升高。在SD 1破乳体系中加入降黏剂AES后,因AES分子能够插入SD 1分子聚集体中,减弱AES分子极性头基之间的静电斥力;同时SD 1分子中的EO基团在水中吸附质子带微弱正电荷,与AES分子产生微弱的静电引力,形成层状结构的混合胶束,致使混合界面膜的界面弹性模量高于SD 1吸附膜,因而脱水率降低。     

A modified lateral flow immunoassay for the detection of trace aflatoxin M1 based on immunomagnetic nanobeads with different antibody concentrations

A modified lateral flow immunoassay (two-step assay) was developed to detect trace aflatoxin M1 (AFM1) in raw milk. In contrast to conventional LFIA, two kinds of immunomagnetic nanobeads (IMNBs) were used. One IMNB with high antibody concentration was used to capture AFM1 in the test sample, whereas the other IMNB with low antibody concentration was used to elucidate the results of the test. Critical factors, such as antibody concentration of IMNBs and size of IMNBs, were investigated. The two-step assay exhibited an ideal sensitivity to screen trace AFM1 in milk samples without extra sample pretreatment. The cutoff value of the naked eye was 0.02 μg/L and satisfied the European Union's maximum limit of AFM1 in raw milk, heat-treated milk, and milk used to manufacture milk-based products and even in baby foods. With the same antibody, sensitivity was enhanced approximately 25 and 50 times when compared with conventional IMNB-based LFIA and gold-based LFIA, respectively. Corresponding results of 13 raw milk samples were obtained between this two-step assay and referenced enzyme-linked immunosorbent assay.     

髓鞘碱性蛋白对脂筏微区结构影响的模式化研究

本文主要通过原子力显微镜(AFM)和Langmuir单层膜技术研究不同浓度的髓鞘碱性蛋白(MBP)与"脂筏"(PC/SM/Cholesterol)模型相互作用形成仿生膜的物理特性.利用表面压缩模量(Cs-1)和二维维里状态方程对π-A曲线进行分析,计算了MBP与"脂筏"单层膜分子间相互作用的第二维里系数.根据二维维里状...     

Surface structure of (111)A HgCdTe

The surface of (111)A HgCdTe has been studied by reflection high-energy electron diffraction and atomic force microscopy (AFM). The as-grown liquid-phase epitaxy (LPE) surface has bilayer (3.7 ± 0.2 Å) step/terrace structures, macro-steps, and cross-hatch patterns. Macro-steps occur about the $[11\bar 2]$ and are from 10–40 Å in height. AFM and x-ray measurements indicate the as-grown epilayer is ≈0.2° off-cut (random polar angle) from the (111). 〈110〉 cross-hatch lines consistent with bilayer (step height=3.9 ± 0.2 Å) {111} slip dislocation are observed. The native oxide/carbon layer for the as-grown LPE (111)A HgCdTe is ≈8 Å. The experimental results suggest that the as-grown LPE surface approximates an equilibrium vicinal crystal structure. The 0.1% Br:ethylene glycol wet chemically etched surfaces retained the macro-step structure, but numerous small protrusions (10–100 Å height, ≈300 Å diameter) developed. The plasma-etched (111)A HgCdTe surface is crystalline, but exhibits surface disorder and is roughened.     

双功能弯曲光纤探针的制作

探针是所有扫描探针显微镜的关键部件。本文提出了一种采用普通单模光纤制作在原子力和光子扫描隧道组合显微镜(AF/PSTM)上使用的弯曲光纤探针的方法。通过合理的选择实验参数,经过热拉伸与化学腐蚀两个过程,得到弯曲部分的角度为110°~120°、锥角约60°~80°的弯曲光纤探针。经扫描电镜观察,光纤探针的尖端直径小于100nm。此种方法加工光纤探针的成品率约70%左右。     

Wavelength dependent laser-induced etching of Cr-O doped GaAs: Morphology studies by SEM and AFM

The laser induced etching of semi-insulating GaAs 〈100〉 is carried out to create porous structure under super- and sub-bandgap photon illumination (h v). The etching mechanism is different for these separate illuminations where defect states play the key role in making distinction between these two processes. Separate models are proposed for both the cases to explain the etching efficiency. It is observed that under sub-bandgap photon illumination the etching process starts vigorously through the mediation of intermediate defect states. The defect states initiate the pits formation and subsequently pore propagation occurs due to asymmetric electric field in the pore. Formation of GaAs nanostructures is observed using scanning electron (SEM) and atomic force microscopy (AFM).     

Structural entropy in detecting background patterns of AFM images

Structural entropy was developed for detecting the type of localization in charge distributions on a finite grid, especially in mesoscopic electronic systems. However, it is possible to detect and analyze superstructures, i.e., topologies consisting of more structures with different types of localization properties. In the definition of the structural entropy, the von Neumann entropy of the system is divided into two parts: first, the extension entropy, which is simply the logarithm of the occupation number; the second part is the structural entropy. On a structural entropy versus logarithm of the spatial filling factor map, the different types of localizations follow different, well-characterized curves. Spatial filling factor measures the percentage of the “filled” (i.e., high intensity) pixels of the image.An atomic force microscopy (AFM) image can be interpreted as some kind of charge distribution on a grid: after normalization, the darkness (or lightness) of the pixels fulfills all the necessary conditions. AFM image artifacts can be detected by plotting the structural entropy versus the logarithm of the spatial filling factor maps of the images. Not only the type of an added large-scale Gaussian, parabolic, exponential, or other function can be identified, but also by careful study of the curves belonging to the structures, the parameters can be detected, too.     

Unusual crystallization of polyethylene at melt/atomically flat interface: Lamellar thickening growth under normal pressure

The morphology of polyethylene (PE) crystallized at the melt/atomically flat substrate interface was studied using atomic force microscopy (AFM). Our attention is concentrated on isothermal crystallization of PE on HOPG and MoS₂ substrates at high temperatures up to 135 °C. By quenching after different times of crystallization, it was possible to “freeze” the lamellar morphology at various stages of its development at a given supercooling. After detachment of the PE sample from the substrate, individual lamellae (even 150 nm thick) and stacks of the edge-on lamellae after different stages of growth were observed. The similarity of the individual lamellae with those grown from the hexagonal phase under high pressure (characteristic tapered edges), allows to conclude that at the interface, even under normal pressure, the crystallization proceeds according to the mechanism of lamellar thickening growth.     

Calibration of AFM cantilever stiffness: a microfabricated array of reflective springs

Calibration of the spring constant of atomic force microscope (AFM) cantilevers is necessary for the measurement of nanonewton and piconewton forces, which are critical to analytical applications of AFM in the analysis of polymer surfaces, biological structures and organic molecules.

We have developed a compact and easy-to-use reference standard for this calibration. The new artifact consists of an array of 12 dual spiral-cantilever springs, each supporting a mirrored polycrystalline silicon disc of 160 μm in diameter. These devices were fabricated by a three-layer polysilicon surface micromachining method, including a reflective layer of gold on chromium. We call such an array a Microfabricated Array of Reference Springs (MARS). These devices have a number of advantages. Cantilever calibration using this device is straightforward and rapid. The devices have very small inertia, and are therefore resistant to shock and vibration. This means they need no careful treatment except reasonably clean laboratory conditions.

The array spans the range of spring constant from around 0.16 to 11 N/m important in AFM, allowing almost all contact-mode AFM cantilevers to be calibrated easily and rapidly. Each device incorporates its own discrete gold mirror to improve reflectivity. The incorporation of a gold mirror both simplifies calibration of the devices themselves (via Doppler velocimetry) and allows interferometric calibration of the AFM z-axis using the apparent periodicity in the force–distance curve before contact. Therefore, from a single force–distance curve, taking about one second to acquire, one can calibrate the cantilever spring constant and, optionally, the z-axis scale. These are all the data one needs to make accurate and reliable force measurements.     

Structural diversity of sphingomyelin microdomains

In cells plasma membrane, sphingomyelin (SM) plays a key role in the formation of a category of lipid microdomains enriched in cholesterol (Chl) often referred to as rafts. Atomic force microscopy (AFM) was used to analyze the mesoscopic topography of enriched SM microdomains in supported bilayers made of SM/dioleoylphosphatidylcholine (SM/DOPC) and SM/palmitoyl-oleoyl-phosphatidylcholine (SM/POPC) equimolar mixtures, in buffer, at room temperature. Gel–fluid phase separation occurs in both SM/DOPC and SM/POPC bilayers. The gel phase SM-enriched microdomains adopt a variety of size, shape and mesoscopic structure, from homogeneous flat domains of a few hundreds of nanometer in diameter to domains of several micrometers made of closely packed globular structures. Gel–gel phase separation in SM domains is also observed which gives rise to different structures for the diunsaturated and the mixed-saturated PC species. These differences could also extend to the interactions with Chl. This suggests that studies on rafts formation commonly performed using SM/DOPC mixture as a model should also include the physiologically more relevant POPC species.