阴离子型水性聚氨酯的制备及进展

综述了阴离子型水性聚氨酯亲水基团的研究状况。亲水基团的引入方式有多种,可以通过小分子扩链剂引入,也可通过含有离子基团的聚酯或聚醚引入,或在水性聚氨酯的分子结构中同时引入磺酸盐和羧酸亲水基团,形成混合内乳化剂,可提高水性聚氨酯的耐水性和其他物理性能,降低溶剂的使用量。     

渗透蒸发透水膜的研究进展

根据渗透蒸发透水材料的发展过程特征，对已有的渗透蒸发透水膜材料进行了系统综述，并对各种透水膜的渗透蒸发分离性能作了阐述．     

Self-assembly: a minimalist route to the fabrication of nanomaterials

Self-assembly of molecular or nonmolecular components by non-covalent interactions offers an invaluable tool for the preparation of discrete nanostructures and extended 2D and 3D materials, which are often not accessible by any other fabrication process. In this article we summarize the most recent advances in the generation of nanomaterials such as self-assembled monolayers (SAMs) and structures formed from amphiphilic molecules, colloids, peptides, and polymers by nontemplated self-assembly either at the solid state or in solution. The current status of templated self-assembly and the use of self-assembled structures as template and for patterning other materials is also covered. A special emphasis is placed on strategies presenting either original and somehow exploratory approaches, eventually combining bottom-up and top-down methods, or that concern methods for the production of materials with potential application, e.g., in photonics, as sensors, for drug delivery and electric and magnetic devices. In all the sections, we outline self-organization and applications enabled with self-separated block copolymers.     

Solid self microemulsification of Atorvastatin using hydrophilic carriers: a design

Context: Atorvastatin has a limited advantage to formulate oral dosage forms.

Objective: To enhance the solubility of Atorvastatin and to design the suitable solid self-microemulsifying drug delivery systems (S-SMEDDS)

Materials and methods: The clear and transparent self-microemulsifying drug delivery system (SMEDDS) were formulated using coconut oil and isopropyl myristate as lipid phases; Tween 80 as surfactant; PEG 400 and glycerin as co-surfactant at 2:1, 3:1, 1:2 and 1:3 ratio. The pseudo ternary phase diagrams were constructed to identify the microemulsion region. The SMEDDS were evaluated for zeta potential, poly dispersity index, globule size, pH, viscosity and drug release. The solid SMEDDS were developed by employing adsorption and melt granulation methods. The S-SMEDDS were evaluated for micromeritics, morphology, solid state property, reconstitution ability, drug release and stability.

Results: The micro formulations formed with particle size of 25?nm had shown a 3-folds rise in drug release. The solid SMEDDS had reconstituted to a good microemulsion rapidly in 1–3?min, with a release of 94.62% at the end of 30?min and behaved as immediate releasing capsules. Their shelf-life was found to be 1.3 years.

Discussion: The 1:3 ratio SMEDDS had shown more drug release owing to their less particle size. The solid SMEDDS had shown an increased dissolution profiles than atorvastatin. The solid state of the drug had changed in formulation inferring their enhanced solubility.

Conclusion: The solid form of atorvastatin liquid SMEDDS had been formulated successfully with enhanced shelf life and solubility.     

Self-assembly of silver nanoparticles: Formation of a thin silver film in a polymer matrix

A synthetic route is presented for the preparation of a silver film in presence of UV-radiation. Methoxy polyethylene glycol, a water-soluble polymer, was used as the reducing agent of the silver ions in the presence of an ultraviolet source to produce silver nanoparticles. During solution stirring, a centrifugal force was generated at the center of the solution. At this point on the surface of the solution, the nanoparticles coalesced to form a self-assembly of small subunits that ultimately develops into a film-like network.     

Self-assembly of a silica-surfactant nanocomposite in a porous alumina membrane

A mesoporous membrane composed of nanochannels with a uniform diameter has a potential use for precise size-exclusive separation of molecules. Here, we report a novel method to form a hybrid membrane composed of silica-surfactant nanocomposite and a porous alumina membrane, by which size-selective transport of molecules across the membrane becomes possible. The nanocomposite formed inside each columnar alumina pore was an assembly of surfactant-templated silica-nanochannels with a channel diameter of 3.4 nm; the channel direction being predominantly oriented along the wall of the columnar alumina pore. Molecules could be transported across the membrane including the silica-surfactant nanocomposite with a capability of nanometre-order size-exclusive separation. Our proposed membrane system has a potential use not only for separation science, but also catalysis and chip technologies.     

Nucleotide identification and orientation discrimination of DNA homopolymers immobilized in a protein nanopore

Nanopores have been used as extremely sensitive resistive pulse sensors to detect analytes at the molecular level. There has been interest in using such a scheme to rapidly and inexpensively sequence single molecules of DNA. To establish reference current levels for adenine, cytosine, and thymine nucleotides, we measured the blockage currents following immobilization of single-stranded DNA polyadenine, polycytosine, and polythymine within a protein nanopore in chemical orientations in which either the 3' or the 5' end enters the pore. Immobilization resulted in low-noise measurements, yielding sharply defined current distributions for each base that enabled clear discrimination of the nucleotides in both orientations. In addition, we find that not only is the blockage current for each polyhomonucleotide orientation dependent, but also the changes in orientation affect the blockage currents for each base differently. This dependence can affect the ability to resolve polyadenine and polythymine; with the 5' end entering the pore, the separation between polyadenine and polythymine is double that observed for the 3' orientation. This suggests that, for better resolution, DNA should be threaded through the 5' end first in nanopore DNA sequencing experiments.     

Self-assembly of silver nanoparticles in a polymer solvent: formation of a nanochain through nanoscale soldering

By exploiting the orientation of the polymer methoxy polyethylene glycol (MPEG), directional growth of silver particles has been obtained in the presence of ultraviolet irradiation for the first time. MPEG generates free radicals, serves as the reducing agent in presence of ultraviolet irradiation towards the silver ions, and also acts as the template for the silver particles involved in the formation of a silver chain.     

Self-assembly of a sulphur-terminated graphene nanoribbon within a single-walled carbon nanotube

The ability to tune the properties of graphene nanoribbons (GNRs) through modification of the nanoribbon's width and edge structure widens the potential applications of graphene in electronic devices. Although assembly of GNRs has been recently possible, current methods suffer from limited control of their atomic structure, or require the careful organization of precursors on atomically flat surfaces under ultra-high vacuum conditions. Here we demonstrate that a GNR can self-assemble from a random mixture of molecular precursors within a single-walled carbon nanotube, which ensures propagation of the nanoribbon in one dimension and determines its width. The sulphur-terminated dangling bonds of the GNR make these otherwise unstable nanoribbons thermodynamically viable over other forms of carbon. Electron microscopy reveals elliptical distortion of the nanotube, as well as helical twist and screw-like motion of the nanoribbon. These effects suggest novel ways of controlling the properties of these nanomaterials, such as the electronic band gap and the concentration of charge carriers.     

Biological colloid engineering: Self-assembly of dipolar ferromagnetic chains in a functionalized biogenic ferrofluid

We have studied the dynamic behavior of nanoparticles in ferrofluids consisting of single-domain, biogenic magnetite (Fe(3)O(4)) isolated from Magnetospirillum magnetotacticum (MS-1). Although dipolar chains form in magnetic colloids in zero applied field, when dried upon substrates, the solvent front disorders nanoparticle aggregation. Using avidin-biotin functionalization of the particles and substrate, we generated self-assembled, linear chain motifs that resist solvent front disruption in zero-field. The engineered self-assembly process we describe here provides an approach for the creation of ordered magnetic structures that could impact fields ranging from micro-electro-mechanical systems development to magnetic imaging of biological structures.     

Structural analysis of polymer end groups by electrospray ionization high-energy collision-induced dissociation tandem mass spectrometry

Chemical structures of polymer end groups play an important role in determining the functional properties of a polymeric system. We present a mass spectrometric method for determining end group structures. Polymeric ions are produced by electrospray ionization (ESI), and they are subject to source fragmentation in the ESI interface region to produce low-mass fragment ions. A series of source-fragment ions containing various numbers of monomer units are selected for high-energy collision-induced dissociation (CID) in a sector/time-of-flight tandem mass spectrometer. It is shown that high-energy CID spectra of source-induced fragment ions are very informative for end group structure characterization. By comparing the CID spectra of fragment ions with those of known chemicals, it is possible to unambiguously identify the end group structures. The utility of this technique is illustrated for the analysis of two poly(ethylene glycol)-based slow-releasing drugs where detailed structural characterization is of significance for drug formulation, quality control, and regulatory approval. Practical issues related to the application of this method are discussed.     

Self-assembly of fractal magnetite-silica aggregates in a static magnetic field

This paper examines the mechanism underlying the formation of linear and fractal aggregates of high-conductivity magnetic nanoparticles in a static magnetic field. A transition between dendritic and fractal structures in response to a change in magnetic field is investigated by scanning electron microscopy and atomic force microscopy.     

Self-assembly of cadmium metasilicate nanowires as a broadband optical limiter

Cadmium metasilicate nanowires (CdSiO₃ NWs) have been synthesized through a facile, eco-friendly, low-cost water–ethanol mixed-solution hydrothermal route. The transmission electron microscopy measurements of as-prepared samples indicate that the CdSiO₃ NWs with diameters in the range of 10–60 nm and lengths of more than 1 μm were constructed by self-assembly of 5–10-nm CdSiO₃ nanoparticles with good crystallinity. The monoclinic phase formation of the sample is studied in detail by X-ray diffraction, Fourier-transform infrared spectroscopy, and thermo gravimetric analysis. The results indicate that a pure monoclinic phase of CdSiO₃ can be obtained by a hydrothermal route without further calcinations and SiO₄ tetrahedra were the main constituents of the CdSiO₃ NWs. The nanosecond optical limiting (OL) effects were characterized by using an open-aperture (OA) Z-scan technique with 4-ns laser pulses at both 532 and 1064 nm. Theses CdSiO₃ NWs displayed an excellent OL performance at 532 and 1064 nm, which was better than carbon nanotubes, a benchmark optical limiter. Input-fluence dependent scattering measurements suggested than nonlinear scattering played an important role in the observed optical limiting behavior in CdSiO₃ NWs at 532 and 1064 nm. More significantly, the NLO performance in CdSiO₃ NWs incorporated solid silica gel glass has been improved in comparison to those dispersed in water. The unique structure and excellent OL property render these CdSiO₃ NWs competitors in the realms of optical limiting applications.     

Italian sociologists: a community of disconnected groups

Examining coauthorship networks is key to study scientific collaboration patterns and structural characteristics of scientific communities. Here, we studied coauthorship networks of sociologists in Italy, using temporal and multi-level quantitative analysis. By looking at publications indexed in Scopus, we detected research communities among Italian sociologists. We found that Italian sociologists are fractured in many disconnected groups. The giant connected component could be split into five main groups with a mix of three main disciplinary topics: sociology of culture and communication (present in two groups), economic sociology (present in three groups) and general sociology (present in three groups). By applying an exponential random graph model, we found that collaboration ties are mainly driven by the research interests of these groups. Other factors, such as preferential attachment, gender and affiliation homophily are also important, but the effect of gender fades away once other factors are controlled for. Our research shows the advantages of multi-level and temporal network analysis in revealing the complexity of scientific collaboration patterns.

     

Bicycle injuries: a matter of mechanism and age

Bicycle riding is a popular form of recreation with positive health and environmental effects. These road users are vulnerable to serious injuries, especially when motor vehicles are involved. The goal of this study was to characterize cyclist-related injuries according to motor vehicle involvement for adults versus children. A retrospective study was carried out using data from 11 trauma centers in the Israeli National Trauma Registry (2001-2007). Injuries were classified according to whether a motor vehicle was involved, and differences in injury characteristics were assessed for adults (18+ years) versus children (1-17 years). A total of 5529 patients were hospitalized for bicycle injuries, of whom 1765 were adults and 3764 were children. Thirty percent (n=1662) of all bicycle injuries involved motor vehicles, although the rate of injuries resulting in hospitalization was 37% among adults and 27% among children. Injury characteristics and hospital resource utilization differed substantially by age group. Cyclists struck by a motor vehicle presented with more severe injuries requiring more hospital resources and resulting in poorer outcomes than those not involved with motor vehicles. The interaction effect between motor vehicle involvement and age was significant for torso injuries and need for medical imaging. We found that injury characteristics, hospital resource utilization and health-related outcomes for bicycle injuries are highly dependent on patient's age and mechanism of injury. Effect modification of motor vehicle involvement by age may in part reflect physicians' attitudes toward pediatric imaging. The risks identified in this study should be used for preparedness and management of trauma hospitalizations from bicycle injuries.     

Self-assembly of single-stranded RNA on carbon nanotube: polyadenylic acid to form a duplex structure

All messenger-RNA (mRNA) molecules in eukaryotic cells have a polyadenylic acid [poly(rA)] tail at the 3'-end and human poly(rA) polymerase (PAP) has been considered as a tumor-specific target. A ligand that is capable of recognizing and binding to the poly(rA) tail of mRNA might interfere with the full processing of mRNA by PAP and can be a potential therapeutic agent. We report here for the first time that single-walled carbon nanotubes (SWNTs) can cause single-stranded poly(rA) to self-structure and form a duplex structure, which is studied by UV melting, atomic force microscopy, circular dichroism spectroscopy, and NMR spectrometry. SWNTs have shown potential applications that range from nanodevices, gene therapy, and drug delivery to membrane separations. Our studies may provide new insights into the application of SWNTs under physiological conditions, possibly being used as probes that target specific gene sequences.     

亲水性高分子-陶瓷复合膜的制备与表征

采用均质的氧化铝支撑体和不同表面层孔径的非对称氧化铝支撑体直接接枝聚丙烯酸(PAA)制备亲水性PAA-Al2O3复合膜。对所制备出复合膜的红外光谱(IR)分析、光电子能谱(XPS)分析、扫描电子显微镜(SEM)分析和表面的水接触角分析表明,成功地制备出了PAA-Al2O3复合膜。在相同实验条件下对所制备的复合膜进行纯水和纯乙醇的通量实验以及质量分数95%乙醇的脱水分离试验表明,最适合用于制备PAA-Al2O3复合膜的陶瓷膜支撑体是孔径为2～3μm的均质氧化铝支撑体,用其制备的复合膜的分离因子为139.33,通量为0.61kg/(m2.h),可以达到分离效率高、通量较大的效果.