Significant change in water contact angle of electrospray‐synthesized SiO2 films depending on their surface morphology

Amorphous SiO₂ films were deposited by means of an electrospray technique. The relation between the water contact angle (WCA) of the deposited SiO₂ films and the surface morphology is investigated. The feeding rate of the electrospray process greatly affects the morphology of the synthesized SiO₂ films. There is also a significant change in the WCA on the surface of the films: the rougher the surface, the greater the WCA. A model based on the Cassie–Baxter formulation is used to explain the change observed in the WCA on the SiO₂ films. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of the second step microstructure for superhydrophobic surfaces

A selection of suitable microstructures is critical to fabrication and properties of superhydrophobic surfaces (SHS). In this study, we introduce a three‐dimensional droplet model to thermodynamically analyze the superhydrophobic properties for the purpose of determining the second step of a two‐step microstructure suitable for the SHS based on the common models within the reach of the existing macro‐machining technology. It is found that a sinusoidal microstructure is the most suitable, followed by a cone frustum and a prism in the composite wetting state, as well as the transition from hydrophilic to hydrophobic depends basically on the solid fraction rather than non‐determinative surface microscopic topography. The predictions of the model are found in quite good agreement with the experimental observations. This study will facilitate fabrication of the SHS on how to select the suitable morphology. Copyright © 2012 John Wiley & Sons, Ltd.     

Novel Azobenzene-Functionalized Polyelectrolytes of Different Substituted Head Groups 2: Control of Surface Wetting in Self-Assembled Multilayer Films

A novel set of light-responsive polyelectrolytes has been developed and studied, to control and tune surface wettability by introducing various types of substituted R head-groups of azo polyelectrolytes in self-assembled multilayer (SAMU) films. As part of a larger project to develop polymer surfaces where one can exert precise control over properties important to proteins and cells in contact, photo-reversibly, we describe here how one can tune quite reliably the contact angle of a biocompatible SAMU, containing a photo-reversible azo chromophore for eventual directed cell growth. The azo polyelectrolytes described here have different substituted R head-group pairs of shorter-ionized hydrophilic COOH and SO₃H, shorter non-ionized hydrophobic H and OC₂H₅, and larger non-ionized hydrophobic octyl C₈H₁₇ and C₈F₁₇, and were employed as polyanions to fabricate the SAMU onto silicon substrates by using the counter-charge polycation PDAC. The prepared SAMU films were primarily characterized by measurement of their contact angles with water. The surface wetting properties of the thin films were found to be dependent on the type of substituted R-groups of the azo polyelectrolytes through their degree of ionization, size, hydrophobicity/hydrophilicity, solubility, conformation, and inter-polymeric association and intra-polymeric aggregation. All these factors appeared to be inter-related, and influenced variations in hydrophobic/hydrophilic character to different extents of aggregates/non-aggregates in solution because of solvation effects of the azo polyanions, and were thus manifested when adsorbed as thin films via the SAMU deposition process. For example, one interesting observation is significantly higher contact angles of 79° for SAMU films of larger octyl R groups of PAPEA-C₈F₁₇ and PAPEA-C₈H₁₇ than for others with contact angles of 64° observed for non-polar R-groups of OC₂H₅ and H. Furthermore, lower contact angle values of 59° for SAMU films with polar R-groups of COOH and SO₃H relative to that of non-polar R-groups are in accordance with their expected order of the hydrophilicity or hydrophobicity. It is possible that the large octyl groups are more effective in shielding the ionic functional groups on the substrate surface, and contributed less to the water drop-molecule interactions with ionic groups of the PDAC and/or AA groups. In addition, higher hydrophobicity of the SAMU films may be due to the incorporation of bulky and hydrophobic groups in these polyelectrolytes, which can produce aggregates on the surfaces of the SAMU films. Through understanding and controlling the complex aggregation behavior of the different substituted R-groups of these azo polyelectrolytes, and hence their adsorption on substrates, it appears possible to finely tune the surface energy of these biocompatible films over a wide range, enhance the photo-switching capabilities of the SAMU films, and tailor other surface properties for the development and application of new devices in diverse areas of microfluidics, specialty coatings, sensors, and biomedical sciences.     

Numerical methods for light propagation in large LC cells: a new approach

Accurate numerical methods for the propagation of light in large 3D samples with strong lateral variation of the director field require prohibitive amounts of time. We consider and compare a standard spectral method and the Finite Difference in Frequency Domain method, showing that the CPU time can be reduced by one or two orders of magnitude using a perturbation approach or a recently developed Reduced Order Method. The equations obtained are applied to liquid crystal cells with in-plane switching, illuminated by a large incoherent source. The developed formalism, based on numerically exact equations, is particularly suitable for treating magnetic or optically active media and for extending to such media the well known approximations based on the 4 × 4 (Berreman) or 2 × 2 (Jones) matrices.     

Polymer-dispersed liquid crystal composites for bio-applications: thermotropic,surface and optical properties

Polymer-dispersed liquid crystal (PDLC) systems based on polysulfone as carrying matrix and 4-cyano-4?-pentylbiphenyl (5CB) liquid crystal (LC) were obtained as thin transparent films. The PDLC films were prepared by solvent- and thermally induced phase separation methods, with various compositions in the two components. Information on the phase separation was obtained by polarised light optical microscopy, differential scanning calorimetry and scanning electron microscopy. The PDLC composites show well-defined droplets of submicrometric size, around 650 nm for a medium content of LC and around 250 nm for a low one. The droplets show a radial configuration and a homeotropic alignment of the LC molecules within. By contact angle measurement and surface free energy calculations, it was established that self-assembling of aliphatic units of the two composite components, at droplet interface, is the driving force of the homeotropic alignment. Moreover, these data indicated the potential biocompatibility of the studied composites. The photophysical behaviour shows a better light emission of the PDLCs containing bigger droplets.     

Dihedral angle study in Hesperidin using NMR Spectroscopy

Hesperidin is flavonoid molecule found in citrus fruits (Citrus reticulata), especially difficult to extract, classify and characterize. Present work is to study the unresolved relative configuration of Hesperidin through the dihedral angle, coupling constant and different NMR techniques. The Karplus equation and its modifications have been originated from the valence bond theory and associated with dihedral angle and coupling constant. The result data set of calculated dihedral angle can probe significant method to assign the virtual configuration of natural products and also resolved stereochemistry of Hesperidin at C‐2 position in. Copyright © 2016 John Wiley & Sons, Ltd.     

MATLAB在光学界面发生反射时的分析与应用

基于MATLAB的计算功能及可视化功能计算并分析了光学中的菲涅耳公式,更加直观的揭示了光波在两介质界面发生反射时的变化规律。使学生更加深入、直观地掌握光波在界面发生变化的条件、实质及布儒斯特角与全反射临界角的物理意义,同时也学会了分析研究方法,且提高了学习的主动性和创造性。     

Robustness in deterministic multi-objective linear programming with respect to the relative interior and angle deviation

This paper deals with the robustness issue in deterministic multi-objective linear programming from two new standpoints. It is shown that a robustness notion recently reported in the literature is equivalent to strict efficiency. Corresponding to an efficient solution, a new quantity, robustness order (RO) is defined with respect to the interiority order of the cost matrix in the binding cone. A linear programming problem is provided to calculate the RO of a given efficient solution. The second part of the paper is devoted to investigating the robustness with respect to the eligible angle deviation of the cost matrix in the binding cone. Theoretical results are given to obtain the maximum eligible angle deviation. Finally, the relationship between two above-mentioned robustness standpoints is established. To have a better geometrical view, we prove the results for single-objective LP problems at first, and then we extend them to the multi-objective case. In addition to the theoretical results, some clarifying examples are given.     

The Ablowitz–Ladik hierarchy integrability analysis revisited: the vertex operator solution representation structure

A regular gradient-holonomic approach to studying the Lax type integrability of the Ablowitz–Ladik hierarchy of nonlinear Lax type integrable discrete dynamical systems in the vertex operator representation is presented. The relationship to the Lie-algebraic integrability scheme is analyzed and the connection with the τ-function representation is discussed.     

Solid‐state drawing of β‐nucleated polypropylene: Effect of additives on drawability and mechanical properties

Isotactic polypropylene (i‐PP) can crystallize in different crystal modifications. In this article, the effect of sepiolite (one‐dimensional) and carbon black (three‐dimensional) fillers on the solid‐state drawability of i‐PP is discussed. The cross‐hatched structure of thermodynamically most stable α‐crystal phase in i‐PP does not allow for perfect chain alignment during solid‐state drawing. The β‐phase i‐PP, obtained by addition of specific nucleating agents, crystallizes in a non‐cross‐hatched spherulitic structure and allows more easy drawing. Depending on the filler type, β–α transformation takes place at different draw ratios, as was observed by in situ wide‐angle X‐ray diffraction measurements. It was observed that β‐nucleated i‐PP has a lower yield stress and can be drawn further than i‐PP crystallized in the α‐crystal phase. If added in the right amount, both carbon black and sepiolite have a reinforcing effect on PP tapes. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1071–1082