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.     

Anisotropic sound and shock waves in dipolar Bose-Einstein condensate

We study the propagation of anisotropic sound and shock waves in dipolar Bose-Einstein condensate in three dimensions (3D) as well as in quasi-two (2D, disk shape) and quasi-one (1D, cigar shape) dimensions using the mean-field approach. In 3D, the propagation of sound and shock waves are distinct in directions parallel and perpendicular to dipole axis with the appearance of instability above a critical value corresponding to attraction. Similar instability appears in 1D and not in 2D. The numerical anisotropic Mach angle agrees with theoretical prediction. The numerical sound velocity in all cases agrees with that calculated from Bogoliubov theory. A movie of the anisotropic wave propagation in a dipolar condensate is made available as supplementary material.     

Surface modification of polyamide 12 angioplasty balloons by photochemical reaction with an aromatic azide

Polyamide 12 (PA12) is used in a variety of applications when low moisture absorption, good dimensional stability, and toughness are required. Polyamide 12 is one of the polymers most frequently employed to fabricate angioplasty balloon catheters; however, its high hydrophobicity and chemical inertness require the application of coatings to make its surface more hydrophilic and biocompatible. In this work, an alternative method, based on the photochemical reaction of PA12 with a hydrophilic aromatic azide, was developed. Static and dynamic contact angle measurements evidenced that the surface modification process was able to improve PA12 wettability and that the effects were retained even after 12 months from surface treatment. Polyamide 12 modification resulted in an increase of its surface free energy, as evaluated by the van Oss, Good, and Chaudhury method. X‐ray photoelectron spectroscopy confirmed the presence of the aromatic azide on PA12 surface. Finally, compliance tests showed that the modification process did not reduce the mechanical performance of balloons.     

反导火力单元空间杀伤区内拦截概率研究

拦截概率是评价反导作战效能的重要指标,对交战前任务规划至关重要。选取某一拦截弹建立其在空间的可达集区域,针对中段反导逆轨拦截情况,确立其在空间中的杀伤区。针对杀伤区内任一点可能为拦截点的情况,对某一来袭导弹的弹道轨迹,选取可拦截弧段上的理论拦截点,通过在选取不同高度上的理论拦截点上,调整拦截弹的发射位置,从而得到拦截点在杀伤区内不同高度,不同距离以及在不同的交汇角时对拦截概率的影响。为反导作战的阵地部署研究和交战策略提供了一定的参考。     

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.     

Critical Trace Trudinger-Moser Inequalities on a Compact Riemann Surface with Smooth Boundary

In this paper, the author concerns two trace Trudinger-Moser inequalities and obtains the corresponding extremal functions on a compact Riemann surface (Σ, g) with smooth boundary ?Σ. Explicitly, let λ₁(?Σ) = inf u∈W^1,2 (Σ,g),R ?Σ udsg=0,u6≡0 R Σ(|?gu|2 + u2 )dvg R ?Σ u2 dsg and H = n u ∈ W^1,2 (Σ, g) : Z Σ(|?gu|2 + u2 )dvg ? α Z ?Σ u2dsg ≤ 1 and Z ?Σ u dsg = 0o ,where W^1,2 (Σ, g) denotes the usual Sobolev space and ?g stands for the gradient operator.By the method of blow-up analysis, we obtain sup u∈H Z ?Σ e πu2 dsg ( < +∞, 0 ≤ α < λ1(?Σ),= +∞, α ≥ λ1(?Σ).Moreover, the author proves the above supremum is attained by a function uα ∈ H∩C∞(Σ)for any 0 ≤ α < λ1(?Σ). Further, he extends the result to the case of higher order eigenvalues. The results generalize those of [Li, Y. and Liu, P., Moser-Trudinger inequality on the boundary of compact Riemannian surface, Math. Z., 250, 2005, 363–386], [Yang,Y., Moser-Trudinger trace inequalities on a compact Riemannian surface with boundary,Pacific J. Math., 227, 2006, 177–200] and [Yang, Y., Extremal functions for TrudingerMoser inequalities of Adimurthi-Druet type in dimension two, J. Diff. Eq., 258, 2015,3161–3193]     

Powder‐XRD and 14N magic angle‐spinning solid‐state NMR spectroscopy of some metal nitrides

Some metal nitrides (TiN, ZrN, InN, GaN, Ca₃N₂, Mg₃N₂, and Ge₃N₄) have been studied by powder X‐ray diffraction (XRD) and ¹⁴N magic angle‐spinning (MAS) solid‐state NMR spectroscopy. For Ca₃N₂, Mg₃N₂, and Ge₃N₄, no ¹⁴N NMR signal was observed. Low speed (ν_r = 2 kHz for TiN, ZrN, and GaN; ν_r = 1 kHz for InN) and ‘high speed’ (ν_r = 15 kHz for TiN; ν_r = 5 kHz for ZrN; ν_r = 10 kHz for InN and GaN) MAS NMR experiments were performed. For TiN, ZrN, InN, and GaN, powder‐XRD was used to identify the phases present in each sample. The number of peaks observed for each sample in their ¹⁴N MAS solid‐state NMR spectrum matches perfectly well with the number of nitrogen‐containing phases identified by powder‐XRD. The ¹⁴N MAS solid‐state NMR spectra are symmetric and dominated by the quadrupolar interaction. The envelopes of the spinning sidebands manifold are Lorentzian, and it is concluded that there is a distribution of the quadrupolar coupling constants Q_cc's arising from structural defects in the compounds studied. Copyright © 2015 John Wiley & Sons, Ltd.     

Quasi-normal modes of extremal black holes from hidden conformal symmetry

In this Letter, we construct the quasi-normal modes of three-dimensional extremal black holes in an algebraic way. We show that the infinite towers of the quasi-normal modes of scalar, vector and tensor could be constructed as the descendents of the highest weight modes. Our investigation shows that the hidden conformal symmetry suggested in Chen et al. (2010) [5] is an intrinsic property of the extremal black hole. Moreover, we notice that we need to fix the freedom in defining the local vector fields and find the right hidden conformal symmetry to obtain the physical quasi-normal modes.