Connectivity Defects and Collective Assemblies in Model Metallo‐Supramolecular Dual‐Network Hydrogels

Double network hydrogels are composed of chemical and physical bonds, whose influences on the macroscopic material properties are convoluted. To decouple these, a model dually crosslinked network with independently tunable permanent and reversible crosslinks is introduced. This is realized by interlinking linear and tetra‐arm poly(ethylenegycol) (PEG) precursors with complementary reactive terminal groups. The former also carries a terpyridine ligand at each end, which forms reversible metallo‐supramolecular bonds upon addition of metal ions. These dual networks display different types and amounts of network defects, as studied by light scattering and proton double‐quantum (DQ) NMR. Dynamic light scattering suggests that the network mesh size decreases upon introduction of metal ions, as supported by a decrease of the residual dipolar coupling constant in NMR. Static light scattering indicates larger static inhomogeneities in those networks composed of stronger ions. This is complemented by a fast solid‐like component in the DQ buildup in NMR, attributed to the formation of nanoscopic clusters of charged complexes. The DQ buildup curves also suggest that the presence of strong physical bonds increases the fraction of mobile segments, like loops and dangling ends. This combined study unveils the interplay of chemical and physical bonds toward the formation of a hierarchical structure.     

Making yttria-stabilized tetragonal zirconia translucent

ObjectiveThe aim of this study was to provide a design guideline for developing tetragonal yttria-stabilized zirconia with improved translucency.MethodsThe translucency, the in-line transmission in particular, of 3 mol.% yttria-stabilized tetragonal zirconia (3Y-TZP) has been examined using the Rayleigh scattering model. The theory predicts that the in-line transmission of 3Y-TZP can be related to its thickness with grain size and birefringence the governing parameters. To achieve a threshold value of translucency, the critical grain size of 3Y-TZP was predicted for various thicknesses (0.3–2.0 mm). The threshold value was defined by a measured average in-line transmission value of a suite of dental porcelains with a common thickness of 1 mm. Our theoretical predictions were calibrated with one of the very few experimental data available in the literature.ResultsFor a dense, high-purity zirconia, its in-line transmission increased with decreasing grain size and thickness. To achieve a translucency similar to that of dental porcelains, a nanocyrstalline 3Y-TZP structure was necessitated, due primarily to its large birefringence and high refractive index. Such a grain size dependence became more pronounced as the 3Y-TZP thickness increased. For example, at a thickness of 1.3 mm, the mean grain size of a translucent 3Y-TZP should be 82 nm. At 1.5 mm and 2 mm thicknesses, the mean grain size needed to be 77 nm and 70 nm, respectively.SignificanceA promising future for zirconia restorations, with combined translucency and mechanical properties, can be realized by reducing its grain size.     

Banded structures in collagen vitrigels for corneal injury repair

There is a growing interest in using collagen vitrigels for corneal injury repair. We recently reported the synthesis and thermal denaturation behavior of these gels. In this paper, the banded structure in these vitrified gels is studied by small-angle X-ray scattering (SAXS) one-dimensional (1-D) correlation function analysis and transmission electron microscopy (TEM). Results demonstrate that the collagen vitrigel possess banded structures similar to those of the starting type I collagen, with an average D-spacing of 64 nm (by SAXS) or 57 nm (by TEM). A combination of SAXS 1-D correlation function analyses and TEM show that overlap and gap distances ranged from 30 to 33 nm and from 23 to 25 nm, respectively. Changing the vitrification condition does not impact on the banded structure significantly.     

Metasurfaces for Far-Field Radiation Pattern Correction of Antennas under Dielectric Seamed-Radomes

A high-index dielectric radome seam is camouflaged with respect to a low-index dielectric radome panel by tuning the seam with carefully engineered metasurfaces. A transmission-line approach is used to model the metasurface-tuned seam and analytically retrieve the corresponding surface impedance, from which the unit-cell design is then tailored. Full-wave simulations and microwave antenna measurements performed on a proof-of-concept prototype validate the undesired scattering suppression effect in the case of normally and obliquely incident transverse electric and transverse magnetic wave illuminations. Robustness of the proposed solution to fabrication tolerances is also reported. The study presents metasurface-tuning as an easily implementable, frequency adjustable, and polarization insensitive solution to reduce the scattering of dielectric mechanical seams and improve the overall transparency performance of radome structures.     

Electrochemical Self-Assembled Gold Nanoparticle SERS Substrate Coupled with Diazotization for Sensitive Detection of Nitrite

The accurate determination of nitrite in food samples is of great significance for ensuring people’s health and safety. Herein, a rapid and low-cost detection method was developed for highly sensitive and selective detection of nitrite based on a surface-enhanced Raman scattering (SERS) sensor combined with electrochemical technology and diazo reaction. In this work, a gold nanoparticle (AuNP)/indium tin oxide (ITO) chip as a superior SERS substrate was obtained by electrochemical self-assembled AuNPs on ITO with the advantages of good uniformity, high reproducibility, and long-time stability. The azo compounds generated from the diazotization-coupling reaction between nitrite, 4-aminothiophenol (4-ATP), and N-(1-naphthyl) ethylenediamine dihydrochloride (NED) in acid condition were further assembled on the surface of AuNP/ITO. The detection of nitrite was realized using a portable Raman spectrometer based on the significant SERS enhancement of azo compounds assembled on the AuNP/ITO chip. Many experimental conditions were optimized such as the time of electrochemical self-assembly and the concentration of HAuCl₄. Under the optimal conditions, the designed SERS sensor could detect nitride in a large linear range from 1.0 × 10⁻⁶ to 1.0 × 10⁻³ mol L⁻¹ with a low limit of detection of 0.33 μmol L⁻¹. Additionally, nitrite in real samples was further analyzed with a recovery of 95.1−109.7%. Therefore, the proposed SERS method has shown potential application in the detection of nitrite in complex food samples.     

FSC/SSC和CD45/SSC分群法流式T淋巴细胞亚群分析的实验研究

目的 建立并标准化流式细胞术外周血T淋巴细胞亚群含量测定方法,探讨CD45/SSC和FSC/SSC分群法检测的特点与适用性.方法 采用FSC/SSC分群的三色流式细胞术和CD45/SSC分群的四色流式细胞术,对194例健康人外周血T细胞亚群进行测定,并调查两种方法检测结果的精密性及临床应用的成功分群率.结果 FSC/SSC分群法健康人外周血总T细胞、T4细胞、T8细胞、T4/T8比值、DN-T细胞、DP-T细胞的百分含量依次为(69.98±5.79)%、(35.25±5.16)%、(25.08±4.34)%、(6.17±3.08)%、(0.71±0.36)%和(1.45±0.28)%;CD45/SSC分群法结果依次为(71.42±6.02)%、(35.82±5.78)%、(24.98±4.45)%、(5.98±3.11)%、(0.67±0.32)%和(1.47±0.30)%,两种方法检测结果之间差异无统计学意义(F检验,P＞0.05).精密度实验显示,FSC/SSC分群法和CD45/SSC分群法的变异系数均在4%以内,两者之间差异无统计学意义(P＞0.05).临床945份标本分析中,FSC/SSC分群法和CD45/SSC分群法的成功分群率分别为97.78%和99.83%,两者之间差异无统计学意义(P＞0.05).结论 FSC/SSC分群法和CD45/SSC分群法均可用于外周血淋巴细胞亚群含量的检测;FSC/SSC分群法成本相对低廉,上机操作简便,适合大规模临床应用开展,CD45/SSC分群法适合用于特殊标本的复查.     

Fingerprints of order and disorder on the high-frequency dynamics of liquids

It is largely accepted that liquids are characterized by a short-range order usually corresponding to that of the solid phase at the same density. It is less clear to what extent dynamic properties of liquids and crystals can be compared. In particular, high-frequency collective excitations reminiscent of phonons in solids exist as well in liquids. They are however traditionally discussed in terms of relaxation processes characteristic of the liquid phase. We report here on a quantitative comparison of the collective excitations in liquid and polycrystalline sodium. We show that liquid sodium exhibits acoustic excitations of both longitudinal and transverse polarization at frequencies strictly related to those of the corresponding crystal. The only relevant difference between the liquid and the polycrystal appears in the broadening of the excitations: An additional disorder-induced contribution comes into play in the case of the liquid, which we show to be related to the distribution of local structures around the average one. These results establish a direct connection between structural and dynamic properties of liquids, with short-range order and overall structural disorder leaving very specific fingerprints.     

Cyrene™ as an Alternative Sustainable Solvent for the Preparation of Poly(lactic-co-glycolic acid) Nanoparticles

Toxic and environmental harmful organic solvents are widely applied to prepare poly(lactic-co-glycolic acid) (PLGA)-based nanoparticles (NP) in standard preparation methods. Alternative non-toxic solvents suffer from disadvantages like high viscosity and plasticizing effects. To overcome these hurdles, Cyrene? as a new sustainable, non-toxic and low viscous solvent was used to formulate PLGA NPs. A new preparation method was developed and optimized. Small sized blank NPs around 220 nm with a narrow size distribution and highly negative charge (<?23 mV) were obtained. To test the application for drug delivery, the lipophilic model drug atorvastatin was encapsulated in high drug loads with comparable physicochemical characteristics as the blank NPs, and a total drug release within 24 h. No changes of the crystallinity or plasticizing effects could be observed. Highly purified NPs were obtained with a residual Cyrene? content <2.5%. Finally, the biocompatibility of Cyrene? itself and of the NPs formed in the presence of Cyrene? was demonstrated in a hen's egg test. Conclusively, the use of Cyrene? as solvent offers a simple, fast and non-toxic procedure for preparation of PLGA NPs as drug delivery systems circumventing the downsides of standard methods.