A new microstructure-based constitutive model for human blood

A new constitutive equation for whole human blood is derived using ideas drawn from temporary polymer network theory to model the aggregation and disaggregation of erythrocytes in normal human blood at different shear rates. Each erythrocyte is represented by a dumbbell. The use of a linear spring law in the dumbbells leads to a multi-mode generalized Maxwell equation for the elastic stress and both the relaxation times and viscosities are functions of a time-dependent structure variable. An approximate constitutive equation is derived by choosing a single mode corresponding to the cell aggregate size where the largest number of cells are to be found. This size is identified in the case of steady flows. The model exhibits shear-thinning, viscoelasticity and thixotropy and these are clearly related to the microstructural properties of the fluid. Agreement with the experimental data of Bureau et al. [M. Bureau, J.C. Healy, D. Bourgoin, M. Joly, Rheological hysteresis of blood at low shear rate, Biorheology 17 (1980) 191–203] in the case of a simple triangular step shear rate flow is convincing.     

Silicification‐Induced Cell Aggregation for the Sustainable Production of H2 under Aerobic Conditions

Photobiological hydrogen production is of great importance because of its promise for generating clean renewable energy. In nature, green algae cannot produce hydrogen as a result of the extreme sensitivity of hydrogenase to oxygen. However, we find that silicification‐induced green algae aggregates can achieve sustainable photobiological hydrogen production even under natural aerobic conditions. The core–shell structure of the green algae aggregates creates a balance between photosynthetic electron generation and hydrogenase activity, thus allowing the production of hydrogen. This finding provides a viable pathway for the solar‐driven splitting of water into hydrogen and oxygen to develop green energy alternatives by using rationally designed cell–material complexes.     

利用基于Gouy-Chapman模型的离子有效电荷定量表征离子特异性效应

离子特异性效应在固-液界面反应中是普遍存在的. 近期研究指出, 在较低电解质浓度的某些体系中, 离子特异性效应可能并非来源于色散力、经典诱导力、离子半径或水合半径的大小等, 而是界面附近强电场中的离子极化作用. 这种作用可使界面附近的吸附态反号离子被强烈极化(高达经典极化的10⁴倍). 强烈极化的结果将导致离子在界面附近受到的库仑力远远超过离子电荷所能产生的库仑力, 这体现在离子的有效电荷将远大于离子的实际电荷. 因此胶体体系中基于这种强极化的离子有效电荷可以用来定量表征离子特异性效应的强度. 本研究在蒙脱石-胡敏酸混合悬液凝聚过程中发现了Na⁺、K⁺、Ca²⁺、Cu²⁺四种离子的离子特异性效应, 提出了基于激光散射技术测定离子有效电荷的方法, 并成功获得了被强烈极化后的离子有效电荷数值. 实验测得的Na⁺、K⁺、Ca²⁺、Cu²⁺四种离子的有效电荷值分别为: Z_{Na(effective)}=1.46, Z_K(effective)=1.86, Z_{Ca(effective)}=3.92, Z_{Cu(effective)}=6.48.该结果表明: (1) 离子在强电场中的极化将大大提高离子的有效电荷, 从而极大地增强离子所受的库仑作用力;(2) 离子的电子层数越多, 离子极化越强烈, 离子的有效电荷增加越多.     

Tris(Znsalen) cryptand minimizes Znsalen aggregation arising from intermolecular Zn…O interaction

Exploring the factors to control Znsalen aggregation is of importance to design functional materials in catalysis, optical materials and biological imaging. In this work, we synthesized and characterized four cryptand type triZnsalen complexes and found that cryptand structure could efficiently minimize intermolecular Zn···O interaction. More importantly, encapsulated by PLGA nanoparticles, cryptand triZnsalen 1 displayed visible intracellular fluorescence whereas monomeric Znsalen 5 could not. These results provide a new access to design new luminescent materials with the potential application in optics and biological studies.     

Behavior of thermosensitive graft copolymer with aromatic polyester backbone and poly-2-ethyl-2-oxazoline side chains in aqueous solutions

Thermoresponsive graft copolymers with alkylene-aromatic polyester main chain and poly-2-ethyl-2-oxazoline side chains were synthesized. Two copolymer samples which differed in grafting density (0.5 and 0.7) were studied using dynamic and static light scattering and turbidimetry in aqueous solutions at concentration 0.0053?g?cm^?3. Hydrodynamic radii of scattering objects and their contribution to light scattering were obtained as a function of temperature in a wide temperature interval. Temperatures of phase separation were found out. Effect of grafting density on the copolymer behavior in aqueous solutions upon heating was determined. In particular, the phase separation temperature reduces with the decreasing grafting density.     

硫粉为硫源,多元醇辅助合成硫化钼纳米片

MoS₂ nanosheets are prepared with sulfur powder and Na₂MoO₄ by a one-pot two-phase method at 170-200 ℃ for 8 h. In addition, a three-step growth mechanism based on the aggregation and coalescence model is proposed. The reassembly of sulfur powder ensures the transformation from sulfur powder to H₂S to reduce Na₂MoO₄ and plays a key role in the successful preparation of MoS₂ nanosheets. The as-prepared MoS₂ nanosheets are rich in unsaturated sulfur atoms, probably resulting from the dislocation cores of the MoS₂ nanosheets, which have been found to be beneficial for hydrogen evolution reaction catalysis. The method and growth mechanism adopted in this study may be applied to other transition metal dichalogenides for similar structures. The facile and green method provides an alternative for the preparation of MoS₂ nanosheets.     

Organic-coated silver nanoparticles in biological and environmental conditions: Fate,stability and toxicity

This review paper presents the overview of processes involved in transformation of organic-coated silver nanoparticles (AgNPs) in biological systems and in the aquatic environment. The coating on AgNPs greatly influences the fate, stability, and toxicity of AgNPs in aqueous solutions, biological systems, and the environment. Several organic-coated AgNP systems are discussed to understand their stability and toxicity in biological media and natural water. Examples are presented to demonstrate how a transformation of organic-coated AgNPs in an aqueous solution is affected by the type of coating, pH, kind of electrolyte (mono- or divalent), ionic strength, organic ligands (inorganic and organic), organic matter (fulvic and humic acids), redox conditions (oxic and anoxic), and light. Results of cytotoxicity, genotoxicity, and ecotoxicity of coated AgNPs to food chain members (plants, bacteria, and aquatic and terrestrial organisms) are reviewed. Key factors contributing to toxicity are the size, shape, surface coating, surface charge, and conditions of silver ion release. AgNPs may directly damage the cell membranes, disrupt ATP production and DNA replication, alternate gene expressions, release toxic Ag⁺ ion, and produce reactive oxygen species to oxidize biological components of the cell. A progress made on understanding the mechanism of organic-coated AgNP toxicity using different analytical techniques is presented.     

Trace analysis of uranyl ion (UO2) in aqueous solution by fluorescence turn-on detection via aggregation induced emission enhancement effect

A sensitive fluorescence turn-on method for trace amounts of uranyl ion (UO₂²⁺) in solution has been developed in this study, based on aggregation induced emission enhancement (AIEE) characteristics of 4-pethoxycarboxyl salicylaldehyde azine (PCSA) induced by complex interaction between UO₂²⁺ and PCSA. Under optimized conditions, a fluorescence enhancement at 540 nm could be observed, which was linearly related to the concentration of UO₂²⁺ in the range of 1–25 ppb (part per billion). Analytical data showed that a detection limit of 0.2 ppb was achieved with the relative standard deviation (R.S.D.) 1.3% (n = 5). The proposed method was successfully utilized in quantifying UO₂²⁺ in fuel processing wastewaters.     

Synthesis, characterization and photophysical study of a series of neutral isocyano rhodium(I) complexes with pyridylindolide ligands

Pyridylindole ligand and its chloro substituted derivatives have been synthesized and incorporated into the square planar bis(phenylisocyano) rhodium(I) complexes to give a series of neutral rhodium(I) complexes with general formula of [Rh(X-pyind)(CNR)₂] (R = 2,6-(CH₃)₂-4-BrC₆H₂, 2,4-Cl₂-6-(CH₃O)C₆H₂, 2,4,6-Br₃C₆H₂, 2,4,6-Cl₃C₆H₂; L = 2-(2′-pyridyl)indole, 5-chloro-2-(2′-pyridyl)indole, 4,6-dichloro-2-(2′-pyridyl)indole). The structures of two complex precursors [Rh(cod)(Cl-pyind)] and [Rh(cod)(Cl₂pyind)], and the target complex [Rh(pyind)(CNC₆H₂-2,4-Cl₂-6-(OCH₃))₂] were determined by X-ray crystallography. The UV-vis absorption properties of these complexes and their responses towards the change of temperature were also investigated.