Micelle,microemulsions, and gels for the conservation of cultural heritage

Past restorations performed with acrylic and vinyl polymers showed detrimental effects to wall paintings that lead to the complete disfiguration of the painted surfaces. The removal of these materials performed with the traditional solvent-based methodology represents a real challenge to conservators and usually achieves very poor results. This review reports on the new palette, nowadays available to restorers, based on microemulsions, micellar systems, physical and chemical gels specifically formulated for the cleaning of cultural heritage artefacts. These systems have been developed in the last twenty years within the cultural framework of colloids and surface science.     

利用X光散射实验研究C-S-H的微观结构

为了了解波特兰水泥中的水化硅酸钙(C-S-H)的微观结构,对有无含添加剂superplasticizers(SPs)、从5天到68天的不同老化时间的波特兰水泥样品的X光散射实验,实验数据结果分析表明C-S-H中钙硅层间距的大小是0.98±0.01nm,结果说明波特兰水泥样品中C-S-H中钙硅层间距与样品是否含SPs以及样品的老化时间无关。     

Polarization catastrophe in the polaronic Wigner crystal

We consider a three dimensional Wigner crystal of electrons lying in a host ionic dielectric. Owing to their interaction with the lattice polarization, each localized electron forms a polaron. We study the collective excitations of such a polaronic Wigner crystal at zero temperature, taking into account the quantum fluctuations of the polarization within the Feynman harmonic approximation. We show that, contrary to the ordinary electron crystal, the system undergoes a polarization catastrophe when the density is increased. An optical signature of this instability is derived, whose trend agrees with the experiments carried out in Nd-based cuprates. Received 4 July 2002 Published online 17 September 2002     

A Copula-Based Method to Build Diffusion Models with Prescribed Marginal and Serial Dependence

This paper investigates the probabilistic properties that determine the existence of space-time transformations between diffusion processes. We prove that two diffusions are related by a monotone space-time transformation if and only if they share the same serial dependence. The serial dependence of a diffusion process is studied by means of its copula density and the effect of monotone and non-monotone space-time transformations on the copula density is discussed. This approach provides a methodology to build diffusion models by freely combining prescribed marginal behaviors and temporal dependence structures. Explicit expressions of copula densities are provided for tractable models.     

Atomically Local Electric Field Induced Interface Water Reorientation for Alkaline Hydrogen Evolution Reaction

The slow water dissociation process in alkaline electrolyte severely limits the kinetics of HER. The orientation of H₂O is well known to affect the dissociation process, but H₂O orientation is hard to control because of its random distribution. Herein, an atomically asymmetric local electric field was designed by IrRu dizygotic single-atom sites (IrRu DSACs) to tune the H₂O adsorption configuration and orientation, thus optimizing its dissociation process. The electric field intensity of IrRu DSACs is over 4.00×10¹⁰ N/C. The ab initio molecular dynamics simulations combined with in situ Raman spectroscopy analysis on the adsorption behavior of H₂O show that the M−H bond length (M=active site) is shortened at the interface due to the strong local electric field gradient and the optimized water orientation promotes the dissociation process of interfacial water. This work provides a new way to explore the role of single atomic sites in alkaline hydrogen evolution reaction.     

Breaking K+ Concentration Limit on Cu Nanoneedles for Acidic Electrocatalytic CO2 Reduction to Multi-Carbon Products

Electrocatalytic CO₂ reduction reaction (CO₂RR) to multi-carbon products (C₂₊) in acidic electrolyte is one of the most advanced routes for tackling our current climate and energy crisis. However, the competing hydrogen evolution reaction (HER) and the poor selectivity towards the valuable C₂₊ products are the major obstacles for the upscaling of these technologies. High local potassium ions (K⁺) concentration at the cathode's surface can inhibit proton-diffusion and accelerate the desirable carbon-carbon (C−C) coupling process. However, the solubility limit of potassium salts in bulk solution constrains the maximum achievable K⁺ concentration at the reaction sites and thus the overall acidic CO₂RR performance of most electrocatalysts. In this work, we demonstrate that Cu nanoneedles induce ultrahigh local K⁺ concentrations (4.22 M) – thus breaking the K⁺ solubility limit (3.5 M) – which enables a highly efficient CO₂RR in 3 M KCl at pH=1. As a result, a Faradaic efficiency of 90.69±2.15 % for C₂₊ (FE_C2+) can be achieved at 1400 mA.cm⁻², simultaneous with a single pass carbon efficiency (SPCE) of 25.49±0.82 % at a CO₂ flow rate of 7 sccm.     

Ready Biodegradability study and insights with ultra-high-performance liquid chromatograph coupled to a quadrupole time of flight of a Metformin-based drug and of Metarecod,a natural substance-based medical device

Drugs are indispensable products with incontrovertible benefits to human health and lifestyle. However, due to their overuse and improper disposal, unwanted residues of active pharmaceutical ingredients (APIs) have been found in different compartments of the environment and now are considered as contaminants of emerging concern (CECs). Therefore, they are very likely to have a boomerang effect on human health, because they can enter into the food cycle. In the current legislation framework, one of the tests first used to evaluate biodegradation of APIs as well as chemical compounds is the ready biodegradability test (RBT). This test can be performed according to a series of protocols prepared by Organization for Economic Co-operation and Development (OECD) and usually is carried out on pure compounds. RBTs, largely used due to their relatively low cost, perceived standardization, and straightforward implementation and interpretation, are known to have a number of well-documented limitations. In this work, following a recently reported approach, we propose to improve the evaluation of the RBT results applying advanced analytical techniques based on mass spectrometry, not only to the APIs but also to complex formulated products, as the biodegradability can potentially be affected by the formulation. We evaluated the ready biodegradability of two therapeutic products, Product A —a drug based on Metformin—and Product B —Metarecod a natural substance-based medical device—through the acquisition of the fingerprint by ultra-high-performance chromatograph coupled to a quadrupole time of flight (UHPLC-qToF) of samples coming from the RBT OECD 301F. Untargeted and targeted evaluation confirmed the different behavior of the two products during the respirometry-manometric test, which showed a difficulty of the Metformin-based drug to come back in the life cycle, whereas Metarecod resulted ready biodegradable. The positive results of this research will hopefully be useful in the future for a better evaluation of the risk/benefit ratio of APIs extended to the environment.     

Raney镍催化下生物活性化合物的微波辅助脱硫反应

微波辅助脱硫反应具有反应速度快、收率高等优点, 已成为一种有效的脱硫方法, 在生物活性化合物的合成中将得到越来越广泛的应用. 以乙醇为溶剂, 通过微波辅助还原相应苯硫基取代的前体化合物, 制备了一系列具有显著生物活性的化合物.     

Neodymium, gadolinium, and terbium complexes containing hexafluoroacetylacetonate and 2,2'-bipyrimidine: structural and spectroscopic characterization

Lanthanide complexes of the form Ln(hfa)3bpm (where Ln=Nd(III), Gd(III), or Tb(III); hfa=1,1,1,5,5,5-hexafluoroacetylacetone and bpm=2,2'-bipyrimidine) have been structurally characterized. The Nd and Gd complexes form one-dimensional arrays when X-ray-quality crystals are grown by the slow evaporation of concentrated solutions of the complexes. Each metal is 10-coordinate with repeating Ln-bpm units. The Tb complex does not form a one-dimensional array under these conditions. Its structure is 9-coordinate with the ninth position occupied by a covalently bonded water molecule that is hydrogen-bonded to the bpm group from another complex in solution. Luminescent studies show that the Nd complex undergoes nonradiative relaxation through solvent vibrational deactivation, while the lowest excited state of the Gd complex, 6P7/2, is higher in energy than the T1 state of the hfa ligand, making luminescence improbable for both of these complexes. In contrast, the Tb complex emits in the visible region of the spectrum when solutions of the complex are excited at 304 nm associated with the pi-pi* transition of the hfa ligand. Emission lines corresponding to transitions from the 5D4 state to the 7FJ manifold of the Tb(III) are observed. The intensity of these emissions decreases as temperature is increased. Lifetime measurements of the Tb monometallic complex fit to a monoexponential with the lifetime decreasing as the temperature is increased.     

Threading, growth, and aggregation of pseudopolyrotaxanes

The formation of supramolecular inclusion compounds (pseudopolyrotaxanes) produced by cyclodextrins and polymers can be monitored through turbidimetry. In this paper, we studied the kinetics of the threading of linear poly(ethylene glycol) chains of different molecular weights and of a four-arm star-like polymer as a function of temperature. The main thermodynamic parameters are extracted. The aggregation and precipitation of pseudopolyrotaxanes are described in terms of the Avrami-Erofe'ev model, which provides relevant information on the mechanism of these processes. SAXS and TGA experiments confirm the structure and hydration of the final products obtained from the different polymers. A new hypothesis for the interaction between pseudopolyrotaxanes that leads to aggregation and precipitation, based on the spatial dielectric anisotropy, is proposed.