Bioactive Natural Products for Chemical Control of Microorganisms: Scientific Prospecting (2001–2021) and Systematic Review

The inappropriate use of synthetic antibiotics has become a global public health problem. Therefore, the study of new alternatives for the treatment of infectious diseases is relevant and natural bioactive products are on the rise. This study conducted a scientific prospection of bioactive natural products with promising applications in the chemical control of microorganisms. A systematic review of the most recent articles was performed according to the following three steps: (i) eligibility assessment, (ii) screening, and (iii) inclusion of articles and information extraction. There has been an increase in the number of scientific publications on bioactive natural products for microbial control in the CAPES and SciELO databases (2001–2021). Seventeen relevant articles were included, most of which focused on extracts. Ascorbic acid, chlorogenic acid, chrysin, and quercetin were the most cited compounds. Natural products were shown to be effective in inhibiting more than 30 microorganisms. A discussion was presented on the research trends.     

Oscillatory oxidation of Co over a Pt catalyst

We report measurements of the temporal oscillatory oxidation rates of CO over a polycrystalline Pt wire. The experiments were conducted near atmospheric pressure in a clean flow reactor system. Reproducible oscillations in both the temperature of the Pt wire and in the rate of CO₂ production were found over a wide range of gas compositions, $\text{0.001 <}\text{P}{}_{\mathrm{CO}}\text{P}{}_{\mathrm{O}}{}_2\text{< 0.045,}$ and temperatures, 150°C < T_g < 350°C, where PCO and po₂ are the respective partial pressures of carbon monoxide and oxygen in the gas stream, and T_g is the temperature of the gas. The oscillations are believed to occur between two branches of a Langmuir-Hinshelwood reaction mechanism. It is suggested that the slow formation and removal of subsurface oxygen drives the reaction between the two branches. A simple kinetic model based on this hypothesis gives excellent qualitative agreement with the observed oscillations.     

普适性的光学双稳及激光动力学方程和稳定性分析

本文从慢包络近似的麦克斯韦方程出发,在优质腔极限下,结合腔的边界条件与平均场极限,建立了适用于任何物质的光学双稳系统及相应的激光系统的动力学方程;并通过对方程的线性稳定性分析,得到了一个普适性的失稳判据。 关键词：     

In-plane thermal conductivity of Nd2CuO4: evidence for magnon heat transport

We report the temperature and magnetic field dependence of the in-plane thermal conductivity (kappa(ab)) of high-quality monocrystalline Nd2CuO4. Isothermal measurements of the field dependence of kappa(ab) at low temperatures (2 K相似文献   

Light Front Fermion Model Propagation

In this work we consider the propagation of two fermion fields interacting with each other by the exchange of intermediate scalar bosons in the light front. We obtain the corrections up to fourth order in the coupling constant using hierarchical equations in order to obtain the bound state equation (Bethe-Salpeter equation).     

Thermal study and evaluation of new menthol-based ionic liquids as polymeric additives

Thermal properties of new ionic liquids (ILs) were investigated by thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC). Chlorides, tetrafluoroborates and hexafluorophosphates of (−)mentholpyrrolidinium and (−)-mentholimidazolium cations revealed good thermal stability at air atmosphere. Morphological characteristics of poly(methyl methacrylate) (PMMA) matrices doped with 10% of these ILs were also investigated by DRX and water absorption test. Into the matrix, they exhibited a very satisfactory pattern concerning the polymer thermal stabilization. DSC results show that some of these ILs also present plasticizer features since they can lower the polymer glass transition temperature (T _g) up to 317.15 K.     

化学反应中的双稳性的临界现象及Landau相变理论

本文通过两个典型事例,即Langmuir形式的交换过程和Schlogle用以模拟一级相变的自催化反应,阐明化学反应系统的双稳性临界现象同样可以纳入Landau相变理论的模式。从而进一步揭示了双稳系统一级相变线临界点的二级(连续)相变特征,同时也揭示了作为远离平衡的化学反应双稳性临界现象的共性,以至于在更大范围内临界现象的共性。将相变的Landau理论,由原来的处于热平衡的凝聚物质推广到范围更宽广,表现更为丰富多彩的远离平衡系统的临界现象。     

A Diels-Alder approach to the stereoselective synthesis of 2,3,5,6-tetra- and 2,3,4,5,6-pentasubstituted piperidines

[structures: see text] A stereoselective synthesis of 2,3,5,6-tetra- and 2,3,4,5,6-pentasubstituted piperidines was achieved from oxidative cleavage of 2-aza-bicyclo[2.2.2]octene Diels-Alder adducts derived from N-protected 2-methyl-1,2-dihydropyridine. A chiral auxiliary mediated asymmetric synthesis of the pentasubstituted piperidine is also demonstrated. This methodology incorporates orthogonal protecting groups, thus providing a piperidine scaffold with easily modified points of diversity.