Recent performance improvements to the DFT and TDDFT in GAMESS

The general atomic and molecular electronic structure system (GAMESS) is a quantum chemistry package used in the first-principles modeling of complex molecular systems using density functional theory (DFT) as well as a number of other post-Hartree-Fock methods. Both DFT and time-dependent DFT (TDDFT) are of particular interest to the materials modeling community. Millions of CPU hours per year are expended by GAMESS calculations on high-performance computing systems; any substantial reduction in the time-to-solution for these calculations represents a significant saving in CPU hours. As part of this work, three areas for improvement were identified: (1) the exchange-correlation (XC) integration grid, (2) profiling and optimization of the DFT code, and (3) TDDFT parallelization. We summarize the work performed in these task areas and present the resulting performance improvement. These software enhancements are available in 12JAN2009R3 or later versions of GAMESS.     

Current examples of practical and fundamental applications of DC polarography

Examples of recent applications—applied, analytical, and fundamental are given. For these types of applications, an understanding of at least the number of electrons and protons transferred and the sequences of electron transfers and chemical reactions is essential. Polarography can be used for the determination of the active component in tablets and injection solutions, where it offers speed and sensitivity of the analytical method. Electroactive species can also be determined in heterogeneous systems without pre-separation. This has been taken advantage of in the investigation of reactions of bile salts with heavy metal ions or of binding of pesticides and other toxins on lignin. Polarography can also be used in the investigation of alkaline cleavage of lignin under mild conditions. Kinetics of this cleavage was used as a tool in proving that humic acids are not natural products. Among fundamental applications belong proofs of limited delocalization in groupings >C=N–N=C<, of diprotonation of hydrazones and oximes at the electrode surface, as well as of formation of imines as intermediates in reductions of hydrazones and oximes. Simultaneous determination of benzaldehyde and its hydrazone enabled providing experimental evidence for formation of carbinolamines as reaction intermediates and interpretation of the pH dependence of the equilibrium constant of this reaction. Differences in hydration of three isomeric phthalaldehydes are discussed as well as the covalent hydration of 1,2,4- and 1,3,5-triazines and pyrimidines. The ω,ω,ω-trifluoroacetophenone oxime the C=N bond is covalently hydrated.Dedicated to Professor Dr. Alan Bond on the occasion of his 60th birthday.     

Electrical properties of filled polymers and some examples of their applications

Polymers containing electrically conductive fillers show interesting electrical properties like semiconductors and metals without losing the processability of polymers. Typical applications are as antistatic (electrostatic dissipation) materials, electro-magnetic interference shielding materials, heaters and sensors. The selection of filler and polymer governs the properties obtained in such composites.     

Recent applications of capillary electrochromatography

A review is presented of the most important recent applications of capillary electrochromatography (CEC) for the analysis of acidic, basic, and neutral compounds, of biomolecules, environmental substances, natural products, pharmaceuticals, and chiral compounds. Packed-column CEC (packed-CEC), open-tubular (OT-CEC), as well as pressure-assisted CEC (pseudo-CEC) are hereby considered. Papers published between July 1999 and April 2001 were taken into account. Applications before July 1999 have been reviewed in Electrophoresis 1999, 20, 3027-3065.     

Recent advances in the environmental applications of biosurfactants

Biosurfactants can be used for heavy metal or organic contaminant removal from contaminated soil or for bioremediation enhancement. Most research has been performed on the use of rhamnolipids. However, present and future studies involve new biosurfactants and new applications as sustainable, renewable additives for nanoparticle production and use.     

Recent advances in the synthesis and applications of furocoumarin derivatives

Furocoumarins are an important class of heterocyclic compounds with a fused tricyclic structure of coumarin and furan rings. They are commonly found in bioactive natural products and have a diverse range of biological and pharmaceutical properties, including cytotoxicity, photosensitivity, insecticidal, antibacterial, and antifungal activity, among others. The elegant linear/angular tricyclic skeleton and superior pharmacological properties, make them ideal for building and developing advanced biological scaffolds for biomedical applications. As a result, the family of furocoumarins has been the focus of intensive research, and lots of encouraging progress have been achieved in recent years. This review summarizes the most recent methods reported for the synthesis of the furocoumarin derivative family, along with their applications in medicinal chemistry covering from 2018 to 2022.     

硫酯类化合物的合成与应用研究进展

综述了近年来硫酯类化合物的合成,及其在有机合成中应用的研究进展。提供参考文献65篇。     

Rephasing ion packets in the orbitrap mass analyzer to improve resolution and peak shape

A method is described to improve resolution and peak shape in the Orbitrap under certain experimental conditions. In these experiments, an asymmetric anharmonic axial potential was first produced in the Orbitrap by detuning the voltage on the compensator electrode, which results in broad and multiply split mass spectral peaks. An AC waveform applied to the outer electrode, 180° out of phase with ion axial motion and resonant with the frequency of ion axial motion, caused ions of a given m/z to be de-excited to the equator (z=0) and then immediately re-excited. This process, termed “rephasing,” leaves the ion packet with a narrower axial spatial extent and frequency distribution. For example, when the Orbitrap axial potential is thus anharmonically de-tuned, a resolution of 124,000 to 171,000 is obtained, a 2- to 3-fold improvement over the resolution of 40,000 to 60,000 without rephasing, at 10 ng/μL reserpine concentration. Such a rephasing capability may ultimately prove useful in implementing tandem mass spectrometry (MS/MS) in the Orbitrap, bringing the Orbitrap’s high mass accuracy and resolution to bear on both the precursor and product ions in the same MS/MS scan and making available the collision energy regime of the Orbitrap, ∼1500 eV.     

Recent developments in the properties and applications of polyelectrolyte multilayers

Complexity and innovation in the application of layer-by-layer adsorbed polyelectrolyte systems continues to grow. In this review, we will recap recent findings on the application of multilayers at the biological interface, and as thin films for controlling wetting properties. We also review recent experiments on determining the mechanical properties of polyelectrolyte multilayers.     

Recent progress on the frontiers of polyoxometalates structures and applications

<正>Polyoxometalates (POMs), a class of discrete anionic metal oxides in groups Ⅴ and Ⅵ, are constructed via the condensation of metal oxide polyhedral (MO_x, M=W~(Ⅵ), Mo~(Ⅵ),V~Ⅴ, Nb, Ta, etc. and x=4–7) with each other in a corner-,edge-, or rarely in a face-sharing manner [1–3]. Up to now,the broadening family of POM derivatives ranges from small     

Recent advances in the synthesis and applications of azo initiators

This mini-review describes recent developments and trends in the area of syntheses and applications of azo compounds, which are planned to act as initiators of radical reactions, particularly polymerizations. The paper reports chemical modifications of well-known initiators (AIBN, etc.) or variants of syntheses of new types of these compounds. The chemical modifications of basic skeletons of azo initiators are discussed in the context with their properties and applications. Also discussed are the contemporary trends in the development of these initiators, particularly in preparation of microparticles and nanoparticles of polymers or hybrid inorganic–organic microparticles and nanoparticles prepared for intentional studies and applications.     

Thermal behavior of typical weak basic ion exchange resin

Thermal behaviors of typical weak basic ion exchange resins (301 and 315) were studied with thermogravimetry, elemental analysis, and Fourier transform infrared spectrometer in this study. Results indicated that there were three stages for 301 resin mass loss, the first stage and the second stage were mainly related to the decomposition of functional group, and the third stage was the decomposition of main chain. Whereas there were two stages for 315 resin mass loss, the first stage was elimination of moisture, and the second stage was the decompositions of functional group and main chain. Moreover, the decomposition of tertiary amine had three stages, the polyamine was a continuous mass loss process, and the thermostability of tertiary amine was weaker than that of polyamine.     

Recent advances and applications in QDs-based sensors

As a unique nanomaterial, quantum dots (QDs) are not only applied in fluorescent labeling and biological imaging, but are also utilized in novel sensing systems. Because QDs have attractive optoelectronic characteristics, QD-based sensors present high sensitivity in detecting specific analytes in the chemical and biochemical fields. In this review, we describe the basic principles and different conjugation strategies in QD-based sensors. An overview of recent advances and various models of QD-sensing systems is also provided. Furthermore, perspectives for sensors based on QDs are discussed.