Cosmology

The main features of the universe and its history, and the application of GR to the universe as a whole are presented. The observed near-isotropy and homogeneity of the universe are described, along with a survey of its history. The Saha equation is applied to the recombination process. Cosmic proper time and comoving coordinates are defined, and the form of the metric (Friedmann-Lemaitre-Robertson-Walker) applicable to such a universe is obtained. The main features of the resulting geometry are discussed at length, with a view to both accurate calculation and sound intuition. Redshift and the cosmic expansion are described from several perspectives. Distance measures (luminosity, angular diameter) are defined and the main elements of the observational cosmic distance ladder are outlined.

Creative DNA Computing: Splicing Systems for Music Composition

Splicing systems are a form of DNA computing as they mimic the recombination process among DNA molecules. This work discusses the use of splicing systems to build automatic tools for reproducing human beings' creativity, in the context of automatic music composition. More specifically, this work describes three general splicing system approaches for automatic music composition, and their application to two specific cases, namely composing 4-voice music and composing Jazz solos in a given style. Examples of music composed by the systems are presented.

Revealing the etching process of water-soluble Au25 nanoclusters at the molecular level

Etching (often considered as decomposition) is one of the key considerations in the synthesis, storage, and application of metal nanoparticles. However, the underlying chemistry of their etching process still remains elusive. Here, we use real-time electrospray ionization mass spectrometry to study the reaction dynamics and size/structure evolution of all the stable intermediates during the etching of water-soluble thiolate-protected gold nanoclusters (Au NCs), which reveal an unusual “recombination” process in the oxidative reaction environment after the initial decomposition process. Interestingly, the sizes of NC species grow larger and their ligand-to-metal ratios become higher during this recombination process, which are distinctly different from that observed in the reductive growth of Au NCs (e.g., lower ligand-to-metal ratios with increasing sizes). The etching chemistry revealed in this study provides molecular-level understandings on how metal nanoparticles transform under the oxidative reaction environment, providing efficient synthetic strategies for new NC species through the etching reactions.

Enantioselective Hydroalkylation of α,β-Unsaturated Amides through Reversed syn-Hydrometallation of NiH

Enantioselective synthesis of a wide range of structurally diverse <a>β</a>-chiral amides has been achieved through nickel-catalyzed regio-reversed hydroalkylation of α,β-unsaturated amides with alkyl iodides in the presence of a hydrosilane. Different from the classical homolysis/enantioconvergent recombination process of Ni(III) intermediates as the enantio-determining step, chiral induction in this reductive hydroalkylation was achieved through an enantiodifferentiating regio-reversed <i>syn</i>-hydrometallation process of α,β-unsaturated amides.

Enantioselective Hydroalkylation of α,β-Unsaturated Amides through Reversed syn-Hydrometallation of NiH

Enantioselective synthesis of a wide range of structurally diverse <a>β</a>-chiral amides has been achieved through nickel-catalyzed regio-reversed hydroalkylation of α,β-unsaturated amides with alkyl iodides in the presence of a hydrosilane. Different from the classical homolysis/enantioconvergent recombination process of Ni(III) intermediates as the enantio-determining step, chiral induction in this reductive hydroalkylation was achieved through an enantiodifferentiating regio-reversed <i>syn</i>-hydrometallation process of α,β-unsaturated amides.

Boosting charge carrier separation efficiency by constructing an intramolecular DA system towards efficient photoreduction of CO2

The charge carrier excitation–recombination process between the donor and acceptor, and the photocatalytic reduction of CO2 to CO over CN based DA composites.

Interfacial Energetic Disorder Induced by the Molecular Packing Structure at the Conjugated Polymer-based Donor/Acceptor Heterojunction

The energetic disorder in conjugated polymer films plays a crucial role in determining the charge separation and recombination process at the donor/acceptor heterojunction, thus dominates the photocurrent and photovoltage in...