Cosmic reionization, which took place in the first billion years after the Big Bang, was a major event in the cosmic history. This transformation of all neutral hydrogen to ionize was probably caused by the first stars, galaxies and quasars. However, a direct proof of which sources were dominant is still missing. Dr. Ivana Orlitová from the Institute of Astronomy of the CAS reviews results of the serach for ionizing sources in both distant and nearby Universe, and presents a recent discovery of starforming galaxies that show signs of strong ionizing activity. and Ivana Orlitová.
Nebezpečným, ale mezi studenty oblíbeným pokusem demonstrujícím explozivní chemickou reakci je vhodit kousek kovového sodíku do vody. Každý učitel chemie ví, že výbuch nastává kvůli uvolňování tepla při přechodu elektronů z kovu do vody, přičemž vzniká pára, hydroxid a vodík, který se může vznítit. Plyny vznikající na rozhraní mezi kovem a vodou by ale měly od sebe tyto reaktanty oddělit a tím reakci potlačit. Jak to, že k výbuchu přesto dochází? Pomocí záběrů ultrarychlé kamery a molekulových simulací se podařilo odhalit dosud neznámý primární mechanismus explozivní reakce alkalických kovů ve vodě. Poté, co elektrony přejdou z alkalického kovu do vody, vytvoří se na jeho povrchu značně veliký kladný náboj. Kvůli vzájemnému odpuzování těchto nábojů dojde k takzvané coulombické explozi, kdy s povrchu ohromnou rychlostí vylétají kousky kovu do vody. Tím se reaktanty efektivně promíchají, což je podmínkou výbuchu., Throwing a piece of sodium into water is a dangerous, but popular experiment demonstrating an explosive chemical reaction. Every chemistry teacher knows that during the explosion heat is released when electrons move from the metal to water generating water vapor, hydroxide, and hydrogen which can ignite. Gases generated at the interface between the metal and water should, however, separate the reactants and thus quench the explosion. How is it possible that the explosion can nevertheless take place? Thanks to pictures from an ultrafast camera and molecular simulations researchers from the Institute of Organic Chemistry and Biochemistry found a hitherto unknown primary mechanism of the explosive reaction of alkali metals in water. When the electrons move from the metal to water, the former acquires a large positive charge. Repulsion between these charges leads to a Coulomb explosion with metal spikes shooting into water. This leads to effective mixing of reactants thus enabling the explosion., and Pavel Jungwirth.
This new project of the Institute of Physics of the CAS is a Widening Excellence, Twinning project aimed at boosting the scientific excellence and technology-transfer capacity in advanced scintillating materials of the Institute of Physics from the Czech Academy of Sciences by creating a network with four other partners: CERN, Institute Lumière Matière - Université Claude Bernard Lyon 1, Università degli Studi di Milano - Biocca and Intelligentsia Consultants. and Jana Olivová.
Zeolites are some of the most important solids in modern technology and the search for new types of zeolite and new methods of making zeolites remains at the forefront of research. Recently, we have developed a new synthetic strategy called ADOR (Assembly-Disassembly-Organization-Reassembly). This strategy starts from germanosilicate zeolites being vulnerable to hydrolysis providing zeolites layers of the original structure. Appropriate manipulation with the layers connected with intercalation chemistry and followed by their condensation resulted in the synthesis of six new zeolites, some of them being considered as "unfeasible" due to the high energy of their frameworks. Basic principles of ADOR chemistry are described in this short overview. and Pavla Eliášová, JIří Čejka, Petr Nachtigall.