The history of semiconductor injection lasers is briefly outlined and the need for lasers integrated on Si chips is explained. Several approaches to overcome inadequate properties of silicon are followed; including (i) silicon nanocrystals and other lowdimensional structures (ii) Si Raman laser, (iii) rare-earth doped Si, and (iv) non-silicon-material lasers integrated to Si chips. Finally, the recent germanium laser is described., Jan Valenta., and Obsahuje bibliografii
Motto z webu JB: "Víš ty, že většina vědců vůbec neuznává existenci magie? Když přidáš magii do energetické rovnice, tak se ukáže, že skoro všechny současné zákony fyziky mají vážné trgliny." Eoin Colfer v knize Artemis Fowl a ztracený ostrov and Jiří Bouchala. (Otázky kladl Jan Valenta.)
Matematicko-fyzikální fakulta Univerzity Karlovy v Praze slaví v roce 2012 šedesáté výročí svho vzniku (formálně vznikla oddělením od Přírodovědecké fakulty ke dni 1. září 1952). Při této příležitosti je organizováno množství akcí pro veřejnost. Mezi nejoriginálnější a nejzdařilejší bude jistě možné zařadit FilmFest. Tento soutěžní festival filmů o matematice, fyzice a informatice (MF) získal neobvykle velký ohlas především mezi studenty středních škol. and Jan Valenta.
Starting with the basic principles of light emitting diodes (LED), the history of blue LED development is briefly described in order to justify and explain the awarding of the Nobel Prize for physics in 2014 to I. Akasaki, H. Amano and S. Nakamura. Exploitation of blue LEDs in lighting techniques enables a substantial decrease in energy consumation and enables emerging smart applications, which could be considered as the most important lighting revolution after the introduction of incandescent bulbs more than a century ago., Jan Valenta, Ivan Pelant., and Obsahuje seznam literatury
Photography started to be applied in sciences shortly after the announcement of the daguerreotype in 1839 and become one of the most important supporting disciplines for science. This review concentrates on the history of scientific research on photographing processes which was conducted at Charles University. The most important was development of sensitometry which started by work of Vojtěch Šafařík (1829-1902) who thoroughly studied the dry proces. Photographic work in the Institute of Physics (IP) of the Czech part of "Carlo-Ferdinand University" was initiated due to studies of X-rays (from 1895) and later the Institute of Photochemistry and Scientific Photography was founded within IP by Professor Viktorin Vojtěch (1879-1948). In 1950-s this institute disappear and splitted into chemical part (colloidal chemistry and photochemistry) at Faculty of Natural Sciences and physical part (photophysics, studies of latent image and silver halogenides) at Faculty of Mathematics and Physics under leadership of Professor Ladislav Zachoval (1906-1982). His follower Professor Karel Vacek then turned interest from scientific photography into modern subjects of chemical physics and biophysics., Jan Valenta., and Obsahuje bibliografii