background preloader

Table of Contents

Table of Contents

PubMed home Welcome to the Chemical Education Digital Library Microscale Gas Chemistry Our Gas Reaction Catalyst Tube can be used to demonstrate a variety of gas phase chemical reactions. The catalyst contains a layer of disbursed palladium atoms on a ceramic material and enclosed within a glass housing as per the fugure. Hydrogenation of alkenes occurs at very temperatures (even < 0 deg C). Gas Bags For classroom use, gases can be prepared and stored in sealable plastic food bags equipped with a dispensing tube. Mini-Ozone Generator Ozone is generated for in situ use. Left: Apparatus dispensing O3 to a flask. [IUPAC] Résumer un cours ou un article avec XMind Comment résumer un cours ? Ou un article ? Ou tout autre texte pas trop long ? Beaucoup de personnes éprouvent des difficultés à résumer : étudiants en période d’examen, journalistes qui doivent présenter une nouvelle loi en 1500 signes, cadres à qui leur supérieur vient de demander un rapport en « en deux pages maxi » sur la situation de l’agence de Trifouillis-les-Oies… Par où commencer ? Autant de points qui suscitent l’angoisse, voire la panique chez certains… et pas chez les plus stupides, contrairement à ce qu’on pourrait croire. D’abord un peu de théorie. Qu’est-ce qu’un résumé ? C’est une version raccourcie d’un texte existant. Jetez un coup d’oeil sur cette carte heuristique : elle illustre la méthode que je propose aux étudiants que j’aide en coaching scolaire et aux participants de nos Ateliers Triple A : Apprendre A Apprendre. Un résumé de cours avec XMind Première étape : la préparation Ne plongez pas directement sur votre stylo, votre crayon ou votre clavier. Comment ?

A particle like slow light: Particles known as 'Weyl fermions' were discovered in materials with strong interaction between electrons. Just like light particles, they have no mass but nonetheless they move extremely slowly. -- ScienceDaily Weyl particles are not particles which can move on their own (like electrons or protons), they only exist as 'quasiparticles' within a solid material. Now, for the first time, such Weyl particles has been found in a special kind of material, which is particularly interesting for novel technological applications: scientists have measured Weyl fermions in a material with highly correlated electrons. Surprisingly, these fermions move very slowly, despite having no mass. There was great excitement back in 2015, when it was first possible to measure these 'Weyl fermions' -- outlandish, massless particles that had been predicted almost 90 years earlier by German mathematician, physician and philosopher, Hermann Weyl. Quasiparticles: only possible in a solid state "Quasiparticles are not particles in the conventional sense, but rather excitations of a system consisting of many interacting particles," explains Prof. A "light speed" of just 100 m/s In search of new effects

Stereoisomers Stereoisomers As defined in an earlier introductory section, isomers are different compounds that have the same molecular formula. When the group of atoms that make up the molecules of different isomers are bonded together in fundamentally different ways, we refer to such compounds as constitutional isomers. For example, in the case of the C4H8 hydrocarbons, most of the isomers are constitutional. Shorthand structures for four of these isomers are shown below with their IUPAC names. Note that the twelve atoms that make up these isomers are connected or bonded in very different ways. The bonding patterns of the atoms in these two isomers are essentially equivalent, the only difference being the relative orientation or configuration of the two methyl groups (and the two associated hydrogen atoms) about the double bond. Configurational Stereoisomers of Alkenes Some examples of this configurational stereoisomerism (sometimes called geometric isomerism) are shown below. Ethane Conformations

Scientists discover crystal exhibiting exotic spiral magnetism An exotic form of magnetism has been discovered and linked to an equally exotic type of electrons, according to scientists who analyzed a new crystal in which they appear at the National Institute of Standards and Technology (NIST). The magnetism is created and protected by the crystal's unique electronic structure, offering a mechanism that might be exploited for fast, robust information storage devices. The newly invented material has an unusual structure that conducts electricity but makes the flowing electrons behave as massless particles, whose magnetism is linked to the direction of their motion. In other materials, such Weyl electrons have elicited new behaviors related to electrical conductivity. "Our research shows a rare example of these particles driving collective magnetism," said Collin Broholm, a physicist at Johns Hopkins University who led the experimental work at the NIST Center for Neutron Research (NCNR). More information: Gaudet, J. et al.