Tungsten evaporated crystals and 1cm3 cube (
Tungsten is an incredible material. It is dense and hard, and it has the lowest vapor pressure and highest melting temperature of all metals. This combination of properties makes tungsten extremely valuable for a myriad of applications, while at the same time creates great challenges in the processing of the metal.
As a child, I was fascinated by how things work and spent a lot of time taking things apart. As with most budding engineers, I rarely reassembled them. Incandescent bulbs were one of my first quarries, carefully disassembled to reveal a hidden treasure: a tungsten filament. It was amazing that this tiny wire could be heated to white-hot temperatures to produce light.
Also at an early age, I was introduced to vacuum tubes, and to this day they are magical in my eyes. When a tungsten filament is heated in a vacuum, the electrons near the surface become energetic enough to be emitted into the surrounding space. Additional tungsten conductors, in the form of grids and plates, can be added to the bulb, and the electrons can then be manipulated to switch, rectify and amplify These electronic switches were crucial in the development of modern electronics.
Tungsten at a Glance: Name: From the Swedish tung sten, meaning heavy stone. The symbol is from mineral wolframite, from which the element was originally isolated. Atomic mass: 183.84. History: Isolated in 1783 by Spanish chemists Juan Jose and Fausto Elhuyar. Occurrence: China has 75% of the world’s tungsten ores. Appearance: Silvery white metal. Behavior: Tungsten has the highest melting point and highest boiling point of all metals. Uses: Tungsten is used in high-temperature applications such as heating.
It’s Elemental: Tungsten
Chemical & Engineering News, September 8, 2003
Language of Life : Mycoplasma
Mycoplasma refers to a genus of bacteria that lack a cell wall. Without a cell wall, they are unaffected by many common antibiotics, such as penicillin, that target cell wall synthesis.
The first strains of mycoplasma were isolated at the Pasteur Institute in 1898. Mycoplasmas are the smallest free-living organisms and considered the simplest of bacteria. Owing to their extremely basic genomes, they are like parasites exploiting host cells to fulfill their energy requirements and biosynthesis of their components.
Several species are pathogenic in humans, including M. pneumoniae, which is an important cause of atypical pneumonia and other respiratory disorders, and M. genitalium, which is believed to be involved in pelvic inflammatory diseases. Mycoplasma are the smallest living cells yet discovered,can survive without oxygen, and are usually about 0.1 µm in diameter.