However, much has happened since it went up, including the Blogger outage.
New Year, New Emitter We can easily forgive a child who is afraid of the dark; the real tragedy of life is when men are afraid of the light.
Think of it as a very fancy light bulb, but for electrons instead of photons. Traditional optical microscopes use light to illuminate a sample.
Sunlight, LEDs, lasers, or any other source of light can be used. Lenses focus that light into an image that you can see with your naked eye or a camera. The trouble with using light as an illumination source is that it moves as a wave.
This is known as the diffraction limit. For imaging anything smaller than a couple of hundred nanometers, light simply becomes impractical. Like light, electrons also have a wavelength that depends on how fast they are moving.
Keep in mind that the diffraction limit is just the ultimate restriction that physics imposes on us. Electron sources Many SEMs use a thermionic heat driven electron source. It works a bit like an old fashioned light bulb: It does this by using a tiny metal tip that can be as small as a couple of tungsten atoms.
The sharper the tip, the stronger electric field and potentially, the smaller the beam. To sum it up in one word: This is about ten thousand times better vacuum than a thermionic emitter needs to function. But that brings us to the other big cost difference between a cold cathode FEG emitter and a thermionic filament: Of course, there are many other engineering considerations and physical constraints beyond cost as well.
See this presentation for a nice overview of the differences between various electron sources. And the tip is just a tungsten atom or two. Since Milly developed beam stability issues earlier this year, I began to suspect that her emitter might need replacing.
This is quite a bit outside my fun budget, so I decided to try my hand at making one. I did exactly that and ended up with very straight, very brittle tungsten. The biggest light bulb in the lab. My first welding experiments were a total disaster.
First I tried to use a benchtop power supply and lithium ion batteries to make the weld. But while this provided plenty of power, the rise time of the current was far too slow.
Instead of a good weld, I got broken wire. Too much heat for too long: Also, this wire is 2. I later realized that what I needed was a capacitive discharge CD welder. The only trouble being that they cost about as much as a replacement emitter.Expanded Edition Includes these Bonus Tracks: Amongst this collection of bonus material, there are several examples of the magical early takes and in this re-mastered version of Pyramid, for those interested in the process, there is a unique opportunity to glimpse behind the .
Career Author, educator, and lecturer, —. Professor, New York University, New York, NY, ; visiting professor of creative writing, University of Miami. Behind These Hazel Eyes (Kelly Clarkson) Verse 1: Em C Seems like just yesterday G D You were a part of me Em C I used to stand so tall G D I use to be so strong Em C Your arms around me tight G D Em Everything, it felt so right C G D.
The idea of this study struck me six years ago after the first mention of the Black Irish as told to me in variant four of the myth. The question of its origin, meaning, and purpose has haunted me ever since, primarily due to my own Irish heritage (my mother's family .
This is an abridged version of Peter Parker's history. For a complete history see Peter Parker's Expanded History Peter Benjamin Parker was born in Queens to Richard and Mary Parker.
While Peter was still an infant, his parents were assigned by the CIA to infiltrate the Algerian based spy ring. Many small terra-cotta figurines from Greece of the fourth century BC have survived with traces of paint. They show light hair, usually reddish brown, and blue eyes, as do larger statues from the time of the Persian Wars in the early fifth century BC.