Acoustic Levitator

Real-world levitation to inspire better pharmaceuticals

Getting pharmaceuticals from solution into an amorphous state, however, is no easy task. If the solution evaporates while it is in contact with part of a vessel, it is far more likely to solidify in its crystalline form. "It's almost as if these substances want to find a way to become crystalline," Benmore said.

In order to avoid this problem, Benmore needed to find a way to evaporate a solution without it touching anything. Because liquids conform to the shape of their containers, this was a nearly impossible requirement -- so difficult, in fact, that Benmore had to turn to an acoustic levitator, a piece of equipment originally developed for NASA to simulate microgravity conditions.

The acoustic levitator uses two small speakers to generate sound waves at frequencies slightly above the audible range -- roughly 22 kilohertz. When the top and bottom speakers are precisely aligned, they create two sets of sound waves that perfectly interfere with each other, setting up a phenomenon known as a standing wave.

At certain points along a standing wave, known as nodes, there is no net transfer of energy at all. Because the acoustic pressure from the sound waves is sufficient to cancel the effect of gravity, light objects are able to levitate when placed at the nodes.

"SCIENCE!"

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iTunes and streaming

Here are some things that I have learned about iTunes and streaming. Or think that I have learned. I place them here to hopefully prevent others from banging their heads against this wall in the future.

In iTunes 8 and 9, and possibly earlier versions, streaming audio works like this:

  • The Content-Length header is used to compute the "Time" column based on the MP3 bitrate. The x-audiocast-bitrate header may also be implicated in this but I'm not sure.
  • If there is no Content-Length, "Time" shows as "Continuous".

  • If headers contain both "Content-Length" and "Accept-Ranges: bytes" then the "seek" slider in the UI is active, and moving it re-loads the URL using "Range:bytes=N-M". The server must then respond with status 206, a "Content-Range" header, etc.

  • You can set the title of the stream (as displayed in both the track listing and at the top of the window) by sending either the "x-audiocast-name" or "icy-name" headers. Case-sensitive!

  • You can accomplish the same thing by sending an ID3v2 TIT2 tag at the front of the MP3 data.

  • If you send multiple ID3 tags, only the first is used (you can't just send multiple tags to update streaming metadata).

  • iTunes supports Icecast/Shoutcast-style inline metadata, but does not advertise this. It should be sending "icy-metadata:1" to indicate that it is capable, but it does not. However, if you send icy-metaint:NNNN and encode it properly, it works. This is the only way to update streaming metadata, e.g., to change the title when the song changes. This metadata will be displayed at the top of the window, but does not overwrite the track name.

Now here's where it gets fun. iTunes 10 changed things. As far as I can tell, inside the black box there is now a "mode" that distinguishes between two cases. Let's call these cases "streaming" and "playing a remote file". You might think that those two cases are exactly the same god damned thing, and you're right, but iTunes disagrees.

When iTunes 10 has decided to be in "streaming" mode:

  • Regardless of Content-Length, "Time" always shows as "Continuous".
  • Titles and metadata can be updated with x-audiocast-name, icy-name and/or inline icy-metaint metadata.
  • The "seek" slider is inactive. No byte-range requests will be made, period.

When iTunes 10 has decided to be in "remote file" mode:

  • "Time" is displayed properly.
  • The "seek" slider is active, and byte-ranges work.
  • The x-audiocast-name and icy-name headers are ignored. Sending an ID3v2 TIT2 tag works, though.
  • Sending icy-metaint inline metadata will cause audio glitches. It's not interpreting it at all.

Now, how does it decide between these two modes, you might ask? Well I'll tell you:

    Whether the URL ends with the string .mp3.

No, I am not making this up.

So what this means in practice is that there is no way to have a stream that is seekable and also has dynamically-updated metadata. Either you have a single title for the whole thing that never changes, and you can enable seeking; or you can have continuously-updating metadata, but never seek. In iTunes 9, you could have it all; no longer.

So what's changed in iTunes 11?

I haven't tested it personally, because I still depend heavily on a couple of features they've deleted, but from talking to others who are running it, the situation appears to be:

  • iTunes 11.0.1 will now send the icy-metadata header when it is in the mood to accept inline metadata. Unlike earlier versions where you had to guess, at least now they're being explicit about it. Not that that helps much, since you still have to guess for older versions of iTunes.
  • The "seek" bar never works, ever. If the bits came from a URL, then the "Size" field says "Stream" and you can't seek, even if the URL provided a Content-Length and Accept-Ranges. It now won't even tell you how long the stream is, though the information is there.

So, having only recently crippled the functionality of "stream" by dividing it into the "stream" and "remote file" false dichotomy, they appear to have gone farther and nuked the "remote file" capabilities entirely.

Joy.

Seeking and metadata still work in VLC, for what it's worth, assuming that you can bring yourself to tolerate that program's catastrophically terrible UI.

If you're messing around with this crap at all, then you will probably be interested in my streaming servers: slowcat.c, audiofs.pl and mixtape.pl.

If you work for Apple, please hassle somebody about bug reports 13004973, 13004985 and 10737146.

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DNA Lounge update

DNA Lounge update, wherein the webcasts get an upgrade, and this year's photos begin.
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"RePOOPulate"

Synthetic Shit Transplants

But faecal transplants have hardly become common practice. The procedure faces regulatory hurdles since it doesn't involve a typical drug or device. By its nature, it is very hard to standardise and test through randomised clinical trials -- the gold standard of medicine. There are concerns about spreading new diseases along with the helpful bacteria. The stool needs to be freshly collected and used within several hours. And, understandably, there's the "ick factor" (for that reason, many people prefer that the donor be a spouse or relative).

To circumvent these obstacles, Elaine Petrof and Gregory Gloor from Kingston General Hospital in Ontario have developed a pseudo-poo -- a blend of 33 different gut bacteria that mimics the community found in a healthy gut. This "stool substitute" can be cooked up again and again according to the same recipe, and infused into patients without any of the extra faecal matter that makes such transplants so viscerally off-putting or potentially dangerous. Think of it as a rectally applied yoghurt. [...]

Petrof and Gloor based their substitute on the gut bacteria of a healthy 41-year-old woman. They isolated 62 species from her bowels and excluded any that showed even mild signs of antibiotic resistance -- those aren't microbes you want to be deliberately applying to someone's gut. Thirty-three species remained, which Petrof and Gloor balanced according to their typical proportions in a healthy gut.

The result is a standardised bacterial broth that's clear of any other disease-causing microbes or viruses, and that can be applied as an enema. (I can go for years without reading the words "drizzled throughout the transverse colon as the colonoscope was withdrawn" in a paper again.)

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"Aspiration Therapy"

Get one for the bulimic in your life today!

The AspireAssist gives patients control over their weight loss by a method known as Aspiration Therapy. With Aspiration Therapy, patients "aspirate" (drain) a portion of their stomach contents into the toilet after each meal through an endoscopically-implanted tube, reducing the number of calories absorbed by the body. The tube is implanted in the stomach, and leads to a small, low-profile port at the surface of the skin. Aspiration performed about twenty minutes after a meal will remove about a third of the calories consumed.


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H.P. Lovecraft Writes Descriptions for the Sample Clips on Brazzers

Breakfast Squirt Break (Shes Gonna Squirt)

Come closer, Randolph. Let me tell you of what I saw. Do not be afraid, this madness is not contagious, unless you look upon what I have. I dare to say that after you have heard my warning, you shan't. I do not know what became of Manuel Ferrera, I do not like to guess, but the last I looked upon him he was gibbering from exposure to a queer essence I will now describe to you as best I can. It has no colour and only a fool would guess at its odor or taste. It appears with the consistency of water, but my friend, Randolph, heed my words: it is not water. It emerges with little warning, a riot of action that drenches everything in the area, from beyond a human threshold I dare not describe. The winds of the stars shiver the curtain that hangs upon the stage of our reality, then this essence stirs mortal curtains as easily as the forgotten gods lost to history. Go! Randolph, begone! Forget me and my plight. Forget I ever existed! But remember the squirt.

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You know this is how it actually went down.

Colleen Coover: Friday Bat-Dismount


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