Category: Methods

“How To Do Stuff”

My “geostrings” project, and coming attractions.

I have set up a more permanent “page” for my little project to come up with a way to embed geotags in things like mp3, Ogg/Vorbis, video files, text documents, image formats besides jpeg and geotiff, and so forth. I’ve got a definition of the format and a basic description of the parsing algorithm for it up there. Embedding and decoding examples and so forth will follow soon, though I’m hoping for some comments before I get too deep into assuming I’ve got the format finalized.

Meanwhile, I’ve signed on for this year’s “Just Science” week, So I’ve got to get together at least five consecutive days worth of science posts to go up between February 4th and 8th. Fortunately, I think I can fill most if not all of it with the brewing science (and yeast culture in particular) stuff I’ve been researching. I’d still like to get my hands on at least one more paper which isn’t readily available to me (Gasent-Ramírez JM, Castrejón F, Querol A, Ramón D, Benítez T.: “Genomic stability of Saccharomyces cerevisiae baker’s yeasts.”; Syst Appl Microbiol. 1999 Sep;22(3):329-40.) but I do have quite a few others that I’m going over.

Gather and harken unto my tale of woe!

Well, this roadtrip has been rather difficult so far. Not necessarily bad, but definitely difficult.

It was about a week before the weather would let up enough for us to even escape our home state. I came down with a cold as we were leaving. The campground we were originally going to be staying at on the second night was mysteriously closed for the season despite supposedly being open year-round. Panoramio appears to have forgotten that I exist and won’t let me login to upload more to my photos (and I’ve not yet heard back from the email contacts there about getting back in). And then on the third night, neither of the truckstops next to our campground had sour cream. And the following morning, after stopping briefly to pick up some food for breakfast, the truck sputtered and died on the way up the onramp to continue the trip. And then we had some stress and confusion getting things worked out initially with the RV’ers organization to get towed to a repair shop and a campground. And then my wife has apparently picked up the cold that I’m getting over now. And then someone took a doody in my sandbox…oh, wait. That was just a “song” on one of my CD’s. Never mind.

On the other hand, we did manage to finally escape our home state, we did find a replacement campground for the second night, we did get everything worked out okay, and our truck’s problem turned out to be a relatively minor issue with the distributor though it evidently took a fair amount of labor to extract, fix, reassemble, and reinstall it, and we should be able to get back on the road in the morning. So, enough whining from me for now.

Meanwhile, I’ve thought about my “geotagging arbitrary files” issue a bit more. At this point I’m favoring the “geostrings” approach, split into what I’m calling “Where, When, and Whither” fields, which is to say, a field containing location (latitude, longitude, elevation), a field containing time-related information (timestamp, track-id), and a field containing direction (heading and angle) information. I’ve actually started putting geostrings in this form into some of the pictures I’ve been taking, just to get a feel for how easy or hard they are to work with. An example containing all information including the optinal stuff would look like this:

geostr:35.068531033,-106.5019369,1716.0905m:20080104T122418-06,track01:60,20:geostr

The “where” field is latitude, longitude, and elevation, separated by commas. The “when” is the ISO8601 standard simplified timestamp and a track ID, and the “whither” indicates a heading of 60° and an upward angle of 20°. The colon-separated fields and the comma-separated data within each field are in order from (as I perceive it) most important to least important. Aside from the latitude and longitude, and the “geostr” markers on either side, everything is optional.

Comments?

Linking this more-relevant latter portion of the post to the whining at the beginning is the fact that the cold I’m now getting over has messed up my voice. I did bring microphones and both my computer and some cheap portable recording gadgets, so at some point along the way I still want to do at least one short audio recording, geotagged and including an embedded image to go with it. I just need to wait for my voice to properly return (and to spot something about which I feel an urge to inflict people with my blabbering.)

Proposed format(s) for geotagging arbitrary types of media

Yet more thoughts on geotagging – here’s what I’ve come up with so far.

The format needs to handle only two fundamental data types – points and polygons. It also obviously needs to handle “lines” or tracks, but those are made of “points”. Polygon, for my purposes, might be unnecessary and I’m not sure if I should leave it in. I’m reluctant to leave it out – that way you could easily georeference media to a building or field’s outline, for example. On the other hand, I’m trying to keep this format terse and concise – I’m not trying to merely embed .gpx or .kml files in things.

A “point”, as I am thinking of defining it here, is made of up to seven attributes (more or less in order of importance): a latitude/longitude pair, elevation, timestamp, track-ID, heading, and angle. A polygon is the same, except that it contains a list of at least three lat/lon/optional-elevation sets. It still only has a single timestamp, though, just like a “point”. I suppose in some odd cases one could even define a track as a series of polygons – defining the field of view in a video taken from the bottom of an airplane that’s taking off, for example.

Leaving aside the question of polygons for now, I’m envisioning two possible formats which I will arbitrarily name “geotag” (XML-type) and “geostring”(simple text) for the moment.

I picture a geotag entry looking something like this:

<geotag:point lat="41.228063" lon="-115.058119" elev="1720.901m" datetime="20071115T143000-06" trackid="1" heading="340" angle="-5.0">Metropolis Hotel</geotag:point>

In this format, the optional description of the point is between the opening and closing tags there. “lat” and “lon” might be better as a single “latlon” or “coord” attribute, with the latitude and longitude separated by commas (i.e. <geotag:point coord="41.228063,-115.058119">:</geotag:point>)

A “geotring” point might look something like this instead:

geostring:point:41.228063:-115.058119:1720.901m:20071115T143000-06:1:340:-5.0:geostring

Not sure if the closing “geostring” is really necessary here, but it would make backwards-compatibility easier if fields were added to future revisions. As with the geotag, it might be better to treat the lat/lon pair (the only mandatory information for a minimal “point” definition) as a single field, so the minimal “geotag” example above done as a “geostring” would look something like: geostring:41.228063,-115.058119::::::geostring

Even as I write this, I find myself leaning towards combining the latitude and longitude into a single field, if for no other reason than it means each point only has one required field. Either way, I currently think the fields ought to be defined thus:

  • latitude and longitude are decimal degrees. Either may be prefixed by a + or – (lat: +=”Northern Hemisphere”, -=”Southern Hemisphere”, Lon: +=East, -=West) – if neither is there, + will be assumed. Latitude and longitude are required for every point.
  • Elevation may be suffixed by “m” or “f” (for “meters” or “feet”). If neither is specified, meters are assumed.
  • Timestamp is in the ISO 8601 “basic format”. If neither “Z” or an offset from UTC are specified, “the viewer’s local time” should be assumed (which is kind of silly, but it still would allow one to synchronize a track with, say, an audio recording or video.)
  • trackid is any arbitrary alphanumeric term with a maximum of, say, 16 characters (is that enough?) Any points with the same trackid are assumed to be part of the same track. If unspecified, the point is assumed to be unrelated to any other points (if any exist) that may be in the same file.
  • Heading is in decimal degrees from 0 to 360. This represents facing a particular (horizontal) direction from the point in question. “Which direction the camera was pointing” in the case of a photograph.
  • Angle is in decimal degrees from -90 to 90. This represents an angle above or below the current elevation at that point (for a picture, this would represent the upward or downward angle that the camera was pointing when the picture was taken.)

Hmmm, if I shorten “geostring” to “geostr” and either eliminate the “data type” field (“point”) or just reduce it to a single letter, that entire and complete “geostring” example would fit even into a single tiny 64-character comment field, if there are any file formats still floating around limited to that kind of small metadata size.

My main goal here is to make it easy to create files tagged with this information. So long as it’s easily read and not likely to get separated from the file it describes, using the data for anything ought to be easy, even if one has to do it “by hand”. As was mentioned on the “Into the Pudding” blog (found via the GeoRSS blog), having applications that can read metadata is useless if nobody’s putting the metadata in their files to begin with. If an acceptable format can be worked out, I intend to start making as much georeferenced information available as possible.

Who’s with me? Comments, suggestions, offers of patronage, anyone?

More on geotagging

Some good comments came up in the last post on georeferencing. I thought a followup post was
merited.

The itch I’m trying to scratch here is that I want to be able to georeference just about any kind of data,
and I want to be able to embed the georeference information directly in the data file, whether it’s a
graphic, or audio, or video, or gene sequence data, or anything else. I want to have a standard form for tagging any of these files. And I don’t want to store the location metadata in a separate file.

What I think I need, then, is a standard, simple way of making geographic notations in a terse, concise format that is both easily parsed by and readily recognizeable to a computer, is reasonably human readable, and can be made to fit just about anywhere that arbitrary text is allowed.

Right now, there are only two types of files that have some way of embedding geographic information into them that I know of. The obvious one is that EXIF data in JPEG files can contain “GPS” tags. For hardcore GIS people, GeoTIFF is the other one. Both are for photographs or other still-image data only. What about the rest?

A variation of one of the current geotagging XML formats like the W3C (“<geo:lat>41.4354840</geo:lat><geo:lon>-112.6660845</geo:lon>”) or GeoRSS is an obvious possibility. XML has two potential problems though, as I see it. First, it’s not very terse – the markup substantially increases the amount of space the information takes up. I think in most cases that wouldn’t necessarily be a problem, but I suspect there are a few file formats out there with only comparatively small spaces set aside for a “comment” or “description” field.

The second potential “problem” is something odd that occurred to me today: it’s hard to pronounce out loud. There are some popular audio formats (e.g. “.wav”) that as far as I know have no space whatsoever for arbitrary text…but if my little standard was something that could be distinctly spoken, someone making a recording could literally speak the metadata in a format that a speech-to-text engine (like Sphinx) might be able to recognize and convert to a compatible string of text which could be parsed just like data from anywhere else. This is something of a corner case, I admit, but I think it’s at least worth considering.

Another good point that came up was what you do if your data extends beyond a single point. For example, if I want to georeference an audio recording I might make while narrating what I’m seeing out the window of a speeding train, it makes good sense to at least try to store line segments rather than just a point. That way, if someone wants to find the spot within a several-mile stretch where I suddenly exclaim “Hey, wow, look at that!” they can. The ability to define areas with a polygon or a point-and-radius seems like it would be handy, too, though obviously much more optional.

So, let’s see, I’m looking for a format with minimal markup, but which is easily recognized, is made of plain text which could be crammed into, say, a PNG tEXt chunk, an mp3 comment frame, a Genbank “Source” field, or any other field which allows arbitrary text. I want a form that’s minimally objectionable to anyone else who might be willing to use it. And I think I want it to be able handle points consisting of at least latitude, longitude, optional elevation, optional timestamp, and possibly even an optional heading and angle, and can handle more than one point per file (for the case of lines). Am I forgetting anything?

Besides “going to bed before 3am”?

I want to geotag something besides photographs!

Cornelia - Queen of the Snow!For no particular reason, here is a picture of The Dog in her natural habitat. This picture really has nothing to do with today’s blog post, but since this is supposed to be a happy time of year, I suppose a happy picture is in order.

In case anyone is wondering if I’ve forgotten the supposed microbiological emphasis on this blog, the answer is no. In fact, I’ve got a post on amateur yeast culture brewing, but I’m still researching it a bit.

Meanwhile, it seems reasonable to post about geolocation, which after all is an important and useful trick for associating information with its place in The Big Room.

Geolocation of photographs is well established, at least for JPEG images. There are standard ways of tagging a JPEG file with an ICBM address, and I’ve been having a lot of fun doing this with my own pictures. (If you’re bored, you can browse them on Panoramio, and perhaps in a few weeks may stumble on some of them in Google Earth.)

There doesn’t appear to be any standard way of tagging other forms of media files, though. What if I want to geotag an .mp3 or OGG/Vorbis audio file recorded at a particular spot? Or a “DivX/Xvid” or OGG/Theora video?

Irritatingly, it seems as though a few people have mused about it, but nobody seems to have addressed it. There are projects like The Freesound Project which does geolocate sounds, but the geographic information is not actually embedded into the sound files in any way. As far as I can tell, the location is tracked in their own server’s database only. A Google search turned up a post on the “Random Connections” Blog musing about this, but the only application mentioned is adding georss tags to the RSS for a podcast feed, not to the podcast’s audio file itself. Even the otherwise excellent Mapping Hacks book (written before O’Reilly’s current decline into yet another “Proprietary Product® How-To Guides” publisher over the last couple of years) mentions the topic in Hack #59, but disappointingly appears to have really had nothing to do with tagging files so much as “interpolating a position from a GPS track, given a timestamp”.

This all comes up because we’re about to go on a roadtrip to check out a part of the country where we seem likely to end up living next year. I’ve been told I’ve got a pretty good voice, so I was considering generating a travelogue series along the way. It appears to be relatively easy to generate a “narrated picture” as a standard mp3 file, the picture being loaded as though it were “album art”. The only aspect of the whole thing that’s missing is geolocation. For now, just being able to easily obtain the ICBM address associated with the file while playing it so that one could plug the coordinates into Google Maps to see where the recording was done, but ideally I’d like to do it in a way that could be considered standardized, so that later on people might be encouraged to add geolocalization plugins to their media-playing software.

Sure, I can just generate a .kml file with a track of where we were, with markers containing picture and audio links. In fact, I probably will, but I don’t want people to have to use Google Maps or Google Earth to make use of the geolocation information associated with the audio.

Any suggestions, anyone?

Why you really do or don’t want me as a student…

Of the classes I took this last semester, there’s only one I haven’t blogged about at least once.

Masochist that I am, I went and took “Applied Calculus”, even though I’d gotten approval to count my previous semester of calculus (about 8 years ago) as fulfilling the mathematics requirement for graduation. The “applied” in the title of the class caught my eye, and after speaking to the instructor before the semester to find out what the class was like I decided that if there was time and money left I’d take the class. So I did.

Although I’d rank it as only the second most useful “Mathematics” course I’ve taken so far, Dr. Wolper was one of the best mathematics instructors I’ve had up to this point, so I’ve got no regrets for having spent the time and money to take it. I suspect I’ll remember a lot more of it than I did of the previous calculus class.

Anyway, getting to the point of this post:

There are times when I am unable to restrain myself and answer homework or exam questions in a terse, boring manner, regardless of the subject. If you’re an instructor and are wondering if you want me in your class, here is something to judge by.

Calculus (for those who don’t know) is more or less the math you use to deal with when, how, and how fast things change. In practical terms, when dealing with real-world applications this often means dealing with a graph of some data. A number of homework (and exam) problems this semester dealt with questions along the lines of “what would a graph of such-and-such a situation look like and how would you interpret it?”. Here’s one from early in the semester:

This was my answer:

You may judge for yourself whether this is a good answer or not…

Give a man a fish, and you feed him for a day…

…but teach a man to fish, and he’ll sit in a boat and drink beer all day.

-== We interrupt this blog post to bring you this important announcement: Happy Birthday, Dad!==-

(His birthday was actually yesterday, but this week of school has been grinding me pretty hard and I’d forgotten all about it. He must be so proud – his son can handle a couple of semesters of biochemistry, complex microbial science, working with dangerous chemicals in a lab…but doesn’t seem to know how to use a simple calendar…I am filled with shame.)

We now return you to your regularly scheduled blog post:

This here critter is our resident fish. “He” is a classic specimen of real, old-fashioned, Honest-to-Aquaman Carassius auratus auratus – the Goldfish. And not one of those poor mutant freaks who can barely swim, either. No this here fish was rescued from the overcrowded “feeder goldfish” tank of a local Wal-Mart®. Handsome, ain’t he? I had a tough time getting even this good of a picture – every time I get near the tank he swims back and forth in front of me frantically, perhaps worshipping me as the magical fishfood god. He’s been here for about three years now, so I think he’s having a much longer life than most of them.

I’ve had no time to get into it, but part of the reason for having a fish is that I have a casual interest in aquaculture. That is, while I don’t currently have any intention of becoming a professional full-scale fish-farmer, the subject is interesting and, I think, very important in the near future. Once we figure out where we’re going to end up living next year and get settled in somewhere, I have considered trying to do the aquaculture equivalent of a backyard garden, though.

I think aquaculture is going to become extremely important in the relatively near future, as we run into the combination of overfishing of natural stocks, water shortages, contamination of natural waters with pollutants that build up in naturally-existing populations of fish, and the overall effects of climate change. I think understanding how to raise healthy and nutritious aquatic food without wasting water or causing environmental problems is going to be a useful set of knowledge to have. (There, see, not only do I love kittens and puppies and want to make the world a better place, but I’m also interested in Sustainable Environmental Practices™. While feeding the hungry. [Uphill. In the snow. With no shoes…]).

You may be wondering what interest an ex-professional-computer-nerd microbiologist would have in tending a pond full of eukaryotes. Well, aside from the obvious “Hey, I can have more than one interest, you know”, there actually is a lot of microbiological activity involved in the natural processes of the fishes’ homes. Plus, of course, the aforementioned beer doesn’t ferment and bottle itself, you know.

Since one of my interests in this context is water conservation, my main interest is in figuring out how to maintain a healthy “closed” system. In an aquaculture context, a “closed” system is one that you don’t normally add substantial amounts of water to. (An example of an “open” system might include raising fish in pens floating in a natural lake, or having a constant stream of fresh ground or river water pumping through your tanks). This poses certain problems, since you have to feed the fish, and this adds an ever-increasing load of potentially uneaten fishfood and especially of eaten fishfood – that is, fish wastes.

Fishfood being digested by either fish or bacteria ends up adding ammonia to the water, which is poisonous to the fish (and crawdads and whatever else is in there). Also excreted is carbon dioxide, which makes the water more acidic, and unused food also dumps sulfur and phosphorous into the system.

If you’ve ever had a fishtank, you may know about the ammonia. Certain kinds of Oxygen-using bacteria can actually get some of their biochemical energy from turning reduced nitrogen into oxidized nitrogen, ultimately turning the ammonia (NH3) into much less poisonous nitrate (NO3). These bacteria tend to colonize the tank’s filter, where they do their thing using the oxygen in the water that flows through. Even nitrate is dangerous if it builds up too much, though. In an aquarium, they usually recommend just taking out some of the tank’s water and replacing it with fresh water every week or two to get rid of the build-up. I’d show you pictures of the bacteria, but I still can’t afford a decent microscope. (sniffle.)

Anyway, I want to build a denitrification column one of these days. There are bacteria that can “breathe” nitrate in place of oxygen, and in the process they can reduce the nitrate back down to plain old harmless nitrogen gas, which just bubbles out of the water. If you build a long, tall tube full of something like gravel that bacteria can grow on, and then pump the water through it slowly, oxygen-breathing bacteria near the bottom of the tube rapidly use up the oxygen in the water, leaving the nitrate. With no oxygen further up the tube, bacteria that can breathe the nitrate instead can grow like crazy, and exhale the extra nitrogen out of the system.

That’s one way of avoiding the need to use up as much fresh water as you’d need if you relied only on replacing the water to get rid of the nitrate.

I’ll save the sulfur and phosphorous parts for another day. Meanwhile, I think the next podcast or two will deal with MRSA, since it’s been in the news so much lately. I normally find the neglected non-medical microbiology more interesting, but the biochemistry and genetics involved with Methicillin Resistant Staphylococcus Aureus (not to mention S. aureus itself) is pretty interesting, and I find the media discussions of it unsatisfying.

Stay tuned…

Poor-boy science: should I build my own electrophoresis platform?

I want to build my own little electrophoresis gizmo to play with.

I did pick up a small tube of powdered graphite and some liquid tape. With this, I should be able to make a waterproof electrically-conducting glue that I can use for the electrodes. I’ve got numerous old “wall-wart”-type power adapters that I ought to be able to use for power supply.

The main thing I’m trying to work out in my head before I start trying to actually put this together is exactly how I’m going to arrange it so that I can have either a thin gel or a piece of paper or other fibrous material in between the electrodes so that I can best separate things.

I suppose it’s kind of bizarre, but this is actually part of the ongoing Expired JellO® projects. I was wondering to myself what actual changes might possibly occur in a packet of dry gelatin mix over time, and how would I be able to tell?  My previous experiments have shown no indication that there are any easily detectable differences (no obvious changes in taste or texture, no strange eerie glow, no acquisition of superpowers upon eating it…) so I’ll have to look more closely.

It occurred to me that just maybe over time the strands of protein that make up gelatin might get damaged by oxidation from the air in the pouch (or do they seal the pouch in a relatively inert gas, like argon or nitrogen?). This isn’t something one can really tell just by looking, obviously. One MIGHT be able to tell indirectly by making fresh and “expired” packets of gelatin with the same precisely-measured amount of water, poured on at the same precisely-measured temperature, and ideally with the same amount of mixing. Believe it or not, there are actually special scientific devices for measuring the firmness of gels like this. The hypothesis would be that expired gelatin might end up “degraded” into smaller strands of protein than a fresh packet, and that this would be reflected in a reduced firmness of the gel, or perhaps reduced water-holding capacity.

However, I don’t have access to precise devices for measuring things like that, and in any case since I suspect the difference would be pretty minimal, I’m not sure any difference in firmness would really be detectable with any kind of instrument I could cobble together on my own. What to do?…

I thought that if I had a way to subject a sample of dissolved gelatin to electrophoresis, I could then use a protein-staining substance to see how broad of a range of protein-fragment sizes were existent, or perhaps even spot distinct fragments if oxidative damage tended to happen at the juncture between particular amino acids or something.

I’m not quite sure why, but I have a strong desire to do this experiment from scratch as a “hillbilly biotech” exercise (including building the equipment and obtaining my supplies from grocery or hardware stores rather than specialty scientific supply places).

There are special protein staining compounds I can use at the end to see where my bits of protein ended up after electrophoresis. “Coomassie Brilliant Blue“, for example, but they don’t have that down at the grocery store. (And if you think that’s a funny name for a dye, consider “Light Green SF Yellowish”…)

Then, I ran into a post indirectly about henna over on scienceblogs.com. It seems the natural orange-staining ingredient in henna, called lawsone, may be specifically a protein-staining substance. I’m not certain about this, but a dark-orange protein-staining dye would work for my purposes I think. If so, that solves my need to get a protein stain from an ordinary store.

It’ll be a little while before I can try to put this plan into action, but I think I’ll be able to get to it in the next month or two.

In other news, I think I’ll try to post my “Microbial fuel cells in 90 seconds” audio sometime tomorrow. Then I can work on more. Anybody want to hear me attempting to explain something in 90 seconds? So far I’ve considered MRSA, and perhaps how cow flatulence threatens the world’s climate (which is also a microbiological topic). I’m sure there must be plenty of other possible topics. Any suggestions?

P.S. Who wants audio in Ogg Vorbis format in addition to mp3?

Electricity-breathing bacteria! (Microbial fuel cells)

I made a 90-second “pod”cast of why microbial fuel cells work. I don’t yet know if This Week in Science is or was interested in playing it. [Update: this was featured in the November 6, 2007 broadcast! Hooray!] Either way, once I find a way to make it available without killing my bandwidth I shall. I’ll probably do more of them – if nothing else I obviously need the practice.

It was oddly difficult getting myself to actually talk to the microphone – more so than actually publically speaking to real people. I’m not sure why. It strikes me as something I’ll get over quickly once I’ve done it a few times, and my voice won’t sound quite so bland in the future.

In any case, microbial fuel cells are possibly the topic that got me really interested in a college education in applied biotechnology. I’ve been meaning to do a post on why they work for a while, so here’s one, in somewhat more detail than the 90-second audio version.

First, some quick review: We all remember that atoms are made of positively-charged protons, uncharged neutrons, and negatively-charged electrons, right? Protons and usually neutrons in the middle, and electrons hovering around. When atoms chemically react with each other, they’re really just having a fight over who gets to keep the electrons. When the reaction is over, some kinds of atoms or groups of atoms will have gained at least partial custody of electrons that used to belong to some of the other atoms or groups of atoms. The ability of a kind of atom to take electrons away from other atoms is called “electronegativity”. The second most electronegative element in the universe just happens to be a major part of our atmosphere – Oxygen.

As bacteria break down food molecules to get biological energy, there are electrons left over along the way. The bacterial cells have specific carrier molecules that take these extra electrons away, where they can be later dumped elsewhere into any of a variety of other useful biological reactions that need them. The one we’re concerned with today is called the Electron Transport Chain.

In many bacteria, and in the mitochondria of plants, fungi, and animals, the Electron Transport Chain regenerates a huge amount of a cell’s biochemical energy. The extra electrons get sucked into the beginning of this chemical chain, and as they are pulled along, the force of this pull drives a process which regenerates the cells’ main energy-carrying molecule, called ATP. This process is “respiration”, and it’s also exactly the reason you need to breathe oxygen. Humans need so much energy just to remain alive that we couldn’t survive without the huge amount of extra energy that respiration provides.

What drives this whole chain is some chemical at the other end pulling the electrons out. In aerobic organisms, this is oxygen. Some bacteria can use other chemicals, like nitrates, sulfates, and ferric iron (yes, there are bacteria that can breathe rust…) None of these chemicals provide quite as much energy as oxygen does, but it’s better than nothing and gives bacteria that could be damaged by oxygen something to breathe.

Normally, this last step happens inside the cell, but some bacteria have ways of extending this last step so that the final hand-off of the electrons happens outside itself. Some bacteria even make electrically-conducting biological “nano-wires” that this can happen through. Others make “shuttle” molecules that can pick up electrons, dissolve out of the cell, hand off the electrons somewhere outside, and then dissolve back into the cell to pick up more.

Now, we can make a microbial fuel cell. An electrode is put where the bacteria are growing – without oxygen – and a wire runs from this, out of the area where the bacteria are and to another electrode which is exposed to oxygen. It’s like an electric snorkel for bacteria. From the electrode and through the wire, the oxygen sucks electrons away from the bacteria. An electrical device stuck between the ends of the wire can use this energy exactly the same way that it could use the energy from electrons being sucked from one end of a battery to another.

Interestingly, the common “simple stain” Methylene Blue can also act as an artificial “shuttle” molecule. When reduced (carrying extra electrons) methylene blue is actually colorless, and I would swear I’ve seen protocols somewhere that use this to measure just how active a yeast culture is, and one of the demonstration microbial fuel cell setups actually uses a culture of yeast in methylene blue rather than a microbe that can naturally breath through electrodes.

By the way, if you thought you could tell a human from a realistic humanoid robot bent on world domination by the fact that only humans eat, I’ve got bad news for you. One interesting application of microbial fuel cells is Gastrobots. Literally, robots with digestive systems, where bacteria breaking down the contents of the “stomach” act as a microbial fuel cell to power the robot.

I hope you find this explanation useful and interesting. If you have (or even if you haven’t) please let me know. I can’t necessarily tell if I’m doing anybody any good without feedback!

Libel! Blasphemy! Slander!…

Injustice! Perfidy! HUMBUG!

Periodically, someone puts up a “could you pass a grade-school science class” quiz. The one linked to the image below goes to one that I just broke down and took, purely out of curiousity. Take a look at this outrage!:

JustSayHi - Science Quiz

Oh, sure, it LOOKS good, but what you don’t see is that it only gave me a 96%, implying that I missed one (it was a short quiz)! Sure, the quiz was very much in the modern fashion for “standardized testing” (aka the “No Child Left Awake” project) where the emphasis is on memorizing stuff for a test rather than actual comprehension. So, I thought, maybe I hadn’t correctly memorized which word was correct for one of the word-memorization questions. But, no, according to the “answer sheet”, the one I supposedly got wrong was this one:

(Note: If you’re planning to actually take that quiz, do so now before you read on and I give away one of the answers…)

“How do mammals respire?”

The options were:

  • Aerobically
  • Anaerobically
  • Both aerobically and anaerobically

Come on, I may hardly ever concern myself with perverse eukaryotic systems but…never mind just “mammals”, as far as I know, all eukaryotes (animals, plants, and fungi) only possess aerobic (oxygen-requiring) respiratory systems.

However, the “answer sheet” for the quiz claims that the answer is “Both aerobically and anaerobically”.

So….they’re wrong. I’m pretty sure what what they were intending to ask, given this answer, is “what kind of metabolism do mammals have?”, in which case their answer is correct.

See, “respiration” is only one part of the cellular energy-generating system. Specifically, it’s our friend, the Electron Transport Chain, which (to grossly oversimplify) harnesses the energy of oxygen sucking electrons off the end of the chain various biochemicals to recharge molecules of ATP. That’s not the only way a cell can get ATP, though. What the quiz authors are presumably alluding to is that there are non-oxygen-requiring biochemical pathways that animal cells can take to make energy – such as the one your muscles use when they can’t get enough oxygen, which involves production of lactic acid, which in turn gets blamed for the “burn” sensation you get when you work your muscles hard.

So, the authors of this quiz are bad, bad people, besmirching my reputation and harming my precious self-esteem by giving me less than 100% on that quiz!

On a related subject: breathing causes cancer in Sprague-Dawley™ rats!

No, seriously, it’s true – try raising one group of Sprague-Dawley™ rats with air, and one group with no air, and examing both populations 150 days later. I guarantee you’ll find many more cancerous growths in the “with air” group than in the group that was denied air to breathe…

What brought this outburst on? It was this blog article. “No, It’s for Real: Aspartame Causes Cancer”, the post proclaims. They’re talking about This study(pdf). Go ahead, take a look, but in particular, look at the tables of actual data, not the paper’s abstract. In particular, take a look at Figure 1, especially “D” and “E” (showing survival rates for the different groups of Sprague-Dawley™ rats as the study progressed), and at the number of “tumor-bearing animals” in Table 2.

Notice that at around 120 days on the survival graphs, the groups with the highest percentage of members still alive were the groups receiving the most aspartame in their feed. It’s worth noting that the highest-Aspartame group there was getting roughly the equivalent of a human drinking <em>thousands</em> of cans of diet soda every day. Also note, in fairness, that both graphs seem to show little difference between the groups, so rather than assuming that Aspartame makes Sprague-Dawley™ rats live longer, I would tend to assume that there’s really not much difference.

Notice also that in terms of the percentage of Sprague-Dawley™ rats that developed one or more tumors, there were fewer of them in the group that got the equivalent of 500 mg/kg of aspartame: which scaled up to human terms means about 200-250 cans of diet soda EVERY DAY worth of aspartame.

You may be wondering why I keep mentioning Sprague-Dawley™. It’s because this is a particular commercially-bred strain of rat that’s popular with labs for this kind of thing. One point that isn’t always mentioned is this: Sprague-Dawley™ rats are known to be prone to developing cancer spontaneously. This can be handy if you’re doing studies of “borderline” carcinogens. The hope is that if something has even a tiny ability to cause cancer, you’ll be able to measure the effect in a population of critters known to get cancer at the drop of a metaphorical hat, when in a human population the incidence might be so rare that you can’t distinguish it from random chance. To my admittedly-not-big-on-the-biochemistry-of-perverse-eukaryotes mind, this study really seems to show that there’s little or no effect – and certainly no dose-dependent effect – of aspartame even on cancer-prone lab rats.

I don’t know what it is, but “artificial sweeteners”, and especially aspartame, seem to generate such passionate hatred in some people. It reminds me a great deal of people’s reactions to “genetically modified” crops. People just really want to hate it. The authors of this paper are obviously trying REALLY hard to show somehow that aspartame is a dangerous poison, despite the inconclusive-appearing actual results. Though I suppose one could argue that they showed Aspartame to be at least as much of a deadly poison as Expired JellO®.

And now that I have exposed my readers to several times the Recommended Daily Allowance of Humbug, I bid you all a good night – I have Art History and Philosophy to attend in the morning…