Category Archives: Technology

Why are our veins blue?

I was asked this, and it’s pretty good question. As I have an MD/PhD myself I figure that I’m fairly reasonably equipped to answer this. Although, I do feel that I need to mention that while having gone to medical school may provide essential knowledge to debunking the popular misconceptions, it won’t actually provide the answer we’re looking for. I’ll explain a bit later where we actually find this elusive little answer. First, the misconceptions.

So why are our veins blue? The first and most common answer that people give is “well, it’s deoxygenation. When blood isn’t exposed to oxygen it’s blue.” But despite its popularity, this one is actually quite wrong. The only thing that I know of with blue blood is something like a horseshoe crab whose blood is bound to copper – it clots significantly faster, so it’s often used for testing purposes.

Deoxygenated venous blood is actually a dark maroon, while oxygenated arterial blood is bright red. You can debunk this little myth yourself if you look at a thin membrane that has blood vessels. Some examples include: the eyes, eyelids, underside of the tongue, and the scrotum (if you’re a boy or happen to have one available). You’ll clearly notice that these are indeed red. So that one’s out.

Okay so if our blood isn’t blue… then maybe our veins are! This is the next most common misconception. Anyone that has ever dissected anything, or even viewed pictures thereof can tell you that veins are most definitely not blue, nor green, nor even purple. Though if you’ve seen a medical diagram it’s a reasonable assumption considering they’re almost always colored blue. But they’re not. If you google image “open surgery” you can see for yourself, though I warn you… these pictures are not for the squeamish. Veins are red. Though, I do know that veins in the brain can appear blue.

Okay so then if our blood isn’t blue and our veins aren’t blue, then why the heck do our veins look blue?!

Believe it or not, this actually has less to do with your internal biology and more to do with our perception of light. Though, it does also have to do with the light absorbing properties of our blood and our skin. Specifically, how light is absorbed by our blood and how it is reflected by our skin. And this is where we get into our answer. For this, I go to the expertise of Dr. Alwin Kienle and associates who specialize in the study of optics and photonics.

What it essentially comes down to is that skin generally reflects light rather than absorbs it while blood absorbs all wavelengths of light, albeit less of the red spectrum.

And well, the jist of it is that the blue wavelength isn’t as good at penetrating skin as the red spectrum. If you have a very thin membrane like mentioned above, then blue light will be absorbed and the vessel will appear red.

But if we go deeper then not nearly as much light is absorbed and much less of the blue/green side of the spectrum than the red. And thus, blue veins are born. It essentially just comes down to optical properties. If you’re more interested in the technical details of, you can grab a pdf on Dr. Kienle and associates research here. I’ll quote below for you the summary of their findings:

To summarize, the reason for the bluish color of a vein is not greater remission of blue light compared with red light; rather, it is the greater decrease in the red remission above the vessel compared to its surroundings than the corresponding effect in the blue. At first it seems astonishing that red light is more attenuated above the vessel than blue light, since, as Table 1 shows, the absorption of blood is much less in the red than in the blue. This is the result of the spectral characteristics of light propagation in tissue. Blue light does not penetrate as deeply into tissue as red light. Therefore, if the vessel is sufficiently deep, the reflectance in the blue will be affected to a lesser extent. Deoxygenated venous blood has a greater absorption coefficient than oxygenated arterial blood in the red spectral region, and this difference of two, rather small, values is amplified because of the long path length of red light in scattering tissue. As a result, veins are more likely to look blue than arteries at the same diameter and depth. Often arteries are not seen at all because they are generally smaller than veins and have thicker vessel walls. It has been shown that a small vessel will look red when close to the surface. However, if a superficial vessel is large it can still look bluish, particularly in the case of the vein. On the other hand, if the depth of a vessel is large, even red remitted light will not be influenced by the vessel, and it will not be seen. We note that, for the calculations here, we assumed an oxygen saturation of 50% for venous blood. This is somewhat arbitrary, but other possible realistic values do not change the conclusions.

As shown in Fig. 8, even above the vein more red than blue light is remitted. Thus, for a complete explanation of the perceived color of the vessel one needs the retinex theory. With the retinex theory the color can be determined by the relative intensities at the three wave bands from a particular scene compared to the surrounding area. The intensities of these wave bands are weighted by spectral functions that represent the human spectral vision. In this study we used single wavelengths that are representative of these spectral functions, and, therefore, a retinex color three space based on selected wavelengths should be applied. However, we chose typical wavelengths for the long-wave, middle-wave, and short-wave regions and made qualitative estimates of the colors. Therefore, we believe that we are justified in applying the usual retinex three-color space. In one example, we calculated the remission at several wavelengths and used the spectral sensitivity of the cones to show that the approach of using only three single wavelengths is justified.

It is interesting to speculate whether retinex theory is necessary for other color perception issues in medicine 1e.g., the color of port-wine stains, vitiligo lesions, blue nevi, age spots, eyes, hair2, or whether the perceived color can be simply related to the absorption spectra of hromophores, possibly modified by the presence of light scattering and measured with a reflectometer. If the problem of vessel color is any guide, it seems that retinex theory may provide an essential step in the description of color perception.

What I don’t quite understand however is how hypoxia is causing the cyanosis of skin (acute arterial thrombosis for instance).

My only guess was perhaps the onset of necrosis such as seen in ischemia, or perhaps the change to venous blood is enough to alter the optical properties of the entire effected region to a blue hue, as it has a greater optical effect than arterial blood. Or perhaps some combination of the two.

Having had a chance to talk to Dr. Kienle, he acknowledged as much albeit mentioning that for a thorough investigation one would have to look more closely to the haemodynamics (and geometrical changes caused by) of cyanosis. Although, he did laugh in saying that he was Physicist, not a Dermatologist. 😛

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Google Censors the Internet

Jan 29 2013 Update#3: As of yesterday or so, when Google rolled out their new interface they also included the SafeSearch changes for all other English domains that I know of, such as the UK’s, Canada’s, Australia’s, New Zealand’s, South Africa’s, etc. Google Image has essentially been killed. Looks like I’m switching over to Bing.

Are you in the US? Have you tried searching Google Images for anything since December 12th, like oh say… boobs?

null

Go ahead, go google image boobs. I’ll wait. Of course, if you were lucky you may have SafeSearch disabled and you only get the UK equivalent of “Moderate SafeSearch” which has been permanently forced upon us. There is no longer an “off” switch to their censorship.

If you search for boobs with it “on” you will get no results at all. If you search with it “off” then you will get boobs, minus explicit results.

At this point you’re probably like “Okay, I’ve had enough of this bullshit!” Or at least, if you’re anything like me then you are. Oh it’s not limited to boobs, by the way. It’s the same for everything.

‘We are not censoring any adult content, and want to show users exactly what they are looking for — but we aim not to show sexually-explicit results unless a user is specifically searching for them,’ Google said in a statement.

‘We use algorithms to select the most relevant results for a given query. If you’re looking for adult content, you can find it without having to change the default setting — you just may need to be more explicit in your query if your search terms are potentially ambiguous. The image search settings now work the same way as in Web search,’ it continued.

“Specifically searching for them,” eh? Okay, Google. Let’s google “blowjob” and see what we find… So uh, hey… if I specifically search for blowjob, that… does mean I’m looking for pictures of blowjobs…. right? Right?! …No? 😦

If you don’t like it, sadly the only choice is to either switch to a different search engine (Hey this is a good time to throw this out there: If you have any Google stock… abort, abort! Abandon ship!), or use a different country’s version of Google. If you’re using Internet Explorer or Firefox you can add Google’s Search Engine for other countries to your browser’s search options. I’m using Google CA-en SSL myself – Canada’s version Google, which hasn’t been censored… yet.

If they do roll this out to other countries, I’ve gotta say… I’m leaving Google entirely and going to Bing, Yahoo, or somewhere else. I won’t stand for this shit. When I search for something I expect to find it, not for my results to be censored. This is America… and you know what? China, where porn is illegal, has a less censored Google now. Laugh at that for awhile, before you start crying when you realize how terrible it is.

So tell me, what happened to “Don’t censor the web,” assholes?

Jan 13, 2013 Update#1: I don’t use Chrome, but if anyone out there uses Google Chrome and is looking to find out how to bypass it as well, here’s how you do it…

For Chrome just click the = thing up at the top right then go to Settings then under Search go to Manage Search Engines.

Then down at the bottom use this info:

Google CA (SSL)

google.ca

https://www.google.ca/search?q=%s{google:acceptedSuggestion}{google:originalQueryForSuggestion}{google:assistedQueryStats}{google:searchFieldtrialParameter}sourceid=chrome&ie={inputEncoding}

Then just hit enter. Then hover over it and hit “Default” and it’ll be your default.

Jan 13, 2013 Update#2 I was informed that the recent changes are also adversely effective reverse google image searching. I’ve already fixed mine, so here’s how you do that…

If you have Firefox, grab this Add-on: https://addons.mozilla.org/en-US/firefox/addon/image-search-options/

By default I don’t think it has Google Image search, so here’s the info for that…

Sub-Menu ->
http://www.google.com/favicon.ico

Left Click Settings
http://www.google.ca/searchbyimage

Variables (one per line)
image_url=::$URL::

GET Var Markers:
?
&

(unchecked) Use POST instead of GET

Right Click Settings
http://www.google.ca/searchbyimage/upload

Variables (one per line)
encoded_image=::$IMGDATA::

GET Var Markers:
?
&

(checked) Use POST instead of GET

Doing it like this will give you a right click contextual menu where you can use google image search via Canada’s version of google which is uncensored. I personally also use IQDB, which is useful for anime style art.

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Rewatched Watchmen

So, I was watching Watchmen… rewatching, I should say. I saw it way back when it came out. But I was watching it again, and I guess I didn’t really notice something the first time that really bothered me this time around…

Ozymandias, the smartest man in the world, used “Ramesses II” as his password, for which has a book on a shelf directly next to the computer.

Smartest man? Obviously an idiot at computer security.

Ah, just felt like saying that. Oh, but on a closing note… jeez, they could have given Dr. Manhattan a bigger cock, ey?

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Firefox, gone retarded again.

Yep, yet again Firefox has gone even more retarded.

In the new Firefox 11, they’ve decided that the way images have displayed since the dawn of time is wrong and that they should instead be on a dark gray background and centered.

What the fuck is with these crackheads?

Anyways, if you want to fix it, there’s an add-on for that here: https://addons.mozilla.org/en-US/firefox/addon/old-default-image-style/

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Internet 1. RIAA/MPAA 0.

Okay okay, so there was the whole MegaUpload thing… a-aand… Napster… ahem… But this is an assured victory for the Internet!

Tribler Makes BitTorrent Impossible to Shut Down

While the file-sharing ecosystem is currently filled with uncertainty and doubt, researchers at Delft University of Technology continue to work on their decentralized BitTorrent network. Their Tribler client doesn’t require torrent sites to find or download content, as it is based on pure peer-to-peer communication. “The only way to take it down is to take the Internet down,” the lead researcher says.

The Tribler BitTorrent client is no newcomer to the BitTorrent scene. It has been in development for more than 5 years and has delivered many innovative features, which have mostly been ignored by the masses.

Today, however, Tribler is more relevant than ever before.

Developed by a team of researchers at Delft University of Technology, the main goal is to come up with a robust implementation of BitTorrent that doesn’t rely on central servers. Instead, Tribler is designed to keep BitTorrent alive, even when all torrent search engines, indexes and trackers are pulled offline.

“Our key scientific quest is facilitating unbounded information sharing,” Tribler leader Dr. Pouwelse tells TorrentFreak.

“We simply don’t like unreliable servers. With Tribler we have achieved zero-seconds downtime over the past six years, all because we don’t rely on shaky foundations such as DNS, web servers or search portals.”

So how does it work?

Like many other BitTorrent clients, Tribler has a search box at the top of the application. However, the search results that appear when users type in a keyword don’t come from a central index. Instead, they come directly from other peers.

Tribler’s decentralized search results

Downloading a torrent is also totally decentralized. When a user clicks on one of the search results, the meta-data is pulled in from another peer and the download starts immediately. Tribler is based on the standard BitTorrent protocol and uses regular BitTorrent trackers to communicate with other peers. But, it can also continue downloading when a central tracker goes down.

The same is true for spam control. Where most torrent sites have a team of moderators to delete viruses, malware and fake files, Tribler uses crowd-sourcing to keep the network clean. Content is verified by user generated “channels”, which can be “liked” by others. When more people like a channel, the associated torrents get a boost in the search results.

The latest addition to Tribler is a Wikipedia-style editing system dubbed “Open2Edit,” where users have the option to edit names and descriptions of torrents in public channels. All without a central server, totally decentralized.

open2Edit

According to Dr. Pouwelse, Tribler is fully capable of resisting any pressure from outside, and it will still work when all torrent sites and trackers are gone. It simply can’t be shutdown, blocked or censored, whatever laws politicians may come up with.

“The only way to take it down is to take The Internet down.” Pouwelse told us.

One thing that could theoretically cause issues, is the capability for starting users to find new peers. To be on the safe side the Tribler team is still looking for people who want to act as so called bootstraptribler peers. These users will act as superpeers, who distribute lists of active downloaders.

“Together with software bugs and a code cleanup, that is now our last known weakness,” says Pouwelse.

While the Tribler client only has a few thousand users at the moment, for avid file-sharers it must be a relief to know that it’s out there. No matter what crazy laws may pass in the future, people will always be able to share.

Those who want to give it a spin are welcome download Tribler here. It’s completely Open Source and with a version for Windows, Mac and Linux.

Source

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Firefox 10 & Woes

I just upgraded from Firefox 9.0.1, because apparently Firefox 10 came out Feburary 1st (where was I when this happened..?). Anyways, it never told me there was an update, but I found out that it had coinsidentally while googling a problem I’ve been having since Firefox 7.

But before I tell you about the problem I’ve been having, I should probably talk about Firefox 10.

It’s Firefox 9 with a new number. Excited? I wasn’t either. Yeah okay there was some small crap hardly anyone will care about, like a forward button that will only appear if you’ve gone back, and only appears using the regular size icons. I don’t even know about any of that crap since mine doesn’t use it. I guess I’m using a custom theme or something. And I guess Firefox Sync is easier now, and Firefox 10 has support for a year now, multi-touch gesture support for the mobile version, and anti-aliasing in webGL. I’m pretty sure I keep webGL disabled because of that horrendous security concern that could melt your computer if someone exploited it – which, by the way, was never fixed.

Oh. There were two things I liked. “Firefox 10 assumes that extensions are compatible, even if they haven’t been specifically updated for it. The browser will only reject extensions that have been specficially marked as incompatible.” and “Add-ons can now hotfix update themselves to address minor issues.” These two things seem useful. Extension incompatibility with all of these rapid releases was a major pain in the ass. I actually had to manually edit the versions on some of them to make them keep working.

Anywho… onto my problem.

Bug 702748. Such a cute little name, isn’t it? No? Not really? Well lemme tell ya, it’s a major pain in my ass. Here’s a little explanation of the problem. But lemme break it down for ya…

“Save Image As” keeps changing directories on a per site/server basis, rather than staying consistent until I change it.

Let’s say I’m just browsing some image boards, blogs or forums with images, and I’m saving images – something I’ve done since the dawn of time, and I’m sure a lot of others have done too. Well, it seems that starting in Firefox 7, a new “feature” was introduced that changes the download directory per server. So when you have one link like “i32.site.com” then another on “m22.site.com” that these pictures are being fetched from, guess what? The next time you get a picture from either of those servers, it’s going to remember the last directory you saved to for that server. Stay with me here. Let’s say we’re browsing something about kittens, we save a bunch of pictures. Then later, maybe we’re looking at pictures of rabbits. We have our folders very organized like “Pictures/Animals/Cats/Kittens”, “Pictures/Animals/Rabbits”, and what have you. So we start saving the rabbit pictures and then suddenly we realize that some of them (not even all of them, just some) are going to the Kittens folder. No, what’s worse is that some are going to maybe Giraffes, or Whales, Sharks, Lions, or who the fuck knows what! This is really fucking stupid, man. Whoever made this “feature” deserves a nice good ass chewing, I can tell you that much.

No… Since we’ve had it now for what, 5 months now? And we’re going to have it for another… 1? At least? This guy deserves to get his ass kicked. No permanent damage or anything, just a nice good old fashioned playground ass kicking. Fucking idiots, I swear to the flying spaghetti monster

Anyways…

  • Intentional change: Bug 536503 – Last downloaded-to directory should be remembered on a site-by-site basis
    • and note also Bug 693153 – “arbitrary” selection of download directory in multiple tabs (tabs with different server name)

Firefox 11 will fix this issue by adding a pref browser.download.lastdir.savePerSite

  • Bug 702748 – Use a pref for disabling per-site remembering of download directory

Unfortunately, if you check their release schedule… it isn’t planned to be released until March-something. What’s 6 weeks from Feb 1? March 7th? So March 7th I guess.

Anyways, when Firefox 11 rolls around you’re going to have to go to about:config then create a new bool entry: browser.download.lastDir.savePerSite, and set that to false. Till then, I hope some asshole makes an extension that hotfixes this, cause it’s really fucking shit up. I don’t even know where my pictures are anymore…

Someone suggested just downgrading to Firefox 6.0.2 until we get the fix, and I dunno if I’m gonna do that. I’m considering using another browser for a month possibly though. Eh, if I can find add-ons for it.

If you wanna downgrade, here it is from the official Mozilla FTP: ftp://ftp.mozilla.org/pub/mozilla.org/firefox/releases/6.0.2/

Here’s some English specific links:
Win-32 Eng-US
Mac En-US
Linux i686 En-US
Linux x86-64 En-US

But from what I hear, there are security problems to worry about. So it’s better to go for the 3.6.x branch which is kept updated instead, since it’s still supported. The 6.x.x branch isn’t.

Here’s 3.6.9, I don’t know if it fixes this or not or if it’s the latest on the 3.6.x branch, but here’s a link: ftp://ftp.mozilla.org/pub/mozilla.org/firefox/releases/3.6.9/; Now, someone did report that 3.6.3 didn’t have the issue and that was 3 weeks ago, so if 3.6.9 doesn’t work, then here’s a link to 3.6.3: ftp://ftp.mozilla.org/pub/mozilla.org/firefox/releases/3.6.3/

Update#1
It seems there’s a temporary fix for this. Here’s the procedure:

  1. Select Tools | Option and choose Privacy tab
  2. Click on “clear your recent history”
  3. Time range to clear : choose Everything (last option in the listbox)
  4. Click on Details if necessary
  5. **Uncheck** all options **except** Site Preferences (thus only Site Preferences is checked at the end).
  6. And apply with Clear Now !

The folder proposed by Save Image As should now be the session’s last downloaded-to folder (no longer the site’s).

Now where does the magic come from ? Starting indeed with FF 7, someone has decided that “Last downloaded-to directory should be remembered on a site-by-site basis” (as noted here by John99. It’s in bug#536503).

And… it was added. Ugh…

And documented in Using_content_preferences (look for the table entitled “Build-in site-specific preferences”, the preference browser.download.lastDir is stamped “New in Firefox 7”). As a techie can see there, the information is stored in a file named content-prefs.sqlite (a database file stored in your profile — a brutal workaround would be to delete or rename this file, but I discourage such manipulation while FF is running)(BTW if you delete it when FF is not running, the file is recreated when FF is launched).

The workaround I propose simply resets the content preferences, meaning that you will get rid of current site-download folder mappings (good news !) but also of upload site-folder mappings and site-zoom preferences. Which may be a problem depending on your needs…

If someone could find a javascript snippet that could remove only site-download folder mappings from the content preference database, that would really fix all these problems.

What I’ve been doing in the meantime is just copying the full path to the folder I want to be saving to and pasting it up in the top part before I save. It’s inconvenient at best, but it works and it’s better than manually browsing to the right folder again.

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