5 ms·

The title of the article's pretty misleading. "sugar" means to most people either sucrose or glucose. Fructose, lactose, etc. could also qualify. No, this us

The title of the article's pretty misleading. "sugar" means to most people either sucrose or glucose. Fructose, lactose, etc. could also qualify. No, this uses a very obscure and expensive chemical called thymidine (most cost-effectively harvested from herring sperm, and primary precursor for anti-AIDS drug AZT). It may be "a sugar", but this article's playing fast and loose, akin to calling any pharmaceutical that ends with citrate or chloride "salt".

mrob 9y ago
It also calls polycarbonate "scratch-resistant" when anybody who's worked with it knows it isn't. "Scratch-resistant coatings for phones, CDs and DVDs", really? CDs and DVDs are made of polycarbonate and they scratch easily.
- Retric 9y ago
  Resistant is always a though word. The important, but hidden measurements are cost to produce, etc but relative to most other cheap, though, and clear materials... CD's are actually very scratch resistant even though they often get lot's of small scratches.
  - jdmichal 9y ago
    > CD's are actually very scratch resistant even though they often get lot's of small scratches. This is a bit of an oxymoronic sentence. How can something be both scratch resistant, while accumulating a large number of scratches? The scratches a CD accumulates won't typically affect the ability to read from them, but that's due to the focal length of the reader, not the material. https://en.wikipedia.org/wiki/Compact_disc#Integrity https://en.wikipedia.org/wiki/Compact_disc#Integrity
    - Retric 9y ago
      Resistance is not immunity. Bullet proof glass for example gets damaged by bullets. The trade off is always in how much damage and how quickly. CD's will easily survive with even moderate levels of care. What people forget is the covering is really designed to protect the data layer not the surface. And in that context the clear plastic is actually better protection than the backside.
      - jdmichal 9y ago
        > What people forget is the covering is really designed to protect the data layer not the surface. Right. But that this started explicitly about calling the polycarbonate -- that clear layer -- as scratch resistant. And this is just flat out wrong: "Polycarbonate is a durable material. Although it has high impact-resistance, it has low scratch-resistance." https://en.wikipedia.org/wiki/Polycarbonate#Properties_and_processing https://en.wikipedia.org/wiki/Polycarbonate#Properties_and_p... I agree that it serves its purpose of protecting the data layer of the CD. But again, CDs and their readers were designed in a way that typical surface scratches and other imperfections would not inhibit reading. And so polycarbonate was an acceptable choice. The same approach applies to eye glass lenses; a scratch on a lens is typically not in focus and therefore has little to no effect on vision. So, TL;DR: Polycarbonate the material is not scratch resistant. CDs are scratch resistant, but that is due to their optical design and in spite of the polycarbonate.
        Retric 9y ago
        I don't directly disagree with what your saying, my point is there is more than one type of scratch resistance. Because not all scratches are created equal. If you look at say :https://omnexus.specialchem.com/polymer-properties/properties/hardness-shore-d https://omnexus.specialchem.com/polymer-properties/propertie... You find it's good relative to other plastics at preventing penetration which is also why it's good at preventing deep scratches. So, yes if you want a crystal clear optical element then it's not scratch resistant and look for something high on the Mos scale. But, if you want a coating that protects from deeper scratches it's quite good. In that context it's good material to protect CD's from scratches that matter. Which again is why I find the word resistance tricky because it's always resistant in some context.
        jdmichal 9y ago
        Ah, I understand your point now. Thanks for clarifying for me.
- Florin_Andrei 9y ago
  It's a common confusion. Poly-c is Lexan. It's amazingly impact-resistant, at least for a plastic. A window pane made of Lexan cannot be easily broken with a crowbar or a rock. But then people start attributing it characteristics that it doesn't really have, such as being scratch-resistant, which it clearly isn't.
maxerickson 9y ago
It is synthesized in bulk. At the time someone figured out AZT was a good AIDS drug it was sourced from herring sperm. But they got a chemical company to start producing it by the ton...
ams6110 9y ago
Even more misleading by including the photo of candy. What is involved in the production of thymidine? Even if the process did use conventional "sugar" the usual production source (corn syrup, sugar cane or beets) is not exactly environmentally friendly at scale.
fabian2k 9y ago
Thymidine is one of the nucleosides in DNA, I'd hardly call that obscure. Not as easy and cheap to obtain as e.g. glucose or fructose, sure. But the other two papers describe syntheses using mannose and ribose, so they did not use thymidine exclusively.
dang 9y ago
Ok, we'll spot you an indefinite article above.
GuB-42 9y ago
Yep, from the title it almost looks like they are making a soda bottle from its content.
mirimir 9y ago
The graphic indicates that both the sugars and CO2 come from domestic waste. First extract with water, and then burn the residue. But it seems unlikely that domestic waste is such a great source of thymidine. And even if it were, the thymidine would mainly be part of DNA. So who knows?
chicob 9y ago
There's a good side to that, since thymidine isn't a dietary sugar. Should we use dietary sugars for any other end than human consumption, we will risk coupling the surge in that commodity 's price to food prices. Like biofuels - mass production of corn for biofuel at the current level of demand for fuels would probably mean, in the worst scenario, that popcorn would become prohibitively expensive.
- maxerickson 9y ago
  There's 20+ pounds of corn in a gallon of ethanol. That gives popcorn quite a bit of runway (it isn't the same corn, but I guess the dollars/acre work out okay for popcorn).
  - chicob 9y ago
    Maybe popcorn was a bad example, but biofuels do drive food prices. http://www.reuters.com/article/idUSN28615016 http://www.reuters.com/article/idUSN28615016

mrob 9y ago

It also calls polycarbonate "scratch-resistant" when anybody who's worked with it knows it isn't. "Scratch-resistant coatings for phones, CDs and DVDs", really? CDs and DVDs are made of polycarbonate and they scratch easily.

Retric 9y ago
Resistant is always a though word. The important, but hidden measurements are cost to produce, etc but relative to most other cheap, though, and clear materials... CD's are actually very scratch resistant even though they often get lot's of small scratches.
- jdmichal 9y ago
  > CD's are actually very scratch resistant even though they often get lot's of small scratches. This is a bit of an oxymoronic sentence. How can something be both scratch resistant, while accumulating a large number of scratches? The scratches a CD accumulates won't typically affect the ability to read from them, but that's due to the focal length of the reader, not the material. https://en.wikipedia.org/wiki/Compact_disc#Integrity https://en.wikipedia.org/wiki/Compact_disc#Integrity
  - Retric 9y ago
    Resistance is not immunity. Bullet proof glass for example gets damaged by bullets. The trade off is always in how much damage and how quickly. CD's will easily survive with even moderate levels of care. What people forget is the covering is really designed to protect the data layer not the surface. And in that context the clear plastic is actually better protection than the backside.
    - jdmichal 9y ago
      > What people forget is the covering is really designed to protect the data layer not the surface. Right. But that this started explicitly about calling the polycarbonate -- that clear layer -- as scratch resistant. And this is just flat out wrong: "Polycarbonate is a durable material. Although it has high impact-resistance, it has low scratch-resistance." https://en.wikipedia.org/wiki/Polycarbonate#Properties_and_processing https://en.wikipedia.org/wiki/Polycarbonate#Properties_and_p... I agree that it serves its purpose of protecting the data layer of the CD. But again, CDs and their readers were designed in a way that typical surface scratches and other imperfections would not inhibit reading. And so polycarbonate was an acceptable choice. The same approach applies to eye glass lenses; a scratch on a lens is typically not in focus and therefore has little to no effect on vision. So, TL;DR: Polycarbonate the material is not scratch resistant. CDs are scratch resistant, but that is due to their optical design and in spite of the polycarbonate.
      - Retric 9y ago
        I don't directly disagree with what your saying, my point is there is more than one type of scratch resistance. Because not all scratches are created equal. If you look at say :https://omnexus.specialchem.com/polymer-properties/properties/hardness-shore-d https://omnexus.specialchem.com/polymer-properties/propertie... You find it's good relative to other plastics at preventing penetration which is also why it's good at preventing deep scratches. So, yes if you want a crystal clear optical element then it's not scratch resistant and look for something high on the Mos scale. But, if you want a coating that protects from deeper scratches it's quite good. In that context it's good material to protect CD's from scratches that matter. Which again is why I find the word resistance tricky because it's always resistant in some context.
        jdmichal 9y ago
        Ah, I understand your point now. Thanks for clarifying for me.
Florin_Andrei 9y ago
It's a common confusion. Poly-c is Lexan. It's amazingly impact-resistant, at least for a plastic. A window pane made of Lexan cannot be easily broken with a crowbar or a rock. But then people start attributing it characteristics that it doesn't really have, such as being scratch-resistant, which it clearly isn't.

maxerickson 9y ago

It is synthesized in bulk. At the time someone figured out AZT was a good AIDS drug it was sourced from herring sperm. But they got a chemical company to start producing it by the ton...

ams6110 9y ago

Even more misleading by including the photo of candy. What is involved in the production of thymidine? Even if the process did use conventional "sugar" the usual production source (corn syrup, sugar cane or beets) is not exactly environmentally friendly at scale.

fabian2k 9y ago

Thymidine is one of the nucleosides in DNA, I'd hardly call that obscure. Not as easy and cheap to obtain as e.g. glucose or fructose, sure. But the other two papers describe syntheses using mannose and ribose, so they did not use thymidine exclusively.

dang 9y ago

Ok, we'll spot you an indefinite article above.

GuB-42 9y ago

Yep, from the title it almost looks like they are making a soda bottle from its content.

mirimir 9y ago

The graphic indicates that both the sugars and CO2 come from domestic waste. First extract with water, and then burn the residue. But it seems unlikely that domestic waste is such a great source of thymidine. And even if it were, the thymidine would mainly be part of DNA. So who knows?

chicob 9y ago

There's a good side to that, since thymidine isn't a dietary sugar. Should we use dietary sugars for any other end than human consumption, we will risk coupling the surge in that commodity 's price to food prices. Like biofuels - mass production of corn for biofuel at the current level of demand for fuels would probably mean, in the worst scenario, that popcorn would become prohibitively expensive.

maxerickson 9y ago
There's 20+ pounds of corn in a gallon of ethanol. That gives popcorn quite a bit of runway (it isn't the same corn, but I guess the dollars/acre work out okay for popcorn).
- chicob 9y ago
  Maybe popcorn was a bad example, but biofuels do drive food prices. http://www.reuters.com/article/idUSN28615016 http://www.reuters.com/article/idUSN28615016