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The Digitization of Analog Media
Published in Gabriele Balbi, Paolo Magaudda, A History of Digital Media, 2018
Gabriele Balbi, Paolo Magaudda
While today what is generally meant by digital music is music in compressed form (commonly called MP3) circulating on the internet or via streaming services, in actual fact the history of music digitization started well before the onset of file sharing, iPods and Spotify. It was, in fact, in 1979 that the first Compact disc (CD) player—a music reproduction system based on laser technology capable of reading optical discs containing audio signals codified into digital format—was made. CDs could hold 650 MBs (i.e. around 74 minutes of music) of data in their initial form, promised consumers higher audio quality than analog supports could deliver and, above all, guaranteed this quality practically forever. While records on analog supports like vinyl deteriorated every time a needle was placed on them, CDs were at least initially free of wear and tear issues (Immick, 1998; Millard, 2005).
Let There Be Light: The Bright World of Photonics
Published in John D. Cressler, Silicon Earth, 2017
For another wonderful example of photonics in action, you need look no further than your portable CD player, or its close cousin, the DVD/Blu-ray player, lurking inside your laptop or perhaps connected to your home theater with surround-sound. Ah yes … the ubiquitous CD (Figure 12.68). Workhorse of the digital data storage industry. Friend to the audiophile. Care to guess how many CDs are out there in the world? From 1982 to 2007, the first 25 years, over 200 billion were produced! Wow … that’s a lot of CDs. Moral: Must have been a good idea! The compact disc (CD for short) is simply an optical disc used to store digital data (see the “A Brief History of CDs” sidebar). In short, a CD represents cheap, portable memory. They make nice Frisbees, too! Yep, the CD player that reads (writes, or both) all those CDs/DVDs/Blu-rays hinges completely on a semiconductor laser diode. No semiconductors, no CDs or DVDs or Blu-rays. No tunes. No movies. Bummer.
Radio Studios
Published in Skip Pizzi, Graham A. Jones, A Broadcast Engineering Tutorial for Non-Engineers, 2014
A CD is reliable because the information is permanently etched, or carved, into the plastic of the disc as very small indentations or pits. It cannot be erased by passing through a magnetic field like the information on a recording tape can, and the only way to damage the information is to physically damage the CD by breaking or severely scratching it. Small scratches are often not a problem because CD players are able to miss a few bits of digital information and still accurately reconstruct the recorded music. They can do this because the digital audio data includes additional bits, added in a specially coded manner, called forward error correction. These enable the CD player to determine what the correct value of a missing piece of data is. In addition, the CD format includes error concealment, which tries to cover up small errors that it cannot completely correct. An error correction or concealment system is only capable of fixing errors up to a certain point, however. If there are too many missing or damaged pieces of data, all attempts at recovery will fail, and the CD will skip or stop playing.
Synthesis and characterization of mono-6-deoxy-6-aminopropylamino-β-cyclodextrin polymer functionalized with graphene oxide
Published in Inorganic and Nano-Metal Chemistry, 2020
Santosh Kumar, Md Morshedur Rahman, Sanghyun Yoon, Shekh Md Mamun Kabir, Joonseok Koh
Currently a great interest is focused in developing multifunctional nanostructures materials for various pharmaceutical and biomedical applications. Cyclodextrins (CDs) are found after enzymatic hydrolysis of starch. It is a cyclic oligosaccharide which consists of glucopyranoses connected to α (1→4) glycosidic bond. There are three main types of CDs (i) α: 6 D-glucose units, (ii) β: 7 D-glucose units, and (iii) γ: 8 D-glucose units. CDs are hydrophilic on their outer surface due to the several hydroxyl groups and hydrophobic on their inner cavity. CDs are soluble in water, which show capability to host lipophilic molecules. β-CD is mostly well known to form host-guest inclusion complexes with a varied diversity of molecules containing a hydrophobic moiety. Due to its special behavior of self-assembly, host-guest interactions properties, low toxicity, biocompatibility, and biodegradability; CD and its modified derivative have been found in several pharmaceutical,[1,2] cosmetic,[3] catalysis,[4] biomedical,[5–7] sensor,[8] regenerative medicine,[9] and environmental[10–14] fields. Recently CDs have been developed as promising materials.[15] Song et al. have developed hydroxypropyl-β-CD functionalized Fe3O4/carbon nanoparticles for pH/near-infrared responsive drug release, magnetic resonance/NIR fluorescence imaging-guided combined chemo/photothermal therapy.[16] The supramolecular hydrogel has found based on inclusion complexation between biodegradable polylactic acid/chitosan diblock copolymer and β-CD application in controlled dual drug delivery.[17] Lee et al. have demonstrated tumor targeting and lipid rafting to destroy hyaluronic acid-CD-based nanostructured for breast cancer treatment.[18] Santos et al have reported xylanase-β-CD complex in polyvinyl alcohol through electrospinning methods to improves enzyme activity at a varied pH and temperature range.[19] Wang et al. have demonstrated poly(β-CD)-conjugated magnetic graphene oxide (GO) by surface originated reversible addition fragmentation chain transfer polymerization to improve synergetic adsorption of heavy metal ions and organic pollutants.[20]