question: Why does Pykrete have the physical properties that it does?
comment: Composite materials are strong. Combining a brittle substance with a flexible one yields a strong material that can be much stronger than either material alone. Wood fibers add flexibility allowing the material to have some ability to bend and return to it's shape, like the rebar in concrete. The combination of wood fiber and ice has a very low rate of thermal conductivity, so it doesn't melt as easily as just ice.
passages: Copper, zinc, manganese, and nickel are confirmed PrP ligands that bind to its octarepeat region. Ligand binding causes a conformational change with unknown effect. Heavy metal binding at PrP has been linked to resistance to oxidative stress arising from heavy metal toxicity.
  
  Section::::Structure.:PrP (normal cellular) isoform.
   Thiarubrine B is the most prevalent among several related light-sensitive pigments that have been isolated from the Giant Ragweed ("Ambrosia trifida"), a plant used in herbal medicine. The thiarubrines have antibiotic, antiviral, and nematocidal activity, and activity against HIV-1 that is mediated by exposure to light.
  
  Falcarindiol is the main compound responsible for bitterness in carrots, and is the most active among several polyynes with potential anticancer activity found in Devil's club ("Oplopanax horridus").
   Section::::Function.:Material properties.
  
  The molecular weight of this rare amino acid that is found in elastin is 526.611 g/mol. The desmosine pyridinium ring has three allysyl side chains and one unaltered lysyl side chain. It has been tested to show that the pyridinium core of Desmosine remains intact even at very high collision energies.
  
  Section::::Function.:Material properties.:Current usage in medicine.
   In 2009, the Discovery Channel program "MythBusters" episode 115 tested the properties of pykrete and the myths behind it. First, the program's hosts, Adam Savage and Jamie Hyneman compared the mechanical properties of common ice, pykrete, and a new material specially created for the show, dubbed "super pykrete", using newspapers instead of woodpulp. Both versions of pykrete indeed proved to be much stronger than the chunk of ice, withstanding hundreds of pounds of weight. The super pykrete was much stronger than the original version.
   Pyr1 is classified as a small molecule that belongs to the group of pyridocarbazoles. Its small size gives it special properties: as a light molecule it is a valuable tool for studying dynamic biological processes. Therefore, it is a key discovery in medical and biological investigation. It is a high degree protein temporal controller, as it is able to interact in a few minutes or even seconds with molecules such as LIMK1. Its reversibility enables it to quickly activate and inhibit itself, making the molecule a specific inhibitor both "in vitro" and "in cellulo".
   The addition of polystyrene to PPE increases the glass transition temperature above 100 °C, owing to the high T of PPE, so NORYL resin is stable in boiling water. The precise value of the transition depends on the exact composition of the grade used. There is a smooth linear relation between weight content of polystyrene and the T of the blend. Due to its good electrical resistance, it is widely used in switch boxes. However, product design is important in maximising the strength of the product, especially in eliminating sharp corners and other stress concentrations. Injection molding must ensure that moldings are stress-free.
   Pyrolytic carbon is also in medical use to coat anatomically correct orthopaedic implants, a.k.a. replacement joints. In this application it is currently marketed under the name "PyroCarbon". These implants have been approved by the U.S. Food and Drug Administration for use in the hand for metacarpophalangeal (knuckle) replacements. They are produced by two companies: Tornier (BioProfile) and Ascension Orthopedics. (On September 23, 2011, Integra LifeSciences acquired Ascension Orthopedics.) The FDA has also approved PyroCarbon interphalangeal joint replacements under the Humanitarian Device Exemption.
   While it was one of the cheapest high-temperature resistant plastics, processing was difficult, while the impact and heat resistance gradually decreased with time. Mixing it with polystyrene in any ratio could compensate for the disadvantages. In the 1960s, modified PPE came into the market under the trademark Noryl.
  
  Section::::Properties.
  
  PPE is an amorphous high-performance plastic. The glass transition temperature is 215 °C, but it can be varied by mixing with polystyrene. Through modification and the incorporation of fillers such as glass fibers, the properties can be extensively modified.
  
  Section::::Applications.
   Section::::Pyroelectric materials.
  
  Although artificial pyroelectric materials have been engineered, the effect was first discovered in minerals such as tourmaline. The pyroelectric effect is also present in bone and tendon.
  
  The most important example is gallium nitride, a semiconductor. The large electric fields in this material are detrimental in light emitting diodes (LEDs), but useful for the production of power transistors. 
   Section::::Pharmacology.
  
  Many commonly prescribed medications target P2Y receptors, and active research is being conducted into developing new drugs targeting these receptors. The most commonly prescribed drug targeting P2Y receptors is clopidogrel, an antiplatelet medication which acts on the P2Y receptor in a manner shared with other thienopyridines. Other pharmaceutical applications include Denufosol, which targets P2Y and is being investigated for the treatment of cystic fibrosis, and diquafosol, a P2Y agonist used in the treatment of dry eye disease.
   BULLET::::- PTFE tubing is used for Bowden tubing in 3D printers because its low friction allows the extruder stepper motor to push filament through it more easily.
  
  BULLET::::- PTFE is commonly used as an aftermarket add-on for gaming mice to reduce friction of the mouse against the mouse pad, resulting in a smoother glide.
  
  Section::::Safety.
  
  Pyrolysis of PTFE is detectable at , and it evolves several fluorocarbon gases and a sublimate. An animal study conducted in 1955 concluded that it is unlikely that these products would be generated in amounts significant to health at temperatures below .
   As in metal alloys the properties of a TPO product depend greatly upon controlling the size and distribution of the microstructure. PP and PE form a vaguely crystalline structure known as a spherulite. Unlike metals, a spherulite cannot be described in terms of a lattice or unit cell, but rather as a set of polymer chains that pack down closely next to one another and form a dense core. The PP and PE components of a blend constitute the "crystalline phase", and the rubber gives the "amorphous phase".
   In the field of purinergic signaling, the P2Y protein is found mainly but not exclusively on the surface of blood platelets, and is an important regulator in blood clotting.
  
  Section::::Clinical significance.
  
  The drugs clopidogrel (Plavix), prasugrel (Efient, Effient), ticagrelor (Brilinta), and cangrelor (Kengreal) bind to this receptor and are marketed as antiplatelet agents.
   The cresol is a mixture of three isomers ("ortho", "meta", and "para"). The fact that tricresyl phosphate is derived from a mixture and itself is a mixture ensures that it remains liquid over a wide span of temperatures.
  
  Section::::Use.
   PrP messenger RNA contains a pseudoknot structure (prion pseudoknot), which is thought to be involved in regulation of PrP protein translation.
  
  Section::::Structure.:Ligand-binding.
  
  The mechanism for conformational conversion to the scrapie isoform is speculated to be an elusive ligand-protein, but, so far, no such compound has been identified. However, a large body of research has developed on candidates and their interaction with the PrP.
   Pyr1
  
  Pyr1 (LIMINIB) is an organic compound composed of carbon, hydrogen, oxygen and nitrogen that inhibits the enzyme LIM kinase.
  
  It was recently discovered by the Cure and Inserm Institute, CNRS and CEA, in collaboration with British and Australian investigators. The studies "in vitro" and with animals, published in "Cancer Research", prove that this molecule has a completely new mechanism of action that could be used against chemotherapy resistant cells, providing a new alternative treatment to cancer that does not have major side effects.
   In addition, ((Dipp)P)Ge was modified such that an iPr groups was added to the para position of (Dipp)P, to make (Tripp)P. The donating effect of an additional iPr group has little effect on the bonding and structure of the diphosphagermylene.
  
  Section::::Structure and Bonding.:P-Ge p(π)-p(π) Stabilized Systems: ((Dipp)P)Ge and ((Tripp)P)Ge.:Solution and Solid State Nuclear Magnetic Resonance (NMR).
   BULLET::::- Radial head prosthesis.
  
  BULLET::::- It is also used in automotive industries where a desired amount of friction is required between two components
  
  BULLET::::- Highly oriented pyrolytic graphite (HOPG) is used as the dispersive element in HOPG spectrometers, which are used for X-ray spectrometry.
  
  Section::::Applications.:Biomedical applications.
   Polyphenylene oxide (PPO), which is obtained from the free-radical, step-growth oxidative coupling polymerization of 2,6-xylenol, has many attractive properties such as high heat distortion and impact strength, chemical stability to mineral and organic acids, and low water absorption. PPO is difficult to process, and hence the commercial resin (Noryl) is made by blending PPO with high-impact polystyrene (HIPS), which serves to reduce the processing temperature.
  
  Section::::Polyphenylene sulfide.
   The disease causing PrPSc is proteinase K resistant and insoluble. Attempts to purify it from the brains of infected animals invariably yield heterogeneous mixtures and aggregated states that are not amenable to characterization by NMR spectroscopy or X-ray crystallography. However, it is a general consensus that PrPSc contains a high percentage of tightly stacked β-sheets than the normal PrPc that renders the protein insoluble and resistant to proteinase. Using techniques of cryoelectron microscopy and structural modeling based on similar common protein structures, it has been discovered that PrPSc contains ß-sheets in the region of aa 81-95 to aa 171, while the carboxy terminal structure is supposedly preserved, retaining the disulfide-linked α-helical conformation in the normal PrPc. These ß-sheets form a parallel left-handed beta-helix. Three PrPSc molecules are believed to form a primary unit and therefore build the basis for the so-called scrapie-associated fibrils. The catalytic activity depends on the size of the particle. PrPSc particles which consist of only 14-28 PrPc molecules exhibit the highest rate of infectivity and conversion.
   Section::::Structural comparison to thrombin.
  
  Cerastocytin, like most other serine proteases, thrombin specifically, has three distinguishing features: the hydrophobic pocket, the positive surface and the catalytic triad. Additionally, the tertiary structure of cerastocytin is maintained by disulfide bridges similar to those formed in other serine proteases. This structural similarity results of cerastocytin’s ability to clot platelets and hydrolyze fibrinogen at the concentration of 5 nM, closely mimics the activity of thrombin at 1nM.
  
  Section::::Structural comparison to thrombin.:Hydrophobic pocket.
   Section::::Clinical significance of the SP-NK1R.
  
  Section::::Clinical significance of the SP-NK1R.:Quantification in disease.
  
  Elevation of serum, plasma, or tissue SP and/or its receptor (NK1R) has been associated with many diseases: sickle cell crisis; inflammatory bowel disease; major depression and related disorders; fibromyalgia; rheumatological; and infections such as HIV/AIDS and respiratory syncytial virus, as well as in cancer.
   Section::::Physical properties.:Surface tension.
  
  PPEs have high surface tension; hence these fluids have a lower tendency to wet metal surfaces. The surface tension of the commercially available 5R4E is 49.9 dynes/cm, one of the highest in pure organic liquids. This property is useful in applications where migration of the lubricant into the surrounding environment must be avoided.
  
  Section::::Applications.
   From Youngstown, McGinness moved to the Physics Department of The University of Texas M. D. Anderson Cancer Center. The department had an interest in the physical properties of melanin as a possible hook to treating melanoma. While of enormous importance now, this area was a research backwater at the time. With the notable exception of Bolto "et al.", who had reported high conductivity in iodine-doped polypyrrole, few but melanoma researchers had much reason to look at the electronic properties of such rigid-backbone polymer "blacks". This is why the putative first molecular electronic device came from a cancer hospital.
   Tricresyl phosphate
  
  Tricresyl phosphate, abbreviated TCP, is an organophosphate compound that is used as a plasticizer and diverse other applications. It is a toxic substance that causes neuropathy through ingestion, and has been the cause of several mass poisonings in history. It is a colourless, viscous liquid, although commercial samples are typically yellow. It is virtually insoluble in water.
  
  Section::::Production.
  
  Tricresyl phosphate is manufactured by reaction of cresols with phosphorus oxychloride:
  