Closed sponge

Due to plant closings, sponge fines are less readily available and alternative production methods for elemental titanium powders are being evaluated. These include various electrolytic and vapor phase reduction methods. Of course, elemental... 

Foam. PhenoHc resin foam is a cured system composed of open and closed ceUs with an overall density of 16—800 g/cm. Principal appHcations are in the areas of insulation and sponge-like floral foam. The resins are aqueous resoles cataly2ed by NaOH at a formaldehyde phenol ratio of ca 2 1. Free phenol and formaldehyde content should be low, although urea may be used as a formaldehyde scavenger. 

The cells in foams are polyhedral, like grains in a metal (Fig. 25.8). The cell walls, where the solid is concentrated, can be open (like a sponge) or closed (like a flotation foam), and they can be equiaxed (like the polymer foam in the figure) or elongated... 

Latrunculins A and B are macrolides from the sponge Latrunculia magnified. Latrunculin A (>50 11M) binds close to the nucleotide binding site of G-actin and blocks the assembly with F-actin without promoting disassembly. 

The most common spill on a laboratory floor is water, not generally considered hazardous. It may, however, create hazardous conditions by making the floor slippery. It is dangerous to walk on a wet floor with certain types of soles. A wet area should always be blocked off until it is dry. Mop and bucket should always be available close by, not in a janitor s closet down the hall. String mops are superior to sponge mops for getting the floor dry. 

Preliminary kinetic analysis revealed that the reactions mentioned for various sugars were close to first order with respect to the organic reactant, while the reaction order with respect to hydrogen varied between 0.5 and 2.2, being 0.7 for hydrogenation of lactose on sponge nickel and about 2 for fructose hydrogenation on CuO/ZnO. 

Closed-cell sponge is used in a number of articles such as insulation and shock absorbing media and in seals of various types. 

He even proposed the existence of polyvalent atoms producing "sponge or net like" molecular mass in 1878. Towards the end of his career, he advanced the hypothesis that natural organic substances-those most closely associated with life, proteins, starch, and cellulose-may consist of very long chains, and derive their special properties from this structure. 

Pederin (104), the powerful cytotoxin of staphylinid beetles of the genus Paederus, has been the object of renewed interest due to the unexpected discovery of a series of closely related compounds in marine sponges that display antitumor activities. The latter, as well as pederin, were prepared by total synthesis and their biological activities were reported [219,220]. A recent review summarizing present knowledge on this family of compounds has been published [221]. 

Porous materials can be either open-pored such as a common sponge, or closed-pored such as the bubble-wrap packaging. Aerogels are open-pored materials such that unbonded material can move from one pore to another. 

Until 1920, the only flexible foam available was the natural sponge, but chemically foamed rubber and mechanically foamed rubber latex were introduced before World War II. These foams may consist of discrete unit cells (unicellular, closed cell), or they may be composed of interconnecting cells (multicellular, open cells) depending on the viscosity of the system at the time the blowing agent is introduced. Over 1.5 million tons of foamed plastic is produced annually in the United States. 

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