Shrink-wrap surfaces

Once the pharmacophore is generated, the active compounds are superimposed and the shrink-wrap surface, defined as the surface of smallest volume that encloses at least one conformer of each active molecule, is calculated. This surface can be analyzed to provide raw shape information (figure 10). Regions of the shrink-wrap surface that are penetrated by inactives that otherwise match the pharmacophore can be marked as forbidden regions . Other regions which haven t been explored can be marked as terra incognita , or unknown regions. 

Identify shrink-wrap surface Surface of smallest volume that encloses at least one con former of each active ... 

Van Drie, J.H. "Shrink-wrap" Surfaces A New Method for Incorporating Shape into Pharmacophoric 3D Database Searching. J. Chem. Inf. Comput. Sci., 1997, 37, 38-42. 

Van Drie JH. Shrink-Wrap surfaces a new method for incorporating shape into phar-macophoric 3D database searching. J Chem Inf Comput Sci 1997 37 38 42. 

Protecting the can from the effect of corrosion is very important in order to achieve the very long shelf life that metal cans offer. Discussion with the can manufacturer will ensure the use of the appropriate grades of lacquers on the internal surfaces to prevent primary corrosion. The external surfaces must also be considered in order to prevent secondary corrosion, which will result in leakage. Handling on the filling line must ensure the smooth flow of cans and eliminate any sharp objects that may scratch or pierce them. A lot of moisture is present on the line because of the use of conveyor lubricants or from the pasteuriser, and it is important that cans are dried before being packed, particularly if they are to be shrink-wrapped. Cold cans, below the dew point, must be wanned to ambient temperature or else they will become wet when packed. 

Polyethylene, as LDPE, LLDPE or a mixture or blend involving combinations of LDPE, MDPE, HDPE, EVA, etc., finds a wide usage in bags, sacks, sachets, overwraps, shrink wraps, stretch wraps, etc. Most deep freeze packs, for example, use LDPE or an LDPE mixture which is produced from a reel on a form fill seal type machine. However, as many of these packs are up to 100% printed, even ink of 2-5 Pm could be considered as a separate layer which modifies some of the physical and chemical properties. As all polyolefins need a surface (oxidative) treatment to ensure a good print key, this or any other surface treatment process may further modify the film properties. 

Monolithic columns are another approach to provide lower pressure drops and higher rates of mass transfer. These are continuous solid columns of porous silica stationary phase instead of packed particles. Like perfusion packings, they have a bimodal pore structure (Figure 21.7). Macropores, which act as flowthrough pores, are about 2 fim in diameter. The silica skeleton contains mesopores with diameters of about 13 nm (130 A). It can be surface modified with stationary phases like Cig. The rod is shrink-wrapped in a polyetheretherketone (PEEK) plastic holder to prevent waU effects of solution flowing along the walls. The surface area of the mesopores is about 300 mVg, and the total porosity is 80%, compared with 65% for packed particles. The colunm exhibits a van Deemter curve approximating... 

In general, texture mapping is a technique that applies a picture to an object surface as if the picture were a decal or cellophane shrink-wrap. But the texture need not to be 2D. it can be ID as well as 3D or higher dimensional. 

Elaborations upon the accessible surface include the contact, re-entrant, and molecular surfaces. The contact surface is that part of the van der Waals surface that can be touched by a probe sphere, without that sphere experiencing overlap with any other atom. The re-entrant surface is made up of the inward-facing part of the probe sphere as it touches more than one atom. Together, the contact and re-entrant surfaces form a continuous envelope, which is called the molecular surface. This surface resembles shrink wrap placed around a hard sphere model. 

The term film is also applied to sheets of cellophane, polyethylene, polyvinylidene chloride, etc., used for wrapping and packaging of food products, meats, and poultry (especially shrink films that are stretched before application). These function as a moisture vapor harrier. Plaslic lilms are also used as slip surfaces in concrete structures such as airstrips, ice rinks, and highways. Photographic film is made from cellulose acetate. 

Technical processes that employ ionizing radiation are widely applied in the polymer field, and include the production of crosslinked wire insulation and of heat-shrink food wrappings and tubings for electrical connections, the vulcanization of rubber tires and rubber lattices, and the curing of coatings and inks. Moreover, various X-ray methods can also be appUed for the characterization and analysis of polymers, especially of the polymer surfaces. Both, X-ray imaging and X-ray microscopy allow the derivation of quantitative composition maps of polymer surfaces. Notable in this context are also near-edge X-ray absorption fine structure spectroscopy (NEXAFS), extended X-ray absorption fine structure spectroscopy (EXAFS) and X-ray photoelectron spectroscopy (XPS). 

The lug screen is basically a wire wrap screen located on vertical bars on a perforated pipe, facilitating free entry of fluid over the entire exposed surface of the screen, to increase its efficiency. This principle is further extended in the lug plus version, where the bars are welded to the wedge-wire screen, and the whole is shrink-fitted to the perforated pipe. The slip-on screen is of similar construction, but is a slip on fit. In the weld screen the wedge-wires are welded to vertical rods. The Protecto-Screen mcorpoiates a perforated protective shell guard over the wedge-wire screen. 

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