Perforated pores

Perforated pores (a) different sizes in graded manner (b) different sizes in banded manner (c) different density of perforations in a graded manner (d) different density of perforations in a banded manner (e) perforations with different cross sections (f) plan view of perforations with extra passages and grooves. (From D. Knights et al. (2003) US Patent 2003039876.)... 

Staphylococcal a-hemolysin is another widely studied pore-forming toxin. It is used by infectious bacteria to perforate host animal cells by a mechanism that is distinct from that of gramicidin. Several aspects of the stmcture and function of this heptameric protein complex have been smdied. 

Loch, n. hole, opening cavity eye pore prison, -blende, /. perforated screen or diaphragm. -eisen, n. puncher, pimch. locben, v.t. perforate, punch, pierce, locherig, a. full of holes, perforated, porous. Locherstelle,/. open place, gap, hole. Loch-frass, m. pitting (as of metals), -karte,/. punch (ed) card, -kultur,/. (Bact.) stab culture. -scheibe, /. perforated disk, apertured disk. 

With the Monte Carlo technique, a very large number of membrane problems have been worked on. We have insufficient space to review all the data available. However, the formation of pores is of relevance for permeation. The formation of perforations in a polymeric bilayer has been studied by Muller by using Monte Carlo simulation [67] within the bond fluctuation model. In this particular MC technique, realistic moves are incorporated, such that the number of MC steps can be linked to a simulated time. 

Aravamudhan, Rahman, and Bhansali. [70] developed a micro direct ethanol fuel cell with silicon diffusion layers. Each silicon substrate had a number of straight micropores or holes that were formed using microelec-tromechanical system (MEMS) fabrication techniques. The pores acted both as microcapillaries/wicking structures and as built-in fuel reservoirs. The capillary action of the microperforations pumps the fuel toward the reaction sites located at the CL. Again, the size and pattern of these perforations could be modified depending on the desired properties or parameters. Lee and Chuang [71] also used a silicon substrate and machined microperforations and microchannels on it in order to use it as the cathode diffusion layer and FF channel plate in a micro-PEMFC. 

In addition to the sensilla styloconica, lepidopterous larvae possess gustatory sensilla on the maxillary palps. Eight basiconic sensilla are located on top of each palpus (see Figure 1). Five of them possess a terminal pore, and for that reason these sensilla might be considered as contact chemoreceptors. The remaining three show numerous small perforations all over the cuticle, which indicates an olfactory function (.8). The response spectra of these sensilla are, however, still obscure. 

The porous plate usually consists of microsize pores with mean diameters ranging between 1.7 and 300 pm (Smith et al., 1996 Vial et al., 2001 Bouaifi et al., 2001). The perforated plate design, however, takes into account the number, pitch, and diameter of the... 

The nuclear envelope is perforated with huge macromolecular assemblies of 30 different proteins that form nuclear pore complexes with a central channel of 25-30 nm in diameter. This channel allows proteins smaller than 30 kDa to passively traverse the outer and inner nuclear membranes. Larger proteins are actively transported across the nuclear envelope and contain nuclear localization signal (NLS) sequence motifs. These signals consist of one or two clusters of four or five basic residues localized usually within the polypeptide chain. The import of proteins with NLS through the channel is facilitated by the carrier heterodimer of importin-a ( > (Gorlich and Kutay 1999 Pemberton and Paschal... 

Cell construction is mainly confined to two types, using either pocket plate electrodes (vented cells) or sintered , bonded or fibre plate electrodes (vented and sealed cells). In the former, the active materials are retained within pockets of finely perforated nickel-plated sheet steel which are interlocked to form a plate. Positive and negative plates are then interleaved with insulating spacers placed between them. In sintered plate electrodes, a porous sintered nickel mass is formed and the active materials are distributed within the pores. In sintered plate vented cells, cellulose or other membrane materials are used in combination with a woven nylon separator. In sealed or recombining cells, special nylon separators are used which permit rapid oxygen diffusion through the electrolyte layer. 

Two complex tissues, the xylem and phloem, provide the conducting network or "circulatory system" of plants. In the xylem or woody tissue, most of the cells are dead and the thick-walled tubes (tracheids) serve to transport water and dissolved minerals from the roots to the stems and leaves. The phloem cells provide the principal means of downward conduction of foods from the leaves. Phloem cells are joined end to end by sieve plates, so-called because they are perforated by numerous minute pores through which cytoplasm of adjoining sieve cells appears to be connected by strands 5-9 pm in diameter.154 Mature sieve cells have no nuclei, but each sieve cell is paired with a nucleated "companion" cell. 

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