Skin permeability, among

It is worth noting that differences among membranes, such as the presence of different lipids, the amount of surface lipid, differences in size and shape of proteins, or physical features of bonding, may cause differences in permeability among membranes. These biochemical and biophysical differences are thought to be responsible for permeability differences in skin from different anatomical regions of the body. 

Among the many other works in this area, some studies have been attempted on skin permeability measurements other than the permeability coefficient. Skin permeability coefficients are usually utilized in QSAR modeling because they provide steady-state constants with the possibility of varying across a large number of orders of magnitude (the limitations of this type of data are described in the section... 

Wearley, L. Antonacci, B. Cacciapuoti, A. Assenza, S. Chaudry, L Eckhart, C. Levine, N. Loebenberg, D. Norris, C. Parmegiani, R. Sequeira, J. Yarosh-Tomaine, T. Relationship among physicochemical properties, skin permeability, and topical activity of the racemic compound and pure enantiomers of a new antifungal. Pharm. Res. 1993, 10, 136-140. 

The point is that acidizing in sandstones realistically addresses skin only, which can have a drastic effect on well productivity. As shown in equation (3.1), well production rate, q, can be defined by Darcy s law for steady-state liquid flow in a radial reservoir as a function of permeability, k, and skin, s, among other factors. Again, skin, s, is a multicomponent term representing total skin s), composed of different skin contributors, as given in equation (3.3). 

The skin is a complex multilayered tissue with a large surface area exposed to the environment. Skin anatomy, physiology, and biochemistry vary among species, within species, and even between anatomic sites within an individual animal or human. Logically these biological factors alone can influence dermal absorption. What is consistent is that the outer layer, the stratum corneum (SC), can provide as much as 80% of the resistance to absorption to most ions as well as aqueous solutions. However, the skin is permeable to many toxicants, and dermal exposure to agricultural pesticides and industrial solvent can result in severe systemic toxicity. 

A peel to the papillary dermis therefore marks the safety limit beyond which the risks are higher, though most often controllable. How far this limit can be stretched depends -among other things - on how permeable the skin is in local areas of increased permeability, the TCA can penetrate too deeply. 

Human skin has a multifunctional role, primary among which is its role as a barrier against both the egress of endogenous substances such as water and the ingress of xenobiotic material (chemicals and drugs). This barrier function of the skin is reflected by its multilayered structure (Fig. 5.1). The top or uppermost layer of the skin known as the stratum comeum (SC) represents the end product of the differentiation process initially started in the basal layer of the epidermis with the formation of keratinocytes by mitotic division. The SC, therefore, is composed of dead cells (comeocytes) interdispersed within a lipid rich matrix. It is the brick and mortar architecture and lipophilic nature of the SC, which primarily accounts for the barrier properties of the skin [1,2]. The SC is also known to exhibit selective permeability and allows only relatively lipophilic compounds to diffuse into the lower layers. As a result of the dead nature of the SC, solute transport across this layer is primarily by passive diffusion [3] in accordance with Pick s Law [4] and no active transport processes have been identified. 

HEMA is a known contact allergen [70,71], but despite this there do not seem to have been any reports of dermatitis among dental personnel, either dentists or then-assistants [61]. Latex gloves are inadequate to protect the skin because they are permeable to HEMA [79]. The volatility HEMA may also cause problems with these materials, and inhalation of the vapour should be avoided [61]. There are anecdotal reports of dental personnel developing allergies to resin-modified glass-ionomers, but again there seem to be no detailed reports or case studies in the literature about this. 

---