Absorbance fluids

As with carrageenan, another seaweed extract, the ability to bind to calcium makes alginates useful in dairy products as a thickener. It also makes alginates useful as wound dressings, where they absorb fluids, and stop bleeding, and act as a scaffold. 

Any polymer contains some inner free space free volume distributed in a dynamic manner between its molecular chains (see Section 23.2). When it is exposed to a fluid (liquid or gas) the physical possibility exists for fluid absorption by the polymer, if the fluid molecules or atoms are small enough to fit into local regions of this distributed space during kinetic movements. As this happens, subsequent kinetic chain motion must allow for the newly absorbed fluid molecules and, hence, the polymer s overall volume will adjust accordingly this action will coincide with the formation of more free space around these fluid molecules—so the polymer will swell a little. This process will be continued until an equilibrium is reached ( equilibrium swelling ), by which time the extent of swelling can be considerable. The amount of fluid taken up and the rate at which this happens are both important, and are discussed in this and following sections. 

EUler Swelling is reduced by the use of high filler loadings, with less elastomer then available to absorb fluid. 

Dextrans are produced commercially for use as plasma substitutes (plasma expanders) which can be administered by intravenous injection to maintain or restore the blood volume. They can be used in applications to ulcers or bum wounds where they form a hydrophilic layer which absorbs fluid exudates. 

The intestinal wall is optimized to absorb fluids and nutrients while keeping away different xenobiotics. Which factors, from a theoretical point of view, are the most influential in intestinal absorption ... 

The homy layer consists of about 10% extracellular components such as lipids, proteins, and mucopolysaccharides. Around 5% of the protein and lipids form the cell wall. The majority of the remainder is present in the highly organized cell contents, predominantly as keratin fibers, which are generally assigned an a-helical structure. They are embedded in a sulphur-rich amorphous matrix, enclosed by lipids that probably he perpendicular to the protein axis. Since the stratum comeum is able to take up considerably more water than the amount that corresponds to its volume, it is assumed that this absorbed fluid volume is mainly located in the region of these keratin structures. 

Formation of a continuous barrier type film after absorbing fluids... 

Finally, the particulate barrier did serve to absorb pools of blood ( 150x), adhered to the injured tissue and provide physical abrasion properties that may eventually be a compliment or pretreatment to a wound instead of an environmentally protective barrier dressing. A demonstration of rapid blood absorption by the barrier dressing is shown in Figs. 2.35-2.38. Theoretically, only seconds would be required to absorb fluid from bleeding wounds and form a protective gelatinous layer over the wound. 

In Europe, the TNO [27] and Kvaerner [19] are both developing contactors to remove water and carbon dioxide from natural gas. Glycol or amines are used as the absorbent fluid. The goal is to reduce the size and weight of the unit to allow use on offshore platforms, so oftentimes only the absorber, the largest piece of equipment in a traditional absorber/stripper, is replaced with a membrane contactor. Kvaerner has taken this technology to the demonstration phase and commercial units are expected to be introduced soon. 

As Roylance [25] pointed out, in contrast to the instantaneous nature of the energetically controlles elasticity, the conformational or entropic changes are processed whose rates are sensitive to the local molecular mobility. This mobility is influenced by a variety of physical and chemical factors, such as molecular architecture, temperature, or the presence of absorbed fluids which may swell the polymer. Often a simple mental picture of free volume - roughly, the space available for molecular segments to act cooperatively so as to carry out the motion or reaction in question-is useful in intuiting these rates. 

Employees should be cautioned about wearing contact lens in certain, if not all, pesticide environments. Dusty or chemical environments may represent particular hazards to contact lens wearers. Soft contact lenses can be especially problematic. Their design makes them hydrophilic (absorb fluids) , as a result they will also absorb chemical mists. If an employee is working in these conditions, it is best that he or she not wear contact lenses. 

Polymeric foam dressings are a diverse group of products with a wide range of properties. At their simplest, they are foamed polymers that have been made into sheets. The wound contact layer is often heat treated and pressure modified to produce a hydrophilic porous membrane about 0.5 mm thick to give a smooth, nonadherent wound contact surface that absorbs fluids by... 

When contacted with hydrogen sulfide in natural gas under high pressures at near ambient temperatures in a tray-type absorber (Fig. 9.6), this solvent mixture forms a monoethanolammonium salt. This remains dissolved in the absorbing fluid to collect as a solution at the bottom of the absorbing unit (Eq. 9.9). 

This scrubbing mixture also dries the incoming natural gas. The light hydrocarbon component of the gas stream is only very slightly soluble in the absorbing fluid and passes through the absorber unchanged. 

PPG is an improved super absorbent polymer (SAP). SAPs are a unique group of materials that can absorb over a hundred times their weight in liquids, and they do not easily release the absorbed fluids under pressure. Super absorbent polymers are used primarily as an absorbent for water and aqueous... 

Sump pad Acts to absorb fluids as they reach the top of the lateral flow strip... 

The radiation properties of weakly absorbing fluids are usually determined by the experimental setup shown in Fig. 10.3. The fluid fills a container with two windows. One of the windows faces a known radiation source (say a black body) and the other faces a spectroscope which resolves the radiation beam. The container at a uniform pressure and temperature provides a uniform density and absorption coefficient. 

Kaolin/pectin is an antidiarrheal combination that absorbs fluid, and binds and removes digestive tract irritants. They are used for symptomatic treattnent of diarrhea. Kaopectate (190 mg kaolin/mL and 4.34 mg pectin/mL) is an antidiarrheal agent. By being absorbent, it recovers excess fluid in bowel dysfunction. It is contraindicated in obstructive bowel dysfunction. When used concomitantly, kaolin/pectin may impair absorption of the following drugs antidyski-netics, antimuscarinics (especially atropine), chloroquine. 

Under normal circumstances, these quantities are well within the range of the total absorptive capacity of the small bowel ( 16 L) and colon (4-5 L). Neurohumoral mechanisms, pathogens, and drugs can alter these processes, resulting in changes in either secretion or absorption of fluid by the intestinal epithelium. Altered motility also contributes to this process, as the extent of absorption parallels transit time. With decreased motility and excess fluid removal, feces can become inspissated and impacted, leading to constipation. When the capacity of the colon to absorb fluid is exceeded, diarrhea will occur. 

Additional techniques exist for measuring fluid absorption at adhesive interfaces. Fourier transform infrared spectroscopy in the multiple internal reflection mode (FTIR-MIR) is an available technique for studying diffusion at the interface. FTlR-MlR has provided direct evidence of water accumulation, and therefore adhesive debonding, at the interface [12,13]. The technique of neutron reflectivity has also shown that the concentration of absorbed fluid can be significantly greater at the interface than in the bulk adhesive [14-18]. 

Glass-ionomers have other advantages over composites in this appUcadon, namely that they are hydrophilic and dimensionally stable. Their hydrophilic character enables them to absorb fluid that can be left at the bottom of the fissure without jeopardizing the adhesion to enamel. The dimensional stability is important because it allows the cement to retain its marginal adaption and seal, so that there is no risk of caries developing under the fissure sealing material. Fluoride release is also potentially advantageous. 

Another application where PEO-PPO-PEO block copolymer gels have shown promise is as wound dressings in the treatment of thermal bums. Such dressings should be easy to apply, and should adhere to the uninjured skin surrounding the wound, but also come off easily when removed. Furthermore, the adherence should be uniform since small areas of non-adherence may lead to fluid-filled pockets where bacteria could proliferate. Moreover, dressings should absorb fluid and... 

Typical gels are formed if substances like rubber, gelatin, polystyrene and cellulose are allowed to swell through absorbing fluids the original dry substances have therefore also been classified as gels. 

Superabsorbent materials are frequently used in disposable absorbent articles to help improve the absorbent properties of such articles. Superabsorbent materials are generally polymer-based and are available in many forms, such as powders, granules, microparticles, films and fibers. Upon contact with fluids, superabsorbent materials swell by absorbing fluid into their structure. The superabsorbent materials quickly absorb fluids insulted into the articles and retain such fluids to prevent leakage and provide a dry feel even after fluid insult (3). 

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