Artificial devices

Renal replacement by an artificial device providing intermittent clearance of plasma based on the physical principle of diffusion. 

Treatment of these samples with SF4 gas to convert the carboxylic acids produced in the weathering process into carbonyl fluorides showed [2, 11] that the acids are actually a mixture of aliphatic and aromatic acids (Figure 18.12). Aromatic acid species are by far the predominant ones, however. The origin of these acids will be discussed below in conjunction with the overall mechanisms of photodegradation. Aliphatic acid species were detected by GC/MS in the artificial device exposure of PECT [11], Note that the PECT copolymer produced more aromatic acids with the same exposure as PET but that the aliphatic acid production was several times higher for the PECT copolymer. The photo-oxidation of the co-glycol must be the reason for this difference. 

The tunnel correction is an artificial device to correct an artificial treatment, in which the real vibrations of the transition state are treated quantum mechanically, but the passage along the reaction coordinate over the barrier is treated classically. This correction has the property that Qh > Qd > 1 it thus can only increase the isotope effect. It is dependent on several factors12 including especially i>, and the QhIQd can only be much greater than unity if i>fH >. It can be shown11,13 ... 

A schematic cycle describing the principle of light capture and energy storage via a photosensitized electron transfer process In an artificial device Is presented In Figure 2. In this system a synthetic sensitizer, S, substitutes for the natural chlorophyll as the light capturing entity. Excitation of the sensitizer, followed by an electron transfer to electron acceptor. A, results In the oxidized sensitizer and a reduced species, A. Oxidation of an electron donor, D, recycles the sensitizer and produces an... 

Miscellaneous. Many other organs sometimes become diseased or defective, and some artificial device has been used to replace them. For example, the gastrointestinal (GI) tract has often been replaced, totally or partially, by some type of plastic tubing. Such a prosthesis does not perform the normal GI tract functions but merely connects existent, nondiseased tubular parts in the body. Many materials have been used such as polyamides, polyesters, polysilicones, and polyethylene. In a similar manner, various ducts have been replaced by plastic tubing. Finally, the bladder, trachea, ureter, and similar organs have been replaced by nonfunctional plastic tubing (]J. 

Tliese developments will provide amputees and patients with a variety of motor disorders such as paralysis, amyotropic lateral sclerosis with the means to act and communicate by replacing tlie control of muscles with the control of artificial devices by brain activity. 

There is a lack of good detailed pathologic studies performed on heart valves prostheses recovered at surgery and/or autopsy. The lack of such studies will hinder the progress and development of not only better heart valve prostheses, but also other future artificial devices such as left ventricular assist devices and the total artificial heart. 

Kolff tried his machine on the first humans in 1943. The first 16 cases were helped but not saved by the device. The 17th patient, however, was a 67-year-old woman dying from kidney failure who was in prison when she became ill. She had been accused by her husband of being a Nazi collaborator. She was already comatose and on the verge of death when Dr. Kolff bypassed her kidneys with his artificial device. After 12 h, he leaned close to her face and asked if she was able to hear him. The woman opened her eyes, looked at Kolff, and said, 1 am going to divorce my husband. She lived, and she did (Fenster, 1998). 

J.M. Andawn and K.K. Marchant, Platelet interaction with biomaterials and artificial devices, CRC Critical Review in Biocompatibility, 1 111-204 (198S). 

In addition to the mechanical performance Umitations of prosthetic limbs, the other major impediment to full restoration of limb capability with an artificial device is the command and control interface between the prosthesis and amputee user. The typical approach for direct amputee control of a prosthetic limb is to use myoelectric potentials from muscles in the amputee s residual limb as user commands to the limb... 

Bleeding from injured blood vessels can be arrested by the activation of the hemostatic mechanism [24]. However, an artificial device surface placed in contact with blood can disturb the balance of this mechanism [24]. Excessive blood clotting with increased risk of embolization can occur due to the adhesion of platelets and lenkocytes to device surface and the formation of fibrin network following the... 

A comparison with Eq. A. 10 shows we were using the Newton-Raphson scheme by the artificial device of division by x. 

D Annis, T V How, A C Fisher, Recent Advances in the Development of Artificial Devices to Replace Diseased Arteries in Man A New Elastomeric Synthetic Artery. In Polyurethanes in Biomedical Engineering, Planck H, Egbers G, Syre I (Eds), Elsevier Science Publishers B.V. Netherlands, 1984. 

Wendel, H. P., and Ziemer, G., Coating-techniques to improve the hemocompatibility of artificial devices used for extracorporeal circulation, European Journal of Cardiothoracic Surgery, 1999 16(3) 342-350. 

This book is highly recommended. This state-of-the-art text covers in detail essentially all important hematological aspects of cardiovascular device blood compatibility. In particular, Chapter 76, Interaction of blood with artificial surfaces, which considers many theoretical, experimental, and animal studies, and Chapter 77, Artificial devices in clinical practice, which describes clinical device thromboembolic complications, are of great practical value. 

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