ABSTRACT
Circulatory support devices require 10-20 W. Currently, several devices are under development for the transmission of this power via transcutaneous transformers, with the secondary implanted subcutaneously and the primary worn externally. Because these devices are air cored, they have relatively large, bulky external appliances, poor coil to coil coupling, and result in significant stray fields passing through adjacent tissues. This article reports on the engineering design of a novel, high permeability cored transformer implanted in a transenteric configuration using an isolated intestinal pouch. Such an approach offers greater energy transmission efficiency, less heat dissipation, less stray electromagnetic energy, and greatly reduced device size. Two competing designs using this concept have been developed and tested. Each consists of the transformer, together with power interface electronics, forming a direct current (DC)/DC resonant converter. Operating frequencies are 90.2 and 14.7 kHz, respectively, with primary/secondary turns ratios of 10/10 and 11/14, respectively. In addition, data interface electronics allows communication across the transformer of up to four signals at a per channel sample rate of 10 Hz. Both designs are able to continuously transmit 25 W at an output level of 12 Vdc into a 5.8 omega load. Calorimetry tests indicate DC to DC efficiencies greater than 75% and coil to coil efficiencies greater than 96%. Total package size for the implantable portion of each device (including sensor internal interface electronics) is less than 40 ml, with a weight weight of less than 100 g. The results of short-term implantation studies have been favorable. Long-term implantation studies currently are under way.
Subject(s)
Electronics, Medical/instrumentation , Heart-Assist Devices , Animals , Biomedical Engineering , Dogs , Equipment Design , Evaluation Studies as Topic , Humans , Ileum/surgery , In Vitro Techniques , Male , PermeabilityABSTRACT
Ethyl acetate appears to be a satisfactory subsitute solvent for diethyl ether in the Formalin-ether sedimentation technique. In comparative studies, concentration of organisms with ethyl acetate was equal to or greater than that with diethyl ether. No distortion or alteration of morphology was observed with eigher solvent, and preparations were comparable in appearance and ease of examination. In addition, ethyl acetate is less flammable and less hazardous to use than diethyl ether.
Subject(s)
Acetates , Parasitology/methods , Animals , Ether , Eukaryota/isolation & purification , Female , Helminths/isolation & purification , Ovum , SolventsABSTRACT
Parasitologic, serologic, and epidemiologic studies were done during 1967 in Calion, Arkansas (population 544). Infection with Entamoeba histolytica was found to be endemic but was segregated along racial lines. Twenty-two (9.9%) black compared with only one (0.6%) white had E. histolytica demonstrated in one stool examination; only two blacks had symptoms suggestive of amebiasis. No positive amebiasis indirect hemaggulination titers were found in 135 white residents. In contrast, 41 (17.9%) blacks had positive titers. Age, sex, and geographic location were not associated with stool or seropositivity. Within the black population, clustering of stool and seropositivity occurred. Significantly higher rates of stool and seropositivity were seen in households with crowding and poor sanitation as evidenced by lack of indoor toilet facilities. The presence of contaminated water supplies did not correlate with stool or seropositivity. The probable importance of person-to-person transmission is suggested by the observed clustering of infection within households with crowding and unsanitary conditions. The absence of evidence for transmission by food or water further supports this hypothesis.
