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Biomedical subjects

D Haberstock

Publications and source records attributed to D Haberstock.

4 recordsLinked to original sources

Three-dimensional force systems from vertically activated orthodontic loops.

When both vertical alignment and first-order rotation of teeth are to occur simultaneously, a 3-dimensional force system is required. This numerical study evaluated several appliances (rectangular loops and L-loops) used to vertically align teeth. Consideration was given to how these designs might be modified to produce the appropriate force system to allow both movements to occur simultaneously. It was found that the rectangular loop was the most appropriate choice for first-order corrections. For the rectangular loops studied, the in-plane force system was shown to be essentially independent of the out-of-plane effects, which allowed the 2 corrections to be controlled separately.

Algorithms↗

Performance of the Baxter Flo-Gard 6201 volumetric infusion pump for monoplace chamber applications.

For non-hyperbaric purposes, the Baxter Flo-Gard 6201 volumetric pump is capable of infusing multiple types of fluids at rates of 1-1,999 ml x h(-1). We designed a study to determine flow accuracy of this pump at variable rates, fluid viscosities, and volumes over a range of chamber pressures. For hyperbaric use, the pump pressure sensor was adjusted. Sodium chloride solution 0.9% (NS), enteral formula, and packed red blood cells (PRBC) were infused at varying rates from 86.1 to 304 kPa (0.85 to 3.0 atm abs). For NS, measured compared to set flow rates ranged from 12.5% to -7.5% at settings of 1 and 5 ml x h(-1) from 86.1 to 304 kPa (0.85 to 3.0 atm abs) pressures, respectively. For NS infusions at a set rate of 100 ml x h(-1), the measured flow was identical to the set rate at all pressures. At flow settings of 1,999 ml x h(-1), the measured flow varied from the set flow by +/-4.9% Enteral infusion at 100 ml x h(-1) showed approximately a 3% increase in the measured vs. set flow rate. PRBC measured flow rates ranged from -0.4 to 6% of the set rate. During chamber compression and decompression, with set flow rates from 1 to 10 ml x h(-1), the measured flow was considerably less than expected during compression and more than expected during decompression. In conclusion, the Baxter Flo-Gard 6201 infusion pump demonstrated acceptable performance for infusing saline, enteral formula, and PRBC at low and high infusion rates into the pressurized monoplace hyperbaric chamber up to 304 kPa (3 atm abs), with the exception of low rates during compression and decompression.

Atmosphere Exposure Chambers↗

A parametric study of the force/moment systems produced by T-loop retraction springs.

This study considers the effects of several parameters on the force/moment systems produced by T-loop retraction springs. The springs are studied by using the finite element method and by experimentally measuring the forces and moments from the various designs. The results show that varying the spring height can produce larger moment to force ratios as the height increases. Changes in the preactivation bends result in unsymmetric moment characteristics and also produce large intrusive/extrusive forces. The addition of helices at the bends did little to alter the springs' mechanical characteristics.

Computer Simulation↗

Analysis and design of multiple-beam appliances.

A new approach for the analysis of multiple-beam structures, such as headgear bows, is developed for beams which contain arbitrary curvatures, twists, and material properties. The generalized transfer matrix of a single-beam analysis is converted to a stiffness matrix and inserted into a global matrix which describes the entire system. The effect of inner bow wire size (0.044 inch and 0.051 inch) on the force system is demonstrated. The inner bow with the larger cross section shows only a slight (not clinically significant) reduction in rotational moment and buccal force applied because of its greater ability to resist deformation during the loading process. Small amounts of tooth and/or tube rotations ("play") result in a significant reduction of the crown rotational moment. With increasing rotation of the tube to the inner bow, the high lateral forces and large moments found about the long axis of the teeth are found to reduce. Symmetrical headgears are chosen to illustrate the analysis and to indicate the manner in which this approach may be used to study and design similar orthodontic appliances.

Elasticity↗