Parametric Analysis Using the Finite Element Method to Investigate Prosthetic Interface Stresses for Persons with Trans-tibial Amputation

A finite element (FE) model of the below-knee residual limb and prosthetic socket was created to investigate the effects of parameter variations on the interface stress distribution during static stance. This model was based upon geometric approximations of anthropometric residual limb geometry. The model was not specific to an individual with amputation, but could be scaled to approximate the limb of a particular subject. Parametric analyses were conducted to investigate the effects of prosthetic socket design and residual limb geometry on the residual limb/prosthetic socket interface stresses. Behavioral trends were illustrated via sensitivity analysis. The results of the parametric analyses indicate that the residual limb/prosthetic socket interface stresses are affected by variations in both prosthetic design and residual limb geometry. Specifically, the analyses indicate : 1) the residual limb/prosthetic liner interface pressures are relatively insensitive to the socket stiffness ; 2) the stiffness of the prosthetic liner influences the interface stress distribution for both the unrectified and patellar-tendon-bearing (PTB) rectified models-- the external load state appears to influence the interface pressure distribution, while the prosthetic socket rectification appears to influence the interface shear stress distribution ; 3) the interface pressures are - very sensitive to the prosthetic rectification ; 4) the shape and relative bulk of soft tissue may significantly influence the interface pressure distribution ; 5) the interface pressure distribution is also influenced by the residual limb length; and 6) the stiffness/compliance of the residual limb soft tissues may significantly alter the interface pressure distribution

Generic, Geometric Finite Element Analysis of the Transtibial Residual Limb and Prosthetic Socket

Finite element analysis was used to investigate the stress distribution between the residual limb and prosthetic socket of persons with transtibial amputation (TTA). The purpose of this study was to develop a tool to provide a quantitative estimate of prosthetic interface pressures to improve our understanding of residual limb/prosthetic socket biomechanics and prosthetic fit. FE models of the residual limb and prosthetic socket were created. In contrast to previous FE models of the prosthetic socket/residual limb system, these models were not based on the geometry of a particular individual, but instead were based on a generic, geometric approximation of the residual limb. These models could then be scaled for the limbs of specific individuals. The material properties of the bulk soft tissues of the residual limb were based upon local in vivo indentor studies. Significant effort was devoted toward the validation of these generic, geometric FE models; prosthetic interface pressures estimated via the FE model were compared to experimentally determined interface pressures for several persons with TTA in a variety of socket designs and static load/alignment states. The FE normal stresses were of the same order of magnitude as the measured stresses (0-200 kPa); however, significant differences in the stress distribution were observed. Although the generic, geometric FE models do not appear to accurately predict the stress distribution for specific subjects, the models have practical applications in comparative stress distribution studies

A Review of Prosthetic Interface Stress Investigations

Over the last decade, numerous experimental and numerical analyses have been conducted to investigate the stress distribution between the residual limb and prosthetic socket of persons with lower limb amputation. The objectives of these analyses have been to improve our understanding of the residual limb/prosthetic socket system, to evaluate the influence of prosthetic design parameters and alignment variations on the interface stress distribution, and to evaluate prosthetic fit. The purpose of this paper is to summarize these experimental investigations and identify associated limitations. In addition, this paper presents an overview of various computer models used to investigate the residual limb interface, and discusses the differences and potential ramifications of the various modeling formulations. Finally, the potential and future applications of these experimental and numerical analyses in prosthetic design are presented

The Florida Railroad after the Civil War

David Levy Yulee was the most enthusiastic of the early railroad promoters in Florida. On January 8, 1853, he incorporated the Florida Railroad to construct a line from the Atlantic Ocean to a point on the Gulf of Mexico south of the mouth of the Suwannee River. The charter was amended by the legislature in 1855, and the company was authorized to build from Amelia Island on the east coast to Tampa Bay on the Gulf of Mexico with a branch line to Cedar Key. In addition the company was authorized to own and operate steam vessels on Florida’s rivers. Yulee’s dream was to construct a railroad across Florida and to establish a steamship line from Cedar Key to other Gulf ports, Central America, and the Caribbean islands. He believed it would be cheaper for the shipper to use ships and the railroad, even if it entailed loading and unloading at each end of the line, than to brave the waters of the Florida Straits. Also Yulee hoped to attract to the state immigrants interested in producing vegetables. Their products could be carried by the railroad to Fernandina where fast steamships would transport them to northern markets

White Blood Cell Counts, Parasite Prevalence, and Plasma Cortisol Levels of Dogs in a County Animal Shelter: Changes over Days and Impact of a Program of Repeated Human Interaction

Animal shelter housing is highly stressful for a dog, compromising welfare and leading to undesirable behaviors and unknown health consequences. We documented the changes in circulating numbers of white blood cells, plasma cortisol, and fecal parasite shedding of dogs housed for 10 days at a county animal shelter. White blood cell changes were most prominent on Day 10 after arrival to the shelter. Changes included increased total leukocytes, mature neutrophils, and lymphocytes, with less consistent increases in monocytes and neutrophil to lymphocyte ratio (N:L). Fecal parasite shedding was elevated and not affected by day. Cortisol levels of shelter dogs declined over time, and when compared with dogs living in stable home environments were higher on all days measured (1, 3, and 10). Total leukocytes, neutrophils, monocytes, and N:L were also higher in shelter dogs than control dogs. Petting sessions of 30 minutes daily for 10 days reduced the cortisol of shelter dogs, but did not have an effect on white blood cells or parasite shedding. This study documents high rates of parasitic infection, large and increasing immunological responses, and plasma cortisol elevations of dogs in an animal shelter. Increasing opportunities for daily interaction with caregivers is likely to improve the welfare of shelter dogs, but additional research must be done to identify potential health benefits

Plant\u27s Lieutenants

Henry Bradley Plant, native of Connecticut and owner of the Southern Express Company, successfully developed a rail network from the Georgia line to Charlotte Harbor. One of his lines was the first to reach the small, backwater village of Tampa where he built the lavish Tampa Bay Hotel in 1891. He also bought or constructed hotels in Port Tampa, Beleair, Punta Gorda, Ocala, Kissimmee, and Winter Park. He established a steamship line to Havana, Cuba, with stops at various ports along the West coast of Florida and at Key West, and his riverboats operated on the St. Johns, the Apalachicola, and the Chattahoochee. Plant did all this between 1879 when he purchased his first railroad and 1899 when he died. In addition, his companies owned large tracts of land received from the state, and his express company shipped Florida products to northern markets. Few men have been more intimately connected with the economic development of Florida, and none was more important to the area west of the St. Johns River and south to Punta Gorda on the lower Gulf coast during the latter part of the nineteenth century than Henry Plant

Henry Bradley Plant and Florida

Florida was a fertile field for developers during the last quarter of the nineteenth century. Lumbermen were at work in the northern part of the state; the citrus industry was in its infancy; phosphate mining was just beginning; and northern vacationers and some invalids were discovering the restorative powers of Florida’s climate. Railroads were needed to serve and to further develop these diverse interests. Many men dreamed of building a network of rails in the state, and some began the project. Most failed, although a few succeeded. Henry Bradley Plant was one of the more successful. He constructed railroads, hotels, and steamship lines, and in the process served the various business enterprises in the state while earning a respectable profit for himself

White Blood Cell Counts, Parasite Prevalence, and Plasma Cortisol Levels of Dogs in a County Animal Shelter: Changes over Days and Impact of a Program of Repeated Human Interaction

Animal shelter housing is highly stressful for a dog, compromising welfare and leading to undesirable behaviors and unknown health consequences. We documented the changes in circulating numbers of white blood cells, plasma cortisol, and fecal parasite shedding of dogs housed for 10 days at a county animal shelter. White blood cell changes were most prominent on Day 10 after arrival to the shelter. Changes included increased total leukocytes, mature neutrophils, and lymphocytes, with less consistent increases in monocytes and neutrophil to lymphocyte ratio (N:L). Fecal parasite shedding was elevated and not affected by day. Cortisol levels of shelter dogs declined over time, and when compared with dogs living in stable home environments were higher on all days measured (1, 3, and 10). Total leukocytes, neutrophils, monocytes, and N:L were also higher in shelter dogs than control dogs. Petting sessions of 30 minutes daily for 10 days reduced the cortisol of shelter dogs, but did not have an effect on white blood cells or parasite shedding. This study documents high rates of parasitic infection, large and increasing immunological responses, and plasma cortisol elevations of dogs in an animal shelter. Increasing opportunities for daily interaction with caregivers is likely to improve the welfare of shelter dogs, but additional research must be done to identify potential health benefits

Magnetic shielding and exotic spin-dependent interactions

Experiments searching for exotic spin-dependent interactions typically employ magnetic shielding between the source of the exotic field and the interrogated spins. We explore the question of what effect magnetic shielding has on detectable signals induced by exotic fields. Our general conclusion is that for common experimental geometries and conditions, magnetic shields should not significantly reduce sensitivity to exotic spin-dependent interactions, especially when the technique of comagnetometry is used. However, exotic fields that couple to electron spin can induce magnetic fields in the interior of shields made of a soft ferro- or ferrimagnetic material. This induced magnetic field must be taken into account in the interpretation of experiments searching for new spin-dependent interactions and raises the possibility of using a flux concentrator inside magnetic shields to amplify exotic spin-dependent signals.Comment: 8 pages, 5 figure