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Biomedical subjects

Mark Taylor

Publications and source records attributed to Mark Taylor.

At least 127 records · Page 7Linked to original sources
PubMed2005

Finally, after 16 years of trying to tie the knot, Ohio city's two acute-care hospitals have put half a century of competition behind them.

It was a long, dramatic courtship. Finally, after 16 years and two frustrating tries, Springfield, Ohio's two acute-care hospitals have completed their merger, ending a half-century of competition. City leaders call the deal a testament to the two hospitals' boards and leaders. A. David Jimenez, left, an executive at Catholic Healthcare Partners, says that ultimately, it is the community that must come first.

Catholicism↗
PubMed2005

Picking up the tab. Healthcare chains put the past behind them, resolving past unpleasantries in order to make a clean start in the new year.

It's something of a holiday tradition: legal settlements at major investor-owned healthcare companies. But will Tenet's and HealthSouth's multimillion-dollar mea culpas over allegations of providing unnecessary care have the same healing effect that HCA's pair of year-end settlements yielded? Tenet's E. Peter Urbanowicz, left, said his company's moves show "the real progress we are making to put our legal challenges ... behind us".

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PubMed2005

Damage accumulation, fatigue and creep behaviour of vacuum mixed bone cement.

The behaviour of bone cement under fatigue loading is of interest to assess the long-term in vivo performance. In this study, uniaxial tensile fatigue tests were performed on CMW-1 bone cement. Acoustic emission sensors and an extensometer were attached to monitor damage accumulation and creep deformation respectively. The S-N data exhibited the scatter synonymous with bone cement fatigue, with large pores generally responsible for premature failure; at 20 MPa specimens failed between 2 x 10(3) and 2 x 10(4) load cycles, while at 7 MPa specimens failed from 3 x 10(5) load cycles but others were still intact after 3 x 10(6) load cycles. Acoustic emission data revealed a non-linear accumulation of damage with respect to time, with increasing non-linearity at higher stress levels. The damage accumulation process was not continuous, but occurred in bursts separated by periods of inactivity. Damage in the specimen was located by acoustic emissions, and allowed the failure site to be predicted. Acoustic emission data were also used to predict when failure was not imminent. When this was the case at 3 million load cycles, the tests were terminated. Creep strain was plotted against the number of load cycles and a linear relationship was found when a double logarithmic scale was employed. This is the first time a brand of cement has been characterised in such detail, i.e. fatigue life, creep and damage accumulation. Results are presented in a manner that allows direct comparison with published data for other cements. The data can also be used to characterise CMW-1 in computational simulations of the damage accumulation process. Further evidence is provided for the condition-monitoring capabilities of the acoustic emission technique in orthopaedic applications.

Biocompatible Materials↗
PubMed2005

Damage rate is a predictor of fatigue life and creep strain rate in tensile fatigue of human cortical bone samples.

We present results on the growth of damage in 29 fatigue tests of human femoral cortical bone from four individuals, aged 53-79. In these tests we examine the interdependency of stress, cycles to failure, rate of creep strain, and rate of modulus loss. The behavior of creep rates has been reported recently for the same donors as an effect of stress and cycles. In the present paper we first examine how the evolution of damage (drop in modulus per cycle) is associated with the stress level or the "normalized stress" level (stress divided by specimen modulus), and results show the rate of modulus loss fits better as a function of normalized stress. However, we find here that even better correlations can be established between either the cycles to failure or creep rates versus rates of damage than any of these three measures versus normalized stress. The data indicate that damage rates can be excellent predictors of fatigue life and creep strain rates in tensile fatigue of human cortical bone for use in practical problems and computer simulations.

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PubMed2005

On the importance of considering porosity when simulating the fatigue of bone cement.

Fatigue cracking in the cement mantle of total hip replacement has been identified as a possible cause of implant loosening. Retrieval studies and in vitro tests have found porosity in the cement may facilitate fatigue cracking of the mantle. The fatigue process has been simulated computationally using a finite element/continuum damage mechanics (FE/CDM) method and used as a preclinical testing tool, but has not considered the effects of porosity. In this study, experimental tensile and four-point bend fatigue tests were performed. The tensile fatigue S-N data were used to drive the computational simulation (FE/CDM) of fatigue in finite element models of the tensile and four-point bend specimens. Porosity was simulated in the finite element models according to the theory of elasticity and using Monte Carlo methods. The computational fatigue simulations generated variability in the fatigue life at any given stress level, due to each model having a unique porosity distribution. The fracture site also varied between specimens. Experimental validation was achieved for four-point bend loading, but only when porosity was included. This demonstrates that the computational simulation of fatigue, driven by uniaxial S-N data can be used to simulate nonuniaxial loadcases. Further simulations of bone cement fatigue should include porosity to better represent the realities of experimental models.

Biocompatible Materials↗