Publications (12) View all
-
Article: Are Zeolite Films Flexible?
02/2011; -
Article: Ninety-degree chevron osteotomy for correction of hallux valgus deformity: clinical data and finite element analysis.
[show abstract] [hide abstract]
ABSTRACT: Hallux valgus is a very common foot disorder, with its prevalence estimated at 33% in adult shoe-wearing populations. Conservative management is the initial treatment of choice for this condition, but surgery is sometimes needed. The 60(0) angle Chevron osteotomy is an accepted method for correction of mild to moderate hallux valgus in adults less than 60 years old. A modified 90(0) angle Chevron osteotomy has also been described; this modified technique can confer some advantages compared to the 60(0) angle method, and reported results are good. In the current work we present clinical data from a cohort of fifty-one female patients who had surgery for sixty-two hallux valgus deformities. In addition, in order to get a better physical insight and study the mechanical stresses along the two osteotomies, Finite Element Analysis (FEA) was also conducted. FEA indicated enhanced mechanical bonding with the modified 90(0) Chevron osteotomy, because the compressive stresses that keep the two bone parts together are stronger, and the shearing stresses that tend to slide the two bone parts apart are weaker, compared to the typical 60(0) technique. Follow-up data on our patient cohort show good or excellent long-term clinical results with the modified 90(0) angle technique. These results are consistent with the FEA-based hypothesis that a 90(0) Chevron osteotomy confers certain mechanical advantages compared to the typical 60(0) procedure.The Open Orthopaedics Journal 01/2010; 4:152-6. -
Article: Effect of Gas Adsorption on the Elastic Properties of Faujasite Films Measured Using Magnetoelastic Sensors
[show abstract] [hide abstract]
ABSTRACT: A novel method is presented for measuring the elastic properties of zeolite films using magnetoelastic sensors. The method is relatively simple and can be used to determine the effect of adsorbed molecules on the mechanical properties of the zeolite film. It is demonstrated using NaX films grown on Metglas ribbons. Measurements were taken as a function of temperature (10−40 °C) and gas (CO2, N2, vacuum) for a range of sensors with different faujasite masses (0.25−8.0 mg). For each temperature and gas, the modulus of elasticity of the faujasite crystalline film was extracted by analyzing the measurements as a function of film thickness. For all temperatures examined, it was found that the elastic modulus of the NaX films in vacuum was 38.7 ± 1.7 GPa. On the other hand, in the presence of N2, it varied between 24 and 38 GPa and, when in contact with CO2, between 39 and 52 GPa. Our results show for first time that the adsorption of gases in zeolites might induce changes in the elastic properties of the zeolite crystals. Finally, even though this method was applied to a zeolite film, it is quite general, and it can be used for measuring the elastic modulus of any microporous or mesoporous film.01/2008; -
Article: Monitoring blood coagulation with magnetoelastic sensors.
[show abstract] [hide abstract]
ABSTRACT: The determination of blood coagulation time is an essential part of monitoring therapeutic anticoagulants. Standard methodologies for the measurement of blood clotting time require dedicated personnel and involve blood sampling procedures. A new method based on magnetoelastic sensors has been employed for the monitoring of blood coagulation. The ribbon-like magnetoelastic sensor oscillates at a fundamental frequency, which shifts linearly in response to applied mass loads or a fixed mass load of changing elasticity. The magnetoelastic sensors emit magnetic flux, which can be detected by a remotely located pick-up coil, so that no direct physical connections are required. During blood coagulation, the viscosity of blood changes due to the formation of a soft fibrin clot. In turn, this change in viscosity shifts the characteristic resonance frequency of the magnetoelastic sensor enabling real-time continuous monitoring of this biological event. By monitoring the signal output as a function of time, a distinct blood clotting profile can be seen. The relatively low cost of the magnetoelastic ribbons enables their use as disposable sensors. This, along with the reduced volume of blood required, make the magnetoelastic sensors well suited for at-home and point-of-care testing devices.Biosensors and Bioelectronics 06/2003; 18(5-6):675-81. · 5.60 Impact Factor -
Article: The frequency response of magnetoelastic sensors to stress and atmospheric pressure
[show abstract] [hide abstract]
ABSTRACT: Earlier work demonstrated that the characteristic resonant frequency of magnetoelastic thick-film sensors shifts linearly downwards in response to increasing atmospheric pressure. In this paper, the response mechanism is detailed and shown to be a function of both pressure and the way that the sensor is mechanically stressed. Stressing the sensor, in either the elastic or plastic regime, induces out-of-plane vibrations that act as a pressure-dependent damping force to the longitudinal sensor oscillations excited by the interrogation field. This damping force, in turn, acts to shift the resonant frequency of the magnetoelastic sensor lower in response to increasing pressure.Smart Materials and Structures 11/2000; 9(6):885. · 2.09 Impact Factor
