Search results for "zoe"

On the use of the electromechanical impedance technique for the assessment of dental implant stability: Modeling and experimentation

2014

We propose the electromechanical impedance technique to monitor the stability of dental implants. The technique consists of bonding one wafer-type piezoelectric transducers to the implant system. When subjected to an electric field, the transducer induces structural excitations which, in turn, affect the transducer’s electrical admittance. The hypothesis is that the health of the bone surrounding the implant affects the sensor’s admittance. A three-dimensional finite element model of a transducer bonded to the abutment of a dental implant placed in a host bone site was created to simulate the progress of the tissue healing that occurs after surgery. The healing was modeled by changing the …

A new method to calculate external mechanical work using force-platform data in ecological situations in humans: Application to Parkinson's disease

2016

Abstract Background and aim To accurately quantify the cost of physical activity and to evaluate the different components of energy expenditure in humans, it is necessary to evaluate external mechanical work ( W EXT ). Large platform systems surpass other currently used techniques. Here, we describe a calculation method for force-platforms to calculate long-term W EXT . Methods Each force-platform (2.46 × 1.60 m and 3.80 × 2.48 m) rests on 4 piezoelectric sensors. During long periods of recording, a drift in the speed of displacement of the center of mass (necessary to calculate W EXT ) is generated. To suppress this drift, wavelet decomposition is used to low-pass filter the source signal.…

The influence of surgical experience on the rate of intraoperative aneurysm repture and its impact on aneurysm treatment outcome.

2001

Abstract BACKGROUND The influence of surgical experience on the result of aneurysm surgery remains unclear. To determine the impact of surgical experience we considered the occurrence of intraoperative aneurysm rupture (IAR) during microneurosurgery for intracranial aneurysms as an objective factor that could be evaluated. METHODS A retrospective study was performed on 379 consecutive patients with 490 cerebral aneurysms operated upon from 1989 to 1995. RESULTS IAR occurred in 6.7% of aneurysms and 8.7% of patients. There was a direct inverse relationship between the annual caseload of the surgeon and the risk of IAR. New neurological deficits (NND) occurred in 21% of patients with IAR, whi…

Clinical evaluation of piezoelectric ear surgery

2008

We evaluated the use of piezoelectric surgery (Piezosurgery; Mectron Medical Technology; Carasco, Genoa, Italy) as a means of avoiding some complications of osteotomy and osteoplasty in otologic surgery, particularly in classic canal-wall-up mastoidectomy. Piezoelectric surgery is a recently developed system for cutting bone with microvibrations created by the piezoelectric effect. This effect occurs when an electric current is passed through certain ceramics and crystals, causing them to oscillate at ultrasonic frequencies. Our study population was made up of 20 adults with unilateral chronic otitis media. In all patients, piezoelectric surgery allowed for effective, precise, safe, easy, …

Evidence of noncentrosymmetry of human tooth hydroxyapatite crystals

2014

Herein, we investigate human single hydroxyapatite crystals (enamel and dentine) by convergent-beam electron diffraction (CBED) and automated electron-diffraction tomography (ADT). The CBED pattern shows the absence of the mirror plane perpendicular to the c axis leading to the P63 space group instead of the P63 /m space group considered for larger-scale crystals, this is confirmed by ADT. This experimental evidence is of prime importance for understanding the morphogenesis and the architectural organization of calcified tissues.

Aristotle

2017

Caractérisation quantitative de la pulvérisation de pesticides par imagerie

2015

In recent years, advances in plant protection have contributed considerably to increasing crop yields in a sustainable way. Easy to apply and rather inexpensive, pesticides have proven to be very efficient. However, when pesticides are applied to crops some of the spray may not reach the target, but move outside the intended spray area. This can cause serious economic and environmental problems. Most of the pesticides are applied using agricultural sprayers. These sprayers use hydraulic nozzles which break the liquid into droplets with a wide range of droplet sizes and velocities and determine the spray pattern. Small droplets are prone to wind drift, while large droplets can runoff from th…

Comparative analysis of acoustic emission signals generated by electrical discharges measured by the hydrophone and the wideband contact transducer

2005

The paper presents a comparative analysis of the acoustic emission (AE) pulses and signals generated by PDs. For this purpose the measurements of the acoustic emission signals generated by PDs were taken in the multipoint-plane system using a hydrophone placed directly in the area of discharge generation, and the AE pulses using a piezoelectric contact transducer which was on a side wall of a power transformer tub. Next, time runs and amplitude density spectra were drawn. Also the descriptors describing signals in the frequency domain were determined and the time-frequency analysis was carried out, which determined spectrograms for the energy density spectrum.

Label-free piezoelectric biosensor for prognosis and diagnosis of Systemic Lupus Erythematosus

2017

[EN] An autoantigen piezoelectric sensor to quantify specific circulating autoantibodies in human serum is developed. The sensor consisted on a quartz crystal microbalance with dissipation monitoring (QCM-D) where TRIM21 and TROVE2 autoantigens were covalently immobilized, allowing the selective determination of autoantibodies for diagnosis and prognosis of Systemic Lupus Erythematosus (SLE). The sensitivity of the biosensor, measured as IC50 value, was 1.51 U/mL and 0.32 U/mL, for anti-TRIM21 and anti-TROVE2 circulating autoantibodies, respectively. The sensor is also able to establish a structural interaction fingerprint pattern or profile of circulating autoantibodies, what allows scorin…

Application of dual boundary element method in active sensing

2013

In this paper, a boundary element method (BEM) for the dynamic analysis of 3D solid structures with bonded piezoelectric transducers is presented. The host structure is modelled with BEM and the piezoelectric transducers are formulated using a 3D semi-analytical finite element approach. The elastodynamic analysis of the entire structure is carried out in Laplace domain and the response in time domain is obtained by inverse Laplace transform. The BEM is validated against established finite element method (FEM).