Monitoring of polyethylene wear in nonmetal-backed acetubular cups by digitized anteroposterior pelvic radiography

The aim of this study was to assess polyethylene wear in a total hip prosthesis by digitized radiography of the whole pelvis in the anteroposterior (AP) plane. The three-dimensional (3-D) pose of the nonmetal-backed acetubular cup, materialized by its metal ring and the femoral head made of metal or ceramic, was estimated using iterative algebraic algorithms with inner bias correction and bootstrapping for variance reduction. Points of interest were obtained by maximizing the correlation between sampled density profiles and 3-D geometric models degraded by the modulation transfer function (MTF) of the radiographic system and the film scanner. The error in the maximal correlation estimate were inferred from noise power spectra (NPS) and allowed the calculation of the point covariance matrix. Both NPS and MTF were modeled for each stage and estimated using least-square fitting of the overall NPS model to the autospectral density function calculated in stationary regions. Comparison of the radiographic time series was made possible by the high accuracy level and 3-D matching from the cup orientation. The feasibility of the full 3-D measurement, the assumption of negligible lateral wear and its influence on AP wear are discussed on simulated and real radiographic data.     

Gas discrimination in an air-conditioned system

In this work, an identification system based on an array of semiconductor tin dioxide gas sensors has been developed. This system has provided a good success rate in the discrimination of carbon dioxide, forane R134a or their mixtures without a sensor dedicated to carbon dioxide. After a characterization of the five-sensor array, pretreatment was tested on the collected data to select the most representative parameters. Then the information contained in the resulting look-up table was analyzed with PCA, but no significant result was observed. Discriminant factorial analysis was then used and has shown a better separation of the different clusters. Next, unknown data were taken to validate the classification. The results show that a reliable system can be designed using nondedicated chemical semiconductor gas sensors     

Impact of power level and refill liquid composition on the aerosol output and particle size distribution generated by a new-generation e-cigarette device

The new high-power Electronic Nicotine Delivery System (ENDS) can generate aerosols with higher nicotine concentrations than older ENDS. Aerosol particle sizes affect deposition patterns and then plasma nicotine levels in vapers. Consequently, understanding the factors influencing particle size distribution of high-power ENDS is relevant to assess their performance in terms of nicotine delivery. The particle size distribution and the aerosol output (aerosol mass) were measured using cascade impactors. The effects of the refill liquid composition (80% PG/20% VG vs. 80% VG/20% PG; PG refers to propylene glycol and VG to vegetable glycerin) and the power level of the battery (from 7 W to 22 W) were investigated. The aerosol output increases significantly with the power level following a logarithmic law. The PG/VG ratio also has an impact on the aerosol output. The higher the VG content in the refill liquid, the higher is the aerosol output. Besides, particle size distribution is positively related to the power level, following linear correlations between the mass median aerodynamic diameter (MMAD) and the power level in the range of 7–22 W. A moderate impact of the PG/VG ratio on size distribution is equally observed. Changes in the power level allow the transition between a dominant mode with MMAD from 613 nm to 949 nm. We demonstrated that the power level can strongly change the aerodynamic properties of high-power ENDS, especially at high voltage. Associated with the aerosol nicotine level assessment, MMAD could be determined as a means for comparing ENDS devices and nicotine delivery.

Copyright © 2018 American Association for Aerosol Research     

Layer thickness impact on the capacity of poly(urethaneimide) for sorbing toxic gases

The sensitivity of a thick layer (500 nm) of poly(urethaneimide) to toxic gases such as pyridine and hexamethyleneimine was studied by the quartz crystal microbalance method. The resonant frequency was registered by a spectrum analyzer. The successful overcoming of the unfavorable impact of the increased viscous damping, typical for the standard oscillator measurement method, allowed complete understanding of the behavior of a thick polymer layer toward highly pollutant gases. Quantitative information for polymer adsorption capacity and gas diffusivity was extracted. The comparison with our recent results for thinner layers revealed strong dependence on layer thickness for pyridine whereas the corresponding effect with hexamethyleneimine was found much less significant. Intermolecular interactions and the impact of the gas physical adsorption on the polymer matrix properties were shown as the driving parameters for the sensors response. The thickness dependence provides a tool for tuning the sensitivity of a potentially efficient poly(urethaneimide) sensor for pyridine. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44214.     

Theoretical and Experimental Identification of Love Wave Frequency Peaks in Layered Structure ZnO/Quartz SAW Device

In this paper, the layered structure ZnO/Quartz (90^deg rotated ST-cut) is investigated theoretically and experimentally. Both waves, Rayleigh and Love, are analyzed. Dispersion curves of phase velocities, electromechanical coupling coefficient (K ²) and temperature coefficient of frequency (TCF) were calculated as a function of normalized thickness ZnO film (kh _ZnO = 2pih _ZnO /lambda) and the optimum value of h _ZnO was determined for experimental study. Experimental results combined with simulation lead to clearly identify the generated waves and their higher modes in this structure except the mode 0 that shows comparable velocity for both Rayleigh and Love waves. The identification of the wave type was performed by studying the frequency response of the device with or without a droplet of water in the wave path. We also demonstrate that the highest elastic velocity is obtained for the mode 1 of the Love wave. This Love wave mode exhibits very interesting electrical characteristics, good K ², high-frequency rejection, low TCF, and very low attenuation in liquid making it very attractive for gas and liquid sensor applications.     

Nonsupervised ranking of different segmentation approaches: application to the estimation of the left ventricular ejection fraction from cardiac cine MRI sequences

A statistical methodology is proposed to rank several estimation methods of a relevant clinical parameter when no gold standard is available. Based on a regression without truth method, the proposed approach was applied to rank eight methods without using any a priori information regarding the reliability of each method and its degree of automation. It was only based on a prior concerning the statistical distribution of the parameter of interest in the database. The ranking of the methods relies on figures of merit derived from the regression and computed using a bootstrap process. The methodology was applied to the estimation of the left ventricular ejection fraction derived from cardiac magnetic resonance images segmented using eight approaches with different degrees of automation: three segmentations were entirely manually performed and the others were variously automated. The ranking of methods was consistent with the expected performance of the estimation methods: the most accurate estimates of the ejection fraction were obtained using manual segmentations. The robustness of the ranking was demonstrated when at least three methods were compared. These results suggest that the proposed statistical approach might be helpful to assess the performance of estimation methods on clinical data for which no gold standard is available.     

Immersive front-projection analysis using a radiosity-based simulation method

Video projectors are designed to project onto flat white diffuse screens. Over the last few years, projector-based systems have been used, in virtual reality applications, to light non-specific environments such as the walls of a room. However, in these situations, the images seen by the user are affected by several radiometric disturbances, such as interreflection. Radiometric compensation methods have been proposed to reduce the disturbance caused by interreflection, but nothing has been proposed for evaluating the phenomenon itself and the effectiveness of compensation methods. In this paper, we propose a radiosity-based method to simulate light transfer in immersive environments, from a projector to a camera (the camera gives the image a user would see in a real room). This enables us to evaluate the disturbances resulting from interreflection. We also consider the effectiveness of interreflection compensation and study the influence of several parameters (projected image, projection onto a small or large part of the room, reflectivity of the walls). Our results show that radiometric compensation can reduce the influence of interreflection but is severely limited if we project onto a large part of the walls around the user, or if all the walls are bright.     

GHz frequency ZnO/Si SAW device

The demand for high-frequency low-loss filters generates intensive research on innovative wave guide solutions. In this work, a GHz SAW device based on a ZnO/Si structure was fabricated using classical UV photolithography. The thickness of the piezoelectric thin film was optimized and a specific interdigital transducer structure was used to generate third and fifth harmonic guided waves at 2.5 GHz and 3.5 GHz, respectively, with an aluminum strip larger than 1 micrometer. Different modes have been measured and theoretically identified thanks to an advanced finite-element/boundary-elementbased model. Good agreement is found between theory and experiments. The high-frequency modes have been fully characterized, allowing for accurate design of SAW devices exploiting such modes.     

Mechanistic investigation of 9-bromoanthracene photodimers as initiators in atom transfer radical polymerization

Mechanistic pathways accounting for the lack of control in polymerizations employing photodimers of 9-bromoanthracene as alkyl halide initiators in atom transfer radical polymerization (ATRP) reactions are presented. Converting the aryl bromide on the anthracene moiety into an alkyl bromide via a [4+4] cycloaddition reaction effectively generated the photodimer with two alkyl halide sites, which were investigated as potential initiating sites for the ATRP of styrene and n-butyl acrylate. Polymers synthesized using these photodimers as initiators possessed relatively broad polydispersity index (PDI) values and displayed a non-linear relationship between their number average molecular weights (M_n) and monomer consumption, consistent with slow initiation from the bridgehead alkyl halide. Reactions performed at 80 °C in bulk or THF generated polystyrene with M_n values 3-5 times higher than calculated based on monomer-to-initiator ratios. UV-vis spectrometry of the products demonstrated absorbance bands indicative of polymer-bound anthracene, caused by thermal degradation of the photodimer during the polymerization. When the initiator was introduced last into the reaction mixture in an attempt to suppress photodimer cleavage prior to initiation, PDI values and M_n values were generally lowered with the resulting polymers showing similarly high anthracene content. Composition of polystyrene and poly(n-butyl acrylate) products was also studied as a function of reaction temperature, with decreased anthracene labeling observed at lower temperatures (40 and 60 °C), further validating a model of heat-induced cleavage of the photodimer.