A damped forward EMI model for a horizontally stratified earth

If a magnetic dipole is placed above the surface of the earth, the Electromagnetic Induction (EMI) effect, encoded in Maxwell's equations, causes eddy currents in the soil which, on their turn, induce response electromagnetic fields. The magnetic field can be measured in geophysical surveys to determine the conductivity profile of the ground in a non-destructive manner. The forward model used in the inversion of experimental data usually consists of a set of horizontal homogeneous layers. A frequently used analytical model, proposed by McNeill, does not include the interaction between the eddy currents, and therefore fails for larger conductivities. In this paper we construct a new forward, analytical, model to estimate the magnetic field caused by a horizontally stratified earth but which approximates the interaction between eddy currents. This makes it valid for a broader range of parameters than the current state of the art. Furthermore, the error with the (numerically obtainable) exact result is substantially decreased. We also calculate the vertical sensitivity ("depth of exploration") of the model and observe that it is in good agreement with the values obtained from the exact model.Comment: Accepted for publication in Exploration Geophysic

Development of an experimental inactivated PRRSV vaccine that induces virus-neutralizing antibodies

Porcine reproductive and respiratory syndrome virus (PRRSV) can induce reproductive disorders and is involved in the porcine respiratory disease complex, causing tremendous economic losses to the swine industry. Inactivated PRRSV vaccines are preferred over attenuated vaccines because of their safety and flexibility towards emerging virus strains, but the efficacy of current inactivated PRRSV vaccines is questionable. In this study, experimental inactivated PRRSV vaccines were developed, based on two formerly optimized inactivation procedures: UV irradiation and treatment with binary ethylenimine (BEI). In a first experiment, it was shown that vaccination with UV- or BEI-inactivated virus in combination with Incomplete Freund's Adjuvant induced virus-specific antibodies and strongly primed the virus-neutralizing (VN) antibody response. Subsequently, the influence of adjuvants on the immunogenicity of neutralizing epitopes on the inactivated virus was investigated. It was shown that vaccination with BEI-inactivated virus in combination with a commercial oil-in-water adjuvant induced high titers (3.4 log(2)) of VN antibodies in 6/6 pigs, instead of only priming the neutralizing antibody response. After challenge, neutralizing antibody titers in these vaccinated animals rose to a mean value of 5.5 log(2), and the duration of the viremia was reduced to an average of 1 week. This study shows that, by the use of an optimized inactivation procedure and a suitable adjuvant, inactivated PRRSV vaccines can be developed that induce VN antibodies and offer partial protection upon challenge

Spontaneous variability of pre-dialysis concentrations of uremic toxins over time in stable hemodialysis patients

Background and aim : Numerous outcome studies and interventional trials in hemodialysis (HD) patients are based on uremic toxin concentrations determined at one single or a limited number of time points. The reliability of these studies however entirely depends on how representative these cross-sectional concentrations are. We therefore investigated the variability of predialysis concentrations of uremic toxins over time. Methods : Prospectively collected predialysis serum samples of the midweek session of week 0, 1, 2, 3, 4, 8, 12, and 16 were analyzed for a panel of uremic toxins in stable chronic HD patients (N = 18) while maintaining dialyzer type and dialysis mode during the study period. Results : Concentrations of the analyzed uremic toxins varied substantially between individuals, but also within stable HD patients (intra-patient variability). For urea, creatinine, beta-2-micro-globulin, and some protein-bound uremic toxins, Intra-class Correlation Coefficient (ICC) was higher than 0.7. However, for phosphorus, uric acid, symmetric and asymmetric dimethylarginine, and the protein-bound toxins hippuric acid and indoxyl sulfate, ICC values were below 0.7, implying a concentration variability within the individual patient even exceeding 65% of the observed inter-patient variability. Conclusion : Intra-patient variability may affect the interpretation of the association between a single concentration of certain uremic toxins and outcomes. When performing future outcome and interventional studies with uremic toxins other than described here, one should quantify their intra-patient variability and take into account that for solutes with a large intra-patient variability associations could be missed

Uraemic toxin concentration variability in HD patients: can we still rely on the results of cross-sectional studies?

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Simulation study of the localization of a near-surface crack using an air-coupled ultrasonic sensor array

The importance of Non-Destructive Testing (NDT) to check the integrity of materials in different fields of industry has increased significantly in recent years. Actually, industry demands NDT methods that allow fast (preferably non-contact) detection and localization of early-stage defects with easy-to-interpret results, so that even a non-expert field worker can carry out the testing. The main challenge is to combine as many of these requirements in one single technique. The concept of acoustic cameras, developed for low frequency NDT, meets most of the above mentioned requirements. These cameras make use of an array of microphones to visualize noise sources by estimating the Direction Of Arrival (DOA) of the impinging sound waves. Until now, however, because of limitations in frequency range and lack of integrated nonlinear post-processing, acoustic camera systems have never been used for the localization of incipient damage. The goal of the current paper is to numerically investigate the capabilities of locating incipient damage by measuring the nonlinear airborne emission of the defect using a non-contact ultrasonic sensor array. We will consider a simple case of a sample with a single near-surface crack and prove that after efficient excitation of the defect sample, the nonlinear defect responses can be detected by a uniform linear sensor array. These responses are then used to determine the location of the defect by means of three different DOA algorithms. The results obtained in this study can be considered as a first step towards the development of a nonlinear ultrasonic camera system, comprising the ultrasonic sensor array as hardware and nonlinear post-processing and source localization software.status: publishe

Recent advances in the ultrasonic polar scan method for characterizing (degraded) fiber reinforced plastics

The ultrasonic polar scan (UPS) technique originated in the 1980's as a sophisticated method for inspecting composites. However, it is only in recent times that the true capabilities and strengths of the UPS methodology have been evidenced through experiment and simulation. Nowadays, the UPS method exists in different versions which led to several novel applications in the field of material inspection and characterization. This contribution gives an overview of our recent advances

The effects of feedback valence and style on need satisfaction, self-talk, and perseverance among tennis players : an experimental study

Grounded in self-determination theory, this experimental study examined whether the valence (ire., positive vs. negative) and style (i.e., autonomy-supportive vs. controlling) of normative feedback impact the self-talk, motivational experiences (i.e., psychological need satisfaction and enjoyment), and behavioral functioning (i.e., perseverance and performance) of tennis players (N = 120; M-age = 24.50 +/- 9.86 years). Positive feedback and an autonomy-supportive style positively influenced players' enjoyment and perseverance, with psychological need satisfaction and self-talk playing an intervening role. While positive feedback yielded its beneficial effect via greater competence satisfaction and decreased negative self-talk, the beneficial impact of an autonomy-supportive communication style was explained via greater autonomy satisfaction