Dielectric characterisation of soil

The potential of dielectric measuring techniques for soil characterisation has not been fully explored. This is attributed to the complex and incomplete theory on dielectrics, as well as to the lack of sensors suited for practical applications.The theory on dielectric properties of soils is described, evaluated, and expanded. Colloidal polarisation of soil particles appears to be negligible. The polarisability of air bubbles in the soil matrix is made plausible. The Maxwell-Wagner effect is expressed in the form of a Debye function. A soil texture parameter is introduced that can be derived from dielectric measurements at three frequencies. Newly derived are a relationship between the soil water matric pressure and the dielectric relaxation frequency, a dielectric mixture equation with depolarisation factors that account for electromagnetic field refractions at the boundary between two soil materials, and a model to predict permittivity versus frequency from soil porosity, water content, and matric pressure.A model of sensors for Frequency Domain (FD) measurements as well as for Time Domain Reflectometry (TDR) is described. An integrated circuit (ASIC) has been developed that is based on synchronous detection and is intended for practical low-cost dielectric sensors. Algorithms correct for phase errors, parasitic impedances of the ASIC and electrical length of electrodes and wiring. These elements are incorporated in a new FD sensor, operated at 20 MHz.The new theory is tested in different ways using the new FD sensor and TDR. Calibration curves of water content versus electrical permittivity of different soil types compare reasonably well with predicted curves. The Maxwell-Wagner effect increases with increasing water content and specific surface area. The electrical conductivity of the extracted soil solution can be determined by simultaneous measurements of the electrical permittivity and bulk conductivity. This method proved accurate for glass beads and for most tested soils. Soil layers polluted with chlorinated solvents or oil are detected by measuring the same parameters as function of depth. The frequency dependence of the bulk electrical conductivity, attributed to the Maxwell-Wagner effect, is analysed by measurements at three frequencies.Hydrating concrete is shown to simulates the dielectric behaviour of soils of different textures. Its dielectric spectrum from 10 MHz to I GHz illustrates the effect of water binding (> 100 MHz) and the Maxwell-Wagner effect (&lt; 100 MHz). Around 100 MHz concrete exhibits only small changes of the dielectric properties; this is known to occur also for soils of different textures. The compressive strength of concrete appears to be predictable from the electrical permittivity at 20 MHz, due to the Maxwell-Wagner effect.Due to the simplification to apply a single sine wave rather than a pulse or step function, existing theory is inadequate to correct TDR measurements of water content for the effect of electrical conductivity. TDR electrical conductivity measurements are found to be low-frequency (< 3 MHz) measurements

Reduction of methane emissions from manure

An investigation is made of potential CH4 emission reduction options evaluated in the context of NH3 and N2O emissions

Should health care professionals encourage living kidney donation?

Living kidney donation provides a promising opportunity in situations where the scarcity of cadaveric kidneys is widely acknowledged. While many patients and their relatives are willing to accept its benefits, others are concerned about living kidney programs; they appear to feel pressured into accepting living kidney transplantations as the only proper option for them. As we studied the attitudes and views of patients and their relatives, we considered just how actively health care professionals should encourage living donation. We argue that active interference in peoples’ personal lives is justified - if not obligatory. First, we address the ambiguous ideals of non-directivity and value neutrality in counselling. We describe the main pitfalls implied in these concepts, and conclude that these concepts cannot account for the complex reality of living donation and transplantation. We depict what is required instead as truthful information and context-relative counselling. We then consider professional interference into personal belief systems. We argue that individual convictions are not necessarily strong, stable, or deep. They may be flawed in many ways. In order to justify interference in peoples’ personal lives, it is crucial to understand the structure of these convictions. Evidence suggests that both patients and their relatives have attitudes towards living kidney donation that are often open to change and, accordingly, can be influenced. We show how ethical theories can account for this reality and can help us to discern between justified and unjustified interference. We refer to Stephen Toulmin’s model of the structure of logical argument, the Rawlsian model of reflective equilibrium, and Thomas Nagel’s representation of the particularistic position

On a free boundary problem for a two-species weak competition system

[[abstract]]We study a Lotka–Volterra type weak competition model with a free boundary in a one-dimensional habitat. The main objective is to understand the asymptotic behavior of two competing species spreading via a free boundary. We also provide some sufficient conditions for spreading success and spreading failure, respectively. Finally, when spreading successfully, we provide an estimate to show that the spreading speed (if exists) cannot be faster than the minimal speed of traveling wavefront solutions for the competition model on the whole real line without a free boundary.[[incitationindex]]SCI[[booktype]]紙本[[booktype]]電子

Expanding the genetic and phenotypic spectrum of ACTA2-related vasculopathies in a Dutch cohort

Purpose: Heterozygous pathogenic/likely pathogenic (P/LP) variants in the ACTA2 gene confer a high risk for thoracic aortic aneurysms and aortic dissections. This retrospective multicenter study elucidates the clinical outcome of ACTA2-related vasculopathies. Methods: Index patients and relatives with a P/LP variant in ACTA2 were included. Data were collected through retrospective review of medical records using a standardized questionnaire. Results: A total of 49 individuals from 28 families participated in our study. In total, 20 different ACTA2 variants were detected. Aortic events occurred in 65% of the cases (78.6% index patients and 47.6% relatives). Male sex and hypertension emerged as significantly associated with aortic events. Of 20 individuals, 5 had an aortic diameter of <45 mm (1.77 inches) at the time of the type A dissection. Mean age at first aortic event was 49.0 ± 12.4 years. Severe surgical complications for type A and type B dissection occurred in 25% and 16.7% of the cases and in-hospital mortality rates were 9.5% and 0%, respectively. Conclusion: P/LP ACTA2 variants are associated with an increased risk for an aortic event and age-related penetrance, which emphasizes the importance of early recognition of the disease. Caregivers should be aware of the risk for aortic dissections, even in individuals with aortic diameters within the normal range