Moose and snowshoe hare competition and a mechanistic explanation from foraging theory

Moose ( Alces alces ) and snowshoe hare ( Lepus americanus ) appear to compete with each other. This was determined using the “natural experiments” of populations found in sympatry and allopatry on islands at Isle Royale National Park, Michigan, and manipulated exclosures. The population densities from these areas are fit to a series of competition models based upon different competitive mechanisms (Schoener 1974a), using non-linear regression techniques. A model of competition for food where the food can be separated into exclusively used and shared categories is found to predict observed densities of moose and hare best. Finally, the competition model's parameters (fraction of food shared and competition coefficients) are shown to agree with values predicted independently from a foraging model.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47750/1/442_2004_Article_BF00396753.pd

Sunlight exposure exerts immunomodulatory effects to reduce multiple sclerosis severity

Multiple sclerosis (MS) disease risk is associated with reduced sun-exposure. This study assessed the relationship between measures of sun exposure (vitamin D [vitD], latitude) and MS severity in the setting of two multicenter cohort studies (n(NationMS) = 946, n(BIONAT) = 990). Additionally, effect-modification by medication and photosensitivity-associated MC1R variants was assessed. High serum vitD was associated with a reduced MS severity score (MSSS), reduced risk for relapses, and lower disability accumulation over time. Low latitude was associated with higher vitD, lower MSSS, fewer gadolinium-enhancing lesions, and lower disability accumulation. The association of latitude with disability was lacking in IFN-β-treated patients. In carriers of MC1R:rs1805008(T), who reported increased sensitivity toward sunlight, lower latitude was associated with higher MRI activity, whereas for noncarriers there was less MRI activity at lower latitudes. In a further exploratory approach, the effect of ultraviolet (UV)-phototherapy on the transcriptome of immune cells of MS patients was assessed using samples from an earlier study. Phototherapy induced a vitD and type I IFN signature that was most apparent in monocytes but that could also be detected in B and T cells. In summary, our study suggests beneficial effects of sun exposure on established MS, as demonstrated by a correlative network between the three factors: Latitude, vitD, and disease severity. However, sun exposure might be detrimental for photosensitive patients. Furthermore, a direct induction of type I IFNs through sun exposure could be another mechanism of UV-mediated immune-modulation in MS

On the transient process of contact erosion (instabilities during granular erosion)

Internal erosion is one of the major threats for water retaining structures like embankment dams or levees. Numerous design criteria were developed in the last decades for this reason. As the main concern of the geotechnical engineer is to prevent erosion, it is not astonishing that a vast majority of the criteria are focussed on the onset or initiation of erosion, or more precise, to avoid it. However, many existing structures have already experienced the one or other event of internal erosion. Thus, it is beneficial to understand not only the initiation, but also the progression of the erosion process. This process is though still not completely understood.Among the different types of internal erosion, contact erosion is characterised by two soils (base and filter) of different grain size distributions (PSD) forming an interface to each other. The erosion process is triggered by a water flow, which can be either parallel or perpendicular to the interface. The latter configuration is sometimes referred to as filtration and is in the focus of this research. If erosion occurs, base particles are transported into the pores of the filter by a water flow, forming a mixture zone with a lower porosity and permeability. For a better understanding of the contact erosion process, the formation of this zone must be understood. Two main aspects can be identified: The behaviour of the base material under the hydraulic load and the arrangement of the particles in the mixture zone, which is expressed in the porosity as a macroscopic parameter.Porosity alterations during erosion tests can be determined in different ways. These are among others: Direct observations of changes in layer heights, Computed Tomography (CT) and radiometric methods. Electromagnetic methods take advantage of the different dielectric permittivity of the solid, liquid and gaseous phases of a soil, which interact with an electric pulse travelling along a sensor surrounded by the material under test. An average value can be obtained with Time Domain Reflectometry (TDR). With an inversion algorithm, the spatial distribution of the parameter of interest, e.g. porosity or moisture, can be computed out of the TDR-trace. This method is called Spatial TDR (STDR), which was chosen for this research work. The three step inverse model was established and refined for this setup and its accuracy proven in calibration and verification measurements.In order to study the behaviour of the base material alone under hydraulic load, a test stand called Fluidisation Setup was developed. Different base materials were tested under increasing hydraulic potentials up to the point of hydraulic heave. The inner stress conditions during this tests were checked with vane-shear-tests. A clear correlation of shear resistance and hydraulic load was found. Additionally, the dielectric permittivity of the material was measured up to high porosities obtained during the fluidisation.A Coaxial Erosion Cell (CEC) was developed to act as a sensor by itself for the erosion tests. The coaxial arrangement ensures an even and defined distribution of the electromagnetic field, which is beneficial for the accuracy of the measurements. The material under test is positioned in the annulus between inner and outer conductor. An inspection window allows visual observations and pressure transducers the reading of the distribution of the hydraulic head along the cell. With this cell and the STDR-measurements, the longitudinal distribution of the porosity during the tests can be determined in nearly real time in short intervals. A second cell of a more conventional setup was used for verifying the results of the CEC. Additionally, superimposed loads were applied in this tests in order to study the influence of different effective stresses on onset and progress of contact erosion.It was found that the size ratio of base and filter pores has a considerable influence on the initiation and progress of the erosion process. It not only influences the hydraulic gradient at which the process may initiate, but also the porosity and the distribution of the hydraulic gradient in the formed MZ as well as the elevation of the MZ for a given gradient. It further has an influence on the effect of effective stresses on the onset of erosion

Electromagnetic characterization of coarse-grained soils with a one port large coaxial cell

This paper reports the design, the calibration and the application of a one port large coaxial cell. The objective of the device is to characterize the electromagnetic properties of compacted and partly saturated coarse grained soil under controlled boundary conditions. The dielectric spectra were obtained by means of fitting the measured scattering function using a Transvers electromagnetic mode (TEM) propagation model considering the frequency dependent complex permittivity. The method was applied on a construction site material with aggregate up to 15 mm. 6 samples were characterized, the results showing a good agreement in terms of Root Mean square error

Determination of the porosity distribution during an erosion test using a coaxial line cell

The detection of porosity changes within a soil matrix caused by internal erosion is beneficial for a better understanding of the mechanisms that induce and maintain the erosion process. In this paper, an electromagnetic approach using Spatial Time Domain Reflectometry (STDR) and a transmission line model is proposed for this purpose. An original experimental setup consisting of a coaxial cell which acts as an electromagnetic waveguide was developed. It is connected to a transmitter/receiver device both measuring the transmitted and corresponding reflected electromagnetic pulses at the cell entrance. A gradient optimization method based on a computational model for simulating the wave propagation in a transmission line is applied in order to reconstruct the spatial distribution of the soil dielectric permittivity along the cell based on the measured signals and an inversion algorithm. The spatial distribution of the soil porosity is deduced from the dielectric permittivity profile by physically based mixing rules. Experiments were carried out with glass bead mixtures of known dielectric permittivity profiles and subsequently known spatial porosity distributions to validate and to optimize both, the proposed computational model and the inversion algorithm. Erosion experiments were carried out and porosity profiles determined with satisfying spatial resolution were obtained. The RMSE between measured and physically determined porosities varied among less than 3% to 6%. The measurement rate is sufficient to be able to capture the transient process of erosion in the experiments presented here

Experimental investigation of the dielectric properties of soil under hydraulic loading

An experimental set-up was developed in order to determine the coupled hydraulic, dielectric and mechanical properties of granular media under hydraulic loading. The set-up consisted of a modified column for permeability tests involving a flow meter and pressure transducers along the sample to quantify the hydraulic gradient. A newly developed open-ended coaxial probe allowed the measurement of the frequency dependent dielectric permittivity of the material under test. The shear strength of the sample within the column was measured using a conventional vane shear device. In this paper, the overall set-up is introduced with focus on the open-ended coaxial probe. The design and calibration of the probe are introduced in detail. A numerical study showed that the sensitive cylindrical volume of the probe was approximately 150 mm in diameter with a depth of 65 mm. An investigation with glass beads showed that the set-up allowed the parameterization of the hydraulic, mechanic and dielectric parameters of granular materials under the influence of vertical flow. A satisfactorily good correlation between porosity and the real part of the dielectric permittivity was detected. The critical hydraulic gradient defining the transition of a fixed bed of particles to fluidization was characterized by a sharp peak in the evolution of the hydraulic conductivity and could easily be determined from the measurements. The shear strength of the material under test reduces linearly with increasing hydraulic gradient. Future investigations will be carried out to provide the required parameterizations for experimental and numerical investigations of the internal erosion of granular media

A large coaxial reflection cell for broadband dielectric characterization of coarse-grained materials

Knowledge of the frequency-dependent electromagnetic properties of coarse-grained materials is imperative for the successful application of high frequency electromagnetic measurement techniques for near and subsurface monitoring. This paper reports the design, calibration and application of a novel one-port large coaxial cell for broadband complex permittivity measurements of civil engineering materials. It was designed to allow the characterization of heterogeneous material with large aggregate dimensions (up to 28 mm) over a frequency range from 1 MHz-860 MHz. In the first step, the system parameters were calibrated using the measured scattering function in a perfectly known dielectric material in an optimization scheme. In the second step, the method was validated with measurements made on standard liquids. Then the performance of the cell was evaluated on a compacted coarse-grained soil. The dielectric spectra were obtained by means of fitting the measured scattering function using a transverse electromagnetic mode propagation model considering the frequency-dependent complex permittivity. Two scenarios were systematically analyzed and compared. The first scenario consisted of a broadband generalized dielectric relaxation model with two Cole-Cole type relaxation processes related to the interaction of the aqueous phase and the solid phase, a constant high frequency contribution as well as an apparent direct current conductivity term. The second scenario relied on a three-phase theoretical mixture equation which was used in a forward approach in order to calibrate the model. Both scenarios provide almost identical results for the broadband effective complex relative permittivity. The combination of both scenarios suggests the simultaneous estimation of water content, density, bulk and pore water conductivity for road base materials for in situ applications

Design of two large coaxial cells for studying physical process using spatial TDR

This paper reports the design of two large coaxial cells for studying spatial distribution of state parameters during physical process using Spatial Time Domain Reflectometry (Spatial TDR). The first cell is designed to measure the spatial distribution of porosity during erosion. The main idea is to integrate in a large coaxial cell a water flow to induce erosion. The second cell is designed to study spatial distribution of water content during smouldering. The innovation here is to transform an existing smouldering reactor into a large coaxial cell for measuring the spatial distribution of the apparent dielectric permittivity. Both examples illustrate the versatility of electromagnetic measurement methods thanks to innovative cell design

Soluble Neuropilin-1 is an independent marker of poor prognosis in early breast cancer

Background!#!Neuropilin-1 (NRP-1) is a transmembrane protein that acts as a multifunctional non-tyrosine kinase receptor with an established role in development and immunity. NRP-1 also regulates tumor biology, and high expression levels of tissue NRP-1 have been associated with a poor prognosis. Recently, ELISA-based quantification of soluble NRP-1 (sNRP-1) has become available, but little is known about the prognostic value of sNRP-1 in malignancies.!##!Materials and methods!#!We measured sNRP-1 in the serum of 509 patients with primary early breast cancer (BC) at the time of diagnosis using ELISA.!##!Results!#!Mean serum values of sNRP-1 were 1.88 ± 0.52 nmol/l (= 130.83 ± 36.24 ng/ml). SNRP-1 levels weakly correlated with age, and were higher in peri- and postmenopausal patients compared to premenopausal patients, respectively (p < 0.0001). Low levels of sNRP-1 were associated with a significant survival benefit compared to high sNRP-1 levels at baseline (p = 0.005; HR 1.94; 95%CI 1.23-3.06). These findings remained significant after adjustment for tumor stage including lymph node involvement, grading, hormone receptor, HER2 status, and age (p = 0.022; HR 1.78; 95%CI 1.09-2.91).!##!Conclusion!#!Our findings warrant further investigations into the prognostic and therapeutic potential of sNRP-1 in BC