Proton NMR relaxometry as a useful tool to evaluate swelling processes in peat soils

Dramatic physical and physico-chemical changes in soil properties may arise due to temperature and moisture variations as well as swelling of soil organic matter (SOM) under constant conditions. Soil property variations may influence sorption/desorption and transport processes of environmental contaminants and nutrients in natural-organic-matterrich soils. Notwithstanding the studies reported in literature, a mechanistic model for SOM swelling is unavailable yet. The objective of the present study was the evaluation of the swelling of peat soils, considered as SOM models, by 1H NMR relaxometry and differential scanning calorimetry (DSC). Namely, information on the processes governing physical and physicochemical changes of peat during re-hydration were collected. The basic hypothesis of the present study was that the changes are slow and may affect water state as well as amounts of different water types into the peats. For this reason, such changes can be evidenced through the variations of mobility and thermal behaviour of the involved H2O molecules by using 1H NMR relaxometry and DSC. According to the experimental results, a mechanistic model, describing the fundamental processes of peat swelling, was obtained. Two different peats re-wetted at three temperatures were used. The swelling process was monitored by measuring spin-spin relaxation time (T2) over a hydration time of several months. Moreover, DSC, T1 – T2 and T2 – D correlation measurements were done at the beginning and at the end of the hydration. Supplementary investigations were also done in order to discriminate between the swelling effects and the contributions from soil solution, internal magnetic field gradients and/or soil microorganisms to proton relaxation. All the results revealed peat swelling. It was evidenced by pore size distribution changes, volumetric expansion and redistribution of water, increasing amounts of nonfreezable and loosely bound water, as well as formation of gel phases and reduction of the translational and rotational mobility of H2O molecules. All the findings implied that changes of the physical and physicochemical properties of peats were obtained. In particular, three different processes having activation energies comprised in the interval 5 – 50 kJ mol-1 were revealed. The mechanistic model which was, then, developed included water reorientation in bound water phases, water diffusion into the peat matrix and reorientation of SOM chains as fundamental processes governing SOM swelling. This study is of environmental significance in terms of re-naturation and re-watering of commercially applied peatlands and of sorption/desorption and transport processes of pollutants and nutrients in natural organic matter rich soil

Experimental investigations on the fatigue resistance of automatically welded tubular X-joints for jacket support structures

The development within the offshore wind sector towards more powerful turbines combined with increasing water depth for new wind parks is challenging both the designer as well as the manufacturer of bottom fixed support structures. Besides XL-monopiles, the market developed an innovative and economic jacket support structure which is based on automatically manufactured tubular joints combined with standardized pipes. Besides the improvements for a serial manufacturing process the automatically welded tubular joints show a great potential in terms of fatigue resistance e.g. due to a smooth weld geometry without sharp notches. However, these benefits are not considered yet within the fatigue design process of automatically manufactured jacket substructures according to current standards due to the lack of suitable S-N curves. Therefore, 32 axial fatigue tests on single and double-sided automatically welded tubular X-joints have been performed to determine a new hot spot stress related S-N curve. Based on these constant amplitude fatigue tests a new S-N curve equal to a FAT 126 curve was computed which implicitly includes the benefits of the automatically welding procedure. © Published under licence by IOP Publishing Ltd

The bend stiffness of S-DNA

We formulate and solve a two-state model for the elasticity of nicked, double-stranded DNA that borrows features from both the Worm Like Chain and the Bragg--Zimm model. Our model is computationally simple, and gives an excellent fit to recent experimental data through the entire overstretching transition. The fit gives the first value for the bending stiffness of the overstretched state as about 10 nm*kbt, a value quite different from either B-form or single-stranded DNA.Comment: 7 pages, 1 figur

Processes governing development of ecotoxicity in clayey and silty soils incubated with olive mill wast water under different temperature and humidity conditions

Olive oil production generates olive mill wastewater (OMW) with a high content in nutrients and phenolic substances. Its application to soil could be a cost-effective solution for recycling. However, the degree of toxic effects of OMW on soil biota is widely unknown and has to be considered when searching for adisposal strategy. The objective of this study was to understand the degradation process of OMW organic matter and its influence on toxic effects as well as soil properties. We hypothesized that OMW toxicity decreases with degradation of its phenolic components. A higher soil biological activity was expected to increase degradation. We incubated a clayey soil and a silty soil with OMW for 60 days under conditions typical for this region in order to simulate the application during various seasons (winter, spring, summer dry, summer wet). Soil respiration, pH, electrical conductivity, total phenolic content as well as anion and cation content, specific ultraviolet absorbance at 254 nm and dissolved organic carbon were measured at ten points of time during incubation. Soils and methanolic soil extracts were tested for ecotoxicity using Lepidium sativum germination and Folsomia candida egg hatching rate. The degradation and transformation of OMW-organic matter was stronger under warm and humid conditions than under cold and dry conditions. It was furthermore enhanced in the clayey soil compared to the silty soil. Most severe ecotoxicological effects were found under summer dry conditions while spring as well as summer wet conditions led to a fast recovery of both germination and hatching. However, the silty soil did not recover to preapplication levels. In the clayey soil, germination parameter were higher than in control after around 30 days suggesting a fertilizing effect. Effects in methanol extracts were higher in all soils and climatic scenarios. Therefore, remobilization of OMW derived toxic compounds has to be considered on a long-term scale. Egg hatching as most sensitive life-cycle parameter of Folsomia candida showed also the same relation to climatic conditions and soil type but was more robust to OMW compared to Lepidium sativum. Environmental conditions as well as soil type are key factors determining degradation of OMW organic matter and OMW derived ecotoxicity. Therefore, spring application (warm and wet) of OMW seems to be a compromise with regard to OMW recycling, OMW occurrence in winter and farmer considerations

Optimization-based calibration of hydrodynamic drag coefficients for a semisubmersible platform using experimental data of an irregular sea state

For the simulation of the coupled dynamic response of floating offshore wind turbines, it is crucial to calibrate the hydrodynamic damping with experimental data. The aim of this work is to find a set of hydrodynamic drag coefficients for the semisubmersible platform of the Offshore Code Comparison Collaboration, Continuation, with Correlation and unCertainity (OC6) project which provides suitable results for an irregular sea state. Due to the complex interaction of several degrees of freedom (DOF), it is common to calibrate drag coefficients with the time series of decay tests. However, applying these drag coefficients for the simulation of an irregular sea state results in misprediction of the motions. By using numerical optimization, it is possible to calibrate multiple drag coefficients simultaneously and effectively, while also considering several DOF. This work considers time series of structural displacements from wave tank tests of the OC6 project and from simulations of the same load cases in OpenFAST. Results are transferred into the frequency domain and the deviation between power spectral densities of surge, pitch and heave from experiment and numerical simulation is used as an objective function to obtain the best fitting drag coefficients. This novel numerical optimization approach enables finding one set of drag coefficients for different load cases, which is a major improvement compared to decay-test-tuned drag coefficients. © Published under licence by IOP Publishing Ltd

Multi-site H-bridge breathers in a DNA--shaped double strand

We investigate the formation process of nonlinear vibrational modes representing broad H-bridge multi--site breathers in a DNA--shaped double strand. Within a network model of the double helix we take individual motions of the bases within the base pair plane into account. The resulting H-bridge deformations may be asymmetric with respect to the helix axis. Furthermore the covalent bonds may be deformed distinctly in the two backbone strands. Unlike other authors that add different extra terms we limit the interaction to the hydrogen bonds within each base pair and the covalent bonds along each strand. In this way we intend to make apparent the effect of the characteristic helicoidal structure of DNA. We study the energy exchange processes related with the relaxation dynamics from a non-equilibrium conformation. It is demonstrated that the twist-opening relaxation dynamics of a radially distorted double helix attains an equilibrium regime characterized by a multi-site H-bridge breather.Comment: 27 pages and 10 figure

Morphological aspects of male and female hands

This is an electronic version of an article published in Annals of Human Biology, 1996, 23(6), 491-494. Annals of Human Biology is available online at informaworldTM http://www.informaworld.com/smpp/content~content=a739339013~db=all~order=pageThis journal article discusses a series of hand radiographs from Gwynedd, North Wales, which were assessed for frequencies in digital and metacarpal formulae between the genders

Combined proton NMR wideline and NMR relaxometry to study SOM-water interactions of cation-treated soils

Focusing on the idea that multivalent cations affect SOM matrix and surface, we treated peat and soil samples by solutions of NaCl, CaCl2 or AlCl3. Water binding was characterized with low field 1H-NMR-relaxometry (20 MHz) and 1H wideline NMR spectroscopy (400 MHz) and compared to contact angles. From 1H wideline, we distinguished mobile water and water involved in water molecule bridges (WaMB). Large part of cation bridges (CaB) between SOM functional groups are associated with WaMB. Unexpectedly, 1H NMRrelaxometry relaxation rates suggest that cross-linking in the Al-containing peat is not stronger than that by Ca. The relation between percentage of mobile water and WaMB water in the context of wettability and 1H NMR relaxation times confirms that wettability controls the water film surrounding soil particles. Wettability is controlled by WaMB-CaB associations fixing hydrophilic functional groups in the SOM interior. This can lead to severe water repellency. Wettability decreases with increasing involvement of functional groups in CaB-WaMB associations. The results demonstrate the relevance of CaB and WaMB for the dynamics of biogeochemical and hydrological processes under field conditions, as only a few percent of organic matter can affect the physical, chemical, and biological functioning of the entire 3-phase ecosystem

DNA as a programmable viscoelastic nanoelement

The two strands of a DNA molecule with a repetitive sequence can pair into many different basepairing patterns. For perfectly periodic sequences, early bulk experiments of Poerschke indicate the existence of a sliding process, permitting the rapid transition between different relative strand positions [Biophys. Chem. 2 (1974) 83]. Here, we use a detailed theoretical model to study the basepairing dynamics of periodic and nearly periodic DNA. As suggested by Poerschke, DNA sliding is mediated by basepairing defects (bulge loops), which can diffuse along the DNA. Moreover, a shear force f on opposite ends of the two strands yields a characteristic dynamic response: An outward average sliding velocity v~1/N is induced in a double strand of length N, provided f is larger than a threshold f_c. Conversely, if the strands are initially misaligned, they realign even against an external force less than f_c. These dynamics effectively result in a viscoelastic behavior of DNA under shear forces, with properties that are programmable through the choice of the DNA sequence. We find that a small number of mutations in periodic sequences does not prevent DNA sliding, but introduces a time delay in the dynamic response. We clarify the mechanism for the time delay and describe it quantitatively within a phenomenological model. Based on our findings, we suggest new dynamical roles for DNA in artificial nanoscale devices. The basepairing dynamics described here is also relevant for the extension of repetitive sequences inside genomic DNA.Comment: 10 pages, 7 figures; final version to appear in Biophysical Journa