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  • 1
    Language: English
    In: Plant physiology, January 2014, Vol.164(1), pp.24-35
    Description: Root system traits are important in view of current challenges such as sustainable crop production with reduced fertilizer input or in resource-limited environments. We present a novel approach for recovering root architectural parameters based on image-analysis techniques. It is based on a graph representation of the segmented and skeletonized image of the root system, where individual roots are tracked in a fully automated way. Using a dynamic root architecture model for deciding whether a specific path in the graph is likely to represent a root helps to distinguish root overlaps from branches and favors the analysis of root development over a sequence of images. After the root tracking step, global traits such as topological characteristics as well as root architectural parameters are computed. Analysis of neutron radiographic root system images of lupine (Lupinus albus) grown in mesocosms filled with sandy soil results in a set of root architectural parameters. They are used to simulate the dynamic development of the root system and to compute the corresponding root length densities in the mesocosm. The graph representation of the root system provides global information about connectivity inside the graph. The underlying root growth model helps to determine which path inside the graph is most likely for a given root. This facilitates the systematic investigation of root architectural traits, in particular with respect to the parameterization of dynamic root architecture models.
    Keywords: Image Processing, Computer-Assisted -- Methods ; Lupinus -- Physiology ; Plant Roots -- Physiology ; Radiography -- Methods
    ISSN: 00320889
    E-ISSN: 1532-2548
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  • 2
    Language: English
    In: Plant and Soil, 2015, Vol.397(1), pp.273-287
    Description: BACKGROUND AND AIMS: Water is often heterogeneously distributed in soils. Understanding roots’ responses to this soil-water heterogeneity is a key parameter defining plant survival in dry climates. To determine local root water uptake for partly dry conditions in a plant’s root system, we prepared soil patches with different water contents, then used neutron radiography to monitor daily changes in root structure and water uptake. METHODS: Lupin plants were grown in 30 × 25 × 1 cm³ aluminum containers filled with sandy soil. In two partitioning set-ups, the soil-root zone was divided into either two or nine hydraulically-isolated soil compartments. This was done by packing layers of coarse sand as capillary barriers, by which vertical and/or horizontal soil water heterogeneity as well as homogeneous well-watered treatments were applied for control. Daily changes in soil water content in each compartment, water uptake and root growth were monitored non-invasively and quantified by neutron radiography during a period of 15 consecutive days. RESULTS: In optimal homogeneously-wet soil, lateral roots in the top 10 cm of the root system showed the highest water uptake rate, up to around 10 mg/(mm. root. day), which on average was twice as much as that for younger lateral roots in lower position and taproot. In heterogeneous treatments, root water uptake declined strongly in compartments with the soil water content below 0.13–0.10 cm³/cm³ while in parallel an enhanced uptake rate, rising by up to 100 %, was observed for the roots in wet compartments, presumably to compensate for roots in dry compartments and, therefore, sustain the total transpiration. Also, our observations showed that in the drying compartment a reduction of soil water content to 0.10–0.15 triggered local cluster root formation. CONCLUSIONS: With the experimental set-up presented the pattern of water uptake across a lupin root system can be quantified and normalized to root length. Water uptake was shown to be highly variable in different parts of the root system. A threshold for water stress to cause cessation of local water uptake was identified, and the considerable amount of compensation by water uptake in other parts identified. The dynamic trade-off among different parts of the root system seems to regulate total root uptake also during water stress to sustain the daily transpirational demand. ; p. 273-287.
    Keywords: Compensation ; Neutron radiography ; Partial root-zone drying ; Plant root ; Root length ; Soil water heterogeneity ; Water uptake
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 3
    Language: English
    In: Plant and Soil, 2010, Vol.332(1), pp.163-176
    Description: Water flow from soil to plants depends on the properties of the soil next to roots, the rhizosphere. Although several studies showed that the rhizosphere has different properties than the bulk soil, effects of the rhizosphere on root water uptake are commonly neglected. To investigate the rhizosphere’s properties we used neutron radiography to image water content distributions in soil samples planted with lupins during drying and subsequent rewetting. During drying, the water content in the rhizosphere was 0.05 larger than in the bulk soil. Immediately after rewetting, the picture reversed and the rhizosphere remained markedly dry. During the following days the water content of the rhizosphere increased and after 60 h it exceeded that of the bulk soil. The rhizosphere’s thickness was approximately 1.5 mm. Based on the observed dynamics, we derived the distinct, hysteretic and time-dependent water retention curve of the rhizosphere. Our hypothesis is that the rhizosphere’s water retention curve was determined by mucilage exuded by roots. The rhizosphere properties reduce water depletion around roots and weaken the drop of water potential towards roots, therefore favoring water uptake under dry conditions, as demonstrated by means of analytical calculation of water flow to a single root.
    Keywords: Root water uptake ; Water retention curve ; Rhizosphere ; Neutron radiography ; Mucilage ; Hysteresis
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 4
    Language: English
    In: Analytical chemistry, 19 December 2017, Vol.89(24), pp.13541-13549
    Description: In this study, distillation, precipitation, and ion-exchange methods were chosen for the separation of the long-lived β-emitters I, Cl and the α-emitters Dy, Gd, Gd, and Sm from Ta targets irradiated with protons up to 2.6 GeV to determine their production cross sections. Measurements of I/I and Cl/Cl ratios were performed with accelerator mass spectrometry. After separation of the lanthanides, the molecular plating technique was applied to prepare thin samples to obtain highly resolved α-spectra. Autoradiography and focused ion beam/scanning electron microscopy techniques were used to characterize the lanthanide deposited layer. Experimental cross-section data are compared with theoretical predictions obtained with INCL++ and ABLA07 code, and a satisfactory agreement is observed.
    Keywords: Chemistry ; Protons ; Heavy Metals ; Scanning Electron Microscopy ; Ion Exchange ; Measurement ; Mass Spectrometry ; Gadolinium ; Tantalum ; Scanning Electron Microscopy ; Radiochemistry ; Separation ; Mass Spectrometry ; Radioisotopes ; Irradiated ; Protons ; Radioisotopes ; Emitters (Electron) ; Molecular Plating ; Lanthanides ; Autoradiography ; Distillation ; Lanthanides ; Cross Sections ; Radioisotopes ; Emitters ; Tantalum ; Tantalum ; Distillation ; Mass Spectroscopy ; Ion Beams ; Scanning Electron Microscopy ; Proton Irradiation ; Autoradiography ; Ion Exchanging;
    ISSN: 00032700
    E-ISSN: 1520-6882
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  • 5
    Language: English
    In: Cement and Concrete Research, 2015, Vol.75, p.1(13)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.cemconres.2015.05.001 Byline: Christof Schroefl, Viktor Mechtcherine, Peter Vontobel, Jan Hovind, Eberhard Lehmann Abstract: Water sorption of two superabsorbent polymers in cement-based pastes has been characterized by neutron radiography. Cement pastes with W/C of 0.25 and 0.50 and one additionally containing silica fume (W/C=0.42) were investigated. The SAPs differed in their inherent sorption kinetics in extracted cement pore solution (SAP 1: self-releasing; SAP 2: retentive). Desorption from SAP 1 started very early after paste preparation. Hence, its individual non-retentiveness governs its behavior only. SAP 2 released water into all matrices, but its kinetics were different. In the paste with the highest W/C, some moderate water release was recorded from the beginning. In the other two pastes, SAP 2 retained its stored liquid during the dormant period, i.e., up to the percolation threshold. Intense desorption then set in and continued throughout the acceleration period. These findings explain the pronouncedly higher efficiency of SAP 2 as internal curing admixture as compared to SAP 1. Article History: Received 2 February 2015; Accepted 1 May 2015
    Keywords: Polymer Industry ; Radiography ; Cements (Building Materials) ; Polymers
    ISSN: 0008-8846
    Source: Cengage Learning, Inc.
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  • 6
    In: New Phytologist, November 2011, Vol.192(3), pp.653-663
    Description: • Despite the importance of rhizosphere properties for water flow from soil to roots, there is limited quantitative information on the distribution of water in the rhizosphere of plants. • Here, we used neutron tomography to quantify and visualize the water content in the rhizosphere of the plant species chickpea (Cicer arietinum), white lupin (Lupinus albus), and maize (Zea mays) 12 d after planting. • We clearly observed increasing soil water contents (θ) towards the root surface for all three plant species, as opposed to the usual assumption of decreasing water content. This was true for tap roots and lateral roots of both upper and lower parts of the root system. Furthermore, water gradients around the lower part of the roots were smaller and extended further into bulk soil compared with the upper part, where the gradients in water content were steeper. • Incorporating the hydraulic conductivity and water retention parameters of the rhizosphere into our model, we could simulate the gradual changes of θ towards the root surface, in agreement with the observations. The modelling result suggests that roots in their rhizosphere may modify the hydraulic properties of soil in a way that improves uptake under dry conditions.
    Keywords: Extent Of Rhizosphere ; Modelling ; Neutron Tomography ; Rhizosphere Hydraulic Properties ; Root Water Uptake ; Soil Moisture Profile ; Water Distribution
    ISSN: 0028-646X
    E-ISSN: 1469-8137
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  • 7
    Language: English
    In: Materials and Structures, 2013, Vol.46(1), pp.105-121
    Description: Penetration of moisture into building materials is at the origin of several damage mechanisms. In the case of cement-based materials crack formation is a common problem and highly accelerates the ingress of water and aggressive substances. Crack repair may be needed, however, repair works are expensive and in some cases cracks are even not accessible. Therefore, in this research we aim at autonomous crack sealing. Upon crack appearance, damage is sealed autonomously by the release of encapsulated agents. Visualization of the water uptake by means of neutron radiography for samples with manually and autonomously sealed cracks showed that in both cases ingress of water into the crack can be prevented depending on the type of agent. The efficiency of three different agents was examined and it was shown that the use of polyurethane or a water repellent agent were most promising. Neutron tomography scans demonstrated that poor results were obtained when encapsulated methyl methacrylate was used, since one component of the agent hardened inside the capsules before crack appearance. From the results we can conclude that autonomous sealing of cracks is feasible and that neutron radiography and tomography are suitable non-destructive test techniques to visualize the autonomous crack sealing efficiency.
    Keywords: Mortar ; Glass tubes ; Polymers ; Bending cracks ; Capillary water uptake ; Neutron beam attenuation
    ISSN: 1359-5997
    E-ISSN: 1871-6873
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  • 8
    Language: English
    In: Nuclear Engineering and Design, 2011, Vol.241(12), pp.4758-4766
    Description: ► For the first time water movement in cement-based materials could be quantified in a non-destructive way. ► neutron radiography has a sensitivity and a spatial resolution unknown so far. ► Results are essential for prediction of service life. ► Results will contribute to more durable and more ecological construction. Service life of reinforced concrete structures is often limited by penetration of water and compounds dissolved in water into concrete. Concrete can be damaged in this way and corrosion of steel reinforcement can be initiated. There is an urgent need to study water penetration into concrete in order to better understand deterioration mechanisms and to find appropriate ways to improve durability. Neutron radiography provides us with an advanced non-destructive technique with high spatial resolution and extraordinary sensitivity. In this contribution, neutron radiography was successfully applied to study the process of water absorption of two types of concrete with different water–cement ratios, namely 0.4 and 0.6. The influence cracks and of water repellent treatment on water absorption has been studied on mortar specimens. It is possible to visualize migration of water into concrete and other cement-based composites and to quantify the time-dependent moisture distributions as function of time with high spatial resolution by means of neutron radiography. Water penetration depth obtained from neutron radiography is in good agreement with corresponding values obtained from capillary suction tests. Surface impregnation of concrete with silane prevents capillary uptake of water. Even fine cracks are immediately filled with water as soon as the surface gets in contact. Results provide us with a solid basis for a better understanding of deteriorating processes in concrete and other cement-based materials.
    Keywords: Engineering
    ISSN: 0029-5493
    E-ISSN: 1872-759X
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  • 9
    Language: English
    In: Fire Technology, 2015, Vol.51(6), pp.1433-1445
    Description: Connections are often the weakest link in timber structures so that their failure during fire exposure may result in local or total collapse of a building. The failure modes are complex and poorly understood due to wood’s orthotropicity, the temperature and moisture dependency of wood’s properties, and the presence of metal fasteners that complicates the stress distribution and changes the process of heat transfer into the timber element. In this study, we investigated the coupled physics of heat and mass transfer in a test specimen made from spruce, with a steel fastener inserted in a pre-drilled hole. It imitates a central slice of a timber-to-timber connection exposed to the elevated temperature of 523 K from one side. The heat induced redistribution of the hygroscopic moisture in wood was quantified and visualized by means of neutron radiography. The temperature gradient was measured inside the specimen, at different distances from the heated surface. As the temperature increased in wood, moisture was displaced downstream of the heat source, resulting in a zone with increased moisture content ahead of the drying front and beneath the steel fastener. This wet front occurred where the temperature was below the water evaporation point. It was shown that the steel fastener affected the transport of heat and moisture within the test specimen. The occurring phenomena during the transient state may play a critical role in the embedment strength of wood and therefore influence the load-carrying capacity of timber connections in fire.
    Keywords: Neutron radiography ; Fire ; Hygroscopic moisture ; Moisture displacement ; Timber joint
    ISSN: 0015-2684
    E-ISSN: 1572-8099
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  • 10
    Language: English
    In: International Journal of Materials Research, 09/2011, Vol.102(9), pp.1101-1105
    Description: The Swiss spallation neutron source SINQ operated at the Paul Scherrer Institut is driven by PSIs 590 MeV proton accelerator at a beam power of 0.8 MW, as such being the most powerful (CVV) spallation source worldwide. The core element of such a facility is the neutron production target. Since the commissioning in 1997, PSI has always fostered combined efforts in the development of the spallation target, including dedicated materials research for high dose radiation environments. The overall goal was to achieve optimized neutron production, combined with sufficient robustness, thermo-mechanical stability and radiation resistance to withstand the severe loads of high-dose irradiation and frequent thermal cycling over an acceptable lifetime. The target itself has been improved in several steps by searching for the optimal materials and geometries. In parallel, numerous experiments have been conducted in the targets of SINQ for studying radiation damage effects induced by high energy protons and spallation neutrons.
    Keywords: Commissioning ; Neutron Sources ; Spallation ; Acceptability ; Robustness ; Thermal Cycling ; Stability ; Proton Accelerators ; Optimization ; General and Nonclassified (MD) ; General and Nonclassified (Ep) ; General and Nonclassified (Ed) ; General and Nonclassified (EC) ; Spallation Target ; Spallation Materials ; Radiation Damage ; Stip Program ; Stip Program;
    ISSN: 1862-5282
    E-ISSN: 2195-8556
    Source: CrossRef
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