Recent improvements in the methodology of neutron imaging

The focus of this article is on further improvements of methods in neutron imaging: the increased spatial resolution for microtomography and options for energy-selective neutron imaging. Before going into details, some common statements are given in respect to the state-of-the-art in neutron imaging. A relation to the X-ray methods is mentioned, where complementary results are obtained. The potential for the energy selection is of particular interest for future installations at the new pulsed sources, based on spallation (SNS, J-PARC, ISIS-TS2). First results from preliminary studies look very promising for future material and industrial research. Therefore, statements about the set-up of the best possible imaging systems are included in the articl

Increased copulation duration before ejaculate transfer is associated with larger spermatophores, and male genital titillators, across bushcricket taxa

Copulation duration varies considerably across species, but few comparative studies have examined factors that might underlie such variation. We examined the relationship between copulation duration (prior to spermatophore transfer), the complexity of titillators (sclerotized male genital contact structures), spermatophore mass and male body mass across 54 species of bushcricket. Using phylogenetic comparative analyses, we found that copulation duration was much longer in species with titillators than those without, but it was not longer in species with complex compared with simple titillators. A positive relationship was found between spermatophore size and copulation duration prior to ejaculate transfer, which supports the hypothesis that this represents a period of mate assessment. The slope of this relationship was steeper in species with simple rather than complex titillators. Although the data suggest that the presence of titillators is necessary to maintain long copulation prior to ejaculate transfer, mechanisms underlying this association remain unclear

Neutron imaging at PSI: a promising tool in materials science andtechnology

Neutron imaging as a method for non-destructive studies takes advantage of the alternative contrast mechanism of neutrons compared to X-rays: most of the light elements feature high contrast, whereas heavy elements are relatively transparent to neutrons. In the previous decade, the neutron imaging technique has made substantial progress in well-tailored and well-equipped beam lines, in improvements of the image recording quality and efficiency by new and modern imaging techniques, and in modern image processing tools. This article gives an overview of PSI's activities in this promising and still developing field combining high potential as research tool and as technique for industrial investigation and non-destructive testing. Examples are chosen from the fields of energy and mobility and inspection of highly activated samples. Furthermore, recent developments in phase contrast imaging and energy selective imaging studies are highlighted. Finally, future trends in neutron imaging are addresse

Non-destructive Investigation of “The Violinist” a Lead Sculpture by Pablo Gargallo, Using the Neutron Imaging Facility NEUTRA in the Paul Scherrer Institute

AbstractThe Violinist (1920), the only sculpture made by Gargallo using lead sheet and wood, is being corroded by carbonation, most probably due to the organic vapours released by the wood inside, a material not chemically compatible with lead. Hydrogen plasma has been tested and proved to be an effective treatment meaning that the sculpture has to be dismantled in order to give the plasma gas access to the lead carbonate crusts on the inner surface of the lead sheet. Prior to dismantling, a complete exploration and diagnosis of this lead sculpture has been carried out through neutron imaging at the Paul Scherrer Institute. This non-destructive technique has produced different sets of images including radiography, tomography and 3D reconstruction. Despite the presence of a core made of an organic material such as wood, the digital processing of the images and their in depth visual analysis have yielded new three-dimensional information of inaccessible details of the sculpture, allowing us to assess its present state of conservation and the manufacturing technique and materials used by the artist. The results presented in this article highlight how information from neutron imaging can be of great value when it comes to set the strategies for future conservation treatmen

Neutron attenuation coefficients for non-invasive quantification of wood properties

Attenuation coefficients and mass attenuation coefficients of wood were determined theoretically and experimentally for thermal and cold neutrons. Experiments were carried out at the neutron imaging facilities at the Paul Scherrer Institute, Villigen (CH). For the calculation of theoretical attenuation coefficients, only the three main elemental components (carbon, oxygen and hydrogen) were taken into consideration. While hydrogen accounts only for 6% (by wt) of wood, over 90% of the attenuation can be attributed to this element. Nitrogen and other trace elements were estimated to have a negligible impact on the theoretical attenuation coefficient. For the experimental determination of the attenuation coefficients, samples from different European and tropical wood species were tested in order to examine the influence of density and extractives content. Experimental results show a very strong linear correlation between attenuation coefficient and wood density irrespective of the tested species and extractives content that play only a minor role. As neutrons are very susceptible to scattering, it is necessary to apply a scattering correction if a quantitative evaluation is intende

Neutron imaging versus standard X-ray densitometry as method to measure tree-ring wood density

Neutron imaging is a new non-destructive testing method in wood science. It is similar to X-ray methods but with differing sensitivities for different elements. In this study, neutron imaging was used to ascertain the density profiles of thin spruce samples and compared with results generated with standard X-ray microdensitometry. Data obtained through neutron imaging were similar to those resulting from the X-ray method. The advantage of neutron imaging is its higher sensitivity to some elements such as hydrogen. Together with the high neutron-sensitivity of the applied detectors (imaging plates) this makes shorter exposure times possible, and yields more detailed information on the inner composition of wood. X-ray film, which is still most commonly used in X-ray densitometry, has the disadvantage that the relationship between the optical density of the film and the density of wood is non-linear. This means that corrections and calibration with step wedges are necessary, whereas with neutron imaging the digital values can be used directly to calculate the density at a certain point of the specimen. Thus neutron imaging appears to be an appropriate method, which can be used as complement to established X-ray methods for fast and straightforward investigations of tree rings, growth zones and wood densit

Basics of Neutron Imaging

Neutron imaging is established at many neutron sources around the world as a method for noninvasive investigations of samples and object on the macroscopic scale. Similarly to X-ray imaging, it provides the possibility to “look through” materials and allows one to “see” the inner, hidden content. However, owing to the complete different interaction mechanism, neutron imaging provides very different and complementary contrasts compared to X-rays, even if the image quality often is about the same. We report about the method’s principles, describe the state of the art, and give an outlook for new trends and developments

Neutron radiography, tomography, and diffraction of commercial lithium-ion polymer batteries

Imaging an intact, commercial battery as it cycles and wears is proved possible with neutron imaging. The wavelength range of imaging neutrons corresponds nicely with crystallographic dimensions of the electrochemically active species and the metal electrodes are relatively transparent. The time scale of charge/discharge cycling is well matched to dynamic tomography as performed with a golden ratio based projection angle ordering. The hydrogen content does create scatter which tends to blur internal structure. In this report, three neutron experiments will be described: 3D images of charged and discharged batteries were obtained with monochromatic neutrons at the FRM II reactor. 2D images (PSI) of fresh and worn batteries as a function of charge state may show a new wear pattern. In situ neutron diffraction (SNS) of the intact battery provides more information about the concentrations of electrochemical species within the battery as a function of charge state and wear. The combination of 2D imaging, 3D imaging, and diffraction data show how neutron imaging can contribute to battery development and wear monitoring. © 2013 The Authors. © 2013 The Authors

Functional equivalence of grasping cerci and nuptial food gifts in promoting ejaculate transfer in katydids.

The function of nuptial gifts has generated longstanding debate. Nuptial gifts consumed during ejaculate transfer may allow males to transfer more ejaculate than is optimal for females. However, gifts may simultaneously represent male investment in offspring. Evolutionary loss of nuptial gifts can help elucidate pressures driving their evolution. In most katydids (Orthoptera: Tettigoniidae), males transfer a spermatophore comprising two parts: the ejaculate-containing ampulla and the spermatophylax-a gelatinous gift that females eat during ejaculate transfer. Many species, however, have reduced or no spermatophylaces and many have prolonged copulation. Across 44 katydid species, we tested whether spermatophylaces and prolonged copulation following spermatophore transfer are alternative adaptations to protect the ejaculate. We also tested whether prolonged copulation was associated with (i) male cercal adaptations, helping prevent female disengagement, and (ii) female resistance behavior. As predicted, prolonged copulation following (but not before) spermatophore transfer was associated with reduced nuptial gifts, differences in the functional morphology of male cerci, and behavioral resistance by females during copulation. Furthermore, longer copulation following spermatophore transfer was associated with larger ejaculates, across species with reduced nuptial gifts. Our results demonstrate that nuptial gifts and the use of grasping cerci to prolong ejaculate transfer are functionally equivalent