1,721,035 research outputs found
Transmission X-ray microscopy of spider dragline silk
No full textWe have investigated the structure of spider silk fibers from two different Nephila species and three different Araneus species by transmission X-ray microscopy (TXM). Single fibers and double fibers have been imaged. All images are in agreement with a homogenous density on length scales between the fiber diameter and the resolution of the instrument, which is about 25 nm. (c) 2006 Elsevier B.V. All rights reserved
Terminal contact elements of insect attachment devices studied by transmission X-ray microscopy
No full textFor the first time, the terminal elements (spatulae) of setal ( hairy) attachment devices of the beetle Gastrophysa viridula ( Coleoptera, Chrysomelidae) and the fly Lucilia caesar(Diptera, Calliphoridae) were studied using transmission X-ray microscopy (TXM) with a lateral resolution of about 30 nm. Since images are taken under ambient conditions, we demonstrate here that this method can be applied to study the contact behaviour of biological systems, including animal tenent setae, in a fresh state. We observed that the attached spatulae show a viscoelastic behavior increasing the contact area and providing improved adaptability to the local topography of the surface. The technique can be extended to TXM tomography, which would provide three-dimensional information and a deeper insight into the details of insect attachment structures
Concept and realization of the novel rotating condenser-monochromator at the Göttingen TXM at BESSY II
No full textThe new transmission X-ray microscope (TXM) at BESSY II is the first X-ray microscope
working with a rotating condenser-monochromator (RK) for the object illumination [1]. This condenser
concept uses a linear monochromator with an off-axis transmission zone plate (OTZ) followed by a pair
of rotating mirrors. Details of the design and characteristics are shown
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Magnetization reversal of a multilayered FeGd dot array imaged by transmission x-ray microscopy
No full textThe magnetization reversal of an array of 1 mum squared FeGd dots has been studied by magnetic transmission x-ray microscopy (MTXM). A (4 Angstrom Fe/4 Angstrom Gd) x 75 multilayered FeGd system has been prepared on a 30 nm thin Si3N4 membrane by sputtering and structured by optical lithography and ion beam etching techniques. Both the domain structure within each single dot and the collective switching behavior could be observed with MTXM. A large variation in the nucleation field of the dots was found and can be attributed to the shape of the dots. A correlation between the nucleation field and the perimeter of each dot could be deduced. Hysteresis loops of individual dots are derived, taking into account the proportionality of the dichroic contrast to the magnetization of the sample. The stepped profile of the magnetization loop of a single dot is found to be clearly distinct from a continuous film. The high lateral resolution and the possibility to record the images in varying external magnetic fields proves that MTXM is a highly adapted tool to investigate nanostructured magnetic systems. (C) 2001 American Institute of Physics
Computed tomography of cryogenic biological specimens based on X-ray microscopic images
No full textSoft X-ray microscopy employs the photoelectric absorption contrast between water and protein in the 2.34-4.38 nm wavelength region to visualize protein structures down to 30 nm size without any staining methods. Due to the large depth of focus of the Fresnel zone plates used as X-ray objectives, computed tomography based on the X-ray microscopic images can be used to reconstruct the local linear absorption coefficient inside the three-dimensional specimen volume. High-resolution X-ray images require a high specimen radiation dose, and a series of images taken at different viewing angles is needed for computed tomography. Therefore, cryo microscopy is necessary to preserve the structural integrity of hydrated biological specimens during image acquisition. The cryo transmission X-ray microscope at the electron storage ring BESSY I (Berlin) was used to obtain a tilt series of images of the frozen-hydrated green alga Chlamydomonas reinhardtii. The living specimens were inserted into borosilicate glass capillaries and, in this first experiment. rapidly cooled by plunging into liquid nitrogen. The capillary specimen holders allow image acquisition over the full angular range of 180 degrees. The reconstruction shows for the first time details down to 60 nm size inside a frozen-hydrated biological specimen and conveys a clear impression of the internal structures. This technique is expected to be applicable to a wide range of biological specimens, such as the cell nucleus. It offers the possibility of imaging the three-dimensional structure of hydrated biological specimens close to their natural living state. (C) 2000 Elsevier Science B.V. All rights reserved
Microscopy and spectroscopy with X-rays for studies in the environmental sciences
No full textX-ray spectromicroscopy is a powerful tool for addressing key questions in the environmental sciences due to its high spectral and spatial resolution. It has been used successfully for material research, biology and environmental studies, e.g. in the form of mu-X-ray fluorescence and spectromicroscopy with a spatial resolution of <100 nm. With the combination of high-resolution microscopy and spectroscopy it is possible to determine elemental composition as well as chemical speciation, and also identify trace elements to nm-resolution. Samples from soils and groundwater aquifers have been imaged to visualize the appearance of structures on the nm- and mu m-scale. The effect of changing chemical conditions in ail aqueous environment on the appearance of these structures has been imaged and evaluated. Clay dispersions, microhabitats and morphological effects of biologically-induced redox changes Of humic substances have been imaged tomographically, conveying a detailed three-dimensional presentation of the specimen structure. Using the spectromicroscopy potential, the distribution of organic and inorganic components, as well as different inorganic components, has been studied. Spectra were analysed for major chemical constituents and were used, for example, to assess different sulphur species in ail entire soil profile
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