Visualization of a lost painting by Vincent van Gogh using synchrotron radiation based X-ray fluorescence elemental mapping

Vincent van Gogh (1853-1890), one of the founding fathers of modern painting, is best known for his vivid colors, his vibrant painting style, and his short but highly productive career. His productivity is even higher than generally realized, as many of his known paintings cover a previous composition. This is thought to be the case in one-third of his early period paintings. Van Gogh would often reuse the canvas of an abandoned painting and paint a new or modified composition on top. These hidden paintings offer a unique and intimate insight into the genesis of his works. Yet, current museum-based imaging tools are unable to properly visualize many of these hidden images. We present the first-time use of synchrotron radiation based X-ray fluorescence mapping, applied to visualize a woman's head hidden under the work Patch of Grass by Van Gogh. We recorded decimeter-scale, X-ray fluorescence intensity maps, reflecting the distribution of specific elements in the paint layers. In doing so we succeeded in visualizing the hidden face with unprecedented detail. In particular, the distribution of Hg and Sb in the red and light tones, respectively, enabled an approximate color reconstruction of the flesh tones. This reconstruction proved to be the missing link for the comparison of the hidden face with Van Gogh's known paintings. Our approach literally opens up new vistas in the nondestructive study of hidden paint layers, which applies to the oeuvre of Van Gogh in particular and to old master paintings in general.     

Employment effects of changes in transportation infrastructure: methodological aspects of the gravity model

Assessing the employment effects of changes in transport infrastructure, such as the construction of the Channel Tunnel or high-speed rail connections, is not an easy task. The gravity model is sometimes used to analyse changes in the potentials of the regions concerned. One sttep further would be the translation of changes in potentials into changes in employment per region. This paper will be devoted to analysing some properties and limitation of such a translation process. Special attention is paid to an operational model developed by Evers et al. (1987) for this purpose. It is shown that this model is almost consistent with the theory of locational behaviou of firms.     

Interfacial phenomena: an in vitro study of the effect of calcium phosphate (Ca-P) ceramic on bone formation

Vertebral fractures are a common and important consequence of osteoporosis and are often identified via morphometric analysis of conventional lateral spine radiographs (morphometric radiography or MRX). A new method of performing vertebral morphometry using images acquired on dual-energy X-ray absorptiometry (DXA) scanners (morphometric X-ray absorptiometry or MXA) has recently been developed. In this study, we derive reference data for vertebral heights and height ratios using MXA scans as the data source and compare the results with previously published MRX studies. One thousand and nineteen Caucasian women (mean age 63 years, range 33-86) were recruited. An MXA scan, covering 13 vertebrae from L4 to T4, was acquired for each subject on one of four DXA systems located at three centers in the U.K. Analysis of variance found statistically significant but relatively small differences among centers, machines, and scan modes, and therefore data were pooled for reference range calculations. Three vertebral heights (anterior, mid, and posterior) were measured and four ratios (wedge, mid-wedge, and two crush) calculated. These data sets were trimmed using an iterative algorithm to remove extreme values assumed to represent deformed vertebrae, then mean and SD values were calculated using the remaining data. When the data were split by age, a small but statistically significant decrease in vertebral height between the sixth and eighth decades was found, but this was not replicated for the vertebral height ratios. Marked differences were observed between MXA data and MRX, but were comparable to those between different MRX studies. These may result from differences in image quality and point placement protocols, population differences, differences in radiographic technique, and differences in the derivation of a group of "normal" vertebrae. This study suggests that reference data of vertebral dimensions should be specific to the technique which uses those data as a reference, i.e., MXA.     

Non-bilayer lipids are required for efficient protein transport across the plasma membrane of Escherichia coli

The construction of a mutant Escherichia coli strain which cannot synthesize phosphatidylethanolamine provides a tool to study the involvement of non-bilayer lipids in membrane function. This strain produces phosphatidylglycerol and cardiolipin (CL) as major membrane constituents and requires millimolar concentrations of divalent cations for growth. In this strain, the lipid phase behaviour is tightly regulated by adjustment of the level of CL which favours a nonbilayer organization in the presence of specific divalent cations. We have used an in vitro system of inverted membrane vesicles to study the involvement of non-bilayer lipids in protein translocation in the secretion pathway. In this system, protein translocation is very low in the absence of divalent cations but can be enhanced by inclusion of Mg2+, Ca2+ or Sr2+ but not by Ba2+ which is unable to sustain growth of the mutant strain and cannot induce a non-bilayer phase in E. coli CL dispersions. Alternatively, translocation in cation depleted vesicles could be increased by incorporation of the non-bilayer lipid DOPE (18:1) but not by DMPE (14:0) or DOPC (18:1), both of which are bilayer lipids under physiological conditions. We conclude that non-bilayer lipids are essential for efficient protein transport across the plasma membrane of E. coli.     

Evaluation of experimental techniques to validate numerical computations of the hydraulics inside a UV bench-scale reactor

Computational fluid dynamics (CFD) is widely used to predict the hydraulics in environmental systems, but the validity of these predictions continues to receive attention. The hydraulics of a UV bench-scale reactor was evaluated by numerical and experimental techniques. Different experimental techniques were used to examine the hydraulics: salt injection to measure the residence time distribution, dye injection to visualize the mixing patterns, and LDA to measure the local velocity profiles. The combination of these measurements techniques provides information in unprecedented detail of the hydraulics inside UV systems. A CFD model with a standard k?ε turbulence model was used for comparison with the experimental results. The main flow patterns were predicted well. The largest differences were found at regions in the reactor where recirculation occurred, for example in the wake region of a lamp. Also, the CFD model predicted a larger mixing over the flow cross-section, resulting in a narrower residence time distribution.     

Encephalocytozoon intestinalis-specific monoclonal antibodies for laboratory diagnosis of microsporidiosis

Two monoclonal antibodies which can be used for the unambiguous identification by fluorescence microscopy of Encephalitozoon intestinalis spores in clinical specimens are described. Monoclonal antibody Si91 is specific for the extruded polar filament, and Si13 recognizes the surfaces of E. intestinalis spores. No cross-reaction with spores of Encephalitozoon hellem was observed. Immunogold electron microscopy confirmed the specific reactivities of both antibodies. Combined in an indirect immunofluorescence assay, these antibodies are used to identify spores in feces. Although there was some cross-reaction with fecal bacteria and fungi, the typical morphology of the extruded polar filaments enabled proper identification of the E. intestinalis spores. Parasites could also be demonstrated to be present in urine, nasal swabs, lung brush biopsy specimens, and bronchoalveolar lavage fluid from a patient with disseminated infection with E. intestinalis. The use of these monoclonal antibodies facilitates the detection and species determination of E. intestinalis in clinical specimens.