Synchrotron x ray induced axonal transections in the brain of rats assessed by high-field diffusion tensor imaging tractography

Since approximately two thirds of epileptic patients are non-eligible for surgery, local axonal fiber transections might be of particular interest for them. Micrometer to millimeter wide synchrotron-generated X-ray beamlets produced by spatial fractionation of the main beam could generate such fiber disruptions non-invasively. The aim of this work was to optimize irradiation parameters for the induction of fiber transections in the rat brain white matter by exposure to such beamlets. For this purpose, we irradiated cortex and external capsule of normal rats in the antero-posterior direction with a 4 mm×4 mm array of 25 to 1000 µm wide beamlets and entrance doses of 150 Gy to 500 Gy. Axonal fiber responses were assessed with diffusion tensor imaging and fiber tractography; myelin fibers were examined histopathologically. Our study suggests that high radiation doses (500 Gy) are required to interrupt axons and myelin sheaths. However, a radiation dose of 500 Gy delivered by wide minibeams (1000 µm) induced macroscopic brain damage, depicted by a massive loss of matter in fiber tractography maps. With the same radiation dose, the damage induced by thinner microbeams (50 to 100 µm) was limited to their paths. No macroscopic necrosis was observed in the irradiated target while overt transections of myelin were detected histopathologically. Diffusivity values were found to be significantly reduced. A radiation dose ≤ 500 Gy associated with a beamlet size of < 50 µm did not cause visible transections, neither on diffusion maps nor on sections stained for myelin. We conclude that a peak dose of 500 Gy combined with a microbeam width of 100 µm optimally induced axonal transections in the white matter of the brain.

Anisotropic diffusion at the field scale in a 4-year multi-tracer diffusion and retention experiment – I: Insights from the experimental data

Abstract Claystones are considered worldwide as barrier materials for nuclear waste repositories. In the Mont Terri underground research laboratory (URL), a nearly 4-year diffusion and retention (DR) experiment has been performed in Opalinus Clay. It aimed at (1) obtaining data at larger space and time scales than in laboratory experiments and (2) under relevant in situ conditions with respect to pore water chemistry and mechanical stress, (3) quantifying the anisotropy of in situ diffusion, and (4) exploring possible effects of a borehole-disturbed zone. The experiment included two tracer injection intervals in a borehole perpendicular to bedding, through which traced artificial pore water (APW) was circulated, and a pressure monitoring interval. The APW was spiked with neutral tracers (HTO, HDO, H2O-18), anions (Br, I, SeO4), and cations (Na-22, Ba-133, Sr-85, Cs-137, Co-60, Eu-152, stable Cs, and stable Eu). Most tracers were added at the beginning, some were added at a later stage. The hydraulic pressure in the injection intervals was adjusted according to the measured value in the pressure monitoring interval to ensure transport by diffusion only. Concentration time-series in the APW within the borehole intervals were obtained, as well as 2D concentration distributions in the rock at the end of the experiment after overcoring and subsampling which resulted in �250 samples and �1300 analyses. As expected, HTO diffused the furthest into the rock, followed by the anions (Br, I, SeO4) and by the cationic sorbing tracers (Na-22, Ba-133, Cs, Cs-137, Co-60, Eu-152). The diffusion of SeO4 was slower than that of Br or I, approximately proportional to the ratio of their diffusion coefficients in water. Ba-133 diffused only into �0.1 m during the �4 a. Stable Cs, added at a higher concentration than Cs-137, diffused further into the rock than Cs-137, consistent with a non-linear sorption behavior. The rock properties (e.g., water contents) were rather homogeneous at the centimeter scale, with no evidence of a borehole-disturbed zone. In situ anisotropy ratios for diffusion, derived for the first time directly from field data, are larger for HTO and Na-22 (�5) than for anions (�3�4 for Br and I). The lower ionic strength of the pore water at this location (�0.22 M) as compared to locations of earlier experiments in the Mont Terri URL (�0.39 M) had no notable effect on the anion accessible pore fraction for Cl, Br, and I: the value of 0.55 is within the range of earlier data. Detailed transport simulations involving different codes will be presented in a companion paper.

Long-term diffusion experiment at Mont Terri: first results from field and laboratory data

The diffusion of radionuclides is an important safety aspect for nuclear waste disposal in argillaceous host rocks. A long-term diffusion experiment, termed DI-A, is being carried out at the Mont Terri Rock Laboratory in the Opalinus Clay formation. The aim of this experiment is the understanding of the migration and sorption behaviour of cationic and anionic species in consolidated clays. This study reports on the experimental layout and the first results obtained from the DI-A experiment, which include the investigation of HTO, Na-22(+), Cs+, and I- migration during a period of 1 year by analysing these tracers in the water circulating in the borehole. In addition, results obtained from through-diffusion experiments on small-sized samples with HTO, I-, and Cl-36(-) are presented. The decrease of tracer concentrations in the borehole is fastest for Cs+, followed by Na-22(+), HTO, and finally I-. The chemical composition of the artificial pore water in the borehole shows very little variation with time, thus indicating almost no chemical disturbance around the borehole. Through-diffusion experiments in the laboratory that were performed parallel to the bedding plane with two different methods yielded effective diffusion coefficients for HTO of 4-5 X 10(-11) m(2) s(-1) and significantly lower ones for anions Cl- and I- (0.7-1.6 X 10(-11) m(2) s(-1)). The results indicate the importance of anion exclusion effects arising from the negatively charged clay surfaces. Furthermore, they demonstrate the anisotropic diffusion properties of the clay formation with significantly increased diffusion rates parallel to bedding relative to the perpendicular direction. The tracer data of the in situ experiment were successfully described with 2D diffusion models using diffusion and sorption parameters obtained from the above mentioned and other laboratory studies. The modelling results indicate that HTO and I- diffused with no retardation. The retardation of Na+ and Cs+ could be described by empirical sorption expressions from previously derived batch sorption (Cs+) or diffusion (Na+) experiments. Overall, the obtained results demonstrate the feasibility of the technical concept to study the diffusion of nonsorbing and sorbing tracers in consolidated clays. (C) 2004 Elsevier B.V. All rights reserved.

Diffusion-weighted MR imaging of upper abdominal organs: field strength and intervendor variability of apparent diffusion coefficients

PURPOSE To determine the variability of apparent diffusion coefficient (ADC) values in various anatomic regions in the upper abdomen measured with magnetic resonance (MR) systems from different vendors and with different field strengths. MATERIALS AND METHODS Ten healthy men (mean age, 36.6 years ± 7.7 [standard deviation]) gave written informed consent to participate in this prospective ethics committee-approved study. Diffusion-weighted (DW) MR imaging was performed in each subject with 1.5- and 3.0-T MR systems from each of three vendors at two institutions. Two readers independently measured ADC values in seven upper abdominal regions (left and right liver lobe, gallbladder, pancreas, spleen, and renal cortex and medulla). ADC values were tested for interobserver differences, as well as for differences related to field strength and vendor, with repeated-measures analysis of variance; coefficients of variation (CVs) and variance components were calculated. RESULTS Interreader agreement was excellent (intraclass coefficient, 0.876). ADC values were (77.5-88.8) ×10(-5) mm(2)/sec in the spleen and (250.6-278.5) ×10(-5) mm(2)/sec in the gallbladder. There were no significant differences between ADC values measured at 1.5 T and those measured at 3.0 T in any anatomic region (P >.10 for all). In two of seven regions at 1.5 T (left and right liver lobes, P < .023) and in four of seven regions at 3.0 T (left liver lobe, pancreas, and renal cortex and medulla, P < .008), intervendor differences were significant. CVs ranged from 7.0% to 27.1% depending on the anatomic location. CONCLUSION Despite significant intervendor differences in ADC values of various anatomic regions of the upper abdomen, ADC values of the gallbladder, pancreas, spleen, and kidney may be comparable between MR systems from different vendors and between different field strengths.

High-field 1H T1 and T2 NMR Relaxation Time Measurements of H2O in Homeopathic Preparations of Quartz, Sulfur and Copper Sulfate

Quantitative meta-analyses of randomized clinical trials investigating the specific therapeutic efficacy of homeopathic remedies yielded statistically significant differences compared to placebo. Since the remedies used contained mostly only very low concentrations of pharmacologically active compounds, these effects cannot be accounted for within the framework of current pharmacology. Theories to explain clinical effects of homeopathic remedies are partially based upon changes in diluent structure. To investigate the latter, we measured for the first time high-field (600/500 MHz) 1H T1 and T2 nuclear magnetic resonance relaxation times of H2O in homeopathic preparations with concurrent contamination control by inductively coupled plasma mass spectrometry (ICP-MS). Homeopathic preparations of quartz (10c–30c, n = 21, corresponding to iterative dilutions of 100−10–100−30), sulfur (13x–30x, n = 18, 10−13–10−30), and copper sulfate (11c–30c, n = 20, 100−11–100−30) were compared to n = 10 independent controls each (analogously agitated dilution medium) in randomized and blinded experiments. In none of the samples, the concentration of any element analyzed by ICP-MS exceeded 10 ppb. In the first measurement series (600 MHz), there was a significant increase in T1 for all samples as a function of time, and there were no significant differences between homeopathic potencies and controls. In the second measurement series (500 MHz) 1 year after preparation, we observed statistically significant increased T1 relaxation times for homeopathic sulfur preparations compared to controls. Fifteen out of 18 correlations between sample triplicates were higher for controls than for homeopathic preparations. No conclusive explanation for these phenomena can be given at present. Possible hypotheses involve differential leaching from the measurement vessel walls or a change in water molecule dynamics, i.e., in rotational correlation time and/or diffusion. Homeopathic preparations thus may exhibit specific physicochemical properties that need to be determined in detail in future investigations.

Space, diffusion and mobility

Given its origins in traditional dialectology, and given advances in our understanding of the social embedding of language variation, it is paradoxical that space should be one of the categories that has received least attention of all in variationist sociolinguistics. Until recently, space has largely been treated as an empty stage on which sociolinguistic processes are enacted. It has been unexamined, untheorized, and its role in shaping and being shaped by variation and change untested. One function of this chapter, therefore, is to assert that space makes a difference, and to begin, in a very hesitant way, to map out what a geographically informed variation analysis might need to address. It also examines variationist interactions with the related concept of mobility. It might be reasonable to think that human geographers would provide some clues on how to proceed. As we will see, they have engaged in a great deal of soul searching about the goals of their discipline, its very existence as a separate field of enquiry, and the directions it should take. Indeed there are remarkable parallels between the recent history of human geographic thought, and interest in language variation across space. Although space has been undertheorized in variation studies, a number of researchers, from the traditional dialectologists through to those interested in the dialectology of mobility and contact, have, of course, been actively engaged in research on geographical variation and language use. Their work will be contextualized here to highlight both the parallels with theory-building in human geography, but also some of the criticisms of earlier approaches which have fed through to human geography, but remain largely unquestioned in variationist practice. The chapter therefore presents a brief theoretical background to space and mobility, before exemplifying these concepts in variationist research through an examination of, for example, the spatial diffusion of linguistic innovations, the spatial configuration of linguistic boundaries and initial steps to examine the consequences of mobility for variationist research.

An estimate of heavy quark momentum diffusion coefficient in gluon plasma

We calculate the momentum diffusion coefficient for heavy quarks in SU(3) gluon plasma at temperatures 1-2 times the deconfinement temperature. The momentum diffusion coefficient is extracted from a Monte Carlo calculation of the correlation function of color electric fields, in the leading order of expansion in heavy quark mass. Systematics of the calculation are examined, and compared with perturbtion theory and other estimates.

In-situ diffusion of HTO, 22Na+, Cs+ and I- in Opalinus Clay at the Mont Terri underground rock laboratory

The diffusion properties of the Opalinus Clay were studied in the underground research laboratory at Mont Terri (Canton Jura, Switzerland) and the results were compared with diffusion data measured in the laboratory on small-scale samples. The diffusion of HTO, Na-22(+), Cs+ and I- were investigated for a period of 10 months. The diffusion equipment used in the field experiment was designed in such a way that a solution of tracers was circulated through a sintered metal screen placed at the end of a borehole drilled in the formation. The concentration decrease caused by the diffusion of tracers into the rock could be followed with time and allowed first estimations of the effective diffusion coefficient. After 10 months, the diffusion zone was over-cored and the tracer profiles measured. From these profiles, effective diffusion coefficients and rock capacity factors Could be extracted by applying a two-dimensional transport model including diffusion and sorption. The simulations were done with the reactive transport code CRUNCH. In addition, results obtained from through-diffusion experiments oil small-sized samples with HTO, Cl-36(-) and Na-22(+) are presented and compared with the in situ data. In all cases. excellent agreement between the two data sets exists. Results for Cs+ indicated five times higher diffusion rates relative to HTO. Corresponding laboratory diffusion measurements are still lacking. However. our Cs+ data are in qualitative agreement wish through-diffusion data for Callovo-Oxfordian argillite rock samples. which also indicate significantly higher effective diffusivities for Cs+ relative to HTO.

Diffusion of HTO, Br-, I-, Cs+, Sr-85(2+) and Co-60(2+) in a clay formation: Results and modelling from an in situ experiment in Opalinus Clay

The migration of radioactive and chemical contaminants in clay materials and argillaceous host rocks is characterised by diffusion and retention processes. Valuable information on such processes can be gained by combining diffusion studies at laboratory scale with field migration tests. In this work, the outcome of a multi-tracer in situ migration test performed in the Opalinus Clay formation in the Mont Terri underground rock laboratory (Switzerland) is presented. Thus, 1.16 x 10(5) Bq/L of HTO, 3.96 x 10(3) Bq/L of Sr-85, 6.29 x 10(2) Bq/L of Co-60, 2.01 x 10(-3) mol/L Cs, 9.10 x 10(-4) mol/L I and 1.04 x 10(-3) mol/L Br were injected into the borehole. The decrease of the radioisotope concentrations in the borehole was monitored using in situ gamma-spectrometry. The other tracers were analyzed with state-of-the-art laboratory procedures after sampling of small water aliquots from the reservoir. The diffusion experiment was carried out over a period of one year after which the interval section was overcored and analyzed. Based on the experimental data from the tracer evolution in the borehole and the tracer profiles in the rock, the diffusion of tracers was modelled with the numerical code CRUNCH. The results obtained for HTO (H-3), I- and Br- confirm previous lab and in situ diffusion data. Anionic fluxes into the formation were smaller compared to HTO because of anion exclusion effects. The migration of the cations Sr-85(2+), Cs+ and Co-60(2+) was found to be governed by both diffusion and sorption processes. For Sr-85(2+), the slightly higher diffusivity relative to HTO and the low sorption value are consistent with laboratory diffusion measurements on small-scale samples. In the case of Cs+, the numerically deduced high diffusivity and the Freundlich-type sorption behaviour is also supported by ongoing laboratory data. For Co, no laboratory diffusion data were yet available for comparison; however, the modelled data suggests that Co-60(2+) sorption was weaker than would be expected from available batch sorption data. Overall, the results demonstrate the feasibility of the experimental setup for obtaining high-quality diffusion data for conservative and sorbing tracers. (C) 2007 Elsevier Ltd. All rights reserved.

Dry grasslands of Central-Eastern and South-Eastern Europe shaped by environmental heterogeneity and human land use – Editorial to the 10th Dry Grassland Special Feature

Der diesjährige 10. Trockenrasen-Sonderteil von Tuexenia beginnt mit einem Bericht über die aktuellen Aktivitäten der European Dry Grassland Group (EDGG). Zunächst geben wir einen Überblick über die Entwicklung der Mitgliederzahl. Dann berichten wir vom letzten European Dry Grassland Meeting in Tula (Russland, 2014) und vom letzten European Dry Grassland Field Workshop in Navarra (Spanien, 2014) und informieren über künftige Veranstaltungen der EDGG. Anschließend erläutern wir die Publikationsaktivitäten der EDGG. Im zweiten Teil des Editorials geben wir eine Einführung zu den fünf Artikeln des diesjährigen Trockenrasen-Sonderteils. Zwei Artikel beschäftigen sich mit der Syntaxonomie von Trockenrasen in Ost- bzw. Südosteuropa: der eine präsentiert erstmalig eine Gesamtklassifikation der Trockenrasengesellschaften Serbiens und des Kosovo während der andere Originalaufnahmen sub-montaner Graslandgesellschaften aus den bislang kaum untersuchten ukrainischen Ostkarpaten analysiert. Zwei weitere Artikel behandeln Trockenrasen-Feuchtwiesen-Komplexe im ungarischen Tiefland: Der eine behandelt den Einfluss der Landnutzung auf die Phytodiversität von Steppen und Feuchtwiesen, der andere den Einfluss von Niederschlagsschwankungen in einem Zeitraum von drei Jahren auf die Ausbildung salzbeeinflusster Steppen-Feuchtwiesen-Komplexe. Der fünfte Artikel analysiert landnutzungsbedingte Veränderungen des Graslands des Tsentralen-Balkan-Nationalparks in Bulgarien über einen Zeitraum von 65 Jahren

Editorial genesis: From comparing texts (product) to interpreting rewritings (process)

In literary genetics, “editorial genetics” deals with the “public life” of texts, whereas the writing process is affected by edition and diffusion. Editorial genetics frequently has to deal with cases of “editorial rewriting”: in the literary domain for example, authors frequently modify previously published works, so that several versions may co-exist. We are especially interested in Balzac’s La Bourse (translated in English as The Purse) since we know three authorized versions of this specific work.By comparing different texts associated with a single work, the literary geneticist is facing different products that are themselves the result of a writing process. However, different specificities should be outlined: (1) the writing process does not leave any trace: we just have access to different products/texts and (2) since the texts we compare seem to be achieved, differences must be referred, not to programmatic or temporary linguistic structures, but to the reconfiguration of a pre-existing textuality.Do such products still reflect the processes that have given birth to them? Does the comparison between two texts considered as variations of a same text give access to this transformation’s processes? After describing the objects of this particular textual comparison and the terminology that permits to give an account of such phenomenon, this contribution suggests to express these questions differently, as a matter of poetics of transitions between texts, or, further digging, an hermeneutics of the transition between texts.