Quantitative aspects of the microvascular system in macaque visual cortex

The basic principle of the most frequently used functional neuroimaging methods is the brain’s local dynamic regulation of blood flow. For a correct interpretation of neuroimaging results the structural and functional neurovascular coupling underlying this regulation must be well understood. Here we report quantitative anatomical data of the microvasculature in the macaque visual cortex. Formalin-fixed frozen sections of 4 animals (M. mulatta) were processed for double fluorescence immunohistochemistry. Sections were incubated with anti-collagen type IV and DAPI to stain for vessels and cell nuclei. In one additional animal, the anti-collagen procedure was combined with cytochrome oxidase staining in V1. The length density (LD), surface density (SD), volume fraction (VF) and diameter (D) of the vessels were stereologically determined. Furthermore, synchrotron-based computed tomographies (SRCT) of formalin-fixed and barium sulfate-perfused brain samples from another 2 animals were used to corroborate the histological results. In V1, the vascular density was highest in layer IVc- (LD 674.7 mm/mm3, SD 15.2 mm2/mm3, VF 2.6 , D 7.2 microns) and lowest in layer I (LD 461.5 mm/mm3, SD 10.9 mm2/mm3, VF 1.9 , D 7.5 microns). In all extrastriate visual areas analyzed (V2, V3, V4, V5), the vascular density was generally lower, and the difference between layer IV and the remaining layers was less prominent when compared to V1. These density values were similar compared to the ones tomographically obtained from SRCT. The vascular density in cytochrome oxidase rich blobs in V1 was 14 higher as compared to the interblob region. In summary, V1 is different from all extrastriate areas analyzed with respect to the laminar vessel distribution and overall vascular density. Differences between extrastriate areas were negligible. The overall vascular volume fraction in visual cortex derived from immunostaining was approximately 2 , a value that was well reproduced by the SRCT

Surface Core Level Shifts of Clean and Oxygen Covered Ru(0001)

We have performed high resolution XPS experiments of the Ru(0001) surface, both clean and covered with well-defined amounts of oxygen up to 1 ML coverage. For the clean surface we detected two distinct components in the Ru 3d_{5/2} core level spectra, for which a definite assignment was made using the high resolution Angle-Scan Photoelectron Diffraction approach. For the p(2x2), p(2x1), (2x2)-3O and (1x1)-O oxygen structures we found Ru 3d_{5/2} core level peaks which are shifted up to 1 eV to higher binding energies. Very good agreement with density functional theory calculations of these Surface Core Level Shifts (SCLS) is reported. The overriding parameter for the resulting Ru SCLSs turns out to be the number of directly coordinated O atoms. Since the calculations permit the separation of initial and final state effects, our results give valuable information for the understanding of bonding and screening at the surface, otherwise not accessible in the measurement of the core level energies alone.Comment: 16 pages including 10 figures. Submitted to Phys. Rev. B. Related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Engineered nanomaterials: toward effective safety management in research laboratories

It is still unknown which types of nanomaterials and associated doses represent an actual danger to humans and environment. Meanwhile, there is consensus on applying the precautionary principle to these novel materials until more information is available. To deal with the rapid evolution of research, including the fast turnover of collaborators, a user-friendly and easy-to-apply risk assessment tool offering adequate preventive and protective measures has to be provided.Results: Based on new information concerning the hazards of engineered nanomaterials, we improved a previously developed risk assessment tool by following a simple scheme to gain in efficiency. In the first step, using a logical decision tree, one of the three hazard levels, from H1 to H3, is assigned to the nanomaterial. Using a combination of decision trees and matrices, the second step links the hazard with the emission and exposure potential to assign one of the three nanorisk levels (Nano 3 highest risk; Nano 1 lowest risk) to the activity. These operations are repeated at each process step, leading to the laboratory classification. The third step provides detailed preventive and protective measures for the determined level of nanorisk.Conclusions: We developed an adapted simple and intuitive method for nanomaterial risk management in research laboratories. It allows classifying the nanoactivities into three levels, additionally proposing concrete preventive and protective measures and associated actions. This method is a valuable tool for all the participants in nanomaterial safety. The users experience an essential learning opportunity and increase their safety awareness. Laboratory managers have a reliable tool to obtain an overview of the operations involving nanomaterials in their laboratories; this is essential, as they are responsible for the employee safety, but are sometimes unaware of the works performed. Bringing this risk to a three-band scale (like other types of risks such as biological, radiation, chemical, etc.) facilitates the management for occupational health and safety specialists. Institutes and school managers can obtain the necessary information to implement an adequate safety management system. Having an easy-to-use tool enables a dialog between all these partners, whose semantic and priorities in terms of safety are often different

Risk analysis in research environment - Part I: Modeling Lab Criticity Index using Improved Risk Priority Number

Current available risk analysis techniques are well adapted to industry needs since they were developed for its purpose. All hazards present in industry are also met in research/academia, although quantities of some hazardous substances are smaller. Still, because of its characteristics e.g., high turnover of collaborators, rapid reorientation of research programs, freedom of research, equipment often in development stage, difficulty to obtain accidents statistics, not well described processes, etc., research/academia milieu is an environment whose risks are difficult to assess by available risk analysis techniques. In the present paper, a new methodology, Laboratory Assessment and Risk Analysis - LARA, for research and/or complex environment is proposed. When multiple hazards are analyzed, the result of assessment is a risk ranking calculated using a Lab Criticity Index - LCI, providing identification of critical areas and prioritization of safety actions. LCI is conceived through two approaches: the Risk Priority Number - RPN and the Analytic Hierarchy Process - AHP. It is suggested to estimate risk as a combination of severity, probability, detectability, worsening factors and research specificities. © 2011 Elsevier Ltd. All rights reserved

Risk analysis in research environment - Part II: Weighting Lab Criticity Index using the Analytic Hierarchy Process

A new methodology for risk analysis, namely Laboratory Assessment and Risk Analysis - LARA, is proposed in the companion paper to assess risks in research/academia environment. The core of this methodology relies on defining the adequate role player factors to assess risks in research environment and their mathematical combination to quantify and assess the risk. Quantitative outcome of the analysis results in a Lab Criticity Index - LCI, constructed as a rather comprehensive function of probability, severity, risk worsening factors, research specificities and Hazard Detectability. Even though the LCI model can be used at this stage, its "surjective" and "linear" properties were outlined; the non differentiation between LCI factors remains to be solved. The present article addresses this problematic, bringing a solution based on a Multicriteria Decision Making - MCDM modeling, namely Analytic Hierarchy Process -AHP. This leads to a refined criticity index being "bijective" and unique for every combination of factors. A preliminary risk assessment based on the LARA methodology is discussed for a research lab working with lasers. © 2010 Elsevier Ltd. All rights reserved

Coherence-enhanced synchrotron radiology: simple theory and practical applications

The advanced characteristics of synchrotron x-ray sources make it possible to implement radiology with powerful and innovative approaches. We review in simple terms the conceptual background of such approaches, then we present a number of selected examples. The practical tests concern life-sciences specimens as well as materials-science systems.X1164sciescopu

3D experimental investigation of the microstructure of cement pastes using synchrotron X-ray microtomography (mu CT)

Cement pastes aged from 1 to 60 days were studied using synchrotron microtomography on the MS-X04SA beam line at the Swiss Light Source. This allowed three dimensional images to be obtained with a resolution approaching that of backscattered electron images in the SEM. From these images, several features can be extracted and studied, both quantitatively and morphologically. In this study, attention was focused on the reacting anhydrous cement grains and porosity. Three dimensional imaging of capillary porosity allowed the connectivity and tortuosity of the pore network to be studied. It is shown that the degree of connectivity of the pore network is very sensitive to both the spatial resolution of the images and the evolution of contrast resolution during ageing of the cement. (C) 2006 Elsevier Ltd. All rights reserved