Development of a Biological Dosimeter for Translocation Scoring Based on Two-Color Fluorescence in Situ Hybridization of Chromosome Subsets

Recently fluorescence in situ hybridization protocols have been developed which allow the paining of individual chromosomes using DNA-libraries from sorted human chromosomes. This approach has the particular advantage that radiation induced chromosome translocations can be easily detected, if chromo-somes of distinctly different colors take part in the translocation event. To enhance the sensitivity of this approach two metaphase chromosome subsets A and B (A: chromosomes 1, 2, 4, 8, 16; B: 3, 5, 9, 10, 13) were simultaneously painted in green and red color. Counterstaining of the chromosomes with DAPI resulted in a third subset which exhibited blue fluorescence only. Green-red, green-blue and red-blue translocation chromosomes could be easily detected after irradiation of lymphocyte cultures with ^Cs-γ-rays. Analyses of painted chromosomes can be combined with conventional GTG-banding analyses. This new biological dosimeter should become useful to monitor both long term effects of single irradiation events and the cumulative effects of multiple or chronic irradiation exposures. In contrast to translocation scoring based on the analysis of banded chromosomes, this new approach has the particular advantage that a rapid, automated scoring of translocations can now be envisaged

Rapid metaphase and interphase detection of radiation-induced chromosome aberrations in human lymphocytes by chromosomal suppression in situ hybridization

Chromosomal in situ suppression (CISS)-hybridization of biotinylated phage DNA-library inserts from sorted human chromosomes was used to decorate chromosomes 1 and 7 specifically from pter to qter and to detect structural aberrations of these chromosomes in irradiated human peripheral lymphocytes. In addition, probe pUC1.77 was used to mark the Iq12 subregion in normal and aberrant chromosomes 1. Low LET radiation (60Co--rays; 1.17 and 1.33 MeV) of lymphocyte cultures was performed with various doses (D = 0, 2, 4, 8 Gy) 5 h after stimulation with phytohaemagglutinin. Irradiated cells were cultivated for an additional 67 h before Colcemid arrested metaphase spreads were obtained. Aberrations of the specifically stained chromosomes, such as deletions, dicentrics, and rings, were readily scored after in situ hybridization with either the 1q12 specific probe or DNA-library inserts. By the latter approach, translocations of the specifically stained chromosomes could also be reliably assessed. A linear increase of the percentage of specifically stained aberrant chromosomes was observed when plotted as a function of the square of the dose D. A particular advantage of this new approach is provided by the possibility to delineate numerical and structural chromosome aberrations directly in interphase nuclei. These results indicate that cytogenetic monitoring of ionizing radiation may be considerably facilitated by CISS-hybridization

Parametrization of Surface Albedo for Nadir Aerosol Retrieval SYNAER

Aerosol retrieval working in the visible channels has to deal with an ill-posed problem. AOD and surface albedo are both unknown parameters within a nadir-only aerosol retrieval as the synergistic aerosol retrieval SYNAER. SYNAER is a retrieval algorithm using a combination of radiometer and spectrometer measurements onboard the same satellite platform. In a first step the aerosol amount can only be estimated with the knowledge of the surface albedo within the visible channel. Kaufman, et al.1 introduced a linear parametrization of the albedo, which is dependent on the shortwave infrared radiometer measurement. This parametrization is a common way in the so called dark field method for aerosol retrievals2. For a general understanding of the dependences between red, near and shortwave infrared channels ASRVN datasets were analyzed. ASRVN is a MODIS based dataset of surface albedo, atmospheric corrected with adjacent AERONET aerosol measurements. Additionally measured surface spectra were investigated on synthetic radiometer channels. A linear relationship between shortwave infrared (1.6 um) and red (670 nm) can be determined as Kaufman suggested, but the relationship is not constant. As suggested by Holzer-Popp2, et al. for AATSR and by Mei et al.3 for AVHRR these linear relationship can be related to the NDVI (normalized differential vegetation index). By analyzing the ASRVN and spectrometer measurements it turned out that a simple linear relationship only by using the NDVI is not sufficient for a larger variety of surface types. In order to describe the SWIR to RED dependence an additional vegetation index has to be introduced. This index accounts not only for the vegetation amount of the surface as the NDVI does, but also allows a measure for the water amount of the surface, which affects the NIR and SWIR channels of a radiometer. Introducing the NDII (normalized differential infrared index) promises a more accurate determination of the RED surface reflectance based on the SWIR channel reflectance. Additionally, an analytical equation for the SWIR to RED reflectance can be derived including both vegetation indices NDVI and NDII. Nevertheless it has to be considered that the vegetation indices themselves are affected by the aerosol amount, so the approach needs their iterative correction for the aerosol impact. The extended parametrization of surface albedo is used in the synergistic aerosol retrieval. Theoretical calculations and application to satellite datasets will be discussed in the presentation

Near-equilibrium measurement of quantum size effects using Kelvin probe force microscopy

In nano-structures such as thin films electron confinement results in the quantization of energy levels in the direction perpendicular to the film. The discretization of the energy levels leads to the oscillatory dependence of many properties on the film thickness due to quantum size effects. Pb on Si(111) is a specially interesting system because a particular relationship between the Pb atomic layer thickness and its Fermi wavelength leads to a periodicity of the oscillation of two atomic layers. Here, we demonstrate how the combination of scanning force microscopy (SFM) and Kelvin probe force microscopy (KPFM) provides a reliable method to monitor the quantum oscillations in the work function of Pb ultra-thin film nano-structures on Si(111). Unlike other techniques, with SFM/KPFM we directly address single Pb islands, determine their height while suppressing the influence of electrostatic forces, and, in addition, simultaneously evaluate their local work function by measurements close to equilibrium, without current-dependent and non-equilibrium effects. Our results evidence even-odd oscillations in the work function as a function of the film thickness that decay linearly with the film thickness, proving that this method provides direct and precise information on the quantum states.Comment: This document is the unedited author's version of a Submitted Work that was subsequently accepted for publication in Nanoscale, copyright Royal Society of Chemistry after peer review. To access the final edited and published work see doi belo

Precise Control of Molecular Self-Diffusion in Isoreticular and Multivariate Metal-Organic Frameworks.

Understanding the factors that affect self-diffusion in isoreticular and multivariate (MTV) MOFs is key to their application in drug delivery, separations, and heterogeneous catalysis. Here, we measure the apparent self-diffusion of solvents saturated within the pores of large single crystals of MOF-5, IRMOF-3 (amino-functionalized MOF-5), and 17 MTV-MOF-5/IRMOF-3 materials at various mole fractions. We find that the apparent self-diffusion coefficient of N,N-dimethylformamide (DMF) may be tuned linearly between the diffusion coefficients of MOF-5 and IRMOF-3 as a function of the linker mole fraction. We compare a series of solvents at saturation in MOF-5 and IRMOF-3 to elucidate the mechanism by which the linker amino groups tune molecular diffusion. The ratio of the self-diffusion coefficients for solvents in MOF-5 to those in IRMOF-3 is similar across all solvents tested, regardless of solvent polarity. We conclude that average pore aperture, not solvent-linker chemical interactions, is the primary factor responsible for the different diffusion dynamics upon introduction of an amino group to the linker

Periodic array-based substrates for surface-enhanced infrared spectroscopy

At the beginning of the 1980s, the first reports of surface-enhanced infrared spectroscopy (SEIRS) surfaced. Probably due to signal-enhancement factors of only 101 to 103, which are modest compared to those of surface-enhanced Raman spectroscopy (SERS), SEIRS did not reach the same significance up to date. However, taking the compared to Raman scattering much larger cross-sections of infrared absorptions and the enhancement factors together, SEIRS reaches about the same sensitivity for molecular species on a surface in terms of the cross-sections as SERS and, due to the complementary nature of both techniques, can valuably augment information gained by SERS. For the first 20 years since its discovery, SEIRS relied completely on metal island films, fabricated by either vapor or electrochemical deposition. The resulting films showed a strong variance concerning their structure, which was essentially random. Therefore, the increase in the corresponding signal-enhancement factors of these structures stagnated in the last years. In the very same years, however, the development of periodic array-based substrates helped SEIRS to gather momentum. This development was supported by technological progress concerning electromagnetic field solvers, which help to understand plasmonic properties and allow targeted design. In addition, the strong progress concerning modern fabrication methods allowed to implement these designs into practice. The aim of this contribution is to critically review the development of these engineered surfaces for SEIRS, to compare the different approaches with regard to their performance where possible, and report further gain of knowledge around and in relation to these structures