TOF-SIMS characterization of planktonic foraminifera

Oceanic sediment properties that are closely related to former environmental (e.g. climatic) parameters are called "proxies". Planktonic foraminifera are small animals which make up part of the plankton. Certain element concentrations, element ratios and isotopic ratios of their calcite shell found in the sediment can be used as "proxies" reflecting the state of the ocean during the life of the animal; they supply useful information for the reconstruction of environmental parameters. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to examine the inner and outer part of foraminiferal shells, as well as foraminiferal shells dissolved in HCL. High resolution elemental images and mass spectra were obtained from the foraminifera. The data show that TOF-SIMS is a useful technique for determining the elemental distribution and for measuring isotope ratios such as dB with high precision in a single foraminiferal shell

Hochsensitive markierungsfreie DNA-Mikrochip-Analytik. Teilvorhaben: TOF-SIMS Diagnostik von DNA auf Biosensor-Chips Abschlussbericht

SIGLEAvailable from TIB Hannover: F03B1137 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman

Chronic obstructive pulmonary disease stage and risk of hospitalization for infectious disease.

The surface chemistry and ionization state of cross-linked poly(dimethylsiloxane) (PDMS) exposed to UV/ozone were studied as a function of treatment time. Various complementary and independent experimental techniques were utilized, which yielded information on the macroscopic as well as the nanometric scale. The average chemical composition of the PDMS surface was quantitatively investigated by time-of-flight secondary ion mass spectrometry (ToF-SIMS). It was found that the top 1-2 nm surface layer was dominated by silanol groups (-SiOH) for which the concentration increased with increasing treatment dose. The lateral distributions of the silanol groups were analyzed on the nanometer scale by means of atomic force microscopy (AFM) with chemically functionalized tip probes in aqueous buffer solutions at varying pHs. Spatially dependent pull-off force curves (also called "force volume" imaging) indicated the presence of strong chemical heterogeneity of the probed surface. This heterogeneity took the form of patches of silanol functionalities with high local concentration surrounded by a matrix of predominantly hydrophobic domains at low pH. The average pull-off forces for the entire surface scanned were significantly reduced for pH values larger than a characteristic pKa constant (in the range between 4.5 and 5.5). The extent of the decrease in the pull-off force and the particular value of pKa were found to be a function of treatment time and to differ from the commonly reported values for silanol functional groups on a homogeneous silica surface. These dependences were ascribed to the evoking of a protonation/deprotonation process of the surface silanol groups which was sensitive to the hydrophobic/hydrophilic balance of their close molecular environment. Intermolecular hydrogen bonding may also account for the shifts in the surface pKa. Furthermore, depending on the nature of the electrolyte, a third effect related to double layer composition, as determined by specific ion adsorption, was quantitatively analyzed by streaming potential measurements in the presence of sodium chloride and phosphate electrolytes