AMS-C14 analysis of graphite obtained with an Automated Graphitization Equipment (AGE III) from aerosol collected on quartz filters

AMS-14C applications often require the analysis of small samples. Such is the case of atmospheric aerosols where frequently only a small amount of sample is available. The ion beam physics group at the ETH, Zurich, has designed an Automated Graphitization Equipment (AGE III) for routine graphite production for AMS analysis from organic samples of approximately 1 mg. In this study, we explore the potential use of the AGE III for graphitization of particulate carbon collected in quartz filters. In order to test the methodology, samples of reference materials and blanks with different sizes were prepared in the AGE III and the graphite was analyzed in a MICADAS AMS (ETH) system. The graphite samples prepared in the AGE III showed recovery yields higher than 80% and reproducible 14C values for masses ranging from 50 to 300 lg. Also, reproducible radiocarbon values were obtained for aerosol filters of small sizes that had been graphitized in the AGE III. As a study case, the tested methodology was applied to PM10 samples collected in two urban cities in Mexico in order to compare the source apportionment of biomass and fossil fuel combustion. The obtained 14C data showed that carbonaceous aerosols from Mexico City have much lower biogenic signature than the smaller city of Cuernavaca.

Gaseous radiocarbon measurements of small samples

Radiocarbon dating by means of accelerator mass spectrometry (AMS) is a well-established method for samples containing carbon in the milligram range. However, the measurement of small samples containing less than 50 lg carbon often fails. It is difficult to graphitise these samples and the preparation is prone to contamination. To avoid graphitisation, a solution can be the direct measurement of carbon dioxide. The MICADAS, the smallest accelerator for radiocarbon dating in Zurich, is equipped with a hybrid Cs sputter ion source. It allows the measurement of both, graphite targets and gaseous CO2 samples, without any rebuilding. This work presents experiences dealing with small samples containing 1-40 lg carbon. 500 unknown samples of different environmental research fields have been measured yet. Most of the samples were measured with the gas ion source. These data are compared with earlier measurements of small graphite samples. The performance of the two different techniques is discussed and main contributions to the blank determined. An analysis of blank and standard data measured within years allowed a quantification of the contamination, which was found to be of the order of 55 ng and 750 ng carbon (50 pMC) for the gaseous and the graphite samples, respectively. For quality control, a number of certified standards were measured using the gas ion source to demonstrate reliability of the data.

Iodine-129: Sample preparation, quality control and analyses of pre-nuclear materials and of natural waters from Lower Saxony, Germany

Sample preparation procedures for AMS measurements of 129I and 127I in environmental materials and some methodological aspects of quality assurance are discussed. Measurements from analyses of some pre-nuclear soil and thyroid gland samples and of a systematic investigation of natural waters in Lower Saxony, Germany, are described. Although the up-to-now lowest 129I/127I ratios in soils and thyroid glands were observed, they are still suspect to contamination since they are significantly higher than the pre-nuclear equilibrium ratio in the marine hydrosphere. A survey on all available 129I/127I isotopic ratios in precipitation shows a dramatic increase until the middle of the 1980s and a stabilization since 1987 at high isotopic ratios of about (3.6–8.3)×10−7. In surface waters, ratios of (57–380)×10−10 are measured while shallow ground waters show with ratios of (1.3–200)×10−10 significantly lower values with a much larger spread. The data for 129I in soils and in precipitation are used to estimate pre-nuclear and modern 129I deposition densities.

MeV ion beam lithography of biocompatible halogenated Parylenes using aperture masks

Parylenes are poly(p-xylylene) polymers that are widely used as moisture barriers and in biomedicine because of their good biocompatibility. We have investigated MeV ion beam lithography using 16O+ ions for writing defined patterns in Parylene-C, which is evaluated as a coating material for the Cochlear Implant (CI) electrode array, a neuroprosthesis to treat some forms of deafness. Parylene-C and -F on silicon and glass substrates as well as 50 μm thick PTFE were irradiated to different fluences (1×1013-1×10161×1013-1×1016 1 MeV 16O+ ions cm−2) through aperture masks under high vacuum and a low pressure (<10−3 mbar) oxygen atmosphere. Biocompatibility of the irradiated and unirradiated surfaces was tested by cell-counting to determine the proliferation of murine spiral ganglion cells. The results reveal that an oxygen ion beam can be used to pattern Parylene-C and -F without using a liquid solvent developer in a similar manner to PTFE but with a ∼25× smaller removal rate. Biocompatibility tests showed no difference in cell adhesion between irradiated and unirradiated areas or ion fluence dependence. Coating the Parylene surface with an adhesion-promoting protein mixture had a much greater effect on cell proliferation.

NONLINEAR TIME SERIES/SYSTEM ANALYSIS (STATE-SPACE, DYNAMICS, INTERVENTION, RESILIENCE, KALMAN)

A discussion of nonlinear dynamics, demonstrated by the familiar automobile, is followed by the development of a systematic method of analysis of a possibly nonlinear time series using difference equations in the general state-space format. This format allows recursive state-dependent parameter estimation after each observation thereby revealing the dynamics inherent in the system in combination with random external perturbations.^ The one-step ahead prediction errors at each time period, transformed to have constant variance, and the estimated parametric sequences provide the information to (1) formally test whether time series observations y(,t) are some linear function of random errors (ELEM)(,s), for some t and s, or whether the series would more appropriately be described by a nonlinear model such as bilinear, exponential, threshold, etc., (2) formally test whether a statistically significant change has occurred in structure/level either historically or as it occurs, (3) forecast nonlinear system with a new and innovative (but very old numerical) technique utilizing rational functions to extrapolate individual parameters as smooth functions of time which are then combined to obtain the forecast of y and (4) suggest a measure of resilience, i.e. how much perturbation a structure/level can tolerate, whether internal or external to the system, and remain statistically unchanged. Although similar to one-step control, this provides a less rigid way to think about changes affecting social systems.^ Applications consisting of the analysis of some familiar and some simulated series demonstrate the procedure. Empirical results suggest that this state-space or modified augmented Kalman filter may provide interesting ways to identify particular kinds of nonlinearities as they occur in structural change via the state trajectory.^ A computational flow-chart detailing computations and software input and output is provided in the body of the text. IBM Advanced BASIC program listings to accomplish most of the analysis are provided in the appendix. ^

Sobre el argumento del érgon o sobre por qué la naturaleza no es un factor determinante del éthos

El presente trabajo tiene como objeto reevaluar el rol que desempeña el argumento del érgon en la EN, el cual ha sido largamente utilizado como elemento favorable a una lectura determinista de la virtud en Aristóteles. En esta lectura decir que toda naturaleza tiene una función que le es propia equivale a decir que por naturaleza aquello está llamado a cumplir necesariamente con esa función. La naturaleza entonces es entendida a la vez como condición necesaria y suficiente para llevar a cabo una función específica. En lo que sigue procuraremos mostrar que esta lectura es errónea, ya que la disposición natural, si bien es condición necesaria no es a la vez condición suficiente para llevar a cabo una función. Para ello partiremos de una elucidación de dos sentidos de naturaleza en Física II y reconstruiremos el argumento del érgon a la luz de estos nuevos elementos

Sobre el argumento del érgon o sobre por qué la naturaleza no es un factor determinante del éthos

El presente trabajo tiene como objeto reevaluar el rol que desempeña el argumento del érgon en la EN, el cual ha sido largamente utilizado como elemento favorable a una lectura determinista de la virtud en Aristóteles. En esta lectura decir que toda naturaleza tiene una función que le es propia equivale a decir que por naturaleza aquello está llamado a cumplir necesariamente con esa función. La naturaleza entonces es entendida a la vez como condición necesaria y suficiente para llevar a cabo una función específica. En lo que sigue procuraremos mostrar que esta lectura es errónea, ya que la disposición natural, si bien es condición necesaria no es a la vez condición suficiente para llevar a cabo una función. Para ello partiremos de una elucidación de dos sentidos de naturaleza en Física II y reconstruiremos el argumento del érgon a la luz de estos nuevos elementos

Sobre el argumento del érgon o sobre por qué la naturaleza no es un factor determinante del éthos

El presente trabajo tiene como objeto reevaluar el rol que desempeña el argumento del érgon en la EN, el cual ha sido largamente utilizado como elemento favorable a una lectura determinista de la virtud en Aristóteles. En esta lectura decir que toda naturaleza tiene una función que le es propia equivale a decir que por naturaleza aquello está llamado a cumplir necesariamente con esa función. La naturaleza entonces es entendida a la vez como condición necesaria y suficiente para llevar a cabo una función específica. En lo que sigue procuraremos mostrar que esta lectura es errónea, ya que la disposición natural, si bien es condición necesaria no es a la vez condición suficiente para llevar a cabo una función. Para ello partiremos de una elucidación de dos sentidos de naturaleza en Física II y reconstruiremos el argumento del érgon a la luz de estos nuevos elementos

Physical properties of ODP Sites 123-765 and 123-766

During Ocean Drilling Program Leg 123, two sites were drilled in the deep Indian Ocean. Physical properties were measured in soft Quaternary and Lower Cretaceous sediments to relatively fresh, glass-bearing pillow lavas and massive basalts. Porosities ranged from 89% near the seafloor to 1.6% for the dense basalts. This self-consistent set of measurements permitted some descriptive models of physical properties to be more rigorously tested than before. Predictive relationships between porosity and compressional-wave velocity have generally been based upon the Wyllie time average equation. However, this equation does not adequately describe the actual relationship between these two parameters, and many have attempted to improve it. In most cases, models were derived by testing them against a set of data representing a relatively narrow range of porosity values. Similarly, the use of the Wyllie equation has often been justified by a pseudolinear fit to the data over a narrow range of porosity values. The limitations of the Wyllie relationship have been re-emphasized here. A semi-empirical acoustic impedance equation is developed that provides a more accurate porosity-velocity transform, using realistic material parameters, than has hitherto been possible. A closer correlation can be achieved with this semi-empirical relationship than with more theoretically based equations. In addition, a satisfactory empirical equation can be used to describe the relationship between thermal conductivity and porosity. If enough is known about core sample lithologies to provide estimates of the matrix and pore water parameters, then these predictive equations enable one to describe completely the behavior of a saturated rock core in terms of compressional-wave velocity, thermal conductivity, porosity, and bulk density.

Compilation of d18O data, living planktic foraminifera

Most of the isotopic paleotemperature equations used for paleoceanographic reconstructions have been derived from culture experiments or inorganic precipitates of calcium carbonate. To test these equations in the modern ocean, we measured the oxygen isotope composition of planktonic foraminifera (Globigerinoides ruber, Globigerinoides sacculifer, Globigerina bulloides and Neogloboquadrina pachyderma) collected from Atlantic and Southern Ocean surface waters, and added published plankton tow data from the Pacific, Indian and Arctic Oceans. The resulting species-specific regression equations of the temperature:d18O relationships for G. ruber, G. sacculifer and G. bulloides are statistically indistinguishable. The equations derived for G. sacculifer and G. bulloides agree with relationships obtained from laboratory experiments, in which these species were cultured at pH values close to modern surface waters. The equation derived from N. pachyderma has a significantly lower slope and offset than the other three species but produces a regression equation that is nearly identical to the one for the epifaunal benthic foraminifer Cibicides sp. Our work on plankton tow and pumped samples indicates that culture-derived equations appear to be more appropriate for predicting the absolute d18O of the species examined compared to equations derived from inorganic precipitates. However, over the oceanic temperature range, the slopes of the equations we derive for living species agree with the slopes obtained from inorganic precipitates.

Registry of all samples from the Tara Oceans Expedition (2009-2013)

The Tara Oceans Expedition (2009-2013) sampled the world oceans on board a 36 m long schooner, collecting environmental data and organisms from viruses to planktonic metazoans for later analyses using modern sequencing and state-of-the-art imaging technologies. Tara Oceans Data are particularly suited to study the genetic, morphological and functional diversity of plankton. Data sets in this collection provide methodological and environmental context to all samples collected during the Tara Oceans Expedition (2009-2013).