New approaches for removing the Si-OH layer of biogenic silica before analysing oxygen isotopes - Helium Flow Dehydration (HFD) and Vacuum Bead Melting (VBM) technique

The analysis of oxygen isotopes from diatom silica (&#948;18OSi) in sediment cores has obtained importance for palaeoclimate reconstruction especially where carbonate proxies are either rare or not available. Compared to the widely accepted relation of oxygen isotopes of carbonate origin to climate-relevant parameters, challenges still occur using biogenic silica. These questions arise at sample preparation as well as and the analysis itself, but are especially related to the removal of loosely bound oxygen of the hydrous layer. It is the common view that diatoms consist of an isotopically homogenous inner Si-O-Si layer and a less dense, hydrous layer forming Si-OH bonds, which has to be removed from the sample prior to analysis. Three methods have been accepted so far to perform this step: Controlled Isotopic Exchange (CIE) followed by fluorination, Stepwise Fluorination (SWF) and inductive High-Temperature carbon reduction (iHTR). The former method of vacuum dehydration (VD) proved to be unable to remove all exchangeable oxygen.Here, a new, remotely-operated laser-fluorination based mass spectrometry unit is used for the analysis. The silica is reacted with a CO2 laser in a BrF5 atmosphere and oxygen is then transferred to and analysed in a mass spectrometer (PDZ Europa 20-20). As CIE is both time-consuming and work-intense and SWF is impractical for this setup mainly due to the high pressure increase during dehydration, a new, efficient and fast method should be developed to remove the hydrous layer using the laser-fluorinationprocess.Two approaches were tested to remove the Si-OH layer and the impact on &#948;18OSi was assessed by performing tests on internal standard materials of marine and lacustrine biogenic silica and of quartz. For VBM, a minimum of 1.5 mg of pure sample is melted to a bead with a defocused laser to eliminate the hydrous outer layer and to reduce the surface. After the bead has formed it is transferred into the reaction chamber completely reacted with a focused laser under BrF5 atmosphere and subsequently analysed on-line.The second method, HFD is an improvement of the outdated VD technique. The sample is heated to 1050°C in a He flow transporting away any removed exchangeable oxygen immediately and thus, not allowing it to re-react with the sample. Various tests have been performed considering pre-heating at 200°C, He flow adjustments and the time of the sample exposed to 1050°C.VBM has difficulties to fully remove the hydrous layer, which results in comparatively lower &#948;18O values. The final set-up was not found yet. The HFD generated similar data than SWF in other laboratories with a high reproducibility and accuracy (standard deviation <0.2 ). Best results could be achieved by pre-heating the sample at 200°C and later on expose it for 15 minutes under a Helium counter flow at 1050°C. Experience with both techniques will be discussed and the reliability of the data compared to other methods

A monograph on the morphology of stigmarioid branches

No abstract availabl

Cooperative Simultaneous Localization and Synchronization in Mobile Agent Networks

Cooperative localization in agent networks based on interagent time-of-flight measurements is closely related to synchronization. To leverage this relation, we propose a Bayesian factor graph framework for cooperative simultaneous localization and synchronization (CoSLAS). This framework is suited to mobile agents and time-varying local clock parameters. Building on the CoSLAS factor graph, we develop a distributed (decentralized) belief propagation algorithm for CoSLAS in the practically important case of an affine clock model and asymmetric time stamping. Our algorithm allows for real-time operation and is suitable for a time-varying network connectivity. To achieve high accuracy at reduced complexity and communication cost, the algorithm combines particle implementations with parametric message representations and takes advantage of a conditional independence property. Simulation results demonstrate the good performance of the proposed algorithm in a challenging scenario with time-varying network connectivity.Comment: 13 pages, 6 figures, 3 tables; manuscript submitted to IEEE Transaction on Signal Processin

A Membrane Component Essential for Vectorial Translocation of Nascent Proteins across the Endoplasmic Reticulum: Requirements for Its Extraction and Reassociation with the Membrane

Previous reports have shown that rough microsomes treated with high salt (Warren and Dobberstein, 1978, Nature, 273:569-571) or proteases (Walter et al ., 1979, Proc. Nati. Acad. Sci. U. S. A., 76:1,795) are unable to vectorially translocate nascent proteins. Readdition of the high salt or protease extracts restored activity to such inactive rough microsomes. A detailed study was carried out to determine how this factor interacts with the rough microsomal membrane. Proteolytic cleavage was found to be necessary but not sufficient to remove this factor from the membrane. A subsequent treatment with high salt had to be carried out . Endogenous (pancreatic) protease could effect the required cleavage, but low levels of trypsin, clostripain, or elastase were far more efficient. Several proteases were not effective. The minimum level of salt (after proteolysis) required to solubilize the active factor was -200 mM KCI. Salt extracts prepared by treatment with one of the effective proteases were capable of restoring activity to inactive microsomes produced by treatment with one of the others

The niche party concept and its measurement

The concept of the niche party has become increasingly popular in analyses of party competition. Yet, existing approaches vary in their definitions and their measurement approaches. We propose using a minimal definition that allows us to compare political parties in terms of their ‘nicheness’. We argue that the conceptual core of the niche party concept is based on issue emphasis and that a niche party emphasizes policy areas neglected by its rivals. Based on this definition, we propose a continuous measure that allows for more fine-grained measurement of a party’s ‘nicheness’ than the dominant, dichotomous approaches and thereby limits the risk of measurement error. Drawing on data collected by the Comparative Manifesto Project, we show that (1) our measure has high face validity and (2) exposes differences among parties that are not captured by alternative, static or dichotomous measures

Personalized Brain-Computer Interface Models for Motor Rehabilitation

We propose to fuse two currently separate research lines on novel therapies for stroke rehabilitation: brain-computer interface (BCI) training and transcranial electrical stimulation (TES). Specifically, we show that BCI technology can be used to learn personalized decoding models that relate the global configuration of brain rhythms in individual subjects (as measured by EEG) to their motor performance during 3D reaching movements. We demonstrate that our models capture substantial across-subject heterogeneity, and argue that this heterogeneity is a likely cause of limited effect sizes observed in TES for enhancing motor performance. We conclude by discussing how our personalized models can be used to derive optimal TES parameters, e.g., stimulation site and frequency, for individual patients.Comment: 6 pages, 6 figures, conference submissio