When spectroscopy fails: The measurement of ion pairing

Spectroscopic techniques such as UV/vis, NMR, and Raman are powerful tools for the investigation of chemical speciation in solution. However, it is not widely recognized that such techniques do not always provide reliable information about ion association equilibria. Specifically, spectroscopic measurements do not in general produce thermodynamically meaningful association constants for non-contact ion pairs, where the ions are separated by one or more solvent molecules. Such systems can only be properly quantified by techniques such as dielectric or ultrasonic relaxation, which can detect all ion-pair types (or equilibria), or by traditional thermodynamic methods, which detect the overall level of association. Various types of quantitative data are presented for metal ion/sulfate systems in aqueous solution that demonstrate the inadequacy of the major spectroscopic techniques for the investigation of systems that involve solvent-separated ion pairs. The implications for ion association equilibria in general are briefly discussed

Counterexamples to regularities for the derivative processes associated to stochastic evolution equations

In the recent years there has been an increased interest in studying regularity properties of the derivatives of stochastic evolution equations (SEEs) with respect to their initial values. In particular, in the scientific literature it has been shown for every natural number $n\in\mathbb{N}$ that if the nonlinear drift coefficient and the nonlinear diffusion coefficient of the considered SEE are $n$-times continuously Fr\'{e}chet differentiable, then the solution of the considered SEE is also $n$-times continuously Fr\'{e}chet differentiable with respect to its initial value and the corresponding derivative processes satisfy a suitable regularity property in the sense that the $n$-th derivative process can be extended continuously to $n$-linear operators on negative Sobolev-type spaces with regularity parameters $\delta_1,\delta_2,\ldots,\delta_n\in[0,1/2)$ provided that the condition $\sum^n_{i=1} \delta_i < 1/2$ is satisfied. The main contribution of this paper is to reveal that this condition can essentially not be relaxed

Decomposition of Bayer process organics: Phenolates, polyalcohols, and additional carboxylates

The degradation of nineteen low-molecular-weight phenolates, polyalcohols and selected aliphatic and aromatic carboxylates of relevance to the Bayer process has been studied in 6 mol kg-1 NaOH(aq) at 90 °C for up to 36 days, and (for some species) at 180 °C for up to 12 days, using HPLC and 13C NMR spectroscopy. Aliphatic polyalcohols degraded readily at 90 °C to lactate, oxalate, acetate, and formate. As observed previously, aliphatic carboxylates with hydroxyl groups also degraded readily at 90 °C but there is evidence that the position of the hydroxyl group may be important. The observed degradation products for most, but not all, of these species can be explained in terms of well-known organic reaction mechanisms. Phenolate and 5-hydroxyisophthalate were stable at 180 °C but other phenolic species degraded partially at 90 °C. However, the reaction products could not be identified and no trends in reactivity were discernible. Consistent with previous studies both aliphatic and aromatic carboxylates without hydroxyl groups were generally stable in NaOH(aq) even at 180 °C

Heat capacities of aqueous sodium hydroxide/aluminate mixtures and prediction of the solubility constant of boehmite up to 300 °C

A modified commercial (Setaram C80) calorimeter has been used to measure the isobaric volumetric heat capacities of concentrated alkaline sodium aluminate solutions at ionic strengths from 1 to 6 mol kg-1, with up to 40 mol.% substitution of hydroxide by aluminate, at temperatures from 50 to 300 °C and a pressure of 10 MPa. Apparent molar heat capacities for the mixtures, Cpφ{symbol}, derived from these data were found to depend linearly on the aluminate substitution level, i.e., they followed Young's rule. These quantities were used to estimate the apparent molar heat capacities of pure, hypothetical sodium aluminate solutions, Cpφ{symbol} ('NaAl(OH)4'(aq)). Slopes of the Young's rule plots were invariant with ionic strength at a given temperature but depended linearly on temperature. The heat capacities of ternary aqueous sodium hydroxide/aluminate mixtures could therefore be modelled using only two parameters in addition to those needed for the correlation of Cpφ{symbol} (NaOH(aq)) reported previously from these laboratories. An assessment of the standard thermodynamic quantities for boehmite, gibbsite and the aluminate ion yielded a set of recommended values that, together with the present heat capacity data, accurately predicts the solubility of gibbsite and boehmite at temperatures up to 300 °C

Mobilität älterer Menschen : State of the Art und Schlussfolgerungen für das Projekt COMPAGNO

Mobil zu sein ist ein menschliches Grundbedürfnis und gleichzeitig Bedingung sozialer Teilhabe in der Gesellschaft. Das Ziel von COMPAGNO ist es, Menschen bis ins hohe Alter in ihrer selbstständigen Mobilität zu unterstützen. Dieses Diskussionspapier gibt einen Überblick über den aktuellen Stand der Forschung zur Mobilität älterer Menschen. Es fasst zentrale Mobilitätskenngrößen älterer Menschen aus verschiedenen Studien zusammen. Anhand gerontologischer Theorien und Ansätze werden Zusammenhänge zwischen Prozessen des Alterns und Veränderungen der Mobilität hergestellt. Zentrales Thema dieses Diskussionspapiers ist außerdem der komplexe Entstehungsprozess von Mobilitätsbarrieren im Alter. Zudem wird ein bestehendes Zielgruppenmodell älterer Menschen für COMPAGNO adaptiert. Im abschließenden Kapitel werden Rückschlüsse für das weitere Vorgehen im Projekt COMPAGNO gezogen.About this textMobility is a basic human need and at once a basic condition for social participation. The project COMPAGNO wants to enable elderly persons to stay mobile up to an old age. This discussion paper presents the state of the art of research in the field mobility of older people. It wraps-up central data on mobility and mobility behavior of the elderly from different studies. Connections between the ageing process and changes in mobility behavior are made on the basis of gerontological theories and approaches. Another central topic discussed in this paper is the complex process which leads to mobility-barriers for elderly persons. Additionally, an existing target group model of the elderly will be adapted for the project COMPAGNO. The closing chapter presents conclusions for the further work process in the COMPAGNO project

Inverse Methods and Relative Nuclear Radii

Inverse methods are applied to the nuclear bound-state problem. Considering only the self-interactions of these states analytical solutions results for potentials and densities. The simplest possible approximation to the full expression yields immediately ⊿R0i2 ≡ 〈r2 (Ai)〉 - 〈r2 (A0)〉 ~ - [B (Ai) - B (A0)] for the differences in the squared nuclear radii as functions of the respective binding energies per nucleon, B (Ai)

The Inverse Mean Field Method and the Energy Dependence of the Nuclear Potential

The foundations of the inverse mean field method (Imefim) and its relation to traditional approaches are discussed. Imefim predicts the energy dependence of the real central (nuclear) part of the optical model potential to have the functional form (1 + eEp)‒3. Treating for the time being the constant e as an adjustable parameter, this prediction is shown to compare nicely with well-established formal and heuristic results. © 1983, Walter de Gruyter. All rights reserved

First year of routine measurements at the AWI MICADAS 14C dating facility.

In November 2016, the first Mini-Carbon-Dating-System (MICADAS) manufactured by Ionplus AG was delivered and installed at the Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research (AWI), Germany. After one year of establishing the instrument and preparation methods, we started routine operation for scientific purposes in January 2018. The new facility includes a graphitization unit (AGE3) connected to an elemental analyser (EA) or a carbonate handling system (CHS), and a gas inlet system (GIS). The facility at AWI focuses on analysing carbonaceous materials from samples of marine sediments, sea-ice, and water to investigate various aspects of the global carbon cycle. A particular emphasis will be on sediments from high-latitude oceans, in which radiocarbon-based age models are often difficult to obtain due to the scarcity of carbonate microfossils (e.g., foraminifera). One advantage of the MICADAS is the potential to analyse samples as CO2 gas, which allows radiocarbon measurements on samples containing as little as 10 µgC. For example, it is possible to determine 14C ages of foraminifera from carbonate-lean sediments allowing paleoclimate reconstructions in key locations for the Earth’s climate system, such as the Southern Ocean. Likewise, compound-specific 14C analyses receive growing attention in carbon cycle studies and require handling of small samples of typically <100 µgC. The wide range of applications including gas analyses (e.g., foraminifera and isolated compounds), and graphite targets require establishing routine protocols for various methods including sample preparation and precise blank assessment. We report on our standard procedures for dating organic matter from sediments or water including carbonate removal, combustion and graphitization using the AGE3 coupled to the EA, as well as on the methodology applied for carbonate samples using the CHS system and the GIS. We have investigated different sample preparation protocols and present the results using international standard reference materials (e.g., IAEA-C2 F14C = 0.4132 + 0.0052 (n= 14); Ref = 0.4114 + 0.0003). Additionally, we present the first results of process blanks for sediments (Eocene Messel shale F14C= 0.0007; equivalent to an conventional 14C age of > 52000yr (n=29)), as well as Eemian foraminifera (F14C = 0.005; equivalent to an conventional 14C age of >42700yr (n=98)). We are also presenting results of samples processed and analysed as graphite and directly as gas showing a good reproducibility irrespective of the method used