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Das Advisory Committee on the Traffic in Women and Children des Völkerbunds. Internationale Problemwahrnehmung und Wissensproduktion zu Frauen- und Kinderhandel in der Zwischenkriegszeit
Full text linkDer Völkerbund hat bei seiner Gründung nach dem Ersten Weltkrieg neben seiner zentralen Aufgabe, für die Erhaltung des Weltfriedens zu sorgen, auch Aufgaben in sogenannten technischen Bereichen erhalten. Einer dieser „technischen“ Bereiche war die Überwachung der internationalen Abkommen zur Bekämpfung von Frauen- und Kinderhandel. Um dieses Aufgabe wahrzunehmen, richtete der Völkerbund 1921 eine internationale Konferenz zum Thema aus und beschloss ein Advisory Committee on the Traffic in Women and Children dazu einzusetzen. Dieses Komitee setzte sich aus staatlichen Delegierten sowie Beisitzern und Beisitzerinnen von internationalen Freiwilligenorganisationen zusammen. Es tagte ein Mal jährlich, um den aktuellen Stand der Umsetzung der internationalen Konventionen sowie die allgemeine Lage zu besprechen und dem Völkerbundsrat politische Empfehlungen abzugeben.
Auf Initiative des Komitees wurde eine Vielzahl von Daten zu Frauen- und Kinderhandel und zu Themen, welche das Komitee damit in Beziehung setzte, erhoben. Im Fokus der vorliegenden Dissertation stehen drei dieser Erhebungen, sogenannte Enqueten, diejenige zu Frauen- und Kinderhandel in Asien von 1932, diejenige zum Einsatz von weiblichen Polizeibeamten von 1927 und diejenige zu den „Antécédents“, den Vorgeschichten, von Prostituierten von 1938. Die Arbeit zeigt auf, wie diese Enqueten entstanden, welche Funktion, beziehungsweise welchen diskursiven und damit auch politischen Nutzen sie hatten beziehungsweise welches diskursive und politische Potential ihnen innewohnte und welche Ordnungsvorstellungen in die Konzeption dieser Enqueten einflossen. Dabei zeigen sich beispielsweise die Schwierigkeiten einer Erhebung in einem grösstenteils kolonial strukturierten Gebiet wie Asien, oder die Prävalenz von dualistischen Geschlechtervorstellungen bei Überlegungen zu den Aufgaben weiblicher Polizeibeamter oder die neue Bedeutung psychiatrischer Herangehensweisen an soziale Probleme.
Um die Folgen dieser Wissensproduktion möglichst konkret nachzuzeichnen, wurden in der vorliegenden Dissertation die Auswirkungen der Arbeit des Komitees auf die Schweiz detailliert untersucht. Dabei zeigen sich nicht nur die Charakteristika des schwachen Schweizer Bundesstaates in der Zwischenkriegszeit, sondern auch die neuen diskursiven Spielräume, die das Interesse und die Untersuchungen von internationaler Seite innenpolitisch eröffneten.
Neben der Frage nach den Auswirkungen auf nationaler Ebene, untersucht die Arbeit auch das Zusammenspiel von internationalen Freiwilligenorganisationen mit internationalen und nationalen Institutionen und zeigt, welche Einflussmöglichkeiten sich diesen Organisationen und den dort engagierten Frauen und Männern in der Zwischenkriegszeit mit der Schaffung des Komitees eröffneten
Bargaining for power and information : an experimental and theoretical analysis of the interaction between institutions, externalities and adverse selection
Full text linkBargaining is the building block of many economic interactions, ranging from bilateral to multilateral encounters and from situations in which the actors are individuals to negotiations between firms or countries. In all these settings, economists have been intrigued for a long time by the fact that some projects, trades or agreements are not realized even though they are mutually beneficial. On the one hand, this has been explained by incomplete information. A firm may not be willing to offer a wage that is acceptable to a qualified worker, because it knows that there are also unqualified workers and cannot distinguish between the two types. This phenomenon is known as adverse selection. On the other hand, it has been argued that even with complete information, the presence of externalities may impede efficient outcomes. To see this, consider the example of climate change. If a subset of countries agrees to curb emissions, non-participant regions benefit from the signatories’ efforts without incurring costs. These free riding opportunities give rise to incentives to strategically improve ones bargaining power that work against the formation of a global agreement.
This thesis is concerned with extending our understanding of both factors, adverse selection and externalities. The findings are based on empirical evidence from original laboratory experiments as well as game theoretic modeling. On a very general note, it is demonstrated that the institutions through which agents interact matter to a large extent. Insights are provided about which institutions we should expect to perform better than others, at least in terms of aggregate welfare.
Chapters 1 and 2 focus on the problem of adverse selection. Effective operation of markets and other institutions often depends on good information transmission properties. In terms of the example introduced above, a firm is only willing to offer high wages if it receives enough positive signals about the worker’s quality during the application and wage bargaining process. In Chapter 1, it will be shown that repeated interaction coupled with time costs facilitates information transmission. By making the wage bargaining process costly for the worker, the firm is able to obtain more accurate information about the worker’s type. The cost could be pure time cost from delaying agreement or cost of effort arising from a multi-step interviewing process. In Chapter 2, I abstract from time cost and show that communication can play a similar role. The simple fact that a worker states to be of high quality may be informative.
In Chapter 3, the focus is on a different source of inefficiency. Agents strive for bargaining power and thus may be motivated by incentives that are at odds with the socially efficient outcome. I have already mentioned the example of climate change. Other examples are coalitions within committees that are formed to secure voting power to block outcomes or groups that commit to different technological standards although a single standard would be optimal (e.g. the format war between HD and BlueRay). It will be shown that such inefficiencies are directly linked to the presence of externalities and a certain degree of irreversibility in actions. I now discuss the three articles in more detail.
In Chapter 1, Olivier Bochet and I study a simple bilateral bargaining institution that eliminates trade failures arising from incomplete information. In this setting, a buyer makes offers to a seller in order to acquire a good. Whenever an offer is rejected by the seller, the buyer may submit a further offer. Bargaining is costly, because both parties suffer a (small) time cost after any rejection. The difficulties arise, because the good can be of low or high quality and the quality of the good is only known to the seller. Indeed, without the possibility to make repeated offers, it is too risky for the buyer to offer prices that allow for trade of high quality goods. When allowing for repeated offers, however, at equilibrium both types of goods trade with probability one. We provide an experimental test of these predictions. Buyers gather information about sellers using specific price offers and rates of trade are high, much as the model’s qualitative predictions. We also observe a persistent over-delay before trade occurs, and this mitigates efficiency substantially. Possible channels for over-delay are identified in the form of two behavioral assumptions missing from the standard model, loss aversion (buyers) and haggling (sellers), which reconcile the data with the theoretical predictions.
Chapter 2 also studies adverse selection, but interaction between buyers and sellers now takes place within a market rather than isolated pairs. Remarkably, in a market it suffices to let agents communicate in a very simple manner to mitigate trade failures. The key insight is that better informed agents (sellers) are willing to truthfully reveal their private information, because by doing so they are able to reduce search frictions and attract more buyers. Behavior observed in the experimental sessions closely follows the theoretical predictions. As a consequence, costless and non-binding communication (cheap talk) significantly raises rates of trade and welfare. Previous experiments have documented that cheap talk alleviates inefficiencies due to asymmetric information. These findings are explained by pro-social preferences and lie aversion. I use appropriate control treatments to show that such consideration play only a minor role in our market. Instead, the experiment highlights the ability to organize markets as a new channel through which communication can facilitate trade in the presence of private information.
In Chapter 3, I theoretically explore coalition formation via multilateral bargaining under complete information. The environment studied is extremely rich in the sense that the model allows for all kinds of externalities. This is achieved by using so-called partition functions, which pin down a coalitional worth for each possible coalition in each possible coalition structure. It is found that although binding agreements can be written, efficiency is not guaranteed, because the negotiation process is inherently non-cooperative. The prospects of cooperation are shown to crucially depend on i) the degree to which players can renegotiate and gradually build up agreements and ii) the absence of a certain type of externalities that can loosely be described as incentives to free ride. Moreover, the willingness to concede bargaining power is identified as a novel reason for gradualism. Another key contribution of the study is that it identifies a strong connection between the Core, one of the most important concepts in cooperative game theory, and the set of environments for which efficiency is attained even without renegotiation
Sozialismus ohne Wachstum und Technologie? Die Linke in der Schweiz und die Umweltfrage 1968–1990
Full text linkDie Arbeiterbewegung hat sich ursprünglich der sozioökonomischen Schattenseite der Industrialisierung verschrieben. Für die ökologischen Nebenfolgen der technoökonomischen Entwicklung haben die linken Gesellschaftskritiker insofern kein Gespür gezeigt, als der historische Naturschutz bis in die 1970er Jahre eine traditionelle Domäne der Konservativen war. Die Linke verstand sich selbst als „progressiv“ und glaubte, einzig mit dem Fortschreiten von Wachstum und Technologie die Utopie einer sozialistischen Zukunft realisieren zu können. Dann aber – im Zuge der ökologischen Zäsur Ende der 1960er Jahre – wurde das Verhältnis zur Natur aus einer neuen Perspektive betrachtet. Die sich für die Umwelt zuständig fühlenden Kräfte gruppierten sich um. Das Umweltthema geriet in das Blickfeld der Arbeiterparteien, die sich mit dem eigenen Fortschrittsmythos auseinander zu setzen hatten. Wie haben die „Progressiven“ die Diskussion um die Grenzen der wirtschaftlichen und technologischen Entwicklung geführt? Welche traditionellen Denkmuster wurden im Zuge der Lernprozesse ökologisch aufgebrochen? Welchen Einfluss hatte der Umweltdiskurs der Linken auf das gesamtgesellschaftliche Reden und Denken über die Umwelt
Oberflächenveränderung verschiedener zahnmedizinischer Werkstoffe nach in-vitro Alterung
Full text linkSusceptibility of different restorative materials to toothbrush abrasion and coffee staining
Objective: The aim of this study was to evaluate the susceptibility of different restorative materials to surface alterations after an aging simulation.
Methods: Specimens (n=15 per material) of five different restorative materials (CER: ceramic/Vita Mark II; EMP: composite/Empress Direct; LAV: CAD/CAM composite/Lava Ultimate; COM: prefabricated composite/Componeer; VEN: prefabricated composite/Venear) were produced. Whereas CER was glazed, EMP and LAV were polished with silicon polishers, and COM and VEN were left untreated. Mean roughness (Ra and Rz) and colorimetric parameters (L*a*b*), expressed as colour change (E), were measured. The specimens underwent an artificial aging procedure. After baseline measurements (M1), the specimens were successively immersed for 24 hours in coffee (M2), abraded in a toothbrushing simulator (M3), immersed in coffee (M4), abraded (M5) and repeatedly abraded (M6). After each aging procedure (M2-M6), surface roughness and colorimetric parameters were recorded. Differences between the materials regarding Ra/Rz and E were analysed with a nonparametric ANOVA analysis. The level of significance was set at α=0.05.
Results: The lowest roughness values were obtained for CER. A significant increase in Ra was detected for EMP, COM and VEN compared to CER. The Ra/Rz values were found to be highly significantly different for the materials and measuring times (M) (p<0.0001). Regarding E most alterations were found for EMP and COM, whereas CER and LAV remained mostly stable. The E values were significantly different for the materials and M (p<0.0001).
Conclusion: The ceramic and the CAD/CAM composite were the most stable materials with regard to roughness and colour change and the only materials that resulted in Ra values below 0.2 μm (the clinically relevant threshold). Venears and Componeers were more inert than the direct composite material and thus might be an alternative for extensive restorations in the aesthetic zone
What makes a canon? Analysis of the Prātimokṣasūtra tradition in Mongolia in the context of canonical studies
Full text linkEssays on Behavioral Aspects of the Design and Disclosure of Compensation Contracts
Full text linkThis thesis consists of four essays on the design and disclosure of compensation contracts. Essays 1, 2 and 3 focus on behavioral aspects of mandatory compensation disclosure rules and of contract negotiations in agency relationships. The three experimental studies develop psychology-
based theory and present results that deviate from standard economic predictions. Furthermore, the results of Essay 1 and 2 also have implications for firms’ discretion in how to communicate their top management’s incentives to the capital market. Essay 4 analyzes the role of fairness perceptions for the evaluation of executive compensation. For this purpose, two surveys targeting representative eligible voters as well as investment professionals were conducted.
Essay 1 investigates the role of the detailed ‘Compensation Discussion and Analysis’, which is part of the Security and Exchange Commission’s 2006 regulation, on investors’ evaluations of executive performance. Compensation disclosure complying with this regulation clarifies the relationship between realized reported compensation and the underlying performance measures and their target achievement levels. The experimental findings suggest that the salient presentation of executives’ incentives inherent in the ‘Compensation Discussion and Analysis’ makes investors’ performance evaluations less outcome dependent. Therefore, investors’ judgment and investment decisions might be less affected by noisy environmental factors that drive financial performance. The results also suggest that fairness perceptions of compensation contracts are essential for investors’ performance evaluations in that more transparent disclosure increases the perceived fairness of compensation and the performance evaluation of managers who are not responsible for a bad financial performance. These results have important practical implications as firms might choose to communicate their top management’s incentive compensation more transparently in order to benefit from less volatile expectations about their future performance.
Similar to the first experiment, the experiment described in Essay 2 addresses the question of more transparent compensation disclosure. However, other than the first experiment, the second experiment does not analyze the effect of a more salient presentation of contract information but the informational effect of contract information itself. For this purpose, the experiment tests two conditions in which the assessment of the compensation contracts’ incentive compatibility, which determines executive effort, is either possible or not. On the one hand, the results suggest that the quality of investors’ expectations about executive effort is improved, but on the other hand investors might over-adjust their prior expectations about executive effort if being confronted with an unexpected financial performance and under-adjust if the financial performance confirms their prior expectations. Therefore, in the experiment, more transparent compensation disclosure does not lead to more correct overall judgments of executive effort and to even lower processing quality of outcome information. These results add to the literature on disclosure which predominantly advocates more transparency. The findings of the experiment however, identify decreased information processing quality as a relevant disclosure cost category. Firms might therefore carefully evaluate the additional costs and benefits of more transparent compensation disclosure. Together with the results from the experiment in Essay 1, the two experiments on compensation disclosure imply that firms should rather focus on their discretion how to present their compensation disclosure to benefit from investors’ improved fairness perceptions and their spill-over on performance evaluation.
Essay 3 studies the behavioral effects of contextual factors in recruitment processes that do not affect the employer’s or the applicant’s bargaining power from a standard economic perspective. In particular, the experiment studies two common characteristics of recruitment processes: Pre-contractual competition among job applicants and job applicants’ non-binding effort announcements as they might be made during job interviews. Despite the standard economic irrelevance of these factors, the experiment develops theory regarding the behavioral effects on employees’ subsequent effort provision and the employers’ contract design choices. The experimental findings largely support the predictions. More specifically, the results suggest that firms can benefit from increased effort and, therefore, may generate higher profits. Further, firms may seize a larger share of the employment relationship’s profit by highlighting the competitive aspects of the recruitment process and by requiring applicants to make announcements about their future effort.
Finally, Essay 4 studies the role of fairness perceptions for the public evaluation of executive compensation. Although economic criteria for the design of incentive compensation generally do not make restrictive recommendations with regard to the amount of compensation, fairness perceptions might be relevant from the perspective of firms and standard setters. This is because behavioral theory has identified fairness as an important determinant of individuals’ judgment and decisions. However, although fairness concerns about executive compensation are often stated in the popular media and even in the literature, evidence on the meaning of fairness in the context of executive compensation is scarce and ambiguous. In order to inform practitioners and standard setters whether fairness concerns are exclusive to non-professionals or relevant for investment professionals as well, the two surveys presented in Essay 4 aim to find commonalities in the opinions of representative eligible voters and investments professionals. The results suggest that fairness is an important criterion for both groups. Especially, exposure to risk in the form of the variable compensation share is an important criterion shared by both groups. The higher the assumed variable share, the higher is the compensation amount to be perceived as fair. However, to a large extent, opinions on executive compensation depend on personality characteristics, and to some extent, investment professionals’ perceptions deviate systematically from those of non-professionals. The findings imply that firms might benefit from emphasizing the riskiness of their managers’ variable pay components and, therefore, the findings are also in line with those of Essay 1
HIV-assoziierte Neuritis des Nervus vestibulocochlearis. Fallbeschreibung und systematische Literaturanalyse der HIV-assoziierten Polyneuropathien
Full text linkDie Polyneuropathien sind Komplikationen der Infektion mit dem Human-
Immunodeficiency-Virus (HIV). Dazu gehören Polyradikulopathien, distale (sensible)
Polyneuropathien, Mono- und Oligoneuropathien und brachiale Neuritiden. Selten
gibt es Formen, die sich nicht kategorisieren lassen. In dieser Dissertation
präsentieren wir einen aussergewöhnlichen Fall einer bilateralen Neuritis des Nervus
vestibulo-cochlearis (N. vestibulocochlearis). In einer ausgedehnten
Literaturrecherche ist das erst der dritte beschriebene Fall. Gleichzeitig wurde die
Literaturrecherche genutzt, um epidemiologische, klinische und laborchemische
Parameter der HIV-assoziierten Polyneuropathien zu analysieren. Dazu wurden
Daten von 539 Patientinnen aus 67 Publikationen extrahiert und ausgewertet. Die
Daten wurden bezüglich ihrer Qualität gewertet, um den Schlussfolgerungen eine
Gewichtung zu geben. Die Literaturanalyse ergab, dass die meisten Daten zu HIVassoziierten
– und bezüglich antiretroviraler Therapie (ART) naiven –
Polyneuropathien von afrikanischen Patienten stammen. Die meisten europäischen
und nordamerikanischen Studien zu diesem Thema wurden vor 1996 publiziert.
Polyradikulopathien präsentieren sich typischerweise früh und distale (sensible)
Polyneuropathien spät in der HIV-Krankheit. Das Guillain-Barré-Syndrom war das
häufigste Krankheitsbild der Polyradikulopathien. Die häufigste Präsentation distaler
Polyneuropathien sind Sensibilitätsausfälle an den unteren Extremitäten. Bei den
Mono- und Oligoneuropathien hat ein Grossteil der Personen Mononeuropathien,
wobei der N. facialis am häufigsten betroffen ist. Die Rolle der ART zur Erholung der
Neuropathien konnte nicht beurteilt werden. Unter den HIV-assoziierten
Polyneuropathien haben die distalen (sensiblen) Polyneuropathien die schlechtere
und die Polyradikulopathien und Mono- oder Oligoneuropathien die bessere
Prognose bezüglich Erholun
Characterization of choline uptake in Trypanosoma brucei and involvement of a mitochondrial carrier in resistance to choline analogs
Full text linkCholine is an essential nutrient for eukaryotic cells, where it is used as precursor for the synthesis of choline-containing phospholipids, such as phosphatidylcholine (PC). Our experiments showed – for the first time – that Trypanosoma brucei, the causative agent of human African sleeping sickness, is able to take up choline from the culture medium to use for PC synthesis, indicating that trypanosomes express a transporter for choline at the plasma membrane. Further characterization in procyclic and bloodstream forms revealed that choline uptake is saturable and can be inhibited by HC-3, a known inhibitor of choline uptake in mammalian cells.
To obtain additional insights on choline uptake and metabolism, we investigated the effects of choline-analogs that were previously shown to be toxic for T. brucei parasites in culture. Interestingly, we found that all analogs tested effectively inhibited choline uptake into both bloodstream and procyclic form parasites. Subsequently, selected compounds were used to search for possible candidate genes encoding choline transporters in T. brucei, using an RNAi library in bloodstream forms. We identified a protein belonging to the mitochondrial carrier family, previously annotated as TbMCP14, as prime candidate. Down‐regulation of TbMCP14 by RNAi prevented drug-induced loss of mitochondrial membrane potential and conferred 8‐fold resistance of T. brucei bloodstream forms to choline analogs. Conversely, over‐expression of the carrier increased parasite susceptibility more than 13-fold. However, subsequent experiments demonstrated that TbMCP14 was not involved in metabolism of choline. Instead, growth curves in glucose‐depleted medium using RNAi or knock‐out parasites suggested that TbMCP14 is involved in metabolism of amino acids for energy production. Together, our data demonstrate that the identified member of the mitochondrial carrier family is involved in drug uptake into the mitochondrion and has a vital function in energy production in T. brucei
Three Essays on Age and Firm Performance
Full text linkOld captains at the helm: Chairman age and firm performance
Urs Waelchli and Jonas Zeller
December, 2012
This paper examines whether the chairmen of the board (COBs) impose their life-cycles on the firms over which they preside. Using a large sample of unlisted firms we find a robust negative relation between COB age and firm performance. COBs age much like ‘ordinary’ people. Their cognitive abilities deteriorate and they experience significant shifts in motivation. Deteriorating cognitive abilities are the main driver of the performance effect that we observe. The results imply that succession planning problems in unlisted firms are real. Mandatory retirement age clauses cannot solve these problems.
Corporate Aging around the World
Jonas Zeller
January, 2014
This paper examines whether firms internationally age as US firms do (Loderer, Stulz, and Wälchli, 2013). Using a large panel, I find that Tobin’s Q monotonically falls with firm Age across all nineteen countries in the sample. The decrease varies across countries but is generally extremely robust and economically significant. ROA, sales growth, and market share decrease over a firm’s lifetime in most countries as well. Furthermore, older firms reduce their capital expenditures and R&D outlays. Instead, they distribute more cash to their shareholders. Overall, the results suggest that corporate aging is not confined to the US but is a genuine phenomenon that affects listed firms worldwide. This evidence supports the hypothesis that corporate aging is driven by managers who optimally focus on managing their assets in place and neglect the development of growth opportunities. I finally ask whether the managers’ choice and with it the magnitude of the decline in Tobin’s Q is a function of country-level institutional settings. I find that most notably firms age faster in countries where employees are relatively well protected by labor regulation.
Is employment protection the fountain of corporate youth?
Claudio Loderer, Urs Wälchli, Jonas Zeller*
September 2014
Acharya, Baghai, and Subramanian (2012, 2013) find that employment protection legislation (EPL) encourages innovation. We argue that this effect should be particularly strong in mature firms. We would therefore also expect EPL to boost growth opportunities. Using the natural Experiment created by the staggered passage of changes in EPL across seventeen countries, we find evidence that employment protection legislation does indeed stimulate Innovation efforts, especially in mature firms. The effect is stronger in countries in which patents are owned by the firm and in the context of regular contracts. Consistent with that, EPL encourages risk taking. Overall, however, there is Little evidence that the effect of EPL on innovation effort translates into higher firm value, not even in mature firms. EPL does motivate employees in those firms to put in a greater effort, as evidenced by stronger sales growth. Yet it also increases costs, reduces profitability, and depresses Tobin’s Q ratios in all firms, especially the mature ones, possibly because of the rigidities that characterize these firms [Loderer, Stulz, and Waelchli (2014)]
Water–montmorillonite systems: Neutron scattering and tracer throughdiffusion studies
Full text linkDesigns for deep geological respositories of nuclear waste include bentonite as a
hydraulic and chemisorption buffer material to protect the biosphere from leakage of radionuclides. Bentonite is chosen because it is a cheap, naturally occurring material with the required properties. It consists essentially of montmorillonite, a swelling clay mineral. Upon contact with groundwater such clays can seal the repository by incorporating water in the interlayers of their crystalline structure. The intercalated water exhibits significantly different properties to bulk water in the surrounding interparticle pores, such as lower diffusion coefficients (González Sánchez et. al. 2008). This doctoral thesis presents water distribution and diffusion behavior on various time and space scales in montmorillonite. Experimental results are presented for Na- and Cs-montmorillonite samples with a range of bulk dry densities (0.8 to 1.7 g/cm3). The experimental methods employed were neutron scattering (backscattering, diffraction, time-of-flight), adsorption measurements (water, nitrogen) and tracer-through diffusion. For the tracer experiments the samples were fully saturated via the liquid phase under volume-constrained conditions. In contrast, for the neutron scattering experiments, the samples were hydrated via the vapor phase and subsequently compacted, leaving a significant fraction of interparticle pores unfilled with water. Owing to these differences in saturation, the water contents of the samples for neutron scattering were characterized by gravimetry whereas those for the tracer experiments were obtained from the bulk dry density. The amount of surface water in interlayer pores could be successfully discriminated
from the amount of bulk-like water in interparticle pores in Na- and Csmontmorillonite
using neutron spectroscopy. For the first time in the literature, the distribution
of water between these two pore environments was deciphered as a function of
gravimetric water content. The amount was compared to a geometrical estimation of the amount of interlayer and interparticle water determined by neutron diffraction and adsorption measurements. The relative abundances of the 1 to 4 molecular water layers in the interlayer were determined from the area ratios of the (001)-diffraction peaks. Depending on the characterization method, different fractions of surface water
and interlayer water were obtained. Only surface and interlayer water exists in amontmorillonite with water contents up to 0.18 g/g according to spectroscopic measurements and up to 0.32 g/g according to geometrical estimations, respectively. At higher water contents, bulk-like and interparticle water also exists. The amounts increase monotonically, but not linearly, from zero to 0.33 g/g for bulk-like water and to 0.43 g/g for interparticle water. It was found that water most likely redistributes between the surface and interlayer sites during the spectroscopic measurements and therefore the reported fraction is relevant only below about -10 ºC (Anderson, 1967). The redistribution effect can explain the discrepancy in fractions between the methods.
In a novel approach the fractions of water in different pore environments were
treated as a fixed parameter to derive local diffusion coefficients for water from quasielastic neutron scattering data, in particular for samples with high water contents. Local diffusion coefficients were obtained for the 1 to 4 molecular water layers in the interlayer of 0.5·10–9, 0.9·10–9, 1.5·10–9 and 1.4·10–9 m²/s, respectively, taking account of the different water fractions (molecular water layer, bulk-like water). The diffusive transport of 22Na and HTO through Na-montmorillonite was measured on the laboratory experimental scale (i.e. cm, days) by tracer through-diffusion experiments. We confirmed that diffusion of HTO is independent of the ionic strength of the external solution in contact with the clay sample but dependent on the bulk dry density. In contrast, the diffusion of 22Na was found to depend on both the ionic strength of the pore solution and on the bulk dry density. The ratio of the pore and surface diffusion could be experimentally determined for 22Na from the dependence of the diffusion coefficient on the ionic strength. Activation energies were derived from the temperaturedependent diffusion coefficients via the Arrhenius relation. In samples with high bulk dry density the activation energies are slightly higher than those of bulk water whereas in low density samples they are lower. The activation energies as a function of ionic strengths of the pore solutions are similar for 22Na and HTO. The facts that (i) the slope of the logarithmic effective diffusion coefficients as a function of the logarithmic ionic strength is less than unity for low bulk dry densities and (ii) two water populations can be observed for high gravimetric water contents (low bulk dry densities) support the interlayer and interparticle porosity model proposed by Glaus et al. (2007), Bourg et al. (2006, 2007) and Gimmi and Kosakowski (2011)
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