Interaction of water with oxide glass structures

The aim of this thesis is to investigate the influence of different network converters on different glass structures. A special focus lies hereby on the incorporation of water regarding its corrosive behavior on the glass network. This in turn improves the understanding of water-related material fatigue and subcritical crack growth in technical glasses. For this purpose, two lithium-magnesium aluminophosphate glasses (30Li2O 20-xMgO xAl2O3 50P2O5 with x = 0 and 5), 4 silicoborate glasses (15- xNa2O xCaO 15SiO2 70B2O3 with x = 0; 7.5 and 10, as well as 10Na2O 15SiO2 and 75B2O3) and three aluminosilicate glasses (22.5-xNa2O xK2O 22.5 Al2O3 55SiO2 with x = 0; 7.5; 11.25) were prepared. Water bearing glasses between 0-8 wt% H2O were synthesized at 500 MPa using an Internally Heated Pressure Vessel (IHPV) at temperatures between 1473 – 1873 K. With respect to the structure and water speciation in the glasses, anhydrous and hydrous glasses have been analyzed using MAS-NMR (Magic Angle Spinning Nuclear Magnetic Resonance) and infrared-spectroscopy (IR). The glass transition temperature (Tg) was determined by Differential Thermal Analysis (DTA). IR spectroscopy on phosphate glasses reveal that OH groups are the dominating water species. A similar trend was observed in silicoborates. The incorporation of water results in a dominance of hydroxyl groups, here too. A dominance of OH groups was also observed in aluminum-containing phosphates. However, the proportion of molecular water is higher compared to aluminum-free phosphates. In aluminosilicates, on the other hand, the incorporated water is present in molecular form at water contents above 3 % wt%. The decrease in Tg upon hydration is similarly continuous for phosphates and silica borates, while a dramatic decrease has been observed for aluminosilicates. This indicates that the incorporation of OH groups has a significantly weaker effect on structural relaxation in phosphate and borate systems than in silicate dominated glasses. The depolymerization of the glass network during hydration varies depending on the glass system. The incorporation of water has a very strong depolymerizing effect on the phosphate structure, as more and more Q1 and even Q0 species are formed at the expense of Q3 and Q2 species as the water content increases. 11B MAS NMR in silicoborates reveals that the BO4 species depends mainly on the alkali and alkaline earth content and that water plays only a minor role in the formation of the BO4 species. However, the efficiency for the formation of BO4 units in silicoborates is higher than in pure borate glasses. 27Al MAS NMR spectra of aluminosilicates reveal that aluminum is exclusively present in the form of AlO4 tetrahedra in both dry and hydrous glasses. The incorporation of water causes the relaxation of highly distorted Q4 species by forming slightly depolymerized Q3 species.Ziel dieser Arbeit ist es den Einfluss verschiedener Netzwerkwandler auf unterschiedliche Glasstrukturen zu Untersuchen. Ein besonderer Fokus liegt dabei auf dem Einbau von Wasser hinsichtlich seines korrosiven Verhaltens auf das Glasnetzwerk. Dies wiederum verbessert das Verständnis von wasserbedingter Materialermüdung und dem subkritischen Risswachstum in technischen Gläsern. Hierfür wurden zwei Lithium-Magnesium-Aluminophosphate (30Li2O 20-xMgO xAl2O3 50P2O5 mit x = 0 und 5), vier Silicoborat Gläser (15- xNa2O xCaO 15SiO2 70B2O3 mit x = 0; 7,5 und 10, sowie 10Na2O 15SiO2 und 75B2O3) und drei Aluminosilikat Gläser (22,5-xNa2O xK2O 22,5 Al2O3 55SiO2 mit, x = 0; 7,5; 11,25) hergestellt. Die wasserhaltigen Gläser zwischen 0-8 Gew.% H2O wurden bei 500 MPa in einer intern beheizten Gasdruckanlage (IHPV) bei Temperaturen zwischen 1473 – 1873 K hergestellt. Die Struktur der trockenen und wasserhaltigen Gläser wurde hinsichtlich der Netzwerkstruktur und Wasserspeziation mittels MAS-NMR- (Magic Angle Spinning Nuclear Magnetic Resonance) und Infrarot-Spektroskopie (IR) untersucht. Die Glasübergangstemperatur (Tg) wurde mittels Differentieller Thermischer Analyse (DTA) bestimmt. Die IR-Spektroskopie an Phosphaten zeigt, dass OH Gruppen die dominierende Wasserspezies sind. Ein ähnlicher Trend wurde in Silicoboraten beobachtet. Auch dort resultiert der Einbau von Wasser in einer Dominanz von Hydroxylgruppen. In aluminiumhaltigen Phosphaten wurde ebenfalls eine Dominanz von OH gruppen beobachtet. Allerdings ist der Anteil von molekularem Wasser im Vergleich zu den aluminiumfreien Phosphaten größer. In Aluminiumsilikaten hingegen, liegt das eingebaute Wasser ab Wassergehalten von ca. 3 Gew.% in molekularer Form vor. Die im Zuge des Wassereinbaus abnehmende Tg läuft für Phosphate und Silicoborate ähnlich kontinuierlich ab, während ein dramatischer Abfall für Aluminosilikaten beobachtet wurde. Das deutet darauf hin, dass der Einbau von OH Gruppen einen deutlich schwächeren Effekt auf die strukturelle Relaxation in Phosphat- und Borat Systemen, hat als in Silikat dominierten Gläsern. Die Depolymerisierung des Glasnetzwerks, im Zuge der Hydratisierung, ist abhängig vom Glassystem unterschiedlich stark ausgeprägt. So wirkt sich der Einbau von Wasser auf die Phosphatstruktur sehr stark depolymerisierend aus, indem mit steigendem Wassergehalt mehr und mehr Q1 und sogar Q0 Spezies auf kosten von Q3 und Q2 Spezies gebildet werden. 11B MAS NMR in Silicoboraten zeigt, dass die BO4 Spezies hauptsächlich vom Alkali und Erdalkali Gehalt abhängt und Wasser nur eine untergeordnete Rolle für die Bildung der BO4 Spezies spielt. Allerdings ist die Effizienz zur Bildung von BO4 Einheiten in Silicoboraten größer als in reinen Boraten. 27Al MAS NMR Spektren von Aluminosilikaten zeigen, dass Aluminium sowohl in trockenen als auch in hydratisierten Gläsern ausschließlich in Form von AlO4 Tetraedern vorliegt. Der Einbau von Wasser bewirkt die Entspannung von stark verzerrten Q4 Spezies indem leicht depolymerisierte Q3 Spezies gebildet werden.

Logical Relations for Session-Typed Concurrency

Program equivalence is the fulcrum for reasoning about and proving properties of programs. For noninterference, for example, program equivalence up to the secrecy level of an observer is shown. A powerful enabler for such proofs are logical relations. Logical relations only recently were adopted for session types -- but exclusively for terminating languages. This paper scales logical relations to general recursive session types. It develops a logical relation for progress-sensitive noninterference (PSNI) for intuitionistic linear logic session types (ILLST), tackling the challenges non-termination and concurrency pose, and shows that logical equivalence is sound and complete with regard to closure of weak bisimilarity under parallel composition, using a biorthogonality argument. A distinguishing feature of the logical relation is its stratification with an observation index (as opposed to a step or unfolding index), a crucial shift to make the logical relation closed under parallel composition in a concurrent setting. To demonstrate practicality of the logical relation, the paper develops an information flow control (IFC) refinement type system for ILLST, with support of secrecy-polymorphic processes, and shows that well-typed programs are self-related by the logical relation and thus enjoy PSNI. The refinement type system has been implemented in a type checker, featuring local security theories to support secrecy-polymorphic processes.Comment: arXiv admin note: text overlap with arXiv:2208.1374

Self-Adaptive Systems for Information Survivability: PMOP and AWDRAT

Information systems form the backbones of the critical infrastructures of modern societies. Unfortunately, these systems are highly vulnerable to attacks that can result in enormous damage. Furthermore, traditional approaches to information security have not provided all the protections necessary to defeat and recover from a concerted attack; in particular, they are largely irrelevant to the problem of defending against attacks launched by insiders.This paper describes two related systems PMOP and AWDRAT that were developed during the DARPA Self Regenerative Systems program. PMOP defends against insider attacks while AWDRAT is intended to detect compromises to software systems. Both rely on self-monitoring, diagnosis and self-adaptation. We describe both systems and show the results of experiments with each

Predictive Ability of the Stability and Workload Index for Transfer Score to Predict Unplanned Readmissions After ICU Discharge

Objective: Unplanned readmission of hospitalized patients to an ICU is associated with an increased mortality and hospital length of stay. The ability to identify patients at risk, who would benefit from prolonged ICU treatment, is limited. The aim of this study is to validate a previously published numerical index named the Stability and Workload Index for Transfer in a heterogeneous group of ICU patients. Design: In this retrospective data analysis, the Stability and Workload Index for Transfer score was calculated for all patients, and the ability of the score to predict readmission was compared with the original publication. Setting: Four ICUs, one intermediate care unit, and one postanesthesia care unit of the department of anesthesia and intensive care of a university hospital. Patients: All consecutive patients treated in one of the units. Interventions: None. Measurements and Main Results: Unplanned ICU readmissions or unexpected death within 7 days of ICU discharge. The data of 7,175 patients were included in the analysis. Five hundred ninety-six patients were readmitted or died within 7 days of discharge. The patients who are readmitted to the ICU are significantly older and have significantly higher scores that define the severity of disease at the time of admission and discharge of their first ICU stay. The source of admission for the initial ICU stay did not differ (p = 0.055), and the last Glasgow Coma Scale and the last Pao(2)/Fio(2) ratio before discharge from the ICU were higher in patients who did not need a readmission to the ICU. The performance of the Stability and Workload Index for Transfer score is poor with an area under the receiver operator curve of 0.581 (95% CI, 0.556-0.605; p < 0.001). Conclusions: Based on the data from our patients, the proposed Stability and Workload Index for Transfer score by Gajic et al is not ideal in aiding the clinician in the decision, if a patient can be discharged safely from the ICU and further research is necessary to define the patients at risk for readmission

Water in Alkali Aluminosilicate Glasses

To understand the influence of water and alkalis on aluminosilicate glasses, three polymerized glasses with varying ratios of Na/K were synthesized [(22. 5-x)Na2O-xK2O-22.5 Al2O3-55 SiO2 with x = 0, 7.5, and 11.25]. Subsequently, these glasses were hydrated (up to 8 wt% H2O) in an internally heated gas pressure vessel. The density of hydrous glasses linearly decreased with water content above 1 wt%, consistent with the partial molar volume of H2O of 12 cm3/mol. Near-infrared spectroscopy revealed that hydroxyl groups are the dominant species at water content of &lt;4 wt%, and molecular water becomes dominating at water content of &gt;5 wt%. The fraction of OH is particularly high in the pure Na-bearing glass compared to the mixed alkali glasses. 27Al magic angle spinning-NMR spectroscopy shows that aluminum is exclusively fourfold coordinated with some variations in the local geometry. It appears that the local structure around Al becomes more ordered with increasing K/Na ratio. The incorporation of H2O reinforces this effect. The differential thermal analysis of hydrous glasses shows a significant mass loss in the range of glass transition already during the first upscan, implying the high mobility of water in the glasses. This observation can be explained by the open structure of the aluminosilicate network and by the low dissociation enthalpy of H2O in the glasses (≈ 8 kJ/mol). The effect of the dissolved H2O on the glass transition temperature is less pronounced than for other aluminosilicate glasses, probably because of the large fraction of Al in the glasses. © Copyright © 2020 Balzer, Behrens, Waurischk, Reinsch, Müller, Kiefer, Deubener and Fechtelkord

Automated Analysis of Slow Crack Growth in Hydrous Soda-Lime Silicate Glasses

To explore the impact of ambient and structural water on static fatigue, the initiation and growth of 3279 Vickers induced median radial cracks were automatically recorded and analyzed. We find that humidity is more efficient in initiating cracks and promoting their growth than water, which is dissolved in the glass structure. In particular for slow crack growth (< 3 × 10–6 m s–1), tests in dry nitrogen showed a considerable decrease in the crack growth exponent with increasing water content of the glasses. On the other hand, if tests were performed in humid air, the crack growth exponent was independent of the water content of the hydrous glasses, while stress intensity decreased slightly. These observations indicate that water promotes the processes at the crack-tip regardless of its origin. However, ambient water is more efficient

Automated analysis of slow crack growth in hydrous soda-lime silicate glasses

To explore the impact of ambient and structural water on static fatigue, the initiation and growth of 3279 Vickers induced median radial cracks were automatically recorded and analyzed. We find that humidity is more efficient in initiating cracks and promoting their growth than water, which is dissolved in the glass structure. In particular for slow crack growth (< 3 × 10−6 m s−1), tests in dry nitrogen showed a considerable decrease in the crack growth exponent with increasing water content of the glasses. On the other hand, if tests were performed in humid air, the crack growth exponent was independent of the water content of the hydrous glasses, while stress intensity decreased slightly. These observations indicate that water promotes the processes at the crack-tip regardless of its origin. However, ambient water is more efficient

Does adherence to a quality indicator regarding early weaning from invasive ventilation improve economic outcome? A single-centre retrospective study

ObjectivesTo measure and assess the economic impact of adherence to a single quality indicator (QI) regarding weaning from invasive ventilation.DesignRetrospective observational single-centre study, based on electronic medical and administrative records.SettingIntensive care unit (ICU) of a German university hospital, reference centre for acute respiratory distress syndrome.ParticipantsRecords of 3063 consecutive mechanically ventilated patients admitted to the ICU between 2012 and 2017 were extracted, of whom 583 were eligible adults for further analysis. Patients’ weaning protocols were evaluated for daily adherence to quality standards until ICU discharge. Patients with <65% compliance were assigned to the low adherence group (LAG), patients with ≥65% to the high adherence group (HAG).Primary and secondary outcome measuresEconomic healthcare costs, clinical outcomes and patients’ characteristics.ResultsThe LAG consisted of 378 patients with a median negative economic results of −€3969, HAG of 205 (−€1030), respectively (p<0.001). Median duration of ventilation was 476 (248; 769) hours in the LAG and 389 (247; 608) hours in the HAG (p<0.001). Length of stay (LOS) in the LAG on ICU was 21 (12; 35) days and 16 (11; 25) days in the HAG (p<0.001). LOS in the hospital was 36 (22; 61) days in the LAG, and within the HAG, respectively, 26 (18; 48) days (p=0.001).ConclusionsHigh adherence to this single QI is associated with better clinical outcome and improved economic returns. Therefore, the results support the adherence to QI. However, the examined QI does not influence economic outcome as the decisive factor

Level 1-to-2 Data Processor Version 3.0: A Major Upgrade of the GOME/ERS-2 Total Ozone Retrieval Algorithm,

Abstract The Global Ozone Monitoring Experiment (GOME) was launched in April 1995, and the GOME Data Processor (GDP) retrieval algorithm has processed operational total ozone amounts since July 1995. GDP Level 1-to-2 is based on the two-step Differential Optical Absorption Spectroscopy (DOAS) approach, involving slant column fitting followed by Air Mass Factor (AMF) conversions to vertical column amounts. We present a major upgrade of this algorithm to Version 3.0. GDP 3.0 was implemented in July 2002, and the 9-year GOME data record from July 1995 to December 2004 has been processed using this algorithm. The key component in GDP 3.0 is an iterative approach to AMF calculation, in which AMFs and corresponding vertical column densities are adjusted to reflect the true ozone distribution as represented by the fitted DOAS effective slant column. A neural networkensemble is used to optimize the fast and accurate parameterization of AMFs. We describe results of a recent validation exercise for the operational version of the total ozone algorithm; in particular, seasonal and meridian errors are reduced by a factor of two. On a global basis, GDP 3.0 ozone total column results lie between -2% and +4% of ground-based values for moderate solar zenith angles lower than 70°. A larger variability of about +5% and -8% is observed for higher solar zenith angles up to 90°. Copyright OCIS codes 01

High spatial resolution analysis of the iron oxidation state in silicate glasses using the electron probe

The iron oxidation state in silicate melts is important for understanding their physical properties, although it is most often used to estimate the oxygen fugacity of magmatic systems. Often high spatial resolution analyses are required, yet the available techniques, such as μXANES and μMössbauer, require synchrotron access. The flank method is an electron probe technique with the potential to measure Fe oxidation state at high spatial resolution but requires careful method development to reduce errors related to sample damage, especially for hydrous glasses. The intensity ratios derived from measurements on the flanks of FeLα and FeLβ X-rays (FeLβf/FeLαf) over a time interval (time-dependent ratio flank method) can be extrapolated to their initial values at the onset of analysis. We have developed and calibrated this new method using silicate glasses with a wide range of compositions (43–78 wt% SiO2, 0–10 wt% H2O, and 2–18 wt% FeOT, which is all Fe reported as FeO), including 68 glasses with known Fe oxidation state. The Fe oxidation state (Fe2+/FeT) of hydrous (0–4 wt% H2O) basaltic (43–56 wt% SiO2) and peralkaline (70–76 wt% SiO2) glasses with FeOT > 5 wt% can be quantified with a precision of ±0.03 (10 wt% FeOT and 0.5 Fe2+/FeT) and accuracy of ±0.1. We find basaltic and peralkaline glasses each require a different calibration curve and analysis at different spatial resolutions (∼20 and ∼60 μm diameter regions, respectively). A further 49 synthetic glasses were used to investigate the compositional controls on redox changes during electron beam irradiation, where we found that the direction of redox change is sensitive to glass composition. Anhydrous alkali-poor glasses become reduced during analysis, while hydrous and/or alkali-rich glasses become oxidized by the formation of magnetite nanolites identified using Raman spectroscopy. The rate of reduction is controlled by the initial oxidation state, whereas the rate of oxidation is controlled by SiO2, Fe, and H2O content