Structure and Dynamics of the Quasi-Liquid Layer at the Surface of Ice from Molecular Simulations

We characterized the structural and dynamical properties of the quasi-liquid layer (QLL) at the surface of ice by molecular dynamics simulations with a thermodynamically consistent water model. Our simulations show that for three low-index ice surfaces only the outermost molecular layer presents short-range and mid-range disorder and is diffusive. The onset temperature for normal diffusion is much higher than the glass temperature of supercooled water, although the diffusivity of the QLL is higher than that of bulk water at the corresponding temperature. The underlying subsurface layers impose an ordered template, which produces a regular patterning of the ice/water interface at any temperature, and is responsible for the major differences between QLL and bulk water, especially for what concern the dynamics and the mid-range structure of the hydrogen-bonded network. Our work highlights the need of a holistic approach to the characterization of QLL, as a single experimental technique may probe only one specific feature, missing part of the complexity of this fascinating system.Comment: 6 Figure

Experimental and theoretical evidence for bilayer-by-bilayer surface melting of crystalline ice

On the surface of water ice, a quasi-liquid layer (QLL) has been extensively reported at temperatures below its bulk melting point at 273 K. Approaching the bulk melting temperature from below, the thickness of the QLL is known to increase. To elucidate the precise temperature variation of the QLL, and its nature, we investigate the surface melting of hexagonal ice by combining noncontact, surface-specific vibrational sum frequency generation (SFG) spectroscopy and spectra calculated from molecular dynamics simulations. Using SFG, we probe the outermost water layers of distinct single crystalline ice faces at different temperatures. For the basal face, a stepwise, sudden weakening of the hydrogen-bonded structure of the outermost water layers occurs at 257 K. The spectral calculations from the molecular dynamics simulations reproduce the experimental findings; this allows us to interpret our experimental findings in terms of a stepwise change from one to two molten bilayers at the transition temperature

Like ice in the sunshine: surface rearrangement and pre-melting of the three most prominent surfaces of hexagonal ice

Ice is ubiquitous in nature and all around us. Of particular interest is the surface, where interactions with the environment take place. The surface of the most stable polymorph, hexagonal ice I his known to pre-melt at temperatures close to the melting point. In this thesis, the low-index surfaces of ice I h —namely the basal (0001), the primary prismatic (101̄0), and the secondary prismatic (1̄21̄0) plane—are examined in a temperature range from 200 K to 270 K, using classical molecular dynamics simulations employing the TIP4P/Ice rigid water model. With structural analysis we probed the transition from ordered to disordered arrangements at the top surface layers. Our structural analysis, including radial distribution functions, hydrogen bond analysis, medium-range network topology, and order parameters, indicates that 2–3 layers (≈ 8 Å–12 Å) are disordered, with a structure similar to that of liquid water at 270 K for the basal plane, 1–2 layers (≈ 4.5 Å–8.5 Å) for the primary prismatic plane, and 2–4 layers (≈ 5 Å–9.5 Å) for the secondary prismatic plane. A sudden increase of disorder is detected for the second layer of the basal plane between 260 K–270 K explaining a peak shift observed in sum-frequency-generation spectroscopy measurements. [1] Even though local order is lost within the top layer at the highest temperatures, the surfaces retain an ordered structure averaging over several snapshots as revealed by two-dimensional density maps explained by a templating effect induced by the underlying layer. A different picture is obtained from dynamical analysis. According to the mean square displacement calculation only the top layer displays normal diffusion and can be considered liquid-like for all surfaces at high temperatures. Diffusion is isotropic. At lower temperatures, sub-diffusion is observed. The next few layers are only structurally similar to liquid water close to the melting point, but do not diffuse or display glass-like dynamics.Eis ist allgegenwärtig in der Natur und unserer Umgebung. Von besonderem Interesse ist die Eisoberfläche, auf der die Interaktion mit der Umgebung stattfindet. Für die Oberfläche der stabilsten Modifikation, Eis I h, ist die Bildung einer quasi flüssigen Schicht an der Oberfläche schon vor dem Schmelzpunkt bekannt. In dieser Arbeit werden die Oberflächen mit niedrigem Index, das heißt die Basalfläche (0001), die primäre prismatische Fläche (101̄0) und die sekundäre prismatische Fläche (1̄21̄0), in einem Temperaturbereich von 200 K bis 270 K mit klassischen Molekulardynamiksimulationen, die das starre TIP4P/Ice-Wassermodell verwenden, untersucht. Mittels Strukturanalysen untersuchen wir den Übergang von einer geordneten zu einer ungeordneten Anordnung in den obersten Schichten der Oberfläche. Die Strukturanalyse, die sowohl radiale Verteilungsfunktionen, Wasserstoffbrückenbindungsanalyse, mittelreichweitige Netzwerktopologie, als auch Ordnungsparameter verwendet, ergibt, dass etwa 2–3 Schichten (≈ 8 Å–12 Å) bei der Basalfläche, 1–2 Schichten (≈ 4.5 Å–8.5 Å) bei der primären prismatischen Fläche und 2–4 Schichten (≈ 5 Å–9.5 Å) bei der sekundären prismatischen Fläche eine ungeordnete, wasserähnliche Struktur aufweisen. Ein plötzlicher Anstieg der Unordnung wird bei der Basalfläche zwischen 260 K und 270 K gemessen und erklärt eine Verschiebung des Maximums des experimentell bestimmten Summenfrequenzspektroskopiesignals. Obwohl die Ordnung innerhalb der ersten Schicht verloren geht, behält die Oberfläche im zeitlichen Mittel eine geordnete Struktur. Dies sieht man in zweidimensionalen Dichteprofilen und wird durch einen Templateffekt der darunterliegenden Schicht erklärt. Ein anderes Bild ergibt sich aus der dynamischen Analyse. Aus der Berechnung der mittleren quadratischen Verschiebung ergibt sich, dass nur die erste Schicht normale Diffusion zeigt und als einer Flüssigkeit ähnlich bei allen Oberflächen und hohen Temperaturen angesehen werden kann. Die nächsten Schichten sind nur strukturell wasserähnlich nahe am Schmelzpunkt, aber diffundieren kaum oder zeigen eine glasartige Dynamik

Thematisierung und Repräsentation von Homosexualität im deutschsprachigen Reality-TV

Die kommunikationswissenschaftliche Auseinandersetzung mit Homosexualität ist ein bislang wenig erforschtes Themengebiet. Die folgende Magisterarbeit setzt sich mit der Problematik der Darstellung von Homosexualität im deutschsprachigen Reality-TV auseinander und die daraus resultierende Wahrnehmung durch den Rezipienten. Dabei wird ein theoretischer Schwerpunkt auf die Begriffe Homosexualität und Reality-TV gelegt und die Fragestellung in einen kommunikationswissenschaftlichen Rahmen verankert. Anhand von qualitativen Leitfaden-Interviews und mithilfe von Videobeispielen werden Rezipienten unterschiedlicher sexueller Orientierung zu ihrer Wahrnehmung von Homosexualität im Fernsehen befragt. Mittels einer qualitativen Inhaltsanalyse werden anhand eines Kategoriensystems die vorliegenden Transkripte ausgewertet und interpretiert.Homosexuality is to date a little explored topic in academic communication science. The following Master's thesis addresses the problem of representation of homosexuality in German Reality-TV and the resulting perception by the recipient. The theoretical focus lies on the terms homosexuality and Reality-TV. The research question is situated in the framework of communication science. By means of qualitative guided interviews and with the help of video examples, recipients of different sexual orientation are questioned about their perception of homosexuality on television. Using a qualitative content analysis the transcripts on hand are evaluated and interpreted based on a category system

Safety, immunogenicity, and preliminary clinical efficacy of a vaccine against extraintestinal pathogenic Escherichia coli in women with a history of recurrent urinary tract infection: a randomised, single-blind, placebo-controlled phase 1b trial

Escherichia coli infections are increasing worldwide in community and hospital settings. The E coli O-antigen is a promising vaccine target. We aimed to assess the safety and immunogenicity of a bioconjugate vaccine containing the O-antigens of four E coli serotypes (ExPEC4V)

Amisulpride and olanzapine combination treatment versus each monotherapy in acutely ill patients with schizophrenia in Germany (COMBINE): a double-blind randomised controlled trial

Background Combining antipsychotics is common in schizophrenia treatment, despite evidence-based guidelines generally not recommending such practice. Otherwise, evidence remains inconclusive, especially regarding specific combinations. The trial aimed to test whether a combination of amisulpride plus olanzapine is more effective than either intervention as a monotherapy. Methods A multicentre, 16-week, randomised, double-blind, controlled trial was done at 16 psychiatric in-patient centres throughout Germany. Inclusion criteria were adults aged 18-65 years with non-first episode schizophrenia or schizoaffective disorder and with a Positive and Negative Syndrome Scale (PANSS) total score of at least 70 and at least two items of the positive symptoms subscale rated at least 4. Patients were randomly assigned to receive 16 weeks of treatment with either amisulpride plus olanzapine, amisulpride plus placebo, or olanzapine plus placebo (1:1:1), and block randomisation was stratified by study site. To keep patients and investigators masked throughout the duration of the trial, amisulpride, olanzapine, and placebo were administered as identical capsules. Flexibly dosed monotherapy of oral amisulpride (amisulpride plus placebo, 200-800 mg per day) or olanzapine (olanzapine plus placebo, 5-20 mg per day) was compared with a combination of amisulpride plus olanzapine. The primary outcome was symptom reduction measured by the PANSS total score after 8 weeks, in the modified intention-to-treat population (all patients randomly assigned to an intervention and receiving at least one study drug dose). As determined a priori, group differences were examined by t tests (Bonferroni-Holm-adjustment) followed by pre-planned Bayesian analyses as well as imputation methods based on mixed models to account for missing values and post-hoc ANCOVA adjusting for PANSS baseline scores. The study was registered on ClinicalTrials.gov, NCT01609153; the German Clinical Trials Register, DRKS00003603; and the European Union Drug Regulating Authorities Clinical Trials Database, EudraCT-No. 2011-002463-20. Findings Between June 15, 2012, and Dec 15, 2018, 13 692 patients were assessed for eligibility. 13 364 patients were excluded (including for not meeting inclusion criteria, declining to participate, or inappropriate reasons for changing pharmacological treatment), and 328 were then randomly assigned to an intervention group. 112 patients were randomly assigned to receive amisulpride plus olanzapine, 109 were randomly assigned to receive amisulpride plus placebo, and 107 were randomly assigned to receive olanzapine plus placebo. 321 patients were analysed for the primary outcome in the modified intention-to-treat population after exclusion of screening failures and patients who did not receive the intervention (110 for amisulpride plus olanzapine, 109 for amisulpride plus placebo, and 102 for olanzapine plus placebo). Among the 321 patients who were randomly assigned to intervention groups and analysed for the primary outcome, 229 (71%) were male, 92 (29%) were female; the mean age was 40.2 years (SD 11.7); and 296 (92%) were White and 25 (8%) were classified as other ethnicity. PANSS total score improved significantly more at 8 weeks in the amisulpride plus olanzapine group (-29.6 [SD 14.5]) than in the olanzapine plus placebo group (-24.1 [13.4], p=0.049, Cohen's d=0.396). A significant difference was not observed in reduction of PANSS total score between the amisulpride and olanzapine group compared with the amisulpride and placebo group (-25.2 [SD 15 .9], p=0.095, Cohen's d=0.29). After 8 weeks and 16 weeks, sexual dysfunction, weight, and waist circumference increase were significantly higher for patients receiving amisulpride plus olanzapine than for those receiving amisulpride plus placebo, with no differences in serious adverse events. Two patients died during study participation; one randomly assigned to the amisulpride plus olanzapine group, and one assigned to the olanzapine plus placebo group (both assessed with no relation to treatment). Interpretation The advantages of amisulpride plus olanzapine have to be weighed against a higher propensity for side-effects. The use of this specific combination therapy could be an alternative to monotherapy in certain clinical situations, but side-effects should be considered. Copyright (C) 2022 Elsevier Ltd. All rights reserved