Ultrafast photoinduced electron transfer in coumarin 343 sensitized TiO2-colloidal solution

Photoinduced electron transfer from organic dye molecules to semiconductor nanoparticles is the first and most important reaction step for the mechanism in the so called “wet solar cells” [1]. The time scale between the photoexcitation of the dye and the electron injection into the conduction band of the semiconductor colloid varies from a few tens of femtoseconds to nanoseconds, depending on the specific electron transfer parameters of the system, e.g., electronic coupling or free energy values of donor and acceptor molecules [2–10]. We show that visible pump/ white light probe is a very efficient tool to investigate the electron injection reaction allowing to observe simultaneously the relaxation of the excited dye, the injection process of the electron, the cooling of the injected electron and the charge recombination reaction

Beyond Vibrationally Mediated Electron Transfer: Coherent Phenomena Induced by Ultrafast Charge Separation

Wave packet propagation succeeding electron transfer (ET) from alizarin dye molecules into the nanocrystalline TiO2 semiconductor has been studied by ultrafast transient absorption spectroscopy. Due to the ultrafast time scale of the ET reaction of about 6 fs the system shows substantial differences to molecular ET systems. We show that the ET process is not mediated by molecular vibrations and therefore classical ET theories lose their applicability. Here the ET reaction itself prepares a vibrational wave packet and not the electromagnetic excitation by the laser pulse. Furthermore, the generation of phonons during polaron formation in the TiO2 lattice is observed in real time for this system. The presented investigations enable an unambiguous assignment of the involved photoinduced mechanisms and can contribute to a corresponding extension of molecular ET theories to ultrafast ET systems like alizarin/TiO2.Comment: This work was supported by the German Research Foundation (DFG) (Hu 1006/6-1, WA 1850/6-1) and European Union projects FDML-Raman (FP7 ERC StG, contract no. 259158) and ENCOMOLE-2i (Horizon 2020, ERC CoG no. 646669

Sharp Interface Limits for Diffuse Interface Models with Contact Angle

We consider the sharp interface limit for the Allen-Cahn equation and some variants in a bounded smooth domain in the case of boundary contact. The Allen-Cahn equation is a diffuse interface model since (after a short generation time) solutions typically develop so-called diffuse interfaces, where the solution stays smooth but experiences steep gradients. Moreover, the equation contains a small parameter $\varepsilon>0$ that corresponds to the thickness of the diffuse interfaces. The limit $\varepsilon\rightarrow 0$ is called \enquote{sharp interface limit} because - at least heuristically - the solutions should converge to step functions with the jump set evolving in time according to some sharp interface problem. We show the rigorous sharp interface limit, i.e.~that solutions to the diffuse interface and the sharp interface model are related rigorously. The results are local in time and applicable as long as a smooth solution to the limit problem exists. We consider the following cases: \begin{itemize} \item Convergence of the Allen-Cahn equation with Neumann boundary condition to the mean curvature flow with $90^\circ$-contact angle in any dimension $N\geq 2$. \item Convergence of the vector-valued Allen-Cahn equation involving different choices for the potential and with Neumann boundary condition to the mean curvature flow with $90^\circ$-contact angle in any dimension $N\geq 2$, but without the triple junction situation. For this case we expect that a similar strategy works. We give some comments in this direction. \item Convergence of an Allen-Cahn equation with a non-linear Robin boundary condition to the mean curvature flow with an $\alpha$-contact angle in 2D for $\alpha$ close to $90^\circ$. \end{itemize} For the convergence proofs we use the method of de Mottoni, Schatzman \cite{deMS}, i.e.~we \begin{enumerate} \item Rigorously construct an approximate solution for the diffuse interface model with asymptotic expansions. \item Estimate the difference of the exact and approximate solution to the diffuse interface model with a spectral estimate for a linear operator associated to the model. \end{enumerate} The major novelty in the thesis is the consideration of boundary contact for the diffuse interfaces within the method of \cite{deMS}. Therefore we construct suitable curvilinear coordinates. Based on the latter we rigorously set up the asymptotic expansions. In this process new parameter-dependent elliptic problems on the half space in $\mathbb{R}^2$ appear. For the $90^\circ$-case these problems are solved with a splitting method in exponentially weighted Sobolev spaces. The latter seems not possible for angles $\alpha\neq 90^\circ$ and we use the Implicit Function Theorem with respect to $\alpha$ in this case. Moreover, for the spectral estimate for the Allen-Cahn operator in every case (which is obtained by linearization at the approximate solution) we use a new idea: we construct an approximate first eigenfunction using asymptotic expansions. Then we split the space of $H^1$-functions over the domain into a \enquote{small} explicit space formally approximating the first eigenfunctions and the complementing space. Finally, we analyze the associated bilinear form on every part

The Power Spectrum of Mass Fluctuations Measured from the Lyman-alpha Forest at Redshift z=2.5

We measure the linear power spectrum of mass density fluctuations at redshift z=2.5 from the \lya forest absorption in a sample of 19 QSO spectra, using the method introduced by Croft et al. (1998). The P(k) measurement covers the range 2\pi/k ~ 450-2350 km/s (2-12 comoving \hmpc for \Omega=1). We examine a number of possible sources of systematic error and find none that are significant on these scales. In particular, we show that spatial variations in the UV background caused by the discreteness of the source population should have negligible effect on our P(k) measurement. We obtain consistent results from the high and low redshift halves of the data set and from an entirely independent sample of nine QSO spectra with mean redshift z=2.1. A power law fit to our measured P(k) yields a logarithmic slope n=-2.25 +/- 0.18 and an amplitude \Delta^2(k_p) = 0.57^{+0.26}_{-0.18}, where $\Delta^2$ is the contribution to the density variance from a unit interval of lnk and k_p=0.008 (km/s)^{-1}. Direct comparison of our mass P(k) to the measured clustering of Lyman Break Galaxies shows that they are a highly biased population, with a bias factor b~2-5. The slope of the linear P(k), never previously measured on these scales, is close to that predicted by models based on inflation and Cold Dark Matter (CDM). The P(k) amplitude is consistent with some scale-invariant, COBE-normalized CDM models (e.g., an open model with \Omega_0=0.4) and inconsistent with others (e.g., \Omega=1). Even with limited dynamic range and substantial statistical uncertainty, a measurement of P(k) that has no unknown ``bias factors'' offers many opportunities for testing theories of structure formation and constraining cosmological parameters. (Shortened)Comment: Submitted to ApJ, 27 emulateapj pages w/ 19 postscript fig

Digitale Transformation in Hochschulen: auf dem Weg zu offenen Ökosystemen

Digitale Ökosysteme bieten in Form von offenen Lernsystemen einen neuen Gestaltungsrahmen, um die Chancen der fortgeschrittenen Digitalisierung in einer Netzwerkökonomie zu nutzen. Bildungsprozesse in einem Ökosystem ermöglichen eine individualisierte Studiengestaltung, personalisiertes Lernen auf der Basis intelligenter Systeme sowie eine stärkere Verknüpfung von Forschung und Lehre. Offene Lernökosysteme können in diesem Zusammenhang als Bindeglied zu Open Education im digitalen Bildungsraum aufgefasst werden. Das Fallbeispiel ‚Digital Israel‘ zeigt ein derartiges Ökosystem auf der Ebene des Bildungssystems

Metformin's Role in Hyperlactatemia and Lactic Acidosis in ICU Patients: A Systematic Review.

INTRODUCTION Metformin-treated patients may experience severe hyperlactatemia or lactic acidosis (LA). LA often requires intensive-care-unit (ICU) treatment, and mortality rates are high. Here, we investigate the impact of renal dysfunction and renal replacement therapy (RRT) on the outcomes of critically ill patients with metformin-associated LA (MALA). Furthermore, we assessed associations between mortality and metformin dose, metformin plasma/serum concentrations, lactate level, and arterial pH. Finally, we investigated whether the recommended classification in MALA, metformin-unrelated LA, metformin-induced LA, and LA in metformin therapy appears useful in this regard. METHODS We performed a retrospective analysis based on a systematic PubMed search for publications on hyperlactatemia/LA in metformin-treated ICU patients from January 1995 to February 2020. Case-level data including demographics and clinical conditions were extracted, and logistic regression analyses were performed. RESULTS A total of 92 ICU patients were reported. Two of these patients had no comorbidities interfering with lactate metabolism. In the overall group, arterial pH, lactate levels, and metformin plasma/serum concentrations were similar in survivors versus non-survivors. Ingested daily metformin doses and plasma/serum creatinine levels were significantly higher in survivors versus non-survivors (p = 0.007 vs. p = 0.024, respectively). Higher plasma/serum creatinine levels, higher lactate levels, and lower arterial pH were all associated with patients receiving RRT (all p < 0.05). Overall mortality was 22% (20 out of 92 patients) and did not differ between the RRT and non-RRT groups. CONCLUSION Mortality is high in ICU patients with metformin-associated hyperlactatemia/LA. Unexpectedly, higher ingested metformin dose and plasma/serum creatinine were associated with a better outcome. Survival was similar in patients with or without need for RRT

Beyond vibrationally mediated electron transfer: interfacial charge injection on a sub-10-fs time scale

The electron transfer (ET) from organic dye molecules to semiconductor-colloidal systems is characterized by a special energetic situation with a charge transfer reaction from a system of discrete donor levels to a continuum of acceptor states. If these systems show a strong electronic coupling they are amongst the fastest known ET systems with transfer times of less than 10 fs. In the first part a detailed discussion of the direct observation of an ET reaction with a time constant of about 6 fs will be given, with an accompanying argumentation concerning possible artifacts or other interfering signal contributions. In a second part we will try to give a simple picture for the scenario of such superfast ET reactions and one main focus will be the discussion of electronic dephasing and its consequences for the ET reaction. We show that the actual ET process can be understood as a kind of dispersion process of the initially located electron into the colloid representing a real motion of charge density from the alizarin to the colloid

Ultrafast photoinduced electron transfer in coumarin 343 sensitized TiO2-colloidal solution

Photoinduced electron transfer from organic dye molecules to semiconductor nanoparticles is the first and most important reaction step for the mechanism in the so called “wet solar cells” [1]. The time scale between the photoexcitation of the dye and the electron injection into the conduction band of the semiconductor colloid varies from a few tens of femtoseconds to nanoseconds, depending on the specific electron transfer parameters of the system, e.g., electronic coupling or free energy values of donor and acceptor molecules [2–10]. We show that visible pump/ white light probe is a very efficient tool to investigate the electron injection reaction allowing to observe simultaneously the relaxation of the excited dye, the injection process of the electron, the cooling of the injected electron and the charge recombination reaction

The effect of duration of antimicrobial treatment for bacteremia in critically ill patients on in-hospital mortality - Retrospective double center analysis.

PURPOSE Excessive duration of antibiotic treatment is a major factor for inappropriate antibiotic consumption. Although in some instances shorter antibiotic courses are as efficient as longer ones, no specific recommendations as to the duration of antimicrobial treatment for bloodstream infections currently exist. In the present study, we investigated the effect of antibiotic treatment duration on in-hospital mortality using retrospective data from two cohorts that included patients with bacteremia at two Swiss tertiary Intensive Care Units (ICUs). MATERIALS AND METHODS Overall 8227 consecutive patients requiring ICU admission were screened for bacteremia between 01/2012-12/2013 in Lausanne and between 07/2016-05/2017 in Bern. Patients with an infection known to require prolonged treatment or having single positive blood culture with common contaminant pathogens were excluded. The primary outcome of interest was the time from start of antimicrobial treatment to in-hospital death or hospital discharge, whichever comes first. The predictor of interest was adequate antimicrobial treatment duration, further divided into shorter (≤10 days) and longer (>10 days) durations. A time-dependent Cox model and a cloning approach were used to address immortality bias. The secondary outcomes were the median duration of antimicrobial treatment for patients with bacteremia overall and stratified by underlying infectious syndrome and pathogens in the case of secondary bacteremia. RESULTS Out of the 707 patients with positive blood cultures, 382 were included into the primary analysis. Median duration of antibiotic therapy was 14 days (IQR, 7-20). Most bacteremia (84%) were monomicrobial; 18% of all episodes were primary bacteremia. Respiratory (28%), intra-abdominal (23%) and catheter infections (17%) were the most common sources of secondary bacteremia. Using methods to mitigate the risk of confounding associated with antibiotic treatment durations, shorter versus longer treatment groups showed no differences in in-hospital survival (time-dependent Cox-model: HR 1.5, 95% CI (0.8, 2.7), p = 0.20; Cloning approach: HR 1.0, 95% CI (0.7,1.5) p = 0.83). Sensitivity analyses showed that the interpretation did not change when using a 7 days cut-off. CONCLUSIONS In this restrospective study, we found no evidence for a survival benefit of longer (>10 days) versus shorter treatment course in ICU patients with bacteremia. TRIAL REGISTRATION The study was retrospectively registered on clinicatrials.gov (NCT05236283), 11 February 2022. The respective cantonal ethics commission (KEK Bern # 2021-02302) has approved the study

Discriminative performance of pancreatic stone protein in predicting ICU mortality and infection severity in adult patients with infection: a systematic review and individual patient level meta-analysis.

BACKGROUND Several studies suggested pancreatic stone protein (PSP) as a promising biomarker to predict mortality among patients with severe infection. The objective of the study was to evaluate the performance of PSP in predicting intensive care unit (ICU) mortality and infection severity among critically ill adults admitted to the hospital for infection. METHODS A systematic search across Cochrane Central Register of Controlled Trials and MEDLINE databases (1966 to February 2022) for studies on PSP published in English using 'pancreatic stone protein', 'PSP', 'regenerative protein', 'lithostatin' combined with 'infection' and 'sepsis' found 46 records. The search was restricted to the five trials that measured PSP using the enzyme-linked immunosorbent assay technique (ELISA). We used Bayesian hierarchical regression models for pooled estimates and to predict mortality or disease severity using PSP, C-Reactive Protein (CRP) and procalcitonin (PCT) as main predictor. We used statistical discriminative measures, such as the area under the receiver operating characteristic curve (AUC) and classification plots. RESULTS Among the 678 patients included, the pooled ICU mortality was 17.8% (95% prediction interval 4.1% to 54.6%) with a between-study heterogeneity (I-squared 87%). PSP was strongly associated with ICU mortality (OR = 2.7, 95% credible interval (CrI) [1.3-6.0] per one standard deviation increase; age, gender and sepsis severity adjusted OR = 1.5, 95% CrI [0.98-2.8]). The AUC was 0.69 for PSP 95% confidence interval (CI) [0.64-0.74], 0.61 [0.56-0.66] for PCT and 0.52 [0.47-0.57] for CRP. The sensitivity was 0.96, 0.52, 0.30 for risk thresholds 0.1, 0.2 and 0.3; respective false positive rate values were 0.84, 0.25, 0.10. CONCLUSIONS We found that PSP showed a very good discriminative ability for both investigated study endpoints ICU mortality and infection severity; better in comparison to CRP, similar to PCT. Combinations of biomarkers did not improve their predictive ability