Charakterisierung der Leistungsfähigkeit von PEM-Wasser-Elektrolysezellen, die mit und ohne Strömungskanäle arbeiten, basierend auf experimentell validierten semi-empirischen gekoppelten physikalischen Modellen

PEM water electrolysis is a clean technology for hydrogen production. In spite of its many advantages, the costs of the conventional PEM electrolysis cell makes it commercially less competitive vis-à-vis its peers. An alternative cell design has been proposed which has up to a 25 % costs advantage over the conventional cell. In this alternative cell design, the flow channel plate which bears the most costs in the conventional cell design has been replaced with a 3-D Porous Transport Layer (PTL) structure. It has however, been observed that the conventional cell by far out performs the low cost cell at high current density operations, due to increased mass transport limitation in the later. Industrial and commercial hydrogen production efforts are focused towards high current density operation (> 3 A/cm²), so the alternative cell design must be optimized for mass transport limitation. PEM water electrolysis is a clean technology for hydrogen production. In spite of its many advantages, the costs of the conventional PEM electrolysis cell makes it commercially less competitive vis-à-vis its peers. An alternative cell design has been proposed which has up to a 25 % costs advantage over the conventional cell. In this alternative cell design, the flow channel plate which bears the most costs in the conventional cell design has been replaced with a 3-D Porous Transport Layer (PTL) structure. It has however, been observed that the conventional cell by far out performs the low cost cell at high current density operations, due to increased mass transport limitation in the later. Industrial and commercial hydrogen production efforts are focused towards high current density operation (> 3 A/cm²), so the alternative cell design must be optimized for mass transport limitation. This work seeks to understand the source of, and to eliminate the mass transport losses in the alternative cell design to get it performing at least as good as the conventional cell at current densities up to 5 A/cm². A 2-D non-isothermal semi-empirical fully-coupled models of both cell designs have been developed and experimentally validated. The developed validated models were then used as tools to simulate and predict the best operating conditions, design parameters and micro-structural properties of the PTL at which the mass transport issues in the alternate cell will be at its minimum, at high current densities. The models are based on a multi-physics approach in which thermodynamic, electrochemical, thermal and mass transport sub-models are coupled and solved numerically, to predict the cell polarization and individual overpotentials, as well as address heat and water management issues. The most unique aspect of this work however, is the development of own semi-empirical equations for predicting the mass transport overpotential imposed by the gas phase (bubbles) at high current densities. For the very first time, calculated polarization curves up to 5 A/cm² have been validated by own experimental data. The results show that, the temperature and pressure, water flowrate and thickness of the PTL are the critical parameters for mitigating mass transport limitation. It was found that, for the size of the cells studied (25 cm² active area each), when both cells are operating at the same temperature of 60 °C, alternative design will have a comparable performance to the conventional designed cell even at 5 A/cm² current density when; the operating pressure is ≥ 5 bar, the feed water flowrate is ≥ 0.024l/min∙cm², PTL porosity is 50 %, PTL pore size is ≥ 11 µm and PTL thickness is 0.5 mm. At these operating, design and micro-structural conditions, the predicted difference between the polarizations of both cells will be only ~10 mV at 5 A/cm² operating current density.Die PEM Wasser Elektrolyse gilt als effiziente Technologie zur Herstellung von sauberem Wasserstoff zur Energiespeicherung. Trotz der vielen Vorteile führen hohe Kosten für die Produktion konventioneller Komponenten und Stacks zu einer nicht konkurrenzfähigen Technologie. Ein alternatives und kostengünstiges Zelldesign wurde vorgestellt, das, verglichen mit einem konventionellen Design, einen Kostenvorteil von bis zu 25 % hervorbringt. Bei diesem alternativen Zelldesign wird die Platte mit Strömungskanälen, die den größten Kostenanteil birgt, durch eine 3-D poröse Struktur (PTL) ersetzt. Bei hohen Stromdichten zeigt aber ein Design ohne Strömungskanäle niedrigere Leistungsdaten, was durch eine gesteigerte Limitierung des Massentransportes erklärt werden kann. Da sich die industrielle und kommerzielle Wasserstoffproduktion in Richtung hoher Stromdichten (> 3 A/cm²) entwickelt, scheint das erforderliche Verständnis von Massentransporteffekten offensichtlich das kosteneffiziente Design gegenüber dem konventionellen Design voran zu treiben. Diese Arbeit versucht den Ursprung von Massentransportlimitierung des kostengünstigen Zelldesigns zu verstehen und zu eliminieren. Um diese Zielvorgabe zu erreichen, wurden 2-D nicht-isotherme, semi-empirische, vollständig gekoppelte Modelle beider Zelldesigns entwickelt und experimentell validiert. Die entwickelten und validierten Modelle wurden als Werkzeug zur Simulation und Vorhersage der am besten geeigneten Betriebs- und Designparameter, sowie Eigenschaften der Mikrostrukur der PTL verwendet. Die hierin entwickelten Modelle basieren auf einem multiphysikalischen Ansatz, worin thermodynamische, elektrische und thermische Effekte sowie Massentransportuntermodelle gekoppelt und gelöst wurden, um sowohl die Zellpolarisation und individuelle Überpotentiale vorherzusagen, als auch Wärme- und Wassermanagement zu adressieren. Das Alleinstellungsmerkmal dieser Arbeit ist jedoch die Entwicklung von semi-empirischen Gleichungen, um die Überpotentiale der Massentransporthemmung, ausgehend von Gasblasen, vorhersagen zu können. Ebenso wurden zum ersten Mal berechnete PEM Wasser Elektrolyse Polarisationskurven bis zu einer Stromdichte von 5 A/cm² mit eigenen Daten validiert. Die Ergebnisse zeigen, dass Temperatur und Druck, sowie Wasserflußrate und Dicke der PTL die kritischen Parameter sind, um Massentransportlimitierung zu vermeiden. Es wurde sogar gezeigt, dass bei der verwendeten Zellgröße (aktive Fläche = 25 cm²) vergleichbare Leistungsdaten bei 60 °C und 5 A/cm² erreicht werden können, sofern der Betriebsdruck 5 bar übersteigt, die Wasserflussrate größer als 0.024 l/min ist, die Porosität der PTL 50 % übersteigt, die Porendurchmesser größer als 11 µm sind und die PTL Dicke bei 0.5 mm liegt. Bei diesen Parametern wurden Unterschiede zwischen den beiden Zelldesigns von etwa 10 mV bei 5 A/cm² vorhergesagt

Polarization-selective out-coupling of whispering gallery modes

Whispering gallery mode (WGM) resonators are an important platform for linear, nonlinear and quantum optical experiments. In such experiments, independent control of in- and out-coupling rates to different modes can lead to higher conversion efficiencies and greater flexibility in the generation of non-classical states based on parametric down conversion. In this work, we introduce a scheme that enables selective out-coupling of WGMs belonging to a specific polarization family, while the orthogonally polarized modes remain largely unperturbed. Our technique utilizes material birefringence in both the resonator and the coupler such that a negative (positive) birefringence allows for polarization-selective coupling to TE (TM) WGMs. We formulate a new coupling condition suitable for describing the case where the refractive indices of the resonator and the coupler are almost the same, from which we derive a criterion for polarization-selective coupling. Finally, we experimentally demonstrate our proposed method using a lithium niobate disk resonator coupled to a lithium niobate prism, where we show a \SI{22}{dB} suppression of coupling to TM modes relative to TE modes

Non-interventional 1-year follow-up study of peri-implant soft tissues following previous soft tissue augmentation and crown insertion in single-tooth gaps

AIM To assess peri-implant soft tissue dimensions at implant sites, previously augmented with a collagen matrix (VCMX) or an autogenous subepithelial connective tissue graft (SCTG), between crown insertion and 1 year. METHODS Twenty patients with single-tooth implants received soft tissue augmentation prior to abutment connection randomly using VCMX or SCTG. Following abutment connection 3 months later, final reconstructions were fabricated and inserted (baseline). Patients were recalled at 6 months (6M) and at 1 year (FU-1). Measurements included clinical data, soft tissue thickness, volumetric outcomes and patient-reported outcome measures (PROMs). RESULTS The buccal soft tissue thickness showed a median decrease of -0.5 mm (-1.0;0.3) (VCMX) and 0.0 mm (-0.5;1.0) (SCTG) (p = .243) up to FU-1. The soft tissue volume demonstrated a median decrease between BL and FU-1 of -0.1 mm (-0.2;0.0) (p = .301) for VCMX and a significant decrease of -0.2 mm (-0.4; -0.1) (p = .002) for SCTG, respectively. Intergroup comparisons did not reveal any significant differences between the groups for peri-implant soft tissue dimensions and changes up to FU-1 (p > .05). PROMs did not show any significant changes over time nor differences between the groups. CONCLUSION Between crown insertion and 1 year, the buccal peri-implant soft tissue dimensions remained stable without relevant differences between sites that had previously been grafted with VCMX or SCTG

Lung adenocarcinoma originates from retrovirus infection of proliferating type 2 pneumocytes during pulmonary post-natal development or tissue repair

Jaagsiekte sheep retrovirus (JSRV) is a unique oncogenic virus with distinctive biological properties. JSRV is the only virus causing a naturally occurring lung cancer (ovine pulmonary adenocarcinoma, OPA) and possessing a major structural protein that functions as a dominant oncoprotein. Lung cancer is the major cause of death among cancer patients. OPA can be an extremely useful animal model in order to identify the cells originating lung adenocarcinoma and to study the early events of pulmonary carcinogenesis. In this study, we demonstrated that lung adenocarcinoma in sheep originates from infection and transformation of proliferating type 2 pneumocytes (termed here lung alveolar proliferating cells, LAPCs). We excluded that OPA originates from a bronchioalveolar stem cell, or from mature post-mitotic type 2 pneumocytes or from either proliferating or non-proliferating Clara cells. We show that young animals possess abundant LAPCs and are highly susceptible to JSRV infection and transformation. On the contrary, healthy adult sheep, which are normally resistant to experimental OPA induction, exhibit a relatively low number of LAPCs and are resistant to JSRV infection of the respiratory epithelium. Importantly, induction of lung injury increased dramatically the number of LAPCs in adult sheep and rendered these animals fully susceptible to JSRV infection and transformation. Furthermore, we show that JSRV preferentially infects actively dividing cell in vitro. Overall, our study provides unique insights into pulmonary biology and carcinogenesis and suggests that JSRV and its host have reached an evolutionary equilibrium in which productive infection (and transformation) can occur only in cells that are scarce for most of the lifespan of the sheep. Our data also indicate that, at least in this model, inflammation can predispose to retroviral infection and cancer

Immunotherapies in neuromyelitis optica spectrum disorder: efficacy and predictors of response

OBJECTIVE: To analyse predictors for relapses and number of attacks under different immunotherapies in patients with neuromyelitis optica spectrum disorder (NMOSD). DESIGN: This is a retrospective cohort study conducted in neurology departments at 21 regional and university hospitals in Germany. Eligible participants were patients with aquaporin-4-antibody-positive or aquaporin-4-antibody-negative NMOSD. Main outcome measures were HRs from Cox proportional hazard regression models adjusted for centre effects, important prognostic factors and repeated treatment episodes. RESULTS: 265 treatment episodes with a mean duration of 442 days (total of 321 treatment years) in 144 patients (mean age at first attack: 40.9 years, 82.6% female, 86.1% aquaporin-4-antibody-positive) were analysed. 191 attacks occurred during any of the treatments (annual relapse rate=0.60). The most common treatments were rituximab (n=77, 111 patient-years), azathioprine (n=52, 68 patient-years), interferon-beta (n=32, 61 patient-years), mitoxantrone (n=34, 32.1 patient-years) and glatiramer acetate (n=17, 10 patient-years). Azathioprine (HR=0.4, 95% CI 0.3 to 0.7, p=0.001) and rituximab (HR=0.6, 95% CI 0.4 to 1.0, p=0.034) reduced the attack risk compared with interferon-beta, whereas mitoxantrone and glatiramer acetate did not. Patients who were aquaporin-4-antibody-positive had a higher risk of attacks (HR=2.5, 95% CI 1.3 to 5.1, p=0.009). Every decade of age was associated with a lower risk for attacks (HR=0.8, 95% CI 0.7 to 1.0, p=0.039). A previous attack under the same treatment tended to be predictive for further attacks (HR=1.5, 95% CI 1.0 to 2.4, p=0.065). CONCLUSIONS: Age, antibody status and possibly previous attacks predict further attacks in patients treated for NMOSD. Azathioprine and rituximab are superior to interferon-beta

Exchange of functional domains between a bacterial conjugative relaxase and the integrase of the human adeno-associated virus

Endonucleases of the HUH family are specialized in processing single-stranded DNA in a variety of evolutionarily highly conserved biological processes related to mobile genetic elements. They share a structurally defined catalytic domain for site-specific nicking and strand-transfer reactions, which is often linked to the activities of additional functional domains, contributing to their overall versatility. To assess if these HUH domains could be interchanged, we created a chimeric protein from two distantly related HUH endonucleases, containing the N-terminal HUH domain of the bacterial conjugative relaxase TrwC and the C-terminal DNA helicase domain of the human adeno-associated virus (AAV) replicase and site-specific integrase. The purified chimeric protein retained oligomerization properties and DNA helicase activities similar to Rep68, while its DNA binding specificity and cleaving-joining activity at oriT was similar to TrwC. Interestingly, the chimeric protein could catalyse site-specific integration in bacteria with an efficiency comparable to that of TrwC, while the HUH domain of TrwC alone was unable to catalyze this reaction, implying that the Rep68 C-terminal helicase domain is complementing the TrwC HUH domain to achieve site-specific integration into TrwC targets in bacteria. Our results illustrate how HUH domains could have acquired through evolution other domains in order to attain new roles, contributing to the functional flexibility observed in this protein superfamily.This work was supported by the Medical Research Council (MRC) grant MR/N022890/1 to EH and grant 1001764 to RML; National Institutes of Health (NIH) grant RO1-GM09285 to CRE; Spanish Ministry of Economy and competitiveness (MINECO) grant BIO2013-46414-P to ML and AFM is supported by a Doc.Mobility fellowship from the Swiss National Science Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Implementación del Proyecto Planta de Alimentos para la Integración Social de la Universidad Nacional de La Plata (PAIS-UNLP)

En el marco de la crisis alimentaria global, durante el bienio 2016-2018 cerca de 14.2 millones de argentinos padecían inseguridad alimentaria, moderada o grave, valor que duplicaba lo registrado para el bienio anterior (FAO, 2019). En este aspecto el INDEC informó que, para 2021, existían en nuestro país casi 12 millones de personas por debajo de la línea de pobreza, de los cuales 3 millones se encontraban por debajo de la línea de indigencia. En la ciudad de La Plata, entre 2018 y 2019, el Consejo Social llevó adelante un relevamiento de Sitios de Distribución de Alimentos del Gran La Plata, encontrando también datos alarmantes: casi un 41% de la población por debajo de la línea de pobreza y un 13.5% por debajo de la línea de indigencia. Frente a este panorama, la Universidad Nacional de La Plata (UNLP) priorizó la necesidad de un accionar urgente planteando nuevas herramientas. Por este motivo, en el marco del Plan Argentina Contra el Hambre, en 2019, la UNLP puso a disposición toda su capacidad científica y técnica y se propuso como objetivo principal la creación de la Planta de Alimentos para la Integración Social (P.A.I.S) con el propósito de generar productos de alta calidad nutricional, de fácil acceso para las personas más vulnerables, que permitan articular las capacidades productivas del Cinturón Hortícola Platense fortaleciendo el sistema productivo local y en particular la cadena de valor alimentaria.Facultad de Ingenierí