Understanding spermatogenesis is a prerequisite for treatment

Throughout spermatogenesis multiplication, maturation and differentiation of germ cells results in the formation of the male gamete. The understanding of spermatogenesis needs detailed informations about the organization of the germinal epithelium, the structure and function of different types of germ cells, endocrine and paracrine cells and mechanisms, intratesticular and extratesticular regulation of spermatogenesis. Normal germ cells must be discriminated from malformed, apoptotic and degenerating germ cells and tumor cells. Identification of the border line between normal and disturbed spermatogenesis substantiate the diagnosis of impaired male fertility. The profound knowledge of the complicate process of spermatogenesis and all cells or cell systems involved with is the prerequisite to develop concepts for therapy of male infertility or to handle germ cells in the management of assisted reproduction

Reversible and Irreversible Degradation Phenomena in PEMFCs

The presentation is focused on reversible and irreversible degradation phenomena in polymer electrolyte membrane fuel cells (PEMFCs). Analytical methods for the determination of component degradation will be presented and a new systematic approach for the analysis of reversible and irreversible degradation rates in an operating fuel cell will be introduced. A detailed description of voltage loss rates and particularly of the discrimination between reversible and irreversible voltage losses will be given. A major motivation of the presented work is the lack of common description procedures and determination approaches of voltage losses in durability tests of fuel cell. This issue results in severe difficulties in the comparison of results obtained by different testing facilities or within different research projects especially if only one value for a degradation rate is reported. In order to systematically analyze voltage losses we have performed single cell durability measurements of several hundreds of hours in 25 cm2 lab-scale cells. Specific test protocols containing regular refresh procedures were used for this purpose (see Figure 1). This enables distinguishing between reversible and irreversible voltage losses. To test the refresh procedures and analyze their effect on cell performance, parameters such as the duration of e.g. a soak time step have been varied. Between these refresh steps the cells were typically operated for 50 to 150 h. Conventional 5-layer MEAs with PFSA membranes, carbon supported Pt-catalysts and hydrophobized carbon fiber substrates with micro porous layers as GDLs were used for this study. For in-situ diagnostics of the operated cells polarization curves, impedance spectra, and CVs were recorded in order to determine the impact of the refresh procedures on the cells. Ex-situ methods were used to determine the causes for the reversible and irreversible voltage losses. Using different methods, detailed information about the physical composition of the individual fuel cell components can be obtained in order to optimize them and increase cell durability. Depending on the examined component and the analytical objective infrared absorption spectroscopy (FTIR), Raman, and X-ray photoemission spectroscopy (XPS) can be used to analyze the degradation effects and the sources for reversible and irreversible voltage loss during fuel cell operation. An overview of the different methods and their application will be given. It will be shown, that a combination of complementary methods is necessary to gather a comprehensive view of the occurring processes and mechanisms. As an example, depth profiling techniques combined with XPS can be used to determine the composition changes inside the fuel cell electrodes

Local Impact of Humidification on Degradation in Polymer Electrolyte Fuel Cells

Water management represents one of the main challenges in the design and operation of Polymer Electrolyte Fuel Cells (PEFCs). Besides performance, the water level also affects the durability of the cell. Understanding the degradation processes is of vital importance for extending durability of PEFCs by suitable mitigation strategies. In this work, the degradation processes related to operation with fully- and non-humidified gas streams were locally studied. The differences were analyzed using in-situ diagnostic tools, such as segmented cell for local current density measurements, during a 300 h test operating under constant conditions, in combination with local post-test analysis, i.e. SEM/EDX and XPS. The results showed the deep impact of the RH on homogeneity during the degradation process due to the fact that different water distribution influences the chemical environment. Under non-humidified gas streams, the cathode inlet region exhibited increased degradation, whereas with fully humidified gases the bottom of the cell had the higher performance losses. The degradation and the degree of reversibility produced by Pt dissolution, PTFE defluorination, and contaminants such as silicon (Si) and nickel (Ni) were locally evaluate

Durability Testing of Polymer Electrolyte Fuel Cells Under Stationary and Automotive Conditions

Our presentation focuses on durability testing and degradation of fuel cells. A major motivation of our work is the lack of common description procedures and determination approaches of voltage losses in durability tests of fuel cell for both stationary and automotive applications; this issue leads to severe difficulties in the comparison of results obtained by different institutions or within different projects, especially if only a single value for the degradation rate is reported. In this context, special attention is devoted to the discrimination between so called reversible and irreversible voltage losses. The first are permanent and determine the maximum lifetime of a fuel cell. The latter strongly depend on the chosen operation conditions and can be recovered by specific procedures. In order so systematically address voltage losses we have performed single cell durability measurements of several hundreds of hours in 25 cm2 lab-scale cells using different test protocols containing regular refresh procedures (soak time) allowing to distinguish between reversible and irreversible losses. Furthermore, operation strategies to minimize reversible degradation without using the time consuming refresh procedures are provided. To test the refresh procedures and analyze their effect on cell performance, parameters such as duration of the soak time steps have been varied. Between these refresh steps the cells were typically operated for 50 to 150 h. As samples conventional 5-layer membrane electrode assemblies were used with PFSA membranes, Pt-based catalysts and hydrophobized carbon fiber substrates with micro porous layers as GDLs. For in-situ diagnosis of the operated cells polarization curves, electrochemical impedance spectra, and cyclic voltammograms were recorded in order to determine the impact of the operation conditions and the refresh procedures on degradation. The interpretation of the degradation of the measured membrane electrode assemblies is supported by post-mortem analysis using physical characterization techniques. Additionally, we provide possible approaches to quantitatively determine irreversible voltage decay rates. For instance, voltage values before or after voltage recovery steps can be used to calculate the irreversible loss rate. The advantages and drawbacks of different approaches are discussed. One clear conclusion is that short time tests in the range of 100 hour are not conclusive since this time is too short to make a reliable discrimination between reversible and irreversible losses; also, the decay rate of reversible loss observed after each refresh step increases substantially upon long time operation independent on the type of the refresh procedure. In summary, in our presentation strategies for determination of fuel cell voltages loss rates are compared, evaluated and assessed according to their suitability to distinguish between reversible and irreversible degradation rates; a description of voltage loss rates is proposed. Moreover, operation strategies to minimize reversible degradation are provided. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) for Fuel Cell and Hydrogen Joint Technology Initiative under Grant No. 621216 (SecondAct) and No. 303452 (Impact)

Silicon Promotes Exodermal Casparian Band Formation in Si-Accumulating and Si-Excluding Species by Forming Phenol Complexes

We studied the effect of Silicon (Si) on Casparian band (CB) development, chemical composition of the exodermal CB and Si deposition across the root in the Si accumulators rice and maize and the Si non-accumulator onion. Plants were cultivated in nutrient solution with and without Si supply. The CB development was determined in stained root cross-sections. The outer part of the roots containing the exodermis was isolated after enzymatic treatment. The exodermal suberin was transesterified with MeOH/BF3 and the chemical composition was measured using gas chromatography-mass spectroscopy (GC-MS) and flame ionization detector (GC-FID). Laser ablation-inductively coupled plasma-mass spectroscopy (LA-ICP-MS) was used to determine the Si deposition across root cross sections. Si promoted CB formation in the roots of Si-accumulator and Si non-accumulator species. The exodermal suberin was decreased in rice and maize due to decreased amounts of aromatic suberin fractions. Si did not affect the concentration of lignin and lignin-like polymers in the outer part of rice, maize and onion roots. The highest Si depositions were found in the tissues containing CB. These data along with literature were used to suggest a mechanism how Si promotes the CB development by forming complexes with phenols.DFG/SCHR 506/12-

Safety, tolerability, pharmacodynamics and pharmacokinetics of the soluble guanylyl cyclase activator BI 685509 in patients with diabetic kidney disease:A randomized trial

Aims: Albuminuria is associated with abnormalities in the nitric oxide (NO)–soluble guanylyl cyclase (sGC)–cyclic guanosine monophosphate pathway. We assessed safety and efficacy of the NO-independent sGC activator BI 685509 in patients with diabetic kidney disease and albuminuria. Materials and methods: In this Phase Ib trial (NCT03165227), we randomized patients with type 1 or 2 diabetes, estimated glomerular filtration rate (eGFR) 20–75 mL/min/1.73 m2 and urinary albumin:creatinine ratio (UACR) 200–3500 mg/g to oral BI 685509 (1 mg three times daily, n = 20; 3 mg once daily, n = 19; 3 mg three times daily, n = 20, after final titration) or placebo (n = 15) for 28 days. Changes from baseline in UACR in first morning void (UACRFMV) and 10-hour (UACR10h) urine (3 mg once daily/three times daily only) were assessed. Results: Baseline median eGFR and UACR were 47.0 mL/min/1.73 m2 and 641.5 mg/g, respectively. Twelve patients had drug-related adverse events (AEs; 16.2%: BI 685509, n = 9; placebo, n = 3), most frequently hypotension (4.1%: BI 685509, n = 2; placebo, n = 1) and diarrhoea (2.7%: BI 685509, n = 2; placebo, n = 0). Four patients experienced AEs leading to study discontinuation (5.4%: BI 685509, n = 3; placebo, n = 1). Placebo-corrected mean UACRFMV decreased from baseline in the 3-mg once-daily (28.8%, P = 0.23) and three-times-daily groups (10.2%, P = 0.71) and increased in the 1-mg three-times-daily group (6.6%, P = 0.82); changes were not significant. UACR10h decreased by 35.3% (3 mg once daily, P = 0.34) and 56.7% (3 mg three times daily, P = 0.09); ≥50.0% of patients (UACR10h 3 mg once daily/three times daily) responded (≥20% UACR decrease from baseline). Conclusions: BI 685509 was generally well tolerated. Effects on UACR lowering merit further investigation.</p

Experiments with polarized 3He at MAMI

Experiments with polarized 3He at MAMI have already a long tradition. The A3 collaboration started in 1993 with the aim to measure the electric form factor of the neutron. At this time MAMI was the second accelerator where experiments with 3He were possible. Some years before this pilot experiment the development of the apparatus to polarize 3He in Mainz started. There are two techniques which allow to polarize sufficient large quantities of 3He. Both techniques will be compared and the benefit of 3He for nuclear physics will be discussed. An review of the experiments done so far with 3He at MAMI will be given and the progress in the target development, the detector setup and the electron beam performance will be pointed out.Comment: Contribution to the Symposium "20 Years of Physics at the Mainz Microtron MAMI", to be published in Eur. Phys. Journal

Evaluation of reversible and irreversible degradation rates of polymer electrolyte membrane fuel cells tested in automotive conditions

This work provides single cell durability tests of membrane electrode assemblies in dynamic operation regularly interrupted by recovery procedures for the removal of reversible voltage losses. Degradation rates at different loads in one single test can be determined from these tests. Hence, it is possible to report degradation rates versus current density instead of a single degradation rate value. A clear discrimination between reversible and irreversible voltage loss rates is provided. The irreversible degradation rate can be described by a linear regression of voltage values after the recovery steps. Using voltage values before refresh is less adequate due to possible impacts of reversible effects. The reversible contribution to the voltage decay is dominated by an exponential decay after restart, eventually turning into a linear one. A linear-exponential function is proposed to fit the reversible voltage degradation. Due to this function, the Degradation behavior of an automotive fuel cell can be described correctly during the first hours after restart. The fit parameters decay constant, exponential amplitude and linear slope are evaluated. Eventually, the reasons for the voltage recovery during shutdown are analyzed showing that ionomer effects in the catalyst layer and/or membrane seem to be the key factor in this process

Translation and cross-cultural adaptation of the young children participation and environment measure for its use in Austria, Germany, and Switzerland

Background: Concepts such as participation and environment may differ across cultures. Consequently, cultural equivalence must be assured when using a measure like the Young Children Participation and Environment Measure (YC-PEM) in other settings than the original English-speaking contexts. This study aimed to cross-culturally translate and adapt the YC-PEM into German as it is used in Germany, Austria, and Switzerland. Methods: Following international guidelines, two translations were compared, and the research and expert team made the first adaptations. Twelve caregivers of children with and without disabilities from three German-speaking countries participated in two rounds of think-aloud interviews. Data were analyzed by content analysis to look for item, semantic, operational, conceptual, and measurement equivalence to reach a cultural equivalence version in German. Results: Adaptations were needed in all fields but prominently in item, operational, and conceptual equivalence. Operational equivalence resulted in graphical adaptations in the instructions and questions to make the German version of YC-PEM, YC-PEM (G), more user-friendly. Conclusion: This study presents a cross-cultural translation and adaptation process to develop a German version of the YC-PEM suitable for Germany, Austria, and Switzerland. A culturally adapted YC-PEM (G) is now available for research, practice, and further validation