In Vitro Fossilization for High Spatial Resolution Quantification of Elements in Plant-Tissue Using LA-ICP-TOFMS.

Laser ablation in combination with an inductively coupled plasma time-of-flight mass spectrometer (LA-ICP-TOFMS) is an upcoming method for rapid quantitative element mapping of various samples. While widespread in geological applications, quantification of elements in biotissues remains challenging. In this study, a proof-of-concept sample preparation method is presented in which plant-tissues are fossilized in order to solidify the complex biotissue matrix into a mineral-like matrix. This process enables quantification of elements by using silicone as an internal standard for normalization while also providing consistent ablation processes similar to minerals to reduce image blurring. Furthermore, it allows us to generate a quantitative image of the element composition at high spatial resolution. The feasibility of the approach is demonstrated on leaves of sunflowers (Helianthus annuus), soy beans (Glycine max), and corn (Zea mays) as representatives for common crops, which were grown on both nonspiked and cadmium-spiked agricultural soil. The quantitative results achieved during imaging were validated with digestion of whole leaves followed by ICP-OES analysis. LA-ICP-TOFMS element mapping of conventionally dried samples can provide misleading trends due to the irregular ablation behavior of biotissue because high signals caused by high ablation rates are falsely interpreted as enrichment of elements. Fossilization provides the opportunity to correct such phenomena by standardization with Si as an internal standard. The method demonstrated here allows for quantitative image acquisition without time-consuming sample preparation steps by using comparatively safe chemicals. The diversity of tested samples suggests that this sample preparation method is well-suited to achieve reproducible and quantitative element maps of various plant samples.

A Nature-Inspired Antioxidant Strategy based on Porphyrin for Aromatic Hydrocarbon Containing Fuel Cell Membranes.

The use of hydrocarbon-based proton conducting membranes in fuel cells is currently hampered by the insufficient durability of the material in the device. Membrane aging is triggered by the presence of reactive intermediates, such as HO⋅, which attack the polymer and eventually lead to chain breakdown and membrane failure. An adequate antioxidant strategy tailored towards hydrocarbon-based ionomers is therefore imperative to improve membrane lifetime. In this work, we perform studies on reaction kinetics using pulse radiolysis and γ-radiolysis as well as fuel cell experiments to demonstrate the feasibility of increasing the stability of hydrocarbon-based membranes against oxidative attack by implementing a Nature-inspired antioxidant strategy. We found that metalated-porphyrins are suitable for damage transfer and can be used in the fuel cell membrane to reduce membrane aging with a low impact on fuel cell performance.

LA-ICP-MS using a nitrogen plasma source.

Here we describe the first study of a nitrogen based inductively coupled plasma mass spectrometry system in conjunction with laser ablation (LA-(N2-ICP)-MS). Therefore, a microwave-sustained, inductively coupled, atmospheric-pressure plasma source was mounted onto the interface of a quadrupole ICP-MS to investigate the capabilities of such an instrument. The proof of concept study was focused on the quantification capabilities of major to trace elements. Therefore, the plasma background species under dry plasma conditions were investigated to identify the most suitable isotopes for the analysis and to describe the newly formed nitrogen plasma interferences. In addition, the instrumental drift was investigated. Selected elements in the reference materials NIST SRM 612 and BCR-2G were quantified using NIST SRM 610 as an external standard and could be determined within the uncertainty of the reference values. Finally, the limits of detection for LA-(N2-ICP)-MS and LA-(Ar-ICP)-MS were compared indicating similar or even lower LODs for most elements using LA-(N2-ICP)-MS. Therefore, a nitrogen plasma source coupled to a mass spectrometer could challenge the argon-sustained ICP-MS in element analysis by overcoming argon interferences and has the potential to reduce the plasma gas expenses significantly.

Insights into Nucleation and Growth of Colloidal Quaternary Nanocrystals by Multimodal X-ray Analysis.

Copper chalcogenide nanocrystals find applications in photovoltaic inks, bio labels, and thermoelectric materials. We reveal insights in the nucleation and growth during synthesis of anisotropic Cu2ZnSnS4 nanocrystals by simultaneously performing in situ X-ray absorption spectroscopy (XAS) and small-angle X-ray scattering (SAXS). Real-time XAFS reveals that upon thiol injection into the reaction flask, a key copper thiolate intermediate species is formed within fractions of seconds, which decomposes further within a narrow temperature and time window to form copper sulfide nanocrystals. These nanocrystals convert into Cu2ZnSnS4 nanorods by sequentially incorporating Sn and Zn. Real-time SAXS and ex situ TEM of aliquots corroborate these findings. Our work demonstrates how combined in situ X-ray absorption and small-angle X-ray scattering enables the understanding of mechanistic pathways in colloidal nanocrystal formation.

[Pharmacological prophylaxis of thromboembolism in daily clinical practice: Evaluation of the clinical decision-making process]. / Medikamentöse Thrombembolieprophylaxe im klinischen Alltag-Evaluation der ärztlichen Entscheidungsfindung.

BACKGROUND: Considering the amount of national and international scientific evidence regarding the use of anticoagulants in the periprocedural prevention of thromboembolism, the decision-making process when prescribing anticoagulants is complex. Due to frequent prescriptions for inpatients, the topic is of high significance. This decision-making process in our hospital is the main focus of the study. METHODS: In a standardised survey, a target group of physicians was asked about their decision-making process with regard to the prescription of anticoagulants in the periprocedural period. For this study a questionnaire was developed consisting of 12 survey questions. Data from 130 participants was collected and analysed. RESULTS: Generally, there was a high level of agreement on the importance of venous thromboembolism prophylaxis. Significant differences exist between medical specialities. A gap between scientific evidence and clinical practice among the respondents could be identified. The decision-making process when prescribing anticoagulants was not documented by the physicians. CONCLUSIONS: A combined approach consisting of structured documentation with electronic decision support in combination with standardised treatment methods and educational measures can be a useful solution.

Serum Levels of MicroRNA miR-371a-3p: A Sensitive and Specific New Biomarker for Germ Cell Tumours.

BACKGROUND: Clinical management of germ cell tumours (GCTs) relies on monitoring of serum tumour markers. However, the markers α-fetoprotein (AFP), the ß-subunit of human chorionic gonadotropin (bHCG), and lactate dehydrogenase (LDH) are expressed in <60% of GCT cases. OBJECTIVE: To test the utility of the microRNAs (miRNAs) miR-371a-3p, miR-372-3p, miR-373-3p, and miR-367-3p as sensitive and specific GCT serum biomarkers. DESIGN, SETTING, AND PARTICIPANTS: Serum levels of miRNAs were measured in 166 consecutive patients with GCT before and after treatment and in 106 male controls. In the first 50 consecutive patients, all four miRNAs were measured. In the main study, only the most sensitive miRNA was further analysed. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: The specificity and sensitivity of the four miRNAs were studied using receiver operating characteristic curves. miRNA sensitivities were compared to those of classical markers. Statistical cross-comparisons of miRNA levels for GCT subgroups and controls were performed at various time points during treatment. RESULTS AND LIMITATIONS: Overall, miR-371a-3p performed best, with 88.7% sensitivity (95% confidence interval [CI] 82.5-93.3%) and 93.4% specificity (95% CI 86.9-97.3%) and an area under the curve of 0.94, outperforming AFP, bHCG, and LDH (combined sensitivity 50%). According to Kernel density estimation, the sensitivity and specificity were 86.3% and 92.5%, respectively. miR-371a-3p levels dropped to normal after completion of treatment. The miRNA levels correlated with treatment failure and relapse. Teratoma did not express miR-371a-3p. CONCLUSIONS: The miRNA miR-371a-3p is a specific and sensitive novel serum GCT biomarker that accurately correlates with disease activity. Validation of this test in a large-scale prospective study is needed. PATIENT SUMMARY: miR-371a-3p is a novel serum marker for germ cell tumours that is expressed by 88.7% of patients and thus is far more sensitive and specific than classical serum markers. It correlates with tumour burden and treatment results. Validation in a large patient cohort is needed.

Circulating tumor cells in patients with testicular germ cell tumors.

PURPOSE: Germ cell tumors (GCTs) represent the most frequent malignancies among young men, but little is known about circulating tumor cells (CTCs) in these tumors. Considering their heterogeneity, CTCs were investigated using two independent assays targeting germ cell tumor and epithelial cell-specific markers, and results were correlated with disease stage, histology, and serum tumor markers. EXPERIMENTAL DESIGN: CTCs were enriched from peripheral blood (n = 143 patients) and testicular vein blood (TVB, n = 19 patients) using Ficoll density gradient centrifugation. For CTC detection, a combination of germ cell tumor (anti-SALL4, anti-OCT3/4) and epithelial cell-specific (anti-keratin, anti-EpCAM) antibodies was used. In parallel, 122 corresponding peripheral blood samples were analyzed using the CellSearch system. RESULTS: In total, CTCs were detected in 25 of 143 (17.5%) peripheral blood samples, whereas only 11.5% of patients were CTC-positive when considering exclusively the CellSearch assay. The presence of CTCs in peripheral blood correlated with clinical stage (P < 0.001) with 41% of CTC positivity in patients with metastasized tumors and 100% in patients with relapsed and chemotherapy-refractory disease. Histologically, CTC-positive patients suffered more frequently from nonseminomatous primary tumors (P < 0.001), with higher percentage of yolk sac (P < 0.001) and teratoma (P = 0.004) components. Furthermore, CTC detection was associated with elevated serum levels of α-fetoprotein (AFP; P = 0.025), ß-human chorionic gonadotropin (ßHCG; P = 0.002), and lactate dehydrogenase (LDH; P = 0.002). Incidence and numbers of CTCs in TVB were much higher than in peripheral blood. CONCLUSIONS: The inclusion of germ cell tumor-specific markers improves CTC detection in GCTs. CTCs occur frequently in patients with more aggressive disease, and there is a gradient of CTCs with decreasing numbers from the tumor-draining vein to the periphery.

Self-assembled GaN quantum wires on GaN/AlN nanowire templates.

We present a novel approach for self-assembled growth of GaN quantum wires (QWRs) exhibiting strong confinement in two spatial dimensions. The GaN QWRs are formed by selective nucleation on {112[combining macron]0} (a-plane) facets formed at the six intersections of {11[combining macron]00} (m-plane) sidewalls of AlN/GaN nanowires used as a template. Based on microscopy observations we have developed a 3D model explaining the growth mechanism of QWRs. We show that the QWR formation is governed by self-limited pseudomorphic growth on the side facets of the nanowires (NWs). Quantum confinement in the QWRs is confirmed by the observation of narrow photoluminescence lines originating from individual QWRs with emission energies up to 4.4 eV. Time-resolved photoluminescence studies reveal a short decay time (~120 ps) of the QWR emission. Capping of the QWRs with AlN allows enhancement of the photoluminescence, which is blue-shifted due to compressive strain. The emission energies from single QWRs are modelled assuming a triangular cross-section resulting from self-limited growth on a-plane facets. Comparison with the experimental results yields an average QWR diameter of about 2.7 nm in agreement with structural characterization. The presented results open a new route towards controlled realization of one-dimensional semiconductor quantum structures with a high potential both for fundamental studies and for applications in electronics and in UV light generation.