New TiO₂ double layer nano particulate photo anode for highly efficient dye sensitized solar cells (DSSC)

In this work, a new process chain for the realization of high performance dye sensitized solar cells (DSSC) will be introduced. The photo anode consists of two titania layers, the first layer facing the FTO/glass substrate is fabricated by spin coating using a commercial titania (P25), the second one is deposited by gas phase synthesis. Different synthesis parameters, optional post treatments, two different sensitizers and three different electrolyte mixtures have been systematically varied to optimize the photovoltaic conversion properties. A good efficiency value around 9.1% could be realized after comprehensive process evaluation

Electrochemical performance of tin-based nano-composite electrodes using a vinylene carbonate-containing electrolyte for Li-ion cells

Tin represents a promising material to increase the specific capacity compared to the state of the art graphite anodes in lithium ion cells. The aim of this work is to explain the electrochemical behavior of tin based hydrocarbon nanoparticulate composite electrodes, synthesized by means of a microwave plasma technique without any binder or slurry process. A comprehensive electrochemical character ization shows that adding vinylene carbonate (VC) to the electrolyte improves the electrochemical performance. Electrochemical impedance spectroscopy (EIS) and post mortem investigations of the cycled electrode material by X ray photoelectron spectroscopy (XPS) reveal the formation of a polymeric SEI during the first cycles, being responsible for the improvement. The differential capacity plots of the discharging process show that the lithium richest phase (Li22Sn5) is formed during electrochemical loading. A comprehensive characterization with specially designed electrochemical tests finally dem onstrates the decrease of capacity with increasing temperature. This is due to intensified mechanical stresses and a fresh SEI formation. Due to destruction of the electrode material degradation is also observed with increasing current density. The SEI layer on the surface of the electrodes is confirmed by scanning electron microscopy (SEM) investigations and energy dispersive X ray spectroscopy (EDS) elemental mapping

Surface Analytical Study Regarding the Solid Electrolyte Interphase Composition of Nanoparticulate SnO₂ Anodes for Li-Ion Batteries

This work presents a comparative surface analytical study on the solid electrolyte interphase (SEI) composition influenced by additives in the electrolyte using nanoparticulate SnO2 as anode active material for lithium ion b a t t e r i e s ( L I B s ) . In pa r t i c u l a r , l i t h i u m b i s (trifluoromethanesulfonyl)imide (LiTFSI) based electrolytes in combination with vinylene carbonate (VC) and 1 fluoroethylene carbonate (FEC) as electrolyte additives are used. The SEI composition of the electrodes is investigated at two different aging stages by means of the complementary X ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (ToF SIMS), providing chemical and molecular information on the topmost surface layers. We are able to show that the additives evolve different influences on the chemical composition of the formed SEI. The use of both additives generally results in an improved cycling stability of the nanoparticulate SnO2 anodes. In consequence, these results open an effective possibility to improve the cycling stability of SnO2 based electrode materials for LIBs by defined tailoring of the electrolyte’s SEI composition

African soil properties and nutrients mapped at 30 m spatial resolution using two-scale ensemble machine learning

Soil property and class maps for the continent of Africa were so far only available at very generalised scales, with many countries not mapped at all. Thanks to an increasing quantity and availability of soil samples collected at field point locations by various government and/or NGO funded projects, it is now possible to produce detailed pan-African maps of soil nutrients, including micro-nutrients at five spatial resolutions. In this paper we describe production of a 30 m resolution Soil Information System of the African continent using, to date, the most comprehensive compilation of soil samples (N ≈ 150, 000) and Earth Observation data. We produced predictions for soil pH, organic carbon (C) and total nitrogen (N), total carbon, effective Cation Exchange Capacity (eCEC), extractable—phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), sodium (Na), iron (Fe), zinc(Zn)—silt, clay and sand, stone content, bulk density and depth to bedrock, at three depths (0, 20 and 50 cm) and using 2-scale 3D Ensemble Machine Learning framework implemented in the mlr (Machine Learning in R) package. As covariate layers we used 250 m resolution (MODIS, PROBA-V and SM2RAIN products), and 30 m resolution (Sentinel-2, Landsat and DTM derivatives) images. Our fivefold spatial Cross-Validation results showed varying accuracy levels ranging from the best performing soil pH (CCC = 0.900) to more poorly predictable extractable phosphorus (CCC = 0.654) and sulphur (CCC = 0.708) and depth to bedrock. Sentinel-2 bands SWIR (B11, B12), NIR (B09, B8A), Landsat SWIR bands, and vertical depth derived from 30 m resolution DTM, were the overall most important 30 m resolution covariates. Climatic data images—SM2RAIN, bioclimatic variables and MODIS Land Surface Temperature—however, remained as the overall most important variables for predicting soil chemical variables at continental scale. This publicly available 30-m Soil Information System of Africa aims at supporting numerous applications, including soil and fertilizer policies and investments, agronomic advice to close yield gaps, environmental programs, or targeting of nutrition interventions

Improving survey methods in sero-epidemiological studies of injecting drug users: a case example of two cross sectional surveys in Serbia and Montenegro

BACKGROUND: Little is known about the prevalence of HIV or HCV in injecting drug users (IDUs) in Serbia and Montenegro. We measured prevalence of antibodies to HIV (anti-HIV) and hepatitis C virus (anti-HCV), and risk factors for anti-HCV, in community-recruited IDUs in Belgrade and Podgorica, and determined the performance of a parallel rapid HIV testing algorithm. METHODS: Respondent driven sampling and audio-computer assisted survey interviewing (ACASI) methods were employed. Dried blood spots were collected for unlinked anonymous antibody testing. Belgrade IDUs were offered voluntary confidential rapid HIV testing using a parallel testing algorithm, the performance of which was compared with standard laboratory tests. Predictors of anti-HCV positivity and the diagnostic accuracy of the rapid HIV test algorithm were calculated. RESULTS: Overall population prevalence of anti-HIV and anti-HCV in IDUs were 3% and 63% respectively in Belgrade (n = 433) and 0% and 22% in Podgorica (n = 328). Around a quarter of IDUs in each city had injected with used needles and syringes in the last four weeks. In both cities anti-HCV positivity was associated with increasing number of years injecting (eg Belgrade adjusted odds ratio (AOR) 5.6 (95% CI 3.2-9.7) and Podgorica AOR 2.5 (1.3-5.1) for >or= 10 years v 0-4 years), daily injecting (Belgrade AOR 1.6 (1.0-2.7), Podgorica AOR 2.1 (1.3-5.1)), and having ever shared used needles/syringes (Belgrade AOR 2.3 (1.0-5.4), Podgorica AOR 1.9 (1.4-2.6)). Half (47%) of Belgrade participants accepted rapid HIV testing, and there was complete concordance between rapid test results and subsequent confirmatory laboratory tests (sensitivity 100% (95%CI 59%-100%), specificity 100% (95%CI 98%-100%)). CONCLUSION: The combination of community recruitment, ACASI, rapid testing and a linked diagnostic accuracy study provide enhanced methods for conducting blood borne virus sero-prevalence studies in IDUs. The relatively high uptake of rapid testing suggests that introducing this method in community settings could increase the number of people tested in high risk populations. The high prevalence of HCV and relatively high prevalence of injecting risk behaviour indicate that further HIV transmission is likely in IDUs in both cities. Urgent scale up of HIV prevention interventions is needed

Enumeration of labelled quasi-initially connected digraphs

A new class of connected digraphs is introduced - the class of quasi-initially connected digraphs. They are enumerated in the labelled case. Using the apparatus developed for labelled quasi-initially connected digraphs respective results for other classes of labelled connected digraphs were obtained