Iron as recyclable metal fuel: Unraveling oxidation behavior and cyclization effects through thermogravimetric analysis, wide-angle X-ray scattering and Mössbauer spectroscopy.

The carbon-free chemical storage and release of renewable energy is an important task to drastically reduce CO2 emissions. The high specific energy density of iron and its recyclability makes it a promising storage material. Energy release by oxidation with air can be realized by the combustion of micron-sized iron powders in retro-fitted coal fired power plants and in fixed-bed reactors under milder conditions. An experimental parameter study of iron powder oxidation with air was conducted based on thermogravimetric analysis in combination with wide-angle X-ray scattering and Mössbauer spectroscopy. In agreement with literature the oxidation was found to consist of a very fast initial oxidation of the outer particle layer followed by much slower oxidation due to diffusion of iron ions through the Fe2O3/Fe3O4 layer being the ratelimiting step. Scanning electron microscopy analysis of the iron particle before and after oxidation reveal a strong particle morphology transformation. This impact on the reaction was studied by cyclization experiments. Up to 10 oxidation-reduction cycles show that both, oxidation and reduction rates, increase strongly with cycling due to increased porosity.

Exploring the oxidation behavior of undiluted and diluted iron particles for energy storage: Mössbauer spectroscopic analysis and kinetic modeling.

Iron is an abundant and non-toxic element that holds great potential as energy carrier for large-scale and long-term energy storage. While from a general viewpoint iron oxidation is well-known, the detailed kinetics of oxidation for micrometer sized particles are missing, but required to enable large-scale utilization for energy production. In this work, iron particles are subjected to temperature-programmed oxidation. By dilution with boron nitride a sintering of the particles is prevented enabling to follow single particle effects. The mass fractions of iron and its oxides are determined for different oxidation times using Mössbauer spectroscopy. On the basis of the extracted phase compositions obtained at different times and temperatures (600-700 °C), it can be concluded that also for particles the oxidation follows a parabolic rate law. The parabolic rate constants are determined in this transition region. Knowledge of the particle size distribution and its consideration in modeling the oxidation kinetics of iron powder has proven to be crucial.

Impact of climate change on vector- and rodent-borne infectious diseases.

Background: Endemic and imported vector- and rodent-borne infectious agents can be linked to high morbidity and mortality. Therefore, vector- and rodent-borne human diseases and the effects of climate change are important public health issues. Methods: For this review, the relevant literature was identified and evaluated according to the thematic aspects and supplemented with an analysis of surveillance data for Germany. Results: Factors such as increasing temperatures, changing precipitation patterns, and human behaviour may influence the epidemiology of vector- and rodent-borne infectious diseases in Germany. Conclusions: The effects of climatic changes on the spread of vector- and rodent-borne infectious diseases need to be further studied in detail and considered in the context of climate adaptation measures.

Detection of target-site and metabolic resistance to pyrethroids in the bed bug Cimex lectularius in Berlin, Germany.

Knockdown-resistance (kdr) against pyrethroids in bed bugs (Cimex lectularis) is associated with the presence of several point mutations in the voltage-sensitive sodium channel α-subunit gene and/or an increased metabolic detoxification by cytochrome P450 monooxygenases (CYPs). In the present study, pyrosequencing assays were developed to quantify the presence of the kdr substitutions (V419L or L925I substitution) in bed bugs in Berlin, Germany. In 14 of 17 bed bug field strains, pyrosequencing revealed the presence of the substitution L925I with allele frequencies between 30% and 100%. One field strain additionally carried the substitution V419L with allele frequencies of 40% in males and 96% in females. In seven of the 17 field strains, mRNA levels of four CYP genes were examined using RT-qPCR. Relative to a susceptible laboratory reference strain, five field strains showed significantly higher mRNA levels of cyp397a1 with 7.1 to 56-fold increases. One of these strains additionally showed a 4.9-fold higher mRNA level of cyp398a1 compared to the reference strain, while cyp4cm1 and cyp6dn1 showed no significant differences. Our findings indicate that multiple resistance mechanisms are present in German C. lectularius populations simultaneously.

Microsatellite typing of Aedes albopictus (Diptera: Culicidae) populations from Germany suggests regular introductions.

The global spread of the Asian tiger mosquito Aedes albopictus is of concern, as this mosquito species constitutes an important vector of a number of emerging pathogens including dengue virus, chikungunya virus and Zika virus. Since its first appearance in Albania (1979) and Italy (1990), the species has been reported from more than twenty-five European countries. However, the dispersion process in Europe is largely unknown, as information on population genetic structure is lacking, which is relevant to understand the observed spread. In order to determine whether the ten Ae. albopictus populations detected in Germany until 2017 originate from a single introduction event or from independent importations, genetic analyses with a set of sixteen microsatellite markers were performed. The samples included specimens from three locations with potentially overwintering populations, collected in three consecutive years. The results indicate a heterogeneous population structure consisting of two clusters with significant substructuring, suggesting regular, independent introductions instead of a continuous spread across Germany originating from one or few sites. Moreover, the analyses provide further evidence for Ae. albopictus overwintering in Germany as samples from identical locations collected in three consecutive years had a relatively high genetic similarity. However, the population structure is probably influenced by local mosquito control activities. The results presented provide further evidence for regular introductions of Ae. albopictus specimens into Germany, probably leading to local establishment north of the Alps. This highlights the need for constant surveillance and control of Ae. albopictus not only in southern, but also in Central Europe.

A Novel Simulated-Use Test for Determining the Efficacy of Insecticides Against Bed Bugs (Hemiptera: Cimicidae).

The common bed bug Cimex lectularius L. has undergone a worldwide expansion in recent years, due to increased opportunities for dispersal and development of insecticide resistance. For successful control, efficacy testing of products against bed bugs and determination of insecticide resistance under practical conditions are of outstanding importance. A new test system mimicking the practical use situation of residual insecticides was developed and evaluated. Bed bugs were attracted by CO2 and heat to cross surfaces treated with alpha-cypermethrin and bendiocarb. In contrast to the complete efficacy of alpha-cypermethrin (less than 1% surviving bed bugs [with one exception of 5%]), only 45.3, 46, and 29% of insecticide-susceptible bed bugs showed lethal damage 7 d after contact with freshly bendiocarb-treated wallpaper or insecticide aged for 1 or 2 wk. Results show that the efficacy of different insecticides can be assessed with this new test system. Moreover, susceptibility to deltamethrin of five bed bug field strains, collected from infested apartments in Berlin, Germany, was determined in a filter paper contact bioassay. Resistance ratios (RRs) ranged between 4.3 and 20.7. In the novel simulated-use test, efficacy of alpha-cypermethrin was tested against the bed bug strain with the highest RR. In contrast to the insecticide-susceptible laboratory strain, alpha-cypermethrin was not effective against the field strain, where 26-50% of the bed bugs survived and even laid eggs. These results provide evidence for the presence of practically relevant pyrethroid resistance in bed bugs in Germany.

Experimental risk assessment for chikungunya virus transmission based on vector competence, distribution and temperature suitability in Europe, 2018.

BackgroundOver the last decade, the abundant distribution of the Asian tiger mosquito Aedes albopictus in southern Europe and the import of chikungunya virus (CHIKV) by infected travellers has resulted in at least five local outbreaks of chikungunya fever in France and Italy. Considering the ongoing spread of Ae. albopictus to central Europe, we performed an analysis of the Europe-wide spatial risk of CHIKV transmission under different temperature conditions. Methods:Ae. albopictus specimens from Germany and Italy were orally infected with CHIKV from an outbreak in France and kept for two weeks at 18 °C, 21 °C or 24 °C. A salivation assay was conducted to detect infectious CHIKV. Results: Analyses of mosquito saliva for infectious virus particles demonstrated transmission rates (TRs) of > 35%. Highest TRs of 50% for the mosquito population from Germany were detected at 18 °C, while the Italian population had highest TRs of 63% at 18 °C and 21 °C, respectively. Temperature data indicated a potential risk of CHIKV transmission for extended durations, i.e. sufficiently long time periods allowing extrinsic incubation of the virus. This was shown for areas already colonised by Ae. albopictus, as well as for large parts of central Europe that are not colonised. Conclusion: The current risk of CHIKV transmission in Europe is not primarily restricted by temperature, which allows extrinsic incubation of the virus, but rather by the vector distribution. Accordingly, all European countries with established populations of Ae. albopictus should implement respective entomological surveillance and monitoring systems, as basis for suitable control measures.

First mass development of Aedes albopictus (Diptera: Culicidae)-its surveillance and control in Germany.

The Asian tiger mosquito Aedes albopictus has undergone a dramatic expansion of its range in the last few decades. Since its first detection in 2007 in Germany at the motorway A5 coming from Italy via Switzerland to Germany, it has been continuously introduced by vehicles, most probably from Italy. After a hint from an alert gardener in an allotment garden area in Freiburg, Southwest Germany, in 2015, a surveillance programme was started focusing on the garden area and adjacent areas as well as most of the cemeteries as potential infestation areas. The surveillance programme confirmed a high infestation of the allotment garden. The container index (CI) exceeded almost 30% in August 2015. In lethal gravid Aedes traps (GATs) and BG-Sentinel traps, 4038 adults were caught. It could be proven that the Aedes population is more or less still spatially restricted to the allotment garden area which is adjacent to a train station where trucks from Novara, Italy, arrive loaded on trains. Outside the garden area, only a few breeding sites with developmental stages and adults were found within a radius of approximately 600 m from the highly infested garden area. It is most likely that Ae. albopictus females are constantly introduced as 'blind passengers' to Freiburg via trucks from Italy to Freiburg, Germany. After the first detection of the mass development of Ae. albopictus immediate and comprehensive control measures were initiated to reduce or even eliminate the Aedes population. Citizen awareness, especially of the gardeners, was increased by providing thorough information about the biology and control of Ae. albopictus. Beside environmental management, tablets based on Bacillus thuringiensis israelensis (Bti) were applied. The success of the control activities by the gardeners is reflected by the data gained during monthly inspection of the garden plots. The number of gardens without any container increased from 17% in July to 22% in August and 35% in September, 2015, resulting in a successful reduction of the Ae. albopictus population. The study underlines the importance of a comprehensive surveillance programme to assess the population density of Ae. albopictus as a basis for integrated control activities.