Integrated dielectric spectrometer for wideband and highspeed measurements using pseudo-noise codes

The paper gives a short introduction into some system-theoretic aspects and features of dielectric measurements by periodic wideband signals. Based on these considerations, a related measurement concept will be presented which is well suited for both compact device implementation and monolithic integration. Some implementation examples are shown and first measurement results are presented

Analysis of planetary analogue materials by laser-induced breakdown spectroscopy

Laser Induced Breakdown Spectroscopy (LIBS) is a promising tool for elemental chemical analysis in planetary science, because it allows real-time and fast in-situ determination of the elemental composition of materials down to minute concentrations. The technique requires no special preparation of samples, can provide high lateral resolution (as low as several tenths μm), depth profiling (down to mm) and, therefore, is not disturbed by dust layers. Miniaturized LIBS instruments are currently considered for the next NASA (Mars Science Laboratory) and ESA (ExoMars) missions to Mars, as well as studied for the international Europa Lander Mission. Here we present the LIBS laboratory facility at the German Aerospace Center in Berlin for the chemical elemental analysis under simulated planetary (Mars, Europa) conditions. The main purpose of the system is the study of the LIBS capability for in-situ spectroscopy for diverse planetary missions as well as the development of a LIBS spectral database under simulated planetary conditions for planetary analogue materials

Highly sensitive and specific detection of E. coli by a SERS nanobiosensor chip utilizing metallic nanosculptured thin films

A nanobiosensor chip, utilizing surface enhanced Raman spectroscopy (SERS) on nanosculptured thin films (nSTFs) of silver, was shown to detect Escherichia coli (E. coli) bacteria down to the concentration level of a single bacterium. The sensor utilizes highly enhanced plasmonic nSTFs of silver on a silicon platform for the enhancement of Raman bands as checked with adsorbed 4-aminothiophenol molecules. T-4 bacteriophages were immobilized on the aforementioned surface of the chip for the specific capture of target E. coli bacteria. To demonstrate that no significant non-specific immobilization of other bacteria occurs, three different, additional bacterial strains, Chromobacterium violaceum, Paracoccus denitrificans and Pseudomonas aeruginosa were used. Furthermore, experiments performed on an additional strain of E. coli to address the specificity and reusability of the sensor showed that the sensor operates for different strains of E. coli and is reusable. Time resolved phase contrast microscopy of the E. coli-T4 bacteriophage chip was performed to study its interaction with bacteria over time. Results showed that the present sensor performs a fast, accurate and stable detection of E. coli with ultra-small concentrations of bacteria down to the level of a single bacterium in 10 μl volume of the sample

Comparative analysis of the ftness of Drosophila virilis lines contrasting in response to stress

One of the crucial elements contributing to the adaptation of organisms to unfavorable environmental conditions is the reaction of stress. The study of its genetic control and role in adaptation to unfavorable conditions are of special interest. The juvenile hormone (JH) acts as a gonadotropic hormone in adult insects controlling the development of the ovaries, inducing vitellogenesis and oviposition. It was shown that a decrease in JH degradation in individuals reacting to adverse conditions by stress reaction (R­individuals) causes delay in egg laying and seems to allow the population to “wait out” the unfavorable conditions, thereby contributing to the adaptation at the population level. However, monitoring natural populations of D. melanogaster for the capability of stress reaction demonstrated that they have a high percentage of individuals incapable of it (NR­individuals). The study of reproductive characteristics of R­ and NR­individuals showed that under normal conditions R­individuals have the advantage of procreating offspring. Under unfavorable conditions, if the stressor is intense enough, NR­individuals die, but if its intensity is low, then they, unlike R­individuals, continue to produce offspring. Based on these data, it was hypothesized that the balance of R­ and NR­alleles in the population ensures its adaptation under frequent stresses of low intensity. To verify the hypothesis by an experiment, the ftness characteristics (lifespan, fecundity) of the R and NR lines of D. virilis were studied under normal conditions and under regular heat stress of various frequency

A preparative mass spectrometer to deposit intact large native protein complexes

Electrospray ion-beam deposition (ES-IBD) is a versatile tool to study the structure and reactivity of molecules from small metal clusters to large protein assemblies. It brings molecules gently into the gas phase, where they can be accurately manipulated and purified, followed by controlled deposition onto various substrates. In combination with imaging techniques, direct structural information on well-defined molecules can be obtained, which is essential to test and interpret results from indirect mass spectrometry techniques. To date, ion-beam deposition experiments are limited to a small number of custom instruments worldwide, and there are no commercial alternatives. Here we present a module that adds ion-beam deposition capabilities to a popular commercial MS platform (Thermo Scientific Q Exactive UHMR mass spectrometer). This combination significantly reduces the overhead associated with custom instruments, while benefiting from established high performance and reliability. We present current performance characteristics including beam intensity, landing-energy control, and deposition spot size for a broad range of molecules. In combination with atomic force microscopy (AFM) and transmission electron microscopy (TEM), we distinguish near-native from unfolded proteins and show retention of the native shape of protein assemblies after dehydration and deposition. Further, we use an enzymatic assay to quantify the activity of a noncovalent protein complex after deposition on a dry surface. Together, these results not only indicate a great potential of ES-IBD for applications in structural biology, but also outline the challenges that need to be solved for it to reach its full potential

A hydrodynamically optimized nano-electrospray ionization source and vacuum interface

The coupling of atmospheric pressure ionization (API) sources like electrospray ionization (ESI) to vacuum based applications like mass spectrometry (MS) or ion beam deposition (IBD) is done by differential pumping, starting with a capillary or pinhole inlet. Because of its low ion transfer efficiency the inlet represents a major bottleneck for these applications. Here we present a nano-ESI vacuum interface optimized to exploit the hydrodynamic drag of the background gas for collimation and the reduction of space charge repulsion. Up to a space charge limit of 40 nA we observe 100% current transmission through a capillary with an inlet and show by MS and IBD experiments that the transmitted ion beams are well defined and free of additional contamination compared to a conventional interface. Based on computational fluid dynamics modelling and ion transport simulations, we show how the specific shape enhances the collimation of the ion cloud. Mass selected ion currents in the nanoampere range available further downstream in high vacuum open many perspectives for the efficient use of electrospray ion beam deposition (ES-IBD) as a surface coating method

On the correlation between the oxygen in hydrogen content and the catalytic activity of cathode catalysts in PEM water electrolysis

Altogether five platinum group metal (PGM) and PGM-free cathode catalysts were investigated in full PEM water electrolysis cells regarding their polarisation behaviour and their hydrogen and oxygen recombination properties. It was shown that the recombination activity of permeated oxygen and evolved hydrogen within the cathodic catalyst layer correlates with the activity of the oxygen reduction reaction (ORR) which was determined ex situ with linear sweep voltammetry. We found that the investigated PGM-free cathode catalysts had a low activity for the ORR resulting in higher measurable oxygen in hydrogen volume fractions compared to the PGM catalysts, which are more active for the ORR. Out of the three investigated PGM-free catalysts, only one commercially available material based on a Ti suboxide showed a similar good polarisation behaviour as the state of the art cathode catalyst platinum, while its recombination activity was the lowest of all catalysts. In addition to the recombination of hydrogen and oxygen on the electrocatalysts, we found that the prevalent carbon-based cathodic porous transport layers (PTL) also offer catalytically active recombination sites. In comparison to an inactive PTL, the measurable oxygen flux using carbon-based PTLs was lower and the recombination was enhanced by microporous coatings with high surface areas. © 2021 The Author(s)