Electrical conductivity of monolithic and powdered carbon aerogels and their composites

Carbon aerogels are three-dimensional, open-porous, amorphous materials introduced by R. Pekala 1989. Starting from organic aerogels, carbon aerogels exhibit unique properties such as well-controlled pore size distribution, high porosity, large specific surface area, high electrical conductivity, and low envelope density. This make them promising material for applications in adsorption, catalysis, supercapacitors or as a sulfur hosting material in cathodes of metal-sulfur battery cells. One of the key factors for electrochemical applications is the electrical conductivity. For amorphous carbon materials it is related to their electronic structure, the size of graphitic lattices or graphitic character, heteroatoms and so-called bulk electrical conductivity. In most electrochemical applications, the carbon materials are used as powders for e.g. electrode materials. Therefore, the measurement of the electrical conductivity of powder materials is of great importance. For powders, conductivity consists of: 1) the conductivity of individual grains and 2) the conductivity of the powder. The conductivity of individual grains depends only on monolithic conductivity of the material. In contrast, the conductivity of powder depends on several factors e.g. the shape of grains, their packing, compressibility, and the contact between the grains. Measurements of the electrical resistivity of powders are usually performed on the bed of grains under pressure. Within this presentation, we will report on our recent studies showing the correlation between structural, physical, mechanical and electrical properties of pure and activated carbon aerogels, as well as aerogel-composites. For this purpose, the influence of applied force, compressibility of aerogels and composites, and particle shape were investigated using the four-pin method to measure electrical conductivity. Monoliths and powders were measured at room temperature, and for powders the resistivity was determined in the force range from 1 to 20 kN. For structural and physical characterization nitrogen sorption, scanning electron microscopy, and pycnometry were used

Homo- and Heteroassociations Drive Activation of ErbB3

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Broadening the phenotypic and molecular spectrum of FINCA syndrome: Biallelic NHLRC2 variants in 15 novel individuals

FINCA syndrome [MIM: 618278] is an autosomal recessive multisystem disorder characterized by fibrosis, neurodegeneration and cerebral angiomatosis. To date, 13 patients from nine families with biallelic NHLRC2 variants have been published. In all of them, the recurrent missense variant p.(Asp148Tyr) was detected on at least one allele. Common manifestations included lung or muscle fibrosis, respiratory distress, developmental delay, neuromuscular symptoms and seizures often followed by early death due to rapid disease progression.Here, we present 15 individuals from 12 families with an overlapping phenotype associated with nine novel NHLRC2 variants identified by exome analysis. All patients described here presented with moderate to severe global developmental delay and variable disease progression. Seizures, truncal hypotonia and movement disorders were frequently observed. Notably, we also present the first eight cases in which the recurrent p.(Asp148Tyr) variant was not detected in either homozygous or compound heterozygous state.We cloned and expressed all novel and most previously published non-truncating variants in HEK293-cells. From the results of these functional studies, we propose a potential genotype-phenotype correlation, with a greater reduction in protein expression being associated with a more severe phenotype.Taken together, our findings broaden the known phenotypic and molecular spectrum and emphasize that NHLRC2-related disease should be considered in patients presenting with intellectual disability, movement disorders, neuroregression and epilepsy with or without pulmonary involvement

Biallelic and monoallelic variants in PLXNA1 are implicated in a novel neurodevelopmental disorder with variable cerebral and eye anomalies.

PURPOSE: To investigate the effect of PLXNA1 variants on the phenotype of patients with autosomal dominant and recessive inheritance patterns and to functionally characterize the zebrafish homologs plxna1a and plxna1b during development. METHODS: We assembled ten patients from seven families with biallelic or de novo PLXNA1 variants. We describe genotype-phenotype correlations, investigated the variants by structural modeling, and used Morpholino knockdown experiments in zebrafish to characterize the embryonic role of plxna1a and plxna1b. RESULTS: Shared phenotypic features among patients include global developmental delay (9/10), brain anomalies (6/10), and eye anomalies (7/10). Notably, seizures were predominantly reported in patients with monoallelic variants. Structural modeling of missense variants in PLXNA1 suggests distortion in the native protein. Our zebrafish studies enforce an embryonic role of plxna1a and plxna1b in the development of the central nervous system and the eye. CONCLUSION: We propose that different biallelic and monoallelic variants in PLXNA1 result in a novel neurodevelopmental syndrome mainly comprising developmental delay, brain, and eye anomalies. We hypothesize that biallelic variants in the extracellular Plexin-A1 domains lead to impaired dimerization or lack of receptor molecules, whereas monoallelic variants in the intracellular Plexin-A1 domains might impair downstream signaling through a dominant-negative effect

Effect of Microstructure of Porous Carbon Materials on Electrical Conductivity

Lithium-Ionen-Batterien sind die aktuell marktbeherrschenden Batteriesysteme. Die Leistungsfähigkeit von konventionellen Li-Ionen Batterien ist jedoch allmählich ausgereizt. Um die Leistungsfähigkeit zu verbessern, wird an alternativen Anodenmaterialien geforscht, die eine erhöhte Kapazität mit ausreichender elektrischer Leitfähigkeit kombinieren. In dieser Arbeit wurden hochporöse Kohlenstoffaerogele mit unterschiedlichen kohlenstoffhaltigen Additiven gemischt. Leitfähigkeitsmessungen wurden für Belastungen von 1 bis 20 kN für die Ausgangsmaterialien und für Aerogel-AdditivKomposite in verschiedenen Mischungsverhältnissen durchgeführt. Die Mikrostrukturen wurden mittels Physisorption und Rasterelektronenmikroskopie analysiert. Die Materialien wurden anhand selbstdefinierter Partikelformen charakterisiert. Es wurde gezeigt, dass die Leitfähigkeit von Kohlenstoffaerogel durch den Einsatz von Additiven erheblich gesteigert werden konnte. Die höchsten Leitfähigkeiten konnten mit großen plättchenförmigen Partikeln erzielt werden, wohingegen flockenartige Partikelformen und gebrochene Fasern geringere Leitfähigkeiten aufgewiesen haben. Der Einfluss der Mikrostruktur auf die elektrische Leitfähigkeit hängt von vielen Faktoren ab, wie der Partikelgeometrie, Dichte, Reinheit, Porosität und der spezifischen Oberfläche. Aerogel-Additiv-Komposite wiesen eine erfolgreiche Kombination aus hoher spezifischer Oberfläche und guter elektrische Leitfähigkeit auf, die vielversprechende Anodenmaterialen in zukünftigen Batteriezellen sein könnten und deshalb weiter erforscht werden sollten

Electrical conductivity of monolithic and powdered carbon aerogels and their composites

Carbon aerogels are three-dimensional, open-porous, amorphous materials produced via carbonization of organic aerogels such as resorcinol-formaldehyde, phenol-formaldehyde, resorcinol-formaldehyde-melamine, or biomass-based ones. Unique properties of carbon aerogels such as well-controlled porosity, large specific surface area, high electrical conductivity, and low envelope density make them promising material for applications in adsorption, catalysis, supercapacitors or as a cathode host in lithium-sulfur battery cells. Their electrical conductivity, remarkable for porous materials, is one of the key factors for electrochemical applications. The electrical conductivity of amorphous carbon materials is related to their electronic structure, the size of graphitic lattices or graphitic character, heteroatoms and so-called bulk electrical conductivity. In most electrochemical applications, the carbon aerogels are used as powders for e.g. electrode materials. Therefore, the measurement of the electrical conductivity of powder materials is of great importance. For powders, conductivity consists of: 1) the conductivity of individual grains and 2) the conductivity of the powder. The conductivity of individual grains depends only on conductivity of the material (monolithic conductivity). In contrast, the conductivity of powder depends on several factors e.g. the shape of grains, their packing, compressibility, and the contact between the grains. Measurements of the electrical resistivity of powders are usually performed on the bed of grains under pressure. Within the presentation, we will report on our studies showing the correlation between structural, physical, mechanical and electrical properties of pure and activated carbon aerogels, as well as aerogel-composites. Furthermore, the influence of applied force, compressibility of aerogels and composites, and particle shape were investigated by using the four-pins-method. The conductivity of monoliths and powders was measured at room temperature, for powders the resistivity was determined in the force range from 0.1 to 20.0 kN. For structural and physical characterization Raman spectroscopy, nitrogen sorption, scanning electron microscopy, and pycnometry were used

Combining of small fragment screws and large fragment plates for open reduction and internal fixation of periprosthetic humeral fractures

Operative treatment of periprosthetic humeral fractures in elderly patients with osteoporotic bone requires a stable fixations technique. The combination of 3.5 cortical screws with washers in a 4.5 Arbeitsgemeinschaft für Osteosynthesefragen, Limited-contact dynamic compression plate or Locking plate, allows a stable periprosthetic fixation with the small 3.5 screws and 4.5 screws above and below the prosthesis, respectively. This combination is a cost-effective technique to treat periprosthetic humeral fractures

Ca(2+)-independent activation of BK(Ca) channels at negative potentials in mammalian inner hair cells

The defining characteristic of large-conductance Ca(2+)- and voltage-activated K(+) channels (BK(Ca)) is their allosteric activation by two distinct stimuli, membrane depolarization and cytosolic Ca(2+) ions. In this allosteric gating, increasing cytosolic Ca(2+) concentration ([Ca(2+)](i)) shifts the depolarization required for channel opening into the physiological voltage range. In fact, according to present knowledge, elevation of [Ca(2+)](i) to micromolar levels is the only means to activate BK(Ca) at membrane potentials below 0 mV. We recorded BK(Ca)-mediated currents from auditory inner hair cells (IHCs) in acutely isolated organs of Corti using the patch-clamp technique in whole-cell and excised patch configuration. In inside-out and outside-out patches, activation of BK(Ca) channels from IHCs showed the prototypic sensitivity to increased [Ca(2+)](i). However, channel activation at 0 [Ca(2+)](i) occurred at unusually negative potentials (half-maximal activation (V(h)) around 0 mV), indicating that a large fraction of the channels can be activated at physiological voltages without elevated [Ca(2+)](i). In intact IHCs, the activation curve of BK(Ca) currents recorded in whole-cell configuration exhibited a V(h) of −42 mV together with a high voltage dependence (slope factor of 10 mV) and submillisecond onset of current. Surprisingly, this activation was independent of changes in local [Ca(2+)](i) as shown by experiments that interfered with Ca(2+) influx through voltage-gated Ca(2+) (Cav) channels, release of Ca(2+) from internal stores, or intracellular buffer capacity. This behaviour is not due to β-subunits of BK(Ca) (BKβ), as genetic inactivation of the β-subunit expressed in IHCs, KCNMB1, did not affect BK(Ca) gating. We conclude that the BK(Ca) channel protein in IHCs may be modified in order to rapidly activate and deactivate at resting [Ca(2+)](i). Our results suggest that BK(Ca) may function as a purely voltage-gated K(+) channel with exceptionally rapid activation kinetics, challenging the view that both increased cytosolic Ca(2+) and depolarization are generally required for activation of BK(Ca)

1,135 Genomes Reveal the Global Pattern of Polymorphism in Arabidopsis thaliana

SummaryArabidopsis thaliana serves as a model organism for the study of fundamental physiological, cellular, and molecular processes. It has also greatly advanced our understanding of intraspecific genome variation. We present a detailed map of variation in 1,135 high-quality re-sequenced natural inbred lines representing the native Eurasian and North African range and recently colonized North America. We identify relict populations that continue to inhabit ancestral habitats, primarily in the Iberian Peninsula. They have mixed with a lineage that has spread to northern latitudes from an unknown glacial refugium and is now found in a much broader spectrum of habitats. Insights into the history of the species and the fine-scale distribution of genetic diversity provide the basis for full exploitation of A. thaliana natural variation through integration of genomes and epigenomes with molecular and non-molecular phenotypes

Epigenomic Diversity in a Global Collection of Arabidopsis thaliana Accessions

The epigenome orchestrates genome accessibility, functionality, and three-dimensional structure. Because epigenetic variation can impact transcription and thus phenotypes, it may contribute to adaptation. Here, we report 1,107 high-quality single-base resolution methylomes and 1,203 transcriptomes from the 1001 Genomes collection of Arabidopsis thaliana. Although the genetic basis of methylation variation is highly complex, geographic origin is a major predictor of genome-wide DNA methylation levels and of altered gene expression caused by epialleles. Comparison to cistrome and epicistrome datasets identifies associations between transcription factor binding sites, methylation, nucleotide variation, and co-expression modules. Physical maps for nine of the most diverse genomes reveal how transposons and other structural variants shape the epigenome, with dramatic effects on immunity genes. The 1001 Epigenomes Project provides a comprehensive resource for understanding how variation in DNA methylation contributes to molecular and non-molecular phenotypes in natural populations of the most studied model plant