Quantum Hall resistance standards from graphene grown by chemical vapor deposition on silicon carbide

Replacing GaAs by graphene to realize more practical quantum Hall resistance standards (QHRS), accurate to within $10^{-9}$ in relative value, but operating at lower magnetic fields than 10 T, is an ongoing goal in metrology. To date, the required accuracy has been reported, only few times, in graphene grown on SiC by sublimation of Si, under higher magnetic fields. Here, we report on a device made of graphene grown by chemical vapour deposition on SiC which demonstrates such accuracies of the Hall resistance from 10 T up to 19 T at 1.4 K. This is explained by a quantum Hall effect with low dissipation, resulting from strongly localized bulk states at the magnetic length scale, over a wide magnetic field range. Our results show that graphene-based QHRS can replace their GaAs counterparts by operating in as-convenient cryomagnetic conditions, but over an extended magnetic field range. They rely on a promising hybrid and scalable growth method and a fabrication process achieving low-electron density devices.Comment: 12 pages, 8 figure

Ethnopharmacology, Ethnomedicine, and Wildlife Conservation

Ethnopharmacological relevance: There are longstanding traditions of animal-derived products being employed as medicines, and they continue to be important in many traditional cultural healthcare practices. However, the populations of numerous so-used animals are known to be threatened with extirpation by such practices. Ethnopharmacological studies documenting these animal-derived drug products are not only interesting from an anthropological standpoint, but they are also relevant from a wildlife conservation perspective - especially since ethnopharmacologists are intermediaries between indigenous and scientific communities, placing them at the forefront of being able to ethically access information to address these issues. Methods: Using the example of documenting culturally acceptable substitute materials for animal products (which ultimately also extends to flora), we explore the intersection of ethnopharmacology, biocultural resources, and wildlife conservation. Results: Pharmacological efficacy and symbolism are factors influencing the utilization of traditional medicines. Achieving the integration of conservation aims with ethnopharmacology requires a nuanced understanding of both factors, along with fair adjudication when conservation and cultural aims diverge. Ethnopharmacology is suitably placed for making conservation-orientated recommendations - including investigating more sustainable substitutes for animal products in the context of medical efficacy, and for engaging ethically with local communities to facilitate information generation aimed at protecting the environment and their traditions. Conclusion: We suggest an integrative approach to ethnopharmacological studies investigating medicinal bioresource use. This approach is considerate of species' conservation profiles, the substitutability and pharmacological efficacy of biocultural resources, indigenous and cultural rights, and a collaborative ethos for stakeholder engagement

The effect of yeast on the anthocyanin characteristics of fermented model solutions

The sensory quality of red wines is basically determined by the colour, which depends on the amount and on the evolution of anthocyanins and other phenolic compounds extracting from the berries into the wine during wine-making. The anthocyanin-monomers are responsible for the development of the red colour, and their acylated derivatives provide stability for the colour of the wines. The anthocyanin profile of wines is affected by several factors: the grape variety, the conditions during wine-making, and also the yeast culture used for the fermentation. In our experiments a self-compiled model solution was fermented by spontaneous fermentation, as well as by four commercial yeasts under laboratory conditions. After fermentation total polyphenolics, anthocyanins, anthocyanin monomer profile, colour intensity, hue, and the ratio of polymeric anthocyanins were studied. Our results show that the spontaneous yeast fermentation resulted in a higher anthocyanin concentration in the fermented model solution, but the commercial yeast strains provided a more advantageous colour characteristic compared to the spontaneous fermentation. After the spontaneous fermentation less sediment was left than in the commercial yeast fermented samples

Characterization of Fabric-to-Fabric Friction: Application to Medical Compression Bandages

Fabric-to-fabric friction is involved in the action mechanism of medical compression devices such as compression bandages or lumbar belts. To better understand the action of such devices, it is essential to characterize, in their use conditions (mainly pressure and stretch), the frictional properties of the fabrics they are composed of. A characterization method of fabric-to-fabric friction was developed. This method was based on the customization of the fourth instrument of the Kawabata Evaluation System, initially designed for fabric roughness and friction characterization. A friction contactor was developed so that the stretch of the fabric and the applied load can vary to replicate the use conditions. This methodology was implemented to measure the friction coefficient of several medical compression bandages. In the ranges of pressure and bandage stretch investigated in the study, bandage-to-bandage friction coefficient showed very little variation. This simple and reliable method, which was tested for commercially available medical compression bandages, could be used for other medical compression fabrics

Polarimetric interferometer for nanoscale positioning applications

International audienceWe propose and demonstrate a displacement control method at the subnanometric scale based on a Michelson interferometer combined with a polarimeter and a phase-locked loop electronic board. Step by step displacements with a step value of 5 nm are presented. A repeatability of 0.47 nm is obtained from back and forth displacements over 1 m range. We show that a residual ellipticity of less than 10° on the polarization state leads to a positioning error of less than 1 nm. Such system could be used over millimeter range displacements in a controlled surrounding environment leading to numerous applications in nanometrology

Compact and accurate concept of laser wavemeters based on ellipsometry

Common laser wavemeters are based on a scanning Michelson interferometer. Displacements of the moving mirror as long as tens of centimeters are needed to reach a relative accuracy of 1 × 10−6 (1σ) on the unknown laser wavelengths. Such a long displacement range makes the system very sensitive to mechanical vibrations and to misalignments of the laser beams. The purpose of this paper is to demonstrate a new concept of laser wavemeter based on the measurements of the ellipsometric parameters ψ and of the laser beams. Experimental results show that a 10−6 (1σ) accuracy level could be reach with a displacement range of only 4 μm. Implementations of the device are described. Comparisons between our polarimetric wavemeter and a calibrated wavemeter are presented for two lasers, an extended cavity laser diode at 656 nm and a 532 nm green line Nd:YAG laser