A hybrid metal/semiconductor electron pump for quantum metrology

Electron pumps capable of delivering a current higher than 100pA with sufficient accuracy are likely to become the direct mise en pratique of the possible new quantum definition of the ampere. Furthermore, they are essential for closing the quantum metrological triangle experiment which tests for possible corrections to the quantum relations linking e and h, the electron charge and the Planck constant, to voltage, resistance and current. We present here single-island hybrid metal/semiconductor transistor pumps which combine the simplicity and efficiency of Coulomb blockade in metals with the unsurpassed performances of silicon switches. Robust and simple pumping at 650MHz and 0.5K is demonstrated. The pumped current obtained over a voltage bias range of 1.4mV corresponds to a relative deviation of 5e-4 from the calculated value, well within the 1.5e-3 uncertainty of the measurement setup. Multi-charge pumping can be performed. The simple design fully integrated in an industrial CMOS process makes it an ideal candidate for national measurement institutes to realize and share a future quantum ampere

Demonstration experiments for solid state physics using a table top mechanical Stirling refrigerator

Liquid free cryogenic devices are acquiring importance in basic science and engineering. But they can also lead to improvements in teaching low temperature an solid state physics to graduate students and specialists. Most of the devices are relatively expensive, but small sized equipment is slowly becoming available. Here, we have designed several simple experiments which can be performed using a small Stirling refrigerator. We discuss the measurement of the critical current and temperature of a bulk YBa2Cu3O(7-d) (YBCO) sample, the observation of the levitation of a magnet over a YBCO disk when cooled below the critical temperature and the observation of a phase transition using ac calorimetry. The equipment can be easily handled by students, and also used to teach the principles of liquid free cooling

Selective Anion Binding by a Cofacial Binuclear Zinc Complex of a Schiff-Base Pyrrole Macrocycle

The synthesis of the new cofacial binuclear zinc complex [Zn(2)(L)] of a Schiff-base pyrrole macrocycle is reported. It was discovered that the binuclear microenvironment between the two metals of [Zn(2)(L)] is suited for the encapsulation of anions, leading to the formation of [K(THF)(6)][Zn(2)(μ-Cl)(L)].2THF and [Bu(n)(4)N][Zn(2)(μ-OH)(L)] which were characterized by X-ray crystallography. Unusually obtuse Zn-X-Zn angles (X=Cl: 150.54(9)° and OH: 157.4(3)°) illustrate the weak character of these interactions and the importance of the cleft pre-organization to stabilize the host. In the absence of added anion, aggregation of [Zn(2)(L)] was inferred and investigated by successive dilutions and by the addition of coordinating solvents to [Zn(2)(L)] solutions using NMR spectroscopy as well as isothermal microcalorimetry (ITC). On anion addition, evidence for de-aggregation of [Zn(2)(L)], combined with the formation of the 1:1 host-guest complex, was observed by NMR spectroscopy and ITC titrations. Furthermore, [Zn(2)(L)] binds to Cl(−) selectively in THF as deduced from the ITC analyses, while other halides induce only de-aggregation. These conclusions were reinforced by DFT calculations, which indicated that the binding energies of OH(−) and Cl(−) were significantly greater than for the other halides

Quantum Metrology Triangle Experiments: A Status Review

Quantum Metrology Triangle experiments combine three quantum electrical effects (the Josephson effect, the quantum Hall effect and the single-electron transport effect) used in metrology. These experiments allow important fundamental consistency tests on the validity of commonly assumed relations between fundamental constants of nature and the quantum electrical effects. This paper reviews the history, results and the present status and perspectives of Quantum Metrology Triangle experiments. It also reflects on the possible implications of results for the knowledge on fundamental constants and the quantum electrical effects.Comment: 36 pages, 8 figure

Methodology to evaluate the uncertainty associated with nanoparticle dimensional measurements by SEM

International audienceThe scanning electron microscopy (SEM) technique is widely used for the characterizing of nanoparticle (NP) size, but very few papers deal with NP dimensional metrology. This article reports on a methodology with which to evaluate the uncertainty budget associated with the measurement of the mean diameter of a standard silica NP population by SEM. In this context, the effects of potential error sources have been evaluated though a metrological qualification of the instrument. The measuring method, consisting of determining the area equivalent diameter taken at middle height (D eq-FWHM), has been tested on a reference silica NP with an indicative certification value given by SEM/TEM (number-based modal diameter). Because agglomeration phenomena can cause measurements errors, semi-automatic homemade software has been employed to build the diameter distribution histogram, selecting only isolated particles. Finally, an uncertainty budget, including the main experimental components, has been established for the mean diameter measurement of this silica NP population. The main contributors to this uncertainty budget are the resolution linked to the dimension of the electron beam diameter at the focal plane, the calibration uncertainty on reference NPs, and the measurement repeatability

Thermal conductivity of pure and Si-doped CuGeO3

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Human TR146 cells and pig buccal mucosa to assess oral transmucosal passage and buccal toxicity of foodgrade titanium dioxide

International audienceBackground: Today, the use of titanium dioxide (TiO 2) as food additive (E171) has been banned by the European Commission, due to concerns for human health based on studies showing TiO 2 particles systematically available, tissue accumulation, a genotoxic risk and possible promotion of precancerous lesions. However, E171 is still present in toothpastes and pharmaceutical tablets as a whitening powder mixing nano-and submicronic particles. Risk assessment of TiO 2 intake by oral route is mainly based on the assumption that particles are mainly absorbed by the intestine. However, while the buccal mucosa is the first exposed area, the possibility of an oro-transmucosal passage has not been documented so far. In order to gain insight on possible adverse effects for human health associated to E171 buccal exposure, we analyzed in vivo the translocation of TiO 2 (E171) in the buccal mucosa of pigs used as human mouth model. Moreover, we evaluated in vitro the particle translocation on human buccal TR146 cell line, and measured cytotoxic and genotoxic effects on proliferative and differentiated epithelial cells. Methods & Results: Under realistic exposure conditions with 50 µg/ml of food-grade TiO 2 in water suspension (size distribution 20-440 nm; mean size of 105 nm) deposited under the tongue of pigs, TEM-EDX data revealed the presence of small aggregates of TiO 2 particles translocated into the buccal mucosa from 30 minutes of exposure, reaching submaxillary lymph nodes after 4 hours. In human TR146 cells exposed to E171, kinetic analysis using confocal, TEM and SIMS imaging showed progressive and large uptake of isolated or small aggregates of both submicronic and nanosized particles, showing high permeability capacity. At 2h of E171 exposure, cytotoxicity, genotoxicity and oxidative stress were investigated on both proliferative or differentiated TR146 cells, in comparison with two TiO 2 size standards of 115 nm and 21 nm in diameter. All tested TiO 2 particles were reported cytotoxic on proliferative TR146 cells, and this effect was almost abolished following differentiation. Oxidative stress and genotoxicity assessed through γH2AX and 53BP1 foci formation and comet assay were only reported for E171 sample and TiO 2 particles of 115 nm, suggesting the particles above 20 nm responsive of these effects, and mainly on proliferative cells. Conclusions: Taken together, these results show in vivo and in vitro that the buccal mucosa is an important absorption route for systemic passage of foodborne TiO 2 (E171) particles. In human cells, uptake of TiO2 particles was cytotoxic without size effects, while they generate further oxidative and genotoxic stresses in proliferative buccal cells, that could impair epithelium renewal in the mouth. Altogether, these data emphasize that buccal exposure should be considered for toxicokinetic and risk assessments of TiO2 in human when used as food additive, including in toothpaste and pharmaceutical formulations