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On-site calibration of instruments in the Arctic: assessment of temperature records at Climate Change Tower in Ny-Ålesund, Svalbard
Get PDFThe Arctic is as a key place to perform environmental measurements given its combination of reduced human activity and increased sensitivity to climate change. The Svalbard archipelago constitutes an invaluable measurement location, due to its ease of access and the presence of the Ny-Ålesund research center. Sensors are usually not designed to sustain prolonged periods of time in demanding environments like the Arctic; therefore, chances of failures, drift, and errors are higher than elsewhere. Maintenance and calibration of these sensors must be rigorous and frequent, to avoid poor-quality data, or even their loss. Within the frame of EURAMET EMRP project “MeteoMet 2”, calibration of the temperature sensors hosted by the Climate Change Tower (CCT), a unique research facility designed to monitor lower-atmosphere profiles of several meteorological quantities, has been performed. The calibration campaign pointed out sensor errors up to 1 °C and corrected the measurements, straightening the skewed temperature profiles. Absolute calibration uncertainties have been evaluated at ∼0.2 °C, less than half of those stated by the manufacturer, while an evaluation of relative uncertainties yielded values of just few 0.01 °C. This experience stimulated the creation of an in-situ calibration facility, to the benefit of the whole scientific community based in Ny-Ålesund
Enhanced optoelectronic characteristics of La-doped ZnO and its compatibility with Cs-doped MAPbI3 perovskite absorber material
No full textThe present study investigates the structural, electrical and optical characteristics of pristine and lanthanum (La)-doped zinc oxide (ZnO) electron transport layers fabricated by the sol–gel method and their compatibility with Cs0.10MA0.90Pb(I0.9Br0.10)3 absorber layer for perovskite solar cells. All the electron transport layers were deposited under the same deposition conditions, with the only difference in La percentage in the precursor solutions, ranging from 0 to 6%. X-ray diffraction analysis demonstrated the presence of crystalline ZnO thin films and the absence of any impurity phases after La-doping. The calculated crystallite size, determined using Scherrer's equation, increased from 11.13 to 21.76 nm after the introduction of dopant. The doping with 4% La led to the decrease in the optical band gap from 3.32 eV of pristine ZnO to 3.23 eV. Scanning electron microscopy analysis revealed better morphology of perovskite / 4% La:ZnO specimen, which facilitated the absorbance and reduced the charge carrier recombination. It also exhibited superior resilience towards moisture and humidity which will eventually contribute to the development of more stable and efficient planar perovskite solar cells
Bayesian inference of the mean power of several Gaussian data
Get PDFThe uniform prior probability density for the means of normal data leads to inconsistent Bayesian inference of their mean power and jeopardizes the possibility of selecting among different models that explain the data. We reinvestigated the problem avoiding delivering unrecognised information and looking at it in a novel way. Namely, to consider a finite power, we used a normal prior minimally diverging from the uniform one, hyperparameterised by the mean and variance, and left the data to choose the most supported parameters. We also obtained an extended James–Stein estimator averaging the hyper-parameters and avoiding empirical Bayes techniques
Pilot study comparison of developed and improved mass scale measurement capabilities
Get PDFThe objective of the Pilot Study was the calibration of sub-multiples of the kilogram, which was organised as a EURAMET Pilot Study in order to demonstrate a diagnostic comparison for the developed and improved Calibration Measurement Capability (CMC), while realising the mass scale of the participating National Measurement Institutes (NMIs). Due to the instability of some weights a simplified method was used to evaluate the results. It compares the laboratory result for each weight with the reference value obtained by the fitted weighted trendline, including the correlation due to the Consensus Value. It was the first time that the method of subdivision of a decade has been compared among laboratories by comparing the individual mass differences of the design matrix. The aim of improving capabilities and realising the mass scale with uncertainties of 1/3 mpe of the OIML Class E1 tolerance was achieved by the participating NMIs
Magnetic nanoparticles in square-wave fields for breakthrough performance in hyperthermia and magnetic particle imaging
Get PDFDriving immobilized, single-domain magnetic nanoparticles at high frequency by square wave fields instead of sinusoidal waveforms leads to qualitative and quantitative improvements in their performance both as point-like heat sources for magnetic hyperthermia and as sensing elements in frequency-resolved techniques such as magnetic particle imaging and magnetic particle spectroscopy. The time evolution and the frequency spectrum of the cyclic magnetization of magnetite nanoparticles with random easy axes are obtained by means of a rate-equation method able to describe time-dependent effects for the particle sizes and frequencies of interest in most applications to biomedicine. In the presence of a high-frequency square-wave field, the rate equations are shown to admit an analytical solution and the periodic magnetization can be therefore described with accuracy, allowing one to single out effects which take place on different timescales. Magnetic hysteresis effects arising from the specific features of the square-wave driving field results in a breakthrough improvement of both the magnetic power released as heat to an environment in magnetic hyperthermia treatments and the magnitude of the third harmonic of the frequency spectrum of the magnetization, which plays a central role in magnetic particle imaging
Unraveling the dealloying mechanism of a Au33Fe67 metastable precursor for a low-cost nanoporous gold production
No full textA low-cost Nanoporous Gold (NPG) has been successfully prepared by chemical dealloying of a Au33Fe67 supersaturated solid solution, whose ribbons were obtained by rapid solidification using melt-spinning technique. The dealloying procedures were carried out in 1 M HNO3 at 70 degrees C for varying durations. As-quenched ribbon and dealloyed samples have been structurally and compositionally investigated using XRD, FESEM and EDS techniques. The obtained NPG is homogeneous with tunable ligament size and shape, easy-to-handle and freestanding. Most notably, a metastable precursor has been favourably obtained from an immiscible Au-Fe system. Furthermore, according to the characterization results, a mechanism of dealloying has been proposed. Pairing Au with cheap and abundant Fe and fabricating an Fe-rich precursor gives an exceedingly cost-effective starting material. No usage of critical raw materials is involved. Then, employing a straight-forward and rapid dealloying procedure to obtain the NPG sample, makes for an overall inexpensive and sustainable production
Spectroscopic Characterization of Ti Sites in MWW Zeolite in Presence of Hydrogen Peroxide
Get PDFTi-MWW zeolite is a promising catalyst for partial oxidation reactions. In the present work, a Ti-MWW sample with high TiO2 loading was synthesized. It was revealed that the Ti insertion in the purely siliceous MWW framework mainly occurs during the post treatment washing with HNO3, when the double structure directing agent synthetic method is used. By exploiting carbon monoxide, acetonitrile, pyridine and ammonia as probe molecules in infrared spectroscopy and diffuse reflectance ultraviolet spectroscopy, the acidic behavior of the Ti sites and the interaction of the Ti sites with hydrogen peroxide (H2O2) were revealed. The Ti Lewis acid sites showed stronger acidity than the one observed in Titanium Silicalite-1 (TS-1), with MFI framework. This is coherent with previously reported results, suggesting that a significative fraction of the Ti sites in Ti-MWW are TiOH(SiO)(3) instead of Ti(OSi)(4). The Ti-peroxo and -hydroperoxo complexes formed upon H2O2 were shown to be more labile than in TS-1 and they were shown to be completely reversible upon calcination
