Determination of the Distribution of the Relaxation Times from Dielectric Spectra

The dielectric susceptibility measurements are usually interpreted in terms of the relaxation times of various dynamical processes. Using the simple examples of the simulated spectra it is shown how the distribution of these relaxation times can be obtained by means of the integral equations solved with the Tikhonov regularization technique, and the criteria for the choice of the regularization parameter is discussed

Cortisol levels and neuropsychiatric diagnosis as markers of postoperative delirium: a prospective cohort study

Polish Ministry of Science and Higher Education, Grant No. 0174/P01/2010/70; 504-06-011

X- and Q-band EPR with cryogenic amplifiers independent of sample temperature

Inspired by the success of NMR cryoprobes, we recently reported a leap in X-band EPR sensitivity by equipping an ordinary EPR probehead with a cryogenic low-noise microwave amplifier placed closed to the sample in the same cryostat [Šimėnas et al. J. Magn. Reson. 322, 106876 (2021)]. Here, we explore, theoretically and experimentally, a more general approach, where the amplifier temperature is independent of the sample temperature. This approach brings a number of important advantages, enabling sensitivity improvement irrespective of sample temperature, as well as making it more practical to combine with ENDOR and Q-band resonators, where space in the sample cryostat is often limited. Our experimental realisation places the cryogenic preamplifier within an external closed-cycle cryostat, and we show CW and pulsed EPR and ENDOR sensitivity improvements at both X- and Q-bands with negligible dependence on sample temperature. The cryoprobe delivers signal-to-noise ratio enhancements that reduce the equivalent pulsed EPR measurement time by 16× at X-band and close to 5× at Q-band. Using the theoretical framework we discuss further improvements of this approach which could be used to achieve even greater sensitivity

La-doped and La/Mn-co-doped Barium Titanate Ceramics

Barium titanate ceramics doped with 0.3 mol.% lanthanum and co-doped with 0.3 mol.% lanthanum and 0.05 mol.% manganese were investigated. The powders were prepared by a modified polymeric precursor method based on the Pechini process. The ceramics were obtained by sintering at 1300 degrees C for 8 h. The influence of dopants on structural changes and grain size reduction was analyzed. The presence of dopants influenced the tetragonality of the barium titanate crystal structure. Reduction of polygonal grain size with dopant addition was noticed. In the doped ceramics, characteristic phase transitions were shifted to lower temperatures in comparison with pure barium titanate. The dielectric permittivity value showed the tendency of a slight increase with lanthanum addition and further increase with adding of manganese. La as a single dopant increased the diffuseness of phase transitions indicating the formation of a diffuse ferroelectric material but in the co-doped ceramics the phase transition diffuseness decreased. The resistivity of the co-doped ceramics was higher than for lanthanum doped ceramics, indicating possible segregation of manganese at grain boundaries that influenced the total resistivity of the material

Ocena dynamiki mózgowego stężenia fenyloalaniny u pacjentów z fenyloketonurią

Background: Phenylketonuria (PKU) is the most common inborn error of metabolism in man. Brain phenylalanine kinetics can determine neurological treatment outcome in phenylketonuria. The aim of our study was to test a simplified magnetic resonance spectroscopy method for assessment of brain phenylalanine dynamics in PKU patients. Material/Methods: Brain phenylalanine concentration (measured by means of magnetic resonance spectroscopy) and blood phenylalanine concentrations changes occurring within 24 hours after oral phenylalanine loading were analyzed in 5 PKU patients. Results/Conclusions: The brain/blood phenylalanine ratio in 3 persons with normal intelligence was lower than in 2 with borderline intelligence or mild mental retardation. In our opinion the proposed method could be useful for assessment of brain phenylalanine dynamics in PKU patients

Effect of sintering under CO+N2/H2 and CO2+air atmospheres on the physicochemical features of a commercial nano-YSZ

Given the need to process anodes and composites based on nano-YSZ in reducing or in air containing additional CO2 atmospheres for the fabrication of solid oxide fuel cells (SOFCs), and solid oxide electrolysis cells (SOECs), we have studied the effect of the exposure to CO+N2/H2 or CO2+air mixtures during sintering of YSZ green pellets, prepared from commercial nanopowders, on their structure, microstructure, chemical composition and their electrical properties. The reduced sample shows Raman bands at 1298 and 1605 cm−1 that are assigned to the D and G bands of carbon, respectively. The bands intensity ratio ID/IG indicates a larger content of disordered carbon. X-ray photoelectron spectroscopy (XPS) shows that C is present in the reduced samples as reduced carbon. However, the samples sintered in CO2+air present C as carbonate-type. Impedance spectroscopy reveals that the highest total conductivity is for the reduced samples in the whole range of studied temperatures. In addition, sintering in CO2+air causes a detrimental effect on the grain boundary conductivity and therefore, on the total electrical conductivity of YSZ. It can be due to the presence of impurities such as carbonates and oxidised or even, polymerised carbonaceous species located at those areas.España Ministerio de Ciencia e Innovación and cofinanced with FEDER Funds under the Grant PID2019-104118RB-C2