Estimation and testing for spatially indexed curves with application to ionospheric and magnetic field trends

We develop methodology for the estimation of the functional mean and the functional principal components when the functions form a spatial process. The data consist of curves $X(\mathbf{s}_k;t),t\in[0,T],$ observed at spatial locations $\mathbf{s}_1,\mathbf{s}_2,...,\mathbf{s}_N$. We propose several methods, and evaluate them by means of a simulation study. Next, we develop a significance test for the correlation of two such functional spatial fields. After validating the finite sample performance of this test by means of a simulation study, we apply it to determine if there is correlation between long-term trends in the so-called critical ionospheric frequency and decadal changes in the direction of the internal magnetic field of the Earth. The test provides conclusive evidence for correlation, thus solving a long-standing space physics conjecture. This conclusion is not apparent if the spatial dependence of the curves is neglected.Comment: Published in at http://dx.doi.org/10.1214/11-AOAS524 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Application of genetic algorithm for extraction of the parameters from powder EPR spectra

The application of the stochastic genetic algorithm in tandem with the deterministic Powell method to automated extraction of the magnetic parameters from powder EPR spectra was described. The efficiency and robustness of such hybrid approach were investigated as a function of the uncertainty range of the parameters, using simulated data sets. The discussed results demonstrate superior performance of the hybrid genetic algorithm in fitting of complex spectra in comparison to the common Monte Carlo method joint with the Powell refinement

Interaction of diatomic molecules with nickel ions inside the channels of high silica zeolites : an EPR and DFT study

Interaction of CO, NO, and O-2 diatomics with Ni-II and ions dispersed in ZSM-5 zeolite was investigated by electron paramagnetic resonance (EPR) spectroscopy and density functional theory (DFT) modelling. The resulting adducts Ni-I-CO, Ni-II-NO, and Ni-I-O-2 were identified based on g-tensor parameters, obtained by computer fitting of the powder EPR spectra, and next ascertained by parallel relativistic DFT calculations of the corresponding g-tensor values. The structures of the Ni-I-CO, Ni-II-NO, and Ni-I-O-2 complexes were obtained by geometry optimization with the Kohn-Sham method. Binding of the diatomics was discussed in terms of the spin-pairing and electron density transfer events. Interaction of CO with Ni-I cations led to the pronounced change in the coordination and electronic structure of the Ni-I center, however, no redox processes were observed in agreement with the "innocent" nature of CO as a ligand. On the contrary, strong electron and spin density redistribution was observed upon NO and O-2 interaction ("non-innocent ligands") leading to the formation of the bound nitrosonium NO delta+ and superoxo O-2(-) species, respectively

Probability Tails of Wavelet Coefficients of Magnetometer Records

The ground-based magnetometer network has long been a powerful tool for monitoring and observing the variations of the currents flowing in the magnetosphere-ionosphere (M-I) system. The time series of magnetograms are nonstationary and their frequency behavior changes over time. They are therefore not amenable to traditional time domain or spectral (Fourier) analysis. In recent years, various new mathematical techniques have been developed to analyze magnetometer data and the wavelet technique has stood out as being particularly relevant. In order to correctly make statistical inferences based on wavelet analysis, the wavelet coefficient distributions of magnetograms must be examined. In this work, we apply the discrete wavelet transform to the 1-min magnetometer records and then use several statistical techniques to analyze the probability distributions of the wavelet coefficients. It is found that the distributions of these coefficients for both storm and quiet times are highly nonnormal and can be classified as being heavy tailed. This finding suggests that when applying statistical techniques to the wavelet coefficients of the magnetograms, one must make sure that these techniques are robust to large departures from Gaussianity manifested by the presence of heavy probability tails. It is also found that the tail indexes for storm times are on average smaller than those of quiet times, which reflects the stronger impulsive and nonstationary features in magnetometer data during storm times, and the shifts are most significant for the wavelet coefficients corresponding to physical scales of 4–8 min

Role of electronic factor in soot oxidation process over tunnelled and layered potassium iron oxide catalysts

This paper describes the investigations of the catalytic activity in soot oxidation over well-defined iron oxide based materials. The nanostructuration of iron oxide by potassium into tunnelled (KFeO 2 ) and layered (K 2 Fe 22 O 34 ) ferrites and the surface promotion with CeO 2 results in the marked increase in the catalytic activity (decrease of the ignition temperature down to 210 ° C and T 10 % to 310 ° C). The measurements of the catalysts work function showed that both nanostructuration and surface promotion with ceria of the best KFeO 2 phase led to increase of the electron availability (decrease of the work function). Strong correlation of the catalytic activity in soot combustion of the Ce–K–Fe–O systems with the work function value was revealed for the first time in the model studies, and can be used as a guideline for optimisation of the real catalytic filters

Diagnostic features of EPR spectra of superoxide intermediates on catalytic surfaces and molecular interpretation of their g and A tensors

The use of electron paramagnetic resonance spectroscopy to study the superoxide intermediates, generated by end-on and side-on adsorption of the naturally abundant and 17O-enriched dioxygen on catalytic surfaces is discussed. Basic mechanisms of O2 − radical formation via a cationic redox mechanism, an anionic redox mechanism, and an electroprotic mechanism are illustrated with selected oxide-based systems of catalytic relevance. Representative experimental spectra of various complexities are analyzed and their diagnostic features have been identified and interpreted. The molecular nature of the g and A tensors of the electrostatic and covalent superoxide adducts is discussed in detail within the classic and density functional theory based approaches

Toxicity of the bacteriophage λ cII gene product to Escherichia coli arises from inhibition of host cell DNA replication

AbstractThe bacteriophage λ cII gene codes for a transcriptional activator protein which is a crucial regulator at the stage of the “lysis-versus-lysogeny” decision during phage development. The CII protein is highly toxic to the host, Escherichia coli, when overproduced. However, the molecular mechanism of this toxicity is not known. Here we demonstrate that DNA synthesis, but not total RNA synthesis, is strongly inhibited in cII-overexpressing E. coli cells. The toxicity was also observed when the transcriptional stimulator activity of CII was abolished either by a point mutation in the cII gene or by a point mutation, rpoA341, in the gene coding for the RNA polymerase α subunit. Moreover, inhibition of cell growth, caused by both wild-type and mutant CII proteins in either rpoA+ or rpoA341 hosts, could be relieved by overexpression of the E. coli dnaB and dnaC genes. In vitro replication of an oriC-based plasmid DNA was somewhat impaired by the presence of the CII, and several CII-resistant E. coli strains contain mutations near dnaC. We conclude that the DNA replication machinery may be a target for the toxic activity of CII

Effectiveness and safety of ICA stenting in conjunction with mechanical thrombectomy (antegrade approach) in acute ischaemic stroke patients due to tandem occlusion

Aim of study. We investigated the effectiveness and safety of an antegrade approach consisting of emergency ICA stenting in conjunction with mechanical thrombectomy (MT) in a one-stage procedure as a treatment for Tandem Occlusion (TO).Clinical rationale for study. We here describe our experience in the treatment of TO with an antegrade approach with long-term results. We also discuss the advantages and drawbacks of this treatment modality with special attention to possible haemorrhagic complications that can be encountered in patients with ischaemic stroke who receive antiplatelet treatment. We believe that our study adds to the limited number of reports on this topic.Materials and methods. We selected 34 patients diagnosed with acute ischaemic stroke due to ICA and ipsilateral intracranial occlusion treated with ICA stenting in conjunction with MT. We analysed the short- and long-term results as well as investigating complications with special regard to haemorrhagic transformationassociated with the need for antiplatelet treatment after stent implantation in patients after acute ischaemic stroke treatment.Results. A favourable angiographic outcome was defined as mTICI 2b–3. This was achieved in 33/34 patients (97%). On average, NIHSS at 24 hours after the procedure was 8.5 ± 7, which indicates a significant clinical improvement. Four cases of symptomatic ICH were observed (11.8%). One re-occlusion in stent was noted. At three-month follow-up, mRS scores were 0 in 11 (34.3%), 1 in 5 (16%), 2 in 1 (3%), 3 in 3 (9.3%), 4 in 3 (9.3%), and 5 in 2 (6%) patients. Seven patients did not survive (22%). Overall, a favourable outcome (mRS 0–2) was achieved in 17/34 patients (50%). The final mortality rate was 26.5% (9/34 patients).Conclusions and clinical implications. We conclude that an antegrade approach is a feasible and effective method for treating acute TO stroke, giving the patient the chance to regain his or her full independence in everyday life, with low overall complication and final mortality rates