Tracking power system events with accuracy-based PMU adaptive reporting rate

Fast dynamics and transient events are becoming more and more frequent in power systems, due to the high penetration of renewable energy sources and the consequent lack of inertia. In this scenario, Phasor Measurement Units (PMUs) are expected to track the monitored quantities. Such functionality is related not only to the PMU accuracy (as per the IEC/IEEE 60255-118-1 standard) but also to the PMU reporting rate (RR). High RRs allow tracking fast dynamics, but produce many redundant measurement data in normal conditions. In view of an effective tradeoff, the present paper proposes an adaptive RR mechanism based on a real-time selection of the measurements, with the target of preserving the information content while reducing the data rate. The proposed method has been tested considering real-world datasets and applied to four different PMU algorithms. The results prove the method effectiveness in reducing the average data throughput as well as its scalability at PMU concentrator or storage level

The Domain Chaos Puzzle and the Calculation of the Structure Factor and Its Half-Width

The disagreement of the scaling of the correlation length xi between experiment and the Ginzburg-Landau (GL) model for domain chaos was resolved. The Swift-Hohenberg (SH) domain-chaos model was integrated numerically to acquire test images to study the effect of a finite image-size on the extraction of xi from the structure factor (SF). The finite image size had a significant effect on the SF determined with the Fourier-transform (FT) method. The maximum entropy method (MEM) was able to overcome this finite image-size problem and produced fairly accurate SFs for the relatively small image sizes provided by experiments. Correlation lengths often have been determined from the second moment of the SF of chaotic patterns because the functional form of the SF is not known. Integration of several test functions provided analytic results indicating that this may not be a reliable method of extracting xi. For both a Gaussian and a squared SH form, the correlation length xibar=1/sigma, determined from the variance sigma^2 of the SF, has the same dependence on the control parameter epsilon as the length xi contained explicitly in the functional forms. However, for the SH and the Lorentzian forms we find xibar ~ xi^1/2. Results for xi determined from new experimental data by fitting the functional forms directly to the experimental SF yielded xi ~ epsilon^-nu} with nu ~= 1/4 for all four functions in the case of the FT method, but nu ~= 1/2, in agreement with the GL prediction, in the the case of the MEM. Over a wide range of epsilon and wave number k, the experimental SFs collapsed onto a unique curve when appropriately scaled by xi.Comment: 15 pages, 26 figures, 1 tabl

The nature and evolution of Nova Cygni 2006

AIMS: Nova Cyg 2006 has been intensively observed throughout its full outburst. We investigate the energetics and evolution of the central source and of the expanding ejecta, their chemical abundances and ionization structure, and the formation of dust. METHOD: We recorded low, medium, and/or high-resolution spectra (calibrated into accurate absolute fluxes) on 39 nights, along with 2353 photometric UBVRcIc measures on 313 nights, and complemented them with IR data from the literature. RESULTS: The nova displayed initially the normal photometric and spectroscopic evolution of a fast nova of the FeII-type. Pre-maximum, principal, diffuse-enhanced, and Orion absorption systems developed in a normal way. After the initial outburst, the nova progressively slowed its fading pace until the decline reversed and a second maximum was reached (eight months later), accompanied by large spectroscopic changes. Following the rapid decline from second maximum, the nova finally entered the nebular phase and formed optically thin dust. We computed the amount of formed dust and performed a photo-ionization analysis of the emission-line spectrum during the nebular phase, which showed a strong enrichment of the ejecta in nitrogen and oxygen, and none in neon, in agreement with theoretical predictions for the estimated 1.0 Msun white dwarf in Nova Cyg 2006. The similarities with the poorly investigated V1493 Nova Aql 1999a are discussed.Comment: in press in Astronomy and Astrophysic

Partial Photoionization Cross Sections And Photoelectron Angular Distributions For Double Excitations Up To The N=5 Threshold In Helium

Partial photoionization cross sections sigma(n) and photoelectron angular distributions beta(n) were measured for all possible final ionic states He+(n) in the region of the double excitations N(K,T)(A) up to the N=5 threshold. At a photon energy bandpass of 12 meV below the thresholds N=3,4, and 5, this level of differentiation offers the most critical assessment of the dynamics of the two-electron excitations to date. The experimental data are very well described by the most advanced theoretical calculations. Weaker double-excitation series with K=N-4 are clearly visible in the beta(n) data, and even previously unobserved extremely weak series members with A=-1 can be discerned, showing the high sensitivity of the angular resolved measurements. The shapes of the resonance-induced variations of sigma(n) or beta(n) in the double excitations below a given threshold N change radically depending on the final ionic state n but display striking similarities when comparing the satellite states with n=N-1 and n=N-2 below each threshold N. These systematic patterns may indicate a general rule for the underlying two-electron dynamics

Ciprofloxacin and levofloxacin attenuate microglia inflammatory response via TLR4/NF-kB pathway

BACKGROUND: Neuroinflammation is the response of the central nervous system to events that interfere with tissue homeostasis and represents a common denominator in virtually all neurological diseases. Activation of microglia, the principal immune effector cells of the brain, contributes to neuronal injury by release of neurotoxic products. Toll-like receptor 4 (TLR4), expressed on the surface of microglia, plays an important role in mediating lipopolysaccharide (LPS)-induced microglia activation and inflammatory responses. We have previously shown that curcumin and some of its analogues harboring an α,β-unsaturated 1,3-diketone moiety, able to coordinate the magnesium ion, can interfere with LPS-mediated TLR4-myeloid differentiation protein-2 (MD-2) signaling. Fluoroquinolone (FQ) antibiotics are compounds that contain a keto-carbonyl group that binds divalent ions, including magnesium. In addition to their antimicrobial activity, FQs are endowed with immunomodulatory properties, but the mechanism underlying their anti-inflammatory activity remains to be defined. The aim of the current study was to elucidate the molecular mechanism of these compounds in the TLR4/NF-κB inflammatory signaling pathway. METHODS: The putative binding mode of five FQs [ciprofloxacin (CPFX), levofloxacin (LVFX), moxifloxacin, ofloxacin, and delafloxacin] to TLR4-MD-2 was determined using molecular docking simulations. The effect of CPFX and LVFX on LPS-induced release of IL-1β and TNF-α and NF-κB activation was investigated in primary microglia by ELISA and fluorescence staining. The interaction of CPFX and LVFX with TLR4-MD-2 complex was assessed by immunoprecipitation followed by Western blotting using Ba/F3 cells. RESULTS: CPFX and LVFX bound to the hydrophobic region of the MD-2 pocket and inhibited LPS-induced secretion of pro-inflammatory cytokines and activation of NF-κB in primary microglia. Furthermore, these FQs diminished the binding of LPS to TLR4-MD-2 complex and decreased the resulting TLR4-MD-2 dimerization in Ba/F3 cells. CONCLUSIONS: These results provide new insight into the mechanism of the anti-inflammatory activity of CPFX and LVFX, which involves, at least in part, the activation of TLR4/NF-κB signaling pathway. Our findings might facilitate the development of new molecules directed at the TLR4-MD-2 complex, a potential key target for controlling neuroinflammation

Site-specific, synchrotron radiation induced surface photochemistry

This paper discusses recent research directed at understanding the nature of surface photochemistry driven by soft x-ray synchrotron radiation (SR). The research is motivated by the potential of x-rays for both high spatial resolution and site specificity. Although a number of systems indicate the potential for site specificity, the authors chose to study the system of SiF{sub 4}/Ge because the adsorbate`s photoabsorption spectrum is rich in structure near the Si 2p threshold (106 eV) while that of the substrate is structureless. This allows them to differentiate substrate-induced effects from those of the adsorbate. By performing time-dependent measurements of the changes induced in the photoemission spectra by SR, they have found that this system`s photochemistry is site-specific in the Si 2p region and have also determined the nature of the products produced by the reaction

Investigations of solutions of Einstein's field equations close to lambda-Taub-NUT

We present investigations of a class of solutions of Einstein's field equations close to the family of lambda-Taub-NUT spacetimes. The studies are done using a numerical code introduced by the author elsewhere. One of the main technical complication is due to the S3-topology of the Cauchy surfaces. Complementing these numerical results with heuristic arguments, we are able to yield some first insights into the strong cosmic censorship issue and the conjectures by Belinskii, Khalatnikov, and Lifschitz in this class of spacetimes. In particular, the current investigations suggest that strong cosmic censorship holds in this class. We further identify open issues in our current approach and point to future research projects.Comment: 24 pages, 12 figures, uses psfrag and hyperref; replaced with published version, only minor corrections of typos and reference

Galaxy-galaxy(-galaxy) lensing as a sensitive probe of galaxy evolution

The gravitational lensing effect provides various ways to study the mass environment of galaxies. We investigate how galaxy-galaxy(-galaxy) lensing can be used to test models of galaxy formation and evolution. We consider two semi-analytic galaxy formation models based on the Millennium Run N-body simulation: the Durham model by Bower et al. (2006) and the Garching model by Guo et al. (2011). We generate mock lensing observations for the two models, and then employ Fast Fourier Transform methods to compute second- and third-order aperture statistics in the simulated fields for various galaxy samples. We find that both models predict qualitatively similar aperture signals, but there are large quantitative differences. The Durham model predicts larger amplitudes in general. In both models, red galaxies exhibit stronger aperture signals than blue galaxies. Using these aperture measurements and assuming a linear deterministic bias model, we measure relative bias ratios of red and blue galaxy samples. We find that a linear deterministic bias is insufficient to describe the relative clustering of model galaxies below ten arcmin angular scales. Dividing galaxies into luminosity bins, the aperture signals decrease with decreasing luminosity for brighter galaxies, but increase again for fainter galaxies. This increase is likely an artifact due to too many faint satellite galaxies in massive group and cluster halos predicted by the models. Our study shows that galaxy-galaxy(-galaxy) lensing is a sensitive probe of galaxy evolution.Comment: 11 pages, 8 figures, accepted in A&