Phase Anomalies Research Articles

Solar flare induced ionospheric D-region perturbation as observed at a low latitude station Agra, India

The results of solar flare induced D-region perturbation studies along a short great circle path (GCP=6690 km) lying entirely in the low and equatorial latitude region are presented. We use SoftPAL receiver at Agra (Geograph. lat. 27.2°N, long. 78°E), India and monitor NWC signal (f=19.8 kHz) transmitted from Australia. We analyze the data for the year 2011 and find that the results of amplitude and phase perturbations, time delay, zenith angle independence, and electron density variation in the lower ionosphere are consistent with those observed along similar paths at low and high latitudes. The new work includes; (i) the distribution of peak X-ray flares in the mixed solar cycle period 2011 responsible for clear and measurable sudden phase anomalies (SPAs) is different from that in minimum solar cycle period, though the cut off hardening factor is the same; (ii) the phase anomalies are evaluated in terms of X-ray fluence (J/m2); (iii) the perturbation due to X-class of flare is used to calculate the electron densities in 70–60 km height range which are found to be 60–80 % lower than those in the polar region where X-ray flare is followed by solar proton event.

B43 Huntington's Disease And Circadian Rhythms: What Can Flies Teach Us?

<h3>Background</h3> Circadian rhythms are daily rhythms that control every aspect of our behaviour and physiology in a 24 h fashion. They are common to nearly all living organisms from cyanobacteria to plants and from flies to humans. The underlying molecular mechanisms that control circadian rhythms are well understood and flies are an excellent model to study them as their clock is very similar to ours. Additionally we have high-throughput techniques to analyse the fly’s locomotor activity rhythms, which are equivalent to our sleep/wake cycles. Circadian rhythms are also very sensitive physiological markers of wellbeing and can be easily disturbed by life style changes such as inter continental travel or shift work. Circadian problems can also be the direct or indirect result of brain pathologies as in the case with Huntington’s disease (HD). <h3>Aims</h3> We are characterising a new fly model of HD that is inducible, tuneable and cell type specific. Our aim is to understand early cellular and physiological processes that lead to neuronal dysfunction by using the circadian clock as a readout. Our work may shed light on several under explored areas. For instance: Is HD pathology directly caused by progressive accumulation of mutated huntingtin (HTT) protein over time or by the ageing cell not being able to cope with the mutant protein? Can we reverse HD pathology by turning off the mutated gene? If so, when is the critical point of no return? <h3>Methods</h3> Using the molecular toolkit available for flies, we can over-express mutant human HTT protein in the brain targeting the clock neurons. We can then analyse rhythms of locomotor activity, looking for anomalies in period, phase or amount of locomotion. Turning the mutant HTT gene on or off throughout the life span of the fly we can probe the effects of ageing on rhythmic phenotypes. <h3>Results</h3> Here we show that over expression of mutant human HTT in clock neurons causes arrhythmic behaviour in flies and that this effect is modulated by ageing. <h3>Conclusions</h3> Using circadian rhythms as a tool and fruit flies as a model we have a powerful experimental system to study the pathology caused by the mutated HD protein. In the future, we will focus on the cellular mechanisms leading to neuronal dysfunction/ neurodegeneration in HD and define the critical point in the progression of the disease before which intervention should be made.

Variability of tidal constants in the Río de la Plata estuary associated to the natural cycles of the runoff

We analyze the only long-term (47-years long) hourly tide-gauge record available for the Río de la Plata estuary for variability in the amplitude and phase of the dominant principal lunar semi-diurnal (M2) constituent. The tidal record was first filtered to isolate the signal at the frequency of M2. Then harmonic analysis was applied to the filtered data for periods of one year with progressive lags of one month. This way, monthly time series of M2 amplitude and phase were obtained, which were then analyzed by means of several spectral techniques. Both M2 amplitude and phase present a long-term trend/inter-decadal cycles and significant pseudo-periodicities at frequencies which are known as typical of the El Niño – Southern Oscillation (ENSO) cycles. A joint multi-channel singular spectral analysis of the tidal constants and the runoff to the estuary (which variability is dominated by the ENSO cycles effect on precipitation over southern South America) reveals co-movements at periods around 2.5, 3.5 and 6.5 years, as well as long-term trends/inter-decadal cycles. Positive (negative) runoff anomalies are associated with negative (positive) amplitude anomalies and negative (positive) phase anomalies. The detected variability in the tidal constants seems to be the result of the interaction between the tidal wave propagating upstream and the downstream currents due to the runoff, rather than a result of the variability in the mean sea level caused by the runoff.

Liquid-crystallinity of cubic phase of BABH(6) through thermal analysis of solid–solid phase transitions

• Clarification of complicated phase relation of a cubic mesogen by DSC and microscopy. • Irregularly tiny and spiky anomalies in DSC trace upon collapse of crystals. • Crystal growth by visiting the cubic phase. • Demonstration of liquid-crystallinity of the cubic phase. Phase transition behavior of 1,2-bis(4′- n -hexyloxybenzoyl)hydrazine (BABH(6)) was studied by differential scanning calorimetry (DSC) and polarizing microscopy. While the DSC trace above melting temperature is consistent with the existing report, it is not for crystalline states. A number of tiny and spiky anomalies was observed in the first cooling run whereas the number of anomalies decreases, and finally disappeared in repeated runs. Microscopic observation revealed that the tiny and spiky anomalies arise from collapsing of crystals. When the sample was cooled from the cubic phase (430 K), the tiny and spiky anomalies revived on the cooling process, which can be ascribed to the liquid-crystallinity of the cubic phase.

Monitoring electrochemical reactions in situ using steady-state free precession 13C NMR spectroscopy

All attempts to use in situ13C NMR in spectroelectrochemical studies, using static cells and unlabeled substrates, have failed due to the very long average time (several hours). In this paper, we demonstrated that steady-state free precession (SSFP) pulse sequence can enhance signal to noise ratio and reduces the average time of 13C NMR signals by more than one order of magnitude. The results showed that each 13C NMR spectrum during the electrochemical reduction of 9-chloroanthracene, in a static cell, can be acquired in eleven minutes. This short averaging time allowed the analysis of the reaction every 30min during 3h. The phase and truncation anomalies present in SSFP spectra were minimized using Traff apodization function and Krylov basis diagonalization method (KBDM).

Anomalous melting scenario of the two-dimensional core-softened system.

We present a computer simulation study of the phase behavior of two-dimensional (2D) classical particles repelling each other through an isotropic core-softened potential. As in the analogous three-dimensional (3D) case, a reentrant-melting transition occurs upon compression for not too high pressures, along with a spectrum of waterlike anomalies in the fluid phase. However, in two dimensions in the low density part of the phase diagram melting is a continuous two-stage transition, with an intermediate hexatic phase. All available evidence supports the Kosterlitz-Thouless-Halperin-Nelson-Young scenario for this melting transition. On the other hand, at the high density part of the phase diagram one first-order transition takes place.

Suppression of spectral anomalies in SSFP-NMR signal by the Krylov Basis Diagonalization Method

Krylov Basis Diagonalization Method (KBDM) is a numerical procedure used to fit time domain signals as a sum of exponentially damped sinusoids. In this work KBDM is used as an alternative spectral analysis tool, complimentary to Fourier transform. We report results obtained from 13C Nuclear Magnetic Resonance (NMR) by Steady State Free Precession (SSFP) measurements in brucine, C23H26N2O4. Results lead to the conclusion that the KBDM can be successfully applied, mainly because it is not influenced by truncation or phase anomalies, as observed in the Fourier transform spectra.

Re-analysis of pluvial precipitation in southern Brazil

This study examined precipitation in southern Brazil based on a data set provided by the Brazilian National Water Agency, covering the period from 1976 to 2010. Data were homogenized using the R software and the Climatol subroutine, which allow completing missing data. Isohyets were drawn using the Geostatistics software to obtain a semivariogram for each analysis. There was a remarkable interannual variability in this region, with positive anomalies in the warm phase (El Niño) and negative anomalies in the cold phase (La Niña) of ENSO. Also, the responses of this variability were not uniform in the entire region, since there was variability from year to year and from event to event.

Anomalous variations in elastic properties of lead zirconate niobate-lead titanate single crystals in the vicinity of its ferroelectric phase transition

The acoustic phonon mode anomalies in the paraelectric phase of tetragonal and rhombohedral (1 − x)Pb(Zn1/3Nb2/3)O3−xPbTiO3 single crystals were systematically investigated by Brillouin light scattering measurements. The inverse relaxation time in the paraelectric phase of both crystals showed a stretched-type slowing-down temperature dependence approaching the structural phase transition temperature instead of a normal critical slowing-down. The observed anomalous part of the elastic constant in the paraelectric phase of the tetragonal crystal in the vicinity of , exhibited a -type dependence in the temperature range from to . On the other hand, the elastic constant of the rhombohedral ferroelectric crystal exhibited a deviation from such a temperature dependence. This was attributed to the interaction of acoustic phonon modes with strong polarization fluctuations and elastic deformation arising from the complex dynamics of polar nanoregions.

Perspective on Materials Genome®

The author’s perspective on Materials Genome® is presented in this paper through several related projects. Current thermodynamic and kinetic databases of multicomponent materials consist of Gibbs energy functions and atomic mobility of individual phases as functions of temperature, composition, and sometimes pressure, i.e., with the individual phases based on crystal structures as the genome (building blocks) of materials. It is articulated that if an individual phase has its internal configurations, such as magnetic spin configurations and ferroelectric polarization, change significantly with respect to temperature, stress, and magnetic and electric fields, then those individual configurations instead should be considered as the genome of the individual phase. The “mutation” of an individual phase is governed by the entropy of mixing among the individual stable and metastable configurations, named as microstate configurational entropy, and responsible to anomalies in individual phases. Our ability to tailor the properties of those individual configurations as a function of compositions is the key for the design of materials.

Laboratory study of spectral induced polarization responses of magnetite — Fe2+ redox reactions in porous media

Spectral induced polarization (SIP) phase anomalies in field surveys at contaminated sites have previously been shown to correlate with the occurrence of chemically reducing conditions and/or semiconductive minerals, but the reasons for this are not fully understood. We report a systematic laboratory investigation of the role of the semiconductive mineral magnetite and its interaction with redox-active versus redox-inactive ions in producing such phase anomalies. The SIP responses of quartz sand with 5% magnetite in solutions containing redox-inactive [Formula: see text] and [Formula: see text] versus redox-active [Formula: see text] were measured across the pH ranges corresponding to adsorption of these metals to magnetite. With redox inactive ions [Formula: see text] and [Formula: see text], SIP phase response showed no changes across the pH range 4–10, corresponding to their adsorption, showing [Formula: see text] anomalies peaking at [Formula: see text]–74 Hz. These large phase anomalies are probably caused by polarization of the magnetite-solution interfaces. With the redox-active ion [Formula: see text], frequency of peak phase response decreased progressively from [Formula: see text] to [Formula: see text] as effluent pH increased from four to seven, corresponding to progressive adsorption of [Formula: see text] to the magnetite surface. The latter frequency (3 Hz) corresponds approximately with those of phase anomalies detected in field surveys reported elsewhere. We conclude that pH sensitivity arises from redox reactions between [Formula: see text] and magnetite surfaces, with transfer of electrical charge through the bulk mineral, as reported in other laboratory investigations. Our results confirm that SIP measurements are sensitive to redox reactions involving charge transfers between adsorbed ions and semiconductive minerals. Phase anomalies seen in field surveys of groundwater contamination and biostimulation may therefore be indicative of iron-reducing conditions, when semiconductive iron minerals such as magnetite are present.

Magnetization vector imaging for borehole magnetic data based on magnitude magnetic anomaly

Remanent magnetization and self-demagnetization change the magnitude and direction of the magnetization vector, which complicates the interpretation of magnetic data. To deal with this problem, we evaluated a method for inverting the distributions of 2D magnetization vector or effective susceptibility using 3C borehole magnetic data. The basis for this method is the fact that 2D magnitude magnetic anomalies are not sensitive to the magnetization direction. We calculated magnitude anomalies from the measured borehole magnetic data in a spatial domain. The vector distributions of magnetization were inverted methodically in two steps. The distributions of magnetization magnitude were initially solved based on magnitude magnetic anomalies using the preconditioned conjugate gradient method. The preconditioner determined by the distances between the cells and the borehole observation points greatly improved the quality of the magnetization magnitude imaging. With the calculated magnetization magnitude, the distributions of magnetization direction were computed by fitting the component anomalies secondly using the conjugate gradient method. The two-step approach made full use of the amplitude and phase anomalies of the borehole magnetic data. We studied the influence of remanence and demagnetization based on the recovered magnetization intensity and direction distributions. Finally, we tested our method using synthetic and real data from scenarios that involved high susceptibility and complicated remanence, and all tests returned favorable results.

Rare earth elements and Nd isotopes tracing water mass mixing and particle-seawater interactions in the SE Atlantic

Distributions of dissolved and particulate rare earth elements (REEs) and seawater neodymium isotopic composition (εNd) were established in samples from the BONUS GoodHope (BGH) IPY-GEOTRACES cruise in the SE Atlantic sector of the Southern Ocean (36°S-13°E to 57°S-0°, Feb.–Mar. 2008). Close to the South African continent in the subtropical domain, particulate REEs show the highest concentrations and flat PAAS-normalized patterns, clearly tracing their lithogenic origin. Active cerium oxidation onto suspended particles is evidenced by the mirror-image relationship of the cerium anomaly between dissolved and particulate phases. Unradiogenic dissolved neodymium in surface waters (εNd= -17.1) traces the influence of old sedimentary material brought by the Agulhas current and rings to the Cape Basin area. A mass balance calculation suggests that the release of Nd from dissolution of lithogenic material corresponds to a remobilization of 154×106T of sediment per year, i.e., 5% of the total sediment delivered to the southeast African coast annually. At open ocean stations, both dissolved and particulate REEs present negative cerium anomalies, indicating that particles have acquired a marine signature. The increasing REE concentrations with depth, and the strong linear correlations of dissolved REE with silica, indicate that surface removal and deep re-mineralisation of REEs are partially related to the biogeochemical cycle of silicate, which involves biogenic silica (diatoms). Combined with marine carbonates, these authigenic phases could explain the observed REE patterns in suspended particles, except for La. We suggest that the positive La anomalies in both phases are linked to the oceanic barium cycle and the partial dissolution of barite crystals, especially in the Polar Frontal Zone.The εNd composition behaves conservatively in intermediate and deep waters, while input processes affect the isotopic signal of subtropical surface waters and Weddell Gyre bottom waters. An Indian Ocean and an Atlantic variety of AAIW have been isotopically differentiated (εNd=−9.3±0.3 and εNd=−8.0±0.5, respectively). Homogeneous signatures characterize circumpolar waters (εNd from −8.2 to −8.4 for CDW). A binary mixing model has been used to assess the contribution of undiluted NADW reaching southern latitudes.

Further observations of GPS satellite oscillator anomalies mimicking ionospheric phase scintillation

An incident has previously been reported where the signal from the Navstar 43 Global Positioning System (GPS) satellite contained phase anomalies in such a way as to mimic ionospheric scintillation. We have observed another 25 events from the same satellite, plus events from three more satellites. Our data includes simultaneous observations from widely spaced receivers (up to 6,590 km apart), from different manufacturers, further ruling out the possibility of local effects. Two of the events involved a satellite (GPS IIF SV-2) broadcasting the L2C signal. This signal contained phase deviations matching those of the L1 signal, but with a 120/154 multiplicative factor. This rules out the possibility of a genuine ionospheric scintillation event, as it does not match the plasma dispersion relation. It does, however, agree with what can be expected from an anomaly in the satellite's oscillator. While the previously reported event could be dismissed as a freak occurrence, it is now apparent that these events are a persistent phenomenon. They have the potential to corrupt geophysical research with false data and to generate false alarms in systems to forewarn of GPS outages due to scintillation.

Seismic attenuation beneath Europe and the North Atlantic: Implications for water in the mantle

It is well known that anelasticity has significant effects on the propagation of seismic waves, as manifested by physical dispersion and dissipation. Investigations of anelasticity provide complementary constraints on the physical properties of Earth materials, but — contrary to imaging with elastic waves — progress in mapping Earthʼs anelasticity has been relatively slow, and there is only limited agreement between different studies or methodologies. Here, within the framework of adjoint tomography, we use frequency-dependent phase and amplitude anomalies between observed and simulated seismograms to simultaneously constrain upper mantle wavespeeds and attenuation beneath the European continent and the North Atlantic Ocean. In the sea-floor spreading environment beneath the North Atlantic, we find enhanced attenuation in the asthenosphere and within the mantle transition zone (MTZ). In subduction zone settings, for example beneath the Hellenic arc, elevated attenuation is observed along the top of the subducting slab down to the MTZ. No prominent reductions in wavespeeds are correlated with these distinct attenuation features, suggesting that non-thermal effects may play an important role in these environments. A plausible explanation invokes the transport of water into the deep Earth by relatively cold subducting slabs, leading to a hydrated MTZ, as previously suggested by mineral physics and geodynamics studies.

Common features of simple water models

We compare three different simple models for water. They all show a phase behavior and anomalies that are characteristic of water. We compare these models and their features and evaluate the phase diagram, the density anomaly, and the liquid-liquid transition line. Additionally, we show that the characteristic behavior present in all three models can be deduced from the fact that all three models include three microscopic states for nearest neighbor configurations. We therefore propose an even simpler three-state model for water that still captures the phase transitions and the density anomaly. Finally, we show that this simple three-state model shows in fact all four possible scenarios discussed in the literature for the phase behavior of liquid water, if the parameters are adjusted accordingly.

Variation of the components of the induction vector and the horizontal tensor before the Tohoku earthquake March 11, 2011 according to the data of Japanese geomagnetic observatories

This work is a continuation of a work [Babak et al., 2013]. The sources of variable magnetic field observed at the surface of the Earth are presented in the introductory part. The most reliable cases of lithospheric emission registered before strong earthquakes are described for five seismic regions of the World. The changes of electrical conductivity of the Earth's crust as a precursor of earthquakes are discussed. The review shows that geomagnetic response functions (induction vector and horizontal tensor) can be used as an earthquake precursor, which carry information both on lithospheric emission and changes in the electrical conductivity. Analysis of 18 Japanese geomagnetic observatories data (6 of them are away from the Tohoku earthquake epicenter less than 400 km) shows the presence of intense noise for periods less than 500 s. Application of noiseproof algorithms for calculation of response function components only partially reduced their influence. A large amount of processing was carried out and database of response functions for 10-20 years for 18 Japanese observatories was created. During the processing variety of record deficiencies were found, the cause of which is not always clear. Detailed processing of one-second data for 10 weeks before the Tohoku earthquake reveals anomalies of response functions temporal behavior: 7-9, 19-21, 33-36 and perhaps ~ 60 days before the event. Moments of amplitude and phase anomalies vary slightly for different periods of variations, for different components of the response functions, for different stations. This behavior is caused, on one hand, by the influence of geomagnetic activity and the contribution of noise, on the other hand, it can be the manifestation of precursors and co-seismic events, and this behavior may reflect a migration of lithospheric emission and/or changes in the electrical conductivity of the Earth's lithosphere. Decoding of this information can provide valuable information for understanding the physics of earthquake preparation and precursors formation.

Phase anomalies in Talbot light carpets of self-images

An interesting feature of light fields is a phase anomaly, which occurs on the optical axis when light is converging as in a focal spot. Since in Talbot images the light is periodically confined in both transverse and axial directions, it remains an open question whether at all and to which extent the phase in the Talbot images sustains an analogous phase anomaly. Here, we investigate experimentally and theoretically the anomalous phase behavior of Talbot images that emerge from a 1D amplitude grating with a period only slightly larger than the illumination wavelength. Talbot light carpets are observed close to the grating. We concisely show that the phase in each of the Talbot images possesses an anomalous axial shift. We show that this phase shift is analogous to a Gouy phase of a converging wave and occurs due to the periodic light confinement caused by the interference of various diffraction orders. Longitudinal-differential interferometry is used to directly demonstrate the axial phase shifts by comparing Talbot images phase maps to a plane wave. Supporting simulations based on rigorous diffraction theory are used to explore the effect numerically. Numerical and experimental results are in excellent agreement. We discover that the phase anomaly, i.e., the difference of the phase of the field behind the grating to the phase of a referential plane wave, is an increasing function with respect to the propagation distance. We also observe within one Talbot length an irregular wavefront spacing that causes a deviation from the linear slope of the phase anomaly. We complement our work by providing an analytical model that explains these features of the axial phase shift.

Development of nanoscale polarization fluctuations in relaxor-based (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3ferroelectrics studied by Brillouin scattering

The precursor dynamics of ferroelectric phase transitions in relaxor-based ferroelectric ($1\ensuremath{-}x$)Pb(Zn${}_{1/3}$Nb${}_{2/3}$)O${}_{3}$-$x$PbTiO${}_{3}$ single crystals, with $x=0.07$, 0.10, and 0.12, were investigated using inelastic light scattering from a longitudinal acoustic phonon. An acoustic anomaly in a broad temperature range, which is characteristic of relaxor ferroelectrics, was observed. We describe the anomalies in the paraelectric phase by assuming local piezoelectric coupling inside polar nanoregions, which are surrounded by a nonpolar matrix. On the basis of local piezoelectric coupling, a relaxation time $\ensuremath{\tau}$ and a dynamic characteristic length $L$ of the order-parameter (polarization) fluctuations were determined to be in the order of 10${}^{\ensuremath{-}13}$ s and 10${}^{\ensuremath{-}9}$ m, respectively. The $\ensuremath{\tau}$ and $L$ values increase sharply upon cooling from high temperatures but more gradually below the intermediate temperature ${T}^{*}$ ($=493\ensuremath{-}510\phantom{\rule{0.28em}{0ex}}\mathrm{K}$). This result implies that the local polarization fluctuations grow rapidly upon cooling down to above ${T}^{*}$ and the growth rate decreases below ${T}^{*}$. The inflexion point of this growth process in the paraelectric phase is related to the characteristic properties of relaxor-based solid solutions.

Coarse-grained models of stripe forming systems: Phase diagrams, anomalies, and scaling hypothesis

Two coarse-grained models which capture some universal characteristics of stripe forming systems are studied. At high temperatures, the structure factors of both models attain their maxima on a circle in reciprocal space, as a consequence of generic isotropic competing interactions. Although this is known to lead to some universal properties, we show that the phase diagrams have important differences, which are a consequence of the particular k dependence of the fluctuation spectrum in each model. The phase diagrams are computed in a mean field approximation and also after inclusion of small fluctuations, which are shown to modify drastically the mean field behavior. Observables like the modulation length and magnetization profiles are computed for the whole temperature range accessible to both models and some important differences in behavior are observed. A stripe compression modulus is computed, showing an anomalous behavior with temperature as recently reported in related models. Also, a recently proposed scaling hypothesis for modulated systems is tested and found to be valid for both models studied.